U.S. patent application number 14/298243 was filed with the patent office on 2014-09-25 for photoalignment method and liquid crystal display.
The applicant listed for this patent is Samsung Display Co., Ltd.. Invention is credited to Soo-Ryun CHO, Baek-Kyun JEON, Suk-Hoon KANG, Sung-Yi KIM, Tae-Ho KIM, Jun-Woo LEE.
Application Number | 20140285759 14/298243 |
Document ID | / |
Family ID | 45564615 |
Filed Date | 2014-09-25 |
United States Patent
Application |
20140285759 |
Kind Code |
A1 |
KANG; Suk-Hoon ; et
al. |
September 25, 2014 |
PHOTOALIGNMENT METHOD AND LIQUID CRYSTAL DISPLAY
Abstract
A photoalignment method includes irradiating light in a first
direction to a first alignment layer, and irradiating light in a
second direction opposite the first direction, after disposing a
first mask on the first alignment layer.
Inventors: |
KANG; Suk-Hoon; (Seoul,
KR) ; JEON; Baek-Kyun; (Yongin-si, KR) ; LEE;
Jun-Woo; (Suwon-si, KR) ; KIM; Tae-Ho; (Seoul,
KR) ; KIM; Sung-Yi; (Gwangju-si, KR) ; CHO;
Soo-Ryun; (Gunpo-si, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Samsung Display Co., Ltd. |
Yongin-City |
|
KR |
|
|
Family ID: |
45564615 |
Appl. No.: |
14/298243 |
Filed: |
June 6, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13169438 |
Jun 27, 2011 |
8767154 |
|
|
14298243 |
|
|
|
|
Current U.S.
Class: |
349/123 |
Current CPC
Class: |
G02F 1/1337 20130101;
G02F 2001/133765 20130101; G02F 1/133753 20130101; G02F 2001/133761
20130101 |
Class at
Publication: |
349/123 |
International
Class: |
G02F 1/1337 20060101
G02F001/1337 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 10, 2010 |
KR |
10-2010-0077001 |
Claims
1. A liquid crystal display, comprising: a first substrate and a
second substrate facing each other; a first alignment layer and a
second alignment layer formed on the first substrate and the second
substrate, respectively, and a liquid crystal layer formed between
the first substrate and the second substrate and including liquid
crystal molecules, wherein the first alignment layer and the second
alignment layer are photoaligned via a photoalignment operation,
the first alignment layer and the second alignment layer include a
first irradiation region and a second irradiation region having
different light irradiation amounts during the photoalignment
operation, respectively, and an alignment direction of liquid
crystal molecules of a liquid crystal layer positioned in the first
irradiation region is different from an alignment direction of
liquid crystal molecules of a liquid crystal layer positioned in
the second irradiation region.
2. The liquid crystal display of claim 1, wherein: absolute values
of alignment polar angles of the liquid crystal molecules
positioned in the first irradiation region and the second
irradiation region are a same as or different from each other and
the alignment directions are opposite to each other.
3. The liquid crystal display of claim 1, wherein: a light
irradiation direction of the first alignment layer is disposed
vertical to alight irradiation direction of the second alignment
layer, and the liquid crystal molecules of the liquid crystal layer
form at least four regions having different alignment polar angles
of the liquid crystal molecules.
4. The liquid crystal display of claim 3, wherein: each of the at
least four regions is at least one of a cycle-type in which the
alignment direction of the liquid crystal molecules are cycled, a
central-type in which the alignment direction of the liquid crystal
molecules faces the center of the first alignment layer or the
second alignment layer, a diffusion type in which the alignment
direction of the liquid crystal molecules faces the edge of the
first alignment layer or the second alignment layer, and a
mixed-type including any combination thereof.
5. The liquid crystal display of claim 1, wherein: the first
alignment layer and the second alignment layer each comprise
cinnamate.
6. The liquid crystal display of claim 5, wherein: the first
alignment layer and the second alignment layer further comprise
benzene, and a ratio of cinnamate/benzene (C/B) of the first
alignment layer and the second alignment layer is in a range of
about 0<C/B<0.5.
7. The liquid crystal display of claim 1, further comprising: a
third irradiation region positioned between the first irradiation
region and the second irradiation region, wherein a polar angle of
the third irradiation region is smaller than polar angles of the
first irradiation region and the second irradiation region.
8. The liquid crystal display of claim 1, further comprising: a
third irradiation region positioned at edges of the first
irradiation region and the second irradiation region, wherein a
polar angle of the third irradiation region is smaller than polar
angles of the first irradiation region and the second irradiation
region.
Description
[0001] This application is a divisional of U.S. application Ser.
No. 13/169,438, filed on Jun. 27, 2011, which claims priority to
Korean Patent Application No. 10-2010-0077001 filed on Aug. 10,
2010, and all the benefits accruing therefrom under 35 U.S.C.
.sctn.119, the contents of which in their entirety are herein
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a photoalignment method and
a liquid crystal display utilizing the same.
[0004] 2. Description of the Related Art
[0005] A liquid crystal display ("LCD") typically includes two
display panels where a field generating electrode such as a pixel
electrode, and a common electrode are formed and a liquid crystal
layer interposed therebetween. The LCD generates an electric field
in an LC layer by applying voltage to the field generating
electrode, to determine orientations of LC molecules of the LC
layer and to control a polarization of incident light, thereby
resulting in the display of an image.
[0006] The LC molecules of the LCD may be initially aligned in a
predetermined direction by a conventional rubbing process. Even in
a vertically aligned LCD, liquid crystals have a pre-tilt angle by
rubbing, to determine a direction of the liquid crystals at the
time of applying the electric field.
[0007] A conventional method enabling the liquid crystals to have
the pre-tilt angle includes a contact-type rubbing method of
applying physical pressure to an alignment layer thereof by using a
roller, and a photoalignment method for forming the pre-tilt angle
by irradiating ultraviolet ("UV") light to the alignment layer.
There are drawbacks associated with the use of the conventional
photoalignment method. One drawback is that the UV irradiation
process may have to be performed several times in order to acquire
the liquid crystal alignment of various directions. A plurality of
masks is required when performing the UV irradiation process, to
form a plurality of domains. These masks may be repetitively used
based on the number of times the UV radiation process is performed.
If the plurality of masks is misaligned, the liquid crystal
alignment of the LCD may become distorted, thereby reducing
transmittance.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention obviates the above-mentioned drawbacks
by providing a method for photoalignment which reduces the number
of times the masks are used, and thereby prevents the reduction of
transmittance due to any misalignment of the masks.
[0009] According to one exemplary embodiment of the present
invention a photoalignment method is provided. The method includes
irradiating light in a first direction to a first alignment layer,
and irradiating light in a second direction opposite the first
direction, after disposing a first mask on the first alignment
layer.
[0010] According to one exemplary embodiment, a light irradiation
energy of the light irradiated in the second direction may be about
50% to about 500% of that in first direction.
[0011] According to one exemplary embodiment, the light irradiation
energy of the light irradiated in the second direction may be
different from that in the first direction.
[0012] According to another exemplary embodiment, the light
irradiation energy of the light irradiated in the first direction
may range from about 1 mJ to about 5000 mJ.
[0013] According to another exemplary embodiment, the light
irradiated in the first direction may be linearly polarized or
partially polarized.
[0014] According to another exemplary embodiment the light
irradiated in the first direction may be irradiated slantingly with
respect to the first alignment layer.
[0015] According to an exemplary embodiment, irradiation angles (T)
of the light irradiated in the first direction and the second
direction may be in the range of about 0<T<90.
[0016] According to an exemplary embodiment, the mask may include a
light blocking unit to partially shield a part of the first
alignment layer.
[0017] According to an exemplary embodiment, the light blocking
unit may be disposed in a predetermined pattern.
[0018] According to another exemplary embodiment, the light
blocking unit may be randomly disposed.
[0019] According to an exemplary embodiment, the mask may include
at least one of a light blocking region, a transmissive region, and
a transflective region.
[0020] According to an exemplary embodiment, the light blocking
region, the transmissive region, and the transflective region may
be disposed in a predetermined pattern.
[0021] According to an exemplary embodiment, the light blocking
region, the transmissive region, and the transflective region may
be disposed to form rows and columns.
[0022] According to an exemplary embodiment, the transflective
region may include two or more regions having different
transmittances from each other.
[0023] According to another exemplary embodiment, a light
transmittance of the transflective region may be greater than that
of the light blocking region and smaller than that of the
transmissive region.
[0024] According to an exemplary embodiment, the light blocking
region, the transmissive region, and the transflective region may
be randomly disposed.
[0025] According to an embodiment of present invention, the method
may further include irradiating light in a third direction to a
second alignment layer facing the first alignment layer, and
irradiating light in a fourth direction opposite direction the
third direction after disposing a second mask on the second
alignment layer. The first mask and the second mask may each
include the light blocking region and the transmissive region, and
patterns of the light blocking region and the transmissive region
of the first mask and the second mask may be different from each
other.
[0026] According to an exemplary embodiment, at least one of the
first mask and the second mask may further include the
transflective region.
[0027] According to an exemplary embodiment, at least one of the
first mask and the second mask may include at least one of the
light blocking region, the transmissive region, and the
transflective region.
[0028] According to an exemplary embodiment, the light blocking
region, the transmissive region, and the transflective region may
each be disposed in a predetermined pattern.
[0029] According to an exemplary embodiment, the light blocking
region, the transmissive region, and the transflective region may
be disposed to form rows and columns.
[0030] According to an exemplary embodiment, the transflective
region may include two or more regions having different
transmittances from each other.
[0031] According to an exemplary embodiment, a light transmittance
of the transflective region may be greater than that of the light
blocking region and smaller than that of the transmissive
region.
[0032] According to an exemplary embodiment, at least one of the
first mask and the second mask may include at least one of the
light blocking region, the transmissive region, and the
transflective region.
[0033] According to an exemplary embodiment, the light blocking
region, the transmissive region, and the transflective region may
be randomly disposed.
[0034] According to an exemplary embodiment, an ultraviolet ("UV")
wavelength of the irradiated light may range from about 270 nm to
about 360 nm.
[0035] According to another exemplary embodiment of the present
invention a liquid crystal display ("LCD") is provided. The LCD
includes a first substrate and a second substrate facing each
other, a first alignment layer and a second alignment layer formed
on the first substrate and the second substrate, respectively, and
a LC layer formed between the first substrate and the second
substrate and including liquid crystal molecules. The first
alignment layer and the second alignment layer are photoaligned via
a photoalignment operation, the first alignment layer and the
second alignment layer include a first irradiation region and a
second irradiation region having different light irradiation
amounts during the photoalignment operation, respectively, and an
alignment direction of liquid crystal molecules of a LC layer
positioned in the first irradiation region is different from an
alignment direction of liquid crystal molecules of a LC layer
positioned in the second irradiation region.
[0036] According to an exemplary embodiment, absolute values of
alignment polar angles of the liquid crystal molecules positioned
in the first irradiation region and the second irradiation region
may be the same as or different from each other, and the alignment
directions may be opposite to each other.
[0037] According to an exemplary embodiment, a light irradiation
direction of the first alignment layer may be disposed vertical to
a light irradiation direction of the second alignment layer, and
the liquid crystal molecules of the liquid crystal layer may form
at least four regions having different alignment polar angles of
the liquid crystal molecules from each other.
[0038] According to an exemplary embodiment, each of the four
regions may be at least one of a cycle-type in which the alignment
direction of the liquid crystal molecules are cycled, a
central-type in which the alignment direction of the liquid crystal
molecules faces the center of the first alignment layer or the
second alignment layer, a diffusion type in which the alignment
direction of the liquid crystal molecules faces the edge of the
first alignment layer or the second alignment layer, and a
mixed-type including at least one of them.
[0039] According to an exemplary embodiment, the first alignment
layer and the second alignment layer may include cinnamate.
[0040] According to another exemplary embodiment, the first
alignment layer and the second alignment layer may further include
benzene, and a ratio of cinnamate/benzene ("C/B") of the first
alignment layer and the second alignment layer may be in the range
of 0<C/B<0.5.
[0041] According to an exemplary embodiment, the liquid crystal
display may further include a third irradiation region positioned
between the first irradiation region and the second irradiation
region and a polar angle of the third irradiation region may be
smaller than polar angles of the first irradiation region and the
second irradiation region.
[0042] According to an exemplary embodiment, the liquid crystal
display may further include a third irradiation region positioned
at edges of the first irradiation region and the second irradiation
region and a polar angle of the third irradiation region may be
smaller than polar angles of the first irradiation region and the
second irradiation region.
[0043] According to yet another exemplary embodiment of the present
invention a method for photoalignment is provided. The method
includes performing a primary photoalignment by irradiating light
in a primary photoalignment direction onto a first alignment layer
and placing a first mask on the first alignment layer. The method
also includes performing secondary photoalignment by irradiating
light in a secondary photoalignment direction onto the first
alignment layer, the secondary photoalignment direction being
opposite to the primary photoalignment direction, wherein in
performing of the secondary photoalignment, exposure of the first
alignment layer to irradiating light is performed while fixing the
first alignment layer with respect to the first mask and then
moving the first mask or while fixing the first mask with respect
to the first alignment layer and then moving the first alignment
layer.
[0044] According to an exemplary embodiment, the first mask may
include a light blocking region and a plurality of transmissive
regions.
[0045] According to an exemplary embodiment, the widths of the
transmissive regions may be different from each other, and the
width of one of the transmissive regions may correspond to a length
in a movement direction of the first alignment layer in the
transmissive region.
[0046] According to an exemplary embodiment, the method may further
include performing a tertiary photoalignment by irradiating light
in a tertiary photoalignment direction onto a second alignment
layer facing the first alignment layer and placing a second mask on
the second alignment layer. The method may also include performing
a quaternary photoalignment by irradiating light in a quaternary
photoalignment direction onto the second alignment layer, the
quaternary photoalignment direction being opposite to the tertiary
photoalignment direction, wherein in the performing of the
quaternary photoalignment, exposure of the second alignment layer
to irradiating light may be performed while fixing the second
alignment layer with respect to the second mask and then moving the
second mask or while fixing the second mask with respect to the
second alignment layer and then moving the second alignment
layer.
[0047] According to an exemplary embodiment, the first mask may
include a light blocking region and a plurality of transmissive
regions.
[0048] According to an exemplary embodiment, the widths of the
transmissive regions may be different from each other, and the
width of one of the transmissive regions may correspond to a length
in a movement direction of the first alignment layer in the
transmissive region.
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] The patent or application file contains at least one drawing
executed in color. Copies of this patent or patent application
publication with color drawing(s) will be provided by the Office
upon request and payment of the necessary fee.
[0050] FIGS. 1 and 2 are diagrams illustrating an exemplary
embodiment of a photoalignment method according to the present
invention.
[0051] FIGS. 3 and 4 are diagrams illustrating a misalignment
occurring during a conventional photo alignment operation.
[0052] FIGS. 5 to 7 are diagrams illustrating an exemplary of a
misalignment occurring during a photoalignment according to the
present invention.
[0053] FIG. 8 is a flowchart illustrating an exemplary embodiment
of a method for manufacturing a liquid crystal cell of a liquid
crystal display according to the present invention.
[0054] FIG. 9 is a diagram illustrating an exemplary embodiment of
photoalignment of liquid crystal molecules after a photoalignment
operation according to the present invention.
[0055] FIG. 10 is a photograph illustrating a texture of
conventional a liquid crystal display.
[0056] FIG. 11 is a photograph illustrating an exemplary embodiment
of a texture of a liquid crystal display according to the present
invention.
[0057] FIG. 12 is an equivalent circuit diagram of an exemplary
embodiment of one pixel of a liquid crystal display according to
the present invention.
[0058] FIG. 13 is an exemplary embodiment of a layout view of a
liquid crystal display according to the present invention.
[0059] FIG. 14 is a cross-sectional view taken along line XIV-XIV
of FIG. 13.
[0060] FIGS. 15 to 17 are diagrams illustrating another exemplary
embodiment of a photoalignment method according to the present
invention.
[0061] FIGS. 18 to 28 are diagrams illustrating exemplary
embodiments of a photomask including various layouts of a light
blocking region, a transflective region, and a transmissive region
according to the present invention.
[0062] FIGS. 29A- to 34E are diagrams illustrating an exemplary
embodiments of a photoalignment method using the photomasks of
FIGS. 18 to 28 according to the present invention.
[0063] FIGS. 35 and 36 are diagrams showing exemplary embodiments
of a photomask according to the present invention.
[0064] FIG. 37 is a diagram showing an exemplary embodiment of a
pixel electrode and a photoalignment direction of a pixel formed
according to the present invention.
[0065] FIGS. 38A to 38E are diagrams for describing an exemplary
embodiment of a method for photoalignment by using the
photoalignment mask of FIG. 35.
[0066] FIGS. 39A to 39E are diagrams for describing an exemplary
embodiment of a method for photoalignment by using the
photoalignment mask of FIG. 36.
[0067] FIGS. 40 and 41 are diagrams showing exemplary embodiments
of a photomask according to the present invention.
[0068] FIG. 42 is a diagram for describing an exemplary embodiment
of a method for photoalignment according to the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0069] The invention now will be described more fully hereinafter
with reference to the accompanying drawings, in which various
embodiments are shown. This invention may, however, be embodied in
many different forms, and should not be construed as limited to the
embodiments set forth herein. Rather, these embodiments are
provided so that this disclosure will be thorough and complete, and
will fully convey the scope of the invention to those skilled in
the art. Like reference numerals designate refer to like elements
throughout.
[0070] It will be understood that when an element is referred to as
being "on" another element, it can be "directly on" another
element, there are no intervening elements present. As used herein,
the term "and/or" includes any and all combinations of one or more
of the associated listed items. It will be understood that,
although the terms "first," "second," "third" etc. may be used
herein to describe various elements, components, regions, layers
and/or sections, these elements, components, regions, layers and/or
sections should not be limited by these terms. These terms are only
used to distinguish one element, component, region, layer or
section from another element, component, region, layer or section.
Thus, "a first element," "component," "region," "layer" or
"section" discussed below could be termed a second element,
component, region, layer or section without departing from the
teachings herein.
[0071] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting. As
used herein, the singular forms "a," "an" and "the" are intended to
include the plural forms as well, unless the context clearly
indicates otherwise. It will be further understood that the terms
"comprises" and/or "comprising," or "includes" and/or "including"
when used in this specification, specify the presence of stated
features, regions, integers, steps, operations, elements, and/or
components, but do not preclude the presence or addition of one or
more other features, regions, integers, steps, operations,
elements, components, and/or groups thereof.
[0072] Furthermore, relative terms, such as "lower" or "bottom" and
"upper" or "top," may be used herein to describe one element's
relationship to another elements as illustrated in the Figures. It
will be understood that relative terms are intended to encompass
different orientations of the device in addition to the orientation
depicted in the Figures. For example, if the device in one of the
figures is turned over, elements described as being on the "lower"
side of other elements would then be oriented on "upper" sides of
the other elements. The exemplary term "lower," can therefore,
encompasses both an orientation of "lower" and "upper," depending
on the particular orientation of the figure. Similarly, if the
device in one of the figures is turned over, elements described as
"below" or "beneath" other elements would then be oriented "above"
the other elements. The exemplary terms "below" or "beneath" can,
therefore, encompass both an orientation of above and below.
[0073] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
disclosure belongs. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and the present
disclosure, and will not be interpreted in an idealized or overly
formal sense unless expressly so defined herein.
[0074] Exemplary embodiments are described herein with reference to
cross section illustrations that are schematic illustrations of
idealized embodiments. As such, variations from the shapes of the
illustrations as a result, for example, of manufacturing techniques
and/or tolerances, are to be expected. Thus, embodiments described
herein should not be construed as limited to the particular shapes
of regions as illustrated herein but are to include deviations in
shapes that result, for example, from manufacturing. For example, a
region illustrated or described as flat may, typically, have rough
and/or nonlinear features. Moreover, sharp angles that are
illustrated may be rounded. Thus, the regions illustrated in the
figures are schematic in nature and their shapes are not intended
to illustrate the precise shape of a region and are not intended to
limit the scope of the present claims.
[0075] FIGS. 1 and 2 are diagrams illustrating an exemplary
embodiment of a photoalignment method according to the present
invention.
[0076] As shown in FIGS. 1 and 2, the photoalignment method
according to an exemplary embodiment of the present invention. As
shown in FIG. 1 as a "first photoalignment" operation is performed
in which a total surface is exposed without a mask and a "second
photoalignment" operation in which light is irradiated to only a
partial region by using a mask. As shown in FIGS. 1 and 2 an arrow
represents a photoalignment direction.
[0077] As shown in FIG. 1, light is irradiated onto an alignment
layer 10 in a first direction, to form a first irradiation region
L1. According to an exemplary embodiment, an irradiation
ultraviolet (UV) wavelength ranges from about 270 nm to about 360
nm and the irradiation energy of the irradiated light is in the
range of about 1 mJ to about 5000 mJ.
[0078] According to an exemplary embodiment of the present
invention, the irradiated light may be linearly polarized
ultraviolet ("LPUV") or partially polarized ultraviolet. The LPUV
is irradiated at an angle oblique to a surface of the alignment
layer to have an effect as if the surface of the alignment layer is
rubbed in a predetermined direction. A method of irradiating the
LPUV obliquely to the surface of the alignment layer is performed
by tilting the alignment layer or tilting a linearly polarized
irradiation device.
[0079] Further, shown in FIG. 1, a "first photoalignment" operation
is performed by irradiating light in a first direction which may be
in any direction, but illustration purposes, in the exemplary
embodiment of the present invention, the first direction is from
the top to the bottom as indicated by the arrow shown.
[0080] Next, as shown in FIG. 2, the method further includes
disposing of a light blocking mask M corresponding to a portion of
the alignment layer 10, and performing a "second photoalignment"
operation to form a second irradiation region L2. The light
blocking mask M does not transmit light and shields half of the
first irradiation region L1. As further shown in FIG. 2, light is
then irradiated in a second direction (as indicated by the solid
arrow) opposite to the first direction (as indicated by the dotted
arrow).
[0081] As shown in FIG. 2, the light blocking mask M according to
the exemplary embodiment of the present invention is disposed to
cover half of the first irradiation region L1, but may be of
various sizes and shapes depending on the type of a domain to be
formed and may be formed for a light blocking unit to have a
predetermined pattern or to be randomly disposed within the mask
M.
[0082] According to an exemplary embodiment, a polar angle of the
alignment layer 110 may be controlled to have different values
depending on an irradiation energy amount and in the exemplary
embodiment of the present invention, the irradiation energy amount
of the light irradiated in the second direction may be greater than
that of the first direction, to form the first irradiation region
L1 and the second irradiation region L2 which have a first polar
angle and a second polar angle of different polarities.
[0083] Thus, according to an exemplary embodiment, an irradiation
energy of the light irradiated in the second direction is greater
than an irradiation energy of the light irradiated in the first
direction, to form the second irradiation region L2 such that the
first polar angle is a same angle as that of the second polar angle
and polarities of the first and second polar angles are opposite to
each other.
[0084] Table 1 illustrates a change of the polar angle depending on
irradiation energy of the light.
TABLE-US-00001 Photolithography condition 2.sup.nd Glass Alignment
1.sup.st (opposite-direction Pre-tilt No. layer (positive
direction) photolithography) angle #1 1035R1 50.degree., 50 mJ
50.degree./25 mJ -89.9 #2 50.degree./50 mJ -89.1 #3 50.degree./100
mJ -88.2 Ref. -- 88.3
[0085] Referring to Table 1, during the "first photoalignment"
operation, an irradiation energy amount of 50 mJ and at an
irradiation slope of 50.degree. and thereafter, the irradiation
energy amount is changed in the order of 25 mJ, 50 mJ, and 100 mJ,
second polar angles of the opposite polarity such as 89.9.degree.,
89.1.degree. and 88.2.degree. may be acquired. Herein, (-) means an
opposite direction.
[0086] When the second polar angle of the second irradiation region
L2 includes a pre-tilt angle of 89.9.degree. or 89.1.degree., which
has a direction opposite to and a value different from the first
polar angle when the first polar angle of the first irradiation
region L1 is 88.3.degree., for example, a luminance difference
between the irradiation regions L1 and L2 may occur. However, when
the second polar angle is of a value similar to the first polar
angle, e.g., 88.2.degree., the luminance difference between the
irradiation regions L1 and L2 decreases.
[0087] Therefore, as shown in Table 1, by irradiating light in the
second direction with an amount of irradiation energy for example,
two times greater than the irradiation energy amount of the light
irradiated in the first direction, the first polar angle and the
second polar angle may have the same value. However, since the
amount irradiation energy of the light irradiated in the second
direction may depend on a material of the alignment layer 110, an
irradiation angle, an irradiation intensity, and the like, it is
selected within the range of about 50% to about 500% of the
irradiation energy of the light irradiated in the first direction.
Therefore, according to the current exemplary embodiment, the first
polar angle and the second polar angle are of a same value.
[0088] As a result of the photoalignment method shown in FIGS. 1
and 2, according to an exemplary embodiment of the present
invention, a first irradiation region L1 and a second irradiation
region L2 which have different polar angles may be acquired. The
alignment polar angle as an angle at which liquid crystal molecules
form with a substrate, and a viewing angle may improve the response
speed of the liquid crystal molecules. Further, the viewing angle
may also be improved by forming various alignment polar angles.
[0089] FIGS. 3 and 4 are diagrams illustrating a misalignment
occurring during a conventional photoalignment operation while
FIGS. 5 to 7 are diagrams illustrating an exemplary embodiment of a
misalignment occurring during a photoalignment operation according
to the present invention.
[0090] As shown in FIGS. 3 and 4, in the conventional
photoalignment method, when a photoalignment operation is performed
in order to form the first irradiation region and the second
irradiation region having different polar angles, the
photoalignment operation is performed using different masks M1 and
M2 for each irradiation region. Therefore, when the misalignment
occurs in the case in which the mask M2 for forming the second
irradiation region L2 is disposed after forming the first
irradiation region L1, a third irradiation region L3 in which the
masks M1 and M2 are not overlapped with each other as shown in FIG.
3 and both masks M1 and M2 are overlapped with each other is formed
as shown in FIG. 4. The third irradiation region L3 has a polar
angle different from the first irradiation region L1 and the second
irradiation region L2 which have the polar angles to be aligned,
thus decreasing transmittance.
[0091] When the photoalignment method is performed as described in
the exemplary embodiment of the present invention, only shapes or
dimensions of the first irradiation region L1 and the second
irradiation region L2 are different, but the third irradiation
region L3 having an undesired polar angle is not generated as shown
in FIGS. 3 and 4, even though the misalignment occurs as shown in
FIGS. 5 to 7. As a result, when the photoalignment method is
performed as described in the exemplary embodiment of the present
invention, a decrease in transmittance is prevented.
[0092] According to an exemplary embodiment, a method of
manufacturing a liquid crystal cell for a liquid crystal display by
using a photoalignment method according to the present invention
will now be described.
[0093] FIG. 8 is a flowchart illustrating an exemplary embodiment
of a method for manufacturing a liquid crystal cell for a liquid
crystal display according to the present invention; and FIG. 9 is a
diagram illustrating an exemplary embodiment of a photoalignment of
liquid crystal molecules after performing a photoalignment
operation according to the present invention.
[0094] Referring to FIG. 8, in operations 102 and 202,
respectively, upper and lower mother substrates are formed.
According to an exemplary embodiment, the upper mother substrate
includes a common electrode, an alignment layer, and a color
filter. The lower mother substrate includes a thin film transistor,
a pixel electrode, and the alignment layer.
[0095] Next, at operations 104 and 204, respectively, a
photoalignment operation is performed on each of the lower mother
substrate and the upper mother substrate as shown in FIGS. 1 and 2,
respectively.
[0096] According to an exemplary embodiment, the alignment layer 10
may be made of a material containing cinnamate and the value of
cinnamate/benzene which is contained in the alignment layer 110
after the photoalignment operation may be about 0<CB<0.5.
[0097] The directions in which the photoalignment operations are
performed on the lower mother substrate and the upper mother
substrate are vertical to each other as shown in FIG. 9. The
alignment direction (as depicted by the linear arrow) of liquid
crystal molecules is determined to have an azimuth angle which is
inclined in a slanting direction with respect to the alignment
direction of the upper and lower mother substrates. The alignment
direction of the lower mother substrate is represented by an arrow
in the vertical direction, and the alignment direction of the upper
mother substrate is represented by an arrow in the horizontal
direction. Small domains Da, Db, Dc, and Dd having four different
azimuth angles are formed by a vector sum depending on the
alignment direction of both the upper and lower mother
substrates.
[0098] In the liquid crystal display, since transmittance becomes
the maximum at an alignment azimuth angle of about 45.degree., the
photoalignment is performed to be inclined at 45.degree. with
respect to a transmittance axis of a polarizer.
[0099] Referring back to FIG. 8, from operation 204 the process
continues to operation 206, where a sealant for preventing the
liquid crystals from being leaked is formed. According to an
exemplary embodiment, the sealant is made of a material for
combining the upper and lower mother substrates with each other and
defines a portion filled with the liquid crystals. According to one
exemplary embodiment, the sealant may be formed on the upper mother
substrate. According to an alternative exemplary embodiment, the
sealant may be formed on the lower mother substrate.
[0100] Next, at operation 208, the liquid crystals are dropped, and
from operation 208, the process continues to operation 300 where
the lower mother substrate and the upper mother substrate are
bonded to each other. From operation 300, the process continues to
operation 302 where a liquid crystal display assembly is separated
into liquid crystal cells by being scribed along a cut line. When
the liquid crystals are filled by a liquid crystal injection
method, the liquid crystal cells are separated and thereafter, the
liquid crystals are injected.
[0101] According to an exemplary embodiment of the present
invention, the liquid crystals may not be aligned by using
different masks for each domain. Therefore, the number of masks for
the photoalignment method may be reduced. Accordingly, a
photoalignment method may be simplified, and a manufacturing time
of the liquid crystal display may be shortened.
[0102] FIG. 10 is a photograph illustrating a texture of a
conventional LCD; and FIG. 11 is a photograph illustrating an
exemplary embodiment of a texture of a LCD according to the present
invention.
[0103] [In FIGS. 10 and 11, polar angles of two liquid crystal
displays are the same as 88.3.degree. and textures of the two
liquid crystal displays are the same.] Note to client: please
confirm the wording of this sentence.
[0104] Unlike the conventional photoalignment method, by using the
mask only in the "second photoalignment" operation according to an
exemplary embodiment of the present invention, a plurality of small
domains having different azimuth angles may be easily formed and
the texture is not increased as compared with that of the
conventional LCD. Thus, when the photoalignment operations are
performed as described in the exemplary embodiment of the present
invention, since the masks are not aligned during the second
photoalignment operation depending on the arrangement of the masks
during the first photoalignment operation, the present invention
may be free from the misalignment as compared with the conventional
photoalignment method. Further, during the second photoalignment
operation, since the masks may not be aligned depending on the
positions of the masks in the first photoalignment operation, an
arrangement time is decreased, thereby decreasing the processing
time. Further, as described above, since a third irradiation region
having an undesired polar angle is not generated in the present
invention, transmittance is increased.
[0105] Next, a liquid crystal display formed by using a method for
manufacturing a liquid crystal cell of the liquid crystal display
according to another exemplary embodiment of the present invention
will now be described in detail.
[0106] FIG. 12 is an equivalent circuit diagram illustrating an
exemplary embodiment of one pixel of a liquid crystal display
according to the present invention.
[0107] Referring to FIG. 12, the LCD includes signal lines
including a plurality of gate lines GL, a plurality of pair of data
lines DLa and DLb, and a plurality of storage electrode lines SL,
and a plurality of pixels PX connected thereto. The LCD further
includes a lower display panel 100 and an upper display panel 200,
and a liquid crystal layer 3 interposed therebetween.
[0108] According to an exemplary embodiment, each pixel PX includes
a pair of subpixels PXa and PXb. The subpixels PXa and PXb include
switching elements Qa and Qb and liquid crystal capacitors Clca and
Clcb, and storage capacitor Csta and Cstb.
[0109] According to an exemplary embodiment, the switching elements
Qa and Qb may each be a three-terminal element such as a thin film
transistor, and the like, which are provided on the lower display
panel 100 and include control terminals connected with the gate
line GL and input terminals connected with the data lines DLa and
DLb, and output terminals connected with the liquid crystal
capacitors Clca and Clcb and the storage capacitors Csta and
Cstb.
[0110] According to an exemplary embodiment, the liquid crystal
capacitors Clca and Clcb include subpixel electrodes 191a and 191b
and a common electrode 270 as two terminals and the liquid crystal
layer 3 interposed therebetween is formed by a dielectric
material.
[0111] According to an exemplary embodiment, the storage capacitors
Csta and Cstb that perform an auxiliary role of the liquid crystal
capacitors Clca and Clcb are configured by overlapping the storage
electrode line SL and the subpixel electrodes 191a and 191b that
are provided on the lower display panel 100 with each other with an
insulator interposed therebetween. A predetermined voltage such as
a common voltage Vcom or the like is applied to the storage
electrode line SL.
[0112] According to an exemplary embodiment, voltages charged in
the liquid crystal capacitors Clca and Clcb are set to show a
slight difference. For example, a data voltage applied to the
liquid crystal capacitor Clca may be set to be lower or higher than
a data voltage applied to the liquid crystal capacitor Clcb. Thus,
an image viewed from the side of the LCD may appear closer than an
image viewed from the front by appropriately adjusting the voltages
of liquid crystal capacitors Clca and Clcb, thereby improving the
side visibility of the LCD.
[0113] Referring to FIGS. 13 and 14 another exemplary embodiment of
a liquid crystal display according to the present invention will
now be described in more detail.
[0114] Specifically, FIG. 13 is a layout view of a liquid crystal
display according to an exemplary embodiment of the present
invention; and FIG. 14 is a cross-sectional view taken along line
XIV-XIV of FIG. 13.
[0115] Referring to FIGS. 13 and 14, the liquid crystal display
includes a lower display panel 100 and an upper display panel 200
which face each other and a liquid crystal layer 3 interposed
between two display panels 100 and 200.
[0116] First, an exemplary embodiment of the lower display panel
100 will be described.
[0117] A plurality of gate lines 121 and a plurality of storage
electrode lines 131 and 135 are formed on an insulation substrate
110.
[0118] According to an exemplary embodiment, the gate lines 121
transfer a gate signal and extend substantially in a horizontal
direction. Each gate line 121 includes a plurality of first gate
electrodes 124a and second gate electrodes 124b which protrude
upwards and a protrusion 122 which protrudes downwards.
[0119] The storage electrode lines 131 and 135 include a stem 131
which extends substantially in parallel to the gate line 121 and a
ring-type storage electrode 135. The width of a part of the storage
electrode 135 extends, and shapes and layouts of the storage
electrode lines 131 and 135 may be changed to various forms.
[0120] A gate insulating layer 140 as shown in FIG. 14 is formed on
the gate line 121 and the storage electrode lines 131 and 135. A
plurality of semiconductors 154a and 154b which are made of
amorphous or crystalline silicon are formed on the gate insulating
layer 140.
[0121] According to an exemplary embodiment, a plurality of pair of
ohmic contacts 163a, 163b, 165a, and 165b are formed on the
semiconductors 154a and 154b, respectively. The ohmic contacts
163a, 163b, 165a, and 165b may be made of a material such as
silicide or an n+ hydrogenated amorphous silicon doped with n-type
impurities in high concentration, for example.
[0122] A plurality of pair of data lines 171a and 171b and a
plurality of pair of first drain electrodes 175a and second drain
electrodes 175b may be formed on the ohmic contacts 163a, 163b,
165a, and 165b and the gate insulating layer 140.
[0123] According to an exemplary embodiment, the data lines 171a
and 171b transfer a data signal and may extend substantially in a
vertical direction to cross the gate line 121 and the stem 131 of
the storage electrode line. The data lines 171a and 171b include a
first source electrode 173a and a second source electrode 173b
which extend toward a first gate electrode 124a and a second gate
electrode 124b to be bent in a U shape. The first source electrode
173a and the second source electrode 173b face a first drain
electrode 175a and a second drain electrode 175b on the basis of
the first gate electrode 124a and the second gate electrode 124b,
respectively.
[0124] According to an exemplary embodiment, the first drain
electrode 175a and the second drain electrode 175b extend upwards
from ends which are surrounded by the first source electrode 173a
and the second source electrode 173b, respectively and the other
ends may have a large dimension for connecting other layers.
[0125] The shapes and layouts of the data lines 171a and 171b in
addition to the first drain electrode 175a and the second drain
electrode 175b may be varied as needed. The first gate electrode
124a, the first source electrode 173a, and the first drain
electrode 175a form a first switching element Qa (e.g., a thin film
transistor ("TFT") together with the first semiconductor 154a and
the second gate electrodes 124a and 124b, the second source
electrode 173b, and the second drain electrode 175b form a second
switching element Qb (e.g., a TFT) together with the second
semiconductor 154b.
[0126] According to an exemplary embodiment, channels of the
switching elements Qa and Qb are formed in the first semiconductor
154a between the first source electrode 173a and the first drain
electrode 175a and in the second semiconductor 154b between the
second source electrode 173b and the second drain electrode 175b,
respectively.
[0127] According to an exemplary embodiment, the ohmic contacts
163a, 163b, 165a, and 165b are provided only between the
semiconductors 154a and 154b therebelow and the data lines 171a and
171b and the drain electrodes 175a and 175b thereabove and reduce a
contact resistance therebetween. Parts which are exposed without
being covered by the data lines 171a and 171b and the drain
electrodes 175a and 175b are provided in the semiconductors 154a
and 154b in addition to spaces between the source electrodes 173a
and 173b and the drain electrodes 175a and 175b.
[0128] According to an exemplary embodiment, a lower passivation
layer 180p made of silicon nitride or silicon oxide, for example,
may be formed on the data lines 171a and 171b, the drain electrodes
175a and 175b, and the exposed parts of the semiconductors 154a and
154b.
[0129] Further, according to an exemplary embodiment, a color
filter 230 may be formed on the lower passivation layer 180p. The
color filter 230 elongates in a length direction of a pixel. The
color filter 230 may be formed by using a photolithography process
or using an inkjet printing method. If the color filter 230 is
formed by the inkjet printing method, a partition for containing
the color filter and the like may further be formed.
[0130] Further, an upper passivation layer 180q is formed on the
color filter 230. According to an exemplary embodiment, the upper
passivation layer 180q may be made of an in organic insulation or
an organic insulation and may include a flat surface. An example of
the inorganic insulation may include silicon nitride and silicon
oxide. The organic insulation may have photosensitivity and a
dielectric constant thereof may be about 4.0 or less. A plurality
of pixel electrodes 191 are formed on the upper passivation layer
180q.
[0131] According to an exemplary embodiment, each pixel electrode
191 includes a first subpixel electrode 191a and a second subpixel
electrode 191b which are separated from each other with a gap 95
interposed therebetween. The gap 95 is overlapped with the storage
electrode 135 to prevent light leakage due to the gap 95. The gap
95 may be bent depending on the form of the texture. Upper and
lower parts of two subpixel electrodes 191a and 191b engage in each
other with the gap 95 interposed therebetween by a bent part.
[0132] Further, a lower corner of the first subpixel electrode 191a
may have a substantially quadrangular shape which is concaved on
the boundary line between the first drain electrode 175a and the
second drain electrode 175b.
[0133] The first subpixel electrode 191a includes a protrusion 195a
which protrudes toward the first drain electrode 175a and is
physically and electrically connected with the first drain
electrode 175a through a contact hole 185a.
[0134] In addition, the second subpixel electrode 191b includes a
pair of branches 196 which extend along the data lines 171a and
171b. According to an exemplary embodiment, the branches 196 are
positioned between the first subpixel electrode 191a and the data
lines 171a and 171b and connected to a connector 197 on the bottom
of the first subpixel electrode 191a. Therefore, the first subpixel
electrode 191b is surrounded by the second subpixel electrode 191b,
the branches 196, and the connector 197. According to an exemplary
embodiment of the present invention, one of the branches 196 of the
second subpixel electrode 191b includes the protrusion 195b. The
protrusion 195b is physically and electrically connected with the
second drain electrode 175b through the contact hole 185b.
[0135] According to an exemplary embodiment, a dimension occupied
by the second subpixel electrode 191b may be greater than that
occupied by the first subpixel electrode 191a. Thus, the dimension
of the second subpixel electrode 191b may be about 1.0 to about 2.2
times greater than that of the first subpixel electrode 191a.
[0136] An upper boundary line of the second subpixel electrode 191b
is overlapped with a protrusion 122 of the previous gate line to
form a storage capacitor.
[0137] An alignment layer 11 is formed on the pixel electrode
191.
[0138] Next, the upper display panel 200 according to an exemplary
embodiment of the present invention will now be described.
[0139] Further as shown, a light blocking member 220 preventing
light leakage is formed on a transparent insulation substrate 210
in the upper display panel 200. The light blocking member 220 is
formed along the data lines 171a and 171b and includes a part
corresponding to the thin film transistor. In the exemplary
embodiment of the present invention, a light blocking member 220
which is overlapped with the gate line 121 is not formed, but a
light blocking member 220 corresponding to the gate line 121 may
further be formed.
[0140] In the exemplary embodiment of the present invention, the
light blocking member 220 is formed on an upper substrate, but may
be formed on a lower substrate.
[0141] A common electrode 270 is formed on an overall surface of
the light blocking member 220 and an alignment layer 21 is formed
on the common electrode 270.
[0142] According to an exemplary embodiment of the present
invention, a pixel of the liquid crystal display shown in FIGS. 13
and 14 is aligned by the photoalignment method of FIGS. 2 and 3
described above, and includes a plurality of small domains Da to Dd
which are aligned in various directions. In the exemplary
embodiment of the present invention, the small domains Da to Dd
corresponding to the first subpixel 191a and the second subpixel
electrode 191b, respectively are formed as shown in FIG. 13, but
the small domains Da to Dd may be formed to correspond to the pixel
electrode 191. That is, two domains of the small domains Da to Dd
are formed in a region corresponding to the first subpixel
electrode 191a and the rest two domains of the domains are formed
in the second subpixel electrode 191b.
[0143] In the above exemplary embodiment, four domains are formed
to have a cycle type layout in which a photoalignment direction is
progressed in one direction.
[0144] However, a method for forming various layouts by using
various masks will now be described.
[0145] FIGS. 15 and 16 are diagrams for describing another
exemplary embodiment of a photoalignment method according to the
present invention.
[0146] The photoalignment method of FIG. 15 is the same as the
photoalignment method shown in FIGS. 1 and 2. However, the mask M
including a light blocking region and a transmissive region is used
in the second photoalignment operation according as shown in FIGS.
1 and 2, but the photoalignment operation is performed using a mask
M including a transflective region in the second photoalignment
operation according to the photoalignment method of FIG. 15. The
photoalignment using the mask including the transflective region
may be progressed on only one of the lower display panel or the
upper display panel or may be progressed on both the display
panels.
[0147] More specifically, first, a first irradiation region R1 is
formed by performing a first photoalignment operation on the
alignment layer 10 as shown in FIG. 15. According to an exemplary
embodiment, the irradiation UV wavelength is in the range of about
270 nm to about 360 nm and the irradiation energy of UV is in the
range of about 1 mJ to about 5000 mJ.
[0148] In the first photoalignment operation, light is irradiated
in a first direction which may be any direction, and is linearly
polarized.
[0149] When the first photoalignment operation is performed, the
alignment direction of liquid crystal molecules is inclined to
include a first polar angle .theta.1 with respect to a substrate
surface as shown in FIG. 15.
[0150] Next, as shown in FIG. 16, the mask M corresponding to a
part of the alignment layer 10 is disposed. Further, the second
photoalignment operation is performed with the linearly polarized
light to form a second irradiation region R2 having polar angles
.theta.2 and .theta.3 which are different from the first angle
.theta.1. The mask M includes a light blocking region which does
not transmit light, the transflective region which transmits only
part of light, and the transmissive region which transmits the
entire light. During the second photoalignment operation light is
irradiated at in a second direction which is opposite to the first
direction.
[0151] The light blocking region, the transflective region, and the
transmissive region of the mask M shown in FIG. 16 may be
separately disposed with the same dimension and as shown in FIG. 2,
the transmissive region may be disposed to correspond to a half of
the first irradiation region R1.
[0152] According to an exemplary embodiment of the present
invention, the light blocking region, the transflective region, and
the transmissive region of the mask may be formed to have various
dimensions and shapes depending on the form of a domain to be
formed and the light blocking region and the transflective region
are may be formed to have a predetermined pattern or to be randomly
disposed in the mask.
[0153] Since the polar angle of the alignment layer has different
values depending on the energy amount as shown in FIGS. 1 and 2,
the irradiation energy amount may be adjusted using the mask
including the transflective region as described in the exemplary
embodiment of the present invention.
[0154] According to an exemplary embodiment, when the second
photoalignment operation is performed as shown in FIG. 16, regions
having different polar angles .theta.1, .theta.2, and .theta.3 of
liquid crystal molecules are formed depending on the corresponding
region of the mask as shown in FIG. 17.
[0155] That is, as shown in FIG. 15, the liquid crystal molecules
which are aligned only in one direction while the first irradiation
have a changed alignment to have an opposite direction to the first
polar angle .theta.1 depending on irradiation energy while the
second irradiation, as a result, the liquid crystal molecules are
aligned to have the second polar angle .theta.2 and the third polar
angle .theta.3.
[0156] According to an exemplary embodiment of the present
invention, a slope may be diversified depending on the
transmittance of the transflective region, and when the
transmittance of the transflective region is about 50% and the
irradiation energy amount is two times greater than that in the
first irradiation, most of liquid crystal molecules in a part
corresponding to the transflective region may be aligned
substantially vertical to the substrate and liquid crystal
molecules in a part corresponding to the transmissive region may be
aligned opposite to the polar angle of liquid crystal molecules in
a part corresponding to the light blocking region.
[0157] Now referring to FIGS. 18 to 34E, various liquid crystal
molecule alignments resulting from the performance of the
photoalignment method described above will now be described.
[0158] FIGS. 18 to 28 are diagrams illustrating exemplary
embodiments of a photomask including various layouts of a light
blocking region T0, a transflective region T1, T2, and a
transmissive region T3 according to of the present invention; and
FIGS. 29A to 34E are diagrams illustrating an exemplary embodiment
of a photoalignment method using the photomask of FIGS. 18 to 28
according to the present invention.
[0159] The photomask shown in FIGS. 18 and 19 may include a light
blocking region T0 and a transmissive region T3 which each form two
columns and one row or may be disposed to form one column and four
rows like the photomask shown in FIG. 20.
[0160] In addition, according to an exemplary embodiment, the
photomask shown in FIGS. 21 to 28 includes a transflective region
T1, T2 in addition to the light blocking region T0 and the
transmissive region T3.
[0161] According to an exemplary embodiment, the transflective
region T1, T2 of FIGS. 21 to 28 may be divided into a first
transflective region T1 and a second transflective region T2
depending on a light transmission level. A light transmission
amount in the first transflective region T1 may be smaller than
that in the second transflective region T2. The light transmission
amounts of the first transflective region T1 and the second
transflective region T2 may be variably set in the range of about
0%<transmittance of T1, T2<100% depending on the alignment
direction of liquid crystal molecules to be formed. For example,
the light transmission amount in the first transflective region T1
may be set to about 25% and the light transmission amount in the
second transflective region T2 may be set to about 75% or the light
transmission amount in the first transflective region T1 may be set
to about 30% and the light transmission amount in the second
transflective region T2 may be set to about 70%.
[0162] According to an exemplary embodiment, the light blocking
region T0, the transmissive region T3, and the transflective region
T1, T2, the light blocking region T0, the first transflective
region T1, the second transflective region T2, and the transmissive
region T3 may be arranged in sequence as shown in FIG. 21.
Alternately, as shown in FIG. 22, the first transflective region
T1, the transmissive region T3, the light blocking region T0, and
the second transflective region T2 may be arranged in sequence, or
as shown in FIG. 23, the transmissive region T3, the light blocking
region T0, the second transflective region T2, and the first
transflective region T1 may be arranged in sequence.
[0163] Alternately, as shown in FIG. 24, according to another
exemplary embodiment, the light region T0 and the transmissive
region T3 may be alternately arranged not to include the
transflective region.
[0164] The transmissive region T3, the light blocking region T0,
and the transflective region T1, T2 may be divided into smaller
regions as shown in FIGS. 25 to 28.
[0165] The photomask of FIGS. 25 to 28 is disposed for the light
blocking region T0, the transmissive region T3, and the
transflective region T1, T2 to form two columns and four rows.
[0166] According to an exemplary embodiment, the light blocking
region T0, the transmissive region T3, and the transflective
regions T1 and T2 may have various sizes and layouts and may be
variously divided depending on the form and size of the domain.
[0167] A photoalignment method by using the above-identified
photomask will now be described in detail.
[0168] A photoalignment operation is performed on each of an upper
alignment layer and a lower alignment layer. Any one of two
alignment layers may be aligned as one of the photomasks of FIGS.
18 to 20 and the other one may be aligned as one of the photomasks
of FIGS. 21 to 28.
[0169] As shown in FIG. 29A, a first photoalignment operation is
performed on the lower alignment layer 11 without the photomask.
The light is irradiated in a first direction which may be any
direction, and for better comprehension and ease of description,
light is irradiated from the bottom to the top in FIG. 29A.
[0170] Thereafter, as shown in FIG. 29B, the photomask of FIG. 18
is disposed on the lower alignment layer 11 and a second
photoalignment operation is then performed. The light is irradiated
in a second direction that is opposite to the first direction.
[0171] For better comprehension, the irradiation direction of the
light is displayed as an arrow and irradiation energy transferred
to the alignment layer 11 is displayed by changing thickness of the
arrow. The greater the thickness of a straight line of the arrow
is, the more the light energy is transferred to the alignment layer
11.
[0172] Next, according to an exemplary embodiment, a third
photoalignment operation is performed on the upper alignment layer
21 without the photomask as shown in FIG. 29C. The light is
irradiated in a third direction vertical to the first
direction.
[0173] In addition, according to an exemplary embodiment, the
photomask of FIG. 21 is disposed on the upper alignment layer 21
and thereafter, a fourth photoalignment operation is performed as
shown in FIG. 29D. The light is irradiated in a fourth direction
that is opposite to the third direction.
[0174] According to an exemplary embodiment, when the upper and
lower alignment layers 11 and 21 are aligned using the photomasks
of FIGS. 18 and 21, eight regions having different alignment
directions may be formed as shown in FIG. 29E. Specifically, four
regions which are disposed at the center of the alignment layer
form a first group G1 and four regions which form the first group
G1 are arranged in the cycle-type liquid crystal alignment.
[0175] In addition, four regions which are positioned in upper and
lower parts of the first group G1 form a second group G2 and four
regions which form the second group G2 are arranged in the
cycle-type liquid crystal alignment in the same direction as the
first group G1.
[0176] According to an exemplary embodiment, absolute values of
alignment azimuth angles of the first group G1 and the second group
G2 are different from each other and the absolute value of the
azimuth angle of the first group G1 may be greater than that of the
azimuth angle of the second group G2.
[0177] FIGS. 30A-30E depict a diagram illustrating photoalignment
method performed using the photomasks of FIGS. 23 and 27. The
photoalignment method of FIGS. 30A-30E is similar to the
photoalignment method of FIGS. 29A-29E.
[0178] That is, as shown in FIGS. 30A and 30C, a first
photoalignment operation of the lower alignment layer 11 and a
third photoalignment operation of the upper alignment layer 21 are
performed without the photomask. However, a second photoalignment
operation is performed using the photomask of FIG. 27 as shown in
FIG. 30B and a fourth photoalignment operation is performed using
the photomask of FIG. 23 as shown in FIG. 30D.
[0179] As such, when the photoalignment operations are performed
using the photomasks of FIGS. 23 and 27, the alignment of the
liquid crystal molecules in which the cycling direction of the
first group G1 and the cycling direction of the second group G2 are
opposite to each other may be acquired as shown in FIG. 30E.
According to an exemplary embodiment, the absolute value of the
azimuth angle of the first group G1 and the absolute value of the
azimuth angle of the second group G2 may be different from each
other.
[0180] FIG. 31A illustrates a photoalignment method performed using
the photomasks of FIGS. 19 and 21 which is similar to the
photoalignment method of FIGS. 29A-29E.
[0181] That is, as shown in FIGS. 31A and 31C, a first
photoalignment operation of the lower alignment layer 11 and a
third photoalignment operation of the upper alignment layer 21 are
performed without the photomask. However, a second photoalignment
operation is performed using the photomask of FIG. 21 as shown in
FIG. 31B and a fourth photoalignment operation is performed using
the photomask of FIG. 19 as shown in FIG. 31D.
[0182] According to an exemplary embodiment, when the
photoalignment operation is performed using the photomask of FIGS.
19 and 21, the alignment of the liquid crystal molecules which has
a direction diffused from the center of each of the groups G1 and
G2 to the outside may be acquired as shown in FIG. 31E. The
absolute value of the azimuth angle of the first group G1 and the
absolute value of the azimuth angle of the second group G2 may be
different from each other.
[0183] FIGS. 32A-32E illustrate a photoalignment method using the
photomasks of FIGS. 20 and 28 which is similar to the
photoalignment method of FIG. 29.
[0184] That is, as shown in FIGS. 32A and 32C, a first
photoalignment operation of the lower alignment layer 11 and a
third photoalignment operation of the upper alignment layer 21 are
performed without the photomask. However, the second photoalignment
operation is performed using the photomask of FIG. 20 as shown in
FIG. 32B and the fourth photoalignment operation is performed using
the photomask of FIG. 28 as shown in FIG. 32D.
[0185] According to an exemplary embodiment, when the
photoalignment method is performed using the photomask of FIGS. 20
and 28, the first group G1 forms a centralized alignment which is
aligned from the outside to the center and the second group G2
forms a diffused alignment as shown in FIG. 32E. In this case, In
this case, the absolute value of the azimuth angle of the first
group G1 and the absolute value of the azimuth angle of the second
group G2 may be different from each other.
[0186] FIGS. 33A-33E illustrate a photoalignment method using the
photomasks of FIGS. 18 and 23, which is similar to the
photoalignment method of FIG. 27.
[0187] That is, as shown in FIGS. 33A and 33C, a first
photoalignment operation of the lower alignment layer 11 and a
third photoalignment operation of the upper alignment layer 21 are
performed without the photomask. However, a second photoalignment
operation is performed using the photomask of FIG. 18 as shown in
FIG. 33B and the fourth photoalignment operation is performed using
the photomask of FIG. 23 as shown in FIG. 33D.
[0188] According to an exemplary embodiment, when the
photoalignment method is performed using the photomask of FIGS. 18
and 23, the first group G1 includes parts which are aligned in both
the central type and the diffusion type and the second group G2
forms the cycle-type alignment as shown in FIG. 33E. Further, the
absolute value of the azimuth angle of the first group G1 and the
absolute value of the azimuth angle of the second group G2 may be
different from each other.
[0189] FIGS. 34A-34E illustrate a photoalignment method using the
photomasks of FIGS. 18 and 24, which is similar to the
photoalignment method of FIG. 29.
[0190] That is, as shown in FIGS. 34A and 34C, a second
photoalignment operation of the lower alignment layer 11 and third
photoalignment operation of the upper alignment layer 21 are
performed without the photomask. However, a second photoalignment
operation is performed using the photomask of FIG. 18 as shown in
FIG. 34B and a fourth photoalignment operation is performed using
the photomask of FIG. 24 as shown in FIG. 34D.
[0191] According to an exemplary embodiment, when the
photoalignment method is performed using the photomask of FIGS. 18
and 23, the first group G1 and the second group G2 may include
parts which are aligned in both the central type and the diffusion
type as shown in FIG. 34E. Further, the absolute value of the
azimuth angle of the first group G1 and the absolute value of the
azimuth angle of the second group G2 may be different from each
other.
[0192] According to an exemplary embodiment, regarding the first
group G1 and the second group G2 of FIGS. 29 to 34, the first group
G1 may correspond to the lower part of the first pixel electrode
shown in FIG. 13. According to another exemplary embodiment, the
first group G1 and the second group G2 may be applied even to the
second pixel electrode 191b and separately positioned in the upper
and lower parts of the second pixel electrode 191b based on the
first pixel electrode 191a.
[0193] According to an exemplary embodiment, the photomasks of
FIGS. 18 to 28 may be appropriately combined and used depending on
the division shape of the domain or pixel electrode to be
formed.
[0194] In an exemplary embodiment, when the above-mentioned pattern
of the photoalignment mask is formed more variously, it is possible
to effectively prevent the formation of the texture more
effectively.
[0195] FIGS. 35 and 36 are diagrams showing exemmplary embodiments
of a photomask according to the present invention.
[0196] The photomask of FIG. 35 includes a first transmittance
region T4, a second transmittance region T5 and a third
transmittance region T6. The first, the second and the third
transmittance regions T4, T5 and T6, respectively, have different
transmittances.
[0197] In an exemplary embodiment, the transmittance of the first
transmittance region T4 may be less than the second transmittance
region T5, which may be less than the third transmittance region
T6.
[0198] In an exemplary embodiment, when the first transmittance
region T4 is a light blocking region having transmittance of 0% and
the third transmittance region T6 is a transmissive region having
transmittance of about 100%, the transmittance of the second
transmittance region T5 may be from 0% to about 100%.
[0199] Further, when both the second transmittance region T5 and
the third transmittance region T6 are transflective regions, the
transmittance of the third transmittance region T6 may be higher
than that of the second transmittance region T5.
[0200] In an exemplary embodiment, the first transmittance region
T4 and the second transmittance region T5 are disposed adjacent to
each other horizontally and bisect a pixel horizontally.
[0201] In addition, the third transmittance region T6 is positioned
parallel to to the first transmittance region T4 and the second
transmittance region T5 and disposed at a position where the
texture is generated.
[0202] The photomask of FIG. 36 includes the first transmittance
region T4, the second transmittance region T5, and the third
transmittance region T6 like the photomask of FIG. 35.
[0203] In an exemplary embodiment, the first transmittance region
T4 and the second transmittance region T5 are disposed adjacent to
each other horizontally and bisect the pixel horizontally.
[0204] In addition, the third transmittance region T6 is positioned
between the first transmittance region T4 and the second
transmittance region T5 and disposed at the position where the
texture is generated.
[0205] Hereinafter, an exemplary embodiment of a method for
photoalignment by using the photoalignment masks of FIGS. 35 and 36
will be described in detail with reference to FIGS. 37 to 39.
[0206] FIG. 37 is a diagram showing an exemplary embodiment of a
pixel electrode and a photoalignment direction of a pixel formed
according to the present invention.
[0207] FIGS. 38A to 38E are diagrams for describing an exemplary
embodiment of a method for photoalignment by using the
photoalignment mask of FIG. 35.
[0208] FIGS. 39A to 39E are diagrams for describing an exemplary
embodiment of a method for photoalignment by using the
photoalignment mask of FIG. 36. Referring to FIGS. 12-14 and 37,
the pixel electrode 191 includes two subpixel electrodes 191a and
191b positioned in upper and lower parts of the pixel electrode
191. Each of the subpixel electrodes 191a and 191b includes four
domains and liquid crystal molecules of four domains form
circulating alignment.
[0209] In an exemplary embodiment, the texture may be generated in
a part where an alignment direction of the liquid crystal molecules
aligned by an electric field formed by an edge boundary line of the
pixel electrode 191 and an alignment direction of the liquid
crystal molecules in a domain are different from each other. For
ease of description, this part will be hereinafter referred to as a
first texture region TL1.
[0210] In addition, the texture may be generated in a part where
the alignment directions of the liquid crystal molecules of two
adjacent domains are opposite to each other. For ease of
description, this part will be hereinafter referred to as a second
texture region TL2.
[0211] First, an exemplary embodiment of a photoalignment method
for reducing the first texture region by using the photomask of
FIG. 35 will be described with reference to FIG. 38. Specifically,
first, as shown in FIG. 38A, a primary photoalignment is performed
on the entirety of a lower alignment layer 11 through whole
exposure of lower alignment layer 11. A method for the primary
photoalignment is the same as the photalignment method of FIG.
1.
[0212] In addition, as shown in FIG. 38B, the photomask of FIG. 35
is disposed and thereafter, a secondary photoalignment is performed
in an opposite direction to the primary photoalignment direction.
In an exemplary embodiment, the third transmittance region T6 of
the photomask is disposed to correspond to the first texture region
TL1.
[0213] Next, as shown in FIG. 38C, a tertiary photoalignment is
performed on an upper alignment layer 21 without the photoalignment
mask. In an exemplary embodiment, an irradiation direction of light
is vertical to the primary photoalignment direction.
[0214] In addition, the photoalignment mask of FIG. 35 is disposed
on the upper alignment layer 21 and thereafter, as shown in FIG.
38D, a quaternary photoalignment is performed. In an exemplary
embodiment, the irradiation direction of the light is opposite to
the tertiary photoalignment direction. As such, when the
photoalignment is performed using the photoalignment mask of FIG.
35, a plurality of domains having different alignment directions
are formed as shown in FIGS. 37 and 38E.
[0215] In an exemplary embodiment, when the pixel is bisected
vertically, 6 domains positioned in the upper part constitute a
third group G3 and 6 domains positioned in the lower part
constitute a fourth group G4. Each of the third group G3 and the
fourth group G4 forms circulating liquid crystal alignment
placement.
[0216] In an exemplary embodiment, an alignment polar angle of
liquid crystal molecules positioned in the first texture region TL1
is different from an alignment polar angle of liquid crystal
molecules of domains De, Df, Dg, and Dh. That is, as shown in FIGS.
15 to 17, a degree in which the liquid crystal molecules are
aligned in the opposite direction varies depending on the energy of
light irradiated when the secondary photoalignment is performed in
an opposite direction after the primary photoalignment.
[0217] In an exemplary embodiment, the third transmittance region
T6 having the highest transmittance is placed in the first texture
region TL1 to transfer much more exposure energy to the first
texture region TL1 than the domains De, Df, Dg, and Dh. Therefore,
the liquid molecules positioned in the first texture region TL1 are
more slant and have the smaller polar angle than the liquid crystal
molecules positioned in the domains De, Df, Dg, and Dh. As such,
when the polar angle of the liquid crystal molecules of the first
texture region TL1 is smaller than the polar angle of the liquid
crystal molecules of the domains De, Df, Dg, and Dh, it is possible
to minimize distortion of the alignment of the liquid crystal
molecules due to the electric field formed at the edge of the pixel
electrode.
[0218] Next, a photoalignment method for reducing the second
texture region by using the photomask of FIG. 36 will be described
with reference to FIGS. 39A to 39E. Specifically, first, as shown
in FIG. 39A, the primary photoalignment is performed on the
entirety of the lower alignment layer 11 through whole exposure.
The photoalignment method is the same as the photoalignment method
of FIG. 1.
[0219] In addition, as shown in FIG. 39B, the photomask of FIG. 36
is disposed and thereafter, the secondary photoalignment is
performed in the opposite direction to the primary photoalignment
direction. In an exemplary embodiment, the third transmittance
region T3 of the photomask is disposed to correspond to a second
texture region TL2.
[0220] Next, as shown in FIG. 39C, the tertiary photoalignment is
performed on the upper alignment layer 21 without the
photoalignment mask. In an exemplary embodiment, the irradiation
direction of the light is vertical to the primary photoalignment
direction.
[0221] In addition, the photomask of FIG. 36 is disposed on the
upper alignment layer 21 and thereafter, as shown in FIG. 39D, the
quaternary photoalignment is performed. In an exemplary embodiment,
the irradiation direction of the light is opposite to the tertiary
photoalignment direction. As such, when the photoalignment is
performed using the photoalignment mask of FIG. 36, the plurality
of domains having the circulating alignment are formed in the upper
and lower parts thereof as shown in FIGS. 37 and 39E.
[0222] In an exemplary embodiment, the liquid crystal molecules
positioned in the second texture region TL2 have the same azimuth
angle as the domains Dg and Dh positioned at the right side around
the second texture region TL2. However, the polar angle of the
liquid crystal molecules positioned in the second texture region
TL2 may be smaller than the polar angle of the liquid crystal
molecules of the domains Dg and Dh positioned at the right side,
and may be the same as the polar angle of the liquid crystal
molecules of the domains De and Df positioned at the left side and
the alignment direction of the liquid crystal molecules may be
opposite to the alignment direction of the liquid crystal molecules
of the domains De and Df.
[0223] In an exemplary embodiment, although the exposure energy
varies by diversifying the transmittance of the photomask, a method
of diversifying the exposure energy by only the light blocking
region and the transmissive region will be hereinafter described in
detail with reference to FIGS. 40 to 42.
[0224] FIGS. 40 and 41 are diagrams showing exemplary embodiments
of a photomask according to the present invention.
[0225] The photomasks shown in FIGS. 40 and 41 include a fourth
transmittance region T7, a fifth transmittance region T8, a sixth
transmittance region T9 and a seventh transmittance region T10,
each which are constituted by the light blocking region and the
transmissive region.
[0226] The fourth transmittance region T7 is formed by only the
light blocking region having transmittance of 0% and the seventh
transmittance region T10 is formed by only the transmissive region
having transmittance of about 100%.
[0227] In addition, both the fifth transmittance region T8 and the
sixth transmittance region T9 include the transmissive region and
the light blocking region and are opposite to each other in the
sizes of the transmissive region and the light blocking region. In
an exemplary embodiment, the size of the light blocking region of
the fifth transmittance region T8 is the same as the size of the
transmissive region of the sixth transmittance region T9 and the
size of the transmissive region of the fifth transmittance region
T8 is the same as the size of the light blocking region of the
sixth transmittance region T9. Therefore, the photomasks of FIGS.
40 and 41 are inversely symmetric to each other around a virtual
vertical center line bisecting the photomask horizontally. As such,
the exposure energy in the photoalignment may be diversified by
varying the size of the transmissive region as will be described in
detail with reference to FIG. 42 and FIG. 40 described above.
[0228] FIG. 42 is a diagram for describing an exemplary embodiment
of a method for photoalignment according to the present
invention.
[0229] Referring to FIG. 42, first, the photomask MP of FIG. 40 is
fixed onto the upper or lower alignment layer. In addition, the
photoalignment is performed while moving an alignment layer 111 in
an arrow direction.
[0230] In an exemplary embodiment, the alignment layer 111 may be
fixed and the photomask MP may be moved. As such, the alignment
layer corresponding to the transmissive region T8 is exposed by the
light while passing through the transmissive region T8. In an
exemplary embodiment, since a time and an area in which the
alignment layer 111 is exposed by the light vary depending on the
width of the transmissive region T8, energy transferred to the
alignment layer 11 also varies. In an exemplary embodiment, the
width of the transmissive region corresponds to the length of the
transmissive region in a movement direction of the alignment layer
111.
[0231] Accordingly, exposure may be made with various energies by
diversifying the size of the transmissive region T8, and as a
result, domains having various polar angles and azimuth angles may
be formed.
[0232] As described in the exemplary embodiments of the present
invention, the photoalignment masks are combined by various methods
to arrange the liquid crystal molecules in various directions. As
such, when the photoalignment is variously formed, the visibility
and transmittance of the liquid crystal display can be improved. In
addition, when ions generated at the time of driving each pixel
concentrates on any one point, an afterimage, and the like may
occur, but it is possible to prevent the ions in the pixel from
concentrating in any one direction by aligning the liquid crystals
in various directions as described in the exemplary embodiments of
the present invention. Therefore, since the afterimage which is
caused due to the ions does not occur, it is possible to improve
the response speed of the pixel.
[0233] According to the exemplary embodiments of the present
invention, since the number of times a mask is used can be reduced
by performing the photoalignment method according to the present
invention, it is possible to reduce a process time for aligning the
mask. In addition, since an alignment margin for aligning the mask
which is repetitively used can be reduced, it is possible to design
the mask to be free from misalignment. Further, since an undesired
region by the misalignment is not generated, it is possible to
minimize the reduction of transmittance.
[0234] Further, since liquid crystal alignment of various
directions can be acquired using a photomask including a
transflective region, the visibility and transmittance of a liquid
crystal display are improved and an afterimage is reduced.
[0235] While this invention has been described in connection with
what is presently considered to be practical exemplary embodiments,
it is to be understood that the invention is not limited to the
disclosed embodiments, but, on the contrary, is intended to cover
various modifications and equivalent arrangements included within
the spirit and scope of the appended claims.
* * * * *