JPS6244033B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention provides high brightness during electron beam irradiation, and
The present invention relates to a lanthanum oxychloride phosphor having small variations. [Technical background of the invention and its problems] Terbium-activated lanthanum oxychloride phosphors have the advantage of high luminous efficiency when excited by electron beams or X-rays, especially when excited by electron beams. Therefore, it has been proposed to be used in the fluorescent screen of color cathode ray tubes (UK patent no.
1203124). When the present inventors adopted this phosphor as the green component of a color projection video device, the brightness was significantly improved compared to the conventionally used green projection tube using, for example, terbium-activated gadolinium oxysulfide. It was discovered that the green color component could be put to practical use as a green component of a color projection image device, and the patent application No. 57-201159 was filed. However, when a large quantity of the above-mentioned projection tubes was manufactured using this phosphor, it was found that the projection tubes had large variations in brightness on the phosphor screen, resulting in a decrease in product yield during manufacture. [Object of the Invention] The object of the present invention is to provide a lanthanum oxychloride phosphor that does not cause the above-mentioned problems. [Summary of the Invention] As a result of extensive research in order to eliminate the above-mentioned luminance variation phenomenon, the present inventors found that a lanthanum oxychloride phosphor whose surface is coated with a predetermined amount of zinc silicate has a luminance variation. The inventors discovered that the lanthanum oxychloride phosphor of the present invention can be improved while reducing the variation and at the same time increasing the luminance itself. That is, the lanthanum oxychloride phosphor of the present invention is characterized in that its surface is coated with zinc silicate. In the phosphor of the present invention, the lanthanum oxychloride phosphor whose surface is coated with zinc silicate is
Any type of lanthanum oxychloride phosphor can be used as long as it has been baked in air or in a reducing atmosphere by a conventional method and is ready for practical use. Particularly preferred are terbium-activated lanthanum oxychloride phosphors. The amount of zinc silicate used to coat the surface of the phosphor is preferably 0.3 to 3% by weight based on 1 mole of the lanthanum oxychloride phosphor to be coated. If the coating amount is less than 0.3% by weight,
As with the case without coating, the brightness varies and reproducibility is poor, and if it exceeds 3% by weight, for example, when this phosphor is applied to the inner surface of a projection tube by a commonly used precipitation method, the phosphor film to be formed will be This is not desirable because it will flow. The coating process is performed as follows. first,
The lanthanum oxychloride phosphor whose surface is to be coated is thoroughly washed with pure water, and an aqueous solution of water glass (K 2 O 3SiO 2 ) of a predetermined concentration, for example, is added thereto, and then an aqueous solution of water glass (K ₂ O 3SiO ₂ ) of a predetermined concentration, for example, is added thereto. Add the solution and stir. Water glass and zinc sulfate react on the surface of the phosphor to produce zinc silicate, which covers the surface. Therefore, the amount of zinc silicate that coats the surface of the phosphor can be easily adjusted by appropriately selecting the concentration or amount of the solution described above. After thoroughly washing the treated phosphor with pure water,
The phosphor of the present invention can be obtained by filtering with ethanol and finally drying at a temperature of 80 to 130°C. In addition, in the present invention, aluminum silicate can also be used in place of zinc silicate. [Example of the Invention] 5000 ml of pure water was added to 1000 g of lanthanum oxychloride phosphor powder prepared by a conventional method and stirred. An appropriate amount of water glass (K ₂ O.3SiO ₂ ) having a concentration of 25% was added thereto, and the mixture was further stirred for about 10 minutes. Then,
An appropriate amount of an aqueous zinc sulfate solution having a concentration of 0.4 mol/1000 ml was added thereto, and the mixture was stirred for about 10 minutes. Thereafter, it was thoroughly washed with pure water, filtered with ethanol, and dried at about 120°C to obtain the phosphor of the present invention. In this process, the amounts of water glass and zinc sulfate aqueous solution added were varied to prepare phosphors with different amounts of surface coating of zinc silicate. The various powder phosphors obtained were measured for brightness variation, powder brightness increase rate, and initial brightness improvement rate according to the following specifications. Variation in brightness: Five or more 7-inch projection tubes coated with treated powder phosphor on the inside using a commonly used sedimentation method are manufactured in the same lot, and the luminance is 28KV, 1200μA,
After stabilizing it with a raster size of 130 x 100 mm ² for 3 hours of steady operation, we measured the brightness of this projection tube and looked at the width of its dispersion. Powder brightness increase rate (%): Treated powdered phosphor was packed in a dish, irradiated with an electron beam of 10KV, 1μA/cm ^{2 ,} and the brightness L ₁ at that time was measured, and the untreated powdered phosphor was The brightness L ₀ was similarly measured for the powder, and L ₁ −L ₀ /L ₁ ×100 (%) was calculated, and this value was taken as the powder brightness increase rate. Initial brightness improvement rate (%): A 7-inch projection tube coated with treated powder phosphor on the inner surface was manufactured by applying the commonly used sedimentation method, and it was operated steadily for 3 hours at 28 KV, 1200 μA, and raster size of 130 × 100 mm ^2. After stabilizing at , the brightness L ₂ of this projection tube was measured. A projection tube with the same specifications is manufactured using untreated powder phosphor,
Similarly, this luminance L' ₀ is measured and L ₂ - L' ₀ /L ₀ ×10
0 (%) was taken as the initial brightness improvement rate. The above results are shown in the table, FIG. 1, and FIG. 2, respectively. In each figure, all straight lines parallel to the horizontal axis represent the level of unprocessed samples.

〔Effect of the invention〕

As is clear from the table and each figure, the phosphor of the present invention has
The variation in brightness has been reduced by ±7%, and the powder brightness increase rate is up to 5%, and the initial brightness improvement rate is up to 10%. As described above, the phosphor of the present invention has smaller variations in brightness, higher brightness when irradiated with electron beams, and less decrease in brightness even when used at high temperatures, compared to untreated phosphors. When applied to a color projection video device, the reduction in brightness and variation in the steady state of operation (panel temperature of 80° C.) is small, so it has great industrial value.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the powder brightness increase rate of the phosphor of the present invention and the coating amount of zinc silicate, and Figure 2 is the relationship between the initial brightness improvement rate and the zinc silicate coating amount of the projection tube coated with the phosphor of the present invention. It is a relationship diagram with the amount of coverage. In addition, in each figure,
The straight line parallel to the horizontal axis represents the case of untreated phosphor.

Claims (1)

[Claims] 1. A lanthanum oxychloride phosphor whose surface is coated with zinc silicate. 2. The lanthanum oxychloride phosphor according to claim 1, wherein the coating amount of the zinc silicate is equivalent to 0.3 to 3% by weight per mole of the lanthanum oxychloride phosphor. 3. The lanthanum oxychloride phosphor according to claim 1 or 2, wherein the lanthanum oxychloride phosphor is a terbium-activated lanthanum oxychloride phosphor.