JP2003195042A - Polarizing sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing sheet with a high polarization degree. <P>SOLUTION: The polarizing sheet contains a dichroic dye having a substituent expressed by a general formula (a). In the formula, Het represents an oxygen atom, an NR-group or a sulfur atom and R represents a hydrogen atom, an alkyl group, an aryl group or a heteroaryl group. Each of B<SP>1</SP>represents a bivalent aryl, heteroaryl or cycloaliphatic hydrocarbon group. C<SP>1</SP>represents an alkyl group, a cycloalkyl group, an alkoxy group, an alkoxycarbonyl group or an acyloxy group, j represents 0 or 1, p represents an integer from 3 to 6 and three to six B<SP>1</SP>s may be mutually different. A general formula (a): -(Het)<SB>j</SB>-(B<SP>1</SP>)<SB>p</SB>-C<SP>1</SP>. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a dye-type polarizing sheet utilizing the dichroism of a dye.

[0002]

2. Description of the Related Art Conventionally, an iodine type polarizing sheet showing a high degree of polarization has been generally used as a polarizing sheet.
This iodine type polarizing sheet has a structure in which a polynuclear complex of iodine is adsorbed on a stretched polyvinyl alcohol. However, since the polynuclear complex of iodine has low thermal stability, when the iodine type polarizing sheet is attached to a liquid crystal display for use, the durability is insufficient when the liquid crystal display is used in a place with severe environmental conditions. There is a problem that becomes.
On the other hand, the dye-type polarizing sheet dyed with a dichroic dye has excellent durability as compared with the iodine-type polarizing sheet,
In recent years, the demand has been increasing more and more. For example, a dye-type polarizing sheet is described in JP-A-58-68008. Further, as a dye-type polarizing sheet using a dye having a high dichroic ratio, an example of an azo dye is disclosed in JP-A-2-
No. 89008, No. 2-96102, No. 5-3
No. 20530, No. 6-128498, No. 7-
No. 49475, No. 8-73762, and No. 9-2.
No. 30142, No. 10-259311, and examples of anthraquinone dyes are disclosed in JP-A-61-285259, 62-296101, and 63-6400.
JP-A-61-2 is an example of a dioxazine-based dye.
It is described in Japanese Patent No. 75703. However, the dye-type polarizing sheet dyed with a dichroic dye still has a low dichroic ratio of the dye, and its improvement has been desired.

[0003]

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a polarizing sheet containing a dichroic dye having a high dichroic ratio and giving a high degree of polarization. And

[0004]

In order to solve the above-mentioned problems, the polarizing sheet of the present invention is characterized by containing at least one dichroic dye having a substituent represented by the following general formula (a). And Formula _{(a) - (Het) j} - in (B ¹⁾ _p -C ¹ formula, Het represents an oxygen atom, NR- or a sulfur atom, R represents a hydrogen atom, an alkyl group, an aryl group or a heteroaryl group Represent B ¹ represents a divalent aryl group, a heteroaryl group or a cycloaliphatic hydrocarbon group, and C 1
¹ represents an alkyl group, a cycloalkyl group, an alkoxy group, an alkoxycarbonyl group or an acyloxy group, and j
Represents 0 or 1, p represents an integer of 3 to 6, and B ¹ of 3 to 6 may be the same or different.

As a preferred embodiment of the present invention, there is provided the above polarizing sheet, wherein the dichroic dye is a compound represented by the following general formula (1).

General formula (1)

[Chemical 2]

In the formula, Het, B ¹ , C ¹ , j and p have the same meanings as in formula (a),
R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ each independently represent a hydrogen atom or a substituent.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. In addition, in this specification, "-" shows the range which includes the numerical value described before and after that as a minimum value and a maximum value, respectively.

The present invention is a polarizing sheet exhibiting dichroism by containing at least one dichroic dye. First, the dichroic dye used in the present invention will be described. The dichroic dye used in the present invention may be a dye having any chromophore, for example, azo dye, anthraquinone dye, perylene dye, merocyanine dye, azomethine dye, phthaloperylene dye, indigo dye, azulene dye, Examples thereof include dioxazine dyes and polythiophene dyes. Specifically, “Dichr
oic Dyes for Liquid Cryst
al Display ”(A.V. Ivashc
Henko, CRC, 1994). Among them, azo dyes, anthraquinone dyes or perylene dyes are preferable, and anthraquinone dyes are particularly preferable.

Azo dyes are monoazo dyes, bisazo dyes,
Any of trisazo dyes, tetrakisazo dyes, pentakisazo dyes and the like may be used, but monoazo dyes, bisazo dyes and trisazo dyes are preferable. The ring structure contained in the azo dye includes aromatic rings (benzene ring, naphthalene ring, etc.), as well as heterocycles (quinoline ring, pyridine ring, thiazole ring, benzothiazole ring, oxazole ring, benzoxazole ring, imidazole ring, benzo ring). Imidazole ring, pyrimidine ring, etc.).

The substituent of the anthraquinone dye is preferably one containing an oxygen atom, a sulfur atom or a nitrogen atom, and for example, an anthraquinone dye containing an alkoxy, aryloxy, alkylthio, arylthio, alkylamino or arylamino group is preferable. The number of substitutions of these substituents may be any number, but di-substitution, tri-substitution and tetrakis-substitution are preferable, and di-substitution and tri-substitution are particularly preferable. The substitution position of the substituent is not particularly limited, but preferably 1,4-disubstituted, 1,5
Position di substitution, 1,4,5 position tri substitution, 1,2,4 position tri substitution, 1,2,5 position tri substitution, 1,2,4,5 position tetra substitution, 1,2,5,6 position It is a tetra-substituted structure.

The dichroic dye used in the present invention has a substituent represented by the following general formula (a). Formula _{(a) - (Het) j} - (B 1) k -C 1

In the above formula, B ¹ represents a divalent aryl group, heteroaryl group or cycloaliphatic hydrocarbon group. The divalent aryl group is preferably an aryl group having 2 to 20 carbon atoms. Specifically, an aryl group consisting of a benzene ring, a naphthalene ring and an anthracene ring is preferable, an aryl group consisting of a benzene ring and a substituted benzene ring is more preferable, and a 1,4-phenylene group is particularly preferable. 2 above
As the valent heteroaryl group, a heteroaryl group having 1 to 20 carbon atoms is preferable. Specifically, it comprises a pyridine ring, quinoline ring, isoquinoline ring, pyrimidine ring, pyrazine ring, thiophene ring, furan ring, oxazole ring, thiazole ring, imidazole ring, pyrazole ring, oxadiazole ring, thiadiazole ring, triazole ring. A heteroaryl group and a heteroaryl group consisting of a condensed ring formed by condensation of these are preferable. The divalent cyclic hydrocarbon group is preferably a cyclohexane-1,2-diyl group, a cyclohexane-1,3-diyl group, a cyclohexane-1,4-diyl group, a cyclopentane-1,3-diyl group, Particularly preferred is (E) -cyclohexane-1,4-diyl group.

B ¹ may further have a substituent, and examples of the substituent include the following substituent group V. Substituent group V: halogen atom (for example, chlorine, bromine, iodine,
Fluorine); mercapto group; cyano group; carboxyl group;
Phosphoric acid group; sulfo group; hydroxy group; carbon number 1-10,
Preferably, it has 2 to 8 carbon atoms, more preferably 2 to 5 carbon atoms
A carbamoyl group (for example, a methylcarbamoyl group, an ethylcarbamoyl group, a morpholinocarbamoyl group); a sulfamoyl group having 0 to 10 carbon atoms, preferably 2 to 8 carbon atoms, and more preferably 2 to 5 carbon atoms (eg, methylsulfamoyl group). , An ethylsulfamoyl group, a piperidinosulfamoyl group); a nitro group; an alkoxy group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, and more preferably 1 to 8 carbon atoms (eg, methoxy group, ethoxy group). , 2-methoxyethoxy group, 2-phenylethoxy group); carbon number 6 to
20, preferably an aryloxy group having 6 to 12 carbon atoms, more preferably 6 to 10 carbon atoms (for example, a phenoxy group,
p-methylphenoxy group, p-chlorophenoxy group, naphthoxy group); carbon number 1-20, preferably carbon number 2
12, more preferably an acyl group having 2 to 8 carbon atoms (eg acetyl group, benzoyl group, trichloroacetyl group);
An acyloxy group having 1 to 20 carbon atoms, preferably 2 to 12 carbon atoms, more preferably 2 to 8 carbon atoms (for example, acetyloxy group, benzoyloxy group); 1 to 20 carbon atoms, preferably 2 to 12 carbon atoms, More preferably, it has 2 to 8 carbon atoms.
An acylamino group (for example, acetylamino group); a sulfonyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, and more preferably 1 to 8 carbon atoms (for example, methanesulfonyl group, ethanesulfonyl group, benzenesulfonyl group); 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms sulfinyl group (for example, methanesulfinyl group, ethanesulfinyl group, benzenesulfinyl group); 1 to 20 carbon atoms, preferably carbon number 1-1
0, more preferably a sulfonylamino group having 1 to 8 carbon atoms (eg, methanesulfonylamino group, ethanesulfonylamino group, benzenesulfonylamino group);

0 to 20 carbon atoms, preferably 0 to 1 carbon atoms
2, more preferably a substituted or unsubstituted amino group having 0 to 8 carbon atoms (for example, an unsubstituted amino group, dimethylamino group, benzylamino group, anilino group, diphenylamino group, 4-methylphenylamino group, 4 -Ethylphenylamino group, 3-n-propylphenylamino group, 4-
n-propylphenylamino group, 3-n-butylphenylamino group, 4-n-butylphenylamino group, 3-n
-Pentylphenylamino group, 4-n-pentylphenylamino group, 3-trifluoromethylphenylamino group, 4-trifluoromethylphenylamino group, 2-pyridylamino group, 3-pyridylamino group, 2-thiazolylamino group, 2- (Oxazolylamino group, N, N-methylphenylamino group, N, N-ethylphenylamino group); C0-15, preferably C3-10, more preferably C3-6 ammonium group. (For example, trimethylammonium group, triethylammonium group); C0-15, preferably C1-10, more preferably C1-6 hydrazino (e.g. trimethylhydrazino); C1-15, A ureido group having preferably 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms (for example, ureido group, N N-dimethylureido group); C1 to C15, preferably C1 to C10, more preferably C1 to C6 imide group (eg succinimide group); C1 to C20, preferably C1 to C1 1
2, more preferably an alkylthio group having 1 to 8 carbon atoms (eg, methylthio group, ethylthio group, propylthio group);
Arylthio groups having 6 to 80 carbon atoms, preferably 6 to 40 carbon atoms, and more preferably 6 to 30 carbon atoms (for example, phenylthio group, p-methylphenylthio group, p-chlorophenylthio group, 2-pyridylthio group, 1- Naphthylthio group, 2-naphthylthio group, 4-propylcyclohexyl-4'-biphenylthio group, 4-butylcyclohexyl-4'-biphenylthio group, 4-pentylcyclohexyl-4'-biphenylthio group, 4-propylphenyl-
2-ethynyl-4′-biphenylthio group);
80, preferably 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms heteroarylthio group (for example, 2-pyridylthio group, 3-pyridylthio group, 4-pyridylthio group,
2-quinolylthio group, 2-furylthio group, 2-pyrrolylthio group);

C2-20, preferably C2-1
2, more preferably an alkoxycarbonyl group having 2 to 8 carbon atoms (eg, methoxycarbonyl group, ethoxycarbonyl group, 2-benzyloxycarbonyl group); 6 to carbon atoms
20, preferably 6 to 12 carbon atoms, more preferably 6 to 10 carbon atoms aryloxycarbonyl group (for example, phenoxycarbonyl group); 1 to 18 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 carbon atoms. 5 to 5 unsubstituted alkyl groups (for example, methyl group, ethyl group, propyl group, butyl group); C1 to C18, preferably C1 to C1
0, more preferably a substituted alkyl group having 1 to 5 carbon atoms (for example, a hydroxymethyl group, a trifluoromethyl group, a benzyl group, a carboxyethyl group, an ethoxycarbonylmethyl group, an acetylaminomethyl group, and a carbon number of 2 here.
To 18, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms, unsaturated hydrocarbon groups (eg vinyl group, ethynyl group 1-cyclohexenyl group, benzylidine group, benzylidene group) are also included in the substituted alkyl group. A substituted or unsubstituted aryl group having 6 to 20 carbon atoms, preferably 6 to 15 carbon atoms, and more preferably 6 to 10 carbon atoms (eg, phenyl group, naphthyl group, p-carboxyphenyl group, p-nitrophenyl group, 3,5-dichlorophenyl group, p-cyanophenyl group, m-fluorophenyl group, p-tolyl group, 4-propylcyclohexyl-4'-biphenyl, 4-butylcyclohexyl-
4'-biphenyl, 4-pentylcyclohexyl-4 '
-Biphenyl, 4-propylphenyl-2-ethynyl-
4′-biphenyl); a substituted or unsubstituted heterocyclic group having 1 to 20 carbon atoms, preferably 2 to 10 carbon atoms, and more preferably 4 to 6 carbon atoms (eg pyridyl group, 5-methylpyridyl group, thienyl group) , A furyl group, a morpholino group, and a tetrahydrofurfuryl group). These substituent groups V can have a structure in which a benzene ring or a naphthalene ring is condensed. Further, any of the substituents selected from the substituent group V may be further substituted on these substituents.

Among the substituent groups V, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a halogen atom, an amino group, a substituted amino group, a hydroxy group, an alkylthio group and an arylthio group are preferable, and an alkyl group, an aryl group, A halogen atom is more preferred.

In the above formula, C ¹ represents an alkyl group, a cycloalkyl group, an alkoxy group, an alkoxycarbonyl group, an acyl group or an acyloxy group. Preferably C
¹ has 1 to 30 carbon atoms, more preferably 1 to 1 carbon atoms
2, more preferably an alkyl group or cycloalkyl group having 1 to 8 carbon atoms (for example, methyl group, ethyl group, propyl group, butyl group, tert-butyl group, i-butyl group, s-butyl group, pentyl group, tert-pentyl group, hexyl group, heptyl group, octyl group, cyclohexyl group, 4-methylcyclohexyl group, 4-ethylcyclohexyl group, 4-propylcyclohexyl group, 4-butylcyclohexyl group, 4-pentylcyclohexyl group, hydroxymethyl group , Trifluoromethyl group, benzyl group); carbon number 1 to 20, more preferably carbon number 1 to
10, more preferably an alkoxy group having 1 to 8 carbon atoms (eg, methoxy group, ethoxy group, 2-methoxyethoxy group, 2-phenylethoxy group); 1 to 20 carbon atoms,
More preferred is an acyloxy group having 2 to 12 carbon atoms, more preferably 2 to 8 carbon atoms (eg, acetyloxy group, benzoyloxy group); 1 to 30 carbon atoms, more preferably 1 to 12 carbon atoms, and further preferably 1 to 8 carbon atoms
(For example, an acetyl group, a formyl group, a pivaloyl group, a 2-chloroacetyl group, a stearoyl group, a benzoyl group, a pn-octyloxyphenylcarbonyl group); a carbon number of 2 to 20, preferably a carbon number of 2 12, more preferably an alkoxycarbonyl group having 2 to 8 carbon atoms (eg, methoxycarbonyl group, ethoxycarbonyl group, 2-benzyloxycarbonyl group); C ¹
Is particularly preferably an alkyl group or an alkoxy group, and further preferably an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group or a trifluoromethoxy group. C ¹ may further have a substituent, and examples of the substituent include the above-mentioned substituent group V.

In the above formula, Het represents an oxygen atom, NR- or a sulfur atom. It is preferably a sulfur atom. In the above formula, R represents a hydrogen atom, an alkyl group, an aryl group or a heteroaryl group. Specific examples of the alkyl group, aryl group, and heteroaryl group include the same as the specific examples of the above-mentioned substituent group V. R is preferably a hydrogen atom.

In the above formula, j represents 0 or 1, preferably 1. p represents an integer of any of 3 to 6, preferably 3 or 4, and particularly preferably 3.
In the above formula, B ¹ contained in 3 to 6 may be different or the same.

The substituent represented by the general formula (a),-(Het) _j- (B ¹ ) _p -C ¹ preferably contains a partial structure exhibiting liquid crystallinity. The liquid crystal referred to here may be in any phase, but is preferably a nematic liquid crystal, a smectic liquid crystal or a discotic liquid crystal, and particularly preferably a nematic liquid crystal. Specific examples of the liquid crystal compound include those described in Liquid Crystal Handbook Editorial Committee, edited by Liquid Crystal Handbook, Maruzen, 2000, Chapter 3, "Molecular Structure and Liquid Crystallinity".

Specific examples of-(B ¹ ) _p -C ¹ which is the partial structure of the general formula (a) will be shown below, but the present invention is not limited thereto (in the figure, a wavy line). Represents the position of connection with Het).

[0023]

[Chemical 3]

[0024]

[Chemical 4]

The number of substituents represented by the general formula (a) contained in the dichroic dye used in the present invention is not particularly limited, but is usually 1 to 8 and preferably 1 to 4
More preferably, 1 or 2 is particularly preferable.

Preferred examples of the dichroic dye used in the present invention include anthraquinone compounds represented by the following general formula (1).

[0027]

[Chemical 5]

In the formula, Het, B ¹ , C ¹ , j and p have the same meanings as in formula (a), and the preferred ranges are also the same.

In the formula, R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ each independently represent a hydrogen atom or a substituent.
Examples of the substituent include the above-mentioned substituent group V. Preferably, R ^{1 to} R ⁷ each have 6 to 80 carbon atoms, more preferably 6 to 40 carbon atoms, and further preferably 6 carbon atoms.
~ 30 arylthio groups (eg phenylthio group, p-
Methylphenylthio group, p-chlorophenylthio group, 4
-Methylphenylthio group, 4-ethylphenylthio group,
4-n-propylphenylthio group, 2-n-butylphenylthio group, 3-n-butylphenylthio group, 4-n-
Butylphenylthio group, 2-tert-butylphenylthio group, 3-tert-butylphenylthio group, 4-t
ert-butylphenylthio group, 3-n-pentylphenylthio group, 4-n-pentylphenylthio group, 4-amylpentylphenylthio group, 4-hexylphenylthio group, 4-heptylphenylthio group, 4-octyl Phenylthio group, 4-trifluoromethylphenylthio group,
3-trifluoromethylphenylthio group, 2-pyridylthio group, 1-naphthylthio group, 2-naphthylthio group, 4
-Propylcyclohexyl-4'-biphenylthio group,
4-butylcyclohexyl-4'-biphenylthio group,
4-pentylcyclohexyl-4'-biphenylthio group, 4-propylphenyl-2-ethynyl-4'-biphenylthio group); C1-80, more preferably C1-40, still more preferably C1. To 30 heteroarylthio groups (for example, 2-pyridylthio group, 3-pyridylthio group, 4-pyridylthio group, 2-quinolylthio group, 2-furylthio group, 2-pyrrolylthio group); substituted or unsubstituted amino group (for example, , Methylamino group, dimethylamino group, benzylamino group, anilino group, diphenylamino group, 4-methylphenylamino group, 4-ethylphenylamino group, 3-n-propylphenylamino group, 4-n-propylphenylamino group Group, 3-n-butylphenylamino group, 4-n-butylphenylamino group, 3-n-pentyl Eniruamino group, 4-n-pentylphenyl group, 3-trifluoromethylphenyl group, 4-trifluoromethylphenyl group, 2-pyridylamino, 3-pyridylamino group, 2
-Thiazolylamino group, 2-oxazolylamino group,
N, N-methylphenylamino group, N, N-ethylphenylamino group); hydroxy group; halogen atom; aryl group; heteroaryl group. If possible, these substituents may be further substituted with any of the above-mentioned substituent group V.

Specific examples of the compound represented by the general formula (1) are shown below, but the invention is not limited to the following specific examples.

[0031]

[Chemical 6]

[0032]

[Chemical 7]

[0033]

[Chemical 8]

The compounds of the present invention are "Dichroic"
Dyes for Liquid Crystal Di
spray "(A. V. Ivashchenko
, CRC Co., 1994), “Review Synthetic Dyes” (Horiguchi Hiroshi, Sankyo Publishing, 1968) and the methods described in the literatures cited therein can be used for the synthesis.

The polarizing sheet of the present invention has the above general formula (a).
It suffices to contain at least one dichroic dye having a substituent represented by (preferably the compound represented by the general formula (1)), and two or more dichroic dyes may be used in combination. . Furthermore, when using two or more dichroic dyes,
You may use the dichroic dye which does not contain the substituent represented by the said General formula (a) with the said dichroic dye.

In one embodiment of the present invention, the above general formula (a) is used.
A polarizing sheet having a film containing a dichroic dye having a substituent represented by and a support for protecting the film. In the present embodiment, the film material is preferably polyvinyl alcohol (PVA). PVA
Is usually saponified polyvinyl acetate,
For example, it may contain a component copolymerizable with vinyl acetate such as unsaturated carboxylic acid, unsaturated sulfonic acid, olefins and vinyl ethers. Further, a modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group or the like can also be used. PV
The saponification degree of A is not particularly limited, but solubility, polarization,
From the viewpoint of heat resistance, moisture resistance, etc., 80 to 100 mol% is preferable, and 90 to 100 mol% is particularly preferable. Also PV
The degree of polymerization of A is not particularly limited, but 1000 to 10000 is preferable, and 1500 to 5000 is particularly preferable, from the viewpoint of film strength, heat resistance, moisture resistance, stretchability and the like. Also, P
The syndiotacticity of VA is not particularly limited and can be any value depending on the purpose.

The polarizing sheet of the present invention may be produced by any method, and a dichroic dye is vapor-deposited on the raw film before stretching or on the stretched film after stretching, or a solution of the dichroic dye. Can be manufactured by dyeing a dichroic dye by a method such as coating. For more information,
142nd Committee, Japan Society for the Promotion of Science, Liquid Crystal Device Handbook, Nikkan Kogyo Shimbun, 1989, Chapter 4, 26
3 to 272. Specifically, a raw film (for example, PVA film) is stretched in a dry or wet manner and then immersed in a solution of a dichroic dye; a raw film (for example, PVA) in a solution of the dichroic dye. A method of stretching and orienting a film); a method of dipping a raw film (for example, a PVA film) in a solution of a dichroic dye, and then stretching by a wet or dry method for orientation. Moreover, when forming a raw material into a film by a solution film forming method, a method of previously containing a dichroic dye in a polymer (for example, PVA) solution can be used.

A typical method for producing a polarizing sheet having a PVA stretched film by wet stretching will be described below. First, the original fabric PVA film is pre-swelled with an aqueous solution. Various organic solvents, inorganic salts, plasticizers, boric acids and the like may be added to the aqueous solution of the preliminary swelling liquid. Then, the original PVA film is immersed in a dichroic dye solution to adsorb the dichroic dye. The dyeing time is preferably 30 to 5000 seconds, and the liquid temperature is preferably 5 to 50 ° C. It is also preferable to add a compound that crosslinks PVA, such as a boron compound, to the dyeing solution. Next, the dyed PVA original film is uniaxially stretched in the traveling direction in an aqueous solution of a boron compound. Boric acid is particularly preferable as the boron compound used in the stretching bath. The boric acid concentration in the stretching bath is preferably 1 to 20.
0 g / L, more preferably 10-120 g / L
Is. In addition to the boron compound, the stretching bath may contain an inorganic salt such as potassium iodide, various organic solvents, or a dichroic dye. Then, if necessary, the obtained PVA stretched film may be immersed in a tint adjusting bath, a curing bath or the like. In addition to the dichroic dye, an inorganic salt such as potassium iodide, a boron compound and the like can be contained in the color adjusting bath and the curing bath, if necessary. When the stretched PVA film has dried to some extent, a protective film is attached using an adhesive such as PVA, and further dried to obtain a polarizing sheet.

As a stretching process of a raw film (for example, a PVA film), a method is generally used in which a tension is applied in the advancing direction of a continuous film so that the film is stretched and oriented in the advancing direction. A method of applying tension in the width direction of the film by a stretching means such as a so-called tenter system to orient the film in the width direction is also applicable. Stretching is preferably performed 3 times or more in the uniaxial direction, and more preferably 4.5 times or more. Biaxial stretching may be performed depending on the purpose of use of the polarizing film. The film thickness after stretching is not particularly limited,
From the viewpoint of handleability, durability and economy, 5-100μ
m is preferable, and 10 to 40 μm is more preferable. The temperature during stretching varies depending on the stretching conditions, but is usually 10 to 250.
℃. When performing dry stretching at a temperature of 100 ° C or higher,
It is preferably performed in an atmosphere of an inert gas such as nitrogen. Also, before dyeing a pre-stretched film,
It is preferable to perform the crystallization treatment at the above temperature.

As the dyeing method, not only the dipping method exemplified above, but also any means such as coating or spraying with a dye solution is possible. Further, not only the liquid layer adsorption described above, but also the adsorption in the gas phase can be performed as necessary.

A support as a protective film can be attached to the stretched film having the dichroic dye adsorbed thereon. The material for the support is not particularly limited, but it is preferable to use a polymer film which is transparent and has small optical anisotropy. In addition, that the support is transparent means that the light transmittance is 80% or more. Regarding the magnitude of optical anisotropy, the in-plane retardation (Re) can be used as an index, and the smaller Re is, the smaller the optical anisotropy is. Re of the support is preferably 20 nm or less, more preferably 10 nm or less, and most preferably 5 nm or less. Further, the retardation (Rth) in the thickness direction is preferably 100 nm or less, more preferably 50 nm or less, and most preferably 30 nm or less.
The in-plane retardation (Re) and the thickness direction retardation (Rth) are defined by the following formulas, respectively. Re = (nx−ny) × d Rth = [{(nx + ny) / 2} −nz] × d where nx and ny are in-plane refractive indices of the support,
nz is the refractive index in the thickness direction of the support, and d is the thickness of the support.

The polymer used for the material of the support is cellulose ester, polycarbonate, polysulfone, polyether sulfone, polyacrylate,
Included are polymethacrylate, polyethylene, polyethylene terephthalate and polyvinyl alcohol (PVA).

The thickness of the support is preferably 20 to 500 μm, more preferably 50 to 200 μm. In order to improve the adhesion between the support and the layer provided thereon, the support is subjected to a surface treatment (eg glow discharge treatment,
Corona discharge treatment, ultraviolet (UV) treatment, flame treatment) may be performed. An adhesive layer (undercoat layer) may be provided on the support.

In the present embodiment, the form of the polarizing sheet provided with the support as the protective film is shown, but the support may be omitted, that is, the film itself containing the dichroic dye may be used as the polarizing sheet. You may use as. Further, the film may be used as a polarizing sheet for a liquid crystal display device or the like, and other members may function as a protective film for the polarizing sheet.

The polarizing sheet of the present invention can be applied to a liquid crystal display device. The polarizing sheet of the present invention can be used in both transmissive and reflective liquid crystal display devices as long as it controls light transmission. Specifically, it can be applied to various driving methods described in Chapter 142, Liquid Crystal Device Handbook, Nikkan Kogyo Shimbun, edited by Japan Society for the Promotion of Science, 142nd Committee.

The polarizing ability of the polarizing sheet is represented by the degree of polarization ρ, and is defined by the following formula (I) using the transmittances Y ¹ and Y ² . (I) ρ (%) = {(Y ¹ −Y ² ) / (Y ¹ + Y ² )} ^1/2 × 100 In the above formula, the parallel transmittance Y ¹ is the same as the polarization axes of the polarizing sheet in the same direction. The orthogonal transmittance Y ² represents the transmittance when the two sheets are stacked, and the orthogonal transmittance Y ² represents the transmittance when the two sheets are stacked with the polarization axes of the polarizing sheets perpendicular to each other.

[0047]

EXAMPLES The present invention will be described in more detail with reference to the following examples. The materials, reagents, substance amounts and ratios, operations, etc. shown in the following examples can be appropriately changed without departing from the gist of the present invention. Therefore, the scope of the present invention is not limited to the following specific examples. . Example 1 A PVA film (75 μm) was prepared by using 1.0 g / L of the dichroic dye shown in Table 1 and potassium iodide 6
Immerse in 0.0 g / L aqueous solution (25 ° C.) for 10 minutes, and further in boric acid 80 g / L, potassium iodide 30 g / L, and ferrous chloride 10 g / L aqueous solution (50 ° C.),
It was stretched 5.0 times. After drying at 60 ℃ for 5 minutes, PV
A 4% aqueous solution of A (PVA-117H manufactured by Kuraray Co., Ltd.) was used as an adhesive, and a cellulose (acetate) film was attached on both sides, and further dried at 80 ° C. to obtain a polarizing sheet. The polarization degree ρ of this polarizing sheet is shown in Table 1. The degree of polarization ρ
Was calculated by the above formula (I).

[0048]

[Table 1]

[0049]

[Chemical 9]

From Table 1, it was found that the polarizing sheet of the present invention gives a higher degree of polarization than when the conventional dichroic dye is used.

[0051]

As described above, according to the present invention, a polarizing sheet having a high degree of polarization and excellent light stability can be provided.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H049 BA02 BA26 BA28 BA37 BB33                       BB43 BC03 BC22                 2H091 FA08 FB02 LA30                 4H056 AA01 AB03 AB05 AC01 AD13B                       AD19B AD28B

Claims (2)

[Claims] 1. A compound having a substituent represented by the following general formula (a):
A polarizing sheet containing at least one dichroic dye. General formula (a) -(Het)_j-(B¹)_p-C¹ (In the formula, Het represents an oxygen atom, NR- or a sulfur atom.
R is a hydrogen atom, an alkyl group, an aryl group or
Represents a lower aryl group. B¹Is a divalent aryl group, hetero
Represents an aryl group or a cycloaliphatic hydrocarbon group, and C¹Is
Alkyl group, cycloalkyl group, alkoxy group, alcohol
Represents a oxycarbonyl group or an acyloxy group, and j is 0
Or 1 represents, p represents an integer of 3 to 6,
B of 3-6 ¹Are the same, but different
Good. ) 2. The polarizing sheet according to claim 1, wherein the dichroic dye is a compound represented by the following general formula (1). General formula (1) (In the formula, Het, B ¹ , C ¹ , j, and p have the same meanings as those in the general formula (a), and R ¹ , R ² ,
R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ each independently represent a hydrogen atom or a substituent. )