JPH0680182B2 - Method for manufacturing shed mask - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for manufacturing a shadow mask for a color picture tube, and more particularly to a method for forming a dark oxide film when the material is an iron-nickel alloy.

[Technical background of the invention and its problems]

Generally, high purity low carbon steel sheets such as rimmed steel or aluminum killed steel are used as the material of the sheer mask for color picture tubes, but these are comprehensively determined by the material supply capacity, cost, workability and strength. Is. However, their biggest drawback is the large coefficient of thermal expansion (0-100
℃ about 12 × 10 ^-6 / ℃). In the case of a shadow mask type color picture tube, if the positional relationship between the opening of the shadow mask and the phosphor layer corresponding thereto shifts outside the permissible range, color misregistration occurs, which is a fatal problem. In particular, the thermal deformation of the shead mask due to thermal expansion causes the required curvature of the shed mask to collapse and disturbs the relative positional relationship between the openings of the shed mask and the phosphor layer.There are various means for suppressing the thermal deformation of the shed mask. Proposed. As one of them, as shown in JP-B-42-25446, JP-A-50-58977 and JP-A-50-68650, an iron-nickel alloy having a small coefficient of thermal expansion, for example, 36Ni- A shadow mask using Fe amber alloy (0 to 100 ° C, about 0 to 2.0 × 10 ^-6 / ° C) and 42Ni-Fe alloy (0 to 100 ° C, about 5.0 × 10 ^-6 / ° C) as materials has been proposed. There is.

By the way, in recent years, "easy-to-see" and "fineness" of images are required for display for PC, character multiplex broadcasting, hygiene broadcasting, captain system, etc. Along with this, the opening pitch of the shadow mask is small and electronic The amount of electron beams from the gun has also increased. As a result, the riding margin of the electron beam on the phosphor screen becomes smaller, and the color shift due to the thermal deformation of the shear mask is severe, and the use of the iron-nickel alloy material that is a low thermal expansion material as described above has become an important issue. It was However, the amber material and the like have many problems such as poor etching property and formability as compared with the conventional low carbon steel sheet, and there are many problems such as JP-A-57-147740 and JP-A-58-1908.
Various proposals have been made as shown in Japanese Patent Publication No. 5 and the like.

On the other hand, the conventional shadow mask made of iron-based material has a black or gray-black dark oxide film (hereinafter referred to as blackening film) formed on the surface of the shadow mask from the viewpoint of rust prevention and heat dissipation. Poor breakdown voltage due to the film falling off becomes a problem.
On the other hand, it has been generally considered that it is not necessary to form a blackened film because amber or the like has good corrosion resistance. However, when a shadow mask made of amber material that does not form a blackening film was incorporated into the tube and the electron beam movement amount (PD amount) due to thermal deformation of the shadow mask was compared with that of the iron material, a remarkable difference was found despite the small thermal expansion coefficient. Was not recognized. It is considered that this is because the blackened film was not formed, so that the heat radiation from the shadow mask was not sufficiently performed, and the temperature of the mask itself was considerably higher than that of the iron material shadow mask on which the blackened film was formed. However, it is difficult to form a dense and highly adherent blackened film on this alloy having good corrosion resistance by a conventional method. In particular, the blackened film was apt to become inhomogeneous due to the amount of impurities in the alloy or a slight stain on the mask surface, and the generation of red rust could not be partially avoided. Also, due to the difference in the thermal expansion coefficient between the blackening film and the shed mask base, a large amount of stress is applied during the blackening film growth on the inner wall of the electron beam passage hole where the base material is extremely rough, and if the adhesion is poor, the blackening film Peeling was easy to occur. In the red rust generation portion, rust grows during the heat treatment in the subsequent process and disturbs the mask hole size, and the adhesion to the substrate is poor as compared with the blackened film, and it easily falls off. The blackened film and red rust that have fallen off cause a pressure resistance defect, which becomes a fatal defect of the color picture tube, which is a serious problem.

[Object of the Invention]

It is an object of the present invention to provide a means for forming a dark oxide film which is uniform and has good adhesion, excellent corrosion resistance and thermal radiation properties on a sheer dough mask made of an iron-nickel alloy material.

[Outline of Invention]

The present invention, in forming a dark oxide film after forming a large number of holes in a thin metal plate containing iron and nickel as the main components, and forming a dark oxide film in a heating furnace in a steam atmosphere, the former stage is an atmosphere with weak oxidizing power. Among them, the latter stage is similarly processed in an atmosphere having a strong oxidizing power to obtain a dark oxide film which is dense, has good adhesion, and has sufficient blackness and film thickness.

Example of Invention

Examples of the present invention in which an amber alloy is used as a material for a shead mask made of an iron-nickel alloy will be described below. Table 1 shows the material composition of Amber alloy and aluminum-killed low carbon steel.

Using the 36Ni amber alloy having the above composition as a raw material, a flat mask having a large number of pores having a desired pore size is obtained by ordinary photoetching.

Next, this mask is press-molded to obtain a desired curved surface shape, but if the yield strength of the mask material is high, the spherical shape is destroyed due to the occurrence of spring back, and the molded mask cannot be put to practical use. Therefore, it is necessary to reduce the yield strength to a value at which a high-quality press-formed product can be obtained by performing annealing. Air annealing or hydrogen annealing is generally used as the annealing, but it is impossible to reduce the yield strength to a value (20 kg / mm ² ) that allows press forming. Therefore, 10 ^-3 torr 1 30
It was annealed for 20 minutes to make it 20 kg / mm ² or less. Then, the press oil is removed by steam cleaning with trichlene to form a dark oxide film (hereinafter referred to as a blackening film). Air blackening as a blackening method,
Although there are gas blackening, vapor blackening, chemical conversion treatment blackening, etc., vapor blackening is the most excellent in terms of film blackness, denseness and adhesion. In this vapor blackening, when treated in an atmosphere with a small amount of vapor and a strong oxidizing power, rust occurs and only a blackened film with poor adhesion can be formed. On the other hand, when treated in an atmosphere with a large amount of vapor and weak oxidizing power, a dense and highly adherent film is formed, but it takes a long time to grow a blackened film and obtain sufficient blackness. , Not suitable for mass production. Therefore, it is considered that it is good to form a dense black thin film with good adhesiveness in an atmosphere with weak oxidizing power in the first stage of blackening, and to grow the blackened film in an atmosphere with strong oxidizing power in the latter stage. I went. As a result, 20 to 50 per cubic meter of the reaction furnace are formed before the blackening film formation.
After having conducted over 10 minutes blackening in an atmosphere of added water vapor m ³ / Hr 500~700 ℃, subsequent stage as 0~20m ³ / Hr of added water vapor 550 to 750 in an atmosphere of ° C. 10 minutes or more black As a result, a blackened film having sufficient blackness and good adhesion was obtained.
The adhesion was evaluated by applying a cellophane tape to the blisters after the 90 ° blush test and performing a peeling test of the blackening film. Further, the state of the blackened film was observed by a scanning electron microscope, and it was confirmed that the blackened film was a dense black film without cracks and pinholes. Since the structure of the blackening furnace used in forming the blackened film is different, the blackened film quality may change even if the treatment is performed under the same conditions. Therefore, it is necessary to select the conditions suitable for the blackening furnace used within the above range. Also, it is of course possible to change the amount of water vapor and the temperature during the entire blackening process stepwise from weak oxidizing power to strong oxidizing power without clearly dividing the blackening process into the first and second steps. Is.

Although the above examples have been described using the 36Ni amber alloy as the material for the shear mask, the present invention is not limited to this, 42Ni alloy and 32Ni-5Co and other alloys containing iron and nickel as a main component containing super umber. It goes without saying that the same can be applied if any. Further, it goes without saying that the present blackening method can be applied not only to the sheer dough mask but also to the mask frame and the inner sill which are incorporated in the color picture tube as long as the alloy mainly contains iron and nickel.

〔The invention's effect〕

As described above, according to the present invention, it is possible to obtain a dark-colored oxide film which is dense and has good adhesiveness to a thin metal plate containing iron and nickel as main components, and which has sufficient blackness and film thickness.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuhiko Inaba 1 Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa Tokyo Shibaura Electric Co., Ltd. (56) Reference JP-A-55-19715 (JP, A)

Claims (2)

[Claims] 1. A method of manufacturing a shadow mask, comprising at least a step of forming a dark oxide film on a thin metal plate containing iron and nickel as main components and having a large number of holes formed therein.
The former stage of the formation of the dark oxide film is 20 ~ per unit volume of the processing furnace.
Characteristically, after injecting 50 m ³ / Hr of steam and treating at 500 to 700 ° C for 10 minutes or more, the latter stage also introduces less steam than the range of the amount of steam in the preceding stage and treats at 550 to 750 ° C for 10 minutes or more. Method for manufacturing shadow mask. 2. The shadow according to claim 1, wherein the atmosphere having a weak oxidizing power is gradually changed to an atmosphere having a strong oxidizing power also in the former stage and the latter stage of the formation of the dark color oxide film. Mask manufacturing method.