KR19990024966A - 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 using an asymmetric main lens, so that the beam distortion phenomenon can be suppressed in an electron gun using an asymmetric main lens to improve the resolution over the entire area of the screen.

To this end, the cathodes to which electrons are emitted, the first and second grids 10 and 11 for controlling and accelerating the amount of electron beams emitted from the cathodes, and the accelerated electron beams are focused and reworked so that spots are formed on the screen. Correction for correcting astigmatism by fixing to the third and fourth grids 12 and 13, the internal electrodes 16 installed in the third and fourth grids, and the shield cup to be positioned in the fourth grid. In an electron gun for a color cathode ray tube composed of electrodes, an electron beam passage hole is formed by forming a step portion 19 recessed into the electron beam through hole sides 18a, 18b, and 18c on one side of the correction electrode on the correction electrode 17. The key is configured to have a hole shape.

Description

Electron gun for colored cathode ray tube

The present invention relates to an electron gun for a color cathode ray tube, and more particularly to an electron gun for a color cathode ray tube using a non-axisymmetric main lens.

FIG. 1 is a cross-sectional view showing a general color cathode ray tube, in which red, green, and blue phosphors are applied to an inner surface of a panel 1 to form a phosphor film 2, and a neck portion 3a behind the panel 1. ), The funnel (3) in which the electron gun (4) is encapsulated is fused by the glass to maintain a high vacuum of about 10 ^-7 Torr.

A shadow mask 6, which serves as color screening of the electron beam 5 emitted from the electron gun 4, is fixed to the support frame 7 at a portion adjacent to the fluorescent film 2 coated on the inner surface of the panel 1. It is installed as it is.

FIG. 2 illustrates a BPF type electron gun of the inline electron gun used in the color cathode ray tube as shown in FIG. 1.

When the heater 8 installed inside the cathode of the electron gun receives power from the stem pin 9 and generates heat, hot electrons are radiated from the cathode, so the radiated electron beam 5 is vertically spaced vertically from the cathode in the screen direction. Accelerated and focused while passing through the holes of the plurality of electrodes provided to reach the fluorescent film (2).

The process of the electron beam starting from the cathode reaching the screen will be described in detail as follows.

The electron beam 5 emitted from the cathode of the electron gun has a first grid (also called a control electrode) 10, a second grid (also called a first accelerating electrode) 11, and a third grid (also called a focused electrode) 12 It is properly controlled and accelerated while passing through a beam forming region composed of the lower end of the beam.

The electron beam 5 then uses a bi-potential electrostatic lens formed by the voltage difference applied to the third grid 12 and the fourth grid (also called the acceleration electrode) 13. Focused and accelerated while passing.

The electron beam passing through the electrostatic lens, which is the main lens of the electron gun 4, has its path determined due to the magnetic field effect of the deflection yoke 14 installed in the neck portion 3a, and then proceeds along the path, thereby providing a shadow placed close to the fluorescent surface. After passing through the mask 6, the screen is reproduced by colliding with the fluorescent film 2.

When the screen is reproduced by the above-described process, the electrostatic lens is configured so that the three electron beams 5 that implement the colors of blue, green, and red coincide at the center of the screen. Offset the electron beam passing hole through which the outer beam (blue and red electron beam) passes through the electrode, or in another suitable way, direct the path of the outer beam toward the center beam (green electron beam). An electrostatic lens is formed.

In addition, the self-convergence deflection yoke 14 is used to match the electron beam 5 that implements the colors of blue, green, and red in the in-line electron gun over the entire area of the screen.

The deflection yoke 14 is formed by forming a pin-cushion in the horizontal direction and a barrel magnetic field in the vertical direction to match the three electron beams 5 over the entire area of the screen. .

At this time, the three electron beams (blue, green, red) are diverged in the horizontal direction of the electron beam by the above-described magnetic field and subjected to a focusing force in the vertical direction, but the vertical direction is caused by the geometry of the panel (1). This results in a halo phenomenon that is overfocused.

Therefore, in order to eliminate the phenomenon that the astigmatism increases in the negative direction, the asymmetry of the electron gun is asymmetrical so that the astigmatism takes a positive value in the center of the screen. Although the astigmatism value in the periphery is negative, the absolute value is reduced so that the resolution is improved in all areas of the screen.

In addition, the size of the main lens formed by the voltage difference between the third grid 12 and the fourth grid 13 used to cause the three electron beams 5 to form a small spot on the screen is the neck portion 3a. Depends largely on the diameter of

As the three electron beams 5 pass through, the larger the size of the electron beam through holes facing each other of the third grid 12 and the fourth grid 13 forming the main lens, the smaller the spot is formed on the screen. It is a well known fact.

This is because spherical aberration and magnification are reduced.

In general, the inline electron gun allows three electron beams 5 to pass through respective electron beam passing holes of the third grid 12 and the fourth grid 13 provided at the diameter of the constant neck portion 3a.

Therefore, the three independent main lenses through which the three electron beams 5 pass are retracted to the inner side of the electron beam through-holes on the opposite surface, as shown in FIG.

As a result, the spherical aberration of the lens can be reduced and the magnification can be reduced, so that a smaller spot can be obtained on the screen.

3, the correction electrode 15 provided in the fourth grid 13 serves to correct astigmatism generated when the above structure and the self-convergence deflection yoke 14 are used.

That is, it serves to raise the just focus voltage in the horizontal direction and to lower the just focus voltage in the vertical direction.

As shown in FIG. 4, since the rectangular internal electrode 16 has a longer length in the diagonal direction than the horizontal and vertical lengths, a spot as shown in FIG. 5 is formed on the screen.

FIG. 5 illustrates a simulation of spots formed on the screen when the internal electrodes 16 are installed in the third grid 12 and the fourth grid 13.

That is, since the just focus voltage in the diagonal direction of the spot is the lowest, the size of the spot becomes the largest in the diagonal direction of the spot, which indicates a problem in that the largest spot in the diagonal direction causes resolution deterioration.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem in the related art, and an object thereof is to suppress beam distortion in an electron gun using an asymmetric main lens and to improve resolution over the entire area of the screen.

According to an aspect of the present invention for achieving the above object, a spot is formed on the screen of the cathode, the first and second grids for controlling and accelerating the amount of electron beam emitted from the cathode, and the accelerated electron beam A color cathode ray composed of a third and fourth grid for focusing and re-accelerating, an internal electrode installed inside the third and fourth grid, and a correction electrode fixed to a shield cup to be positioned in the fourth grid to correct astigmatism In the conventional electron gun, there is provided an electron gun for a color cathode ray tube configured to form a step portion recessed from one side of the correction electrode to the electron beam passing hole side in the correction electrode so that the electron beam passing hole has a keyhole shape as a whole.

1 is a cross-sectional view showing a typical colored cathode ray tube

Figure 2 is a cross-sectional view and a longitudinal cross-sectional view showing an embodiment of a conventional in-line BPF electron gun.

Figure 3 is a cross-sectional view and a longitudinal cross-sectional view showing another embodiment of a conventional in-line BPF electron gun.

4 is a perspective view illustrating an internal electrode installed in FIG. 3;

5 is a spot shape when using a conventional internal electrode

6 is a cross-sectional view and a longitudinal cross-sectional view showing one embodiment of the present invention in-line BPF electron gun.

Figure 7 is a front view and a cross-sectional view showing an embodiment of the correction electrode applied to the present invention

Figure 8 is a front view and a cross-sectional view showing another embodiment of the correction electrode applied to the present invention

Figure 9 is a front view and a cross-sectional view showing another embodiment of the correction electrode applied to the present invention

Figure 10 is a spot shape when using the correction electrode of the present invention

Explanation of symbols for main parts of the drawings

10: first grid 11: second grid

12: third grid 13: fourth grid

16: internal electrode 17: correction electrode

18a, 18b, 18c: electron beam passing hole 19: stepped portion

Hereinafter, the present invention will be described in more detail with reference to FIGS. 6 and 7 as an embodiment.

6 is a cross-sectional view and a longitudinal cross-sectional view showing an embodiment of the present invention in-line BPF electron gun and Figure 7 is a front view and a cross-sectional view showing an embodiment of the correction electrode applied to the present invention, The same parts will be omitted and the same reference numerals will be given.

According to the present invention, the length of the electrode to the in-line axis increases from the electron beam through hole center toward the outer direction of the electron beam through hole, and the correction electrode 17 corrects astigmatism in the shield cup so as to be positioned in the fourth grid 13. Is fixed.

The correction electrode 17 forms electron beam through holes 18a, 18b and 18c in a plate electrode having a predetermined thickness, and forms square stepped portions 19 having a predetermined depth symmetrically about the electron beam through holes. .

The stepped portion 19 is formed in the horizontal direction of the electron beam through holes 18a, 18b and 18c as shown in FIG. 7, or as shown in FIG. 8 shown in another embodiment, the electron beam through holes 18a and 18b ( It may be formed in the vertical direction of 18c).

Since the stepped portions 19 recessed toward the electron beam through holes 18a, 18b, and 18c are formed in the correction electrode 17, the electron beam through holes 18a, 18b, and 18c are entirely keyholes. -holl).

Accordingly, the action of diverging the electron beam in the horizontal direction is the strongest, and the divergence in the diagonal direction is weakened rather than the conventional correction electrode 17, so that the just focus voltage in the vertical direction is kept the lowest, so the beam spot on the inline axis is reduced. The maximum effect is obtained when the length to the outside is the center of the electron beam.

Here, the depth of the stepped portion 19 of the quadrangular shape is largely related to the effect of astigmatism correction. When the thickness of the correction electrode 17 used in the present invention is t, the depth L of the stepped portion 19 is t. Is more than t / 3, the effect of astigmatism correction is prominent.

That is, in order to obtain the beam shape shown in FIG. 10 from the beam shape shown in FIG. 5, the electron beam must be strongly pulled in the vertical direction. When the depth L of the stepped portion 19 is set to t / 3 or less, This is because the left and right symmetric electron beam through holes 18a, 18b, and 18c are heavily influenced, so that the effect of astigmatism correction cannot be seen.

Therefore, in order to efficiently correct astigmatism, the depth l of the stepped portion 19 should be at least t / 3.

FIG. 10 is a result of simulating a spot shape appearing on a screen when the correction electrode 17 having the shape shown in FIG. 7 is used.

In addition, FIG. 9 shows another embodiment in which the difference in the just focus voltage in the horizontal direction and the vertical direction due to the asymmetry of the internal electrode 16 passes through the central electron beam so that the resolution of the resolution is degraded on the screen due to the difference between the three electron beams. The ball 18b and the outer electron beam passing holes 18a and 18c are formed in different shapes.

That is, the stepped portions 19 formed in the electron beam through holes 18a, 18b and 18c are formed in the direction perpendicular to the outer electron beam through holes 18a and 18c, and are horizontal in the center electron beam through holes 18b. Formed.

Thus, the stepped portion 19 formed in the shape of a key hole is a hole of a key hole type completely as in the case of being configured to be recessed by a predetermined depth to the left or right or up and down about the electron beam passing hole.

As described above, the present invention provides a non-symmetrical geometry used to form the main lens by forming the stepped portion 19 on one side of the electron beam through holes 18a, 18b, and 18c formed in the correction electrode 17. The shape of the beam spot generated by the structure is improved, resulting in better resolution over the entire area of the screen.

Claims (5)

A first and second grids for controlling and accelerating the amount of electron beams emitted from the cathodes, third and fourth grids for focusing and reaccelerating the accelerated electron beams to form spots on the screen; An electron gun for a color cathode ray tube composed of an internal electrode installed inside the third and fourth grids and a correction electrode fixed to a shield cup to be positioned in the fourth grid to correct astigmatism, wherein one of the correction electrodes is connected to the correction electrode. An electron gun for a color cathode ray tube configured to form a stepped portion recessed from the side to the electron beam passing hole side, so that the electron beam passing hole has a keyhole shape as a whole. The method of claim 1, An electron gun for a color cathode ray tube, wherein the stepped portion is formed in a direction perpendicular to the electron beam passing hole. The method of claim 1, An electron gun for a color cathode ray tube, wherein the stepped portion is formed in a horizontal direction in an electron beam passing hole. The method of claim 1, An electron gun for a color cathode ray tube, wherein the stepped portion is formed in a direction perpendicular to the outer electron beam passing hole and formed in a horizontal direction in the central electron beam passing hole. The method according to any one of claims 1 to 4, An electron gun for color cathode ray tubes, in which the depth of the stepped portion is set to 1/3 or more of the thickness of the correction electrode.