U.S. patent application number 11/961886 was filed with the patent office on 2008-06-19 for pixel structure for liquid crystal display.
This patent application is currently assigned to HANNSTAR DISPLAY CORPORATION. Invention is credited to Po-Sheng Shih, Chao-Hui Wu, Kei-Hsiung Yang.
Application Number | 20080143905 11/961886 |
Document ID | / |
Family ID | 34525652 |
Filed Date | 2008-06-19 |
United States Patent
Application |
20080143905 |
Kind Code |
A1 |
Wu; Chao-Hui ; et
al. |
June 19, 2008 |
PIXEL STRUCTURE FOR LIQUID CRYSTAL DISPLAY
Abstract
The present invention builds a metal electrode that is
controlled by the common electrode in each pixel cell. During
operation, a voltage is first applied to this metal electrode to
transform the liquid crystal molecule over this metal electrode
from the splay state into the bend state. Next, a voltage is
applied to the pixel electrode to transform the liquid crystal
molecule in the whole pixel region from the splay state into the
bend state. Two different voltage field also can be respectively
applied to the common electrode and the pixel electrode.
Inventors: |
Wu; Chao-Hui; (Taoyuan
Hsien, TW) ; Yang; Kei-Hsiung; (Yang Mei Town,
TW) ; Shih; Po-Sheng; (Tao-yuan Hsien, TW) |
Correspondence
Address: |
LOWE HAUPTMAN HAM & BERNER, LLP
1700 DIAGONAL ROAD, SUITE 300
ALEXANDRIA
VA
22314
US
|
Assignee: |
HANNSTAR DISPLAY
CORPORATION
Taoyuan Hsien
TW
|
Family ID: |
34525652 |
Appl. No.: |
11/961886 |
Filed: |
December 20, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10936752 |
Sep 9, 2004 |
7349052 |
|
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11961886 |
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10672906 |
Sep 25, 2003 |
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10936752 |
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Current U.S.
Class: |
349/42 |
Current CPC
Class: |
G02F 1/1368 20130101;
G02F 1/136286 20130101; G09G 2300/0426 20130101; G09G 2300/0491
20130101; G09G 3/3655 20130101; G02F 1/1395 20130101; G02F 1/134309
20130101; G09G 2310/0245 20130101 |
Class at
Publication: |
349/42 |
International
Class: |
G02F 1/1368 20060101
G02F001/1368 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 3, 2004 |
TW |
93105642 |
Claims
1. A liquid crystal display driving method, wherein said liquid
crystal display comprises a first substrate having a plurality of
scan lines, video data lines and pixel regions disposed therein, a
second substrate having a conductor electrode disposed therein and
a liquid crystal layer sandwiched between said first substrate and
said second substrate, each pixel region comprising a switching
transistor, a pixel electrode connected with said switch
transistor, and a common electrode and a metal electrode extending
from said common electrode, wherein said pixel electrode, said
common electrode and said metal electrode are isolated from each
other, said drive method comprising the steps: (a) transforming a
voltage applied in said common electrode from a first voltage to a
second voltage; (b) conducting said switching transistors, wherein
video data is transferred from said video data lines to said pixel
regions; (c) closing said switching transistors to maintain said
video data in said pixel regions; (d) transforming the voltage
applied to said common electrode from said second voltage to said
first voltage; (e) conducting said switching transistors, wherein
said video data is released from said pixel regions; (f) closing
said switching transistors; and (g) repeating (a) step to (f)
step.
2. The liquid crystal display driving method of claim 1, wherein
said (a) step and (b) step can be performed together, and when said
(a) step and (b) step are performed together, said (d) step and (e)
step are also performed together.
3. The liquid crystal display driving method of claim 1, wherein
said second voltage is higher than said first voltage.
4. The liquid crystal display driving method of claim 1, wherein
the gate electrodes of said switching transistors are connected to
said scan lines.
5. The liquid crystal display driving method of claim 1, wherein
said pixel electrodes are connected to said video data lines when
said switching transistors are conducted.
Description
[0001] This application is a continuation application of Ser. No.
10/936,752, filed on Sep. 9, 2004, which is a continuation-in-part
of application Ser. No. 10/672,906, filed on Sep. 25, 2003.
FIELD OF THE INVENTION
[0002] The present invention relates to a pixel structure for a
liquid crystal display and more particularly to a high speed
response pixel structure for a liquid crystal display.
BACKGROUND OF THE INVENTION
[0003] Twisted nematic (TN) cells, which at present are widely used
in TFT color liquid crystal display devices (TFT/LCDs), have a
small view-field angle. This results in a decrease in contrast and
image inversion when an LCD panel surface is viewed from an oblique
direction. Various methods have been proposed to solve this
problem, i.e., to realize a wide view-field angle. Among these
methods is an orientation division method in which each pixel of an
LCD is divided into two parts and orientation is affected in
different directions in the two parts.
[0004] However, these methods require cumbersome manufacturing
steps. For example, in the case of the orientation division method,
two rubbing steps are required. These steps include the further
steps of coating, baking, patterning, developing and removing
photoresist.
[0005] In recent years, studies on an OCB cell that is to be used
as a liquid crystal cell instead of a TN cell have been made. If
the OCB cell technique is used, it becomes possible to obtain a
wide view-field angle more easily than with the orientation
division method as well as a high-speed response characteristic
that is one order faster than with conventional TN cells.
[0006] FIG. 1 is a perspective view illustrating the structure of
an OCB cell. A liquid crystal material that exhibits splay
orientation 104 is sealed between two (top and bottom) glass
substrates 100 and 102. Polarizing plates 106 and 108 are disposed
outside the two respective glass substrates 100 and 102. When a
voltage is applied to the glass substrates 100 and 102, the liquid
crystal material is transformed from splay orientation 104 to bend
orientation 110 as shown in FIG. 1B. In a bend orientation 110
cell, since top and bottom liquid crystal molecules are always
oriented symmetrically, the view-field-angle dependence is
symmetrical around the AA' line. An optically compensated bend
(OCB) mode LCDs compensates for the birefringence of liquid crystal
molecules so as to obtain the uniform viewing angle characteristic
at all directions.
[0007] An OCB cell is in a splay orientation state when no bias
voltage is applied thereto, and exhibits a bend orientation state
when a given high voltage is applied thereto. To allow an OCB cell
to operate as a liquid crystal display device, the cell must be
transformed from a splay orientation to bend orientation at the
start of operation. This process requires a restart time, which
reduces the response speed.
[0008] FIG. 2A shows a pixel structure plan diagram of a thin-film
transistor LCD. The gate electrode 306a of the switch transistor
306 is connected to the scan line 302. The drain electrode 306b of
the switch transistor 306 is connected to the pixel electrode 308
and the source electrode 306c is connected to the video data line
304. A common line 310 is used as the common electrode of the pixel
electrode 308. The switch transistor 306 is usually a thin-film
transistor (TFT) that is deposited on a transparent substrate such
as glass. By scanning the scan lines 302 and in accordance with the
scan signals, all of the switch transistors 306 in a given scan
line 302 are turned on. At the same time, video signals are
provided in the video data lines synchronously with the selected
scan line 302.
[0009] FIG. 2B is a cross-sectional view along the BB' line in FIG.
2A. A liquid crystal material 326 is sealed between two (top and
bottom) glass substrates 320 and 322. A conductor electrode 324 is
located on the top glass substrate 320. Referring to FIG. 2A and
FIG. 2B, typically, the liquid crystal molecule 328 over the pixel
electrode 308 is in splay state and the liquid crystal molecule 326
over the other region is in bend state. Then, a high voltage is
applied between the conductor electrode 324 and the pixel electrode
308 for a given period at the start of operation of a liquid
crystal display device using the OCB cell. At this time, the liquid
crystal molecule 326 in bend orientation change the orientation
state of the liquid crystal molecule 328 over the pixel electrode
308 from splay orientation to bend orientation. However, a part of
the liquid crystal molecule 328 over the pixel electrode 308 may be
unsuccessfully transformed and remain in bend orientation, which
reduces the display quality of the LCD. In addition, the two
orientation states required in this method increase the
manufacturing cost. Moreover, it is difficult to maintain the high
angle of inclination of a bend orientation state liquid crystal
molecule. Although this allows the liquid crystal display device to
have a desired wide view-field angle characteristic, the image
quality required for it cannot be obtained easily. Further, the
above measure is not practical.
[0010] FIG. 2C shows another orientation state in accordance with
the conventional method. The liquid crystal molecule 330 in the
whole pixel is in splay state. In accordance with this method, a
high voltage is applied between the conductor electrode 324 and the
pixel electrode 308 for a given period at the start of operation of
a liquid crystal display device using the OCB cell to transform the
liquid crystal molecule 330 from splay state into the bend state.
This fixed start time usually takes more than several tens of
seconds. The liquid crystal molecule 330 returns to splay state
when the LCDs is turned off. However, part of the liquid crystal
molecule 330, such as the liquid crystal molecule between the video
data line 304 and the pixel electrode 308, is applied to the high
voltage in this mode, which causes two liquid crystal molecule
states when the LCDs is turned on. Yet another problem is that even
if the liquid crystal molecule 330 is transformed from splay
orientation to bend orientation at the start of operation, the OCB
cell may return to splay orientation during operation. The LCD must
be restarted for display to return to normal.
[0011] On the other hand, recent battery-driven systems such as
notebook-type personal computers equipped with a TFT color liquid
crystal display device are increasingly required to be of a
power-saving type. To conserve power, such a liquid crystal display
device has a driving mode stop function to turn off a display
thereof. Once the LCD is turned off, an OCB cell returns to splay
orientation from bend orientation. A period of time is needed to
restore the bend orientation state; thus the display cannot be
turned on instantaneously.
SUMMARY OF THE INVENTION
[0012] In accordance with the foregoing description, the typical
liquid crystal display using OCB cell requires transformation of
the liquid crystal molecule orientation state from splay
orientation to bend orientation during operation, which involves
two liquid crystal molecule orientation states. There are two
typical transformation methods. In one method the liquid crystal
molecule over the pixel electrode is first in a splay state while
the liquid crystal molecule over the other region is in a bend
state. Then, a high voltage is applied between the conductor
electrode and the pixel electrode to transform the liquid crystal
molecule over the pixel electrode from splay state into the bend
state. However, this method requires two different orientation
states, splay state and bend state, and the manufacturing cost is
increased. In another method, the liquid crystal molecule in the
whole pixel in a splay state. Although an LCD employing this method
is convenient to manufacture, this method requires a given period
at the start of operation of a liquid crystal display device to
transform the liquid crystal molecule from splay state into the
bend state. In other words, this method does not provide an
instantaneous response. Moreover, part of the liquid crystal
molecule does not accept high voltage, which affects the display
quality.
[0013] Therefore, it is the main object of the present invention to
provide a pixel structure capable of obtaining a wide viewing angle
as well as improving picture quality.
[0014] Another purpose of the present invention is to provide a
pixel structure only using an unique orientation state in the whole
cell and for which a given period at the start of operation of a
liquid crystal display device is not necessary.
[0015] Yet another purpose of the present invention is to provide a
driving method of a liquid crystal display device, which method
allows an OCB cell to transform from a splay orientation to a bend
orientation state in a short period.
[0016] A further purpose of the present invention is to provide a
liquid crystal display that can be manufactured in a simple and
relatively inexpensive manufacturing method.
[0017] In accordance with the present invention, a metal electrode
is built in the pixel region. The metal electrode is controlled by
the common electrode. The liquid crystal molecule in the whole
pixel region is in a splay state. A voltage is applied to the metal
electrode to transform the liquid crystal molecule over the metal
electrode from splay state into the bend state during during
operation. Then, a voltage is applied to the pixel electrode. At
this time, the liquid crystal molecule in the bend state transforms
the liquid crystal molecule over the pixel electrode from the splay
state into the bend state. Therefore, the liquid crystal molecule
in the whole pixel region exhibits the bend state.
[0018] The metal electrode can be positioned in the center of the
pixel electrode or around the pixel electrode in accordance with
the present invention. A complicated manufacturing process can be
avoided because the present invention does not require two
orientation states in a liquid crystal cell. Moreover, a given
period for transforming the liquid crystal molecule from the splay
state into the bend state at the start of LCDs operation is not
necessary. Therefore, the LCDs using the pixel structure of the
present invention exhibits a high speed response as well as a high
display quality.
[0019] On the other hand, the present invention also provides a
drive circuit for driving the metal electrode. The drive circuit
includes an inverter to invert the field frame inputted to the
source/drain electrode of a transistor. The inverted field frame is
used to control the common electrode. On the other hand, this
transistor is controlled by a scan signal. Therefore, this
transistor operation is synchronized with the switch transistor
operation. In other words, if a voltage is applied in sequence to
the metal electrode and the pixel electrode, the drive circuit
first turns on the transistor and then inverts the field frame.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The foregoing aspects and many of the attendant advantages
of this invention will become more readily appreciated and better
understood by referencing the following detailed description, when
taken in conjunction with the accompanying drawings, wherein:
[0021] FIG. 1A illustrates a schematic configuration diagram of a
liquid crystal display using OCB mode, wherein the liquid crystal
molecule is in the splay state;
[0022] FIG. 1B illustrates a schematic configuration diagram of a
liquid crystal display using OCB mode, wherein the liquid crystal
molecule is in the bend state;
[0023] FIG. 2A illustrates a pixel structure plan diagram of a
thin-film transistor LCD;
[0024] FIG. 2B illustrates a cross-sectional view along the BB'
line of FIG. 2A, in which some of the liquid crystal molecules are
in the splay state and some are in the bend state;
[0025] FIG. 2C illustrates a cross-sectional view along the BB'
line of FIG. 2A, wherein all of the liquid crystal molecules are in
the splay state;
[0026] FIG. 3A illustrates a top view of the pixel region in
accordance with the first embodiment of the present invention;
[0027] FIG. 3B illustrates a cross-sectional view from the AA' line
of FIG. 3A, wherein all of the liquid crystal molecules are in the
splay state;
[0028] FIG. 3C illustrates a cross-sectional view from the AA' line
of FIG. 3A, in which some of the liquid crystal molecules are
transformed into the bend state;
[0029] FIG. 4A illustrates a top view of the pixel region in
accordance with the second embodiment of the present invention;
[0030] FIG. 4B illustrates a cross-sectional view along the AA'
line of FIG. 4A, in which all of the liquid crystal molecules are
in the splay state;
[0031] FIG. 4C illustrates a cross-sectional view along the AA'
line of FIG. 4A, in which some of the liquid crystal molecules are
transformed into the bend state;
[0032] FIG. 5A illustrates a top view of the pixel region in
accordance with the third embodiment of the present invention;
[0033] FIG. 5B illustrates a cross-sectional view from the AA' line
of FIG. 5A, in which all of the liquid crystal molecule are in the
splay state;
[0034] FIG. 5C illustrates a cross-sectional view from the AA' line
of FIG. 5A, in which parts of the liquid crystal molecules are
transformed into the bend state;
[0035] FIG. 6A illustrates a top view of the pixel region in
accordance with the fourth embodiment of the present invention;
[0036] FIG. 6B illustrates a cross-sectional view from the AA' line
of FIG. 6A, in which all of the liquid crystal molecules are in the
splay state;
[0037] FIG. 6C illustrates a cross-sectional view from the AA' line
of FIG. 6A, in which some of the liquid crystal molecules are
transformed into the bend state;
[0038] FIG. 7A illustrates a top view of a pixel region that the
common electrode line with connected metal line and the video data
line are arranged in the same layer;
[0039] FIG. 7B illustrates a cross-sectional view from the AA' line
of FIG. 7A, in which some of the liquid crystal molecules are
transformed into the bend state;
[0040] FIG. 8A illustrates a waveform from negative to positive of
drive timing in accordance with the first embodiment;
[0041] FIG. 8B illustrates a waveform from positive to negative of
drive timing in accordance with the first embodiment;
[0042] FIG. 9A illustrates a waveform from negative to positive of
drive timing in accordance with the second embodiment;
[0043] FIG. 9B illustrates a waveform from positive to negative of
drive timing in accordance with the second embodiment;
[0044] FIG. 10A illustrates a waveform from negative to positive of
drive timing in accordance with the third embodiment;
[0045] FIG. 10B illustrates a waveform from positive to negative of
drive timing in accordance with the third embodiment;
[0046] FIG. 11 illustrates a top view of using the pixel electrode
structure of the present invention to a TFT-LCDs;
[0047] FIG. 12A illustrates a drive circuit schematic diagram for
generating a drive voltage;
[0048] FIG. 12B illustrates a detailed diagram of a drive circuit
for generating a drive voltage;
[0049] FIG. 13A illustrates a schematic diagram of the liquid
crystal molecules aligned in the direction perpendicular to the
metal electrode;
[0050] FIG. 13B illustrates a schematic diagram of the liquid
crystal molecules affected by a crosswise electrical field;
[0051] FIG. 14A illustrates a schematic diagram of the liquid
crystal molecules aligned in the direction parallel to the metal
electrode;
[0052] FIG. 14B illustrates a schematic diagram of the liquid
crystal molecules affected by a crosswise electrical field;
[0053] FIG. 15A illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the first embodiment of the present
invention;
[0054] FIG. 15B illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the second embodiment of the present
invention;
[0055] FIG. 15C illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the third embodiment of the present
invention;
[0056] FIG. 15D illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the fourth embodiment of the present
invention;
[0057] FIG. 15E illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the fifth embodiment of the present
invention;
[0058] FIG. 15F illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the sixth embodiment of the present
invention;
[0059] FIG. 15G illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the seventh embodiment of the present
invention;
[0060] FIG. 15H illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the eighth embodiment of the present
invention;
[0061] FIG. 16A illustrates a schematic diagram of a pixel
structure appearance change of FIG. 5A cooperating with this
alignment method according to the first embodiment of the present
invention;
[0062] FIG. 16B illustrates a schematic diagram of a pixel
structure appearance change of FIG. 5A cooperating with this
alignment method according to the second embodiment of the present
invention;
[0063] FIG. 16C illustrates a schematic diagram of a pixel
structure appearance change of FIG. 5A cooperating with this
alignment method according to the third embodiment of the present
invention;
[0064] FIG. 17A illustrates a top view of holes located in a pixel
electrode to expose a metal electrode, in which no voltage is
applied to the metal electrode;
[0065] FIG. 17B illustrates a top view of holes located in a pixel
electrode to expose a metal electrode, in which a voltage is
applied to the metal electrode;
[0066] FIG. 18A illustrates a top view of a metal electrode with a
sawtooth appearance, in which no voltage is applied to the metal
electrode;
[0067] FIG. 18B illustrates a top view of a metal electrode with a
sawtooth appearance, in which a voltage is applied to the metal
electrode;
[0068] FIG. 19A illustrates a top view of a trench formed in a
pixel electrode to expose a common electrode, in which no voltage
is applied to the common electrode;
[0069] FIG. 19B illustrates a top view of a trench formed in a
pixel electrode to expose a common electrode, in which a voltage is
applied to the common electrode;
[0070] FIG. 20A illustrates a top view of a metal electrode
extended out of the pixel electrode, in which no voltage is applied
to the metal electrode; and
[0071] FIG. 20A illustrates a top view of a metal electrode
extended out of the pixel electrode, in which a voltage is applied
to the metal electrode.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0072] Without limiting the spirit and scope of the present
invention, the circuit structure proposed in the present invention
is illustrated with one preferred embodiment. One with ordinary
skill in the art, upon acknowledging the embodiment, can apply the
pixel electrode structure using the OCB mode and the operation
method of the present invention to various liquid crystal displays.
In accordance with the pixel structure, a complicated manufacturing
process can be avoided because the pixel region does not require
two orientation states in a liquid crystal cell. Moreover, the
present invention does not require a given period for transforming
the liquid crystal molecule from the splay state into the bend
state at the start of LCD operation. Therefore, LCDs using the
pixel structure of the present invention have a high speed response
as well as a high display quality. The application of the present
invention is not limited by the preferred embodiments described in
the following.
[0073] In accordance with the present invention, a metal electrode
is built in the pixel region. The metal electrode is controlled by
the common electrode. The liquid crystal molecules in the entire
pixel region are in the splay state. A voltage is applied to the
metal electrode to transform the liquid crystal molecule over the
metal electrode from the splay state into the bend state during
operation. Then, a voltage is applied to the pixel electrode. At
this time, the liquid crystal molecules in the bend state transform
the liquid crystal molecule over the pixel electrode from the splay
state into the bend state. Therefore, the liquid crystal molecule
in the whole pixel region exhibit the bend state.
The First Embodiment
[0074] FIG. 3A shows a top view of the pixel region in accordance
with the first embodiment of the present invention. The silicon
island 506a of the switch transistor 506 is connected to the scan
line 502. When the switch transistor 506 is selected, a scan signal
is sent via the scan line 502 to turn the switch transistor 506 on.
The video signal in the video data line 504 is transferred to the
pixel electrode 508 through the switch transistor 506. The drain
electrode 506b of the switch transistor 506 is connected to the
pixel electrode 508. The source electrode 506c of the switch
transistor 506 is connected to the video data line 504. A common
electrode line 510 is used as the common electrode of the pixel
electrode 508. An "S"-type metal electrode 512 is built around the
pixel region. The metal electrode 512 is controlled by the common
electrode line 510.
[0075] Typically, the source electrode 506c and the drain electrode
506b of the switch transistor 506 can receive video data from the
video data line 504. Therefore, by scanning the scan lines 502 and
in accordance with the scan signals, the switch transistors 506 in
a given scan line 502 are turned on. At the same time, video
signals in the video data line 504 are transferred to the pixel
electrode 508 through the switch transistor 506 to show a picture
on the liquid crystal display.
[0076] FIG. 3B shows a cross-sectional view along line AA' of FIG.
3A, in which all of the liquid crystal molecule are in the splay
state. A lower substrate 514 and an upper substrate 516 are
opposite each other with a specific distance therebetween. The
lower substrate 514 and the upper substrate 516 are preferably made
of a transparent insulator. A liquid crystal layer 518 having a
plurality of liquid crystal molecules is sandwiched between the
lower substrate 514 and the upper substrate 516, in which the
plurality of liquid crystal molecules is in the splay state. The
video data line 504 and the metal line 512 are sequentially formed
over the lower substrate 514. An isolation layer 530 is located
between the video data line 504 and the metal line 512. A pixel
electrode 508 is formed on the inner surface of the lower substrate
514. Another isolation layer 532 is located between the video data
line 504 and the pixel electrode 508. A conductor electrode 520 is
formed on an inner surface of the upper substrate 516. Both the
pixel electrode 508 and the conductor electrode 520 are formed from
a transparent conductor, and preferably, for example, an ITO
material. Further, alignment layers (not shown in figure) are
formed on an inner surface of the lower substrate 514 whereon the
pixel electrode 508 is disposed and the upper substrate 516 whereon
the conductor electrode 520 is disposed. Herein, the alignment
layers have a pre-tilt angle of about 5 degrees in the splay
state.
[0077] A voltage is applied to the metal electrode 512 to transform
the liquid crystal molecule over the metal electrode 512 from the
splay state into the bend state during operation as shown in FIG.
3C. FIG. 3C shows a cross-sectional view along line AA' of FIG. 3A,
in which parts of the liquid crystal molecule are transformed into
the bend state. In accordance with the first embodiment, a voltage
is applied between the common electrode 510 and the conductor
electrode 520 located on the upper substrate 516. Therefore, a
voltage difference also exists between the metal electrode 512
controlled by the common electrode 510 and the conductor electrode
520. Therefore, the liquid crystal molecule between the metal
electrode and the upper substrate 516 is transformed from splay
state into bend state due to the voltage difference.
[0078] Further reference is made to FIG. 3C. The pixel electrode
508 is divided into two parts, 508a and 508b. A liquid crystal
molecule 518a in bend state is used to divide the two parts 508a
and 508b. It is noted that this liquid crystal molecule 518a has an
isolating function. The voltage difference between the metal
electrode 512 and the conductor electrode 520 still exists after
the voltage difference between the pixel electrode and the
conductor electrode 520 is created. In other words, this
still-existing voltage difference ensures that the liquid crystal
molecules 518a remain in the bend state. Therefore, the liquid
crystal molecules 518a isolate influence from outside of the pixel
electrode in which the liquid crystal molecule is in a splay state.
When the liquid crystal display is turned off, the voltage applied
to the common electrode 510 is removed. At this time, the liquid
crystal molecule between the common electrode 510 and the metal
electrode 512 is transformed from the bend state into the splay
state.
[0079] Reference is made to FIG. 3A again. During operation, the
liquid crystal molecule between the common electrode 510 and the
metal electrode 512 is first transformed from the original splay
state into the bend state before a voltage is applied to pixel
electrode 508. Next, by scanning the scan lines 502 and in
accordance with the scan signals, the switch transistor 506 in a
given scan line 502 is turned on. At the same time, video signals
in the video data line 504 are transferred to the pixel electrode
508 through the switch transistor 506. In other words, a voltage
difference is created between the pixel electrode 508 and the
conductor electrode 520 in the upper substrate 516. At this time,
the liquid crystal molecule in the pixel region are transformed
from the splay state into the bend state. Therefore, the liquid
crystal molecules in the whole liquid crystal region are in the
bend state. On the other hand, part of the metal electrode 512 may
overlap with the pixel electrode 508. The overlapping part then
functions as a capacitor, which raises the response velocity of the
pixel electrode.
The Second Embodiment
[0080] FIG. 4A shows a top view of the pixel region in accordance
with the second embodiment of the present invention. The silicon
island 706a of the switch transistor 706 is connected to the scan
line 702. When the switch transistor 706 is selected, the scan
signal in the scan line 702 turns on the switch transistor 706. The
video signal in the video data line 704 is transferred to the pixel
electrode 708 through the switch transistor 706. The drain
electrode 706b of the switch transistor 706 is connected to the
pixel electrode 708. The source electrode 706c of the switch
transistor 706 is connected to the video data line 704. A common
electrode line 710 is used as the common electrode of the pixel
electrode 708. A metal electrode 712 is built around the pixel
region. The metal electrode 712 is controlled by the common
electrode line 710.
[0081] FIG. 4B shows a cross-sectional view along line AA' of FIG.
4A. A lower substrate 714 and an upper substrate 716 are opposite
each other with a specific distance therebetween. The lower
substrate 714 and the upper substrate 716 are preferably made of a
transparent insulator. A liquid crystal layer 718 having a
plurality of liquid crystal molecules is sandwiched between the
lower substrate 714 and the upper substrate 716, in which the
plurality of liquid crystal molecules is in the splay state. The
video data line 704 and the metal line 712 are sequentially formed
over the lower substrate 714. An isolation layer 730 is located
between the video data line 704 and the metal line 712. A pixel
electrode 708 is formed on the inner surface of the lower substrate
714. Another isolation layer 732 is located between the video data
line 704 and the pixel electrode 708. A conductor electrode 720 is
formed on an inner surface of the upper substrate 716. Both the
pixel electrode 708 and the conductor electrode 720 are formed from
a transparent conductor, and preferably, for example, an ITO
material. Further, alignment layers (not shown in figure) are
formed on an inner surface of the lower substrate 714 whereon the
pixel electrode 708 is disposed and the upper substrate 716 whereon
the conductor electrode 720 is disposed. Herein, the alignment
layers have a pre-tilt angle of about 5 degrees in the splay
state.
[0082] A voltage is applied to the metal electrode 712 to transform
the liquid crystal molecule 718a over the metal electrode 712 from
the splay state into the bend state during operation as shown in
FIG. 4C. FIG. 4C shows a cross-sectional view along line AA' of
FIG. 4A in accordance with the second embodiment, in which parts of
the liquid crystal molecule are transformed into the bend state. In
accordance with the second embodiment, a voltage is applied between
the common electrode 710 and the conductor electrode 720 located on
the upper substrate 716. Therefore, a voltage difference also
exists between the metal electrode 712 controlled by the common
electrode 710 and the conductor electrode 720. Therefore, the
liquid crystal molecule between the metal electrode 712 and the
upper substrate 716 is transformed from the splay state into the
bend state due to the voltage difference as shown in FIG. 4C.
[0083] Again referring to FIG. 4C, a liquid crystal molecule 718a,
which is in bend state, is used to isolate the pixel electrode 708.
The voltage difference between the metal electrode 712 and the
conductor electrode 720 still exists after the voltage difference
between the pixel electrode 708 and the conductor electrode 720 is
built. In other words, this still-existent voltage difference
ensures that the liquid crystal molecules 718a maintain the bend
state. Therefore, the liquid crystal molecule 718a isolates the
pixel electrode 708 from the influence outside of the pixel
electrode 708 in which the liquid crystal molecule is in a splay
state. When the liquid crystal display is turned off, the voltage
applied to the common electrode 710 is removed. At this time, the
liquid crystal molecule between the common electrode 710 and the
metal electrode 712 can be transformed from the bend state into the
splay state.
[0084] During operation, the liquid crystal molecule between the
common electrode 710 and the metal electrode 712 is first
transformed from the original splay state into the bend state
before a voltage is applied to pixel electrode 708. Next, by
scanning the scan lines 702 and in accordance with the scan
signals, the switch transistor 706 in a given scan line 702 is
turned on. At the same time, video signals in the video data line
704 are transferred to the pixel electrode 708 through the switch
transistor 706. In other words, a voltage difference is created
between the pixel electrode 708 and the conductor electrode 720 in
the upper substrate 716. At this time, the liquid crystal molecule
in the pixel region can be transformed from the splay state into
the bend state. Therefore, the liquid crystal molecules in the
whole liquid crystal region are in the bend state now. On the other
hand, part of the metal electrode 712 may overlap with the pixel
electrode 708. The overlapping part functions as a capacitor, which
raises the response velocity of the pixel electrode.
The Third Embodiment
[0085] FIG. 5A shows a top view of the pixel region in accordance
with the third embodiment of the present invention. The silicon
island 806a of the switch transistor 806 is connected to the scan
line 802. The drain electrode 806b of the switch transistor 806 is
connected to the pixel electrode 808. The source electrode 806c of
the switch transistor 806 is connected to the video data line 804.
A common electrode line 810 is used as the common electrode of the
pixel electrode 808. In accordance with the third embodiment, the
metal electrode 812 and the common electrode 810 are in the shape
of an "H". The metal electrode 812 is controlled by the common
electrode line 810.
[0086] FIG. 5B shows a cross-sectional view along line AA' of FIG.
5A. A lower substrate 814 and an upper substrate 816 are opposite
each other with a specific distance therebetween. The lower
substrate 814 and the upper substrate 816 are preferably made of a
transparent insulator. A liquid crystal layer 818 having a
plurality of liquid crystal molecules is sandwiched between the
lower substrate 814 and the upper substrate 816, in which the
plurality of liquid crystal molecules is in the splay state. The
video data line 804 and the metal line 812 are sequentially formed
over the lower substrate 814. An isolation layer 830 is located
between the video data line 804 and the metal line 812. A pixel
electrode 808 is formed on the inner surface of the lower substrate
814. Another isolation layer 832 is located between the video data
line 804 and the pixel electrode 808. A conductor electrode 820 is
formed on an inner surface of the upper substrate 816. Both the
pixel electrode 808 and the conductor electrode 820 are formed from
a transparent conductor, and preferably, for example, an ITO
material. Further, alignment layers (not shown in figure) are
formed on an inner surface of the lower substrate 814 whereon the
pixel electrode 31 is disposed and the upper substrate 816 whereon
the conductor electrode 820 is disposed. Herein, the alignment
layers have a pre-tilt angle of about 5 degrees in the splay state.
During operation, a voltage is applied to the metal electrode 812
to transform the liquid crystal molecule 818a over the metal
electrode 812 from the splay state into the bend state as shown in
FIG. 5C.
[0087] Referring to FIG. 5C again, a liquid crystal molecule 818a,
which is in the bend state, is used to isolate the pixel electrode
808. In other words, the voltage difference between the metal
electrode 812 and the conductor electrode 820 still exists after
the voltage difference between the pixel electrode 808 and the
conductor electrode 820 is created. In other words, this
still-existent voltage difference ensures that the liquid crystal
molecule 818a maintains the bend state. Therefore, the liquid
crystal molecule 818a isolates the pixel electrode 808 from
influence from outside of the pixel electrode 808 in which the
liquid crystal molecules are in a splay state. When the liquid
crystal display is turned off, the voltage applied to the common
electrode 810 is removed. At this time, the liquid crystal molecule
between the common electrode 810 and the metal electrode 812 is
transformed from the bend state into the splay state.
[0088] During operation, the liquid crystal molecule between the
common electrode 810 and the metal electrode 812 is first
transformed from the original splay state into the bend state
before a voltage is applied to pixel electrode 808. Next, by
scanning the scan lines 802 and in accordance with the scan
signals, the switch transistor 806 in a given scan line 802 is
turned on. At the same time, video signals in the video data line
804 are transferred to the pixel electrode 808 through the switch
transistor 806. In other words, a voltage difference is built
between the pixel electrode 808 and the conductor electrode 820 in
the upper substrate 816. At this time, the liquid crystal molecule
in the pixel region can be transformed from the splay state into
the bend state. Therefore, the liquid crystal molecule in the whole
liquid crystal region is now in the bend state. On the other hand,
part of the metal electrode 812 overlaps the pixel electrode 808.
The overlapping part functions as a capacitor, which can raise the
response velocity of the pixel electrode.
The Fourth Embodiment
[0089] FIG. 6A shows a top view of the pixel region in accordance
with the fourth embodiment of the present invention. The silicon
island 906a of the switch transistor 906 is connected to the scan
line 902. The drain electrode 906b of the switch transistor 906 is
connected to the pixel electrode 908. The source electrode 906c of
the switch transistor 906 is connected to the video data line 904.
A common electrode line 910 is used as the common electrode of the
pixel electrode 909. In accordance with the fourth embodiment, the
metal electrode 912 and the common electrode 910 are in the shape
of a cross. The metal electrode 912 is controlled by the common
electrode line 910.
[0090] FIG. 6B shows a cross-sectional view along line AA' of FIG.
5A. A lower substrate 914 and an upper substrate 916 are opposite
each other with a specific distance therebetween. The lower
substrate 914 and the upper substrate 916 are preferably made of a
transparent insulator. A liquid crystal layer 918 having a
plurality of liquid crystal molecules is sandwiched between the
lower substrate 914 and the upper substrate 916, wherein the
plurality of liquid crystal molecules is in the splay state. The
video data line 904 and the metal line 912 are sequentially formed
over the lower substrate 914. An isolation layer 930 is located
between the video data line 904 and the metal line 912. A pixel
electrode 908 is formed on the inner surface of the lower substrate
914. Another isolation layer 932 is located between the video data
line 904 and the pixel electrode 908. A conductor electrode 920 is
formed on an inner surface of the upper substrate 916. Both the
pixel electrode 908 and the conductor electrode 920 are formed from
a transparent conductor, and preferably, for example, an ITO
material. Further, alignment layers (not shown in figure) are
formed on an inner surface of the lower substrate 914 whereon the
pixel electrode 31 is disposed and the upper substrate 916 whereon
the conductor electrode 920 is disposed. Herein, the alignment
layers have a pre-tilt angle of about 5 degrees in the splay
state.
[0091] Referring to FIG. 5C again, a liquid crystal molecule 918a,
which is in the bend state, is used to isolate the pixel electrode
908. In other words, the voltage difference between the metal
electrode 912 and the conductor electrode 920 still exists after
the voltage difference between the pixel electrode 908 and the
conductor electrode 920 is created. This still-existent voltage
difference ensures that the liquid crystal molecule 918a maintains
the bend state. Therefore, the liquid crystal molecule 918a
isolates pixel electrode 908 from the influence the outside of the
pixel electrode 908 in which the liquid crystal molecule is in a
splay state. When the liquid crystal display is turned off, the
voltage applied to the common electrode 910 is removed. At this
time, the liquid crystal molecule between the common electrode 910
and the metal electrode 912 is transformed from the bend state into
the splay state.
[0092] During operation, the liquid crystal molecule between the
common electrode 910 and the metal electrode 912 is first
transformed from the original splay state into the bend state
before a voltage is applied to pixel electrode 909. Next, by
scanning the scan lines 902 and in accordance with the scan
signals, the switch transistor 906 in a given scan line 902 is
turned on. At the same time, video signals in the video data line
904 are transferred to the pixel electrode 908 through the switch
transistor 906. In other words, a voltage difference is created
between the pixel electrode 908 and the conductor electrode 920 in
the upper substrate 916. At this time, the liquid crystal molecules
in the pixel region are transformed from the splay state into the
bend state. Therefore, the liquid crystal molecules in the whole
liquid crystal region are now in the bend state. On the other hand,
part of the metal electrode 912 overlaps with the pixel electrode
908. The overlapping part functions as a capacitor, which can raise
the response velocity of the pixel electrode.
[0093] It is noted that the common electrode line with the
connected metal electrode line and the video data line are located
on different layers according to the foregoing four embodiments.
However, the common electrode line with the connected metal
electrode line and the video data line can be located on the same
layer in another embodiments. For example, FIG. 7A and FIG. 7B
illustrate the structure of the common electrode line with the
connected metal electrode line and the video data line, described
in the first embodiment, are located on the same layer.
[0094] In FIG. 7A, the silicon island 506a of the switch transistor
506 is connected to the scan line 502. When the switch transistor
506 is selected, a scan signal is sent via the scan line 502 to
turn the switch transistor 506 on. The video signal in the video
data line 504 is transferred to the pixel electrode 508 through the
switch transistor 506. The drain electrode 506b of the switch
transistor 506 is connected to the pixel electrode 508. The source
electrode 506c of the switch transistor 506 is connected to the
video data line 504. A common electrode line 510 is used as the
common electrode of the pixel electrode 508. The common electrode
line 510 is arranged in parallel with the video data line 504. An
"S"-type metal electrode 512 is built around the pixel region. The
metal electrode 512 is controlled by the common electrode line 510.
The common electrode line with the connected metal electrode line
and the video data line are located on the same layer.
[0095] FIG. 7B shows a cross-sectional view along line AA' of FIG.
7A, in which all of the liquid crystal molecule are in the splay
state. A lower substrate 514 and an upper substrate 516 are
opposite each other with a specific distance therebetween. The
lower substrate 514 and the upper substrate 516 are preferably made
of a transparent insulator. A liquid crystal layer 518 having a
plurality of liquid crystal molecules is sandwiched between the
lower substrate 514 and the upper substrate 516, in which the
plurality of liquid crystal molecules is in the splay state. The
video data line 504 and the metal line 512 are formed over the
lower substrate 514 and located on the same layer but isolated from
each other. A pixel electrode 508 is formed on the inner surface of
the lower substrate 514. Another isolation layer 532 is located
between the video data line 504, the metal line 512 and the pixel
electrode 508. A conductor electrode 520 is formed on an inner
surface of the upper substrate 516. Both the pixel electrode 508
and the conductor electrode 520 are formed from a transparent
conductor, and preferably, for example, an ITO or IZO material.
[0096] The structure of the common electrode line with the
connected metal line and the video data line are located on the
same layer can be applied in the foregoing four embodiments.
[0097] In accordance with the foregoing description, an additional
metal electrode is built in the pixel region. The metal electrode
is controlled by the common electrode. The liquid crystal molecules
in the whole pixel region are in the splay state. During operation,
a voltage is first applied to the metal electrode to transform the
liquid crystal molecule over the metal electrode from the splay
state into the bend state. Then, a voltage is applied to the pixel
electrode to make the whole pixel region exhibit the bend
state.
[0098] It is noted that the metal electrode can be positioned in
the center of the pixel electrode or around the pixel electrode.
The metal electrode and the common electrode can be in the shape of
a cross or in the shape of an "H". In accordance with the present
invention, a complicated manufacturing process is avoided because
the present invention does not require two orientation states in a
liquid crystal cell. Moreover, a given period for transforming the
liquid crystal molecule from the splay state into the bend state at
the start of LCDs operation is not necessary. Therefore, the LCDs
using the pixel structure of the present invention has a high speed
response as well as a high display quality.
[0099] On the other hand, the present invention also provides a
drive circuit for driving the metal electrode. FIG. 8A shows a
waveform from negative to positive of drive timing in accordance
with the first embodiment. The waveform can be used in the
foregoing four embodiments. According to FIGS. 3A to 3C and FIG.
8A, a voltage signal 404 is first applied to the common electrode
510. Therefore, the metal electrode 512 controlled by the common
electrode is also applied by this voltage signal 404. At this time,
the liquid crystal molecule located over the metal electrode 512 is
transformed from the splay state into the bend state. On the other
hand, part of the metal electrode 512 overlaps with the pixel
electrodes 508a and 508b and a voltage exists in the metal
electrode 512, as shown in FIGS. 3B and 3C. All the metal electrode
and pixel electrodes 508a and 508b are conductors. Therefore, the
overlapping parts 524 and 526 can function as capacitors. In other
words, this voltage applied to the metal electrode 512 charges
these overlapping parts 524 and 526 to raise the electrical
potential of the pixel electrode.
[0100] At time T.sub.1, by scanning the scan lines 502 and in
accordance with the scan signals 402, the switch transistor 506 in
a given scan line 502 is turned on. At the same time, pixel
electrical potential 406 in the video data line 504 is transferred
to the pixel electrode 508 through the switch transistor 506. In
other words, a voltage difference is created between the pixel
electrode 508 and the conductor electrode 520 in the upper
substrate 516 to transform the liquid crystal molecule from the
splay state into the bend state. It is noted that because the
overlapping parts 524 and 526 function as a capacitor, an initial
electric potention exists in the pixel electrode 508. In other
words, it is easier to create a voltage in the pixel electrode 508
for transforming the liquid crystal molecule from the splay state
into the bend state. Therefore, the response velocity can be
raised.
[0101] FIG. 8B shows a waveform from positive to negative of drive
timing. The waveform may be used in the foregoing four embodiments.
According to FIGS. 3A to 3C and FIG. 8B, a voltage signal 408
applied to the common electrode 510 is first switched from a high
voltage to a low voltage. Therefore, the metal electrode 512
controlled by the common electrode is also in a low voltage state.
On the other hand, part of the metal electrode 512 overlaps with
the pixel electrodes 508a and 508b as shown in FIGS. 3B and 3C. All
of the metal electrode, pixel electrodes 508a and 508b are
conductors. Therefore, the overlapping parts 524 and 526 function
as a capacitor. Therefore, when the metal electrode 512 is in a low
electrical potential, the electrical potential 410 of the pixel
electrodes 508a and 508b is also reduced to a specific value at
time T.sub.2. However, because the scan signal 412 does not select
the switch transistor 506 at this time, the switch transistor 506
is still turned off. In other words, the electrical potential 410
of the pixel electrodes 508a and 508b is maintained at a fixed
value. At time T.sub.3, when the scan signal 412 in the scan line
502 selects the switch transistor 506, the switch transistor 506 is
turned on. The potential of the pixel electrodes 508a and 508b is
discharged through the switch transistor 506 to reduce the
electrical potential 410.
[0102] FIG. 9A and FIG. 9B are the waveforms in accordance with the
second embodiment, of which FIG. 9A shows a waveform from positive
to negative of drive timing. The waveform may be used in the
foregoing four embodiments. According to FIGS. 3A to 3C and FIG.
9A, by scanning the scan lines 502 and in accordance with the scan
signals 602, the switch transistor 506 in a given scan line 502 is
turned on. At the same time, pixel electrical potential 606 in the
video data line 504 is transferred to the pixel electrode 508
through the switch transistor 506. Next, at time T.sub.1, a voltage
signal 604 is transformed from a low electrical potential to a high
electrical potential. In other words, the common electrode is also
in a high electrical potential. Therefore, the metal electrode 512
controlled by the common electrode 510 is also in a high electrical
potential that transforms the liquid crystal molecule from the
splay state into the bend state.
[0103] On the other hand, part of the metal electrode 512 overlaps
with the pixel electrodes 508a and 508b and a voltage exists in the
metal electrode 512, as shown in FIGS. 3B and 3C. All of the metal
electrode and pixel electrodes 508a and 508b are conductors.
Therefore, the overlapping parts 524 and 526 function as a
capacitor. In other words, this voltage applied to the metal
electrode 512 charges these overlapping parts 524 and 526 to raise
the electrical potential 606 of the pixel electrode. It is easier
to create a voltage in the pixel electrode 508 for transforming the
liquid crystal molecule from the splay state into the bend
state.
[0104] FIG. 9B shows the waveform from positive to negative of
drive timing in accordance with the second embodiment. The waveform
may be used in the foregoing four embodiments. According to FIGS.
3A to 3C and 9B, by scanning the scan lines 502 and in accordance
with the scan signals 612, the switch transistor 506 in a given
scan line 502 is turned on to reduce the pixel electrical potential
610. On the other hand, part of the metal electrode 512 overlaps
with the pixel electrodes 508a and 508b as shown in FIGS. 3B and
3C. The overlapping parts 524 and 526 function as a capacitor. This
capacitor function maintain the pixel electrical potential of the
pixel electrode 508 at a fixed value. At time T.sub.2, the voltage
signal 608 in the common electrode 510 is transferred from a high
electrical potential to a low electrical potential. The metal
electrode 512 controlled by the common electrode 510 is also at a
low electrical potential, which discharges the charge stored in the
overlapping parts 524 and 526 to reduce the pixel electrical
potential 610 of the pixel electrode 508.
[0105] FIG. 10A and FIG. 10B are the waveforms in accordance with
the third embodiment, in which FIG. 10A shows a waveform from
positive to negative of drive timing. The waveform may be used in
the foregoing four embodiments. According to FIGS. 3A to 3C and 9A,
by scanning the scan lines 502 and in accordance with the scan
signals 202, the switch transistor 506 in a given scan line 502 is
turned on at time T.sub.1. Next, pixel electrical potential 206 in
the video data line 504 is transferred to the pixel electrode 508
through the switch transistor 506. At the same time, a voltage
signal 204 is transformed from a low electrical potential into a
high electrical potential. In other words, the common electrode is
also at a high electrical potential. Therefore, the metal electrode
512 controlled by the common electrode 510 is also at a high
electrical potential to transform the liquid crystal molecule from
the splay state into the bend state.
[0106] On the other hand, part of the metal electrode 512 overlaps
with the pixel electrodes 508a and 508b, as shown in FIGS. 3B and
3C. All the metal electrodes and pixel electrodes 508a and 508b are
conductors. The overlapping parts 524 and 526 function as a
capacitor. Therefore, this voltage applied to the metal electrode
512 charges these overlapping parts 524 and 526 to raise the
electrical potential 206 of the pixel electrode. It is easier to
build a voltage in the pixel electrode 508 for transforming the
liquid crystal molecule from the splay state into the bend
state.
[0107] FIG. 10B shows a waveform from positive to negative of drive
timing in accordance with the third embodiment. The waveform may be
used in the foregoing four pixel structure embodiments. According
to FIGS. 3A to 3C and 8B, by scanning the scan lines 502 and in
accordance with the scan signals 212, the switch transistor 506 in
a given scan line 502 is turned on to reduce the pixel electrical
potential 210 at time T.sub.2. At this time, the voltage signal 208
in the common electrode 510 is transformed from a high electrical
potential in to a low electrical potential. The metal electrode 512
controlled by the common electrode 510 is also at a low electrical
potential. On the other hand, part of the metal electrode 512
overlaps with the pixel electrodes 508a and 508b as shown in FIGS.
3B and 3C. The overlapping parts 524 and 526 function as a
capacitor. Because the electrical potential in the common electrode
510 is at a low electrical potential, the charge stored in the
overlapping parts 524 and 526 is discharged to reduce the pixel
electrical potential 210 of the pixel electrode 508.
[0108] In accordance with the pixel structure of the present
invention, part of the metal electrode overlaps with the pixel
electrodes to function as a capacitor, which raises the response
velocity.
[0109] FIG. 11 shows a top view of using the pixel electrode
structure of the present invention in a TFT-LCD, in which the
foregoing four pixel structures may be used in the embodiment. The
gate electrodes of the switch transistors 14, 16, 18 and 19 are
respectively connected to the scan lines 82, 84, 86 and 88. The
drain electrodes of the switch transistor 14, 16, 18 and 19 are
respectively connected to the pixel electrodes 24, 26, 28 and 19
and the source electrodes are respectively connected to the video
data line 72. The common lines 90, 92, 94 and 96 are used as the
common electrode of the pixel electrode 24, 26, 28 and 19,
respectively, to control the metal electrodes (not shown in
figure). When the switch transistor 14 is selected by a given scan
line, the video signals provided in the video data lines 72 are
transferred to the pixel electrode 24 through the switch transistor
14 to show a picture in the display.
[0110] FIG. 12A shows a drive circuit schematic diagram for
generating a waveform as shown in FIGS. 8A and 8B for application
to the pixel structure as shown in FIG. 11. It is noted that FIG.
12A only depicts the common electrode for driving two different
pixel electrodes. However, this drive circuit may be extending for
driving the whole pixel structure. The drive method is same as is
described in the following.
[0111] Referring to FIG. 11 and FIG. 12A, in accordance with the
drive circuit of the present invention, the voltage signal in the
output end V.sub.com1 is used to drive the common electrode 92 and
the voltage signal in the output end V.sub.com2 is used to drive
the common electrode 94. The switch of transistor 30 is controlled
by the scan line 82 and the switch of transistor 32 is controlled
by the scan line 84. An inverter 34 is located between the
transistor 30 and the output end V.sub.com1 to invert the input
signal from the transistor 30. Another inverter 36 is located
between the transistor 32 and the output end V.sub.com2 to invert
the signal in the output end V.sub.com1.
[0112] During operation, a frame signal V.sub.in composed of two
fields 38 and 40 is input from the transistor 30, in which the time
of each field is 1/60 second. When the transistor 30 is turned on
by the scan line 82, the first field signal 38 is transferred to
the inverter 34 through the transistor 30. The inverter 34 inverts
the first field signal 38 and sends out the inverted first field
signal 38 from the output end V.sub.com1 to drive the common
electrode 92. Next, when the scan line 84 turns on the transistor
32, the inverted first field signal 38 is transferred to the
inverter 36 through the transistor 32. The inverter 36 inverts the
received signal again and sends out the same from the output end
V.sub.com2 to drive the common electrode 94.
[0113] Therefore, in accordance with the waveform generated by the
drive circuit of the present invention, the switch transistor 16 of
the pixel electrode 26 is turned on by the scan signal in the scan
line 84 after the common electrode 92 is driven by the drive signal
from the output end V.sub.com1. Therefore, the waveform shown in
FIG. 7A is formed, in which the waveform 404 is the signal in the
output end V.sub.com1 and the waveform 402 is the signal in the
scan line 84.
[0114] Next, when the transistor 30 receives the signal in the scan
line 82 again, the second field signal 40 is transferred to the
inverter 34 through the transistor 30. The inverter 34 may invert
the second field signal 40 and sends out the inverted second field
signal 40 from the output end V.sub.com1 to drive the common
electrode 92. Next, when the scan line 84 turns on the transistor
32, the inverted second field signal 40 is transferred to the
inverter 36 through the transistor 32. The inverter 36 inverts the
received signal again and sends out the same from the output end
V.sub.com2 to drive the common electrode 94.
[0115] Therefore, the switch transistor 16 of the pixel electrode
26 is turned on by the scan signal in the scan line 84 after the
common electrode 92 receives the signal from the output end
V.sub.com1. The waveform shown in FIG. 8B is thus formed, in which
the waveform 408 is the signal in the output end V.sub.com1 and the
waveform 412 is the signal in the scan line 84.
[0116] FIG. 12B shows a detailed diagram of the drive circuit in
FIG. 12A for generating a drive voltage. The operation method of
the inverter is described in the following. When the transistor 30
is turned on by the signal in the scan line 82, the first field
signal 38 is transferred to the gate electrodes of the transistors
42 and 44 through the transistor 30. The transistors 42 and 44 are
still turned off because the first field signal 38 is at a low
electrical potential. The transistor is turned on because the drain
electrode and the source electrode are connected together. The
transistor is also turned on by the high voltage through the
transistor 46. Therefore, the signal in the output end V.sub.com1
is a high voltage signal.
[0117] Similarly, when the signal in the scan line 82 turns the
transistor 30 on again, the second field signal 40 is transferred
to the gate electrodes of the transistors 42 and 44 through the
transistor 30. The transistors 42 and 44 are turned on because the
second field signal 40 is at a high electrical potential. The gate
electrode of the transistor 48 are connected to the low electrical
potential through the transistor 42. Therefore, the transistor 48
is turned off. Therefore, the output end V.sub.com1 is connected to
a low voltage signal through the transistor 44.
[0118] The drive circuit shown in FIG. 12A also can be used to
generate a waveform as shown in FIGS. 9A and 9B. Referring to FIG.
11 and FIG. 12A together, the voltage signal in the output end
V.sub.com1 is used to drive the common electrode 92 and the voltage
signal in the output end V.sub.com2 is used to drive the common
electrode 94. However, the switch of the transistor 30 is
controlled by the scan line 86 and the switch of the transistor 32
is controlled by the scan line 88. An inverter 34 is located
between the transistor 30 and the output end V.sub.com1 to invert
the input signal from the transistor 30. Another inverter 36 is
located between the transistor 32 and the output end V.sub.com2 to
invert the signal in the output end V.sub.com1.
[0119] During operation, a frame signal V.sub.in composed of two
fields 38 and 40 is input from the transistor 30, where the time of
each field is 1/60 seconds. When the transistor 30 is turned on by
the scan signal in the scan line 86, the first field signal 38 is
transferred to the inverter 34 through the transistor 30. The
inverter 34 inverts the first field signal 38 and sends out the
inverted first field signal 38 from the output end V.sub.com1 to
drive the common electrode 92. Next, when the scan line 88 turns on
the transistor 32, the inverted first field signal 38 is
transferred to the inverter 36 through the transistor 32. The
inverter 36 inverts the received signal again and sends out the
same from the output end V.sub.com2 to drive the common electrode
94.
[0120] Therefore, in accordance with the waveform generated by the
drive circuit of the present invention, the common electrode 92 is
driven by the drive signal from the output end V.sub.com1 after the
switch transistor 18 of the pixel electrode 28 is turned on by the
scan signal in the scan line 86. Therefore, the waveform shown in
FIG. 8A is formed, in which the waveform 604 is the signal in the
output end V.sub.com2 and the waveform 602 is the signal in the
scan line 86.
[0121] Next, when the transistor 30 receives the signal in the scan
line 86 again, the second field signal 40 is transferred to the
inverter 34 through the transistor 30. The inverter 34 inverts the
second field signal 40 and sends out the inverted second field
signal 40 from the output end V.sub.com1 to drive the common
electrode 92. Next, when the scan line 88 turns on the transistor
32, the inverted second field signal 40 is transferred to the
inverter 36 through the transistor 32. The inverter 36 inverts the
received signal again and sends out the same from the output end
V.sub.com2 to drive the common electrode 94.
[0122] Therefore, the common electrode 94 receives the signal from
the output end V.sub.com2 after the switch transistor 18 of the
pixel electrode 28 is turned on by the scan signal in the scan line
86. The waveform shown in FIG. 8B is thus formed, in which the
waveform 608 is the signal in the output end V.sub.com2 and the
waveform 612 is the signal in the scan line 86.
[0123] The drive circuit showing in FIG. 12A also can be used to
generate a waveform as shown in FIGS. 10A and 10B. Referring to
FIG. 11 and FIG. 12A together, the voltage signal in the output end
V.sub.com1 is used to drive the common electrode 92 and the voltage
signal in the output end V.sub.com2 is used to drive the common
electrode 94. However, the switch of the transistor 30 is
controlled by the scan line 84 and the switch of the transistor 32
is controlled by the scan line 86. An inverter 34 is located
between the transistor 30 and the output end V.sub.com1 to invert
the input signal from the transistor 30. Another inverter 36 is
located between the transistor 32 and the output end V.sub.com2 to
invert the signal in the output end V.sub.com1.
[0124] During operation, a frame signal V.sub.in composed of two
fields 38 and 40 is input from the transistor 30, in which the time
of each field is 1/60 second. When the transistor 30 is turned on
by the scan signal in the scan line 84, the first field signal 38
is transferred to the inverter 34 through the transistor 30. The
inverter 34 inverts the first field signal 38 and sends out the
inverted first field signal 38 from the output end V.sub.com1 to
drive the common electrode 92. Next, when the scan line 86 turns on
the transistor 32, the inverted first field signal 38 is
transferred to the inverter 36 through the transistor 32. The
inverter 36 inverts the received signal again and sends out the
same from the output end V.sub.com2 to drive the common electrode
94.
[0125] Therefore, in accordance with the waveform generated by the
drive circuit of the present invention, the switch transistor 16 of
the pixel electrode 26 is turned on by the scan signal in the scan
line 84. At the same time, the common electrode 92 is driven by the
drive signal from the output end V.sub.com1. The waveform shown in
FIG. 9A is thus formed, in which the waveform 204 is the signal in
the output end V.sub.com1 and the waveform 202 is the signal in the
scan line 84.
[0126] Next, when the transistor 30 receives the signal in the scan
line 84 again, the second field signal 40 is transferred to the
inverter 34 through the transistor 30. The inverter 34 inverts the
second field signal 40 and sends out the inverted second field
signal 40 from the output end V.sub.com1 to drive the common
electrode 92. Next, when the scan line 86 turns on the transistor
32, the inverted second field signal 40 is transferred to the
inverter 36 through the transistor 32. The inverter 36 inverts the
received signal again and sends out the same from the output end
V.sub.com2 to drive the common electrode 94.
[0127] Therefore, the switch transistor 16 of the pixel electrode
26 is turned on by the scan signal in the scan line 84. At the same
time, the common electrode 92 receives the signal from the output
end V.sub.com1. The waveform shown in FIG. 9B is thus formed, in
which the waveform 208 is the signal in the output end V.sub.com2
and the waveform 212 is the signal in the scan line 84.
[0128] On the other hand, the liquid crystal molecules filling the
pixel region need be aligned. The alignment arranges the
orientation of the liquid crystal molecules before a field is
applied to the liquid crystal display to sure all the liquid
crystal molecule is arranged in the same direction. A rubbing
method is used to arrange the orientation. An orientation line is
generated on the orientation layer during the rubbing process.
These liquid crystal molecules are oriented along these lines.
[0129] In accordance with the present invention, a metal electrode
is built in the pixel region. The metal electrode is controlled by
the common electrode. The liquid crystal molecules in the entire
pixel region are in the splay state. A voltage is first applied to
the metal electrode to transform the liquid crystal molecule over
the metal electrode from the splay state into the bend state during
operation. Then, a voltage is applied to the pixel electrode. In
other words, liquid crystal molecules located over the metal
electrode are first transformed. However, when the voltage is
applied to the common electrode, an unwanted crosswise field is
also generated around the common electrode. This crosswise
electrical field affects the transformation of the liquid crystal
molecules located around the electrode. Therefore, the present
invention provides an alignment method to reduce the effect the
crosswise electrical field.
[0130] FIG. 13A illustrates a schematic diagram of the liquid
crystal molecules aligned in the direction perpendicular to the
metal electrode. The liquid crystal molecules 746 located over the
metal electrode 742 and the pixel electrode 744 are aligned in the
direction as indicated by the arrow 740 perpendicular to the metal
electrode 742. In FIG. 5A, the metal electrode 812 is built around
the pixel electrode. Therefore, according to the alignment method
illustrated in FIG. 13A, the liquid crystal molecules 818 located
over the metal electrode 812 and the pixel electrode are aligned in
the direction perpendicular to the metal electrode 812.
[0131] FIG. 13B illustrates a schematic diagram of the liquid
crystal molecules affected by a crosswise electrical field. When a
voltage is applied to a pixel electrode 744, a crosswise electrical
field 750 is generated, the direction of which is the reverse of
the direction of the electrical field 748 used to transform the
liquid crystal molecules 746. In other words, a larger voltage must
be applied to the pixel electrode 744 to overcome the crosswise
electrical field so as to finish the transformation of the liquid
crystal molecules 746. Such a larger voltage requirement consumes
power and time to finish the transformation of the liquid crystal
molecules.
[0132] In FIG. 14A, illustrates a schematic diagram of the liquid
crystal molecules that is aligned in the direction parallel to the
metal electrode. The liquid crystal molecules 746 located over the
metal electrode 742 and the pixel electrode 744 are aligned in the
direction as indicated by the arrow 752 that is parallel to the
metal electrode 742. In FIG. 5A, the metal electrode 812 is built
around the pixel electrode. Therefore, according to the alignment
method as shown in FIG. 14A, the liquid crystal molecules 818
located over the metal electrode 812 and the pixel electrode are
aligned in the direction parallel to the metal electrode 812.
[0133] FIG. 14B illustrates a schematic diagram of the
transformation of the liquid crystal molecules when a voltage is
applied to a pixel electrode 744. The alignment direction of the
liquid crystal molecules 746 is parallel to the arrangement
direction of the metal electrode 742 in FIG. 14A. Therefore, the
crosswise electrical field generated by the metal electrode 742
does not obstruct the liquid crystal molecules transformation. In
other words, it is not necessary to apply a larger voltage to the
pixel electrode 744 to overcome the obstruction of the crosswise
electrical field.
[0134] Accordingly, the alignment direction of the liquid crystal
molecules in the foregoing embodiments is parallel to the arranged
direction of the metal electrode. However, the arranged direction
of the metal electrode is not always in the same direction in a
pixel region in the embodiments, which causes disorder in the
liquid crystal molecule alignment direction in a pixel region. For
solving this problem, The metal electrode is designed and
additional holes passing through the pixel electrode are formed in
positions corresponding to the metal electrode or common electrode
so as to reduce the effect of the crosswise electrical field and
improve the transmission efficiency. The following eight
embodiments illustrate the pixel structure appearance change of the
FIG. 4A to cooperate with the alignment direction of the liquid
crystal molecules.
[0135] FIG. 15A illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the first embodiment of the present
invention. The silicon island 706a of the switch transistor 706 is
connected to the scan line 702. When the switch transistor 706 is
selected, the scan signal in the scan line 702 turns on the switch
transistor 706. The video signal in the video data line 704 is
transferred to the pixel electrode 708 through the switch
transistor 706. The drain electrode 706b of the switch transistor
706 is connected to the pixel electrode 708. The source electrode
706c of the switch transistor 706 is connected to the video data
line 704. A common electrode line 710 is used as the common
electrode of the pixel electrode 708. A metal electrode 756 is
built around the pixel region. The metal electrode 756 is
controlled by the common electrode line 710. When operating the
liquid crystal display, a voltage is applied to the common
electrode and the metal electrode at the same time.
[0136] Cooperating with the alignment direction of the liquid
crystal molecules parallel to the arranged direction of the metal
electrode 756, a plurality of additional holes 758 passing through
the pixel electrode 708 is formed in positions corresponding to the
common electrode line 710. The hole 758 is an ellipse, a rectangle
or another shape with a major axis. It is noted that the direction
of the major axis is parallel to the alignment direction of the
liquid crystal molecules as indicated by the arrow 754. On the
other hand, the metal electrode 756 adjacent to the scan line 702
is sawtoothed so that this metal electrode 756 has a major axis in
the direction indicated by an arrow 754. In other words, the liquid
crystal molecules located over the metal electrode 756 adjacent to
the scan lines 702 can be aligned in the direction indicated by an
arrow 754.
[0137] FIG. 17A is an enlarged schematic diagram of the region 760
in FIG. 15A. A plurality of holes 758 passing through the pixel
electrode 708 is formed in positions corresponding to the common
electrode line 710. According to the preferred embodiment, the hole
758 is ellipsoidal. The liquid crystal molecules 718 located over
the pixel electrode are aligned in the direction parallel to the
major axis of the hole 758, as indicated by the arrow 754. Holes
758 are separated from each other. Therefore, each hole 758 is
treated as an independent electrode and has a major axis, which
cause a major crosswise electrical field, in the direction
indicated by the arrow 754. Therefore, the liquid crystal molecules
718 is aligned in the direction parallel to the major axis of the
hole 758 to reduce the effect of the crosswise electrical field, as
shown in FIG. 17A. FIG. 17B illustrates a schematic diagram of the
liquid crystal molecules when a voltage is applied to the common
electrode.
[0138] FIG. 18A is an enlarged schematic diagram of the region 762
in FIG. 15A. The metal electrode 756 is sawtoothed. In this region
762, the metal electrode 756 is composed of a base body 756a and a
plurality of extending parts 756b. Partial extending parts 756b
protrude from the pixel electrode 708. In other words, the metal
electrode 756 has a major axis, which cause a major crosswise
electrical field, in the direction indicated by the arrow 754.
Therefore, the liquid crystal molecules 718 is aligned in the
direction parallel to the major axis, the extending parts 756b, to
reduce the effect of the crosswise electrical field, as shown in
FIG. 18A. FIG. 18B illustrates a schematic diagram of the liquid
crystal molecules when a voltage is applied to the common
electrode.
[0139] On the other hand, the region 764 and the region 762 both
have the same structure of the metal electrode 756 in FIG. 15A.
[0140] FIG. 15B illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the second embodiment of the present
invention. The silicon island 706a of the switch transistor 706 is
connected to the scan line 702. When the switch transistor 706 is
selected, the scan signal in the scan line 702 turns on the switch
transistor 706. The video signal in the video data line 704 is
transferred to the pixel electrode 708 through the switch
transistor 706. The drain electrode 706b of the switch transistor
706 is connected to the pixel electrode 708. The source electrode
706c of the switch transistor 706 is connected to the video data
line 704. A common electrode line 710 is used as the common
electrode of the pixel electrode 708. A metal electrode 770 is
built around the pixel region. The metal electrode 770 is
controlled by the common electrode line 710. When operating the
liquid crystal display, a voltage is applied to the common
electrode and the metal electrode at the same time.
[0141] Cooperating with the alignment direction of the liquid
crystal molecules parallel to the arranged direction of the metal
electrode 770, the metal electrode 770 adjacent to the video data
line 704 is sawtoothed so that metal electrode 770 has a major axis
in the direction indicated by an arrow 766. In other words, the
liquid crystal molecules can be aligned in the direction indicated
by an arrow 766. On the other hand, the pixel electrode 708 in a
pixel region is partially separated into two parts so as to expose
the positions corresponding to the common electrode line 710. The
main purpose is to align the liquid crystal molecules in the
direction indicated by the arrow 766.
[0142] FIG. 19A is an enlarged schematic diagram of the region 768
in FIG. 15B. A trench passing through the pixel electrode 708 is
formed in the position corresponding to the common electrode line
710 to separate the pixel electrode into two parts. According to
the preferred embodiment, the trench is a rectangular that has a
major axis, which cause a major crosswise electrical field, in the
direction indicated by the arrow 766. Therefore, the liquid crystal
molecules 718 located over the pixel electrode 708 are aligned in a
direction, indicated by the arrow 766, parallel to the common
electrode line 710 to reduce the effect of the crosswise electrical
field. FIG. 19B illustrates a schematic diagram of the liquid
crystal molecules when a voltage is applied to the common
electrode.
[0143] On the other hand, the metal electrode 770 adjacent to the
video data line 704 is sawtoothed, whose diagram is similar to FIG.
18A. The metal electrode 770 has a plurality of extending parts
outside the pixel electrode 708. These extending parts cause a
major crosswise electrical field in the direction indicated by the
arrow 766. Therefore, the liquid crystal molecules 718 are aligned
in the direction indicated by the arrow 766.
[0144] FIG. 15C illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the third embodiment of the present
invention. The silicon island 706a of the switch transistor 706 is
connected to the scan line 702. When the switch transistor 706 is
selected, the scan signal in the scan line 702 turns on the switch
transistor 706. The video signal in the video data line 704 is
transferred to the pixel electrode 708 through the switch
transistor 706. The drain electrode 706b of the switch transistor
706 is connected to the pixel electrode 708. The source electrode
706c of the switch transistor 706 is connected to the video data
line 704. A common electrode line 710 is used as the common
electrode of the pixel electrode 708. A metal electrode 772 is
built around the pixel region. The metal electrode 772 is
controlled by the common electrode line 710. When operating the
liquid crystal display, a voltage is applied to the common
electrode and the metal electrode at the same time.
[0145] Cooperating with the alignment direction of the liquid
crystal molecules parallel to the arranged direction of the metal
electrode 772, a plurality of additional holes 758 passing through
the pixel electrode 708 is formed in the positions corresponding to
the common electrode line 710. On the other hand, a plurality of
additional holes 782 passing through the pixel electrode 708 is
formed in the positions corresponding to the metal electrode 772
adjacent to the scan lines 702. The holes 758 are ellipses,
rectangles or any other shape with a major axis. It is noted that
the direction of the major axis is parallel to the alignment
direction of the liquid crystal molecules as indicated by the arrow
754. On the other hand, the metal electrode 772 adjacent to video
data line 704 is out of the pixel electrode 708. The alignment
direction of the liquid crystal molecules according to the
preferred embodiment is parallel to the direction indicated by the
arrow 754.
[0146] FIG. 20A is an enlarged schematic diagram of the region 784
in FIG. 15C. The metal electrode 772 adjacent to the video data
line is out of the pixel electrode 708. According to the preferred
embodiment, the metal electrode 772 out of the pixel electrode 708
has a major axis, which cause a major crosswise electrical field,
in the direction indicated by the arrow 754. Therefore, the liquid
crystal molecules 718 located over the pixel electrode 708 are
aligned in the direction, as indicated by the arrow 754, parallel
to the metal electrode 772 to reduce the effect of the crosswise
electrical field. FIG. 20B illustrates a schematic diagram of the
liquid crystal molecules when a voltage is applied to the common
electrode.
[0147] On the other hand, a plurality of holes 758 passing through
the pixel electrode 708 is formed on the positions corresponding to
the metal electrode 772 adjacent to the scan lines 702, whose
diagram is similar to FIG. 17A. According to the preferred
embodiment, the holes 758 are rectangular in shape. However, any
other shape with a major axis also can be used in the preferred
embodiment. The liquid crystal molecules 718 located over the pixel
electrode 708 are aligned in the direction parallel to the major
axis of the holes 758, as indicated by the arrow 754.
[0148] FIG. 15D illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the fourth embodiment of the present
invention. The silicon island 706a of the switch transistor 706 is
connected to the scan line 702. When the switch transistor 706 is
selected, the scan signal in the scan line 702 turns on the switch
transistor 706. The video signal in the video data line 704 is
transferred to the pixel electrode 708 through the switch
transistor 706. The drain electrode 706b of the switch transistor
706 is connected to the pixel electrode 708. The source electrode
706c of the switch transistor 706 is connected to the video data
line 704. A common electrode line 710 is used as the common
electrode of the pixel electrode 708. A metal electrode 774 is
built around the pixel region. The metal electrode 774 is
controlled by the common electrode line 710. When operating the
liquid crystal display, a voltage is applied to the common
electrode and the metal electrode at the same time.
[0149] Cooperating with the alignment direction of the liquid
crystal molecules parallel to the arranged direction of the metal
electrode 774, a plurality of additional holes 786 passing through
the pixel electrode 708 is formed in the positions corresponding to
the metal electrode 774 adjacent to the video data lines 704. The
holes 786 are ellipses, rectangles or any other shape with a major
axis. It is noted that the direction of the major axis is parallel
to the alignment direction of the liquid crystal molecules as
indicated by the arrow 766. On the other hand, the metal electrode
774 adjacent to scan lines 702 is out of the pixel electrode 708. A
trench passing through the pixel electrode 708 is formed in the
position corresponding to the common electrode line 710.
[0150] The metal electrode 774 adjacent to the scan lines 702 is
out of the pixel electrode 708. According to the preferred
embodiment, the metal electrode 774 out of the pixel electrode 708
has a major axis, which causes a major crosswise electrical field
in the direction indicated by the arrow 766. Therefore, the liquid
crystal molecules located over the pixel electrode 708 are aligned
in the direction, indicated by arrow 766, parallel to the metal
electrode 774 to reduce the effect of the crosswise electrical
field, whose diagram is similar to FIG. 20A.
[0151] On the other hand, a trench passing through the pixel
electrode 708 is formed in the position corresponding to the common
electrode line 710 to separate the pixel electrode into two parts.
According to the preferred embodiment, the trench is a rectangle
with a major axis, which causes a major crosswise electrical field,
in the direction indicated by the arrow 766. Therefore, the liquid
crystal molecules located over the pixel electrode 708 are aligned
in the direction indicated by arrow 766.
[0152] Additionally, a plurality of holes 786 passing through the
pixel electrode 708 is formed in positions corresponding to the
metal electrode 774 adjacent to the video data lines 704, whose
diagram is similar to FIG. 17A. According to the preferred
embodiment, the holes 786 are rectangular in shape. However, any
other shape with a major axis also can be used in the preferred
embodiment. The liquid crystal molecules located over the pixel
electrode 708 are aligned in the direction parallel to the major
axis of the holes 786, as indicated by the arrow 766.
[0153] FIG. 15E illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the fifth embodiment of the present
invention. The silicon island 706a of the switch transistor 706 is
connected to the scan line 702. When the switch transistor 706 is
selected, the scan signal in the scan line 702 turns on the switch
transistor 706. The video signal in the video data line 704 is
transferred to the pixel electrode 708 through the switch
transistor 706. The drain electrode 706b of the switch transistor
706 is connected to the pixel electrode 708. The source electrode
706c of the switch transistor 706 is connected to the video data
line 704. A common electrode line 710 is used as the common
electrode of the pixel electrode 708. A metal electrode 790 is
built around the pixel region. The metal electrode 790 is
controlled by the common electrode line 710. When operating the
liquid crystal display, a voltage is applied to the common
electrode and the metal electrode at the same time.
[0154] Cooperating with the alignment direction of the liquid
crystal molecules parallel to the arranged direction of the metal
electrode 790, a plurality of additional holes 758 passing through
the pixel electrode 708 is formed in positions corresponding to the
common electrode line 710. The hole 758 is an ellipse, a rectangle
or any other shape with a major axis. It is noted that the
direction of the major axis is parallel to the alignment direction
of the liquid crystal molecules, as indicated by the arrow 754. On
the other hand, the metal electrode 790 adjacent to the scan line
702 is sawtoothed so that this metal electrode 790 has a major axis
in the direction indicated by an arrow 754. In other words, the
liquid crystal molecules located over the metal electrode 790
adjacent to the scan lines 702 can be aligned in the direction
indicated by an arrow 754. The main difference between the first
embodiment and the fifth embodiment is that additional holes 791
passing through the pixel electrode 708 are formed in positions
corresponding to the metal electrode 790 adjacent to the scan lines
702. The hole 791 is an ellipse, a rectangle or any other shape
with a major axis. It is noted that the direction of the major axis
is parallel to the alignment direction of the liquid crystal
molecules as indicated by the arrow 754.
[0155] A plurality of holes 758 passing through the pixel electrode
708 is formed on the positions corresponding to the common
electrode line 710. According to the preferred embodiment, hole 758
is rectangular in shape. The liquid crystal molecules located over
the pixel electrode are aligned in the direction parallel to the
major axis of the hole 758, as indicated by the arrow 754 in FIG.
17A. Each hole 758 has a major axis, which causes a major crosswise
electrical field, in the direction indicated by the arrow 754.
Therefore, the liquid crystal molecules are aligned in the
direction parallel to the major axis of the hole 758 to reduce the
effect of the crosswise electrical field.
[0156] The metal electrode 790 adjacent to the scan lines 702 is
sawtoothed, whose diagram is similar to FIG. 18A. The metal
electrode 790 has a plurality of extending parts 792 outside the
pixel electrode 708. On the other hand, additional holes 791
passing through the pixel electrode 708 are formed in the positions
corresponding to the metal electrode 790 and adjacent to the scan
lines 702. The hole 791 is an ellipse, a rectangle or any other
shape with a major axis. The main purpose of forming the additional
holes 791 is to reduce the effect of the crosswise electrical field
generated by the scan lines 702.
[0157] FIG. 15F illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the sixth embodiment of the present
invention. The silicon island 706a of the switch transistor 706 is
connected to the scan line 702. When the switch transistor 706 is
selected, the scan signal in the scan line 702 turns on the switch
transistor 706. The video signal in the video data line 704 is
transferred to the pixel electrode 708 through the switch
transistor 706. The drain electrode 706b of the switch transistor
706 is connected to the pixel electrode 708. The source electrode
706c of the switch transistor 706 is connected to the video data
line 704. A common electrode line 710 is used as the common
electrode of the pixel electrode 708. A metal electrode 792 is
built around the pixel region. The metal electrode 792 is
controlled by the common electrode line 710. When operating the
liquid crystal display, a voltage is applied to the common
electrode and the metal electrode at the same time.
[0158] Cooperating with the alignment direction of the liquid
crystal molecules parallel to the arranged direction of the metal
electrode 792, the metal electrode 792 adjacent to the video data
line 704 is sawtoothed so that this metal electrode 792 has a major
axis in the direction indicated by an arrow 766. In other words,
the liquid crystal molecules can be aligned in the direction
indicated by an arrow 766. On the other hand, the pixel electrode
708 in a pixel region is partially separated into two parts so that
the positions corresponding to the common electrode line 710 are
exposed. The main purpose is to align the liquid crystal molecules
in the direction indicated by the arrow 766. The main difference
between the second embodiment and the sixth embodiment is that
additional holes 793 passing through the pixel electrode 708 are
formed in the positions corresponding to the metal electrode 792
and adjacent to the video data lines 704. The hole 793 is an
ellipse, a rectangle or any other shape with a major axis. It is
noted that the direction of the major axis is parallel to the
alignment direction of the liquid crystal molecules as indicated by
the arrow 766.
[0159] A trench passing through the pixel electrode 708 is formed
in the position corresponding to the common electrode line 710 to
separate the pixel electrode into two parts, whose diagram is
similar to FIG. 19A. According to the preferred embodiment, trench
is a rectangle with a major axis, which causes a major crosswise
electrical field in the direction indicated by the arrow 766.
Therefore, the liquid crystal molecules located over the pixel
electrode 708 are aligned in the direction indicated by the arrow
766.
[0160] On the other hand, metal electrode 792 adjacent to the video
data line 704 is sawtoothed, whose diagram is similar to FIG. 18A.
The metal electrode 792 has a plurality of extending parts 794
outside the pixel electrode 708. These extending parts cause a
major crosswise electrical field in the direction indicated by the
arrow 766. Therefore, the liquid crystal molecules are aligned in
the direction indicated by the arrow 766. Additionally, additional
holes 793 passing through the pixel electrode 708 are formed in
positions corresponding to the metal electrode 792 and adjacent to
the video data lines 704. The hole 793 is a rectangle according to
the preferred embodiment. However, an ellipse or any other shape
with a major axis also can be used in the present invention. The
main purpose of forming the additional holes 793 is to reduce the
effect of the crosswise electrical field generated by the video
data lines 704. The liquid crystal molecules located over the pixel
electrode 708 are aligned in the direction parallel to the major
axis of the holes 793, as indicated by the arrow 766.
[0161] FIG. 15G illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the seventh embodiment of the present
invention. The silicon island 706a of the switch transistor 706 is
connected to the scan line 702. When the switch transistor 706 is
selected, the scan signal in the scan line 702 turns on the switch
transistor 706. The video signal in the video data line 704 is
transferred to the pixel electrode 708 through the switch
transistor 706. The drain electrode 706b of the switch transistor
706 is connected to the pixel electrode 708. The source electrode
706c of the switch transistor 706 is connected to the video data
line 704. A common electrode line 710 is used as the common
electrode of the pixel electrode 708. A metal electrode 795 is
built around the pixel region. The metal electrode 795 is
controlled by the common electrode line 710. When operating the
liquid crystal display, a voltage is applied to the common
electrode and the metal electrode at the same time.
[0162] Cooperating with the alignment direction of the liquid
crystal molecules parallel to the arranged direction of the metal
electrode 795, a plurality of holes 758 passing through the pixel
electrode 708 is formed in the positions corresponding to the
common electrode line 710. Additionally, holes 758 passing through
the pixel electrode 708 are also formed in the positions
corresponding to the metal electrode 795 adjacent to the scan lines
702. The main difference between the third embodiment and the
seventh embodiment is that additional holes 796 are respectively
formed between any two adjacent holes 758. The hole 758 or 796 is
an ellipse, a rectangle or any other shape with a major axis. It is
noted that the direction of the major axis is parallel to the
alignment direction of the liquid crystal molecules as indicated by
the arrow 754.
[0163] The metal electrode 795 adjacent to the video data line 704
is out of the pixel electrode 708, whose diagram is similar to FIG.
20A. According to the preferred embodiment, the metal electrode 795
out of the pixel electrode 708 has a major axis, which causes a
major crosswise electrical field, in the direction indicated by the
arrow 754. Therefore, the liquid crystal molecules located over the
pixel electrode 708 is aligned in the direction, indicated by arrow
754, parallel to the metal electrode 795 to reduce the effect of
the crosswise electrical field.
[0164] Additionally, a plurality of holes 758 passing through the
pixel electrode 708 is formed in the positions corresponding to the
metal electrode 795 adjacent to the scan line 702, whose diagram is
similar to FIG. 17A. Additional holes 796 are respectively formed
between any two adjacent holes 758. The main purpose of forming the
additional holes 796 is to reduce the effect of the crosswise
electrical field generated by the scan lines 702. The liquid
crystal molecules located over the pixel electrode 708 are aligned
in the direction parallel to the major axis of the holes 796, as
indicated by the arrow 754.
[0165] FIG. 15H illustrates a schematic diagram of a pixel
structure appearance change of FIG. 4A cooperating with this
alignment method according to the eighth embodiment of the present
invention. The silicon island 706a of the switch transistor 706 is
connected to the scan line 702. When the switch transistor 706 is
selected, the scan signal in the scan line 702 turns on the switch
transistor 706. The video signal in the video data line 704 is
transferred to the pixel electrode 708 through the switch
transistor 706. The drain electrode 706b of the switch transistor
706 is connected to the pixel electrode 708. The source electrode
706c of the switch transistor 706 is connected to the video data
line 704. A common electrode line 710 is used as the common
electrode of the pixel electrode 708. A metal electrode 797 is
built around the pixel region. The metal electrode 797 is
controlled by the common electrode line 710. When operating the
liquid crystal display, a voltage is applied to the common
electrode and the metal electrode at the same time.
[0166] Cooperating with the alignment direction of the liquid
crystal molecules parallel to the arranged direction of the metal
electrode 797, a plurality of holes 786 passing through the pixel
electrode 708 is formed in the positions corresponding to the metal
electrode 797 adjacent to the video data lines 704. Additionally,
additional holes 798 are respectively formed between any two
adjacent holes 786. The hole 786 or 798 is an ellipse, a rectangle
or any other shape with a major axis. It is noted that the
direction of the major axis is parallel to the alignment direction
of the liquid crystal molecules as indicated by the arrow 766. On
the other hand, the metal electrodes 797 adjacent to the scan lines
702 are out of the pixel electrode 708. Moreover, the pixel
electrode 708 in a pixel region is partially separated into two
parts so that the positions corresponding to the common electrode
line 710 are exposed.
[0167] The metal electrode 797 adjacent to the scan lines 702 is
out of the pixel electrode 708. According to the preferred
embodiment, the metal electrode 797 out of the pixel electrode 708
has a major axis, which causes a major crosswise electrical field,
in the direction indicated by the arrow 766. Therefore, the liquid
crystal molecules located over the pixel electrode 708 are aligned
in the direction, indicated by the arrow 766, that is parallel to
the metal electrode 797 to reduce the effect of the crosswise
electrical field, whose diagram is similar to FIG. 20A.
[0168] On the other hand, a trench passing through the pixel
electrode 708 is formed in the position corresponding to the common
electrode line 710 to separate the pixel electrode into two parts,
as illustrated in FIG. 19A. According to the preferred embodiment,
the trench is a rectangle that has a major axis, which causes a
major crosswise electrical field, in the direction indicated by the
arrow 766. Therefore, the liquid crystal molecules located over the
pixel electrode 708 are aligned in the direction indicated by the
arrow 766.
[0169] Additionally, holes 786 passing through the pixel electrode
708 are formed in the positions corresponding to the metal
electrode 797 and adjacent to the video data lines 704 whose
diagram is similar to FIG. 17A. Additional holes 798 are
respectively formed between any two adjacent holes 786. The main
purpose of forming the additional holes 798 is to reduce the effect
of the crosswise electrical field generated by the scan lines video
data lines 704. The liquid crystal molecules located over the pixel
electrode 708 is aligned in the direction parallel to the major
axis of the holes 798, as indicated by the arrow 766.
[0170] Accordingly, the method of changing the pixel structure
appearance of FIG. 4A described in the foregoing eight embodiments
cooperating with this alignment method to reduce the effect of the
crosswise electrical field also can be used in other types of pixel
structure. For example, the following embodiment describes the
method is used to change the pixel structure appearance of FIG.
5A.
[0171] FIG. 16A illustrates a schematic diagram of a pixel
structure appearance change of FIG. 5A cooperating with this
alignment method according to the ninth embodiment of the present
invention. The silicon island 806a of the switch transistor 806 is
connected to the scan line 802. The drain electrode 806b of the
switch transistor 806 is connected to the pixel electrode 808. The
source electrode 806c of the switch transistor 806 is connected to
the video data line 804. A common electrode line 810 is used as the
common electrode of the pixel electrode 808. A "H" type pixel
structure composed of the metal electrode 856 and the common
electrode 810 is formed in the pixel region. The metal electrode
856 is controlled by the common electrode line 810. When operating
the liquid crystal display, a voltage is applied to the common
electrode and the metal electrode at the same time.
[0172] Cooperating with the alignment direction of the liquid
crystal molecules parallel to the arranged direction of the metal
electrode 856, a plurality of additional holes 858 passing through
the pixel electrode 808 is formed in the positions corresponding to
the common electrode line 810. The hole 858 is an ellipse, a
rectangle or any other shape with a major axis. It is noted that
the direction of the major axis is parallel to the alignment
direction of the liquid crystal molecules as indicated by the arrow
854. On the other hand, the metal electrode 856 adjacent to the
video data line 804 is out of the pixel electrode 808. Therefore,
the liquid crystal molecules located over the metal electrode 856
adjacent to the video data lines 804 can be aligned in the
direction indicated by an arrow 854.
[0173] The metal electrode 856 adjacent to the video data line 804
is out of the pixel electrode 808, whose diagram is similar to FIG.
20A. According to the preferred embodiment, the metal electrode 856
out of the pixel electrode 808 has a major axis, which causes a
major crosswise electrical field in the direction indicated by the
arrow 854. Therefore, the liquid crystal molecules located over the
pixel electrode 808 is aligned in the direction, indicated by the
arrow 854, that is parallel to the metal electrode 856 to reduce
the effect of the crosswise electrical field.
[0174] On the other hand, a plurality of holes 858 passing through
the pixel electrode 808 is formed in the positions corresponding to
the common electrode line 810, whose diagram is similar to FIG.
17A. According to the preferred embodiment, the hole 858 is a
rectangle. However, an ellipse or any other shape with a major axis
also can be used in the preferred embodiment. The liquid crystal
molecules located over the pixel electrode are aligned in the
direction parallel to the major axis of the hole 858, as indicated
by the arrow 854.
[0175] FIG. 16B illustrates a schematic diagram of a pixel
structure appearance change of FIG. 5A cooperating with this
alignment method according to the tenth embodiment of the present
invention. The silicon island 806a of the switch transistor 806 is
connected to the scan line 802. The drain electrode 806b of the
switch transistor 806 is connected to the pixel electrode 808. The
source electrode 806c of the switch transistor 806 is connected to
the video data line 804. A common electrode line 810 is used as the
common electrode of the pixel electrode 808. A "H" type pixel
structure composed of the metal electrode 870 and the common
electrode 810 is formed in the pixel region. The metal electrode
870 is controlled by the common electrode line 810. When operating
the liquid crystal display, a voltage is applied to the common
electrode and the metal electrode at the same time.
[0176] Cooperating with the alignment direction of the liquid
crystal molecules parallel to the arranged direction of the metal
electrode 870, the metal electrode 870 adjacent to the video data
line 804 is sawtoothed so that this metal electrode 870 has a major
axis in the direction indicated by an arrow 866. In other words,
the liquid crystal molecules can be aligned in the direction
indicated by an arrow 866. On the other hand, the pixel electrode
808 in a pixel region is partially separated into two parts so that
the positions corresponding to the common electrode line 810 are
exposed. The main purpose is to align the liquid crystal molecules
in the direction indicated by the arrow 866.
[0177] A trench passing through the pixel electrode 808 is formed
in the position corresponding to the common electrode line 810 to
separate the pixel electrode into two parts, whose diagram is
similar to FIG. 19A. According to the preferred embodiment, the
trench is a rectangle with a major axis, which causes a major
crosswise electrical field in the direction indicated by the arrow
866. Therefore, the liquid crystal molecules located over the pixel
electrode 808 are aligned in the direction, indicated by the arrow
866, that is parallel to the common electrode line 810 to reduce
the effect of the crosswise electrical field.
[0178] On the other hand, the metal electrode 870 adjacent to the
video data line 804 is sawtoothed, whose diagram is similar to FIG.
18A. The metal electrode 870 has a plurality of extending parts out
of the pixel electrode 808. These extending parts cause a major
crosswise electrical field in the direction indicated by the arrow
866. Therefore, the liquid crystal molecules are aligned in the
direction indicated by the arrow 866.
[0179] FIG. 16C illustrates a schematic diagram of a pixel
structure appearance change of FIG. 5A cooperating with this
alignment method according to the eleventh embodiment of the
present invention. The silicon island 806a of the switch transistor
806 is connected to the scan line 802. The drain electrode 806b of
the switch transistor 806 is connected to the pixel electrode 808.
The source electrode 806c of the switch transistor 806 is connected
to the video data line 804. A common electrode line 810 is used as
the common electrode of the pixel electrode 808. A "H" type pixel
structure composed of the metal electrode 878 and the common
electrode 810 is formed in the pixel region. The metal electrode
878 is controlled by the common electrode line 810. When operating
the liquid crystal display, a voltage is applied to the common
electrode and the metal electrode at the same time.
[0180] Cooperating with the alignment direction of the liquid
crystal molecules parallel to the arranged direction of the metal
electrode 878, the metal electrode 878 adjacent to video data line
804 is sawtoothed so that this metal electrode 878 has a major axis
in the direction indicated by an arrow 880. In other words, the
liquid crystal molecules can be aligned in the direction indicated
by an arrow 880. On the other hand, the pixel electrode 808 in a
pixel region is partially separated into two parts so that the
positions corresponding to the common electrode line 810 are
exposed. The main purpose is to align the liquid crystal molecules
in the direction indicated by the arrow 880.
[0181] A trench passing through the pixel electrode 808 is formed
in the position corresponding to the common electrode line 810 to
separate the pixel electrode into two parts, whose diagram is
similar to FIG. 19A. According to the preferred embodiment, the
liquid crystal molecules located over the pixel electrode 808 are
aligned in the direction, indicated by the arrow 866, that is
parallel to the common electrode line 810 to reduce the effect of
the crosswise electrical field.
[0182] The metal electrode 878 adjacent to the video data line 804
is sawtoothed, whose diagram is similar to FIG. 18A. The metal
electrode 878 has a plurality of extending parts 874 out of the
pixel electrode 808. Holes 876 are respectively formed in any two
adjacent extending parts 874 to reduce the effect of the crosswise
electrical field generated by the video data line 804.
[0183] It is noted that although all of the embodiments are related
to the structure of the common electrode line with the connected
metal electrode line and the video data line located on different
layers, these embodiments also can be used in the structure where
the common electrode line with the connected metal electrode line
and the video data line are located on the same layer.
[0184] Accordingly, for reducing the crosswise electrical field
effect during liquid crystal molecules transformation, the
alignment direction is parallel to the metal electrode in the
present invention. On the other hand, additional holes passing
through the pixel electrode are formed in the positions
corresponding to the metal electrode or common electrode so as to
reduce the crosswise electrical field. The hole 858 is an ellipse,
a rectangle or any other shape with a major axis.
[0185] As is understood by a person skilled in the art, the
foregoing descriptions of the preferred embodiment of the present
invention are an illustration of the present invention rather than
a limitation thereof. Various modifications and similar
arrangements are included within the spirit and scope of the
appended claims. The scope of the claims should be accorded to the
broadest interpretation so as to encompass all such modifications
and similar structures. While a preferred embodiment of the
invention has been illustrated and described, it will be
appreciated that various changes can be made therein without
departing from the spirit and scope of the invention.
* * * * *