U.S. patent application number 12/771731 was filed with the patent office on 2010-09-02 for optical compensation film, and polarizing plate and liquid crystal display employing the same.
This patent application is currently assigned to KONICA MINOLTA OPTO, INC.. Invention is credited to Takashi SERA.
Application Number | 20100221457 12/771731 |
Document ID | / |
Family ID | 40625639 |
Filed Date | 2010-09-02 |
United States Patent
Application |
20100221457 |
Kind Code |
A1 |
SERA; Takashi |
September 2, 2010 |
OPTICAL COMPENSATION FILM, AND POLARIZING PLATE AND LIQUID CRYSTAL
DISPLAY EMPLOYING THE SAME
Abstract
The present invention provides an optical compensation film,
which has excellent visibility such as light leakage, uneven color
tone and front contrast, and can simultaneously realize retardation
and wavelength dispersion. The optical compensation film is
characterized by containing a cellulose ester, the following
polymer (a), and the following compound (b). (a) A polymer produced
by copolymerizing an ethylenically unsaturated monomer having in
its molecule a partial structure represented by Formula (1) with at
least one ethylenically unsaturated monomer. (b) An esterified
compound produced by esterifying all or a part of OH groups in a
compound (A) having one furanose structure or one pyranose
structure, or an esterified compound produced by esterifying all of
or a part of OH groups in a compound (B) containing nor less than 2
and not more than 12 structures of at least one of a furanose
structure or a pyranose structure. ##STR00001##
Inventors: |
SERA; Takashi; (Tokyo,
JP) |
Correspondence
Address: |
LUCAS & MERCANTI, LLP
475 PARK AVENUE SOUTH, 15TH FLOOR
NEW YORK
NY
10016
US
|
Assignee: |
KONICA MINOLTA OPTO, INC.
Tokyo
JP
|
Family ID: |
40625639 |
Appl. No.: |
12/771731 |
Filed: |
April 30, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/JP2008/069447 |
Oct 27, 2008 |
|
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12771731 |
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Current U.S.
Class: |
428/1.31 ;
524/58 |
Current CPC
Class: |
C09K 2323/031 20200801;
C08J 2339/04 20130101; C08L 1/04 20130101; C08K 5/151 20130101;
C09K 2323/00 20200801; C08L 1/14 20130101; B29D 11/00788 20130101;
G02B 1/04 20130101; C08J 5/18 20130101; Y10T 428/1041 20150115;
G02B 5/3083 20130101; Y10T 428/10 20150115; C08L 1/10 20130101;
G02B 1/04 20130101; C08L 1/14 20130101; G02B 1/04 20130101; C08L
33/14 20130101 |
Class at
Publication: |
428/1.31 ;
524/58 |
International
Class: |
C08K 5/10 20060101
C08K005/10; C09K 19/00 20060101 C09K019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 5, 2007 |
JP |
2007287153 |
Claims
1. An optical compensation film characterized by comprising Polymer
(a) and Compound (b), wherein Polymer (a): A polymer produced by
copolymerizing an ethylenically unsaturated monomer having a
partial structure represented by Formula (1) in its molecule with
at least one ethylenically unsaturated monomer, ##STR00025##
wherein, R.sub.1, R.sub.2 and R.sub.3 each independently represent
an aliphatic group which may have a substituent, an aromatic group
which may have a substituent, or a heterocycle group which may have
a substituent, provided that any two of R.sub.1, R.sub.2 and
R.sub.3 are combined with each other to form a 5 to 7 member ring
structure together with a nitrogen atom to which the two of
R.sub.1, R.sub.2 and R.sub.3 are bonded or together with the
nitrogen atom and a carbon atom, and Compound (b): An esterified
compound in which all or a part of OH groups in Compound (A) having
one furanose or pyranose structure are esterified, or an esterified
compound in which all or a part of OH groups in Compound (B), in
which 2 to 12 structures of at least one of furanose or pyranose
structure are bonded, are esterified.
2. The optical compensation film of claim 1, characterized by
satisfying Formulas (i), (ii) and (iii), 20.ltoreq.Ro.ltoreq.100
(nm) (i) 70.ltoreq.Rt.ltoreq.200 (nm) (ii)
0.82.ltoreq.Ro(480)/Ro(630).ltoreq.0.96 (iii) wherein,
Ro=(nx-ny).times.d Rt=((nx+ny)/2-nz).times.d in the formulas, nx
represents a refractive index in retarded phase axis direction in a
plane of the optical compensation film, ny represents a refractive
index in a direction perpendicular to the retarded phase axis
direction in a plane, nz represents a refractive index in a
thickness direction and d represents a thickness (nm) of the
optical compensation film respectively, the measuring wavelength
for the refractive index being 590 nm, and Ro (480) and Ro (630)
represent Ro measured with the wavelength of 480 nm and Ro measured
with the wavelength of 630 nm, respectively.
3. The optical compensation film of claim 1, characterized by that
weight average molecular weight (Mw) of the Polymer (a) is within a
range of 1,000 to 70,000.
4. The optical compensation film of claim 1, characterized by that
ethylenically unsaturated monomer having a substructure represented
by Formula (1) in a molecule is N-vinyl pyrrolidone, N-acryloyl
morpholine, N-vinyl piperidone, N-vinyl caprolactam, or a mixture
thereof.
5. The optical compensation film of claim 1, characterized by that
the esterified compound is benzoate of monosaccharide
(.alpha.-glucose, .beta.-fructose) or benzoate of polysaccharide
prepared by dehydration condensation of arbitrary two or more parts
of --OR.sub.12, --OR.sub.15, --OR.sub.22 and --OR.sub.25 in
monosaccharide represented by Formula (2), in which m+n=2 to 12.
##STR00026##
6. A polarizing plate characterized by employing the optical
compensation film of any one of above described claim 1 on at least
one surface of a polarizing plate.
7. A liquid crystal display characterized by employing the
polarizing plate of above described claim 6 on at least one surface
of a liquid crystal cell.
Description
[0001] This is a U.S. National Phase Application under 35 U.S.C.
371 of International Application PCT/TP2008/069447, filed on Oct.
27, 2008.
[0002] This application claims the priority of Japanese application
No. 2007-287153, filed Nov. 5, 2007, the entire content of which is
hereby incorporated by reference.
TECHNICAL HELD
[0003] The present invention relates to an optical compensation
film used for a liquid crystal display, in particular, relates in
detail to an optical compensation film which is excellent in
visibility (light leakage, color tone unevenness, front contrast),
and compatible to both retardation and wavelength dispersion
characteristic.
TECHNICAL BACKGROUND
[0004] A cellulose ester film, a polycarbonate film, a poly cyclic
olefin film, and so on are widely used as an optical film for
liquid crystal displays.
[0005] Since the transparency of a cellulose ester film is
optically high and also its birefringence is low, it has been
mainly used as a protective film (hereinafter; referred to as a
polarizing plate protective film) of a polarization film of a
liquid crystal display. A polycarbonate film and a poly cyclic
olefin film have mainly been used as an optical compensation film
for adjusting retardation.
[0006] Moreover; in order to control retardation and its wavelength
dispersion characteristic, an optical compensation film has been
usually used in combination with plural sheets of optical films.
However, since the combination of the plural sheets of optical
films has a large load in productivity in terms of combination
precision and an increase in the number of processes, an optical
compensation technology with a small number of sheets has been
studied.
[0007] For example, a technology to make it into one sheet with a
polycarbonate film and a poly cyclic olefin film has been proposed
in Non Patent document 1. However, even if such a technology is
used, as an optical compensation film which serves as a polarizing
plate protective film, it has an insufficient pasting ability with
polyvinyl alcohol being a polarization film, and a polarizing plate
protective film consisting of a cellulose ester film has been
recognized to be an indispensable optical film in a liquid crystal
display even now.
[0008] Then, it has been studied to provide a function as an
optical compensation film to the cellulose ester film which is
excellent as this polarizing plate protective film.
[0009] Basically, since cellulose ester film has the circumstances
where it has been used as polarizing plate protective film due to
its low birefringence characteristic, it may be not easy to provide
the function.
[0010] In order to acquire a desired retardation value, a technique
to add a compound having a retardation increasing effect to a
cellulose ester film and to further stretch the film is proposed
(Patent Documents 1 and 2), but there are problems that the
wavelength dispersion characteristic does no stabilize over time
and the permeability of the film is deteriorated by the
stretching.
[0011] If the wavelength dispersion characteristic is insufficient,
phenomena such as light leakage from a polarizing plate (especially
light leakage with an elapse of time), uneven color tone of an
image on a liquid crystal display and front contrast deterioration
occur.
[0012] Therefore, it has been desired eagerly to provide a desired
retardation value and a decrease of haze simultaneously to a
cellulose ester film.
[0013] Patent Document 1: JP-A 2000-111914
[0014] Patent Document 2: JP-A 2002-131538
[0015] Non Patent document: Japanese Liquid Crystal Society Journal
Liquid Crystal "Various functional films for liquid crystal display
elements" Special edition Vol. 9 No. 4
DISCLOSURE OF THE INVENTION
Problem to be Dissolved by the Invention
[0016] An object of the present invention is to provide an optical
compensation film which is excellent in visibility (light leakage,
color tone unevenness, front contrast) and simultaneously satisfies
both retardation and wavelength dispersion properties.
Means to Solve the Problems
[0017] The above-mentioned objects of the present invention can be
attained by the following structures.
1. An optical compensation film characterized by comprising
following Polymer (a) and following Compound (b). (a) A polymer
produced by copolymerizing an ethylenically unsaturated monomer
having a partial structure represented by Formula (1) in its
molecule with at least one ethylenically unsaturated monomer.
##STR00002##
[0018] In the Formula, R.sub.1, R.sub.2 and R.sub.3 each
independently represent an aliphatic group which may have a
substituent, an aromatic group which may have a substituent, or a
heterocycle group which may have a substituent, provided that any
two of R.sub.1, R.sub.2 and R.sub.3 may be combined with each other
to form a 5 to 7 member ring structure together with a nitrogen
atom to which the two of R.sub.1, R.sub.2 and R.sub.3 are bonded or
together with the nitrogen atom and a carbon atom.
(b) An esterified compound in which all or a part of OH groups in
Compound (A) having one furanose or pyranose structure are
esterified, or an esterified compound in which all or a part of OH
groups in Compound (B), in which 2 to 12 structures of at least one
of furanose or pyranose structure are bonded, are esterified.
[0019] Any two of R.sub.1, R.sub.2 and R.sub.3 are preferably
combined with each other to form a 5 to 7 member ring structure
together with a nitrogen atom to which the two of R.sub.1, R.sub.2
and R.sub.3 are bonded or together with the nitrogen atom and a
carbon atom.
2. The optical compensation film of item 1, characterized by
satisfying Formulas (i), (ii) and (iii),
20.ltoreq.Ro.ltoreq.100 (nm) (i)
70.ltoreq.Rt.ltoreq.200 (nm) (ii)
0.82.ltoreq.Ro(480)/Ro(630)5.096 (iii)
wherein,
Ro=(nx-ny).times.d
Rt=((nx+ny)/2-nz).times.d
[0020] in the formulas, nx represents a refractive index in
retarded phase axis direction in a plane of the optical
compensation film, ny represents a refractive index in a direction
perpendicular to the retarded phase axis direction in a plane, nz
represents a refractive index in a thickness direction and d
represents a thickness (nm) of the optical compensation film
respectively, the measuring wavelength for the refractive index
being 590 nm, and Ro (480) and Ro (630) represent Ro measured with
the wavelength of 480 nm and Ro measured with the wavelength of 630
nm, respectively.
3. The optical compensation film of item 1, characterized by that
weight average molecular weight (Mw) of the Polymer (a) is within a
range of 1,000 to 70,000. 4. The optical compensation film of item
1, characterized by that ethylenically unsaturated monomer having a
substructure represented by Formula (1) in a molecule is N-vinyl
pyrrolidone, N-acryloyl morpholine, piperidone, caprolactam, or a
mixture thereof. 5. The optical compensation film of item 1,
characterized by that the esterified compound is benzoate of
monosaccharide (.alpha.-glucose, .beta.-fructose) or benzoate of
polysaccharide prepared by dehydration condensation of arbitrary
two or more parts of --OR.sub.12, --OR.sub.15, --OR.sub.22 and
--OR.sub.25 in monosaccharide represented by Formula (2), in which
m+=2 to 12.
##STR00003##
6. A polarizing plate characterized by employing the optical
compensation film of any one of above described items 1 to 5 on at
least one surface of a polarizing plate. 7. A liquid crystal
display characterized by employing the polarizing plate of above
described item 6 on at least one surface of a liquid crystal
cell.
ADVANTAGE OF THE INVENTION
[0021] An optical compensation film having excellent visibility
such as light leakage, color tone unevenness, front contrast and
having compatibility of retardation and wave length dispersion
properties can be provided by this invention.
BEST EMBODIMENT TO PRACTICE THE INVENTION
[0022] The best embodiment to practice the invention is described
in detail, however this invention is not restricted thereto.
[0023] The liquid crystal display elements generally have viewing
angle characteristics, and there is problem of lowering contrast
when observed remote angle from normal angle. It is known that it
is effective to provide an optical compensation film (a phase
difference film) between the crystal cell and a polarizer to
dissolve this problem. It is preferable in general the retardation
within a plane (Ro) in the range of 20 to 200 nm, and the
retardation in the thickness direction (Rt) in the range of 70 to
400 nm.
[0024] The optical compensation film of this invention is
characterized by comprising Polymer (a) manufactured by
copolymerizing an ethylenically unsaturated monomer having a
partial structure represented by Formula (1) in its molecule with
at least one ethylenically unsaturated monomer, and esterified
Compound (b) in which all or a part of OH groups in Compound (A)
having one furanose or pyranose structure are esterified, or an
esterified compound in which all or a part of OH groups in Compound
(B), in which 2 to 12 of at least one type of furanose or pyranose
structure are bonded, are esterified.
[0025] Further improvement of visibility such as front contrast is
expected according to generalization of large format liquid crystal
display recently. The inventors studied the above mentioned problem
and found that improvement of visibility (light leakage color tone
unevenness, front contrast) in addition to compatibility of
retardation control and wave length dispersion property are
attained by employing Polymer (a) obtained by copolymerizing
ethylenically unsaturated monomer having a partial structure
represented by Formula (1) in its molecule with at least one
ethylenically unsaturated monomer, and accomplished this
invention.
[0026] The elements of this invention will be described in
detail.
Polymer (a) mentioned above
[0027] The optical compensation film of this invention comprises at
least one polymer manufactured by copolymerizing an ethylenically
unsaturated monomer having a partial structure represented by
Formula (1) in its molecule with at least one ethylenically
unsaturated monomer.
[0028] In Formula (A), R.sub.1, R.sub.2 and R.sub.3 each
independently represent an aliphatic group which may have a
substituent, an aromatic group which may have a substituent, or a
heterocycle group which may have a substituent, provided that any
two of R.sub.1, R.sub.2 and R.sub.3 may be combined with each other
to form a 5 to 7 member ring structure together with a nitrogen
atom to which the two of R.sub.1, R.sub.2 and R.sub.3 are bonded or
together with the nitrogen atom and a carbon atom. The substituents
represented by R.sub.1, R.sub.2 and R.sub.3 are not specifically
limited. Examples of substituents represented by R.sub.1, R.sub.2
and R.sub.3 include an alkyl group (such as a methyl group, an
ethyl group, a propyl group, an isopropyl group, a t-butyl group, a
pentyl group, a hexyl group, an octyl group, a dodecyl group and
trifluoromethyl group), a cycloalkyl group (such as a cyclopentyl
group and a cyclohexyl group), an aryl group (such as a phenyl
group and a naphthyl group), an acylamino group (such as an
acetylamino group and a benzoylamino group), an alkylthio group
(such as a methylthio group and an ethylthio group), an arylthio
group (such as a phenylthio group and a naphthylthio group), an
alkenyl group (such as a vinyl group, a 2-propenyl group, a
3-butenyl group, a 1-methyl-3-propenyl group, a 3-pentenyl group, a
1-methyl-3-butenyl group, a 4-hexenyl group and a cyclohexenyl
group), a halogen atom (such as a fluorine atom, a chlorine atom, a
bromine atom and an iodine atom), an alkynyl group (such as a
propargyl group), a heterocyclic group (such as a pyridyl group, a
thiazolyl group, an oxazolyl group and an imidazolyl group), an
alkylsulfonyl group (such as a methylsulfonyl group and an
ethylsulfonyl group), an arylsulfonyl group (such as a
phenylsulfonyl group and a naphthylsulfonyl group), an
alkylsulfinyl group (such as a methylsulfinyl group), an
arylsulfinyl group (such as a phenylsulfinyl group), a phosphono
group, an acyl group (such as an acetyl group, a pivaloyl group and
a benzoyl group), a carbamoyl group (such as an aminocarbonyl
group, a methylaminocarbonyl group, a dimethylaminocarbonyl group,
a butylaminocarbonyl group, a cyclohexylaminocarbonyl group, a
phenylaminocarbonyl group and a 2-pyridylaminocarbonyl group), a
sulfamoyl group (such as an aminosulfonyl group, a
methylaminosulfonyl group, a dimethylaminosulfonyl group, a
butylaminosulfonyl group, a hexylaminosulfonyl group, a
cyclohexylaminosulfonyl group, an octylaminosulfonyl group, a
dodecylaminosulfonyl group, a phenylaminosulfonyl group, a
naphthylaminosulfonyl group and a 2-pyridylaminosulfonyl group), a
sulfonamide group (such as a methanesulfonamide group and a
benzenesulfonamido group), a cyano group, an alkoxy group (such as
a methoxy group, an ethoxy group and a propoxy group), an aryloxy
group (such as a phenoxy group and a naphthyloxy group), a
heterocyclicoxy group, a siloxy group, an acyloxy group (such as an
acetyloxy group and a benzoyloxy group), a sulfonic acid group, a
salt of sulfonic acid, an aminocarbonyloxy group, an amino group
(such as an amino group, an ethylamino group, a dimethylamino
group, a butylamino group, a cyclopentylamino group, a
2-ethylhexylamino group and a dodecylamino group), an aniline group
(such as a phenylamino group, a chlorophenylamino group, a
toluidino group, an anisidino group, a naphthylamino group and a
2-pyridylamino group), an imido group, a ureido group (such as a
methylureido group, an ethylureido group, a pentylureido group, a
cyclohexylureido group, an octylureido group, a dodecylureido
group, a phenylureido group, a naphthylureido group and a
2-pyridylaminoureido group), an alkoxycarbonylamino group (such as
a methoxycarbonylamino group and a phenoxycarbonylamino group), an
alkoxycarbonyl group (such as methoxycarbonyl group, ethoxycarbonyl
group and phenoxycarbonyl group), an aryloxycarbonyl group (such as
a phenoxycarbonyl group), a heterocyclicthio group, a thioureido
group, a carboxyl group, a salt of carboxylic acid, a hydroxyl
group, a mercapto group and a nitro group. These groups may be
father substituted by a similar substituent to those represented by
R.sub.1, R.sub.2 and R.sub.3.
[0029] In the present invention, any two of R.sub.1, R.sub.2 and
R.sub.3 may be combined with each other to form a 5 to 7 member
ring structure together with a nitrogen atom to which the two of
R.sub.1, R.sub.2 and R.sub.3 are bonded or together with the
nitrogen atom and a carbon atom. In this case, the ring may further
contain a nitrogen atom, a sulfur atom or an oxygen atom, and the
ring may be a saturated or unsaturated single ring, a polycyclic
ring, or a condensed ring. Examples of such a ring include hetero
rings such as a pyrrolidine ring, a piperidine ring, a piperazine
ring, a pyrrole ring, a morpholine ring, a thiamorpholine ring, an
imidazole ring, a pyrazole ring, a pyrrolidone ring and a
piperidone ring. These rings may further be substituted by the
substituents which the group represented by the above R.sub.1,
R.sub.2, and R.sub.3 may have further.
[0030] In the present invention, the ethylenically unsaturated
monomer having a substructure represented by Formula (A) in the
molecule has an ethylenically unsaturated bond in the molecule.
This means that at least one of the groups represented by R.sub.1,
R.sub.2 and R.sub.3 is an alkenyl group as a group having an
ethylenically unsaturated bond, or at least one of the groups
represented by R.sub.1, R.sub.2 and R.sub.3 has an ethylenically
unsaturated bond as a substructure Specific examples of an
ethylenically unsaturated bond include a vinyl group, an allyl
group, an acryloyl group, a methacryloyl group, a styryl group, an
acrylamide group, a methacrylamide group, a vinyl cyanide group, a
2-cyanoacryloxy group, a 1,2-epoxy group, a vinylbenzyl group, and
a vinylether group. Of these, preferable are a vinyl group, an
acryloyl group, a methacryloyl group and a methacrylamide
group.
[0031] Examples of an ethylenically unsaturated monomer having a
substructure represented by Formula (1) employed in the present
invention will be shown below, however, the present invention is
not limited thereto.
##STR00004## ##STR00005## ##STR00006## ##STR00007## ##STR00008##
##STR00009## ##STR00010##
[0032] The ethylenically unsaturated monomer having a substructure
represented by Formula (1) in the molecule may be used alone or in
combination of two or more kinds. Specifically preferable examples
include N-vinyl pyrrolidone, N-acryloyl morpholine, N-vinyl
piperidone, N-vinyl caprolactam, or a mixture thereof, more
preferably N-vinyl pyrrolidone, N-acryloyl morpholine or a mixture
thereof, and particularly preferably N-acryloyl morpholine.
[0033] The ethylenically unsaturated monomer having a substructure
represented by Formula (1) in the molecule are commercially
available in the market or may be synthesized by referring to known
documents in the art.
[0034] Examples of an ethylenical unsaturated monomer capable of
copolymerization with the ethylenically unsaturated monomer having
a substructure represented by Formula (1) in the molecule may be
the ethylenically unsaturated monomer having a substructure
represented by Formula (1) in the molecule, but preferably other
unsaturated monomers, for example, a methacrylic acid or its ester
derivative (such as methyl methacrylate, ethyl methacrylate, propyl
methacrylate, butyl methacrylate, butyl methacrylate, t-butyl
methacrylate, octyl methacrylate, cyclohexyl methacrylate,
2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,
tetrahydrofurfuryl methacrylate, benzyl methacrylate,
dimethylaminoethyl methacrylate and diethylaminoethyl
methacrylate), acrylic acid or its ester derivative (such as methyl
acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, i-butyl
acrylate, t-butyl acrylate, octyl acrylate, cyclohexyl acrylate,
2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,
tetrahydrofurfuryl acrylate, 2-ethoxyethyl acrylate,
diethyleneglycolethoxylate acrylate, 3-methoxybutyl acrylate,
benzyl acrylate, dimethylamino acrylate and diethylamino acrylate),
an alkyl vinylether (such as methyl vinylether, ethyl vinylether,
and butyl vinylether), an alkyl vinylester (such as vinyl formate,
vinyl acetate, vinyl butylate, vinyl caproate, and vinyl stearate),
a styrene derivative (such as styrene, .alpha.-methylstyrene,
o-methylstyrene, m-methylstyrene, p-methylstyrene and vinyl
naphthalene), crotonic acid, maleic acid, fumaric acid, itaconic
acid, acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene
chloride, acrylamide, N,N-dimethyl amide and methacrylamide. These
monomers maybe used alone or in combination of two or more kinds to
polymerize with monomers represented by Formula (1).
[0035] Preferable examples among these ethylenically unsaturated
monomers are acrylate and methacrylate (such as methyl
methylacrylate, ethyl methylacrylate, propyl methacrylate, butyl
methacrylate, methyl acrylate, methyl acrylate, ethyl acrylate,
propyl acrylate and butyl acrylate), alkyl vinylester (such as
vinyl formate, vinyl acetate, vinyl butylate, vinyl caproate, and
vinyl stearate), styrene derivative (such as styrene,
.alpha.-methylstyrene, o-methylstyrene, m-methylstyrene,
p-methylstyrene and vinyl naphthalene), and methylmethacrylate and
methyl acrylate are more preferable and methyl methacrylate is most
preferable.
[0036] Weight average molecular weight (Mw) of the above mentioned
Polymer (a) used in this invention is preferably within a range of
1,000 to 70,000. More preferably is within the range of 2,000 to
50,000, and particularly preferable is within the range of 3,000 to
30,000. Ratio of weight average molecular weight (Mw)/number
average molecular weight (Mn) of the Polymer (a) is preferably 1.5
to 10.0, and particularly preferable is 1.5 to 5.0.
[0037] The above mentioned Polymer (a) used in this invention is a
copolymer obtained by polymerizing an ethylenically unsaturated
monomer having a partial structure represented by Formula (1) in
its molecule with at least one ethylenically unsaturated monomer
and preferably at least methyl (meth)acrylate, and preferably has
weight average molecular weight within a range of 3,000 to 30,000.
N-acryloyl morpholine is above exemplified AM-2,
methyl(meth)acrylate includes methyl methacrylate and methyl
acrylate.
[0038] Mn and Mn/Mw are determined using gel permeation
chromatography according to the following manner.
[0039] Measurement conditions are as follows:
[0040] Solvent: tetrahydrofuran
[0041] Apparatus: HLC-8220 GPC (produced by TOSOH Corp.)
[0042] Column: TSK gel SUPER HM-M (produced by TOSOH Corp.)
[0043] Temperature: 40.degree. C.
[0044] Sample concentration: 0.1% by weight
[0045] Amount of injection: 10 .mu.l
[0046] Flow rate: 0.6 ml/min
[0047] Calibration curve: standard polystyrene PS-1 (produced by
Polymer Laboratories)
[0048] There was used a calibration curve prepared by 9 samples of
standard polystyrene having Mw=2,560,000 to 580.
[0049] The content of an ethylenically unsaturated monomer having a
substructure represented by Formula (1) in the molecule in the
Polymer (a) used in the present invention is determined by
considering compatible solubility of the copolymer to be obtained
with transparent resin, and affects to transparency and mechanical
strength of the optical compensation film. The ethylenically
unsaturated monomer having a substructure represented by Formula
(1) in the molecule is preferably incorporated in an amount of 5 to
80% by weight, more preferably 10 to 50% by weight of the
copolymer.
[0050] The method of polymerizing the Polymer (a) of the present
invention is not specifically limited, and conventional methods can
be widely employed, examples of which include a radical
polymerization, an anionic polymerization and a cationic
polymerization. As an initiator used for the radical
polymerization, for example, an azo compound and a peroxide are
cited, examples of which include azobis isobutyronitile (AIBN), an
azobis isobutyric acid diester derivative and peroxy benzoyl.
Solvents used in the polymerization are not particularly limited
and examples thereof include an aromatic hydrocarbon solvent such
as toluene and chlorobenzene, a halogenated hydrocarbon solvent
such as dichloroethane and chloroform, an ether solvent such as
tetrahydrofuran and dioxane, an amide solvent such as dimethyl
formamide, an alcohol solvent such as methanol, an ester solvent
such as methyl acetate and ethyl acetate, a ketone solvent such as
acetone, cyclohexanone and methylethyl ketone, and an aqueous
solvent. By selecting a solvent, a solution polymerization carried
out in a homogenous system, a precipitation polymerization in which
produced polymer precipitates an emulsion polymerization carried
out in a micelle state, suspension polymerization in which
polymerization is carried out in suspension state and bulk
polymerization under circumstances can also be conducted.
[0051] The weight average molecular weight of the above mentioned
polymer can be controlled according to a conventional method of
controlling the molecular weight. As such a molecular weight
control method, a method to add a chain transfer agent, for
example, carbon tetrachloride, lauryl mercaptan or octyl
thioglycolate may be cited. The polymerization temperature is
usually from an ambient temperature to 130.degree. C. and more
preferably 50.degree. C. to 110.degree. C.
[0052] The content of the above mentioned Polymer (a) based on the
mass of the cellulose ester resin which forms the optical
compensation film is preferably 0.1 to 50% by weight and more
preferably 5 to 30% by weight. The haze of the formed optical film
is not specifically limited if it is 1.0 or less, however, the haze
of the formed optical film is preferably 0.5 or less and more
preferably 0.3 or less.
<Compound Having Furanose Structure or Pyranose Structure
According to this Invention>
[0053] The optical compensation an is characterized by containing
Polymer (a) as well as an esterified compound in which all or a
part of OH groups in Compound (A) having one furanose structure or
pyranose structure are esterified, or an esterified compound in
which all or a part of OH groups in Compound (B) bonding 2 to 12 of
at least one type of furanose structures or pyranose structures are
esterified. The esterified compound of (A) and the esterified
compound of (B) are called a sugar ester compound in this
invention.
[0054] Further, the above mentioned esterified compound is
preferably benzoate of monosaccharide (.alpha.-glucose,
.beta.-fructose) or benzoate of polysaccharide prepared by
dehydration condensation of arbitrary two of --OR.sub.12,
--OR.sub.15, --OR.sub.22 and --OR.sub.25 in monosaccharide
represented by the aforesaid Formula (2), in which m+n=2 to 12.
[0055] The benzoyl group may be further have a substituent which
includes such as an alkyl group, an alkenyl group, an alkoxy group
and a phenyl group, and the alkyl, alkenyl and phenyl group may
further have a substituent.
[0056] Preferable examples of the Compound (A) and Compound (B)
include the following; however, this invention is not limited
thereto.
[0057] Examples of the Compound (A) are listed as glucose,
galactose, mannose, fructose, xylose and arabinose.
[0058] Examples of the Compound (B) are listed as lactose, sucrose,
nistose, 1F-fructosyl nistose, stachyose, maltitol, lactitol,
lactulose, cellobiose, maltose, cellotriose, maltotriose, raffinose
or kestose. In addition to these, listed are such as gentiobiose,
gentiotriose, gentiotetraose, xylotriose and galactosylscurose.
Among these the Compound (A) and Compound (B), compounds having the
both of a pyranose. Such as sucrose, kestose, nistose, 1F-fructosyl
nistose and stachyose are preferable, and sucrose is more
preferable. The compound bonding 2 or 3 of at least one type of
furanose structure and pyranose structure in Compound (B) is a
preferable embodiment.
[0059] Monocarboxylic acid utilized for esterification of a part of
or all of OH groups in the Compound (A) and Compound (B) according
to this invention is not specifically limited, and conventional
compound such as aliphatic monocarboxylic acid, alicyclic
monocarboxylic acid and aromatic monocarboxylic acid can be
utilized. Carboxylic acid utilized may be one type or a mixture of
not less than two types.
[0060] Preferable aliphatic monocarboxylic acid includes saturated
fatty acid such as acetic acid, propionic acid, butyric acid,
isobutyric acid, valeric acid, caproic acid, enanthic aid, caprylic
acid, pelargonic acid, capric acid, 2-ethyl-hexane carboxylic acid,
undecylic acid, lauric acid, tridecylic acid, myristic acid,
pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid,
nonadecanoic acid, arachic acid, behenic acid, ligunoceric acid,
cerotic acid, heptacosanoic acid, montanic acid, melissic acid and
lacceric acid, and unsaturated fatty acid such as undecylenic acid,
oleic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic
acid and octenoic acid.
[0061] Examples of preferable alicyclic monocarboxylic acid include
cyclopentanecarboxylic acid, cyclohexanecarboxylic acid,
cyclooctanecarboxylic acid or derivatives thereof.
[0062] Examples of aromatic monocarboxylic acid include aromatic
monocarboxylic acid in which an alkyl group or an alkoxy group is
introduced to a benzene ring of such as benzoic acid and toluic
acid; aromatic monocarboxylic acid having at least two benzene
rings such as benzilic acid, biphenyl carboxylic acid, naphthalene
carboxylic acid, tetralin carboxylic acid or derivatives thereof;
and more specifically, include xylylic acid, hemellitic acid,
mesitylenic acid, prehnitylic acid, .gamma.-isodurylic acid,
durylic acid, mesitonic acid, .alpha.-isodurylic acid, carminic
acid, .alpha.-toluic acid, hydroatropic acid, atropic acid,
hydrocinnamic acid, salicylic acid, o-anisic acid, m-anisic acid,
p-anisic acid, creosote acid, o-homosalicylic acid, m-homosalicylic
acid, p-homosalicylic acid, o-pyrocatechuic acid, .beta.-resorcylic
acid, vanillic acid, isovanillic acid, veratric acid, o-veratric
acid, gallic acid, asarylic acid, mandelic acid, homoanisic acid,
homovanillic acid, homoveratric acid, o-homoveratric acid,
phthalonic acid and p-coumaric acid; specifically preferable is
benzoic acid.
[0063] Among the esterified compounds of Compound (A) and Compound
(B) is preferably an acetylated compound in which acetyl group is
introduced by esterification.
[0064] A manufacturing method of the acetylated compound is
described in, for example, JP-A H08-245678.
[0065] In addition to the esterified compounds of Compound (A) and
Compound (B), an ester compound of oligosaccharide can be applied
as a compound having 1 to 12 of at least one type of a pyranose
structure or a furanose structure according to this invention.
[0066] Oligosaccharide is manufactured by acting an enzyme such as
amylase on such as starch and saccharose, and oligosaccharide
applicable in this invention includes such as maltooligosaccharide,
isomaltooligosaccharide, furactooligosaccharide,
galactooligosaccharide and xylooligosaccharide.
[0067] Oligosaccharide can be acetylated by the similar method to
those of Compound (A) and Compound (B).
[0068] An example of manufacturing method of the esterified
compound.
[0069] Acetic anhydride (200 ml) was dripped to a solution of
glucose (29.8 g, 166 mmol) in 100 ml of pyridine, and reaction was
conducted for 24 hours. Solution was condensed by evaporation, and
poured into iced water. After standing for one hour, solid was
separated from water by a glass filter. Solid on the glass filter
was dissolved with chloroform, and was separated by cold water
until neutralization. Organic phase was separated and dried with
anhydrous sodium sulfate. After removing anhydrous sodium sulfate
by filtration, chloroform was removed by evaporator, and glucose
pentaacetate (58.8 g, 150 mmol, yield of 90.9%) was thus obtained.
Monocarboxylic acid described above can be used instead of the
above mentioned acetic anhydride.
[0070] In the following, specific examples of an esterified
compound according to this invention will be listed; however, this
invention is not limited thereto.
##STR00011## ##STR00012## ##STR00013## ##STR00014##
##STR00015##
[0071] Optical film of this invention preferably contains 1 to 30
weight % of esterified compound in which all or a part of OH groups
in Compound (A) having one furanose structure or pyranose structure
are esterified, or an esterified compound in which all or a part of
OH groups in Compound (B) bonding 2 to 12 of at least one type of
furanose structures or pyranose structures are esterified, and
specifically preferably contains 5 to 30 weight %, for the purpose
of inhibiting variation of phase difference to stabilize display
quality. It is preferable that an excellent effect of this
invention is exhibited as well as no bleed out is generated in the
case of this range.
[0072] The Polymer (a) and all or a part of OH groups in Compound
(A) having one furanose structure or pyranose structure or Compound
(B) bonding 2 to 12 of at least one type of furanose structures or
pyranose structures may be used in combination with other
plasticizer.
(Cellulose Ester)
[0073] The optical compensate film of this invention contains
cellulose ester. The cellulose ester is not specifically limited;
however, cellulose ester is carboxylic acid ester having a carbon
number of approximately 2 to 22, may be ester of aromatic
carboxylic acid and specifically preferably is lower fatty acid
ester of cellulose. In lower fatty acid ester of cellulose, lower
fatty acid means fatty acid having a carbon number of not more than
6. An acyl group bonding to a hydroxyl group may be a straight
chain or a branched chain, or may form ring. Further, the acyl
group may be substituted by other substituents. In the case of a
same substitution degree, it is preferable to select among acyl
groups having a carbon number of preferably 2 to 6. The carbon
number of the aforesaid cellulose ester is preferably 2 to 4 and
more preferably 2 to 3.
[0074] The aforesaid cellulose ester can employ acyl groups derived
from mixed acid, and specifically preferably can employ acyl groups
having carbon numbers of 2 and 3, or carbon numbers of 2 and 4. As
cellulose ester of this invention, utilized can be mixed fatty acid
ester of cellulose, in which propionate group or a butyrate group
bonds in addition to an acetyl group, such as cellulose acetate
propionate, cellulose acetate butyrate or cellulose acetate
propionate butyrate. Herein, as a butyryl group to form butyrate
may be either a straight chain form or branched. As cellulose ester
of this invention, cellulose acetate, cellulose acetate butyrate,
cellulose acetate propionate and cellulose acetate phthalate are
specifically preferably utilized.
[0075] The retardation value can be suitably controlled by
selecting kinds of above mentioned acyl group of the cellulose
ester and substitution degree of the acyl group to pyranose ring of
cellulose resin skeleton.
[0076] Cellulose satisfying the following Formulas (1) and (2)
simultaneously is preferably used in this invention.
2.0.ltoreq.X+Y.ltoreq.2.9 Formula (1)
0.1.ltoreq.Y.ltoreq.2.0 Formula (2)
In the formulas, X is substitution degree of acetyl group, Y is
substitution degree of propionyl group or butylyl group. Those
satisfying the two Formulas are suitable for manufacturing the
optical compensation film exhibiting excellent optical property
according to the object of this invention.
[0077] Resins having different substitution degree may used by
mixture to obtain optical property suitable for the object of this
invention.
[0078] Of these, cellulose acetate propionate is preferably
employed. Cellulose acetate propionate satisfies
1.0.ltoreq.X.ltoreq.2.5, and it is preferable to use cellulose
esters satisfying the following formulas of
0.1.ltoreq.Y.ltoreq.1.5, and 2.0.ltoreq.X+Y.ltoreq.3.0. The acyl
substitution degree of the cellulose ester can be measured
according to ASTM-D817-96.
[0079] In case that the substitution degree of the acyl group is
too low, unreacted parts of hydroxy groups in the pyranose ring
composing cellulose resin skeleton, and it may cause variation of
retardation by moisture or lowering the ability of protecting
polarizer as the polarizing plate protective film because a plenty
of hydroxy groups reside.
[0080] The number average molecular weight of the cellulose ester
is preferably 60,000 to 300,000 to obtain film having good
mechanical strength and those of 70,000 to 200,000 are used more
preferably.
[0081] The number average molecular weight of the cellulose ester
is measured according to a method described below.
[0082] Measurement is carried out under the conditions described
below, employing a high speed liquid chromatography.
Solvent Acetone
[0083] Column: MPW.times.1 (manufactured by TOSOH Corp.) Sample
concentration: 0.2 weight/volume percent Flow rate: 1.0 ml/minute
Injected sample volume: 300 .mu.l Standard sample: Standard
polymethyl methacrylate
Temperature: 23.degree. C.
[0084] Cellulose as raw material for a cellulose ester used in the
present invention is not particularly limited, and may be various
kinds of cotton linter, wood pulp kenaf and so on may be listed.
Cellulose esters made from these may be optimally mixed or singly
used.
[0085] Cellulose ester according to this invention, in the case
that an acylation agent as a cellulose starting material is acid
anhydride, is prepared by a reaction utilizing a proton type
catalyst such as sulfuric acid in an organic acid such as acetic
acid or in an organic solvent such as methylene chloride. In the
case that an acylation agent is acid chloride (CH.sub.3COCl,
C.sub.2H.sub.5COCl or C.sub.3H.sub.7COCl), the reaction is
performed utilizing a basic compound such as amine as a catalyst.
Specifically, the synthesis can be performed referring to a method
described in JP-A H10-45804.
[0086] An average substitution degree of an acyl group at the
6-position of a glucose unit of cellulose ester utilized in this
invention is preferably 0.5 to 0.9.
[0087] A highly reactive primary hydroxyl group is present at the
6-position of a glucose unit constituting cellulose ester,
different from the 2-position and the 3-position, and this primary
hydroxyl group preferentially forms sulfuric ester in a
manufacturing process of cellulose ester employing sulfuric acid as
a catalyst. Therefore, in an esterification reaction of cellulose,
the average substitution degree at the 2-position and the
3-position of a glucose unit can be made larger that that at the
6-position by increasing the amount of sulfuric acid as a catalyst,
compared to general cellulose ester. Further, when necessary, since
a hydroxyl group at the 6-position of a glucose unit can be
selectively protected when cellulose is tritylated, it is possible
to make the average substitution degree at 2-position and the
3-position of a glucose unit larger than that at the 6-position, by
protecting a hydroxyl group at the 6-position by tritylation and
releasing a trityl group (a protective group) after esterification.
Specifically, cellulose ester manufactured by a method described in
JP-A 2005-281645 can be also preferably utilized.
[0088] It is necessary to prolong the time of an acetylation
reaction to increase an acetylation degree in the case of acetyl
cellulose. However, when the reaction time is excessively long,
decomposition will proceed simultaneously to cause such as cut off
of a polymer chain and decomposition of an acetyl group, which
leads to an unfavorable result. Therefore, it is necessary to set
the reaction time of a certain range to increase the acetylation
degree and depress decomposition to some extent. To regulate by
reaction time is not suitable because the reaction conditions are
various to be changed depending on the reaction equipment and
installation and other conditions. Since molecular weight
distribution is broadened as decomposition of polymer proceeds,
also in the case of cellulose ester, the degree of decomposition
can be determined by a value of weight average molecular weight
(Mw)/number average molecular weight (Mn), which is generally
utilized. That is, in a process of acetylation of cellulose
triacetate, a value of weight average molecular weight (Mw)/number
average molecular weight (Mn) can be utilized as one index not to
advance decomposition too much due to prolonged reaction time but
to perform acetylation reaction for sufficient time.
[0089] An example of a manufacturing method of cellulose ester will
be shown below. Cotton linter of 100 weight parts as a cellulose
starting material was crushed, being added with 40 weight parts of
acetic acid, and the resulting system was subjected to a
pre-treatment activation at 36.degree. C. for 20 minutes.
Thereafter, the system was added with 8 weight parts of sulfuric
acid, 260 weight parts of acetic acid anhydride and 350 weight
parts of acetic acid, and the resulting system was subjected to
esterification at 36.degree. C. for 120 minutes. After
neutralization with 11 weight parts of a 24% magnesium acetate
aqueous solution, saponification repining at 63.degree. C. for 35
minutes was performed to prepare acetyl cellulose. The product,
after having been stirred for 160 minutes at mom temperature by use
of 10 times of an acetic acid aqueous solution (acetic
acid/water=1/1 (weight ratio)), was filtered and dried to prepare
purified acetyl cellulose having an acetyl substitution degree of
2.75. This acetyl cellulose had. Mn of 92,000, Mw of 156,000 and
Mw/Mn of 1.7. In a similar manner, by adjusting esterification
conditions (temperature, time, stirring) and hydrolysis conditions,
cellulose ester having a different substitution degree and a
different Mw/Mn can be synthesized. Cellulose ester having an Mw/Mn
ratio of 1.4 to 5.0 is preferably utilized.
[0090] Cellulose ester synthesized is preferably subjected to
purification to remove a low molecular weight component and to
filtration to remove a component which has not been acetylated or
has a low acetylation degree.
[0091] Further, mixed acid cellulose ester can be prepared by a
method described in JP-A H10-45804.
[0092] Cellulose ester is also affected by trace amounts of metal
components in cellulose ester. These are considered to be related
with water utilized in a manufacturing process, and a component
which forms insoluble nuclei is preferably as small as possible in
quantity; and metal ions of such as iron, calcium and magnesium,
which may form an insoluble product by salt formation with such as
polymer decomposition product possibly containing an organic acid
group, are preferably small in quantity. An iron (Fe) component is
preferably not more than 1 ppm. A calcium (Ca) component is easily
form a coordination compound, that is a complex, with a acid
component such as carboxylic acid and sulfonic acid as well as with
many ligands, to form many insoluble scum (insoluble sediment,
muddiness) derived from calcium.
[0093] A calcium (Ca) component is not more than 60 ppm and
preferably 0 to 30 ppm. A magnesium (Mg) component is preferably 0
to 70 ppm and specifically preferably 0 to 20 ppm, since an excess
amount thereof also generates an insoluble product Metal components
such as a content of iron (Fe), calcium (Ca) and magnesium (Mg) can
be analyzed by use of an ICP-AES (an induction coupling plasma
emission spectrophotometer) after completely dried cellulose ester
is subjected to pretreatment by a micro-digest wet decomposition
apparatus (sulfuric nitric acid decomposition) and alkali
fusion.
(Plasticizer)
[0094] Optical compensate film of this invention can be
appropriately incorporated with a plasticizer to achieve the
effect, of this invention. A plasticizer is not specifically
limited, however, is preferably selected from such as a
polycarboxylic ester type plasticizer, a glycolate type
plasticizer, a phthalic ester type plasticizer, a fatty acid ester
type plasticizer, a polyhydric alcohol ester type plasticizer, a
polyester type plasticizer and an acryl type plasticizer. When not
less than two types among them are utilized, at least one type is
preferably a polyhydric alcohol ester type plasticizer.
[0095] A polyhydric alcohol ester type plasticizer is a plasticizer
comprising ester of fatty acid polyhydric alcohol of not less than
divalent and monocarboxylic acid, and is preferably provided with
an aromatic ring or a cycloalkyl ring in a molecule. It is
preferably fatty acid polyhydric alcohol ester of 2 to 20
valent.
[0096] Polyhydric alcohol preferably utilized in this invention is
represented by following formula (a).
R1-(OH)n Formula (a)
wherein, R1 is a n-valent organic group, n is a positive integer of
not less than 2 and OH is an alcoholic and/or phenolic hydroxyl
group.
[0097] Examples of preferable polyhydric alcohol include such as
the following however, this invention is not limited thereto.
Listed are such as adonitol, arabitol, ethylene glycol, diethylene
glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol,
1,3-propanediol, dipropylene glycol, tripropylene glycol,
1,2-butanediol, 1,3-butanediol, 1,4-butanediol, dibutylene glycol,
1,2,4-butanetriol, 1,5-pentanediol, 1,6-hexanediol, hexanetriol,
galactitol, mannitol, 3-methylpentane-1,3,5-triol, pinacol,
sorbitol, trimethylolpropane, trimethylolethane and xylitol.
Specifically preferable are triethylene glycol, tetraethylene
glycol, dipropylene glycol, tripropylene glycol, sorbitol,
trimethylolpropane and xylitol.
[0098] Monocarboxylic acid utilized in polyhydric alcohol ester is
not specifically limited and such as conventionally known fatty
acid monocarboxylic acid, alicyclic monocarboxylic acid and
aromatic monocarboxylic acid can be utilized. It is preferable to
utilize alicyclic monocarboxylic acid or aromatic monocarboxylic
acid with respect to improvement of moisture permeability and
reservation property.
[0099] Examples of preferable monocarboxylic acid include the
followings; however, this invention is not limited thereto.
[0100] As fatty acid monocarboxylic acid, fatty acid having a
straight chain or a branched chain of carbon number of 1 to 32 can
be preferably utilized. The carbon number is more preferably 1 to
20 and specifically preferably 1 to 10. It is preferable to
incorporate acetic acid because of increasing compatibility with
cellulose ester, and it is also preferable to utilize acetic acid
and other monocarboxylic acid by mixing.
[0101] Preferable monocarboxylic acid includes saturated fatty acid
such as acetic acid, propionic acid, butyric acid, valeric acid,
caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric
acid, 2-ethyl-hexanoic acid, undecylic acid, lauric acid,
tridecylic acid, myristic acid, pentadecylic acid, palmitic acid,
heptadecylic acid, stearic acid, nonadecanoic acid, arachic acid,
behenic acid, lignoceric acid, cerotic acid, heptacosanoic acid,
montanic acid, melissic acid and lacceric acid; and unsaturated
fatty acid such as undecylenic acid, oleic acid, sorbic acid,
linoleic acid, linolenic acid and arachidonic acid.
[0102] Examples of preferable alicyclic monocarboxylic acid include
cyclopentane carboxylic acid, cyclohexane carboxylic acid and
cyclooctane carboxylic acid or derivatives thereof.
[0103] Examples of preferable aromatic monocarboxylic acid include
those in which 1 to 3 of alkoxy groups such as an alkyl group, a
methoxy group or an ethoxy group are introduced into a benzene ring
of such as benzoic acid and toluic acid, aromatic carboxylic acid
having at least two benzene ring such as biphenyl carboxylic acid,
naphthalene carboxylic acid and tetralin carboxylic acid, or
derivatives thereof. Benzoic acid is specifically preferable.
[0104] A molecular weight of polyhydric alcohol ester is not
specifically limited, however, is preferably 300 to 1,500 and more
preferably 350 to 750. The molecular weight is preferably the
larger because of being hard to evaporate, while the smaller is
preferable with respect to moisture permeability and compatibility
with cellulose ester.
[0105] Carboxylic acid utilized in polyhydric alcohol may be either
one type or a mixture of two or more types. Further, OH groups in
polyhydric alcohol may be all esterified or may partly remain as an
OH group.
[0106] In the following, specific examples of polyhydric alcohol
will be exemplified.
##STR00016## ##STR00017## ##STR00018## ##STR00019##
##STR00020##
[0107] A glycolate type plasticizer is not specifically limited,
however, alkylphthalylalkyl glycolates are preferably utilized.
Alkylphthayalkyl glycolates include such as methylphthalylmethyl
glycolate, ethylphthalylethyl glycolate, propylphthalylpropyl
glycolate, butylphthalylbutyl glycolate, octylphthalyloctyl
glycolate, methylphthalylethyl glycolate, ethylphthalylmethyl
glycolate, ethylphthalylpropyl glycolate, methylphthalylbutyl
glycolate, ethylphthalylbutyl glycolate, butylphthalylmethyl
glycolate, butylphthlylethyl glycolate, propylphthalylbutyl
glycolate, butylphthalylpropyl glycolate, methylphthalyloctyl
glycolate, ethylphthalyloctyl glycolate, octylphthalylmethyl
glycolate and octylphthalylethyl glycolate.
[0108] A phthalic acid ester type plasticizer includes such as
diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate,
dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate,
dicyclohexyl phthalate and dicyclohexyl terephthalate.
[0109] A citric acid ester type plasticizer includes such as
acetyltrimethyl citrate, acetyltriethyl citrate and acetyltributyl
citrate.
[0110] A fatty acid ester type plasticizer includes such as butyl
oleate, nethylacetyl ricinoleate and dibutyl sebacate.
[0111] A phosphoric acid ester type plasticizer includes such as
triphenyl phosphate, tricresyl phosphate, cresyldiphenyl phosphate,
octyldiphenyl phosphate, diphenylbiphenyl phosphate, trioctyl
phosphate and tributyl phosphate.
[0112] Polycarboxylic acid ester compound is comprised of ester of
polycarboxylic acid of not less than 2 valent, preferably of 2 to
20 valent, and alcohol. Further, aliphatic polycarboxylic acid is
preferably of 2 to 20 valent. In the case of aromatic
polycarboxylic acid and alicyclic polycarboxylic acid, 3 to 20
valent are preferable.
[0113] Polycarboxylic acid is represented by following Formula
(b).
R.sup.2(COOH).sub.m(OH).sub.n Formula (b)
(wherein, R.sup.2 is an (m+n) valent organic group; m is an integer
of not less than 2; n is an integer of not less than 0; COOK group
is a carboxyl group; and OH group is an alcoholic or phenolic
hydroxyl group.)
[0114] Examples of preferable polycarboxylic acid include the
followings, however, this invention is not limited thereto.
Aromatic polycarboxylic acid of not less than 3 valent such as
trimellitic acid, trimesic acid and pyromellitic acid, and
derivatives thereat aliphatic polycarboxylic acid such as succinic
acid, adipic acid, azelaic acid, sebacic acid, oxalic acid, fumaric
acid, maleic acid and tetrahydrophthalic acid; oxypolycarboxylic
acid such as tartaric acid, tartronic acid, malic acid and citric
acid; can be preferably utilized. It is specifically preferable to
utilize oxypolycarboxylic acid with respect to such as improvement
of storage stability.
[0115] Alcohol utilized in a polycarboxylic ester compound, which
can be utilized in this invention, is not specifically limited and
conventionally known alcohols and phenols can be utilized. For
example, straight chain or branched aliphatic saturated alcohol or
aliphatic unsaturated alcohol, having a carbon number of 1 to 32,
can be preferably utilized. The carbon number is more preferably 1
to 20 and specifically preferably 1 to 10. Further, such as
alicyclic alcohol such as cyclopentanol and cyclohexanol or
derivatives thereof, and aromatic alcohol such as benzyl alcohol
and cinnamyl alcohol or derivatives thereof can be also preferably
utilized.
[0116] When oxypolycarboxylic acid as polyvalent carboxylic acid is
utilized, an alcoholic or phenolic hydroxyl group of polycarboxylic
acid may be esterified by use of monocarboxylic acid. Preferable
monocarboxylic acid includes the following however, this invention
is not limited thereto.
[0117] As aliphatic monocarboxylic acid, straight chain or branched
fatty acid having a carbon number of 1 to 32 is preferably
utilized. The carbon number is more preferably 1 to 20 and
specifically preferably 1 to 10.
[0118] Preferable aliphatic monocarboxylic acid includes saturated
fatty acid such as acetic acid, propionic acid, butyric acid,
valeric acid, caproic acid, enanthic acid, caprylic acid,
pelargonic acid, capric acid, 2-ethyl-hexane carboxylic acid,
undecylic acid, lauric acid, tridecylic acid, myristic acid,
pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid,
nonadecanoic acid, arachic acid, behenic acid, lignoceric acid,
cerotic acid, heptacosanoic acid, montanic acid, melissic acid and
lacceric acid; and unsaturated fatty acid such as undecylenic acid,
oleic acid, sorbic acid, linoleic acid, linolenic acid and
arachidonic acid.
[0119] Examples of preferable alicyclic monocarboxylic acid include
cyclopentane carboxylic acid, cyclohexane carboxylic acid and
cyclooctane carboxylic acid; or derivatives thereof.
[0120] Examples of preferable aromatic monocarboxylic acid include
those in which an alkyl group is introduced in a benzene ring of
benzoic acid such as benzoic acid and toluic acid; aromatic
monocarboxylic acid having at least two benzene rings such as
biphenyl carboxylic acid, naphthalene carboxylic acid and terrain
carboxylic acid, or derivatives thereof. Acetic acid, propionic
acid and benzoic acid are specifically preferable.
[0121] The molecular weight of a monocarboxylic ester compound is
not specifically limited, however, is preferably in a range of 300
to 1,000 and more preferably in a range of 350 to 750. The
molecular weight is preferably the larger with respect to storage
stability, while it is preferably smaller with respect to moisture
permeability and compatibility with cellulose ester.
[0122] Alcohols, which are utilized in polycarboxylic ester
applicable in this invention, may be either one type or a mixture
of at least two types.
[0123] An acid value of a polycarboxylic ester compound utilizable
in this invention is preferably not more than 1 mg KOH/g and more
preferably not more than 0.2 mg KOH/g. By setting the acid value
within the above-described range, variation of retardation due to
environment is preferably suppressed.
(Acid Value)
[0124] An acid value refers to a milligram value of potassium
hydroxide required to neutralize acid contained in 1 g of a sample
(carboxyl groups existing in a sample). An acid value is measured
according to JIS K0070.
[0125] Specifically preferable examples of a polycarboxylic ester
compound will be shown below, however, this invention is not
limited thereto. For example, listed are diethyl citrate, tributyl
citrate, acetyltriethyl citrate (ATEC), acetyltributyl citrate
(ATBC), benzoyltributyl citrate, acetyltriphenyl citrate,
acetyltribenzyl citrate, dibutyl tartrate, diacetyldibutyl
tartrate, tributyl trimellitate and tetrabutyl pyromellitate.
[0126] A polyester type plasticizer is not specifically limited,
however, a polyester type plasticizer having an aromatic ring or a
cycloalkyl ring in a molecule can be utilized. A polyester type
plasticizer is not specifically limited, however, such as an
aromatic terminal ester type plasticizer represented by following
Formula (c) can be utilized.
B-(G-A).sub.n-G-B Formula (c)
(wherein, B is a benzene monocarboxylic acid residual group; G is
an alkylene glycol residual group having a carbon number of 2 to
12, an aryl glycol residual group having a carbon number of 6 to
12, or an oxyalkylene glycol residual group having a carbon number
of 4 to 12; A is an alkylene dicarboxylic acid residual group
having a carbon number of 4 to 12 or an aryl dicarboxylic acid
residual group having a carbon number of 6 to 12; and n is an
integer of not less than 1.)
[0127] A compound represented by Formula (c) is comprised of
benzene monocarboxylic acid residual group represented by B, an
alkylene glycol residual group, an oxyalkylene glycol residual
group or an arylglycol residual group represented by G, and an
alkylen dicarboxylic acid residual group or an aryl dicarboxylic
acid residual group represented by A; and can be prepared by a
reaction similar to that of a general polyester type
plasticizer.
[0128] A benzene monocarboxylic acid component of polyester type
plasticizer utilized in this invention includes such as benzoic
acid, p-tertiary-butylbenzoic acid, ortho-toluic acid, metha-toluic
acid, para-toluic acid, dimethylbenzoic acid, ethylbenzoic acid,
n-propylbenzoic acid, aminobenzoic acid and acetoxybenzoic acid,
and these each may be utilized alone or as a mixture of not less
than two types.
[0129] An alkylene glycol component having a carbon number of 2 to
12, which can be utilized in this invention, includes such as
ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol,
1,2-butanediol, 1,3-butanediol, 1,2-propanediol,
2-methyl-1,3-propanediol, 1,4-butanediol, 1,5-pentanediol,
2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2,2-diethyl-1,3
propanediol (3,3-dimethylol pentane),
2-n-butyl-2-ethyl-1,3-propanediol (3,3-dimethylol heptane),
3-methyl-1,5-pentanediol, 1,6-hexanediol,
2,2,4-trimethyl-1,3-pentanediol, 2-ethyl-1,3-hexanediol,
2-methyl-1,8-octanediol, 1,9-nonanediol, 1,10-decanediol and
1,12-octadecanediol; and these glycols are utilized alone or as a
mixture of at least two types. An alkylene glycol having a carbon
number of 2 to 12 is specifically preferable because of excellent
compatibility with cellulose ester.
[0130] Further, an oxyalkylene glycol component, having a carbon
number of 4 to 12, of the above-described aromatic terminal ester
includes such as diethylene glycol, triethylene tetraethylene
glycol, dipropylene glycol and tripropylene glycol; and these
glycols can be utilized alone or as a mixture of two or more
types.
[0131] An alkylene dicarboxylic acid component, having a carbon
number of 4 to 12, of aromatic terminal ester includes such as
maleic acid, fumaric acid, glutaric acid, adipic acid, azelaic
acid, sebacic acid and dodecane dicarboxylic acid; and these may be
utilized alone or as a mixture of not less than two types. An
arylene dicarboxylic acid component having a carbon number of 6 to
12 is phthalic acid, terephthalic acid, isophthalic acid,
1,5-naphthalene dicarboxylic acid and 1,4-naphthalene dicarboxylic
acid.
[0132] A polyester type plasticizer utilized in this invention
preferably has a number average molecular weight in a range of 300
to 1,500 and more preferably of 400 to 1,000. Further, an acid
value thereof is not more than 0.5 mg KOH/g and a hydroxyl group
value of not more than 25 mg KOH/g; and more preferably the acid
value is not more than 0.3 mg KOH/g and the hydroxyl group value of
not more than 15 mg KOH/g.
[0133] In the following, synthesis examples of an aromatic terminal
ester type plasticizer utilizable in this invention will be
shown.
<Sample No. 1 (Aromatic Terminal Ester Sample)>
[0134] Phthalic acid of 410 parts, 610 parts of benzoic acid, 737
parts of dipropylene glycol and 0.40 parts of tetraisopropyl
titanate as a catalyst were charged together in a reaction vessel
which was attached with a reflux condenser, and the system was kept
heated at 130 to 250.degree. C. to continuously remove the
generated water while excess monohydric alcohol was refluxed with
stirring in nitrogen gas flow. Next, the distillate was removed at
200 to 230.degree. C. under a reduced pressure of not higher than
1.33.times.10.sup.4 Pa and finally of not higher than
4.times.10.sup.2 Pa, followed by being filtered to prepare an
aromatic terminal ester type plasticizer having the following
characteristics.
[0135] Viscosity (25.degree. C., mPas); 43,400
[0136] Acid value; 0.2
<Sample No. 2 (Aromatic Terminal Ester Sample)>
[0137] An aromatic terminal ester type plasticizer having the
following characteristics was prepared in an exactly similar manner
to sample No. 1, except that phthalic acid of 410 parts, 610 parts
of benzoic acid, 341 parts of ethylene glycol and 0.35 parts of
tetraisopropyl titanate as a catalyst were utilized.
[0138] Viscosity (25.degree. C., mPas); 31,000
[0139] Acid value; 0.1
<Sample No. 3 (Aromatic Terminal Ester Sample)>
[0140] An aromatic terminal ester type plasticizer having the
following characteristics was prepared in an exactly similar manner
to sample No. 1, except that phthalic acid of 410 parts, 610 parts
of benzoic acid, 418 parts of 1,2-propanediol and 0.35 parts of
tetraisopropyl titanate as a catalyst were utilized.
[0141] Viscosity (25.degree. C., mPas); 38,000
<Sample No. 4 (Aromatic Terminal Ester Sample)>
[0142] An aromatic terminal ester type plasticizer having the
following characteristics was prepared in an exactly similar manner
to sample No. 1, except that phthalic acid of 410 parts, 610 parts
of benzoic acid, 418 parts of 1,3-propanediol and 0.35 parts of
tetraisopropyl titanate as a catalyst were utilized.
[0143] Viscosity (25.degree. C., mPas); 37,000
[0144] Acid value; 0.05
[0145] In the following, specific examples of an aromatic terminal
ester type plasticizer utilizable in this invention will be shown;
however, this invention is not limited thereto.
##STR00021## ##STR00022##
(Ultraviolet Absorber)
[0146] Protective film according to this invention may also contain
an ultraviolet absorber. An ultraviolet absorber has an object to
improve durability by absorbing ultraviolet rays of not longer than
400 nm, and in particular, transmittance at a wavelength of 370 nm
is preferably not more than 10%, more preferably not more than 5%
and still more preferably not more than 2%.
[0147] An ultraviolet absorber utilized in this invention is not
specifically limited, however, includes such as an oxybenzophenone
type compound, a benzotriazole type compound, a salicylic ester
type compound, a benzophenone type compound, a cyano acrylate type
compound, a triazine type compound, a nickel complex salt type
compound and inorganic powder.
[0148] For example listed are
5-chloro-2-(3,5-di-sec-butyl-2-hydroxylphenyl)-2H-benzotriazole,
(2-2H-benzotriazole-2-yl)-6-(straight chain and branched
dodecyl)-4-methylphenol, 2-hydroxy-4-benzyloxybenzophenone and
2,4-benzyloxybenzophenone; and also listed and preferably utilized
are TINUVIN, such as TINUVIN 109, TINUVIN 171, TINUVIN 234, TINUVIN
326, TINUVIN 327 and TINUVIN 328, which are available on the market
from Ciba Specialty Chemicals.
[0149] Ultraviolet absorbers utilized in this invention are
preferably a benzotriazole type ultraviolet absorber, a
benzophenone type ultraviolet absorber and a triazine type
ultraviolet absorber, and specifically preferably a benzotriazole
type ultraviolet absorber and a benzophenone type ultraviolet
absorber.
[0150] For example, as a benzotriazole type ultraviolet absorber, a
compound represented by following Formula (d) can be utilized.
##STR00023##
[0151] In the formula, R.sub.1, R.sub.2, R.sub.3, R.sub.4 and
R.sub.5, which may be same or different, are a hydrogen atom, a
halogen atom, a nitro group, a hydroxyl group, an alkyl group, an
alkenyl group, an aryl group, an alkoxy group, an acyloxy group, an
aryloxy group, an alkylthio group, an arylthio group, mono- or
di-alkylamino group, an acylamino group or a 5 to 6 member
heterocyclic group; and R.sub.4 and R.sub.5 may perform ring
closure in form a 5 to 6 member carbon ring.
[0152] Further, these groups described above may be provided with a
substituent
[0153] In the following, specific examples of a benzotriazole type
ultraviolet absorber utilized in this invention will be listed.
UV-1: 2-(2'-hydroxy-5'-methylphenyl)benzotriazole UV-2:
2-(2'-hydroxy-3',5'-di-tert-butylphenyl)benzothiazole UV-3:
2(2'-hydroxy-3'-tert-5'-methylphenyl)benzotriazole UV-4:
2(2'-hydroxy-3',5-di-tert-butylphenyl)-chlorobenzotriazole UV-5:
2(2'-hydroxy-3'-(3'',4'',5'',6''-tetrahydropthalimidomethyl)-5'-methylphe-
nyl)-benzotriazole UV-6:
2,2-methylenebis-(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole-2-yl)p-
henol) UV-7:
2-(2'-hydroxy-3'-di-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole
UV-8: 2-(2H-benzotriazole-2-yl)-6-(straight chain and branched
dodecyl)-4-methylphenol (Tinuvin 171) UV-9: A mixture of
octyl-3-[3-tert-butyl-4-hydroxy-5-(chloro-2H-benzotriazole-2-yl)phenyl]pr-
opionate and
2-ethylhexyl-3-[3-tert-butyl-4-hydroxy-5-(5-chloro-2H-benzotriazole-2-yl)-
phenyl]propionate (Tinuvin 109)
[0154] Further, a compound represented by following Formula (e) is
preferably utilized as a benzophenone type ultraviolet
absorber.
##STR00024##
[0155] In the formula, Y is a hydrogen atom, a halogen atom, an
alkyl group, an alkenyl group, an alkoxy group and a phenyl group;
and these alkyl group, alkenyl group and phenyl group may have a
substituent. A is a hydrogen atom, an alkyl group, an alkenyl
group, a phenyl group, a cycloalkyl group, an alkylcarbonyl group,
an alkylsulfonyl group or --CO(NH).sub.n-1-D group; and D is an
alkyl group, an alkenyl group or a phenyl group which may have a
substituent m and n are 1 or 2.
[0156] In the above description, an alkyl group is, for example, a
straight chain or branched aliphatic group having a carbon number
of up to 24; an alkoxy group is, for example, an alkoxy group
having a carbon number of up to 18; and an alkenyl group is for
example, an alkenyl group having a carbon number of up to 16 such
as an allyl group and a 2-butenyl group. Further, a substituent to
an alkyl group, an alkenyl group and a phenyl group includes such
as a halogen atom (such as a chlorine atom, a bromine atom and a
fluorine atom), a hydroxyl group and a phenyl group (this phenyl
group maybe substituted by such as an alkyl group or a halogen
atom).
[0157] In the following, specific examples of a benzophenone type
ultraviolet absorber represented by Formula (e).
UV-10: 2,4-dihydroxybenzophenone UV-11:
2,2'-dihydroxy-4-methoxybenzophenone UV-12:
2-hydroxy-4-methoxy-5-sulfobenzophenone UV-13:
bis(2-methoxy-4-hydroxy-5-benzoylphenylmethane)
[0158] In addition to these, a disc form compound such as a
compound having a 1,3,5-triazine ring is preferably utilized as an
ultraviolet absorber.
[0159] Polarizing plate protective film according to this invention
preferably contains more than two types of ultraviolet
absorbers.
[0160] Further, a polymer ultraviolet absorber may also be
preferably utilized as an ultraviolet absorber, and polymer type
ultraviolet absorbers described in JP-A H06-148430 are specifically
preferably utilized.
[0161] As a method adding an ultraviolet absorber, an ultraviolet
absorber may be added into a dope after having been dissolved in an
organic solvent such as alcohol like methanol, ethanol and butanol,
methylene chloride, methyl acetate, acetone and dioxane; or may be
directly added into a dope composition. Those insoluble in an
organic solvent, such as inorganic powder, will be added into a
dope after having been dispersed in an organic solvent and
cellulose ester by use of such as a dissolver or a sand mill.
[0162] The using amount of an ultraviolet absorber is not uniform
depending on a type and a using condition of an ultraviolet
absorber, however, in the case of the dry layer thickness of
polarizing plate protective film of 30 to 200 .mu.m, it is
preferably 0.5 to 10 percent by weight and more preferably 0.6 to 4
percent by weight, for a polarizing plate protective film.
(Micro-Particles)
[0163] Polarizing plate protective film according to this invention
preferably contains micro-particles.
[0164] As inorganic micro-particles utilized in this invention,
examples of an inorganic compound include silicon dioxide, titanium
dioxide, aluminum oxide, zirconium oxide, calcium carbonate, talc,
clay, burned kaolin, burned calcium silicate, hydrated calcium
silicate, aluminum silicate, magnesium silicate and calcium
phosphate. Micro-particles are preferably those containing silicon
because turbidity is decreased, and silicon dioxide is specifically
preferred.
[0165] An average particle diameter of a primary particle of
micro-particles is preferably 5 to 400 nm and more preferably 10 to
300 nm. These may be contained as secondary aggregate having a
particle size of 0.05 to 0.3 .mu.m, or may be contained as primary
particles without aggregation in the case of particles having an
average particle size of 100 to 400 nm. The content of these
micro-particles in polarizing plate protective film is preferably
0.01 to 1 percent by weight and specifically preferably 0.05 to 0.5
percent by weight. In the case of a polarizing plate protective
film comprising a constitution of plural layers by a co-casting
method, micro-particles of this addition amount are preferably
incorporated in the surface.
[0166] As micro-particles of silicon dioxide, for example, products
under the names of AEROSIL R972, R972V, 8974, R812, 200, 200V, 300,
R202, OX50 and TT600 (produced by Nippon Aerosil Co., Ltd.) are
available on the market and can be utilized.
[0167] As micro-particles of zirconium oxide, for example, products
under the names of Aerosil R976 and R811 (produced by Nippon
Aerosil Co., Ltd.) are available on the market and can be
utilized.
[0168] Examples of polymer include silicone resin,
fluorine-containing resin and acrylic resin. Silicone resin is
preferred and those, having a three dimensional net structure, are
specifically preferable-, for example, products under the name of
TOSPEARL 103, 105, 108, 120, 145, 3120 and 240 (produced by Toshiba
Silicones Co., Ltd.) are available on the market and can be
utilized.
[0169] Among these, AEROSIL 200V and AEROSIL R972 are specifically
preferably utilized because of a large effect to decrease a
friction coefficient while keeping turbidity of polarizing plate
protective film to be low. In polarizing plate protective film
utilized in this invention, a dynamic friction coefficient of at
least one of the surfaces is preferably 0.2 to 1.0.
[0170] Various types of additives may be batch-wise added into a
dope as a cellulose ester containing solution before casting, or
may be inline-wise added by preparing a solution of dissolved
additives. In particular, a part of or the total amount of
micro-particles are preferably added by an inline method to reduce
a load on a filter medium.
[0171] In the case of addition of an additive solution is performed
by an inline method, it is preferable to dissolve a small amount of
cellulose ester in the solution to increase compatibility with a
dope. The preferable amount of cellulose ester is 1 to 10 weight
parts and more preferably 3 to 5 weight parts based on 100 parts of
a solvent.
[0172] To perform inline addition and mixing in this invention, for
example, an inline mixer such as Static Mixer (manufactured by
Toray Engineering Corp.) and SWJ (Toray Static Inline Mixer,
Hi-Mixer) is preferably utilized.
(Manufacturing Process of the Optical Compensation Film)
[0173] Manufacturing process of the optical compensation film of
this invention will be described.
[0174] Film manufactured by solution cast method or melt cast
method may be preferably used for the optical compensation film of
this invention.
[0175] The optical compensation film of this invention is
manufactured by a process of preparing dope in which cellulose
ester and additives are dissolved in a solvent, a process of
casting the dope on running endless metal support, a process of
drying the cast dope as a web, a process of separating from the
metal support, a process of expand or maintaining the width, a
process of drying further, and a process of winding the finished
film.
[0176] A process to prepare a dope will be now described. The
concentration of cellulose in a dope is preferably the higher with
respect to decreasing a drying load after the dope has been cast on
a metal support, while, when the concentration of cellulose ester
is excessively high, filtering precision will be deteriorated due
to an increased load at the time of filtering. The concentration to
balance these is preferably 10 to 35 percent by weight and more
preferably 15 to 25 percent by weight.
[0177] A solvent utilized in a dope of this invention, one type
alone or at least two types in combination may be utilized,
however, a good solvent and a poor solvent of cellulose ester are
preferably utilized in combination with respect to manufacturing
efficiency. A preferable range of a mixing ratio of a good solvent
to a poor solvent is 70 to 98 percent by weight of good solvent to
2 to 30 percent by weight of a poor solvent. As a good solvent and
a poor solvent, one dissolves cellulose ester, which is utilized,
by itself alone is defined as a good solvent and one swells or can
not dissolve cellulose ester is defined as a poor solvent.
Therefore, a good solvent and a poor solvent may differ depending
on an average acetylation degree (an acetyl substitution degree),
and for example, when acetone is utilized as a solvent, it becomes
a good solvent for acetic ester of cellulose ester (an acetyl
substitution degree of 2.4) and cellulose acetate propionate, while
it becomes a poor solvent for acetic ester of cellulose (an acetyl
substitution degree of 2.8) of cellulose.
[0178] A good solvent utilized in this invention is not
specifically limited, however, includes an organic halogen compound
such as methylene chloride, dioxolan, acetone, methylacetate and
methyl acetoacetate. Methylene chloride and methyl acetate are
specifically preferable.
[0179] Further, a poor solvent utilized in this invention is not
specifically limited, however, such as methanol, ethanol,
n-butanol, cyclohexane and cyclohexanone are preferably utilized.
Further, a dope preferably contains 0.01 to 2 percent by weight of
water. Further, as a solvent utilized for dissolution of cellulose
ester, a solvent removed from film by drying in a film casting
process is recovered and reused, after purified if necessary.
[0180] As a dissolution method of cellulose ester at the time of
preparation of the dope described above, a general method eau be
employed. By combination of heating and increased pressure, it is
possible to heat up to higher than a boiling point at an ordinary
pressure. It is preferable because generation of a granular
insoluble residue, which is called as gel or flocculates, is
inhibited, when cellulose ester is dissolved with stirring while
being heated at a temperature in a range of not lower than a
boiling point under ordinary pressure and not to boil the solvent
under increased pressure. Further, preferably utilized is a method,
in which cellulose ester is dissolved by further adding a good
solvent after having been wetted or swelled by mixing with a poor
solvent.
[0181] Pressure increase may be performed by a method to introduce
an inert gas such as a nitrogen gas or a method to increase vapor
pressure of a solvent by heating. Heating is preferably performed
from outside and, for example, a jacket type equipment is
preferable with respect to easy temperature control.
[0182] Heating temperature with addition of a solvent is prefer
ably the higher in view of solubility of cellulose ester, however,
productivity may be deteriorated due to increase of a required
pressure when the heating temperature is excessively high. The
heating temperature is preferably 45 to 120.degree. C., more
preferably 60 to 110.degree. C. and still more preferably 70 to
105.degree. C. Further, pressure is adjusted not to boil a solvent
at the set temperature.
[0183] In addition to these, a cold dissolution method is also
preferably applied, and cellulose ester can be dissolved in such as
methyl acetate by this method.
[0184] Next, this cellulose ester solution is filtered by use of a
suitable filter medium such as filter paper. As a filter medium,
the absolute filtering precision is preferably the smaller to
eliminate insoluble residue, however, there is a problem of easy
clogging of a filter medium when the absolute filtering precision
is excessively small. Therefore, the absolute filtering precision
of a filter medium is preferably not larger than 0.008 mm, more
preferably 0.001 to 0.008 min and furthermore preferably 0.003 to
0.006 mm. The material of a filter medium is not specifically
limited and an ordinary filter medium can be utilized, however, a
filter medium made of plastic such as polypropylene and TEFLON.RTM.
and a filter medium made of metal such as stainless steel are
preferable because of such as no release of fiber of a filter
medium.
[0185] It is preferable to eliminate and reduce impurities,
particularly foreign materials causing a bright spot defect having
been contained in cellulose ester as a raw material by
filtration.
[0186] Foreign materials causing bright spot defects means a spot
(a foreign material) which is visible due to light leak, when two
sheets of polarizing plates, between which polarizing plate
protective film is placed, are arranged in a crossed Nicols state,
and light is irradiated from one of the polarizing plate side to be
observed from the other polarizing plate side. The number of bright
spots having a diameter of not less than 0.01 mm is preferably not
more than 200 spots/cm.sup.2. More preferably not more than 100
spots/not more than 200 spots/cm.sup.2, furthermore preferably not
more than 50 spots/cm.sup.2 and most preferably 0 to 10 sport/ml.
Further, the number of a bright spot defect of not larger than 0.01
mm is also preferably the smaller.
[0187] Filtering of a dope can be performed by an ordinary method,
however, a method to filter while heating at a temperature of not
lower than a boiling point of a solvent at ordinary pressure and of
not to boil the solvent under an increased pressure is preferable
because of small increase of a difference of filter pressures
before and after filtering (referred to as a pressure difference).
The preferable temperature is 45 to 120.degree. C., more preferably
45 to 70.degree. C. and furthermore preferably 45 to 55.degree.
C.
[0188] Filter pressure is preferably the lower. The filter pressure
is preferably not higher than 1.6 MPa, more preferably not higher
than 12 MPa and furthermore preferably not higher than 1.0 MPa.
[0189] Casting of a dope will now be explained.
[0190] A metal support in a casting process is preferably those the
surface of which is mirror finished, and a stainless steel belt or
a drum made of castings, the surface of which is mirror finished,
is utilized The cast width can be set to 1 to 4 m. The surface
temperature of a metal support in a cast process is from
-50.degree. C. to lower than a boiling point of a solvent and it is
preferable the temperature is the higher since web drying speed is
fast; however, excessively high temperature may sometimes cause
foaming of a web or deterioration of flatness. The support
temperature is preferably 0 to 40.degree. C. and more preferably 5
to 30.degree. C. It is also a preferable method to make a web
gelled by cooling and to peel off the web from a drum with a plenty
of residual solvent contained. A method to control the temperature
of a metal support is not specifically limited, however, there are
a method to blow a hot wind or a cold wind on the web and a method
to make hot water contact the rear side of a metal support. A
method to utilize hot water is preferable because time required to
make a metal support become a constant temperature is short due to
more efficient heat transfer by use of a hot water. In the case of
employing a hot wind, a wind of a temperature higher than the aimed
temperature may be employed.
[0191] To provide a good flatness of polarizing plate protective
film, the residual solvent amount at the time of peeling off a web
from a metal support is preferably 10 to 150 percent by weight,
more preferably 20 to 40 percent by weight or 60 to 130 percent by
weight and specifically preferably 20 to 30 percent by weight or 70
to 120 percent by weight.
[0192] A residual solvent amount is defined by the following
formula in this invention.
Residual solvent amount(percent by weight)={(M-N)/N}.times.100
[0193] Herein, M is a weight of a sample picked at an arbitrary
time during or after manufacturing of a web or film and N is a
weight after heating at 115.degree. C. for 1 hour.
[0194] Further, in a drying process of polarizing plate protective
film, a web is preferably peeled off from a metal support and
further dried to make a residual solvent amount of not more than 1
percent by weight, more preferably not more than 0.1 percent by
weight and specifically preferably 0 to 0.01 percent by weight.
[0195] In a film drying process, a roll drying method (in which a
web is dried while being alternately passed through many rolls
which are arranged up and down) or a method to dry a web while
being transported by a tenter method will be applied.
[0196] It is specifically preferable that a web is stretched in the
width direction by means of a tenter method to grip the both edges
of the web by such as clips to prepare optical compensation film of
this invention. It is preferable to peel off at a peel-off tension
of not less than 300 N/m.
[0197] A means to dry a web is not specifically limited, and it can
be generally performed by such as a hot wind, infrared rays, a heat
roll and microwaves, however, preferably performed by a hot wind
with respect to convenience.
[0198] Drying temperature in a drying process of a web is
preferably 40 to 200.degree. C. and stepwise raised. The layer
thickness of optical compensation film is not specifically limited;
however, a layer thickness of 10 to 200 .mu.m is applied. The layer
thickness is specifically preferably 10-100 .mu.m and furthermore
preferably 20 to 60 .mu.m.
[0199] Optical compensation film of this invention has a width of 1
to 4 in. The width is preferably 1.4 to 4 m and specifically
preferably 1.6 to 3 in. When the width exceeds 4 m, the
transportation becomes difficult
(Stretching Operation, Refractive Index Control)
[0200] The optical compensation film preferably has retardation
values Ro and Rt which satisfy the following Formulas (i) to
(iii).
20.ltoreq.Ro.ltoreq.100 (nm) (i)
70.ltoreq.Rt.ltoreq.200 (nm) (ii)
0.82.ltoreq.Ro(480)/Ro(630).ltoreq.0.96 (iii)
[0201] Here, Ro=(nx-ny).times.d
Rt=((nx+ny)/2-nz).times.d
[0202] (In these formulas, nx represents a refractive index in the
retarded phase axis direction in a plane of the optical
compensation film, ny represents a refractive index in a direction
perpendicular to the retarded phase axis direction in a plane, nz
represents a refractive index in a thickness direction and d
represents the thickness (nm) of the optical compensation film
respectively. The measuring wavelength for the refractive index is
590 nm. Ro (480) and Ro (630) represent Ro measured with the
wavelength of 480 nm and Ro measured with the wavelength of 630 nm,
respectively).
[0203] The above-described refractive index can be determined by
the use of, for example, KOBRA-21ADH (manufactured by Oji
Instrument Co., Ltd.) at a wavelength of 590 nm under an
environment of 23.degree. C. and 55% RH.
[0204] Wave length dispersion property as well as retardation can
be adjusted as desired by adding the Polymer (a) and the compound
having furanose structure or pyranose structure of this invention
in optional combination.
[0205] In the present invention, even if the phase differences are
20.ltoreq.Ro.ltoreq.100 (nm) and 70.ltoreq.Rt.ltoreq.200 (nm), the
wavelength dispersion characteristic of 0.82.ltoreq.Ro(480)/Ro(630)
.delta. 0.95 can be attained.
[0206] The desirable range in the present invention is
20.ltoreq.Ro.ltoreq.100 (nm), and is especially preferably
45.ltoreq.Ro.ltoreq.75 (nm).
[0207] The desirable range in the present invention is
70.ltoreq.Rt.ltoreq.200 (nm), and is especially preferably
105.ltoreq.Rt.ltoreq.140 (nm).
[0208] To achieve retardation values Ro and Rt which are described
above, it is preferable that optical compensation film employs a
constitution of this invention and refractive index control is
further performed by a stretching operation.
[0209] For example, it is possible to perform successive or
simultaneous stretching in the longitudinal direction of film (the
cast direction) and in the direction perpendicular thereto, that
is, in the width direction.
[0210] The stretching magnifications in the biaxial directions
perpendicular to each other are preferably set to finally 0.8 to
1.5 times in the cast direction and 1.1 to 2.5 times in the width
direction, and more preferably set to 0.8 to 1.0 times in the cast
direction and 12 to 2.0 times in the width direction.
[0211] The stretching temperature is preferably 120.degree. C. to
200.degree. C., more preferably 160.degree. C. to 200.degree. C.,
still more preferably higher than 170.degree. C. and not higher
than 200.degree. C. It may be preferable to stretch a film under
the condition where the content of the residual solvent in the film
is 20 to 0%, more preferably 15 to 0%. More concretely, the film is
preferably stretched under the condition that the content of the
residual solvent is 11% at 155.degree. C., or the content of the
residual solvent is 2% at 155.degree. C. Otherwise, the content of
the residual solvent is 11% at 165.degree. C., or the content of
the residual solvent is not higher than 1% at 165.degree. C.
[0212] A method to stretch a web is not specifically limited. For
example, listed a method to stretch in the longitudinal direction
by making a circumferential speed difference among plural rolls and
utilizing the roll circumferential speed difference among them, a
method to stretch in the longitudinal direction by fixing the both
edge of a web with clips or pins and widening the intervals between
clips and pins toward the proceeding direction, a method to stretch
by widening similarly along the width direction, or a method to
stretch in the both of longitudinal and width directions by
simultaneously widening along the longitudinal and width
directions. Of cause, these methods can be utilized in combination.
In a so-called tenter method, it is preferable that a smooth
stretching can be performed by driving the clip portion by a linear
chive method which reduces risk to such as break.
[0213] It is preferable to perform the width holding or stretching
in the width direction by a tenter, which may be either a pin
tenter or a clip tenter.
[0214] The retardation axis or the advanced axis of optical
compensation film of this invention preferably is present in a film
plane and .theta.1 is preferably not less than -1.degree. and not
more than +1.degree., and more preferably not less than
-0.5.degree. and not more than +0.5.degree., when the angle against
the casting direction is .theta.1. This .theta.1 can be defined as
an orientation angle, and measurement of .theta.1 can be performed
by use of automatic birefringence meter KOBRA-21ADH (Oji Scientific
Instruments). To satisfy the above-described relationships by
.theta.1 can contributes to obtain a high luminance and to restrain
or prevent light leak, and to obtain good fidelity color
reproduction in a color liquid display.
(Physical Properties)
[0215] Moisture permeability of optical compensation film according
to this invention is preferably 10 to 1,200 g/m.sup.224 h, more
preferably 20 to 1,000 g/m.sup.224 h and specifically preferably 20
to 850 g/m.sup.224 h at 40.degree. C., 90% RH. Moisture
permeability can be measured according to a method described in JIS
Z 0208.
[0216] Elongation percentage of the optical compensation film
according to this invention is preferably 10 to 80% and more
preferably 20 to 50%.
[0217] Visible light transmittance of optical compensation film
according to this invention is preferably not less than 90% and
more preferably not less than 93%.
[0218] Haze of optical compensation film according to this
invention is preferably less than 1% and specifically preferably 0
to 0.1%.
[0219] Further, if a liquid crystal layer is coated on the optical
compensation film of the present invention, retardation values
extending over a more wide range may be obtained.
(Polarizing Plate)
[0220] A polarizing plate and a liquid crystal display device using
it according to this invention will be now explained.
[0221] A polarizing plate of this invention is characterized by
being a polarizing plate constituted of a polarizer, adhered with
the aforesaid optical compensation film of this invention as a
polarizing protective film on at least one surface. A liquid
crystal display device of this invention is characterized in that a
polarizing plate according to this invention is adhered up on at
least one liquid crystal cell surface via an adhesive layer.
[0222] A polarizing plate of this invention can be prepared by an
ordinary method. The optical compensation film of this invention,
the polarizer side of which is subjected to an alkaline
saponification treatment, is preferably adhered up on at least one
surface of a polarizer which has been prepared by immersion
stretching in an iodine solution by use of a completely
saponificated type polyvinyl alcohol aqueous solution. On the other
surface, said optical compensation film may be utilized or another
polarizing plate protective film may be utilized. Cellulose ester
film (such as Konica Minolta TAC KC8UX, KC4UX, KC5UX, KC8UCR3,
KC8UCR4, KC8UCR5, KC8UY, KC4UY, KC12UR, KC4UE, KC8UE, KC8UY-HA,
KC8UX-RHA, KC8UXW-RHA-C, KC8UXW-RHA-NC, and KC4UXW-RHA-NC
manufactured by Konica Minolta Opto. Inc.) available on the market
is also preferably utilized.
[0223] Onto the polarizing plate protective film used for the
surface side of a display unit, it is desirable to provide an
antireflection layer, an antistatic layer, an antifouling layer,
and a back coat layer in addition to an antiglare layer or a clear
hard coat layer.
[0224] A polarizer as a primary composing element of the polarizing
plate is an element to pass light of a polarized wave plane of a
predetermined direction, and a typical polarizer known at present
is polyvinyl type polarizing film, which includes polyvinyl alcohol
film dyed with iodine and one dyed with dichroic dye. As a
polarizer, utilized is one in which a polyvinyl alcohol aqueous
solution is made to film, and the obtained film is uniaxially
stretched and dyed, or is uniaxially stretched after having been
dyed, preferably followed by being subjected to a durability
treatment with a boron compound. The layer thickness of a polarizer
is preferably 5 to 30 .mu.m and specifically preferably 10 to 20
.mu.m.
[0225] Further, ethylene modified polyvinyl alcohol which is
described in such as JP-A 2003-248123 and JP-A 2003-342322 and has
an ethylene unit content of 1 to 4 mol %, a polymerization degree
of 2,000 to 4,000 and a saponification degree of 99.0 to 99.99 mol
% is also preferably utilized. Among them, ethylene modified
polyvinyl alcohol having a hot water breaking temperature of 66 to
73.degree. C. is preferably utilized. Further, a difference of hot
water breaking temperature between two, points remote from each
other by 5 cm in the film TD direction is preferably not more than
1.degree. C. and more preferably not more than 0.5.degree. C., in
order to reduce color spottiness.
[0226] A polarizer utilizing this ethylene modified polyvinyl
alcohol film is excellent in polarizing ability and durability, as
well as exhibits few color spottiness, and is specifically
preferably applied in a large size liquid crystal display
device.
[0227] A polarizer prepared in the above manner, generally on the
both surface or one surface of which protective film is adhered up,
is utilized as a polarizing plate. An adhesive employed at the time
of paste up includes a PVA type adhesive and an urethane type
adhesive, however, among them preferably utilized is a PVA type
adhesive.
(Liquid Crystal Display)
[0228] By using the polarizing plate according to the third
embodiment of the present invention for a liquid crystal display,
various kinds of the liquid crystal displays of the present
invention excellent in visibility can be produced. The optical
compensation film of the present invention can be used for liquid
crystal displays with various drive systems, such as STN, TN, OCB,
HAN, VA (MVA, PVA), IPS, and OCB. It is desirable to use for a VA
(MVA, PVA) type liquid crystal display. Especially, even if a
liquid crystal display has a huge screen more than 30 type, it is
possible to obtain a liquid crystal display in which there are few
environmental variations, light leakage is reduced, and visibility,
such as color tone unevenness and front contrast is excellent.
Especially, the frequency of occurrence of light leakage can be
reduced by the group of the liquid crystal display manufactured by
the use of the optical compensation film of the present
invention.
EXAMPLE
[0229] The invention is concretely illustrated by means of
Examples, to which this invention is not limited.
Example 1
[0230] Cellulose ester, Polymer (a), a compound having a furanose
or pyranose structure (Compound (b), sugar ester compound),
plasticizers, and UV absorber used in the Examples are listed in
Table 1.
TABLE-US-00001 TABLE 1 Total substitu- Cellulose tion degree of
Ester Substitution Degree of Acyl group acyl group A Acetyl group:
1.9 Propionyl group: 0.8 2.7 B Acetyl group: 1.6 Propionyl group:
0.9 2.5 C Acetyl group: 1.1 Propionyl group: 0.9 2.0 D Acetyl
group: 1.2 Propionyl group: 1.1 2.3 E Acetyl group: 2.4 2.4 F
Acetyl group: 1.3 Propionyl group: 1.2 2.5 Sugar Ester Compound A
Exemplified Compound 3 B Exemplified Compound 5 C Mixture of the
same weight of Exemplified Compounds 6 and 7 D Exemplified Compound
8 Plasticizer A Triphenyl phosphate B Ethylphthalyl ethylglycolate
C Trimethylol propanetribenzoate UV Absorber A TINUVIN 326 Ciba
Specialty Chemicals B TINUVIN 109 Ciba Specialty Chemicals C
TINUVIN 171 Ciba Specialty Chemicals
[0231] Polymer (a) used in the Example is described below.
Synthesis Example 1
[0232] Copolymer AMP-6 of exemplified compound AM-2 and
methylmethacrylate was synthesized in accordance the following
method.
[0233] Hundred and twenty five grams of polymer raw material
composed of 100 parts by weight of monomer mixture of 20% by weight
of exemplified compound AM-2 and 80% by weight of
methylmethacrylate to which 2.0 parts by weight of peroxy lauroyl,
0.25 parts by weight of n-octylmercaptan and 0.1 parts by weight of
stearic alcohol were added, and 250 g of deionized water dissolving
preliminarily 0.2 g of 1% aqueous solution of sodium
polymethacrylate, 0.05 g of sodium dihydrogen phosphate and 0.15 g
of disodium hydrogen phosphate were charged in a flask having
stirrer, air was substituted with nitrogen, polymerization was
carried out at 70.degree. C. for 3 hours, and then polymerization
was further carried out at 100.degree. C. for 1 hour. Bead form of
copolymer AMP-6 was obtained through cooling, filtration, washing
and drying processes after completion of polymerization. The
copolymer was confirmed to have an weight average molecular weight
of 12,000 and Mw/Mn of 2.8 by GPC analysis employing standard
polystyrene.
[0234] Thus obtained copolymer was confirmed as a copolymer of the
exemplified compound AM-2 and methylmethacrylate by NMR spectrum.
Composition content of AM-2/methylmethacrylate was approximately
20180.
Synthesis Example 2
[0235] Copolymer AMP-7 of exemplified compound AM-2 and
methylacrylate was synthesized in accordance the following
method.
[0236] Into 100 ml of toluene, 10 g of monomer mixture of 50 weight
parts of AM-2 and 50 weight parts of methyl methacrylate was added,
then 0.1 g of azobisisobutyronitrile was added. Temperature was
raised up to 80.degree. C. and polymerization was carried out for 5
hours in nitrogen atmosphere. After removing 70 ml of toluene by
evaporation under reduce pressure, the content was dripped far
excess amount of methanol. Deposited precipitation was subjected to
filtration, washing, and drying processes, and powder copolymer
AMP-7 was obtained. The copolymer was confirmed to have an weight
average molecular weight of 30,000 and Mw/Mn of 3.0 by GPC analysis
employing standard polystyrene.
[0237] Thus obtained copolymer was confirmed as a copolymer of the
exemplified compound AM-2 and methylacrylate by NMR spectrum.
Composition content of AM-2/methylacrylate was approximately
50/50.
[0238] Polymer (a) of AMP-1 through 5, and 8 through 20,
respectively was synthesized in the similar manner. Weight average
molecular weight and composition content of synthesized polymers
was each measured in the same way as Synthesize Example 1. Details
of polymers are shown in Table 2.
TABLE-US-00002 TABLE 2 Monomer Component Weight average Polymer (a)
Content molecular weight AMP 1 AM-1 20 MMA 80 22,000 AMP 2 AM-1 40
MMA 60 9,000 AMP 3 AM-1 50 MA 50 38,000 AMP 4 AM-1 50 St 50 14,000
AMP 5 AM-2 50 VAC 50 28,000 AMP 6 AM-2 20 MMA 80 12,000 AMP 7 AM-2
50 MA 50 30,000 AMP 8 AM-2 60 St 40 7,000 AMP 9 AM-2 50 VAC 50
9,000 AMP 10 AM-2 20 MMA 80 5,000 AMP 11 AM-2 30 MMA 70 8,000 AMP
12 AM-3 50 HEMA 50 8,000 AMP 13 AM-4 30 HEMA 70 38,000 AMP 14 AM-5
50 MA 50 21,000 AMP 15 AM-5 30 HEA 70 19,000 AMP 16 AM-5 50 HEMA 50
12,000 AMP 17 AM-6 20 MMA 80 30,000 AMP 18 AM-7 40 MMA 60 15,000
AMP 19 AM-13 30 MA 70 45,000 AMP 20 AM-15 60 MMA 40 73,000
[0239] In Table 2 MA, MMA, HEA, St, and VAC are abbreviation of the
following compound, respectively.
MA: Methylacrylate
MMA: Methylmethacrylate
HEA: 2-Hydroxyethylmethacrylate
St: Styrene
[0240] VAC: Vinyl acetate
<Producing Optical Compensation Film 101>
<Microparticles Dispersion 1>
TABLE-US-00003 [0241] Microparticles (AEROSIL R972V, manufactured
11 parts by weight by Nippon Aerosil Co., Ltd.) Ethanol 89 parts by
weight
These were mixed and agitated for 50 minutes by means of dissolver
and the dispersed by Manton-Gaurin.
<Liquid for In-Line Addition>
[0242] Cellulose ester B was added into a dissolution tank
containing methylene chloride, and was dissolved completely by
heating, then it was filtered employing AZUMI FILTER PAPER No. 244
manufactured by Azumi Filter Paper Co., Ltd.
[0243] Dispersion of microparticles was added slowly in filtered
cellulose acetate solution while sufficiently agitating. Dispersion
was carried out by an attritor mill so that particle diameter of
secondary particles reached to predetermined size. The resultant
was filtered by FINEMET NT manufactured by Nippon seisen Co. Ltd,
and liquid 1 for in-line addition was obtained.
TABLE-US-00004 Methylene chloride 99 parts by weight Cellulose
ester B 4 parts by weight Microparticles Dispersion 1 11 parts by
weight
[0244] Primary dope composition having the following components was
prepared. Methylene chloride and ethanol were added into a
pressured dissolution tank. Cellulose acetate B was poured into the
pressured dissolution tank containing solvent while agitating.
Polymer (a) and sugar ester compound of this invention were added
and completely dissolved by heating with agitation, and was
filtered by employing AZUMI FILTER PAPER No. 244, to obtain dope
composition.
<Primary Dope Components>
TABLE-US-00005 [0245] Methylene chloride 380 parts by weight
Ethanol 70 parts by weight Cellulose ester B 100 parts by weight
Polymer (a) of this Invention 3.5 parts by weight Sugar ester
compound of this Invention 11.5 parts by weight
[0246] Dope composition was filtered by FINEMET NT manufactured by
Nippon seisen Co. Ltd. in the film forming line. Liquid for in-line
addition was filtered by Nippon seisen Co. Ltd. in the in-line
liquid addition line. Two parts by weight of filtered in-line
addition liquid was added to 100 parts by weight of filtered dope
composition, and was mixed well by means of in-line mixer (Static
type in-line mixer Hi-Mixer SWJ, manufactured by Toray), then the
dope was cast on stainless steel belt support with uniformity at
width of 1.8 meter at 35.degree. C. by employing a belt casting
apparatus. Solvent was evaporated so as to have solvent residue
amount of 120% on the stainless belt support, then it was separated
from the stainless belt support. Solvent of the separated cellulose
ester web was evaporated at 50.degree. C., and the web was slit to
have 1.65 m width, and stretched to TD direction (orthogonal
direction to film conveying direction) at a temperature with
stretching magnification as shown in Table. Drying was completed by
conveying with a plenty of rolls in a drying zone at 120.degree.
C., the web was slit to have 1.5 m width, and was subjected to a
knurling process so as to have an average height of 10 .mu.m at
both side of 15 mm. Thus Optical Compensation Film 101 having an
average thickness of 40 .mu.m was manufactured. The width of the
film was 1.5 in, winding length was 5,000 in.
[0247] Optical Compensation Films 102 to 134 were manufactured by
the same manner except that kinds of cellulose ester, Polymer (a),
sugar ester compound, plasticizer and UV absorber, and stretching
magnifier and film thickness were changed as described in Tables 3
and 4. Further, comparative Optical. Compensation Films to which
Polymer (a) or sugar ester compound was not added were
manufactured.
[0248] Retardation values for each obtained samples were measured
in the following way at each wave length. The result is summarized
in Tables 3 and 4.
(Measuring Retardation Ro and Rt)
[0249] Samples having size of 35 mm.times.350 mm was cut from
obtained film, and was subjected to moisture conditioning at
25.degree. C., 55% RH for 2 hours. The values were calculated via
extrapolation method from retardation values measured in
perpendicular direction and inclined direction at 480 nm, 500 nm
and 630 nm by an automatic birefringence meter (KOBRA 21DH,
manufactured by Oji Instrument Co., Ltd.)
TABLE-US-00006 TABLE 3 Dope composition Optical Sugar ester UV
Manufacture condition compensation Cellulose ester Polymer (a)
compound Plasticizer Absorber Stretch Film Stretch film No. Kind *1
Kind *1 Kind *1 Kind *1 (*) (*) magnification thickness temperature
101 B 100 -- -- AMP1 3.5 A 11.5 -- -- 1.4 40 150 102 B 90 C 10 AMP2
3.5 B 11.5 -- -- 1.4 40 150 103 B 80 C 20 AMP3 3.5 C 11.5 -- -- 1.4
40 150 104 B 70 C 30 AMP4 3.5 D 11.5 -- -- 1.3 40 150 105 B 60 C 40
AMP5 3.5 A 11.5 -- -- 1.3 40 150 106 B 100 -- -- AMP6 3.5 B 11.5 --
-- 1.6 60 171 107 B 100 -- -- AMP7 3.5 C 11.5 -- -- 1.5 60 160 108
B 100 -- -- AMP8 3.5 D 11.5 -- -- 1.5 50 150 109 B 100 -- -- AMP9
3.5 B 11.5 B (5.3) -- 1.2 40 140 110 B 90 A 10 AMP10 5.5 A 5.5 --
-- 1.4 40 155 111 B 80 A 20 AMP11 5.5 A 5.5 -- -- 1.4 40 160 112 B
70 A 30 AMP12 5.5 A 5.5 -- -- 1.4 40 165 113 B 60 A 40 AMP13 5.5 A
5.5 -- -- 1.4 40 170 114 F 100 -- -- AMP14 5.5 A 5.5 -- A (0.4) 1.4
40 180 B (0.7) C (0.6) 115 A 100 -- -- AMP15 3.5 A 11.5 -- -- 1.3
30 200 116 A 100 -- -- AMP16 3.5 B 11.5 -- -- 1.3 40 190 117 A 100
-- -- AMP17 3.5 C 11.5 -- -- 1.4 40 190 118 E 100 -- -- AMP18 5.2 C
5.5 -- A (0.4) 1.3 40 190 119 A 100 -- -- AMP19 5.5 D 11.5 -- --
1.4 40 190 120 A 100 -- -- AMP20 5.5 A 11.5 -- -- 1.4 40 190
Optical Propertied Optical Retardation compensation Ro Rt Ro(480)
Ro(630) Wave dispersion film No. (nm) (nm) (nm) (nm)
Ro(480)/Ro(630) Remarks 101 60 130 57 61 0.93 Invention 102 55 140
53 56 0.95 Invention 103 58 120 55 59 0.93 Invention 104 45 125 40
46 0.87 Invention 105 52 130 48 53 0.91 Invention 106 62 125 94 101
0.93 Invention 107 88 160 80 89 0.90 Invention 108 70 140 60 71
0.85 Invention 109 60 120 59 62 0.95 Invention 110 54 124 52 55
0.95 Invention 111 50 120 48 51 0.94 Invention 112 45 115 42 46
0.91 Invention 113 40 110 37 41 0.90 Invention 114 54 124 52 55
0.95 Invention 115 20 70 17 21 0.81 Invention 116 35 90 31 36 0.86
Invention 117 44 99 40 45 0.89 Invention 118 59 119 55 63 0.87
Invention 119 39 78 35 40 0.88 Invention 120 45 97 39 45 0.87
Invention *1: Parts by weight
TABLE-US-00007 TABLE 4 Dope composition Optical Sugar ester UV
Manufacture condition compensation Cellulose ester Polymer (a)
compound Plasticizer Absorber Stretch Film Stretch film No. Kind *1
Kind *1 Kind *1 Kind *1 (*) (*) magnification thickness temperature
121 A 100 -- -- AMP1 3.5 B 11.5 -- -- 1.4 40 200 122 A 100 -- --
AMP2 3.5 C 11.5 -- -- 1.2 40 200 123 A 100 -- -- AMP3 3.5 D 11.5 --
-- 1.3 40 200 124 A 100 -- -- AMP4 3.5 D 0.4 A (5.5) 1.4 40 180 125
C 100 -- -- AMP5 11.5 A 3.5 -- -- 1.1 40 175 126 C 100 -- -- AMP6
11.5 B 3.5 -- -- 1.4 40 175 127 C 100 -- -- AMP7 11.5 C 3.5 -- --
1.5 50 175 128 D 100 -- -- AMP8 4.9 B 0.9 A (5.5) -- 1.3 40 175 129
C 100 -- -- AMP9 11.5 D 3.5 -- -- 1.3 60 200 130 C 100 -- -- AMP10
11.5 A 3.5 -- -- 1.3 40 175 131 C 100 -- -- AMP11 11,5 B 3.5 -- --
1.2 40 175 132 C 100 -- -- AMP12 11.5 C 3.5 -- -- 1.4 60 175 133 C
100 -- -- AMP13 11.5 D 3.5 -- -- 1.4 60 175 134 C 100 -- -- AMP14
11.5 D 0.5 C (5.1) 1.5 60 160 201 A 100 -- -- -- -- -- -- A (5.5)
-- 1.4 40 175 202 A 100 -- -- -- -- A 11.0 -- -- 1.4 40 175 203 A
100 -- -- AMP1 25.0 -- 0.0 -- -- 1.4 50 175 Optical Propertied
Optical Retardation compensation Ro Rt Ro (480) Ro (630) Wave
dispersion film No. (nm) (nm) (nm) (nm) Ro(480)/Ro(630) Remarks 121
37 94 35 38 0.92 Invention 122 22 60 20 23 0.87 Invention 123 38 55
34 39 0.87 Invention 124 58 120 51 59 0.86 Invention 125 20 200 18
21 0.86 Invention 126 70 150 67 71 0.94 Invention 127 65 160 61 66
0.92 Invention 128 61 122 56 63 0.89 Invention 129 100 70 93 101
0.92 Invention 130 45 110 44 47 0.94 Invention 131 37 103 36 38
0.95 Invention 132 96 180 93 98 0.95 Invention 133 84 130 81 85
0.95 Invention 134 88 160 80 89 0.90 Invention 201 30 100 27 36
0.75 Comparative 202 45 110 37 46 0.80 Comparative 203 63 130 52 65
0.80 Comparative *1: Parts by weight
[0250] It is understood that the optical compensate films 101 to
134 according to this invention obtain desirable retardation and
are excellent in wave dispersion property in comparison with the
comparative films.
Example 2
Manufacturing Polarizing Plate
[0251] Polyvinyl alcohol film having thickness of 120 mm was
stretched mono-axially at 110.degree. C. with stretch magnification
of 5 times. This was immersed in aqueous solution containing 0.075
g of iodine and 5 g of potassium iodide in 100 g of water for 60
seconds, and then was immersed in aqueous solution containing 6 g
of potassium iodide and 7.5 g of boric acid in 100 g of water at
68.degree. C. A polarizing plate was obtained by water washing and
drying.
[0252] Next, polarizing plates were prepared in accordance with the
following steps 1 to 5, wherein the polarizing film and the optical
compensation films of the present invention 101 to 134 and
comparative samples 201 to 203 were adhered onto the front side and
a Konica Minolta TAC KC4UY (cellulose ester film manufactured by
Konica Minolta Opt. Corp.) was adhered on the back side.
[0253] Step 1: The optical compensation film was immersed for 90
seconds in 2 mol/L of sodium hydroxide solution at 60.degree. C.
and then washed and dried, and the optical compensation film
subjected to saponification on one side to be adhered to a
polarizing element was obtained.
[0254] Step 2: The polarizing film was immersed in a tank of
polyvinyl alcohol adhesive having a solid content of 2% by weight
for 1 to 2 seconds.
[0255] Step 3: Excess adhesive attached to the polarizing film in
Step 2 was gently wiped off and then the polarizing film was placed
on the cellulose ester film processed in Step 1.
[0256] Step 4: Each of the cellulose ester films 101 to 134 and 201
to 203 having the polarizing film stacked in Step 3 was adhered to
the cellulose ester axis on the back side at a pressure of 20 to 30
N/cm.sup.2 and a conveyance speed of approximately 2 m/minute.
[0257] Step 5: The samples in which each of the optical
compensation films 101 to 134 and 201 to 203, the polarizing film
and Konica Minolta TAC KC4UY were adhered in Step 4 were dried for
2 minutes in a dryer at 80.degree. C., and the polarizing plates
101 to 134 of the present invention and the comparative polarizing
plates 201 to 203 were prepared.
[0258] An amount of light leakage was measured for each of the
obtained polarizing plate. Results are shown in Table 5.
<<Evaluation of an Amount of Light Leakage>>
[0259] Two sheets of the prepared polarizing plates were arranged
in the state of cross Nicol, and the transmittance (T1) at 590 nm
was measured by the use of the spectrophotometer U3100 manufactured
by Hitachi, Ltd.
[0260] Further, after the two sheets of the polarizing plates were
processed on the condition of 80.degree. C. 90% RH for 100 hours,
the transmittance (12) when the two sheets of the prepared
polarizing plates were arranged in the state of cross Nicol as same
as the above was measured, a change of the transmittance before and
after the thermal treatment was investigated, and an amount of
light leakage was measured in accordance with the following
formula.
Amount (%) of light leakage=T2(%)-T1(%)
[0261] The amount of light leakage is preferably 0 to 13%, and more
preferably 1% or less.
<Production of a Liquid Crystal Display>
[0262] A liquid crystal panel for view field angle measurement was
produced as follows, and the characteristics as a liquid crystal
display was evaluated.
[0263] The polarizing plates preliminarily adhered on both sides of
a 40 type display KLV-40V1000 manufactured by SONY Corp. were
removed, and the polarizing plates 101 to 134, 201 to 203 which
prepared as mentioned above were adhered onto both sides of a glass
surface of a liquid crystal cell respectively. At this time, the
polarizing plates were adhered in such a direction that the plane
of the cellulose ester film of the present invention became the
liquid crystal cell side and the absorption axis was directed to
the same direction as the preliminarily adhered polarizing plate,
whereby the liquid crystal displays 101 to 134 of the present
invention and the comparative liquid crystal displays 201 to 203
were produced respectively.
[0264] These liquid crystal displays were evaluated in terms of
uneven color tone and front contrast. Results are shown in Table
5.
<<Evaluation of Uneven Color Tone>>
[0265] The uneven color tone was measured by use of a measuring
device (EZ-Contrast 160D manufactured by ELDIM) for each of the
liquid crystal displays produced as mentioned above as follows. The
maximum uneven color tone range (.DELTA.u'v') was compared in CIE
1976, UCS coordinate, the display was inclined 60.degree. from
normal direction and observed during rotating 360.degree..
<<Evaluation of Front Contrast>>
[0266] In the environment of 23.degree. C. 55% RH, after the
backlight of each of the liquid crystal displays was continuously
lighted for one week, the measurement was performed. EZ-Contrast
160D manufactured by ELDIM was used for the measurement in such a
way that the luminance from the normal line direction of the
display screen was measured on a white display mode and a black
display mode of the liquid crystal display, and the ratio between
the luminance values on the white display mode and the black
display mode was made as the front contrast.
[0267] Front contrast (luminance on the white display mode measured
from the normal line direction of the display device)/(luminance on
the black display mode measured from the normal line direction of
the display device)
TABLE-US-00008 TABLE 5 Optical compensation Light Liquid crystal
Uneven color Front film No. leakage display No. tone (.DELTA. u'v')
contrast Remarks 101 0.15 101 0.05 1270 Invention 102 0.25 102 0.07
1250 Invention 103 0.65 103 0.06 1220 Invention 104 0.85 104 0.07
1220 Invention 105 0.15 105 0.06 1230 Invention 106 0.15 106 0.04
1270 Invention 107 0.15 107 0.04 1240 Invention 108 0.25 108 0.05
1220 Invention 109 0.25 109 0.05 1210 Invention 110 0.25 110 0.05
1250 Invention 111 0.15 111 0.05 1250 Invention 112 0.25 112 0,05
1250 Invention 113 0.35 113 0.06 1250 Invention 114 0.35 114 0.07
1250 Invention 115 0.15 115 0.06 1200 Invention 116 0.65 116 0.06
1270 Invention 117 0.45 117 0.05 1250 Invention 118 0.45 118 0.05
1250 Invention 119 0.35 119 0.07 1240 Invention 120 0.45 120 0.06
1250 Invention 121 0.35 121 0.07 1230 Invention 122 0.55 122 0,06
1240 Invention 123 0.25 123 0.06 1250 Invention 124 0.45 124 0.07
1260 Invention 125 0.35 125 0.06 1270 Invention 126 0.45 126 0.06
1250 Invention 127 0.45 127 0.06 1230 Invention 128 0.15 128 0.04
1240 Invention 129 0.35 129 0.05 1260 Invention 130 0.45 130 0.06
1250 Invention 131 0.35 131 0.07 1230 Invention 132 0.25 132 0.05
1220 Invention 133 0.35 133 0.07 1220 Invention 134 0.45 134 0.08
1220 Invention 201 4.8 201 0.17 900 Comparative 202 4.5 202 0.15
950 Comparative 203 4.6 203 0.18 980 Comparative
[0268] It is apparent that the polarizing plates of this invention
101 to 134 are excellent in light leakage. It is also apparent that
the liquid crystal displays of this invention 101 to 134 are
excellent in uneven color tone and front contrast.
* * * * *