JPH08321264A - Color picture tube - Google Patents

Abstract

PURPOSE: To provide a color picture tube having a high resolution by furnishing two auxiliary electrodes between a convergence electrode and final acceleration electrode, enlarging the bore of a main lens electric field without increasing the neck diameter of a glass bulb, and thereby reducing ill influence of eventual spherical aberration. CONSTITUTION: Two auxiliary electrodes 9, 10 are installed between a convergence electrode 7 on which a focus voltage is impressed and a final acceleration electrode 8 on which an anode voltage is impressed, wherein the convergence electrode 7 and final acceleration electrode 8 are composed of respective cylinders 12, 14 having a long circular section and end plates 11, 13 in the form of long circle which are fitted inside of the cylinders in positions retreated from openings on the aux. electrode side. The aux. electrodes 9, 10 consist of respective cylinders having a long circular section. The four electrodes are arranged coaxially, and the anode voltage is impressed on one aux. electrode 9 opposing to the convergence electrode 7, while the focus voltage is impressed on the other aux. 10 which is opposing to the final acceleration electrode 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color picture tube improved so that a high resolution can be obtained over the entire area of the phosphor screen surface.

[0002]

2. Description of the Related Art The resolution characteristic of a color picture tube depends on the shape and size of a beam spot formed on the surface of a phosphor screen. In order to obtain high resolution, the electrodes must be configured so that a circular beam spot with a small diameter is formed. On the other hand, the diameter of the electron beam passing through the main lens electric field of the electron gun increases as the beam current increases, and the beam spot diameter increases due to the spherical aberration of the main lens electric field. Therefore, usually, the diameter of the main lens electric field is made as large as possible to reduce the influence of spherical aberration.

Japanese Patent Publication No. 18540/1990 and Japanese Unexamined Patent Publication No.
In the color picture tube disclosed in Japanese Patent No. 133247, etc., as shown in FIGS. 5 and 6, the focusing electrode 1 has a cylindrical body 3 having an oval cross section, and an opening 3a on the inner side thereof on the final acceleration electrode side.
It is composed of an oval end plate 4 fitted in a position retracted from. The end plate 4 has three electron beam passage holes 4
a, 4b, and 4c are arranged inline. Similarly to the focusing electrode 1, the final accelerating electrode 2 is also composed of a tubular body 5 having an oval cross section, and an oval end plate 6 fitted inside the tubular body 5 at a position retracted from the opening 5a on the bundle electrode side. In the end plate 6, three electron beam passage holes 6a, 6b and 6c are arranged inline.

In this case, 3 formed between the three electron beam passage holes 4a, 4b, 4c of the focusing electrode 1 and the three electron beam passage holes 6a, 6b, 6c of the final acceleration electrode 2.
By overlapping the two main lens electric fields adjacent to each other, a large-diameter main lens electric field can be formed. Therefore, even if the diameter of the electron beam passing through the electric field of the main lens increases as the beam current increases,
The adverse effect of spherical aberration can be reduced. Further, since the lens magnification can be reduced, a small-diameter beam spot can be formed on the phosphor screen surface.

[0005]

However, there is a limit to the enlargement of the aperture of the main lens electric field by the above-mentioned structure. That is, when the outer diameters of the focusing electrode and the final accelerating electrode approach the inner diameter of the neck portion of the glass bulb, the wall electric field of the neck portion invades the main lens electric field, which exerts a bad influence. Further, if the diameter of the neck portion is increased, the deflection sensitivity is reduced. Therefore,
It is an object of the present invention to provide a color picture tube having an improved resolution by further enlarging the diameter of the main lens electric field to reduce spherical aberration without enlarging the neck diameter of the glass bulb.

[0006]

To achieve the above object, the color picture tube according to the present invention is characterized in that at least two electrodes are provided between a focusing electrode to which a focus voltage is applied and a final accelerating electrode to which an anode voltage is applied. A number of auxiliary electrodes are provided, each of the focusing electrode and the final accelerating electrode,
It is composed of a tubular body having an oval cross section and an oval end plate fitted inside thereof, and at least one end plate of the focusing electrode or the final accelerating electrode is retracted inward from an opening on the auxiliary electrode side. The auxiliary electrodes are each formed of a cylindrical body having an oval cross section, the focusing electrode, the final accelerating electrode, and the auxiliary electrode are coaxially arranged, and an anode voltage is applied to the auxiliary electrode facing the focusing electrode. The focus voltage is applied to each of the auxiliary electrodes facing the final acceleration electrode.

[0007]

According to the above characteristic structure, the three main lens electric fields formed between the focusing electrode and the final accelerating electrode overlap with each other as in the conventional case, and
By the action of the auxiliary electrode provided between the focusing electrode and the final acceleration electrode, the axial potential gradient in the main lens electric field forming region becomes gentle, so that the effective lens aperture is enlarged. As a result, the spherical aberration of the main lens electric field is reduced and the resolution is improved.

[0008]

Embodiments of the present invention will now be described with reference to the drawings. As shown in FIG. 1, two auxiliary electrodes 9 and 10 are provided between the focusing electrode 7 to which the focus voltage Vf is applied and the final accelerating electrode 8 to which the anode voltage Va is applied. The auxiliary electrodes 9 and 10 are arranged coaxially with the focusing electrode 7 and the final accelerating electrode 8, and
The anode voltage Va is applied to the auxiliary electrode 9 on the side, and the focusing voltage Vf is applied to the auxiliary electrode 10 on the side of the final acceleration electrode 8.

The focusing electrode 7 comprises a cylindrical body 12 having an oval cross section, and an oval end plate 11 fitted inside the cylindrical body 12 at a position retracted from the opening 12a on the auxiliary electrode 9 side. End plate 11
Are arranged inline as shown in FIG.
It has individual electron beam passage holes 11a, 11b and 11c. The final accelerating electrode 8 is, like the focusing electrode 7, a cylindrical body 14 having an oval cross section, and an opening 14 on the auxiliary electrode 10 side inside thereof.
The end plate 13 has an oval end plate 13 fitted in a position retracted from a, and the end plate 13 has three electron beam passage holes 13a, 13b, 13c arranged in-line. On the other hand, as shown in FIG. 2B, the auxiliary electrodes 9 and 10 are made of only a cylindrical body having an oval cross section and do not have an end plate.

As shown in FIG. 3, the main lens portion consisting of the focusing electrode 7, the auxiliary electrodes 9 and 10, and the final accelerating electrode 8 has three cathodes 15, a control electrode 16, an accelerating electrode 17 and the like arranged in-line. Together with the electron gun,
This electron gun is enclosed in a neck portion 18a of a glass bulb 18 forming an envelope of a color picture tube. In addition, on the outer peripheral surface of the funnel portion 18b of the glass bulb 18,
A deflection yoke 19 that generates a deflection magnetic field that acts on the three electron beams 20 emitted from the electron gun is mounted.

The distance between the focusing electrode 7 and the final accelerating electrode 8 is widened, and the anode voltage Va and the focusing voltage Vf are applied to the two auxiliary electrodes 9 and 10 provided therebetween, as described above. As a result, although the overlap of the electric fields of the three main lenses is similar to the conventional one, the electric potential distribution on the Z axis between the focusing electrode 7 and the final accelerating electrode 8 is the same as that of the conventional one as shown by the thick line in FIG. The slope is gentler than (thin line). Therefore, the effective lens aperture is enlarged, and both spherical aberration and lens magnification can be reduced. Further, since the wall electric field of the neck portion 18a and the main lens electric field are shielded by the auxiliary electrodes 9 and 10, the wall electric field is prevented from adversely affecting the electron beam trajectory.

The inner diameter of the neck portion 18a of the glass bulb 18 is set to 17.5 mm, the distance between the focusing electrode 7 and the auxiliary electrode 9,
The distance between the auxiliary electrode 9 and the auxiliary electrode 10, and the auxiliary electrode 1
The distance between 0 and the final acceleration electrode 14 is all 0.85 mm,
In the present embodiment in which the thickness of the auxiliary electrodes 9 and 10 was set to 0.6 mm, the effective lens diameter was about 7.2 mmφ, which was the same as the main lens diameter (5.5 mmφ) in the conventional electrode configuration shown in FIG. It has been expanded by about 30%. The anode voltage Va is 25 kV and the focus voltage Vf is 7
Each was set to kV.

The present invention is not limited to the above embodiments, but the present invention can be implemented by making various modifications to the above embodiments. For example, the auxiliary electrode may be composed of three or more cylinders. At least one of the auxiliary electrodes is
As described above, an end plate having three beam passage holes may be provided similarly to the focusing electrode and the like within a range in which the effect of grading the potential gradient is maintained.

Further, the shape of the three beam passage holes arranged inline in the end plate of the focusing electrode and the end plate of the final acceleration electrode is not limited to the shape shown in FIG. It may be circular or circular. Alternatively, the outer contours of the two beam passage holes on both sides may be combined with the inner wall of the cylindrical body.

[0015]

As described above, according to the present invention, in addition to the configuration in which the three main lens electric fields partially overlap each other adjacent to each other, at least two electric fields are provided between the focusing electrode and the final accelerating electrode. With the configuration in which individual auxiliary electrodes are provided,
The gradient of the axial potential distribution of the main lens portion becomes gentle. As a result, the effective main lens aperture is enlarged, and the spherical aberration and the lens magnification are both reduced, so that the beam spot can be further narrowed and a high resolution can be obtained over the entire area of the phosphor screen.

[Brief description of drawings]

FIG. 1 is a side sectional view of a main lens portion of a color picture tube according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a focusing electrode and an auxiliary electrode that form the main lens unit of FIG. 1 in a plane perpendicular to the Z axis.

FIG. 3 is a side sectional view showing a main part of the color picture tube of FIG.

FIG. 4 is a characteristic diagram showing a comparison of potential distributions on the Z axis between the main lens unit of FIG. 1 and a conventional main lens unit.

FIG. 5 is a side sectional view of a main lens portion of a color picture tube according to a conventional example.

6 is a cross-sectional view of the main lens portion of FIG. 5 taken along a plane perpendicular to the Z axis.

[Explanation of symbols]

 7 Focusing electrode 8 Final accelerating electrode 9,10 Auxiliary electrode 11,12 End plate 13,14 Cylindrical body

Claims (1)

[Claims] 1. At least two auxiliary electrodes are provided between a focusing electrode to which a focus voltage is applied and a final accelerating electrode to which an anode voltage is applied, and each of the focusing electrode and the final accelerating electrode has a cross-sectional length. It is composed of a circular cylinder and an oval end plate fitted inside thereof, and at least one end plate of the focusing electrode or the final accelerating electrode is retracted inward from the opening on the auxiliary electrode side, Each of the auxiliary electrodes is composed of a cylindrical body having an oval cross section, the focusing electrode, the final accelerating electrode, and the auxiliary electrode are coaxially arranged, and an anode voltage is applied to the auxiliary electrode facing the focusing electrode and the final accelerating electrode. A color picture tube characterized in that a focus voltage is applied to each of the auxiliary electrodes facing the electrodes.