JP6538383B2 - Polarizer and circular polarizer - Google Patents

Description

  The present invention relates to a polarizing plate and a circularly polarizing plate.

  In the organic EL image display device, a circularly polarizing plate is used to prevent external light reflection in a bright place. As such a circularly polarizing plate, for example, one including a polarizing plate (iodine-PVA polarizing plate) obtained by dyeing PVA (polyvinyl alcohol) with iodine is known (see Patent Document 1).

  In particular, when a circularly polarizing plate is applied to an organic EL image display device, a polarizing plate having a low absorbance is desired so as not to absorb light emitted from the organic EL element. In the case of an iodine-PVA polarizing plate, the absorbance can be lowered by decreasing the dye concentration of iodine.

Japanese Patent Application Laid-Open No. 7-142170

  However, in the iodine-PVA polarizing plate having such a low concentration, depending on the use environment, the iodine may be sublimated / denatured to change the color, or the warp may be generated due to relaxation of the stretching of the PVA. There is. In addition, it is difficult to reduce the thickness of the iodine-PVA polarizing plate, and there is a limit in applying it to a display device that is required to be thinner.

  Therefore, an object of the present invention is to provide a polarizing plate and a circularly polarizing plate which have high light absorption selectivity even in a thin film and are excellent in heat resistance.

The present invention includes the following aspects.
[1] A polarizing plate comprising a substrate and a polarizer, wherein the polarizer has a polarizing layer with a thickness of 5 μm or less, in which the dichroic dye is oriented, and is represented by the following formula (I) The polarizing plate whose absorbance retention is 80% or more.
Absorbance retention (%) = A1 (85 ° C.) / A1 (23 ° C.) × 100 (I)
(Wherein, A1 (85 ° C.) represents the absorbance in the absorption axis direction at the absorption maximum wavelength of the dichroic dye after holding the polarizing plate in a heat-resistant oven at 85 ° C. for 100 hours, A1 (23 ° C.) Represents the absorbance in the absorption axis direction at the absorption maximum wavelength of the dichroic dye measured at 23 ° C. before the polarizing plate is put into the heat-resistant oven.)
[2] The polarizing plate according to [1], wherein the value of A1 (23 ° C.) is 0.3 or more and 2.0 or less.
[3] The value of absorbance A2 (23 ° C.) in the transmission axis direction at the absorption maximum wavelength of the dichroic dye measured at 23 ° C. before the polarizing plate is put into the heat resistant oven is 0.001 or more and 0.1 or less The polarizing plate as described in [1] or [2].
[4] The polarizing plate according to any one of [1] to [3], wherein the dichroic dye is an organic dye.
[5] The polarizing plate according to any one of [1] to [4], wherein the polarizing layer contains a polymer of a polymerizable liquid crystal compound.
[6] The polarizing plate according to [5], wherein the polymerizable liquid crystal compound is a compound exhibiting a smectic liquid crystal phase.
[7] The polarizing plate according to [5], wherein the polymerizable liquid crystal compound is a compound exhibiting a high-order smectic liquid crystal phase.
[8] The polarizing plate according to any one of [1] to [7], which shows a Bragg peak in X-ray diffraction measurement.
[9] A circularly polarizing plate including the polarizing plate according to any one of [1] to [8] and a 1⁄4 wavelength plate.
[10] The birefringence of the quarter-wave plate for light of wavelength 450 nm, the birefringence for light of wavelength 550 nm, and the birefringence for light of wavelength 650 nm are represented by the following formulas (II) and (III) The circularly polarizing plate according to [9], having an inverse wavelength dispersion satisfying the above.
Δn (450) / Δn (550) ≦ 1.00 (II)
1.00 ≦ Δn (650) / Δn (550) (III)
(Wherein, Δn (λ) represents the birefringence for light of wavelength λ nm)

  According to the present invention, it is possible to provide a polarizing plate and a circularly polarizing plate which have high light absorption selective performance even in a thin film and are excellent in heat resistance.

It is a sectional view showing typically one embodiment of a polarizing plate. It is a sectional view showing typically one embodiment of a circularly polarizing plate. It is a sectional view showing typically one embodiment of a circularly polarizing plate. It is a sectional view showing typically one embodiment of a circularly polarizing plate.

The polarizing plate of the present embodiment includes a substrate and a polarizer, and the polarizer has a polarizing layer with a thickness of 5 μm or less, in which the dichroic dye is oriented, and is represented by the following formula (I) It is characterized in that the absorbance retention rate is 80% or more.
Absorbance retention (%) = A1 (85 ° C.) / A1 (23 ° C.) × 100 (I)

  In the above formula, A1 (85 ° C.) represents the absorbance in the absorption axis direction at the absorption maximum wavelength of the dichroic dye after holding the polarizing plate for 100 hours in a heat-resistant oven at 85 ° C., A1 (23 ° C.) The absorbance in the absorption axis direction at the absorption maximum wavelength of the dichroic dye measured at 23 ° C. before the polarizing plate is put into a heat-resistant oven.

  It is preferable that the value of said A1 (23 degreeC) is 0.3 or more and 2.0 or less. In addition, the value of the absorbance A2 (23 ° C) in the transmission axis direction at the absorption maximum wavelength of the dichroic dye measured at 23 ° C before the polarizing plate is put into the heat-resistant oven is 0.001 or more and 0.1 or less Is preferred.

  The polarizing plate of the present embodiment having the above-described configuration, even a thin film, has high light absorption selection performance and is excellent in heat resistance. The absorbance retention rate is preferably 85% or more, more preferably 90% or more, and still more preferably 95% or more.

1. Polarizer The polarizer according to the present embodiment has a polarizing layer with a thickness of 5 μm or less in which the dichroic dye is oriented. The polarizing layer can be formed using a composition containing a dichroic dye (hereinafter, sometimes referred to as “a composition for forming a polarizer”).

1-1. Dichroic Dye As the dichroic dye, a dye having absorption in a wavelength range of 380 to 800 nm can be used, and it is preferable to use an organic dye. As a dichroic dye, an azo compound is mentioned, for example.

As an azo compound, a dichroic dye (1) having an absorption maximum in the wavelength range of 380 to 550 nm can be used. Examples of the dichroic dye (1) include a compound represented by the following formula (1) (hereinafter, sometimes referred to as “compound (1)”). The geometric isomerism of the azobenzene site of the compound (1) is preferably trans.

Y in Formula (1) is a group represented by the following Formula (Y1) or Formula (Y2), and preferably a group represented by Formula (Y1).

In Formula (Y1) and Formula (Y2), the straight line at both ends represents a bond, the bond on the left is bonded to a phenylene group having an azo group, and the bond on the right is bonded to a phenylene group having R ² doing. L is an oxygen atom or -NR-, and R is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group and t-butyl group. Among them, L is preferably an oxygen atom or -NH-, more preferably an oxygen atom.

R ¹ is represented by the following formula ^(R 1 -1), a group represented by the formula ^(R 1 -2) or formula ^(R 1 -3), preferably of formula ^(R 1 -2) and formula ^{(R 1} A group represented by -3). * In the formula represents a bond.

Each of ma in the group represented by formula (R ¹ -2) is preferably independently an integer of 0 to 10, and more preferably an integer of 0 to 5. The two mas may be identical or different, but are preferably identical.

R ² is represented by the formula (R ² -1), the formula (R ² -2), the formula (R ² -3), the formula (R ² -4), the formula (R ² -5) or the formula (R ² -6) And a group represented by the formula (R ² -2), the formula (R ² -5) or the formula (R ² -6), which is preferably a group represented by the formula (R ² -6) It is more preferable that it is a group represented.

When R ² is a group represented by Formula (R ² -1), Formula (R ² -2), Formula (R ² -3), Formula (R ² -5) or Formula (R ² -6) The mb contained in the group is preferably an integer of 0 to 10, and more preferably an integer of 0 to 5.

Examples of the compound (1) include compounds represented by the following formulas (1-1) to (1-8).

  Among them, compounds represented by Formula (1-1), Formula (1-2), Formula (1-3), Formula (1-5), Formula (1-7) and Formula (1-8) are preferable. The compounds represented by Formula (1-1), Formula (1-2), Formula (1-3) and Formula (1-7) are more preferable.

Here, the manufacturing method of a compound (1) is demonstrated. The compound (1) is produced, for example, from a compound represented by the formula (1X) [compound (1X)] and a compound represented by the formula (1Y) [compound (1Y)] by a reaction shown in the following diagram. be able to.

In the above scheme, R ¹ , R ² and Y have the same meaning as described above, and Re ¹ and Re ² are groups which react with each other to be a group represented by Y. Examples of combinations of Re ¹ and Re ² include a combination of a carboxy group and a hydroxyl group, a combination of a carboxy group and an amino group (such an amino group may be substituted with R), a combination of a carbonyl halide group and a hydroxyl group, a carbonyl halide A combination of a group and an amino group (wherein such amino group may be substituted with R), a combination of a carbonyloxyalkyl group and a hydroxyl group, a carbonyloxyalkyl group and an amino group (wherein such an amino group may be substituted with R) Combinations of In addition, although the compound (1X) having R ¹ and the compound (1Y) having R ² are described here, a compound in which R ¹ is protected with an appropriate protecting group and R ² is protected with an appropriate protecting group The compounds (1) can also be produced by reacting the compounds with one another and then performing appropriate deprotection reaction.

As the reaction conditions for reacting the compound (1X) and the compound (1Y), optimum known conditions can be appropriately selected depending on the types of the compound (1X) and the compound (1Y) to be used.
For example, as reaction conditions in the case where Re ¹ is a carboxy group, Re ² is a hydroxyl group, and Y is -C (= O) -O-, for example, in a solvent, in the presence of an esterifying condensation agent Conditions for condensation may be mentioned. Examples of the solvent include solvents in which both compound (1X) and compound (1Y) are soluble, such as chloroform. As an esterifying condensing agent, a diisopropyl carbodiimide (IPC) is mentioned, for example. Here, a base such as dimethylaminopyridine (DMAP) is further preferably used in combination. Although reaction temperature is selected according to the kind of compound (1X) and compound (1Y), the range of -15-70 degreeC is mentioned, for example, Preferably it is the range of 0-40 degreeC. The reaction time is, for example, in the range of 15 minutes to 48 hours.

  With respect to the reaction time, the reaction mixture during the reaction is appropriately sampled, and the degree of disappearance of the compound (1X) and the compound (1Y) or formation of the compound (1) by known analytical means such as liquid chromatography or gas chromatography You can also determine the degree of

  From the reaction mixture after the reaction, compound (1) can be removed by a known method such as recrystallization, reprecipitation, extraction, and various chromatography, or by combining these operations.

  As an azo compound, the dichroic dye (2) which has an absorption maximum in the range of wavelength 550-700 nm can be used.

  The dichroic dye (2) is a dichroic dye (2-1) having an absorption maximum in a wavelength range of 550 to 600 nm and / or a dichroic dye having an absorption maximum in a wavelength range of 600 to 700 nm (2- 2) may be included. It is more preferable that the dichroic dye (2-1) has an absorption maximum in a wavelength range of 570 to 600 nm, and it is more preferable that the dichroic dye (2-2) has an absorption maximum in a wavelength range of 600 to 680 nm.

Examples of the dichroic dye (2) include a compound represented by the following formula (2) (hereinafter, sometimes referred to as “compound (2)”). The geometric isomerism of the azobenzene site of the compound (2) is preferably trans. In formula (2), n is 1 or 2.

Ar ¹ and Ar ³ are each independently a group represented by Formula (AR-1), Formula (AR-2), Formula (AR-3) or Formula (AR-4). * Represents a bond.

Ar ² is a group represented by Formula (AR2-1), Formula (AR2-2) or Formula (AR2-3).

A ₁ and A ₂ are each independently a group represented by any one of Formula (A-1) to Formula (A-9). In formulas (A-2), (A-3), (A-5) and (A-6), when mc is an integer of 0 to 10 and there are two mc in the same group, The two mcs are identical or different from each other.

The compound (2) which can be used as a dichroic dye (2-1) by combining Ar ¹ , Ar ² and Ar ³ so that the compound (2) has an absorption maximum in the wavelength range of 550 to 600 nm It will be determined. Similarly, a compound (2) which can be used as a dichroic dye (2-2) by combining Ar ¹ , Ar ² and Ar ³ such that the compound (2) has absorption in the wavelength range of 600 to 700 nm Is defined.

  Specific examples of the compound (2) include compounds represented by formulas (2-11) to (2-39).

  Among the specific examples of the compound (2), as the dichroic dye (2-1), the compound (2-12), the formula (2-13), the formula (2-18) and the formula (2-20) can be used. ), Formula (2-21), Formula (2-22), Formula (2-23), Formula (2-24), Formula (2-26), Formula (2-27), Formula (2-28) The compounds represented by the formula (2-29) and the formula (2-30) respectively correspond to the formula (2-31), the formula (2-32), and the like as the dichroic dye (2-2). What is represented by Formula (2-33), Formula (2-34), Formula (2-35), and Formula (2-36) respectively corresponds. In addition, although what is represented by Formula (2-11), Formula (2-15), and Formula (2-16), respectively is not a pigment | dye which shows absorption at wavelength 550-700 nm, it is used together with other dichroic dyes can do.

  Among the specific examples of the compound (2), as the dichroic dye (2), the compound (2-15), the compound (2-16), the compound (2-18), the compound (2-20), the compound (2-20) 2-21), Formula (2-22), Formula (2-23), Formula (2-27), Formula (2-29), Formula (2-31), Formula (2-32), Formula (2) -33), what is represented by Formula (2-34) and Formula (2-35) respectively is preferable.

  The dichroic dye (2) is produced by a known method described in, for example, JP-A-58-38756, JP-A-63-301850, and the like.

  The above-mentioned dichroic dyes may be used alone or in combination of two or more. When the composition for forming a polarizer contains two or more kinds of dichroic dyes, each content of the dichroic dye in the composition for forming a polarizer is a content with respect to 100 parts by mass of a polymerizable liquid crystal compound described later 6 mass parts or less are preferable, 0.1 mass part or more and 4 mass parts or less are more preferable, and 1 mass part or more and 3 mass parts or less are still more preferable. When the content of the dichroic dye is in the above range, the dichroic dye in the composition for forming a polarizer exhibits sufficient solubility in a solvent, and thus a polarizer using the composition for forming a polarizer is used. Can be obtained to obtain a polarizer free from the occurrence of defects. This makes it easier to produce a polarizing plate that has high light absorption selectivity even with a thin film and is excellent in heat resistance. The total amount of dichroic dyes contained in the composition for forming a polarizer is preferably 20 parts by mass or less and 0.1 parts by mass or more and 12 parts by mass or less, as represented by the content relative to 100 parts by mass of the polymerizable liquid crystal compound described later. Is more preferably 1 to 9 parts by mass.

1-2. Polymerizable Liquid Crystal Compound The polarizer according to the present embodiment preferably has a polarizing layer containing a polymer of a polymerizable liquid crystal compound. That is, the composition for forming a polarizer can contain a polymerizable liquid crystal compound together with the dichroic dye.

  A polymerizable liquid crystal compound is a liquid crystal compound that can be polymerized while being oriented, and has a polymerizable group in the molecule. The composition for polarizer formation containing a polymeric liquid crystal compound forms a cured film by polymerizing in the state which the polymeric liquid crystal compound was orientated. The polymerizable group is particularly preferably a radical polymerizable group. The radically polymerizable group means a group involved in a radical polymerization reaction.

  The polymerizable liquid crystal compound is a smectic liquid crystal phase (hereinafter sometimes referred to as “smectic liquid crystal phase”) even if it shows a nematic liquid crystal phase (hereinafter sometimes referred to as “nematic liquid crystal phase”). Or a smectic liquid crystal phase, but it is preferably a polymerizable smectic liquid crystal compound showing at least a smectic liquid crystal phase. The composition for forming a polarizer, which contains a polymerizable smectic liquid crystal compound, has good neutral hue and is excellent in polarization performance due to the interaction with the dichroic dye.

  As a smectic liquid crystal phase which a polymerizable smectic liquid crystal compound shows, a high-order smectic liquid crystal phase is more preferable. The higher-order smectic liquid crystal phase referred to here means smectic B phase, smectic D phase, smectic E phase, smectic F phase, smectic G phase, smectic H phase, smectic I phase, smectic J phase, smectic K phase and smectic L phase Among them, smectic B phase, smectic F phase and smectic I phase are more preferable.

  When the smectic liquid crystal phase of the polymerizable liquid crystal compound is such a high-order smectic liquid crystal phase, a polarizer having a higher degree of alignment order can be produced. In addition, a polarizer produced from a high-order smectic liquid crystal phase having a high degree of alignment order in this way is such that a Bragg peak derived from a higher-order structure such as a hexatic phase or a crystal phase can be obtained in X-ray diffraction measurement. The said Bragg peak is a peak originating in the surface periodic structure of molecular orientation, and according to the composition for polarizer formation which concerns on this embodiment, the polarizer whose period space | interval is 3.0-5.0 angstrom is obtained. be able to.

  Whether or not the polymerizable liquid crystal compound exhibits a nematic liquid crystal phase or a smectic liquid crystal phase can be confirmed, for example, as follows. After a suitable base material is prepared and a composition for forming a polarizer is coated on the base material to form a coating film, the composition is contained in the coating film by heat treatment or reduced pressure treatment under the condition that the polymerizable liquid crystal compound is not polymerized. Remove the solvent. Subsequently, the coating film formed on the substrate is heated to an isotropic phase temperature, and the liquid crystal phase developed by gradually cooling is inspected by texture observation with a polarizing microscope, X-ray diffraction measurement or differential scanning calorimetry Do. In this test, for example, a polymerizable liquid crystal compound which exhibits a nematic liquid crystal phase by cooling and further exhibits a smectic liquid crystal phase by cooling is particularly preferable. That the polymerizable liquid crystal compound and the dichroic dye are not phase separated in the nematic liquid crystal phase and the smectic liquid crystal phase can be confirmed, for example, by surface observation with various microscopes or measurement of the degree of scattering with a haze meter.

Examples of the polymerizable liquid crystal compound include a compound represented by the formula (4) (hereinafter, sometimes referred to as “compound (4)”).
^{U 1 -V 1 -W 1 -X 1} -Y 1 -X 2 -Y 2 -X 3 -W 2 -V 2 -U 2 (4)

In formula (4), X ¹ , X ² and X ³ are each independently a 1,4-phenylene group which may have a substituent or cyclohexane-1,4 which may have a substituent -Represents a diyl group. Preferably, at least one of X ¹ , X ² and X ³ is a cyclohexane-1,4-diyl group which may have a substituent. -CH _2- constituting the optionally substituted cyclohexane-1,4-diyl group may be replaced by -O-, -S- or -NR-. R is a C1-C6 alkyl group or a phenyl group.

The optionally substituted cyclohexane-1,4-diyl group is preferably an optionally-substituted trans-cyclohexane-1,4-diyl group, and the substituted group is preferably a substituted group. More preferred is a trans-cyclohexane-1,4-diyl group having no In the formula (4), at ^{least two of} X ¹ , X ² and X ³ may be a 1,4-phenylene group which may have a substituent; It is preferably -phenylene group.

  As a substituent which a 1,4-phenylene group which may have a substituent or a cyclohexane-1,4-diyl group which may have a substituent optionally has, for example, a methyl group, ethyl Examples thereof include alkyl groups having 1 to 4 carbon atoms such as a group and a butyl group, a cyano group and a halogen atom.

Wherein (4), ^{Y 1} and ^{Y 2,} independently of one _{another, -CH 2 CH 2 -, -} CH 2 O -, - COO -, - OCOO-, a single bond, -N = N -, - CR a It represents = CR ^b- , -C≡C- or -CR ^a = N-. R ^a and R ^b independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Y ¹ is preferably -CH ₂ CH _2- , -COO- or a single bond, and Y ² is preferably -CH ₂ CH _2- , -COO- or -CH ₂ O-.

In Formula (4), U ¹ is a hydrogen atom or a polymerizable group, preferably a polymerizable group. U ² is a polymerizable group. Both U ¹ and U ² are preferably polymerizable groups, and more preferably photopolymerizable groups. The photopolymerizable group refers to a group capable of participating in a polymerization reaction by an active radical, an acid or the like generated from a photopolymerization initiator described later. The polymerizable liquid crystal compound having a photopolymerizable group is advantageous in that it can be polymerized under lower temperature conditions.

The polymerizable groups of U ¹ and U ² may be different from each other, but are preferably the same type of group. Examples of the polymerizable group include vinyl group, vinyloxy group, 1-chlorovinyl group, isopropenyl group, 4-vinylphenyl group, acryloyloxy group, methacryloyloxy group, oxiranyl group and oxetanyl group. Among them, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxiranyl group and an oxetanyl group are preferable as the polymerizable group, and an acryloyloxy group is more preferable.

In formula (4), V ¹ and V ² independently represent an alkanediyl group having 1 to 20 carbon atoms which may have a substituent, and -CH _2- constituting the alkanediyl group is , -O-, -S- or -NH- may be substituted. Examples of the alkanediyl group having 1 to 20 carbon atoms include methylene, ethylene, propane-1,3-diyl, butane-1,3-diyl, butane-1,4-diyl and pentane-1. 3,5-diyl group, hexane-1,6-diyl group, heptane-1,7-diyl group, octane-1,8-diyl group, decane-1,10-diyl group, tetradecane-1,14-diyl group And icosan-1,20-diyl group. V ¹ and V ² are preferably alkanediyl groups having 2 to 12 carbon atoms, and more preferably alkanediyl groups having 6 to 12 carbon atoms. As a substituent which a C1-C20 alkanediyl group optionally has, a cyano group and a halogen atom can be mentioned, for example. The alkanediyl group is preferably unsubstituted, and more preferably unsubstituted and linear.

In formula (4), W ¹ and W ² independently represent a single bond, -O-, -S-, -COO- or -OCOO-, preferably a single bond or -O-.

  As a compound (4), the compound represented by Formula (4-1)-Formula (4-43) is mentioned, for example. When a specific example of the compound (4) has a cyclohexane-1,4-diyl group, the cyclohexane-1,4-diyl group is preferably a trans-isomer.

  A polymerizable liquid crystal compound can be used for the composition for polarizer formation individually or in mixture of 2 or more types. When two or more polymerizable liquid crystal compounds are mixed, it is preferable that at least one be a compound (4). As a mixing ratio in the case of mixing two types of polymerizable liquid crystal compounds, usually, the ratio of the polymerizable liquid crystal compound other than the compound (4): the compound (4) is 1:99 to 50:50, preferably 5:95. 50: 50, more preferably 10: 90 to 50: 50.

  Among the compounds (4), the compounds of the formula (4-5), the formula (4-6), the formula (4-7), the formula (4-8), the formula (4-9), the formula (4-10) and the formula (4-11), formula (4-12), formula (4-13), formula (4-14), formula (4-15), formula (4-22), formula (4-24), formula (4) 4-25), the compound represented by Formula (4-26), Formula (4-27), Formula (4-28), and Formula (4-29) are preferable. These compounds are polymerized by the interaction with other polymerizable liquid crystal compounds, under temperature conditions easily below the crystal phase transition temperature, that is, while maintaining the liquid crystal state of the higher smectic phase sufficiently. Can. Specifically, these compounds can be polymerized under a temperature condition of 70 ° C. or less, preferably 60 ° C. or less, while sufficiently maintaining the liquid crystal state of the high-order smectic phase.

  The content ratio of the polymerizable liquid crystal compound in the composition for forming a polarizer is preferably 50 to 99.9% by mass, and more preferably 80 to 99.9% by mass with respect to the solid content of the composition for forming a polarizer. If the content ratio of the polymerizable liquid crystal compound is in the above range, the orientation of the polymerizable liquid crystal compound tends to be high. The solid content refers to the total amount of components excluding volatile components such as a solvent from the composition for forming a polarizer.

  Polymerizable liquid crystal compounds are described, for example, in Lub et al. Recl. Trav. Chim. It manufactures by the well-known method as described in Pays-Bas, 115, 321-328 (1996), the patent 4719156 grade | etc.,.

1-3. Solvent The composition for forming a polarizer preferably contains a solvent. As the solvent, a solvent capable of completely dissolving the dichroic dye and the polymerizable liquid crystal compound is preferable. Moreover, it is preferable that it is a solvent inactive to the polymerization reaction of the polymeric liquid crystal compound contained in the composition for polarizer formation.

  Examples of solvents 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; ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ -Ester solvents such as butyrolactone, 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; nitrile solvents such as acetonitrile; Furan and ether solvents such as dimethoxyethane; and chloroform and chlorine-containing solvents such as chlorobenzene and the like. 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 with respect to the total amount of the composition for forming a polarizer. In other words, the solid content in the composition for forming a polarizer is preferably 2 to 50% by mass. When the solid content is 2% by mass or more, a thin polarizing plate, which is one of the objects of the present invention, can be easily obtained. Moreover, since the viscosity of the composition for polarizer formation will become it low that this solid content is 50 mass% or less, since the thickness of a polarizer becomes substantially uniform, it becomes difficult to produce a nonuniformity in the said polarizer. The solid content can be determined in consideration of the thickness of the polarizer.

1-4. Additive The composition for forming a polarizer according to the present embodiment can optionally contain an additive. As an additive, a polymerization initiator, a photosensitizer, a polymerization inhibitor, and a leveling agent are mentioned, for example.

1-4-1. Polymerization Initiator The composition for forming a polarizer preferably contains a polymerization initiator. The polymerization initiator is a compound capable of initiating the polymerization reaction of the polymerizable liquid crystal compound. As the polymerization initiator, a photopolymerization initiator is preferred in that the polymerization reaction can be initiated under low temperature conditions. Specifically, a compound that generates an active radical or an acid by the action of light is used as a photopolymerization initiator. Among the photopolymerization initiators, those which generate active radicals by the action of light are more preferable.

  Examples of the polymerization initiator include benzoin compounds, benzophenone compounds, alkylphenone compounds, acyl phosphine 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, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4′-methyldiphenyl sulfide, 3,3 ′, 4,4′-tetra (tert-butylperoxycarbonyl) And benzophenone and 2,4,6-trimethylbenzophenone.

  As the alkyl phenone compound, for example, 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 2-hydroxy-2-methyl-1- [4- (1-methylvinyl) phenyl] propane-1-propane On oligomers are included.

  Examples of the acyl phosphine oxide compound include 2,4,6-trimethyl benzoyl diphenyl phosphine oxide and bis (2,4,6-trimethyl benzoyl) phenyl phosphine oxide.

  As a triazine compound, for example, 2,4-bis (trichloromethyl) -6- (4-methoxyphenyl) -1,3,5-triazine, 2,4-bis (trichloromethyl) -6- (4-methoxy Naphthyl) -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) 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 (trichloro) Methyl)- - [2- (3,4-dimethoxyphenyl) ethenyl] -1,3,5-triazine.

  A commercially available thing can also be used for a polymerization initiator. Commercially available polymerization initiators include, for example, “Irgacure 907”, “Irgacure 184”, “Irgacure 651”, “Irgacure 819”, “Irgacure 250”, “Irgacure 369” (BASF Japan Ltd.); "Seikool BZ", "Seikool Z", "Seikool BEE" (Seiko Chemical Co., Ltd.); "kayacure BP 100" (Nippon Kayaku Co., Ltd.); "UVI-6992" (made by Dow Chemical Co.); “Adeka Optomer SP-152”, “Adeka Optomer SP-170” (ADEKA Corporation), “TAZ-A”, “TAZ-PP” (DKSH Japan), and “TAZ-104” And Sanwa Chemical).

  When the composition for forming a polarizer contains a polymerization initiator, the content thereof can be appropriately adjusted according to the type and the amount of the polymerizable liquid crystal compound contained in the composition for forming a polarizer, but usually, The content of the polymerization initiator is 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 with respect to a total of 100 parts by mass of the base liquid crystal compound is there. If the content of the polymerizable initiator is in this range, it is preferable because polymerization can be performed without disturbing the alignment of the polymerizable liquid crystal compound.

1-4-2. Photosensitizer The composition for forming a polarizer, when containing a photopolymerization initiator, may further contain a photosensitizer. Examples of photosensitizers include xanthone compounds such as xanthone and thioxanthone (for example, 2,4-diethylthioxanthone, 2-isopropylthioxanthone and the like); anthracenes such as anthracene and alkoxy group-containing anthracene (for example, dibutoxyanthracene and the like) Compounds; include phenothiazine and rubrene.

  When the composition for forming a polarizer contains a photopolymerization initiator and a photosensitizer, the polymerization reaction of the polymerizable liquid crystal compound contained in the composition for forming a polarizer is further promoted. The content of the photosensitizer can be appropriately adjusted according to the type and the amount of the photopolymerization initiator and the polymerizable liquid crystal compound to be used in combination, but generally, 0 parts by weight relative to 100 parts by mass of the content of the polymerizable liquid crystal compound 1 to 30 parts by mass, preferably 0.5 to 10 parts by mass, and more preferably 0.5 to 8 parts by mass.

1-4-3. Polymerization Inhibitor The composition for forming a polarizer may contain a polymerization inhibitor in order to stably advance the polymerization reaction of the polymerizable liquid crystal compound. The degree of progress of the polymerization reaction of the polymerizable liquid crystal compound can be controlled by the polymerization inhibitor.

  Examples of the polymerization inhibitor include radicals such as hydroquinone, alkoxy group-containing hydroquinone, alkoxy group-containing catechol (eg, butyl catechol etc.), pyrogallol, 2,2,6,6-tetramethyl-1-piperidinyloxy radical and the like. Thiophenols; β-naphthylamines and β-naphthols are included.

  When the composition for forming a polarizer contains a polymerization inhibitor, the content thereof is appropriately adjusted according to the type and amount of the polymerizable liquid crystal compound used, the content of the photosensitizer, etc. The amount is 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 with respect to 100 parts by mass of the polymerizable liquid crystal compound. If content of a polymerization inhibitor is in the said range, since it can polymerize, without disturbing the orientation of the polymeric liquid crystal compound contained in the composition for polarizer formation, it is preferable.

1-4-4. Leveling Agent The composition for forming a polarizer preferably contains a leveling agent. The leveling agent has the function of adjusting the flowability of the composition for forming a polarizer, making the coated film obtained by applying the composition for forming a polarizer flatter, and includes surfactants and the like. be able to. As a leveling agent, the leveling agent which has a polyacrylate compound as a main component, and the leveling agent which has a fluorine atom containing compound as a main component are mentioned, for example.

  As a leveling agent which has a polyacrylate compound as a main component, for example, “BYK-350”, “BYK-352”, “BYK-353”, “BYK-354”, “BYK-355”, “BYK-358N” “BYK-361N”, “BYK-380”, “BYK-381” and “BYK-392” [BYK Chemie].

  As a leveling agent which has a fluorine atom containing compound as a main component, Megafac "R-08", "R-30", "R-90", "F-410", "F-411", "F", for example -443 "," F-445 "," F-470 "," F-471 "," F-477 "," F-479 "," F-482 "and" F-483 "[DIC Corporation] Surfrons "S-381", "S-382", "S-383", "S-393", "SC-101", "SC-105", "KH-40" and "SA-100" [AGC Seimi Chemical Co., Ltd.]; "E1830", "E5844" [Daikin Industries, Ltd.]; F-top "EF301", "EF303", "EF351" and "EF352" [Mitsubishi Materials Electronics Kasei Co., Ltd.] Can be mentioned.

  When the composition for forming a polarizer contains a leveling agent, the content thereof is usually 0.3 parts by mass or more and 5 parts by mass or less, preferably 100 parts by mass of the content of the polymerizable liquid crystal compound. 0.5 parts by mass or more and 3 parts by mass or less. When the content of the leveling agent is in the above range, it is easy to horizontally align the polymerizable liquid crystal compound, and the obtained polarizer tends to be smoother. When the content of the leveling agent with respect to the polymerizable liquid crystal compound exceeds the above range, unevenness tends to easily occur in the obtained polarizer. The composition for forming a polarizer may contain two or more types of leveling agents.

  The polarizer according to this embodiment preferably has an absorbance (A1) in the absorption axis direction at a wavelength of 380 to 760 nm of 0.3 or more and 2.0 or less, and an absorbance (A2) in the transmission axis direction of 0.001 It is preferable that it is 1.0 or less.

  The absorbance is controlled by controlling the type of dichroic dye contained in the polarizer, the amount of dichroic dye, the solid content concentration in the composition for forming a polarizer, or the coating amount. Adjustment can be made as appropriate.

2. Method of Forming Polarizer A method of forming a polarizer using the composition for forming a polarizer will be described. In such a method, the polarizer is formed by applying the composition for forming a polarizer to a substrate, preferably to a transparent substrate.

2-1. Substrate The transparent substrate is a substrate having transparency to such an extent that it can transmit light, particularly visible light. The term "transparency" refers to the property that the transmittance to light having a wavelength of 380 to 780 nm is 80% or more. Specifically, as the transparent substrate, for example, a glass substrate and a plastic substrate can be mentioned, and preferably a plastic substrate. Examples of plastics constituting the plastic substrate include polyolefins such as polyethylene, polypropylene and norbornene polymers; cyclic olefin resins; polyvinyl alcohol; polyethylene terephthalate; polymethacrylates; polyacrylates; triacetylcelluloses and diacetylcelluloses And cellulose esters such as cellulose acetate propionate; polyethylene naphthalate; polycarbonates; polysulfones; polyethersulfones; polyether ketones; polyether ketones; polyphenylene sulfides and polyphenylene oxides. Among them, particularly preferred are cellulose ester, cyclic olefin resin, polyethylene terephthalate or polymethacrylic acid ester in view of easy availability from the market and excellent transparency. When manufacturing a polarizer using a transparent substrate, it can be easily handled without causing breakage such as breakage when carrying or storing the transparent substrate, a transparent substrate, etc. You may paste it. Moreover, although mentioned later, when manufacturing a circularly-polarizing plate from a polarizer, retardation may be provided to a plastic base material. In this case, the plastic substrate may be provided with retardation by drawing treatment or the like.

  When giving a phase difference to a plastic base material, the plastic base material which consists of a cellulose ester or cyclic olefin resin is preferable at the point that it is easy to control the phase difference value.

  The cellulose ester is one in which at least a part of hydroxyl groups contained in cellulose is esterified with acetic acid. Cellulose ester films comprising such cellulose esters are readily available from the market. Examples of commercially available triacetyl cellulose films include "Fujitack Film" (Fuji Photo Film Co., Ltd.); "KC8UX2M", "KC8UY" and "KC4UY" (Konica Minolta Opto Co., Ltd.). Such a commercially available triacetyl cellulose film can be used as a transparent substrate as it is or after imparting retardation as required. Moreover, it can be used as a transparent base material, after performing surface treatments, such as a glare-proof process, a hard-coat process, an antistatic process, or an antireflection process, on the surface of the prepared transparent base material.

  In order to impart retardation to the plastic substrate, as described above, a method of stretching the plastic substrate can be used. Although any plastic base material made of a thermoplastic resin can be stretched, a plastic base material made of a cyclic olefin-based resin is more preferable in that it is easy to control retardation. The cyclic olefin resin is, for example, one composed of a polymer or copolymer of cyclic olefin such as norbornene or polycyclic norbornene monomer. The cyclic olefin resin may partially include a ring opening, or may be one obtained by hydrogenating the cyclic olefin resin including the ring opening. The cyclic olefin-based resin is, for example, a copolymer of a cyclic olefin and a chain olefin or a vinylated aromatic compound (such as styrene) in that the transparency is not significantly impaired and the hygroscopicity is not significantly increased. May be In addition, a polar group may be introduced into the molecule of the cyclic olefin resin.

  When the cyclic olefin resin is a copolymer of a cyclic olefin and an aromatic compound having a chain olefin or a vinyl group, examples of the chain olefin include ethylene and propylene, and a vinylated aromatic compound Examples include, for example, styrene, α-methylstyrene and alkyl-substituted styrene. In such a copolymer, the content ratio of the structural unit derived from the cyclic olefin is 50 mol% or less, for example, about 15 to 50 mol%, with respect to the total structural units of the cyclic olefin resin. When the cyclic olefin-based resin is a ternary copolymer obtained from cyclic olefin, chain olefin and vinylated aromatic compound, for example, the content ratio of the structural unit derived from chain olefin is the cyclic olefin The content of the structural unit derived from the vinylated aromatic compound is about 5 to 80 mol%, based on about 5 to 80 mol% based on the total structural units of the resin. Such a terpolymer cyclic olefin resin has an advantage that the amount of expensive cyclic olefin used can be relatively reduced when producing the cyclic olefin resin.

  Cyclic olefin resins are readily available from the market. Examples of commercially available cyclic olefin-based resins include “Topas” (Ticona (Germany)); “Arton” (JSR Corporation); “ZEONOR” and “ZEONEX” (Nippon ZEON Corporation ]]; "Apple" (manufactured by Mitsui Chemicals, Inc.). Such a cyclic olefin resin can be formed into a film (cyclic olefin resin film) by, for example, a known film forming method such as a solvent casting method or a melt extrusion method. In addition, cyclic olefin-based resin films that are already commercially available in the form of films can also be used. As such commercially available cyclic olefin resin films, for example, “ESSINA” and “SCA 40” (Sekisui Chemical Co., Ltd.); “ZEONOR Film” [Optes Co., Ltd.]; and “Arton Film” [JSR (JSR Stock)].

  Subsequently, a method for imparting retardation to a plastic substrate will be described. The plastic substrate can be provided with retardation by a known stretching method. For example, a roll (rolling body) in which the plastic substrate is wound into a roll is prepared, the plastic substrate is continuously unwound from the wound body, and the unwound plastic substrate is transferred to the heating furnace. Transport The setting temperature of the heating furnace is in the range of around glass transition temperature (° C.) to [glass transition temperature + 100] (° C.) of the plastic substrate, preferably around glass transition temperature (° C.) to [glass transition temperature + 50] (° C.) Range of In the heating furnace, when stretching in the direction of movement of the plastic base material or in the direction perpendicular to the direction of movement, the transport direction and tension are adjusted, an arbitrary angle is inclined, and uniaxial or biaxial thermal stretching processing is performed. Do. The magnification of stretching is usually in the range of about 1.1 to 6 times, preferably in the range of about 1.1 to 3.5 times. Moreover, as a method of extending | stretching diagonally, if an orientation axis | shaft can be continuously made to incline to a desired angle, it will not be specifically limited, A well-known extending | stretching method is employable. As such an extending | stretching method, the method described in Unexamined-Japanese-Patent No. 50-83482 and Unexamined-Japanese-Patent No. 2-113920 can be mentioned, for example.

  The thickness of the transparent substrate is preferably as thin as possible in terms of practical handling weight and sufficient transparency can be ensured, but if it is too thin, the strength decreases and the processability is inferior. Tend. A suitable thickness of the glass substrate is, for example, about 100 to 3000 μm, preferably about 100 to 1000 μm. An appropriate thickness of the plastic substrate is, for example, about 5 to 300 μm, and preferably about 20 to 200 μm. When using the polarizing plate of this embodiment as a circularly-polarizing plate mentioned later, and using it as a circularly polarizing plate especially a mobile device application, the thickness of the transparent base material is preferably about 20 to 100 μm. In addition, when providing retardation to a film by extending | stretching, the thickness after extending | stretching is determined by the thickness and extending ratio before extending | stretching.

  FIG. 1 is a cross-sectional view schematically showing an embodiment of a polarizing plate 10 according to the present invention. The polarizing plate 10 has a base 1 and a polarizer (polarizing layer) 3 provided on the base 1. In the polarizer 3, the dichroic dye 3 a is oriented. An alignment layer 2 described later may be formed on the base material 1.

2-2. Alignment layer It is preferable that the alignment layer is formed in the base material used for manufacture of a polarizer. In this case, the composition for forming a polarizer is to be applied on the alignment layer. For this reason, it is preferable that the orientation layer has solvent resistance to such an extent that it does not dissolve by application of the composition for forming a polarizer. In addition, it is preferable to have heat resistance in heat treatment for removal of a solvent and alignment of liquid crystal. The alignment layer can be formed of an alignment polymer.

  Examples of orientation polymers include polyamides, gelatins, polyimides, polyamic acids, polyvinyl alcohols, alkyl-modified polyvinyl alcohols, polyacrylamides, polyoxazoles, polyethylene imines, polystyrenes, polyvinyl pyrrolidones, polyacrylic acids and polyacrylic esters. be able to. Among these, polyvinyl alcohol is preferable. These orientable polymers may be used alone or as a mixture of two or more.

  An orientation polymer can form an orientation layer on a base material by apply | coating on a base material as an orientation polymer composition (solution containing an orientation polymer) melt | dissolved in the solvent. As the solvent, for example, water; alcohol solvents such as methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, methyl cellosolve, butyl cellosolve and propylene glycol monomethyl ether; ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone Ester solvents such as 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; toluene And aromatic hydrocarbon solvents such as xylene, nitrile solvents such as acetonitrile; tetrahydrofuran and dimethoxymethane Ether solvents emissions and the like; as well as chloroform and chlorinated hydrocarbon solvents such as chlorobenzene. These solvents may be used alone or in combination of two or more.

  A commercially available alignment film material may be used as it is as an alignment polymer composition. Examples of commercially available alignment film materials include Sun Ever (registered trademark, manufactured by Nissan Chemical Industries, Ltd.) and Optomer (registered trademark, manufactured by JSR Corporation).

  As a method of forming an alignment layer on a substrate, for example, a method of applying an alignment polymer composition or a commercially available alignment film material on a substrate and annealing may be mentioned. The thickness of the orientation layer obtained in this manner is usually in the range of 10 nm to 10000 nm, preferably in the range of 10 nm to 1000 nm.

  In order to impart an alignment regulating force to the alignment film, it is preferable to perform rubbing as necessary (a rubbing method). The polymerizable liquid crystal compound can be aligned in a desired direction by applying an alignment control force.

  As a method of imparting alignment control force by rubbing method, for example, a rubbing cloth is wound, and a rotating rubbing roll is prepared, and a laminate having a coating film for forming an alignment layer formed on a substrate is obtained. A method of bringing the coating film for forming an alignment layer and the rotating rubbing roll into contact with each other by placing the film on the stage and conveying it toward the rotating rubbing roll.

  The alignment layer may be a photo alignment layer. In the photoalignment layer, a composition containing a polymer or monomer having a photoreactive group and a solvent (hereinafter referred to as “composition for forming a photoalignment layer” as the case may be) is applied to a substrate and polarized (preferably Refers to an alignment layer to which an alignment regulating force is imparted by irradiating polarized UV light. The photoreactive group refers to a group that generates liquid crystal alignment ability by irradiating light. Specifically, it generates a photoreaction that is the source of liquid crystal alignment ability, such as alignment induction or isomerization reaction of molecules generated by light irradiation, dimerization reaction, photocrosslinking reaction, or photolysis reaction. is there. A photoreactive group that causes a dimerization reaction or a photocrosslinking reaction is preferable in that it is excellent in the orientation and retains the smectic liquid crystal state at the time of forming a polarizer. The photoreactive group is preferably one having an unsaturated bond, particularly a double bond, and preferably a carbon-carbon double bond (C = C bond), a carbon-nitrogen double bond (C = N bond), a nitrogen-nitrogen A group having at least one selected from the group consisting of a double bond (N 結合 N bond) and a carbon-oxygen double bond (C = O bond) is more preferable.

  Examples of the photoreactive group having a C = C bond include vinyl group, polyene group, stilbene group, stilbazole group, stilbazolium group, chalcone group and cinnamoyl group. Examples of photoreactive groups having a C = N bond include groups having structures such as aromatic Schiff bases and aromatic hydrazones. Examples of the photoreactive group having an N = N bond include an azobenzene group, an azonaphthalene group, an aromatic heterocyclic azo group, a bisazo group and a formazan group, and a group having an azoxybenzene as a basic structure. Examples of the photoreactive group having a C = O bond include benzophenone group, coumarin group, anthraquinone group and 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 or a halogenated alkyl group. Among them, a photoreactive group capable of causing a photodimerization reaction is preferable, and a cinnamoyl group and a chalcone group have a relatively small irradiation amount of polarized light necessary for photoalignment, and a photoalignment layer excellent in thermal stability and temporal stability It is preferable because it is easily obtained. Furthermore, as a polymer which has a photoreactive group, what has a cinnamoyl group which the terminal part of a polymer side chain becomes a cinnamic acid structure is more preferable.

  As a solvent of the composition for photo-alignment layer formation, what melt | dissolves the polymer and monomer which have a photoreactive group is preferable, For example, the solvent used for the above-mentioned orientation polymer composition is mentioned.

  The concentration of the polymer or monomer having a photoreactive group relative to the composition for forming a photoalignment layer can be appropriately adjusted depending on the type of the polymer or monomer having a photoreactive group and the thickness of the photoalignment layer to be produced. The concentration is preferably at least 0.2% by mass, and more preferably in the range of 0.3 to 10% by mass. The composition for forming a photoalignment layer may contain a polymer material such as polyvinyl alcohol or polyimide, and a photosensitizer within the range that the characteristics of the photoalignment layer are not significantly impaired.

  As a method of applying an oriented polymer composition or a composition for forming a photoalignment layer on a substrate, a spin coating method, an extrusion method, a gravure coating method, a die coating method, a bar coating method, an applicator method, etc. A known method such as a coating method or a printing method such as flexo method may be employed. In addition, when manufacturing polarizer by the continuous manufacturing method of a RolltoRoll type | mold, as a coating method, printing methods, such as a gravure coating method, a die coating method, or a flexographic method, are normally employ | adopted.

  Note that when rubbing or polarized irradiation is performed, masking can be performed to form a plurality of regions (patterns) having different alignment directions.

2-3. Method for Producing Polarizing Plate A composition for forming a polarizer is coated on a substrate or an alignment layer formed on the substrate to obtain a coated film. As a method of apply | coating the composition for polarizer formation, the same method as what was illustrated as a method of apply | coating the composition for alignment polymer composition or the composition for photo-alignment layers formation to a base material is mentioned, for example.

  Next, a dry film is formed by drying and removing the solvent under the condition that the polymerizable liquid crystal compound contained in the coating film is not polymerized. Examples of the drying method include a natural drying method, a ventilation drying method, a heat drying method and a reduced pressure drying method.

  As a preferable mode, once the liquid crystal state of the polymerizable liquid crystal compound contained in the dried film is changed to a nematic liquid crystal, the nematic liquid crystal phase is transferred to a smectic liquid crystal phase. Thus, in order to form a smectic liquid crystal phase via a nematic liquid crystal phase, for example, the polymerizable liquid crystal compound contained in the dry film is heated to a temperature at which the nematic liquid crystal phase is exhibited, and then the polymerizable liquid crystal compound is A method of cooling to a temperature showing a smectic liquid crystal phase is employed.

  In the case where the polymerizable liquid crystal compound in the dried film is a smectic liquid crystal phase or the polymerizable liquid crystal compound is a smectic liquid crystal phase via a nematic liquid crystal phase, the phase transition temperature of the polymerizable liquid crystal compound is measured. Conditions (heating conditions) for controlling the liquid crystal state can be determined. The measurement conditions of the phase transition temperature are described in the examples of the present specification.

  Next, the polymerization process of the polymerizable liquid crystal compound will be described. Here, after the composition for forming a polarizer contains a photopolymerization initiator, and the liquid crystal state of the polymerizable liquid crystal compound in the dried film is made a smectic liquid crystal phase, polymerization is carried out while the liquid crystal state of this smectic liquid crystal phase is maintained. The method of photopolymerizing a crystalline liquid crystal compound is described in detail.

  In the photopolymerization, as light to be applied to the dried film, the type of photopolymerization initiator contained in the dried film, or the type of polymerizable liquid crystal compound (in particular, the type of polymerizable group of the polymerizable liquid crystal compound) and the amount thereof Depending on the case, it can carry out by the light and active electron beam suitably selected from the group which consists of visible light, an ultraviolet light, and a laser beam. Among these, ultraviolet light is preferred in that the progress of the polymerization reaction can be easily controlled and that a device widely used in the field as an apparatus for photopolymerization can be used. Therefore, it is preferable to select the kind of the polymerizable liquid crystal compound and the photopolymerization initiator contained in the composition for forming a polarizer so as to allow photopolymerization by ultraviolet light. When the polymerization is carried out, the polymerization temperature can also be controlled by cooling the dried film by an appropriate cooling means together with ultraviolet light irradiation. If the polymerization of the polymerizable liquid crystal compound can be carried out at a lower temperature by adopting such a cooling means, there is also an advantage that a polarizer can be appropriately formed even if a substrate having relatively low heat resistance is used as the substrate. In addition, the patterned polarizer can also be obtained by performing masking and image development in photopolymerization.

  By performing the photopolymerization as described above, the polymerizable liquid crystal compound is polymerized while maintaining the nematic liquid crystal phase or the smectic liquid crystal phase, preferably, the high-order smectic liquid crystal phase as exemplified above, and a polarizer is formed. Be done. A polarizer obtained by polymerizing a polymerizable liquid crystal compound while holding a smectic liquid crystal phase is a conventional host-guest-type polarizer, that is, polymerizes a polymerizable liquid crystal compound etc. while holding the liquid crystal state of a nematic liquid crystal phase. There is an advantage that the polarization performance is high compared to the polarizer obtained. Furthermore, it has the advantage of being superior in strength as compared with those coated with only the lyotropic dichroic dye.

  The thickness of the polarizer is preferably in the range of 0.5 μm to 5 μm, and more preferably 1 μm to 5 μm. Therefore, the thickness of the coating film for forming a polarizer is determined in consideration of the thickness of the obtained polarizer. The thickness of the polarizer can be determined by measurement with an interference film thickness meter, a laser microscope or a stylus film thickness meter.

  It is particularly preferable that the formed polarizer is one that can obtain a Bragg peak in X-ray diffraction measurement as described above. As a polarizer from which a Bragg peak is obtained, a polarizer which shows a diffraction peak derived from a hexatic phase or a crystal phase can be mentioned, for example.

The polarizer according to the present embodiment is excellent in neutral hue. With a polarizer excellent in neutral hue property, color coordinates a * value and b * value in L * a * b * (Lab) color system satisfy the relationship of the following formulas (1F) and (2F) It is a thing.
−3 ≦ chromaticity a * ≦ 3 (1F)
-3 ≦ chromaticity b * ≦ 3 (2F)

  The color coordinates a * value and b * value are also referred to as “chromaticity a *” and “chromaticity b *”. As a * and b * are both closer to 0 (zero), it is determined that the polarizer exhibits a neutral hue. In a display provided with such a polarizer, a good white display without coloring is obtained.

In the hue of the polarizer, two polarizers are overlapped so that the absorption axes are orthogonal to each other, the hue at that time is determined in the same manner as above, and “orthogonal a *” and “orthogonal b *” are calculated, It is further preferable that each of the orthogonal a * and the orthogonal b * satisfy the relationship of the following equation (1F ′) and the equation (2F ′). The orthogonal a * and the orthogonal b * are indices indicating whether or not the hue of black display is neutral in a display device provided with a polarizer. The closer this orthogonal a * and the orthogonal b * are to 0 (zero), the better the good black display without coloring.
-3 直交 orthogonal a * 3 3 (1F ')
−3 ≦ orthogonal b * ≦ 3 (2F ′)

  In the case of commercially manufacturing a polarizer, a method capable of continuously forming a polarizer is required. Such a continuous manufacturing method is of the RolltoRoll type and is sometimes referred to as "the present manufacturing method". In addition, in this manufacturing method, it demonstrates centering on the case where a base material is a transparent base material. When the substrate is a transparent substrate, what is finally obtained is a polarizing plate having a transparent substrate and a polarizer.

  This manufacturing method includes, for example, a step of preparing a first roll in which a transparent substrate is wound around a first core, a step of continuously feeding the transparent substrate from the first roll, and a transparent substrate A step of continuously forming an alignment layer thereon, a step of continuously applying a composition for forming a polarizer on the alignment layer, and a polymerizable liquid crystal compound which is applied to the composition for forming a polarizer A step of continuously forming a dry film on the alignment layer by drying under conditions that do not polymerize, and after making the polymerizable liquid crystal compound contained in the dry film a nematic liquid crystal phase, preferably a smectic liquid crystal phase A step of continuously obtaining a film as a polarizer by polymerizing a polymerizable liquid crystal compound while holding a smectic liquid crystal phase, and winding up the continuously obtained polarizer on a second core, Obtaining a second roll.

  The polarizing plate obtained by the present manufacturing method is a polarizing film having a film-like shape and a long shape. When this polarizing plate is used for a liquid crystal display to be described later, it is cut to a desired size according to the scale of the liquid crystal display and the like.

  The polarizing plate can take the form of a laminate of transparent substrate / photoalignment layer / polarizer, but the polarizer can also be obtained as a single layer by peeling the photoalignment layer or the transparent substrate. In addition, the polarizing plate may have a form in which a layer or film other than the transparent substrate / photoalignment layer / polarizer is laminated. As these layers and films, as described above, the polarizing plate may further include a retardation film, and may further include an antireflective layer or a brightness enhancement film.

  For example, the polarizing plate of the present embodiment becomes a circularly polarizing plate by including a 1⁄4 wavelength plate. In FIG. 2, it is sectional drawing which shows typically one Embodiment of the circularly-polarizing plate 100 which concerns on this invention. The circularly polarizing plate 100 is provided on the surface opposite to the surface of the substrate 1 on which the alignment layer 2 is formed, the polarizer 3 provided on the alignment layer 2, and the surface on which the alignment layer 2 of the substrate 1 is formed. And a retardation film 4 which is a quarter wave plate. The retardation film 4 may be formed on the polarizer 3 side. In this case, as shown in FIG. 3, the circularly polarizing plate 110 can also take a form in which the base material 1, the alignment layer 2, the polarizer 3 and the retardation film 4 are arranged in this order.

  When producing a circularly-polarizing plate, you may bond together the base material 1 or the polarizer 3, and the retardation film 4 through the adhesion layer formed from an adhesive using a suitable adhesive.

  The transparent substrate itself may have a function as a retardation layer by using the substrate 1 (retardation film 4) to which retardation is given in advance as the transparent substrate. By setting the transparent substrate itself as a retardation film, it is also possible to form a circularly polarizing plate or an elliptically polarizing plate in the form of retardation film / photoalignment layer / polarizer. For example, in the case of using a quarter-wave plate uniaxially stretched as a retardation film, by setting the irradiation direction of polarized UV to be approximately 45 ° with respect to the transport direction of the transparent substrate, a circle is created by RolltoRoll. It is possible to make a polarizer. Thus, it is preferable that the 1⁄4 wavelength plate used when manufacturing the circularly polarizing plate has a characteristic that the in-plane retardation value with respect to visible light decreases as the wavelength becomes shorter. FIG. 4 is a cross-sectional view schematically showing an embodiment of the circularly polarizing plate 120 in the case where the base material itself functions as a retardation film. The circularly polarizing plate 120 can take the form of a retardation film 4 on which the alignment layer 2 is formed, and a polarizer 3 provided on the alignment layer 2.

  Using a half-wave plate as a retardation film, a linear polarizing plate roll was prepared by shifting the angle of its slow axis and absorption axis of the polarizer, and on the opposite side to the surface on which the polarizer was formed It is also possible to obtain a wide-range circularly polarizing plate by further forming a quarter wavelength plate.

The birefringence for the light of wavelength 450 nm, the birefringence for light of wavelength 550 nm, and the birefringence for light of wavelength 650 nm of the quarter wavelength plate used as the retardation film are given by the following formulas (II) and (III) It is preferable to have reverse wavelength dispersion which satisfies the relationship shown. In the formula, Δn (λ) represents a birefringence for light of wavelength λ nm.
Δn (450) / Δn (550) ≦ 1.00 (II)
1.00 ≦ Δn (650) / Δn (550) (III)
A retardation film exhibiting such reverse wavelength dispersion characteristics can be produced by the method described in Japanese Patent No. 5463666.

4. Application of Polarizing Plate The polarizing plate can be used for various display devices. The display device is a device having a display element, and includes a light emitting element or a light emitting device as a light emitting source. As a display device, for example, a liquid crystal display device, an organic electroluminescence (EL) display device, an inorganic electroluminescence (EL) display device, an electron emission display device (for example, an electric field emission display (FED), a surface field emission display (SED) ), Electronic paper (display using electronic ink or electrophoretic element, plasma display, projection display (for example, grating light valve (GLV) display, display having digital micro mirror device (DMD)), Examples of the liquid crystal display device include a transmissive liquid crystal display device, a semi-transmissive liquid crystal display device, a reflective liquid crystal display device, a direct view liquid crystal display device, and a projection liquid crystal display device. Is a display device that displays a two-dimensional image Stone, or it may be a three-dimensional display apparatus for displaying a three dimensional image. The polarizing plate of the present embodiment can be effectively used in particular display device of the organic EL display device or an inorganic EL display device.

  As an electronic paper, one represented by molecules such as optical anisotropy and dye molecule orientation, one represented by particles such as electrophoresis, particle migration, particle rotation, phase change, one end of a film is displaced What is displayed by this, what is displayed by color development / phase change of a molecule, what is displayed by light absorption of a molecule, that by which an electron and a hole are combined and is displayed by self-emission may be mentioned. More specifically, microcapsule electrophoresis, horizontal migration electrophoresis, vertical migration electrophoresis, spherical twist ball, magnetic twist ball, cylindrical twist ball system, charged toner, electronic powder fluid, magnetophoresis, magnetic thermosensitive Formula, electrowetting, light scattering (transparent / white turbidity change), cholesteric liquid crystal / photoconductive layer, cholesteric liquid crystal, bistable nematic liquid crystal, ferroelectric liquid crystal, dichroic dye / liquid crystal dispersion type, movable film, leuco dye And photochromic, electrochromic, electrodeposition, and flexible organic EL. Electronic paper may be used not only for personal use of texts and images but also for advertisement display (signage) and the like. According to the polarizing plate of the present embodiment, the thickness of the electronic paper can be reduced.

  As a three-dimensional display device, for example, a method of arranging different retardation films alternately as in a micropole system has been proposed (Japanese Patent Application Laid-Open No. 2002-185983), but when the polarizing plate of this embodiment is used, printing is performed. Since patterning is easy by inkjet, photolithography or the like, the manufacturing process of the display device can be shortened, and the retardation film is not necessary.

  Hereinafter, the present invention will be described in more detail by way of examples. Unless otherwise indicated, "%" and "parts" in the examples are% by mass and parts by mass.

[Absorbance measurement]
The absorbance of the polarizer was measured as follows. The absorbance (A1) in the alignment direction (absorption axis direction) of the dichroic dye and the absorbance (A2) in the plane of the polarizer and in the alignment perpendicular direction (transmission axis direction) are measured using a spectrophotometer (manufactured by Shimadzu Corporation) It measured in a 2 nm step 380-680 nm wavelength range by the double beam method using the apparatus which set the folder with a polarizer to UV-3150). In addition, in order to remove the contribution of the light loss due to the surface reflection of the polarizing plate, after setting the measurement sample, the measurement was performed after correcting the zero point at 800 nm without light absorption.

[Heat resistance evaluation]
The triacetyl cellulose film surface in a polarizing plate was bonded to a glass substrate via an adhesive. Then, the absorbance A1 in the absorption axis direction at 23 ° C. was measured by the above method (A1 (23 ° C.)). Thereafter, it was put into an oven at 85 ° C. for 100 hours, and after taking it out, absorbance measurement was carried out again by the above method. Absorbance retention (%) was calculated by the following formula (I).
Absorbance retention (%) = A1 (85 ° C.) / A1 (23 ° C.) × 100 (I)
In the formula, A1 (85 ° C.) is the absorbance in the direction of the absorption axis after holding the polarizing plate in a heat-resistant oven at 85 ° C. for 100 hours, and A1 (23 ° C.) is the absorption when measured at 23 ° C. before the heat resistance test. The absorbance in the axial direction is shown.

[Film thickness measurement]
After cutting the polarizing plate with a microtome, a carbon vapor deposited cross section is observed with a scanning transmission electron microscope (STEM, field emission scanning electron microscope (FE-STEM), model number: “S-5500”, manufactured by Hitachi, Ltd.) By doing this, the thickness of the polarizer (polarizing layer) was measured.

Example 1
[Production of Composition for Forming Photo-alignment Layer]
The photoalignment material (2 parts) represented by the following formula (3) and o-xylene (98 parts) as a solvent are mixed, and the resulting mixture is stirred at 80 ° C. for 1 hour to conduct photoalignment. The composition for layer formation was obtained.

[Production of Composition for Forming Polarizer]
The following components were mixed and stirred at 80 ° C. for 1 hour to obtain a composition for forming a polarizer.
Polymerizable liquid crystal compound; 75 parts of a compound represented by the following formula (4-6)
25 parts of a compound represented by the following formula (4-7)

Dichromatic dye; Magenta dye represented by the following formula (2-18) 2.6 parts
2.6 parts of Yellow dye represented by the following formula (2-15)
Cyan dye represented by the following formula (2-27) 2.6 parts

Polymerization initiator: 2-dimethylamino-2-benzyl-1- (4-morpholinophenyl) butan-1-one (IRGACURE 369; manufactured by BASF Japan Ltd.) 6 parts Leveling agent; polyacrylate compound (BYK-361N; BYK- Chemie product) 1.2 parts Solvent: 250 parts xylene

[Production of Polarizing Film (Polarizing Plate)]
A film of triacetylcellulose film (KC4UY-TAC 40 μm, manufactured by Konica Minolta Co., Ltd.) with a width of 600 mm is continuously unwound at a speed of 8 m / min and subjected to plasma treatment on the film surface. The composition was discharged at a flow rate of 16 mL / min and applied to a width of 400 mm in the center of the film to form a first coated film. Furthermore, the solvent was removed by conveying for 2 minutes in the ventilation drying furnace set to 100 degreeC, and the 1st dry film was formed. Thereafter, polarized UV light polarized in a 45 ° direction with respect to the film transport direction is applied to the first dry film so as to have an intensity of 20 mJ / cm ² (based on 313 nm) to give an orientation control force, A substrate film with a photoalignment layer was produced. The composition for forming a polarizer was discharged at a flow rate of 36 mL / min by a slot die coater on the surface of the light alignment layer, and applied to a width of 400 mm in the center of the film to form a second coated film. Furthermore, the solvent was removed by conveying for 2 minutes in the ventilation drying furnace set to 110 degreeC, and the 2nd dry film was formed. Thereafter, UV light was irradiated at 500 mJ / cm ² (based on 365 nm) to polymerize and cure the polymerizable liquid crystal compound to form a polarizer. Then, the polarizing film roll which has an absorption axis in 45 degrees direction was produced by winding up in roll shape continuously. Various evaluations were carried out using as a polarizing plate what was cut out to a size of 3 cm square from the long polarizing film roll produced in this way. The film thickness of the polarizer, the absorbance at the maximum absorption wavelength of each dichroic dye, and the absorbance retention are shown in Table 1.

Example 2
A polarizing film roll was produced in the same manner as in Example 1 except that the coating flow rate of the composition for forming a polarizer was changed to 33 mL / min, and the same measurement as in Example 1 was performed.

Example 3
A polarizing film roll was produced in the same manner as in Example 1 except that the coating flow rate of the composition for forming a polarizer was changed to 30 mL / min, and the same measurement as in Example 1 was performed.

Example 4
A polarizing film roll was produced in the same manner as in Example 1 except that the coating flow rate of the composition for forming a polarizer was changed to 27 mL / min, and the same measurement as in Example 1 was performed.

Example 5
A polarizing film roll is prepared in the same manner as in Example 3 except that the amount of each of the three dichroic dyes in the composition for forming a polarizer is 1.3 parts, and the same measurement as in Example 1 is carried out. Carried out.

Example 6
A polarizing film roll was produced in the same manner as in Example 5 except that the coating flow rate of the composition for forming a polarizer was changed to 15 mL / min, and the same measurement as in Example 1 was performed.

Comparative Example 1
[Preparation of Iodine-PVA Polarizer]
A polyvinyl alcohol film with an average degree of polymerization of about 2400 and a degree of saponification of 99.9 mol% or more and a thickness of 75 μm was uniaxially stretched by about 5.5 times in a dry state, and further pure water at 60 ° C while maintaining tension. And then immersed in an aqueous solution of iodine / potassium iodide / water at a weight ratio of 0.05 / 5/100 at 23.degree. C. for 30 seconds. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 ° C. for 300 seconds. Subsequently, the film was washed with pure water at 23 ° C. for 15 seconds and then dried at 70 ° C. for 2 minutes to obtain a polarizer in which iodine was adsorbed and oriented to a polyvinyl alcohol resin. The polarizer was measured by a contact-type film thickness meter and was 25 μm. On both sides of the thus obtained polarizer, 3 parts of carboxyl group-modified polyvinyl alcohol (Kuraray Co., Ltd. Kuraray Poval KL 318) and a water-soluble polyamide epoxy resin (Suzumi Chemtex Co., Ltd. Sumireze Resin (registered trademark)) 650 (30% aqueous solution of solid content): A triacetylcellulose film (KC 4 UY-TAC 40 μm, Konica Minolta Co., Ltd.) saponified via a polyvinyl alcohol adhesive prepared from 1.5 parts on both sides It protected and produced the polarizing plate. This polarizing plate was sampled, and the same measurement as in Example 1 was carried out. As a result, light absorption due to the I3-PVA complex with 474 nm as the maximum absorption wavelength and light absorption due to the I5-PVA complex with 594 nm as the maximum absorption wavelength It was measured.

Comparative example 2
A polarizing film was produced in the same manner as in Comparative Example 1 except that the film was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.06 / 6/100 at 23 ° C. for 30 seconds. This polarizing film was sampled, and the same measurement as in Example 1 was carried out. As a result, light absorption due to I3-PVA complex with 474 nm as the maximum absorption wavelength and light absorption due to I5-PVA complex with 594 nm as the maximum absorption wavelength It was measured.

Comparative example 3
A polarizing film was produced in the same manner as in Comparative Example 1 except that the film was immersed in an aqueous solution of iodine / potassium iodide / water at a weight ratio of 0.06 / 6/100 for 40 seconds at 23.degree. This polarizing film was sampled, and the same measurement as in Example 1 was carried out. As a result, light absorption due to I3-PVA complex with 474 nm as the maximum absorption wavelength and light absorption due to I5-PVA complex with 594 nm as the maximum absorption wavelength It was measured.

  Although the polarizing plates of Examples 1 to 6 were thin films, they had high light absorption selective performance and very high heat resistance. Moreover, in the polarizing plate of Examples 1-6, the curvature etc. did not generate | occur | produce at all after a heat test, but were hold | maintaining favorable film shape.

  In the polarizing plates of Comparative Examples 1 to 3, the absorbance due to the light absorption of the I5-PVA complex decreases to about 70 to 77% after the heat resistance test, and the long wavelength light absorption is weak compared to the short wavelength light absorption. As a result, it has a reddish hue as a whole. Moreover, in the polarizing plate of Comparative Examples 1-3, the deformation | transformation by the heat of PVA was large and big curvature generate | occur | produced.

  The polarizing plate of the present invention is extremely useful for producing a liquid crystal display device, an (organic) EL display device and a projection type liquid crystal display device since it has high light absorption selection performance even with a thin film and is excellent in heat resistance. .

  DESCRIPTION OF SYMBOLS 1 ... base material, 2 ... orientation layer, 3 ... polarizer, 3a ... dichroic dye, 4 ... retardation film, 10 ... polarizing plate, 100, 110, 120 ... circularly-polarizing plate.

Claims (6)

A polarizing plate comprising a substrate and a polarizer,
The polarizer has a polarizing layer with a thickness of 5 μm or less in which a dichroic dye is oriented,
The polarizing layer contains a polymer of a polymerizable liquid crystal compound exhibiting a higher smectic liquid crystal phase,
The polarizing plate whose absorbance retention shown by following formula (I) is 80% or more.
Absorbance retention (%) = A1 (85 ° C.) / A1 (23 ° C.) × 100 (I)
(Wherein, A1 (85 ° C.) represents the absorbance in the absorption axis direction at the absorption maximum wavelength of the dichroic dye after holding the polarizing plate in a heat-resistant oven at 85 ° C. for 100 hours, A1 (23 ° C.) The absorbance at the absorption maximum wavelength of the dichroic dye measured at 23 ° C. before putting the polarizing plate into the heat-resistant oven, and the value of A1 (23 ° C.) is 0.3 or more, and 0. 0. 83 or less.)   The absorbance A2 (23 ° C) in the transmission axis direction at the absorption maximum wavelength of the dichroic dye measured at 23 ° C before the polarizing plate is put into the heat-resistant oven is 0.001 or more and 0.1 or less The polarizing plate of Claim 1.   The polarizing plate of Claim 1 or 2 whose said dichroic dye is an organic dye. The polarizing plate according to any one of claims 1 to 3 , wherein the polarizer exhibits a Bragg peak in X-ray diffraction measurement. The circularly-polarizing plate containing the polarizing plate as described in any one of Claims 1-4 , and a quarter wavelength plate. The birefringence for the light of wavelength 450 nm, the birefringence for light of wavelength 550 nm, and the birefringence for light of wavelength 650 nm of the quarter wavelength plate satisfy the relationship represented by the following formulas (II) and (III) The circularly polarizing plate according to claim 5 , having reverse wavelength dispersion.
Δn (450) / Δn (550) ≦ 1.00 (II)
1.00 ≦ Δn (650) / Δn (550) (III)
(Wherein, Δn (λ) represents the birefringence for light of wavelength λ nm)