JPS5951703B2 - Method for forming blackened film on frame for shadow mask - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a blackened film on a shadow mask frame used in a color cathode ray tube.

Generally, a color cathode ray tube is composed of a panel section, a funnel section, and a neck section, and a shadow mask is disposed and engaged with the inner surface of the panel section.

This shadow mask is shown in FIGS. 1 and 2.

Of these, FIG. 1 is a perspective view for explaining the frame, and FIG. 2 is a partially cutaway perspective view for explaining the shadow mask.

1 and 2, 1 is a frame, 2 is a shadow mask body, 3 is a spring clip, and 4 is a shadow mask. The shadow mask 4 consists of a shadow mask body 2 having many pores, and a panel pin. a spring clip 3 suspended from the spring clip 3 and a spring clip 3 suspended from the
．． The frame 1 is formed from a hot or cold steel plate having a thickness of 8 mm to 2.5 mm.

The shadow mask body 2 and the frame 1 have a blackening film 5 mainly composed of triiron tetroxide on their surfaces for the purpose of preventing rust during the color cathode ray tube manufacturing process and improving emissivity. It is formed by darkening the atmosphere.

However, the assembly of the shadow mask body 2, spring clip 3, and frame 1 is done by electric resistance welding.
At this time, the blackened film 5 near the welding point has already peeled off at the time of assembly, and this becomes especially noticeable when the spring clip 3 and frame 1, which are thick-walled products, are combined welded. This caused clogging of the shadow mask 4 having pores.

Furthermore, when manufacturing color cathode ray tubes, the temperature is 350°C.
There are 3 to 4 heat treatment steps in the atmosphere at ~450°C, and each time this process is repeated, the aforementioned blackened film 15 lifts up at locations other than the assembly welding points, and also peels off, especially on the frame. This caused fatal flaws in the color cathode ray tube's mask clogging and withstand voltage characteristics.

As one measure against the peeling off of the blackened film 5, by changing the selection and proportion of the zero-shiki type in atmosphere blackening, the blackened film 5
A method has been reported to improve the adhesion of the blackening film 5 by changing the thickness and composition of the blackening film, but it is not yet perfect, and another countermeasure is to Methods have been proposed and implemented to improve the adhesion of the blackened film formed by roughening the surface by applying pickling, sandblasting, plating with different metals, or by dissolving the surface. The reality is that this method has not yet been applied to all frames, as there are drawbacks such as investment in equipment, manufacturing costs, and rust and dirt on the finished frame.

This invention was made to eliminate the above-mentioned conventional drawbacks, and as an alternative to pickling, sandblasting, plating, etc., heat treatment is performed under certain conditions in a reducing atmosphere before blackening. An object of the present invention is to provide a method for forming a blackened film on a frame for a shadow mask, which can improve the adhesion of the blackened film.

Examples of the present invention will be described below.

1.6mm~2. A rectangular frame 1 is created by press-molding a hot or cold rolled mesh of 0 mm.

This frame 1 is washed with an organic solvent or the like to remove press oil and dust attached to the surface.

Next, heat treatment is performed in a reducing atmosphere at a temperature of 500°C or higher for 3 minutes or more, preferably for 5 minutes or more in a reducing atmosphere at a temperature of 550°C to 850°C.

Next, a blackened film 5 is formed on the heat-treated frame 1 by atmospheric blackening.

The blackened film 5 formed in this way exhibits an adhesion force that is about 3 to 4 times that of the blackened film 5 of the frame 1 that has not been subjected to any treatment before blackening. There is little blackening film near the welding points during assembly welding, and there is no blackening even when the tube is repeatedly passed through a heat treatment furnace in the air at temperatures of 350°C to 450°C twice in the cathode ray tube manufacturing process. No lifting or peeling of the film 5 was observed, and no acid washing or peeling was observed.
The adhesion strength of the blackened film was comparable to that of Frame 1, which had been subjected to sandblasting etc.

Here, the reducing atmosphere refers to the H2 force, but any other reducing atmosphere may be used, such as NH3 decomposition gas or a combination with an inert gas. Of course, it is not limited to.

Furthermore, the surface of the material subjected to the pre-blackening treatment according to the present invention has no surface stains.

Moreover, even when stored for a long period of time, the degree of rusting is small.

Since the press distortion of the frame 1 itself is removed before assembling the spring clip 3 and the shadow mask main body 2, it has been confirmed that when these are assembled to form the shadow mask 4, the assembly accuracy is improved.

As described above, according to the present invention, as an alternative to pickling, sand branding, plating, etc., heat treatment under certain conditions in a reducing atmosphere is performed before blackening to improve the adhesion. Therefore, the manufacturing cost is low, the adhesion of the blackened film is improved, and a frame with excellent characteristics can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a perspective view for explaining the frame, and FIG. 2 is a partially cutaway perspective view for explaining the shadow mask. 1...Frame, 2...Shadow mask body, 3...Spring clip, 4...
Shadow mask, 5...blackening film. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. After molding the frame that holds the shadow mask main body,
A method for forming a blackened film on a frame for a shadow mask, which comprises heating the frame in a reducing atmosphere at a temperature of 500° C. or more for 3 minutes or more, and then blackening the atmosphere to form a blackened film. 2. The method for forming a blackened film on a shadow mask frame according to claim 1, wherein the reducing atmosphere contains H2 gas or NH3 decomposition gas. 3. The method for forming a blackened frame film for a shadow mask according to claim 1, wherein the heat treatment is performed at a temperature of 550° C. to 850° C. for 5 minutes or more. 4. The method for forming a blackened film on a frame for a shadow mask according to any one of claims 1 to 3, wherein the blackened film is made of triiron tetroxide.