JPH0578660A - Method for producing fluorescent substance of rare earth element - Google Patents

Abstract

PURPOSE:To obtain the subject fluorescent substance of large particles suitable for large-sized color television, having high luminance in high yield by blending a specific oxide of rare earth element with S and a specific alkali carbonate- containing flux and a specific phosphate-containing flux followed by burning. CONSTITUTION:(A) An oxide (e.g. Y2O3 or Eu2O3) of rare earth element selected from Eu, Tb, Pr, Er and Sm is blended with (B) >=50wt.% based on total weight of the component A of sulfur, (C) >=50wt.% based on total weight of the component A of alkali carbonate flux selected from Na2CO3, K2CO3 and (K, Na)2CO3, and (D) an alkali metal phosphate (e.g. K3PO4 or Li3PO4) and 0.1-10wt.% based on total weight of the component A of ammonium hydrogen phosphate (e.g. NH2PO4) as a phosphate flux, and the prepared mixture, for example, is burnt at 1,100-1,250 deg.C for about 2-7 hours to give the objective fluorescent substance of the formula (Y, A)2O2S (A is Eu, Tb, Pr, Er or Sm).

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 rare earth oxysulfide phosphor which has large particles and emits red light with high brightness.

[0002]

2. Description of the Related Art In recent years, large-sized directivity has progressed in color cathode ray tubes, and in color display tubes, higher definition of dot or stripe size has been further advanced. Therefore, with respect to the phosphors used, it is required that large-sized tubes should have high brightness with large particles, and that color display tubes should have high-brightness with small to medium particles.

By the way, as a red phosphor for a color cathode ray tube, Y ₂ O ₂ S: Eu, which is a rare earth oxysulfide phosphor, is widely used, as is well known. The manufacturing technique of this rare earth oxysulfide phosphor is disclosed in Japanese Patent Publication No. 47-9562, and this method is most commercially established. Based on this method, various attempts have been made to improve the characteristics of the phosphor in order to meet the above requirements.

For example, until now, the addition of Mn (Japanese Patent Publication No. 47)
-13244), addition of Al (see Japanese Patent Publication No. 49-3572), addition of Sc (see Japanese Patent Application No. 63-101479), addition of V (see Japanese Patent Application No. 63-101480), etc. , It has been proposed to improve the brightness. Further, a method of substituting a part of the oxide raw material with a phosphate compound to increase the particle size and improve the brightness (see Japanese Patent Publication No. 51-35555), or La
To increase the particle size (see Japanese Patent Laid-Open No. 15793/1975), and a method of improving the brightness by using sodium pyrophosphate as a flux (Japanese Patent Publication No. 60-599).
No. 45) is proposed.

[0005]

As described above, various attempts have been made to improve the characteristics of the phosphor in order to satisfy the persistent image quality improvement requirements of the color CRT. However, recently, the required characteristics of the color cathode ray tube have become more severe, and it is required that the rare earth red phosphor used for the color cathode ray tube has larger particles and higher brightness. ing.

The present invention has been made in order to solve such a problem, and provides a method for producing a rare earth red phosphor which is capable of obtaining a large particle and high brightness rare earth red phosphor with good reproducibility. It is intended to be provided.

[0007]

Means and Actions for Solving the Problems A method for producing a rare earth red phosphor according to the present invention comprises firing a mixture of a rare earth oxide, sulfur, and a flux containing an alkali carbonate and a phosphate, (Y, Upon synthesizing rare-earth phosphor represented by a) ₂ O ₂ S, the (Y, a) as a rare-earth element phosphor represented by _{2 O 2 S, Eu, Tb} , Pr, from Er and Sm At least one selected element is used, and the sulfur and Na ₂ CO ₃ , K ₂ as the alkali carbonate flux are used.
At least one selected from CO ₃ and (K, Na) ₂ CO _{3 is} added in an amount of 50% by weight or more based on the total weight of the rare earth oxide, and the phosphate flux is an alkali metal phosphorus. An acid salt and 0.1 wt% to 10 wt% of ammonium hydrogen phosphate based on the total weight of the rare earth oxide are added.

That is, according to the present invention, a red phosphor having large particles and high brightness characteristics can be obtained by limiting the conventional flux amount and by using two kinds of phosphates together as a phosphate flux. It was made by finding that. The raw material composition used in the production method of the present invention is prepared by adding sulfur and an alkali carbonate flux to a rare earth oxide raw material, and further adding two kinds of phosphate fluxes of an alkali metal phosphate and ammonium hydrogen phosphate. It was done. Here, the alkali carbonate flux in the raw material composition, that is, Na ₂ CO
₃ , at least one alkali carbonate selected from K ₂ CO ₃ and (K, Na) ₂ CO ₃ is added to the rare earth oxide raw material at 50%.
It should be added in an amount of at least wt%. If the amount of the alkali carbonate flux added is less than 50% by weight with respect to the rare earth oxide raw material, the emission brightness cannot be sufficiently improved. However, if it exceeds 100% by weight, the fired product becomes too hard,
Processing after firing becomes difficult. Therefore, the amount of alkali carbonate flux added is 50% by weight with respect to the rare earth oxide raw material.
It is preferably in the range of up to 100% by weight.

Further, the sulfur in the raw material composition is 50% with respect to the rare earth oxide raw material, like the alkali carbonate flux.
It should be added in an amount of at least wt%. This is because alkali carbonate and sulfur form polysulfides in the crucible during firing, which react with rare earth oxides to form rare earth oxysulfides. Therefore, it is preferable to change the amount of sulfur as the amount of alkali carbonate flux added increases or decreases. However, it is not necessary to add the same amount as the alkali carbonate flux, and the addition amount can be changed within the range of 50% by weight to 100% by weight.

In the raw material composition used in the present invention, as described above, two kinds of phosphate fluxes of alkali metal phosphate and ammonium hydrogen phosphate are used.
By using an appropriate amount of two types of phosphate fluxes together, it is possible to satisfy both the large particle size and high brightness of the phosphor. That is, the crystal growth of the phosphor is favorably maintained by the alkali metal phosphate, and the phosphor hydrogen is made to have a large particle size by ammonium hydrogenphosphate.

As the alkali metal phosphate serving as the first phosphate flux, K ₃ PO ₄ , Li ₃ PO ₄ or the like is used. The amount of the alkali metal phosphate added is not particularly limited, but it is based on the rare earth oxide raw material.
It is preferably in the range of 3% by weight to 30% by weight.

Further, as ammonium hydrogen phosphate serving as the second phosphate flux, (NH ₄ ) ₂ H PO ₄ , NH
₄ H ₂ PO ₄ or the like is used. The amount of ammonium hydrogen phosphate added was 0.1% with respect to the total weight of the rare earth oxide raw material.
The range is from 10% to 10% by weight. If the amount of ammonium hydrogen phosphate is less than 0.1% by weight, the particle size will not be sufficiently large, and if it exceeds 10% by weight, the decrease in brightness will be significant. A more preferable addition amount is in the range of 1% by weight to 8% by weight.

In the rare earth phosphor represented by (Y, A) ₂ O ₂ S, the elements A are Eu, Tb, Pr, Er and Sm.
At least one element selected from shall be used. In addition, these A element raw materials have Eu in the range of 3 wt% to 8 wt% and Tb, Pr, and Er of 5 × 10 ^-4 wt% to the Y raw material.
It is preferably added in the range of 5 × 10 ⁻³ % by weight.

In the manufacturing method of the present invention, after thoroughly mixing the raw material compositions satisfying the above-mentioned conditions,
Fill this mixture into a heat-resistant container such as a crucible with a lid,
Bake at a temperature of about 1100 ℃ to 1250 ℃ for about 2 to 7 hours. After firing, the obtained fired product is washed with a water method and an aqueous solution of a mineral acid such as hydrochloric acid to obtain the desired rare earth red phosphor. There is no problem even if a coprecipitated product of Y ₂ O ₃ and AO is used as the rare earth oxide raw material.

[0015]

EXAMPLES Examples of the present invention will be described below.

Example 1 94.3 g of Y ₂ O ₃ containing 10 ppm of Tb, 5.7 g of Eu ₂ O ₃ and Na ₂ CO
₃ 60g, S 69g, K ₃ PO ₄ 11.5g and (NH ₄ ) ₂ H PO
The ₄ 3 g were mixed thoroughly, the resulting mixture was filled in an alumina crucible and fired for five hours at a temperature of 1160 ° C.. After firing
The fired product obtained was thoroughly washed with pure water and then washed 3 times with a 1% HCl solution. Further, it was washed with pure water until the pH became 5.5 or more, filtered, and dried at 150 ° C. for 8 hours.

When the particle size of the Y ₂ O ₂ S: Eu phosphor thus obtained was measured, it was confirmed that the average particle size was 7.5 μm and that the particle size was large. The average particle size is a value measured by the aeration method. Also, the above Y ₂ O ₂ S: Eu
The phosphor was subjected to the characteristic evaluation described below.

Comparative Example 1 94.3 g of Y ₂ O ₃ containing 10 ppm of Tb, 5.7 g of Eu ₂ O ₃ and Na ₂ CO
₃ 31g, S 37g and K ₃ PO ₄ 11.5g are thoroughly mixed,
The obtained mixture was filled in an alumina crucible and fired at a temperature of 1160 ° C for 5 hours. After firing, the obtained fired product was thoroughly washed with pure water and then washed 3 times with a 1% HCl solution. Further, it was washed with pure water until the pH became 5.5 or more, filtered, and dried at 150 ° C. for 8 hours.

When the particle size of the Y ₂ O ₂ S: Eu phosphor thus obtained was measured, the average particle size was 6.2 μm. In addition, the Y ₂ O ₂ S: Eu phosphor was subjected to the characteristic evaluation described later.

Comparative Example 2 94.3 g of Y ₂ O ₃ containing 10 ppm of Tb, 5.7 g of Eu ₂ O ₃ and Na ₂ CO
₃ 60 g, S 69 g and K ₃ PO ₄ 11.5 g are thoroughly mixed,
The obtained mixture was filled in an alumina crucible and fired at a temperature of 1160 ° C for 5 hours. After firing, the obtained fired product was thoroughly washed with pure water and then washed 3 times with a 1% HCl solution. Further, it was washed with pure water until the pH became 5.5 or more, filtered, and dried at 150 ° C. for 8 hours.

When the particle size of the Y ₂ O ₂ S: Eu phosphor thus obtained was measured, the average particle size was 6.3 μm. In addition, the Y ₂ O ₂ S: Eu phosphor was subjected to the characteristic evaluation described later.

Comparative Example 3 94.3 g of Y ₂ O ₃ containing 10 ppm of Tb, 5.7 g of Eu ₂ O ₃ and Na ₂ CO
₃ 60 g, S 69 g and (NH ₄ ) ₂ H PO ₄ 10 g were thoroughly mixed, and the resulting mixture was charged into an alumina crucible.
It was baked at a temperature of ℃ for 5 hours. After firing, the obtained fired product was thoroughly washed with pure water and then washed 3 times with a 1% HCl solution.
Further, it was washed with pure water until the pH became 5.5 or more, filtered, and dried at 150 ° C. for 8 hours.

When the particle size of the Y ₂ O ₂ S: Eu phosphor thus obtained was measured, the average particle size was 5.6 μm. In addition, the Y ₂ O ₂ S: Eu phosphor was subjected to the characteristic evaluation described later.

Example 2 94.3 g of Y ₂ O ₃ containing 10 ppm of Tb, 5.7 g of Eu ₂ O ₃ and Na ₂ CO
₃ 60g, S 69g, K ₃ PO ₄ 11.5g and (NH ₄ ) ₂ H PO
₄ 0.5 g was thoroughly mixed, and the obtained mixture was filled in an alumina crucible and fired at a temperature of 1160 ° C. for 5 hours. After firing, wash the obtained fired product thoroughly with pure water and then wash with 1% HCl.
The solution was washed 3 times. Further, it was washed with pure water until the pH became 5.5 or more, filtered, and dried at 150 ° C. for 8 hours.

When the particle size of the Y ₂ O ₂ S: Eu phosphor thus obtained was measured, the average particle size was 6.6 μm, which was a good value. In addition, the Y ₂ O ₂ S: Eu phosphor was subjected to the characteristic evaluation described later.

Example 3 94.3 g of Y ₂ O ₃ containing 10 ppm of Tb, 5.7 g of Eu ₂ O ₃ and Na ₂ CO
₃ 60g, S 69g, K ₃ PO ₄ 11.5g and (NH ₄ ) ₂ H PO
The ₄ 9 g was mixed thoroughly, the resulting mixture was filled in an alumina crucible and fired for five hours at a temperature of 1160 ° C.. After firing
The fired product obtained was thoroughly washed with pure water and then washed 3 times with a 1% HCl solution. Further, wash with pure water until pH becomes 5.5 or more, filter, and dry at 150 ° C for 8 hours.

When the particle size of the Y ₂ O ₂ S: Eu phosphor thus obtained was measured, the average particle size was 8.0 μm, which was a good value. In addition, the Y ₂ O ₂ S: Eu phosphor was subjected to the characteristic evaluation described later.

Example 4 94.3 g of Y ₂ O ₃ containing 10 ppm of Tb, 5.7 g of Eu ₂ O ₃ and (K, N
a) ₂ CO ₃ 50g, S 50g, K ₃ PO ₄ 11.5g and NH ₄ H ₂
3.3 g of PO ₄ was thoroughly mixed, the obtained mixture was filled in an alumina crucible, and the mixture was baked at a temperature of 1160 ° C. for 5 hours. After firing, wash the obtained fired product thoroughly with pure water and then wash with 1% HCl.
The solution was washed 3 times. Further, it was washed with pure water until the pH became 5.5 or more, filtered, and dried at 150 ° C. for 8 hours.

When the particle size of the Y ₂ O ₂ S: Eu phosphor thus obtained was measured, the average particle size was 7.9 μm, which was a good value. In addition, the Y ₂ O ₂ S: Eu phosphor was subjected to the characteristic evaluation described later.

Example 5 94.3 g of Y ₂ O ₃ containing 10 ppm of Tb, 5.7 g of Eu ₂ O ₃ and Na ₂ CO
₃ 80g, S 89g, K ₃ PO ₄ 11.5g and NH ₄ H ₂ PO ₄ 3.
3 g was thoroughly mixed, the obtained mixture was filled in an alumina crucible, and the mixture was baked at a temperature of 1160 ° C. for 5 hours. After firing, wash the obtained fired product thoroughly with pure water and then use a 1% HCl solution.
Washed 3 times. Further, it was washed with pure water until the pH became 5.5 or more, filtered, and dried at 150 ° C. for 8 hours.

When the particle size of the Y ₂ O ₂ S: Eu phosphor thus obtained was measured, the average particle size was 7.5 μm, which was a good value. In addition, the Y ₂ O ₂ S: Eu phosphor was subjected to the characteristic evaluation described later.

Example 6 Y ₂ O ₃ 94.3 g, Eu ₂ O ₃ 5.7 g, Na ₂ CO containing 20 ppm of Er
₃ 100g, S 100g, K ₃ PO ₄ 11.5g and NH ₄ H ₂ PO ₄ 3.
3 g was thoroughly mixed, the obtained mixture was filled in an alumina crucible, and the mixture was baked at a temperature of 1160 ° C. for 5 hours. After firing, wash the obtained fired product thoroughly with pure water and then use a 1% HCl solution.
Washed 3 times. Further, it was washed with pure water until the pH became 5.5 or more, filtered, and dried at 150 ° C. for 8 hours.

When the particle size of the Y ₂ O ₂ S: Eu phosphor thus obtained was measured, the average particle size was 7.7 μm, which was a good value. In addition, the Y ₂ O ₂ S: Eu phosphor was subjected to the characteristic evaluation described later.

Example 7 Y ₂ O ₃ 94.4 g, Eu ₂ O ₃ 5.3 g, Sm ₂ O containing 10 ppm of Pr
₃ 0.3g, K ₂ CO ₃ 55g, S 55g, Li ₃ PO ₄ 18g and
3 g of (NH ₄ ) ₂ H PO ₄ was thoroughly mixed, and the obtained mixture was filled in an alumina crucible and calcined at a temperature of 1160 ° C. for 5 hours. After firing, the obtained fired product was thoroughly washed with pure water and then washed 3 times with a 1% HCl solution. Furthermore, the pH can be adjusted with pure water.
It was washed to 5.5 or more, filtered, and dried at 150 ° C for 8 hours. When the particle size of the Y ₂ O ₂ S: Eu phosphor thus obtained was measured, the average particle size was 7.8 μm, which was a good value. In addition, the Y ₂ O ₂ S: Eu phosphor was subjected to the characteristic evaluation described later.

The emission brightness of each Y ₂ O ₂ S: Eu phosphor obtained in each of the above Examples and Comparative Examples was measured. The results are shown in Table 1 together with the average particle size. The emission brightness is shown as a relative value (%) when the emission brightness of the phosphor according to Comparative Example 1 is 100.

[0036]

[Table 1]

As is clear from the measurement results shown in Table 1, each of the Y ₂ O ₂ S: Eu phosphors obtained in the above Examples has large particles and has good characteristics with high brightness. ..

Further, a plurality of Y ₂ O ₂ S: Eu fluorescences were obtained under the same conditions except that the amount of ammonium hydrogen phosphate [(NH ₄ ) ₂ H PO ₄ ] in the raw material composition in Example 1 was changed. A body was prepared, and the average particle size and the emission brightness of these were prepared.
The results are shown in FIG. 1 as a relationship with the addition amount of ammonium hydrogen phosphate. The emission luminance is shown as a relative value when the phosphor of which the amount of ammonium hydrogen phosphate is zero (x = 0) is 100. As is clear from FIG. 1, both the average particle size and the emission brightness gradually increase with an increase in the amount of ammonium hydrogenphosphate, but it is understood that if the addition amount is excessively increased, the emission brightness is lowered. Therefore, the addition amount of ammonium hydrogen phosphate is appropriately in the range of 0.1 wt% to 10 wt% with respect to the rare earth oxide raw material.

[0039]

As described above, according to the method for producing a rare earth red phosphor of the present invention, it is possible to reproducibly obtain a large-particle and high-luminance phosphor suitable for a large-sized color cathode ray tube. Becomes

[Brief description of drawings]

FIG. 1 shows (NH ₄ ) in a raw material composition according to an embodiment of the present invention.
Is a graph showing the relationship between the average particle size of the light emission luminance in the case of changing the ₂ H PO ₄ amount.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Hiroyasu Yashima 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Electronic Engineering Co., Ltd.

Claims (1)

[Claims] 1. A method of firing a mixture of a rare earth oxide, sulfur, and a flux containing an alkali carbonate and a phosphate to synthesize a rare earth phosphor represented by (Y, A) ₂ O ₂ S, As the A element of the rare earth phosphor represented by (Y, A) ₂ O ₂ S, at least one selected from Eu, Tb, Pr, Er and Sm.
One element is used, and the sulfur and Na ₂ CO ₃ , K ₂ CO ₃ and (K, Na) ₂ C as the alkali carbonate flux are used.
At least one selected from O _{3 is} added in an amount of 50% by weight or more based on the total weight of the rare earth oxide, and as the phosphate flux, alkali metal phosphate and rare earth oxide are added. 0.1% by weight to total weight ~ 10
A method for producing a rare earth red phosphor, comprising adding ammonium hydrogenphosphate in a weight percentage.