JPS6056053A - Iron-nickel alloy for shadow mask which suppresses generation of uneven stripe during etching - Google Patents

Abstract

PURPOSE:To prevent generation of an uneven stripe defect in the stage of perforating very small holes by photoetching by forming a shadow mask for a color cathode ray tube of an Fe-Ni alloy, and controlling strictly the segregation rate of Ni and the distributing condition and size of the segregated matter. CONSTITUTION:A shadow mask to be used for a cathode ray tube for image receiving of a color television set is manufactured of a thin sheet consisting of an Fe-Ni alloy. The Fe-Ni alloy sheet in which the component segregation rate of Ni expressed by the formula (1) for said alloy is <=10%, the segregated matter in unit volume is <=5vol% and the length of one segregated matter just prior to perforating by etching is <=30mm. is used in this case. The generation of uneven stripes in the stage of perforating by etching is obviated and since the Fe-Ne alloy itself has a low coefft. of thermal expansion, the shadow mask forming the sharp image without color deviation is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an iron-nickel alloy for use as a material for shadow masks of color television lounge tubes, and more particularly to an iron-nickel alloy for use in shadow masks that suppresses the occurrence of uneven streaks during etching.

Mild steel is generally known as a shadow mask material for color television cathode ray tubes. In a color television cathode ray tube, electron beams emitted from three electron guns pass through microscopic holes in a shadow mask and are precisely irradiated onto a predetermined point on a fluorescent screen, giving a specific color tone.

However, when such a cathode ray tube is used continuously, the temperature of the fluorescent surface and shadow mask supported by the glass body onto which the electron beam is irradiated gradually increases. In particular, the shadow mask is considerably hotter than the fluorescent surface supported by the glass body.

Moreover, since the shadow mask material has a much larger coefficient of thermal expansion than the glass body, a mutual positional shift occurs, and the electron beam irradiation is not performed accurately, resulting in blurring of the two strokes.

For this reason, attempts have been made to compensate for this by devising the structure of the support that serves as a suspension device for the shadow mask, but this is not sufficient.

Therefore, it has been proposed to use a low thermal expansion material such as an iron-nickel alloy such as invar as a shadow mask material.

However, although such an iron-nickel alloy was supposed to give good results in terms of image clarity, it was difficult to obtain a good hole shape during photoetching during the process of manufacturing a shadow mask from this shadow mask material. When the etched shadow mask was visually observed from the surface, it was found that defects called uneven streaks remained. It is known that non-metallic inclusions in the steel or charcoal (Fθ, 0) are the cause of uneven streaks in mild steel. (Unexamined Japanese Patent Publication No. 55-6.2123) L-shaped,
The uneven streaks that occur in iron-nickel alloys such as amber do not disappear even if these nonmetallic inclusions are reduced;
It is believed that the cause is inherent to nickel-based alloys, and improvements have been desired.

The inventors of the present invention have conducted various studies on uneven streaks in iron-nickel alloys, and have found that the cause of uneven streaks is the segregation of nickel components, and that there is a difference in etching performance between the nickel segregated area and the base metal. It was found that the shape of the hole had deteriorated. The occurrence of this streak unevenness becomes particularly noticeable when the amount of nickel exceeds 20% by weight.

In view of this point Kfi, the present invention improves the drawback of the conventional iron-nickel based alloy, which is the generation of uneven streaks during etching, and provides an iron-nickel alloy for shadow masks that suppresses the occurrence of uneven streaks during etching. This is what we are trying to provide.

In the present invention, the component segregation rate of nickel expressed by a linear equation is 10 cm or less, the segregation rate in a unit volume is 5 volume 1% or less, and the length of one of the segregation particles in the shadow mask material immediately before etching is This is an iron-nickel alloy for shadow masks that suppresses the occurrence of streak unevenness during etching with a thickness of 50 wm or less.

Next, the reasons for limiting the nickel segregated substances constituting the alloy of the present invention will be explained.

The reason for setting 10- or less is that the component segregation rate of nickel is 10- or less.
This is because if the value exceeds -, the difference in etching performance with the base material becomes significant, and the occurrence of cystoscopic unevenness becomes noticeable. The reason why the number of segregated substances is set to be 5 or less in a unit volume is that if the number of segregated substances exceeds 5 in a unit volume, the occurrence of uneven streaks becomes noticeable. The reason why the length of one of the segregated particles is set to 30 m or less in the material before etching is that if the length of one of the segregated particles exceeds 3011I+, the occurrence of streak unevenness becomes noticeable.

In this way, only by strictly controlling the segregation rate of nickel, the distribution state, and the size of the segregated substances can the occurrence of uneven etching streaks be suppressed.

Furthermore, due to the characteristics of these materials, which have a low coefficient of thermal expansion), images have an extremely excellent feature of becoming even clearer.

A manufacturing method that satisfies these conditions can be achieved by preventing segregation during ingot manufacturing or performing nickel diffusion treatment by heat treatment during the strip manufacturing process.

The alloy of the present invention will be explained below using examples.

(Example) After melting an ingot of the alloy of the present invention shown in Table 1 in an electroslag melting furnace or a vacuum degassing furnace,
It was hot rolled at 0°C to form a plate with a thickness of 511!1. If there is a large amount of nickel segregation, heat treatment at 110 (FX) for 1 hour or more is performed to perform nickel diffusion treatment.

Next, this plate was subjected to ordinary pickling treatment, and then cold rolled to a thickness of 1
．． It was set to 0 tone. After further annealing at 65'oC for 1 hour, the sample was cold rolled to a thickness of 1145 m. This cold rolled material was further annealed at 650° C. for 1 hour, and then cold rolled into a plate having a thickness of α13. As an evaluation of the sample prepared in this way, actual photoetching holes were performed to investigate the occurrence of uneven streaks. The results are shown in Table 1 along with comparative alloys.

As shown in Table 1, it is clear that the alloy according to the present invention does not produce uneven streaks during cross-etching compared to conventional iron-nickel alloys, and is an excellent alloy as a material for shadow masks.

Claims (1)

[Claims] The component segregation rate of nickel expressed by the following formula is 10 cm or less,
The volume of segregated substances in a unit volume is less than '5, and the length of one segregated substance in the shadow mask material immediately before etching is 3 (
Iron-nickel alloy for shadow masks that suppresses the occurrence of uneven streaks during etching of 1 m or less