JPH11204052A - Cathode and cathode-ray tube using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cathode with high thermal conductivity and a cathode-ray tube at low cost. SOLUTION: This cathode 23 attached to a neck part of a cathode-ray tube and capable of emitting electrons being heated by a heater is constituted of a cathode sleeve 25 formed into a cylinder to insert a heater into and a cathode cap 26 made of the same material for the cathode sleeve part 25 and integrally formed at the end of the cathode sleeve part 25 and bearing an electron emitting part 27 which emits electrons being heated by the heater.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode, and more particularly to a cathode for improving the performance of an electron gun and a cathode ray tube using the same.

[0002]

2. Description of the Related Art A television receiver emits a phosphor on an inner surface of a picture tube by an electron beam controlled by a video signal.
It reproduces black and white or color images. The electron beam is formed by heating a cylindrical member called a cathode, and accelerating, controlling, and focusing generated electrons. FIG. 6 is a sectional view showing an example of a conventional cathode.
The cathode 1 comprises a cathode sleeve 2, a cathode cap 3, and an electron emitting section 4. A cathode cap 3 is provided on an upper portion of the cathode sleeve 2, and an electron emitting section 3 is formed on an upper surface of the cathode cap 3. A heater is inserted into the hollow portion of the cathode sleeve 2, and when the cathode sleeve 2 is heated, electrons are emitted from the electron emission section 4.

FIG. 7 is a flowchart showing an example of a conventional method for manufacturing a cathode. The method for manufacturing the cathode 1 will be described with reference to FIG. The production of the cathode sleeve is mainly classified into the following three steps. First, as a first step, the cathode cap 3 is formed. The cathode cap 3 is formed of an alloy mainly composed of nickel and mixed with a small amount of a reducing agent such as magnesium or tungsten (ST1). Then, after this nickel alloy is rolled, it is formed into a cup shape by pressing from above and below, and the cathode cap 3 is formed (ST2).

Next, as a second step, the cathode sleeve 2 is formed. For example, a nichrome alloy is used as a material of the cathode sleeve 2, and a thin plate of the nichrome alloy is drawn or formed into a cylindrical shape (ST3). Then, the cylindrical nichrome alloy is subjected to a drawing process to complete the cathode sleeve 2 (ST4). Here, the cathode sleeve 2 is formed so that the outer dimensions match the inner diameter of the cathode cap 3. Finally, as a third step, the cathode cap 4 is joined and fixed to the tip of the cathode sleeve 2 by laser welding or the like (ST5). Thereafter, an alkaline earth metal carbonate powder made of barium, strontium, calcium, or the like, which becomes the electron emitting portion 4, is applied to the upper surface of the cathode cap 3 by a spraying method or the like to complete the cathode 1 (ST6).

Next, the process in which the cathode sleeve 1 emits electrons will be described in detail. When the cathode sleeve 1 is incorporated in a cathode ray tube and heated in vacuum, the applied alkaline earth metal carbonate is thermally decomposed at, for example, about 1300K. As the alkaline earth metal carbonate, a ternary carbonate which is a double salt of an alkaline earth metal containing barium as a main component is widely used. When the alkaline earth metal carbonate is thermally decomposed, barium oxide, which is an alkaline earth metal oxide, is formed. Magnesium, tungsten or the like contained in the cathode cap 3 becomes a reducing agent, and barium oxide is reduced at the interface of the cathode cap 3 to form free barium. For example, when magnesium is used as a reducing agent, free barium that contributes to electron emission is formed by the following chemical reaction formula.

BaO + Mg → Ba + MgO (1) The formed free barium is heated to about 1000 K by a heater incorporated in the cathode sleeve 1.
Good electron emission is performed.

[0006]

As described above, in order to emit electrons from the electron emitting portion 4 applied to the cathode cap 3, the electron emitting portion 4 and free barium are heated to a high temperature. There must be. Therefore, the cathode sleeve 2 needs to be sufficiently heated by the heater. However, in the above-mentioned cathode 1, since the cathode cap 3 and the cathode sleeve 2 are fixed by welding only at several places, the heat of the cathode sleeve 2 heated by the heater is transmitted to the cathode cap 3 only from the welded portion. However, there is a problem that the thermal efficiency of the heater is deteriorated due to a decrease in the thermal conductivity. In addition, when forming the cathode 1, three main steps of a manufacturing process of the cathode cap 3, a manufacturing process of the cathode sleeve 2, and a welding process of both are required, which takes a long manufacturing time and increases the manufacturing cost. There is a problem.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and to provide a cathode having good thermal conductivity and reduced cost, and a cathode ray tube using the same.

[0008]

According to the present invention, there is provided a cathode ray tube which is attached to a neck portion of a cathode ray tube and is formed into a cylindrical shape at a cathode which is heated by a heater and emits electrons. A cathode sleeve portion into which a heater is inserted into the hollow portion, and an electron emission portion which is integrally formed on the end face of the cathode sleeve portion with the same material as the cathode sleeve portion and emits electrons when heated by the heater. Is achieved by a cathode having a cathode cap portion to which is attached.

In the present invention, the cathode sleeve for inserting the heater and the cathode cap for emitting electrons are integrally formed of the same material. Thereby, the heat of the cathode sleeve portion is easily conducted to the cathode cap portion, and the thermal efficiency of the heater is improved. Further, in the production of the cathode, the cathode sleeve portion and the cathode cap portion can be formed at the same time, so that the production time can be reduced and the production cost can be reduced.

[0010]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Note that the embodiments described below are preferred specific examples of the present invention,
Although various technically preferable limits are given, the scope of the present invention is not limited to these modes unless otherwise specified in the following description.

FIG. 1 is a sectional view showing a preferred embodiment of a cathode ray tube using the cathode of the present invention. The cathode ray tube 10 will be described with reference to FIG. The cathode ray tube (C
The RT tube 10 has a panel glass 11, a funnel glass 12, a phosphor screen 13, an electron gun 17, and the like. The panel glass 11 and the funnel glass 12 are fused with frit glass, and the inside is maintained at a high vacuum. A fluorescent screen 13 is formed on the inner surface of the panel glass 11,
An aperture grill (shadow mask) 14 is provided on the back of the phosphor screen 13. When an electron beam is irradiated from the electron gun 17 described below toward the panel glass 11,
The aperture grill 14 selects an electron beam of each color, and the selected electron beam is applied to the phosphor screen 13 so that the phosphor screen 13 emits light.

An inner carbon 12c is applied to the inner peripheral surface of the cone portion 12a of the funnel glass 12, and an anode button 12b is embedded in the cone portion 12a. The stem 1 is attached to the neck 15 of the funnel glass 12.
6, an electron gun 17 and the like are built in. The stem 16 has a plurality of pins 16 a and is heat-welded to the neck 15. The electron gun 17 is welded to the stem 16 and outputs three electron beams of red, blue and green. A deflection yoke 18 is arranged on the outer peripheral surface of the neck portion 15. The deflection yoke 18 deflects the electron beam output from the electron gun 17 to scan the entire surface of the fluorescent screen 13 with the electron beam.

FIG. 2 is an enlarged sectional view of the electron gun 17, and the electron gun 17 will be described in detail with reference to FIG. The electron gun 17 includes a cathode structure 19, a first G grid G1,
The second G grid G2, the third G grid G3, the fourth G grid G4, and the fifth G grid G5. The cathode structure 19 emits electrons, and the first grid G1
A fifth grid G5 is a cylindrical grid for emitting, controlling, and focusing an output electron beam. The cathode structure 19, the first grid G1, and the second grid G2 are current control electrodes, and voltages of, for example, 50 V, 0 V, and 300 V are applied to the respective electrodes. The third grid G3, the fourth grid G4, and the fifth grid G5 are electrodes for acceleration and focusing, and are approximately 27 kV, 27 kV, and 9 kV, respectively.
Is applied.

FIG. 3 is an enlarged sectional view of the cathode assembly 19, and the cathode assembly 19 will be described in detail with reference to FIG. The cathode structure 19 has a heater rest 20, a supporting metal bar 21, a ceramic disk 22, a cathode sleeve 23, and the like. The heater rest 20 has a plurality of supporting metal rods 2.
One end is embedded, and the other ends of the plurality of support metal rods 21 are fixed to the disk portion 22 by welding or the like.
The heater rest 20 holds and fixes the ceramic disk 22 at a predetermined position and also holds the heater 24. For example, three holes 22 are formed in the ceramic disk 22.
The cathode 23 is inserted into each of the three holes 22a. A heater 24 is inserted into the hollow portion 22a of the cathode 23.

FIG. 4 is an enlarged sectional view of the cathode 23. The cathode 23 will be described in detail with reference to FIG.
The cathode 23 has a cathode sleeve 25, a cathode cap 26,
It consists of an electron emitting section 27. The cathode sleeve portion 25 and the cathode cap portion 26 are formed of the same material such as a nickel alloy, for example, and an electron emission portion 27 is formed on the upper surface of the cathode cap portion 26. The electron emitting portion 27 is made of an alkaline earth metal such as barium, strontium, and calcium.

Next, referring to FIG. 1 to FIG.
The operation of will be described in detail. First, a desired voltage is applied to the stem pin 16a and the anode button 12b to the cathode ray tube 10 of FIG. 1, whereby a desired voltage is applied to each part inside the cathode ray tube 10. When an electric current is applied to the heater 24, the heater 24 heats and the upper portion of the cathode 23 is heated. When the cathode sleeve 25 and the cathode cap 26 of the cathode 23 are heated to a predetermined temperature, thermionic electrons are emitted from the electron emitting portion 27 attached to the upper surface of the cathode 23. On the other hand, a desired voltage is applied to each part inside the cathode ray tube 10 and the deflection yoke 18, and the first grid G
The first to fifth grids G5 emit, control, and focus electrons generated at the cathode 23 to form an electron beam. Then, when the formed electron beam irradiates the fluorescent screen 13 of the panel glass 11, an image is displayed on the outer surface of the panel glass 11.

FIG. 5 is a flow chart of a method for manufacturing the cathode, and the method for manufacturing the cathode 23 will be described in detail with reference to FIG. First, a nickel alloy in which a small amount of a reducing agent such as magnesium or tungsten is mixed with nickel is produced (ST10). The nickel alloy is pressed from above and below to form a desired cathode 23 (ST11). Thereafter, an electron emission portion 27 is formed by spraying an alkaline earth metal carbonate powder made of, for example, barium, strontium, calcium, or the like on the upper surface of the cathode cap portion 26 by spraying or the like (ST12), and the cathode 23 is completed. I do.

Next, the manufacturing process of the electron gun 17 and the cathode ray tube 10 will be described in detail. First, a V-shaped refractory metal wire (not shown) is laser-welded to the cathode sleeve portion 25 of the cathode 23. Thereafter, a V-shaped metal wire is welded to the supporting metal rod 21 embedded in the ceramic disk 22, and the cathode 23 is held by the ceramic disk 22. Further, the heater rest 20 is welded to the supporting metal bar 21, and the heater 24 is inserted into each cathode 23. At this time, the heater 24 and the heater rest 20 are welded, and the heater 24 is held by the heater rest 20. Thereby, the cathode 23 is formed.

On the other hand, the panel glass 11 and the funnel glass 12 are fused with frit glass (not shown), an exhaust pipe is inserted therein, and a vacuum is created by an exhaust furnace. And
A first grid G is provided on the neck 15 of the funnel glass 12.
The first to fifth grids G5 are built in, and the cathode 23 is heated and welded from the outside. At this time, the electron gun 17 is mounted on the panel glass 11.
And functions as a valve for keeping the inside of the funnel glass 12 at a vacuum. The alkaline earth metal carbonate, which is an electron emitting substance of the electron emitting portion 27, is thermally decomposed in a vacuum to form an alkaline earth metal oxide. Thereafter, the exhaust pipe is chipped off from the cathode ray tube 10. Then, an activation process is performed by performing an aging process for accelerating a chemical reaction, and an oxide cathode structure is formed, whereby the cathode ray tube 10 is completed.

According to the above embodiment, since the cathode sleeve portion 25 and the cathode cap portion 26 are integrally formed, the cathode manufacturing process is greatly reduced, and the cathode is manufactured in a short time and at low cost. be able to. Also,
In the conventional cathode 1, since the cathode cap 3 and the cathode sleeve 2 are fixed by welding at several points, the heat efficiency of the heat of the cathode sleeve 2, which is heated to the maximum by the heater, is low.
In the above embodiment, since the cathode cap portion 25 and the cathode sleeve portion 26 are integrally formed, the thermal efficiency is improved, and the heater power applied to the cathode can be reduced.

The embodiment of the present invention is not limited to the above embodiment. For example, although the electron gun 17 has been described as applied to a color cathode ray tube, the electron gun 17 can be applied to a cathode ray tube having an oxide cathode other than the color cathode ray tube.

[0022]

As described above, according to the present invention,
A cathode having good thermal conductivity and reduced cost and a cathode ray tube using the same can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a preferred embodiment of a cathode ray tube using a cathode sleeve of the present invention.

FIG. 2 is a sectional view showing an electron gun in which the cathode sleeve of the present invention is incorporated.

FIG. 3 is a sectional view showing a cathode portion of the electron gun of the present invention.

FIG. 4 is an enlarged sectional view showing a preferred embodiment of the cathode sleeve of the present invention.

FIG. 5 is a flowchart showing a method for manufacturing a cathode sleeve of the present invention.

FIG. 6 is an enlarged sectional view showing a conventional cathode sleeve.

FIG. 7 is a flowchart showing a conventional method for manufacturing a cathode sleeve.

[Explanation of symbols]

Reference numeral 10: cathode ray tube; 23, cathode; 25, cathode sleeve portion; 26, cathode cap portion; 27, electron emission portion.

Claims (3)

[Claims] 1. A cathode, which is attached to a neck of a cathode ray tube and emits electrons when heated by a heater, is formed in a tubular shape, and has a cathode sleeve portion in which a heater is inserted into a hollow portion; A cathode cap portion integrally formed on the end surface of the sleeve portion with the same material as the cathode sleeve portion and having an electron emission portion for emitting electrons when heated by a heater attached thereto; Characteristic cathode. 2. The cathode according to claim 1, wherein the cathode sleeve and the cathode cap are integrally formed by pressing a nickel alloy. 3. A cathode ray tube having a cathode attached to a neck portion of a cathode ray tube and emitting electrons when heated by a heater, wherein the cathode is formed in a tubular shape and the heater is inserted into a hollow portion. A sleeve portion and a cathode cap portion formed integrally with the same material as the cathode sleeve portion on the bottom portion of the cathode sleeve portion and having an electron emission portion that emits electrons when heated by a heater attached thereto. A cathode ray tube using a cathode, comprising: a cathode;