JP2005141921A - Organic electroluminescent device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element of a new constitution provided with a layer having a two-dimensional photonic crystal structure, emitting a light having a wave length different from that of the light emitted from an organic layer (light of arbitrary color). <P>SOLUTION: The element 1 is provided with the organic layer 3 interposed between a pair of electrodes 2, 4, emitting light by the voltage impressed on both electrodes 2, 4. The element 1 has the two-dimensional photonic crystal layer 5 arranged at light take-out side of the organic layer 3, and a wavelength converting layer 6 to convert the wavelength of an incident light into the light of a longer wavelength is arranged on whole surface or a part of the light take-out side of the two-dimensional photonic crystal layer 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  An organic electroluminescent device comprising an organic layer that is sandwiched between a pair of electrodes and emits light when a voltage is applied between both electrodes, and more specifically, any color employing a two-dimensional photonic crystal technique The present invention relates to an organic electroluminescent element that displays

  Conventionally, organic electroluminescent devices (hereinafter, appropriately referred to as “organic EL devices”) such as displays and lighting devices using organic electroluminescent elements (hereinafter, appropriately described as “organic EL elements”) have been proposed. ing. The organic EL element has a structure in which an organic layer having an organic light emitting region containing an organic light emitting material is sandwiched between a pair of electrodes.

  It has been pointed out that such organic EL elements cannot sufficiently utilize the light emitted from the organic layer, and many proposals have been made to solve this problem. First, the reason why the light emitted from the organic layer cannot be sufficiently utilized will be described, and then, the prior art proposed for solving this problem will be exemplified.

For example, in a bottom emission type organic EL device in which an organic EL element is formed on a transparent substrate and light is extracted from the transparent substrate side, all the light emitted from the organic layer and incident on the transparent substrate is Is not taken out from a plane parallel to the light (light exit surface). The light not extracted in this way is light incident on the light exit surface at an angle larger than the critical angle. This light may be emitted to the outside from the end of the transparent substrate, or may be extinguished while traveling while reflecting inside the transparent substrate or the organic EL element.
Further, not all the light emitted from the light emitting surface is emitted in the direction in which the device is desired to emit light. For example, in a device used as a display such as a portable terminal, it is desirable to emit light in a direction in which the user is normally assumed (for example, the normal direction of the light emitting surface), but light is also emitted in other directions. It will be emitted. Therefore, it can be said that the latter light is extracted from the light emitting surface to the outside, but cannot be practically used.

Conventional techniques proposed to solve the above problems include, for example, a conventional technique in which a prism sheet is provided on the light extraction surface, and the amount of light in a specific direction is increased based on the light emission surface (for example, Patent Document 1), or a conventional technique (for example, patent) that provides a plurality of projections and depressions on an organic layer, an electrode, a substrate, etc., changes the traveling direction of light, and extracts light that could not be extracted from a conventional light exit surface Reference 2) is proposed.
These conventional technologies contribute to increasing the light extraction efficiency and light utilization efficiency, such as increasing the amount of light extraction than before or increasing the amount of light emitted in a specific direction depending on the design. ing.
Conventionally, these methods have been used to increase the light extraction efficiency and light utilization efficiency.

  On the other hand, organic EL elements using photonic crystals have also been proposed. Hereinafter, a photonic crystal will be described first, and then a conventional technique related to an organic EL element using the photonic crystal will be described.

  A photonic crystal is a substance / element device having a periodic structure having a length of about the wavelength of light or electromagnetic waves, which can freely control light. Specifically, a photonic crystal has a periodic structure with a length of about the wavelength of light, in which there is a photonic band-gap that does not relax the presence of light in a certain wavelength range. appear. The origin of this photonic panda gap can be explained in the same way as the origin of the band gap, forbidden band for electrons in a solid crystal, ie, the band gap where the presence of electrons in a specific energy range is not allowed.

When atoms are regularly arranged in a certain period in a solid crystal, the band gap for electrons appears because the wavelength when the electrons are viewed as waves is just as large as the atomic spacing. Bragg reflection is received by the periodic potential, and a state without energy is formed.
In the same way, when light is transmitted through a structure with a periodic refractive index (dielectric constant) distribution that is about the same length as the wavelength of the light, photonics are prohibited from propagating light in a certain wavelength region. A band gap is formed. This periodic structure may be one-dimensional, two-dimensional, or three-dimensional.

  In addition, when a defect is introduced into a photonic crystal having a complete periodic structure, the band edge has a tail in the photonic band gap, and a defect level (localized level) appears in the band. By using this defect level, it is possible to enhance the light emission characteristics of the light emitting substance. In addition, the group velocity of light becomes extremely small at the band edge, and as a result, it is possible to enhance the light emission characteristics of the entire device (see, for example, Non-Patent Document 1).

  And the research which applied this photonic crystal technique to the organic EL element is also announced (for example, refer nonpatent literature 2 and nonpatent literature 3). In these studies, if the photonic crystal technology described above was used for an organic EL element, the intensity of light emitted from the organic EL element could be increased, or broad light could be converted into sharp light. It has been reported.

  However, as is clear from the above description, the photonic crystal technique only works on light of a single wavelength. That is, the photonic crystal can act on only a small part of the light emitted from the organic layer.

  It is also very difficult to create a display using photonic crystal technology. For each sub-pixel, a layer using photonic crystal technology corresponding to the color emitted from each sub-pixel has to be stacked, so that the structure becomes extremely complicated and difficult to manufacture. For this reason, the occurrence of problems such as a decrease in yield and an extremely large number of manufacturing processes is naturally conceivable.

That is, it is practically impossible or extremely difficult to express an arbitrary color by applying the photonic crystal technology to the organic EL element.
Japanese Patent Laid-Open No. 2002-6776 JP 2001-76864 A “Control of Light Field by Photonic Crystal”, Surface Science Vol. 11, pp 702-709, 2001) "Characteristic evaluation of photonic crystal organic EL device", Proceedings of the 64th JSAP academic lecture, p938 “Preparation and optical properties of organic semiconductor photonic crystals”, Proceedings of the 64th JSAP Scientific Meeting, p938

The present invention has been made in view of the above problems, and in an organic electroluminescence device having a layer having a two-dimensional photonic crystal structure, light other than the wavelength emitted from the organic layer (light of any color) is emitted. An object of the present invention is to provide an organic electroluminescence device having a novel structure.
Another object of the present invention is to provide a bottom emission type organic electroluminescent device in which the organic electroluminescent element is formed on a transparent substrate and light is extracted from the transparent substrate side to the outside.

  In order to achieve the above object, an organic electroluminescent element according to the present invention is an element including an organic layer that is sandwiched between a pair of electrodes and emits light when a voltage is applied between the two electrodes. The two-dimensional photonic crystal layer is disposed on the light extraction side of the organic layer, and the wavelength of the incident light is changed to a longer wavelength light on a part or the entire surface of the light extraction side of the two-dimensional photonic crystal layer. A wavelength conversion layer for conversion is disposed.

  In addition, the wavelength conversion layer may be configured by arranging two or more members (two-dimensional photonic crystal layers) having different wavelengths after changing the incident light on the same layer. In addition, when arranging in this way, you may make each member integral.

  The electrode on the light extraction side of the organic layer may be provided with the two-dimensional photonic crystal structure so as to function as a two-dimensional photonic crystal layer.

  The organic electroluminescent device according to the present invention is formed as an element in which the organic electroluminescent element is formed on a transparent substrate, and the light emitted from the organic layer is extracted from the transparent substrate side to the outside. The transparent substrate has a two-dimensional photonic crystal structure and functions as a two-dimensional photonic crystal.

  In the present specification, “transparent” means that the light emitted from the organic layer has transparency to light having at least one wavelength, or light having a wavelength within a certain region including this wavelength. Unless otherwise specified, it preferably has a transmittance of 50% or more, desirably 70% or more. The term “transmitting light” is also used appropriately in the same meaning as “transparent”.

  In the present specification, the “two-dimensional photonic crystal layer” means a layer having the above-described two-dimensional photonic crystal structure, and in the layered transparent member (first dielectric), A member in which a large number of portions (second dielectrics) having a refractive index different from that of the member are periodically introduced in a direction perpendicular to the surface, that is, in a thickness direction.

ADVANTAGE OF THE INVENTION According to this invention, the organic electroluminescent element of a novel structure which emits lights (light of arbitrary colors) other than the wavelength emitted from the organic layer can be provided.
It is also possible to provide an organic electroluminescence device having a novel configuration capable of displaying a specific color, that is, capable of color display.

  Furthermore, it is possible to provide a bottom emission type organic electroluminescent device in which the organic electroluminescent element is formed on a transparent substrate and light is extracted from the transparent substrate side to the outside.

Hereinafter, the organic EL device according to the embodiment of the present invention will be described in detail with reference to the drawings, and the organic EL element according to the present embodiment will also be described. This organic EL device has a bottom emission structure, but it is naturally possible to appropriately change the structure such as a top emission structure or a structure in which light is extracted from both electrode sides based on the organic layer.
1 to 3, the same or similar components are denoted by the same reference numerals. 1 to 3 are diagrams for explaining the structure of the organic EL element. One or a plurality of components are shown in dimensions extremely different from those in an actual organic EL element. .
First, the basic structure of the organic EL element according to this embodiment will be described with reference to FIG.

<Basic structure>
In the organic EL device according to the present embodiment, the organic EL element 1 is formed on the transparent substrate 9. As shown in FIG. 1, the organic EL element 1 is an element including an organic layer 3 that is sandwiched between a pair of electrodes 2 and 4 and emits light when a voltage is applied between the electrodes. Among the electrodes, the electrode 4 provided on the light extraction side with respect to the organic layer 3 is transparent (transparent electrode), and light is extracted from the transparent electrode 4 side.
A two-dimensional photonic crystal layer 5 is disposed on the light extraction side of the organic layer 3. In the configuration shown in FIG. 1, a two-dimensional photonic crystal layer 5 is provided on the surface of the transparent electrode 4 opposite to the surface facing the organic layer 3.
A wavelength conversion layer 6 that converts the wavelength of incident light into light having a longer wavelength is disposed on a part or the entire surface of the light extraction side of the two-dimensional photonic crystal layer 5. In the configuration shown in FIG. 1, a wavelength conversion layer 6 is provided on the surface of the two-dimensional photonic crystal layer 5 opposite to the surface facing the transparent electrode 4.

The organic layer 3 is a layer containing an organic light emitting material that emits light of at least one wavelength when a voltage is applied to both electrodes 2 and 4.
The two-dimensional photonic crystal layer 5 is a layer that enhances one wavelength included in the light incident from the organic layer 3 or a wavelength that is substantially the same as this wavelength. Refer to the above description for the principle and effect of this layer.
The wavelength conversion layer 6 is a layer that converts the wavelength of light incident from the two-dimensional photonic crystal layer 5, and more specifically, the incident light is emitted with the wavelength peak shifted to the long wavelength side. It is a layer to do.
Hereinafter, the electrode 2 is referred to as a back electrode 2.

Since the organic EL device and the organic EL element 1 according to the present embodiment have the above-described configuration, they have the following action.
(1) Since the two-dimensional photonic crystal layer 5 is provided, the intensity of light emitted from the organic layer 3 is increased. It emits so-called sharp light in which the intensity of a specific wavelength is extremely stronger than the intensity of adjacent wavelengths.
(2) The wavelength conversion layer 6 converts the light emitted from the two-dimensional photonic crystal layer 5 into an arbitrary wavelength.

Therefore, the organic EL device and the organic EL element 1 according to the present embodiment can emit any color regardless of employing the photonic crystal technique. Naturally, since the photonic crystal technology is used, the intensity of light (the amount of light) becomes larger than before. Furthermore, the luminance in a specific direction can be increased. That is, the organic EL device and the organic EL element 1 can emit any color with extremely high luminance in a specific direction.
Moreover, the organic EL element 1 and the organic EL device which are planar light sources that emit sharp light can be provided.

In addition, in the two-dimensional photonic crystal layer, a place where the two-dimensional photonic crystal is provided and a place where the two-dimensional photonic crystal is not provided are provided (a part of the two-dimensional photonic crystal is provided instead of the entire surface). And the light of the color converted by the wavelength conversion layer 6 can be emitted to the outside of the organic EL device (organic EL element 1). That is, various colors such as white can be expressed as additive colors of these lights.
Naturally, since the above-described effects can be obtained, the organic EL device and the organic EL element 1 that can express an arbitrary color with extremely high luminance in a specific direction are obtained. The emitted light also has a sharp wavelength. In addition, the luminance can be increased.

As the two-dimensional photonic crystal layer, a layer in which two or more members having different wavelengths after conversion of incident wavelengths are arranged on the same layer may be employed. As a result, the light emitted from the organic layer is converted into light having different wavelengths by the plurality of members and emitted to the outside. Therefore, if the member (two-dimensional photonic crystal) is appropriately designed, an arbitrary color that is not limited to the wavelength of light emitted from the organic layer can be expressed.
In addition, although expressed as “the above members are arranged in the same layer” in terms of expression, different photonic crystals may be arranged side by side, or photonic crystals having different structures may be formed in the same member, Of course, a plurality of photonic crystals may be integrated together.

<Two-dimensional photonic crystal layer 5>
As shown in FIG. 2A, the two-dimensional photonic crystal layer 5 is in a layered (plate-shaped) material (first dielectric) 51 that is transparent to the wavelength of light emitted from the organic layer 3. In addition, a portion (second dielectric) 52 that is transparent to the light and has a refractive index (dielectric constant) different from that of the material in the thickness direction, that is, the normal direction of the layer is the longitudinal direction. The layers are arranged periodically. In FIG. 2A, the second dielectric 52 in the first dielectric 51 is also shown by a solid line for the sake of explanation.

The two-dimensional photonic crystal layer 5 has a structure that increases the intensity as described above with respect to one wavelength included in the light emitted from the organic layer 3 or a wavelength within a predetermined range centered on the wavelength. That's fine. That is, the refractive index of the first dielectric 51 and the second dielectric 52 and the arrangement method (periodicity) of the second dielectric are calculated using a known photonic crystal technique, it may be made of work in response.

  Examples of the periodic structure of the second dielectric include a square arrangement as shown in FIG. 2B and a triangular lattice arrangement as shown in FIG. Among such structures, a triangular lattice arrangement having a six-way symmetry and regularly arranged in a honeycomb shape is preferable as shown in FIG.

The material constituting the first dielectric 51 and the second dielectric 52 may be any refractive index different from each other. For example, any glass material, semiconductor material, oxide material, organic material, etc. are applicable. .
In addition, air or vacuum can be regarded as one material. That is, the two-dimensional photonic crystal layer 5 may be formed by making a hole in the first dielectric 51 and filling the hole with a gas such as air or nitrogen, or by making a vacuum. When such a structure is adopted, the gas sealed in the hole is preferably a gas that does not deteriorate or hardly deteriorate the organic layer 3 or the like. For example, nitrogen or a rare gas is sealed. Is preferred.
Also, a two-dimensional photonic crystal layer can be produced as follows.

・ Capillary / plate type photonic crystal fabrication method An air rod type trigonal crystal that can be prepared by regularly arranging and stretching optical fibers whose cores are made of lead glass, and then dissolving only the core part with hydrochloric acid. is there. A surface perpendicular to the fiber is a two-dimensional surface, that is, a surface substantially parallel to the light extraction surface. This is a production method useful for producing a two-dimensional photonic crystal layer 5 having a large size.

-Light absorption method using a photo-curing medium The light absorption method uses a special organic material that is altered (cured) by one-photon absorption or two-photon absorption of laser light. For example, a portion cured by three-dimensional holography is used. Make and melt the part.

<Wavelength conversion layer 6>
The wavelength conversion layer 6 is provided on the light extraction side of the two-dimensional photonic crystal layer 5 and absorbs short wavelength light (blue light, etc.) and emits long wavelength light (red light, green light, etc.). Yes, for example, it contains a fluorescence conversion substance that converts light emitted from the light emitting layer into light of another low energy wavelength.

As the wavelength conversion layer 6, it can form as a layer which consists of fluorescent dye and resin, or a layer which consists only of fluorescent dye, for example. Specific examples of the former layer include a solid state layer in which a fluorescent dye is dissolved or dispersed in a pigment resin and / or a binder resin.
Below, the specific fluorescent pigment | dye which can be contained in the wavelength conversion layer 6 is illustrated.

  Examples of fluorescent dyes that convert the light emission of violet organic EL elements from near-ultraviolet light into blue light emission include 1,4-bis (2-methylstyryl) benzene (Bis-MSB), trans-4, 4′-. Dimethyl stilbene (DPS) and other stilbene dyes, coumarin dyes such as 7-hydroxy-4-methylcoumarin (coumarin 4), and aromatic dimethylidin series such as 4,4'-bis (2,2-diphenylvinyl) biphenyl A pigment | dye etc. can be mentioned.

  Examples of fluorescent dyes that convert blue or blue-green light emission into green light emission include 2, 3, 5, 6-1H, 4H-tetrahydro-8-trifluoromethylquinolidino (9, 9a, 1-gh). Coumarin dyes such as coumarin (coumarin 153), 3- (2′-benzothiazolyl) -7-diethylaminocoumarin (coumarin 6), 3- (2′-benzimidazolyl) -7-N, N-diethylaminocoumarin (coumarin 7) Other examples include coumarin dyes such as basic yellow 51, and naphthalimide dyes such as solvent yellow 11 and solvent yellow 116.

  Examples of the fluorescent dye that converts light emission from blue to green to light emission from orange to red include, for example, 4-dicyanomethylene-2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (DCM), 4- (dicyanomethylene) -2-phenyl-6- (2- (9-eurolidyl) ethenyl) -4H-pyran, 4- (dicyanomethylene) -2,6-di (2- (9-eurolidyl) ethenyl) -4H-pyran, 4- (dicyanomethylene) -2-methyl-6- (2- (9-eurolidyl) ethenyl) -4H-pyran, 4- (dicyanomethylene) -2-methyl-6- (2- ( Cyanine dyes such as 9-eurolidyl) ethenyl) -4H-thiopyran, 1-ethyl-2- (4- (p-dimethylaminophenyl) -1,3-butadienyl) -pyridinium-parkro Over preparative (pyridine 1) pyridine such as dyes, Rhodamine B, Rhodamine-based pigments such as rhodamine 6G, and oxazine dyes.

  Various dyes such as direct dyes, acid dyes, basic dyes, and disperse dyes can be used as long as they have fluorescence.

  Examples of the pigment resin include polymethacrylic acid ester, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, alkyd resin, aromatic sulfonamide resin, urea resin, melamine resin, and benzoguanamine resin. When such a pigment resin is employed, a pigment obtained by previously kneading a fluorescent dye as described above into the resin may be employed.

  The binder resin is preferably a transparent material. Examples thereof include transparent resins (polymers) such as polymethyl methacrylate, polyacrylate, polycarbonate, polyvinyl alcohol, polyvinyl pyrrolidone, hydroxyethyl cellulose, and carboxymethyl cellulose.

In addition, when the wavelength conversion layer 6 is separately disposed in a plane, a photosensitive resin to which a photolithography method can be applied is also selected. That is, this is a case where the wavelength conversion layer 6 disperses and arranges wavelength conversion members for different wavelengths and expresses an arbitrary color as an additional color or configures a display.
As the binder resin material suitably employed in such a configuration, for example, a photocurable resist material having a reactive vinyl group such as an acrylic acid type, a methacrylic acid type, a polyvinyl cinnamate type, and a ring rubber type can be cited. It is done.

  Further, when the wavelength conversion layer 6 is configured by providing a plurality of wavelength changing members using a printing method, printing ink (medium) using a transparent resin is selected. For example, polyvinyl chloride resin, melamine resin, phenol resin, alkyd resin, epoxy resin, polyurethane resin, polyester resin, maleic acid resin, polyamide resin monomer, oligomer, polymer, polymethyl methacrylate, polyacrylate, polycarbonate, polyvinyl alcohol Transparent resins such as polyvinyl pyrrolidone, hydroxyethyl cellulose, and carboxymethyl cellulose can be used.

  When the wavelength conversion layer 6 is mainly composed of a fluorescent dye, the film is formed by vacuum deposition or sputtering through a desired wavelength conversion layer 6 pattern mask. In the case of a fluorescent dye and a resin, the fluorescent dye, the resin and a suitable solvent are mixed, dispersed or solubilized to form a liquid, and formed into a film by a method such as spin coating, roll coating, or casting, and photolithography Generally, patterning is performed with a desired wavelength conversion layer pattern, or patterning is performed with a desired wavelength conversion layer pattern by a method such as screen printing.

  The above-mentioned fluorescent dyes, pigments, and binder resins may be used alone or in combination as necessary.

The film thickness of the wavelength conversion layer 6 is not limited as long as it does not interfere with the function of generating fluorescence by sufficiently receiving (absorbing) the light emitted from the organic EL element, but it is 10 nm to 1 mm, preferably 1 μm to 500 μm, More preferably, the thickness is 10 μm to 100 μm.
Fluorescent dyes are more sensitive to concentration than color filter dyes, and are more fluorescent when dispersed or solubilized in pigment resin or binder resin at a lower concentration, but on the other hand, they fully absorb the light emitted from organic EL element 1 Therefore, the same level of absorbance as the color filter is required. Therefore, if the light absorption coefficient of the dye is made constant according to Lambert-Beer's law (Equation 1) below, the wavelength conversion layer 6 is preferably a thick film.
The concentration of the fluorescent dye in the wavelength conversion layer 6 including the pigment resin and / or the binder resin varies depending on the fluorescent dye, but is 1 to 10 ⁻⁴ mol / kg, preferably 0.1 to 10 ⁻³ mol / kg, More preferably, it is 0.05-10 ^<-2 > mol / kg.

Lambert-Beer's Law A = εcl (Equation 1)
A: Absorbance ε: Absorption coefficient (specific to dye)
c: Dye concentration l: Film thickness

  In order to flatten the unevenness of the surface of the wavelength conversion layer 6 on the organic layer side, it is advantageous to make the thickness of each wavelength conversion layer 6 uniform. The thickness is preferably 10 μm or more.

Note that the wavelength conversion layer 6 that emits red light emits fluorescence that is shifted to a longer wavelength side from the wavelength of the light emitting member (has a large Stokes shift), and therefore generally includes a mixture of a plurality of types of fluorescent dyes. Therefore, the concentration of the fluorescent dye increases. Therefore, as described above, the film thickness of the red wavelength conversion layer is increased in order to sufficiently absorb the light emission of the light emitting member and enhance the fluorescence. Therefore, when the wavelength conversion layer 6 that emits red is provided, a part or all of the wavelength conversion layer 6 may be embedded in an adjacent layer (such as the transparent substrate 9 in FIG. 1). Since the wavelength conversion layer 6 that emits another color may be provided on the light extraction side with respect to the wavelength conversion layer 6, part or all of the wavelength conversion layer 6 may be embedded in another member such as a substrate. Of course.
Next, the organic layer 3 will be described.

<Organic layer 3>
The organic layer 3 is a layer containing an organic light emitting material that is provided between the transparent electrode 4 and the back electrode 2 and emits light when a voltage is applied to both electrodes, and is a known layer in a known organic EL element. What is necessary is just to make it a layer of a structure and a well-known material, and it can manufacture with a well-known manufacturing method. The emission wavelength is designed to be light having a wavelength that is transmitted through the two-dimensional photonic crystal layer 5 for the reason described above.

The organic layer 3 only needs to realize at least the following functions. The organic layer 3 may have a laminated structure, and each layer may have any of the functions, or the following functions may be realized by a single layer.
-Electron injection function Function to inject electrons from the electrode (cathode). Electron injection.
-Hole injection function A function for injecting holes (holes) from the electrode (anode). Hole injection property.
-Carrier transport function A function to transport at least one of electrons and holes. Carrier transportability.
The function of transporting electrons is called an electron transport function (electron transportability), and the function of transporting holes is called a hole transport function (hole transportability).
-Luminescence function A function that emits light when returning to the ground state by recombining injected and transported electrons and carriers to generate excitons (in an excited state).

  When the transparent electrode 4 is used as an anode, the organic layer 3 may be configured by providing layers in the order of a hole injection / transport layer, a light emitting layer, and an electron injection / transport layer from the transparent electrode 4 side, for example.

  The hole injecting and transporting layer is a layer that transports holes from the anode to the light emitting layer. Examples of the material for forming the hole transport layer include metal phthalocyanines such as copper phthalocyanine and tetra (t-butyl) copper phthalocyanine and metal-free phthalocyanines, quinacridone compounds, 1,1-bis (4-di-p- Tolylaminophenyl) cyclohexane, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-biphenyl-4,4′-diamine, N, N′-di (1-naphthyl) ) -N, N'-diphenyl-1, 1'-biphenyl-4, 4'-diamine and other low molecular weight materials such as polyamines, polyaniline and other high molecular weight materials, polythiophene oligomer materials, etc. Of hole transport materials.

  The light-emitting layer is a layer that emits light when the holes transported from the anode side and the electrons transported from the cathode side are recombined to be in an excited state and return from the excited state to the ground state. As the material of the light emitting layer, a fluorescent material or a phosphorescent material can be employed. Further, a dopant (fluorescent material or phosphorescent material) may be contained in the host material.

  Examples of the material for forming the light emitting layer include 9,10-diallylanthracene derivative, pyrene derivative, coronene derivative, perylene derivative, rubrene derivative, 1,1,4,4-tetraphenylbutadiene, tris (8-quinolinola). -To) aluminum complex, tris (4-methyl-8-quinolinolato) aluminum complex, bis (8-quinolinolato) zinc complex, tris (4-methyl-5-trifluoromethyl-8-quinolinolato) Aluminum complex, tris (4-methyl-5-cyano-8-quinolinolato) aluminum complex, bis (2-methyl-5-trifluoromethyl-8-quinolinolato) [4- (4-cyanophenyl) phenola -To] aluminum complex, bis (2-methyl-5-cyano-8-quinolinolato) [4- (4-cyanophen L) phenolate] aluminum complex, tris (8-quinolinolato) scandium complex, bis [8- (para-tosyl) aminoquinoline] zinc complex and cadmium complex, 1,2,3,4-tetraphenylcyclopentadiene , Pentaphenylcyclopentadiene, poly-2,5-diheptyloxy-para-phenylene vinylene, coumarin phosphor, perylene phosphor, pyran phosphor, anthrone phosphor, porphyrin phosphor, quinacridone phosphor Low molecular weight materials such as N, N'-dialkyl-substituted quinacridone phosphor, naphthalimide phosphor, N, N'-diaryl-substituted pyrrolopyrrole phosphor, polyfluorene, polyparaphenylene vinylene, polythiophene Other existing light emitting materials can be used. In the case of adopting a host / guest type configuration, a host and a guest (dopant) may be appropriately selected from these materials.

  The light emitting layer may be designed to emit light having a wavelength that is transmitted through the two-dimensional photonic crystal layer 5 by using one or a plurality of materials as described above.

  The electron injection / transport layer is a layer that transports electrons from the cathode (back electrode 2 in this example) to the light emitting layer. Examples of the material for forming the electron transport layer include 2- (4-bifinylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazol, 2,5-bis (1-naphthyl). ) -1,3,4-oxadiazol and oxadiazol derivatives, bis (10-hydroxybenzo [h] quinolinolato) beryllium complexes, triazole compounds and the like.

It should be noted that the organic layer 3 can naturally be provided with a layer that can be employed as a known organic electroluminescence layer, such as a buffer layer, a hole blocking layer, an electron injection layer, and a hole injection layer. These layers can also be provided by a known production method using a known material. For example, the electron injecting and transporting layer may be laminated by separating the function into an electron injecting layer responsible for the electron injecting function and an electron transporting layer responsible for the electron transport function. The material constituting each of these layers may be appropriately selected from known materials according to the function of each layer, and may be selected from the materials for forming the electron injecting and transporting layer described above.
Next, the transparent electrode 4 and the back electrode 2 will be described together.

<electrode>
One of the transparent electrode 4 and the back electrode 2 functions as an anode, and the other functions as a cathode. In the present embodiment, any electrode may be an anode (a cathode). First, the anode will be described.

(anode)
The anode is an electrode that injects holes into the organic layer 3.
The material for forming the anode may be any material that imparts the above-described properties to the anode. Generally, a known material such as a metal, an alloy, an electrically conductive compound, or a mixture thereof is selected and contacted with the anode ( The work function of the (surface) is 4 eV or more.

Examples of the material for forming the anode include the following.
Metal oxides and metal nitrides such as ITO (indium-tin-oxide), IZO (indium-zinc-oxide), tin oxide, zinc oxide, zinc aluminum oxide, titanium nitride;
Metals such as gold, platinum, silver, copper, aluminum, nickel, cobalt, lead, chromium, molybdenum, tungsten, tantalum, niobium;
These metal alloys and copper iodide alloys,
Conductive polymers such as polyaniline, polythiophene, polypyrrole, polyphenylene vinylene, poly (3-methylthiophene), and polyphenylene sulfide.

  When the transparent electrode 4 is used as an anode, generally, the transmittance for the extracted light is set to be larger than 10%. When extracting light in the visible light region, ITO having high transmittance in the visible light region is preferably used.

When the back electrode 2 is used as an anode, it is preferably configured as a reflective electrode. In this case, among the above materials, a material having the ability to reflect the light extracted to the outside is appropriately selected, and in general, a metal, an alloy, or a metal compound is selected.
Further, the back electrode 2 may be provided with absorption performance in order to prevent contrast and the like and to prevent reflection of external light. In order to give the back electrode 2 the absorption performance, a material that exhibits the absorption performance when the electrode is formed may be appropriately selected from the materials as described above.

  The anode may be formed of only one kind of material as described above, or may be formed by mixing a plurality of materials. Moreover, the multilayer structure which consists of several layers of the same composition or a different composition may be sufficient.

  Although the film thickness of the anode depends on the material used, it is generally in the range of about 5 nm to 1 μm, preferably about 10 nm to 1 μm, more preferably about 10 nm to 500 nm, particularly preferably about 10 nm to 300 nm, desirably 10 nm to 200 nm. Selected.

The anode is formed by a known thin film forming method such as a sputtering method, an ion plating method, a vacuum vapor deposition method, a spin coat method, or an electron beam vapor deposition method using the above-described materials.
The sheet electrical resistance of the anode is preferably set to several hundred Ω / □ or less, more preferably about 5 to 50 Ω / □.

Further, the surface of the anode may be subjected to UV ozone cleaning or plasma cleaning.
In order to suppress the occurrence of short circuits and defects in the organic EL element, the surface roughness may be controlled to 20 nm or less as a mean square value by a method of reducing the particle size or a method of polishing after film formation.

(cathode)
The cathode is an electrode that injects electrons into the organic layer 3 (in the above-described layer configuration, an electron injection transport layer).
As a material for forming the cathode, a metal, an alloy, an electrically conductive compound having a work function of, for example, less than 4.5 eV, generally 4.0 eV or less, typically 3.7 eV or less in order to increase electron injection efficiency, and A mixture of these is employed.

  Examples of the electrode material as described above include lithium, sodium, magnesium, gold, silver, copper, aluminum, indium, calcium, tin, ruthenium, titanium, manganese, chromium, yttrium, aluminum-calcium alloy, and aluminum-lithium alloy. , Aluminum-magnesium alloys, magnesium-silver alloys, magnesium-indium alloys, lithium-indium alloys, sodium-potassium alloys, magnesium / copper mixtures, aluminum / aluminum oxide mixtures, and the like. Moreover, the material employable as a material used for an anode can also be used.

  When the back electrode 2 is a cathode, a material having the ability to reflect the light extracted to the outside is preferably selected from the above materials, and generally a metal, an alloy, or a metal compound is selected. .

  When the transparent electrode 4 is a cathode, generally, the transmittance for extracted light is set to be larger than 10%. For example, a transparent conductive oxide is laminated on an ultra-thin magnesium-silver alloy. An electrode formed by the above method is employed. In this cathode, a buffer layer to which copper phthalocyanine or the like is added is preferably provided between the cathode and the organic layer 3 in order to prevent the light emitting layer from being damaged by plasma when the conductive oxide is sputtered.

  The cathode may be formed of the above materials alone or a plurality of materials. For example, if 5% to 10% of silver or copper is added to magnesium, the oxidation of the cathode can be prevented and the adhesion of the cathode to the organic layer 3 can be improved.

The cathode may have a multilayer structure composed of a plurality of layers having the same composition or different compositions.
For example, the following structure may be used.
In order to prevent oxidation of the cathode, a protective layer made of a corrosion-resistant metal is provided on the portion of the cathode that does not contact the organic layer 3.
For example, silver or aluminum is preferably used as the material for forming the protective layer.

In order to reduce the work function of the cathode, an oxide, fluoride, metal compound or the like having a small work function is inserted into the interface portion between the cathode and the organic layer 3.
For example, a material in which the cathode material is aluminum and lithium fluoride or lithium oxide is inserted in the interface portion is also used.

The cathode can be formed by a known thin film deposition method such as a vacuum deposition method, a sputtering method, an ionization deposition method, an ion plating method, or an electron beam deposition method.
The sheet electrical resistance of the cathode is preferably set to several hundred Ω / □ or less.

<Other layers and components>
In addition to the above, the organic EL element 1 can employ a known layer configuration or material used for a known organic EL element as appropriate. The layers and materials that are preferably employed will be described below.
(Insulating layer)
In order to prevent the transparent electrode 4 and the back electrode 2 from being short-circuited, an insulating layer may be provided on the outer periphery of the organic layer 3.
As a material for forming an insulating layer, a material for forming an insulating portion employed in a known organic EL element can be appropriately employed. As a forming method, a known forming method can be adopted, and for example, a sputtering method, an electron beam evaporation method, a CVD method, or the like can be adopted.

(Auxiliary electrode)
It is naturally possible to provide an auxiliary electrode. The auxiliary electrode is provided so as to be electrically connected to the anode and / or the cathode, and is made of a material having a lower volume resistivity than the electrode to be connected. If the auxiliary electrode is formed of such a material, the volume resistivity of the entire electrode provided with the auxiliary electrode can be reduced, and the maximum difference in the magnitude of the current flowing to each point constituting the organic layer 3 is The size can be reduced compared with the case where no auxiliary electrode is provided.

Examples of the material for forming the auxiliary electrode include tungsten (W), aluminum (Al), copper (Cu), silver (Ag), molybdenum (Mo), tantalum (Ta), gold (Au), and chromium (Cr). , Titanium (Ti), neodymium (Nd), and alloys thereof.
Specific examples of these alloys include alloys such as Mo—W, Ta—W, Ta—Mo, Al—Ta, Al—Ti, Al—Nd, and Al—Zr. Further, as the material of the auxiliary wiring layer, which is a compound of metal and _{silicon, TiSi 2, ZrSi 2, HfSi} 2, VSi 2, NbSi 2, TaSi 2, CrSi 2, WSi 2, CoSi 2, NiSi 2, PtSi Pd ₂ Si and the like are also preferable. Moreover, the structure which laminated | stacked these metals and * silicon compounds, respectively may be sufficient.

The auxiliary electrode may be a single-layer film made of the above materials, but it is also preferable to use two or more types of multilayer films in order to improve the stability of the film. Such a multilayer film can be formed using the above metals or their alloys. For example, in the case of three layers, Ta layer and Cu layer and Ta layer, and Ta layer and Al layer and Ta layer, in the case of two layers, Al layer and Ta layer, Cr layer and Au layer, Cr layer and Al layer, and A combination of an Al layer and a Mo layer can be given.
Here, the stability of the film refers to a property that can maintain a low volume resistivity and is not easily corroded by a liquid or the like used for the treatment during etching. For example, when the auxiliary electrode is made of Cu or Ag, the auxiliary electrode may have a low volume resistivity but may be easily corroded. On the other hand, the stability of the auxiliary electrode is enhanced by laminating a metal with excellent corrosion resistance, such as Ta, Cr, Mo, etc., on the upper and / or lower part of the metal film made of Cu or Ag. be able to.

In general, the thickness of the auxiliary electrode is preferably set to a value within the range of 100 nm to several tens of μm, and more preferably set to a value within the range of 200 nm to 5 μm.
The reason for this is that when the film thickness is less than 100 nm, the resistance value increases, which is not preferable as the auxiliary electrode. On the other hand, when the film thickness exceeds several tens of μm, it becomes difficult to flatten and the organic EL element 1 may be defective. Because there is.

For example, the width of the auxiliary electrode is preferably a value within a range of 2 μm to 1,000 μm, and more preferably a value within a range of 5 μm to 300 μm.
The reason is that if the width is less than 2 μm, the resistance of the auxiliary electrode may be increased. On the other hand, if the width exceeds 100 μm, extraction of light to the outside may be hindered. .

(Protective layer: passivation film, sealing can)
In order to protect the organic layer 3 and the like from the outside air, the organic EL element 1 may be protected by a passivation film or a sealing can.

  The passivation film is a protective layer (sealing layer) provided on the side opposite to the substrate 9 in order to prevent the organic EL element 1 from coming into contact with oxygen or moisture. Examples of the material used for the passivation film include organic polymer materials, inorganic materials, and photocurable resins. The material used for the protective layer may be used alone, Or you may use together. The protective layer may have a single layer structure or a multilayer structure. The thickness of the passivation film may be a thickness that can block moisture and gas from the outside.

  Examples of organic polymer materials include fluorinated resins such as chlorotrifluoroethylene polymer, dichlorodifluoroethylene polymer, a copolymer of chlorotrifluoroethylene polymer and dichlorodifluoroethylene polymer, polymethyl methacrylate Acrylic resins such as polyethylene and polyacrylate, epoxy resins, silicone resins, epoxy silicone resins, polystyrene resins, polyester resins, polycarbonate resins, polyamide resins, polyimide resins, polyamideimide resins, polyparaxylene resins , Polyethylene resin, polyphenylene oxide resin and the like.

  Examples of the inorganic material include polysilazane, diamond thin film, amorphous silica, electrically insulating glass, metal oxide, metal nitride, metal carbonide, metal sulfide and the like.

  The sealing can is a member constituted by a sealing member such as a sealing plate or a sealing container for blocking moisture and oxygen from the outside. The sealing can may be installed only on the electrode side on the back side (the side opposite to the substrate 9) or may cover the entire organic EL element 1. The thickness, the size, the thickness, and the like of the sealing member are not particularly limited as long as the organic EL element 1 can be sealed and external air can be blocked. As a material used for the sealing member, glass, stainless steel, metal (aluminum, etc.), plastic (polychlorotrifluoroethylene, polyester, polycarbonate, etc.), ceramic, etc. can be used.

  When installing the sealing member on the organic EL element 1, a sealing agent (adhesive) may be used as appropriate. When covering the organic EL element 1 whole with a sealing member, you may heat-seal sealing members without using a sealing agent. As the sealant, an ultraviolet curable resin, a thermosetting resin, a two-component curable resin, or the like can be used.

  Note that a moisture absorbent may be inserted into the space between the passivation film or the sealing can and the organic EL element 1. The moisture absorbent is not particularly limited, and specific examples include barium oxide, sodium oxide, potassium oxide, calcium oxide, sodium sulfate, calcium sulfate, magnesium sulfate, phosphorus pentoxide, calcium chloride, magnesium chloride, copper chloride, cesium fluoride. , Niobium fluoride, calcium bromide, vanadium bromide, molecular sieve, zeolite, magnesium oxide and the like.

Further, an inert gas may be enclosed in the passivation film or the sealing can. The inert gas refers to a gas that does not react with the organic EL element 1, and for example, a rare gas such as helium or argon or a nitrogen gas can be employed.
Next, the substrate 9 will be described.

<Substrate 9>
The substrate 9 is a mainly plate-like member that supports the organic EL element 1. The organic EL element 1 is generally manufactured as an organic EL device supported by a substrate 9 because the constituent layers are very thin.

Since the substrate 9 is a member on which the organic EL element 1 is laminated, the substrate 9 preferably has planar smoothness.
Further, when the substrate 9 is on the light extraction side with respect to the organic layer 3, it is transparent to the extracted light. Since the organic EL element 1 is a bottom emission type element, the substrate 9 is transparent, and the plane 90 opposite to the plane in contact with the organic EL element 1 of the substrate 9 is the light extraction surface.

  A known substrate can be used as the substrate 9 as long as it has the above-described performance. In general, a ceramic substrate such as a glass substrate, a silicon substrate, or a quartz substrate, or a plastic substrate is selected. Moreover, the board | substrate etc. which formed metal foil in the metal substrate and the support body are used. Furthermore, a substrate made of a composite sheet in which a plurality of substrates of the same or different types are combined can be used.

In the above example, a bottom emission type organic EL device in which the transparent electrode 4, the organic layer 3, and the back electrode 2 are sequentially laminated on the substrate 9 is shown. However, the substrate 9 is not configured as an organic EL device. Of course, it may be configured as the organic EL element 1 that does not. In this case, the organic EL element 1 may be manufactured without using the substrate 9 from the beginning, or after the organic EL device is manufactured, the substrate 9 is deleted by a known substrate stripping technique such as etching. May be manufactured.
Further, as described above, it may be configured as a top emission type device or a device that extracts light from both sides.

That is, in order to manufacture the bottom emission type organic EL element 1, the transparent electrode 4, the organic layer 3, and the back electrode 2 may be formed on the substrate 9 by using the respective film forming methods described above. In order to manufacture a top emission type organic EL element, the back electrode 2, the organic layer 3, and the transparent electrode 4 may be sequentially formed on the substrate 9.
Next, modified examples of the organic EL element 1 and the organic EL device will be described.

<Modification>
In the organic EL element 1 and the organic EL device described above, the two-dimensional photonic crystal layer 6 may have other functions.
For example, as shown in FIG. 3A, the two-dimensional photonic crystal layer 5 may serve as a transparent substrate 9. That is, the transparent substrate 9 may be provided with a two-dimensional photonic crystal structure by the method described above.
Further, as shown in FIG. 3B, the two-dimensional photonic crystal layer 5 may serve as the transparent electrode 4. That is, the transparent electrode 4 may be provided with a two-dimensional photonic crystal structure by the method described above.

  Moreover, although the said organic EL device may be used as a whole surface light emitting element, such as a backlight and an illuminating device, it is good also as a display which each employ | adopted the said structure for each sub pixel or each pixel.

It is principal part sectional drawing for demonstrating the structure of the organic EL element 1 which concerns on this Embodiment, and an organic EL device. 4 is a diagram for explaining the structure of a two-dimensional photonic crystal layer 5. FIG. It is principal part sectional drawing for demonstrating the other structural example of the organic EL element 1 which concerns on this Embodiment, and an organic EL device.

Explanation of symbols

1: Organic EL element 2: Back electrode 21: First dielectric 22: Second dielectric 3: Organic layer 4: Transparent electrode 5: Two-dimensional photonic crystal layer 6: Wavelength conversion layer 9: Substrate

Claims (4)

An organic electroluminescent element comprising an organic layer that is sandwiched between a pair of electrodes and emits light when a voltage is applied between both electrodes,
In the device, a two-dimensional photonic crystal layer is disposed on the light extraction side of the organic layer, and the wavelength of incident light is longer on a part or the entire surface of the light extraction side than the two-dimensional photonic crystal layer. An organic electroluminescent device comprising a wavelength conversion layer for converting light having a wavelength. The organic electroluminescent device according to claim 1,
2. The organic electroluminescence device according to claim 1, wherein the wavelength conversion layer is formed by arranging two or more members having different wavelengths after changing incident light on the same layer. The organic electroluminescent element according to claim 1 or 2,
The organic electroluminescent element, wherein the two-dimensional photonic crystal layer also has a function as an electrode disposed on the light extraction side of the organic layer. An organic electroluminescent device in which the organic electroluminescent element according to claim 1 or 2 is formed on a transparent substrate,
The organic electroluminescent element is formed on a transparent substrate, and is formed as an element that extracts light emitted from the organic layer from the transparent substrate side to the outside.
The organic electroluminescence device, wherein the two-dimensional photonic crystal layer is provided in the transparent substrate.

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