JPS6346558B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a dispersed EL light emitting device using a zinc sulfide phosphor. Conventional configurations and their problems Conventionally, distributed EL light emitting elements have been used as planar light sources and simple display elements, but they have drawbacks such as low brightness and the need for high voltage. .
The drawing shows the configuration of a typical EL light emitting device. That is,
A transparent electrode 1 such as ITO, a light emitting layer 2 made of phosphor powder and a binder, an insulating layer 3 made of an insulating powder such as BaTiO ₂ and a binder, and a back electrode 4 such as Al foil are laminated, and finally a moisture-proof film is layered. 5 seals the whole thing. In order to achieve low voltage and high brightness in a distributed EL light emitting device, it is necessary to increase the dielectric constant of the binder used in the light emitting layer, and to increase the electric field strength applied to the light emitting layer by increasing the film thickness of the light emitting layer. It is possible to reduce the thickness. However, in the past, cyanoethylated cellulose with a dielectric constant of about 18 was generally used as a binder, and zinc sulfide phosphors with an average particle size of around 20 μm were used to emit light with a film thickness of 40 μm to 70 μm. layer was formed, and it was difficult to further reduce the thickness of the light emitting layer. OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and aims to provide a low-voltage, high-brightness distributed EL light-emitting element. Structure of the Invention In order to achieve the above object, the distributed EL of the present invention
The light-emitting element is a dispersed EL light-emitting element in which a light-emitting layer is formed by dispersing a powder phosphor containing zinc sulfide as a main component in a binder, and the average particle size of the powder phosphor is 3 μm to 10 μm; Moreover, the thickness of the light emitting layer is 10 μm to 25 μm. Description of Examples Examples of the present invention will be described below. Example 1 Copper sulfate CuSO ₄ was added to 1 mol of zinc oxide as an activator.
5H ₂ O and ammonium alum NH ₄ Al(SO ₄ ) ₂ .
12H ₂ O was added in an amount of 0.5 mol% and mixed wet, and after drying, heat treatment was performed in a quartz tubular furnace at 600°C for 2 hours in a carbon disulfide gas atmosphere, and then at 950°C for 6 hours in a hydrogen sulfide gas atmosphere. . Next, it was washed with a cyan aqueous solution and pure water to obtain a Cu- and Al-activated zinc sulfide phosphor. Next, this powder was classified into four groups having an average particle size as shown in Table 1 by using a sieve or a sedimentation method in ethanol. The average particle size was measured using a Fissure particle size meter. Dispersed EL light emitting devices were fabricated using these phosphors using a conventional method, and the brightness was measured. That is, as a binder component, a binder solution was prepared by dissolving cyanoethylated pullulan having a relative dielectric constant of about 21 and cyanoethylated sucrose having a relative dielectric constant of about 39 in a weight ratio of 5:1 in DMF (dimethylformamide). Barium titanate powder was dissolved in this binder solution, and this was applied onto a 125 μm aluminum foil to form a dry coating film of about 8 μm to form an insulating layer. Further, a phosphor was dispersed in the same binder solution and applied onto the insulating layer to form a dry film of about 18 μm to form a light-emitting layer. The blending ratio of the binder component and the phosphor was 6:4 in terms of volume ratio in the coating film. Then on top of the emissive layer
Polyester films coated with transparent conductive films such as ITO were stacked together, and the entire structure was laminated using a rubber press method at 170℃ and a pressure of 40Kg/ ^cm2 .
It was used as a light emitting element. Furthermore, for comparison, a light-emitting layer using cyanoethylated cellulose as a binder component was prepared in the same manner as above, and an EL light-emitting element was constructed as a comparative example. Furthermore, as a comparative example,
Commercially available Cu, Al-based zinc sulfide phosphor (average particle size 21.3μ
An EL light-emitting device was produced using the same method as above, cyanoethylated cellulose was used as a binder component, and the thickness of the light-emitting layer was 48 μm. An alternating current electric field of 1 KHz and 100 V was applied to these EL light emitting devices, and the brightness was measured. The results are shown in Table 1, and the brightness of the product using cyanoethylated pullulan and cyanoethylated sutucarose was about 1.5 times higher than that of the product using cyanoethylated cellulose. In addition, an EL light emitting element (No. 4) using phosphor with an average particle size of 14.5 μm
It was not possible to form a homogeneous coating film and showed poor pressure resistance.
Furthermore, EL with a 48 μm luminescent layer formed using commercially available phosphor.
The light emitting element (No. 6) had a considerably low level.

[Table] Example 2 A Cu- and Al-activated zinc sulfide phosphor was obtained in the same manner as in Example 1. Next, classify the 7.9μ
A phosphor having an average particle size of m was prepared. Furthermore, cyanoethylated pullulan and cyanoethylated sutucarose
An EL light emitting device was produced in the same manner as in Example 1 using a DMF solution as a binder component.
The dry coating thickness of the insulating layer was set to about 8 μm.
In addition, the dry coating thickness of the luminescent layer is 10μm, 18μm, and 25μm.
Each coating was applied to a thickness of 32 μm. An alternating current electric field of 1 KHz and 100 V was applied to these EL light emitting devices, and the brightness was measured. The results are shown in Table 2.

[Table] As is clear from the above Examples and Tables 1 and 2, the dispersed EL light emitting device obtained by the present invention has an average particle size of 3 μm to 10 μm of the phosphor used.
m, and when the thickness of the light emitting layer was 10 μm to 25 μm, the brightness was significantly improved compared to the conventional EL light emitting device. In the present invention, when the average particle size of the phosphor becomes smaller than 3 μm, the brightness decreases rapidly. Moreover, if it is larger than 10 μm, it becomes difficult to form a thin and homogeneous coating film. Furthermore, when using a phosphor with an average particle size of 3 μm to 10 μm, if the thickness of the light emitting layer is thinner than 10 μm, it is difficult to ensure sufficient voltage resistance, and if it is thicker than 25 μm, the voltage applied to the phosphor in the light emitting layer becomes difficult. voltage is reduced. Note that the present invention is not limited to the above examples, and similar results can be obtained not only with Cu-Al but also with Cu-Mn, Cu-Br, Cu-Cl, Cu-I, etc. as the activator. Needless to say, you can obtain Results of the Invention As described above, according to the present invention, it is possible to provide an EL light emitting element which has significantly improved brightness compared to conventional EL light emitting elements and is capable of displaying high brightness even when driven at a low voltage. It is also possible to make the drive circuit system more compact and lower in cost.

[Brief explanation of the drawing]

The drawing is a cross-sectional view of a distributed EL light emitting device. DESCRIPTION OF SYMBOLS 1... Transparent electrode, 2... Light emitting layer, 3... Insulating layer, 4... Back electrode, 5... Moisture-proof film.

Claims (1)

[Claims] 1. Dispersed EL in which a light-emitting layer is formed by dispersing powdered phosphor containing zinc sulfide as a main component in a binder.
A light emitting device, wherein the powder phosphor has an average particle size of
3 μm to 10 μm, and the thickness of the light emitting layer is 10 μm
Dispersed EL light emitting device with a diameter of ~25 μm. 2. The dispersed EL light-emitting device according to claim 1, wherein the binder components of the light-emitting layer are cyanoethylated pullulan and cyanoethylated sucarose.