JPH04334851A - Electron gun - Google Patents

Abstract

PURPOSE:To enhance focus performance and withstand voltage performance as well by reducing the occurrence of cracks and chips in bead glass caused by electric breakdown and creeping discharge in a seasoning process. CONSTITUTION:A bipotential type lens formed between a G3 electrode 13 and G4 electrode 14 is disposed at the front stage of an unipotential type main lens formed among the G4 electrode 14, a G5 electrode 15 and a G6 electrode 16, and voltage fairly higher than focus voltage is constituted to be applied to the G4 electrode 14 at the high potential side of the bipotential type lens.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun designed to improve the focusing performance and withstand voltage characteristics of a color cathode ray tube.

0002

2. Description of the Related Art FIG. 2 is a cross-sectional view showing the structure of a conventional electron gun disclosed in Japanese Patent Publication No. 1899/1989 and Japanese Patent Publication No. 47695/1989.
10 is a cathode, 11 is a G1 electrode, 12 is a G2 electrode, 1
3 is the G3 electrode, 14 is the G4 electrode, 15 is the G5 electrode, 16
is a G6 electrode, and an electron gun 1 is constructed by holding these cathode 10 and G1 to G6 electrodes 11 to 16 on a bead glass 4. This electron gun 1 is connected to the neck of a color cathode ray tube (hereinafter referred to as CRT). It is built in part 2.

In the electron gun 1, the G3 electrode 13 and the G
It is electrically connected to the 5 electrode 15 by a connector 18,
8 to 10 from the lead wire provided on the stem portion 3 of the neck portion 2
A medium-high focus voltage of KV is applied. Further, the G4 electrode 14 and the G6 electrode 16 are electrically connected by a connector 19, and the G6 electrode 16 is electrically connected to a high voltage application anode button (not shown) of the CRT via an internal conductive film (not shown). It is connected to the. In addition, in the figure, 17 is a shield cup.

In the electron gun having the above configuration, the G4 electrode 1
By applying a high voltage of 25 to 29 KV to 4,
An accelerating bipotential lens is configured between the G3 electrode 13 and the G4 electrode 14, and the G4 electrode 14 and the G5
A unipotential lens is constructed between the electrode 15 and the G6 electrode 19.

[0005]

[Problems to be Solved by the Invention] In the conventional electron gun configured as described above, a high voltage is applied to the G4 electrode 14 arranged in the center among the plurality of constituent electrodes. In the so-called seasoning process, in which the surface of each electrode is cleaned up by forcibly sparking between the electrodes by applying ,1
A high voltage of approximately 70 KV is applied between the G3 electrode 13 and the G4 electrode 14, which are made up of the electrode holding bead glass 4 that supports these cup-shaped electrodes 13a, 13b, 14a, and 14b. creeping discharge on the top,
Bead glass 4 is prone to cracking due to insulation breakdown.
There was a problem in that a portion of the electron beam was chipped and fell into the inside of the CRT, clogging the electron beam passage hole in the shadow mask (not shown).

Furthermore, since a high voltage is applied to the G4 electrode 14, the potential rises to near the stem portion 3 in the neck portion 2, and the G1 electrode 11, which is the low voltage side electrode of the electron gun 1, and the G2 electrode
There was also the problem that a discharge phenomenon occurred between the electrode 12 and the inner wall of the neck portion 2.

[0007] This invention was made to solve the above-mentioned problems, and can reduce by half the occurrence of dielectric breakdown during the seasoning process and cracks and chips in the bead glass due to creeping discharge, and improves the withstand voltage characteristics. The purpose is to provide an electron gun that can be significantly improved.

[0008]

[Means for Solving the Problems] The electron gun according to the present invention is configured to apply a medium-high voltage higher than the focus voltage to the high potential side electrode of the bipotential lens disposed in front of the main lens. It is characterized by what it did.

In particular, it is preferable to apply a voltage obtained by resistance-dividing the high voltage through a built-in resistance divider as the medium-high voltage to be applied to the high-potential side electrode of the bipotential lens.

0010

[Operation] According to this invention, by applying a medium-high voltage higher than the focus voltage to the bipotential lens, the difference in electrode voltage during the seasoning process is reduced to less than half of the conventional one, and the discharge phenomenon between the electrodes is reduced. At the same time,
The occurrence of dielectric breakdown of the bead glass for holding the electrode is suppressed,
It is possible to improve the withstand voltage characteristics.

In particular, by extracting an appropriate percentage of the high voltage through a built-in resistor divider and applying it to the high potential side electrode of the bipotential lens, it is possible to apply a voltage lower than the high voltage of the CRT. , CR in operation
The spark inside the T can also be halved.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the configuration of an electron gun according to an embodiment of the present invention.
18 are the same components as those in the conventional example shown in FIG. 2, so the same reference numerals are given to the corresponding parts and detailed explanation thereof will be omitted.

In FIG. 1, 5 is a built-in resistor divider, the high voltage side terminal 5a of which is attached to the shield cup 17 connected to the high voltage of the CRT, and the other terminal 5b is connected to the stem portion (indicated by 3 in FIG. 2). ) is connected to ground potential 6 through. By appropriately dividing the resistance of this built-in resistor divider 5, an arbitrary medium-high voltage, for example, about 60% of the high voltage, is taken out from the intermediate terminal 5c, and this is applied to the G4 electrode forming the bipotential lens. 14. Note that a focus voltage EF of about 30% of the high voltage is applied to the G3 electrode 13 and G5 electrode 15 on both sides of the G4 electrode 14 through the connector 18.
is applied.

In the electron gun having the above configuration, the potential difference between the G3 electrode 13 and the G4 electrode 14 and between the G4 electrode 14 and the G5 electrode 15 in the seasoning process is (1/2) that of the conventional one, and therefore The occurrence of cracks and chips due to dielectric breakdown due to creeping discharge is sufficiently suppressed.

[0015] Also, each of the above-mentioned electrodes 13,
The potential difference between 14, 14, and 15 is also 1/2 that of the conventional one, and the spark phenomenon is reduced.Furthermore, since no high voltage is applied to the lower part of the electron gun 1, the inner wall potential of the neck is lowered, and G1 The discharge phenomenon between the electrode 11, the G2 electrode 12 and the inner wall of the neck portion is also eliminated, and the withstand voltage characteristics of the electron gun 1 as a whole are improved.

[0016]

[Effects of the Invention] As described above, according to the present invention, since a medium-high voltage is applied to the high-potential side electrode of a bipotential lens, the difference in electrode voltage during the seasoning process is less than half that of the conventional one. It is possible to suppress the occurrence of cracks and chips in the electrode holding bead glass due to discharge phenomena between the electrodes, creeping discharge on the bead glass, and dielectric breakdown, and it is possible to improve the withstand voltage characteristics. In addition, the generation of sparks can be reduced by reducing the potential difference in the operating state of the CRT.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of an electron gun according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the configuration of a conventional electron gun.

FIG. 3 is a diagram illustrating the electrode arrangement and discharge phenomenon of a conventional electron gun.

[Explanation of symbols]

1 Electron gun 4 Bead glass for holding electrodes 5 Built-in resistor divider 10 Cathode 11 G1 electrode 12 G2 electrode 13 G3 electrode 14 G4 electrode 15 G5 electrode 16 G6 electrode

Claims (2)

[Claims] Claim 1: In an electron gun having an accelerating bipotential lens disposed in front of a unipotential main lens, a medium-high voltage higher than a focus voltage is applied to the high potential side electrode of the bipotential lens. An electron gun characterized in that it is configured to apply a voltage. 2. The electron gun according to claim 1, wherein the medium-high voltage applied to the high-potential side electrode of the bipotential lens is applied via a built-in resistance divider that divides the high voltage by resistance.