JP2012248696A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element that increases an amount of light extraction and prevents dark spots.SOLUTION: An organic electroluminescent element includes: a substrate 1; a first electrode 2; an organic layer 6 including a luminescent layer 5; and a second electrode 7. Thereinside, the luminescent layer 5 has particles 8, with a lower refractive index than those of luminescent materials of which the luminescent layer 5 is made, out of contact with interfaces with adjacent layers. The luminescent layer 5 may be formed by laminating a first region 51 that does not include the particles 8 and a second region 52 that includes the particles 8 at an interface with the first region 51.

Description

  The present invention relates to an organic electroluminescence element.

  Conventionally, an organic electroluminescence element is known as a light emitting element. The light propagation of the organic electroluminescence element will be described with reference to FIG. In this organic electroluminescence element, a light-transmissive first electrode 2, an organic layer 6 including a hole injection layer 3, a hole transport layer 4, and a light emitting layer 5 are formed on a substrate 1, and a reflective second electrode. The electrodes 7 are formed sequentially. The organic layer 6 may include other layers such as an electron injection layer and an electron transport layer, but is omitted in FIG. In such an organic electroluminescence element, light generated by the light source 10 in the light emitting layer 5 propagates in the direction toward the substrate and is emitted to the atmosphere 9. In addition, although there is light toward the second electrode 7, the description thereof is omitted here.

  As a material of the substrate 1 used for the organic electroluminescence element, glass is often used from the viewpoints of excellent transparency, strength, low cost, gas barrier layer, chemical resistance, heat resistance and the like. The refractive index of soda lime glass, which is a general glass substrate material, is about 1.52. In addition, when the first electrode 2 is an anode and exhibits optical transparency, the first electrode 2 is made of indium tin oxide (ITO) or indium zinc oxide (IZO) in which indium oxide is doped with tin oxide. Widely used from the viewpoint of electrical conductivity and electrical conductivity. Here, the refractive index of ITO or IZO varies depending on its composition, film forming method, crystal structure, etc., but ITO is about 1.7 to 2.3, and IZO is about 1.9 to 2.4. In any case, it is a material having a very high refractive index. Note that the refractive index of the atmosphere 9 is 1.0.

  Further, the refractive index of the light emitting material, electron transporting material, hole transporting material, etc. used for the organic layer 6 such as the light emitting layer 5 of the organic electroluminescence element generally contains a large number of benzene rings in its molecular structure. It is often a π-conjugated bond material. Therefore, the refractive index of the organic layer 6 is often about 1.6 to 2.0, and the refractive index is higher than that of a general organic material.

  Accordingly, in a general organic electroluminescence element, the refractive index of each layer is in the relationship of air <substrate <organic layer <first electrode (anode).

  By the way, when light propagates from a certain medium to a medium with a different refractive index, especially when propagating from a medium with a high refractive index to a medium with a low refractive index, the criticality from Snell's law depends on the refractive index between the media at the interface. The corner is determined. Then, light above the critical angle is totally reflected at the interface, confined in a medium having a high refractive index, and lost as guided light.

In the embodiment of FIG. 3, the refractive indexes of the atmosphere 9, the substrate 1, the first electrode 2, the hole transport layer 4, and the light emitting layer 5 are n ₉ , n ₁ , n ₂ , n ₄ , and n ₅ , respectively. At this time, when the substrate 1, the first electrode 2, the hole transport layer 4, and the light emitting layer 5 are formed of the materials described above, for example, n ₉ = 1.0, n ₁ = 1.52 , N ₂ = 1.9, n ₄ = 1.6, and n ₅ = 1.8. Since the hole injection layer 3 often has a small refractive index difference from the hole transport layer 4, light refraction at the interface between the hole injection layer 3 and the hole transport layer 4 is ignored and the hole injection layer 3 is ignored. And the hole transport layer 4 may be considered as an integral layer.

The propagation of light from the light source 10 of the light emitting layer 5 to the atmosphere 9 and the substrate 1 can be calculated using Snell's law. The incident angles from the light emitting layer 5 to the hole transport layer 4, from the hole transport layer 4 to the first electrode 2, from the first electrode 2 to the substrate 1, and from the substrate 1 to the atmosphere 9 are respectively θ _5-4 , θ _4-2 , θ _{When 2-1} and θ _1-9 are set, and the emission angle to the atmosphere 9 is θ ₉ , the relationship of the following equation (1) is established from Snell's law.

  When attention is paid to the hole transport layer 4, the substrate 1, and the atmosphere 9 having a refractive index lower than that of the light emitting layer 5 from the formula (1)

  It becomes. From the above refractive index values, the critical angles with the hole transport layer 4, the substrate 1, and the atmosphere 9 when viewed from the light emitting layer 5 are 63 °, 58 °, and 34 °, respectively. When the light emitted from the source 10 is incident at these angles or more, it is confined in the light emitting layer 5, the first electrode 2, and the substrate 1 and lost as guided light.

  Therefore, in the organic electroluminescence element, light emitted obliquely at a high angle from the light emitting source 10 of the light emitting layer 5 is totally reflected at the interface between the substrate 1 and the atmosphere 9 and the interface between the first electrode 2 and the substrate 1. Occurs (see arrows in FIG. 3). And when total reflection of light occurs, the problem that light extraction efficiency falls will arise.

Applied PhysicsLetters, 71 (9), p.1145, 1997

  In order to reduce the total reflection loss and increase the light extraction efficiency, the method of Non-Patent Document 1 is disclosed. The element disclosed in this document is a glass (substrate 1) on which ITO (first electrode 2), polyaniline (hole transport layer 4) and poly (2-methoxy-5- (2′-ethyl) hexoxy-phenylene vinylene. ) (Hereinafter MEH-PPV, light emitting layer 5) and Ca (cathode 7) are formed. Note that the hole injection layer 3 in FIG. 3 is not provided. By the way, in this document, the role of the polyaniline layer is not particularly specified. However, since polyaniline is generally known as a hole transport material, polyaniline may be considered as the hole transport layer 4.

In Non-Patent Document 1, in order to reduce the loss of total reflection, MEH-PPV (light emitting layer 5) is mixed with SiO ₂ having a particle size of 30 to 80 nm having a lower refractive index than MEH-PPV which is a light emitting material. is doing. By mixing a relatively low SiO ₂ particles having a refractive index, the quantum efficiency is improved is the refractive index of the light-emitting layer 5 is low. However, in this document, since SiO ₂ particles and the light emitting material are mixed in the same solvent and formed into a film, the SiO ₂ particles and the light emitting layer 5 and the interface between the second electrode 7 and the light emitting layer 5 are SiO. _Two particles are considered to exist, and as a result, the movement of electrons and holes at the interface is hindered and a dark spot is generated.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an organic electroluminescence device that increases the amount of light extraction and suppresses the generation of dark spots.

  An organic electroluminescence device according to the present invention includes a substrate, a first electrode, an organic layer including a light emitting layer, and a second electrode, and the light emitting layer has a lower refraction than a light emitting material constituting the light emitting layer. It is characterized by having particles of a ratio inside without contacting the interface with an adjacent layer.

  The light emitting layer is preferably formed by laminating a first region not containing the particles and a second region containing the particles at the interface with the first region.

  According to the present invention, the light emitting layer contains particles having a refractive index lower than that of the light emitting material, so that the refractive index of the light emitting layer is reduced, and the amount of light extraction can be reduced compared to the case where the light emitting layer is made of only the light emitting material. In addition to being able to increase, the absence of particles at the interface between the light emitting layer and the adjacent layer can suppress the generation of dark spots.

It is a schematic sectional drawing which shows an example of embodiment of an organic electroluminescent element. It is a schematic sectional drawing which shows another example of embodiment of an organic electroluminescent element. It is a schematic sectional drawing explaining the propagation of the light in an organic electroluminescent element.

  FIG. 1 shows an example of the layer structure of the organic electroluminescence element. This organic electroluminescence element includes a substrate 1, a first electrode 2, an organic layer 6 including a light emitting layer 5, and a second electrode 7 in this order. In this embodiment, the organic layer 6 includes the hole injection layer 3 and the hole transport layer 4 in this order between the first electrode 2 and the light emitting layer 5. In addition to the light emitting layer 5, other layers such as an electron transport layer and an electron injection layer may be appropriately provided in the organic layer 6. Further, the light emitting layer 5 has particles 8 having a refractive index lower than that of the light emitting material constituting the light emitting layer 5 inside the light emitting layer 6 in a state of not contacting the interface with the adjacent layer. That is, the particles 8 included in the light emitting layer 5 do not exist at the interface of the light emitting layer 5 and do not contact the layers adjacent to the light emitting layer 5 (in this embodiment, the hole transport layer 4 and the second electrode 7). It has become.

  As the substrate 1, in the case of substrate-side single-sided light emission or double-sided light emission, any substrate 1 made of an appropriate material can be used without particular limitation as long as it transmits light. For example, an arbitrary material such as a rigid transparent glass plate such as soda glass or non-alkali glass, or a flexible transparent plastic plate such as polycarbonate or polyethylene terephthalate can be used, but is not limited thereto. Alternatively, single-sided light emission on the opposite side of the substrate may be used. In this case, as the substrate 1, in addition to the above rigid transparent glass plate, transparent plastic plate and flexible transparent plastic plate, there is no light transmission, but excellent strength, low cost, gas barrier layer, chemical resistance Those having heat resistance and heat resistance can be used. Further, a material exhibiting conductivity such as a rigid metal plate or a flexible metal foil is more preferable because it may serve as an electrode. Even when light is extracted from the surface opposite to the substrate 1, the light extraction amount is improved by lowering the refractive index of the light emitting layer 5.

  In the substrate 1, the refractive index can be set to about 1.5 to 1.7. Further, the thickness of the substrate 1 can be set to about 10 to 1000 μm.

At least one of the first electrode 2 and the second electrode 7 is formed as a light transmissive electrode for extracting light. As materials for the first electrode 2 and the second electrode 7, in the case of an electrode having optical transparency, a metal such as gold, CuI, ITO (indium-tin oxide), SnO ₂ , ZnO, IZO (indium-zinc oxide) And metal oxides such as GZO (gallium-zinc oxide). Using these materials, an electrode can be formed by a vacuum deposition method, a sputtering method, or the like. The refractive index of ITO or IZO varies depending on its composition, film formation method, crystal structure, etc., but ITO is approximately 1.7 to 2.3, and IZO is approximately 1.9 to 2.4.

  Alternatively, a light transmissive electrode can be formed by spin coating, screen printing, dip coating, die coating, casting, spray coating, or gravure coating of a transparent material that holds metal nanoparticles and metal nanowires. As this permeable substance, acrylic resin, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polystyrene, polyether sulfone, polyarylate, polycarbonate resin, polyurethane, polyacrylonitrile, polyvinyl acetal, polyamide, polyimide, diacryl phthalate resin , Cellulose resins, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, other thermoplastic resins, and copolymers of two or more monomers constituting these resins. Examples of conductive materials such as metal nanoparticles and metal nanowires include indium-tin oxide (ITO), indium-zinc oxide (IZO), and tin oxide in addition to fine metal particles such as silver and gold. Metal oxide fine particles, conductive polymer, conductive organic material, dopant (donor or acceptor) -containing organic material, a mixture of a conductor and a conductive organic material (including polymer), and the like.

In the case where the first electrode 2 or the second electrode 7 is an electrode that does not have optical transparency, Al, Ag, or the like can be used as an electrode material. You may do. Such electrode material combinations include a laminate of an alkali metal and Al or Ag, a laminate of an alkali metal halide and Al or Ag, a laminate of an alkali metal oxide and Al or Ag, an alkali Examples include laminates of earth metals or rare earth metals and Al or Ag, and alloys of these metal species with other metals, such as sodium, sodium-potassium alloy, lithium, magnesium, barium, etc. For example, a laminate of Al and Al, a laminate of calcium and Ag, a magnesium-silver mixture, a magnesium-indium mixture, an aluminum-lithium alloy, a LiF / Al mixture / laminate, an Al / Al ₂ O ₃ mixture, etc. be able to. The materials and forms listed above are examples, and are not limited to these. When the electrode facing the light transmissive electrode is formed as a light reflective electrode, in this embodiment, it is possible to reduce the total reflection loss of light reflected by the reflective electrode.

  Although it does not specifically limit as thickness of the 1st electrode 2 and the 2nd electrode 7, For example, it can set to about 50-200 nm. Moreover, in a light transmissive electrode, a refractive index can be set to about 1.5-2.4, for example.

  In the organic layer 6, the light emitting material (organic electroluminescence material) for forming the light emitting layer 5 is, for example, anthracene, naphthalene, pyrene, tetracene, coronene, perylene, phthaloperylene, naphthaloperylene, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxalate, and the like. Diazole, bisbenzoxazoline, bisstyryl, cyclopentadiene, coumarin, oxadiazole, bisbenzoxazoline, bisstyryl, cyclopentadiene, quinoline metal complex, tris (8-hydroxyquinolinato) aluminum complex, tris (4-methyl) -8-quinolinato) aluminum complex, tris (5-phenyl-8-quinolinato) aluminum complex, aminoquinoline metal complex, benzoquinoline metal complex, tri- (p-turf) Nyl-4-yl) amine, pyran, quinacridone, rubrene, and derivatives thereof, or 1-aryl-2,5-di (2-thienyl) pyrrole derivative, distyrylbenzene derivative, styrylarylene derivative, styrylamine derivative , Polyfluorene derivatives, and compounds or polymers having a group consisting of these luminescent compounds as part of the molecule. In addition to fluorescent dye-derived compounds typified by the above compounds, so-called phosphorescent materials such as Ir complexes, Os complexes, Pt complexes, europium complexes, etc., or compounds or polymers having these in the molecule Can also be suitably used. These materials can be appropriately selected and used as necessary.

  Layers other than the light-emitting layer 5 in the organic layer 6, specifically, the hole injection layer 3 and the hole transport layer 4, and the electron transport layer and the electron injection layer have appropriate functions for injecting or transporting electrons or holes. Can be made of material.

  The thickness of each layer constituting the organic layer 6 is not particularly limited. For example, the light emitting layer 5 is about 10 to 100 nm, the hole injection layer 3 is about 10 to 100 nm, and the hole transport layer 4 is 10. The electron injection layer can be set to about 1 to 50 nm, and the electron transport layer can be set to about 10 to 100 nm. The refractive index of each layer constituting the organic layer 6 is not particularly limited, but the light emitting layer 5 is about 1.6 to 2.0, and the hole injection layer 3 is 1.5 to 1.8. The hole transport layer 4 can be set to about 1.5 to 1.8.

  Here, the light emitting material used for the light emitting layer 5 of the organic electroluminescence element is mostly a π-conjugated bond material containing a large number of benzene rings in its molecular structure, and its refractive index is about 1.6 to 2.0. There are many things. Therefore, it is preferable to use a substance having a refractive index lower than 1.6 for the particles 8 having a lower refractive index than the light emitting material. The lower limit of the refractive index is not particularly limited, but is actually higher than the atmosphere 9 and may be higher than 1.1, for example.

  Examples of the material of the particles 8 include particles 8 made of a metal or a metal compound such as silica, calcium carbonate, and magnesium fluoride. In addition, acrylic resin, polyethylene, polypropylene, polymethyl methacrylate, polystyrene, polyethersulfone, polyarylate, polycarbonate resin, polyurethane, polyamide, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, other resins, and fluorine-containing low Examples thereof include, but are not limited to, particles 8 composed of molecular compounds.

  Further, among the particles 8 made of the metal or metal compound shown above, a porous material made of a metal compound or metal oxide that contains voids in the particles and exhibits a lower refractive index than usual (when there is no void). Particles are more preferred. These porous particles include silica porous particles. Examples of the silica porous particles include hollow silica, nanoporous silica, and mesoporous silica.

From the porosity [volume%] of the refractive index of porous silica,
(Refractive index of silica) × (1−porosity / 100) + porosity / 100
Is required.

  The porosity is preferably higher. For example, the porosity can be 20 to 40% by volume.

  The particle 8 having a refractive index lower than that of the light-emitting material mixed in the light-emitting layer 5 has a size (particle diameter) of 10 because the light-emitting layer 5 of a general organic electroluminescence element is several tens nm to several hundreds nm. ˜100 nm is preferred. The particle size of the particles 8 can be measured by a laser diffraction scattering method using a laser diffraction particle size distribution meter or the like, an electron microscope, or the like.

Mesoporous silica can be produced, for example, by preparing surfactant composite silica fine particles having a surfactant in mesopores and extracting and removing the surfactant from the surfactant composite silica fine particles. Specifically, for example, first, water, NH ₃ aqueous solution, ethylene glycol, hexadecyltrimethylammonium bromide (CTAB), 1,3,5-trimethylbenzene (TMB), tetraethoxysilane, γ-aminopropyltriethoxysilane Are mixed and stirred to produce surfactant composite silica fine particles. Next, isopropanol, 5N HCl, and hexamethyldisiloxane are mixed and stirred, and a synthetic reaction liquid of surfactant composite silica fine particles is added thereto, followed by stirring and refluxing. By the above operation, the surfactant and the hydrophobic part-containing additive are extracted from the surfactant composite silica fine particles, and mesoporous silica fine particles whose surface is trimethylsilylated are obtained. Then, the solution after trimethylsilylation is centrifuged, the liquid is removed, ethanol is added to the precipitated solid phase, and the particles are shaken in ethanol with a shaker to wash the mesoporous silica fine particles. Furthermore, by adding isopropanol to the prepared mesoporous silica fine particles and redispersing with a shaker, mesoporous silica fine particles dispersed in isopropanol can be obtained. The above example is an example of a method for producing mesoporous silica, and is not limited to this method.

  In order to prevent the particles 8 included in the light emitting layer 5 from coming into contact with the interface between the light emitting layer 5 and the adjacent layer, the light emitting layer 5 is formed by laminating a plurality of regions as shown in FIG. Preferably it is. Specifically, the light emitting layer 5 can be formed as follows. First, a laminated body in which a light-transmissive first electrode 2, a hole injection layer 3, and a hole transport layer 4 are sequentially formed on the surface of the substrate 1 is formed. Next, only the light emitting material is deposited on the surface of the hole transport layer 4 of this laminate, and the first region 51 of the light emitting layer 5 is formed. Then, only the particles 8 having a refractive index lower than that of the light emitting material are stacked on the surface of the first region 51 of the light emitting layer 5. The lamination of the particles 8 can be performed by applying a particle dispersion or spraying particles. Further, only the light emitting material is deposited on the surface on which the particles 8 are stacked, and the second region 52 of the light emitting layer 5 is formed. At this time, since the particles 8 adhere to the first region 51 or adhere to each other, the particles 8 are embedded by the second region 52. The second region 52 is formed as a region where the particles 8 exist at the interface with the first region 51. And after laminating | stacking the other layer of an organic layer as needed, the organic electroluminescent element as shown in FIG. 2 is obtained by forming the 2nd electrode 7 on it. In this organic electroluminescence, the plurality of particles 8 are arranged on substantially the same plane inside the light emitting layer 5. Further, the same light emitting material is used for the first region 51 and the second region 52, whereby the integrated light emitting layer 5 is formed after lamination. In addition, the manufacturing method of the light emitting layer 5 is not limited to this method. For example, a mixed region in which the particles 8 and the light emitting material are mixed is formed on the first region 51 (light emitting material region) of the light emitting layer 5 manufactured as described above, and the light emitting material is further formed thereon. Alternatively, the light emitting material region may be formed by forming only the film.

  The amount of the particles 8 in the light emitting layer 5 is not particularly limited. From the viewpoint of lowering the refractive index and ensuring light emitting properties, for example, the volume ratio with respect to the entire light emitting layer 5 is 20 to 20%. It is preferable that it is 40 volume%.

  In said organic electroluminescent element, the refractive index of the light emitting layer 5 is reduced because the light emitting layer 5 contains the particle | grains of a lower refractive index than a light emitting material. Further, the low-refractive-index particles 8 present in the light-emitting layer 5 can hardly totally reflect light from the light source 10 such as light emitted obliquely from the light source 10 at a high angle (FIG. 3). reference). This is presumably because the critical angles at the interface between the first electrode 2 and the substrate 1 and at the interface between the substrate 1 and the atmosphere 9 can be increased. Further, it is presumed that light is emitted from the light emitting layer 5 toward the substrate 1 at an angle at which the light angle is changed by the light emitting layer 5 and is not easily totally reflected. As described above, the organic electroluminescence element of the present embodiment includes the first electrode 2 to the substrate 1 as compared with the case where the light emitting layer 5 is made of only the light emitting material because the light emitting layer 5 includes the particles 8. Since the amount of light extracted to the substrate and the amount of light extracted from the substrate 1 to the atmosphere 9 can be increased, the light extraction efficiency can be improved. Further, since the low refractive index particles 8 are not present at the interface between the light emitting layer 5 and the adjacent layer, the generation of dark spots can be suppressed.

Example 1
(Preparation of low refractive index particles)
In a separable flask equipped with a condenser, a stirrer, and a thermometer, H ₂ O: 120 g, 25% NH ₃ aqueous solution: 5.4 g, ethylene glycol: 20 g, hexadecyltrimethylammonium bromide (CTAB): 1.2 g, 1 , 3,5-trimethylbenzene (TMB): 1.58 g (substance quantity ratio TMB / CTAB = 4), TEOS: 1.29 g, γ-aminopropyltriethoxysilane: 0.23 g are mixed, and 4 at 60 ° C. Surfactant composite silica fine particles were prepared by stirring for a period of time.

  Next, isopropanol: 30 g, 5N-HCl: 60 g, hexamethyldisiloxane: 26 g are mixed and stirred at 72 ° C., a synthetic reaction solution of surfactant composite silica fine particles is added, and the mixture is stirred and refluxed for 30 minutes. did. Through the above operation, the surfactant and the hydrophobic part-containing additive were extracted from the surfactant composite silica fine particles to obtain mesoporous silica fine particles whose surface was trimethylsilylated.

  The solution after trimethylsilylation was centrifuged at 20,000 rpm for 20 minutes, and then the liquid was removed. Ethanol was added to the precipitated solid phase, and the mesoporous silica fine particles were washed by shaking the particles in ethanol with a shaker. Centrifugation was performed at 20,000 rpm for 20 minutes, and the liquid was removed to obtain mesoporous silica fine particles.

  When 3.8 g of isopropanol was added to 0.2 g of the prepared mesoporous silica fine particles and redispersed with a shaker, mesoporous silica fine particles dispersed in isopropanol were obtained. The particle diameter of the mesoporous silica fine particles was about 50 nm. Further, a solution in which mesoporous silica fine particles were redispersed in 1-butanol was prepared by the same method. The refractive index (wavelength 650 nm) of the mesoporous silica fine particles was 1.3.

(Production of element)
An alkali-free glass plate (Corning “No. 1737”, refractive index of 1.50 to 1.53 (wavelength 500 nm), thickness of 0.7 μm) was used as the substrate 1. Sputtering was performed on the substrate 1 using an ITO (tin-doped indium oxide) target (manufactured by Tosoh Corp.) to form an ITO layer having a thickness of 150 nm. The obtained glass substrate with an ITO layer was annealed at 200 ° C. for 1 hour in an Ar atmosphere to form a first electrode 2 having a sheet resistance of 18Ω / □. It was 2.05 when the refractive index in wavelength 650nm of the 1st electrode 2 was measured with FilmTek made from SCI.

  Next, polyethylenedioxythiophene / polystyrene sulfonic acid (PEDOT-PSS) (“CLEVIOS PAI4083” manufactured by HC Starck, PEDOT: PSS = 1: 6) is formed to a thickness of 30 nm on the first electrode 2. Thus, the hole injection layer 3 was produced by applying with a spin coater and baking at 150 ° C. for 10 minutes. The refractive index of the hole injection layer 3 at a wavelength of 650 nm was measured with a FilmTek manufactured by SCI, and found to be 1.55.

  Next, TFB (Poly [(9,9-dioc tylfluorenyl-2,7-diyl) -co- (4,4 ′-(N- (4-sec-butylphenyl)) diphenylamine)]) (American Dye Source) "HoleTransport Polymer ADS259BE") in THF solvent was applied to the hole injection layer 3 with a spin coater to a film thickness of 12 nm to form a TFB film, which was baked at 200 ° C for 10 minutes. By doing so, the hole transport layer 4 was produced. It was 1.7 when the refractive index in wavelength 650nm of the hole transport layer 4 was measured with FilmTek made from SCI.

  Next, a solution in which a red polymer ("LightEmittingpolymer ADS111RE" manufactured by American Dye Source Co., Ltd., refractive index of about 1.7 at a wavelength of 650 nm) is dissolved in a THF solvent is formed on the hole transport layer 4 to a film thickness of 20 nm. Thus, the 1st area | region 51 containing only a luminescent material was produced among the light emitting layers 5 by apply | coating with a spin coater and baking for 10 minutes at 100 degreeC. On this 1st area | region 51, the solution which disperse | distributed the mesoporous silica prepared above in 1-butanol was apply | coated. Further, a solution obtained by dissolving a red polymer (“Light Emitting polymer ADS111RE” manufactured by American Dye Source) in a THF solvent is applied on a spin coater and baked at 100 ° C. for 10 minutes, whereby the light emitting layer 5 is formed. Among them, the second region 52 having particles having a refractive index lower than that of the light emitting material at the interface with the first region 51 was manufactured. At this time, the film was formed such that the entire thickness of the light emitting layer 5 was 100 nm. It was 1.60 when the refractive index in wavelength 650nm of the light emitting layer 5 was measured by the FilmTek by SCI.

  Ba (manufactured by High-Purity Chemical) was formed as an electron injection layer on the light-emitting layer 5 by vacuum deposition with a film thickness of 5 nm. And Al (made by a high purity chemical company) was vacuum-deposited with the film thickness of 80 nm on the electron injection layer, and the 2nd electrode 7 was formed as a cathode. Thereby, an organic electroluminescence element was obtained.

  Then, the board | substrate 1 in which each said layer was formed was conveyed, without exposing to air | atmosphere to the glove box of a dew point-80 degreeC or less dry nitrogen atmosphere. On the other hand, a water absorbing agent (manufactured by Dynic) was attached to a glass sealing cap and an ultraviolet curable resin sealing agent was applied to the outer periphery of the sealing cap in advance. Then, the sealing cap is bonded to the substrate 1 with a sealing agent so as to surround each layer in the glove box, and the sealing agent is cured by irradiating with ultraviolet rays, whereby each layer is sealed with the sealing cap, and the sealed organic electro A luminescence element was obtained.

(Comparative Example 1)
For the light emitting layer 5, a solution obtained by dissolving a red polymer (“Light Emitting polymer ADS111RE” manufactured by American Dye Source) in a THF solvent is applied onto the hole transport layer 4 with a spin coater so that the film thickness becomes 100 nm. The light emitting layer 5 was formed by baking at 100 ° C. for 10 minutes. Other than that was carried out similarly to Example 1, and produced the organic electroluminescent element. It was 1.70 when the refractive index in wavelength 650nm of the light emitting layer 5 was measured with FilmTek by SCI.

(Comparative Example 2)
For the light-emitting layer 5, a red polymer (“Light Emitting polymer ADS111RE” manufactured by American Dye Source) and mesoporous silica prepared in Example 1 were mixed in a THF solvent (luminescent material: mesoporous silica in a volume ratio). 4: 1) was applied onto the hole transport layer 4 with a spin coater so as to have a film thickness of 100 nm, and baked at 100 ° C. for 10 minutes to form the light emitting layer 5. Other than that was carried out similarly to Example 1, and obtained the organic electroluminescent element. It was 1.60 when the refractive index in wavelength 650nm of the light emitting layer 5 was measured by the FilmTek by SCI.

(Evaluation)
Table 1 shows the evaluation of the characteristics of the organic electroluminescence elements obtained in Examples and Comparative Examples.

  As can be seen from Table 1, the light emitting layer 5 contains low refractive index particles 8 and the light emitting layer 5 has a reduced refractive index. The light extraction efficiency is improved as compared with Comparative Example 1 having 5. Further, in Comparative Example 2 in which the low refractive index particles 8 are in contact with the hole transport layer 4 and the electron injection layer, dark spots are generated, and the light extraction property cannot be evaluated.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 1st electrode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Organic layer 7 2nd electrode 8 Particle | grain 9 Atmosphere 51 1st area | region 52 2nd area | region

Claims (2)

  A substrate, a first electrode, an organic layer including a light-emitting layer, and a second electrode, wherein the light-emitting layer includes particles having a refractive index lower than that of the light-emitting material constituting the light-emitting layer and an adjacent layer. An organic electroluminescence element characterized in that the organic electroluminescence element is inside without contacting the interface.   The said light emitting layer is formed by laminating | stacking the 1st area | region which does not contain the said particle | grain, and the 2nd area | region which contains the said particle | grain in the interface with a 1st area | region. Organic electroluminescence device.

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