Graphic fluorescent display device

Details Graphic fluorescent display device Graphic fluorescent display device

2001-06-01

2002-12-31

Wong, Don (Department: 2821)

Electric lamp and discharge devices: systems

Plural power supplies

Plural cathode and/or anode load device

C315S169100, C313S503000

Reexamination Certificate

active

06501229

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a graphic fluorescent display device; and, more particularly, to a graphic fluorescent display device incorporating therein a planar grid.
BACKGROUND OF THE INVENTION
FIGS. 1A
to
2
B provide schematic views for illustrating the arrangements and operation methods of anodes and grids of conventional graphic fluorescent display devices.
FIG. 1A
is a top view for showing the arrangement of the anodes and the grids, in which reference notations A
11
to A
52
represent anodes; G
1
to G
5
, the grids; A
1
and A
2
, two anode lead wires. And in
FIG. 1A
, only three rows of the anodes and five grids are described. Every second anodes in a same row are connected to a same anode lead wire. When viewed from top of the fluorescent display device, the anodes, grids and filaments (not shown) are vertically disposed in that order while maintaining certain distances therebetween. Electrons emitted from the filaments pass through the grids G
1
to G
5
and reach the anode A
11
to A
52
.
In
FIG. 1A
, the grid G
1
controls the anodes A
11
and A
12
and the gird G
2
does the anodes A
21
and A
22
. The grids G
3
to G
5
also function similarly.
FIG. 1B
is a schematic view for explaining operation scheme of the graphic fluorescent display device shown in FIG.
1
A.
For instance, in order to turn on the anode A
22
to emit light, negative voltages are respectively applied to the grids G
1
, G
3
, G
4
and G
5
and the anode lead wire A
1
, while a positive voltage is respectively applied to the grid G
2
and the anode lead wire A
2
. The electrons emitted from the filament can pass through the grid G
2
but cannot pass through the remaining grids G
1
, G
3
, G
4
and G
5
since the electrons moving toward the grid G
1
, G
3
, G
4
and G
5
are repulsed by the negative electric fields created by negative voltages applied thereto. The electrons passing through the grid G
2
can reach the anode A
22
to which positive voltage is applied but cannot reach the anode A
21
to which negative voltage is applied.
Since, however, the electrons moving toward the anode A
22
are affected by the negative electric field generated by the grid G
3
of negative potential, the electrons may not reach an edge part of the anode A
22
adjacent to the grid G
3
. As a result, there occurs the so-called eclipse phenomenon where an anode has a dark spot at the edge adjacent to a neighboring grid.
Referring to
FIG. 1C
, there is illustrated another conventional graphic fluorescent display device having anodes controlled by three anode lead wires A
1
to A
3
wherein every third anodes are connected to a same anode lead wire.
For instance, if negative voltages are applied to grids G
1
, G
3
and G
4
, while a positive voltage is applied to the grid G
2
, electrons emitted from filaments can pass through only the grid G
2
as shown in FIG.
1
C. Further, if the anode lead wires A
1
and A
3
are of positive potentials, the electrons can reach the anodes A
22
and A
32
. In this case, since the electrons moving toward the anodes A
22
and A
32
are affected by negative electric fields generated by the grids G
1
and G
3
of negative potentials, the electrons may not reach an edge part of the anode A
22
adjacent to the anode G
1
and an edge part of the anode A
32
adjacent to the anode G
3
. Therefore, such edge parts do not emit sufficient light, which results in dark streaks thereat (See, e.g., Japanese Laid-Open Publication Number JP63-35037).
Referring to
FIGS. 2A and 2B
, there are illustrated conventional operation methods employed in order to prevent the non-uniformity in the brightness of the fluorescent display device described above with reference to
FIGS. 1A
to
1
C.
In
FIGS. 2A and 2B
, there are four anode lead wires A
1
to A
4
and every fourth anodes are connected to a same anode lead wire. Each of the grids G
1
to G
5
controls two anodes.
In
FIG. 2A
, the grids G
2
and G
3
are of positive potentials and the grids G
1
, G
4
and G
5
are of negative potentials. Since the anodes A
22
and A
31
are selected to emit light, the anode lead wires A
1
and A
4
are of positive potential. In this case, since the anodes A
22
and A
31
are away from the grids G
1
and G
4
, the negative electric fields created by the grids G
1
and G
4
scarcely influence the passages of the electrons emitted from filaments to the anodes A
22
and A
31
.
The arrangement of the anodes, the grids and the anode lead wires shown in
FIG. 2B
is identical to the one shown in
FIG. 2A
, but grid selection scheme is different from that of FIG.
2
A.
In
FIG. 2B
, positive potentials are applied to the grids G
2
, G
3
and G
4
and negative potentials are applied to the grids G
1
and G
5
. Since the anodes A
31
, A
32
controlled by the grid G
3
are selected to be turned on, positive potentials are applied to the anode lead wires A
1
and A
2
. In this case, since the anodes A
31
and A
32
are away from the grids G
1
and G
5
of negative potential, the negative electric fields created by the grids G
1
and G
5
hardly influence the passages of the electrons emitted from the filaments to the anodes A
31
and A
32
. Further, the effect of the negative electric fields created by the grids G
1
and G
5
is less than that described in
FIG. 2A
(See, e.g., Japanese Laid-open Publication supra).
In
FIGS. 1A
to
1
C, the non-uniformity in the brightness due to electronic fields of neighboring grids may not be avoided. Such a non-uniformity problem can be avoided by the control schemes as shown in
FIGS. 2A and 2B
. However, the configurations of
FIGS. 2A and 2B
require one grid for every two anodes, even though the anodes are controlled by four anode lead wires. Resultantly, still a large number of grids are required, complicating the structure of a fluorescent display device with a large number of drivers of the grids. Further, a duty factor becomes lower to thereby decrease the luminance level of the device.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to eliminate the above-mentioned disadvantages of the prior art.
In accordance with the present invention, there is provided a fluorescent display device including:
a first substrate;
an insulating layer formed on the first substrate;
n columns or rows of m anodes, each anode having a fluorescent layer thereon;
Q anode lead wires provided for each column or row of the m anodes, every Qth anodes being connected to a same anode lead wire; and
z grids, z being a positive integer equal to or greater than m/Q but smaller than (m/Q)+1, formed on the insulating layer, each grid being arranged across the n columns of m anodes, each grid being provided with openings for each column or row of m anodes, each opening exposing a portion of the insulating layer and one anode being formed on the exposed portion of the insulating layer,
wherein the insulating layer, the anodes, the anode lead wires and grids are thin films.


REFERENCES:
patent: 4218636 (1980-08-01), Miyazawa
patent: 4459514 (1984-07-01), Morimoto et al.
patent: 6392356 (2002-05-01), Stevens

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