KR19980059947A - Electron gun for colored cathode ray tube - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun for a color cathode ray tube, and is capable of improving the resolution by suppressing beam distortion caused by the use of an asymmetric main lens.

The present invention provides a cathode for emitting electrons, a first grid and a second grid for controlling and accelerating an electron beam emitted from the cathode, and a third grid and a fourth grid for focusing and accelerating the electron beam to focus on a screen. In the electron gun for a color cathode ray tube composed of a grid, the opposing surface of the third grid and the fourth grid as a common opening through the beam barrel, and the internal electrode is provided inside the third grid and the fourth grid, the common opening inside the fourth grid The correction electrode having a pair of parallel plates is provided so that the distance from the electron beam to the correction electrode is shorter at the outer edge of the electron beam than at the electron beam center.

Description

Electron gun for colored cathode ray tube

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron gun for color cathode ray tubes, and particularly, to suppress distortion of an electron beam shape caused by the use of non-axisymmetric main lenses so as to improve screen resolution.

In general, the color cathode ray tube is divided into a panel (1), a funnel-shaped funnel (2), a neck (Neck) (3) formed in the funnel is divided into large as shown in FIG. It consists of the electron gun 5 and the deflection yoke 4 provided in the said neck part.

FIG. 2 is a cross-sectional view of a Bi Potential Focusing (BPF) electron gun, which is a form of an inline electron gun used in a color cathode ray tube, wherein the electron gun includes a plurality of cathodes 10 incorporating a heater and a screen orientation at the cathodes. It consists of a plurality of electrodes 11, 12, 13, 14 arranged at regular intervals vertically.

Therefore, when a heater in each cathode 10 receives power from the stem pin 7 and generates heat, hot electrons are radiated from the cathode by this heat, and the emitted electron beam 6 is a first grid (also called a control electrode) 11. And the beam forming region (Beam Forming Reging) consisting of the lower end of the second grid (also called the first acceleration electrode) 12 and the third grid (also called the focusing electrode) 13 is controlled and accelerated. The electron beam is focused and accelerated by a bi-potential electrostatic lens formed by a voltage difference applied to the third grid 13 and the fourth grid (also called an acceleration electrode) 14. do.

The electron beam passing through the electrostatic lens, which is the main lens of the electron gun, is determined by the influence of the magnetic field formed by the strength of the current applied to the deflection yoke 4, and the electron beam traveling along the determined path is shadowed in front of the fluorescent surface. After passing through the mask 8, the light impinges upon the fluorescent surface 9 to emit light.

Also, in order to make the three electron beams implementing the RGB three colors coincide with the center of the screen, the ball passing through the outer beams (electron beams implementing the blue and red colors) passes through the electrodes constituting the electrostatic lens (the third and fourth grids). Iv) Offset, or in another suitable way, the electrostatic lens is configured to direct the path of the outer beam towards the center beam (electron beam that implements green).

On the other hand, self-convergence deflection yoke is also used to match the RG, B color beams in front of the screen in the in-line gun, and the self-convergence deflection yoke is a pincushion in the horizontal direction. Since the magnetic field of the pin-cushion is formed and the barrel magnetic field is formed in the vertical direction, the three electron beams coincide in the front of the screen by the magnetic field formation.

At this time, each of the RG and B electron beams is diverged in the horizontal direction and focused in the vertical direction by the magnetic field as described above, and accordingly, the halo is concentrated in the vertical direction by the geometry of the panel 1. Halo) phenomenon.

In order to eliminate the increase of astigmatism in the negative direction at the periphery of the screen according to the above-mentioned halo phenomenon, the asymmetry of the electron gun is asymmetrical so that the astigmatism has a positive value at the center of the screen. Even if the astigmatism in E is negative, the absolute value is reduced, so that the resolution of the entire screen can be improved.

The size of the main lens used to cause the electron beam to form a small spot on the screen, that is, the size of the main lens formed by the voltage difference between the third grid 14 and the fourth grid 15 is the neck (3). ) Is large left and right in diameter.

It is well known that the larger the size of the balls facing each other of the third grid 13 and the fourth grid 14 forming the main lens to allow electron beams to pass through, smaller spots are formed on the screen. This is due to the reduction in magnification.

In general, the in-line electron gun passes through the respective balls of the third grid 13 and the fourth grid 14 with an electron beam of R.G.B at a constant diameter of the neck 3.

Therefore, as shown in FIG. 3, when the balls formed on the opposite surfaces of the third grid 13 and the fourth grid 14 are retracted inward, the substantial size of the three independent main lenses through which the RGB electron beam passes can be increased. With this structure, smaller spots can be obtained on the screen by reducing the magnification while reducing the spherical aberration of the lens.

In addition, the correction electrode 16 shown in FIG. 4 installed in the fourth grid 14 has the astigmatism by increasing the just focus voltage in the horizontal direction and the just focus voltage in the vertical direction when the structure and the self-convergence deflection yoke are used. It serves to correct.

FIG. 5 is a cross-sectional view illustrating the internal electrodes 15 installed in the third grid 13 and the fourth grid 14 in the configuration of the electron gun shown in FIG. 3, wherein the internal electrodes have a rectangular shape and have an electron beam. A hole is formed so that it can pass.

As described above, since the internal electrodes have a longer length in the diagonal direction than the horizontal and vertical lengths, the just focus voltage in the diagonal direction of the spot on the screen is the lowest and the size of the spot in the diagonal direction is the largest.

That is, a spot as shown in Figure 6 is formed, which appeared as a simulation result.

Thus, the largest spot in the diagonal direction results in degradation of the resolution.

It is an object of the present invention to obtain improved resolution by improving the shape of the beam spot generated by the asymmetric geometry used to form larger main lenses.

In an embodiment of the present invention for achieving the above object, the opposing surfaces of the third grid and the fourth grid are formed by the beam opening and the common opening to install an internal electrode in one of them, and astigmatism in the acceleration electrode. An electron gun for a color cathode ray tube provided with a correction electrode for correction is provided.

1 is a block diagram of a typical color cathode ray tube

2 is a cross-sectional view of a typical in-line type BPF gun.

3 is a cross-sectional view of a conventional inline BF electron gun equipped with a correction electrode;

4 is a cross-sectional view of the correction electrode shown in FIG.

5 is a cross-sectional view of the internal electrode shown in FIG.

6 is an enlarged view showing a spot shape when using a conventional correction electrode

7 is a cross-sectional view of the inline BF electron gun according to the present invention.

8 is a cross-sectional view of the correction electrode shown in FIG.

9 is a cross-sectional view showing another embodiment of a correction electrode;

10 is an enlarged view showing a spot shape when using the correction electrode according to the present invention

Explanation of symbols for main parts of the drawings

13: Fourth Grid 13: Fourth Grid

15: internal electrode 20, 21: correction electrode

7 is a cross-sectional view of an electron gun showing an embodiment of the present invention, in which the electron gun emits hot electrons, and the first and second grids 11 and 12 control and accelerate the electron beam emitted from the cathode. And a third grid 13 and a fourth grid 14 constituting a bi-type lens for focusing and accelerating the electron beam so as to focus on a screen coated with a fluorescent surface. It consists of an internal electrode 15 provided in four grids, and a correction electrode 20 provided in said fourth grid.

The opposing surface of the third grid 13 and the fourth grid 14 has a beam opening and a common opening, and the internal electrode 15 is provided at a predetermined position in the third grid and the fourth grid.

As shown in FIG. 8, the correction electrode 20 forms a U-shaped cross-sectional phenomenon, and the top and bottom pairs of parallel plates form an uneven shape 20a.

Therefore, the distance from the common opening to the correction electrode 20 is shorter at the outside of the electron beam than at the center of the electron beam.

9 is a view showing another embodiment of the correction electrode to be applied to the present invention, the correction electrode 21 is a c-shaped cross-sectional shape and a pair of parallel plate front end is a concave-convex shape (21a).

However, in the embodiment of FIG. 8, the protrusions are arc-shaped, in contrast to the uneven protrusions.

As described above, the main lens of the electron gun of the present invention includes the internal electrode 15 installed in the third grid 13 and the fourth grid 14, the correction electrode 20 provided in the fourth grid, and the third grid and the third lens. The propagation and aberration is determined by the beam opening and the common opening formed opposite the four grids.

Therefore, the main lens causes negative astigmatism due to the structure and the dimensions of the internal electrodes 15 and the third and fourth grids 13 and 14 provided in the third and fourth grids 13 and 14. In this case, the correction electrodes 20 and 21 in the fourth grid 14 have positive astigmatism. In this case, the internal electrode 15 is shaped as shown in FIG. 5 so that the electron beam just focus voltage in the diagonal direction is increased. The lowest and diagonal focus is the weakest, resulting in the largest beam size on the screen.

However, since the uneven type parallel plates are formed in the correction electrodes 20 and 21 according to the present invention so that the distance from the common opening of the electrode is long at the center of the electron beam and short at the outer edge, the diverging action of the electron beam is most strongly in the vertical direction. In the diagonal direction, it is weaker than the conventional correction electrode, so that the just focus voltage in the vertical direction can be the lowest.

Therefore, when the length from the inline axis to the outside of the beam spot is at the center of the electron beam, it is possible to obtain a good spot shape as shown in FIG. 10 simulating the spot shape.

The present invention can form the uneven shape on the parallel plate on the correction electrode provided in the fourth grid as described above, so that the just focus voltage in the vertical direction can be the lowest, so that the length from the inline axis to the outside of the beam spot is centered on the electron beam. In this case, since the beam distortion is suppressed to the greatest extent, the screen resolution is greatly improved.

Claims (2)

A color consisting of a cathode to which electrons are emitted, a first grid and a second grid to control and accelerate the electron beam emitted from the cathode, and a third grid and a fourth grid to focus and accelerate the electron beam to focus on a screen. In the electron gun for cathode ray tube, the opposite surface of the third grid and the fourth grid is the common opening with the beam barrel, and the distance from the common opening to the correction electrode is within the third grid and the fourth grid at the center of the electron beam than at the outside of the battery beam. An electron gun for a color cathode ray tube, characterized in that a correction electrode having a pair of equilibrium plates is provided so as to be short. The electron gun for color cathode ray tubes according to claim 1, wherein an uneven shape is formed in a parallel plate so that the distance from the common opening to the correction electrode is different from the center of the electron beam.