JPS6067585A - Production of zinc sulfide fluorescent substance - Google Patents

Abstract

PURPOSE:To obtain a zinc sulfide fluorescent substance having fine particles of uniform particle size, by adding ammonia to a melt mixture of thiourea with a zinc salt and an activator to deposit zinc sulfide, and calcining the resultant zinc sulfide at a low temperature and then at a high temperature. CONSTITUTION:A mixture of thiourea with a zinc salt and an activator is melted and mixed, and ammonia is then added thereto to deposit zinc sulfide containing the activator in the melt. The resultant deposited zinc sulfide is then calcined at 350-600 deg.C in an inert atmosphere or sulfiding atmosphere to remove components other than the aimed fluorescent substance. The resultant calcined material is then calcined at 950-1,250 deg.C in the same atmosphere to give the aimed zinc sulfide fluorescent substance. USE:For cathode-ray tubes and electroluminescence.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a method for producing a zinc sulfide phosphor, and is a method for obtaining a zinc sulfide phosphor having fine particles with uniform particle size and high brightness. It provides: The zinc sulfide phosphor obtained by the method of the present invention can be used as a phosphor for cathode ray tubes,
It can be used as a phosphor for electroluminescence.

(Conventional structure and problems) Zinc sulfide phosphors emit light when stimulated with cathode rays, and are mainly used in cathode ray tubes, etc., or emit light when an external electric field is applied. ) is used. It is well known that the phosphor used in the above-mentioned EL light-emitting device is made by adding and baking zinc sulfide, an activator such as copper or manganese, and a co-activator such as aluminum, sodium chloride or bromine. Zinc sulfide, which is the base material for these materials, is obtained by introducing hydrogen sulfide into an aqueous zinc sulfate solution kept acidic using a buffer solution to saturate it, and precipitating zinc sulfide. However, the particle size of zinc sulfide obtained by these methods is distributed over a wide range, and it is difficult to obtain a uniform particle size. In addition, activator, zinc sulfide obtained by this method,
If a co-activator is added and heat treated, abnormal grain growth may occur1.
- It is difficult to obtain a zinc sulfide phosphor with uniform particle size.

In terms of brightness, it also promotes grain growth and reduces the average grain size to 10μ.
It is difficult to obtain high luminance unless the luminance is about m or more. Therefore, the inventors obtained zinc sulfide containing an activator from a molten salt of thiourea and zinc salt, an activator, and an alkali, and washed it with pure water to remove byproducts generated by the reaction and unreacted substances. The inventors have discovered that if the zinc sulfide phosphor is then fired in either an inert atmosphere or a sulfuric atmosphere, a zinc sulfide phosphor with small and uniform particle size and high brightness can be obtained. However, since the zinc sulfide obtained by this method is washed with water, it has a high moisture content and requires sufficient drying, and also has the disadvantage that some of it is oxidized or becomes zinc sulfate. Therefore, even higher brightness can be expected if the moisture contained in zinc sulfide and the oxidation of zinc sulfide are prevented.

(Objective of the Invention) The present invention eliminates the above-mentioned drawbacks and provides a method for producing a zinc sulfide phosphor with fine particles of uniform particle size and high brightness.

(Structure of the Invention) The present invention provides zinc sulfide containing an activator from a molten salt of thiourea and zinc salt, an activator, and ammonia in a first step, and a second step in which zinc sulfide containing an activator is obtained from a molten salt of thiourea and a zinc salt, and The obtained zinc sulfide is subjected to low temperature treatment in either an inert atmosphere or a sulfiding atmosphere, and in the third step, the zinc sulfide obtained from the second step is treated in either an inert atmosphere or a sulfiding atmosphere. The present invention provides a method for manufacturing a zinc sulfide phosphor, which is characterized by high-temperature treatment. In the second step, specifically, the activator-containing zinc sulfide obtained in the first step is heated in an inert atmosphere (
N2 gas, Ar gas, etc.) and sulfidic atmosphere (CS2 gas,
The present invention provides a method for producing a zinc sulfide phosphor, which is characterized by performing low temperature treatment in a temperature range of 350 to 600° C. using either H2S gas, etc.). More specifically, in the third step, the zinc sulfide obtained in the second step is mixed in an inert atmosphere (N2 gas, Ar gas, etc.) and a sulfidic atmosphere (
C82 gas, H2S gas, etc.), 950 to 1
The present invention provides a method for producing a zinc sulfide phosphor, which is characterized by high temperature treatment in a temperature range of 250°C.

(Description of Examples) Example 1 Zinc chloride znC7!21 mol and thiourea C3 (NF2)
21.5 mol was placed in a flask at 500 mA, and 0.2 mol percent of cuprous chloride CuCjl and aluminum chloride Aj? CA13・6
140-15 while adding H20 and stirring inside the flask.
Heated to 0°C in an oil bath. When thiourea and zinc chloride have become molten salt, ammonia gas NH3 is added into the flask at a flow rate of 21/min while stirring the molten salt.
It was run for 0 minutes. After cooling, the powder obtained by this cooling was placed in a quartz tube furnace and subjected to low temperature treatment at 600°C for 1 hour in a hydrogen sulfide gas H2S atmosphere to remove components other than the phosphor. In a gas H2S atmosphere, 1150
High temperature treatment was performed at ℃ for 1 hour. Thereafter, in order to remove the excess copper compound, it was thoroughly washed with a 5 weight part sodium cyanide aqueous solution and pure water to obtain a copper- and aluminum-activated phosphor. The particle size distribution of the zinc sulfide phosphor thus obtained was measured using a scanning electron microscope.
Its distribution range was 20-7.0 μm. Using this phosphor, an EL light emitting device was fabricated using a conventional method, and its brightness was evaluated. A phosphor powder was dispersed in an acetone solution of cyanoethyl cellulose, and this mixture was coated on a glass substrate with a transparent electrode layer. The mixing ratio of cyanoethyl cellulose and phosphor was 1=1 in terms of volume ratio.

Furthermore, an insulating layer was formed using a mixture of titanium oxide powder dispersed in an acetone solution of cyanoethyl cellulose, and then a metal electrode was deposited to form an EL light emitting device.

The thicknesses of the light emitting layer and the insulating layer were 15 μm and 7 μm, respectively. When a 1kHz, 100V alternating current electric field was applied to this device, it emitted green light with a brightness of 11
It was 8fL.

Example 2 Zinc chloride ZnCA 21 mol, thiourea C3 (NF2)2
6- 1.5 mole plus zinc chloride ZnCA! Cuprous chloride CuC7 and aluminum chloride AβC13.6H20 were added in an amount of 03 mole percent based on 21 moles, and the flask was heated to 140 to 150° C. in an oil bath while stirring.

When thiourea and zinc chloride have become molten salt, while stirring the molten salt, add 2j! of ammonia gas NH3 into the flask. The solution was allowed to flow for 60 minutes at a flow rate of /min to precipitate zinc sulfide containing an activator. After cooling, this powder was placed in a quartz tube furnace and subjected to a low temperature treatment at 350°C for 1 hour in a nitrogen gas N2 atmosphere, and then a high temperature treatment at 950°C for 2 hours in a nitrogen gas N2 atmosphere, followed by a cyanide aqueous solution and pure water. Wash with
Copper and aluminum activated phosphors were obtained. The particle size distribution of this phosphor was 1.0 to 60 μm. Using this phosphor, an EL light emitting device was produced in the same manner as in Example 1. The thickness of the insulating layer of the light emitting layer 1 was 14 μm and 13 μm. When a 1 kHz, 100 V alternating current electric field was applied to this device, it emitted green light with a brightness of 90
It was fL.

Comparative Example 1 For comparison, a method discovered by the present inventors for producing a zinc sulfide phosphor by washing with pure water will be described as a comparative example. That is, 21 moles of zinc chloride ZnCA and 21.5 moles of thiourea C3 (NH2) were placed in a flask, and cuprous chloride and aluminum chloride were added in an amount of 0.2 moles per 1 mole of zinc chloride. 140-1
Heated at 50°C. When thiourea and zinc chloride have become molten salt, while stirring, add 2 ammonia gas.
It was run for 60 minutes at a flow rate of 13/rn i n. After cooling,
After washing with pure water, it was dried at 150°C. This powder was placed in a quartz tube furnace at 750°C in a hydrogen sulfide gas atmosphere.
After treatment at 1150° C. for 0.5 hour and 1 hour at 1150° C., the phosphor was obtained by washing with a cyan aqueous solution and pure water. The particle size distribution of this phosphor was 20 to 7.0 μm, and Example 1
An EL light emitting device was manufactured in the same manner as described above. The thicknesses of the light emitting layer and the insulating layer were 15 μm and 7 μm, respectively. 1k
Hz.

When an alternating current electric field of 100 V was applied, it emitted green light with a luminance of 100 fL.

Comparative Example 2 For comparison, a zinc sulfide phosphor was obtained using a method slightly different from that of Comparative Example 1. That is, 1 mole of zinc chloride,
0 for 1.5 mole of thio element and 1 mole of zinc chloride
．． Add 3 moles of cuprous chloride and aluminum chloride,
It was heated to 140-150°C while stirring. When thiourea and zinc chloride became molten salt, ammonia gas was flowed at a flow rate of 2j+/min for 60 minutes while stirring.
Zinc sulfide containing an activator was deposited. After cooling and washing with pure water, this powder was heat-treated at 950°C for 2 hours in a nitrogen gas atmosphere in a quartz tubular furnace, and then treated with a cyanide aqueous solution,
A phosphor was obtained by washing with pure water. The particle size distribution of this phosphor was 1.5 to 6.0 μm.
An L-light emitting device was fabricated. The thicknesses of the light emitting layer and the insulating layer were 14 μm and 7 μm, respectively. l kHz to this device
, when an AC electric field of 100V was applied, it emitted green light,
Its brightness was 75 fL.

As is clear from the above Examples and Comparative Examples, the zinc sulfide phosphor obtained by the present invention has higher brightness than that of the Comparative Example.

9- Note that the low temperature treatment temperature is preferably 350 to 600°C.

This temperature ranges from the sublimation temperature of by-products such as ammonium chloride to a temperature at which the adhesion of decomposition products such as carbon has little effect. Further, the high temperature treatment temperature is preferably 950 to 1250°C. This temperature ranges from a temperature above which the particle size is relatively large and high brightness can be expected, to a temperature at which sublimation of the zinc sulfide matrix is small.

(Effects of the Invention) The zinc sulfide phosphor obtained by the method of the present invention has a smaller and more uniform particle size than that obtained from a conventional zinc sulfate aqueous solution, and also has thiourea It has the advantage of higher brightness than a zinc sulfide phosphor obtained by washing zinc sulfide obtained from a molten salt of zinc salt, an activator, and ammonia with pure water, drying it, and then treating it at high temperature. Since the zinc sulfide phosphor obtained by the method of the present invention has the above-mentioned advantages, when used as a phosphor for an EL light-emitting device, for example, a homogeneous and thin light-emitting layer can be easily formed. It is possible to achieve low voltage, high brightness, ease of manufacture, reliability, etc.

Patent applicant: Matsushita Electric Industrial Co., Ltd. 11-

Claims (2)

[Claims] (1) A first step of melting and mixing a mixture of thiourea, ammonium salt, and an activator, and adding ammonia to the mixture to precipitate zinc sulfide containing an activator in the melt;
A second step in which the zinc sulfide obtained in the step is subjected to low temperature treatment in either an inert atmosphere or a sulfuric atmosphere to remove components other than the phosphor; A method for manufacturing a zinc sulfide phosphor, comprising a third step of treating the zinc sulfide obtained at high temperature in either an inert atmosphere or a sulfiding atmosphere. (2) A second step in which the low temperature treatment temperature is maintained in the range of 350 to 600 °C, and the high temperature treatment temperature is maintained in the range of 950 to 12 °C.
A method for producing a zinc sulfide phosphor according to claim 1, which comprises a third step of maintaining the temperature in a range of 50°C.