JPH0246630A - Color cathode ray tube and its manufacturing method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention suppresses local and temporary thermal expansion of the shadow mask of a shadow mask type color cathode ray tube due to electron beam impact, thereby preventing deterioration of the electron beam concentration state. The present invention relates to a color cathode ray tube that suppresses the occurrence of color shift caused by color shift, and a method for manufacturing the same.

[Prior art] The shadow mask of a shadow mask type color cathode ray tube is
During use, the chamber is hit by an electron beam, and the heat generated at that time causes the temperature to rise and cause thermal expansion.

When the shadow mask expands (as a result of the expansion, the shadow mask deforms so that it protrudes toward the phosphor surface side, this phenomenon is usually called doming), the concentration state of the three electron beams generally deteriorates, causing problems such as color shift. Since extremely conspicuous defective phenomena are observed, many countermeasures have been proposed and implemented since ancient times.

Countermeasures have been taken against the overall and average thermal expansion of the shadow mask, such as by inserting a bimetal into a part of the shadow mask support mechanism installed inside the panel skirt of the bulb. ing.

The metal substrate of the shadow mask is quite thin, so if an extremely bright part suddenly appears in one displayed image, and if a large amount of heat is suddenly generated locally, the heat is immediately transferred to the surroundings by thermal conduction. Therefore, local expansion of the shadow mask metal substrate occurs at the heat generating portion, causing protrusion deformation toward the fluorescent surface side. Although there have been no measures to prevent this type of phenomenon in the past, there have been no definitive countermeasures. As a conventional technique, for example,
Publication No. 7-9184 discloses that a heat insulating layer and a metal thin film covering this heat insulating layer are formed on the electron beam incident portion of the shadow mask on the electron gun side, excluding the electron beam passing hole, to reduce heat generated by the electron beam. A structure is described in which heat radiation is emitted from the metal thin film, and examples include coating an acrylic emulsion liquid on the electron gun side surface of the shadow mask,
Dry.

An aluminum film is formed thereon, and the acrylic emulsion film is decomposed and vaporized in a panel baking process to form a cavity to form a thermal insulating layer, or a vapor-deposited film of ZnS, ZnC1, CdS, CdTa, etc. is used as a thermal insulating layer. has been shown to be used. FIG. 3 is a cross-sectional view of a shadow mask according to the prior art. In the figure, 1 is a shadow mask opening, 2 is a shadow mask metal substrate, 3 is a heat emitting film, and 4 is a heat insulating layer. However, as mentioned above, it is necessary to vaporize the acrylic emulsion to form a cavity under the metal film that will serve as a thermal insulation layer during the color cathode ray tube manufacturing process.

In particular, consideration must be given to the large amount of gas generated during the vacuum evacuation process, and problems such as peeling of the metal film for heat radiation may occur. Further, although it is possible to use a vapor deposited film such as ZnS as a thermal insulating layer, it is not practical due to the material cost. Also, in Japanese Patent Application Laid-open No. 154524/1986,
A doming-suppressing material (for example, polytitanocarbosilane or semiconductor glass) is applied to the shadow mask surface in a dust-removal atmosphere, and laser light is irradiated to turn this material into a ceramic, which shows that this ceramic is more rigid than mild steel. It is disclosed that the method is used to prevent doming.

However, this method has problems with mass production.

[Problems to be Solved by the Invention] An object of the present invention is to provide a simple and inexpensive color cathode ray tube with a shadow mask coated with a layer having heat insulating properties and heat emitting properties.

[Means for Solving the Problems] In order to achieve the above object, a material that contains a substance that generates gas when heated during the manufacturing process of a color cathode ray tube, and that forms an insulating porous structure with the generated gas, is used. It is sufficient to deposit it on the electron gun side surface of the shadow mask. Specifically, the gas generating substance is a gas that does not affect the electron emission characteristics of the electron gun cathode of a color cathode ray tube (for example, nitrogen). It may be a substance that decomposes at the heating temperature during the tube panel baking process. An example of a substance suitable for this purpose is potassium azide (thermal decomposition temperature is 350°C).Also, an example of a substance that confines the gas and forms an insulating porous structure is the panel of the bulb of a color cathode ray tube. and frit glass (low melting point crystallized glass) used for welding funnels.

[Operation: Fritted glass powder containing potassium coagide is applied, and the dried shadow mask is fitted onto a panel and subjected to a baking process. During this baking process, potassium azide begins to thermally decompose at around 350°C and begins to release nitrogen gas, but at the same time the frit glass also melts at around 350°C, so the nitrogen gas generated causes bubbles in the frit glass. After that, the frit glass gradually crystallizes to form a porous film. This porous membrane has a small portion that contributes to heat conduction.

Works as a thermal insulation layer even in vacuum.

When such a heat insulating layer is applied to a shadow mask, its heat insulating properties act extremely effectively against the sudden large amount of heat generated locally on the shadow mask, and this heat insulating layer protects the shadow mask. If the transfer of heat to the metal substrate is suppressed and the amount of heat generated in that local area decreases to an average value while the temperature of the metal substrate in that area does not rise too high, local expansion of the shadow mask will occur. , protrusion can be suppressed.

[Example] The procedure for forming a heat insulating porous layer according to an example of the present invention is shown in Figure 1.
FIG. 2 shows a cross section of a shadow mask according to the present invention. On the electron gun side of the shadow mask formed according to the normal process, potassium azide and low melting point crystallized glass (ASF-1307B, manufactured by Asahi Glass Co., Ltd.) were used as a binder with an organic substance such as nitrocellulose and isoamyl acetate as a solvent. Make a slurry and apply by spraying. Next, by heating in a panel baking process, the potassium azide begins to decompose at 350° C., and at the same time, the low-melting point crystallized glass melts, and a large number of bubbles are generated in the glass. During panel baking, the glass gradually crystallizes to form a strong porous structure. The main points of this process are shown in FIG. In this way, the heat insulating porous material 5 shown in FIG. 2 is formed on the electron gun side of the shadow mask 2.

Note that 6 in FIG. 2 is a hole.

Experiments using this example revealed that it did not affect the electron emission characteristics of the cathode of the color cathode ray tube or its lifespan, and that a heat insulating porous layer could be formed, so that the shadow mask could be locally -
Temporal thermal expansion could be effectively suppressed.

By forming the heat insulating porous layer to a thickness of 5 to 10 μm, the amount of electron beam movement due to doming could be reduced by 20 to 30%.

In the above embodiment, a gas that decomposes and releases nitrogen is explained, but other gases may be used as long as they have almost no adverse effect on the electron emission characteristics from the cathode.1For example, hydrogenation that releases hydrogen gas Potassium (decomposition temperature is 417℃
) can also be used.

In addition to frit glass, structural materials include JP-A-6
Polytitanocarbosilane or semiconductor glass disclosed in Japanese Patent No. 2-154524 may be used.

[Effects of the Invention] As explained above, according to the present invention, a heat insulating porous layer can be easily formed on the electron gun side of a shadow mask, so that it can be easily formed during operation of a color cathode ray tube.

The effect of reducing the amount of color shift due to doming by 20 to 30% can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing main processing steps according to the present invention, FIG. 2 is a cross-sectional view of a shadow mask according to the present invention, and FIG. 3 is a cross-sectional view of a shadow mask using a conventional anti-expansion technique. DESCRIPTION OF SYMBOLS 1...Shadow mask opening, standard metal substrate, 3...Heat emitting film, 2...Shadrama 4...Heat insulating layer, Figure 1, Figure 2, Figure 3.

Claims (1)

[Scope of Claims] 1. In a shadow mask type color cathode ray tube, a heat insulating porous layer is provided on the metal substrate surface of the electron beam emitting part excluding the electron beam passing hole on the side of the shadow mask facing the electron gun. A color cathode ray tube characterized by being coated. 2. A slurry of potassium azide and low melting point crystallized glass powder suspended in a volatile solvent together with an organic binder is applied to the metal substrate surface of the shadow mask and dried, followed by baking of the shadow mask. A method for manufacturing a color cathode ray tube, characterized in that the porous layer is formed by gas bubbles generated in the molten glass due to temperature rise over time.