JPH11144614A - Manufacturing method of impregnated cathode for electron tube - Google Patents

Abstract

(57) [Problem] To provide a manufacturing method capable of improving the mass productivity of an impregnated cathode for an electron tube. SOLUTION: An electron emitting substance 11 (for example, B) is provided on a porous tungsten disk 10 which is a porous high melting point metal substrate.
a) is impregnated at, for example, 1650 ° C. and then washed in a washing step 30. Next, an Ir film is formed on the surface of the porous tungsten disk 10. The obtained cathode is then subjected to a vacuum heat treatment in a vacuum heat treatment step 40, for example, at 1650 ° C. for 5 minutes to activate the cathode.
Subsequently, the cap 50 and the sleeve 60 are brazed to obtain a completed inner sleeve 80.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an impregnated cathode for an electron tube, and more particularly to a method for producing a coating film, for example, an Ir film, which is excellent in mass productivity and efficiently. The present invention relates to a method for manufacturing an impregnated cathode for an electron tube, which can prevent deterioration of the emission characteristics of the cathode due to an increase in the thickness of the coating film.

[0002]

2. Description of the Related Art In a conventional impregnated cathode for an electron tube, an electron-emitting substance, for example, Ba, evaporates from the cathode and adheres to a GUN part to change the dimension of the first grid (G1) hole diameter and plate thickness. . For this reason, there has been a problem that the cutoff voltage fluctuates, the white balance is lost during the life of the CRT, and the image is disturbed by causing grid emission.

In order to solve this problem, it is effective to suppress the amount of Ba evaporating from the cathode. For example, conventionally, a coating film such as Ir (iridium)
A technique of coating a film is employed. FIG. 2 is a schematic view of a conventional cathode provided with such an Ir film. Porous refractory metal substrate, such as porous tungsten disk 10
Is impregnated with an electron-emitting substance 11 (for example, Ba). On the upper surface of the porous tungsten disk 10,
An Ir film 12 is provided. Due to the presence of the Ir film 12, the amount of Ba evaporating from the cathode is suppressed, and the change in the hole diameter and the thickness of the first grid 20 are also suppressed. It is known that as the thickness of the Ir film 12 increases, the amount of Ba evaporating from the cathode decreases. However, if the Ir film thickness 12 is too thick (300 nm or more), the emission characteristics of the cathode deteriorate, making it impossible to use it for a CRT.

FIG. 3 is a flowchart showing an example of a conventional method for manufacturing an impregnated cathode for an electron tube. A porous refractory metal substrate, for example, a porous tungsten disk 10
The electron emitting substance 11 (for example, Ba) is, for example, 1650 ° C.
And is washed in a washing step 30. The obtained cathode is then subjected to, for example, 1650 ° C.
For 5 minutes to activate the cathode.
Subsequently, the cap 50 and the sleeve 60 are brazed to form the assembled inner sleeve 70, and then the electron emitting material 1
For example, the surface of the substrate 1 is subjected to an Ir film deposition process (with an Ir film), and the inner sleeve 80 is completed. As described above, in manufacturing a conventional impregnated cathode for an electron tube, a porous high-melting-point metal substrate impregnated with an electron-emitting substance was subjected to a vacuum heating treatment to form an assembled inner sleeve, and then an Ir film was formed.

[0005]

Therefore, when forming an Ir film, it is necessary to perform the Ir film forming process together with the assembled inner sleeve, and there is a disadvantage that sufficient mass productivity cannot be obtained. Was. Further, as described above, the deterioration of the emission characteristics of the cathode is observed when the Ir film thickness is 300 nm or more. Even when the Ir film thickness is increased to the maximum of 300 nm, the amount of Ba evaporating from the cathode is still sufficiently reduced. Could not be suppressed. The present invention solves the conventional problems as described above, is excellent in mass productivity, and efficiently forms a coating film, for example, Ir.
It is an object of the present invention to provide a method of manufacturing an impregnated cathode for an electron tube, which can obtain a sufficient film thickness of the film and can prevent deterioration of the emission characteristics of the cathode due to an increase in the film thickness of the coating film.

[0006]

Means for Solving the Problems As a result of intensive studies, the present inventors have solved the above-mentioned conventional problems. That is, the present invention relates to a method for manufacturing an impregnated cathode for an electron tube having a porous high-melting metal substrate impregnated with an electron emitting material, wherein a coating film is formed on the surface of the impregnated cathode for an electron tube, Before the incorporation, the porous high melting point metal substrate is heated in a vacuum or in a non-oxidizing atmosphere.

In the present invention, a coating film is formed on the surface of a porous high-melting-point metal substrate impregnated with an electron-emitting substance, and then a vacuum heating treatment is performed. It is excellent in mass productivity of cathodes for electron tubes.
In addition, by performing a vacuum heating treatment after forming a coating film to activate the cathode, the activation time can be shortened if the coating thickness is the same as the conventional technology, and the coating thickness can be increased if the same activation time is used. Excellent efficiency.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a flow chart showing one embodiment of a method for producing an impregnated cathode for an electron tube according to the present invention. A porous refractory metal substrate, for example, a porous tungsten disk 10 is made of an electron emitting material 11 (for example, Ba).
For example, it is impregnated at 1650 ° C. and washed in the washing step 30. Next, the surface of the porous tungsten disk 10
An r film is formed. The order of these steps is a feature of the present invention. In FIG. 1, the step of forming an Ir film is shown as Ir film-added 1. The obtained cathode is then subjected to a vacuum heat treatment step 4
At 0, for example, a vacuum heat treatment is performed at 1650 ° C. for 5 minutes to activate the cathode. Subsequently, the cap 50 and the sleeve 60 are brazed to obtain a completed inner sleeve 80, and the cathode is incorporated into the electron tube.

In the vacuum heat treatment step 40, 1650 ° C. and 5 minutes are exemplified as one embodiment, but besides this condition, a heating temperature in the range of 1400 to 1800 ° C. can be adopted, and the heating time is also 0 hour. It can be appropriately selected within a range of 1 minute to 60 minutes. In order to further suppress the amount of evaporation of the electron emitting material, it is preferable that the heating temperature be 1650 ° C. or less and the heating time be 5 minutes or less. The vacuum heat treatment 40 is preferably performed in a vacuum or in a non-oxidizing atmosphere, for example, in an inert atmosphere such as nitrogen. In the above description, Ir is exemplified as a material of the coating film.
A platinum group metal such as u can be suitably used.

In the present invention, a coating film is formed on the surface of a porous refractory metal substrate impregnated with an electron-emitting substance, and then a vacuum heat treatment is performed. Since it can be heated alone and does not need to be subjected to the Ir film forming process together with the assembled inner sleeve, there is an advantage that the mass productivity of the cathode for an electron tube is excellent. In addition, by performing a vacuum heating treatment after forming the coating film to activate the cathode, the activation time is shortened if the coating film thickness is the same as that of the related art, for example, the Ir film thickness, and conversely, the Ir film thickness is reduced if the same activation time is used. Can be increased. Also in this respect, excellent production efficiency is recognized. Further, it was confirmed that sufficient activity was obtained even when heating was performed at 1650 ° C. or lower for 5 minutes or less, which is a preferable vacuum heat treatment condition in the present invention.

Although the reason has not been clarified, when the coating film thickness is increased by, for example, increasing the coating film thickness by performing a vacuum heating treatment and activating the cathode after the coating film formation,
Even when the thickness was set to 0 nm or more, deterioration of the emission characteristics of the cathode could be prevented. According to the present invention, the thickness of the coating film can be appropriately selected in the range of 10 nm to 1000 nm, and even if the coating film thickness is increased, deterioration of the emission characteristics of the cathode can be prevented.

[0012]

As is clear from the above description, the present invention
In the method for manufacturing an impregnated cathode for an electron tube having a porous high-melting metal substrate impregnated with an electron emitting material, a coating film is formed on the surface of the impregnated cathode for an electron tube, and the porous film is impregnated before being incorporated into the electron tube. The refractory metal substrate was heated in a vacuum or in a non-oxidizing atmosphere. Therefore, it is possible to obtain a sufficient thickness of the coating film, for example, an Ir film, with excellent mass productivity and efficiently, and also to prevent deterioration of the emission characteristics of the cathode due to an increase in the thickness of the coating film. it can.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating one embodiment of a method for producing an impregnated cathode for an electron tube according to the present invention.

FIG. 2 is a schematic view of a conventional cathode provided with an Ir film.

FIG. 3 is a flowchart illustrating an example of a conventional method for manufacturing an impregnated cathode for an electron tube.

[Explanation of symbols]

1,100 with Ir film, 10 with porous tungsten disk, 11 with electron emitting material, 12 with Ir film, 2
0: First grid, 30: Cleaning step, 40: Vacuum heat treatment, 50: Cap, 60: Sleeve, 70
... Assembled inner sleeve, 80 ... Inner sleeve.

Claims (5)

[Claims] 1. A method for manufacturing an impregnated cathode for an electron tube having a porous refractory metal substrate impregnated with an electron emitting material, comprising: forming a coating film on the surface of the impregnated cathode for an electron tube;
A method for producing an impregnated cathode for an electron tube, wherein the porous high-melting metal substrate is heated in a vacuum or in a non-oxidizing atmosphere before being incorporated into the electron tube. 2. A heating temperature for heating the porous refractory metal substrate in a vacuum or a non-oxidizing atmosphere is 140.
0-1800 ° C., and the heating time is 0.1
The method for producing an impregnated cathode for an electron tube according to claim 1, wherein the time is in the range of minutes to 60 minutes. 3. The method for producing an impregnated cathode for an electron tube according to claim 1, wherein in the heating step, the porous high melting point metal substrate is heated alone. 4. The method for producing an impregnated cathode for an electron tube according to claim 1, wherein the coating film is a platinum group metal of Ir, Os or Ru. 5. The method according to claim 1, wherein said coating film has a thickness of 10 nm to 1000 nm.
The method for producing an impregnated cathode for an electron tube according to claim 1, wherein the diameter is in the range of nm.