JP2008219033A - Organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a cathode which functions as a transparent and effective electron injecting electrode, in an organic EL element. <P>SOLUTION: In an organic EL element which is formed by laminating an anode 20, a positive hole transport layer 40, a light emitting layer 50, an electron transport layer 60, and a cathode 70 one after another, the cathode 70 is a transparent film which is formed by laminating a first electron injecting layer 71 made of lithium oxides, a buffer layer 72 made of porphyrin compounds, a second electron injecting layer 73 made of lithium oxides, and a transparent conductive film layer 74 made of ITO, IZO or ZnO, one after another from the electron transport layer 60 side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic EL (electroluminescence) element having a transparent cathode excellent in electron injection efficiency, and is particularly suitable for application to a transparent organic EL element and a top emission type organic EL element.

  Since the organic EL element is self-luminous, it has excellent visibility and can be driven at a low voltage of several volts to several tens of volts, so that the weight including the driving circuit can be reduced. Therefore, the organic EL element is expected to be used as a thin film display, illumination, and backlight.

  The organic EL element is also characterized by abundant color variations. Furthermore, a combination of a plurality of light emission colors enables various light emission by color mixing.

  In general, such an organic EL element is formed by sequentially laminating an anode as a lower electrode, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode as an upper electrode on a substrate. Electrons are injected from the cathode into the light emitting layer, respectively, so that the light emitting layer emits light. In this general configuration, light of the light emitting layer is extracted from the lower electrode side, that is, the substrate side.

  Here, the driving method of the organic EL element is roughly divided into a passive method (simple matrix method) and an active method.

  In the passive method, it is necessary to emit each row line with a luminance obtained by multiplying the required luminance of the panel by the number of row lines (scanning lines). For this reason, as the panel size increases, the luminance of light emitted from each row line increases, which is not suitable for a large panel.

  On the other hand, in the active method, TFT (Thin Film Transistor) technology is applied, and each pixel always emits light with the necessary panel brightness, which is advantageous for a large panel.

  However, in this active method, since the TFT is disposed on the substrate portion, the aperture ratio is limited when light is extracted from the substrate direction. Therefore, as a light extraction method, a top emission method has been developed in which light is extracted from the direction opposite to the substrate that is not limited by the aperture ratio, that is, from the upper electrode direction.

  When this top emission method is adopted, it is possible to form a device in which the entire panel is transparent by making the upper electrode transparent. With the top emission structure, an improvement in aperture ratio, which is a problem in active driving, is expected, and a device with excellent luminance reduction characteristics can be formed.

  Specifically speaking, in the active drive, a pixel driving TFT (thin film transistor) is provided below the lower electrode for each pixel in the active drive. When light is extracted from the lower electrode side, In the area occupied by the TFT in the pixel, light is not transmitted, and the aperture ratio is reduced by that area.

  However, when light is extracted from the upper electrode side, light can be extracted regardless of the TFT region, and the problem of a decrease in aperture ratio is avoided.

  As described above, in the top emission method, the upper electrode cathode needs to be transparent. However, since an opaque metal layer such as MgAg or Al is generally used for the cathode, a transparent cathode is conventionally used. Development is underway.

  For example, as such a transparent cathode, an organic EL element having a two-layer cathode structure in which a MgAg layer is thinned and a thick ITO film is formed thereon has been proposed (see Non-Patent Document 1). ).

  Further, as such a transparent cathode, a thin film layer of copper phthalocyanine (CuPc) was used instead of the MgAg thin film layer in the cathode described in Non-Patent Document 1, and an ITO film was formed thereon by sputtering. A two-layer cathode has been proposed (see Non-Patent Document 1 and Non-Patent Document 2).

As such a transparent cathode, for example, an electron injector thin film made of Li or the like, a metal thin film layer made of Al or the like, and a transparent layer (for example, MgO) having a refractive index of 1.2 or more are used. An organic EL element having a cathode structure has been proposed (see Patent Document 1).
JP 2001-52878 A G. Gu et al., APPLIED PHYSICS LETTERS, (USA), VOLUME 68, p. 2606 (1996) Parthasarathy et al., APPLIED PHYSICS LETTERS, (USA), VOLUME 72, p. 2138 (1998) Hung et al., APPLIED PHYSICS LETTERS, (USA), VOLUME 74, p. 3209 (1999)

  However, in the organic EL element having a cathode described in Non-Patent Document 1, an electrode is short-circuited, that is, an anode as a lower electrode and a cathode as an upper electrode due to damage of an underlying organic layer due to the formation of an ITO film. A short circuit occurred between.

  As a countermeasure, in order to suppress the damage of the underlying organic layer ITO film, it is conceivable to reduce the sputtering power to, for example, 5 W at the time of forming the ITO film, but in that case, the sputtering speed becomes extremely slow. (For example, about 0.3 nm / min), it was not practical.

  Further, in the organic EL device having the cathode described in Non-Patent Document 2 and Non-Patent Document 3, the CuPc thin film layer is a buffer layer that obviously reduces the short-circuit problem caused by the sputtering process of the ITO film thereon. Acts as This is presumably because CuPc is relatively thick compared to the MgAg thin film layer in the cathode described in Non-Patent Document 1 and can be made relatively thick.

  However, since this CuPc thin film layer has a large electron injection barrier at the interface with the electron transport layer made of Alq3 or the like, recombination of electrons and holes occurs in the non-luminous CuPc thin film layer, and current efficiency is improved. A substantial decrease occurs.

  Therefore, in order to reduce the electron injection barrier at the interface and improve the current efficiency, it is necessary to introduce an electron injection layer made of Li or the like at the interface between the electron transport layer and the CuPc thin film layer. It was.

  However, according to an experimental study conducted by the present inventor, the organic EL device having such a cathode structure did not have sufficient current efficiency when compared with an organic EL device using a normal metal cathode. .

  That is, in the cathodes described in Non-Patent Document 2 and Non-Patent Document 3, the cathode can be configured by introducing an electron injection layer made of Li or the like at the interface between the electron transport layer and the CuPc thin film layer. Does not function sufficiently as an electron injection electrode.

  In addition, in the organic EL element having a cathode described in Patent Document 1, all the cathode films can be formed by thermal evaporation by using the above-described cathode structure. And less damage to the underlying organic layer.

However, in this case, since a metal thin film layer having a high reflectance is used, even when the reflection is suppressed by a transparent layer having a refractive index of 1.2 or more, a transmittance of only about 60% can be obtained.
Therefore, current efficiency is reduced as compared with a normal organic EL element. That is, in this case, the permeability of the cathode is insufficient.

  The present invention has been made in view of the above problems, and in an organic EL device in which an anode, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode are sequentially laminated, a highly transmissive and effective electron injection. The object is to realize a cathode that works as an electrode.

  In order to achieve the above object, the present inventor has conducted intensive studies and found that a transparent cathode structure using two electron injection layers has excellent current efficiency and is effective.

  That is, in the invention according to claim 1, an organic EL element comprising an anode (20), a hole transport layer (40), a light emitting layer (50), an electron transport layer (60) and a cathode (70) laminated in order. The cathode (70) includes a first electron injection layer (71), a buffer layer (72), a second electron injection layer (73), and a transparent conductive film layer (74) from the electron transport layer (60) side. It is characterized by being a transparent film formed by sequentially laminating.

  The present invention has been found experimentally. According to this, the cathode (70) having the above-described configuration can realize high transmittance of 90% or more even when the top emission method is adopted. .

  In addition, the buffer layer (72) can absorb energy when the transparent conductive film layer (74) is formed by sputtering or the like, and can reduce damage to the underlying organic layer. , That is, the short circuit between the anode (20) and the cathode (70) can be prevented.

  Further, a first electron injection layer (71) and a second electron are interposed between the electron transport layer (60) and the buffer layer (72) and between the buffer layer (72) and the conductive film layer (74), respectively. Since the injection layer (73) is interposed, the current efficiency can be significantly improved as compared with the conventional organic EL element.

  The first electron injection layer (71) diffuses into the electron transport layer (60) and the buffer layer (72) during film formation, so that the electron energy between the electron transport layer (60) and the buffer layer (72) is obtained. It is thought to reduce the barrier.

  Further, the second electron injection layer (73) diffuses into the buffer layer (72) at the time of film formation, and is formed on the conductive film layer (74) to form an electric double layer with the conductive film layer (74). The work function is reduced closer to the second electron injection layer (73). Therefore, the electron injection efficiency from the conductive film layer (74) can be increased.

  Thus, according to the present invention, it is considered that the current efficiency can be improved.

  Therefore, according to the present invention, in the organic EL element, it is possible to realize a cathode (70) that functions as a highly transmissive and effective electron injection electrode.

  The organic EL device of the present invention having such an excellent cathode (70) can be suitably used as a top emission type organic EL device that extracts light from the light emitting layer (50) from the cathode (70) side. it can.

  The invention according to claim 2 is characterized in that in the organic EL element according to claim 1, the transparent conductive film layer (74) is made of ITO, IZO or ZnO.

  According to this, general ITO (indium-tin oxide), IZO (indium-zinc oxide), or ZnO (zinc oxide) that can also be used as an anode can be used as the transparent conductive film layer (74). . Therefore, the same material as the anode (20) can be used for the cathode (70).

  The invention according to claim 3 is the organic EL element according to claim 1 or 2, wherein the buffer layer (72) is made of a porphyrin compound.

  The invention according to claim 4 is the organic EL device according to claim 3, wherein the porphyrin compound is copper phthalocyanine.

  Thus, as the buffer layer (72), a porphyrin compound usually used as a hole injection layer can be used. Among these, in particular, when copper phthalocyanine (hereinafter abbreviated as “CuPc”) is used, it is stable against the impact of sputtering and is optimal for the buffer layer.

  According to a fifth aspect of the present invention, in the organic EL device according to the first to fourth aspects, at least one of the first electron injection layer (71) and the second electron injection layer (73) is lithium oxide. It is characterized by being a layer.

  As described above, as one or both of the first electron injection layer (71) and the second electron injection layer (73), an inexpensive lithium oxide layer used in a normal organic EL element is used. it can.

  The invention according to claim 1 is characterized in that the glass transition temperature of the three layers of the hole transport layer (40), the light emitting layer (50) and the electron transport layer (60) is 120 ° C. or higher. . Accordingly, it is preferable for improving durability at high temperatures.

  By the way, when providing a positive hole injection layer (30) between an anode (20) and a positive hole transport layer (40) like invention of Claim 10, what consists of CuPc is preferable. This is because CuPc has a high intramolecular polarization and therefore has high adhesion to the anode (20).

  In order to improve the stability at high temperatures, it is important to improve the adhesion at the interface with the anode (20). Therefore, it is preferable to provide a porphyrin-based compound layer having a small shape change as the hole injection layer (30) in contact with the anode (20).

  The present inventor paid attention to the change in the crystalline state of the CuPc film when CuPc, which is a porphyrin-based compound, is employed as the hole injection layer (30) in contact with the anode (20).

  As a result, the present inventors have found that the crystalline state of this CuPc film is greatly different before and after being left in a high temperature environment. The results of a specific investigation on the change in the crystalline state of this CuPc film are shown.

  In order to check the change in the crystalline state efficiently, the standing environment temperature was increased to 120 ° C. to accelerate, and the standing time was evaluated as 2 hours. Hereinafter, the leaving under this condition is referred to as accelerated high temperature leaving.

  An anode made of ITO (indium-tin oxide) was formed on a glass substrate, surface treatment was performed on the anode surface with a plasma of a mixture of argon and oxygen, and CuPc was formed on the anode. FIG. 2 shows the result of analyzing the crystal state of the CuPc film in this case by X-ray diffraction before and after the accelerated high temperature exposure.

  As shown in FIG. 2, the diffraction peak at 2θ = 6.68 ° is derived from the crystal structure of CuPc. In FIG. 2, the peak indicated by the solid line in this peak is the peak before the accelerated high temperature exposure, that is, the initial peak, and the peak indicated by the broken line is the peak after the accelerated high temperature exposure, that is, the peak after standing at 120 ° C. for 2 hours It is.

  The larger the integrated value of the peak value, that is, the higher the peak value, the higher the crystallinity of the CuPc film. In FIG. 2, the peak value (integrated value) changes to 1.5 times that at 120 ° C. for 2 hours after accelerating high temperature exposure before the acceleration high temperature exposure.

  From this, the present inventors have formed a light emitting device after a hole transport layer, a light emitting layer, an electron transport layer, a cathode, etc. are formed on a CuPc film which is a crystalline hole injection layer. Later, it was considered that such a change in the crystal state of the CuPc film was a cause of a decrease in adhesion of the CuPc film.

  That is, it was considered that the adhesion of the CuPc film, particularly the interface with the anode, can be improved by forming the film so that the crystallinity of the CuPc film is as high as possible.

  And as a result of intensive studies, as in the invention according to claim 10, when a hole injection layer (30) made of CuPc is provided between the anode (20) and the hole transport layer (40), If the amount of change in the diffraction peak due to heating within the operating temperature of the organic EL element is within ± 25% of the diffraction peak before heating in the value of the diffraction peak that appears by the X-ray diffraction method of CuPc I found it good.

  Thus, if the change of the crystal state of the CuPc film as the hole injection layer (30) in a high temperature environment is reduced, the adhesion of the CuPc film can be improved. As a result, it is advantageous for improving durability at high temperatures. Further, the unevenness of the CuPc film caused by the temperature change can be reduced as much as possible, and the occurrence of short circuit and leakage can be suppressed.

  In addition, the code | symbol in the bracket | parenthesis of each said means is an example which shows a corresponding relationship with the specific means as described in embodiment mentioned later.

  The organic EL element in the present embodiment includes an anode, a hole transport layer, a light emitting layer, an electron transport layer, and a cathode, and a hole injection layer is provided between the anode and the hole transport layer as necessary. It may be provided.

  FIG. 1 is a diagram showing a schematic cross-sectional configuration of an organic EL element S1 according to an embodiment of the present invention. The organic EL element S <b> 1 of this example has a hole injection layer 30 provided between the anode 20 and the hole transport layer 40.

  In FIG. 1, the substrate 10 is usually glass such as soda glass, barium silicate glass, aluminosilicate glass, plastic such as polyester, polycarbonate, polysulfone, polymethylmethacrylate, polypropylene, polyethylene, ceramic such as quartz and ceramics. The general-purpose substrate material to be used is formed into a plate shape, a sheet shape or a film shape, and these are appropriately laminated and used as necessary.

  Desirable substrate materials are transparent glass and plastic, and opaque ceramics such as silicon are used in combination with transparent electrodes. Adjust the chromaticity of the light emission. When necessary, chromaticity adjusting means such as a filter film, a chromaticity conversion film, and a dielectric reflection film is provided at an appropriate position on the substrate 10.

  The anode 20 is electrically low in resistivity and has one or more of a metal or a conductive compound having a high light transmittance over the entire visible region, for example, vacuum deposition, sputtering, chemical vapor deposition (CVD), atomic It is made to adhere to one side of substrate 10 by methods, such as layer epitaxy (ALE), application, and immersion.

  Here, the anode 20 has a thickness of 10 to 1000 nm, preferably 50 to 500 nm, so that the resistivity of the anode 20 is 1 kΩ / □ or less, preferably 5 to 50Ω / □. It is formed by forming a film.

  Examples of the conductive material for the anode 20 include metals such as gold, platinum, silver, copper, cobalt, nickel, palladium, vanadium, tungsten, and aluminum, zinc oxide, tin oxide, indium oxide, and tin oxide and indium oxide. Examples thereof include metal oxides such as mixed systems (that is, indium-tin oxide, hereinafter abbreviated as “ITO”), and conductive oligomers and conductive polymers having aniline, thiophene, pyrrole, etc. as repeating units. .

  Among these, ITO is characterized in that a low resistivity can be easily obtained and a fine pattern can be easily formed by etching using an acid or the like.

  The hole injection layer 30 is usually formed by depositing a hole injecting material to a thickness of 1 to 100 nm in close contact with the anode 20 by the same method as in the anode 20.

As the hole injecting material, so makes it easier to transport and hole injection from the anode 20, low ionization potential, and, for example, in the electric field of 10 ⁴ ~10 ⁶ V / cm, at least, 10 ^-6 Those exhibiting a hole mobility of cm ² / V · sec are desirable.

  As individual hole injecting substances, for example, porphyrin derivatives, phthalocyanine derivatives, particularly copper phthalocyanine, which are widely used in organic EL devices, are most preferable.

  The hole transport layer 40 is usually formed by depositing a hole transport material to a thickness of 1 to 100 nm, for example, in close contact with the hole injection layer 30 by the same method as in the anode 20. .

  Examples of the individual hole-transporting substances that are widely used in organic EL devices include, for example, arylamine derivatives, imidazole derivatives, oxadiazole derivatives, oxazole derivatives, triazole derivatives, chalcone derivatives, styrylanthracene derivatives, stilbene derivatives, tetraaryls. Ethene derivatives, triarylamine derivatives, triarylethene derivatives, triarylmethane derivatives, phthalocyanine derivatives, fluorenone derivatives, hydrazone derivatives, N-vinylcarbazole derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylanthracene derivatives, phenylenediamine derivatives, polyarylalkanes Derivatives, polysilane derivatives, polyphenylene vinylene derivatives and the like can be mentioned, and these are used in combination as appropriate.

  A compound having a large intramolecular polarization and high adhesion to the anode 20, that is, ITO or the like can also be used as a hole injecting material or a hole injecting / transporting layer material.

  The light emitting layer 50 is usually obtained by closely contacting the hole transport layer 40 and depositing a host compound or co-depositing a host compound and a dopant. Further, if necessary, the light emitting layer is formed by separating the light emitting layer into a single layer or a multilayer and depositing each layer to a thickness of 10 to 100 nm.

  In the region of the light emitting layer 50, electron-hole recombination occurs, and as a result, light emission is observed.

  A preferred embodiment of the light emitting layer comprises a composite material composed of a host material doped with one or more fluorescent dye components. When this method is used, a highly efficient organic EL element can be configured. The emission color can be adjusted by laminating light emitting layers that generate different emission wavelengths.

  As a dopant in the light emitting layer 50, the fluorescent pigment material generally used in an organic EL element can be used. Examples of such fluorescent dye materials include perylene that emits blue light, rubrene that emits yellow light, and coumarin that emits green light.

  Moreover, as a host material in the light emitting layer 50, what has the characteristic of both hole transport property and electron transport property is preferable. Such a host material may be formed from one compound such as tris (8-quinolinolato) aluminum (hereinafter referred to as “Alq3”) or a mixture of a hole transporting material and an electron transporting material. You may do it.

  In the case of mixing, a substance selected from the hole transporting substances used for the hole transporting layer 40 can be used as the hole transporting substance in the host material. Further, as the electron transporting substance in the host material, a substance selected from electron transporting substances used for the electron transporting layer 60 described later can be used.

  Moreover, the dopant in the light emitting layer 50 can be made into the ratio of 0.05 to 50 weight% with respect to the whole host material, desirably 0.1 to 30 weight%.

  Next, in FIG. 1, the electron transport layer 60 positioned on the light emitting layer 50 is usually in close contact with the light emitting layer 50 to form one or more organic compounds having a high electron affinity to a thickness of 10 to 100 nm. It is formed by filming.

  In the case of using a plurality of electron transporting substances, even if the plurality of electron transporting substances are uniformly mixed to form a single layer, they are not mixed but are mixed in a plurality of adjacent layers for each electron transporting substance. It may be formed.

  Preferred electron transporting substances are quinolinol metal complexes, cyclic ketones such as benzoquinone, anthraquinone, and fluorenone, derivatives thereof, and silazane derivatives. Among these, quinolinol metal complexes are most preferred.

  The quinolinol metal complex here has a pyridine residue and a hydroxy group in the molecule, for example, quinolinols as ligands such as 8-quinolinols and benzoquinolin-10-ols, and the pyridine residue. Periodic table of lithium, beryllium, magnesium, calcium, zinc, aluminum, gallium, indium, etc. as a central atom that forms a coordination bond with a ligand by receiving an electron pair from a nitrogen atom in the group In general, it means a complex made of a metal belonging to Group 1, Group 2, Group 12 or Group 13 or an oxide thereof.

  When the ligand is either 8-quinolinols or benzoquinolin-10-ol, they may have one or more substituents, other than the 8th or 10th carbon to which the hydroxy group is attached. For example, halogen groups such as fluoro group, chloro group, bromo group, iodo group, methyl group, trifluoromethyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group, aliphatic hydrocarbon group such as tert-pentyl group, methoxy group, trifluoromethoxy group, ethoxy group, propoxy group, isopropoxy group, butoxy group, isobutoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, isopentyloxy group, Ether groups such as noxy group and benzyloxy group, acetoxy group, trifluoroacetoxy group, benzoyloxy group, methoxycarbonyl group, trifluoromethoxycarbonyl group, ethoxycarbonyl group, propoxycarbonyl group and other ester groups, and cyano group It does not prevent one or more substituents such as nitro group and sulfo group from being bonded. When the quinolinol metal complex has two or more ligands in the molecule, these ligands may be the same as or different from each other.

  Specific examples of the quinolinol metal complex include Alq3, tris (3,4-dimethyl-8-quinolinolato) aluminum, tris (4-methyl-8-quinolinolato) aluminum, and tris (4-methoxy-8-quinolinolato). Aluminum, Tris (4,5-dimethyl-8-quinolinolato) aluminum, Tris (4,6-dimethyl-8-quinolinolato) aluminum, Tris (5-chloro-8-quinolinolato) aluminum, Tris (5-bromo-8- Quinolinolato) aluminum, tris (5,7-dichloro-8-quinolinolato) aluminum, tris (5-cyano-8-quinolinolato) aluminum, tris (5-sulfonyl-8-quinolinolato) aluminum, tris (5-propyl-8- Quinolino Over G) aluminum, aluminum complexes such as bis (2-methyl-8-quinolinolato) aluminum oxide.

  Examples of the zinc complex include bis (8-quinolinolato) zinc, bis (2-methyl-8-quinolinolato) zinc, bis (2,4-dimethyl-8-quinolinolato) zinc, and bis (2-methyl-5). -Chloro-8-quinolinolato) zinc, bis (2-methyl-5-cyano-8-quinolinolato) zinc, bis (3,4-dimethyl-8-quinolinolato) zinc, bis (4,6-dimethyl-8-quinolinolato) ) Zinc, bis (5-chloro-8-quinolinolato) zinc, bis (5,7-dichloro-8-quinolinolato) zinc and the like.

  Furthermore, examples of the beryllium complex include bis (8-quinolinolato) beryllium, bis (2-methyl-8-quinolinolato) beryllium, bis (2,4-dimethyl-8-quinolinolato) beryllium, and bis (2-methyl-5). -Chloro-8-quinolinolato) beryllium, bis (2-methyl-5-cyano-8-quinolinolato) beryllium, bis (3,4-dimethyl-8-quinolinolato) beryllium, bis (4,6-dimethyl-8-quinolinolato) ) Beryllium, bis (5-chloro-8-quinolinolato) beryllium, bis (5,7-dichloro-8-quinolinolato) beryllium, bis (10-hydroxybenzo [h] quinolinolato) beryllium and the like.

  Examples of quinolinol metal complexes other than the above include bis (8-quinolinolato) magnesium, bis (2-methyl-8-quinolinolato) magnesium, bis (2,4-dimethyl-8-quinolinolato) magnesium, and bis (2-methyl). -5-chloro-8-quinolinolato) magnesium, bis (2-methyl-5-cyano-8-quinolinolato) magnesium, bis (3,4-dimethyl-8-quinolinolato) magnesium, bis (4,6-dimethyl-8) -Quinolinolato) magnesium, bis (5-chloro-8-quinolinolato) magnesium, magnesium complexes such as bis (5,7-dichloro-8-quinolinolato) magnesium, indium complexes such as tris (8-quinolinolato) indium, tris (5 -Chloro-8-quinori Acrylate) gallium complexes such as gallium, calcium complexes such as bis (5-chloro-8-quinolinolato) calcium can be cited. In addition, the above-described quinolinol metal complex is used in appropriate combination as necessary.

  The above-described electron transporting materials are merely examples, and the electron transporting materials used in the present embodiment should never be limited to these.

  Here, in this embodiment, the hole transport layer 40, the light emitting layer 50, and the electron transport layer 60 preferably have a glass transition temperature of 120 ° C. or higher in order to improve durability at high temperatures.

  In the present embodiment, as shown in FIG. 1, the cathode 70 on the electron transport layer 60 includes a first electron injection layer 71, a buffer layer 72, and a second electron injection layer from the electron transport layer 60 side. 73 and a transparent conductive film layer 74 are sequentially laminated.

  The first and second electron injection layers 71 and 73 are made of metal fluoride or metal oxide. Here, the metal fluoride layer can be selected from alkali metal fluorides or alkaline earth metal fluorides. The metal oxide layer can be selected from alkali metal oxides or alkaline earth metal oxides.

  The alkali metal fluoride includes lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, or cesium fluoride. The alkali metal oxide includes lithium oxide, sodium oxide, potassium oxide, rubidium oxide, or cesium oxide.

  The alkaline earth metal fluoride includes magnesium fluoride, calcium fluoride, strontium fluoride, or barium fluoride, and the alkaline earth metal oxide includes magnesium oxide, calcium oxide, Strontium oxide or barium oxide is included.

  The first and second electron injection layers 71 and 73 made of the metal fluoride layer or the metal oxide layer can be formed by an evaporation method, and the thickness thereof is, for example, 0.2 nm to 2.0 nm. Range.

  The buffer layer 72 is made of a porphyrin compound. Porphyrin compounds are either natural or synthetic compounds that contain porphyrin itself or that are derived from a porphyrin structure. A preferred porphyrin compound is represented by the following chemical formula (1).

上記化学式（１）において、Ｑは、ＮまたはＣ−Ｒ（置換基Ｒを持つＣ）であり、Ｍは、金属、金属酸化物、または金属ハロゲン化物であり、上記Ｃ−ＲにおけるＲは水素、アルキル、アラルキル、アリール、またはアルカリルであり、Ｔ１およびＴ２は水素を表すかまたは一緒になってアルキル若しくはハロゲン等の置換基を含みうる不飽和６員環を完成する。好ましい６員環は炭素、硫黄、および窒素環原子から形成されるものである。好ましいアルキル部分は約１から６炭素原子を含み、一方フェニルは好ましいアリール部分を構成する構造のものである。

In the chemical formula (1), Q is N or C—R (C having a substituent R), M is a metal, a metal oxide, or a metal halide, and R in the C—R is hydrogen. , Alkyl, aralkyl, aryl, or alkaryl, and T1 and T2 together represent hydrogen or complete an unsaturated six-membered ring that may contain a substituent such as alkyl or halogen. Preferred 6-membered rings are those formed from carbon, sulfur, and nitrogen ring atoms. Preferred alkyl moieties contain about 1 to 6 carbon atoms, while phenyl is of a structure that constitutes a preferred aryl moiety.

  Moreover, in another preferable form, a porphyrin compound is represented by following Chemical formula (2).

この化学式（２）は、上記化学式（１）と比較して金属原子Ｍを二つの水素で置換した点で異なる。

This chemical formula (2) differs from the above chemical formula (1) in that the metal atom M is replaced with two hydrogen atoms.

  Moreover, in this embodiment, a phthalocyanine compound is the most preferable among the said porphyrin compounds. Further, a compound containing a metal having a valence of +2 at the center is preferable. Specific examples include copper phthalocyanine, zinc phthalocyanine, and calcium phthalocyanine.

  Examples of the other buffer layer 72 include vanadium oxide, molybdenum oxide, and ruthenium oxide.

  The buffer layer 72 can be formed by a vapor deposition method, and has a thickness in the range of several nm to several tens of nm, for example.

  The transparent conductive layer 74 includes a compound selected from the group consisting of metal oxides, nitrides (for example, gallium nitride), selenides (for example, zinc selenide), and sulfides (for example, zinc sulfide). .

  Suitable metal oxides include indium-tin oxide (ITO), indium-zinc oxide (IZO), zinc oxide (ZnO), aluminum-doped or indium-doped zinc oxide, tin oxide, magnesium-indium oxide, nickel tungsten oxide, Or cadmium-tin oxide can be mentioned.

  This conductive film layer 74 can be formed by a sputtering method, and its thickness is, for example, in the range of 100 nm to several hundred nm.

  In addition, in this embodiment, in order to improve the adhesiveness between the cathode 70 and the electron carrying layer 60 containing an organic compound, as needed, for example, an aromatic diamine compound, a quinacridone compound, a naphthacene compound, an organic An interface layer containing a silicon compound or an organic phosphorus compound may be provided.

In forming the layers 20 to 70 in the organic EL element S1, in order to minimize the oxidation and decomposition of the organic compound, and the adsorption of oxygen and moisture, etc., under high vacuum, specifically 10 ^−5. It is desirable to work consistently below Torr.

  In addition, in the light emitting layer 50, the host and the dopant are mixed in a predetermined ratio in advance, or the heating rate of both in vacuum deposition is controlled independently of each other, thereby mixing the both in the light emitting layer 50. Adjust the ratio.

  In the organic EL element S1 formed in this way, a part or the whole of the element is sealed with, for example, sealing glass or a metal cap in an inert gas atmosphere in order to minimize deterioration in the use environment. Alternatively, it is desirable to cover with a protective layer made of an ultraviolet curable resin or the like.

  The method of using the organic EL element S1 of the present embodiment will be described. The organic EL element S1 applies a relatively high voltage pulsed voltage intermittently or has a relatively low voltage depending on the application. A DC voltage (usually 3 to 50 V) is applied continuously to drive.

  The organic EL element S1 emits light only when the potential of the anode 20 is higher than the potential of the cathode 70. Therefore, the voltage applied to the organic EL element S1 may be direct current or alternating current, and the waveform and period of the applied voltage may be appropriate.

  When alternating current is applied, in principle, the organic EL element S1 increases or decreases in luminance or blinks repeatedly according to the waveform and cycle of the applied alternating current. In the case of the organic EL element S <b> 1 shown in FIG. 1, when a voltage is applied between the anode 20 and the cathode 70, holes injected from the anode 20 pass through the hole injection layer 30 and the hole transport layer 40 and the light emitting layer 50. Further, electrons injected from the cathode 70 reach the light emitting layer 50 through the electron transport layer 60.

  As a result, recombination of holes and electrons occurs in the light emitting layer 50, and light emission of a target color is emitted from the excited dopant generated thereby through the anode 20 and the substrate 10 and is transparent. The light is transmitted through the negative cathode 70.

  By the way, according to the present embodiment, as shown in FIG. 1, in the organic EL element S1 in which the anode 20, the hole transport layer 40, the light emitting layer 50, the electron transport layer 60, and the cathode 70 are sequentially laminated, 70 is a transparent film formed by sequentially laminating a first electron injection layer 71, a buffer layer 72, a second electron injection layer 73, and a transparent conductive film layer 74 from the electron transport layer 60 side. An organic EL element S1 is provided.

  According to this, by setting the cathode 70 as described above, even when the organic EL element S1 of the present embodiment is adopted as a top emission method, a high transmittance of 90% or more can be realized.

  Moreover, by having the buffer layer 72, the energy at the time of forming the transparent conductive film layer 74 by sputtering or the like can be absorbed, and damage to the underlying organic layers 30 to 60 can be reduced. Therefore, a short circuit of the electrodes, that is, a short circuit between the anode 20 and the cathode 70 can be prevented.

  In addition, since the first electron injection layer 71 and the second electron injection layer 73 are interposed between the electron transport layer 60 and the buffer layer 72 and between the buffer layer 72 and the conductive film layer 74, respectively. The current efficiency can be greatly improved as compared with the conventional organic EL element.

  The first electron injection layer 71 diffuses into the electron transport layer 60 and the buffer layer 72 during film formation, thereby reducing the electron energy barrier between the electron transport layer 60 and the buffer layer 72.

  In addition, the second electron injection layer 73 diffuses into the buffer layer 72 at the time of film formation, and the work function of the conductive film layer 74 is further increased in order to form an electric double layer with the conductive film layer 74. The size is reduced closer to the electron injection layer 73. Therefore, the injection efficiency of electrons from the conductive film layer 74 can be increased.

  Thereby, according to the organic EL element S1 of this embodiment, it is thought that current efficiency can be improved.

  Therefore, according to the present embodiment, in the organic EL element, it is possible to realize the cathode 70 that functions as a highly transmissive and effective electron injection electrode. In addition, the specific example of this effect is described in the Example mentioned later.

  The organic EL element S1 of this embodiment having such an excellent cathode 70 can be suitably used as a top emission type organic EL element that extracts light from the light emitting layer 50 from the cathode 70 side.

  Further, in the organic EL element S1 of the present embodiment, it is preferable to employ ITO, IZO or ZnO as the transparent conductive film layer 74.

  According to this, general ITO (indium-tin oxide), IZO (indium-zinc oxide), or ZnO (zinc oxide) that can also be used as an anode can be used as the transparent conductive film layer 74. Therefore, the same material as the anode 20 can be used for the cathode 70, and simplification can be achieved.

  Further, in the organic EL element S1 of the present embodiment, a porphyrin compound can be adopted as the buffer layer 72. Among them, in particular, when CuPc is used, it is stable against the impact of sputtering and is also used in the buffer layer. Is optimal.

  Further, in the organic EL element S1 of the present embodiment, it is preferable to employ inexpensive lithium oxide for at least one of the first electron injection layer 71 and the second electron injection layer 73. An element can be provided.

  Furthermore, as described above, in the organic EL element S1 of the present embodiment, the three layers of the hole transport layer 40, the light emitting layer 50, and the electron transport layer 60 preferably have a glass transition temperature of 120 ° C. or higher. Accordingly, it is preferable for improving durability at high temperatures.

  As described above, the organic EL element S1 of the present embodiment has high current efficiency and, as a result, has high luminance. Therefore, the organic EL element S1 has a wide variety of uses in light emitters and information display devices that visually display information.

  The light emitter using the organic EL element S1 as a light source has low power consumption and can be configured in a light panel shape. Therefore, in addition to the light source for general illumination, for example, a liquid crystal element, a copying apparatus, and a printing apparatus. , Electrophotographic equipment, computers and their application equipment, industrial control equipment, electronic measuring instruments, analytical equipment, instruments in general, communication equipment, medical electronic measuring equipment, vehicles including automobiles, ships, aircraft, spacecrafts, etc. It is useful as an energy-saving and space-saving light source for aircraft control equipment, interiors, signboards, signs, etc.

  In addition, when this organic EL element S1 is used for information display devices such as computers, televisions, videos, games, watches, telephones, car navigation systems, in-vehicle multimeters, oscilloscopes, radars, sonars, etc. Or a combination of organic EL elements that emit light in the green, blue, and red regions can be used for a full color display.

  Among these, the characteristics of the organic EL element S1 of the present embodiment can be best utilized when used for a display for in-vehicle use that requires particularly durability. As a driving method, a general-purpose simple matrix method (passive method) or an active matrix method can be applied. In particular, when the top emission method is adopted and applied to the active method, an organic EL element with high luminance can be obtained.

  In addition, when the organic EL element S1 of the present embodiment is used by being mounted on an automobile or a vehicle, it is inevitable that the environment becomes a high temperature environment (for example, about 70 to 80 ° C.). Among the organic layers, an amorphous organic layer is crystallized when the glass transition temperature (Tg) or higher is reached, and unevenness on the surface of the film is increased, and current leakage tends to occur.

  Therefore, when it is used for in-vehicle use, as described above, it is preferable that Tg of all the organic layers in the organic EL element S1 is 120 ° C. or more.

  In addition, when the organic EL element S1 of the present embodiment is employed in, for example, an in-vehicle display, the use temperature is about −40 ° C. to 120 ° C.

  In order to improve the stability under a high temperature environment at such a use temperature, it is necessary to improve the adhesion of the hole injection layer 30, particularly the adhesion at the interface with the anode 20. This is presumably because the difference in linear expansion coefficient between the two is large.

  Therefore, as the hole injection layer 30 in contact with the anode 20, it is preferable to provide a porphyrin-based compound layer with a small change in shape.

  Specifically, when CuPc is used as the porphyrin-based compound, the diffraction peak change amount due to heating within the use temperature of the organic EL element S1 is the diffraction before heating in the value of the diffraction peak that appears by the X-ray diffraction method of CuPc. Those within ± 25% of the peak are preferred. The operating temperature is −40 to 120 ° C. in this example.

  Here, the diffraction peak of CuPc indicates the crystallinity of CuPc. When the hole injection layer 30 made of CuPc, that is, the CuPc film 30, is measured by the X-ray diffraction method, the (200) of the CuPc film 30 parallel to the substrate 10 is obtained. ) Surface diffraction peak. Specifically, this corresponds to the peak occurring at 2θ = 6.68 ° shown in FIG. 2, and this is hereinafter referred to as a CuPc crystallinity peak.

  In the present embodiment, the CuPc crystallinity peak (2θ = 6.68 °), that is, the integrated value of the peak, the CuPc by heating within the use temperature (−40 ° C. to 120 ° C.) of the organic EL element S1. It is preferable that the amount of change in the crystalline peak is within ± 25% of the value of the CuPc crystalline peak before heating.

  By suppressing the amount of change of the CuPc crystallinity peak value before and after heating to within ± 25%, the adhesion of the CuPc film can be improved. And even if it uses in a high temperature environment, the change of the crystal state of an organic material can be made small to such an extent that a short circuit and a leak do not generate | occur | produce.

  Incidentally, in the data shown in FIG. 2 above, the value of the CuPc crystallinity peak after heating is greatly changed by 1.5 times compared to the value of the CuPc crystallinity peak before heating, and short circuit and leakage occur. It has become easier.

  Such a CuPc film 30 in which the amount of change in the value of the CuPc crystallinity peak before and after heating is kept small within ± 25% is obtained by, for example, subjecting the surface of the anode 20 as a base to ultraviolet ozone treatment at 150 ° C. This can be realized by depositing CuPc at a material heating temperature of 520 ° C. to form a film.

  And in this embodiment, if the hole injection layer 30 is made into such a CuPc film | membrane 30, the adhesiveness of the hole injection layer 30 will be improved, and organic EL element S1 suitable for a higher temperature environment can be provided. it can.

  In addition, as described above, it is important that the crystallinity of the hole injection layer 30 is difficult to change in a high temperature environment after the element is formed.

  Therefore, in FIG. 1, the surface roughness of the anode 20 is important in order to form the crystalline material immediately above the anode 20 into a stable film having high crystallinity. That is, a flatter film can form a stable film with higher crystallinity.

  In the present embodiment, when ITO is used as the anode 20, specifically, the average surface roughness Ra is preferably 2 nm or less, and the 10-point average surface roughness Rz is preferably 20 nm or less. In the embodiment of FIG. 1, for example, by polishing the surface of ITO as the anode 20 formed on the glass substrate 10, Ra can be about 1 nm or less and Rz can be about 10 nm.

  Next, the present embodiment will be described more specifically with reference to the following examples and comparative examples, although not limited thereto.

  An anode 20 made of ITO having a thickness of 150 nm was formed on the glass substrate 10 by sputtering. After patterning, the ITO surface is polished to flatten the surface.

  Specifically, the average surface roughness Ra is desirably 2 nm or less, and the 10-point average surface roughness Rz is desirably 20 nm or less. In this example, the surface of ITO was polished so that Ra was about 1 nm or less and Rz was about 10 nm.

  On the anode 20, as a hole injection layer 30, CuPc (copper phthalocyanine) was formed to a thickness of 10 nm by vacuum deposition. Further, a triphenylamine tetramer was formed to 40 nm as the hole transport layer 40 by vacuum deposition.

  Then, as the light emitting layer 50, a layer using Alq3 as a host material and 1% dimethylquinacridone as a doping material was formed to 40 nm by a vacuum deposition method. Furthermore, 20 nm of Alq3 was formed as the electron transport layer 60 by a vacuum deposition method.

After these organic layers are formed, a first electron injection layer 71 made of Li ₂ O (lithium oxide) is formed as a cathode 70 from the electron transport layer 60 side by a vacuum deposition method to 0.5 nm and a buffer layer 72 made of CuPc. was 150nm formed by sputtering 10 nm, the second 0.5nm by vacuum deposition electron injection layer 73 made of Li ₂ O, and the conductive layer 74 made of IZO by vacuum deposition. Thus, in this example, the cathode 70 including the four layers 71 to 74 was formed on the electron transport layer 60.

  The organic EL element of this example emitted green light and had a transmittance of 90% or more as a top emission method. Moreover, the current efficiency (1/16 duty drive) is 2.5 cd / A, which is very high as a transparent organic EL.

(Comparative Example 1)
As a cathode 70, an electron injection layer made of Li ₂ O from the electron-transporting layer 60 side by vacuum evaporation 0.5 nm, by vacuum vapor deposition buffer layer made of CuPc 10 nm, and the conductive layer made of IZO by sputtering An organic EL element was produced in the same manner as in Example 1 except that the thickness was 150 nm.

  That is, in the organic EL element of this example, in the organic EL element shown in FIG. 1, the cathode 70 does not have the second electron injection layer 73, but the first electron injection layer 71, the buffer layer 72, and the conductive film layer. It consisted of 74 3 layers.

  This configuration corresponds to a configuration in which an electron injection layer made of Li or the like is introduced at the interface between the electron transport layer and the CuPc thin film layer in the cathode described in Non-Patent Document 2 and Non-Patent Document 3. To do.

  The organic EL element of this example emits green light and has a transmittance of 90% or more as a top emission method, but its current efficiency (1/16 duty drive) is 0.4 cd / A. Compared with transparent organic EL, the efficiency was low.

(Comparative Example 2)
As the cathode 70, from the electron transport layer 60 side, a buffer layer made of CuPc is 10 nm by vacuum deposition, an electron injection layer made of Li ₂ O is 0.5 nm by vacuum deposition, and a conductive layer made of IZO is sputtered. An organic EL element was produced in the same manner as in Example 1 except that the thickness was 150 nm.

  That is, in the organic EL element of this example, in the organic EL element shown in FIG. 1, the cathode 70 does not have the first electron injection layer 71, but the buffer layer 72, the second electron injection layer 73, and the conductive film layer. It consisted of 74 3 layers.

  The organic EL element of this example emits green light and has a transmittance of 90% or more as a top emission method, but its current efficiency (1/16 duty drive) is 0.5 cd / A. Compared with transparent organic EL, the efficiency was low.

  As the cathode 70, from the electron transport layer 60 side, the first electron injection layer 71 made of LiF (lithium fluoride) is 0.5 nm by a vacuum vapor deposition method, and the buffer layer 72 made of CuPc is 10 nm by a vacuum vapor deposition method and made of LiF. The second electron injection layer 73 was formed to a thickness of 0.5 nm by a vacuum evaporation method, and the conductive film layer 74 made of IZO was formed to a thickness of 150 nm by a sputtering method.

Other than that produced the organic EL element similarly to the said Example 1. FIG. The organic EL element S1 of this example is obtained by changing the material of the first and second electron injection layers 71 and 73 from Li ₂ O to LiF as compared with the first example.

  The organic EL element of this example emitted green light and had a transmittance of 90% or more as a top emission method. Moreover, the current efficiency (1/16 duty drive) was 2.0 cd / A, and it was very high efficiency as transparent organic EL.

As the cathode 70, from the electron transport layer 60 side, the first electron injection layer 71 made of Li ₂ O is 0.5 nm by a vacuum deposition method, the buffer layer 72 made of CuPc is 10 nm by a vacuum deposition method, and the first electron injection layer 71 made of Li ₂ O is made. The second electron injection layer 73 was formed to 0.5 nm by a vacuum deposition method, and the conductive film layer 74 made of ITO was formed to 150 nm by a sputtering method.

  Other than that produced the organic EL element similarly to the said Example 1. FIG. In the organic EL element S1 of this example, the material of the conductive film layer 74 is changed from IZO to ITO as compared with the first embodiment.

  The organic EL element of this example emitted green light and had a transmittance of 90% or more as a top emission method. In addition, the current efficiency (1/16 duty drive) was 2.3 cd / A, which was very high as a transparent organic EL.

As the cathode 70, from the electron transport layer 60 side, the first electron injection layer 71 made of Li ₂ O is 0.5 nm by a vacuum deposition method, the buffer layer 72 made of CuPc is 10 nm by a vacuum deposition method, and the first electron injection layer 71 made of Li ₂ O is made. The second electron injection layer 73 was formed to 0.5 nm by a vacuum evaporation method, and the conductive film layer 74 made of ZnO was formed to 150 nm by a sputtering method.

  Other than that produced the organic EL element similarly to the said Example 1. FIG. The organic EL element S1 of this example is obtained by changing the material of the conductive film layer 74 from IZO to ZnO as compared to the first example.

  The organic EL element of this example emitted green light, and the transmittance was 90% or more as a top emission method. Moreover, the current efficiency (1/16 duty drive) was 2.0 cd / A, and it was very high efficiency as transparent organic EL.

As the cathode 70, from the electron transport layer 60 side, the first electron injection layer 71 made of Li ₂ O is 0.5 nm by a vacuum deposition method, the buffer layer 72 made of VOx (vanadium oxide) is 10 nm by a vacuum deposition method, Li ₂ A second electron injection layer 73 made of O was formed to a thickness of 0.5 nm by a vacuum deposition method, and a conductive film layer 74 made of IZO was formed to a thickness of 150 nm by a sputtering method.

  Other than that produced the organic EL element similarly to the said Example 1. FIG. The organic EL element S1 of this example is obtained by changing the material of the buffer layer 72 from CuPc to VOx as compared with the first example.

  The organic EL element of this example emitted green light, and the transmittance was 90% or more as a top emission method. Moreover, the current efficiency (1/16 duty drive) was 2.5 cd / A, which was very high as a transparent organic EL.

  As described above, in the embodiment described above, in the organic EL element in which the anode 20, the hole transport layer 40, the light emitting layer 50, the electron transport layer 60, and the cathode 70 are sequentially stacked, the cathode 70 includes the electron transport layer. Provided is an organic EL element characterized by being a transparent film formed by sequentially laminating a first electron injection layer 71, a buffer layer 72, a second electron injection layer 73, and a transparent conductive film layer 74 from the 60 side. Is.

  In other words, the organic EL element S1 absorbs energy when a film formed on the organic EL element S1 is formed, and a buffer layer 72 for reducing damage to the base film and the buffer layer 72 thereon. An electron injection layer 71 between the buffer layer 72 and the electron transport layer 60 and between the buffer layer 72 and the conductive film layer 74. 73 is interposed.

  In this way, the transparent cathode structure using two electron injection layers above and below the buffer layer realizes the cathode 70 as an electron injection electrode excellent in electric pole efficiency while ensuring sufficient transparency. It is made.

  And about the anode 20, the positive hole transport layer 40, the light emitting layer 50, and the electron carrying layer 60 other than what was shown in the said embodiment, it may be used for a normal organic EL element, or may be used. A certain material or configuration may be used as appropriate.

It is a schematic sectional drawing of the organic EL element which concerns on embodiment of this invention. It is a figure which shows the result of having analyzed the crystalline state of the CuPc film | membrane by X-ray diffraction before and after acceleration high temperature leaving-to-stand.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Board | substrate, 20 ... Anode, 30 ... Hole injection layer, 40 ... Hole transport layer,
50 ... Light emitting layer, 60 ... Electron transport layer, 70 ... Cathode,
71: a first electron injection layer in the cathode; 72: a buffer layer in the cathode;
73: a second electron injection layer in the cathode; 74: a conductive film layer in the cathode.

Claims (10)

In an organic EL device in which an anode (20), a hole transport layer (40), a light emitting layer (50), an electron transport layer (60) and a cathode (70) are sequentially laminated,
The cathode (70) includes a first electron injection layer (71), a buffer layer (72), a second electron injection layer (73), and a transparent conductive film layer (74) from the electron transport layer (60) side. Is a transparent film formed by sequentially laminating
In the electron transport layer (60) and the buffer layer (72), the components of the first electron injection layer (71) are diffused,
The second electron injection layer (73) is an alkali metal fluoride, an alkaline earth metal fluoride, an alkali metal oxide, or an alkaline earth metal oxide,
The organic EL element, wherein the hole transport layer (40), the light emitting layer (50), and the electron transport layer (60) have a glass transition temperature of 120 ° C. or higher.   The organic EL element according to claim 1, wherein the transparent conductive film layer (74) is made of ITO, IZO or ZnO.   The organic EL device according to claim 1 or 2, wherein the buffer layer (72) is made of a porphyrin compound.   The organic EL device according to claim 3, wherein the porphyrin compound is copper phthalocyanine.   The organic material according to any one of claims 1 to 4, wherein at least one of the first electron injection layer (71) and the second electron injection layer (73) is a lithium oxide layer. EL element.   5. The organic EL device according to claim 1, wherein the alkali metal fluoride is lithium fluoride, sodium fluoride, potassium fluoride, rubidium fluoride, or cesium fluoride. .   5. The organic EL device according to claim 1, wherein the alkaline earth metal fluoride is magnesium fluoride, calcium fluoride, strontium fluoride, or barium fluoride.   5. The organic EL device according to claim 1, wherein the alkali metal oxide is lithium oxide, sodium oxide, potassium oxide, rubidium oxide, or cesium oxide.   5. The organic EL element according to claim 1, wherein the alkaline earth metal oxide is magnesium oxide, calcium oxide, strontium oxide, or barium oxide. Between the anode (20) and the hole transport layer (40), a hole injection layer (30) made of copper phthalocyanine is provided,
In the value of the diffraction peak that appears by the X-ray diffraction method of the copper phthalocyanine, the amount of change in the diffraction peak due to heating within the operating temperature of the organic EL element is within ± 25% of the diffraction peak before the heating. The organic EL device according to claim 1, wherein the organic EL device is a liquid crystal display device.

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