JPH0222496B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a method for manufacturing a shadow mask for a color picture tube. [Technical Background and Problems of the Invention] As shown in Fig. 3, a general color picture tube emits three electron beams 1, corresponding to red, green, and blue, emitted from an electron gun (not shown). 2 and 3 correctly correspond to the phosphors 7, 8, and 9 that emit red, green, and blue light applied to the inner surface of the panel 6 through the regularly arranged fine apertures 5 of the shadow mask 4. It has a structure that projects color images by emitting sudden light. The shadow mask for such a color picture tube is made by precisely drilling regularly arranged fine holes, molding it into a curved shape similar to the inner surface of the panel without any shape distortion, and making sure that the shadow mask matches the inner surface of the panel. Interval (hereinafter referred to as q value)
It is required to maintain the value correctly at a predetermined value. The materials for this kind of shadow mask are:
Generally, the main component is iron with a high degree of dullness, e.g. 0.10
Aluminum killed decarburized steel with a thickness of about mm to 0.3 mm is used. This is determined comprehensively from the material supply capacity, cost, workability, strength, etc. However, the shadow mask of a color picture tube is
Even if all of the above conditions are managed within the permissible range in each step up to incorporation into pipes, there are still some problems. One of these problems is the problem of thermal expansion caused by the rise in temperature of the shadow mask. In other words, when a color picture tube is operated, less than 1/3 of the electron beams pass through the apertures in the shadow mask, and the remaining electron beams impinge on the shadow mask, which can sometimes reach temperatures as high as 80 degrees Celsius. It will be heated to about 100 ml. As a result, the shadow mask undergoes thermal expansion and deviates from the correct q value. This causes the so-called "doming phenomenon" and deteriorates color dullness.
Conventionally, commonly used materials whose main component is iron have an expansion coefficient of approximately 12×10 ^-6 /deg at 0 to 100°C.
Because of its considerable size, this doming phenomenon is likely to occur and has become an important problem. Therefore, various proposals have been made to reduce the purity drift, that is, the deterioration of color purity caused by this doming phenomenon, but no effective measures have been found, especially for the early stages of tube operation and localized doming. Not served. Therefore, examples of using a material with a small coefficient of thermal expansion, such as an iron-nickel alloy, as the material of the shadow mask are disclosed in Japanese Patent Publication No. 42-25446, Japanese Patent Application Laid-open No. 58977-1982, and Japanese Patent Application Laid-open No. 68650-1989. However, it has not yet reached the point where it satisfies practical conditions. One of the reasons for this is the difficulty in processing metal plates made of iron-nickel alloy. In other words, in order to keep the q value within the allowable range, the curved surface of the shadow mask must have high precision, and the allowable tolerance for a radius of curvature (R) of 1000 mm is:
±5mm is extremely strict. However, since iron-nickel alloys retain considerable elasticity after annealing compared to conventional alloys whose main component is iron, they have the disadvantage of poor spherical formability by pressing or the like. For example, as shown in Figure 4, the thickness is 0.2
If a local dent is created with respect to the standard radius during spherical forming of a mm iron-nickel plate, the amount of dent d is
It has been confirmed that if the thickness is 20 μm or less, deterioration in color purity is substantially tolerable. Regarding the amount of depression (d) and the yield point strength of the shadow mask material, for example, a 14-inch shadow mask exhibits the characteristics as shown in FIG. In other words, the amount of depression
In order to make it 20μm or less, the yield point strength is 20Kg/mm ²
It is necessary to keep it below. However, when a shadow mask made of an iron-nickel alloy is annealed in a mask annealing furnace in hydrogen in the same way as a conventional shadow mask made of aluminum-killed decarburized steel, the yield point strength is as shown in Figure 6. , characteristic (b) of the iron-nickel alloy is much higher than characteristic (a) of aluminum killed decarburized steel. In other words, even after annealing at a high temperature of 900℃, the yield point strength is still 29 to 30.
It only decreases to Kg/ ^mm2 . Here, in FIG. 5, since a clear boundary cannot be obtained for the yield point strength of the iron-nickel alloy, the tensile strength at 0.2% elongation is substituted as the corresponding value. The same can be said of shadow masks annealed in vacuum or in the air. In this way, iron-
The shadow mask is made of nickel-based alloy.
In particular, since the deformation and depression around the effective area are large, the deterioration of color purity caused by thermal expansion of the mask is almost no problem due to the small expansion coefficient, but the deterioration of color purity due to deformation is considered to be a major problem. [Object of the Invention] The purpose of the present invention is to improve the curved surface formability of a shadow mask whose main component is an iron-nickel alloy, and to obtain a method for manufacturing a shadow mask that can prevent deformation and achieve high precision. . [Summary of the Invention] The present invention is a metal plate mainly composed of an iron-nickel alloy, which is made by punching a large number of holes, annealing it in an oxidizing atmosphere, and then performing warm press forming. Therefore, the yield point strength is lowered to provide a highly accurate shadow mask without deformation, thereby preventing deterioration of color purity. [Embodiments of the Invention] Examples in which an amber alloy is used as a material for a shadow mask whose main component is an iron-nickel alloy will be described below. Table 1 shows the weight composition ratio of the amber alloy used as an example and the conventional aluminum killed decarburized steel.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to improve the curved surface formability of a shadow mask containing iron-nickel alloy as a main component, to prevent deformation, and to obtain a highly accurate curved surface quality, and to avoid color purity problems. A picture tube can be obtained.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between tensile test temperature and yield point strength, Figure 2 is a characteristic diagram showing the relationship between warm press temperature and the amount of dent in the shadow mask, and Figure 3 is a characteristic diagram showing the operation of the color picture tube. Schematic diagram for explanation,
Figure 4 is a schematic diagram of the main parts to explain the deformation of the shadow mask, Figure 5 is a characteristic diagram showing the relationship between the amount of deformation of the shadow mask material and the yield point strength, and Figures 6 and 7 are annealing of the shadow mask. FIG. 3 is a characteristic diagram showing the relationship between temperature and yield point strength. 4...Shadow mask, 5...Open hole.

Claims (1)

[Claims] 1. A process of drilling a large number of holes in a thin metal plate mainly composed of iron and nickel, and annealing the metal plate with the large number of holes in an oxidizing atmosphere. A method for producing a shadow mask, comprising the steps of: forming an oxide film on the metal plate; and forming the annealed metal plate into a shadow mask by warm pressing. 2. The method for manufacturing a shadow mask according to claim 1, characterized in that the warm pressing temperature is 120° C. or higher.