Computer graphics processing and selective visual display system – Display driving control circuitry
Reexamination Certificate
2002-03-06
2004-10-05
Nguyen, Jimmy H. (Department: 2673)
Computer graphics processing and selective visual display system
Display driving control circuitry
C345S087000, C349S056000, C349S059000
Reexamination Certificate
active
06801195
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flat panel type display device of such as a color liquid crystal display device and, in particular, the present invention relates to a flat panel type display device constructed such that unnecessary electromagnetic radiation, which may bring about EMI (Electro-magnetic Interference), etc., is restricted.
2. Description of the Prior Art
As a flat panel type display device, a color liquid crystal display device of an active matrix system, for example, includes a liquid crystal display panel and a backlight for illuminating a lower surface of the liquid crystal display panel. A horizontal drive circuit substrate and a vertical drive circuit substrate are arranged outside an outer peripheral portion of the liquid crystal display panel. Further, a signal processing substrate for converting an externally supplied image signal into a horizontal drive signal and supplying the latter signal to a liquid crystal driving IC on the horizontal drive circuit substrate by way of a connecting substrate is arranged on a rear surface side of the liquid crystal display panel. The liquid crystal display panel, the backlight and the horizontal and vertical drive circuit substrates are accommodated in a casing constructed with a front shield plate, which is formed of a metal and has a display window, and a metal rear shield plate for accommodating and holding the backlight.
FIG. 1A
is a perspective view of an example of a conventional liquid crystal display device, illustrating a positional relation between a liquid crystal display panel, a horizontal drive circuit substrate and a signal processing substrate thereof and
FIG. 1B
is a plan view of the signal processing substrate and a connecting unit for connecting the horizontal liquid crystal display panel to the signal processing substrate, which are extended in a plane. Further, FIG.
2
A and
FIG. 2B
are cross sections taken along a line A—A′ in
FIG. 1A
, illustrating a portion of a second shield plate, which has no nail portion for fixing the connecting substrate to the second shield plate and a portion thereof, which has a nail portion provided appropriately, respectively. Incidentally, in order to simplify the illustration, the vertical drive circuit substrate, the front shield plate, the rear shield plate and the backlight, etc, are not shown in FIG.
1
A.
FIG. 3
is a cross section taken along a line B—B′ in FIG.
1
A.
Referring to
FIG. 1A
to
FIG. 3
, the conventional liquid crystal display device
510
is constructed with the liquid crystal display panel
511
, a front shield plate
531
, a first rear shield plate
533
, a second rear shield plate
534
, the signal processing substrate
521
, the horizontal drive circuit substrate
524
in the form of a TCP (Tape Carrier Package) on which horizontal driving IC's
526
are mounted, the connecting substrate
523
, a flexible printed circuit substrate (referred to as FPC, hereinafter)
522
and a light diffusing plate
513
for uniformly dispersing light from the backlight (not shown), etc. Incidentally, the horizontal drive circuit substrate
524
will be referred to as TCP, hereinafter.
A peripheral portion of the display panel
511
, which is a non-display region, is sandwiched between the front shield plate
531
and the second rear shield plate
534
by way of a first spacer
546
and a second spacer plate
547
, respectively. The light diffusing plate
513
received and held by the first rear shield plate
533
and the backlight (not shown) are provided on the side of a rear surface (opposite to a display surface) of the liquid crystal display panel
511
.
As shown in
FIG. 3
, the signal processing substrate
521
is fixed to a rear surface side of the first rear shield plate
533
via an insulating sheet
555
and the connecting substrate
523
is fixed to the second rear shield plate
534
in a plane substantially perpendicular to the display surface of the liquid crystal display panel
511
via the insulating sheet
551
. This fixation of the connecting substrate
523
is performed by at least one nail portion
537
provided in an appropriate portion of the second rear shield plate
534
, as shown in FIG.
2
B. The portion of the second rear shield plate
534
in which the nail portion
537
is provided corresponds to a region of the connecting substrate
523
in which any wiring pattern is not formed. Incidentally, a connecting unit
520
for connecting the signal processing substrate
521
to the liquid crystal display panel
511
includes the FPC
522
, the connecting substrate
523
and the TCP
524
, as shown in FIG.
1
B.
One end of the TCP
524
(on the output end side) is bonded to electrodes provided in an edge portion of the liquid crystal display panel
511
by thermocompression bonding with using, for example, a thermoplastic, anisotropic electrically conductive film and the other end (input end side) thereof is connected to the connecting substrate
523
by, for example, soldering. The connecting substrate
523
and the signal processing substrate
521
are connected to each other by the FPC
522
.
Incidentally, an outer casing (not shown) having at least an electrically conductive inner surface portion and covering the whole rear surface of the liquid crystal display panel including the signal processing substrate
521
is provided on the rear surface side of the liquid crystal display device
510
. The front shield plate, the first rear shield plate and the second rear shield plate are connected to the inner surface portion of the outer casing.
In the conventional liquid crystal display device
510
described above, an electromagnetic shield structure for restricting EMI, etc., due to unnecessary electromagnetic radiation from electronic parts and wiring mounted on the signal processing substrate
521
, the TCP
524
and/or the vertical driving circuit substrate, which is not shown, etc., is formed by connecting at least the electrically conductive inner surface portion of the outer casing covering these components to a common ground terminal (not shown) of the liquid crystal display device
510
.
However, with the recent tendency of increase of the operating frequency, particularly, the horizontal driving frequency, of the liquid crystal display device, unnecessary electromagnetic radiation becomes a problem in, particularly, the connecting substrate
523
in which a number of horizontal drive signals are transmitted along a long wiring within a limited region. As shown in
FIG. 2A
, FIG.
2
B and
FIG. 3
, the connecting substrate
523
is fixed to the second rear shield pate
534
via the thin insulating sheet
551
and, therefore, the electric insulation is maintained. However, it has been found that, when a number of high frequency signals flow in the connecting substrate
523
, the signals are leaked between the first rear shield plate
533
and the second rear shield plate
534
by such as capacitive coupling and unnecessary electromagnetic radiation occurs through the first rear shield plate
533
and the second rear shield plate
534
as an antenna.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a display device such as a color liquid crystal display device having a structure with which unnecessary electromagnetic radiation, which may cause EMI, etc., can be restricted even when a number of high frequency signals are transmitted through a long wiring in a connecting substrate having limited wiring space.
In order to achieve the above object, the display device according to the present invention is featured by comprising at least a display unit for displaying an image on a front surface of the display unit, a signal processing unit for processing an externally supplied image signal and outputting a first signal for displaying the image, a drive unit for receiving the first signal and outputting a second signal for driving the display unit, a connecting unit for connecting the signal processing unit to the display unit,
NEC LCD Technologies Ltd.
Nguyen Jimmy H.
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