U.S. patent application number 12/858073 was filed with the patent office on 2010-12-09 for optical film and information technology apparatus comprising the same.
This patent application is currently assigned to LG CHEM, LTD.. Invention is credited to Sae-Han Cho, Dong-Ryul Kim, Jong-Hun Lee, Min-Hee Lee, Nam-Jeong Lee, Jun-Geun Um.
Application Number | 20100311910 12/858073 |
Document ID | / |
Family ID | 41255572 |
Filed Date | 2010-12-09 |
United States Patent
Application |
20100311910 |
Kind Code |
A1 |
Um; Jun-Geun ; et
al. |
December 9, 2010 |
OPTICAL FILM AND INFORMATION TECHNOLOGY APPARATUS COMPRISING THE
SAME
Abstract
The present invention relates to an optical film comprising an
aromatic based unit having chain having the hydroxy group
containing portion and aromatic moiety; and a styrene-based unit
comprising one or more styrene-based derivatives, and has absolute
values of in-plane retardation (R.sub.in) and thickness retardation
(R.sub.th) of 10 nm or less regardless of stretching, and a
polarizing plate and an information technology apparatus including
the same.
Inventors: |
Um; Jun-Geun; (Daejeon
Metropolitan City, KR) ; Lee; Min-Hee; (Daejeon
Metropolitan City, KR) ; Lee; Nam-Jeong; (Daejeon
Metropolitan City, KR) ; Lee; Jong-Hun; (Daejeon
Metropolitan City, KR) ; Kim; Dong-Ryul; (Daejeon
Metropolitan City, KR) ; Cho; Sae-Han; (Daejeon
Metropolitan City, KR) |
Correspondence
Address: |
LGCHEM;Lerner, David, Littenberg, Krumholz & Mentlik, LLP
600 South Avenue West
Westfield
NJ
07090
US
|
Assignee: |
LG CHEM, LTD.
Seoul
KR
|
Family ID: |
41255572 |
Appl. No.: |
12/858073 |
Filed: |
August 17, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12387553 |
May 4, 2009 |
|
|
|
12858073 |
|
|
|
|
PCT/KR2009/002303 |
Apr 30, 2009 |
|
|
|
12387553 |
|
|
|
|
Current U.S.
Class: |
525/205 |
Current CPC
Class: |
C09D 125/14 20130101;
G02B 5/3083 20130101; C09K 2323/031 20200801; Y10T 428/105
20150115; C09K 2323/035 20200801; Y10T 428/1041 20150115 |
Class at
Publication: |
525/205 |
International
Class: |
C08L 39/04 20060101
C08L039/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 30, 2008 |
KR |
10-2008-0040843 |
Jan 9, 2009 |
KR |
10-2009-0002070 |
Claims
1. An optical film comprising: an aromatic based unit having chain
having the hydroxy group containing portion and aromatic moiety;
and a styrene-based unit comprising one or more styrene-based
derivatives, wherein absolute values of in-plane retardation
(R.sub.in) and thickness retardation (R.sub.th) are defined by the
following Equation are 10 nm or less regardless of stretching:
R.sub.in=(n.sub.x-n.sub.y).times.d,
R.sub.th=[(n.sub.x+n.sub.y)/2-n.sub.z].times.d n.sub.x is the
largest refractive index among in-plane refractive indexes of the
film, n.sub.y is the refractive index in a direction that is
vertical to n.sub.x of the in-plane refractive index of the film,
n.sub.z is the thickness refractive index of the film, and d is the
thickness of the film.
2. The optical film of claim 1, wherein in the optical film,
regardless of the stretching, the absolute value of the
photoelasticity coefficient is 3.times.10.sup.-12 m.sup.2/N or
less.
3. The optical film of claim 1, further comprising: one or more a
(meth)acrylate-based unit that include (meth)acrylate-based
derivative.
4. The optical film of claim 1, wherein the content ratio of the
aromatic-based unit and the styrene-based unit is in the range of
65 to 75:100 on the basis of mole.
5. The optical film of claim 1, wherein the content ratio of the
aromatic-based unit and the styrene-based unit is in the range of
45 to 55:100 on the basis of weight.
6. The optical film of claim 3, wherein the ratio of the sum total
of the contents of the aromatic-based unit and the styrene-based
unit and the content of the (meth)acrylate-based unit is in the
range of 1:99 to 50:50 on the basis of weight.
7. The optical film of claim 1, further comprising: a cyclic-based
unit having a cyclic moiety.
8. The optical film of claim 7, wherein the cyclic moiety is
selected from the group consisting of maleic anhydride, maleimide,
glutaric anhydride, glutalimide, lactone and lactame.
9. The optical film of claim 3, wherein the (meth)acrylate-based
unit is a copolymer of the (meth)acrylate derivative and a
cyclic-based unit having a cyclic moiety.
10. The optical film of claim 9, wherein the cyclic moiety of the
cyclic-based unit is selected from the group consisting of maleic
anhydride, maleimide, glutaric anhydride, glutalimide, lactone and
lactame.
11. The optical film of claim 9, wherein the content of the
(meth)acrylate derivative of the copolymer is in the range of about
50% to about 99% on the basis of the weight of the copolymer.
12. The optical film of claim 1, wherein the styrene-based unit is
a copolymer of the styrene derivative and the cyclic-based unit
having the cyclic moiety.
13. The optical film of claim 12, wherein the cyclic moiety of the
cyclic-based unit is selected from the group consisting of maleic
anhydride, maleimide, glutaric anhydride, glutalimide, lactone and
lactame.
14. The optical film of claim 12, wherein the copolymer includes
about 30% to about 99% of styrene-based derivative and about 1% to
about 70% of cyclic-based unit on the basis of the weight of the
copolymer.
15. The optical film of claim 1, wherein the styrene-based unit
forms a copolymer in conjunction with one or more
(meth)acrylate-based units.
16. The optical film of claim 1, wherein the aromatic-based unit
includes a phenoxy-based resin.
17. The optical film of claim 16, wherein the aromatic-based unit
has a number average molecular weight in the range of 1,500 to
2,000,000 g/mol.
18. The optical film of claim 1, wherein the aromatic-based unit
includes 5 to 10,000 at least one type of units represented by
Formula 1: ##STR00010## wherein X is a divalent group comprising at
least one benzene cycle and R is a straight- or branched-chained
alkylene group having 1 to 6 carbon atoms.
19. The optical film of claim 3, wherein the (meth)acrylate-based
unit is the copolymer of the (meth)acrylate derivative and the
cyclic-based unit having the cyclic moiety, and the styrene-based
unit is the copolymer of the styrene derivative and the
cyclic-based unit having the cyclic moiety.
20. The optical film of claim 3, wherein the optical film includes
the copolymer of the (meth)acrylate-based unit, the styrene-based
unit and the cyclic-based unit.
21. The optical film of claim 1, wherein the optical film is a
protective film for polarizer.
22. A polarizing plate comprising: a polarizer; and the optical
film of claim 1, which is provided on at least one side of the
polarizer.
23. A liquid crystal display device comprising: the polarizing
plate of claim 22.
24. An information technology apparatus comprising: the optical
film of claim 1.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of application
Ser. No. 12/387,553, filed May 4, 2009, which is a continuation of
International Application No. PCT/KR2009/002303, filed Apr. 30,
2009, which claims the benefit of Korean Patent Application No.
10-2008-0040843, filed Apr. 30, 2008 and 10-2009-00020070, filed
Jan. 9, 2009. The disclosures of said applications are incorporated
by reference herein.
TECHNICAL FIELD
[0002] The present invention relates to an optical film having
excellent heat resistance and optical transparency, low haze, and
excellent optical property, is not easily broken, and has excellent
mechanical strength and durability, and a polarizing plate and an
information technology apparatus including the same.
BACKGROUND OF THE INVENTION
[0003] Recently, display technologies using various methods such as
a plasma display panel (PDP), a liquid crystal display (LCD) and
the like that are used instead of a known braun tube in accordance
with the development of optical technologies are suggested and
sold. The higher properties of the polymer material for displays
are required. For example, in the case of the liquid crystal
display, according to the development toward the thin film, the
lightness, and enlargement of the picture area, the wide viewing
angle, the high contrast, the suppression of change in picture
color tone according to the viewing angle and the uniformity of the
picture display are particularly considered as important
problems.
[0004] Therefore, various polymer films such as a polarizing film,
a polarizer protection film, a retardation film, a plastic
substrate, a light guide plate and the like are used, and as the
liquid crystal, various modes of liquid crystal displays such as
twisted nematic (TN), super twisted nematic (STN), vertical
alignment (VA), in-plane switching (IPS) liquid crystal cells are
developed. Since these liquid crystal cells have all intrinsic
liquid crystal alignment, the intrinsic optical anisotropic
property is ensured, and in order to compensate the optical
anisotropic property, a film in which a retardation function is
provided by stretching various kinds of polymers has been
suggested.
[0005] In detail, since a liquid crystal display device uses high
birefringence property and alignment of liquid crystal molecules,
the birefringences are different according to the viewing angle and
thus the color and brightness of the picture are changed. Thus, a
retardation compensation according to the kind of liquid crystal
molecule is required. For example, since most liquid crystal
molecules that are used in a vertical alignment method have the
thickness refractive index that is larger than the average in-plane
refractive index in a liquid crystal display surface, in order to
compensate this, a compensation film in which the thickness
refractive index has retardation property which is smaller than the
average in-plane refractive index is required.
[0006] In addition, light does not pass through the front sides of
two polarizing plates that are vertical to each other, but if the
angle is inclined, the light axes of two polarizing plates are not
vertical to each other, thus light leakage occurs. In order to
compensate this, the compensate film having the in-plane
retardation is required. In addition, the display device using the
liquid crystal requires both the thickness retardation compensation
and the in-plane retardation compensation in order to widen the
angle view.
[0007] Requirement of the retardation compensation film is to
easily control the birefringence. However, the film birefringence
is formed by a basic birefringence which belongs to the material
and the orientation of polymer chains in the film. The orientation
of the polymer chains is mostly forcibly performed by force applied
from the outside or is caused by the intrinsic properties of the
material, and the orientation method of the molecules by the
external force is to uniaxially or biaxially stretch the polymer
film.
[0008] In the related art, there is a need to develop a polymer
material that satisfies the above requirement properties in order
to be used in displays.
SUMMARY OF THE INVENTION
[0009] The present invention relates to an optical film having
excellent optical property and optical transparency, and low haze,
that is not easily broken unlike an acryl-based film that is easily
broken while stretching processes are carried out, and has
excellent mechanical strength and processability, and durability
such as heat resistance, and in particular, has a low absolute
value of in-plane retardation and thickness retardation and a low
absolute value of photoelasticity coefficient regardless of the
stretching, and a polarizing plate and an information technology
apparatus including the same.
[0010] The present invention provides an optical film that
comprises an aromatic based unit having chain having the hydroxy
group containing portion and aromatic moiety; and a styrene-based
unit comprising one or more styrene-based derivatives, wherein
absolute values of in-plane retardation (R.sub.in) and thickness
retardation (R.sub.th) of 10 nm or less regardless of stretching.
Here, the in-plane retardation (R.sub.in) and the thickness
retardation (R.sub.th) are defined by the following Equation:
R.sub.in=(n.sub.x-n.sub.y).times.d
R.sub.th=[(n.sub.x+n.sub.y)/2-n.sub.z].times.d
[0011] In Equations 1 and 2, n.sub.x is the largest refractive
index among in-plane refractive indexes of the film,
[0012] n.sub.y is the refractive index in a direction that is
vertical to n.sub.x of the in-plane refractive index of the
film,
[0013] n.sub.z is the thickness refractive index of the film,
and
[0014] d is the thickness of the film.
[0015] In addition, the present invention provides a polarizing
plate that comprises a polarizer; and the optical film which is
provided on at least one side of the polarizer.
[0016] In addition, the present invention provides a liquid crystal
display device that comprises the polarizing plate.
[0017] In addition, the present invention provides an information
technology apparatus that comprises the optical film.
[0018] An optical film according to the present invention has
excellent optical property and optical transparency, and low haze,
is not easily broken unlike an acryl-based film that is easily
broken while stretching processes are carried out, and has
excellent mechanical strength and processability, and heat
resistance, and has a low absolute value of in-plane retardation
and thickness retardation and a low absolute value of
photoelasticity coefficient regardless of the stretching.
Accordingly, the optical film may be useful for the case of when
the retardation and the photoelasticity coefficient are low like a
protective film of a polarizer.
DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a graph that illustrates a retardation
distribution according to a width direction of the film that is
produced in Example.
DETAILED DESCRIPTION
[0020] An optical film according to the present invention comprises
an aromatic-based unit comprising chain and aromatic moiety having
a hydroxyl group containing portion; and a styrene-based unit
comprising one or more styrene-based derivatives, and has absolute
values of in-plane retardation (R.sub.in) and thickness retardation
(R.sub.th) of 10 nm or less and preferably 5 nm or less regardless
of stretching. In addition, preferably, the optical film according
to the present invention has an absolute value of photoelasticity
coefficient of 3.times.10.sup.-12 m.sup.2/N or less regardless of
stretching.
[0021] Since the optical film according to the present invention
has the small in-plane retardation and thickness retardation, the
protective film of the polarizer and the optical film having the
small retardation value may be usefully applied to the desired
purpose. In addition, since the optical film according to the
present invention has the low photoelasticity coefficient, a change
in retardation value by external stress is small, such that a light
leakage phenomenon may be reduced.
[0022] It is preferable that the content ratio of the
aromatic-based unit and the styrene-based unit is in the range of
65 to 75:100 on the basis of mole. In addition, it is preferable
that the content ratio of the aromatic-based unit and the
styrene-based unit is in the range of 45 to 55:100 on the basis of
weight. By the composition within the above range, it is easy to
obtain the above retardation value and photoelasticity
coefficient.
[0023] The optical film according to the present invention may
further include a (meth)acrylate-based unit comprising one or more
(meth)acrylate-based derivatives.
[0024] In addition, it is preferable that the ratio of the sum
total of the contents of the aromatic-based unit and the
styrene-based unit and the content of the (meth)acrylate-based unit
is in the range of 1:99 to 50:50 on the basis of weight. The
composition within the above range is useful to obtain the above
retardation value and photoelasticity coefficient.
[0025] The (meth)acrylate-based unit comprising one or more
(meth)acrylate-based derivatives, the aromatic-based unit that
comprises the chain and aromatic moiety including the hydroxy group
containing portion, and the styrene-based unit comprising one or
more styrene-based derivatives may be each included in different
compounds, or two or more units of the above units may be included
in one compound.
[0026] In the present invention, the (meth)acrylate-based unit
provides a weak negative in-plane retardation (Rin) and a weak
thickness retardation (Rth), the aromatic-based unit comprising the
chain and aromatic moiety having the hydroxy group containing
portion provides a positive in-plane retardation (Rin) property and
a positive thickness retardation (Rth) property, and the
styrene-based unit provides a strong negative in-plane retardation
(Rin) and a negative thickness retardation (Rth). Here, the
negative in-plane retardation means the highest in-plane refractive
index that is perpendicular in respects to the stretching
direction, the positive in-plane retardation means the highest
refractive index in respects to the stretching direction, the
negative thickness retardation means that the thickness retardation
is larger than the in-plane average refractive index, and the
positive thickness retardation means that the in-plane average
refractive index is larger than the thickness retardation. Because
of the retardation characteristics of the above units, the
retardation characteristics of the optical film may depend on the
composition, the stretching direction, the stretching ratio, and
the stretching method such as uniaxial or biaxial stretching of
each component. Therefore, in the present invention, while a
stretching process is carried out by appropriately combining the
compositions of the components, an effect in which birefringences
of the units offset each other may be obtained. Accordingly, in the
present invention, since the film maintains an optical refractive
index isotropic property, the film having the absolute values of
the in-plane retardation and thickness retardation of 10 nm may be
manufactured, and the optical film that hardly has the remaining
retardation may be provided.
[0027] In addition, the resin composition according to the present
invention is capable of providing an optical film having excellent
mechanical properties unlike an acryl based film that is easily
broken. In addition, the (meth)acrylate-based unit is capable of
providing excellent optical properties, and the
(meth)acrylate-based unit is capable of providing excellent
miscibility with the compound comprising the (meth)acrylate-based
unit. In addition, since the resin composition according to the
present invention is capable of controlling a value of
photoelasticity coefficient according to the content of the
aromatic based unit having chain having the hydroxy group
containing portion and aromatic portions, the film having a small
change in retardation value by external stress may be
manufactured.
[0028] The optical film according to the present invention may
further include the cyclic-based unit having the cyclic moiety. The
cyclic-based unit having the cyclic moiety may be included in at
least one of the (meth)acrylate-based unit, the aromatic-based unit
comprising the chain and aromatic moiety having the hydroxy group
containing portion, and the styrene-based unit, and may be included
in the compound that is different from the compound in which at
least one of the (meth)acrylate-based unit, the aromatic-based unit
comprising the chain and aromatic moiety having the hydroxy group
containing portion, and the styrene-based unit is included. The
cyclic-based unit having the cyclic moiety may provide excellent
heat resistance to the film.
[0029] According to an embodiment of the present invention, the
copolymer comprising the (meth)acrylate-based unit and the
cyclic-based unit having the cyclic moiety, the copolymer
comprising the (meth)acrylate-based unit and the styrene-based
unit, the copolymer comprising the styrene-based unit and the
cyclic-based unit having the cyclic moiety, and the copolymer
comprising the (meth)acrylate-based unit, the aromatic-based unit
comprising the chain and aromatic moiety having the hydroxy group
containing portion, and the styrene-based unit may be used. At this
time, the above copolymers may include at least one of two types or
more units.
[0030] As a detailed example, the copolymer comprising the
(meth)acrylate-based unit such as methyl(meth)acrylate and the
cyclic-based unit such as N-cyclohexylmaleimide, that is,
poly(N-cyclohexylmaleimide-co-methyl(meth)acrylate), may be used.
In addition, the copolymer comprising the styrene-based unit such
as styrene and cyclic-based unit such as maleic anhydride may be
used. In addition, the copolymer comprising methyl methacrylate as
the (meth)acrylate-based unit, styrene and alpha methyl styrene as
the styrene-based unit, and N-cyclohexylmaleimide as the
cyclic-based unit may be used. In addition, the copolymer
comprising methyl methacrylate as the (meth)acrylate-based unit,
styrene or alpha methyl styrene as the styrene-based unit, and
N-cyclohexylmaleimide and maleic anhydride as the cyclic-based unit
may be used. However, the above examples are set forth to
illustrate the present invention, but are not to be construed to
limit the present invention.
[0031] The content of each unit is not particularly limited, and in
consideration of the role of each component, in order to obtain
desired in-plane retardation, thickness retardation, optical
property, mechanical property, transparency, miscibility and the
like, the content of each unit may be determined. For example, the
contents of the (meth)acrylate-based unit, an aromatic based resin
having chain having the hydroxy group containing portion and
aromatic moiety, the styrene-based unit and the cyclic-based unit
may be selected within the range of about 0.1 to 99 wt %. In
detail, it is preferable that the content of the
(meth)acrylate-based unit is in the range of about 50 to 98 wt %,
it is preferable that the content of an aromatic based resin having
chain having the hydroxy group containing portion and aromatic
moiety is in the range of about 0.5 to about 40 wt %, and it is
preferable that the content of the styrene-based unit is in the
range of about 0.5 to about 30 wt %. It is preferable that the
content of the cyclic-based unit may is in the range of about 0.5
to about 45 wt %.
[0032] In the present invention, the compound comprising the
(meth)acrylate-based unit, the aromatic based unit having chain
having the hydroxy group containing portion and aromatic moiety,
the styrene-based unit and the cyclic-based unit may be a
homopolymer or a copolymer, and the compound may further include
units other than the (meth)acrylate-based unit, the aromatic based
unit having chain having the hydroxy group containing portion and
aromatic moiety, the styrene-based unit and the cyclic-based unit
within the scope of the present invention. The copolymer may be a
random or block copolymer.
[0033] In the present invention, it should be understood that the
(meth)acrylate-based unit may include (meth)acrylate and a
(meth)acrylate derivative. To be specific, as the (meth)acrylate
based monomer, there are methyl methacrylate, methyl acrylate,
ethyl acrylate, butyl acrylate, 2-ethylhexyl methacrylate, lauryl
methacrylate, benzyl methacrylate and the like, but it is not
limited thereto. In particular, it is most preferable that methyl
methacrylate (MMA) is used.
[0034] In the present invention, as the compounds comprising the
(meth)acrylate-based unit, a copolymer comprising the
(meth)acrylate based unit and the cyclic based unit having the
cyclic moiety may be used. The content of the (meth)acrylate based
unit in the copolymer comprising the (meth)acrylate based unit and
the cyclic based unit having the cyclic moiety is in the range of
about 50 to 99% by weight, and preferably in the range of about 70
to about 98% by weight, and the content of the cyclic based unit
having the cyclic moiety is in the range of about 1 to 50% by
weight and preferably about 2 to about 30% by weight. When the
content of the cyclic based unit having the cyclic moiety is 50% by
weight or less, it is useful to reduce a haze value of the
film.
[0035] The cyclic based unit having the cyclic moiety of the
copolymer comprising the (meth)acrylate based unit and the cyclic
based unit having the cyclic moiety functions to improve heat
resistance of the film. Examples of the cyclic based unit having
the cyclic moiety will be described below. However, it is most
preferable that the cyclic based unit having the cyclic moiety,
which is included in the copolymer in conjunction with the
(meth)acrylate based unit, is a maleimide based unit including a
maleimide portion. The maleimide based unit may include a cyclic
moiety that is derived from N-cyclohexylmaleimide,
N-phenylmaleimide, N-methylmaleimide, N-butylmaleimide and the
like, but is not limited thereto. In particular, it is most
preferable that it includes the cyclic moiety that is derived from
N-cyclohexylmaleimide.
[0036] The copolymer comprising the (meth)acrylate based unit and
the cyclic based unit having the cyclic moiety may be manufactured
by a method such as a bulk polymerization, a solution
polymerization, a suspension polymerization, an emulsion
polymerization and the like using a (meth)acryl based monomer and a
cyclic based monomer such as a maleimide based monomer.
[0037] In the present invention, it is preferable that the number
average molecular weight of the aromatic based unit having chain
having the hydroxy group containing portion and aromatic moiety
comprising the chain having the hydroxy group containing portion
and aromatic moiety is in the range of 1,500 to 2,000,000 g/mol. It
is preferable that the aromatic based resin includes the phenoxy
based resin. Here, the phenoxy based resin includes a structure in
which at least one oxygen radical is bonded to the benzene cycle.
For example, the aromatic based unit having chain having the
hydroxy group containing portion and aromatic moiety having the
chain having the hydroxy group containing portion and aromatic
moiety may include one or more units that are represented by the
following Formula 1. The aromatic based unit having chain having
the hydroxy group containing portion and aromatic moiety includes 5
to 10,000 of the unit of the following Formula 1, preferably 5 to
7,000 of the unit of the following Formula 1, and more preferably 5
to 5,000 of the unit of the following Formula 1. In the case when
two kinds or more units of the following Formula 1 are included in
the aromatic based unit having chain having the hydroxy group
containing portion and aromatic moiety, they may be included in a
random form, an alternating form, or a block form.
##STR00001##
[0038] wherein X is a divalent group comprising at least one
benzene cycle and R is a straight- or branched-chained alkylene
group having 1 to 6 carbon atoms.
[0039] To be specific, it is preferable that X is a divalent group
that is derived from the compounds of the following Formulas 2 to
4, but is not limited thereto.
##STR00002##
[0040] R.sup.1 is a direct bond, straight- or branched-chained
alkylene having 1 to 6 carbon atoms, or cycloalkylidene having 3 to
20 carbon atoms,
[0041] R.sup.2 and R.sup.3 are each hydrogen, straight- or
branched-chained alkyl having 1 to 6 carbon atoms, or straight- or
branched-chained alkenyl having 2 to 6 carbon atoms, and n and m
are each an integer in the range of 1 to 5.
##STR00003##
[0042] R.sup.4 is each hydrogen, straight- or branched-chained
alkyl having 1 to 6 carbon atoms, or straight- or branched-chained
alkenyl having 2 to 6 carbon atoms, and p is an integer in the
range of 1 to 6.
##STR00004##
[0043] R.sup.6 and R.sup.7 are each a direct bond, straight- or
branched-chained alkylene having 1 to 6 carbon atoms, or
cycloalkylidene having 3 to 20 carbon atoms,
[0044] R.sup.5 and R.sup.8 are each hydrogen, straight- or
branched-chained alkyl having 1 to 6 carbon atoms, or straight- or
branched-chained alkenyl having 2 to 6 carbon atoms, and q and r
are each an integer in the range of 1 to 5.
##STR00005##
[0045] R.sup.4 is each hydrogen, straight- or branched-chained
alkyl having 1 to 6 carbon atoms, or straight- or branched-chained
alkenyl having 2 to 6 carbon atoms, and p is an integer in the
range of 1 to 6.
##STR00006##
[0046] R.sup.6 and R.sup.7 are each a direct bond, straight- or
branched-chained alkylene having 1 to 6 carbon atoms, or
cycloalkylidene having 3 to 20 carbon atoms,
[0047] R.sup.5 and R.sup.8 are each hydrogen, straight- or
branched-chained alkyl having 1 to 6 carbon atoms, or straight- or
branched-chained alkenyl having 2 to 6 carbon atoms, and q and r
are each an integer in the range of 1 to 5.
[0048] Detailed examples of the compounds that are represented by
Formulas 2 to 4 are the same as the following compounds, but are
not limited thereto:
##STR00007##
[0049] It is most preferable that the aromatic based unit includes
one kind or more 5 to 10,000 phenoxy based units that are
represented by the following Formula 5:
##STR00008##
wherein R.sup.9 is a direct bond, straight- or branched-chained
alkylene having 1 to 6 carbon atoms, and R.sup.10 is a direct bond,
straight- or branched-chained alkylene having 1 to 6 carbon
atoms.
[0050] It is preferable that Formula 5 is represented by the
following Formula 6.
##STR00009##
[0051] An end of the aromatic based resin may be an OH group.
[0052] In the present invention, the styrene-based unit is
construed to include the styrene-based derivative as well as
styrene. The styrene-based derivative includes a compound
comprising one or more substituent groups having aliphatic
hydrocarbons or hetero atoms at a benzene cycle or vinyl group of
styrene, and in detail, it includes alpha methyl styrene.
[0053] In the present invention, as the compound comprising the
unit, the copolymer comprising the styrene-based unit and the
cyclic moiety may be used. The content of the styrene-based unit in
the copolymer comprising the styrene-based unit and the
cyclic-based unit having the cyclic moiety is in the range of about
1 to about 99 wt %, preferably in the range of about 30 to about 99
wt %, and more preferably in the range of about 40 to about 95 wt
%, and the content of the cyclic-based unit having the cyclic
moiety is in the range of about 1 to about 99 wt %, preferably in
the range of about 1 to about 70 wt %, and more preferably in the
range of about 5 to about 60 wt %. By melting and mixing the
copolymer comprising the styrene-based unit and the cyclic-based
unit having the cyclic moiety and using it, the adhesion property
and heat resistance of the film may be improved. If the content of
the cyclic-based unit having the cyclic moiety is very low, the
miscibility may be slightly reduced. Examples of the cyclic-based
unit having the cyclic moiety will be described later. However, it
is most preferable that the cyclic-based unit having the cyclic
moiety that is included in the copolymer in conjunction with the
cyclic-based unit is a maleic anhydride-based unit including a
maleic anhydride portion.
[0054] In the present invention, the cyclic-based unit may improve
the heat resistance of the film. The content of the cyclic-based
unit is in the range of about 0.1 to about 99 wt %, and preferably
about 0.5 to about 45 wt %. Examples of the cyclic moiety of the
cyclic-based unit include maleic anhydride, maleimide, glutaric
anhydride, glutalimide, lactone and lactame, but are not limited
thereto.
[0055] According to an embodiment of the present invention, as the
components that include the units, 1) a copolymer comprising the
(meth)acrylate based unit and the maleimide based unit, 2) the
resin comprising the phenoxy based (phenoxy-based) unit, and 3) the
copolymer comprising the styrene-based unit and the maleic
anhydride unit may be used. In this case, it is preferable that the
content of each component is in the range of 1 to 99 wt %. To be
specific, the content of 1) the copolymer is preferably in the
range of about 50 to about 99 wt % and more preferably in the range
of about 75 to about 98 wt %. The content of the 2) resin is
preferably in the range of about 0.5 to about 40 wt % and more
preferably in the range of about 1 to about 30 wt %. The content of
3) the copolymer is preferably in the range of about 0.5 to about
30 wt % and more preferably in the range of about 1 to about 20 wt
%.
[0056] In particular, in the case when the content of the maleimide
based monomer in the copolymer comprising 1) the (meth)acrylate
based unit and maleimide based unit is 50% by weight or less,
regardless of the mixing ratio of 1) to 2) components, it can show
miscibility in respects to the entire range, and the optical film
having the resin composition is advantageous in that it has a
single glass transition temperature T.sub.g.
[0057] The thickness of the optical film according to the present
invention is in the range of 5 to 500 .mu.m, and more preferably 5
to 300 .mu.m, but is not limited thereto. The transmittance of the
optical film is 90% or more, the haze is 2.5% or less, preferably
1% or less, and more preferably 0.5% or less. It is preferable that
the glass transition temperature of the optical film according to
the present invention is 100.degree. C. or more.
[0058] The optical film may control the value of the
photoelasticity coefficient at a very small value according to the
content of the aromatic based unit having chain having the hydroxy
group containing portion and aromatic moiety and the styrene-based
unit, and in this case, a characteristic in which a change in
retardation caused by the external stress hardly occurs is ensured,
such that a light leakage phenomenon may be reduced.
[0059] The method for manufacturing the optical film according to
the present invention comprises the steps of preparing the above
resin composition; and casting a film by using the resin
composition. The manufacturing method may further comprise the step
of uniaxially or biaxially stretching the film.
[0060] The resin composition may be manufactured by melting and
blending the above components. The melting and the mixing of the
components may be carried out by using an extruder.
[0061] The resin composition may further include a lubricant, an
antioxidant, a UV stabilizer, a thermal stabilizer and absorber and
the like that are generally used.
[0062] When the optical film according to the present invention is
manufactured, a method that is known in the art may be used, and in
detail, an extrusion molding method may be used. For example, after
the resin composition is dried under a vacuum and removes water and
dissolved oxygen, the composition is supplied from the raw material
hopper to a single or twin extruder that is filled with nitrogen,
and melted at a high temperature to obtain a raw material pellet,
the obtained raw material pellet is dried under a vacuum, melted
from the raw material hopper to a single extruder that is
substituted with nitrogen, passes through a coat hanger type T-die,
and a chrome-coated casting roll and a drying roll to manufacture
the film.
[0063] When the optical film according to the present invention is
manufactured, the manufacturing method may further comprise the
step of uniaxially or biaxially stretching the film. The stretching
process may be carried out by using any one of a longitudinal
direction (MD) stretching and a transverse direction (TD)
stretching or both of the longitudinal direction stretching and the
transverse direction stretching. In the case of when both of the
longitudinal direction stretching and the transverse direction
stretching are carried out, any one of them may be first carried
out and then the other may be carried out, or both of them may be
carried out simultaneously. The stretching may be carried out
through a single step or through multi-steps. In the case of when
the stretching is carried out in the longitudinal direction, the
stretching may be carried out by using a difference in speed
between rolls, and in the case of when the stretching is carried
out in the transverse direction, the tenter may be used. The rail
initiating angle of the tenter is 10.degree. or less, a bowing
phenomenon that occurs when the transverse direction stretching is
carried out is suppressed, and the angle of the optical axis is
regularly controlled. By carrying out the transverse direction
stretching through multi-steps, the suppression phenomenon of the
bowing phenomenon may be obtained.
[0064] The stretching may be carried out at a temperature in the
range of (Tg-20.degree. C.) to (Tg+30.degree. C.) when the glass
transition temperature of the resin composition is T.sub.g. The
glass transition temperature means a range from a temperature at
which storage elasticity of the resin composition starts to be
reduced and the loss elasticity starts to be larger than the
storage elasticity to a temperature at which alignment of the
polymer chain is loosened and removed. The glass transition
temperature may be measured by using a differential scanning
calorimeter (DSC).
[0065] In the case of a small stretching machine (Universal testing
machine, Zwick Z010), it is preferable that the stretching rate is
in the range of 1 to 100 mm/min. In the case of a pilot stretching
machine, it is preferable that the stretching rate is in the range
of 0.1 to 2 mm/min. In addition, it is preferable that the film is
stretched by using a stretching ratio in the range of 5 to
300%.
[0066] The stretching may be carried out through a separate step
that is different from the shaping of the film, or carried out
through one step in the same process as the shaping of the
film.
[0067] The composition of each unit may be combined with the
longitudinal direction stretching ratio, the transverse direction
stretching ratio, the stretching temperature and the stretching
rate.
[0068] In addition, since toughness of the stretched film is
increased, a disadvantage of the (meth)acrylate based film that is
easily broken may be effectively compensated.
[0069] The optical film according to the present invention has the
absolute value of in-plane retardation and thickness retardation of
10 nm or less and preferably 5 nm or less regardless of the
stretching. In addition, the optical film according to the present
invention has the absolute value of photoelasticity coefficient of
3.times.10.sup.-12 m.sup.2/N or less regardless of the
stretching.
[0070] The optical film according to the present invention may be
provided with an additional layer comprising at least one of an
organic substance and an inorganic substance on at least one side,
and an adhesion property in respects to a retardation value, a
compensation property and/or a polarizer may be controlled.
Examples of the organic substance include cellulose, polyimide,
polyester, polyurethane, liquid crystal and/or a derivative
thereof, and examples of the inorganic substance include TiO.sub.2,
ITO and the like, but are not limited thereto.
[0071] In addition, the present invention provides a polarizing
plate that comprises a polarizer, and the optical film which is
provided on at least one side of the polarizer. Since a polarizer
comprises a dichromic pigment and consists of a polyvinyl alcohol
film that is uniaxially stretched, it is very weak and has the
reduced durability in respects to the temperature or moisture, and
laminated with the protective film. In the related art, a liquid
crystal display device having the polarizing plate mostly consists
of a device having a relatively small display area, such as clocks
or instrument boards, or a light diffusion type device, a surface
of which is subjected to reflection prevention treatment.
Currently, a liquid crystal display device has a large display area
like a display having a large image or has a surface that is
subjected to low haze reflection prevention treatment, such as
polished surfaces, by using a multilayered reflection way. In this
case, defects such lines, curve marks, scars, stains and the like
formed on the surface of the protective film for polarizing plate
are observed. This is because the most protective film for
polarizing plate uses triacetylcellulose films.
[0072] A cellulose derivative has excellent moisture permeation, in
a process for manufacturing the polarizing plate, it is
advantageous in that moisture contained in the polarizer may be
volatilized through the film. However, under the high temperature
and high humidity atmosphere, the dimensional change according to
the absorption or the optical property change is relatively
significant and in the case of when the humidity is changed at
around room temperature, a change in retardation value is large,
and there is a limit in improvement of the stable angle view, thus
there is a problem in that the durability of the optical property
of the polarizing plate is reduced.
[0073] In addition, in a polycarbonate-based, since the glass
transition temperature is high, the stretching process is required
at high temperatures, and since the light elasticity-coefficient of
the film is large, light deformation occurs by the stress. In the
case of when the norbornene-based film is stretched, there are
problems in that the stress is increased in the stretching or the
stress nonuniformity occurs in the stretching. The solving of the
above problems is capable of being solved by adopting the
acryl-based retardation film having the excellent angle view
compensation effect and a small change in retardation value even
though the environment is changed.
[0074] If the photoelasticity coefficient, that is, the change rate
of birefringence when a stress load is received is high, since
adhesion nonuniformity when adhesion is carried out in conjunction
with a liquid crystal layer or a polarizing plate, a difference
between thermal expansions of constituent materials formed by
receiving heat from a backlight or an external environment, and a
change in retardation that is caused by an effect of stress
generated by shrinkage of a polarizing film and the like are
increased, color uniuniformity of the display device is reduced or
contrast is reduced. The acryl-based film may control the value of
the photoelasticity coefficient at a very small value, and in this
case, a characteristic in which a change in retardation caused by
the external stress hardly occurs is ensured, such that a light
leakage phenomenon may be reduced.
[0075] The optical film according to the present invention may be
provided on one side of the polarizer or on both sides of the
polarizer.
[0076] In the case of when the optical film according to the
present invention is provided on only any one side of the
polarizer, a protective film that is known in the art may be
provided on the other side thereof. As the protective film that is
known in the art, a triacetate cellulose (TAC) film, a
polynorbonene-based film that is produced by using a ring opening
metathesis polymerization (ROMP), a HROMP (ring opening metathesis
polymerization followed by hydrogenation) polymer film that is
obtained by hydrogenating the ring opening cyclic olefin-based
polymer again, a polyester film, a polynorbonene-based film that is
produced by the addition polymerization and the like may be used.
In addition to this, a film that is produced by using a transparent
polymer material may be used as the protective film, but not
limited thereto.
[0077] As the polarizer, a film that consists of polyvinyl alcohol
(PVA) comprising iodine or a dichromic dye may be used. The
polarizing film may be produced by dyeing iodine or the dichromic
dye on the PVA film, but the production method thereof is not
particularly limited thereto. In the present specification, the
polarizing film means a state that does not comprise the protective
film, and the polarizing plate means a state that comprises the
polarizing film and the protective film.
[0078] In the present invention, the protection film and the
polarizer may be combined by using the method that is known in the
art.
[0079] In addition, the present invention provides a liquid crystal
display that comprises the polarizing plate. For example, the
liquid crystal display device according to the present invention is
a liquid crystal display device comprising a liquid crystal cell
and a first polarizing plate and a second polarizing plate that are
provided on both sides of the liquid crystal cell, and at least one
of the first polarizing plate and the second polarizing plate is
the polarizing plate according to the present invention. It is
preferable that the optical film or the polarizer protective film
that are provided on the side that is opposite to the liquid
crystal cell of the polarizing plate includes a UV absorbing
agent.
[0080] In addition, the present invention provides an information
electronic device comprising the optical film. Examples of the
information electronic device include display devices such as a
liquid crystal display (LCD), an organic light emitting diode
(OLED) and the like.
[0081] In one embodiment, the liquid crystal display according to
the present invention is a liquid crystal display device comprising
a liquid cell, and a first polarizing plate and a second polarizing
plate that are provided on both sides of the liquid crystal cell,
and between at least one of the first polarizing plate and the
second polarizing plate and the liquid crystal cell, the optical
film according to the present invention may be provided. That is,
between the first polarizing plate and the liquid crystal cell,
between the second polarizing plate, and the liquid crystal cell,
or both between the first polarizing plate and the liquid crystal
cell and between the second polarizing plate and the liquid crystal
cell, one or more optical films according to the present invention
may be provided.
[0082] Hereinbelow, the present invention will be described in
detail with reference to Examples. The present invention may,
however, be embodied in many different forms and should not be
construed as being limited to the Examples set forth herein.
EXAMPLES
Example 1
[0083] The resin composition in which
poly(N-cyclohexylmaleimide-co-methylmethacrylate), the
styrene-maleic anhydride resin and the phenoxy-based resin were
uniformly mixed with each other at a weight ratio of 100:2.5:5 was
provided to a 24.phi. extruder in which nitrogen was substituted
from the raw material hopper to the extruder, and melted at
250.degree. C. to manufacture the raw material pellet.
[0084] As the phenoxy-based resin, PKFE (Mw=60,000, Mn=16,000, and
Tg=95.degree. C.) manufactured by InChemRez.RTM., Co., Ltd. was
used, and Dylarck 332 that included 85 wt % of styrene and 15 wt %
of maleic anhydride was used as the styrene-maleic anhydride
copolymer resin. In the
poly(N-cyclohexylmaleimide-co-methylmethacrylate) resin, the
content of N-cyclohexylmaleimide was 6.5 wt % which was analyzed by
using the NMR.
[0085] The obtained raw material pellets were dried in the vacuum,
melted at 260.degree. C. by using the extruder, and passed through
the coat hanger type of T-die, the chrome-coated casting roll and
the dry roll to manufacture the film that had the thickness of 150
.mu.m. This film was stretched by using the pilot stretching device
at 125.degree. C. in the MD direction using a difference between
speeds of rolls at the ratios described in the following Table 1,
and stretched in the TD direction at 125.degree. C. by using the
tenter at the ratios described in the following Table 1 to
manufacture the film. The in-plane retardation value and the
thickness retardation of the film are described in the following
Table 1. In addition, the retardation distribution according to the
width direction is shown in FIG. 1.
TABLE-US-00001 TABLE 1 MD stretching TD stretching retardation
value (nm) thickness ratio ratio R.sub.in R.sub.th (.mu.M) 100%
100% 0.4 +0.6 160 150% 100% 0.2 +1.0 118 150% 200% 1.0 -1.6 59 150%
250% 0.9 -1.1 47 160% 100% 0.4 +0.1 116 160% 200% 0.9 -1.5 56 160%
250% 0.8 -1.3 46 170% 100% 1.0 +1.9 114 170% 200% 0.7 -1.9 55 170%
220% 0.5 -1.5 50 170% 250% 0.5 -1.4 42
Example 2
[0086] The resin composition in which
poly(N-cyclohexylmaleimide-co-methylmethacrylate), the
styrene-maleic anhydride resin and the phenoxy-based resin were
uniformly mixed with each other at a weight ratio of 100:2.5:5 was
provided to a 24.phi. extruder in which nitrogen was substituted
from the raw material hopper to the extruder, and melted at
250.degree. C. to manufacture the raw material pellet.
[0087] The obtained raw material pellets were dried in the vacuum,
melted at 260.degree. C. by using the extruder, and passed through
the coat hanger type of T-die, the chrome-coated casting roll and
the dry roll to manufacture the film that had the thickness of 150
.mu.m. This film was stretched by using the pilot stretching device
at 125 to 140.degree. C. in the MD direction using a difference
between speeds of rolls at the ratio of 170% described in the
following Table 2, and stretched in the TD direction at 125 to
140.degree. C. by using the tenter at the ratio of 250% described
in the following Table 2 to manufacture the film. The in-plane
retardation value and the thickness retardation of the film are
described in the following Table 2.
TABLE-US-00002 TABLE 2 Stretching temperature MD stretching TD
stretching retardation value (nm) (.degree. C.) ratio ratio
R.sub.in R.sub.th 125 170% 250% 0.5 +1.7 130 170% 250% 0.0 -0.1 135
170% 250% 1.0 -0.9 140 170% 250% 1.3 -1.1
Examples 3 to 5 and Comparative Examples 1 to 3
[0088] As the poly(N-cyclohexylmaleimide-co-methylmethacrylate)
resin, IE830HR resin that was manufactured by LGMMA, Co., Ltd. was
used, as the phenoxy-based resin, InChemRez Phenoxy PKFE.RTM. resin
that was the phenoxy resin manufactured by InChem Corporation was
used, and as the styrene-maleic anhydride copolymer resin,
DYLARK.RTM. 332 (styrene 85 wt %, maleic anhydride 15 wt %) that
was manufactured by NOVA Chemicals, Co., Ltd. was used to
manufacture the film by using the same method as Example 1 and
measure physical properties thereof. The composition and physical
properties of the film are described in the following Tables 3 and
4.
TABLE-US-00003 TABLE 3 Parts by weight wt % Mol Mole ratio Tg HR
Dylark PKFE Dylark Styrene PKFE Styrene PKFE PKFE/St (.degree. C.)
Example 3 100.0 2.9 5.0 2.7 2.3 4.6 0.02 0.02 0.71 120 Example 4
100.0 4.7 8.0 4.2 3.5 7.1 0.03 0.02 0.71 120 Example 5 100.0 7.1
12.0 5.9 5.0 10.1 0.05 0.03 0.71 120 Comparative 100.0 0.0 0.0 0.0
0.0 0.0 0.00 0.00 -- 125 Example 1 Comparative 100.0 0.0 9.0 0.0
0.0 8.3 0.00 0.03 -- 120 Example 2 Comparative 100.0 11.8 10.0 9.7
8.2 8.2 0.08 0.03 0.36 121 Example 3
TABLE-US-00004 TABLE 4 MD stretching TD stretching Stretching
Stretching Stretching Stretching Retardation photoelasticity
temperature ratio temperature ratio (nm) coefficient (.degree. C.)
(%) (.degree. C.) (%) Rin Rth 10.sup.-12 m.sup.2/N Example 3 120 25
120 50 1.0 -3.1 0.5 Example 4 120 25 120 50 1.5 -3.8 0.6 Example 5
120 25 120 50 0.8 1.7 0.4 Comparative 125 25 150 50 1.9 -5.3 -4.6
Example 1 Comparative 120 25 120 50 10.1 18.5 2.2 Example 2
Comparative 120 25 120 50 24.5 13.6 -3.1 Example 3
[0089] As seen from the above Examples, in the optical film
according to the present invention, the absolute value of each of
in-plane retardation, thickness retardation and photoelasticity
coefficient is almost 0 before and after the stretching.
* * * * *