U.S. patent application number 11/551548 was filed with the patent office on 2007-03-01 for liquid crystal display device.
This patent application is currently assigned to SANYO ELECTRIC CO., LTD.. Invention is credited to Mitsugu Kobayashi, Masayuki Koga, Yasushi Miyajima, Ryuji Nishikawa.
Application Number | 20070046876 11/551548 |
Document ID | / |
Family ID | 27338787 |
Filed Date | 2007-03-01 |
United States Patent
Application |
20070046876 |
Kind Code |
A1 |
Nishikawa; Ryuji ; et
al. |
March 1, 2007 |
Liquid Crystal Display Device
Abstract
When the orientation of liquid crystal molecules in a pixel are
divided by an orientation divider, a boundary of the orientation is
produced at any part of the pixel. A drain signal line (54) is
formed to overlap with the boundary so that a light-shielding
region in the pixel is decreased and an aperture ratio can be
improved. Leakage of light caused when the orientation is disturbed
can be shielded by the drain signal line (54), and contrast can be
enhanced. The orientation divider can be an orientation control
window (36), an orientation control slope (90) or the like.
Inventors: |
Nishikawa; Ryuji; (Gifu-shi,
Gifu-ken, JP) ; Miyajima; Yasushi; (Gifu-shi,
Gifu-ken, JP) ; Koga; Masayuki; (Anpachi-gun,
Gifu-ken, JP) ; Kobayashi; Mitsugu; (Nagoya-shi,
Aichi-ken, JP) |
Correspondence
Address: |
HOGAN & HARTSON L.L.P.
1999 AVENUE OF THE STARS
SUITE 1400
LOS ANGELES
CA
90067
US
|
Assignee: |
SANYO ELECTRIC CO., LTD.
5-5, Keihan-Hondori 2-chome, Moriguchi-shi
Osaka
JP
|
Family ID: |
27338787 |
Appl. No.: |
11/551548 |
Filed: |
October 20, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11250088 |
Oct 12, 2005 |
7139056 |
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11551548 |
Oct 20, 2006 |
|
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09446378 |
Feb 7, 2000 |
6440932 |
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11250088 |
Oct 12, 2005 |
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Current U.S.
Class: |
349/125 ;
349/130 |
Current CPC
Class: |
G02F 1/133765 20210101;
G02F 1/136209 20130101; G02F 1/1362 20130101; G02F 1/134336
20130101; G02F 2203/64 20130101; G02F 1/134309 20130101; G02F
1/133707 20130101; G02F 1/136286 20130101; G02F 1/1393
20130101 |
Class at
Publication: |
349/125 ;
349/130 |
International
Class: |
G02F 1/1337 20060101
G02F001/1337 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 27, 1998 |
JP |
10-337840 |
Nov 30, 1998 |
JP |
10-340500 |
Oct 27, 1999 |
JP |
11-305804 |
Claims
1-37. (canceled)
38. A vertical orientation liquid crystal display device, in which
vertical orientation liquid crystal is sealed between a first
substrate and a second substrate which are opposed to each other; a
plurality of pixel electrodes each formed for each pixel and
switching elements connected to the pixel electrodes, respectively,
are formed on a side of the first substrate; an opposing electrode
is formed on a side of the second substrate so as to oppose the
plurality of pixel electrodes; a rubbingless orientation film is
formed over each of the first substrate and the second substrate,
at an interface between a liquid crystal layer and each of the
first substrate and the second substrate; each pixel includes an
orientation control window for dividing an orientation direction of
the liquid crystal within a single pixel region into a plurality of
directions, the orientation control window dividing the orientation
direction of the liquid crystal by an electric field which is
inclined with respect to a normal line of at least one of the pixel
electrode and the opposing electrode; a region in which the
orientation control window is formed and a region in which a
light-shielding line made of a light-shielding material which is
used within a forming region of the pixel electrode is formed
overlap with each other; and in the overlapping portion in which
the light-shielding line and the orientation control window overlap
with each other, a width of the light-shielding line is smaller
than a width of the orientation control window.
39. A vertical orientation liquid crystal display device according
to claim 38, wherein a gate signal line and a data signal line are
further formed on the side of the first substrate; the
light-shielding line is the data signal line; a region in which the
orientation control window is formed and a region in which the data
signal line is formed overlap with each other; and in a region in
which the data signal line and the orientation control window
overlap with each other, a width of the data signal line is smaller
than a width of the orientation control window.
40. A liquid crystal display device according to claim 39, wherein
the liquid crystal has a negative anisotropy of dielectric
constant, and the orientation film is formed so as to cover each of
the pixel electrodes and the opposing electrode.
41. A liquid crystal display device according to claim 39, wherein
the orientation control window is formed by forming an opening in
the opposing electrode in a region where the opposing electrode is
opposed to the pixel electrode.
42. A liquid crystal display device according to claim 39, wherein
the orientation control window is formed by forming an opening in
the pixel electrode in a region where the opposing electrode is
opposed to the pixel electrode.
43. A liquid crystal display device according to claim 39, wherein
the pixel electrodes are disposed in a matrix, and the pixel
electrodes disposed in mutually adjacent rows are disposed to be
displaced by a width corresponding to 1.5 pixels or less with
respect to each other in the row direction.
44. A liquid crystal display-device according to claim 39) wherein
the pixel electrodes are disposed in a matrix, and the pixel
electrodes disposed in mutually adjacent rows are disposed to be
displaced by a width corresponding to 1.2 pixels or less with
respect to each other in the row direction.
45. A liquid crystal display device according to claim 39, wherein
in an overlapping portion of the region in which the data signal
line is formed and the region in which the orientation control
window is formed, the region in which the data signal line is
formed overlaps at least a center portion of the region in which
the orientation control window is formed.
46. A liquid crystal display device according to claim 39, wherein
in an overlapping portion of the region in which the data signal
line is formed and the region in which the orientation control
window is formed, the region in which the data signal line is
formed extends no further than the region in which the orientation
control window is formed.
47. A vertical orientation liquid crystal display device according
to claim 38, wherein a storage capacitor line is further formed on
the side of the first substrate, the storage capacitor line forming
a storage capacitor which is connected in parallel to a liquid
crystal capacitor formed in a region where the pixel electrode is
opposed to the opposing electrode with a liquid crystal layer being
disposed therebetween; the light-shielding line is the storage
capacitor line; a region in which the orientation control window is
formed and a region in which the storage capacitor line is formed
overlap with each other; and in a region in which the storage
capacitor line and the orientation control window overlap with each
other, a width of the storage capacitor line is smaller than a
width of the orientation control window.
48. A liquid crystal display device according to claim 47, wherein
the liquid crystal has a negative anisotropy of dielectric
constant, and the orientation film is formed so as to cover each of
the pixel electrodes and the opposing electrode.
49. A liquid crystal display device according to claim 47, wherein
the orientation control window is formed by forming an opening in
the opposing electrode in a region where the opposing electrode is
opposed to the pixel electrode.
50. A liquid crystal display device according to claim 47, wherein
the orientation control window is formed by forming an opening in
the pixel electrode in a region where the opposing electrode is
opposed to the pixel electrode.
51. A liquid crystal display device according to claim 47, wherein
the pixel electrodes are disposed in a matrix, and the pixel
electrodes disposed in mutually adjacent rows are disposed to be
displaced by a width corresponding to 1.5 pixels or less with
respect to each other in the row direction.
52. A liquid crystal display device according to claim 47, wherein
the pixel electrodes are disposed in a matrix, and the pixel
electrodes disposed in mutually adjacent rows are disposed to be
displaced by a width corresponding to 1.2 pixels or less with
respect to each other in the row direction.
53. A liquid crystal display device according to claim 47, wherein
in an overlapping portion of the region in which the storage
capacitor line is formed and the region in which the orientation
control window is formed, the region in which the storage capacitor
line is formed overlaps at least a center portion of the region in
which the orientation control window is formed.
54. A liquid crystal display device according to claim 47, wherein
in an overlapping portion of the region in which the storage
capacitor line is formed and the region in which the orientation
control window is formed, the region in which the storage capacitor
line is formed extends no further than the region in which the
orientation control window is formed.
55. A vertical orientation liquid crystal display device according
to claim 38, wherein a storage capacitor line connected to a
storage capacitor, a gate signal line, and a data signal line are
further formed on a side of the first substrate; a region in which
the orientation control window is formed and each of regions in
which the gate signal line, the data signal line, and the storage
capacitor line are formed, respectively, overlap with each other;
and in each of the overlapping portions in which the orientation
control window overlaps with the gate signal line, the data signal
line, and the storage capacitor line, respectively, a width of the
gate signal line, a width of the data signal line, and a width of
the storage capacitor line are smaller than a width of the
orientation control window at corresponding overlapping
portions.
56. A liquid crystal display device according to claim 55, wherein
the liquid crystal has a negative anisotropy of dielectric
constant, and the orientation film is formed so as to cover each of
the pixel electrodes and the opposing electrode.
57. A liquid crystal display device according to claim 55, wherein
the orientation control window is formed by forming an opening in
the opposing electrode in a region where the opposing electrode
opposes the pixel electrodes.
58. A liquid crystal display device according to claim 55, wherein
the orientation control window is formed by forming an opening in
the pixel electrode in a region where the opposing electrode
opposes the pixel electrodes.
59. A liquid crystal display device according to claim 55, wherein
the pixel electrodes are disposed in a matrix, and the pixel
electrodes disposed in mutually adjacent rows are disposed to be
displaced by a width corresponding to 1.5 pixels or less with
respect to each other in the row direction.
60. A liquid crystal display device according to claim 55, wherein
the pixel electrodes are disposed in a matrix, and the pixel
electrodes disposed in mutually adjacent rows are disposed to be
displaced by a width corresponding to 1.2 pixels or less with
respect to each other in the row direction.
61. A liquid crystal display device according to claim 55, wherein
in a region where each of the region in which the gate signal line
is formed, the region in which the data signal line is formed, and
the region in which the storage capacitor line is formed overlaps
the region in which the orientation control window is formed, each
of the region in which the gate signal line is formed, the region
in which the data signal line is formed, and the region in which
the storage capacitor line is formed overlaps at least a center
portion of the region in which the orientation control window is
formed.
62. A liquid crystal display device according to claim 55, wherein
in a region where each of the region in which the gate signal line
is formed, the region in which the data signal line is formed, and
the region in which the storage capacitor line is formed overlaps
the region in which the orientation control window is formed, each
of the region in which the gate signal line is formed, the region
in which the data signal line is formed, and the region in which
the storage capacitor line is formed extends no further than the
region in which the orientation control window is formed.
63. A liquid crystal display device according to claim 55, wherein
a storage capacitor electrode for forming the storage capacitor
with the storage capacitor line is formed on the side of the first
substrate; and the region in which the orientation control window
is formed further overlaps a region in which the storage capacitor
electrode is formed.
64. A liquid crystal display device according to claim 55, wherein
in an overlapping portion of the region in which the storage
capacitor electrode is formed and the region in which the
orientation control window is formed, the region in which the
storage capacitor electrode is formed overlaps at least a center
portion of the region in which the orientation control window is
formed.
65. A liquid crystal display device according to claim 55, wherein
in an overlapping portion of the region in which the storage
capacitor electrode is formed and the region in which the
orientation control window is formed, the region in which the
storage capacitor electrode is formed extends no further than the
region in which the orientation control window is formed.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a liquid crystal display
device provided with an orientation divider for dividing the
orientation direction of a liquid crystal.
[0003] 2. Description of the Related Art
[0004] FIG. 1 shows a plan diagram of a conventional liquid crystal
display device. FIG. 2 shows a sectional diagram taken along line
B-B of FIG. 1 and FIG. 3 shows a sectional diagram taken along line
D-D of FIG. 1.
[0005] In can be seen in FIG. 2 and FIG. 3 that a plurality of
drain signal lines 50 and a plurality of gate signal lines 51
intersect each other on a first substrate 10 which is made of an
insulating substrate such as glass or quartz, and in the vicinity
of each intersection of lines 50 and 51 there are provided a
thin-film transistor (hereinafter called TFT). Pixel electrodes 19
made of a transparent conductive film such as ITO (Indium Tin
Oxide) are connected to sources 13s of the TFT. The drain signal
lines 50 are intersected with the gate signal lines 51 and are
overlapped with the pixel electrodes 19.
[0006] A storage capacitor electrode line 52 is disposed near the
TFT in parallel to the gate signal line 51. The storage capacitor
electrode line 52 is made of chromium and makes a storage capacitor
for storing electric charges by forming a capacitor with an
electrode 53 connected to the source 13s of the TFT through an
interlayer insulating film 15. This storage capacitor is disposed
to be electrically parallel to a liquid crystal 21 which is also a
capacitor in order to suppress the electric charges stored in the
liquid crystal 21 by a leak current of the TFT and to keep the
stored electric charges.
[0007] An opposing electrode 34 on the side of a second substrate
30 is a common electrode which is formed to overlap the plurality
of pixel electrodes 19. An orientation control window 36, which is
formed by removing the ITO as an opposing electrode material so
that one end of letter Y indicated by a dotted line in FIG. 1 is
made to have the same forked shape as the other end, is disposed at
positions corresponding to the respective pixel electrodes 19.
[0008] As can be seen in FIG. 2 and FIG. 3, the interlayer
insulating film 15, the drain signal line 50 disposed for each
pixel, and a planarization insulating film 17 are sequentially
formed on the insulating substrate 10, while the pixel electrode 19
made of ITO is disposed for each pixel on the planarization
insulating film 17. The pixel electrode 19 is disposed to overlap
with the drain signal line 50. A vertical orientation film 20 for
orienting the liquid crystal 21 is further disposed on the pixel
electrode 19. A polarizer 41 is disposed on the opposite side of
the insulating substrate 10 facing the liquid crystal 21.
[0009] A color filter 31 comprising red (R), green (G), and blue
(B) for showing such colors and a black matrix for shielding light
is disposed on the opposite side of the second substrate 30 facing
the liquid crystal 21. A protective film 33 made of a resin is
formed on the color filter 31 to protect its surface and the
opposing electrode 34, which is made of a transparent conductive
film of ITO or the like, is formed on the protective film 33. As
described above, the orientation control windows 36 for controlling
the orientation of the liquid crystal 21 are formed on the opposing
electrode 34. A vertical orientation film 35 which vertically
orients the liquid crystal 21 is disposed on the orientation
control windows 36. A polarizer 42 is disposed on the opposite side
of the second substrate 30 facing the liquid crystal 21. The
polarizer 42 and the polarizer 41 are disposed so that their
polarization axes intersect at right angles.
[0010] The insulating substrate 10 and the second substrate 20 are
joined at their peripheries using a sealing adhesive agent (not
shown), and a nematic liquid crystal 21 which has a negative
anisotropy of dielectric constant is filled in a gap formed to
complete a liquid crystal display panel. The orientation control
windows 36 formed in the opposing electrode 34 are disposed at two
positions for each pixel because the orientation control window 36
shows the forked shape in letter Y in FIG. 3.
[0011] The liquid crystal 21 has a negative anisotropy of
dielectric constant. Here, the behavior of liquid crystal molecules
will be described. In a state that a voltage is not applied to the
liquid crystal 21, the liquid crystal molecules between the
substrates 10 and 30 are vertically oriented with respect to the
substrates 10, 30. Therefore, incident light which is linearly
polarized by the polarizer 41 on the side of the TFT substrate 10
is not double refracted in the liquid crystal 21 but shielded by
the polarizer 42 on the side of the second substrate 30 to show
black. This is called a normally black method.
[0012] As shown in FIG. 2, when a voltage is applied to the liquid
crystal 21, the major axes of the liquid crystal molecules are
oriented in the vertical direction with respect to the electric
flux line, but controlled to incline in a plurality of orientation
directions with respect to one pixel electrode 19 by the electric
flux line produced in a slanting direction at the end of the pixel
electrode 19 and the end of the orientation control window 36. The
incident light which is linearly polarized by the polarizer 41
becomes an elliptical polarized light upon receiving the double
refractory by the liquid crystal 21 which has a negative anisotropy
of dielectric constant so to pass through the polarizer 42 and have
a transmissivity corresponding to a voltage of the drain signal
line.
[0013] Thus, when the orientation direction of the liquid crystal
is divided into multiple numbers in the pixel, the respective
regions have a different viewing angle characteristic so that the
viewing angle of the pixels as a whole can be enlarged.
[0014] In this specification, a means for dividing the orientation
direction of the liquid crystal (orientation divider) is indicated
as an orientation divider. In addition to the orientation divider
described above, other arts, such as an orientation control slope
or division of a rubbing direction into multiple numbers, have been
proposed.
[0015] In the state that a voltage is applied to the liquid crystal
21, however, the liquid crystal molecules as a continuous body are
continuously inclined to allow the passage of light according to an
electric field produced at the edge of the orientation control
window 36 outside the region of the orientation control window 36
formed on the opposing electrode 34, but, in the region of the
orientation control window 36, the liquid crystal molecules remain
in the vertically oriented state with respect to the substrates 10,
30, so that the light does not pass through the orientation control
window and a light-shielding state is kept.
[0016] Even when an orientation divider other than the orientation
control window is used, a boundary in the orientation direction of
the liquid crystal may exist at any position. Such a boundary in
the orientation direction is consistently in a state of shielding
the light in a normally black mode type and in a state of allowing
the light in a normally white mode type because the orientation
does not change even if a voltage is applied to between the
electrodes.
[0017] As shown in FIG. 1 through FIG. 3, the drain signal lines 50
overlap with the pixel electrodes 19 and made of a light-shielding
material such as metal. However, when the drain signal line 50 is
disposed between the pixel electrodes 19, the liquid crystal is
oriented by a signal voltage applied to the drain signal line 50,
which results in degraded display quality.
[0018] Therefore, there are disadvantages in the conventional art
that an effective display region in the pixel electrode forming
region must decreased because of the orientation control windows 36
and the drain signal lines 50, an aperture ratio was heavily
degraded, and a bright display could not be obtained.
SUMMARY OF THE INVENTION
[0019] The present invention was conceived in response to the
disadvantages described above. It is an object of the present
invention to provide a liquid crystal display device which has a
wide viewing angle and can provide bright display with an improved
aperture ratio.
[0020] The invention was created to remedy the disadvantages as
described above. The invention is a liquid crystal display device
which controls the orientation of a liquid crystal by means of a
plurality of pixel electrodes formed for each pixel and an opposing
electrode formed to cover the plurality of pixel electrodes, which
has an orientation divider for dividing an orientation direction of
the liquid crystal into a plurality of orientation directions
within a single pixel and a light-shielding film formed to overlap
with boundaries of the orientation directions of the liquid crystal
formed by the orientation divider.
[0021] According to another aspect of the invention, the liquid
crystal of the liquid crystal display device is sealed between a
first substrate and a second substrate which are disposed so as to
oppose each other; the first substrate has gate signal lines, drain
signal lines, and switching elements connected to the gate signal
lines and the drain signal lines; the pixel electrodes are
connected to the switching elements; and the opposing electrode is
formed on the second substrate to oppose the liquid crystal.
[0022] Thus, the present invention has an orientation divider for
dividing the orientation direction of the liquid crystal into a
plurality of directions in a single pixel, and a light-shielding
film is disposed to overlap with the boundaries of the orientation
directions produced by the orientation divider. The boundaries of
the orientation directions of the liquid crystal exhibit a
light-shielding function under a normal situation, so that an area
of the light-shielding region for each pixel does not change, even
when the light-shielding film overlaps the boundaries. As compared
with a liquid crystal display device which has the light-shielding
film formed not to overlap with the boundaries of the orientation,
the area of the light-shielding region can be decreased, and an
aperture ratio of the liquid crystal display device can be
improved.
[0023] In a plan view, the light-shielding film overlaps the
boundaries of the orientation directions of the liquid crystal, so
that light can be prevented from leaking out of the liquid crystal
display device by virtue of the presence of the light-shielding
film. Even if the orientation of the liquid crystal is disturbed in
the vicinity of the boundary in the orientation direction of the
liquid crystal to weaken a light-shielding property at the
boundary, higher contrast images can still be displayed.
[0024] According to another aspect of the invention, the
orientation divider divides the orientation directions of the
liquid crystal by generating an electric field which is inclined
with respect to the normal line of the pixel electrode and/or the
opposing electrode.
[0025] In the liquid crystal display device which divides the
orientation directions of the liquid crystal by forming the
electric field which is inclined with respect to the normal line of
the pixel electrode and/or the opposing electrode, orientation
direction restraint ability of the orientation divider is weak
compared with when the orientation is controlled by rubbing or the
like, so that the orientation of the liquid crystal tends to be
disturbed, and light may leak in the vicinity of the boundary in
the orientation direction. The present invention, however, can
securely shield the light in the vicinity of the boundary in the
orientation direction because the light-shielding film is disposed
to overlap with the boundary.
[0026] According to another aspect of the present invention, the
light-shielding film is a conductive substance made of metal, e.g.,
the drain signal line. When a storage capacitor electrode for
forming the storage capacitor on each pixel electrically connected
in parallel with the liquid crystal is provided, the storage
capacitor electrode can also be used as the light-shielding
film.
[0027] According to still another aspect of the present invention,
the liquid crystal has a negative anisotropy of dielectric
constant, and a vertical orientation film is formed to cover the
pixel electrodes.
[0028] Thus, by using as the light-shielding film the storage
capacitor electrode when the conductive substance is made of metal,
e.g., the drain signal line or the storage capacitor electrode, is
provided, an aperture ratio is not substantially lowered, even when
the drain signal line or the storage capacitor electrode is
disposed in the pixel region.
[0029] Where the drain signal line is disposed between the pixels,
the electric field produced by the drain signal line leaks to a
layer of the liquid crystal and the orientation direction of the
liquid crystal may be disturbed because the drain signal line is
not shielded by the pixel electrode. However, where the drain
signal line is arranged to overlap with the boundary in the
orientation direction, the aperture ratio is not lowered even if
the drain signal line is present in the pixel region. Therefore,
the drain signal line can be disposed on a layer below the pixel
electrode. Then, the electric field of the drain signal line can be
shielded by the pixel electrode, and the orientation of the liquid
crystal can be prevented from being disturbed.
[0030] According to still another aspect of the present invention,
the orientation divider is an orientation control window, which is
formed at a position to overlap with the pixel electrode of the
opposing electrode, or an orientation control slope.
[0031] According to a still further aspect of the present
invention, the orientation control slope is formed by having a
projection made of an insulating substance formed on the pixel
electrode and/or the opposing electrode.
[0032] The orientation control slope may be formed by having a
projection made of an insulating substance formed between the pixel
electrode and the first substrate and/or between the opposing
electrode and the second substrate.
[0033] According to yet another aspect of the invention, a liquid
crystal display device is characterized in that liquid crystal is
sealed between a first substrate and a second substrate which are
disposed so as to oppose each other; the first substrate has
switching elements connected to gate signal lines and drain signal
lines, pixel electrodes which are connected to the switching
elements and made of a conductive material and a vertical
orientation film for orienting the liquid crystal; the second
substrate has an opposing electrode which has the orientation
control window (formed as an orientation divider) at positions that
overlap with the pixel electrodes to control the orientation of the
liquid crystal and a vertical orientation film for orienting the
liquid crystal; and the drain signal lines are disposed on the
first substrate at positions that overlap with the orientation
control windows.
[0034] According to yet another aspect of the invention, a liquid
crystal display device is characterized in that liquid crystal is
sealed between a first substrate and a second substrate which are
disposed so as to oppose each other; the first substrate has gate
signal lines, drain signal lines, switching elements connected to
the gate signal lines and the drain signal lines, pixel electrodes
connected to the switching elements and made of a conductive
material, storage capacitor signal lines for forming the storage
capacitors with semiconductor layers of the switching elements, and
a vertical orientation film for orienting the liquid crystal; the
second substrate has an opposing electrode which controls the
orientation of the liquid crystal and has the orientation control
windows (formed as an orientation divider) at positions that
overlap with the pixel electrodes and a vertical orientation film
for orienting the liquid crystal; and a part of the gate signal
lines, a part of the storage capacitor signal lines and the drain
signal lines are disposed on the first substrate at positions that
overlap with the orientation control windows.
[0035] According to another aspect of the invention, the
orientation divider such as the orientation control window has a
width different from that of the light-shielding film or the signal
line overlapping the orientation control window or the like.
[0036] Because the width of the orientation control window is thus
different from the width of the signal line overlapping it,
specifically the drain signal line, and when a part of the gate
signal line and the storage capacitor signal line also overlaps the
orientation control window, the width of a part of the gate and the
storage capacitor signal line, the orientation can be prevented
from being disturbed and the light from leaking, even if the
orientation control window and the drain signal line or the like
are not correctly aligned.
[0037] According to a still further aspect of the present
invention, the pixel electrodes are disposed in a matrix; the drain
signal lines are connected to a plurality of pixel electrodes in
the same column via the switching elements; the pixel electrodes
which are connected to the same drain signal line and positioned in
the mutually adjacent rows are disposed to displace by a distance
corresponding to about 1.5 pixels or smaller in a direction that
the gate signal lines are extended.
[0038] For example, the pixel electrodes positioned on the adjacent
rows are displaced by about 1.2 pixels from each other, and the
pixel electrodes connected to the same drain signal line have a
corresponding color filter with the same color.
[0039] Where the pixel electrodes (the electrodes designed to
indicate the same color) positioned on the adjacent rows are in a
so-called delta arrangement in which they are displaced by about
1.5 pixels in the direction that the gate signal lines are
extended, the drain signal lines are disposed in a meandering or
zigzag pattern so that the drain signal lines overlap the
boundaries in the orientation directions of the liquid crystal of
the respective displaced pixels. Thus, an aperture ratio is
prevented from lowering, light can be prevented from leaking from
the respective pixels, and the display quality of the device can be
improved. Also, where the displacement of the pixels between the
neighboring rows is smaller than 1.5 pixels (e.g., 1.2 pixels), the
drain signal line extends while bending to pass through the pixel
regions of the same color in the same way as the delta arrangement
but its length is shorter than that in the delta arrangement.
Therefore, the drain signal line can have a lower resistance than
in the delta arrangement.
[0040] In another aspect, the present invention is in the form of a
liquid crystal display device for displaying by controlling the
orientation of a liquid crystal of each pixel by means of a
plurality of pixel electrodes formed for respective pixels and an
opposing electrode disposed to oppose the plurality of pixel
electrodes with the liquid crystal therebetween, which comprises an
orientation divider for forming a boundary in the orientation
direction of the liquid crystal in a single pixel; wherein a
light-shielding film is disposed so that at least a part of it is
arranged through the pixel electrode region so to overlap with the
boundary in the orientation direction of the liquid crystal.
[0041] According to another aspect of the present invention, the
light-shielding film is a drain signal line for supplying the
switching element disposed for each pixel with a display signal in
order to control the orientation of the liquid crystal for each
pixel.
[0042] Thus, even when the drain signal line passes through the
pixel electrode regions, the aperture ratio is not lowered because
the drain signal line inherently passes along the boundary in the
orientation direction of the liquid crystal.
[0043] According to still another aspect of the present invention,
in the aforesaid liquid crystal display device, a plurality of
pixels are disposed as a matrix and corresponded with any of red,
green, and blue colors to be displayed; the pixels having the same
color are displaced from each other in a direction of the row
between the adjacent rows; and the drain signal line is extended in
a direction of the column in a zigzag form so to overlap with at
least a part of the boundary in the orientation direction of the
liquid crystal formed in the pixel electrode region of the pixels
with the same color displaced in the respective rows and supplies
the pixels of the same color with a display signal through the
switching element.
[0044] And, according to a still further aspect of the invention,
in the aforesaid liquid crystal display device, the drain signal
line is bent to extend in a direction of the column so to cross the
one and same pixel electrode region a plurality of times.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1 is a plan diagram of a conventional liquid crystal
display device;
[0046] FIG. 2 is a sectional diagram of the liquid crystal display
device taken along line B-B of FIG. 1;
[0047] FIG. 3 is a sectional diagram of the liquid crystal display
device taken along line D-D of FIG. 1;
[0048] FIG. 4 is a plan diagram of a liquid crystal display device
according to a first embodiment of the invention;
[0049] FIG. 5 is a sectional diagram of the liquid crystal display
device taken along line A-A of FIG. 4;
[0050] FIG. 6 is a sectional diagram of the liquid crystal display
device taken along line B-B of FIG. 4;
[0051] FIG. 7 is a plan diagram of a liquid crystal display device
according to a second embodiment of the invention;
[0052] FIG. 8 is a sectional diagram of the liquid crystal display
device taken along line C-C of FIG. 7;
[0053] FIG. 9 is a plan diagram of a liquid crystal display device
according to a third embodiment of the invention;
[0054] FIG. 10 is a sectional diagram of the liquid crystal display
device taken along line D-D of FIG. 9;
[0055] FIG. 11 is a plan diagram of a liquid crystal display device
according to a fourth embodiment of the invention;
[0056] FIG. 12 is a plan diagram of a layout of pixels and drain
signal lines of a liquid crystal display device according to a
fifth embodiment of the invention;
[0057] FIG. 13 is a plan diagram of the liquid crystal display
device according to the fifth embodiment of the invention;
[0058] FIG. 14 is a plan diagram of a liquid crystal display device
according to a sixth embodiment of the invention;
[0059] FIG. 15 is a sectional diagram of the liquid crystal display
device taken along line E-E of FIG. 14;
[0060] FIG. 16 is a sectional diagram of a liquid crystal display
device according to another embodiment of the invention; and
[0061] FIG. 17 is a sectional diagram of a liquid crystal display
device according to another embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0062] A liquid crystal display device of the present invention
will be described.
[0063] FIG. 4 is a plan diagram of a liquid crystal display device
of the invention, FIG. 5 is a sectional diagram of the liquid
crystal display device taken along line A-A of FIG. 4, and FIG. 6
is a sectional diagram of the liquid crystal display device taken
along line B-B of FIG. 4.
[0064] As shown in FIG. 4, a plurality of gate signal lines 55 each
integrally having a gate electrode 11 are disposed horizontally,
and a plurality of drain signal lines 54 are disposed vertically. A
thin-film transistor (TFT), which is a switching element, is
disposed in the vicinity of each intersection of the gate signal
line 55 and the drain signal line 54, and a pixel electrode 19 made
of a transparent conducting material such as ITO is connected to
the TFT.
[0065] FIG. 4 shows that orientation control windows 36, which are
formed by removing the ITO, which is a material for the opposing
electrode in the same way as shown in FIG. 1, are disposed on the
same side of an opposing electrode 34 facing a second substrate 30.
The orientation control window 36 has a shape that the bottom end
of letter Y indicated by a dotted line has the same forked shape as
the top end, namely two letters Y are mutually connected with one
of them turned upside down. In other words, the orientation control
window 36 has a shape that either end of its center region, which
is rectangular and extending in a longitudinal direction of each
pixel, is forked into two to extend toward two corners of the
pixel.
[0066] The structure described above is substantially the same as
that of a conventional liquid crystal described elsewhere in this
specification. A feature of this embodiment is that the drain
signal line 54 is formed along the orientation control window 36
disposed on the second substrate 30. In FIG. 4, the drain signal
line 54 in the vicinity of the TFT enters the pixel region from its
upper left, bends to extend in the lower right-hand direction to
follow a branch section 36a at the upper left part of the
orientation control window 36, and at a section 36b of the
orientation control window 36 extending vertically in FIG. 4,
extends vertically in the same way. The drain signal line 54
further bends to extend in the lower left direction to follow a
branch section 36c extending in a lower left direction of the
orientation control window 36, leaves the pixel from its lower
left, and extends to a pixel in the next row. Thus, the drain
signal line 54 is disposed to overlap with the left-side branch
sections and the vertical section of the orientation control window
36.
[0067] The liquid crystal immediately below the orientation control
window 36 keeps a vertically oriented state because an electric
field is not produced and the orientation is not controlled.
Therefore, it becomes a light-shielding region which always does
not allow the passage of light. In this embodiment, the drain
signal line 54 which is a metal line and has a light-shielding
function is disposed there, so that the two light-shielding regions
are overlapped. As a result, the light-shielding region occupying
the pixel region becomes small, and an aperture ratio is improved.
The region immediately below the orientation control window 36 is a
boundary of the liquid crystal in its orientation direction in the
pixel, so that the orientation direction tends to be disturbed.
When the orientation direction is disturbed, light may leak
erroneously. But, since the drain signal line 54 having the
light-shielding function is disposed in this embodiment, the
present invention can prevent the light from leaking and can
further enhance contrast.
[0068] It is here desirable that a width 54w of the drain signal
line 54 be different from a width 36w of the orientation control
window 36. If they have the same size, the drain signal line 54 and
the orientation control window 36 are displaced from each other
when both the substrates 10, 30 are bonded but not correctly
aligned. Therefore, the region for shielding the light is increased
for the segment of the displacement, the aperture ratio is lowered,
and the respective pixels are made to have variable aperture
ratios. By having either of the widths made lager than the other in
advance, the light-shielding region does not come to have a width
larger than the predetermined width when the displacement is within
a range of the difference in width even if the bonding is made with
some displacement. Thus, variations among the respective pixels can
be prevented. Either of the widths 54w and 36w may be made larger,
but if the width 36w of the orientation control window 36 is
excessively narrow, the orientation direction cannot be divided
securely, so that it is desirable to make the width 36w of the
orientation control window 36 larger. However, when the width 54w
of the drain signal line 54 is made large, its electric resistance
can be lowered, so that when the width 36w of the orientation
control window 36 is sufficiently secured, the width 54w of the
drain signal line 54 can be made much larger. In this embodiment,
the orientation control window 36 is determined to have a width of
6 to 8 .mu.m for example, then the drain signal line 54 is
determined to have a width of 4 .mu.m.
[0069] Next, a sectional structure of the liquid crystal display
device taken along line A-A of FIG. 4 will be described. As shown
in FIG. 5, a gate electrode 11 made of refractory (high melting
point) metal such as chromium (Cr) or molybdenum (Mo), a gate
insulating film 12, and an active layer 13 made of a polysilicon
film are formed in this order on an insulating substrate 10 made of
quartz glass, non-alkali glass or the like.
[0070] In an active layer 13, a channel 13c is disposed above the
gate electrode 11, and a source 13s and a drain 13d, which are
formed by ion doping with a stopper insulating film 14 on the
channel 13c used as a mask, are disposed on either side of the
channel 13c.
[0071] An interlayer insulating film 15 comprising SiO.sub.2 film,
SiN film, and then SiO.sub.2 film laminated in this order is formed
to fully cover the gate insulating film 12, the active layer 13,
and the stopper insulating film 14, and metal such as Al is filled
into a contact hole formed to correspond to the drain 13d to form a
drain electrode 16. Further, a planarization insulating film 17
which is made of, for example, an organic resin is formed to fully
cover the interlayer insulating film 15 to provide a flat surface.
A contact hole is formed in the planarization insulating film 17 at
a position corresponding to the source 13s, and a pixel electrode
19 which is made of a transparent conductive material such as ITO
and in contact with the source 13s through the contact hole is
formed on the planarization insulating film 17. A vertical
orientation film 20, which is made of an organic resin such as a
polyimide and vertically orients a liquid crystal 21 having a
negative anisotropy of dielectric constant, is formed on the pixel
electrode 19. Rubbing treatment of the vertical orientation film 20
is not required. A polarizer 41 is disposed on the outside of the
insulating substrate 10, namely on the side not facing to the
liquid crystal.
[0072] A color filter 31 comprising respective colors R, G, and B,
and a black matrix 32 having a light-shielding function and a
protective film 33 made of an acrylic resin or the like for
protecting the color filter 31 are disposed inside of the second
substrate 30, specifically on the side facing the liquid crystal 21
of the second substrate 30. The opposing electrode 34 which is
opposed to the respective pixel electrodes 19 and partly provided
with the orientation control window 36 is disposed on the
protective film 33. A vertical orientation film 35 made of a
polyimide is formed on the entire surface of the opposing electrode
34.
[0073] A polarizer 42 is disposed on the opposite side of the
second substrate 30 facing the liquid crystal 21, being the side
where a viewer 101 will view the display.
[0074] In addition, the liquid crystal 21 used is one having a
negative anisotropy of dielectric constant. Specifically, the
liquid crystal shall have the liquid crystal molecules vertically
oriented with respect to the substrate when a voltage is not
applied and oriented substantially in parallel when a voltage is
applied.
[0075] The insulating substrate 10 having the TFT produced as
described above and the opposing substrate 30 provided with the
orientation film 35 and the opposing electrode 34 facing the
substrate 10 are mutually adhered by applying a sealing adhesive
agent (not shown) to their peripheries. Liquid crystal 21 is filled
into the space formed between them to complete the liquid crystal
display panel.
[0076] By disposing the drain signal line 54 at the position
corresponding to the orientation control window 36 as described
above, the boundary in the orientation direction can be overlapped
with the region keeping to shield light, which is called wiring. In
other words, a portion of light shielding effected by a
conventional drain signal line can be removed, and the aperture
ratio can be improved. Because the width of the drain signal line
54 differs from that of the orientation control window 36, the
light-shielding section does not have a width exceeding the
predetermined level, and the aperture ratios of respective pixels
do not vary.
Second Embodiment
[0077] FIG. 7 is a plan diagram of a liquid crystal display device
according to a second embodiment of the present invention, and FIG.
8 is a sectional diagram of the liquid crystal display device taken
along line C-C of FIG. 7. This embodiment corresponds to that of
the first embodiment in that the drain signal lines 54 are disposed
at the positions corresponding to the orientation control windows
36 formed on the opposing electrode 34, but differs in that
portions 36d, 36e of the orientation control window 36, which are
not covered with the drain signal line 54, overlap regions 37, 38
branched from a storage capacitor electrode 53 and the gate signal
line 55 to fully cover the orientation control window 36.
[0078] The structure of the liquid crystal display device of this
embodiment will be described with reference to FIG. 7 and FIG. 8.
The gate signal lines 55 which have gate electrodes 11 partly made
of refractory (high melting point) metal such as Cr or Mo, and
storage capacitor electrode lines 52 are simultaneously formed on
the insulating substrate 10 made of quartz glass, non-alkali glass
or the like as shown in the drawings. At this point, the gate
signal lines 55 and the storage capacitor electrode lines 52
correspond to the orientation control windows 36 by their portions
37, 38 to cover the sections which are not covered with the drain
signal line 54. Specifically, as shown in FIG. 7, the orientation
control window 36e on the side close to the gate signal line 55 has
a part of the gate signal line 55 indirectly overlapping the
overlap electrode 38 having a shape corresponding to the
orientation control window 36, and an orientation control window
36d on the side close to the other storage capacitor electrode line
52 has a part of the storage capacitor electrode 53 indirectly
overlapping the overlap electrode 37 having a shape corresponding
to the orientation control window 36.
[0079] Thus, the aperture ratio can be improved by having the drain
signal lines 54 overlapped with the orientation control windows 36
which are always in the light-shielding state in the same way as in
the first embodiment.
[0080] The division of the orientation division in this embodiment
is controlled according to the direction of the electric field
only, so that restraint ability of the orientation direction of the
liquid crystal is low as compared with, for example, the rubbing
treatment. Therefore, the orientation may be disturbed by an
external factor such as an external magnetic field. On the other
hand, in this embodiment, even a region which does not overlap with
the drain signal line 54 of the orientation control window 36 is
arranged to overlap with the overlap electrodes 37, 38, so that the
shielding of light by the orientation control window 36 of the
pixel can be made perfect. Therefore, even if light leaks in case
of the disturbance of the orientation of the liquid crystal of the
orientation control window 36, it can be shielded completely, and
complete black display can be made when black color is displayed.
Thus, high-contrast display can be made.
[0081] Since the storage capacitor electrode 53 made of the same
polysilicon film as the active layer 13 is disposed to overlap with
the overlap electrode 37 branched from the storage capacitor
electrode line 52, the storage capacitor is increased. Further,
because the storage capacitor electrode 53 overlaps the orientation
control window 36, the aperture ratio is not lowered by the
increase in area of the storage capacitor.
[0082] It is desirable that either the drain signal line 54 or the
orientation control window 36 have a width larger than the other in
the same way as in the first embodiment. Similarly, the overlap
electrodes 37, 38 and the orientation control windows 36d, 36e
preferably have a different width so that either pair of them has a
larger width than the other pair.
[0083] As shown in FIG. 7, a single pixel is divided into four
regions 19U, 19D, 19R and 19L by the orientation control window 36
and the drain signal line 54. Among them, it is preferable that the
pixel region 19L on the left side of the drain signal line 54 has
the same area as the pixel region 19R on its right side.
[0084] At an end of the pixel electrode 19, the liquid crystal
molecules are stabilized by having an angle of inclination from the
direction of the normal line depending on the intensity of the
electric field controlled and the direction of inclination
controlled by the electric field produced obliquely to expand
toward the opposing electrode 34.
[0085] The directions of inclination of the liquid crystal
molecules at the ends of the pixel electrode 19 are different among
the four regions divided by the orientation control window 36.
[0086] The liquid crystal molecules having their orientation
controlled in different directions in the respective regions of the
pixel electrode 19 are influenced toward the center of the pixel
electrode because of the continuity of the liquid crystal.
Specifically, the orientation direction of the liquid crystal
molecules in the vicinity of the center is controlled so as not to
be substantially oblique with respect to the direction of the
normal line of the panel due to the presence of the orientation
control window 36 disposed on the opposing electrode 34 and less
influenced by the orientation control by the orientation control
window 36 as the liquid crystal molecules are away from the
vicinity of the center. The liquid crystal molecules are oriented
to be parallel to the substrate because of the potential difference
between the pixel electrode 19 and the opposing electrode 34.
[0087] Therefore, the orientation direction of the liquid crystal
in the pixel region 19L is oblique from the side of the insulating
substrate 10 in the direction of an arrow 19La in FIG. 7, and the
orientation direction of the liquid crystal in the pixel region 19R
is oblique in the direction of an arrow 19Rb in FIG. 7.
Accordingly, when the liquid crystal display panel is seen from the
right or left direction, a viewing angle from either direction
becomes large, so that a wide viewing angle can be realized. When
the right and left pixel regions 19R, 19L have a different area, a
viewing angle from, for example, the right side, becomes large, but
a viewing angle from the left side becomes narrow. Therefore, the
right and left pixel regions 19R, 19L are made to have the same
area.
[0088] The liquid crystal molecules of the upper and lower pixel
regions 19D, 19U are obliquely oriented from the side of the
insulating substrate 10 toward the directions of arrows 19Dc, 19Ud.
In order to have the same viewing angle from the right and left
directions and also to have the same viewing angle when viewed from
the upper and lower directions, it is desirable to form the pixel
regions 19D, 19U with the same area.
Third Embodiment
[0089] FIG. 9 is a plan diagram of the third embodiment, and FIG.
10 is a sectional diagram taken along line D-D of FIG. 9. The
subject matter of this embodiment is the same as the second
embodiment. In the second embodiment, the overlap electrodes 37, 38
were formed by partly branching the gate signal line 55 and the
storage capacitor electrode 53. This embodiment differs from that
of the second embodiment in that a light-shielding film 56 is made
of a light-shielding material such as metal which is different from
the gate signal line 55 and the storage capacitor electrode 53.
Thus, the same effect as in the second embodiment can be obtained
by using a different body to form the light-shielding film 56.
[0090] In this embodiment, the light-shielding film 56 is described
as being disposed on a layer different from the drain signal line,
but the present invention is not limited to such a configuration.
The light-shielding layer may be formed on the same layer as the
drain signal line at the same time when the drain signal line is
formed and may be formed with the drain signal line in one body, or
the light-shielding film may be formed on the side of the second
substrate 30, for example, on the same layer as the black matrix
32.
Fourth Embodiment
[0091] FIG. 11 shows a plan diagram of the fourth embodiment. This
embodiment adopts a delta arrangement in that the pixel electrodes
19 are connected to the same drain signal line 60, and the
respective pixel electrodes 19 in the adjacent row are displaced by
1.5 pixels in the extending direction of a gate signal line 51. The
delta arrangement is extensively used in an audiovisual field for
DSC (digital still camera) and the like used to show video.
[0092] In the delta arrangement, when attention is directed to one
specific row, respective colors of a pixel (R) for red color, a
pixel (G) for green color and a pixel (B) for blue color are
repeatedly arranged in this order, and in the next row, the same
respective colors as those in the first row are repeatedly arranged
in the same way except that the arranged positions of the
respective colors are displaced to the right by 1.5 pixels with
respect to the first row.
[0093] As shown in FIG. 11, a TFT is formed in the vicinity of the
intersection between the gate signal line 55 which is linearly
arranged from side to side and the drain signal line 60 which is
connected to the same color pixels. This TFT has the gate electrode
11 which forms a part of the gate signal line 55 and the
semiconductor layer 13 made of polysilicon which comprises the
drain 13d connected to the drain signal line 60 and the source 13s
connected to the pixel electrode 19. The drain signal line 60 is
connected to the same color pixels which are displaced by the
segment of 1.5 pixels in the direction of the column. Accordingly,
the drain signal line 60 arranged so as to overlap the orientation
control window 36 of each pixel is bent from a corner of the pixel
electrode 19 toward the vicinity of the center and, as a whole,
extends in a zigzag form so to cross the respective center regions
of the same color pixels displaced by 1.5 pixels. In the same way
as in the previous embodiments, the orientation control window 36
has a shape that one of two conjoined letters `Y` with portion
extending toward the corners of the pixel electrode and in the
vertical direction (the portion extending along the sides of the
pixels). The drain signal line 60 extended from the upper left of
the pixel extends in a lower right direction along the region 36a
at the upper left of the orientation control window 36, in a
vertical direction along the region 36b and in a lower left
direction along the region 36c and leaves the pixel from the lower
left of the pixel electrode. Subsequently, the drain signal line 60
enters the next pixel which is displaced to the left by 1.5 pixels
from its upper right section, extends in a lower left direction
along the region 36d at the upper right section of the orientation
control window 36, in a vertical direction along the region 36b and
in a lower right direction along the lower right region 36e and
leaves the pixel. The same pattern is repeated so that the drain
signal line 60 is disposed to extend in a zigzag pattern in the
direction of the column.
[0094] At the intersection of the storage capacitor signal line 52
and a drain signal line 50, a short-circuit prevention film 57 is
intervened in a shape corresponding to the intersection between
them to prevent the signal lines 52, 50 from short circuiting. The
short-circuit prevention film 57 can be formed of a semiconductor
film, for example, a polysilicon film or the like which is used as
the active layer of the TFT.
[0095] Thus, the short-circuit prevention film 57 can be formed
without adding a special process by applying the material which is
used for the TFT to the short-circuit prevention film 57. Since the
drain signal line 60 is arranged as described above, the drain
signal line 60 in the delta arrangement can be arranged in the
shortest distance. Therefore, there is also provided an effect that
any increase of wiring resistance caused by a long drain signal
line 60 can be prevented.
[0096] Further, a separate light-shielding film may be formed at
the orientation control window 36 where light is not shielded in
the same way as in the second and third embodiments.
Fifth Embodiment
[0097] As described above, in the fourth embodiment the drain
signal line 60 can be arranged along the shortest length according
to the delta arrangement with the pixels displaced by 1.5 pixels,
but the drain signal line 60 is still very long and has a large
wiring resistance. Especially, a high-resolution liquid crystal
display device requires that the drain signal line 60 be made thin,
so that a video signal is rounded (delayed) due to the wiring
resistance at a part away from the signal input section, and normal
display may not be obtainable.
[0098] Where the drain signal line 60 is extended from a single
pixel 72 to the next pixel 73 in order to connect the respective
pixels arranged in the pattern displaced by 1.5 pixels, its oblique
angle is gentle as compared with its extension to a pixel 74
positioned just below the pixel 72. Specifically, the storage
capacitor electrode 53 which forms the capacitor with the storage
capacitor signal line 52 has a small intersection angle with
respect to the storage capacitor signal line 52, so that the area
of the overlapped section also becomes small. Thus, despite the
ratio of sacrificing the aperture ratio, a large storage capacitor
cannot be obtained, and efficiency is not high. As a result, should
TFT current leak, voltage applied to the liquid crystal may not be
retained.
[0099] The fifth embodiment, then, efficiently forms a large
storage capacitor which is sufficient to retain the orientation of
the liquid crystal for a predetermined period even if TFT had a
leak current. FIG. 12 is a plan diagram showing a positional
relation of pixels, drain signal lines and gate signal lines of the
liquid crystal displace device of this embodiment. FIG. 13 is a
partially expanded plan diagram showing the vicinity of some pixels
of the liquid crystal display device.
[0100] As shown in FIG. 12 and FIG. 13, the pixels 19 of the liquid
crystal display device are arranged in a matrix. In the first row
at the top in the drawings, a pixel (R) showing red color, a pixel
(G) showing green color and a pixel (B) showing blue color are
repeatedly arranged in this order. In the next row below the first
row, the same three color pixels are repeatedly arranged in the
same way, except that the arranged positions of the respective
colors are displaced to the right by 1.2 pixels with respect to the
first row.
[0101] Therefore, the drain signal line 50 which is vertically
extended to connect the pixels to supply the same drain signal can
be made to have a much shorter wiring length than in the fourth
embodiment. Accordingly, the wiring resistance can be lowered, and
a uniform display can be created over the entire surface of the
display area.
[0102] In this embodiment, since the vertically neighboring pixels
19 which are connected to the same drain signal line 60 are
displaced by only 1.2 pixels from each other between adjacent rows,
the drain signal line 60 has a smaller bending angle. Since the
capacitor electrode 53 is formed to oppose a region not overlapped
with the drain signal line 60 of the storage capacitor signal line
52, a parallelogram surrounded by the drain signal line 60 and the
storage capacitor signal line 52 is formed. Therefore, the drain
signal line 60 has a small bending angle, the parallelogram of the
capacitor electrode 53 has a small inclination at its both sides
and comes to have a shape similar to rectangular. As the tops
facing each other with the center therebetween are fixed depending
on the pixel size, the pitch, and the width of the storage
capacitor signal line 52, when the parallelogram of the capacitor
electrode 53 has a large inclination at both sides, the area of the
parallelogram grows small. Therefore, according to this embodiment
capable of decreasing the bending angle of the drain signal line
60, the capacitor electrode 53 can have a large area, and the
storage capacitor signal line 52 and the capacitor electrode 53 can
have a large overlapped area. In this way, the storage capacitor is
increased, and the voltage applied to the liquid crystal can be
retained even if TFT has a leak voltage. The liquid crystal can be
stably driven, and a quality display can be obtained.
[0103] Because the drain signal line 60 has a small bending angle,
the drain signal line 60 has a much shorter wiring length as
compared with the aforesaid embodiments. Therefore, the wiring
resistance can be decreased, and more uniform display can be
obtained on the entire surface of the display area.
[0104] Also, the overlap area of the storage capacitor signal line
52 and the capacitor electrode 53 can be made large, and driving
stability of the liquid crystal can be further improved.
[0105] In the above description of a preferred embodiment, the
pixels of the adjacent rows connected to the same drain signal line
are displaced by 1.2 pixels in the row direction. However, the
invention is not limited to such an arrangement. When the
displacement is smaller than 1.5 pixels forming the delta
arrangement, preferably in a range of one pixel or more and less
than 1.5 pixels, high-resolution display can be obtained depending
on the delta arrangement.
Sixth Embodiment
[0106] In the aforesaid first to fifth embodiments, the orientation
control window 36 was used as the orientation divider. However, the
orientation divider is not limited to the orientation control
window 36. This embodiment has an orientation control slope formed
as the orientation divider. FIG. 14 is a plan diagram of the liquid
crystal display device of this embodiment, and FIG. 15 is a
sectional diagram of FIG. 14.
[0107] In this embodiment, the orientation direction of the liquid
crystal is divided by an orientation control slope 90.
Specifically, the orientation control slope 90 is one example of
the orientation divider. Since the orientation control slope 90 is
an insulating substance, an electric line of force produced between
the pixel electrode 19 and the opposing electrode 34 avoids the
orientation control slope 90 in an oblique direction as indicated
by dotted lines in FIG. 15. Thus, the orientation direction of the
liquid crystal in the pixel is divided in the same way as the
orientation control window 36 of the first to fifth embodiments,
and a viewing angle can be expanded. The orientation control slope
is described in detail in Japanese Patent Application No. Hei
6-104044, and its description is not repeated here.
[0108] A first orientation control slope 90 is formed on the side
of the first substrate 10 to extend from the upper left of a pixel
in a particular row to its lower right so to cross the pixel to
leave the pixel temporarily at the middle right side of the pixel,
to bend so to reenter the same pixel region, to cross it again in
the lower left direction and to leave the pixel. A second
orientation control slope 91 is formed on the side of the second
substrate 30 substantially in parallel to the first orientation
control slope 90. The orientation control slope 90 and the
orientation control slope 91 formed on the side of the second
substrate are alternately formed as shown in the plan diagram of
FIG. 14. The orientation control slopes 90, 91 are insulating and
formed on the vertical orientation films 20, 35 respectively.
[0109] In those orientation control slopes, the major axes of the
liquid crystal molecules just above the orientation control slopes
remain es directed in the vertical direction so to form a region
wherein light is shielded. Then, this embodiment forms drain signal
lines 80 to overlap with the orientation control slopes 90. With
such an arrangement, the light-shielding region can be formed in
the overlapped form in the same way as in the aforesaid
embodiments, so that the aperture ratio can be improved. Further,
the orientation control slope 90 temporarily crosses the pixel and
bends outside of the pixel electrode. Because the drain signal line
is formed along the orientation control slope 90, it also bends
outside of the pixel electrodes. At the bent part of the drain
signal line within the pixel, the electric field tends to
concentrate but since the bent part is outside of the pixel
electrode, the possibility of influencing on the orientation of the
liquid crystal is lowered.
[0110] The orientation control slope 90 may be formed between the
pixel electrode 19 and the first substrate 10 to form a slope on
the surface of the pixel electrode 19, as shown in FIG. 17 for
example. In this case, an oblique electric field is produced
because of the slope of the pixel electrode. Meanwhile, the
orientation control slope 90 may be formed between the pixel
electrode 19 and the vertical orientation film 20. In this case,
the orientation is divided by the sloped vertical orientation film
20. In any event, since the region just above the orientation
control slope 90 keeps to shield light, the aperture ratio can be
improved by disposing the drain signal line 80 there.
[0111] The orientation control slope 90 may have the same
"conjoined Y" shape as in the first to fifth embodiments. However,
the orientation control slope 36 may also be formed in a shape such
that the region extending to the upper right and the region
extending to the lower right are connected, as in this embodiment
for example.
[0112] Naturally, the orientation control window and the
orientation control slope may be combined as the orientation
divider. For example, orientation control windows 93 are formed in
the pixel electrode 19 and the orientation control slopes 91 are
formed on the opposing electrode 34 as shown in the sectional
diagram of FIG. 16. FIG. 16 is a sectional diagram showing a single
pixel in which the pixel electrode 19 is shown in multiple numbers
divided by the orientation control windows 93 but connected into
one at a region not shown.
[0113] In FIG. 16, the region just below the orientation control
slope 91 is a boundary in the orientation direction of the liquid
crystal and forms a light-shielding region. And, the drain signal
line 80 is disposed there to overlap with the light-shielding
region, so that the aperture ratio can be improved. The orientation
control window 93 on the pixel electrode 19 is also a boundary in
the orientation direction to form the light-shielding region. By
disposing the drain signal line 80 there, the distance between the
orientation control window 93 and the drain signal line 80 becomes
so close that the orientation of the liquid crystal is disturbed by
the electric field produced from the drain signal line 80 different
from the aforesaid first to fifth embodiments in which the liquid
crystal and the like are present therebetween. Therefore, the drain
signal line 80 is most preferably disposed on an area which is the
boundary of the orientation and where the pixel electrode 19 is
formed.
[0114] The subject matter of the present invention seen from the
aforesaid respective embodiments is that wiring is disposed to
overlap with the boundary in the orientation direction produced by
the orientation divider. Specifically, the boundary in the
orientation direction is produced whatever orientation divider is
adopted, and the liquid crystal is not oriented in the vicinity of
the boundary. This boundary forms a region always shielding light.
Therefore, the wiring is overlapped as a light-shielding region
with the boundary to decrease the light-shielding area, and the
aperture ratio can be improved.
[0115] It is to be understood that the sixth embodiment can adopt
the delta arrangement of color pixels to perform the fourth and
fifth embodiments in combination.
[0116] While there have been described that what are at present
considered to be preferred embodiments of the invention, it is to
be understood that various modifications may be made thereto, and
it is intended that the appended claims cover all such
modifications as fall within the true spirit and scope of the
invention.
* * * * *