U.S. patent application number 10/096905 was filed with the patent office on 2002-09-19 for active matrix type liquid crystal display device and method of manufacturing the same.
This patent application is currently assigned to NEC CORPORATION. Invention is credited to Matsumoto, Kimikazu.
Application Number | 20020131003 10/096905 |
Document ID | / |
Family ID | 18931246 |
Filed Date | 2002-09-19 |
United States Patent
Application |
20020131003 |
Kind Code |
A1 |
Matsumoto, Kimikazu |
September 19, 2002 |
Active matrix type liquid crystal display device and method of
manufacturing the same
Abstract
In an active matrix type liquid crystal display device in which
a common electrode and a second pixel electrode have portions
opposing each other, and an electric field parallel to substrates
is formed between the two electrodes, Y direction extending
portions of the common electrode are provided above data lines via
a second interlayer insulation film. Slits are opened in the Y
direction extending portions of the common electrode along the data
lines. Portions of a black matrix which are set to a common
electric potential with tie common electrode arc provided on an
opposing substrate at positions opposing the slits.
Inventors: |
Matsumoto, Kimikazu; (Tokyo,
JP) |
Correspondence
Address: |
FOLEY AND LARDNER
SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
NEC CORPORATION
|
Family ID: |
18931246 |
Appl. No.: |
10/096905 |
Filed: |
March 14, 2002 |
Current U.S.
Class: |
349/139 |
Current CPC
Class: |
G02F 1/1345 20130101;
G02F 1/136218 20210101; G02F 1/134363 20130101 |
Class at
Publication: |
349/139 |
International
Class: |
G02F 001/1343 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2001 |
JP |
073880/2001 |
Claims
What is claimed is:
1. An active matrix type liquid crystal display device comprising:
a pair of substrates; a liquid crystal sealed between said pair of
substrates; a plurality of data lines and a plurality of scanning
lines which are arranged so as to intersect each other on one
surface of one of said pair of substrates; a switching element
having an electric current path one end of which is connected to
corresponding one of said data lines, and having a control terminal
which is connected to corresponding one of said scanning lines; a
pixel electrode which is provided above said data lines via an
insulation film, and is connected to the other end of the electric
current path of said switching element; and a common electrode
which opposes to said data lines via said insulation film, has
slits in portions overlapping said data lines, to generate an
electric field between said pixel electrode.
2. The active matrix type liquid crystal display device according
to claim 1, wherein: said common electrode and said pixel electrode
respectively have linear portions which oppose with each other
almost in parallel by a predetermined length; said overlapping
portions are provided along said linear portions; and said slits
have a length which is almost the same as that of said liner
portions.
3. The active matrix type liquid crystal display device according
to claim 1, wherein said slits are formed in almost a center of a
width of said overlapping portions.
4. The active matrix type liquid crystal display device according
to claim 1, wherein said overlapping portions of said common
electrode have a width equal to or wider than that of said data
lines.
5. The active matrix type liquid crystal display device according,
to claim 1, wherein said slits have a width smaller than that of
said data lines.
6. The active matrix type liquid crystal display device according
to claim 1, wherein said common electrode and said pixel electrode
are on a same plane.
7. The active matrix type liquid crystal display device according
to claim 1, wherein said common electrode aid said pixel electrode
are made of a transparent conductive material.
8. The active matrix type liquid crystal display device according
to claim 1, wherein said common electrode and said pixel electrode
are on different planes respectively.
9. The active mats type liquid crystal display device according to
claim 1, wherein an electric field in a direction parallel to said
pair of substrates is formed between said common electrode and said
pixel electrode.
10. An active matrix type liquid crystal display device comprising:
a pair of substrates; a liquid crystal sealed between said pair of
substrates; a plurality of data lines and a plurality of scanning
lines which are arranged so as to intersect each other on one
surface of one of said pair of substrates; a switching element
having an electric current path one end of which is connected to
corresponding one of said data lines, and having a control terminal
which is connected to corresponding one of said scanning lines; a
pixel electrode which is provided above said data lines via an
insulation film, and is connected to the other end of the electric
current path of said switching element; a common electrode which
opposes to said data lines via said insulation film, has slits in
portions overlapping said data lines, to generate an electric field
between said pixel electrode; and a first conductive film which is
provided on the other of said pair of substrates so as to oppose to
said data lines via said slits, and is set to a common electric
potential with said common electrode.
11. The active matrix type liquid crystal display device according
to claim 10, wherein: said common electrode and said pixel
electrode respectively have linear portions which oppose with each
other almost in parallel by a predetermined length; said
overlapping portions are provided along said linear portions; and
said slits have a length which is almost the same as that of said
liner portions.
12. The active matrix type liquid crystal display device according
to claim 10, wherein said slits are formed in almost a center of a
width of said overlapping portions.
13. The active matrix type liquid crystal display device according
to claim 10, wherein said overlapping portions of said common
electrode have a width equal to or wider than that of said data
lines.
14. The active matrix type liquid crystal display device according
to claim 10, wherein said slits have a width smaller than that of
said data lines.
15. The active matrix type liquid crystal display device according
to claim 10, wherein said common electrode and said pixel electrode
are on a same plane.
16. The active matrix type liquid crystal display device according
to claim 10, wherein said common electrode and stud pixel electrode
are made of a transparent conductive material.
17. The active matrix type liquid crystal display device according
to claim 10, wherein said common electrode and said pixel electrode
are on different planes respectively.
18. The active matrix type liquid crystal display device according
to claim 10, further comprising a plug which electrically connects
said first conductive film and said common electrode with each
other.
19. The active matrix type liquid crystal display device according
to claim 10, further comprising: a common wiring which is provided
an a plane different from that of said common electrode, and is
electrically connected to said common electrode; and a plug which
is connected to said common wiring, and electrically connects said
first conductive film and said common electrode with each
other.
20. The active matrix type liquid crystal display device according
to claim 19, wherein a second conductive film is provided between
said first conductive film and said common wiring in order to
enhance connection between said first conductive film and said
common wiring.
21. The active matrix type liquid crystal display device according
to claim 20, wherein said second conductive film is, made of a
material same as that of said common electrode and/or said pixel
electrode.
22. The active matrix type liquid crystal display device according
to claim 10, wherein said first conductive film has a width equal
to or wider than that of said slits.
23. The active matrix type liquid crystal display device according
to claim 10, wherein said first conductive film functions as a
black matrix.
24. The active matrix type liquid crystal display device according
to claim 10, further comprising a black matrix which is arranged on
the other one of said pair of substrates in a predetermined
pattern, and is covered by a flattening film, wherein said first
conductive film is provided on said flattening film.
25. The active matrix type liquid crystal display device according
to claim 24, wherein said first conductive film has a pattern which
is almost the same as that of said black matrix.
26. The active matrix type liquid crystal display device according
to claim 10, wherein an electric field parallel to said pair of
substrates is generated between said common electrode and said
pixel electrode.
27. A method of manufacturing an active matrix type liquid crystal
display device, which is a method of manufacturing a liquid crystal
display device comprising: a pair of substrates; a thin film
transistor which is provided on one of said pair of substrates;
data lines which are connected to a drain of said thin film
transistor; a pixel electrode which is connected to a source of
said thin film transistor; and a common electrode which generates
an electric field between said pixel electrode, said method
comprising forming an insulation film on said data lines; forming a
first metal film on said insulation film; and forming said common
electrode by patterning said first metal film, with forming slits
in portions of said common electrode that overlap said data
lines.
28. The method of manufacturing an active matrix type liquid
crystal display device according to claim 27, further comprising
forming said pixel electrode in a shape having linear portions
having a predetermined length, wherein in said forming said common
electrode, portions which oppose to said linear portions of said
pixel electrode are formed, and said slits are formed to have a
length which is almost the same as that of said linear
portions.
29. The method of manufacturing an active matrix type liquid
crystal display device according to claim 27, wherein in said
forming said common electrode, said slits are formed in almost a
center of a width of said overlapping portions.
30. The method of manufacturing an active matrix type liquid
crystal display device according to claim 27, wherein in said
forming said common electrode said overlapping portions of said
common electrode are formed to have a width equal to or wider than
that of said data lines.
31. The method of manufacturing an active matrix type liquid
crystal display device according to claim 27, wherein in said
forming said common electrode, said slits are formed to have a
width smaller than that of said data lines.
32. The method of manufacturing an active matrix type liquid
crystal display device according to claim 27, wherein said common
electrode and said pixel electrode are formed in a substantially
same step.
33. A method of manufacturing an active matrix type liquid crystal
display device, which is a method of manufacturing a liquid crystal
display device comprising: a pair of substrates, a thin film
transistor which is provided on one of said pair of substrates;
data lines which are connected to a drain of said thin film
transistor; a pixel electrode which is connected to a source of
said thin film transistor, and a common electrode which generates
an electric field between said pixel electrode, said method
comprising: forming an insulation film which covers said data
lines; forming a first metal film on said insulation film; forming,
said common electrode by patterning said first metal film, with
forming slits in portions of said common electrode that overlap
said data lines; and forming a first conductive film on die other
one of said pair of substrates, said first conductive film opposing
to said data lines via said slits.
34. The method of manufacturing an active matrix type liquid
crystal display device according to claim 33, further comprising
forming said pixel electrode in a shape having linear portions
having a predetermined length, wherein in said forming said common
electrode, portions which oppose to said linear portions of said
pixel electrode are formed, and said slits are formed to have a
length which is almost the materials film of said linear
portions.
35. The method of manufacturing an active matrix type liquid
crystal display device according to claim 33, wherein in said
forming said common electrode, said slits are formed in almost a
center of a width of said overlapping portions.
36. The method of manufacturing at active matrix type liquid
crystal display device according to claim 33, wherein in said
forming said common electrode, said overlapping portions of said
common electrode are formed to have a width equal to or provider
than that of said data lines.
37. The method of manufacturing an active matrix type liquid
crystal display device according to claim 33, wherein in said
forming said common electrode, said slits are formed to have a
width smaller than that of said data lines.
38. The method of manufacturing all active matrix type liquid
crystal display device according to claim 33, wherein said common
electrode and said pixel electrode are formed in a substantially
same step.
39. The method of manufacturing an active matrix type liquid
crystal display device according to claim 33, wherein: said common
electrode is connected to a common wiring which is provided on a
plane different from a plane on which said common electrode is
formed; and said method further comprises forming a plug which
electrically connects said common wiring and said first conductive
film with each other.
40. The method of manufacturing an active matrix type liquid
crystal display device according to claim 39, further comprising
forming a second conductive film between said common wiring and
said plug.
41. The method of manufacturing an active matrix type liquid
crystal display device according to claim 40, wherein said second
conductive film is formed together with said common electrode
and/or said pixel electrode in a same step.
42. The method of manufacturing an active matrix type liquid
crystal display device according to claim 33, further comprising:
forming a black matrix having a predetermined pattern on one
surface of the other one of said pair of substrates; and forming a
flattening film on said black matrix, wherein said first conductive
film is formed on said flattening film.
43. The method of manufacturing an active matrix type liquid
crystal display device according to claim 42, wherein in said
forming said first conductive film, said first conductive film is
formed in a pattern same as that of said black matrix.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the invention
[0002] The present invention relates to an active matrix type
liquid crystal display device having a high performance
characteristic and a method of manufacturing the same.
[0003] 2. Description of the Related Art
[0004] There has been developed a so-called In-Plane Switching
(IPS) method in which an electric field parallel to a substrate is
applied to a liquid crystal for all active matrix type liquid
crystal display device. An IPS type liquid crystal display device
has such advantages in that a wide angle of view can be
obtained.
[0005] FIG. 14 shows one example of a plan layout of a unit pixel
area included in an active matrix type liquid crystal display
device according to the IPS method. FIG. 15 shows a cross section
of the liquid crystal display device shown in FIG. 14 as sectioned
along a direction PP. As shown in FIG. 15, the liquid crystal
display device comprises a TFT substrate 100, an opposing substrate
200, and a liquid crystal 300. The liquid crystal display device is
structured by filling a space between the TFT substrate 100 and the
opposing substrate 200 which are set opposite from each other via a
spacer and sealing member (both not illustrated) with the liquid
crystal 300.
[0006] The TFT substrate 100 comprises a first transparent
substrate 101 made of transparent glass or the like. Scanning lines
102 (not illustrated in FIG. 15) and common wirings 103 are formed
on one surface of the first transparent substrate 101. As shown in
FIG. 14, adjacent two scanning lines 102 having a predetermined
space therebetween extend toward an X direction almost in parallel,
and determine the X direction of the unit pixel area. The common
wirings 103 extend almost in parallel with the scanning line 102,
and are so arranged that two of the common wirings 103 sandwich one
scanning line 102. That is, a unit pixel area has two common
wirings 103 crossing thereinside. The two common wirings 103 are
connected to each other by three common electrodes 111 which extend
in the unit pixel area toward a Y direction almost perpendicularly
to the common wirings 103. The common electrodes 111 include a
center portion 111a which extends almost in the center of the pixel
area, and edge portions 111b which extend in the both sides of the
center portion 111a and have a larger width than that of the center
portion 111a.
[0007] In FIG. 15, there is shown an interlayer insulation film
104a which is formed on the first transparent substrate 101, the
scanning lines 102, and the common wirings 103. Data lines 106 and
a pixel electrode 112 are formed on the interlayer insulation film
104a. A semiconductor island 105 shown in FIG. 14 is also formed on
the interlayer insulation film 104a. The semiconductor island 105
constitutes a TFT (Thin Film Transistor). The semiconductor island
105 is provided on the scanning line 102 via the interlayer
insulation film 104a.
[0008] The data lines 106 extend toward the Y direction almost
perpendicularly to the scanning line 102, and determine the Y
direction of the unit pixel area. The pixel electrode 112 is
arranged in the center of the unit pixel area. The pixel electrode
112 includes two opposing portions 112a which extend toward the Y
direction along the common electrodes 111, and two supporting
portions 112b each of which is arranged so as to overlap a common
wiring 103 and to support one edge of the opposing portions 112a.
The opposing portions 112a of the pixel electrode 112 are arranged
between the adjacent common electrodes 111 so as to oppose those
common electrodes 111. Needless to say, as shown in FIG. 15, the
interlayer insulation film 104a exists between the common
electrodes 111 and the pixel electrode 112. Storage capacitors are
formed between the common wirings 103 and the supporting portions
112b of the pixel electrode 112 which oppose each other via the
interlayer insulation film 104a.
[0009] A passivation film 104b is formed on the interlayer
insulation film 104a, the data lines 106, the pixel electrode 112,
and the TFT. An orientation film 116 which has been subjected to a
surface alignment treatment is formed on the passivation film 104b.
A polarizing plate 119 is provided on the other surface of the fist
transparent substrate 101.
[0010] The opposing substrate 200 includes a second transparent
substrate 201. A black matrix 202 having an opening is formed on
one surface of the second transparent substrate 201. The black
matrix 202 is made of a material having a light shielding effect,
and provided so as to oppose the data lines 106 which determine the
unit pixel area. The opening of the black matrix 202 is covered by
a color layer 203. A flattening film 204 and an orientation film
205 are formed on the black matrix 202 and the color layer 203. A
conductive layer 207 and a polarizing plate 208 are formed on the
external surface of the second transparent substrate 201.
[0011] This liquid crystal display device operates as follows. In
order to drive the liquid crystal display device, a driver circuit
(not illustrated) applies a gate pulse to scanning lines 102
sequentially, and applies a data signal whose voltage corresponds
to the display tone to the data lines 106 almost synchronously with
the gate pulse. A TFT which is connected to a scanning line 102 to
which a gate pulse is applied (selected) scanning line 102 is
turned on, and a voltage which is applied to the data lines 106 at
this time is applied to the pixel electrode 112 via a drain
electrode 107, the semiconductor island 105, and a source electrode
108.
[0012] When the gate pulse is cut off, the TFT is turned off. The
voltage applied to the pixel electrode 112 at that time is stored
in the capacitors between pixel electrode 112 and the common
electrode 111, and between the common wirings 103 and the pixel
electrodes 112.
[0013] Thus, the voltage which corresponds to the display tone is
applied to the liquid crystal of each unit pixel area until the
next selection period. While this voltage is applied, an electric
field parallel to the substrate is formed between the common
electrodes 111 and the opposing portions 112a of the pixel
electrode 112, and the liquid crystal is oriented in a desired
state. Therefore, the color of the color layer 203 is displayed in
a desired tone.
[0014] As described above, in this liquid crystal display device,
an electric field is formed between the common electrodes 111 and
the opposing portions 112a of the pixel electrode 112, and this
electric field parallel to the substrate is applied to the liquid
crystal 300. However, the data lines 106 are also formed closed to,
and along the opposing portions 112a of the pixel electrode 112.
Thus, an electric field is formed also between the data lines 110
and the pixel electrode 112 due to the potential difference between
them. Part of this electric field "leaks" to some parts of the
liquid crystal 300 that are close to the data lines 106. The
so-called leak electric field disturbs the orientation of the
liquid crystal 300 and causes disclination, thus display quality is
deteriorated.
[0015] It is undesirable that the electric field caused by the data
lines 106 leaks to the liquid crystal 300. Thus, the wide edge
portions 111b of the common electrodes 111 are provided to reduce
this leak electric field. As shown in FIG. 15, the electric field
caused by the data lines 106 is terminated mainly by the edge
portions 111b of the common electrodes 111, not by the pixel
electrode 112. Therefore, electric field leakage to the liquid
crystal 300 is prevented.
[0016] However, in order to obtain a sufficiently high prevention
effect (shield effect) against leakage, it is necessary to widen
the width of the edge portions 111b of the common electrodes 111.
The common electrodes 111 are usually made of a metal having a
light blocking effect such as chromium or the like. Therefore, as
the width of the edge portions 111b is widened, a ratio of the
display area to the unit pixel area of the liquid crystal display
device, i.e., the aperture ratio is reduced.
[0017] A structure wherein a common electrode is formed above a
data line, such as disclosed in Unexamined Japanese Patent
Application KOKAI Publication No. H11-119237, is proposed as a
structure which can obtain a high shield effect while preventing
reduction in the aperture ratio. FIG. 16 shows an example of a plan
layout of a liquid crystal display device having such a structure.
FIG. 17 shows a cross section of the display device shown in FIG.
16 when it is sectioned along a direction QQ. Components identical
to those shown in FIGS. 14 and 15 are given the same reference
numerals, and explanation for those components is omitted.
[0018] Unlike the liquid crystal display device shown in FIG. 15,
in this liquid crystal display device, a pixel electrode 112 and a
common electrode 111 are formed in a same plane above data lines
106.
[0019] As shown in FIG. 17, parts of the common electrode 111 are
formed on a second interlayer installation film 110 just above the
data lines 106. As shown in FIG. 16, the common electrode 111
includes a supporting portion which overlaps a common wiring 103
shown in the upper side of FIG. 16 and extends toward an X
direction, and two opposing portions which extend from the
supporting portion toward a Y direction. The opposing portions have
a length which is almost the same as a distance between two
adjacent common wirings 103 existing in a unit pixel area. The
common electrode 111 is electrically connected to the common wiring
103 via a contact hole 113 which penetrates a first interlayer
insulation film 104 and the second interlayer insulation film
110.
[0020] As shown in FIG. 17, the pixel electrode 112 includes a
first pixel electrode 109 formed on the first interlayer insulation
film 104, and a second pixel electrode 112a formed on the second
interlayer insulation film 110.
[0021] As shown in FIG. 16, the first pixel electrode 109 is formed
in an H letter shape. That is, the first pixel electrode 109 has
two linear portions arranged so as to overlap the common wirings
103, and a linear portion arranged so as to oppose the second pixel
electrode 112 and to connect the two linear portions. A part of the
first pixel electrode 109 is connected to a source electrode 108. A
compensating capacitor is formed between the common wiling 103 and
the first pixel electrode 109 which opposes the common wiring
103.
[0022] The second pixel electrode 112 includes three opposing
portions, and a supporting portion for supporting the three
opposing portions, and thus forms an H letter shape. The second
pixel electrode 112 is arranged so as to engage with the common
electrode 111 which is formed on the same surface. Adjacent two
opposing portions of the second pixel electrode 112 sandwich one
opposing portion of the common electrode 111a. The supporting
portion of the common electrode 111 is arranged so as to overlap
the common wiring 103 shown in the upper side of the FIG. 16, and
is electrically connected to the common wiring 103 via the contact
hole 113 for common electrode. The common electrode 111 and the
second pixel electrode 112 are made of, for example, a material
having an optical transmittance characteristic, such as ITO (Indium
Tin Oxide) or the like.
[0023] In this liquid crystal display device, edge portions 111b
included in the common electrode 111 that have a width wider than
that of the data lines 106 are provided above the data lines 106.
An electric field formed from the data lines 106 is terminated by
the edge portions 111b of the common electrode 111 as indicated in
FIG. 17 by arrows. Therefore, leakage of the electric field to the
liquid crystal 300 is prevented. Thus, influence given on the
electric field between the common electrode 111 and the pixel
electrode 112 is reduced, and the deterioration of the displayed
image is lowered.
[0024] However, since the data lines 106 and the edge portions 111b
of the common electrode 111 oppose each other by almost the entire
surfaces thereof via the second interlayer insulation film 110,
electrostatic capacitance between the data lines 106 and the edge
portions 111b of the common electrode 111 is relatively large.
Thus, delay of the signal applied to the data lines 106 cannot be
ignored.
[0025] To reduce such electrostatic capacitance, the second
interlayer insulation film 110 between the data lines 106 and the
edge portions 111b may be formed thicker. However, in this case, a
longer time is required for forming the second interlayer
insulation film 110, and thus the manufacturing throughput is
lowered. And since the second interlayer insulation film 110 is
formed thicker, a contact hole having a high aspect ratio will be
formed. Thus, the yield is lowered, and the manufacturing cost is
increased.
[0026] And since the opposing areas of the data lines 106 and the
edge portions 111b of the common electrode 111 via the second
interlayer insulation film 110 are large, there is a high
possibility that an electrical short circuit (interlayer short
circuit) is caused between the data lines 106 and the edge portions
111b due to a defect such as a pinhole caused in the second
interlayer insulation film 110. The electrical short circuit
increases the possibility that a line defect is caused when the
display operation is performed.
[0027] In the above-indicated publication, an embodiment in which
the edge portions of the common electrode are formed so as to cover
a part of the data lines is also disclosed. However, in such a case
where the edge portions of the common electrode are formed so as to
overlap a part of the data lines, an electric field leaks to other
parts of the unit pixel area than the data lines.
[0028] Moreover, in a case where the second interlayer insulation
film 110 is made of an inorganic fin such as a silicon oxide film
or the like, the second interlayer insulation film 110 needs to be
formed relatively thick, approximately 1 to 10 .mu.m, since the
dielectric constant is high. This brings about the same problems as
described above. On the other hand, in a case where the second
interlayer installation film 110 is made of an organic film such as
acrylic resin or the like, it can be formed to have a thickness of
approximately 0.5 to 5 .mu.m, since the dielectric constant is low.
Thus, the problems caused by a thick film can be avoided. However,
an organic film has a high permeability against ions. Thus, to
prevent adhesion of ions to the back channel of a TFT, there is a
limitation on materials which can be used as the organic film. And
in a case where the second interlayer insulation film 110 is formed
of a double-layered film made of an inorganic film and an organic
film, there is a need to form openings respectively in the
inorganic film and the organic film. Thus, manufacturing steps and
manufacturing costs are largely increased.
[0029] To sum up, there has not conventionally been provided an
active matrix type liquid crystal display device which can be
manufactured without largely increasing the manufacturing steps and
manufacturing costs, and which has lowered delay of a signal, and
has decreased display defects.
SUMMARY OF THE INVENTION
[0030] To solve the above problems, an object of the present
invention is to provide an active matrix type liquid crystal
display device having a lowered delay of a signal and decreased
display defects, and a manufacturing method thereof.
[0031] Another object of the present invention is to provide an
active matrix type liquid crystal display device which is capable
of preventing leakage of an electric field from data lines while
lowering delay of a signal, and a manufacturing method thereof.
[0032] To accomplish the above objects, an active matrix type
liquid crystal display device according to a first aspect of the
present invention comprises:
[0033] a pair of substrates;
[0034] a liquid crystal sealed between the pair of substrates;
[0035] a plurality of data lines and a plurality of scanning lines
which are arranged so as to intersect each other on one surface of
one of the pair of substrates;
[0036] a switching element having an electric current path one end
of which is connected to corresponding one of the data lines, and
having a control terminal which is connected to corresponding one
of the scanning lines;
[0037] a pixel electrode which is provided above the data lines via
an insulation film and is connected to the other end of the
electric current path of switching element; and
[0038] a common electrode which opposes the data lines via the
insulation film, has slits in portions overlapping the data lines,
to generate an electric field between the pixel electrode.
[0039] The common electrode and the pixel electrode may
respectively have linear portions which oppose with each other
almost in parallel by a predetermined length.
[0040] The overlapping portions may be provided along the linear
portions.
[0041] The slits may have a length which is almost the same as that
of the liner portions.
[0042] The slits may be formed in almost a center of a width of the
overlapping portions.
[0043] The overlapping portions of the common electrode may have a
width equal to or wider than that of the data lines.
[0044] The slits may have a width smaller than that of the data
lines.
[0045] The common electrode and the pixel electrode may be on a
same plane.
[0046] The common electrode and die pixel electrode may be made of
a transparent conductive material.
[0047] The common electrode and the pixel electrode may be on
different planes respectively.
[0048] An electric field in a direction parallel to the pair of
substrates may be formed between the common electrode and the pixel
electrode.
[0049] An active matrix type liquid crystal display device
according to a second aspect of the present invention comprise:
[0050] a pair of substrates,
[0051] a liquid crystal sealed between the pair of substrates;
[0052] a plurality of data lines and a plurality of scanning lines
which are arranged so as to intersect each other on one surface of
one of the pair of substrates;
[0053] a switching element having an electric current path one end
of which is connected to corresponding one of the data lines, and
having a control terminal which is connected to corresponding one
of the scanning lines;
[0054] a pixel electrode which is provided above the data lines via
an insulation film, and is connected to the other end of the
electric current path of the switching element;
[0055] a common electrode which opposes to the data lines via the
insulation film, has slits in portions overlapping the data lines,
to generate an electric field between the pixel electrode; and
[0056] a first conductive film which is provided on the other of
the pair of substrates so as to oppose to the data lines via the
slits, and is set to a common electric potential with the common
electrode.
[0057] The common electrode and the pixel electrode may
respectively have linear portions which oppose with each other
almost in parallel by a predetermined length. The overlapping
portions may be provided along the linear portions.
[0058] The slits may have a length which is almost the same as that
of the linear portions.
[0059] The slits may be formed in almost a center of a width of the
overlapping portions.
[0060] The overlapping portions of the common electrode may have a
width equal to or wider than that of the data lines.
[0061] The slits may have a width smaller than that of the data
lines.
[0062] The common electrode and the pixel electrode may be on a
same plane.
[0063] The common electrode and the pixel electrode may be made of
a transparent conductive material.
[0064] The common electrode and the pixel electrode may be on
different planes respectively.
[0065] The active matrix type liquid crystal display device may
further comprise a plug which electrically connects the first
conductive film and the common electrode with each other.
[0066] The active matrix type liquid crystal display device may
further comprise:
[0067] a common wiring which is provided on a plane different from
that of the common electrode, and is electrically connected to the
common electrode; and
[0068] a plug which is connected to the common wiring, and
electrically connects the first conductive film and the common
electrode with each other.
[0069] A second conductive film may be provided between the first
conductive film and the common wiring in order to enhance
connection between the first conductive film and the common
wiring.
[0070] The second conductive film may be made of a material same as
that of the common electrode and/or the pixel electrode.
[0071] The first conductive film may have a width equal to or wider
than that of the slits
[0072] The first conductive film may function as a black
matrix.
[0073] The active matrix type liquid crystal display device may
further comprise a black matrix which is arranged on the other one
of the pair of substrates in a predetermined pattern, and is
covered by a flattening film.
[0074] The first conductive film may be provided on the flattening
film.
[0075] The first conductive film may have a pattern which is almost
the same as that of the black matrix.
[0076] An electric field parallel to the pair of substrates may be
generated between the common electrode and the pixel electrode.
[0077] To accomplish the above objects, a method of manufacturing
an active matrix type liquid crystal display device according to a
third aspect of the present invention is a method of manufacturing
a liquid crystal display device comprising: a pair of substrates; a
thin film transistor which is provided on one of the pair of
substrates; data lines which are connected to a drain of the thin
film transistor; a pixel electrode which is connected to a source
of the thin film transistor; and a common electrode which generates
an electric field between the pixel electrode, the method
comprising:
[0078] forming an insulation film on the data lines;
[0079] forming a first metal film on the insulation film; and
[0080] forming the common electrode by patterning the first metal
film, with forming slits in portions of the common electrode that
overlap the data lines.
[0081] The method of manufacturing an active matrix type liquid
crystal display device may further comprise forming the pixel
electrode in a shape having linear portions having a predetermined
length.
[0082] In the forming the common electrode, portions which oppose
to the linear portions of the pixel electrode may be formed, and
the slits may be formed to have a length which is almost the same
as that of the linear portions.
[0083] In the forming the common electrode, the slits may be formed
in almost a center of a width of the overlapping portions.
[0084] In the forming the common electrode, the overlapping
portions of the common electrode may be formed to have a width
equal to or wider than that of the data lines.
[0085] In the forming the common electrode, the slits may be formed
to have a width smaller than that of the data lines.
[0086] The common electrode and the pixel electrode may be formed
in a substantially same step.
[0087] A method of manufacturing a liquid crystal display device
according to a fourth aspect of the present invention is a method
of manufacturing a liquid crystal display device comprising: a pair
of substrates; a thin film transistor which is provided on one of
the pair of substrates; data lines which are connected to a drain
of the thin film transistor; a pixel electrode which is connected
to a source of the thin film transistor; and a common electrode
which generates an electric field between the pixel electrode, the
method comprising:
[0088] forming an insulation film which covers the data lines;
[0089] forming a first metal film on the insulation film;
[0090] forming the common electrode by patterning the first metal
film, with forming slits in portions of the common electrode that
overlap the data lines; and
[0091] forming a first conductive film on the other one of the pair
of substrates, the first conductive film opposing to the data lines
via the slits.
[0092] The method of manufacturing an active matrix type liquid
crystal display device may further comprise forming the pixel
electrode in a shape having linear portions heaving a predetermined
length, wherein in said forming said common electrode, portions
which oppose to said linear portions of said pixel electrode may be
formed, and said slits may be formed to have a length which is
almost the same as that of said linear portions.
[0093] In the forming the common electrode, portions which oppose
the linear portions of the pixel electrode may be formed, and the
slits may be formed to have a length which is almost the same as
that of the liner portions.
[0094] In the forming the common electrode, the slits may be formed
in almost a center of a width of the overlapping portions.
[0095] In the forming the common electrode, the overlapping
portions of the common electrode may he formed to have a width
equal to or wider that of the data lines.
[0096] In the forming the common electrode, the slits may be formed
to have a width smaller than that of the data lines.
[0097] The common electrode and the pixel electrode may be formed
in a substantially same step.
[0098] The common electrode may be connected to a common wiring
which is provided on a plane different from a plane on which the
common electrode is formed.
[0099] The method of manufacturing an active matrix type liquid
crystal display device may further comprise forming a plug which
electrically connects the common wiring and the first conductive
film with each other.
[0100] The method of manufacturing an active matrix type liquid
crystal display device may further comprise forming a second
conductive film between the common wiring and the plug.
[0101] The second conductive film may be formed together with the
common electrode and/or the pixel electrode in a same step.
[0102] The method of manufacturing ax active matrix type liquid
crystal display device may further comprise:
[0103] forming a black matrix having a predetermined pattern on one
surface of the other one of the pair of substrates; and
[0104] forming a flattening film on the black matrix.
[0105] The first conductive film may be formed on the flattening
filial.
[0106] In the forming the first conductive film, the first
conductive film may be formed in a pattern same as that of the
black matrix.
BRIEF DESCRIPTION OF THE DRAWINGS
[0107] These objects and other objects and advantages of the
present invention will become more apparent upon reading of the
following detailed description and the accompanying drawings in
which:
[0108] FIG. 1 shows an entire structure of an active matrix type
liquid crystal display device according to a first embodiment of
the present invention;
[0109] FIG. 2 shows a partially enlarged view of FIG. 1;
[0110] FIG. 3 shows a plan layout of a unit pixel area according to
the first embodiment of the present invention;
[0111] FIG. 4 is a cross sectional view of FIG. 3 when sectioned
along a line AA;
[0112] FIG. 5 is a diagram showing patterns of components included
in a TFT substrate;
[0113] FIG. 6 is a diagram showing patterns of components included
in a TFT substrate;
[0114] FIG. 7 is a diagram schematically showing an electric field
above a data line;
[0115] FIGS. 8A to 8J are diagrams showing a manufacturing process
of the TFT substrate according to the first embodiment step by
step;
[0116] FIG. 9 is a plan layout of a TFT substrate according to a
modification of the first embodiment;
[0117] FIG. 10 shows a cross section of an active matrix type
liquid crystal display device according to a second embodiment of
the present invention;
[0118] FIG. 11 shows a cross section of an active matrix type
liquid crystal display device according to a third embodiment of
the present invention;
[0119] FIG. 12 shows a cross section of an active matrix type
liquid crystal display device according to a fourth embodiment of
the present invention;
[0120] FIG. 13 shows a cross section of an active matrix type
liquid crystal display device according to a fifth embodiment of
the present invention;
[0121] FIG. 14 shows a plan layout of a conventional active matrix
type liquid crystal display device;
[0122] FIG. 15 shows a cross section of FIG. 14 when sectioned
along a line PP;
[0123] FIG. 16 shows a plan layout of a conventional active matrix
type liquid crystal display device; and
[0124] FIG. 17 shows a cross section of FIG. 16 when sectioned
along a line QQ.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0125] First Embodiment
[0126] An active matrix type liquid crystal display device
according to a first embodiment of the present invention will now
be explained with reference to the drawings. The active matrix type
liquid crystal display device according to the first embodiment
constitutes an active matrix type liquid crystal display device of
an IPS (in-Plane Switching) mode which uses an electric field
formed parallel to the substrate.
[0127] FIG. 1 shows a plan layout of the whole active matrix type
liquid crystal display device according to the first embodiment.
FIG. 2 shows an enlarged view of an edge part of the liquid crystal
display device 1 shown in FIG. 1. FIG. 3 shows a plan layout of a
unit pixel of the liquid crystal display device 1 shown in FIG. 1.
FIG. 4 shows a cross section of the unit pixel shown in FIG. 3 as
sectioned along a direction A-A.
[0128] As shown in FIG. 1, the liquid crystal display device 1 has
almost a rectangular shape. The liquid crystal display device 1 has
two parts, a pixel area 11 having almost a square shape and formed
almost all over the liquid crystal display device 1, and a
peripheral area 12 surrounding the pixel area 11.
[0129] As will be described later, the pixel area 11 comprises a
plurality of unit pixel areas arranged in a matrix. A color layer,
a TFT (Thin Film Transistor) as a switching element, and the like
are provided in each unit pixel area.
[0130] The peripheral area 12 forms a terminal area of the liquid
crystal display device 1. Data line terminals 2, scanning line
terminals 3, and a common wiring terminal 4 are provided in the
peripheral area 12.
[0131] The data line terminals 2 are provided along one line (the
line extending toward an X direction) of tie liquid crystal display
device. A plurality of data line terminals 2 are provided at
regular intervals. As shown in FIG. 2, a plurality of data lines
106 are connected to each data line terminal 2, The data lines 106
extend almost vertically toward a Y direction from the line on
which the data line terminals 2 arc provided. A data signal applied
to the data line terminals 2 is supplied to the drains of TFT's via
the data lines 106, as will be described later.
[0132] As shown in FIG. 1, the scanning line terminals 3 are
provided along two opposing lines (lines extending toward the Y
direction) of the liquid crystal display device 1. A plurality of
scanning line terminals 3 are provided at regular intervals. As
shown in FIG. 2, a plurality of scanning lines 102 are connected to
each scanning line terminal 3. The scanning lines 102 extend almost
vertically toward the X direction from the lines on which the
scanning line terminals 3 are provided. A scanning signal applied
to the scanning line terminals 3 is supplied to the gates of TFTs
via the scanning lines 102.
[0133] As shown in FIG. 1 and FIG. 2, the common wiring terminal 4
is provided so as to cover the circumference of the liquid crystal
display device 1. A common voltage applied to the common wiring
terminal 4 is supplied to a common electrode, as will be described
later.
[0134] FIG. 3 shows a plan layout of a unit pixel area 11a of the
liquid crystal display device 1. FIG. 4 shows a cross sectional
structure of the liquid crystal display device 1. This cross
section corresponds to a section of the liquid crystal display
device 1 shown in FIG. 3 as sectioned along a line A-A, and also to
a section of the peripheral area 12.
[0135] As shown in FIG. 4, the liquid crystal display device 1
according to this embodiment comprises a TFT substrate 100, an
opposing substrate 200, and a liquid crystal 300.
[0136] The TFT substrate 100 and the opposing substrate 200 are
arranged so as to oppose each other via a spacer (not illustrated).
The peripheries of the TFT substrate 100 and opposing substrate 200
are connected by a sealing member (not illustrated). The liquid
crystal 300 is filled in a liquid crystal cell (scaled container)
formed by the TFT substrate 100, the opposing substrate 200, and
the scaling member.
[0137] The TFT substrate 100 comprises a first transparent
substrate 101 made of transparent glass, transparent plastic, or
the like. The scanning lines 102 (not illustrated in FIG. 4), and
common wirings 103 are formed on one surface of the first
transparent substrate 101. The scanning lines 102 and the common
wirings 103 are made of, for example, chromium, aluminum,
molybdenum, tantalum, copper, aluminum-copper,
aluminum-silicon-copper, titanium, or tungsten, or an opaque film
such as a compound metal made of mainly those metals, or a film
having a light transmittance characteristic such as ITO (Indium Tin
Oxide), or a layered film of those films.
[0138] FIG. 5 shows patterns of the scanning lines 102 and the
common wirings 103. As shown in FIG. 5, the scanning lines 102
extend toward the X direction, and determine the X direction of the
unit pixel area 11a.
[0139] The common wirings 103 extend toward the X direction along
the scanning lines 102. Two common wirings 103 extend between
adjacent two scanning lines 102. Thus, two common wirings 103 exist
in a unit pixel area 11a.
[0140] As shown in FIG. 4, a first interlayer insulation film 104
is formed on the first transparent substrate 101, the scanning
lines 102, and the common wirings 103. The first interlayer
insulation film 104 is made of, for example, a silicon oxide film,
a silicon nitride film, or a layered film of those films.
[0141] The data lines 106 and a first pixel electrode 109 are
formed on the first interlayer insulation film 104. The data lines
106 and the first pixel electrode 109 are made of, for example,
chromium, aluminum, molybdenum, tantalum, copper, aluminum-copper,
aluminum-silicon-copper, tantalum, or tungsten, or an opaque film
such as a compound metal made of mainly those metals, or a film
having a light transmittance characteristic such as ITO, or a
layered film of those films.
[0142] Patterns of the data lines 106 and the first pixel electrode
109 are shown in FIG. 5. As shown in FIG. 5, the data lines 106
extend toward the Y direction with having a space between them in
the X direction. The data lines 106 extend toward the Y direction
and determine the sides of the unit pixel area 11a in the Y
direction.
[0143] The first pixel electrode 109 is formed in almost an H
letter shape, and is arranged in almost the center of the unit
pixel area 11a. The two opposing line portions of the first pixel
electrode 109 having an H letter shape are arranged so as to
overlap the common wirings 103 which go across inside the unit
pixel area 11a. The center line portion of the H letter shape of
die first pixel electrode 109 extend in almost the center of the
unit pixel area 11a toward the Y direction along the data lines
106. Compensating capacitors are formed between the first pixel
electrode 109 and the common wirings 103 which oppose each other
via the first interlayer insulation film 104.
[0144] A semiconductor island 105 which constitutes a TFT is
provided in the unit pixel area 11a. As shown in FIG. 5, the
semiconductor island 105 is formed in a position near the junction
of the scanning line 102 and the data line 106 and overlaps the
scanning line 102. Although not shown in FIG. 4, the semiconductor
island 105 is formed on the first interlayer insulation film 104
above the data line 106. The semiconductor island 105 is made of
amorphous silicon, polysilicon, or the like. A drain area and a
source area on which phosphorus or the like is doped, are formed on
the surface of the semiconductor island 105.
[0145] A drain electrode 107 and a source electrode 108 are
connected to the drain area and the source area of the
semiconductor island 105, respectively. The drain electrode 107 is
connected to the data line 106, and is formed as a metal film
substantially shared with the data line 106. The source electrode
108 is connected to the first pixel electrode 109, and is formed as
a metal film substantially shared with the first pixel electrode
109. The semiconductor island 105 is provided above the scanning
line 102 via the first interlayer insulation film 104. The scanning
line 102 acts as a gate electrode of the TFT.
[0146] In FIG. 4, a second interlayer insulation film 110 is formed
on the data lines 106, the first pixel electrode 109, and the first
interlayer insulation film 104. The second interlayer insulation
film 110 is made of transparent resin such as acrylic resin or the
like. One surface of the second interlayer insulation film 110 is
flattened, thus, the second interlayer insulation film 110 act as a
flattening film. The second interlayer insulation film 110 may be
made of an inorganic insulation film having no flattening effect,
such as a silicon oxide film, a silicon nitride film, or the
like.
[0147] A common electrode 111 and a second pixel electrode 112 are
formed on the second interlayer insulation film 110. The common
electrode 111 and the second pixel electrode 112 are made of, for
example, chromium, aluminum, molybdenum, tantalum, copper,
aluminum-copper, aluminum-silicon-copper, titanium, or tungsten, or
a opaque film such as a compound metal made of mainly those metals,
or a film having a light transmittance characteristic such as ITO
(Indium Tin Oxide), or a layered film of those film. A material
having a light transmittance characteristic such as ITO or the like
is preferred in order to obtain a high aperture ratio.
[0148] FIG. 6 shows patterns of the common electrode 111 and the
second pixel electrode 112. As shown in FIG. 6, the common
electrode 111 includes an X direction extending portion 111a, Y
direction extending portions 111b, and opposing portions 111c.
[0149] The X direction extending portion 111a and Y direction
extending portions 111b of the common electrode 111 extend toward
the X direction and Y direction respectively, and are set almost at
right angles to each other. As shown in FIG. 3, the X direction
extending portion 111a is arranged so as to overlap one of the
common wirings 103 that does not overlap the semiconductor island
105. That is, the X direction extending portion 111a is arranged so
as to overlap the upper one of the two common wirings 103 shown in
FIG. 5. The common electrode 111 is electrically connected to the
common wiring 103 via a contact hole 113 for common electrode whose
position is indicated in FIG. 3 and FIG. 5.
[0150] The Y direction extending portions 111b of the common
electrode 111 extend toward the Y direction, and are arranged so as
to overlap the data lines 106 shown in FIG. 5 along those data
lines 106. The Y direction extending portions 111b have a width
equal to or wider than that of the data lines 106. As will be
described later, an electric field generated from the data line 106
is terminated by the Y direction extending portions 111b of the
common electrode 111 via the second interlayer insulation film
110.
[0151] As shown in FIG. 6, the opposing portions 111c of the common
electrode 111 are formed as linear portions which project toward
the Y direction from the X direction extending portion 111a. The
opposing portions 111c are formed in the unit pixel area 11a in a
plural number, for example, 2. As shown in FIG. 3, the opposing
portions 111c has a length in the Y direction that is almost the
same as the length of the portion of the first pixel electrode 109
that is opposed to the opposing portions 111c.
[0152] The second pixel electrode 112 is arranged in almost the
center of the unit pixel area 11a, and is formed in a comb shape.
The second pixel electrode 112 having a comb shape includes a
plurality of, for example, 3 linear opposing portions 112a
extending toward the Y direction, and a linear supporting portion
112b supporting the opposing portions 112a and extending toward the
X direction. The second pixel electrode 112 is arranged so that the
opposing portions 112a thereof oppose the opposing portions 111c of
the common electrode 111 almost in parallel with each other. As
will be described later, an electric field for directing the liquid
crystal molecules is generated between the opposing portions 112a
of the second pixel electrode 112, and the opposing portions 111c
of the common electrode 111.
[0153] As shown in FIG. 3, the second pixel electrode 112 is
arranged so that a part of the second pixel electrode 112 overlaps
the source electrode 108. A contact hole 114 for pixel electrode is
formed in the overlapping position of the source electrode 108 and
the part of the second pixel electrode 112. The second pixel
electrode 112 is electrically connected to the source electrode 108
(i.e., the first pixel electrode 109) via the contact hole 114 for
pixel electrode which penetrates the second interlayer insulation
film 110.
[0154] The Y direction extending portions 111b of the common
electrode 111 respectively have slits 115 in the center of the
width. Each slit 115 is formed along almost the full length of the
Y direction extending portion 111b except the crossing portion of
the X direction extending portion 11a and the Y direction extending
portion 111b.
[0155] In a case where the data line 106 has a width of 10 .mu.m
and the Y direction extending portion 111b has a width of 18 .mu.m,
the width of the slit 115 is set to, for example, 5 .mu.m. In this
case, the Y direction extending portion 111b has extra 4 .mu.m
widths from the both sides of the data line 106, and covers the
both sides of the data line 106 symmetrically. In a case where the
measures are set as above, it is preferred that the Y direction
extending portion 111b has at least extra 115 .mu.m widths from the
both sides of the data line 106.
[0156] As shown in FIG. 4, an orientation film 116 is formed on the
common electrode 111, the second pixel electrode 112, and the
second interlayer insulation film 110. The orientation film 116 is
made of, for example, polyimide resin. The surface of the
orientation film 1 16 is flattened, and has been subjected to an
alignment treatment such as rubbing, or the like.
[0157] In the peripheral area 12, a contact hole 117 for connecting
the substrates is opened which penetrates the second interlayer
insulation film 110 and the first interlayer insulation film 104. A
plug 118 which electrically connects the TFT substrate with the
opposing substrate 200 is embedded in the contact hole 117 for
connecting the substrates. The plug 118 is made of for example,
silver paste. The plug 118 may be made of paste of other metals,
etc.
[0158] A polarizing plate 119 is adhered to the other surface of
the first transparent substrate 101.
[0159] The opposing substrate 200 comprises a second transparent
substrate 201 made of transparent glass, transparent plastic, or
the like.
[0160] A black matrix 202 is formed on one surface of the second
transparent substrate 201. The black matrix 202 is made of a
conductive material having a light blocking characteristic, such as
chromium, carbon black, or the like.
[0161] The black matrix 202 has a function for increasing contrast
between pixels. The black matrix 202 is formed in a pattern having
a plurality of openings. The black matrix 202 includes portions
202a which overlap at least the data lines 106, and a portion 202b
provided in the peripheral area 12.
[0162] As shown in FIG. 4, the Y direction attending portion 111b
exists between the portion 202a of the black matrix 202 and the
data line 106. As described above, the Y direction extending
portion 111b has the slit 115. Thus, the portion 202a of the black
matrix 202 and the data line 106 oppose each other via the slit
115.
[0163] The portion 202a of the black matrix 202 is formed so as to
overlap the slit 115, and to have a width equal to or wider than
tat of the slit 115. For example, in a case where the width of the
slit 115 is 5 .mu.m as described above, the width of the portion
202a of the black matrix 202 is set to at least equal to or wider
than 5 .mu.m. As will be described later, the portion 202a of the
black matrix 202 which is formed so as to barely cover the slit 115
terminates an electric field film the data line 106 that leaks
through the slit 115.
[0164] A color layer 203 is formed in a part of each opening of the
black matrix 202. The part corresponds to a display area. The color
layer 203 is made of resin, for example, including acrylic resin in
which one or three pigments, red (R), green (G), and blue (B) is
dispersed.
[0165] A flattening film 204 is formed on the black matrix 202, the
color layer 203, and the second transparent substrate 201. The
flattening film 204 is made of transparent resin such as acrylic
resin or the like. The surface of the flattening film 204 is
flattened.
[0166] An orientation film 205 is formed on the flattening film
204. The orientation film 205 is made of, for example, imide resin.
The surface of the orientation film 205 is flattened, and hams been
subjected to an alignment treatment such as rubbing or the
like.
[0167] Another portion of the black matrix 202 (i.e., the portion
202b) is formed in the peripheral area 12 of the opposing substrate
200. A contact hole 206 for connecting the substrates is formed in
the flattening film 204. The portion 202b of the black matrix 202
is exposed to the bottom of the contact hole 206 for connecting the
substrates. It should be noticed that the orientation film 205 is
not provided in the peripheral area 12.
[0168] The contact hole 206 for connecting the substrates is
provided so as to oppose the contact hole 117 for connecting the
substrates which is provided in the TFT substrate 100. The same
plug 118 is embedded in the contact hole 206 for connecting the
substrates. Thus, the common wiring 103 of the TFT substrate 100
and the black matrix 202 of the opposing substrate 200 are
electrically connected to each other, and can be set to the sane
electric potential.
[0169] A conductive layer 207 made of ITO or the like and having a
light transmittance characteristic is formed on the other surface
of the second transparent substrate 201. A polarizing plate 208 is
adhered onto the conductive layer 207.
[0170] A display operation of the liquid crystal display device 1
having the above-explained structure will be explained below. In
order to drive the liquid crystal display device 1, a driver
circuit (not illustrated) applies a gate pulse to the scanning
lines 102 sequentially, and applies a data signal having a voltage
corresponding to a display tone to the data line 106 almost
synchronously with the gate pulse. A TFT which is connected to a
scanning line 102 to which the gate pulse is applied (i.e., a
scanning line 102 which is selected) is turned on, and the voltage
applied to the data line 106 at this time is applied to the second
pixel electrode 112 via the drain electrode 107, the semiconductor
island 105, the source electrode 108, and the contact hole 114 for
pixel electrode.
[0171] When the gate pulse is cut off, the TFT is turned off. And
the voltage that has been applied to the second pixel electrode 112
till that time is stored in capacitors (pixel electrodes) between
the second pixel electrode 112 and die common electrode 111, and in
the compensating capacitors between the first pixel electrode 109
and the common wirings 103.
[0172] Therefore, the voltage which corresponds to the display tone
is applied to the liquid crystal 300 in each unit pixel area 11a
until the next selection period. At this time, electric fields
parallel to the substrate are formed between the opposing portions
112a of the second pixel electrode 112, and the Y direction
extending portions 111b and opposing portions 111c of the common
electrode 111. The liquid crystal 300 is oriented in a desired
state by those parallel electric fields, and the color of the color
layer 203 is displayed in a desired tone.
[0173] An electric field which is formed near the data line 106 at
the time of the above-described display operation is schematically
shown in FIG. 7. The electric field generated from the data line
106 is terminated at the Y direction extending portion 111b of the
common electrode 111 provided above the data line 106. Since the Y
direction extending portion 111b has a width almost equal to or
greater than that of the data line 106, the electric field
generated from the data line 106 is mostly terminated by the Y
direction extending portion 111b. Accordingly, leakage of the
electric field to the liquid crystal 300 in the unit pixel areas
11a that are located above both sides of the data line 106 is
prevented. Thus, occurrence of a defect in the displayed image due
to the leak electric field is prevented.
[0174] The slit 115 is formed in the Y direction extending portion
111b. Thus, the opposing area of the data line 106 and the Y
direction extending portion 111b is reduced by the area of the
opening formed by the slit 115. Accordingly, electrostatic
capacitance stored between the data line 106 and the Y direction
extending portion 111b can be suppressed to a relatively low level,
and signal delay can be reduced.
[0175] Part of the electric field generated from the data line 106
leaks through the slit 115 to the liquid crystal 300 above the slit
115. However, the portion 202a of the black matrix 202 is formed in
the opposing substrate 200 so as to oppose the data line 106. As
described above, the black matrix 202 is connected to the common
wiring 103 by the plug 118 in the peripheral area 12, and is set to
have the common electric potential as that of the common wiring
103. The electric field leaking out through the slit 115 is
terminated by the portion 202a of the black matrix 202 which is
provided right above the slit 115.
[0176] The portion 202a of the black matrix 202 has a width equal
to or wider than that of the slit 115. Thus, the electric field
which leaks through the slit 115 is mostly terminated by the
portion 202a of the black matrix 202.
[0177] As described above, according to the first embodiment, the
electric field caused from the data line 106 is terminated by the Y
direction extending portion 111b of the common electrode 111 which
is provided so as to oppose the data line 106 via the insulation
film. The Y direction extending portion 111b is formed to have a
width equal to or wider than that of the data line 106, and thus
leakage of the electric filed to the liquid crystal 300 is
sufficiently prevented.
[0178] The Y direction extending portion 111b has the slit 115.
Thus, the opposing area of the Y direction extending portion 111b
and the data line 106 is relatively small, and therefore,
electrostatic capacitance stored between the Y direction extending
portion 111b and the data line 106 can be suppressed to a
relatively low level. Accordingly, signal delay due to the
electrostatic capacitance can be relatively reduced.
[0179] This reduction in the electrostatic capacitance is achieved
by providing the slit 115 in the common electrode 111. Accordingly,
it is unnecessary to employ the relatively thin second interlayer
insulation film 110, and it is possible to avoid increase in a
possibility of an interlayer short circuit due to a pinhole opened
in the second interlayer insulation film 110.
[0180] The Y direction extending portion 111b is formed to have
almost the same width as that of the data line 106. Thus, even in
case where the common electrode 111 is made of an opaque material
such as chromium or the like, it is possible to prevent leakage of
an electric filed and to reduce signal delay without substantially
reducing the aperture ratio.
[0181] Further, the electric field that leaks through the slit 115
is terminated by the portion 202a of the black matrix 202 which is
provided above the slit 115 and set to the common electric
potential as that of the common wiring 103 and the common electrode
111. Accordingly, it is possible to sufficiently prevent leakage of
the electric field with reducing electrostatic capacitance.
[0182] Still further, such a structure of the liquid crystal
display device 1 as described above can be manufactured by only
modification of an ordinary manufacturing process such as change of
an etching pattern of the common electrode 111 except embedding of
the plug 118, and requires no large increase in the number of
manufacturing steps and manufacturing costs.
[0183] A method of manufacturing the liquid crystal display device
having the above structure will now be explained below with
reference to the drawings. FIGS. 8A to 8J show manufacturing steps
of the TFT substrate 100. FIGS. 8A to 8J show cross sections of
liquid crystal display device 1 shown in FIG. 3 as sectioned along
a direction BB, a direction CC, and a direction DD, and cross
sectional structures for each area in which the contact hole 117
for connecting the substrates, the data line terminal 2, or the
scanning line terminal 3 is to be formed step by step.
[0184] The manufacturing method to be described below is just for
an example, and any other method that can achieve the sample result
is employable. And materials to be used are not limited to those
which will be described below.
[0185] First, as shown in FIG. 8A, a first metal film 131 made of
chromium or the like is formed on one surface of the first
transparent substrate 101 by sputtering, for example. Then, as
shown in FIG. 8B, the scanning lines 102, the common wirings 103,
etc. are formed by patterning the first metal film 131 by a
photolithography technique.
[0186] Then, as shown in FIG. 8C, a silicon oxide film 132 is
formed on the first transparent substrate 101 by a CVD method, for
example. Further, a silicon nitride film 133 is formed on the
silicon oxide film 132 by a plasma CVD method, for example. The
silicon oxide film 132 and the silicon nitride film 133 constitute
the first interlayer insulation film 104.
[0187] Then, an amorphous silicon layer 134 and an n.sup.+ type
doped silicon layer 135 are sequentially formed on the silicon
nitride film 133 by a plasma CVD method, for example. And as shown
in FIG. 8D, the semiconductor island 105 is formed by patterning
the amorphous silicon layer 134 and the n.sup.+ type doped silicon
layer 135 using a photolithography technique. The n.sup.+ type
doped silicon layer 135 may be formed by implanting phosphorus or
the like into the amorphous silicon layer 134 by sputtering or the
like.
[0188] Then, as shown in FIG. 8E, a second metal film 136 made of
chromium or the like is formed on the substrate by sputtering, for
example. And as shown in FIG. 8F, the data lines 106, the drain
electrode 107, the first pixel electrode 109, and die source
electrode 108 are formed by patterning the second chromium film 136
by a photolithography technique.
[0189] Further, the n.sup.+ type doped silicon layer 135 between
the drain electrode 107 and the source electrode 108 is selectively
etched to form a groove which goes to the amorphous silicon layer
134. Thus, a drain and source area is formed in the n.sup.+ type
doped silicon layer 135, and a TFT whose channel is the amorphous
silicon layer 134 and whose ohmic layer is the n.sup.+ type doped
silicon layer 135 is formed.
[0190] Next, as shown in FIG. 8G, a silicon nitride film 137 is
formed on the substrate by a plasma CVD method, for example. Then,
an organic film 138 made of for example, acrylic resin is formed on
the silicon nitride film 137 by spin coating to form the plane
second interlayer insulation film 110. The silicon nitride film 137
and the organic film 138 constitute the second interlayer
insulation film 110.
[0191] Then, an opening is formed by etching die organic film 138.
Then, openings are formed by etching tie silicon nitride film 137,
the silicon nitride film 133, and the silicon oxide film 132. The
organic film 138 is etched so as to form the opening having a
tapered shape. The silicon nitride film 137 and the like are etched
so as to expose the metal film in the openings.
[0192] As shown in FIG. 8H, the contact hole 113 for common
electrode, the contact hole 114 for pixel electrode, the contact
hole 117 for connecting the substrates, a contact hole 120 for data
line, and a contact hole 121 for scanning line are formed by the
etching.
[0193] Then, as shown in FIG. 8I, a third metal film 139 made of
ITO or the like is formed on the substrate by sputtering, for
example. Thereafter, the third metal film 139 is patterned by a
photolithography technique to form the common electrode 111 and the
second pixel electrode 112 having the formations shown in FIG. 8J
and FIG. 6. At this time, the common electrode 111 having the slits
115 is formed.
[0194] After the etching, the third metal film 139 in the contact
hole 117 for connecting the substrates is removed, thus, the common
wiring 103 is exposed at the bottom of the contact hole 117. An
electrode 122 and an electrode 123 formed in the contact hole 120
for data line and in the contact hole 121 for scanning line
respectively form a data line terminal 2 and a scanning line
terminal 3.
[0195] Thereafter, as shown in FIG. 4, the orientation film 116
made of imide resin or the like is formed on the substrate except
the peripheral area 12. Afterwards, the surface of the orientation
film 116 is rubbed for an alignment treatment. Thus, the TFT
substrate 100 is completed.
[0196] The opposing substrate 200 is formed as will be described
below. A light blocking conductive film made of chromium, carbon
block, or the like is formed on one surface of the second
transparent substrate 201. And the conductive film is patterned in
a predetermined shape. By the patterning, the black matrix 202 is
formed. At this time, as described above, the portions 202a of the
black matrix 202 shown in FIG. 4 that have a predetermined width
are formed.
[0197] Then, a resin layer made of photosensitive resin or the like
is formed on the substrate. Then, the color layer 203 for covering
the openings of the black matrix 202 is formed by patterning the
resin layer.
[0198] Thereafter, the flattening film 204 made of acrylic resin or
the like is formed on the substrate. Then, the contact hole 206 for
connecting the substrates is formed by etching the flattening film
204.
[0199] Then, the orientation film 205 made of made resin or the
like is formed on the flattening film 204. The surface of the
orientation film 205 is rubbed for an alignment treatment. The
rubbing direction is opposite to tie direction of rubbing applied
to the TFT substrate 100. Thus, the opposing substrate 200 is
completed.
[0200] Thus formed TFT substrate 100 and opposing substrate 200 are
integrated via a spacer and sealing member (both not illustrated)
so that the respective orientation films 116 and 205 face each
other. Then, the liquid crystal 300 is filled in a space (cell)
between the two substrates formed by the sealing member, and the
cell is scaled. Finally, polarizing plates 119 and 208 are adhered
onto the other surface of the first transparent substrate 101 and
the other surface of the second transparent substrate 201,
respectively.
[0201] Before integrating the TFT substrate 100 and the opposing
substrate 200, silver paste is filled in the contact hole 117 for
connecting the substrates so as to overflow therefrom. When the TFT
substrate 100 and the opposing substrate 200 are integrated, the
top of the silver paste moves and is filled in the contact hole 206
for connecting the substrates which is formed in the opposing
substrate 200. Thus, the plug 118 for electrically connecting the
common wiring 103 and the black matrix 202 is formed. The liquid
crystal display device 1 according to the first embodiment is thus
completed.
[0202] According to the above-described first embodiment, the Y
direction extending portions 111b of the common electrode 111
prevent leakage of an electric field to the liquid crystal 300 in
the unit pixel area 11a. Accordingly, the Y direction extending
portions 111b need only to he provided along the side lines of the
unit pixel area 11a, and do not have to extend over a plurality of
unit pixel areas continuously in the Y direction. Thus, the common
electrode 111 may be consecutive in the X direction, while the Y
direction extending portions 111b maybe separated in the Y
direction by each of the unit pixel areas, as shown in FIG. 9.
[0203] Second Embodiment
[0204] FIG. 10 shows a structure of a liquid crystal display device
according to a second embodiment of the present invention. The plan
layout of a unit pixel area of the liquid crystal display device
according to the second embodiment is identical to the plan layout
of the unit pixel area of the first embodiment shown in FIG. 3.
Thus, illustration of the plan layout is omitted, and a cross
section of the unit pixel area as sectioned along a line
corresponding to the line AA of FIG. 3 is shown in FIG. 10.
Components identical to those shown in FIG. 3 and FIG. 4 are given
the same reference numerals in FIG. 10, and explanation for those
components will be omitted.
[0205] As shown in PIG. 10, according to the second embodiment, a
connection film 139a is formed on the internal wall of the contact
hole 117 for connecting the substrates which is formed in the TFT
substrate 100, and on the surface of the common wiring 103 which is
exposed at the bottom of the contact bole 117. The connection film
139a is made of substantially the same material as that of the
common electrode 111, the pixel electrode 112, etc., made of ITO or
the like. That is, the connection film 139a is formed as the third
metal film 139 in the step shown in FIG. 8I, and remains in the
contact hole 117 in the etching step shown in FIG. 8J (i.e., not
etched in the etching step).
[0206] The silver paste which constitutes the plug 118 is provided
on the connection film 139a. Thus, the plug 118 is connected to the
common wiring 103 via the connection film 139a. In a case where the
common wiring 103 is made of a material which is easily oxidized
such as chromium or the like, the connection film 139a is provided
to compensate for the deterioration of connection between the
silver paste and the common wiring 103.
[0207] This structure is effective particularly in a case where the
common electrode 111, the second pixel electrode 112, etc. are made
of ITO. With reluctantly oxidized ITO on the common wiring 103
which is exposed in the contact hole 117, deterioration of
connection between the silver paste and the common wiring 103 is
compensated for. Due to this, a voltage drop in the common electric
potential between the common wiring 103 and the black matrix 202 is
prevented, and protection against leakage of an electric field is
improved.
[0208] The second embodiment shown in FIG. 10 also suggests an
example in which the portion 202a of the black matrix 202 has a
width smaller than that of the portion 202a according to the first
embodiment.
[0209] As described above, the portion 202a of the black matrix 202
needs only to have a width enough to cover the slit 115 of the Y
direction extending portion 111b of the common electrode 111. The
structure shown in FIG. 10, the portion 202a of the black matrix
202 has a width almost the same as that of the data line 106. Thus,
the width of the portion 202a of the black matrix 202 can be
reduced with respect to the unit pixel area, and thereby the
aperture ratio can be improved.
[0210] Third Embodiment
[0211] FIG. 11 shows a structure of a liquid crystal display device
according to a third embodiment of the present invention. The plan
layout of a unit pixel area of the liquid crystal display device
according to the third embodiment is identical to the plan layout
of the unit pixel area of the first embodiment shown in FIG. 3.
Thus, illustration of the plan layout is omitted, and a cross
section of the unit pixel area as sectioned along a line
corresponding to the line AA of FIG. 3 is shown in FIG. 11.
Components identical to those shown in FIG. 3 and FIG. 4 are given
the same reference numerals in FIG. 11, and explanation for those
components will be omitted.
[0212] According to the third embodiment, a conductive film for
terminating an electric field which leaks through the slit 115 is
provided, aside from the black matrix 202.
[0213] As shown in FIG. 11, a conductive film 209 is formed on the
flattening film 204 of the opposing substrate 200. The conductive
film 209 is made of, for example, chromium, aluminum, molybdenum,
tantalum, copper, aluminum-copper, aluminum-silicon-copper,
titanium, or tungsten, or an opaque film such as a compound metal
made of mainly those metals, or a film having a light transmittance
characteristic such as ITO (Indium Tin Oxide), or a layered film of
those films. The conductive film 209 is covered by the orientation
film 205.
[0214] The conductive film 209 is formed by patterning with using a
mask which is used for patterning the black matrix 202, or using a
mask having almost the same pattern as this. Thus, the conductive
film 209 includes portions 209a and a portion 209b which
respectively overlap the portions 202a and portion 202b of the
black matrix 202.
[0215] The portion 209a of the conductive film 209 is provided
between the Y direction extending portion 111b of the common
electrode 111 and the portion 202a of the black matrix 202, and
opposes the data line 106 via the slit 115.
[0216] The portion 202b of the conductive film 209 is provided so
as to oppose the common wiring 103 in the peripheral area 12. In
the liquid crystal display device according to the third
embodiment, the contact hole 206 for connecting die substrates is
not provided in the flattening film 204. The portion 209b of the
conductive film 209 is electrically connected of the common wiring
103 by the plug 118. Thus, the conductive film 209 is set to have
the common electric potential as that of the common wiring 103.
[0217] The portion 209a of the conductive film 209 terminates an
electric field which leaks through the slit 115, instead of the
portion 202a of the black matrix 202 according to the first
embodiment.
[0218] The structure having the conductive film 209 for terminating
a leak electric field has the following advantages. First, there is
no limit on materials to be used as the black matrix 202. For
example, since there is no need of connecting the black matrix 202
to the common wiring 103 via the plug 118, carbon black, which has
a poor connection characteristics with metals, and high resistance,
but has a high light blocking effect, can be used for the black
matrix 202.
[0219] In contrast, since the light blocking characteristics is not
required to the conductive film 209, the conductive film 209 can be
made of a material having low resistance and good connection
characteristics. Accordingly, the possibility of a voltage drop in
the common electric potential of the conductive film 209 can be
reduced, and thus a shield effect against a leak electric field can
be improved.
[0220] According to the third embodiment, the conductive film 209
is formed with using the same pattern as that of the black matrix
202. However, this is not the limitation for the conductive film
209. The conductive film 209 and the black matrix 202 may be formed
by different patterns from each other. For example, the conductive
film 209 may be made of a transparent material such as ITO, and the
portion 209a may be formed to have a wider width than that of the
portion 202a of the black matrix 202. In this also, the width of
the portion 209a of the conductive film 209 can be appropriately
set so that an optimum shield effect against a leak electric field
can be obtained with no consideration for the width of the portion
202a of the black matrix 202. And in a case where the portion 209a
of the conductive film 209 is narrower than the portion 202a of the
black matrix 202, the portion 209a of the conductive film 209 can
be made of an opaque material having low resistance. In either
case, reduction in the aperture ratio can be prevented.
[0221] Fourth Embodiment
[0222] FIG. 12 shows a structure of a liquid crystal display device
according to a fourth embodiment of the present invention. The plan
layout of a unit pixel area of the liquid crystal display device
according to the fourth embodiment is identical to the plan layout
of the unit pixel area of the first embodiment shown in FIG. 3.
Thus, illustration of the plan layout is omitted, and a cross
section of the unit pixel area as sectioned along a line
corresponding to the line AA of FIG. 3 is shown in FIG. 12.
Components identical to those shown in FIG. 3, FIG. 4, FIG. 10, and
FIG. 11 are given the same reference numerals in FIG. 12, and
explanation for those components will be omitted.
[0223] As shown in FIG. 12, the liquid crystal display device
according to the fourth embodiment has a connection film 139a
similar to that of the second embodiment, and a conductive film 209
similar to that of the third embodiment.
[0224] With such a structure of the liquid crystal display device,
effects similar to those accomplished in the second and third
embodiments can be obtained. That is, connection between the plug
118 and the common wiring 103 is enhanced, and a possibility of
occurrence of a voltage drop can be reduced. And prevention against
leakage of an electric field can be improved.
[0225] Fifth Embodiment
[0226] FIG. 13 shows a structure of a liquid crystal display device
according to a fifth embodiment of the present invention. The plan
layout of a unit pixel area of the liquid crystal display device
according to the fifth embodiment is identical to the plan layout
of the unit pixel area of the first embodiment shown in FIG. 3.
Thus, illustration of the plan layout is omitted, and a cross
section of the unit pixel area as sectioned along a line
corresponding to the line AA of FIG. 3 is shown in FIG. 13.
Components identical to those shown in FIG. 3, FIG. 4, and FIG. 12
are given the same reference numerals in FIG. 13, and explanation
for those components will be omitted.
[0227] The liquid crystal display device according to the fifth
embodiment has almost the same structure as that of the liquid
crystal display device shown in FIG. 12. As shown in FIG. 13, in
the TFT substrate 100 of the fifth embodiment, the second pixel
electrode 112 is formed on a different layer from the layer on
which the common electrode 111 is formed. That is, a third
interlayer insulation film 124 which covers the common electrode
111 is formed on the second interlayer insulation film 110, as
shown in FIG. 13. The second pixel electrode 112 is formed on the
third interlayer insulation film 124, and covered by the
orientation film 116. The third interlayer insulation film 124 is
made of a silicon oxide film, an inorganic film such as a silicon
nitride film, or an organic film such as resin, or a multi-layered
film made of those films.
[0228] The second pixel electrode 112 is connected to the source
electrode 108 via the contact hole 114 for pixel electrode shown in
FIG. 3, which is made so as to penetrate the third interlayer
insulation film 124.
[0229] Such a structure of the liquid crystal display device in
which the common electrode and the second pixel electrode 112 are
formed on different layers has the following advantages. For
example, since the common electrode 111 and the second pixel
electrode 112 arc relatively apart from each other, a display
defect such as an unlit pixel due to an electric short circuit
between the two electrodes is caused less frequently. And from a
viewpoint of design, different layouts and materials can be
employed for other common electrode 111 and the second pixel
electrode 112 respectively, because the two electrodes are not
manufactured in a same step. Accordingly, display quality can
further be improved.
[0230] In the first to fifth embodiments, an active matrix type
liquid crystal display device comprising TFTs is explained for an
example. However, TFTs are not the limitation for the present
invention, but diodes, MIMs, or the like may be used as the active
elements. The TFTs may be either a reverse staggered type or a
normal staggered type. Further, the liquid crystal display device
may be the passive type which does not comprise active
elements.
[0231] Various embodiments and changes may the made thereunto
without departing from the broad spirit and scope of the invention.
The above-described embodiments are intended to illustrate the
present invention, not to limit the scope of the present invention.
The scope of the present invention is shown by the attached claims
rather than the embodiment. Various modifications made within the
meaning of an equivalent of the claims of the invention aid within
the claims are to be regarded to be in the scope of the present
invention.
[0232] This application is based on Japanese Patent Application No.
2001-073880 filed on Mar. 15, 2001 and including specification,
claims, drawings and summary. The disclosure of the above Japanese
Patent Application is incorporated herein by reference in its
entirety.
* * * * *