JPH01194242A - Cathode-ray tube - Google Patents

Abstract

PURPOSE:To prevent an image from chromatic misconvergence and distortion by forming superconductive material at the front and the sides of a cathode-ray tube, and eliminating turbulence of an electron beam due to external magnetic flux. CONSTITUTION:Superconductor is formed at the front 15a of a cathode-ray tube or its periphery 15b and sides 16. A light permeative superconductive material is used at the front 15a and the periphery 15b. When for ex. an external magnetic flux 17 is applied to the cathode-ray tube because of external speaker, terrestrial magnetism, etc., the external flux 17 can not intrude into the tube because the superconductor is formed at the front 15a or at the periphery 15b and sides 16. Thereby turbulence of the electron beam due to external flux is suppressed, and the screen is prevented from chromatic misconvergence and distortion.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a cathode ray tube for reproducing images.

BACKGROUND OF THE INVENTION In recent years, with the integration of the audio and video fields, cathode ray tubes have been made larger and have higher image quality.

Therefore, a cathode ray tube for reproducing images is required to be extremely resistant to the effects of leakage magnetic flux from speakers and external magnetic fields such as earth's magnetism.

An example of the conventional cathode ray tube mentioned above will be described below with reference to the drawings.

FIG. 3 shows a cross-sectional view of a conventional shadow mask type color cathode ray tube. In FIG. 3, 1 is an electron gun. A structural cross-section of the electron gun is shown in FIG. 5, and 7 is a heater that heats the cathode 8. 9.10,11,1
．． 2 are electrodes called a console grid, a screen grid, a focus electrode, and a high-voltage electric bridge, respectively. Also, screen grid 10 ~ focus electric grid 1
1 and between the focus electrode 11 and the high voltage electrode 12.
Prefocus lens 13 caused by potential difference between electrodes
．． Two electrostatic lenses of the focus lens 14 are formed. 2 and 3 in FIG. 3 are a convergence coil and a polarization coil, respectively. Reference numeral 5 denotes a metal plate (shadow mask) with hundreds of thousands of holes on the back side of the fluorescent film 6. The fluorescent film 6 is made of three types of fluorescent materials that emit red, green, and blue light.

The operation of the cathode ray tube configured as described above will be explained below.

First, when the cathode 8 is heated by the heater 7 shown in FIG. 5, thermoelectrons are emitted from the cathode 8. Three electrons 14 emitted from the cathode 8 pass through small holes in the control grid 9 and are attracted to the positive voltage of the screen grid 10. At this time, the control grid 9 has a cathode 8
A lower voltage is applied and the amount of electrons is controlled by the potential difference between the cathode 8 and the control grid. The electrons that have passed through the screen grid 10 are further accelerated by the positive voltage applied to the focus electrode 11 and the high voltage electrode 12, and reach the fluorescent film 6 at a constant speed. The focus electrode 11 has 4
~5KV, and a high voltage of about 20 to 25KV is applied to the high voltage electrode 12. The electron beam 4 is focused by an electrostatic lens 13, 14 caused by a potential difference between the screen grid 10, the focus electrode 11, and the high voltage electrode 12, and appears as a spot on the screen.

In the cathode ray tube of a television, in order to illuminate the entire screen, an electron beam 4a (FIG. 3) is moved horizontally and vertically (FIG. 3, 4b). The operating principle is as shown in Figure 4.
Horizontal deflection coils 3a, 3b and vertical deflection coils 3c, 3
d to the neck of the cathode ray tube, and horizontal deflection coil 3.
When a current is passed through the deflection coils a and 3b, the direction of the electron beam can be changed horizontally by the action of an electromagnetic field, and when a current is passed through the vertical deflection coils 3c and 3d, the direction of the electron beam can be changed vertically. Cathode (Fig. 5 8)
) are emitted from three electron beams 4, each of which causes a fluorescent film to emit red, green, and blue, which are the three primary colors of light. At this time, the three electron beams pass through the holes in the shadow mask 5, are restricted in direction, and strike the red, green, and blue fluorescent films, respectively.

A color image is reproduced in the above manner. (for example,
Television Technology (February 1984 issue, pages 115-120).

Problems to be Solved by the Invention However, in the above configuration, the traveling direction of the electron beam is determined by the action of the electromagnetic field. There have been problems such as the image being distorted due to a deviation in the direction, and the shadow mask being magnetized by an external magnetic field, resulting in color unevenness.

In view of the above problems, the present invention provides a cathode ray tube that is not affected by external magnetic fields.

Means for Solving the Problems In order to solve the above-mentioned problems, the cathode ray tube of the present invention is provided with a structure in which a superconductor is formed on the front surface (or the periphery thereof) and side surfaces of the cathode ray tube.

Operation The present invention has the above-mentioned configuration, and the Meissner effect of the superconducting material (loop current is generated in the very surface layer of the superconducting material placed in an external magnetic field, and the magnetic field generated by this loop current causes the superconducting material to This phenomenon in which magnetic flux does not enter the interior of the cathode ray tube prevents external magnetic fields from entering the cathode ray tube, thereby preventing changes in the hue of the cathode ray tube and distortion of the image.

EXAMPLE A cathode ray tube according to an example of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view of a cathode ray tube. The material, shape, etc. are the same as the conventional cathode ray tube described above. CRT front 1
A superconductor is formed on the side surface 16 of 5a (or its peripheral portion 15bL).A superconducting material having translucency is used for 15a and 15b.

Regarding the cathode ray tube configured as above, the following is the second part.
The operation will be explained using figures. The principle behind how cathode ray tubes project images is the same as before.

In FIG. 2, 17 is an external magnetic flux applied to the cathode ray tube by, for example, an external swivel or the earth's magnetism. However, the cathode ray tube 15a (or its surrounding area 15b)
), since a superconducting material is formed on the side surface 16, external magnetic flux cannot enter the inside of the cathode ray tube due to the Meissner effect (described above).

As described above, according to this embodiment, by forming a superconducting material on the front surface (or the peripheral portion thereof) and side surfaces of the cathode ray tube, external magnetic flux is prevented from entering the inside of the cathode ray tube,
The sagging of the electron beam due to external magnetic flux is suppressed. In other words, color shift in the image.

No distortion occurs.

Effects of the Invention As described above, the present invention can prevent external magnetic flux from entering the interior of the cathode ray tube by forming a superconducting material on the front surface (or the peripheral portion thereof) and side surfaces of the cathode ray tube. There is no distortion of the electron beam due to external magnetic flux, and color shift and distortion of images can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the cathode ray tube of the present invention, Fig. 2 is an explanatory diagram showing the distribution of external magnetic flux, Fig. 3 is a sectional view of a conventional cathode ray tube, Fig. 4 is an enlarged view of the deflection coil, and Fig. 5 is an explanatory diagram showing the distribution of external magnetic flux. It is an enlarged view of the gun. ■・・・・・・Subgun, 2・・・Convergence coil, 3・・・Deflection coil, 3a, 3b...
...Horizontal deflection coil, 3c, 3d... Vertical deflection coil, 4.4a. 4b... Electron beam, 5... Shadow mask, 6... Fluorescent film, 7... Heater,
8...Cathode, 9...Control grid, 10...Screen grid, 11
... Focus electrode, 12 ... High voltage electrode, 13 ... Prefocus lens, 14 ...
...Focus lens, 15a, 15b, 16...
...Part formed with superconducting material. Name of agent: Patent attorney Toshio Nakao (1 person) Figure 1 Figure 2 Figure 3 Figure 4 b8 Figure 5

Claims (1)

[Claims] A cathode ray tube characterized by forming a superconducting material on the front and side surfaces of the cathode ray tube.