JP2022148334A - Light-emitting device and light extraction layer - Google Patents

Abstract

To provide a light-emitting device and a light extraction layer capable of having improved light extraction efficiency.SOLUTION: A light-emitting device according to an embodiment includes a transparent substrate, a transparent electrode, a reflection electrode, and a light-emitting layer. The transparent electrode is disposed on the transparent substrate, and the light-emitting layer is disposed between the transparent electrode and the reflection electrode. The light-emitting device includes a light extraction layer disposed on an optical path of light emitted from the light-emitting layer, and is used to extract light emitted from the light-emitting layer to the outside. The light extraction layer includes a light scattering layer including a base material and scattering particles with a refractive index different from that of the base material. When the thickness of the light scattering layer is A [μm], the volume concentration of the scattering particles in the base material is B [vol%], and the yellow index of the light scattering layer is C, A and B satisfy the expression (I) and C satisfies the expression (II): 25≤A×B≤145...(I), and 5≤C≤25...(II).SELECTED DRAWING: Figure 1

Description

The present invention relates to light emitting devices and light extraction layers.

A light-emitting device includes a device having a transparent substrate, a transparent electrode provided on the transparent substrate, a reflective electrode paired with the transparent electrode, and a light-emitting layer disposed between the transparent electrode and the reflective electrode. In such a light-emitting device, one of the transparent electrode and the reflective electrode is used as an anode, and the other is used as a cathode to supply electric power to the light-emitting layer. This causes light to be generated in the light-emitting layer. Light generated in the light-emitting layer passes through the transparent electrode and the transparent substrate and is output from the transparent substrate side. Of the light generated in the light-emitting layer, the light traveling toward the reflective electrode is reflected by the reflective electrode, transmitted through the transparent electrode and the transparent substrate, and output from the transparent substrate. As described above, in a light-emitting device using a transparent substrate, light is output from the transparent substrate side, but part of the light generated in the light-emitting layer is confined in the transparent substrate and the transparent electrode. Therefore, it is known to use a light extraction layer as disclosed in Patent Document 1 in order to improve the luminous efficiency of the light emitting device.

WO2014/087462

The light extraction layer described in Patent Document 1 has a base material and scattering particles dispersed in the base material, and scatters part of the light incident on the light extraction layer. This extracts the light generated within the light emitting device. By using the light extraction layer in this way, the light extraction efficiency from the light emitting device is improved as compared with the case where the light extraction layer is not used. However, in recent years, there has been a demand for further improvement in light extraction efficiency.

Accordingly, it is an object of the present invention to provide a light-emitting device and a light-extraction layer capable of improving light-extraction efficiency.

The inventors of the present application have made intensive research into improving light extraction efficiency using a light extraction layer. As a result, the volume concentration of the scattering particles in the base material and the thickness of the light scattering layer (the layer in which the scattering particles are dispersed in the base material) of the light extraction layer have a constant relationship, and the thickness of the light scattering layer has a constant relationship. The inventors have found that the light extraction efficiency can be improved by adjusting the yellow index, and have completed the present invention.

A light-emitting device according to one aspect of the present invention includes a transparent substrate, a transparent electrode, a reflective electrode, and a light-emitting layer. The transparent electrode is disposed on the transparent substrate, and the light-emitting layer includes the transparent electrode. and the reflective electrode, the light-emitting device is arranged on the optical path of the light emitted from the light-emitting layer, for extracting the light emitted from the light-emitting layer to the outside A light extraction layer is provided, the light extraction layer has a light scattering layer containing a base material and scattering particles having a refractive index different from that of the base material, and the thickness of the light scattering layer is A [μm]. , where B [vol%] is the volume concentration of the scattering particles in the base material, and C is the yellow index of the light scattering layer, A and B satisfy formula (I), and C is It satisfies formula (II).
25≦A×B≦145 (I)
5≦C≦25 (II)

The light emitting device has a light extraction layer on the optical path of light emitted from the light emitting layer. Since the light extraction layer has the light scattering layer, the light incident on the light extraction layer is easily extracted to the outside of the light emitting device. In the light-emitting device having the above configuration, the light-scattering layer is configured to satisfy the formulas (I) and (II), so that the light extraction efficiency is improved.

The light extraction layer may be arranged between the transparent substrate and the transparent electrode. With such an arrangement, light generated in the light-emitting layer passes through the light-scattering layer. As a result, light extraction by the light extraction layer can be reliably performed.

The base material may have a refractive index of 1.6 or more and 2.0 or less, and the scattering particles may have a refractive index of 2.0 or more and 2.4 or less.

The base material may have a refractive index of 1.6 or more and 2.0 or less, and the scattering particles may have a refractive index of 1.3 or more and 1.5 or less.

The light emitting device according to one embodiment further includes an inorganic thin film layer having a refractive index equal to or higher than the refractive index of the base material between the light extraction layer and the transparent electrode, and the inorganic thin film layer has a water vapor transmission rate of , 1×10 ⁻¹ g/(m ² ·day) or less.

The light-emitting layer may be an organic light-emitting layer. In this case, the light emitting device functions as an organic electroluminescent device.

A light extraction layer according to another aspect of the present invention includes a light scattering layer having a base material and scattering particles having a refractive index different from that of the base material. When B is the volume concentration of the particles in the base material and C is the yellow index of the light scattering layer, A and B satisfy formula (III), and C satisfies formula (IV).
light extraction layer.
25≦A×B≦145 (III)
5≦C≦25 (IV)

The light extraction layer has a light scattering layer that satisfies formula (III) and formula (IV). Therefore, when the light extraction layer is applied to, for example, a light emitting device, it is possible to efficiently extract light.

ADVANTAGE OF THE INVENTION According to this invention, the light emitting device and light extraction layer which can improve light extraction efficiency can be provided.

FIG. 1 is a diagram illustrating the basic configuration of an organic electroluminescence device (organic EL device), which is an example of a light-emitting device according to one embodiment. FIG. 2 is a schematic diagram of an example of an organic EL device (light-emitting device) provided with a sealing member. FIG. 3 is a chart showing experimental results.

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and overlapping descriptions are omitted. The dimensional proportions of the drawings do not necessarily match those of the description.

FIG. 1 is a diagram illustrating the basic configuration of an organic electroluminescence device (organic EL device), which is an example of a light-emitting device according to one embodiment.

The organic EL device 10 includes a transparent substrate 11 , a light extraction layer 12 , a transparent electrode 13 , an organic EL layer (device functional layer) 14 and a reflective electrode 15 . One of the transparent electrode 13 and the reflective electrode 15 functions as an anode, and the other functions as a cathode. In the following, unless otherwise specified, a configuration in which the transparent electrode 13 functions as an anode and the reflective electrode 15 functions as a cathode will be described.

The transparent substrate 11 is transparent to light (including visible light) output from the organic EL device 10 . The transparent substrate 11 may be a rigid substrate such as a glass substrate and a quartz substrate, or a flexible substrate such as a plastic substrate and a polymer film. A flexible substrate is a substrate that can be bent without being sheared or broken even when a predetermined force is applied to the substrate. An example of the refractive index of the transparent substrate 11 is 1.4 or more and 1.8 or less.

When the transparent substrate 11 is a rigid substrate, the thickness of the transparent substrate 11 is, for example, 50 μm to 1100 μm. When the transparent substrate 11 is a flexible substrate, the thickness of the transparent substrate 11 is, for example, 10 μm to 700 μm.

The light extraction layer 12 is arranged on the transparent substrate 11 . The light extraction layer 12 is a layer for extracting light generated within the organic EL device 10 to the outside. The light extraction layer 12 will be described later.

An electrode exhibiting optical transparency is used for the transparent electrode 13 . As the electrode exhibiting light transmittance, thin films of metal oxides, metal sulfides, metals, and the like with high electrical conductivity and laminates thereof can be used, and thin films with high light transmittance are preferably used. The transparent electrode 13 may have a network structure made of a conductor (for example, metal). The thickness of the transparent electrode 13 can be determined in consideration of light transmittance, electrical conductivity, and the like. The thickness of the transparent electrode 13 is usually 10 nm to 10 μm, preferably 20 nm to 1 μm, more preferably 30 nm to 500 nm.

Materials for the transparent electrode 13 include, for example, indium oxide, indium tin oxide (abbreviated as ITO), indium zinc oxide (abbreviated as IZO), zinc oxide, and aluminum-doped zinc oxide (Aluminium Zinc Oxide: AZO), Gallium Zinc Oxide (GZO), Tin Oxide, Antimony Tin Oxide (ATO), Fluorine Tin Oxide (FTO), gold, platinum, silver, copper, etc., and among these, ITO or IZO is preferred. The transparent electrode 13 can be formed as a thin film made of the exemplified materials. Organic materials such as polyaniline and its derivatives, polythiophene and its derivatives may be used as the material of the transparent electrode 13 . In this case, the transparent electrode 13 can be formed as a transparent conductive film.

The transparent electrode 13 can be formed by a dry film-forming method. Examples of the dry film forming method include a vacuum deposition method, a sputtering method, an ion plating method, and a CVD method.

The organic EL layer 14 is arranged on the transparent electrode 13 . The organic EL layer 14 is positioned between the transparent electrode 13 and the reflective electrode 15 . The size of the organic EL layer 14 (the size when viewed in the thickness direction) is smaller than the transparent substrate 11 . The organic EL layer 14 is a functional layer that contributes to light emission of the organic EL device 10 such as charge transfer and charge recombination according to power applied to the transparent electrode 13 and the reflective electrode 15 . The organic EL layer 14 has a light-emitting layer (organic light-emitting layer) 14a.

The light emitting layer 14a is a functional layer that emits light (including visible light). The thickness of the light emitting layer 14a is, for example, 1 nm to 1 μm, preferably 2 nm to 500 nm, more preferably 3 nm to 200 nm.

The light-emitting layer 14a is usually formed of an organic material that mainly emits at least one of fluorescence and phosphorescence, or the organic material and a dopant material that assists the organic material. Therefore, the light-emitting layer 14a is an organic light-emitting layer. The organic substance contained in the light-emitting layer 14a may be a low-molecular compound or a high-molecular compound.

Organic substances that mainly emit at least one of fluorescence and phosphorescence include the following dye-based materials, metal complex-based materials, polymer-based materials, and the like.

Examples of dye materials include cyclopentamine or its derivatives, tetraphenylbutadiene or its derivatives, triphenylamine or its derivatives, oxadiazole or its derivatives, pyrazoloquinoline or its derivatives, distyrylbenzene or its derivatives, di styrylarylene or derivatives thereof, pyrrole or derivatives thereof, thiophene ring compounds, pyridine ring compounds, perinone or derivatives thereof, perylene or derivatives thereof, oligothiophene or derivatives thereof, oxadiazole dimers or derivatives thereof, pyrazoline dimers or derivatives thereof, Examples include quinacridone or its derivatives, coumarin or its derivatives, and the like.

Examples of metal complex materials include rare earth metals such as Tb, Eu, and Dy, or Al, Zn, Be, Pt, Ir, etc., as central metals, and oxadiazole, thiadiazole, phenylpyridine, phenylbenzimidazole, and quinoline. A metal complex having a structure or the like as a ligand can be mentioned. Examples of metal complexes include metal complexes that emit light from a triplet excited state such as iridium complexes and platinum complexes, aluminum quinolinol complexes, benzoquinolinol beryllium complexes, benzoxazolyl zinc complexes, benzothiazole zinc complexes, azomethyl zinc complexes, porphyrin zinc complex, phenanthroline europium complex, and the like.

Examples of polymeric materials include polyparaphenylene vinylene or derivatives thereof, polythiophene or derivatives thereof, polyparaphenylene or derivatives thereof, polysilane or derivatives thereof, polyacetylene or derivatives thereof, polyfluorene or derivatives thereof, polyvinylcarbazole or derivatives thereof, Examples thereof include materials obtained by polymerizing at least one of the dye material and the metal complex material.

A dopant material is added, for example, to improve the luminous efficiency or change the luminous wavelength. Dopant materials mainly assisting organic substances that emit at least one of fluorescence and phosphorescence include, for example, perylene or its derivatives, coumarin or its derivatives, rubrene or its derivatives, quinacridone or its derivatives, squarium or its derivatives, porphyrin or its derivatives. , styryl dyes, tetracene or derivatives thereof, pyrazolones or derivatives thereof, decacyclene or derivatives thereof, phenoxazone or derivatives thereof, and the like.

The organic EL layer 14 may include various functional layers in addition to the light emitting layer 14a. Examples of the functional layer disposed between the transparent electrode 13, which is an anode, and the light-emitting layer 14a include the hole injection layer 14b and the hole transport layer 14c, as shown in FIG.

The hole injection layer 14b is a functional layer having a function of improving the efficiency of hole injection from the transparent electrode (anode) 13 to the light emitting layer 14a. The hole injection layer 14b may be an inorganic layer or an organic layer. The hole injection material forming the hole injection layer 14b may be a low-molecular compound or a high-molecular compound.

Examples of the hole injection material include metal oxides such as vanadium oxide, molybdenum oxide, ruthenium oxide, and aluminum oxide, and amorphous carbon. When the hole injection material is a low-molecular-weight compound, examples of the low-molecular-weight compound include phenylamine compounds, starburst-type amine compounds, and phthalocyanine compounds. Examples include amine compounds, starburst type amine compounds, and phthalocyanine compounds.

When the hole injection material is a polymer compound, examples of the polymer compound include polyaniline, polythiophene, polythiophene derivatives such as polyethylenedioxythiophene (PEDOT), polypyrrole, polyphenylene vinylene, polythienylene vinylene, polyquinoline and poly Examples include quinoxaline and derivatives thereof; and conductive polymers such as polymers containing an aromatic amine structure in the main chain or side chain.

The optimum thickness of the hole injection layer 14b varies depending on the material used. The thickness of the hole injection layer 14b can be appropriately determined in consideration of the required properties and the simplicity of film formation. The thickness of the hole injection layer 14b is, for example, 1 nm to 1 μm, preferably 2 nm to 500 nm, more preferably 5 nm to 200 nm.

The hole-transporting layer 14c is a functional layer having a function of improving the efficiency of hole injection from the hole-injecting layer 14b (the transparent electrode (anode) 13 in a form in which the hole-injecting layer 14b does not exist) to the light-emitting layer 14a. .

Hole transport layer 14c is an organic layer containing a hole transport material. The hole-transporting material is not limited as long as it is an organic compound having a hole-transporting function. Examples of organic compounds having a hole transport function include polyvinylcarbazole or derivatives thereof, polysilane or derivatives thereof, polysiloxane derivatives having aromatic amine residues in side chains or main chains, pyrazoline derivatives, arylamine derivatives, and stilbene derivatives. , triphenyldiamine derivative, polyaniline or its derivative, polythiophene or its derivative, polypyrrole or its derivative, polyarylamine or its derivative, poly(p-phenylene vinylene) or its derivative, polyfluorene derivative, having an aromatic amine residue Polymer compounds, and poly(2,5-thienylenevinylene) or derivatives thereof.

Examples of hole transport materials include JP-A-63-70257, JP-A-63-175860, JP-A-2-135359, JP-A-2-135361, JP-A-2-209988, Also included are hole transport materials described in JP-A-3-37992 and JP-A-3-152184.

The optimum thickness of the hole transport layer 14c differs depending on the material used. The thickness of the hole-transporting layer 14c can be appropriately determined in consideration of the required properties, the simplicity of film formation, and the like. The thickness of the hole transport layer 14c is, for example, 1 nm to 1 μm, preferably 2 nm to 500 nm, more preferably 5 nm to 200 nm.

The organic EL layer 14 may have an electron transport layer, an electron injection layer, etc. between the light emitting layer 14 a and the reflective electrode (cathode) 15 .

The electron transport layer is a functional layer that has the function of improving the efficiency of electron injection from the electron injection layer (the reflective electrode (cathode) 15 if the organic EL layer 14 does not have an electron injection layer) to the light emitting layer 14a.

The electron-transporting layer is an organic layer containing an electron-transporting material. A known material can be used as the electron transport material. Specific examples of electron transport materials include oxadiazole derivatives, anthraquinodimethane or derivatives thereof, benzoquinone or derivatives thereof, naphthoquinone or derivatives thereof, anthraquinone or derivatives thereof, tetracyanoanthraquinodimethane or derivatives thereof, fluorenone derivatives, Diphenyldicyanoethylene or its derivatives, diphenoquinone derivatives, metal complexes of 8-hydroxyquinoline or its derivatives, polyquinoline or its derivatives, polyquinoxaline or its derivatives, polyfluorenes or its derivatives, and the like.

The thickness of the electron-transporting layer can be appropriately determined in consideration of the required properties, ease of film formation, and the like. The thickness of the electron transport layer is, for example, 1 nm to 1 μm, preferably 2 nm to 500 nm, more preferably 5 nm to 200 nm.

The electron injection layer is a functional layer having a function of improving the electron injection efficiency from the reflective electrode (cathode) 15 to the light emitting layer 14a. When the organic EL layer 14 has an electron transport layer, the electron injection layer is arranged between the electron transport layer and the reflective electrode 15 . In this case, the electron transport layer injects electrons from the electron injection layer to the light emitting layer 14a. The electron injection layer may be an inorganic layer or an organic layer. The electron injection layer may be part of the reflective electrode 15 .

As the material forming the electron injection layer, an optimum material is appropriately selected according to the type of the light emitting layer 14a. Examples of materials constituting the electron injection layer include alkali metals, alkaline earth metals, alloys containing one or more of alkali metals and alkaline earth metals, oxides of alkali metals or alkaline earth metals, and halides. , carbonates, or mixtures of these substances. Examples of alkali metals, alkali metal oxides, halides and carbonates include lithium, sodium, potassium, rubidium, cesium, lithium oxide, lithium fluoride, sodium oxide, sodium fluoride, potassium oxide, potassium fluoride, Rubidium oxide, rubidium fluoride, cesium oxide, cesium fluoride, lithium carbonate, and the like may be mentioned. Examples of alkaline earth metals or alkaline earth metal oxides, halides and carbonates include magnesium, calcium, barium, strontium, magnesium oxide, magnesium fluoride, calcium oxide, calcium fluoride, barium oxide, fluoride Barium, strontium oxide, strontium fluoride, magnesium carbonate and the like.

In addition, a layer in which a conventionally known electron-transporting organic material and an organometallic complex of an alkali metal are mixed can be used as the electron injection layer.

The thickness of the electron injection layer is, for example, 1 nm to 1 μm, preferably 2 nm to 500 nm, more preferably 3 nm to 200 nm.

Examples of layer structures that the organic EL layer 14 can have are shown below. In the description of the layer structure of the organic EL layer 14, the transparent electrode 13 and the reflective electrode 15 are referred to as anodes in order to show the arrangement relationship between the anode (transparent electrode 13) and the cathode (reflective electrode 15) and the arrangement relationship among various functional layers. and the cathode. In the arrangement examples below, the anode and cathode are also listed in brackets.
(a) (anode)/hole injection layer/light-emitting layer/(cathode)
(b) (anode)/hole injection layer/light emitting layer/electron injection layer/(cathode)
(c) (Anode)/Hole Injection Layer (or Hole Transport Layer)/Emitting Layer/Electron Transport Layer/Electron Injection Layer/(Cathode)
(d) (anode)/hole injection layer/hole transport layer/light-emitting layer/(cathode)
(e) (Anode)/Hole Injection Layer/Hole Transport Layer/Emitting Layer/Electron Injection Layer/(Cathode)
(f) (Anode)/Hole Injection Layer/Hole Transport Layer/Emitting Layer/Electron Transport Layer/Electron Injection Layer/(Cathode)
(g) (anode)/light emitting layer/electron transport layer (or electron injection layer)/(cathode)
(i) (anode)/light emitting layer/electron transport layer/electron injection layer/(cathode)
The symbol "/" means that the layers on both sides of the symbol "/" are joined together.

The number of light-emitting layers 14a included in the organic EL layer 14 may be one, or two or more. In any one of the above layer configurations (a) to (i), the laminated structure arranged between the anode and the cathode is referred to as [structural unit I]. In this case, the structure of the organic EL layer 14 having two light-emitting layers 14a includes the layer structure shown in (j) below. The layer configurations of the two structural units I may be the same or different.
(j) (anode)/[structural unit I]/charge generation layer/[structural unit I]/(cathode)

The charge generation layer is a layer that generates holes and electrons by applying an electric field. Examples of the charge generation layer include thin films containing vanadium oxide, ITO, molybdenum oxide, and the like.

When "[structural unit I]/charge generation layer" is referred to as [structural unit II], the structure of the organic EL layer 14 having three or more light-emitting layers 14a includes the layer structure shown in (k) below. .
(k) (anode)/[structural unit II]x/[structural unit I]/(cathode)
The symbol "x" represents an integer of 2 or more, and "[structural unit II]x" represents a laminated structure in which [structural unit II] is laminated in x stages. A plurality of structural units II may have the same or different layer configurations.

The organic EL layer 14 may be configured by directly stacking a plurality of light emitting layers 14a without providing the charge generation layer.

The organic EL layer 14 can be formed by a coating method. Examples of coating methods include spin coating, inkjet printing, slit coating, micro gravure coating, gravure coating, bar coating, roll coating, wire bar coating, spray coating, screen printing, and flexographic coating. A printing method, an offset printing method, a reverse printing method, a nozzle printing method, and the like can be mentioned. The gravure coating method, screen printing method, flexographic printing method, offset printing method, reverse printing method, and inkjet printing method are preferable in that pattern formation and multicolor application are easy. When the organic EL layer 14 has a plurality of functional layers, each functional layer can be formed by a coating method.

A reflective electrode 15 is arranged on the organic EL layer 14 . The optimum thickness of the reflective electrode 15 differs depending on the material used, and is set in consideration of electrical conductivity, durability, and the like. The thickness of the reflective electrode 15 is usually 10 nm to 10 μm, preferably 20 nm to 1 μm, more preferably 50 nm to 500 nm.

The material of the reflective electrode 15 is selected from the organic EL layer 14 so that the light from the organic EL layer 14 (specifically, the light from the light-emitting layer 14a) is reflected by the reflective electrode 15 and travels toward the transparent electrode 13. A material having a high reflectance with respect to the light (especially visible light) emitted from the light emitting layer 14a is preferable. Materials for the reflective electrode 15 include, for example, alkali metals, alkaline earth metals, transition metals, and metals containing Group 13 elements of the periodic table. A transparent conductive electrode containing a conductive metal oxide, a conductive organic substance, or the like may be used as the reflective electrode 15 . The reflective electrode 15 may have multiple layers.

The reflective electrode 15 can be formed by a dry film forming method, a coating method, or the like. Examples of the dry film forming method and the coating method are as described above.

[Light extraction layer]
Next, the light extraction layer 12 will be described. The light extraction layer 12 is arranged on the optical path of the light emitted from the light emitting layer 14a. In the form shown in FIG. 1, the light extraction layer 12 is arranged between the transparent substrate 11 and the transparent electrode 13 . The light extraction layer 12 has a light scattering layer 12 a including a base material 121 (or base material layer) and scattering particles 122 dispersed in the base material 121 . The light extraction layer 12 may have a planarization layer 12b as shown in FIG.

An example of the material of the base material 121 is transparent resin. An example of the transparent resin used for the base material 121 is not particularly limited as long as it is a resin that transmits light emitted from the light emitting layer. Thermoplastic, thermosetting, light (electromagnetic wave) curing by visible light, ultraviolet rays, infrared rays, or the like, and electron beam curing by electron beam irradiation are preferably used.

Examples of such resins include polycarbonate (PC), polystyrene (PS), polyether, polyester, polyarylate, polyamide, polyimide, phenol-formaldehyde resin (phenolic resin), polydiethylene glycol bisallyl carbonate, acrylonitrile-styrene co- Polymers (AS resins), methyl methacrylate/styrene copolymers (MS resins), poly-4-methylpentene, norbornene-based polymers, urethane resins, epoxy resins, oxetane resins, acrylic resins, silicone resins, and the like. In addition, an organic-inorganic nanocomposite in which an organic polymer matrix and highly refractive inorganic nanoparticles are combined can also be used, but the present invention is not necessarily limited to these. These can be used singly or as a mixture of two or more at any ratio as required.

The compound constituting the photocurable resin may have two or more polymerizable functional groups per molecule. When the photocurable resin is composed of a compound having two or more polymerizable functional groups, it is possible to obtain a dense coating layer with a high crosslink density, effectively suppressing the permeation of moisture in the coating layer. This can contribute to improving the storage durability of the organic EL device 10 . The compound having two or more polymerizable functional groups is not particularly limited. It may be a compound having two or more kinds of polymerizable functional groups in one molecule, if necessary.

If necessary, nanoparticles may be added to the transparent resin used for the base material 121 in order to improve the refractive index. Examples of nanoparticles include zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ), zinc oxide (ZnO), tin oxide (SnO ₂ ), hafnium oxide (HfO ₂ ), Tantalum pentoxide (Ta ₂ O ₅ ) and the like are included. An example of the particle size of the nanoparticles is 0.001 μm or more and 0.05 μm or less.

An example of the refractive index of the base material 121 (including the base material 121 in which nanoparticles are dispersed) is 1.6 or more and 2.0 or less. The refractive index of the base material 121 is preferably 1.7 or higher. The refractive index at a wavelength of 589 nm (D-line wavelength) is the refractive index of the base material 121, and the refractive index of the base material 121 can be measured with a multi-wavelength Abbe refractometer, prism coupler, spectral interferometer, spectral ellipsometer, or the like.

The scattering particles 122 are particles for scattering light generated within the organic EL device 10 . The scattering particles 122 include titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ), zinc oxide (ZnO), tin oxide (SnO ₂ ), oxide hafnium ₍ HfO2), tantalum pentoxide ₍ Ta2O5), calcium oxide ₍ CaO), calcium carbonate ( _CaCO3 ), barium oxide (BaO), barium carbonate (BaCO3) _, barium titanate (BaTiO3) _, etc. inorganic particles, polymethyl methacrylate beads, acrylic-styrene copolymer beads, melamine resin beads, polycarbonate beads, polystyrene beads, crosslinked polystyrene beads, polyvinyl chloride beads, and organic particles such as benzoguanamine-melamine formaldehyde condensate beads. be done.

The particle diameter of the scattering particles 122 is larger than the particle diameter of the nanoparticles. An example of the particle diameter of the scattering particles 122 is 0.1 μm or more and 10 μm or less.

Since the scattering particles 122 scatter light, the refractive index of the scattering particles 122 is different from the refractive index of the base material 121 . Examples of the refractive index of the scattering particles 122 may be 2.0 or more and 2.4 or less, or 1.3 or more and 1.5 or less. The refractive index of the scattering particles 122 is the refractive index at a wavelength of 589 nm (D-line wavelength) and can be measured by a multi-wavelength Abbe refractometer, prism coupler, spectroscopic interferometer, spectroscopic ellipsometer, or the like. For materials such as inorganic particles that are difficult to measure the refractive index of, values from various databases can be used. The difference between the refractive index of the scattering particles 122 and the refractive index of the base material 121 can be 0.3 or more. An example of the upper limit of the difference between the refractive index of the scattering particles 122 and the base material 121 is 0.8. The particle size of the scattering particles 122 dispersed in the base material 121 may be different. That is, scattering particles 122 having different particle diameters may be dispersed in the base material 121 .

When the thickness of the light scattering layer 12a is A [μm], the volume concentration of the scattering particles 122 in the base material 121 is B [vol%], and the yellow index (YI) of the light scattering layer 12a is C, A and B satisfies formula (1) and C satisfies formula (2).
25≦A×B≦145 (1)
5≦C≦25 (2)

The product (A×B) of A [μm] indicating the thickness and B [vol %] indicating the volume concentration may be 30 or more and 120 or less. C representing YI may be 6 or more and 13 or less. Therefore, for example, the light scattering layer 12a may satisfy the following formula.
30≦A×B≦120
6≦C≦13

An example of the thickness of the light scattering layer 12a is 0.5 μm or more and 10 μm or less. The thickness of the light scattering layer 12a can be the in-plane average thickness in the plane orthogonal to the thickness direction of the light scattering layer 12a. The light scattering layer 12a can be measured with a thickness gauge. An example of the volume concentration of the scattering particles 122 is 5 vol % or more and 80 vol % or less.

The light scattering layer 12a can be formed by a coating method. Examples of coating methods are described above.

The planarization layer 12b is a layer for reducing unevenness of the surface caused by the scattering particles 122 of the light scattering layer 12a. The material of the flattening layer 12b can be a material that does not cause a refractive index difference with the base material 121 of the light scattering layer 12a. In one embodiment, the planarization layer 12b is made of the same material as the base material 121 described above. An example of the thickness of the planarization layer 12b is 0.5 μm or more and 10 μm or less. The planarizing layer 12b can be formed by a coating method. Examples of coating methods are described above.

The organic EL device 10 may have an inorganic thin film layer 16 between the light extraction layer 12 and the transparent electrode 13, as shown in FIG.

An inorganic thin film layer 16 is disposed on the light extraction layer 12 . The inorganic thin film layer 16 is positioned between the light extraction layer 12 and the transparent electrode 13 . The inorganic thin film layer 16 functions as a barrier layer. An example of the water vapor permeability of the inorganic thin film layer 16 is 1×10 ⁻¹ g/(m ² ·day) or less. The water vapor transmission rate can be a value calculated by a calcium corrosion method (method described in Japanese Patent Application Laid-Open No. 2005-283561) under conditions of a temperature of 40° C. and a humidity of 90% RH.

The inorganic thin film layer 16 has a refractive index equal to or higher than that of the base material 121 . An example of the refractive index of the inorganic thin film layer 16 is 1.8 or more and 2.4 or less. As the material of the inorganic thin film layer 16, a layer of an inorganic material having a known gas barrier property can be appropriately used from the viewpoint of refractive index and transparency. Examples of inorganic materials include metal oxides, metal nitrides, metal oxynitrides, metal oxycarbides, and mixtures comprising at least two of these. Moreover, a multilayer film in which two or more layers of the thin film layers described above are laminated can also be used. In addition, inorganic polymeric materials such as perhydropolysilazanes can also be used. An example of the thickness of the inorganic thin film layer 16 is 10 nm or more and 1000 nm or less.

The inorganic thin film layer 16 can be formed by a dry film forming method, a coating method, or the like. Examples of the dry film forming method and the coating method are as described above.

Organic EL device 10 can be manufactured, for example, by forming light extraction layer 12 , transparent electrode 13 , organic EL layer 14 and reflective electrode 15 on transparent substrate 11 in this order. When the organic EL device 10 has the inorganic thin film layer 16 , the inorganic thin film layer 16 may be formed after forming the light extraction layer 12 and before forming the transparent electrode 13 .

The organic EL device 10 may include a sealing member 40 that seals the organic EL layer 14 . FIG. 2 is a drawing for explaining an example of an organic EL device with a sealing member. The organic EL device 10 shown in FIG. 2 is called an organic EL device 10A.

As shown in FIG. 2, the organic EL device 10A includes a transparent substrate 11, a light extraction layer 12, a transparent electrode 13, an organic EL layer 14, a reflective electrode 15, an auxiliary electrode 31, and a sealing member 40. and Although omitted in FIG. 3, the organic EL device 10A may include an inorganic thin film layer 16 between the light extraction layer 12 and the transparent electrode 13, as in the case of the organic EL device 10. FIG.

The configuration and arrangement relationship of the transparent substrate 11 and the light extraction layer 12 are the same as in the case of the organic EL device 10, so description thereof will be omitted.

The transparent electrode 13 and the auxiliary electrode 31 are spaced apart on the light extraction layer 12 (on the inorganic thin film layer 16 when the organic EL device 10A has the inorganic thin film layer 16). Since the configuration of the transparent electrode 13 is the same as that of the organic EL device 10, the description thereof is omitted.

The auxiliary electrode 31 is electrically connected to the reflective electrode 15 . An external terminal is connected to the auxiliary electrode 31 . The auxiliary electrode 31 is an electrode for supplying electric power to the reflective electrode 15 arranged inside the sealing member 40, as shown in FIG.

The thickness and material of the auxiliary electrode 31 may be the same as those of the transparent electrode 13 . In this case, the auxiliary electrode 31 and the transparent electrode 13 are formed by forming an electrode layer using the same material as those, and then patterning the transparent electrode 13 and the auxiliary electrode 31 by finely processing the electrode layer. can be formed. The auxiliary electrode 31 may be made of a conductive material different from that of the transparent electrode 13 . The auxiliary electrode 31 may be formed so as to be separated from the transparent electrode 13 in advance when the transparent electrode 13 is formed. That is, the transparent electrode 13 and the auxiliary electrode 31 may be individually formed without patterning one electrode layer as described above. The auxiliary electrode 31 may be formed before or after forming the transparent electrode 13 .

The configurations of the organic EL layer 14 and the reflective electrode 15 are the same as those of the organic EL device 10 . In the organic EL device 10A, the organic EL layer 14 can also be arranged between the transparent electrode 13 and the auxiliary electrode 31. FIG. In the organic EL device 10A, the reflective electrode 15 is formed on the organic EL layer 14 as in the case of the organic EL device 10 and is also formed on the auxiliary electrode 31 . Thereby, the reflective electrode 15 and the auxiliary electrode 31 are electrically connected.

The sealing member 40 is not particularly limited as long as it suppresses deterioration of the organic EL device 10 due to moisture, oxygen, etc. that enter from the outside. There is a sealing member. A case where the sealing member 40 is of a cap type will be described. An example of the sealing member 40 is sealing glass. The sealing member 40 covers the organic EL layer 14 and the reflective electrode 15, and is fixed to the transparent electrode 13 and the auxiliary electrode 31 so that a part of the transparent electrode 13 and the auxiliary electrode 31 is located outside the sealing member 40. It is The sealing member 40 can be fixed to the transparent electrode 13 and the auxiliary electrode 31 with an adhesive 41 . An example of the adhesive 41 is an ultraviolet (UV) curable adhesive (adhesive containing UV curable resin). When the cap-shaped sealing member 40 is used, the space formed by the cap-shaped sealing member 40 can be filled with an absorbent material (getter material) for moisture and oxygen. By doing so, it is possible to prevent deterioration of the organic EL device 10 due to moisture or oxygen that has penetrated into the space formed by the sealing member 40 through the adhesive 41 .

For the convenience of the following explanation, the parts of the organic EL device 10A other than the sealing member 40, that is, the light extraction layer 12, the inorganic thin film layer 16, the transparent electrode 13, the auxiliary electrode 31, the organic EL layer 14 and the reflective electrode The transparent substrate 11 on which 15 is formed is called a device substrate 30 .

The organic EL device 10A can be manufactured as follows. A device substrate 30 is manufactured in the same manner as the organic EL device 10 except that the auxiliary electrode 31 is formed as described above. After that, the sealing member 40 is fixed to the transparent electrode 13 and the auxiliary electrode 31 via the adhesive 41 so as to cover the organic EL layer 14 and the reflective electrode 15 . Thereby, the organic EL device 10A is obtained.

Actions and effects of the organic EL devices 10 and 10A will be described. The organic EL device 10A has a configuration similar to that of the organic EL device 10 as a basic configuration. Therefore, since the organic EL device 10A has the same operational effects as the organic EL device 10, the operational effects of the organic EL devices 10 and 10A will be described for the organic EL device 10 unless otherwise specified.

In the organic EL device 10 , when power is supplied to the transparent electrode 13 and the reflective electrode 15 , light is generated in the light emitting layer 14 a within the organic EL layer 14 . The light generated in the light emitting layer 14a passes through the transparent electrode 13 and is output from the transparent substrate 11 side. Of the light generated in the light emitting layer 14a, the light traveling toward the reflective electrode 15 is reflected by the reflective electrode 15 and then output from the transparent substrate 11 side.

The organic EL device 10 has the light extraction layer 12 on the optical path of the light emitted from the light emitting layer 14a. The light incident on the light extraction layer 12 after being emitted from the light emitting layer 14 a is scattered by the scattering particles 122 in the light scattering layer 12 a of the light extraction layer 12 . Therefore, light confinement due to total reflection inside the transparent electrode 13, the transparent substrate 11, etc. is suppressed, so that the light extraction efficiency is improved. The light scattering layer 12a in the present embodiment is a yellowish layer that satisfies formula (1) and is represented by formula (2). Therefore, the light extraction efficiency of the organic EL device 10 is further improved.

When the refractive index difference between the scattering particles 122 and the base material 121 is within the range illustrated, light scattering is likely to occur.

When the organic EL device 10 has the inorganic thin film layer 16, it is possible to prevent moisture from entering the organic EL layer 14 from the transparent substrate 11 side. Therefore, the product life of the organic EL device 10 is improved.

The organic EL device 10</b>A includes a sealing member 40 that seals the organic EL layer 14 . Therefore, deterioration of the organic EL layer 14 can be prevented. This improves the product life of the organic EL device 10A.

Next, an experimental example will be described. The present invention is not limited to the experimental examples described below. For convenience of explanation, elements corresponding to the elements described in the above embodiment are denoted by the same reference numerals in the description of the experimental example.

<Measurement and evaluation method>
Methods for measuring or evaluating physical quantities used in experimental examples will be described.

(Method for measuring refractive index)
The refractive index was determined by analyzing the optical constants of the absolute reflectance measurement results obtained with a reflection spectroscopic film thickness meter (manufactured by Otsuka Electronics Co., Ltd., FE-3000).

(Method for measuring film thickness)
A stylus-type film thickness measuring device (P-16, manufactured by KLA-Tencor) was used for the film thickness measurement.

(Method for measuring total light transmittance and haze)
Total light transmittance and haze were measured using a haze meter (manufactured by Suga Test Instruments Co., Ltd., HZ-V3), using air as a blank and a C light source as a light source, according to JISK7105.

(Measurement of YI of light scattering layer)
The YI of the light scattering layer was measured using a spectrophotometer (CM-3600A, manufactured by Konica Minolta Co., Ltd.), using air as a blank, allowing light to enter from the light scattering layer side, and measuring according to ASTM D1925 (C light source). .

(Method for evaluating gas barrier properties)
The gas barrier properties of laminated films having barrier properties were evaluated by water vapor transmission rate (WVTR). The water vapor transmission rate was calculated by the calcium corrosion method (method described in Japanese Patent Application Laid-Open No. 2005-283561) under conditions of a temperature of 40° C. and a humidity of 90% RH. That is, after the laminated film is dried, metallic calcium is vapor-deposited, then metallic aluminum is vapor-deposited thereon, and finally, glass is bonded using a sealing resin to bond the sample. The increase in corrosion points on the laminated film side due to changes over time under the conditions of 40° C. and 90% RH was examined by image analysis to calculate the water vapor transmission rate.

In addition, when calculating such a water vapor transmission rate, the corrosion point is photographed with a microscope, the image is taken into a personal computer, the image of the corrosion point is binarized, and the corrosion area is calculated and obtained. Water vapor permeability was calculated. The smaller the water vapor transmission rate, the better the gas barrier properties.

(Method for measuring sheet resistance)
Sheet resistance was measured by a four-terminal, four-probe method (Mitsubishi Chemical Analytic Tech Loresta GP).

<Manufacture of organic EL device>
Next, a method for manufacturing the organic EL device used in the experimental examples will be described. In the experimental example, an organic EL device 10A having a sealing member 40 was manufactured as shown in FIG. In the experimental example, as shown in the table of FIG. 3, 18 organic particles having different volume concentrations of the scattering particles 122 contained in the light scattering layer 12a, thickness of the light scattering layer 12a, and YI of the light scattering layer 12a were used. An EL device 10A was manufactured. [A], [B] and [C] in FIG. 3 indicate the volume concentration, thickness and YI, and are described corresponding to formulas (1) and (2). As shown in FIG. 3, the cases satisfying the formulas (1) and (2) are referred to as Examples 1-11, and the other cases are referred to as Comparative Examples 1-7. The manufacturing method will be specifically described using the case of Example 1 as an example.

(1) Example 1
(Preparation of light extraction layer)
Titanium oxide (TiO ₂ ) having an average primary particle size of 15 nm is subjected to dispersion treatment in a state in which a dispersant is added to a dispersion solvent to obtain a titanium oxide nanoparticle dispersion liquid, and then photocuring having a refractive index of 1.5. A base material dispersion solution was obtained by mixing and adding the titanium oxide nanoparticle dispersion into the organic resin monomer solution, followed by dispersion treatment.

The obtained base material dispersion solution was coated on a glass substrate (EagleXG manufactured by Corning) by a spin coating method under the conditions of a slope of 1 second, a number of revolutions of 1000 rpm, and a holding time of 30 seconds. dried for a minute. After drying, the coating layer was subjected to a curing treatment using a UV irradiation device (SP-9, manufactured by Ushio Inc.) under the conditions of an illuminance of 30 mW/cm ² and an integrated light intensity of 800 mJ/cm ² to remove the base material coating layer. Obtained. The obtained base material coating layer had a refractive index of 1.88 at a wavelength of 589 nm, a thickness of 1.0 μm, a total light transmittance Tt of 84%, and a haze of 0.7%.

As the scattering particles 122, silicon oxide (SiO ₂ , KE-P50 manufactured by Nippon Shokubai Co., Ltd.) having a refractive index of 1.43 and an average particle diameter of 0.5 μm was used. PGME (propylene glycol monomethyl ether) was added as a dispersion medium to the above silicon oxide and subjected to dispersion treatment to obtain a silicon oxide particle dispersion. Thereafter, the base material dispersion and the silicon oxide particle dispersion were mixed so that the volume concentration was the ratio set in Example 1 shown in FIG. 3 to obtain a coating solution for forming a light scattering layer.

(Preparation of transparent substrate)
As the transparent substrate 11, a glass substrate (manufactured by Corning, EagleXG) with a thickness of 0.7 mm was washed with a brush scrub, two fluids, rinsed with pure water, and dried with an air knife. ) was subjected to surface modification treatment for 10 minutes using UV-312 manufactured by Technovision.

(Formation of light scattering layer)
Then, the coating solution for forming a light scattering layer was dropped onto a glass substrate placed on the coater head of a spin coater, spin-coated, and then dried on a hot plate at 90° C. for 2 minutes. The thickness of the light scattering layer was adjusted to the thickness set in Example 1 by changing the number of rotations of the spin coater. After drying, the coating layer was cured using a UV irradiation device (SP-9, manufactured by Ushio Inc.) under conditions of illuminance of 30 mW/cm ² and integrated light intensity of 800 mJ/cm ² , followed by a hot plate. A degassing treatment was performed at 200° C. for 10 minutes to obtain a substrate with a light scattering layer. YI was measured for the obtained substrate with a light scattering layer. The measurement result was taken as the YI of the light scattering layer 12a of Example 1. Further, the thickness of the obtained light scattering layer 12a was measured by the stylus type film thickness measuring device described above. The thickness (A) and YI (C) of the light scattering layer 12a of Example 1 were as shown in FIG.

<Formation of planarization layer>
Furthermore, the base material dispersion solution was spin-coated on the substrate with the light scattering layer prepared under the same conditions as the substrate with the light scattering layer whose thickness and YI were measured, with a slope of 1 second, a rotation speed of 1000 rpm, and a holding time of 30. After coating for 2 seconds, drying was performed on a hot plate at 90°C for 2 minutes. After drying, the coating layer (corresponding to the flattening layer 12b in FIG. 1) was subjected to the conditions of an illuminance of 30 mW/cm ² and an integrated light amount of 800 mJ/cm ² using a UV irradiation device (manufactured by Ushio Inc., SP-9). A hardening treatment was performed with and a flattening treatment was performed. In addition, degassing was performed on a hot plate at 200° C. for 10 minutes. As a result, the light extraction layer 12 having the light scattering layer 12a and the flattening layer 12b laminated on the light scattering layer 12a was formed, and as a result, the substrate with the light extraction layer was obtained.

(Formation of inorganic barrier layer (inorganic thin film layer))
An inorganic barrier layer (corresponding to the inorganic thin film layer 16 in FIG. 1) was formed on the flattening layer 12b of the substrate with the light extraction layer using a plasma CVD apparatus. Specifically, after loading the substrate with the light extraction layer into the discharge chamber of the plasma CVD device, the chamber was evacuated to 1×10 ⁻³ Pa or less. Then, SiH ₄ , N ₂ , and NH ₃ gases were introduced into the discharge chamber, and under the condition that the pressure was adjusted to 1.0 Pa, a high-frequency power of 13.56 kHz was applied to the induction coil, whereby the dielectric window was opened. plasma was generated in the chamber to form a silicon oxynitride film layer. The refractive index of the silicon oxynitride film layer at a wavelength of 200 nm and a wavelength of 589 nm was 1.87. Therefore, the obtained silicon oxynitride film layer (inorganic barrier layer) was a high refractive index barrier layer. At the same time, the water vapor transmission rate of the laminated film with the silicon oxynitride film formed on the COP film (Zeonor film ZF16, 50 μm thick, manufactured by Nippon Zeon Co., Ltd.) placed in the chamber was measured and found to be 5 × 10 ^-3 g. /(m ² ·day). The water vapor transmission rate of the laminate film with the silicon oxynitride film was measured by the method described in the evaluation method for gas barrier property described above.

(Formation of transparent electrode and auxiliary electrode)
Next, an ITO (In ₂ O ₃ —SnO ₂ ) film was formed on the inorganic barrier layer of the substrate with the light extraction layer by sputtering using a metal shadow mask so as to have a thickness of 45 nm. A film was patterned to form an electrode 31 . The sheet resistance of the obtained ITO was 39Ω/□. The resulting transparent electrode-attached substrate was ultrasonically cleaned with an organic solvent, an alkaline detergent and ultrapure water in this order, then boiled in an organic solvent for 10 minutes and dried. Then, the surface on which the ITO thin film was formed was subjected to surface modification treatment for 10 minutes using a UV ozone cleaning device (manufactured by Technovision Co., Ltd., trade name: UV-312).

(Formation of organic EL layer)
<Hole injection layer>
A coating film having a thickness of 35 nm was formed by applying a hole injection material, which is a combination of an organic material having a charge-transporting property and an electron-accepting material, onto a substrate with a transparent electrode by a spin coating method. The coating film was dried on a hot plate in the atmosphere to form the hole injection layer 14b. In drying using a hot plate, drying was first performed at 80° C. for 4 minutes, and then further dried at 230° C. for 15 minutes.

<Hole transport layer>
A hole-transporting material, which is a polymer material, and xylene were mixed to obtain a composition for forming a hole-transporting layer having a solid matter (hole-transporting material) concentration of 0.7% by mass. The obtained composition for forming a hole transport layer was applied onto the hole injection layer 14b by a spin coating method to obtain a coating film having a thickness of 20 nm. The substrate provided with this coating film is placed in a nitrogen atmosphere (inert atmosphere), using a hot plate, heated at 200 ° C. for 30 minutes to evaporate the solvent, and then naturally cooled to room temperature to transport holes. Layer 14c was obtained.

<Light emitting layer>
The light-emitting conjugated polymer material and xylene were mixed to obtain a composition for forming a light-emitting layer in which the concentration of the light-emitting conjugated polymer material was 1.3%. A green light-emitting conjugated polymer material was used as the light-emitting conjugated polymer material. The obtained composition for forming a light emitting layer was applied onto the hole transport layer 14c by a spin coating method to obtain a coating film having a thickness of 60 nm. The substrate provided with this coating film is placed in a nitrogen atmosphere (inert atmosphere), using a hot plate, heated at 180° C. for 10 minutes to evaporate the solvent, and then naturally cooled to room temperature to obtain the light-emitting layer 14a. got

(reflective electrode)
After forming the light-emitting layer 14a, the reflective electrode 15 was formed in a vapor deposition chamber dedicated to metal. Specifically, on the light-emitting layer 14a, sodium fluoride (NaF) is vapor-deposited to a thickness of 3 nm by a vacuum vapor deposition method, and then aluminum (Al) is vapor-deposited to a thickness of 100 nm. , a reflective electrode 15 was formed. Thus, a device substrate 30 was obtained.

(sealing)
The device substrate 30 is transported from the vapor deposition chamber to the sealing processing chamber without being exposed to the atmosphere, and in a nitrogen atmosphere (inert atmosphere), a sealing glass (sealing member 40) coated with a UV curable resin around it. and the device substrate 30 transported from the vapor deposition chamber were bonded together and irradiated with UV light to cure the UV curing resin, and the device substrate 30 was sealed with glass. Thus, the organic EL device 10A was manufactured.

(2) Production of organic EL devices of Examples 2 to 11 and Comparative Examples 1 to 7 The volume concentration (B) of the scattering particles 122 in the light scattering layer 12a and the thickness (A) of the light scattering layer 12a are shown in FIG. Organic EL devices 10A of Examples 2 to 11 and Comparative Examples 1 to 7 were manufactured in the same manner as in Example 1, except for the changes (adjustments) shown in the chart. The YI of the light scattering layer 12a measured in the manufacturing process in the same manner as in Example 1 was as shown in FIG. The thickness (A) of the light scattering layer 12a shown in FIG. 3 is a measured value measured in the same manner as in the first embodiment.

<Evaluation of organic EL device>
(1) Evaluation of Organic EL Device of Example 1 A reference device having the same configuration as the organic EL device 10A of Example 1 was manufactured, except that it did not have a light extraction layer.

Using a total luminous flux measurement device, the total luminous flux of the organic EL device 10A was measured under the condition of a current density of 2.5 mA/cm ² , and the external quantum efficiency (EQE) was calculated as the light extraction efficiency. Furthermore, the EQE was similarly calculated for the reference device. After that, the EQE improvement factor was obtained by dividing the EQE of the organic EL device 10A by the EQE of the reference device. The calculation results were as shown in FIG.

(2) Evaluation of the organic EL devices of Examples 2 to 11 and Comparative Examples 1 to 7 The same configuration as the organic EL devices 10A of Examples 2 to 11 and Comparative Examples 1 to 7, except for not having a light extraction layer. A reference device was manufactured.

Example 1 except that the organic EL devices 10A of Examples 2 to 11 and Comparative Examples 1 to 7 were used, and the reference devices of Examples 2 to 11 and Comparative Examples 1 to 7 were used. Similarly, EQE improvement ratios were obtained for Examples 2 to 11 and Comparative Examples 1 to 7, respectively. The calculation results were as shown in FIG.

From the results shown in FIG. 3, in Examples 1 to 11 having the light scattering layer 12a that satisfies the formulas (1) and (2), at least one of the formulas (1) and (2) is not satisfied. A higher EQE improvement ratio than ~7 was achieved. That is, it can be understood that the light extraction efficiency can be improved by using the light scattering layer 12a that satisfies the formula (1) and is yellowish as defined by the formula (2).

The present invention is not limited to the above embodiments and experimental examples, but includes the scope indicated by the claims, and all changes within the meaning and scope equivalent to the claims intended to be included.

For example, the transparent electrode 13 may be the cathode and the reflective electrode 15 may be the anode.

When the organic EL device is provided with a sealing member, the sealing member is not limited to a cap type (or frame type), and may be a sheet-like sealing member. For example, a sheet-like sealing member can have a sealing layer having a moisture barrier function and an adhesive layer. Examples of the sealing layer include a metal foil, a barrier film in which a barrier function layer is formed on the surface or the back surface of a transparent plastic film, or both surfaces thereof, flexible thin glass, or a metal having a barrier property on a plastic film. Examples include laminated films. The adhesive layer is a layer for bonding the sealing layer (or sealing member) to the transparent substrate (or transparent electrode), and is a known adhesive (including the concept of adhesive) that can be used in organic EL devices. can be formed with

By raising the refractive index of the light extraction layer to the same or higher than that of the organic EL layer, the light generated in the light emitting layer of the organic EL layer is taken into the light extraction layer with less loss such as total reflection, resulting in light extraction efficiency. is increasing. Therefore, for example, by making the refractive index of the transparent substrate or the like equal to or higher than that of the organic EL layer, the same effect can be exhibited even when the light extraction layer is arranged on the side opposite to the transparent electrode.

The present invention can also be applied to light-emitting devices other than organic EL devices. For example, the light-emitting layer may be made of an inorganic material.

A light-outcoupling film may be attached to the side of the transparent substrate opposite to the side on which the light-outcoupling layer is arranged. Light extraction films include those coated with scattering particles and those that improve the light extraction efficiency by surface shaping such as microlenses, but the light extraction efficiency is maximized in combination with the light extraction layer. An appropriate light extraction film may be selected. The light extraction film can reduce total reflection loss caused by the refractive index difference between the transparent substrate and the air interface.

The above embodiments and various modifications may be combined as appropriate without departing from the scope of the present invention.

10, 10A... Organic EL device (light emitting device), 11... Transparent substrate, 12... Light extraction layer, 12a... Light scattering layer, 13... Transparent electrode, 14... Organic EL layer, 14a... Light emitting layer (organic light emitting layer), DESCRIPTION OF SYMBOLS 15... Reflective electrode, 16... Inorganic thin film layer, 40... Sealing member, 121... Base material, 122... Scattering particles.

Claims (7)

It comprises a transparent substrate, a transparent electrode, a reflective electrode, and a luminescent layer, the transparent electrode being disposed on the transparent substrate, and the luminescent layer being disposed between the transparent electrode and the reflective electrode. a light emitting device comprising:
A light extraction layer disposed on the optical path of the light emitted from the light emitting layer and for extracting the light emitted from the light emitting layer to the outside,
The light extraction layer has a light scattering layer containing a base material and scattering particles having a refractive index different from that of the base material,
Let A [μm] be the thickness of the light scattering layer, B [vol %] be the volume concentration of the scattering particles in the base material, and C be the yellow index of the light scattering layer. B satisfies formula (I) and said C satisfies formula (II);
luminous device.
25≦A×B≦145 (I)
5≦C≦25 (II) wherein the light extraction layer is disposed between the transparent substrate and the transparent electrode;
11. The light emitting device of claim 1. The base material has a refractive index of 1.6 or more and 2.0 or less,
The scattering particles have a refractive index of 2.0 or more and 2.4 or less.
3. A light emitting device according to claim 2. The base material has a refractive index of 1.6 or more and 2.0 or less,
The scattering particles have a refractive index of 1.3 or more and 1.5 or less.
3. A light emitting device according to claim 2. further comprising an inorganic thin film layer having a refractive index equal to or higher than the refractive index of the base material between the light extraction layer and the transparent electrode;
The inorganic thin film layer has a water vapor permeability of 1×10 ⁻¹ g/(m ² day) or less.
A light-emitting device according to any one of claims 1-4. wherein the light-emitting layer is an organic light-emitting layer;
A light-emitting device according to any one of claims 1-5. A light scattering layer having a base material and scattering particles having a refractive index different from that of the base material,
When A is the thickness of the light scattering layer, B is the volume concentration of the scattering particles in the base material, and C is the yellow index of the light scattering layer, A and B satisfy formula (III). if said C satisfies formula (IV),
light extraction layer.
25≦A×B≦145 (III)
5≦C≦25 (IV)

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