JPH0821334B2 - Color picture tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color picture tube, and more particularly to a green-emitting phosphor coating that constitutes the phosphor surface thereof.

In recent years, in a color picture tube, a higher current has been applied along with an increase in applied voltage and improvements in electron guns, etc., and the current density tends to be remarkably high.

However, in the conventional color picture tube, it is difficult to keep the color of the image excellent over a wide range from the low current region to the high current region. That is, the phosphor of the conventional color picture tube, generally europium-activated sulfide yttrium as a red emitting phosphor _{(Y 2 O 2 S: E} u) phosphor or europium oxide yttrium (Y
₂ O ₂ : E _u ), silver-activated zinc sulfide (ZnS: Ag) phosphor as a blue-emitting phosphor, copper, aluminum activated zinc sulfide (ZnS: Cu, Al) as a green-coloring phosphor ) Fluorescent material or copper, gold, aluminum activated zinc sulfide (ZnS: Cu, A
u, Al) phosphors are used. However, among the above-mentioned phosphors of each color, the green-emitting phosphor has a remarkable tendency that the emission luminance is saturated by the high current stimulation as compared with the red-emitting phosphor, and the color of the image is excellent over a wide range. Difficult to keep. In addition, since the electron beam thickness is different between the central portion and the peripheral portion of the screen, the current density is different, which causes a problem that the white uniformity of the entire image is deteriorated.

Less brightness saturation in such a high current region, and ZnS: Cu, Al or ZnS: Cu, Au, Al as a green light emitting phosphor having a light emission brightness comparable to that of the conventional phosphor, a conventional rare earth, respectively. Specifically, terbium activated gadolinium oxysulfide (Gd ₂ O ₂ S: Tb), yttrium oxysulfide (Y ₂ O ₂ S: Tb)
b), lanthanum oxysulfide (La ₂ O ₂ S: Tb) and other phosphors are known. However, these terbium-activated green light-emitting phosphors have, for example, ZnS emission spectra shown in FIG. 1B, as shown in FIG. 1A for the case of Ga ₂ O ₂ S: Tb. : Cu, Al is very different from the conventional ones, and light emission is also on the short wavelength side, so the color purity as green is poor. This is shown in FIG. That is, the figure shows CI
It shows the E-system chromaticity values. The figure (a) shows ZnS: Cu, Al.
Fluorescent material, (b) ZnS: Cu, Au, Al fluorescent material, (c) Gd
₂ O ₂ S: Tb phosphor, (d) is Y ₂ O ₂ S: Tb phosphor, (e)
Indicates the case of La ₂ O ₂ S: Tb phosphor. As shown in the figure, in the case of the conventional ZnS-based phosphor, the x value is 0.28 to 0.32, y
While the value is 0.60 to 0.63, the so-called rare earth green phosphor activated by terbium has a green color with an x value of about 0.34 and a y value of about 0.57 even if the material composition and phosphor synthesis conditions are optimized. The purity is extremely poor.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a color picture tube having a fluorescent film that does not saturate the green luminance with respect to the stimulation current density and has high green luminance. To do.

In order to achieve such an object, the color picture tube according to the present invention is formed by adding a green pigment to a terbium-activated rare earth green light-emitting phosphor to form a green light-emitting phosphor coating film. . That is, Gd ₂ O ₂ S: Tb phosphor, Y ₂ O ₂ S: Tb phosphor, La ₂ O ₂ S: Tb as a rare earth green light emitting phosphor.
A green pigment is adhered to or mixed with the phosphor or the like. Examples of this green pigment include chrome green {PbCrO ₄ + Fe ₄ [Fe (C
N) ₆ ] ₃・ nH ₂ O}, cobalt green C ₀ O ₂・ nZnO, chromium oxide Cr
₂ O ₃ etc.

FIG. 3 shows the spectral reflectance characteristics of such a green pigment. The figure shows the case of chromium oxide, but the others also show almost the same characteristics. As is clear from the figure, while such a green pigment exhibits a high reflectance in the green wavelength region near 540 nm, it has a low reflectance in the blue wavelength region near 450 nm and the red wavelength region of 600 nm or more, and is selective. It has the property of absorbing light in the blue and red wavelength ranges. Therefore, by mixing or adhering this green pigment to the rare earth green light emitting phosphor, the emission intensity of blue and red light of 500 nm or less and 600 nm or more is weakened. At the same time, in this case, since the emission spectrum of the rare earth green light emitting phosphor is distributed as the emission line spectrum as shown in FIG. If added,
The decrease in brightness is less than when a green pigment is added to a conventional ZnS-based phosphor having a broad emission spectrum. For this reason, it is possible to obtain green light with excellent green purity without significantly lowering the luminance, and it is possible to obtain a phosphor film in which the green luminance is not saturated at a high stimulation current density. In addition, in the conventional ZnS-based green light-emitting phosphor, since the original body color itself is green, the addition of a green pigment has caused a problem that the appearance of the color picture tube screen becomes more and more green and the appearance of the color picture tube is deteriorated. Since the body color of the rare earth green light emitting phosphor is almost white, even if a green pigment is added, there is almost no problem in terms of appearance color.

As an example, Gd with chromium oxide green pigment attached to the surface
₂ O ₂ S: using a green pigment phosphor consisting of Tb to form a green light emitting phosphor coating film by a known coating method, and further as a blue light emitting phosphor, ZnS: Ag phosphor, red Gd ₂ O ₂ S: Tb was used for a color picture tube in which a blue light emitting phosphor coating film and a red light emitting phosphor coating film were similarly formed by using Y ₂ O ₂ S: Eu phosphor as the light emitting phosphor. The table below shows the emission color and the green brightness of the green light-emitting phosphor when the amount of chromium oxide was variously changed. Here, the emission color is indicated by the CIE display system chromaticity value. The green brightness is the value when the amount of chromium oxide is zero.
The relative value is 100. In this case, the coverage of Gd ₂ O ₂ S: Tb with chromium oxide is roughly indicated by a value (%) obtained by multiplying the value (%) of the amount of chromium oxide in the table below by 20.

As is clear from the above table, by attaching a pigment, the emission color of the rare earth green light emitting phosphor can be improved to almost the same level as that of the conventional ZnS-based phosphor.

When the pigment concentration is about 2.0 wt% or more with respect to the phosphor, the decrease in brightness becomes remarkable, so the pigment concentration is 0.1
Practically desirable is about 2.0 wt%.

 Hereinafter, a specific example will be described.

First, as a phosphor with a green pigment, Y ₂ O ₂ S: Tb was 0.
Those coated with 3 wt% of the chromium oxide pigments, ZnS as the optical member has attached blue pigment: 3% cobalt pigment aluminate those coated against Ag, Y ₂ O ₂ S as a light body has put red pigment:
Eu coated with 0.5 wt% of iron oxide pigment (may be 1% of cadmium sulphide selenide pigment) is used to prepare each color slurry having the composition shown below.

Pigment phosphor 30wt% Polyvinyl alcohol (solid content) 2.2wt% Ammonium dichromate (solid content) 0.22wt% Surfactant (solid content) 0.15wt% Water balance Then, a green slurry having the above composition is applied to the inner surface of the panel. After being applied to the substrate, it is exposed to ultraviolet light through a shear mask.
Subsequently, the unexposed portion is removed by hot water development to obtain a green phosphor stripe. Then, the same process was repeated using the blue slurry and the red slurry to form a blue phosphor stripe and a red phosphor stripe, respectively, and then a color picture tube was manufactured through the same process as the conventional process.

In the color picture tube thus obtained, the emission color of the green phosphor has an x value of 0.330 and ay value of 0.595,
The purity was significantly improved. The green cathode current is 2mA
Even in the case of a high current (20 inch color picture tube) above, it is possible to obtain a bright fluorescent surface without brightness saturation. Further, since the green pigment in the fluorescent film absorbs extraneous light that illuminates the fluorescent surface, the contrast of the image is improved.

The emission spectrum of the Tb-activated rare earth green light-emitting phosphor generally has a dominant wavelength near 545 nm, and thus exhibits greenish light emission which is somewhat yellowish. In order to improve this point, a conventional ZnS-based phosphor such as ZnS: Cu, Al may be mixed and used. However, in this case, when the ratio of ZnS-based phosphors becomes high, the brightness saturation phenomenon in the high current region occurs, so
It is desirable to keep the mixing ratio of the S-based phosphor at about 50 wt% or less of the total amount of the phosphor.

Further, in the above-mentioned embodiment, the green pigment having the spectral reflectance characteristic as shown in FIG. 3 was used.
It is even more desirable if the slope of the curve with a peak near m is sharper. Further, the pigment to be used is not limited to one kind, and a mixed pigment containing two or more kinds of pigments may be used as long as it selectively exhibits a high reflectance for light near 540 nm. Of course.

Although the conventional ZnS: Ag phosphor was used as the blue-emitting phosphor in the above-mentioned examples, by increasing terbium, Y ₂ O ₂ S: Tb or other terbium-activated rare earth phosphor. The body can also be used as a blue-emitting phosphor.

Further, in the above-mentioned embodiments, only the ordinary color picture tube in which the phosphor coating films of three colors are arranged on the inner surface of the panel has been described, but the present invention is not limited to this, and, for example, green, The same applies to the green-emitting fluorescent surface even in a projection-type color picture tube that magnifies and projects an image of three picture tubes having fluorescent surfaces emitting in blue and red colors using an optical system. Of course, the effect can be obtained.

As described above, according to the method for forming a color picture tube fluorescent surface according to the present invention, the green light emitting phosphor coating film is constituted by the terbium-activated rare earth green light emitting phosphor containing the green pigment. This has an excellent effect that it is possible to obtain a bright image with excellent green purity, no brightness saturation in a high current region, and no color unevenness.

[Brief description of drawings]

FIG. 1 is a characteristic diagram showing an emission spectrum of a green phosphor,
FIG. 2 is a characteristic diagram showing the CIE color system chromaticity value of the light emitted from the green phosphor, and FIG. 3 is a diagram showing the spectral reflectance characteristic of the green pigment.

Claims (1)

[Claims] 1. A color picture tube having a green light-emitting phosphor coating applied to the inner surface of a panel, wherein the green light-emitting phosphor coating comprises a terbium-activated rare earth green light-emitting phosphor. And a green picture tube containing a green pigment.