JPS61293287A - Production of rare earth element oxide phosphor - Google Patents

Abstract

PURPOSE:To obtain the title phosphor which exhibits a high degree of luminance and is excellent in dispersion, by blending a mixture of calcined Y2O3 and/or Gd2O3 and EuO with a borate compd. and/or alkali metal compd. and calcining the blend, followed by pulverization. CONSTITUTION:A mixture of Y2O3 and/or Gd2O3 with Euo is subjected to pri mary calcination in an oxidative atmosphere at 1,300-1,500 deg.C to obtain a pri mary calcination product (a). 1 mol of component (a) and 1X10<-4>-4X10<-2> mol of a borate compd. (b) selected from among Li3BO3, Na3BO3, K3BO3, Ba2(BO3)2 and (NH3)3BO3 and/or 3X10<-4>-3X10<-2> mol of at least one alkali metal compd. (c) selected from among Li3PO4, LiF, LiCl and NaF are mixed and subjected to secondary calcination in an oxidative atmosphere at 1,200-1,400 deg.C, followed by pulverization.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to rare earth oxide phosphors, particularly y, o, :E
u or Gd, 0. : Concerning rare earth oxide phosphors such as Eu.

[Technical background of the invention and its problems]

Y, 03:Eu, Gd, O, :Eu, as red-emitting phosphors used in mercury vapor discharge lamps and projection cathode ray tubes.
(Y.

There are rare earth oxide phosphors such as Gd), O, etc.

Conventionally, there are two methods for manufacturing these rare earth oxide phosphors: a primary method.

[Conventional method 1] A raw material mixture containing a predetermined amount of yttrium oxide or gadolinium oxide as a raw material and europium oxide as an activator is placed in a crucible and heated and calcined in an oxidizing atmosphere in a temperature range of 1300° C. to 1600° C.

However, the phosphor obtained by this manufacturing method has the following problems.

First, the particle size of the phosphor obtained by pulverization varies widely, and the particle size distribution is wide.

Second, it contains a large amount of fine particle phosphor, which tends to fuse or aggregate.

Thirdly, the crystallinity of the phosphor particles is poor.

[Conventional method 2] Borate chloride or an alkali metal compound, etc., are further added and mixed as a flux to the raw material mixture obtained in Conventional method 1, and 1
30 minutes to 10 minutes within the temperature range of 200℃ to 1500℃
Heat for an hour.

However, the phosphor obtained by this manufacturing method has the following problems.

First, the fired body after heating and firing is hard and requires a long time to be pulverized.

Second, it is difficult to control the particle size of the phosphor.

This means that, for example, small-particle phosphors are desired for three-wavelength fluorescent lamps and large-particle phosphors are desired for projection type cathode ray tubes, but it is not easy to supply these demands.

Thirdly, as a result of the above, the luminance of the emitted light is insufficient and the productivity is poor.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and in particular, it is an object of the present invention to provide a method for producing a rare earth oxide phosphor that can increase luminance.

[Summary of the invention]

In order to achieve the above-mentioned purpose, the inventors have developed Y,O,:l
We investigated the manufacturing method of Eu phosphor and obtained the results shown in FIG.

That is, after pulverizing the primary fired product, barium borate is added and secondary firing is performed at 1300°C for 3 hours. (mol), and the vertical axis shows the luminance when barium borate is not added in both primary firing and secondary firing.
When the phase and luminance are taken, the result is as shown in curve (b).

As a comparative example, when the primary firing temperature was set to 1200°C, the result was as shown in curve (a), and the primary firing temperature was set to 1550°C.
When the temperature was changed to ℃, the result was as shown in curve (C).

As shown in FIG. 1, the luminance is improved by adding barium borate, and the amount added is preferably in the range of 3 x 10-4 mol to 3 x 10-2 mol.

The range of 1X10-' moles to 5X10-' moles is more preferable.Then, the amount of barium borate added is 3X10-' moles.
If the amount exceeds a molar amount, fusion between single particles of the phosphor occurs, resulting in poor dispersibility and particle shape distribution.

That is, the primary firing temperature of 1200° C., that is, curve (a), and that of 1550° C., that is, curve 1 (c), have lower luminance than that of the present invention, that is 1350° C., that is, curve (b). As a result of detailed experiments, if the primary firing is below 1200°C, the growth of the phosphor particles is insufficient, and if the primary firing exceeds 1500°C, fusion of single phosphor particles occurs, resulting in poor dispersibility, particle shape, and particle size distribution. I understand.

In addition, FIG. 2 similarly shows an example of the method for producing Y, 03:[Eu phosphor, in which after pulverizing the primary fired product, lithium fluoride is added and lithium borate is added and mixed, The relative luminance of the phosphor obtained by secondary firing at 1300''C for 3 hours and pulverization is shown in curve (d) for lithium fluoride and curve (e) for lithium borate.

As can be seen from FIG. 2, good characteristics are exhibited when the amount of lithium fluoride or lithium borate added is in the range of 3.times.10-' moles to 3.times.10-12 moles.

Next, the effect of adding a borate compound or an alkali metal compound in secondary firing will be explained.

That is, Table 1 shows the results obtained by the inventors' experiments. This table shows an example in which the primary firing temperature and the secondary firing temperature were each 1350°C, and barium borate was used as the flux, using Y2O,:Eu phosphor as an example.

Table 1 As can be seen from Table 1, the phosphors in which no fluxing agent was added in the primary firing and the fluxing agent was added in the secondary firing had high luminance.

This tendency is similar for other combinations of phosphors and additives.

[Embodiments of the invention]

(Example 1) Yttrium oxide 416.2g, europium oxide 3
3.8 g was dissolved in 6N nitric acid 20001d and kept at 70°C, and 900 g of oxalic acid was added thereto and stirred to obtain coprecipitated oxalate precipitate. This precipitate is washed with water, dehydrated, filtered,
After drying, the mixture is dried at 100°C to 200°C, placed in a quartz crucible, and heated at 1000°C for 2 hours to obtain a mixed rare earth oxide. This oxide is placed in a quartz crucible and subjected to primary firing at 1350° C. for 3 hours in the atmosphere.

Next, after crushing this primary fired product and sifting it,
Barium borate 0.28g for 150g of fired product
Added and mixed, packed in a quartz crucible, and heated in air for
Secondary firing is performed at 0°C for 3 hours.

Next, this secondary fired product was pulverized, washed with water, filtered, and dried to obtain a Y2O,:Eu phosphor.

Table 2 shows the results of evaluating the luminance of this phosphor by irradiating it with ultraviolet rays, and Table 3 shows the results of evaluating the brightness of the lamp when this phosphor was used in an annular fluorescent lamp. Tables 2 and 3 show comparative examples of similar phosphors that do not use a flux, that is, conventional method 1 and those that add gallium borate as a flux during primary firing and do not perform secondary firing. , that is, the conventional method 2 is shown in comparison.

(Example 2) Primary fired product 150 obtained by the same manufacturing method as Example 1
0.08 g of lithium fluoride is added and mixed with respect to g, and secondary firing is performed at 1200° C. for 3 hours. Next, this secondary fired product was pulverized, washed with water, filtered, and dried to obtain a Y□O,:Eu phosphor. Table 2 shows the results of evaluating the luminance of this phosphor by irradiating it with ultraviolet rays, and Table 3 shows the results of evaluating the brightness of the lamp when it was used in an annular fluorescent lamp.

(Example 3) A primary fired product is obtained through the same steps as in Example 1 using 668.2 g of gadolinium oxide and 33.8 g of europium oxide. To 150 g of this fired product, 0.28 g of barium borate was added and mixed, and secondary firing was performed at 1300°C for 3 hours.
, :Eu phosphor was obtained. Tables 2 and 3 show the luminance of this phosphor and the brightness used in the fluorescent lamp.

Table 2 Table 3 In the above embodiments, barium borate was mainly used as the flux added during secondary firing, but the flux is not limited to this, and lithium borate, sodium borate, potassium borate, ammonium borate, etc. Salt compounds, lithium phosphate, lithium fluoride, lithium chloride,
Almost the same effect can be obtained by using an alkali metal compound such as sodium fluoride, or both a borate compound and an alkali metal compound.

〔Effect of the invention〕

As described above, according to the production method of the present invention, a rare earth oxide phosphor with a narrow particle size distribution, good dispersibility (no super-aggregated particles), arbitrary particle diameters, and high brightness can be obtained. 6

[Brief explanation of drawings]

Figure 1 is a curve diagram showing the relative brightness according to the primary firing temperature and the amount of gallium borate between the examples of the present invention and comparative examples during primary firing, and Figure 2 is a rare earth phosphor obtained by crushing after secondary firing. FIG. 2 is a curve diagram showing the relationship between relative luminance and the amounts of lithium fluoride and lithium borate added during secondary firing.

Claims (1)

[Claims] A step of primary firing a raw material mixture containing at least one of yttrium oxide or gadolinium oxide and europium oxide in an oxidizing atmosphere within a temperature range of 1300°C to 1500°C, and a primary fired product 1 obtained by this primary firing. For moles, 1×10^-^4 moles to 4×
at least one borate compound of lithium borate, sodium borate, potassium borate, barium borate, ammonium borate in the range of 10^-^2 moles, and or from 3 x 10^-^4 moles to 3 x 10^-^2 At least one alkali metal compound of lithium phosphate, lithium fluoride, lithium chloride, and sodium fluoride is added and mixed in a molar range, and this mixture is mixed in an oxidizing atmosphere with a
A method for producing a rare earth oxide phosphor, comprising the steps of secondary firing within a temperature range of 200°C to 1400°C, and pulverizing the fired body.