JP2000348619A - Manufacture of cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove contamination sticking on a fourth grid electrode by spot- knocking. SOLUTION: According to this method, a cathode-ray tube is manufactured that has an electron gun 20 sealed in a picture tube bulb and made up of at least a cathode electrode 21, a first grid electrode 23, a focus electrode 25, and a high-voltage electrode 26. The electrodes other than the high-voltage electrode 26 are given an earth potential while at least a part of the outer circumference of the picture tube bulb 11 confronting a gap between the focus electrode 25 and the high-voltage electrode 26 is given the earth potential by an earth electrode 31, and the high-voltage electrode 26 is spot-knocked by applying thereto a voltage higher than the maximum voltage used in normal operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a cathode ray tube, and more particularly to a so-called spot knocking process for improving the withstand voltage characteristics of a cathode ray tube in a process of manufacturing the cathode ray tube.

[0002]

2. Description of the Related Art In a cathode ray tube, if foreign matter such as dust or evaporating substance adheres to an electrode constituting an electron gun, a discharge or a leak current is easily generated between the electrodes. Become. In order to improve the withstand voltage characteristics of the cathode ray tube, in the process of manufacturing the cathode ray tube, performing a spot knocking process as one step after the exhaust step,
For example, it is well known as disclosed in Japanese Patent Application Laid-Open No. 1-105439.

Here, regarding this spot knocking process, while applying a high voltage to the fourth grid electrode,
A case of a bipotential electron gun using a grid electrode as a focus electrode will be described as an example.

In the conventional spot knocking process, as shown in FIG. 5, a high voltage of 45 to 50 kV is applied to a fourth grid electrode 106 from a DC high-voltage power supply 110 connected to the fourth grid electrode 106. , Other electrodes,
That is, the operation is performed by setting the cathode electrode 101, the heater 102, the first grid electrode 103, the second grid electrode 104, and the third grid electrode 105 to the ground potential.

That is, in this spot knocking process, a voltage higher than the maximum voltage in normal use is applied to the fourth grid electrode 106, so that the fourth grid electrode 106 and the third grid electrode 105 Discharge is performed, and foreign matters such as dust and evaporative substances adhered to the third grid electrode 105 are removed by burning and evaporating the heat generated during the discharge.

Since the fourth grid electrode 106 is a positive electrode, foreign substances such as dust and evaporating substances adhered to the fourth grid electrode 106 cannot be removed. Regarding foreign matter adhering to the fourth grid electrode 106,
Since the fourth grid electrode 106 is a positive electrode and a leak current does not flow, there is no particular problem as long as the state where the foreign matter remains attached is maintained.

[0007]

However, after completion of the cathode ray tube, vibration due to transportation and power ON / OFF of the television are required.
Foreign matter adhering to the fourth grid electrode 106 may be separated by the electric field change in the picture tube bulb due to F and may adhere to the third grid electrode 105. If foreign matter is attached to the third grid electrode 105, the fourth grid electrode 10
Discharge and leak current are likely to occur between them and this, which causes deterioration of withstand voltage characteristics.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a cathode ray tube capable of removing even a foreign substance adhering to a fourth grid electrode by spot knocking. It is to provide a manufacturing method.

[0009]

To achieve the above object, according to the present invention, an electron gun comprising at least a cathode electrode, a first grid electrode, a focus electrode and a high voltage electrode is sealed in a picture tube valve. In the method for manufacturing a cathode ray tube, the cathode electrode, the first grid electrode, and the focus electrode are set to the ground potential, and at least a part of the outer periphery of the picture tube bulb at a portion facing the gap between the focus electrode and the high-voltage electrode is also provided. A spot knocking process is performed by applying a voltage higher than the maximum voltage in normal use to the high voltage electrode at the ground potential.

Each electrode other than the high voltage electrode is set to the ground potential,
By applying a voltage higher than the maximum voltage during normal use to the high-voltage electrode, a normal spot knocking process for removing foreign matter adhering to the focus electrode is performed.
At the time of this spot knocking process, at least a part of the outer periphery of the picture tube valve at a portion facing the gap between the focus electrode and the high voltage electrode is also set to the ground potential,
Since an electric field is generated on the inner wall of the picture tube valve between the focus electrode and the high-voltage electrode, foreign matters adhering to the high-voltage electrode are also removed by the influence of the electric field.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic perspective view showing an overall image of a cathode ray tube to which the present invention is applied.

In FIG. 1, a panel 12 having a fluorescent screen provided on an inner surface is attached to an opening of a picture tube valve 11.
An electron gun 13 for emitting an electron beam is sealed in the rear end of the picture tube valve 11. A cone-shaped deflection yoke 14 for deflecting the electron beam emitted from the electron gun 13 is attached to the neck of the picture tube valve 11.

FIG. 2 is a schematic diagram showing an example of the electron gun 13. Here, a case where a high voltage is applied to the fourth grid electrode and a bipotential electron gun using the third grid electrode as a focus electrode will be described as an example.

In FIG. 2, a bipotential electron gun 20 includes a cathode electrode 21, a heater 22, a first cathode electrode 23, a second grid electrode 24, and a third grid electrode 2.
5 and the fourth grid electrode 26. The periphery of each of these electrodes is covered with a bead glass 27.

The bipotential type electron gun 2 having such a configuration
0, the second grid electrode 24 serves as a screen electrode, and the third grid electrode 25 serves as a focus electrode.
The fourth grid electrodes 26 function as high voltage electrodes. The inner conductive film carbon 28 is applied to the inner wall on the neck side of the picture tube valve 11.

Next, a method of manufacturing a cathode ray tube provided with the bipotential electron gun 20 having the above-described structure, in particular, a spot knocking process for improving the withstand voltage characteristic of the electron gun 20 as one step after the exhaust step is completed. Will be described. This spot knocking processing method is a feature of the present invention. FIG. 3 is a conceptual diagram for explaining the processing method.

In performing the spot knocking process, a DC high-voltage power supply 30 for generating a voltage higher than the maximum voltage of the high-voltage electrode (fourth grid electrode) 26 during normal use, for example, a DC high voltage of about 45 to 50 kV, is prepared. Focus electrode (third grid electrode) 25 and high voltage electrode 26 on the outer peripheral wall of picture tube valve (neck portion) 11
A ground electrode 31 made of a conductive material is provided at a portion facing the gap between the two.

The ground electrode 31 is formed, for example, by attaching a conductive tape to the outer peripheral wall of the picture tube valve (neck portion) 11. In this case, a conductive tape may be wound around the entire circumference of the neck portion of the picture tube valve 11,
Alternatively, a conductive tape may be attached only to a part. Since the gap between the focus electrode 25 and the high-voltage electrode 26 is about 0.9 mm, the gap is about 10 to 30 times the gap, for example, 1 to 30 times.
It is preferable to form the ground electrode 31 with a width of about 3 cm.

The ground electrode 31 is grounded (earthed) via a resistor 32 in order to keep the potential at the ground potential. The resistor 32 is a protection resistor provided to prevent dielectric breakdown of the picture tube valve 11 caused by a potential difference between the high voltage electrode 26 and the interior conductive carbon 28. The protection resistor 32 has a resistance of about 10 to 100 MΩ.

The high voltage electrode 26 is connected to a DC high voltage power supply 30.
To the positive electrode side. In addition, each electrode other than the high voltage electrode 26, that is, the cathode electrode 21, the heater 22, the first cathode electrode 23, the screen electrode 24, and the focus electrode 2
5 is connected by an external socket 33, and a ground potential is applied to each electrode through the external socket 33.

In the above state, a voltage higher than the maximum voltage in normal use, for example, a DC high voltage of about 45 to 50 kV is applied to the high voltage electrode 26 from the DC high voltage power supply 30. Thereby, discharge occurs between the focus electrode 25 and the high-voltage electrode 26. Foreign substances such as dust and evaporative substances adhered to the focus electrode 25 are burned and evaporated by the heat generated during the discharge, and the foreign substances are removed.

At this time, since the ground electrode 31 is provided on the outer peripheral wall of the neck portion of the picture tube valve 11 at the portion facing the gap between the focus electrode 25 and the high voltage electrode 26, the ground electrode 31 is provided. An electric field is generated on the inner wall of the neck portion provided with the electrodes, and the foreign matter adhering to the high-voltage electrode 26 moves and adheres to the focus electrode 25 due to the influence of the electric field. The foreign matter adhering to 25 moves (splashes).

The moved foreign matter adheres to the inner surface of the bead glass 27 on the first grid electrode 23 side and the inner surface of the neck portion of the picture tube valve 11. That is, by repeating the discharge between the focus electrode 25 and the high-voltage electrode 26, not only the foreign matter adhering to the focus electrode 25 but also the foreign matter adhering to the high-voltage electrode 26 affects the withstand voltage characteristics. It can be moved over non-giving insulators.

FIG. 4 shows the results of experiments conducted by the inventor. Here, ten cathode ray tubes were prepared as samples, in which foreign matter adhered to the high voltage electrode 26 and no foreign matter adhered to the focus electrode 25, and when the discharge was performed under the following conditions, the cathode ray tube was adhered to the high voltage electrode 26. Observation was made on the situation in which the foreign matter moved. As the ground electrode 31, one having a width of 1.25 cm and one having a width of 2.5 cm were used.

The discharge conditions are as follows.
0 V, 500 V to the screen electrode 24, 6.5 kV to the focus electrode 25, and 27 kV to the high-voltage electrode 26, respectively.
A portion of the outer periphery of the neck portion facing the gap portion between them is set to the ground potential (the ground electrode 31 is provided on a portion of the outer periphery of the neck portion), and laser forced discharge is performed.

As apparent from the experimental results shown in FIG.
After one or two discharges, 50
%, And most of the moved foreign matter adhered to the focus electrode 25. Specifically, sample 10
The foreign matter adhering to the high voltage electrode 26 moved in five of the books, and the foreign matter moved in four of them adhered to the focus electrode 25.

At this time, it was observed that a leak current of 100 nA or more flowed in the sample in which foreign matter adhered to the focus electrode 25. Further, when the discharge is performed three times or more, the foreign matter attached to the focus electrode 25 moves, and the leak current also returns to 0 nA. The leak current between the other electrodes is also 0 nA, and the foreign matter that has moved due to the discharge energy is the bead glass 27.
It is considered that it adhered to the insulator at the neck portion of.

In the above-described embodiment, the case where a high voltage is applied to the fourth grid electrode and the bipotential electron gun uses the third grid electrode as the focus electrode has been described as an example. However, the present invention is not limited to this. Not something
The same applies to other types of electron guns such as a unipotential type, a uni-unipotential type, and a uni-bipotential type.

[0029]

As described above, according to the present invention,
At the time of manufacturing the cathode ray tube, while each electrode other than the high-voltage electrode is set to the ground potential, at least a part of the outer periphery of the picture tube bulb at the portion facing the gap between the focus electrode and the high-voltage electrode is also set to the ground potential, By applying a voltage higher than the maximum voltage during normal use to the high-voltage electrode to perform spot knocking, foreign substances adhering to the high-voltage electrode can also be removed. The characteristics can be improved, and the reliability of the cathode ray tube can be greatly improved.

Further, since foreign matter adhering to the high-voltage electrode is reduced, it is attached to the high-voltage electrode due to vibration caused by transportation after the completion of the cathode ray tube or electric field change in the picture tube bulb due to turning on / off of the television. Since the amount of the detached foreign matter is extremely small, the occurrence of discharge and leakage current due to the detached foreign matter can be suppressed, and accordingly, the withstand voltage characteristics of the cathode ray tube hardly deteriorate.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an overall image of a cathode ray tube to which the present invention is applied.

FIG. 2 is a schematic configuration diagram showing an example of an electron gun, showing a case of a bi-potential type electron gun.

FIG. 3 is a conceptual diagram for explaining a processing method of spot knocking processing according to the present invention.

FIG. 4 is a view showing an experimental result by the present inventor.

FIG. 5 is a conceptual diagram for describing a processing method of a spot knocking process according to a conventional example.

[Explanation of symbols]

11 picture tube bulb, 13, 20 electron gun, 21 cathode electrode, 23 first cathode electrode, 24 screen electrode (second grid electrode), 25 focus electrode (third grid electrode), 26 high voltage Electrode (fourth grid electrode), 27: bead glass, 31: earth electrode, 32 ...
Insulation resistance

Claims (1)

[Claims] 1. A method for manufacturing a cathode ray tube comprising: an electron gun including at least a cathode electrode, a first grid electrode, a focus electrode, and a high-voltage electrode sealed in a picture tube bulb. The grid electrode and the focus electrode are set to the ground potential, and at least a part of the outer periphery of the picture tube valve at a portion facing the gap between the focus electrode and the high-voltage electrode is also set to the ground potential. A method for manufacturing a cathode ray tube, wherein a spot knocking process is performed by applying a voltage higher than a maximum voltage in normal use.