JPS641895B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a shadow mask attached to a color picture tube.

The color cathode ray tube has an anode voltage of 30 when in operation.
Since a high voltage of ~20KV is applied, if dust is generated inside the tube, sparks will be generated and the image on the screen will be disturbed. With respect to the shadow mask, this dust includes fallen blackened films and rust, and splash generated when the shadow mask is welded to the mask frame.

As is well known, the manufacturing process for color cathode ray tubes involves several heating processes at temperatures of 370 to 460°C, including the stabilizing process, film baking process, sealing process, and exhaust process. When the film is thin and smooth, the shadow mask, which is made of a thin iron plate with a thickness of 0.1 to 0.18, is likely to rust due to these thermal processes, and even a small impact on the shadow mask will cause relatively large vibrations. Items with weak adhesion, such as rust, will easily fall off.

On the other hand, if the blackened film is too thick, splashes will occur frequently during welding with the mask frame, which will reduce the welding strength.

Next, the manufacturing process of the shadow mask will be described: (1) a process of cleaning a long shadow mask member and forming a photosensitive resin film on both main surfaces; (2) a process of exposing and developing using a predetermined negative pattern mask; (3) Forming a large number of electron beam passage holes and extraction lines by etching, (4) Forming a extraction flat mask along the extraction lines, (5) Performing sintered leveling press molding, (6) Degreasing. The main process is blackening.

The flat mask formed in step (4) will last for at least one week until step (5) is performed.
It is normal for items to be stored as is for several months at most, and if they are not wrapped in anti-rust paper during that time, rusting will be inevitable. In this case, the next step, annealing, is performed in a reducing atmosphere of 600° to 950°C in a mixed gas of H ₂ = 1:4, for example, so the rust itself can be reduced, but the surface of the fine electron beam passage hole is Even if the rust that grows up is reduced, it will remain in the same shape and the shape of the electron beam passage hole will be distorted, which will have a negative effect on the exposure of the screen and the passage of the electron beam. will not be obtained. Therefore, even when annealing is performed in a reducing atmosphere, the flat mask must be preserved with anti-corrosion treatment.

Also, as mentioned above, flat masks are annealed in a reducing atmosphere, and the reason for this is that the annealing temperature is
Since the temperature is 600 to 950℃, if it is placed in an oxidizing atmosphere, most of the surface will rust, and the negative effects of this rust are as described above.Furthermore, in the state where rust occurs, CO ₂ : O ₂ : _N2 =8~13%: approx. 0.2
%: Even when blackened in an atmosphere of 580 to 620°C in the remaining mixed gas, the adhesion of the blackened film is much lower than in the normal case, and its negative effects are obvious. Additionally, a large amount of hydrogen is used to create a reducing atmosphere, and the furnace requires various safety measures to prevent explosions. Furthermore, due to the recent material situation, the prices of gas, electricity, etc. have risen dramatically, leading to an increase in the manufacturing price of shadow masks. Typical examples include hydrogen gas and electricity in the annealing process, and city gas (which is combusted to produce blackening gas) and electricity in the blackening process.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a method for manufacturing a shadow mask that can manufacture a shadow mask having good characteristics while saving resources.

The inventors conducted various experiments on methods of simultaneously performing the above-mentioned annealing and blackening for the purpose of resource saving, and found that the purpose could be achieved if annealing was performed using a certain type of gas.

Next, a first embodiment of the present invention will be described.

That is, 600 to 950 degrees Celsius at wet _N2 with a dew point of -10 to 40 degrees.
When a flat mask is annealed in an atmosphere of 0.2~
A blackened film with a thickness of 0.8μ is formed. However, since this film _is thin, it is easy to rust if it is sent to _the color cathode ray tube manufacturing process.
N ₂ = 8 to 13%: Approx. 0.2%: A second blackening is performed in the remaining mixed gas, but the blackening temperature at this time is lowered by 20 to 30 degrees Celsius than before, and is set at 560 to 580 degrees Celsius. Even if this is done, the thickness of the blackened film can be made 1.5 to 3μ. Also, since hydrogen is not used in the annealing furnace, there is no safety measure against hydrogen explosions, and the drying section of the etching process can be extended to allow etching and annealing to be performed continuously, making the flat mask suitable for annealing and mild etching. Since it is already blackened, it will hardly rust even if it is stored in a flat mask, and the drying part of the etching process can be extended so that etching and annealing can be performed continuously. And since it is slightly blackened, it will hardly rust even if it is stored in a flat mask, and there is no need to wrap it in anti-rust paper. Furthermore, the mechanical properties of the shadow mask manufactured according to this example were the same as those of conventional products, and press molding could be carried out without any problem.

In this example, if the amount of water vapor is further increased, the blackened film can be formed thicker, but the excess water vapor condenses into water droplets at the gas line piping and the entrance/exit of the furnace, and falls onto the flat mask during annealing. It is obvious that rust will occur and if the amount of water vapor is small, the thickness of the blackened film will be too thin and the desired effect will not be obtained.

Next, a second embodiment of the present invention will be described.

That is, annealing is carried out in an atmosphere of 600 to 950° C. in a mixed gas of CO ₂ :O ₂ :N ₂ :0.5 to 8% (varies depending on temperature): trace amount: remainder. This mixed gas uses the combustion gas (CO ₂ ) used in conventional blackening, but since the annealing temperature is high at 600 to 950°C, the reaction rate becomes faster, so the higher the temperature of the combustion gas, the more It needs to be thin. For example, nitrogen gas is used to dilute 1 at 600°C to 1/2 at 700, 1/5 to 6 at 800°C, and 1/10 to 12 at 900°C.

In the case of this embodiment, as in the first embodiment, since hydrogen is not used, there is no need for safety measures against furnace explosions, and the drying section of the etching process is extended so that etching and annealing can be performed continuously. become,
Since the flat mask has been annealed and blackened, it will hardly rust even if it is stored as a flat mask, and there is no need to wrap it in anti-rust paper. In the case of this example, a blackened film with a thickness of 1.5 to 3μ is formed during the annealing process, so cracks may occur locally in the blackened film during press molding, and rust may occur in these areas. It is desirable to carry out slight blackening at a low temperature of 20 to 450°C in wet nitrogen at 10 to 40°C.

The mechanical properties of the shadow mask manufactured in this example were the same as those of conventional products, and press molding could be performed without any problems.

However, if the material requires decarburization annealing, the atmosphere should of course be kept in a wet state with a dew point of 0 to 20°C.

As mentioned above, the present invention requires supplementary blackening, and the content must be controlled relatively strictly, but it is possible to contain various oxidizing gases in nitrogen and perform annealing and blackening at the same time. This makes it possible to eliminate the use of expensive hydrogen gas, lower the supplementary blackening temperature than before, and save electricity.Also, by making the etching process and annealing process continuous, the annealing and blackening It is now possible to supply a flat mask that will not rust even if left undisturbed.

Claims (1)

[Claims] 1. Annealing and blackening are performed simultaneously on a flat mask with a perforated electron beam passage hole in an atmosphere containing nitrogen gas, at least water vapor or carbon dioxide gas, and a trace amount of oxygen, and replenishing blackening is performed after press forming. A method for manufacturing a shadow mask, characterized by performing the following steps.