DE102016005626A1 - Switchable lighting device and its use - Google Patents

Abstract

The invention relates to a lighting device (1) which can be operated in at least two operating modes B1 for a free viewing mode and B2 for a restricted viewing mode, comprising a planar-like backlight (2), which in the operating mode B2 for a limited viewing mode light in a At least one in the viewing direction in front of the backlight (2) located, plate-shaped and transparent optical element (3), and lighting means (4), which are arranged laterally on narrow sides of the optical element (3), wherein the optical element (3 ) is formed as a light guide, which consists of a thermoplastic or thermoelastic plastic in which said light guide homogeneously distributed are present, the said scattering particles of titanium dioxide, barium sulfate, silsesquioxane particles and / or crosslinked polystyrene particles having a mean particle size of 150- 500 nm, which are used in a concentration based on the weight of the optical element (3) of 0.01-300 ppm by weight, said light guide has no printing and no light-scattering impurities and for the outgoing of the backlight (2) light is at least 85% transparent, wherein in the operating mode B2, the backlight (2) on and the lighting means (4) are turned off, and wherein in the operating mode B1 at least the lighting means (4) are turned on.

Description

Field of the invention

In recent years, great progress has been made in broadening the viewing angle of LCDs. However, there are often situations in which this very large viewing area of a screen can be disadvantageous. Increasingly, information is also becoming available on mobile devices such as notebooks and tablet PCs, such as bank details or other personal information, and sensitive data. Accordingly, people need control over who can see this sensitive data; you have to be able to choose between a wide viewing angle to share information on your display with others, eg. B. when viewing holiday photos or for promotional purposes. On the other hand, they need a small viewing angle if they want to treat the image information confidentially.

State of the art

Supplementary films based on micro-blades have already been used for mobile displays to achieve their optical data protection. However, these slides were not (re) switchable, they always had to be placed by hand and then removed again. Also you have to transport them separately to the display, if you do not need them right now. A major disadvantage of the use of such lamellar films is also associated with the accompanying loss of light.

The US 6,765,550 describes such a screen by micro-blades. The biggest disadvantage here is the mechanical removal or mechanical attachment of the filter as well as the loss of light in the protected mode.

In the US 5,993,940 the use of a film is described, which has evenly arranged on its surface, small prism strips to achieve a privacy mode. Development and production are quite expensive.

In the WO 2012/033583 the switching between free and limited vision is generated by means of the control of liquid crystals between so-called "chromonic" layers. This creates a loss of light and the effort is quite high.

The font US 2009/0067156 discloses a variety of ideas for designing a lighting system and display device. The there in the 3A and 3B shown variant uses in particular two backlights, so-called backlights, consisting of wedge-shaped light guides, and an LCD panel, the rear backlight 40 Mandatory a wide angle of illumination and the front backlight 38 imperative to produce a narrow illumination angle. However, the functionality remains unclear, as the backlight 38 To create a narrow illumination angle without the light with a wide illumination angle, which from the backlight 40 when passing through the backlight 38 is essentially converted into light with a narrow illumination angle.

To the design after 5 of the US 2009/0067156 It should be noted that both light guides 46 and 48 each produce "narrow light", ie light with a narrow illumination angle. The light of the light guide 48 becomes only through a complex to be created with prismatic submirror 50 in "wide light", ie light with a wide illumination angle, converted. This conversion extremely curtails the light intensity, since the light, which is initially emitted into a narrow illumination angle and is available as the only light, is then fanned out into a large illumination angle, generally the half space. As a result, depending on the parameters, the brightness is reduced by a factor of 5 or more (in terms of luminance). It is therefore a less relevant design.

In the embodiment according to 7 of the US 2009/0067156 A phosphor layer is absolutely necessary, this is to convert UV light into visible light. This effort is great and in the desire for sufficient light from the backlight to illuminate a LCD panel readable, very large intensities of UV light are needed. Thus, this is expensive, expensive and even from the shielding of the required UV radiation ago not practicable.

The US 2012/0235891 describes a very elaborate backlight in a screen. There according to 1 and 15 not only multiple optical fibers are used, but also other complex optical elements such as microlens elements 40 and prismatic structures 50 which transform the light from the rear lighting on the way to the front lighting. This is expensive and expensive to implement and also associated with loss of light. According to the variant 17 in the US 2012/0235891 produce both light sources 4R and 18 Light with a narrow illumination angle, with the light from the rear light source 18 only consuming in light with a large illumination angle, is converted. This complex transformation is - as already noted above - greatly brightness-reducing.

According to the JP 2007-155783 become special optical surfaces that are difficult to calculate and produce 19 used, which then divert light depending on the angle of light in different narrow or wide areas. These structures are similar to Fresnel lenses. There are also interfering edges which deflect light in undesired directions. Thus, it remains unclear whether really meaningful light distributions can be achieved.

The abovementioned methods and arrangements generally have the disadvantage that they significantly reduce the brightness of the basic screen and / or require an active optical element for mode switching and / or require costly and expensive manufacture and / or resolution in freely viewable Reduce the mode.

Description of the invention

It is therefore an object of the invention to describe a switchable illumination device that allows at least two illumination modes, one of which mode only illuminates a limited solid angle and the other mode allows illumination in the largest possible solid angle. Thus, when using the illumination device with a screen, a secure display of information is to be realized by an optionally restricted viewing angle, wherein in a second mode a free, as far as possible unobstructed viewing angle should be possible. The lighting device should be inexpensive to implement with simple means. In both operating modes, the highest possible resolution, particularly preferably the native resolution of the screen used, should be visible. Furthermore, only the least possible loss of light should be introduced through the solution.

• – eine flächenartig ausgedehnte Hintergrundbeleuchtung, die in der Betriebsart B2 für einen eingeschränkten Sichtmodus Licht in einen eingeschränkten Winkelbereich abstrahlt, wobei das von der Hintergrundbeleuchtung ausgehende Licht in mindestens einer Richtung, die in einem Winkel größer als 45 Grad zur Flächennormale der Hintergrundbeleuchtung gelegen ist, mit höchstens 6% der maximalen Lichtstärke abgestrahlt wird,
• – mindestens ein in Betrachtungsrichtung vor der Hintergrundbeleuchtung gelegenes, plattenförmiges und transparentes optisches Element, und
• – Leuchtmittel, die seitlich an Schmalseiten des optischen Elements angeordnet sind,
• – wobei – das optische Element als Lichtleiter ausgebildet ist, welcher aus einem thermoplastischen oder thermoelastischen Kunststoff besteht, – in dem besagten Lichtleiter homogen verteilte Streupartikel (welche als Lichtstreumittel wirken) vorhanden sind, – die besagten Streupartikel aus Titandioxid, Bariumsulfat, silsesquioxanen Partikeln und/oder vernetzten Polystyrol-Partikeln mit einer mittleren Partikelgröße von 150–500 nm bestehen, welche in einer Konzentration bezogen auf das Gewicht des optischen Elementes von 0.01–300 Gew.-ppm eingesetzt werden, – der besagte Lichtleiter keine Bedruckung und keine lichtstreuenden Störstellen aufweist und für das von der Hintergrundbeleuchtung ausgehende Licht zu mindestens 85% transparent ist, – so dass das aus den Leuchtmitteln (wenn diese eingeschaltet sind) seitlich in das optische Element einfallende Licht für einen freien Sichtbereich in der Betriebsart B1 in Richtungen, die in Winkeln zwischen 45 Grad und 75 Grad zur Flächennormale der Hintergrundbeleuchtung gelegen sind, mit mindestens 12% der maximalen Lichtstärke des aus dem Lichtleiter senkrecht zur Oberfläche austretenden Lichtes abgestrahlt wird, – und so dass das aus dem Lichtleiter an mindestens einem Punkt seiner Oberfläche austretende Licht, welches von den Leuchtmitteln herrührt, wenn diese eingeschaltet sind, in mindestens einem Winkel α zur Oberfläche des Lichtleiters, mit α < 80 Grad, eine höhere Lichtstärke aufweist, als das an dem besagten Punkt der Oberfläche des Lichtleiters senkrecht zur Oberfläche des Lichtleiters austretende Licht, (bevorzugt weist mindestens die Hälfte der Oberfläche des Lichtleiters derartige Punkte auf)
• – wobei in der Betriebsart B2 die Hintergrundbeleuchtung ein- und die Leuchtmittel ausgeschaltet sind, und wobei in der Betriebsart B1 mindestens die Leuchtmittel eingeschaltet sind.

The object of the invention is achieved by a lighting device that can be operated in at least two operating modes B1 for a free viewing mode and B2 for a limited viewing mode, comprising

• An areal-extended backlight which, in the restricted viewing mode B2, emits light within a restricted angular range, with the light emanating from the backlight in at least one direction at an angle greater than 45 degrees to the surface normal of the backlight no more than 6% of the maximum intensity is emitted
• At least one plate-shaped and transparent optical element located in the viewing direction in front of the backlight, and
• Illuminants, which are arranged laterally on narrow sides of the optical element,
• - wherein - the optical element is formed as a light guide, which consists of a thermoplastic or thermoelastic plastic, - in said light guide homogeneously distributed scattering particles (which act as a light scattering agent) are present, - said scattering particles of titanium dioxide, barium sulfate, silsesquioxanen particles and / or crosslinked polystyrene particles having a mean particle size of 150-500 nm, which are used in a concentration based on the weight of the optical element of 0.01-300 ppm by weight, - said light guide has no printing and no light-scattering impurities and is at least 85% transparent to the light emanating from the backlight, so that the light from the bulbs (when switched on) is incident laterally into the optical element for a clear field of view in mode B1 in directions which are at angles between 45 Degrees and 75 degrees z ur surface normal of the backlight are located, is radiated with at least 12% of the maximum light intensity of the light emerging from the optical fiber perpendicular to the surface light, and so that the emerging from the light guide at least at one point of its surface light, which originates from the bulbs, if These are turned on, in at least one angle α to the surface of the light guide, with α <80 degrees, a higher light intensity than the light emerging at the said point of the surface of the light guide perpendicular to the surface of the light guide, (preferably, at least half of Surface of the light guide such points on)
• - In the operating mode B2, the backlight is switched on and the lighting means are switched off, and wherein in the operating mode B1 at least the lighting means are switched on.

For operating mode B1, it is essential that the lamps are switched on while the backlight can be switched on or off. If the backlight is switched off, only the light from the bulbs ensures that the illumination is not restricted at an angle. If, on the other hand, both the light source and the backlight are switched on for operating mode B1, greater brightness can be achieved. It is then particularly advantageous that the emerging from the light guide at least at one point of its surface light, which originates from the bulbs when they are turned on, in at least one angle α to the surface of the light guide, with α <80 degrees, a higher Luminous intensity than that at the said point of the surface of the light guide perpendicular to Surface of the light guide emerging light. Namely, this technical realization means that the light which originates from the light sources and does not have its strongest brightness (s) approximately along the mid-perpendicular of the illumination device with the light which originates from the backlight and its strongest brightness approximately along the mid-perpendicular of the illumination device, very well complemented, over at least one half-angle away (eg., The angle spectrum of the horizontal before the illumination device) to achieve a more homogeneous and brighter illumination than if only the said bulbs for the operating mode B1 would be turned on ,

As scattering particles for the optical element are preferably titanium dioxide particles in a concentration based on the weight of the optical element of 0.1-50 ppm by weight, preferably 0.1-10 ppm by weight, used, and / or the titanium dioxide particles have an average Particle size of 160 to 450 nm and more preferably from 170 to 400 nm.

Furthermore, the optical element has a Haze value of less than 7%, preferably less than 2%, measured according to ASTM D1003.

It is furthermore advantageous if the optical element comprises at least 40 percent by weight of polymethyl methacrylate, preferably at least 60 percent by weight of polymethyl methacrylate, based on its weight.

Another useful embodiment of the illumination device provides that for the operating mode B2, the light originating from the backlight and emerging from the optical element at each point of its surface (in the viewing direction) at angles β> 30 degrees, measured perpendicular to the surface of the optical element and in horizontal orientation to the surface of the optical element, at most 5% of the luminous intensity having the light emerging from such a point of the surface of the optical element perpendicular to its surface.

Particularly preferably, the backlight for this purpose contains at least one optical layer for collimating light in order to achieve an angle-limited radiation characteristic of the light emitted by it. The backlight is preferably a backlight, for example a side-light, edgelight, direct LED backlight, edge LED backlight, OLED or another surface radiator onto which a permanent privacy filter, also as a privacy filter (eg Vikuiti ^™ from 3M ^™ or LCF from Shin Etsu ^TM ) is applied, which acts as a light collimator or spatial light filter, after the passage of which the light from the backlight is radiated substantially only in a limited angular range. In addition to the collimating layer (s), 3M ^™ type "Optical Lighting Film" (OLF) Type 2301 crossed components may still be present to achieve pre-collimation while transmitting the light bundle up.

Furthermore, it is possible for the next optical component below the optical element to have at least one partially reflecting surface for light exiting downwardly from the optical element in operating mode B1, and thus light emitted downwards to be at least partially reflected back onto the optical element, and at least partially passes through it. Since the optical element implemented as a light guide emits light from both large areas, that is to say upwards and downwards (the direction pointing downwards in the direction of the backlighting), a kind of light recycling is made possible in this way. Here it may suffice that the said next optical component, often the optical layer for collimation (eg privacy filter), is not antireflection-coated or has a partial mirroring which is suitable for from below, i. H. from the backlight, incoming light is as transparent as possible.

Basically, the performance of the invention is maintained when the parameters described above are varied within certain limits. For example, the backlight emits light with such a radiation characteristic that in directions which are located at angles greater than 10 ... 45 degrees to the surface normal of the backlight, at most 0 ... 20% of the maximum light intensity are emitted.

Nevertheless, the optical element located in the viewing direction from the backlight, which is at least 85% - or even less than 85%, approximately 70% or even only 50% - of the light emanating from the backlight, can also be made of light sources deflecting incident light into the largest possible angular range, so that in directions that are located at angles greater than 10 ... 100 degrees to the surface normal of the backlight, at least 10 ... 70% of the maximum light intensity are emitted.

The bulbs are z. B. LEDs or laser diodes. In addition, it makes sense if the light coupling from the laterally arranged light sources into the optical element takes place from at least two sides, preferably from opposite sides.

Most preferably, a transmissive image display device, for example an LCD panel, is arranged in front of the illumination device. Thus, the two modes B1 and B2 can be implemented accordingly for the image display device.

Alternatively, it is possible for the optical element to be partially mirrored on its side facing the background illumination, wherein the intensity of the reflection for varying brightness differences in mode B1 is varied over the area of the light coupled out of the optical element, or only those regions partially mirrored, in which the brightness has fallen below a predetermined limit without mirroring. Furthermore, the illumination device may comprise a controller which, in mode B1, compensates differences in brightness over the surface of the light coupled out of the optical element by means of a control of the image contents displayed on the transmissive image display device, which control is complementary to these brightness differences, so that an image which is substantially homogeneous in terms of brightness is perceptible on the transmissive image display device.

Finally, the illumination device according to the invention, in which a transmissive image display device is connected upstream, can advantageously be used for entering or displaying confidential data, for example PIN PIN numbers, e-mails, SMS or passwords, at ATMs, payment terminals or mobile devices.

Moreover, a partial mirroring on the back of the transmissive image display device for further homogenization of the light output from the optical element is advantageous. These can be designed to compensate for differences in brightness similar to the partial mirroring on the optical element varying or applied only in areas.

An advantage is also a backlight already collimated by design as a backlight, d. H. the light source is designed so that its light is emitted only in a prescribed, limited angle range. Furthermore, it may be favorable if always the same light sources, for. B. the said laterally arranged bulbs are used for both modes. The light is then coupled for the switching between the two operating modes B1 and B2, for example via an optoelectronic and / or optomechanical switch once in the optical element and / or once in the backlight. As a switch comes here z. As a shutter or a mechanical switching such as a tilting mirror in question. Also, the bulbs can be formed in two lines, in which case only the desired or corresponding line is turned on.

Furthermore, the desired or allowed irradiation directions for the restricted view mode B2 can be independently defined and translated for the horizontal and vertical directions, respectively. For example, in the vertical direction, a larger angle might be useful than in the horizontal direction, such as when ATMs are supposed to see something of different sizes, while side-ins should be severely restricted. This is especially by the choice of light collimating layers, eg. As the privacy filter achieved.

• – eine flächenartig ausgedehnte Hintergrundbeleuchtung, die in der Betriebsart B2 für einen eingeschränkten Sichtmodus Licht in einen eingeschränkten Winkelbereich abstrahlt, wobei das von der Hintergrundbeleuchtung ausgehende Licht in mindestens einer Richtung, die in einem Winkel größer als 45 + γ Grad zur Flächennormale der Hintergrundbeleuchtung gelegen ist, mit höchstens 6% der maximalen Lichtstärke abgestrahlt wird, wobei die Hintergrundbeleuchtung mindestens eine Schicht zur Kollimation des von ihr abgestrahlten Lichtes enthalt, welche das die höchste Lichtdurchlässigkeit in einem Winkel von γ mit 0 < γ < 45 Grad zur Flächennormale der Hintergrundbeleuchtung aufweist (hierbei kann es sich z. B. um einen oder mehrere Privacy-Filter handeln, deren Mikrolamellen gegenüber der Flächennormalen des Privacy-Filters um den Winkel γ geneigt sind, wie etwa aus der Produktreihe Shin Etsu^TM LCF),
• – mindestens ein in Betrachtungsrichtung vor der Hintergrundbeleuchtung gelegenes, plattenförmiges und transparentes optisches Element, und
• – Leuchtmittel, die seitlich an Schmalseiten des optischen Elements angeordnet sind,
• – wobei – das optische Element als Lichtleiter ausgebildet ist, welcher aus einem thermoplastischen oder thermoelastischen Kunststoff besteht, – in dem besagten Lichtleiter homogen verteilte vorhanden sind, – die besagten Streupartikel aus Titandioxid, Bariumsulfat, silsesquioxanen Partikeln und/oder vernetzten Polystyrol-Partikeln mit einer mittleren Partikelgröße von 150–500 nm bestehen, welche in einer Konzentration bezogen auf das Gewicht des optischen Elementes von 0.01–300 Gew.-ppm eingesetzt werden, – der besagte Lichtleiter keine Bedruckung und keine lichtstreuenden Störstellen aufweist und für das von der Hintergrundbeleuchtung ausgehende Licht zu mindestens 85% transparent ist, – so dass das aus den Leuchtmitteln seitlich in das optische Element einfallende Licht für einen freien Sichtbereich in der Betriebsart B1 in Richtungen, die in Winkeln zwischen 45 Grad und 75 Grad zur Flächennormale der Hintergrundbeleuchtung gelegen sind, mit mindestens 12% der maximalen Lichtstärke des aus dem Lichtleiter senkrecht zur Oberfläche austretenden Lichtes abgestrahlt wird, – und so dass das aus dem Lichtleiter an mindestens einem Punkt seiner Oberfläche austretende Licht, welches von den Leuchtmitteln 4 herrührt, wenn diese eingeschaltet sind, in mindestens einem Winkel α zur Oberfläche des Lichtleiters, mit α < 80 Grad, eine höhere Lichtstärke aufweist, als das an dem besagten Punkt der Oberfläche des Lichtleiters senkrecht zur Oberfläche des Lichtleiters austretende Licht,
• – wobei in der Betriebsart B2 die Hintergrundbeleuchtung ein- und die Leuchtmittel ausgeschaltet sind, und wobei in der Betriebsart B1 mindestens die Leuchtmittel eingeschaltet sind.

A particular solution of the task is finally the following lighting device according to the invention, which can be operated in at least two modes B1 for a free viewing mode and B2 for a limited viewing mode comprising

• An areal-like backlight that emits light in a restricted angle range in the limited viewing mode B2, the backlight illuminating light being in at least one direction at an angle greater than 45 + γ degrees to the surface normal of the backlight with at most 6% of the maximum light intensity, the backlight containing at least one layer for collimation of the light emitted by it, which has the highest light transmission at an angle of γ with 0 <γ <45 degrees to the surface normal of the backlight (here it may, for example, be one or more privacy filters whose microlenses are inclined relative to the surface normal of the privacy filter by the angle γ, as for example from the product series Shin Etsu ^™ LCF),
• At least one plate-shaped and transparent optical element located in the viewing direction in front of the backlight, and
• Illuminants, which are arranged laterally on narrow sides of the optical element,
• - wherein - the optical element is formed as a light guide, which consists of a thermoplastic or thermoelastic plastic, - are homogeneously distributed in said light guide, - said scattering particles of titanium dioxide, barium sulfate, silsesquioxane particles and / or crosslinked polystyrene particles with a mean particle size of 150-500 nm exist, which be used in a concentration based on the weight of the optical element of 0.01-300 ppm by weight, - said light guide has no printing and light scattering impurities and is at least 85% transparent to the outgoing light from the backlight, - so that the light incident from the illuminants laterally into the optical element for a free viewing area in the mode B1 in directions located at angles between 45 degrees and 75 degrees to the surface normal of the backlight, with at least 12% of the maximum intensity of the vertical out of the optical fiber emitted to the surface of the light emitted, and so that the light emerging from the light guide at least at one point of its surface, which of the light sources 4 when these are turned on, at least at an angle α to the surface of the light guide, with α <80 degrees, a higher light intensity than the light emerging at said point of the surface of the light guide perpendicular to the surface of the light guide light,
• - In the operating mode B2, the backlight is switched on and the lighting means are switched off, and wherein in the operating mode B1 at least the lighting means are switched on.

For this variant of the invention apply mutatis mutandis, the design information given above.

The lateral tilt by the angle γ is advantageous for various applications. For example, in a cockpit of an aircraft, information may only be selectively visible to a pilot, for example if the illumination device together with the image display device is arranged in the center of the control console. Due to the inclination angle γ, in the operating mode B2, the visibility on an oblique view, namely that of only one pilot, is then limited to the system.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the specified combinations but also in other combinations or alone, without departing from the scope of the present invention.

The invention will be explained in more detail below with reference to drawings, which also show features essential to the invention. It shows

1 a schematic diagram for the extraction of light, which is coupled laterally into an optical element, in the largest possible solid angle,

2 a schematic diagram for the passage of light, which results from a backlight, through the optical element,

3 a schematic diagram of a lighting device in a first mode of operation B1 for a free viewing mode in which a maximum solid angle is illuminated, the lighting device is used together with an image display device, and wherein the backlight is turned off,

4 a schematic diagram of a lighting device in a first operating mode B1 for a free viewing mode in which the largest possible solid angle is illuminated, the lighting device is used together with an image display device, and wherein the backlight is turned on,

5 1 is a schematic diagram of the illumination device in a second operating mode B2 for a restricted viewing mode in which a limited solid angle is illuminated, wherein the illumination device is used together with an image display device,

6 a schematic diagram of a further embodiment of a lighting device in a first mode of operation B1 for a free viewing mode in which the largest possible solid angle is illuminated, the illumination device is used together with an image display device, and wherein the backlight is turned on, as well

7 a diagram of an exemplary brightness distribution in different spatial directions with respect to the decoupled from an optical element light.

The drawings are not true to scale and only represent schematic representations.

In 1 is a schematic diagram for the extraction of light, the side of bulbs 4 in an optical element 3 - shown here only as a small section in sectional view - is coupled, in the largest possible solid angle, shown. The small dots stylize scattering particles as scattering centers for the light, which laterally from the bulbs 4 is coupled. As scattering particles for the optical element 3 Titanium dioxide particles are preferably used here in a concentration based on the weight of the optical element (US Pat. 3 ) of 0.1-50 ppm by weight, preferably 0.1-10 ppm by weight., And / or the titanium dioxide particles have an average particle size of 160 to 450 nm and more preferably from 170 to 400 nm. Due to total reflection, rays of the injected light become the outer wall back into the light guide, so the optical element 3 , thrown until they finally hit a scattering article to the desired extraction. The representation in 1 is highly stylized for better visibility; In reality, there are a very large number of optical paths in the optical element 3 implemented.

2 shows a schematic diagram for the passage of light from a - not graphically illustrated - backlight 2 due to the optical element 3 , The scattering particles play a negligible role as the light is directed from the backlight 2 originates and is not or hardly steered by total reflection in the light guide back and forth.

The 3 gives a schematic diagram of a lighting device 1 in a first operating mode B1 for a free viewing mode again, in which the largest possible solid angle is illuminated, wherein the lighting device 1 together with a picture display device 5 is used, and where the backlight 2 is off. 4 shows a variation to this, here the backlight 2 is turned on (the black arrows show the light coming from there). 6 Again, a schematic diagram of a further embodiment of the variant according to 4 in which a partial reflection on the surface of the backlight 2 leads to a kind of light recycling for the light, which down from the large area of the optical element 3 exit (see dashed arrows). This improves the light output. Further shows 5 a schematic diagram of the lighting device in a second operating mode B2 for a limited viewing mode in which a limited solid angle is illuminated, here also the lighting device is used together with an image display device.

• – eine flächenartig ausgedehnte Hintergrundbeleuchtung 2, die in der Betriebsart B2 für einen eingeschränkten Sichtmodus Licht in einen eingeschränkten Winkelbereich abstrahlt, wobei das von der Hintergrundbeleuchtung 2 ausgehende Licht in mindestens einer Richtung, die in einem Winkel größer als 45 Grad zur Flächennormale der Hintergrundbeleuchtung 2 gelegen ist, mit höchstens 6% der maximalen Lichtstärke abgestrahlt wird,
• – mindestens ein in Betrachtungsrichtung vor der Hintergrundbeleuchtung 2 gelegenes, plattenförmiges und transparentes optisches Element 3, und
• – Leuchtmittel 4, die seitlich an Schmalseiten des optischen Elements 3 angeordnet sind, (in den Zeichnungen stilisiert an einer Stelle, diese können aber gleichzeitig an mehreren Schmalseiten des optischen Elements 3 angeordnet sein),
• – wobei – das optische Element 3 als Lichtleiter ausgebildet ist, welcher aus einem thermoplastischen oder thermoelastischen Kunststoff besteht, – in dem besagten Lichtleiter homogen verteilte Streupartikel (welche als Lichtstreumittel wirken) vorhanden sind, – die besagten Streupartikel aus Titandioxid, Bariumsulfat, silsesquioxanen Partikeln und/oder vernetzten Polystyrol-Partikeln mit einer mittleren Partikelgröße von 150–500 nm bestehen, welche in einer Konzentration bezogen auf das Gewicht des optischen Elementes 3 von 0.01–300 Gew.-ppm eingesetzt werden, – der besagte Lichtleiter, also das optische Element 3, keine Bedruckung und keine lichtstreuenden Störstellen aufweist und für das von der Hintergrundbeleuchtung 2 ausgehende Licht zu mindestens 85% transparent ist, – so dass das aus den Leuchtmitteln 4 (wenn diese eingeschaltet sind) seitlich in das optische Element 3 einfallende Licht für einen freien Sichtbereich in der Betriebsart B1 in Richtungen, die in Winkeln zwischen 45 Grad und 75 Grad zur Flächennormale der Hintergrundbeleuchtung 2 gelegen sind, mit mindestens 12% der maximalen Lichtstärke des aus dem Lichtleiter senkrecht zur Oberfläche austretenden Lichtes abgestrahlt wird, – und so dass das aus dem Lichtleiter an mindestens einem Punkt seiner Oberfläche austretende Licht, welches von den Leuchtmitteln 4 herrührt, wenn diese eingeschaltet sind, in mindestens einem Winkel α zur Oberfläche des Lichtleiters, mit α < 80 Grad, eine höhere Lichtstärke aufweist, als das an dem besagten Punkt der Oberfläche des Lichtleiters senkrecht zur Oberfläche des Lichtleiters austretende Licht, (bevorzugt weist mindestens die Hälfte der Oberfläche des Lichtleiters derartige Punkte auf)
• – wobei in der Betriebsart B2 die Hintergrundbeleuchtung 2 ein- und die Leuchtmittel 4 ausgeschaltet sind, und wobei in der Betriebsart B1 mindestens die Leuchtmittel 4 eingeschaltet sind.

The in the drawings 3 to 6 schematic illustrated illumination device according to the invention 1 which are operated in at least two operating modes B1 for a free viewing mode and B2 for a restricted viewing mode

• - an arealwide backlight 2 which emits light in a restricted angle range in the operating mode B2 for a limited viewing mode, that of the backlight 2 outgoing light in at least one direction at an angle greater than 45 degrees to the surface normal of the backlight 2 is located at a maximum of 6% of maximum light output,
• - at least one viewing direction in front of the backlight 2 located, plate-shaped and transparent optical element 3 , and
• - Illuminants 4 , which are laterally on narrow sides of the optical element 3 are arranged (in the drawings stylized at one point, but these can simultaneously on several narrow sides of the optical element 3 be arranged),
• - where - the optical element 3 is formed as a light guide, which consists of a thermoplastic or thermoelastic plastic, - in the said light guide homogeneously distributed scattering particles (which act as light scattering agent) are present - the said scattering particles of titanium dioxide, barium sulfate, silsesquioxane particles and / or crosslinked polystyrene particles with have an average particle size of 150-500 nm, which in a concentration based on the weight of the optical element 3 0.01-300 ppm by weight are used, - said optical fiber, so the optical element 3 , no printing and no light scattering impurities and for that of the backlight 2 Outgoing light is at least 85% transparent, so that's from the bulbs 4 (when they are turned on) laterally into the optical element 3 incident light for a clear field of view in mode B1 in directions that are at angles between 45 degrees and 75 degrees to the surface normal of the backlight 2 are located, is radiated with at least 12% of the maximum light intensity of the light emerging from the optical fiber perpendicular to the surface light, and so that the light emerging from the light guide at least at one point of its surface, which of the light sources 4 comes when they are turned on, at least at an angle α to the surface of the light guide, with α <80 degrees, a higher light intensity than that at said point of the surface of the light guide perpendicular to the surface of the light guide emerging light, (preferably at least half of the surface of the light guide on such points on)
• - In the operating mode B2, the backlight 2 on and the bulbs 4 are switched off, and wherein in the operating mode B1 at least the bulbs 4 are turned on.

The said light guide, so the optical element 3 , has no printing and no light scattering defects and is for that of the backlight 2 outgoing light at least 85% transparent. Would it be a printing and / or light-scattering impurities on one or both large surfaces of the light guide, ie the optical element 3 , give, so in the mode B2 that of the backlight 2 originating and through the optical element 3 Light passing through it scattered and thus no longer be radiated only to a limited angular range.

For operating mode B1, it is absolutely necessary that the lamps 4 are turned on while the backlight 2 can be on or off. Is the backlight 2 switched off, only the light from the bulbs ensures 4 for the unrestricted lighting. Are on the other hand for the operating mode B1, both the bulbs 4 as well as the backlight 2 turned on, a greater brightness can be achieved. It is then particularly advantageous that the light emerging from the light guide at at least one point of its surface, which of the light sources 4 when these are turned on, at least at an angle α to the surface of the light guide, with α <80 degrees, a higher light intensity than the light emerging at said point of the surface of the light guide perpendicular to the surface of the light guide, as in 7 is indicated. The arrow labeled "I" stands for the respective light intensity, which is radiated horizontally to the optical element in the respective angle α. This technical implementation means that the light, which from the bulbs 4 and its strongest brightness is not approximately along the mid-perpendicular of the illumination device 1 exhibits with the light coming from the backlight 2 and its strongest brightness is approximately along the mid-perpendicular of the illumination device 1 has, very well complemented, over at least one half-angle (eg the angle spectrum of the horizontal in front of the illumination device 1 ) to achieve a more homogeneous and overall brighter illumination than if only the bulbs 4 would be turned on for the operating mode B1.

As scattering particles for the optical element 3 Titanium dioxide particles are preferably used in a concentration based on the weight of the optical element 3 from 0.1-50 ppm by weight, preferably 0.1-10 ppm by weight., And / or the titanium dioxide particles have an average particle size of 160 to 450 nm and more preferably from 170 to 400 nm.

Furthermore, the optical element ( 3 ) has a Haze value less than 7%, preferably less than 2%, measured according to ASTM D1003.

It is also advantageous if the optical element 3 at least 40 weight percent polymethyl methacrylate, preferably at least 60 weight percent polymethylmethacrylate, based on its weight.

Another useful embodiment of the lighting device 1 provides that for the operating mode B2 only from the backlight 2 originating and out of the optical element 3 At each point of its surface in the direction of viewing light exiting in angles β> 30 degrees (see also 5 with respect to the angular definition of β), measured perpendicular to the surface of the optical element 3 and in horizontal orientation to the surface of the optical element 3 , at most 5% of the light intensity having the light, which from such a point of the surface of the optical element 3 emerges perpendicular to its surface. Particularly preferably, the backlight contains 2 at least one optical layer for the collimation of light in order to achieve an angle-limited radiation characteristic of the light emitted by it. In the backlight 2 is preferably a backlight, for example, a side-light, Edgelight, direct LED backlight, edge LED backlight, OLED or other surface spotlight, on which a permanent privacy filter, as a privacy filter (eg Vikuit ^TM 3M ^TM or LCF from Shin Etsu ^TM ), which acts as a light collimator or spatial light filter after which it passes the light from the backlight 2 essentially only in a limited angular range is radiated. In addition to the collimating layer (s), 3M ^™ type "Optical Lighting Film" (OLF) Type 2301 crossed components may still be present to achieve pre-collimation while transmitting the light bundle up.

Furthermore, it is possible for the next optical component to be below the optical element 3 at least one partially reflecting surface for in the mode B1 from the optical element 3 has downwardly exiting light and thereby such downwardly radiated light at least partially back to the optical element 3 is reflected back and at least partially passes through it, as in 4 indicated by the dashed arrows. Since the optical element implemented as a light guide 3 Light emanating from both large areas, ie radiating upwards and downwards (the direction downward points in the direction of the backlight 2 ), a kind of light recycling is possible in this way. Here it may be sufficient that the said next optical component, often the optical layer of the backlight 2 for collimation (eg Privacy Filter), is not anti-reflective or has a partial mirroring, which for from below, ie from the backlight 2 , incoming light is as transparent as possible.

At the bulbs 4 is it z. For example, LEDs. Besides, it makes sense if the Light coupling from the laterally arranged bulbs 4 in the optical element 3 from at least two sides, preferably from opposite sides.

Very particularly preferred is in front of the lighting device 1 a transmissive image display device 5 For example, an LCD panel arranged as in the drawings 3 to 6 located. Thus, the two modes B1 and B2 corresponding to the image display device 5 be implemented. The first operating mode B1 for a free field of view then allows on the Bildwiedergabeqeinrichtung 5 to perceive the image from the largest possible solid angle in full resolution. Conversely, in the second operating mode B2 for a limited field of view, the image on the image display device is the same 5 also in full resolution, but only from a limited solid angle perceptible, which corresponds to a private viewing mode (so-called privacy or privacy mode). Depending on the configuration of the parameters for the illumination angles, the visible region of the image reproduction device is then also visible 5 displayed image correspondingly limited in the solid angle perceptible.

Moreover, a partial mirroring is on the back of the transmissive image display device 5 for further homogenization of the light output from the optical element 3 advantageous. This can also compensate for brightness differences analogous to the partial mirroring on the optical element 3 be configured varying or applied only partially.

Another advantage is an already collimated by design backlight (a so-called "Directional Backlight") as a backlight, ie the light source is designed so that their light is emitted only in a prescribed, limited angle range. Furthermore, it may be favorable if always the same light sources, for. B. the laterally arranged bulbs 4 , used for both modes. The light is then for switching between the two modes B1 and B2, for example, via an optoelectronic and / or optomechanical switch once in the optical element 3 and / or once in the backlight 2 coupled. As a switch comes here z. As a shutter or a mechanical switching such as a tilting mirror in question. Also, the bulbs can 4 be formed two lines, in which case only the desired or corresponding line is turned on.

Furthermore, the desired or allowed irradiation directions for the restricted view mode B2 can be independently defined and translated for the horizontal and vertical directions, respectively. For example, in the vertical direction, a larger angle might be useful than in the horizontal direction, such as when ATMs are supposed to see something of different sizes, while side-ins should be severely restricted. This is especially by the choice of light collimating layers, eg. As the privacy filter achieved.

The lighting device according to the invention 1 in which in particular a transmissive image display device 5 upstream, can be used advantageously for entering or displaying confidential data, for example PIN PIN numbers, e-mails, SMS or passwords, ATMs, payment terminals or mobile devices.

This achieves what was desired: When using the lighting device 1 with a picture display device 5 (For example, LCD screen), a secure display of information by an optionally limited viewing angle can be realized, in a second mode, a free, if possible in the viewing angle unrestricted view is possible. The lighting device 1 is inexpensive to implement with simple means. In both described operating modes B1 and B2 is the full native resolution of the screen used, ie the image display device 5 , visible, noticeable. Furthermore, a loss of light is kept as low as possible.

In contrast to the prior art, neither a strong UV light source has to be used, nor do complex angle-limited light distributions have to be converted into unrestricted light distributions - which massively reduces the brightness - nor are elaborate prism or microlens structures necessary.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 6765550 [0003]
• US 5993940 [0004]
• WO 2012/033583 [0005]
• US 2009/0067156 [0006, 0007, 0008]
• US 2012/0235891 [0009, 0009]
• JP 2007-155783 [0010]

Claims (10)

Lighting device ( 1 ), which can be operated in at least two operating modes B1 for a free viewing mode and B2 for a restricted viewing mode, comprising - an areally extended backlighting ( 2 ), which emits light in a limited angle range in the operating mode B2 for a limited viewing mode, whereby that of the backlight ( 2 ) emitted light in at least one direction, which at an angle greater than 45 degrees to the surface normal of the backlight ( 2 ) is emitted with at most 6% of the maximum light intensity, - at least one in the viewing direction in front of the backlight ( 2 ), plate-shaped and transparent optical element ( 3 ), and - illuminant ( 4 ), which laterally on narrow sides of the optical element ( 3 ), wherein - the optical element ( 3 ) is formed as a light guide, which consists of a thermoplastic or thermoelastic plastic, - are homogeneously distributed in the said light guide, - said scattering particles of titanium dioxide, barium sulfate, silsesquioxane particles and / or crosslinked polystyrene particles having a mean particle size of 150- 500 nm, which in a concentration based on the weight of the optical element ( 3 ) of 0.01-300 ppm by weight, - said optical fiber has no printing and no light-scattering impurities and for the of the backlight ( 2 ) outgoing light is at least 85% transparent, so that the light sources ( 4 ) laterally into the optical element ( 3 ) incident light for a free field of view in the operating mode B1 in directions which are at angles between 45 degrees and 75 degrees to the surface normal of the backlight ( 2 ), is radiated with at least 12% of the maximum light intensity of the light emerging from the optical fiber perpendicular to the surface of the light, and so that the light emerging from the light guide at least at one point of its surface, which of the light sources 4 comes when they are turned on, at least at an angle α to the surface of the light guide, with α <80 degrees, a higher light intensity than that at said point of the surface of the light guide perpendicular to the surface of the light guide emerging light, - wherein in the Mode B2 the backlight ( 2 ) and the bulbs ( 4 ) are switched off, and wherein in the operating mode B1 at least the lighting means ( 4 ) are turned on. Lighting device ( 1 ) according to claim 1, characterized in that the optical element ( 3 ) has a Haze value less than 7%, preferably less than 2%, measured according to ASTM D1003. Lighting device ( 1 ) according to one of claims 1 or 2, characterized in that as scattering particles titanium dioxide particles in a concentration based on the weight of the optical element ( 3 ) of 0.1-50 ppm by weight, preferably 0.1-10 ppm by weight, are used, and / or that the titanium dioxide particles have an average particle size of 160 to 450 nm and more preferably from 170 to 400 nm. Lighting device ( 1 ) according to one of claims 1 to 3, characterized in that the optical element ( 3 ) comprises at least 40% by weight of polymethylmethacrylate, preferably at least 60% by weight of polymethyl methacrylate, based on its weight. Lighting device ( 1 ) according to one of claims 1 to 4, characterized in that for the operating mode B2 exclusively from the backlight ( 2 ) and from the optical element ( 3 ) light emerging at any point of its surface at angles β> 30 degrees measured perpendicular to the surface of the optical element ( 3 ) and in horizontal orientation to the surface of the optical element ( 3 ), a maximum of 5% of the light intensity, which comprises the light, which from such a point of the surface of the optical element ( 3 ) emerges perpendicular to its surface. Lighting device ( 1 ) according to one of claims 1 to 5, characterized in that the next optical component below the optical element ( 3 ) at least one partially reflecting surface for in the mode B1 from the optical element ( 3 ) has light exiting downwardly and thereby at least partially re-irradiates such downwardly emitted light onto the optical element ( 3 ) is reflected back and at least partially passes through it. Lighting device ( 1 ) according to one of claims 1 to 6, characterized in that in front of the illumination device ( 1 ) a transmissive image display device ( 5 ), for example an LCD panel. Lighting device ( 1 ) according to claim 1 or 7, characterized in that the backlight ( 2 ) contains at least one optical layer for collimating light. Lighting device ( 1 ) according to one of claims 1 to 8, characterized in that the backlight ( 2 ) a backlight, for example a sidelight, edgelight, direct led backlight, edge LED backlight, OLED or another surface radiator, is on which at least one permanent privacy filter is applied. Lighting device ( 1 ), which can be operated in at least two operating modes B1 for a free viewing mode and B2 for a restricted viewing mode, comprising - an areally extended backlighting ( 2 ), which emits light in a limited angle range in the operating mode B2 for a limited viewing mode, whereby that of the backlight ( 2 ) outgoing light in at least one direction, which is at an angle greater than 45 + γ degrees to the surface normal of the backlight ( 2 ) is emitted with at most 6% of the maximum light intensity, the backlight ( 2 ) contains at least one layer for collimation of the light emitted by it, which has the highest light transmission at an angle of γ with 0 <γ <45 degrees to the surface normal of the backlight ( 2 ), - at least one viewing direction in front of the backlight ( 2 ), plate-shaped and transparent optical element ( 3 ), and - illuminant ( 4 ), which laterally on narrow sides of the optical element ( 3 ), wherein - the optical element ( 3 ) is formed as a light guide, which consists of a thermoplastic or thermoelastic plastic, - are homogeneously distributed in the said light guide, - said scattering particles of titanium dioxide, barium sulfate, silsesquioxane particles and / or crosslinked polystyrene particles having a mean particle size of 150- 500 nm, which in a concentration based on the weight of the optical element ( 3 ) of 0.01-300 ppm by weight, - said optical fiber has no printing and no light-scattering impurities and for the of the backlight ( 2 ) outgoing light is at least 85% transparent, so that the light sources ( 4 ) laterally into the optical element ( 3 ) incident light for a free field of view in the operating mode B1 in directions which are at angles between 45 degrees and 75 degrees to the surface normal of the backlight ( 2 ), is radiated with at least 12% of the maximum light intensity of the light emerging from the optical fiber perpendicular to the surface of the light, and so that the light emerging from the light guide at least at one point of its surface, which of the light sources 4 comes when they are turned on, at least at an angle α to the surface of the light guide, with α <80 degrees, a higher light intensity than that at said point of the surface of the light guide perpendicular to the surface of the light guide emerging light, - wherein in the Mode B2 the backlight ( 2 ) and the bulbs ( 4 ) are switched off, and wherein in the operating mode B1 at least the lighting means ( 4 ) are turned on.

Images