JPS593839B2 - Electroluminescent device and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 5 The present invention relates to a distributed electroluminescent device that applies an electric field to phosphor powder to emit light.

It is widely known that when an electric field is applied to a phosphor powder such as ZnS in which manganese is diffused, the phosphor powder emits light, and this phenomenon, called electroluminescence (EL), can be utilized. An electroluminescent device, which is a display device based on the above, has been developed.

However, conventional electroluminescent devices have various problems, and only a few have been put into practical use. Figure 1 shows
151 is a transparent electrode formed on one surface of a transparent insulating substrate 2 such as a glass substrate or a plastic film substrate, and has a sheet resistance of Ω/□.
It is made of the following thin films such as In2O3 and SNO2, metal thin films such as gold and palladium, or aluminum foil with small mesh-like holes. 3 is the other electrode, which is one in which metal powder such as silver is dispersed in an organic polymer or inorganic binder, or one in which a metal plate such as aluminum or copper is attached. A typical electric field translucent device is
Between the transparent electrode 1 and the electrode 3 that face each other,
A light-emitting layer 4 in which a phosphor powder made by doping ZnS with an activator such as copper or manganese and an activator such as chlorine is dispersed in an organic polymer binder, and a high dielectric constant material such as TiO2 or BaTi03. It has a structure in which an insulating layer 5 in which powder is dispersed in an organic polymer binder is sandwiched, and the entire structure is further covered with a moisture-proof protective film 6 made of trifluoroethylene chloride, epoxy resin, or the like. Note that some phosphor powders utilize rare earth elements, monovalent metals, transition metals, and the like. In FIG. 1, when an alternating current voltage is applied between both electrodes 1 and 3, an electric field corresponding to the voltage and frequency is applied to the light emitting layer 4, causing it to emit light. In order to increase the luminescence intensity,
Increase the applied voltage. (2) The thickness of the light emitting layer 4 and the insulating layer 5 is reduced.

(3) The organic polymer binder used in the light emitting layer 4 and the insulating layer 5 has a high dielectric constant. (4) Increase the frequency of alternating current.

etc.

However, increasing the voltage or making the light emitting layer 4 and the insulating layer 5 thinner may cause dielectric breakdown between the electrodes 1 and 3, so there is a limit. Additionally, increasing the AC frequency requires a separate power source, and changing the frequency also results in different emission wavelengths. Therefore, in order to increase the luminance of the electroluminescent device without deteriorating its various characteristics, it is sufficient to use an organic polymer binder with a high dielectric constant for the light emitting layer 4 and the insulating layer 5. However, the cyanoethylated cellulose and epoxy resin conventionally used as the organic polymer binder have the following drawbacks. That is, although cyanoethylated cellulose has a high dielectric constant, it has weak film adhesion and further has disadvantages of poor heat resistance and moisture resistance. Furthermore, although epoxy resin has somewhat excellent heat resistance and moisture resistance, it has the disadvantage of a low dielectric constant. Furthermore, the phosphor powder used in electroluminescent devices has the disadvantage that if a voltage is applied in a humid state, it will decompose within an extremely short period of time and lose its light emitting function. Even when covered with the film 6, conventional electroluminescent devices are sensitive to humidity, have a short lifespan, and are unreliable.

SUMMARY OF THE INVENTION An object of the present invention is to provide a reliable electroluminescent device that overcomes the above-mentioned drawbacks, has excellent heat resistance and moisture resistance, and has high luminance. The feature of the present invention is that the light emitting layer 4
The organic polymer binder used in the insulating layer 5 is a copolymer of vinylidene fluoride and propylene hexafluoride to which a vulcanizing agent is added.

The copolymer of vinylidene fluoride and propylene hexafluoride is commonly called fluorocarbon rubber, and it is highly flexible, has a dielectric constant of 15 (60 Hz), and has strong adhesive strength (and has the highest heat resistance among other rubbers). Excellent properties and moisture resistance.

In this way, as the organic polymer binder used in the light-emitting layer 4 and the insulating layer 5, a copolymer of vinylidene fluoride and propylene hexafluoride, which has excellent properties, and a vulcanizing agent are used. The resulting electroluminescent device has excellent heat resistance and moisture resistance, high luminance, long life, and high reliability. Next, a method for manufacturing an electroluminescent device according to the present invention will be explained using FIG.

First, on a transparent substrate 2 such as a glass substrate, etching method,
In2 formed by screen printing method, vapor deposition method, etc.
A transparent electrode 1 made of a thin film of O3, snO2, etc., a metal thin film of gold, palladium, etc., or aluminum foil with small mesh holes is coated by spraying, coating, or screen printing. After the phosphor paste is applied by a method such as the method, heat treatment is performed at 150° C. for 10 hours to vulcanize, and the light emitting layer 4 is formed. The phosphor paste is prepared by adding and mixing a vulcanizing agent, a solvent, and phosphor powder to raw rubber, which is a copolymer of vinylidene fluoride and propylene hexafluoride. For example, create it like this: First, the raw rubber is dissolved in an organic solvent such as acetone or methyl ethyl ketone to prepare a 25% solution (this will be referred to as A). Next, a 2% solution (this will be referred to as B) is prepared by dissolving a vulcanizing agent such as amines, polyols, and peroxides in an organic solvent. These solutions and phosphor powder are mixed at a mixing ratio of A:B:phosphor powder=4:1:7 to create a phosphor paste. The light-emitting layer 4 obtained using the phosphor paste was a dense film with a thickness of 20 to 30 ttm and was insoluble in organic solvents. Next, the light emitting layer 4
An insulating paste is applied thereon by a spraying method, coating method, screen printing method, etc., and heat treatment is performed at 150° C. for 10 hours to vulcanize, thereby forming an insulating layer 5. The insulating layer 5 had a thickness of about 25 μm and was insoluble in organic solvents. The insulating paste is created, for example, as follows. That is, in the same manner as when preparing the phosphor paste, both liquids A and B were prepared and mixed with TiO2 powder, which is a high dielectric constant powder, at a blending ratio of A:B:TiO2 powder = 4:1:1.5. and create. Next, a silver paste electrode or an aluminum paste electrode is placed on the insulating layer 5 in the same manner as before.
An electrode 3 made of a metal plate such as copper is formed. lastly,
Moisture-proof protective film 6 made of ethylene trifluoride chloride, epoxy resin, etc.
Cover the whole thing with the wafer and complete the electroluminescent device. When an alternating voltage of 100 and 50 Hz is applied between the transparent electrode 1 and the electrode 3 of the electroluminescent device created in this way, the luminance is approximately 25 cd/d, which is twice as much light as the conventional one. Brightness was obtained. In addition, heat resistance load test at 85°C, 100V, 50Hz and 40°C, 90-95% RHM, 100V, 50H
A humidity-resistant load test was conducted for z, and the luminance half-life was 1.000 H under heat-resistant load and 2.000 H under humidity-resistant load. This is more than 20 times that of conventional products. In the above description, fuso rubber was used for both the light emitting layer and the insulating layer, but the same effect can be obtained even if it is used for only one of them.

As can be seen from the above description, in the present invention, a copolymer of vinylidene fluoride and propylene hexafluoride with a vulcanizing agent added is used as a binder for the light emitting layer and the insulating layer. As a result, it has excellent heat resistance, moisture resistance, and high luminance.
This has the great advantage of providing a long-life and reliable electroluminescent device.

[Brief explanation of drawings]

FIG. 1 is a partially enlarged side sectional view of a general electroluminescent device, showing the basic configuration of the electroluminescent device. DESCRIPTION OF SYMBOLS 1... Transparent electrode, 2... Transparent insulating substrate, 3... Electrode, 4... Light emitting layer, 5... Insulating layer, 6... Moisture-proof protective film.

Claims (1)

[Claims] 1. Between two opposing electrodes, at least one of which is transparent,
In an electroluminescent device comprising a light emitting layer and an insulating layer, the light emitting layer is made of a copolymer of vinylidene fluoride and propylene hexafluoride containing dispersed phosphor powder, and the insulating layer is made of a high dielectric constant powder. The copolymer is made of a copolymer of vinylidene fluoride and propylene hexafluoride, which contains dispersed polyvinylidene fluoride and propylene hexafluoride; Characteristic electroluminescent device. 2. A phosphor paste formed by mixing phosphor powder, a copolymer of vinylidene fluoride and propylene hexafluoride, a vulcanizing agent, and an organic solvent on a transparent electrode formed on a transparent insulating substrate. 1. A method for manufacturing an electroluminescent device, comprising the step of applying the material and then performing a heat vulcanization treatment to form a light emitting layer. 3 After applying an insulating paste made of a mixture of a high dielectric constant powder, a copolymer of vinylidene fluoride and propylene hexafluoride, a vulcanizing agent, and an organic solvent on the light emitting layer, heat is applied. 3. The method of manufacturing an electroluminescent device according to claim 2, further comprising the step of performing a vulcanization treatment to form an insulating layer.