Electric lamp and discharge devices – Cathode ray tube – Ray generating or control
Reexamination Certificate
1999-07-27
2003-03-25
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
Cathode ray tube
Ray generating or control
C313S452000, C313S441000, C313S409000, C315S382000, C315S382100, C315S015000, C315S381000
Reexamination Certificate
active
06538370
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cathode-ray tube electron gun in which unwanted radiation can be reduced and an electron gun having such an cathode-ray tube.
2. Description of the Related Art
Recently, a problem of an unwanted radiation from a cathode-ray tube, in particular, a display monitor driven at a high-frequency voltage, becomes highlighted.
To cope with the unwanted radiation in the display monitor, there is a mainstream that a shield cover is provided to cover the whole of the cathode-ray tube so that unwanted radio waves can be prevented from being radiated to the outside of the cathode-ray tube. Accordingly, there is no technology in which a generation source itself of radio waves generated from a cathode-ray tube is analyzed and a fundamental countermeasure is devised.
When the cathode-ray tube is protected with the large shield cover as described above, it is unavoidable that a manufacturing cost of the cathode-ray tube increases.
On the other hand, the assignee of the present application has analyzed the related-art electron gun, and has discovered an unwanted radiation generation source for an electron gun.
FIG. 1
of the accompanying drawings shows a structure of a typical electron gun for use with a color cathode-ray tube.
As shown in
FIG. 1
, this electron gun
12
comprises three cathodes K
R
, K
G
and K
B
corresponding to red, green and blue arranged in an inline fashion. A first electrode (G
1
)
1
, a second electrode (G
2
)
2
, a third electrode (G
3
)
3
, a fourth electrode (G
4
)
4
, a fifth electrode (G
5
)
5
, a sixth electrode (G
6
)
6
are sequentially arranged on the same axis so as to become common to the three cathodes K
R
, K
G
and K
B
. A shield cup
7
is provided at the final stage, and this electron gun is arranged as a so-called unibipotential system three-beam single electron gun. The first electrode
1
and the second electrode
2
are each formed of a plate-like material.
The first electrode
1
is supplied with about 0V from a first electrode lead (electrically-conducting lead)
9
, the second electrode
2
and the fourth electrode
4
are supplied with about 200V to 800V from a second electrode lead (electrically-conducting lead)
10
and the third electrode
3
and the fifth electrode
5
are supplied with a focusing voltage of about 20% to 35% of an anode voltage (high voltage) from a focus lead (electrically-conducting lead). The first electrode lead
9
, the second electrode lead
10
and the focusing lead
11
are connected to stem pins, respectively. The sixth electrode
6
and the shield cup
7
are supplied with an anode voltage of about 20 kV to 32 kV. The three cathodes K
R
, K
G
, K
B
are driven by a high-frequency voltage (i.e., a so-called video signal).
In this electron gun
1
, electron beams B
R
, B
G
and B
B
generated and controlled y the cathodes K
R
, K
G
, K
B
and the first electrode
1
and the second electrode
2
are adjusted in divergence angle by a front-stage electron lens or a front-stage focusing lens comprising the third electrode
3
, the fourth electrode
4
and the fifth electrode
5
and then focused by a main electron lens (i.e., a main focusing lens) comprising the fifth electrode
5
and the sixth electrode
6
.
FIG. 2
shows a color cathode-ray tube having such electron gun
12
.
As shown in
FIG. 2
, in a color cathode-ray tube
13
, the above-mentioned electron gun
12
is disposed within a neck portion
15
of a cathode-ray tube assembly (i.e., a so-called glass bulb)
14
in an opposing relation to a fluorescent screen
17
. A color selection mechanism is closely opposed to the fluorescent screen
17
, although not shown. Further, there are disposed a deflection yoke
16
outside the cathode-ray tube assembly
14
for deflecting the electron beams B
R
, B
G
, B
B
in the horizontal and vertical directions. In
FIG. 2
, reference numeral
18
denotes a video base plate disposed on the end portion of the neck portion
15
. This color cathode-ray tube
13
is covered at its whole rear portion except the front surface of a panel portion
19
with a shield cover material
20
in order to protect it from the influence of unwanted radiation, a terrestrial magnetism or the like.
In general, the first electrode lead
9
and the second electrode lead
10
of the above-mentioned electron gun
12
are each a single electrode lead because it is intended to supply a voltage for electrically conducting the electron gun
12
. In particular, in the case of the plate-like first electrode
1
and second electrode
2
, the first electrode lead
9
and the second electrode lead
10
are each a single electrode lead.
FIG. 3
is a schematic diagram showing the first electrode
1
having the cathodes K
R
, K
G
, K
B
and one lead
9
as a model example. In
FIG. 3
, reference numerals
22
denote electron beam apertures defined in the first electrode
1
to pass electron beams. With this arrangement, when the cathodes K
R
, K
G
, K
B
are driven by a high-frequency voltage, the first electrode
1
, which is spaced apart from the cathodes K
R
, K
G
, K
B
by a short distance of about 50 &mgr;m to 200 &mgr;m has a capacity between it and the cathodes K
R
, K
G
, K
B
, so that the cathodes K
R
, K
G
, K
B
, the first electrode
1
and the first electrode lead
9
constitute a high-efficiency antenna, thereby causing unwanted radiation.
That is, the assignee of the present application has discovered that, when the first electrode lead
9
is the single electrode lead, the cathodes (K
R
, K
G
, K
B
) and the first electrode
1
constitute the high-efficiency antenna which serves as an unwanted radio wave generation source.
This is also considered in the second electrode
2
.
FIG. 4
is a schematic diagram showing the first electrode
1
having the cathodes K
R
, K
G
, K
B
and one lead
9
and the second electrode
2
having one lead
10
as a model example. In
FIG. 4
, reference numerals
23
designate electron beam apertures defined in the second electrode
2
to pass electron beams.
Since the second electrode
2
is spaced apart from the first electrode
1
by a distance of about 0.1 mm to 0.3 mm, although a magnitude of capacity becomes small as compared with that of the first electrode
1
, the second electrode has a capacity between it and the cathodes K
R
, K
G
, K
B
to form an antenna to cause unwanted radiation.
Unwanted radiation generated from the electron gun
12
where the first electrode
1
and the second electrode
2
have each single leads
9
and
10
as shown by the model example in
FIG. 3
or
4
is represented as shown by a curve I in
FIG. 15
which shows unwanted radiation level.
The graph of
FIG. 15
shows unwanted radiation level measured by a detection antenna located at the position distant from the electron gun
12
by a distance of 1 m when the high-frequency voltage is applied to the cathodes K
R
, K
G
, K
B
. In the graph of
FIG. 15
, the vertical axis represents a relative value of unwanted radiation level, and the horizontal axis represents the frequency of the high-frequency voltage applied to the cathodes.
Accordingly, in the color cathode-ray tube
13
having the electron gun
12
which is arranged as shown in
FIGS. 3 and 4
, the shield cover material
20
shown in
FIG. 2
should have a considerably strong shielding effect.
The radio wave generation source itself of the electron gun according to the related art has been described so far.
SUMMARY OF THE INVENTION
In view of the results obtained when the above-mentioned radio wave generation source itself was analyzed, it is an object of the present invention to provide a cathode-ray tube electron gun in which unwanted radiation can be alleviated and a cathode-ray tube including such electron gun.
According to the present invention, there is provided a cathode-ray tube electron in which a first electrode includes a plurality of electrical conduction leads.
Since the first electrode includes a plurality of conduction leads, the first electrode can achieve a shiel
Amano Yasunobu
Endou Mitsunori
Kikuchi Norifumi
Shirai Takashi
Sugimoto Kazuo
Kananen, Esq. Ronald P.
Patel Nimeshkumar D.
Santiago Mariceli
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