JPH08138537A - Manufacture of cathode-ray tube - Google Patents

Abstract

PURPOSE: To restrain generation of grid emission by preventing heating of a grid electrode with a whole coating film formed thereon at a temperature higher than a specified value before heating an emission source of a low work function substance such as a cathode and getter. CONSTITUTION: A second grid electrode 12 is composed of an Ni-Fe alloy and heated for degassing. A high voltage is applied only to a third grid electrode 13 side to form a whole coating film. Grid electrodes 11-16 and an oxide cathode 1 are combined with each other to assemble an electron gun, which is fused with a panel 3 with a built-in fluorescent screen 4, a shadow mask 5 and the like, and a funnel part, thus forming a cathode-ray tube. In this case, a getter 6 is attached inside the tube. Then, while the cathode-ray tube whole body is being heated at 350 deg.C, vacuum evacuation is conducted. At the time point of reaching a pressure of about several mPa, the cathode 1 is heated at about 10000 deg.C for activation. After a vacuum degree is recovered, chipping-off of an exhaust pipe is conducted, the getter 6 is heated to vaporize Ba so as to adsorb residual gas.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for manufacturing a cathode ray tube.

[0002]

2. Description of the Related Art In a cathode ray tube to which a high voltage is applied, useless electron emission called grid emission from the surface of the grid electrode, which should not originally generate electron emission, may occur due to the high electric field accompanying the high voltage. . This grid emission becomes more frequent after the cathode is heated to 550 ° C. or higher, for example. This occurs because the substance used for lowering the work function of the cathode surface evaporates and adheres to the grid electrode surface. The same substance is used for the getter used to improve the degree of vacuum in the tube in addition to the cathode, and grid emission occurs even after the getter is heated.

A conventional technique for suppressing this grid emission is described in, for example, Japanese Patent Laid-Open No. 184240/1988. In this conventional technique, a gold coating film is formed on the surface of a grid electrode used for a vacuum tube. This effect is
This is because the gold coating film diffuses the barium adhering to the surface inside and alloys it to reduce the amount of barium present on the surface of the grid electrode. Therefore, the effect of barium evaporated from the heated cathode and adhering to the surface of the grid electrode to lower the work function of the surface of the grid electrode can be suppressed, and generation of unnecessary electron emission from the grid electrode can be suppressed.

Further, in the conventional method for manufacturing a cathode ray tube, for example, it is described in "Practical Vacuum Technology Guide", Practical Vacuum Technology Guide, Editorial Committee, Industrial Technology Service Center, Ltd., issued on November 26, 1990, page 521. In order to obtain a high degree of vacuum, the electron gun electrode should be 700 ℃
It was being heated to a degree.

[0005]

In the above-mentioned prior art, the heat treatment process of the grid electrode having the gold coating film formed thereon is not limited at all, and as shown in the conventional example of the method for manufacturing a cathode ray tube, In addition, a high temperature heat treatment was previously performed for the purpose of degassing. However, the gold coating film formed on the grid electrode surface by a method such as vacuum deposition or plating is 550
After being heated to a high temperature of ℃ or higher, the effect of diffusing barium inside the gold coating film decreases. The prior art did not consider any measures in this regard.

The object of the present invention is to more effectively utilize the ability of the gold coating film formed so as to suppress unnecessary electron emission from the grid electrode, and to obtain a higher performance cathode ray tube. It is to provide a manufacturing method of.

[0007]

In order to achieve the object, the present invention provides a method for treating an electrode having a gold coating film formed thereon, after the gold coating film is formed and before the low work function substance is deposited. Is 5
Do not heat above 50 ° C.

[0008]

The cathode ray tube has a structure as shown in FIG. 1, for example, and the electron beam 2 focused and accelerated by an electron gun composed of a plurality of grid electrodes 11 to 16 and the cathode 1 and the like is provided on the inner surface of the panel 3. An image is displayed by irradiating the fluorescent film 4 formed in step 1 through a shadow mask 5. For this purpose, in the vicinity of the second grid electrode 12 and the third grid electrode 13 in the electron gun, a strong electric field reaching several tens kV / mm is applied to the electrode surface. Due to this strong electric field, unnecessary electron emission called grid emission may occur particularly from the surface of the second grid electrode 12. Further, although a weaker electric field is applied to the surface of the first grid electrode 11 as compared with the second grid electrode 12, grid emission may occur due to heating by the radiation heat from the cathode 1.

These grid emissions are likely to occur after heating the cathode 1 and the getter 6 used to obtain a high vacuum. This is because when the cathode 1 and the getter 6 are heated, the low work function substance such as barium contained in them is attached to the grid electrode. Especially cathode 1
With regard to (1), a large amount of the low work function substance evaporates during the activation treatment performed after the inside of the cathode ray tube is evacuated, and a small amount evaporates during normal operation. Further, the getter 6 also evaporates the low work function substance due to heating during manufacturing, and is no longer heated during normal operation. Therefore, in order to suppress the generation of grid emission, it is important to deal with the low work function substance attached to the surface of the grid electrode during the activation treatment of the cathode 1.

Further, it was found by electron microscope observation that the gold coating film formed on the grid electrode as shown in FIG. 2 was recrystallized by heating at 550 ° C. or higher. Furthermore, as a result of measuring the work function change when barium, which is generally used in cathode ray tubes as a low work function substance on the surface of the gold coating film, was measured, it was confirmed that barium was attached to the unrecrystallized gold coating film. The work function decreases by only about 1 eV, whereas when barium is attached to the surface of the gold coating film that has been recrystallized by heating at 700 ° C., for example, about 2 eV.
It turned out that it also falls.

That is, when barium is attached to the surface of the recrystallized gold coating film, the work function tends to be lower than that of the non-recrystallized gold coating film, and grid emission is likely to occur. . Therefore, as in the present invention, before the low work function substance is attached to the gold-coated grid electrode, when the low work function substance is attached by preventing the grid electrode from being heated to 550 ° C. or higher. It is possible to suppress a decrease in work function on the surface of the grid electrode. As a result, it is possible to suppress the occurrence of grid emission due to the low work function substance adhering to the surface of the grid electrode on which the gold coating film is formed. Since the grid emission occurs in the cathode ray tube in the area where a high electric field is applied in the vicinity of the grid hole, even when the gold coating film is formed only in this area, the gold coating film is formed on the entire surface of the grid electrode. The same effect as in the case can be obtained, and it is not necessary to form the gold coating film on the entire surface of the grid electrode.

Further, after barium is attached to the grid electrode on which the gold coating film is formed by heating the getter 6 or activating the cathode 1, the electrode is heated to 600 ° C. or higher to remove the barium attached to the surface from the gold. It can be diffused in the coating film, and a higher grid emission suppressing effect can be obtained. After this heating, the effect of suppressing grid emission due to the diffusion of barium into the gold coating film is reduced, but the getter 6 is no longer heated, and the cathode 1 during normal operation is compared with that during activation treatment. It is unlikely that new grid emissions will occur because only a small amount of barium evaporates.

[0013]

EXAMPLE An example of a manufacturing method according to the present invention of a cathode ray tube in which a gold coating film is formed on the second grid electrode 12 where a high electric field is easily applied to cause grid emission is shown below. In this example, the cathode ray tube for color display shown in FIG. 1 was produced according to the method for producing a cathode ray tube according to the present invention shown in FIG. Similarly, a cathode ray tube having the same structure manufactured by the conventional manufacturing method shown in FIG. 3 was manufactured and compared with that according to the present invention.

Second grid electrode 12 used in this embodiment
Is a cathode ray tube for color display using 42 wt% Ni-Fe alloy as a base material. Ni with a thickness of 0.4 mm
A —Fe thin plate was punched and pressed into a predetermined shape as shown in FIG. 2, and after degreasing and cleaning, heat treatment was performed at 700 ° C. for 10 minutes for the purpose of degassing. As the gold coating film, a coating film having a thickness of 5 μm was formed inside the grid holes and on the side of the third grid electrode 13 by a vacuum deposition method. Of the surface of the second grid electrode 12, the third grid electrode 13
Since the high electric field is applied only to the side, the first grid electrode 1
No gold coating film was formed on the surface on the 1st side.

Second grid electrode 12 having a gold coating film formed thereon
Is assembled with other grid electrodes 11, 13 to 16 and the oxide cathode 1 to assemble an electron gun, and the electron gun is welded to the panel 3 incorporating the fluorescent film 4, the shadow mask 5 and the like and the funnel portion to form a cathode ray tube. did. At this time, a getter 6 in which nickel powder was mixed with barium-aluminum alloy was mounted inside.

Thereafter, the entire cathode ray tube was heated to about 350 ° C. and evacuated by an oil diffusion pump. When the pressure reaches about several mPa, the cathode 1 is set to about 1000
By heating to ℃, barium carbonate was decomposed into carbon dioxide and metallic barium to form a low work function surface. During this thermal decomposition, carbon dioxide gas was released to deteriorate the degree of vacuum, and part of barium was evaporated and adhered to the surface of each grid electrode. After the degree of vacuum is restored, chip off the exhaust pipe,
Further, the getter 6 was heated to evaporate barium, form a barium film on the inner wall of the cathode ray tube, and adsorb the residual gas in the tube. Even when the getter was heated, part of barium as a getter agent adhered to the surface of each grid electrode.

After the getter agent was evaporated, the withstand voltage of this cathode ray tube was evaluated in a state where the degree of vacuum was stable.
This measurement is performed on the second grid electrode 12 and the third grid electrode 1.
The voltage applied when the bright spot due to the emission generated from the second grid electrode 12 is generated on the phosphor screen is gradually increased, that is, the grid emission generation voltage is measured.

According to this measurement, the voltage applied to these grid electrodes during normal operation of the cathode ray tube of this embodiment was 18 k.
While the voltage was V, the grid emission generation voltage was also 18 kV.

For comparison, a second grid electrode 12 is used which has been heat-treated at 700 ° C. for 30 seconds in the same manner as the electrode firing shown below while exhausting with an oil diffusion pump according to the conventional cathode ray tube manufacturing method. When the cathode ray tube produced as described above was measured in the same manner, generation of grid emission was confirmed at 17 kV. At this point, it cannot be said that the cathode ray tube manufactured according to the manufacturing method of the present invention has a higher withstand voltage, although it cannot be said that it has a sufficient withstand voltage against the applied voltage during operation.

Further, a high frequency coil was installed near the second grid electrodes 12 of both cathode ray tubes, and the electrodes were baked by high frequency induction heating at about 600 ° C. for 30 seconds. In the cathode ray tube using the second grid electrode 12 for comparison, even if the electrode firing was performed, the grid emission generation voltage was improved to only 18 kV, whereas heating at 550 ° C. or higher was not performed in advance according to the present invention. Second
In the cathode ray tube using the grid electrode 12, the grid emission generation voltage was improved to 22 kV or more, and sufficient withstand voltage characteristics against the applied voltage during normal operation could be obtained.

[0021]

According to the present invention, before heating the emission source of the low work function substance such as the cathode or getter, the grid electrode on which the gold coating film is formed is prevented from being heated to 550 ° C. or more, so that the grid emission is achieved. It becomes possible to suppress the occurrence. As a result, a higher voltage can be applied to the grid electrode, so that a high-performance cathode ray tube with high definition and high brightness can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view of a cathode ray tube.

FIG. 2 is an explanatory diagram of a shape of a second grid electrode.

FIG. 3 is an explanatory diagram for comparison with a conventional example of a method for manufacturing a cathode ray tube according to the present invention.

[Explanation of symbols]

1 ... Cathode, 2 ... Electron beam, 3 ... Panel, 4 ... Fluorescent film, 5 ...
Shadow mask, 6 ... Getter, 11 ... 1st grid electrode, 12 ... 2nd grid electrode, 13 ... 3rd grid electrode, 14 ... 4th grid electrode, 15 ... 5th grid electrode, 16 ... 6th grid electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Narisei 1-280, Higashi Koikeku, Kokubunji, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (72) Hayato Amano 1-280, Higashi Koikeku, Kokubunji, Tokyo Hitachi Ltd. (72) Inventor Toshiaki Kusunoki 1-280, Higashi Koikekubo, Kokubunji, Tokyo, Hitachi, Ltd. Central Research Lab. (72) Inventor, Emiko Yamada 1-280, Higashi Koikeku, Kokubunji, Tokyo Hitachi, Ltd. Central Research Lab.

Claims (2)

[Claims] 1. An electrode having a portion containing a low work function substance, to which the low work function substance released from the portion may adhere, and having an electrode having a gold coating film formed on at least a part of the surface thereof. In the method of manufacturing a cathode ray tube, the method of manufacturing a cathode ray tube in which the electrode is not heated to 550 ° C. or higher after the gold coating film is formed and before the low work function substance is attached to the surface of the gold coating film. 2. The method of manufacturing a cathode ray tube according to claim 1, wherein barium is contained in the low work function substance.