Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
1999-09-02
2002-09-24
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
C313S458000, C313S460000, C313S409000
Reexamination Certificate
active
06455994
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electron gun for a color cathode ray tube, and more particularly, to an electrode of an electron gun for a color cathode ray tube which can extend an electric field for forming an electronic lens.
2. Description of the Related Art
In a general electron gun for a color cathode ray tube, spherical aberration and focusing characteristics are greatly affected by a main lens. Thus, in order to obtain good focusing characteristics, the spherical diameter of the main lens must be increased. Also, in order to reduce deflection power, it is preferable to reduce the diameter of the neck portion of a cathode ray tube. In this case, the area in which electron beam passing apertures of an electrode are located is decreased. It is necessary to increase the area of the electron beam passing apertures as much as possible in a limited area.
However, in an in-line electron gun, since three electron beam passing apertures are formed at at least two electrodes constituting an electronic lens in an in-line configuration, it is impossible to make the diameter of an electron beam passing aperture larger than a distance between centers of two adjacent electron beam passing apertures.
An electrode for solving the above-described problem is disclosed in U.S. Pat. No. 4,510,413. This electrode comprises a flat portion
11
having three electron beam passing apertures RH, GH and BH, a cylindrical skirt portion
12
extending from the edge of the flat portion
11
, and an embedded portion
13
extending from an end of the skirt portion
12
in a radial direction, as shown in
FIG. 1. A
tapering portion
14
leading to the flat portion
11
is formed at the edges of the respective electron beam passing apertures RH, GH and BH.
In the above-described electrode, the tapering portion
14
extends the electric field to increase the area of an electronic lens. However, since the electron beam passing apertures RH, GH and BH are independently formed, the effect of increasing the electronic lens is not satisfactory.
FIG. 2
shows an example of an electrode for forming a large-diameter lens, which is disclosed in U.S. Pat. No. 4,370,592.
As shown in
FIG. 2
, burring portions
5
b
and
6
b
are formed at edges of an electron outlet surface
5
a
of a focusing electrode
5
and an electron inlet surface
6
a
of a final accelerating electrode
6
, and large-diameter electron beam passing apertures
5
H ′ and
6
H ′ through which R, G and B electron beams pass commonly by slanted surfaces
5
c
and
6
c
recessed a predetermined depth from the burring portions
5
b
and
6
b
. R, G and B small-diameter electron beam passing apertures are formed adjacent the slanted surfaces
5
c
and
6
c.
According to the above-described electrode, an electric field can be extended by the large-diameter electron beam passing apertures
5
H and
6
H. However, a continuously smooth electric field cannot be formed around the burring portions
5
b
and
6
b
. This finally distorts the electronic lens formed by the electric field.
In particular, since the small-diameter electron beam passing apertures
5
H ′ and
6
H′ are formed adjacent the slanted surfaces
5
c
and
6
c
, there is a limit in increasing the eccentric distance between the small-diameter electron beam passing apertures
5
H ′ and
6
H′.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide an electrode of an electron gun for a color cathode ray tube which can reduce spherical aberration and improve focusing characteristics, by extending an electric field for forming a main lens.
Accordingly, to achieve the above objective, there is provided an electrode of an electron gun for a cathode ray tube comprising a first electrode member having a large-diameter electron beam passing aperture through which three electron beams pass, and a second electrode member installed in the first electrode member so as to be spaced apart from the edge of the first electrode member and having three small-diameter electron beam passing apertures, wherein a slant portion is formed to extend from the edge of the first electrode member toward the interior of the large-diameter electron beam passing aperture.
Also, slant surfaces extending to the surface of the second electrode member are formed at circumferences of the small-diameter electron beam apertures of the second electrode member.
According to another aspect of the present invention, an electrode of an electron gun for a cathode ray tube comprising a first electrode member having a large-diameter electron beam passing aperture through which three electron beams pass and a burring portion formed at the edge of the large-diameter electron beam passing aperture, and a second electrode member installed in the first electrode member so as to be spaced apart from the burring portion and having three small-diameter electron beam passing apertures, wherein slant surfaces extending to the surface of the second electrode member are formed at the circumferences of the small-diameter electron beam passing apertures of the second electrode member.
REFERENCES:
patent: 4370592 (1983-01-01), Hughes et al.
patent: 4510413 (1985-04-01), Yabe et al.
patent: 5834887 (1998-11-01), Spanjer et al.
Clove Thelma Sheree
Leydig , Voit & Mayer, Ltd.
Patel Nimeshkumar D.
Samsung Display Devices Co., LTD
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