JPH0630226B2 - Electron gun for cathode ray tube - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an electron gun for a cathode ray tube.

[Technical background of the invention and its problems]

An electron gun for a cathode ray tube generally has two basic components including an object point forming section including an electron beam generating section and an accelerating focusing lens section that focuses an electron beam from the object point forming section onto a predetermined phosphor screen. Composed of parts. Usually, the former is referred to as a quadrupole part and the latter is referred to as a main lens part. The final electrode of the quadrupole part and the first electrode of the main lens part are the same.

Most of the lenses formed in the main lens section are electrostatic lenses, and a predetermined potential is applied to at least two focusing electrodes having predetermined electron beam passage holes (hereinafter simply referred to as openings). Is formed by.

In such an electron gun for a cathode ray tube, the lens performance of the main lens portion can be changed depending on the potential of each electrode forming the main lens, the electrode length, the distance between electrodes, and the size of the opening.
In practice, the physical design of the electron gun imposes some limitations.

On the other hand, the interelectrode capacitance is an important factor that determines the performance of the electron gun for a cathode ray tube. In particular, the smaller the inter-electrode capacitance between the cathode or the first grid to which a signal is applied and the other electrode, the more the decrease in signal gain can be suppressed, and the better the performance of the electron gun. That is, it is desirable that the area of the electrodes forming the electron gun is small.

Further, in a cathode ray tube that uses a plurality of electron guns at the same time, the distance Sg between electron guns is another important factor that determines the performance of the electron gun. In such a cathode ray tube, since a plurality of electron beams are concentrated (converged) at a single point over the entire surface of the phosphor screen by electromagnetic deflection, it is extremely desirable that one with a small electron gun distance Sg is less susceptible to deflection aberration. Also, it is economically advantageous because it requires less deflection power.

A typical example of such an electron gun for a cathode ray tube is an electron gun for a color picture tube in which a main lens portion is a bipotential type lens. This bipotential lens is composed of a first focusing electrode and a second focusing electrode, an anode high voltage is applied to the second focusing electrode, and a medium voltage of several thousand volts is applied to the first focusing electrode. When such an electron gun is used for a color picture tube of an in-line array shadow mask system, for example, three electron guns are arranged in a row in the horizontal direction, and the electron guns are enclosed in a neck of a glass cylinder for use. To be done.

In order to improve the lens performance of the main lens portion of such an electron gun, it is best to increase the lens aperture, that is, the aperture diameter. However, three electron guns arranged in a row are installed in a neck with a constant inner diameter. Since it is arranged, the diameter of the opening cannot be made very large. In addition to the lens performance, as the performance of the electron gun as a whole, as described above, it is desired to reduce the inter-electrode capacitance and the electron gun distance Sg to be small, which is inconsistent with increasing the lens aperture. It is extremely difficult to increase the lens aperture to significantly improve the lens performance and the electron gun performance.

As another structure for significantly improving the lens performance, a technique for increasing the distance between electrodes is disclosed in Japanese Patent Publication No. 55-48674 and Japanese Patent Laid-Open No. 57-1.
It is disclosed in, for example, the 03246 publication. Since the structure for increasing the distance between the electrodes to improve the lens performance is consistent with improving the electron gun performance, it is possible to significantly improve the lens performance and the electron gun performance. It is said that it can provide a high-performance electron gun.

However, in Japanese Examined Patent Publication No. 55-48674, a resistor is used to apply a predetermined potential to at least one electrode of the electron gun, which causes problems with the material of the resistor and the structure of the electron gun. In many cases, practical application is extremely difficult. Also, JP-A-57
-103246, the electrode area, especially the first grid, the second
Since the electrode area of the object forming portion such as the grid is kept large, the inter-electrode capacitance is large, and as a result, the performance of the electron gun is deteriorated.

[Object of the Invention]

The present invention has been made in view of the above-mentioned problems, and improves the lens performance by setting the inter-electrode distance of the main lens portion to be substantially long, and at least reduces the electrode area of the object point forming portion. The purpose of the present invention is to provide a practical electron gun for cathode ray tubes with excellent overall electron gun performance by suppressing the inter-electrode capacitance and reducing the distance between the electron guns in the case of multiple electron guns. I am trying.

[Outline of Invention]

That is, according to the present invention, an object point forming part including a plurality of electrodes including an electron beam generating part, and a main lens part including a plurality of electrodes for focusing the electron beam from the object point forming part on the phosphor screen. In the electron gun for a cathode ray tube having, the main lens portion has at least four focusing electrodes, and these focusing electrodes have first and second electrodes having three openings, and between these first and second electrodes. It is composed of third and fourth electrodes having one large opening arranged, and the distance between these electrodes is 1 mm, and the large openings of the third and fourth electrodes from the outermost end of the opening of the first electrode. The distance L to the inner diameter portion of the portion and the thickness T of the third and fourth electrodes in the tube axis direction have a relation of L ≧ 2 × T, and the first electrode and the third electrode adjacent to the first electrode The potential of the electrode and the potential of the second electrode and the fourth electrode adjacent to this second electrode are different from each other. An electron gun for a cathode ray tube having such a structure, and by having such a configuration, the interelectrode capacitance can be suppressed to be small in the object point forming portion and the main lens has excellent lens performance. It is what

Example of Invention

1 to 4, an electron gun used for a shadow mask type color picture tube in which three electron guns are arranged in a line will be described as an embodiment of the electron gun for a cathode ray tube according to the present invention.

As shown in the figure, the electron gun (1) is arranged in the neck (42), and is composed of a plurality of electrodes described later and a plurality of insulating supports (2) that support these electrodes by implantation.

The plurality of electrodes are red constituting a phosphor screen,
A heater for generating three electron beams (3a), (3b) and (3c) which respectively impinge on the phosphor layers which emit green and blue colors respectively.
Three cathodes arranged in a row containing (6a), (6b), (6c)
(9a), (9b), (9c) and the first grid (12) of an integrated structure provided with predetermined openings corresponding to the three cathodes (9a), (9b), (9c). ), Second grid (13), first focusing electrode (14), third
It is composed of a focusing electrode (16), a fourth focusing electrode (17), a second focusing electrode (15) and a convergence electrode (18) attached to the second focusing electrode (15). 12), (1
3), first, third, fourth and second focusing electrodes (14), (16), (17),
(15) are planted and fixed to the insulating support (2) in this order. However, the third focusing electrode (16) and the fourth focusing electrode (17) are composed of one large electrode as described later,
In order to implant the third focusing electrode (16) and the fourth focusing electrode (17), (2) spreads outward at these focusing electrodes (16) and (17).

To further explain, the first grid (12) and the second grid (13)
Is a plate-like electrode that is placed in close proximity to the first focusing electrode (1
4) is arranged close to the second grid (13) and is composed of two cup-shaped electrodes (14a), (14b) joined together, and the third focusing electrode (1)
6) is a cup-shaped electrode adjacent to the first focusing electrode 14, and the fourth focusing electrode 17 is a cup-shaped electrode adjacent to the third focusing electrode 16. Then, each cup-shaped electrode (14a), (14
The bottom of b) and the first grid (12), which is a plate-shaped electrode, the second
Each electron beam (3a), (3b), (3
It has three openings aligned with c) and has a third focusing electrode (1
6) The fourth focusing electrode (17) is provided with one large opening.

These openings are the first grid (12) and the second grid (13).
Is relatively small, the opening (32a) of the cup-shaped electrode (14a),
(32b) and (32c) are larger than that, and the openings (33a), (33b) and (33c) of the cup-shaped electrode (14b) are formed larger. On the other hand, the third focusing electrode (16) and the fourth focusing electrode (1
7), the openings (32a), (32) of the cup-shaped electrode, respectively.
One large opening (36), (37) larger than b), (32c) is formed, and as shown in FIG. 3, these third focusing electrode (16) and fourth
The focusing electrode (17) is formed in an elliptic ring shape. The third
In the figure, (41) is the planting part. That is, the third focusing electrode (1
Although 6) and the fourth focusing electrode (17) are cup-shaped electrodes, they have almost no bottom surface. Moreover, the outer diameters of the electrodes, which are a × b portions not including the implanting portions (41) of the third focusing electrode (16) and the fourth focusing electrode (17), are the first grid (12) and the second outer diameter.
It is larger than the outer diameter of the electrodes of the grid (13).

Regarding the second focusing electrode (15) and the convergence electrode (18), the second focusing electrode (15) is a cup-shaped electrode having openings (39a), (39b), (39c) formed in a line on the bottom surface. Of the openings (39a), (39b), (39c), the central opening (39b) is aligned with the openings from the first grid (12) to the first focusing electrode (14). Co-axial but with openings (3
9a) and (39c) are slightly offset from the central opening (39b) to the outside, and are aligned with the opening from the first grid (12) to the second focusing electrode (14). I haven't.

The deviation between the openings (39a) and (39c) on both sides is slightly different because the three electron beams (3a), (3b) and (3c) intersect at one electron beam passage hole of the shadow mask. This is for forming an asymmetric electric field and for deflecting the electron beams (3a) and (3c).

The second focusing electrode (15) has an electron beam (3a), (3b), (3
A bottomed cylindrical convergence electrode (18) having openings (40a), (40b), (40c) substantially aligned with the path of c) is attached. A valve spacer (20) for guiding a high voltage of about 25 KV applied to an anode terminal (not shown) is attached to the convergence electrode (18).

Such an electron gun (1) has a thin glass cylinder neck (42).
Enclosed inside.

The potential of each electrode of this electron gun is as follows.

That is, the cathodes (9a), (9b), and (9c) are kept at a cutoff voltage of about 150V, and a modulation signal is applied thereto. 1st grid (1
2) is the ground potential, the second grid (13) is about 700V,
An anode high voltage of about 6.5 KV is applied to the first focusing electrode 14 and the fourth focusing electrode 17, and an anode high voltage of about 25 KV is applied to the third focusing electrode 16 and the second focusing electrode 15.

Next, a lens formed by the first focusing electrode (14), the third focusing electrode (16), the fourth focusing electrode (17) and the second focusing electrode (15), which is the main part of the present invention, will be described. The equipotential curve (45) of the potential distribution of this lens shows that the potential distribution is approximately equal to the openings (33a), (33b), (33c) of the first focusing electrode (14) that determine the lens diameter. In the ideal state, a potential distribution equivalent to that when the inter-electrode distance between the first focusing electrode (14) and the second focusing electrode (15) is simply increased is formed. However, FIG. 4 shows a simplified electrode structure for explaining the main lens portion of the present embodiment.

Therefore, the potential distribution on the tube axis (Z axis) becomes fairly gentle, and this lens reduces the electro-optical magnification and the spherical aberration coefficient and remarkably improves the lens performance.

Further, in this embodiment, the outer diameter of the electrode of the object point forming portion is relatively small. That is, since the electrode area is small, the interelectrode capacitance is small, and particularly when a signal is applied, the interelectrode capacitance between the cathode and another electrode, for example, the first grid is small. Therefore, it is a high-performance electron gun with little reduction in gain.

Further, in this embodiment, the lens performance of the main lens portion is improved while the distance between the electron guns of the three electron guns is small. Therefore, it is a high-performance electron gun that can obtain accurate convergence characteristics even when the electron beam is deflected and has a small deflection power.

The electron gun of this embodiment is a neck in which a normal electron gun is enclosed.
It is smaller than the space in (42) and looks very useless, but it has an extremely rational structure in terms of fully exploiting the overall electron gun performance.

In the electron gun of this embodiment, the large openings (36), (37) of the third focusing electrode (16) and the fourth focusing electrode (17) are respectively formed by the first focusing electrode (1).
From the openings (33a), (33b) and (33c) of 4), the plate thickness (thickness in the tube axis direction) of the third focusing electrode (16) and the fourth focusing electrode (17) is about twice or more, that is, Large opening so as to satisfy L ≧ 2 × T in FIG.
The inner diameters of (36) and (37) need to be separated from the outermost ends of the openings of (33a), (33b), and (33c). On the other hand, in order to further improve the lens performance, the plate thickness of the third focusing electrode (16) and the fourth focusing electrode (17) is increased to increase the distance between the first focusing electrode (14) and the second focusing electrode (15). It is preferable to increase the size of the large apertures (36), (3) of the third focusing electrode (16) and the fourth focusing electrode (17).
The inner diameter of 7) must be increased, and the structure is as shown in Figs.

The detailed specifications of this embodiment are as follows, for example.

That is, the electron gun distance Sg is 4.92 mm, and the outer diameters of the first grid (12), the second grid (13), and the first focusing electrode (14) are about 7.6 mm × 1.
5.5 mm, opening diameter of the first focusing electrode (14) is about 4.52 mm, length (electrode length) is about 22.0 mm, plate thickness of the third focusing electrode (16) and the fourth focusing electrode (17) (electrode Length) is about 0.8 mm, its large opening (36),
(37) is about 2.0 mm away from the openings (33a), (33b), (33c) of the first focusing electrode (14) and is an ellipse of 8.52 mm × 18.36 mm,
Its outer diameter is approximately 12.0 mm x 22.0 mm.

The length of the second focusing electrode (15) (electrode length) is about 5.0 mm,
The diameter of the openings (39a), (39b), (39c) is 4.52 mm, and the distance between the openings is about 5.02 mm. The first focusing electrode (14), the third focusing electrode (16), and the fourth The distance between the focusing electrode (17) and the second focusing electrode (15) is about 1.0 mm. Then, this electron gun was attached to the neck (42) having an inner diameter of about 23.9 mm, but there was no influence of other electric fields in the neck on the main lens portion.

In the embodiment described above, the third focusing electrode 16 and the fourth focusing electrode 1
Although 7) is a cup-shaped electrode, it may be a plate-shaped electrode. However, the cup-shaped electrode is preferable in terms of withstand voltage characteristics. Further, although the third focusing electrode 16 and the fourth focusing electrode 17 have the same structure, it goes without saying that they may have different structures. Further, the third focusing electrode (16) and the first focusing electrode (14) are brought into contact with each other or have the same potential, and the fourth focusing electrode (17) and the second focusing electrode (15) are brought into contact with each other or have the same potential. Kaisho 57-1
The same connection as the electron gun shown in JP 03246 may be made. However, in this case, the electrode outer diameters of the first grid (12) and the second grid (13) are set to the third focusing electrode (16) and the fourth focusing electrode.
It must be smaller than the outer diameter of (17).

Next, another embodiment of the electron gun for a cathode ray tube of the present invention will be described with reference to FIGS.

FIG. 5 is a schematic view of a main lens portion of another embodiment, which includes a first focusing electrode (51), a second focusing electrode (52), and a third focusing electrode (53).
Between the first focusing electrode (51) and the second focusing electrode (52) and the second focusing electrode (52) of the unipotential type main lens part consisting of
A fourth focusing electrode (54), a fifth focusing electrode (55), and a sixth focusing electrode (54) each having two large openings between the third focusing electrode (53) and the third focusing electrode (53).
The focusing electrode (56) and the seventh focusing electrode (57) are provided, and the first focusing electrode
An anode electrode is applied to (51), the fifth focusing electrode (55), the sixth focusing electrode (56) and the third focusing electrode (53), and the fourth focusing electrode (54), the second focusing electrode (52), The seventh focusing electrode (57) is set to another potential, or the first focusing electrode (51), the fourth focusing electrode (54), the seventh
An anode voltage is applied to the focusing electrode (57) and the third focusing electrode (53) to set the fifth focusing electrode (55), the second focusing electrode (52) and the sixth focusing electrode (56) to other potentials. . The effect is almost the same as that of the above-mentioned embodiment.

6 and 7 are examples in which the present invention is applied to a quadrapotential type main lens unit in which a unipotential type lens and a bipotential type lens, which the applicant previously applied, are connected in series. .

Among them, the electron gun of FIG. 6 is a quadrapotential type main lens unit including a first focusing electrode (61), a second focusing electrode (62), a third focusing electrode (63) and a fourth focusing electrode (64). The fifth focusing electrode (65) and the sixth focusing electrode (66) having a large opening are provided between the third focusing electrode (63) and the fourth focusing electrode (64), and the second focusing electrode (62 ) For several 100V, the first focusing electrode (61), the third focusing electrode (6
3) and the sixth focusing electrode (66) several thousand V, the fifth focusing electrode (65)
An anode voltage of 25 KV to 30 KV is applied to the fourth focusing electrode (64).

The electron gun of this structure has a first focusing electrode (61) and a third focusing electrode (6
Since the voltage of 3) and the sixth focusing electrode (66) can be easily set to 8KV to 9KV, the electron beam from the object forming unit can be used in the best condition, and the overall performance of the electron gun is further improved. . Also in this example, the third focusing electrode (63) and the fifth focusing electrode (6
5) It goes without saying that the sixth focusing electrode 66 and the fourth focusing electrode 64 may be connected.

The next electron gun of FIG. 7 is the same as the electron gun of FIG. 6 except that the anode voltage is applied to the second focusing electrode (62). Do not do.

In the above embodiment, the insulating support is displaced outward in the implantation part of the focusing electrode having the large opening, and the withstand voltage characteristic of the insulating support is improved. A structure with the This structure will be described with reference to FIG. In the figure, the same reference numerals as those in FIG.

This electron gun (81) has a heater (6b), a cathode (9b) and a first grid.
(12), second grid (13), first focusing electrode (14), third focusing electrode (16), fourth focusing electrode (17), second focusing electrode (15) and convergent electrode (18) Other than the third focusing electrode (16) and the fourth focusing electrode (17), the other electrodes are the implant parts (6 ₁ ), (9 ₁ ), (12 ₁ ), (13 ₁ ), (14 ₁ ), and (15 ₁ ) are extended and planted on the rod-shaped insulating support (2). Also in this case, it is particularly desirable to design so that the areas of the first grid (12) and the second grid (13) are suppressed as much as possible.

In each of the above-described embodiments, the electron gun for a color picture tube in which the three electron guns are arranged in a line in the lateral direction and the grid and the focusing electrode are integrated has been described, but the present invention is not limited to this. Of course, the present invention can be applied as it is to a structure in which three electron guns are arranged in an equilateral triangle and an electron gun that emits three electron beams with one electron gun. Further, it is needless to say that the number of focusing electrodes having a large opening does not have to be one set and the number may be increased.

[Advantages of the Invention] As described above, according to the present invention, the main lens portion has at least four focusing electrodes, and these focusing electrodes have the first and second electrodes and the first and second electrodes. , A third and a fourth electrode having one large opening arranged between the second electrodes, and the inner diameters of the large openings of the third and fourth electrodes from the outermost end of the opening of the first electrode By configuring the distance L to the portion and the thickness T of the third and fourth electrodes in the tube axis direction to satisfy L ≧ 2 × T, a high-performance lens can be obtained in the main lens portion,
It is possible to suppress the inter-electrode capacitance of the object point forming part, and further to reduce the distance between electron guns in the case of multiple electron guns, for a practical cathode ray tube with excellent electron gun performance. An electron gun can be provided.

[Brief description of drawings]

1 to 4 are views showing an embodiment of an electron gun for a cathode ray tube according to the present invention. FIGS. 1 and 2 are longitudinal sectional views taken from different directions, and FIG. FIG. 4 is a perspective view of a focusing electrode having a large opening, FIG. 4 is a potential distribution diagram of the main lens portion, and FIGS. 5 to 7 are schematic views of the main lens portion of another embodiment of the electron gun for a cathode ray tube according to the present invention. 8 and 9 are side views of still another embodiment of the electron gun for cathode ray tubes according to the present invention. 2 ... Insulating support, 3a, 3B, 3C ... Electron beam 6a, 6b, 6c ... Heater, 9a, 9b, 9c ... Cathode 12 ... First grid, 13 ... Second grid 14,15, 16,17,51,52,53,54,55,56,57,61,62,63,64,65,66
...... Focusing electrode 32a, 32b, 32c, 33a, 33b, 33c, 39a, 39b, 39c …… Aperture 36, 37 …… Large aperture

Claims (1)

[Claims] 1. An object point forming section including a plurality of electrodes including an electron beam generating section, and a main lens section including a plurality of electrodes for focusing an electron beam from the object point forming section onto a phosphor screen. In the electron gun for a cathode ray tube having, the main lens portion has at least four focusing electrodes, and these focusing electrodes have first and second electrodes having three openings, and between these first and second electrodes. It is composed of third and fourth electrodes having one large opening arranged, and the distance between these electrodes is set to 1 mm, and the third and fourth electrodes are arranged from the outermost end of the opening of the first electrode. The distance L to the inner diameter of the large opening,
The thickness T of the third and fourth electrodes in the tube axis direction is L ≧ 2 × T, and the potential of the first electrode and the third electrode adjacent to the first electrode and the second electrode Electrode and this second
An electron gun for a cathode ray tube, wherein the potentials of the fourth electrodes adjacent to the electrodes are different from each other.