JPH0741083Y2 - Electron gun for cathode ray tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial Application Field >> The present invention relates to an electron gun for a cathode ray tube, and relates to an electron gun for a cathode ray tube having a final acceleration and focusing lens with low spherical aberration and astigmatism. .

<< Prior Art and its Problems >> In order to improve the spherical aberration of the electron lens of the electron gun, it is necessary to weaken the electric field strength of the main lens as much as possible and to enlarge its aperture. However, since the spherical diameter of the lens is limited by the diameter of the neck of the cathode ray tube, the range of improvement of the spherical aberration by expanding the aperture of the lens is practically narrow. Therefore, at present, a large number of electron lenses having a weak electric field strength are mainly overlapped to form one group of main lens systems. That is, a multi-stage focusing electron gun as described in U.S. Pat. No. 4,253,041 has been developed as an electron gun of the form shown in FIG.

Also, in US Pat. No. 3,772,554, as shown in FIG. 2, the plane in which the beam passage hole is formed is made concave so that the main lens, which is the final acceleration and focusing lens of the main lens system, can be made large in diameter. Although the electron gun in the formed form is disclosed, this can obtain the effect that a large number of electron lenses are superposed like the multi-stage focusing electron gun.
However, in such an electron gun, since the entire plane in which the beam passage hole is formed must be pressed concavely,
The die structure of the press for processing this becomes complicated, which causes difficulty in manufacturing and processing.

<Purpose of Invention> The present invention is intended to improve the above problems.
An object of the present invention is to provide an electron gun for a cathode ray tube, which has a simple structure, is easy to manufacture, and has spherical aberration and astigmatism efficiently improved.

<< Means for Solving the Problems >> In order to achieve the above object, the present invention provides a beam passing plane of a focus electrode and a beam passing plane of an anode electrode which form a final acceleration and focusing lens of a main lens system. And a central beam passage hole, and an electron gun for a cathode ray tube having outer beam passage holes provided on both sides of the central beam passage hole, wherein the beam is provided between the central beam passage hole and the outer beam passage hole. It has a flat bottom surface that is parallel to the passing plane, and recesses formed on both sides of this bottom surface with inclined surfaces at a predetermined angle, and the outer side edge of the inclined surface of this recessed portion is the outer beam passage hole. The inner side portion of the outer beam passage hole that extends toward the central beam passage hole is located on the inclined surface.

<< Effect >> Therefore, the electron beam passing through the electron lens formed by the central beam passage hole has, for example, a beam passage hole with a small diameter, but receives a small focusing force because the distance between the opposite beam passage spaces is large. To reduce spherical aberration. On the other hand, the electron beam passing through the electron lens formed by the outer beam passage hole receives a small focusing force due to the large diameter of each beam passage hole in spite of the narrow space between the lens forming spaces, so spherical aberration is reduced. To be done.

Further, a part or the whole of the outer beam passage hole is formed to be inclined with respect to the electron beam passage plane, which is advantageous for concentration. That is, since the electric field is formed to be inclined with respect to the electron traveling direction by the inclined outer beam passage hole, the focusing direction between the beam bundles passing therethrough becomes substantially constant, resulting in the outer electron beam astigmatism. Is reduced.

<< Embodiment >> FIG. 3 schematically shows an electron gun of the present invention of a single electron lens type. In the figure, this electron gun is a cathode K, grid
G1, screen grid G2, focus electrode G3, anode G
It consists of 4 electrodes. Then, the depressions PR and RR having the slope TR are formed in the central portion of the plane 3P on the beam emitting side of the focus electrode G3 that forms the main lens system and in the central portion of the plane 4P on the beam incident side of the final accelerating electrode G4. Has been formed.

At this time, the central beam passage holes 3G, 4G are located on the bottom surfaces of the depressions PR, RR, and the outer beam passage holes 3R, 3B, 4 on both sides thereof are located.
R and 4B are located on the slope TR, but the region of the slope TR is from the boundary line L between the central beam passing holes 3G and 4G and the outer lens forming holes 3R, 3B, 4R and 4B to the outer lens forming holes 3R and 3B, It is up to the approximate center of 4R and 4B. However, the slope TR may be formed so as to extend from the boundary line L to the outer ends of the outer lens forming holes 3R, 3B, 4R, 4B, and in this case, the outer beam passing holes 3R, 3B, 4R, 4B.
B is entirely formed on the slope TR, and is entirely inclined with respect to the traveling direction of the electron beam. On the other hand, the central beam passage holes 3G, 4G have a smaller diameter than the outer beam passage holes 3R, 3B, 4R, 4B. Lip formed at the edge of each beam passage hole
Regarding the height of BR, the lip B of the central beam passage holes 3G and 4G
R is shorter than the average length of the lip BR of the outer beam passage holes 3R, 3B, 4R, 4B.

Looking at the electron beam characteristics of the electron gun configured as described above, first, the central electron beam passing through the electron lens formed by the central beam passing holes 3G and 4G is a beam passing hole having a small diameter, Since the distance between the beam passing holes 3G and 4G facing each other is large, a small focusing force is received, so that spherical aberration is reduced. On the other hand, the outer beam passage holes 3R, 3B, 4R, 4B
The outer electron beam passing through the electron lens formed by means of the above has a small focusing force due to the large diameter of each beam passage hole in spite of the narrow space of the beam passage space, so that the spherical aberration is reduced. In addition, since a part or the whole of the outer beam passage hole is formed to be inclined with respect to the electron beam passage plane, it acts in the direction in which the beam is concentrated, so the focusing direction between the beam bundles (Flux) passing therethrough is Be constant.

This will be described in detail. As shown in FIG. 5, the state of focusing and concentration of the electron beam passing through the tilted outer lens ML is shown, and when the outer electron beam R passes through the tilted outer main lens ML. Since the beam bundle Ro that is obliquely incident from the outside of the main lens ML receives a weak diverging force, it has a large refraction angle, while the beam bundle Ri that is obliquely incident from the inside of the main lens ML has a strong divergent force. Although it receives it, it has a small refracting power because it is inclined inward in the incident direction.

Therefore, since a large number of beam bundles are adjusted according to the above-mentioned conditions and focused at one point, the beam spot is formed to have a normal circle shape.

<Effect> Since the electron gun of the present invention has a simple structure to improve both the spherical aberration and the astigmatism of the electron beam, the structural aberration correcting means of the conventional electron gun having a complicated shape is eliminated. You can. Therefore, the reliability is improved and the image quality of the cathode ray tube can be greatly improved.

[Brief description of drawings]

1 and 2 are sectional views of a conventional electron gun, FIG. 3 is a drawing showing an embodiment of the electron gun according to the present invention, and FIG. 4 is a main lens in the electron gun shown in FIG. FIG. 5 is a front view of an electrode forming a main lens of the system, and FIG. 5 is a view showing a focused state and a focused state of an electron beam controlled by an electron gun of the present invention. 3R, 3G, 3B, 4R, 4G, 4B …… Beam passage hole RR, PR …… Depression part TR …… Sloping surface L …… Boundary line of depression bottom surface BR …… Beam passage hole lip

Claims (2)

[Scope of utility model registration request] 1. A central beam passage hole in each of a beam passage plane of a focus electrode and a beam passage plane of an anode electrode which form a final acceleration and focusing lens of a main lens system, and on both sides of the central beam passage hole. In an electron gun for a cathode ray tube having an outer beam passage hole provided, between the central beam passage hole and the outer beam passage hole, a bottom surface parallel to the beam passage plane and flat, and predetermined on both sides of the bottom surface. There is a recessed portion formed by an inclined surface having an angle, and the outer side edge of the inclined surface of the recessed portion overlaps with the substantially central portion of the outer beam passage hole and the outer beam passage toward the central beam passage hole. An electron gun for a cathode ray tube, wherein an inner part of the hole is located on an inclined surface. 2. The electron gun for a cathode ray tube according to claim 1, wherein the central beam passage hole is formed to have a diameter smaller than that of the outer beam passage hole.