JPS61203530A - Manufacture of electron tube cathode - Google Patents

Abstract

PURPOSE:To eliminate lowering and fluctuation of electron emission current during service life by applying specific suspension onto at least one of main face of Ni metal substrate and sintered layer of metal powder in layer then burning. CONSTITUTION:1vol. of Ni powder having average grain size of about 7-8mum is added with 2.5vol. of mixture liquid of 20wt% of iso-buthyl metaacrylate and amyl alcohol to condition the metal powder suspension. Then Ni metal substrate 1 is mounted onto a fixing member 5. Thereafter, metal hole plate 6 having a metal plate 8 of about 58mum thick is mounted then positioned and secured and several drips of suspension 10 are dripped near the through hole 7 of said plate 6 thus to burry the through-hole 7 with suspension 10 by means of a squeeze 11. Then it is sintered to form a sintered layer. Consequently, lowering or fluctuation of electron emission current during service life are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing an electron tube cathode used in a television picture tube or the like.

[Conventional technology]

FIG. 3 is a longitudinal sectional view schematically showing a conventional electron tube cathode disclosed in, for example, Japanese Patent Laid-Open No. 186128/1983. In the figure, +11- is the Ni metal substrate, and this Ni
The metal substrate contains at least one reducing element among Si, Zr, Mg, AI, W, and the like.

(2) is a sintered layer (hereinafter referred to as sintered layer) of Ni metal powder deposited in a layered manner on the main surface of the Ni metal substrate il+, and this sintered layer (2) has a thickness of, for example, 7 to 50 microns. (μm)
It is formed to a thickness of .

(3) is an electron emissive oxide layer (hereinafter referred to as oxide layer) formed on this sintered layer (2), and n) is a heater that heats this oxide layer (3) to an appropriate operating temperature. It is.

The sintered layer and oxide layer are formed in the following steps.

First, a suspension of Ni metal powder is prepared by mixing Ni metal powder with a particle size of 3 to 4 microns, nitrocellulose, and butyl acetate, and it is sprayed onto the main surface of the Ni metal substrate tll. , applied to a thickness of approximately 30 microns by a printing method, and heated at approximately 1000°C in a hydrogen atmosphere for 1 hour.
A sintering process of heating for 0 minutes is performed to form a sintered layer (2) of reduced Ni metal powder.

Next, Ba.

Sr, Ca ternary carbonate, nitrocellulose,
Add and mix the suspension with butyl acetate to the sintered layer (2).
It is applied to a thickness of about 100 microns by spraying or printing, dried, and activated by heating in a vacuum during the electron tube manufacturing process to form an oxide layer (
3) Form.

In this activation process, first, the ternary carbonate is +11
It decomposes into metal oxides as shown in the formula.

(Ba, Sr, Ca) C0B-* (Ba, Sr, Ca) O+ CO2-(1
) Then, Si contained in the Ni metal substrate fil
, Zr, Mg, AI, W, etc., diffuse onto the surface of the sintered layer (2), and reduce BaO in the metal oxide, for example, as shown in equation (2).

BaO+Mg-Ba+MgO-[21 This generates an element a that is effective for electron emission, and at the same time forms an oxide of a reducing element such as MgO on the surface of the Ni metal substrate and within the sintered layer. Although these oxides have high resistance and reduce the conductivity of the cathode, the porous nature of the sintered layer suppresses the decrease in conductivity due to these oxides, resulting in a high current density of 1 to 2 A/cId. A cathode capable of emitting electrons is obtained.

In order to enhance the effect of such a sintered layer, it is important to form a sintered layer with a uniform thickness and little variation.

Additionally, if the thickness of the oxide layer deposited on top of the sintered layer is uneven or there are variations within the loft, the emitted current will decrease or vary during its lifetime. The thickness of the carbonate coating layer applied on top of the layer is uniform and
It is important that there is little variation.

[Problem that the invention seeks to solve]

The conventional method for manufacturing an electron tube cathode is as described above, and has the following problems.

■ Metal powders and carbonate powders in suspensions tend to settle, and butyl acetate also evaporates easily, so the content ratio of metal powders and carbonate powders in suspensions tends to change and Even if the suspension is applied to a uniform thickness, the sintered layer formed and the thickness of the carbonate coating layer vary, resulting in variations in current emission characteristics.

In order to solve the problem of
The amount of O and the amount of C remaining in the sintered layer or in the oxide layer increase, and these effects result in a greater decrease in electron emission current during the lifetime.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a method for manufacturing an electron tube cathode in which the emission current decreases during its lifetime and has less variation.

[Means for solving problems]

In the method for producing an electron tube cathode according to the present invention, at least one suspension of a metal powder suspension or a carbonate suspension contains a metal powder or a carbonate powder, a lower alcohol, and a lower alcohol of methacrylic acid. alcohol ester, and the mixed suspension is applied in a layered manner to at least one of the main surface of the Ni metal substrate and the sintered layer of the metal powder, and then sintered. shall be.

[For production]

An alcohol solution of a lower alcohol ester of methacrylic acid has a high viscosity and the alcohol evaporates slowly, so there is less change in the concentration of metal powder and carbonate in the suspension, which reduces the thickness of the coating layer. The loft is uniform and the variation within the loft is reduced.

In addition, lower alcohol ester of methacrylic acid has a lower decomposition temperature than nitrocellulose, so the amount of C remaining in the sintered layer and oxide layer is reduced, and it does not produce NO during decomposition. , the functions of the sintered layer and the oxide layer are increased.

[Embodiments of the invention]

Fig. 1 is a cross-sectional view showing a state in which a metal powder suspension is applied onto the main surface of a Ni metal substrate using a metal stencil and a squeegee, and Fig. 2 is a plan view of the metal stencil. is a fixing member that holds the Ni metal substrate (1) vertically, and (6) is a metal stencil, a thin metal plate with a through hole (7) formed in the center that is slightly smaller than the Ni metal substrate fl). (5) and a frame (7) that holds the fixed member (6).
), the through hole (7) is located coaxially on the main surface of the Ni metal substrate fil, and the through hole (7)
The peripheral edge thereof is configured to abut against the main surface of the Ni metal substrate (1). (lO) is metal powder suspension, (lt)
is a squeegee.

First, as a comparative example, an example in which a sintered layer is formed by a conventional method will be described.

A metal powder suspension is prepared by mixing Ni powder with an average particle size of 7 to 8 μm, nitrocellulose, and butyl acetate, and this is sprayed onto Ni metal with a target thickness of 20 μm after sintering. Coated on the main surface of substrate m and heated in hydrogen for 10
A sintering treatment was performed by heating at 00°C for 10 minutes. As a result of measuring the film thickness of 30 samples, the variation was 8 to 3.
The average value at 0 μm was 12 μm. Further, as a result of observing the coated surface with a microscope, it was not found that the coated surface was uniformly coated.

Next, one embodiment of the present invention will be described.

20 wt per volume of Ni powder with an average particle size of 7-8 pm'
2.5 volumes of a mixture of inbutyl methacrylate and amyl alcohol (hereinafter referred to as lacquer) were added and mixed to prepare a metal powder suspension (hereinafter referred to as suspension).

Next, the Ni metal substrate (1) is attached to the fixing member (5), and then a metal stencil (6) having a metal plate (8) with a thickness of 58 μm is placed, positioned and fixed, and suspended. Turbid liquid 9
Drop a few drops of 0) near the hole (7) of the metal stencil plate (6), and use a squeegee (no. 11) to clean the hole (7) with the suspension.
It was applied so as to fill the area, and was subjected to a sintering treatment to form a sintered layer (2).

The results obtained by measuring the film thickness of 30 specimens produced in this way had a variation of 19 to 21 μm, and an average value of 20 μm.
Met. Further, the coated surface was in a uniform coating state.

Using a cathode coated with a ternary carbonate suspension of barium, strontium, and calcium to a thickness of 100 μm on the sintered layer (2) created in this way, a diode vacuum tube was constructed. When manufactured and tested, it was confirmed that electron emission of 1 to 2 A/ciI was obtained at a cathode temperature of 700 to 800°C.

In addition, as a comparative example, a cathode manufactured by the conventional method and a cathode manufactured by the example described above were each
1.6A/csf by mounting 0 pieces on a color cathode ray tube
A life test was conducted at a current density of , and the electron emission current was measured after operating for 6000 hours. The results showed that the comparative example had 59 to 80% of the initial emission current, and the average value was 71%.
%, whereas in the example, the initial emission current was 7%.
It ranged from 9 to 90 inches, and the average value was 86%. The reason why the life characteristics of this cathode have little variation and are good is considered to be due to the following reasons.

■The evaporation of the amyl alcohol in the suspension at room temperature is small, and the viscosity change of the suspension during the process of coating it on the main surface of the Ni metal substrate is small, resulting in a uniform and constant thickness. Can be applied with

(2) Since the decomposition temperature of isobutyl methacrylate as a binder is lower than that of nitrocellulose, the amount of C remaining in the sintered layer is reduced. Furthermore, since highly corrosive nitrogen oxide is not produced, it is possible to suppress the phenomenon in which the Ni metal substrate and the Ni powder in the sintered layer are oxidized during the sintering process. Therefore, during the sintering process to form this sintered layer, and during the sintering and activation processes, Si and Mg that have diffused from the Ni metal substrate are oxidized on the main surface of the Ni metal substrate, the sintering layer, and the sintered layer. 5i02 by reacting with nickel.

Reactions that produce high resistance oxides such as MgO are suppressed.

Incidentally, in the above embodiment, an example was explained in which the sintered layer was formed of Ni powder, but Co or Ni and C may be used.

A similar effect can be obtained when forming a sintered layer with a metal powder containing.

In addition, in the above example, an example was shown in which inbutyl methacrylate was used as a binder and amyl alcohol was used as a solvent. Similar effects were obtained by using one or a mixture of two or more lower alcohol esters, and by using one or a mixture of two or more lower alcohols such as butyl alcohol in addition to amyl alcohol as a solvent. .

Further, in the above example, a sintered layer is formed on the main surface of a Ni metal substrate, but a carbonate suspension is applied on the sintered layer and activated. Needless to say, the present invention can be similarly applied to the step of forming an oxide layer, and similar effects can be obtained.

〔Effect of the invention〕

As described in detail above, the present invention provides a method for applying a suspension formed by mixing a metal powder or a carbonate powder, a lower alcohol, and a lower alcohol ester of methacrylic acid to the main surface of a Ni metal substrate and the above-mentioned metal powder. Since the powder is applied in a layered manner to at least one of the sintered layers and sintered, it is possible to obtain an electron tube cathode with less decrease and variation in electron emission air flow during its life.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view for explaining the coating method using a metal stencil and a squeegee applied in the present invention, and FIG.
FIG. 3, which is a plan view of the metal stencil, is a longitudinal sectional view of the electron tube cathode. +l)...Ni metal substrate, (2)...Ni powder sintered layer, (3)...electron emissive oxide layer, flol...
Metal powder suspension. In the figures, the same reference numerals indicate the same parts. Agent Masuo Oiwa Figure 1

Claims (3)

[Claims] (1) A metal powder suspension containing a metal powder made of at least one of Ni or Co is deposited in a layer on the main surface of a Ni metal substrate containing a reducing element, and then sintered to sinter the metal powder. An electron tube cathode in which a carbonate suspension containing at least one alkaline earth metal carbonate among alkaline earth metals such as Ba is deposited on the sintered layer in a layered manner and then sintered. In the manufacturing method, at least one of the above suspensions is a mixture of metal powder or carbonate powder, lower alcohol, and lower alcohol ester of methacrylic acid, and this mixed suspension is A method for manufacturing an electron tube cathode, comprising depositing a slurry on at least one of the main surface of the Ni metal substrate and the sintered layer of metal powder in a layered manner and sintering the suspension. (2) The method for producing an electron tube cathode according to claim 1, wherein the lower alcohol is at least one of amyl alcohol and butyl alcohol. (3) The method for producing an electron tube cathode according to claim 1 or 2, wherein the lower alcohol ester of methacrylic acid is at least one of methyl methacrylate, ethyl methacrylate, and butyl methacrylate.