JP2004303724A - Electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EL element with reduced total reflection not only at the interface between the air layer and a transparent substrate but also at the interface on the light extraction side of the transparent electrode layer, with sufficiently improved light extraction efficiency. <P>SOLUTION: A negative electrode 1, EL layer 2, particle-containing transparent electrode layer 3', low refractive index layer, and translucent substrate 5 such as a glass substrate are laminated in this order. The light from the EL layer 2 is emitted to the transparent electrode layer 3' side in the state of as it is or reflected by the negative electrode and passing through the EL layer 2, and passes through the low refractive index layer 4 and the substrate 5, and extracted. Since the low refractive index layer 4 is provided, the light entered from the transparent electrode layer 3' side to the low refractive index layer side 4 enters the interface between the substrate 5 and low refractive index layer 4 at an incident angle almost perpendicular to the substrate face of the substrate 5, and thereby, total reflection on the air layer 7 side of the transparent substrate 5 decreases.As the transparent electrode layer 3' contains particles. total reflection on interface of low refractive-index layer and particle-containing transparent electrode layer also decreases and the light extraction efficiency is improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electroluminescence (EL) device, and more particularly to an electroluminescence device having a high light extraction efficiency from an electroluminescence layer.

  As shown in FIG. 4A, an electroluminescent element used for an EL display has at least a transparent substrate 5, a transparent electrode layer (anode) 3, an electroluminescent layer 2, and a cathode 1. In this electroluminescent element, holes injected from the transparent electrode layer 3 as an anode and electrons injected from the cathode 1 are recombined in the electroluminescent layer 2, and the recombination energy excites a light emission center to emit light. It has a light emitting principle of

  In the EL display, it is preferable that the light emitted from the electroluminescence layer 2 is efficiently extracted to the transparent substrate 5 side. However, as shown in FIG. The light is totally reflected at the interface between the substrate and the air 7, and becomes guided light 12 that travels while totally reflecting inside the transparent substrate 2 in the plane direction. Also, there is guided light that is totally reflected at the interface between the transparent electrode layer and the transparent substrate and travels in the plane direction inside the transparent electrode or inside the transparent electrode and the electroluminescent layer, and this guided light is absorbed and attenuated inside the element. It is not taken out to the outside (Non-Patent Documents 1 and 2).

  The light extraction efficiency (the ratio of light generated in the electroluminescence layer 2 to the outside of the electroluminescence element) extracted from the transparent substrate 2 by these guided lights 12 is as low as about 20%.

To solve such a problem, as shown in FIG. 5, a low-refractive-index layer 4 is provided on the electroluminescent layer 2 side of the transparent substrate 5, and the low-refractive-index layer 4 refracts the light 11 having a large emission angle to generate guided light. Reduction of generation and improvement of light extraction efficiency are being studied. For example, Patent Literature 1 described below describes an electroluminescence device having a low refractive index layer having a refractive index of 1.01 to 1.3 formed by a silica airgel film technique.
JP-A-2002-278777 (paragraphs 0010 to 0012) Chutinan et al. "Preliminary Proceedings of Spring Society of Materials Science" 2003 27P-A-16 Fujita et al. "Preliminary Proceedings of the Spring Society of Materials Science" 2003 29-YN-13

  By providing the low refractive index layer 4 between the transparent electrode layer 3 and the transparent substrate 5 as described in JP-A-2002-278777, total reflection at the interface between the transparent substrate 5 and the air layer 7 is reduced. However, in this publication, total reflection at the interface between the transparent electrode layer 3 and the low refractive index layer 4 is not improved. Rather, the provision of the low refractive index layer 4 has a problem in that the total reflection amount at the interface between the transparent electrode layer 3 and the low refractive index layer 4 is increased.

  An object of the present invention is to provide an electroluminescent element in which total reflection at an interface on a light extraction side of a transparent electrode layer is reduced in addition to an interface with an air layer of a transparent substrate, and light extraction efficiency is sufficiently improved. And

  The electroluminescent device of the present invention (claim 1) is an electroluminescent device in which a cathode, an electroluminescent layer, a transparent electrode layer, and a light transmitting body are arranged in this order, wherein the transparent electrode layer is formed of light from the electroluminescent layer. Which is characterized by containing particles that scatter.

  The particle-containing transparent electrode layer increases the amount of light entering the light transmitting body from the particle-containing transparent electrode layer as described below, and improves light extraction efficiency.

  The light generated in the electroluminescent layer reaches the light-transmitting body, and must pass through a transparent substance having a different refractive index to emit light into the air, and must exit the air from the light-transmitting body. Total reflection, in particular, total reflection when light is emitted from the light transmitting body to the air layer and total reflection when light is emitted from the transparent electrode layer toward the light transmitting body are major factors that hinder light emission. In particular, in the latter case, since the transparent electrode layer and the electroluminescent layer absorb light in the visible region, there is a problem that the light is attenuated (light energy is changed to heat or other energy) while being guided. That is, light that enters at an angle of total reflection does not reach light.

  In the present invention, particles having a different refractive index from the matrix constituting the transparent electrode layer, that is, particles that scatter light, are present in the transparent electrode layer which is an essential layer constituting the electroluminescence. By doing so, the angle of light that is originally totally reflected and confined is changed, and the light is changed to an angle that does not cause total reflection and light is emitted.

  This function also works when a low-refractive-index layer (a layer made of a material having a lower refractive index than the transparent electrode layer) is provided on the transparent body side surface of the transparent electrode layer.

  In the case of an electroluminescent element, a low-refractive-index layer is often present on the surface of the transparent electrode layer on the light-transmitting body side. Therefore, the following description will be mainly made of a configuration in which the low-refractive-index layer is present.

  That is, of the light incident on the interface between the particle-containing transparent electrode layer and the low-refractive-index layer, light having an incident angle smaller than the critical angle proceeds from the particle-containing transparent electrode layer into the low-refractive-index layer as it is. Light having an incident angle larger than the critical angle is totally reflected at the interface with the low refractive index layer and returns to the particle-containing transparent electrode layer side. A part of the light returning to the particle-containing transparent electrode layer in this manner is scattered by the particles in the particle-containing transparent electrode layer. Part of the scattered light is directly or indirectly re-injected into the interface with the low refractive index layer via reflection at the cathode layer or the like. Among them, light having an incident angle smaller than the critical angle enters the low refractive index layer from the particle-containing transparent electrode layer without being totally reflected. Of the scattered light incident on the interface, those having an incident angle larger than the critical angle return to the particle-containing transparent electrode layer again, and a part thereof is again scattered by the particles. By sequentially repeating this, the remaining light gradually enters the low refractive index layer side.

  Of the light totally reflected at the interface between the low-refractive-index layer and the particle-containing transparent electrode layer, the light that reaches the interface between the electroluminescent layer and the particle-containing transparent electrode layer has an incident angle to this interface smaller than the critical angle. When it is large, the light is totally reflected at the interface and returns to the interface between the low refractive index layer and the particle-containing transparent electrode layer again. The behavior of the light thereafter is the same as described above, and gradually enters the low refractive index layer.

  On the other hand, light incident on the interface between the particle-containing transparent electrode layer and the electroluminescence layer from the particle-containing transparent electrode layer side at an incident angle smaller than the critical angle directly enters the electroluminescence layer, and the interface between the electroluminescence layer and the cathode. , Again pass through the electroluminescence layer and the particle-containing transparent electrode layer, and return to the interface between the particle-containing transparent electrode layer and the low refractive index layer. The subsequent behavior of this light is the same as above.

  As described above, according to the electroluminescent device of the present invention (claim 1), total reflection on the transparent electrode layer side is reduced more than on the low refractive index layer, and the reduced amount enters the low refractive index layer side. By refracting and entering the transparent substrate layer (light-transmitting body) in a direction substantially perpendicular to the transparent substrate, total reflection at the air layer side interface of the transparent substrate is suppressed, and light extraction efficiency is improved. .

  An electroluminescent device according to the present invention (claim 2) is an electroluminescent device in which a cathode, an electroluminescent layer, a transparent electrode layer, and a light-transmitting member are arranged in this order. Is provided with a particle-containing layer comprising a matrix and particles that scatter light from the electroluminescence layer dispersed in the matrix, wherein the matrix has a refractive index equal to or higher than that of the transparent electrode layer. It is a feature.

  In the present specification, “equivalent in refractive index” means that the difference between one refractive index and the other is less than 0.3, preferably 0.2 or less, more preferably 0.1 or less. That means.

  The particle-containing layer provided between the transparent electrode layer and the light-transmitting member increases the amount of light transferred from the transparent electrode layer to the light-transmitting member as described below, and improves light extraction efficiency. That is, since the refractive index of the matrix of the particle-containing layer is equal to the refractive index of the transparent electrode layer, almost no total reflection occurs at the interface between the transparent electrode layer and the particle-containing layer.

  It will be easily understood that this configuration has the same optical effect as the above-described case where the transparent electrode layer contains particles.

  As described above, in the case of an electroluminescent element, a low-refractive-index layer is often present on the surface of the transparent electrode layer on the light-transmitting body side. The light that travels from the transparent electrode layer into the particle-containing layer and is incident on the interface between the particle-containing transparent electrode layer and the low-refractive-index layer in the particle-containing layer is light whose incident angle is smaller than the critical angle. It proceeds from the containing layer into the low refractive index layer.

  Light having an incident angle larger than the critical angle is totally reflected at the interface with the low refractive index layer and returns to the particle-containing layer side. Part of the light that has returned to the particle-containing layer in this way is scattered by the particles in the particle-containing layer. A part of the scattered light is directly or after being reflected by a cathode, for example, an aluminum reflective film, again incident on the interface with the low refractive index layer. Of these, light having an incident angle smaller than the critical angle enters the low refractive index layer from the particle-containing layer without being totally reflected. Of the scattered light incident on the interface, those having an incident angle larger than the critical angle return to the particle-containing layer again, and a part thereof is again scattered by the particles. By sequentially repeating this, the remaining light gradually enters the low refractive index layer side.

  Of the light totally reflected at the interface between the low-refractive-index layer and the particle-containing layer, the light that reaches the interface between the particle-containing layer and the transparent electrode layer has almost no refractive index difference at this interface. And returns to the interface between the transparent electrode layer and the electroluminescent layer. When the angle of incidence on the interface is larger than the critical angle, the light is totally reflected at the interface and returns to the interface between the low refractive index layer and the particle-containing layer. The behavior of the light thereafter is the same as in the case of the above-described electroluminescent element, and gradually enters the low refractive index layer.

  On the other hand, light incident on the interface between the transparent electrode layer and the electroluminescent layer at an angle of incidence smaller than the critical angle from the transparent electrode layer side enters the electroluminescent layer as it is, and is reflected at the interface between the electroluminescent layer and the cathode, The light passes through the electroluminescent layer and the transparent electrode layer again, and returns to the interface between the transparent electrode layer and the particle-containing layer. The subsequent behavior of this light is the same as above.

  As described above, according to this electroluminescent element (claim 2), the total reflection on the transparent electrode layer side is reduced more than the low refractive index layer, and the reduced amount enters the low refractive index layer, and By refracting and entering the transparent substrate layer in a direction almost perpendicular to the transparent substrate, total reflection at the interface of the transparent substrate on the air layer side is suppressed, and light extraction efficiency is improved. In addition to the proposal using this type of scattering particles, irregularly arranged irregularities such as forming a grating or a planar photonic crystal (which has a function of controlling diffracted light) microlenses are formed in the transparent electrode or in the transparent electrode. Although there is a proposal to form the electrode between the electrode and the transparent substrate, all of these methods are disadvantageous in that they require a lot of processing.

  According to the present invention, the light extraction efficiency of the electroluminescent element can be significantly improved. INDUSTRIAL APPLICABILITY The present invention can be widely applied to electroluminescent devices regardless of inorganic light emitting materials and organic light emitting materials, and regardless of display applications and planar light source applications.

  Hereinafter, the present invention will be described in more detail with reference to embodiments. 1 and 2 are cross-sectional views each showing an electroluminescent device according to an embodiment of the present invention.

  FIG. 1A shows an electroluminescent device according to an embodiment of the present invention, in which a cathode 1, an electroluminescent layer 2, a particle-containing transparent electrode layer 3 ', a low refractive index layer 4 (the low refractive index layer is A light-transmitting substrate 5 such as a glass substrate is not necessarily required and may not be provided.

  The light from the electroluminescent layer 2 is emitted as it is or reflected by the cathode 1, passes through the electroluminescent layer 2, exits to the particle-containing transparent electrode layer 3 ′, and is then extracted through the low refractive index layer 4 and the substrate 5. It is.

  When the low refractive index layer 4 is provided, light components scattered by the particle-containing transparent electrode layer 3 'and totally reflected are reduced. That is, the low-refractive-index layer 4 allows the light to enter the interface between the substrate 5 and the low-refractive-index layer 4 at an incident angle close to the perpendicular to the substrate surface of the substrate 5, and is totally reflected at the interface of the substrate 5 on the air layer side Decrease.

  In this electroluminescent element, the particle-containing transparent electrode layer 3 'increases the amount of light entering the low refractive index layer 4 from the particle-containing transparent electrode layer 3' as described below, and improves light extraction efficiency. That is, of the light incident on the interface between the particle-containing transparent electrode layer 3 ′ and the low refractive index layer 4, the light whose incident angle is smaller than the critical angle is directly transmitted from the particle-containing transparent electrode layer 3 ′ to the low refractive index layer 4. Proceed inside. Light having an incident angle larger than the critical angle is totally reflected at the interface with the low refractive index layer 4 and returns to the particle-containing transparent electrode layer side 3 '. Part of the light returning to the particle-containing transparent electrode layer side 3 'is scattered by the particles in the particle-containing transparent electrode layer 3'. Part of the scattered light is again incident on the interface with the low refractive index layer 4. Among them, light whose incident angle is smaller than the critical angle enters the low refractive index layer 4 from the particle-containing transparent electrode layer 3 'without being totally reflected. Of the scattered light incident on the interface, those having an incident angle larger than the critical angle return to the particle-containing transparent electrode layer 3 'side again, and a part thereof is again scattered by the particles. By repeating this sequentially, the remaining light gradually enters the low refractive index layer 4 side.

  When the low refractive index layer 4 is provided, the light totally reflected at the interface between the electroluminescent layer 2 and the particle-containing transparent electrode layer 3 'reaches the interface between the electroluminescent layer 2 and the particle-containing transparent electrode layer 3'. When the incident angle to the interface is larger than the critical angle, the light is totally reflected at the interface and returns to the interface between the low refractive index layer 4 and the particle-containing transparent electrode layer 3 '. The behavior of the light thereafter is the same as described above, and gradually enters the low refractive index layer 4.

  On the other hand, light incident on the interface between the particle-containing transparent electrode layer 3 ′ and the electroluminescence layer 2 from the particle-containing transparent electrode layer 3 ′ side at an incident angle smaller than the critical angle directly enters the electroluminescence layer 2, and The light is reflected at the interface between the layer 2 and the cathode 1, passes through the electroluminescence layer 2 and the particle-containing transparent electrode layer 3 'again, and returns to the interface between the particle-containing transparent electrode layer 3' and the low refractive index layer 4. The subsequent behavior of this light is the same as above.

  Thus, the total reflection on the transparent electrode layer side with respect to the low refractive index layer 4 is reduced, and the light extraction efficiency is improved.

  Next, a preferred configuration of the substrate 5 and each of the layers 1 to 4 will be described.

A: Substrate 5 The substrate has a refractive index of 1.4 to 1.9, preferably 1.45 to 1.70, more preferably 1.47 to 1.65, and most preferably 1.48 to 1. .60 are used.

  If the refractive index of the substrate exceeds 1.9, the difference in the refractive index between the substrate and air is large, so that the total reflection amount here is large. Since the thickness of the substrate usually exceeds 100 μm, especially in the case of EL display applications, if the total reflection here is large, the total reflected light will return to the diffusion layer and will be scattered again to increase the amount of emitted light. Emitted light is mixed between pixels having a size of 100 μm square or less, and a phenomenon such as pixel bleeding or color bleeding which lowers the resolution occurs, which is not preferable.

  When the refractive index of the substrate exceeds 1.9, reflection of external light on the surface of the substrate increases, which is also undesirable because it lowers the resolution of the display.

  If the refractive index of the substrate is lower than 1.4, there is no suitable material as a self-supporting transparent substrate material, which is not preferable.

  This refractive index is an average refractive index in the entire depth direction determined by measurement with an ellipsometer based on ASTM D-542, and is represented by a value with respect to a sodium D line (589.3 nm) at 23 ° C. As a substrate having such a refractive index, a transparent substrate made of a general-purpose material can be used. For example, various shot glasses such as BK7, SF11, LaSFN9, BaK1, and F2, synthetic fused silica glass, optical crown glass, low expansion borosilicate glass, sapphire, soda glass, alkali-free glass, and the like, polymethyl methacrylate, and cross-linked Acrylic resin such as acrylate, aromatic polycarbonate resin such as bisphenol A polycarbonate, styrene resin such as polystyrene, amorphous polyolefin resin such as polycycloolefin, epoxy resin, polyester resin such as polyethylene terephthalate, polysulfone such as polyether sulfone Resins and synthetic resins such as polyetherimide resins can be mentioned. Among them, shot glass such as BK7 and BaK1, synthetic fused silica glass, optical crown glass, low expansion borosilicate glass, soda glass, alkali-free glass, acrylic resin, aromatic polycarbonate resin, and amorphous polyolefin resin are preferable. , BK7 shot glass, synthetic fused silica glass, optical crown glass, low expansion borosilicate glass, soda glass, non-alkali glass, acrylic resin, aromatic polycarbonate resin, and polyether sulfone resin are particularly preferable.

  If the refractive index of the substrate exceeds 1.9, the difference in the refractive index between the substrate and air is large, so that the total reflection amount here is large. Since the thickness of the substrate usually exceeds 100 μm, especially in the case of EL display applications, if the total reflection here is large, the total reflected light will return to the diffusion layer and will be scattered again to increase the amount of emitted light. Emitted light is mixed between pixels having a size of 100 μm square or less, and a phenomenon such as pixel bleeding or color bleeding which lowers the resolution occurs, which is not preferable.

  When the refractive index of the substrate exceeds 1.9, reflection of external light on the surface of the substrate increases, which is also undesirable because it lowers the resolution of the display.

B: About Low Refractive Index Layer 4 First, it is important that the low refractive index layer 4 has a refractive index substantially lower than the refractive index of the light transmitting body (transparent substrate). In particular, those having about 1.2 to 1.35, for example, transparent fluoride resins such as silica and cyclic Teflon, and magnesium fluoride are preferable, and porous silica is particularly preferable. In silica, an organic component may be introduced as necessary to impart hydrophobicity, impart flexibility, prevent cracks, and the like. If the refractive index is too low, the mechanical strength of the film tends to be insufficient. If it is too high, the amount of total reflection between the low refractive index layer and the light transmitting body or between the light transmitting body and air increases, and the extraction efficiency decreases. In addition, in the embodiment (top emission type) shown in FIG. 3 described later, even if the low refractive index layer is air (void), there is no problem in device configuration. The refractive index in this case is 1.0.

A porous silica film suitable as the low refractive index layer 4 is formed by, for example, the following steps.
(1) A step of preparing a raw material liquid for forming a porous silica film (2) A step of applying the raw material liquid on a substrate to form a primary film (3) The applied primary film is converted into a high molecular weight intermediate Step of forming a film (4) Step of forming a porous silica film by bringing a water-soluble organic solvent into contact with the intermediate film (5) Step of drying the porous silica film

Hereinafter, each step will be described.
However, since the purpose is to form a low-refractive-index film, in the present invention, the method of forming the low-refractive-index layer 4 is not particularly limited to this manufacturing method as long as the requirements are satisfied. For example, a porous film (mesoporous film) formed by a manufacturing process as shown in the following document can be used as long as it satisfies the requirements for a low refractive index layer.
JP 2002-278477 A
USP Pat.No.US6592764B1 (BLOCK COPOLYMER PROCESSING FOR MESOSTRUCTURED INORGANIC
OXIDE MATERIALS Inventors; Galen D. Stucky et al.)
ULVAC Technical Report No. 57, September 2002, pages 34-36
Proceedings of IDW2002, pp.1633-1166
Application of Low Refractive Materials for Optical Windows of Displays T. Nakayama
Et al. ULVAC

(1) a step of preparing a raw material liquid for forming a porous silica film;
The raw material liquid for forming a porous silica film is mainly composed of alkoxysilanes, and is a water-containing organic solution containing a raw material compound capable of causing a high molecular weight by a hydrolysis reaction and a dehydration condensation reaction.

  The aqueous organic solution as the raw material liquid contains alkoxysilanes, a hydrophilic organic solvent, water, and a catalyst that is added as needed.

  Examples of the alkoxysilanes include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetra (n-propoxy) silane, tetraisopropoxysilane, tetra (n-butoxy) silane, trimethoxysilane, triethoxysilane, methyl Trialkoxysilanes such as trimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dialkoxysilanes such as dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, bis (Trimethoxysilyl) methane, bis (triethoxysilyl) methane, 1,2-bis (trimethoxysilyl) ethane, 1,2-bis (triethoxysilyl) ethane, 1,4-bis (tri Organic residues such as (toxisilyl) benzene, 1,4-bis (triethoxysilyl) benzene, and 1,3,5-tris (trimethoxysilyl) benzene having two or more trialkoxysilyl groups bonded thereto; Aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-acryloyloxypropyltrimethoxysilane, Examples thereof include those having a reactive functional group in which an alkyl group substituted on a silicon atom, such as 3-carboxypropyltrimethoxysilane, may be a partially hydrolyzed product or an oligomer thereof.

  Among these, particularly preferred are tetramethoxysilane, tetraethoxysilane, trimethoxysilane, triethoxysilane, tetramethoxysilane or oligomers of tetraethoxysilane. In particular, an oligomer of tetramethoxysilane is most preferably used in view of reactivity and controllability of gelation.

  Further, the alkoxysilanes may be mixed with monoalkoxysilanes having two or three hydrogens, alkyl groups or aryl groups on silicon atoms. By mixing monoalkoxysilanes, the resulting porous silica film can be made hydrophobic to improve water resistance. Examples of the monoalkoxysilanes include triethylmethoxysilane, triethylethoxysilane, tripropylmethoxysilane, triphenylmethoxysilane, triphenylethoxysilane, diphenylmethylmethoxysilane, diphenylmethylethoxysilane, and the like. The mixing amount of the monoalkoxysilanes is desirably 70 mol% or less of all the alkoxysilanes. If the mixing amount exceeds 70 mol%, gelation may not occur.

  Alkyl fluorides such as (3,3,3-trifluoropropyl) trimethoxysilane, (3,3,3-trifluoropropyl) triethoxysilane, pentafluorophenyltrimethoxysilane, and pentafluorophenyltriethoxysilane; When an alkoxysilane having a group or a fluoroaryl group is used in combination, excellent water resistance, moisture resistance, stain resistance and the like may be obtained.

  In this raw material liquid, the oligomer may be a crosslinked or cage-type molecule (silsesquioxane or the like). Practically, as the upper limit of the condensate contained in the water-containing organic solution, the transparency of the solution is preferably in the range of 90 to 100%, for example, as a light transmittance at a wavelength of 400 nm, 23 ° C. and an optical path length of 10 mm. Used. The lower limit of the light transmittance of the solution is preferably 92% or more, more preferably 95% or more.

  When applying the above-described raw material liquid, it is necessary that a certain degree of high molecular weight (that is, a state in which condensation has progressed to some extent) has already been achieved. It is preferable that the molecular weight has been increased to such an extent that insolubles cannot be formed. The reason is that if there is a visible insoluble matter in the raw material liquid before the coating, large surface irregularities can be surely formed and the film quality is deteriorated.

  As the organic solvent, those having an ability to mix the alkoxysilanes constituting the raw material liquid, water, and a hydrophilic organic compound having a boiling point of 80 ° C. or higher, which will be described later, are preferably used. Examples of usable organic solvents include monohydric alcohols having 1 to 4 carbon atoms, dihydric alcohols having 1 to 4 carbon atoms, and alcohols such as polyhydric alcohols such as glycerin and pentaerythritol; diethylene glycol, ethylene glycol monomethyl ether, and ethylene. Glycol dimethyl ether, 2-ethoxyethanol, propylene glycol monomethyl ether, propylene glycol methyl ether acetate and the like; ethers or esterified products of the above alcohols; ketones such as acetone and methyl ethyl ketone; formamide, N-methylformamide, N-ethylformamide, N , N-dimethylformamide, N, N-diethylformamide, N-methylacetamide, N-ethylacetamide, N, N-dimethylacetamide, N, N-di Tylacetamide, N-methylpyrrolidone, N-formylmorpholine, N-acetylmorpholine, N-formylpiperidine, N-acetylpiperidine, N-formylpyrrolidine, N-acetylpyrrolidine, N, N'-diformylpiperazine, N, N Amides such as' -diformylpiperazine and N, N'-diacetylpiperazine; lactones such as γ-butyrolactone; ureas such as tetramethylurea and N, N'-dimethylimidazolidine; dimethylsulfoxide and the like. . These water-soluble organic solvents may be used alone or as a mixture. Among these, preferred organic solvents in terms of film-forming properties (particularly, volatility) on a substrate include acetone, methyl ethyl ketone, and monohydric alcohols having 1 to 4 carbon atoms. Among them, methanol, ethanol, n-propanol, isopropyl alcohol and acetone are more preferred, and methanol or ethanol is most preferred.

  A hydrophilic organic compound having a boiling point of 80 ° C. or higher has a hydrophilic functional group such as a hydroxyl group, a carbonyl group, an ether bond, an ester bond, a carbonate bond, a carboxyl group, an amide bond, a urethane bond, or a urea bond in a molecular structure. An organic compound. The hydrophilic organic compound may have a plurality of these hydrophilic functional groups in the molecular structure. Here, the boiling point is a boiling point under a pressure of 760 mmHg. When a hydrophilic organic compound having a boiling point of less than 80 ° C. is used, the porosity of the porous silica film may be extremely reduced. Preferred examples of the hydrophilic organic compound having a boiling point of 80 ° C. or higher include alcohols having 3 to 8 carbon atoms, polyhydric alcohols having 2 to 6 carbon atoms, and phenols. More preferred hydrophilic organic compounds include C3-8 alcohols, C2-8 diols, C3-8 triols, and C4-8 tetraols. More preferred hydrophilic organic compounds include alcohols having 4 to 7 carbon atoms such as n-butanol, isobutyl alcohol, t-butyl alcohol, n-pentanol, cyclopentanol, n-hexanol, cyclohexanol, and benzyl alcohol; C2-4 diols such as ethylene glycol, propylene glycol and 1,4-butanediol, C3-6 triols such as glycerol and trishydroxymethylethane, and C4 carbon such as erythritol and pentaeristol. To 5 tetraols. If the number of carbon atoms in this hydrophilic organic compound is too large, the hydrophilicity may be too low.

  The catalyst is blended as required. Examples of the catalyst include a substance that promotes the hydrolysis and dehydration condensation reaction of the alkoxysilanes described above. Specific examples include acids such as hydrochloric acid, nitric acid, sulfuric acid, formic acid, acetic acid, oxalic acid, and maleic acid; amines such as ammonia, butylamine, dibutylamine, and triethylamine; bases such as pyridine; and Lewis such as aluminum acetylacetone complex. Acids; and the like.

  Examples of the metal species of the metal chelate compound used as the catalyst include titanium, aluminum, zirconium, tin, antimony and the like. Specific examples of the metal chelate compound include the following.

  Examples of the aluminum complex include di-ethoxy mono (acetylacetonate) aluminum, di-n-propoxy mono (acetylacetonate) aluminum, di-isopropoxy mono (acetylacetonate) aluminum, di-n-butoxy. Mono (acetylacetonato) aluminum, di-sec-butoxy mono (acetylacetonato) aluminum, di-tert-butoxymono (acetylacetonato) aluminum, monoethoxybis (acetylacetonato) aluminum, mono-n -Propoxy bis (acetylacetonato) aluminum, monoisopropoxybis (acetylacetonato) aluminum, mono-n-butoxybis (acetylacetonato) aluminum, mono-sec-butoxybi (Acetylacetonato) aluminum, mono-tert-butoxybis (acetylacetonato) aluminum, tris (acetylacetonato) aluminum, diethoxymono (ethylacetoacetate) aluminum, di-n-propoxymono (ethylacetoacetate) ) Aluminum, diisopropoxy mono (ethyl acetoacetate) aluminum, di-n-butoxy mono (ethyl acetoacetate) aluminum, di-sec-butoxy mono (ethyl acetoacetate) aluminum, di-tert-butoxy mono (Ethyl acetoacetate) aluminum, monoethoxy bis (ethyl acetoacetate) aluminum, mono-n-propoxy bis (ethyl acetoacetate) aluminum, monoisopro Xybis (ethylacetoacetate) aluminum, mono-n-butoxybis (ethylacetoacetate) aluminum, mono-sec-butoxybis (ethylacetoacetate) aluminum, mono-tert-butoxybis (ethylacetoacetate) Aluminum chelate compounds such as aluminum and tris (ethyl acetoacetate) aluminum can be exemplified.

  Examples of the titanium complex include triethoxy mono (acetylacetonate) titanium, tri-n-propoxy mono (acetylacetonate) titanium, triisopropoxy mono (acetylacetonate) titanium, and tri-n-butoxy mono (acetyl). Acetonato) titanium, tri-sec-butoxymono (acetylacetonato) titanium, tri-tert-butoxymono (acetylacetonato) titanium, diethoxybis (acetylacetonato) titanium, di-n-propoxybis (Acetylacetonate) titanium, diisopropoxy bis (acetylacetonate) titanium, di-n-butoxybis (acetylacetonate) titanium, di-sec-butoxybis (acetylacetonate) titanium, di-tert -Butoxy bis (ace Luacetonate) titanium, monoethoxy tris (acetylacetonate) titanium, mono-n-propoxy tris (acetylacetonate) titanium, monoisopropoxy tris (acetylacetonate) titanium, mono-n-butoxy tris (acetyl) Acetonato) titanium, mono-sec-butoxytris (acetylacetonato) titanium, mono-tert-butoxytris (acetylacetonato) titanium, tetrakis (acetylacetonato) titanium, triethoxymono (ethylacetoacetate) titanium Tri-n-propoxy mono (ethyl acetoacetate) titanium, triisopropoxy mono (ethyl acetoacetate) titanium, tri-n-butoxy mono (ethyl acetoacetate) titanium, tri-sec-butyl Titanium xy-mono (ethyl acetoacetate), tri-tert-butoxy mono (ethyl acetoacetate) titanium, diethoxy bis (ethyl acetoacetate) titanium, di-n-propoxy bis (ethyl acetoacetate) titanium, diiso Propoxy bis (ethyl acetoacetate) titanium, di-n-butoxy bis (ethyl acetoacetate) titanium, di-sec-butoxy bis (ethyl acetoacetate) titanium, di-tert-butoxy bis (ethyl acetoacetate) Titanium, monoethoxy tris (ethyl acetoacetate) titanium, mono-n-propoxy tris (ethyl acetoacetate) titanium, monoisopropoxy tris (ethyl acetoacetate) titanium, mono-n-butoxy tris (ethyl acetoacetate) Acetate titanium, mono-sec-butoxy tris (ethyl acetoacetate) titanium, mono-tert-butoxy tris (ethyl acetoacetate) titanium, tetrakis (ethyl acetoacetate) titanium, mono (acetyl acetonate) tris (ethyl acetoate) Acetate titanium, bis (acetylacetonate) bis (ethylacetoacetate) titanium, tris (acetylacetonate) mono (ethylacetoacetate) titanium and the like can be mentioned.

  In addition to these catalysts, a weakly alkaline compound, for example, a basic catalyst such as ammonia may be used. In this case, it is preferable to appropriately adjust the silica concentration, the type of the organic solvent, and the like. When adjusting the aqueous organic solution, it is preferable not to rapidly increase the catalyst concentration in the solution. As a specific example, there is a method in which alkoxysilanes and a part of an organic solvent are mixed, then water is mixed therein, and finally, the remaining organic solvent and a base are mixed in this order.

  In particular, Lewis acids such as hydrochloric acid, which is highly volatile and easily removed, and aluminum acetylacetone complex, are preferred. The amount of the catalyst to be added is generally 0.001-1 mol, preferably 0.01-0.1 mol, per 1 mol of the alkoxysilane. If the amount of the catalyst exceeds 1 mol, a precipitate composed of coarse gel particles is formed, and a uniform porous silica film may not be obtained.

  The raw material liquid for forming the porous silica film is formed by mixing the above-mentioned raw materials. The compounding ratio of the alkoxysilanes is preferably from 10 to 60% by weight, more preferably from 20 to 40% by weight, based on the whole raw material liquid. When the compounding ratio of the alkoxysilanes exceeds 60% by weight, the porous silica film may be broken at the time of film formation. On the other hand, when the mixing ratio of the alkoxysilanes is less than 10% by weight, the hydrolysis reaction and the dehydration condensation reaction become extremely slow, and the film formability may deteriorate (film unevenness).

  Water is added in an amount of 0.01 to 10 times, preferably 0.05 to 7 times, more preferably 0.07 to 5 times the weight of the alkoxysilanes used. If the amount of water is less than 0.01 times the weight of the alkoxysilanes, the degree of progress of the hydrolysis-condensation reaction becomes insufficient, and the film may become cloudy. On the other hand, when the amount of water exceeds 10 times the weight of the alkoxysilanes, the surface tension of the raw material liquid becomes extremely large, and the film formability may be deteriorated (such as cissing of the liquid).

  Water is necessary for the hydrolysis of alkoxysilanes, and is important from the viewpoint of improving the film-forming properties of the target porous silica film. Therefore, when the preferred amount of water is defined by the molar ratio with respect to the amount of the alkoxide group, the amount is 0.1 to 1.6 mole times, preferably 0.3 to 1.2 mole times, per mole of the alkoxide group in the alkoxysilane. In particular, the amount is preferably 0.5 to 0.7 mole times.

  The addition of water may be performed at any time after the alkoxysilanes are dissolved in the organic solvent, but desirably, the alkoxysilanes, the catalyst and other additives are sufficiently dispersed in the solvent, and then the water is preferably added. Most preferred.

  The purity of the water used may be one subjected to ion exchange, distillation, or one or both of the treatments. When the porous silica film of the present invention is used in an application field that particularly dislikes minute impurities, such as a semiconductor material or an optical material, since a porous silica film having higher purity is required, distilled water was further ion-exchanged. It is desirable to use ultrapure water. In this case, for example, water that has passed through a filter having a pore size of 0.01 to 0.5 μm may be used.

  When using a hydrophilic organic compound having a boiling point of 80 ° C or higher in the aqueous organic solution, the content of the hydrophilic organic compound having a boiling point of 80 ° C or higher is reduced to the total content of the organic solvent and the hydrophilic organic compound having a boiling point of 80 ° C or higher. On the other hand, it is important that the amount is not more than the specified amount. The content of the hydrophilic organic compound having a boiling point of 80 ° C. or higher based on the total content is 90% by weight or less, and preferably 85% by weight or less.

  If the proportion of the hydrophilic organic compound having a boiling point of 80 ° C. or higher is too small, the porosity of the porous silica film becomes extremely small, and it may be difficult to achieve a low refractive index of the porous silica film. Generally, the total content of the organic solvent and the hydrophilic organic compound having a boiling point of 80 ° C. or higher is preferably 30% by weight or more, more preferably 50% by weight or more, and particularly preferably 60% by weight or more. On the other hand, when the compounding ratio of the hydrophilic organic compound exceeds 90% by weight of the total content, the coating film may become cloudy during the film formation or the porous silica film may be broken. Therefore, the content of the hydrophilic organic compound having a boiling point of 80 ° C. or more in the water-containing organic solution is 30% by weight or more and 90% by weight or less, preferably 50% by weight or more and 85% by weight or less, particularly 60% by weight or more and 85% by weight of the total content. % Is preferable.

  The atmosphere temperature and the mixing order in the preparation of the coating liquid are arbitrary, but it is preferable to mix the water last to obtain a uniform structure in the coating liquid. In addition, in order to suppress the extreme hydrolysis and condensation reaction of silicon alkoxide in the coating solution, the adjustment of the coating solution should be performed under the temperature range of 0 to 60 ° C, especially 15 to 40 ° C, particularly 15 to 30 ° C. Is preferred.

  At the time of liquid preparation, the operation of stirring the coating solution is optional, but it is more preferable to stir with a stirrer for each mixing.

  Further, after preparing the coating solution, it is preferable to ripen the solution in order to promote hydrolysis and dehydration condensation reaction of silicon alkoxides. During the aging period, it is preferable that the resulting hydrolyzed condensate of the silicon alkoxide is in a state of being more uniformly dispersed in the coating solution. Therefore, it is preferable to stir the solution.

  The temperature during the ripening period is arbitrary, and generally it may be heated to room temperature or continuously or intermittently. Above all, rapid heat aging is preferably performed in order to form a three-dimensional nanoporous structure using a hydrolyzed condensate of silicon alkoxides. Further, in the case of heat aging, heat aging immediately after the preparation of the coating solution is preferred, and heating aging within 15 days, further within 12 days, especially within 3 days, particularly within one day after the preparation of the coating solution is preferred.

  Specifically, accelerated aging at 40 to 70 ° C. for 1 to 5 hours is preferable, and in that case, stirring is preferably performed to obtain a uniform porous structure. In particular, from the viewpoint of making porous, accelerated aging at a temperature near 60 ° C. for 2 to 3 hours is preferable.

  The viscosity of the raw material liquid is 0.1 to 1000 centipoise, preferably 0.5 to 500 centipoise, and more preferably 1 to 100 centipoise. It is preferable to use a raw material liquid having a viscosity in this range from the viewpoint of production.

(2) forming a primary film from the raw material liquid;
The primary film is formed by applying a water-containing organic solution as a raw material liquid on a substrate. Examples of the substrate include semiconductors such as silicon and germanium, compound semiconductors such as gallium-arsenide and indium-antimony, substrates such as ceramics and metals, and transparent substrates such as glass substrates and synthetic resin substrates.

  When the porous silica film of the present invention is formed on a substrate, the properties of the substrate surface may influence the properties of the porous silica film. Therefore, not only cleaning of the substrate surface but also surface treatment of the substrate may be performed in some cases. Examples of the substrate surface cleaning include immersion treatment in an acid such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, alkalis such as an aqueous sodium hydroxide solution, and an oxidizing mixture of hydrogen peroxide and concentrated sulfuric acid, hydrochloric acid, and ammonia. Can be In particular, from the viewpoint of adhesion to the porous silica film, it is more preferable to perform a surface treatment on the silicon substrate or the transparent glass substrate with an acid such as sulfuric acid or nitric acid.

  Means for applying the raw material liquid include a bar coating method using a bar coater, an applicator or a doctor blade, or the like, a casting method in which the raw material liquid is spread on a substrate, a dip method in which the substrate is immersed in the raw material liquid, and a spin coating method. Well-known can be mentioned. Among these means, the casting method and the spin coating method are preferably adopted because the raw material liquid can be uniformly applied.

  The casting speed when the raw material liquid is applied by the casting method is 0.1 to 1000 m / min, preferably 0.5 to 700 m / min, and more preferably 1 to 500 m / min.

  The rotation speed when the raw material liquid is applied and formed by the spin coating method is 10 to 100,000 rotations / minute, preferably 50 to 50,000 rotations / minute, and more preferably 100 to 10,000 rotations / minute.

  In the dip coating method, the substrate may be immersed in a coating solution at an arbitrary speed and pulled up. The lifting speed at this time is preferably 0.01 to 50 mm / sec, more preferably 0.05 to 30 mm / sec, and particularly preferably 0.1 to 20 mm / sec. There is no limitation on the speed at which the substrate is immersed in the coating solution, but it may be preferable to immerse the substrate in the coating solution at a speed similar to the pulling speed. The immersion may be continued for an appropriate time until the substrate is immersed in the coating solution and pulled up. The immersion time is generally 1 second to 48 hours, preferably 3 seconds to 24 hours, more preferably 5 seconds to 12 hours. Time. The atmosphere during the coating may be air or an inert gas such as nitrogen or argon, and the temperature is usually 0 to 60 ° C, preferably 10 to 50 ° C, more preferably 20 to 40 ° C. The humidity is usually 5 to 90%, preferably 10 to 80%, more preferably 15 to 70%. In addition, since the drying rate is lower in the dip coating method than in the spin coating method, there is a tendency that a stable film with less distortion is formed by a sol-gel reaction after coating. Therefore, the film structure can be preferably controlled by the surface treatment of the substrate.

  The film forming temperature is 0 to 100 ° C, preferably 10 to 80 ° C, and more preferably 20 to 70 ° C.

(3) a step of forming an intermediate film by increasing the molecular weight of the applied film;
The applied film is made high molecular weight, and an intermediate film is formed. This reaction is called a sol-gel method, and the elementary reaction is composed of two elementary reactions of a hydrolysis reaction of alkoxysilanes and a dehydration condensation reaction of silanol groups generated by the hydrolysis reaction.

  The hydrolysis reaction is caused by adding water, but the water can be added as a liquid, as an aqueous alcohol solution, or as steam, and is not particularly limited. If water is added rapidly, the hydrolysis reaction and the dehydration-condensation reaction may occur too quickly depending on the type of alkoxysilane, resulting in precipitation. Therefore, to avoid such precipitation, take sufficient time for the addition of water, make the water uniformly added by coexisting the alcohol solvent, and add the water at a low temperature when adding. It is preferable to use means such as suppressing the reaction alone or in combination.

  As the hydrolysis-condensation reaction of alkoxysilanes proceeds by the sol-gel method, the condensate of alkoxysilanes gradually increases in molecular weight. In the hydrolysis-condensation reaction, phase separation considered to be caused by a change in the phase equilibrium may occur. The phase separation is controlled to occur on the nanometer scale by balancing the degree of hydrophilicity. As a result, the separated phase of the hydrophilic organic compound is formed on the substrate while being retained in the gel network of the alkoxysilane condensate, thereby forming an intermediate film.

  For this reason, it is important to control the hydrophilicity of the hydrophilic organic compound having a boiling point of 80 ° C. or higher, and when the hydrophilic organic compound is expressed in terms of relative dielectric constant, it is preferably 10 to 20, more preferably 13 to 20. 19 can be defined.

  From the viewpoint of balancing the degree of hydrophilicity, it is desirable that the aqueous organic solution as the raw material liquid contains an organic solvent having a relative dielectric constant of 23 or more (specifically, methanol, ethanol, or the like). In particular, when the weight ratio (weight of organic solvent / weight of hydrophilic organic compound) of an organic solvent having a relative dielectric constant of 23 or more and a hydrophilic organic compound having a boiling point of 80 ° C. or more is in the range of 5/5 to 2/8. Achieve more desirable phase separation behavior. This weight ratio is most preferably 4/6 to 2/8.

(4) a step of forming a porous silica film by bringing a water-soluble organic solvent into contact with the intermediate film (extraction step);
By bringing a water-soluble organic solvent into contact with the intermediate film, the hydrophilic organic compound in the intermediate film is extracted and removed, and water in the intermediate film is removed. Since the water present in the intermediate film is not only dissolved in the organic solvent but also adsorbed on the inner wall of the film constituents, it is necessary to use an organic solvent to effectively remove the water in the intermediate film. Control the content of water in it. Therefore, the content of water in the organic solvent is 0 to 10% by weight, preferably 0 to 5% by weight, and more preferably 0 to 3% by weight. If the dehydration is not performed sufficiently, the pores may collapse and disappear or become smaller in the subsequent heating or drying step of the film.

  As a means for extracting and removing the hydrophilic organic compound in the intermediate film, for example, immersing the intermediate film in a water-soluble organic solvent, washing the surface of the intermediate film with a water-soluble organic solvent, Examples of the method include spraying a water-soluble organic solvent on the surface and spraying a vapor of the water-soluble organic solvent on the surface of the intermediate film. Of these, immersion means and cleaning means are preferred. The contact time between the intermediate film and the water-soluble organic solvent can be set in the range of 1 second to 24 hours, but from the viewpoint of productivity, the upper limit of the contact time is preferably 12 hours, more preferably 6 hours. On the other hand, the lower limit of the contact time is preferably 10 seconds, and more preferably 30 seconds, since it is necessary to sufficiently remove the hydrophilic organic compound having a boiling point of 80 ° C. or higher and water.

(5) drying the porous silica membrane;
The drying step is performed for the purpose of removing volatile components remaining in the porous silica film and / or for promoting the hydrolysis-condensation reaction of alkoxysilanes. The drying temperature is 20 to 500 ° C, preferably 30 to 400 ° C, more preferably 50 to 350 ° C, and the drying time is 1 minute to 50 hours, preferably 3 minutes to 30 hours, more preferably 5 minutes to 5 minutes. 15 hours. The drying method can be performed by a known method such as blast drying or reduced-pressure drying, or a combination thereof. Note that if the drying is too strong and volatile components are rapidly removed, cracks occur in the porous silica film. Therefore, a gentle drying method such as blast drying is preferable. After the blast drying, drying under reduced pressure for the purpose of sufficiently removing volatile components can be added.

  Note that this drying step can be used in place of the above-described extraction step. That is, as a step of removing the hydrophilic organic compound having a boiling point of 80 ° C. or higher from the intermediate film formed in the step (3), the drying step described herein is not used, regardless of the extraction step in the above (4). Can be implemented.

  The method for manufacturing a laminated substrate capable of removing the above hydrophilic organic compound in such a drying step includes a raw material compound mainly composed of alkoxysilanes that cause a hydrolysis reaction and a dehydration condensation reaction, and a hydrophilic organic compound having a boiling point of 80 ° C. or more. Forming a primary film by applying a water-containing organic solution comprising a substrate, a step of forming an intermediate film by causing a hydrolysis reaction and a dehydration condensation reaction of the water-containing organic solution forming the primary film, A step of contacting the intermediate film with a catalyst substance that promotes a hydrolysis reaction and a dehydration condensation reaction to form a dense layer in the surface layer region of the intermediate film, and drying the intermediate film to obtain the boiling point of 80 ° C. It can be specified by a configuration including at least the step of forming the porous silica film by removing the above hydrophilic organic compound.

C: Regarding the particle-containing transparent electrode layer 3 'The particle-containing transparent electrode layer 3' functions as an anode of the electroluminescence device. As a matrix of the particle-containing transparent electrode layer 3 ′, indium oxide to which tin is added (commonly referred to as ITO) and zinc oxide to which aluminum is added (commonly referred to as AZO) are oxidized by adding indium. A composite oxide thin film such as zinc (commonly called IZO) is preferably used. Particularly, ITO is preferable.

The particle-containing transparent electrode layer 3 'can be formed by a coating method in which a raw material liquid containing particles that scatter light from the electroluminescent layer (hereinafter, may be referred to as "light scattering particles") is applied. The larger the light transmittance of the formed particle-containing transparent electrode layer 3 ′ in the visible light wavelength region is, the more preferable it is, for example, 50 to 99%. A preferred lower limit is 60%, more preferably 70%. The electrical resistance of the particle-containing transparent electrode layer 3 ′ is preferably as small as the sheet resistance, but is usually 1 to 100 Ω / □ (= 1 cm ² ), and the upper limit is preferably 70 Ω / □, more preferably 50 Ω / □. □. Further, the thickness of the particle-containing transparent electrode layer 3 ′ is usually 0.01 to 10 μm, and the lower limit is 0.03 μm from the viewpoint of conductivity, as long as the light transmittance and the sheet resistance described above are satisfied. Preferably, it is more preferably 0.05 μm. On the other hand, from the viewpoint of light transmittance, the upper limit is preferably 1 μm, and more preferably 0.5 μm. The coating liquid for forming the particle-containing transparent electrode layer 3 ′ is, for example, a dispersion in which fine particles of a conductive material such as ITO or a semiconductor material are dispersed in an organic solvent together with a conductive polymer or other resin binder, or a conductive liquid. The polymer itself can be used, but is not limited thereto. In addition, light scattering particles are contained in this coating solution.

  As the light scattering particles contained in the particle-containing transparent electrode layer 3 ′, the particle weight ratio (weight percentage) is 60% or more (sometimes referred to as “60% weight ratio diameter”), and the particle diameter is 20 to 400 nm, preferably. Silica, colloidal silica, titania, ITO, ATO, alumina, zirconia, and the like having a thickness of about 30 to 300 nm, particularly about 40 to 200 nm, particularly about 60 to 120 nm are preferable. The size and shape of the particles can be used as long as they have the function of scattering light, but those that cause Mie scattering are particularly preferable. For this reason, the particle size is the wavelength λ of light to be scattered by the optical size (usually : 400 to 700 nm), preferably at least 1 / 20λ, more preferably at least 1 / 10λ, and the difference in refractive index from the matrix material is preferably large.

  In addition, if the particle diameter of the light scattering particles is too large, problems tend to occur in the flatness of the diffusion film, which is not preferable. If a problem occurs in the flatness of the diffusion film, the electric field in the EL light emitting layer becomes non-uniform, and problems such as a decrease in the luminance of the element and a decrease in the life of the element tend to occur. On the other hand, particles that are too small are not preferred because they have little scattering effect. For the above reasons, it is desired that the physical particle diameter has a 60% weight ratio diameter in the range of 20 to 400 nm, preferably 40 to 200 nm, and most preferably 60 to 120 nm.

  In the present invention, the measurement of the 60% weight particle diameter of the light scattering particles is performed as follows.

[1] A cross section of the diffusion layer was observed by FIB-SEM.
FIB (focused ion beam) is an abbreviation for focused ion beam processing observation device, and the device used was "FB-2000A" manufactured by Hitachi, Ltd. The cross section processing conditions are as follows.
(1) A Pt (platinum) sputtered film was formed before FIB processing.
(2) A W (tungsten) film was locally formed on the relevant portion by FIB before the cross section was formed.
(3) A hole for observation (about 20 μ × 30 μ square) was made in the FIB, and the surface used for observation was finished by lowering the ion beam current. The ion species was Ga +, and the ion beam acceleration voltage was 30 kV.

  The SEM observation was performed with "S4100" manufactured by Hitachi, Ltd. The observation conditions were an acceleration voltage of 5.0 kV, and an image was taken of the observation surface of the hole made by FIB with an inclination of about 80 degrees from the vertical direction of the sample film (corresponding to observing the film cross section almost from the front). The magnification was × 10000.

The cross-sectional observation image was observed in the following manner.
Twenty images having a width of 20 μm were randomly collected from the sample film in the plane direction of the sample film, and the particle diameter of the observed particles in the image was observed. When the particle cross-sectional shape was irregular, the particle diameter of the particle was determined by using the particle diameter assuming that the particle had a circular cross-section having substantially the same area.

For each of the particles observed here, the cube of the particle diameter is proportional to the weight of the particles and the weight is converted, and the range of 60% by weight or more of all the particles in the particle diameter conversion defined above is derived. Was.
When the particles were aggregated into a lump, the particles were treated as one particle (basically, the measurement according to the present method was employed).

  When the above method was not applicable because the sample film was brittle or the particle shape was difficult to understand by SEM or TEM, the particle diameter was measured using the following means.

[2] At the stage of preparing the coating solution before forming the sample film, the particle suspension was passed through a particle size distribution meter to measure the particle size distribution.
As the particle size distribution meter, MICROTEC particle size distribution analyzer model “9230 UPA” manufactured by Nikkiso Co., Ltd. was used. The solvent for suspending the particles is not particularly limited as long as it can be suspended. However, when the titania particles are dispersed in a silicate solution to form a film by a sol-gel method, an alcohol-based solvent is preferable.
From the measured particle size distribution, data on particle size, frequency and cumulative ratio can be obtained. From this data, it was assumed that the particle diameter was almost the diameter of a spherical particle, and the range of the 60% weight particle diameter was derived in the same manner as above.

  The average particle diameter of the light-scattering particles is measured by the method described above (FIB-SEM, particle size distribution measurement of the particle dispersion before application when not applied), and the value which becomes 50% by volume is used. Was.

  The content of the light scattering particles in the particle-containing transparent electrode layer 3 'is preferably about 0.1 to 40% by volume, particularly about 1 to 10% by volume. If the light scattering particle content is too small, a sufficient scattering effect cannot be obtained. If the amount is too large, the concealing effect increases, and the ratio of light that can be extracted decreases.

  The particle-containing transparent electrode layer 3 ′ is formed into a pattern required as an electrode of an electroluminescence element by using a coating liquid containing such light scattering particles and by a printing method such as a photolithography method or an inkjet method. The line width after patterning is typically about 1 to 10 μm, but is not limited thereto.

D: Electroluminescence Layer 2 The electroluminescence layer 2 is formed of a material that exhibits a light-emitting phenomenon when an electric field is applied, and the material includes activated zinc oxide ZnS: X (where X Is an activating element such as Mn, Tb, Cu, Sm, etc.), CaS: Eu, SrS: Ce, SrGa ₂ S ₄ : Ce, CaGa ₂ S ₄ : Ce, CaS: Pb, BaAl ₂ S ₄ : Conventionally used inorganic EL materials such as Eu, 8-hydroxyquinoline aluminum complex, aromatic amines, low molecular weight dye-based organic EL materials such as anthracene single crystal, poly (p-phenylenevinylene), poly [ 2-methoxy-5- (2-ethylhexyloxy) -1,4-phenylenevinylene], poly (3-alkylthiophene), polyvinylca Conventionally used organic EL materials such as conjugated polymer organic EL materials such as rubazole can be used. The thickness of the electroluminescent layer is usually from 10 to 1000 nm, preferably from 30 to 500 nm, more preferably from 50 to 200 nm. The electroluminescent layer can be formed by a vacuum film forming process such as vapor deposition or sputtering, or a coating process using chloroform or the like as a solvent.

E: Cathode The cathode 1 is provided so as to oppose the above-mentioned transparent electrode layer 3 and sandwich the electroluminescence layer 2. The cathode 1 is formed of aluminum, tin, magnesium, indium, calcium, gold, silver, copper, nickel, chromium, palladium, platinum, magnesium-silver alloy, magnesium-indium alloy, aluminum-lithium alloy or the like. In particular, it is preferably formed of aluminum. The thickness of the cathode is generally 10 to 1000 nm, preferably 30 to 500 nm, and more preferably 50 to 300 nm. The cathode can be formed by a vacuum film forming process such as evaporation or sputtering.

F: Other layers A hole injection layer or a hole transport layer can be further laminated between the electroluminescent layer 2 and the transparent electrode layer 3, and between the electroluminescent layer 2 and the cathode 1. Further, an electron injection layer and an electron transport layer can be further laminated. Known layers other than these may be applied.

  Next, an embodiment of the present invention will be described with reference to FIG.

  In this embodiment, a transparent electrode layer 3 containing no particles is provided. The particle-containing transparent electrode layer 3 ″ is provided between the transparent electrode layer 3 and the low refractive index layer 4. The matrix components of the transparent electrode layer 3 and the particle-containing transparent electrode layer 3 ″ have the same refractive index. Other configurations of the electroluminescence element in FIG. 2 are the same as those in FIG. 1, and the same reference numerals indicate the same parts.

  As the matrix component of the transparent electrode layer 3 ″ in FIG. 2, the same matrix component as that of the transparent electrode layer 3 can be used. The matrix component of the transparent electrode layer 3 ″ is preferably the same composition as that of the transparent electrode layer 3, but may be different.

  The refractive index difference between the matrix component of the particle-containing transparent electrode layer 3 ″ and the transparent electrode layer 3 is less than 0.3, preferably 0.2 or less, particularly preferably 0.1 or less.

  The particle-containing transparent electrode layer 3 ″ can be formed in the same manner as the particle-containing transparent electrode layer 3 ′ of FIG. The transparent electrode layer 3 containing no particles can be formed in the same manner as the transparent electrode layer 3 'containing particles shown in FIG. Further, it can also be formed by a film forming process such as vapor deposition or sputtering.

  The thickness of the transparent electrode layer 3 containing no particles is preferably 100 to 5000 nm, particularly preferably 200 to 1000 nm. The thickness of the particle-containing transparent electrode layer 3 ″ is preferably 100 to 5000 nm, particularly preferably 200 to 1000 nm.

  In this electroluminescent device, the particle-containing transparent electrode layer 3 ″ provided between the transparent electrode layer 3 and the low refractive index layer 4 is changed from the transparent electrode layer 3 to the low refractive index layer 4 as follows. It increases the amount of light that enters and improves the light extraction efficiency. That is, since the refractive index of the matrix of the particle-containing transparent electrode layer 3 ″ is equivalent to the refractive index of the transparent electrode layer 3, total reflection occurs at the interface between the transparent electrode layer 3 and the particle-containing transparent electrode layer 3 ″. Does not occur.

  Light that travels from the transparent electrode layer 3 into the particle-containing transparent electrode layer 3 ″ and enters the interface between the particle-containing transparent electrode layer 3 ″ and the low refractive index layer 4 in the particle-containing transparent electrode layer 3 ″ Among them, the light whose incident angle is smaller than the critical angle proceeds from the particle-containing transparent electrode layer 3 ″ into the low refractive index layer 4 as it is. Light having an incident angle larger than the critical angle is totally reflected at the interface with the low refractive index layer 4 and returns to the particle-containing transparent electrode layer 3 ″. Part of the light that has returned to the particle-containing transparent electrode layer 3 ″ side is scattered by the particles in the particle-containing transparent electrode layer 3 ″. Part of the scattered light is again incident on the interface with the low refractive index layer 4. Of these, light having an incident angle smaller than the critical angle enters the low refractive index layer 4 from the particle-containing transparent electrode layer 3 ″ without being totally reflected. Among the scattered light incident on the interface, those having an incident angle larger than the critical angle return to the particle-containing transparent electrode layer 3 ″ side again, and a part thereof is again scattered by the particles. By repeating this sequentially, the remaining light gradually enters the low refractive index layer 4 side.

  Among the light totally reflected at the interface between the low refractive index layer 4 and the particle-containing transparent electrode layer 3 ″, the light that reaches the interface between the particle-containing transparent electrode layer 3 ″ and the transparent electrode layer 4 is generated at this interface. Since there is no difference in the refractive index, the light enters the transparent electrode layer 3 as it is, and returns to the interface between the transparent electrode layer 3 and the electroluminescent layer 2. When the angle of incidence on the interface is larger than the critical angle, the light is totally reflected at the interface and returns to the interface between the low refractive index layer 4 and the particle-containing transparent electrode layer 3 ″. The behavior of the light thereafter is the same as described above, and gradually enters the low refractive index layer.

  On the other hand, light that has entered the interface between the transparent electrode layer 3 and the electroluminescent layer 2 from the transparent electrode layer 3 side at an incident angle smaller than the critical angle directly enters the electroluminescent layer 2, and Is reflected at the interface, and again passes through the electroluminescent layer 2 and the transparent electrode layer 3 and returns to the interface between the transparent electrode layer 3 and the particle-containing transparent electrode layer 3 ″. The subsequent behavior of this light is the same as above.

  Thus, also with this electroluminescent element, the total reflection on the transparent electrode layer 3 side is reduced more than the low refractive index layer 4, and the light extraction efficiency is improved.

  Although the particle-containing transparent electrode layer 3 ″ is provided in FIG. 2, a particle-containing layer in which a material having the same refractive index as the transparent electrode layer 3 containing no particles is formed as a matrix may be formed instead. Good. As such a material, an aromatic resin such as polyethersulfone or the like as a matrix material, or a material obtained by dispersing fine particles of a high refractive index material such as titania or zirconia in the material and making them transparent, and light scattering particles such as titania and Examples thereof include zirconia, silica, air (air), and the like, which are scattered in such a size that light is scattered.

  In the embodiments shown in FIGS. 1 and 2, the substrate 5 is provided on the outermost layer as viewed from the electroluminescent layer 2; however, the substrate is provided outside the cathode, and the outermost layer is provided as a layer as viewed from the electroluminescent layer. May be provided with a protective cover. The former embodiment may be referred to as a bottom emission type, and the latter embodiment may be referred to as a top emission type.

  FIG. 3 shows an embodiment having such a configuration in the embodiment of FIG. 1, in which a cathode 1 is formed on a substrate 5, and an electroluminescent layer 2, a particle-containing transparent electrode layer 3 'and a cathode 1 are sequentially formed thereon. A low refractive index layer 4 is formed, and a protective cover 6 is formed on the low refractive index layer 4. As the material of the protective cover 6, any material can be used as long as it is transparent and can be flattened. In addition to the various glass and resin materials used for the substrate 5, a transparent coating material having no self-supporting property, for example, UV-curable or thermosetting acrylic resin, sol-gel reactive material (silicate material) and the like are exemplified. The thickness of the protective cover 6 is preferably about 100 to 1000 μm, particularly preferably about 100 to 200 μm.

  FIG. 3 shows the substrate 5 arranged on the cathode 1 side in the embodiment of FIG. 1, but the substrate 5 may be arranged on the cathode 1 side in FIG.

  Hereinafter, Reference Examples 1 to 5 and Comparative Examples 1 to 3 corresponding to Examples will be described. In the following Reference Examples 1 to 5 and Comparative Examples 1 to 3, the cathode and the electroluminescence layer were not formed, and a fluorescent dye layer was formed on the transparent electrode layer. And the fluorescence was taken out from the substrate side.

<Reference Example 1 (corresponding to the embodiment of FIG. 1)>
The surface of a 0.7 mm thick, 75 mm square glass substrate made of non-alkali glass AN100 manufactured by Asahi Glass Co., Ltd. is immersed in 0.1 N nitric acid for about 1 hour, degreased, washed with pure water, and heated at 60 ° C. Dried in oven.

  On the other hand, a small amount of an acid catalyst (aluminum acetylacetonate) was added to 30 wt% of MS51 (oligomer of tetramethoxysilane), 50 wt% of BtOH, 8 wt% of demineralized water, and 12 wt% of MeOH manufactured by Mitsubishi Chemical Corporation, followed by stirring at 60 ° C. for 3 hours, Aged for one week.

  This was coated on the above-mentioned glass substrate 1 with a dip coater, dried for 15 minutes, immersed in methanol for 5 minutes, pulled up, dried for 5 minutes, and heated in a 150 ° C. oven for 15 minutes to obtain a low refractive index layer 4. . At the time of dip coating, a protective film was stuck on the back surface and peeled off after coating, so that a coating film was formed only on one side.

  The thickness of the film of the low refractive index layer 4 was 600 nm, and the refractive index of the film was measured with an ellipsometer manufactured by Sopra to be 1.27 at a wavelength of 550 mm. Further, it was 1.31 at a wavelength of 633 nm as measured with a prism coupler model 2010 manufactured by Metricon Co., USA.

  In the following, the refractive index measurement was carried out using an ellipsometer manufactured by Sopra based on D542 in principle. However, if it is difficult to measure the refractive index of a matrix portion of a meso (nano) porous material or a particle dispersion material using an ellipsometer, a prism manufactured by Metricon, USA Refractive index measurements were performed at 25 ° C. using a coupler model 2010 with a laser having a wavelength of 633 nm.

  Regarding the film thickness, the film thickness of the vapor-deposited film or the sputtered film was confirmed by time management from a calibration curve or by a quartz oscillation type film thickness meter. The thickness of the coating film was measured by an optical interference type thickness meter or by measuring a step with a scratch on the film. For a thick substrate such as a glass substrate, the thickness was measured with a micro-calipers or the like.

  The particle-containing transparent electrode layer 3 'was formed on the low refractive index layer 4 as follows.

  That is, the same amount of a polythiophene-based conductive polymer, poly (3-alkylthiophene), is added to ITO fine particles having an average particle size of 50 nm, and the average particle size is about 120 nm, 60 wt. % Titania particles having a weight ratio of 70 to 140 nm were dispersed, and these were dissolved and dispersed in chloroform to prepare an ITO / titania particle-containing coating solution (hereinafter, this coating solution is referred to as “coating solution I”). This coating solution I was applied onto the low refractive index layer 4 by a spin coater and then dried. The thickness of the formed particle-containing transparent electrode layer 3 ′ was 1000 nm, and the refractive index of the matrix portion was 1.8. The content of the titania particles was 5% by volume.

  AlQ3 (fluorescent dye) was deposited to a thickness of 1000 on the particle-containing transparent electrode layer 3 '.

  The back surface of this laminated body is irradiated with excitation light having a wavelength of 400 nm or less, and the intensity of light taken out at 420 to 750 nm is measured with a detector installed in the direction of the emission angle of 45 degrees on the front surface, and the emission energy integrated at all wavelengths is obtained. Was. For the measurement, a fluorescence spectrophotometer F-4500 manufactured by Hitachi, Ltd. was used.

  The amount of light taken out was determined relative to the case of Comparative Example 1 below as 100%, and found to be 170%.

<Comparative Example 1 (corresponding to the conventional example in FIG. 5)>
In the same manner as in Reference Example 1 except that the titania fine particles were not added to the coating solution for forming the transparent electrode layer, a fluorescent light emitting device having a layer configuration corresponding to FIG. 5 was manufactured. In this case, the extracted light amount was set to 100%.

<Comparative Example 2 (corresponding to the conventional example in FIG. 4)>
A fluorescent light emitting device was manufactured in the same manner as in Comparative Example 1 except that the low refractive index layer 4 was omitted and the layer configuration shown in FIG. 4A was used. It was 91% of the case of Comparative Example 1.

<Reference Example 2 (corresponding to the embodiment of FIG. 2)>
In Reference Example 1, the coating liquid I was formed except that a 500 nm-thick particle-containing transparent electrode layer 3 ″ was formed on the low refractive index layer 4 using the coating liquid I, and no titania fine particles were added thereon. A transparent electrode layer 3 having a thickness of 500 nm was formed using the coating solution prepared in the same manner as in Example 1, and AlQ3 was further evaporated to a thickness of 1000 mm.

  The amount of light taken out of the fluorescent light-emitting device thus manufactured was measured in the same manner. As a result, it was 170% that of Comparative Example 1.

<Reference Example 3>
A fluorescent light emitting device was manufactured in the same manner as in Reference Example 1 except that the low refractive index layer 4 was not provided, and the amount of light taken out was measured in the same manner. The amount of light taken out was 150% of that in Comparative Example 1. .

<Reference Example 4>
A glass substrate was prepared in the same manner as in Reference Example 1.
1 tetraisopropyl oxytitanium _{(Ti (O-i-C} 3 H 7) 4) and absolute ethanol _{(C 2} H 5 OH) in a molar ratio: stirred at room temperature for 4 and mixed. In anhydrous ethanol, silica particles having an average particle diameter of 200 nm and a 60% weight ratio diameter of 150 to 220 nm are preliminarily dispersed such that the weight percentage of the resulting particle-containing layer is 10 wt% (19 volume%). Was. The weight percentage in the particle-containing layer was determined by the same method as that for determining the particle size distribution in the film. The volume conversion by weight was performed by examining the particle and matrix densities. The density when the matrix was a porous body was calculated from the refractive index obtained by obtaining the X-ray reflectivity or the refractive index.

  A mixture of ethanol, water, and hydrochloric acid at a molar ratio of 4: 1: 0.08 was added to the mixture at 0 ° C by a burette, and hydrolysis was allowed to proceed to obtain a titania sol.

  The coating liquid thus adjusted was dip-coated on the treated surface of the glass substrate to form a coating film. At the time of dip coating, a protective film was stuck on the back surface and peeled off after application so that the coating film was formed only on one side. Then, it heated at 300 degreeC for 10 minutes, and obtained the scattering film. The thickness of this scattering film was 500 nm. The measured refractive index of the matrix portion was 2.1.

  On top of this, ITO was sputtered at room temperature to form a 500 ° transparent conductive film. The measured refractive index of the transparent conductive film was 1.9. Further, in the same manner as in Reference Example 1, AlQ3 was vapor-deposited to form a light-emitting layer, thereby manufacturing a fluorescent light-emitting device.

  With respect to this fluorescent light-emitting element, the extraction light amount was measured in the same manner, and the extraction light amount was relatively determined assuming that the case of Comparative Example 3 below was 100%, and was 170%.

<Comparative Example 3>
In Reference Example 3, a fluorescent light-emitting device was prepared and evaluated in exactly the same manner except that silica particles were not added to anhydrous ethanol, and the amount of light taken out was set to 100%.

<Reference Example 5>
In Reference Example 3, prior to the formation of the light emitting layer, a fluorescent light emitting device was manufactured in the same manner as in Reference Example 4, except that a transparent conductive film of ITO was formed. It was 140% when it was relatively determined assuming that the case of Comparative Example 1 was 100%.

FIG. 2 is a cross-sectional view of the electroluminescent element according to the embodiment. FIG. 2 is a cross-sectional view of the electroluminescent element according to the embodiment. FIG. 2 is a cross-sectional view of the electroluminescent element according to the embodiment. It is sectional drawing of the electroluminescent element which concerns on a prior art example. It is sectional drawing of the electroluminescent element which concerns on a prior art example.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Cathode 2 Electroluminescent layer 3 Transparent electrode layer 3 ', 3''Transparent electrode layer containing particles 4 Low refractive index layer 5 Glass substrate 6 Protective cover

Claims (4)

A cathode, an electroluminescence layer, a transparent electrode layer, and an electroluminescence element in which a light transmitting body is arranged in this order,
An electroluminescent device, wherein the transparent electrode layer contains particles that scatter light from the electroluminescent layer. A cathode, an electroluminescence layer, a transparent electrode layer, and an electroluminescence element in which a light transmitting body is arranged in this order,
A particle-containing layer comprising a matrix and particles that scatter light from the electroluminescence layer dispersed in the matrix is provided between the transparent electrode layer and the light-transmitting member,
An electroluminescent device, wherein the matrix has a refractive index equivalent to that of the transparent electrode layer.   3. The electroluminescent device according to claim 1, wherein the light transmitting body is a transparent substrate.   3. The electroluminescent element according to claim 1, wherein the cathode is formed on a transparent substrate, and the light transmitting body is a protective cover.

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