U.S. patent application number 09/208261 was filed with the patent office on 2001-11-29 for liguid crystal display device.
Invention is credited to HIRAISHI, YOUICHI, SHIMADA, TAKAYUKI, TAGUSA, YASUNOBU.
Application Number | 20010046024 09/208261 |
Document ID | / |
Family ID | 17194126 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010046024 |
Kind Code |
A1 |
HIRAISHI, YOUICHI ; et
al. |
November 29, 2001 |
LIGUID CRYSTAL DISPLAY DEVICE
Abstract
A liquid crystal display device is provided with a switching
element in neighborhoods of crossing points of a gate wiring and a
data wiring. An interlayer insulating film is provided on the
switching element. A pixel electrode connected with the switching
element is provided on the interlayer insulating film. Moreover, a
spacer for keeping a thickness of a liquid crystal layer constant
is disposed in the liquid crystal layer and in a sealing member for
sealing the liquid crystal layer. Materials of the interlayer
insulating film and spacers are optimized. This configuration
prevents degradation of a defective ratio and reliability due to
the spacer disposed in the liquid crystal layer sinking into the
interlayer insulating film.
Inventors: |
HIRAISHI, YOUICHI;
(TENRI-SHI, JP) ; TAGUSA, YASUNOBU; (IKOMA-SHI,
JP) ; SHIMADA, TAKAYUKI; (YAMATOKORIYAMA-SHI,
JP) |
Correspondence
Address: |
NIXON & VANDERHYE
1100 NORTH GLEBE ROAD 8TH FLOOR
ARLINGTON
VA
22201
|
Family ID: |
17194126 |
Appl. No.: |
09/208261 |
Filed: |
December 9, 1998 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09208261 |
Dec 9, 1998 |
|
|
|
08697277 |
Aug 27, 1996 |
|
|
|
6204907 |
|
|
|
|
Current U.S.
Class: |
349/155 |
Current CPC
Class: |
G02F 1/136227 20130101;
G02F 1/13392 20130101; G02F 1/1339 20130101; G02F 1/133357
20210101 |
Class at
Publication: |
349/155 |
International
Class: |
G02F 001/1339 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 27, 1995 |
JP |
7-249515 |
Claims
What is claimed is:
1. A liquid crystal display device, comprising: a liquid crystal
layer including therein at least one first spacer for maintaining a
thickness of the liquid crystal layer; a first substrate provided
on one side of the liquid crystal layer; a second substrate
including: an interlayer insulating film of the same hardness with
the first spacer or a greater hardness than the first spacer, the
interlayer insulating film being provided on respective sides
thereof with a pixel electrode and at least one switching element
for controlling a display state of a pixel; and a base substrate
facing the first substrate through the liquid crystal layer and the
interlayer insulating film; and a sealing member for sealing the
liquid crystal layer between the first and second substrates.
2. The liquid crystal display device as defined in claim 1, wherein
the interlayer insulating film is made of resin having a
transmittance of the visible ray area of not less than 90%.
3. The liquid crystal display device as defined in claim 2, wherein
the resin is at least one resin selected from the group consisting
of polyamide imide, polyalylate, polyetherimide, epoxy and
polyimide.
4. The liquid crystal display device as defined in claim 1, wherein
the interlayer insulating film is made of a photosensitive
material.
5. The liquid crystal display device as defined in claim 1, wherein
the interlayer insulating film has a rough surface provided with
film property improvement treatment.
6. A liquid crystal display device, comprising: a liquid crystal
layer including therein at least one first spacer for maintaining a
thickness of the liquid crystal layer; a first substrate provided
on one side of the liquid crystal layer; a second substrate
including: an interlayer insulating film made of elastic body and
provided on respective sides thereof with a pixel electrode and at
least one switching element for controlling a display state of a
pixel; and a base substrate facing the first substrate through the
liquid crystal layer and the interlayer insulating film; and a
sealing member for sealing the liquid crystal layer between the
first and second substrates.
7. The liquid crystal display device as defined in claim 6, wherein
the interlayer insulating film is made of resin having a
transmittance of the visible ray area of not less than 90%.
8. The liquid crystal display device as defined in claim 7, wherein
the resin is at least one resin selected from the group consisting
of butadienestyrene copolymer, butyl rubber and fluororubber.
9. The liquid crystal display device as defined in claim 6, wherein
the interlayer insulating film is made of a rubber-like elastic
macromolecule.
10. The liquid crystal display device as defined in claim 9,
wherein the rubber-like elastic macromolecule is at least one
macromolecule selected from the group consisting of polyolefin
elastomer and polyurethane rubber.
11. The liquid crystal display device as defined in claim 6,
wherein the interlayer insulating film is made of a photosensitive
material.
12. The liquid crystal display device as defined in claim 6,
wherein the interlayer insulating film has a rough surface provided
with film property improvement treatment.
13. A method of manufacturing a liquid crystal display device
including a pixel electrode and a switching element for determining
a display state of a pixel, an interlayer insulating film disposed
between the switching element and the pixel electrode, and a base
substrate provided with the interlayer insulating film, the
switching element and the pixel electrode, said manufacturing
method comprising the steps of: (1) providing the switching element
on the base substrate; (2) providing the interlayer insulating film
on the switching element; (3) improving film property by making an
interlayer insulating film surface rough; and (4) providing the
pixel electrode on the interlayer insulating film.
14. The method of manufacturing the liquid crystal display device
as defined in claim 13, wherein the third step includes the step of
making the interlayer insulating film surface rough with light
radiation.
15. The method of manufacturing the liquid crystal display device
as defined in claim 13, wherein the third step includes the step of
making the interlayer insulating film surface rough with ashing
treatment.
16. A method of manufacturing a liquid crystal display device
including a pixel electrode and a switching element for determining
a display state of a pixel, an interlayer insulating film disposed
between the switching element and the pixel electrode, and a base
substrate provided with the interlayer insulating film, the
switching element and the pixel electrode, said manufacturing
method comprising the steps of: providing the switching element on
the base substrate; providing the interlayer insulating film on the
switching element; drying the interlayer insulating film with
prebaking treatment before patterning the interlayer insulating
film; patterning the interlayer insulating film; and providing the
pixel electrode on the interlayer insulating film.
17. A liquid crystal display device, comprising: a liquid crystal
layer including therein at least one first spacer for maintaining a
thickness of the liquid crystal layer; a first substrate provided
on one side of the liquid crystal layer; a second substrate
including: a base substrate facing the first substrate through the
liquid crystal layer; and an interlayer insulating film which is
disposed between the base substrate and the liquid crystal layer
except in a sealing area on the base substrate, and which is
provided on respective sides thereof with a pixel electrode and at
least one switching element for controlling a display state of a
pixel; and a sealing member, in contact with the second substrate
in the sealing area, for sealing the liquid crystal layer between
the first and second substrates.
18. The liquid crystal display device as defined in claim 17,
wherein the sealing member includes a second spacer, larger than
the first spacer, for maintaining a thickness of the sealing
member.
19. The liquid crystal display device as defined in claim 17,
wherein the sealing member includes a second spacer, having a
greater hardness than the first spacer, for maintaining a thickness
of the sealing member.
20. The liquid crystal display device as defined in claim 17,
further comprises a middle film, provided on the sealing area of
the base substrate, having better adherence than the base
substrate.
21. The liquid crystal display device as defined in claim 20,
wherein the middle film is at least one film selected from the
group consisting of a metallic film, a nitride film and an oxide
film.
22. The liquid crystal display device as defined in claim 17,
wherein the interlayer insulating film in a neighborhood of the
sealing area is provided to be thinner than the interlayer
insulating film in the other areas and to form a downward slope
towards the sealing area.
23. A method of manufacturing a liquid crystal display device
including: a liquid crystal layer having therein at least one first
spacer for maintaining a thickness of the liquid crystal layer; and
a sealing member, including a different second spacer from the
first spacer, for sealing the liquid crystal layer with a first
substrate and a second substrate disposed on respective sides of
the liquid crystal layer, said manufacturing method comprising the
steps of: (1) including the second spacer in the sealing member in
advance; and (2) sealing the first spacer and a material composing
the liquid crystal layer between the first and second substrates
with the sealing member including the second spacer.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an active matrix type
liquid crystal display device incorporating switching elements,
such as Thin Film Transistors (TFTs), and further relates to a
manufacturing method of such a device.
BACKGROUND OF THE INVENTION
[0002] FIG. 5(a) is a plan view showing a pixel region of an active
matrix substrate incorporated in a conventional liquid crystal
display device. As shown in FIG. 5(a), the active matrix substrate
has a plurality of pixel electrodes 54 provided in a matrix form.
Gate wirings 51 and source wirings 52 are provided around the pixel
electrodes 54 so as to orthogonally cross each other. A TFT 53 is
provided in neighborhoods of crossing points of the gate and source
wirings 51 and 52 as a switching element connected to the pixel
electrode 54 through a contact hole.
[0003] FIG. 5(b) is a cross-sectional view taken along line B-B of
the active matrix substrate incorporated in the liquid crystal
display device shown in FIG. 5(a). As shown in FIG. 5(b), a gate
electrode 61 branching off from the gate wiring 51 shown in FIG.
5(a) is provided on a transparent insulating substrate 60. A gate
insulating film 55 is provided to cover the gate electrode 61. A
semiconductor layer 64 is provided on the gate insulating film 55
above the gate electrode 61. A channel protection layer 65 is
provided on the center of the semiconductor layer 64. Two n.sup.+
layers 66, respectively serving as a source area and a drain area,
are provided so as to cover both ends of the semiconductor layer 64
and the channel protection layer 65, and to be separated from each
other on the channel protection layer 65. The n.sup.+ layers 66 are
connected respectively to the source electrode 62 branching off
from the source wiring 52 and the drain electrode 63. An interlayer
insulating film 59 is provided to cover the TFT 53 and the gate and
source wirings 51 and 52 provided in this manner. The pixel
electrode 54 is provided on the interlayer insulating film 59. The
pixel electrode 54 is connected to the drain electrode 63 of the
TFT 53 through the contact hole in the interlayer insulating film
59.
[0004] Finally, the manufacturing process of the conventional
liquid crystal display device becomes complete with sealing liquid
crystal 58 between a TFT substrate 70 configured in the above
manner and an opposite substrate 71 equipped with an opposite
electrode 56. Here, spacers 57 are sandwiched between the TFT
substrate 70 and the opposite substrate 71 to maintain a
predetermined space therebetween (disclosed in Japanese Laid-Open
Patent Application No. 61-156025/1986 Tokukaishou 61-156025).
[0005] Polyimide resin is used as the interlayer insulating film 59
in the conventional liquid crystal display device disclosed in the
above laid-open patent application. However, other highly
transparent materials, such as acrylic resin, polystyrene and
polyester, are also generally used.
[0006] Although no disclosure is made about the spacers 57, plastic
beads and hard materials, such as glass, are usually used. The
plastic bead spacer is generally made of polyimide, epoxy and
polystyrene.
[0007] Nevertheless, if the above-mentioned acrylic resin is used
as the interlayer insulating film 59 and the spacers 57 are made
using epoxy resin, Newton rings are observed in a lighting test
after injecting and sealing the liquid crystal (Newton rings are a
series of circular bright and dark bands, which look like a wave
pattern created on water surface by a stone dropping into the
water). Especially the phenomenon frequently occurs in the sealing
portion, and the rings were even more clearly observed with a
liquid crystal display device incorporating an interlayer
insulating film in an underlayer of the sealing portion.
Consequently, such a liquid crystal display device has problems of
a high defective ratio and low reliability.
SUMMARY OF THE INVENTION
[0008] An object of the present invention is to provide a liquid
crystal display device which does not cause Newton rings to occur
and which has a low defective ratio and good reliability.
[0009] As a step toward achieving the above object, the inventors
of the present invention conducted researches to pinpoint causes of
Newton rings, and found out that if acrylic resin is used as an
interlayer insulating film and epoxy resin is used as spacers as in
a conventional liquid crystal display device, the spacers press a
pixel electrode, sink into the interlayer insulating film, and thus
change the space between a TFT substrate and an opposite substrate,
thereby causing Newton rings to occur.
[0010] On the contrary, in order to achieve the above object, a
liquid crystal display device in accordance with the present
invention is configured in a preferred embodiment so that the
spacers do not sink into the interlayer insulating film by
optimizing materials of the interlayer insulating film and spacers.
As a result, various problems with the liquid crystal display
device using the resin-made interlayer insulating film are
successfully solved.
[0011] Specifically, in a first preferred embodiment, the liquid
crystal display device includes: a liquid crystal layer; a first
substrate provided on one side of the liquid crystal layer; a
second substrate provided on the other side of the liquid crystal
layer; and a sealing member for sealing the liquid crystal layer
between the first and second substrates. The liquid crystal layer
has therein at least one first spacer for maintaining a thickness
of the liquid crystal layer. The second substrate has: an
interlayer insulating film of the same hardness with the first
spacer or a greater hardness than the first spacer; a pixel
electrode disposed on one side of the interlayer insulating film;
at least one switching element disposed on the other side of the
interlayer insulating film for controlling a display state of a
pixel; and a base substrate facing the first substrate through the
liquid crystal layer and the interlayer insulating film.
[0012] With the above configuration, the hardness of the interlayer
insulating film is either the same as or greater than the hardness
of the first spacer. Therefore, the first spacer can be prevented
from sinking in the interlayer insulating film surface. Newton
rings can be thus prevented from occurring, which improves
reliability and defective ratio in manufacture of the liquid
crystal display device. Moreover, even if pressure is applied by,
for example, a user wiping the liquid crystal display device
surface after the liquid crystal display device is manufactured,
the space between the substrates are kept constant. The liquid
crystal display device with high display quality is obtained for
these reasons.
[0013] While the interlayer insulating film is formed to have a
predetermined hardness in the above liquid crystal display device,
an interlayer insulating film of a second preferred embodiment is
made of elastic body. The second preferred embodiment is configured
in the same manner as the first preferred embodiment, except that a
different material is used for the interlayer insulating film. With
this configuration, if pressure is applied to the display surface
of the liquid crystal display device, the first spacer sinks in the
interlayer insulating film surface and the space between the
substrates changes temporarily. Nevertheless, as the pressure is
removed, resilient power occurs and the space recovers to the
predetermined space. Therefore, the space between the substrates of
the liquid crystal display device are kept constant. The liquid
crystal display device with good reliability, a low defective ratio
and high display quality can be provided for these reasons in the
same manner as in the first preferred embodiment.
[0014] In either of the liquid crystal display devices of the first
and second preferred embodiments, the interlayer insulating film is
preferably made of resin having a transmittance in the visible ray
area of not less than 90%. With this configuration, especially if
the interlayer insulating film is incorporated in a transparent
type liquid crystal display device, it is possible to obtain
beautiful image display with no coloring. Moreover, since
transmittance can be prevented from deteriorating, it is possible
to restrain increase of power consumption of the backlight.
[0015] Incidentally, in the two embodiments above, the material for
the interlayer insulating film is restricted in terms of hardness
or elasticity, compared with prior art. As a result, there occurs a
case where only an inferior material to conventional materials in
terms of adherence and the like can be selected to satisfy this
point.
[0016] The following description discusses a preferred method of
manufacturing a liquid crystal display device when, for example,
the material for the interlayer insulating film does not have
desirable adherence as mentioned above. A method of manufacturing a
liquid crystal display device including: a pixel electrode and a
switching element for determining a display state of a pixel; an
interlayer insulating film disposed between the switching element
and the pixel electrode; and a base substrate provided with the
interlayer insulating film, the switching element and the pixel
electrode preferably includes steps of: (1) providing the switching
element on the base substrate; (2) providing the interlayer
insulating film on the switching element; (3) improving film
property by making an interlayer insulating film surface rough; and
(4) providing the pixel electrode on the interlayer insulating
film.
[0017] The third step includes, for example, a step of ashing
treatment or light radiation in which the interlayer insulating
film surface is made rough prior to the fourth step of providing
the pixel electrode. As a result, even if a material of poor
surface adherence is used as the resin forming the interlayer
insulating film, the interlayer insulating film and the pixel
electrode can adhere to each other with no trouble. Note that if
the film property improving treatment is ashing treatment or light
radiation treatment, the treatment can be carried out as follows.
If the interlayer insulating film is photosensitive, the treatment
can be carried out at the same time with a process of removing
residue of the photosensitive resin, whereas if the interlayer
insulating film is not photosensitive, the treatment can be carried
out at the same time with a process of removing photoresist during
patterning of the interlayer insulating film. This can avoid an
increase of the number of manufacturing processes, compared with
prior art.
[0018] Moreover, a method of manufacturing the above liquid crystal
display device preferably includes steps of: providing the
switching element on the base substrate; providing the interlayer
insulating film on the switching element; drying the interlayer
insulating film with prebaking treatment before patterning the
interlayer insulating film; patterning the interlayer insulating
film; and providing the pixel electrode on the interlayer
insulating film.
[0019] With the configuration, the interlayer insulating film is
dried with prebaking treatment before pattering the interlayer
insulating film. Therefore, it is possible to prevent bad
affection, such as dimensional distortion when the resin really
cures, and to reduce viscosity of the resin forming the interlayer
insulating film. Consequently, it is possible to improve
productivity and dimensional accuracy in manufacture of the liquid
crystal display device.
[0020] Moreover, the inventors of the present invention studied
occurrence frequency of Newton rings with the above conventional
liquid crystal display device, and confirmed among other things
that Newton rings frequently occur in the sealing portion and that
the rings were more clearly observed with a liquid crystal display
device incorporating an interlayer insulating film in an underlayer
of the sealing portion.
[0021] On the other hand, in a preferred embodiment, the liquid
crystal display device in accordance with the present invention
includes: a liquid crystal layer; a first substrate provided on one
side of the liquid crystal layer; and a second substrate having a
base substrate facing the first substrate through the liquid
crystal layer. On the base substrate of the second substrate, a
sealing area is provided outside the display area, such as in the
periphery of the base substrate. Moreover, an interlayer insulating
film is provided between the base substrate and the liquid crystal
layer, except in the sealing area. At least one switching element
for controlling a display state of a pixel is provided on one side
of the interlayer insulating film, whereas the pixel electrode is
provided on the other side of the interlayer insulating film. In
addition, the liquid crystal display device includes a sealing
member, disposed to be in contact with the second substrate in the
sealing area, for sealing the liquid crystal layer between the
first and second substrates.
[0022] In the above configuration, the interlayer insulating film
is not provided in the area where the sealing member and the second
substrate are in contact with each other. Therefore, the space
between the substrates can be prevented from varying when the
sealing member cures. As a result, it is possible to prevent Newton
rings to occur in a neighborhood of the sealing member. Besides,
the defective ratio and reliability can be improved in manufacture
of the liquid crystal display device.
[0023] As an addition to the above configuration, a second spacer
is provided in the sealing member to maintain a thickness of the
sealing member. Preferably, the second spacer satisfies at least
one of the two conditions: the second spacer (1) is larger in size
than the first spacer and (2) has a greater hardness than the first
spacer. With this configuration, the space between the first and
second substrates can be maintained with certainty. Therefore, the
liquid crystal display device with high display quality can be
realized.
[0024] In addition, in order to keep the space between the
substrates constant, the liquid crystal display device preferably
includes a middle film, provided on the sealing area of the base
substrate, having better adherence than the base substrate. With
this configuration, the adherence of the sealing member portion is
improved, and the highly reliable liquid crystal display device can
be obtained. Moreover, the middle film is preferably at least one
film selected from the group consisting of a metallic film, a
nitride film and an oxide film. In this case, the material for the
middle film becomes the same with the material for the source
wiring of the switching element and the like. Therefore, one
process can be shared for forming the switching element and for
forming the middle film, which is especially preferable.
[0025] For a fuller understanding of the nature and advantages of
the invention, reference should be made to the ensuing detailed
description taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1(a) is a plan view showing an arrangement of a pixel
region of an active matrix substrate incorporated in a liquid
crystal display device of a first embodiment in accordance with the
present invention.
[0027] FIG. 1(b) is a cross-sectional view taken along line A-A of
the active matrix substrate incorporated in the liquid crystal
display device shown in FIG. 1(a).
[0028] FIG. 2 is an enlarged cross-sectional view showing a
neighborhood of a sealing portion in a liquid crystal display
device of a third embodiment in accordance with the present
invention.
[0029] FIG. 3 is an enlarged cross-sectional view showing a
neighborhood of a sealing portion in a variant example of the above
liquid crystal display device.
[0030] FIG. 4 is an enlarged cross-sectional view showing a
neighborhood of a sealing portion in another variant example of the
above liquid crystal display device.
[0031] FIG. 5(a) is a plan view showing a pixel region of an active
matrix substrate incorporated in a conventional liquid crystal
display device.
[0032] FIG. 5(b) is a cross-sectional view taken along line B-B of
the active matrix substrate incorporated in the liquid crystal
display device shown in FIG. 5(a).
DESCRIPTION OF THE EMBODIMENTS
[0033] [First Embodiment]
[0034] FIG. 1(a) is a plan view showing an arrangement of a pixel
region of an active matrix substrate incorporated in a liquid
crystal display device of a first embodiment in accordance with the
present invention.
[0035] As shown in FIG. 1(a), the active matrix substrate has a
plurality of pixel electrodes 4 provided in a matrix form. Gate
wirings 1 as scanning wirings and source wirings 2 as signal
wirings are provided in an underlayer of the pixel electrodes 4 so
as to surround each of the pixel electrodes 4 and orthogonally
cross each other. Parts of the gate and source wirings 1 and 2 are
provided so as to overlap with a periphery of the pixel electrodes
4. A TFT 3 as a switching element is provided in a neighborhood of
a crossing point of the gate and source wirings 1 and 2. The TFT 3
may be a switching element such as an MIM
(Metal-Insulator-Metal).
[0036] In the TFT 3, a gate electrode 31 and a source electrode 32
are provided so as to branch off from the gate wiring 1 and the
source wiring 2 respectively. A drain electrode 33 is connected to
the pixel electrode 4 in an upper layer of the drain electrode 33
through a contact hole 37.
[0037] Moreover, on the active matrix substrate, a wiring for
providing storage capacity (Cs wiring) 12 is provided in the middle
of the pixel electrode 4 in the same layer with the gate wirings 1
in the same process as the gate wirings 1. Since Cs on Com method
is adopted as the wiring method of the Cs wirings 12 in the present
embodiment, the Cs wirings 12 are all connected to a common
wiring.
[0038] FIG. 1(b) is a cross-sectional view taken along line A-A of
the active matrix substrate incorporated in the liquid crystal
display device shown in FIG. 1(a).
[0039] As shown in FIG. 1(b), a TFT substrate 10 having the TFT 3
and pixel electrode 4, and an opposite substrate 20 having an
opposite electrode 6 are provided so as to face each other through
liquid crystal 8.
[0040] The following description will explain a structure of the
TFT substrate 10, beginning with the lowest layer and then upwards.
The gate electrode 31 branching off from the gate wiring 1 shown in
FIG. 1(a) is provided on a transparent insulating substrate 11. A
gate insulating film 5 is provided to cover the gate electrode 31.
A semiconductor layer 34 is provided on the gate insulating film 5
above the gate electrode 31. A channel protection layer 35 is
provided on the center of the semiconductor layer 34. Two n.sup.+
layers 36, respectively serving as a source area and a drain area,
are provided so as to cover both ends of the channel protection
layer 35 and a part of the semiconductor layer 34 provided on both
sides of the channel protection layer 35, and to be separated from
each other on the channel protection layer 35. The n.sup.- layers
36 are connected respectively to the source electrode 32 and the
drain electrode 33.
[0041] An interlayer insulating film 9 is provided to cover the TFT
3 provided in this manner. The pixel electrode 4 is provided on the
interlayer insulating film 9. The pixel electrode 4 is connected to
the drain electrode 33 of the TFT 3 through the contact hole 37 in
the interlayer insulating film 9. An orientation film (not shown)
is provided on the pixel electrode 4.
[0042] Meanwhile, another orientation film is provided on the
opposite electrode 6 on the opposite substrate 20. The liquid
crystal layer 8 is sealed between the TFT substrate 10 and opposite
substrate 20, or more precisely, between the orientation films
provided respectively on the TFT and opposite substrates 10 and
20.
[0043] Spacers 7 are provided between the TFT substrate 10 and the
opposite substrate 20 to maintain the space therebetween. Here, an
acrylic resin having a Rockwell hardness of M90 is used as the
interlayer insulating film 9, and a polystyrene having a Rockwell
hardness of M80 is used as the spacers 7.
[0044] Since such a highly transparent acrylic resin is used as the
material of the interlayer insulating film 9 in the present
embodiment, a liquid crystal display device of excellent display
quality with no coloring is obtained. Moreover, the polystyrene
used as the material of the spacers 7 is softer than the interlayer
insulating film 9. Therefore, the spacers 7 do not sink into the
TFT substrate 10, thereby keeping the space between the substrates
10 and 20 constant. Consequently, the liquid crystal display device
causing no Newton ring to occur and having high display quality is
obtained.
[0045] The active matrix substrate of the first embodiment in
accordance with the present invention is configured in the above
manner. The following description will explain a manufacturing
method of the active matrix substrate.
[0046] First, the gate wirings 1 (the gate electrode 31), gate
insulating film 5, semiconductor layer 34, channel protection layer
35 and n.sup.+ layer 36 are formed sequentially with film
disposition patterning. The gate wirings 1 (the gate electrode 31)
are made of metals, such as Al, Ta and Cr: the gate insulating film
5 is made of, for example, SiNx and SiO.sub.2: the semiconductor
layer 34 is made of, for example, Si: the channel protection layer
35 is made of, for example, SiNx. The manufacturing process so far
is the same as a conventional method of manufacturing active matrix
substrates.
[0047] Next, the source wirings 2 (the source electrode 32 and the
drain electrode 33) are formed. In the present embodiment, a
two-layered wiring is provided by forming ITO (Indium Tin Oxide) on
a wiring made of metals such as Al, Ta and Cr when the
above-mentioned members 2, 32 and 33 are formed. This enables the
wiring to have disconnection redundancy, and mounting terminal
portions to have low resistance.
[0048] Next, on the source wirings 2, a photosensitive acrylic
resin film is formed as the interlayer insulating film 9 with spin
coat method to have a thickness of, for example, 3 .mu.m. The film
thickness depends on permittivity of the film made of, for example,
the resin. This is because a parasitic capacity is caused by the
stacking of the wirings and the pixel electrode 4. Therefore, the
permittivity of the resin used is preferably as low as possible.
The resin is then exposed in a necessary pattern and treated with
an alkaline solution. Thus, only the exposed part is etched with
the alkaline solution, and the contact hole 37 is formed through
the interlayer insulating film 9.
[0049] Here, if the resin can be made photosensitive, the resin is
preferably made photosensitive. This is because if a photosensitive
acrylic resin is used, it is possible to perform patterning with
photo processing alone. More preferably, a low viscosity resin is
used and the resin is dried with prebaking treatment before
patterning. More specifically, a film having a thickness of 3 .mu.m
is formed as the interlayer insulating film 9 with spin coat method
from a solution including the photosensitive acrylic resin. For
example, an acrylic resin having a viscosity of 29.0 cp is applied
at a spin rotation of 900 to 1000 rpm. This makes the interlayer
insulating film 9 even, thereby eliminating roughness
conventionally occurring on the pixel electrodes 4. As a result,
undesirable orientation of the liquid crystal is restrained, which
improves display quality of the liquid crystal display device.
Next, the substrate coated with the above solution is heated up to
about 100.degree. C. and then solvent for the photosensitive
transparent acrylic resin (e.g., ethyl lactate and propylene glycol
monomethylether acetate) is dried. The prebaking treatment in this
manner improves productivity and prevents bad affection, such as
dimensional distortion when the resin really cures.
[0050] Resin with poor surface adherence may be improved by making
the surface rough with ashing treatment or light radiation at this
stage. If a photosensitive resin is used as the interlayer
insulating film 9, those treatments can be carried out at the same
time with a process of removing residue of the photosensitive
resin. In contrast, if a non-photosensitive material is used as the
interlayer insulating film 9, the treatments can be carried out at
the same time with the photoresist removing process. Therefore, in
either case, the treatments can be carried out without changing the
conventional number of manufacturing processes of the liquid
crystal display device.
[0051] The above ashing treatment is carried out in the following
manner before the pixel electrodes 4 are formed. Oxygen plasma
treatment is carried out to the surface of the interlayer
insulating film 9 with, for example, a dry etching device to the
depth (film thickness) of 1000 to 3000 .ANG. from the surface of
the interlayer insulating film 9.
[0052] More specifically, for example, the acrylic resin surface
receives ashing treatment with a parallel plate plasma etching
device at an RF power of 1.2 kW, a pressure of 800 mTorr, an oxygen
flow of 300 sccm, a temperature of 70.degree. C. and an RF
application time of 120 sec. Here, the acrylic resin surface is rid
of water and carbon dioxide due to oxidation and discomposition of
organic substance in the oxygen plasma. As a result, the acrylic
resin surface becomes rough. Apart from the above mentioned dry
etching device, dry etching devices of other types, such as of a
barrel type and of an RIE (Reactive Ion Etching) type, can also
achieve the same effects in adherence improvement.
[0053] Ashing treatment is effective when the interlayer insulating
film 9 is treated to the depth of more than 1000 .ANG. from the
surface thereof. However, if ashing treatment is carried out too
deeply into the interlayer insulating film 9, the film thickness is
decreased by a large amount, and thus the thickness of the
interlayer insulating film 9 becomes uneven. As a result, the
orientation also becomes disordered, which affects display by the
liquid crystal display device. Therefore, ashing treatment is
controlled so as to reach the depth of not more than 5000 .ANG.,
and preferably the depth of not more than 3000 .ANG..
[0054] Meanwhile, specifically, light radiation treatment is
carried out by, for example, radiating an ultraviolet ray, such as
an excimer ray, to the surface of the interlayer insulating film 9
in ozone atmosphere. The radiation makes the surface of the
interlayer insulating film 9 rough, and thereby achieving the same
effect as the above mentioned ashing treatment. Note that
conditions for light radiation treatment, such as the film depth
receiving the light radiation, are set in the same manner as ashing
treatment.
[0055] After the interlayer insulating film 9 is formed with
patterning and the contact hole 37 is formed, the ITO as the pixel
electrode 4 is formed with sputtering method and treated with
patterning. The pixel electrode 4 is thus connected to the drain
electrode 33 of the TFT 3 through the contact hole 37 in the
interlayer insulating film 9.
[0056] The TFT substrate 10 manufactured in this manner and the
opposite substrate 20 on which the opposite electrodes 6 are formed
are put together, with a sealing member (not shown) maintaining the
space of the peripheral portion and the spacers 7 maintaining the
space of the other portions. Then, the liquid crystal layer 8 is
enclosed between the two substrates. The liquid crystal display
device of the first embodiment in accordance with the present
invention is manufactured in this manner.
[0057] Here, the acrylic resin having a Rockwell hardness of M90 is
used as the material of the interlayer insulating film 9, and the
polystyrene having a Rockwell hardness of M80 is used as the
material of the spacers 7. However, other materials may be used for
the interlayer insulating film 9 and the spacer 7 as described in
the following.
[0058] If the active matrix substrate is incorporated in a
transparent type liquid crystal display device, the interlayer
insulating film 9 is preferably highly transparent, and more
specifically an interlayer insulating film 9 with a transmittance
in the visible ray area of more than 90% is preferred. Here,
visibility of a blue color (400 to 500 nm) is slightly inferior to
visibility of green and red colors. Therefore, if a material with
slight coloring is to be used, considering that spectral
transmittance varies depending on colors, a material having a
spectral transmittance as close to 100% as possible for the green
and red colors and having a slightly inferior spectral
transmittance for the blue color may be used. Therefore, preferred
material examples of the interlayer insulating film 9 of the
above-mentioned active matrix substrate include polyamide imide
(E61 to 74), polyalylate (M87 to 93), polyetherimide (M105 to 109),
epoxy (M80 to 110), highly transparent polyimide (E45 to 58; for
example, a composition of diamine and acid dianhydride including
hexafluoropropylene).
[0059] Meanwhile, if the active matrix substrate is incorporated in
such a transparent type liquid crystal display device, the spacers
7 are not necessary transparent: for example, black-colored spacers
may be also used. Therefore, the spacers 7 have more material
choices than the interlayer insulating film 9, and may be made of
the same material as the interlayer insulating film 9 or a softer
material than the interlayer insulating film 9.
[0060] Moreover, if the active matrix substrate is incorporated in
a reflection type liquid crystal display device, the interlayer
insulating film 9 has much more material choices than in the
previous case where the active matrix substrate is incorporated in
the transparent type liquid crystal display device. For example, a
coloring agent, such as well-known Kapton (trademark of E. I. du
Pont de Nemours and Co.) may be used in polyimide.
[0061] [Second Embodiment]
[0062] A liquid crystal display device of a second embodiment in
accordance with the present invention is basically configured in
the same manner as that of the first embodiment. The only change is
that in an active matrix substrate incorporated in the liquid
crystal display device of the second embodiment, an interlayer
insulating film 9 is formed using a resin of a high elastic
modulus, especially of high impact resilience.
[0063] Here, the liquid crystal display device employing the
interlayer insulating film 9 made of the high impact resilience
resin has the following advantage: if pressure is applied on a
panel surface (for example, while the upper and lower substrates
are being put together, or when the panel is pushed by a finger
after the panel is manufactured), the surface of the interlayer
insulating film 9 temporarily caves in. However, as the pressure is
removed, the surface of the interlayer insulating film 9 returns to
the original state with the elasticity (resilience), and the space
between the substrates, which has been distorted by the pressure,
also returns to the original state.
[0064] Preferred examples of the resin of a high elastic modulus
employed in the second embodiment in accordance with the present
invention include butadienestyrene copolymer, butyl rubber and
fluororubber for the transparent type liquid crystal display
device; and rubber-like elastic macromolecule, such as polyolefin
elastomer and polyurethane rubber, for the reflection type liquid
crystal display device.
[0065] [Third Embodiment]
[0066] FIG. 2 is an enlarged cross-sectional view showing a
neighborhood of a sealing portion in a liquid crystal display
device of a third embodiment in accordance with the present
invention. Here, for convenience, members having the same function
as members illustrated in FIGS. 1(a) and 1(b) are indicated by the
same reference numerals and description thereof is omitted.
[0067] First, TFT substrate 10 is manufactured in the same manner
as in the first embodiment. Then as shown in FIG. 2, a part of an
interlayer insulating film 9 under a seal 14 is removed during
patterning of the interlayer insulating film 9. Therefore, gate
wirings 1 and a gate insulating film 5 formed on the gate wirings 1
are provided on a transparent insulating substrate 11 below the
seal 14. The interlayer insulating film 9 and a pixel electrode 4
are stacked on the gate wirings 1 and gate insulating film 5 on the
transparent insulating substrate 11 inside the seal 14.
[0068] Then, a TFT substrate 10 and an opposite substrate 20 on
which opposite electrodes 6 are formed are put together,
sandwiching the seal 14 with a predetermined space therebetween.
The predetermined space is maintained by spacers 7 and 13. The
spacer 13 disposed in the seal 14 is larger in diameter than the
spacer 7 disposed in a display area (in a liquid crystal layer
8).
[0069] With this configuration, the problem of inappropriate
display in a neighborhood of the seal 14, that is, frequent
occurrence of Newton rings, is solved. If hard substance, such as
glass beads, is used as the spacers 13 in the seal 14, the problem
is solved more effectively. The spacers 7 in the display area are
preferably, for example, plastic beads, such as polyimide, epoxy
and polystyrene beads. The spacers 7 in the display area may flow
into the seal 14 during the manufacture of the liquid crystal
display device. Nonetheless, this does not cause a serious
problem.
[0070] The adherence of the seal 14 is improved by adding a middle
layer 40 to the liquid crystal display device manufactured in the
above-mentioned manner. As shown in FIG. 3, the middle layer 40 is
provided above the transparent insulating substrate 11 under the
seal 14 so as to include source wirings 2 and ITO therein. The
middle layer 40 is also effective in handling static electricity.
Examples of preferred material for the source wirings 2 and pixel
electrodes 4 include metals, nitrides and oxides.
[0071] Moreover, foam and the like can be prevented from occurring
during injection of the liquid crystal layer 8 by a sloping edge of
an interlayer insulating film 9a formed as shown in FIG. 4. The
liquid crystal 8 can be thus smoothly injected.
[0072] The active matrix substrate of the third embodiment in
accordance with the present invention is configured in the above
manner. The following description will explain a manufacturing
method of the active matrix substrate. Explanation of the same
processes as in the manufacturing method for the first embodiment
is omitted.
[0073] The same method as the first embodiment is employed from the
first process through the process of providing the interlayer
insulating film 9 on the transparent insulating substrate 11. Next,
a contact hole is formed with patterning of the interlayer
insulating film 9. A periphery of the display area, i.e., a part of
the interlayer insulating film 9 under a portion where the seal 14
is provided is removed during the patterning of the interlayer
insulating film 9 in the same manner as the contact hole portion is
removed. Then, the pixel electrodes 4 are provided on a portion
corresponding to the display area of the interlayer insulating film
9. An orientation film (not shown) is then disposed.
[0074] The peripheral portions of the TFT substrate 10 manufactured
in this manner and of the opposite substrate 20 on which the
opposite electrodes 6 are formed are sealed with the seal 14 made
from a thermosetting resin, such as an epoxy resin, a photosetting
resin and the like. The space between the two substrates is kept
constant with the spacers 7 and 13.
[0075] Finally, the last manufacturing processes of the liquid
crystal display device of the third embodiment in accordance with
the present invention are to cure the seal 14 and to inject the
liquid crystal layer 8.
[0076] In the third embodiment in accordance with the present
invention, since the interlayer insulating film 9 is not provided
under the portion where the seal 14 is provided, the space between
the two substrates does not change due to curing shrinkage or
thermal expansion of the resin forming the interlayer insulating
film 9 when the seal 14 cures.
[0077] Moreover, in the third embodiment in accordance with the
present invention, the gate insulating film 5 is provided under the
portion where the seal 14 is provided to improve adherence with the
seal 14. At this time, the seal 14 including the spacers 13 in
advance is preferred for use to improve productivity.
[0078] The present invention is explained with the liquid crystal
display device adopting Cs on Com method as the wiring method of
the wiring for providing storage capacity (Cs wiring). However,
this may be a liquid crystal display device adopting Cs on Gate
method.
[0079] As discussed above, the main object of the liquid crystal
display device of the first through third embodiments is to
eliminate the problem of the conventional liquid crystal display
device, that is, occurrence of Newton rings observed in a lighting
test after injecting the liquid crystal.
[0080] As a step toward achieving the above object, the inventors
of the present invention conducted researches to pinpoint causes of
Newton rings, and found out that if acrylic resin is used as the
interlayer insulating film 59 and epoxy resin is used as the
spacers 57 as in the conventional liquid crystal display device
shown in FIG. 5(b), the spacers 57 press the pixel electrode 54,
sink into the interlayer insulating film 59, and thus change the
space between the TFT substrate 70 and the opposite substrate 71,
thereby causing Newton rings to occur.
[0081] Despite the fact that the pixel electrodes 54 made of ITO,
Al and the like are formed on the interlayer insulating film 59,
the spacers 57 still sink. This is likely to be caused by the
absolutely thin pixel electrode 54: the pixel electrode 54 has a
thickness of 500 .ANG. to 2000 .ANG.. and the interlayer insulating
film 59 has a thickness of 1.5 .mu.m to 4 .mu.m. The same reasoning
is likely to apply to the orientation film (not shown).
[0082] In this manner, in the conventional liquid crystal display
device, the spacer 57 sinking into the interlayer insulating film
59 causes Newton rings to occur during the lighting test, thereby
resulting in a deteriorating defective ratio and reliability.
[0083] On the contrary the liquid crystal display devices of the
first and second embodiments are configured so that the spacers do
not sink into the interlayer insulating film by optimizing the
materials of the interlayer insulating film and spacers. As a
result, various problems with the liquid crystal display device
using the resin-made interlayer insulating film are successfully
solved.
[0084] Specifically, in the first embodiment, the hardness of the
spacers and the interlayer insulating film are adjusted. The liquid
crystal display device of the first embodiment includes: a liquid
crystal layer; a first substrate (the opposite substrate 20)
provided on one side of the liquid crystal layer; a second
substrate (the TFT substrate 10) provided on the other side of the
liquid crystal layer; and a sealing member (the seal 14) for
sealing the liquid crystal layer between the first and second
substrates. The liquid crystal layer has therein at least one first
spacer (the spacer 7) for maintaining a thickness of the liquid
crystal layer. The second substrate has: an interlayer insulating
film of the same hardness with the first spacer or a greater
hardness than the first spacer; a pixel electrode disposed on one
side of the interlayer insulating film; at least one switching
element (the TFT 3) disposed on the other side of the interlayer
insulating film for controlling a display state of a pixel; and a
base substrate (the transparent insulating substrate 11) facing the
first substrate through the liquid crystal layer and the interlayer
insulating film.
[0085] With the above configuration, the hardness of the interlayer
insulating film is either the same as or greater than the hardness
of the first spacer. Therefore, the first spacer can be prevented
from sinking in the interlayer insulating film surface. Newton
rings can be thus prevented from occurring, which improves
reliability and defective ratio in manufacture of the liquid
crystal display device. Moreover, even if pressure is applied by,
for example, a user wiping the liquid crystal display device
surface after the liquid crystal display device is manufactured,
the space between the substrates are kept constant. The liquid
crystal display device with high display quality is obtained for
these reasons.
[0086] While the interlayer insulating film is formed to have a
predetermined hardness in the first embodiment, the interlayer
insulating film of the second embodiment is made of elastic body.
The second embodiment is configured in the same manner as the first
embodiment, except that a different material is used for the
interlayer insulating film. With this configuration, if pressure is
applied to the display surface of the liquid crystal display
device, the first spacer sinks in the interlayer insulating film
surface and the space between the substrates changes temporarily.
Nevertheless, as the pressure is removed, resilient power occurs
and the space recovers to the predetermined space. Therefore, the
space between the substrates of the liquid crystal display device
are kept constant. The liquid crystal display device with good
reliability, a low defective ratio and high display quality can be
provided for these reasons in the same manner as in the first
embodiment.
[0087] In either of the liquid crystal display devices of the first
and second embodiments, the interlayer insulating film is
preferably made of resin having a transmittance of the visible ray
area of not less than 90%. With this configuration, especially if
the interlayer insulating film is incorporated in a transparent
type liquid crystal display device, it is possible to obtain
beautiful image display with no coloring. Moreover, since
transmittance can be prevented from deteriorating, it is possible
to restrain increase of power consumption of the backlight.
[0088] Preferred materials with high transmittance for the liquid
crystal display device of the first embodiment include polyamide
imide, polyalylate, polyetherimide, epoxy and polyimide. Any of
these materials can be used not only for the interlayer insulating
film, but also for the first spacer which requires to be at least
as hard as the interlayer insulating film. Preferred materials for
the liquid crystal display device of the second embodiment include
butadienestyrene copolymer, butyl rubber and fluororubber.
[0089] Meanwhile, if the interlayer insulating film is incorporated
in a reflection type liquid crystal display device, the
transmittance of the interlayer insulating film is not restricted.
Preferred materials for the first embodiment include a coloring
agent, such as Kapton (trademark of E. I. du Pont de Nemours and
Co.). Preferred materials for the second embodiment include
rubber-like elastic macromolecule, such as polyolefin elastomer and
polyurethane rubber.
[0090] Moreover, in the two embodiments mentioned above, the
interlayer insulating film is preferably made of a photosensitive
material. In this case, it is possible to perform patterning with
photo processing alone, and therefore it is also possible to reduce
the number of manufacturing processes.
[0091] Incidentally, in the two embodiments above, the material for
the interlayer insulating film is restricted in terms of hardness
or elasticity, compared with prior art. As a result, there occurs a
case where only an inferior material to conventional materials in
terms of adherence and the like can be selected to satisfy this
point. If a material of poor surface adherence is used, and the
interlayer insulating film and the pixel electrode do not adhere to
each other, the distance between the base substrate and the pixel
electrode varies undesirably. Therefore, if the liquid crystal is
injected and sealed between the first substrate (the opposite
substrate 20) and the second substrate (the TFT substrate 10)
including the base substrate and the pixel electrode, the layer
thickness of the liquid crystal layer varies, thereby damaging the
display quality. Consequently, if a conventional manufacturing
method is employed for the liquid crystal display device, such a
material of poor surface adherence may not be used as resin forming
the interlayer insulating film.
[0092] The following description discusses a preferred method of
manufacturing a liquid crystal display device when, for example,
the material for the interlayer insulating film does not have
desirable adherence as mentioned above. A method of manufacturing a
liquid crystal display device including: a pixel electrode and a
switching element (the TFT 3) for determining a display state of a
pixel; an interlayer insulating film disposed between the switching
element and the pixel electrode; and a base substrate (the
transparent insulating substrate 11) provided with the interlayer
insulating film, the switching element and the pixel electrode
preferably includes steps of: (1) providing the switching element
on the base substrate; (2) providing the interlayer insulating film
on the switching element; (3) improving film property by making an
interlayer insulating film surface rough; and (4) providing the
pixel electrode on the interlayer insulating film.
[0093] The third step includes, for example, a step of ashing
treatment or light radiation in which the interlayer insulating
film surface is made rough prior to the fourth step of providing
the pixel electrode. As a result, even if a material of poor
surface adherence is used as the resin forming the interlayer
insulating film, the interlayer insulating film and the pixel
electrode can adhere to each other with no trouble. Note that if
the film property improving treatment is ashing treatment or light
radiation treatment, the treatment can be carried out as follows.
If the interlayer insulating film is photosensitive, the treatment
can be carried out at the same time with a process of removing
residue of the photosensitive resin, whereas if the interlayer
insulating film is not photosensitive, the treatment can be carried
out at the same time with a process of removing photoresist during
patterning of the interlayer insulating film. This can avoid an
increase of the number of manufacturing processes, compared with
prior art.
[0094] Moreover, a method of manufacturing a liquid crystal display
device including: a pixel electrode and a switching element (the
TFT 3) for determining a display state of a pixel; an interlayer
insulating film disposed between the switching element and the
pixel electrode; and a base substrate (the transparent insulating
substrate 11) provided with the interlayer insulating film, the
switching element and the pixel electrode preferably includes steps
of: providing the switching element on the base substrate;
providing the interlayer insulating film on the switching element;
drying the interlayer insulating film with prebaking treatment
before patterning the interlayer insulating film; patterning the
interlayer insulating film; and providing the pixel electrode on
the interlayer insulating film.
[0095] With the configuration, the interlayer insulating film is
dried with prebaking treatment before pattering of the interlayer
insulating film. Therefore, it is possible to prevent bad
affection, such as dimensional distortion when the resin really
cures, and to reduce viscosity of the resin forming the interlayer
insulating film. Consequently, it is possible to improve
productivity and dimensional accuracy in manufacture of the liquid
crystal display device.
[0096] Moreover, the inventors of the present invention studied
occurrence frequency of Newton rings, and confirmed among other
things that Newton rings frequently occur in the sealing portion
and that the rings were more clearly observed with a liquid crystal
display device incorporating an interlayer insulating film in an
underlayer of the sealing portion.
[0097] In order to prevent occurrence of Newton rings in a
neighborhood of the sealing portion, the liquid crystal display
device of the third embodiment includes: a liquid crystal layer; a
first substrate (the opposite substrate 20) provided on one side of
the liquid crystal layer; and a second substrate (the TFT substrate
10) having a base substrate facing the first substrate through the
liquid crystal layer. On the base substrate of the second
substrate, a sealing area is provided outside the display area,
such as in the periphery of the base substrate. Moreover, an
interlayer insulating film is provided between the base substrate
and the liquid crystal layer, except in the sealing area. At least
one switching element (the TFT 3) for controlling a display state
of a pixel is provided on one side of the interlayer insulating
film, whereas the pixel electrode is provided on the other side of
the interlayer insulating film. In addition, the liquid crystal
display device includes a sealing member, disposed to be in contact
with the second substrate in the sealing area, for sealing the
liquid crystal layer between the first and second substrates.
[0098] If the areas to which the interlayer insulating film is
provided include an area where the sealing member and the second
substrate are in contact with each other (such as the portion below
the sealing member) as in prior art, there may occur curing
shrinkage or thermal expansion with the resin forming the
interlayer insulating film when the resin cures. This causes the
space between the first and second substrate to vary and Newton
rings to occur, thereby resulting in degradation of the display
quality.
[0099] On the contrary, in the above configuration, the interlayer
insulating film is not provided in the area where the sealing
member and the second substrate are in contact with each other.
Therefore, the space between the substrates can be prevented from
varying when the sealing member cures. As a result, it is possible
to prevent Newton rings to occur in a neighborhood of the sealing
member. Besides, the defective ratio and reliability can be
improved in manufacture of the liquid crystal display device.
[0100] Moreover, the sealing member preferably includes a second
spacer, larger than the first spacer, for maintaining a thickness
of the sealing member. The second spacer can maintain the space
between the substrates with certainty even when the space between
the first and second substrates in the sealing area is wider than
the other areas by a value equivalent to the thickness of the
interlayer insulating film. Therefore, the varying of the space
between the substrates can be prevented, which otherwise would
occur with the sealing member, and the occurrence of Newton rings
can be restrained in a neighborhood of the sealing member.
Consequently, the liquid crystal display device of high display
quality can be realized.
[0101] In addition, more preferably, the sealing member includes a
second spacer, having a greater hardness than the first spacer, for
maintaining a thickness of the sealing member. With this
configuration, the space between the substrates can be maintained
with certainty. Consequently, the liquid crystal display device of
high display quality can be realized.
[0102] In the above-mentioned cases where the sealing member
includes the second spacer which is at least either larger than the
first spacer or has a greater hardness than the first spacer, it is
hoped that the following manufacturing method is adopted. A method
of manufacturing a liquid crystal display device including: a
liquid crystal layer having therein at least one first spacer for
maintaining a thickness of the liquid crystal layer; and a sealing
member, having a different second spacer from the first spacer, for
sealing the liquid crystal layer with a first substrate and a
second substrate disposed on respective sides of the liquid crystal
layer preferably includes the steps of: (1) including the second
spacer in the sealing member in advance; and (2) sealing the first
spacer and a material composing the liquid crystal layer between
the first and second substrates with the sealing member including
the second spacer.
[0103] With this configuration, the second spacer disposed in the
sealing member can be prevented from being mixed with the liquid
crystal layer. As a result, the productivity can be improved when
the first spacer and a material composing the liquid crystal layer
are sealed between the first and second substrates with the sealing
member. Note that since the first spacer is smaller in size or has
a smaller hardness than the second spacer, even if the first spacer
flows into the sealing member, the first spacer does not create a
bad affection to the space between the first and second
substrates.
[0104] In addition, in order to keep the space between the
substrates constant, the liquid crystal display device preferably
includes a middle film, provided on the sealing area of the base
substrate, having better adherence than the base substrate. With
this configuration, the adherence of the sealing member portion is
improved, and the highly reliable liquid crystal display device can
be obtained. Moreover, the middle film is preferably at least one
film selected from the group consisting of a metallic film, a
nitride film and an oxide film. In this case, the material for the
middle film becomes the same with the material for the source
wiring of the switching element and the like. Therefore, one
process can be shared for forming the switching element and for
forming the middle film, which is especially preferable.
[0105] Moreover, the interlayer insulating film in the neighborhood
of the sealing area is preferably provided to form a slope so that
the sealing area is thinner than the other area. With this
configuration, foam and the like can be prevented in advance from
occurring during injection of the liquid crystal, and the liquid
crystal can be thus smoothly injected.
[0106] The invention being thus described, it will be obvious that
the same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art intended to be include within the scope of the following
claims.
* * * * *