U.S. patent application number 16/630804 was filed with the patent office on 2020-05-07 for liquid crystal panel and manufacturing method thereof.
The applicant listed for this patent is LG CHEM, LTD.. Invention is credited to Gae Sung KIM, Keon Woo KIM, Yoo Bin KIM, Young Gon KIM, Young Tae KIM, Eung Ki LEE, Hyun Soo LEE.
Application Number | 20200142256 16/630804 |
Document ID | / |
Family ID | 65002175 |
Filed Date | 2020-05-07 |
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United States Patent
Application |
20200142256 |
Kind Code |
A1 |
KIM; Gae Sung ; et
al. |
May 7, 2020 |
LIQUID CRYSTAL PANEL AND MANUFACTURING METHOD THEREOF
Abstract
The present invention relates to a liquid crystal panel and a
method for manufacturing the same, and according to one aspect of
the present invention, there is provided a liquid crystal panel
comprising a liquid crystal cell having a first surface and a
second surface opposite to the first surface, a first polarizing
plate provided on the first surface and a second polarizing plate
provided on the second surface, where each of the first and second
polarizing plates includes a polarizer layer and a low moisture
permeable base layer bonded to the polarizer layer, and a flexural
balance between the first polarizing plate and the second
polarizing plate is controlled by adjusting shrinkage force of the
first polarizing plate and the second polarizing plate.
Inventors: |
KIM; Gae Sung; (Daejeon,
KR) ; LEE; Eung Ki; (Daejeon, KR) ; KIM; Young
Gon; (Daejeon, KR) ; LEE; Hyun Soo; (Daejeon,
KR) ; KIM; Yoo Bin; (Daejeon, KR) ; KIM; Keon
Woo; (Daejeon, KR) ; KIM; Young Tae; (Daejeon,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
LG CHEM, LTD. |
Seoul |
|
KR |
|
|
Family ID: |
65002175 |
Appl. No.: |
16/630804 |
Filed: |
July 16, 2018 |
PCT Filed: |
July 16, 2018 |
PCT NO: |
PCT/KR2018/008021 |
371 Date: |
January 13, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02F 2202/28 20130101;
G02B 5/3033 20130101; G02B 1/14 20150115; G02F 1/133528 20130101;
C09J 7/38 20180101; G02B 5/3041 20130101; B29D 11/00644 20130101;
G02F 2201/501 20130101; G02F 2201/54 20130101; G02B 5/30 20130101;
G02F 2201/50 20130101 |
International
Class: |
G02F 1/1335 20060101
G02F001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 14, 2017 |
KR |
10-2017-0089485 |
Jul 16, 2017 |
KR |
10-2017-0081996 |
Claims
1. A liquid crystal panel comprising: a liquid crystal cell having
a first surface and a second surface opposite to the first surface;
a first polarizing plate provided on the first surface; and a
second polarizing plate provided on the second surface, wherein the
first and second polarizing plates each comprise a polarizer layer
and a low moisture permeable base layer bonded to the polarizer
layer, and wherein the liquid crystal panel satisfies Equation 1:
|.alpha..sub.MD-.alpha..sub.TD|.ltoreq.1 [Equation 1] wherein,
.alpha..sub.MD is a value determined by Equation 2 and
.alpha..sub.TD is a value determined by Equation 3:
.alpha..sub.MD=(sum of absorption axial bending moments acting on
each layer of the first polarizing plate)/(sum of transmission
axial bending moments acting on each layer of the second polarizing
plate) [Equation 2] .alpha..sub.TD=(sum of transmission axial
bending moments acting on each layer of the first polarizing
plate)/(sum of absorption axial bending moments acting on each
layer of the second polarizing plate) [Equation 3] wherein; the
absorption axial bending moment acting on each layer is determined
by the product of the distance from the center of the liquid
crystal panel to the center of the relevant layer and the
absorption axial shrinkage force acting on the relevant layer, and
wherein the transmission axial bending moment acting on each layer
is determined by the product of the distance from the center of the
liquid crystal panel to the center of the relevant layer and the
transmission axial shrinkage force acting on the relevant
layer.
2. The liquid crystal panel according to claim 1, wherein each of
.alpha..sub.MD and .alpha..sub.TD is a value of 0.8 to 1.2.
3. The liquid crystal panel according to claim 2, Wherein each of
.alpha..sub.MD and .alpha..sub.TD is a value of 0.85 to 1.15.
4. The liquid crystal panel according to claim 1, wherein each of
.alpha..sub.MD and .alpha..sub.TD is 1.
5. The liquid crystal panel according to claim 1, wherein
.alpha..sub.MD and .alpha..sub.TD have the same value.
6. The liquid crystal panel according to claim 1, wherein the
liquid crystal panel satisfies Equation 4:
(.alpha..sub.MD-1)(.alpha..sub.TD-1).ltoreq.0. [Equation 4]
7. The liquid crystal panel according to claim 1, wherein the
shrinkage force is determined based on a shrinkage ratio.
8. The liquid crystal panel according to claim 1, wherein the
polarizer layer has an absorption axial shrinkage force of 5N to 9N
when the polarizer layer is kept at 80.degree. C. for 2 hours.
9. The liquid crystal panel according to claim 1, wherein the low
moisture permeable base layer has a transmission axial shrinkage
force of 3N to 10N when the low moisture permeable base layer is
kept at 80.degree. C. for 2 hours.
10. The liquid crystal panel according to claim 1, wherein the
polarizer layer and the low moisture permeable base layer are
bonded to each other via a UV adhesive layer.
11. The liquid crystal panel according to claim 1, wherein the
numbers of layers constituting the first polarizing plate and the
second polarizing plate, respectively, are the same.
12. The liquid crystal panel according to claim 1, wherein the
numbers of layers constituting the first polarizing plate and the
second polarizing plate, respectively, are different.
13. A method for manufacturing a liquid crystal panel comprising:
attaching a first polarizing plate and a second polarizing plate to
both surfaces of a liquid crystal cell, respectively, wherein the
first and second polarizing plates each comprise a polarizer layer
and a low moisture permeable base layer bonded to the polarizer
layer, and wherein the method further comprises a step of producing
the first and second polarizing plates so that the liquid crystal
panel satisfies Equation 1:
|.alpha..sub.MD-.alpha..sub.TD|.ltoreq.1 [Equation 1] wherein,
.alpha..sub.MD is a value determined by Equation 2 and
.alpha..sub.TD is a value determined by Equation 3:
.alpha..sub.MD=(sum of absorption axial bending moments acting on
each layer of the first polarizing plate)/(sum of transmission
axial bending moments acting on each layer of the second polarizing
plate) [Equation 2] .alpha..sub.TD=(sum of transmission axial
bending moments acting on each layer of the first polarizing
plate)/(sum of absorption axial bending moments acting on each
layer of the second polarizing plate) [Equation 3] wherein the
absorption axial bending moment acting on each layer is determined
by the product of the distance from the center of the liquid
crystal panel to the center of the relevant layer and the
absorption axial shrinkage force acting on the relevant layer, and
wherein the transmission axial bending moment acting on each layer
is determined by the product of the distance from the center of the
liquid crystal panel to the center of the relevant layer and the
transmission axial shrinkage force acting on the relevant
layer.
14. The method for manufacturing a liquid crystal panel according
to claim 13, wherein each of .alpha..sub.MD and .alpha..sub.TD is a
value of 0.8 to 1.2.
15. The method for manufacturing a liquid crystal panel according
to claim 14, wherein each of .alpha..sub.MD and .alpha..sub.TD is a
value of 0.85 to 1.15.
16. The method for manufacturing a liquid crystal panel according
to claim 13, wherein each of .alpha..sub.MD and .alpha..sub.TD is
1.
17. The method for manufacturing a liquid crystal panel according
to claim 13, wherein the liquid crystal panel satisfies Equation 4:
(.alpha..sub.MD-1)(.alpha..sub.TD-1).ltoreq.0 [Equation 4]
18. The method for manufacturing a liquid crystal panel according
to claim 13, wherein the polarizer layer has an absorption axial
shrinkage force of 5N to 9N when the polarizer layer is kept at
80.degree. C. for 2 hours.
19. The method for manufacturing a liquid crystal panel according
to claim 13, wherein the low moisture permeable base layer has a
transmission axial shrinkage force of 3N to 10N when the low
moisture permeable base layer is kept at 80.degree. C. for 2 hours.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a National Stage Application of
International Application No. PCT/KR2018/008021, filed on Jul. 16,
2018, which claims the benefit of priority based on Korean Patent
Application No. 10-2017-0089485 filed on Jul. 14, 2017 and Korean
Patent Application No. 10-2018-0081996 filed on Jul. 16, 2018, the
disclosures of which are incorporated herein by reference in their
entirety.
TECHNICAL FIELD
[0002] The present invention relates to a liquid crystal panel and
a method for manufacturing the same.
BACKGROUND ART
[0003] A liquid crystal display device is a display for visualizing
polarized light due to the switching effect of the liquid crystals,
which is used in various categories ranging from a small and
medium-sized display such as a computer, a notebook, an electronic
watch and a portable terminal to a large-sized TV.
[0004] A large number of polarizing plates that have been
mass-produced and put into practical use for display devices at
present are those obtained by bonding a protective film, which is
optically transparent and also has mechanical strength, to both
sides or one side of a polarizing film (polarizer) formed by dyeing
a polyvinyl alcohol-based film with iodine or a dichroic material
such as a dichroic dye and crosslinking the film with a boron
compound, followed by stretching and orientation.
[0005] However, the stretched polyvinyl alcohol-based film has a
problem that shrinkage deformation easily occurs under a durability
condition such as high temperature and high humidity. If the
polarizer is deformed, the stress affects the protective film and
the liquid crystal cell to cause warpage, and as a result, there
arise problems such as a change in physical properties of the
polarizing plate comprising them and a light leakage phenomenon in
the liquid crystal display device.
DISCLOSURE
Technical Problem
[0006] It is a problem to be solved by the present invention to
provide a liquid crystal panel that can adjust a flexural balance
of upper/lower polarizing plates through adjustment of shrinkage
force of polarizing plates and a method for manufacturing the
same.
Technical Solution
[0007] To solve the above-described problem, a liquid crystal panel
is provided, which comprises a liquid crystal cell having a first
surface and a second surface opposite to the first surface; a first
polarizing plate provided on the first surface; and a second
polarizing plate provided on the second surface, wherein the first
and second polarizing plates each comprise a polarizer layer and a
low moisture permeable base layer bonded to the polarizer layer,
and satisfies Equation 1 below.
|.alpha..sub.MD-.alpha..sub.TD|.ltoreq.1 [Equation 1]
[0008] In Equation 1, .alpha..sub.MD is a value determined by
Equation 2 and .alpha..sub.TD is a value determined by Equation
3:
.alpha..sub.MD=(sum of absorption axial bending moments acting on
each layer of the first polarizing plate)/(sum of transmission
axial bending moments acting on each layer of the second polarizing
plate) [Equation 2]
.alpha..sub.TD=(sum of transmission axial bending moments acting on
each layer of the first polarizing plate)/(sum of absorption axial
bending moments acting on each layer of the second polarizing
plate) [Equation 3]
[0009] In Equations 2 and 3, the absorption axial bending moment
acting on each layer is determined by the product of the distance
from the center of the liquid crystal panel to the center of the
relevant layer and the absorption axial shrinkage force acting on
the relevant layer, and
[0010] the transmission axial bending moment acting on each layer
is determined by the product of the distance from the center of the
liquid crystal panel to the center of the relevant layer and the
transmission axial shrinkage force acting on the relevant
layer.
Advantageous Effects
[0011] As described above, the liquid crystal panel and the method
for manufacturing the same related to at least one embodiment of
the present invention have the following effects.
[0012] The flexural balance of the upper/lower polarizing plates
can be adjusted through the adjustment of the shrinkage force of
the polarizing plate.
[0013] Furthermore, cracks of the polarizing plate can be
prevented, and the light leakage phenomenon of the liquid crystal
display device can be prevented.
BRIEF DESCRIPTION OF DRAWINGS
[0014] FIG. 1 is a schematic sectional diagram showing a liquid
crystal panel.
[0015] FIG. 2 shows bending evaluation results of a polarizing
plate.
[0016] FIG. 3 is a conceptual diagram for explaining Equations 1
and 2.
MODE FOR INVENTION
[0017] Hereinafter, a liquid crystal panel according to one
embodiment of the present invention and a method for manufacturing
the same will be described in detail with reference to the
accompanying drawings.
[0018] In addition, the same or similar reference numerals are
given to the same or corresponding components regardless of
reference numerals, of which redundant explanations will be
omitted, and for convenience of explanation, the size and shape of
each constituent member as shown may be exaggerated or reduced.
[0019] FIG. 1 is a schematic sectional diagram showing a liquid
crystal panel (10).
[0020] In addition, FIG. 2 shows bending evaluation results of a
polarizing plate, and FIG. 3 is a conceptual diagram for explaining
Equations 1 and 2.
[0021] Referring to FIG. 1, the liquid crystal panel (10) related
to one embodiment of the present invention comprises a liquid
crystal cell (100) having a first surface (101) and a second
surface (102) opposite to the first surface (101), a first
polarizing plate (200) provided on the first surface (101) and a
second polarizing plate (300) provided on the second surface
(102).
[0022] Also, the first and second polarizing plates (200, 300)
comprise polarizer layers (210, 310) and low moisture permeable
base layers (220, 320) bonded to the polarizer layers (210, 310),
respectively. In addition, in the first and second polarizing
plates (200, 300), the polarizer layers (210, 310) and the low
moisture permeable base layers (220, 320) may be bonded via UV
adhesive layers (230, 330). When the first and second polarizing
plates (200, 300) are bonded to the liquid crystal cell (100), the
first and second polarizing plates (200, 300) each are bonded to
the liquid crystal cell (100) such that the polarizer layers (210,
310) are adjacent to the liquid crystal cell (100) as compared with
the low moisture permeable base layers (220, 320).
[0023] In this document, the MD direction represents the absorption
axis direction and the TD direction represents the transmission
axis direction.
[0024] Also, the first and second polarizing plates (200, 300) may
comprise each a protective layer (240, 340) and an adhesive layer
(250, 350). Each of the polarizing plates (200, 300) may be bonded
to the liquid crystal cell (100) via the adhesive layers (250,
350). In addition, in the liquid crystal panel (10), the low
moisture permeable base layers (220, 320) are located on the
outside. Each of the first and second polarizing plates (200, 300)
may have a thickness of 200 .mu.m or less.
[0025] Furthermore, the polarizer layers (210, 310) may each have a
first surface and a second surface opposite to the first surface.
Here, the first surface represents the surface facing the liquid
crystal cell (100). UV adhesive layers (230, 330) are each provided
on the second surfaces of the polarizer layers (210, 310) and low
moisture permeable base layers (220, 320) are provided on the UV
adhesive layers (230, 330). Also, protective layers (240, 340) are
each provided on the first surfaces of the polarizer layers (210,
310) and pressure-sensitive adhesive layers (250, 350) are provided
on the protective layers (240, 340).
[0026] In addition, the low moisture permeable base layers (220,
320) may be formed of a resin material having transmittance of 90%
or more, may have a thickness of 100 .mu.m or less, and may have
moisture permeability of 50 g/m.sup.2 day or less. The moisture
permeability means an amount that the moisture passes through a
certain external environment per unit time and unit area, which can
be usually measured in an environment where the humidity difference
between the inside and the outside of the film is 90% at 40.degree.
C., and the moisture permeability described herein is a result
measured by a WVTR instrument (instrument name: WVTR TSY-T3) from
Labthink. The instrument has a structure in which a balance is
placed in a closed chamber, and the environment in the chamber is
maintained at 40.degree. C. and a humidity of 10%. Furthermore,
water is poured into the moisture permeable cup, and then the low
moisture permeable base film is covered and fixed thereon. The
humidity inside the moisture permeable cup is 100% because it is
filled with water, so that the humidity difference between inside
and outside of the moisture permeable cup becomes 90%. After 24
hours, the weight of the moisture permeable cup can be measured to
calculate the amount of the evaporated water through the difference
with the initial weight.
[0027] Furthermore, the low moisture permeable base layers (220,
320) may be formed of polyester (PET). Also, the low moisture
permeable base layers (220, 320) may have TD direction shrinkage
force of 3N to 10N and may have TD direction shrinkage force of
more than 3N and less than 10N.
[0028] On the other hand, the shrinkage force can be measured by a
DMA measuring instrument from TA Corporation. For example, the
measuring instrument has no temperature acceleration condition,
starts at 25.degree. C., reaches 75.degree. C. after 3 minutes and
is stabilized at 80.degree. C. after 7 minutes. The measurement
time is 2 hours (120 minutes), and the value is measured 120
minutes after stabilization at 80.degree. C. In the measurement
method, a sample is clamped to the clamp, and pulled and fixed so
as to maintain strain 0.1% under a preload of 0.01N, and then the
shrinkage force applied upon maintaining the strain 0.1% at a high
temperature is measured. The sample is made to have a width of
about 5.3 mm and a length of about 15 mm, and both ends of the
sample in the longitudinal direction are fixed to the clamp of the
measuring instrument, and then the shrinkage force is measured.
Here, the sample length of 15 mm is the length excluding the
portion to be fixed to the clamp.
[0029] Referring to FIG. 2 and Tables 1 and 2, the base materials A
to C constitute low moisture permeable base layers, which are low
moisture permeable base materials that only TD thermal shrinkage
properties are different and other properties are the same. At this
time, the shrinkage force is data measured at 80.degree. C. for 2
hours using the DMA measuring instrument from TA Corporation.
[0030] The polarizer layers and the low moisture permeable base
layers used in Categories 1 to 5 of Table 2 and FIG. 2 are as
follows. In Categories 1 to 5, the polarizer layers are all the
same and the low moisture permeable base layers have a difference
only in the TD direction shrinkage force.
[0031] With respect to the polarizing plates (upper polarizing
plate and lower polarizing plate), a PET film (MD shrinkage force:
0 to 1N, TD shrinkage force: 4 to 12N (Categories 1 to 5),
thickness: 80 .mu.m) as a polarizer layer was attached to one side
of a PVA polarizing film (MD shrinkage force: 8N, thickness: 17
.mu.m) as a low moisture base layer using an epoxy-based
ultraviolet curable adhesive (thickness: 2 to 3 .mu.m). Upon the
attachment, the TD direction of the PET film and the MD direction
(absorption axis direction) of the PVA polarizing film were
attached so as to be substantially perpendicular to each other.
Subsequently, a hard coating layer was formed to a thickness of
about 5 to 7 .mu.m using a material containing an epoxy compound
and an oxetane compound on the surface of the PVA polarizing film
to which the PET film was not attached. Thereafter, an acrylic
pressure-sensitive adhesive layer having a thickness of about 25
.mu.m was formed in the lower part of the hard coating layer to
produce a polarizing plate.
[0032] The upper polarizing plate was attached to the upper surface
of a general 32 inch LCD (liquid crystal display) panel (liquid
crystal cell, thickness: about 400 .mu.m) through a
pressure-sensitive adhesive layer, and the lower polarizing plate
was attached to the lower surface through a pressure-sensitive
adhesive layer.
[0033] Subsequently, the LCD panel was introduced into a chamber at
a temperature of 60.degree. C. for 72 hours, taken out, and the
panel change amounts at the elapsed time of 2 hours and the elapsed
time of 24 hours were measured and summarized in Table 3 below, and
the results were described in FIG. 1 (flatness after 24 hours). In
Table 3 below, the term flatness is a difference between the
portion of the liquid crystal panel that is most bent toward the
upper polarizing plate (for example, the first polarizing plate)
and the portion that is most bent toward the lower polarizing plate
(for example, the second polarizing plate), and this flatness can
be confirmed by using a known three-dimensional measuring machine
(Dukin Co., Ltd.).
TABLE-US-00001 TABLE 1 Product After 2 hours After 24 hours Base
Drying shrinkage force Initial (Out 2 hrs) (Out 2 hrs) Category
material condition MD (N) TD (N) MD/TD Flatness Flatness Change
amount Flatness Change amount 1 A .alpha. 8 4 2 1.5 -3.1 -4.6 -3.1
-4.6 2 B .gamma. 6 1.3 1.0 -2.7 -3.7 -2.7 -3.7 3 .beta. 8 1 2.2 2.0
-0.2 1.8 -0.4 4 .alpha. 10 0.8 1.5 2.8 1.3 2.7 1.2 5 C .alpha. 12
0.6 2.3 3.2 0.9 3.1 0.8
TABLE-US-00002 TABLE 2 Drying condition .alpha. X .beta. Tg +
20.degree. C. .gamma. Tg + 30.degree. C.
[0034] In [Table 2], a of the drying conditions represents a case
where drying is not performed, .beta. represents a case where
drying is performed at a temperature of Tg+20.degree. C., and
.gamma. represents a case where drying is performed at a
temperature of Tg+30.degree. C. That is, when the low moisture
permeable base layer runs in the facility, it can be dried at the
above temperature to adjust the TD direction shrinkage force
(transmission axial shrinkage force).
[0035] In summary, the shape of the flatness changes according to
the base material having different TD thermal shrinkage properties
of the low moisture permeable base layer, where it can be confirmed
that the flatness is improved when the TD thermal shrinkage
properties are further controlled by changing the drying
temperature condition.
[0036] Also, the polarizer layers (210, 220) may have a thickness
of less than 25 .mu.m, a polarization degree of 99% or more and
transmittance of 40% or more, and may be formed of PVA.
Furthermore, the polarizer layers (210, 220) may have MD direction
shrinkage force of 5N to 9N. In addition, the polarizer layers
(210, 220) may have MD direction shrinkage force of more than 5N
and less than 9N. The polarizer layers (210, 220) are provided by
stretching them in the MD direction, and when the MD direction
shrinkage force has a value larger than the above range, there is a
high possibility that heat-resistant cracks are generated.
[0037] On the other hand, the UV adhesive layers (230, 330) may
have a thickness of 1 .mu.m to 4 .mu.m, and the protective layers
(240, 340) may have a thickness of 3 .mu.m to 9 .mu.m.
[0038] In this document, the MD direction (absorption axis
direction) represents the machine direction, the TD direction
(transmission axis direction) represents the traverse direction,
and the MD direction and the TD direction are orthogonal to each
other.
[0039] Also, in the state where the first polarizing plate (200)
and the second polarizing plate (300) are attached to both surfaces
of the liquid crystal cell (100), respectively, the MD direction of
the first polarizing plate (200) is the same as the TD direction of
the second polarizing plate, and the TD direction of the first
polarizing plate (200) is the same as the MD direction of the
second polarizing plate.
[0040] Furthermore, the numbers of layers constituting the first
polarizing plate (200) and the second polarizing plate (300),
respectively, may be the same. For example, the first polarizing
plate (200) and the second polarizing plate (300) may have the same
layer structure.
[0041] Alternatively, the numbers of layers constituting the first
polarizing plate (200) and the second polarizing plate (300),
respectively, may be different. For example, the first polarizing
plate (200) and the second polarizing plate (300) may have
different layer structures. In addition, the first polarizing plate
(200) and the second polarizing plate (300) may also have different
thicknesses.
[0042] Referring to FIG. 3, the liquid crystal panel (10) satisfies
Equation 1 below.
|.alpha..sub.MD-.alpha..sub.TD|.ltoreq.1 [Equation 1]
[0043] In Equation 1, .alpha..sub.MD is a value determined by
Equation 2 and .alpha..sub.TD is a value determined by Equation
3:
.alpha..sub.MD=(sum of absorption axial bending moments acting on
each layer of the first polarizing plate)/(sum of transmission
axial bending moments acting on each layer of the second polarizing
plate) [Equation 2]
.alpha..sub.TD=(sum of transmission axial bending moments acting on
each layer of the first polarizing plate)/(sum of absorption axial
bending moments acting on each layer of the second polarizing
plate) [Equation 3]
[0044] In Equations 2 and 3, the absorption axial bending moment
acting on each layer is determined by the product of the distance
(unit: m) from the center of the liquid crystal panel to the center
of the relevant layer and the absorption axial shrinkage force
(unit: N) acting on the relevant layer.
[0045] Also, the transmission axial bending moment acting on each
layer is determined by the product of the distance (unit: m) from
the center of the liquid crystal panel to the center of the
relevant layer and the transmission axial shrinkage force (unit: N)
acting on the relevant layer.
[0046] In this document, the center of the liquid crystal panel
means the center of the total thickness of the liquid crystal cell
(100), the first polarizing plate (200) and the second polarizing
plate (300). For example, when the first polarizing plate (200) and
the second polarizing plate (300) have the same thickness, the
center of the liquid crystal panel may be the center of the liquid
crystal cell, as shown in FIG. 3(a). Alternatively, when the first
polarizing plate (200) and the second polarizing plate (300) have
different thicknesses, the center of the liquid crystal panel does
not coincide with the center of the liquid crystal cell.
[0047] Furthermore, .alpha..sub.MD and .alpha..sub.TD defined by
Equations 2 and 3 are each 0.8 to 0.12.
[0048] That is, with respect to each of the orthogonal directions
(MD, TD), the ratios of the bending moments acting on the first
polarizing plate (200) to the bending moments acting on the second
polarizing plate (300) may be each 0.8 to 1.2. Accordingly, the
flexural balance of the liquid crystal panel (10) can be
controlled.
[0049] In addition, it is preferred that .alpha..sub.MD and
.alpha..sub.TD are each 0.85 to 1.15, and it is preferred that
.alpha..sub.MD and .alpha..sub.TD are each 1.
[0050] Therefore, in Equation 1 above, preferably, the value of
|.alpha..sub.MD-.alpha..sub.TD| may be 0.4 or less, and more
preferably, the value of |.alpha..sub.MD-.alpha..sub.TD| may be 0.3
or less.
[0051] Also, .alpha..sub.MD and .alpha..sub.TD can have the same
value.
TABLE-US-00003 TABLE 3 Bending moment Category MD TD .alpha..sub.MD
.alpha..sub.TD Polarizer (PVA) 1968.7 1332.95 Base material 1
1037.9 1349.83 1.121 0.892 Base material 2 1037.9 1834.8 0.949
1.054 Base material 3 1037.9 1592.31 1.028 0.973 Base material 4
1037.91 1689.31 0.995 1.005
[0052] Table 3 has been derived based on room temperature data at
60.degree. C. after 72 hours and when the bending moment of the
polarizer layer is constant, it represents the results adjusted so
that .alpha..sub.MD and .alpha..sub.TD approach 1, respectively, by
controlling the TD direction bending moment of the low moisture
permeable base layer (base materials 1 to 4) (see base materials 3
and 4). In particular, the corresponding data is similar to the
experimental results at 80.degree. C. for 2 hours, which can be
substituted for the corresponding results.
[0053] Furthermore, the liquid crystal panel may satisfy Equation 4
below.
(.alpha..sub.MD-1)(.alpha..sub.TD-1).ltoreq.0 [Equation 4]
[0054] By satisfying Equation 4 above, it is possible to prevent a
twist risk.
[0055] In addition, the MD direction bending moment acting on each
layer may be determined by the product of the distance (z1 to z4,
unit: m) from the center of the liquid crystal panel to the center
of each layer and the MD direction shrinkage force (unit: N) acting
on the relevant layer, and the TD bending moment acting on each
layer may be determined by the product of the distance (z1 to z4,
unit: m) from the center of the liquid crystal panel to the center
of each layer and the TD direction shrinkage force (unit: N) acting
on the relevant layer.
[0056] For example, referring to FIG. 3, .alpha..sub.MD and
.alpha..sub.TD can be determined by Equations 5 and 6 as
follows.
.alpha..sub.MD=(MD direction shrinkage force of the polarizer layer
in the first polarizing plate*z1+MD direction shrinkage force of
the low moisture permeable layer in the first polarizing
plate*z2)/(TD direction shrinkage force of the polarizer layer in
the second polarizing plate*z3+TD direction shrinkage force of the
low moisture permeable base layer in the second polarizing
plate*z4) [Equation 5]
.alpha..sub.TD=(TD direction shrinkage force of the polarizer layer
in the first polarizing plate*z1+TD direction shrinkage force of
the low moisture permeable layer in the first polarizing
plate*z2)/(MD direction shrinkage force of the polarizer layer in
the second polarizing plate*z3+MD shrinkage force of the low
moisture permeable base layer in the second polarizing plate*z4)
[Equation 6]
[0057] z1 may be a distance from the center of the liquid crystal
panel (10) to the center of the polarizer layer (210) in the first
polarizing plate (200) and z2 may be a distance from the center of
the liquid crystal panel (10) to the center of the low moisture
permeable base layer (220) in the first polarizing plate (200). z3
may be a distance from the center of the liquid crystal panel (10)
to the center of the polarizer layer (310) in the second polarizing
plate (300) and z4 may be a distance from the center of the liquid
crystal panel (10) to the center of the low moisture permeable base
layer (320) in the second polarizing plate. In this document, the
center also means the center in the thickness direction. Thus, the
distances z1 to z4 can be adjusted by adjusting the thickness of
each layer. That is, if the thickness of the relevant layer
increases, the distance from the center of the liquid crystal panel
may increase, and if the thickness of the layer decreases, the
distance from the center of the liquid crystal panel may
decrease.
[0058] As examples of Equations 2 and 3, only the bending moments
(shrinkage force) of the polarizer layer and the low moisture
permeable base layer have been considered, but in Equations 2 and
3, the respective layers constituting the polarizing plate may be
all or alternatively included.
[0059] Furthermore, the shrinkage force can be determined based on
a shrinkage ratio. That is, the equation based on the shrinkage
force can be replaced with the equation based on the shrinkage
ratio.
[0060] In summary, in the liquid crystal panel (10) to which the
first polarizing plate (upper polarizing plate) and the second
polarizing plate (lower polarizing plate) are attached,
respectively, as the bending moment of a specific layer of the
first polarizing plate (200) and the second polarizing plate (300)
is adjusted, the flexural balance can be adjusted, cracks can be
prevented, and the light leakage phenomenon can be prevented. At
this time, as a method of controlling a bending moment, the
shrinkage force of each layer constituting the first and second
polarizing plates may also be adjusted, and for example, the
flexural balance can be adjusted by adjusting only the bending
moments of the low moisture permeable base layers of the first and
second polarizing plates. The adjustment of the bending moment of
the low moisture permeable base layer can be achieved by
controlling the TD direction (transmission axial) shrinkage
force.
[0061] In addition, a method for manufacturing a liquid crystal
panel (100) related to one embodiment of the present invention is a
method for manufacturing a liquid crystal panel (100) by attaching
a first polarizing plate (200) and a second polarizing plate (300)
to both surfaces of a liquid crystal cell (100), respectively.
[0062] As described above, the first and second polarizing plates
(200, 300) comprise polarizer layers (210, 310) and low moisture
permeable base layers (220, 320) bonded to the polarizer layers,
respectively.
[0063] Also, it comprises a step of producing the first and second
polarizing plates so as to satisfy Equation 1 below.
|.alpha..sub.MD-.alpha..sub.TD|.ltoreq.1 [Equation 1]
[0064] In Equation 1, .alpha..sub.MD is a value determined by
Equation 2 and .alpha..sub.TD is a value determined by Equation
3:
.alpha..sub.MD=(sum of absorption axial bending moments acting on
each layer of the first polarizing plate)/(sum of transmission
axial bending moments acting on each layer of the second polarizing
plate) [Equation 2]
.alpha..sub.TD=(sum of transmission axial bending moments acting on
each layer of the first polarizing plate)/(sum of absorption axial
bending moments acting on each layer of the second polarizing
plate) [Equation 3]
[0065] In Equations 2 and 3, the absorption axial bending moment
acting on each layer is determined by the product of the distance
from the center of the liquid crystal panel to the center of the
relevant layer and the absorption axial shrinkage force acting on
the relevant layer, and
[0066] the transmission axial bending moment acting on each layer
is determined by the product of the distance from the center of the
liquid crystal panel to the center of the relevant layer and the
transmission axial shrinkage force acting on the relevant
layer.
[0067] Furthermore, it may comprise a step of producing the first
and second polarizing plates such that .sub.MD and .sub.TD defined
by Equations 2 and 3 below are each 0.8 to 1.2.
[0068] In addition, it is preferred that .alpha..sub.MD and
.alpha..sub.TD are each 0.85 to 1.15, and it is preferred that
.alpha..sub.MD and .alpha..sub.TD are each 1.
[0069] Also, it is preferred that the step of producing the first
and second polarizing plates satisfies Equation 4 below.
(.alpha..sub.MD-1)(.alpha..sub.TD-1).ltoreq.0 [Equation 4]
[0070] Furthermore, in the step of producing the first and second
polarizing plates, the MD direction (absorption axial) shrinkage
force of the polarizer layer may be adjusted so as to satisfy
Equations 2 and 3, where the MD direction shrinkage force may be 5N
to 9N. Preferably, the MD direction shrinkage force may be more
than 5N and less than 9N.
[0071] In addition, in the step of producing the first and second
polarizing plates, the TD direction (transmission axial) shrinkage
force of the low moisture permeable base layer may be adjusted so
as to satisfy Equations 2 and 3, where the TD direction shrinkage
force may be 3N to 10N, and preferably, the TD direction shrinkage
force may be more than 3N and less than 10N.
[0072] The preferred embodiments of the present invention as
described above are disclosed for exemplary purpose, where those
skilled in the art having ordinary knowledge for the present
invention can make various corrections, modifications and additions
within idea and scope of the present invention, and such a
correction, modification and addition should be considered as
falling within the scope of the following claims.
INDUSTRIAL APPLICABILITY
[0073] According to the liquid crystal panel related to at least
one embodiment of the present invention and the method for
manufacturing the same, the flexural balance of the upper/lower
polarizing plates can be adjusted, cracks of the polarizing plate
can be prevented and the light leakage phenomenon of the liquid
crystal display device can be prevented, by adjusting the shrinkage
force of the polarizing plate.
* * * * *