WO2005026830A1

WO2005026830A1 - Illuminator and liquid crystal display

Info

Publication number: WO2005026830A1
Application number: PCT/JP2004/013499
Authority: WO
Inventors: Kouya Kawabata; Shuhei Okude
Original assignee: Zeon Corporation
Priority date: 2003-09-12
Filing date: 2004-09-09
Publication date: 2005-03-24
Also published as: JPWO2005026830A1; TW200517688A

Abstract

An illuminator suitably employed as the back light of a liquid crystal display in which unevenness in color is retarded at any view angle even when the liquid crystal display is viewed from the front or from an oblique direction, and a high luminance liquid crystal display can be realized, and a liquid crystal display comprising the illuminator. The illuminator includes an illuminator having a polarizing/separating element for separating an incident light into a transmission light and a reflection light different in polarization state, and a planar light source for supplying light to the polarizing/separating element. Outgoing angle θ of light from the planar light source satisfies a relational expression (a); sinθ≤1.5×[1-(630/A)2]1/2 (a) where A (nm) is the red band edge for a normal incident light of the polarizing/separating element.

Description

Description Lighting device and liquid crystal display device

The present invention relates to a lighting device and a liquid crystal display device. More specifically, the present invention relates to a lighting device particularly preferably used as a backlight unit of a liquid crystal display device, and a liquid crystal display device provided with the lighting device. Background art

In recent years, various devices equipped with a compact and compact liquid crystal display device as compared to a CRT display device have become widespread. For example, there is a high market need for miniaturization of various types of equipment such as personal computers and video cameras, and specifically, miniaturized portable equipment called laptop computers or cameras with LCD monitors. Has become widespread. It is essential to equip these devices with a liquid crystal display, and at the same time, there is a strong demand for high performance and high performance such as color display and high brightness.

In this liquid crystal display device, a backlight system in which a liquid crystal layer is illuminated from the back surface to emit light has become widespread, and a backlight unit is provided on a lower surface side of the liquid crystal layer. The backlight unit generally includes a light source such as a cold-cathode tube, a light guide plate arranged so that an incident end face is located near the light source, and an optical sheet provided on an emission side surface (front surface side) of the light guide plate. And a light reflection sheet disposed on the opposite side (back side) of the light guide plate from the optical sheet. Then, a fine pattern of a predetermined shape is formed on the surface on the light reflection sheet side or the surface on the emission side of the light guide plate in order to obtain uniform diffused light. Examples of the optical sheet provided on the surface side of the light guide plate include a light diffusion sheet and a prism sheet.

However, in such a conventional liquid crystal display device, the utilization efficiency of light energy emitted from the backlight unit is low, and increasing the utilization efficiency of the light energy is an important technical problem. I was The light emitted from the backlight unit is unpolarized light. On the other hand, a polarizing plate is provided on the entrance and exit surfaces of the liquid crystal display device. The polarizing plate is linearly polarized and does not transmit power, and other light is absorbed in the polarizing plate. Therefore, the light transmitted as linearly polarized light is 50% or less of the light incident on the polarizing plate, which makes it difficult to increase the brightness and reduce the power consumption of the liquid crystal display device. I was

Therefore, if the light emitted from the backlight unit can be converted to linearly polarized light, or if the light absorbed by the polarizing plate can be reused, the efficiency of using the light energy emitted from the backlight unit as a whole can be improved. Can be.

As the latter method, various kinds of brightness enhancement members have been developed and put to practical use in order to increase the efficiency of using light energy. For example, a multilayer laminated film in which a low-refractive-index film and a high-refractive-index film are alternately laminated (for example, see Patent Document 1), or a circularly polarized light separating film using a cholesteric liquid crystal layer (for example, Patent Documents 2 and 3) See also).

The multilayer laminated film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, and absorbing the transmitted light as it is by aligning the polarization axis with the polarization plate as it is to be absorbed by the polarization plate. , And can be efficiently transmitted. However, the multilayer laminated film has an extremely large laminated structure in which about 800 layers of two kinds of films having different refractive indexes are alternately laminated, and the production thereof is complicated. This has the disadvantage that the cost is high.

The circularly polarized light separating film has a cholesteric liquid crystal layer having a structure in which a liquid crystal group of a rod-like liquid crystal molecule or a side chain type liquid crystalline polymer is twisted in a thickness direction with a helical axis parallel to a layer normal as a rotation axis. It uses the selective reflection characteristics to separate left-right rotating circularly polarized light into transmitted light and reflected light. When this selective reflection layer is formed using ordinary liquid crystal, the wavelength range of the selective reflection is about several tens of nm, and it cannot be applied as it is for the purpose of the luminance improving member. Therefore, it is necessary to widen the reflection band in the visible region in order to perform circularly polarized light separation over the entire visible light region.

To increase the bandwidth, a method of providing a plurality of liquid crystal layers having different reflection bands and a method of gradually changing the helical pitch of the cholesteric liquid crystal layer in the thickness direction are known. However, both methods still have challenges in terms of productivity 'cost In the case of a circularly polarized light separating element using a cholesteric liquid crystal layer, there is no effect on the light incident in a direction parallel to the layer normal without affecting the display characteristics. However, the cholesteric liquid crystal layer itself produces a phase difference with respect to the light obliquely incident, thereby deteriorating the display characteristics. In particular, there is a problem that the light is colored in an oblique direction. In order to cope with such a problem, for example, a reflective polarizer in which a selective reflection band for normal incident light is extended to an infrared region is disclosed (for example, see Patent Document 4). However, in such a reflective polarizer extended to the infrared region, it is necessary to increase the layer thickness and the number of layers, and there is a problem that the material cost is increased.

In addition, the liquid crystal display device has a problem in that the display contrast and the viewing angle characteristics of display colors are inferior to those of the CRT display device due to birefringence and optical rotation caused by the alignment of the liquid crystal. For this reason, it has been proposed to improve the viewing angle by incorporating, for example, a retardation plate (see, for example, Patent Document 4). Further, by controlling the orientation of the liquid crystal, it is possible to improve the birefringence of the liquid crystal. Attempts have been made to reduce the adverse effects. Compared to the display characteristics of CRT displays, they are not yet sufficient.

Further, in the liquid crystal display device, one of the causes of deterioration in display quality is that light incident on the liquid crystal layer is not parallel light but diffuse light having a spread. Light incident on the liquid crystal layer at various angles other than the vertical direction causes a reduction in display quality due to coloring. Therefore, if light close to parallel light can be incident on the liquid crystal layer, a decrease in display characteristics due to birefringence of the liquid crystal can be suppressed, and display characteristics can be improved.

Under such circumstances, the present invention is suitably used particularly as a backlight unit of a liquid crystal display device, etc., and has a high light energy utilization efficiency, and can be viewed from an oblique direction even when viewed from the front. However, it is possible to provide a high-brightness liquid crystal display device in which color unevenness does not easily occur at a viewing angle, and furthermore, an illuminating device which is advantageous in terms of manufacturing cost, and the above-described excellent functions provided with the illuminating device. The purpose of the present invention is to provide a liquid crystal display device having the same.

[Patent Document 1] Japanese Patent Application Laid-Open No. Hei 9-191

[Patent Document 2] Japanese Patent Application Laid-Open No. Hei 6-230590 [Patent Document 3] Japanese Patent Application Laid-Open No. 8-271731

[Patent Document 4] Japanese Translation of PCT International Publication No. 2000-51 59 94

Disclosure of the invention

The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that a polarization separation element that separates incident light into transmitted light and reflected light having different polarization states, particularly a selective reflection band for normal incident light. An illumination device having at least a broadband polarization separation element having a long wavelength side critical value within a specific range, and a surface light source device having a diffusion angle of light emitted to the polarization separation element within a specific range, They have found that the object can be achieved, and have completed the present invention based on this finding.

That is, the present invention

(1) A lighting device having at least a polarization separation element that separates incident light into transmitted light and reflected light having different polarization states, and a surface light source device that supplies light to the polarization separation element.

When the red band edge of the polarized light separating element with respect to the normal incident light is A (nm), the light emission angle 0 of the surface light source device is expressed by the relational expression (a).

s ι η θ≤ 1.5 Χ Cl- (630 / A) ² ] ^1/2 (a)

A lighting device characterized by being within a range satisfying

(2) The illumination device according to (1), wherein the red band edge of the polarization separation element is at least 630 nm and less than 759 nm for normal incident light.

(3) The illumination device according to paragraph 1 or 2, wherein the polarization separation element is a broadband polarization separation element.

(4) The surface light source device is a device comprising at least a light guide plate, a light source provided on an end surface side of the light guide plate, and a plurality of light sources provided on a lower surface side, wherein the light guide plate has a polarized light. The surface on the separation element side is parallel to the light emission side surface of the polarization separation element, and the opposite back side has a plurality of angle regions that are not parallel to the light emission side surface of the polarization separation element, and has inside thereof. The lighting device according to any one of claims 1 to 3, wherein the lighting device has regions having different compositions, and a light source is arranged in each of the plurality of angle regions.

(5) main refractive indices n _x, n _y and n _z (however, n _x, n _y is 2 refractive index in the direction orthogonal to each other perpendicular to the thickness direction, n _z is a refractive index in a thickness direction Note that n _x , n _y Are defined such that n _x — n _y is maximized. The lighting device according to any one of Items 1 to 4, including a phase difference element in which the relationship of _nz > _nx , _nz > _ny , and _nx ^ ny is _satisfied .

(6) the retardation element has substantially no in-plane retardation, and

R th = _{_{[[(n x + n y)}} / 2] - nj XD

(However, D is the thickness of the retardation element.)

The illumination device according to claim 5, wherein the retardation in the thickness direction defined by the above is in the range of -20 to 1000 nm.

(7) The lighting device according to any one of (1) to (6), further comprising a quarter-wave plate, (8) the lighting according to paragraph 7, wherein the one-four-wave plate is a broadband one-four-wave plate. apparatus,

(9) The illumination device according to any one of (1) to (8), further including a prism sheet between the surface light source device and the polarization beam splitter, and

(10) A liquid crystal display device characterized by using the lighting device according to any of paragraphs 1 to 9;

Is to provide. Brief Description of Drawings

FIG. 1 is a schematic diagram of a liquid crystal layer showing a general cholesteric phase, FIG. 2 is a schematic diagram of selective reflection of a liquid crystal layer showing a general cholesteric phase, and FIG. FIG. 4 is a graph for explaining the viewing angle dependence of selective reflection, FIG. 4 is a schematic view showing a cholesteric liquid crystal layer having a spiral helical axis, and FIG. 5 is a method of tilting a helical axis. FIG. 6 is an explanatory view showing the principle when cholesteric liquid crystal layers are arranged on both sides of the optical path conversion layer, and FIG. 7 is used in the present invention. FIG. 8 is a perspective view of a main part of an example of a surface light source device, FIG. 8 is a cross-sectional view showing a configuration of an example of a tandem-type surface light source device used in the present invention, and FIG. FIG. 2 is a schematic diagram showing an example of the principle and configuration of the lighting device of FIG.

In the figure, reference numeral 1 denotes an alignment-treated surface of a substrate, 2 denotes liquid crystal molecules, 3 denotes a layer normal, 4 denotes a helical axis, 5 denotes a transmission spectrum for oblique incident light, and 6 denotes a transmission spectrum for parallel incident light. Vector, base material with square pyramid irregularities, cholesteric liquid crystal layer 8, 9 Scattering sheet, La is circularly polarized light, La # is diffused light, 31 is a light-scattering light-guiding element, 32 is an incident surface, 33 is a light extraction surface, 34 is a back surface, 35 is a reflection means, 35 6 is a terminal surface, 40 is a wedge-shaped emission direction adjusting element, 41 and 42 are both end surfaces, 43 is a light intake surface, 44 is a light emission surface, 51 is a light guide plate, 52 a and 5 2 b is a light source, 5 3 is a region with different composition, 5 4 is an emission side surface, 6 1 is a prism sheet I, 6 2 is a circularly polarized light separating element, 6 3 is a phase difference element, and 6 4 is a 1/4 wavelength plate , 65 is a prism sheet II, 66 is a polarizing plate, A is a light source, B is a reflector, and AR is an air layer. BEST MODE FOR CARRYING OUT THE INVENTION

The illumination device of the present invention may include at least a polarization separation element and a surface light source device.

The polarization separation element may be any element that can separate incident light into transmitted light and reflected light having different polarization states, and is not particularly limited, and may be any of a linear polarization separation element and a circular polarization separation element. However, a broadband polarization separation element is particularly preferable. The broadband polarization separation element referred to here means linearly polarized light in any of the wavelength ranges from 410 to 470 nm, from 52 to 580 nm, and from 600 to 660 nm. An element having a separation function or a circularly polarized light separation function. Here, as the linearly polarized light separating element, for example, a multilayer laminated film described in Japanese Patent Application Laid-Open No. 9-50683, Japanese Patent Application Laid-Open No. 10-511032, etc. may be used. Can be used. This multilayer laminated film has a property of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, and the transmitted light is directly incident on the polarizing plate with the polarization axis aligned. It is possible to transmit light efficiently while suppressing absorption. As such a multilayer laminated film, for example, a multilayer laminated film [trade name “D_BEF]) manufactured by 3M Company may be mentioned.

On the other hand, as the circularly polarized light separating element, an element having at least a liquid crystal layer formed on a substrate can be used.

The substrate is not particularly limited as long as it is an optically transparent substrate, but is preferably in the form of a long film in order to efficiently produce the liquid crystal layer. Further, in order to avoid unnecessary change of the polarization state, it is more preferable that the film is an optically isotropic film. In addition, from the viewpoint of material cost and thinner and lighter weight, the thickness is 5 to 300 μm. m, more preferably 30 to 100 tm. Such a transparent substrate is not particularly limited as long as it has a thickness of 1 mm and a total light transmittance of 80% or more, and examples thereof include a polymer having an alicyclic structure, polyethylene, and polypropylene. A simple resin consisting of a synthetic resin such as linear olefin polymer, triacetyl cellulose, polyvinyl alcohol, polyimide, polyarylate, polyester, polycarbonate, polysulfone, polyether sulfone, modified acrylic polymer, epoxy resin, etc. Examples include layered or laminated films and glass plates. Among these, a polymer having an alicyclic structure or a chain olefin polymer is preferable, and a polymer having an alicyclic structure is preferred from the viewpoints of transparency, low moisture absorption, dimensional stability, light weight, and the like. Is particularly preferred.

A polymer having an alicyclic structure is a polymer having an alicyclic structure in the repeating unit of the polymer, and a polymer having an alicyclic structure in the main chain and a polymer having an alicyclic structure in the side chain. Any of the bodies can be used. Examples of the alicyclic structure include a cycloalkane structure and a cycloalkene structure, and a cycloalkane structure is preferred from the viewpoint of thermal stability and the like. The number of carbon atoms constituting the alicyclic structure is not particularly limited, but is usually 4 to 30, preferably 5 to 20, and more preferably 5 to 15.

The proportion of the repeating unit having an alicyclic structure in the polymer having an alicyclic structure is usually at least 50% by weight, preferably at least 70% by weight, more preferably at least 90% by weight. If the number of repeating units having an alicyclic structure is too small, heat resistance may be reduced.

Examples of the polymer having an alicyclic structure include (1) a norbornene-based polymer, (2) a monocyclic cyclic olefin-based polymer, (3) a cyclic conjugated gen-based polymer, and (4) a vinyl alicyclic hydrocarbon. Polymers, and hydrogenated products thereof, and the like. Among these, a norbornene-based polymer is more preferable from the viewpoint of transparency and moldability.

Examples of the norbornene-based polymer include a ring-opening polymer of a norbornene-based monomer, a ring-opening copolymer of a norbornene-based monomer and another monomer capable of ring-opening copolymerization, and hydrogenated products thereof, and norbornene-based polymers. Examples include an addition polymer of a monomer, and an addition copolymer of a norbornene-based monomer with another monomer copolymerizable with the norbornene-based monomer. Among these, from the viewpoint of heat resistance and transparency, the development of norbornene-based monomers Most preferred are hydrogenated ring polymers and hydrogenated ring-opening copolymers of norbornene-based monomers and other monomers capable of ring-opening copolymerization.

The polymer having an alicyclic structure is selected from known polymers disclosed in, for example, JP-A-2002-321302.

It is preferable to provide an alignment film for aligning the liquid crystal compound on the substrate. The alignment film can be provided by means such as rubbing of a polymer film for an alignment film, oblique deposition of an inorganic compound, formation of microgroups, or formation of an organic film by the Langmuir's projet method (LB film). . Further, it is also possible to use an alignment film that generates an alignment function by applying an electric or magnetic field or irradiating light. Further, in order to impart adhesion between the base material and the alignment film, it is preferable that the base material be subjected to surface treatment in advance. As means for this, glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment And flame treatment. It is also effective to provide an adhesive layer (undercoat layer) between the substrate and the alignment film.

As the alignment film, an alignment film formed by rubbing a polymer film for an alignment film is preferable from the viewpoint of enabling continuous processing. The rubbing treatment is achieved by rubbing the surface of the polymer film in a certain direction with a cloth. The type of the polymer for an alignment film used as such an alignment film is not particularly limited, but may be selected according to the type of the liquid crystal compound and the desired alignment. Further, these alignment films preferably have a polymerizable group for the purpose of imparting adhesion between the liquid crystal compound and the substrate. Examples of the polymerizable group include an acryloyl group, a metharyloyl group, and a butyl group. The thickness of the alignment film is preferably from 0.01 to 5 / m, more preferably from 0.05 to 1 μm.

As the circularly polarized light separating element in the present invention, as the liquid crystal layer, a broadband liquid crystal layer having a circularly polarized light separating function over the entire wavelength region of visible light (broadband circularly polarized light separating element) is preferable, for example, a wavelength of 410 to 470 nm. A cholesteric liquid crystal layer having a circularly polarized light separating function can be used for light in any of the wavelength ranges of 520 to 580 nm and 600 to 660 nm. Such a cholesteric liquid crystal layer is composed of (a) a combination of cholesteric liquid crystal layers having different center wavelengths of selectively reflected light. (B) One cholesteric liquid crystal layer having a spiral shape in the thickness direction. Pitch (C) a liquid crystal layer provided on a substrate, wherein the liquid crystal layer is formed in a first alignment state and then formed first by changing the layer shape. (D) a cholesteric liquid crystal layer disposed on both sides of an optical path conversion layer provided on a substrate having the above-mentioned alignment film; and the like. Is mentioned.

In the case of the cholesteric liquid crystal layer of the type (a), the phase state of the circularly polarized light reflected by each layer is aligned to prevent different polarization states in each wavelength region, and the polarized light in a usable state is prevented. From the viewpoint of increasing the amount, it is preferable to combine those that reflect circularly polarized light in the same direction. Further, in this case, it is more preferable that the cholesteric liquid crystal layers are stacked in the order of increasing or decreasing the center wavelength of the reflected light, from the viewpoint of suppressing wavelength shift when the viewing angle increases.

As a method of laminating the cholesteric liquid crystal layers in the wavelength order based on the center wavelength of the reflected light, for example, when the center wavelength of the selectively reflected light is 470 nm, 550 nm, 640 nm, and 770 nm, There is a method in which a certain cholesteric liquid crystal layer is formed, these cholesteric liquid crystal layers are arbitrarily selected, and three to seven layers are laminated in the order of the central wavelength of the selectively reflected light.

As a method of laminating a plurality of cholesteric liquid crystal layers having different central wavelengths of the selectively reflected light, a method of laminating each cholesteric liquid crystal layer; a method of laminating each cholesteric liquid crystal layer via an adhesive or an adhesive; Can be

The cholesteric liquid crystal layer of the type (b) can be formed as follows. First, a liquid crystal layer containing a compound, a liquid crystal and an ultraviolet absorber which isomerizes by irradiation with ultraviolet light of a specific wavelength to become a chiralizing agent, is continuously irradiated in the depth direction from the surface (ultraviolet irradiation surface) side. The ultraviolet light having the specific wavelength is irradiated so that the light intensity is attenuated. As a result, a liquid crystal layer in which the amount of the chiralizing agent is continuously reduced from the surface side in the depth direction, that is, the helical pitch of the liquid crystal is continuously changed in the thickness direction of the liquid crystal layer is obtained. Next, the liquid crystal layer is irradiated with ultraviolet light having a wavelength different from the specific wavelength ultraviolet light to cure the liquid crystal layer as a whole, thereby fixing the state in which the helical pitch is inclined. The cholesteric liquid crystal layer obtained in this manner has a helical pitch that changes continuously in the depth direction, and the cholesteric liquid crystal layer covers all wavelength bands in the visible light range. It has a circularly polarized light separating function in the region.

Examples of cholesteric liquid crystal layers of this type include, for example, SID'95, Asia Display, p. 735 (1995), Liquid Crystal, Vol. 2, No. 2, 32-39 (1998). Etc. are described.

As a material constituting the cholesteric liquid crystal, a liquid crystal polymer is preferable. Examples of the liquid crystal polymer include a liquid crystal polymer having a conjugated linear atomic group (mesogen) imparting liquid crystal orientation introduced into a polymer main chain, and a liquid crystal polymer having a mesogen introduced into a side chain of the polymer. Various things such as can be used.

The thickness of the cholesteric liquid crystal layer (or the total thickness in the case of multiple layers) is usually determined from the viewpoints of preventing alignment disorder and transmittance reduction, and widening the wavelength range of selective reflection (reflection wavelength range). :! 5050 im, preferably 2 to 30 μηι, more preferably 2 to: I 0 m. When a base material is provided, the total thickness including the base material is usually 20 to 200 / xm, preferably 25 to 150 / xm, and more preferably 30 to: μm.

As a method of forming a liquid crystal layer on a substrate, for example, a solvent solution of a liquid crystal polymer is coated on a substrate on which an alignment film is formed by spin coating, roll coating, flow coating, printing, dip coating. And a method of forming a coating film by a known coating method such as a casting method, a casting film forming method, a bar coating method, a gravure printing method, and the like, followed by a drying treatment. Examples of the solvent for the liquid crystal polymer include dimethylene chloride, cyclohexanone, trichloroethylene, tetrachloroethane, N-methylpyrrolidone, and tetrahydrofuran.

In addition, as a method of forming a liquid crystal layer, a heated melt of a liquid crystal polymer, preferably a heated melt having an isotropic phase, is coated on a substrate by a method according to the above-described coating method. It is possible to adopt a method of forming a thin layer and solidifying it while maintaining the melting temperature as needed.

The temperature of the heat treatment for forming the liquid crystal layer is in the temperature range from the glass transition temperature to the isotropic phase transition temperature of the liquid crystal polymer, that is, the temperature range in which the liquid crystal polymer exhibits liquid crystal. In addition, the orientation state can be fixed by cooling below the glass transition temperature. The cholesteric liquid crystal layer of the above-mentioned (C) type is formed by coating a coating liquid containing a liquid crystal compound, a solvent, a surfactant, a polymerization initiator, a chiralizing agent, an alignment controlling agent and the like on a substrate having the alignment film. It is preferable that the first alignment state is formed by applying to the first alignment state. As the liquid crystal compound, a rod-shaped liquid crystal compound, a discotic liquid crystal compound, a polymer liquid crystal, and the like are known, and can be appropriately selected depending on a desired alignment state. In addition, in order to fix the alignment state, it is preferable to fix in a target alignment state by heat or ultraviolet rays, and for this purpose, it is preferable that a polymerizable functional group is introduced into the molecule.

Among such liquid crystal compounds, examples of the rod-shaped liquid crystal compound include compounds represented by the following formula (I).

R1 -L 1 -S 1 -L 3 -ML 4 -S 2 -L 2 -R2 (I) wherein R 1 and R 2 represent a polymerizable functional group, and L1, L2, L3 and L 4 represents a single bond or a divalent linking group, and at least one of L 3 and L 4 represents one O—CO—O—, and S 1 and S 2 are spacers having 2 to 20 carbon atoms. Represents one group, and M represents a mesogen group. The mesogen group M includes azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic esters, hexa-hexacarboxylic acid phenyl esters, cyanophenyl hex-hexanes, cyano-substituted phenylpyrimidines , Alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes and alkenylcyclohexylbenzonitrile are preferably used. Specific examples of R 1 and R 2 of the polymerizable functional group include

H ₂ C-

HC,

H

O N

H2C, ”CH, H2C-CH ヽ

-SH -OH -NH2

And the like, but are not limited thereto.

As discotic liquid crystalline compounds, various literatures (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); Chemical Society of Japan, quarterly chemistry review, No. 22 2, Liquid Crystal Chemistry, Chapter 5, Chapter 10, Section 2 (1994); Liquid Crystal Handbook Editing Committee, Liquid Crystal Flight Listed in Chapter 2, Section 2.1.1 (2000) include the same linking groups, spacers, and polymerizable functional groups as those listed for the rod-like liquid crystalline compound described above. Can be used.

As the liquid crystal polymer, those described in Liquid Crystal Handbook Editing Committee, Liquid Crystal Handbook, Chapter 3, Section 3.8 (2000) can be used, but are not limited thereto. From the viewpoint of alignment uniformity, a side chain type liquid crystalline polymer is preferably used. As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of the organic solvent include ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. Particularly, ketones are preferable in consideration of the burden on the environment. Two or more organic solvents may be used in combination. As a surfactant for adjusting the surface tension of the coating liquid and the liquid crystal layer before polymerization, a commercially available surfactant can be used. Particularly preferred is a nonionic surfactant, which has a molecular weight of about several thousand. It is preferred that it is an origin. Examples of such a surfactant include KH-40 manufactured by Seimi Chemical Co., Ltd.

Examples of the polymerization initiator include a thermal polymerization initiator and a photopolymerization initiator, but it is preferable to use a photopolymerization initiator because the photopolymerization reaction is rapid. Examples of the photopolymerization initiator include polynuclear quinone compounds (described in U.S. Pat. Nos. 3,046,127 and 2,951,758), oxadiazole compounds (described in U.S. Pat. No. 4,212,970), a-- Carbonyl compounds (described in U.S. Pat. Nos. 2,736,661 and 2,736,670), acyloin ethers (described in U.S. Pat. No. 2,488,828), c-hydrocarbon-substituted aromatic acyloin compounds ( U.S. Pat. No. 2722512), a combination of triarylimidazole dimer and p-aminophenol ketone (described in U.S. Pat. No. 3,549,367), ataridine and phenazine compounds (Japanese Unexamined Patent Publication No. No. 105667, U.S. Pat. No. 4,239,850).

The amount of the photopolymerization initiator used is preferably from 0.01 to 20% by weight, more preferably from 0.5 to 5% by weight, based on the solid content of the coating solution. It is preferable to use ultraviolet light for light irradiation for polymerizing the liquid crystal compound. The light irradiation energy is preferably l mj / ^ πι2 to 50 jZcn ^. ~ 800mjZcm2 Is more preferred.

The alignment state of the liquid crystalline compound to which the alignment treatment according to the present invention can be applied includes a nematic phase, a cholesteric phase, and a smectic phase. The nematic phase refers to a state in which the position of the center of gravity of the liquid crystal molecules is disordered and the long axes of the molecules are uniaxially oriented. The cholesteric phase refers to a state in which the position of the center of gravity of liquid crystal molecules is disordered, and the long axis of the molecules is twisted in a certain direction between the molecules. The smectic phase is characterized by having a layered structure with one-dimensional order at the center of gravity in addition to the order of the nematic phase. It is known that these alignment states develop depending on the temperature of the liquid crystalline compound, and these are called thermopic pick liquid crystals. Furthermore, the temperature at which each phase develops is called the phase transition temperature.

In the case of the cholesteric phase, a method using a liquid crystalline compound having an optically active site in a molecule and a method of adding an optically active substance to a liquid crystalline compound having no optically active site are known. ing. Optically active substances are also called chiralizing agents. As the chiralizing agent, those having a large HTP (Helical Twisting Power), which is an index indicating the efficiency of twisting the liquid crystalline compound, are preferable from the viewpoint of economy. HTP is represented by formula (II).

H T P = 1 Z Pc (II)

Here, P represents the helical pitch length of the cholesteric phase, and c represents the concentration of the chiralizing agent. Further, in order to avoid an unintended change in the phase transition temperature due to the addition of the chiralizing agent, it is preferable to use a chiralizing agent which itself exhibits liquid crystallinity.

The alignment controlling agent is for controlling the alignment state of the air-side surface of the liquid crystal layer formed on the substrate, and may also serve as the surfactant, but may be appropriately determined depending on the desired alignment state. Resins are used. Examples of such a resin include, but are not limited to, polyvinyl alcohol, polyvinyl butyral, and modified products thereof. The application of the coating solution can be performed by a known method, for example, an extrusion coating method, a direct dalvia coating method, a reverse gravure coating method, a die coating method, or the like.

The liquid crystal layer applied on the base material exhibits the above-mentioned liquid crystal phase according to the properties and temperature of the liquid crystal compound and other materials. Furthermore, it is known that various alignment states also exist in these phases depending on the properties of the contact interface (the alignment film side and the interface facing the same). Have been. In particular, as disclosed in JP-A-8-338913, JP-A-8-209127 and JP-A-2000-66192, the long axis of the rod-like liquid crystalline compound and the layer It is known that an orientation state (spray orientation) in which the angle formed with the normal line gradually changes from one layer interface to the other layer interface exhibits important characteristics for optical film applications. Hereinafter, the reason why a wide area and a reflection band can be realized by the alignment processing will be described by taking a liquid crystal layer exhibiting a cholesteric phase as an example.

FIG. 1 schematically shows a liquid crystal layer showing a general cholesteric phase. In FIG. 1, the liquid crystal molecules 2 in contact with the alignment treatment surface 1 applied to the substrate surface are drawn so as to align the long axes of the liquid crystal molecules in a direction corresponding to the alignment treatment. In addition, the liquid crystal molecules are twisted at a helical pitch P according to the HTP of the chiralizing agent between the interface on the alignment treatment surface and the surface facing the liquid crystal molecule.

FIG. 2 schematically shows selective reflection of a liquid crystal layer exhibiting a general cholesteric phase. It is known that when light is incident on a liquid crystal layer exhibiting a cholesteric phase, it exhibits a reflection characteristic (selective reflection) only with respect to any one of right and left circularly polarized lights in a specific wavelength region. This is illustrated in FIG. Here, 6 j is the incident angle when white incident light L 1 is incident, L 2 is the circularly polarized light selectively reflected, θ ₂ is the incident light when the incident light L 1 is refracted in the liquid crystal layer according to Snell's law. It represents the angle between the light traveling direction and the layer normal 3. If helical axis 4 which represents the rotational axis when the liquid crystal compound is twisted is perpendicular to the layer, since the layer normal 3 and the spiral shaft 4 are parallel, this case, 0 ₂ inside the liquid crystal layer It can be said that this is the angle between the spiral axis and the incident light. The center wavelength of the circularly polarized light L2 subjected to selective reflection is expressed by the following equation (III), and the reflection band is expressed by the following equation (IV).

λ = η X Ρ X cos θ 2 (III) no X PX cos 0 ₂ ≤ λ ≤ ne XPX cos 6 ₂ (IV) n = (ne + no) / 2

n o: Refractive index in the minor axis direction of the rod-like liquid crystalline compound

n e: refractive index in the major axis direction of the rod-shaped liquid crystalline compound

P: pitch length of twist

FIG. 3 is a graph for explaining the viewing angle dependence of the selective reflection. Formula (IV ), The wavelength of the reflected light for light incident obliquely is shorter than the wavelength of the reflected light for light incident parallel (0 ₂ = 0) to the helical axis. Shift to As a result, in the transmission spectrum 5 for light incident obliquely with respect to the helical axis, the position of the peak shifts to the shorter wavelength side with respect to the transmission spectrum 6 for light incident parallel (0 ₂ = 0). . This is shown in FIG. Here, considering that the wavelength range of selective reflection Δe (ne XPX cos 0 ₂ -no XPX cos 0 ₂ ) is extended to the entire visible wavelength range, that is, to broaden the band, ne and no of the rod-like liquid crystal compound are considered. It is necessary to increase the difference Δη (birefringence).

As a technique for widening the bandwidth, a technique disclosed in JP-A-6-235900 can be used. Disclosed here is a structure in which the helical pitch P gradually changes in the thickness direction of the layer of the type (b). In such a structure, since there are regions where the helical pitch P differs in the thickness direction, broadband reflection characteristics can be obtained as the sum of the wavelength regions λ of the reflected light in each region. This can be said to be the result of controlling the spiral pitch 式 in equation (IV).

As still another method, there is a method of controlling cos θ ₂ in the equation (IV). Since θ ₂ is the angle between the helical axis inside the liquid crystal layer and the incident light, the structure in which the helical axis of the liquid crystal layer is inclined so that O ₂ gradually changes in the path of the incident light inside the layer If the incident light is lifting is bracts considered different reflection bands in different 0 ₂ regions of the line path. Incidence angle dependence of the wavelength of the selective reflection light formula (III), Formula (IV), and F i g. 3 the same as described, the angle of incidence, that is, as theta ₂ is large, shifts to the short wavelength side Therefore, it is possible to widen the bandwidth by adjusting the inclination angle of the spiral axis of the liquid crystal layer and the spiral pitch length over the entire path of the incident light. This is shown in Fig. 4. FIG. 4 is a schematic diagram showing a cholesteric liquid crystal layer in which the helical axis is inclined. Here, as the incident light L 1 travels through the liquid crystal layer, the angle theta ₂ which the helical axis and L 1 is formed by a, b, how changes c (a>b> c) is depicted. The larger the value of θ ₂ is, the more the wavelength of the reflected light shifts to the shorter wavelength side. Therefore, the wavelength of each reflected light is shorter when Θ ₂ = a than when 0 ₂ = c.

As described above, it is clear that a structure in which the helical axis is tilted with respect to the incident light is effective as a technique for broadening the band, but a more specific structure and its obtainment A method for this will be described.

In general, the above-described splay alignment is realized by changing the alignment state of liquid crystal molecules at the interface of the liquid crystal layer on the alignment film side and the interface facing the splay alignment layer. For example, if one interface is the interface with the alignment film and the other interface is the air, select a material for the alignment film that adsorbs the liquid crystal compound molecules horizontally to the alignment film surface. One method is to select an alignment modifier so that the liquid crystal compound molecules are aligned obliquely to the same interface, and then add it to the coating solution for forming the liquid crystal layer. . JP-A-8-338913 discloses an example in which a polyvinyl alcohol derivative is used as an alignment film and a cellulose acetate butyrate as an alignment regulator for a discotic liquid crystalline compound.

On the other hand, when the helical axis of the cholesteric liquid crystal layer is tilted to widen the band of visible light, the tilt angle range required is as follows, when the helical pitch P is 470 nm and n is 1.5. From the formula (III) i = n XPX cos 0 ₂ Θ _{2 (700)} (upper limit wavelength of reflection band), Θ 2 (400) (lower limit wavelength of reflection band) are θ _{2 (700)} 0 ° and 0 _{2 (400)} 56 degrees. Therefore, it is preferable that the distribution comprising 5 6 ° from the slope 6 ₂ least 0 ° of helical axes of the liquid crystal layer with respect to the traveling direction of the incident light inside the layer. However, it is difficult to create such a large inclination angle distribution by the above-mentioned known method.

As a means for creating a large tilt angle distribution on the helical axis of the cholesteric liquid crystal layer, a liquid crystal layer having a first alignment state is formed on a base material, and then the layer shape is changed to change to a second alignment state. A method is conceivable. Here, the first alignment state refers to a state in which the helical axis of the cholesteric liquid crystal layer is parallel to the layer normal direction, and the second alignment state refers to a state in which the helical axis is not parallel to the layer normal. It is. Examples of the means for changing the layer shape include a method in which a substrate having concaves and convexes is brought into contact with a liquid crystal layer in a first alignment state. If it is used in a state integrated with the liquid crystal layer having the second alignment state, a material that is optically transparent and has a phase difference due to birefringence as small as possible is preferable. Examples of such a material include those described above in the base material of the circularly polarized light separating element. Also, from the viewpoint of making chain! Possible, use a long film Preferably, there is.

The shape of the unevenness is not particularly limited as long as it is in a range where the inclination of the helical axis is generated. Examples include polygonal pyramids, hemispheres, and domes. In the case where the shape is changed so that an apparent phase difference is not generated, it is preferable that the rotationally symmetric axis is in the normal direction of the base material as the concavo-convex shape. The height of the unevenness is preferably from 0.1 to 10 m, more preferably from 0.5 to 3 / z m, from the bottom to the apex of the projection. Further, the in-plane period of the irregularities is preferably from 0.5 to 1.0 m, more preferably from 0.5 to 3 m. FIG. 5 is an explanatory view showing an example of a method of inclining the helical axis, and a cross section of a state where a quadrangular pyramid 7 is used as a concavo-convex shape and integrated with a liquid crystal layer having a second alignment state. Is drawn. Here, a curve 4 traversing the liquid crystal layer LC is a planar shape in which the helical axis was initially parallel to the normal of the liquid crystal layer, as shown in Fig. 5, which represents the helical axis of the cholesteric liquid crystal layer. The first orientation state is deformed by a quadrangular pyramid-shaped concave and convex surface, and has a structure in which the helical axis in the second orientation state is curved.

Means for bringing the substrate having the unevenness into contact with the liquid crystal layer include a method in which the substrate having the uneven surface is opposed to the liquid crystal layer with a generally used press machine, and a method of heating between the jaws. A lamination method in which pressure is applied can be applied. Further, a method of pressing an embossed hole or the like on the liquid crystal layer having the first alignment state formed thereon and transferring an uneven shape on the embossed hole may be applied.

In the cholesteric liquid crystal layer in which the first alignment state is formed, it is important that the helical structure of the cholesteric phase itself be maintained as much as possible in the subsequent step of deforming the layer shape. For this purpose, it is preferable that the first alignment state is fixed to some extent. The method of immobilization is to use a liquid crystal compound in which the types of polymerizable functional groups and the number per molecule are adjusted, or to use a mixture of a non-polymerizable liquid crystal and a polymerizable liquid crystal as a liquid crystal compound. A method of fixing by heating or irradiating light; and a method of fixing by rapidly cooling when a first alignment state is obtained using a polymer liquid crystal.

In the cholesteric liquid crystal layer of the type (d) described above, the liquid crystal compound, a solvent, It is preferable to first form a coating solution containing a surfactant, a polymerization initiator, a chiralizing agent, an alignment controlling agent and the like as appropriate on the substrate having the alignment film. The thickness of the cholesteric liquid crystal layer is preferably from 1 to 1 Om, and from the viewpoint of alignment uniformity, is preferably from 1 to 5 μπι.

Examples of the liquid crystal compound include a rod-shaped liquid crystal compound, a discotic liquid crystal compound, and a liquid crystal polymer, and any of them can be appropriately selected depending on a desired alignment state. Further, in order to fix the alignment state, it is preferable to solidify by heat or ultraviolet rays in the target alignment state, and for this purpose, it is preferable that a polymerizable functional group is introduced into the molecule.

The rod-shaped liquid crystal compound, the discotic liquid crystal compound, and the liquid crystal polymer are each appropriately selected from cholesteric liquid crystal from the rod-shaped liquid crystal compound, the discotic liquid crystal compound, and the liquid crystal polymer described in the above (c) type. Can be used.

The solvent, surfactant, polymerization initiator, chiralizing agent, orientation adjusting agent, and the method of applying the coating solution used in the preparation of the coating solution are the same as those described in the above (c) type.

The polarization separation characteristics of the cholesteric liquid crystal layer are the same as those of the type (c) described above with reference to FIGS.

The optical path conversion layer used in the circularly polarized light separating element of the type (d) indicates one in which the incident angle of light on the incident surface and the exit angle on the incident surface are different. Here, the incident angle of light on the incident surface is the angle between the direction of the incident light and the normal to the incident surface, and the exit angle on the same surface is the direction of the light exiting from the optical path conversion layer. It refers to the angle between and the normal to the plane of incidence. Therefore, the incident light is emitted with its traveling direction changed by the optical path conversion layer. Such a function of the optical path conversion layer may be applied to the entire incident light or may be applied to only a part of the incident light. Examples of such an optical path conversion layer include a film in which one surface of a base material is unevenly processed, and a diffusion sheet in which particles are dispersed in the base material. Examples of the film in which one side surface of the base material is unevenly processed include a film having a matte surface by embossing or the like, a prism sheet, and the like. As the diffusion sheet in which the particles are dispersed in the base material, a commercially available diffusion sheet can be appropriately used, but a diffusion sheet having a large haze value and high transparency is preferable. The haze value of the substrate is “Haze, transparent The standard test method for the transmittance of plastics "is preferably 3 to 65% as a haze value with respect to normal incident light measured by" Haze Card Plus "manufactured by Toyo Seiki Co., Ltd., according to AS TMD 1003, and 30 to 60%. % Is more preferable. The transparency of the substrate is preferably 80% or more, and more preferably 90% or more, with respect to the vertically incident light, as measured with the same evaluator in the haze value test method. Further, a substrate obtained by applying a diffusion layer having the above-mentioned haze value and transparency on a substrate can also be used.

The above-mentioned (d) type circularly polarized light separating element is formed by laminating and integrating the above-mentioned cholesteric liquid crystal layer and the optical path conversion layer. Examples of the lamination method include a method of bonding using a commercially available transparent pressure-sensitive adhesive, and a method of directly applying the above-mentioned diffusion layer on the cholesteric liquid crystal layer.

Regarding the stacking order, it is preferable to stack the first cholesteric liquid crystal layer, the optical path conversion layer, and the second cholesteric liquid crystal layer in this order from the light source side of the liquid crystal display device. In order to adjust the reflection band, an optical path conversion layer and a cholesteric liquid crystal layer may be further laminated on the second cholesteric liquid crystal layer.

The reason why the reflection band is widened in the circularly polarized light separating element in which the cholesteric liquid crystal layer and the optical path conversion layer are stacked will be described with reference to FIG. FIG. 6 is an explanatory view showing the principle when cholesteric liquid crystal layers are arranged on both sides of the optical path conversion layer. The cholesteric liquid crystal layers 8 and 9 have a reflection band in the red region for vertically incident light. It is depicted as having. First, as shown in Equation (III), the lights L l, L2, and L 3 incident on the cholesteric liquid crystal layer 8 from the light source are selectively reflected lights LI (R) and L2 ( G) produces L3 (B). As a result, the light that passes through the cholesteric liquid crystal layer 8 is circularly polarized light La in the rotation direction that is not selectively reflected by the cholesteric layer 8 and light L 1 (GB) having a wavelength other than the selective reflection band at each angle. , L 2 (RB) and L 3 (RG). L a and LI (GB), L 2 (RB), and L 3 (RG) enter the diffusion sheet 10, where the incident angle history is eliminated and ordinary diffused light L a # and L 1 (GB) #, L The light enters the cholesteric liquid crystal layer 9 as 2 (RB) ^# and L3 (RG) ^# . Since the diffusion sheet used here has low depolarization, the diffused light L a # L1 (GB) ^# , L2 (RB) #, L3 (RG) ^# is La, LI (GB), L The polarization state of 2 (RB) and L 3 (RG) can be maintained. The cholesteric liquid crystal layer 9 reflects the reflected light L 1 (R) #, L with respect to the diffused light L a # and LI (GB) #, L 2 (RB) #, L 3 (RG) # as in the cholesteric liquid crystal layer 8. 2 (G) # and L 3 (B) # are generated. The reflected light LI (R) #, L 2 (G) #, and L 3 (B) ^# pass through the diffusion sheet 10 again, and the incident angle history is eliminated.As a result, the reflected light enters the cholesteric layer 8 as diffused light. Some of the light is transmitted to the light source side as L 11 (R), L 21 (G), and L 31 (B). L 1 1 (R), L 2 1 (G), and L 3 1 (B) maintain the same polarization state as LI (R), L 2 (G), and L 3 (B) for the same reason as above. I have. As a result, the first reflected L 1 (R), L 2 (G), and L 3 (B) plus L ll (R), L 2 1 (G), and L 3 1 (B) are the light source. Will be reflected to the side. Regarding the light transmitted through the cholesteric layer 9, by further laminating the diffusion sheet and the cholesteric liquid crystal layer, it is possible to extract reflected light while maintaining the polarization state in the same manner as above. In this way, this type of circularly polarized light separating element (d) can separate incident light into circularly polarized light having different rotation directions as transmitted light and reflected light.

An illumination device according to the present invention is a device in which each of the above-described polarization splitting elements is combined with a surface light source device that supplies light to the polarization splitting element. When the band edge is A (nm), the light emission angle 面 of the surface light source device is expressed by the relational expression (a).

si η Θ≤ 1.5 X [11 (630ZA) 2] ^1/2 (a)

It is within the range satisfying. The emission angle here means the normal to the emission surface of the surface light source device, and the angle at which the rate of decrease in luminance when gradually inclined from the normal is within 5% of the luminance in the normal direction. Say. In the illumination device of the present invention, the polarization separation element preferably has a red band edge with respect to normal incident light in a range of 630 nm or more and less than 759 nm, and in a range of 63 O nm or more and less than 690 nm. Something is better. The red band edge for normal incident light indicates a critical value on the long wavelength side of the selective reflection band for normal incident light.

The wavelength of light from the backlight is usually about 400 to 630 nm. Therefore, if the relationship between the diffusion angle and the red band edge with respect to the normal incidence light of the polarization separation element satisfies the above equation (a), the red band edge is expanded to 759 nm or more. Even without stretching, the light from the backlight is separated into transmitted light and reflected light having sufficiently different polarization states by the polarization separation element. If the red band edge is less than 630 nm, light having a wavelength of 630 nm or more among the vertical lights from the knock light may be transmitted without being separated.

Next, in the illumination device of the present invention, a surface light source device in which the emission angle 0 of the light emitted to the above-mentioned polarization splitting element is within the range satisfying the above relational expression (a) is used.

As such a surface light source device, it is sufficient that the emission angle 光 of the light emitted to the polarization separation element satisfies the relational expression (a), and the configuration is not particularly limited. It may be.

For example, (1) a backlight unit in which a viewing angle control member (louver) is provided on the emission side surface of a general-purpose light guide plate; (2) a wedge-shaped emission direction characteristic disclosed in Japanese Patent Application Laid-Open No. 7-270708. A surface light source device using an adjusting element; (3) a tandem surface light source device disclosed in Japanese Patent Application Laid-Open No. H11-288611, (4) in the tandem surface light source device, Surface light source devices using devices having regions with different compositions; and (5) devices in which a prism sheet is disposed on a general-purpose direct-type backlight unit.

As the surface light source device of the above (2), for example, the value of the effective scattering irradiation parameter E [c mi] is in the range of 0.5 E ≤ 50, and the correlation function γ (r ) Is approximated by τ / (r) = exp [-r / a] (where r is the distance between two points in the light scattering light guide) and the value of the correlation distance a [/ im] is 0.06 a≤35 The light-scattering light-guiding element having directivity including a volume region having a wedge-shaped cross section provided with uniform scattering power in the range of: and a small space between the light-extracting surface of the light-scattering light-guiding element. A wedge-shaped emission direction characteristic adjusting element formed and arranged in a complementary positional relationship with the light-scattering light-guiding element; and an end face having a relatively large cross-sectional area of the wedge-shaped cross section of the light-scattering light-guiding element. And a wedge-shaped emission direction characteristic adjusting element, wherein the effective scattering irradiation parameter is smaller than the light scattering light-guiding element. A light-scattering light guide having E, and a light-receiving surface of the wedge-shaped light-emitting direction characteristic adjusting element facing the light-receiving surface of the light-scattering light-guiding element or a side opposite to the light-receiving surface. At least one of the light exit surfaces of the A surface light source device using a wedge-shaped emission direction characteristic adjustment element having a prismatic undulation for correcting the emission direction can be used.

FIG. 7 is a perspective view of a main part of an example of the surface light source device. In FIG. 7, reference numeral 31 denotes a wedge-shaped light-scattering light-guiding element composed of a directional light-emitting light-scattering lightguide. L is a fluorescent lamp, and the light directed rightward from the lamp L is made incident on the light scattering light guide element 31 素子 from the incident surface 32. Reference numeral 33 denotes a light extraction surface, from which light of the light scattering / guiding element 31 is extracted. On the back surface 3 4 opposite to the light extraction surface 33, a regular reflection 14 or a diffuse reflection reflection means 35 is closely attached.

The reflecting means 35 may be a reflecting member (for example, a silver foil sheet) separate from the light-scattering light-guiding element 31, or a reflecting film (for example, aluminum) formed on the back surface 34. (A vapor-deposited film). Reference numeral 40 denotes a wedge-shaped emission direction characteristic adjustment element arranged in a complementary positional relationship with the light scattering light guiding element 31. Both end faces 41, 4 2 are light scattering light guiding elements, respectively. A prism-shaped undulating array is formed that opposes the light-extraction surface 33 of the light-scattering light-guiding element 31 that is in alignment with the light-incident surface 3 2 and the terminal surface 36 of the air layer AR. The light intake surface is 4 3. The surface opposite to the light entrance surface 43 is the light exit surface 44, and the light (indicated by the arrow group) 4 4f or 4 4 から emitted from the light exit surface 44 is Used as light emitted from the surface light source device.

The light-scattering light-guiding element 31 is made of a material obtained by uniformly dispersing a small amount (for example, about 0.07% by weight) of a silicone resin or the like in a transparent resin such as polymethyl methacrylate. . On the other hand, the wedge-shaped emission direction characteristic adjusting element 40 is composed of a light scattering light guide provided with a low scattering power, and is made of, for example, silicone resin in a transparent resin such as polymethylmetharylate. A resin obtained by uniformly dispersing a small amount (for example, about 0.05% by weight) of a base resin or the like is used.

On the other hand, the tandem-type surface light source device of (3) and (4) is a device comprising at least a light guide plate, a light source provided on an end surface side, and a plurality of light sources provided on a lower surface side. In the light guide plate, the polarization separation element side surface is parallel to the light emission side surface of the polarization separation element, and the opposite back side has a plurality of angles that are not parallel to the light emission side surface of the polarization separation element. Having an area, each of the plurality of angle areas having light A structure in which a source is arranged can be used. In this tandem type surface light source device, a light guide plate having a region having a different composition inside is particularly preferable.

FIG. 8 is a cross-sectional view showing an example of the configuration of a tandem-type surface light source device, in which a light guide plate 51, a light source 52a provided on an end surface thereof, and a plurality of light guides provided on a lower surface thereof are provided. It comprises a light source 52b. In the light guide plate 51, the surface 54 on the side of the polarization separation element (outgoing side) is parallel to the surface on the light emission side of the polarization separation element (not shown), and the opposite back side is the side of the polarization separation element. It has a plurality of angle regions that are not parallel to the light emission side surface, and a light source 52b is arranged in each of the plurality of angle regions. There is no particular limitation on the shape of the angle region. In addition, the shape of the side end portion facing the incident surface of the side is preferably thinner than that of the incident surface.

Reference numeral 53 denotes a region having a different composition existing inside the light guide plate 51. The regions having different compositions have a non-uniform structure on the order of microns, and specific examples thereof include the same ones as described in the light scattering light-guiding element.

The light guide plate used for the surface light source device in the lighting device of the present invention can be formed of a transparent material such as a norbornene-based polymer, polymethyl methacrylate, polycarbonate, or polystyrene. The light source is not particularly limited, and includes a conventionally known one such as a cold cathode tube, an electroluminescence element (ELD), and a light emitting diode (LED). A cold cathode tube is preferable, and a three-wavelength type is particularly preferable. Cold cathode tubes are preferred.

In the illumination device of the present invention, the principal refractive index n _x, 1 ^及Pi 1 ₂ (where, n _x, n _y is 2 refractive index in the direction orthogonal to each other perpendicular to the thickness direction, n _y is are those inner minimum orthogonal axial direction refractive index of the direction of the plane, n _z is a refractive index in the thickness direction Here, the orthogonal axes of the n _x, n _y is, n _x -. n _y is the maximum defined as. relations n _z> n _x of), n _z> n _y, it preferably has a retardation element is n ^ n _y. When the phase difference element is composed of a plurality of layers, the main refractive index of the average value of the entire element should satisfy the above relationship. This main refractive index can be measured by an automatic birefringence meter [for example, “KO BR II series” manufactured by Oji Scientific Instruments).

Note that n _x n _y means that the difference in refractive index is usually within 0.0002, preferably 0.000 It is within 1 and more preferably within 0.0005.

The phase difference element is essentially no retardation Chillon plane, and R th two [[(n _x + n _y) Bruno 2] - eta _zeta] ChO (although, D is the phase difference element It is preferable that the retardation in the thickness direction defined by) is in the range of 120 to 100 nm. Plane retardation Chillon R e is defined by R e two (n _x -n _y) xD. Having substantially no in-plane retardation means that the in-plane retardation Re force is usually 20 nm or less, preferably 10 nm or less, more preferably 5 nm or less. . Further, the retardation R th in the thickness direction is appropriately set according to the purpose of use, but in order to function as a phase difference compensating member, a range of 120 ^^ — 100 nm is preferable. The range of 1550 nm is particularly preferred. Examples of the retardation element having such optical characteristics include those including a layer obtained by stretching and orienting a material having at least a negative intrinsic birefringence value (hereinafter, sometimes simply referred to as a negative material). be able to. Here, a material having a negative intrinsic birefringence refers to a material having a property of exhibiting optically negative uniaxiality when molecules are oriented in a uniaxial order.

Examples of the material having the negative intrinsic birefringence value include discotic liquid crystal, discotic liquid crystal polymer, aromatic vinyl polymer, polyacrylitol polymer, polymethacrylate polymer, cellulose ester polymer, and the like. (Binary, ternary, etc.) copolymers. These can be used alone or in combination of two or more.

Among these, at least one selected from an aromatic butyl polymer, a polyacrylonitrile polymer and a polymethyl methacrylate polymer is preferable. Above all, from the viewpoint of high birefringence manifestation, an aromatic vinyl polymer is more preferable. The aromatic vinyl polymer is a polymer of an aromatic vinyl monomer or an aromatic vinyl monomer and a copolymer thereof. It means a copolymer with a polymerizable monomer. Examples of aromatic vinyl monomers include styrene; styrene derivatives such as 4-methylstyrene, 4-chlorostyrene, 3-methylstyrene, 4-methoxystyrene, 4-tert-butoxystyrene, and α-methylstyrene; And the like. These may be used alone or in combination of two or more. May be used.

Monomers that can be copolymerized with aromatic vinyl monomers include propylene, butene; acrylonitrile; acrylic acid, methacrylic acid, maleic anhydride; acrylic esters, methacrylic esters; maleimide; And biel chloride;

Among aromatic vinyl polymers, a copolymer of styrene and / or a styrene derivative and maleic anhydride is preferred from the viewpoint of high heat resistance.

The glass transition temperature of the aromatic vinyl polymer used in the present invention is preferably 110 ° C. or higher, more preferably 120 ° C. or higher, from the viewpoint of obtaining excellent optical properties. As the retardation element used in the present invention, a film or sheet made of the material having the negative intrinsic birefringence value obtained by uniaxially stretching or unbalanced biaxially stretching the stretching direction is used.

(In the direction in which the refractive index becomes maximum or minimum), two layers are stacked perpendicularly to each other; a film or sheet made of a material having a negative intrinsic birefringence is biaxially stretched in a balanced manner (arbitrary in-plane And a layer formed of a material having a negative intrinsic birefringence value and a layer made of a transparent resin material provided on at least one surface of the layer made of a material having a negative intrinsic birefringence value. From the viewpoint of mechanical strength, etc., at least one layer made of a material having a negative intrinsic birefringence value (hereinafter sometimes referred to as “A layer”) is made of a transparent resin material on at least one side (Hereinafter, sometimes referred to as “B layer”) is preferable.

The polymer having the alicyclic structure is as described in the base material of the above-mentioned circularly polarized light separating element.

In the present invention, the thickness of the layer (layer B) made of a transparent resin material is not particularly limited, but is usually 15 to 250 μπι, preferably 25 to 150 μιη.

Further, the retardation element used in the present invention has a laminated structure of a layer (Α layer) made of a material having such a negative intrinsic birefringence value and a layer (Β layer) made of a transparent resin material. The thickness of the layer is not particularly limited, but is usually 5 to 400 111, preferably 15 to 250 μm.

Further, the retardation element used in the present invention includes a layered structure of a layer (A layer) made of a material having such a negative intrinsic birefringence value and a layer (B layer) made of a transparent material having a luster. If The glass transition temperature T g _{A of the} material having a negative intrinsic birefringence value used for the layer _A and the glass transition temperature T g _{B of the} transparent resin material used for the layer _B are T g _A > T g _B. And more preferably T g _A — 20≥T g _B. If T g _B is equal to or greater than T g _A , the refractive index anisotropy of the B layer caused by stretching, if the intrinsic birefringence value of the transparent resin material used for the B layer is positive, will be expressed in the A layer. The refractive index anisotropy may be canceled out, and a desired relationship between the in-plane refractive index and the thickness direction refractive index may not be obtained. Further, when the retardation element used in the present invention includes a laminated structure of a layer (A layer) made of a material having such a negative intrinsic birefringence value and a layer (B layer) made of a transparent resin material, From the viewpoint of preventing moisture absorption, temperature change, or warpage due to aging, a layer made of a transparent resin material (layer B) and a layer made of a material having a negative intrinsic birefringence (layer A) are provided on both sides. Preferably, the two layers B have substantially the same thickness. When the B layer is laminated on only one side, the number of the B layers to be laminated is not limited, but is usually one layer.

The material having a negative intrinsic birefringence value and the Z or transparent resin material used in the present invention may include an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, an antistatic agent, and a dispersant, if necessary. , Chlorine scavenger, flame retardant, crystallization nucleating agent, anti-blocking agent, anti-fog agent, release agent, pigment, organic or inorganic filler, neutralizer, lubricant, decomposer, metal deactivator, contamination Known additives such as inhibitors, antibacterial agents and other resins, and heat-countable elastomers can be added within a range that does not impair the effects of the present invention.

The retardation element used in the present invention comprises an adhesive layer (C layer) between a layer (A layer) made of a material having a negative intrinsic birefringence value and a layer (B layer) made of a transparent resin material. May be provided.

The adhesive layer (C layer) can be formed of a material having affinity for both the material having a negative intrinsic birefringence value used for the A layer and the transparent resin material used for the B layer. For example, ethylene-acrylate copolymers such as ethylene-methyl acrylate copolymer and ethylene-ethyl acrylate copolymer; ethylene such as ethylene-methyl methacrylate copolymer and ethylene-ethyl methacrylate copolymer Ethylene monomethacrylate copolymer; ethylene-based copolymer such as ethylene-vinyl acetate copolymer and ethylene-styrene copolymer; and other polyolefin copolymers. Also this Modified products obtained by modifying these copolymers by oxidation, saponification, chlorination, chlorosulfonation or the like can also be used. In the present invention, when the ethylene-based copolymer is modified, it is possible to improve the handleability at the time of forming the laminated structure and the heat resistance deterioration of the adhesive strength. The thickness of the adhesive layer (C layer) is preferably 1 to 50 / ri, more preferably 5 to 30 μm.

Further the phase difference element for use in the present invention, the case comprising an adhesive layer (C layer), a glass transition temperature or softening point T g _c of the adhesive used in layer C, with T g _A> T g _C Is more preferable, and it is more preferable that T g _A— 20≥T g _c .

The method for producing the retardation element used in the present invention is not particularly limited, but a preferable production method is that at least one side of a layer (A layer) made of a material having a negative intrinsic birefringence value is formed. A method of laminating a layer (layer B) made of a transparent resin material to obtain an unstretched laminate and uniaxially or biaxially stretching it.

Examples of methods for obtaining an unstretched laminate include a coextrusion T-die method, a coextrusion inflation method, a coextrusion molding method such as a coextrusion lamination method, a film lamination method such as a dry lamination method, and a base resin film. A well-known method such as a coating molding method in which a resin solution is coated can be appropriately used. Among them, a molding method by co-extrusion is preferable from the viewpoint of production efficiency and the like. The extrusion temperature at the time of co-extrusion may be appropriately selected depending on the material having a negative intrinsic birefringence value, the transparent resin material to be used and the adhesive used, if necessary. The method of stretching the laminate is not particularly limited, and a conventionally known method can be applied. Specifically, a uniaxial stretching method such as a method of uniaxially stretching in the longitudinal direction using a difference in peripheral speed on the roll side, a method of uniaxially stretching in the lateral direction using a tenter, and the like. At the same time as stretching in the longitudinal direction, a simultaneous biaxial stretching method in which the film is stretched in the horizontal direction according to the spread angle of the guide rail, or stretching in the longitudinal direction using the difference in peripheral speed between the rolls, then gripping both ends of the clips Biaxial stretching such as sequential biaxial stretching in which the film is stretched in the transverse direction using a tenter. In order to balance the refractive index in the plane direction and make the in-plane retardation practically zero (positive retarder), a biaxial stretching method is preferable.

The stretching temperature of the unstretched laminate is not particularly limited. When the retardation element has the laminate structure, the glass transition temperature T g _A of a material having a negative intrinsic birefringence value is as follows: (TgA-10) (° C) to (Tg _A +20) (° C), preferably (Tg _A — 5)

The range of (° C) to (Tg _A + 15) (° C) is more preferable. By setting the stretching temperature within the above range, it is possible to make it difficult for the layer B to exhibit refractive index anisotropy during stretching, and to easily make the relationship between the refractive index in the direction perpendicular to the target surface and the thickness direction. Can be obtained. Here, the draw ratio is usually 1.:! It is up to 30 times, preferably 1.3 to 10 times. If the stretching ratio is out of the above range, the orientation may be insufficient and the refractive index anisotropy, and hence the expression of the retardation may be insufficient, or the laminate may be broken.

In the lighting device of the present invention, it is preferable that the lighting device further includes a 1/4 wavelength plate. As the 1/4 wavelength plate, a broadband 1Z 4 wavelength plate is particularly suitable. Here, the broadband 1/4 wavelength plate is a 1/4 wavelength plate having a phase difference (letter decision) of approximately 1Z4 wavelength over the entire visible light range including a wavelength of 410 to 660 nm.

The quarter-wave plate used in the present invention includes at least one layer (D layer) made of a material having a positive intrinsic birefringence value and a layer (E layer) made of a material having a negative intrinsic birefringence value. Having at least one layer having the same orientation of molecular chains in the D layer and the E layer; described in JP-A-5-100114, JP-A-11-231132, etc. A 1 1/24 wave plate and a 1 44 wave plate; broadband retardation film WRF [manufactured by Teijin Limited];

As a 1Z4 wave plate, at least one layer made of a material having a positive intrinsic birefringence value (D layer) and at least one layer made of a material having a negative intrinsic birefringence value (E layer) In the case where a material having the same orientation of molecular chains in the D layer and the E layer is used, a material having a positive intrinsic birefringence constituting the D layer (hereinafter, simply referred to as a positive material) ) Means that the molecules have the property of exhibiting optically positive uniaxiality when the molecules are oriented in a uniaxial order. Materials having a positive intrinsic birefringence value include rod-like liquid crystals, rod-like liquid crystal polymers, polymers having an alicyclic structure, chain-like olefin polymers such as polyethylene-polypropylene, triacetyl cellulose, polyvinyl alcohol, and the like. Examples include polyarylate, polyester, polycarbonate, polysulfone, polyethersulfone, polychlorinated biel, and multi-component (binary, ternary, etc.) copolymers thereof. These can be used alone or in combination of two or more. In the present invention, among these, a polymer having an alicyclic structure or a linear olefin-based polymer is preferable, and from the viewpoint of light transmittance characteristics, heat resistance, dimensional stability, photoelastic characteristics, etc. Polymers having an alicyclic structure are more preferred.

The polymer having the alicyclic structure is as described for the base material of the circularly polarized light separating element.

The glass transition temperature of the polymer having an alicyclic structure may be appropriately selected according to the purpose of use, but is preferably 80 ° C. or higher, more preferably, from the viewpoint of obtaining excellent optical properties. The temperature is in the range of 100 to 250 ° C., and more preferably 120 to 200 ° C. On the other hand, for the material having a negative intrinsic birefringence constituting the layer (E), the phase difference This is as described in the element.

There is no particular limitation on the method for manufacturing the 1/4 wavelength plate. For example, (a) the D layer and the E layer are separately formed and laminated by dry lamination via the adhesive layer (F layer). And a method for obtaining a laminate by forming a film by a co-extrusion method. Among them, a film forming method by a co-extrusion method is preferable because a laminate having a large delamination strength can be obtained and the production efficiency is excellent. The method of obtaining a laminate by coextrusion is as follows. Specifically, a plurality of extruders are used to extrude a material having a positive intrinsic birefringence value and a material having a negative intrinsic birefringence value from a multilayer die. In this way, a film is formed.

The thickness of the laminate obtained in this way can be appropriately determined according to the intended use of the obtained laminate. The thickness of the film is preferably from 10 to 300 in, more preferably from 30 to 200 x m, from the viewpoint of obtaining a homogeneous stretched film by a stable stretching treatment.

Various additives and other thermoplastic resins or elastomers shall be added to materials having a positive intrinsic birefringence value and materials having a negative intrinsic birefringence value or a material having a negative intrinsic birefringence value within a range not to impair the object of the present invention. Can be. Examples of the various additives include a plasticizer and a deterioration inhibitor. The plasticizer is added to improve the mechanical properties of the film or to increase the drying speed. Examples of the plasticizer used include a phosphoric acid ester and a carboxylic acid ester. The amount of these additives is usually 0 to 20% by weight, preferably 0 to 10% by weight, based on the material having a positive intrinsic birefringence value and / or the material having a negative intrinsic birefringence value. Preferably it is 0 to 5% by weight.

To stack a layer made of a material having a positive intrinsic birefringence value (D layer) and a layer made of a material having a negative intrinsic birefringence value (E layer) with their slow axes orthogonal to each other, the molecular chain of each layer It is sufficient to make the orientation directions of the two equal. In other words, since the 1Z4 wave plate is a laminate of layers (D layer and E layer) made of materials having different signs of intrinsic birefringence, if the extending directions of the D layer and the E layer match, The two slow axes can inevitably be orthogonal.

Such a 1Z4 wavelength plate can be manufactured by stretching the laminate.

The method for stretching the laminate is not particularly limited, and a conventionally known method can be employed. Examples of the stretching method include a method of uniaxially stretching in the longitudinal direction using a difference in peripheral speed on the roll side, and a method of uniaxially stretching in the lateral direction using a tenter. Among these, uniaxial stretching in the machine direction is preferred. The stretching ratio of the uniaxial stretching is not particularly limited, but is preferably 1.1 to 3 times, and more preferably 1.2 to 2.2 times.

The temperature at which the laminate is stretched is preferably (Tg-30), where Tg is the glass transition temperature of the resin constituting the D layer and the E layer. The temperature range is from (Tg + 60) ° C, more preferably (Tg-10) to (Tg + 50) ° C. The stretching ratio is usually from 1.01 to 30 times, preferably from 1.01 to 10 times, and more preferably from 1.01 to 5 times.

Further, when the laminate is manufactured by the co-extrusion method described above, the cutting of a stretched film chip and the bonding of the cut chip, which are necessary when manufacturing a conventional 1/4 wavelength plate, are performed. This eliminates the need for such operations, and the so-called roll-to-roll method enables continuous production of long 1/4 wavelength plates.

The quarter-wave plate has at least one D layer and at least one E layer, and if the optical layered body has the same molecular chain orientation in the D layer and the E layer, the layer structure is particularly limited. Although not limited, it is preferable to have a layer structure of D layer, E layer / D layer, or E layer, ZD layer, and ZE layer. Further, an F layer (adhesive layer) is further provided between the D layer and the E layer. It can have a three-layer structure of F layer-E layer, or a five-layer structure of D layer-F layer-E layer-F layer-D layer or E layer-F layer-D layer-F layer-E layer.

The adhesive constituting the F layer is as described in the phase difference element.

In the illumination device of the present invention, it is preferable to further provide a prism sheet between the surface light source device and the polarization beam splitter. This prism sheet has a function of making the light within a diffusion angle satisfying the relational expression (a) from the surface light source device closer to the parallel light and incident on the polarization separation element. ing. The prism sheet is not particularly limited as long as it has the above function, and can be appropriately selected from prism sheets conventionally used for a surface light source device of a liquid crystal display device and the like.

FIG. 9 is a schematic view showing an example of the principle and configuration of the lighting device of the present invention. As shown in FIG. 9, the lighting device of the present invention is such that white light L 1 within an angle satisfying the relational expression (a) emitted from a surface light source device having a light source A and a reflector B is The light is incident on a prism sheet I 61 provided as desired and is made closer to parallel light, and then is incident on a circularly polarized light separating element 62. In the light incident on the circularly polarized light separating element 62, one of the left and right circularly polarized lights is transmitted, and the other circularly polarized light is reflected, reflected by the reflection plate B, and again incident on the circularly polarized light separating element 62. It is separated again into transmitted light and reflected light. By repeating this, the light emitted from the light source A is effectively used, and the effect of improving the luminance can be obtained. The circularly polarized light transmitted through the circularly polarized light separating element 62 is transmitted through a phase difference element 63 provided as required, the phase difference is compensated, and further converted into linearly polarized light by a 14-wave plate 64. The light passes through the polarizing plate 66 through a prism sheet II 65 provided as required. Incidentally, the polarizing plate 66 can be omitted. Further, the phase difference element 63 may be provided on the light transmitting side of the 1/4 wavelength plate 64.

The illumination device according to the present invention includes a polarization splitting element and a surface light source device in which an emission angle 光 of light emitted to the polarization splitting element satisfies the relational expression (a). Even if the red band edge for line incident light is not extended to 759 nm, when used in a backlight unit of a liquid crystal display device, the viewing angle characteristics are improved, color unevenness due to oblique viewing is suppressed, and power To provide a liquid crystal display device with high brightness You can. In addition, since the reflection band of the polarization separation element can be narrowed, the number of stacked layers can be reduced, and the cost of the polarization separation element can be reduced by generalizing liquid crystal materials, which is advantageous in terms of manufacturing cost. A liquid crystal display device can be provided.

The liquid crystal display device of the present invention has the lighting device of the present invention as a backlight unit, and the configuration is not particularly limited. Specifically, a liquid crystal display device having a configuration in which the lighting device is arranged on the back side of the liquid crystal cell via a polarizing plate, and a polarizing plate and a light diffusion sheet are sequentially provided on the front surface side of the liquid crystal cell. Examples can be given.

The liquid crystal mode used is not particularly limited. The liquid crystal modes include, for example, TN (£ wistednematic) type, STN (Super Twisted Nematic) type, HAN (hybrid Alig nment nt Nematic) type, VA (Vertical Alig nment), MVA ( Mu 1 tipie Vertical Alignment (IPS) type, IPS (In Plane Switching) type, OCB (Optical Coupled Bend) type, and the like.

The polarizing plate is not particularly limited, and a conventionally known polarizing plate can be used. Since the liquid crystal display device of the present invention has the lighting device of the present invention as a backlight unit, the light energy utilization efficiency is improved. In addition, it has high brightness, is hard to cause color unevenness at a viewing angle when viewed from the front and obliquely, and has high brightness. Example

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

The thickness of the laminate was measured using a scanning thickness gauge. The three-dimensional refractive index distribution and the retardation of the retardation element were measured using an automatic birefringence meter [“KOBR A-21” manufactured by Oji Scientific Instruments].

In the evaluation of the characteristics of the liquid crystal display device, the brightness was evaluated on a five-point scale of 1, 2, 3, 4, and 5, with 5 being the brightest and 1 being the worst. Production Example 1 Production of retardation element (positive letterer)

Styrene-maleic anhydride copolymer [“Dairark D 332”, manufactured by Nova Chemical Co., Tg = 131 ° C] as a material having a negative intrinsic birefringence value, norbornene-based polymer as a transparent resin layer material [ "ZEONOR 1020", manufactured by Nippon Zeon Co., Ltd., T g = 105 ° C], norbornene-based polymer layer (thickness 50 πι) at an extrusion temperature of 260 ° C by co-extrusion method. An unstretched laminate having a three-layer structure of a polymer layer (thickness 200 / im) / a norbornene-based resin layer (thickness 50 μπι) was obtained. Next, the unstretched laminate was sequentially fed to a zone-heated longitudinal uniaxial stretching apparatus and a tenter stretching (horizontal uniaxial stretching) apparatus and successively biaxially stretched to obtain a retardation element. The stretching temperature was 140 ° C for both longitudinal stretching and transverse stretching, and the stretching ratio was 1.8 times for longitudinal stretching and 1.5 times for transverse stretching.

The average thickness of the laminate after stretching (phase difference element) is 120 m, the refractive index of the surface direction is _{_{n x = 1.5732, n y =}} 1.5731, the refractive index in the thickness direction was n _z = 1.5757. The retardation was in-plane R e = 10 nm, and the retardation in the thickness direction R th = —300 nm.

Manufacturing example 2 Manufacture of broadband 1/4 wavelength plate

As a material having a positive intrinsic birefringence value, a norbornene-based polymer [“ZEON〇R 1420”, manufactured by Zeon Corporation, T g = 136 ° C], and a material having a negative intrinsic birefringence value, styrene A maleic anhydride copolymer [“Dylark D 332”, manufactured by Novake Mikanore Co., Ltd., Tg = 131 ° C.] was used. First, the norbornene-based polymer and the styrene-maleic anhydride copolymer in a molten state were stored in respective extruders of an extrusion die in which two extruders were combined with an extrusion die. The extrusion channel of the extruder containing the norbornene-based polymer is branched into two, and the norbornene-based polymer extruded from the branched channel is styrene-maleic anhydride extruded from another extruder. The acid copolymer was sandwiched, and a three-layered laminated body was formed inside the extrusion die. Further, a filter is disposed at a communication port of the two extruders to an extrusion die, and the norbornene-based polymer and the styrene-maleic anhydride copolymer are extruded into the extrusion die after passing through the filter. I did it. The extrusion temperature was 260 ° C. The thickness unevenness of the three-layered laminate extruded from the extrusion die was measured using a scanning thickness gauge. The measurement was performed by continuously scanning in the longitudinal direction of the laminate. The obtained laminate had an average thickness of 120 μπι, and the thickness unevenness was 2.5% with respect to the average thickness.

Next, when the obtained laminate was stretched 70% at 125 ° C, the ratio of the retardation to the wavelength at wavelength λ = 450ηπι, 550 nm and 650 nm was 0.235, 0.250 and 0.232, respectively. A 14-wave plate was obtained.

Production example 3 Manufacture of circularly polarized light separating element

(1) Circularly polarized light separating element I (13 layers)

An optically isotropic norbornene-based polymer film having a thickness of 100 / xm, a width of 68 Omm, and a length of 500 m was used as a substrate. After performing plasma discharge treatment on both sides of the substrate, an alignment film coating solution consisting of 10 parts by weight of polyvinyl alcohol and 371 parts by weight of water is continuously applied to one side of the substrate and dried to form an alignment film having a thickness of 1 μπι. Formed. Next, a rubbing treatment was continuously performed on the alignment film in a direction parallel to the longitudinal direction of the substrate.

On the other hand, 81.5 parts by weight of a liquid crystalline compound represented by the following formula (1), 3.1 parts by weight of a photopolymerization initiator represented by the following formula (2), a surfactant [“KH_40” manufactured by Seimi Chemical Co., Ltd.] A cholesteric liquid crystal layer coating solution 1 was prepared, which contained 0.1 part by weight, 7.04 parts by weight of a chiralizing agent 1 represented by the following formula (3), and 240.8 parts by weight of methylethyl ketone.

—,

Further, in the preparation of the coating liquid 1, the coating liquid 2 to the coating liquid 1 were prepared in the same manner as the coating liquid 1 except that the amount of the chiralizing agent represented by the formula (3) was changed as shown in Table 1. 3 was prepared. Table 1

(Center wavelength: center wavelength of selective reflection region of liquid crystal layer) Next, liquid crystal layers are sequentially laminated on the alignment film by using the coating liquids 1 to 13 shown in Table 1 by the following method. Then, a circularly polarized light separating element I (13 layers) consisting of 13 liquid crystal layers each having a thickness of 5.0 m was produced. The red band edge is 800 nm. The liquid crystal layer coating solution 1 is first coated with a bar coater, dried and heated (alignment ripened) on the alignment film, and then irradiated with ultraviolet light to form a 5.0 μιη thick cholesteric liquid crystal layer. Was formed. Next, the same operation was sequentially performed using liquid crystal layer coating liquids 2 to 13 to form 13 liquid crystal layers.

(2) Circularly polarized light separating element II (1 layer)

Using the liquid crystal layer coating liquids 3 to 13 shown in Table 1, in the same manner as in (1) above, the circularly polarized light separating element II (1 layer 1 layer) consisting of a 1 layer liquid crystal layer having a thickness of 5.0ίπι ) Was prepared. The red band edge is at 759 nm. (3) Circularly polarized light separating element III (9 layers)

Using the liquid crystal layer coating liquids 5 to 13 shown in Table 1, a circularly polarized light separating element III (9 layers) consisting of a 9-layer liquid crystal layer having a thickness of 5.0 / zm was prepared in the same manner as (1) above. Produced. The red edge is 680 nm.

Example 1

A louver (viewing angle control member) is provided on the exit side of a general-purpose light guide plate in which a cold cathode tube is arranged on the incident end face side and a light reflection sheet is provided on the back side. : ± 65 °), and the circularly-polarized light separating element I (13 layers) obtained in Production Example 3 and the broadband 1/4 wavelength plate obtained in Production Example 2 are sequentially arranged on the emission surface side of the light guide plate. Thus, a lighting device was manufactured. Further, a polarizing plate, a viewing angle widening film [Fuji Photographic Film Co., Ltd., "WV film"], a transmissive TN liquid crystal display element, and a polarizing plate are sequentially disposed on the side of the 14-wavelength plate. Produced.

When this liquid crystal display device was observed from the light-emitting surface side in a white display mode, the brightness was 3, the color viewing angle was good, and there was no coloring over the entire display surface. Here, a good color viewing angle means that there is little change in color when the viewing angle is changed.

Example 2

In Example 1, a circularly polarized light separating element II (11 layers) was used as the circularly polarized light separating element instead of the circularly polarized light separating element I (11 layers), and the louver was adjusted to adjust the emission angle of the light emitted from the light guide plate. A liquid crystal display device was manufactured in the same manner as in Example 1 except that the angle was set to ± 55 °. When this liquid crystal display device was set to a white display mode and observed from the light emitting surface side, the brightness was 3, and the color field was The corners were good and there was no coloring over the entire display surface.

Example 3

In Example 2, a circularly polarized light separating element III (9 layers) was used instead of the circularly polarized light separating element II (11 layers) as a circularly polarized light separating element, and the louvers were adjusted to adjust the outgoing angle of the outgoing light of the light guide plate ± A liquid crystal display device was manufactured in the same manner as in Example 2 except that the angle was set to 35 °. When this liquid crystal display device was observed from the light-emitting surface side in a white display mode, the brightness was 3, the color viewing angle was good, and there was no coloring over the entire display surface. Example 4

In Example 1, in place of the combination of the cold cathode tube, the general-purpose light guide plate, and the louver, the surface light source device shown in FIG. 7 disclosed in Japanese Patent Application Laid-Open No. 7-270708 ( In the same manner as in Example 1 except that the emission angle of the emitted light: ± 30 °) was used, and the circularly polarized light separating element III (9 layers) was used instead of the circularly polarized light separating element I (13 layers). Thus, a liquid crystal display device was manufactured.

When this liquid crystal display device was observed in the white display mode from the light emitting surface side, the brightness was 4, and the color viewing angle was slightly colored depending on the position in the plane. Example 5

In Example 4, in the same manner as in Example 4, except that the retardation element obtained in Production Example 1 was arranged between the circularly polarized light separating element III (9 layers) and the broadband 1Z 4 wavelength plate, A liquid crystal display device was manufactured.

When this liquid crystal display device was observed from the light-emitting surface side in a white display mode, the brightness was 5, and the color viewing angle was slightly colored depending on the position in the plane. Example 6

A liquid crystal display device was manufactured in the same manner as in Example 5 except that the prism sheet I was disposed between the surface light source device shown in FIG. 7 and the circularly polarized light separating element III (9 layers). did.

When this liquid crystal display device was observed in the white display mode from the light emitting surface side, the brightness was 5, the color viewing angle was good, and there was no coloring over the entire display surface.

Comparative Example 1

A liquid crystal display device was fabricated in the same manner as in Example 1 except that no louver was provided on the emission surface side of the general-purpose light guide plate (the emission angle of the emitted light: ± 90 °). Made.

When this liquid crystal display was set in a white display mode and observed from the light-emitting surface side, the brightness was 3 and the color viewing angle was colored red.

Table 2 summarizes the above results. Table 2

Examples Comparison

1 2 3 4 5 6 1-surface light source device General-purpose + louver General-purpose + louver General-purpose + looper Fig. 7 Fig. 7 Fig. 7 General-purpose

(Emission angle of emitted light) (± 65.) (± 55.) (± 35.) (± 30 °) (± 30.) (± 30 °) (± 90) Prism sheet I None None None None None None Liquid crystal Layer

O 13 11 9 9 9 9 13 Circularly polarized light

Separation element Red band 800 nm 759 nm 680 nm 680 nm 680 nm 680 nm 800

Edge

Phase difference element No No No No Yes Yes Yes No

Quarter-wave plate Yes Yes Yes Yes Yes Yes Yes Brightness 3 3 3 4 5 5 3 Characteristics In-plane position In-plane position

Color viewing angle Good Good Good

More, slightly colored good

More, slightly colored red

Industrial applicability

INDUSTRIAL APPLICABILITY The lighting device of the present invention is advantageous in terms of cost, is particularly suitably used as a backlight unit of a liquid crystal display device, etc., has a high light energy use efficiency, and can be viewed obliquely even from the front. It is possible to provide a high-brightness liquid crystal display device in which color unevenness at a viewing angle hardly occurs even when viewed.

Claims

The scope of the claims

1. A polarization separation element that separates at least incident light into transmitted light and reflected light with different polarization states

And an illumination device having a surface light source device for supplying light to the polarization separation element, wherein a red band edge of the polarization separation element with respect to normal incident light is A (nm). The light emission angle Θ is given by the relational expression (a)

s ϊ η θ≤ 1.5 Χ [1- (630 / Α) ² ] ^1/2 (a)

A lighting device characterized by being within a range satisfying the following.

2. The illuminating device according to claim 1, wherein a red band edge of the polarization separation element is at least 630 nm and less than 759 nm for normal incident light.

3. The illumination device according to claim 1, wherein the polarization separation element is a broadband polarization separation element.

4. The surface light source device is a device comprising at least a light guide plate, a light source provided on an end face side of the light guide plate, and a plurality of light sources provided on a lower surface side, wherein the light guide plate includes: The element side surface is parallel to the light exit side surface of the polarization separation element, and the opposite back side has a plurality of angle regions that are not parallel to the light exit side surface of the polarization separation element, and has a composition inside. 4. The illuminating device according to claim 1, further comprising a plurality of different regions, and a light source disposed in each of the plurality of angle regions.

5. PRIMARY refractive indices n _x, n _y and n _z (however, n _x, n _y is the refractive index perpendicular to each other straight intersects two directions in the thickness direction, n _z is a refractive index in a thickness direction there should be noted that orthogonal axes n _x, n _y is, n _x -. is n _y is determined to be the maximum) the relationship of _{_{_{n z> n x, n z}}} > n y, n x n y. 5. The lighting device according to claim 1, further comprising a phase difference element.

6. the retardation element has substantially no in-plane retardation; and

R th = [[(n _x + n _y ) / 2] —n _z ] XD

(However, D is the thickness of the retardation element.)

6. The illumination device according to claim 5, wherein the retardation in the thickness direction defined by the following is in the range of −20 to 1000 nm.

7. The lighting device according to any one of claims 1 to 6, further comprising a 1/4 wavelength plate.

8. The lighting device according to claim 7, wherein the 14 wavelength plate is a broadband 14 wavelength plate.

9. The lighting device according to claim 1, further comprising a prism sheet between the surface light source device and the polarization splitting element.

10. A liquid crystal display device using the lighting device according to any one of claims 1 to 9.