JP2006040642A - Color conversion film and electroluminescent element using this - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color conversion film with improved brightness by improving color conversion efficiency of light from a light emitter layer (2), and an electroluminescent element (EL) using the same. <P>SOLUTION: The color conversion film has phosphor dyes dispersed in a inorganic oxide medium, and dispersants of the inorganic oxide medium are further dispersed in resin. The EL element (30) is provided with a light-emitting layer (5) between two electrodes (2, 7) opposed to each other and contains color conversion films (13a, 13b, 13c) and a surface substrate (11) at a light-taking-out side. An electrode (7) on the surface substrate side out of the two electrodes is to be a transparent electrode, and the color conversion films (13a, 13b, 13c) have phosphor dyes (15a, 15c) dispersed in the inorganic medium, and particles (14a, 14c) of the inorganic medium dispersants are further dispersed in the resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a color conversion film and an electroluminescence (EL) element using the same.

  In recent years, flat displays have attracted attention as display devices, and plasma displays have been put into practical use as an example. Plasma displays are attracting attention because they can be easily enlarged, have high brightness, and have a wide viewing angle. However, since the structure of the display is complicated and the manufacturing process is also complicated, the improvement is progressing, but it is still expensive at present.

  In addition, a display using an electroluminescence (EL) phenomenon has been proposed. In inorganic EL, an electrode is disposed on a semiconductor inorganic phosphor, and light is emitted by recombination or excitons of electrons and holes of the inorganic phosphor when voltage is applied, or accelerated electrons in the semiconductor collide with the emission center, When the atom or ion that becomes the emission center is excited and returns to its original state, it emits light. The EL element displays characters and images (hereinafter referred to as “images”) using the principle of emitting light by sandwiching a phosphor layer between upper and lower electrodes and applying an electric field to the phosphor layer. Of course, single light display is possible, but single light can be color-converted by a color conversion film to display full color. However, when performing color conversion, there is a problem that the light conversion efficiency decreases and the luminance decreases.

In order to solve this problem, a translucent layer and a color conversion film are provided on the light emitting surface side, the refractive index of the color conversion film is made larger than the refractive index of the translucent layer, and the color conversion film, the translucent layer, There is a proposal to make the interface of the surface uneven (Patent Document 1 below). As another proposal, there is an example in which the refractive index from the electrode on the light extraction side of the organic EL to the substrate is arranged in a specific order (Patent Document 2 below).
JP 2000-284705 A International Publication WO 02 / 17689A1

  However, the color conversion film is basically based on a resin, and it is difficult to finely disperse the dye in the resin. As a result, there is a problem that the color conversion efficiency is hindered by aggregation of the pigments and the luminance is lowered.

  In order to solve the above-described conventional problems, the present invention provides a color conversion film having improved luminance by improving the color conversion efficiency of light from a light emitting layer and an EL element using the same.

  In the color conversion film of the present invention, a fluorescent dye is dispersed in an inorganic oxide medium, and the inorganic oxide medium dispersion particles are further dispersed in a resin.

  The EL element of the present invention includes at least a light emitting layer between two opposing electrodes, includes a color conversion film and a surface substrate on the light extraction side, and the surface substrate side electrode of the two electrodes is a transparent electrode. In the device, the color conversion film is characterized in that a fluorescent dye is dispersed in an inorganic oxide medium, and a dispersion of the inorganic oxide medium is further dispersed in a resin.

  In the color conversion film of the present invention, the fluorescent dye is dispersed in an inorganic medium, and the inorganic medium dispersion particles are further dispersed in a resin, so that the fluorescent dye is present in a finely dispersed state. A color conversion film having improved luminance and an EL element using the same can be provided by improving the color conversion efficiency, preventing the quenching action caused by the collision of the color-converted light, improving the color conversion efficiency of the light from the light emitting layer. .

  In the color conversion film, a fluorescent dye is dispersed in an inorganic medium, and the inorganic medium dispersion particles are further dispersed in a resin. As the fluorescent pigment, a commonly used fluorescent pigment such as a pigment or a dye is used. For example, coumarin 540 (3- (2′-benzothiazolyl) -7 diethylaminocoumarin) is used to convert blue light emitted from the light emitting layer into green light, and DCM (4 is used to convert blue light into red light. -Dicyanomethylene-2-methyl-6- (p-dimethylaminostyryl) -4H-pyran). Further, since it is sufficient to transmit blue as it is, a colorless and transparent resin layer is used.

  The average particle diameter of the inorganic medium dispersion particles is preferably in the range of 2 μm to 10 μm. Within this range, the color conversion efficiency can be kept high without causing aggregation even when mixed with the resin.

  The ratio of the fluorescent dye in the inorganic medium dispersion particles is preferably in the range of 1% by weight to 50% by weight. This is to keep the fine dispersion of the fluorescent dye good.

  The ratio of the inorganic medium dispersion particles in the color conversion film is preferably in the range of 5 wt% to 80 wt%. Within this range, the color conversion efficiency can be kept good.

  The color conversion film is manufactured as follows, for example. First, a solution in which a fluorescent dye is dispersed in a solution and a dispersion solution containing silica particles are mixed, dried and fired to obtain a sintered body. The sintered body is pulverized to obtain particles having an average particle diameter of 2 to 10 μm. This is an inorganic medium dispersion particle. The inorganic medium dispersion particles are dispersed in a transparent resin such as methyl methacrylate (PMMA) or styrene, for example, to prepare a paste, and pattern the color conversion films by a screen printing method or the like. As an example, the thickness after drying is about 5 to 20 μm.

  A black matrix may be disposed on the color conversion film.

  The EL element of the present invention includes at least a light emitting layer between two opposing electrodes. The light emitting layer is formed by layering a light emitting object such as an inorganic or organic phosphor. An electric insulating layer (dielectric layer) may be disposed on both sides or one side of the light emitting layer. In the case of an inorganic phosphor, a dielectric layer is provided between two opposing electrodes, and light is emitted by an electric field using the principle of a capacitor.

  The color conversion film is formed on the observation surface side substrate with respect to the light emitting layer. A transparent electrode is interposed between the color conversion film and the light emitting layer.

  As the transparent electrode, a transparent electrode layer made of an indium-tin oxide alloy (ITO) having a thickness of 200 to 300 μm is used.

Examples of the light-emitting substance that can be used in the light-emitting layer include ZnS: Ag, ZnS: Cu, ZnS: Mn, SrS: Ce: Eu, ZnS: Sm: Cl, CaS: Eu, ZnS: Tb: F, and CaS: Ce. _{ZnMgS: Mn, CaGa 2 S 4} : Ce, SrS: Cu, CaS: Pb, BaAl 2 S 4: Eu, Y 2 O 3: Eu, Ca 2 Ge 2 O 7: generally known as a phosphor, such as Mn Can be used.

As the dielectric layer, Y ₂ O ₃ , Li ₂ O, MgO, CaO, BaO, SrO, Al ₂ O ₃ , SiO ₂ , MgTiO ₃ , CaTiO ₃ , BaTiO ₃ , SrTiO ₃ , ZrO ₂ , TiO ₂ , At least one of B ₂ O ₃ , PbTiO ₃ , PbZrO ₃ , and PbZrTiO ₃ (PZT) can be used. Further, a ferroelectric layer may be interposed between both electrodes, and a means for further increasing the luminous efficiency may be taken.

(Embodiment 1)
This will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a light extraction portion 20 including a transparent substrate and a color conversion film of an EL element according to an embodiment of the present invention. As described above, the light extraction unit 20 has the black matrix 12 formed on the glass transparent substrate 11, and G and B (colorless and transparent, the light emitting layer emits blue light, so color conversion is unnecessary), Color conversion films 13a, 13b, 13c made of R are formed.
(1) Preparation of inorganic dispersion of fluorescent dye A solution (a) benzyl alcohol: 50 g
(B) Green conversion membrane dye, manufactured by Exciton, Coumarin 540: 0.3 g
(C) Dye for red conversion film, manufactured by Exciton, DCM: 0.3 g
(D) Blue, none (colorless and transparent resin layer)
Liquid B (a) 60% by weight nitric acid: 0.1 g
(B) Isopropyl alcohol: 30 g
(C) Butanol: 30 g
(D) Pure water: 1g
(E) SiO ₂ : 2 g
(F) ZrO ₂ : 1 g
(G) Methyl silicate: 0.5g
The liquid A and liquid B were stirred at 60 ° C. for 1 hour, mixed, heated to 170 ° C. over 1 hour, the solvent was removed, and the mixture was baked at 170 ° C. for 3 hours. Then, it cooled to room temperature and grind | pulverized and obtained particle | grains (14a, 14c) with an average particle diameter of 2-10 micrometers. 15a and 15c are fluorescent dyes.
(2) Preparation of color conversion film The following components were mixed at 90 ° C for 1 hour to prepare a coating material paste.
(A) Inorganic medium dispersion particles of the fluorescent dye: 4 g
(B) Transparent binder resin Polymethyl methacrylate powder (PMMA: manufactured by Sumitomo Chemical Co., Ltd., refractive index 1.49): 2 g (c) Solvent butyl carbitol acetate: 10 g
(1-2) Coating Method A black matrix containing graphite and PMMA and having a thickness of 2 μm, a width of 50 μm, and a pitch interval of 150 μm was formed on the surface of the glass substrate. On the black matrix, the green, red and colorless pastes are printed in the order of G, B (colorless) and R by screen printing method over the pitch interval, and the solvent is gradually evaporated to 170 ° C. , Dried in 60 minutes. The film thickness after drying was 15 μm.

FIG. 2 is a cross-sectional view showing the light emitting unit 10 from the back side substrate of the EL element to the translucent resin protective layer on the transparent electrode in one embodiment of the present invention. First, a back electrode 2 made of copper wiring having a thickness of 10 μm was formed on the back glass 1 in parallel in a stripe shape. Furthermore, a dielectric layer 3 made of BaTiO ₃ with a thickness of 30 μm, a smooth layer 4 made of a BaTiO ₃ organic acid with a thickness of 0.6 μm, and a fluorescent light made of BaAl ₂ S ₄ : Eu with a thickness of 0.6 μm thereon. A body light emitting layer 5 and a diffusion preventing layer 6 made of Al ₂ O ₃ having a thickness of 0.5 μm were formed. A transparent electrode 7 made of an indium-tin oxide alloy (ITO) layer (refractive index n1 = 2.1) having a thickness of 0.5 μm and a width of 150 μm is formed in parallel in a stripe shape in a direction perpendicular to the back electrode 2. did. The back electrode 2 to the transparent electrode 7 were formed by sputtering.

  Next, as shown in FIG. 3, the light extraction unit 20 is aligned and placed on the light emitting unit 10, and the display element 30 is assembled by sealing the periphery with an epoxy resin.

  When an alternating voltage of 1 kHz, 10 μA, and 180 V was applied to the EL element 30, it was about 20 compared to a color conversion film in which a fluorescent dye was directly mixed with a resin without using an inorganic medium dispersion of the fluorescent dye. % Brightness improvement was observed.

  In the said embodiment, although the example which applies a color conversion film to an inorganic EL element was shown, the color conversion film of this invention is not only an inorganic EL element but an organic EL element, a liquid crystal display element, a plasma display display element ( The present invention can be applied to color displays such as PDP), field emission display elements (FED), and cathode ray tube display elements (CRT). Further, it can be applied to a lighting device, for example, blue light emission can be converted into orange to make light easy on the eyes.

It is sectional drawing of the light extraction part in Embodiment 1 of this invention. It is sectional drawing which shows the light emission part of the EL element in Embodiment 1 of this invention. It is sectional drawing of the EL element in Embodiment 1 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Back glass 2 Back electrode 3 Dielectric layer 4 Smooth layer 5 Phosphor emitting layer 6 Diffusion prevention layer 7 Transparent electrode 10 Light extraction part 11 Transparent substrate 12 Black matrix 13a, 13b, 13c Color conversion film 14a, 14c Inorganic oxide dispersion Body particles 15a and 15c Fluorescent dye 20 Light emitting part 30 EL element

Claims (5)

  A color conversion film comprising a layer in which a fluorescent dye is dispersed in an inorganic oxide medium, and particles of the inorganic oxide medium dispersion are further dispersed in a resin.   The color conversion film according to claim 1, wherein an average particle diameter of the inorganic oxide medium dispersion particles is in a range of 2 μm to 10 μm.   The color conversion film according to claim 1, wherein a ratio of the fluorescent dye in the inorganic oxide medium dispersion is in a range of 1 wt% to 50 wt%.   The color conversion film according to claim 1, wherein a ratio of the inorganic oxide medium dispersion particles in the color conversion film is in a range of 5 wt% to 80 wt%. In an EL element including at least a light emitting layer between two opposing electrodes, including a color conversion film and a surface substrate on the light extraction side, and using the electrode on the surface substrate side of the two electrodes as a transparent electrode,
The electroluminescent element according to claim 1, wherein the color conversion film is the color conversion film according to claim 1.

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