阅读说明：本技术 偏光膜形成用组合物、偏光膜、偏光板及其制造方法 (Composition for forming polarizing film, polarizing plate, and method for producing same ) 是由 幡中伸行 太田阳介 村野耕太 德田真芳 于 2019-01-29 设计创作，主要内容包括：一种偏光膜形成用组合物,其包含呈现近晶型液晶性的聚合性液晶化合物、二色性色素、及至少2种以上有机溶剂,前述有机溶剂包含有机溶剂A和有机溶剂B,所述有机溶剂A具有比前述聚合性液晶化合物的各向同性相转变温度高-20℃以上且50℃以下的沸点,所述有机溶剂B具有比前述聚合性液晶化合物的各向同性相转变温度高超过50℃的沸点。(A composition for forming a polarizing film, comprising a polymerizable liquid crystal compound exhibiting smectic liquid crystallinity, a dichroic dye, and at least 2 or more organic solvents, wherein the organic solvent comprises an organic solvent A and an organic solvent B, the organic solvent A has a boiling point higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by-20 ℃ to 50 ℃, and the organic solvent B has a boiling point higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by more than 50 ℃.)

1. A composition for forming a polarizing film, comprising a polymerizable liquid crystal compound exhibiting smectic liquid crystallinity, a dichroic dye, and at least 2 kinds of organic solvents, wherein the organic solvents comprise an organic solvent A and an organic solvent B, the organic solvent A has a boiling point higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by-20 ℃ to 50 ℃, and the organic solvent B has a boiling point higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by more than 50 ℃.

2. The composition for forming a polarizing film according to claim 1, wherein the content of the organic solvent A is 51 to 99 parts by mass and the content of the organic solvent B is 1 to 49 parts by mass with respect to 100 parts by mass of all the organic solvents contained in the composition for forming a polarizing film.

3. The composition for forming a polarizing film according to claim 1 or 2, wherein the boiling point of the organic solvent a is higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by 0 ℃ to 50 ℃, and the boiling point of the organic solvent B is higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by more than 50 ℃ to 150 ℃.

4. The polarizing film-forming composition according to any one of claims 1 to 3, further comprising a polymerization initiator.

5. The polarizing film forming composition according to any one of claims 1 to 4, wherein the organic solvent A is a ketone solvent or an aromatic solvent.

6. The polarizing film-forming composition according to any one of claims 1 to 5, wherein the organic solvent B is selected from the group consisting of glycol solvents, ketone solvents, and amide solvents.

7. The polarizing film-forming composition according to any one of claims 1 to 6, wherein the solid content of the polarizing film-forming composition is 5 to 40% by mass.

8. The composition for forming a polarizing film according to claim 7, wherein the proportion of the polymerizable liquid crystal compound in the solid content is 40 to 99.9% by mass.

9. The composition for forming a polarizing film according to claim 7 or 8, wherein the dichroic dye is contained in the solid component in an amount of 1 to 20% by mass.

10. A polarizing film which is a cured product of the polarizing film-forming composition according to any one of claims 1 to 9, wherein the polymerizable liquid crystal compound and/or the polymer thereof is oriented in a smectic liquid crystal state.

11. The polarizing film of claim 10 wherein a bragg peak is obtained in an X-ray diffraction measurement.

12. A polarizing plate comprising the polarizing film according to claim 10 or 11, a substrate, and an oriented film.

13. The method for manufacturing the polarizing plate comprises the following steps:

forming a coating film of the polarizing film-forming composition according to any one of claims 1 to 9;

heating and drying the coating film to a temperature not lower than the isotropic phase transition temperature of the polymerizable liquid crystal compound contained in the composition for forming a polarizing film, and then cooling the coating film to convert the polymerizable liquid crystal compound into a smectic liquid crystal phase; and

the polarizing film is formed by polymerizing the polymerizable liquid crystal compound while maintaining the smectic liquid crystal phase.

14. The method for manufacturing a polarizing plate according to claim 13, wherein a coating film of the composition for forming a polarizing film is formed on the photo-alignment film,

the photo-alignment film is formed using a method including the steps of,

forming a coating film from a composition containing a polymer or monomer capable of generating an orientation restriction force by light and a solvent;

drying and removing the solvent from the coating film to obtain a dried coating film; and

irradiating the dried coating film with polarized ultraviolet rays.

Technical Field

The invention relates to a composition for forming a polarizing film, a polarizing plate and a method for manufacturing the same.

Background

In a Flat Panel Display (FPD), a polarizing plate has been conventionally used in a state of being bonded to an image display element such as a liquid crystal cell or an organic EL display element. As such a polarizing plate, a polarizing plate having the following structure is widely used: a protective layer such as a triacetyl cellulose film is laminated on at least one surface of a polarizer obtained by adsorbing a compound exhibiting dichroism such as iodine or a dichroic dye to a polyvinyl alcohol resin film and aligning the compound with the polyvinyl alcohol resin film, with an adhesive layer interposed therebetween.

In recent years, with the demand for reduction in thickness of flat panel display devices, further reduction in thickness has been demanded for polarizing plates and polarizing films, which are one of the components thereof, and various polarizing plates and polarizing films have been proposed for such a demand. For example, patent document 1 discloses a polarizer including a polymer formed of a polymerizable liquid crystal compound exhibiting a smectic liquid crystal phase and a dichroic dye. Patent document 2 discloses a polymerizable liquid crystal composition in which a polymerizable liquid crystal compound exhibiting a smectic phase and a dichroic dye are dissolved in a solvent, and a polarizing film is formed by a wet coating method. Patent document 3 discloses a thin polarizing film that contains a plurality of dichroic dyes and a polymerizable liquid crystal compound exhibiting a smectic liquid crystal phase and exhibits polarizing performance over the entire visible light range.

Disclosure of Invention

Problems to be solved by the invention

The polarizing plate and the polarizing film (polarizer) disclosed in the above patent documents are generally produced by the following steps: a composition for forming a polarizing film, which contains a polymerizable liquid crystal compound, a dichroic dye, and a solvent, is applied to a film such as a base film to form a coating film, and the coating film is heated and dried to change the phase of the polymerizable liquid crystal compound into a liquid crystal state. The inventors of the present application have found that, in the above-mentioned step, when the solvent is volatilized from the coating film before the polymerizable liquid crystal compound is changed to the liquid crystal state, the polymerizable liquid crystal compound is likely to precipitate as fine crystals. When such microcrystals are precipitated, it is difficult to obtain a good mixed encapsulated state of the polymerizable liquid crystal compound and the dichroic dye even if subsequent heat drying is performed, and this causes a leak or an alignment defect in the obtained polarizing film. Such crystallization of the fine crystals is considered to be caused by the fact that smectic liquid crystals have a structure closer to crystals than general nematic liquid crystals, and is particularly problematic in a polarizing film formed of a polymerizable liquid crystal compound exhibiting smectic liquid crystallinity.

Accordingly, an object of the present invention is to provide a composition for forming a polarizing film, which can form a polarizing film having no leak spot or alignment defect and having a high degree of alignment order.

Means for solving the problems

The present inventors have conducted intensive studies to solve the above problems, and as a result, have completed the present invention. That is, the present invention provides the following preferred embodiments.

[1] A composition for forming a polarizing film, comprising a polymerizable liquid crystal compound exhibiting smectic liquid crystallinity, a dichroic dye, and at least 2 kinds of organic solvents, wherein the organic solvent comprises an organic solvent A and an organic solvent B, the organic solvent A has a boiling point higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by-20 ℃ to 50 ℃, and the organic solvent B has a boiling point higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by more than 50 ℃.

[2] The composition for forming a polarizing film according to the above [1], wherein the content of the organic solvent A is 51 to 99 parts by mass and the content of the organic solvent B is 1 to 49 parts by mass based on 100 parts by mass of all the organic solvents contained in the composition for forming a polarizing film.

[3] The composition for forming a polarizing film according to the above [1] or [2], wherein the boiling point of the organic solvent A is higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by 0 ℃ or more and 50 ℃ or less, and the boiling point of the organic solvent B is higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by more than 50 ℃ and 150 ℃ or less.

[4] The polarizing film-forming composition according to any one of the above [1] to [3], further comprising a polymerization initiator.

[5] The composition for forming a polarizing film according to any one of the above [1] to [4], wherein the organic solvent A is a ketone solvent or an aromatic solvent.

[6] The composition for forming a polarizing film according to any one of the above [1] to [5], wherein the organic solvent B is selected from the group consisting of glycol solvents, ketone solvents and amide solvents.

[7] The composition for polarizing film formation according to any one of the above [1] to [6], wherein the solid content of the composition for polarizing film formation is 5 to 40 mass%.

[8] The composition for forming a polarizing film according to the above [7], wherein the proportion of the polymerizable liquid crystal compound in the solid content is 40 to 99.9% by mass.

[9] The composition for forming a polarizing film according to the above [7] or [8], wherein the dichroic dye is present in the solid component in an amount of 1 to 20% by mass.

[10] A polarizing film which is a cured product of the composition for forming a polarizing film according to any one of the above [1] to [9], wherein the polymerizable liquid crystal compound and/or the polymer thereof is oriented in a smectic liquid crystal state.

[11] The polarizing film according to the above [10], wherein a Bragg peak is obtained in X-ray diffraction measurement.

[12] A polarizing plate comprising the polarizing film according to [10] or [11], a substrate and an oriented film.

[13] The method for manufacturing the polarizing plate comprises the following steps:

a coating film for forming the polarizing film-forming composition according to any one of the above [1] to [9 ];

heating and drying the coating film to a temperature not lower than the isotropic phase transition temperature of the polymerizable liquid crystal compound contained in the composition for forming a polarizing film, and then cooling the coating film to convert the polymerizable liquid crystal compound into a smectic liquid crystal phase; and

the polymerizable liquid crystal compound is polymerized while being maintained in the smectic liquid crystal phase to form a polarizing film.

[14] The method for producing a polarizing plate according to item [13], wherein a coating film of the composition for forming a polarizing film is formed on the photo-alignment film,

the photo-alignment film is formed by a method including the steps of,

forming a coating film from a composition containing a polymer or monomer capable of generating an orientation restriction force by light and a solvent;

drying and removing the solvent from the coating film to obtain a dried coating film; and

irradiating the dried coating film with polarized ultraviolet rays.

ADVANTAGEOUS EFFECTS OF INVENTION

The present invention can provide a composition for forming a polarizing film, which can form a polarizing film having no leak point or alignment defect and having a high degree of alignment order.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail. The scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without departing from the spirit of the present invention.

< composition for forming polarizing film >

The composition for forming a polarizing film of the present invention contains a polymerizable liquid crystal compound (hereinafter, also referred to as "polymerizable liquid crystal compound (a)") exhibiting smectic liquid crystallinity. By using a polymerizable liquid crystal compound exhibiting smectic liquid crystallinity, a polarizing film having a high degree of alignment order can be formed. The liquid crystal state exhibited by the polymerizable liquid crystal compound (a) is a smectic phase (smectic liquid crystal state), and from the viewpoint of enabling a higher degree of alignment order to be achieved, a higher order smectic phase (higher order smectic liquid crystal state) is more preferably exhibited. Here, the higher order smectic phase means a smectic B phase, a smectic D phase, a smectic E phase, a smectic F phase, a smectic G phase, a smectic H phase, a smectic I phase, a smectic J phase, a smectic K phase and a smectic L phase, and among these, the smectic B phase, the smectic F phase and the smectic I phase are more preferable. The liquid crystal may be a thermotropic liquid crystal or a lyotropic liquid crystal, and is preferably thermotropic liquid crystal in view of enabling a dense film thickness control. The polymerizable liquid crystal compound may be a monomer, or an oligomer or polymer obtained by polymerizing a polymerizable group.

The polymerizable liquid crystal compound (a) is not particularly limited as long as it is a polymerizable liquid crystal compound exhibiting smectic liquid crystallinity, and known polymerizable liquid crystal compounds can be used.

Examples of the polymerizable liquid crystal compound (a) include a compound represented by the formula (a1) and a polymer of the compound (hereinafter, the compound and the polymer are also collectively referred to as "polymerizable liquid crystal compound (a 1)").

U¹-V¹-W¹-X¹-Y¹-X²-Y²-X³-W²-V²-U²(A1)

[ in the formula (A1),

X¹、X²and X³The aromatic group having a valence of 2 or the alicyclic hydrocarbon group having a valence of 2 independently of each other, wherein a hydrogen atom contained in the aromatic group having a valence of 2 or the alicyclic hydrocarbon group having a valence of 2 may be substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, a fluoroalkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group or a nitro group, and a carbon atom constituting the aromatic group having a valence of 2 or the alicyclic hydrocarbon group having a valence of 2 may be substituted with an oxygen atom, a sulfur atom or a nitrogen atom. Wherein, X¹、X²And X³At least 1 of them is a1, 4-phenylene group which may have a substituent or a cyclohexane-1, 4-diyl group which may have a substituent.

Y¹And Y²Independently of one another, a single bond or a divalent linking group.

U¹Represents a hydrogen atom or a polymerizable group.

U²Represents a polymerizable group.

W¹And W²Independently of one another, a single bond or a divalent linking group.

V¹And V²Independently represent optionally substituted alkanediyl having 1 to 20 carbon atoms, -CH constituting the alkanediyl₂-may be replaced by-O-, -CO-, -S-or NH-.]

In the polymerizable liquid crystal compound (A1), X¹、X²And X³Independently of one another, it is preferably a1, 4-phenylene group which may have a substituent, or a cyclohexane-1, 4-diyl group which may have a substituent, X¹、X²And X³At least 1 of them is a1, 4-phenylene group which may have a substituent, or a cyclohexane-1, 4-diyl group which may have a substituent. In particular, X¹And X³Preferred is cyclohexane-1, 4-diyl which may have a substituent, and the cyclohexane-1, 4-diyl is further preferred to be trans-cyclohexane-1, 4-diyl. Examples of the optionally substituted 1, 4-phenylene group which may have a substituent or the optionally substituted cyclohexane-1, 4-diyl group include an alkyl group having 1 to 4 carbon atoms such as a methyl group, an ethyl group, a butyl group and the like, a cyano group, a halogen atom such as a chlorine atom, a fluorine atom and the like. Preferably unsubstituted. In addition, Y¹And Y²When they are the same structure, X is preferably¹、X²And X³At least 1 of which is a different structure. X¹、X²And X³When at least 1 of them have different structures, smectic liquid crystallinity tends to be easily exhibited.

Y¹And Y²Independently of one another, are preferably-CH₂CH₂-、-CH₂O-、-CH₂CH₂O-, -COO-, -OCOO-, single bond, -N ═ N-, -CR^a＝CR^b-、-C≡C-、-CR^aN-or-CO-NR^a-。R^aAnd R^bIndependently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms。Y¹More preferably-CH₂CH₂-, -COO-or a single bond, Y²More preferably-CH₂CH₂-or CH₂O-is formed. In addition, X¹、X²And X³When all are of the same structure, Y¹And Y²Preferably of mutually different configurations. Y is¹And Y²When they have different structures, smectic liquid crystallinity tends to be easily exhibited.

U²Is a polymerizable group. U shape¹Is a hydrogen atom or a polymerizable group, and is preferably a polymerizable group. Preferably U¹And U²All of them are polymerizable groups, and preferably all of them are radical polymerizable groups. Examples of the polymerizable group include a vinyl group, a vinyloxy group, a 1-chloroethenyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxetanyl group, and the like. Among them, radical polymerizable groups are preferable, acryloyloxy, methacryloyloxy, vinyl, and vinyloxy groups are more preferable, and acryloyloxy and methacryloyloxy groups are preferable. U shape¹The polymerizable group represented by (a) and U²The polymerizable groups represented by the above groups may be different from each other, but the same type of groups is preferable.

As V¹And V²Examples of the alkanediyl group include a methylene group, an ethylene group, a propane-1, 3-diyl group, a butane-1, 4-diyl group, a pentane-1, 5-diyl group, a hexane-1, 6-diyl group, a heptane-1, 7-diyl group, an octane-1, 8-diyl group, a decane-1, 10-diyl group, a tetradecane-1, 14-diyl group, and an eicosane-1, 20-diyl group. V¹And V²Preferably a C2-12 alkanediyl group, and more preferably a C6-12 alkanediyl group.

Examples of the substituent optionally contained in the alkanediyl group include a cyano group and a halogen atom, and the alkanediyl group is preferably an unsubstituted, more preferably an unsubstituted, linear alkanediyl group.

W¹And W²Independently of one another, is preferably a single bond, -O-, -S-, -COO-or OCOO-, preferably a single bond or-O-.

Examples of the polymerizable liquid crystal compound (A1) include compounds represented by the formulae (A-1) to (A-25). When the polymerizable liquid crystal compound (a1) has a cyclohexane-1, 4-diyl group, the cyclohexane-1, 4-diyl group is preferably a trans-isomer.

Of these, at least 1 selected from the group consisting of the compounds represented by the formula (A-2), the formula (A-3), the formula (A-4), the formula (A-5), the formula (A-6), the formula (A-7), the formula (A-8), the formula (A-13), the formula (A-14), the formula (A-15), the formula (A-16) and the formula (A-17) is preferable. The polymerizable liquid crystal compound (a1) may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

The polymerizable liquid crystal compound (A1) can be produced by a known method described in Recl.Trav.Chim.Pays-Bas, 115, 321-328(1996), Lub et al, or Japanese patent No. 4719156, etc.

The composition for forming a polarizing film of the present invention may contain other polymerizable liquid crystal compounds than the polymerizable liquid crystal compound (a) as long as the effects of the present invention are not impaired. From the viewpoint of obtaining a polarizing film having a high degree of orientation order, the proportion of the polymerizable liquid crystal compound (a) relative to the total mass of all polymerizable liquid crystal compounds in the polarizing film-forming composition is preferably 51 mass% or more, more preferably 70 mass% or more, and still more preferably 90 mass% or more of the polymerizable liquid crystal compound (a), and may be all (100 mass%) of the polymerizable liquid crystal compound (a).

The content of the polymerizable liquid crystal compound in the polarizing film forming composition of the present invention is preferably 40 to 99.9% by mass, more preferably 60 to 99.9% by mass, and even more preferably 70 to 99% by mass, based on the solid content of the polarizing film forming composition. When the content of the polymerizable liquid crystal compound is within the above range, the alignment property of the polymerizable liquid crystal compound tends to be improved. In the present specification, the solid content means the total amount of components remaining after the solvent is removed from the polarizing film-forming composition.

The composition for forming a polarizing film of the present invention contains a dichroic dye. Here, the dichroic dye is a dye having a property that the absorbance of molecules in the major axis direction is different from the absorbance of molecules in the minor axis direction. The dichroic dye that can be used in the present invention is not particularly limited, and may be a dye or a pigment as long as it has the above properties. More than 2 kinds of dyes or pigments may be used in combination, respectively, or the dyes and pigments may be used in combination.

The dichroic dye preferably has a maximum absorption wavelength (lambda) in the range of 300 to 700nm_MAX) The dichroic dye of (4). Examples of such dichroic dyes include acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes, and anthraquinone dyes.

Examples of the azo dye include monoazo dyes, disazo dyes, trisazo dyes, tetraazo dyes, and stilbene azo dyes, and the disazo dyes and the trisazo dyes are preferable, and examples thereof include compounds represented by the formula (I) (hereinafter, also referred to as "compound (I)").

K¹(-N＝N-K²)_p-N＝N-K³(I)

[ in the formula (I), K¹And K³Independently of one another, represents an optionally substituted phenyl group, an optionally substituted naphthyl group or an optionally substituted 1-valent heterocyclic group. K²Represents an optionally substituted p-phenylene group, an optionally substituted naphthalene-1, 4-diyl group or an optionally substituted 2-valent heterocyclic group. p represents an integer of 1 to 4. When p is an integer of 2 or more, a plurality of K²May be the same or different from each other. The — N ═ N-bond may be replaced by — C ═ C-, -COO-, -NHCO-, -N ═ CH-bond as long as it is in a range that exhibits absorption in the visible light region.]

Examples of the heterocyclic group having a valence of 1 include groups obtained by removing 1 hydrogen atom from a heterocyclic compound such as quinoline, thiazole, benzothiazole, thienothiazole, imidazole, benzimidazole, oxazole, and benzoxazole. Examples of the 2-valent heterocyclic group include groups obtained by removing 2 hydrogen atoms from the above-mentioned heterocyclic compound.

As K¹And K³Phenyl, naphthyl and heterocyclic group having a valence of 1 in (1), and K²The substituent optionally having the p-phenylene group, naphthalene-1, 4-diyl group and 2-valent heterocyclic group in (1) includes an alkyl group having 1 to 4 carbon atoms; alkoxy groups having 1 to 4 carbon atoms such as methoxy, ethoxy, butoxy and the like; a fluorinated alkyl group having 1 to 4 carbon atoms such as a trifluoromethyl group; a cyano group; a nitro group; a halogen atom; a substituted or unsubstituted amino group such as an amino group, a diethylamino group, or a pyrrolidinyl group (the substituted amino group means an amino group having 1 or 2 alkyl groups having 1 to 6 carbon atoms or an amino group in which 2 substituted alkyl groups are bonded to each other to form an alkanediyl group having 2 to 8 carbon atoms, and the unsubstituted amino group is-NH₂. ) And the like.

Among the compounds (I), the compounds represented by any one of the formulae (I-1) to (I-6) are preferred.

[ formulae (I-1) to (I-8),

B¹～B³⁰independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group, a nitro group, a substituted or unsubstituted amino group (the definitions of the substituted amino group and the unsubstituted amino group are as described above), a chlorine atom or a trifluoromethyl group.

n1 to n4 each independently represents an integer of 0 to 3.

When n1 is 2 or more, a plurality of B²May be the same as or different from each other,

when n2 is 2 or more, a plurality of B⁶May be the same as or different from each other,

when n3 is 2 or more, a plurality of B⁹May be the same as or different from each other,

when n4 is 2 or more, a plurality of B¹⁴May be the same or different from each other.]

As the anthraquinone dye, a compound represented by the formula (I-9) is preferable.

[ in the formula (I-9),

R¹～R⁸independently of each other, a hydrogen atom, -R^x、-NH₂、-NHR^x、-NR^x ₂、-SR^xOr a halogen atom.

R^xRepresents an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 12 carbon atoms.]

As the oxazinone dye, a compound represented by the formula (I-10) is preferable.

[ in the formula (I-10),

R⁹～R¹⁵independently of each other, a hydrogen atom, -R^x、-NH₂、-NHR^x、-NR^x ₂、-SR^xOr a halogen atom.

R^xRepresents an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 12 carbon atoms.]

As the acridine pigment, a compound represented by the formula (I-11) is preferable.

[ in the formula (I-11),

R¹⁶～R²³independently of each other, a hydrogen atom, -R^x、-NH₂、-NHR^x、-NR^x ₂、-SR^xOr a halogen atom.

R^xRepresents an alkyl group having 1 to 4 carbon atoms or a C-containing group6-12 aryl groups.]

In the formula (I-9), the formula (I-10) and the formula (I-11), as R^xExamples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, propyl, butyl, pentyl and hexyl, and examples of the aryl group having 6 to 12 carbon atoms include phenyl, toluyl, xylyl and naphthyl.

As the cyanine dye, a compound represented by the formula (I-12) and a compound represented by the formula (I-13) are preferable.

[ in the formula (I-12),

D¹and D²Independently of each other, represents a group represented by any one of the formulae (I-12a) to (I-12 d).

n5 represents an integer of 1 to 3. ]

[ in the formula (2-13),

D³and D⁴Independently of each other, represents a group represented by any one of the formulae (1-13a) to (1-13 h).

n6 represents an integer of 1 to 3. ]

The content of the dichroic dye in the polarizing film forming composition of the present invention may be appropriately determined depending on the type of the dichroic dye used, and is preferably 1 to 60% by mass, more preferably 1 to 20% by mass, and still more preferably 1 to 15% by mass, based on the solid components of the polarizing film forming composition. When the content of the dichroic dye is within the above range, the orientation of the polymerizable liquid crystal compound is not easily disturbed, and a polarizing film having a high degree of orientation order can be obtained.

The polarizing film-forming composition of the present invention contains at least 2 organic solvents. The 2 kinds of organic solvents include at least an organic solvent A having a boiling point higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by-20 ℃ to 50 ℃ and an organic solvent B having a boiling point higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by more than 50 ℃. In the composition for forming a polarizing film of the present invention, by including at least 2 kinds of organic solvents having different boiling points, the solvent is less likely to volatilize before the step of heat-drying the coating film of the composition for forming a polarizing film to change the polymerizable liquid crystal compound into a liquid crystal state (hereinafter, also referred to as "heat-drying step"), but the solvent is more likely to be dried and removed in the heat-drying step, and a polarizing film having excellent polarizing performance in which alignment defects and leak points are less likely to occur can be obtained. When the composition for forming a polarizing film of the present invention contains 2 or more polymerizable liquid crystal compounds, the organic solvents a and B are selected based on the isotropic phase transition temperature in the mixed state of the polymerizable liquid crystal compounds contained in the composition for forming a polarizing film.

The organic solvent a generally exerts the following effects: the polymerizable liquid crystal compound and the dichroic dye are dissolved, and a good mixed encapsulated state of the polymerizable liquid crystal compound and the dichroic dye is easily generated in the coating film, and the solid content concentration and viscosity of the composition for forming a polarizing film are adjusted. In particular, a compound which generally exhibits smectic liquid crystallinity tends to have a high viscosity, and the composition for forming a polarizing film contains the organic solvent a, whereby the handling property of the composition becomes good, and as a result, the formation of a polarizing film becomes easy. In order to suppress volatilization of the organic solvent from the coating film before the heating and drying step of the coating film of the composition for forming a polarizing film, the boiling point of the organic solvent a is higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound contained in the composition for forming a polarizing film by-20 ℃ to 50 ℃, preferably 0 ℃ to 50 ℃, more preferably 10 ℃ to 50 ℃, and more preferably 20 ℃ to 40 ℃. When the boiling point of the organic solvent a is lower than the isotropic phase transition temperature of the polymerizable liquid crystal compound by more than-20 ℃, the organic solvent is easily volatilized before the heat drying step, and thus, fine crystals of the polymerizable liquid crystal compound are easily precipitated. When the boiling point of the organic solvent a is higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by more than 50 ℃, although volatilization of the solvent before the heat-drying step can be suppressed, the solvent becomes less volatile in the heat-drying step, and alignment defects are easily generated. At the same time, since the amount of the solvent remaining after the heat drying step can be reduced, the occurrence of alignment defects due to the remaining solvent can be suppressed. The organic solvent A may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

The organic solvent B is a high boiling point solvent, and has an effect of imparting a moisture-retaining effect to the coating film before the heating and drying step. From the viewpoint of suppressing the volatilization of the coating film before the heating and drying step, the boiling point of the organic solvent B is higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound contained in the polarizing film-forming composition by more than 50 ℃, preferably higher by 55 ℃ or higher, preferably higher by 150 ℃ or lower, more preferably higher by 60 ℃ or higher and 150 ℃ or lower, and further preferably higher by 60 ℃ or higher and 120 ℃ or lower. By including the organic solvent B having a boiling point higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by the above range, volatilization of the organic solvent from the coating film before the heating and drying step can be effectively suppressed, and a good mixed encapsulated state of the polymerizable liquid crystal compound and the dichroic dye can be maintained in the coating film. This can effectively suppress the occurrence of missing dots in the obtained polarizing film. The organic solvent B may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

The difference between the boiling point of the organic solvent A and the boiling point of the organic solvent B is preferably 20 ℃ or more, more preferably 30 ℃ or more, preferably 120 ℃ or less, and more preferably 100 ℃ or less. When the boiling points of the organic solvents a and B are in the above-described relationship, the effect of suppressing the generation of fine crystals of the polymerizable liquid crystal compound before the heat-drying step of the coating film of the composition for forming a polarizing film and the effect of facilitating the removal of the solvent in the heat-drying step are easily balanced, and the formation of the leak point and the alignment defect in the obtained polarizing film is less likely to occur.

The organic solvents a and B may be appropriately selected from known organic solvents capable of dissolving the polymerizable liquid crystal compound and the dichroic dye, depending on the polymerizable liquid crystal compound and the dichroic dye used, and the isotropic phase transition temperature of the polymerizable liquid crystal compound.

Examples of the organic solvent include the following solvents:

ketone solvents such as methyl isobutyl ketone (116 ℃), cyclohexanone (156 ℃), cyclopentanone (131 ℃), methyl amyl ketone (151 ℃), isophorone (215 ℃), gamma-butyrolactone (GBL) (204 ℃);

aromatic solvents such as xylene (144 ℃ C.), mesitylene (165 ℃ C.), cumene (152 ℃ C.), ethylbenzene (136 ℃ C.), anisole (154 ℃ C.), aniline (184 ℃ C.), benzaldehyde (178 ℃ C.), benzyl alcohol (205 ℃ C.), methyl benzoate (199 ℃ C.), ethyl benzoate (213 ℃ C.), propyl benzoate (230 ℃ C.), butyl benzoate (250 ℃ C.), nitrobenzene (211 ℃ C.), and tetrahydronaphthalene (207 ℃ C.);

long-chain hydrocarbon solvents such as octane (125 ℃ C.), nonane (151 ℃ C.), decane (174 ℃ C.), undecane (196 ℃ C.), dodecane (216 ℃ C.);

ethylene glycol monomethyl ether (124 ℃), ethylene glycol monoethyl ether (202 ℃), ethylene glycol n-propyl ether (151 ℃), ethylene glycol isopropyl ether (141 ℃), ethylene glycol n-butyl ether (171 ℃), ethylene glycol monomethyl ether (124 ℃), diethylene glycol dimethyl ether (162 ℃), diethylene glycol diethyl ether (189 ℃), dipropylene glycol dimethyl ether (171 ℃), diethylene glycol monomethyl ether (194 ℃), diethylene glycol monoethyl ether (202 ℃), diethylene glycol monobutyl ether (230 ℃), diethylene glycol ethyl methyl ether (176 ℃), diethylene glycol butyl methyl ether (212 ℃), propylene glycol monomethyl ether (120 ℃), propylene glycol dimethyl ether (120 ℃), dipropylene glycol monomethyl ether (188 ℃), dipropylene glycol dimethyl ether (171 ℃), propylene glycol dimethyl ether (97 ℃), tripropylene glycol dimethyl ether (215 ℃), triethylene glycol monomethyl ether (249 ℃), propylene glycol dimethyl ether (249 ℃), and mixtures thereof, Glycol solvents such as triethylene glycol dimethyl ether (216 ℃ C.), tetraethylene glycol dimethyl ether (276 ℃ C.), propylene glycol monomethyl ether acetate (146 ℃ C.), ethylene glycol monomethyl ether acetate (145 ℃ C.), diethylene glycol monoethyl ether acetate (217 ℃ C.), and diethylene glycol monobutyl ether acetate (245 ℃ C.);

ester-based solvents such as propyl acetate (102 ℃ C.), butyl acetate (126 ℃ C.), pentyl acetate (149 ℃ C.), ethyl lactate (155 ℃ C.), methyl methoxypropionate (143 ℃ C.), ethyl ethoxypropionate (170 ℃ C.), isoamylpropionate (156 ℃ C.), isoamyl isobutyrate (179 ℃ C.), ethyl butyrate (121 ℃ C.), propyl butyrate (143 ℃ C.), butyl butyrate (165 ℃ C.), ethylene carbonate (244 ℃ C.), and propylene carbonate (242 ℃ C.);

amide solvents such as N, N-dimethylformamide (153 ℃ C.), N-dimethylacetamide (165 ℃ C.), N-methylpyrrolidone (202 ℃ C.), and γ -butyrolactam (245 ℃ C.); and

a halogen-based solvent such as chlorobenzene (131 ℃ C.) or 1,1,2, 2-tetrachloroethane (147 ℃ C.).

It is more advantageous to select an organic solvent having high solubility in the polymerizable liquid crystal compound and the dichroic dye as the organic solvent a. In a preferred embodiment of the present invention, the organic solvent a is a ketone solvent or an aromatic solvent, and more preferably an aromatic solvent. Further, it is more advantageous to select, as the organic solvent B, an organic solvent having a high boiling point with respect to the isotropic phase transition temperature of the polymerizable liquid crystal compound and high solubility with respect to the polymerizable liquid crystal compound and the dichroic dye. In a preferred embodiment of the present invention, the organic solvent B is selected from the group consisting of a glycol-based solvent, a ketone-based solvent, and an amide-based solvent, and more preferably a glycol-based solvent, a ketone-based solvent, and an amide-based solvent having a boiling point of 150 ℃.

The content of the organic solvent a in the polarizing film-forming composition of the present invention is preferably 51 to 99 parts by mass, more preferably 60 parts by mass or more, further preferably 70 parts by mass or more, more preferably 95 parts by mass or less, and further preferably 90 parts by mass or less, based on 100 parts by mass of the total organic solvents contained in the polarizing film-forming composition. The content of the organic solvent B is preferably 1 to 49 parts by mass, more preferably 5 parts by mass or more, further preferably 10 parts by mass or more, more preferably 40 parts by mass or less, and further preferably 30 parts by mass or less, based on 100 parts by mass of the total organic solvent contained in the polarizing film-forming composition. When the organic solvents a and B are contained within the above content ranges, respectively, the solvent is suppressed from being volatilized in the coating film before the heat-drying step, whereby a good mixed encapsulated state of the polymerizable liquid crystal compound and the dichroic dye can be obtained, and in the heat-drying step, the solvent can be sufficiently removed even at a temperature near the phase transition temperature of the polymerizable liquid crystal compound without heating more than necessary, and alignment defects due to the remaining solvent can be suppressed, and a polarizing film having excellent polarizing performance can be obtained. When the organic solvent a and/or the organic solvent B contains 2 or more species, the content means the total amount of each of the organic solvent a and/or the organic solvent B. The composition for forming a polarizing film of the present invention may contain an organic solvent other than the organic solvents a and B as long as the effects of the present invention are not impaired.

The composition for forming a polarizing film of the present invention preferably contains an organic solvent in such an amount that the solid content thereof is 5 to 40 mass%. In other words, the content of the organic solvent in the polarizing film forming composition of the present invention (the total amount of the organic solvents a and B and the organic solvents a and B when the organic solvents a and B are included) is preferably 60 to 95% by mass based on the total mass of the polarizing film forming composition. When the content of the organic solvent is in the above range, volatilization of the solvent can be suppressed in the coating film before the heat drying, and the solvent can be easily dried and removed without heating more than necessary in the heat drying step, thereby reducing the amount of the residual solvent. Thus, a polarizing film having excellent polarizing performance can be obtained.

The polarizing film-forming composition of the present invention preferably contains a polymerization initiator. The polymerization initiator is a compound capable of initiating the polymerization reaction of the polymerizable liquid crystal compound, and is preferably a photopolymerization initiator in terms of being capable of initiating the polymerization reaction at a relatively low temperature. Specifically, a photopolymerization initiator which can generate an active radical or an acid by the action of light is exemplified, and among them, a photopolymerization initiator which generates a radical by the action of light is preferable. The polymerization initiator may be used alone or in combination of 2 or more.

Examples of the polymerization initiator include benzoin compounds, benzophenone compounds, alkylphenone compounds, acylphosphine oxide compounds, triazine compounds, iodonium salts, sulfonium salts, and the like.

Examples of the benzoin compound include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether.

Examples of the benzophenone compound include benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4 ' -methyldiphenyl sulfide, 3 ', 4,4 ' -tetrakis (t-butylperoxycarbonyl) benzophenone, and 2,4, 6-trimethylbenzophenone.

Examples of the alkylphenone compound include diethoxyacetophenone, 2-methyl-2-morpholino-1- (4-methylthiophenyl) propan-1-one, 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) butan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1, 2-diphenyl-2, 2-dimethoxyethane-1-one, 2-hydroxy-2-methyl-1- [ 4- (2-hydroxyethoxy) phenyl ] propan-1-one, 1-hydroxycyclohexylphenyl ketone and 2-hydroxy-2-methyl-1- [ 4- (1-methylvinyl) phenyl ] propan-1-one Oligomers of alk-1-ones, and the like.

Examples of the acylphosphine oxide compound include 2,4, 6-trimethylbenzoyldiphenylphosphine oxide and bis (2,4, 6-trimethylbenzoyl) phenylphosphine oxide.

Examples of the triazine compound include 2, 4-bis (trichloromethyl) -6- (4-methoxyphenyl) -1,3, 5-triazine, 2, 4-bis (trichloromethyl) -6- (4-methoxynaphthyl) -1,3, 5-triazine, 2, 4-bis (trichloromethyl) -6- (4-methoxystyryl) -1,3, 5-triazine, 2, 4-bis (trichloromethyl) -6- [ 2- (5-methylfuran-2-yl) vinyl ] -1,3, 5-triazine, 2, 4-bis (trichloromethyl) -6- [ 2- (furan-2-yl) vinyl ] -1,3, 5-triazine, 2, 4-bis (trichloromethyl) -6- [ 2- (4-diethylamino-2-methylphenyl) vinyl ] -1,3, 5-triazine and 2, 4-bis (trichloromethyl) -6- [ 2- (3, 4-dimethoxyphenyl) vinyl ] -1,3, 5-triazine.

As the polymerization initiator, a commercially available polymerization initiator can be used. Examples of commercially available polymerization initiators include "Irgacure (イルガキュア) (registered trademark) 907", "Irgacure (registered trademark) 184", "Irgacure (registered trademark) 651", "Irgacure (registered trademark) 819", "Irgacure (registered trademark) 250", "Irgacure (registered trademark) 369" (Ciba Specialty Chemicals, Inc.); "SEIKUOL (registered trademark) BZ", "SEIKUOL (registered trademark) Z", "SEIKUOL (registered trademark) BEE" (fine chemical strain)); "kayacure (カヤキュアー) (registered trademark) BP 100" (japan chemical (ltd.)); "kayacure (registered trademark) UVI-6992" (manufactured by DOW Chemical Company); "ADEKA OPTOMER SP-152", "ADEKA OPTOMER SP-170" ((strain) ADEKA); "TAZ-A", "TAZ-PP" (Siber Hegner, Japan); and "TAZ-104" (Sanwa Chemical Co., Ltd.), and the like.

When the composition for forming a polarizing film contains a polymerization initiator, the content thereof may be determined appropriately depending on the kind and amount of the polymerizable liquid crystal compound contained in the composition for forming a polarizing film, and is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 10 parts by mass, and still more preferably 0.5 to 8 parts by mass, based on 100 parts by mass of the polymerizable liquid crystal compound. When the content of the polymerizable initiator is within the above range, the polymerizable liquid crystal compound can be polymerized without disturbing the orientation thereof.

When the composition for forming a polarizing film contains a photopolymerization initiator, the composition may further contain a photosensitizer. By using the photosensitizer, the polymerization reaction of the polymerizable liquid crystal compound can be further promoted. Examples of the photosensitizing agent include xanthone compounds such as xanthone and thioxanthone (e.g., 2, 4-diethylthioxanthone and 2-isopropylthioxanthone); anthracene compounds such as anthracene and alkoxy-containing anthracene (dibutoxyanthracene and the like); phenothiazine, rubrene, and the like. The photosensitizing agent may be used alone or in combination of 2 or more.

The content of the photosensitizer in the composition for forming a polarizing film of the present invention may be determined as appropriate depending on the kind and amount of the photopolymerization initiator and the polymerizable liquid crystal compound, and is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 10 parts by mass, and still more preferably 0.5 to 8 parts by mass, based on 100 parts by mass of the polymerizable liquid crystal compound.

The composition for forming a polarizing film of the present invention may further contain a leveling agent. The leveling agent has a function of adjusting the fluidity of the composition for forming a polarizing film and flattening a coating film obtained by applying the composition for forming a polarizing film, and specifically includes a surfactant. The leveling agent is preferably at least 1 selected from the group consisting of a leveling agent containing a polyacrylate compound as a main component and a leveling agent containing a compound containing a fluorine atom as a main component. The leveling agent may be used alone or in combination of 2 or more.

Examples of the leveling agent containing a polyacrylate compound as a main component include "BYK-350", "BYK-352", "BYK-353", "BYK-354", "BYK-355", "BYK-358N", "BYK-361N", "BYK-380", "BYK-381", and "BYK-392" (BYK Chemie Co., Ltd.).

Examples of the leveling agent containing a fluorine atom-containing compound as a main component include "MEGAFACE (registered trademark) R-08", MEGAFACE "R-30", MEGAFACE "R-90", MEGAFACE "F-410", MEGAFACE "F-411", MEGAFACE "F-443", MEGAFACE "F-445", MEGAFACE "F-470", MEGAFACE "F-471", MEGAFACE "F-477", MEGAFACE "F-479", MEGAFACE "F-482" and MEGAFACE "F-483" (DIC corporation); "Surflon (registered trademark) S-381", Surflon "S-382", Surflon "S-383", Surflon "S-393", Surflon "SC-101", Surflon "SC-105", "KH-40" and "SA-100" (AGC Seimi Chemical Co., Ltd.); "E1830", "E5844" (DaikinFine Chemical Kenkyusho, K.K.); "EFTOP EF 301", "EFTOP EF 303", "EFTOP EF 351" and "EFTOP EF 352" (Mitsubishi Materials Electronic Chemicals Co., Ltd.), etc.

The content of the leveling agent in the composition for forming a polarizing film of the present invention is preferably 0.05 to 5 parts by mass, and more preferably 0.05 to 3 parts by mass, based on 100 parts by mass of the polymerizable liquid crystal compound. When the content of the leveling agent is within the above range, the following tendency is present: the polymerizable liquid crystal compound is easily oriented horizontally, and a smoother polarizing film is obtained with less unevenness.

In order to more stably perform the polymerization reaction of the composition for forming a polarizing film, an appropriate amount of a polymerization inhibitor may be contained in the composition, and thus the degree of progress of the polymerization reaction of the polymerizable liquid crystal compound can be easily controlled.

Examples of the polymerization inhibitor include radical scavengers such as hydroquinone, alkoxy-containing catechol (e.g., butylcatechol), pyrogallol, and 2,2,6, 6-tetramethylpiperidine-1-oxyl; thiophenols; beta-naphthylamines and beta-naphthols, and the like.

When the composition for forming a polarizing film contains a polymerization inhibitor, the content thereof may be appropriately adjusted depending on the kind and amount of the polymerizable liquid crystal compound, the amount of the photosensitizer used, and the like, and is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 10 parts by mass, and still more preferably 0.5 to 8 parts by mass, based on 100 parts by mass of the polymerizable liquid crystal compound. When the content of the polymerization inhibitor is within the above range, the polymerizable liquid crystal compound can be polymerized without disturbing the orientation thereof.

The composition for forming a polarizing film may contain other additives besides a photopolymerization initiator, a leveling agent, a photosensitizing agent, and a polymerization inhibitor. Examples of the other additives include colorants such as antioxidants, mold release agents, stabilizers, and bluing agents, flame retardants, and lubricants. When the polarizing film-forming composition contains other additives, the content of the other additives is preferably higher than 0% by mass and 20% by mass or less, more preferably higher than 0% by mass and 10% by mass or less, relative to the solid content of the polarizing film-forming composition.

The solid content of the composition for forming a polarizing film of the present invention is preferably 5 to 40% by mass. When the concentration of the solid component in the composition for forming a polarizing film is not less than the lower limit, volatilization of the solvent and precipitation of fine crystals of the polymerizable liquid crystal compound before the step of heating and drying the coating film of the composition for forming a polarizing film can be prevented, and occurrence of leak spots in the polarizing film can be suppressed. When the solid content is not more than the above upper limit, the organic solvent is easily removed in the heating and drying step, and an alignment defect is not easily generated in the obtained polarizing film. In addition, since the compound exhibiting smectic liquid crystallinity generally has a high viscosity, the solid content concentration in the above range facilitates application, and as a result, the polarizing film can be easily formed. In the present invention, the solid content of the polarizing film-forming composition is more preferably 10% by mass or more, still more preferably 15% by mass or more, still more preferably 35% by mass or less, and still more preferably 30% by mass or less. The solid content concentration can be adjusted mainly by the amount of the organic solvent or the polymerizable liquid crystal compound added.

The composition for forming a polarizing film of the present invention can be usually prepared by mixing and stirring a polymerizable liquid crystal compound, a dichroic dye, an organic solvent, and the above-mentioned additives as necessary.

The composition for forming a polarizing film of the present invention can provide a polarizing film which is less likely to cause missing dots and orientation defects and has a high degree of orientation order. Therefore, the present invention also includes a polarizing film formed by curing the composition for forming a polarizing film of the present invention (i.e., a cured product of the composition for forming a polarizing film). In the polarizing film of the present invention, it is preferable that the polymerizable liquid crystal compound and/or the polymer thereof forming the polarizing film be oriented in a smectic liquid crystal state. The polarizing film of the present invention exhibits a high degree of alignment order by being aligned in a smectic liquid crystal state.

In the case of a polarizing film having a high degree of orientation order, bragg peaks derived from a high-order structure such as a hexagonal phase (hexagonal phase) or a crystal phase can be obtained in X-ray diffraction measurement. The bragg peak is a peak derived from a plane periodic structure of molecular orientation. The polarizing film formed from the composition for forming a polarizing film of the present invention preferably exhibits bragg peaks in X-ray diffraction measurement, and the polymerizable liquid crystal compound and/or the polymer thereof is more preferably "horizontally oriented" in which molecules are oriented in the direction of absorbing light. In the present invention, the plane period interval of the preferred molecular orientation is

The polarizing film of (1).

The polarizing film of the present invention can be produced, for example, by a method for forming a polarizing film in the method for producing a polarizing plate of the present invention described later.

The present invention also relates to a polarizing plate comprising the polarizing film of the present invention. In one embodiment of the present invention, the polarizing plate of the present invention includes not only the polarizing film of the present invention but also a substrate and an alignment film, and particularly preferably includes a substrate and a photo-alignment film.

The polarizing plate of the present invention can be produced, for example, by a method including the steps of:

forming a coating film of the polarizing film-forming composition of the present invention;

heating and drying the coating film to a temperature not lower than the nematic-isotropic phase transition temperature of the polymerizable liquid crystal compound contained in the composition for forming a polarizing film, and then cooling the coating film to change the phase of the polymerizable liquid crystal compound into a smectic liquid crystal phase (smectic liquid crystal state); and

the polarizing film is formed by polymerizing the polymerizable liquid crystal compound while maintaining the smectic liquid crystal phase (smectic liquid crystal state).

The coating film of the polarizing film-forming composition can be formed, for example, by applying the polarizing film-forming composition to a substrate, an alignment film described later, or the like. In addition, the polarizing plate of the present invention may be directly coated with the composition for forming a polarizing film, for example, when the polarizing plate includes a retardation film.

The substrate is typically a transparent substrate. The substrate may not be provided on the display surface of the display element, and for example, in the case where a laminate obtained by removing the substrate from the polarizing film is provided on the display surface of the display element, the substrate may be opaque. The transparent substrate is a substrate having transparency which allows light, particularly visible light, to pass through, and the transparency is a characteristic that transmittance with respect to light having a wavelength of 380 to 780nm is 80% or more. Specific examples of the transparent substrate include a light-transmitting resin substrate. Examples of the resin constituting the light-transmitting resin substrate include polyolefins such as polyethylene and polypropylene; cyclic olefin resins such as norbornene polymers; polyvinyl alcohol; polyethylene terephthalate; polymethacrylates; a polyacrylate; cellulose esters such as triacetyl cellulose, diacetyl cellulose, and cellulose acetate propionate; polyethylene naphthalate; a polycarbonate; polysulfones; polyether sulfone; a polyether ketone; polyphenylene sulfide, polyphenylene ether, and the like. From the viewpoint of ease of obtaining and transparency, polyethylene terephthalate, polymethacrylate, cellulose ester, cycloolefin resin, or polycarbonate is preferable. Cellulose esters are products obtained by esterifying a part or all of the hydroxyl groups contained in cellulose, and are readily available on the market. In addition, cellulose ester substrates are also readily available from the market. Examples of commercially available cellulose ester substrates include "Fujitac Film" (Fujifilm Corporation); "KC 8UX 2M", "KC 8 UY", and "KC 4 UY" (Konica Minolta Opto Products Co., Ltd.), etc.

When the thickness of the substrate is too small, the strength tends to be lowered and the processability tends to be poor, and therefore, the thickness is usually 5 to 300. mu.m, preferably 20 to 200. mu.m, and more preferably 20 to 100. mu.m.

Examples of the method for applying the composition for forming a polarizing film to a substrate include known methods such as spin coating, extrusion, gravure coating, die coating, bar coating, coating methods such as applicator method, and printing methods such as flexo method.

Next, the coating film obtained from the polarizing film-forming composition is heated to a temperature equal to or higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound contained in the polarizing film-forming composition, and the polymerizable liquid crystal compound is phase-changed to a liquid phase while the solvent is dried and removed. Then, the temperature is decreased to change the phase of the polymerizable liquid crystal compound to a smectic phase (smectic liquid crystal state).

The heating temperature of the coating film may be appropriately determined in consideration of the polymerizable liquid crystal compound to be used, the material of the film such as a substrate on which the coating film is formed, and the like. In order to sufficiently remove the organic solvent and sufficiently bring the polymerizable liquid crystal compound into an isotropic state, the heating temperature is preferably higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound by 1 ℃ or more, more preferably 5 ℃ or more, and still more preferably 7 ℃ or more. The upper limit of the heating temperature is not particularly limited, but is preferably 150 ℃ or less, and more preferably 130 ℃ or less, in order to avoid damage to a coating film, a substrate, and the like by heating.

The heating time is suitably determined depending on the heating temperature, the type of the polymerizable liquid crystal compound used, the type of the organic solvent, the boiling point and the amount thereof, and the like, and is usually 0.5 to 10 minutes, preferably 1 to 5 minutes.

The film-forming composition may further include a pre-drying step of appropriately removing the solvent from the coating film without polymerizing the polymerizable liquid crystal compound contained in the coating film, before heating to a temperature equal to or higher than the isotropic phase transition temperature of the polymerizable liquid crystal compound. By providing this drying step, the orientation of the polymerizable liquid crystal compound can be improved. Examples of the drying method include a natural drying method, a forced air drying method, a heat drying method, a reduced pressure drying method, and the like, and the drying temperature (heating temperature) in the drying step may be appropriately determined depending on the kind of the polymerizable liquid crystal compound used, the kind of the organic solvent, the boiling point, the amount thereof, and the like, and is usually 30 to 150 ℃, preferably 50 to 130 ℃ from the viewpoint of suppressing the precipitation of crystallites of the polymerizable liquid crystal compound. The drying time is suitably determined depending on the drying temperature, the kind of the organic solvent used, and the like, and is usually 0.1 to 5 minutes, preferably 0.1 to 3 minutes.

Next, in the dried coating film obtained by the above-mentioned heat drying, the polymerizable liquid crystal compound is polymerized while maintaining the smectic liquid crystal state of the polymerizable liquid crystal compound, whereby a cured film of the composition for forming a polarizing film can be formed as a polarizing film. The polymerization method is preferably a photopolymerization method. In photopolymerization, the light to be irradiated to the dried coating film may be appropriately selected depending on the kind of photopolymerization initiator contained in the dried coating film, the kind of polymerizable liquid crystal compound (particularly, the kind of polymerizable group contained in the polymerizable liquid crystal compound), and the amount thereof. Specific examples thereof include 1 or more kinds of light selected from the group consisting of visible light, ultraviolet light, infrared light, X-ray, α -ray, β -ray and γ -ray, and an active electron beam. Among them, ultraviolet light is preferable from the viewpoint that the progress of the polymerization reaction is easily controlled and an apparatus widely used in the art as a photopolymerization apparatus can be used, and it is preferable to select the kinds of the polymerizable liquid crystal compound and the photopolymerization initiator contained in the composition for forming a polarizing film in advance so that photopolymerization can be performed by ultraviolet light. In addition, during polymerization, the polymerization temperature may be controlled by irradiating with light while cooling the dried coating film by an appropriate cooling means. By employing such a cooling means, polymerization of the polymerizable liquid crystal compound is carried out at a relatively low temperature, and thus a polarizing film can be suitably formed even when a substrate having relatively low heat resistance is used as the substrate. In the photopolymerization, a patterned polarizing film can be obtained by masking, development, or the like.

Examples of the light source of the active energy ray include a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a xenon lamp, a halogen lamp, a carbon arc lamp, a tungsten lamp, a gallium lamp, an excimer laser, an LED light source emitting light having a wavelength range of 380 to 440nm, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, and a metal halide lamp.

The ultraviolet irradiation intensity is usually 10-3,000 mW/cm². The ultraviolet irradiation intensity is preferably an intensity in a wavelength region effective for activation of the photopolymerization initiator. The time for irradiating light is usually 0.1 second to 10 minutes, preferably 0.1 second to 5 minutes, more preferably 0.1 second to 3 minutes, and still more preferably 0.1 second to 1 minute. When the ultraviolet irradiation intensity is applied for 1 or more times, the cumulative light amount is 10 to 3,000mJ/cm²Preferably 50 to 2,000mJ/cm²More preferably 100 to 1,000mJ/cm²。

By photopolymerization, the polymerizable liquid crystal compound is polymerized while being kept in a liquid crystal state of a smectic phase, preferably a high-order smectic phase, to form a polarizing film. The polarizing film obtained by polymerizing the polymerizable liquid crystal compound while maintaining the liquid crystal state of the smectic phase has an advantage of higher polarizing performance than that of a conventional bulk-guest polarizing film, that is, a polarizing film formed from a liquid crystal state of the nematic phase, with the function of the dichroic dye. Further, there is an advantage that the film is superior in strength as compared with a film coated with only a dichroic dye or a lyotropic liquid crystal.

The thickness of the polarizing film can be selected as appropriate according to the display device to be used, and is preferably 0.5 to 10 μm, more preferably 1 to 5 μm, and still more preferably 1 to 3 μm.

The coating film of the composition for forming a polarizing film is preferably formed on an alignment film. The alignment film is a film having an alignment regulating force for aligning the liquid crystal of the polymerizable liquid crystal compound in a desired direction. The alignment film preferably has solvent resistance that does not dissolve in an organic solvent contained in the composition for forming a polarizing film, and heat resistance in heat treatment for removing the solvent and aligning the polymerizable liquid crystal compound. Examples of the alignment film include an alignment film containing an alignment polymer, a photo-alignment film formed from a composition containing a polymer capable of generating an alignment regulating force by light and a solvent, a groove alignment film having a concave-convex pattern and a plurality of grooves on the surface, and a stretched film stretched in the alignment direction, and the photo-alignment film is preferable from the viewpoint of being less likely to generate static electricity and foreign substances and having excellent quality as an optical film.

Examples of the orientation polymer include polyamides having an amide bond in the molecule, gelatins, polyimides having an imide bond in the molecule, and polyamic acids, polyvinyl alcohols, alkyl-modified polyvinyl alcohols, polyacrylamides, polyoxazoles, polyethyleneimines, polystyrenes, polyvinylpyrrolidones, polyacrylic acids, and polyacrylates as hydrolysates thereof. Among them, polyvinyl alcohol is preferable. The alignment polymer may be used alone or in combination of 2 or more.

The alignment film containing an alignment polymer can be generally obtained by: a method for producing a substrate having a structure in which a composition obtained by dissolving an oriented polymer in a solvent (hereinafter, sometimes referred to as "oriented polymer composition") is applied to a substrate and the solvent is removed; alternatively, the oriented polymer composition is applied to a substrate, the solvent is removed, and rubbing is performed (rubbing method). Examples of the solvent include the same solvents as those listed above as organic solvents usable in the composition for forming a polarizing film.

The concentration of the oriented polymer in the oriented polymer composition may be in a range in which the oriented polymer material can be completely dissolved in the solvent, and is preferably 0.1 to 20%, and more preferably about 0.1 to 10% in terms of solid content with respect to the solution.

As the alignment polymer composition, a commercially available alignment film material can be used as it is. Examples of commercially available alignment film materials include suniver (registered trademark, manufactured by nippon chemical industry corporation), OPTOMER (registered trademark, manufactured by JSR corporation), and the like.

The method of applying the oriented polymer composition to the substrate may be the same as the method exemplified as the method of applying the composition for forming a polarizing film to the substrate.

Examples of the method for removing the solvent contained in the oriented polymer composition include a natural drying method, a forced air drying method, a heat drying method, a reduced pressure drying method, and the like.

In order to impart an alignment regulating force to the alignment film, a rubbing treatment (rubbing method) may be performed as necessary.

Examples of the method for imparting orientation restriction by the rubbing method include: a method of bringing a rubbing roll, which is wound with a rubbing cloth and rotated, into contact with a film of an alignment polymer, which is formed on the surface of a base material by applying an alignment polymer composition to the base material and annealing the same.

The photo alignment film may be generally formed by: a composition containing a polymer or monomer having a photoreactive group and capable of generating an alignment regulating force by light and a solvent (hereinafter, also referred to as a "composition for forming a photoalignment film") is applied to a film such as a substrate to form a coating film, the solvent is dried and removed from the obtained coating film, and then the obtained dried coating film is irradiated with polarized ultraviolet rays. The photo-alignment film is more preferable in that the direction of alignment regulating force can be arbitrarily controlled by selecting the polarization direction of the irradiated polarized ultraviolet ray.

The photoreactive group refers to a group that generates liquid crystal alignment ability by light irradiation. Specifically, there may be mentioned groups which participate in photoreaction originating from liquid crystal aligning ability, such as orientation induction or isomerization reaction, dimerization reaction, photocrosslinking reaction, or photolysis reaction of molecules by light irradiation. Among them, a group participating in dimerization reaction or photocrosslinking reaction is preferable from the viewpoint of excellent orientation. As the photoreactive group, a group having an unsaturated bond, particularly a double bond is preferable, and a group having at least 1 selected from the group consisting of a carbon-carbon double bond (C ═ C bond), a carbon-nitrogen double bond (C ═ N bond), a nitrogen-nitrogen double bond (N ═ N bond), and a carbon-oxygen double bond (C ═ O bond) is particularly preferable.

Examples of the photoreactive group having a C ═ C bond include a vinyl group, a polyene group, a stilbene group, a stilbenazolyl group, a stilbazolium group, a chalcone group, and a cinnamoyl group. Examples of the photoreactive group having a C ═ N bond include groups having a structure of an aromatic schiff base, an aromatic hydrazone, or the like. Examples of the photoreactive group having an N ═ N bond include an azophenyl group, an azonaphthyl group, an aromatic heterocyclic azo group, a bisazo group, and a methyl groupA group having an azoxybenzene structure. Examples of the photoreactive group having a C ═ O bond include a benzophenone group, a coumarin group, an anthraquinone group, and a maleimide group. These groups may have substituents such as alkyl, alkoxy, aryl, allyloxy, cyano, alkoxycarbonyl, hydroxyl, sulfonic acid, and haloalkyl.

Among them, a photoreactive group participating in a photodimerization reaction is preferable, and cinnamoyl group and chalcone group are preferable in terms of a small amount of polarized light irradiation required for photo-alignment, easy obtainment of a photo-alignment film having excellent thermal stability and temporal stability. As the polymer having a photoreactive group, a polymer having a cinnamoyl group in which a terminal portion of a side chain of the polymer has a cinnamic acid structure is particularly preferable.

By applying the composition for forming a photo-alignment film on a substrate, a photo-alignment inducing layer can be formed on the substrate. The solvent contained in the composition includes the same solvents as those exemplified above as the organic solvent usable in the composition for forming a polarizing film, and can be appropriately selected depending on the solubility of the polymer or monomer having a photoreactive group.

The content of the polymer or monomer having a photoreactive group in the composition for forming a photo alignment layer may be appropriately determined according to the kind of the polymer or monomer and the thickness of the target photo alignment layer, and is preferably at least 0.2 mass%, and more preferably in the range of 0.3 to 10 mass% with respect to the total mass of the composition for forming a photo alignment layer. The composition for forming a photo-alignment film may contain a polymer material such as polyvinyl alcohol or polyimide, and a photosensitizer within a range that does not significantly impair the characteristics of the photo-alignment film.

As a method of applying the composition for forming a photo-alignment film to a substrate, the same method as that of applying the alignment composition to a substrate can be exemplified. Examples of the method for removing the solvent from the coated composition for forming the photo-alignment film include a natural drying method, a forced air drying method, a heat drying method, and a reduced pressure drying method.

The temperature for drying and removing the solvent may be suitably determined depending on the kind and amount of the solvent used, and is usually 30 to 150 ℃ and preferably 60 to 130 ℃. The time for drying and removing is usually 0.1 to 10 minutes, preferably 0.5 to 5 minutes.

The irradiation with polarized light may be performed by irradiating a product obtained by removing the solvent from the composition for forming a photo-alignment film applied to the substrate with polarized ultraviolet light, or by irradiating the product with polarized ultraviolet light from the substrate side and transmitting the polarized ultraviolet light. The polarized ultraviolet rays are particularly preferably substantially parallel light. The wavelength of the polarized ultraviolet ray to be irradiated may be a wavelength in a wavelength region where the photoreactive group of the polymer or monomer having the photoreactive group can absorb light energy. Specifically, ultraviolet rays having a wavelength of 250 to 400nm are particularly preferable. Examples of the light source used for the polarized light irradiation include a xenon lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, and ultraviolet laser such as KrF and ArF, and more preferably a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, and a metal halide lamp. Among these, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, and a metal halide lamp are preferable because the emission intensity of ultraviolet rays having a wavelength of 313nm is large. Polarized ultraviolet rays can be irradiated by irradiating light from the light source through an appropriate polarizing plate. As the polarizer, a polarizing filter, a polarizing prism of glan-thompson, glan-taylor, or the like, a wire grid type polarizer may be used.

In the case of rubbing or polarized light irradiation, a plurality of regions (patterns) having different liquid crystal alignment directions may be formed by masking.

The groove (groove) alignment film is a film having a concave-convex pattern or a plurality of grooves (grooves) on the film surface. When a polymerizable liquid crystal compound is applied to a film having a plurality of linear grooves arranged at equal intervals, liquid crystal molecules are aligned in a direction along the grooves.

As a method for obtaining a trench alignment film, the following methods can be mentioned: a method of forming a concave-convex pattern by exposing the surface of a photosensitive polyimide film through an exposure mask having a slit with a pattern shape, and then performing development and rinsing; a method of forming a layer of a UV curable resin before curing on a plate-like original plate having grooves on the surface thereof, transferring the formed resin layer to a substrate, and then curing the same; a method of pressing a roll-shaped original plate having a plurality of grooves against a film of a UV-curable resin before curing, which is formed on a base material, to form irregularities, and then curing the irregularities; and so on.

The thickness of the alignment film (alignment film or photo-alignment film containing an alignment polymer) is usually in the range of 10 to 10000nm, preferably 10 to 1000nm, more preferably 500nm or less, still more preferably 10 to 200nm, and particularly preferably 50 to 150 nm.

The thickness of the polarizing plate of the present invention is preferably 10 to 300 μm, more preferably 20 to 200 μm, and still more preferably 25 to 100 μm from the viewpoint of flexibility and visibility of the display device.

The polarizing film and the polarizing plate of the present invention are excellent in polarizing performance, and therefore, can be suitably used for various display devices. The display device is a device having a display mechanism, and includes a light emitting element or a light emitting device as a light emitting source. Examples of the display device include a liquid crystal display device, an organic Electroluminescence (EL) display device, an inorganic Electroluminescence (EL) display device, a touch panel display device, an electron emission display device (a field emission display device (FED), a surface conduction field emission display device (SED)), electronic paper (a display device using electronic ink or an electrophoretic element, a plasma display device, a projection display device (for example, a Grating Light Valve (GLV) display device, a display device having a Digital Micromirror Device (DMD), or the like), a piezoelectric ceramic display, or the like, and particularly, an organic EL display device and a touch panel display device are preferable, and a display device including the polarizing plate of the present invention can be obtained by bonding the polarizing plate of the present invention to the surface of the display device through an adhesive or a bonding agent.