JPH06260112A - Color picture tube - Google Patents

Abstract

PURPOSE:To keep convergence drift caused by potential alteration of the inner face of a neck part at the time of operating a color picture tube at almost the same level as that of a conventional picture tube and at the same time to lower the deterioration of the high pressure quality caused by adhesion of graphite coating to an electrode part of an electron gun at the time the electron gun is inserted in the inside of the neck part wherein the graphite of the coating is produced by peeling or damaging by friction between a spring and the inner face of the neck part installed to put the electron gun at proper position and to connect it electrically. CONSTITUTION:The coating area of a graphite coating 10 which used to to be coated up to the periphery of a shield cup 12 is narrowed up to a spring 11 and the periphery of the contact part of the inner face of a neck part 2 to suppress peeling or damaging of the graphite coating. Further after the assembly and sealing, mainly the metal part of a high pressure part 9 of an electron gun wherein the metal part is sealed in the neck part is evaporated by a laser light beam 14 radiation through the neck part and a metal thin film 15 is formed in the inner face of the neck part by evaporation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention prevents convergence drift of an electron beam which occurs when a voltage is applied to an electron gun enclosed in a neck portion of a color picture tube, and prevents occurrence of discharge in a tube due to inclusion of foreign matter. The present invention relates to a color picture tube which can be prevented.

[0002]

2. Description of the Related Art In recent years, color picture tubes have been widely used as display devices for consumer televisions and OA equipment.

FIG. 2 is a sectional view showing a structure of a neck portion of a conventional color picture tube. In FIG. 2, a glass support rod 3 is provided in a neck portion 2 of a glass bulb 1 of the color picture tube.
The control electrode 4, the accelerating electrode 5, the focusing electrode 6 and the final accelerating electrode 7 supported by the are enclosed to form an electron gun. Here, a relatively low voltage is applied to the control electrode 4 and the acceleration electrode 5 to form the low-voltage portion 8 together with the focusing electrode 6. Further, a very high voltage of about 30 kV is applied to the final accelerating electrode 7 to form a high voltage portion 9.

A part of the graphite coating film 10 formed on the inner wall surface of the funnel to form an accelerating electric field on the inner wall of the neck portion 2 is the final accelerating electrode 7 which is the high voltage portion of the electron gun.
Is extended to the vicinity of and is coated.

In the electron gun described above, a plurality of springs 11 each having a bowl-shaped contact portion at the tip of a leaf-spring-shaped metal strip are concentric with the glass bulb 1 in order to arrange them concentrically in the glass bulb 1. These springs 11 are provided so as to project in the axial direction, and in addition to the supporting function of the electron gun described above, the spring 11 is connected to the final accelerating electrode 7 through the graphite coating 10 and the shield cup 12 which constitutes the electron gun. It has a structure that also has a general connection function at the same time.

[0006]

In order to satisfy the function of the spring as described above, it is necessary for the spring 11 to firmly contact the inner wall of the glass bulb 1. However, when the electron gun is inserted into the neck portion 2, the spring 11 slides on the upper surface of the graphite coating film 10 in a strong contact state, which causes peeling or damage of the graphite coating film. The peeled or damaged graphite coating film falls into the glass bulb and adheres to the electrode portion of the electron gun, which causes deterioration of high-pressure quality.

In order to prevent such a phenomenon, by coating the position where the graphite coating is applied up to the vicinity of the contact portion of the spring 11, the graphite coating which is peeled off or damaged due to friction with the contact portion of the spring It is possible to significantly reduce the amount. However, the inner surface of the neck portion 2 facing the vicinity of the shield cup 12 of the electron gun is charged during the operation of the picture tube because the graphite coating film 10 is not applied, and the potential of the inner surface of the neck portion 2 changes.

The situation is shown in FIG. The potential distribution immediately after the color picture tube is operated becomes the distribution shown by the curve c. On the other hand, during operation, the electrons emitted from the cathode collide with the inner surface of the neck portion 2, and secondary electrons are emitted from the surface of the inner surface of the neck portion 2, and the neck portion 2 is positively charged. Therefore, the potential distribution on the inner surface of the neck portion 2 in operation is as shown by the curve d. Due to the charging, the change ΔV in the potential of the inner surface of the neck portion 2 near the main lens 13 is large, which affects the electric field of the electron lens formed between the electrodes and causes a deviation in the traveling direction of the electron beam. This causes a problem of causing so-called convergence drift.

The present invention solves the above-mentioned problems by providing a high-potential thin film instead of the graphite coating film up to the vicinity of the shield cup in order to prevent the graphite coating film from peeling or being damaged. It is an object of the present invention to provide a color picture tube in which the change in the electric potential is about the same as when a graphite coating is applied as in the past.

[0010]

In order to achieve this object, in the color picture tube of the present invention, in order to reduce peeling or damage of the graphite coating film applied to the inner surface of the contact portion and the neck portion of the spring, The position where the graphite coating is applied is reduced to near the contact portion of the spring. Further, after the assembly and sealing, the metal part of the electron gun, which is mainly enclosed in the neck part of the glass bulb, of the high pressure part is evaporated by the laser beam irradiated through the neck part, and a metal thin film is formed on the inner surface of the neck part by vapor deposition. The thin film and the graphite coating are electrically connected.

[0011]

According to the present invention, when the position where the graphite coating film is applied is reduced to the vicinity of the contact portion of the spring, convergence drift occurs during the operation of the color picture tube. However, the change in the potential on the inner surface of the neck during the operation of the color picture tube by vapor deposition of a metal thin film with a laser beam is as small as that of a graphite coating applied to the vicinity of the final acceleration electrode as in the past. Therefore, it is possible to prevent the convergence drift as described above. As a result, the convergence drift is almost the same as the conventional one, and it is possible to prevent the deterioration of the high voltage quality caused by the peeled or damaged graphite coating film attached to the electron gun.

[0012]

1 is a sectional view showing a structure of a neck portion of a color picture tube and an electric potential distribution curve thereof in one embodiment of the present invention. In FIG. 1, the neck portion 2 of the color picture tube is controlled. An electron gun composed of an electrode 4, an accelerating electrode 5, a focusing electrode 6 and a final accelerating electrode 7 is enclosed, and a part of a graphite coating film 10 formed on the inner wall of the neck portion 2 on the inner wall surface of the funnel. Is extended and applied to the vicinity of the contact portion between the spring 11 provided in the shield cup 12 of the electron gun and the inner surface of the neck portion 2. After the assembly and sealing, the metal part of the electron gun, which is enclosed in the neck portion 2 of the glass bulb 1, mainly the high pressure portion 9 is vaporized by the laser beam 14 irradiated through the neck portion 2, and the metal is formed on the inner surface of the neck portion 2. The thin film 15 is formed by vapor deposition.

The operation of the color picture tube constructed as above will be described.

When the color picture tube is operated, the potential distribution on the inner surface of the neck portion 2 immediately after the operation has a distribution as shown by a curve a. On the other hand, during operation, the neck portion 2 is positively charged by the electrons emitted from the cathode.

Therefore, the potential distribution on the inner surface of the neck portion 2 during operation is as shown by the curve b, and the potential change ΔV on the inner surface of the neck portion 2 in the vicinity of the main lens 13 is the same as the conventional one when the graphite coating film It becomes as small as when it is applied to the vicinity of the acceleration electrode.

Therefore, the influence on the electric field of the electron lens formed between the electrodes is reduced, the above-mentioned convergence drift is maintained at the same level as in the conventional case, and the peeled or damaged graphite coating film adheres to the electron gun. It is possible to prevent the deterioration of the high-pressure quality caused by this.

[0017]

As described above, the color picture tube of the present invention can significantly reduce the deterioration of the high-pressure quality due to the peeling or damage of the graphite coating film, and the glass can be treated by a relatively simple process of irradiating a laser beam. Convergence drift caused by a change in the electric potential on the inner surface of the neck portion of the valve can be prevented. Moreover, this metal thin film has an advantage that it can be selectively formed after determining the high-pressure quality and the convergence drift for the color picture tube which is in an operable state after the exhaust treatment.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of a neck portion of a color picture tube and an electric potential distribution curve thereof in an embodiment of the present invention.

FIG. 2 is a sectional view showing a structure of a neck portion of a conventional color picture tube.

FIG. 3 is a diagram showing a potential distribution curve of a neck portion in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass bulb, 2 ... Neck part, 3 ... Vitreous support rod, 4 ... Control electrode, 5 ... Accelerating electrode, 6 ... Focusing electrode, 7 ... Final accelerating electrode, 8 ... Low pressure part, 9 ... High pressure part, 10 ... Graphite coating, 11 ... Spring, 12 ... Shield cup, 13 ... Main lens, 14 ... Laser beam,
15 ... Metal thin film.

Claims (1)

[Claims] 1. A metal part of an electron gun enclosed in a neck portion of a glass bulb is evaporated by a laser beam irradiated through the neck portion, and a metal thin film is formed by vapor deposition on an inner surface of the neck portion mainly in a high potential region. Characteristic color picture tube.