Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2000-08-16
2002-03-19
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169400, C345S204000
Reexamination Certificate
active
06359390
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a structure of a display device for preventing electromagnetic interference (EMI). The display device comprises a display panel with a plurality of pixels formed between substrates.
2. Background of the Invention
Many conventional display devices such as a plasma display device and others employ an electromagnetic shield as a measure against EMI so that an electromagnetic wave generated by the display devices would not have an undesirable effect on various adjacent control circuits or communication systems.
FIG. 16
shows a sectional structure of a display device
100
comprising such a display panel. One example of a display panel
10
(hereinafter referred to as a panel) is an AC type plasma display panel (PDP). As shown in
FIG. 16
, in order to electromagnetically shield the display device
100
, the panel
10
and a drive circuit substrate
12
equipped with a drive circuit for driving the panel
10
are disposed within a conductive shielding case
20
made of metal. In the conductive shielding case
20
, a holding board
15
is provided on a non-display surface side of the panel
10
(below the broken line in the figure), which is opposed to a display surface
10
a
, to hold the panel
10
made of a glass substrate or the like. The panel
10
and the drive circuit substrate
12
are connected by a wiring board
14
including signal wiring, such as a flexible printed circuit (FPC). The wiring board
14
is also deposited within the conductive shielding case
20
.
If the conductive shielding case
20
totally covers the whole surfaces of the panel
10
and the drive circuit substrate
12
which is the biggest source of noise, a reliable electromagnetic shield becomes possible. In the display device as shown in
FIG. 16
, however, the conductive shielding case
20
does not cover the display surface of the panel
10
which is thus covered by a transparent or translucent conductive filter
18
to be electrically connected to the conductive shielding case
20
. By surrounding the panel
10
and the drive circuit substrate
12
with the conductive shielding case
20
and the conductive filter
18
, an electromagnetic noise emitted outside the display device
100
is excluded.
Employed as the conductive filter
18
for covering the display surface of the panel
10
is, for example, a glass or acrylic filter with a transparent conductive film, such as an indium tin oxide (ITO) film or a considerably thin silver evaporation film, formed on the internal or external surface thereof, or a filter with fine conducting wires formed lengthwise and crosswise with a small pitch, that is, a filter with a fine wire gauze laminated thereto.
Though conductive, the transparent conductive film such as an ITO has a higher electrical resistance compared to a metal material such as the conductive shielding case
20
, thereby providing less shield effect. Thus, in order to reduce the electrical resistance and increase the shield effect, the transparent conductive film needs to be thicker. However, the increased film thickness of the transparent conductive film deteriorates transmittance of light. This reduces display brightness or contrast, thereby reducing display quality. Further, it takes time and increases manufacturing cost to form a thick transparent conductive film.
The fine wire gauze, on the other hand, causes low transmittance of light, and in some cases, generates moire' on the display surface side in relation to a dot pitch of each pixel of the panel
10
. Thus, in this case, it is difficult to prevent deterioration in display quality.
SUMMARY OF THE INVENTION
A first aspect of the present invention is directed to a display device having a display panel with a plurality of pixels formed between a pair of substrates and giving a desired display by controlling each of the pixels. The display device comprises: a conductive shielding case with the display panel and a drive circuit for driving the display panel disposed therein, the conductive shielding case having an opening at the side of a display surface of the display panel; and a conductive member disposed between the drive circuit and the display panel. The drive circuit is disposed in the side of an non-display surface of the display panel formed within the conductive shielding case, and the conductive member and the conductive shielding case are connected to provide an electromagnetic shield to the drive circuit.
Preferably, according to a second aspect of the present invention, the display device of the first aspect further comprises a conductive portion having a ground potential; and a signal wire for electrically connecting the drive circuit and the display panel. The conductive portion and the signal wire make a static capacitance.
Preferably, according to a third aspect of the present invention, the display device of the second aspect further comprises an insulating layer formed on the signal wire: and a conductive layer formed on the insulating layer. The conductive layer is forced to have a ground potential.
Preferably, according to a fourth aspect of the present invention, the display device of the third aspect further comprises a connecting means for connecting the conductive layer to the conductive shielding case so that the conductive layer is forced to have a ground potential.
Preferably, according to a fifth aspect of the present invention, the display device of the second aspect further comprises insulating films covering top and bottom surfaces of the signal wire, respectively; and conductive layers formed on each of the insulating films. The conductive layers are forced to have a ground potential.
Preferably, according to a sixth aspect of the present invention, the display device of the second aspect further comprises insulating films covering top and bottom surfaces of the signal wire, respectively; and conductive layers formed on each of the insulating films. One of the conductive layers, disposed at the side of the conductive member disposed between the drive circuit and the display panel, is connected to the conductive member, while the other disposed at the side of the conductive shielding case is connected to the conductive shielding case.
Preferably, according to a seventh aspect of the present invention, the display device of the fifth or sixth aspect further comprises a variable-shape member having conductivity at least on the surface thereof and deposited at least between the conductive layer and the conductive shielding case. The conductive member and the conductive shielding case are electrically connected with the variable-shape member.
Preferably, according to an eighth aspect of the present invention, the display device according to either of the first to third aspects further comprises a noise filter inserted into paths of a power wire and a signal wire extracted from the drive circuit to the outside of the conductive shielding case; and an inductance component added to a grounded wiring path for electromagnetically shielding each of the power wire and the signal wire
A ninth aspect of the present invention is directed to an AC type plasma display panel comprising: a pair of substrates; a plurality of discharge pixel cells formed between the pair of substrates; and a pair of sustain electrodes formed on one of the pair of substrates, to which sustain pulses are applied to control discharge at each of the plurality of discharge pixel cells so as to alternatively reverse polarity between the pair of sustain electrodes to make an instantaneous average voltage almost constant at the pair of sustain electrodes during a sustained discharge period for each of the discharge pixel cells.
Preferably, according to a tenth aspect of the present invention, the display device according to either of the first to ninth aspects further comprises a transparent conductive layer formed on a display surface of the display panel. The transparent conductive layer is connected to the conductive shielding case.
According to the p
Mitsubishi Denki & Kabushiki Kaisha
Tran Thuy Vinh
Wong Don
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