JPH0127252Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a cathode ray tube electron gun equipped with an electromagnetic deflection device.

In order to facilitate understanding of the present invention, a conventionally used color cathode ray tube in-line electron gun will be explained. FIG. 1 is a longitudinal sectional view of a color cathode ray tube using an in-line electron gun. The three in-line electron beams emitted from the in-line electron gun 1 are aligned on a straight line and lie in the same plane, and the three in-line electron beams emitted from the in-line electron gun 1 are placed in an electromagnetic deflection device (hereinafter referred to as A phosphor surface is deflected horizontally and vertically by a deflection yoke 5, and on the front part of the glass envelope 2, a plurality of phosphor elements emitting red, green, and blue are coated on the inside thereof. A scanning screen is formed on 3. A color selection mechanism consisting of a perforated mask 4 is disposed within this tube adjacent to the phosphor surface 3 so that each scanning electron beam stimulates only the phosphor elements of the color corresponding to the respective electron beam. .

Figure 2 shows, as an example, the configuration of an in-line electron gun used in the above-mentioned color cathode ray tube, in which the main electron lens adopts a bipotential focus method, and the electrode structures are insulated from each other and spaced at equal intervals. Three cathode assemblies 11 arranged in a line while keeping a distance from each other, and a G1 electrode 12, a G2 electrode 13, and a G3 electrode arranged in sequence in the electron beam traveling direction facing the cathode structures 11.
Consisting of an electrode 14, a G4 electrode 15, and a shielding magnetic pole 16, each electrode except the shielding magnetic pole 16 is fused and fixed to an insulator support rod 17 via each electrode support part, and a predetermined electrode spacing is maintained. keeping. In this case, the G3 electrode 14 and the G4 electrode 15 form a bipotential focus lens which is the main electron lens.

A static convergence device 6 is disposed on the deflection yoke 5 side of the electron gun assembly 1, which is sealed in the neck part following the funnel-shaped part of the glass envelope 2. It is designed to correct small errors in the center of the optical surface. Furthermore, a color purification device 7 is arranged adjacent to the static convergence device 6 to correct the three electron beams so that they correctly stimulate the phosphor elements of the corresponding colors. The three electron beams emitted from the electron gun assembly 1 are corrected by an electron beam position correction device and a deflection yoke 5 that generates a magnetic field distribution in which the horizontal deflection magnetic field has pincushion distortion and the vertical deflection magnetic field has barrel distortion. By combining these, a reproduced image in which images of three colors are correctly superimposed can be obtained.

However, in order to achieve high resolution of the synthesized reproduced image, it is necessary to focus the electron beam narrowly with the main electron lens of the electron gun assembly 1, and for this purpose, the main electron lens has a structure with low aberrations and low image formation against spherical aberrations, etc. High performance focusing characteristics with magnification, long focal length, etc. are required. Conventionally, various improvements and improvements have been made to these. However, even if the characteristics of the main electron lens described above are improved, the influence of the leakage magnetic field at the rear end of the deflection yoke 5 on the electron lens is a factor that deteriorates the focusing characteristics of the electron lens. That is, as shown in FIG. 1, the leakage magnetic field 51 at the rear end of the deflection yoke 5 enters the G4 electrode 15, the G3 electrode 14, which forms the main electron lens electric field, and the gap between the two electrodes, and the magnetic field acts on the electron beam. This disturbs the path of the electron beam determined by the electric field of the main electron lens, causes aberrations in the main electron lens due to the magnetic field, and degrades resolution. Particularly when the electron beam current is large, the aberration of the electron lens causes a faint halo to appear around the electron beam spot, significantly deteriorating the resolution.

The object of the present invention is to provide a high-performance cathode ray tube electron gun assembly that eliminates the above-mentioned drawbacks.

In order to prevent the leakage magnetic field from the rear end of the deflection yoke from entering the electric field of the main electron lens, the main electron lens electrode and the gap therebetween, which are close to the deflection yoke side opposite to the electron beam exit side, are magnetically , and includes means for electrostatically shielding.

FIG. 3 is a configuration diagram of an electron gun electrode assembly 10 showing an embodiment of the present invention. Hereinafter, for the purpose of simplifying the explanation, the same reference numerals are given to the same parts as in the prior art. 1
8 is a magnetic shielding plate formed in an annular shape from a conductive and high permeability magnetic material such as permalloy, which is an iron-nickel alloy, and G4 electrode 15, G3 forming a main electron lens of a bi-potential focusing system. It covers a part of the side of the electrode 14 facing the G4 electrode 15 and the periphery of the gap between the two electrodes, and is fixed to the cylindrical side near the bottom of the shielding magnetic pole 16.

According to this embodiment, the main electron lens electric field is formed.
Since the G4 electrode 15, the G3 electrode 14, and the gap between the electrodes are comprehensively covered with the magnetic shielding plate 18, the rear end leakage magnetic field 51 of the deflection yoke 5 does not enter into the main electron lens electric field. Therefore, the influence of extra magnetic field is removed from the electron beam, and the original function of the main electron lens is fully demonstrated, and the resolution of the reproduced image on the fluorescent surface will not deteriorate due to the formation of a halo at high currents. It disappears.

Furthermore, since the gap between the G4 electrode 15 and the G3 electrode 14 is covered with a conductive magnetic material, it has a shielding effect against external electric fields penetrating the main electron lens electric field, and the sealed glass outer envelope of the electron gun assembly 10 has a shielding effect. The penetration of the unstable electric field formed by the charges on the inner wall of the neck part of the vessel 2 is electrostatically shielded, and the effect of simultaneously preventing changes in convergence over time, where the reproduced image in which three colors are superimposed shifts over time. Also have.

Although the above description has been made regarding an electron gun in which the main electron lens is of a bi-potential focus type, it goes without saying that the present invention can also be applied to an electron gun assembly having a main electron lens of other types.

As described above, according to the present invention, the main electron lens electrode near the deflection yoke side opposite to the electron beam exit side;
And the gap between the electrodes can be comprehensively shielded magnetically and electrostatically from the leakage magnetic field at the rear end of the deflection yoke by using a conductive magnetic material, so that the characteristics of the electron lens do not deteriorate, and in the case of color cathode ray tubes, the convergence Changes over time can also be prevented.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of a color cathode ray tube, Fig. 2 is a side view of a bipotential focus type electron gun assembly used in a color cathode ray tube, and Fig. 3 is an electron gun assembly showing an embodiment of the present invention. FIG. DESCRIPTION OF SYMBOLS 1... In-line electron gun structure, 2... Glass envelope, 3... Fluorescent surface, 5... Deflection yoke, 51...
...Deflection yoke rear end leakage magnetic field, 14...G3 electrode,
15...G4 electrode, 18...magnetic shielding plate.

Claims (1)

[Scope of utility model registration request] The main electron lens forming electrode near the deflection yoke side opposite to the electron beam exit side and the periphery of the electrode gap are comprehensively magnetically and electrostatically shielded with a conductive magnetic material fixed to the electron gun electrode structure. Characteristic cathode ray tube electron gun structure.