JP4650025B2 - Electroluminescence element - Google Patents

Description

  The present invention relates to an electroluminescence (EL) element, and in particular, an electroluminescence display element having high light extraction efficiency from an electroluminescence layer, little pixel bleeding, high resolution and excellent visibility, or high transparency. The present invention relates to an electroluminescence surface illumination element having a transparent feeling and a clear feeling.

  In the bottom emission type, the electroluminescence element used for the EL display has at least a transparent substrate 5, a transparent electrode layer 3, an electroluminescence layer 2, and a reflective electrode layer 1, as shown in FIG. Depending on the purpose and configuration, the transparent electrode layer and the reflective electrode layer may be either a cathode or an anode, but in a normal bottom emission type, the transparent electrode layer corresponds to an anode and the reflective electrode layer corresponds to a cathode. To do. As shown in FIG. 5C, the top emission type includes a substrate 5, a transparent electrode layer 3, an electroluminescent layer 2, a reflective electrode layer 1, and a translucent layer 5A as necessary.

  In this electroluminescence element, holes injected from the transparent electrode layer 3 as an anode are recombined with electrons injected from the reflective electrode layer 1 in the electroluminescence layer 2, and the emission center is excited by the recombination energy. Have a light emission principle of emitting light.

  Conventionally, in such an electroluminescent device, it is assumed that the light extraction efficiency is improved, and a matrix made of a low refractive index material is interposed between the transparent substrate 5 and the transparent electrode layer 3 as shown in FIG. There has been proposed an electroluminescence element provided with a leaching light diffusion layer 6 containing particles that scatter light (Patent Document 1).

  Thus, when the leaching light diffusion layer 6 containing particles that scatter light in a matrix made of a low refractive index material is provided between the transparent electrode layer 3 and the transparent substrate 5, the electroluminescence layer 2, The total reflection amount of the light incident on the interface between the transparent electrode layer 3 and the leaching light diffusion layer 6 is reduced.

  The reason is considered as follows. That is, light is incident at an incident angle larger than the critical angle on the interface with the light diffusion layer 6 containing particles that scatter light from the electroluminescence layer 2 through the transparent electrode layer 3 into a matrix made of a low refractive index material. When incident, this light is totally reflected at the interface. However, as shown in FIG. 6B, during this total reflection, a phenomenon occurs in which part of the light oozes out from the interface to the low refractive index layer side (layer side made of a low refractive index material). (This penetrating light may be called evanescent wave or near-field light). That is, the electric field and magnetic field of incident light exist even on the low refractive index layer side from the interface.

  Using this leaching phenomenon, the low refractory layer leached out by allowing particles of different refractive index from the matrix made of low refractive index material to exist within the light bleed distance (depth). Part of the light is scattered by the particles and is no longer returned to the total reflected light in the transparent electrode layer, but after being scattered directly or after being reflected by, for example, an aluminum reflective film of the reflective electrode layer, into the low refractive index layer To spread. In this way, by including particles that scatter light (hereinafter sometimes referred to as “light scattering particles”) in the low refractive index layer that is in contact with the transparent electrode layer, the reflectance of total reflection is reduced. A lot of light enters from the transparent electrode layer to the low refractive index layer side. As a result, the light extraction efficiency of the electroluminescence element is improved.

  In Patent Document 1, as shown in FIG. 7, the reflective electrode layer 1, the electroluminescence layer 2, the transparent electrode layer 3, the leaching light diffusion layer 6a, the low refractive index layer 4 and the transparent substrate 5 are laminated in this order. In addition, a mode is also proposed in which the refractive index of the matrix of the leaching light diffusing layer 6 a is equal to the refractive index of the low refractive index layer 4 and lower than the refractive index of the transparent electrode layer 3. Yes.

  Even in this embodiment, at the interface of the leaching light diffusion layer 6a provided between the transparent electrode layer 3 and the low refractive index layer 4, the leaching containing particles is performed in the same manner as in FIG. Due to the light diffusing action of the light diffusing layer 6a, the total reflection of the light leached from the transparent electrode layer 3 to the low refractive layer 4 side is reduced. That is, when total reflection occurs at the interface between the transparent electrode layer 3 and the leaching light diffusing layer 6a, the light leached into the particle-containing leaching light diffusion layer 6a during total reflection is the particle-containing leaching light diffusion. Scattered by the particles in the layer 6a and extracted to the particle-containing leaching light diffusion layer 6a side. Thereby, after being reflected directly from the transparent electrode layer, or after being reflected by, for example, an aluminum reflective film of the reflective electrode, the transparent electrode layer 3 oozes out without being totally reflected at the interface on the leaching light diffusing layer 6a side. The amount of light entering 6a increases.

  Since the matrix of the particle-containing exuded light diffusing layer 6 a and the low refractive index layer 4 have the same refractive index, total reflection occurs at the interface between the particle-containing exuded light diffusing layer 6 a and the low refractive index layer 4. Hard to occur. As a result, most of the light entering the particle-containing exuded light diffusing layer 6a from the transparent electrode layer 3 and reaching the interface between the particle-containing exuding light diffusing layer 6a and the low refractive index layer 4 remains as it is. Enter the rate layer 4. In this way, the light extraction efficiency from the electroluminescence element is improved.

In addition to Patent Document 1, the following is proposed as an electroluminescent element provided with a layer for diffusing guided light using such a permeation light diffusion layer or a transparent electrode layer as a waveguide. .
(1) The surface on the transparent substrate side of the transparent electrode layer is a light scattering uneven surface (Patent Document 2).
(2) A high refractive index layer having a refractive index equivalent to that of the transparent electrode layer is provided on the surface of the transparent electrode layer on the transparent substrate side, and the surface on the transparent substrate side of the high refractive index layer is a light scattering uneven surface. Thing (patent document 2).
(3) A transparent electrode layer containing particles that scatter light from the electroluminescence layer (Patent Document 3).
(4) A particle-containing layer in which particles that scatter light from the electroluminescent layer are dispersed in the matrix between the transparent electrode layer and the transparent substrate (the refractive index of this matrix is the refractive index of the transparent electrode layer) (Patent Document 3).
(5) A low refractive index layer containing particles that scatter light from the electroluminescent layer is provided between the transparent electrode layer and the transparent substrate, and a low refractive index is provided between the low refractive index layer and the transparent electrode layer. What provided the barrier layer which prevents the substance in a layer from diffusing to the transparent electrode layer side (patent document 4).
(6) A low refractive index layer is provided between the transparent electrode layer and the transparent substrate, and particles that scatter light from the electroluminescence layer are dispersed in the matrix between the transparent electrode layer and the low refractive index layer. (The refractive index of this matrix is the same as the refractive index of the low refractive index layer.) Between the particle-containing layer and the transparent electrode layer, the substance in the particle-containing layer is on the transparent electrode layer side. Provided with a barrier layer for preventing diffusion into the surface (Patent Document 4).
JP 2004-296437 A JP 2004-296438 A JP 2004-303724 A JP 2004-319331 A

  However, it diffuses visible light such as the electroluminescent element of the prior application with a leaching light diffusing layer, or the diffusing layer that disperses dark spots and luminance unevenness, or microlenses, gratings, photonic crystals, etc. In an electroluminescent element provided with an optical interface having a concavo-convex shape of a size that scatters and refracts, a problem of pixel bleeding occurs for the following reason (hereinafter, the above exemplified layers are collectively referred to as a diffusion layer).

  Hereinafter, a pixel bleeding generation mechanism of a conventional electroluminescence element provided with such a diffusion layer will be described with reference to FIG.

  8A to 8C show bottom emission type organic EL elements. In the organic EL element, the light emitted from the EL light emitting layer is reflected directly or after being reflected by the reflective cathode, and then travels toward the viewing side. At this time, in the organic EL element provided with the diffusion layer, the following light scattering occurs. Get up.

(1) Mechanism 1
As shown in FIG. 8A, the light totally reflected at the interface between the transparent substrate and air (A in FIG. 8A) once returns to the diffusion layer, where some light rays are diffused, It is emitted at an angle as it enters the eye. That is, two or more positions (for example, * 1 and * 2 in FIG. 8A), even though one EL position (one pixel: the position indicated by * 1 in FIG. 8A) emits light. Visible in the same way as when emitting light.
This is one of the causes of pixel bleeding.

(2) Mechanism 2
As shown in FIG. 8A, the partially reflected light (B in FIG. 8A) in the light emitted from the transparent substrate to the air once returns to the diffusion layer, where some of the light is diffused. The light beam is emitted at an angle as it enters the eye. That is, two or more positions (for example, * 1 and * 3 in FIG. 8A) are emitted even though one EL position (one pixel: the position indicated by * 1 in FIG. 8A) emits light. ).
This is one of the causes of pixel bleeding. However, as compared with the mechanism 1, since the ratio of reflection at the interface between the transparent substrate and air is usually small, the ratio contributing to pixel bleeding is small.

(3) Mechanism 3
As shown in FIG. 8B, when the diffusion layer is sufficiently separated from the reflective cathode with respect to the pixel size, a part of the light diffused by the diffusion layer is directly reflected or further reflected by the reflective cathode. It is emitted and enters the eye (B, C in FIG. 8B). That is, * 1 is the same as emitting light (eg, * 2, * 3 in addition to * 1 in Fig. 8 (b)) even though one position (pixel) emitted light. It looks like it looks blurred. This also causes pixel bleeding.

(4) Mechanism 4
As shown in FIG. 8C, when the thickness of the diffusion layer is sufficiently thick with respect to the pixel size, a part of the light diffused in the diffusion layer is propagated directly or in the plane direction in the diffusion layer. Or, after being reflected by the reflecting cathode, it is emitted and enters the eye (B, C, D in FIG. 8C). That is, although one position (pixel) at * 1 in FIG. 8C emits light, a plurality of positions emit light (for example, * 2, * 3 in addition to * 1 in FIG. 8C). * 4) It looks the same as when it emits light, so it is visible. This also causes pixel bleeding.

  Accordingly, an object of the present invention is to provide an electroluminescence element that eliminates pixel bleeding in an electroluminescence element provided with a light diffusion layer, has high resolution and excellent visibility, or has a high transparency and a clear feeling. To do.

This onset Ming gist, the electroluminescent layer, a transparent electrode layer, and the electroluminescent device transparent substrate, which are disposed in this order, electroluminescent device having an optical diffusion layer between the transparent electrode layer and the transparent substrate a is, satisfies the following conditions (2), and, as the outermost layer, characterized by having a pixel bleeding prevention layer comprises at least one selected from the antireflection film, and a polarization-fill beam by Li Cheng group It exists in an electroluminescence element.
( 2) A reflective electrode layer is provided on the surface of the electroluminescent layer opposite to the transparent electrode layer, and the distance between the surface of the light diffusion layer farthest from the reflective electrode layer and the reflective electrode layer is equal to or smaller than the pixel size. There is .

  In the present invention, the “outermost layer” of the electroluminescent element refers to the outermost layer of the layers formed with high adhesion to the transparent substrate, and is usually used for protecting the element. Simple protective covers that are not involved in light polarization and phase modulation, visible wavelength absorption, surface reflection control, etc., such as hard coat films and protective films are eliminated.

  Therefore, in the electroluminescent element of the present invention, a protective cover can be further provided on the outermost pixel blur preventing layer.

  Further, in the present invention, the “reflecting electrode layer” is not limited to a single layer that functions as light reflection and an electrode, and may be a layer in which a reflection layer and a conductive layer as an electrode are laminated. good.

According to a second aspect of the present invention, there is provided the electroluminescence device according to the first aspect, wherein the pixel blur preventing layer includes a polarizing film and a retardation film .

  The electroluminescent device according to claim 3 is the electroluminescent device according to claim 2, wherein the polarizing film is provided with a retardation film on the viewing side (surface on the exit side), that is, the outermost surface (excluding the protective cover as described above). A retardation film is disposed on the substrate.

According to a fourth aspect of the present invention, in the electroluminescent device according to any one of the first to third aspects, the following condition (2) is satisfied .
( 2) A reflective electrode layer is provided on the surface of the electroluminescent layer opposite to the transparent electrode layer, and the distance between the surface of the light diffusion layer farthest from the reflective electrode layer and the reflective electrode layer is 1 pixel size. / 2 or less .

The electroluminescent device according to claim 5 is characterized in that in claim 4, the following condition (2) is satisfied .
( 2) A reflective electrode layer is provided on the surface of the electroluminescent layer opposite to the transparent electrode layer, and the distance between the surface of the light diffusion layer farthest from the reflective electrode layer and the reflective electrode layer is 1 pixel size. / 10 or less .

  The electroluminescent element according to claim 6 is characterized in that, in any one of claims 1 to 5, the light diffusion layer is a layer having a function of diffusing light guided using a transparent electrode as a waveguide. To do.

  The electroluminescent device according to claim 7 is the electroluminescent device according to claim 6, wherein the light diffusion layer is a layer having a function of diffusing the light leached out from the transparent electrode among the light guided using the transparent electrode as a waveguide. It is characterized by being.

  The electroluminescent device according to claim 8 is the electroluminescent device according to any one of claims 1 to 7, wherein the light diffusion layer is a layer containing particles that diffuse light in a matrix made of a low refractive index material. Features.

  The electroluminescent device according to claim 9 is the electroluminescent device according to claim 8, wherein a low refractive index layer is provided between the light diffusion layer and the transparent substrate, and the refractive index of the matrix of the light diffusion layer is the low refractive index. The refractive index is equivalent to the refractive index of the refractive index layer and lower than the refractive index of the transparent electrode layer.

In the following,
When the electroluminescence element has a plurality of light diffusion layers, a distance between the most distant surfaces of the plurality of light diffusion layers,
The distance between the reflective electrode layer and the surface of the light diffusion layer farthest from the reflective electrode layer when the electroluminescent element has the reflective electrode layer on the surface opposite to the transparent electrode layer of the electroluminescent layer;
Or
The thickness of the light diffusion layer in the case where the electroluminescence element does not have the reflective electrode layer and one light diffusion layer is provided may be referred to as “light diffusion distance”.

  ADVANTAGE OF THE INVENTION According to this invention, the pixel bleeding in the electroluminescent element which provided the light-diffusion layer can be eliminated by providing the pixel bleeding prevention layer of a specific structure, and the electroluminescent element excellent in visibility can be provided. For this reason, using this electroluminescence element, it is possible to realize a display having no visibility between pixels and having excellent visibility. In addition, even in electroluminescence lighting applications, it is possible to provide an electroluminescence element that has no blur at the light emission portion and has a transparent feeling and a clear feeling.

  Hereinafter, embodiments of the electroluminescence element of the present invention will be described in detail.

[Light diffusion layer]
The electroluminescence element of the present invention is provided with a pixel bleeding prevention layer as the outermost layer of the electroluminescence element provided with the light diffusion layer, and the above-mentioned light diffusion distance by the light diffusion layer is the above (1) to ( As long as the condition of 3) is satisfied, there is no particular limitation on the configuration of the light diffusion layer provided in the electroluminescence element, and as described in Patent Documents 1 to 4 above, Light extraction layer using diffusion, light diffusion layer using diffusion of light by rough surface, other light diffusion layer using dispersion by bubbles and diffusion by bubbles, prism surface, hemispherical surface, etc. All of the layers having the function of diffusing and scattering light provided for the purpose of improving the rate, concealing dark spots, uniforming the appearance of light emission, and controlling the viewing angle are included.

[Light diffusion distance]
The electroluminescent element of the present invention is an electroluminescent element having the light diffusion layer as described above, and is applied to an electroluminescent element that satisfies any of the following conditions (1) to (3).
(1) It has a plurality of light diffusion layers, and the distance between the most distant surfaces of the plurality of light diffusion layers is the pixel size or less, preferably 1/2 or less, more preferably 1/10 or less. For example, a plurality of light diffusion layers 6A as shown in FIG. 4 (a), the out of 6B, a distance L ₁ between the light-emitting light emitting side of the surface emitting the light incident side surface of the light diffusion layer 6B of the light diffusion layer 6A Equivalent to.
(2) having a reflective electrode layer on the surface of the electroluminescent layer opposite to the transparent electrode layer, and the distance between the surface of the light diffusion layer farthest from the reflective electrode layer and the reflective electrode layer is less than or equal to the pixel size; Preferably it is 1/2 or less, more preferably 1/10 or less. In this case, the light diffusion distance corresponds to the distance L ₂ between the light-emitting light emitting side of the surface light-emitting the light incident side of the reflective electrode layer 1 of the light diffusion layer 6A, as in Figure 4 (b).
(3) There is no reflective electrode layer, and one light diffusion layer is provided, and the thickness of the light diffusion layer is not more than the pixel size, preferably not more than 1/2, more preferably not more than 1/10. In this case, the light diffusion distance corresponds to the thickness L ₃ of the light diffusing layer 6 as shown in FIG. 4 (c).

  In an electroluminescence element having a light diffusion distance larger than the image size, it is not possible to obtain a pixel blur preventing effect by the pixel blur preventing layer according to the present invention, as is apparent from the result of a comparative example described later.

  When used for electroluminescence illumination, the light diffusion distance is preferably 1 mm or less, particularly 0.5 mm or less in terms of sharpness and bleeding at the light emission portion or transparency of illumination light. Although the light diffusion distance is preferably as thin as possible, it is usually about 10 μm from the viewpoint of clearness and bleeding at the time of light emission and transparency of illumination light.

[Pixel bleeding prevention layer]
The electroluminescent device of the present invention has a pixel bleeding including one or more selected from the group consisting of an antireflection film, a polarizing film, a retardation film and a dye filter on the outermost layer of the electroluminescent device having the above-described configuration. It has a prevention layer, preferably a pixel bleeding prevention layer having the following constitution.
(I) A circularly polarizing film comprising a polarizing film and a retardation film. In particular, the retardation film is provided so as to be the outermost surface with respect to the emission light emission side.
(Ii) An antireflection film is provided so as to be the outermost surface with respect to the emission light emitting side.
(Iii) A polarizing film or an absorption filter is provided alone so as to be the outermost surface with respect to the emission light emission side.

Hereinafter, the pixel blur preventing mechanism will be described for each pixel blur preventing layer with reference to the drawings.
Note that when the light extraction surface (viewing surface) is on both sides as in a see-through display, the pixel bleeding prevention layer is effective only by providing it on one surface, but it is more preferable to provide it on both surfaces.

  (I) A circularly polarizing film comprising a polarizing film and a retardation film (¼ wavelength film) (the polarizing film may be arranged on either the viewing side or the light emitting layer side. A pixel bleeding prevention mechanism in the case where a layer on the layer side is more preferable will be described with reference to FIG.

  The interface where total reflection (A in FIG. 1) or reflection loss light of transmitted light (B in FIG. 1) occurs when the circular polarizing film is not provided is the transparent substrate-air interface by providing the circular polarizing film. It moves from the polarizing film to the air interface.

  The quarter-wave film has a function of rotating the direction of polarization clockwise by 45 degrees regardless of the light incident from either side. Therefore, after passing through the polarizing film once and passing through the quarter-wave film twice, the polarization turns 90 degrees. Further, when the light passes through the polarizer that has been first reflected after being reflected by the reflective cathode or diffused by the diffusion layer, since it is rotated 90 degrees, almost all light is blocked. Therefore, as shown on the right side of FIG. 1, the total reflected light (C in FIG. 1) and the reflected loss light (D in FIG. 1) are reflected at the interface with air when the polarizing film is followed by the retardation film. When the light passes through, is further diffused by the diffusion layer, and returns to the viewing side, the light further passes through the retardation film and enters the polarizing film. In this case, almost all light is absorbed and pixel blurring is prevented.

In addition, about the lamination | stacking order of a polarizing film and retardation film, it is more preferable that a polarizing film exists in the light emitting layer side (opposite side of the surface of an output side).
The reason for this is that if it is on the light emitting layer side, it is transmitted through the polarizing film → the retardation film twice → the polarizing film at the time of total reflection from the first air interface or partial reflection of transmitted light. This is because almost the entire amount is absorbed. If this order is reversed, it will be absorbed when transmitted through the retardation film or polarizing film after returning to the diffusion layer or reflecting cathode once after the total reflection or partial reflection. When the polarization state changes due to birefringence or the like in the transparent substrate or the light emitting layer, the pixel blurring prevention effect is reduced.

  (Ii) A pixel bleeding prevention mechanism when an antireflection film (AR film) is provided will be described with reference to FIG.

  When the antireflection film is not provided, the total reflection light (A in FIG. 2), the partially reflected light of the transmitted light (reflection loss light; B in FIG. 2) is generated by providing the antireflection film. Move from transparent substrate to air to AR film to air.

  As shown on the right side of FIG. 2, guided light in the substrate (total reflection light) cannot be suppressed (ineffective, C in FIG. 2), but partially reflected light in the substrate can be suppressed (D in FIG. 2). As a result, pixel blurring due to this loss light can be prevented.

  (Iii) A pixel blur prevention mechanism when a polarizing film or an absorption filter (which absorbs light in the visible range) is provided will be described with reference to FIG.

  When the polarizing film or the absorption filter is not provided, the total reflection light (A in FIG. 3) and the partially reflected light of the transmitted light (reflection loss light; B in FIG. 3) are generated at the interface of the polarizing film or the absorption filter. By providing, it moves from a board | substrate-air to a polarizing film-air.

  As shown on the right side of FIG. 3, both the polarizing film and the absorption filter absorb visible light at a certain ratio, so that both the total reflection light and the reflection loss light are absorbed by passing through the polarizing film and the absorption filter at least three times ( C, D) in FIG. Since the light rays rising from the light emitting layer to the viewer side pass only once, the ratio of absorption is small. Therefore, pixel blurring is reduced by the difference.

  Hereinafter, examples and comparative examples will be described.

The details of each film used in the following Examples and Comparative Examples are as follows.
AR film: “8201UV” manufactured by NOF Corporation was used. In use, the release paper was peeled off and attached via an adhesive layer.
1/4 wavelength film (retardation film); stretched polycarbonate film (thickness 200 nm, retardation 140 ± 20 nm) was used. At the time of use, it stuck through the adhesive layer.
Polarizing film: A polyvinyl alcohol film doped with iodine and then stretched and sandwiched between triacetyl cellulose films (thickness 200 μ, contrast 200, polarization transmittance 44%) was used. In use, it was pasted through an adhesive layer.

In addition, pixel bleeding was examined visually from the image of the digital camera and evaluated according to the following criteria.
○: Pixel blur that occurred when no film was present disappeared.
(Triangle | delta): Pixel blurring decreased compared with the case where there is no film.
X: Almost no change with respect to the case where there is no film.

  In each example, the refractive index measurement was performed with a sopra ellipsometer based on 0542 in principle. If the refractive index of the matrix portion of a meso (nano) porous material or particle dispersion material is difficult to measure with an ellipsometer, Refractive index measurements were performed at 25 ° C. with a 633 nm wavelength laser using a company's Prism Coupler Model 2010.

  Regarding the film thickness, the film thickness of the deposited film or the sputtered film was confirmed by time management from a calibration curve or by a crystal oscillation type film thickness meter.

  The film thickness of the coating film was measured by measuring the level difference by scratching the optical interference film thickness meter or the film. Thick substrates such as glass substrates were measured with a micro caliper or the like.

  The average particle size was measured by the FIB-SEM method.

In addition, when the produced electroluminescent element was caused to emit light, the light emission state was compared with the light emission luminance of 300 cd / m ² , and the pixel size was set to 0.4 mm (400 μm) square.

[When light diffusion distance ≤ pixel size]
Examples 1 to 4 and Comparative Examples 1 and 2
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 degreased by immersing it in 0.1 N nitric acid for about 1 hour, washed with pure water, and then heated in a 60 ° C. oven. Dried in.

  On the other hand, an acid catalyst (aluminum acetylacetonate) is added to a solution of 30% by weight of MS51 (tetramethoxysilane oligomer) manufactured by Mitsubishi Chemical Corporation, 50% by weight of butyl alcohol, 8% by weight of demineralized water, and 12% by weight of methanol. A small amount was added. The mixture was stirred at 60 ° C. for 3 hours and left to mature for 1 week.

  This was coated on the above glass substrate with a spin coater, dried for 15 minutes, dipped in methanol for 5 minutes, pulled up, dried for 5 minutes, and then heated in an oven at 150 ° C. for 15 minutes to form a low refractive index layer. . The thickness of the obtained low refractive index layer was 300 nm. When the refractive index of the matrix portion of the low refractive index layer was measured with an sopra ellipsometer, it was 1.36 at a wavelength of 550 nm. Further, when the refractive index was measured with a laser having a wavelength of 633 nm using a prism coupler model 2010 manufactured by Metricon Corporation, the refractive index was 1.33.

  Next, an acid catalyst (aluminum acetylacetonate) was added to a solution of 30% by weight of MS51 (tetramethoxysilane oligomer) manufactured by Mitsubishi Chemical Corporation, 50% by weight of butyl alcohol, 8% by weight of demineralized water, and 12% by weight of methanol. In addition, titania particles having an average particle diameter of 200 nm (60% weight particle diameter is 150 to 250 nm) in butyl alcohol are made 15% by weight as a percentage by weight in the resulting particle-containing leachable light diffusion layer. Dispersed in advance. The mixture was stirred at 60 ° C. for 3 hours and left to mature for 1 week. The weight percentage in the particle-containing layer was measured in the same manner as that for obtaining the particle size distribution in the film. The density in the case where the matrix is a porous body was determined by obtaining the X-ray reflectance or obtaining the refractive index.

  This coating solution is applied on the low refractive index layer on the above glass substrate with a dip coater, dried for 15 minutes, immersed in methanol for 5 minutes, pulled up, dried for 5 minutes, and then heated in a 150 ° C. oven for 15 minutes. A leaching light diffusion layer was obtained. At the time of dip coating, a protective film was applied to the back surface and peeled off after coating, so that a coating film was formed only on one side.

  The obtained scattering particle-containing exuded light diffusion layer had a thickness of 600 nm and a structure in which scattering particles were overlapped in almost three steps.

  The refractive index of the matrix portion of the light diffusing layer which was soaked with a sopra ellipsometer was 1.40 at a wavelength of 550 nm. In addition, when the refractive index measurement was carried out using the prism coupler model 2010 manufactured by Metricon Inc. in the United States, the refractive index was 1.38 with a laser having a wavelength of 633 nm.

  The surface roughness of the scattering particle-containing leached light diffusion layer was measured using a P-15 type manufactured by KLA-Tencor. When measured by scanning 0.5 μm, Ra = 8 nm and Rmax = 120 nm.

  Moreover, the transmission loss light (scattering loss light) with respect to the parallel rays of the scattering particle-containing leaching light diffusion layer was 52% at a wavelength of 550 nm. A spectrophotometer manufactured by Hured Packard was used for the measurement, and a glass substrate before forming the coating film was used as a reference.

A transparent electrode layer is formed by sputtering at room temperature with a thickness of 115 nm of ITO (indium tin oxide) on the leaching light diffusion layer containing scattering particles, and further a CuPC (copper phthalocyanine) layer 25 nm, an NPB (naphthylpentylbenzidine) layer 45 nm. AlQ ₃ (aluminum quinoline complex, green luminescent dye) 60 nm was formed by vapor deposition, and finally an aluminum reflective electrode layer was formed to a thickness of 80 nm by vapor deposition. The refractive index of the ITO layer was measured and found to be 2.04 (550 nm). The obtained electroluminescence element is a laminate of glass substrate / low refractive index layer / penetrating light diffusion layer / transparent electrode layer (ITO) / electroluminescence layer / reflection electrode layer (Al), and the light diffusion distance is , 855 nm and a pixel size smaller than 400 μm.

  The film shown in Table 1 was provided on the glass substrate of the electroluminescence element thus obtained, and pixel bleeding was examined, and the results are shown in Table 1.

  From Table 1, it can be seen that according to the present invention, it is possible to reduce pixel bleeding of an electroluminescence element having a seepage light diffusion layer.

[When light diffusion distance> pixel size]
(Comparative Examples 3 to 8)
In Example 1, an electroluminescent element was produced in exactly the same manner as in Example 1, except that dip coating was performed without applying a protective film on the back surface when the leaching light diffusion layer was applied. The obtained electroluminescence element is a laminate of a leaching light diffusion layer / glass substrate / low refractive index layer / leaching light diffusing layer / transparent electrode layer (ITO) / electroluminescence layer / reflection electrode layer (Al). It is. In this electroluminescence element, the light diffusion layer formed on both sides of the glass substrate, the light diffusion distance, that is, the distance of the light diffusion layer is 0.7 mm or more, which is larger than the size of the pixel. It became.

  The film shown in Table 2 was provided on the leached light diffusion layer of the obtained electroluminescent device, and pixel bleeding was examined. The results are shown in Table 2.

  From Table 2, when the light diffusion distance is larger than the pixel size, there is a large proportion of guided light between the light diffusion distances, and even if the pixel bleeding according to the present invention is provided, the pixel bleeding suppression effect cannot be obtained. I understand.

(Comparative Examples 9-13)
In Example 1, after leaching and forming a light diffusion layer, a 0.5 mm thick glass substrate was laminated, and a transparent electrode layer (ITO), an electroluminescence layer, and a reflective electrode layer (Al) were laminated thereon. An electroluminescent element was produced in the same manner except for the above. A UV curable adhesive was used for bonding the glass substrates. The thickness of the adhesive was 5 μm. This electroluminescent element is a laminate of glass substrate / penetrating light diffusing layer / adhesive layer / glass substrate / transparent electrode layer (ITO) / electroluminescent layer / reflecting electrode layer (Al). The distance between the diffusion layer and the aluminum reflective electrode was about 0.5 mm or more, which was larger than the pixel size.

  The film shown in Table 3 was provided on the glass substrate of the obtained electroluminescent element to examine pixel bleeding. The results are shown in Table 3.

  From Table 3, when the light diffusion distance is larger than the pixel size, there is a large proportion of guided light between the light diffusion distances, and even if the pixel bleeding according to the present invention is provided, the pixel bleeding suppression effect cannot be obtained. I understand.

The electroluminescence element of the present invention is effective for display, illumination, and the like, but is particularly effective for display from the viewpoint of improving the visibility due to the pixel bleeding prevention effect.
The electroluminescent element of the present invention may be either an organic electroluminescent element or an inorganic electroluminescent element, but is particularly suitable for an organic electroluminescent element.

In this invention, it is a schematic diagram explaining the pixel bleeding prevention mechanism at the time of providing a polarizing film or a pigment | dye filter in the outermost layer. In this invention, it is a schematic diagram explaining the pixel bleeding prevention mechanism at the time of providing an antireflection film in the outermost layer. In this invention, it is a schematic diagram explaining the pixel bleeding prevention mechanism at the time of providing a circularly-polarizing film in the outermost layer. It is a schematic diagram which shows the light diffusion distance which concerns on this invention. In FIG. 4, members having the same functions as those in FIG. It is sectional drawing of the electroluminescent element which concerns on a prior art example. It is sectional drawing of the electroluminescent element which provided the light-diffusion layer. It is sectional drawing of the electroluminescent element which provided the light-diffusion layer. It is a schematic diagram explaining the mechanism of the pixel bleeding generation | occurrence | production of the conventional electroluminescent element which provided the light-diffusion layer.

Explanation of symbols

1 Reflective electrode layer (cathode)
2 Electroluminescence layer 3 Transparent electrode layer 4 Low refractive index layer 5 Transparent substrate 6, 6a Light diffusion layer

Claims (9)

In an electroluminescence element in which an electroluminescence layer, a transparent electrode layer, and a transparent substrate are arranged in this order, an electroluminescence element in which a light diffusion layer is provided between the transparent electrode layer and the transparent substrate,
Satisfy the following condition (2) ,
And, as the outermost layer, antireflection film, and a polarization fill electroluminescent element characterized by having a pixel bleeding prevention layer contains at least one beam by selected from Li Cheng group.
( 2) A reflective electrode layer is provided on the surface of the electroluminescent layer opposite to the transparent electrode layer, and the distance between the surface of the light diffusion layer farthest from the reflective electrode layer and the reflective electrode layer is equal to or smaller than the pixel size. There is . 2. The electroluminescence element according to claim 1, wherein the pixel blur preventing layer includes a polarizing film and a retardation film .   The electroluminescence device according to claim 2, wherein a retardation film is provided above the surface on the emission side of the polarizing film. 4. The electroluminescence device according to claim 1, wherein the following condition (2) is satisfied .
( 2) A reflective electrode layer is provided on the surface of the electroluminescent layer opposite to the transparent electrode layer, and the distance between the surface of the light diffusion layer farthest from the reflective electrode layer and the reflective electrode layer is 1 pixel size. / 2 or less . 5. The electroluminescence element according to claim 4, wherein the following condition (2) is satisfied .
( 2) A reflective electrode layer is provided on the surface of the electroluminescent layer opposite to the transparent electrode layer, and the distance between the surface of the light diffusion layer farthest from the reflective electrode layer and the reflective electrode layer is 1 pixel size. / 10 or less .   6. The electroluminescence element according to claim 1, wherein the light diffusion layer is a layer having a function of diffusing light guided by using the transparent electrode as a waveguide.   7. The electroluminescence device according to claim 6, wherein the light diffusion layer is a layer having a function of diffusing the light that has penetrated from the transparent electrode in the light guided using the transparent electrode as a waveguide. .   8. The electroluminescence device according to claim 1, wherein the light diffusion layer is a layer containing particles that diffuse light in a matrix made of a low refractive index material.   9. The low refractive index layer is provided between the light diffusion layer and the transparent substrate according to claim 8, and the refractive index of the matrix of the light diffusion layer is equal to the refractive index of the low refractive index layer. An electroluminescent element having a refractive index lower than that of the transparent electrode layer.

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