JPH0472873B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color picture tube, and particularly to a phosphor constituting a phosphor surface thereof.

In general, the phosphor that makes up the phosphor surface of a color picture tube is Y ₂ O ₂ S as a red-emitting phosphor:
Eu or Y ₂ O ₈ :Eu phosphor, ZnS:Cu, Al or ZnS:Cu, Au, Al phosphor as green phosphor, also Y ₂ SiO ₅ :Tb, Gd ₂ O ₂ S:Tb ，
A Y ₂ O ₂ S:Tb phosphor is used, and a ZnS:Ag phosphor is used as a blue phosphor.

By the way, in a picture tube that uses a high-resolution electron gun, such as a projection color picture tube, the spot diameter of the electron beam on the fluorescent surface is small, so even with the same cathode current, the current density at the center of the spot is higher than that of other ordinary picture tubes. It is more expensive than a picture tube. Therefore, in a color picture tube using a high-resolution electron gun, there is a problem of deterioration in image quality due to brightness saturation of the phosphor.

That is, among the phosphors mentioned above, the luminance of sulfide phosphors generally increases relatively linearly as the current density increases in the low current operating region, but saturates and increases linearly in the high current operating region. It has the property of losing its sexuality. Therefore, a difference occurs in the color temperature of the white screen between the low current range and the high current range, resulting in loss of white uniformity. In particular, when forming a white screen, the green cathode current generally occupies a large proportion, and this causes brightness saturation in green, resulting in a significant loss of image quality.

The present invention has been made in view of these circumstances, and its purpose is to provide a color picture tube with good color reproducibility and excellent afterglow characteristics suitable for high resolution and high brightness tubes. .

In order to achieve such an objective, the present invention
A mixed phosphor of a terpium-activated yttrium aluminate phosphor and a zinc silicate phosphor is used as the green phosphor.

That is, zinc silicate-based phosphors, such as zinc silicate phosphors, are used as green phosphors that are less prone to brightness saturation in high current ranges.
There is Zn ₂ SiO ₄ :Mn, but this phosphor has on the other hand the disadvantage that the afterglow time is too long.

However, this zinc silicate-based phosphor can be replaced with a terbium-activated yttrium aluminate-based phosphor, such as Y ₈ Al ₅ O ₁₂ :Tb, Y ₈ (Al, Ga) ₅ O ₁₂ :Tb, etc. It was confirmed that the afterglow time was shortened and a green phosphor suitable for use in high-resolution, high-brightness tubes could be obtained by mixing the green phosphor with the following. That is, Y ₈ Al ₅ O ₁₂ :Tb, Y ₈ (Al,
Ga) ₅ O ₁₂ :Tb phosphor is also a phosphor that does not easily cause luminance saturation in a high current range, but because its emitted light color is yellow-green, it is less likely to cause luminance saturation in a high current range, so it is less likely to cause luminance saturation in a high current range. Physically, there were problems with color reproducibility. However, by combining this with the zinc silicate-based phosphor, the chromaticity is improved due to the dark green color of the zinc silicate-based phosphor, but the afterglow properties of the zinc silicate-based phosphor are prolonged. It became clear that the shortcoming of being too much could be compensated for.

Figure 1 shows the CIE system chromaticity values of the luminescent color of the phosphor. In the figure, point A is a Y ₈ Al ₅ O ₁₂ :Tb phosphor, and point B is a zinc silicate phosphor. _{Zn2SiO4 :}
Mn phosphor, C indicates the chromaticity value of ZnS:Cu, Al phosphor, which is a conventionally commonly used green-emitting phosphor. Also, the points on the line connecting points A and B are Y ₈ Al ₅ O ₁₂ :Tb phosphor and
It represents the chromaticity value of the mixed phosphor with Zn ₂ SiO ₄ :Mn phosphor, and the number attached next to each point is the weight of the Zn ₂ SiO ₄ :Mn phosphor in the above mixed phosphor. Indicates the mixing ratio (percentage).

As is clear from the figure, Y ₈ Al ₅ O ₁₂ :Tb is x
=0.35, y=0.565, showing yellow-green color, but Zn ₂ SiO ₄ :
By mixing Mn, the chromaticity is improved,
Zn ₂ SiO ₄ :Mn mixing ratio is 5% or more, preferably
By setting the amount to 10% or more, it is possible to obtain a green luminescent color suitable for use in the fluorescent surface of a color picture tube. However, if the mixing ratio of Zn ₂ SiO ₄ :Mn becomes too large, image afterglow becomes a problem.

Figure 2 shows the total amount of mixed phosphor mentioned above.
This shows the relationship between the weight mixing ratio of Zn ₂ SiO ₄ :Mn phosphor and the 10% afterglow time.
%, that is, Zn ₂ SiO ₄ : When a phosphor surface is formed by coating only the Mn phosphor, the 10% afterglow time is approximately 25
At msec, afterglow is noticeable in moving images.
When the mixing ratio is set to 50%, this afterglow time is significantly shortened, and the afterglow becomes almost unnoticeable even in the case of moving images.

When using a mixed phosphor of a terbium-activated yttrium aluminate phosphor and a zinc silicate phosphor, if the mixing ratio of the zinc silicate phosphor is small, there will be problems with the luminescent color. On the other hand, if this mixing ratio is too large, color reproducibility is improved, but afterglow increases significantly, impairing practicality. Therefore, the above mixing ratio is practically 5 to 5.
It is desirably about 50 wt%, more preferably about 10 to 50 wt%. It goes without saying that these two types of phosphors may be used as the main components and other phosphors may be mixed.

As explained above, according to the present invention, a phosphor mixture of a terbium-activated yttrium aluminate-based phosphor and a zinc silicate-based phosphor is used as a green-emitting phosphor to form a phosphor surface. As a result, brightness saturation in the high current range is improved, and a color picture tube with good color reproducibility and excellent afterglow characteristics can be obtained. Extremely effective.

[Brief explanation of drawings]

FIG.
The chromaticity diagram, FIG. 2, is a graph showing the dependence of the afterglow time of a mixed phosphor composed of the above two types of phosphors on the mixing ratio.

Claims (1)

[Claims] 1. In a color picture tube equipped with a phosphor surface having a green-emitting phosphor on the inner surface of the panel, the green-emitting phosphor is composed of a terbium-activated yttrium aluminate-based phosphor and a zinc silicate-based phosphor. A color picture tube characterized by consisting of a phosphor mixed with a light body. 2. The color picture tube according to claim 1, wherein the zinc silicate phosphor is contained in an amount of 5 to 50% by weight based on the total amount of the mixed phosphor.