U.S. patent application number 10/769916 was filed with the patent office on 2004-11-04 for polarizer, process for preparing the same, optical member and liquid crystal displaying apparatus.
This patent application is currently assigned to SUMITOMO CHEMICAL COMPANY, LIMITED. Invention is credited to Hayashi, Narutoshi, Matsuoka, Yoshiki.
Application Number | 20040218117 10/769916 |
Document ID | / |
Family ID | 33019331 |
Filed Date | 2004-11-04 |
United States Patent
Application |
20040218117 |
Kind Code |
A1 |
Matsuoka, Yoshiki ; et
al. |
November 4, 2004 |
Polarizer, process for preparing the same, optical member and
liquid crystal displaying apparatus
Abstract
An object of the present invention is to provide a polarizer
which is thin and light as well as has durability, and an optical
member capable of forming a liquid-crystalline displaying apparatus
for mobiles which is excellent in reliance. According to the
present invention, there is provided a polarizer, which comprises a
protecting film comprising an epoxy resin as a main component on at
least one side of a polarizing film. This polarizer can be produced
by a method of coating an uncured epoxy resin composition on at
least one side of a polarizing film, and then curing the
composition to form a protecting film. Also, an optical member
comprising a laminate of the aforementioned polarizer and other
optical layer exhibiting the optical function is provided and,
further, a liquid crystal displaying apparatus comprising the
optical member disposed on one side or both sides of a
liquid-crystalline cell is provided.
Inventors: |
Matsuoka, Yoshiki;
(Tsukuba-shi, JP) ; Hayashi, Narutoshi;
(Niihama-shi, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
SUMITOMO CHEMICAL COMPANY,
LIMITED
|
Family ID: |
33019331 |
Appl. No.: |
10/769916 |
Filed: |
February 3, 2004 |
Current U.S.
Class: |
349/96 |
Current CPC
Class: |
G02B 5/3083 20130101;
G02B 1/10 20130101; G02B 5/3033 20130101; G02B 1/105 20130101; G02B
1/14 20150115 |
Class at
Publication: |
349/096 |
International
Class: |
G02F 001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 12, 2003 |
JP |
2003-033320 |
Claims
1. A polarizer comprising a polarizing film and a protecting film
which comprises an epoxy resin as a main component on at least one
side of the polarizing film.
2. The polarizer according to the claim 1, wherein the epoxy resin
is free from an aromatic ring.
3. The polarizer according to claim 1, wherein the polarizing film
is a film of polyvinylalcohol in and/or on which a dichromatic dye
is adsorbed and oriented.
4. A process for producing a polarizer comprising coating an
uncured epoxy resin composition on at least one side of a
polarizing film, and then curing the composition to form a
protecting film.
5. The process according to claim 4, wherein the curing is
performed by cation polymerization with at least one selected from
the group consisting of heat and active energy ray.
6. An optical member comprising a laminate of the polarizer
according to any one of claims 1 to 3 and other optical layer
exhibiting the optical function.
7. The optical member according to claim 6, wherein the optical
layer is a retarder.
8. A liquid-crystalline displaying apparatus comprising a
liquid-crystalline cell and the optical member according to claim 6
which is disposed on one side or both sides of the
liquid-crystalline cell.
9. A liquid-crystalline displaying apparatus comprising a
liquid-crystalline cell and the optical member according to claim 7
which is disposed on one side or both sides of the
liquid-crystalline cell.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a polarizer which is thin
and light weight, and is suitable for forming a liquid crystal
display used for a cellular phone and so on, and a process for
producing the same. The present invention also relates to an
optical member and a liquid crystal displaying apparatus using the
polarizer.
BACKGROUND OF THE INVENTION
[0002] A polarizer is widely used as an element providing polarized
light for a liquid crystal displaying apparatus, and as an element
detecting polarized light. As such the polarizer, a polarizing film
composed of polyvinylalcohol to which a protecting film composed of
triacetylcellulose is adhered, has been previously used. However,
recently, with expansion of a liquid crystal displaying apparatus
in mobile equipments such as a note-type personal computer and a
cellular phone, thin and light polarizer are desired. In addition,
since a mobile equipments are use in various place due to
portability, improvement of the durability is also desired.
[0003] However, in the previous method of adhering a protecting
film composed of triacetylcellulose to a polarizing film, from a
viewpoint of the handling during producing process and the
durability, it is difficult to make thickness of a protecting film
below 20 .mu.m. In order to solve such the problem, for example, JP
2000-199819 A discloses the method of forming a protecting film
which is thin and has the better durability, by coating a solution
of a cyclic polyolefin on at least one side of a polarizing film
composed of hydrophilic polymer, and drying it.
[0004] An object of the present invention is to provide a polarizer
which is thin and light as well as has durability, and an optical
member which is excellent in reliance and can form a liquid crystal
displaying apparatus used in mobiles.
SUMMARY OF THE INVENTION
[0005] That is, according to the present invention, there is
provided a polarizer having a protecting film comprising an epoxy
resin as a main component on at least one side of a polarizing
film. This polarizer can be prepared by a method of coating an
uncured epoxy resin composition on at least one side of a
polarizing film, and curing the composition to form a protecting
film. In addition, according to the present invention, there is
provided an optical member comprising a laminate of the polarizer
and an optical layer exhibiting other optical function than
polarizing function and, further, there is provided a liquid
crystal displaying apparatus comprising the optical member arranged
on one side or both sides of a liquid crystal cell.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0006] The present invention will be specifically explained below.
As a polarizing film, a film of polyvinylalcohol in and/or on which
a dichromatic coloring matter is adsorbed and oriented is generally
used. The polyvinylalcohol constituting a polarizing film is
obtained by saponifying polyvinylacetates. Examples of the
polyvinylacetates include polyvinylacetate which is a homopolymer
of vinyl acetate, a copolymer of vinyl acetate and other monomer
which can be copolymerized with vinyl acetate, and the like.
Examples of other monomer which is copolymerized with vinyl acetate
include unsaturated carboxylic acids, olefins, vinylethers,
unsaturated sulfonic acids, and the like. Degree of saponification
of polyvinylalcohol is usually in a range of about 85 to about 100
mol %, preferably about 98 to about 100 mol %. The polyvinylalcohol
may be further modified and, for example, polyvinylformal or
polyvinylacetal modified with aldehydes, and the like may be used.
Degree of polymerization of polyvinylalcohol is usually in a range
of about 1,000 to about 10,000, preferably about 1,500 to about
10,000.
[0007] The polarizing film is produced by a process comprising a
step of uniaxially stretching a film of polyvinylalcohol, a step of
adsorbing a dichromatic coloring matter in and/or on the film of
the polyvinylalcohol, a step of treating the film of
polyvinylalcohol with the dichromatic coloring matter adsorbed
therein and/or thereon with an aqueous boric acid solution, a step
of washing the film with water after treatment with an aqueous
boric acid solution, and a step of forming a protecting film on the
uniaxially stretched film of polyvinyl alcohol in and/or on which
the dichromatic coloring matter is adsorbed and oriented by these
steps. Uniaxial stretching may be performed before dyeing with a
dichromatic coloring matter, may be performed at the same time with
dyeing with a dichromatic coloring matter, or may be performed
after dying with a dichromatic coloring matter. When uniaxial
stretching is performed after dyeing with a dichromatic coloring
matter, this uniaxial stretching may be performed before treatment
with boric acid, or may be performed during treatment with boric
acid. In addition, uniaxial stretching may be also performed at
these plural stages. For performing uniaxial stretching, a film may
be uniaxially stretched between rolls having different peripheral
velocity with each other, or may be uniaxially stretched using a
hot roll. In addition, uniaxial stretching may be dry stretching
which is performed in the air, or may be wet stretching which is
performed in the state where a film is swollen with a solvent. A
stretching ratio is around 4 to 8 times.
[0008] A method for dyeing a film of polyvinylalcohol with a
dichromatic coloring matter includes, for example, a method in
which a film of polyvinylalcohol may be soaked in an aqueous
solution containing a dichromatic coloring matter. As the
dichromatic coloring matter, iodine or a dichromatic dye may be
used.
[0009] When iodine is used as a dichromatic coloring matter, a
preferably method of dyeing a film of polyvinylalcohol is a method
of immersing the film in an aqueous solution containing iodine and
potassium iodide. A content of iodine in the aqueous solution is
around 0.01 to 0.5 part by weight per 100 parts by weight of water,
and a content of potassium iodide is around 0.5 to 10 parts by
weight per 100 parts by weight of water. A temperature of the
aqueous solution is usually around 20 to 40.degree. C., and an
immersing time in this aqueous solution is usually about 30 to 300
seconds.
[0010] On the other hand, when a dichromatic dye is used as the
dichromatic coloring matter, a preferable method of dyeing a film
of polyvinylalcohol is a method of immersing the film in an aqueous
solution containing a water-soluble dichromatic dye. A content of a
dichromatic dye in this aqueous solution is usually around
1.times.10.sup.-3 to 1.times.10.sup.-2 part by weight per 100 parts
by weight of water. The aqueous solution may contain an inorganic
salt such as sodium sulfate. A dyeing temperature in this case
(temperature of aqueous dye solution) is usually around 20 to
80.degree. C., and an immersing time in this aqueous solution is
usually around 30 to 300 seconds.
[0011] Treatment with boric acid after dyeing with a dichromatic
coloring matter is performed by immersing the dyed film of
polyvinyl alcohol in an aqueous boric acid solution. A content of
boric acid in an aqueous boric acid solution is usually around 2 to
15 parts by weight, preferably around 5 to 12 parts by weight per
100 parts by weight of water. When iodine is used as the
dichromatic coloring matter, it is preferable that this aqueous
boric acid solution contains potassium iodide. A content of
potassium iodide in the aqueous boric acid solution is usually
around 2 to 20 parts by weight, preferably 5 to 15 parts by weight
per 100 parts by weight of water. An immersing time in the aqueous
boric acid solution is usually around 100 to 1,200 seconds,
preferably around 150 to 600 seconds, more preferably around 200 to
400 seconds. A temperature of the aqueous boric acid solution is
usually 50.degree. C. or higher, preferably 50 to 85.degree. C.
[0012] The film of polyvinyl alcohol after treatment with boric
acid is subjected to water washing treatment. Water washing
treatment is performed, for example, by immersing the boric
acid-treated film of polyvinylalcohol in water. A temperature of
water at water washing treatment is around 5 to 40.degree. C., and
an immersing time is around 2 to 120 seconds. After washing with
water, the film is subjected to drying treatment to obtain a
polarizing film. Drying treatment may be performed using a hot air
dryer or a far-infrared heater. A drying temperature is usually 40
to 100.degree. C. A time for drying treatment is usually around 120
to 600 seconds.
[0013] Thus, a polarizing film in which a dichromatic coloring
matter is adsorbed and oriented in and/or on a film of polyvinyl
alcohol can be produced. A protecting film is formed on at least
one side of this polarizing film to obtain a polarizer. In the
present invention, a protecting film is formed by a method
comprising coating a resin composition comprising, as a main
component, epoxy resin which is excellent in transparency, adhesive
strength, mechanical strength, thermal stability, water resistance
and the like, and curing the composition. When a polarizer is
produced by the above method, a dye type polarizing such as a
polarizing film in which a dichromatic dye is adsorbed and oriented
in and/or on a film of polyvinyl alcohol is preferably used, from
the viewpoint that the polarizing film suffer less effect of heat
or active energy ray of formation of protecting film. The present
invention may be applied similarly to an iodine series polarizing
film. An epoxy resin used in the present invention refers to a
compound which has two or more epoxy groups in a molecule on
average and is cured by a reaction. In this field, even a monomer
is referred to as epoxy resin as far as it has two or more epoxy
groups in a molecule.
[0014] In the present invention, from a viewpoint of the weather
resistance, a refractive index, the cationic polymerization, and
the like, it is preferable to use an epoxy resin containing no
aromatic ring in a molecule as a main component. Examples of such
epoxy resin containing no aromatic ring in a molecule include
hydrogenated epoxy resin, alicyclic epoxy resin, aliphatic epoxy
resin, and the like.
[0015] Hydrogenated epoxy resin can be obtained by a selective
hydrogenation of aromatic rings in aromatic epoxy resin under a
pressure in the presence of a catalyst. Examples of the aromatic
epoxy resin include bisphenol-type epoxy resins such as diglycidyl
ether of bisphenol A, diglycidyl ether of bisphenol F, and
diglycidyl ether of bisphenol S; novolac-type epoxy resins such as
phenol novolac epoxy resin, cresol novolac epoxy resin, and
hydroxybenzaldehydiphenol novolac resin; polyfunctional-type epoxy
resins such as glycidyl ether of tetrahydroxy phenylmethane,
glycidyl ether of tetrahydroxybenzophenone, epoxylated polyvinyl
phenol, and the like. It is preferable to use glycidyl ether of
hydroganeted bisphenol A.
[0016] The alicyclic epoxy resin is a compound having at least one
epoxy group bound to an alicylic ring in a molecule as shown by the
following formula: 1
[0017] wherein m represents an integer of from 2 to 5.
[0018] A compound in which a group obtained by removing one or
plural hydrogen atom (s) in (CH.sub.2).sub.m in this formula is
bound to other chemical structure without aromatic ring is an
alicyclic epoxy resin. In addition, hydrogen of an alicyclic ring
may be substituted with a linear alkyl group such as a methyl group
and an ethyl group. It is preferable to use a compound having an
oxabicyclohexane ring (m=3 in the above formula) or an
oxabicycloheptane ring (m=4 in the above formula). Structures of an
alicyclic epoxy resin are as follows, but the structure is not
limited to these compounds.
[0019] (1) Epoxycyclohexylmethyl epoxycyclohexanecarboxylates
corresponding to the following formula (I): 2
[0020] wherein R.sup.1 and R.sup.2 represent each independently a
hydrogen atom or a linear alkyl group having a carbon number of 1
to 5.
[0021] (2) Alkanediol epoxycyclohexanecarboxylates corresponding to
the following formula (II): 3
[0022] wherein R.sup.3 and R.sup.4 represent each independently a
hydrogen atom or a linear alkyl group having a carbon number of 1
to 5, and n represents an integer of 2 to 20.
[0023] (3) Dicarboxylic acid epoxy cyclohexylmethyl esthers
corresponding to the following formula (III): 4
[0024] wherein R.sup.5 and R.sup.6 represent each independently a
hydrogen atom or a linear alkyl group having a carbon number of 1
to 5, and p represents an integer 2 to 20.
[0025] (4) Polyethylene glycol epoxycyclohexylmethyl ethers
corresponding to the following formula (IV): 5
[0026] wherein R.sup.7 and R.sup.8 represent each independently a
hydrogen atom or a linear alkyl group having a carbon number of 1
to 5, and q represents an integer 2 to 10.
[0027] (5) Alkanediol epoxycyclohexylmethyl ethers corresponding to
the following formula (V): 6
[0028] wherein R.sup.9 and R.sup.10 represent each independently a
hydrogen atom or a linear alkyl group having a carbon number of 1
to 5, and r represents an integer of 2 to 20.
[0029] (6) Diepoxytrispiro compound corresponding to the following
formula (VI): 7
[0030] wherein R.sup.11 and R.sup.12 represent each independently a
hydrogen atom or a linear alkyl group having a carbon number of 1
to 5.
[0031] (7) Diepoxymonospiro compound corresponding to the following
formula (VII): 8
[0032] wherein R.sup.13 and R.sup.14 represent each independently a
hydrogen atom or a linear alkyl group having a carbon number of 1
to 5.
[0033] Vinylcyclohexenediepoxides corresponding to the following
formula (VIII): 9
[0034] wherein R.sup.15 represents a hydrogen atom or a linear
alkyl group having a carbon number of 1 to 5.
[0035] (9) Epoxycyclopentyl ethers corresponding to the following
formula (IX): 10
[0036] wherein R.sup.16 and R.sup.17 represent each independently a
hydrogen atom or a linear alkyl group having a carbon number of 1
to 5.
[0037] (10) Diepoxytricyclodecanes corresponding to the following
formula (X): 11
[0038] wherein R.sup.18 represents a hydrogen atom or a linear
alkyl group having a carbon number of 1 to 5.
[0039] Among them, a suitable alicyclic epoxy resin includes the
following:
[0040] ester of 7-oxabicyclo[4.1.0]heptane-3-carboxylic acid and
(7-oxa-bicyclo[4.1.0]hept-3-yl)methanol [compound wherein
R.sup.1=R.sup.2=H in formula (I)],
[0041] ester of 4-methyl-7-oxabicyclo[4.1.0]heptane-3-carboxylic
acid and (4-methyl-7-oxa-bicyclo[4.1.0]hept-3-yl)methanol [compound
wherein R.sup.1=4-CH.sub.3, R.sup.2=4-CH.sub.3 in formula (I)],
[0042] ester of 7-oxabicyclo[4.1.0]heptane-3-carboxylic acid and
1,2-ethanediol [compound wherein R.sup.3=R.sup.4=H, n=1 in formula
(II)],
[0043] ester of (7-oxabicyclo[4.1.0]hept-3-yl)methanol and adipic
acid [compound wherein R.sup.5=R.sup.6=H, p=2 in formula
(III)],
[0044] ester of (4-methyl-7-oxabicyclo[4.1.0]hept-3-yl)methanol and
adipic acid [compound wherein R.sup.5=4-CH.sub.3,
R.sup.6=4-CH.sub.3, p=2 in formula (III)],
[0045] ester of (7-oxabicyclo[4.1.0]hept-3-yl)methanol and
1,2-ethanediol [R.sup.9=R.sup.10=H, r=1 in formula (V)].
[0046] The aliphatic epoxy resin is polyglycidyl ether of aliphatic
polyhydric alcohol or an alkylene oxide adduct thereof. Examples
thereof include diglycidyl ether of 1,4-butanediol, diglycidyl
ether of 1,6-hexanediol, triglycidyl ether of glycerin, triglycidyl
ether of trimethylolpropane, diglycidyl ether of polyethylene
glycol, diglycidyl ether of propylene glycol, polyglycidyl ethers
of polyether polyol obtained by adding one or more alkylene oxides
(ethylene oxide or propylene oxide) to aliphatic polyhydric alcohol
such as ethylene glycol, propylene glycol and glycerin, and the
like.
[0047] These epoxy resins herein may be used alone, or plural epoxy
resins may be used by mixing them.
[0048] Equivalent of the epoxy resin used in the present invention
is usually 30 to 3,000 g/eq, preferably 50 to 1,500 g/eq. When the
equivalent weight of epoxy resin is below 30 g/eq, flexibility of a
protecting film after curing may be reduced, or the adhering
strength may be reduced. On the other hand, when the equivalent
weight of epoxy resin exceeds 3,000 g/eq, the compatibility with
other components may be reduced.
[0049] In the present invention, from a viewpoint of the
reactivity, cation polymerization is preferably used as a reaction
for curing an epoxy resin. Therefore, it is preferable to
incorporate a cationic polymerization initiator into a resin
composition. The cationic polymerization initiator generates a
cationic species or Lewis acid by irradiation with active energy
ray such as visible light, an ultraviolet ray, an X-ray, and an
electron beam, or heating, whereby, initiates a reaction for
polymerizing an epoxy group. It is preferable from a viewpoint of
the workability that even any type of a cationic polymerization
initiator is given the potentiality.
[0050] When the photocationic polymerization initiator, which
generates a cationic species or Lewis acid by irradiation with
active energy ray, is used, a protecting film may be form at a room
temperature and a protecting film can be adhered better. In
addition, since the photocationic polymerization initiator acts as
a catalyst by irradiation of the light, the storage stability and
the workability are excellent even when mixed into an epoxy resin.
Examples of a photocationic polymerization initiator include an
onium salt such as an aromatic diazonium salt, an aromatic iodonium
salt and an aromatic sulfonium salt, and an iron-allene complex,
and the like.
[0051] The aromatic diazonium salt include:
[0052] benzenediazonium hexafluoroantimonate,
[0053] benzenediazonium hexafluorophosphate,
[0054] benzenediazonium hexafluoroborate, and the like.
[0055] The aromatic iodonium salt include:
[0056] diphenyliodonium tetrakis(pentafluorophenyl)borate,
[0057] diphenyliodonium hexafluorophosphate,
[0058] diphenyliodonium hexafluoroantimonate,
[0059] di(4-nonylphenyl)iodonium hexafluorophosphate, and the
like.
[0060] The aromatic sulfonium salt include:
[0061] triphenylsulfonium hexafluorophosphate,
[0062] triphenylsulfonium hexafluoroantimonate,
[0063] triphenylsulfonium tetrakis(pentafluorophenyl)borate,
[0064] 4,4'-bis[diphenylsulfonio]diphenylsulfide
bishexafluorophosphate,
[0065]
4,4'-bis[di(.beta.-hydroxyethoxy)phenylsulfonio]diphenylsulfide
bishexafluoroantimonate,
[0066]
4,4'-bis[di(.beta.-hydroxyethoxy)phenylsulfonio]diphenylsulfide
bisdhexafluorophosphate,
[0067]
7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthonehexafluoroantimonat-
e,
[0068]
7-[di(p-toluyl)sulfonio]-2-isopropylthioxanthonetetrakis(pentafluor-
ophenyl)borate,
[0069] 4-phenylcarbonyl-4'-diphenylsulfonio-diphenylsulfide
hexafluorophosphate,
[0070]
4-(p-tert-butylphenylcarbonyl)-4'-diphenylsulfonio-diphenylsulfide
hexafluoroantimonate,
[0071]
4-(p-tert-butylphenylcarbonyl)-4'-di(p-toluyl)sulfonio-diphenylsulf-
ide tetrakis(pentafluorophenyl)borate, and the like.
[0072] The iron-allene complex include:
[0073] xylene-cyclopentadienyliron(II) hexafluoroantimonate,
[0074] cumene-cyclopentadienyliron(II) hexafluorophosphate,
[0075] xylene-cyclopentadienyliron(II)
[0076] tris(trifluoromethylsulfonyl)methanide, and the like.
[0077] These photocationic polymerization initiators may be used
alone, or two or more of them may be used by mixing. Since an
aromatic sulfonium salt has the ultraviolet absorbing property even
in a wavelength region of 300 nm or longer, the salt is excellent
in curing epoxy resin and, since the salt can give a cured material
having the higher mechanical strength and adhering strength, the
salt is preferably used.
[0078] These initiators are easily commercially available, such as
"Kayarad PCI-220", "Kayarad PCI-620" (these are manufactured by
Nippon Kayaku Co., Ltd.), "UVI-6990" (manufactured by Union Carbide
Corporation), "Adekaoptomer SP-150", "Adekaopotomer SP-170" (these
are manufactured by Asahi Denka Co., Ltd.), "CI-5102", "CIT-1370",
"CIT-1682", "CIP-1866S", "CIP-2048S", "CIP-2064S" (these are
manufactured by Nippon Soda Co., Ltd.), "DPI-101", "DPI-102",
"DPI-103", "DPI-105", "MPI-103", "MPI-105", "BBI-101", "BBI-102",
"BBI-103", "BBI-105", "TPS-101", "TPS-102", "TPS-103", "TPS-105",
"MDS-103", "MDS-105", "DTS-102", "DTS-103" (these are manufactured
by MidoriKagakuCo., Ltd.), "PI-2074" manufactured by Rhodia Ltd.),
and the like, respectively, as a trade name. "CI-5102" manufactured
by Nippon Soda Co., Ltd. is one of preferable initiators.
[0079] A content of the photocationic polymerization initiator is
usually 0.5 to 20 parts by weight, preferably 1 part by weight or
larger, and preferably 15 parts by weight or smaller per 100 parts
by weight of an epoxy resin. When the content is below 0.5 part by
weight resin, curing may become insufficient, and resultantly the
mechanical strength and the adhering strength may be lowered. On
the other hand, when the content exceeds 20 parts by weight, the
hygroscopicity of a cured material becomes high due to increase in
an ionic material in the cured material, and the durability may be
lowered.
[0080] Further, if necessary, a photosensitizer may be used
together. The reactivity is improved by use of the photosensitizer,
and the mechanical strength and the adhering strength of a cured
material may be improved. Examples of the photosensitizer include a
carbonyl compound, an organosulfur compound, a persulfide, a redox
series compound, azo and diazo compounds, a halogen compound, and a
photoreductive pigment, and the like. Examples of the
photosensitizer is not limited to, but include benzoin derivatives
such as benzoinmethyl ether, benzoin isopropyl ether, and
.alpha.,.alpha.-dimethoxy-.alpha.-phenylacetophenone; benzophenone
derivatives such as benzophenone, 2,4-dichlorobenzophenone, methyl
o-benzoylbenzoate, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis
(diethylamino)benzophenone; thioxanthone derivatives such as
2-chlorothioxanthone, and 2-isopropylthioxanthone; anthraquinone
derivatives such as 2-chloroanthraquinone, and
2-methylanthraquinone; acridone derivatives such as
N-methylacridone, and N-butylacridone; and
.alpha.-.alpha.-diethoxyacetophenone, benzyl, fluorenone, xanthone,
uranyl compound, and halogen compound, and the like. These may be
used alone, or may be used by mixing. It is preferable that the
photosensitizer is contained in a range of 0.1 to 20 parts by
weight per 100 parts by weight of the photocationic polymerizable
epoxy resin composition which is a mixture of epoxy resin and
photocationic polymerization initiator as mentioned above.
[0081] Then, the thermal cationic polymerization initiator will be
explained. The thermal cationic polymerization initiator is a
compound which generates a cation species or Lewis acid by heating.
Examples of the compound include a benzylsulfonium salt, a
thiophenium salt, a thiolanium salt, benzylammonium, a pyridinium
salt, a hydrazinium salt, carboxylic acid ester, sulfonic acid
ester, amineimide, and the like. These initiators are easily
commercially available, such as "Adekaptone CP77" and "Adekaptone
CP66" (these are manufactured by Asahi Denka Co., Ltd.), "CI-2639"
and "CI-2624" (these are manufactured by Nippon Soda Co., Ltd.),
"Sunaid SI-60L", "Sunaid SI-80L" and "Saneid SI-100L" (these are
manufactured by Sanshin Chemical Industry Co., Ltd.), and the like,
respectively, as a trade name.
[0082] It may be useful technique to use above-explained
photocationic polymerization and thermal cationic polymerization
together.
[0083] The epoxy resin composition for forming a protecting film in
the present invention may contain a compound which promotes cation
polymerization, such as oxetanes and polyols.
[0084] The oxetanes are a compound having a 4-membered cyclic ether
in a molecule, and examples thereof include
3-ethyl-3-hydroxymethyloxetane,
1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene,
3-ethyl-3-(phenoxymethyl)oxetane,
di[(3-ethyl-3-oxetanyl)methyl]ether,
3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, phenol novolac oxetane,
and the like. These oxetane compounds are easily commercially
available, such as "Allonoxetane OXT-101", "Allonoxetane OXT-121",
"Allonoxetane OXT-211", "Allonoxetane OXT-221", and "Allonoxetane
OXT-212" (these are manufactured by Toagosei Co., Ltd.),
respectively as a trade name. These oxetane ring-containing
compounds are usually used at a ratio of 5 to 95% by weight,
preferably 30 to 70% by weight in an epoxy resin composition.
[0085] Polyols having no acidic group other than a phenolic hydroxy
group are preferable, and examples thereof include a polyol
compound having no functional group other than a hydroxy group, a
polyester polyol compound, a polycaprolactone polyol compound, a
polyol compound having a phenolic hydroxy group, polycarbonate
polyol, and the like. A molecular weight of these polyols is
usually 48 or larger, preferably 62 or larger, more preferably 100
or larger, further preferably 1,000 or smaller. A content of these
polyols is usually 50% by weight or smaller, preferably 30% by
weight or smaller in an epoxy resin compositions.
[0086] Further, other additives such as an ion trapping agent, an
antioxidant, a chain transferring agent, a sensitizer, an tacking
fire, a thermoplastic resin, a filler, a flow adjusting agent, a
plasticizer, and an anti-forming agent may be added to an epoxy
resin composition. Examples of the ion trapping agent include
powdery inorganic compounds such as a bismuth series, an antimony
series, a magnesium series, an aluminum series, a calcium series, a
titanium series and a mixture series thereof, and examples of the
antioxidant include a hindered phenol series antioxidant and so
on.
[0087] A protecting film in the present invention is formed by
coating an uncured epoxy resin composition on at least one side of
a polarizer, and then curing the coated layer by irradiation with
active energy ray such as a visible light, an ultraviolet ray, an
X-ray, an electron beam and the like and/or heating.
[0088] A method of coating a polarizing film is not particularly
limited, but various coating apparatus such as a doctor blade, a
wire bar, a die coater, a comma coater, and a gravure coater can be
utilized. Since each coating apparatus has each optimal viscosity
range, it is also useful to adjust a viscosity using a solvent. As
a solvent therefor, solvents which do not deteriorate the optical
performance of the polarizer and dissolve an epoxy resin
composition well are used, and a kind of the solvent is not
particularly limited. For example, organic solvents such as
hydrocarbons represented by toluene, and esters represented by
ethyl acetate can be used.
[0089] When polymerization is performed by irradiation with active
energy ray, a light source to be used is not particularly limited,
but light sources having an emission distribution at a wavelength
of 400 nm or shorter, such as a low pressure mercury lamp, an
intermediate pressure mercury lamp, high pressure mercury lamp, an
ultrahigh pressure mercury lamp, a chemical lamp, a black light
lamp, a microwave excitation mercury lamp, a metal halide lamp can
be used. A light intensity to be irradiated to an epoxy resin
composition is determined depending on a composition used, and is
not particularly limited, however, it is preferable that an
irradiation intensity at a wavelength region which is effective in
activating an initiator is 0.1 to 100 mW/cm.sup.2. When a light
intensity to be irradiated to a resin composition is smaller than
0.1 mW/cm.sup.2, a reaction time may become too long and, when the
intensity exceeds 100 nW/cm.sup.2, yellowing of an epoxy resin
composition and deterioration of a polarizing film may be caused by
the heat generated by radiation from a lamp or by or by exothermal
polymerization of the composition. A light irradiation time to a
composition is determined depending on a composition to be cured,
and is not particularly limited, however, it is preferable to set
the time so that an accumulated light amount obtained from a
product of irradiation intensity and an irradiation time becomes 10
to 5,000 mJ/cm.sup.2. When an accumulated light amount to the epoxy
resin composition is smaller than 10 mJ/cm.sup.2, generation of an
active species derived from an initiator may not be sufficient, and
curing of the resulting protecting film may become insufficient. On
the other hand, when an accumulated light amount exceeds 5,000
mJ/cm.sup.2, an irradiation time may become very long, whereby
improving the productivity may not be sufficient.
[0090] When polymerization is performed by the heat, heating can be
performed by the generally known method, and the conditions
therefor, and so on, are not particularly limited. Usually, heating
is performed at such a temperature that a thermal cation
polymerization initiator incorporated into an epoxy resin
composition generates a cation species or Lewis acid, or higher
temperature, usually from about 50 to about 200.degree. C.
[0091] When curing is performed under any condition of irradiation
with an active energy ray or heat, it is preferable to perform
curing in such a range that various performances such as a
polarization degree and a transmittance of a polarizing film are
not lowered. From a viewpoint of thinning and light weight,
protecting function, handling and the like, a thickness of a
protecting film is preferably 40 .mu.m or smaller, more preferably
20 .mu.m or smaller. When a protecting film is provided on both
sides of a polarizing film, protecting films having different
compositions on one side from the other may be used.
[0092] In a polarizer on which a protecting film comprising the
aforementioned epoxy resin composition is provided in the present
invention, if necessary, various layers such as a hard coating
layer, a anti-reflection layer, and a anti-glare layer may be
formed on the protecting film.
[0093] An optical member in which an optical layer exhibiting the
optical function other than the polarizing function is provided via
a protecting film layer in the present invention, may be obtained.
Examples of an optical layer provided on a polarizer for the
purpose of forming an optical member include a reflecting layer, a
semi-transmission type reflecting layer, a light diffusing layer, a
phase retardation plate, a light collecting plate, a luminance
improving film and the like, which are used in forming a liquid
crystal displaying apparatus and the like. The aforementioned
reflecting layer, a semi-transmission type reflecting layer and a
light diffusing layer are used when an optical member comprising a
polarizing plate of reflection type or semi-transmission type,
diffusion type, or combined type is formed.
[0094] A reflection-type polarizing plate is used in a liquid
crystal displaying apparatus of such a type that reflects an
incident light from a recognition side to display it, and a light
source such as a back light can be omitted, whereby, a liquid
crystal displaying apparatus is easily thinned. In addition, a
semi-transmission type polarizing plate is used in a liquid crystal
displaying apparatus of such a type that displays as a
reflection-type in light places, and via a light source such as a
backlight in dark places. In an optical member as a reflection type
polarizer, a reflecting layer can be formed, for example, by
providing a foil or a deposition film composed of a metal such as
aluminum on a protecting film on a polarizer. In addition, an
optical member as a semi-transmission type polarizer can be formed
by converting the aforementioned reflecting layer into a half
mirror, or adhering a reflecting plate containing a pearl pigment
and the like and exhibiting the light transmission onto a
polarizer. On the other hand, in an optical member as a
diffusion-type polarizer, a fine structure of roughness is formed
on the surface thereof, for example, by using various methods such
as a method of performing mat treatment on a protecting film on a
polarizer, a method of coating a fine particle-containing resin,
and a method of adhering a fine particle-containing film.
[0095] Further, formation of an optical member as a polarizer for
reflection and diffusion can be performed, for example, by a method
of providing on a fine structural of surface roughness of a
diffusion-type polarizer a reflecting layer representing the
structure of roughness. A reflecting layer having a fine structure
of roughness has advantages that it diffuses an incident light by
irregular reflection, prevents directivity and glare, and
suppresses uneveness of light and darkness. A resin layer or film
containing a fine particle has an advantage that it is diffused
when an incident light and a reflecting light therefrom transmit
through the layer, whereby suppressing uneveness of light and
darkness. A reflecting layer representing a fine structure of
surface roughness can be formed by directly providing a metal on
the surface having a fine structure of roughness, for example, by
methods of deposition such as vacuum deposition, ion plating,
sputtering and the like, plating and the like. As a fine particle
to be incorporated for forming a fine structure of surface
roughness, inorganic fine particles composed of silica, aluminum
oxide, titanium oxide, zirconia, tin oxide, indium oxide, cadmium
oxide, antimony oxide and the like, and organic fine particles
composed of cross-linked, uncross-linked polymers, or the like,
which have an average particle diameter of 0.1 to 30 .mu.m can be
utilized.
[0096] On the other hand, the aforementioned phase retardation
plate as an optical layer is used for the purpose of compensating
for a phase difference due to a liquid-crystalline cell and so on.
Examples thereof include birefringent films composed of stretched
films of various plastics and so on, films in which a discotheque
liquid-crystalline or a nematic liquid-crystalline is
orientation-fixed, and film substrates on which the aforementioned
liquid-crystalline layer is formed, and the like. In this case, as
a film substrate for supporting an oriented liquid-crystalline
layer, cellulose series films such as triacetylcellulose are
preferably used.
[0097] Examples of a plastic for forming the birefringent film
include polycarbonate, polyvinyl alcohol, polystyrene, polymethyl
methacrylate, polyolefin such as polypropylene, polyarylate,
polyamide and the like. The stretched film may be a film which was
appropriately uniaxial- or biaxial-streched. In addition,
birefringent films in which a refractive index in a direction of a
film thickness is controlled by applying a constricting force
and/or a stretching force under adhesion between a thermally
constricting film may be used. For the purpose of controlling the
optical properties such as band broadening, two or more of retarder
may be used in combination.
[0098] The light collecting plate is used for the purpose of
optical path control and so on, and may be formed as a prism array
sheet, a lens array sheet, a dot-provided sheet, or the like.
[0099] The luminance improving film is used for the purpose of
improving a luminance in a liquid-crystalline displaying apparatus
and the like, and examples thereof include a reflection-type
polarization separating sheet designed to laminate plural thin
films having different refractive index anisotropies to generate
anisotropy in a reflectance, an oriented film of a cholesteric
liquid-crystalline polymer, a circularly polarized separating sheet
in which an oriented liquid-crystalline layer thereof is supported
on a film substrate, and the like.
[0100] The optical member can be produced by combining a polarizer
with one or more optical layers selected from the aforementioned
reflecting layer or semi-transmission reflecting layer, light
diffusing layer, retarder, light collecting plate, luminance
improving film and the like depending on the use purpose, to obtain
a laminate of two or more layers. In that case, two or more optical
layers such as the light diffusing layer, the retarder, the light
collecting plate and the luminance improving film may be disposed
respectively. Disposition of each optical layer is not particularly
limited.
[0101] Various optical layers for forming the optical member are
integrated by using an adhesive, and an adhesive used therefor is
not particularly limited as far as an adhered layer is formed
better. From a viewpoint of simplicity of the adhering working,
prevention of occurrence of optical distortion, and the like, it is
preferable that a self-adhesive (also referred to as
pressure-sensitive adhesive) is used. As the self-adhesive, those
using acrylic polymers, silicone polymers, polyesters,
polyurethanes, polyethers, or the like as a base polymer can be
used. An acrylic polymers self-adhesive, is preferably since they
are excellent in the optical transparency, retain the appropriate
wettability and cohesive force, are also excellent in the
adherability with a substrate, further have the weather resistance,
heat resistance, and the like, do not cause a peeling problem such
as lifting and peeling under the conditions of heating and
moistening. In the acrylic polymers self-adhesive, an acrylic
copolymer having a weight average molecular weight of 100,000 or
larger obtained by copolymerizing an alkyl ester of (meth)acrylic
acid having an alkyl group of a carbon number of 20 or less such as
a methyl group, an ethyl group and a butyl group, with a functional
group-containing acrylic monomer comprising (meth)acrylic acid,
hydroxyethyl (meth)acrylate, or the like so that a glass transition
temperature becomes preferably 25.degree. C. or lower, more
preferably 0.degree. C. or lower is preferable.
[0102] Formation of a self-adhesive layer on a polarizer can be
performed by dissolving or dispersing a self-adhesive composition
in an organic solvent such as toluene or ethyl acetate to prepare a
10 to 40% by weight solution, and coating the solution directly on
a polarizer to form a self-adhesive layer, or by forming a
self-adhesive layer on a protecting film in advance, and
transferring the layer onto a polarizer to form a self-adhesive
layer. A thickness of a self-adhesive layer is determined depending
on its adhering force or the like, and is usually in a range of
about 1 to about 50 .mu.m.
[0103] If necessary, a filler composed of a glass fiber, a glass
bead, a resin bead, a metal powder, other inorganic powder or the
like, a pigment, a coloring agent, an antioxident, an ultraviolet
absorbing agent and the like may be incorporated into a
self-adhesive layer. Examples of the ultraviolet absorbing agent
include a salicylic acid ester series compound, a benzofenone
series compound, a benzotriazole series compound, a cyanoacrylate
series compound, and a nickel complex salt series compound, and the
like.
[0104] The optical member may be disposed on one side or both sides
of a liquid-crystalline cell. A liquid-crystalline cell used is
arbitrary. For example, a liquid-crystalline displaying apparatus
can be formed by using various liquid-crystalline cells such as
active matrix-driving type represented by a thin film transistor
type, and a simple matrix-driving type represented by super twisted
nematic type. Optical members provided on both sides of a
liquid-crystalline cell may be the same or different.
EXAMPLES
[0105] Examples of the present invention will be shown below, but
the present invention is not limited by these Examples.
Example 1
[0106] 10.0 g of trade name "Epicoat YX8000" which is a
hydrogenated epoxy resin manufactured by Japan Epoxy Resins Co.,
Ltd., 4.0 g of trade name "CI5102" which is a photocationic
polymerization initiator manufactured by Nippon Soda Co., Ltd. and
1.0 g of trade name "CS7001" which is a photosensitizer
manufactured by Nippon Soda Co., Ltd. were weighed into a 100 ml
disposable cup, the materials were mixed and defoamed and the
mixture was coated on the surface of a polyvinyl alcohol-dye type
polarizer using an applicator having a clearance of 100 .mu.m.
After coating, this polarizing film was passed once through an
ultraviolet irradiating apparatus manufactured by Japan Storage
Battery Co., Ltd. (an ultraviolet ray lamp "HAL 400NL" was used at
80 W, and an irradiation distance was 50 cm) at a line rate of 1.0
m/min. Thereupon, the curability of an epoxy resin composition was
found good. In addition, the adherability with a polarizing film
was assessed by a grid method described in JIS K 5400, and the
number of non-peeled grid relative to the number of formed grid was
100/100, demonstrating the better adherability. Further, the
polarizing performance was assessed by using a spectrophotometer
(trade name "UV2200") manufactured by Shimadzu Corporation, a
simple transmittance was found to be 38.9% and a polarization
degree was found to be 99.98%, maintaining the excellent polarizing
performance also after a curing reaction.
[0107] The trade name "Epicoat YX 8000" used herein which is a
hydrogenated epoxy resin is diglycidyl ether of nuclear
hydrogenated bisphenol A, and has an epoxy equivalent weight of
about 205 g/eq.
Example 2
[0108] 7.0 g of a hydrogenated epoxy resin "Epicoat YX8000", 3.0 g
of trade name "Allonoxetane OXT-121" which is an oxetane resin
manufactured by Toagosei Co., Ltd., 4.0 g of a photocationic
polymerization initiator "CI5102" and 1.0 g of a photosensitizer
"CS7001" were weighed into a 100 ml disposable cup, the materials
were mixed and defoamed, and the mixture was coated on the surface
of a polyvinyl alcohol-dye type polarizing film using an applicator
having a clearance of 100 .mu.m. After coating, this polarizer was
passed once through the same ultraviolet ray irradiating apparatus
as that used in Example 1 at a line rate of 1.0 m/min. Thereupon,
the curability of an epoxy resin composition was better. In
addition, the adherability with a polarizing film was assessed by a
grid method described in JIS K 5400, and the number of non-peeled
grid relative to the number of formed grid was 100/100,
demonstrating the better adherability. Further, the polarizing
performance was assessed as in Example 1, a simple transmittance
was found to be 38.6% and a polarizing degree was found to be
99.96%, maintaining the excellent polarizing performance also after
a curing reaction.
[0109] The oxetane resin "Allonoxetane OXT-121" used herein is a
mixture containing
1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene as a main
component and ten and a few % of di(3-ethyl-3-oxetanylmethyl)ether
which is a dimer or a higher multimer of p-xylilene glycol.
Example 3
[0110] 7.0 g of trade name "Epicoat YX 8034" which is a
hydrogenated epoxy resin manufactured by Japan Epoxy Resins Co.,
Ltd., 3.0 g of trade name "Adekaoptomer KRM2199" which is an
alicyclic epoxy resin manufactured by Asahi Denka Co., Ltd., and
1.5 g of trade name "Adekaoptone CP77" which is a thiolanium salt
series thermal cation polymerization initiator manufactured by
Asahi Denka Co., Ltd. were weighed into a 100 ml disposable cup,
the materials were mixed and defoamed, and the mixture was coated
on the surface of a polyvinyl alcohol-dye type polarizer using an
applicator having a clearance of 100 .mu.m. After coating, this
polarizing film was allowed to stand for 10 minutes in a hot air
oven heated at 130.degree. C. Thereupon, the curability of an epoxy
resin composition was better. In addition, the adherability with a
polarizing film was assessed by a grid test described in JIS K
5400, and the number of non-peeled grid relative to the number of
formed grid was 100/100, demonstrating the better adherability.
Further, the polarizing performance was assessed as in Example 1, a
simple transmittance was found to be 37.1% and a polarizing degree
was 99.97%, maintaining the excellent polarizing performance also
after a curing reaction.
[0111] The hydrogenated epoxy resin "Epicoat YX8034" used herein is
a diglycidyl ether of nuclear hydrogenated bisphenol A, and has an
epoxy equivalent weight of about 290 g/eq.
Comparative Example 1
[0112] A 30% by weight toluene solution of trade name "Arton" which
is a cyclic polyolefin resin manufactured by JSR Corporation was
prepared, and this solution was coated on the surface of a
polyvinyl alcohol-iodine type polarizing film using an applicator
having a clearance of 100 .mu.m. After coating, this polarizing
film was dried for 10 minutes in a hot air oven heated at
100.degree. C. After drying, the adherability with a polarizing
film was assessed by a grids method described in JIS K 5400, and
the number of non-peeled grids relative to the number of formed
grids was 0/100, demonstrating no adherability with a polarizing
film.
[0113] According to the present invention, there can be easily
obtained a polarizer which has the durability and is thin and light
while maintaining the better adherability with a polarizing film.
As a result, thin and light polarizer and optical members which can
well stand the heating treatment at apparatus assembling and the
environmental conditions at use of an apparatus can be obtained,
and liquid-crystalline displaying apparatuses for mobiles which are
excellent in reliance can be formed by using them.
* * * * *