JPH04237930A - Cathode body structure for cathode ray tube of color picture tube - Google Patents

Abstract

PURPOSE:To prevent imbalance of color tone of a screen until a cathode current is stabilized from the time when a heater is ignited by providing a particular relation between the heat radiation coefficient of the surface of the cathode sleeve positioned in the center and those of the surfaces of the cathode sleeves positioned at both external sides. CONSTITUTION:Cathodes 1 are arranged in parallel on a straight line and supported to be fixed to a glass rod through a cathode sleeve supporter 6 and a cathode supporter 7. The cathode 1 is made up of a sleeve 4 and an alkali earth oxide 3 applied to the apex of the cathode body structure 2 fixed to the sleeve 4 by welding, and a heater 5 is inserted into the sleeve 4 to be fixed to a heater supporter by welding. The external surface of the sleeve 4 of the cathode 1 positioned in the center is blackened so that its heat radiation coefficient epsilon1 is made to be greater by 10-20% than the heat radiation coefficient epsilon2 of the external surfaces of the sleeves 4 of the cathode 1 positioned at both external sides. The rate of heat exchange of the central cathode is thereby lowered than those on both external sides and the speed of temperature rise can be equalized to those of the cathodes on both external sides, so that it is possible to balance the color tones which are caused from ignition of the heater to stabilization of a cathode current.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cathode assembly for a cathode ray tube of a color picture tube, and more particularly to a cathode assembly for a cathode ray tube of a color picture tube that balances the temperature rise of three cathodes when a heater is ignited.

0002

2. Description of the Related Art Conventionally, a cathode assembly (hereinafter referred to as cathode assembly) for a cathode ray tube of this type of color picture tube is as shown in FIG.
It is composed of three cathodes 1 arranged in-line, is heated by a heater 5 inserted from the open end of a cathode sleeve 4, and is contained in a substantially cap-shaped cathode base 2 fixed by welding to the nape of the cathode sleeve 4. The reaction between the reducing agent and the alkaline earth oxide 3 applied to the cathode substrate 2 is promoted, and 7
Electron emission occurs at an operating temperature of 00-800°C.

Normally, in this type of cathode structure, heat loss from the heater 5 occurs due to thermal conduction or thermal radiation until the heater 5 is ignited and the cathode 1 reaches a temperature of 700 to 800° C. at which it emits electrons. It takes several seconds.

0004

In this conventional cathode assembly, due to the in-line structure, the temperature of the cathode located at the center increases rapidly due to heat conduction and radiation from the cathodes located on both outer sides. Therefore, the electron emission from the cathode located in the center is faster than the electron emission from the cathodes located on both outer sides, and if a white color is displayed on the screen from the heater ignition until the cathode current stabilizes, There was a problem that the color balance was lost and the color became greenish.

[0005] An object of the present invention is to provide a cathode assembly that does not cause a change in the color balance of the screen from when the heater is ignited until the cathode current is stabilized.

[0006]

[Means for Solving the Problems] The present invention has the following features: 1. In the cathode assembly for a cathode ray tube of an in-line color picture tube, the heat radiation coefficient ε1 of the cathode sleeve surface of the cathode located in the center
The thermal radiation coefficient ε2 of the surface of the cathode sleeve of the cathode located on both outer sides has a relationship of ε1=1.1ε2 to 1.2ε2.

2. In the cathode assembly for a cathode ray tube of an in-line color picture tube, the amount of heat generated Q1 by the heater inserted into the cathode located in the center and the amount of heat generated Q2 from the heaters inserted into the cathodes located on both outer sides are Q2=1.1Q1~ 1.2Q
There is a relationship of 1.

[0008]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a first embodiment of the present invention.

In the first embodiment, as shown in FIG.
are arranged in parallel on a straight line, and are supported and fixed to a glass rod (not shown) via a cathode sleeve support 6 and a cathode support 7. Each cathode 1 consists of a cathode sleeve 4 and an alkaline earth oxide 3 coated on the top of the cathode base 2 of a cathode base 2 welded and fixed to the cathode sleeve 4. A heater 5 is inserted and fixed by welding to a heater support (not shown).

Furthermore, the thermal radiation coefficient ε1 of the outer surface of the cathode sleeve 4 of the cathode 1 located at the center is 1 greater than the thermal radiation coefficient ε2 of the outer surface of the cathode sleeve 4 of the cathode 1 located on both outer sides.
Blackening treatment is applied to increase the strength by 0 to 20%.

FIG. 2 is a longitudinal sectional view of a second embodiment of the invention.

In the second embodiment, as shown in FIG. 2, the calorific value Q1 of the heater 5 inserted into the cathode sleeve 4 of the cathode 1 located at the center is the same as that of the cathode sleeves of the cathodes 1 located on both outer sides. In order to make the heat generation amount 10 to 20% smaller than the heat generation amount Q2 of the heater 5 inserted in the heater 5, the heater pitch of the heat generating portion of the heater 5 is widened by 10 to 20%.

FIG. 3 is a characteristic diagram showing changes in cathode current with respect to time after heater ignition.

As shown in FIG. 3, the I of the central cathode of this embodiment
It was confirmed that the change in the K characteristic approached the IK characteristic of both outer cathodes compared to the conventional IK characteristic of the central cathode, and that imbalance in color tone could be prevented.

[0016]

[Effects of the Invention] As explained above, the cathode structure of the present invention has
By lowering the heat exchange rate of the cathode located in the center compared to the cathodes located on both outer sides, the rate of temperature rise of the cathode located in the center is made to be the same as the speed of temperature rise of the cathodes located on both outer sides. By doing so, it has the effect of adjusting the balance of color tone that occurs from the time of heater ignition until the cathode current becomes stable.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a first embodiment of the invention.

FIG. 2 is a longitudinal cross-sectional view of a second embodiment of the invention.

FIG. 3 is a characteristic diagram showing changes in cathode current with respect to time after heater ignition.

FIG. 4 is a longitudinal cross-sectional view of an example of a conventional cathode assembly.

[Explanation of symbols]

1 Cathode 2 Cathode base 3 Alkaline earth oxide 4 Cathode sleeve 5 Heater 6 Cathode sleeve support 7 Cathode support

Claims (2)

[Claims] Claim 1: In a cathode assembly for a cathode ray tube of an in-line color picture tube, the heat radiation coefficient ε1 of the cathode sleeve surface of the cathode located in the center and the heat radiation coefficient ε2 of the cathode sleeve surfaces of cathodes located on both outer sides are ε1. =1.1ε2~
A cathode assembly for a cathode ray tube of a color picture tube, characterized by having a relationship of 1.2ε2. Claim 2: In a cathode assembly for a cathode ray tube of an in-line color picture tube, the amount of heat generated by the heater inserted into the central cathode Q1 and the amount of heat generated by the heaters inserted into the cathodes located on both outer sides Q2 are equal to Q2. =1.1Q1~1.2Q
1. A cathode assembly for a color cathode ray tube, characterized by having the following relationship.