JP2011154809A - Organic el element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate having a simple manufacturing process and moreover capable of obtaining an external extraction efficiency of a higher light emission and provide an organic EL element using the above. <P>SOLUTION: The organic EL element is provided with a substrate, a transparent electrode arranged on the substrate, an organic EL layer, a transparent inorganic insulation layer surrounding the organic EL layer, and a reflection electrode. It is desirable that the transparent inorganic insulation layer has a larger refractive index than that of the transparent electrode. The manufacturing method of the element is provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a surface light emitter used for various displays, display elements, liquid crystal backlights, and the like, and more specifically, a structure of an element for improving light extraction efficiency (external quantum efficiency) from the surface light emitter, a manufacturing method thereof, The present invention relates to an organic EL element having the structure.

  In recent years, various displays such as an inorganic EL, an inorganic LED, and a transmissive liquid crystal having a backlight have been developed as a thin film type light emitter with the progress of the information society. As a typical thin film type light emitting element used for such a display, there is, for example, an organic electroluminescence (EL) element.

  An organic EL element is a self-luminous element, and has a great advantage such as high visibility and low power consumption compared to an inorganic EL element. Development has been actively promoted for the purpose of use as a pixel of a display device such as a display panel or a surface light source. When an organic EL element is used as a pixel, a plurality of organic EL elements are arranged on the same plane, and wiring for applying a voltage is configured in a matrix and driven independently to perform a desired display. In addition, since the surface light source can be configured in a thin film shape, for example, it can be easily reduced in size and weight by being used in an element or apparatus having a light source such as a reading light source or a writing light source of a printer.

  FIG. 1 schematically shows a structure of a conventional organic EL device in a cross-sectional view. The organic EL element has a laminated structure of the substrate 100 / transparent electrode 200 / organic EL layer 300 / reflecting electrode 400 in FIG. 1, and light from the organic EL light source is emitted from the atmosphere side surface of the substrate 100 through the substrate 100. By doing so, it is taken out to the atmosphere. Specifically, in the organic EL element shown in FIG. 1, since the refractive index of the substrate 100 and the transparent electrode 200 is different, about 45% of light is guided through the transparent electrode 200 by total reflection at the interface between them. Light 504 or light 503 guided laterally through the substrate 100 / transparent electrode 200 interface. Next, light 501 having an incident angle smaller than the critical angle is extracted outside the substrate 100 / air interface, but light 502 having an incident angle greater than the critical angle is extracted from the substrate 100 / air. / The air interface is guided in the lateral direction and cannot be taken out. Actually, the light emitted from the substrate 100 to the outside is only about 20% of the light emitted from the organic EL layer 300. This phenomenon is one of the main causes for keeping the external extraction efficiency of light emission of the organic EL element low.

  Conventionally, various contrivances have been made to avoid such a phenomenon and increase the light extraction efficiency from the exposed surface of the substrate 100.

  It has been proposed to improve the light extraction efficiency by providing irregularities on the display side outermost surface and the laminated surface of the substrate (see Patent Document 1). However, in this configuration, since the pair of electrodes (anode and cathode) and the organic EL layer are stacked on the uneven surface, the thickness of the organic EL layer formed between the pair of electrodes becomes non-uniform. In addition, defects such as a short circuit between the anode and the cathode and dielectric breakdown of the organic EL layer may occur.

  A transparent layer (for example, an airgel layer) made of a low refractive index porous body (refractive index of 1.003 to 1.300) having an optical film thickness smaller than the cut-off wavelength of visible light and having an ultrafine structure An organic EL element inserted between a glass substrate and an ITO transparent electrode has been proposed (see Non-Patent Document 1). Also, light emission is made by using a composite thin film holding substrate in which a composite thin film is formed on the surface of the substrate, which is composed of a filler having a refractive index lower than that of the substrate and a binder having a refractive index higher than that of the filler. It has been proposed to improve the external extraction efficiency (see Patent Documents 2 and 3). Recently, in an organic EL element, an external light diffusion layer containing a light scattering particle containing light scattering particles in a matrix made of a low refractive index material is provided between a transparent electrode layer and a substrate. Proposals for improving the extraction efficiency have also been made (see Patent Documents 4 to 6).

  Alternatively, a method for suppressing a waveguide mode in a glass substrate by forming a plurality of mesa structures on a glass substrate and forming an organic EL element on the upper surface of the mesa structure has been proposed ( Non-patent document 2). In this proposal, based on the results of ray analysis, the current luminance efficiency was improved by a factor of about 2 in a panel having a mesa structure with a taper angle of 35-40 ° and an aspect ratio of 0.7.

  Light emitted obliquely with respect to the substrate surface from the light emitting layer is refracted in a direction perpendicular to the substrate surface by a microlens array provided on the substrate emission surface and emitted to the outside of the device, so that the outside of the light emission It has been proposed to improve the extraction efficiency (see Patent Document 7 and Non-Patent Document 3). Therefore, almost all of the light emitted from the light emitting layer can be emitted out of the organic EL device, and the light can reach the naked eye.

  A two-dimensional periodic structure (photonic array) of the wavelength order is formed on one side of the substrate, and the reflection angle of the light wave is converted to the front direction by utilizing the diffraction effect of the guided light in the substrate. It has been proposed to extract wave light to the outside (see Non-Patent Document 4).

  The light emitted from the organic EL light-emitting part composed of the two reflective electrodes and the organic EL layer sandwiched between the electrodes is taken out from the end face of the organic EL layer, and emitted toward the front surface of the substrate by a triangular micromirror formed on the substrate. Thus, a method for improving the external extraction efficiency of light emission has been proposed (see Non-Patent Document 5).

  It has been proposed that a condensing lens is provided between the substrate and the lower transparent electrode constituting the organic EL light emitting element so as to correspond to the organic EL light emitting element in a one-to-one correspondence in plan view (Patent Document). 8). Here, “the organic EL light emitting element and the condensing lens correspond one-to-one in plan view” means (a) that one organic EL light emitting element overlaps only one condensing lens; (B) The optical axis of the condensing lens and the center of the organic EL light emitting element in plan view substantially coincide with each other, and (c) the size of the organic EL light emitting element overlaps the organic EL light emitting element. This means that the size is less than or equal to the size circumscribing the condensing lens, preferably the size that overlaps each other, more preferably the size that is less than the size that is inscribed, and at the same time. In addition, an underlayer is provided between the substrate and the lower transparent electrode to provide a substantially flat surface for forming the lower transparent electrode substrate, and at the same time the distance between the condenser lens and the lower transparent electrode. By adjusting the above, it is possible to achieve high emission luminance when viewed from the front.

JP 2004-258380 A Japanese Patent Laid-Open No. 2003-216061 JP 2005-274741 A JP 2004-296437 A JP 2001-202827 A JP 2002-260845 A JP 2004-39500 A Japanese Patent Laid-Open No. 10-172756 JP 2002-352956 A JP-A-11-71103 Japanese Patent Laid-Open No. 11-228139 Japanese Patent Laid-Open No. 11-79746 JP 2002-206062 A JP-A-5-330825 JP-A-11-263620 Japanese National Patent Publication No. 11-512336 European Patent Publication No. 0335773 JP 2003-288029 A JP-A-11-233262 JP 2000-182774 A

Yokogawa, Organic Molecular Bioelectronics Subcommittee, 2001.3.9 .; T. Tsutsui, M. Yahiro, H. Yokogawa, Advanced materials, 13, No. 15, P.1149 (2001) G.Gu, D.Z.Garbuzov, P.E.Burrows, S.Venkatesh, S.Venkatesh, S.R.Forrest, Optics Lett., 22, No.6, P.396 (1997) C.F.Madigan, M.H.Lu, J.C.Sturm, Appl.Phys. Lette., 76, p.1650 (2000) T. Yamadaki, K. Sumioka, T. Tsutsui, Appl. Phys. Lett., 76, No. 10, p, 1243 (2000) W.M.Cranton, C.B.Thomas, R.Stavens, Information Display, 4 & 5/02, p.22 (22) Kozo Tabe et al., "Metal oxides and complex oxides" (Kodansha, Ltd., published in 1978) Jpn. J. Appl. Phys., 32, 4158-4162 (1993) Shunichi Gonda, Junzo Ishikawa, Eiji Kamijo, "Ion Beam Applied Technology" (CMC Corporation), 1989 Yasushi Aoki, Surface Science, 18 (5), 262, 1998 Masakazu Anbo, Surface Science, 20 (2), 60, 1999

  The prior art organic EL device configuration proposed for achieving an improvement in the external extraction efficiency of light emission has problems such as a complicated manufacturing process or a further improvement in the external extraction efficiency of light emission.

  Accordingly, it is an object of the present invention to provide an organic EL element configuration that has a simple manufacturing process and that can obtain higher emission external extraction efficiency, an organic EL element including the configuration, and a manufacturing method thereof.

    The present invention is an organic EL element comprising a substrate and a transparent electrode, an organic EL layer and a reflective electrode provided on the substrate, wherein the organic EL layer is surrounded by a transparent inorganic insulating layer. The present invention relates to an EL element.

  In the organic EL element of the present invention, the refractive index of the transparent inorganic insulating layer is preferably larger than the refractive index of the transparent electrode.

The present invention is also a method for producing an organic EL device,
Forming a transparent inorganic insulating layer that surrounds the organic EL layer on the transparent electrode provided on the substrate;
The present invention relates to a method for producing an organic EL element, comprising a step of forming an organic EL layer on the transparent electrode and a step of forming a reflective electrode on the organic EL layer.

  By adopting the configuration as described above, the organic EL device of the present invention can realize high light extraction efficiency, and display with high quality with improved brightness when viewed from the front. Further, in the above manufacturing method, the manufacturing process is simple, and the organic EL element can be manufactured advantageously in terms of manufacturing cost.

FIG. 1 is a cross-sectional view schematically illustrating light propagation in an organic EL element having a conventional structure. FIG. 2 is a cross-sectional view for schematically explaining the propagation of light in the organic EL device of the present invention. FIG. 3 is a schematic plan view of the organic EL layer of the organic EL element of the present invention. FIG. 4 is a schematic view illustrating the constituent components of each layer in a cross-sectional view schematically illustrating the organic EL element of Example 1 of the present invention.

  The organic EL element of the present invention is characterized in that the organic EL layer is surrounded by a transparent inorganic insulating layer. Moreover, it is preferable that the transparent inorganic insulating layer of this invention has a refractive index larger than the refractive index of a transparent electrode. It is a surprising effect that the light emission extraction efficiency from the organic EL layer is greatly improved by adopting such an element configuration.

  The transparent inorganic insulating layer is preferably a transparent metal oxide layer having a refractive index higher than that of the transparent electrode, or a layer having a refractive index higher than that of the transparent electrode, comprising transparent inorganic particles and a matrix. May be configured. The transparent inorganic insulating layer may preferably be colorless.

  The transparent inorganic insulating layer may preferably have a refractive index of 2.3 or higher.

  More specifically, the transparent metal oxide is a metal of Group 2 to Group 15 of the periodic table, for example, any one of Ti, Zn, Sb, Sn, Zr, Ce, Ta, La, and In. Or a complex oxide composed of a Ti oxide and a second metal oxide of any one of Group 2 to Group 15 metals of the periodic table, for example, Sr, Ni, Zn, Co and Zr. Good.

Hereinafter, the present invention will be described in more detail.
The substrate used in the present invention may be glass, a thermoplastic resin such as PET, or a photocurable resin. It is preferable that a board | substrate has a refractive index smaller than the refractive index of a transparent inorganic insulating layer, for example, may have a refractive index of 1.3-1.7.

  The transparent inorganic insulating layer surrounding the organic EL layer preferably has a refractive index larger than that of the transparent electrode, that is, a refractive index of 2.3 or more. By setting the refractive index within this range, it is possible to prevent light generated in the organic EL layer from being easily guided in the transparent inorganic insulating layer. That is, it is presumed that the efficiency of external extraction of light emission can be improved by a mechanism that smoothly reflects, propagates and confines light at the interface between the organic EL layer and the transparent inorganic insulating layer. There is nothing to be caught in the mechanism.

The transparent inorganic insulating layer surrounding the organic EL layer is a layer having a transparent metal oxide film layer or transparent inorganic particles and a matrix. The term “transparent” as used herein means that the transmittance with respect to visible light is 70% or more, preferably 80% or more, and more preferably 90% or more, as measured according to JIS-R-3106 standard. The insulating layer referred to here may be a layer whose electrical resistivity usually exhibits a value of 10 ⁵ Ω · m or more, for example, 10 ¹⁰ Ω · m or more.

  The transparent metal oxide film layer in the present invention preferably has a refractive index of 2.3 or more, and may preferably be a colorless transparent metal oxide. Alternatively, it may be a metal-doped mixed metal oxide formed from a plurality of metals. Transparent metal oxides that can be used may include high resistance oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La and In having a high oxygen content. Of these, Ti oxide is particularly preferable. The metal-doped composite oxide that can be used is a composite oxide containing titanium oxide and an oxide of at least one second metal doped with at least one doped metal. Here, the at least one second metal is selected from metals in which an oxide of the second metal preferably exhibits a refractive index of 2.3 or more. In the present invention, the undoped composite oxide may preferably have a refractive index of 2.3 or more. The content of the titanium oxide in the transparent metal composite oxide is 60 to 99 mass%, preferably 70 to 95 mass%, more preferably 75 to 90 mass%, based on the mass of the composite oxide, in terms of titanium dioxide. It is. Second metals that can be used include Sr, Ni, Zn, Co and Zr. The composite oxide may have a rutile crystal structure, a rutile / anatase mixed crystal structure, an anatase crystal structure, or an amorphous structure, and particularly preferably has a rutile crystal structure. The composite oxide layer can be formed by a method known in the art such as a sintering method, a sol-gel method, a sputtering method, and a CVD method (see Patent Documents 10 to 13 and Non-Patent Documents 6 and 7).

  The transparent inorganic particles in the present invention preferably have a refractive index of 2.3 or more and may be a transparent metal oxide. Alternatively, it may be a metal-doped composite oxide formed from a plurality of metals. Transparent metal oxides that can be used may include high resistance oxides such as Ti, Zn, Sb, Sn, Zr, Ce, Ta, La and In having a high oxygen content. The metal-doped composite oxide that can be used is a composite metal oxide containing titanium oxide and an oxide of at least one second metal doped with at least one doped metal. Here, the at least one second metal is selected from metals in which the oxide of the second metal preferably has a refractive index of 2.3 or more. In the present invention, the undoped composite oxide may preferably have a refractive index of 2.3 or more. The content of titanium oxide in the transparent inorganic composite oxide is 60 to 99 mass%, preferably 70 to 95 mass%, more preferably 75 to 90 mass%, based on the mass of the composite oxide, in terms of titanium dioxide. It is. The second metal that can be used may include Sr, Ni, Zn, Co and Zr. The composite oxide may have a rutile crystal structure, a rutile / anatase mixed crystal structure, an anatase crystal structure or an amorphous structure, and particularly preferably has a rutile crystal structure. The composite oxide layer can be formed by a method known in the art such as a sintering method, a sol-gel method, a sputtering method, and a CVD method (see Patent Documents 10 to 13 and Non-Patent Documents 6 and 7).

The at least one doped metal used for doping the metal oxide or composite metal oxide in the present invention is Co, Zr or Al, preferably Co or Zr, and particularly preferably Co. The doped metal may be present as either a simple metal or a metal ion in the metal-doped composite oxide. Further, the doped metal may be unevenly distributed on the surface or inside of the metal-doped composite oxide, but it is preferably present homogeneously on the surface and inside. The doped metal is 25% by mass or less, preferably 0.05 to 10% by mass, more preferably 0.1 to 5% by mass based on the mass of all metals (titanium and second metal) constituting the metal-doped composite oxide. %, Most preferably 0.3 to 3% by weight. By using a doping amount within such a range, metal-doped composite oxide particles having good transparency in the wavelength range of 380 to 650 nm, a high refractive index, and suppressing or eliminating undesirable photocatalytic activity of titanium. Is obtained. The refractive index of the metal-doped composite metal oxide obtained can be adjusted in the range of 2.3 to 2.60, more specifically in the range of 2.4 to 2.60, depending on the doping amount. As a method for doping a mixed metal oxide with a doped metal, methods known in the art such as an ion implantation method can be used (see Patent Documents 14 to 17 and Non-Patent Documents 8 to 10).

  In the transparent inorganic insulating layer in the present invention, the material used as a matrix of transparent inorganic particles disperses the transparent inorganic particles and imparts a film forming property to the transparent inorganic insulating layer for flattening the upper surface in contact with the transparent electrode. Material. Matrix materials that can be used include fluorene-based epoxy resins (for example, epoxy resins having bisarylfluorene as the basic core (manufactured by Nagase Sangyo Co., Ltd.)). The contents of the metal-doped composite oxide and the matrix vary depending on the refractive index of each material and the desired refractive index of the transparent inorganic insulating layer to be obtained. Alternatively, an inorganic polymer having a high refractive index can be used directly as a matrix. For example, a transparent inorganic polymer manufactured by Rasa Industries can be used. It is possible to adjust the refractive index of the obtained film between 2.3 and 2.4 by forming the coating solution of the inorganic polymer by spin coating and controlling the temperature at the post-baking. . Here, in order to form a transparent film having a larger film thickness, the film forming process can be repeated.

  The layer having the highly refractive inorganic particles and the matrix as the transparent inorganic particles is, for example, a technique in which a metal-doped composite metal oxide and a coating liquid in which the matrix is dispersed in a solvent are used, such as spin coating, knife coating, and roll coating. Can be formed by applying to one side of a support having irregularities on both surfaces and then volatilizing the solvent. Prior to application of the coating solution, surface treatment of the coated surface of the support may be performed. Surface treatments that can be used include UV treatment, plasma treatment, surfactant treatment, polishing and the like. These surface treatments are effective in improving the flatness of the top surface of the obtained transparent inorganic insulating layer or reducing particles, and contribute to improving the yield in the production of organic EL elements and improving the quality of the obtained organic EL elements. To do.

  The transparent inorganic insulating layer, which is a feature of the present invention, preferably has a plurality of sections surrounding the organic light emitting layer. For example, after covering a portion where the organic light emitting layer on the transparent electrode can be formed with a mask, the transparent inorganic insulating layer The material constituting the layer is applied by a method such as a vapor deposition method, a sputtering method (including a reactive sputtering method), a chemical vapor deposition (CVD) method, or a spin coating method to form a transparent inorganic insulating layer.

  Various types of masks can be used. For example, a mask made of metal (stainless steel, aluminum, etc.), a resist formed on a substrate by lithography, a metal pattern, or the like. The shape, number, and dimensions of the plurality of sections surrounding the organic light emitting layer in the mask are not particularly limited. For example, the shape of the compartment is a polygon, an ellipse, a fan, or a Roule polygon, the number is one or more, and the dimensions are determined by the size of the cathode and anode of the organic light emitting layer. Here, considering that one of the gist of the present invention is to smoothly reflect, propagate and confine light at the interface between the organic light emitting layer and the transparent inorganic insulating layer and improve the external extraction efficiency of light emission, The shape of the plurality of sections surrounding the organic light emitting layer in the mask may be a polygon such as a quadrangle, a circle or an ellipse. The number of compartments can be 1 or more, for example 4 or more, preferably 10 or more. The size of the compartment is preferably determined by the size of the cathode of the organic light emitting layer.

  Regarding the film thickness of the transparent inorganic insulating layer, one of the gist of the present invention is to smoothly reflect, propagate and confine light at the interface between the organic light emitting layer and the transparent inorganic insulating layer, and to improve the external extraction efficiency of light emission. In view of this, the thickness of the transparent inorganic insulating layer is preferably equal to or greater than the thickness of the organic light emitting layer, but can be determined in consideration of the optimum efficiency of the entire device structure. For example, the film thickness of the transparent inorganic insulating layer is usually 100 to 10,000 nm, preferably 100 to 2000 nm, and particularly preferably 100 to 1000 nm.

  The transparent inorganic insulating layer in the present invention will be described with reference to FIGS. 2, 3 and 4 as examples. The transparent inorganic insulating layer is made of titanium oxide, and three openings (2 mm × 2 mm) are formed on the patterned ITO electrode. In addition, a contact portion connecting the ITO electrode and the conductive wire is left. The refractive index of titanium oxide is about 2.3.

  To illustrate one embodiment, a glass substrate with an ITO electrode masked except for the anode part and the light emitting part, a transparent inorganic insulating layer of titanium oxide is formed by sputtering, the mask is removed, and the glass substrate with an ITO electrode is washed. Further, PEDOT / PSS (poly (3,4-ethylenedioxy) -2,5-thiophene / polystyrenesulfonic acid) can be formed by spin coating to obtain a hole injection layer. Next, PVCz (polyvinylcarbazole) for the hole transport layer and PBD (2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadi as an electron transport material Azole) and a compound as a fluorescent coloring dye can be dissolved in a solvent (toluene or the like), and a light emitting layer can be obtained by a spin coating method. Further, after vapor deposition of lithium fluoride to form an electron injection layer thereon, aluminum is deposited to form a reflective electrode as a cathode, whereby an organic EL element can be obtained.

Next, each component which comprises an organic EL element is demonstrated.
The transparent electrode is an electrode that functions as an anode (hole injection electrode) of the organic EL element, and is made of a material having a large work function in order to reduce the hole injection barrier. Materials for forming the transparent electrode include indium-tin oxide (ITO), indium-zinc oxide (IZO), SnO ₂ , ZnO ₂ , TiN, ZrN, HfN, TiO _x , VO _x , CuI, and InN. , GaN, CuAlO ₂ , CuGaO ₂ , SrCu ₂ O ₂ , LaB ₆ , RuO ₂ and other conductive inorganic compounds can be used. Among these, indium-tin oxide (ITO), indium-zinc oxide (IZO), SnO ₂ and ZnO ₂ are preferably used, and more preferably indium-tin oxide (ITO) and indium-zinc oxide. The product (IZO) is used. The transparent electrode is formed using a vapor deposition method, a sputtering method (including a reactive sputtering method), or a chemical vapor deposition (CVD) method, and preferably formed using a sputtering method (including a reactive sputtering method). . The transparent electrode usually has a thickness of 50 nm or more, preferably 50 nm to 1 μm, more preferably 100 to 300 nm. When a transparent electrode composed of a plurality of partial electrodes is required as will be described later, a conductive inorganic compound is uniformly formed over the entire surface, and then etched to give a desired pattern. You may form the transparent electrode which consists of a partial electrode. Or you may form the transparent electrode which consists of a some partial electrode using the mask which gives a desired shape.

The reflective electrode is an electrode that functions as a cathode (electron injection electrode) of the organic EL element, and is made of a material having a small work function in order to reduce the electron injection barrier. Materials for forming the reflective electrode include alkali metals such as Li, alkaline earth metals such as Mg and Ca, and rare earth metals such as Eu; simple alkali metals, alkali metals, rare earth metals and Al, Ag Alternatively, alloys with In or the like; metals / semiconductors such as Al, Zr, Ti, Y, Sc or Si, and alloys containing these metals / semiconductors can be used (see Patent Documents 19 and 20). Alternatively, reflective metal / transparent conductive oxide (ITO, IZO, SnO ₂ , ZnO, etc.) / Buffer layer (alkali metal, alkaline earth metal or alloys containing them, rare earth metals, fluorides of these metals, etc. ) May be used as a reflective electrode. Among these, preferably, alkaline earth metals such as Mg and Ca, alloys of the above alkaline earth metals and Al and Ag, metals such as Al and Ag, reflective metals / transparent conductive oxides (ITO , IZO, SnO ₂ , ZnO, etc.) / Buffer layer (alkali metal, alkaline earth metal or alloys containing them, rare earth metals, or fluorides of these metals), more preferably Mg, Alloys of alkaline earth metals such as Ca and alloys of Al and Ag, metals such as Al and Ag, reflective metals / transparent conductive oxides (ITO, IZO) / buffer layers (alkaline metals, alkaline earth metals or those A laminated body of alloys, rare earth metals, or fluorides of these metals).

The organic EL layer 30 in the present embodiment can be formed of a single layer film containing a light emitting substance or a multilayer film. Examples of the configuration in the case of forming a multilayer film include a hole transport layer, an electron transporting light emitting layer or a hole transporting light emitting layer, a two-layer structure comprising an electron transport layer, a hole transport layer, a light emitting layer, and an electron transport layer. A three-layer structure composed of, and further, if necessary, a layer that blocks hole (or electron) injection function and hole (or electron) transport function, or blocks hole (or electron) transport It is more preferable to form a multi-layer by inserting. A specific element structure is illustrated below. When the light emitting layer is a single layer film, it is anode / light emitting layer / cathode. In the case of a multilayer film, an anode / hole transport layer / electron transport light emitting layer / cathode, anode / hole transport light emitting layer / electron transport layer / cathode two-layer structure type element, anode / hole transport layer / Three-layer structure type device comprising light emitting layer / electron transport layer / cathode, anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / cathode, anode / hole transport layer / light emitting layer / electron transport layer A multilayer structure type device comprising: / electron injection layer / cathode, anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode. In each layer structure, the layer that blocks the transport of holes (hole blocking layer) is between the light emitting layer and the cathode, and the layer that blocks the transport of electrons (electron blocking layer) is the light emitting layer and the anode. Can be inserted between.
Examples of hole transport materials 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, Aromatic amine low molecular hole injection and transport materials such as N′-diphenyl-1,1′-biphenyl-4,4′-diamine, polyaniline, polythiophene, polyvinylcarbazole, poly (3,4-ethylenedioxythiophene) ) And polystyrene sulfonic acid and other polymer hole transport materials, polythiophene oligomer materials, and other existing hole transport materials Door can be.

  As the light-emitting material, 9,10-diarylanthracene derivatives, pyrene, coronene, perylene, rubrene, 1,1,4,4-tetraphenylbutadiene, tris (8-quinolinolato) 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) phenolate] aluminum complex, bis (2-methyl-5-cyano-8-quinolinolato) [4- (4- Cyanophenyl) phenolate] aluminum complex, tri (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, N, N'-dialkyl-substituted quinacridone phosphor Low molecular weight light emitting materials such as phosphorescent light emitters such as Ir complexes, polyfluorene, polyparaphenylene vinylene, polythiophene, polyspiro, naphthalimide phosphor, N, N′-diaryl substituted pyrrolopyrrole phosphor, etc. Polymer materials such as polyvinyl carbazole, and these polymers The materials and dispersed or copolymerization of low molecular weight material, it is possible to use other existing luminescent material cost.

Examples of the electron transport material include 2- (4-bifinylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole, 2,5-bis (1-naphthyl) -1, 3,4-oxadiazole, oxadiazole derivatives, bis (10-hydroxybenzo [h] quinolinolato) beryllium complexes, triazole compounds, and the like can be used.
The film thickness of the organic EL layer 30 is usually 1000 nm or less, preferably 30 to 1000 nm, more preferably 50 to 500 nm, and particularly preferably 50 to 150 nm even when the organic EL layer 30 is formed as a single layer or a stacked layer. It's okay. In particular, the hole transport material of the polymer EL element has a large effect of covering the surface protrusions of the base material and the anode layer, and preferably forms a thick film of about 10 to 200, more preferably about 20 to 100 nm. Is more preferable.
As a method for forming the organic EL layer 30, depending on the material, a vacuum deposition method, a coating method such as spin coating, spray coating, nozzle coating, flexo, gravure, micro gravure, intaglio offset, printing method, ink jet method, etc. Can be used.

FIG. 2 shows an example of the organic EL element of the present invention. In the example of FIG. 2, in the substrate 10, the transparent electrode 20 and the reflective electrode 40 sandwich the organic EL layer 30. A transparent inorganic insulating layer 12 is formed.
FIG. 3 shows an arrangement example of the organic EL layer 30 and the transparent inorganic insulating layer 12 of the organic EL element of the present invention. In the example of FIG. 3, the transparent inorganic insulating layer 12 is formed so as to sandwich the organic EL layer 30 so that the transparent inorganic insulating layer 12 and the organic EL layer 30 do not overlap.
FIG. 4 schematically shows the organic EL element structure and the contents of each component in Examples 1 and 2 of the present application. The organic EL layer (thickness 120 nm) is composed of a hole transfer layer made of PVCz + OBD, an organic light emitting layer containing a fluorescent light emitting dye surrounded by a transparent inorganic insulating layer, and an electron transporting material layer. The organic EL layer is sandwiched between a cathode (reflecting electrode: Al: film thickness 200 nm) and an anode (transparent electrode: ITO).

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to these.

In the embodiment, the deposition rate control and the film thickness control of the deposition material are attached to the deposition machine. A film formation monitor CRTM-8000 (manufactured by ULVAC, Inc.) using a crystal resonator was used. In addition, a P10 stylus type step gauge manufactured by Tencor was used for measurement of the actual film thickness after film formation. For the device characteristic evaluation, a Keithley source meter 2400 and a Topcon BM-8 luminance meter were used.
In the examples, all mixing ratios are weight ratios unless otherwise specified. The vacuum deposition method was performed in a vacuum of 10 ⁻⁴ Pa. In the evaluation of the light emission characteristics of the element, the characteristics of an organic EL element having an electrode area of 2 mm × 2 mm were measured.

Example 1
A transparent inorganic insulating layer of titanium oxide was formed by sputtering on a glass substrate with an ITO electrode masked except for the anode part and the light emitting part (film thickness 200 nm). PEDOT / PSS (poly (3,4-ethylenedioxy) -2,5-thiophene / polystyrene sulfonic acid) is formed on the cleaned glass substrate with an ITO electrode by spin coating, and the film thickness is removed. A 40 nm hole injection layer was obtained. Next, 69.7 wt% of PVCz (polyvinylcarbazole) for the hole transfer layer and PBD (2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3 as an electron transporting material , 4-oxadiazole) was dissolved in toluene at a concentration of 30 wt% and a fluorescent coloring dye at a concentration of 0.3 wt%, and a light emitting layer having a thickness of 120 nm was obtained by spin coating. Further thereon, 0.5 nm of lithium fluoride was deposited to form an electron injection layer, and then 200 nm of aluminum was deposited to form a reflective electrode as a cathode to obtain an organic EL device. When an energization test was performed on this device, green light emission with a maximum light emission luminance of 3125 cd / m ² was obtained.

ＰＥＤＯＴ／ＰＳＳ

PEDOT / PSS

ＰＶＣｚ

PVCz

ＰＢＤ

PBD

化合物１

Compound 1

Example 2
A transparent inorganic insulating layer of titanium oxide was formed by sputtering on a glass substrate with an ITO electrode masked except for the anode part and the light emitting part (film thickness 200 nm). PEDOT / PSS (poly (3,4-ethylenedioxy) -2,5-thiophene / polystyrene sulfonic acid) is formed on the cleaned glass substrate with an ITO electrode by spin coating, and the film thickness is removed. A 40 nm hole injection layer was obtained. Next, 69.7 wt% of PVCz (polyvinylcarbazole) for the hole transfer layer and PBD (2- (4-biphenylyl) -5- (4-tert-butylphenyl) -1,3 as an electron transporting material , 4-oxadiazole) was dissolved in toluene at a concentration of 30 wt% and a fluorescent coloring dye at a concentration of 0.3 wt%, and a light emitting layer having a thickness of 120 nm was obtained by spin coating. Further thereon, 1 nm of cesium fluoride was deposited to form an electron injection layer, and then 200 nm of aluminum was deposited to form a reflective electrode as a cathode to obtain an organic EL device. When an energization test was performed on this device, green light emission with a maximum light emission luminance of 9246 cd / m ² was obtained.

Comparative Example 1
An organic EL was produced in the same manner as in Example 1 except that titanium oxide in Example 1 was not sputtered. When this device was subjected to an energization test, green light emission with a maximum light emission luminance of 2781 cd / m ² was obtained.

Comparative Example 2
An organic EL was produced in the same manner as in Example 2 except that titanium oxide in Example 2 was not sputtered. When an energization test was performed on this element, green light emission with a maximum light emission luminance of 6865 cd / m ² was obtained.

Table 1 shows the evaluation results of these elements.

Table 1

Example 3
An organic EL was prepared in the same manner as in Example 2 except that the iridium complex Ir-1 was used in place of the compound 1 as the fluorescent coloring dye in Example 2. When this device was subjected to an energization test, green light emission with a maximum light emission luminance of 7842 cd / m ² was obtained.

Comparative Example 3
An organic EL was produced in the same manner as in Example 3 except that titanium oxide in Example 3 was not sputtered. When this device was subjected to an energization test, green light emission with a maximum light emission luminance of 6897 cd / m ² was obtained.

10 Substrate 12 Transparent inorganic insulating layer 20, 200 Transparent electrode 30, 300 Organic EL layer 40, 400 Reflective electrode 100 Substrate 501, 502, 503, 504 Light

Claims (9)

  An organic EL device comprising a substrate and a transparent electrode, an organic EL layer and a reflective electrode provided on the substrate, wherein the organic EL layer is surrounded by a transparent inorganic insulating layer.   The organic EL element according to claim 1, wherein a refractive index of the transparent inorganic insulating layer is larger than a refractive index of the transparent electrode.   The organic EL element according to claim 1, wherein the transparent inorganic insulating layer is a transparent metal oxide layer or a layer having transparent inorganic particles and a matrix.   The organic EL element according to claim 1, wherein the transparent inorganic insulating layer has a refractive index of 2.3 or more.   The transparent metal oxide layer is made of an oxide of any one of Ti, Zn, Sb, Sn, Zr, Ce, Ta, La and In, or Ti oxide and Sr, Ni, Zn, Co and Zr. The organic EL element according to claim 3, wherein the organic EL element is a layer of a composite metal oxide composed of any one kind of second metal oxide.   The transparent inorganic particles are any one of Ti, Zn, Sb, Sn, Zr, Ce, Ta, La and In metal oxide, or Ti oxide and Sr, Ni, Zn, Co and Zr. The organic EL element according to claim 3, wherein the organic EL element is a composite metal oxide composed of a kind of a second metal oxide. A method for producing an organic EL device, comprising:
Forming a transparent inorganic insulating layer that surrounds the organic EL layer on the transparent electrode provided on the substrate;
The manufacturing method of an organic EL element including the process of forming an organic electroluminescent layer on the said transparent electrode, and the process of forming a reflective electrode on the said organic electroluminescent layer.   The said transparent inorganic insulating layer is a manufacturing method described in Claim 7 which has a refractive index larger than the refractive index of a transparent electrode.   The manufacturing method according to claim 7 or 8, wherein the transparent inorganic insulating layer has a refractive index of 2.3 or more.

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