JPH0572437B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD OF THE INVENTION This invention relates to a blue pigment-coated zinc sulfide blue-emitting phosphor for color television. [Technical background of the invention and its problems] In recent years, in order to improve the contrast of the screen in color television cathode ray tubes, the so-called phosphor surface is coated with a pigment that transmits the emitted color of the phosphor and absorbs other visible light. Pigment-coated phosphors are used. Pigments currently known as pigments for pigment-coated phosphors include cobalt aluminate pigments as blue;
Ultramarine and red colors include red iron, cadmium selenide sulfide, and indium sulfide, all of which are adjusted to have an average particle size of about 0.05 μm to 3 μm and attached to a 4 μm to 15 μm phosphor. The pigments used in these color cathode ray tube phosphors are those that match the emission spectrum of the phosphor, and the better the coloring power of the pigment, the better the pigment. However, when it comes to actual use, cobalt aluminate is used instead of ultramarine, which has good pigment properties, as a blue pigment. This is because ultramarine blue fades with acid, so when coating the surface of a phosphor, it can only be used in a limited range from neutral to alkaline. Ultramarine blue fades when exposed to heat, so it cannot withstand the high temperatures involved in sealing in the cathode ray tube manufacturing process. The dichromate used in forming the phosphor film has a strong oxidation effect, and if it contains trace amounts of hexavalent chromium, the ultramarine blue color may fade even at relatively low temperatures.
Among these fading of ultramarine blue, in the cathode ray tube manufacturing process, as a method to improve luminance without significantly fading the ultramarine blue, as disclosed in Japanese Patent Application Laid-open No. 57-207675, a cobalt aluminate pigment of less than 30% is added to the ultramarine pigment. Techniques for using a mixture are known. However, recently, in order to obtain even higher quality cathode ray tubes for color televisions, there has been a demand for improvements in phosphors, such as increasing contrast, forming dense phosphor films, and improving life characteristics. In other words, regarding the contrast characteristics of the pigment-coated phosphor powder, it is best to use ultramarine alone, which has excellent reflectance and coloring power, when the pigment concentration is kept constant, and cobalt aluminate pigments are better compared to that. Far inferior. Therefore, when a mixture of ultramarine and cobalt aluminate pigments is used, the contrast deteriorates as the amount of cobalt aluminate pigment in the total pigment increases. Further, when the contrast is kept constant, ultramarine blue with a lower pigment concentration coated on the phosphor has higher brightness, but when both are mixed, the brightness decreases as the amount of cobalt aluminate pigment increases. However, when used in a cathode ray tube, the ultramarine blue color fades as described above, and the phosphor disclosed in Japanese Patent Application Laid-Open No. 57-207675 becomes more advantageous in terms of brightness and contrast. In forming a dense phosphor film, it goes without saying that a dense phosphor film with a larger amount of phosphor in a certain area is more advantageous in terms of luminance characteristics. If the phosphor film becomes rough and has pinhole-like holes, not only will the luminance be reduced, but the phosphor applied in the next process will easily enter the pinholes, causing color mixing and causing blue When the phosphors emit light, they emit light at the same time, leading to a decline in the quality of the cathode ray tube. In order to form a dense phosphor film, it is necessary to improve the dispersibility of the phosphor. Dispersion such as bead milling is required to disperse the phosphor, but if bead milling is performed for a long time, the brightness will decrease. In order to achieve dispersion with as little bead milling as possible in the phosphor manufacturing process, a phosphor with better dispersibility can be obtained by minimizing the amount of adhesive used to coat the surface of the phosphor with the pigment. However, the amount of adhesive used is proportional to the surface area of the pigment, and if the concentration of the pigment is kept constant and only the amount of adhesive is decreased in order to improve the dispersibility of the phosphor, the pigment will peel off. Considering such a fluorescent film and the above-mentioned contrast, JP-A-57-207675 is very excellent. However, considering the improvement in the life characteristics of cathode ray tubes, even though it is better than ultramarine alone, there is a need for further improvements in characteristics. [Object of the invention] The present invention not only provides a high-quality color cathode ray tube with high contrast and dense fluorescent film formation by optimizing the mixing ratio of ultramarine and cobalt aluminate pigments, but also produces a blue pigment with excellent life characteristics. It is an object of the present invention to provide a coated zinc sulfide blue-emitting phosphor. [Summary of the Invention] The present invention provides a blue pigment-coated zinc sulfide blue-emitting phosphor coated with ultramarine and cobalt aluminate pigments, in which the cobalt aluminate pigment accounts for 30% of the total pigment content.
A blue pigment-coated zinc sulfide blue-emitting phosphor characterized in that the amount of zinc sulfide is within the range of ~70% by weight. If it is less than 30%, the life of the color cathode ray tube as a phosphor screen will not be sufficient. If it exceeds 70%, a large amount of pigment must be coated to obtain a certain contrast, and the pigment is likely to peel off when preparing a phosphor slurry. Cobalt aluminate contains all pigments.
Most preferably, it is within the range of 43 to 56% by weight. From the viewpoint of brightness and contrast, the coating amount of the pigment is preferably in the range of 0.5 to 10% by weight, most preferably in the range of 2 to 7% by weight, based on the coated phosphor. The zinc sulfide blue-emitting phosphor suitable for the present invention is
ZnS:Ag, Cl and ZnS:Ag, Al, etc. Figure 1 shows the ratio of cobalt aluminate pigment in a mixed pigment of ultramarine pigment and cobalt aluminate pigment, and the ratio of the mixed pigment to the ultramarine pigment alone.
% so that the reflectance is the same as when covered.
ZnS: Blue pigment coated on Ag, Cl phosphor Using zinc sulfide blue emitting phosphor, the brightness is 100% that of the ultramarine pigment used alone in color cathode ray tubes.
FIG. 3 is a diagram showing the relationship with relative brightness when
Curve a is 0 hours of color cathode ray tube operation, curve b is
After 1000 hours, curve c is the characteristic after 2000 hours. As this figure shows, at 0 hours, the relative brightness is relatively high when the proportion of cobalt aluminate pigment is small, but at 1000 hours and 2000 hours, the relative brightness is high when the proportion of cobalt aluminate pigment is large. Cobalt aluminate pigments exhibit practical properties at 30% by weight. [Embodiments of the invention] Example 1 Weighed 100 g of ultramarine blue, dispersed it in pure water, and reduced the total amount to 1
Make it. Weigh 100g of cobalt aluminate, disperse it in pure water, and make the total amount 1. This solution is used as an ultramarine blue dispersion solution and a cobalt aluminate pigment solution. Separately, 1 kg of silver and chlorine-activated zinc sulfide blue-emitting phosphor was dispersed in 10 g of pure water, and 210 ml of ultramarine dispersion solution (21 g as ultramarine) was gradually added while stirring.
Stir for 30 minutes. Next, 82 ml of a 0.1% solution of polyacrylamide, an adhesive between the phosphor and the pigment, was gradually added to allow the ultramarine blue to adhere to the surface of the phosphor. Next, 210 ml of cobalt aluminate pigment solution (21 g as cobalt aluminate pigment) was gradually added, and 82 ml of a 0.1% polyacrylamide solution was added in the same manner as ultramarine to adhere the cobalt aluminate pigment to the surface of the phosphor. After washing the phosphor with pure water, it is dispersed for 20 minutes using glass beads, then dried and sieved. The phosphor thus obtained is a blue pigment-coated zinc sulfide blue-emitting phosphor with a pigment coverage of 4.2 percent by weight in the phosphor and a concentration of cobalt aluminate pigment in the total pigment of 50 percent by weight. Polyvinyl alcohol, dichromic hydrochloric acid, and a dispersant are added to this to prepare a phosphor slurry, which is then applied. Next, we went through the normal cathode ray tube manufacturing process, produced a prototype cathode ray tube, and conducted a life test.
As shown in Table 1, the phosphor obtained in Example 1 provided a high quality phosphor film and was excellent in the life test. Examples 2 to 7 Cathode ray tubes were fabricated using phosphors prototyped by varying the pigment concentration and resin amount in the same manufacturing process as in Example 1, and a life test was conducted. As shown in Table 1, these phosphors provide high quality phosphor films and are excellent in life tests. For comparison of Examples 1 to 7, JP-A-57-207675
The blending ratio where the cobalt aluminate pigment concentration in the ultramarine blue shown in the publication is 33.3 percent (in other words, the cobalt aluminate pigment concentration in the total pigment is 25 percent), which is the same as the reflectance in the square example. A prototype was made by changing the pigment concentration so that In addition, the brightness is shown as a relative comparison when a prototype coated with ultramarine alone has the same reflectance as the example, and the brightness at the initial, 1000 hours, and 2000 hours life time is set as 100. . [Effects of the Invention] As explained above, the blue pigment-coated zinc sulfide blue-emitting phosphor of the present invention is particularly effective in life tests and is particularly excellent as a blue-pigment-coated zinc sulfide blue-emitting phosphor for color cathode ray tubes. be. In Table 1, when a cathode ray tube was prototyped using a phosphor not coated with pigment in Examples 1, 2, and 3, when the relative value when the outside light reflectance of the cathode ray tube was 100 was 50%, 4, 5 is when the external light reflectance relative value is 60%, and 6 and 7 are when it is 42.5%. The luminance in the life characteristics is the initial value of the ultramarine-coated phosphor, after 1000 hours,
This is the relative brightness when the brightness after 2000 hours is set as 100. As shown in this example [Table 1], the characteristics of the cathode ray tube phosphor in high contrast were able to improve the life characteristics without significantly impairing the density of the film.

【table】

【table】 [Brief explanation of drawings]

Figure 1 shows the concentration of cobalt aluminate pigment in a mixed pigment of ultramarine pigment and cobalt aluminate pigment, and the ZnS coated with 2% by weight of the mixed pigment:
FIG. 3 is a diagram showing the relationship with relative brightness when Ag and Cl phosphors are used in a color cathode ray tube.

Claims (1)

[Scope of Claims] 1. In a blue pigment-coated zinc sulfide blue-emitting phosphor coated with ultramarine and cobalt aluminate pigments, the cobalt aluminate pigment accounts for 30% of the total pigments.
A blue pigment-coated zinc sulfide blue-emitting phosphor characterized in that it is within the range of 70 weight percent. 2. The blue pigment-coated zinc sulfide blue-emitting phosphor of claim 1, wherein the cobalt aluminate pigment is in the range of 43.0 to 56.0 weight percent of the total pigment. 3 Pigment coverage relative to the weight of the phosphor coated
A blue pigment-coated zinc sulfide blue-emitting phosphor according to claim 1, characterized in that the blue pigment-coated zinc sulfide blue-emitting phosphor is in the range of 0.5 to 10.0 weight percent. 4. A blue pigment-coated zinc sulfide blue-emitting phosphor according to claim 1, characterized in that the pigment coverage is in the range of 2 to 7 weight percent based on the weight of the phosphor coated. 5. The blue pigment-coated zinc sulfide blue-emitting phosphor according to claim 1, wherein the phosphor is a zinc sulfide blue-emitting phosphor activated with either silver and chlorine, or silver or aluminum.