KR20010017759A - electron gun for color cathode ray tube - Google Patents

Abstract

PURPOSE: An electron gun for a color cathode-ray tube is provided to acquire a high resolution image without a moire over an entire screen by improving structures of a fourth grid electrode and a focusing electrode. CONSTITUTION: A cathode(7), a control electrode(8) and an accelerating electrode(9) are provided. A shear focusing lens for focusing an electron beam generated from the cathode on a fluorescent screen is formed by a third grid electrode(10), a fourth grid electrode(11) and a focusing electrode(12). A main electrostatic lens to finally focus and accelerate the electron beam focused by the focusing lens are formed by a focusing lens and an anode electrode(13). An inline type electron gun to which the accelerating electrode and the fourth grid electrode are electrically connected respectively is provided. The ratio of the length of the fourth grid electrode(11) to the diameter of an opening thereof is in the range of 0.26-0.33 to 1. And, the ratio of the length of the focusing electrode(12) to the diameter of the opening of the fourth grid electrode is in the range of 5.6-6.0 to 1.

Description

Electron gun for color cathode ray tube

The present invention relates to an electron gun used in a color cathode ray tube or a high-definition industrial monitor, and more particularly, a fourth grid electrode and a focus used for obtaining high-quality images without moiré over the entire area of the screen. It relates to the structure of the electrode.

FIG. 1 is a cross-sectional view of a general color cathode ray tube, in which a panel 1 having three R, G, and B fluorescent films 2 are coated on its inner surface, and fused with bead glass at the rear of the panel to vacuum the inside thereof. A funnel 3 which is kept in a state, an electron gun 4 which is enclosed in the neck portion 3a of the funnel and scans the electron beam toward the fluorescent film side, and an electron beam which is provided on the outer circumferential surface of the neck portion and radiated from the electron gun horizontally and vertically A deflection yoke 5 for deflecting in a direction, and a shadow mask 6 for adjoining the panel and serving as color discrimination of the electron beam deflected by the deflection yoke.

In the cathode ray tube configured as described above, the electron gun 4, which is enclosed in the neck portion 3a and scans the electron beam toward the fluorescent film 2 side, has a heater (not shown), as shown in FIG. Three cathodes 7 arranged horizontally side by side, a control electrode 8 arranged to maintain a predetermined distance from the cathode to control hot electrons generated from the cathode, and a predetermined distance maintained from the control electrode Acceleration electrode 9 and third grid electrode 10, fourth grid electrode 11, and fifth grid electrode which serve to draw and accelerate hot electrons gathered on the electron emission material surface of the cathode (not shown). 12a and 12b and the anode electrode 13 are sequentially arranged, and a shield cup 14 for shielding an external electric field and a magnetic field is fixed to the upper portion of the anode electrode 13, and an electron gun (C) is attached to the shield cup. 4) and neck part 3a Three B.S.C (Bulb Space Connector) (not shown) are used to secure the electron gun to the neck while connecting the electronics.

As shown in FIG. 3, the fourth grid electrode 11 is a plate-shaped electrode, in which circular electron beam through holes 11a, 11b, and 11c are formed at regular intervals, and beads are formed at upper and lower portions of the electron beam through holes. A bead supporter 11d is formed to be fused and fixed to the glass 15.

In the electron gun 4 having the structure as described above, the electron beam emitted from the cathode 7 is pulled by the control electrode 8 and the acceleration electrode 9 so that the third grid electrode 10, the fourth grid electrode 11, The voltage is applied primarily to the focusing electrode 12b and the anode electrode 13 by focusing largely by a shear focusing lens formed by the potential difference across the fifth grid electrode (hereinafter referred to as a "focusing electrode") 12a. As the light is focused and accelerated through the main lens formed by the difference to the screen side, a circular electron beam spot is formed on the screen.

In this case, the third grid electrode 10 and the focusing electrode 12a have the same potential, and a voltage of about 6000 to 10000 V is applied, and the acceleration electrode 9 and the fourth grid electrode 11 are 300 to 300 m. A voltage of 100 V is applied.

In order to reproduce a desired color in each of the inline R, G and B electron guns corresponding to the red (R), green (G) and blue (B) applied to the inner surface of the panel 1, the electron beam of each electron gun is screened. It can be realized only when it is collected at one point.

In order to collect the three electron beams at one point, a series of operations (ITC) are performed to artificially adjust the position of the magnet 16 installed on the outer circumferential surface of the neck portion 3a during assembly of the cathode ray tube.

When the beam spot is formed on the screen by the electrostatic lens system, 3 arranged inline on the third grid electrode 10 side of the acceleration electrode 9 as shown in FIG. 4 so that the beam spot does not deteriorate at the periphery of the screen. The technique of enclosing the two electron beam through holes 9a, 9b, and 9c, respectively, to form a transversely long recessed groove 9d, 9e, 9f is described in Japanese Patent Laid-Open No. 53-18866. It is known.

By setting the depth of the concave grooves 9d, 9e, and 9f in the electrode thickness direction deeply, the electron beam has a large astigmatism and removes the deflection aberration.

However, the cathode ray tube employing the inline electron gun configured as described above has a problem in that moire is generated.

The moiré refers to a phenomenon in which, when the beam spot diameter is smaller than a certain value, interference with the periodic structure of the phosphor dot and the scanning line or periodic video signal of the beam is generated to reduce the resolution by generating stripes on the screen. It is referred to as raster moiré 17 or transverse moire as shown in 5a, and the latter is referred to as video moire 18 or longitudinal moire as shown in FIG. 5b.

In the color cathode ray tube having an inline electron gun in which the elongated recesses 9d, 9e, 9f are formed in the electron beam through holes 9a, 9b, 9c of the acceleration electrode 9, as shown in FIG. Since the electron beam is formed long in the longitudinal direction due to the mouth grooves 9d, 9e and 9f, the video moiré is generated remarkably.

Therefore, it is necessary to maintain the ratio of the spot diameter formed at the center of the screen to 0.7 mm or less and the ratio between the spot diameter formed at the periphery of the screen and the spot diameter formed at the center of the screen at 1.0 to 1.4.

If the accelerating electrode 9 is not formed with the horizontally recessed grooves 9d, 9e, and 9f, the spot diameter formed around the screen is significantly degraded due to the influence of the deflection aberration. The ratio between the spot diameter formed around the screen and the spot diameter formed at the center of the screen cannot be maintained at 1.0 to 1.4.

Therefore, as shown in FIG. 4, horizontally formed recessed grooves 9d, 9e, and 9f are formed in the acceleration electrode 9, but the deflection aberration is reduced by setting the depth of the recessed groove to have a large astigmatism in the electron beam. In addition, the spot diameter ratio at the center of the screen is maintained at 1.0 to 1.4 at the periphery of the screen.

However, with respect to the spot diameter at the center of the screen, the diameter in the vertical direction becomes large due to astigmatism, and in order to keep the spot diameter at the center of the screen at 0.7mm or less, the diameter in the horizontal direction becomes very small. There is a problem that the horizontal diameter of the spot becomes small over, and thus the video moiré 18 occurs in the entire area of the screen.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem in the related art, and the object of the present invention is to improve the focus characteristics by simultaneously preventing the degradation of the video moiré and the beam spot by improving the structure of the fourth grid electrode and the focusing electrode. have.

According to an aspect of the present invention for achieving the above object, a third pole electrode consisting of a cathode, a control electrode, an acceleration electrode, and a third grid electrode for forming a shear focusing lens to focus the electron beam generated by the cathode on a fluorescent surface, A grid electrode, a focusing electrode, and a focusing electrode and an anode electrode forming a main electrostatic lens for final focusing and acceleration of the electron beam focused in the shear focusing lens, and the accelerating electrode and the fourth grid electrode are electrically A cathode ray tube having an inline electron gun connected thereto, wherein a ratio of the length of the fourth grid electrode to the opening diameter of the fourth grid electrode is set to 0.26 to 0.33, and is located between the anode electrode and the fourth grid electrode. The ratio of the axial length of the electrode and the diameter of the opening of the fourth grid electrode is set to 5.6 to 6.0 for the color cathode ray tube An electron gun is provided.

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

FIG. 2 is a side view of the electron gun applied to FIG. 1. FIG.

3 is a front view showing a conventional fourth grid electrode

4 is a front view showing a conventional acceleration electrode

5a and 5b is a state in which moiré is generated on the screen

6 is a longitudinal cross-sectional view of an electron gun showing the present invention;

7 is a graph showing the ratio of the length of the focusing electrode to the diameter of the fourth grid electrode and the ratio of the length and diameter of the fourth grid electrode in the present invention.

Explanation of symbols for main parts of the drawings

7 cathode 8 control electrode

9 acceleration electrode 10 third grid electrode

11: fourth grid electrode 12: focusing electrode

13: anode electrode

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

FIG. 6 is a longitudinal cross-sectional view of an electron gun showing the present invention, and FIG. 7 is a graph showing the ratio of the length of the focusing electrode to the diameter of the fourth grid electrode and the ratio of the length and diameter of the fourth grid electrode in the present invention.

In the color cathode ray tube, it is well known that video moiré does not occur when the diameter of the beam spot is maintained at 0.6 mm or more.

Therefore, in order to prevent video moiré on the screen, the horizontal diameter of the spot should be maintained at 0.6 mm or more at the center of the screen, and in order to maintain good resolution, the average diameter of the spot should be 0.7 mm or less at the center of the screen. In consideration, the horizontal diameter of the spot at the center of the screen should be kept below 0.8 mm.

In addition, since the vertical diameter of the spot at the center of the screen is changed by the beam diameter incident on the main lens, it is necessary to increase the beam diameter incident on the main lens to some extent.

Therefore, when the diameter of the opening of the fourth grid electrode 11 is 4 mm, when the length of the focusing electrode 12 is set to 22.4 mm (5.6) or more, the vertical diameter of the spot formed at the center of the screen is 0.8 mm or less. It can be maintained.

However, when the length of the focusing electrode 12 is 24 mm (6.0) or more, the focus voltage ratio is increased and the beam spot diameter in the horizontal direction is about 0.6 mm, which causes video moiré.

Moreover, it is necessary to make ratio of the spot diameter of the periphery of a screen, and the spot diameter of the screen center into 1.0-1.4.

The ratio of the spot diameter around the screen to the spot diameter at the center of the screen varies with the beam diameter in the deflection field, and to reduce the beam diameter incident on the main lens as opposed to the spot diameter at the center of the screen, The ratio of spot diameters in the center of the screen can be reduced.

The ratio between the axial length of the fourth grid electrode 11 and the opening diameter of the fourth grid electrode 11 where the ratio of the spot diameter around the screen to the spot diameter at the center of the screen is 1.4 was found to be satisfactory as calculated from 0.26 or more. .

However, when the ratio is 0.33, it becomes impossible to manufacture the fourth grid electrode 11 using the mold, and the ratio of the focus voltage and the high pressure becomes 33% or more, resulting in deterioration of the breakdown voltage characteristic.

The area indicated by diagonal lines in Fig. 7 schematically shows a region in which high-quality image display without moiré can be obtained in all areas of the screen by eliminating deterioration of focus characteristics.

As described above, the present invention eliminates the deterioration of the focus characteristic by a simple structure change of the fourth grid electrode 11 and the focusing electrode 12, and obtains a high quality image quality in which moiré does not occur over the entire area of the screen. Will be.

Claims (1)

In the third grid electrode, the fourth grid electrode, the focusing electrode, and the shear focusing lens, which form a three-pole portion consisting of a cathode, a control electrode, an acceleration electrode, and a shear focusing lens to focus the electron beam generated by the cathode on a fluorescent surface In a cathode ray tube having an in-line electron gun composed of a focusing electrode and an anode electrode to form a main electrostatic lens for the final focusing and acceleration of the narrowly focused electron beam, the acceleration electrode and the fourth grid electrode, respectively, The ratio of the length of the fourth grid electrode to the opening diameter of the fourth grid electrode is set to 0.26 to 0.33, and the axial length of the focusing electrode located between the anode electrode and the fourth grid electrode and the opening of the fourth grid electrode. An electron gun for color cathode ray tubes, wherein the ratio of the diameters is set to 5.6 to 6.0.