Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-10-01
2004-03-09
Kim, Robert H. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S113000
Reexamination Certificate
active
06704081
ABSTRACT:
This application claims the benefit of Korean Patent Application No. 2002-10657, filed on Feb. 27, 2002 in Korea, 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 transflective liquid crystal display (LCD) device and a method of manufacturing the same.
2. Discussion of the Related Art
In general, the liquid crystal display (LCD) device includes two substrates, which are spaced apart and facing each other, and a liquid crystal layer interposed between the two substrates. Each of the substrates includes an electrode and the electrodes of each substrate are also facing each other. Voltage is applied to each electrode and an electric field is induced between the electrodes. An alignment of the liquid crystal molecules is changed by varying the intensity of the electric field. The LCD device displays a picture by varying transmittance of the light according to the arrangement of the liquid crystal molecules.
Because the liquid crystal display (LCD) device is not luminescent, it needs an additional light source in order to display images. The liquid crystal display device is categorized into a transmissive type and a reflective type depending on the type of light source.
In the transmissive type, a backlight is used as a light source behind a liquid crystal panel. Light incident from the backlight penetrates the liquid crystal panel, and the amount of the transmitted light is controlled depending on the alignment of the liquid crystal molecules. Here, the substrates are usually transparent and the electrodes of each substrate are usually formed of transparent conductive material. As the transmissive liquid crystal display (LCD) device uses the backlight as a light source, it can display a bright image in dark surroundings. Because an amount of the transmitted light is very small for the light incident from the backlight, the brightness of the backlight must be increased in order to increase the brightness of the LCD device. Consequently, the transmissive liquid crystal display (LCD) device has high power consumption due to the operation of the backlight.
On the other hand, in the reflective type LCD device, sunlight or artificial light is used as a light source of the LCD device. The light incident from the outside is reflected at a reflective plate of the LCD device according to the arrangement of the liquid crystal molecules. Since there is no backlight, the reflective type LCD device has much lower power consumption than the transmissive type LCD device. However, the reflective type LCD device cannot be used in dark surroundings because it depends on an external light source.
Therefore, a transflective LCD device, which can be used both in a transmissive mode and in a reflective mode, has been recently proposed. A conventional transflective LCD device will be described hereinafter more in detail.
FIG. 1
is an exploded perspective view illustrating a conventional transflective LCD device. The conventional transflective LCD device
11
has upper and lower substrates
15
and
21
, which are spaced apart from and facing each other, and also has a liquid crystal layer
14
interposed between the upper substrate
15
and the lower substrate
21
.
A gate line
25
and a data line
39
are formed on the inner surface of the lower substrate
21
. The gate line
25
and the data line
39
cross each other to define a pixel area “P”. The pixel area “P” includes a transmissive region “B” and a reflective region “A”. A thin film transistor “T” is situated at the crossing of the gate line
25
and the data line
39
. A reflective electrode
49
having a transmissive hole
49
a
and a transparent electrode
61
overlapping the reflective electrode
49
are formed in the pixel area “P”. The reflective electrode
49
and/or the transparent electrode
61
are connected to the thin film transistor “T”. The transmissive hole
49
a
corresponds to the transmissive region “B”.
Meanwhile, a black matrix
16
, which has an opening corresponding to the reflective electrode
49
and the transparent electrode
61
, is formed on the inside of the upper substrate
15
, and a color filter
17
corresponding to the opening of the black matrix
16
is formed on the black matrix
16
. The color filter
17
is composed of three colors: red (R), green (G) and blue (B). Each color corresponds to each pixel area “P”. Subsequently, a common electrode
13
is formed on the color filter
17
.
FIG. 2
is a schematic cross-sectional view of a conventional transflective LCD device.
FIG. 2
indicates a pixel area of the conventional transflective LCD device. In the conventional transflective LCD device
11
, a reflective electrode
49
is formed on the inner surface of a lower substrate
21
and an insulating layer
50
is formed on the reflective electrode
49
. The reflective electrode
49
has a transmissive hole
49
a
corresponding to a transmissive region “B”. A transparent electrode
61
is formed on the insulating layer
50
. As stated above, the lower substrate
21
includes a gate line (not shown), a data line (not shown) and a transistor (not shown) thereon.
An upper substrate
15
is spaced apart from and facing the lower substrate
21
. A common electrode
13
is formed on the inner surface of the upper substrate
15
. Though not shown in the figure, a black matrix and a color filter are subsequently formed between the upper substrate
15
and the common electrode
13
.
A liquid crystal layer
14
is disposed between the lower and upper substrates
21
and
15
, and molecules of the liquid crystal layer
14
are arranged horizontally with respect to the substrates
21
and
15
.
Polarizers (not shown) are arranged on the outer surface of the lower and upper substrate
21
and
15
. The transmission axes of polarizers are perpendicular to each other.
A backlight
41
is located under the outside of the lower substrate
21
. The backlight
41
is used as a light source of a transmissive mode of the transflective LCD device.
In a transmissive mode, the first light “F
1
” from the back light
41
penetrates the transparent electrode
61
in the transmissive region “B”. Next, while the first light “F
1
” passes through the liquid crystal layer
14
, the amount of the first light “F
1
” is controlled by the arrangement of the liquid crystal layer depending on applied voltage. Then the first light “F
1
” is emitted.
On the other hand, in a reflective mode, the second light “F
2
” incident from the outside such as sunlight or artificial light passes through the liquid crystal layer
14
and is reflected at the reflective electrode
49
in a reflective region “A”. The second light “F
2
” goes through the liquid crystal layer
14
again and is emitted. At this time, the amount of emitted second light “F
2
” is controlled according the arrangement of liquid crystal molecules.
Because of different optical paths of the first and second lights “F
1
” and “F
2
”, the polarizing properties of the emitted lights are different from each other. That is, the first light “F
1
” passes through the liquid crystal layer only once while the second light “F
2
” passes through the liquid crystal layer twice. Therefore, the transmittance is different in the transmissive mode and in the reflective mode as the cell gap is uniform, and it is difficult to realize high definition.
Recently, transflective LCD devices that simultaneously optimize the transmittance of a transmissive mode with the brightness of a reflective mode have been proposed. These transflective LCD devices are described with reference to the attached figures.
FIG. 3
is a plan view showing an array substrate for a transflective liquid crystal display (LCD) device according to a first embodiment of the related art. In
FIG. 3
, a gate line
25
is formed horizontally in the context of the figure and a data line
39
is formed vertically in the context of the figure. The gate and d
Baek Heum-Il
Ha Kyoung-Su
Kim Dong-Guk
Kim Robert H.
LG. Philips LCD Co. Ltd.
McKenna Long & Aldridge LLP
Schechter Andrew
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