JP2003197086A - Impregnated cathode, method of manufacturing the cathode, electron gun using the cathode, and cathode ray tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend an emission life and suppress an electric leakage between a cathode and a grid electrode by suppressing the evaporation of electron emission substance. <P>SOLUTION: Metal powder for cathode substrate is put in a metal mold 26 having a recessed part of the same shape as that of a projected part 20a at the front of a cathode substrate 20, and press-formed by using a metal mold 27 having a projected part of the same shape as that of the projected part 20a at the front thereof. By using these metal molds 26 and 27, a uniform pressure can be applied to the metal powder for cathode at the time of pressing. Accordingly, the density distributions of the projected part 20a and base part 20b of the formed cathode substrate 20 are made uniform. Thus, the evaporation of the electron emission substance, for example, Ba during the operation can be suppressed, the emission life can be extended, and the electric leak between the cathode 16 and the grid electrode can be suppressed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impregnated cathode, a method for manufacturing the same, an electron gun and a cathode ray tube using the same. Specifically, the above-mentioned protrusion and base portion of the cathode substrate, which is composed of a protrusion formed in a convex shape and a base portion integrally formed with this protrusion, are molded by, for example, press working, Impregnated cathode and its manufacture that can suppress the evaporation of electron emission material during operation, extend the emission life, and suppress electrical leakage between the cathode and grid electrode etc. by making the density distribution uniform. It relates to the method.

[0002]

2. Description of the Related Art The cathode is an important component that influences the efficiency and life of a cathode ray tube. Among the cathodes, the impregnated cathode can obtain a high current density and can be expected to have a long life. It is attracting attention as a cathode for color cathode ray tubes.

The cathode ray tube has a panel whose inner surface is coated with a fluorescent surface, and a color selection mechanism installed inside the panel.
It is composed of a neck part to which an electron gun is attached and a funnel connecting the panel and the neck part.

An electron gun mounted on the neck is generally
In front of the cathode, a plurality of cylindrical metal electrodes are arranged on the same axis. A single electron gun type electron gun used in a color cathode ray tube has three cathodes corresponding to red (R), green (G) and blue (B), that is, cathodes. This 3
There are two methods of arranging the cathodes: in-line (single row) arrangement and delta (triangle) arrangement.

Conventionally, in the electron gun of the cathode ray tube, the screen brightness is controlled by controlling the bias voltage between the first grid and the cathode to adjust the amount of the electron beam emitted from the cathode. . Further, in order to improve the focus characteristics of the electron gun so that high-resolution display can be performed, the diameter of the hole provided in the first grid facing the cathode has been reduced.

However, if the hole diameter of the first grid is reduced, the amount of electrons extracted as an electron beam out of the electrons emitted from the cathode is reduced and the brightness of the screen is reduced. This can be improved by increasing the drive voltage to increase the amount of electrons emitted from the cathode, but when the drive voltage becomes high, when driving at a high frequency for high resolution display, this drive signal The follow-up operation cannot be performed and the frequency characteristic is deteriorated.

In order to solve such a problem, the present applicant previously used an impregnated cathode 1 in which the surface of a cathode substrate 2 was formed in a convex shape, as shown in FIG. 8, and the same. An electron gun and a cathode ray tube have been proposed (Japanese Patent Application No. 2001-24).
6678).

The cathode is a heater 5 as shown in FIG.
Has a structure in which a cathode base 2 impregnated with an electron emitting substance such as BaO, CaO, Al ₂ O ₃ or the like at a predetermined ratio is attached to the tip of a cylindrical sleeve 4 made of Mo or Ta.

FIG. 8 shows a schematic cross-sectional view of the cathode 1 and the first grid G1. At the tip of the cathode 1, a cap 3 having a cathode substrate 2 made of, for example, tungsten, is attached. The surface of the substrate 2 has a convex shape and is impregnated with an electron emitting substance. Further, the tip of the cathode substrate 2 is attached so as to enter the holes of the first grid.

In addition to the above-described mounted state of the cathode base 2 shown in FIG. 8, it is also possible to mount the cathode base 2 so that the tip end of the cathode base 2 enters into the holes of the first grid and projects (see Japanese Patent Application No. 2001-2001). 246678).

When such an impregnated cathode 1 is used, the drive characteristics of the cathode 1 are improved and the focus characteristics are also improved, so that high brightness and high resolution can both be achieved.

Such a cathode substrate 2 can be manufactured by the manufacturing method shown in FIG. FIG. 9A shows a state where the cathode substrate 2 is press-molded, and FIG. 9B shows a state of the cathode substrate 2 after press-molding.

In the method shown in FIG. 9, a refractory metal powder having a high melting point, for example, tungsten powder for the cathode base 2 is placed in a mold 6 having a recess having the same shape as the shape of the projection on the front surface of the cathode base 2. As shown in FIG. 9A, the cathode substrate 2 is pressed and molded with a flat metal mold 7 from a portion corresponding to the back surface thereof. As shown in FIG. 9B, after press molding, the cathode substrate 2 having a protrusion on the front surface is obtained.
Next, on the cathode substrate 2, BaO, which is an electron emitting substance,
A mixture of CaO and Al ₂ O ₃ in a predetermined ratio is melt-impregnated, mounted on the cap 3, and fixed to the sleeve 4.

[0014]

As described above, when the convex mold 6 and the flat mold 7 are press-molded, the density of the protrusions 2a of the cathode substrate 2 and the central portion 2c thereunder is reduced. The density becomes lower than that of the portion 2b, and the cathode base 2
The density is uneven.

When the cathode substrate 2 has a non-uniform density as described above, when the cathode substrate 2 is impregnated with an electron-emitting substance (emitter), the diffusion rate is high in a portion having a low density, so that the emitter is fast on the surface. To reach. As a result, the amount of the emitter that evaporates during operation increases in the low density portion of the protrusion 2a and the lower central portion 2c thereof, which causes uneven consumption of the emitter. As a result, the emission life characteristics are affected, and the life of the electron gun and the cathode ray tube is reduced.

When the cathode substrate 2 is impregnated with the electron emitting substance, the number of emitters impregnated in the low density portions of the protrusion 2a and the lower central portion 2c thereof is larger than that of the peripheral portion 2b. Further, in the low density portion as described above, since the diffusion rate is high, the amount of the emitter evaporated during the operation is large, and electric leakage between the cathode and the grid, the heater, and the focus electrode may occur.

Therefore, according to the present invention, an impregnated cathode capable of extending the emission life and suppressing electrical leakage between the cathode and the grid electrode, a method of manufacturing the same, an electron gun and a cathode ray tube using the same. The purpose is to provide.

[0018]

An impregnated cathode according to the present invention has a protrusion formed in a convex shape and a base integrally formed with the protrusion, and is impregnated with an electron emitting substance. An impregnated cathode in which a cathode base made of metal powder is attached to a cap, and the cap is fixed to a sleeve, and the cathode base has a protrusion and a base having a uniform density distribution. Is.

Further, the method of manufacturing an impregnated cathode according to the present invention has a projection formed in a convex shape and a base formed integrally with the projection, and impregnated with an electron-emitting substance. A method of manufacturing an impregnated cathode in which a cathode base made of metal powder is attached to a cap, and the cap is fixed to a sleeve, and a mold having a recess having the same shape as the shape of the protrusion on the front surface of the cathode base, Using a mold having a protrusion having the same shape as the shape of the protrusion on the front surface of the cathode substrate,
Assembly in which a pressing step of press-molding metal powder, a flattening step of flattening a lower concave portion of the cathode base molded by the pressing step, and a cathode base flattened in the flattening step are mounted on a cap And a fixing step of fixing the cap on which the cathode substrate is mounted to the sleeve.

The electron gun according to the present invention is an electron gun comprising an impregnated cathode and a plurality of grid electrodes arranged so as to face the impregnated cathode, and the impregnated cathode has a convex shape. A cathode base made of metal powder impregnated with an electron-emitting substance is attached to a cap, and the cap is fixed to the sleeve, which has a projection formed in a shape and a base formed integrally with the projection. The cathode substrate has a protrusion and a base having a uniform density distribution.

Further, the cathode ray tube according to the present invention comprises a panel portion having a phosphor screen, a neck portion accommodating an electron gun having an impregnated cathode, and a funnel portion connecting the neck portion and the panel portion. An impregnated cathode, which is a cathode ray tube, has a protrusion formed in a convex shape and a base formed integrally with the protrusion, and is a cathode made of metal powder impregnated with an electron emitting substance. The base is mounted on a cap, and the cap is fixed to the sleeve. The cathode base has a protrusion and a base having a uniform density distribution.

According to the present invention, the above-mentioned projection and base portion of the cathode substrate, which is composed of a projection formed in a convex shape and a base formed integrally with the projection,
For example, it is formed by press working and its density distribution is made uniform. Therefore, it is possible to suppress evaporation of the electron emission material during operation, extend the emission life, and suppress electrical leakage between the cathode and the grid electrode. Therefore, it becomes possible to easily manufacture a long-life electron gun and a cathode ray tube using the same.

Further, metal powder is pressed using a die having a recess having the same shape as the shape of the protrusion on the front surface of the cathode substrate and a die having a protrusion having the same shape as the shape of the protrusion on the front surface of the cathode substrate. By molding and flattening the recessed portion of the lower part of the molded cathode substrate, a cathode substrate having a uniform density distribution can be easily obtained, and the welding workability between the cathode substrate and the cap is improved. It becomes possible.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a cathode ray tube 1 according to an embodiment.
00 configuration is shown. This cathode ray tube 100 has a panel 10 having an inner surface coated with a phosphor screen 9, a color selection mechanism 11 installed inside the panel 10, a neck portion 13 having an electron gun 12 mounted thereon, the panel 10 and the neck portion. It is composed of a funnel 14 connecting 13 together. An internal magnetic shield 15 is provided inside the cathode ray tube 100. In addition, the conductive film 8 is formed inside the funnel 14.

FIG. 2 shows an electron gun 1 used in the cathode ray tube 100.
2 shows the configuration. This electron gun 12 has a cathode 1
6 and a plurality of grid electrodes G1 to G6 and a shield cup 17 are in-line type electron guns. The in-line type electron gun 12 is formed as a so-called multi-beam single electron gun, and has three cathodes 16 (KR) and 16 (K) corresponding to red (R), green (G) and blue (B).
G) and 16 (KB) are arranged in-line (one horizontal row), and the three grids 16 (KR), 16 (KG) and 16 (KB) are directed toward the anode side, and the first grid G
The first grid G2, the third grid G3, the fourth grid G4, the fifth grid G5, the sixth grid G6 and the shield cup 17 are coaxially arranged.

The electron gun 12 is an electron lens of a plurality of main lens types, and the second grid G2 and the fourth grid G4 are electrically connected. Further, the fifth grid G5 corresponding to the focus electrode is divided into two, that is, a fifth grid G5a serving as the first focus electrode and a fifth grid G5b located on the anode side and serving as the second focus electrode. There is. Further, the third grid G3 and the fifth grid G5b are electrically connected.

For example, 0V is applied to the first grid G1.
(Or several tens of V) is applied to the second grid G
A voltage of, for example, 200 to 800 V is applied to the second grid 4 and the fourth grid G4, and a voltage of 22 k is applied to the sixth grid G6.
An anode voltage of V-30 kV is applied.

A constant focus voltage, for example, is applied to the third grid G3 and the fifth grid G5b. on the other hand,
For example, a dynamic focus voltage is applied to the divided fifth grid G5a. As a result, a quadrupole lens is formed between the bisected fifth grids G5a and G5b, and the fifth grid G5 is formed by the quadrupole lens.
The main lens (focus lens) formed between 5b and the sixth grid G6 is changed in intensity so that the shape of the electron beam around the screen in the horizontal direction of the phosphor screen becomes good.

The thermoelectrons emitted from the cathode 16 are accelerated and focused by passing through each of the grids G1 to G6 of the electron gun 12, and further pass through a predetermined electron beam passage hole of the color selection mechanism 11 so that the fluorescent screen 9 is formed. Irradiated on. The cathode 16 is an impregnated cathode. The cathode 16 is attached so that the tip of the cathode 16 enters the hole of the first grid G1.

FIG. 3 shows the structure of the impregnated cathode 16 and the cathode substrate 20. FIG. 3A is a cross-sectional view of the cathode 16 and the first grid G1, FIG. 3B.
Shows the structure of the cathode substrate 20. In FIG. 3, parts corresponding to those in FIG. 8 are designated by the same reference numerals.

As shown in FIG. 3A, the cathode base 2 made of, for example, tungsten is provided at the tip of the cathode 16.
0 is provided. The cathode substrate 20 is mounted on the cap 3, and the cap 3 is fitted into the tip of the sleeve 4 and fixed by a method such as welding.

As shown in FIG. 3B, the cathode substrate 2
0 is composed of a protruding portion 20a and a base portion 20b. The protrusion 20a is formed by forming the surface of the cathode base 20 into a convex shape, and the base 20b is formed by the portion of the cathode base 20 other than the protrusion 20a. The protruding portion 20a of the cathode substrate 20 and the base portion 2
0b is pressed as described later to have a uniform density distribution. Further, the bottom surface of the cathode substrate 20 is flat.

The manufacturing process of the impregnated cathode 16 will be described below with reference to FIGS. FIG. 4 shows a manufacturing process of the impregnated cathode 16. First, in step S1, the cathode substrate 20 is press-molded. The cathode substrate 20 is molded by pressing a powdery metal for the cathode substrate, for example, tungsten powder, using a mold to mold it into a predetermined shape. Next, in step S2, the bottom surface of the molded cathode substrate 20 is flattened.

FIG. 5 shows a method of forming the cathode substrate 20. 5A shows a press molding process for the cathode substrate 20, FIG. 5B shows a state of the cathode substrate 20 after press molding, and FIG. 5C shows a bottom surface flattening process.

As shown in FIG. 5A, the cathode substrate 20 is molded by a mold 26 having a recess having the same shape as the shape of the protrusion on the front surface of the cathode substrate 20, and the shape of the protrusion on the front surface of the cathode substrate 20. And a metal mold 27 having a convex portion having the same shape as the above, metal powder for the cathode substrate is put into the metal mold 26 corresponding to the front surface of the cathode substrate 20, and then the same shape as the shape of the protrusion portion 20a on the front surface. The metal powder for the cathode substrate is pressed and molded by using the mold 27 having the protruding portion. By using such molds 26 and 27, it is possible to apply a uniform pressure to the metal powder for the cathode substrate during press working. Therefore, the density distribution of the molded cathode substrate 20 becomes uniform. As shown in FIG. 5B, the cathode substrate 20 after press molding has a protrusion 20 having a convex shape on the front surface.
a is formed, and a recess 20c having the same shape is formed on the bottom surface of the lower base portion 20b.

As will be described later, when the cathode substrate 20 is attached to the cap 3, welding is performed after the central portion of the bottom surface of the base portion 20b is melted. However, if the recessed portion 20c is provided as described above, it becomes difficult to obtain a molten state by laser irradiation. In order to solve this problem, as shown in FIG. 5C, a portion of the lower base portion 20b of the cathode substrate 20 including the recessed portion 20c is cut to flatten the bottom surface of the cathode substrate 20. This improves the workability of welding with the cap 3. The lower portion of the cathode substrate 20 including the recessed portion 20c may be scraped off to be flat.

Returning to FIG. 4, next, in step S3, the cathode substrate 20 is coated with an electron-emitting material such as BaO or Ca.
A mixture of O and Al ₂ O ₃ in a predetermined ratio is melt-impregnated. The cathode substrate 20 after the impregnation treatment is processed in steps S4 to S4.
In S6, the cap 3 is mounted and fixed to the sleeve 4.

FIG. 6 shows an assembly process for mounting the cathode substrate 20 on the cap 3. 6A shows a pretreatment state before welding, FIG. 6B shows a state in which the cathode substrate 20 is mounted on the cap 3, and FIG. 6C shows a state in which the cathode substrate 20 is welded to the cap 3. Is shown.

In the assembly process for mounting the cathode substrate 20 on the cap 3, first, in step S4, the central portion of the bottom surface of the cathode substrate 20 is melted by laser as shown in FIG. , As shown in FIG. 6 (b),
The cathode substrate 20 is put into the cap 3, and then, in step S5, as shown in FIG. 6C, laser is irradiated from the bottom surface of the cap 3 to weld and fix it.

Then, after the cathode substrate 20 is mounted on the cap 3, the cap 3 is fitted into the tip of the sleeve 4 and fixed by welding or the like in step S6. As a result, the impregnated cathode 16 is obtained.

The bottom surface of the cathode substrate 20 may be flattened as follows. That is, as shown in FIG. 7, in step S1 described above, a mold 36 having a shape corresponding to the front surface of the cathode base 20 and a mold 37 having a protruding portion having the same shape as the shape of the projection on the front surface of the cathode base 20 are provided. Then, metal powder (tungsten powder) for the cathode substrate is put into the mold 36 and pressed (see FIG. 7A). Next, a metal powder for the cathode substrate, for example, tungsten powder, is further placed in the recess 20c in the lower portion of the cathode substrate 20 after press molding, and then a flat mold 38 is used as shown in FIG. 7 (b). Press molding again to make the recess 20c flat.

In the above-described embodiment, the cathode substrate 20 is composed of the protruding portion 20a formed in a convex shape and the base portion 20b formed integrally with the protruding portion 20a.
In addition, since the protrusion 20a and the base 20b have a uniform density distribution by press working, it is possible to suppress the evaporation of the electron emission material, for example, Ba during operation, to extend the emission life, and at the same time as the cathode. It is possible to suppress electrical leakage between grid electrodes and the like. Therefore, it becomes possible to easily manufacture the long-life electron gun 12 and the cathode ray tube 100 using the same.

Further, the metal mold 26 having a recess having the same shape as the shape of the projection on the front surface of the cathode substrate 20, and the cathode substrate 2
Mold 27 having a protrusion having the same shape as the protrusion on the front surface of 0
By using and to press-mold metal powder and flatten the lower portion of the molded cathode substrate 20 having the recessed portion 20c, the cathode substrate 20 having a uniform density distribution can be easily obtained. Further, the workability of welding the cathode substrate 20 and the cap 3 can be improved. In addition, in the present invention, the present invention can be applied to the case where the shape of the projection 20a of the cathode substrate 20 is a shape other than the above, for example, a conical shape.

[0044]

According to the present invention, the projection and the base of the cathode substrate, which is composed of the projection formed in a convex shape and the base formed integrally with the projection,
For example, it is molded by press working and has a uniform density distribution. Therefore, it is possible to suppress evaporation of the electron emission material during operation, extend the emission life, and suppress electrical leakage between the cathode and the grid electrode. Therefore, it becomes possible to easily manufacture a long-life electron gun and a cathode ray tube using the same.

Further, metal powder is press-molded by using a die having a recess having the same shape as the protrusion on the front surface of the cathode substrate and a die having a protrusion having the same shape as the protrusion on the front surface of the cathode substrate. The flattened portion of the molded cathode base having a recess is to easily obtain a cathode base having a uniform density distribution, and improve the workability of welding the cathode base and the cap. .

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a cathode ray tube according to an embodiment.

FIG. 2 is a diagram showing a configuration of an electron gun.

FIG. 3 is a diagram showing a configuration of a cathode.

FIG. 4 is a manufacturing flowchart of an impregnated cathode.

FIG. 5 is a diagram showing a method of forming a cathode substrate.

FIG. 6 is a diagram showing an assembly process for mounting the cathode substrate on the cap.

FIG. 7 is a diagram showing another example of the cathode substrate bottom surface flattening step.

FIG. 8 is a schematic cross-sectional view of a cathode 1 and a first grid G1.

FIG. 9 is a diagram showing an example of a method of forming a cathode substrate.

[Explanation of symbols]

1, 16 ... Cathode, 2, 20 ... Cathode substrate, 21 ... 3 ... Cap, 4, ... Sleeve, 5 ... Heater, 6, 7, 26, 27, 36 , 3
7, 38 ... Mold, 8 ... Conductive film, 9 ... Phosphor screen, 10 ... Panel, 11 ... Color selection mechanism, 12 ...
..Electron gun, 13 ... Neck part, 14 ... Funnel, 15 ... Internal magnetic shield, 16, 16 KR, 16
KG, 16KB ... Cathode, 17 ... Shield cup, 20a ... Projection, 20b ... Base, 2
0c: recessed portion, 21: fused portion, 100: cathode ray tube

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshinori Suzuki             2-17-1, Higashigotanda, Shinagawa-ku, Tokyo             NMC Co., Ltd. F-term (reference) 5C027 CC10 CC14

Claims (8)

[Claims] 1. A cap is provided with a cathode substrate having a protrusion formed in a convex shape and a base formed integrally with the protrusion, the cathode substrate being made of metal powder impregnated with an electron emitting substance. An impregnated cathode in which the cap is fixed to a sleeve, wherein the cathode substrate has the protrusion and the base having a uniform density distribution. 2. The impregnated cathode according to claim 1, wherein the metal powder is tungsten powder. 3. A cap is provided with a cathode base made of metal powder, which has a protrusion formed in a convex shape and a base formed integrally with the protrusion, and is impregnated with an electron emitting substance. A method of manufacturing an impregnated cathode in which the cap is fixed to a sleeve, the mold having a recess having the same shape as the shape of the projection on the front surface of the cathode substrate, and the shape of the projection on the front surface of the cathode substrate. Using a mold having a convex portion of the same shape, a press step of press-molding the metal powder, and a flattening step of flattening the lower recessed portion of the cathode substrate molded in the press step, The method further comprises an assembling step of mounting the cathode base body flattened in the flattening step on the cap, and a fixing step of fixing the cap on which the cathode base body is mounted to the sleeve. Impregnated cathode manufacturing method of. 4. The production of the impregnated cathode according to claim 3, wherein in the flattening step, the lower concave portion of the cathode substrate molded in the pressing step is removed by cutting. Method. 5. The flattening step is characterized by removing the lower recessed portion of the cathode substrate molded in the pressing step by scraping off.
The method for manufacturing an impregnated cathode according to item 1. 6. In the flattening step, the metal powder is further placed in the lower depression of the cathode substrate formed in the pressing step, and press molding is performed again with a flat die to form a flat bottom surface having the depression. The method for producing an impregnated cathode according to claim 3, wherein 7. An electron gun comprising an impregnated cathode and a plurality of grid electrodes arranged to face the impregnated cathode, wherein the impregnated cathode is a protrusion formed in a convex shape. And a base portion integrally formed with the protrusion, and a cathode base made of metal powder impregnated with an electron emitting substance is attached to a cap, and the cap is fixed to a sleeve. An electron gun having the protrusion and the base having a uniform density distribution. 8. A cathode ray tube comprising a panel section having a phosphor screen, a neck section accommodating an electron gun having an impregnated cathode, and a funnel section connecting the neck section and the panel section. The mold cathode has a protrusion formed in a convex shape and a base formed integrally with the protrusion, and a cathode base made of metal powder impregnated with an electron emitting substance is attached to a cap, A cathode ray tube, comprising the cap fixed to a sleeve, and the cathode substrate having the protrusion and the base having a uniform density distribution.