Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2001-06-26
2004-03-16
Dudek, James (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
Reexamination Certificate
active
06707520
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a liquid crystal display, and more particularly to a method of fabricating a liquid crystal display capable of forming a bend structure of a liquid crystal in a fast and stable manner.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) includes switching devices consisting of thin film transistors having gate electrodes, a gate insulating film, an active layer, an ohmic contact layer and source and drain electrodes, and a liquid crystal injected between a lower plate provided with pixel electrodes and an upper plate provided with color filters.
FIG. 1
is a plan view showing a structure of a conventional LCD, and
FIG. 2
is a sectional view taken along the A—A′ line in FIG.
1
.
Referring to FIG.
1
and
FIG. 2
, in the conventional LCD, a gate electrode
5
made from a metal such as aluminum (Al) or copper (Cu) is formed on a lower substrate
1
in such a manner to be connected to a gate line
3
. A gate insulating film
15
is formed on the transparent substrate
1
to cover the gate electrode
5
and the gate line
3
. The gate insulating film
15
is made from silicon nitride or silicon oxide.
An active layer
6
and an ohmic contact layer
7
are provided at a portion corresponding to the gate electrode
5
on the gate insulating film
15
. The active layer
6
is formed from amorphous silicon or polycrystalline silicon undoped with an impurity. The ohmic contact layer
7
is made from amorphous silicon or polycrystalline silicon doped with an n-type or p-type impurity at a high concentration.
Source and drain electrodes
13
and
11
are formed at each side of the active layer
6
on the gate insulating film
15
in such a manner to contact the ohmic contact layer
7
. The source and drain electrodes
13
and
11
are made from a metal such as molybdenum (Mo), chrome (Cr), titanium (Ti) or tantalum (Ta), etc., or a molybdenum alloy such as MoW, MoTa or MoNb, etc. The source electrode
13
is connected to a data line
2
, and the drain electrode
11
opposes the source electrode
13
with the gate electrode
5
in between. A thin film transistor is constituted by the gate electrode
5
, the gate insulating film
15
, the active layer
6
and the source and drain electrodes
13
and
11
as described above. A passivation layer
9
is formed on the gate insulating film
15
to cover the thin film transistor. The passivation layer
9
is made from an inorganic insulating material such as silicon nitride or silicon oxide, etc. A contact hole
19
for exposing the drain electrode
11
is defined at the passivation layer
9
. A pixel electrode
17
contacting the drain electrode
11
via the contact hole
19
is formed on the passivation layer
9
. The pixel electrode
17
is formed from a transparent conductive material such as indium tin oxide (ITO), tin oxide (TO) or indium zinc oxide (IZO) at an area excluding a portion corresponding to the thin film transistor on the passivation layer
9
. A storage electrode (not shown) provided at an overlapping portion between the pixel electrode
17
at the next stage and the gate line
3
constitutes a storage capacitor along with the gate line
3
intervening with the gate insulating film
15
.
Meanwhile, an upper substrate
21
of the LCD is provided with a plurality of color filters
25
for transmitting desired color, a black matrix
23
for shutting such light transmission, and a common electrode
26
for applying a voltage to the liquid crystal. The color filters
25
are formed to correspond to a pixel area of the lower substrate
1
while the black matrix
23
is formed to correspond to an area excluding the pixel area.
The upper substrate and the lower substrate formed in this manner are joined with each other, and a liquid crystal is injected therebetween. The liquid crystal injected between the upper substrate and the lower substrate is arranged as shown in FIG.
3
A and
FIG. 3B
by an aligned state of an alignment film and an external voltage.
Referring to
FIG. 3A
, a liquid crystal
32
injected into a space between the upper substrate
21
and the lower substrate
1
is arranged within said space in a splay structure. The splay structure has a desired pre-tilt depending on an aligned state of alignment films
27
formed on the upper substrate
21
and the lower substrate
1
. When a desired voltage V is applied to molecules of the liquid crystal
32
arranged in such a splay structure, the liquid crystal
32
is re-arranged as shown in FIG.
3
B. In other words, when a desired voltage is applied to the common electrode
26
and the pixel electrode
17
, the liquid crystal
32
primarily arranged in a splay structure is re-arranged into a bend structure. At this time, the liquid crystal
32
injected within a pixel area between the common electrode
26
and the pixel electrode
17
is liable to re-arrangement into a bend structure having a large pre-tilt, by a desired voltage applied from the common electrode
26
and the pixel electrode
17
. However, the liquid crystal
32
injected within the black matrix area
23
and the pixel electrode
17
, keeps the splay structure as is. The liquid crystal
32
arranged in a splay structure within the black matrix area
23
has a more stable state than the liquid crystal
32
arranged in a bend structure within the pixel area. For this reason, the liquid crystal
32
arranged in a bend structure, adjacent to the liquid crystal
32
arranged in a splay structure, is liable to change into a splay structure. Also, formation of a liquid crystal having the bend structure at the entire LCD panel not only requires lot of time, but also results in a failure of a uniform liquid crystal arrangement at the entire LCD panel.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method of fabricating a liquid crystal display, capable of arranging a liquid crystal injected within a liquid crystal display panel, into a stable bend structure within a short time.
In order to achieve these and other objects of the invention, a method of fabricating a liquid crystal display device according to the present invention includes the steps of rubbing alignment films positioned at a non-display area and a display area, and exposing the non-display area to the light to adjust a pre-tilt angle of a liquid crystal included in each of the non-display area and the display area.
The method further includes the steps of arranging a photo mask on the alignment film within the display area excluding the alignment film within the non-display area, and exposing the display area and the non-display area to the light through the photo mask. The liquid crystal included in the non-display area has a larger pre-tilt angle than the liquid crystal included in the display area.
REFERENCES:
patent: 6313898 (2001-11-01), Numano et al.
patent: 6323926 (2001-11-01), Watanabe et al.
T. Miyashita et al., “Wide Viewing Angle Display Mode For Active Matrix LCD Using Bend Alignment Liquid Crystal Cell”, The 13th International Display Research Conference, Aug. 31-Sep. 3, 1993, Strasbourg-France, pp. 149-152.
Hirouki Mori, “A Wide-Viewing-Angle &pgr; Cell Compensated With A Discotic Film”, IEICE Trans. Electron, vol. E82-C, No. 10, Oct. 10, 1999, pp. 1787-1791.
Park Ku Hyun
Son Hyeon Ho
LG.Philips LCD Co. , Ltd.
Morgan & Lewis & Bockius, LLP
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