JPH04112489A - Manufacture of electroluminescence phosphor - Google Patents

Abstract

PURPOSE:To obtain an electroluminescence(EL) phosphor having high luminance and a long lifetime by treating the EL phosphor of a specific zinc sulfide type in a plasma including oxygen gas as an essential component. CONSTITUTION:A zinc sulfide type electroluminescence phosphor, where an activator including an additive activator and an additive co-activator is added into a base material, followed by baking, is treated in a plasma incorporating oxygen gas as an essential component. The plasma incorporating oxygen gas as an essential component may be diluted with inactive gas such as argon, neon and helium, and in this case, it is desirable that the oxygen gas should be more than 8mol%. As the additive activator, a substance incorporating an element capable of forming an acceptor level of zinc sulfide such as copper and silver, for example, copper acetate, silver nitrate or the like is used. As the additive co-activator, a substance incorporating an element capable of forming a donor level of zinc sulfide such as chlorine, bromine and aluminum, e.g. ammonium chloride, bromine chloride, ammonium acetate or the like is used. Therefore, the treatment in the plasma including oxygen gas can remarkably enhance a lifetime without deteriorating luminance.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to electroluminescence (hereinafter referred to as EL).
Concerning a method for manufacturing a phosphor.

(Prior art) Conventionally, EL phosphors have been made using zinc sulfide as the main raw material, and copper, which forms an acceptor level for zinc sulfide, as an activator.
Adding an activator, which is a substance containing elements such as silver, and a donor activator, which is a substance containing elements such as chlorine, bromine, and aluminum, which form the donor level of zinc sulfide, creates a flux. After firing with alkali metal, alkaline earth metal halide, ammonium halide, etc., it is treated with a solution containing cyanide to remove excess copper on the surface, and then subjected to appropriate surface modification treatment. was.

Surface modification methods include a method of etching a phosphor as seen in Jikai No. 57-96494, and Jikai 1-1.
There is a method of re-firing as shown in Japanese Patent No. 38287. US Patent No. 308 is a surface modification method using gas.
As shown in Publication No. 2344, air, NH3, N2,
There are reports that re-firing in a gas such as Co or SO2 increases the lifespan. On the other hand, regarding plasma processing,
No. 3-278990 and Jikai No. 1-129090 disclose a method of processing in a plasma containing nitrogen gas and fluorine compound gas.

(Problem to be Solved by the Invention) However, with the above method, the life of the EL element is still not sufficient.Especially when used as a backlight source for a liquid crystal backlight, it is necessary to use an EL element with higher reliability and a longer life.
elements are in demand.

The present invention provides a method for manufacturing an EL phosphor with high brightness and long life.

(Means for Solving the Problems) The present invention provides a zinc sulfide type EL phosphor, which is produced by adding an activator consisting of an activator and an activator to a base material and firing the zinc sulfide type EL phosphor. It is characterized by processing inside.

As a result of studying plasma treatment in various gases as a surface treatment method for zinc sulfide type EL phosphor, the present invention proposes a method for treating the surface in a plasma containing oxygen as a component, and further etching the surface as necessary. This was based on the discovery that the lifespan was significantly extended.

The plasma used in the present invention contains oxygen gas as an essential component and may be diluted with an inert gas such as argon, neon, helium, etc. In this case, the oxygen gas is 8 mol%.
The above is desirable.

The gas pressure introduced into the plasma generator is 0.01 to 2.
0 TOrr is preferable, and 0.05 to 5 Torr is more preferable. Also, the plasma generation power source is voltage io
o~10000V, preferably 500~3000
A high frequency power source of V is used.

In the present invention, after plasma treatment, if the plasma conditions are excessive, zinc sulfide will be generated on the surface, so it is preferable to perform etching treatment to remove the oxide layer. The etching method is carried out by immersion in an acetic acid aqueous solution or the like.

Zinc sulfide EL phosphors to which the treatment of the present invention is applied include zinc sulfide EL phosphors obtained by adding an activator and an activator to zinc sulfide and firing them together with a flux; There is a zinc sulfide type EL phosphor obtained by firing a mixture of zinc and an activator in a hydrogen sulfide gas atmosphere.

A zinc sulfide type EL phosphor obtained by firing a mixture of zinc oxide and an activator in a hydrogen sulfide gas atmosphere can be obtained by heating a mixture of zinc oxide and an activator by passing hydrogen sulfide gas through the mixture. In this method, the sulfidation reaction of zinc oxide and the diffusion of the activator were carried out simultaneously with the reaction, thereby attempting to efficiently diffuse the activator into the zinc sulfide in a short period of time.

Activator refers to activator and activator. The activator is a substance containing an element such as copper or silver that forms an acceptor level of zinc sulfide, and examples include copper acetate and silver nitrate. The activator is a substance containing an element that forms a donor level of zinc sulfide, such as chlorine, bromine, and aluminum, and includes ammonium chloride, bromine chloride, ammonium acetate, and the like.

The phosphor of the present invention described above is used for manufacturing a distributed EL element and the like. Dispersion type EL elements are made of ITO (Indium Tin Oxide) on a transparent substrate such as a glass plate.
), a light-emitting layer is formed on the transparent electrode with phosphor dispersed in a resin, an insulating layer is formed with insulator particles dispersed in the resin, and an electrode such as aluminum is formed. is formed.

(Effect) It has been reported in the literature that re-firing in S% air, ammonia, S02, and CO increases the lifespan, but there are many unknowns about the cause. It is thought that more active oxygen atoms acted upon the treatment in plasma, but the reason for this is unknown. However, when the treatment time is increased, the formation of a ZnO layer becomes visible by X-ray diffraction. Since this ZnO is electrically conductive, it is thought that etching with acid is necessary.

There is a literature on re-firing phosphors in an oxygen atmosphere, but in this method, the luminescence characteristics differ greatly between the surface layer that is in contact with the gas and the inside of the filled phosphor group, but in the method of the present invention using plasma, , there is no such difference.

(Example 1) 0.2T of mixed gas with a mixing ratio of 02 and Ar of 1:1
orr, input power 0.2W/cm2.13.56M
A high frequency voltage of Hz was applied to generate oxygen plasma. 20g of zinc sulfide type phosphor for distributed EL is uniformly dispersed on the electrode plate in plasma, and the substrate temperature is 200℃.
and processed for 5 minutes. This phosphor was dispersed in a dimethylformamide solution of cyanoethyl pullulan to form a transparent electrode and coated on a glass substrate to form a light-emitting layer. The volume ratio of the phosphor to the resin was 1:1. Furthermore, after forming an insulating layer of a mixture of titanium oxide powder dispersed in a dimethylformamide solution of cyanoethyl pullulan, metal electrodes were deposited to obtain an EL element. The film thicknesses of the light emitting layer and the insulating layer were 50 μm and 120 μm, respectively.

An alternating current electric field of 400 Hz and 115 V was applied to this EL element to measure its brightness and life. The results are shown in Table 1.

(Example 2) Oxygen plasma was generated by applying a high frequency voltage of 2.13.56 MHz and an input power of 0.1 W/cm in an 0.2 gas atmosphere of 0.15 Torr. 20% of zinc sulfide type phosphor for distributed EL is placed on the electrode plate in the plasma.
g It was uniformly dispersed and treated at a substrate temperature of 200° C. for 5 minutes. Furthermore, the phosphor was dissolved in a water bath at 80°C using acetic acid.
It was etched for 0 minutes, then washed with water and dried. This phosphor was dispersed in a dimethylformamide solution of cyanoethyl pullulan to form a transparent electrode and coated on a glass substrate to form a light-emitting layer.

The volume ratio of the phosphor to the resin was 1:1. Furthermore, after forming an insulating layer of a mixture of titanium oxide powder dispersed in a dimethylformamide solution of cyanoethyl pullulan, metal electrodes were deposited to obtain an EL element.

The film thicknesses of the light emitting layer and the insulating layer were 50 μm and 120 μm, respectively. An alternating current electric field of 400 Hz and 115 V was applied to this EL element to measure its brightness and life. The results are shown in Table 1.

(Comparative Example) The phosphor used in the example was used as an EL element in the same manner as in the example without undergoing the above treatment, and its characteristics were evaluated.

Table 1 However, the life test was conducted at 50°C in a desiccator.

(Effects) By processing in a plasma containing oxygen gas as in the present invention, the lifetime can be significantly improved without reducing brightness. Furthermore, there is no variation in characteristics among the treated phosphor particles.

Procedure correction band (voluntary) Heisei April 2nd

Claims (1)

[Claims] 1. An electroluminescent phosphor characterized by processing a zinc sulfide type electroluminescent phosphor obtained by adding an activator and a donor activator to a base material and firing it in a plasma containing oxygen gas as an essential component. Method for manufacturing luminescent phosphors.