JPS61139683A - Manufacture of shadow mask - Google Patents

Abstract

PURPOSE:To enable the press-working of a blank for a shadow mask allowed to stand for a long time after piercing by photoetching into a shadow mask for a color cathode-ray tube without requiring annealing or leveling by subjecting the blank to recrystallization softening under specified conditions after the piercing. CONSTITUTION:A blank of <=0.30mm thickness fo a shadow mask for a color cathode-ray tube is manufactured by hot rolling and cold rolling a low carbon steel cong. <0.06% C. The blank is pierced by photoetching and subjected to recrystallization softening in a web hydrogen atmosphere at 600-800 deg.C so that the rate of decarburization is regulated to >=5%. The resulting blank can be press-worked into a shadow mask for a color cathode-ray tube by a tube maker without requiring annealing or level ing even after the lapse of a long period.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention enables recrystallization by simply performing annealing once under specific conditions at any time after drilling by photoetching, regardless of the elapsed period thereafter. The present invention relates to a method of manufacturing a shadow mask for a color cathode ray tube in which press molding is performed without softening annealing, leveling processing, etc.

[Background of the invention]

Figure 2 is a side sectional view of a shadow mask type color cathode ray tube, in which 1 is a panel section, 2 is a funnel section, 3 is a neck section, and 4 is a side sectional view of a shadow mask type color cathode ray tube.
5 is a fluorescent surface, 5 is an electron gun, and 6 is a shadow mask. As is well known, the shadow mask 6 has a large number of electron beam passing holes (hereinafter referred to as mask holes), and the three electron beams for causing the three primary color phosphors to emit light are emitted after passing through the mask holes. , just so as to reach phosphor dots or stripes of respective corresponding colors.

The above-mentioned shadow mask has conventionally been made from a cold-rolled steel strip with a carbon content of 0.06% or less that is cold-rolled into a thin plate of 0.30 tm or less, and holes are perforated by photo-etching. Later, it was manufactured by press molding. Even if you try to form it as it is without any treatment during press molding, the moldability is poor and it is practically impossible to work, so cathode ray tube manufacturers generally use 700 to 80
After improving the press formability by annealing at 0° C. for 5 to 20 minutes (it remained a flat plate up to this point), it was press formed into a curved shape as shown in FIG. However, (a)
The mask after annealing tends to elongate at the yield point and cause stretcher strain during press forming, and must be formed within a few days after annealing. (c) Deformation of the mask hole after photoetching is likely to occur due to leveling treatment after annealing. The fact that press forming work must be carried out within several days after annealing has sometimes placed a heavy burden on cathode ray tube manufacturers engaged in mass production. Additionally, cathode ray tube manufacturers had the problem that the optimum annealing conditions were not necessarily clear.

As a countermeasure against such situations,
As described in Japanese Patent Publication No. 54-102224, etc., the material is subjected to recrystallization softening annealing and then temper-rolled and then perforated by photoetching.
A shadow mask original plate material (hereinafter abbreviated as AF material) has been developed in which annealing and reshaping treatment immediately before press forming can be omitted, that is, the process shown in FIG. 4 is sufficient. but,(
a) AF material is annealed and skin-pass rolled at the material stage, so the material cost is relatively high; (b) AF material is soft because it has been annealed, and defects such as scratches and bends are likely to occur during the photo-etching process. (C) There were problems such as poor press formability compared to conventional materials that are annealed immediately before press forming.

[Purpose of the invention]

It is an object of the present invention to annealing a mask blank perforated by photoetching under specific conditions at any time, preferably (due to the process allocation rather than the properties of the material) directly at the photoetching company following the photoetching. By applying AF material, press forming can be performed without annealing or leveling immediately before pressing, regardless of the elapsed time, and the press formability is better than when using AF material. The purpose is to provide a manufacturing method.

[Summary of the invention]

In order to achieve the above object, in the present invention, a shadow mask original plate made of a low-carbon cold-rolled steel strip with a carbon content of 0.06% or less is perforated by photoetching, and then at a temperature of 600 to 800 °C and in an atmosphere. The time was set so that the decarburization rate after annealing (here, decarburization rate is defined as the percentage of the carbon content reduced by annealing to the carbon content before annealing) was 5% or more, and the process was repeated. We decided to perform crystal softening annealing. In this case, annealing may be performed, for example, in a wet hydrogen atmosphere. The reason is not clear, but if the decarburization rate by annealing is 5% or more, age hardening will not appear regardless of changes in composition or other conditions, and regardless of the length of time elapsed after annealing, the decarburization rate during annealing will not occur. It maintains its properties and can be press-molded as is without any treatment.

If the annealing work according to the present invention is performed immediately after the photoetching work at the photoetcher's workshop, although equipment such as an annealing furnace is required, the work can be performed very efficiently. Regardless of the period of time that has passed since the manufacturer delivered the perforated shadow mask original plate,
Since press molding can be performed without any pretreatment, mass productivity can be greatly improved as a whole, and manufacturing costs can be reduced.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in more detail with reference to Examples.

First, when carrying out the annealing according to the present invention, for example, dry hydrogen is moistened and the temperature is actually maintained at a specified temperature in an atmosphere adjusted so that the dew point is 10 to 20°C. The time may be set to about 10 minutes (actually, the time is determined by the condition that the decarburization rate is 5% or more).

In general, it is well known that press molding of a shadow mask is possible if it has the mechanical properties listed in the "Press Formability" column in Table 1 on the next page. However, by performing the annealing according to the present invention, the following preferable properties can be obtained.

(°) If the falling point or tensile strength is too high, it will be shown in Figure 5G.
As shown in the figure, the first surface warpage A (warp deformation amount θ) of the mask skirt portion after press molding becomes larger than the shape that should originally be used as a shadow mask, causing local deformation within the effective surface. B occurs. On the other hand, if the descending point or tensile strength is too low, deformation will occur frequently during handling, as shown in Figure 1 (a).
As shown in the case of a descending point, descending point: 9 to 15
kg/w2, tensile crab 25-35 kg/# range is best. Therefore, the method of annealing according to the present invention is better than the AF material.

(b) Press forming is possible if the work hardening index n value is normally 0.2 or more, but as shown in Figure 1 (b), the smaller the n value, the less elongation of each part due to work hardening during press forming. Non-uniformity occurs, and the uneven transmission of the shadow mask is significantly degraded compared to before pressing. For this reason, the n value is inevitably 0.
However, while the current n value of AF materials is 0.24 to 0.30, the n value when annealing according to the present invention is performed is 0.35 or more (Fig. 1). (b) The hatched area), making it easier to process.

(C) When the crystal grain size is large, during photoetching drilling,
Since irregularities are likely to occur on the side walls of the holes, the dimensional accuracy of the mask holes and the unevenness of transmission in the shadow mask original plate deteriorate. For this reason, current AF materials have a grain size of A S TM No.
Although it is kept to a small value of 3 to 9, if it is too small, the mechanical properties such as the above-mentioned falling point, tensile strength, and elongation at yield point will become large, and stretcher strain and mask deformation will easily occur. However, when annealing according to the present invention is carried out, problems related to grain size are completely eliminated (
It is far superior to current AF materials.

(d) In the case of leveling treatment, it can be used as long as the elongation at yield point is 6% or less, but in order to omit the leveling treatment, the elongation must be 0.5% or less. In the conventional method in which annealing is performed immediately before press forming, as shown in FIG. 1(C), age hardening occurs when left after annealing, resulting in elongation at yield point. Therefore, although it can be used initially by leveling treatment, re-annealing must be performed in the end, resulting in large machining losses and defects. For this reason, annealing has been performed immediately before press forming, or a mask made of a non-aging material such as AF material has been used. If the annealing according to the present invention is performed, age hardening can be suppressed and properties similar to those of the AF material can be obtained, as shown in FIG. 1(C).

(e) Current AF materials require additional annealing and temper rolling processes at the time of raw materials, so an increase in cost is inevitable.

Furthermore, since the material is soft during the photo-etching and perforation process, defects such as scratches and bends are more likely to occur. For this reason, the total cost when using the AF material is inevitably about 3 to 5% higher than that of the current material that is annealed and leveled immediately before pressing. On the other hand, if the present invention is implemented and annealing is performed under the conditions according to the present invention immediately after photoetching, the annealing itself can be performed intensively or continuously very efficiently. The total cost will be lower than that of the processing method.

〔Effect of the invention〕

As explained above, according to the present invention, by simply performing annealing under specific conditions after photoetching, the degree of freedom of the process during mass production of shadow mask manufacturing is greatly improved, and the cost is high and the defective rate is also high. There is no need to use easy-to-use AF materials, and the total cost of the entire shadow mask manufacturing process can be kept lower than in any conventional method.

[Brief explanation of drawings]

Figure 1(a) is a diagram showing the relationship between the lower yield point of the material during pressing and the amount of warp deformation θ° of the formed shadow mask.
Figure (b) shows the relationship between the work hardening index n and the deterioration level of permeation unevenness before and after pressing. Figure 1 (C) shows the relationship between the number of days left after annealing and the age hardening yield point elongation. The figure is a side sectional view of a shadow mask type color cathode ray tube.
The figure is a processing process diagram when AF material is used, and FIG. 5 is a diagram showing shadow mask deformation after molding when the mechanical properties of the material are inappropriate. 1-panel section, 2-funnel section, 3-neck section, 4-fluorescent surface, 5-electron gun, 6-shadow mask.禦 - り平 ◇ Invitation loan - To 11 row C 舅攬 9 下かし fig. 1 (C) 吋翿 τ 1 former soot (Japanese) □ Fig. 2

Claims (1)

[Claims] After perforating a shadow mask original plate made of a low-carbon cold-rolled steel strip with a carbon content of 0.06% or less by photoetching, the decarburization rate after annealing at a temperature of 600 to 800°C in an atmosphere for a time of 5% or more Production of a shadow mask characterized in that after recrystallization softening annealing is performed with settings such that Method.