JP2000100571A - Distributed type electroluminescent device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain a device with high brightness, long life and low cost by controlling the amount of water entering the non-coated part of a phosphor with a mean space factor of a water cut-off coating layer and a material of a cover film whereby the average area filling factor of the water cut-off coating layer against the phosphor of an electloluminescent phosphor applied with a water cut-off coating is within a specific range. SOLUTION: In this device, an insulating layer 2 and a luminescent layer 3 are successively laminated and coated on an aluminum backside electrode 1 and vacuum drying is performed to remove a remaining organic solvent. A device is made whereby a transparent electrode 4 and the luminescent layer 3 are affixed by hot rolling, and sandwiched and laminated with a low dampproof cover film 5. Preferably, the device is that the luminescent layer 3 consists of an electloluminescent phosphor and a cyanoethylation high dielectric constant bond resin moisture permeability ratio of the cover film is 8 g/m2.24 hr or more and the material of the cover film is a synthetic resin selected from polypropylene, polyethylene, and polyethylene terephthalate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-brightness, long-life, flexible and low-cost organic dispersion type EL device.

[0002]

2. Description of the Related Art An organic dispersion type EL device has been used as a surface light source or a light emitting display device, for example, a backlight of a liquid crystal display device because of its thinness, uniform light emission, light weight, and the like. In addition, since large-area bodies are easy to manufacture, they are also used as backlights for signboards and signs, signboards, and the like. In general,
The organic dispersion type EL element has a thickness of 10 to 30 μm in which a high dielectric constant inorganic substance such as barium titanate having a particle size of 1 to 10 μ is dispersed in a high dielectric constant organic binder on a back electrode such as an aluminum electrode.
And a light emitting layer having a thickness of 20 to 70 μ in which a phosphor having a particle diameter of 10 to 50 μ is dispersed in a high dielectric constant organic binder is formed in order, and a transparent film such as PET is further formed on the light emitting layer. Indium oxide (IT)
O) or the like, and a transparent electrode having a thickness of 0.05 to 1 μm is provided, and these electrodes are made of PCTFE (polychlorotrifluoroethylene).
And sealed with a highly moisture-proof cover film.
Since the lifetime of the organic dispersion type EL element is determined by the moisture deterioration of the phosphor, a nylon water-trapping film is provided outside the transparent electrode and the back electrode before sealing with a highly moisture-proof cover film, and the moisture-proof property is further improved. In general, it is sealed with a cover film to enhance the properties. From such a viewpoint, recently, a phosphor powder coated with a moisture barrier with alumina or silica has been known.
There is known a thin dispersion type EL element in which a light emitting layer is formed of this phosphor powder and a fluororesin having low hygroscopicity, and a cover film having high moistureproofness is removed.

[0003]

A conventional dispersion-type EL device using a phosphor which is not coated with a moisture barrier is PCTFE.
Even if a cover film or a water catching film made of nylon is used, the water barrier property is insufficient, and it is difficult to bring out the performance exceeding the present condition. In a dispersive EL device in which a conventional phosphor is replaced with a phosphor powder coated with a moisture barrier coating, although the life is extended, the brightness is reduced due to the complete coverage with the moisture barrier coating layer. There is. Further, when a fluororesin is used as the organic binder for forming the light emitting layer, there is a problem that the adhesive strength with the transparent electrode is extremely low and the resin is easily peeled off.

[0004]

As a result of various studies from the above-mentioned viewpoints, the present inventor has found that in a conventional dispersion type EL device using a phosphor which is not coated with a moisture barrier coating, the initial luminance becomes higher as moisture is absorbed. Paying attention to the increase in
It has been found that by optimizing the amount of water entering the light emitting layer of the L element, it is possible to improve the initial luminance and extend the life. In other words, by controlling the amount of water entering the uncoated portion of the phosphor coated with the moisture-blocking coating by the average area occupancy of the moisture-blocking coating layer and the material of the cover film, high brightness, long life and low cost can be achieved. (1) A dispersion-type EL element comprising a pair of electrodes, at least one of which is a transparent electrode, comprising an insulating dielectric layer and a light-emitting layer containing an electroluminescent phosphor coated with a moisture-blocking coating. Wherein the average area occupancy of the moisture blocking coating layer with respect to the phosphor of the electroluminescent phosphor having the moisture blocking coating is 75 to 98%, and (2) at least one of them is transparent. In a dispersion-type EL device in which an element body having an insulating dielectric layer and a light-emitting layer containing an electroluminescent phosphor coated with a moisture barrier between a pair of electrodes is sealed with a cover film, The cover film is made of a low moisture-proof synthetic resin film, (3) the light-emitting layer is made of an electroluminescent phosphor and a cyanoethylated high dielectric constant binding resin, and (4) the moisture permeability of the cover film is 8 g / m or ² · 24 hr or more, (5) the material of the cover film of polypropylene, polyethylene,
It has been found that the device is a dispersion type EL device which is a synthetic resin selected from polyethylene terephthalate.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with examples. An insulating layer 2 on an aluminum foil back electrode 1
The light emitting layer 3 is sequentially coated on the aluminum foil 1 by a doctor blade method or the like, and vacuum dried to remove the organic solvent remaining in each layer. Next, the element is completed by laminating the transparent electrode 4 and the upper surface of the light emitting layer 3 by pressing with a hot roll, and finally sandwiching the film with a low moisture-proof cover film 5 (FIG. 1).

The components and structure of the back electrode 1 are not particularly limited as long as they have conductivity. Preferably, a metal foil or a thin plate can be used. Examples of the metal include aluminum, copper and its alloys, nickel and the like, and carbon may be used. The same material as the transparent electrode described later may be used. Next, the insulating layer 2 is made of a high dielectric insulating powder and an organic binder. As the high dielectric insulating powder, barium titanate,
Zirconium titanate, lead titanate, titanium oxide, or the like can be used. The light emitting layer 3 is made of a phosphor powder having a moisture barrier coating and an organic binder. The phosphor powder is obtained by adding an activator or a coactivator serving as a luminescent center to a base material. Examples of the base material include sulfides such as ZnS and CdS, and examples of the activator and the co-activator include copper (C
u), chlorine (Cl), bromine (Br), iodine (I), manganese (Mn), aluminum (Al) and the like.

The material for forming the moisture blocking layer of the phosphor is SiO.
2, glass-based compounds such as TiO 2 —SiO 2 and ZrO 2 —SiO 2, and inorganic compounds made of translucent ceramics such as alumina, titanium oxide, zirconium oxide, tantalum pentoxide, and silicon nitride. The water barrier layer is formed by sol-gel method, sputtering method, liquid layer deposition method, thermal CVD
Method, a plasma CVD method, or the like. It is desirable to select the thickness of the moisture barrier layer in the range of 0.1 μm to 3 μm.
The average area occupancy (average coverage (area of the moisture-blocking coating / surface area of the phosphor)) of the moisture-blocking coating layer with respect to the electroluminescent phosphor to which the moisture-blocking coating has been applied can be changed by changing the conditions when forming the coating layer, The coating layer can be adjusted by chemical treatment such as acid treatment or the like, or by physically peeling the coating layer using a ball mill or the like.

Considering that the organic binder used for the insulating layer 2 and the light emitting layer 3 is a capacitive element, a high dielectric material is preferable, and a fluorine resin (having a dielectric constant of about 6) is preferred.
%) And cyanoethylated resin (dielectric constant 10% or more). It is known that a fluororesin is decomposed under the influence of moisture under an applied electric field to generate fluorine ions or hydrofluoric acid, thereby destroying the moisture barrier coating layer. Further, since the adhesiveness with the transparent electrode is extremely weak, peeling occurs between the light emitting layer and the device due to bending or the like, and there is a problem that stable operation of the element cannot be obtained, which is not appropriate. In contrast, a cyanoethylated resin is preferable because it has good adhesion to a transparent electrode and, moreover, does not generate a moisture barrier coating layer destructive component. More specifically, cyanoethylated pullulan, cyanoethylated saccharose, cyanoethylated cellulose, cyanoethylated polyvinylalcohol, cyanoethylated hydroxysaccharose, cyanoethylated compounds such as cyanoethylated hydroxycellulose and polyfluorinated resins such as polyvinylidene fluoride. The insulating layer and the light emitting layer may be the same or different. Further, a mixture thereof may be used.

Electroluminescent phosphors not coated with moisture barrier, for example, ZnS: Cu, C, emit light in the presence of moisture, but their initial luminance is remarkably large, but their life is significantly reduced. For example, in the structure shown in FIG. 1, an EL including a phosphor in which the conditions are constant with a thin element without the cover film 5 and the coating rate of the phosphor of the light emitting layer is adjusted so that the thickness of the moisture barrier coating of alumina is constant. When the luminance and the life of the device are evaluated, the luminance monotonously decreases with an increase in the coverage, but the life reaches a maximum around 80 to 98%, and the life decreases even more than that (see FIG. 2). In other words, the life of the device is extended by introducing an appropriate amount of water into the device rather than by completely blocking the water. The transparent electrode 4 is made of a transparent conductive thin film made of, for example, an oxide of indium or tin.
A transparent conductive film deposited on a T film can be used.

The cover film 5 need not be provided from the above viewpoint. However, it is preferable to seal with a synthetic resin film which is transparent and has an appropriate moisture permeability, since the electrode or the like lacks electrical safety such that protection by an insulator is lost. Considering the life of the element, the moisture permeability is 8 g / m ² · 24.
It is preferable to use a synthetic resin film having an hour or more, more preferably 10 g / m ² · 24 hr or more. Specifically, considering the above moisture permeability and flexibility, 300
Examples include polyethylene, polyethylene terephthalate, polypropylene, polyester, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polystyrene, polyvinyl fluoride, polyvinylidene fluoride, and tetrafluoroethylene / ethylene copolymer having a thickness of not more than μm. Impact on the environment after cost reduction and waste disposal, 1
Considering the shape stability at 00 ° C. or lower, polyethylene, polypropylene, and polyethylene terephthalate are more preferable.

[0011] The average coverage of the moisture barrier coating layer of the phosphor is 7
It is preferably from 5 to 98%, more preferably from 80 to 95%.
When a high moisture-proof cover film such as PCTFE is used, excellent characteristics can be obtained even if the average coverage of the moisture barrier coating layer of the phosphor is out of the above range, but the cost is reduced because the film is expensive. Can not do. The phosphor without moisture blocking coating used in the organic dispersion type EL device reacts with the adsorbed moisture on the crystal surface under ultraviolet irradiation to precipitate metallic zinc, so that the body color is blackened and the brightness is greatly reduced. It is known to The device can be used outdoors by subjecting the cover film or the like to UV treatment. For example, a method of providing a thin film layer of a metal oxide such as ZnO as an ultraviolet blocking layer on a cover film, or a method of including an ultraviolet absorbent in an adhesive layer of the cover film can be used.

[0012]

EXAMPLES (Coating of Moisture Shielding Layer) Hereinafter, the present invention will be specifically described with reference to Examples. ZnS: C with an average particle size of 25μ
A method of coating the surface of the electroluminescent phosphor composed of u and Cl with a moisture barrier layer of, for example, titanium oxide will be described. Uncoated Z
10 parts by weight of the nS phosphor was heat-treated at 300 ° C. for 1 hour, dispersed in 100 parts by weight of special grade ethyl alcohol (99.5%), and 0.2 parts by weight of titanium tetraisopropoxide was added thereto for 2 hours. Mix well. Then, after filtration to remove the solvent, 0.2N ammonia water 100
The ZnS phosphor was dispersed in parts by weight for 1 hour, filtered again, vacuum-dried at 200 ° C. for 4 hours, and a phosphor covered with titanium oxide in a moisture-proof manner was obtained. The surface Zn element intensity of the phosphor thus provided with the moisture barrier coating was measured by X-ray photoelectron spectroscopy (XPS) and compared with the surface Zn element intensity of the phosphor before treatment. 100%. Analysis in the depth direction by Ar etching showed that the Zn intensity was 90% in 1 minute etching, 95% in 3 minutes, and 99% in 5 minutes, indicating that the phosphor surface was coated with titanium oxide. I confirmed. Further, it was confirmed by SEM observation that black AgS was not precipitated by immersion in a dilute silver nitrate aqueous solution, and it was determined that the coverage was 100%.
By changing the type of metal alkoxide such as titanium tetraisoproxide, alumina, silica,
The moisture-blocking coated phosphor obtained by the above-mentioned method is put into a container together with alumina balls, and the coating layer is physically peeled off by a ball mill, and the peeled pieces are removed by sieving. %, 98% of a moisture blocking coated phosphor.

(Preparation of Device) Example 1 67 parts by weight of barium titanate (average particle size: 5 μm), 10 parts by weight of cyanoethylated pullulan, and 23 parts by weight of dimethylformamide were mixed and stirred to prepare a paste for an insulating layer. The product was coated on an 80 μm aluminum foil by a doctor blade method, and dried with hot air at 130 ° C. for 3 minutes.
Further, 55 parts by weight of the above-mentioned phosphor having a moisture blocking film ratio of 75%,
16 parts by weight of cyanoethylated pullulan and 29 parts by weight of dimethylformamide were mixed and stirred, and a paste prepared as a light emitting layer paste was coated on the insulating layer in the same manner, and then heated at 100 ° C.
For 3 minutes with hot air. This laminated body is 10cm × 15c
Those cut into a size of m were vacuum dried at 75 ° C. for 20 hours. The thickness of each layer was adjusted in advance so that after vacuum drying, the blade gap was adjusted so that the insulating layer was 25 μm and the light emitting layer was 50 μm. After drying, a PET film transparent electrode was placed on the light emitting layer at 150 ° C., 30 kgf / cm 2, 40 cm / min.
Under a condition of the following. Finally, a 150 μm PET cover film having a moisture permeability of 20 g / m ² · 24 hr was laminated to produce an organic dispersion type EL device.

<Example 2> [0014] The phosphor of the above-mentioned light emitting layer was treated in the same manner as in Example 1 using an average water blocking rate of 90%.
A 150 μm PET cover film having a moisture permeability of 20 g / m ² · 24 hr was laminated to produce an organic dispersion type EL device.

<Example 3> The phosphor of the above-mentioned light emitting layer was prepared in the same manner as in Example 1 by using an average water blocking rate of 98%.
A 150 μm PET cover film having a moisture permeability of 20 g / m ² · 24 hr was laminated to produce an organic dispersion type EL device.

<Example 4> The phosphor of the above-mentioned light emitting layer was treated in the same manner as in Example 1 by using an average water blocking rate of 90%.
A thin organic dispersion type EL element without a cover film was produced.

<Embodiment 5> The phosphor of the above-mentioned light emitting layer was prepared in the same manner as in Embodiment 1 by using an average water blocking rate of 90%.
A 200 μm polyethylene cover film having a moisture permeability of 25 g / m ² · 24 hr is laminated, and an organic dispersion type E is laminated.
An L element was produced.

<Example 6> The phosphor of the above-mentioned light emitting layer was prepared in the same manner as in Example 1 by using an average water blocking rate of 90%.
A 100 μm polypropylene cover film having a moisture permeability of 22 g / m ² · 24 hr was laminated to produce an organic dispersion type EL device.

<Example 7> The phosphor of the above-mentioned light emitting layer was prepared in the same manner as in Example 1 by using an average water blocking rate of 90%.
A 100 μm cover film made of ethylene tetrafluoride / ethylene copolymer resin having a moisture permeability of 8 g / m ² · 24 hr was laminated to produce an organic dispersion type EL device.

<Comparative Example 1> A 150 μm PE having a moisture permeability of 20 g / m ² · 24 hr was prepared in the same manner as in Example 1 except that the above-mentioned phosphor of the light emitting layer was used with an average water blocking rate of 100%.
Laminated T cover film, organic dispersion EL
An element was manufactured. <Comparative Example 2> The above-described phosphor of the light-emitting layer was subjected to moisture permeability of 20 g in the same manner as in Example 1 using an average water blocking rate of 70%.
An organic dispersion type EL device was produced by laminating a 150 μm PET cover film of / m ² · 24 hr. <Comparative Example 3> The above-mentioned phosphor of the light-emitting layer was subjected to moisture permeability of 0.1 in the same manner as in Example 1 using an average water blocking rate of 90%.
A 250 μm cover film made of PCTFE of g / m ² · 24 hr was laminated to produce an organic dispersion type EL device. <Comparative Example 4> In the same manner as in Example 1 except that the above-mentioned phosphor of the light emitting layer was changed to polyvinylidene fluoride as an organic binder and cellosolve acetate as an organic solvent using an average water blocking rate of 90%, the moisture permeability was 20 g / 15 m ² · 24hr
A PET film of 0 μm is laminated, and an organic dispersion type E
An L element was produced. <Comparative Example 5> The phosphor of the light emitting layer described above was used in the same manner as in Example 1 using an average water blocking average coverage of 100%.
A 250 μm PCTFE film of 1 g / m ² · 24 hr was laminated to produce an organic dispersion type EL device.

Each of the organic dispersion type EL devices produced was 20
The initial luminance was measured under the conditions of ° C. and 65% RH. Also,
An acceleration test was performed in a constant temperature and humidity layer at 40 ° C. and 90% RH.
In both cases, 100 V and 400 Hz were applied. The accelerated test life is a continuous lighting time until the luminance decreases to half of the initial luminance. The results are summarized in Table 1.

[0022]

[Table 1]

[0023]

As described above, the dispersion type EL of the present invention is used.
The device controls the amount of water that enters the uncoated part of the phosphor coated with the moisture barrier coating by controlling the average area occupancy of the moisture barrier coating layer and the material of the cover film to achieve high brightness, long life and low cost. By achieving the above, performances higher than those of the related art can be exhibited, and therefore, it can be suitably used.

[Procedure amendment]

[Submission date] December 3, 1998 (1998.12.
3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Added

[Correction contents]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a dispersion-type EL element of the present invention.

FIG. 2 is a graph showing a state in which the luminance and the lifetime of the dispersion type EL element of the present invention are evaluated.

[Description of Signs] 1-back electrode, 2-insulating layer, 3-light-emitting layer, 4-transparent electrode, 5-moisture-proof film.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Minoru Kanda 1-297 Kitabukurocho, Omiya City, Saitama Prefecture Inside Mitsubishi Materials Research Institute (72) Inventor Masaharu Ishiwata 1-297 Kitabukurocho, Omiya City, Saitama Mitsubishi Materials Inside Research Institute Co., Ltd.

Claims (5)

[Claims] 1. A dispersion-type EL device comprising a pair of electrodes, at least one of which is a transparent electrode, having an insulating dielectric layer and a light-emitting layer containing an electroluminescent phosphor coated with a moisture-blocking coating. Wherein the average area occupancy of the moisture blocking coating layer with respect to the phosphor of the electroluminescent phosphor provided with the moisture blocking coating is 75 to 98%. 2. A dispersion-type EL in which an element body having an insulating dielectric layer and a light-emitting layer containing an electroluminescent phosphor coated with a moisture barrier between at least one of a pair of transparent electrodes is sealed with a cover film. 2. The dispersion-type EL device according to claim 1, wherein said cover film is made of a low moisture-proof synthetic resin film. 3. The dispersion type E according to claim 2, wherein the light emitting layer comprises an electroluminescent phosphor and a cyanoethylated high dielectric constant bonding resin.
L element. 4. A cover film having a moisture permeability of 8 g / m ² ···
4. The dispersion-type EL device according to claim 3, which is 24 hours or longer. 5. The dispersion-type EL device according to claim 4, wherein the material of the cover film is a synthetic resin selected from polypropylene, polyethylene, and polyethylene terephthalate.