JPS61208721A - Manufacture of cathode for electron tube - Google Patents

Abstract

PURPOSE:To reduce the decrease in an electron emission current during the life of a cathode, by mixing a powder of a metal with a prescribed lower alcohol ester to prepare a suspension, and by coating the main surface of an Ni base with the suspension, and sintering them in a reducing atmosphere. CONSTITUTION:1 part by volume of a metal Ni powder of 7-8mum in mean grain diameter is mixed with 2.5 parts by volume of a mixed liquid consisting of 20wt% of an isobutyl metaacrylate and the rest of amyl alcohol, to prepare a metal powder suspension 10. The main surface of an Ni base 1 is coated with the suspension 10 by using a punched metal plate 6 and a squeegee 11. The main surface and the suspension 10 coating it are heated at a temperature of 800 deg.C under hydrogen for 10min to make a sintered layer which has a large void ratio and contains less residues. The decrease in an electron emission current during the life of a cathode is thus 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 Application Laid-Open No. 186128/1983. In the figure, (1) is the Ni1 cathode substrate C (hereinafter referred to as Ni substrate), and the Ni substrate (1) is St, Zr, M
Contains at least one reducing element among g, AI, W, etc.

(2) is a sintered layer (hereinafter referred to as sintered layer) of N1 gold powder deposited on the main surface of this Ni substrate (1), and this sintered layer (2) is, for example, 50゛micron (μm
) is formed on the shore of the river.

(3) is an electron-emitting oxide layer (hereinafter referred to as oxide layer) formed on this sintered layer (2), and (4) is heating this oxide layer (3) to an appropriate operating temperature. The sintered layer and the oxide layer, which are heaters, are formed in the following steps.

First, Ni gold powder with a particle size of 3 to 4 microns, nitrocellulose, and butyl acetate are mixed to prepare a Ni gold powder suspension, which is sprayed onto the main surface of the Ni substrate (1). This is coated to a thickness of about 30 microns using a printing method, and then subjected to a ThM treatment in which it is heated at about 1000°C for 10 minutes in a hydrogen gas atmosphere to form a 1fli layer of reduced Ni gold powder ( 2) Form.

Next, to the ternary carbonate of Bas S r e Ca,
A mixed suspension of nitrocellulose and butyl acetate is applied onto the sintered layer (2) to a thickness of about 100 microns by spraying or printing, and after drying, the electron tube is During the manufacturing process, activation is performed by heating in vacuum to form an oxide layer (3).

In this activation process, first, the ternary carbonate is (1)
It decomposes into metal oxides as shown in the formula.

(Ba, Sr, Ca) Co3→ (Ba, Sr, Ca) o+co2...-(1) Next, SL contained in the Ni base (1).

Trace amounts of reducing elements such as Z r , M g , A I , and W diffuse onto the surface of the sintered layer (2) and reduce BaO in the entire oxide, as shown in equation (2), for example. .

BaO+M'g-+Ba+MgO... (2) This produces a, which is effective for electron emission, and at the same time forms oxides of cyclic elements such as MgO on the surface of the 1cNi 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, and 1
A single pole capable of electron emission with a high current density of ~2 A/d is obtained.

[Problem that the invention seeks to solve]

The conventional electron tube-electrode manufacturing method failed as described above and had the following problems.

Since a lacquer containing a large amount of nitrocellulose is used for the metal powder suspension, it is necessary to sufficiently decompose the nitrocellulose during the sintering process and avoid any negative effects on the electron emission characteristics due to its shallowness. , it was necessary to heat the sintered layer at a high temperature of 1000°C or higher.As a result, the sintered layer became excessively sintered, and the porosity (porosity) of the sintered layer became insufficient. [The contact area between the particles and the oxide layer is small], and during the decomposition process of the ternary carbonate in the activation treatment process, and during the activation process, reducing elements such as St and Mg from within the sN1 substrate are absorbed into the sintered layer. Even if the electrons diffuse into the interior, the reaction with the alkaline earth metal oxide in the baride layer is insufficient, resulting in a problem in that the electron emission current decreases significantly during the lifetime.

This invention was made with the aim of eliminating such a sintered point, and it is possible to form a sintered layer with a sufficiently large porosity, thereby reducing the drop in electron emission current during the life of an electron f@ The purpose of the present invention is to provide a method for manufacturing poles.

[Means to solve the problem]

The method for manufacturing an electron tube-electrode according to the present invention includes metal powder,
A suspension consisting of a mixture of a lower alcohol and a lower alcohol ester of methacrylic acid is deposited in a layer on the main surface of a Ni substrate and sintered at 800 to 990°C in a reducing atmosphere. shall be.

[Effect]

The methacrylic acid lower alcohol ester used to prepare the metal powder suspension has a lower decomposition temperature and faster decomposition rate than nitrocellulose. Therefore, the heating temperature in the sintering process can be lowered, and the porosity of the sintered layer can be increased. In addition, since the sintered layer is less shallow, the adverse effect on electron emission characteristics can be reduced, so the oxide layer can be brought into a good activated state.

[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 the N1 substrate using a metal stencil and a squeegee, and Fig. 2 is a plan view of the metal stencil. The fixing member that holds the Ni metal substrate (1) vertically, (6) is a metal stencil, a thin metal plate with a through hole (7) slightly smaller than the s N im body (1) formed in the center. (5) and a frame (7) that holds it, and when positioned and placed on the fixing member (5), the through hole (7)
It is located coaxially on the main surface of the Ni substrate (1) and is configured to abut on the main surface of the Ni substrate (1) at the periphery of the through hole (7). (10) is a metal powder suspension, and αD is a squeegee.

First, as a comparative example, a sintered layer was formed using a conventional manufacturing method.

A metal powder suspension was prepared by mixing Ni gold powder with an average particle size of 7 to 8 μm, nitrocellulose, and butyl acetate, and this was sprayed using a spray method, aiming at a sintered layer thickness of 20 μm. It was applied onto the main surface of the Ni substrate (1) and subjected to a sintering treatment of heating at 1000° C. for 10 minutes in hydrogen.

As a result of measuring the film thickness of 30 samples manufactured in this way, the variation was 8 to 30 μm, and the average value was 12 μm.
It was m. Further, as a result of observing the coated surface under a microscope, it was found that the coated surface was not uniformly coated.An example of the present invention will be described below.

20 w per volume of Ni metal powder with an average particle size of 7 to 8 μm
2. Mixture of inbutyl methacrylate of tX and amyl alcohol. ．． A metal powder suspension (hereinafter referred to as suspension) was prepared by mixing 5 volumes of the metal powder.

Spread this suspension using a metal stencil (6) and a squeegee (11J).
was applied onto the main surface of the Nl substrate (1) and subjected to a sintering treatment of heating at 800° C. for 10 minutes in hydrogen to form a sintered layer (2).

The results of measuring the film thickness of 30 samples produced in this manner showed that the variation was 19 to 21 μm.

The average value was 20 μm. Moreover, the coated surface was a uniform coated surface.

A diode vacuum tube was manufactured and tested using a cathode coated with a ternary carbonate suspension to a thickness of 100 μm by spraying on the sintered layer (2) thus prepared. However, it has been confirmed that electron emission of 1 to 2 A/- can be obtained at a -polar temperature of 700 to 800°C.

Next, as a comparative example, 10 cathodes manufactured by the conventional method and 10 cathodes manufactured by the above example were mounted on a color cathode ray tube, and a life test was conducted at a current density of 1.6 A/-. The electron emission current was measured after operating for a certain period of time. The results showed that the comparative example had 59 to 80% of the initial emission current, and the average value was 7.1.
% of the initial emission current, whereas that of the example is 8% of the initial emission current.
The average value was 89%, ranging from 3 to 94%.

The reason why there is little variation in the life characteristics of this cathode and little decrease in emission current density is considered to be due to the following reasons.

Inbutyl methacrylate, which is a binder, has a low decomposition temperature, so it is easily separated from gases such as 003 generated during decomposition.
Ni constituting the sintered layer, Ni in the Ni metal substrate, St
, Mg, etc., and the generation of high-resistance substances such as 5i02 and MgO is reduced. In addition, since there is little C at a shallow depth within the sintered layer, the reaction between this C and alkaline earth gold oxidation and materials within the oxide layer is suppressed.
The negative effect on electron emission characteristics is reduced. In addition, since the heating temperature is low, the porosity of the sintered layer increases, and the contact area between the sintered layer and the oxide layer increases, causing St to diffuse into the sintered layer from the Nl substrate. The reaction between reducing elements such as and Mg and alkaline earth metal oxides is sufficiently carried out, and the porosity is also increased.

This is because reduction in conductivity due to products of the reduction reaction, such as StO and MgO, is suppressed.

Figure 3 is a characteristic diagram showing the relationship between heat retention in the sintering process and the current emission current at the end of the life test.The heating time was varied from 750°C to 1050°C, and the heating time was 10 minutes each. The sample was mounted on a color cathode ray tube, and the actuator emission current after 6000 hours of operation at a current density of 1.6 A/cII is shown as a relative value to the initial emission current. As can be seen from this result, when the temperature is lower than 800°C and higher than 990°C, the relative discharge current 1 [il] decreases to a sudden freeze. This is thought to be due to the following reasons.

If the heating temperature is less than 800°C, the sintered layer may be insufficiently sintered, resulting in peeling between the sintered layer and the carbide layer during operation, or residues of the binder in the suspension may remain. This is thought to be because it becomes difficult to maintain the tube current. Moreover, if the temperature exceeds 990°C, the sintering of the sintered layer becomes excessive, resulting in insufficient diffusion of reducing elements in the Ni substrate into the oxide layer, or This is because if the contact is insufficient, it will be difficult to maintain a high current density.

Incidentally, in the above embodiment, an example was explained in which the sintered layer was formed with Ni metal powder, but the +5J-like effect can also be obtained when the sintered layer is formed with CO or metal powder containing Ni and Co. can get.

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. Use one or a mixture of two types of low alcohol esters, and use one or a mixture of two or more types of lower alcohols such as amyl alcohol as well as butyl alcohol for bath additives. [Effects of the Invention] As described in detail of this invention, a metal powder made of at least one of Ni or Co, a lower alcohol, and a lower alcohol ester of methacrylic acid are mixed. A sintered layer is formed by applying a metal powder suspension of As a result, a sintered layer with less electron emission current can be formed during the N life period.

[Brief explanation of the drawing]

FIG. 1 is a sectional view for explaining the method of spreading a metal powder suspension using a metal stencil and a squeegee applied in the present invention, FIG. 2 is a plan view of the metal stencil, and FIG. , a characteristic diagram showing the relationship between the heat treatment temperature of the sintered layer and the relative emission current after the life test.
It is a diagram. (1)...Ni [polar substrate, (2)...Ni powder sintered layer, (3)...electron emissive compound layer, αα...metal powder suspension. In addition, in the figures, the same reference numerals indicate the same parts.

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 cathode substrate containing a reducing element, and then sintered to sinter the metal powder. An electron nuclear cathode in which a carbonate suspension containing at least one kind of alkaline earth metal carbonate among alkaline earth metals such as Ba is deposited on the sintered layer in a layered manner and sintered. In the manufacturing method, the metal powder suspension is
A suspension obtained by mixing the metal powder, a lower alcohol, and a lower alcohol ester of methacrylic acid was deposited on the main surface of the Ni cathode substrate, and
A method for manufacturing an electron tube cathode, comprising a step of sintering at a temperature of ~990°C. (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. .