JPH04334849A - Composite shadow mask and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a composite shadow mask which is high in prevention effect against thermal deformation, and furthermore hardly deteriorates its cathode with oxygen emitted. CONSTITUTION:A composite shadow mask is so constituted that a film 4 is plated on a shadow mask 3 in which the film is made of bismuth alloys containing 3 to 17% copper by atom, or bismuth alloys containing 2 to 6% germanium by atom, or bismuth alloys containing 1 to 6% tungsten by atom and/or of bismuth alloys containing 1 to 10%, plural kinds of elements out of copper, germanium and tungsten by atom in total.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shadow mask for a cathode ray tube for color television.

0002

2. Description of the Related Art Conventionally, in order to prevent thermal deformation of a shadow mask, a coating of Bi2O3 powder has been provided on the shadow mask. This technology was developed in the inventors' earlier application (
Special Publication No. 61-6969 “Color Braun Tube”)
This is disclosed in detail in FIG. In the figure, 1 is a glass envelope that maintains a high vacuum inside, 2 is an electron gun that emits an electron beam, and 3 is a shadow mask that constitutes a color selection electrode.For example, it is made of a thin iron plate with many slits. Become. 4 is a coating made of Bi2O3 powder. Note that water glass is usually used for attaching the Bi2O3 powder.

Bi2O provided on the shadow mask 3
The coating 4 of No. 3 effectively reflects the electron beam from the electron gun 2 that impinges on parts other than the slit holes of the shadow mask 3, and as a result, the temperature rise of the shadow mask 3 is prevented. Heat deformation of the shadow mask 3 is prevented. The thermal deformation prevention ability of the Bi2O3 film in the conventional example, that is, the anti-doming effect, was 30
It was ~35%.

0004

[Problem to be solved by the invention] However, Bi2
Since O3 is an oxide, it releases a small amount of oxygen when exposed to electron beam irradiation in a cathode ray tube. The released oxygen degrades the cathode and reduces the life of the cathode ray tube.

On the other hand, since metal bismuth does not contain oxygen, it is more promising than Bi2O3 from various points of view, but because its melting point is as low as 270°C, it cannot withstand heat treatment (450°C) during the cathode ray tube manufacturing process. figure,
When the bismuth coating that had been formed was heated to 450°C, it melted, turned into small round particles, and peeled off, making it impossible to put it into practical use.

[0006] This invention was made to solve the above-mentioned problems, and aims to obtain a film that has a greater anti-doming effect than a Bi2O3 film and is less likely to release oxygen gas, and is intended to improve the practical use of bismuth metal. It is something that opens the door to change.

[0007]

[Means for Solving the Problems] A composite shadow mask according to the present invention is made of a bismuth alloy containing 3 to 17 atom % of copper, a bismuth alloy containing 2 to 6 atom % of germanium, or a bismuth alloy containing 1 to 6 atom % of tungsten. % bismuth alloy or multiple elements of copper, germanium, and tungsten as a total amount of 1 to 10
A film made of a bismuth alloy containing % atoms is provided on a shadow mask.

[0008] A method for manufacturing a composite shadow mask according to another aspect of the present invention includes a step of synthesizing bismuth alloy powder containing at least one of copper, germanium, and tungsten by a mechanical alloying method; This method includes a step of forming a film of bismuth alloy powder on a shadow mask.

[0009]

[Operation] In this invention, the copper, germanium, and tungsten added in predetermined amounts to bismuth increase the melting point of bismuth to 500°C or higher, and as a result, the bismuth coating melts and peels off as described above. Such inconveniences will disappear.

[0010] The production of these alloy powders can be done by first preparing an alloy ingot and then pulverizing it into a powder form, but it is very time-consuming. Since the amount added is small, by mixing the bismuth powder and the powder of the additive element in a predetermined ratio and using an appropriate grinding and mixing means such as a ball mill,
Alloying can be easily achieved using a mechanical alloying method. By such means, the powder becomes equiaxed crystallized, which is convenient for handling such as mixing with water glass and spraying.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The structure of the composite shadow mask according to an embodiment of the present invention is the same as the conventional one shown in FIG. 1, and only the material of the coating 4 is different.

[0012] A bismuth alloy containing 3 to 17 at % of copper, or a bismuth alloy containing 2 to 6 at % of germanium, or a bismuth alloy containing 1 to 6 at % of tungsten, or one of copper, germanium, and tungsten. 1 to 10 as the total amount of multiple types of elements
A bismuth alloy containing % atoms is made by adding an appropriate amount of Cu, Ge, or W to bismuth, the main component, melting it at an appropriate temperature, making it have a uniform composition, and then rapidly cooling it.
A common method is to atomize the material using appropriate pulverization means. However, since bismuth is a soft and brittle metal, mechanical alloying can be applied to this alloy system. That is, by weighing appropriate amounts of bismuth powder of several tens of micrometers and Cu, Ge, or W powder of similar size, and grinding and mixing them using a high-energy ball mill, etc., alloy powder with a desired composition can be easily obtained. can be obtained. By using the alloy powder thus obtained in place of Bi2O3 and spraying it with water glass added thereto, a film made of the powder of these alloys can be created on the shadow mask. After forming these films, heat treatment is applied according to the normal manufacturing process, but these alloy powders not only do not melt, but also have greater oxidation resistance than pure Bi powder, so they are oxidized to a large extent. Never. That is,
This is because the additive elements Cu, Ge, and W themselves are partially oxidized faster than Bi, and the resulting oxide film suppresses subsequent oxidation.

[0013] Regarding the mechanical alloying method, for example, the literature ("Bulletin of the Japan Institute of Metals", Vol. 27, 1988
, October issue, "Recent Research Trends in Mechanical Alloying").

[0014] Although the film thus prepared is not completely metal and has a thin oxide layer on the surface, it is mainly metal, so its electron beam reflectivity is much higher than that of the Bi2O3 film. Furthermore, since the electrical conductivity is high, the thermal conductivity of the coating is also high, and as a result, the surface heat transfer coefficient of the mask is also high. Because of the thin oxide layer on the surface, the thermal emissivity is comparable to that of the conventional Bi2O3 film. As a result, as an anti-doming effect,
Values exceeding 50% can be obtained. Furthermore, since this film does not contain much oxide, the amount of outgassing is small even when exposed to electron beam irradiation, and the cathode is less likely to deteriorate.

[0015] If the particle size of the alloy powder produced by mechanical alloying is too large to be used for spraying, it may be dispersed in a solvent containing an appropriate dispersant and then pulverized by an appropriate pulverizing means. Can be done.

Example 1. To 100 g of bismuth powder with a particle size of 20 to 30 μm, 7 atom% (2.24% by weight) of copper powder with a particle size of 20 to 30 μm was added, and the mixture was placed in a copper alloy container. , the same copper alloy cylinder (10mmφ×10
mm length) as a ball, using a planetary ball mill device.
After replacing the air in the container with argon gas for an hour, pulverization and mixing were performed to obtain an alloy powder with a size of several μm. To this powder, 80 cc of sodium water glass, 120 g of water, and 0.4 nt% of anionic surfactant were added to create a spray solution, and after forming a film several μm thick on the shadow mask, it was heated at 450°C for 30 minutes. A CRT was fabricated by baking it twice in air and incorporating it into a CRTφ. Anti-doming effect raster size 100 x 10
When measured at 0mm, 26kV, 90μA, 5
0% was obtained. Furthermore, when a life test was conducted on this CRT without adding a getter, it showed stable characteristics for over 1000 hours.

Example 2. Ge powder of several μm was added to 100 g of bismuth powder with a particle size of 20 to 30 μm at 5 atom % (
1.8% by weight) was added and pulverized and mixed for 5 hours in the same planetary ball mill using an alumina container and alumina balls (10 mmφ x 10) to obtain an alloy powder with a size of several μm. A shadow mask was prepared using this powder in the same manner as in Example 1, a CRT was assembled, and the antidoming effect was measured in the same manner. As in Example 1, a value of 50% was obtained. Similarly, a life test was conducted without a getter, and as in Example 1, good life characteristics were obtained.

Example 3. To 100 g of bismuth powder with a particle size of 20 to 30 μm, W powder of several μm was added at 3 atom % (2
．． In addition, an alloy powder was prepared using the same equipment as in Example 2 under the same conditions as in Example 2 to obtain an alloy powder with a particle size of several μm. A shadow mask was created in the same manner as in Example 1, and C
After RT assembly, the anti-doming effect was measured and was found to be 50%. Similar to Example 2, the results of the life test conducted without a getter were good, with no deterioration of the cathode observed even after 1000 hours.

[0019] The metal added to bismuth is 3 copper.
~17 atom%, germanium is 2 to 6 atom%, tungsten is 1 to 6 atom%, and in the case of multiple elements among copper, germanium, and tungsten, a total amount of 1 to 10 atom% is appropriate; If it is less than that, the melting point of bismuth will not rise, and if it is more than that, production will be difficult or expensive, especially when synthesized by mechanical alloying.

[0020]

As described above, according to the present invention, a bismuth alloy containing 3 to 17 at % of copper, a bismuth alloy containing 2 to 6 at % of germanium, or a bismuth alloy containing 1 to 6 at % of tungsten can be used. bismuth alloy,
Alternatively, a film made of a bismuth alloy containing 1 to 10 atom% of multiple elements among copper, germanium, and tungsten in total is provided on the shadow mask, effectively preventing thermal deformation of the shadow mask. I can do it,
Moreover, the cathode is less susceptible to deterioration due to oxygen gas.

According to another aspect of the present invention, there is also a step of synthesizing a bismuth alloy powder containing at least one of copper, germanium, and tungsten by a mechanical alloying method, and a step of synthesizing the bismuth alloy powder with a shadow mask. Since the step of forming a film thereon is included, it is possible to easily manufacture a composite shadow mask that is highly effective in preventing thermal deformation and is less likely to release oxygen gas.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a composite shadow mask according to a conventional method and an embodiment of the present invention.

[Explanation of symbols]

3 Shadow mask 4 Coating

Claims (2)

[Claims] Claim 1: A bismuth alloy containing 3 to 17 at % of copper, or a bismuth alloy containing 2 to 6 at % of germanium, or a bismuth alloy containing 1 to 6 at % of tungsten, or copper, germanium, and tungsten. The total amount of multiple types of elements is 1~
A composite shadow mask in which a coating made of bismuth alloy containing 10 atom% is provided on the shadow mask. 2. A composite shadow comprising a step of synthesizing a bismuth alloy powder containing at least one of copper, germanium, and tungsten by a mechanical alloying method, and a step of forming a film on a shadow mask with the bismuth alloy powder. How to make a mask.