JP2000082396A - Manufacture of cathode substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance an electron emission performance without impairing an electrode substrate surface by coating one surface of a metal sintered body thin plate with a brazing filler metal, irradiating it with a laser to generate burrs on a surface on which the brazing filler metal is not applied, cutting it off, removing the burrs and impregnating it with an electron emission substance. SOLUTION: A brazing filler metal comprising a ruthenium-molybdenum alloy is applied on one surface of a porous tungsten thin plate 12 and is dried. The thin plate is heated in a reducing atmosphere to form a ruthenium-molybdenum alloy layer 13. When a cathode substrate is cut off by irradiating it with a laser, a burr does not generate on a surface on which the brazing filler metal comprising a strong alloy layer 13 is applied and fragile burrs B of a metal sintered body is generated only on the thin body 12 side. Accordingly, the burrs B can be removed without crushing an opening of a hole on a cathode surface and a reduction of the electron emission performance can be prevented. An electron emission substance 14 comprising barium oxide is laded on the tungsten-exposed surface side of the thin plate 12 and the substance 14 melts in the hole of the cathode substrate in a reducing atmosphere to perform impregnation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an impregnated cathode substrate used for an electron gun structure provided in an electron tube such as a color picture tube.

[0002]

2. Description of the Related Art In recent years, an electron gun assembly provided in an electron tube such as a color picture tube uses an impregnated cathode structure using an impregnated cathode substrate which can obtain a large current density as compared with an oxide cathode. Have been.

FIG. 4 is a partially cutaway perspective view showing an impregnated yin-shade structure. In the figure, reference numeral 1 denotes a disk-shaped impregnated cathode substrate, for example, which is formed by impregnating a substrate made of a high-melting-point metal sintered body such as tungsten with an electron-emitting substance. This cathode base 1 is fitted and fixed to a cup 3 via a brazing material 2. The cup 3 is attached to the negative end of the cathode sleeve 4, and a heater (not shown) is provided inside the cathode sleeve 4. A cathode support tube 5 is coaxially arranged outside the cathode sleeve 4, and the cathode support tube 5 supports the cathode sleeve 4 via a plurality of cathode supports 6.

The cathode substrate 1 provided on such a cathode assembly is conventionally manufactured by the method shown in FIGS. 5 and 6 show the steps of manufacturing the cathode substrate, respectively.

First, as shown in FIG. 5A, for example, a rod-shaped tungsten sintered body 11 made of porous tungsten is used.
Prepare The rod-shaped tungsten sintered body 11 is formed as thick as possible (currently, a sintered body with a diameter of up to 100 mm can be obtained). Next, in order to improve the machinability, the rod-shaped tungsten sintered body 11 is subjected to a process of impregnating the inside of the holes with copper, and thereafter, as shown in FIG. The tungsten sintered body 11 is subjected to slicing and divided into thin plates to have a thickness of, for example, 320 μm.
A plurality of porous tungsten thin plates 12 of about m are formed. Next, the porous tungsten thin plate 11 is subjected to an acid treatment and a hydrogen treatment to remove copper Cu impregnated in the pores.

[0006] Next, as shown in FIG. 6 (a), a brazing material made of ruthenium-molybdenum is applied to one surface of the porous tungsten thin plate 12, dried, and then heated in a reducing atmosphere to form ruthenium-molybdenum. An alloy layer 13 is formed. The thickness of the alloy layer 13 is, for example, about 15 μm. Next, as shown in FIG. 6B, the other surface of the porous tungsten thin plate 12, that is, the surface on which the ruthenium-molybdenum alloy layer 13 is not formed, is loaded with an electron emitting material 14 made of barium oxide or the like. 14 is melted and impregnated in the pores of the porous tungsten thin plate 12 in a reducing atmosphere.

Next, as shown in FIG. 6 (c), a porous tungsten thin plate 12 impregnated with an electron emitting material 14 and having a ruthenium-molybdenum alloy layer 13 formed on one surface is irradiated with a YAG laser by high-speed pulse oscillation. Then, a plurality of cathode bases 15 having a predetermined shape are cut out from the porous tungsten thin plate 12. The obtained cathode substrate 15 is made of porous tungsten, and has a ruthenium-molybdenum alloy layer 13 formed on one surface and an electron emission surface on the other surface.

In this laser processing, the electron emission surface of the porous tungsten thin plate 12 (the electron emission surface of the cathode substrate 15), that is, the ruthenium-molybdenum alloy layer 13
In order to protect the other surface on which no is formed, one surface of the porous tungsten thin plate 12, namely, ruthenium-
From the molybdenum alloy layer 13 to the porous tungsten thin plate 12
Incident on In addition, since the entire thickness of the porous tungsten thin plate 12 including the ruthenium-molybdenum alloy layer 13 is as thick as, for example, about 360 μm, it is irradiated with laser light for a long time.

From these facts, as shown in FIG. 6D, in the cathode base 15 obtained by laser irradiation, a part of the ruthenium-molybdenum alloy layer 13 is formed along the outer peripheral edge, that is, along the cutting line by the laser light. A "burr A" having a large height and a strong height of, for example, 50 μm is generated. In addition, when processing by laser beam irradiation,
Further, a strong flash A of the ruthenium-molybdenum alloy layer 13 is formed on the periphery of the cathode base 15,
The flash A of the cathode base 15 is formed along the flash A of the molybdenum alloy layer 13. The flash A in which tungsten is melt-solidified is embrittled by recrystallization of the crystal, so that it can be easily removed by applying rubbing or vibration. But ruthenium
The flash A of the molybdenum alloy layer 13 is strong and cannot be easily removed.

Therefore, conventionally, a tumbling process is performed on the cathode base 15 in order to remove the flash A from the cathode base 15. In this tumbling treatment, for example, about half the amount of an abrasive mainly composed of SiO ₂ and Al ₂ O ₃ having a diameter of several mm is put into a 1-liter pot together with the cathode substrate, and the pot is rotated and revolved to perform tumbling. As a result, the flash A of the ruthenium-molybdenum alloy layer 13 is removed as shown in FIG. This processing is performed on the ruthenium-molybdenum alloy layer 1
Since the flash A of No. 3 is strong, it takes a long time, for example, about one hour. The cathode base 15 corresponds to the cathode base 1 shown in FIG. 4, and the ruthenium-molybdenum alloy layer 13 corresponds to the brazing material 2 shown in FIG.

[0011]

The conventional manufacturing method for manufacturing such a cathode substrate has the following problems. That is, in order to cut the cathode base 15 from the porous tungsten sheet 12 impregnated with the electron emitting material 14 and having the ruthenium-molybdenum alloy layer 13 formed on one surface, a laser beam is applied from the ruthenium-molybdenum alloy layer 13 side to the porous tungsten sheet 12. , A strong flash A is formed in the ruthenium-molybdenum alloy layer 13. Therefore, tumbling is performed for a long time to remove the flash A of the strong ruthenium-molybdenum alloy layer 13.

However, if the tumbling process is performed on the cathode base 15 for a long time as described above, the surface of the cathode base 15 is also processed, and the tungsten particles existing on the surface of the base are extended, so that the vacancy opening on the surface of the base is opened. The opening of the hole may be closed to reach a state. When the pores of the cathode base 15 are crushed in this way, a path through which the electron-emitting substance impregnated inside the cathode base 15 diffuses to the surface of the cathode base is cut off. There is a problem in that the amount of electrons cannot be emitted and the electron emission ability is reduced.

Also, at the time of slicing in the process of manufacturing the porous tungsten thin plate 12, the openings of the holes on the surface of the porous tungsten thin plate 12 are partially crushed. A similar problem has occurred.

Since the present invention has been made in view of the above circumstances, it is possible to obtain a cathode substrate having an excellent electron emission ability by which burrs existing on the surface of the cathode substrate can be easily removed without impairing the condition of the surface of the cathode substrate. It is an object to provide a manufacturing method which can be performed.

[0015]

According to a first aspect of the present invention, there is provided a method of manufacturing a cathode base, comprising: applying a brazing material to one surface of a thin plate made of a metal sintered body; A step of irradiating a laser beam to cut out the cathode base from the sintered thin plate so that burrs are generated only on the other surface side where the brazing material is not applied, and a step of removing burrs from the cut-out cathode base And a step of impregnating the cathode substrate with an electron-emitting substance.

According to the structure of the present invention, when the cathode substrate is cut from the sintered thin plate by irradiating a laser beam, only a brittle bur of the metal sintered body is generated without generating a strong brazing filler metal. The method for manufacturing a cathode substrate according to the invention of claim 2, wherein burrs present on the surface of the cathode substrate can be easily removed without impairing the condition of the surface of the cathode substrate, and a cathode substrate having excellent electron-emitting ability can be obtained. ,
A step of applying a brazing material to one surface of the sintered body thin plate; and irradiating a laser beam to the sintered body thin plate to burr only the other surface side where the brazing material is not applied from the sintered body thin plate. A step of cutting out the cathode substrate so as to generate the gas, a step of removing burrs from the cut-out cathode substrate, a step of impregnating the cathode substrate with an electron emitting material, and a step of impregnating the surface of the impregnated cathode substrate. Removing excess electron emitting material.

A method of manufacturing a cathode substrate according to a third aspect of the present invention comprises the steps of: applying a brazing material to one surface of a sintered compact; and irradiating the sintered compact with a laser beam. A step of cutting out the cathode base from the thin plate so that burrs are generated only on the other surface side where the brazing material is not applied, a step of removing the burrs from the cut-out cathode base, and applying an electron emitting material to the cathode base. The method includes a step of impregnating, a step of removing surplus electron emitting material present on the surface of the impregnated cathode base, and a step of applying a surface coating to the surface of the cathode base.

According to the second and third aspects of the present invention,
In addition to easily removing the burrs without impairing the state of the surface of the cathode substrate and improving the electron emission capability, the surface condition of the substrate after impregnation with the electron emission material can be improved to further enhance the electron emission capability.

According to a fourth aspect of the present invention, in the method of manufacturing a cathode substrate according to any one of the first to third aspects, the step of removing burrs from the cut-out cathode substrate comprises the step of: 6. The method of manufacturing a cathode substrate according to claim 5, wherein the substrate is etched. The method of manufacturing a cathode substrate according to claim 1, further comprising: The step of removing is characterized by performing ultrasonic cleaning after etching the cathode substrate.

According to the fourth and fifth aspects of the present invention, burrs generated on the surface of the cathode base can be reliably removed.
According to a sixth aspect of the present invention, in the method for manufacturing a cathode substrate according to any one of the first to third aspects, the thin sintered body is a thin sheet made of a tungsten sintered body. .

According to a seventh aspect of the present invention, in the method of manufacturing a cathode substrate according to any one of the first to third aspects, the brazing material is made of a ruthenium-molybdenum alloy. I do. According to the configuration of the invention of claims 6 and 7, it is possible to use a material suitable for the material constituting the cathode base.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. FIG. 1 shows steps of a method for manufacturing a cathode substrate. In this embodiment, the same items as those described in the above-described conventional method of manufacturing a cathode base shown in FIGS. 5 and 6 are denoted by the same reference numerals.

First, as shown in FIG. 5, for example, a rod-shaped tungsten sintered body is prepared, and the machinability of the rod-shaped tungsten sintered body is improved in the same manner as in the above-described conventional manufacturing method. For this purpose, a process of impregnating the inside of the holes with copper is performed, and thereafter, a rod-shaped tungsten sintered body is subjected to slicing using a wire saw or the like to be cut into thin plates and cut into thin plates as shown in FIG. Then, a plurality of porous tungsten thin plates 12 having a thickness of, for example, 90 mm and a thickness of about 320 μm are formed. Next, the porous tungsten thin plate 12 is subjected to an acid treatment and a hydrogen treatment to remove copper impregnated in the pores. The tungsten sintered body is suitable as a material for the cathode substrate.

Next, as shown in FIG. 1B, a brazing material made of a ruthenium-molybdenum alloy is applied to one surface of the porous tungsten thin plate 12 and dried, and then heated in a reducing atmosphere to form a ruthenium-containing material. Molybdenum alloy layer 13
To form The thickness of the alloy layer 13 is, for example, about 15 μm.
It is. Ruthenium-molybdenum alloy is a suitable material as a brazing filler metal.

Next, as shown in FIG. 1C, a porous tungsten thin plate 12 having a ruthenium-molybdenum alloy layer 13 formed on one surface was irradiated with a YAG laser.
A plurality of cathode bases 15 having a predetermined shape are cut out from the porous tungsten thin plate 12. The obtained cathode substrate 15 is made of porous tungsten, and has a ruthenium-molybdenum alloy layer 13 formed on one surface and an electron emission surface on the other surface.

In the process of cutting the cathode base 15 from the porous tungsten thin plate 12 by the laser irradiation, burrs are generated along the outer peripheral edge of the cathode base 12, that is, along the cutting line. In the embodiment of the present invention, as shown in FIG. 1D, the ruthenium-molybdenum alloy layer 1 is irradiated by this laser irradiation.
In the process of cutting the cathode substrate 15 from the porous tungsten thin plate 12 on which the electrode 3 is formed, the electron emission surface of the cathode substrate 15, that is, the ruthenium-molybdenum alloy layer 1
The burrs B are formed only on the surface side where the surface of the porous tungsten thin plate is directly exposed without forming 3. That is, burrs B are formed only on the porous tungsten which is the base material of the cathode base 15.

The following method can be used to generate burrs B only on the exposed tungsten side of the cathode base 15. For example, when a high-speed pulse YAG laser (a solid-state laser using yttrium, aluminum, and garnet as a laser medium and having a short wavelength of 14 μm) is used, the laser is irradiated with the tungsten exposed surface of the cathode base 15 as an incident surface. Then, the brittle burrs B of tungsten are generated only on the tungsten exposed surface side. Laser irradiation conditions in this case are, for example, processing 12 times at an output of 24 W, a pulse repetition rate of 4 KHz, and a cutting speed of 7 mm / sec.

When a normal pulse YAG laser is used, the ruthenium-molybdenum alloy layer 13 is used as an incident surface, and the pulse passes through the porous tungsten thin plate 12 on which the ruthenium-molybdenum alloy layer is formed in one pulse. By performing high-energy (for example, 100 mJ / pulse or more) and cutting once, the cathode substrate 15
In this case, the brittle burrs B of tungsten are generated only on the exposed side of tungsten.

Next, as shown in FIG.
Is etched to remove the brittle burrs B of tungsten generated only on the exposed tungsten surface side of the cathode base 15 and to remove impurities that are scattered during laser processing and adhere to the surface of the cathode base 15. In addition, by this etching, the pores on the surface of the cathode base 15 generated during the slicing process in the process of manufacturing the porous tungsten thin plate described above are removed, and the holes on the surface are sufficiently opened. .

Thereafter, the cathode base 15 is subjected to ultrasonic cleaning in a solvent such as pure water and alcohol. At this time, the disk vibrates due to the ultrasonic waves, and all the flashes remaining partially on the surface of the cathode base 15 without being completely removed by etching are removed. That is, burrs can be more reliably removed by performing ultrasonic cleaning in addition to etching.

The porous tungsten thin plate 12 having the ruthenium-molybdenum alloy layer 13 formed on one side is irradiated with a laser beam to apply a ruthenium-molybdenum alloy layer as a brazing material from the porous tungsten thin plate 12. The cathode substrate 15 is cut out so that burrs are generated only on the other surface side, and then the burrs are removed from the cathode substrate 15 and the cathode substrate 15 is impregnated with an electron-emitting substance. When the cathode substrate 15 is cut off by light irradiation, only a brittle burr B of a metal sintered body (tungsten sinter) is generated without generating a strong brazing filler metal. Therefore, burrs existing on the surface of the cathode base 15 can be easily removed without impairing the state of the surface of the cathode base 15. That is, the burrs B can be removed without performing a conventional process such as tumbling to crush the openings of the holes in the surface of the cathode substrate. If the tungsten particles existing on the surface of the cathode base 15 are extended when the burrs B are removed and the openings of the holes opened on the surface of the base are closed to reach the state, the electron emission impregnated inside the cathode base 15 The path through which the substance diffuses to the surface of the cathode substrate is blocked, and the required amount of the electron-emitting substance cannot be emitted, so that the electron-emitting ability is reduced. Accordingly, by removing the burrs B without crushing the openings of the holes on the surface of the cathode base 15, a decrease in the electron emission ability can be prevented.

Next, as shown in FIG.
The electron emitting substance 14 made of barium oxide or the like is loaded on the exposed side of tungsten in the above, and this substance 14 is melted and impregnated into the pores of the cathode substrate 15 in a reducing atmosphere. Thus, the cathode substrate shown in FIG. 1 (g) can be manufactured. The cathode base 15 corresponds to the cathode base 1 shown in FIG. 4, and the ruthenium-molybdenum alloy layer 13 corresponds to the brazing material 2 shown in FIG.

Next, a means such as vibration is applied to the cathode base 15 to remove the excess electron emitting substance 14 attached to the surface of the cathode base 15. As a result, the dimensional accuracy of the surface of the cathode base 15 is improved, and the electron emission can be favorably performed in a required direction. If the surplus electron emitting substance 14 adheres to the surface of the cathode base 15, the dimensional accuracy of the surface of the cathode base 15 decreases, and electrons are emitted in unnecessary directions. As a result, the surface state of the cathode base 15 is improved after the impregnation with the electron emitting substance, and the electron emission characteristics of the cathode base 15 are further improved.

Also, as described above, the surplus electron emitting material 14
After the removal, the cathode body 15 is washed and dried. As a result, the surface condition of the cathode base 15 after the removal of the electron emitting material 14 is further improved, and the electron emission characteristics of the cathode base 15 are further improved.

Furthermore, after this washing and drying,
A surface coating, for example, a coating of iridium Ir, ruthenium Ru, osmium Os, or the like is applied to the surface of the cathode substrate 15. By this surface coating, the electron emission from the surface of the cathode substrate 15 is uniformed, and the electron emission characteristics that are favorably performed are further improved.

As described above, in addition to easily removing the burrs without impairing the condition of the surface of the cathode substrate to increase the electron emission capability, the surface condition of the substrate is improved after impregnation with the electron emission material to further enhance the electron emission capability. Can be increased.

The cathode substrate thus manufactured is assembled in the same manner as in the prior art to form a required impregnated cathode assembly. This cathode structure has excellent characteristics because it uses a cathode base having excellent electron emission ability.

FIG. 2 is an enlarged photograph of the surface of the tungsten sintered body forming the cathode substrate manufactured by the manufacturing method of the present invention under a microscope. According to this photograph, the surface of the cathode substrate manufactured by the present invention is shown. It can be seen that the opening of the hole is not crushed on the surface. FIG. 3 is an enlarged photograph of a surface of a tungsten sintered body forming a cathode substrate manufactured by a conventional manufacturing method, which is shown by a microscope. According to this photograph, the surface of the cathode substrate manufactured by the present invention has pores. It can be seen that the opening is crushed. The present invention is not limited to the above embodiment,
Various modifications can be made.

[0039]

As described above, according to the method for manufacturing a cathode substrate according to the first aspect of the invention, when the cathode substrate is cut from a sintered thin plate by irradiating a laser beam, a flash of a solid brazing material is generated. Since only brittle burrs of the metal sintered body are generated without causing burrs, burrs existing on the surface of the cathode substrate can be easily removed without impairing the state of the surface of the cathode substrate, and a cathode substrate having excellent electron emission ability is obtained. According to the manufacturing method according to the second and third aspects of the present invention, the burrs can be easily removed without impairing the state of the surface of the cathode substrate to enhance the electron emission capability, After the material is impregnated, the surface condition of the substrate can be improved to further enhance the electron emission ability.

According to the invention of claims 4 and 5,
Burrs generated on the surface of the cathode substrate can be reliably removed. According to the configuration of the invention of claims 6 and 7, it is possible to use a material suitable for the material constituting the cathode base.

[Brief description of the drawings]

FIG. 1 is a diagram showing steps of a manufacturing method according to an embodiment of the present invention.

FIG. 2 is an enlarged photograph of a surface of a tungsten sintered body forming a cathode substrate manufactured by the manufacturing method of the present invention under a microscope.

FIG. 3 is an enlarged photograph of the surface of a tungsten sintered body forming a cathode substrate manufactured by a conventional manufacturing method, which is enlarged by a microscope.

FIG. 4 is a partially cutaway perspective view showing an impregnated cathode assembly.

FIG. 5 is a diagram showing steps of a manufacturing method in a conventional mode.

FIG. 6 is a diagram showing steps of a manufacturing method according to the conventional embodiment.

[Explanation of symbols]

 11: Sintered tungsten, 12: Porous tungsten thin plate, 13: Ruthenium-molybdenum alloy layer, 14: Electron emitting material, 15: Cathode substrate

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Naoto, 8-8 Shinsugita-cho, Isogo-ku, Yokohama-shi, Kanagawa F-term in Toshiba Yokohama Office (reference) 5C027 CC02 CC11 CC14

Claims (7)

[Claims] 1. A step of applying a brazing material to one surface of a thin plate made of a metal sintered body, and irradiating a laser beam to the thin plate to apply the brazing material from the sintered body thin plate. A step of cutting out the cathode base so that burrs are generated only on the front side, a step of removing burrs from the cut-out cathode base, and a step of impregnating the cathode base with an electron emitting material. A method for manufacturing a cathode substrate. 2. A step of applying a brazing material to one surface of a sintered body thin plate, and irradiating a laser beam to the sintered body thin plate to apply the brazing material from the sintered body thin plate to the other side. A step of cutting out the cathode substrate so that burrs are generated only on the front side, and a step of removing burrs from the cut-out cathode base,
A method for manufacturing a cathode base, comprising: a step of impregnating the cathode base with an electron emitting substance; and a step of removing excess electron emitting substance present on the surface of the impregnated cathode base. 3. A step of applying a brazing material to one surface of the sintered body thin plate, and irradiating the sintered body thin plate with a laser beam to apply the brazing material from the sintered body thin plate. A step of cutting out the cathode substrate so that burrs are generated only on the front side, and a step of removing burrs from the cut-out cathode base,
A step of impregnating the cathode substrate with an electron emitting material, a step of removing excess electron emitting material present on the surface of the impregnated cathode substrate, and a step of applying a surface coating to the surface of the cathode substrate. A method for manufacturing a cathode substrate, comprising: 4. The method according to claim 1, wherein the step of removing the burrs from the cut-out cathode base is performed by etching the cathode base. 5. The method according to claim 1, wherein the step of removing burrs from the cut-out cathode base is performed by ultrasonic cleaning after etching the cathode base.
The method for producing a cathode substrate according to any one of the above. 6. The method for manufacturing a cathode substrate according to claim 1, wherein said sintered body thin plate is a thin plate made of a tungsten sintered body. 7. The brazing material according to claim 1, wherein said brazing material is made of a ruthenium-molybdenum alloy.
The method for producing a cathode substrate according to any one of the above.