Polymerizable liquid crystal composition, polarizing membrane, polarizing film, circularly polarizing plate and display device

Abstract

To provide a polymerizable liquid crystal composition that is suitable for forming a polarizing film excellent in yellowing suppression effect.SOLUTION: A polymerizable liquid crystal composition contains a polymerizable liquid crystal compound, an organic dichroic dye, and a sulfur-based antioxidant, in which the polymerizable liquid crystal compound has at least one radically polymerizable group, and the sulfur-based antioxidant has an aromatic ring structure and a thiol structure or a thioether structure.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polymerizable liquid crystal composition, a polarizing film formed from a cured film of the polymerizable liquid crystal composition, a polarizing film and a circular polarizing plate each including the polarizing film, and a display device. [Background technology]

[0002] Conventionally, polarizing plates are used by being attached to image display elements such as liquid crystal cells or organic EL display elements in various image display panels such as liquid crystal display panels and organic electroluminescence (organic EL) display panels. In recent years, there has been a continuous demand for thinner displays such as image display panels, and further thinner polarizing plates and polarizers, which are one of the components thereof. In response to such demands, for example, a thin coating-type polarizing film made of a polymerizable liquid crystal compound and a compound exhibiting dichroism has been proposed (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-008683 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, as the applications of thin polarizing plates have expanded, there has been a demand for the development of polarizing films with improved light resistance. However, the present inventors have found that yellowing of polarizing films over time can cause a problem in that blue light emission from organic light-emitting diodes (OLEDs) is inhibited.

[0005] Therefore, an object of the present invention is to provide a polymerizable liquid crystal composition suitable for forming a polarizing film having excellent yellowing suppression effect. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. That is, the present invention provides the following preferred embodiments. [1] A polymerizable liquid crystal composition comprising a polymerizable liquid crystal compound, an organic dichroic dye, and a sulfur-based antioxidant, the polymerizable liquid crystal compound has at least one radically polymerizable group, The polymerizable liquid crystal composition, wherein the sulfur-based antioxidant has an aromatic ring structure and a thiol structure or a thioether structure. [2] The polymerizable liquid crystal composition according to [1], wherein the sulfur-based antioxidant is at least one selected from the group consisting of a thiol compound having an aromatic ring, a sulfide compound having an aromatic ring, and a cyclic sulfide compound having an aromatic ring. [3] The polymerizable liquid crystal composition according to [1] or [2] above, wherein the polymerizable liquid crystal compound is a liquid crystal compound exhibiting smectic liquid crystallinity. [4] The polymerizable liquid crystal composition according to any one of the above [1] to [3], wherein the organic dichroic dye is an azo dye. [5] The polymerizable liquid crystal composition according to any one of the above [1] to [4], wherein the organic dichroic dye has an aromatic ring structure. [6] The polymerizable liquid crystal composition according to any one of [1] to [5] above, wherein the content of the sulfur-based antioxidant is 0.1 to 3 parts by mass relative to 100 parts by mass of the polymerizable liquid crystal compound. [7] A polarizing film comprising a cured film of the polymerizable liquid crystal composition according to any one of [1] to [6] above. [8] The polarizing film according to [7] above, which exhibits a Bragg peak in X-ray diffraction measurement. [9] The polarizing film according to [7] or [8] above, which has a thickness in the range of 0.5 to 4 μm.

[10] A polarizing film comprising the polarizing membrane according to any one of [7] to [9] above and a transparent film.

[11] A circularly polarizing plate comprising the polarizing film according to any one of [7] to [9] above and a retardation film.

[12] The retardation film has the formulas (1) and (2): 100nm ≦ Re(550) ≦ 150nm (1) Re(450) / Re(550)<1 (2) (wherein Re(λ) represents a front retardation value for light with a wavelength of λ nm) The circularly polarizing plate according to

[11] above, which satisfies the above condition.

[13] A display device comprising the polarizing film according to any one of [7] to [9] above, the polarizing film according to

[10] above, or the circular polarizing plate according to

[11] or

[12] above. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a polymerizable liquid crystal composition suitable for forming a polarizing film having an excellent effect of suppressing yellowing. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiments described here, and various modifications can be made without departing from the spirit of the present invention.

[0009] <Polymerizable liquid crystal composition> The polymerizable liquid crystal composition of the present invention contains a polymerizable liquid crystal compound having at least one radically polymerizable group. The polymerizable liquid crystal compound is a compound having at least one radically polymerizable group and liquid crystallinity. The radically polymerizable group may be any functional group capable of undergoing a radical polymerization reaction, such as a group having a carbon-carbon unsaturated double bond, specifically a vinyl group, a vinyloxy group, a 1-chlorovinyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, or a methacryloyloxy group. Among these, an acryloyloxy group, a methacryloyloxy group, or a vinyloxy group is preferred, an acryloyloxy group or a methacryloyloxy group is more preferred, and an acryloyloxy group is even more preferred.

[0010] In the present invention, the polymerizable liquid crystal compound is preferably a liquid crystal compound exhibiting a smectic liquid crystal phase. By using a polymerizable liquid crystal compound exhibiting a smectic liquid crystal phase, a polarizing film with a high degree of orientational order can be formed. From the viewpoint of achieving a higher degree of orientational order, the liquid crystal state exhibited by the polymerizable liquid crystal compound is more preferably a high-order smectic phase (high-order smectic liquid crystal state). Here, the high-order smectic phase refers to a smectic B phase, a smectic D phase, a smectic E phase, a smectic F phase, a smectic G phase, a smectic H phase, a smectic I phase, a smectic J phase, a smectic K phase, and a smectic L phase. Among these, a smectic B phase, a smectic F phase, and a smectic I phase are more preferred. The liquid crystal may be either a thermotropic or lyotropic liquid crystal, but a thermotropic liquid crystal is preferred because it allows precise film thickness control. The polymerizable liquid crystal compound may be a monomer, or may be an oligomer or polymer in which a polymerizable group is polymerized.

[0011] The polymerizable liquid crystal compound is not particularly limited as long as it is a liquid crystal compound having at least one radically polymerizable group, and known polymerizable liquid crystal compounds can be used. Examples of such polymerizable liquid crystal compounds include compounds represented by the following formula (A) (hereinafter also referred to as "polymerizable liquid crystal compound (A)"). U 1 -V 1 -W 1 -(X 1 -Y 1 ) n -X 2 -W 2 -V 2 -U 2 (A) [In formula (A), X 1 and X 2are each independently a divalent aromatic group or a divalent alicyclic hydrocarbon group, wherein a hydrogen atom contained in the divalent aromatic group or 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 divalent alicyclic hydrocarbon group may be substituted with an oxygen atom, a sulfur atom, or a nitrogen atom, provided that X 1 and X 2 At least one of the groups is an optionally substituted 1,4-phenylene group or an optionally substituted cyclohexane-1,4-diyl group. Y 1 is a single bond or a divalent linking group. n is 1 to 3, and when n is 2 or more, multiple X 1 may be the same or different. 2 Multiple X 1 In addition, when n is 2 or more, a plurality of Y 1 may be the same or different. From the viewpoint of liquid crystal properties, n is preferably 2 or more. U 1 represents a hydrogen atom or a polymerizable group. U 2 represents a polymerizable group. W 1 and W 2 are each independently a single bond or a divalent linking group. V 1 and V 2 represent each independently an alkanediyl group having 1 to 20 carbon atoms which may have a substituent, and -CH2- constituting the alkanediyl group may be replaced by -O-, -CO-, -S- or -NH-.

[0012] In the polymerizable liquid crystal compound (A), X 1 and X 2are each independently preferably an optionally substituted 1,4-phenylene group or an optionally substituted cyclohexane-1,4-diyl group, and X 1 and X 2 At least one of these is an optionally substituted 1,4-phenylene group or an optionally substituted cyclohexane-1,4-diyl group, preferably a trans-cyclohexane-1,4-diyl group. The optionally substituted 1,4-phenylene group or the optionally substituted cyclohexane-1,4-diyl group may optionally have a substituent, such as an alkyl group having 1 to 4 carbon atoms, a cyano group, or a halogen atom, such as a chlorine atom or a fluorine atom. Preferably, the group is unsubstituted.

[0013] The polymerizable liquid crystal compound (A) is a compound represented by the formula (A1): -(X 1 -Y 1 ) n -X 2 - (A1) [In the formula, X 1 , Y 1 , X 2 and n have the same meanings as above.] [hereinafter, also referred to as partial structure (A1)] is preferably an asymmetric structure, since this facilitates the development of smectic liquid crystal properties. The polymerizable liquid crystal compound (A) in which the partial structure (A1) is an asymmetric structure is, for example, a compound in which n is 1 and one X 1 and X 2 and Y are different from each other. 1 are compounds having the same structure as each other, and two X 1 have the same structure as each other, and one X 2 These two X 1 Polymerizable liquid crystal compounds with different structures, two X 1 W of 1 X binds to 1 But the other X 1 and X 2The other X 1 and X 2 Furthermore, the polymerizable liquid crystal compound may be a compound in which n is 3 and three Y 1 are compounds having the same structure as each other, and three X 1 and one X 2 Examples of polymerizable liquid crystal compounds include those in which any one of the following structures is different from all of the other three structures.

[0014] Y 1 -CH2CH2-, -CH2O-, -CH2CH2O-, -COO-, -OCOO-, single bond, -N=N-, -CR a =CR b -, -C≡C-, -CR a =N- or -CO-NR a - is preferred. a and R b are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. 1 is more preferably -CH2CH2-, -COO- or a single bond, and 1 If there is an X 2 Y bonded with 1 is more preferably -CH2CH2- or -CH2O-. 1 and X 2 When all of Y are the same structure, two or more Y 1 It is preferable that there are plural Y 1 When the compound has an asymmetric structure, the compound tends to exhibit smectic liquid crystallinity.

[0015] U 2 is a polymerizable group. 1 is a hydrogen atom or a polymerizable group, preferably a polymerizable group. 1 and U 2 one of U is a radical polymerizable group, 1 and U 2Preferably, both of U are polymerizable groups, and more preferably, both are radically polymerizable groups. Examples of the polymerizable group include the same radically polymerizable groups as those exemplified above as the polymerizable group possessed by the polymerizable liquid crystal compound. 1 and a polymerizable group represented by U 2 may be different from each other, but are preferably the same type of group, and U 1 and U 2 Preferably, at least one of the groups is a (meth)acryloyloxy group, and more preferably, both of the groups are (meth)acryloyl groups. The polymerizable group may be in a polymerized state or an unpolymerized state, but is preferably in an unpolymerized state.

[0016] V 1 and V 2 Examples of the alkanediyl group represented by the formula (V) 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. 1 and V 2 is preferably an alkanediyl group having 2 to 12 carbon atoms, and more preferably an alkanediyl group having 6 to 12 carbon atoms.

[0017] Examples of the substituent that the alkanediyl group may optionally have include a cyano group and a halogen atom, but the alkanediyl group is preferably unsubstituted, and more preferably an unsubstituted linear alkanediyl group.

[0018] W 1 and W 2 are each independently preferably a single bond, -O-, -S-, -COO- or -OCOO-, more preferably a single bond or -O-.

[0019] The structure that readily exhibits smectic liquid crystallinity preferably has an asymmetric molecular structure within the molecular structure, and the polymerizable liquid crystal compound (A) is more preferably a polymerizable liquid crystal compound having the following partial structures (Aa) to (Ai) and exhibiting smectic liquid crystallinity. From the viewpoint of readily exhibiting higher-order smectic liquid crystallinity, it is more preferable that the compound has the partial structure (Aa), (Ab) or (Ac). In the following (Aa) to (Ai), * represents a bond (single bond).

[0020] [ka]

[0021] Examples of the polymerizable liquid crystal compound (A) include compounds represented by formulae (A-1) to (A-25). When the polymerizable liquid crystal compound (A) has a cyclohexane-1,4-diyl group, the cyclohexane-1,4-diyl group is preferably a trans isomer.

[0022] [ka]

[0023] [ka]

[0024] [ka]

[0025] Among these, at least one selected from the group consisting of compounds represented by formula (A-2), formula (A-3), formula (A-4), formula (A-5), formula (A-6), formula (A-7), formula (A-8), formula (A-13), formula (A-14), formula (A-15), formula (A-16) and formula (A-17) is preferred. As the polymerizable liquid crystal compound (A), one type may be used alone, or two or more types may be used in combination.

[0026] The polymerizable liquid crystal compound (A) can be 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.

[0027] The polymerizable liquid crystal composition of the present invention may contain a polymerizable liquid crystal compound other than the polymerizable liquid crystal compound (A), as long as the effects of the present invention are not impaired. From the viewpoint of obtaining a polarizing film with a high degree of orientational order, the proportion of the polymerizable liquid crystal compound (A) relative to the total mass of all polymerizable liquid crystal compounds in the polymerizable liquid crystal composition is preferably 51% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. By combining multiple polymerizable liquid crystal compounds, it may be possible to temporarily maintain liquid crystallinity even at temperatures below the liquid crystal-crystalline phase transition temperature.

[0028] The content of the polymerizable liquid crystal compound in the polymerizable liquid crystal composition of the present invention is preferably 40 to 99.9 mass %, more preferably 60 to 99 mass %, and even more preferably 70 to 99 mass %, based on the solid content of the polymerizable liquid crystal composition. When the content of the polymerizable liquid crystal compound is within the above range, the alignment of the polymerizable liquid crystal compound tends to be high. In this specification, the solid content refers to the total amount of components excluding volatile components such as solvents from the polymerizable liquid crystal composition.

[0029] The polymerizable liquid crystal composition of the present invention contains an organic dichroic dye. Here, the organic dichroic dye refers to an organic dye having different absorbances in the long axis direction and the short axis direction of the molecule. The organic dichroic dye that can be used in the present invention is not particularly limited as long as it has the above-mentioned properties, and may be a dye or a pigment. Two or more dyes or pigments may be used in combination, or a dye and a pigment may be used in combination. Furthermore, the dichroic dye may be polymerizable or liquid crystalline.

[0030] As an organic dichroic dye, the maximum absorption wavelength (λ ) is in the range of 300 to 700 nm.MAX ) is preferred.

[0031] Examples of such organic dichroic dyes include acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes, and anthraquinone dyes.

[0032] Examples of azo dyes include monoazo dyes, bisazo dyes, trisazo dyes, tetrakisazo dyes, and stilbene azo dyes, and bisazo dyes and trisazo dyes are preferred, such as a compound represented by formula (I) (hereinafter also referred to as "compound (I)"). K 1 (-N=NK 2 ) p -N=NK 3 (I) [In formula (I), K 1 and K. 3 represent, independently of each other, an optionally substituted phenyl group, an optionally substituted naphthyl group, an optionally substituted benzoic acid phenyl ester group, or an optionally substituted monovalent heterocyclic group. 2 represents a p-phenylene group which may have a substituent, a naphthalene-1,4-diyl group which may have a substituent, a 4,4'-stilbenylene group which may have a substituent, or a divalent heterocyclic group which may have a substituent. p represents an integer of 0 to 4. When p is an integer of 2 or more, a plurality of K 2 may be the same or different. The -N=N- bond may be replaced with a -C=C-, -COO-, -NHCO-, or -N=CH- bond as long as the compound exhibits absorption in the visible region.

[0033] Examples of monovalent heterocyclic groups include groups in which one hydrogen atom has been removed from a heterocyclic compound such as quinoline, thiazole, benzothiazole, thienothiazole, imidazole, benzimidazole, oxazole, benzoxazole, etc. Examples of divalent heterocyclic groups include groups in which two hydrogen atoms have been removed from the above heterocyclic compounds.

[0034] K 1and K. 3 Phenyl group, naphthyl group, benzoic acid phenyl ester group and monovalent heterocyclic group in 2 In the formula (I), the p-phenylene group, the naphthalene-1,4-diyl group, the 4,4'-stilbenylene group, and the divalent heterocyclic group may optionally have a substituent, such as an alkyl group having 1 to 20 carbon atoms, an alkyl group having 1 to 20 carbon atoms and having a polymerizable group, or an alkenyl group having 1 to 4 carbon atoms; an alkoxy group having 1 to 20 carbon atoms, such as a methoxy group, an ethoxy group, or a butoxy group; an alkoxy group having 1 to 20 carbon atoms and having a polymerizable group; a fluorinated alkyl group having 1 to 4 carbon atoms, such as a trifluoromethyl group; Examples of the polymerizable group include an ano group, a nitro group, a halogen atom, and substituted or unsubstituted amino groups such as an amino group, a diethylamino group, and a pyrrolidino group (a substituted amino group refers to an amino group having one or two alkyl groups of 1 to 6 carbon atoms, an amino group having one or two alkyl groups of 1 to 6 carbon atoms and a polymerizable group, or an amino group in which two substituted alkyl groups are bonded to form an alkanediyl group of 2 to 8 carbon atoms. An unsubstituted amino group is -NH2). Examples of the polymerizable group include a (meth)acryloyl group and a (meth)acryloyloxy group.

[0035] Among the compounds (I), compounds represented by any one of the following formulae (I-1) to (I-8) are preferred. [ka] [In formulas (I-1) to (I-8), B 1 ~B 30 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkenyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group, a nitro group, a substituted or unsubstituted amino group (the definitions of a substituted amino group and an unsubstituted amino group are as defined above), a chlorine atom, or a trifluoromethyl group. n1 to n4 each independently represent an integer of 0 to 3. If n1 is 2 or more, multiple B 2 may be the same or different from each other, If n2 is 2 or more, multiple B6 may be the same or different from each other, If n3 is 2 or more, multiple B 9 may be the same or different from each other, If n4 is 2 or more, multiple B 14 may be the same or different.]

[0036] The anthraquinone dye is preferably a compound represented by formula (I-9). [ka] [In formula (I-9), R 1 ~R 8 are, independently of each other, a hydrogen atom, -R x , -NH2, -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.

[0037] The oxazine dye is preferably a compound represented by formula (I-10). [ka] [In formula (I-10), R 9 ~R 15 are, independently of each other, a hydrogen atom, -R x , -NH2, -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.

[0038] The acridine dye is preferably a compound represented by formula (I-11). [ka] [In formula (I-11), R 16 ~R 23 are, independently of each other, a hydrogen atom, -R x , -NH2, -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 formula (I-9), formula (I-10) and formula (I-11), R x Examples of the alkyl group having 1 to 6 carbon atoms 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.

[0039] As the cyanine dye, compounds represented by formula (I-12) and compounds represented by formula (I-13) are preferred. [ka] [In formula (I-12), D 1 and D 2 represent, independently of each other, a group represented by any one of formulae (I-12a) to (I-12d). [ka] n5 represents an integer from 1 to 3. [ka] [In formula (I-13), D 3 and D 4 represent, independently of each other, a group represented by any one of formulas (I-13a) to (I-13h). [ka] n6 represents an integer from 1 to 3.

[0040] The weight-average molecular weight of the organic dichroic dye is usually 300 to 2,000, and preferably 400 to 1,000.

[0041] The polymerizable liquid crystal composition of the present invention is excellent in the effect of suppressing photodegradation of the dichroic dye in a polarizing film when the polarizing film is formed, and therefore the effects of the present invention can be particularly pronounced when an organic dichroic dye that is susceptible to light such as ultraviolet light in sunlight and prone to photodegradation is used. Therefore, the polymerizable liquid crystal composition of the present invention is particularly advantageous when an organic dichroic dye that is prone to photodegradation is used.

[0042] Among the above organic dichroic dyes, azo dyes have high linearity and are therefore suitable for producing polarizing films with excellent polarization performance. Therefore, in one embodiment of the present invention, the organic dichroic dye contained in the polymerizable liquid crystal composition is preferably an azo dye.

[0043] Furthermore, in relation to the sulfur-based antioxidant described later, the organic dichroic dye preferably has an aromatic ring structure. In one embodiment of the present invention, the polymerizable liquid crystal composition more preferably contains an azo dye having an aromatic ring structure as the organic dichroic dye.

[0044] The content of the organic dichroic dye in the polymerizable liquid crystal composition of the present invention can be appropriately determined depending on the type of organic dichroic dye used, but is preferably 0.1 to 50 parts by mass, more preferably 0.1 to 20 parts by mass, and even more preferably 0.1 to 12 parts by mass, relative to 100 parts by mass of the polymerizable liquid crystal compound. When the content of the organic dichroic dye is within the above range, the orientation of the polymerizable liquid crystal compound is unlikely to be disturbed, and a polarizing film having a high degree of orientational order can be obtained.

[0045] The polymerizable liquid crystal composition of the present invention contains a sulfur-based antioxidant having an aromatic ring structure and a thiol or thioether structure. The sulfur-based antioxidant functions as a so-called secondary antioxidant and has the effect of decomposing peroxides generated from radicals upon light irradiation. By including the sulfur-based antioxidant, the polymerizable liquid crystal composition of the present invention can exhibit a high effect of suppressing yellowing over time in the resulting polarizing film.

[0046] The mechanism by which a polarizing film having excellent yellowing suppression can be obtained from the polymerizable liquid crystal composition of the present invention is presumed to be as follows. Specifically, in the polymerizable liquid crystal composition, the sulfur-based antioxidant having an aromatic ring structure can exist in a more cooperatively mixed state in a liquid crystal state comprising the polymerizable liquid crystal compound and the organic dichroic dye, thereby shortening the intermolecular distance with the organic dichroic dye. Therefore, the sulfur-based antioxidant acts more effectively as an antioxidant, not only suppressing photodegradation of the organic dichroic dye but also exhibiting the function of decomposing radicals generated over time in the cured liquid crystal film for a long period of time. The above mechanism is presumed to be due to the fact that a polarizing film having excellent yellowing suppression can be obtained when the organic dichroic dye has an aromatic ring structure in the present invention. Furthermore, a polarizing film having excellent polarizing performance can generally be obtained by cooperatively aligning the organic dichroic dye with the highly ordered polymerizable liquid crystal compound. However, when the sulfur-based antioxidant is structurally similar to the organic dichroic dye, the sulfur-based antioxidant can be present in the liquid crystal without disrupting the cooperative alignment between the polymerizable liquid crystal compound and the organic dichroic dye. This is expected to have an effect of suppressing photodegradation of the organic dichroic dye while maintaining high alignment order of the polymerizable liquid crystal compound and the organic dichroic dye, and therefore a polarizing film with excellent polarization performance can be obtained. Therefore, when the polymerizable liquid crystal composition contains a compound having an aromatic ring structure as an organic dichroic dye, for example, an organic dichroic dye having an aromatic ring structure as exemplified above, the effects of the present invention can be expected to be particularly pronounced.

[0047] The sulfur-based antioxidant having an aromatic ring structure and a thiol or thioether structure (hereinafter also referred to as "sulfur-based antioxidant (S)") is not particularly limited as long as it has an aromatic ring structure and a thiol or thioether structure. The sulfur-based antioxidant (S) may be used alone or in combination of two or more.

[0048] Examples of the aromatic ring structure contained in the sulfur-based antioxidant (S) include an aromatic hydrocarbon ring and a heteroaromatic ring. These aromatic ring structures may be either monocyclic or fused ring structures. The aromatic ring structure is preferably a heteroaromatic ring, more preferably a heteroaromatic ring containing at least one of nitrogen, sulfur, and oxygen, and even more preferably a heteroaromatic ring containing at least one of nitrogen and sulfur. When the aromatic ring structure is a fused ring structure, it may be a fused ring consisting of two rings or a fused ring consisting of three or more rings. Examples of the aromatic ring structure include a benzene ring, a naphthalene ring, a quinoline ring, a thiazole ring, a benzothiazole ring, a thienothiazole ring, an imidazole ring, a benzimidazole ring, an oxazole ring, and a benzoxazole ring. The hydrogen atoms contained in the aromatic ring may be substituted. Examples of the substituent include a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group, and a nitro group.

[0049] From the viewpoints of light resistance, yellowing prevention effect, and ease of obtaining high polarization properties, it is preferable that the sulfur-based antioxidant (S) contains at least one selected from the group consisting of thiol compounds having an aromatic ring, sulfide compounds having an aromatic ring, and cyclic sulfide compounds having an aromatic ring.

[0050] Examples of the sulfur-based antioxidant (S) include a compound having a structure represented by formula (S1) and a compound having a structure represented by formula (S2). [ka]

[0051] In formula (S1), m is 1 or 2, and preferably 1.

[0052] In formula (S1), X is -N- or -CH-, and Y is -NH-, -N(Me)- (Me means a methyl group), -S-, -O-, -C(=O)-, -CH-, or -CH=CH-. Preferably, at least one of X and Y contains at least one heteroatom described above, more preferably, X and Y each contain a heteroatom described above, and even more preferably, X is -N- and Y is -NH-.

[0053] In formula (S1), R1 is a hydrogen atom or a branched or unbranched alkyl group having 1 to 12 carbon atoms, preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom or a methyl group, and even more preferably a hydrogen atom.

[0054] In formula (S1), R2 to R5 are each independently a hydrogen atom, -OH, -NH2, a branched or unbranched alkyl group having 1 to 12 carbon atoms, a branched or unbranched alkoxy group having 1 to 12 carbon atoms, or a branched or unbranched thioalkyl group having 1 to 12 carbon atoms. It is preferred that all of R2, R4, and R5 are hydrogen atoms and R3 is a hydrogen atom, -OH, -NH2, a branched or unbranched alkyl group having 1 to 12 carbon atoms, a branched or unbranched alkoxy group having 1 to 12 carbon atoms, or a branched or unbranched thioalkyl group having 1 to 12 carbon atoms, and it is more preferred that all of R2 to R5 are hydrogen atoms.

[0055] In formula (S2), n is 1 or 2, and preferably 1.

[0056] The two benzene rings in formula (S2) may be bonded via a linking group Z. In formula (S2), --Z-- means that the linking group Z is any bond. Examples of the linking group Z include a single bond, -NH-, -N(Me)- (Me means a methyl group), -S-, -O-, -C(=O)-, and -CH2-. When the two benzene rings are not bonded via a linking group Z, the non-linking sites are each independently a hydrogen atom, -NH2, -OH, -NO2, a branched or unbranched alkyl group having 1 to 12 carbon atoms, a branched or unbranched alkoxy group having 1 to 12 carbon atoms, or a branched or unbranched thioalkyl group having 1 to 12 carbon atoms.

[0057] In formula (S2), the two benzene rings are preferably bonded via a linking group Z, more preferably -NH-, -N(Me)-, -S- or -O-, and further preferably -NH- or -N(Me)-.

[0058] In formula (S2), R6~R 13 are each independently a hydrogen atom, -OH, -NH2, a branched or unbranched alkyl group having 1 to 12 carbon atoms, a branched or unbranched alkoxy group having 1 to 12 carbon atoms, or a branched or unbranched thioalkyl group having 1 to 12 carbon atoms.

[0059] When the linking group Z is -NH-, R6, R8 to R 11 and R 13 are all hydrogen atoms, and R7 and R 12 are each independently a hydrogen atom, -OH, -NH2, a branched or unbranched alkyl group having 1 to 12 carbon atoms, a branched or unbranched alkoxy group having 1 to 12 carbon atoms, or a branched or unbranched thioalkyl group having 1 to 12 carbon atoms, and R7 is more preferably a hydrogen atom.

[0060] When the linking group Z is -N(Me)-, R6, R8 to R 11 and R 13 are all hydrogen atoms, and R7 and R 12are each independently a hydrogen atom, -OH, -NH2, a branched or unbranched alkyl group having 1 to 12 carbon atoms, a branched or unbranched alkoxy group having 1 to 12 carbon atoms, or a branched or unbranched thioalkyl group having 1 to 12 carbon atoms, and R7 is more preferably a hydrogen atom, and R6 to R 13 It is more preferable that all of are hydrogen atoms.

[0061] Examples of the thiol compound having an aromatic ring, the sulfide compound having an aromatic ring, and the cyclic sulfide compound having an aromatic ring include the following compounds.

[0062] [ka]

[0063] The weight-average molecular weight of the sulfur-based antioxidant (S) is preferably 600 or less, more preferably 400 or less, and even more preferably 250 or less. When the weight-average molecular weight is below the upper limit, the polymerizable liquid crystal compound is easily oriented in the liquid crystal molecules without disturbing their alignment, and can be present in the vicinity of the organic dichroic dye, thereby further improving the effect of suppressing photodegradation of the organic dichroic dye and the effect of suppressing yellowing of the polarizing film. The weight-average molecular weight of the sulfur-based antioxidant (S) is not particularly limited, but is usually 50 or more, preferably 100 or more.

[0064] Among these, sulfur-based antioxidants, which have a molecular structure with little steric hindrance and high linearity, are preferred because they tend to be easily aligned with the polymerizable liquid crystal compound and have an excellent effect of suppressing photodegradation of the organic dichroic dye and yellowing of the polarizing film. The sulfur-based antioxidant (S) in the present invention is not limited to, but is preferably a sulfur compound having a benzimidazole ring, such as 2-mercaptobenzimidazole; or a thiophenothiazine having a substituent, such as 10-methylphenothiazine, 2-methoxyphenothiazine, or 2-ethylthiophenothiazine.

[0065] The content of the sulfur-based antioxidant (S) is preferably 0.1 to 3 parts by mass, more preferably 0.3 parts by mass or more, even more preferably 0.5 parts by mass or more, more preferably 2.5 parts by mass or less, and even more preferably 2 parts by mass or less, relative to 100 parts by mass of the polymerizable liquid crystal compound. When the content of the sulfur-based antioxidant (S) is at least the above-mentioned lower limit, photodegradation of the organic dichroic dye and yellowing of the resulting polarized film can be effectively suppressed. On the other hand, when the content of the sulfur-based antioxidant (S) is not more than the above-mentioned upper limit, the alignment of the polymerizable liquid crystal compound is less likely to be disturbed, and a high effect of suppressing photodegradation of the organic dichroic dye and yellowing of the resulting polarized film can be expected.

[0066] The polymerizable liquid crystal composition may contain an antioxidant other than the sulfur-based antioxidant (S). Examples of the antioxidant other than the sulfur-based antioxidant (S) include secondary antioxidants such as sulfur-based antioxidants not having an aromatic ring structure and phosphorus-based antioxidants, as well as primary antioxidants such as phenol-based antioxidants and amine-based antioxidants that have the effect of capturing generated radicals.

[0067] When the polymerizable liquid crystal composition contains an antioxidant other than the sulfur-based antioxidant (S), the content of the sulfur-based antioxidant (S) is preferably 50 mass % or more, and more preferably 70 mass % or more, of the total amount of all antioxidants contained in the polymerizable liquid crystal composition, from the viewpoint of exhibiting a sufficiently high yellowing suppression effect while maintaining the high alignment order of the polymerizable liquid crystal compound.

[0068] The polymerizable liquid crystal composition of the present invention may further contain a polymerization initiator. The polymerization initiator is a compound capable of initiating the polymerization reaction of the polymerizable liquid crystal compound, and a photopolymerization initiator is preferred because it can initiate the polymerization reaction under lower temperature conditions.Specific examples include photopolymerization initiators that can generate active radicals or acids under the action of light, and among these, photopolymerization initiators that generate radicals under the action of light are preferred.The polymerization initiators can be used alone or in combination of two or more.

[0069] Examples of the polymerization initiator include benzoin compounds, benzophenone compounds, alkylphenone compounds, acylphosphine oxide compounds, triazine compounds, iodonium salts, and sulfonium salts.

[0070] Examples of the benzoin compound include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether.

[0071] Examples of the benzophenone compound include benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3',4,4'-tetra(tert-butylperoxycarbonyl)benzophenone, and 2,4,6-trimethylbenzophenone.

[0072] Examples of alkylphenone compounds include diethoxyacetophenone, 2-methyl-2-morpholino-1-(4-methylthiophenyl)propan-1-one, 2-dimethylamino-2-benzyl-1-(4-morpholinophenyl)butan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1,2-diphenyl-2,2-dimethoxyethan-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.

[0073] Examples of the acylphosphine oxide compound include 2,4,6-trimethylbenzoyldiphenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0074] 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.

[0075] Commercially available polymerization initiators can be used. Examples of commercially available polymerization initiators include "Irgacure (registered trademark) 907", "Irgacure (registered trademark) 184", "Irgacure (registered trademark) 651", "Irgacure (registered trademark) 819", "Irgacure (registered trademark) 250", and "Irgacure (registered trademark) 369" (Ciba Japan Co., Ltd.); "Seikuol (registered trademark) BZ", "Seikuol (registered trademark) Z", and "Seikuol (registered trademark) Examples of suitable anti-fungal agents include "Kayacure (registered trademark) BEE" (Seiko Chemical Co., Ltd.); "Kayacure (registered trademark) BP100" (Nippon Kayaku Co., Ltd.); "Kayacure (registered trademark) UVI-6992" (manufactured by Dow Chemical); "ADEKA OPTOMER SP-152" and "ADEKA OPTOMER SP-170" (ADEKA Corporation); "TAZ-A" and "TAZ-PP" (Nippon SiberHegner AG); and "TAZ-104" (Sanwa Chemical Co., Ltd.).

[0076] When the polymerizable liquid crystal composition contains a polymerization initiator, its content may be appropriately determined depending on the type and amount of the polymerizable liquid crystal compound contained in the polymerizable liquid crystal composition, but is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 0.5 to 8 parts by mass, relative to 100 parts by mass of the polymerizable liquid crystal compound. When the content of the polymerization initiator is within the above range, polymerization can be performed without disturbing the alignment of the polymerizable liquid crystal compound.

[0077] When the polymerizable liquid crystal composition contains a photopolymerization initiator, it may further contain a photosensitizer. The use of a photosensitizer can further promote the polymerization reaction of the polymerizable liquid crystal compound. Examples of photosensitizers include xanthone compounds such as xanthone and thioxanthone (e.g., 2,4-diethylthioxanthone, 2-isopropylthioxanthone), anthracene compounds such as anthracene and alkoxy group-containing anthracene (e.g., dibutoxyanthracene), phenothiazine, rubrene, etc. Photosensitizers can be used alone or in combination of two or more.

[0078] The content of the photosensitizer in the polymerizable liquid crystal composition of the present invention may be appropriately determined depending on the types and amounts of the photopolymerization initiator and the polymerizable liquid crystal compound, and is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 0.5 to 8 parts by mass, relative to 100 parts by mass of the polymerizable liquid crystal compound.

[0079] The polymerizable liquid crystal composition of the present invention may further contain a leveling agent. The leveling agent has the function of adjusting the fluidity of the polymerizable liquid crystal composition and making the coating film obtained by applying the polymerizable liquid crystal composition flatter. Specific examples thereof include surfactants. The leveling agent is preferably at least one selected from the group consisting of leveling agents containing a polyacrylate compound as a main component and leveling agents containing a fluorine atom-containing compound as a main component. The leveling agents can be used alone or in combination of two or more.

[0080] Examples of leveling agents containing a polyacrylate compound as a main component include "BYK-350", "BYK-352", "BYK-353", "BYK-354", "BYK-355", "BYK-358N", "BYK-361N", "BYK-380", "BYK-381" and "BYK-392" (BYK Chemie).

[0081] Leveling agents containing fluorine-containing compounds as the main component include "Megafac (registered trademark) R-08", "R-30", "R-90", "F-410", "F-411", "F-443", "F-445", "F-470", "F-471", "F-477", "F-479", "F-482" and "F-483" (DIC Corporation); "Surflon (registered trademark) S-381" and "S-38 2”, “S-383”, “S-393”, “SC-101”, “SC-105”, “KH-40”, and “SA-100” (AGC Seimi Chemical Co., Ltd.); “E1830”, “E5844” (Daikin Fine Chemicals Research Institute, Inc.); “F-TOP EF301”, “F-TOP EF303”, “F-TOP EF351”, and “F-TOP EF352” (Mitsubishi Materials Electronic Chemicals Co., Ltd.).

[0082] The content of the leveling agent in the polymerizable liquid crystal composition of the present invention is preferably 0.05 to 5 parts by mass, more preferably 0.05 to 3 parts by mass, relative to 100 parts by mass of the polymerizable liquid crystal compound. When the content of the leveling agent is within the above range, the polymerizable liquid crystal compound is easily horizontally aligned, unevenness is less likely to occur, and a smoother polarizing film tends to be obtained.

[0083] The polymerizable liquid crystal composition of the present invention may further contain additives other than the polymerization initiator, photosensitizer, and leveling agent. Examples of the additives include a release agent, a stabilizer, a colorant such as a bluing agent, a flame retardant, and a lubricant. When the polymerizable liquid crystal composition contains the additives, the content of the additives is preferably more than 0% and not more than 20% by mass, more preferably more than 0% and not more than 10% by mass, based on the solid content of the polymerizable liquid crystal composition.

[0084] The polymerizable liquid crystal composition of the present invention may further contain a solvent. For example, since compounds exhibiting smectic liquid crystal properties generally have high viscosity, adding a solvent to the polymerizable liquid crystal composition often facilitates coating, thereby facilitating the formation of a polarizing film. The solvent can be appropriately selected depending on the solubility of the polymerizable liquid crystal compound and the organic dichroic dye, and examples thereof include alcohol solvents such as water, 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; nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; and chlorinated hydrocarbon solvents such as chloroform and chlorobenzene. These solvents can be used alone or in combination of two or more. The content of the solvent is preferably 100 to 1900 parts by mass, more preferably 150 to 900 parts by mass, and still more preferably 180 to 600 parts by mass, relative to 100 parts by mass of the solid components constituting the polymerizable liquid crystal composition.

[0085] The polymerizable liquid crystal composition of the present invention can usually be prepared by mixing and stirring the polymerizable liquid crystal compound, the organic dichroic dye, the sulfur-based antioxidant, and, if necessary, the above-mentioned additives and solvent, etc.

[0086] The polymerizable liquid crystal composition of the present invention can provide a cured liquid crystal film that is less likely to yellow over time, and therefore can be suitably used for producing a polarizing film. Accordingly, the present invention is directed to a polarizing film comprising a cured film of the polymerizable liquid crystal composition of the present invention.

[0087] A polarizing film with a high degree of alignment order can be produced using the polymerizable liquid crystal composition of the present invention. Polarizing films with a high degree of orientational order exhibit Bragg peaks derived from higher-order structures such as hexatic and crystalline phases in X-ray diffraction measurements. The Bragg peak refers to a peak derived from the planar periodic structure of molecular orientation. Therefore, in a polarizing film formed from the polymerizable liquid crystal composition of the present invention, the polymerizable liquid crystal compound or its polymer is preferably oriented so that the polarizing film exhibits a Bragg peak in X-ray diffraction measurement, and more preferably is "horizontally oriented" in which the molecules of the polymerizable liquid crystal compound are oriented in the direction of light absorption. In the present invention, a polarizing film in which the planar periodic spacing of the molecular orientation is 3.0 to 6.0 Å is preferred. A high degree of orientational order that exhibits a Bragg peak can be achieved by controlling the type of polymerizable liquid crystal compound used, the type and amount of antioxidant, the type and amount of organic dichroic dye, etc.

[0088] The polarizing film of the present invention can be produced, for example, by forming a coating film of the polymerizable liquid crystal composition of the present invention; removing the solvent from the coating; raising the temperature to a temperature at which the polymerizable liquid crystal compound undergoes a phase transition to a liquid phase or higher, and then lowering the temperature to cause the polymerizable liquid crystal compound to undergo a phase transition to a liquid crystal phase (smectic liquid crystal state); and Polymerizing the polymerizable liquid crystal compound while maintaining the liquid crystal phase (smectic liquid crystal state) It can be produced by a method comprising:

[0089] A coating film of the polymerizable liquid crystal composition can be formed by applying the polymerizable liquid crystal composition, particularly a polymerizable liquid crystal composition whose viscosity has been adjusted by adding a solvent (hereinafter also referred to as a "polarizing film-forming composition"), onto a substrate, an alignment film (described later), etc. The polymerizable liquid crystal composition may also be applied directly onto a retardation film or other layers constituting the polarizing plate of the present invention.

[0090] The substrate is usually a transparent substrate. When the substrate is not placed on the display surface of a display element, for example, when a laminate obtained by removing the substrate from the polarizing film is placed on the display surface of a display element, the substrate does not have to be transparent. A transparent substrate refers to a substrate that is transparent enough to transmit light, particularly visible light, and transparency refers to the property of having a transmittance of 80% or more for light rays with wavelengths of 380 to 780 nm. Specific examples of transparent substrates include translucent resin substrates. Resins that constitute translucent resin substrates include polyolefins such as polyethylene and polypropylene; cyclic olefin resins such as norbornene-based polymers; polyvinyl alcohol; polyethylene terephthalate; polymethacrylic acid esters; polyacrylic acid esters; cellulose esters such as triacetyl cellulose, diacetyl cellulose, and cellulose acetate propionate; polyethylene naphthalate; polycarbonate; polysulfone; polyethersulfone; polyetherketone; polyphenylene sulfide; and polyphenylene oxide. From the viewpoints of availability and transparency, polyethylene terephthalate, polymethacrylate ester, cellulose ester, cyclic olefin resin, or polycarbonate is preferred. Cellulose ester is a material in which some or all of the hydroxyl groups contained in cellulose have been esterified, and is readily available on the market. Cellulose ester substrates are also readily available on the market. Commercially available cellulose ester substrates include "Fujitac Film" (Fuji Photo Film Co., Ltd.); "KC8UX2M," "KC8UY," and "KC4UY" (Konica Minolta Opto, Inc.).

[0091] The properties required of the substrate vary depending on the configuration of the polarizing film, but a substrate with as little retardation as possible is usually preferred. Examples of substrates with as little retardation as possible include cellulose ester films with no retardation, such as Zerotack (Konica Minolta Opto, Inc.) and Z-Tack (Fujifilm Corporation). Unstretched cyclic olefin resin substrates are also preferred. The surface of the substrate on which the polarizing film is not laminated may be subjected to hard coating treatment, antireflection treatment, antistatic treatment, etc.

[0092] If the substrate is too thin, the strength decreases and the processability tends to be poor, so the thickness of the substrate is usually 5 to 300 μm, preferably 20 to 200 μm, and more preferably 20 to 100 μm.

[0093] Examples of a method for applying the polarizing film-forming composition to a substrate or the like include known methods such as coating methods, such as spin coating, extrusion, gravure coating, die coating, bar coating, and applicator methods, and printing methods, such as flexography.

[0094] Next, the solvent is removed by drying or the like under conditions that do not polymerize the polymerizable liquid crystal compound contained in the coating film obtained from the composition for forming a polarizing film, thereby forming a dried coating film. Examples of the drying method include natural drying, ventilation drying, heat drying, and reduced pressure drying.

[0095] Furthermore, in order to cause the polymerizable liquid crystal compound to undergo a phase transition to a liquid phase, the temperature is raised to a temperature at which the polymerizable liquid crystal compound undergoes a phase transition to a liquid phase or higher, and then the temperature is lowered to cause the polymerizable liquid crystal compound to undergo a phase transition to a liquid crystal phase (smectic liquid crystal state). Such a phase transition may be carried out after or simultaneously with the removal of the solvent from the coating film.

[0096] A cured film of the polymerizable liquid crystal composition is formed as a polarizing film by polymerizing the polymerizable liquid crystal compound while maintaining the liquid crystal phase (smectic liquid crystal state) of the polymerizable liquid crystal compound. Photopolymerization is a preferred polymerization method. In photopolymerization, the light irradiated onto the dried coating film is appropriately selected depending on the type of photopolymerization initiator contained in the dried coating film, the type of polymerizable liquid crystal compound (particularly the type and amount of polymerizable groups contained in the polymerizable liquid crystal compound), and the amount of the light. Specific examples include 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, and actinic electron beams. Among these, ultraviolet light is preferred because it is easy to control the progress of the polymerization reaction and photopolymerization equipment widely used in the field can be used. It is also preferable to select the type of polymerizable liquid crystal compound and photopolymerization initiator contained in the polymerizable liquid crystal composition so that they can be photopolymerized by ultraviolet light. Furthermore, the polymerization temperature can be controlled by irradiating the dried coating film with light while cooling it with an appropriate cooling means. By employing such a cooling means, the polymerization of the polymerizable liquid crystal compound can be carried out at a lower temperature, so that a polarizing film can be appropriately formed even if a substrate having a relatively low heat resistance is used. During photopolymerization, a patterned polarizing film can also be obtained by performing masking and development.

[0097] Examples of the light source of the active energy rays include a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a xenon lamp, a halogen lamp, a carbon arc lamp, a tungsten lamp, a gallium lamp, an excimer laser, an LED light source emitting light in a wavelength range of 380 to 440 nm, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, and a metal halide lamp.

[0098] The UV irradiation intensity is usually 10 to 3,000 mW / cm 2The ultraviolet irradiation intensity is preferably an intensity in a wavelength region effective for activating a photopolymerization initiator. The light irradiation time is usually 0.1 seconds to 10 minutes, preferably 1 second to 5 minutes, more preferably 5 seconds to 3 minutes, and even more preferably 10 seconds to 1 minute. When irradiating once or multiple times with such ultraviolet irradiation intensity, the cumulative light amount is 10 to 3,000 mJ / cm. 2 , preferably 50 to 2,000 mJ / cm 2 , more preferably 100 to 1,000 mJ / cm 2 is.

[0099] By photopolymerization, the polymerizable liquid crystal compound is polymerized while maintaining a liquid crystal phase, preferably a smectic phase, and more preferably a higher-order smectic phase, to form a polarizing film. The polarizing film obtained by polymerizing the polymerizable liquid crystal compound while maintaining a smectic phase has the advantage of higher polarization performance, due in part to the action of the dichroic dye, compared to conventional host-guest polarizing films, i.e., polarizing films formed in a nematic liquid crystal phase. Furthermore, the polarizing film has the advantage of being superior in strength compared to films coated with only a dichroic dye or lyotropic liquid crystal.

[0100] The thickness of the polarizing film can be appropriately selected depending on the display device to which it is applied, and is preferably 0.5 to 4 μm, more preferably 0.5 to 3 μm.

[0101] The polarizing film is preferably formed on an alignment film. The alignment film has an alignment-regulating force that aligns the polymerizable liquid crystal compound in the desired direction. The alignment film preferably has solvent resistance that prevents the polymerizable liquid crystal compound from dissolving when applied, and also has heat resistance during heat treatment for removing the solvent and orienting the polymerizable liquid crystal compound. Examples of such alignment films include alignment films containing an orientable polymer, photo-alignment films, groove alignment films having a concavo-convex pattern or a plurality of grooves on the surface, and stretched films stretched in the alignment direction. From the viewpoints of alignment angle precision and quality, photo-alignment films are preferred.

[0102] Examples of oriented polymers include polyamides and gelatins having an amide bond in the molecule, polyimides having an imide bond in the molecule, and their hydrolyzed products 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. The oriented polymers can be used alone or in combination of two or more.

[0103] An alignment film containing an alignment polymer is usually obtained by applying a composition in which an alignment polymer is dissolved in a solvent (hereinafter sometimes referred to as an "alignment polymer composition") to a substrate and then removing the solvent, or by applying an alignment polymer composition to a substrate, removing the solvent, and then rubbing the substrate (rubbing method). Examples of the solvent include the same solvents as those exemplified above as solvents that can be used to form a polarizing film.

[0104] The concentration of the orienting polymer in the orienting polymer composition may be within a range in which the orienting polymer material can be completely dissolved in the solvent, and is preferably 0.1 to 20% in terms of solid content relative to the solution, more preferably about 0.1 to 10%.

[0105] As the oriented polymer composition, commercially available alignment film materials may be used as they are. 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).

[0106] The method for applying the orientable polymer composition to the substrate may be the same as the method exemplified as the method for applying the polarizing film-forming composition to the substrate.

[0107] Methods for removing the solvent contained in the oriented polymer composition include natural drying, ventilation drying, heat drying, and reduced pressure drying.

[0108] In order to impart an alignment control force to the alignment film, a rubbing treatment can be carried out as necessary (rubbing method).

[0109] A method for imparting an orientation control force by a rubbing method includes a method in which an orientation polymer composition is applied to a substrate and annealed to bring an orientation polymer film formed on the surface of the substrate into contact with a rotating rubbing roll wrapped with a rubbing cloth.

[0110] A 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 a "photo-alignment film-forming composition") to a substrate and irradiating the substrate with polarized light (preferably polarized UV). Photo-alignment films are more preferable in that the direction of the alignment control force can be freely controlled by selecting the polarization direction of the polarized light to be irradiated.

[0111] The photoreactive group refers to a group that exhibits liquid crystal alignment ability upon irradiation with light. Specific examples include groups involved in photoreactions that induce molecular alignment upon irradiation with light or that are the origin of liquid crystal alignment ability, such as isomerization, dimerization, photocrosslinking, or photodecomposition. Among these, groups involved in dimerization or photocrosslinking are preferred because of their excellent alignment properties. As the photoreactive group, groups having an unsaturated bond, particularly a double bond, are preferred, and groups having at least one bond 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 particularly preferred.

[0112] Photoreactive groups having a C=C bond include vinyl groups, polyene groups, stilbene groups, stilbazole groups, stilbazolium groups, chalcone groups, and cinnamoyl groups. Photoreactive groups having a C=N bond include groups having structures such as aromatic Schiff bases and aromatic hydrazones. Photoreactive groups having an N=N bond include azobenzene groups, azonaphthalene groups, aromatic heterocyclic azo groups, bisazo groups, formazan groups, and groups having an azoxybenzene structure. Photoreactive groups having a C=O bond include benzophenone groups, coumarin groups, anthraquinone groups, and maleimide groups. These groups may have substituents such as alkyl groups, alkoxy groups, aryl groups, allyloxy groups, cyano groups, alkoxycarbonyl groups, hydroxyl groups, sulfonic acid groups, and halogenated alkyl groups.

[0113] Among these, photoreactive groups involved in photodimerization reactions are preferred, and cinnamoyl and chalcone groups are preferred because they require a relatively small amount of polarized light irradiation for photoalignment and are likely to produce a photoalignment film with excellent thermal stability and stability over time. As a polymer having a photoreactive group, one having a cinnamoyl group such that the terminal of the polymer side chain has a cinnamic acid structure is particularly preferred.

[0114] A photo-alignment-inducing layer can be formed on a substrate by applying the composition for forming a photo-alignment film onto the substrate. The solvent contained in the composition can be the same as the solvents exemplified above as solvents that can be used to form a polarizing film, and can be appropriately selected depending on the solubility of the polymer or monomer having a photoreactive group.

[0115] The content of the polymer or monomer having a photoreactive group in the composition for forming a photo-alignment film can be adjusted appropriately depending on the type of polymer or monomer and the desired thickness of the photo-alignment film, but is preferably at least 0.2 mass % relative to the mass of the composition for forming a photo-alignment film, and more preferably in the range of 0.3 to 10 mass %. The composition for forming a photo-alignment film may contain a polymer material such as polyvinyl alcohol or polyimide, or a photosensitizer, as long as the properties of the photo-alignment film are not significantly impaired.

[0116] The method for applying the composition for forming a photo-alignment film to a substrate may be the same as the method for applying the alignment composition to a substrate. Methods for removing the solvent from the applied composition for forming a photo-alignment film may include natural drying, ventilation drying, heat drying, and reduced pressure drying.

[0117] The polarized light irradiation can be performed by directly irradiating polarized UV onto a substrate from which the solvent has been removed from the composition for forming a photo-alignment film coated on the substrate, or by irradiating the substrate with polarized light and then transmitting the polarized light. It is particularly preferable that the polarized light be substantially parallel. The wavelength of the irradiated polarized light should be 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 particularly preferable. Examples of light sources used for 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. High-pressure mercury lamps, ultra-high-pressure mercury lamps, and metal halide lamps are more preferable. Among these, high-pressure mercury lamps, ultra-high-pressure mercury lamps, and metal halide lamps are preferred due to their high emission intensity of ultraviolet light with a wavelength of 313 nm. Polarized UV can be irradiated by irradiating light from the above light sources through an appropriate polarizer. As such a polarizer, a polarizing filter, a polarizing prism such as a Glan-Thompson or Glan-Taylor, or a wire grid type polarizer can be used.

[0118] If masking is performed during rubbing or polarized light irradiation, a plurality of regions (patterns) with different liquid crystal alignment directions can be formed.

[0119] A groove alignment film is a film with a concave-convex pattern or multiple grooves on its surface. When a polymerizable liquid crystal compound is applied to a film with multiple equally spaced linear grooves, the liquid crystal molecules are oriented in the direction along the grooves.

[0120] Methods for obtaining a grooved alignment film include a method in which the surface of a photosensitive polyimide film is exposed to light through an exposure mask having slits in the shape of a pattern, followed by development and rinsing to form a concave-convex pattern; a method in which a layer of uncured UV-curable resin is formed on a plate-shaped master having grooves on its surface, and the formed 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 an uncured UV-curable resin film formed on a substrate to form concave-convex patterns, followed by curing.

[0121] The thickness of the alignment film (alignment film containing an alignment polymer or photoalignment film) is usually in the range of 10 to 10,000 nm, preferably in the range of 10 to 1,000 nm, more preferably 500 nm or less, even more preferably 10 to 200 nm, and particularly preferably 50 to 150 nm.

[0122] The present invention encompasses a polarizing film comprising the polarizing film of the present invention and a transparent film. The term "transparent film" as used herein refers to a film having transparency that allows light, particularly visible light, to pass through. Transparency refers to a property in which the transmittance for light rays with wavelengths of 380 to 780 nm is 80% or higher. In the polarizing film of the present invention, the transparent film may be, for example, the transparent substrate described above, or a protective film for protecting the polarizing film. In the polarizing film of the present invention, the transparent film may be laminated on only one side or both sides of the polarizing film. When the polarizing film of the present invention includes multiple transparent films, the transparent films may be the same or different. Furthermore, the polarizing film and the transparent films may be in contact with each other or may be separated from each other. Typically, the transparent film can be attached to the polarizing film via an adhesive layer or a pressure-sensitive adhesive layer.

[0123] Furthermore, the present invention encompasses a circular polarizing plate comprising the polarizing film of the present invention and a retardation film. In the circular polarizing plate of the present invention, the retardation film preferably satisfies formulas (1) and (2). When the retardation film includes a layer other than a layer that exhibits retardation (retardation layer), such as when the retardation film is composed of a cured liquid crystal layer formed on a substrate film, it is preferable that the retardation layer satisfies the optical properties represented by formulas (1) and (2). 100 nm ≤ Re(550) ≤ 150 nm (1) Re(450) / Re(550)<1 (2) (wherein Re(λ) represents a front retardation value for light with a wavelength of λ nm)

[0124] When the retardation film has a front retardation value represented by the above formula (1), it functions as a so-called λ / 4 plate. The formula (1) preferably satisfies 120 nm≦Re(550)≦150 nm.

[0125] A retardation film satisfying the above formula (2) has so-called reverse wavelength dispersion and exhibits excellent polarization performance. The value of Re(450) / Re(550) is preferably 0.93 or less, more preferably 0.88 or less, even more preferably 0.86 or less, and is preferably 0.80 or more, more preferably 0.82 or more.

[0126] The front retardation value can be adjusted by the film thickness dA of the retardation film (retardation layer). The front retardation value is determined by the formula Re(λ)=(nx(λ)-ny(λ))×dA (dA represents the thickness of the retardation film (retardation layer), nx represents the principal refractive index at a wavelength of λ nm in a direction parallel to the plane of the retardation film in the index ellipsoid formed by the retardation film, and ny represents the refractive index at a wavelength of λ nm in a direction parallel to the plane of the retardation film and perpendicular to the direction of nx in the index ellipsoid formed by the retardation film). Therefore, in order to obtain a desired front retardation value (Re(λ): in-plane retardation value of the retardation layer at a wavelength of λ (nm)), it is sufficient to adjust the three-dimensional refractive index and the film thickness dA.

[0127] The retardation film may be a stretched film that imparts retardation by stretching a polymer, but from the viewpoint of thinning the circular polarizer, it is preferably a cured product of a polymerizable liquid crystal composition containing a polymerizable liquid crystal compound, and is composed of a polymer of the polymerizable liquid crystal compound in an oriented state. The retardation film that constitutes the circular polarizer of the present invention can be produced by appropriately selecting and employing materials and methods conventionally known in the art, and the polymerizable liquid crystal compound that forms the retardation film may be, for example, a liquid crystal compound described in JP-A-2011-207765.

[0128] The thickness of the retardation film can be appropriately selected depending on the display device to which it is applied, but from the viewpoint of thinning and flexibility, it is preferably 0.1 to 10 μm, more preferably 1 to 5 μm, and even more preferably 1 to 3 μm.

[0129] The circular polarizing plate of the present invention comprises the polarizing film or polarizing film of the present invention and a retardation film, and may further comprise other layers (protective layer, adhesive layer, etc.) in addition to these. In the circular polarizing plate of the present invention, the polarizing film or polarizing film of the present invention and the retardation film may be attached via an adhesive layer or a pressure-sensitive adhesive layer. In addition, in the circular polarizing plate of the present invention, the retardation film may be formed directly on the polarizing film of the present invention by directly applying a retardation film-forming composition to the polarizing film of the present invention.

[0130] In the circular polarizing plate of the present invention, the angle formed by the slow axis of the retardation film and the absorption axis of the polarizing film is preferably substantially 45°. In the present invention, "substantially 45°" means 45°±5°.

[0131] The thickness of the circularly polarizing plate of the present invention is preferably 10 to 300 μm, more preferably 20 to 200 μm, and even more preferably 25 to 100 μm, from the viewpoint of flexibility and visibility of the display device.

[0132] The present invention includes a display device comprising the polarizing film of the present invention or the circular polarizing plate of the present invention. The display device of the present invention can be obtained, for example, by laminating the polarizing film or circularly polarizing plate of the present invention to the surface of the display device via a pressure-sensitive adhesive layer. A display device is a device having a display mechanism and includes a light-emitting element or a light-emitting device as a light source. Examples of display devices include liquid crystal display devices, organic electroluminescence (EL) display devices, inorganic electroluminescence (EL) display devices, touch panel display devices, electron emission display devices (such as field emission displays (FEDs) and surface field emission displays (SEDs)), electronic paper (display devices using electronic ink or electrophoretic elements), plasma display devices, projection display devices (such as grating light valve (GLV) display devices and displays with digital micromirror devices (DMDs)), and piezoelectric ceramic displays. Liquid crystal display devices include transmissive liquid crystal display devices, semi-transmissive liquid crystal display devices, reflective liquid crystal display devices, direct-view liquid crystal display devices, and projection liquid crystal display devices. These display devices may display two-dimensional images or stereoscopic display devices displaying three-dimensional images. In particular, organic EL display devices and touch panel display devices are preferred as the display devices of the present invention, with organic EL display devices being particularly preferred. [Example]

[0133] The present invention will be described in more detail below with reference to Examples and Comparative Examples. In the Examples and Comparative Examples, "%" and "parts" are "% by mass" and "parts by mass" unless otherwise specified.

[0134] Comparative Example 1 The following components were mixed and stirred at 80° C. for 1 hour to obtain a polymerizable liquid crystal composition (1). The polymerizable liquid crystal compound and dichroic dye used were the polymerizable liquid crystal compound and azo dye described in the examples of JP-A-2013-101328. ·Polymerizable liquid crystal compound: [ka] (A-6) 90 copies [ka] (A-7) 10 copies Dichroic dyes: Azo dyes; [ka] (Dichroic dye A) 2.5 parts [ka] (Dichroic dye B) 2.5 parts [ka] (Dichroic dye C) 2.5 parts Polymerization initiator: 2-Dimethylamino-2-benzyl-1-(4-morpholinophenyl)butan-1-one (Irgacure 369; manufactured by Chiba Specialty Chemicals Co., Ltd.) 6 parts Leveling agent: Polyacrylate compound (BYK-361N; manufactured by BYK-Chemie) 1.2 parts ·solvent: o-xylene 400 parts

[0135] Furthermore, according to Table 1, polymerizable liquid crystal compositions (2) to (10) were obtained in the same manner as for the polymerizable liquid crystal composition (1), except that 1 part of an antioxidant described below was mixed with 100 parts by mass of the polymerizable liquid crystal composition (1).

[0136] Examples 1 to 4 and Comparative Examples 2 to 6 Polymerizable liquid crystal compositions of Examples 1 to 4 and Comparative Examples 2 to 6 (polymerizable liquid crystal compositions (2) to (10)) were prepared in the same manner as in Comparative Example 1, except that 1 part by mass of the following antioxidant was mixed into the polymerizable liquid crystal composition (1) in addition to the above-mentioned components. [ka] (Antioxidant A: 2-mercaptobenzimidazole) Used in polymerizable liquid crystal composition (2). [ka] (Antioxidant B: 10-methylphenothiazine) Used in polymerizable liquid crystal composition (3). [ka] (Antioxidant C: 2-methoxyphenothiazine) Used in polymerizable liquid crystal composition (4). [ka] (Antioxidant D: 2-ethylthiophenothiazine) Used in polymerizable liquid crystal composition (5). [ka] (Antioxidant E: 4-butoxy-4'-hydroxybiphenyl) Used in polymerizable liquid crystal composition (6). [ka] (Antioxidant F: 4-ethoxy-4'-hydroxybiphenyl) Used in polymerizable liquid crystal composition (7). [ka] (Antioxidant G: Sumilizer TPL, manufactured by Sumitomo Chemical Co., Ltd.) Used in polymerizable liquid crystal composition (8). [ka] (Antioxidant H: Sumilizer TP-D, manufactured by Sumitomo Chemical Co., Ltd.) Used in polymerizable liquid crystal composition (9). [ka] (Antioxidant I: DTDPA) Used in polymerizable liquid crystal composition (10).

[0137] Furthermore, polarizing films and the like of Examples 1 to 4 and Comparative Examples 1 to 6 were prepared using the polymerizable liquid crystal compositions (1) to (10) according to the following procedure. (1) Preparation of a photo-alignment film on a substrate (i) Preparation of composition for forming photo-alignment film The following components described in JP 2013-033249 A were mixed, and the resulting mixture was stirred at 80° C. for 1 hour to obtain a composition for forming a photoalignment film. Photo-aligned polymers: [ka] 2nd part ·solvent: o-xylene 98 parts

[0138] (ii) Formation of photo-alignment film A triacetyl cellulose film (KC8UX2M, manufactured by Konica Minolta, Inc.) was used as a transparent substrate. After subjecting the film surface to a corona treatment, the composition for forming a photo-alignment film was applied and dried at 120°C to obtain a dried film. Polarized UV light was irradiated onto this dried film to form a photo-alignment film, resulting in a film with a photo-alignment film. The polarized UV treatment was carried out using a UV irradiation device (SPOT CURE SP-7, manufactured by Ushio Inc.) under conditions where the intensity measured at a wavelength of 365 nm was 100 mJ.

[0139] (2) Preparation of polarizing film The polymerizable liquid crystal composition (2) was applied onto the photo-alignment film obtained as described above by a bar coating method (#9 30 mm / s), and the polymerizable liquid crystal compound was heated and dried in a drying oven at 120°C for 1 minute to cause a phase transition to a liquid phase, and then cooled to room temperature to cause a phase transition to a smectic liquid crystal state. Next, using a UV irradiation device (SPOT CURE SP-7; manufactured by Ushio Inc.), the polymerizable liquid crystal compound was exposed to light at an exposure dose of 1000 mJ / cm. 2 By irradiating a layer formed from the polymerizable liquid crystal composition with ultraviolet light (365 nm standard), the polymerizable liquid crystal compound contained in the dried film was polymerized while maintaining the smectic liquid crystal state of the polymerizable liquid crystal compound, and a polarizing film was formed from the dried film, thereby obtaining a polarizing film consisting of a transparent substrate, a photo-alignment film, and a polarizing film laminated in this order. The thickness of the polarizing film was measured using a laser microscope (OLS3000, manufactured by Olympus Corporation) and was found to be 2.3 μm. X-ray diffraction measurements were performed on this polarizing film using an X'Pert PRO MPD X-ray diffractometer (Spectris Corporation). A sharp diffraction peak (Bragg peak) with a full width at half maximum (FWHM) of approximately 0.17° was observed near 2θ = 20.2°. Similar results were obtained with the incident light perpendicular to the rubbing direction. The order period (d) calculated from the peak position was approximately 4.4 Å, confirming the formation of a structure reflecting a highly ordered smectic phase.

[0140] (3) Fabrication of the laminate The polarizing film surface was then subjected to a corona treatment. An aqueous solution (viscosity: 92 cP) containing 7 parts of carboxyl-modified polyvinyl alcohol (Kuraray Poval KL318, manufactured by Kuraray Co., Ltd.) and 3.5 parts of a water-soluble polyamide epoxy resin (Sumirez Resin 650, obtained from Sumika Chemtex Co., Ltd., with a solids concentration of 30% by weight) as a thermal crosslinker was then applied to the corona-treated surface using a wire bar coater (#30). The aqueous solution was dried at 80°C for 5 minutes to form a protective layer, producing a polarizing film with a protective layer. A glass sheet (Corning Eagle XG) was then laminated onto the protective layer via an adhesive layer made of a pressure-sensitive adhesive (Lintec Corporation, 25 μm thick) to obtain a laminate.

[0141] <Measurement of the degree of polarization Py> The polarization degree Py of the laminate was measured as follows. The transmittance (Ta) in the transmission axis direction and the transmittance (Tb) in the absorption axis direction were measured in the wavelength range of 380 nm to 780 nm by the double beam method using a spectrophotometer (Shimadzu Corporation UV-3150) equipped with a folder with a polarizer. A mesh that cuts the amount of light by 50% was installed on the reference side of the folder. The degree of polarization at each wavelength was calculated using the following formula (1), and luminosity correction was further performed using a 2-degree visual field (C light source) according to JIS Z 8701 to calculate the luminosity-corrected degree of polarization (Py). Degree of polarization Py (%) = (Ta - Tb) / (Ta + Tb) × 100 (Equation 1)

[0142] <Measurement of absorbance in the transmission direction> In the same manner as above, the absorbance (A1) in the transmission axis direction was measured by the double beam method using a spectrophotometer (Shimadzu UV-3150) equipped with a folder with a polarizer.

[0143] <Evaluation of light resistance> The light resistance of the laminates of Examples 1 to 4 and Comparative Examples 1 to 6 was evaluated according to the following method. The results are shown in Table 1.

[0144] The laminate was placed in a light resistance tester (Suntest XLS+; manufactured by ATLAS) with the triacetyl cellulose film substrate facing up, and the accumulated light dose was 96120 KJ / m 2 After light irradiation under the conditions above, the degree of polarization Py and absorbance A1 in the transmission axis direction of the laminate were measured again, and the rate of change ΔPy of the degree of polarization Py before and after the light resistance test and the change in absorbance in the transmission axis direction at 420 nm, which is a criterion for suppressing yellowing, were calculated and evaluated according to the following criteria.

[0145] <Evaluation criteria> Change in polarization degree A: The absolute value of the change in the degree of polarization |ΔPy| is less than 0.8 B: The absolute value of the change in polarization degree |ΔPy| is 0.8 or more and less than 1.2 C: The absolute value of the change in polarization degree |ΔPy| is 1.2 or more

[0146] Absorbance change A: Change in absorbance along the transmission axis is 0% or more and less than 5% B: Change in absorbance along the transmission axis is 5% or more but less than 10% C: The change in absorbance along the transmission axis is 10% or more.

[0147] [Table 1]

[0148] The polarizing films of Examples 1 to 4 obtained good results in each evaluation.

Claims

1. A polymerizable liquid crystal composition comprising a polymerizable liquid crystal compound, an organic dichroic dye which is an azo dye, and a sulfur-based antioxidant, The polymerizable liquid crystal compound has at least one radically polymerizable group and exhibits high-order smectic liquid crystallinity, and is represented by the following formula (A): U １ -V １ -W １ -(X １ -Y １ )n-X ２ -W ２ -V ２ -U ２ (A) [In formula (A), X １ and X ２ each independently represents 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 (with the proviso that X １ and X ２ at least one of which is an optionally substituted 1,4-phenylene group or an optionally substituted cyclohexane-1,4-diyl group), Y １ represents a single bond, —CH 2 CH 2 —, —CH 2 O—, —CH 2 CH 2 O—, —COO—, —OCOO—, —N═N—, —CR a ═CR b —, —C≡C—, —CR a ═N— or —CO—NR a —, and R a and R b each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; n is 1 to 3, and when n is 2 or more, a plurality of X １ may be the same or different, and X ２ is multiple X １ may be the same as or different from any one or all of Y １ may be the same as or different from each other, U １ represents a hydrogen atom or a polymerizable group, U ２ represents a polymerizable group, W １ and W ２ are each independently a single bond, —O—, —S—, —COO— or —OCOO—, V １ and V ２ each independently represents an alkanediyl group having 1 to 20 carbon atoms which may have a substituent, and —CH ２ - may be replaced by -O-, -CO-, -S- or -NH-. the content of the polymerizable liquid crystal compound represented by formula (A) is 51% by mass or more with respect to the total mass of all polymerizable liquid crystal compounds in the polymerizable liquid crystal composition, The polymerizable liquid crystal composition, wherein the sulfur-based antioxidant has an aromatic ring structure and a thiol structure or a thioether structure, and has a weight-average molecular weight of 100 or more and 400 or less.

2. 2. The polymerizable liquid crystal composition according to claim 1, wherein the sulfur-based antioxidant is at least one selected from the group consisting of a thiol compound having an aromatic ring, a sulfide compound having an aromatic ring, and a cyclic sulfide compound having an aromatic ring.

3. The polymerizable liquid crystal composition according to claim 1 or 2, wherein the organic dichroic dye has an aromatic ring structure.

4. 4. The polymerizable liquid crystal composition according to claim 1, wherein the content of the sulfur-based antioxidant is 0.1 to 3 parts by mass relative to 100 parts by mass of the polymerizable liquid crystal compound.

5. A polarizing film comprising a cured film of the polymerizable liquid crystal composition according to any one of claims 1 to 4.

6. The polarizing film according to claim 5 , which exhibits a Bragg peak in X-ray diffraction measurement.

7. 7. The polarizing film according to claim 5, wherein the film thickness is in the range of 0.5 to 4 μm.

8. A polarizing film comprising the polarizing membrane according to any one of claims 5 to 7 and a transparent film.

9. A circularly polarizing plate comprising the polarizing film according to any one of claims 5 to 7 and a retardation film.

10. The retardation film is represented by the formulas (1) and (2): 100nm ≦ Re(550) ≦ 150nm (1) Re(450) / Re(550)<1 (2) (wherein Re(λ) represents a front retardation value for light having a wavelength of λ nm) The circularly polarizing plate according to claim 9 , which satisfies the following:

11. A display device comprising the polarizing film according to any one of claims 5 to 7, the polarizing film according to claim 8, or the circular polarizing plate according to claim 9 or 10.

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