JP2014167639A - Liquid crystal layer forming composition, circularly polarized light separation sheet and method of manufacturing the same, and luminance enhancing film and liquid-crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal layer forming composition which enables efficient manufacture of a defect-free uniform liquid crystal layer and has a longer pot life than the prior art.SOLUTION: A liquid crystal layer forming composition comprises: a liquid crystal compound including two or more polymerizable functional groups in each molecule and having a refractive index anisotropy of 0.2 or more; a solvent having a cyclic ketone structure; a solvent having a cyclic ether structure; an antioxidant exhibiting volatility at a temperature lower than the N-I point of the liquid crystal compound; and a compound represented by a given general formula.

Description

  The present invention relates to a composition for forming a liquid crystal layer useful for producing an optical material such as a circularly polarized light separating sheet, a circularly polarized light separating sheet produced from the composition for forming a liquid crystal layer, a method for producing the same, and the circularly polarized light separating material. The present invention relates to a brightness enhancement film including a sheet and a liquid crystal display device.

  In a display device such as a liquid crystal display device, a birefringent film is used for the purpose of improving the viewing angle and contrast and improving the luminance. As such a birefringent film, a stretched polymer film having positive or negative intrinsic birefringence has been known. However, these stretched films sometimes cause deformation and changes in optical properties at high temperatures.

  Therefore, as a film having improved heat resistance, a film using a compound having liquid crystallinity (hereinafter referred to as “liquid crystal compound” as appropriate) has been proposed. For example, a film in which a polymer liquid crystal compound is applied and aligned on a substrate, a film in which a polymerizable liquid crystal compound is applied and aligned on a substrate, and cured by heat or light are known. . However, in the film obtained by forming these liquid crystal compounds, the liquid crystal compounds that can be used are limited due to the low solubility of the liquid crystal compounds, and it is difficult to obtain sufficient optical characteristics. Moreover, it is difficult to apply a liquid crystal compound uniformly without defects, and productivity is lacking. Therefore, Patent Documents 1 to 3 propose improvement methods.

International Publication No. 2006/088101 JP-A-10-104615 Special table 2007-502911

  One of the films obtained using a liquid crystal compound is a circularly polarized light separating sheet. This circularly polarized light separating sheet is manufactured by applying, for example, a cholesteric liquid crystal. When the circularly polarized light separating sheet is used as the brightness enhancement film, the circularly polarized light separating sheet preferably has a wide selective reflection band of 300 nm or more in the wavelength range. In order to realize such a wide selective reflection band, it is desired to use a liquid crystal compound having a refractive index anisotropy Δn as high as 0.20 or more.

  However, in general, a liquid crystal compound having a higher refractive index anisotropy has higher crystallinity and poor solubility, and is difficult to apply uniformly without defects. For example, if an attempt is made to form a liquid crystal compound having a high refractive index anisotropy by the technique described in Patent Documents 1 to 3, the ink composition for forming a liquid crystal layer described in Patent Document 1 is an alcohol that is a poor solvent for the liquid crystal compound. Since it contains a system solvent, a liquid crystal compound may be deposited during the coating process to cause defects. The technique described in Patent Document 2 is suitable for a liquid crystal compound having a relatively low Δn, but 2-butanone is a poor solvent for a high Δn liquid crystal compound having a high crystallinity. When applying the compound, precipitation of the liquid crystal compound may occur and become a defect. Further, in the technique described in Patent Document 3, since a large amount of 1,3-dioxolane having a relatively high vapor pressure is used, thickness unevenness is likely to occur, and uniform film formation is difficult.

  Therefore, the applicant has proposed a novel liquid crystal layer forming composition in Japanese Patent Application No. 2009-223109. This liquid crystal layer forming composition is a composition containing a mixed solvent in which a solvent having a cyclic ketone structure and a solvent having a cyclic ether structure are combined. Since the mixed solvent dissolves a liquid crystal compound having a high refractive index anisotropy satisfactorily, a uniform liquid crystal layer having no defects can be efficiently produced by using the composition for forming a liquid crystal layer.

  However, when the liquid crystal layer-forming composition was further studied, the liquid crystal layer-forming composition has poor stability and tends to gel with time, so that it has a sufficient pot life. Not found out.

  The present invention was devised in view of the above-mentioned problems. A liquid crystal layer-forming composition that can efficiently produce a uniform liquid crystal layer without defects and has a longer pot life than the prior art, and a liquid crystal layer-forming composition are provided. It is an object of the present invention to provide a circularly polarized light separating sheet and a method for producing the same, and a brightness enhancement film and a liquid crystal display device including the circularly polarized light separating sheet.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have further developed a liquid crystal layer forming composition comprising a solvent having a cyclic ketone structure, a solvent having a cyclic ether structure, and a liquid crystal compound having a high refractive index anisotropy. It has been found that when a predetermined antioxidant is included, the gelation over time of the liquid crystal layer forming composition can be suppressed, the pot life can be lengthened, and a uniform liquid crystal layer without defects can be efficiently produced, The present invention has been completed.
That is, the gist of the present invention is the following [1] to [10].

[1] a liquid crystal compound having two or more polymerizable functional groups in one molecule and having a refractive index anisotropy of 0.2 or more;
A solvent having a cyclic ketone structure;
A solvent having a cyclic ether structure;
The composition for liquid crystal layer formation containing the antioxidant which shows volatility at the temperature lower than the NI point of the said liquid crystal compound.
[2] The composition for forming a liquid crystal layer according to [1], wherein the solvent having a cyclic ketone structure is cyclopentanone.
[3] The composition for forming a liquid crystal layer according to [1] or [2], wherein the solvent having a cyclic ether structure is 1,3-dioxolane.
[4] The liquid crystal according to any one of [1] to [3], wherein the solvent having the cyclic ketone structure and the solvent having the cyclic ether structure are 30/70 or more and 90/10 or less in a weight ratio. Layer forming composition.
[5] The composition for forming a liquid crystal layer according to any one of [1] to [4], wherein the antioxidant is 2,6-di-t-butyl-p-cresol.
[6] A step of forming a coating film of the composition for forming a liquid crystal layer according to any one of [1] to [5] on a substrate;
Heating the coating film to align the liquid crystal compound;
Incompletely curing the coating film;
Heating the coating film;
The circularly-polarized-light-separation sheet obtained by passing through the process which hardens the said coating film completely in this order.
[7] A step of forming a coating film of the composition for forming a liquid crystal layer according to any one of [1] to [5] on a substrate;
Heating the coating film to align the liquid crystal compound;
Incompletely curing the coating film;
Heating the coating film;
The manufacturing method of the circularly-polarized-light-separation sheet which has the process of hardening the said coating film completely in this order.
[8] The method for producing a circularly polarized light separating sheet according to [7], wherein the antioxidant volatilizes in a step of aligning the liquid crystal compound by heating the coating film.
[9] A brightness enhancement film comprising the circularly polarized light separating sheet according to [6] and a retardation film.
[10] A liquid crystal display device comprising the brightness enhancement film according to [9] and a liquid crystal panel.

  According to the present invention, a liquid crystal layer forming composition that can efficiently produce a uniform liquid crystal layer without defects and having a long pot life, a circularly polarized light separating sheet using the liquid crystal layer forming composition, a method for manufacturing the same, and A brightness enhancement film and a liquid crystal display device including the circularly polarized light separating sheet can be realized.

  Hereinafter, the present invention will be described in detail with reference to embodiments, examples, etc., but the present invention is not limited to the following embodiments, examples, etc., and can be arbitrarily set within the scope of the present invention. Can be changed and implemented.

[1. Liquid crystal layer forming composition]
The composition for forming a liquid crystal layer of the present invention is a liquid crystal compound having two or more polymerizable functional groups in one molecule and having a refractive index anisotropy of a predetermined value or more (hereinafter referred to as “high Δn polymerizable liquid crystal” as appropriate). Compound ”), a solvent having a cyclic ketone structure (hereinafter referred to as“ cyclic ketone solvent ”as appropriate), a solvent having a cyclic ether structure (hereinafter referred to as“ cyclic ether solvent ”as appropriate), and a predetermined oxidation. A composition comprising an inhibitor. A coating film is obtained by depositing the composition for forming a liquid crystal layer of the present invention on a substrate, and the coating film obtained corresponds to a liquid crystal layer containing a high Δn polymerizable liquid crystal compound. Further, when the liquid crystal layer is cured, a liquid crystal cured product layer is obtained.

[1-1. Liquid crystal compound)
The high Δn polymerizable liquid crystal compound has two or more polymerizable functional groups in one molecule. The polymerizable functional group is a group that causes a polymerization reaction under appropriate conditions to polymerize a high Δn polymerizable liquid crystal compound. When the high Δn polymerizable liquid crystal compound has two or more polymerizable functional groups, when the liquid crystal layer forming composition is formed and cured, the high Δn polymerizable liquid crystal compound is polymerized to form a stable cured product. Can be obtained. On the contrary, when the composition for forming a liquid crystal layer is cured by forming a film having a polymerizable functional group in one molecule of 1 or less, a crosslinked cured product cannot be obtained. As a result, the film strength that can withstand practical use may not be obtained. Even when a cross-linking agent described later is used, the film strength tends to be insufficient and practical use tends to be difficult.
The film strength that can be practically used is HB or more, preferably H or more, in pencil hardness (JIS K5400). If the film strength is lower than HB, the film is easily scratched and lacks handling properties. The upper limit of preferable pencil hardness is not particularly limited as long as it does not adversely affect the optical performance and durability test.

  Examples of the polymerizable functional group include a carboxyl group, a (meth) acryl group, an epoxy group, a thioepoxy group, a mercapto group, an isocyanate group, an isothiocyanate group, an oxetane group, a thietanyl group, an aziridinyl group, a pyrrole group, and a vinyl group. , Allyl group, fumarate group, cinnamoyl group, oxazoline group, hydroxyl group, alkoxysilyl group, amino group and the like. In addition, (meth) acryl refers to acryl and methacryl. Moreover, the polymerizable functional group contained in one molecule may be one type or two or more types.

The refractive index anisotropy of the high Δn polymerizable liquid crystal compound is usually 0.20 or more, preferably 0.21 or more, more preferably 0.23 or more. Due to the high refractive index anisotropy of the high Δn polymerizable liquid crystal compound, the refractive index anisotropy of the composition for forming a liquid crystal layer containing the high Δn polymerizable liquid crystal compound is improved, and excellent optical performance (for example, A circularly polarized light separating sheet having circularly polarized light separating properties can be realized. Further, when the refractive index anisotropy is 0.30 or more, the absorption edge on the long wavelength side of the ultraviolet absorption spectrum may extend to the visible range. It can be used as long as the optical performance is not adversely affected.
The refractive index anisotropy of the compound can be measured by the senalmon method.

Preferred examples of the high Δn polymerizable liquid crystal compound include a rod-like liquid crystal compound represented by the following general formula (1).
^{R 1 -C 1 -D 1 -C 3} -M-C 4 -D 2 -C 2 -R 2 (1)

In the general formula (1), R ¹ and R ² each independently represent a polymerizable functional group.

In the general formula (1), D ¹ and D ² are each independently a single bond, divalent saturated carbonization such as a linear or branched methylene group having 1 to 20 carbon atoms and an alkylene group. It represents a group selected from the group consisting of a hydrogen group and a linear or branched alkylene oxide group having 1 to 20 carbon atoms.

In the general formula (1), C ^{1 to} C ⁴ are each independently a single bond, —O—, —S—, —S—S—, —CO—, —CS—, —OCO—, —CH. _{2 -, - OCH 2 -,} - CH = N-N = CH -, - NHCO -, - OCOO -, - CH 2 COO-, and represents a group selected from the group consisting of _-CH 2 OCO-.

In the general formula (1), M represents a mesogenic group. Specific examples of M include azomethines, azoxys, phenyls, biphenyls, terphenyls, naphthalenes, anthracenes, benzoic acid esters, cyclohexanecarboxylic acid, which may be unsubstituted or have a substituent. 2-4 skeletons selected from the group of acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, alkenylcyclohexylbenzonitriles, —, —S—, —S—S—, —CO—, —CS—, —OCO—, —CH ₂ —, —OCH ₂ —, —CH═N—N═CH—, —NHCO—, —OCOO _-, - CH 2 _COO-, and a group formed by being linked by linking groups _-CH 2 OCO- or the like.

Examples of the substituent that the mesogenic group M may have include, for example, a halogen atom, an optionally substituted alkyl group having 1 to 10 carbon atoms, a cyano group, a nitro group, —O—R ³ , — O—C (═O) —R ³ , —C (═O) —O—R ³ , —O—C (═O) —O—R ³ , —NR ³ —C (═O) —R ³ , -C (= O) -NR < ³ > R < ⁴ > or -O-C (= O) -NR < ³ > R < ⁴ > is represented.
Here, R ³ and R ⁴ represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. When R ³ and R ⁴ are alkyl groups, the alkyl group includes —O—, —S—, —O—C (═O) —, —C (═O) —O—, —O—C. (═O) —O—, —NR ⁵ —C (═O) —, —C (═O) —NR ⁵ —, —NR ⁵ —, or —C (═O) — may be present. (However, the case where two or more of -O- and -S- are adjacent to each other is excluded). Here, R ⁵ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Examples of the substituent in the above-mentioned “optionally substituted alkyl group having 1 to 10 carbon atoms” include a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, an amino group, and 1 to 6 carbon atoms. Alkoxy group, alkoxyalkoxy group having 2 to 8 carbon atoms, alkoxyalkoxyalkoxy group having 3 to 15 carbon atoms, alkoxycarbonyl group having 2 to 7 carbon atoms, alkylcarbonyl having 2 to 7 carbon atoms Examples thereof include an oxy group and an alkoxycarbonyloxy group having 2 to 7 carbon atoms.

  The composition for forming a liquid crystal layer of the present invention may contain one kind of high Δn polymerizable liquid crystal compound alone or may contain two or more kinds of high Δn polymerizable liquid crystal compounds in combination at any ratio. Good.

  The molecular weight of the high Δn polymerizable liquid crystal compound is preferably 600 or more. When the composition for forming a liquid crystal layer of the present invention contains a compound represented by the general formula (2) as will be described later, if the molecular weight of the high Δn polymerizable liquid crystal compound is increased as described above, the general formula (2) The molecules of the compound represented by can enter into the gaps of the high Δn polymerizable liquid crystal compound having a molecular weight larger than that, and the alignment uniformity can be improved.

  In the composition for forming a liquid crystal layer of the present invention, the concentration of the high Δn polymerizable liquid crystal compound is usually 5% by weight or more, preferably 10% by weight or more, more preferably 15% by weight or more, and usually 40% by weight or less. Preferably it is 35 weight% or less, More preferably, it is 30 weight% or less. By keeping the concentration of the high Δn polymerizable liquid crystal compound in such a range, a desired liquid crystal layer can be efficiently formed while suppressing the precipitation of the high Δn polymerizable liquid crystal compound.

[1-2. solvent〕
The composition for forming a liquid crystal layer of the present invention contains a cyclic ketone solvent and a cyclic ether solvent as solvents. Usually, the composition for forming a liquid crystal layer of the present invention is used in the form of a solution in which other components are dissolved in these solvents. By including these cyclic ketone solvent and cyclic ether solvent, the solubility of the high Δn polymerizable liquid crystal compound and the controllability of the drying rate of the solvent are improved in the composition for forming a liquid crystal layer, and a uniform composition free from defects is obtained. A membrane is possible.

  Examples of the cyclic ketone solvent include cyclopropanone, cyclopentanone, cyclohexanone, and the like, among which cyclopentanone is preferable. In addition, a cyclic ketone solvent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Examples of the cyclic ether solvent include tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, etc. Among them, 1,3-dioxolane is preferable. In addition, a cyclic ether solvent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  In the liquid crystal layer forming composition of the present invention, the cyclic ketone solvent preferably has a lower vapor pressure than the cyclic ether solvent. From this viewpoint, the weight ratio of the cyclic ketone solvent to the cyclic ether solvent (cyclic ketone solvent / cyclic ether solvent) is usually 30/70 or more, preferably 40/60 or more, more preferably 45/55 or more. 90/10 or less, preferably 80/20 or less, more preferably 70/30 or less. By setting it to be equal to or more than the lower limit of the above range, it is possible to prevent the drying rate of the solvent from becoming excessively high and suppress the occurrence of thickness unevenness. Moreover, by making it below the upper limit of the said range, it can prevent that the drying rate of a solvent becomes slow too much and can suppress that a solvent remains in a liquid crystal layer and a liquid-crystal hardened | cured material layer.

  The amount of the cyclic ketone solvent and the cyclic ether solvent in the liquid crystal layer forming composition of the present invention is the total amount of the cyclic ketone solvent and the cyclic ether solvent with respect to 100 parts by weight of the high Δn polymerizable liquid crystal compound, and usually 100 parts by weight or more, preferably Is 150 parts by weight or more, more preferably 200 parts by weight or more, usually 1900 parts by weight or less, preferably 900 parts by weight or less, more preferably 500 parts by weight or less. By setting it to the lower limit of this range or more, precipitation of the high Δn polymerizable liquid crystal compound can be stably suppressed. By setting the upper limit of this range or less, the amount of the solvent becomes excessive and the production efficiency of the liquid crystal layer and the liquid crystal cured product layer is increased. Can be prevented from decreasing.

[1-3. Antioxidant〕
The composition for forming a liquid crystal layer of the present invention contains an antioxidant. The cyclic ether solvent contained in the composition for forming a liquid crystal layer of the present invention easily generates a peroxide by auto-oxidation with air. Furthermore, the tendency of the cyclic ether solvent may increase in a mixed system with another solvent such as a cyclic ketone solvent. The generated peroxide generates radicals and advances the polymerization of the high Δn polymerizable liquid crystal compound. For this reason, the conventional composition for forming a liquid crystal layer was easily gelled. On the other hand, the composition for forming a liquid crystal layer of the present invention can suppress polymerization of the high Δn polymerizable liquid crystal compound in the composition for forming a liquid crystal layer by including an antioxidant. Thereby, it can suppress that the composition for liquid crystal layer formation gelatinizes over time, and can lengthen the pot life of the composition for liquid crystal layer formation. The pot life refers to a period during which the liquid crystal layer forming composition can be stored while maintaining its state. That is, if the pot life is long, a sufficient amount of the composition for forming a liquid crystal layer can be prepared in advance, so that the flexibility of the production plan can be increased.

  As the antioxidant, an antioxidant exhibiting volatility at a temperature lower than the NI point of the high Δn polymerizable liquid crystal compound is used. Here, the NI point is a temperature at which the high Δn polymerizable liquid crystal compound transitions from the nematic phase to the isotropic phase, and when the temperature is higher than the NI point, the high Δn polymerizable liquid crystal compound exhibits nematic liquid crystal properties. lose. Volatile means a property that the antioxidant is emitted as a gas, regardless of whether the antioxidant before becoming a gas was solid or liquid.

  When a circularly polarized light separating sheet having a wide selective reflection band is to be produced using the composition for forming a liquid crystal layer of the present invention, usually, after forming a coating film for the liquid crystal layer forming composition, An incomplete curing step of polymerizing the contained high Δn polymerizable liquid crystal compound to incompletely cure the coating film is performed. The incomplete curing step is a step performed for broadening the reflection spectrum of the cholesteric resin layer formed from the liquid crystal layer forming composition. Antioxidants tend to function in the incomplete curing process to prevent polymerization and inhibit incomplete curing, so antioxidants can prevent the broadening of circularly polarized separation sheets and thus prevent efficient production. was there. On the other hand, if an antioxidant exhibiting volatility at a temperature lower than the NI point of the high Δn polymerizable liquid crystal compound is used, the antioxidant can be easily obtained by heating the coating film before the incomplete curing step. Can be removed. In particular, since an alignment treatment step for aligning the high Δn polymerizable liquid crystal compound by heating is usually performed before the incomplete curing step, the antioxidant can be easily removed from the coating film in this alignment treatment step. Therefore, by adopting an antioxidant exhibiting volatility at a temperature lower than the NI point of the high Δn polymerizable liquid crystal compound, the pot life of the liquid crystal layer forming composition is lengthened, and the circularly polarized light reflecting sheet is Both can be made efficient.

  As described above, an antioxidant exhibiting volatility at a low temperature lower than the NI point of the high Δn polymerizable liquid crystal compound has been recognized as being unsuitable for a composition for forming a liquid crystal layer in the conventional technical common sense. The reason for this recognition is that (i) antioxidants exhibiting volatility at low temperatures volatilize during production (that is, emit as gas) and adhere to the production equipment, which easily contaminates the production equipment. (Ii) Antioxidants that exhibit volatility at low temperatures were recognized as being likely to contaminate the product by volatilizing during production and adhering to the product, and (iii) improving the oxidation resistance of the product. In the case where an antioxidant is used for the purpose of increasing, volatilization of the antioxidant during the production cannot be achieved because the purpose cannot be achieved, and so on. In the composition for forming a liquid crystal layer of the present invention, unlike the above-mentioned conventional technical common sense, a high-quality circularly polarized reflection is intentionally used by using an antioxidant that exhibits volatility at a low temperature lower than the NI point. It realizes efficient production of sheets.

  The degree of volatility that the antioxidant exhibits at a temperature lower than the NI point depends on the amount of the antioxidant contained in the composition for forming a liquid crystal layer of the present invention and volatilization of the antioxidant from the composition for forming a liquid crystal layer. It may be set according to the length of time that can be used for removal. For example, when the composition for forming a liquid crystal layer of the present invention is used for the production of a circularly polarized light separating sheet, the circularly polarized light separating sheet can be broadened by heating performed in the alignment treatment process before the incomplete curing process. What is necessary is just to show the volatility that an antioxidant is removed from the composition for liquid crystal layer formation to such an extent that it can be realized.

  When the specific volatility preferable range shown by the antioxidant is given, for example, in the alignment treatment step in the method for producing the circularly polarized light separating sheet described later, usually 90 wt.% Of the antioxidant contained in the liquid crystal layer forming composition. % Or more, preferably 99% by weight or more, more preferably 99.5% by weight or more, and ideally 100% by weight is volatilized. Further, the amount of the antioxidant contained in the liquid crystal cured product layer provided in the obtained circularly polarized light separating sheet is usually 10% by weight or less, preferably 1% with respect to the amount of the antioxidant contained in the composition for forming a liquid crystal layer. % Or less, more preferably 0.5% by weight or less, and ideally 0% by weight.

  Further, the antioxidant is not so volatile under the storage conditions of the composition for forming a liquid crystal layer of the present invention, or the amount of volatilization is small enough not to significantly impair the effects of the present invention even if volatile. Preferably there is. This is because the effect of the present invention of prolonging the pot life can be stably exhibited. The specific degree of volatility of the composition for forming a liquid crystal layer of the present invention under storage conditions is not uniform depending on storage conditions such as storage temperature, pressure, container, and storage time. Usually, the composition for forming a liquid crystal layer of the present invention is stored at a temperature lower than the boiling points of the cyclic ketone solvent and the cyclic ether solvent, specifically, a sealed container at room temperature (usually 25 ° C.) and normal pressure (usually 1013 hPa). It is often stored in. Therefore, it is preferable that the volatility of the antioxidant is such that the concentration of the antioxidant in the composition for forming a liquid crystal layer can be maintained within the range described later throughout the storage period under the storage conditions.

  As examples of antioxidants, generally used antioxidants include phenolic antioxidants, amine antioxidants, sulfur antioxidants, phosphorus antioxidants, and the like. Among them, examples of the preferred antioxidant described above include 2,6-di-t-butyl-p-cresol (BHT), butylated hydroxyanisole (BHA), 2,6-di-t-butyl-4. -Ethylphenol, hydroquinone, etc. are mentioned, BHT is especially preferable. In addition, the composition for liquid crystal layer formation of this invention may contain antioxidant individually by 1 type, and may contain it combining 2 or more types by arbitrary ratios.

  The amount of the antioxidant contained in the composition for forming a liquid crystal layer of the present invention varies depending on the type thereof, but is usually 0.01% or more, preferably 0 with respect to the nonvolatile components contained in the composition for forming a liquid crystal layer. 0.02% or more, more preferably 0.05% or more, and usually 5% or less, preferably 2% or less, more preferably 1% or less. When there is too little antioxidant, there exists a possibility that sufficient pot life may not be obtained. Moreover, when there are too many antioxidants, it may take time for volatilization of an antioxidant and may reduce the efficiency of manufacture, or it may remain in a coating film and may affect an incomplete hardening process.

[1-4. Other ingredients
The composition for forming a liquid crystal layer of the present invention may contain other components in addition to the components described above as long as the effects of the present invention are not significantly impaired.
For example, the composition for forming a liquid crystal layer of the present invention may contain a compound represented by the following general formula (2).
R < ⁶ > -A < ¹ > -ZA < ² > -R < ⁷ > (2)

In General Formula (2), R ⁶ and R ⁷ are each independently a linear or branched alkyl group having 1 to 20 carbon atoms, a linear or branched chain having 1 to 20 carbon atoms, or A group selected from the group consisting of a branched alkylene oxide group, a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a (meth) acryl group, an epoxy group, a mercapto group, an isocyanate group, an amino group, and a cyano group; Represent.

The alkyl group and alkylene oxide group may not be substituted and may be substituted with one or more halogen atoms. Furthermore, when two or more substituents are present in each of the alkyl group and the alkylene oxide group, they may be the same or different.
In addition, the halogen atom, hydroxyl group, carboxyl group, (meth) acryl group, epoxy group, mercapto group, isocyanate group, amino group, and cyano group are alkyl groups and / or alkylene oxides having 1 to 2 carbon atoms. It may be bonded to a group.

Preferred examples of R ⁶ and R ⁷ include a halogen atom, a hydroxyl group, a carboxyl group, a (meth) acryl group, an epoxy group, a mercapto group, an isocyanate group, an amino group, and a cyano group.

At least one of R ⁶ and R ⁷ is preferably a polymerizable functional group. By having a polymerizable functional group as R ⁶ and / or R ⁷ , the compound represented by the general formula (2) is fixed in the liquid crystal layer at the time of curing to form a liquid crystal cured product layer as a stronger film. be able to. Here, examples of the polymerizable functional group include those similar to the high Δn polymerizable liquid crystal compound, and among them, a carboxyl group, a (meth) acryl group, an epoxy group, a mercapto group, an isocyanate group, and an amino group are preferable.

In the general formula (2), A ¹ and A ² are each independently 1,4-phenylene group, 1,4-cyclohexylene group, 1,4-cyclohexenyl group, 4,4′-biphenylene group, 4 , 4′-bicyclohexylene group and a group selected from the group consisting of 2,6-naphthylene group. The 1,4-phenylene group, 1,4-cyclohexylene group, 1,4-cyclohexenyl group, 4,4′-biphenylene group, 4,4′-bicyclohexylene group, and 2,6-naphthylene group are May be unsubstituted, substituted with one or more substituents such as halogen atom, hydroxyl group, carboxyl group, cyano group, amino group, alkyl group having 1 to 10 carbon atoms, halogenated alkyl group, etc. May be. Furthermore, when two or more substituents are present in each of A ¹ and A ² , they may be the same or different.

Particularly preferable examples of A ¹ and A ² include a 1,4-phenylene group, a 4,4′-biphenylene group, and a 2,6-naphthylene group. These aromatic ring skeletons are relatively rigid as compared with the alicyclic skeletons, have high affinity with mesogens of the high Δn polymerizable liquid crystal compound, and have higher alignment uniformity ability.

In the general formula (2), Z represents a single bond, —O—, —S—, —S—S—, —CO—, —CS—, —OCO—, —CH ₂ —, —OCH ₂ —, —CH. = N-N = CH -, - NHCO -, - OCOO -, - CH 2 COO-, and is selected from the group consisting of _-CH 2 OCO-. Particularly preferable examples of Z include a single bond, —OCO—, and —CH═N—N═CH—.

  At least one of the compounds represented by the general formula (2) preferably has liquid crystallinity, and preferably has chirality. Moreover, it is preferable that the composition for liquid crystal layer formation of this invention contains the mixture of a some optical isomer as a compound represented by General formula (2). For example, a mixture of plural kinds of enantiomers and / or diastereomers can be contained. As for at least 1 type of the compound represented by General formula (2), it is preferable that the melting | fusing point exists in the range of 50 to 150 degreeC.

  When the compound represented by the general formula (2) has liquid crystallinity, the refractive index anisotropy is preferably high. Thereby, the refractive index anisotropy of the composition for forming a liquid crystal layer of the present invention can be improved, and a broadband circularly polarized light separating sheet can be produced. At least one refractive index anisotropy of the compound represented by the general formula (2) is preferably 0.18 or more, more preferably 0.22 or more. In addition, some of the compounds represented by the general formula (2) may satisfy the requirements as a high Δn polymerizable liquid crystal compound, and such a compound is handled as the high Δn polymerizable liquid crystal compound according to the present invention. And

  In the liquid crystal layer forming composition of the present invention, the compound represented by the general formula (2) preferably has a molecular weight of less than 600. When the molecular weight of the compound represented by the general formula (2) is less than 600, the compound represented by the general formula (2) can enter the gap of the high Δn polymerizable liquid crystal compound having a larger molecular weight. The alignment uniformity of the high Δn polymerizable liquid crystal compound in the composition for forming a liquid crystal layer of the present invention can be improved.

  Specific examples of particularly preferable compounds represented by the general formula (2) include the following compounds (A1) to (A10). In the compound (A3), “*” represents a chiral center.

  The compounding ratio of the compound represented by the general formula (2) is a weight ratio of (total weight of the compound represented by general formula (2)) / (total weight of the high Δn polymerizable liquid crystal compound). The above is preferable, 0.1 or more is more preferable, 0.15 or more is particularly preferable, 1 or less is preferable, 0.65 or less is more preferable, and 0.45 or less is particularly preferable. If the weight ratio is too small, the alignment uniformity of the high Δn polymerizable liquid crystal compound in the composition for forming a liquid crystal layer of the present invention may be insufficient, and conversely if too large, the composition for forming a liquid crystal layer of the present invention. The orientation uniformity of the high Δn polymerizable liquid crystal compound in the product is lowered, the stability of the liquid crystal phase of the liquid crystal layer forming composition of the present invention is lowered, or the liquid crystal composition of the liquid crystal layer forming composition of the present invention When the film is formed, desired optical performance (for example, circularly polarized light separation characteristics) may not be obtained. The total weight indicates the weight when one type is used, and indicates the total weight when two or more types are used.

  In addition, for example, the composition for forming a liquid crystal layer of the present invention may contain a cross-linking agent in order to improve film strength and durability after curing. The crosslinking agent may react simultaneously with the curing of the liquid crystal layer formed with the composition for forming a liquid crystal layer of the present invention, or heat treatment may be performed after curing to accelerate the reaction, or the reaction may proceed spontaneously due to moisture. And what can raise the crosslinking density of a liquid-crystal hardened | cured material layer, and does not deteriorate alignment uniformity can be selected suitably, and can be used. Moreover, what can harden | cure with an ultraviolet-ray, a heat | fever, moisture etc. can be used conveniently, for example.

  Examples of cross-linking agents include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 2- (2-vinyloxyethoxy) Polyfunctional acrylate compounds such as ethyl acrylate; Epoxy compounds such as glycidyl (meth) acrylate, ethylene glycol diglycidyl ether, glycerin triglycidyl ether, pentaerythritol tetraglycidyl ether; 2,2-bishydroxymethylbutanol-tris [3- ( 1-aziridinyl) propionate], 4,4-bis (ethyleneiminocarbonylamino) diphenylmethane, trimethylolpropane-tri-β-aziridinylpropionate Aziridine compounds such as nates; Isocyanurate type isocyanates derived from hexamethylene diisocyanate, hexamethylene diisocyanate, isocyanurate type isocyanates, biuret type isocyanates, adduct type isocyanates, etc .; Polyoxazoline compounds having an oxazoline group in the side chain; N- (2-aminoethyl) 3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3- (meth) acryloxypropyltrimethoxysilane, N- (1 , 3-dimethylbutylidene) -3- (triethoxysilyl) -1-propanamine and the like alkoxysilane compounds; In addition, 1 type may be used for a crosslinking agent and it may use it combining 2 or more types by arbitrary ratios. Further, the composition for forming a liquid crystal layer of the present invention may contain a known catalyst according to the reactivity of the cross-linking agent to improve productivity in addition to improving the film strength and durability.

  The blending ratio of the cross-linking agent is such that the concentration of the cross-linking agent in the liquid crystal cured product layer obtained by curing the liquid crystal layer forming composition of the present invention is 0.1 wt% to 15 wt%. preferable. If the blending ratio of the crosslinking agent is less than 0.1% by weight, the effect of improving the crosslinking density may not be obtained. Conversely, if the blending ratio is more than 15% by weight, the stability of the liquid crystal cured product layer may be lowered. .

For example, the composition for forming a liquid crystal layer of the present invention may contain a polymerization initiator. A thermal polymerization initiator may be used as the polymerization initiator, but a photopolymerization initiator is usually used. As the photopolymerization initiator, for example, a known compound that generates radicals or acids by ultraviolet rays or visible rays can be used.
Examples of photopolymerization initiators include benzoin, benzylmethyl ketal, benzophenone, biacetyl, acetophenone, Michler's ketone, benzyl, benzylisobutyl ether, tetramethylthiuram mono (di) sulfide, 2,2-azobisisobutyronitrile, 2,2-azobis-2,4-dimethylvaleronitrile, benzoyl peroxide, di-tert-butyl peroxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one 1- (4-Isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-diethylthioxanthone, methylbenzoyl formate 2,2-diethoxyacetophenone, β-ionone, β-bromostyrene, diazoaminobenzene, α-amylcinnacaldehyde, p-dimethylaminoacetophenone, p-dimethylaminopropiophenone, 2-chlorobenzophenone, pp′- Dichlorobenzophenone, pp'-bisdiethylaminobenzophenone, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-propyl ether, benzoin n-butyl ether, diphenyl sulfide, bis (2,6-methoxybenzoyl) -2,4,4-trimethyl- Pentylphosphine oxide, 2,4,6-trimethylbenzoyldiphenyl-phosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide 2-methyl-1 [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, Anthracene benzophenone, α-chloroanthraquinone, diphenyl disulfide, hexachlorobutadiene, pentachlorobutadiene, octachlorobutene, 1-chloromethylnaphthalene, 1,2-octanedione, 1- [4- (phenylthio) -2- (o- Benzoyloxime)] and 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl] ethanone 1- (o-acetyloxime), (4-methylphenyl) [4- (2-Methylpropyl) phenyl] iodonium hexafluoroph Sufeto, 3-methyl-2-butynyl tetramethyl hexafluoroantimonate, diphenyl - (p-phenylthiophenyl) sulfonium hexafluoroantimonate, and the like. Depending on the desired physical properties, one type of polymerization initiator may be used, or two or more types may be used in combination at any ratio. Furthermore, if necessary, the composition for forming a liquid crystal layer of the present invention may contain a known photosensitizer or a tertiary amine compound as a polymerization accelerator to control the curability of the composition for forming a liquid crystal layer. You can also.

  The blending ratio of the polymerization initiator is preferably 0.03% by weight to 7% by weight in the liquid crystal layer forming composition of the present invention. When the blending amount of the polymerization initiator is less than 0.03% by weight, the film strength of the liquid crystal cured product layer that can be obtained may be lowered. On the other hand, if it is more than 7% by weight, the orientation of the high Δn polymerizable liquid crystal compound may be hindered and the liquid crystal phase may become unstable.

For example, the composition for forming a liquid crystal layer of the present invention may contain a surfactant. As the surfactant, those not inhibiting the orientation can be appropriately selected and used.
As examples of the surfactant, a nonionic surfactant containing a siloxane or a fluorinated alkyl group in the hydrophobic group can be preferably used. Of these, oligomers having two or more hydrophobic group moieties in one molecule are particularly suitable. These surfactants include, for example, OM-NOVA PolyFox PF-151N, PF-636, PF-6320, PF-656, PF-6520, PF-3320, PF-651, PF-652; FTX-209F, FTX-208G, FTX-204D; KH-40 of Surflon, Seimi Chemical Co., Ltd. can be used. In addition, 1 type of surfactant may be used and it may use it combining 2 or more types by arbitrary ratios.

  The mixing ratio of the surfactant is such that the concentration of the surfactant in the liquid crystal cured product layer obtained by curing the liquid crystal layer forming composition of the present invention is 0.05 wt% to 3 wt%. Is preferred. When the blending ratio of the surfactant is less than 0.05% by weight, the alignment regulating force at the air interface is lowered and alignment defects may occur. On the other hand, when the amount is more than 3% by weight, an excessive surfactant may enter between the high Δn polymerizable liquid crystal compound molecules, thereby reducing the alignment uniformity.

  For example, the liquid crystal layer forming composition of the present invention may contain a chiral agent. Specific examples of the chiral agent include JP-A-2005-289881, JP-A-2004-115414, JP-A-2003-66214, JP-A-2003-313187, JP-A-2003-342219, JP-A-2003-342219. 2000-290315, JP-A-6-072962, U.S. Pat. No. 6,468,444, WO 98/00428, JP-A 2007-176870, etc. can be used as appropriate. . Specific examples thereof include, for example, LC756, a PASF color produced by BASF. Note that one type of chiral agent may be used, or two or more types may be used in combination at any ratio.

  The blending ratio of the chiral agent is set in a range that does not lower the desired optical performance. A specific blending ratio of the chiral agent is preferably 1% by weight to 60% by weight in the liquid crystal layer forming composition of the present invention.

The composition for forming a liquid crystal layer of the present invention may contain, for example, an ultraviolet absorber or a light stabilizer for improving durability. However, the blending ratio of these other components is within a range that does not deteriorate the desired optical performance.
In addition, 1 type may be used for another component and it may use it combining 2 or more types by arbitrary ratios.

[1-5. Method for producing liquid crystal layer forming composition]
The method for producing the composition for forming a liquid crystal layer of the present invention is not particularly limited, and the composition can be produced by mixing the above components.

[1-6. Main Advantages of Composition for Forming Liquid Crystal Layer of the Present Invention]
The composition for forming a liquid crystal layer of the present invention can suppress the occurrence of defects because the high Δn polymerizable liquid crystal compound is difficult to precipitate during storage and use. Further, since the evaporation rate of the solvent can be easily controlled, uniform film formation with no thickness unevenness is possible. Furthermore, since the composition for forming a liquid crystal layer of the present invention can make a wider range of high Δn polymerizable liquid crystal compounds into a stable dissolved state, various types of liquid crystal layers and liquid crystal curings can be obtained using a wide range of high Δn polymerizable liquid crystal compounds. Applicable to the production of physical layers.

Moreover, gelation can be suppressed with an antioxidant and a pot life can be lengthened. Specifically, a uniform liquid crystal layer having no defects can be formed as described above even when it is usually left in a closed container for 1 week at room temperature.
Furthermore, when producing a circularly polarizing reflective sheet using the composition for forming a liquid crystal layer of the present invention, since the antioxidant can be easily removed, the progress of polymerization of the high Δn polymerizable liquid crystal compound is not hindered during curing, A circularly polarized light reflecting sheet can be produced efficiently.

[2. Method for producing circularly polarized light separating sheet]
The composition for forming a liquid crystal layer of the present invention has an excellent advantage that a uniform liquid crystal layer and a liquid crystal cured product layer can be formed without defects as described above. Utilizing this, a circularly polarized light separating sheet can be produced using the composition for forming a liquid crystal layer of the present invention. For the method for producing the circularly polarized light separating sheet, for example, International Publication No. 2008/007782 may be referred to. Especially when manufacturing a circularly polarized light separation sheet using the composition for liquid crystal layer formation of this invention, it is preferable to employ | adopt the manufacturing method of the circularly polarized light separation sheet of this invention demonstrated below.

  When producing a circularly polarized light separating sheet by the method for producing a circularly polarized light separating sheet of the present invention, at least a film forming step for forming a coating film of the liquid crystal layer forming composition of the present invention on a substrate, and heating the coated film An alignment treatment process for aligning the high Δn polymerizable liquid crystal compound, an incomplete curing process for incompletely curing the coating film, a heating process for heating the coating film, and a complete curing process for completely curing the coating film, Are performed in this order. Moreover, you may make it perform processes other than a film-forming process, an orientation process, an incomplete hardening process, a heating process, and a complete hardening process as needed.

[2-1. Preparation of substrate
A base material is a member used as the object which forms into a film the composition for liquid crystal layer formation of this invention. Although this base material may be peeled off after forming the liquid crystal cured product layer, it may be used as a part of the circularly polarized light separating sheet together with the liquid crystal cured product layer without being peeled off. When the substrate is used as a part of the circularly polarized light separating sheet, a transparent substrate is usually used as the substrate. Although the specific light transmittance of a transparent base material is not uniform according to the use of a circularly polarized light-separating sheet, for example, a base material having a thickness of 1 mm and a total light transmittance of 80% or more can be used.

  For example, a transparent resin sheet or film can be used as the transparent substrate. Specific examples of the transparent substrate material include alicyclic olefin polymers, chain olefin polymers such as polyethylene and polypropylene, triacetyl cellulose, polyvinyl alcohol, polyimide, polyarylate, polyester, polycarbonate, polysulfone, polyethersulfone, Examples thereof include synthetic resins such as modified acrylic polymers, epoxy resins, polystyrene, and acrylic resins. Among these, an alicyclic olefin polymer or a chain olefin polymer is preferable, and an alicyclic olefin polymer is particularly preferable from the viewpoint of transparency, low hygroscopicity, dimensional stability, lightness, and the like. Further, the transparent substrate may have a single-layer structure consisting of only one layer or a laminated structure having two or more layers.

  An alignment film may be provided on the substrate. By providing the alignment film, the high Δn polymerizable liquid crystal compound in the coating film of the composition for forming a liquid crystal layer of the present invention formed thereon can be surely aligned in a desired direction. The alignment film is subjected to corona discharge treatment, if necessary, on the surface of the base material, and then applied with a solution in which the alignment film material is dissolved in water or a solvent, dried, and then rubbed to the dried coating film. Can be formed.

  Examples of the material of the alignment film include cellulose, silane coupling agent, polyimide, polyamide, polyvinyl alcohol, epoxy acrylate, silanol oligomer, polyacrylonitrile, phenol resin, polyoxazole, and cyclized polyisoprene. Polyamide is particularly preferred. In addition, the material of the alignment film may be used alone or in combination of two or more at any ratio.

  Examples of the modified polyamide include those obtained by modifying an aromatic polyamide or an aliphatic polyamide. Of these, a modified aliphatic polyamide is preferred. Specific examples include nylon-6, nylon-66, nylon-12, ternary to quaternary copolymer nylon, fatty acid polyamide, or fatty acid block copolymer (eg, polyether ester amide, polyester amide). And the like added. Examples of the modification include terminal amino modification, carboxyl modification, hydroxyl modification and the like, and modification in which a part of the amide group is alkylaminated or N-alkoxyalkylated. Examples of the N-alkoxyalkylated modified polyamide include N-methoxymethylated part of the amide group of copolymer nylon such as nylon-6, nylon-66, or nylon-12. The weight average molecular weight of the modified polyamide is preferably 5000 or more, more preferably 10,000 or more, preferably 500,000 or less, more preferably 200,000 or less.

  The thickness of the alignment film may be any thickness as long as desired alignment uniformity can be obtained in the liquid crystal layer. Specifically, 0.001 μm or more is preferable, 0.01 μm or more is more preferable, 5 μm or less is preferable, and 2 μm or less is more preferable.

[2-2. Film formation process]
After preparing a base material, the film-forming process which forms the coating film of the composition for liquid crystal layer formation of this invention on a base material is performed. The coating film of the composition for forming a liquid crystal layer of the present invention formed by film formation is a layer containing a high Δn polymerizable liquid crystal compound and corresponds to a liquid crystal layer. When an alignment film is formed on the substrate surface, the liquid crystal layer forming composition of the present invention is formed on the alignment film.

In the film forming step, the solvent is usually removed from the coating film by drying after a certain period of time. At this time, since the mixed solvent containing the cyclic ketone solvent and the cyclic ether solvent dissolves the high Δn polymerizable liquid crystal compound well, defects in the liquid crystal layer due to the precipitation of the high Δn polymerizable liquid crystal compound can be prevented. Moreover, since the drying speed of the mixed solvent containing the cyclic ketone solvent and the cyclic ether solvent is not excessively high, the coating film does not cause uneven thickness, and thus prevents the occurrence of uneven thickness in the liquid crystal layer and the liquid crystal cured product layer. it can.
Depending on the volatility of the antioxidant, the antioxidant may volatilize when the solvent is dried.

  Usually, the liquid crystal layer forming composition of the present invention is formed by coating. Although there is no restriction | limiting in the application | coating method, What is necessary is just to implement by methods, such as the extrusion coating method, the direct gravure coating method, the reverse gravure coating method, the die coating method, the bar coating method, for example.

  The temperature condition during film formation is usually 10 ° C. or higher, preferably 13 ° C. or higher, more preferably 16 ° C. or higher, and is usually 60 ° C. or lower, preferably 45 ° C. or lower, more preferably 35 ° C. or lower. By setting the temperature to be above the lower limit of the above range, it is possible to prevent the drying rate of the solvent from being excessively slowed and lowering the production efficiency, and by setting the temperature to be below the upper limit, the drying rate of the solvent is excessively high and the coating film It is possible to more stably prevent the occurrence of thickness unevenness.

[2-3. (Orientation treatment process)
After the coating film is formed by the film forming process, an alignment treatment process for aligning the high Δn polymerizable liquid crystal compound by heating the coating film is performed before the incomplete curing process.
The heating temperature for the orientation treatment is such that the coating film is usually heated to 50 ° C. or higher, preferably 70 ° C. or higher, more preferably 80 ° C. or higher, and usually 190 ° C. or lower, preferably 170 ° C. or lower, more preferably 160 ° C. or lower. That's fine.
The heating time is usually 0.25 minutes or more, preferably 0.5 minutes or more, more preferably 1 minute or more, and usually 10 minutes or less, preferably 8 minutes or less, more preferably 6 minutes or less.
By performing the alignment treatment, the high Δn polymerizable liquid crystal compound in the coating film can be aligned well.

  Moreover, the antioxidant contained in a coating film volatilizes by heating a coating film in an orientation treatment process. As a result, the antioxidant contained in the coating film is removed, so that the polymerization of the high Δn polymerizable liquid crystal compound in the incomplete curing step performed after the alignment treatment step is prevented by the antioxidant. Can be prevented.

[2-4. Incomplete curing process)
After aligning the high Δn polymerizable liquid crystal compound in the coating film by the alignment treatment process, an incomplete curing process for incompletely curing the coating film is performed. In the incomplete curing step, the coating film is usually irradiated with selective ultraviolet rays (also referred to as broadband ultraviolet rays). When selective ultraviolet rays are irradiated to the coating film, a polymerization reaction or a crosslinking reaction proceeds in the coating film, and the curing of the coating film proceeds.

Here, the selective ultraviolet rays use the light intensity distribution caused by the absorption, scattering, and reflection of the material in the coating film described above, or polymerization inhibition by dissolved oxygen, interaction at the interface with the adjacent layer, etc. It means ultraviolet light in which the wavelength range or illuminance in which the degree of crosslinking (or degree of polymerization) of the high Δn polymerizable liquid crystal compound in the coating film can be varied in the thickness direction of the coating film is selectively controlled. In addition, the coating film is not completely cured (100% polymerization) by irradiation with this selective ultraviolet ray. For this reason, this process is referred to as an “incomplete” curing process.
By irradiation with selective ultraviolet rays, the degree of cross-linking of the high Δn polymerizable liquid crystal compound in the coating film can be varied in the thickness direction of the coating film, and cholesteric regularity can be reflected so that circularly polarized light can be reflected in a wide wavelength bandwidth. Can be adjusted.

  As selective ultraviolet rays, it is preferable to use ultraviolet rays having a wavelength range of 100 nm or less. Specifically, it is preferable to use ultraviolet rays having only wavelengths of 300 nm or more and less than 400 nm. The width of the wavelength range is the full width at half maximum (the width between both ends taking a value half of the peak value of transmittance). For example, a band pass filter or the like may be used to control the wavelength range. Specific examples of the control method include a method using a bandpass filter having a center wavelength of 365 nm, a method using a light source that emits light with a spectrum having a steep peak, and the like. Further, depending on conditions, the wavelength range can be used without controlling.

  As the selective ultraviolet light source, for example, a mercury lamp light source, a metal halide lamp light source, or the like can be used.

The temperature at the time of selective ultraviolet irradiation is usually 20 to 40 ° C. In addition, the integrated light quantity of the selected ultraviolet rays to be irradiated is usually 0.05 mJ / cm ² or more and less than 50 mJ / cm ² . The integrated light quantity is measured using an illuminometer on the substrate surface having a peak sensitivity at the wavelength of the selected ultraviolet ray (specifically, for example, having a peak sensitivity at 360 nm).

  The selective ultraviolet rays may be irradiated from the coating film side, from the substrate side, or from both sides of the coating film side and the substrate side. In particular, when the degree of crosslinking is controlled using the light intensity distribution, it is preferable to irradiate from the substrate side in order to reduce the influence of polymerization inhibition by oxygen. In addition, when irradiating from the coating film side, the stability of illuminance and irradiation time will be controlled more precisely (specifically, usually within ± 3%). Irradiation is preferred.

  Furthermore, when irradiating from the base material side, the cooling process which cools the coating film on a base material and makes the temperature of a coating film 20 to 40 degreeC after an orientation treatment process and before an incomplete hardening process is performed. It is preferable. By irradiating the coating film maintained at 20 ° C. to 40 ° C. with the above-described selective ultraviolet rays, it is possible to form liquid crystal cured product layers having different degrees of crosslinking reflecting the light intensity distribution generated in the thickness direction of the coating film. it can. Examples of the method for cooling the coating film include cooling by cold air supply, cooling by a cooling roll, and the like.

[2-5. Heating process]
After the incomplete curing step, a heating step for heating the coating film is performed. In the heating step, the period of the cholesteric regularity of the coating film is changed by heating the coating film. Here, “changing the cycle of the cholesteric regularity of the coating film” means changing the pitch of the coating film having the cholesteric regularity in the thickness direction.

  As heat treatment conditions in the heating step, considering productivity as well as the effect of broadening the band, it is usually 0.001 to 20 minutes at a temperature of 50 to 115 ° C., preferably 0.001 to 10 minutes at a temperature of 65 to 115 ° C. More preferably, it is 0.01 to 5 minutes at a temperature of 65 to 115 ° C. However, since the temperature range in which the liquid crystal phase is developed varies depending on the type of liquid crystal compound that forms the coating film, the processing temperature and processing time also vary accordingly.

  Examples of the method of changing the cycle of cholesteric regularity include a method of further applying a liquid crystal compound to the coating film and a method of further applying a non-liquid crystal compound to the coating film. Therefore, these methods may be performed in combination with the heat treatment of the coating film.

  The incomplete curing step and the heating step are preferably repeated a plurality of times. By repeating these steps a plurality of times, the pitch of the chiral structure of the coating film can be changed more greatly. The conditions for selective ultraviolet irradiation and cholesteric regularity adjustment are appropriately adjusted for each number of times in order to adjust the reflection band. Although there is no restriction | limiting in the frequency | count of repetition, It is preferable that it is 2 times or more and 4 times or less from a viewpoint on productivity and an installation. If it is performed 5 times or more, the facility becomes large and the productivity may be lowered.

  Here, “repeating” the incomplete curing step and the heating step means repeating a sequence including the implementation of the incomplete curing step and the subsequent heating step. That is, when the incomplete curing step and the heating step are repeated twice, the incomplete curing step, the heating step, the incomplete curing step, and the heating step are performed in this order. You may perform other processes, such as the said cooling, between these processes.

[2-6. Complete curing process)
After performing the incomplete curing process and the heating process for a predetermined number of times, a complete curing process for completely curing the coating film is performed. The method for completely curing the coating film is not particularly limited as long as the coating film is cured to have cholesteric regularity, but the total amount of the cured ultraviolet light is 10 mJ / cm ² or more. It is preferable that the irradiation method is used. Here, the main curing ultraviolet ray means an ultraviolet ray set to a wavelength range or illuminance that can completely cure the coating film. In the case of the main curing ultraviolet ray, it is difficult to vary the degree of crosslinking of the high Δn polymerizable liquid crystal compound in the coating film in the thickness direction of the film.

The integrated light quantity of the main curing ultraviolet ray is preferably 10 mJ / cm ² or more, more preferably 50 mJ / cm ² or more, preferably 1000 mJ / cm ² or less, more preferably 800 mJ / cm ² or less. The integrated light quantity is selected by measuring on the substrate surface using an ultraviolet light quantity meter or measuring the illuminance using an illuminometer and calculating the integrated light quantity = illuminance × time.
The irradiation direction of the main curing ultraviolet ray may be from either the coating film side or the substrate side, but it is preferable to irradiate from the coating film side from the viewpoint of good irradiation efficiency of ultraviolet rays.

  The irradiation of the main curing ultraviolet ray is preferably performed in an atmosphere with a small amount of oxygen gas, such as a nitrogen gas atmosphere. By carrying out in such an atmosphere, it is possible to reduce the influence of polymerization inhibition by oxygen. The oxygen gas concentration at the time of irradiation with the main curing ultraviolet ray is preferably 3% or less, more preferably 1% or less, and particularly preferably 500 ppm or less on a weight basis.

  Furthermore, it is preferable to perform the process which cools the coating film on a base material to 20 to 40 degreeC after a heating process and before a complete curing process. By irradiating the above-mentioned main curing ultraviolet ray to the coating film maintained at 20 ° C. to 40 ° C., the pitch state of the coating film having cholesteric regularity after the heating step can be maintained.

  By this complete curing step, the mechanical properties of the coating film having cholesteric regularity can be improved while maintaining the broad band. A liquid crystal cured product layer is obtained as a cured coating film as described above.

A conventionally well-known thing can be used as a coating-film formation apparatus suitable for the manufacturing method of the circularly polarized light separation sheet mentioned above. For example, a coating device that continuously feeds a substrate and a coating head that forms a coating film by applying a composition for forming a liquid crystal layer on the substrate fed from the feeding device, Cooling means for cooling the formed substrate, selective ultraviolet irradiation device and main curing ultraviolet irradiation device for irradiating the coating film with selected ultraviolet rays and main curing ultraviolet rays each having a selected wavelength range and / or illuminance, and the substrate A coating film forming apparatus provided with two or more systems for heating the film. In such a coating film forming apparatus, the feeding device and the coating head are not particularly limited, and known ones can be used.
Moreover, the cooling means used for the said coating-film formation apparatus can be comprised with a cooling zone apparatus, a cooling roll, etc., for example, and it is preferable to comprise with a cooling zone apparatus. The said cooling means is good also as an apparatus which surrounds a part of conveyance path | route of a base material, and maintains the temperature in it at the fixed temperature suitable for hardening of the composition for liquid crystal layer formation. Moreover, it is preferable to provide all the cooling means before each of the selective ultraviolet irradiation device and the main curing ultraviolet irradiation device, and more preferably, immediately before each of the selective ultraviolet irradiation device and the main curing ultraviolet irradiation device.

[2-7. Other matters in the method of manufacturing a circularly polarized light separating sheet]
The film forming step, the alignment treatment step, the incomplete curing step, the heating step and the complete curing step may be performed only once to form only one liquid crystal cured product layer, and two layers may be repeated twice or more. The above liquid crystal cured product layer can also be formed. However, even when the film forming step, the alignment treatment step, the incomplete curing step, the heating step and the complete curing step are performed only once each, a polymer of a well-aligned high Δn polymerizable liquid crystal compound is included, For example, a liquid crystal cured product layer having a sufficient thickness of 5 μm or more can be easily formed.

[2-8. Configuration of the circularly polarized light separating sheet obtained]
The liquid crystal cured product layer obtained as a coating film cured as described above is usually a cholesteric resin layer. The structure of the cholesteric resin layer is such that the molecular axes are aligned in a certain direction on one plane, but the direction of the molecular axes is slightly offset on the next plane, and the angle is further shifted on the next plane. In addition, the structure has a cholesteric regularity in which the angle of the molecular axis is shifted (twisted) as it proceeds on a plane in which molecules are arranged in a certain direction. Thus, the structure in which the direction of the molecular axis is twisted becomes an optically chiral structure.

The cholesteric resin layer as described above has a circularly polarized light separating function. That is, it has a function of reflecting left-handed or right-handed circularly polarized light in a specific wavelength region and transmitting other circularly-polarized light. Therefore, the sheet provided with this cholesteric resin layer functions as a circularly polarized light separating sheet.
The cholesteric resin layer is preferably a broadband having a circularly polarized light separating function over the entire wavelength region of visible light. Specifically, a cholesteric resin layer having a circularly polarized light separation function with respect to light in a wavelength region of 400 nm to 750 nm is preferable. For example, a cholesteric resin layer having a circularly polarized light separation function is preferable for light in any wavelength region of blue (wavelength 410 to 470 nm), green (wavelength 520 to 580 nm), and red (wavelength 600 to 660 nm).

  The wavelength that exhibits the circularly polarized light separation function depends on the pitch of the chiral structure in the cholesteric resin layer. The pitch of the chiral structure is a distance in the plane normal direction until the angle of the molecular axis in the chiral structure gradually shifts as it advances along the plane and then returns to the original molecular axis direction again. By changing the pitch of this chiral structure, the wavelength at which the circularly polarized light separating function is exhibited can be changed.

  Usually, the cholesteric resin layer obtained as the liquid crystal cured product layer by the above-described production method is a non-liquid crystalline resin layer in which the high Δn polymerizable liquid crystal compound is polymerized in the incomplete curing step and the complete curing step and loses liquid crystallinity. . A non-liquid crystalline resin layer is preferable because the cholesteric regularity does not change depending on the ambient temperature or electric field.

  In addition, the liquid crystal cured product layer obtained by the manufacturing method described above is usually a cholesteric resin layer in which the pitch of the chiral structure is continuously changed. As a result, the cholesteric resin layer can exhibit a circularly polarized light separation function in a wide range of wavelengths corresponding to a continuously changing pitch size.

Moreover, as another structure of the liquid-crystal hardened | cured material layer obtained, the cholesteric resin layer which changed the magnitude | size of the pitch of a chiral structure in steps is mentioned, for example. A cholesteric resin layer in which the pitch of the chiral structure is changed stepwise includes, for example, a cholesteric resin layer having a chiral structure pitch that exhibits a circularly polarized light separation function with light in the blue wavelength range, and a circle with light in the green wavelength range. It can be obtained by laminating a cholesteric resin layer having a chiral structure pitch that exhibits a polarization separation function and a cholesteric resin layer having a chiral structure pitch that exhibits a circular polarization separation function with light in the red wavelength region. . Further, cholesteric resin layers having a central wavelength of reflected circularly polarized light of 470 nm, 550 nm, 640 nm, and 770 nm are respectively produced, and these cholesteric resin layers are arbitrarily selected, and the order of the central wavelengths of reflected light is 3 to 3 It can be obtained by laminating seven layers. When the cholesteric resin layers having different chiral structure pitches are laminated, it is preferable that the rotation directions of the circularly polarized light reflected by the cholesteric resin layers are the same. In addition, in order to obtain a liquid crystal display device having a wide viewing angle, the stacking order of the cholesteric resin layers having different chiral structure pitches may be ascending or descending in order of the chiral structure pitch. preferable. The lamination of these cholesteric resin layers may be merely overlaid, or may be fixed via an adhesive or an adhesive.
In order to manufacture this type of cholesteric resin layer, for example, a cholesteric resin layer corresponding to each pitch is manufactured and bonded by the above-described manufacturing method, or another pitch is formed on the cholesteric resin layer corresponding to a certain pitch. The cholesteric resin layer corresponding to the above may be stacked and manufactured by the method described above.

  As described above, the antioxidant contained in the composition for forming a liquid crystal layer is volatilized and removed in the process of producing the circularly polarized light separating sheet. Therefore, the concentration of the antioxidant in the liquid crystal cured product layer obtained is a low value. The specific concentration of the antioxidant in the liquid crystal cured product layer is usually 0.005% by weight or less, preferably 0.002% by weight or less, more preferably 0.0005% by weight or less. Is zero.

  Although there is no restriction | limiting in the thickness of a liquid-crystal hardened | cured material layer, When providing as a cholesteric resin layer in a circularly polarized light separation sheet, the dry film thickness becomes like this. Preferably it is 3.0 micrometers or more, More preferably, it is 3.5 micrometers or more, Preferably It is 10.0 μm or less, more preferably 8 μm or less. When the dry film thickness of the cholesteric resin layer is thinner than 3.0 μm, the reflectance tends to decrease, and conversely, when it is thicker than 10.0 μm, the cholesteric resin layer may be colored when observed from an oblique direction. In addition, the said dry film thickness points out the sum total of the film thickness of each layer, when a liquid-crystal hardened | cured material layer is two or more layers, and points out the film thickness when a liquid-crystal hardened | cured material layer is one layer.

  The circularly polarized light separating sheet may further include another layer as long as it includes at least the liquid crystal cured product layer as a cholesteric resin layer. For example, the transparent substrate, the alignment film, the protective layer, the adhesive layer, and the like described above can be used.

  Since the circularly polarized light separating sheet of the present invention includes a uniform liquid crystal cured product layer having no defects and unevenness in thickness, it can exhibit a uniform circularly polarized light separating function free from defects and variations from place to place. Moreover, according to the method for producing a circularly polarized light separating sheet of the present invention, the above excellent circularly polarized light separating sheet can be efficiently produced.

[3. (Brightness enhancement film)
The brightness enhancement film of the present invention includes at least the above-described circularly polarized light separating sheet and retardation film. The brightness enhancement film is usually provided in a liquid crystal display device or the like so that the circularly polarized light separating sheet and the retardation film are in this order from the light source side. In a liquid crystal display device or the like, when light from a light source such as a backlight passes through a brightness enhancement sheet, only predetermined polarized light is selectively reflected by the circularly polarized light separating sheet, and the remaining light is transmitted. The transmitted light further passes through the retardation film, is converted into predetermined polarized light, and enters the liquid crystal cell. On the other hand, the light reflected by the circularly polarized light separating sheet is reflected by other components of the liquid crystal display device (reflecting plate, etc.) and enters the circularly polarized light separating sheet again while changing the polarization state. The light that has passed through the predetermined polarized light passes through the circularly polarized light separating sheet, is converted into the predetermined polarized light by the retardation film, and enters the liquid crystal cell. As described above, the brightness enhancement sheet can increase the predetermined polarization necessary for display by the liquid crystal cell and supply it to the liquid crystal cell.

  The retardation film is an optical element that causes a phase difference in light incident thereon. Examples of the retardation film include a half-wave plate that generates a phase difference of 180 °, a quarter-wave plate that generates a phase difference of 90 °, and the like. The brightness enhancement film of the present invention usually includes a quarter wave plate as a retardation film.

  The quarter-wave plate may have a retardation Re (hereinafter, abbreviated as “Re” in some cases) in the front direction to be substantially a quarter wavelength of transmitted light. Here, the wavelength range of the transmitted light can be a desired range required for the brightness enhancement film, and specifically, is, for example, 400 nm to 700 nm. Further, the retardation Re in the front direction is approximately ¼ wavelength of transmitted light, and the Re value is ± 65 nm from the ¼ value of the center value in the center value of the wavelength range of transmitted light, preferably It means ± 30 nm, more preferably ± 10 nm. By having such a retardation value, the quarter-wave plate can exhibit a polarization conversion function, that is, a function of converting circularly polarized light into linearly polarized light.

  The quarter-wave plate desirably has a retardation Rth in the thickness direction (hereinafter sometimes abbreviated as “Rth”) of less than 0 nm. The value of retardation Rth in the thickness direction is preferably −30 nm to −1000 nm, more preferably −50 nm to −300 nm, in the central value of the wavelength range of transmitted light. By employing such a quarter-wave plate having Re value and Rth, the brightness enhancement film can improve the brightness and reduce the brightness unevenness, while also reducing the color unevenness of the emitted light.

Here, the retardation Re in the front direction is represented by the formula I: Re = (nx−ny) × d (where nx is a direction perpendicular to the thickness direction (in-plane direction)) and gives the maximum refractive index. Ny represents a refractive index in a direction perpendicular to the thickness direction (in-plane direction) and orthogonal to the nx direction, and d represents a film thickness. Yes, the retardation Rth in the thickness direction is the formula II: Rth = {(nx + ny) / 2−nz} × d (where nx is the direction perpendicular to the thickness direction (in-plane direction) and has the maximum refractive index) Ny is a refractive index in a direction perpendicular to the thickness direction (in-plane direction) and orthogonal to the direction of nx, nz is a refractive index in the thickness direction, and d is It represents a film thickness.)
In addition, the retardation Re in the front direction and the retardation Rth in the thickness direction are measured using a commercially available phase difference measuring apparatus with a quarter-wave plate in the longitudinal direction and the width direction at intervals of 100 mm (longitudinal or lateral length). If the distance is less than 200 mm, three points are specified at equal intervals in that direction), and measurement is performed in a lattice point shape over the entire surface, and the average value is obtained.

  As the quarter wavelength plate, for example, a stretched film formed by stretching a film-like polymer can be used. A preferable example is a quarter wavelength plate formed by stretching a resin film including a styrene resin layer. More preferably, the optical anisotropic element described below is mentioned.

  The optically anisotropic element constituting the quarter-wave plate preferably has a layer made of styrene resin. Here, the styrene-based resin is a polymer resin having a styrene structure as a part or all of the repeating units, and among them, polystyrene or a copolymer of styrene and maleic anhydride can be suitably used.

  The molecular weight of the styrenic resin used in the optically anisotropic element is appropriately selected according to the purpose of use, but the weight average molecular weight (Mw) in terms of polyisoprene measured by gel permeation chromatography using cyclohexane as a solvent. In general, it is 10,000 or more, preferably 15,000 or more, more preferably 20,000 or more, and usually 300,000 or less, preferably 250,000 or less, more preferably 200,000 or less.

  The optically anisotropic element preferably has a laminated structure of a layer made of the styrenic resin and a layer containing another thermoplastic resin. By having the laminated structure, it is possible to provide an element that has both the optical characteristics of the styrene resin and the mechanical strength of other thermoplastic resins. As the other thermoplastic resin, a resin having an alicyclic structure or a methacrylic resin can be suitably used.

  Examples of the resin having an alicyclic structure include alicyclic olefin polymers. The alicyclic olefin polymer is an amorphous olefin polymer having a cycloalkane structure or a cycloalkene structure in the main chain and / or side chain.

  The methacrylic resin is a polymer containing methacrylic acid ester as a main component, and examples thereof include a homopolymer of methacrylic acid ester and a copolymer of methacrylic acid ester and other monomers. As the methacrylic acid ester, alkyl methacrylate is usually used. In the case of a copolymer, acrylic acid esters, aromatic vinyl compounds, vinylcyan compounds, etc. are used as other monomers copolymerized with methacrylic acid esters.

  As a preferable specific embodiment of the quarter-wave plate, a multilayer film formed by laminating a film (b layer) made of another thermoplastic resin on both surfaces of a film (a layer) made of a styrene resin is stretched. A stretched multilayer film is mentioned.

  The method of laminating the styrenic resin that is the material of the a layer and the other thermoplastic resin that is the material of the b layer, and forming it into a multilayer film is not particularly limited. For example, a coextrusion T-die method, Examples include a coextrusion molding method such as a coextrusion inflation method and a coextrusion lamination method, a film lamination molding method such as dry lamination, and a coating molding method. Among these, a molding method by coextrusion is preferable from the viewpoints of production efficiency and that volatile components such as a solvent do not remain in the film. The extrusion temperature can be appropriately selected according to the type of the styrenic resin to be used and the other thermoplastic resin.

  The multilayer film is usually formed by laminating the b layer on both sides of the a layer. An adhesive layer can be provided between the a layer and the b layer, but the a layer and the b layer are directly laminated (that is, a laminate having a three-layer structure of b layer / a layer / b layer). Is preferred. In the multilayer film, the thickness of the a layer and the b layer laminated on both sides thereof is not particularly limited, but preferably 10 to 300 μm and 10 to 400 μm, respectively.

  The stretched multilayer film is formed by stretching the multilayer film. The stretching can be preferably performed by uniaxial stretching or oblique stretching, and more preferably by uniaxial stretching or oblique stretching by a tenter.

  The thickness of the optically anisotropic element is preferably 50 μm or more, preferably 1000 μm or less, more preferably 600 μm or less.

  The quarter wavelength plate itself may also have a function as an optical compensation layer, but may additionally have an optical compensation layer in addition to the quarter wavelength plate. As such an optical compensation layer, the same optically anisotropic element as described above can be used, and a homeotropic liquid crystal alignment film obtained by homeotropic alignment of a liquid crystal molecule on a substrate and cured (Japanese Patent No. 399969). And a nematic hybrid liquid crystal alignment film (Japanese Patent Laid-Open No. 2000-66192) obtained by curing a state in which liquid crystal molecules are nematic hybrid aligned on a substrate can be used.

  The brightness enhancement film of the present invention may further include another layer in addition to the above-described circularly polarized light separating sheet and retardation film. For example, a light diffusion sheet that diffuses light incident thereon; a light collecting sheet that condenses light incident thereon; an adhesive layer for adhering optical elements constituting the brightness enhancement film; an antifouling property to the brightness enhancement film; Examples thereof include a protective film imparting functions such as scratch resistance; a hard coat layer; an anti-blocking layer.

  Since the brightness enhancement film of the present invention has a uniform liquid crystal cured product layer free from defects and thickness unevenness, when provided in a liquid crystal display device or the like, the brightness is uniformly increased without defects and brightness unevenness. Can do.

[4. Liquid crystal display device)
The liquid crystal display device of the present invention includes the brightness enhancement film of the present invention and a liquid crystal panel. The liquid crystal panel is not particularly limited, and those used in liquid crystal display devices can be used as appropriate. For example, a TN (Twisted Nematic) type liquid crystal panel, an STN (Super Twisted Nematic) type liquid crystal panel, a HAN (Hybrid Alignment Nematic) type liquid crystal panel, an IPS (In Plane Switching) type liquid crystal panel, and a VA (vertical type liquid crystal panel). Examples thereof include a MVA (Multiple Vertical Alignment type liquid crystal panel) and an OCB (Optical Compensated Bend) type liquid crystal panel.

  The liquid crystal display device of the present invention usually further includes a backlight. In this case, the brightness enhancement film is arranged between the backlight and the liquid crystal panel. More specifically, the brightness enhancement film of the present invention is disposed between the backlight of the liquid crystal display device and the liquid crystal cell so that the layer of the circularly polarized light separating sheet is on the backlight side of the layer of the retardation film. , Brightness improvement can be achieved.

  The liquid crystal display device of the present invention comprises a liquid crystal cured product layer produced using the liquid crystal layer forming composition of the present invention. Since there is no defect in the liquid crystal cured product layer, the liquid crystal display device of the present invention can realize high image quality without defects even in the display image. Moreover, since there is no thickness unevenness in the liquid crystal cured product layer, it is possible to suppress the occurrence of uneven brightness in the display image. Furthermore, since a wide variety of high Δn polymerizable liquid crystal compounds can be used, the degree of freedom in design can be increased.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples, and can be arbitrarily modified without departing from the gist of the present invention. In the following description, “parts” representing amounts represent “parts by weight” unless otherwise specified. In the structural formula, Et represents an ethyl group.

[Examples 1-5, Comparative Examples 1-5]
(Preparation of transparent resin substrate having alignment film)
Both surfaces of a film made of an alicyclic olefin polymer (trade name “ZEONOR FILM ZF14-100” manufactured by Optes Co., Ltd.) were subjected to corona discharge treatment. A 5% by weight aqueous polyvinyl alcohol solution was applied to one side of the film using a # 2 wire bar, and the coating film was dried to form an alignment film having a thickness of 0.1 μm. Next, the alignment film was rubbed to prepare a transparent resin substrate having the alignment film.

(Preparation of liquid crystal layer forming composition)
Each component was mixed by the mixture ratio (weight ratio) shown in Table 2, and the liquid crystal layer forming composition was prepared. In addition, the detail of each component contained in the composition for liquid crystal layer formation is as follows.

As compound 1, the following compounds were used. This compound 1 is a high Δn polymerizable liquid crystal compound, and its refractive index anisotropy is 0.22.

As the compound 2, the following compound was used. This compound 2 is a compound having no liquid crystallinity.

As the chiral agent, trade name LC756 (manufactured by BASF) was used.
As a polymerization initiator, trade name Irgacure OXE02 (manufactured by Ciba Japan) was used.
As the surfactant, a fluorine-based surfactant (trade name “Factent 209F” manufactured by Neos) was used.

The structure of the antioxidant (Irganox 1010, manufactured by Ciba Japan) used in Comparative Examples 4 and 5 is as follows.

(Evaluation of pot life)
The prepared composition for forming a liquid crystal layer was stored in a sealed container at room temperature (25 ° C.) for 1 week. The state of the composition for forming a liquid crystal layer after storage was confirmed, and the viscosity was measured. The results are shown in Table 2. In Table 2, “good” indicates that the viscosity did not change after storage, and “bad” indicates that the viscosity increased.

(Production of circularly polarized light separating sheet)
At a temperature of 23 ° C., the liquid crystal layer forming composition prepared as described above was applied to the surface having the alignment film of the transparent resin substrate having the alignment film prepared above using a # 10 wire bar, A liquid crystal layer was formed as a coating film. A process comprising subjecting this coating film to orientation treatment at 100 ° C. for 5 minutes, and subjecting the coating film to irradiation with weak ultraviolet rays of 0.1 to 45 mJ / cm ² , followed by heating treatment at 100 ° C. for 1 minute. After repeating the above twice, a circularly polarized light separating sheet having a cholesteric resin layer (corresponding to a liquid crystal cured product layer) having a dry film thickness of 5 μm is prepared by irradiating with an ultraviolet ray of 2000 mJ / cm ^{2 in} a nitrogen atmosphere and curing. did.

(Evaluation of circularly polarized light separating sheet)
About the circularly polarized light separating sheet produced above, the circularly polarized light separating sheet is placed on a light box in an environment of a temperature of 23 ° C. and a humidity of 50%, and color defects and point defects derived from crystal precipitation are visually observed through a polarizing plate. did. The evaluation results are shown in Table 2. In Table 2, the evaluation of color unevenness was shown as “good” when there was little or no color unevenness, and as “bad” when there was color unevenness. As for the point defects, those having a confirmed number of point defects of less than 3 / m ² were indicated as “good”, and those having a confirmed number of 3 / m ² or more were indicated as “bad”.

  In addition, the circularly polarized light separating sheet produced above was measured for a transmission spectrum in a wavelength range of 450 nm to 700 nm, and evaluated for broadening the band. As a result of the measurement, a spectrum having a transmittance of 58% or less over a wavelength range of 450 nm to 700 nm can be secured without omission of 50 nm or more (that is, a local peak having a transmittance of more than 58%). In other cases, it was determined as “bad”. The results are shown in Table 2.

[Examination of results]
As shown in Table 2, the composition for forming a liquid crystal layer of Examples 1 to 5 of the present invention has a wide-band circularly polarized light separation with a long pot life and less color unevenness and defects compared to Comparative Examples 1 to 5. A sheet is obtained.
Here, when Examples 1 to 5 and Comparative Examples 1 and 2 are compared, when a cyclic ketone solvent and a cyclic ether solvent are combined, a uniform liquid crystal layer can be obtained without defects, thereby causing color unevenness and point defects. It turns out that generation | occurrence | production of is suppressed.
Moreover, when Examples 1-5 are compared with Comparative Examples 3-5, it can be seen that the pot life can be extended without adversely affecting the broadband by using an antioxidant having a predetermined volatility. .

Of particular note, it can be seen that in Example 4, the broad band of the circularly polarized light separating sheet can be realized despite the increase in the amount of the antioxidant compared to the other examples. For this reason, if an antioxidant having a predetermined volatility is used, the antioxidant can be removed by volatilization in the process of manufacturing the circularly polarized light separating sheet. Can be confirmed.
Further, in Comparative Example 3, since a sufficiently long pot life cannot be realized, it is understood that a sufficient pot life cannot be realized when an antioxidant is not used.
Furthermore, in Comparative Example 4, the evaluation of the wide band is poor. Specifically, in Comparative Example 4, even when the conditions were variously changed, the transmittance on the long wavelength side was particularly higher than 58%, and a wide spectrum was not obtained. From this fact, it can be confirmed that the antioxidant having poor volatility can increase the pot life, but the antioxidant prevents the broadband.
Further, in Comparative Example 5, although a wide band can be realized, the pot life evaluation result is poor. Therefore, if the amount of antioxidants with low volatility is reduced to such an extent that does not interfere with broadband, the pot life cannot be made sufficiently long, and the conventional technology cannot achieve both pot life and broadband. Can be confirmed.

The composition for forming a liquid crystal layer of the present invention can be used in any field relating to the production of a liquid crystal layer, and is particularly suitable for use in forming a cholesteric resin layer.
The circularly polarized light separating sheet and the method for producing the same of the present invention can be used as an optical element for any application, but are particularly suitable for use in a liquid crystal display device.
The liquid crystal display device of the present invention can be suitably provided in any device as a display device.

Claims (10)

A liquid crystal compound having two or more polymerizable functional groups in one molecule and having a refractive index anisotropy of 0.2 or more;
A solvent having a cyclic ketone structure;
A solvent having a cyclic ether structure;
An antioxidant exhibiting volatility at a temperature lower than the NI point of the liquid crystal compound;
A compound represented by the following general formula (2) and R ⁶ -A ¹ -ZA ² -R ⁷ (2)
(In general formula (2),
R ⁶ and R ⁷ are each independently a linear or branched alkyl group having 1 to 20 carbon atoms, or a linear or branched alkylene oxide group having 1 to 20 carbon atoms. Represents a group selected from the group consisting of a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a (meth) acryl group, an epoxy group, a mercapto group, an isocyanate group, an amino group, and a cyano group;
A ¹ and A ² are each independently 1,4-phenylene group, 1,4-cyclohexylene group, 1,4-cyclohexenyl group, 4,4′-biphenylene group, 4,4′-bicyclohexyl group. Represents a group selected from the group consisting of a silene group and a 2,6-naphthylene group, the 1,4-phenylene group, 1,4-cyclohexylene group, 1,4-cyclohexenyl group, 4,4′- The biphenylene group, 4,4′-bicyclohexylene group, and 2,6-naphthylene group may not be substituted, and may be substituted with one or more substituents.
Z is a single bond, —O—, —S—, —S—S—, —CO—, —CS—, —OCO—, —CH ₂ —, —OCH ₂ —, —CH═N—N═CH. -, - NHCO -, - OCOO -, - is selected from CH 2 COO- the group consisting of _-CH 2 OCO-. )
A composition for forming a liquid crystal layer, comprising:   The composition for forming a liquid crystal layer according to claim 1, wherein the solvent having a cyclic ketone structure is cyclopentanone.   The composition for forming a liquid crystal layer according to claim 1 or 2, wherein the solvent having a cyclic ether structure is 1,3-dioxolane.   The composition for forming a liquid crystal layer according to any one of claims 1 to 3, wherein the solvent having the cyclic ketone structure and the solvent having the cyclic ether structure are 30/70 or more and 90/10 or less in a weight ratio. .   The composition for forming a liquid crystal layer according to any one of claims 1 to 4, wherein the antioxidant is 2,6-di-t-butyl-p-cresol. Forming a coating film of the composition for forming a liquid crystal layer according to any one of claims 1 to 5 on a substrate;
Heating the coating film to align the liquid crystal compound;
Incompletely curing the coating film;
Heating the coating film;
The circularly-polarized-light-separation sheet obtained by passing through the process which hardens the said coating film completely in this order. Forming a coating film of the composition for forming a liquid crystal layer according to any one of claims 1 to 5 on a substrate;
Heating the coating film to align the liquid crystal compound;
Incompletely curing the coating film;
Heating the coating film;
The manufacturing method of the circularly-polarized-light-separation sheet which has the process of hardening the said coating film completely in this order.   The method for producing a circularly polarized light separating sheet according to claim 7, wherein the antioxidant volatilizes in a step of aligning the liquid crystal compound by heating the coating film.   A brightness enhancement film comprising the circularly polarized light separating sheet according to claim 6 and a retardation film.   A liquid crystal display device comprising the brightness enhancement film according to claim 9 and a liquid crystal panel.