JP7506642B2 - Composite polarizing plate and liquid crystal display device - Google Patents

Description

The present invention relates to a composite polarizing plate and a liquid crystal display device using the same.

Optical films such as polarizing plates and retardation plates are used in flat panel displays (FPDs). As such polarizing plates, iodine PVA polarizing plates are widely used, which are made of a polarizer in which a dichroic dye such as iodine is oriented and adsorbed on a polyvinyl alcohol-based resin film and a protective film. In addition, Patent Document 1 discloses a reflective polarizing plate having a multilayer structure of polymer materials with different in-plane birefringence obtained by extrusion and stretching.
It is known that by disposing this reflective polarizing plate between the panel of a liquid crystal display device (LCD) and the rear backlight, the light utilization efficiency can be improved and black display can be achieved.
However, this reflective polarizing plate does not have sufficient polarizing performance, and cannot achieve clear black display on an LCD by itself. Therefore, as shown in Patent Document 2, it is disclosed that the transmission axis of this reflective polarizing plate is aligned with the transmission axis of an iodine PVA polarizing plate arranged on the back surface of an LCD panel, and the reflective polarizing plate is used in combination with the iodine PVA polarizing plate.

JP 9-506985 A Japanese Patent Application Laid-Open No. 11-160699

However, iodine PVA polarizing plates are thick and require an adhesive layer to be laminated to the reflective polarizing plate, which creates issues with the thickness and makes it difficult to say that the polarizing performance is sufficient.

The present invention provides a composite polarizing plate having improved polarizing performance by combining an absorptive polarizing plate and a reflective polarizing plate, the thickness of which can be reduced.
The present invention includes the following inventions [1] to [12].
[1] A composite polarizing plate having an absorptive polarizing film, an alignment film for orienting the absorptive polarizing film, and a reflective polarizing plate, in which the angle between the reflection axis of the reflective polarizing film and the absorption axis of the absorptive polarizing film is 8° or less.
[2] The composite polarizing plate according to [1], wherein the absorptive polarizing film is a polymer of a polymerizable liquid crystal compound, contains a dichroic dye, and has a thickness of 5 μm or less.
[3] The composite polarizing plate according to [1] or [2], wherein the alignment film is a photo-alignment film that generates an alignment control force by light.
[4] The composite polarizing plate according to any one of [1] to [3], wherein the polymerizable liquid crystal compound is a thermotropic liquid crystal compound.
[5] The composite polarizing plate according to any one of [1] to [4], wherein the ratio of the dichroic dye in the polymer of the polymerizable liquid crystal compound is 20 parts by mass or less per 100 parts by mass of the polymerizable liquid crystal compound.
[6] The composite polarizing plate according to any one of [1] to [5], wherein the absorptive polarizing film is a polymer of a polymerizable liquid crystal compound that is fixed in a smectic liquid crystal phase and aligned in the in-plane horizontal direction.
[7] The composite polarizing plate according to any one of [1] to [6], wherein the absorptive polarizing film is a polarizing film having a Bragg peak in X-ray diffraction measurement.
[8] The composite polarizing plate according to any one of [1] to [7], wherein the reflective polarizing plate is a multilayer laminate of at least two or more polymeric materials having different refractive indices.
[9] The composite polarizing plate according to any one of [1] to [8], which is rectangular and has a transmission axis in the long side direction.
[10] A roll-shaped composite polarizing plate, in which the reflection axis of the reflective polarizing plate is oriented in an in-plane direction of 90°±8° relative to the roll transport direction, the absorption axis of the absorptive polarizing film is oriented in an in-plane direction of 90°±8° relative to the roll transport direction, and the angle between the reflection axis of the reflective polarizing plate and the absorption axis of the absorptive polarizing film is 8° or less.
[11] A method for producing a roll-shaped composite polarizing plate, comprising the following steps 1 to 7:
Step 1: A step of continuously coating a composition containing a polymer that generates an alignment control force by light and a solvent on a surface of the rolled reflective polarizing plate while unwinding the rolled reflective polarizing plate to form a first coating film;
Step 2: A step of heating and drying the first coating film to form a first dried film;
Step 3: Irradiating the first dry film with polarized ultraviolet light to form an alignment film;
Step 4: A step of forming a second coating film by coating a composition containing a dichroic dye, a polymerizable liquid crystal compound, a polymerization initiator, and a solvent on the alignment film;
Step 5: A step of heating and drying the second coating film to form a second dried film;
Step 6: A step of irradiating the second dry film with ultraviolet light to polymerize the polymerizable liquid crystal compound to form an absorptive polarizing film and form a composite polarizing plate. Step 7: A step of winding up the composite polarizing plate on a roll.
[12] A liquid crystal display device in which the composite polarizing plate according to any one of [1] to [9] is disposed between a backlight unit and a liquid crystal cell, with the reflective polarizing plate surface being disposed on the backlight unit side and the absorptive polarizing film surface being disposed on the liquid crystal cell side.

The present invention provides a thin composite polarizing plate and a liquid crystal display device using the same.

The composite polarizing plate of the present invention has an absorptive polarizing film, an alignment film for orienting the absorptive polarizing film, and a reflective polarizing plate, in which the angle between the reflection axis of the reflective polarizing plate and the absorption axis of the absorptive polarizing film is 8° or less.
The present invention will now be described.
[Absorptive polarizing film]
The absorptive polarizing film of the present invention will be described. The absorptive polarizing film of the present invention may contain a dichroic dye. There are no particular limitations on the absorptive polarizing film as long as it contains a dichroic dye.

[Dichroic dye]
The dichroic dye is a dye having different absorbance in the long axis direction and in the short axis direction of the molecule. The dichroic dye preferably has a property of absorbing visible light, and more preferably has a maximum absorption wavelength (λMAX) in the range of 380 to 680 nm.
Examples of such dichroic dyes include acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes, and anthraquinone dyes, among which azo dyes are preferred. Examples of azo dyes include monoazo dyes, bisazo dyes, trisazo dyes, tetrakisazo dyes, and stilbene azo dyes, among which bisazo dyes and trisazo dyes are preferred. The dichroic dyes may be used alone or in combination, but in order to obtain absorption over the entire visible light range, it is preferred to combine three or more dichroic dyes, and more preferred to combine three or more azo dyes.
Examples of the azo dye include a compound represented by formula (I) (hereinafter, sometimes referred to as "compound (I)").
T ¹ -A ¹ (-N=N-A ² ) _p -N=N-A ³ -T ² (I)
[In formula (I),
A ¹ , A ² and A ³ each independently represent a 1,4-phenylene group which may have a substituent, a naphthalene-1,4-diyl group or a divalent heterocyclic group which may have a substituent, and T ¹ and T ^{2 each} represent an electron-withdrawing group or an electron-releasing group, and are located at a position substantially at 180° with respect to the azo bond plane. p represents an integer of 0 to 4. When p is 2 or more, each A ² may be the same or different from each other. The -N=N- bond may be replaced with a -C=C-, -COO-, -NHCO- or -N=CH- bond within the range showing absorption in the visible range.]

In A ¹ , A ² , and A ³ , the 1,4-phenylene group, the naphthalene-1,4-diyl group, and the divalent heterocyclic group may have any of the following substituents: alkyl groups having 1 to 4 carbon atoms, such as methyl, ethyl, and butyl groups; alkoxy groups having 1 to 4 carbon atoms, such as methoxy, ethoxy, and butoxy groups; fluorinated alkyl groups having 1 to 4 carbon atoms, such as trifluoromethyl groups; cyano groups; nitro groups; halogen atoms, such as chlorine and fluorine atoms; substituted or unsubstituted amino groups, such as amino groups, diethylamino groups, and pyrrolidino groups (a substituted amino group means an amino group having one or two alkyl groups having 1 to 6 carbon atoms, or an amino group in which two substituted alkyl groups are bonded to each other to form an alkanediyl group having 2 to 8 carbon atoms. An unsubstituted amino group is -NH _2. ). Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, and a hexyl group. Examples of the alkanediyl group having 2 to 8 carbon atoms include an ethylene group, a propane-1,3-diyl group, a butane-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, and an octane-1,8-diyl group. In order to be included in a highly ordered liquid crystal structure such as a smectic liquid crystal, A ¹ , A ² , and A ³ are preferably unsubstituted 1,4-phenylene groups or divalent heterocyclic groups in which hydrogen is substituted with a methyl group or a methoxy group, and p is preferably 0 or 1. Of these, it is more preferable that p is 1 and at least two of the three structures A ¹ , A ² , and A ³ are 1,4-phenylene groups in terms of both ease of molecular synthesis and high performance.

Examples of the divalent heterocyclic group include groups obtained by removing two hydrogen atoms from quinoline, thiazole, benzothiazole, thienothiazole, imidazole, benzimidazole, oxazole, and benzoxazole. When ^A2 is a divalent heterocyclic group, a structure in which the molecular bond angle is substantially 180° is preferred, and specifically, a benzothiazole, benzimidazole, or benzoxazole structure in which two five-membered rings are condensed is more preferred.

^T1 and ^T2 are preferably electron-withdrawing groups or electron-releasing groups, and have different structures, and more preferably ^T1 is an electron-withdrawing group and ^T2 is an electron-releasing group, or ^T1 is an electron-releasing group and ^T2 is an electron-withdrawing group. Specifically, ^T1 and ^T2 are each independently an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group, a nitro group, an amino group having one or two alkyl groups having 1 to 6 carbon atoms, or an amino group in which two substituted alkyl groups are bonded to each other to form an alkanediyl group having 2 to 8 carbon atoms, specifically, a pyrrolidinyl group, a piperidinyl group, or the like, or a trifluoromethyl group. Among these, in order to be included in a highly ordered liquid crystal structure such as a smectic liquid crystal, it is necessary for the excluded volume of the molecule to be a smaller structure, and therefore, it is preferable to use an alkoxy group having 1 to 4 carbon atoms. Preferred are an amino group having one or two alkyl groups having 1 to 6 carbon atoms, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a cyano group, an amino group having one or two alkyl groups having 1 to 6 carbon atoms, specifically, a di(mono)methylamino group, a di(mono)ethylamino group, a di(mono)propylamino group, a di(mono)butylamino group, a di(mono)pentylamino group, a di(mono)hexylamino group, a methylethylamino group, a methylethylamino group, a methylbutylamino group, or an amino group in which two substituted alkyl groups are bonded to each other to form an alkanediyl group having 2 to 8 carbon atoms.

Examples of such azo dyes include:

In formulas (2-1) to (2-6),
B ¹ to B ²⁰ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a cyano group, a nitro group, a substituted or unsubstituted amino group (the definitions of a substituted amino group and an unsubstituted amino group are as defined above), a chlorine atom, or a trifluoromethyl group.
Each of n1 to n4 independently represents an integer of 0 to 3. From the viewpoint of obtaining high polarizing performance, B ² , B ⁶ , B ⁹ , B ¹⁴ , B ¹⁸ and B ¹⁹ are preferably a hydrogen atom or a methyl group, more preferably a hydrogen atom.
When n1 is 2 or more, each of the multiple ^B2's may be the same or different;
When n2 is 2 or more, each of the multiple ^B6s may be the same or different;
When n3 is 2 or more, each of the multiple ^B9s may be the same or different;
When n4 is 2 or more, each of the multiple B ¹⁴ 's may be the same or different.

The anthraquinone dye is preferably a compound represented by formula (2-7).

[In formula (2-7),
R ¹ to R ⁸ each independently represent a hydrogen atom, -R ^x , -NH ₂ , -NHR ^x , -NR ^x ₂ , -SR ^x or a halogen atom.
R ^x represents an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 12 carbon atoms.

The oxazine dye is preferably a compound represented by formula (2-8).

[In formula (2-8),
R ⁹ to R ¹⁵ each independently represent a hydrogen atom, —R ^x , —NH ₂ , —NHR ^x , —NR ^x ₂ , —SR ^x or a halogen atom.
R ^x represents an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 12 carbon atoms.

The acridine dye is preferably a compound represented by formula (2-9).

[In formula (2-9),
R ¹⁶ to R ²³ each independently represent a hydrogen atom, —R ^x , —NH ₂ , —NHR ^x , —NR ^x ₂ , —SR ^x or a halogen atom.
R ^x represents an alkyl group having 1 to 4 carbon atoms or an aryl group having 6 to 12 carbon atoms.

In the formulas (2-7), (2-8), and (2-9), examples of the alkyl group having 1 to 4 carbon atoms represented by R ^x include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group, and examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a toluyl group, a xylyl group, and a naphthyl group.

As the cyanine dye, a compound represented by formula (2-10) and a compound represented by formula (2-11) are preferred.

[In formula (2-10),
^D1 and ^D2 each independently represent a group represented by any one of formulas (2-10a) to (2-10d).

ｎ５は１～３の整数を表す。］

n5 represents an integer of 1 to 3.

[In formula (2-11),
^D3 and ^D4 each independently represent a group represented by any one of formulas (2-11a) to (2-11h).

ｎ６は１～３の整数を表す。］

n6 represents an integer of 1 to 3.

When used together with a polymerizable liquid crystal compound described later, the content of the dichroic dye (the total amount when multiple types are included) is usually 20 parts by mass or less, preferably 0.1 to 20 parts by mass, more preferably 1 to 20 parts by mass, and even more preferably 3 to 15 parts by mass, per 100 parts by mass of the polymerizable liquid crystal compound, from the viewpoint of obtaining good light absorption characteristics. If the content of the dichroic dye is less than this range, light absorption will be insufficient and sufficient polarization performance will not be obtained, and if the content is more than this range, the alignment may decrease.

[Polymerizable Liquid Crystal]
The absorptive polarizing film of the present invention may contain a polymerizable liquid crystal in addition to the dichroic dye. The polymerizable liquid crystal is a compound having a polymerizable group and having liquid crystal properties (hereinafter, also referred to as a polymerizable liquid crystal compound). The polymerizable group means a group involved in a polymerization reaction, and is preferably a photopolymerizable group. Here, the photopolymerizable group means a group that can be involved in a polymerization reaction by an active radical or an acid generated from a photopolymerization initiator described later.
Examples of the polymerizable group include a vinyl group, a vinyloxy group, a 1-chlorovinyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxiranyl group, and an oxetanyl group. Among these, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxiranyl group, and an oxetanyl group are preferred, and an acryloyloxy group is more preferred. The liquid crystallinity may be thermotropic or lyotropic, but when mixed with a dichroic dye described below, a thermotropic liquid crystal is preferred.

When the polymerizable liquid crystal is a thermotropic liquid crystal, it may be a thermotropic liquid crystal compound exhibiting a nematic liquid crystal phase, or a thermotropic liquid crystal compound exhibiting a smectic liquid crystal phase. When the polymerizable liquid crystal compound exhibits a polarizing function as a cured film by polymerization reaction, the liquid crystal state exhibited by the polymerizable liquid crystal compound is preferably a smectic phase, and a high-order smectic phase is more preferable from the viewpoint of high performance. Among them, a high-order smectic liquid crystal compound forming 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 or a smectic L phase is more preferable, and a high-order smectic liquid crystal compound forming a smectic B phase, a smectic F phase or a smectic I phase is even more preferable. When the liquid crystal phase formed by the polymerizable liquid crystal is one of these high-order smectic phases, a polarizing film with higher polarizing performance can be manufactured. Furthermore, such a polarizing film having high polarizing performance has Bragg peaks derived from a higher-order structure such as a hexatic phase or a crystalline phase in X-ray diffraction measurement.
The Bragg peak is a peak derived from the periodic structure of molecular orientation, and a film can be obtained whose periodic interval is 3 to 6 Å. It is preferable that the polarizing film of the present invention contains a polymer of the polymerizable liquid crystal polymerized in a smectic phase state, from the viewpoint of obtaining higher polarization characteristics.

Specific examples of such compounds include the compound represented by the following formula (A) (hereinafter, sometimes referred to as compound (A)). The polymerizable liquid crystal may be used alone or in combination of two or more types.

U ¹ -V ¹ -W ¹ -X ¹ -Y ¹ -X ² -Y ² -X ³ -W ² -V ² -U ² (A) [In formula (A),
X ¹ , X ² and X ³ each independently represent a divalent aromatic group or a divalent alicyclic hydrocarbon group, wherein a hydrogen atom contained in the divalent aromatic group or the divalent alicyclic hydrocarbon group 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 divalent aromatic group or the divalent alicyclic hydrocarbon group may be substituted with an oxygen atom, a sulfur atom or a nitrogen atom, provided that at least one of X ¹ , X ² and X ³ is a 1,4-phenylene group which may have a substituent or a cyclohexane-1,4-diyl group which may have a substituent.
Y ¹ , Y ² , W ¹ and W ² are each independently a single bond or a divalent linking group.
V ¹ and V ² each independently represent an alkanediyl group having 1 to 20 carbon atoms which may have a substituent, and -CH ₂ - constituting the alkanediyl group may be replaced by -O-, -S- or NH-.
U ¹ and U ² each independently represent a polymerizable group or a hydrogen atom, and at least one of them is a polymerizable group.

In compound (A), at least one of X ¹ , X ² and X ³ is a 1,4-phenylene group which may have a substituent, or a cyclohexane-1,4-diyl group which may have a substituent. In particular, X ¹ and X ³ are preferably a cyclohexane-1,4-diyl group which may have a substituent, and the cyclohexane-1,4-diyl group is more preferably a trans-cyclohexane-1,4-diyl group. When the compound contains a trans-cyclohexane-1,4-diyl group structure, smectic liquid crystallinity tends to be easily exhibited. In addition, examples of the optional substituents of the 1,4-phenylene group which may have a substituent or the cyclohexane-1,4-diyl group which may have a substituent include alkyl groups having 1 to 4 carbon atoms such as a methyl group, an ethyl group and a butyl group, a cyano group and halogen atoms such as a chlorine atom and a fluorine atom, but are preferably unsubstituted.

Y ¹ and Y ² are each preferably independently a single bond, -CH ₂ CH ₂ -, -CH ₂ O-, -COO-, -OCO-, -N=N-, -CR ^a ≡CR ^b -, -C≡C- or CR ^a ≡N-, and R ^a and R ^b are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Y ¹ and Y ² are more preferably -CH ₂ CH ₂ -, -COO-, -OCO- or a single bond, and when none of X ¹ , X ² and X ³ contains a cyclohexane-1,4-diyl group, it is more preferable that Y ¹ and Y ² are bonded in a different manner from each other. When Y ¹ and Y ² are bonded in a different manner from each other, smectic liquid crystallinity tends to be easily exhibited.

W ¹ and W ² are preferably each independently a single bond, —O—, —S—, —COO— or —OCO—, and more preferably each independently a single bond or —O—.

Examples of the alkanediyl group having 1 to 20 carbon atoms represented by V ¹ and V ² include a methylene group, an ethylene group, a propane-1,3-diyl group, a butane-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 icosane-1,20-diyl group. V ¹ and V ² are preferably alkanediyl groups having 2 to 12 carbon atoms, and more preferably linear alkanediyl groups having 6 to 12 carbon atoms. By using a linear alkanediyl group having 6 to 12 carbon atoms, crystallinity is improved and smectic liquid crystallinity tends to be easily expressed.
Examples of the substituent that the optionally substituted alkanediyl group having 1 to 20 carbon atoms may have include a cyano group and a halogen atom such as a chlorine atom or a fluorine atom. The alkanediyl group is preferably unsubstituted, and more preferably an unsubstituted and linear alkanediyl group.

Preferably, U ¹ and U ² are both polymerizable groups, and more preferably, both are photopolymerizable groups. A polymerizable liquid crystal compound having a photopolymerizable group can be polymerized under a lower temperature condition than a thermally polymerizable group, and is therefore advantageous in that the liquid crystal can form a polymer in a state of higher order.

The polymerizable groups represented by ^U1 and ^U2 may be different from each other, but are preferably the same. Examples of the polymerizable group include a vinyl group, a vinyloxy group, a 1-chlorovinyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxiranyl group, and an oxetanyl group. Among these, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxiranyl group, and an oxetanyl group are preferred, and a methacryloyloxy group and an acryloyloxy group are more preferred.

Examples of such polymerizable liquid crystal compounds include the following:

Among the above-listed compounds, at least one selected from the group consisting of compounds represented by formula (1-2), formula (1-3), formula (1-4), formula (1-6), formula (1-7), formula (1-8), formula (1-13), formula (1-14) and formula (1-15) is preferred.

The exemplified compounds (A) can be used alone or in combination in the polarizing film. When two or more types of polymerizable liquid crystals are combined, it is preferable that at least one of them is compound (A), and it is more preferable that two or more types are compound (A). By combining two or more types of polymerizable liquid crystals, it may be possible to temporarily maintain liquid crystallinity even at temperatures below the liquid crystal-crystal phase transition temperature. When combining two types of polymerizable liquid crystals, the mixing ratio is usually 1:99 to 50:50, preferably 5:95 to 50:50, and more preferably 10:90 to 50:50.

Compound (A) is produced by a known method, for example, as described in Lub et al. Recl. Trav. Chim. Pays-Bas, 115, 321-328 (1996) or Japanese Patent No. 4719156.

The content of the polymerizable liquid crystal in the polarizing film is usually 50 to 99.5 parts by mass, preferably 60 to 99 parts by mass, more preferably 70 to 98 parts by mass, and even more preferably 80 to 97 parts by mass, per 100 parts by mass of the solid content of the polarizing film. If the content of the polymerizable liquid crystal is within the above range, the orientation tends to be high. Here, the solid content refers to the total amount of components excluding the solvent from the composition for forming a polarizing film.

[solvent]
The composition for forming an absorptive polarizing film may contain a solvent. Since a polymerizable liquid crystal compound generally has a high viscosity, dissolving the composition for forming a polarizing film in a solvent often facilitates application, and as a result, facilitates the formation of a polarizing film. The solvent is preferably one that can completely dissolve the polymerizable liquid crystal compound, and is preferably a solvent that is inactive to the polymerization reaction of the polymerizable liquid crystal compound.

Examples of the solvent include alcohol solvents such as methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone or propylene glycol methyl ether acetate, and ethyl lactate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, and methyl isobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; aromatic hydrocarbon solvents such as toluene and xylene, and nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; and amide solvents such as dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone. These solvents may be used alone or in combination of two or more.

The content of the solvent is preferably 50 to 98% by mass relative to the total amount of the composition for forming an absorptive polarizing film. In other words, the content of the solid content in the composition for forming an absorptive polarizing film is preferably 2 to 50% by mass. If the content of the solid content is 50% by mass or less, the viscosity of the composition for forming an absorptive polarizing film is low, and the thickness of the polarizing film becomes approximately uniform, so that unevenness tends to be less likely to occur in the polarizing film. In addition, the content of the solid content can be determined in consideration of the thickness of the polarizing film to be manufactured.

[Leveling agent]
The composition for forming an absorptive polarizing film may contain a leveling agent, which is an additive that adjusts the fluidity of the composition and makes the film obtained by applying the composition flatter, and examples of such leveling agents include organic modified silicone oil-based, polyacrylate-based and perfluoroalkyl-based leveling agents. Specifically, DC3PA, SH7PA, DC11PA, SH28PA, SH29PA, SH30PA, ST80PA, ST86PA, SH8400, SH8700, FZ2123 (all manufactured by Dow Corning Toray Co., Ltd.), KP321, KP323, KP324, KP326, KP340, KP341, X22-161A, KF6001 (all manufactured by Shin-Etsu Chemical Co., Ltd.), TSF400, TSF401, TSF410, TSF4300, TSF4440, TSF4445, TSF-4446, TSF4452, TSF4460 (all manufactured by Momentive Performance Materials, Inc.) Japan LLC), Fluorinert (registered trademark) FC-72, FC-40, FC-43, FC-3283 (all manufactured by Sumitomo 3M Limited), Megafac (registered trademark) R-08, R-30, R-90, F-410, F-411, F-443, F-445, F-470, F-477, F-479, F-482, F-483, F-554, F-556 (all manufactured by DIC Corporation), F-top (trade name) EF301, EF303, EF351, EF352 (all manufactured by Mitsubishi Materials Electronics Co., Ltd.), Surflon (registered trademark) S-381, S-382, S-383, S-393, SC-101, SC-105, KH-40, SA-100 (all manufactured by AGC Seimi Chemical Co., Ltd.), trade names E1830, E5844 (manufactured by Daikin Fine Chemical Research Institute Co., Ltd.), BM-1000, BM-1100, BYK-352, BYK-353 and BYK-361N (all trade names: manufactured by BM Chemie Co., Ltd.), etc. Among them, polyacrylate-based leveling agents and perfluoroalkyl-based leveling agents are preferred.

When the composition for forming an absorptive polarizing film contains a leveling agent, the amount is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 5 parts by mass, and even more preferably 0.1 to 3 parts by mass, relative to 100 parts by mass of the polymerizable liquid crystal. When the amount of the leveling agent is within the above range, the polymerizable liquid crystal is easily aligned horizontally, and the resulting polarizing film tends to be smoother. When the amount of the leveling agent relative to the polymerizable liquid crystal exceeds the above range, the resulting polarizing film tends to be uneven. The composition for forming an absorptive polarizing film may contain two or more types of leveling agents.

[Polymerization initiator]
The composition for forming an absorptive polarizing film may contain a polymerization initiator. The polymerization initiator is a compound capable of initiating a polymerization reaction of a polymerizable liquid crystal or the like. As the polymerization initiator, a photopolymerization initiator that generates active radicals by the action of light is preferable from the viewpoint of not depending on the phase state of the thermotropic liquid crystal.

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

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

Examples of benzophenone compounds include benzophenone, o-benzoylmethylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone, and 2,4,6-trimethylbenzophenone.

Examples of alkylphenone compounds include diethoxyacetophenone, 2-methyl-2-morpholino-1-(4-methylthiophenyl)propan-1-one, 2-benzyl-2-dimethylamino-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-hydroxycyclohexyl phenyl ketone, and oligomers of 2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propan-1-one.

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

Examples of triazine compounds 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, and 2,4-bis(trichloromethyl)-6-[2-(5-methylfuran-2-yl)ethenyl ]-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(furan-2-yl)ethenyl]-1,3,5-triazine, 2,4-bis(trichloromethyl)-6-[2-(4-diethylamino-2-methylphenyl)ethenyl]-1,3,5-triazine, and 2,4-bis(trichloromethyl)-6-[2-(3,4-dimethoxyphenyl)ethenyl]-1,3,5-triazine.

Commercially available polymerization initiators can be used. Commercially available polymerization initiators include Irgacure (registered trademark) 907, 184, 651, 819, 250, and 369, 379, 127, 754, OXE01, OXE02, and OXE03 (manufactured by Chiba Specialty Chemicals Co., Ltd.); Seikuol (registered trademark) BZ, Z, and BEE (manufactured by Seiko Chemical Co., Ltd.); and Kayacure (registered trademark) BP1. 00, and UVI-6992 (manufactured by The Dow Chemical Company); ADEKA OPTOMER SP-152, N-1717, N-1919, SP-170, ADEKA ARCLES NCI-831, ADEKA ARCLES NCI-930 (manufactured by ADEKA Corporation); TAZ-A, and TAZ-PP (manufactured by Nippon SiberHegner Co., Ltd.); and TAZ-104 (manufactured by Sanwa Chemical Co., Ltd.). The polymerization initiator in the composition for forming a polarizing film may be one type, or two or more types of polymerization initiators may be mixed together according to the light source.

The content of the polymerization initiator in the composition for forming an absorptive polarizing film can be adjusted as appropriate depending on the type and amount of the polymerizable liquid crystal, but is usually 0.1 to 30 parts by mass, preferably 0.5 to 10 parts by mass, and more preferably 0.5 to 8 parts by mass, per 100 parts by mass of the polymerizable liquid crystal. When the content of the polymerization initiator is within the above range, polymerization can be carried out without disturbing the orientation of the polymerizable liquid crystal.

[Sensitizer]
The composition for forming an absorptive polarizing film may contain a sensitizer. The sensitizer is preferably a photosensitizer. Examples of the sensitizer include xanthone compounds such as xanthone and thioxanthone (e.g., 2,4-diethylthioxanthone, 2-isopropylthioxanthone, etc.); anthracene compounds such as anthracene and an alkoxy group-containing anthracene (e.g., dibutoxyanthracene, etc.); phenothiazine, rubrene, etc.

When the composition for forming an absorptive polarizing film contains a sensitizer, the polymerization reaction of the polymerizable liquid crystal contained in the composition for forming an absorptive polarizing film can be further promoted. The amount of such a sensitizer used is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and even more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the polymerizable liquid crystal content.

[Polymerization inhibitor]
In order to stably proceed with the polymerization reaction, the composition for forming an absorptive polarizing film may contain a polymerization inhibitor, which can control the degree of progress of the polymerization reaction of the polymerizable liquid crystal.

The polymerization inhibitors include radical scavengers such as hydroquinone, alkoxy group-containing hydroquinone, alkoxy group-containing catechol (e.g., butylcatechol, etc.), pyrogallol, and 2,2,6,6-tetramethyl-1-piperidinyloxy radical; thiophenols; β-naphthylamines, and β-naphthols.

When the composition for forming an absorptive polarizing film contains a polymerization inhibitor, the content of the polymerization inhibitor is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and even more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the polymerizable liquid crystal. When the content of the polymerization inhibitor is within the above range, polymerization can be carried out without disturbing the alignment of the polymerizable liquid crystal.

<Manufacturing method of absorption type polarizing film>
The absorptive polarizing film of the present invention can be produced by applying a composition for forming an absorptive polarizing film onto a substrate and an alignment film.
<Coating of the composition for forming an absorptive polarizing film>
Examples of the method for applying the composition for forming an absorptive polarizing film on a substrate or an alignment film include an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a CAP coating method, a slit coating method, a microgravure method, a die coating method, and an inkjet method. Examples of the method for applying the composition using a coater such as a dip coater, a bar coater, or a spin coater are also included. Among these, when applying the composition continuously in a roll-to-roll manner, the application method using the microgravure method, the inkjet method, the slit coating method, or the die coating method is preferred, and when applying the composition to a sheet-like substrate such as glass, the spin coating method, which has high uniformity, is preferred. When applying the composition in a roll-to-roll manner, the composition for forming an absorptive polarizing film can also be continuously applied on the alignment film obtained by applying the composition for forming an alignment film to a substrate to form an alignment film.

<Drying of the composition for forming an absorptive polarizing film>
Examples of drying methods for removing the solvent contained in the composition for forming an absorptive polarizing film include natural drying, ventilation drying, heat drying, reduced pressure drying, and combinations of these. Of these, natural drying or heat drying is preferred. The drying temperature is preferably in the range of 0 to 200°C, more preferably in the range of 20 to 150°C, and even more preferably in the range of 50 to 130°C. The drying time is preferably 10 seconds to 10 minutes, and more preferably 30 seconds to 5 minutes. The composition for forming an alignment film and the alignment polymer composition can also be dried in the same manner.

<Polymerization of polymerizable liquid crystal compound>
Photopolymerization is preferred as a method for polymerizing the polymerizable liquid crystal compound. Photopolymerization is performed by irradiating an active energy ray to a laminate in which an optically anisotropic layer-forming composition containing a polymerizable liquid crystal compound is applied on a substrate or an alignment film. The active energy ray to be irradiated is appropriately selected according to the type of polymerizable liquid crystal compound contained in the dried coating (particularly, the type of photopolymerizable functional group possessed by the polymerizable liquid crystal compound), the type of photopolymerization initiator when a photopolymerization initiator is contained, and the amount thereof. Specifically, one or more types of light selected from the group consisting of visible light, ultraviolet light, infrared light, X-rays, α-rays, β-rays, and γ-rays can be mentioned. Among them, ultraviolet light is preferred in that the progress of the polymerization reaction is easily controlled and that photopolymerization devices widely used in this field can be used, and it is preferable to select the type of polymerizable liquid crystal compound so that it can be photopolymerized by ultraviolet light.

Examples of light sources for the active energy rays include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, xenon lamps, halogen lamps, carbon arc lamps, tungsten lamps, gallium lamps, excimer lasers, LED light sources emitting light in the wavelength range of 380 to 440 nm, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps.

The ultraviolet irradiation intensity is usually 10 mW/cm ² to 3,000 mW/cm ^2. The ultraviolet irradiation intensity is preferably an intensity in a wavelength region effective for activating a cationic polymerization initiator or a radical polymerization initiator. The time for irradiating light is usually 0.1 seconds to 10 minutes, preferably 0.1 seconds to 5 minutes, more preferably 0.1 seconds to 3 minutes, and even more preferably 0.1 seconds to 1 minute. When irradiating once or a plurality of times with such ultraviolet irradiation intensity, the accumulated light amount is usually 10 mJ/cm ² to 3,000 mJ/cm ² , preferably 50 mJ/cm ² to 2,000 mJ/cm ² , and more preferably 100 mJ/cm ² to 1,000 mJ/cm ^2. When the accumulated light amount is less than this range, the polymerizable liquid crystal compound may not be sufficiently cured, and good transferability may not be obtained. Conversely, when the accumulated light amount is more than this range, the performance of the polarizing film may be deteriorated.

[Base material]
The substrate may be a glass substrate or a film substrate, preferably a film substrate, more preferably a long rolled film in terms of being continuously manufactured.The resin constituting the film substrate may be a polyolefin such as polyethylene, polypropylene, or norbornene-based polymer; a cyclic olefin-based resin; polyvinyl alcohol; polyethylene terephthalate; polymethacrylic acid ester; polyacrylic acid ester; cellulose ester such as triacetyl cellulose, diacetyl cellulose, and cellulose acetate propionate; polyethylene naphthalate; polycarbonate; polysulfone; polyether sulfone; polyether ketone; polyphenylene sulfide and polyphenylene oxide.
Examples of commercially available cellulose ester substrates include "FUJITAC FILM" (manufactured by Fuji Photo Film Co., Ltd.); "KC8UX2M", "KC8UY" and "KC4UY" (all manufactured by Konica Minolta Opto, Inc.).
Examples of commercially available cyclic olefin resins include "Topas" (registered trademark) (manufactured by Ticona (Germany)), "Arton" (registered trademark) (manufactured by JSR Corporation), "ZEONOR" (registered trademark), "ZEONEX" (registered trademark) (all manufactured by Zeon Corporation), and "Apel" (registered trademark) (manufactured by Mitsui Chemicals, Inc.). Such cyclic olefin resins can be formed into a film by known means such as a solvent casting method or a melt extrusion method to form a substrate. Commercially available cyclic olefin resin substrates can also be used. Examples of commercially available cyclic olefin resin substrates include "S-Cina" (registered trademark), "SCA40" (registered trademark) (all manufactured by Sekisui Chemical Co., Ltd.), "ZEONOR Film" (registered trademark) (manufactured by Optes Co., Ltd.), and "Arton Film" (registered trademark) (manufactured by JSR Corporation).
The thickness of the substrate is preferably thin in terms of the mass that can be practically handled, but if it is too thin, the strength decreases and the processability tends to be poor. The thickness of the substrate is usually 5 μm to 300 μm, preferably 20 μm to 200 μm. The composite polarizing plate can be formed by combining the substrate with the absorptive polarizing film thus prepared with a reflective polarizing plate. In this case, from the viewpoint of thinning, it is preferable to peel off the substrate and transfer the absorptive polarizing film to the reflective polarizing plate.

As a suitable film substrate, a reflective polarizing plate can be used directly as the substrate. A composite polarizing plate in which a reflective polarizing plate is used as the substrate and a composition for forming an absorptive polarizing film is directly applied thereto is preferred because it has good production efficiency and can achieve a significant reduction in thickness.
Examples of the film substrate include polyethylene naphthalate (PEN) and its isomers (e.g., 2,6-, 1,4-, 1,5-, 2,7-, and 2,3-PEN), polyalkylene terephthalates (e.g., polyethylene terephthalate, polybutylene terephthalate, and poly-1,4-cyclohexanedimethylene terephthalate), polyimide resins (e.g., polyacrylimide), polyetherimide, atactic polystyrene, polycarbonate, polymethacrylates (e.g., polyisobutyl methacrylate, polypropyl methacrylate, polyethyl methacrylate, and polymethyl methacrylate), polyacrylates (e.g., polybutyl acrylate and polymethyl acrylate), cellulose derivatives (e.g., ethyl cellulose, cellulose acetate, cellulose protease, cellulose acrylate ... Examples of suitable polymers include plastics such as polyolefins, polypropylenes, polyisobutylenes, polyisobutylenes, poly(4-methyl)pentenes, polyolefins, polysulfones, polyethersulfones, polyacrylonitriles, polyamides, silicone resins, epoxy resins, polyvinyl acetates, polyether-amides, ionomer resins, elastomers (e.g., polybutadiene, polyisoprene, and neoprene), and polyurethanes.

[Reflective polarizing plate]
The reflective polarizing plate used in the present invention is a polarization conversion element that has the function of separating natural light into transmitted polarized light and reflected polarized light or scattered polarized light. Specifically, the reflective polarizing plate can be an anisotropic multi-layered thin film that can transmit linearly polarized light in one vibration direction and reflect linearly polarized light in the other vibration direction. As commercially available products of this anisotropic multi-layered thin film, for example, product names "DBEF" and "APF" (manufactured by 3M, Sumitomo 3M Limited) can be suitably used. The reflective polarizing plate is not limited by the principle, and may be a combination of a cholesteric liquid crystal and a λ/4 plate.

The thickness of the reflective polarizing plate can be about 10 to 100 μm, but from the viewpoint of thinning the optical laminate, composite polarizing plate, and liquid crystal display device, it is preferably 10 to 50 μm.

[Alignment film]
In the present invention, the alignment film has an alignment regulating force for aligning the polymerizable liquid crystal in a desired direction.

The alignment film facilitates the alignment of the polymerizable liquid crystal. The state of liquid crystal alignment, such as horizontal alignment, vertical alignment, hybrid alignment, and tilt alignment, varies depending on the properties of the alignment film and the polymerizable liquid crystal, and the combination can be selected arbitrarily. For example, if the alignment film is a material that exerts horizontal alignment as an alignment control force, the polymerizable liquid crystal can form a horizontal alignment or a hybrid alignment, and if the alignment film is a material that exerts vertical alignment, the polymerizable liquid crystal can form a vertical alignment or a tilt alignment. The expressions horizontal, vertical, and the like refer to the direction of the long axis of the aligned polymerizable liquid crystal when the polarizing film plane is used as a reference. For example, vertical alignment means that the long axis of the aligned polymerizable liquid crystal is in a direction perpendicular to the polarizing film plane. Here, vertical means 90°±20° to the polarizing film plane. In this composite polarizing plate, the alignment direction of the absorption type polarizing film is preferably horizontal alignment, so a horizontal alignment film is preferably applied.

When the alignment film is made of an alignment polymer, the alignment control force can be adjusted as desired by changing the surface condition and rubbing conditions. When the alignment film is made of a photoalignment polymer, the alignment control force can be adjusted as desired by changing the polarized light irradiation conditions, etc. In addition, the liquid crystal alignment can be controlled by selecting the physical properties of the polymerizable liquid crystal, such as the surface tension and liquid crystallinity.

The alignment film formed between the substrate and the polarizing film is preferably insoluble in the solvent used to form the polarizing film on the alignment film, and is heat resistant to the heat treatment required to remove the solvent and align the liquid crystal. Examples of the alignment film include an alignment film made of an orienting polymer, a photoalignment film, and a groove alignment film. When applied to a long rolled film, a photoalignment film is preferred because the orientation direction can be easily controlled.

The thickness of the alignment film is usually in the range of 10 nm to 5000 nm, preferably in the range of 10 nm to 1000 nm, and more preferably in the range of 30 to 300 nm.

Examples of the alignment polymers used in the rubbed alignment film include polyamides and gelatins having amide bonds in the molecule, polyimides having imide bonds in the molecule, and their hydrolyzates such as polyamic acid, polyvinyl alcohol, alkyl-modified polyvinyl alcohol, polyacrylamide, polyoxazole, polyethyleneimine, polystyrene, polyvinylpyrrolidone, polyacrylic acid, and polyacrylic acid esters. Among these, polyvinyl alcohol is preferred. These alignment polymers may be used alone or in combination of two or more.

Orientation films made of oriented polymers are usually obtained by applying a composition in which an oriented polymer is dissolved in a solvent (hereinafter also referred to as an "oriented polymer composition") to a substrate and then removing the solvent, or by applying an oriented polymer composition to a substrate, removing the solvent, and then rubbing (rubbing method).

Examples of the solvent include water; alcohol solvents such as methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, methyl cellosolve, butyl cellosolve, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone, propylene glycol methyl ether acetate, and ethyl lactate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, methyl amyl ketone, and methyl isobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; aromatic hydrocarbon solvents such as toluene and xylene, and nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; and chlorine-substituted hydrocarbon solvents such as chloroform and chlorobenzene. These solvents may be used alone or in combination of two or more.

The concentration of the oriented polymer in the oriented polymer composition may be within a range in which the oriented polymer can be completely dissolved in the solvent, but is preferably 0.1 to 20% by mass, more preferably 0.1 to 10% by mass, calculated as the solid content of the solution.

As the oriented polymer composition, a commercially available alignment film material may be used as is. Examples of commercially available alignment film materials include Sunever (registered trademark) (manufactured by Nissan Chemical Industries, Ltd.) and Optomer (registered trademark) (manufactured by JSR Corporation).

Methods for applying the oriented polymer composition to a substrate include known methods such as spin coating, extrusion, gravure coating, die coating, bar coating, and applicator methods, and printing methods such as flexography. When the polarizing film of the present invention is produced by a roll-to-roll continuous production method, the coating method typically employs a printing method such as gravure coating, die coating, or flexography.

By removing the solvent contained in the oriented polymer composition, a dry coating of the oriented polymer is formed. Methods for removing the solvent include natural drying, ventilation drying, heat drying, and reduced pressure drying.

One method of rubbing is to bring a film of oriented polymer formed on the surface of a substrate by applying an oriented polymer composition to the substrate and annealing the composition into contact with a rotating rubbing roll wrapped with a rubbing cloth.

The photo-alignment film is usually obtained by applying a composition containing a polymer or monomer having a photoreactive group and a solvent (hereinafter also referred to as "photo-alignment film forming composition") to a substrate and irradiating it with polarized light (preferably polarized UV). Photo-alignment films are more preferable in that the direction of the alignment control force can be arbitrarily controlled by selecting the polarization direction of the irradiated polarized light. In the present invention, an absorption-type polarizing film can be formed in which the absorption axis of the absorption-type polarizing film is substantially in the in-plane direction of 90° to the roll conveying direction by controlling the alignment in a direction substantially in the in-plane direction of 90° to the roll conveying direction. Note that substantially 90° is in the range of 90±8°. Forming a roll-shaped absorption-type polarizing film having an absorption axis in the in-plane range of 90±8° to the roll conveying direction is a preferred form for producing this composite polarizing plate.

A photoreactive group is a group that generates liquid crystal alignment ability when irradiated with light. Specifically, it is a group that generates a photoreaction that is the origin of liquid crystal alignment ability, such as molecular alignment induction or isomerization reaction, dimerization reaction, photocrosslinking reaction, or photodecomposition reaction, which occurs when irradiated with light. Among such photoreactive groups, those that cause a dimerization reaction or photocrosslinking reaction are preferred in terms of excellent alignment ability. As photoreactive groups that can generate the above-mentioned reactions, those having an unsaturated bond, especially a double bond, are preferred, and groups having at least one 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) are more preferred.

Examples of photoreactive groups having a C═C bond include vinyl groups, polyene groups, stilbene groups, stilbazolium groups, chalcone groups, cinnamoyl groups, etc. From the viewpoint of easy control of reactivity and expression of alignment control force during photoalignment, chalcone groups and cinnamoyl groups are preferred.
Examples of the photoreactive group having a C=N bond include groups having structures such as aromatic Schiff bases and aromatic hydrazones.
Examples of photoreactive groups having an N=N bond include an azobenzene group, an azonaphthalene group, an aromatic heterocyclic azo group, a bisazo group, a formazan group, and the like, as well as groups having an azoxybenzene as a basic structure.
Examples of photoreactive groups having a C=O bond include a benzophenone group, a coumarin group, an anthraquinone group, and a maleimide group. These groups may have a substituent such as an alkyl group, an alkoxy group, an aryl group, an allyloxy group, a cyano group, an alkoxycarbonyl group, a hydroxyl group, a sulfonic acid group, and an alkyl halide group.

As the solvent for the composition for forming the photo-alignment film, one that dissolves the polymer and monomer having a photoreactive group is preferred, and examples of such a solvent include the solvents listed as the solvents for the alignment polymer composition described above.

The content of the polymer or monomer having a photoreactive group in the composition for forming a photoalignment film can be adjusted as appropriate depending on the type of polymer or monomer having a photoreactive group and the thickness of the photoalignment film to be produced, but is preferably 0.2% by mass or more, and is preferably in the range of 0.3 to 10% by mass. In addition, polymer materials such as polyvinyl alcohol and polyimide and photosensitizers may be included within a range that does not significantly impair the properties of the photoalignment film.

The method for applying the composition for forming a photo-alignment film to a substrate can be the same as the method for applying the alignable polymer composition to a substrate described above. The method for removing the solvent from the applied composition for forming a photo-alignment film can be the same as the method for removing the solvent from the alignable polymer composition.

To irradiate polarized light, the composition for forming a photo-aligned film coated on a substrate or the like may be directly irradiated with polarized light after removing the solvent, or the polarized light may be irradiated from the substrate side and then transmitted through the substrate. The polarized light is preferably substantially parallel. The wavelength of the polarized light to be irradiated is preferably in a wavelength range in which the photoreactive group of the polymer or monomer having a photoreactive group can absorb light energy. Specifically, UV (ultraviolet light) with a wavelength of 250 to 400 nm is preferred. Examples of light sources used for the polarized light irradiation include xenon lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, and ultraviolet lasers such as KrF and ArF, with high-pressure mercury lamps, ultra-high-pressure mercury lamps, and metal halide lamps being more preferred. These lamps are preferred because they have a high emission intensity of ultraviolet light with a wavelength of 313 nm. Polarized light can be irradiated by passing the light from the light source through an appropriate polarizing element. Examples of such polarizing elements include polarizing filters, polarizing prisms such as Glan-Thompson and Glan-Taylor, and wire grid type polarizing elements.

If masking is performed when rubbing or irradiating with polarized light, multiple regions (patterns) with different liquid crystal orientation directions can be formed.

A groove alignment film is a film that has a concave-convex pattern or multiple grooves on its surface. When liquid crystal molecules are placed on a film that has multiple equally spaced linear grooves, the liquid crystal molecules are oriented in the direction along the grooves.

Methods for obtaining a groove alignment film include a method in which the surface of a photosensitive polyimide film is exposed through an exposure mask having slits in a pattern shape, followed by development and rinsing to form an uneven pattern; a method in which a layer of uncured UV-curable resin is formed on a plate-shaped master having grooves on its surface, the resin layer is transferred to a substrate and then cured; and a method in which a roll-shaped master having multiple grooves is pressed against a film of uncured UV-curable resin formed on a substrate to form unevenness, followed by curing. Specific examples include the methods described in JP-A-6-34976 and JP-A-2011-242743.

To obtain an alignment with minimal alignment disturbance, the width of the convex portion of the groove alignment film is preferably 0.05 μm to 5 μm, the width of the concave portion is preferably 0.1 μm to 5 μm, and the depth of the unevenness is preferably 2 μm or less, and more preferably 0.01 μm to 1 μm or less.

The thickness of the polarizing film thus formed is usually from 0.5 μm to 10 μm, preferably from 1 μm to 5 μm, and more preferably from 1 μm to 4 μm. Therefore, the thickness of the coating film for forming the polarizing film is determined in consideration of the thickness of the polarizing film to be obtained.
The thickness of the polarizing film is determined by measurement using an interference thickness gauge, a laser microscope, or a stylus type thickness gauge.

The composite polarizing plate of the present invention can be obtained as a composite polarizing plate in which an absorptive polarizing film is coated on a reflective polarizing plate as described above, or a composite polarizing plate can be obtained by transferring an absorptive polarizing film, which is coated on a separate substrate, together with an alignment film, onto a reflective polarizing plate via a pressure-sensitive adhesive or adhesive. In this case, the reflection axis of the reflective polarizing plate and the absorption axis of the absorptive polarizing film are formed so as to substantially coincide with each other. The angle between the reflection axis of the reflective polarizing plate and the absorption axis of the absorptive polarizing film is preferably 8° or less, more preferably 4° or less, and even more preferably 2° or less. This angle can be controlled by controlling the alignment regulating force of the alignment film that aligns the absorptive polarizing film in the manner described above.

In the prior art, a composite polarizing plate is industrially produced from a roll of an absorptive polarizing plate and a roll of a reflective polarizing plate. An iodine PVA polarizing plate is used as the absorptive polarizing plate, and its absorption axis is parallel to the roll transport direction because it requires a high degree of vertical uniaxial stretching. On the other hand, a reflective polarizing plate requires horizontal stretching to widen the film width, and its absorption axis is perpendicular to the roll transport direction. In other words, in order to laminate both polarizing plates, it was necessary to cut one of the polarizing plates into a sheet and then paste them together. In this case, it was not applicable to large LCD-TV applications, etc., because a seam would be created.
However, the composite polarizing plate of the present invention can be continuously laminated in a long roll form because the absorption axis of the absorptive polarizing film can be arbitrarily controlled, and production efficiency is greatly improved. In addition, it can be applied to large LCD-TV applications, etc. The long roll form usually has a length of 10 to 10,000 m in the roll transport direction, and preferably 100 to 10,000 m from the viewpoint of productivity.
In the roll-shaped composite polarizing plate, the reflection axis of the reflective polarizing plate is preferably 90°±8°, more preferably 90°±4°, in-plane relative to the roll transport direction, and the absorption axis of the absorptive polarizing film is preferably 90°±8°, more preferably 90°±4°, and even more preferably 90°±2°, in-plane relative to the roll transport direction.

Specifically, the method for continuously forming an absorptive polarizing film on a reflective polarizing plate preferably includes the following steps 1 to 7.
Step 1: A step of continuously coating a composition containing a polymer that generates an alignment control force by light and a solvent on a surface of the roll-shaped reflective polarizing plate while unwinding the roll-shaped reflective polarizing plate to form a first coating film;
Step 2: A step of heating and drying the first coating film to form a first dried film;
Step 3: Irradiating the first dry film with polarized ultraviolet light to form an alignment film;
Step 4: A step of forming a second coating film by coating a composition containing a dichroic dye, a polymerizable liquid crystal compound, a polymerization initiator, and a solvent on the alignment film;
Step 5: A step of heating and drying the second coating film to form a second dried film;
Step 6: A step of irradiating the second dry film with ultraviolet light to polymerize the polymerizable liquid crystal compound to form an absorptive polarizing film and form a composite polarizing plate. Step 7: A step of winding up the composite polarizing plate on a roll.

The obtained roll-shaped composite polarizing plate is generally cut into a rectangular shape to form a single-sheet composite polarizing plate sheet. As mentioned above, the present invention is suitable for producing a large single-sheet composite polarizing plate sheet having a transmission axis in the long side direction. Specifically, it is suitable for producing a rectangular composite polarizing plate having a diagonal of 60 inches or more, preferably 80 inches or more, and more preferably 100 inches or more.

[Liquid crystal display device]
The composite polarizing plate of the present invention, in which a polarizing film formed by coating the composition for forming an absorptive polarizing film on a reflective polarizing plate is provided, can be preferably used in a form in which it is disposed between a backlight unit and a liquid crystal cell of a liquid crystal display device, with the reflective polarizer surface being disposed on the backlight unit side and the absorptive polarizing film formed by coating the composition for forming an absorptive polarizing film containing a dichroic dye being disposed on the liquid crystal cell side. Moreover, such a composite polarizing plate obtained in a long form has no seams and can be suitably applied to large liquid crystal displays.
In a liquid crystal cell having the composite polarizing plate of the present invention, any conventionally known driving method for the liquid crystal cell can be applied, but preferred are in-plane switching (IPS) and vertical alignment (VA) modes.

The present invention will be described in more detail below with reference to examples. In the examples, "%" and "parts" are by mass % and parts by mass unless otherwise specified.

溶剤（９８部）：o-キシレン Example 1
[Production of composition for forming photoalignment film]
The following components were mixed, and the resulting mixture was stirred at 80° C. for 1 hour to obtain a composition for forming a photoalignment film.
Photoalignable material (2 parts):

Solvent (98 parts): o-xylene

〔二色性色素〕

２．５部

２．５部

２．５部
〔他の成分〕
重合開始剤；
２－ジメチルアミノ－２－ベンジル－１－（４－モルホリノフェニル）ブタン－１－オン（イルガキュア３６９；チバスペシャルティケミカルズ社製） ６部
レベリング剤；
ポリアクリレート化合物（ＢＹＫ－３６１Ｎ；ＢＹＫ－Ｃｈｅｍｉｅ社製）
１．２部
溶剤；o-キシレン ２５０部 [Production of composition for forming polarizing film]
The following components were mixed and stirred for 1 hour at 80° C. to obtain a composition for forming a polarizing film. The dichroic dye used was an azo-based dye described in the examples of JP-A-2015-165302.
[Polymerizable Liquid Crystal Compound]

[Dichroic dye]

2.5 parts

2.5 parts

2.5 parts [other ingredients]
Polymerization initiator;
2-Dimethylamino-2-benzyl-1-(4-morpholinophenyl)butan-1-one (Irgacure 369; manufactured by Chiba Specialty Chemicals) 6 parts Leveling agent;
Polyacrylate compound (BYK-361N; manufactured by BYK-Chemie)
1.2 parts Solvent: o-xylene 250 parts

[Measurement of phase transition temperature]
A 2% by mass aqueous solution (composition for forming an alignment layer) of polyvinyl alcohol (polyvinyl alcohol 1000 fully saponified type, manufactured by Wako Pure Chemical Industries, Ltd.) was applied onto a glass substrate by spin coating, and after drying, a film having a thickness of 100 nm was formed. Subsequently, an alignment layer was formed by subjecting the surface of the obtained film to a rubbing treatment. The rubbing treatment was performed using a semi-automatic rubbing device (trade name: LQ-008 type, manufactured by Joyo Engineering Co., Ltd.) with a cloth (trade name: YA-20-RW, manufactured by Yoshikawa Kako Co., Ltd.) under conditions of a pressing amount of 0.15 mm, a rotation speed of 500 rpm, and 16.7 mm/s. A composition for forming a polarizing film (A) was applied onto the alignment film thus prepared by spin coating, and the film was dried by heating on a hot plate at 120 ° C. for 1 minute, and then quickly cooled to room temperature to form a dry film on the alignment layer. The dried film was heated again to 120° C. on a hot plate, and then observed with a polarizing microscope while cooling to measure the phase transition temperatures. As a result, it was confirmed that the film underwent a phase transition to a nematic phase at 115° C., a phase transition to a smectic A phase at 105° C., and a phase transition to a smectic B phase at 74° C.

[X-ray diffraction measurement]
A composition for forming a polarizing film was applied onto the above-mentioned alignment film by spin coating, and the composition was dried by heating on a hot plate at 120°C for 1 minute, and then quickly cooled to room temperature to form a dry film on the alignment layer. Next, the dry film was irradiated with ultraviolet light at an exposure dose of 2000 mJ/cm ² (based on 365 nm) using a UV irradiation device (SPOT CURE SP-7; manufactured by Ushio Inc.), whereby the polymerizable liquid crystal compound contained in the dry film was polymerized while maintaining the liquid crystal state of the polymerizable liquid crystal composition, and a polarizing film was formed from the dry film. The thickness of the polarizing film at this time was measured with a laser microscope (OLS3000 manufactured by Olympus Corporation) to be 1.7 μm. The polarizing film was subjected to similar X-ray diffraction measurement using an X-ray diffraction device X'Pert PRO MPD (Spectris Co., Ltd.). As a result, a sharp diffraction peak with a peak half-width (FWHM) of about 0.312° was obtained near 2θ = 20.1°. Similar results were also obtained with incidence perpendicular to the rubbing. The order period (d) calculated from the peak position was about 4.4 Å, confirming the formation of a structure reflecting a high-order smectic phase.

2. Preparation of a composite polarizing plate [Preparation of photo-alignment layer]
A long APF (manufactured by 3M Company (Sumitomo 3M Limited in Japan)) roll with a width of 800 mm was used as a reflective polarizing plate, and the surface was plasma-treated while continuously unrolling. Then, a composition for forming a photo-alignment film was discharged at a flow rate of 30 ml/min using a slot die coater to form a first coating film in a 750 mm wide range at the center of the film. The film was then transported for 2 minutes in a ventilated drying oven set at 120°C to remove the solvent, forming a first dry film. Thereafter, the first dry film was irradiated with polarized UV light at 90° to the longitudinal direction of the film to an intensity of 20 mJ/cm2 (based on 313 nm) to impart an alignment control force, forming a long photo-alignment film.

[Preparation of Composite Polarizing Plate]
A composition for forming a polarizing film was discharged onto the photoalignment film using a slot die coater at a flow rate of 77.2 ml/min to form a second coating film in a 750 mm wide range at the center of the film.
Further, the solvent was removed by conveying the film through a ventilated drying oven set at 120° C. for 2 minutes to form a second dried film. Thereafter, UV light was irradiated at room temperature at 1000 mJ/cm2 (based on 365 nm) to polymerize the polymerizable liquid crystal compound contained in the second dried film while maintaining its liquid crystal state, and a polarizing film was formed from the dried film. Thereafter, the film was continuously wound up into a roll to obtain a long composite polarizing plate (1) having an absorption axis in the 90° direction of 200 m. The thickness of the composite polarizing plate thus produced was measured using a contact film thickness meter, and was 28 μm throughout the film. In addition, the composite polarizing plate was cut with a microtome, and then carbon deposition was performed on the cross section, and the film was observed with a scanning transmission electron microscope (STEM, field emission scanning electron microscope (FE-STEM), model number: "S-5500", manufactured by Hitachi, Ltd.). As a result, the thickness of the photo-aligned film was 100 nm, and the thickness of the polarizing film was 3.5 μm.

[Evaluation of Composite Polarizing Plate]
The obtained long composite polarizing plate was cut into five pieces, each 5 cm square, in the width direction from a position 3 m from the coating start point and a position 3 m from the coating end point.
3. Measurement of Polarization Performance In order to confirm the usefulness of the composite polarizing plate, the luminosity-corrected polarization degree was measured as follows.
The transmittance (T ¹ ) in the transmission axis direction and the transmittance (T ² ) in the absorption axis direction were measured by the double beam method using a spectrophotometer (Shimadzu Corporation UV-3150) equipped with a folder with a polarizing element. The reference side of the folder was equipped with a mesh that cuts the amount of light by 50%. The transmittance at each wavelength was calculated using the following formula (Formula 1), and the visibility correction was performed using the 2-degree visual field (C light source) of JIS Z 8701 to calculate the visibility-corrected polarization degree (Ty). The polarization degree at each wavelength was calculated using the following formula (Formula 2), and the visibility correction was performed using the 2-degree visual field (C light source) of JIS Z 8701 to calculate the visibility-corrected polarization degree (Py). The angle θ between the reflection axis of the reflective polarizing plate and the absorptive polarizing film was measured by separating the reflective polarizing plate and the absorptive polarizing film from the composite polarizing plate, using the same side as the reference side, and measuring the reflection axis of the reflective polarizing plate and the absorption axis of the absorptive polarizing film by a rotating analyzer method using an automatic birefringence meter "KOBRA-WPR" manufactured by Oji Scientific Instruments Co., Ltd., and obtaining the following formula:
θ = (reflection axis angle of reflective polarizing plate) - (absorption axis angle of absorptive polarizing film)
The results are shown in Tables 1 and 2. The angle θ between the reflection axis of the reflective polarizing plate and the absorptive polarizing film was 0°. It was confirmed that the luminosity-corrected polarization degree (Py) of the composite polarizing plate was 99.7%, which was significantly improved over the luminosity-corrected polarization degree (Py) of 95.5% of the APF alone. It was also confirmed that the composite polarizing plate was stable in both the width direction and the conveying direction.
Single-piece transmittance (%)=(T ¹ +T ² )/2 Formula (1)
Degree of polarization (%)={(T ¹ −T ² )/(T ¹ +T ² )}×100 Equation (2)

Example 2
A composite polarizing plate was produced in the same manner as in Example 1, except that the flow rate of the composition for forming a polarizing film was changed to 68.2 ml/min. The thickness of the photo-alignment film was 100 nm, and the thickness of the polarizing film was 3.1 μm. The measurement results of the polarization performance are shown in Table 2.

Example 3
A composite polarizing plate was prepared in the same manner as in claim 2, except that θ was changed to 2°. The measurement results of the polarization performance are shown in Table 2.

Example 4
A composite polarizing plate was produced in the same manner as in Example 2, except that θ was changed to 4°. The measurement results of the polarization performance are shown in Table 2.

Example 5 (Reference Example)
A composite polarizing plate was produced in the same manner as in Example 2, except that θ was changed to 5°. The measurement results of the polarization performance are shown in Table 2.

Example 6 (Reference Example)
A composite polarizing plate was produced in the same manner as in Example 2, except that θ was changed to 7°. The measurement results of the polarization performance are shown in Table 2.

Example 7 (Reference Example)
A composite polarizing plate was produced in the same manner as in Example 2, except that θ was changed to 8°. The measurement results of the polarization performance are shown in Table 2.

Comparative Example 1
A composite polarizing plate was produced in the same manner as in Example 2, except that θ was changed to 10°. The measurement results of the polarization performance are shown in Table 2.

The composite polarizing plate of the present invention can be suitably used in the manufacture of thin, high-performance liquid crystal display devices.

Claims (9)

the optical element has an absorptive polarizing film, an alignment film for aligning the absorptive polarizing film, and a reflective polarizing plate, the absorptive polarizing film and the reflective polarizing plate are adjacent to the alignment film, the angle between the reflection axis of the reflective polarizing plate and the absorption axis of the absorptive polarizing film is 4° or less, the luminous efficiency-corrected polarization degree (Py) is 98.1 % or more, and the luminous efficiency-corrected transmittance (Ty) is 38.5% or more,
the absorptive polarizing film is a polymer of a polymerizable liquid crystal compound that is aligned and fixed in the in-plane horizontal direction in a smectic liquid crystal phase state, contains a dichroic dye, and has a thickness of 5 μm or less;
The thickness of the reflective polarizing plate is 10 μm or more and less than 50 μm,
The composite polarizing plate , wherein the alignment film has a thickness of 30 to 300 nm . The composite polarizing plate according to claim 1, wherein the alignment film is a photo-alignment film that generates an alignment control force by light. The composite polarizing plate according to claim 1 or 2, wherein the ratio of the dichroic dye in the polymer of the polymerizable liquid crystal compound is 20 parts by mass or less per 100 parts by mass of the polymerizable liquid crystal compound. The composite polarizing plate according to any one of claims 1 to 3, wherein the absorptive polarizing film is a polarizing film that has a Bragg peak in X-ray diffraction measurement. The composite polarizing plate according to any one of claims 1 to 4, wherein the reflective polarizing plate is a multilayer laminate of at least two or more polymeric materials having different refractive indices. The composite polarizing plate according to any one of claims 1 to 5, which is rectangular and has a transmission axis in the direction of the long side. the polarizing plate has an absorptive polarizing film, an alignment film for aligning the absorptive polarizing film, and a reflective polarizing plate, the absorptive polarizing film and the reflective polarizing plate are each adjacent to the alignment film, the reflection axis of the reflective polarizing plate is in-plane at 90°± 4 ° with respect to the roll transport direction, the absorption axis of the absorptive polarizing film is in-plane at 90°± 4 ° with respect to the roll transport direction, the angle formed by the reflection axis of the reflective polarizing plate and the absorption axis of the absorptive polarizing film is 4° or less, the luminous efficiency-corrected polarization degree (Py) is 98.1 % or more, and the luminous efficiency-corrected transmittance (Ty) is 38.5% or more,
the absorptive polarizing film is a polymer of a polymerizable liquid crystal compound that is aligned and fixed in the in-plane horizontal direction in a smectic liquid crystal phase state, contains a dichroic dye, and has a thickness of 5 μm or less;
The thickness of the reflective polarizing plate is 10 μm or more and less than 50 μm,
The thickness of the alignment film is 30 to 300 nm . A method for producing a rolled composite polarizing plate according to claim 7, comprising the following steps 1 to 7:
Step 1: A step of continuously coating a composition containing a polymer that generates an alignment control force by light and a solvent on a surface of the roll-shaped reflective polarizing plate while unwinding the roll-shaped reflective polarizing plate to form a first coating film;
Step 2: A step of heating and drying the first coating film to form a first dried film;
Step 3: Irradiating the first dry film with polarized ultraviolet light to form an alignment film;
Step 4: A step of forming a second coating film by coating a composition containing a dichroic dye, a polymerizable liquid crystal compound, a polymerization initiator, and a solvent on the alignment film;
Step 5: A step of heating and drying the second coating film to form a second dried film;
Step 6: Irradiating the second dry film with ultraviolet light to polymerize the polymerizable liquid crystal compound to form an absorptive polarizing film and form a composite polarizing plate. Step 7: Winding up the composite polarizing plate on a roll. A liquid crystal display device in which the composite polarizing plate according to any one of claims 1 to 6 is disposed between a backlight unit and a liquid crystal cell, with the reflective polarizing plate surface disposed on the backlight unit side and the absorptive polarizing film surface disposed on the liquid crystal cell side.