JPH0841453A - Production of rare earth oxide-sulfide fluorescence body - Google Patents

Abstract

PURPOSE:To efficiently manufacture a rare earth oxide-sulfide fluorescence body having an improved particle size distribution. CONSTITUTION:This is a process for producing a rear earth oxide-sulfide fluorescence body expressed by the formula (Ln1-x, Ln'x)2O2S in which a raw material rear earth oxide, an alkali metal carbonate, an aluminum compound and a raw material S are mixed with each other and the mixture is burnt. In the formula, Ln is at lest one selected from La, Y, Gd and Lu; Ln' is at least one selected from Eu, Sm and Tb; x is a number satisfying the relation 0.001<=x<=0.2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor film surface of a cathode ray tube or the like, and more particularly to a rare earth oxysulfide phosphor suitable for forming a high-definition and pinhole-free dense phosphor film such as a cathode ray tube for a display. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Conventionally, a phosphor obtained by crystal formation by firing has a relatively wide particle size distribution, and when firing with a large amount of flux, a phosphor having a particle size distribution close to a normal distribution has been obtained. can get. When the fluorescent film is formed by the optical printing method, it is not preferable that a large amount of fine particles or coarse particles be present in order to obtain a dense and dense fluorescent film. These fine particles and coarse particles are removed by a classification operation as necessary, but the classification operation has poor workability and lowers the yield. In particular, the production of coarse particles leads to the yield of particles having a desired particle size. It has a great influence and cannot always be reliably removed. Therefore, in forming the fluorescent film for a high-definition cathode ray tube, it is important not to generate unnecessary fine particles and coarse particles, especially coarse particles during firing.

The rare earth oxysulfide phosphor is manufactured by a method of firing a predetermined amount of a rare earth compound together with a sulfurizing agent such as sulfur and a flux such as an alkali metal carbonate, but rare earth oxides and the like. When producing a rare earth oxysulfide phosphor by firing the compound with other raw materials, the particle growth of the phosphor is directly affected by the sulfiding agent, the flux and the firing temperature,
The particle size control was mainly based on the selection of the type and amount of flux and the firing temperature.

However, with these methods, the median particle size of the phosphor can be controlled, but the particle size distribution cannot be controlled. The only way to control the particle size distribution is
A method called a seed method (see Japanese Patent Application Laid-Open No. 3-252495) is known, but this method requires that a rare earth oxysulfide phosphor, which is the same product as the target phosphor, be separately manufactured. However, a total of two firings are required. Therefore, it was not possible to control the particle size distribution by one firing.

[0005]

Therefore, the present invention is intended to solve the above problems and to provide a method for efficiently producing a rare earth oxysulfide phosphor having an improved particle size distribution. .

[0006]

The present invention is based on the general formula (Ln
_1-x, Ln ^_'x) rare earth oxide represented by ₂ O ₃ or compounds to produce a rare earth oxide of the formula by heating or mixture, an alkali metal carbonate, an aluminum compound, and a raw material containing sulfur mixed formula and firing by _{(Ln 1-x, Ln '} x) is a ₂ O ₂ method for producing a rare earth oxysulfide phosphor represented by S. (However, L
n is at least one of La, Y, Gd and Lu, L
n ′ is at least one of Eu, Sm and Tb, and x is 0.001 ≦ x ≦ 0.2, preferably 0.00
It is a number that satisfies the condition of 5 ≦ x ≦ 0.1. )

[0007]

The present inventors can control the particle size distribution by firing once.
As a result of repeated research on various methods,
A sulfurizing agent, a fluxing agent of alkali metal carbonate and a specified amount of
By mixing with an aluminum compound and firing,
A complex oxide of an earth element and aluminum is generated first,
This composite oxide is a rare earth oxysulfide phosphor (Ln ₂O₂
Since the crystal grows as a growth nucleus of (S), the grain size is narrow.
Found that a rare earth oxysulfide phosphor with cloth can be obtained
did.

That is, in the method for producing a rare earth oxysulfide phosphor of the present invention, when the rare earth compound is fired together with a mixture containing an alkali metal carbonate, an aluminum compound and a sulfiding agent, LnAlO ₃ , Ln ₄ Al ₂ O ₃ , L
It is considered that rare earth aluminates such as n ₃ Al ₅ O ₁₂ are formed first. It is considered that all of these rare earth aluminates are generated from about 900 ° C. and become nuclei during the subsequent crystal growth of the rare earth oxysulfide phosphor. That is, since at least one of these rare earth aluminate salts that is initially formed serves as a growth nucleus of the rare earth oxysulfide phosphor, the particle size distribution of the formed phosphor is narrowed so that fine particles and coarse particles are not generated. It is thought to act on. Therefore, the conditions for forming these rare earth aluminates are important factors for narrowing the particle size distribution of the phosphor. Therefore,
As a result of various experiments, the present inventors have found that the preferable condition for the production of the rare earth aluminate is that firing is performed in the coexistence of an alkali metal carbonate and an aluminum compound.

The method for producing a rare earth oxysulfide phosphor of the present invention comprises a predetermined amount of the phosphor raw material, that is, (1) (Ln _1-x, L
(2) Li ₂ CO ₃ , N, a rare earth oxide represented by n ′ _x ) ₂ O ₃ , or a rare earth compound or mixture that forms the oxide by heating a rare earth oxalate, a hydroxide, or the like.
a ₂ CO ₃ , K ₂ CO ₃ or other alkali metal carbonate,
(3) Aluminum chloride compounds such as aluminum chloride and aluminum nitrate, and (4) Sulfur raw materials such as sulfur powder are essential raw materials, and if necessary, other firing aids such as potassium phosphate are added to thoroughly mix them. Then, it is packed in a heat-resistant container such as an alumina crucible and baked.

Among phosphor materials, (Ln _1-x, Ln '
_x ) ₂ O ₃ is a predetermined amount of Ln ₂ O ₃ or Ln ₂ by heating.
The compound of Ln which can be converted to O ₃ and the compound of Ln ′ ₂ O ₃ or Ln ′ which can be converted to Ln ′ ₂ O ₃ by heating may be simply mixed, but a mixture of these rare earth compounds is dissolved in a soluble solvent. After dissolution, oxalic acid, alkali such as NH ₄ OH, etc. are added to co-precipitate as oxalate, hydroxide, etc., which are heated and decomposed to form (Ln _1-X, Ln ^' _x ) ₂ O ₃ The rare earth oxide may be used.

In addition, Li ₂ CO ₃ , Na ₂ CO ₃ and K ₂
The blending amount of the alkali metal carbonate such as CO ₃ is (Ln _1-X,
Ln _{'x) 2} O ₃ 100 parts by weight of 10 to 100 parts by weight, preferably suitable range of 30 to 60 parts by weight. If it is less than 10 parts by weight, the crystal growth of the target rare earth oxysulfide will be insufficient, or a phosphor having a particle size and emission characteristics useful as a phosphor cannot be obtained, and if it exceeds 100 parts by weight, Although the quality of the phosphor is secured, it is not preferable because it deteriorates the equipment for baking the phosphor and the baking container.

Further, the blending amount of the aluminum compound is
(Ln_1-X,Ln '_x)₂O₃1 x 10 for 1 mole^-Four
~ 1 × 10^-2Gram atom, preferably 6 × 10^-Four~ 8 ×
10 ^-3A range of gram atoms is suitable, 10^-FourGram Hara
If the particle size is below the range, the effect of narrowing the particle size distribution of the obtained phosphor is
There are few fruits, 10^-2Beyond gram atom, 20μm
Luminescence of the obtained phosphor as the number of large particles exceeds
The brightness decreases.

The amount of the sulfur raw material compounded is at least stoichiometrically higher than the amount satisfying the composition formula (Ln _1-x, Ln ' _x ) ₂ O ₂ S.

The firing of these raw material mixtures is carried out in air at 1000 to 1300 ° C., preferably 1100 to 12
In the temperature range of 00 ° C., 0.5 to 5 hours, preferably 1 to
After firing for 3 hours, the obtained fired product is washed with an inorganic acid such as hydrochloric acid or sulfuric acid or water, dried, and sieved to obtain a desired rare earth oxysulfide phosphor.

In the method for producing a rare earth oxysulfide phosphor of the present invention, in order to further narrow the particle size distribution of the obtained phosphor and suppress the formation of coarse particles and fine particles, the phosphor material used It is more preferable that the alkali metal carbonate and the aluminum compound are mixed in advance, and the mixture is mixed with the remaining rare earth compound which is the raw material of the phosphor and the sulfiding agent and then baked.

[0016]

【Example】

 [Example 1] Y₂O₃226.0 g, Eu₂O₃1
5.1g was mixed and dissolved in nitric acid, and then added to this solution.
An oxalate salt was produced by the coprecipitation method by adding an acid.
Yield 60 minutes by firing at 00 ℃ for thermal decomposition, Y₂O₃And Eu₂
O₃And a mixed crystal oxide of A in this mixed crystal oxide
lCl₃・ 6H₂1.13 g of O (Y₂O₃And Eu₂O
₃4.48 × 10 per 1 mol^-3Equivalent to gram atom
Aluminum) to be mixed in an aqueous solution and dried.
After that, add 104.0 g of sulfur and Na to it.₂CO ₃(Melt
Agent) 72.0 g and K₃PO_Four(Baking aid) 11.0 g
Are mixed and put in an alumina crucible and baked at 1200 ° C for 1 hour.
After the obtained baked product is thoroughly washed with water, 1
The phosphor of Example 1 was obtained after drying at 20 ° C. for 10 hours.

[Example 2] Using the compounded raw material of Example 1,
Except that AlCl ₃ .6H ₂ O and Na ₂ CO ₃ are thoroughly mixed in advance, and then mixed crystal oxide of Y ₂ O ₃ and Eu ₂ O ₃ , sulfur and K ₃ PO ₄ are mixed. The phosphor of Example 2 was obtained in the same manner as in Example 1.

[Comparative Example 1] In Example 1, AlCl
But omitting the ₃ · 6H ₂ O in formulation, to obtain a phosphor of Comparative Example 1 in the same manner as in Example 1.

[Comparative Example 2] In Example 1, 72.0
A phosphor of Comparative Example 2 was obtained in the same manner as in Example 1 except that 36.7 g of NaCl was used instead of g of Na ₂ CO ₃ .

(Evaluation) When the particle size distributions of the phosphors of Examples 1 and 2 and Comparative Examples 1 and 2 were measured, the results shown in Table 1 were obtained. The phosphor of Example 1 manufactured by mixing an alkali metal carbonate and an aluminum compound in the phosphor raw material is the phosphor of Comparative Example 1 in which the compound of the aluminum compound is omitted, and
As compared with the phosphor of Comparative Example 2 in which the alkali metal carbonate was replaced with sodium chloride, it was found that there were few fine particles and coarse particles and the particle size distribution was narrow. Further, in the preparation of the phosphor raw material, the phosphor of Example 2 manufactured by previously mixing sodium carbonate and aluminum chloride and mixing this with another phosphor raw material has a particle size distribution larger than that of Example 1. It turns out that is narrower.

In Table 1, the column of particle size distribution is shown.
-Log (d₈₄/ D₅₀) And + log (d ₁₆/ D₅₀) Is cumulative
It shows the ratio of weight distribution, and the particle size on the small particle side.
The extent of the distribution spread and the size distribution of the large particles
It is a numerical value that serves as an index of the degree. The smaller the number,
The particle size distribution is narrow and there are few fine particles and coarse particles.
Means and. In particular, it shows the spread of the particle size distribution on the large particle side.
SU + log (d₁₆/ D₅₀If the value of) becomes 10% smaller, the yield
Is improved by about 2-4%, and coating properties are also significantly improved.
Is done. -Log (d₈₄/ D₅₀The smaller the value of), the coating characteristics
Is good.

[0022]

[Table 1]

[Examples 3 to 6 and Comparative Examples 3 to 5] In the same manner as in Example 1, except that only the compounding amount of AlCl ₃ .6H ₂ O in the compounding raw material of Example 1 was changed as shown in Table 2. Thus, the phosphors of Examples 3 to 6 and Comparative Examples 3 to 5 were manufactured, and the particle size distribution and the emission brightness of these phosphors were measured. The emission brightness was 100 when the emission brightness of each phosphor was excited by an electron beam with an accelerating voltage of 20 kV.
Was shown as a relative value.

(Evaluation) As can be seen from Table 2, 1 × 10
-Examples 7-9 with addition of Al in excess of ^-2 gram atom
Although the emission brightness of the phosphor of Example 1 was lowered, a phosphor having a narrow particle size distribution was obtained. On the other hand, it can be seen that the phosphors of Examples 3 to 6 have few fine particles and coarse particles and have excellent emission brightness.

[0025]

[Table 2]

[Embodiment 10] In the first embodiment, 22
The same amount of Gd ₂ O ₃ was used instead of 6.0 g of Y ₂ O ₃ ,
Instead of Eu ₂ O ₃ of 15.1 g 1.2 g of Tb ₂ O ₃
A phosphor of Example 7 was manufactured in the same manner as Example 1 except that was used.

[Comparative Example 2] In Example 10, AlC
but omitting the l ₃ · 6H ₂ O in formulation, to produce a phosphor of Comparative Example 2 in the same manner as in Example 10.

(Evaluation) When the particle size distributions of the phosphors of Example 10 and Comparative Example 2 were measured, the results shown in Table 3 were obtained. The phosphor of Example 10 using an alkali metal carbonate and an aluminum compound as a phosphor raw material has a narrower particle size distribution and less fine particles or coarse particles than the phosphor of Comparative Example 2 in which the aluminum compound is omitted. I understand.

[0029]

[Table 3]

[Embodiment 11] In Embodiments 1 to 9, a small amount of Tb is used together with a compound of Eu as an activator raw material for the phosphor.
In addition, a Sm compound was added as a co-activator raw material to produce a rare earth oxysulfide phosphor in the same manner as in Example 10. As a result, a phosphor having a narrow particle size distribution was obtained as in Example 10. Even when Ln is replaced with La or Lu, the particle size distribution of the obtained phosphor is as narrow as the above,
There were few fine particles and coarse particles.

[0031]

According to the present invention, by adopting the above-mentioned constitution, it is possible to reduce the content of fine particles and coarse particles, to obtain a rare earth oxysulfide phosphor having a narrow particle size distribution and excellent emission brightness. You can get it.

Claims (5)

[Claims] 1. A rare earth oxide represented by the general formula (Ln _1-x, Ln ^′ _x ) ₂ O ₃ or a compound or mixture which produces a rare earth oxide of the above general formula by heating, an alkali metal carbonate, aluminum. A compound of the general formula (Ln _1-x, L
n _'x) a method of producing a rare-earth oxysulfide phosphor represented by ₂ O ₂ S. (However, Ln is at least one of La, Y, Gd, and Lu, Ln ′ is at least one of Eu, Sm, and Tb, and x is 0.001 ≦ x ≦ 0.2. It is the number to meet.) 2. The method for producing a rare earth oxysulfide phosphor according to claim 1, wherein the alkali metal carbonate and the aluminum compound are mixed in advance and then the remaining raw materials are mixed. 3. The production of a rare earth oxysulfide phosphor according to claim 1, wherein the content of the alkali metal carbonate is 10 to 100 parts by weight based on 100 parts by weight of the rare earth oxide. Method. 4. The amount of the aluminum compound compounded is 1 × 10 ⁻⁴ to 1 × 10 ^{−2 with} respect to 1 mol of the rare earth oxide.
The method for producing a rare earth oxysulfide phosphor according to claim 1, wherein the phosphor is a gram atom. 5. The rare earth oxysulfide fluorescence according to claim 1, wherein x in the general formula of the rare earth oxide and the rare earth oxysulfide is in the range of 0.005 ≦ x ≦ 0.1. Body manufacturing method.