Electric lamp and discharge devices – Cathode ray tube – Plural beam generating or control
Reexamination Certificate
2002-08-01
2004-08-03
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Plural beam generating or control
Reexamination Certificate
active
06771016
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an inline electron gun and a color cathode ray tube using the same. More specifically, the present invention relates to a cylindrical electrode and a flat plate electrode with holes, which make up a main electrostatic lens of the inline electron gun.
2. Related Background Art
In conventional inline electron guns, as disclosed in JP 4(1992)-133247 A, for example, a main electrostatic lens is made up of a G3 electrode and a G4 electrode. The G3 electrode includes: a cylindrical outer electrode with a common aperture having an approximately oval-shape in cross-section and surrounding three electron beams; and a flat plate electrode provided within the outer electrode and having three passage holes for letting each of three electron beams pass therethrough. The G4 electrode has the same configuration as the G3 electrode.
In the following, the G3 electrode and G4 electrode included in the conventional inline electron gun disclosed in the above publication will be explained, with reference to FIG.
4
.
FIG. 4A
is a cross-sectional view of the G3 electrode and G4 electrode in the conventional inline electron gun,
FIG. 4B
is a front view of the G3 electrode from the arrow A of
FIG. 4A
, and
FIG. 4C
is an enlarged view of a part of the flat plate electrode illustrated in FIG.
4
B.
In
FIG. 4A
, reference numeral
41
denotes a cylindrical electrode with an aperture having an approximately oval-shape in cross-section,
42
also denotes a cylindrical electrode with an aperture having an approximately oval-shape in cross-section,
43
denotes a flat plate electrode provided within the cylindrical electrode
41
, and
44
also denotes a flat plate electrode provided within the cylindrical electrode
42
. These cylindrical electrode
41
and flat plate electrode
43
make up a G3 electrode
410
, and the cylindrical electrode
42
and the flat plate electrode
44
make up a G4 electrode
420
. Reference numerals
45
to
47
denote passage holes provided in the flat plate electrode
43
, and
50
to
52
denote passage holes provided in the flat plate electrode
44
. These passage holes are provided for letting three electron beams pass therethrough.
The three passage holes provided in each of the flat plate electrodes, as shown in
FIG. 4B
, are arranged along the inline direction (hereinafter also referred to as a “horizontal direction”).
FIG. 4B
shows the passage holes
45
,
46
and
47
provided in the flat plate electrode
43
. The opening geometry of the passage hole
46
and that of the passage hole
47
are symmetric with respect to a center line of the passage hole
45
along a direction orthogonal to the inline direction (hereinafter referred to as a “vertical direction”). It should be noted that the geometries of the passage holes
50
,
51
and
52
provided in the flat plate electrode
44
have the same as the passage holes
44
,
45
and
46
, respectively.
As shown in
FIG. 4C
, the passage hole
45
located at the center of the three holes provided in the flat plate electrode
43
has an oval shape with a major axis along the vertical direction. Whereas, as shown in
FIG. 4C
, the passage hole
47
located at either outer side (
FIG. 4C
shows the passage hole
47
only) has an outer half portion
49
in a semicircle shape and an inner half portion
48
configured in a higher-order curved shape with a degree of n more than 2 and not more than 3. It should be noted that in this specification the “inner side” refers to a direction toward the passage hole located at the center of the flat plate electrode, while the “outer side” refers to a direction away from the passage hole located at the center of the flat plate electrode.
In this way, the G3 electrode
410
and the G4 electrode
420
that make up a main electrostatic lens of an inline electron gun include: the outer cylindrical electrodes
41
and
42
with an opening geometry in an approximately oval shape with a major axis along the horizontal direction as shown in
FIG. 4
; and the flat plate electrodes
43
and
44
provided within the cylindrical electrodes
41
and
42
, respectively, arranged at a recessed position from each opening of the cylindrical electrodes, and having three passage holes.
With this configuration, electron beams passing through the center passage holes
45
and
50
are acted upon by an independent electric field formed by the passage holes
45
and
50
and a superimposed electric field formed by the straight-line portion of the periphery of the cylindrical electrodes
41
and
42
. Electron beams passing through the passage holes
46
and
51
or
47
and
52
, located at both outer sides, are acted upon by an independent electric field formed by the passage holes
46
and
51
or an independent electric field formed by the passage holes
47
and
52
, and the superimposed electric field formed by the curved-line portion of the periphery of the cylindrical electrodes
41
and
42
.
In the conventional inline electron guns, a convergence function (static convergence) for three electron beams can be optimized by appropriately selecting the degree n of the higher-order curved portion (e.g.,
48
in
FIG. 4C
) of the passage holes
46
,
47
and
51
,
52
at either outer side of the flat plate electrodes
43
and
44
, facing to the central passage holes
45
and
50
, and therefore an electron beam that reaches a screen finally can be made close to a perfect circle.
Now, in order to change the size of a cathode ray tube so as to be increased or decreased in size, and not redesigning the above-described conventional inline electron gun, then the cathode ray tube increases or decreases in size along the tube axis direction, which would degrade the static convergence property of three electron beams on the screen.
In the case of a small change in the size of the cathode ray tube, such degradation in the static convergence property may be improved with a magnet or the like disposed outside of the cathode ray tube.
However, when the static convergence property deteriorates beyond the capability of such a magnet or the like, a design of components of the electron gun and the applied voltage have to be changed so as to give a higher priority to the static convergence property on the screen.
More specifically, in order to maintain the static convergence property, the opening geometry of the passage holes provided in the flat plate electrodes of the G3 electrode and the G4 electrode has to be changed significantly, or the voltage applied to the G3 electrode has to be changed. As for the change in the voltage applied to the G3 electrode, there are many restrictions such as the voltage to be applied becoming so high that dielectric breakdown might occur, or the applied voltage cannot be changed in terms of the power source. In such cases, a pitch of small apertures in a G1 electrode has to be changed.
In addition, such a substantial change in the passage holes in the flat plate electrodes of the G3 electrode and the G4 electrode and the aperture pitch of the G1 electrode would lead to a situation where an assembly jig of the electron gun used before change cannot be used, and therefore a new assembly jig should be prepared, which would increase the cost of the assembly of the electron gun.
SUMMARY OF THE INVENTION
Therefore, with the foregoing in mind, it is an object of the present invention to provide an inline electron gun and a color cathode ray tube including the same, by which the manufacturing cost for an assembly jig of the electron gun can be reduced, for example, that might be generated with a change in the size of the cathode ray tube, and a favorable static convergence property can be realized.
To fulfill the above-stated object, an inline electron gun according to the present invention emits three electron beams aligned along a horizontal direction, and the inline electron gun includes: a cylindrical low potential side electrode provided with a first flat plate electrode; and a cylindrical high p
Merchant & Gould P.C.
Patel Vip
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