JPH051575B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an electron gun for a color picture tube, and more particularly to a main electron gun of an in-line type electron gun that is attached to a shadow mask type color picture tube and emits three electron beams in a line. The present invention relates to the structure of an electrode forming a lens portion.

[Background of the invention]

In this type of electron gun for color picture tubes, conventionally, for example, Japanese Patent Application Laid-Open No. 1983-1983
As shown in Japanese Patent No. 103246, opposing main lens electrodes have peripheral rims on their opposite sides, and an elliptical lens space is formed in the concave area between the peripheral rims and the aperture forming surface that is set back. There are known methods of forming

In this method, the potential on the electrode side facing the elliptical lens space penetrates deeply, forming one lens with a large diameter, which can reduce spherical aberration, thereby reducing the electron beam spot diameter. It has been disclosed that it is effective against this.

However, this method does not necessarily consider the strength characteristics and manufacturing cost of the main lens electrode component.

That is, in terms of strength characteristics, the recess formed on the opposing surface side is composed of a cylindrical peripheral rim,
Since the mechanical strength is lower than that of a bottomed cylindrical container with multiple beam passage apertures, which is conventionally used in general main lens electrode parts, the concave rectangular profile size is particularly important in the electron gun assembly process. There is a problem in that it is difficult to obtain a uniform resolution because the resolution tends to change easily.

In addition, regarding manufacturing costs, in order to statically concentrate the two outer beams into a central beam, the spatial dimensions of the elliptical lens are made different between the opposing main lens electrodes, and one side is made smaller than the other. It has been displaced to a large size. In addition, since the amount of displacement generally needs to be varied to approximately correspond to the screen size of the Kerr picture tube, a large number of press molds for manufacturing the main lens electrode parts that are adapted to each are required, leading to an increase in manufacturing costs.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and its purpose is to improve the resolution of a color picture tube and prevent fluctuations by enlarging the main electron lens opening and improving the mechanical strength of the lens electrode parts. It is an object of the present invention to provide an electron gun for a color picture tube, which is capable of reducing manufacturing costs by making electrode parts uniform.

[Summary of the invention]

In order to achieve such an objective, the present invention
A pair of opposing main lens electrode structures is separated into a plate-like member and a container-like member each having a predetermined thickness, and the former is placed on the opposing surface side.

In other words, a vast lens space is formed by a single oval opening in the plate-like member, and static convergence is ensured by making the thickness of the pair of opposing plate-like members different from each other. The size of the circular opening can be made uniform, and by making the elliptical lens space forming part a plate-like member, the necessary and sufficient mechanical strength can be achieved, making it easier to assemble the electron gun. It has become possible to prevent deformation.

[Embodiments of the invention]

FIG. 1 shows the main lens electrode structure of an embodiment in which the present invention is applied to a bipolarity type electron gun. Figure a is a cross-sectional view taken along a plane that includes the tube axis direction and the arrangement direction (horizontal direction) of the three electron beams, and figure b is a cross-sectional view taken along a plane that includes the tube axis direction and the direction in which the three electron beams are arranged (horizontal direction). (c) is a cross-sectional view taken along a plane that includes the direction ( _vertical direction).
FIG. ₃ is a front view of the G3 electrode.

Regarding a in the same figure, the G ₃ electrode 30 and the G ₄ electrode 40 are opposed to each other with a gap g, and the G ₃ electrode 30 is composed of a welded assembly of a lower electrode element 33 and an upper electrode element 34, and the upper electrode The element 34 is composed of a first plate-like member 31 and a second container-like member 32. The G ₄ electrode 40 includes a first plate member 41 and a second plate member 41.
A shield cup 50 is provided on the upper part of the second container-shaped member 42.

Next, the main lens electrode structure of this embodiment will be explained using FIGS. 2 and 3, taking the upper electrode element 34 of the G ₃ electrode 30 as an example.

First, the first member 31 that constitutes the electrode element 34
As shown in FIG. 2, this is a perforated plate-like metal plate having a predetermined thickness t1 and a single oblong hole 311 having a horizontal dimension h and a vertical dimension v. Both horizontal ends of this elliptical hole 311 are semicircular with a radius of 1/2 of the vertical dimension v, and the center position of the semicircle is equal to the arrangement interval s of the beam passages on both sides. is consistent with

On the other hand, as shown in FIG.
1, the bottom surface 321
a semicircle having the same dimensions as both horizontal ends of the oblong aperture 311 of the first member 31 constituting each outer half of the electron beam path on both sides;
Irregularly shaped holes 32 connected to semi-ellipsoids with long diameters in the vertical direction forming the inner half of the electron beam passages on both sides
2 and an elliptical hole 323 having a long diameter in the vertical direction and forming a central electron beam path.

Although the explanation has been given above using the G ₃ electrode as an example, the first member 41 and the second member 42 that constitute the G ₄ electrode have exactly the same configuration. However, the only difference is that the thickness t1 of the first member 31 on the _G3 electrode side is set to t2, which is smaller than t1 on the first member 41 on the _G4 electrode side, as will be described later.

In the above configuration, by arranging the plate members having a single elliptical aperture to face each other, the effect of reducing spherical aberration by enlarging the aperture of the main lens can be achieved. That is, in FIG. 1b, the first plate member 31,
41 have oval openings 311, 411, respectively.
In this case, the potential of the counter electrode penetrates deeply to form a vast lens space, a main electron lens. In other words, the high voltage side potential of the G ₄ electrode is connected to the oblong hole 311 of the G ₃ electrode, and the low voltage side potential of the G ₃ electrode is connected to the oblong hole 311 of the G ₄ electrode. 4
It extends continuously within the 11 apertures, so that
The predominant portion of the main electron lens appears as one large lens extending through three electron beam paths.

However, in a main lens formed by penetrating into such an elliptical space, astigmatism occurs due to the slot effect due to the shape of the space. That is, in general, the lens strength becomes stronger as the size of the aperture is smaller, so in FIG. Become stronger in direction. However, since both ends of the elliptical apertures 311 and 411 in the horizontal direction are semicircles whose centers coincide with the beam centers on both sides, the influence of the astigmatism is affected by the central electron beam and the electron beams on both sides. The effect appears on the inner half.

In order to correct this astigmatism, in the present invention, the openings formed in the second members 32, 42, which are container-shaped members, are made non-circular. That is, by making these elliptical holes and irregularly shaped holes as described above, the lens strength therein is stronger in the horizontal direction where the aperture width is smaller than in the vertical direction, and the lens strength therein is stronger in the horizontal direction where the opening width is smaller than in the vertical direction. It is well balanced with the circular aperture and can eliminate astigmatism.

Next, to explain the problem of electrode strength that occurs when assembling an electron gun, generally when assembling an electron gun, each electrode is assembled into a suitable assembly jig (not shown in the diagram), and pressure is applied in the tube axis direction. In a fixed state, the implanted portion of each electrode is inserted into an electrode support made of molten glass, for example, and fused. During this process, the electrodes are subjected to various mechanical pressures. That is, stress from the jig when assembling into an assembly jig, compression stress when fusing to an electrode support, etc. Due to these mechanical stresses, it is inevitable that the electrode will have some degree of distortion compared to its state before assembly, but this is especially true for electrode parts with recesses such as those disclosed in the above-mentioned known documents. The amount of distortion is larger than that of other general bottomed container-shaped electrode parts, which tends to cause fluctuations in resolution.

On the other hand, in the electrode structure of the present invention, since the portion corresponding to the recess is formed of a single plate-like member having a predetermined thickness, it is not only compared with the peripheral rim forming electrode described above, but also It is obvious that the mechanical strength is superior to that of the bottomed container-shaped electrode. Furthermore, since the second member having the elliptical hole formed therein is welded and fixed in close contact with the plate-shaped member, sufficient strength can be maintained here as well.

Additionally, another advantage of the present invention is its static convergence approach. Next, this will be explained while comparing it with a conventional example.

First, FIG _{. 4} explains the static convergence method in a conventionally known electron gun. It is slightly larger than the width B of 121. When the width of the concave portion of the G ₄ electrode is displaced to be larger than the width of the concave portion of the G ₃ electrode, the beams on both sides are bent inward between the opposing end surfaces of both electrodes due to the action of the tilted electrostatic lens. Convergence takes place. At this time, the amount of bending is determined by the ratio of A and B, and generally G ₃ electrode 12
The width B of the recess 121 of the G 4 electrode 110 is kept constant, and the width A of the recess 111 of the G ₄ electrode 110 is used depending on the screen size of the color picture tube. For this reason,
Since the displacement varies depending on the amount of displacement, in other words, depending on the screen size, _G4 electrode parts are required, resulting in the problem of increased electrode part manufacturing costs. Note that in the conventional example, the depth of the recess indicated by the F dimension is the same for both the G ₃ and G ₄ electrodes.

On the other hand, FIG. 5 is for explaining the static convergence method in the electron gun of this embodiment.
This is a cross-sectional view corresponding to an enlarged view of the opposing portions of the G ₃ and G ₄ electrodes in Figure 1. In the figure, the thickness of the plate member on the G ₃ electrode side is t1 = 3 mm, while the thickness on the G ₄ electrode side is 3 mm. The thickness of the plate member is t2 = 2 mm. In this case, as described above, the counter electrode potential penetrates deeply into the elliptical lens space formed by each plate member, forming one main electron lens with a large diameter. In the vicinity of the side electron beam passage opening, the penetration of the counter potential is shallower than in the vicinity of the central beam passage opening due to the influence of the wall of the edge of the oblong opening. As a result, the electron beams on both sides encounter the inclined equipotential line 60 in the vast lens space area of the _G3 electrode, and are therefore concentrated by the inclined electrostatic lens action here, and the outer electron beams 8, 10 bends inward. However, in this case, t2 is
If it matches t1 (t1 = t2 = F), even if the electron beams 8 and 10 are bent inward by the G ₃ electrode, the electron beams 8 and 10 will remain in the G ₄
The diverging lensing effect at the G ₄ electrode will offset the inward focusing effect described above, since similarly inclined equipotential lines 70 are encountered in the vast lens space of the electrodes. Therefore, in this example, t2 is set 1 mm smaller than t1, and the slope of the equipotential line 70 in the G ₄ electrode side spatial area is made gentler than that of the G ₃ side equipotential line 60. . As a result, G ₃
The beam concentration effect on the electrode side becomes dominant over the beam divergence effect on the _G4 electrode side, and static convergence occurs as shown in Figure 5 by the broken lines 8' and 10' of the electron beam path. It will be done. Note that the values of t1 = 3 mm and t2 = 2 mm in this example correspond to static convergence in a 20-inch color picture tube, but they also apply to color picture tubes of other sizes.
This can be achieved by appropriately selecting the ratio between the thicknesses t1 and t2 of both plate-like members.

In this way, in this embodiment, static convergence suitable for each screen size is performed by selecting the thickness of the plate-like member. Since elliptical openings and the like can be handled with electrode parts of a fixed size regardless of the screen size, this has an extremely large effect in reducing the manufacturing cost of electrode parts.

On the other hand, in connection with press punching of plate-shaped members, a proposal has already been made to improve strength characteristics by forming three beam passage holes by punching (Japanese Patent Laid-Open No. 57-11459). In this case, if you try to increase the hole diameter, the adjacent holes will be very close to each other, so the punching accuracy such as the roundness of each hole should be adjusted to an accuracy that does not adversely affect the beam spot shape. However, according to the present invention, although the thickness of the plate member is 2 to 4 mm when punched, the shape of the punched member is similar to that of the adjacent part as described above. Since it is a single oval hole with no holes, it can be sufficiently manufactured using normal punching techniques within the above-mentioned plate thickness range. Note that differences in screen size can be accommodated simply by selecting the thickness of the plate-shaped member, that is, the thickness of the metal material, and as mentioned above, the punching contour dimensions are unrelated to the screen size. As for the press mold for production, it is possible to use the same mold, and in this respect also it is possible to reduce the production cost.

The container-like members 32 and 42 may be integrally formed by press molding and may be made low, but the container-like members 32 and 42 may be made of a plate-like member of a predetermined thickness with a beam passing hole punched out forming the bottom surface thereof, or a simple cylindrical member. They may be formed separately and then welded and fixed to form a single unit.

Furthermore, in order to eliminate astigmatism caused by the difference in lens strength between the horizontal and vertical directions, another method may be used, such as providing a separate slot-shaped aperture as described in the above-mentioned known document. Ba,
The beam passage openings of the container members 32, 42 do not necessarily have to be elliptical holes or irregularly shaped holes as shown in FIG. 3, but may be simply circular.

〔Effect of the invention〕

As explained above, according to the present invention, by providing a single elliptical hole in each of the facing plate members, the main electron lens aperture can be enlarged and resolution can be improved, and the resolution can be improved. Regarding convergence, while keeping the aperture dimensions of each plate member and container member the same, the thickness of the plate member is made smaller on the high pressure side than on the low pressure side, so that the difference in screen size can be avoided. It is possible to reduce manufacturing costs. Since it is excellent not only in terms of mechanical strength but also in terms of mechanical strength, fluctuations in resolution can be prevented.

[Brief explanation of the drawing]

Figures 1a and 1b are cross-sectional views of a main lens electrode showing an embodiment of the present invention, Figure 1c is a front view of main parts, and Figures 2 and 3 are front views showing the configuration of each main lens electrode element. , a cross-sectional view, and FIGS. 4 and 5 are diagrams for explaining static convergence. 30...G ₃ electrode, 40...G ₄ electrode, 31,4
1... Plate-shaped member, 32, 42... Container-shaped member, 3
11,411...Oval hole, 323,423...
...Oval hole, 322,422...Unusual hole.

Claims (1)

[Claims] 1. In an electron gun for a color picture tube, which is equipped with an electron beam source that emits three electron beams in a line, and a main electron lens section that focuses the electron beam from this electron beam source onto a phosphorescent surface, A single elliptical electron beam passes through a pair of electrodes that are placed opposite each other at a constant interval in the direction of the tube axis forming the electron lens section, and is elongated in the direction in which the electron beams are arranged on the opposing surfaces. It is composed of a plate-like member having a predetermined thickness with openings, and a container-like member having electron beam passing holes on the bottom surface in contact with the plate-like member, and the thickness of the plate-like member is , the difference between the pair of opposing electrodes is such that the high voltage side electrode is smaller than the low voltage side electrode, and the electron beam passage opening in the bottom of the container-shaped member serves as a passage for the central electron beam. An elliptical hole having a major axis in the direction perpendicular to the arrangement direction of the electron beams, a semicircle surrounding approximately the outer half circumference of the electron beam on both sides, and a semiellipse having the major axis in the vertical direction surrounding approximately the inner half circumference of the electron beam, connected to each other. An electron gun for color picture tubes characterized by an irregularly shaped hole.