U.S. patent application number 13/823510 was filed with the patent office on 2013-09-19 for adhesive for polarizing plate, and polarizing plate comprising same.
This patent application is currently assigned to LG CHEM. LTD.. The applicant listed for this patent is Sae-Han Cho, Boong-Goon Jeong, Nam-Jeong Lee, Kyun-Il Rah, Eun-Mi Seo. Invention is credited to Sae-Han Cho, Boong-Goon Jeong, Nam-Jeong Lee, Kyun-Il Rah, Eun-Mi Seo.
Application Number | 20130244041 13/823510 |
Document ID | / |
Family ID | 45032650 |
Filed Date | 2013-09-19 |
United States Patent
Application |
20130244041 |
Kind Code |
A1 |
Cho; Sae-Han ; et
al. |
September 19, 2013 |
ADHESIVE FOR POLARIZING PLATE, AND POLARIZING PLATE COMPRISING
SAME
Abstract
Provided are an adhesive for a polarizing plate and a polarizing
plate comprising the same, and more particularly, an adhesive
composition for a polarizing plate comprising one or more acrylic
monomers having a hydrophilic group, a radical polymerization
initiator, an epoxy resin, and a cationic photopolymerization
initiator, as well as a polarizing plate comprising a polarizer, a
polymer film adhered to one side or both sides of the polarizer,
and an adhesive layer for bonding the polarizer and the polymer
film, in which the adhesive layer is formed of an adhesive
composition comprising one or more acrylic monomers having a
hydrophilic group, a radical polymerization initiator, an epoxy
resin, and a cationic photopolymerization initiator.
Inventors: |
Cho; Sae-Han; (Yuseong-gu,
KR) ; Seo; Eun-Mi; (Yuseong-gu, KR) ; Jeong;
Boong-Goon; (Seo-gu, KR) ; Rah; Kyun-Il;
(Seo-gu, KR) ; Lee; Nam-Jeong; (Seo-gu,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cho; Sae-Han
Seo; Eun-Mi
Jeong; Boong-Goon
Rah; Kyun-Il
Lee; Nam-Jeong |
Yuseong-gu
Yuseong-gu
Seo-gu
Seo-gu
Seo-gu |
|
KR
KR
KR
KR
KR |
|
|
Assignee: |
LG CHEM. LTD.
Seoul
KR
|
Family ID: |
45032650 |
Appl. No.: |
13/823510 |
Filed: |
September 20, 2011 |
PCT Filed: |
September 20, 2011 |
PCT NO: |
PCT/KR2011/006953 |
371 Date: |
June 7, 2013 |
Current U.S.
Class: |
428/412 ;
428/414; 428/480; 428/483; 428/507; 428/515; 428/523; 522/166 |
Current CPC
Class: |
C09J 4/00 20130101; Y10T
428/31909 20150401; G02B 1/08 20130101; C09J 2463/00 20130101; C09J
2433/00 20130101; C08G 59/68 20130101; C09J 163/00 20130101; C08L
33/04 20130101; Y10T 428/31786 20150401; C09J 133/14 20130101; Y10T
428/31938 20150401; Y10T 428/31515 20150401; G02B 5/3033 20130101;
Y10T 428/31507 20150401; Y10T 428/31797 20150401; C09J 7/22
20180101; Y10T 428/3188 20150401; C09J 2203/318 20130101; C09J
2433/00 20130101; C09J 2463/00 20130101; C09J 2463/00 20130101;
C09J 2433/00 20130101; C09J 163/00 20130101; C08L 33/04
20130101 |
Class at
Publication: |
428/412 ;
522/166; 428/523; 428/414; 428/480; 428/507; 428/515; 428/483 |
International
Class: |
C09J 133/14 20060101
C09J133/14 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 20, 2010 |
KR |
10-2010-0092684 |
Apr 18, 2011 |
KR |
10-2011-0035825 |
Claims
1. An adhesive composition for a polarizing plate comprising: one
or more acrylic monomers having a hydrophilic group; a radical
polymerization initiator; an epoxy resin; and a cationic
photopolymerization initiator.
2. The adhesive composition for a polarizing plate of claim 1,
wherein the adhesive composition for a polarizing plate comprises
20 to 80 parts by weight of the one or more acrylic monomers having
a hydrophilic group, 0.5 to 10 parts by weight of the radical
polymerization initiator, 30 to 80 parts by weight of the epoxy
resin and 1 to 10 parts by weight of the cationic
photopolymerization initiator.
3. The adhesive composition for a polarizing plate of claim 1,
wherein the adhesive composition for a polarizing plate comprises
20 to 50 parts by weight of the one or more acrylic monomers having
a hydrophilic group, 0.5 to 5 parts by weight of the radical
polymerization initiator, 20 to 60 parts by weight of the epoxy
resin and 1 to 7 parts by weight of the cationic
photopolymerization initiator.
4. The adhesive composition for a polarizing plate of claim 1,
wherein the adhesive composition for a polarizing plate comprises
30 parts by weight of the one or more acrylic monomers having a
hydrophilic group, 3 parts by weight of the radical polymerization
initiator, 40 parts by weight of the epoxy resin and 3 parts by
weight of the cationic photopolymerization initiator.
5. The adhesive composition for a polarizing plate of claim 1,
wherein the hydrophilic group is a hydroxy group (--OH).
6. The adhesive composition for a polarizing plate of claim 1,
wherein the epoxy resin is comprised of a combination of a first
epoxy resin compound including one or more epoxidized aliphatic
cyclic groups and a second epoxy compound including one or more
glycidyl ether groups.
7. The adhesive composition for a polarizing plate of claim 6,
wherein the first epoxy compound is selected from the group
consisting of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane
carboxylate, bis(3,4-epoxycyclohexylmethyl)adipate
dicyclopentadiene dioxide, limonene dioxide, and 4-vinylcyclohexene
dioxide.
8. The adhesive composition for a polarizing plate of claim 6,
wherein the second epoxy compound is selected from the group
consisting of 1,4-cyclohexanedimethanol diglycidyl ether, a
novolac-based epoxy, a bisphenol A-based epoxy, a bisphenol F-based
epoxy, a brominated bisphenol-based epoxy, 1,6-hexanediol
diglycidyl ether, trimethylolpropane triglycidyl ether, n-butyl
glycidyl ether, aliphatic glycidyl ether(C12-C14), 2-ethylhexyl
glycidyl ether, phenyl glycidyl ether, o-cresyl glycidyl ether, and
nonyl phenyl glycidyl ether.
9. The adhesive composition for a polarizing plate of claim 6,
wherein the adhesive composition for a polarizing plate comprises
15 to 40 parts by weight of the first epoxy compound and 15 to 40
parts by weight of the second epoxy compound based on 100 parts by
weight of the adhesive composition for a polarizing plate.
10. The adhesive composition for a polarizing plate of claim 6,
wherein the first and second epoxy compounds are comprised in a
weight ratio range of 1:3 to 3:1.
11. The adhesive composition for a polarizing plate of claim 1,
wherein the acrylic monomer having a hydrophilic group is selected
from the group consisting of hydroxyethyl acrylate (HEA),
hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl
methacrylate, hydroxybutyl acrylate, or a mixture thereof.
12. The adhesive composition for a polarizing plate of claim 1,
wherein the adhesive composition for a polarizing plate further
comprises greater than 0 and equal to or less than 50 parts by
weight of a monofunctional hydrophobic monomer based on 100 parts
by weight of a total adhesive composition.
13. The adhesive composition for a polarizing plate of claim 12,
wherein the monofunctional hydrophobic monomer comprises at least
one monomer selected from the group consisting of isobornyl
acrylate (IBOA), benzyl(meth)acrylate, nonyl(meth)acrylate,
isobutyl(meth)acrylate, isodecyl acrylate, lauryl acrylate, stearyl
acrylate, 2-ethyl hexyl acrylate, polyethylene glycol methacrylate,
octyl/decyl acrylate, phenoxyethyl acrylate (PEA), nonylphenol
ethoxylate acrylate, dicyclopentenyl acrylate, dicyclopentenyl
oxyethyl acrylate, propylene glycol mono(meth)acrylate, and
ethoxyethoxy ethyl acrylate.
14. The adhesive composition for a polarizing plate of claim 12,
wherein the monofunctional hydrophobic monomer is phenoxyethyl
acrylate and isobornyl acrylate.
15. The adhesive composition for a polarizing plate of claim 14,
wherein the adhesive composition for a polarizing plate comprises
20 to 80 parts by weight of hydroxyethyl acrylate, greater than 0
and equal to or less than 30 parts by weight of phenoxyethyl
acrylate, greater than 0 and equal to or less than 20 parts by
weight of isobornyl acrylate, 30 to 80 parts by weight of an epoxy
resin, 1 to 7 parts by weight of a cationic photopolymerization
initiator, and 0.5 to 5 parts by weight of a radical polymerization
initiator.
16. The adhesive composition for a polarizing plate of claim 1,
wherein the adhesive composition for a polarizing plate has a
viscosity range of 10 cP to 30 cP at 25.degree. C.
17. The adhesive composition for a polarizing plate of claim 1,
wherein the adhesive composition for a polarizing plate further
comprises greater than 0 and equal to or less than 4 parts by
weight of urethane acrylate.
18. A polarizing plate comprising: a polarizer; a polymer film
adhered to one side or both sides of the polarizer; and an adhesive
layer for bonding the polarizer and the polymer film, wherein the
adhesive layer is formed of an adhesive composition comprising one
or more acrylic monomers having a hydrophilic group, a radical
polymerization initiator, an epoxy resin, and a cationic
photopolymerization initiator.
19. The polarizing plate of claim 18, wherein the polarizing plate
comprises 20 to 80 parts by weight of the one or more acrylic
monomers having a hydrophilic group, 0.5 to 10 parts by weight of
the radical polymerization initiator, 30 to 80 parts by weight of
the epoxy resin and 1 to 10 parts by weight of the cationic
photopolymerization initiator.
20. The polarizing plate of claim 19, wherein the hydrophilic group
is a hydroxy group (--OH).
21. The polarizing plate of claim 18, wherein the epoxy resin is
comprised of a combination of a first epoxy resin compound
including one or more epoxidized aliphatic cyclic groups and a
second epoxy compound including one or more glycidyl ether
groups.
22. The polarizing plate of claim 18, wherein the first epoxy
compound is selected from the group consisting of
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate,
bis(3,4-epoxycyclohexylmethyl)adipate dicyclopentadiene dioxide,
limonene dioxide, and 4-vinylcyclohexene dioxide.
23. The polarizing plate of claim 18, wherein the second epoxy
compound is selected from the group consisting of
1,4-cyclohexanedimethanol diglycidyl ether, a novolac-based epoxy,
a bisphenol A-based epoxy, a bisphenol F-based epoxy, a brominated
bisphenol-based epoxy, 1,6-hexanediol diglycidyl ether,
trimethylolpropane triglycidyl ether, n-butyl glycidyl ether,
aliphatic glycidyl ether(C12-C14), 2-ethylhexyl glycidyl ether,
phenyl glycidyl ether, o-cresyl glycidyl ether, and nonyl phenyl
glycidyl ether.
24. The polarizing plate of claim 21, wherein the polarizing plate
comprises 15 to 40 parts by weight of the first epoxy compound and
15 to 40 parts by weight of the second epoxy compound based on 100
parts by weight of an adhesive composition for a polarizing
plate.
25. The polarizing plate of claim 21, wherein the first and second
epoxy compounds are comprised in a weight ratio range of 1:3 to
3:1.
26. The polarizing plate of claim 18, wherein the acrylic monomer
having a hydrophilic group is selected from the group consisting of
hydroxyethyl acrylate (HEA), hydroxyethyl methacrylate,
hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl
acrylate, or a mixture thereof.
27. The polarizing plate of claim 18, wherein the adhesive
composition for a polarizing plate further comprises greater than 0
and equal to or less than 50 parts by weight of a monofunctional
hydrophobic monomer based on 100 parts by weight of a total
adhesive composition.
28. The polarizing plate of claim 27, wherein the monofunctional
hydrophobic monomer comprises at least one monomer selected from
the group consisting of isobornyl acrylate (IBOA),
benzyl(meth)acrylate, nonyl(meth)acrylate, isobutyl(meth)acrylate,
isodecyl acrylate, lauryl acrylate, stearyl acrylate, 2-ethyl hexyl
acrylate, polyethylene glycol methacrylate, octyl/decyl acrylate,
phenoxyethyl acrylate (PEA), nonylphenol ethoxylate acrylate,
dicyclopentenyl acrylate, dicyclopentenyl oxyethyl acrylate,
propylene glycol mono(meth)acrylate, and ethoxyethoxy ethyl
acrylate.
29. The polarizing plate of claim 27, wherein the monofunctional
hydrophobic monomer is phenoxyethyl acrylate and isobornyl
acrylate.
30. The polarizing plate of claim 29, wherein the adhesive
composition for a polarizing plate comprises 20 to 80 parts by
weight of hydroxyethyl acrylate, greater than 0 and equal to or
less than 30 parts by weight of phenoxyethyl acrylate, greater than
0 and equal to or less than 20 parts by weight of isobornyl
acrylate, 30 to 80 parts by weight of an epoxy resin, 1 to 7 parts
by weight of a cationic photopolymerization initiator, and 0.5 to 5
parts by weight of a radical polymerization initiator.
31. The polarizing plate of claim 18, wherein the adhesive
composition for a polarizing plate has a viscosity range of 10 cP
to 30 cP at 25.degree. C.
32. The polarizing plate of claim 18, wherein the adhesive
composition for a polarizing plate further comprises greater than 0
and equal to or less than 4 parts by weight of urethane
acrylate.
33. The polarizing plate of claim 18, wherein the polymer film is
at least one selected from the group consisting of an acrylic film,
a polyethylene terephthalate (PET) film, a PET film treated with an
acrylic primer, a triacetyl cellulose (TAC) film, a cycloolefin
polymer (COP) film, a polycarbonate film, and a polynorbornene
(PNB)-based film.
34. An optical device comprising the polarizing plates of claim 18.
Description
TECHNICAL FIELD
[0001] The present invention relates to a non-aqueous adhesive
composition for a polarizing plate to bond a polarizer and a
protective film or a compensation film, and a polarizing plate
prepared through bonding by using the non-aqueous adhesive
composition.
BACKGROUND ART
[0002] A liquid crystal display device has been used in various
display devices due to having characteristics such as low power
consumption, low-voltage operation, lightweightness, and thinness.
The liquid crystal display device may be composed of many materials
such as a liquid cell, a polarizing plate, a retardation film, a
light collection sheet, a diffusion film, a light guide plate, and
a light reflecting sheet. Therefore, improvements targeting
enhancements of productivity, lightening, and brightness have been
actively undertaken by reducing the number of constituent films, or
decreasing the thicknesses thereof.
[0003] In general, a polarizing plate has been used in a structure,
in which a protective film is stacked on one or both sides of a
polarizer formed of a polyvinyl alcohol (hereinafter, referred to
as "PVA")-based resin dyed with a dichroic dye or iodine by using a
water-based adhesive prepared by dissolving a PVA-based material in
water. However, this may be inconvenient, in that a corona
treatment or a primer treatment may be performed due to low
adhesive strength between the film and the water-based
adhesive.
[0004] The protective film may be formed of triacetyl cellulose
(TAC), polyethylene terephthalate (PET), a cycloolefin polymer
(COP), an acrylic film, or a combination thereof.
[0005] An acrylic adhesive, an adhesive for a dry laminate in which
a polyurethane-based resin solution and a polyisocyanate resin
solution are mixed, a styrene butadiene rubber-based adhesive, an
epoxy-based adhesive, a PVA-based adhesive, a polyurethane-based
adhesive, an adhesive containing a polyester-based ionomer type
urethane resin and a compound having a glycidyloxy group, or a
thermocurable-type adhesive are known as adhesives which may be
used for bonding the polarizer and the protective film. In
particular, a water-based adhesive formed of an aqueous solution
having a PVA-based resin is used in most cases.
[0006] However, when the protective film is an acrylic film,
adhesive strength, with respect to the water-based adhesive may be
low, due to the characteristics thereof. As a result, there may be
limitations in reprocessability or cuttability. For this reason,
there may be inconvenience, in that the protective film may need to
be coated with a primer and then bonded with the water-based
adhesive, or wetting, with respect to water, is increased by
applying corona discharge.
[0007] Meanwhile, in addition to the degradation of adhesive
strength according to a substrate, when different substrates are
used as protective films on one side and the other side of a PVA
device, there may be problems like the occurrence of curling in a
polarizing plate caused by a drying process of the water-based
adhesive and a degradation of initial optical physical properties,
and therefore, a non-aqueous based adhesive was developed in order
to resolve the foregoing problems.
[0008] In general, with respect to the non-aqueous based adhesive,
the thickness of a final adhesive layer tends to be thicker in
comparison to the case of the water-based adhesive. Therefore, the
thickness of the adhesive layer may be decreased by minimizing the
viscosity thereof. At this time, water resistivity becomes poor
when the content of an oligomer is reduced and a hydrophilic
monomer is used in order to maintain the non-aqueous based adhesive
in a state of low viscosity, and a decrease in adhesive strength
generally occurs when a polyfunctional monomer or a hydrophobic
monomer is added in order to improve water resistance. As another
method of increasing water resistance, an isocyanate-based compound
having good water resistivity may be added, but there may be a
limitation in solution stability caused by the hydrophilic monomer
having a reaction therewith.
[0009] Therefore, as an adhesive composition which may be used in
various substrates, e.g., a TAC film, an acrylic film, a COP film,
or a PET film, the development of a non-aqueous adhesive for a
polarizing plate having excellent adhesive strength as well as
improved water resistivity and degree of curing, and particularly
excellent thermal shock properties at low viscosity, and a
polarizing plate bonded by using the non-aqueous adhesive are
required.
DETAILED DESCRIPTION OF INVENTION
Technical Problem
[0010] An aspect of the present invention provides a low viscosity
adhesive for a polarizing plate having excellent adhesive strength,
water resistance, and thermal shock properties while maintaining
the state of low viscosity of the adhesive.
[0011] Another aspect of the present invention provides a
polarizing plate comprising the foregoing adhesive.
[0012] Another aspect of the present invention provides an optical
device comprising the foregoing polarizing plate.
Technical Solution
[0013] According to an aspect of the present invention, there is
provided an adhesive composition for a polarizing plate comprising:
one or more acrylic monomers having a hydrophilic group; a radical
polymerization initiator; an epoxy resin; and a cationic
photopolymerization initiator.
[0014] According to another aspect of the present invention, there
is provided a polarizing plate comprising: a polarizer; a polymer
film adhered to one side or both sides of the polarizer; and an
adhesive layer for bonding the polarizer and the polymer film,
wherein the adhesive layer is formed of an adhesive composition
comprising one or more acrylic monomers having a hydrophilic group,
a radical polymerization initiator, an epoxy resin, and a cationic
photopolymerization initiator.
[0015] According to another aspect of the present invention, there
is provided an optical device comprising a polarizing plate.
[0016] The adhesive composition for a polarizing plate may comprise
20 to 80 parts by weight of the one or more acrylic monomers having
a hydrophilic group, 0.5 to 10 parts by weight of the radical
polymerization initiator, 30 to 80 parts by weight of the epoxy
resin and 1 to 10 parts by weight of the cationic
photopolymerization initiator.
[0017] The adhesive composition for a polarizing plate, for
example, may comprise 20 to 50 parts by weight of the one or more
acrylic monomers having a hydrophilic group, 0.5 to 5 parts by
weight of the radical polymerization initiator, 20 to 60 parts by
weight of the epoxy resin and 1 to 7 parts by weight of the
cationic photopolymerization initiator.
[0018] The hydrophilic group may be a hydroxy group (--OH).
[0019] The epoxy resin may be comprised of a combination of a first
epoxy resin compound including one or more epoxidized aliphatic
cyclic groups and a second epoxy compound including one or more
glycidyl ether groups.
[0020] The first epoxy compound may be at least one selected from
the group consisting of
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate,
bis(3,4-epoxycyclohexylmethyl)adipate dicyclopentadiene dioxide,
limonene dioxide, and 4-vinylcyclohexene dioxide.
[0021] The second epoxy compound may be selected from the group
consisting of 1,4-cyclohexanedimethanol diglycidyl ether, a
novolac-based epoxy, a bisphenol A-based epoxy, a bisphenol F-based
epoxy, a brominated bisphenol-based epoxy, 1,6-hexanediol
diglycidyl ether, trimethylolpropane triglycidyl ether, n-butyl
glycidyl ether, aliphatic glycidyl ether(C12-C14), 2-ethylhexyl
glycidyl ether, phenyl glycidyl ether, o-cresyl glycidyl ether, and
nonyl phenyl glycidyl ether.
[0022] The adhesive composition for a polarizing plate may comprise
15 to 40 parts by weight of the first epoxy compound and 15 to 40
parts by weight of the second epoxy compound based on 100 parts by
weight of the adhesive composition for a polarizing plate.
[0023] The first and second epoxy compounds may be comprised in a
weight ratio range of 1:3 to 3:1.
[0024] The acrylic monomer having a hydrophilic group may be
selected from the group consisting of hydroxyethyl acrylate (HEA),
hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl
methacrylate, hydroxybutyl acrylate, or a mixture thereof.
[0025] The adhesive composition for a polarizing plate may further
comprise greater than 0 and equal to or less than 50 parts by
weight of a monofunctional hydrophobic monomer based on 100 parts
by weight of a total adhesive composition.
[0026] The monofunctional hydrophobic monomer may comprise at least
one monomer selected from the group consisting of isobornyl
acrylate (IBOA), benzyl(meth)acrylate, nonyl(meth)acrylate,
isobutyl(meth)acrylate, isodecyl acrylate, lauryl acrylate, stearyl
acrylate, 2-ethyl hexyl acrylate, polyethylene glycol methacrylate,
octyl/decyl acrylate, phenoxyethyl acrylate (PEA), nonylphenol
ethoxylate acrylate, dicyclopentenyl acrylate, dicyclopentenyl
oxyethyl acrylate, propylene glycol mono(meth)acrylate, and
ethoxyethoxy ethyl acrylate.
[0027] The monofunctional hydrophobic monomer may be phenoxyethyl
acrylate and isobornyl acrylate.
[0028] The adhesive composition for a polarizing plate may comprise
20 to 80 parts by weight of hydroxyethyl acrylate, greater than 0
and equal to or less than 30 parts by weight of phenoxyethyl
acrylate, greater than 0 and equal to or less than 20 parts by
weight of isobornyl acrylate, 30 to 80 parts by weight of an epoxy
resin, 1 to 7 parts by weight of a cationic photopolymerization
initiator, and 0.5 to 5 parts by weight of a radical polymerization
initiator based on 100 parts by weight of the adhesive composition
for a polarizing plate.
[0029] The adhesive composition for a polarizing plate may have a
viscosity range of 10 cP to 30 cP at 25.degree. C.
[0030] The adhesive composition for a polarizing plate may further
comprise greater than 0 and equal to or less than 4 parts by weight
of urethane acrylate.
Effects of Invention
[0031] According to the present invention, an adhesive composition
for a polarizing plate having excellent optical physical properties
such as adhesive strength and water resistance, and particularly
improved thermal shock physical properties while maintaining low
viscosity, and a polarizing plate bonded by using the adhesive
composition may be prepared.
BRIEF DESCRIPTION OF FIGURES
[0032] The above and other aspects, features and other advantages
of the present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0033] FIG. 1 illustrates a polarizer 1 and a protective film or a
viewing angle compensation film 2a which are bonded by an adhesive
layer 3 formed by an adhesive composition of the present invention;
and
[0034] FIG. 2 illustrates a liquid crystal cell C, in which
polarizing plates P comprising the adhesive composition of the
present invention are disposed on both sides thereof.
BEST MODE FOR INVENTION
[0035] Hereinafter, the present invention is described in more
detail.
[0036] The present invention relates to an adhesive composition for
a polarizing plate comprising one or more acrylic monomers having a
hydrophilic group, a radical polymerization initiator, an epoxy
resin, and a cationic photopolymerization initiator, and more
particularly, the adhesive composition for a polarizing plate may
comprise 20 to 80 parts by weight of the one or more acrylic
monomers having a hydrophilic group, 0.5 to 10 parts by weight of
the radical polymerization initiator, 30 to 80 parts by weight of
the epoxy resin, and 1 to 10 parts by weight of the cationic
photopolymerization initiator. In this case, adhesive strength
between the film and the polarizer and water resistivity are
excellent while the state of viscosity is low. In the present
invention, the term "parts by weight" denotes a weight ratio of
each component.
[0037] The adhesive composition for a polarizing plate may comprise
20 to 50 parts by weight of the one or more acrylic monomers having
a hydrophilic group, 0.5 to 5 parts by weight of the radical
polymerization initiator, 20 to 60 parts by weight of the epoxy
resin, and 1 to 7 parts by weight of the cationic
photopolymerization initiator, and for example, may comprise 30
parts by weight of the one or more acrylic monomers having a
hydrophilic group, 3 parts by weight of the radical polymerization
initiator, 40 parts by weight of the epoxy resin, and 3 parts by
weight of the cationic photopolymerization initiator.
[0038] When the acrylic monomer having a hydrophilic group is less
than 20 parts by weight, adhesive strength may decrease, and when
the acrylic monomer having a hydrophilic group is more than 80
parts by weight, water resistivity and adhesive strength of the
polarizing plate may decrease. When the epoxy resin is less than 30
parts by weight, the improvement effects of water resistivity and
endurance reliability may decrease, and when the epoxy resin is
more than 80 parts by weight, compatibility and viscosity may
increase. When the radical polymerization initiator is less than
0.5 parts by weight, a curing rate may decrease due to an increase
in a content of a cationic polymerization component, and when the
radical polymerization initiator is more than 10 parts by weight,
compatibility and optical durability may be poor. When the cationic
photopolymerization initiator is less than 1 part by weight, an
improvement effect of a water resistivity may decrease, and when
the cationic photopolymerization initiator is more than 10 parts by
weight, unit price may increase while an improvement in
effectiveness may be insignificant.
[0039] The adhesive composition of the present invention comprises
one or more monomers selected from the group consisting of acrylic
monomers containing a hydrophilic group as a major component and is
a photocurable-type adhesive for a polarizing plate, in which an
epoxy resin and a cationic polymerization initiator are added in
order to increase water resistivity reduced due to the
hydrophilicity of the foregoing monomer.
[0040] In particular, the epoxy resin, which may be used in the
present invention, may be comprised of a combination of a first
epoxy resin compound including one or more epoxidized aliphatic
cyclic groups and a second epoxy compound including one or more
glycidyl ether groups.
[0041] When the combination of the foregoing first and second
epoxies is used, an adhesive for a polarizing plate having improved
thermal shock physical properties may be prepared. The adhesive for
a polarizing plate may comprise 15 to 40 parts by weight of the
first epoxy compound and 15 to 40 parts by weight of the second
epoxy compound, based on 100 parts by weight of the adhesive
composition for a polarizing plate, and for example, may comprise
20 parts by weight of the first epoxy and the second epoxy,
respectively. When the epoxy resin comprised of the combination of
the first and second epoxy compounds is used, better adhesion with
respect to triacetyl cellulose (TAC) may be provided.
[0042] Meanwhile, the first and second epoxy compounds, for
example, may be comprised in a weight ratio range of 1:3 to 3:1.
When the first epoxy compound is comprised in an amount less than
that of the foregoing range, an improvement effect of a thermal
shock may decrease, and when the first epoxy compound is comprised
in more than the foregoing range, there may be cases in which
adhesive strength with respect to the substrate may be limited.
[0043] The first epoxy compound is not particularly limited, so
long as it increases glass transition temperature (Tg) and provides
hardness to the adhesive layer. The epoxidized aliphatic cyclic
group of the first epoxy compound may be an epoxidized cyclohexyl
group, for example, a 3,4-epoxycyclohexylmethyl group, and may be
at least one selected from the group consisting of
3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate,
bis(3,4-epoxycyclohexylmethyl)adipate dicyclopentadiene dioxide,
limonene dioxide, and 4-vinylcyclohexene dioxide.
[0044] The second epoxy compound is not particularly limited so
long as it includes one or more glycidyl ether groups, and more
particularly, may be selected from the group consisting of
1,4-cyclohexanedimethanol diglycidyl ether, a novolac-based epoxy,
a bisphenol A-based epoxy, a bisphenol F-based epoxy, a brominated
bisphenol-based epoxy, 1,6-hexanediol diglycidyl ether,
trimethylolpropane triglycidyl ether, n-butyl glycidyl ether,
aliphatic glycidyl ether(C12-C14), 2-ethylhexyl glycidyl ether,
phenyl glycidyl ether, o-cresyl glycidyl ether, and nonyl phenyl
glycidyl ether. The second epoxy compound may improve the adhesive
strength of the adhesive layer and in particular, may improve
adhesive strength by providing softness.
[0045] The hydrophilic group of the acrylic monomer may be a
hydroxy group (--OH) or a carboxy group (--COOH), and for example,
may be a hydroxy group (--OH). Particular examples of the monomer
having a hydrophilic group may be selected from the group
consisting of hydroxyethyl acrylate (HEA), hydroxyethyl
methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate,
hydroxybutyl acrylate, and mixtures thereof. However, the monomer
having a hydrophilic group is not limited thereto and may include a
monomer containing a hydrophilic group well known in the art.
[0046] The cationic photopolymerization initiator is a compound
producing cationic species or a Lewis acid by the irradiation of
active energy rays, and for example, may be an onium salt such as
an aromatic diazonium salt, an aromatic iodine aluminum salt, or an
aromatic sulfonium salt, and an iron-arene complex. However, the
cationic photopolymerization initiator is not limited thereto and
may use a photosensitizer according to the efficiency of the
initiator.
[0047] Further, a monofunctional hydrophobic monomer may be added
in order to increase the compatibility of the adhesive with respect
to the initiator of the composition for a polarizing plate of the
present invention and the adhesiveness with respect to the
substrate, and for example, the monofunctional hydrophobic monomer
may be isobornyl acrylate (IBOA), benzyl(meth)acrylate,
nonyl(meth)acrylate, isobutyl(meth)acrylate, isodecyl acrylate,
lauryl acrylate, stearyl acrylate, 2-ethyl hexyl acrylate,
polyethylene glycol methacrylate, octyl/decyl acrylate,
phenoxyethyl acrylate (PEA), nonylphenol ethoxylate acrylate,
dicyclopentenyl acrylate, dicyclopentenyl oxyethyl acrylate,
propylene glycol mono(meth)acrylate, and ethoxyethoxy ethyl
acrylate. The monofunctional hydrophobic monomer is not
particularly limited so long as it is a monofunctional hydrophobic
monomer, but a mixture of phenoxyethyl acrylate and isobornyl
acrylate, for example, may be used.
[0048] The monofunctional hydrophobic monomer may be comprised in
an amount greater than 0 and equal to or less than 50 parts by
weight based on 100 parts by weight of a total adhesive
composition, and for example, when PEA and IBOA are comprised, PEA
may be comprised in an amount greater than 0 and equal to or less
than 30 parts by weight, and IBOA may be comprised in an amount
greater than 0 and equal to or less than 20 parts by weight based
on 100 parts by weight of the total adhesive composition,
respectively. When PEA is added, adhesion with respect to the
hydrophobic substrate is improved, and when PEA is comprised in an
amount greater than 30 parts by weight, the adhesive strength of
the polarizing plate may be limited because adhesive strength with
respect to polyvinyl alcohol (PVA) decreases. When IBOA is added,
adhesion with respect to the hydrophobic substrate is improved, and
when IBOA is comprised in an amount greater than 20 parts by
weight, adhesive strength may significantly decrease. When PEA and
IBOA are comprised within the foregoing range of parts by weight,
the adhesive strength of the adhesive composition according to the
present invention may be improved.
[0049] The present invention relates to a photocurable-type
adhesive composition and the thickness of a final adhesive layer
will be very thick in comparison to the case of a water-based
adhesive because a solid content is 100% when a solvent is not
added with respect to the foregoing photocurable-type adhesive.
Therefore, the thickness of the adhesive layer may be decreased by
minimizing viscosity, and the adhesive composition for a polarizing
plate may have a viscosity range of 10 cP to 30 cP at 25.degree.
C., and for example, may have a viscosity of 20 cP or so.
[0050] The adhesive composition according to the present invention
has low viscosity and comprises an acrylic monomer having a
hydrophilic group as a major component. Adhesive strength and water
resistivity may be improved by adding an epoxy resin and a cationic
photopolymerization initiator. In particular, thermal shock
physical properties may be improved when the combination of the
first epoxy compound including one or more epoxidized aliphatic
cyclic groups and the second epoxy compound including one or more
glycidyl ether groups is used as described in the present
invention.
[0051] The cationic polymerization initiator generates cations or a
Lewis acid according to the irradiation of active energy rays such
as visible light, ultra violet rays, X-rays, and electron beams or
heating, and initiates a polymerization reaction of an epoxy group.
Therefore, the epoxy resin of the present invention may be denoted
as a hybrid curable-type resin according to the cations and the
radical initiator.
[0052] Meanwhile, the radical initiator is one used in the art and
is not particularly limited. For example, a radical initiator such
as a phenylketone-based, an acetophenone-based, a
benzoinether-based, a benzophenone-based, a thioxanthone-based, an
acylphosphine oxide-based, an oxime ester-based, and
camphorquinone-based may be used.
[0053] The adhesive composition for a polarizing plate may further
comprise a photosensitizer, an antioxidant, an oligomer, and an
adhesion promoter as needed, and may further comprise greater than
0 and equal to or less than 4 parts by weight of urethane acrylate.
Viscosity tends to increase when a urethane acrylate is added, but
the increased viscosity of the adhesive may be lowered by
increasing temperature.
[0054] The adhesive composition for a polarizing plate according to
the present invention, in which urethane acrylate is added, may
provide appropriate adhesive strength when being used with respect
to an acrylic film.
[0055] In general, a UV screening agent is included in a polarizer
protective film for protecting a polarizer, and since ultraviolet
rays having a wavelength of 365 nm or less are mostly absorbed by
the UV screening agent when the UV screening agent is included, a
long-wavelength initiator absorbing light in a wavelength of 365 nm
or more may be used as the photopolymerization initiator.
Particular examples of the long-wavelength initiator may be
.alpha.-hydroxyketone, phenylglyoxylate, benzyldimethylketal,
.alpha.-aminoketone, monoacylphosphine, bisacylphosphine, and
combinations thereof. However, the long-wavelength initiator is not
limited thereto.
[0056] A thickness of the adhesive layer formed by the adhesive
composition may be greater than 0 and equal to or less than 10
.mu.m, but the thickness of the adhesive layer is not limited
thereto. When the thickness is more than 10 .mu.m, an increase in
the unit price of the adhesive and changes in durability
characteristics and appearance with respect to the physical
properties of the adhesive layer may be generated.
[0057] FIG. 1 exemplarily illustrates a polarizer 1 and a
transparent protective film or a viewing angle protective film 2a,
which are bonded by an adhesive layer 3 formed by an adhesive
composition according to the present invention.
[0058] The adhesive composition of the present invention provides
hydrophilicity by means of an acrylic monomer having a hydrophilic
group as well as decreases a content of a highly viscous oligomer
for low viscosity, and only a small amount of an epoxy resin and a
photopolymerization initiator is comprised to increase the degree
of curing and improve water resistivity and thermal shock physical
properties.
[0059] According to the present invention, there is provided a
polarizing plate comprising: a polarizer; a polymer film adhered to
one side or both sides of the polarizer; and an adhesive layer for
bonding the polarizer and the polymer film, wherein the adhesive
layer is formed of an adhesive composition comprising one or more
acrylic monomers having a hydrophilic group, a radical
polymerization initiator, an epoxy resin, and a cationic
photopolymerization initiator. The adhesive composition, which may
be used in the preparation of the polarizing plate of the present
invention, is as described above.
[0060] The polymer film, which may be used for the preparation of
the polarizing plate of the present invention, may be at least one
selected from the group consisting of an acrylic film, a
polyethylene terephthalate (PET) film, a PET film treated with an
acrylic primer, a polynorbornene (PNB)-based film, a cycloolefin
(COP) film, a polycarbonate film, and a TAC film including NRT (60
.mu.m, Fujifilm), N TAC (40 .mu.m, Konica), V TAC (80 .mu.m,
Fujifilm), or UZ TAC (60 .mu.m, Fujifilm). However, the polymer
film is not limited thereto and a polymer film known in the art may
be used. Meanwhile, if necessary, a corona treatment or the like
may be further performed during bonding with the polymer film.
[0061] The acrylic film may be a film comprising a copolymer
including an alkyl(meth)acrylate-based unit and a styrene-based
unit, and an aromatic resin having a carbonate portion in the main
chain, or a film comprising an alkyl(meth)acrylate unit, a
styrene-based unit, a 3- to 6-membered heterocyclic unit
substituted with at least one carbonyl group, and a vinyl cyanide
unit, or a film comprising an aromatic unit having a chain with a
hydroxy group-containing portion and an aromatic portion and a
styrene-based unit including one or more styrene-based derivatives.
The film comprising the aromatic unit having a chain with a hydroxy
group-containing portion and an aromatic portion and the
styrene-based unit including one or more styrene-based derivatives
may be a film having an absolute value of an in-plane retardation
value (Rin) and a thickness retardation value (Rth) of 10 nm or
less regardless of the presence of stretching.
[0062] In the polarizing plate according to the present invention,
a film formed of polyvinyl alcohol (PVA) including iodine or a
dichroic dye may be used as the polarizer. The polarizer may be
prepared by dyeing a PVA film with iodine or a dichroic dye, but
the preparation method thereof is not particularly limited. In the
present specification, the polarizer denotes a state not including
a protective film and the polarizing plate denotes a state
including a protective film.
[0063] The polarizing plate according to the present invention may
be prepared through a method known in the art by using the
foregoing polarizer, polarizer protective film or viewing angle
compensation film as a polymer film, and an adhesive composition
according to the present invention. For example, the polarizing
plate according to the present invention may be prepared by coating
the adhesive composition of the present invention on at least one
side of the polarizer or the polarizer protective film or the
compensation film, and then passing the polarizer and the polarizer
protective film or the compensation film through a laminator.
However, the method of preparing the polarizing plate is not
limited thereto.
[0064] Also, the present invention provides an optical device
comprising the foregoing polarizing plate. For example, the optical
device of the present invention may be a liquid crystal display
device as shown in FIG. 2 and is a liquid crystal display device
comprising a liquid cell and the first and second polarizing plates
respectively included on both sides of the liquid cell, in which at
least one of the first and second polarizing plates may be the
polarizing plate according to the present invention.
[0065] Hereinafter, the present invention will be described in more
detail according to examples. However, the following examples are
merely provided to exemplify the present invention, not to limit
the scope of the present invention.
MODE FOR INVENTION
Example
Preparation Example 1
Preparation of Polarizer Protective Film
[0066] (1) Acrylic Polymer Film
[0067] A resin composition, in which a
poly(N-cyclohexylmaleimide-co-methylmethacrylate) resin, a
styrene-maleic anhydride copolymer resin, and a phenoxy-based resin
were uniformly mixed in a weight ratio of 100:2.5:5, was supplied
to an 24.phi. extruder, which was filled with nitrogen from a raw
material hopper to the extruder, and was then melted at 250.degree.
C. to prepare raw material pellets.
[0068] The phenoxy-based resin used was InChemRez.RTM. PKFE
(Mw=60,000, Mn=16,000, Tg=95.degree. C.), the styrene-maleic
anhydride copolymer resin used was Dylaeck 332 containing 85 wt %
of styrene and 15 wt % of maleic anhydride, and the
poly(N-cyclohexylmaleimide-co-methylmethacrylate) resin had a
N-cyclohexylmaleimide content of 6.5 wt % according to the result
of nuclear magnetic resonance (NMR) analysis.
[0069] The raw material pellets thus obtained was vacuum dried and
melted in the extruder at 260.degree. C., and then passed through a
coat hanger type T-die. Thereafter, a 150 .mu.m thick film was
prepared by passing through a chromium-coated casting roll and a
drying roll. The film was stretched using the velocity difference
of rolls at a ratio described in the following Table 1 in a machine
direction (MD) at 125.degree. C. by using a pilot stretching
machine, and then a film was prepared by stretching at a ratio
described in the following Table 1 in a transverse direction (TD)
at 125.degree. C. by using a tenter. In-plane and thickness
retardation values of the foregoing film are presented in the
following Table 1.
TABLE-US-00001 TABLE 1 Retardation MD stretch TD stretch value (nm)
ratio ratio Rin Rth Thickness (.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
[0070] (2) TAC-Based Polymer Film
[0071] Commercial V TAC (Fujifilm), N TAC (Konica), and UZ TAC
(Fujifilm) were used as a TAC-based polymer film.
Example 1
(1) Preparation of Adhesive
[0072] An adhesive composition for a polarizing plate was prepared
by mixing 38.5 wt % of 2-hydroxyethyl acrylate (2-HEA), 10 wt % of
phenoxyethyl acrylate (PEA), and 15 wt % of isobornyl acrylate
(IBOA) as a monomer, 3 wt % of CGI 819 as a radical initiator, 3 wt
% of an iodine initiator (Ciba-Geiger AG, Irgacure 250) as a
cationic photopolymerization initator, 0.5 wt % of a
photosensitizer (Aldrich, isopropyl thioxantone), and wt % of
celloxide 2021P and 15 wt % of 1,4-cyclohexane dimethanol
diglycidyl ether (CHDMGDE) (HAJIN CHEM TECH Co., Ltd.) as an epoxy
resin.
(2) Preparation of Polarizing Plate
[0073] Front and back sides of a PVA device, in which the both
sides were covered with V TAC (or N TAC or an acryl film of
Preparation Example 1(1)) (substrate 1) and TAC (UZ TAC) (substrate
2), was coated with the adhesive prepared in Example 1(1) by a
spoid, and then the PVA device was passed through a laminator (5
m/min). Conditions were set to obtain a final adhesive layer having
a thickness range of 1 .mu.m to 2 .mu.m, and then the laminated
polarizing plate put on a belt was irradiated with ultra violet
rays having an intensity of 2000 mJ/cm.sup.2 by using a UV metal
halide lamp.
Example 2
[0074] A polarizing plate was prepared in the same manner as
Example 1 except that an adhesive comprising 20 wt % of celloxide
2021P and 10 wt % of 1,4-CHDMGDE (HAJIN CHEM TECH Co., Ltd.) as an
epoxy resin was used.
Example 3
[0075] A polarizing plate was prepared in the same manner as
Example 1 except that an adhesive comprising 28.5 wt % of 2-HEA as
a monomer and 20 wt % of celloxide 2021P and 20 wt % of 1,4-CHDMGDE
(HAJIN CHEM TECH Co., Ltd.) as an epoxy resin was used.
Example 4
[0076] A polarizing plate was prepared in the same manner as
Example 1 except that an adhesive comprising 29 wt % of 2-HEA as a
monomer, 20 wt % of celloxide 2021P and 20 wt % of 1,4-CHDMGDE
(HAJIN CHEM TECH Co., Ltd.) as an epoxy resin, 3 wt % of sulphonium
salt initiator, and not comprising an iodine initiator and a
photosensitizer was used.
Example 5
[0077] A polarizing plate was prepared in the same manner as
Example 1 except that an adhesive comprising 28.5 wt % of 2-HEA as
a monomer, 10 wt % of celloxide 2021P and 15 wt % of 1,4-CHDMGDE
(HAJIN CHEM TECH Co., Ltd.) as an epoxy resin, and 15 wt % of
bisphenol-F type (Sigma-Aldrich Co., LLC) epoxy was used.
Comparative Example 1
[0078] A polarizing plate was prepared in the same manner as
Example 1 except that an adhesive not comprising celloxide 2021P
and 1,4-CHDMGDE (HAJIN CHEM TECH Co., Ltd.) as an epoxy resin, but
comprising 68.5 wt % of 2-HEA was used.
Comparative Example 2
[0079] A polarizing plate was prepared in the same manner as
Example 1 except that an adhesive comprising 30 wt % of celloxide
2021P and not comprising 1,4-CHDMGDE (HAJIN CHEM TECH Co., Ltd.) as
an epoxy resin was used.
Comparative Example 3
[0080] A polarizing plate was prepared in the same manner as
Example 1 except that an adhesive not comprising celloxide 2021P
but comprising 30 wt % of 1,4-CHDMGDE (HAJIN CHEM TECH Co., Ltd.)
as an epoxy resin was used.
Comparative Example 4
[0081] A polarizing plate was prepared in the same manner as
Example 1 except that an adhesive comprising 40 wt % of celloxide
2021P and 5 wt % of 1,4-CHDMGDE (HAJIN CHEM TECH Co., Ltd.) as an
epoxy resin was used.
Comparative Example 5
[0082] A polarizing plate was prepared in the same manner as
Example 1 except that an adhesive comprising 5 wt % of celloxide
2021P and 40 wt % of 1,4-CHDMGDE (HAJIN CHEM TECH Co., Ltd.) as an
epoxy resin was used.
Experimental Example 1
Polarizing Plate Peeling Force Evaluation
[0083] Peeling force between a polarizer and a polarizing plate
protective film was measured with respect to the polarizing plates
prepared in the foregoing Examples and Comparative Examples. In a
peeling experiment, peeling force was measured at a rate of 300
m/min and in 90 degrees by using a polarizing plate having a width
of 20 mm and a length of 100 mm. The results thereof are presented
in Table 2 (more than 2 N/cm: OK, 2 N/cm or less: NG).
Experimental Example 2
Viscosity Measurement
[0084] Viscosities of the adhesives prepared in the foregoing
Examples and Comparative Examples were measured at 25.degree. C.
and a TV-22 viscometer (TOK SANGYO) was used for viscosity
measurements. The results thereof are presented in the following
Table 2.
Experimental Example 3
Measurement of Glass Transition Temperature (Tg)
[0085] Glass transition temperatures (Tg) of adhesive layers were
measured by using a differential scanning calorimeter (DSC,
Mettler-Toledo International Inc.). The adhesive layers of the
polarizing plates prepared under the foregoing curing conditions
were separated, and then the glass transition temperatures in the
second run were measured by increasing temperatures from
-50.degree. C. to 150.degree. C. The results thereof are presented
in the following Table 2.
Experimental Example 4
Thermal Shock Physical Properties Evaluation
[0086] Durability evaluations (from -40.degree. C. to 80.degree.
C., 100 cycles) of glass-laminated polarizing plates were
performed, and then the appearances of the polarizing plates were
evaluated (no deformation: OK, generation of PVA cracks: NG). The
results thereof are presented in the following Table 2.
TABLE-US-00002 TABLE 2 Thermal Vis- Shock UZ cosity Eval- V TAC N
TAC TAC G- Tg (cP) uation Corona Corona Corona Corona Example 1 40
16 OK OK OK OK NG Example 2 42 17 OK OK OK OK NG Example 3 45 21 OK
OK OK OK NG Example 4 40 20 OK OK OK OK OK Example 5 47 23 OK NG OK
OK OK Comparative 18 10 NG OK OK OK NG Example 1 Comparative 56 16
OK NG NG OK NG Example 2 Comparative 20 12 NG OK OK OK NG Example 3
Comparative 65 24 OK NG NG NG NG Example 4 Comparative 21 17 NG OK
OK OK NG Example 5
[0087] CHDMGDE: HAJIN CHEM TECH Co., Ltd.
[0088] Bisphenol-F type: Sigma-Aldrich Co., LLC
[0089] Celloxide 2021P: Daicel Corporation
[0090] G-Corona: The acryl film prepared in Preparation Example
1(1)
REFERENCE NUMERALS
[0091] 1: a polarizer [0092] 2a: a protective film or a
compensation film [0093] 2b: a protective film [0094] 3: an
adhesive layer [0095] P: a polarizing plate [0096] C: a liquid
crystal cell
* * * * *