WO2010079678A1 - Organic electroluminescent element, display device, and lighting device - Google Patents

Abstract

Disclosed is an organic electroluminescent element having high light-emission luminance and a low driving voltage.  The organic electroluminescent element comprises a supporting substrate and at least an anode and a cathode both arranged on the supporting substrate, and additionally comprises a light-emitting layer comprising at least an organic substance and arranged between the anode and the cathode.  The light-emitting layer comprises at least a light-emitting dopant and a host compound, wherein the absolute value of the difference between the bipolar moment of the light-emitting dopant and the bipolar moment of the host compound is 2 debyes or less, and the light-emitting layer is formed by coating.

Description

Organic electroluminescence element, display device and lighting device

The present invention relates to an organic electroluminescence element, a display device, and a lighting device.

Conventionally, as a light-emitting electronic display device, there is an electroluminescence display (hereinafter referred to as ELD). Examples of constituent elements of ELD include inorganic electroluminescent elements and organic electroluminescent elements (hereinafter also referred to as organic EL elements).

Inorganic electroluminescent elements have been used as planar light sources, but an alternating high voltage is required to drive the light emitting elements. An organic EL device has a structure in which a light emitting layer containing a compound that emits light is sandwiched between a cathode and an anode, injects electrons and holes into the light emitting layer, and recombines them to generate excitons (exciton). It is an element that emits light using the emission of light (fluorescence / phosphorescence) when this exciton is deactivated, and can emit light at a voltage of several V to several tens V, and it is self-luminous. In addition, it is attracting attention from the viewpoints of space saving, portability and the like because it is a thin film type complete solid element with a wide viewing angle and high visibility.

However, in the organic EL element for practical use in the future, it is desired to develop an organic EL element that emits light with high power and efficiency with lower power consumption.

In Japanese Patent No. 3093796, a small amount of a phosphor is doped into a stilbene derivative, a distyrylarylene derivative or a tristyrylarylene derivative to achieve improvement in light emission luminance and a longer device lifetime. Further, an element having an organic light-emitting layer in which 8-hydroxyquinoline aluminum complex is used as a host compound and a small amount of phosphor is doped thereto (for example, JP-A 63-264692), 8-hydroxyquinoline aluminum complex is used as a host compound. For example, an element having an organic light emitting layer doped with a quinacridone dye (for example, JP-A-3-255190) is known.

In the technique disclosed in the above document, when the emission from the excited singlet is used, the generation ratio of the singlet exciton and the triplet exciton is 1: 3. Therefore, the generation probability of the luminescent excited species is 25%. In addition, since the light extraction efficiency is about 20%, the limit of the external extraction quantum efficiency (ηext) is set to 5%.

However, since the University of Princeton reported on organic EL devices using phosphorescence emission from excited triplets (MA Baldo et al., Nature, 395, 151-154 (1998)), Research on materials that exhibit phosphorescence has become active.

For example, M.M. A. Baldo et al. , Nature, 403, 17, 750-753 (2000), US Pat. No. 6,097,147, and the like.

When the excited triplet is used, the upper limit of the internal quantum efficiency is 100%. In principle, the luminous efficiency is four times that of the excited singlet, and there is a possibility that almost the same performance as a cold cathode tube can be obtained. Therefore, it is attracting attention as a lighting application.

For example, S. Lamansky et al. , J .; Am. Chem. Soc. , 123, 4304 (2001), etc., many compounds are being studied for synthesis centering on heavy metal complexes such as iridium complexes.

Also, the above-mentioned M.M. A. Baldo et al. , Nature, 403, 17, 750-753 (2000), studies have been made using tris (2-phenylpyridine) iridium as a dopant.

The organic EL element is an all-solid element composed of an organic material film having a thickness of only about 0.1 μm between the electrodes, and can emit light at a relatively low voltage of about 2 to 20V. Therefore, it is a technology that is expected as a next-generation flat display and illumination.

However, the configuration of the organic EL element is simple, in which an organic layer is sandwiched between a transparent electrode and a counter electrode, and the manufacturing cost is also low because the number of parts is overwhelmingly smaller than that of a liquid crystal display that is a typical flat display. Although it should be kept low, this is not always the case at present, and a large amount of water is drained into the liquid crystal display in terms of performance and cost.

In particular, in terms of cost, poor productivity is considered as a factor. Most of the organic ELs currently commercialized are manufactured by a so-called vapor deposition method in which a low molecular material is deposited to form a film. In this vapor deposition method, a low-molecular compound that can be easily purified can be used as an organic EL material (high-purity material is easy to obtain), and a laminated structure can be easily formed. Although it is excellent, on the other hand, since the deposition is performed under a high vacuum condition of 10 ⁻⁴ Pa or less, restrictions are imposed on the film forming apparatus, and in practice it can be applied only to a substrate with a small area, and more layers are laminated. The disadvantages are that the film formation takes time and the throughput is low. In particular, it becomes a problem when applied to lighting applications or large-area electronic displays, and organic EL is one of the causes that are not practically used in such applications.

On the other hand, the coating method in which the organic layer is manufactured by processes such as spin coating, ink jet, printing, and spraying can produce a thin film at normal pressure, and is suitable for producing a uniform film over a larger area.

However, for example, when the light emitting layer is prepared by coating, the light emitting dopant and the light emitting host are dissolved and applied in the same solution, and therefore, due to the difference in solubility between the light emitting dopant and the light emitting host or the difference in interaction with the solvent. However, phase separation and non-uniform distribution, which were not observed in the deposited film, occurred, and this was a major factor in performance degradation.

In addition, in order to achieve a longer lifetime, a technique that focuses on the dipole moment of a material used to control the interface between the light emitting layer and the adjacent layer (see, for example, Patent Documents 1 and 2), and device fabrication by a coating method In order to suppress the thickening of the solution, a technique that defines the dipole moment of the solvent (see, for example, Patent Document 3), a dipole that is an isolated island between the organic light emitting layer and the electron injection layer Technology that can realize a device that is stable for a long time when a control layer composed of molecules having a moment of 3 debyes or more is provided (see, for example, Patent Document 4), a host material having a large dipole moment in an organic light emitting layer, and electron attraction Although the technique (for example, refer patent document 5) that drive voltage can be reduced when including the dopant which has a sex group is known, all pay attention to the dipole moment, It differs from the present invention with a focus on the difference in the dipole moment of a light dopant and a host compound.

JP 2003-288888 A JP 2008-53557 A JP 2006-244806 A JP 2004-111173 A JP 2005-158715 A

An object of the present invention is to provide an organic electroluminescence element exhibiting high emission luminance and having a low driving voltage, and an illumination device and a display device using the element.

The above object of the present invention is achieved by the following configuration.

1. In an organic electroluminescence device having at least an anode and a cathode on a support substrate and having a light emitting layer composed of at least an organic substance between the anode and the cathode, the light emitting layer contains at least a light emitting dopant and a host compound, and the light emission An organic electroluminescence device, wherein an absolute value of a difference between a dopant and a dipole moment of the host compound is 2 Debye or less, and the light emitting layer is formed by coating.

2. 2. The organic electroluminescent device according to 1 above, wherein the dipole moment of the host compound is 4 Debye or more.

3. 3. The organic electroluminescence device as described in 1 or 2 above, wherein the host compound is a carbazole derivative or an azacarbazole derivative.

4. 4. The organic electroluminescence device according to 3 above, wherein the carbazole derivative or azacarbazole derivative has a 5-membered or 6-membered aromatic heterocyclic group having a nitrogen atom.

5. 5. The organic electroluminescent device according to 4 above, wherein the aromatic heterocyclic ring in the 5- or 6-membered aromatic heterocyclic group having a nitrogen atom is pyridine, imidazole, pyrazine, triazine, indole or indazole.

6. 6. The organic electroluminescence device according to any one of 1 to 5, wherein a dipole moment of the luminescent dopant is 4 Debye or less.

7. 7. The organic electroluminescence device according to any one of 1 to 6, wherein the light emitting dopant is a phosphorescent dopant.

8. 8. The organic electroluminescence device as described in 7 above, wherein the phosphorescent dopant is an iridium complex.

9. 9. The organic electroluminescence device as described in 8 above, wherein the iridium complex is an iridium complex represented by the following general formula (A).

(In the formula, Ar ₁ represents an aromatic hydrocarbon ring or an aromatic heterocyclic ring, and Ar ₂ represents an aromatic heterocyclic ring.)
10. 10. The organic electroluminescence device as described in 8 or 9 above, wherein the band gap between the ground state and the triplet excited state of the iridium complex is 2.7 eV or less.

11. 11. The organic electroluminescence device as described in any one of 1 to 10 above, wherein a dipole moment of a solvent for applying the light emitting layer is 1 Debye or more.

12. 12. The organic electroluminescence device as described in any one of 1 to 11 above, which emits white light.

13. 13. A display device comprising the organic electroluminescence element as described in 1 to 12 above.

14. 13. An illumination device comprising the organic electroluminescence element as described in 1 to 12 above.

According to the present invention, it was possible to provide an organic electroluminescence element exhibiting high emission luminance and having a low driving voltage, and an illumination device and a display device using the element.

It is the schematic diagram which showed an example of the display apparatus comprised from an organic EL element. 4 is a schematic diagram of a display unit A. FIG. It is a schematic diagram of a pixel. It is a schematic diagram of a passive matrix type full-color display device. It is the schematic of an illuminating device. It is sectional drawing of an illuminating device.

Hereinafter, the present invention will be described in detail.

In the organic electroluminescence device of the present invention, by adopting the configuration defined in any one of claims 1 to 12, it was possible to obtain an organic electroluminescence device having high emission luminance and low driving voltage. .

In the organic electroluminescence device of the present invention, the light emitting layer contains at least a light emitting dopant and a host compound, the absolute value of the difference between the dipole moments is 2 Debye or less, and the light emitting layer is formed by coating. It is characterized by.

In the present invention, the dipole moment is calculated using a general-purpose computer simulation tool. Most molecules were optimized for the Hamiltonian AM1 or PM3 using a MOPAC97 engine on a Chembridge 3 Chembrand soft. When the central metal is a heavy metal such as Ir, the calculation was performed by the ab initio molecular orbital method. Specifically, the calculation was performed using Gaussian 98W manufactured by Gaussian. For the calculation of a complex containing a heavy metal such as Ir, a LANL2DZ basis in which the third and lower periods of the periodic table are represented by an effective shell potential was used.

Hereinafter, the constituent layers of the organic EL element of the present invention will be described.

<< Constituent layers of organic EL elements >>
Although the preferable specific example of the layer structure of the organic EL element of this invention is shown below, this invention is not limited to these.

(I) Anode / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode (ii) Anode / electron blocking layer / light emitting layer / hole blocking layer / electron transport layer / cathode (iii) Anode / Hole transport layer / electron blocking layer / light emitting layer / hole blocking layer / electron transport layer / cathode (iv) Anode / hole transport layer / electron blocking layer / light emitting layer / hole blocking layer / electron transport layer / cathode ( v) Anode / hole transport layer / electron blocking layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode (vi) Anode / anode buffer layer / hole transport layer / electron blocking layer / light emitting layer / Hole blocking layer / electron transport layer / cathode buffer layer / cathode (vii) Anode / anode buffer layer / hole transport layer / electron blocking layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode .

《Electron transport layer》
The electron transport layer is made of a material having a function of transporting electrons, and in a broad sense, an electron injection layer and a hole blocking layer are also included in the electron transport layer. The electron transport layer can be provided as a single layer or a plurality of layers.

Conventionally, in the case of a single electron transport layer and a plurality of layers, an electron transport material (also serving as a hole blocking material) used for an electron transport layer adjacent to the light emitting layer on the cathode side is injected from the cathode. As long as it has a function of transferring electrons to the light-emitting layer, any material selected from conventionally known compounds can be selected and used. For example, nitro-substituted fluorene derivatives, diphenylquinone derivatives Thiopyrandioxide derivatives, carbodiimides, fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives and the like.

Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, and a quinoxaline derivative having a quinoxaline ring known as an electron withdrawing group can also be used as an electron transport material. Furthermore, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used.

Also, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (Alq), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8-quinolinol) aluminum Tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), and the like, and the central metals of these metal complexes are In, Mg, Metal complexes replaced with Cu, Ca, Sn, Ga or Pb can also be used as the electron transport material.

In addition, metal-free or metal phthalocyanine, or those having terminal ends substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron transporting material. In addition, the distyrylpyrazine derivative exemplified as the material for the light emitting layer can also be used as an electron transport material, and an inorganic semiconductor such as n-type-Si, n-type-SiC, etc. as in the case of the hole injection layer and the hole transport layer. Can also be used as an electron transporting material.

The electron transport layer can be formed by thinning the electron transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. The thickness of the electron transport layer is not particularly limited, but is usually about 5 nm to 5 μm, preferably 5 to 200 nm. The electron transport layer may have a single layer structure composed of one or more of the above materials.

It is also possible to use an electron transport layer having a high n property doped with impurities. Examples thereof include JP-A-4-297076, JP-A-10-270172, JP-A-2000-196140, 2001-102175, J.A. Appl. Phys. 95, 5773 (2004), and the like.

In the present invention, it is preferable to use an electron transport layer having such a high n property because an element with lower power consumption can be produced.

<Light emitting layer>
The light emitting layer according to the present invention is a layer that emits light by recombination of electrons and holes injected from the electrode, the electron transport layer, or the hole transport layer, and the light emitting portion is in the layer of the light emitting layer. May be the interface between the light emitting layer and the adjacent layer.

The total thickness of the light emitting layer is not particularly limited, but from the viewpoint of preventing the application of a high voltage unnecessary for the film uniformity and light emission, and improving the stability of the emitted color with respect to the driving current. It is preferable to adjust to a range of 5 μm, more preferably to a range of 2 to 200 nm, and particularly preferably in a range of 10 to 20 nm.

The light emitting layer according to the present invention is produced by, for example, a coating method such as a spin coating method, a casting method, a die coating method, or an ink jet method. If the dipole moment of the coating solvent is too low, the light emitting dopant and the host compound are produced. In order not to disperse or dissolve uniformly, it is preferably 1 Debye or more. When using multiple types together, it is preferable if the dipole moment as an average value is obtained and the dipole moment of the coating solvent is 1 Debye or more.

The light emitting layer of the organic EL device of the present invention contains at least one of a host compound and a light emitting dopant (phosphorescent dopant, fluorescent dopant, etc.).

(Host compound)
The host compound used in the present invention will be described.

In the present invention, the absolute value of the difference between the dipole moments of the luminescent dopant and the host compound is preferably 2 Debye or less, and the dipole moment of the host compound is preferably 4 Debye or more.

In the present invention, the host compound is preferably a carbazole derivative or an azacarbazole derivative, and these further preferably have a 5-membered or 6-membered aromatic heterocyclic group having a nitrogen atom. Examples of the aromatic heterocyclic ring in the 5- or 6-membered aromatic heterocyclic group having a nitrogen atom include pyridine, imidazole, pyrazine, triazine, indole and indazole.

Here, in the present invention, the host compound is a compound having a phosphorescence quantum yield of phosphorescence emission of less than 0.1 at room temperature (25 ° C.). The phosphorescence quantum yield is preferably less than 0.01. Moreover, it is preferable that the mass ratio in the layer is 20% or more among the compounds contained in a light emitting layer.

As the host compound, known host compounds may be used alone or in combination of two or more. By using a plurality of types of host compounds, it is possible to adjust the movement of charges, and the organic EL element can be made highly efficient. Moreover, it becomes possible to mix different light emission by using multiple types of light emission dopants mentioned later, and, thereby, arbitrary light emission colors can be obtained. In the case of using a plurality of types together, the dipole moment as an average value is obtained, and if the absolute value of the difference from the dipole moment of the luminescent dopant is 2 debyes or less, it is within the present invention.

As known host compounds that may be used in combination with the present invention, there are compounds having a hole transporting ability and an electron transporting ability, preventing the emission of longer wavelengths, and having a high Tg (glass transition temperature). preferable.

Specific examples of the host compound according to the present invention are shown below, but the present invention is not limited thereto.

In addition, Table 1 shows dipole moments (calculated values) of typical host compounds according to the present invention.

Specific examples of known host compounds that may be used alone or in combination include compounds described in the following documents.

JP-A-2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002-105445, 2002-343568, 2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453, 2003-3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861, 2002-280183, 2002-299060, 2002 -302516, 2002-305083, 2002-305084, 2002-308837, and the like.

(Luminescent dopant)
The light emitting dopant according to the present invention will be described.

In the present invention, when the dipole moment of the luminescent dopant becomes high, it becomes a trap for charge transport, and the charge transport mobility tends to decrease and the drive voltage tends to increase. Therefore, the dipole moment of the luminescent dopant is not particularly limited, but is preferably 4 Debye or less.

As the light-emitting dopant according to the present invention, a fluorescent dopant or a phosphorescent dopant can be used. From the viewpoint of obtaining an organic EL element with higher luminous efficiency, it is used for the light-emitting layer and the light-emitting unit of the organic EL element of the present invention. As the light-emitting dopant, it is preferable to contain the above-mentioned host compound according to the present invention and simultaneously contain a phosphorescent dopant.

<Phosphorescent dopant>
The phosphorescent dopant according to the present invention will be described.

The phosphorescent dopant according to the present invention is a compound in which light emission from an excited triplet is observed. Specifically, the phosphorescent dopant is a compound that emits phosphorescence at room temperature (25 ° C.) and has a phosphorescence quantum yield of 25 ° C. However, a preferable phosphorescence quantum yield is 0.1 or more.

The phosphorescent quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of the Fourth Edition Experimental Chemistry Course 7. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence dopant according to the present invention achieves the phosphorescence quantum yield (0.01 or more) in any solvent. That's fine.

There are two types of light emission of phosphorescent dopants in principle. One is the recombination of carriers on the host compound to which carriers are transported to generate an excited state of the host compound, and this energy is transferred to the phosphorescent dopant. The energy transfer type that obtains light emission from the phosphorescent dopant, and the other is that the phosphorescent dopant becomes a carrier trap, carrier recombination occurs on the phosphorescent dopant, and light emission from the phosphorescent dopant is obtained. Although it is a trap type, in any case, the excited state energy of the phosphorescent dopant is required to be lower than the excited state energy of the host compound.

The phosphorescent dopant can be appropriately selected from known materials used for the light emitting layer of the organic EL element.

The phosphorescent dopant according to the present invention is preferably a complex compound containing a group 8-10 metal in the periodic table of elements, more preferably an iridium complex, an osmium complex, or a platinum complex (platinum complex compound), Rare earth complexes, most preferably iridium complexes.

In the present invention, the band gap between the ground state and the triplet excited state of the iridium complex is preferably 2.7 eV or less.

Furthermore, in the present invention, it is particularly preferable that the iridium complex is an iridium complex represented by the general formula (A).

In the general formula (A), the aromatic hydrocarbon ring represented by Ar ₁ includes a benzene ring, biphenyl ring, naphthalene ring, azulene ring, anthracene ring, phenanthrene ring, pyrene ring, chrysene ring, naphthacene ring, triphenylene. Ring, o-terphenyl ring, m-terphenyl ring, p-terphenyl ring, acenaphthene ring, coronene ring, fluorene ring, fluoranthrene ring, naphthacene ring, pentacene ring, perylene ring, pentaphen ring, picene ring, pyrene Ring, pyranthrene ring, anthraanthrene ring and the like, and examples of the aromatic heterocycle represented by Ar ₁ include a furan ring, a thiophene ring, an oxazole ring, a pyrrole ring, a pyridine ring, a pyridazine ring, a pyrimidine ring, and a pyrazine ring. , Triazine ring, benzimidazole ring, oxadiazole ring, triazol Ring, imidazole ring, pyrazole ring, thiazole ring, indole ring, indazole ring, benzimidazole ring, benzothiazole ring, benzoxazole ring, quinoxaline ring, quinazoline ring, cinnoline ring, quinoline ring, isoquinoline ring, phthalazine ring, naphthyridine ring, And a carbazole ring, a carboline ring, a diazacarbazole ring (which represents a ring in which one of the carbon atoms constituting the carboline ring is further substituted with a nitrogen atom).

The aromatic heterocycle represented by Ar ₂ has the same meaning as the aromatic heterocycle represented by Ar ₁ described above.

Furthermore, these rings may have a substituent.

Hereinafter, specific examples of the phosphorescent dopant according to the present invention and dipole moments (calculated values) thereof will be shown.

As the luminescent dopant, in addition to the above phosphorescent dopant, a known luminescent dopant may be used alone, or a plurality of kinds may be used in combination. When a plurality of types are used in combination, the dipole moment as an average value is obtained, and if the absolute value of the difference from the dipole moment of the host compound is 2 debyes or less, it is within the present invention.

Specific examples of phosphorescent dopants that can be used alone or in combination with the phosphorescent dopant according to the present invention include the following.

<Fluorescent dopant>
Fluorescent dopants include coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes, perylene dyes, stilbene dyes , Polythiophene dyes, or rare earth complex phosphors.

Next, the charge transport layer used as the constituent layer of the organic EL device of the present invention, that is, the injection layer, the blocking layer, etc. will be described.

<< Injection layer: electron injection layer, hole injection layer >>
The injection layer is provided as necessary, and there are an electron injection layer and a hole injection layer, and as described above, it exists between the anode and the light emitting layer or the hole transport layer and between the cathode and the light emitting layer or the electron transport layer. May be.

An injection layer is a layer provided between an electrode and an organic layer in order to reduce drive voltage and improve light emission luminance. “Organic EL element and its forefront of industrialization (issued by NTT Corporation on November 30, 1998) 2), Chapter 2, “Electrode Materials” (pages 123 to 166) in detail, and includes a hole injection layer (anode buffer layer) and an electron injection layer (cathode buffer layer).

The details of the anode buffer layer (hole injection layer) are described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069 and the like. As a specific example, copper phthalocyanine is used. Examples thereof include a phthalocyanine buffer layer represented by an oxide, an oxide buffer layer represented by vanadium oxide, an amorphous carbon buffer layer, and a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene.

The details of the cathode buffer layer (electron injection layer) are described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specifically, strontium, aluminum, etc. Metal buffer layer typified by lithium, alkali metal compound buffer layer typified by lithium fluoride, alkaline earth metal compound buffer layer typified by magnesium fluoride, oxide buffer layer typified by aluminum oxide, etc. . The buffer layer (injection layer) is preferably a very thin film, and the film thickness is preferably in the range of 0.1 nm to 5 μm, although it depends on the material.

<Blocking layer: hole blocking layer, electron blocking layer>
The blocking layer is provided as necessary in addition to the basic constituent layer of the organic compound thin film as described above. For example, it is described in JP-A Nos. 11-204258 and 11-204359, and “Organic EL elements and the forefront of industrialization (published by NTT Corporation on November 30, 1998)” on page 237. There is a hole blocking (hole blocking) layer.

The hole blocking layer has a function of an electron transport layer in a broad sense, and is made of a hole blocking material that has a function of transporting electrons and has a remarkably small ability to transport holes. The probability of recombination of electrons and holes can be improved by blocking.

Moreover, the structure of the electron transport layer described later can be used as the hole blocking layer according to the present invention, if necessary.

The hole blocking layer of the organic EL device of the present invention is preferably provided adjacent to the light emitting layer. The hole blocking layer contains the carbazole derivative, carboline derivative, or diazacarbazole derivative (showed by replacing one of the carbon atoms constituting the carboline ring of the carboline derivative with a nitrogen atom) as the host compound. It is preferable to do.

In the present invention, when a plurality of light emitting layers having different light emission colors are provided, the light emitting layer having the shortest wavelength of light emission is preferably closest to the anode among all the light emitting layers. In this case, it is preferable to additionally provide a hole blocking layer between the shortest wave layer and the light emitting layer next to the anode next to the anode. Furthermore, it is preferable that 50% by mass or more of the compound contained in the hole blocking layer provided at the position has an ionization potential of 0.3 eV or more larger than the host compound of the shortest wave emitting layer.

The ionization potential is defined by the energy required to emit electrons at the HOMO (highest occupied molecular orbital) level of the compound to the vacuum level, and can be obtained by the following method, for example.

(1) Using Gaussian 98 (Gaussian 98, Revision A.11.4, MJ Frisch, et al, Gaussian, Inc., Pittsburgh PA, 2002.), a molecular orbital calculation software manufactured by Gaussian, USA The ionization potential can be obtained as a value obtained by rounding off the second decimal place of the value (eV unit converted value) calculated by performing structural optimization using B3LYP / 6-31G *. The reason why this calculated value is effective is that there is a high correlation between the calculated value obtained by this method and the experimental value.

(2) The ionization potential can also be obtained by a method of directly measuring by photoelectron spectroscopy. For example, a low energy electron spectrometer “Model AC-1” manufactured by Riken Keiki Co., Ltd. or a method known as ultraviolet photoelectron spectroscopy can be suitably used.

On the other hand, the electron blocking layer has a function of a hole transport layer in a broad sense, and is made of a material that has a function of transporting holes and has an extremely small ability to transport electrons, and transports electrons while transporting holes. By blocking, the recombination probability of electrons and holes can be improved.

Moreover, the structure of the hole transport layer described later can be used as an electron blocking layer as necessary. The film thickness of the hole blocking layer and the electron transporting layer according to the present invention is preferably 3 to 100 nm, more preferably 5 to 30 nm.

《Hole transport layer》
The hole transport layer is made of a hole transport material having a function of transporting holes, and in a broad sense, a hole injection layer and an electron blocking layer are also included in the hole transport layer. The hole transport layer can be provided as a single layer or a plurality of layers.

The hole transport material has either hole injection or transport or electron barrier properties, and may be either organic or inorganic. For example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives and pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, Examples thereof include stilbene derivatives, silazane derivatives, aniline copolymers, and conductive polymer oligomers, particularly thiophene oligomers.

The above-mentioned materials can be used as the hole transport material, but it is preferable to use a porphyrin compound, an aromatic tertiary amine compound and a styrylamine compound, particularly an aromatic tertiary amine compound.

Representative examples of aromatic tertiary amine compounds and styrylamine compounds include N, N, N ′, N′-tetraphenyl-4,4′-diaminophenyl; N, N′-diphenyl-N, N′— Bis (3-methylphenyl)-[1,1′-biphenyl] -4,4′-diamine (TPD); 2,2-bis (4-di-p-tolylaminophenyl) propane; 1,1-bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ′, N′-tetra-p-tolyl-4,4′-diaminobiphenyl; 1,1-bis (4-di-p-tolyl) Aminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, N ' Di (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N ', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) quadriphenyl N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino -(2-diphenylvinyl) benzene; 3-methoxy-4'-N, N-diphenylaminostilbenzene; N-phenylcarbazole, and also two described in US Pat. No. 5,061,569 Having a condensed aromatic ring of, for example, 4,4'-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (NPD), JP-A-4-308 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which three triphenylamine units described in Japanese Patent No. 88 are linked in a starburst type ( MTDATA) and the like.

Further, a polymer material in which these materials are introduced into a polymer chain or these materials are used as a polymer main chain can also be used. In addition, inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole injection material and the hole transport material. JP-A-11-251067, J. Pat. Huang et. al. A so-called p-type hole transport material described in a book (Applied Physics Letters 80 (2002), p. 139) can also be used. In the present invention, these materials are preferably used because a light-emitting element with higher efficiency can be obtained.

The hole transport layer can be formed by thinning the hole transport material by a known method such as a vacuum deposition method, a spin coating method, a casting method, a printing method including an ink jet method, or an LB method. it can. The thickness of the hole transport layer is not particularly limited, but is usually about 5 nm to 5 μm, preferably 5 to 200 nm. The hole transport layer may have a single layer structure composed of one or more of the above materials.

It is also possible to use a hole transport layer having a high p property doped with impurities. Examples thereof include JP-A-4-297076, JP-A-2000-196140, JP-A-2001-102175, J. Pat. Appl. Phys. 95, 5773 (2004), and the like. In the present invention, it is preferable to use a hole transport layer having such a high p property because a device with lower power consumption can be produced.

"anode"
As the anode in the organic EL element, an electrode material made of a metal, an alloy, an electrically conductive compound, or a mixture thereof having a high work function (4 eV or more) is preferably used. Specific examples of such electrode materials include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO.

Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) capable of forming a transparent conductive film may be used. For the anode, these electrode materials may be formed into a thin film by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by a photolithography method, or when pattern accuracy is not required (about 100 μm or more) A pattern may be formed through a mask having a desired shape at the time of vapor deposition or sputtering of the electrode material.

Alternatively, when a material that can be applied such as an organic conductive compound is used, a wet film forming method such as a printing method or a coating method can be used. When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%, and the sheet resistance as the anode is preferably several hundred Ω / □ or less. Further, although the film thickness depends on the material, it is usually selected in the range of 10 to 1000 nm, preferably 10 to 200 nm.

"cathode"
On the other hand, as the cathode, a material having a low work function (4 eV or less) metal (referred to as an electron injecting metal), an alloy, an electrically conductive compound, and a mixture thereof as an electrode material is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like.

Among these, from the point of durability against electron injection and oxidation, etc., a mixture of an electron injecting metal and a second metal which is a stable metal having a larger work function than this, for example, a magnesium / silver mixture, Magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred.

The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The sheet resistance as the cathode is preferably several hundred Ω / □ or less, and the film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm. In order to transmit the emitted light, if either the anode or the cathode of the organic EL element is transparent or translucent, the light emission luminance is improved, which is convenient.

In addition, a transparent or semi-transparent cathode can be produced by producing the conductive transparent material mentioned in the description of the anode on the cathode after producing the metal with a film thickness of 1 to 20 nm. By applying this, an element in which both the anode and the cathode are transmissive can be manufactured.

《Support substrate》
As a support substrate (hereinafter also referred to as a substrate, substrate, substrate, support, etc.) that can be used in the organic EL device of the present invention, there is no particular limitation on the type of glass, plastic, etc., and it is transparent. May be opaque.

When extracting light from the support substrate side, the support substrate is preferably transparent. Examples of the transparent support substrate preferably used include glass, quartz, and a transparent resin film. A particularly preferable support substrate is a resin film capable of giving flexibility to the organic EL element.

Examples of the resin film include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, cellulose acetate propionate (CAP), Cellulose esters such as cellulose acetate phthalate (TAC) and cellulose nitrate or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate, norbornene resin, polymethylpentene, polyether ketone, polyimide , Polyethersulfone (PES), polyphenylene sulfide, polysulfone , Polyetherimide, polyetherketoneimide, polyamide, fluororesin, nylon, polymethylmethacrylate, acrylic or polyarylates, cyclone resins such as Arton (trade name, manufactured by JSR) or Appel (trade name, manufactured by Mitsui Chemicals) Etc.

On the surface of the resin film, an inorganic film, an organic film or a hybrid film of both may be formed. The water vapor permeability (25 ± 0.5 ° C.) measured by a method according to JIS K 7129-1992. And a relative humidity (90 ± 2)% RH) of 0.01 g / (m ² · 24 h) or less is preferable, and oxygen permeability measured by a method according to JIS K 7126-1987. A high barrier film having a degree of 10 ⁻³ ml / (m ² · 24 h · atm) or less and a water vapor permeability of 10 ⁻⁵ g / (m ² · 24 h) or less is preferable.

The material for forming the barrier film may be any material that has a function of suppressing the intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like can be used. Further, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and organic material layers. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.

The method for forming the barrier film is not particularly limited. For example, the vacuum deposition method, the sputtering method, the reactive sputtering method, the molecular beam epitaxy method, the cluster ion beam method, the ion plating method, the plasma polymerization method, the atmospheric pressure plasma weight A combination method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, and the like can be used. However, an atmospheric pressure plasma polymerization method described in JP-A-2004-68143 is particularly preferable.

Examples of the opaque support substrate include metal plates such as aluminum and stainless steel, films, opaque resin substrates, ceramic substrates, and the like.

The external extraction efficiency at room temperature of light emission of the organic EL element of the present invention is preferably 1% or more, more preferably 5% or more. Here, the external extraction quantum efficiency (%) = the number of photons emitted to the outside of the organic EL element / the number of electrons sent to the organic EL element × 100.

Also, a hue improvement filter such as a color filter may be used in combination, or a color conversion filter that converts the emission color from the organic EL element into multiple colors using a phosphor may be used in combination. In the case of using a color conversion filter, the λmax of light emission of the organic EL element is preferably 480 nm or less.

<Sealing>
As a sealing means used for this invention, the method of adhere | attaching a sealing member, an electrode, and a support substrate with an adhesive agent can be mentioned, for example. As a sealing member, it should just be arrange | positioned so that the display area | region of an organic EL element may be covered, and concave plate shape or flat plate shape may be sufficient. Further, transparency and electrical insulation are not particularly limited.

Specific examples include a glass plate, a polymer plate / film, and a metal plate / film. Examples of the glass plate include soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer plate include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, and polysulfone. Examples of the metal plate include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium, and tantalum.

In the present invention, a polymer film and a metal film can be preferably used because the element can be thinned. Furthermore, the polymer film has an oxygen permeability measured by a method according to JIS K 7126-1987 of 1 × 10 ⁻³ ml / (m ² · 24 h · atm) or less, and a method according to JIS K 7129-1992. It is preferable that the water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) measured in (1) is 1 × 10 ⁻³ g / (m ² · 24 h) or less.

For processing the sealing member into a concave shape, sandblasting, chemical etching, or the like is used. Specific examples of the adhesive include photocuring and thermosetting adhesives having reactive vinyl groups of acrylic acid oligomers and methacrylic acid oligomers, and moisture curing adhesives such as 2-cyanoacrylates. be able to. Moreover, heat | fever and chemical curing types (two-component mixing), such as an epoxy type, can be mentioned. Moreover, hot-melt type polyamide, polyester, and polyolefin can be mentioned. Moreover, a cationic curing type ultraviolet curing epoxy resin adhesive can be mentioned.

In addition, since an organic EL element may deteriorate by heat processing, what can be adhesively cured from room temperature to 80 ° C. is preferable. A desiccant may be dispersed in the adhesive.

Application of the adhesive to the sealing portion may be performed using a commercially available dispenser or may be printed like screen printing.

In addition, it is also preferable that the electrode and the organic layer are coated on the outside of the electrode facing the support substrate with the organic layer interposed therebetween, and an inorganic or organic layer is formed in contact with the support substrate to form a sealing film. . In this case, the material for forming the film may be any material that has a function of suppressing intrusion of elements that cause deterioration of elements such as moisture and oxygen. For example, silicon oxide, silicon dioxide, silicon nitride, or the like may be used. it can.

In order to further improve the brittleness of the film, it is preferable to have a laminated structure of these inorganic layers and layers made of organic materials. The method for forming these films is not particularly limited. For example, vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma A polymerization method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

In the gap between the sealing member and the display area of the organic EL element, an inert gas such as nitrogen or argon, or an inert liquid such as fluorinated hydrocarbon or silicon oil can be injected in the gas phase and liquid phase. preferable. A vacuum is also possible. Moreover, a hygroscopic compound can also be enclosed inside. Examples of the hygroscopic compound include metal oxides (for example, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide) and sulfates (for example, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate). Etc.), metal halides (eg calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide etc.), perchloric acids (eg perchloric acid) Barium, magnesium perchlorate, and the like), and anhydrous salts are preferably used in sulfates, metal halides, and perchloric acids.

《Protective film, protective plate》
In order to increase the mechanical strength of the element, a protective film or a protective plate may be provided on the outer side of the sealing film on the side facing the support substrate with the organic layer interposed therebetween or on the sealing film. In particular, when the sealing is performed by the sealing film, the mechanical strength is not necessarily high, and thus it is preferable to provide such a protective film and a protective plate. As a material that can be used for this, the same glass plate, polymer plate / film, metal plate / film, and the like used for the sealing can be used, but the polymer film is light and thin. Is preferably used.

《Light extraction》
The organic EL element emits light inside a layer having a refractive index higher than that of air (refractive index is about 1.7 to 2.1) and can extract only about 15% to 20% of the light generated in the light emitting layer. It is generally said. This is because the light incident on the interface (interface between the transparent substrate and air) at an angle θ greater than the critical angle causes total reflection and cannot be taken out of the element, or between the transparent electrode or the light emitting layer and the transparent substrate. This is because the light is totally reflected between the light and the light is guided through the transparent electrode or the light emitting layer, and as a result, the light escapes in the direction of the element side surface.

As a method of improving the light extraction efficiency, for example, a method of forming irregularities on the surface of the transparent substrate and preventing total reflection at the transparent substrate and the air interface (US Pat. No. 4,774,435), A method for improving efficiency by providing light condensing property to a substrate (Japanese Patent Laid-Open No. 63-314795), a method of forming a reflective surface on a side surface of an organic EL element (Japanese Patent Laid-Open No. 1-220394), a substrate A method of forming an antireflection film by introducing a flat layer having an intermediate refractive index between the substrate and the light emitter (Japanese Patent Laid-Open No. 62-172691), and lowering the refractive index between the substrate and the light emitter than the substrate. A method of introducing a flat layer having a structure (Japanese Patent Laid-Open No. 2001-202827), a method of forming a diffraction grating between any one of the substrate, the transparent electrode layer and the light emitting layer (including between the substrate and the outside world) No. 283751) That.

In the present invention, these methods can be used in combination with the organic EL device of the present invention. However, a method of introducing a flat layer having a lower refractive index than the substrate between the substrate and the light emitter, or a substrate, transparent A method of forming a diffraction grating between any layers of the electrode layer and the light emitting layer (including between the substrate and the outside) can be suitably used.

In the present invention, by combining these means, it is possible to obtain an organic EL device having higher luminance or durability.

When a medium having a low refractive index is formed between the transparent electrode and the transparent substrate with a thickness longer than the wavelength of light, the efficiency of taking out the light from the transparent electrode to the outside increases as the refractive index of the medium decreases.

Examples of the low refractive index layer include aerogel, porous silica, magnesium fluoride, and a fluorine-based polymer. Since the refractive index of the transparent substrate is generally about 1.5 to 1.7, the low refractive index layer preferably has a refractive index of about 1.5 or less, more preferably 1.35 or less. preferable.

Also, the thickness of the low refractive index medium is preferably at least twice the wavelength in the medium. This is because the effect of the low refractive index layer is diminished when the thickness of the low refractive index medium is about the wavelength of light and the electromagnetic wave that has exuded by evanescent enters the substrate.

The method of introducing a diffraction grating into an interface or any medium that causes total reflection is characterized by a high effect of improving light extraction efficiency. This method uses the property that the diffraction grating can change the direction of light to a specific direction different from refraction by so-called Bragg diffraction such as first-order diffraction and second-order diffraction. Introducing a diffraction grating into any layer or medium (inside a transparent substrate or transparent electrode) diffracts light that cannot be emitted outside due to total internal reflection between layers. It is intended to be taken out.

It is desirable that the diffraction grating to be introduced has a two-dimensional periodic refractive index. This is because light emitted from the light-emitting layer is randomly generated in all directions, so in a general one-dimensional diffraction grating having a periodic refractive index distribution only in a certain direction, only light traveling in a specific direction is diffracted. Therefore, the light extraction efficiency does not increase so much.

However, by making the refractive index distribution a two-dimensional distribution, the light traveling in all directions is diffracted, and the light extraction efficiency is increased.

As described above, the position where the diffraction grating is introduced may be in any of the layers or in the medium (in the transparent substrate or the transparent electrode), but is preferably in the vicinity of the organic light emitting layer where light is generated.

At this time, the period of the diffraction grating is preferably about 1/2 to 3 times the wavelength of light in the medium.

The arrangement of the diffraction grating is preferably two-dimensionally repeated such as a square lattice, a triangular lattice, or a honeycomb lattice.

<Condenser sheet>
The organic EL device of the present invention is processed to provide, for example, a microlens array-like structure on the light extraction side of the substrate, or in combination with a so-called condensing sheet, so that the organic EL device is in front of a specific direction, for example, the device light emitting surface. By condensing in the direction, the luminance in a specific direction can be increased.

As an example of a microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are arranged two-dimensionally on the light extraction side of the substrate. One side is preferably 10 to 100 μm. If it becomes smaller than this, the effect of diffraction will generate | occur | produce and color, and if too large, thickness will become thick and is not preferable.

As the condensing sheet, it is possible to use, for example, a sheet that has been put to practical use in an LED backlight of a liquid crystal display device. As such a sheet, for example, Sumitomo 3M brightness enhancement film (BEF) can be used.

As the shape of the prism sheet, for example, the base material may be formed by forming a △ -shaped stripe having a vertex angle of 90 degrees and a pitch of 50 μm, or the vertex angle is rounded and the pitch is changed randomly. Other shapes may be used.

Further, in order to control the light emission angle from the light emitting element, a light diffusion plate / film may be used in combination with the light collecting sheet. For example, a diffusion film (light-up) manufactured by Kimoto Co., Ltd. can be used.

<< Method for producing organic EL element >>
As an example of the method for producing the organic EL device of the present invention, a method for producing an organic EL device comprising an anode / hole injection layer / hole transport layer / light emitting layer / hole blocking layer / electron transport layer / cathode buffer layer / cathode. Will be described.

First, a thin film made of a desired electrode material, for example, a material for an anode is formed on a suitable substrate by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably 10 to 200 nm to produce an anode. . Next, a thin film containing an organic compound such as a hole injection layer, a hole transport layer, a light emitting layer, a hole blocking layer, or an electron transport layer, which is an element material, is formed thereon.

As a method for thinning a thin film containing an organic compound, there are a spin coat method, a cast method, an ink jet method, a vapor deposition method, a printing method, etc., but a homogeneous film is easily obtained and pinholes are not easily generated. From this point, the vacuum deposition method or the spin coating method is particularly preferable. Further, different film forming methods may be applied for each layer, but the light emitting layer of the present invention is formed by coating, and preferably a spin coating method.

When a vapor deposition method is employed for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally a boat heating temperature of 50 to 450 ° C., a degree of vacuum of 10 ⁻⁶ to 10 ⁻² Pa, and a vapor deposition rate of 0.01 to It is desirable to select appropriately within a range of 50 nm / second, a substrate temperature of −50 to 300 ° C., and a film thickness of 0.1 to 5 μm.

After these layers are formed, a thin film made of a cathode material is formed thereon by a method such as vapor deposition or sputtering so as to have a film thickness of 1 μm or less, preferably in the range of 50 to 200 nm, and a cathode is provided. Thus, a desired organic EL element can be obtained.

It is also possible to reverse the production order to produce a cathode, a cathode buffer layer, an electron transport layer, a hole blocking layer, a light emitting layer, a hole transport layer, a hole injection layer, and an anode in this order.

When a DC voltage is applied to the multicolor display device thus obtained, light emission can be observed by applying a voltage of about 2 V to 40 V with the positive polarity of the anode and the negative polarity of the cathode. An alternating voltage may be applied. The alternating current waveform to be applied may be arbitrary.

In the production of the organic EL device of the present invention, the light emitting layer is produced by coating, but other layers may be subjected to different film forming methods. When producing by evacuation, it is necessary to consider that the operation is performed in a dry inert gas atmosphere.

<Application>
The organic EL element of the present invention can be used as a display device, a display, and various light emission sources. For example, lighting devices (home lighting, interior lighting), clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources of optical storage media, light sources of electrophotographic copying machines, light sources of optical communication processors, light Although the light source of a sensor etc. are mentioned, It is not limited to this, Especially, it can use effectively for the use as a backlight of a liquid crystal display device, and a light source for illumination.

In the organic EL device of the present invention, patterning may be performed by a metal mask, an ink jet printing method, or the like during film formation, if necessary. In the case of patterning, only the electrode may be patterned, the electrode and the light emitting layer may be patterned, or the entire layer of the element may be patterned, and a conventionally known method may be used in the fabrication of the element. it can.

The light emission color of the organic EL device of the present invention and the compound according to the present invention is shown in FIG. 4.16 on page 108 of “New Color Science Handbook” (edited by the Japan Color Society, University of Tokyo Press, 1985). It is determined by the color when the result measured with a total CS-1000 (manufactured by Konica Minolta Sensing) is applied to the CIE chromaticity coordinates. The white color of the organic EL white element according to the present invention means that the color temperature at 1000 cd / m ² is 7000 K to 2500 K (deviation from the black body locus Δuv = It is in the range of ± 0.02).

<Display device>
The display device of the present invention will be described.

The display device of the present invention comprises the organic EL element of the present invention.

The configuration of the organic EL element included in the display device is selected from the above-described configuration examples of the organic EL element as necessary.

Moreover, the manufacturing method of the organic EL element is as shown in the embodiment of the manufacturing of the organic EL element of the present invention.

When a DC voltage is applied to the obtained display device, light emission can be observed by applying a voltage of about 2 V to 40 V with the positive polarity of the anode and the negative polarity of the cathode. Further, even when a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Further, when an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the-state. The alternating current waveform to be applied may be arbitrary.

The display device can be used as a display device, a display, and various light emission sources.

Display devices and displays include televisions, personal computers, mobile devices, AV devices, teletext displays, information displays in automobiles, and the like. In particular, it may be used as a display device for reproducing still images and moving images, and the driving method when used as a display device for reproducing moving images may be either a simple matrix (passive matrix) method or an active matrix method.

Light emitting sources include home lighting, interior lighting, clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, light sources for optical sensors, etc. However, the present invention is not limited to these.

Hereinafter, an example of a display device having the organic EL element of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view showing an example of a display device composed of organic EL elements. It is a schematic diagram of a display such as a mobile phone that displays image information by light emission of an organic EL element.

The display 1 includes a display unit A having a plurality of pixels, a control unit B that performs image scanning of the display unit A based on image information, and the like.

The control unit B is electrically connected to the display unit A, and sends a scanning signal and an image data signal to each of a plurality of pixels based on image information from the outside, and the pixels for each scanning line respond to the image data signal by the scanning signal. The image information is sequentially emitted to scan the image and display the image information on the display unit A.

FIG. 2 is a schematic diagram of the display unit A. The display unit A includes a wiring unit including a plurality of scanning lines 5 and data lines 6 and a plurality of pixels 3 on the substrate. The main members of the display unit A will be described below.

In the figure, the light emitted from the pixel 3 is extracted in the direction of the white arrow (downward).

The scanning line 5 and the plurality of data lines 6 in the wiring portion are each made of a conductive material, and the scanning lines 5 and the data lines 6 are orthogonal to each other in a grid pattern and are connected to the pixels 3 at the orthogonal positions (details are illustrated). Not) When a scanning signal is applied from the scanning line 5, the pixel 3 receives an image data signal from the data line 6 and emits light according to the received image data.

A full color display can be achieved by appropriately arranging pixels in the red region, the green region, and the blue region on the same substrate.

Next, the light emission process of the pixel will be described.

FIG. 3 is a schematic diagram of a pixel. The pixel includes an organic EL element 10, a switching transistor 11, a driving transistor 12, a capacitor 13, and the like. A full color display can be performed by using red, green, and blue light emitting organic EL elements as the organic EL elements 10 in a plurality of pixels, and juxtaposing them on the same substrate.

3, an image data signal is applied from the control unit B to the drain of the switching transistor 11 via the data line 6. When a scanning signal is applied from the control unit B to the gate of the switching transistor 11 via the scanning line 5, the driving of the switching transistor 11 is turned on, and the image data signal applied to the drain is supplied to the capacitor 13 and the driving transistor 12. Is transmitted to the gate.

By transmitting the image data signal, the capacitor 13 is charged according to the potential of the image data signal, and the drive transistor 12 is turned on. The drive transistor 12 has a drain connected to the power supply line 7 and a source connected to the electrode of the organic EL element 10, and the power supply line 7 connects to the organic EL element 10 according to the potential of the image data signal applied to the gate. Current is supplied.

When the scanning signal moves to the next scanning line 5 by the sequential scanning of the control unit B, the driving of the switching transistor 11 is turned off. However, even if the driving of the switching transistor 11 is turned off, the capacitor 13 maintains the potential of the charged image data signal, so that the driving of the driving transistor 12 is kept on and the next scanning signal is applied. Until then, the light emission of the organic EL element 10 continues. When the scanning signal is next applied by sequential scanning, the driving transistor 12 is driven according to the potential of the next image data signal synchronized with the scanning signal, and the organic EL element 10 emits light.

That is, the light emission of the organic EL element 10 is performed by providing the switching transistor 11 and the drive transistor 12 which are active elements with respect to the organic EL element 10 of each of the plurality of pixels. It is carried out. Such a light emitting method is called an active matrix method.

Here, the light emission of the organic EL element 10 may be light emission of a plurality of gradations by a multi-value image data signal having a plurality of gradation potentials, or on / off of a predetermined light emission amount by a binary image data signal. But you can. The potential of the capacitor 13 may be held continuously until the next scanning signal is applied, or may be discharged immediately before the next scanning signal is applied.

In the present invention, not only the active matrix method described above, but also a passive matrix light emission drive in which an organic EL element emits light according to a data signal only when a scanning signal is scanned.

FIG. 4 is a schematic view of a passive matrix display device. In FIG. 4, a plurality of scanning lines 5 and a plurality of image data lines 6 are provided in a lattice shape so as to face each other with the pixel 3 interposed therebetween. When the scanning signal of the scanning line 5 is applied by sequential scanning, the pixels 3 connected to the applied scanning line 5 emit light according to the image data signal.

In the passive matrix method, the pixel 3 has no active element, and the manufacturing cost can be reduced.

《Lighting device》
The lighting device of the present invention will be described. The illuminating device of this invention has the said organic EL element.

The organic EL element of the present invention may be used as an organic EL element having a resonator structure. The purpose of use of the organic EL element having such a resonator structure is as follows. The light source of a machine, the light source of an optical communication processing machine, the light source of a photosensor, etc. are mentioned, However, It is not limited to these. Moreover, you may use for the said use by making a laser oscillation.

Further, the organic EL element of the present invention may be used as a kind of lamp for illumination or exposure light source, a projection device for projecting an image, or a display for directly viewing a still image or a moving image. It may be used as a device (display).

The drive method when used as a display device for moving image reproduction may be either a simple matrix (passive matrix) method or an active matrix method. Alternatively, a full-color display device can be manufactured by using two or more organic EL elements of the present invention having different emission colors.

Moreover, the organic EL material of the present invention can be applied to an organic EL element that emits substantially white light as a lighting device. A plurality of emission colors are simultaneously emitted by a plurality of emission dopants to obtain white emission by color mixing. The combination of a plurality of emission colors may include three emission maximum wavelengths of the three primary colors of blue, green, and blue, or two using the relationship of complementary colors such as blue and yellow, blue green and orange, etc. The thing containing the light emission maximum wavelength may be used.

In addition, the combination of light emitting dopants for obtaining a plurality of emission colors is a combination of a plurality of phosphorescent or fluorescent materials, a light emitting dopant that emits fluorescence or phosphorescence, and excitation of light from the light emitting dopant. Any combination with a dye material that emits light as light may be used, but in the white organic EL device according to the present invention, it is only necessary to mix and mix a plurality of light emitting dopants. It is only necessary to provide a mask only when forming a light emitting layer, a hole transport layer, an electron transport layer, etc., and simply arrange them separately by coating with the mask. Since other layers are common, patterning of the mask or the like is not necessary. In addition, for example, an electrode film can be formed by a vapor deposition method, a cast method, a spin coating method, an ink jet method, a printing method, etc., and productivity is also improved.

According to this method, unlike the white organic EL device in which light emitting elements of a plurality of colors are arranged in parallel in an array, the elements themselves are luminescent white.

The light emitting dopant used in the light emitting layer is not particularly limited. For example, in the case of a backlight in a liquid crystal display element, the metal complex according to the present invention or the metal complex according to the present invention so as to conform to the wavelength range corresponding to the CF (color filter) characteristics, Any one of known light-emitting dopants may be selected and combined to whiten.

<< One Embodiment of Lighting Device of the Present Invention >>
One aspect of the lighting device of the present invention that includes the organic EL element of the present invention will be described.

The non-light emitting surface of the organic EL element of the present invention is covered with a glass case, a 300 μm thick glass substrate is used as a sealing substrate, and an epoxy photo-curing adhesive (Lux Track LC0629B manufactured by Toagosei Co., Ltd.) is used as a sealing material. ), And this is placed on the cathode and adhered to the transparent support substrate, irradiated with UV light from the glass substrate side, cured and sealed, and an illumination device as shown in FIGS. Can be formed.

FIG. 5 shows a schematic diagram of the lighting device, and the organic EL element 101 of the present invention is covered with a glass cover 102 (in addition, the sealing operation with the glass cover is performed without bringing the organic EL element 101 into contact with the atmosphere. (This was performed in a glove box under a nitrogen atmosphere (in an atmosphere of high-purity nitrogen gas having a purity of 99.999% or more)).

FIG. 6 shows a cross-sectional view of the lighting device. In FIG. 6, 105 denotes a cathode, 106 denotes an organic EL layer, and 107 denotes a glass substrate with a transparent electrode. The glass cover 102 is filled with nitrogen gas 108 and a water catching agent 109 is provided.

Hereinafter, although an example explains the present invention, the present invention is not limited to these. The structures of the compounds used in the following examples are shown below.

Example 1
<< Production of Organic EL Element 1 >>
After patterning on a substrate (made of NH Techno Glass: NA-45) having a 150 nm ITO film on glass as an anode, the transparent support substrate provided with this ITO transparent electrode was ultrasonically cleaned with iso-propyl alcohol, Drying was performed with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes.

This transparent support substrate was fixed to a substrate holder of a commercially available vacuum deposition apparatus, while α-NPD, BAlq, and Alq ₃ were placed in _three tantalum resistance heating boats, respectively, and attached to the vacuum deposition apparatus (first vacuum chamber). .

Furthermore, lithium fluoride was put into a resistance heating boat made of tantalum and aluminum was put into a resistance heating boat made of tungsten, respectively, and attached to the second vacuum tank of the vacuum evaporation apparatus.

First, the first vacuum chamber is depressurized to 4 × 10 ⁻⁴ Pa, and then heated by energizing the heating boat containing α-NPD, and the transparent support substrate is deposited at a deposition rate of 0.1 to 0.2 nm / sec. The film was deposited to a thickness of 20 nm, and a hole injection / transport layer was provided.

Subsequently, a solution in which 5 mg of BD-15 (band gap 2.51 eV) was dissolved in 1 L of a mixed solvent of methanol and acetonitrile (methanol / acetonitrile = 85/15) was prepared, and 50 mg of H1 was dissolved in 10 ml of this solution. Then, a coating solution was prepared. Since the dipole moment of methanol is 1.7 and the dipole moment of acetonitrile is 3.92, the dipole moment of the mixed solvent (methanol / acetonitrile = 85/15) is pseudo from the mixing ratio of the solvent. 1.7 × 0.85 + 3.92 × 0.15 = 2.03. With this coating solution, a light emitting layer was provided by spin coating on the above layer under conditions of 1500 rpm and 30 seconds.

Next, the heating boat containing BAlq was energized and heated to provide a 10 nm thick hole blocking layer at a deposition rate of 0.1 to 0.2 nm / second. Further, the heating boat containing Alq ₃ was heated by energization to provide an electron transport layer having a film thickness of 20 nm at a deposition rate of 0.1 to 0.2 nm / second.

Next, the element formed up to the electron transport layer is transferred to the second vacuum chamber while being vacuumed, and then remotely controlled from outside the device so that a stainless steel rectangular perforated mask is placed on the electron transport layer. Installed.

After depressurizing the second vacuum tank to 2 × 10 ⁻⁴ Pa, a current was passed through a boat containing lithium fluoride to provide a cathode buffer layer having a thickness of 0.5 nm at a deposition rate of 0.01 to 0.02 nm / second, Next, a boat containing aluminum was energized, a cathode having a film thickness of 150 nm was attached at a deposition rate of 1 to 2 nm / second, and an organic EL element 1 was produced.

<< Production of organic EL elements 2 to 25 >>
Organic EL elements 2 to 25 were prepared in the same manner as in the production of organic EL element 1, except that BD-15 and H1 of the light emitting layer were changed to the combinations described in the column of evaluation results in Table 2.

<< Evaluation of organic EL elements >>
When evaluating the obtained organic EL elements 1 to 25, the non-light-emitting surface of each organic EL element after production was covered with a glass case, and a glass substrate having a thickness of 300 μm was used as a sealing substrate, and a sealing material around it. As an epoxy-based photo-curing adhesive (Lux Track LC0629B manufactured by Toagosei Co., Ltd.), it is placed on the cathode and brought into close contact with the transparent support substrate, and UV light is irradiated from the glass substrate side to cure. Then, the lighting device as shown in FIGS. 5 and 6 was formed and evaluated.

FIG. 5 is a schematic view of the lighting device, and the organic EL element 101 is covered with a glass cover 102 (in addition, the sealing operation with the glass cover is performed in a nitrogen atmosphere without bringing the organic EL element 101 into contact with the atmosphere. (In a high purity nitrogen gas atmosphere with a purity of 99.999% or more).

FIG. 6 shows a cross-sectional view of the lighting device. In FIG. 6, 105 denotes a cathode, 106 denotes an organic EL layer, and 107 denotes a glass substrate with a transparent electrode. The glass cover 102 is filled with nitrogen gas 108 and a water catching agent 109 is provided.

(External quantum efficiency)
By lighting the organic EL element under a constant current condition of room temperature (about 23 to 25 ° C.) and 2.5 mA / cm ² , and measuring the emission luminance (L) [cd / m ² ] immediately after the start of lighting, External extraction quantum efficiency (ηext) was calculated.

Here, CS-1000 (manufactured by Konica Minolta Sensing) was used for measurement of light emission luminance.

External quantum efficiency was expressed as a relative value with the organic EL element 1 as 100.

(Drive voltage)
Each voltage was measured when the organic EL element was driven at room temperature (about 23 ° C. to 25 ° C.) under a constant current condition of ^2.5 mA / cm ² , and the measurement results are as follows. Comparative example) is taken as 100, and each is shown as a relative value.

Voltage = (drive voltage of each element / drive voltage of the organic EL element 1) × 100
A smaller value indicates a lower drive voltage for comparison.

From the above, the organic EL elements 3 to 6, 10 to 14, 17 to 21 and 23 to 25 of the present invention emit higher light than the comparative organic EL elements 1, 2, 7, 8, 9, 15, 16 and 22. It is clear that a reduction in efficiency and drive voltage can be achieved. The band gaps of the light-emitting dopants used in the examples are BD-16 (2.66 eV), BD-17 (2.70 eV), BD-36 (2.70 eV), and BD-37 (2.70 eV), respectively. ).

Example 2
<Production of full-color display device>
(Production of blue light emitting element)
The organic EL element 5 of Example 1 was used as a blue light emitting element.

(Production of green light emitting element)
A green light emitting device was produced in the same manner as in the organic EL device 5 of Example 1 except that BD-36 was changed to BD-15, and this was used as the green light emitting device.

(Production of red light emitting element)
A red light emitting device was produced in the same manner as in the organic EL device 5 of Example 1 except that BD-36 was changed to Ir-8, and this was used as a red light emitting device.

The red, green, and blue light emitting organic EL elements produced above were juxtaposed on the same substrate to produce an active matrix type full color display device having a configuration as shown in FIG. In FIG. 2, only the schematic diagram of the display part A of the produced display device is shown.

That is, a plurality of pixels 3 (light emission color is a red region pixel, a green region pixel, a blue region pixel, etc.) juxtaposed with a wiring portion including a plurality of scanning lines 5 and data lines 6 on the same substrate. The scanning lines 5 and the plurality of data lines 6 in the wiring portion are each made of a conductive material, and the scanning lines 5 and the data lines 6 are orthogonal to each other in a lattice shape and are connected to the pixels 3 at the orthogonal positions (for details, see FIG. Not shown).

The plurality of pixels 3 are driven by an active matrix system provided with an organic EL element corresponding to each emission color, a switching transistor as an active element, and a driving transistor, and a scanning signal is applied from a scanning line 5. The image data signal is received from the data line 6 and light is emitted according to the received image data. In this way, a full color display device was produced by appropriately juxtaposing red, green, and blue pixels.

It was found that when this full-color display device is driven, high brightness, high durability, and a clear full-color moving image display can be obtained.

Example 3
<< Preparation of white light emitting element and white lighting device >>
The electrode of the transparent electrode substrate of Example 1 was patterned to 20 mm × 20 mm, and α-NPD was formed as a hole injection / transport layer with a thickness of 25 nm thereon as in Example 1, and BD-36, BD-15 and Ir-8 were each weighed in an amount of 5 mg and mixed to prepare a solution dissolved in 1 L of a mixed solvent of methanol and acetonitrile (methanol / acetonitrile = 85/15). 50 ml of H8 was dissolved in 10 ml of this solution. It melt | dissolved and the coating liquid was prepared. Using this coating solution, a film was formed by spin coating on the above layer under conditions of 1500 rpm and 30 seconds to provide a light emitting layer.

Next, BAlq was deposited to a thickness of 10 nm to provide a hole blocking layer. Furthermore, H42 was deposited at 40 nm to provide an electron transport layer.

Next, as in Example 1, a square perforated mask having the same shape as the transparent electrode made of stainless steel was placed on the electron injection layer, and lithium fluoride 0.5 nm was used as the cathode buffer layer and aluminum 150 nm was used as the cathode. Evaporated film was formed.

This device was equipped with a sealing can having the same method and the same structure as in Example 1, and a flat lamp as shown in FIGS. 5 and 6 was produced. When this flat lamp was energized, almost white light was obtained, and it was found that it could be used as a lighting device.

DESCRIPTION OF SYMBOLS 1 Display 3 Pixel 5 Scan line 6 Data line 7 Power supply line 10 Organic EL element 11 Switching transistor 12 Drive transistor 13 Capacitor A Display part B Control part 102 Glass cover 105 Cathode 106 Organic EL layer 107 Glass substrate with a transparent electrode 108 Nitrogen gas 109 Water catcher

Claims (14)

1. In an organic electroluminescence device having at least an anode and a cathode on a support substrate and having a light emitting layer composed of at least an organic substance between the anode and the cathode, the light emitting layer contains at least a light emitting dopant and a host compound, and the light emission An organic electroluminescence device, wherein an absolute value of a difference between a dopant and a dipole moment of the host compound is 2 Debye or less, and the light emitting layer is formed by coating.
2. 2. The organic electroluminescence device according to claim 1, wherein the dipole moment of the host compound is 4 Debye or more.
3. 3. The organic electroluminescence device according to claim 1, wherein the host compound is a carbazole derivative or an azacarbazole derivative.
4. 4. The organic electroluminescence device according to claim 3, wherein the carbazole derivative or azacarbazole derivative has a 5-membered or 6-membered aromatic heterocyclic group having a nitrogen atom.
5. The organic electroluminescent device according to claim 4, wherein the aromatic heterocyclic ring in the 5-membered or 6-membered aromatic heterocyclic group having a nitrogen atom is pyridine, imidazole, pyrazine, triazine, indole or indazole. .
6. 6. The organic electroluminescence device according to claim 1, wherein a dipole moment of the luminescent dopant is 4 Debye or less.
7. The organic electroluminescence device according to any one of claims 1 to 6, wherein the light-emitting dopant is a phosphorescent dopant.
8. The organic electroluminescence device according to claim 7, wherein the phosphorescent dopant is an iridium complex.
9. The organic luminescence device according to claim 8, wherein the iridium complex is an iridium complex represented by the following general formula (A).
   

   

   (In the formula, Ar ₁ represents an aromatic hydrocarbon ring or an aromatic heterocyclic ring, and Ar ₂ represents an aromatic heterocyclic ring.)
10. 10. The organic electroluminescence device according to claim 8, wherein a band gap between the ground state and the triplet excited state of the iridium complex is 2.7 eV or less.
11. The organic electroluminescent device according to any one of claims 1 to 10, wherein a dipole moment of a solvent for applying the light emitting layer is 1 Debye or more.
12. The organic electroluminescence device according to any one of claims 1 to 11, which emits white light.
13. A display device comprising the organic electroluminescence element according to any one of claims 1 to 12.
14. An illumination device comprising the organic electroluminescence element according to any one of claims 1 to 12.

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