JPS6237501B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for processing an electron gun built into a cathode ray tube, and particularly relates to a method for processing an electron beam passage hole of a second grid and its vicinity among a plurality of electrodes constituting the electron gun. The present invention relates to an electron gun processing method that improves the withstand voltage of the electron gun and removes stray emission sources by separately cleaning the electron gun. For example, a color picture tube, which is an example of a cathode ray tube, has a phosphor layer 1 formed on its inner surface that emits red, green, and blue light upon impact with an electron beam, as shown in FIG. a face plate 2, a color selection electrode 3 disposed opposite to the fluorescent surface 1, a neck 5 connected to the face plate 2 via a funnel 4, and an electron gun 6 housed in the neck 5.
As shown in FIG. 2, when the electron gun 6 is of a bipotential type, the electron gun 6 is composed of a cathode 7 which is equipped with a heater (not shown), and an electron beam emitted from the cathode 7. control,
It consists of a first grid 8, a second grid 9, a third grid 10, a fourth grid 11, an insulating support 12, etc. for acceleration and focusing, and the fourth grid 1
Since a high voltage of 20KV to 30KV is applied to the electron gun 1, during the manufacturing process of the color picture tube, the electron gun
A voltage several times higher than that in actual use is applied to 6 via an induction coil or Tesla transformer to remove undesired substances adhering to the surface of each electrode and the surface of the insulating support 12 constituting the electron gun. However, there is a so-called cleaning step which primarily removes or reduces stray emissions from the second grid 9 and/or the third grid 10. In this case, depending on the setting conditions of the applied voltage and application time, glow discharge occurs in the tube not only through each electrode but also through the insulating support, and heating caused by this glow discharge may cause cracks in the insulating support 12 or Since there is a risk that the substances constituting the material may locally gasify, the current situation is that in the cleaning process, the applied voltage and application time are set within limits that do not cause the above-mentioned phenomenon. However, even if the cleaning process is performed using a limited applied voltage and applied time as described above, the surface of the electrode constituting the electron gun assembly 6 is almost cleaned, but in this case, the surface that requires the most cleaning due to the repulsion of the electric field The cleaning effect is insufficient in the electron beam passing hole portion of the second grid 9 and in the vicinity thereof, and especially in the portion of the second grid 9 in the electron beam passing hole portion and in the vicinity of the electron beam passing hole portion opposite to the third grid 10. If a substance that is likely to generate emission remains in the area, the electrons emitted from this area will take a different path from the main electron beam emitted from the cathode 7, and the main electron beam on the fluorescent surface 1 shown in FIG. There is a drawback that stray emission tends to occur, which causes a phosphor layer other than the phosphor layer to emit light and deteriorates image quality. The present invention has been made in view of the various drawbacks of the prior art, and includes cleaning the electron beam passage hole of the second grid where stray emission is most likely to occur and its vicinity before and/or after the normal cleaning process. By adding a process,
It is an object of the present invention to provide a method for processing an electron gun, which makes it possible to obtain a cathode ray tube with good characteristics. Next, an embodiment of the electron gun processing method of the present invention will be explained with reference to FIG. 3, but in this case, the processing method for an electron gun using a conventional induction coil or Tesla transformer is the same as the conventional method, so the explanation will be omitted. . That is, the electron gun 16 built into the cathode ray tube has at least a cathode 17, a first grid 18, and a second grid 1.
9, a third grid 20, and an insulating support 21, the cathode 17 of the electron gun 16 having such an electrode configuration is set to a steady voltage, the first grid 18 and the third grid 20 are set to approximately ground potential, and the second grid 19 is set to approximately ground potential.
When a predetermined voltage is applied to this second grid 1
If the voltage applied to the grid 9 is 100V to 200V, a bluish-white glow 22, 23 is generated around the electron beam passage hole of the second grid 19, as shown in FIG. This is because the electron beam 24 from the cathode 17 that has passed through the electron beam passage hole of the second grid 19 is turned back from near the third grid 20 and then passed through the second grid 19.
The electron beams are concentrated near the electron beam passage holes on the surface of the grid 19 facing the third grid 20, and the stray electrons that were present in the electron beam passage holes of the second grid 19 and in its vicinity are destroyed by collision of these electrons. The emission source is discharged or activated, and stray emission is more likely to occur, but the second
When the voltage applied to the grid 19 is increased to about 400V to 500V, the second grid 19 starts to become red hot, and if this continues for about 2 to 3 minutes, the electron collision described above takes place, but the emission source becomes red.
Since the grid 19 is red-hot, it is destroyed, and the electron beam passage hole of the grid 19 and its vicinity are completely cleaned. If the voltage is high enough to make the second grid 19 red-hot, there is no danger of cracking the insulating support or causing glow inside the tube. By heating the desired part of the second grid before and/or after the process of cleaning each electrode constituting the electron gun using the high voltage from the induction coil or Tesla transformer, which is normally carried out, the most important part can be heated. By removing the electron beam passage hole of the second grid and the stray emission source in its vicinity, a cathode ray tube with good image quality can be obtained. Although the above embodiment has mainly been explained with respect to a color picture tube, this can be applied to all types of cathode ray tubes for monochrome picture tube observation, as well as electron guns consisting of at least a cathode, a first grid, a second grid, and a third grid. It is also effective to heat only the electron beam passage hole of the second grid and its vicinity by using a cathode ray tube with an internal electron gun or a laser beam in the electron gun itself, but in this case, the third grid When heating the cathode 17 with a laser beam from the direction 20, it is desirable to intervene with a heat insulating member or heat the cathode 17 before attaching it so that the cathode 17 is not affected. As mentioned above, according to the electron gun processing method of the present invention, the stray emission source of the second grid can be completely removed, and therefore its industrial value is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a simplified sectional view of a color picture tube, FIG. 2 is an elevational view of a main part of an electron gun, and FIG. 3 is an explanatory diagram of one step of the electron gun processing method of the present invention. 6 , 16 ... Electron gun, 22, 23... Glow.

Claims (1)

[Scope of Claims] 1. At least a cathode installed in a cathode ray tube, a first
Before the step of applying high voltage from an induction coil or a Tesla transformer to an electron gun consisting of a grid, a second grid and a third grid to clean desired surfaces of the first grid, second grid and third grid, and/or A method for processing an electron gun, further comprising means for subsequently heating a desired portion of the second grid to remove a stray emission source in the desired portion. 2. The electron gun processing method according to claim 1, wherein the means for removing the stray emission source in a desired portion of the second grid applies a voltage to the second grid to cause an overcurrent to flow therethrough. . 3. The electron gun processing method according to claim 1 or 2, wherein the desired portion of the second grid is an electron beam passage hole of the second grid and its vicinity.