Liquid crystal cells – elements and systems – Particular structure – Holder – support – frame – or housing
Reexamination Certificate
2001-02-23
2002-05-21
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Holder, support, frame, or housing
Reexamination Certificate
active
06392724
ABSTRACT:
CROSS REFERENCES TO RELATED APPLICATIONS
This application claims the benefit, under 35 U.S.C. § 119, of Korean Patent Application No. 2000-8969, filed on Feb. 24, 2000, the entirety of which is hereby incorporated by reference for all purposes as if fully set forth herein.
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a structure of a liquid crystal display module having metallic frames for fixing a back light unit and a liquid crystal display panel.
2. Description of Related Art
Liquid crystal displays (LCDs) are gaining in popularity for use in systems such as television receivers, computer monitors, avionics displays, aerospace displays, and other military-related displays where the elimination of cathode ray tube (CRT) technology is desirable for several reasons. In particular, CRTs are characterized by large depth dimensions, undesirably high weight, and fragility. Additionally, CRTs require a relatively high voltage power supply in order to sufficiently accelerate electron beams for displaying images.
The aforementioned shortcomings of CRTs are overcome by flat panel liquid crystal displays in which matrix arrays of liquid crystal picture elements or pixels are arranged in a plurality of rows and columns. In general, LCD devices have various advantages in comparison with CRT display devices in that they are thin in thickness and low in power consumption, etc. Therefore, such LCD devices might be expected to be substituted for CRT display devices and have been a matter of great interest in some industry fields.
In contrast to the CRT, the liquid crystal display device requires a light source, because the liquid crystal is not a fluorescent material. A cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL) or the like is used as the light source of the liquid crystal display device. The lamp is included in a back light unit of the liquid crystal display device. Back light units are classified into direct back light type (or direct type) units and edge light type (or edge type) units, according to a position of the lamp.
In the case where the direct type back light unit is used for a liquid crystal display device, incident rays irradiating from a lamp are directly incident to a liquid crystal display panel after a diffusion sheet uniformly diffuses the incident rays. In the case where the edge type back light unit is used, rays from a lamp are incident to a liquid crystal display panel via a light guide. A detailed explanation of the edge type will be provided subsequently.
The edge type back light unit generally includes a lamp, a light guide on a side surface of the lamp, a diffusion sheet on the top surface of the light guide, and a reflection sheet on the bottom surface of the light guide. The light guide uniformly scatters rays irradiating from the ramp such that rays are uniformly incident on the diffusion sheet. The reflection sheet reflects rays directed opposite to the diffusion sheet such that most of the rays from the lamp are incident on the diffusion sheet. The diffusion sheet diffuses the rays to provide a uniform luminance throughout a light exit surface of the diffusion sheet. Additionally, a set of two prism sheets is beneficially disposed on the light exit surface of the diffusion sheet. The prism sheet set selectively changes the light rays as they pass through the sheets such that the luminance is enhanced at a particular viewing angle range. The rays from the prism sheet set are incident to the liquid crystal display panel of the liquid crystal display device such that images are displayed.
A mold frame of the liquid crystal display device supports the back light unit including the above-mentioned sheets and lamp such that the liquid crystal display panel and back light unit are fixed with each other in a fixing structure. However, as the liquid crystal display device becomes thinner and thinner, the fixing or supporting structure of the above-mentioned back light unit including the light guide et al. becomes more difficult to design. That is to say, a space for fixing the back light unit is so limited that a merely normal impact may break the fixing structure of the back light unit.
With reference to
FIGS. 1 and 2
, a conventional fixing structure of the back light unit will now be provided.
FIG. 1
is a plan view illustrating a lower frame made from a plastic with a molding, and
FIG. 2
is a cross-sectional view illustrating how the back light unit is assembled with the conventional lower frame in a typical liquid crystal display module.
As shown in
FIG. 2
, a typical liquid crystal display module
10
includes an upper frame
20
and a lower frame
30
, which oppose each other. A liquid crystal display panel
60
and a back light unit
40
are disposed between the upper and lower frames
20
and
30
. The liquid crystal display panel
60
includes first and second substrates (not shown) and a liquid crystal layer (not shown) sandwiched therebetween. The back light unit
40
is the edge type and includes a lamp
44
, a light guide
42
, a reflection sheet
48
, a diffusion sheet
45
, and a prism sheet
46
. A panel guide
50
is further interposed between the upper and lower frames
20
and
30
and supports the liquid crystal panel
60
.
As shown in
FIG. 1
, a conventional lower frame
30
, having the lamp (reference
44
in
FIG. 2
) at a first side (a long side), includes a rib
32
at each second side (short side) perpendicular to the first side where the lamp is disposed. The ribs
32
fix the light guide
42
. In addition, the lower frame
30
includes protrusions
34
at one of the second sides to fix the various sheets (reference
46
and the like in FIG.
2
).
In assembling the back light unit
40
of
FIG. 2
with the lower frame
30
of
FIG. 1
, at first, the lamp
44
is disposed on a long side of the lower frame
30
. Then, the reflection sheet
48
is mounted on the lower frame
30
, and the light guide
42
is mounted on the reflection sheet
48
. Thereafter, the diffusion sheet
45
and prism sheet
46
are sequentially mounted on the light guide
42
. At this point, a double-coated tape (not shown) is used between the diffusion and prism sheet
45
and
46
to fix their relative position.
Returning to
FIG. 1
, the ribs
32
and protrusions
34
serve to fix the light guide
42
, diffusion and prism sheets
45
and
46
(see
FIG. 2
) such that a defect due to a movement thereof is prevented. Specifically, the ribs
32
prevent the movement of the light guide
42
, and the protrusions
34
prevent movement of the diffusion and prism sheets
45
and
46
. Each protrusion
34
has a cylindrical shape and protrudes upward from the rib
32
disposed at one of the second sides of the lower frame
30
.
Meanwhile, the number of lamps used in the conventional art is increased in order to improve the brightness of the large scale LCD device, and thus the power consumption increases. However, some problems occur in the LCD device because of the heat from the lamp as well as a printed circuit board (PCB), which is conventionally interposed between the upper and lower frames and electrically connected with the liquid crystal display panel. That is to say, the lower frame is conventionally made with plastic molding, and since plastic has poor thermal radiation and conductivity properties, heat from the lamp or PCB cannot be conducted or radiated away. This causes heating of the liquid crystal display panel, a deterioration of luminance, and a wrinkle in the sheets.
To solve the problems caused by the heat, the lower frame
30
is beneficially made of a metallic material, usually aluminum (Al) that has good thermal conductivity and good thermal radiation. However, at this point, since the rib and protrusions are difficult to form on a metallic lower frame, additional elements are needed to fix the light guide and sheets.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to an LCD module that su
An Sam-Young
Hwang Yun-Ho
LG. Philips LCD Co. Ltd.
Long Aldridge & Norman LLP
Rude Tim
Sikes William L.
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