Illumination – Revolving
Reexamination Certificate
2002-03-25
2004-08-24
Quach-Lee, Y. My (Department: 2875)
Illumination
Revolving
C362S027000, C362S330000
Reexamination Certificate
active
06779902
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a back light assembly for maximizing a light incident efficiency by changing a structure of a light guide plate for guiding lights from a lamp to a display unit for displaying images and a liquid display device having the same.
2. Description of the Related Art
At the present time, information processing devices are rapidly developing with trends towards various architectures, functions and faster information processing speed. Information processed in these information processing devices has an electrical signal format. In order to visually confirm information processed in an information processing device, a display should be provided as an interface device. An example of such a display device is the liquid crystal display (LCD).
LCDs offer numerous advantages as display devices such as light weight, small size, high resolution, and low power consumption. They are also environmentally friendly and they offer a display of full colors compared with the traditional cathode ray tube (CRT). Such advantages allow the LCDs to replace the CRTs and to be recognized as a next generation display.
LCDs apply electric power to liquid crystal having a specific molecular configuration so as to vary the molecular arrangement of the liquid crystal. The variation in the molecular configuration of the liquid crystal causes a variation in optical properties such as birefringence, optical rotary power, dichroism and light scattering. The LCDs utilize such variations in optical properties to display an image.
In the LCD device, functions of a backlight assembly bring attention to a more important problem. The reason is that the backlight assembly affects both the mechanical and optical characteristics of the LCD device such that the size and the light efficiency of the LCD device undergo a change. This is discussed, along with a description of prior art systems, in conjunction with
FIGS. 1-3
below.
FIG. 1
is an exploded perspective view schematically showing the LCD device according to the conventional art schematically.
FIG. 2
is a sectional view schematically showing the constructions of a lamp unit and a light guide unit in the backlight assembly as shown in FIG.
1
.
FIG. 3
is a view showing a pathway of the light in the light guide plate shown in FIG.
2
.
Referring first to
FIG. 1
, the LCD device
900
has a LCD module
700
for displaying images when image signals are applied thereto and a case (not shown) for receiving the LCD module
700
. The LCD module
700
includes a display unit
710
having a LCD panel for showing the images.
The display unit
710
includes the LCD panel
712
, a data-side printed circuit board (PCB)
714
, a gate-side PCB
717
, a data-side tape carrier package
716
and a gate-side tape carrier package
718
.
The LCD panel
712
includes a thin film transistor substrate
712
a
, a color filter substrate
712
b
and liquid crystal (not shown) between the thin film transistor substrate
712
a
and the color filter substrate
712
b.
The thin film transistor substrate
712
a
is a transparent glass on which the thin film transistors are formed in a matrix form. Data lines are respectively connected with source terminals of the thin film transistors and gate lines are connected with gate terminals of the thin film transistors. Furthermore, pixel electrodes are respectively formed at drain terminals of the thin film transistors, which are made of a transparent conductive material such as Indium Tin Oxide (ITO).
The color filter substrate
712
b
is provided to face the thin film transistor substrate
712
a
. RGB pixels are formed on the color filter substrate
712
b
by means of a thin film process, which presents a predetermined color while the light passes through the color filter substrate
712
b
. Common electrodes made of the ITO are coated on the front surface of the color filter substrate
712
b.
When the thin film transistors of the thin film transistor substrate
712
a
are turned on, an electric field is created between the pixel electrodes of the thin film transistor substrate
712
a
and the common electrodes of the color filter substrate
712
b
. The electric field causes the liquid crystal to change the array angle, which results in the permeability of the light being changed. As a result, the desired pixels are obtained.
A driving signal and a timing signal are applied to the gate lines and data lines of the thin film transistor in order to control the array angle of the liquid crystal and the time of arraying the liquid crystal in the LCD panel
712
. A source part for providing the data driving signal to the LCD panel
712
is formed on the data-side PCB
714
, and a gate part for providing the gate driving signal to the gate lines is formed on the gate-side PCB
717
. In other words, the PCBs
714
and
717
generate and apply the gate driving signal and the data signal for driving the LCD device as well as a plurality of timing signals for applying the gate driving signal and the data signal to the gate lines and the data lines of the LCD panel
712
.
Continuing with
FIG. 1
, the backlight assembly
720
is provided under the display unit
710
so as to uniformly supply the light to the display unit
710
. The backlight assembly
720
includes a lamp
721
for generating the light. The lamp
721
is protected by means of a lamp cover
722
.
The light guide plate
724
has a size corresponding to that of the liquid crystal panel
712
of the display unit
710
, which is disposed under the liquid crystal panel
712
to guide the light emitted by the lamp
721
toward the display unit
710
by changing a pathway of the light.
A plurality of optical sheets is provided on the light guide plate
724
so as to uniformly adjust the brightness of the light that transmitted from the light guide plate
724
to the LCD panel
712
. In addition, a light reflecting plate
728
is provided under the light guide plate
724
to reflect the light, which is leaked from the light guide plate
724
, towards the light guide plate
728
so as to improve the efficiency of the light.
The display unit
710
and the backlight assembly
720
are supported by means fo a mold frame
820
used as a receptacle. The mold frame
820
is provided with a chassis
810
for preventing the display unit
710
from departing from the mold frame
820
while the data-side PCB
714
and the gate-side PCB
7171
are bent towards the outside of the mold frame
820
and are fixed to the bottom surface of the mold frame
820
.
Referring now to
FIG. 2
, the light guide plate
724
is of an edge-type having a uniform thickness, and a lamp
721
for supplying the light is provided at an end of the light guide plate
724
. Typically, the light emitted from the lamp
721
of the edge-type light guide plate
724
is transmitted through a pathway as shown in FIG.
3
.
As shown in
FIG. 3
, the light emitted from the lamp
721
is transmitted to the top and bottom surfaces
724
a
and
724
b
of the light guide plate
724
according to the incidence angle thereof. A part of the light transmitted to the top surface
724
a
of the light guide plate
724
is provided to the display unit
710
after passing through the top surface
724
a
of the light guide plate
724
, while the remainder of the light is reflected at the bottom surface
724
b
of the light guide plate
724
and then transmitted toward the top surface
724
a
of the light guide plate
724
.
Meanwhile, the light transmitted to the bottom surface
724
b
of the light guide plate
724
is reflected by means of printed patterns (not shown) that are formed on the bottom surface
724
b
of the light guide plate
724
, and then the light passes through the top surface
724
a
of the light guide plate
724
. Ultimately, the light is provided to the display unit
710
. At this time, a part of the light transmitted to the bottom surface
724
b
of the light guide plate
724
passes through the bot
Cha Guy-Ho
Chang Se-In
Kang Sung-Yong
McGuireWoods LLP
Neils Peggy A.
Quach-Lee Y. My
LandOfFree
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