JP2743400B2 - Electron gun for color picture tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention improves the deterioration of the spot shape of an electron beam,
The present invention also relates to an electron gun for a color picture tube having excellent convergence characteristics.

[Conventional technology]

In order to increase the resolution of the color picture tube, it is necessary to reduce the spot diameter of the electron beam and to concentrate the spots of the three electron beams at one point over the entire area of the screen. This also degrades resolution and image quality.

In a general color picture tube, as shown in FIGS. 6A and 6B, three electron beams emitted from three in-line electron guns arranged side by side on the same horizontal plane. 1B, 1G, and 1R, the horizontal deflection magnetic field distribution is a pincushion-shaped distortion as shown in FIG. 6A, and the vertical deflection magnetic field distribution is a barrel-shaped distortion as shown in FIG. 6B. By combining them, a so-called in-line self-convergence method that can concentrate three electron beams at an arbitrary point on the screen is adopted. The in-line self-convergence method has many advantages in that an electric circuit, adjustment, and the like required for concentrating the three electron beams are small, and high accuracy can be achieved.

However, when the electron beam passes through the above-mentioned self-convergence deflection magnetic field, when the electron beam spot which was circular at the center of the screen and is not deflected due to the influence of the magnetic field distortion is deflected to the periphery of the screen, Results in a distorted electron beam shape with a horizontally long beam core 5 and radial halos 6 above and below the beam core 5 as shown in FIG. Since the diameter of the distorted electron beam around the screen is larger than that of the circular electron beam at the center of the screen,
There is a disadvantage that the resolution around the screen is significantly deteriorated.

When observing the distortion of the electron beam shape around the screen in detail, the focus voltage V _FH that can minimize the horizontal diameter and the focus voltage V _FV that can minimize the vertical diameter are different, and the focus voltage difference ΔV _F = V _FH -V _FV is negative. That is, since the focusing state of the electron beam in the vertical direction is an overfocus state, a halo tends to appear in the vertical direction.

Various proposals have been made as a method for improving the shape of the electron beam around the screen by the above-described self-convergence deflection magnetic field. For example, JP-A-61-99249 discloses that
As shown in FIG. 8, a vertically elongated electron beam passage hole is formed on the end face of the first focusing electrode 7 on the second focusing electrode 8 side, and a horizontally elongated electron beam passing hole is formed on the end face of the second focusing electrode 8 on the first focusing electrode 7 side. An electron beam passage hole is provided, a constant first focus voltage is applied to the first focusing electrode 7, and a dynamic focusing as shown in FIG. 10 is applied to the second focusing electrode 8 as the deflection angle of the electron beam increases. By applying a voltage, a quadrupole lens 9 as shown in FIG. 9 is formed between the first focusing electrode and the second focusing electrode,
A diverging force is applied to the electron beam 10 in the vertical direction, and a converging force is applied in the horizontal direction to offset the electron beam distortion due to the self-convergence magnetic field. How to get it has been proposed.

[Problems to be solved by the invention]

When assembling an in-line type electron gun, usually, two core rods having a predetermined interval which become thinner toward the tip are opened on both sides of the electrodes in the order of a final accelerating electrode, a focusing electrode, an accelerating electrode, and a control electrode. Assemble through the hole. Since the distance between the core rod and the openings on both sides and the hole diameter are designed to be fitted very accurately, the accuracy of the in-line type electron gun is very good.

However, as shown in FIG.
In the in-line type electron gun according to the method described in -99249, a vertically elongated electron beam passage hole is arranged in the first focusing electrode and a horizontally elongated electron beam passage hole is orthogonally arranged in the second focusing electrode. It is difficult to assemble using two core rods as in the related art. For this reason, there is a problem that the accuracy of the electron gun is degraded, and the cost of the electron gun is increased by adopting a complicated assembling method to maintain the accuracy.

In general, in a color picture tube, the pitch of the electron beam passage holes of the final accelerating electrode is adjusted so that the three electron beams taken out of the three cathodes arranged side by side are concentrated at one point at the center of the screen. An electric field that refracts the electron beams on both sides inward is created by making the pitch of the electron beam passage holes of the focusing electrode opposed to the first electrode larger. By the way, Japanese Patent Application Laid-Open No. Sho 61-61 cancels the distortion of the electron beam shape due to the self-convergence deflection magnetic field described above.
The electron gun for a color picture tube described in -99249 attempts to obtain a predetermined focus characteristic by applying a dynamic voltage to a second focusing electrode facing the final accelerating electrode. When the applied voltage is increased, the potential difference between the second focusing electrode and the final accelerating electrode is reduced, so that the electric field for inwardly refracting the electron beams on both sides is weakened, and the concentration of the electron beams on both sides is insufficient. Therefore, on the screen, the three electron beams 1B, 1G, 1R are concentrated at the center of the screen, but form a convergence pattern that separates as the distance from the center of the screen increases. If the three electron beams cannot be concentrated at one point over the entire screen, a color shift will occur, which will degrade the resolution and the image quality extremely.

[Means for solving the problem]

The electron gun for a color picture tube of the present invention comprises at least a cathode,
A control electrode, an accelerating electrode, a first focusing electrode, a second focusing electrode, and a final accelerating electrode; a vertically elongated electron beam passage hole provided on the second focusing electrode side of the first focusing electrode; 1
A circular electron beam passage hole is provided on the focusing electrode side, and the major axis dimension of the vertically elongated electron beam passage hole provided in the first focusing electrode is set to a circular electron beam provided on the first focusing electrode side of the second focusing electrode. A constant focusing voltage is applied to the first focusing electrode, and a dynamic voltage is applied to the second focusing electrode to cancel the distortion of the electron beam due to the self-convergence deflecting magnetic field. In addition, excellent focus characteristics and resolution can be obtained over the entire screen.

Further, in the present invention, the pitch of the vertically elongated electron beam passing holes provided on the second focusing electrode side of the first focusing electrode is made larger than the pitch of the electron beam passing holes provided on the first focusing electrode side of the second focusing electrode. To improve the convergence characteristics.

〔Example〕

Next, the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a first embodiment of a color picture tube electron gun according to the present invention. 21B, 21G, and 21R are cathodes each serving as an electron source, and the electron beam emitted from the cathode is a control electrode 22,
The light passes through the accelerating electrode 23, the first focusing electrode 24, and the second focusing electrode 25, reaches the final accelerating electrode 26, and then reaches the display surface. Thus, vertically elongated electron beam passage holes 34B, 34G, 34R are provided on the second focusing electrode 25 side of the first focusing electrode 24,
On the first focusing electrode side of the second focusing electrode, circular electron beam passage holes 35B, 35G, and 35R are provided, which constitute a quadrupole lens.

FIG. 2 is a view of the quadrupole lens portion in FIG. 1 viewed from the final accelerating electrode side. The long axis dimension of the vertically elongated electron beam passage holes 34B, 34G, and 34R of the first focusing electrode is the second axis. The hole diameter of the circular electron beam passage holes 35B, 35G, and 35R of the focusing electrode is equal to or smaller than the diameter of the holes. Therefore, when assembling the electron gun, the final accelerating electrode, the second focusing electrode, and the first focusing electrode are provided on two core rods having a predetermined interval which become thinner toward the tip as in the case of the conventional in-line type electron gun. , The accelerating electrode, and the control electrode in this order through the apertures on both sides of the electrode. In addition, since the electron beam passage holes 34B, 34G, and 34R of the first focusing electrode are vertically elongated, the quadrupole lens can be assembled. effective.

FIG. 3 is a view of a quadrupole lens portion of a second embodiment of the electron gun for a color receiving tube according to the present invention viewed from the final accelerating electrode, and shows a vertically elliptical electron beam passage hole 36B of the first focusing electrode. ,
The major axis dimension of 36G, 36R is equal to or smaller than the diameter of the circular electron beam passage holes 35B, 35G, 35R of the second focusing electrode.

A projected edge called burring may be provided around the circular electron beam passage holes 35B, 35G, and 35R of the second focusing electrode shown in FIGS. 2 and 3.

FIG. 4 is a horizontal sectional view of a third embodiment of the present invention. Longitudinal electron beam passage holes 34B, 34G, 34R having a horizontal pitch S are provided on the second focusing electrode side of the first focusing electrode 24, and are horizontally provided on the first focusing electrode side of the second focusing electrode 25. Circular electron beam passage holes 35B, 35G, whose directional pitch is So,
35R is provided. Here, S <So is satisfied. Electron beam passage holes 22B, 22G, 22R provided in the control electrode 22, electron beam passage holes 23B, 23G, 23R provided in the acceleration electrode 23, and electron beams provided on the acceleration electrode side of the first focusing electrode 24. Although the pitch of each of the beam passage holes 24B, 24G, and 24R is set to So in this embodiment, it is not necessarily required to be So. Then, in the actual use, the first focusing electrode in advance by applying a constant focus voltage V _F, the second focusing electrode synchronized to the horizontal deflection, vertical deflection as shown in FIG. 10, for example By applying a dynamic voltage having a parabolic waveform, a uniform and small electron beam spot can be obtained over the entire screen. Further, the pitch S of the vertically elongated electron beam passage holes provided on the second focusing electrode 25 side of the first focusing electrode 24 is the pitch of the circular electron beam passing holes provided on the first focusing electrode 24 side of the second focusing electrode 25. Since it is smaller than So, a first concentrated prism 31 as shown in FIGS. 5A and 5B is formed in this portion. Similarly,
The second converging prism 32 for refracting the electron beam inward is formed between the second focusing electrode 25 and the final accelerating electrode 26 as described above. In the electron gun according to the present embodiment configured as described above, when the dynamic voltage applied to the first concentrated electrode 24 is low, as shown in FIG. The force is weak, and conversely, the electron beam concentrating power of the second concentrating prism 32 is high. When the dynamic voltage is high, as shown in FIG. 5 (b), the electron beam concentrating power of the first converging prism 31 becomes stronger, and the electron beam concentrating power of the second converging prism 32 becomes weaker. Therefore, as can be seen from the examples of FIGS. 5 (a) and 5 (b), when the dynamic voltage is changed, the fluctuation of the sum of the electron beam concentrating forces of the first converging prism and the second converging prism is very small. Consequently, the convergence deviation when a dynamic voltage is applied can be extremely reduced.

〔The invention's effect〕

As described above, the present invention provides the first focusing electrode with the second focusing electrode.
A vertically long electron beam passage hole is provided on the focusing electrode side, and a circular electron beam passage hole is provided on the first focusing electrode side of the second focusing electrode. The diameter of the circular electron beam passage hole of the second focusing electrode is equal to or smaller than the diameter of the second focusing electrode.
By applying a dynamic voltage to the focusing electrode to offset the distortion of the electron beam due to the deflecting magnetic field, excellent focus characteristics and resolution can be obtained over the entire screen, and the electron gun assembly is as simple as before. And high accuracy can be maintained.

The present invention also provides a vertically elongated electron beam passage hole having a horizontal pitch of S on the second focusing electrode side of the first focusing electrode.
A circular electron beam passing hole is provided on the first focusing electrode side of the focusing electrode, and an electron beam passing hole pitch S on the second focusing electrode side of the first focusing electrode is provided on the first focusing electrode side of the second focusing electrode. By making the pitch smaller than the pitch of the circular electron beam passage holes, excellent focus characteristics and convergence characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of a first embodiment of a color picture tube electron gun according to the present invention, FIG. 2 is a view showing a quadrupole lens portion of FIG. 1, and FIG. 3 is a second embodiment of the present invention. FIG. 4 is a cross-sectional view of a third embodiment of the present invention, and FIGS. 5 (a) and 5 (b) are views for explaining the effects of the third embodiment. 6 (a) and 6 (b) are deflection magnetic field distribution diagrams of the in-line self-convergence method, FIG. 7 is a diagram showing a distortion pattern of an electron beam spot by the deflection magnetic field of FIG. 6, and FIG. FIG. 9 is a perspective view showing an electron gun for a color picture tube, FIG. 9 is a view showing a quadrupole lens, and FIG. 10 is a view showing an example of an optimum dynamic voltage applied to a second focusing electrode. 1B, 1G, 1R, 10 ... electron beam, 2 ... horizontal deflection magnetic field, 3
... vertical deflection magnetic field, 5 ... beam core, 6 ... halo,
7,24 ... first focusing electrode, 8,25 ... second focusing electrode, 9 ...
Quadrupole lens, 21B, 21G, 21R ... Cathode, 22 ... Control electrode, 23 ... Acceleration electrode, 26 ... Final acceleration electrode, 31 ... First
Focusing prism, 32 …… Second focusing prism, 34B, 34G, 34R,
36B, 36G, 36R: vertical electron beam passage holes in the first focusing electrode, 35B, 35G, 35R: circular electron beam passage holes in the second focusing electrode.

Claims (2)

(57) [Claims] 1. A device according to claim 1, further comprising at least a cathode, a control electrode, an accelerating electrode, a first focusing electrode, a second focusing electrode, and a final accelerating electrode, wherein a vertically elongated electron beam passage hole is provided on the second focusing electrode side of the first focusing electrode. A circular electron beam passage hole is provided on the first focusing electrode side of the second focusing electrode, and the longitudinal dimension of the vertically elongated electron beam passing hole provided on the second focusing electrode side of the first focusing electrode is set to the second focusing position. The diameter of the circular electron beam passage hole provided on the first focusing electrode side of the electrode is equal to or smaller than the diameter of the circular electron beam passing hole. A constant focusing voltage is applied to the first focusing electrode, and the electron beam due to the deflection magnetic field is applied to the second focusing electrode. An electron gun for a color picture tube, characterized in that a dynamic voltage is applied so as to cancel the distortion of the color picture tube. 2. The pitch of a vertically elongated electron beam passage hole provided on the second focusing electrode side of the first focusing electrode is set to the first focusing electrode of the second focusing electrode.
2. The electron gun for a color picture tube according to claim 1, wherein the pitch is smaller than the pitch of the electron beam passage holes provided on the focusing electrode side.