JPS6269429A - Manufacture of crt - Google Patents

Abstract

PURPOSE:To decrease spark current and inhibit decrease of conductive coat resistance if a barium vapour deposition coat is formed due to getter flash, by letting suspension used for coat formation include carbon fiber. CONSTITUTION:The inner surface of a panel 1 made of glass is coated with a mixed liquid containing phosphor material and photo-binding substance, and a mosaic phosphor material layer 3 is formed by exposure and development through a shadow mask 2. Acrylic emulsion is applied to the phosphor material layer 3 to smoothen the rough surface of the layer 3 due to phosphor material particles, and further a metal coat 4 of aluminium is formed by vapor deposition followed by fixation of the shadow mask 2 at a constant distance from the inner surface of the panel 1. On the other hand, the funnel-shaped surface of a funnel 5 made of glass is coated with suspension including carbon fiber. This result in prevention of malfunction or destruction of the device due to spark currents in the ICs of a driver circuit for a color CRT, with resulting picture stability.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an improvement in a method for manufacturing cathode ray tubes, and in particular to a suspension containing graphite for forming a conductive film used for the purpose of making the inner wall of a cathode ray tube conductive. Regarding improvements.

(Background of the Invention) A conductive coating is formed on the inner wall of a cathode ray tube, and a high potential of 10 to 30 KV is applied to this coating from an anode button.This coating is manufactured as follows. Graphite particles, an alkali silicate for improving the adhesion between the graphite particles and between the graphite particles and the inner wall of the tube, a dispersant for improving the dispersion of graphite, and water are mixed to prepare a suspension. This suspension is applied to the inner wall of the tube by means of a brush or spray, and the coating is subsequently dried.

The coated film is further heat-treated at 400° C. to make it strong and used as a conductive film.

During operation of the completed cathode ray tube, sparks occasionally occurred in the electron gun. The spark current that flows at this time flows from the high-voltage power receiving part on the tube wall to the graphite coating to the electron gun to the cathode ray tube drive circuit outside the tube. The spark current can reach more than 500 amperes, causing IC malfunction and destruction in the drive circuit, and impeding product performance.

Several methods have been proposed to protect ICs from this spark current. For example, Tokuko Sho 52-387
Publication No. 13 discloses that iron oxide is included in a suspension to form a highly resistive film to reduce the spark current value.

However, in cathode ray tubes, in order to improve the degree of vacuum inside the tube, a barium metal vapor deposition film is formed on the tube inner wall by getter flash. This vapor-deposited film has the disadvantage that the electrical resistance of the conductive coating on the inner wall of the tube decreases. [Object of the Invention] Therefore, an object of the present invention is to reduce the spark current value and to reduce the barium-deposited film by getter flash. The object of the present invention is to provide a method capable of suppressing a decrease in the resistance value of a conductive film even when a conductive film is formed.

[Summary of the invention]

In the present invention, the conductive film formed on the inner wall of the cathode ray tube affects the continuity of the barium vapor deposited film of the getter,
Furthermore, this study was made with attention to the fact that the degree to which the electrical resistance of the conductive film decreases depends on the degree of continuity of the deposited film, and carbon fibers were included in the suspension used to form the film. It is characterized by:

[Embodiments of the Invention] The present invention will be described in detail below. First, a two-color cathode ray tube was manufactured using the following method. A liquid mixture containing a phosphor and an optical coupling agent is applied to the inner surface of a glass receptacle panel 1, and a mosaic-like phosphor layer 3 is formed by exposure and development through a shadow mask 2.6 phosphor layer 3 An acrylic emulsion is applied on top of the phosphor layer 3 to fill the holes caused by the phosphor particles. Furthermore, a metal film 4 of aluminum is formed by vapor deposition. The shadow mask 2 is fixed at a constant distance from the inner surface of the panel 1.

On the other hand, the inner surface of a funnel-shaped glass funnel 5 is coated with a suspension having the composition shown in Table 1.

Table 1 Composition of Graphite Suspension As a conductive material, cylindrical graphite (carbon fiber) having a diameter of 6 to 7 μm and a length of 12 to 21 μm was used as the graphite material to be mixed in this example. A funnel 5 and a panel 1, which have been processed to form a coating 6 by drying the coating, are combined via a crystalline low-melting frit glass 7.

The panel 1 and the funnel 5 were fused together by heat treatment at about 400°C. During this heat treatment, the organic matter (acrylic resin, etc.) on the inner surface of the panel 1, the coating 6 formed on the inner surface of the funnel 5,
The dispersant inside disappears by thermal decomposition.

An electron gun 9 is inserted into the tube that has been fused through the neck part 8 of the funnel 5, and the electron gun 9 is sealed at the neck part 8. A part 10 called a valve spacer contact is attached to the tip of the electron gun 9, and this part 10 establishes electrical continuity between the conductive coating 6 inside the tube and the electron gun 9.

After completing the sealing of the electron gun 9, the bulb is heated and evacuated from an exhaust pipe (not shown) at the tip of the electron gun 9 (on the side opposite to the bubble spacer contact 10) using a vacuum pump.

The inside of the tube is evacuated and the exhaust tube is removed by heating and melting. Then, the getter 11 attached to one end of the electron gun 9 is flashed by high frequency heating from outside the tube. As a result, a metal barium vapor deposition film (not shown) is formed on the conductive coating 6 on the inner wall of the tube.

After this, activation and aging are performed to make it easier to extract cathode rays. Additionally, the valve will be reinforced for explosion protection.

Operating the color cathode ray tube produced in this way,
Images are obtained by excitation of the phosphor with cathode rays.

Here, the function of the carbon fibers in the conductive coating inside the tube will be described. The carbon fiber used in the present invention has a diameter of 7 μm and a length of 14 μm.
t The conventionally used graphite was simplified into a 7 μm sphere, and the barium from the getter flew obliquely to the coating and adhered to it. Figures 3 and 2 are schematic diagrams of this as seen from above, respectively. Indicated. As can be seen from the comparison between these two figures, the continuity of the barium vapor deposited film 16 is better in the case of FIG. 3 using cylindrical graphite 15 than in the case of FIG. 2 using conventional spherical graphite 14. /JN becomes smaller. Therefore, when the cylindrical graphite 15 is used, compared to the spherical graphite 14, the degree of decrease in resistance of the conductive coating on the inner wall of the tube due to the barium vapor deposited film due to getter flooding is smaller.

In the color cathode ray tube manufactured using the suspension shown in the above example, the spark current was reduced by 50 to 7
I was able to reduce the amperage by 0.

In addition, in the above example, the case where cylindrical graphite (carbon fiber) was used as the conductive material graphite was shown, but according to the idea of the present invention, even if spheroidal graphite and cylindrical graphite are used together, it will be possible to It is clear that the effect can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, malfunction and destruction of the IC of the color cathode ray tube drive circuit due to spark current can be avoided, and images can be stabilized.

[Brief explanation of drawings]

Fig. 1 is a partially cutaway side view of a cathode ray tube manufactured by applying the present invention, and Fig. 2 shows the formation of a barium vapor deposition film by getter flash when conventional spheroidal graphite is used as the conductive material. FIG. 3 is a schematic diagram similar to FIG. 2 in which carbon fiber is used as a conductive material according to the present invention. DESCRIPTION OF SYMBOLS 1... Panel, 2... Shadow mask, 3... Phosphor layer, 4... Aluminum vapor deposition film, 5... Funnel, 6... Conductive coating, 7... Low melting crystal Glass, 8...
・Neck part, 9...Electron gun.

Claims (1)

[Claims] A method for manufacturing a cathode ray tube, comprising the steps of applying a suspension containing graphite as a component to the inner wall of the cathode ray tube, and then drying and baking the coating of the suspension to form a conductive coating layer on the inner wall of the cathode ray tube. A method for manufacturing a cathode ray tube, characterized in that the suspension contains carbon fibers.