JPS6222358A - Color picture tube - Google Patents

Abstract

PURPOSE:To inhibit the thermal expansion of a shadow mask by increasing its ability to absorb heat without preventing the permeation of electron beams by forming heat-absorbing films over the areas of a metal back surface other than those corresponding to phosphors in a fluorescent screen. CONSTITUTION:The heat-absorbing films 7 of a color picture tube are formed on a shadow-mask-side layer formed on a metal back surface 5. After the formation of the metal back surface 5, a liquid suspension prepared by dispersing an aqueous PVA (polyvinyl alcohol) solution nd ammonium dichromate in a quick drying solvent principally composed of an alcohol such as methanol or ethanol is applied to the metal back surface 5 and then the entire surface is exposed to light to form a water-insoluble primer layer. Next, polyvinyl alcohol and a dichromate-system photosensitive resin are applied to the primer layer to form a layer. After that, the thus formed layer is exposed to red, green and blue colors prior to development and then application of graphite and removal of the photosensitized films are performed, thereby forming the heat- absorbing films 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color picture tube in which misalignment between an electron beam and a phosphor dot is improved by reducing thermal deformation of a shadow mask over time.

[Conventional technology]

-m, the color picture tube has a neck part 2, as shown in Figure 2.
2, the funnel part 23, the panel part 1, and the neck part 2
2, a fluorescent surface 26 made of three-color phosphors formed on the inner surface of the face plate of the panel section 1, and a metal back surface 5 covering this fluorescent surface.
and a shadow mask 27 placed a certain distance away from the metal back surface 5.

In such a configuration, an electron beam emitted from the electron gun 24 passes through the hole in the shadow mask 27 and hits the fluorescent surface 26, thereby displaying a predetermined color image. However, in this case, most of the electron beam (approximately 78
~85%) collides with the shadow mask 27, which generates heat and thermally expands. Therefore, there is a drawback that mislanding of the electron beam occurs and color purity deteriorates. Therefore, in order to eliminate this drawback in recent years, a heat absorbing film 7 made of graphite, aluminum oxide, etc. is formed on the shadow mask side surface of the metal back surface 5 as shown in FIG. A method has been devised to suppress the =i tension of the shadow mask 27 by absorbing the
Conventionally, such a heat absorbing film 7 was formed on the metal back surface 5 by the following method. In the case of graphite, graphite is dispersed in a quick-drying solvent mainly composed of alcohols such as methanol and ethanol to create a graphite liquid, and this graphite liquid is sprayed directly onto the metal back surface to form a film. In the case of aluminum oxide, after the metal back surface 5 is formed, aluminum is deposited under a low vacuum to form an aluminum oxide film on the metal back surface.

[Problem that the invention seeks to solve]

In the above-described conventional color picture tube in which the heat absorbing film 7 is formed on the metal back surface 5, the heat absorbing film 7 is also formed on the phosphor 3 via the metal back surface as shown in FIG. Therefore, if the heat absorption film 7 is made blacker, that is, the thickness of the heat absorption film 7 is made thicker, in order to increase the heat absorption ability, the transmission of the electron beam becomes significantly worse, and the luminance of the fluorescent surface 26 decreases. Therefore, the heat absorbing film 7 cannot have a high degree of blackness, and the heat from the shadow mask 27 cannot be absorbed sufficiently.

[Means for solving problems]

In order to solve the above-mentioned drawbacks, the color picture tube of the present invention has a heat absorbing film made of graphite only in a portion of the metal back surface other than the portion contributing to light emission of the phosphor.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows one embodiment of the present invention. 1 is a face panel, 2 is a black matrix film, 3 is a phosphor, 4 is a filming film, 5 is a metal back surface, 6 is a primer layer, and 7 is a heat absorption film.

The heat absorbing film 7 of the color picture tube according to the invention can be formed by adding a separate layer to the shadow mask side of the metal back surface 5, as described in the following examples.

Example 1 After forming the metal back surface, a solution prepared by dispersing PVA (polyvinyl alcohol aqueous solution) and ammonium dichromate in a quick-drying solvent mainly composed of alcohols such as methanol and ethanol was applied, and the entire surface was exposed to light. The primer layer is insoluble in water. After that, polyvinyl alcohol, dichromate-based photosensitive resin coating, red, green, and blue color exposure,
A heat-absorbing film is formed by performing the same steps as those for forming a conventional black matrix film, ie, peeling off a graphite-coated photosensitive film.

Example 2 After forming the same primer layer as in Example 1, a suspension of graphite and a positive resist, such as a 1°2-naphthoquinone diazide compound, which becomes soluble upon light irradiation, was applied onto the primer layer by the Slithie method. Then, a heat-absorbing film is formed by exposing the material to red, green, and blue colors, and developing it to remove unnecessary graphite.

In both of the above embodiments, after the heat absorbing film is formed, it is baked at about 400'C to form a heat absorbing film on the metal back surface.

Although graphite is used as the heat absorbing material in the examples, it is free to select any material that has good geothermal absorbability.

〔Effect of the invention〕

As explained above, the present invention has the ability to absorb heat without interfering with the transmission of electron beams by forming a heat-absorbing film at a location other than the location on the metal back surface corresponding to the position of the phosphor in the phosphor surface. can suppress the thermal expansion of the shadow mask.

Therefore, there is an effect that mislanding of the electron beam can be significantly reduced without reducing the luminance of the fluorescent surface.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the fluorescent surface of the color picture tube of the present invention, FIG. 2 is a longitudinal cross-sectional view of a shadow mask type color picture tube, and FIG.
The figure is a cross-sectional view of the fluorescent surface of a color picture tube with a conventional heat-absorbing film. 1... Face panel, 5... Metal back, 6...
...Primer layer, 7...Heat absorption film, 27...Shadow mask. Figure 1

Claims (1)

[Claims] A color picture tube characterized in that a heat-absorbing film is formed on the side of the metal back surface coated on the phosphor surface of the cathode ray tube, on the side facing the shadow mask, except for the portion that contributes to light emission of the phosphor. .