JPH0458517B2 - - Google Patents

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, a phosphor for electroluminescence, and the like.

(Conventional structure and its 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, and are used in so-called electroluminescence light-emitting devices ( (hereinafter abbreviated as EL light emitting device), and many studies have been made on the host material, additives, firing conditions, etc. Particularly, to explain in detail about the EL light emitting device, the general device structure is shown in the drawing, which consists of a transparent electrode layer 4 as a front electrode, a light emitting layer 3 made of phosphor powder and a suitable binder component, an insulating reflective layer 2, It has a structure in which an electrode layer 1 etc. as a back electrode is laminated on a support substrate 5,
Light is emitted by applying an electric field between the front electrode 4 and the back electrode 1. The phosphor used in the above EL light emitting device is made of zinc sulfide powder with copper as an activator.
It is well known that aluminum, such as manganese, is added as a co-activator, or a halogen element such as chlorine, bromine, etc. and fired. Zinc sulfide, which is the base material for these materials, is generally obtained by the following method. For example, a method in which hydrogen sulfide is introduced into a zinc sulfate aqueous solution kept acidic using a buffer solution to saturate it to precipitate zinc sulfide, or a method in which thiourea or the like is added and reacted in an alkaline aqueous solution containing zinc ions. There is. However, the particle size of zinc sulfide powder obtained by these methods is distributed over a wide range, and in order to obtain a uniform particle size, various operations such as PH control must be performed during the manufacturing process, which is difficult. It is. Furthermore, zinc sulfide obtained by crystallization in an aqueous solution contains various ions. The influence of these ions on crystal growth must also be taken into account, which is one of the causes of increased complexity in the manufacturing process. Furthermore, when an activator or co-activator is added to the zinc sulfide powder obtained by this method and heat treated, abnormal grain growth tends to occur, making it difficult to obtain a zinc sulfide phosphor with uniform grain size. In terms of brightness, it is currently difficult to obtain high brightness unless grain growth is promoted to an average grain size of about 10 μm or more. When producing an EL light emitting device using the zinc sulfide phosphor obtained in this way, the thickness of the light emitting layer becomes large, a high electric field is required for light emission, and it is difficult to obtain a homogeneous film, resulting in poor reliability. This also caused increased difficulties in manufacturing.

(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 method for producing a zinc sulfide powder phosphor of the present invention includes a first step of melt-mixing thiourea, a zinc salt, and an activator to form a molten salt, and adding ammonia or hydroxide to the molten salt. a second step of reacting at least one kind of alkali to precipitate zinc sulfide containing the activator; and a third step of firing the zinc sulfide in either an inert atmosphere or a sulfidic atmosphere.
It is characterized by having the following steps.

Specifically, in the first step described above, thiourea, zinc salt, and activator are added and sufficiently mixed to prepare a molten salt. Next, in the second step, specifically, at least one of ammonia gas and alkali hydroxide is added to the molten salt produced in the first step, and an activator is added to the melt. The contained zinc sulfide is precipitated.

As a more specific example, copper and aluminum chlorides are added as activators for the purpose of obtaining a phosphor that emits green light, and copper and aluminum chlorides are added as activators for the purpose of obtaining a phosphor that emits orange light. and manganese chloride.

Furthermore, in the third step, specifically, the activator-containing zinc sulfide obtained in the second step is heated at approximately 750°C to 1150°C in either an inert atmosphere or a sulfiding atmosphere. Approximately 1 hour at a temperature range of
By baking for 30 minutes to 2 hours,
Create the desired zinc sulfide phosphor.

(Description of Examples) Example 1 1 mol of zinc chloride ZnCl ₂ and 1.5 mol of thiourea CS(NH ₂ ) ₂
mol in a 500 ml flask, and further added 0.2 mol percent of cuprous chloride CuCl and aluminum chloride AlCl ₃ 6H ₂ O to 1 mol of zinc chloride ZnCl 2 , and heated _the flask to 140-150°C while stirring. heated in an oil bath. When thiourea and zinc chloride have become molten salt, ammonia gas NH ₃ is added into the flask at 2/min for 60 min while stirring the molten salt.
It ran for a minute. After cooling and washing with pure water,
It was dried at about ℃. When the particle size distribution of the activator-containing zinc sulfide powder obtained in this way was measured using a scanning electron microscope, the distribution range was 0.2~
It was 0.4 μm. This powder was heated at 750°C in a quartz tube furnace in a hydrogen sulfide gas H ₂ S atmosphere at a temperature of 0.5
After heat treatment at 1150° C. for 1 hour, the product was thoroughly washed with a 5% by weight aqueous sodium cyanide solution and pure water to remove excess copper compound, thereby obtaining a copper- and aluminum-activated phosphor. The particle size distribution of this phosphor was 2.0 to 7.0 μm, and it emitted green light when irradiated with ultraviolet light. Using this fluorophore,
An EL light emitting device was fabricated and its brightness was evaluated. That is, phosphor powder was dispersed in an acetone solution of cyanoethylcellulose, and this mixture was applied onto a glass substrate with a transparent electrode layer. The blending ratio of cyanoethylcellulose and phosphor was 1:1 by volume.
Furthermore, an insulating layer was formed using a mixture of titanium oxide powder dispersed in an acetone solution of cyanoethylcellulose, and then metal electrodes were deposited to form an EL light-emitting device.
The thickness of the light emitting layer and insulating layer is 15μm and 7μm, respectively.
It was hot. When a 1kHz, 100V alternating current electric field was applied to this device, it emitted green light, and its brightness was
It was 100fL.

Example 2 Zinc chloride ZnCl ₂ 1 mol, thiourea CS(NH ₂ ) ₂ 1.5
In addition, 0.1 mol percent cuprous chloride CuCl and 2.0 mol percent manganese chloride MnCl ₂ 4H ₂ O were added to 1 mol of zinc chloride ZnCl 2 in a 500 ml flask, and the oil was heated to _150-160 ℃ with stirring. heated in the bath. When thiourea and zinc chloride had become a molten salt, ammonia gas NH ₃ was flowed into the flask at 2/min for 60 minutes while stirring the molten salt. After cooling, it was washed with pure water and then dried at 150°C. The particle size distribution of the activator-containing zinc sulfide powder thus obtained was 0.1 to 0.3 μm. This powder was heat-treated at 1000° C. for 2 hours in a nitrogen gas N ₂ atmosphere in a quartz tubular furnace, and then washed with an aqueous cyanide solution and pure water to obtain a copper- and manganese-activated phosphor. The particle size distribution of this phosphor was 1 to 5 μm, and it emitted orange light when irradiated with ultraviolet rays. Using this phosphor, an EL light emitting device was produced in the same manner as in Example 1. The thickness of the light emitting layer and the insulating layer are respectively
They were 13μm and 6μm. For this device, 1kHz, 100V
When an alternating current electric field was applied to it, it emitted orange light with a brightness of 35 fL.

Example 3 Zinc chloride ZnCl ₂ 1 mol, thiourea CS(NH ₂ ) ₂ 1.5
Furthermore, 0.3 mol percent cuprous chloride CuCl and aluminum chloride AlCl ₃ 6H ₂ O were added to 1 mol of zinc chloride ZnCl ₂ and heated to 140-150 °C in an oil bath while stirring inside the flask. . When thiourea and zinc chloride became a molten salt, sodium hydroxide (NaOH) was added into the flask while stirring the molten salt to precipitate zinc sulfide containing an activator. After cooling and washing with pure water, heat to 150℃.
It was dried. The particle size distribution of this powder was 0.2-0.4 μm. This powder was heat-treated in a quartz tube furnace at 1150°C for 2 hours in a hydrogen sulfide gas H ₂ S atmosphere, and then washed with a cyanide aqueous solution and pure water to obtain a copper- and aluminum-activated phosphor. . The particle size distribution of this phosphor was 3.0 to 8.0 μm, and it emitted green light when irradiated with ultraviolet rays. Using this phosphor, an EL light emitting device was produced in the same manner as in Example 1. The thicknesses of the light-emitting layer and the insulating layer were 18 μm and 7 μm. This device has 1k
When an AC electric field of 100 V at Hz was applied, it emitted green light with a brightness of 90 fL.

Comparative Example For comparison, hydrogen sulfide was introduced into an acidic zinc sulfate aqueous solution, as is conventionally done.
Zinc sulfide powder was obtained by saturation. Its particle size distribution was 0.1-1.8 μm. Furthermore, 0.2 mole percent each of copper sulfate and aluminum sulfate were added as activators to 1 mole of zinc sulfide, stirred wet, thoroughly dried, and heated in a quartz tube furnace.
After heat treatment at 1100℃ for 1 hour in a hydrogen sulfide gas atmosphere, it was washed with a cyanide aqueous solution and pure water.
A phosphor activated by copper and aluminum was obtained. The particle size distribution of this phosphor was 7 to 23 μm, and it emitted green light when irradiated with ultraviolet rays. Using this phosphor, an EL light emitting device was produced in the same manner as in Example 1. The thicknesses of the light emitting layer and the insulating layer were 40 μm and 10 μm, respectively. By applying an AC electric field of 1kHz, 100V,
It emitted green light with a brightness of 15fL.

As is clear from the above examples and comparative examples,
The zinc sulfide phosphor obtained by the method of the present invention has smaller and more uniform particle sizes than zinc sulfide powder obtained by conventional methods, and has high brightness. be.

In the examples, zinc chloride was used as the zinc salt, but it is clear that other zinc salts can provide the same effect. Further, although sodium hydroxide was used as the alkali hydroxide, the same effect can be obtained with other alkali hydroxides. Although copper, aluminum, copper, and manganese were used as the activated species, it goes without saying that similar effects can be obtained by using other activated species, such as halogen elements such as chlorine and bromine, or silver. stomach.

(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 conventional ones, and has high brightness. Since the zinc sulfide phosphor obtained by the method of the present invention has the above-mentioned features, when used as a phosphor for an EL light-emitting device, for example, a homogeneous and thin emitter layer can be easily formed. It is possible to achieve low voltage, high brightness, ease of manufacture, reliability, etc.

[Brief explanation of drawings]

The drawing is a configuration diagram of an electroluminescence light emitting device. DESCRIPTION OF SYMBOLS 1... Back electrode, 2... Insulation inversion layer, 3... Light emitting layer, 4... Front electrode (transparent electrode), 5... Support substrate.

Claims (1)

[Claims] 1. The first step of melt-mixing thiourea, zinc salt, and activator to form a molten salt, adding at least one of ammonia or alkali hydroxide to the molten salt.
A second step of reacting seeds to precipitate zinc sulfide containing the activator, and a third step of firing the zinc sulfide in either an inert atmosphere or a sulfiding atmosphere. A method for producing a zinc sulfide phosphor.