JP2000136380A - Cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monochromatic cathode-ray tube which is free from unevenness or change in chromaticity without adversely affecting the environment. SOLUTION: A fluorescent screen is formed from a phosphor mixture of a bluish white-emitting phosphor composed of terbium-activated yttrium oxysulfide and a red-emitting phosphor composed of europium-activated yttrium oxysulfide. Both of these phosphors do not contain cadmium and hence do not adversely affect the environment. Since the matrices of these phosphors are the same (yttrium oxysulfide), they disperse well in each other, hardly causing unevenness. Further, since the luminance saturation curve is improved, the shift in chromaticity is markedly reduced even in a highly excited state.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cathode ray tube (CR)
T), and more particularly to the improvement of phosphors for monochrome CRTs.

[0002]

2. Description of the Related Art Conventionally, as a phosphor for a so-called monochrome CRT, for example, a mixture of a blue phosphor and a yellow phosphor, a mixture of phosphors for a normal color television, and the like have been used.

For example, the former includes ZnS: Ag + (ZnCd) S: Ag.

As the latter, ZnS: Ag (blue), ZnS: Ag (blue)
A mixture of S: CuAl (green), Y ₂ O ₂ S: Eu (red) and the like.

[0005]

However, these conventional phosphors for monochrome have the following problems, respectively, and development of a new phosphor for monochrome has been awaited.

For example, since a mixture of a blue phosphor and a yellow phosphor contains cadmium (Cd) as described above, there is a possibility that the mixture may adversely affect the environment. Considering global environmental conservation, it is desirable to avoid using it as much as possible.

On the other hand, an ordinary mixture of phosphors for a color television has a problem in dispersibility when formed into a paint, since the base of the red phosphor is different from the base of the other color phosphors, so that it has been completed. Irregularities and the like easily occur in the cathode ray tube. Further, the green phosphor (ZnS: CuAl) easily saturates, and when three colors are mixed, there is a problem that the chromaticity tends to change when the excitation intensity is increased.

The present invention has been proposed in view of such conventional circumstances, and has no adverse effect on the environment.
It is an object of the present invention to provide a new monochrome phosphor having excellent dispersibility and no saturation problem, thereby providing a monochrome cathode ray tube free from unevenness and chromaticity change.

[0009]

In order to achieve the above-mentioned object, a cathode ray tube according to the present invention comprises a blue-white light-emitting phosphor composed of yttrium oxysulfide activated by terbium and a yttrium oxysulfide activated by europium. The phosphor screen is formed by a mixed phosphor containing the red phosphor.

A blue-white phosphor composed of yttrium oxysulfide activated by terbium and a red phosphor composed of yttrium oxysulfide activated by europium do not contain cadmium. Absent.

Further, since these phosphors have the same base material (yttrium oxysulfide), they have good mutual dispersibility and are unlikely to cause unevenness or the like.

Further, since these phosphors have an improved luminance saturation curve, there is little chromaticity shift even at high excitation.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a cathode ray tube to which the present invention is applied will be described.

A monochrome CRT to which the present invention is applied has, for example, an electron gun for emitting an electron beam attached to a neck portion of a bulb in which the inside is in a vacuum state, and has a panel portion serving as a screen surface. The phosphor screen is formed by applying a phosphor on the inner surface of the panel section.

The structure of the CRT is not limited to this, but can be applied to any known structure, and the type is not limited.

In the present invention, a blue-white phosphor composed of yttrium oxysulfide activated by terbium and a red phosphor composed of yttrium oxysulfide activated by europium are used as the phosphor applied to the inner surface of the panel portion. Are used, and these phosphors will be described below.

The blue-white light-emitting phosphor and the red light-emitting phosphor used in the present invention are both based on yttrium oxysulfide and can be represented by the following general formulas.

Y ₂ O ₂ S: Tb (blue-white emitting phosphor) Y ₂ O ₂ S: Eu (red emitting phosphor) In the present invention, such a blue-white emitting phosphor (Y ₂ O ₂₎
S: Tb) and a red light-emitting phosphor (Y ₂ O ₂ S: Eu) are used as a mixture, but since these phosphors have the same base material, they have good mutual dispersibility, and a blue-white light-emitting phosphor is used. Body T
By changing the b concentration and the Eu concentration of the red light emitting phosphor,
The chromaticity can be set freely.

For example, when a blue-white light emitting phosphor is used alone, the chromaticity is limited to a pale color. In addition, Y ₂ O ₂
S: Tb, Eu has low emission luminance.

Table 1 shows a blue-white emitting phosphor (Y ₂ O ₂ S: T).
This is an example in which the chromaticity adjustment is performed by changing the mixing ratio of b) and the red light emitting phosphor (Y ₂ O ₂ S: Eu).

[0021]

[Table 1]

FIG. 1 shows a red light-emitting phosphor (Y ₂ O ₂ S:
FIG. 2 shows a chromaticity change depending on the Eu concentration of Eu), and FIG. 2 shows a chromaticity change depending on the Tb concentration of the blue-white phosphor (Y ₂ O ₂ S: Tb).

In the red light-emitting phosphor (Y ₂ O ₂ S: Eu), the luminance is high in a region having a low Eu concentration because of a large amount of green components, and the luminance decreases as the Eu concentration increases. In the blue-white phosphor (Y ₂ O ₂ S: Tb),
The lower the Tb concentration, the closer to blue-white.

The reproducible range is a range surrounded by a line in which the Tb concentration is changed in Y ₂ O ₂ S: Tb and a line in which the Eu concentration is changed in Y ₂ O ₂ S: Eu.

As is clear from Table 1 and FIGS. 1 and 2, it is understood that the chromaticity can be freely adjusted by changing the concentration and the mixing ratio of Tb and Eu. considering the use as the phosphor, the blue-white light-emitting phosphor _{(Y 2 O 2 S: Tb} ) and red-emitting phosphor _{(Y 2 O 2 S: Eu} ) mixing ratio of 1: 4 to 4: 1 It is preferable that

When the phosphor screen is formed by the mixed phosphor, a blue-white phosphor and a red phosphor are mixed in a powder state in advance, and the mixture is formed into a paint and applied to the inner surface of the panel section. Alternatively, each may be made into a paint, mixed, and applied to the inner surface of the panel portion.

For example, a phosphor, water, and a dispersant are mixed, stirred, and dispersed, and then a polymer binder and a cross-linking agent (eg, polyvinyl alcohol, ammonium bichromate) are mixed to form a coating.

Here, even when the blue-white light-emitting phosphor and the red light-emitting phosphor are mixed and stirred and dispersed when the first phosphor, water, and dispersant are mixed, they are uniformly dispersed because the matrix is the same.

After a paint is formed for each color by the same method, both paints are mixed to form one paint. Also at this time, since the bases are the same, they are mixed uniformly.

The paint thus uniformly mixed is applied to the inside of the panel.

The above-mentioned mixed phosphor is a normal monochrome CRT.
For high-definition C
It may be used for RT and for high excitation CRT.

When used for a high-definition CRT, it is used after dispersibility is improved and good mixing properties are obtained. Since the base material is the same, it is possible to cope with high definition by performing the dispersion and mixing process up to almost single particles.

When used for a high-excitation CRT, almost the same saturation characteristics are exhibited because the mixture is a mixture of the same base phosphor.

That is, since the luminance saturation curve of the mixed phosphor is improved as compared with the ordinary phosphor for a color television, the chromaticity deviation is small even at high excitation.

FIG. 3 shows yttrium oxysulfide (Y ₂ O ₂ S)
It shows the current-luminance characteristics of a phosphor based on zinc and a zinc sulfide (ZnS) based phosphor, and it can be seen that the former is superior in linearity.

[0036]

As is clear from the above description, the present invention uses a mixed phosphor which does not adversely affect the environment, has excellent dispersibility, and has no problem of saturation. It is possible to provide a monochrome cathode ray tube having no change in chromaticity.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a change in chromaticity depending on the Eu concentration of a red light emitting phosphor (Y ₂ O ₂ S: Eu).

FIG. 2 is a characteristic diagram showing a change in chromaticity depending on the Tb concentration of a blue-white light-emitting phosphor (Y ₂ O ₂ S: Tb).

FIG. 3 is a characteristic diagram showing current-luminance characteristics of an yttrium oxysulfide-based phosphor and a zinc sulfide-based phosphor.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kiyonori Harada 6-35 Kita Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F-term (reference) 4H001 CA06 XA08 XA16 XA39 YA63 YA65 YA65 5C036 AA01

Claims (1)

[Claims] A phosphor screen is formed by a mixed phosphor containing a blue-white light emitting phosphor made of yttrium oxysulfide activated by terbium and a red light emitting phosphor made of yttrium oxysulfide activated by europium. A cathode ray tube characterized by the above.