Liquid crystal cells – elements and systems – Particular structure – Holder – support – frame – or housing
Reexamination Certificate
2002-03-28
2003-12-16
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Holder, support, frame, or housing
C349S058000, C349S150000, C349S152000
Reexamination Certificate
active
06665025
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device and a method for manufacturing a grounding device, and more particularly, to an LCD device that has a plurality of grounding protrusions in a region of the bottom surface of a printed circuit board that contacts a bottom chassis and does not have a signal transmission pattern. This increases a contact area between the printed circuit board and the bottom chassis and minimizes a damage caused by an electromagnetic wave.
2. Description of the Related Art
Generally, an LCD device is well accepted as a flat panel display. Especially, the smaller size, lighter weight and lower power consumption render the LCD device to replace the traditional cathode ray tube (CRT). LCD devices have been sufficiently developed to serve as a flat panel display device, and are used as a monitor for a lap-top computer and even for a desktop computer. Thus, LCD devices are gaining popularity.
Unlike CRTs, LCD devices are light emitting elements that adjust the amount of the light applied from an external device and display images on the screen. Therefore, an additional light source, say, a backlight unit, for irradiating the light onto the LCD panel is required.
Such a backlight assembly is composed of a mold frame, a lamp assembly contained in the mold frame and emitting a light, a light guide contained in the mold frame and guiding the light toward an LCD panel, a bottom chassis installed at the bottom surface of the mold frame and supporting members contained in the mold frame, and a top chassis combined with the mold frame to support the LCD panel.
An LCD device employed as a monitor for a desktop computer has a mold frame and a metal bottom chassis. A metal structure builds a stronger LCD device and shields the device from an electromagnetic wave. It further helps an LCD device discharge a large amount of heat generated when a lamp assembly emits a strong light to match a CRT display.
As shown in
FIG. 1
, if a printed circuit board (PCB)
90
connected to the LCD panel through a tape carrier package (TCP)
75
to drive an LCD panel (not shown) is positioned at the rear surface of a bottom chassis
60
, via holes
92
formed at the bottom surface of PCB
90
as shown in
FIG. 2
contact bottom chassis
60
, which may short electric signals. Therefore, an insulator sheet
85
is inserted between bottom chassis
60
and PCB
90
. Reference numeral
80
denotes a top chassis.
Most of driving elements
94
mounted onto PCB
90
to drive the LCD panel operate at a high frequency, and thus generate an electromagnetic interference (EMI). Such an EMI may interfere the electric signal transmitting to the LCD panel, and further cause an error in other devices when discharged to the outside of an LCD device
1
.
To reduce EMI, as shown in
FIG. 2
, a metal film
97
at the corner of PCB
90
is exposed by partially removing a solder resist film on metal film
97
, and a screw hole
96
is formed at the exposed portion of metal film
97
. Then, PCB
90
is fixed to bottom chassis
60
using a screw
95
, in order to ground an EMI to bottom chassis
60
.
A grounding via hole
92
′ connects a grounding pattern (not shown) formed at the top surface of PCB
90
and metal film
97
formed at the bottom surface of PCB
90
, and has a bridge
93
that connects metal film
97
at its periphery.
However, as described above, since the PCB contacts the bottom chassis only at its corners, the contact area between the PCB and the bottom chassis is limited. Thus, a large amount of EMI generated from the PCB are not grounded to the bottom chassis and may cause an interference with an electric signal applied to the LCD panel. As a result, an LCD device has a degraded screen quality, and the EMI discharged to the outside of the LCD device may cause an error in other devices.
The PCB contacts the bottom chassis ony at its corners because a light guide is installed all over the whole area of a mold frame except its edges corresponding to edges of the PCB.
Moreover, an LCD device used for a monitor has a problem of low productivity caused by an insulator sheet mounting process between the bottom chassis and the PCB in order to insulate the bottom chassis from the PCB.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to increase a contact area between a printed circuit board (PCB) and a bottom chassis to minimize an electromagnetic wave interference and enhance a product's reliability.
It is another object of the present invention to eliminate an insulator sheet attached between a PCB and a bottom chassis.
To achieve the above objects and other advantages, there is provided a liquid crystal display device in which a metal film of the bottom surface of the PCB that contacts a bottom chassis and does not have a signal transmission pattern is exposed by removing partially a solder resist film on the metal film and a conductive substance is deposited onto the exposed metal film to form a plurality of grounding protrusions, to thereby extend a contact area between the PCB and the bottom chassis.
REFERENCES:
patent: 4502059 (1985-02-01), Blessington
patent: 5786239 (1998-07-01), Ohsawa et al.
patent: 402122993 (1990-05-01), None
Kim Robert H.
McGuireWoods LLP
Nguyen Hoan
Samsung Electronics Co,. Ltd.
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