JPS608071B2 - Method for producing zinc sulfide phosphor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a zinc sulfide-based luminescent material used in cathode ray tubes, etc. The present invention aims to provide a method for manufacturing a light body.

The inventor discovered that, for example, when crystals of basic zinc sulfide are precipitated from an acidic solution containing zinc ions, sulfate ions, and ammonium ions, the crystals form a plate shape (Tokukan Sho 53-83996). Public bulletin, Mochikai 1973
1826 Satoshi Publication).

We have also developed a method for manufacturing large-sized zinc sulfide-based photoluminescent materials having a plate-like shape using the above-mentioned basic zinc sulfide plate crystal powder as a raw material (Japanese Patent Application No. 66383/1983). On the other hand, when the zinc sulfide light material obtained by the above method and having a plate-like shape is used in a luminescent screen, the luminous efficiency of the luminescent screen is increased compared to conventional ones, and its strength is greatly improved. (Japanese Unexamined Patent Publication No. 126257/1982). This is due to the following reasons. Conventionally, the luminescent screen of a cathode ray tube is constructed by applying crab-like luminescent particles having a diameter of 5 to 10 Am and having a shape similar to a sphere to a thickness of 10 to several tens of micrometers on the front glass of the cathode ray tube.

Here, the brightness of a cathode ray tube largely depends on how the light-emitting screen's poppy/light film is formed, and it is necessary to extract the light from the light-trapping body as effectively as possible in front of the screen.

To achieve this, it is necessary to reduce the scattering and absorption of light within the saddle rays and increase the light transmittance of the rays. but,
In the conventional crab light screen, the light transmittance cannot be said to be high because the spherical particles are simply stacked on top of each other. On the other hand, in the case of plate-shaped zinc sulfide-based crab photons,
By laying out plate-shaped particles, it is possible to increase the light transmittance compared to the conventional case. The above is the reason why the efficiency of the luminescent screen is improved when the plate-shaped zinc sulfide-based crab luminescent material is used in the luminescent screen.

Conventional zinc sulfide lamps are obtained by adding an activator to a zinc sulfide precipitate formed by passing hydrogen sulfide into an aqueous zinc sulfate solution and firing the mixture in an atmosphere of hydrogen sulfide or the like.

In this method, the zinc sulfide obtained by precipitation is a fine powder, and even after the subsequent calcination process, the particle size remains between 5 and loA.
It is difficult to control the shape into a plate-like shape because it is almost spherical.
From the standpoint of mass production, it is considered almost impossible to produce plate-shaped, large-grained zinc sulfide-based crab phosphors using conventional methods. The present invention eliminates the various drawbacks of the conventional manufacturing method, and makes it possible to produce zinc sulfide-based crystals in large quantities and at low cost, and which has a powder characteristic of being plate-shaped and having high light transmittance in the thickness direction. The present invention provides a method.
More specifically, the present invention uses the basic zinc sulfide plate crystal powder described above as a raw material and further develops a method for producing large particle size plate zinc sulfide-based crab phosphors. The plate-shaped zinc sulfide-based crab phosphor powder is obtained by heat-treating basic zinc sulfide containing an activator.

This plate-shaped zinc sulfide-based crab light powder (the maximum length of the plate-shaped powder particles is 30 to 200 grains, and the thickness is around 10 grains)
is made of a sintered body of minute particles, and the thickness of the plate-like body is dominated by about 3 to 10 particles, although it varies slightly depending on various conditions such as processing. . The present invention aims to increase the light transmittance of the plate-shaped zinc sulfide powder itself by growing the particles constituting the sintered body to a large size to reduce the number of particles occupying the thickness direction of the plate-shaped zinc sulfide powder. That is. If the plate-shaped zinc sulfide powder with increased light transmittance is used as a luminescent material for forming a luminescent screen, the efficiency of the luminescent screen can be improved. The configuration of the present invention will be explained below.

By using plate-shaped crystals of basic zinc sulfide as the main raw material and reacting them with alkali metals during the heat treatment process, it is possible to obtain a plate-shaped zinc sulfide-based crystal with high light transmittance. .

The above-mentioned alkali metals have the effect of promoting the grain growth of the particles constituting the plate-shaped zinc sulfide crystalline bodies, and therefore, due to this action, the particles constituting the crystalline feeder grow larger.

As a result, about one particle occupies the entire thickness of the plate. The configuration of the present invention will be explained in more detail.

Plate crystals of basic zinc sulfate are used as the main raw material. An alkali metal compound is attached to the surface of this basic zinc sulfate plate crystal, and heat treated in a carbon disulfide atmosphere.
After that, a method of high-temperature heat treatment in an inert atmosphere or sulfidic atmosphere, or a low-temperature heat treatment of basic zinc sulfate plate crystals in a carbon disulfide atmosphere, and then an alkali metal compound is attached to the surface, Furthermore, a zinc sulfide-based crab phosphor having a plate shape and high light transmittance in the thickness direction can be obtained by heat treatment in an inert atmosphere or a sulfidic atmosphere, or by the above two methods. The plate-like crystals of basic zinc sulfate used as a raw material were crushed in an aqueous solution containing zinc sulfate and ammonia or urea.
It can be easily produced by slowly heating the resulting precipitate, classifying the disease, and drying it (Japanese Patent Application Laid-Open No. 53-83996, Japanese Patent Application Laid-Open No. 53-1989).
82698).

The powder crystal thus obtained has a hexagonal plate shape. In order to use this as a starting material for a crab photoreceptor, a predetermined activator such as Ag, Cu, Au, or the like may be added to the initial aqueous solution. Regarding low-temperature heat treatment in a carbon disulfide atmosphere, a carbon disulfide atmosphere is introduced into carbon disulfide (liquid at room temperature) using an inert gas (e.g. N2, Ar).
etc.) as a carrier gas, forming it as a source of carbon disulfide vapor. Further, the temperature of the low-temperature heat treatment may be 400° C. or higher, and the time period varies depending on the amount of basic zinc sulfate to be subjected to the low-temperature heat treatment. The supply rate (gas flow rate) of carbon disulfide vapor and the low-temperature heat treatment time are adjusted so that the amount of carbon disulfide supplied is greater than the stoichiometric amount required to convert basic zinc sulfate to zinc sulfide. determined. To attach an alkali metal compound to basic zinc sulfate or basic zinc sulfate sulfurized by low temperature heat treatment in a carbon disulfide atmosphere, add basic zinc sulfate or after low temperature heat treatment to an aqueous solution of an alkali metal compound. (zinc sulfide) and
After leaving it for about 30 minutes, it can be dried in an oven.

When barium chloride is used as the alkali metal compound, the concentration of the aqueous solution is 0.001 to 2.0 mol/
As long as it is within that range. The reason why it is preferable to stay within this range is as follows. That is, when the concentration is 0.001 mol/Z or more, the effect of promoting grain growth is observed, and the light transmittance in the thickness direction of the plate-shaped zinc sulfide increases. When plate-shaped zinc sulfide with increased light transmittance is used in a luminescent screen, the efficiency of the luminescent screen is improved. On the other hand, if the concentration exceeds 2.0 mol/〆, barium will settle into the zinc sulfide, or compounds other than zinc sulfide will be generated on the surface, resulting in a decrease in luminous efficiency. Note that the same can be said of other alkali metal compounds. Regarding high temperature heat treatment in an inert atmosphere or sulfidic atmosphere, the temperature of high temperature heat treatment is 1000 oo
If it is within the range of ~1200 qo, the effect of promoting particle growth due to the use of the alkali metal is recognized, and the transmittance in the thickness direction of the plate-shaped zinc sulfide increases.

The efficiency of the luminescent screen formed using the plate-shaped zinc sulfide is improved by the same method described above. The processing time is 0. It is sufficient if it is longer than insect time. Next, examples will be given and concretely explained.

Example 1 1 mole of zinc sulfate (high purity reagent) and 3 moles of urea (high purity reagent)
mol, plus aluminum sulfate and copper sulfate as activators,
When 10-2 atomic percent of each was dissolved in water, the temperature was gradually raised while praying, and the temperature was left at 9,000 ℃ for 3 hours, a white precipitate was obtained.

When this precipitate was separated in a furnace, washed with water, and dried at a temperature of 80 qo, a fine powder consisting of hexagonal plate-shaped basic zinc sulfate crystals with a maximum particle size of 300 square grains was obtained. This powder was subjected to low temperature heat treatment in a carbon disulfide atmosphere to obtain plate-shaped zinc sulfide powder. The conditions for the low temperature heat treatment were 50,000 and 5 hours. Thereafter, the zinc sulfide powder is soaked in an aqueous solution containing an alkali metal and dried in an oven. Barium chloride is used as the alkali metal compound, and its aqueous solution concentration is 0.06.
Mol/sleeve. A high-temperature heat treatment is performed on the material having the alkali metal attached to its surface as described above. The high temperature heat treatment was performed at 1100° C. for 1 hour in a hydrogen sulfide atmosphere. The plate-shaped zinc sulfide crab light body obtained as described above is made of a light feed body in which zinc sulfide particles with a maximum diameter of 20 to 60 mm are connected in a plane, and the thickness direction of the plate-shaped body is almost It was occupied by one particle, and the light transmittance was increased. The above-mentioned fin photoreceptor was coated on a glass substrate having a conductive film on its surface to a film thickness of 40 cm by a sedimentation method, irradiated with an electron beam at an acceleration voltage of 2 eV, and the luminescence emitted through the glass was measured. Conventional crab photon (crab photon ZnS with particle shape close to spherical)
The brightness was 1.7 times higher than that of the luminescent screen using the luminescent screen (u, AI). Furthermore, compared to the case of a luminescent screen using a plate-shaped zinc sulfide-based saddle light body that had not been subjected to the Alka IJ metal adhesion treatment, the brightness was 1.3 times higher. Example 2 Basic zinc sulfate was prepared in the same manner as in Example 1, immersed in an aqueous solution containing an alkali metal, filtered and dried, and the surface of the basic zinc sulfate was coated with an alkali metal. was attached.

After this, low-temperature heat treatment and high-temperature heat treatment were performed in a carbon disulfide atmosphere. The conditions for the low-temperature heat treatment and high-temperature heat treatment were the same as those in Example 1. The plate-shaped zinc sulfide crab phosphor obtained as described above has a maximum particle diameter of 20
~60 The zinc sulfide particles of the Buddha kite are made of a sintered body connected in a plane, and the thickness (approximately 10 mm) of the plate is as follows:
As in Example 1, the particles were occupied by almost one particle, and the light transmittance was increased. The above crab photoreceptor was coated on a glass substrate having a conductive film on its surface by a precipitation method, irradiated with an electron beam at an acceleration voltage of 20 keV, and the luminescence emitted through the glass was measured. Compared to the case of a luminescent screen using a conventional crab phosphor (crab phosphor ZnS:Cu,M having a nearly spherical particle shape), the brightness was 1.7 times higher. Furthermore, compared to the case of a luminescent screen using a plate-shaped zinc sulfide-based luminescent material that had not been subjected to an alkali metal adhesion treatment, the brightness was 1.3 times higher.
Examples 3 to 17 Using the same machine as in Example 1, plate-shaped zinc sulfide-based crab light bodies were produced.

However, during the manufacturing process, various changes were made in the type of alkali metal salt, the concentration of the aqueous solution of the salt, low-temperature heat treatment conditions, high-temperature heat treatment conditions, and the type of activator. Example 1 using the plate-shaped zinc sulfide crab light body obtained as described above
A luminescent screen was formed in the same manner as above, and the brightness was measured.

The results are shown in the table below. Note that the relative luminance in the table is a value compared with a luminescent screen using the same type of conventional crab light (a zinc sulfide crab light that is manufactured by a conventional method and has a spherical shape).

Further, the comparative example is a plate-shaped zinc sulfide-based crab-light material produced by a manufacturing method that does not use an alkali metal. As described above, according to the method of the present invention, a zinc sulfide-based crab light body having a plate-like shape and high light transmittance can be produced.

Claims (1)

[Claims] 1. A first step of heat-treating plate-shaped basic zinc sulfate containing an activator at 400 to 800°C in a sulfiding atmosphere to obtain a sulfide, and inactivating or sulfurizing the sulfide. 100 in sex
A second step of heat treatment at 0 to 1200°C for 0.5 hours or more, and an alkaline earth metal compound is attached in advance in at least one of the first step and the second step. A method for producing a featured zinc sulfide phosphor. 2. Claim 1, characterized in that in the first step, basic zinc sulfide containing an activator is immersed in an aqueous solution containing an alkaline earth metal compound, filtered, dried, and then heat treated. A method for producing a zinc sulfide-based phosphor. 3. The zinc sulfide-based phosphor according to claim 1, characterized in that in the second step, the sulfide is immersed in an aqueous solution containing an alkaline earth metal compound, filtered, dried, and then heat-treated. Production method. 4 The concentration of the alkaline earth metal compound in the aqueous solution is 0.00.
The method for producing a zinc sulfide-based phosphor according to claim 2 or 3, wherein the amount is in the range of 1 to 2 mol/l. 5. The method for producing a zinc sulfide-based phosphor according to claim 1, characterized in that an atmosphere containing carbon disulfide vapor or hydrogen sulfide is used as the sulfiding atmosphere.