KR910007795B1 - Dispenser cathode and the method of making the same - Google Patents

Abstract

The pellet of the dispenser electrode operating under low temp. is sintered and coated with W and SC2O3. The pellet is mixed by W, Mo, and barium calcium aluminate, and In2O3 with proper mixing ratio. The weight ratio between the In2O3 and the rest material is pref. 1:10 or 1:2. The weight ratio between the W and the Sc2O3 is pref. 100:1 or 25:4.

Description

Dispenser cathode for color cathode ray tube and manufacturing method

1 to 3 are cross-sectional views of conventional storage cathodes, sintered cathodes, and impregnated cathodes.

4 and 5 are cross-sectional views of the negative electrode according to the present invention.

* Explanation of symbols for main parts of the drawings

1P, 2P, 3P, 4P, 5P, 6P: Pellets 1C, 2C, 3C, 4C: Coating Layer

HTR: Heater CNT: Container

SLV: Sleeve

The present invention relates to a dispenser cathode for a color cathode ray tube capable of low temperature operation and a method of manufacturing the same.

The dispenser cathode is a cathode capable of high current density, and is used in an electron gun such as a large cathode ray tube or a projection tube. It is classified into three types.

1 shows a storage cathode, which is a first pellet 1P made of tungsten (W), molybdenum (Mo), barium calcium aluminate, and a porous second pellet formed of tungsten (2P). It has an electron emitting part composed of).

2 shows a sintered cathode. The sintered cathode is a mixed-formed sintered mixture of barium scandate and tungsten powder, or a solid pressed cathode molded and sintered of barium calcium aluminate and powders such as tungsten and molybdenum (3P). It has an electron emitting portion consisting of.

3 shows an impregnated cathode having a high electron emission capability, in which a tungsten porous pellet (4P) is impregnated with an electron emitting material such as barium calcium aluminate, and tungsten and scandium oxide (Sc ₂ O ₃ ) The mixed coating layer (IC) is formed to form an electron emitting part.

Such dispenser type cathodes have excellent electron emission capability and are used for high power transmission tubes such as microwave tubes and microwave tubes such as large cathode ray tubes or imaging tubes.

However, since these cathodes are operated at high temperatures (about 1000 to 1200 ° C.), the evaporation rate of barium or barium oxide is high during cathode operation, and the evaporated barium is attached to other electrodes, which adversely affects the characteristics of the tube. The reduced life expectancy is a problem. In addition, in the manufacturing method of the negative electrode, the impregnated negative electrode undergoes a complicated process such as an impregnation process or a processing process, and the storage negative electrode does not undergo an impregnation process, but must undergo a complicated process of making a plurality of pellets.

SUMMARY OF THE INVENTION An object of the present invention is to provide a dispenser cathode for a color cathode ray tube that can be operated at low temperatures and can improve the above-mentioned problems.

Still another object of the present invention is to provide a method for producing a dispenser cathode for a color cathode ray tube.

In the present invention to achieve the above object, in the dispenser cathode for a color cathode ray tube comprising a pellet containing an electron-emitting material, a container for storing the same and a heater built in the sleeve to heat the pellet, the configuration of the pellet A color cathode ray formed by incorporating indium oxide (In ₂ O ₃ ) in an appropriate ratio into tungsten, molybdenum and barium calcium aluminate as a material, and forming a sintered solid on the surface thereof, and forming a coating layer of scandium oxide and tungsten on the surface thereof. Provide a conventional dispenser cathode.

In order to achieve another object of the present invention, in the present invention, barium calcium aluminate and indium oxide are mixed, heated, melted, cooled and pulverized, and tungsten-molybdenum alloy powder is mixed at an appropriate ratio to form a pellet. Heat-treating at a temperature of 1800 to 1900 ° C. under a vacuum or hydrogen atmosphere after molding into a mold; Provided is a method for producing a dispenser cathode for a color cathode tube comprising the step of forming a coating layer consisting of a scandium oxide and tungsten mixture on the upper surface of the pellet sintered.

The pellets are composed of tungsten, molybdenum and barium calcium aluminate, and the mixing ratio of the pellets to indium oxide is preferably in a weight ratio of 10: 1 to 2: 1.

In addition, the mixing ratio of tungsten and scandium oxide forming the coating layer is 100: 1 to 25: 4 by weight, and the coating layer is formed in multiple layers on the upper surface of the pellet, wherein the first layer is scandium oxide and the second layer is tungsten. It is preferable to make.

Looking at the electron generation process according to the present invention. When pellets (5P, 6P) containing barium calcium aluminate, indium oxide, tungsten and molybdenum forming pellets are heated by a heater (HTR), free barium from barium calcium aluminate is reduced by tungsten and molybdenum reduction. (Ba) is produced, and the production of free barium is further promoted by the activation action of indium oxide, tungsten and molybdenum. When barium reaches the surfaces of the coating layers 2C and 4C, a single molecule layer made of Ba-Sc-O and a single molecule layer made of Ba-In-O are formed together with the scandium of the coating layer. Therefore, the work function is lowered by the dipole moment generated by the monolayer. This allows electrons to be actively generated even at low operating temperatures. That is, high current density of the cathode becomes possible.

Hereinafter, specific embodiments of the present invention will be described in detail.

Example 1

BaCO ₃ , CaCO ₃ and Al ₂ O ₃ are mixed in a molar ratio of 5: 3: 2 to heat and melt the mixture. The melted material is cooled and then ground into powder. A tungsten-molybdenum alloy powder mixed at a weight ratio of 25:75 is prepared, and then mixed with the barium calcium aluminate at a weight ratio of 9: 1. Indium oxide (In ₂ O ₃ ) is additionally mixed by 30% by weight of the mixture and then pressurized (about 11 ton / cm 2) to mold. It is then heat treated to a temperature of 1800-1900 ° C. under vacuum. Tungsten powder having a particle size of about 5 μm and scandium oxide having a particle size of about 3 μm are mixed at a weight ratio of 10: 1 and coated on the upper portion of the pellet with a thickness of about 5000 mm using a sputtering method.

Example 2

The cathode was obtained in the same manner as in Example 1 except that tungsten and scandium oxide were laminated in order to obtain a coating layer as a separate layer.

4 and 5, the dispenser cathode according to the present invention is shown, and the container CTN containing the electron-emitting material is inserted into and fixed in the tip opening of the sleeve SLV in which the heater HTR is incorporated. The container CTN contains an electron-emitting material composed of pellets in which barium calcium aluminate, indium oxide, tungsten and molybdenum are mixed, molded and sintered at an appropriate ratio.

The negative electrode shown in FIG. 4 is a dispenser negative electrode prepared according to Example 1, wherein a mixed coating layer of tungsten and scandium oxide is formed on the upper surface of the pellet, and the negative electrode shown in FIG. 5 is prepared according to Example 2 As the dispenser cathode, the first coating layer 3C made of tungsten and the second coating layer 4C made of scandium oxide are formed on the pellet.

That is, the dispenser negative electrode of the present invention prepared according to the above embodiment is formed by incorporating indium oxide in the negative electrode constituent material of the conventional sintered negative electrode, forming and sintering it into a solid, and forming a coating layer introduced from the conventional impregnated negative electrode thereon. will be.

Indium oxide is a volatile material around 850 ° C. It reduces the temperature at which the barium calcium aluminate and tungsten react to produce free Ba / BaO, which is contributing to electron emission, during the activation process of the cathode. At the same time, In ₂ O ₃ itself is a highly reactive substance at high temperature, and thus acts as an activation accelerator to shorten the activation time. Therefore, the dispenser cathode according to the present invention has an activation temperature lowered by about 100 to 200 ° C. and the activation time is also significantly shortened by 30 to 50 minutes (conventionally, it takes more than 4 hours).

The cathode of the present invention can be operated at a temperature (800 ° C.) lower than the operating temperature (850 to 900 ° C.) of the impregnated cathode having a coating layer, and high current density (5 to 10 A / cm 2) can be achieved as a low temperature operating temperature. Done. Therefore, it is possible to employ the electron gun which used the conventional oxide cathode without changing parts, which has the advantage of greatly reducing the manufacturing cost of the high performance electron gun. In addition, according to the method of manufacturing the dispenser negative electrode according to the present invention, it is possible to obtain a negative electrode having better quality than the conventional three types of dispenser negative electrode without requiring a complicated process such as an impregnation process introduced during the preparation of the impregnated negative electrode.

Claims (6)

A dispenser cathode for a color cathode ray tube, comprising a pellet containing an electron-emitting material, a container for storing the same, and a heater built into the sleeve to heat the pellet, wherein tungsten, molybdenum, and barium calcium aluminium are constituents of the pellet. A dispensing cathode for a color cathode ray tube, characterized in that an indium oxide (In ₂ O ₃ ) is included in an nate to form a solid sintered solid, and a coating layer of scandium oxide and tungsten is formed on the surface thereof. The dispenser negative electrode of a color cathode ray tube according to claim 1, wherein a mixing ratio of the constituent material of the pellet and the indium oxide is in a weight ratio of 10: 1 to 2: 1. The dispenser cathode for a color cathode ray tube according to claim 1, wherein the coating layer is made of a mixture of scandium oxide and tungsten. The dispenser negative electrode of a color cathode ray tube according to claim 3, wherein a mixing ratio of tungsten and scandium oxide forming the coating layer is 100: 1 to 25: 4 by weight. 2. The dispenser cathode of claim 1, wherein the coating layer is formed in multiple layers on the upper surface of the pellet, the first layer is made of tungsten, and the second layer is made of scandium oxide. Mixing barium calcium aluminate and indium oxide, heating and melting the same, and cooling and pulverizing them; Mixing tungsten-molybdenum alloy powder at an appropriate ratio to form pellets of a predetermined shape and then heat-treating them at a temperature of 1800 to 1900 ° C. under vacuum or hydrogen atmosphere; A method of manufacturing a dispenser cathode for a color cathode tube comprising the step of forming a coating layer comprising a mixture of scandium oxide and tungsten on the upper surface of the pellet sintered.

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