KR100447150B1 - Electron gun for color 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 to improve 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 color cathode ray tube composed of a grid, the opposing surface of the third grid and the fourth grid as a common opening with the beam barrel, and the internal electrode is provided in the third grid and the fourth grid, the common opening in 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 outside of the electron beam than at the center of the electron beam.

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), and 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 a beam forming region composed of a lower end of the second grid (also called first accelerating electrode) 12 and the third grid (also called focusing electrode) 13 The electron beam is focused and accelerated by a Bi-Potential Electro-Static Lens formed by a voltage difference applied to the third grid 13 and the fourth grid (also referred to as the 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 provided with a shadow provided 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, a hole through which the outer beams (electron beams implementing the blue and red colors) pass through the electrodes (the third grid and the fourth grid) constituting the electrostatic lens ( Iv) Offset or, alternatively, configure the electrostatic lens to direct the path of the outer beam towards the center beam (green electron beam).

On the other hand, self-convergence deflection yoke is also used to match the electron beam, which realizes the color of RGB in the inline electron gun, in front of the screen, and this self-convergence deflection yoke is a pincushion in the horizontal direction. Since the magnetic field of the 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.

In this case, each of the RGB 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 over-focused in the vertical direction by the geometry of the panel 1. The phenomenon appears.

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 13 and the fourth grid 14 is the neck (3). ) Is largely left and right in diameter.

It is a known fact 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, in-line electron guns have a constant diameter of the neck 3 and an electron beam of R.G.B passes through each ball of the third grid 13 and the fourth grid 14.

Therefore, as shown in FIG. 3, when the ball of the opposing surfaces of the third grid 13 and the fourth grid 14 is formed by retreating to the inside, 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 provided 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 composed of a beam opening and a 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.

7 is a cross-sectional view of an electron gun showing an embodiment of the present invention, in which an electron gun emits hot electrons, a first grid 11 and a second grid 12 that control and accelerate an electron beam emitted from the cathode. And a third grid 13 and a fourth grid 14 constituting a bi-shaped lens for focusing and accelerating the electrons to focus on a screen coated with a fluorescent surface. It consists of the internal electrode 15 provided in the 4th grid, and the correction electrode 20 provided in the 4th grid.

The opposing surfaces of the third grid 13 and the fourth grid 14 have 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 applied to the present invention, the correction electrode 20 forms a cross-sectional shape of the c-shaped cross-section and the pair of flat plate forms a concave-convex shape (21a).

In the embodiment of FIG. 8, the uneven shape 21a of this embodiment has a circular arc shape, whereas the uneven shape 20a is straight.

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

Thus, the third grid 13 and the fourth grid

The correction electrode in the fourth grid 14 when the main lens has negative astigmatism due to the structure and dimensions of the internal electrodes 15 and the third and fourth grids 13 and 14 provided in the rod 14. 20 may have a positive astigmatism. At this time, the internal electrode 15 has a shape as shown in FIG. 5, so that the electron beam just focus voltage in the diagonal direction is the lowest and the focus in the diagonal direction is the weakest. The beam size in the direction will be the largest.

However, in the correction electrode 20 applied to the present invention, since the concave-convex parallel plate is formed 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 the strongest in the vertical direction and diagonal direction. As a result, it is possible to make the just focus voltage in the vertical direction lower than that of the conventional correction electrode.

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 of 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. Since the beam distortion is suppressed at the most, the resolution of the screen is greatly improved.

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

2 is a cross-sectional view of a typical in-line BPF electron 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 phenomenon when using the correction electrode according to the present invention

Explanation of symbols for main parts of the drawings

13: third grid 14: fourth grid

15: internal electrode 20, 21: correction electrode

Claims (1)

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, And a correction electrode having opposing surfaces of the third grid and the fourth grid as a common opening with the beam barrel, and having internal electrodes disposed inside the third grid and the fourth grid, and having a pair of parallel plates formed up and down. In the electron gun for color cathode ray tube installed in the grid, And a concave-convex shape at the tip of each parallel plate of the correction electrode so that the distance from the common opening to the correction electrode is different from the center of the electron beam.