Liquid crystal cells – elements and systems – Particular structure – Holder – support – frame – or housing
Reexamination Certificate
2002-04-17
2004-01-27
Dudek, James (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Holder, support, frame, or housing
Reexamination Certificate
active
06683664
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a sheet for preventing a leakage electric field of low frequency which is produced from a fluorescent tube cable of a liquid crystal display device, and also relates to a liquid crystal display unit and a liquid crystal display device, including the sheet.
In a liquid crystal display device which displays an image by controlling the driving of liquid crystal and the emission of light from a fluorescent tube, based on image data, in order to apply a high voltage to the fluorescent tube, an inputted low voltage is converted into a high voltage by an inverter and the resulting high voltage is supplied to the fluorescent tube through a fluorescent tube cable. In such a liquid crystal display device, a leakage electric field of low frequency is produced from the fluorescent tube cable which serves as a path of the high voltage. This leakage electric field is a noise component, and may disturb the realization of a stable display condition. It is therefore necessary to take some measures to prevent such a leakage electric field.
FIG.
1
and
FIG. 2
are the exploded perspective view and side view of a conventional liquid crystal display unit adopting measures to prevent a leakage electric field. This liquid crystal display unit is configured by superimposing a liquid crystal display panel
21
, a sheet metal shield member
22
, an inverter printed board
23
, and a covering shield member
24
in this order.
The liquid crystal display panel
21
has a flat body including a glass plate on its display surface side (front-face side) and a plastic plate on both of the non-display surface side (rear-face side) and the side-face side. Fluorescent tubes are attached to the upper and lower edges inside the liquid crystal display panel
21
, respectively. Two bundles of fluorescent tube cables
25
composed of a plurality of thin wires for supplying a high voltage to the respective fluorescent tubes are connected to the fluorescent tubes, and each fluorescent tube cable
25
is extended to the non-display surface side (rear-face side) of the liquid crystal display panel
21
. Moreover, screw holes
21
a
for attachment are formed in the four corners of the liquid crystal display panel
21
.
The sheet metal shield member
22
has a flat body made of metal without a lid, and is placed to cover the non-display surface (rear face) of the liquid crystal display panel
21
. The sheet metal shield member
22
has two cut holes
22
a
for pulling out the respective fluorescent tube cables
25
to the inverter printed board
23
side, and screw holes
22
b
in two positions. On the inverter printed board
23
, an inverter circuit for converting an inputted DC voltage into an AC voltage is printed. The inverter printed board
23
has two connecting parts
23
a
serving as high voltage outputting parts to which the fluorescent tube cables
25
are connected respectively. Furthermore, the inverter printed board
23
has screw holes
23
b
which are formed in two positions corresponding to the screw holes
22
b
. The covering shield member
24
has a flat body made of metal without a lid, and is placed to cover the rear face of the sheet metal shield member
22
. The covering shield member
24
has screw holes
24
a
in two positions corresponding to the screw holes
22
b
and the screw holes
23
b.
A conventional liquid crystal display unit is assembled as follows. In a state where the fluorescent tube cables
25
are pulled out from the cut holes
22
a
of the sheet metal shield member
22
to the inverter printed board
23
side, the non-display surface (rear face) of the liquid crystal display panel
21
is covered with the sheet metal shield member
22
, and screws
26
are inserted into the screw holes
21
a
and screwed into the sheet metal shield member
22
so as to attach and secure the sheet metal shield member
22
to the liquid crystal display panel
21
. The tips (connectors) of the fluorescent tube cables
25
pulled out from the cut holes
22
a
are connected to the connecting parts
23
a
of the inverter printed board
23
. Then, the sheet metal shield member
22
is covered with the covering shield member
24
with the inverter printed board
23
between them, and screws
27
are inserted into the screw holes
24
a
, the screw holes
23
b
and the screw holes
22
b
so as to attach and secure the inverter printed board
23
and the covering shield member
24
to the sheet metal shield member
22
with the screws
27
. Note that a protective insulating sheet may also be placed between the sheet metal shield member
22
and the inverter printed board
23
.
In such a conventional liquid crystal display unit, the fluorescent tube cables
25
extended to the non-display surface side (rear-face side) of the liquid crystal display panel
21
are covered with the sheet metal shield member
22
, and the fluorescent tube cables
25
pulled out from the cut holes
22
a
are covered with the covering shield member
24
, so that leakage electric fields of low frequency which are produced from the fluorescent tube cables
25
are prevented by the presence of the sheet metal shield member
22
and covering shield member
24
.
In the conventional liquid crystal display unit, since a sheet metal shield member, a covering shield member etc. are included so as to prevent a leakage electric field from a fluorescent tube cable, there is a problem that the overall thickness of the liquid crystal display unit becomes thicker. Moreover, since such shield members are essential, there is also a problem of high cost.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made with the aim of solving the above problems, and it is an object thereof to provide a leakage electric field preventing sheet capable of preventing a leakage electric field from a fluorescent tube cable without including a shield member like those used conventionally and of significantly reducing the thickness of a liquid crystal display unit and a liquid crystal display device, and to provide a liquid crystal display unit and a liquid crystal display device, including the sheet.
Another object of the present invention is to provide a leakage electric field preventing sheet capable of reducing the costs of a liquid crystal display unit and a liquid crystal display device because it does not require a shield member like those used conventionally, and to provide a liquid crystal display unit and a liquid crystal display device, including the sheet.
A leakage electric field preventing sheet according to the first aspect of the present invention is a non-conductive sheet for preventing a leakage electric field which is produced from a fluorescent tube cable for supplying electric power to one or a plurality of fluorescent tubes attached to a liquid crystal display panel having a conductive non-display surface at the opposite side of a display surface, and is configured so as to bring the fluorescent tube cable into contact with the non-display surface of the liquid crystal display panel. The leakage electric field preventing sheet of the first aspect is a non-conductive sheet, and brings the fluorescent tube cable extended from the conductive non-display surface side (rear-face side) of the liquid crystal display panel into contact with the conductive non-display surface of the liquid crystal display panel. Accordingly, the fluorescent tube cable can be grounded on the conductive non-display surface of the liquid crystal display panel. It is therefore possible to efficiently prevent a leakage electric field from the fluorescent tube cable in a simple manner without using shield members as in the conventional example.
A leakage electric field preventing sheet according to the second aspect of the present invention is based on the first aspect, and comprises a notch portion for holding the fluorescent tube cable. The leakage electric field preventing sheet of the second aspect holds the fluorescent tube cable extended from the conductive non-display surface side (rear-face side) o
Dudek James
Greer Burns & Crain Ltd.
Kim Richard
LandOfFree
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