JPS6410557B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a color picture tube whose phosphor screen is coated with an improved blue-emitting phosphor. Currently, in trichroic color picture tubes, the phosphor screen is comprised of stripes or dots of red, green and blue emitting phosphors. In the color picture tube, the red-emitting phosphor is generally a europium-activated phosphor, the green-emitting phosphor is a copper-activated zinc sulfide or copper-gold co-activated zinc sulfide phosphor, and the blue-emitting phosphor is silver. An activated zinc sulfide phosphor is used. Color adjustment typically changes the beam current to red, green, or
This is done by irradiating blue phosphor and adjusting the white screen by adjusting the ratio at low current, and then evaluating by the tone of the white screen at high current irradiation when the current is increased in that state. Therefore, it is desirable that the luminance of each phosphor increases without changing its ratio at both low and high currents, and such luminance-current characteristics are as follows:
Ideally, it should be a straight line. In the case of commonly used red-emitting phosphors (europium-activated phosphors), when a beam current is passed through the phosphor screen, the brightness increases linearly as the beam current increases. In addition, in the case of a green light-emitting phosphor, the brightness tends to increase in a convex curve as the beam current increases and saturate to a constant value. On the other hand, the conventionally used blue-emitting phosphor (silver-activated zinc sulfide), like the green-emitting phosphor,
As the beam current increases, the brightness increases in a convex curve, and has a current characteristic that tends to be saturated at a constant value. When a white screen is created at low currents using these three-color phosphors of red, green, and blue, and color adjustment is performed, at high currents only the brightness of red increases without being saturated, while the brightness of green and blue increases. Since blue becomes saturated, for example, even if an attempt is made to obtain a high-brightness white color for a character screen, not only will the brightness not be sufficiently high, but an inconvenient situation will occur in which the white color will take on a reddish tinge. Therefore, attempts have been made to reduce the brightness saturation phenomenon of the green and blue current characteristic curves and make them closer to straight lines. It has been proposed to use a mixed phosphor (see Japanese Patent Application No. 44537/1983 and Japanese Patent Application Laid-open No. 130966/1983). However, by simply improving the current characteristics of this green phosphor, it is true that the brightness of a high-brightness screen is about 10% higher than that of a conventional white screen, and the disadvantage of white color becoming reddish is also eliminated, but on the other hand,
The disadvantage is that the white color becomes yellowish-greenish. Furthermore, British Patent No. 1203124 proposes a color picture tube in which the brightness of all three colors does not saturate at high currents. That is, it uses a europium-activated phosphor as a red-emitting phosphor, a terbium, holmium, erbium, or manganese-activated phosphor as a green-emitting phosphor, and a divalent europium- or thulium-activated phosphor as a blue-emitting phosphor. be. However, the blue-emitting phosphor described above has a beam current (10 to 1000 μA) that is about the same as that of a normal color picture tube.
However, since the luminous efficiency is less than 50% and the brightness is significantly reduced, it is not practical to compare it with a normal screen. The present inventors have discovered that silver-activated zinc sulfide containing a predetermined amount of nickel has a brightness that, as a blue-emitting phosphor, exhibits less brightness saturation at high currents and does not decrease as much as rare-earth-activated phosphors. The present invention was completed by discovering the fact that the present invention has current characteristics. SUMMARY OF THE INVENTION An object of the present invention is to provide a color picture tube in which, when forming a white screen, the color of the emitted light does not shift toward green or red even when the color is high brightness white. The blue-emitting phosphor used in the color picture tube of the present invention is a silver-activated zinc sulfide phosphor containing nickel. In the phosphor, the amount of nickel contained is set in the range of 0.3 ppm or more and 3 ppm or less based on the total weight of the phosphor. When the nickel content is less than 0.3 ppm, compared to conventional silver-activated zinc sulfide phosphors that do not contain nickel, no improvement in brightness saturation due to increased beam current is observed, and
If it exceeds 3 ppm, the quenching effect becomes significant, resulting in a decrease in brightness, making it impossible to obtain a high-brightness white color. Such a phosphor is prepared as follows. That is, nickel compounds such as nickel sulfate and nickel nitrate, silver compounds such as silver nitrate and silver thiosulfate, and zinc sulfide precipitates are used as starting materials, and a fluxing agent such as sodium chloride is added to these.
A method of firing in a temperature range of 800 to 1000℃, or
The above nickel compound is adsorbed onto the surface of the silver-activated zinc sulfide phosphor powder prepared in advance.
Examples include a method of firing in a temperature range of 500 to 1000°C. The phosphor obtained by the latter method shows a greater improvement effect than the phosphor obtained by the former method in reducing the contrast caused by the influence of scattered secondary electrons on the dark screen of a color picture tube, and the contrast of the screen is improved. Make it clear. A color picture tube coated with the blue-emitting phosphor prepared as described above as a blue component has the effect of not shifting the white color toward yellow or red on a high-brightness white screen, and improving the contrast on a dark screen. show. In this case, if a phosphor containing a terbium-activated phosphor is used instead of a conventional copper-activated zinc sulfide phosphor or a copper-gold co-activated zinc sulfide phosphor as the green-emitting phosphor, the brightness of the white screen will be improved. The brightness will be higher and a favorable result will be obtained. The present invention will be explained below based on examples. Example 1 For 100 g of zinc sulfide precipitate, 0.02% (0.031 g) of silver nitrate and sodium chloride were added in terms of silver weight.
0.05% (0.05g), magnesium chloride 1% (1g)
and further 0.2 ppm (0.053 mg) of nickel sulfate in terms of the weight of nickel: Sample 1,
0.3ppm (0.079mg): sample 2, 1ppm (0.26mg): sample 3, 3ppm (0.79mg): sample 4, 4ppm (1.04mg): sample 5 were wet mixed and dried at 950°C for 2 hours. Fired to produce 5 types of phosphor powder: a, b,
c, d, and e were prepared. Powder a corresponds to a mixture of sample 1, b corresponds to sample 2, c corresponds to sample 3, d corresponds to sample 4, and e corresponds to a mixture of sample 5. Here, b, c and d are examples of the present invention, and a and e are comparative examples prepared for comparison with these. Next, the blue-emitting phosphor was combined with europium-activated yttrium oxysulfide (Y ₂ O ₂ S: Eu) as a red-emitting phosphor and gold/copper-activated zinc sulfide (ZnS: Au, Cu) as a green-emitting phosphor. Five 18-inch color picture tubes were made by coating the phosphor screen using a conventional method. The fluorescent screens of these five color picture tubes were irradiated with electron beams, and the brightness of the blue light at this time was measured.
The ratio of the measured value to the brightness of blue light when the blue light-emitting phosphor was a conventional silver-activated zinc sulfide phosphor containing no nickel was calculated as relative brightness (%).
The relationship between the relative brightness (%) and beam current is shown in FIG. In addition, in Fig. 1, the values of relative brightness at beam currents of 100 μA (low current) and 1000 μA (high current) are read, and the degree of increase in relative brightness is compared.
It is shown in Table 1.

[Table] As is clear from FIG. 1 and Table 1, the color picture tubes of the present invention (Example b, Example c, Example d)
(coated with phosphor), there is no significant decrease in brightness (relative brightness decreases within 30% even in low current range), and brightness saturation does not occur even when high current is applied. It turned out to be small (relative brightness has a positive slope). In other words, in the color picture tube using Comparative Example a, as is clear from FIG.
It can be seen that the luminance increase rate is 1.1), and the current characteristics are almost the same as those of conventional color picture tubes. This conventional color picture tube exhibits a brightness-current characteristic in which the brightness increases in a convex curve as the beam current increases, and then tends to saturate. The ratio changes greatly at high currents, and white at high currents becomes reddish or yellowish-green, making it impossible to produce ideal white.
On the other hand, in the color picture tubes of Examples b, c, and d, the relative brightness has a significant positive gradient (as can be seen from Table 1, the degree of increase in brightness in Examples b, c, and d is a b is 6 times, c is 11 times, d
(17 times higher than that of the conventional type), in other words, the brightness at low current is slightly lower than that of the conventional type, so the curvature of the convex curve of the characteristic curve is relaxed. Therefore, it is approaching the ideal straight line. Therefore, red during adjustment of white at low current,
The ratio of green and blue does not change significantly even at high currents, so the white at high currents becomes a bright white without a reddish or yellowish-green tinge, and even at high currents. The brightness in terms of current is comparable to that of conventional ones, and the contrast is good. On the other hand, in the color picture tube using Comparative Example e, the gradient of relative brightness is closer to a straight line, but the brightness is significantly lower than that of the conventional color picture tube (low current region - 100μA). (approximately 50%, high current region - approximately 20% at 1000μA), which is not usable. Further, the phosphors of Example b, Example c, and Example d were used as a blue-emitting phosphor, the europium-activated yttrium oxysulfide phosphor was used as a red-emitting phosphor, and the copper-activated zinc sulfide and terbium-activated yttrium oxysulfide were used as a red-emitting phosphor. Three color picture tubes were fabricated using a 1:1 mixture of phosphors as green-emitting phosphors. A current of 8 mA was applied to these three color picture tubes to measure the white brightness of the phosphor screen, and the blue-emitting phosphor was silver-activated zinc sulfide, the red-emitting phosphor was europium-activated yttrium oxysulfide, and the green-emitting phosphor was When compared with the white brightness at the same current value of a conventional color picture tube using gold and copper activated zinc sulfide,
An improvement in brightness of 10%, 3%, and 1% was observed, respectively. From this, even if the blue phosphor according to the present invention shows a slight decrease in brightness compared to the conventional one,
It can be seen that the effect is almost negligible.
Also, compared to the case of low current (300μA) excitation, the white color at that time does not shift toward yellow or red, but rather shifts toward blue, so the high-brightness white appears whiter and the effect of making the screen stand out is enhanced. Obtained. Example 2 For 100g of silver-activated zinc sulfide phosphor, nickel sulfate was converted to nickel weight to be 0.3ppm (0.079
mg): Sample 6, 1ppm (0.26mg): Sample 7, 3ppm
(0.79mg): Add sample 8 to each, add water, wet mix, dry and bake at 750℃ for 2 hours,
Three types of phosphor powders were prepared: Example f, Example g, and Example h. The phosphors of Examples f, g, and h were used as blue-emitting phosphors, and the color picture tube 3 was prepared in the same manner as in Example 1.
I made one. The luminance of these color picture tubes was measured in the same manner as in Example 1, and the relationship between the relative luminance and beam current is shown in FIG. Also, in Figure 2, the beam current is 100μA (low current) and 1000μA.
The relative brightness values at (high current) were read and the relative brightness increases were compared and shown in Table 2.

[Table] From FIG. 2 and Table 2, in the f, g, and h color picture tubes that are examples of the present invention, Example 1
Similarly, it was found that the decrease in brightness was small, and since the relative brightness had a positive slope, the saturation phenomenon of brightness was also small, and an improvement was observed compared to the conventional current saturation characteristics. In addition, the same effect as in Example 1 was obtained with respect to white luminance, and furthermore, the darkness on a dark screen was extremely high, and the contrast was improved.

[Brief explanation of the drawing]

Figures 1 and 2 show the dependence of the blue light emitting output (brightness) on the beam current in the color picture tubes of the example and the comparative example, and the ratio (relative brightness) to the blue light emitting output (brightness) of the conventional color picture tube. :
%).

Claims (1)

[Claims] 1. In a color picture tube whose phosphor screen consists of stripes or dots of red, green and blue emitting phosphors,
A color picture tube whose blue-emitting phosphor is a silver-activated zinc sulfide phosphor containing 0.3 to 3 ppm of nickel.