JPS6240134A - Inline-type electron gun - Google Patents

Abstract

PURPOSE:To enable the imbalance of the diffractive force of a convergent electrode to be corrected by forming recesses, having a flat shape the X axis direction length of which is larger than the Y axis direction length and continuous with the electron beam holes of the first acceleration electrode, on its surface facing the convergent electrode. CONSTITUTION:Recesses 17r, 17g and 17b are adjacent to circular penetrating holes 5r, 5g and 5b respectively and are formed on a surface facing a convergent electrode (G3). They have a rectangular shape the X axis direction length of which is larger than the Y axis direction length. Since the point on which the X axis component of the electron beam is converged by a main lens 12 is more apart from the main lens 12 than the point on which the Y axis component of the electron beam is con verged, the imbalance of the main lens 12 can be corrected by properly adjusting the ratio between the vertical and the horizontal lengths of the flat shape of the recesses 17r, 17g and 17b. The diameter of circular recesses 18 is made sufficiently large in order to make the wall surface sufficiently apart from the electron beam admitted by the penetrating hole and the rectangular recesses. The circular recesses 18 control the height of the wall surfaces of the rectangular recesses 17r, 17g and 17g while maintaining a thickness necessary for maintaining the physical strength of a first acceleration electrode (G2).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an in-line type electron gun for a color cathode ray tube, and particularly relates to improvement of its convergence characteristics.

[Prior Art] FIG. 2 is a longitudinal sectional view of a conventional in-line electron gun (1), in which (2) is a heater, (3) is a cathode, and (4) is a control electrode G1. (5) is the first accelerating electrode G2, (8), (
7) is the first electrode constituting the focusing electrode G3. second member, (8
), (9) is the first acceleration electrode that constitutes the second acceleration electrode G4.
．． The second member (10) is an attached electrode (IIR).

(IIG) and (11B) are electric field lenses (hereinafter referred to as pre-lenses) formed at the through holes (Sr), (8g), and (8b) formed in the member (6),
(12) is member (7).

(8) is an electric field lens (hereinafter referred to as the main lens) formed by the lens.

FIG. 3(a) is a front view of the conventional control electrode G1, and FIG. 3(b) is a front view of the conventional control electrode G1.
) is a cross-sectional view taken along the line b-b, and the through holes (4r), (4g), (4b) through which electron beams R, G, and B pass are circular. The cross-sectional shape is also circular, and the circular through hole of the first accelerating electrode G2 and the Brilens (IIR), (11G), (11B)
After passing through the electron beams, they become electron beams with a circular cross section that uniformly diverge in each direction and enter the main lens (12), where they are converged and impinge on the phosphor screen. The dash-dotted lines in FIG. 2 indicate the center paths of the electron beams R, G, and B, respectively. below,
The convergence effect of the main lens (12) will be described with the direction in which the electron beams R, G, and H are arranged as the X axis, the direction orthogonal to the X axis as the Y axis, and the direction in which each electron beam advances as the X axis.

Figure 4(a) shows the member (7) constituting the main lens (12).
, (8) is an enlarged cross-sectional view, and (b) is a front view of the member (7), taken along the line bb. Through hole (?r).

(7g) and (7b) are formed at equal intervals on the X axis,
An oval wall surface (7w) is formed to surround them. The other member (8) constituting the main lens (12) is also formed symmetrically with the member (7). The broken lines in Figure 0 indicate equipotential surfaces, and this main lens (12) is aligned with the X-axis. A rotationally asymmetric electric field lens whose direction is longer than the Y-axis direction is formed.

FIG. 5 is a schematic diagram showing the configuration of the main lens (12) as an optical lens system, with (13R), (13G),
(13B) are through holes (7r), (7g), and
(14) is a rotationally asymmetric common lens formed between members (7) and (8), (15R) and (15G).

(15B) are the through holes (8r) of the member (8),
(8g).

This is a small lens formed in the part (8b).

[Problems to be Solved by the Invention] Since the common lens (14) is a rotationally asymmetric electric field lens, the focusing electrode G3 has the following refractive power imbalance.

■The refractive power in the Y-axis direction is stronger than the refractive power in the X-axis direction (astigmatism).

■The refractive power in the X-axis direction is stronger on both sides than in the center (spherical aberration).

(2) Regarding the refractive power in the X-axis direction that acts on the electron beams R and H passing through the through holes on both sides, the refractive power in the direction from the outside to the center is stronger than the refractive power in the direction from the center to the outside.

Arrows Fl, F2°F3 in Fig. 4(a) and Fig. 5 indicate the strength of the refractive power in the X-axis direction acting on each electron beam R, G, H, and For the reason, Fl>F
The relationship is 2>F3.

Figure 6 shows electron beams R', G focused on the phosphor screen.
, is a diagram showing an example of the spot shape of H, and the above ■, ■
Due to the above reason, the spot shape of each electron beam is not circular, and furthermore, a halo H in the direction of the refractive power Fl is added to the electron beams R, G, and B due to the above reason.

Since the spot shape of each electron beam is not circular in this way, there are problems in that resolution is lowered, contrast is lowered, and color shift occurs.

In order to solve these problems, control electrode G! There is a prior art technique in which rotational asymmetry of a common lens is corrected by forming four elongated planar parts following a through hole.

FIG. 7(a) is a front view thereof, and FIG. 7(b) is a sectional view taken along line bb. This example is a circular hole (4r).

Following (4g) and (4b), the first accelerating electrode G?
A rectangular recess (16) whose Y-axis direction is longer than the X-axis direction is formed on the surface facing the .

This recess (16) brings the crossover point of the X-axis component of each electron beam closer to the cathode (3) than that of the Y-axis component, and shifts the convergence position of the X-axis component by the main lens (12) to the Y-axis component. Since it acts to bring the axial component closer to the main lens (12) than the convergence position, it has the effect of correcting the imbalance described in (2) above.

However, the control electrode G1 faces the cathode (3) and the first accelerating electrode G2 with a narrow gap, and due to dimensional constraints, it is not possible to make sufficient corrections, and processing is difficult. There was a problem.

The present invention was made to solve these problems, and aims to provide an electron gun that corrects the imbalance described in (2) above.

[Means for Solving the Problems] The electron gun according to the present invention has three through holes formed in the first accelerating electrode on the surface facing the focusing electrode, through which the electron beam passes. Three concave portions are formed in a planar shape in which the X-axis direction is larger than the Y-axis direction and communicate with each other.

[Function] The concave portion formed on the surface of the first accelerating electrode facing the focusing electrode and communicating with the through hole is such that the shorter the distance from the through hole to the side wall surface formed by the concave portion, the more the passing electron beam It acts to reduce the divergence angle, move the crossover point (object point) away from the cathode surface (closer to the main lens), and move the convergence point (image point) of the main lens away from the main lens.

Moreover, this effect becomes stronger as the depth of the recess becomes deeper, that is, as the height of the side wall surface becomes higher.

Therefore, in a planar concave portion where the X-axis direction is larger than the Y-axis direction, the convergence point of the Y-axis component of the electron beam is farther from the main lens than the convergence point of the X-axis component. Balance can be corrected.

[Embodiments of the Invention] FIG. 1(a) is a front view of an embodiment of the first accelerating electrode G2 constituting the main part of the present invention, and FIG. 1(b) is a sectional view taken along the line bb. In one figure, (17r), (17g
) and (17b) are circular through holes (5r), respectively.

Continuing from (5g) and (5b), there is a long sword-shaped recess formed on the surface facing the focusing electrode G3 in which the X-axis direction is larger than the Y-axis direction, and (18) is a recess (17r).
(17g).

(+7b) are circular recesses each having a sufficiently large diameter.

Next, the function of the rectangular recess will be explained.

Rectangular recess (17r), (17g), (
17b) is made into a rectangle whose X-axis direction is larger than the Y-axis direction, so that an effect of correcting the above-mentioned imbalance of the main lens (12) is produced. That is, according to the experimental results, the Y-axis divergence angle of the electron beam is smaller than the X-axis divergence angle,
The crossover point for the Y-axis component is closer to the main lens (12) than that for the X-axis component. As a result, the main lens (1
The convergence point of the Y-axis component according to 2) is farther from the main lens (12) than the convergence point of the Y-axis component, so by setting the aspect ratio of the four-part planar shape to an appropriate value, the main lens (12)
) can correct the imbalance described in (2) above.

The four portions (18) of the circular diameter are formed to have a sufficiently large diameter so that the wall surface is sufficiently far away from the electron beam so as not to affect the electron beam passing through the through hole and the rectangular recess. It has a function of adjusting the height of the wall surface of the rectangular recess while maintaining the thickness necessary to maintain the strength of the accelerating electrode G2.

In the above embodiment, the recess (1?r), (17g
).

Although the example in which the shape of (17b) is a rectangle is shown, it may be a polygon, an ellipse, or an ellipse symmetrical with the X axis.

[Effects of the Invention] As explained above, the present invention provides an X-axis direction on the surface of the first accelerating electrode facing the focusing electrode, which is connected to the through hole through which the electron beam passes, which is formed in the accelerating electrode. has formed a planar concave portion that is larger than the Y-axis direction, so the crossover point of the Y-axis component of the electron beam is closer to the main lens than that of the X-axis component, and the convergence point by the main lens is farther away from the main lens. This has the effect of providing an electron gun in which the refractive power balance described in (1) of the focusing electrode G3 is corrected.

[Brief explanation of drawings]

FIG. 1(a) shows the first accelerating electrode G, which is the main part of this invention.
2, FIG. 3(b) is a sectional view taken along the line bb arrow, FIG. 2 is a longitudinal sectional view of the in-line electron gun, and FIG. 3(a) is a front view of the conventional control electrode G1. 4(b) is an enlarged sectional view of the main lens portion of the electron gun, and FIG. 4(b) is a sectional view taken along line bb. 5 is a schematic diagram showing the main lens as an optical lens, FIG. 6 is a diagram showing the shape of each electron beam spot on the fluorescent screen, and FIG. 7(a) is a control electrode according to the prior art. G1
A front view of an example, and the same figure (b) is the bb arrow cross-sectional view. (1)... In-line electron gun, (5)... First accelerating electrode G 2 , (5r), (5g), (
5bl...Through hole, (8), (7)...Focusing electrode G3, (8), (9)...Second acceleration electrode, (12)...Main lens, (14)...・Common lens, (18), (17r), (17g),
(17b) - Rectangular recess. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] (1) The X-axis direction in which electron beams R, G, and B are lined up is Y
In an in-line electron gun having a focusing electrode that forms a rotationally asymmetric electric field lens that is longer than the axial direction, the X-axis direction is
An in-line electron gun formed with three recesses each having a planar shape larger than the axial direction and communicating with the through holes through which each of the electron beams passes. (2) The in-line electron gun according to claim 1, wherein the planar shape of the recess is a rectangle, an oval, or an ellipse that is symmetrical about the X axis.