JP2000080363A - Preparation of green light-emitting phosphor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for preparing at a low temperature a green light-emitting phosphor excellent in fluorescent intensity. SOLUTION: In a process for preparing a ZnGa2O4:Mn green light-emitting phosphor, a base is added to a solution containing a gallium component to precipitate a hydroxide, which is converted to a GaO(OH) precipitate by heat treatment of the solution, and the precipitate is subsequently dispersed in an aqueous solution of a zinc compound containing a manganese component, to which is added oxalic acid and a base to give mixed precipitates, which are filtered, dried and burned.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a green light-emitting phosphor, and more particularly, to a precipitate obtained by adding a base to a solution containing a gallium component and subjecting the solution to heat treatment and hydrolysis. After dispersing in a solution containing zinc and manganese components and adding oxalic acid to precipitate the zinc and manganese components in oxalate, ZnGa ₂ O ₄ : Mn green by a wet precipitation method in which the mixed precipitate is dried and heat-treated. The present invention relates to a method for manufacturing a light emitting phosphor. The production temperature of the phosphor powder is low, the particles are columnar, the powder has no cohesiveness, and the uniform distribution of manganese, which is an activator, makes the emission intensity extremely excellent compared to the conventional production method. Suitable for electronic display tubes as a phosphor, FED (Field Emission Discharge)
The present invention relates to a new method for producing a green light-emitting phosphor that is excited by an electron beam and exhibits an emission spectrum in the visible region, as widely used in the display industry such as VFD (Vacuum Fluorescence Display).

[0002]

2. Description of the Related Art In the display industry, much research has been conducted on phosphors for electronic display tubes, which are used as a core material in realizing various light colors. Among them, ZnGa having a spinel structure and a low-voltage driven ZnGa with manganese as an activator based on ZnGa ₂ O ₄
Studies on the emission characteristics of ₂ O ₄ : Mn phosphor have been conducted.
In general, it is known that the emission characteristics of a phosphor largely depend on the size and crystal structure of particles. In order to improve the emission characteristics, a new base material and a method for manufacturing a phosphor have been developed. Conventionally, ZnGa ₂ O ₄ : Mn Phosphor has been produced in powder form by a solid-state reaction method in which raw materials are mixed and heat-treated to produce the phosphor.However, the above process requires a high temperature in the final firing process. Since the application causes the phosphor particles to aggregate, the surface of the phosphor is damaged during the crushing operation necessarily included in the process of manufacturing the phosphor, for example, a crushing operation such as ball milling, and the surface of the phosphor is damaged. In addition, there is a problem that the emission intensity is lost due to the formation of a dead layer and the mixing of impurities. In addition, when producing ZnGa ₂ O ₄ : Mn phosphor by a solid-state reaction method, by applying a high firing temperature, volatilization of ZnO and Ga ₂ O ₃ by a high vapor pressure causes various serious problems. Therefore, in order to reduce the volatilization of the above components, a method for producing a ZnGa ₂ O ₄ : Mn phosphor at a low temperature is required. Therefore, other manufacturing methods that can replace the conventional solid phase reaction method are urgently required. On the other hand, in order to produce a phosphor with high efficiency, it is necessary to control the size, pattern and uniform distribution of the activator in the matrix lattice. Therefore, a new manufacturing method capable of manufacturing a phosphor powder having uniform particles and good crystallinity from such a viewpoint is urgently required.

[0003]

SUMMARY OF THE INVENTION The present inventors have developed ZnGa ₂ O
_In view of improving the emission characteristics of the ₄ : Mn phosphor, if the ZnGa ₂ O ₄ : Mn phosphor is produced by a wet precipitation method, even if the phosphor is formed at a low temperature, green light emission with extremely excellent emission intensity is obtained. It has been found that a phosphor can be obtained, and the present invention has been completed. Accordingly, an object of the present invention is to provide a ZnGa ₂ O ₄ : Mn phosphor by a wet precipitation method, in which the phosphor is formed at a lower temperature compared to the conventional method, and the powder particles are coherent as a constant columnar shape. It is another object of the present invention to provide a method for producing a green light-emitting phosphor having excellent fluorescence intensity by a uniform distribution of an activator.

[0004]

According to the present invention, there is provided a method for producing a ZnGa ₂ O ₄ : Mn green light-emitting phosphor, wherein a base containing a gallium component is added to precipitate a hydroxide, and the solution is subjected to a heat treatment. After converting to a GaO (OH) precipitate by dispersing the precipitate in an aqueous solution of a zinc compound containing a manganese component and adding oxalic acid and a base, the mixed precipitate obtained is filtered, dried and calcined. It is a method of manufacturing the body.

[0005] The present invention will be described in more detail as follows. According to the method for producing a green light-emitting phosphor according to the present invention, a base is added to a solution containing a gallium component to precipitate a hydroxide by a wet precipitation method, the mixture is heat-treated, and this is hydrolyzed to obtain a Ga.
After converting to O (OH), the precipitate was filtered and dispersed in a solution containing zinc and manganese.An oxalic acid solution was added thereto, and the pH was adjusted with a base to remove zinc and manganese from oxalic acid. This is a method for producing a ZnGa ₂ O ₄ : Mn phosphor by precipitating as a salt, filtering and drying, and then heat-treating in air and a reducing atmosphere. ZnGa ₂ O ₄ produced according to the present invention:
The Mn phosphor is formed as a single phase at a low temperature of 700 ° C., has a uniform columnar shape with no agglomeration of powder particles, and exhibits an extremely excellent green emission intensity in the visible region when excited by an electron beam.

[0006] The phosphor of the present invention can be produced by the above method using a gallium compound, a zinc compound and a manganese compound as raw materials. In the production method according to the present invention, a base is first added to a solution containing a gallium component to precipitate the hydroxide. Examples of the gallium compound for producing the solution containing the gallium component include at least one selected from an aqueous solution of gallium nitrate, gallium sulfate or gallium chloride and a solution of gallium metal dissolved in nitric acid or hydrochloric acid. From a solution containing the gallium component, ZnGa ₂ O _4: Gallium components as the mixing ratio by the composition of Mn, it is desirable to have a concentration of 0.01～5M. If the concentration of the gallium component is less than 0.01M, the amount of water and energy to be used becomes excessive, which is uneconomical. If the concentration exceeds 5M, stirring and filtration of the formed precipitate becomes difficult. There is a problem.

At this time, it is necessary to adjust the pH of the solution to 5 or more in order to completely precipitate the gallium component.
In particular, it is desirable to adjust the range to 6 to 9. Bases added to precipitate the gallium component include aqueous ammonia, sodium hydroxide, organic amines, and the like, but any base from which the gallium component is precipitated can be used. The precipitated gallium hydroxide is heated and hydrolyzed at 80 to 110 ° C. for 0.5 to 4 hours while stirring in a solution state, and then filtered to obtain a GaO (OH) precipitate. . The GaO (OH) precipitate is dispersed in the aqueous zinc compound solution containing the manganese component.

The aqueous solution of a zinc compound containing a manganese component used in the above process is a mixture of a zinc compound solution and a manganese compound solution. As the zinc compound, one or more selected from an aqueous solution of zinc acetate, zinc chloride, zinc nitrate or zinc sulfate or a solution of zinc metal or zinc oxide dissolved in nitric acid, hydrochloric acid or sulfuric acid is used. Also,
As the manganese compound, water-soluble manganese acetate,
One or more selected from manganese chloride, manganese nitrate and manganese sulfate are used. At this time, the zinc component of the aqueous zinc compound solution containing a manganese component according to the composition was 0.01.
It is preferable to have a concentration of 5 to 5M, and preferably 0.1 to 5M.
Maintain a concentration of 3M. Further, the concentration of manganese used as an activator for the base is preferably in the range of 0.01 to 3 mol%. If the concentration of manganese is less than 0.01 mol% or more than 3 mol%, there is a problem that the emission intensity becomes weak.

To precipitate the zinc and manganese components from the aqueous solution of the zinc compound containing the manganese component in which the GaO (OH) precipitate is dispersed, an oxalic acid solution and a base are added to precipitate the zinc and manganese components.
Is adjusted in the range of 6 to 10, preferably 7 to 9 to precipitate without loss of zinc and manganese components. At this time, the oxalic acid used is suitably in an equivalent ratio of 100 to 110% with respect to the zinc component contained in the solution. The oxalic acid solution is prepared by dissolving oxalic acid in water or alcohol to a concentration of about 1 M, and the base is one of organic amines selected from organic amines such as diethylamine, diethanolamine and triethylamine in order to prevent loss of the zinc component. The above is used.

Subsequently, the mixed precipitate of gallium, zinc and manganese produced above is filtered and dried, and the dried product is filled in a heat-resistant container of a crucible, and 700 to 1,3 in air.
It calcinates for 1 to 10 hours under the condition of 00 ° C. In order to reduce the manganese component as an activator, re-burning is performed again for one hour under the condition of 700 to 1200 ° C. and a weak reducing atmosphere using a mixed gas of hydrogen / nitrogen or carbon monoxide / carbon dioxide. As a result, a ZnGa ₂ O ₄ : Mn phosphor powder is obtained. As mentioned above, the Zn according to the present invention
The method of producing the Ga ₂ O ₄ : Mn phosphor differs from the conventional method in that the phosphor is produced in a single phase at a low temperature of 700 ° C. and forms columnar powder particles without aggregation. These particles show excellent green emission intensity due to the uniform distribution of activator, and are suitable for electronic display tubes as a phosphor for low voltage, FED,
As widely used in the display industry and the like, such as VFD, it has the feature of exhibiting an emission spectrum in the visible region when excited by an electron beam.

From the final baking stage, ZnGa ₂ O ₄ : Mn heat-treated under the conditions of air and a reducing atmosphere at 800 ° C.
According to the analysis result of X-ray diffraction of the phosphor powder,
As shown in FIG. 1, solid phase reaction method [J.
Electrochem. Soc. 141. 1950 (1994)], it was confirmed that a phosphor was formed at a temperature lower than 1,100 ° C. Further, from the result of observing the ZnGa ₂ O ₄ : Mn phosphor powder manufactured according to the present invention with a scanning electron microscope (SEM), as shown in FIG. 2, the phosphor particles did not agglomerate, It was confirmed that it had a certain columnar shape.

On the other hand, the ZnGa ₂ O ₄ : Mn phosphor according to the present invention is excited by an electron beam of 254 nm, and the concentration of manganese and the emission intensity of the phosphor are determined from the phosphor produced by the conventional solid-phase reaction method. As a result of the comparison, as shown in FIG. 3, both of them exhibited the maximum emission intensity when the concentration of manganese was 0.5 mol%. In contrast, the fact that the phosphor according to the present invention exhibited extremely excellent green light emission intensity over the entire manganese concentration indicates that manganese, which is the activator, was evenly distributed in the matrix. Further, according to the production method of the present invention
As a result of confirming the green emission of the ZnGa ₂ O ₄ : Mn phosphor, as shown in FIG. 4, it was confirmed that the phosphor exhibited a green emission spectrum peculiar to manganese ion having an emission center at a wavelength of 505 nm. Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples.

[0013]

EXAMPLE 1 Aqueous ammonia was added to 200 ml of gallium nitrate solution having a concentration of 1 M, and the pH of the solution was adjusted to 8 to precipitate gallium hydroxide. The precipitate was converted into a GaO (OH) precipitate by hydrolysis under a condition of 90 ° C. for 2 hours while stirring the precipitate in a solution state. The precipitate is filtered and contains 0.905 mol of manganese nitrate, 0.9.
A solution of oxalic acid at a concentration of 95M and 100 ml of oxalic acid aqueous solution was added, and while stirring, diethylamine was gradually added to adjust the pH of the solution to 8.
8, stirred for 1 hour and filtered to obtain a mixed precipitate of gallium, zinc and manganese. The mixed precipitate was dried at 80 ° C. for 4 hours and then placed in an alumina crucible and calcined with air at 800 ° C. for 4 hours. 5% hydrogen /
The mixture was fired again for 1 hour under a reducing atmosphere of a mixed gas of nitrogen and 800 ° C. to obtain a target phosphor powder. The phosphor had a composition of ZnGa ₂ O ₄ : 0.005Mn, and showed a green emission spectrum having an emission center at 505 nm as shown in FIG. 4 under excitation by a cathode ray at an acceleration voltage of 800 V.

[0014]

Examples 2 to 5 The same procedure as in Example 1 was carried out except that the composition of the phosphor was as shown in Table 1 to produce a phosphor powder. Table 1 also shows the emission intensity according to the composition of the phosphor.

[0015]

[Table 1]

[0016]

[Comparative Example 1] ZnO 4.980 g Ga ₂ O ₃ 11.529 g MnCO ₃ 0.035 g The above-mentioned high-purity raw material was wet-mixed with 20 ml of ethanol, evaporated and dried, and then placed in an alumina crucible at 1,100 ° C in an air atmosphere. For 4 hours, and again for 1 hour under a reducing atmosphere of a 5% hydrogen / nitrogen mixed gas and 900 ° C. The final fired product was pulverized to produce a phosphor powder. The composition of the obtained phosphor was ZnGa ₂ O ₄ : 0.005Mn, and the accelerating voltage was 800V.
A green emission spectrum having an emission center at 505 nm was shown under the excitation with a cathode ray. The emission intensity according to the composition of the phosphor is shown in Table 2.

[0017]

Comparative Example 2-5 A phosphor powder was manufactured in the same manner as in Comparative Example 1 except that the composition of the phosphor was as shown in Table 2. Table 2 also shows the emission intensity depending on the composition of the phosphor.

[0018]

[Table 2] According to the results of comparing the above Examples 1 to 5 and Comparative Examples 1 to 5, the phosphor according to the production method of the present invention has a much higher emission intensity than the phosphor produced by the conventional method, In particular, it was confirmed that the composition of ZnGa ₂ O ₄ : 0.005Mn showing the maximum light emission intensity showed about twice the green light emission intensity.

[0019]

As described above, the ZnGa ₂ O ₄ according to the present invention:
The new manufacturing method of Mn phosphor is different from the conventional manufacturing method.By manufacturing the phosphor at low temperature, the volatilization of zinc and gallium components is suppressed, and the reproducible physical properties of the phosphor are expected. It is also effective in preventing environmental pollution. In particular, while having a uniform columnar particle shape without agglomeration, it has extremely excellent brightness compared to the conventional method, is suitable for electronic display tubes as a low voltage driving phosphor, and is a useful effect widely used in the display industry and the like. There is.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction diagram of a ZnGa ₂ O ₄ : 0.005Mn phosphor manufactured according to Example 1.

FIG. 2 is a scanning electron micrograph of ZnGa ₂ O ₄ : 0.005Mn phosphor powder particles manufactured according to Example 1.

FIG. 3 is a graph showing the emission intensity of the ZnGa ₂ O ₄ : Mn phosphor according to the present invention and the phosphor prepared by a conventional solid-state reaction method depending on the concentration of manganese as an activator.

FIG. 4 is an emission spectrum of a ZnGa ₂ O ₄ : 0.005Mn phosphor produced according to Example 1.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor He Dong Parc Korea 305-333 Daejeon Yusun-Ku-Waughn-Dong (No address) Hanbit Apartment 111-501

Claims (5)

[Claims] In a method for producing a ZnGa ₂ O ₄ : Mn green light-emitting phosphor, a base is added to a solution containing a gallium component to precipitate a hydroxide, and the solution is subjected to a heat treatment to obtain a GaO (O 2
H) After converting into a precipitate, the precipitate is dispersed in an aqueous solution of a zinc compound containing a manganese component, and oxalic acid and a base are added. The mixed precipitate obtained is filtered, dried and calcined, and is characterized by a green color. A method for producing a light emitting phosphor. 2. The solution containing a gallium component is selected from a solution of gallium nitrate, gallium sulfate or gallium chloride aqueous solution and metal gallium dissolved in nitric acid or hydrochloric acid.
2. The method for producing a green light-emitting phosphor according to claim 1, wherein the number is at least one kind. 3. The method according to claim 1, wherein the heat treatment is performed at 80 to 110 ° C. for 0.5 to 4 hours. 4. The zinc compound aqueous solution containing a manganese component is one selected from an aqueous solution of zinc acetate, zinc chloride, zinc nitrate or zinc sulfate, and a solution of zinc metal or zinc oxide dissolved in nitric acid, hydrochloric acid or sulfuric acid. The method for producing a green light-emitting phosphor according to claim 1, wherein the manganese component is contained in an amount of 0.01 to 3 mol%. 5. The method according to claim 1, wherein the sintering is performed in an air and reducing atmosphere.
The method for producing a green light-emitting phosphor according to claim 1, wherein the method is performed at a temperature of 0 to 1,300 ° C. for 1 to 10 hours.