U.S. patent application number 09/355228 was filed with the patent office on 2002-05-16 for homeotropic and hybrid alignment types of liquid crystal displays and a manufacturing method thereof.
Invention is credited to KOMORI, KAZUNORI, NISHIYAMA, KAZUHIRO, TAKIMOTO, AKIO, TANAKA, YUKIO.
Application Number | 20020057408 09/355228 |
Document ID | / |
Family ID | 26346225 |
Filed Date | 2002-05-16 |
United States Patent
Application |
20020057408 |
Kind Code |
A1 |
NISHIYAMA, KAZUHIRO ; et
al. |
May 16, 2002 |
HOMEOTROPIC AND HYBRID ALIGNMENT TYPES OF LIQUID CRYSTAL DISPLAYS
AND A MANUFACTURING METHOD THEREOF
Abstract
The present invention is intended to eliminate any leakage of
light which would occur, while in a black display state, due to a
disordered alignment of liquid crystals around a pixel electrode in
a liquid crystal device and to provide an improved contrast. The
leakage of light around pixels can be suppressed and the contrast
can be improved, for example, by rubbing the surface in a direction
at an angle of 45 degrees with respect to any of the edges of a
square pixel electrode 25 (a direction shown by the arrow 30) in a
homeotropic type liquid crystal device.
Inventors: |
NISHIYAMA, KAZUHIRO; (OSAKA,
JP) ; TANAKA, YUKIO; (KUSATSU-SHI, JP) ;
KOMORI, KAZUNORI; (SANDA-SHI, JP) ; TAKIMOTO,
AKIO; (OSAKA, JP) |
Correspondence
Address: |
RATNER & PRESTIA
ONE WESTLAKES BERWYN SUITE 301
PO BOX 980
VALLEY FORGE
PA
19482
|
Family ID: |
26346225 |
Appl. No.: |
09/355228 |
Filed: |
July 26, 1999 |
PCT Filed: |
January 19, 1998 |
PCT NO: |
PCT/JP98/00174 |
Current U.S.
Class: |
349/123 |
Current CPC
Class: |
G02F 1/133742 20210101;
G02F 1/1393 20130101; G02F 1/133784 20130101; G02F 1/13712
20210101; G02F 1/133531 20210101 |
Class at
Publication: |
349/123 |
International
Class: |
G02F 001/1337 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 24, 1997 |
JP |
HEI9-010,872 |
Dec 3, 1997 |
JP |
HEI9-332,608 |
Claims
1. A liquid crystal device comprising a first substrate which has
at least rectangular or square electrodes divided into
microstructures, a second substrate which has a transparent
electrode, and a liquid crystal layer which is filled between
said-two substrates and has a negative anisotropy in dielectric
constant wherein a homeotropic alignment is accomplished over said
first substrate, characterized in that said alignment over said
first substrate is accomplished at an angle of 40 to 50 degrees
with respect to any of the edges of an electrode on said first
substrate and a homeotropic alignment is accomplished over said
second substrate.
2. A method of manufacturing a liquid crystal device comprising the
steps of: accomplishing over a first substrate which has at least
rectangular or square electrodes divided into microstructures, an
alignment at angle of 40 to 50 degrees with respect to any of the
edges of an electrode on said first substrate, accomplishing a
homeotropic alignment over a second substrate which has a
transparent electrode, and forming a liquid crystal layer between
said first and second substrates which has a negative anisotropy in
dielectric constant.
3. A liquid crystal device comprising a first substrate which has
at least rectangular or square electrodes divided into
microstructures, a second substrate which has a transparent
electrode, and a liquid crystal layer which is filled between said
two substrates and has a negative anisotropy in dielectric constant
wherein a homeotropic alignment is accomplished over said first
substrate, characterized in that a homogeneous alignment over said
second substrate is accomplished at an angle of 40 to 50 degrees
with respect to any of the edges of an electrode on said first
substrate.
4. A method of manufacturing a liquid crystal device comprising the
steps of: accomplishing a homeotropic alignment over a first
substrate which has at least rectangular or square electrodes
divided into microstructures, accomplishing over a second substrate
which has a transparent electrode, a homogeneous alignment at an
angle of 40 to 50 degrees with respect to any of the edges of an
electrode on said first substrate, and forming a liquid crystal
layer between said first and second substrates which has a negative
anisotropy in dielectric constant.
5. A reflection type liquid crystal device comprising a first
substrate which has at least rectangular or square reflecting
electrodes divided into microstructures, a second substrate which
has a transparent electrode, and a liquid crystal layer which is
filled between said first and second substrates and has a negative
anisotropy in dielectric constant and an anisotropy in refractive
index An between 0.07 and 0.15 wherein a homeotropic alignment is
accomplished over said first substrate, characterized in that said
alignment over said first substrate is accomplished at an angle of
40 to 50 degrees with respect to any of the edges of an electrode
on said first substrate and a homeotropic alignment is accomplished
over said second substrate.
6. A method of manufacturing a reflection type liquid crystal
device comprising a first substrate which has at least rectangular
or square reflecting electrodes divided into microstructures, a
second substrate which has a transparent electrode, and a liquid
crystal layer which is filled between two substrates, such as said
first and second substrates and has a negative anisotropy in
dielectric constant and an anisotropy in refractive index An
between 0.07 and 0.15 wherein a homeotropic alignment is
accomplished over said first substrate, characterized in that said
alignment over said first substrate is accomplished at an angle of
40 to 50 degrees with respect to any of the edges of an electrode
on said first substrate and a homeotropic alignment is accomplished
over said second substrate.
Description
TECHNICAL FIELD
[0001] The present invention relates to a liquid crystal display
and a manufacturing method thereof, and in particular, to
homeotropic and hybrid types of liquid crystal devices and
manufacturing methods thereof.
BACKGROUND ART
[0002] FIG. 5 shows the structure of a electrically controlled
birefringence liquid crystal display cell. There are two types of
liquid crystal display cells, that is, reflection and transmission;
the transmission type will be described herein below as a typical
one.
[0003] The configuration in FIG. 5 comprises a liquid crystal cell
containing liquid crystal molecules 1 whose longitudinal axis is
homeotropic-aligned, that is, aligned in a direction substantially
perpendicular to the electrode surface.
[0004] In FIG. 5, a liquid crystal cell 2 includes two transparent
glass substrates 3 and 4 oppositely arranged at a predetermined
distance, transparent electrodes 5 and 6 formed on the opposite
surfaces of the transparent glass substrates 3 and 4, respectively,
and liquid crystals 1 sandwiched between the transparent
electrodes.
[0005] There are placed, over and under the cell 2, polarizers 7
and 8 whose polarization directions are orthogonal to each
other.
[0006] Incident light 9, when passing through the polarizer 8, is
linearly polarized and then goes into the liquid crystal cell. In
the proximity of the interface between the two substrates 3 and 4,
the liquid crystal molecules are slightly tilted (pretilted) toward
an appropriate direction through an alignment process in order to
tilt the liquid crystal molecules uniformly in the plane.
[0007] If the slight tilt is ignored, the linearly-polarized
incident light passes through the liquid crystal molecules 1 as it
is, but it cannot pass through the polarizer 7 placed
perpendicularly to the polarization axis of the polarizer 8, and
thus the resulting display is in a dark state.
[0008] When a voltage higher than a predetermined threshold voltage
is applied between the transparent electrodes 5 and 6, the
alignment of the liquid crystal molecules 1 is tilted by the
electric field to form a predetermined angle.
[0009] Accordingly, after going into the liquid crystal cell 2, the
linearly-polarized incident light is doubly refracted into two
components orthogonal to each other and then the polarized light
having a component parallel to the polarization axis passes through
the polarizer 7 to bring the display to a bright state.
[0010] At this time, a high contrast is achieved by placing both
the two polarizers 7 and 8 at an angle of 45 degrees with respect
to the tilt direction (pretilt direction) of the liquid crystal
molecules.
[0011] Next, the structure of a hybrid liquid crystal cell will be
described below.
[0012] The configuration in FIG. 6 exhibits a homeotropic alignment
near a substrate 11 wherein the longitudinal axis of a liquid
crystal molecule 10 is aligned in a direction substantially
perpendicular to the surface of a transparent electrode 13 and a
homogeneous alignment near another substrate 12 wherein the
longitudinal axis of a liquid crystal molecule 10 is aligned in a
direction substantially parallel to a transparent electrode 14.
[0013] In FIG. 6, a liquid crystal cell 15 includes two transparent
glass substrates 11 and 12 oppositely arranged at a predetermined
distance, transparent electrodes 13 and 14 formed on the opposite
surfaces of the transparent glass substrates 11 and 12,
respectively, and liquid crystals 10 sandwiched between the
transparent electrodes 13 and 14.
[0014] There are placed, over and under the liquid crystal cell 15,
polarizers 16 and 17 whose polarization directions are orthogonal
to each other and the polarizers are placed in such a manner that
both the polarization axes of these plates are at an angle of 45
degrees with respect to the homogeneous alignment near the glass
substrate 12.
[0015] Incident light 18, when passing through the polarizer 16, is
linearly polarized and then goes into the liquid crystals 10. The
linearly-polarized incident light, which may be slightly subject to
birefringence, passes through the liquid crystal molecules
substantially as it is, but it can hardly pass through the
polarizer 17 placed perpendicularly to the polarization axis of the
polarizer 16, and thus the resulting display is in a dark
state.
[0016] When a voltage higher than a predetermined voltage is
applied between the transparent electrodes 13 and 14, the alignment
of the liquid crystal molecules 10 is tilted by the electric field
to form a predetermined angle.
[0017] Therefore, after going into the liquid crystal cell 15, the
linearly-polarized incident light is doubly refracted into two
components orthogonal to each other and then the polarized light
having a component parallel to the polarization axis of the
polarizer 17 passes through the polarizer 17 to bring the display
to a bright state.
[0018] However, as shown in FIG. 7, when a homeotropic alignment is
achieved over a portion of the substrate 20 which has a pixel
electrode 19, that is, liquid crystal molecules 21 are aligned
perpendicularly to the substrate 20, the liquid crystal molecules
over the edge of the pixel electrode 19 are aligned parallel or
perpendicularly to the edge of the pixel electrode 19.
[0019] Thus, while in a black display state (while no electric
field is applied), the incident light around the pixel is
polarized, causing some leakage of the light 23. This could have
reduced the resulting contrast considerably.
[0020] In particular, for an element of reflection type, because
the light passes through the liquid crystal layer twice, an
outstanding leakage of light occurs around the pixel. Similarly, a
remarkable leakage of light may occur when a kind of material with
a large anisotropy in refractive index is used.
DISCLOSURE OF THE INVENTION
[0021] It is an object of the present invention to provide a liquid
crystal device which causes no leakage of light while in a black
display state with a resulting high contrast and to provide a
manufacturing method thereof.
[0022] The first liquid crystal device of the present invention is
a liquid crystal device comprising a first substrate which has at
least rectangular or square electrodes divided into
microstructures, a second substrate which has a transparent
electrode, and a liquid crystal layer which is filled between said
two substrates and has a negative anisotropy in dielectric constant
wherein a homeotropic alignment is accomplished over said first
substrate, characterized in that said alignment over said first
substrate is accomplished at an angle of 40 to 50 degrees with
respect to any of the edges of an electrode on said first substrate
and a homeotropic alignment is accomplished over said second
substrate. In an embodiment of the present invention, it is
preferable that the angle formed through an alignment process is as
nearly 45 degrees as possible.
[0023] The second liquid crystal device of the present invention is
a liquid crystal device comprising a first substrate which has at
least rectangular or square electrodes divided into
microstructures, a second substrate which has a transparent
electrode, and a liquid crystal layer which is filled between said
two substrates and has a negative anisotropy in dielectric constant
wherein a homeotropic alignment is accomplished over said first
substrate, characterized in that a homogeneous alignment over said
second substrate is accomplished at an angle of 40 to 50 degrees
with respect to any of the edges of an electrode on said first
substrate. In another embodiment of the present invention, it is
preferable that the angle formed through an alignment process for
the second substrate is as nearly 45 degrees as possible with
respect to the edge of a pixel on the first substrate.
[0024] The third liquid crystal device of the present invention is
a reflection type liquid crystal device comprising a first
substrate which has at least rectangular or square reflecting
electrodes divided into microstructures, a second substrate which
has a transparent electrode, and a liquid crystal layer which is
filled between said first and second substrates and has a negative
anisotropy in dielectric constant and an anisotropy in refractive
index An between 0.07 and 0.15 wherein a homeotropic alignment is
accomplished over said first substrate, characterized in that said
alignment over said first substrate is accomplished at an angle of
40 to 50 degrees with respect to any of the edges of an electrode
on said first substrate and a homeotropic alignment is accomplished
over said second substrate. In still another embodiment of the
present invention, it is also preferable that the angle formed
through an alignment process is as nearly 45 degrees as
possible.
[0025] For any of the embodiments, such an alignment process may be
accomplished by rubbing, irradiation of polarized ultraviolet
light, irradiation of non-polarized ultraviolet light, or diagonal
evaporation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1A is a schematic perspective view of a liquid, crystal
device with no electric field applied, according to the present
invention;
[0027] FIG. 1B is a schematic perspective view of a liquid crystal
device with some electric field applied, according to the present
invention;
[0028] FIG. 2 is a diagram showing the direction of tilted liquid
crystal molecules around a pixel of the liquid crystal device
according to the present invention;
[0029] FIG. 3 shows cross sections illustrating the process steps
for manufacturing a liquid crystal device according to an
embodiment 1 of the present invention;
[0030] FIG. 4 shows cross sections illustrating the process steps
for manufacturing a liquid crystal device according to an
embodiment 2 of the present invention;
[0031] FIG. 5 is a schematic cross section showing a conventional
homeotropic cell;
[0032] FIG. 6 is a schematic cross section showing a conventional
hybrid cell; and
[0033] FIG. 7 is a schematic cross section showing that some
leakage of light occurs around a conventional pixel.
DESCRIPTION OF SYMBOLS
[0034] 24 . . . Glass Substrate, 25 . . . Pixel Electrode, 26 . . .
Liquid Crystal, 27 . . . ITO Electrode, 28 . . . Glass Substrate,
29 . . . Liquid Crystal Display Device, 30 . . . Arrow showing the
Direction of a Alignment Process, 31 . . . Polarizer, 32 . . .
Analyzer, 33 . . . Incident Light, 34 . . . Transmission Light, 35
. . . Liquid Crystal Molecule, 36 . . . Incident Light, 37 . . .
Arrow showing the Direction of a Alignment Process, 38 . . .
Substrate, 39 . . . Pixel Electrode, 40 . . . Liquid Crystal, 42 .
. . Liquid Crystal Molecule, 43 . . . Polarization Axis, 44 . . .
Glass Substrate, 45 . . . Transparent Conductive Film, 46 . . .
Input Light Shading Film, 47 . . . p-type a-Si:H Layer, 48 . . .
i-type a-Si:H Layer, 49 . . . n-type a-Si:H Layer, 50 . . . Square
Pixel, 51 . . . Al Reflecting Electrode, 52 . . . Al Output Light
Shading Film, 53 . . . Acrylic Resin Layer, 54 Polyimide Film for
Vertical Alignment, 55 . . . ITO Electrode, 56 . . . Glass
Substrate, 57 . . . Polyimide Film for Vertical Alignment, 58 . . .
Spherical Spacer, 59 . . . Nematic Liquid Crystal, 60 . . . Writing
Light, 61 . . . Polarizer, 62 . . . Reading Light, 63 . . . Light,
64 . . . Analyzer, 65 . . . Glass Substrate, 66 . . . Al Electrode,
67 . . . Glass Substrate, 68 . . . Transparent Conductive Film, 69
. . . Vertical Alignment Film, 70 . . . Vertical Alignment Film, 71
. . . Bead, 72 . . . Resin, 73 . . . Liquid Crystal, 74 . . . Cell,
75 . . . Polarization Beam Splitter, 76 . . . Incident Light, 77 .
. . Reflected Light
BEST MODE FOR CARRYING OUT THE INVENTION
[0035] Now, an embodiment of a liquid crystal display device of
homeotropic type according to the present invention will be
described below.
[0036] Among the liquid crystal devices of the present invention,
that of transmission type is a liquid crystal display device 29, as
shown in FIG. 1A, which includes a glass substrate 24, pixel
electrodes 25 aligned in a predetermined manner, liquid crystal
molecules 26 with a negative anisotropy in dielectric constant, an
ITO electrode 27 aligned in a predetermined manner, and a glass
substrate 28 and which is subject to an alignment process such as
rubbing in the direction shown by the arrow 30.
[0037] When a polarizer 31 and an analyzer 32 are placed so that
their axes are at an angle of 90 degrees with respect to each other
and at an angle of 45 degrees with respect to the direction 30 of
the alignment process as shown in FIG. 1A, the liquid crystal
molecules 26 are tilted in the direction 30 of the alignment
process as shown in FIG. 1B when a voltage is applied, and
therefore, the incident light 33 is doubly refracted by the liquid
crystal molecules 26 to transmit the light 34 and as a result, the
display will be in a bright state.
[0038] Now, consider the case where no light is transmitted (no
voltage is applied).
[0039] As shown in FIG. 1A, while no voltage is applied, any of the
liquid crystal molecules 35 around the pixel electrode 25 is
slightly tilted toward a direction parallel or perpendicular to the
edge of the pixel. However, for the liquid crystal device 29 of the
present embodiment, the direction 30 of the alignment process is
set to an angle between approximately 40 and 50 degrees with
respect to the edge of the pixel electrode 25.
[0040] In other words, since the optical axes of the polarizer 31
and the analyzer 32 are aligned in a direction substantially
parallel or perpendicular to the edge of the pixel electrode 25,
the incident light 36 is hardly subject to birefringence through
the tilted liquid crystal molecules 35 around the pixel electrode
25 and cannot pass through the analyzer 32, and therefore, any
leakage of light may hardly occur around the pixel electrode 25
with a very high contrast. Then, the present embodiment will be
described below in detail with reference to FIG. 2.
[0041] FIG. 2 is a top plan view of a liquid crystal cell according
to the present embodiment. In the figure, an arrow 37 shows the
direction of an alignment process, and a pixel electrode 39 and a
liquid crystal 40 are placed on a substrate 38, and the
longitudinal axis of each liquid crystal molecule 42 slightly
tilted around the pixel electrode 39 is shown by an arrow
therefor.
[0042] The polarization axis 43 of two polarizers is aligned in a
direction parallel or perpendicular to the edge of the pixel
electrode 39 through an alignment process in the direction shown by
the arrow 37. That is, while in a black display state with no
voltage applied, the longitudinal axis of each liquid crystal
molecule 42 around the pixel electrode 39 is tilted, and for any
molecule, the axis is in a direction parallel or perpendicular to
the polarization axis 43 of the polarizers, and thus, the incident
light is not affected by birefringence through the irregularly
aligned liquid crystal molecules 42 around the pixel electrode 39.
This will eventually yield a high contrast display with no leakage
of light.
[0043] It should be appreciated that the alignment process
according to the present invention may be accomplished by applying
an alignment film and rubbing it with cloth made of some material
such as rayon, by rubbing without application of any alignment
film, by ultraviolet irradiation, or by diagonal evaporation.
[0044] It has been described above that the angle for the alignment
process is set to be between 40 and 50 degrees, however, it should
be appreciated that an angle of 45 degrees is most preferable
because the display may not be affected by birefringence with no
leakage of light.
[0045] It should be also appreciated that for reflection type, a
retardation in tilted liquid crystals around the pixel electrode
may become very large when a material having a large anisotropy in
refractive index An, for example, 0.07 to 0.15 is used and that any
display which does not exploit the present invention may cause very
much leakage of light with a resulting low contrast. Therefore, it
should be apparent to those skilled in the art that the present
invention is very effective.
[0046] It should be also appreciated that the present invention may
bring about the same effect for a cell which has a homeotropic
alignment on one substrate with pixels and a homogeneous alignment
on the other substrate (that is, a hybrid type cell).
[0047] It should be further appreciated that the present invention
can be effective for any of the transmission and reflection types
of direct-vision display devices and projection display devices. In
addition, it should be appreciated that although glass substrates
have been used for the embodiments mentioned above, quarts or resin
substrates may be used on the transmission side and Si wafer
substrates may be used on the reflection side.
[0048] Moreover, transparent electrodes such as ITO and organic
conductive film may be used for the transmission type and Al, Ag,
increased reflectivity mirror, dielectric mirror, and any other
electrodes having a high reflectivity may be used for the
reflection type.
[0049] (Embodiment 1)
[0050] FIGS. 3 (1) through (7) are schematic cross sections
illustrating the process steps for manufacturing a liquid crystal
device according to the embodiment 1 of the present invention.
[0051] (1) On an optically-ground glass substrate 44 (75
mm.times.75 mm.times.1.1 mm), a transparent conductive film 45 was
formed to a thickness of 1000 .ANG. by sputtering indium tin oxide
(hereinafter referred to as ITO) onto it. Then, Cr was evaporated
on the surface of ITO 45 to a thickness of 500 .ANG. and it was
patterned through photolithography in a negative pattern which has
substantially 18 .mu.m-edge squares arranged at a pitch of 24 .mu.m
into a vertical delta matrix of 2783.times.1877. This pattern
constitutes a chromium input light shading film 46.
[0052] (2) On the whole surface, three layers comprising a p-type
a-Si:H layer 47 with boron added at 100 ppm (500 .ANG. thick), an
i-type a-Si:H layer 48 with no additive (1.5 .mu.m thick), and an
n-type a-Si:H layer 49 with phosphorus added at 1000 ppm (3000
.ANG. thick) were stacked on top of each other in this order
through plasma CVD to form a photoconductive layer of diode
structure.
[0053] Then, Cr was evaporated on the whole surface to a thickness
of 2000 .ANG. and it was patterned through photolithography in a
pattern 50 which has substantially 22 .mu.m-edge squares arranged
at a pitch of 24 .mu.m into a vertical delta matrix of
2783.times.1877 (in total, 5223691 squares).
[0054] (3) The exposed portions of the a-Si:H layer between Cr
square pixels 50 which serve as a mask for etching were
isotropically etched through chemical dry etching using a mixture
of CF.sub.4 and oxygen.
[0055] When the etching process progressed to a depth of
approximately 1.6 .mu.m, grooves were formed between the Cr pixels
with protruded portions of Cr serving like eaves for the
grooves.
[0056] (4) An Al layer was formed on the whole surface to a
thickness of 500 to 2000 .ANG. through electron-beam
evaporation.
[0057] Consequently, square Al reflection electrodes 51 of 500 to
2000 .ANG. thick were formed on the top of the square Cr pixels 50
and an Al output light shading film 52 was formed on the bottom
surface of each groove.
[0058] (5) Acrylic resin containing carbon was applied thereto
through spin coating. During this process, the grooves formed by
etching were filled with this resin and the Al electrodes 51 were
also covered with this resin.
[0059] The whole surface was etched through reactive ion etching
with oxygen to remove this resin uniformly and then this etching
process finished when the surface of each Al electrode 51 was
exposed.
[0060] Thus, the resin was removed completely from the surface of
each Al electrode 51 but an acrylic resin layer 53 containing
carbon remained within each groove.
[0061] (6) A vertical alignment polyimide film 54 was formed to a
thickness of 200 .ANG. as an alignment film. Similarly, another
polyimide film 57 for vertical alignment was formed to a thickness
of 200 .ANG. on a glass substrate 56 with an ITO electrode 55 which
will be the opposite substrate and then both substrates were rubbed
with nylon cloth.
[0062] The direction of rubbing was at an angle of 45 degrees with
respect to the edge of each pixel electrode on the polyimide film
54 and antiparallel to that angle on the other polyimide film
57.
[0063] (7) On the surface of the polyimide film 57 on the glass
substrate 56 with the ITO electrode 55, SiO.sub.2 spherical spacers
58 having a particle size of 2.0 .mu.m were dispersed through a
wet-spray method to stick it to the other glass substrate 44 as
processed above.
[0064] The liquid crystal cell formed as described above was placed
in a vacuum filling system and after pressure reduction, it was
heated to a temperature of 120.degree. C., nematic liquid crystals
59 having a negative anisotropy in dielectric constant and An=0.08
(manufactured by MERCK JAPAN) were filled by vacuum filling
process.
[0065] (8) Writing into the homeotropic type spacial light
modulator fabricated as described above was accomplished by using a
writing light 60 through the glass substrate 44 and reading from
that light modulator was accomplished by irradiating it with a
reading light 62 which passed through a polarizer 61 placed in a
position parallel or perpendicular to a certain edge of a pixel
electrode and through the glass substrate 56 and by using an
analyzer 64 to capture a light 63 reflected from the Al electrode
51 as an image.
[0066] As a result, no leakage of light occurred around the pixel
electrodes and a contrast ratio more than 500:1 was obtained.
[0067] (Embodiment 2)
[0068] FIGS. 4 (1) through (3) are schematic cross sections
illustrating the process steps for manufacturing a liquid crystal
device according to the embodiment 2 of the present invention.
[0069] (1) As shown in the figure, on an optically-ground glass
substrate 65 (75 mm.times.75 mm.times.1.1 mm), square Al electrodes
66 were arranged into a square matrix of 1024.times.768 through
photolithography.
[0070] On another optically-ground glass substrate 67 (75
mm.times.75 mm.times.1.1 mm), a transparent conductive film 68 was
formed to a thickness of 1000 .ANG. by sputtering ITO onto it.
[0071] (2) The substrates 65 and 67 were spin-coated with vertical
alignment films 69 and 70, respectively (those films may be applied
thereto through printing) and then the surface of the alignment
film on the glass substrate 65 with the Al electrode 66 was rubbed
with rubbing cloth made of rayon at an angle of 45 degrees with
respect to a certain edge of the electrode.
[0072] Furthermore, the alignment film over the other glass
substrate 67 was rubbed in a direction antiparallel to the rubbing
direction for the electrode side when the cell has been
assembled.
[0073] On the alignment film over the glass substrate 67, silica
beads 71 of 2.0 .mu.m were dispersed through a wet-spray method and
then the alignment film was sticked to the opposed alignment film
over the glass substrate 65 with resin 72.
[0074] Liquid crystals 73 having a negative anisotropy in
dielectric constant were filled by vacuum filling process into a
gap between the glass substrates 65 and 67 to form a homeotropic
type liquid crystal cell 74 having liquid crystal molecules aligned
in a direction substantially perpendicular to the substrates.
[0075] (3) When this cell 74 was observed under a crossed
polarizers with the microscope placed parallel to the edge of a
pixel while this cell 74 was not driven, no leakage of light could
be detected around the pixel electrodes.
[0076] When the optical axis of a polarization beam splitter 75 was
placed parallel to a certain edge of a pixel on the side of the
glass substrate 67 and then incident light 76 came into it to
project reflected light 77 onto a screen, the resulting contrast of
400:1 was obtained.
[0077] (Embodiment 3)
[0078] (1) On an optically-ground glass substrate (75 mm.times.75
mm.times.1.1 mm), rectangular Al electrodes were arranged into a
square matrix of 1024.times.768 through photolithography.
[0079] On another optically-ground glass substrate (75 mm.times.75
mm.times.1.1 mm), a transparent conductive film was formed to a
thickness of 1000 .ANG. by sputtering indium tin oxide (hereinafter
referred to as ITO) onto it.
[0080] (2) A glass substrate was spin-coated with a vertical
alignment film (this film may be applied thereto through printing)
and another glass substrate was covered with a homogeneous
alignment film. Then, the surface of the alignment film on the
glass substrate with an Al electrode was rubbed with rubbing cloth
made of rayon at an angle of 45 degrees with respect to a certain
edge of the electrode when the two substrates were sticked to each
other but it should be noted that the rubbing was performed on the
side with no Al electrode.
[0081] (3) On the alignment film over another glass substrate,
silica beads of 2.0 .mu.m were dispersed through a wet-spray mathod
and then the alignment film was sticked to the opposed alignment
film over the other glass substrate with resin.
[0082] (4) Liquid crystals having a negative anisotropy in
dielectric constant were filled by vacuum filling process into a
gap between the two glass substrates to form a hybrid type liquid
crystal cell having liquid crystal molecules on the side of the Al
electrode glass substrate aligned in a direction substantially
perpendicular to the substrate and liquid crystal molecules on the
side of the other glass substrate aligned in a direction
substantially parallel to the substrate.
[0083] (5) When this cell was observed under crossed polarizers
with the microscope placed parallel to the edge of a pixel while
this cell was not driven, no leakage of light could be detected
around the pixel electrodes.
[0084] (6) When the optical axis of a polarization beam splitter
was placed parallel to a certain edge of a pixel on the side of the
glass substrate with no Al electrode and then incident light came
into it to project reflected light onto a screen, the resulting
contrast of 320:1 was obtained.
[0085] Industrial Applicability
[0086] From the foregoing, the present invention is applicable to
homeotropic or hybrid alignment liquid crystal devices of any type
of transmission and reflection or direct-vision and projection, and
in particular, the present invention can advantageously eliminate
almost any leakage of light which would otherwise occur around
pixels in the prior art and therefore, provide an improved contrast
by rubbing the surface in a direction at an angle of 40 to 50
degrees with respect to any of the edges of a square or rectangular
electrode and by placing a polarizer in an appropriate
position.
* * * * *