Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
1999-09-09
2002-08-06
Chow, Dennis-Doon (Department: 2675)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C313S489000, C313S492000
Reexamination Certificate
active
06429832
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a plasma display panel (PDP) unit and, more particularly, to a surface discharge type PDP having a plurality of common electrodes and a plurality of scanning electrodes on a single plane for discharging therebetween.
(b) Description of a Related Art
In general, a PDP has a large number of advantages of smaller thickness, lower flicker, larger contrast, larger display area, quicker response etc., and thus is expected for use as a flat display panel unit in a personal computer system or a workstation system as well as a wall television.
PDPs are categorized by the operational principle thereof into two types: a DC discharge type wherein uninsulated electrodes are exposed to a discharge space (or discharge gas) for operation at a DC voltage; and an AC discharge type wherein electrodes are insulated from the discharge gas by an insulating coat for operation at an AC voltage. The AC discharge type, such as used as a wall television, is further categorized by the operational principle thereof into two types: a memory type using a function of the insulator for storing electric charge in each pixel area (discharge cell); and a refreshing type which does not have a memory function. The brightness or luminance of the PDP is generally proportional to the number of repetitive discharges or the frequency of the driving pulse for the PDP. The present invention relates to any type of PDPs.
FIG. 1
shows a typical configuration of a color PDP, such as described in JP-A-8-55581. The color PDP has a front glass panel
46
, a pair of optical filters
48
sandwiching therebetween the front glass panel
46
for absorbing a specified frequency range of the visible light passed by the front glass panel
46
, and an electromagnetic filter
47
for absorbing electromagnetic waves radiated from the PDP as well as optical waves, which are disposed at the front side of the color PDP
45
.
The described configuration is silent as to the shield for the electromagnetic waves at the rear side of the PDP
45
, and thus does not have a desired electromagnetic shield function.
FIG. 2
shows a color PDP unit, such as described in JP-A-9-145918 and -9-149346. The color PDP unit includes a filter
52
including an electromagnetic shield layer at the front side of the PDP
51
, wherein the filter
52
has an external terminal
52
a
of the electromagnetic shield layer at the rear side of the filter
52
, and the external terminal
52
a
is in electrical contact with a metal fitting
57
used for mounting the PDP
51
at the front frame
53
of the PDP unit. A rear housing
54
of the PDP unit has a plurality of projecting bosses
58
for mounting the PDP
51
at the rear side of the PDP
51
. The filter
52
is connected to the ground of the color PDP
51
through the fittings
57
, the bosses
55
having a conductive coat thereon, the inner wall of the rear housing
54
and the bosses
58
.
Although the described configuration has an electromagnetic shield at both the front and rear sides of the PDP
51
by enclosing the color PDP
51
with the filter
52
, the front frame
53
and the rear housing
54
, the color PDP unit cannot have an effective shield function if there is malfunction in electric contact between the filter
52
and the frame
53
and between the frame
53
and the housing
54
. In addition, even if a sufficient electric contact is achieved between the filter
52
and the ground, a higher level of the electromagnetic radiation is not effectively shielded by the filter
52
.
FIG. 3A
shows another color PDP unit, such as described in JP-A-9-172267, and
FIG. 3B
is a sectional view taken along a plane “C” in FIG.
3
A. The color PDP unit includes a frame body
61
made of a conductive material such as an aluminum alloy for receiving therein a color PDP
60
and a driving circuit thereof. A rear cover
63
made of plastics is fixed onto the rear side of the frame body
61
by screws
65
. A front frame
62
made of plastics is also fixed onto the frame body
61
by way of screws
64
. Thus, the PDP unitis shielded from electromagnetic radiation therefrom by the rear cover
63
and the front frame
62
.
However, the shield function of the frame body
61
, rear cover
63
and the front frame
62
is not sufficient because of the presence of the front opening of the frame body
61
and the front frame
62
. Thus, the described configuration cannot provide an effective electromagnetic shield.
JP-A-9-306366 describes a color PDP unit
75
having a filter
70
shown in FIG.
4
. The filter
70
is provided for shielding the electromagnetic radiation from the PDP, and includes a filter substrate
71
made of plastic resin added with pigments for selectively absorbing radiation, a reflection-resistant film
74
attached onto a side of the filter substrate
71
far from the PDP, and a silver-sputtered film
72
and an AN film
73
consecutively adhered onto the other side of the filter substrate
71
near the PDP. The silver-sputtered film
72
is made of polyethylene terephthalate (PET) sputtered by silver or inorganic substance, and the AN film
73
has a function for preventing generation of a Newton ring. The silver-sputtered film
72
is connected to the ground for discharging the voltage induced by the electromagnetic radiation.
The described configuration is also silent as to the shield from the electromagnetic radiation at the rear side of the PDP, as in the case of JP-A-8-55581 and thus does not have a sufficient electromagnetic shield function.
As described heretofore, the conventional PDP units generally use an electromagnetic shield by surrounding or enclosing the color PDP with a housing or a filter made of an electromagnetic shield substance. The techniques using the shield substance, however, generally involves higher costs because of the accuracy required in fabrication of the housing or the filter for confinement of the electromagnetic radiation within the housing or an insufficient electromagnetic shield function.
Especially, the electromagnetic shield technique using the housing or filter does not reduce the electromagnetic radiation itself. Thus, even if the electromagnetic shield is effectively performed against electromagnetic radiation from the PDP by some elements, leakage from other elements may be the next problem to be solved, iterating this procedure until a sufficient shield can be obtained as a whole. Thus, a long time and complicated fabrication process may be necessary before a sufficient shield can be obtained against the electromagnetic radiation from the PDP unit.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a PDP unit having a function for reducing the electromagnetic waves without using a housing or filter made of an electromagnetic shield substance.
The present invention provides a plasma display panel (PDP) unit comprising first and second substrates opposing each other for defining therebetween a plurality of discharge cells, a plurality of first electrodes each disposed on the first substrate to extend in a row direction, a plurality of second electrodes each disposed on a first surface of the second substrate to extend in a column direction, and a first means for canceling an electromagnetic radiation from the second electrodes.
It is preferable for the first means to cancel the electromagnetic radiation from the second electrodes at least by six decibels.
In accordance with the PDP unit of the present invention, since the electromagnetic radiation from the second electrodes can be cancelled by the first means, a high-performance filter or an expensive housing is not necessary in the PDP unit, thereby reducing the costs of the PDP unit in reducing the electromagnetic radiation from the PDP unit.
REFERENCES:
patent: 4164678 (1979-08-01), Biazzo et al.
patent: 6090464 (2000-07-01), Yoo
patent: 5537753 (1980-03-01), None
patent: 63 076232 (1988-04-01), None
patent: 2028690 (1990-01-01), None
patent: 4287397 (1992-10-01), None
patent: 7319
Harada Takashi
Kuriyama Toshihide
Sekii Yoshizumi
Chow Dennis-Doon
Young & Thompson
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