WO2015045599A1 - Organic electroluminescent element - Google Patents

Abstract

The objective of the present invention is to provide an organic electroluminescent element which has excellent light extraction efficiency of emitted light and excellent light emission uniformity. This organic electroluminescent element (10) is characterized by being obtained by sequentially laminating, on a transparent substrate (13), a light extraction layer (2) for changing the directivity of light, a transparent electrode (1), an organic functional layer (3) and a counter electrode (5a). This organic electroluminescent element (10) is also characterized in that: the light extraction layer (2) comprises a light scattering layer (2a) that contains light scattering particles having an average particle diameter of 150-350 nm; and the light scattering layer (2a) has an in-plane occupancy of the light scattering particles of 20-60%, a thickness of 150-500 nm, a surface roughness (Ra) of 10-50 nm and a maximum height (Rt) of 100-300 nm.

Description

Organic electroluminescence device

The present invention relates to an organic electroluminescence element. In particular, the present invention relates to an organic electroluminescence device excellent in light extraction efficiency and emission uniformity of emitted light.

At present, organic electroluminescence elements (hereinafter also referred to as “organic EL elements”) are attracting attention as thin luminescent materials.
An organic EL element using electroluminescence (EL) of an organic material is a thin-film type completely solid element that can emit light at a low voltage of several V to several tens V, and has high luminance, high luminous efficiency, It has many excellent features such as thinness and light weight. For this reason, it has been attracting attention in recent years as surface light emitters such as backlights for various displays, display boards such as signs and emergency lights, and illumination light sources.

The organic EL element can obtain high luminance with low power and is excellent in terms of visibility, response speed, life, and power consumption. On the other hand, the light utilization efficiency of the organic EL element is about 20%, and there is a problem that the loss in the element is large.
This loss of emitted light will be described below with reference to FIG.

FIG. 6 is a schematic cross-sectional view of a conventional organic EL element.
The organic EL element 100 includes a metal electrode 101, an organic functional layer 102 having a refractive index of approximately 1.8, a transparent electrode 103 having a refractive index of approximately 1.8, and a refractive index of approximately 1.5 in order from the lower layer in the figure. A transparent substrate 104 is laminated. Note that arrows indicated by reference numerals 110a to 110e in the drawing indicate characteristic features of light generated from the organic functional layer 102.
The light 110a is light in a direction perpendicular to the light emitting surface of the organic functional layer 102, passes through the transparent substrate 104, and is extracted to the light extraction side (air side).
The light 110b is light that is incident on the interface between the transparent substrate 104 and air at a shallow angle less than the critical angle, and is refracted at the interface between the transparent substrate 104 and air and extracted to the light extraction side.
The light 110c is light that is incident on the interface between the transparent substrate 104 and air at an angle deeper than the critical angle, and is light that is totally reflected at the interface between the transparent substrate 104 and air and cannot be extracted to the light extraction side. The loss due to this is called “substrate loss”, and there is usually a loss of about 20%.
The light 110 d is light that satisfies the resonance condition among light incident on the interface between the transparent electrode 103 and the transparent substrate 104 at an angle deeper than the critical angle, and is totally reflected at the interface between the transparent electrode 103 and the transparent substrate 104. The light is generated in a guided mode and confined in the organic functional layer 102 and the transparent electrode 103. The loss due to this is called “waveguide loss”, and there is usually a loss of about 20 to 25%.
The light 110 e is light that is incident on the metal electrode 101, interacts with free electrons in the metal electrode 101, generates a plasmon mode that is a kind of waveguide mode, and is confined in the vicinity of the surface of the metal electrode 101. The loss due to this is called “plasmon loss” and there is usually a loss of about 30 to 40%.

As described above, in the conventional organic EL element, the substrate loss, the waveguide loss, and the plasmon loss are generated, so that the utilization efficiency of the emitted light is lowered.

As a technique for suppressing light loss due to such substrate loss and extracting more light, a technique is known in which a light extraction layer that changes the directivity of emitted light is provided on the light extraction side of the organic EL element. (For example, refer to Patent Document 1 and Patent Document 2.) This light extraction layer is composed of light scattering particles and a binder, and the light extraction efficiency is increased by scattering emitted light by the light scattering particles.

When light scattering particles in the light scattering layer are increased in order to further improve the light extraction efficiency, the front direction of the organic EL element (perpendicular to the light emission surface of the organic EL element) due to the light scattering effect of the light scattering particles. The light extraction efficiency in a direction oblique to (direction) is improved, but the light extraction efficiency in the front direction of the organic EL element is lowered.

With respect to such a problem, in Patent Document 3, the light scattering layer has a structure in which a light scattering region in which light scattering particles are aggregated and a light transmission region in which the content ratio of the light scattering particles is low are mixed. The light extraction efficiency in the front direction of the EL element is improved.
However, in the technique described in Patent Document 3, the layer thickness of the light scattering layer is large, and the unevenness of the surface of the light scattering layer is large, so that the layer thickness of the smooth layer that smoothes the surface of the light scattering layer is also large. Therefore, the light extraction efficiency may be reduced due to the absorption of the light scattering layer and the smooth layer.
In the technique described in Patent Document 3, since the average particle diameter of the light scattering particles contained in the light scattering layer is larger than the wavelength of the emitted light generated in the organic functional layer, the emitted light is partially blocked. In some cases, the light emission uniformity may be reduced on the light exit surface of the organic EL element.

JP 2009-054424 A JP 2009-259792 A Japanese Patent No. 5010556

An object of the present invention has been made in view of the above problems and situations, and is to provide an organic electroluminescence element excellent in light extraction efficiency and emission uniformity of emitted light.

As a result of investigating the cause of the above-mentioned problems in order to solve the above-mentioned problems related to the present invention, a light extraction layer, a transparent electrode, an organic functional layer, and a counter electrode that change the directivity of light are sequentially laminated on the transparent substrate. An organic EL device, wherein the light extraction layer has a light scattering layer containing light scattering particles having an average particle size within a specific range, and the light scattering layer occupies in the plane of the light scattering particles Organic electroluminescence device excellent in light extraction efficiency and emission uniformity of emitted light by adjusting absorption and scattering of emitted light, with the ratio, layer thickness, surface roughness Ra, and maximum height Rt within specific ranges Found that can be provided.
That is, the subject concerning this invention is solved by the following means.

1. An organic electroluminescence device in which a light extraction layer that changes the directivity of light, a transparent electrode, an organic functional layer, and a counter electrode are sequentially laminated on a transparent substrate,
The light extraction layer has a light scattering layer containing light scattering particles having an average particle diameter of 150 to 350 nm;
The light scattering layer has an in-plane occupation ratio of the light scattering particles of 20 to 60%, a layer thickness of 150 to 500 nm, a surface roughness Ra of 10 to 50 nm, and a maximum height Rt of 100 to 300 nm. An organic electroluminescence device characterized by that.

2. 2. The organic electroluminescence device according to claim 1, wherein the light extraction layer has a smoothing layer that smoothens a surface of the light scattering layer facing the transparent electrode.

ADVANTAGE OF THE INVENTION According to this invention, the organic electroluminescent element excellent in the light extraction efficiency and emitted light uniformity of emitted light can be provided.
The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.
Since the average particle diameter of the light scattering particles is 150 to 350 nm and the thickness of the light scattering layer is 150 to 500 nm, the light scattering layer has a layer thickness of one or two light scattering particles. . For this reason, absorption of the emitted light by a light-scattering layer is suppressed, and light extraction efficiency improves. Further, since the surface roughness Ra of the light scattering layer is 10 to 50 nm, the light scattering layer has a uniform sparse / dense structure without large aggregation of light scattering particles. In addition, since the maximum height Rt is 100 to 300 nm, there is no portion where the light scattering particles are aggregated and extremely convex, so that the adjacent layer such as the transparent electrode or the organic light emitting layer is not present. A layer requiring high smoothness can be formed without causing current leakage. Since the in-plane occupation ratio of the light scattering particles in the light scattering layer is 20 to 60%, the number of light scattering particles in light incident at an incident angle of 0 to 90 ° with respect to the light scattering layer. On the other hand, since the surface area of the light scattering particles is increased, the scattering opportunity of incident light is increased. Further, since the in-plane occupation ratio of the light scattering particles is 20 to 60%, a light transmission region with a low presence ratio of the light scattering particles is formed in the light scattering layer, and light transmission is also ensured. For this reason, it is estimated that the light extraction efficiency is improved.
In addition, since the average particle diameter of the light scattering particles is 150 to 350 nm, the emitted light generated in the organic functional layer is not shielded, so that the light emission surface of the organic EL element has excellent emission uniformity.

Schematic sectional view of an organic EL device according to the present invention The figure which shows schematic structure of a light extraction layer forming apparatus Sectional drawing which shows schematic structure of wavelength control infrared heater Sectional drawing which shows the modification of the wavelength control infrared heater of FIG. The figure which shows the electron micrograph of the light-scattering layer in the organic EL element of a comparative example The figure which shows the electron micrograph of the light-scattering layer in the organic EL element of an Example. The figure which shows the electron micrograph of the light-scattering layer in the organic EL element of an Example. Schematic sectional view of a conventional organic EL device

The organic EL element of the present invention is an organic EL element in which a light extraction layer, a transparent electrode, an organic functional layer, and a counter electrode that change the directivity of light are sequentially laminated on a transparent substrate, and the light extraction layer includes And a light scattering layer containing light scattering particles having an average particle diameter of 150 to 350 nm. The light scattering layer has an in-plane occupation ratio of the light scattering particles of 20 to 60% and a layer thickness of 150 The surface roughness Ra is 10 to 50 nm, and the maximum height Rt is 100 to 300 nm. This feature is a technical feature common to the inventions according to claims 1 to 2.
In the present invention, it is preferable that the light extraction layer has a smooth layer that smoothes a surface of the light scattering layer facing the transparent electrode. Thereby, the unevenness | corrugation of the surface of a light-scattering layer can be smoothed, and the other layer formed on a light extraction layer can be smoothed. Therefore, a high quality organic EL element can be manufactured.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “˜” representing a numerical range is used in the sense that numerical values described before and after the numerical value range are included as a lower limit value and an upper limit value.

<< Configuration of organic EL element >>
As shown in FIG. 1, the organic EL element 10 of the present invention includes a light extraction layer 2, a transparent electrode 1, an organic functional layer 3 formed using an organic material, and the like, and a counter electrode 5 a in order from the transparent substrate 13 side. They are stacked in this order.
An extraction electrode 16 is provided at the end of the transparent electrode 1. The transparent electrode 1 and an external power source (not shown) are electrically connected via the extraction electrode 16. The organic EL element 10 is configured to extract the generated light (emitted light h) from at least the transparent substrate 13 side.

Further, the layer structure of the organic EL element 10 is not limited to the structure described below, and may be a general layer structure. Here, the transparent electrode 1 functions as an anode (that is, an anode), and the counter electrode 5a functions as a cathode (that is, a cathode). In this case, for example, as the organic functional layer 3, a structure in which a hole injection layer 3a / a hole transport layer 3b / a light emitting layer 3c / an electron transport layer 3d / an electron injection layer 3e are stacked in this order from the transparent electrode 1 side that is an anode. Of these, it is essential to have the light emitting layer 3c composed of at least an organic material. The hole injection layer 3a and the hole transport layer 3b may be provided as a hole transport injection layer. The electron transport layer 3d and the electron injection layer 3e may be provided as an electron transport injection layer. Of these organic functional layers 3, for example, the electron injection layer 3e may be made of an inorganic material.

In addition to these layers, the organic functional layer 3 may be laminated with a hole blocking layer, an electron blocking layer, or the like as necessary. Furthermore, the light emitting layer 3c may have a structure in which each color light emitting layer that generates light emitted in each wavelength region is laminated, and each of these color light emitting layers is laminated via a non-light emitting intermediate layer. The intermediate layer may function as a hole blocking layer and an electron blocking layer. Furthermore, the counter electrode 5a, which is a cathode, may have a laminated structure as necessary. In such a configuration, only a portion where the organic functional layer 3 is sandwiched between the transparent electrode 1 and the counter electrode 5 a becomes a light emitting region in the organic EL element 10.

Further, in the layer configuration as described above, the auxiliary electrode 15 may be provided in contact with the transparent electrode 1 for the purpose of reducing the resistance of the transparent electrode 1.

The organic EL element 10 configured as described above is sealed with a sealing material 17 on the transparent substrate 13 for the purpose of preventing the organic functional layer 3 configured using an organic material or the like from deterioration due to moisture or oxygen. It has been stopped. The sealing material 17 is fixed to the transparent substrate 13 side with an adhesive 19. However, the terminal portions of the transparent electrode 1 (extraction electrode 16) and the counter electrode 5a are provided on the transparent substrate 13 so as to be exposed from the sealing material 17 while being insulated from each other by the organic functional layer 3. Suppose that

Hereinafter, details of each main layer for constituting the organic EL element 10 described above and a manufacturing method thereof will be described.

<Transparent substrate>
The transparent substrate used in the present invention may be composed of any material such as glass, quartz, transparent resin film, etc., and has gas barrier performance such as moisture resistance / gas permeability resistance required for organic EL elements. Is preferred. In the film base material, it is preferable to provide a layer for improving gas barrier performance.
The “transparent substrate” in the present invention refers to a substrate having a light transmittance of 70% or more at a wavelength of 550 nm, and the light transmittance is preferably 80% or more, more preferably 90% or more, particularly preferably 95. % Or more.

Moreover, it is preferable that the transparent substrate has flexibility. The term “flexibility” as used herein refers to a substrate that is wound around a φ (diameter) 50 mm roll and is not cracked before and after winding with a constant tension, and more preferably a substrate that can be wound around a φ30 mm roll. Say.

Examples of the transparent substrate that can be wound around the roll as described above include acrylic acid ester, methacrylic acid ester, polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), cellulose triacetate (TAC), and polycarbonate (PC ), Polyarylate, polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polystyrene (PS), nylon (Ny), aromatic polyamide, polyether ether ketone, polysulfone, polyether sulfone, polyimide, poly Each resin film such as ether imide, heat-resistant transparent film (product name Sila-DEC, manufactured by Chisso Corporation) with silsesquioxane having organic-inorganic hybrid structure as basic skeleton, and resin Formed by laminating two or more layers a resin film, and the like.

In terms of cost and availability, polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), polycarbonate (PC) and the like are preferably used, and optical transparency, heat resistance, inorganic layer, gas In terms of adhesion to the barrier layer, a heat-resistant transparent film having a basic skeleton of silsesquioxane having an organic-inorganic hybrid structure can be preferably used.
Among them, from the viewpoint of transparency, heat resistance, ease of handling, strength and cost, a biaxially stretched polyethylene terephthalate film, a biaxially stretched polyethylene naphthalate film, a polyethersulfone film, and a polycarbonate film are preferable, and a biaxially stretched polyethylene terephthalate film. A biaxially stretched polyethylene naphthalate film is more preferred.
Furthermore, in order to suppress the shrinkage at the time of thermal expansion to the maximum, a low heat recovery processed product subjected to a treatment such as thermal annealing is most preferable.

The thickness of the transparent substrate is preferably in the range of 10 to 500 μm, more preferably in the range of 20 to 250 μm, and still more preferably in the range of 30 to 150 μm. When the thickness of the transparent substrate is in the range of 10 to 500 μm, a stable gas barrier property can be obtained, and it is suitable for a roll-to-roll system.

(Gas barrier layer)
(1) Characteristics and Forming Method In the present invention, it is preferable to provide one or more gas barrier layers (low refractive index layers) having a refractive index in the range of 1.4 to 1.7 on the transparent substrate. . As such a gas barrier layer, a known material can be used without any particular limitation. For example, the following materials can be preferably used.

The gas barrier layer is a layer containing an inorganic precursor compound, and is formed by applying a coating solution containing at least one layer of an inorganic precursor compound on a transparent substrate.

Any appropriate method can be adopted as a coating method.
Specific examples include a roll coating method, a flow coating method, an ink jet method, a spray coating method, a printing method, a dip coating method, a casting film forming method, a bar coating method, and a gravure printing method.

The coating thickness can be set appropriately according to the purpose. For example, the coating thickness is set so that the thickness after drying is preferably about 1 nm to 10 μm, more preferably about 10 nm to 10 μm, and most preferably about 30 nm to 1 μm.

(2) Inorganic precursor compound The inorganic precursor compound used in the present invention is particularly limited as long as it is a compound that forms metal oxide, metal nitride, or metal oxynitride by vacuum ultraviolet irradiation under a specific atmosphere. Although not suitable, the compound suitable for the production method of the present invention is preferably a compound that is modified at a relatively low temperature as described in JP-A-8-112879.

Specifically, polysiloxane having Si—O—Si bond (including polysilsesquioxane), polysilazane having Si—N—Si bond, Si—O—Si bond and Si—N—Si bond. A polysiloxazan containing both may be mentioned. You may use these in mixture of 2 or more types. Moreover, it can be used even if different compounds are sequentially laminated or simultaneously laminated.

(2.1) Polysiloxane The polysiloxane used in the present invention includes [R ₃ SiO _1/2 ], [R ₂ SiO], [RSiO _3/2 ] and [SiO ₂ ] as general structural units. be able to. Here, R is a hydrogen atom, an alkyl group containing 1 to 20 carbon atoms (for example, a methyl group, an ethyl group, a propyl group, etc.), an aryl group (for example, a phenyl group) and an unsaturated alkyl group (for example, Independently selected from the group consisting of vinyl groups (Vi) and the like. Examples of specific polysiloxane groups include [PhSiO _3/2 ], [MeSiO _3/2 ], [HSiO _3/2 ], [MePhSiO], [Ph ₂ SiO], [PhViSiO], [ViSiO _3/2 ]. ], [MeHSiO], [MeViSiO], [Me ₂ SiO], [Me ₃ SiO _1/2 ] and the like. Mixtures and copolymers of polysiloxanes can also be used.

(2.2) Polysilsesquioxane In the present invention, polysilsesquioxane is preferably used among the polysiloxanes described above. Polysilsesquioxane is a compound containing silsesquioxane in a structural unit. “Silsesquioxane” is a compound represented by [RSiO _3/2 ], usually RSiX ₃ (R is a hydrogen atom, an alkyl group, an alkenyl group, an aryl group, an araalkyl group, etc. Is a halogen, an alkoxy group, etc.) A polysiloxane synthesized by hydrolysis-polycondensation of a type compound. The molecular arrangement of cissesoxane typically includes an amorphous structure, a ladder structure, a cage structure or a partially cleaved structure thereof (a structure in which a silicon atom is missing from a cage structure or a silicon structure having a cage structure) A structure in which an oxygen bond is partially broken) is known.

Among these polysilsesquioxanes, it is preferable to use a so-called hydrogen silsesquioxane polymer. Hydrogen silsesquioxane polymers include hydridosiloxane polymers of the formula: HSi (OH) _x (OR) _y O _{z / 2} where each R is an organic group or a substituted organic group, When bonded to silicon, a hydrolyzable substituent is formed, and x = 0 to 2, y = 0 to 2, z = 1 to 3, and x + y + z = 3. Examples of R include an alkyl group (for example, a methyl group, an ethyl group, a propyl group, a butyl group), an aryl group (for example, a phenyl group), and an alkenyl group (for example, an allyl group, a vinyl group). .
These resins are either fully condensed (HSiO _3/2 ) _n , or only partially hydrolyzed (ie, including some Si—OR) and / or partially condensed (ie, Including some Si-OH).

Examples of the cage silsesquioxane include silsesquioxane of the following general formula (I) represented by the chemical formula [RSiO _3/2 ] _{8 and} the following chemical formula of [RSiO _3/2 ] ₁₀ Silsesquioxane of general formula (II), represented by the chemical formula of [RSiO _3/2 ] ₁₂ , and silsesquioxane of the following general formula (III), represented by the chemical formula of [RSiO _3/2 ] ₁₄ Silsesquioxane of the general formula (IV) and silsesquioxane of the following general formula (V) represented by the chemical formula of [RSiO _3/2 ] ₁₆ are mentioned.

The _{[RSiO 3/2]} value of n in the cage-type silsesquioxane represented by _n is an integer of 6-20, preferably 8, 10 or 12, particularly preferably 8 or 8,10 And 12 mixtures. In addition, [RSiO _3/2 ] _nm (O _1/2 H) _{2 + m} (n is an integer of 6 to 20) in which a part of silicon-oxygen bond of cage silsesquioxane is partially cleaved. m is 0 or 1. As a preferable example of a cage silsesquioxane represented by the formula (I), a trisilanol body in which a part of the general formula (I) is cleaved, [RSiO _3/2 ] ₇ (O _{1 / 2} H) Silsesquioxane of the following general formula (VI) represented by ₃ ; Sil of the following general formula (VII) represented by the chemical formula of [RSiO _3/2 ] ₈ (O _1/2 H) ₂ Examples thereof include sesquioxane and silsesquioxane of the following general formula (VIII) represented by a chemical formula of [RSiO _3/2 ] ₈ (O _1/2 H) ₂ .

R in the general formulas (I) to (VIII) is a hydrogen atom, a saturated hydrocarbon group having 1 to 20 carbon atoms, an alkenyl group having 2 to 20 carbon atoms, an araalkyl group having 7 to 20 carbon atoms, or a carbon number of 6 Up to 20 aryl groups. Among these, R is preferably a polymerizable functional group capable of polymerization reaction.

Examples of the saturated hydrocarbon group having 1 to 20 carbon atoms include methyl group, ethyl group, n-propyl group, i-propyl group, butyl group (n-butyl group, i-butyl group, t-butyl group, sec -Butyl group, etc.), pentyl group (n-pentyl group, i-pentyl group, neopentyl group, cyclopentyl group, etc.), hexyl group (n-hexyl group, i-hexyl group, cyclohexyl group etc.), heptyl group (n- Heptyl group, i-heptyl group, etc.), octyl group (n-octyl group, i-octyl group, t-octyl group, etc.), nonyl group (n-nonyl group, i-nonyl group, etc.), decyl group (n- Decyl group, i-decyl group, etc.), undecyl group (n-undecyl group, i-undecyl group, etc.), dodecyl group (n-dodecyl group, i-dodecyl group, etc.) and the like. In consideration of the balance of melt fluidity, flame retardancy and operability during molding, the hydrocarbon is preferably a saturated hydrocarbon having 1 to 16 carbon atoms, and particularly preferably a saturated hydrocarbon having 1 to 12 carbon atoms.

Examples of the alkenyl group having 2 to 20 carbon atoms include acyclic alkenyl groups and cyclic alkenyl groups. Examples thereof include vinyl group, propenyl group, butenyl group, pentenyl group, hexenyl group, cyclohexenyl group, cyclohexenylethyl group, norbornenylethyl group, heptenyl group, octenyl group, nonenyl group, decenyl group, undecenyl group, A dodecenyl group etc. are mentioned. Considering the balance of melt fluidity, flame retardancy and operability during molding, an alkenyl group having 2 to 16 carbon atoms is preferred, and an alkenyl group having 2 to 12 carbon atoms is particularly preferred.

Examples of the aralkyl group having 7 to 20 carbon atoms include a benzyl group, a phenethyl group, a benzyl group or a phenethyl group substituted with one or more of alkyl groups having 1 to 13 carbon atoms, preferably 1 to 8 carbon atoms. Is mentioned.

Examples of the aryl group having 6 to 20 carbon atoms include phenyl group, tolyl group, phenyl group or tolyl group substituted with alkyl group having 1 to 14 carbon atoms, preferably 1 to 8 carbon atoms, xylyl group, and the like. It is done.

As the above-mentioned cage-type silsesquioxanes, compounds commercially available from Aldrich, Hybrid Plastic, Chisso, Amax, etc. may be used as they are, and Journal of American Chemical Society, Vol. 111. 1741 (1989), etc., may be used.

The partial cleavage structure of a polysilsesquioxane cage structure is a Si—O—Si bond formed by cleavage of a Si—O—Si bond from one cage unit represented by the chemical formula [RSiO _3/2 ] _8. A compound having 3 or less OH or a compound having 1 or less Si atom deficiency in a closed cage structure represented by the chemical formula of [RSiO _3/2 ] ₈ is shown.

Also in the cage silsesquioxane, hydrogen silsesquioxane such as [HSiO _3/2 ] ₈ can be preferably used.

(2.3) Polysilazane The polysilazane used in the present invention is a polymer having a silicon-nitrogen bond, and is composed of Si—N, Si—H, NH, etc., SiO ₂ , Si ₃ N ₄ and intermediate solid solutions of both. It is an inorganic precursor polymer such as SiO _x N _y (x: 0.1 to 1.9, y: 0.1 to 1.3).

The polysilazane preferably used in the present invention is represented by the following general formula (A).

Formula (A)
— [Si (R ₁ ) (R ₂ ) —N (R ₃ )] —

In general formula (A), R ₁ , R ₂ and R ₃ each represent a hydrogen atom, an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, an alkylsilyl group, an alkylamino group or an alkoxy group.

In the present invention, perhydropolysilazane in which all of R ₁ , R ₂ and R ₃ are hydrogen atoms is particularly preferable from the viewpoint of the denseness as the gas barrier layer to be obtained.

On the other hand, the organopolysilazane in which the hydrogen part bonded to Si is partially substituted with an alkyl group or the like has an alkyl group such as a methyl group, thereby improving the adhesiveness with a transparent substrate and being hard and brittle polysilazane. Since toughness can be imparted to the ceramic layer, there is an advantage that generation of cracks can be suppressed even when the layer thickness is increased. These perhydropolysilazane and organopolysilazane may be appropriately selected according to the application, and can also be mixed and used.

Perhydropolysilazane is presumed to have a linear structure and a ring structure centered on 6- and 8-membered rings. Its molecular weight is about 600 to 2000 (polystyrene conversion) in terms of number average molecular weight (Mn), and it is a liquid or solid substance depending on the molecular weight. These are marketed in a solution state dissolved in an organic solvent, and the commercially available product can be used as it is as a polysilazane-containing coating solution.

Other examples of polysilazanes that are ceramicized at low temperatures include silicon alkoxide-added polysilazanes obtained by reacting the above polysilazanes with silicon alkoxides (Japanese Patent Laid-Open No. 5-23827), and glycidol-added polysilazanes obtained by reacting glycidol (special No. 6-122852), an alcohol-added polysilazane obtained by reacting an alcohol (Japanese Patent Laid-Open No. 6-240208), and a metal carboxylate-added polysilazane obtained by reacting a metal carboxylate (Japanese Patent Laid-Open No. 6-299118). No. 1), acetylacetonate complex-added polysilazane obtained by reacting a metal-containing acetylacetonate complex (JP-A-6-306329), metal fine particle-added polysilazane obtained by adding metal fine particles (JP-A-7- 1969 6 No.), and the like.

As an organic solvent for preparing a liquid containing polysilazane, it is not preferable to use an alcohol or water-containing one that easily reacts with polysilazane. Examples of the organic solvent preferably used include hydrocarbon solvents such as aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons, ethers such as halogenated hydrocarbon solvents, aliphatic ethers, and alicyclic ethers. Can be mentioned. Specific examples include hydrocarbons such as pentane, hexane, cyclohexane, toluene, xylene, solvesso and turben, halogen hydrocarbons such as methylene chloride and trichloroethane, and ethers such as dibutyl ether, dioxane and tetrahydrofuran. These solvents may be selected according to purposes such as the solubility of polysilazane and the evaporation rate of the solvent, and a plurality of solvents may be mixed.

The polysilazane concentration in the polysilazane-containing coating solution is about 0.2 to 35% by mass, although it varies depending on the target silica layer thickness and the pot life of the coating solution.

The organic polysilazane may be a derivative in which the hydrogen part bonded to Si is partially substituted with an alkyl group or the like. Adhesion with a transparent substrate is improved by having an alkyl group, especially a methyl group having the smallest molecular weight, and it is possible to impart toughness to a hard and brittle silica layer. Even when the layer thickness is increased, cracks are generated. Is suppressed.

Also, an amine or metal catalyst can be added in order to promote the modification treatment to the silicon oxide compound. Specific examples include Aquamica NAX120-20, NN110, NN310, NN320, NL110A, NL120A, NL150A, NP110, NP140, and SP140 manufactured by AZ Electronic Materials Co., Ltd.

(2.4) Polysiloxazan Polysiloxazan has main repeating units of — [(SiH ₂ ) _n (NH) _r ] — and — [(SiH ₂ ) _m O] — (where n, m and r are , 1, 2 or 3)).

(2.5) Catalyst A catalyst may be added to the solution containing the inorganic precursor according to the present invention (also referred to as a coating solution) as necessary.

Specifically, 1-methylpiperazine, 1-methylpiperidine, 4,4'-trimethylenedipiperidine, 4,4'-trimethylenebis (1-methylpiperidine), diazabicyclo- [2,2,2] octane Cis-2,6-dimethylpiperazine, 4- (4-methylpiperidine) pyridine, pyridine, dipyridine, α-picoline, β-picoline, γ-picoline, piperidine, lutidine, pyrimidine, pyridazine, 4,4'-tri N-heterocyclic compounds such as methylenedipyridine, 2- (methylamino) pyridine, pyrazine, quinoline, quinoxaline, triazine, pyrrole, 3-pyrroline, imidazole, triazole, tetrazole, 1-methylpyrrolidine, methylamine, dimethylamine, Trimethylamine, ethylamine, diethylamine, Liethylamine, propylamine, dipropylamine, tripropylamine, butylamine, dibutylamine, tributylamine, pentylamine, dipentylamine, tripentylamine, hexylamine, dihexylamine, trihexylamine, heptylamine, diheptylamine, octyl Amines such as amine, dioctylamine, trioctylamine, phenylamine, diphenylamine, triphenylamine, DBU (1,8-diazabicyclo [5,4,0] 7-undecene), DBN (1,5-diazabicyclo [ 4,3,0] 5-nonene), 1,5,9-triazacyclododecane, 1,4,7-triazacyclononane and the like.

Organic acids, inorganic acids, metal carboxylates, acetylacetona complexes, and metal fine particles are also preferable catalysts.
Examples of organic acids include acetic acid, propionic acid, butyric acid, valeric acid, maleic acid and stearic acid, and inorganic acids include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, hydrogen peroxide, chloric acid and hypochlorous acid. Etc.
The metal carboxylate is represented by the formula: (RCOO) _n M [wherein R represents an aliphatic group or an alicyclic group having 1 to 22 carbon atoms, and M represents Ni, Ti, Pt, Rh, This represents at least one metal selected from the group consisting of Co, Fe, Ru, Os, Pd, Ir, and Al, and n is equivalent to the valence of M. It is a compound represented by this. The metal carboxylate may be an anhydride or a hydrate.
An acetylacetona complex is a complex in which an anion acac ⁻ generated by acid dissociation from acetylacetone (2,4-pentadione) is coordinated to a metal atom, and generally has the formula (CH ₃ COCHCOCH ₃ ) _n M [Wherein M represents a metal having an ionic value of n. ] Is represented. Suitable metals M include, for example, nickel, platinum, palladium, aluminum, rhodium and the like. Metal fine particles can also be used preferably. Specifically, Au, Ag, Pd or Ni is preferable, and Ag is particularly preferable. The particle size of the metal fine particles is preferably smaller than 0.5 μm, more preferably 0.1 μm or less, and still more preferably smaller than 0.05 μm.
In addition to these, organic metal compounds such as peroxide, metal chloride, ferrocene, zirconocene, and the like can also be used. Further, platinum vinyl siloxane used as a curing agent for silicone polymer can also be used.

These catalysts are preferably blended in the range of 0.01 to 10% by mass, more preferably in the range of 0.05 to 2% by mass with respect to the inorganic precursor compound.

<Light extraction layer>
(1) Configuration and Characteristics The light extraction layer 2 is disposed between the transparent substrate 13 and the transparent electrode 1, and a light scattering layer 2a and a smooth layer 2b are laminated in order from the transparent substrate 13 side. (See FIG. 1).

The refractive index of the light extraction layer at a wavelength of 550 nm is preferably in the range of 1.7 or more and less than 2.5.
Waveguide mode light confined in the light emitting layer of the organic EL element and plasmon mode light reflected from the cathode are light of specific optical modes, and in order to extract these lights, a refractive index of at least 1.7 or more is required. is necessary. On the other hand, even in the highest order mode, there is almost no light in a region having a refractive index of 2.5 or higher, and the amount of light that can be extracted does not increase even when the refractive index is higher than this.
Actually, it is preferable that the refractive index of the light scattering layer and the smoothing layer be in the range of 1.7 or more and less than 2.5, respectively, but it may be difficult to measure the refractive index of each layer individually. Therefore, it is sufficient that the refractive index satisfies the above range as the entire light extraction layer.
The refractive index was measured by irradiating the light with the shortest light emission maximum wavelength among the light emission maximum wavelengths of the light emitted from the light emitting unit in an atmosphere at 25 ° C. (The same applies to the measurement of the refractive index of the light scattering layer and the smooth layer).

Moreover, it is preferable that the haze value (ratio of the scattering transmittance to the total light transmittance) of the light extraction layer is 30% or more. If the haze value is 30% or more, the luminous efficiency can be improved.
The haze value is a physical property value calculated under the influence of (i) the refractive index difference of the composition in the layer and (ii) the influence of the surface shape. In the present invention, the haze value as a light extraction layer in which a smooth layer is laminated on the light scattering layer is measured. That is, by measuring the haze value while keeping the surface roughness below a certain level, the haze value excluding the influence of (ii) is measured.

Further, the light extraction layer of the present invention preferably has a transmittance of 50% or more, more preferably 55% or more, and particularly preferably 60% or more.
Although it is preferable that the light extraction layer has a high transmittance, it is assumed that the light extraction layer actually has a value of less than 80%. The transmittance of the light extraction layer is more preferably less than 85%, and particularly preferably less than 90%.

(2) Light Scattering Layer The light scattering layer 2a according to the present invention is a layer containing light scattering particles having an average particle diameter of 150 to 350 nm, and the in-plane occupation ratio of the light scattering particles is 20 to 60. %, A layer thickness of 150 to 500 nm, a surface roughness Ra of 10 to 50 nm, and a maximum height Rt of 100 to 300 nm.
The light scattering layer 2a is formed by applying, drying, and curing a light scattering layer coating solution containing light scattering particles and a binder on the transparent substrate 13.

(2.1) Refractive Index The light scattering layer is preferably a high refractive index layer having a refractive index within a range of 1.7 or more and less than 3.0 in an environment of a temperature of 25 ° C. and a humidity of 55% RH. . In this case, the light scattering layer may be formed of a single material having a refractive index of 1.7 or more and less than 3.0, or two or more compounds are mixed to have a refractive index of 1.7 or more and 3. A layer of less than 0 may be formed. In the case of such a mixed system, the refractive index of the light scattering layer can be substituted by a calculated refractive index calculated by a total value obtained by multiplying the refractive index specific to each material by the mixing ratio. In this case, the refractive index of each material may be less than 1.7 or 3.0 or more, and the mixed layer may have a refractive index satisfying 1.7 or more and less than 3.0.

Further, the light scattering layer of the present invention is a mixed light scattering layer (scattering film) using a difference in refractive index due to a mixture of a layer medium and light scattering particles.

The light scattering layer is a layer that improves light extraction efficiency, and is formed on the outermost surface of the transparent substrate on the transparent electrode side.
The light scattering layer is composed of a layer medium and light scattering particles contained in the layer medium.
The refractive index difference between the resin material (monomer or polymer) described later as the layer medium and the contained light scattering particles is 0.03 or more, preferably 0.1 or more, more preferably 0.2 or more. And particularly preferably 0.3 or more. When the difference in refractive index between the layer medium and the light scattering particles is 0.03 or more, a scattering effect occurs at the interface between the layer medium and the light scattering particles. A larger refractive index difference is preferable because refraction at the interface increases and the scattering effect improves.

(2.2) Average particle diameter of light scattering particles The light scattering layer is a layer that scatters light due to the difference in refractive index between the layer medium and the light scattering particles as described above. For this reason, the contained light scattering particles are preferably transparent particles having a particle size equal to or larger than the region that causes Mie scattering in the visible light region, and the average particle size is 150 to 350 nm.
By setting the upper limit of the average particle size to 350 nm, the layer thickness of the light scattering layer can be reduced, and the layer thickness of the smooth layer that smoothes the surface of the light scattering layer can be reduced. This is also advantageous from the viewpoint of process load and layer absorption. On the other hand, by setting the lower limit of the average particle size to 150 nm, it is possible to reliably obtain the light scattering effect.
Here, the average particle diameter of the high refractive index particles (light scattering particles) can be measured by image processing of a transmission electron micrograph (TEM cross section).

The average particle diameter of the light-scattering particles is within the range of 150 to 350 nm. The smaller the average particle diameter, the easier it is to scatter light having a shorter wavelength, and the larger the average particle diameter, the light having a higher wavelength component. Easy to scatter. Therefore, light scattering particles having a small average particle diameter and light scattering particles having a large average particle diameter may be used in combination.

(2.3) Types of Light Scattering Particles The light scattering particles are not particularly limited and may be appropriately selected depending on the purpose, and may be organic fine particles or inorganic fine particles. Inorganic fine particles having a high refractive index are preferred.

Examples of organic fine particles having a high refractive index include polymethyl methacrylate beads, acrylic-styrene copolymer beads, melamine beads, polycarbonate beads, styrene beads, crosslinked polystyrene beads, polyvinyl chloride beads, and benzoguanamine-melamine formaldehyde beads. Can be mentioned.

Examples of the inorganic fine particles having a high refractive index include inorganic oxide particles made of at least one oxide selected from zirconium, titanium, indium, zinc, antimony, cerium, niobium, tungsten, and the like. Specific examples of the inorganic oxide particles include ZrO ₂ , TiO ₂ , BaTiO ₃ , In ₂ O ₃ , ZnO, Sb ₂ O ₃ , ITO, CeO ₂ , Nb ₂ O _5, and WO ₃ . Among these, TiO ₂ , BaTiO ₃ , ZrO ₂ , CeO ₂ and Nb ₂ O ₅ are preferable, and TiO ₂ is most preferable. Of TiO _2, the rutile type is more preferable than the anatase type because the catalyst activity is low, and the weather resistance of the high refractive index layer and the adjacent layer is high, and the refractive index is high.

In addition, these particles are used in the form of a surface treatment from the viewpoint of improving the dispersibility and stability in the case of using a dispersion liquid described later in order to be included in the light scattering layer having a high refractive index, or the surface. It is possible to select whether to use an untreated one.

When performing the surface treatment, specific materials for the surface treatment include different inorganic oxides such as silicon oxide and zirconium oxide, metal hydroxides such as aluminum hydroxide, organic acids such as organosiloxane and stearic acid, and the like. It is done. These surface treatment materials may be used individually by 1 type, and may be used in combination of multiple types. Among these, from the viewpoint of the stability of the dispersion, the surface treatment material is preferably a different inorganic oxide and / or metal hydroxide, more preferably a metal hydroxide.

When the inorganic oxide particles are surface-coated with a surface treatment material, the coating amount (in general, this coating amount is indicated by the mass ratio of the surface treatment material used on the surface of the particle to the mass of the particles). Is preferably in the range of 0.01 to 99% by mass. When the coating amount of the surface treatment material is 0.01% by mass or more, the effect of improving the dispersibility and stability by the surface treatment can be sufficiently obtained, and when it is within 99% by mass, the light having a high refractive index is obtained. It can suppress that the refractive index of a scattering layer falls.

In addition, quantum dots described in International Publication No. 2009/014707 and US Pat. No. 6,608,439 can be suitably used as the high refractive index material.

The high refractive index particles have a refractive index of 1.7 or more, preferably 1.85 or more, and particularly preferably 2.0 or more. When the refractive index is 1.7 or more, the difference in refractive index from the binder increases, so that the amount of scattering increases and the effect of improving the light extraction efficiency can be obtained.
On the other hand, the upper limit of the refractive index of the high refractive index particles is less than 3.0. If the difference in refractive index from the binder is large, a sufficient amount of scattering can be obtained, and the effect of improving the light extraction efficiency can be obtained.

The arrangement of the high refractive index particles is preferably about the average particle thickness so that the light scattering particles are in contact with or close to the interface between the light scattering layer and the smooth layer. Thereby, when total reflection occurs in the smooth layer, the evanescent light that permeates into the light scattering layer can be scattered by the particles, and the light extraction efficiency is improved.

The content of the high refractive index particles in the light scattering layer is preferably in the range of 1.0 to 70%, more preferably in the range of 5 to 50% in terms of volume filling factor. Thereby, the density distribution of the refractive index can be made dense at the interface between the light scattering layer and the smooth layer, and the light extraction efficiency can be increased by increasing the amount of light scattering.

(2.4) Relationship between Layer Thickness and Average Particle Size In the present invention, the layer thickness of the light scattering layer is set to 150 to 500 nm. When the average particle diameter of the light scattering particles contained in the light scattering layer is D, the value of T / D is preferably in the range of 0.75 to 3.0. More preferably, the T / D value is in the range of 1.0 to 2.5, and even more preferably, the T / D value is in the range of 1.25 to 2.0.
If the T / D value is less than 0.75, the probability of light colliding with the light scattering particles is low, which is not preferable. If the T / D value exceeds 3.0, absorption by the light scattering particles increases. , Light absorption loss is large, which is not preferable.

(2.5) In-plane occupation ratio of light scattering particles in light scattering layer The in-plane occupation ratio of light scattering particles contained in the light scattering layer in the light scattering layer is set to 20 to 60%.
The “in-plane occupation ratio of the light scattering particles in the light scattering layer” refers to the area occupation ratio of the light scattering particles in the plane when the light scattering layer is viewed in plan.

Here, since the light scattering layer of the present invention is configured as described above, a light scattering region with a large amount of light scattering particles and a light transmission region with a small amount of light scattering particles when viewed from the layer thickness direction. However, they are formed in a sea-island structure in the plane direction. For this reason, the light that passes through the light scattering region out of the light that passes through the light scattering layer is scattered by the light scattering particles, and the light extraction efficiency in the oblique direction can be increased. Of the light that passes through the scattering layer, the light that passes through the light transmission region travels straight without being scattered and can be extracted in the front direction of the organic EL element. Therefore, the light extraction efficiency in the oblique direction can be increased while suppressing the reduction of the light extraction to the front, and the light can be extracted with high efficiency.

The ratio of the area of the light scattering region to the light transmission region in the light scattering layer is such that the in-plane occupation ratio of the light scattering particles is 20 to 60%. When the in-plane occupation ratio of the light scattering particles is less than 20%, scattering of light passing through the light scattering layer becomes insufficient, and extraction in an oblique direction becomes insufficient. On the other hand, if the in-plane occupancy ratio of the light scattering particles exceeds 60%, the area of the light transmission region becomes too small, and the extraction of light to the front is much lower than the light that can be extracted in an oblique direction, and the total light extraction The amount decreases. Therefore, by forming the light scattering region and the light transmission region so that the in-plane occupation ratio of the light scattering particles is 20 to 60%, the extraction efficiency of any light can be sufficiently increased.

(2.6) Surface roughness Ra and maximum height Rt in the light scattering layer
In the present invention, the surface roughness Ra of the light scattering layer is set to 10 to 50 nm, and the maximum height Rt is set to 100 to 300 nm.
Here, in the present invention, the surface roughness Ra represents an arithmetic mean roughness, and the surface roughness Ra and the maximum height Rt are an optical interference roughness meter WYKO NT3300 (manufactured by Veecco) and analysis software Vision 32 (ver. 2.303) and measured in the PSI mode with an objective lens 50 times and an internal 1 time (field of view 90 μm × 120 μm).
Since the surface roughness Ra of the light scattering layer is set in the above range, the light scattering particles are not uniformly arranged in the plane, and the light scattering region and the light transmission region as described above exist. It has become a thing.
Further, since the maximum height Rt of the light scattering layer is set in the above range, there is no portion where the light scattering particles are aggregated and the light scattering particles are stacked in the layer thickness direction.

(3) Smooth layer The smooth layer is a layer that smoothes the surface of the light scattering layer that faces the transparent electrode.
The smooth layer according to the present invention is preferably a high refractive index layer having a refractive index of 1.7 or more and less than 2.5. As long as the refractive index is 1.7 or more and less than 2.5, it may be formed of a single material or a mixture. The way of thinking of the refractive index when forming with a mixture is the same as in the case of the light scattering layer.

It is important that the smooth layer has a flatness that allows a transparent electrode to be satisfactorily formed thereon, and the surface roughness Ra is less than 100 nm, preferably less than 30 nm, particularly preferably less than 10 nm, most preferably. It is less than 5 nm.

As the material constituting the smooth layer, any material can be used as long as it can smooth the surface of the light scattering layer and does not inhibit the function of the organic EL element. The same materials (see below) that can be used as the binder of the scattering layer are used.
In order to obtain a smooth layer having a high refractive index, the smooth layer preferably contains a fine particle sol, and particularly preferably contains a metal oxide fine particle sol.

The lower limit of the refractive index of the metal oxide fine particles contained in the high refractive index smooth layer is preferably 1.7 or more, more preferably 1.85 or more in the bulk state, and 2.0 or more. More preferably, it is more preferably 2.5 or more. In addition, the upper limit of the refractive index of the metal oxide fine particles is preferably 3.0 or less. It is preferable that the refractive index of the metal oxide fine particles is 1.7 or more because the object and effects of the present application are improved. It is preferable that the metal oxide fine particles have a refractive index of 3.0 or less because multiple scattering in the smooth layer is reduced and transparency is improved.

The lower limit of the particle diameter of the metal oxide fine particles (inorganic particles) contained in the high refractive index smooth layer is usually preferably 5 nm or more, more preferably 10 nm or more, and further preferably 15 nm or more. preferable. In addition, the upper limit of the particle diameter of the metal oxide fine particles is preferably 70 nm or less, more preferably 60 nm or less, and further preferably 50 nm or less. It is preferable that the particle diameter of the metal oxide fine particles is 5 nm or more because aggregation of the metal oxide fine particles can be suppressed and transparency is improved. Moreover, when the particle size is large, the surface area becomes small, the catalytic activity is lowered, and deterioration of the smooth layer and adjacent layers may be delayed, which is preferable. It is preferable that the particle diameter of the metal oxide fine particles is 70 nm or less because the transparency of the smooth layer is improved. As long as the effect of the present invention is not impaired, the particle size distribution is not limited, and may be wide or narrow and may have a plurality of distributions.

As a minimum of content of metal oxide fine particles in a smooth layer, it is preferred that it is 70 mass% or more to the whole mass, it is more preferred that it is 80 mass% or more, and it is 85 mass% or more. Further preferred. Moreover, as an upper limit of content of metal oxide microparticles | fine-particles, it is preferable that it is 97 mass% or less, and it is more preferable that it is 95 mass% or less. When the content of the metal oxide fine particles in the smooth layer is 70% by mass or more, it becomes substantially easy to set the refractive index of the smooth layer to 1.80 or more. When the content of the metal oxide fine particles in the smooth layer is 95% by mass or less, the smooth layer can be easily applied, the brittleness of the layer after drying is reduced, and the bending resistance is improved.

The metal oxide fine particles contained in the smooth layer are more preferably TiO ₂ (titanium dioxide sol) from the viewpoint of stability. Further, among TiO ₂ , rutile type is particularly preferable than anatase type, because the weather resistance of the smooth layer 2b and adjacent layers is high and the refractive index is high.

Examples of a method for preparing a titanium dioxide sol that can be used in the present invention include JP-A 63-17221, JP-A 7-819, JP-A 9-165218, and JP-A 11-43327. Can be referred to.

Particularly preferred primary particle diameter of the titanium dioxide fine particles is in the range of 5 to 15 nm, and most preferably in the range of 6 to 10 nm.

(4) Light scattering layer / smooth layer The light extraction layer obtained by laminating the light scattering layer and the smooth layer has a refractive index of 1.7 or more and less than 2.5.
The light extraction layer preferably has an absorptance of light in the wavelength range of 450 to 700 nm of less than 15%, more preferably less than 12%, still more preferably less than 10%, and particularly preferably less than 8%. An absorptance of less than 15% is preferable from the viewpoint of light emission efficiency. There is no restriction on the side with a low absorption rate, and it is preferable to use a highly transparent material in a timely manner within the industrially usable range.
The absorptance with respect to light within the wavelength range of 450 to 700 nm is preferably such that the fluctuation of the maximum absorption value (max value) and the minimum absorption value (min value) at each wavelength is small, and the ratio of min value / max value is It is preferably 0.5 or more, more preferably 0.6 or more, still more preferably 0.7 or more, and particularly preferably 0.8 or more. When the ratio of min value / max value is 0.5 or more, the light extraction layer is colored, resulting in a color development different from the original emission spectrum of the organic EL element, and it becomes extremely impossible to extract white light. Can be avoided. The ratio of min value / max value is ideally 1 and is preferably closer to 1, but it is preferable to use a material having visible light transparency in a timely range that can be used industrially.
In the light extraction layer as the light scattering layer / smooth layer laminate formed as described above, the haze value is preferably 30% or more and less than 90%. The haze value is more preferably 35% or more and less than 85%, still more preferably 40% or more and less than 80%, and particularly preferably 45% or more and less than 75%. The above haze value varies depending on the surface shape, and the “haze value” here is a value measured for a layer having an Ra of 1 μm of less than 5 nm measured by an AFM (atomic force microscope). It is.

<< Light Extraction Layer Forming Apparatus and Forming Method >>
(1) Light extraction layer forming apparatus An example of an apparatus for forming the light extraction layer of the organic EL element of the present invention will be described with reference to FIG.
As shown in FIG. 2, the light extraction layer forming apparatus 200 uses a so-called roll-to-roll method to wind up a transparent substrate wound in a roll shape from the original winding roll 202 with the winding roll 204, and to wind and convey the transparent substrate. In the middle of the process, the light extraction layer is formed on the transparent substrate. When forming a light extraction layer using such a light extraction layer forming apparatus 200, it is preferable to use a flexible transparent resin substrate as the transparent substrate. Hereinafter, description will be made assuming that the light extraction layer is formed on the transparent resin substrate. Further, in the light extraction layer forming apparatus 200 described below, it is assumed that an ultraviolet curable resin is used as a binder constituting the light scattering layer.

The light extraction layer forming apparatus 200 mainly includes a transport unit 210, an IJ coating unit 220, an IR drying unit 230, a light curing unit 240, an IJ coating unit 250, an IR drying unit 260, a photo curing unit 270, and a transport unit 280. Has been.

The transport unit 210 is provided with a plurality of transport rollers 212. In the transport unit 210, tension adjustment of the transparent substrate is performed while the transparent substrate is pulled out from the original winding roll 202 by the transport roller 212.
An accumulator can be installed in the transport unit 210. When an accumulator is installed in the transport unit 210, it is possible to select continuous transport or intermittent transport. Therefore, it is preferable to install an accumulator in the transport unit 210.

In the IJ coating unit 220, a transport roller 222, a platen 224, and an IJ head 226 are installed. In the IJ coating unit 220, the transparent substrate is transported by the transport roller 222, and the light scattering layer coating liquid is coated and patterned by the IJ head 226 while the transparent substrate is supported by the platen 224 in the middle.

The IR drying unit 230 is provided with a transport roller 232 and a wavelength control infrared heater 20. In the IR drying unit 230, the transparent substrate is transported by the transport roller 232, and in the middle, the light scattering layer coating liquid applied and patterned on the transparent substrate is irradiated with infrared rays by the wavelength control infrared heater 20, and the light scattering is performed. The layer coating solution is dried.

The wavelength control infrared heater 20 has an infrared absorption mechanism having a wavelength of 3.5 μm or more, and has an outer appearance in a cylindrical shape. As shown in FIG. 3, the filament 22, the protective tube 24, and the filter 26 are mainly used. , 28 are arranged concentrically in this order.
Here, “absorbing infrared rays having a wavelength of 3.5 μm or more” means that in the far infrared region having a wavelength of 3.5 μm or more, the infrared transmittance is 50% or less, preferably 40% or less, more preferably. Means 30% or less.
Specifically, since the filters 26 and 28 themselves are heated by the filament 22 and become high temperature, the filters 26 and 28 themselves become infrared radiators, and emit infrared rays having a longer wavelength than the infrared rays emitted from the filaments 22. However, in the wavelength control infrared heater 20, the refrigerant (for example, cooling air) flows through the hollow portion 30 between the filters 26 and 28, and the cooling function reduces the surface temperature of the filters 26 and 28. The secondary radiation emitted from the filters 26 and 28 can be suppressed. As a result, it is possible to cut far-infrared rays having a wavelength of 3.5 μm or more mainly having an absorption region on the transparent resin substrate. Then, by selectively irradiating the object to be dried with near infrared rays having a wavelength of 3.5 μm or less, which is an absorption region of the solvent, the coating liquid can be dried without deforming the transparent substrate.

Examples of the material of the filters 26 and 28 include quartz glass and borosilicate glass, and quartz glass is preferable from the viewpoint of heat resistance and thermal shock resistance.
The thickness and the number of the filters 26 and 28 can be appropriately selected and changed according to the necessary infrared spectrum.
As a cooling function, as described above, the wavelength control filters can be hollowed by double or multiple layers, and the air can be cooled by flowing air through the hollow part therebetween.
As described above, the shape of the filters 26 and 28 may cover the entire cylindrical filament 22 concentrically. As shown in FIG. 4, the three directions of the filament 22 (and the protective tube 24) are covered by the reflector 32. The filters 26 and 28 may be arranged in parallel plates on the infrared radiation surface side.
In the case of a multiple structure in which another filter is arranged in addition to the filters 26 and 28, it is preferable from the viewpoint of cooling efficiency that cooling air is caused to flow in opposite directions between the hollow portions between the filters. Further, the cooling air on the discharge side may be discharged out of the system or may be used as part of hot air used in the drying process.

According to Wien's displacement law, when the filament temperature is raised, the dominant wavelength of the emitted infrared spectrum becomes 3.5 μm or less, which corresponds to the absorption of the solvent, so the temperature of the filament 22 of the wavelength control infrared heater 20 is 600 degreeC or more is preferable and it is preferable to set it as 3000 degrees C or less from the heat resistant point of the filament 22. FIG. Depending on the filament temperature, the radiation energy in the wavelength region corresponding to the absorption of these solvents can be increased, and the filament temperature can be appropriately selected and changed depending on the desired coating and drying conditions.
The surface temperature of the outermost filter 28 disposed on the object to be dried is preferably 200 ° C. or less, and more preferably 150 ° C. or less, from the viewpoint of suppressing secondary radiation due to its own infrared absorption. . The surface temperature of the filter 28 can be adjusted by allowing air to flow between the filters stacked in a double layer or multiple layers.
Further, in the IR drying unit 230, infrared rays that are not absorbed by the object to be dried can be used with high efficiency by configuring (covering) the drying zone with a material having high infrared reflectivity.

3 and 4, the wavelength control infrared heater 20 is connected to a cooling mechanism 40 for circulating (circulating) the refrigerant in the hollow portion 30, and the cooling mechanism 40 and the filament 22 are connected to a control device. 50 is connected. In such a control circuit, the control device 50 controls the flow rate of the refrigerant through the hollow portion 30 by the cooling mechanism 40, the heat generation temperature of the filament 22, and the like.

As shown in FIG. 2, the photocuring unit 240 is provided with a transport roller 242 and an ultraviolet irradiation device 244. In the photocuring unit 240, the transparent substrate is transported by the transport roller 242, and the light scattering layer coating liquid after infrared irradiation is irradiated with ultraviolet rays by the ultraviolet irradiation device 244 on the way, and the light scattering layer coating liquid coating liquid is Cured. As a result, a light scattering layer is formed on the transparent substrate.
In the photocuring unit 240, an electron beam irradiation device can be preferably used instead of the ultraviolet irradiation device 244.
As the ultraviolet light, ultraviolet light (UV light) having a wavelength of 150 to 230 nm is particularly preferably used.

The irradiation intensity and / or irradiation time are set as the irradiation amount of the ultraviolet rays in such a range that the transparent substrate carrying the applied object to be irradiated is not damaged. When a plastic film is used as the transparent substrate, the distance between the substrate and the lamp is set so that the irradiation intensity of the ultraviolet rays irradiated on the transparent substrate surface is 10 to 300 mW / cm ^2, and the irradiation time of the ultraviolet rays is set. It is preferable to set within the range of 0.1 second to 10 minutes, preferably 0.5 second to 3 minutes.

A commercially available lamp (for example, made by USHIO Inc.) can be used for the ultraviolet irradiation device.

Since ultraviolet rays are larger than the interatomic bonding force of most substances, it is possible to directly break the bond of atoms by the action of only photons called photon processes. By using this action, the reforming process can be efficiently performed at a low temperature without requiring hydrolysis.

Specific examples of the ultraviolet light source of the ultraviolet irradiation device 244 necessary for this include a rare gas excimer lamp that emits ultraviolet light within a range of 100 to 230 nm.
A rare gas atom such as Xe, Kr, Ar, Ne, etc. is called an inert gas because it does not form a molecule by chemically bonding. However, rare gas atoms (excited atoms) that have gained energy by discharge or the like can be combined with other atoms to form molecules.
For example, when the rare gas is Xe (xenon), as shown by the following reaction formula, when the excited excimer molecule Xe ₂ ^* transitions to the ground state, 172 nm excimer light is emitted.

e + Xe → Xe ^*
Xe ^* + 2Xe → Xe ₂ ^* + Xe
Xe ₂ ^* → Xe + Xe + hν (172 nm)

¡The excimer lamp is characterized by high efficiency because radiation concentrates on one wavelength and almost no other light is emitted. Moreover, since extra light is not radiated | emitted, the temperature of a target object can be kept comparatively low. Furthermore, since no time is required for starting and restarting, instantaneous lighting and blinking are possible.

As a light source for efficiently irradiating excimer light, a dielectric barrier discharge lamp can be mentioned.
A dielectric barrier discharge lamp has a structure in which a discharge is generated between electrodes via a dielectric. Generally, at least one electrode is disposed between a discharge vessel made of a dielectric and the outside thereof. It ’s fine. As a dielectric barrier discharge lamp, for example, a rare gas such as xenon is enclosed in a double cylindrical discharge vessel composed of a thick tube and a thin tube made of quartz glass, and a net-like second discharge vessel is formed outside the discharge vessel. There is one in which one electrode is provided and another electrode is provided inside the inner tube. A dielectric barrier discharge lamp generates a dielectric barrier discharge inside a discharge vessel by applying a high-frequency voltage or the like between electrodes, and generates excimer light when excimer molecules such as xenon generated by the discharge dissociate. .

The excimer lamp has high light generation efficiency and can be lit with low power. In addition, since light having a long wavelength that causes a temperature rise is not emitted and energy is emitted at a single wavelength in the ultraviolet region, the temperature rise of the irradiation object due to the irradiation light itself is suppressed.

As described above, a method using dielectric barrier discharge is known as a method for obtaining excimer light emission. Dielectric barrier discharge refers to lightning generated in a gas space by arranging a gas space between both electrodes via a dielectric (transparent quartz in the case of an excimer lamp) and applying a high frequency high voltage of several tens of kHz to the electrode. When the micro discharge streamer reaches the tube wall (dielectric) in a similar very thin discharge called micro discharge, the electric charge accumulates on the dielectric surface, and the micro discharge disappears.
The dielectric barrier discharge is a discharge in which this micro discharge spreads over the entire tube wall and is repeatedly generated and extinguished. For this reason, flickering of light that can be seen with the naked eye occurs. Moreover, since a very high temperature streamer reaches a pipe wall directly locally, there is a possibility that deterioration of the pipe wall may be accelerated.

As a method for efficiently obtaining excimer light emission, electrodeless electric field discharge can be mentioned in addition to dielectric barrier discharge. Electrodeless electric field discharge by capacitive coupling, also called RF discharge. The lamp and electrodes and their arrangement may be basically the same as those of the dielectric barrier discharge, but the high frequency applied between the two electrodes is lit at several MHz. In the electrodeless field discharge, a spatially and temporally uniform discharge can be obtained in this way, so that a long-life lamp without flickering can be obtained.

In the case of dielectric barrier discharge, since micro discharge occurs only between the electrodes, the outer electrode covers the entire outer surface and transmits light to extract light to the outside in order to cause discharge in the entire discharge space. Must be a thing.

For this reason, an electrode in which a thin metal wire is meshed is used. Since this electrode uses as thin a line as possible so as not to block light, it is easily damaged by ozone generated by ultraviolet rays in an oxygen atmosphere.

In order to prevent this, it is necessary to create an atmosphere of inert gas such as nitrogen around the lamp, that is, the inside of the irradiation apparatus, and provide a synthetic quartz window to extract the irradiation light. Synthetic quartz windows are not only expensive consumables, but also cause light loss.

Since the outer diameter of the double cylindrical lamp is about 25 mm, the difference in the distance to the irradiation surface cannot be ignored between the position directly below the lamp axis and the side of the lamp, resulting in a large difference in illuminance. Therefore, even if the lamps are arranged in close contact with each other, a uniform illuminance distribution cannot be obtained. If the irradiation device is provided with a synthetic quartz window, the distance in the oxygen atmosphere can be made uniform, and a uniform illuminance distribution can be obtained.

¡When electrodeless field discharge is used, it is not necessary to make the external electrode mesh. The glow discharge spreads over the entire discharge space only by providing an external electrode on a part of the outer surface of the lamp. As the external electrode, an electrode that also serves as a light reflector, usually made of an aluminum block, is used on the back of the lamp. However, since the outer diameter of the lamp is as large as in the case of the dielectric barrier discharge, synthetic quartz is required to obtain a uniform illuminance distribution.

The biggest feature of the narrow tube excimer lamp is its simple structure. The quartz tube is closed at both ends, and only gas for excimer light emission is sealed inside.

The outer diameter of the tube of the thin tube lamp is about 6-12mm. If it is too thick, a high voltage is required for starting.

The discharge mode can be either dielectric barrier discharge or electrodeless field discharge. The electrode may have a flat surface in contact with the lamp, but if the shape is matched to the curved surface of the lamp, the lamp can be firmly fixed and the discharge is more stable when the electrode is in close contact with the lamp. Also, if the curved surface is made into a mirror surface with aluminum, it also becomes a light reflector.

The Xe excimer lamp emits ultraviolet light having a short wavelength of 172 nm at a single wavelength, and thus has excellent luminous efficiency. Since this light has a large oxygen absorption coefficient, it can generate radical oxygen atom species and ozone at a high concentration with a very small amount of oxygen.

Also, it is known that the energy of light having a short wavelength of 172 nm, which dissociates the bonds of organic substances, is highly capable.

The reaction in a short time can be realized by this active oxygen or ozone and the high energy of ultraviolet radiation.

Therefore, compared to low-pressure mercury lamps and plasmas that emit light with wavelengths of 185 nm and 254 nm, it is possible to shorten the process time associated with high throughput, reduce equipment area, and irradiate organic materials and plastic substrates that are susceptible to heat damage. Yes.

The excimer lamp has high light generation efficiency and can be lit with low power. In addition, light having a long wavelength that causes a temperature increase due to light is not emitted, and energy is irradiated at a single wavelength in the ultraviolet region, so that an increase in the surface temperature of the irradiation object is suppressed. For this reason, it is suitable for flexible film materials such as PET, which are likely to be affected by heat.

If the irradiation intensity is high, the probability that the photons and chemical bonds in the coating solution collide increases, and the modification reaction can be shortened. In addition, since the number of photons penetrating into the interior also increases, the thickness of the modified layer can be increased and / or the layer quality can be improved (densification).

However, if the irradiation time is too long, the flatness may be deteriorated and other materials may be damaged. Generally, the reaction progress is considered by the integrated light quantity expressed by the product of the irradiation intensity and the irradiation time. The value may be important.

Therefore, in the light curing unit 240, it is preferable to perform a curing process that gives a maximum irradiation intensity of 100 to 200 mW / cm ² at least once, from the viewpoint of suppressing damage to the substrate and damage to members of the lamp and the lamp unit.

The irradiation time of the ultraviolet rays can be arbitrarily set, but from the viewpoint of substrate damage and layer defect generation, the irradiation time in the high illuminance process is preferably 0.1 second to 3 minutes, more preferably 0.5 second to 1 minute.

When using vacuum ultraviolet rays (VUV) as ultraviolet rays, the oxygen concentration during irradiation with vacuum ultraviolet rays is preferably in the range of 500 to 10000 ppm (1%), more preferably in the range of 1000 to 5000 ppm.

By adjusting to the above oxygen concentration range, it is possible to prevent the replacement time with the atmosphere from becoming unnecessarily long. At the same time, when performing continuous production such as roll-to-roll, the photocuring unit 240 is conveyed by web conveyance. It is possible to prevent an increase in the amount of air (including oxygen) entrained inside and prevent the oxygen concentration from becoming uncontrollable.

Further, according to the study by the present inventors, oxygen and a small amount of water are mixed in the coating liquid during coating, and there are adsorbed oxygen and adsorbed water on the transparent substrate in addition to the coating liquid. It has been found that there are enough oxygen sources to supply oxygen required for the reforming reaction without introducing oxygen.

Rather, when the VUV light is irradiated in an atmosphere containing a large amount of oxygen gas (a few percent level), the coating solution has a structure with excess oxygen.

Further, as described above, 172 nm vacuum ultraviolet rays (VUV) are absorbed by oxygen and the amount of light at 172 nm reaching the surface of the coating solution is reduced, so that the efficiency of processing with light tends to be reduced.
That is, at the time of irradiation with vacuum ultraviolet rays (VUV), it is preferable to perform the treatment in a state where the VUV light efficiently reaches the coating material in a state where the oxygen concentration is as low as possible.

This is a significant difference between a method of depositing and producing a layer with a composition ratio controlled in advance, such as an atomic deposition method such as CVD, and a method of preparing a precursor layer by coating and a modification process. This is a unique point in the coating method under atmospheric pressure.

At the time of vacuum ultraviolet (VUV) irradiation, a gas other than oxygen is preferably a dry inert gas, and more preferably a dry nitrogen gas from the viewpoint of cost. The oxygen concentration can be adjusted by measuring the flow rates of oxygen gas and inert gas introduced into the irradiation chamber and changing the flow rate ratio.

As shown in FIG. 2, the IJ coating unit 250 has the same configuration and action as the IJ coating unit 220, and the transparent substrate is transported by the transport roller 252, while the transparent substrate is supported by the platen 254 in the middle. The smoothing layer coating solution is applied and patterned by the IJ head 256.
The IR drying unit 260 also has the same configuration and action as the IR drying unit 230. The transparent substrate is transported by the transport roller 262, and a smooth layer coating solution that is coated and patterned on the transparent substrate on the way. On the other hand, infrared light is irradiated by the wavelength control infrared heater 264, and the smooth layer coating solution is dried. The wavelength control infrared heater 264 is the same as the wavelength control infrared heater 20.
The photocuring unit 270 also has the same configuration and action as the photocuring unit 240, and the transparent substrate is transported by the transport roller 272, and an ultraviolet irradiation device 274 is applied to the smooth layer coating liquid after infrared irradiation on the way. Is irradiated with ultraviolet rays to cure the smooth layer coating solution. Thereby, a smooth layer is formed on the light scattering layer, and a light extraction layer is formed on the transparent substrate. The ultraviolet irradiation device 274 is similar to the ultraviolet irradiation device 244.
The transport unit 280 also has the same configuration and operation as the transport unit 210, and the transparent substrate is adjusted by tension on the transparent substrate while the transparent substrate is transported by the transport roller 282, and the transparent substrate is wound on the winding roll 204. It is done.

As described above, the light extraction layer forming apparatus 200 is configured.
In the light extraction layer forming apparatus 200 described above, the photocuring portions 240 and 270 that irradiate the coating solution with ultraviolet rays are provided. However, the present invention is not limited to this, and the light scattering layer and the smooth layer are not limited thereto. It may be provided as appropriate depending on the material. For example, when a thermosetting material is used as the material for the light scattering layer and the smooth layer, a thermosetting treatment unit may be provided instead of the light curing unit, and the material for the light scattering layer and the smooth layer may be provided. In the case where a curable material is not used, the photocuring portion may not be provided.
Further, the light extraction layer forming apparatus 200 has been described as an independent apparatus for forming the light extraction layer on the transparent substrate. However, the light extraction layer forming apparatus 200 is an apparatus for manufacturing an organic EL element or the like. It may be incorporated as a part of.
In addition, the configuration of the light extraction layer forming apparatus is not limited to the above configuration.

(2) Method for forming light extraction layer A method for forming the light extraction layer in the organic EL device of the present invention will be described.
The method for forming the light extraction layer includes a step of forming the light scattering layer 2a on the transparent substrate 13 and a step of forming the smoothing layer 2b on the light scattering layer 2a.

(2.1) Light Scattering Layer In the step of forming the light scattering layer 2a, the following processes (i) to (iii) are mainly performed.
(I) A light scattering layer coating solution is applied and patterned on the transparent substrate 13.
(Ii) The light scattering layer coating solution coated and patterned on the transparent substrate 13 is dried.
(Iii) The dried light scattering layer coating solution is cured.

In the treatment (i), light scattering particles having an average particle size of 150 to 350 nm and preferably a refractive index of 1.7 or more and less than 3.0 are dispersed in a binder solution, and this is used as a light scattering layer coating solution. Coating on the transparent substrate 13.
When a curable material is not used as the material constituting the light scattering layer 2a, the process (iii) may not be performed. In this case, the process (ii) may also serve as a process for curing the light scattering layer coating solution.

(Light scattering layer coating solution)
The light scattering layer coating solution used in the step of forming the light scattering layer 2a will be described below.

The light scattering particles are dispersed in a binder solution (a solvent that does not dissolve light scattering particles) as a medium, and this is used as a light scattering layer coating solution.
Light scattering particles are actually polydisperse particles and difficult to arrange regularly, so although they have a diffraction effect locally, many of the light scattering particles change the direction of light by scattering. Improve extraction efficiency.

As the binder according to the present invention, known resins can be used without particular limitation. For example, acrylic ester, methacrylic ester, polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), polycarbonate (PC ), Polyarylate, polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polystyrene (PS), nylon (Ny), aromatic polyamide, polyether ether ketone, polysulfone, polyether sulfone, polyimide and poly Resin film such as ether imide, heat-resistant transparent film based on silsesquioxane having organic / inorganic hybrid structure (product name: Sila-DEC, manufactured by Chisso Corporation), containing perfluoroalkyl group In addition to orchid compounds (for example, (heptadecafluoro-1,1,2,2-tetradecyl) triethoxysilane), fluorine-containing copolymers having a fluorine-containing monomer and a monomer for providing a crosslinkable group as structural units, etc. Is mentioned. These resins can be used in combination of two or more. Among these, those having an organic-inorganic hybrid structure are preferable.

The following hydrophilic resins can also be used. Examples of the hydrophilic resin include water-soluble resins, water-dispersible resins, colloid-dispersed resins, and mixtures thereof. Examples of hydrophilic resins include acrylic resins, polyester resins, polyamide resins, polyurethane resins, fluorine resins, and the like, such as polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, casein, starch, agar, carrageenan, and polyacrylic resins. Polymers such as acid, polymethacrylic acid, polyacrylamide, polymethacrylamide, polystyrene sulfonic acid, cellulose, hydroxyl ethyl cellulose, carboxyl methyl cellulose, hydroxyl ethyl cellulose, dextran, dextrin, pullulan and water-soluble polyvinyl butyral can be mentioned, but these Among these, polyvinyl alcohol is preferable.
As the resin used as the binder, one type may be used alone, or two or more types may be mixed and used as necessary.

Similarly, conventionally known resin particles (emulsion) and the like can also be suitably used.

Further, as the binder, a resin curable mainly by ultraviolet rays or an electron beam, that is, a mixture of a thermoplastic resin and a solvent in an ionizing radiation curable resin or a thermosetting resin can also be suitably used.
Such a resin is preferably a polymer having a saturated hydrocarbon or a polyether as a main chain, and more preferably a polymer having a saturated hydrocarbon as a main chain.
The resin is preferably cross-linked. For example, a resin having a saturated hydrocarbon as the main chain is preferably obtained by a polymerization reaction of an ethylenically unsaturated monomer. In order to obtain a crosslinked resin, it is preferable to use a monomer having two or more ethylenically unsaturated groups.

In addition, as the binder of the light scattering layer according to the present invention, a compound that forms a metal oxide, a metal nitride, or a metal oxynitride by ultraviolet irradiation under a specific atmosphere is particularly preferably used. As a compound suitable for the present invention, a compound which can be modified at a relatively low temperature described in JP-A-8-112879 is preferable.
Specifically, polysiloxane having Si—O—Si bond (including polysilsesquioxane), polysilazane having Si—N—Si bond, Si—O—Si bond and Si—N—Si bond. A polysiloxazan containing both may be mentioned. These can be used in combination of two or more. Moreover, it can be used even if different compounds are sequentially laminated or simultaneously laminated.
These polysiloxanes (including polysilsesquioxane), polysilazane and polysiloxazan are the same as those described in the gas barrier layer of the transparent substrate.

The solvent used in the light scattering layer coating solution preferably contains a hydroxy group (—OH group).
By the solvent containing —OH group, the dispersibility of the light scattering particles (high refractive index particles) becomes very good, and the adhesion to the transparent substrate and the paintability become good. Furthermore, the light extraction efficiency is also improved.
In the present invention, high-speed drying on the flexible transparent resin substrate can also be realized by a solvent that efficiently absorbs the infrared wavelength region where the absorption of the flexible transparent resin substrate is low.
In the present invention, it is preferable to contain at least 10% of an —OH group-containing solvent, more preferably 50% or more of an —OH group-containing solvent, still more preferably 60% or more, particularly preferably 70% or more. contains.

In the present invention, it is preferable to contain at least one solvent having a boiling point of 120 to 250 ° C., more preferably at least one solvent having a boiling point of 150 to 200 ° C. preferable. In particular, a solvent having a boiling point in the range of 150 to 200 ° C. and containing an —OH group is very preferable. It is preferable not to contain a solvent having no —OH group at a boiling point of 150 ° C. or higher, and it is important to keep such a solvent below 30%, more preferably below 20%, particularly preferably below 10%.

Examples of the solvent containing —OH group include water, methanol, ethanol, n-propanol, isopropanol, butanol, n-amyl alcohol, sec-amyl alcohol: CH ₃ CH ₂ CH ₂ CH (OH) CH ₃ , 3 -Pentanol: CH ₃ CH ₂ CH (OH) CH ₂ CH ₃ , 2-methyl-1-butanol: CH ₃ CH ₂ CH (CH ₃ ) CH ₂ OH, 3-methyl-1-butanol (isoamyl alcohol): CH ₃ CH (CH ₃ ) CH ₂ CH ₂ OH, 2-methyl-2-butanol (tert-amyl alcohol): CH ₃ CH ₂ C (CH ₃ ) ₂ OH, 3-methyl-2-butanol: CH ₃ CH (CH ₃ ) CH (OH) CH ₃ , 2,2-dimethyl-1-propanol and the like, and ethylene glycol And polyhydric alcohol derivatives such as ethylene glycol monoethyl ether (ethicero), ethylene glycol monobutyl ether (buticero), propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, etc. it can.

Examples of the solvent include ethylene glycol monoisopropyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol monomethoxymethyl ether, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol, triethylene. Glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol, tetraethylene glycol monobutyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene group Cole monopropyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monomethyl Ether acetate, tripropylene glycol, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monobutyl ether, 1,3-propanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl- 1,3-propanediol, 2-amino-2-methyl-1,3-propyl Pandiol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, 1,2-pentanediol, 1 , 5-pentanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 2-ethyl-1,3- Hexanediol, 2,5-dimethyl-2,5-hexanediol, polypropylene glycol monomethyl ether, glycerin, monoacetin, trimethylolethane, trimethylolpropane and 2-phenoxyethanol can also be used.

Further, examples of the solvent include 1-butanol, 2-butanol, isobutanol, t-butanol, 3-methoxy-1-butanol, 3-methyl-3-methoxybutanol, 1-pentanol, 1-octanol, 2- Octanol, n-nonyl alcohol, tridecyl alcohol, n-undecyl alcohol, stearyl alcohol, oleyl alcohol, benzyl alcohol, 4-hydroxy-2-butanone, diacetone alcohol, monoethanolamine, 2-aminoethanol, N-methyl Ethanolamine, dimethylethanolamine, diethylethanolamine, Nn-butylethanolamine, 2-dibutylaminoethanol, 2-diisopropylaminoethanol, N-methyl-diethanolamine, diethanolamine 2,2 '-(n-ethyl) iminodiethanol, 2,2'-(n-butyl) iminodiethanol, triethanolamine, 2-amino-2-methyl-1-propanol and 3-amino-1-propanol Can also be used.

In the coating / patterning process (i), a known printing method can be widely used as a patterning method. For example, various methods such as gravure, flexo, screen, microcontact, and ink jet can be suitably used, but ink jet without using a plate is the most preferable method.

In the drying process (ii), any drying method can be used as long as the solvent of the coated / patterned light scattering layer coating solution can be removed. For example, IR drying of the light extraction layer forming apparatus 200 described above is possible. Using the wavelength control infrared heater 20 that absorbs infrared rays having a wavelength of 3.5 μm or more by the unit 230, the light scattering layer coating liquid after application / patterning is irradiated with infrared rays to dry the light scattering layer coating liquid. Is preferred.
As infrared rays, infrared rays having a central wavelength in the region of 1 μm or more and less than 3.5 and 70% or more of the integrated value of all outputs are irradiated in the region.
“In the region where the central wavelength is 1 μm or more and less than 3.5” in infrared means that the filament temperature is in the range of 450 to 2600 ° C., and such a temperature range is derived by the Wien's displacement law.

Although there is no particular limitation on the drying treatment conditions, the irradiation time can be adjusted by the surface temperature of the infrared filament and the wavelength control filter. For example, a drying process in which the filament temperature is 450 to 2600 ° C. (preferably 600 to 1200 ° C.), the wavelength control filter surface temperature is less than 200 ° C. (preferably less than 150 ° C.), and the irradiation time is 10 seconds to 30 minutes. Can do. Thereby, the light-scattering layer 2a having high uniformity of layer thickness distribution and high patterning accuracy can be obtained.

When the curable material is used as the binder contained in the light scattering layer coating solution, the curing process (iii) is performed. In particular, when an ultraviolet curable resin is used as the binder, any ultraviolet irradiation method may be used as long as the light scattering layer coating liquid after drying can be irradiated with ultraviolet rays. It is preferable that the light scattering layer coating liquid after drying is irradiated with light and cured using the light curing unit 240 of the forming apparatus 200.

Moreover, when using an ionizing radiation curable resin composition as a binder contained in a light-scattering layer coating liquid, the usual curing method of an ionizing radiation curable resin composition, ie, an electron beam or an ultraviolet-ray is irradiated. Can be cured.
In the case of curing by electron beam irradiation, for example, it is emitted from various electron beam accelerators such as a Cockrowalton type, a bandegraph type, a resonance transformer type, an insulating core transformer type, a linear type, a dynamitron type, and a high frequency type. An electron beam or the like having an energy in the range of -1000 keV, preferably in the range of 30-300 keV is used. Among these, those having a particularly weak electron beam intensity are preferable, and an electron beam light source “EB engine” manufactured by Hamamatsu Photonics Co., Ltd. is particularly preferably applicable.
In the case of curing by ultraviolet irradiation, for example, ultraviolet rays emitted from light such as an ultra-high pressure mercury lamp, a high-pressure mercury lamp, a low-pressure mercury lamp, a carbon arc, a xenon arc, a metal halide lamp, etc. can be used. used.

(2.2) Smooth Layer In the step of forming the smooth layer 2b, the following processes (iv) to (vi) are performed in the same manner as the step of forming the light scattering layer 2a.
(Iv) A smooth layer coating solution is applied and patterned on the transparent substrate 13.
(V) The smooth layer coating solution applied and patterned on the transparent substrate 13 is dried.
(Vi) The dried smooth layer coating solution is cured.

In the coating / patterning process of (iv), the same smoothing layer coating solution as the binder and solvent described in the step of forming the light scattering layer 2a can be used. A binder and a solvent to be used may be used, or a binder and a solvent different from the binder and the solvent to be used in the treatment (i) may be used.

Further, in the method for forming the light extraction layer, the curing process (iii) and the curing process (vi) are not necessarily essential, and either one of the processes (iii) and (vi) may be omitted. Both may be omitted.

<Transparent electrode>
The transparent electrode according to the present invention is not particularly limited, and a conventionally known electrode can be used. Examples of the electrode material include metals such as Au, and conductive transparent materials such as CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. Alternatively, an amorphous material such as IDIXO (In ₂ O ₃ —ZnO) that can form a transparent conductive film may be used.
Note that the transparency of the transparent metal electrode means that the light transmittance at a wavelength of 550 nm is 50% or more.

For transparent electrodes, these electrode materials may be formed into a thin film by a method such as vapor deposition or sputtering, and a pattern having a desired shape may be formed by photolithography, or when pattern accuracy is not so high (about 100 μm or more) ), A pattern may be formed through a mask having a desired shape when the electrode material is deposited or sputtered.

Alternatively, when a material that can be applied such as an organic conductive compound is used, a wet film forming method such as a printing method or a coating method can be used.

The sheet resistance as the transparent electrode is preferably several hundred Ω / □ or less. Further, although the layer thickness depends on the material, it is usually selected in the range of 10 nm to 1 μm, preferably 10 to 200 nm.

In addition, when the transparent electrode 1 is made of a metal conductive layer containing silver or an alloy containing silver as a main component, the transparent electrode 1 is composed of a two-layer structure of the metal conductive layer and a non-conductive underlayer containing a nitrogen-containing compound. It is preferable. Thereby, the aggregation of silver atoms constituting the metal conductive layer is suppressed, and a transparent electrode having a uniform film thickness while ensuring light transmittance while having a thin film thickness, can do.

《Organic functional layer》
The organic functional layer includes at least a light emitting layer.
The light emitting layer used in the present invention contains a light emitting material. As the light emitting material, a phosphorescent light emitting compound may be used, a fluorescent material may be used, or a phosphorescent light emitting compound and a fluorescent material may be used in combination.

This light emitting layer is a layer that emits light by recombination of electrons injected from the electrode or the electron transport layer and holes injected from the hole transport layer, and the light emitting portion is in the layer of the light emitting layer. Alternatively, it may be the interface between the light emitting layer and the adjacent layer.

Such a light emitting layer is not particularly limited in its configuration as long as the light emitting material contained satisfies the light emission requirements. There may be a plurality of layers having the same emission spectrum and emission maximum wavelength. In this case, it is preferable to have a non-light emitting intermediate layer (not shown) between the light emitting layers.

The total thickness of the light emitting layers is preferably in the range of 1 to 100 nm, and more preferably in the range of 1 to 30 nm because a lower driving voltage can be obtained.
Note that the sum of the thicknesses of the light emitting layers is a layer thickness including the intermediate layers when a non-light emitting intermediate layer exists between the light emitting layers.

In the case of a light-emitting layer having a structure in which a plurality of layers are laminated, the thickness of each light-emitting layer is preferably adjusted within the range of 1 to 50 nm, and more preferably adjusted within the range of 1 to 20 nm. preferable. When the plurality of stacked light emitting layers correspond to the respective emission colors of blue, green, and red, there is no particular limitation on the relationship between the thicknesses of the blue, green, and red light emitting layers.

The light emitting layer as described above is formed by forming a known light emitting material or host compound by a known thin film forming method such as a vacuum deposition method, a spin coating method, a casting method, an LB method, or an ink jet method. Can do.

The light-emitting layer may be a mixture of a plurality of light-emitting materials, or a phosphorescent light-emitting material and a fluorescent light-emitting material (also referred to as a fluorescent dopant or a fluorescent compound) may be mixed and used in the same light-emitting layer. .

The structure of the light emitting layer preferably contains a host compound (also referred to as a light emitting host) and a light emitting material (also referred to as a light emitting dopant) and emits light from the light emitting material.

The organic functional layer includes any of various functional layers such as a hole injection layer, a hole transport layer, an electron blocking layer, a hole blocking layer, an electron transport layer, and an electron injection layer in addition to the light emitting layer described above. May be. Each of these functional layers can be formed by a conventionally known method using a conventionally known material.

《Counter electrode》
The counter electrode is an electrode film that functions as a cathode for supplying electrons to the organic functional layer, and a metal, an alloy, an organic or inorganic conductive compound, and a mixture thereof are used. Specifically, aluminum, silver, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, indium, lithium / aluminum mixture, rare earth metal, ITO, ZnO, TiO ₂ , An oxide semiconductor such as SnO ₂ can be given.

The counter electrode can be produced by forming a thin film of these conductive materials by a method such as vapor deposition or sputtering. The sheet resistance as the counter electrode is preferably several hundred Ω / □ or less, and the film thickness is usually selected within the range of 5 nm to 5 μm, preferably within the range of 5 to 200 nm.

In addition, when this organic EL element is configured to extract emitted light also from the counter electrode side, the counter electrode is configured by selecting a conductive material having good light transmittance from the above-described conductive materials. It only has to be done.

<Extraction electrode>
The extraction electrode is for electrically connecting the transparent electrode and the external power source, and the material thereof is not particularly limited and a known material can be suitably used. For example, a MAM having a three-layer structure can be used. A metal film such as an electrode (Mo / Al · Nd alloy / Mo) can be used.

《Auxiliary electrode》
The auxiliary electrode is provided for the purpose of reducing the resistance of the transparent electrode, and is provided in contact with the metal conductive layer of the transparent metal electrode. The material for forming the auxiliary electrode is preferably a metal with low resistance, such as gold, platinum, silver, copper, and aluminum. Since these metals have low light transmittance, a pattern is formed in a range that does not affect extraction of emitted light from the light extraction surface.

Examples of a method for forming such an auxiliary electrode include a vapor deposition method, a sputtering method, a printing method, an ink jet method, and an aerosol jet method. The line width of the auxiliary electrode is preferably 50 μm or less from the viewpoint of the aperture ratio for extracting light, and the thickness of the auxiliary electrode is preferably 1 μm or more from the viewpoint of conductivity.

<Encapsulant>
The sealing material covers the organic EL element, and may be a plate-like (film-like) sealing member that is fixed to the transparent resin substrate side by the adhesive 19 or may be a sealing film. There may be. Such a sealing material is provided in a state where the terminal portions of the transparent electrode and the counter electrode in the organic EL element are exposed and at least the organic functional layer is covered. Further, an electrode may be provided on the sealing material so that the transparent electrode of the organic EL element and the terminal portion of the counter electrode are electrically connected to this electrode.

Specific examples of the plate-like (film-like) sealing material include a glass substrate, a polymer substrate, a metal substrate, and the like, and these substrate materials may be used in the form of a thinner film. Examples of the glass substrate include soda-lime glass, barium / strontium-containing glass, lead glass, aluminosilicate glass, borosilicate glass, barium borosilicate glass, and quartz. Examples of the polymer substrate include polycarbonate, acrylic, polyethylene terephthalate, polyether sulfide, and polysulfone. Examples of the metal substrate include those made of one or more metals or alloys selected from the group consisting of stainless steel, iron, copper, aluminum, magnesium, nickel, zinc, chromium, titanium, molybdenum, silicon, germanium, and tantalum.

Among these, from the viewpoint of thinning the element, a thin film-like polymer substrate or metal substrate can be preferably used as the sealing material.

Furthermore, the polymer substrate in the form of a film has an oxygen permeability of 1 × 10 ⁻³ ml / (m ² · 24 h · atm) or less measured by a method according to JIS K 7126-1987, and JIS K 7129- The water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) measured by a method according to 1992 is 1 × 10 ⁻³ g / (m ² · 24 h) or less. It is preferable.

Further, the above substrate material may be processed into a concave plate shape and used as a sealing material. In this case, the substrate member described above is subjected to processing such as sandblasting and chemical etching to form a concave shape.

Moreover, the adhesive 19 for fixing such a plate-shaped sealing material to the transparent substrate side is a sealing agent for sealing the organic EL element sandwiched between the sealing material and the transparent substrate. Used. Specific examples of such an adhesive 19 include photocuring and thermosetting adhesives having reactive vinyl groups of acrylic acid oligomers and methacrylic acid oligomers, moisture curing types such as 2-cyanoacrylates, and the like. Can be mentioned.

Further, examples of the adhesive 19 include an epoxy-based thermal and chemical curing type (two-component mixing). Moreover, hot-melt type polyamide, polyester, and polyolefin can be mentioned. Moreover, a cationic curing type ultraviolet curing epoxy resin adhesive can be mentioned.

In addition, the organic material which comprises an organic EL element may deteriorate with heat processing. For this reason, the adhesive 19 is preferably one that can be adhesively cured from room temperature (25 ° C.) to 80 ° C. A desiccant may be dispersed in the adhesive 19.

Application of the adhesive 19 to the bonding portion between the sealing material and the transparent substrate may be performed using a commercially available dispenser or may be printed like screen printing.

Further, when a gap is formed between the plate-shaped sealing material, the transparent substrate, and the adhesive 19, in the gap and in the gas phase and the liquid phase, an inert gas such as nitrogen or argon, or a fluoride It is preferable to inject an inert liquid such as hydrocarbon or silicon oil. A vacuum can also be used. Moreover, a hygroscopic compound can also be enclosed inside.

Examples of the hygroscopic compound include metal oxides (for example, sodium oxide, potassium oxide, calcium oxide, barium oxide, magnesium oxide, aluminum oxide) and sulfates (for example, sodium sulfate, calcium sulfate, magnesium sulfate, cobalt sulfate). Etc.), metal halides (eg calcium chloride, magnesium chloride, cesium fluoride, tantalum fluoride, cerium bromide, magnesium bromide, barium iodide, magnesium iodide etc.), perchloric acids (eg perchloric acid) Barium, magnesium perchlorate, and the like), and anhydrous salts are preferably used in sulfates, metal halides, and perchloric acids.

On the other hand, when a sealing film is used as the sealing material, the organic functional layer in the organic EL element is completely covered, and the transparent electrode and the counter electrode terminal part in the organic EL element are exposed and sealed on the transparent substrate. A membrane is provided.

Such a sealing film is composed of an inorganic material or an organic material. In particular, it is made of a material having a function of suppressing entry of substances such as moisture and oxygen that cause deterioration of the organic functional layer in the organic EL element. As such a material, for example, inorganic materials such as silicon oxide, silicon dioxide, and silicon nitride are used. Further, in order to improve the brittleness of the sealing film, a laminated structure may be formed using a film made of an organic material in addition to a film made of these inorganic materials.

The method for forming these films is not particularly limited. For example, vacuum deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma A polymerization method, a plasma CVD method, a laser CVD method, a thermal CVD method, a coating method, or the like can be used.

《Protective film, protective plate》
Although illustration is omitted, a protective film or a protective plate may be provided with an organic EL element and a sealing material interposed between the transparent substrate and the transparent substrate. This protective film or protective plate is for mechanically protecting the organic EL element, and particularly when the sealing material is a sealing film, mechanical protection for the organic EL element is not sufficient. It is preferable to provide such a protective film or protective plate.

As the above protective film or protective plate, for example, a glass plate, a polymer plate, a polymer film thinner than this, a metal plate, a metal film thinner than this, a polymer material film or a metal material film is applied. . Among these, it is particularly preferable to use a polymer film because it is lightweight and thin.

<< Method for Manufacturing Organic EL Element >>
Here, as an example, a method for manufacturing the organic EL element 10 shown in FIG. 1 will be described.

First, a transparent substrate 13 is prepared, and a light scattering layer 2a is formed thereon by a coating method. The light scattering layer 2a is formed by applying a light scattering layer coating liquid containing light scattering particles having an average particle diameter of 150 to 350 nm on the transparent substrate 13 and drying, followed by curing as necessary. . The formation conditions of the light scattering layer 2a are as follows: the light scattering layer 2a to be formed has an in-plane occupation ratio of 20 to 60%, a layer thickness of 150 to 500 nm, a surface roughness Ra of 150 to 350 nm, and a maximum height Rt of 100 to 300 nm. Set to be. Next, the smooth layer 2b is formed on the light scattering layer 2a by a coating method. Similarly to the formation of the light scattering layer 2a, the smooth layer 2b is formed by applying a smoothing layer coating liquid on the light scattering layer 2a and drying it, and then performing a curing treatment as necessary. In this way, the light extraction layer 2 composed of the light scattering layer 2a and the smooth layer 2b is formed on the transparent substrate 13.

Next, the transparent electrode 1 serving as an anode is formed by using an appropriate method such as vapor deposition using a predetermined electrode material. At the same time, an extraction electrode 16 connected to an external power source is formed at the end of the transparent electrode 1 by an appropriate method such as vapor deposition.

Next, a hole injection layer 3 a, a hole transport layer 3 b, a light emitting layer 3 c, an electron transport layer 3 d and an electron injection layer 3 e are stacked in this order on this, thereby forming the organic functional layer 3.
For example, a spin coat method, a cast method, an ink jet method, a vapor deposition method, a printing method, and the like are used to form each of these layers. However, it is easy to obtain a uniform layer and it is difficult to generate pinholes. A vacuum deposition method or a spin coating method is particularly preferable. Further, different formation methods may be applied for each layer. When a vapor deposition method is employed for forming each of these layers, the vapor deposition conditions vary depending on the type of compound used, but generally a boat heating temperature of 50 to 450 ° C. and a degree of vacuum of 1 × 10 ⁻⁶ to 1 × 10 ⁻² Pa. It is desirable to appropriately select the respective conditions within the range of a deposition rate of 0.01 to 50 nm / second, a substrate temperature of −50 to 300 ° C., and a layer thickness of 0.1 to 5 μm.
Preferably, in the formation of the organic functional layer 3, when the cross-sectional view is formed, the formation region is almost completely overlapped with the position (region) where the light extraction layer 2 is formed, and light emission generated in the organic functional layer 3 It is preferable that the light h is effectively extracted by the light extraction layer 2.

After forming the organic functional layer 3 as described above, the counter electrode 5a serving as the cathode is formed on the upper portion by an appropriate forming method such as a vapor deposition method or a sputtering method. At this time, the counter electrode 5 a is patterned in a shape in which a terminal portion is drawn from the upper side of the organic functional layer 3 to the periphery of the transparent substrate 13 while being kept insulated from the transparent electrode 1 by the organic functional layer 3. Thereby, the organic EL element 10 is obtained. Thereafter, a sealing material 17 covering at least the organic functional layer 3 is provided in a state where the transparent electrode 1 (extraction electrode 16) and the terminal portion of the counter electrode 5a in the organic EL element 10 are exposed.

Thus, a desired organic EL element 10 is obtained on the transparent substrate 13. In the production of such an organic EL element 10, it is preferable to produce from the organic functional layer 3 to the counter electrode 5a consistently by a single evacuation. However, the transparent substrate 13 is taken out from the vacuum atmosphere on the way and formed differently. You may apply the law. At that time, it is necessary to consider that the work is performed in a dry inert gas atmosphere.

When a DC voltage is applied to the organic EL element 10 thus obtained, the transparent electrode 1 as an anode has a positive polarity, the counter electrode 5a as a cathode has a negative polarity, and the voltage is about 2 to 40V. Luminescence can be observed by applying. Moreover, you may apply an alternating voltage. The alternating current waveform to be applied may be arbitrary.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. In addition, although the display of "%" is used in an Example, unless otherwise indicated, "mass%" is represented.

<< Preparation of Light Scattering Layer Coating Solutions 101-122 >>
In the production of organic EL elements 101 to 122 described later, light scattering layer coating solutions 101 to 122 used for forming a light scattering layer of a light extraction layer were prepared as follows.

(1) Preparation of light scattering particle dispersions T-1 to T-4 (Preparation of light scattering particle dispersions T-1)
As the light scattering particle dispersion T-1, TiO ₂ particles having a refractive index of 2.4 and an average particle size of 0.25 μm (JR600A manufactured by Teika Co., Ltd.) and a resin solution (ED230AL (organic / inorganic hybrid resin) manufactured by APM) and the ratio of the TiO ₂ particles and the resin component 95% by volume: as a 5% by volume, 10% by weight and n- propyl acetate and cyclohexanone to be 90 wt%, and TiO ₂ particles and a resin component The formulation was designed at a ratio of 50 ml so that the concentration of

Specifically, the above TiO ₂ particles and the above mixed solvent are mixed and cooled at room temperature, and then placed in an ultrasonic disperser (UH-50 manufactured by SMT Co.) with a microchip step (MS-3 manufactured by SMT Co., Ltd., 3 mmφ). A dispersion of TiO ₂ was prepared by adding dispersion for 10 minutes under the following standard conditions.
Next, while stirring the TiO ₂ dispersion at 100 rpm, the resin was mixed and added little by little. After the addition was completed, the stirring speed was increased to 500 rpm and mixed for 10 minutes.
Thereafter, the mixture was sequentially filtered through a PVDF 0.45 μm filter and a PVDF 0.20 μm filter (manufactured by Whatman) to obtain a target light scattering particle dispersion T-1. The concentration of the TiO ₂ particles and the resin component was 37.8%, and the average particle size of the dispersed particles was 190 nm (particle size distribution meter Zeta Sizer nano-S manufactured by Malvern).

(Preparation of light scattering particle dispersion T-2)
In the preparation of the light scattering particle dispersion T-1, the dispersion T-2 (the concentration of the TiO ₂ particles and the resin component with a concentration of 38. ₂₎ was similarly used except that the dispersion was passed twice through a 0.45 μm filter as a filtration operation. 5% and an average particle diameter of dispersed particles of 260 nm).

(Preparation of light scattering particle dispersion T-3)
In the preparation of the light scattering particle dispersion T-1, the dispersion time was 6 minutes, and the dispersion liquid T-3 was similarly used except that the dispersion liquid was passed once through a 0.45 μm filter as a filtration operation. (The concentration of TiO ₂ particles and the resin component was 38.9%, and the average particle size of dispersed particles was 340 nm).

(Preparation of light scattering particle dispersion T-4)
In the preparation of the light scattering particle dispersion T-1, an average particle size of 0.7 μm (MP-70, manufactured by Teika Co., Ltd.) was used as the TiO ₂ particles, and the dispersion was subjected to filtration operation with a 1.2 μm filter and 0.8 μm. A dispersion T-4 (concentration of 38.7% of TiO ₂ particles and resin component, average particle diameter of dispersed particles 680 nm) was obtained in the same manner except that the filter was sequentially passed.

(2) Preparation of light scattering layer coating liquids 101 to 122 (Preparation of light scattering layer coating liquid 101)
The light scattering particle dispersion T-1 and the resin solution (ED230AL) are the volume ratio of the light scattering particles to the resin component × 100 (%) (hereinafter also referred to as “P / B (pigment / binder)”). In an amount of 10 ml so that the ratio of n-propyl acetate and cyclohexanone is 10% by mass: 90% by mass, and the concentration of TiO ₂ particles and the resin component is 10% by mass. Thus, the light scattering layer coating solution 101 was obtained.

(Preparation of light scattering layer coating solutions 102 to 122)
In the preparation of the light scattering layer coating liquid 101, the light scattering layer coating liquid was changed in the same manner except that the light scattering particle dispersion liquid was changed to the one shown in Table 1 and P / B was changed to the values shown in Table 1. 102-122 were obtained.

<< Preparation of organic EL elements 101 to 122 >>
(1) Preparation of organic EL element 101 (1.1) Preparation of transparent resin substrate On the surface of 100 μm thick polyethylene terephthalate (PET) film (Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.) that has not been undercoated, JSR Co., Ltd. UV curable organic / inorganic hybrid hard coat material: OPSTAR Z7501 was coated with a wire bar so that the average layer thickness after coating and drying was 4 μm, then dried at 80 ° C. for 3 minutes, Curing was performed under a curing condition of 1.0 J / cm ² using a high-pressure mercury lamp in an air atmosphere to form a flat layer.

Next, a 20% by weight dibutyl ether solution of perhydropolysilazane (PHPS, AQUAMICA NN320 manufactured by AZ Electronic Materials Co., Ltd.) on a substrate provided with the above flat layer with a wire bar is dried (average) layer thickness. However, it apply | coated so that it might become 0.30 micrometer, and the coating sample was obtained.
The obtained coated sample was treated for 1 minute in an atmosphere having a temperature of 85 ° C. and a humidity of 55% RH to obtain a dried sample. Further, the dried sample was held for 10 minutes in an atmosphere of a temperature of 25 ° C. and a humidity of 10% RH (dew point temperature −8 ° C.) to perform dehumidification.
The sample subjected to the dehumidification treatment was subjected to a modification treatment under the following conditions using the following apparatus to form a gas barrier layer. The dew point temperature during the reforming process was -8 ° C.

(Modification equipment)
Excimer irradiation equipment MODEL: MECL-M-1-200, wavelength 172 nm, lamp filled gas Xe
(Reforming treatment conditions)
Excimer light intensity 60 mW / cm ² (172 nm)
1mm distance between sample and light source
Stage heating temperature 70 ℃
Oxygen concentration in irradiation device 1%
Excimer irradiation time 3 seconds As described above, a film substrate for a transparent electrode having gas barrier properties was produced.

(1.2) Formation of Light Extraction Layer (1.2.1) Formation of Light Scattering Layer The light scattering layer coating liquid 101 was applied onto the prepared film substrate with a spin coater. In addition, the number of rotations was appropriately adjusted so that the layer thickness after drying became the value described in Table 2. Next, simple drying (80 ° C., 2 minutes) and further drying with a hot plate (120 ° C., 60 minutes) were performed to form a light scattering layer.

(1.2.2) Formation of smooth layer (Preparation of smooth layer coating solution)
Next, as a smooth layer preparation, a nano TiO ₂ dispersion liquid (HDT-760T manufactured by Taca Co., Ltd.) having a refractive index of 2.4 and an average particle size of 0.02 μm and a resin solution (ED230AL (organic inorganic hybrid resin) manufactured by APM) ) So that the ratio of the nano-TiO ₂ particles to the resin component is 45% by volume: 55% by volume, and n-propyl acetate, cyclohexanone, and toluene are 20% by mass: 30% by mass: 50% by mass. The formulation was designed at a ratio of 10 ml so that the concentration of the nano TiO ₂ particles and the resin component was 15% by mass.

Specifically, the nano TiO ₂ dispersion liquid and the solvent are mixed, and the resin solution is mixed and added little by little while stirring at 100 rpm. After the addition is completed, the stirring speed is increased to 500 rpm and mixed for 10 minutes. Got. Then, it filtered with the PVDF 0.45 micrometer filter (made by Whatman), and obtained the target smooth layer coating liquid.

(Formation of smooth layer)
The smooth layer coating solution is applied onto the light scattering layer with a spin coater (500 rpm, 30 seconds), then simply dried (80 ° C., 2 minutes), and further dried with a hot plate (120 ° C., 30 minutes), a smooth layer having a layer thickness of 700 nm was formed.
The refractive index of the smooth layer single layer was 1.85.

(1.3) Formation of transparent electrode On the film substrate on which the light extraction layer is formed, ITO (indium tin oxide) having a thickness of 120 nm is formed by sputtering, patterned by photolithography, and the transparent electrode is formed. Formed.
The surface resistance of the ITO electrode was 120Ω / □.

(1.4) Formation of organic functional layer The film substrate on which the transparent electrode was formed was fixed on a substrate holder of a commercially available vacuum deposition apparatus by overlapping with a mask having a 30 mm × 30 mm wide opening at the center. Moreover, each material which comprises an organic functional layer was filled with the optimal quantity for formation of each layer to each heating boat in a vacuum evaporation system.
In addition, the heating boat used what was produced with the resistance heating material made from tungsten.
Next, the inside of the vapor deposition chamber of the vacuum vapor deposition apparatus was depressurized to a vacuum degree of 4 × 10 ⁻⁴ Pa, and each layer was formed as follows by sequentially energizing and heating the heating boat containing each material.

First, a hole-injecting hole transporting material serving as both a hole-injecting layer and a hole-transporting layer made of α-NPD is heated by energizing a heating boat containing α-NPD represented by the following structural formula as a hole-transporting injecting material. A layer was formed on the transparent metal electrode. At this time, the deposition rate was 0.1 to 0.2 nm / second, and the layer thickness was 140 nm.

Next, each of the heating boat containing the host material H4 represented by the following structural formula and the heating boat containing the phosphorescent compound Ir-4 represented by the following structural formula were energized independently, respectively. A light emitting layer composed of the photoluminescent compound Ir-4 was formed on the hole transport injection layer. At this time, the energization of the heating boat was adjusted so that the ratio of the deposition rate (nm / second) was the host material H4: phosphorescent compound Ir-4 = 100: 6. The layer thickness of the light emitting layer was 30 nm.

Subsequently, a hole-blocking layer made of BAlq was formed on the light-emitting layer by heating a heated boat containing BAlq represented by the following structural formula as a hole-blocking material. At this time, the deposition rate was 0.1 to 0.2 nm / second, and the layer thickness was 10 nm.

Thereafter, as an electron transporting material, the compound No. The heating boat containing 7 and the heating boat containing potassium fluoride were energized independently of each other. An electron transport layer composed of 7 and potassium fluoride was formed on the hole blocking layer. At this time, the ratio of the deposition rate (nm / second) was determined as Compound No. 7: Energization of the heating boat was adjusted so that 7: potassium fluoride = 75: 25. The layer thickness of the electron transport layer was 30 nm.

Next, a heating boat containing potassium fluoride as an electron injection material was energized and heated to form an electron injection layer made of potassium fluoride on the electron transport layer. At this time, the deposition rate was 0.01 to 0.02 nm / second, and the layer thickness was 1 nm.

(1.5) Formation and sealing of counter electrode After that, the transparent substrate formed up to the electron injection layer is kept in a vacuum state in a second vacuum chamber to which a resistance heating boat made of tungsten containing aluminum (Al) is attached. It was transferred as it was. It was fixed by overlapping with a mask having an opening with a width of 20 mm × 50 mm arranged so as to be orthogonal to the transparent electrode (anode).
Next, a reflective counter electrode made of Al having a film thickness of 100 nm was formed as a cathode at a film formation rate of 0.3 to 0.5 nm / second in the processing chamber.

After that, the organic light emitter is covered with a sealing material made of a glass substrate having a size of 40 mm × 40 mm and a thickness of 700 μm, and having a central portion of 34 mm × 34 mm cut to a depth of 350 μm, and the organic light emitter is covered. In an enclosed state, an adhesive (sealant) was filled between the sealing material and the transparent substrate. As the adhesive, an epoxy photocurable adhesive (Luxtrac LC0629B manufactured by Toagosei Co., Ltd.) was used.
Thereafter, the adhesive filled between the sealing material and the transparent substrate was irradiated with UV light from the glass substrate (sealing material) side, and the adhesive was cured to seal the organic light emitting body.

In the formation of the organic light emitter, a vapor deposition mask is used to form each layer, and the central 2.0 cm × 2.0 cm region of the 5 cm × 5 cm transparent substrate is defined as the light emitting region, and the width of the entire circumference of the light emitting region. A non-light emitting area of 1.5 cm was provided.
Further, regarding the transparent metal electrode serving as the anode and the counter electrode serving as the cathode, a terminal portion was drawn to the periphery of the transparent substrate in a state where it was insulated by the organic functional layer from the hole transport injection layer to the electron transport layer.
The organic EL element 101 was produced as described above.

(2) Production of Organic EL Elements 102 to 122 In the production of the organic EL element 101, the organic EL element 102 is similarly produced except that the light scattering layer coating liquids 102 to 122 are used instead of the light scattering layer coating liquid 101. To 122 were produced.

<< Evaluation of organic EL elements 101-122 >>
(1) Evaluation of light extraction layer (1.1) In-plane occupancy The light scattering layer (single layer film) produced was subjected to light scattering using an electron microscope TM-1000 Miniscope (manufactured by Hitachi High-Technologies Corporation). A 5000 times magnified image of the layer was obtained (jpg format). As an example, an electron micrograph of a light scattering layer is shown in FIG. 5 for each of the organic EL elements 103, 114, and 118. 5A shows the light scattering layer of the organic EL element 103 of the comparative example, FIG. 5B shows the light scattering layer of the organic EL element 114 of the present invention, and FIG. 5C shows the light scattering layer of the organic EL element 118, respectively.
Next, using image processing software WinROOF (manufactured by Mitani Shoji Co., Ltd.), after binarizing the image obtained with an electron microscope, light scattering particles (in the in-plane direction) from the area values of the white part and the black part ( The ratio of the occupied area of the white part) was determined, and this was defined as the in-plane occupation ratio (%). 5A has an in-plane occupation ratio of 75%, the organic EL element 114 shown in FIG. 5B has an in-plane occupation ratio of 60%, and the organic EL element 118 shown in FIG. 5C has an in-plane occupation ratio. 45%.

(1.2) Layer thickness of light scattering layer The layer thickness of the light scattering layer was measured using a stylus type surface shape measuring device Dektak XT-S (manufactured by ULVAC), and an average value measured at five points The layer thickness (nm) of the scattering layer was used.

(1.3) Surface roughness Ra and maximum height Rt of the light scattering layer and the light extraction layer (smooth layer)
For the formed light scattering layer and light extraction layer (smooth layer), as the surface roughness, using a light interference roughness meter WYKO NT3300 (manufactured by Veeco) and analysis software Vision 32 (ver. 2.303), in PSI mode The measurement was performed with an objective lens 50 times and an inside 1 time (field of view 90 μm × 120 μm). The values after performing the tilt correction on the measured values were defined as the surface roughness Ra (nm) and the maximum height Rt (nm) of the light scattering layer and the light extraction layer.

(2) Evaluation of organic EL elements For each of the produced organic EL elements 101 to 122, the power efficiency and the light emission uniformity were evaluated as follows.

(2.1) Power efficiency Using a spectral radiance meter CS-1000 (manufactured by Konica Minolta Co., Ltd.), the front luminance and luminance angle dependency were measured, and from the driving voltage and current at which the front luminance was 1000 cd / m ² , The power efficiency (lm / w) was measured.
Next, the relative power efficiency is obtained when the power efficiency of the organic EL element having the same configuration as the organic EL element 101 except that the light extraction layer is not provided is set to 100%. The power efficiency of 101 to 122 was evaluated. It shows that it is excellent in light extraction efficiency, so that power efficiency is high. The evaluation results are shown in Table 2.

◎: 150% or more ○: 100% or more and less than 150% △: 80% or more and less than 100% ×: 50% or more and less than 80% XX: less than 50%

(2.2) Uniformity of light emission Using a source measure unit 2400 made by KEITHLEY, a DC voltage was applied to each of the organic EL elements 101 to 122 to emit light at 1000 cd / m ² . Each light emission luminance unevenness was observed with a microscope with a magnification of 50 times, and evaluated according to the following criteria. The evaluation results are shown in Table 2.

A: Completely uniform light emission.
○: Light is emitted almost uniformly, and there is no practical problem.
(Triangle | delta): Although light emission nonuniformity is seen partially, it is permissible.
X: Uneven light emission is observed over the entire surface, which is not acceptable.

(3) Summary From Table 2, light scattering particles having an average particle diameter of 150 to 350 nm are contained, the in-plane occupation ratio of the light scattering particles is 20 to 60%, the layer thickness is 150 to 500 nm, and the surface roughness Ra is The organic EL elements 114 to 122 of the present invention having a light scattering layer having a maximum height Rt of 10 to 50 nm and a maximum height Rt of 100 to 300 nm have higher power efficiency and uniform light emission than the organic EL elements 101 to 113 of the comparative example. It is clear that the light extraction efficiency and the light emission uniformity are excellent.

As described above, the present invention is suitable for providing an organic electroluminescence device excellent in light extraction efficiency and emission uniformity of emitted light.

DESCRIPTION OF SYMBOLS 1 Transparent electrode 2 Light extraction layer 2a Light scattering layer 2b Smooth layer 3 Organic functional layer 3a Hole injection layer 3b Hole transport layer 3c Light emission layer 3d Electron transport layer 3e Electron injection layer 5a Counter electrode 10 Organic EL element 13 Transparent substrate 15 Auxiliary electrode 16 Extraction electrode 17 Sealing material 19 Adhesive 20 Wavelength control infrared heater 22 Filament 24 Protective tube 26, 28 Filter 30 Hollow portion 32 Reflector 40 Cooling mechanism 50 Control device 100 Organic EL element 101 Metal electrode 102 Organic functional layer 103 Transparent electrode 104 Transparent substrate 110a to 110e Light 200 Light extraction layer forming device 202 Original winding roll 204 Winding roll 210 Conveying section 212 Conveying roller 220 IJ coating section 222 Conveying roller 224 Platen 226 IJ head 230 IR drying 232 Conveying roller 240 Light curing unit 242 Conveying roller 244 Ultraviolet irradiation device 250 IJ coating unit 252 Conveying roller 254 Platen 256 IJ head 260 IR drying unit 262 Conveying roller 264 Wavelength control infrared heater 270 Photo curing unit 272 Conveying roller 274 Ultraviolet irradiation device 280 Conveying section 282 Conveying roller h Emitted light

Claims (2)

1. An organic electroluminescence device in which a light extraction layer that changes the directivity of light, a transparent electrode, an organic functional layer, and a counter electrode are sequentially laminated on a transparent substrate,
   The light extraction layer has a light scattering layer containing light scattering particles having an average particle diameter of 150 to 350 nm;
   The light scattering layer has an in-plane occupation ratio of the light scattering particles of 20 to 60%, a layer thickness of 150 to 500 nm, a surface roughness Ra of 10 to 50 nm, and a maximum height Rt of 100 to 300 nm. An organic electroluminescence device characterized by that.
2. 2. The organic electroluminescence device according to claim 1, wherein the light extraction layer has a smooth layer that smoothes a surface of the light scattering layer facing the transparent electrode.

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