JPH10144223A - Manufacture of cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the formation of an unnecessary electron emitting source, which excites the stray emission, by using a high frequency oscillating device such as a semi-conductor type high frequency oscillating device, which continuously oscillates at a constant amplitude, as a power source for high frequency heating. SOLUTION: In a later-half of an exhausting process, in which inside of a cathode- ray tube achieves the predetermined vacuum degree, in the case where each grid of an electron gun is heated by high frequency heating so as to suck and exhaust the gas, which is included or adhered in/to a metal member used in the electron gun, a semi-conductor high frequency oscillating device is used. Generation of resonance at a low frequency of an electrode unit inside of a cathode-ray tube is prevented, and spattering of the compound carbonate grains on a negative electrode 11, of which binding force is lowered, can be prevented by performing the high frequency heating with a semi-conductor type high frequency oscillating device for generating continuous wave at a constant amplitude. Since the generation of an electron emitting source 16 as a cause of stray emission and in-tube discharge can be prevented, voltage withstanding characteristic of a cathode-ray tube is improved, and deviation of image, and the generation of in-tube discharge and damage of a cathode-ray tube driving circuit due to the in-tube discharge can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a cathode ray tube, and more particularly, to a method for manufacturing a cathode ray tube having an oxide cathode having improved withstand voltage characteristics.

[0002]

2. Description of the Related Art The most important function of a cathode ray tube is faithful image reproduction. This problem is not limited to monitors used in broadcasting stations, but also demands for high-level image quality in industrial monitors, computer monitors, and recently, television receivers used in ordinary households. As it has come, the basic performance of the cathode ray tube must be constantly improved. However, one of the factors that impair the image quality is the problem of stray emission, and measures have been taken by improving the structure of the electron gun. The cause of this stray emission is likely to exist not only in the electron gun structure but also in the cathode ray tube manufacturing process.
It is necessary to verify the process well. Hereinafter, a configuration and a manufacturing method of a trinitron type color picture tube as an example of a cathode ray tube will be described.

FIG. 2 is a schematic configuration diagram of a trinitron type color picture tube, and FIG. 3 is a configuration diagram of the electron gun. FIG.
, A cathode ray tube is formed by a panel 1 and a funnel 2, and a color phosphor screen 3 coated with phosphors of three colors that emit blue, green and red light is formed on the inner surface of the panel 1. A color selection electrode 4, for example, an aperture grille having a large number of slits arranged thereon is provided opposite to the color phosphor screen 3, and a magnetic shield 5 is attached. Further, a conductive film 6 is provided on the inner surface of the funnel 2.
Normally, it is coated with carbon, and the cathode ray tube neck 7
An electron gun 10 is enclosed therein. This electron gun 10
As shown in FIG. 3, a cathode 11 using an oxide as an electron-emitting substance, a heater 12 for heating the cathode 11 (see FIG. 5), and a cathode 11 facing the color phosphor screen 3. And first to fifth grids G <b> 1 to G <b> 5 (electrodes) sequentially arranged at a predetermined distance on the same axis, and these are fixed by a pair of insulating supports 14.

[0004] As described above, the cathode ray tube in which each member is disposed at a predetermined position in the tube enters an evacuation step by a vacuum pump while being heated to a predetermined temperature by a gas or an electric furnace. Then, in the latter half of the evacuation process, the grids G1 to G5 of the electron gun 10 are heated by high-frequency heating, and gas contained or attached to the metal member used in the electron gun 10 is sucked and exhausted. . Normal,
A vacuum tube type high frequency oscillator is used for the high frequency induction heating. The output current waveform of the high-frequency oscillator at this time is an output waveform modulated at a low frequency of about 100 to 120 Hertz as shown in FIG. 4A. Thereafter, a predetermined voltage is applied to the heater 12 to heat the cathode 11, and a composite carbonate of an alkaline earth metal, for example, Ba, Sr, or Ca, applied to one end of the cathode 11 facing the first grid G1. The salt is decomposed into oxide 13 and the oxide 13 is activated to form an electron emitting material. Next, the exhaust pipe 1
5, the electron gun 10 is sealed, and then a getter (not shown) attached to the inside of the cathode ray tube is scattered and evaporated, a getter film is formed on the inner wall of the cathode ray tube, and residual gas in the tube is formed. To absorb. Thereafter, carbon (not shown) is applied to the outer surface of the funnel 2 to complete it.

The above-mentioned stray emission which greatly impairs the image quality of the reproduced image is based on the fact that the composite carbonate particles of the alkaline earth metal cause the metal other than the cathode 11 in the tube in the cathode ray tube manufacturing process as described above. It is considered that one of the causes is adhesion to a member, particularly around the first grid G1. In the electron gun assembling process, the alkaline earth metal composite carbonate particles are used as a cathode 1 with nitrocellulose as a binder.
1 is applied to one end to form a composite carbonate layer.
However, in the step of enclosing the electron gun 10 in the cathode ray tube, when the cathode 11 is heated at 300 to 400 ° C. for several minutes, most of the nitrocellulose is decomposed by heat, and the alkaline earth metal composite carbonate particles Binding power becomes very weak. Then, during high-frequency heating in the latter half of the evacuation process, high-frequency waves emitted from the high-frequency oscillating device heat the grids G1 to G5 of the electron gun 10 and are also guided to the cathode 11. As shown in FIG. 4A, the output current of the conventionally used vacuum tube type high frequency oscillator has a low frequency component around 100 Hz, and the cathode 11 just resonates with this low frequency component. The composite carbonate particles having a weak binding force are scattered and attached to one corner of the first grid G1 or the second grid G2 as shown in FIG. The composite carbonate particles thus adhered become the electron emission source 16 and emit unnecessary secondary electrons, thereby deteriorating the quality of an image and causing discharge in the tube.

[0006]

As described above, according to the conventional method for manufacturing a cathode ray tube, the treatment in the exhausting step of the cathode ray tube having the oxide cathode originally causes a complete electric signal. Despite it should be a black screen image,
A phenomenon occurs in which the light is dimly lit due to unnecessary stray emission. In addition, the source of the stray emission is a factor inducing a discharge in the tube.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a cathode ray tube that solves the above problem and does not form an unnecessary electron emission source that induces stray emission.

[0007]

In order to achieve the above object, a cathode ray tube enclosing an oxide cathode and an electron gun having a plurality of electrodes is evacuated, and the electrodes are subjected to a high-frequency heating treatment. In a method for manufacturing a cathode ray tube having a process, a high-frequency oscillator that continuously oscillates at a constant amplitude, for example, a semiconductor high-frequency oscillator, is used as the power supply for high-frequency heating. By using this semiconductor-type high-frequency oscillator, the low-frequency component of the output current of the conventionally used vacuum-tube-type high-frequency oscillator can be removed, and the resonance of the cathode portion can be prevented. That is, during the high-frequency heating of the electrode portion, the cathode portion does not resonate and the scattering of the composite carbonate particles is prevented, so that the formation of an unnecessary electron emission source can be prevented.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a trinitron color picture tube according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart of a method for manufacturing a color picture tube according to an embodiment of the present invention. In the electron gun enclosing step, the electron gun in which the cathode, the heater, and the first to fifth grids G1 to G5 (electrodes) are fixed at predetermined positions is coated with phosphors of R, G, and B, and the color selection electrode is formed. It is sealed in the attached cathode ray tube, and enters an exhausting process for sucking and exhausting air and gases in the tube. At one end of the cathode,
In a pre-process (not shown) for enclosing the electron gun, composite carbonate particles of an alkaline earth metal, for example, Ba, Sr, and Ca are applied using nitrocellulose as a binder to form a composite carbonate layer.

In the latter half of the evacuation process in which the inside of the tube reaches a predetermined degree of vacuum, each grid G of the electron gun is heated by high-frequency heating.
1 to G5 are heated to suck and exhaust gases contained or attached to the metal member used for the electron gun. Usually, a vacuum tube-type high-frequency oscillator is used for the high-frequency heating, but in the embodiment of the present invention, a semiconductor high-frequency oscillator is used. The reason for this is
The waveform of the output current of the vacuum tube type high frequency oscillator is an output waveform modulated at a low frequency of about 100 to 120 Hz as shown in FIG. 4A, whereas the waveform of the output current of the semiconductor type high frequency oscillator is shown in FIG. This is because the continuous wave has a constant amplitude as shown in FIG.

Usually, in the step of enclosing the electron gun in the cathode ray tube, when the cathode is heated at 300 to 400 ° C. for several minutes, most of the nitrocellulose serving as the binder of the composite carbonate particles is heated. It is decomposed, and the binding power of the alkaline earth metal composite carbonate particles is very weak. At the time of the high-frequency heating, in a conventionally used vacuum tube-type high-frequency oscillator, the output current has a low-frequency component around 100 Hz as shown in FIG. The current causes the cathode to resonate,
The composite carbonate particles having a weak binding force are scattered. The scattered composite carbonate particles adhere to one corner of the first grid G1 or the second grid G2 as shown in FIG. 5 and become an electron radiation source 16 that emits unnecessary secondary electrons, thereby deteriorating the image quality. Also, it may cause a discharge in the tube.

However, since the output current of the semiconductor high-frequency oscillator of this embodiment is a continuous wave having a constant amplitude as shown in FIG. 4B, it has no low-frequency component. The weakened composite carbonate particles are not scattered, and the generation of the electron emission source 16 that emits unnecessary secondary electrons can be prevented.

After the high-frequency heating step, the cathode ray tube is completed through the same cathode oxidation step, getter flash step, and exterior carbon coating step as in the prior art. In the above embodiment, a method for manufacturing a trinitron color picture tube has been described. However, the present invention can be applied to a cathode ray tube having an oxide cathode other than the trinitron color picture tube.

[0013]

As described above, according to the present invention, in a high-frequency heating step performed concurrently with a step of exhausting a cathode ray tube having an oxide cathode, a semiconductor-type high-frequency oscillator for generating a continuous wave having a constant amplitude is provided. By performing high-frequency heating, the electrodes in the cathode ray tube do not resonate at a low frequency, and the scattering of composite carbonate particles on the cathode with reduced binding force can be prevented. The generation of an electron emission source that causes a discharge can be prevented, and the withstand voltage characteristics of the cathode ray tube improve. That is,
It is possible to manufacture a cathode ray tube in which deterioration of an image and discharge in a tube and damage to a cathode ray tube driving circuit due to the discharge are prevented.

[Brief description of the drawings]

FIG. 1 is a flowchart of a method for manufacturing a color picture tube according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a trinitron type color picture tube.

FIG. 3 is a schematic configuration diagram of an electron gun of a trinitron type color picture tube.

FIG. 4 is a waveform diagram of an output current of the high-frequency oscillator.

FIG. 5 is an enlarged view around a cathode illustrating an electron emission source formed by high-frequency heating.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Panel, 2 ... Funnel, 3 ... Color fluorescent screen, 4 ...
Color selection electrode, 5: magnetic shield, 6: conductive film, 7: neck, 10: electron gun, 11: cathode, 12: heater, 13
... oxide, 14 ... insulating support, 15 ... exhaust pipe, 16 ... electron radiation source.

Claims (1)

[Claims] 1. A method for manufacturing a cathode ray tube, comprising the steps of: exhausting a cathode ray tube enclosing an electron gun having an oxide cathode and a plurality of electrodes; and performing a high frequency heating process on the electrodes. A method for manufacturing a cathode ray tube, comprising using a high-frequency oscillator that continuously oscillates at a constant amplitude for the power supply.