JP2007172948A - Organic el element and manufacturing method of same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element of a color conversion system and a simple manufacturing method of the same capable of improving the blurring of an image and the deterioration of visibility and having display characteristics for obtaining converted light with high intensity. <P>SOLUTION: The organic EL element includes a transparent electrode, an organic EL layer, and a reflecting electrode sequentially formed on a transparent substrate. The organic EL layer includes at least a light emitting layer, and a surface layer for forming an interface between a carrier mobile color conversion layer and the reflecting electrode. The interface of the transparent electrode and the organic EL layer is flat, and the interface between the reflecting electrode and the surface layer is uneven. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic EL element and a method for manufacturing the same, and in particular, an organic layer in which irregularities for improving image reflection caused by light incident from the outside and reflected in the element are formed on the surface of the organic EL layer. The present invention relates to an EL element and a manufacturing method thereof.

  As an example of a light-emitting element applied to a display device, an organic electroluminescence element (hereinafter referred to as an “organic EL element”) having a thin film laminated structure of an organic compound is known. As for organic EL elements, organic EL elements with a two-layer structure that realize highly efficient light emission were announced in 1987 (see Non-Patent Document 1), and since then, various organic EL elements have been developed. Some of them are starting to be put into practical use.

  In general, an organic EL element has a structure having a transparent electrode on the light extraction side, a reflective electrode, and an organic EL layer sandwiched between the electrodes on a transparent substrate. Since such an organic EL element is usually produced by sequentially laminating a transparent electrode, an organic EL layer, and a reflective electrode on a flat transparent substrate, the surface of each layer is flat. The flat organic EL layer / reflecting electrode forms a mirror surface, and the light emitted from the organic EL layer is reflected by reflecting the light emitted in the opposite direction to the transparent electrode on the light extraction side to the transparent electrode side. There is an effect of increasing the light utilization efficiency. The organic EL layer includes at least a light-emitting layer and usually has a laminated structure of two or more layers, and the total film thickness is as very thin as 200 nm or less. Therefore, when light enters the element from the outside, the light easily passes through the organic EL layer. As a result, there is a problem that external light transmitted through the organic EL layer is mirror-reflected (regular reflection) at the organic EL layer / reflecting electrode interface which is a mirror surface, and an image is reflected. In addition, there is a problem that the external light reflected by the mirror returns to the transparent electrode side and the visibility on the display surface is lowered.

  As one of the methods for solving the deterioration of display characteristics caused by reflection of light from the outside by the reflection electrode in the element, an antireflection film such as a scattering plate is provided on the front surface of the display surface to There is a method of suppressing incidence and reflection of an image. However, according to such a method, the light emitted from the organic EL layer is also scattered by the scattering plate, and the display image tends to be blurred.

  Recently, there has been an increasing demand for organic EL elements that emit white light. Attempts have been made to use a light-emitting layer serving as a carrier recombination center in an organic EL element as a layer in which a plurality of light-emitting dyes are mixed or a plurality of layers containing different light-emitting dyes (Non-Patent Document 2). And 3, and Patent Documents 1 and 2). In these elements, by balancing the carriers injected from the cathode and the anode, a plurality of light-emitting dyes contained in the light-emitting layer are simultaneously excited to obtain white light from the substrate surface.

  However, if the concentration of the plurality of luminescent dyes is not optimized, energy transfer from a luminescent dye having a high excitation energy to a luminescent dye having a low excitation energy may occur, and a pure white color may not be obtained. . In addition, the concentration of red and blue light emitting dopants necessary for exhibiting good EL light emission characteristics is very low, 0.12% and 0.25% of the host material, which is difficult to control in mass production. is there. Furthermore, even if the initial light emission is pure white, the balance of energy transfer between the light emitting dyes in the light emitting layer is lost due to the magnitude of the energization current or the energization time, and the emission color often changes.

  In recent years, as an example of a multi-color or full-color display method for a display composed of organic EL elements, it absorbs near-ultraviolet light, blue light, blue-green light or white light emitted from the organic EL elements, A color conversion (CCM) method using a color conversion layer including a color conversion dye that emits light in the visible light region by performing wavelength distribution conversion has been studied. For example, green and red light can be obtained by wavelength distribution conversion by applying a color conversion layer to an organic EL element that emits blue or blue-green light.

Japanese Patent No. 2991450 JP 2000-243563 A JP 2003-243152 A JP 2001-74919 A JP 2004-115441 A JP 2003-212875 A JP 2003-238516 A JP 2003-81924 A International Publication No. 2003/048268 Pamphlet C. W. Tang, S. A. Van Slyke, Appl. Phys. Lett., 51, 913 (1987) J. Kido et al., Science 267, 1332 (1995) J. Kido et al., Appl. Phys. Lett. 67 (16) 2281-2283, 1995

  In view of the current situation, methods for improving the reflection of an image without causing blurring of a display image have been studied. In the field of display elements, several methods for forming an uneven surface that can scatter light incident on the element from the outside are known. For example, as a method of forming irregularities on the reflective electrode surface of the organic EL element, a photosensitive material is provided on the substrate, and the irregularities are formed on the substrate surface by patterning them into an irregular shape by photomask exposure and development, A method of sequentially laminating a transparent electrode, an organic EL layer, and a reflective electrode is known (see Patent Document 3). However, the above-described method is complicated because an independent process for forming irregularities on the substrate is required.

  As another method of forming an uneven surface, beads are arranged so as to form an uneven surface on a substrate, and these are fixed with a curable binder such as glass, resin, or metal oxide, and then a curable material is used as a mold. There is a method of forming a scatterer having an uneven surface by injecting (see Patent Document 4). However, since the above-described method also has a large number of steps and is complicated, a simpler method is desired.

  In the above-described method, in addition to the complexity of the process, since the unevenness is formed on the substrate itself, all layers such as the transparent electrode, the organic EL layer, and the reflective electrode that are sequentially stacked on the substrate are formed unevenly. Will be. If the flatness of each layer is impaired, the film thickness of each layer becomes non-uniform, resulting in variations in characteristics, and problems such as leakage and short-circuiting are likely to occur, and the reliability of the organic EL element may be reduced. . Therefore, there is a demand for an organic EL element capable of realizing excellent display characteristics without reducing the reliability of the organic EL element and a simple method for manufacturing the organic EL element.

  On the other hand, when the color conversion method is used, there is usually a problem of how much light is incident on the color conversion layer provided outside the organic EL element. That is, since light emitted from the organic EL layer is emitted in all directions, a part of the emitted light is totally reflected on the surface of the transparent substrate and propagates in the horizontal direction inside the transparent substrate, and does not enter the color conversion layer. There is a problem. In addition, in the case of a display device having a plurality of independent light emitting portions and a plurality of types of color conversion layers, the light transmitted in the horizontal direction is incident on another adjacent color conversion layer and desired. There is a possibility that a phenomenon called “crosstalk” that emits light of a color that is not performed occurs. Organic EL element An organic EL element structure is desired that allows light from the organic EL layer to efficiently enter the color conversion layer and obtain converted light having high converted light intensity.

  Accordingly, an object of the present invention is to provide an organic EL element of a color conversion system having excellent display characteristics that can improve image reflection and visibility reduction and obtain high intensity converted light, and manufacture such an element. It is to provide a simple method for doing this.

  In order to scatter light incident from the outside in order to solve the above-described problems, the interface of the organic EL layer / reflecting electrode as a reflective surface may be uneven, and the other layers of the organic EL layer are as flat as possible. It is desirable. As a result of intensive studies on an organic EL element having a concavo-convex structure for suppressing reflection and a manufacturing method thereof, the present inventors have determined the pressure during vapor deposition when forming an organic EL layer by vapor-depositing an organic material. It has been found that a good uneven surface can be easily obtained by adjusting or using a cohesive material.

  In addition, by providing a color conversion function to the layers other than the light emitting layer constituting the organic EL layer, it has been found that the light from the light emitting layer is efficiently color converted, and color converted light having high intensity can be obtained. The present invention has been completed.

  According to the present invention, it is possible to realize an organic EL device having excellent display characteristics by improving the problems of reflection due to external light and deterioration of visibility due to scattering by the organic EL layer / metal electrode interface having irregularities. Is possible. Moreover, since the organic EL layer of this invention is formed on the transparent electrode formed on the flat transparent substrate, the lower surface of each layer which comprises an organic EL layer is flat. Therefore, the flatness of each layer constituting the organic EL layer (excluding the surface layer) is not impaired, the thickness of each layer other than the surface layer is uniform, and there is no variation in characteristics. Such a problem does not occur. In addition, by providing the carrier mobility color conversion layer in the organic EL layer, light from the light emitting layer can efficiently enter the carrier mobility color conversion layer, and high converted light intensity can be obtained.

  In particular, when a plurality of independent light emitting portions are formed in the organic EL element of the present invention having an organic EL layer / reflective electrode uneven interface and a carrier-movable color conversion layer, the uneven interface is only scattered by external light. It is effective to increase the apparent optical path length in the device of light emitted from the light emitting layer, increase the amount of light absorbed by the color conversion dye in the carrier mobility color conversion layer, and give higher converted light intensity. is there. In addition, scattering of light from the light emitting layer due to the uneven interface suppresses lateral light propagation in the element (particularly in the transparent substrate), and unintentional light emission from the carrier mobility color conversion layer of the adjacent light emitting portion. This is effective in preventing the occurrence of crosstalk due to.

  As shown in FIG. 1, the organic EL element of the first embodiment of the present invention is an organic EL element that has a transparent electrode 20, an organic EL layer 30, and a reflective electrode 40 in this order on a transparent substrate 10. The organic EL layer 30 includes at least a light emitting layer 33, a carrier mobility color conversion layer, and a surface layer forming an interface with the reflective electrode 40, and the interface between the transparent electrode 20 and the organic EL layer 30 is flat. Thus, the interface between the reflective electrode 40 and the surface layer is uneven. Thus, the interface between the reflective electrode 40 and the organic EL layer 30 is uneven, so that the interface from the outside is inside the element. The incident light is scattered by the concavo-convex surface of the reflective electrode 40, and the reflection of the image and the deterioration of visibility are improved. In addition, since the carrier-moving color conversion layer having the function of color conversion is present in the organic EL layer 30, high converted light intensity is obtained without being affected by light propagation in the lateral direction in the transparent substrate 10. be able to.

  The transparent substrate 10 should be able to withstand the conditions (solvent, temperature, etc.) used to form the layer laminated thereon, and is preferably excellent in dimensional stability. Materials that can be used as the transparent substrate 10 are glass, diacetylcellulose, triacetylcellulose (TAC), propionylcellulose, butyrylcellulose, acetylpropionylcellulose, nitrocellulose, and other cellulose esters; polyamides; polycarbonates; polyethylene terephthalate, polyethylenena Polyester such as phthalate, polybutylene terephthalate, poly-1,4-cyclohexanedimethylene terephthalate, polyethylene-1,2-diphenoxyethane-4,4′-dicarboxylate, polybutylene terephthalate, etc .; polystyrene; polyethylene, polypropylene, poly Polyolefin such as methylpentene; Acrylic resin such as polymethyl methacrylate; Polycarbonate; Polysulfone; Polyether sulfone; polyether ketone; polyetherimides; may be a polymer material such as norbornene resins; polyoxyethylene. When a polymer material is used, the transparent substrate 10 may be rigid or flexible. The transparent substrate 10 preferably has a transmittance of 80% or more with respect to visible light, and more preferably has a transmittance of 86% or more.

  The transparent electrode 20 desirably has a transmittance of 80% or more at a wavelength of 380 to 780 nm, which is a visible light region, in order to be on the light extraction side. The transparent electrode 20 is made of IZO (In—Zn oxide), ITO (In—Sn oxide), Sn oxide, In oxide, Zn oxide, Zn—Al oxide, Zn—Ga oxide, or these It can be formed using a conductive transparent metal oxide in which a dopant such as F or Sb is added to the oxide. In the present invention, it is desirable to use the transparent electrode 20 as an anode. Further, when the organic EL element is used as a display, the transparent electrode 20 may be composed of a plurality of partial electrodes.

  The organic EL layer 30 includes at least a light emitting layer, and includes a hole injection layer, a hole transport layer, an electron transport layer, and / or an electron injection layer as necessary. The hole injection layer and the hole transport layer have a function of transmitting holes injected from the anode to the light emitting layer and blocking the movement of electrons from the light emitting layer. The electron injection layer and the electron transport layer have a function of transmitting electrons injected from the cathode to the light emitting layer. That is, by interposing a hole injection layer and / or a hole transport layer between the light emitting layer and the anode, many carriers are injected into the light emitting layer with a lower electric field, and injected carriers (holes and electrons). ) Accumulate and recombine at the hole injection layer or the interface between the hole transport layer and the light emitting layer to emit light, and as a result, the light emission efficiency is improved.

  The organic EL layer 30 of the present invention includes at least one layer that functions as a carrier mobility color conversion layer among a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer. FIG. 2 shows an example of an organic EL layer 30 having a five-layer structure of hole injection layer 31 / hole transport layer 32 / light emitting layer 33 / electron transport layer 34 / electron injection layer 35. In the configuration of FIG. 2, any of the hole injection layer 31, the hole transport layer 32, the electron transport layer 34, and the electron injection layer 35 is a carrier mobility color conversion layer containing a color conversion dye. In the present invention, it is desirable to use the hole injection layer 31 as a carrier mobility color conversion layer.

In addition to the configuration shown in FIG. 2, the organic EL layer 30 can have the following configuration, for example.
(1) Anode / hole injection layer / light emitting layer / electron injection layer / cathode (2) Anode / hole transport layer / light emitting layer / electron injection layer / cathode (3) Anode / hole injection layer / light emitting layer / electron Transport layer / cathode (4) Anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode (5) Anode / hole injection layer / hole transport layer / light emitting layer / electron injection layer / cathode (In the present invention, the anode is preferably the transparent electrode 20 and the cathode is the reflective electrode 40)

  The surface layer which forms the interface with the reflective electrode of the organic EL layer 30 of the present invention has an uneven upper surface. Since the surface layer of the organic EL layer becomes the base layer of the reflective electrode, the unevenness of the surface layer is reflected on the reflective electrode, and a fine concavo-convex structure is formed. In the organic EL device of the present invention, it is desirable to use the reflective electrode 40 as a cathode. Therefore, the surface layer that forms the interface between the reflective electrode 40 and the organic EL layer 30 is preferably the electron injection layer 35 or the electron transport layer 34.

  By adopting such a configuration, the organic EL layer 30 of the present invention is formed on the transparent electrode 20 formed on the flat transparent substrate 10, so that the lower surface of each layer constituting the organic EL layer 30 is flat. It is. Therefore, the flatness of each layer (excluding the surface layer) constituting the organic EL layer 30 is not impaired, the thickness of each layer is uniform, the characteristic does not vary, and there is a problem of leakage or short circuit. It does not occur. Further, by providing the carrier mobility color conversion layer in the organic EL layer 30, the light from the light emitting layer 33 efficiently enters the carrier mobility color conversion layer and is formed on the organic EL layer 30 / reflecting electrode 40. By increasing the apparent optical path length in the device of light emitted from the light emitting layer by the uneven surface formed, and increasing the amount of light absorbed by the color conversion dye in the carrier mobility color conversion layer, high converted light intensity can be obtained. It becomes possible to obtain.

Below, each layer which comprises the organic EL layer 30 is described. The light emitting layer 33 is a layer that emits light by recombination of carriers (holes and electrons) injected by applying a voltage to the transparent electrode 20 and the reflective electrode 40. The material of the light emitting layer 33 can be selected according to a desired color tone. For example, in order to obtain blue to blue-green light emission, fluorescent whitening agents such as benzothiazole, benzimidazole, and benzoxazole, metal chelated oxonium compounds, styrylbenzene compounds, aromatic dimethylidin compounds, etc. Can be used. More specifically, 4,4′-bis (2,2-diphenylvinyl) biphenyl (DPVBi) can be mentioned. In addition, in order to obtain light emission in various wavelength ranges, a host compound (distyrylarylene compound, 4,4′-bis [N- (3-tolyl) -N-phenylamino] biphenyl (TPD), aluminum complex (for example, Tris (8-hydroxyquinolinato) aluminum complex (Alq ₃ , etc.) added with a dopant (perylene, quinacridones, rubrene, etc.) can also be used.

  When the hole injection layer 31 or the hole transport layer 32 is used as a carrier mobility color conversion layer, these layers contain a host material and one or more color conversion dyes. The host material is a material that performs the function of carrier injection and / or movement in the carrier mobility color conversion layer. When the carrier mobility color conversion layer is used as a hole injection layer or a hole transport layer, a high molecular weight perylene hole transport material such as BAPP, BABP, CzPP, CzBP or the like can be used (see Patent Document 5). . Alternatively, a fluorescent material having a hole transporting property, an azaaromatic compound having an azafluoranthene skeleton bonded with an arylamino group (see Patent Document 6), a condensed aromatic compound having a fluoranthene skeleton bonded to an amino group (See Patent Document 7), a triphenylene aromatic compound having an amino group (see Patent Document 8), or a perylene-type aromatic compound having an amino group (see Patent Document 9) can also be used as a host material.

  The color conversion dye is a dye that absorbs light (incident light) emitted from the light emitting layer and performs wavelength distribution conversion to emit light (converted light) having a different wavelength distribution. As the color conversion dye in the present invention, a dye that absorbs light in the blue to blue-green region and emits red light or green light can be used. As a color conversion dye that absorbs light in the blue to blue-green region and emits red light, 4-dicyanomethylene-2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (DCM-1, I) , Dicyanine dyes such as DCM-2 (II) and DCJTB (III); 1-ethyl-2- (4- (p-dimethylaminophenyl) -1,3-butadienyl) -pyridium-perchlorate (pyridine 1) Pyridine-based materials such as: rhodamine-based xanthene-based materials; oxazine-based materials; coumarin-based pigments; acridine pigments; other condensed aromatic ring materials (diketopyrrolo [3,4-c] pyrrole derivatives, Such as fused benzimidazole compounds, porphyrin derivative compounds, quinacridone compounds, bis (aminostyryl) naphthalene compounds ) Can be utilized.

  Examples of color conversion dyes that absorb green light and emit green light include 3- (2′-benzothiazolyl) -7-diethylamino-coumarin (coumarin 6) and 3- (2′-benzoimidazolyl). ) -7-diethylamino-coumarin (coumarin 7), 3- (2′-N-methylbenzimidazolyl) -7-diethylamino-coumarin (coumarin 30), 2,3,5,6-1H, 4H-tetrahydro-8- Coumarin dyes such as trifluoromethylquinolidine (9,9a, 1-gh) coumarin (coumarin 153), or basic yellow 51 which is a coumarin dye dye, and naphthalimides such as solvent yellow 11 and solvent yellow 116 Contains pigments.

  In the carrier mobility color conversion layer of the present invention, a plurality of types of color conversion dyes may be used. For example, a dye that absorbs light in the blue to blue-green region to emit red light (first dye) and a pigment that absorbs light in the blue to blue-green region to emit green light (second dye) are used in combination. First, the second dye absorbs light in the blue to blue-green region, then the energy is transferred to the first dye by energy transfer or absorption by the first dye of light emission from the second dye, and finally the first dye is transferred. You may make it the structure which takes out the red light emitted from 1 pigment | dye outside. By adopting such a configuration, it is possible to maintain the obtained converted light intensity while increasing the difference between the absorption wavelength range and the emission wavelength range. The carrier mobility color conversion layer has a film thickness in the range of 100 nm to 1 μm, more preferably 150 nm to 600 nm, depending on the desired carrier mobility and converted light intensity.

  When the hole injection layer 31 and the hole transport layer 32 are not used as the carrier mobility color conversion layer, the materials thereof are not particularly limited, and those layers can be formed using known materials. For example, the hole injection layer 31 can be formed using phthalocyanines (such as copper phthalocyanine (CuPc)) or indanthrene compounds. Further, the hole transport layer 32 is formed of, for example, TPD, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (α-NPD), 4,4 ′, 4 ″ -tris ( Triarylamine materials such as N-3-tolyl-N-phenylamino) triphenylamine (m-MTDATA), N, N, N ′, N′-tetrabiphenyl-4,4′-biphenylenediamine (TBPB) Can be formed using.

When the electron transport layer 34 and the electron injection layer 35 are used as a carrier mobility color conversion layer, these layers are formed of a host material and one or more kinds of materials, like the hole injection layer 31 and the hole transport layer 32. A color conversion dye. As the color conversion dye, the same dye as in the hole injection layer 31 and the hole transport layer 32 can be used. As the host material, Znsq ₂ or the like can be used.

When the electron transport layer 34 and the electron injection layer 35 are not used as the carrier mobility color conversion layer, those materials are not particularly limited, and known materials can be used. For example, the electron transport layer 34 may include an oxadiazole derivative such as 2- (4-biphenyl) -5- (pt-butylphenyl) -1,3,4-oxadiazole (PBD), a triazole derivative, Triazine derivatives, phenylquinoxalines, quinolinol complexes of aluminum (eg, Alq ₃ ), and the like can be used. The electron injection layer 35 can be formed using an alkali metal or alkaline earth metal such as Li, Cs, Mg, or Ca, or a fluoride or oxide of these metals.

Alternatively, the electron transport layer 34 or the electron injection layer 35 that becomes the surface layer of the organic EL layer 30 can be formed using a coherent material. The cohesive material in the present invention is preferably a material having a planar structure with a low molecular weight (molecular weight of 600 or less). This is because such a material easily aggregates and can easily provide an uneven surface. Examples of the cohesive material that can be used in the present invention include F ₄ -TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane), F ₄ DCNQI (N, N′-dicyano-2,3,5,6-tetrafluoro-1,4-quinonediimine), Cl ₂ DCNQI (N, N′-dicyano-2,5-dichloro-1,4-quinonediimine), Cl ₂ F ₂ DCNQI (N, N′-dicyano-2,5-dichloro-3,6-difluoro-1,4-quinonediimine), F ₆ DCNNQI (N, N′-dicyano-2,3,5,6,7, 8-hexafluoro-1,4-naphthoquinone diimine), CN ₄ TTAQ (1,4,5,8-tetrahydro-1,4,5,8-tetrathia-2,3,6,7-tetracyanoanthraquinone) Etc. Rukoto can. Although the mechanism of action may vary depending on the material used, it is considered that the electron injection property from the reflective electrode 40 is improved by improving the adhesion between the organic EL layer 30 and the reflective electrode 40 or the tunnel effect. When the electron transport layer 34 or the electron injection layer 35 is formed using a coherent material, the electron transport layer 34 or the electron injection layer 35 has a film thickness (irregularity of 0.1 to 5 nm, preferably 0.1 to 0.2 nm. The average thickness and the average height of the film do not coincide with each other because of the structure, but the “film thickness” in the present invention means an average thickness related to the substrate surface).

  In the present invention, the reflective electrode 40 is desirably used as a cathode. In consideration of use as a cathode, the reflective electrode 40 is preferably formed of a metal and an alloy having a work function of less than 4.8 eV. For example, Al, Ag, Mg, Mn, or an alloy containing these metals (AlLi, MgAg, etc.) is preferable. A laminated electrode such as alkali metal fluoride or alkaline earth metal fluoride / metal (for example, LiF / Al) can also be used. Further, when the organic EL element is used as a display, the reflective electrode 40 may be composed of a plurality of partial electrodes.

  The reflective electrode 40 used in the present invention has a fine uneven structure reflecting the unevenness of the surface layer formed when the organic EL layer 30 is formed. Since the surface of the reflective electrode 40 serving as the reflective surface is uneven, it is possible to scatter light incident on the element from the outside, and to improve phenomena such as image reflection and a decrease in visibility. Is possible.

  The organic EL device manufacturing method according to the second embodiment of the present invention includes: a step of forming a transparent electrode 20 on a transparent substrate 10; a light emitting layer 33 and a carrier mobility color conversion layer on the transparent electrode 20; And a step of forming an organic EL layer 30 having at least an irregular surface on the upper surface of the surface layer; and a step of forming a reflective electrode on the organic EL layer 30. In forming the surface layer of the organic EL layer 30, after depositing the organic material in the vacuum deposition apparatus at the first pressure, an inert gas is introduced into the vacuum deposition apparatus to reduce the internal pressure of the apparatus to the second pressure. And then reducing the pressure in the vacuum deposition apparatus to the first pressure again to form irregularities in the surface layer.

  According to the production method of the present invention, the surface layer of the organic EL layer that contacts the reflective electrode to form an interface (that is, the uppermost layer of the organic EL layer composed of a plurality of constituent layers, preferably an electron transport layer or an electron injection layer). It is possible to form irregularities by simply adjusting the pressure in the vacuum deposition apparatus. That is, according to the present invention, in order to form irregularities on the surface of the reflective electrode, it is not necessary to previously treat the substrate surface as in the conventional method. In addition, since the transparent electrode and the organic EL layer are laminated on a substrate having a flat surface, the interface between the transparent electrode and the organic EL layer and the lower surface of each component layer of the organic EL layer are flat, and each layer other than the surface layer The film thickness is uniform and there is no variation in characteristics. Therefore, it is possible to manufacture a highly reliable organic EL element that does not cause problems such as leakage and short circuit.

  The first step of the production method of the present invention is a step of forming the transparent electrode 20 on the transparent substrate 10. The formation of the transparent electrode 20 is performed using a vapor deposition method, a sputtering method, or a chemical vapor deposition (CVD) method, preferably a sputtering method. In addition, when it is desired to form the transparent electrode 20 from a plurality of partial electrodes when used as a display of an organic EL element, a conductive transparent metal oxide is uniformly formed over the entire surface, and then desired. Etching may be performed so as to give a pattern of the transparent electrode 20 formed of a plurality of partial electrodes. Or you may form the transparent electrode 20 which consists of a some partial electrode using the mask which gives a desired shape. Alternatively, patterning can be performed by applying a lift-off method.

The second step of the production method of the present invention includes at least a light emitting layer 33, a carrier mobility color conversion layer, and a surface layer forming an interface with the reflective electrode on the transparent electrode 20, and the upper surface of the surface layer is This is a step of forming the organic EL layer 30 that is uneven. In this step, the materials of the constituent layers of the hole injection layer 31, the hole transport layer 32, the light emitting layer 33, the electron transport layer 34, and / or the electron injection layer 35 are deposited by vapor deposition according to the desired configuration. It is carried out. Either resistance heating evaporation method or electron beam heating evaporation method may be used. The formation of each constituent layer is usually performed under a pressure of 1 × 10 ⁻⁴ Pa or less, preferably 5 × 10 ⁻⁵ Pa or less, more preferably 1 × 10 ⁻⁵ Pa or less.

  The layer formed as the carrier mobility color conversion layer may be formed by a vapor deposition method using a mixture in which a host material and a color conversion dye are mixed in advance at a predetermined ratio as a single vapor deposition source, or Alternatively, the host material and the color conversion dye may be used as a plurality of vapor deposition sources that are independently heated, and may be formed by a co-vapor deposition method at a desired film formation rate ratio.

Furthermore, the uppermost layer of the organic EL layer, that is, the surface layer is formed by setting the pressure in the vacuum vapor deposition apparatus at the start of film formation to the first pressure, and supplying an inert gas into the vacuum vapor deposition apparatus during the film formation. This is carried out by introducing the pressure inside the apparatus to the second pressure and then reducing the pressure inside the vacuum deposition apparatus to the first pressure again. The first pressure is usually 1 × 10 ⁻⁴ Pa or less, preferably 5 × 10 ⁻⁵ Pa or less, more preferably 1 × 10 ⁻⁵ Pa or less. On the other hand, the second pressure is usually within a range of 0.1 Pa to 10 Pa, preferably 0.5 Pa to 5 Pa, more preferably 0.8 Pa to 2 Pa. The surface layer formed in this process is desirably the electron transport layer 34 or the electron injection layer 35.

  The vapor deposition particles flying from the vapor deposition source to the film formation surface reach the film formation surface without being subjected to molecular collision under low pressure conditions, and are deposited in an amorphous state. Although not intending to be bound by any theory, it is considered that when the pressure is increased during the vapor deposition, the collision probability of the vapor deposition particles increases, and the vapor deposition particles are brought into an aggregated state due to the collision. In this state, the pressure is lowered again to reduce the collision probability of the vapor deposition particles during the flight, so that the vapor deposition particles in the aggregated state reach the film formation surface and become fine particles, thereby making the surface uneven. . That is, the surface layer material is deposited in an amorphous state under a first pressure (low pressure condition) to become a flat layer, but is deposited in a fine particle state by applying the second pressure (high pressure condition). As a result, irregularities are formed. By setting the second pressure, which is a high-pressure condition, within the above-described range, the surface layer material is deposited in a sufficiently finely divided state without causing coarse particles so as to cause a short circuit and a leak. Desired irregularities capable of reflecting incident light can be obtained.

Here, as the inert gas, N ₂ or a rare gas such as He, Ne, Ar, or Xe can be used. The pressure increase from the first pressure to the second pressure due to the introduction of the inert gas is usually performed over a period of 1 to 10 seconds, preferably 1 to 5 seconds. Once the predetermined second pressure is reached, the introduction of the inert gas is stopped and the pressure drop to the first pressure is started immediately. Alternatively, the vacuum deposition apparatus may be maintained at the second pressure for a period of 1 to 20 seconds, preferably 5 to 10 seconds. The pressure drop from the second pressure to the first pressure is usually carried out over a period of 1 to 10 seconds, preferably 1 to 5 seconds.

  If necessary, in order to form a surface layer having a desired uneven shape, the pressure increase from the first pressure to the second pressure and the subsequent pressure decrease to the first pressure are repeated a plurality of times. May be. Alternatively, a desired uneven shape may be formed by applying the above-described pressure change after forming a part of the surface layer flatly by forming the film at the first pressure in the initial stage of the surface layer formation. .

  The 3rd process of the manufacturing method of this invention is a process of forming the reflective electrode 40 on the organic electroluminescent layer 30 containing the surface layer which has an unevenness | corrugation on the upper surface. The reflective electrode 40 is formed by vapor deposition, sputtering, or chemical vapor deposition (CVD), preferably vapor deposition. Further, when it is desired to form the reflective electrode 40 from a plurality of partial electrodes when used as a display of an organic EL element, the plurality of partial electrodes are formed by vapor deposition using a mask that gives a desired shape. A reflective electrode 40 may be formed. Alternatively, a plurality of parts can be obtained by providing a reflective electrode separation partition wall having a reverse tapered cross section before forming the organic EL layer 30, forming the organic EL layer 30 as described above, and depositing the reflective electrode material. A reflective electrode 40 made of an electrode may be formed.

  According to the manufacturing method of the present invention, by applying a pressure change when forming the surface layer of the organic EL layer 30 that forms the interface with the reflective electrode 40, unevenness is formed only on the upper surface of the required organic EL layer. Thus, a fine uneven shape can be imparted to the reflective electrode 40. Therefore, it is possible to form a concavo-convex shape more easily as compared with the conventional concavo-convex forming method, and by forming a flat portion other than the interface of the organic EL layer 30 / reflecting electrode 40, variation in characteristics, leak or short It is possible to prevent the occurrence of failure such as. The concavo-convex shape of the reflective electrode 40 formed in this way makes it possible to scatter light from the outside and suppress problems such as reflection and deterioration of visibility.

  As described above, according to the manufacturing method of the present embodiment, it is possible to form irregularities by adjusting the pressure when forming the surface layer that forms the interface between the organic EL layer and the reflective electrode. Therefore, it is possible to more easily form the unevenness on the reflective electrode as compared with the conventional unevenness forming method. Therefore, it is possible to provide a high-quality organic EL element that scatters light from the outside and suppresses reflection and deterioration of visibility at low cost.

  The organic EL device manufacturing method according to the third embodiment of the present invention includes: a step of forming a transparent electrode 20 on a transparent substrate 10; a light emitting layer 33 and a carrier mobility color conversion layer on the transparent electrode 20; And a step of forming an organic EL layer 30 having at least an irregular surface on the upper surface of the surface layer; and a step of forming a reflective electrode on the organic EL layer 30. In forming the surface layer of the organic EL layer 30, the surface layer of the organic EL layer 30 is formed by depositing a cohesive material to form irregularities on the surface layer. In the manufacturing method of this embodiment, the process similar to the manufacturing method of 2nd Embodiment can be used except formation of the surface layer of an organic EL layer.

The surface layer of the organic EL layer in the present embodiment is usually controlled under heating pressure of 1 × 10 ⁻⁴ Pa or less, preferably 5 × 10 ⁻⁵ Pa or less, more preferably 1 × 10 ⁻⁵ Pa or less. Then, it is formed by depositing an aggregating material such as F ₄ -TCNQ at a film forming speed of 0.05 nm / s or less, preferably 0.01 to 0.001 nm / s. By setting the film forming speed within such a range, it is possible to generate more agglomeration nuclei on the film formation surface, to make the surface layer uneven, and to scatter incident external light.

  As described above, it is possible to form irregularities by depositing a cohesive material on the interface between the organic EL layer and the reflective electrode even by the manufacturing method of the present embodiment, which is compared with the conventional irregularity forming method. Thus, it is possible to more easily form irregularities on the reflective electrode. Therefore, it is possible to provide a high-quality organic EL element that scatters light from the outside and suppresses reflection and deterioration of visibility at low cost.

  The organic EL device of the present invention can be applied to display applications by forming a plurality of independent light emitting portions. One method for forming a plurality of independent light emitting portions is to form the transparent electrode 20 from a plurality of stripe-shaped partial electrodes extending in the first direction and the reflective electrode 40 to have a plurality of stripe-shaped extensions extending in the second direction. A partial electrode is formed, and the first direction and the second direction are crossed, preferably orthogonal. In such a structure, when a voltage is applied to specific partial electrodes of the transparent electrode 20 and the reflective electrode 40, light emission occurs at a position where the partial electrodes intersect, and so-called passive matrix driving is possible. Alternatively, one of the transparent electrode 20 and the reflective electrode 40 is formed from a plurality of partial electrodes, and each of the plurality of partial electrodes is connected to a switching element (such as a TFT) in a one-to-one correspondence. By using the other of 40 as an integrated common electrode, so-called active matrix driving is possible.

  When a plurality of independent light emitting portions are formed in the organic EL element of the present invention having the uneven interface formed on the organic EL layer 30 / reflecting electrode 40 and the carrier mobility color conversion layer, the uneven interface is external light. In addition to scattering of light, the apparent optical path length in the device of light emitted from the light emitting layer is increased, the amount of light absorbed by the color conversion dye in the carrier mobility color conversion layer is increased, and higher converted light intensity is given. It is effective. In addition, scattering of light from the light emitting layer due to the uneven interface suppresses lateral light propagation in the element (particularly in the transparent substrate), and unintentional light emission from the carrier mobility color conversion layer of the adjacent light emitting portion. This is effective in preventing the occurrence of crosstalk due to.

  Furthermore, when an organic EL device having a plurality of independent light emitting portions is applied to a display application, one or more color filter layers that transmit light in a specific wavelength range, and absorb light in a specific wavelength range. One or more color conversion layers that emit light of longer wavelengths, a flattening layer for eliminating the steps caused by the plurality of color filter layers / color conversion layers, and organic by blocking the transmission of moisture or oxygen A layer such as a passivation layer for preventing deterioration of the EL element can be provided as necessary. For example, a laminated structure of color filter layer (and / or color conversion layer) / flattening layer / passivation layer may be provided between the transparent substrate 10 and the transparent electrode 20. Alternatively, a color filter layer and / or a color conversion layer may be provided on the surface of the transparent substrate 10 opposite to the transparent electrode. Alternatively, a filter substrate in which a laminate of a color filter layer (and / or a color conversion layer) / passivation layer is provided on a transparent substrate different from the transparent substrate 10 of the organic EL element, and the organic EL element and the filter substrate are manufactured. May be bonded together to form a display. The color filter layer, color conversion layer, planarization layer, and passivation layer may be formed using any known material.

[Example 1]
In this embodiment, as shown in FIG. 3, a multi-layer structure in which a color filter layer 50, a color conversion layer 60, a planarization layer 70, and a passivation layer 80 are inserted between the transparent substrate 10 and the transparent electrode 20. The present invention relates to an organic EL element for a color display.

  A color mosaic CB-7001 (manufactured by Fuji Film Electronics Materials Co., Ltd.) is applied to a transparent glass substrate 10 having a thickness of 0.7 mm, and patterned using a photolithographic method to have a width of 0.1 mm and a film thickness. A blue color filter layer 50B in which a plurality of stripe-shaped portions extending in the first direction of 1 μm are arranged at a pitch of 0.33 mm was formed.

  Subsequently, coumarin 6 (0.9 parts by weight) was dissolved in 120 parts by weight of propylene glycol monoethyl acetate (PGMEA) as a solvent. 100 parts by weight of the photopolymerizable resin composition “V259PA / P5” (Nippon Steel Chemical Co., Ltd.) was added and dissolved to obtain a coating solution. This coating solution is applied onto the substrate 10 using a spin coating method, and patterned by a photolithographic method. A plurality of stripe-shaped portions extending in the first direction having a width of 0.1 mm and a film thickness of 5 μm have a pitch of 0. A green color conversion layer 60G arranged at .33 mm was formed.

  Further, Coumarin 6 (0.5 part by weight), Rhodamine 6G (0.3 part by weight) and Basic Violet 11 (0.3 part by weight) were added and dissolved in 100 parts by weight of “V259PA / P5” to obtain a coating solution. Got. This coating solution is applied onto the transparent substrate 10 using a spin coating method, and patterned by a photolithographic method. A plurality of stripe-shaped portions extending in the first direction having a width of 0.1 mm and a film thickness of 5 μm are pitched. A red conversion layer 60R arranged at 0.33 mm was formed.

  “V259PA / P5” (Nippon Steel Chemical Co., Ltd.) is applied to the transparent substrate 10 on which the color filter layer 50 and the color conversion layer 60 are formed, and is irradiated with light from a high-pressure mercury lamp. The formation layer 70 was formed. At this time, no deformation occurred in the stripe shapes of the color filter layer 50 and the color conversion layer 60, and the upper surface of the planarizing layer 70 was flat.

  A passivation layer 80 made of a 300 nm thick SiOx film was formed on the planarizing layer 70 by sputtering. The sputtering apparatus used was an RF-brener magnetron, and the target used Si. As a sputtering gas during film formation, a mixed gas of Ar and oxygen was used.

An IZO film was formed on the entire upper surface of the passivation layer 80 by sputtering. Using a DC sputtering apparatus, 100 W electric power was applied using In ₂ O ₃ -10% ZnO as a target in an Ar atmosphere at a pressure of 0.3 Pa. The film formation speed at this time was 0.33 nm / s. Next, patterning is performed by a photolithography method, and further, drying processing (150 ° C.) and UV processing (mercury lamp, room temperature and 150 ° C.) are performed, and the width 0 positioned in each sub-pixel (red, green, and blue). A transparent electrode 20 (anode) composed of a plurality of stripe-shaped partial electrodes extending in the first direction having a thickness of 0.094 mm, a pitch of 0.11 mm, and a thickness of 100 nm was obtained.

Next, the substrate on which the transparent electrode 20 is formed is mounted in a resistance heating vapor deposition apparatus, and the vacuum is broken on the organic EL layer 30 including the hole injection layer 31, the hole transport layer 32, the organic light emitting layer 33, and the electron transport layer 34. The film was formed in sequence without. When forming the hole injection layer 31, the hole transport layer 32 and the organic light emitting layer 33, the internal pressure of the vacuum chamber was reduced to 1 × 10 ⁻⁵ Pa. As the hole injection layer 31, 200 nm of CzPP and DCJTB (5 mass%) was laminated. Therefore, in this embodiment, the hole injection layer 31 is a carrier mobility color conversion layer. As the hole transport layer 32, 20 nm of TBPB was laminated. Then, 40 nm of DPVBi was stacked as the light emitting layer 33.

Subsequently, the electron transport layer 34 that is the surface layer of the organic EL layer 30 in this example was formed. Lamination of Alq ₃ was started at a vacuum chamber internal pressure of 1 × 10 ⁻⁵ Pa. When a film thickness of 20 nm was obtained, N ₂ gas was introduced into the vacuum chamber while film formation was continued, the pressure was increased to 1 Pa, the pressure was maintained at 1 Pa for 10 seconds, and then the internal pressure was again 1 × The pressure was reduced to 10 ⁻⁵ Pa, the pressure was maintained for 20 seconds to complete the film formation, and the electron transport layer 34 was obtained. The top surface of the obtained Alq ₃ was uneven.

  Thereafter, using a mask that can obtain a stripe pattern having a width of 0.30 mm and a pitch of 0.33 mm extending in the second direction orthogonal to the first direction without breaking the vacuum, LiF (film thickness: 1 nm) / Al (film thickness 100 nm) was deposited to form a reflective electrode 40 composed of a plurality of stripe-shaped partial electrodes, thereby obtaining an organic EL element.

  The organic EL device thus obtained was moved to a dry nitrogen atmosphere (moisture concentration of 10 ppm or less) in the group box and sealed using a sealing glass (not shown) coated with a getter agent and a UV curable adhesive. .

[Example 2]
In accordance with the same procedure as in Example 1, the layers below the light emitting layer 33 were formed.

Then, the vacuum chamber pressure of 1 × ¹⁰ -5 Pa, to obtain an electron transporting layer 34 by laminating Alq ₃ having a thickness of 20 nm. The upper surface of the electron transport layer 34 was flat. Subsequently, the electron injection layer 35 which is the surface layer of the organic EL layer 30 in the present example was formed. F ₄ -TCNQ having a film thickness of 1 nm was formed at a film formation speed of 0.001 nm / s at a vacuum chamber internal pressure of 1 × 10 ⁻⁵ Pa. The upper surface of the obtained F ₄ -TCNQ was uneven.

  Then, according to the procedure similar to Example 1, formation and sealing of the reflective electrode 40 were performed, and the organic EL element was obtained.

[Comparative Example 1]
In accordance with the same procedure as in Example 1, the layers below the light emitting layer 33 were formed.

Then, the vacuum chamber pressure of 1 × ¹⁰ -5 Pa, to obtain an electron transporting layer 34 by laminating Alq ₃ having a thickness of 20 nm. The upper surface of the electron transport layer 34 was flat.

  Then, according to the procedure similar to Example 1, formation and sealing of the reflective electrode 40 were performed, and the organic EL element was obtained.

[Evaluation]
For the organic EL elements obtained in each Example and Comparative Example, reflection under a fluorescent lamp (visual evaluation), diffuse reflectance (%: measured using a spectrophotometer), R efficiency (only red sub-pixel) Red light intensity when turned on: Relative evaluation assuming that the red light intensity of the element of Comparative Example 1 is 1, crosstalk (chromaticity of light emission when only the green sub-pixel is emitted (CIE)), and drive voltage Evaluation was made on (V: voltage necessary for flowing a current of 200 μA). The results are shown in Table 1.

  As can be seen from Table 1, in Examples 1 and 2 according to the present invention, no reflection occurs and the diffuse reflectance is higher than that of the element of Comparative Example 1, so that the organic EL layer 30 / reflection electrode It can be seen that incident light from the outside is efficiently scattered at the 40 uneven surface. Further, when the R efficiency, which is an index of the efficiency of color conversion to red light, is compared, the elements of Examples 1 and 2 according to the present invention show higher R efficiency, and carriers due to an increase in the apparent optical path length due to the uneven interface. It can be seen that conversion to red light is more efficiently performed with an increase in the amount of light absorbed by the mobile color conversion layer (hole injection layer 31). Further, in the evaluation of crosstalk, only the element of Comparative Example 1 has a large CIE chromaticity coordinate (x, y) value shifted in the yellow direction, and the light emission layer of the green subpixel is adjacent to the red subpixel. It can be seen that crosstalk is generated by being incident on. On the other hand, in the elements of Examples 1 and 2 of the present invention, green light having a desired hue is obtained, and it can be seen that no crosstalk occurs. In addition, the device of Example 2 of the present invention having the electron injection layer 35 made of a coherent material has a lower driving voltage than other devices, and carrier injection into the organic EL layer 30 is smoother. You can see that it is happening. In addition, in the elements of the respective examples and comparative examples, the occurrence of failures such as leakage during driving and short circuits was not recognized.

It is typical sectional drawing which shows an example of the organic EL element of this invention. It is typical sectional drawing which shows an example of a structure of the organic electroluminescent layer of this invention. It is typical sectional drawing which shows an example of the organic EL element of this invention of a multicolor display use.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate 20 Transparent electrode 30 Organic EL layer 31 Hole injection layer 32 Hole transport layer 33 Light emitting layer 34 Electron transport layer 35 Electron injection layer 40 Reflective electrode 50 (B) Color filter layer (blue)
60 (G, R) color conversion layer (green, red)
70 Planarization layer 80 Passivation layer

Claims (7)

  An organic EL element having a transparent electrode, an organic EL layer, and a reflective electrode on a transparent substrate, wherein the organic EL layer comprises a light emitting layer, a carrier mobility color conversion layer, and the reflective electrode. An organic EL device comprising at least a surface layer forming an interface, wherein the interface between the transparent electrode and the organic EL layer is flat, and the interface between the reflective electrode and the surface layer is uneven.   2. The organic EL device according to claim 1, wherein the surface layer is an electron injection layer or an electron transport layer having an uneven surface. Forming a transparent electrode on the transparent substrate;
Forming an organic EL layer including at least a light emitting layer, a carrier mobility color conversion layer, and a surface layer forming an interface with the reflective electrode on the transparent electrode, wherein the upper surface of the surface layer is uneven; ,
Forming a reflective electrode on the organic EL layer, and in forming the surface layer of the organic EL layer, after depositing an organic material in a vacuum deposition apparatus of a first pressure, the vacuum deposition Introducing an inert gas into the device to increase the pressure in the device to the second pressure, and then reducing the pressure in the vacuum deposition device to the first pressure again to form irregularities in the surface layer A method for producing an organic EL element, comprising:   The method of manufacturing an organic EL element according to claim 3, wherein the second pressure is 0.1 to 10 Pa. The method for producing an organic EL element according to claim 3, wherein the first pressure is 1 × 10 ⁻⁴ Pa or less.   The method for manufacturing an organic EL element according to claim 3, wherein the surface layer is an electron injection layer or an electron transport layer. Forming a transparent electrode on the transparent substrate;
Forming an organic EL layer including at least a light emitting layer, a carrier mobility color conversion layer, and a surface layer forming an interface with the reflective electrode on the transparent electrode, wherein the upper surface of the surface layer is uneven; ,
Forming a reflective electrode on the organic EL layer, and forming a surface layer of the organic EL layer, wherein an uneven material is formed on the surface layer by depositing a cohesive material. Manufacturing method of organic EL element.

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