JP2000057963A - Electron gun for cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compose an electron gun having a short full length without increasing the number of part items or working man-hours, even if a large aperture lens is used as a main lens. SOLUTION: In this electron gun for a cathode-ray tube composed by forming a final acceleration electrode G5 composing a main lens in a skirted cylindrical shape having an enlarged diameter part on the phosphor screen side, and by forming a focusing electrode G4 into a stepped cylindrical shape comprising an enlarged diameter part positioned inside the enlarged diameter part of the final acceleration electrode G5 and a reduced diameter part elongated toward the cathode side through the inside of a reduced diameter part of the final acceleration electrode G5, and by installing a shield cup 20 on the phosphor screen side end part of the final acceleration electrode G5, the shield cup 20 is formed into a spherical shape having a convex face on the phosphor screen side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electron gun for a cathode ray tube, and more particularly to an electron gun for a cathode ray tube in which a shield cup is attached to a final acceleration electrode forming a main lens.

[0002]

2. Description of the Related Art Generally, a cathode ray tube is, as shown in FIG.
An electron beam 4 emitted from an electron gun 3 disposed in a cylindrical neck 2 of a funnel-shaped funnel 1 is deflected by a magnetic field generated by a deflecting device 5 mounted outside the funnel 1, and is deflected together with the funnel 1. The phosphor screen 7 provided on the inner surface of the panel 6 constituting the envelope is horizontally and vertically scanned to display an image.

There are various types of electron guns 3 such as a bipotential type and a unipotential type.
Each has a cathode and a plurality of electrodes sequentially arranged in the direction of the phosphor screen 7 from the cathode, and the cathode and the plurality of electrodes are integrally held by a pair of glass insulating support rods. Is formed.

As an example, FIG. 6 shows a unipotential type electron gun used for a projection tube for a video projector or the like which requires high focusing characteristics from a low current range to a high current range. This electron gun 3 has one cathode (not shown)
And five electrodes G1 to G5 sequentially arranged at predetermined intervals from the cathode in the direction of the phosphor screen. The first electrode G1 and the second control electrode G2 are cup-shaped electrodes, the first anode electrode G3 is a stepped cylindrical electrode, and the focusing electrode G4.
Is a cylindrical electrode, and the second anode electrode G5 (final acceleration electrode) is a cup-shaped electrode. A shield cup 7 is attached to an end of the second anode G5 on the phosphor screen side. These cathodes and five electrodes G1 to G
5 are held by a pair of insulating support rods 9 from both sides in one diameter direction via plate-like or linear support parts 8 attached to the respective outer surfaces.

In order to improve the resolution of a cathode ray tube, it is necessary to improve the lens performance of an electron gun and reduce the beam diameter. For this purpose, it is necessary to reduce the lens magnification or reduce the spherical aberration of the lens, and it is effective to increase the diameter of the main lens that finally focuses the electron beam on the phosphor screen. For that purpose, it is necessary to increase the diameters of the focusing electrode and the final acceleration electrode forming the main lens.

However, in the electron gun 3 as described above, a cathode and a plurality of electrodes G1 to G5 are held in a cylindrical neck by holding a pair of insulating support rods 9 from both sides in one diameter direction. Therefore, the size (diameter) of the electrode is limited by the inner diameter of the neck, and it is difficult to obtain a desired size required for increasing the diameter of the main lens.

In order to solve the above problem, as shown in FIG. 7, a cathode (not shown) and five electrodes G1 arranged sequentially from the cathode toward the phosphor screen.
Of the unipotential type electron gun having the following configuration, the second anode electrode G5 and the focusing electrode G4 forming the main lens are stepped cylinders each having a large diameter portion on the phosphor screen side and a small diameter portion on the cathode K side. And the focusing electrode G
4 is positioned inside the large diameter portion of the second anode electrode G5, and the small diameter portion of the focusing electrode G4 is extended to the cathode side through the inside of the small diameter portion of the second anode electrode G5. There is a structure in which a support portion 8 is attached to each of the small-diameter portions of the electrodes G4 and G5, and is held by a pair of insulating support bars 9 from both sides in one diameter direction.

In the electron gun 3, the second anode electrode G
As shown in FIG. 8, a disc-shaped shield cup 7 having an opening 11 in the center is attached to the inside of the phosphor screen side end of No. 5.

When the electron gun 3 is configured in this manner, the aperture of the focusing electrode G4 and the final accelerating electrode G5 can be maximized, and the main lens can be a large aperture lens. However, in such an electron gun 3, it is necessary to increase the distance between the shield cup 7 and the focusing electrode G4 in order to sufficiently exhibit the lens effect of the large-diameter lens.

This is because the shield cup 7 and the focusing electrode G4
Is small, the electric field of the main lens formed by the focusing electrode G4 and the final acceleration electrode G5 is distorted by the plate-shaped shield cup 7 having the same potential as that of the final acceleration electrode G5, and the characteristics of the large-diameter lens are reduced. This is because it is not sufficiently exhibited. Therefore, in order to sufficiently increase the distance between the shield cup 7 and the focusing electrode G4, such an electron gun 3 needs to have a longer overall length than the electron gun shown in FIG. As a result, the overall length of the cathode ray tube becomes longer.

Moreover, the shield cup 7 and the focusing electrode G4
As shown in FIG. 9, the second
If the diameter of the anode electrode G5 is increased, the accuracy of assembling the electrodes and the electron gun is reduced, and the cost is increased.

In order to increase the distance between the shield cup 7 and the focusing electrode G4, as shown in FIG. 10, a cylindrical electrode 1 having the same diameter as the large diameter portion is provided on the large diameter portion of the final acceleration electrode G5.
3 and the shield cup 7 is attached to the cylindrical electrode 13, not only increases the number of parts and the number of processing steps, but also deteriorates accuracy and workability.

[0013]

As described above, in order to improve the resolution of a cathode ray tube, a final accelerating electrode and a focusing electrode which form a main lens for finally focusing an electron beam on a phosphor screen are used. Each of the focusing electrodes is formed into a stepped cylindrical shape having a large diameter portion on the phosphor screen side and a small diameter portion on the cathode side, and the large diameter portion of the focusing electrode is positioned inside the large diameter portion of the final acceleration electrode. In some cases, the small-diameter portion extends to the cathode side through the inside of the small-diameter portion of the final acceleration electrode, and the main lens is a large-diameter lens.

However, when the main lens is a large-diameter lens as described above, in order to sufficiently exhibit the lens effect of the large-diameter lens, a shield cup attached to the end of the final acceleration electrode on the phosphor screen side is required. It is necessary to increase the distance between the electrode and the focusing electrode, and the overall length is longer than that of an electron gun whose main lens is not a large-diameter lens. As a result, the overall length of the cathode ray tube is longer.

In addition, if the diameter of the final accelerating electrode is increased in order to increase the distance between the shield cup and the focusing electrode, the accuracy of assembling the electrodes and the electron gun decreases, and the cost increases. In addition, if a cylindrical electrode with the same diameter as this large diameter part is attached to the large diameter part of the final accelerating electrode and a shield cup is attached to this cylindrical electrode, not only the number of parts and processing man-hours will increase, but also the accuracy will increase. However, there is a problem that workability is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. Even if the main lens is a large-diameter lens, the electron gun has a short overall length without increasing the number of parts, the number of processing steps and the cost. It is intended to constitute.

[0017]

(1) A final acceleration electrode for forming a main lens for finally converging an electron beam from a cathode onto a phosphor screen has a large diameter portion on the phosphor screen side and a large diameter on the cathode side. The focusing electrode, which is formed in a stepped cylindrical shape as a small part and forms a main lens together with the final acceleration electrode, has a large diameter part located inside the large diameter part of the final acceleration electrode, and a diameter of the final acceleration electrode from this large diameter part. It is formed in a stepped cylindrical shape consisting of a small diameter part extending to the cathode side through the inside of the small part, and the end of the large diameter part of the final acceleration electrode on the phosphor screen side end shields the getter from scattering to the cathode side. In the cathode ray electron gun to which the shield cup was attached, the shield cup was formed in a spherical shape having the phosphor screen side as a convex surface.

(2) In the cathode ray electron gun of (1), a side wall portion welded to the inner surface of the large diameter portion of the final acceleration electrode is provided around the spherical portion of the shield cup.

(3) In the cathode ray electron gun of (2), the side wall of the shield cup is formed by folding the peripheral portion of the spherical portion toward the phosphor screen.

(4) In the cathode ray electron gun of (3), the folded portion between the spherical portion and the side wall portion of the shield cup has a curved surface.

(5) In the cathode ray electron gun of (1), the center of the spherical portion of the shield cup protrudes toward the phosphor screen from the end of the large diameter portion of the final acceleration electrode on the phosphor screen side. .

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a unipotential type electron gun as one embodiment. This electron gun has one cathode (not shown) and five electrodes G1 to G5 sequentially arranged from the cathode toward the phosphor screen.

The first electrode G1 and the second control electrode G2 are cup-shaped electrodes, and the first anode electrode G3, the focusing electrode G4 and the second anode electrode G5 (final acceleration electrode) are respectively large in diameter on the phosphor screen side. And a stepped cylindrical electrode having a small diameter portion on the cathode side. The focusing electrode G4 that forms the main lens together with the second anode electrode G5 has a large-diameter portion located inside the large-diameter portion of the second anode electrode G5 and a small-diameter portion located at the second anode electrode G5.
5 extends to the cathode side through the inside of the small diameter portion. Further, at the end of the second anode electrode G5 on the phosphor screen side,
A shield cup 20, which will be described later, which shields the getter disposed on the phosphor screen side from the electron gun from flying toward the cathode side is attached.

The cathode and the five electrodes G
1 to G5 are held by a pair of insulating support rods 9 from both sides in one diameter direction via plate-like or linear support parts 8 attached to the respective outer surfaces. The support portions 8 of the focusing electrode G4 and the second anode electrode G5 are respectively attached to the outer surfaces of the small diameter portions.

As shown in FIG. 2, the shield cup 20 is formed in a spherical shape having a convex surface on the phosphor screen side, and an opening 22 through which an electron beam passes is formed in the center of the spherical portion 21. I have. Also, this spherical portion 21
Is formed by folding back in the direction of the phosphor screen, which is fitted and welded to the inside of the phosphor screen side end of the second anode electrode G5. The folded portion has an appropriate radius (R). The height of the side wall portion 23 from the turn-back portion is lower than the height of the center of the spherical portion 21. When the side wall portion 23 is welded to the second anode electrode G5, the center of the spherical portion 21 becomes the second anode electrode G5. The electrode G5 protrudes toward the phosphor screen from the phosphor screen side end.

When the electron gun is configured as described above, the diameter of the focusing electrode G4 and the second anode electrode G5 is increased, and even if the diameter of the main lens formed by these electrodes G4 and G5 is increased, the number of parts and the number of processings are increased. An electron gun with a short overall length can be configured without increasing man-hours and costs.

In other words, when the diameter of the final acceleration electrode is increased and the phosphor screen side of the focusing electrode is inserted inside the final acceleration electrode to make the main lens a large-diameter lens, the conventional lens shown in FIG. When the shield cup 7 disposed at the end of the final acceleration electrode G5 on the side of the phosphor screen like an electron gun is formed in a disk shape, the shield cup 7 approaches the end of the focusing electrode G4 on the side of the phosphor screen, Since the surface facing the focusing electrode G4 is flat, the electric field of the main lens by the shield cup 7 becomes U-shaped in the direction of the phosphor screen, and the electric field of the main lens is distorted. The effect of the shield cup 7 on the electric field of the main lens becomes greater as the distance between the shield cup 7 and the focusing electrode G4 becomes smaller, and the characteristics of the large-aperture lens cannot be sufficiently exhibited.

However, if the shield cup 20 has a spherical shape with the phosphor screen side as a convex surface as in the electron gun of this embodiment, the spherical portion 21 is formed by the focusing electrode G4 and the final accelerating electrode G5. The shield cup 20 is connected to the focusing electrode G4
, The electric field of the main lens can be reduced. Therefore, FIG.
As shown in FIG. 10 and FIG. 10, the large diameter portion of the final acceleration electrode does not need to be particularly long,
5, the central portion of the spherical portion 21 of the shield cup 20 is made to protrude more toward the phosphor screen than the phosphor screen side end of the second anode electrode G5. Can be configured.

Further, even if the large diameter portion of the second anode electrode G5 is lengthened so that the influence of the shield cup 20 on the main lens electric field is completely eliminated, it is not necessary to greatly increase the large diameter portion. Can also be an electron gun having a short overall length.

As an example, FIG. 3A shows an electron gun of this embodiment in which the distance between the shield cup 20 and the focusing electrode G4 is the same, and FIG. 3B shows a conventional electron gun in comparison. . As is apparent from these figures, the distance a between the shield cup 20 and the focusing electrode G4 of the electron gun according to this embodiment is a.
If the distance b between the shield cup 7 of the conventional electron gun and the focusing electrode G4 is the same (a = b), the electron gun of this embodiment has a larger shielding cup 7 than the conventional electron gun. The overall length is shortened by the height. As a result of the experiment, when the focus performance was the same, the total length was 1
It was confirmed that it could be shortened by about 0%. Furthermore, the area of the electron beam emitting end is 20 to 30% smaller than that of the conventional electron gun.
It was confirmed that the influence of the eddy current caused by coupling with the rear leakage magnetic field of the deflection device was reduced by about 10%.

FIG. 4A shows an electron gun of this embodiment having the same overall length, and FIG. 4B shows a comparison of a conventional electron gun. When the total length is the same, in the electron gun of this embodiment, the distance a between the shield cup 20 and the focusing electrode G4 is about 10% larger than the distance b of the conventional electron gun. Moreover, in the electron gun of this embodiment, the shape of the spherical portion 21 of the shield cup 20 is different from that of the focusing electrode G4.
And the second anode electrode G5 have substantially the same shape as the electric field of the main lens, so that the influence on the distortion of the main lens is small, and the focus performance is 5 times as compared with the conventional electron gun.
It was confirmed as a result of the experiment that it was improved by about 10%.

Although the above embodiment has been described with reference to a unipotential electron gun, the present invention can be applied to other electron guns such as a bipotential electron gun.

The present invention is applicable not only to an electron gun emitting a single electron beam but also to a color image receiving electron gun emitting a plurality of beams.

[0035]

As described above, even if the diameter of the final acceleration electrode forming the main lens together with the focusing electrode is increased, the shield cup attached to the end of the final acceleration electrode on the phosphor screen side can be used. Is formed into a spherical shape having a convex surface, an electron gun having a short overall length can be configured without increasing the number of parts and the number of processing steps and the cost.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a unipotential type electron gun according to an embodiment of the present invention.

FIG. 2A is a plan view showing a shape of a shield cup of the electron gun, and FIG. 2B is a side view shown in cross section.

FIGS. 3 (a) and 3 (b) are comparison diagrams of the electron gun of this embodiment, in which the distance between the shield cup and the focusing electrode is the same, and a conventional electron gun, respectively. Is an electron gun of this embodiment, and FIG. 3B is a diagram of a conventional electron gun.

FIGS. 4 (a) and 4 (b) are comparison diagrams of an electron gun of this embodiment having the same overall length and a conventional electron gun, and FIG. 4 (a) is an electron gun of this embodiment. Gun, figure 4
(B) is a diagram of a conventional electron gun.

FIG. 5 is a diagram showing a configuration of a cathode ray tube.

FIG. 6 is a diagram showing a configuration of a normal unipotential type electron gun of a cathode ray tube.

FIG. 7 is a diagram showing a configuration of a conventional unipotential electron gun in which the diameter of a main lens is increased.

FIG. 8A is a plan view showing a shape of a shield cup of the conventional unipotential type electron gun, and FIG.
Is a side view shown in cross section.

FIG. 9 is a diagram for explaining a problem when a large diameter portion of a second anode electrode of a conventional unipotential electron gun in which the diameter of a main lens is increased is long.

FIG. 10 is a view for explaining a problem when a large-diameter portion of a second anode electrode of a conventional unipotential electron gun in which the diameter of the main lens is increased is also increased.

[Explanation of symbols]

 Reference Signs List 20 shield cup 21 spherical portion 23 side wall G4 focusing electrode G5 second anode electrode

Claims (5)

[Claims] 1. A step in which a final acceleration electrode for forming a main lens for finally focusing an electron beam from a cathode onto a phosphor screen has a large-diameter portion on the phosphor screen side and a small-diameter portion on the cathode side. A focusing electrode which is formed in a cylindrical shape and forms a main lens together with the final acceleration electrode has a large-diameter portion located inside the large-diameter portion of the final acceleration electrode and a small-diameter portion of the final acceleration electrode from the large-diameter portion. It is formed in a stepped cylindrical shape consisting of a small-diameter portion extending to the cathode side through the inside, and the end of the large-diameter portion of the final acceleration electrode on the phosphor screen side end is shielded from scattering of the getter to the cathode side. An electron gun for a cathode ray tube, wherein the shield cup is formed in a spherical shape having a convex surface on the phosphor screen side. 2. The electron gun for a cathode ray tube according to claim 1, wherein a side wall portion welded to an inner surface of a large diameter portion of the final acceleration electrode is provided around a spherical portion of the shield cup. . 3. The electron gun for a cathode ray tube according to claim 2, wherein the side wall of the shield cup is formed by folding a peripheral portion of the spherical portion toward the phosphor screen. 4. The electron gun for a cathode ray tube according to claim 3, wherein the folded portion between the spherical portion and the side wall of the shield cup has a curved surface. 5. The cathode ray tube according to claim 1, wherein the center of the spherical portion of the shield cup projects more toward the phosphor screen than the end of the final acceleration electrode on the phosphor screen side where the diameter is large. Electron gun.