JP2002197976A - Manufacturing method for cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a cathode-ray tube having a long period of service and capable of maintaining good performance of electron emission. SOLUTION: A pyrolytic treatment process is provided in the evacuating process, in which the cathode is heated so that the water and vapor adsorbed in composite carbonates of the cathode are released. For example, a three min. heating is conducted at the temperature set to 550 deg.C. This is followed by a one and half minute heating at the first set temperature where pyrolysis of composite carbonates is generated, for example at 710 deg.C within the range 660-760 deg.C, and pyrolysis of the composite carbonates in the cathode is conducted. This is followed by a two min. heating at a second set temperature higher than the first where turning into solid solution takes place, for example at 980 deg.C within the range 930-1030 deg.C, which will actuate pyrolysis of the carbonate remaining undecomposed and turning of oxides into solid solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a cathode ray tube. Specifically, in a process of manufacturing a cathode ray tube having an oxide cathode, a pyrolysis treatment step of heating a composite carbonate in exhaust gas to convert it into an oxide is provided.

[0002]

2. Description of the Related Art In a manufacturing process of a cathode ray tube conventionally used in a television device or the like, a bulb having required internal members disposed at predetermined positions in the tube is formed, and an electron gun is sealed in the bulb. Thereafter, an exhaust device is connected to exhaust the air in the valve. In addition, the valve is heated during the exhaust, and the unnecessary gas adsorbed and stored in the valve is exhausted. Thereafter, when the exhaust is completed, the valve is sealed by heating and melting the exhaust pipe.

With respect to the cathode ray tube constructed as described above, a getter flash step and a baking step are performed so that the inside of the bulb can be maintained at a high vacuum for a long time and good electron emission from the cathode can be maintained. , An aging process, a knocking process, and the like.

In the getter flash step, the getter material is scattered into the bulb to form a getter film on the inner wall of the bulb. By forming a getter film in this way,
The gas is adsorbed by the getter film. Further, gas generated by irradiating the phosphor screen with an electron beam is also adsorbed by the getter film.

[0005] In the baking step, a high-frequency coil is provided in the grid electrode portion and the electron gun is heated by high-frequency induction to discharge gas from the electron gun, and the released gas is absorbed by the getter film.

In the baking step, the cathode is also thermally decomposed, and the gas released by this pyrolysis is also adsorbed by the getter film. Here, as the cathode, a composite carbonate of an alkaline earth metal, for example, a mixture of (Ba, Sr, Ca) CO ₃ and a binder is used. When the alkaline earth metal composite carbonate is heated, it is decomposed into an alkaline earth metal oxide and releases a gas, and the released gas is adsorbed by the getter film. For example, as shown in the reaction formula (1), BaCO ₃ is decomposed into BaO and C
O ₂ is released and this CO ₂ is adsorbed on the getter film. BaCO ₃ → BaO + CO ₂ (1)

In the aging step, the cathode is heated by the heater of the cathode ray tube. At this time, part of the oxide of the alkaline earth metal is reduced to the metal by heating to stabilize the electron emission characteristics, and the oxide of the cathode is turned into a solid solution. For example, as shown in the reaction formula (2), BaO becomes Ba ²⁺
At the same time, electrons are generated and the electron emission characteristics are stabilized. ^{BaO → Ba 2+ + 2e - ···} (2)

In the knocking step, the electrode surface is cleaned by applying a high voltage to the electron gun to generate a spark. Further, after the knocking step, a raster aging step of causing the cathode ray tube to emit light and performing aging is provided.

[0009]

By the way, in the baking step, each grid electrode of the electron gun is heated to release gas, and when the alkaline earth metal composite carbonate applied to the cathode is thermally decomposed, If moisture remains in the alkaline earth metal composite carbonate, the oxide generated by thermal decomposition reacts with the water vapor released from the composite carbonate,
Local melting (sintering) occurs on the cathode. When such local melting occurs, the life of the cathode is shortened, and the cathode cannot be used for a long time. Therefore, the present invention provides a cathode ray tube manufacturing method for manufacturing a cathode ray tube capable of withstanding long-term use and maintaining good electron emission.

[0010]

According to a method of manufacturing a cathode ray tube according to the present invention, in a process of manufacturing a cathode ray tube having an oxide cathode, a cathode is heated during exhaust to change a composite carbonate of the cathode into an oxide. This is provided with a thermal decomposition process.

In the present invention, the first set temperature, for example, from 660.degree. C. to 760.degree. C. after the cathode is heated during the exhaust to release the moisture adsorbed on the composite carbonate of the cathode.
Heating is performed in the range of ° C. to perform thermal decomposition of the composite carbonate of the cathode. Thereafter, heating is performed at a second set temperature higher than the first set temperature, for example, in a range of 930 ° C. to 1030 ° C., and thermal decomposition of undecomposed carbonate and solid solution formation of oxide are performed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration diagram of a cathode ray tube. On the inner surface of panel 11, red,
A phosphor screen 12 made of a three-color phosphor layer that emits green and blue light is formed, and a metal back (not shown), which is a deposited film of aluminum, is formed on the phosphor screen 12. . Phosphor screen 12
An aperture grill or a shadow mask is mounted as a color selection mechanism 14 on the panel 11 on which the metal back is formed. Further, after the inner magnetic shield 15 is attached, a funnel 16 having a funnel shape is welded to the panel 11 to form a valve. After the electron gun 20 is inserted into the neck 17 of the bulb, the stem 28 and the neck 17 of the electron gun 20 are welded to seal the electron gun. Note that a conductive film 18 that is electrically connected to the metal back is formed inside the funnel 16.

FIG. 2 shows the configuration of the electron gun 20.
The electron gun 20 includes a cathode 21, a heater (not shown) for heating the cathode 21, and a fluorescent screen 12 from the cathode 21.
The first to fifth grid electrodes are sequentially arranged at predetermined intervals in the direction and fixed by bar-shaped beading glass 23. The cathode 21 is connected to the first grid electrode 2.
A cathode base 21a made of a composite carbonate of an alkaline earth metal made of Ba, Sr, and Ca is formed on the side facing the surface 4. An exhaust pipe 29 is formed in the stem 28.

Next, a method of manufacturing a cathode ray tube will be described with reference to FIG. 3 from the exhaust process to the raster aging process. In the evacuation step, the valve is heated during the evacuation, the unnecessary gas adsorbed and occluded in the valve is exhausted, and a thermal decomposition process for converting the composite carbonate of the cathode 21 into an oxide is also performed.

FIG. 4 shows heating conditions in the thermal decomposition process performed during exhaust. In the thermal decomposition process shown in FIG. 4, a moisture release process is performed in which the cathode 21 is heated at a temperature lower than the temperature at which thermal decomposition occurs for a predetermined time to release moisture adsorbed on the composite carbonate of the cathode 21. Includes methods. In this moisture release process, for example, the temperature of the cathode 21 is set to 5
It is desirable to reliably release moisture by heating at 50 ° C. for 3 minutes or more.

In the thermal decomposition treatment, the cathode 21 is heated so that the temperature of the cathode 21 becomes a first set temperature higher than the decomposition temperature of the composite carbonate to decompose the composite carbonate into an oxide. Here, for example, when the decomposition temperature of the composite carbonate is about 600 ° C., the lower limit of the first set temperature is set to 660 ° C. in consideration of an error in temperature measurement, a variation in heating temperature, and the like.
The upper limit of the first set temperature is a temperature at which the life of the cathode 21 is not shortened, for example, 760 ° C., and the cathode 21 is heated within this temperature range. The heating time is the time required for the complex carbonate to be decomposed into oxide. For example, the heating time is set in a range from 10 seconds to 3 minutes. Note that, in the case shown in FIG.
By heating for a minute, the complex carbonate is decomposed into oxide.

When the thermal decomposition process at the first set temperature is completed, the cathode 21 is heated so that the temperature of the cathode 21 becomes the second set temperature higher than the first set temperature. The composite carbonate remaining without being decomposed by the heat treatment is decomposed into an oxide. In addition, the generated oxide is
The solid solution is also formed by heating at the preset temperature. Here, for example, when the temperature at which solid solution is formed is about 880 ° C., the lower limit of the second set temperature is set to a lower limit of the first set temperature in consideration of an error in temperature measurement, a variation in heating temperature, and the like. Set to about 930 ° C. The upper limit of the second set temperature is set to a temperature at which the amount of barium emitted from the cathode 21 does not increase and does not adhere to the facing electrode or the like, for example, about 1030 ° C. By setting the upper limit of the second set temperature to a temperature at which barium does not adhere to the other electrode, barium adheres to the other electrode and electrons are emitted from the barium. Can be prevented. Further, the heating time is set to a time at which solid solution formation occurs. For example, the heating time is set in a range from 10 seconds to 5 minutes. In FIG. 4, the temperature of the cathode 21 is set to 980 ° C. and heating is performed for 2 minutes.

In the above-mentioned decomposition of the composite carbonate, CO ₂ is released by the reaction of the reaction formula (1).
The degree of vacuum is monitored during the heat treatment at the first set temperature, and only the time until the reaction of reaction formula (1) is completed and CO ₂ is not released and a sufficient degree of vacuum is obtained is obtained. It may be heated. Similarly, in the moisture release treatment, the degree of vacuum may be monitored during the heat treatment, and heating may be performed only for a period of time until the release of moisture is completed and a sufficient degree of vacuum is obtained. Thus, after performing the thermal decomposition process in the exhaust gas, the exhaust pipe 29
Is heated and melted to seal the valve.

Thereafter, in the getter flash step shown in FIG. 3, for example, getter materials (Ni and BaAl ₄ ) previously mounted on the color selection mechanism 14 are scattered into the bulb to form a getter film on the inner wall of the bulb. I do. Further, in the baking step, a high-frequency coil is provided in the grid electrode portion to perform high-frequency induction heating of the electron gun, thereby discharging gas from the grid electrode, and adsorbing the released gas by the getter film.

In the aging step, the cathode is heated by the heater of the cathode ray tube to stabilize the electron emission characteristics. In the knocking step, a high voltage is applied to the electrodes of the electron gun to generate sparks, so that the electron gun is activated. Fine projections generated on the surface of each of the constituent electrodes, burrs generated by press molding, and the like are removed. In the raster aging process,
Aging is performed by emitting light from the cathode ray tube.

As described above, since the thermal decomposition process is provided in the exhaust gas, even if water is adsorbed on the composite carbonate, the water is discharged as steam during the thermal decomposition process. In later baking and aging processes,
Generation of sinter due to the reaction between the oxide and water vapor can be prevented. In addition, since the water adsorbed by the composite carbonate is released before the thermal decomposition is started, the generation of water vapor during the thermal decomposition is reduced, and the thermal decomposition of the composite carbonate is performed. Processing can be performed stably without being affected by water vapor.

For this reason, if the life of the cathode ray tube is defined as the time when the beam current is reduced by half, the conventional manufacturing method shown by the broken line B in FIG. As shown by the solid line A, the life could be extended about 1.5 times as compared with the cathode ray tube manufactured in the above. In addition, since a stable oxide cathode can be produced, variations in the characteristics of the cathode can be reduced, and the repair rate, that is, the rate of re-input to the aging step or the like to obtain desired characteristics can be reduced.

[0023]

According to the present invention, the exhaust gas is provided with a pyrolysis treatment step of heating the composite carbonate at the cathode to convert it to an oxide, so that the water adsorbed on the composite carbonate is reduced. Even if it is generated as steam during the thermal decomposition process, since the steam is discharged, it is possible to prevent the generation of sinter due to the reaction between the oxide and the steam in the baking step or the aging step after the exhaust treatment. In addition, in the thermal decomposition process, since the water release process is performed before the start of the thermal decomposition, the generation of water vapor during the thermal decomposition process is assumed to be small. It can be performed stably without being affected.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of a cathode ray tube.

FIG. 2 is a view showing an electron gun.

FIG. 3 is a view showing a part of a manufacturing process of a cathode ray tube.

FIG. 4 is a diagram showing heating conditions in a thermal decomposition process.

FIG. 5 is a diagram showing a relationship between a relative time and a relative current amount.

[Explanation of symbols]

11 panel, 12 phosphor screen, 14
... Color selection mechanism, 15 ... Internal magnetic shield, 16.
..Funnel, 17 ... neck, 20 ... electron gun, 21 ... cathode, 21a ... cathode base, 22 ...
・ Heater, 23 ・ ・ ・ Beading glass, 24 ・ ・ ・ First grid electrode, 28 ・ ・ ・ Stem, 29 ・ ・ ・ Exhaust pipe

Claims (4)

[Claims] 1. A method for manufacturing a cathode ray tube having an oxide cathode, comprising a step of heating a cathode during exhaustion to convert a composite carbonate of the cathode into an oxide. Tube manufacturing method. 2. In the thermal decomposition treatment step, after heating at a first set temperature higher than the thermal decomposition temperature set based on the thermal decomposition temperature of the composite carbonate, the first solution causing solid solution formation 2. The method according to claim 1, wherein the heating is performed at a second set temperature higher than the set temperature. 3. The first set temperature is 660 ° C. to 76 ° C.
0 ° C. and the second set temperature is 930
3. The method for manufacturing a cathode ray tube according to claim 2, wherein the temperature is in a range of from 10 ° C. to 1030 ° C. 4. The method for manufacturing a cathode ray tube according to claim 1, wherein a water release process for releasing water of the composite carbonate during the exhaust is performed at the first set temperature before heating.