WO2021131441A1 - Method for producing cholesteric liquid crystal layer - Google Patents

Abstract

The present disclosure provides a method for producing a cholesteric liquid crystal layer, said method comprising: a step for applying a composition to a base material, said composition containing a liquid crystalline compound and a chiral agent, the helical twisting power of which is changed by light irradiation; a step for applying a shear force to the surface of the composition applied to the base material; and a step for irradiating the composition, to which the shear force has been applied, with ultraviolet light that includes a wavelength that changes the helical twisting power of the chiral agent, the helical twisting power of which is changed by light irradiation.

Description

Manufacturing method of cholesteric liquid crystal layer

This disclosure relates to a method for manufacturing a cholesteric liquid crystal layer.

The properties of liquid crystal change, for example, depending on the molecular arrangement. It is known that the molecular arrangement of liquid crystals changes due to various external factors.

Patent Document 1 discloses a method of inclining the spiral axis direction of a liquid crystal domain in a coating film by spraying a gas onto a coating film formed by using a polymerizable liquid crystal exhibiting cholesteric regularity. There is.

Patent Document 2 discloses a method of shearing a liquid crystal while applying an electric field as a kind of orientation treatment for a smectic layer.

Japanese Unexamined Patent Publication No. 2006-284862 Japanese Unexamined Patent Publication No. 8-320470

A layer containing a cholesteric liquid crystal, which is a type of liquid crystal (hereinafter referred to as "cholesteric liquid crystal layer"), has a property of selectively reflecting either right-handed circularly polarized light or left-handed circularly polarized light in a specific wavelength range, for example. Known as the layer. The cholesteric liquid crystal layer is used, for example, as a projection image display member (for example, a reflective element) of a projection screen. The properties of the cholesteric liquid crystal are considered to be due to the helical structure of the cholesteric liquid crystal. In the helical structure, a plurality of liquid crystal compounds are arranged while twisting along the helical axis. In developing the cholesteric liquid crystal layer for various purposes, for example, the inclination angle of the spiral axis (in a cross-sectional view in the thickness direction of the cholesteric liquid crystal layer, a straight line orthogonal to the spiral axis and the main surface of the cholesteric liquid crystal layer (relative to a curved surface). Refers to the normal line.) Refers to the angle formed by. The same shall apply hereinafter.) There is a demand for a method of adjusting the angle to a desired angle.

However, with the method disclosed in Patent Document 1, since the inclination angle of the spiral axis in the obtained cholesteric liquid crystal layer is small, for example, the cholesteric liquid crystal layer having an inclination angle of 90 degrees cannot be obtained. That is, in the method disclosed in Patent Document 1, the range in which the inclination angle of the spiral axis can be adjusted is limited.

In the method disclosed in Patent Document 2, the members used are limited to members having conductivity. Further, for example, when a material containing an organic solvent is used, the use of a method of applying an electric field to the material containing an organic solvent is limited depending on the working environment from the viewpoint of safety.

This disclosure has been made in view of the above circumstances.
One aspect of the present disclosure is to provide a method for producing a cholesteric liquid crystal layer in which the controllability of the inclination angle of the spiral shaft is improved.

The present disclosure includes the following aspects.
<1> A step of applying a composition containing a liquid crystal compound and a chiral agent whose spiral-inducing force changes by light irradiation on a base material, and on the surface of the composition applied on the base material. , And the step of irradiating the composition to which the shearing force is applied with ultraviolet rays containing a wavelength that changes the spiral-inducing force of the chiral agent whose spiral-inducing force is changed by the light irradiation. A method for producing a cholesteric liquid crystal layer including.
<2> The method for producing a cholesteric liquid crystal layer according to <1>, which comprises a step of curing the composition irradiated with ultraviolet rays.
<3> The method for producing a cholesteric liquid crystal layer according to <1> or <2>, wherein the shear rate in the step of applying a shearing force to the surface of the composition is 1,000 seconds- ^{1 or more.}
<4> The cholesteric liquid crystal layer according to any one of <1> to <3>, which applies a shearing force to the surface of the composition by using a blade in a step of applying a shearing force to the surface of the composition. Manufacturing method.
<5> The method for producing a cholesteric liquid crystal layer according to any one of <1> to <4>, wherein the chiral agent whose spiral-inducing force is changed by light irradiation is a chiral agent that causes photoisomerization.
<6> The method for producing a cholesteric liquid crystal layer according to any one of <1> to <5>, wherein the chiral agent whose spiral-inducing force is changed by light irradiation has an isosorbide skeleton, an isomannide skeleton, or a binaphthol skeleton.
<7> The method for producing a cholesteric liquid crystal layer according to any one of <1> to <6>, wherein the wavelength for changing the spiral inducing force is in the range of 200 nm to 380 nm.
<8> The chiral agent whose spiral-inducing force is changed by light irradiation induces a right-handed helical structure with respect to the liquid crystal compound and a left-handed helical structure with respect to the liquid crystal compound. The method for producing a cholesteric liquid crystal layer according to any one of <1> to <7>, which is at least one selected from the group consisting of chiral agents.
<9> In the above composition, the ratio of the content of the chiral agent whose spiral inducing force is changed by the light irradiation to the content of the liquid crystal compound is 0.1 to 20 on a mass basis. The method for producing a cholesteric liquid crystal layer according to any one of <8>.
<10> The method for producing a cholesteric liquid crystal layer according to any one of <1> to <9>, wherein the composition contains a polymerization initiator.
<11> The method for producing a cholesteric liquid crystal layer according to any one of <1> to <10>, wherein the composition contains a chiral agent whose spiral-inducing force does not change by light irradiation.
<12> When the chiral agent whose spiral-inducing force does not change by light irradiation is a chiral agent that induces a right-handed helical structure with respect to the liquid crystal compound, the chiral agent whose spiral-inducing force changes by light irradiation. However, a chiral agent that induces a left-handed helical structure with respect to the liquid crystal compound, or a chiral agent whose spiral-inducing force does not change with light irradiation induces a left-handed helical structure with respect to the liquid crystal compound. In the case of a chiral agent, the preparation of the cholesteric liquid crystal layer according to <11>, wherein the chiral agent whose spiral-inducing force is changed by light irradiation is a chiral agent that induces a right-handed helical structure with respect to the liquid crystal compound. Method.

According to one aspect of the present disclosure, there is provided a method for manufacturing a cholesteric liquid crystal layer in which the controllability of the inclination angle of the spiral shaft is improved.

Hereinafter, embodiments of the present disclosure will be described in detail. The present disclosure is not limited to the following embodiments, and may be carried out with appropriate modifications within the scope of the purpose of the present disclosure.

In the present disclosure, the numerical range indicated by using "-" indicates a range including the numerical values before and after "-" as the lower limit value and the upper limit value, respectively. In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.

In the present disclosure, the amount of each component in the composition means the total amount of the plurality of substances present in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified. ..

In the present disclosure, the term "process" is included in the term "process" as long as the intended purpose of the process is achieved, not only in an independent process but also in cases where it cannot be clearly distinguished from other processes. ..

In the present disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous.

In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

In the present disclosure, "solid content" means a component obtained by removing a solvent from all the components of an object.

In the present disclosure, the "solid content mass" means the mass obtained by subtracting the mass of the solvent from the mass of the object.

<Manufacturing method of cholesteric liquid crystal layer>
In the method for producing a cholesteric liquid crystal layer according to the present disclosure, a liquid crystal compound and a chiral agent whose spiral-inducing force changes by light irradiation (hereinafter, may be simply referred to as "chiral agent") are placed on a substrate. A step of applying the composition containing the mixture (hereinafter, may be referred to as "step (A)") and a step of applying a shearing force to the surface of the composition coated on the substrate (hereinafter, "step"). (B) ”), and the composition to which the shearing force is applied is irradiated with ultraviolet rays containing a wavelength that changes the spiral-inducing force of the chiral agent whose spiral-inducing force is changed by the light irradiation. It includes a step (hereinafter, may be referred to as “step (C)”). According to the above aspect, there is provided a method for manufacturing a cholesteric liquid crystal layer in which the controllability of the inclination angle of the spiral shaft is improved.

The reason why the method for producing the cholesteric liquid crystal layer according to the present disclosure exerts the above effect is presumed as follows. In the method for producing a cholesteric liquid crystal layer according to the present disclosure, a shearing force is imparted by applying a shearing force to the surface of a composition containing a liquid crystal compound and a chiral agent whose spiral-inducing force changes with light irradiation. Since the spiral shafts are tilted all at once in the direction in which they are tilted, it is possible to reduce variations in the orientation of the tilted spiral shafts. By reducing the variation in the orientation of the spiral shaft, the controllability of the inclination angle of the spiral shaft in the next step (that is, step (C)) can be improved. Then, by irradiating the composition to which the shearing force is applied with ultraviolet rays including a wavelength that changes the spiral-inducing force of the chiral agent, the length of the spiral shaft per one rotation of the spiral (hereinafter referred to as "spiral pitch"). Can be changed. By changing the spiral pitch in the spiral structure, the inclination angle of the spiral axis changes. For example, as the spiral pitch increases, the tilt angle of the spiral axis increases. As the spiral pitch decreases, the tilt angle of the spiral axis decreases. Further, the range of the inclination angle of the spiral shaft that can be controlled by the step (B) is easily affected by, for example, the conditions of the step (B) (for example, temperature, film thickness, and shear rate). By carrying out the step (C) in addition to the step (B), it is possible to control the inclination angle of the desired spiral axis with high accuracy. Therefore, according to the method for manufacturing a cholesteric liquid crystal layer according to the present disclosure, the controllability of the inclination angle of the spiral shaft is improved.

[Step (A)]
In the step (A), a composition containing a liquid crystal compound and a chiral agent whose spiral-inducing force changes with light irradiation is applied onto the base material. Hereinafter, the step (A) will be specifically described.

In the present disclosure, "coating the composition on a base material" is not limited to bringing the composition into direct contact with the base material, but also includes contacting the base material with the composition via an arbitrary layer. .. Any layer may be one of the constituents of the substrate, or it may be a layer formed on the substrate prior to application of the composition. Optional layers include, for example, an alignment layer, an easy-adhesion layer, and an antistatic layer. The method of forming the oriented layer will be described later.

(Base material)
The base material is preferably a base material containing a polymer. Examples of the base material containing the polymer include a polyester-based base material (for example, polyethylene terephthalate and polyethylene naphthalate), a cellulose-based base material (for example, diacetyl cellulose and triacetyl cellulose (abbreviation: TAC)), and a polycarbonate-based base material. Substrate, poly (meth) acrylic substrate (eg, poly (meth) acrylate (eg, polymethylmethacrylate)), polystyrene-based substrate (eg, polystyrene and acrylonitrile styrene copolymer), olefin-based substrate (eg, olefin-based substrate (eg, polystyrene and acrylonitrile styrene copolymer) For example, polyethylene, polypropylene, polyolefins having a cyclic structure (eg, norbornene structure), and ethylene-propylene copolymers), polyamide-based substrates (eg, polyvinyl chloride, nylon, and aromatic polyamides), polyimide-based substrates, Polysulfone-based base material, polyethersulfone-based base material, polyether etherketone-based base material, polyphenylene sulfide-based base material, vinyl alcohol-based base material, polyvinylidene chloride-based base material, polyvinyl butyral-based base material, polyoxymethylene-based base material Examples include materials and epoxy resin-based substrates. The base material may be a base material containing two or more kinds of polymers (that is, a blend polymer). The base material is preferably a cellulosic base material, and more preferably a base material containing triacetyl cellulose.

The total light transmittance of the base material is preferably 80% or more, more preferably 90% or more, and particularly preferably 95% or more. The upper limit of the total light transmittance of the base material is not limited. The total light transmittance of the base material may be determined, for example, in the range of 100% or less. The total light transmittance of the base material is measured using a known spectrophotometer (for example, haze meter, NDH 2000, Nippon Denshoku Kogyo Co., Ltd.).

The shape of the base material is not limited. The shape of the base material may be determined, for example, according to the intended use. The base material is preferably a flat base material.

The thickness of the base material is preferably in the range of 10 μm to 250 μm, more preferably in the range of 40 μm to 150 μm, from the viewpoint of manufacturing suitability, manufacturing cost, and optical characteristics.

(Composition)
-Liquid crystal compound-
The composition comprises a liquid crystal compound.

The type of liquid crystal compound is not limited. As the liquid crystal compound, for example, a known liquid crystal compound that forms a cholesteric liquid crystal can be used.

The liquid crystal compound may have a polymerizable group. The liquid crystal compound may have one kind alone or two or more kinds of polymerizable groups. The liquid crystal compound may have two or more homogeneous polymerizable groups. Since the liquid crystal compound has a polymerizable group, the liquid crystal compound can be polymerized. By polymerizing the liquid crystal compound, the stability of the cholesteric liquid crystal can be improved.

Examples of the polymerizable group include a group having an ethylenically unsaturated double bond, a cyclic ether group, and a nitrogen-containing heterocyclic group capable of causing a ring-opening reaction.

Examples of the group having an ethylenically unsaturated double bond include an acryloyl group, a methacryloyl group, an acryloyloxy group, a methacryloyloxy group, a vinyl group, a vinylphenyl group, and an allyl group.

Examples of the cyclic ether group include an epoxy group and an oxetanyl group.

Examples of the nitrogen-containing heterocyclic group capable of causing a ring-opening reaction include an aziridinyl group.

The polymerizable group is preferably at least one selected from the group consisting of a group having an ethylenically unsaturated double bond and a cyclic ether group. Specifically, the polymerizable group is at least selected from the group consisting of an acryloyl group, a methacryloyl group, an acryloyloxy group, a methacryloyloxy group, a vinyl group, a vinylphenyl group, an allyl group, an epoxy group, an oxetanyl group, and an aziridinyl group. It is preferably one kind, and more preferably at least one kind selected from the group consisting of an acryloyl group, a methacryloyl group, an acryloyloxy group, and a methacryloyloxy group, and more preferably a group consisting of an acryloyloxy group and a methacryloyloxy group. It is particularly preferable that it is at least one selected more.

Liquid crystal compounds are classified into, for example, rod-shaped liquid crystal compounds and disk-shaped liquid crystal compounds according to their chemical structure. The rod-shaped liquid crystal compound is known as a liquid crystal compound having a rod-shaped chemical structure. As the rod-shaped liquid crystal compound, for example, a known rod-shaped liquid crystal compound can be used. The disc-shaped liquid crystal compound is known as a liquid crystal compound having a disc-shaped chemical structure. As the disk-shaped liquid crystal compound, for example, a known disk-shaped liquid crystal compound can be used.

From the viewpoint of manufacturing cost, the liquid crystal compound is preferably a rod-shaped liquid crystal compound, and more preferably a rod-shaped thermotropic liquid crystal compound.

The rod-shaped thermotropic liquid crystal compound is a compound having a rod-shaped chemical structure and exhibiting liquid crystallinity in a specific temperature range. As the rod-shaped thermotropic liquid crystal compound, for example, a known rod-shaped thermotropic liquid crystal compound can be used.

Examples of the rod-shaped thermotropic liquid crystal compound include "Makromol. Chem., 190, 2255 (1989)", "Advanced Materials, 5, 107 (1993)", US Pat. No. 4,683,327, U.S. Pat. US Pat. No. 5,622,648, US Pat. No. 5,770,107, International Publication No. 95/22586, International Publication No. 95/24455, International Publication No. 97/00600, International Publication No. 98/23580, International Publication No. 98/52905, Japanese Patent Application Laid-Open No. 1-272551, Japanese Patent Application Laid-Open No. 6-16616, Japanese Patent Application Laid-Open No. 7-110469, Japanese Patent Application Laid-Open No. 11-513019, Japanese Patent Application Laid-Open No. 11-8801, Japanese Patent Application Laid-Open No. 11-8801 Examples thereof include compounds described in Japanese Patent Application Laid-Open No. 328973 or Japanese Patent Application Laid-Open No. 2007-279688. Examples of the rod-shaped thermotropic liquid crystal compound include a compound represented by the general formula 1 in JP-A-2016-81035 and a compound represented by the general formula (I) or the general formula (II) in JP-A-2007-279688. The compounds to be used are also mentioned.

The rod-shaped thermotropic liquid crystal compound is preferably a compound represented by the following general formula (1).

In the general formula (1), Q ¹ and Q ² each independently represent a polymerizable group, and L ¹ , L ² , L ³ and L ⁴ independently represent a single bond or 2 respectively. Representing a valent linking group, A ¹ and A ² each independently represent a divalent hydrocarbon group having 2 to 20 carbon atoms, and M represents a mesogen group.

^{Examples of the polymerizable group represented by Q 1} and Q ² in the general formula (1) include the above-mentioned polymerizable group. The preferred embodiment of the polymerizable group represented by Q ¹ and Q ² is the same as that of the above-mentioned polymerizable group.

In the general formula (1), the ^{divalent linking groups represented by L 1} , L ² , L ³ , and L ⁴ are -O-, -S-, -CO-, -NR-, and -CO-O. -, -O-CO-O-, -CO-NR-, -NR-CO-, -O-CO-, -O-CO-NR-, -NR-CO-O-, and NR-CO-NR It is preferably a divalent linking group selected from the group consisting of −. R in the above-mentioned divalent linking group represents an alkyl group having 1 to 7 carbon atoms or a hydrogen atom.

In the general formula (1), ^{at least one of L 3} and L ⁴ is preferably —O—CO—O−.

In the general formula (1), Q ^1- L ^1- and Q ^2- L ^2- are independent of each other, CH ₂ = CH-CO-O-, CH ₂ = C (CH ₃ ) -CO-O. -Or, CH ₂ = C (Cl) -CO-O- is preferable, and CH ₂ = CH-CO-O- is more preferable.

In the general formula (1), the ^{divalent hydrocarbon group having 2 to 20 carbon atoms represented by A 1} and A ² has an alkylene group having 2 to 12 carbon atoms and a carbon atom number. It is preferably an alkenylene group having 2 to 12 or an alkynylene group having 2 to 12 carbon atoms, and more preferably an alkylene group having 2 to 12 carbon atoms. The divalent hydrocarbon group is preferably in the form of a chain. The divalent hydrocarbon group may contain oxygen atoms that are not adjacent to each other or sulfur atoms that are not adjacent to each other. The divalent hydrocarbon group may have a substituent. Substituents include, for example, halogen atoms (eg, fluorine, chlorine, and bromine), cyano groups, methyl groups, and ethyl groups.

In the general formula (1), the mesogen group represented by M is a group that forms the main skeleton of a liquid crystal compound that contributes to liquid crystal formation. Regarding the mesogen group represented by M, for example, the description (particularly, pages 7 to 16) of "Flusige Editorial in Table II" (VEB, Editorial, fur, Grundstoff, Industrie, Leipzig, 1984), and liquid crystal (pages 7 to 16). You can refer to the description (especially Chapter 3) of the Handbook Editorial Committee, edited by Maruzen, 2000).

In the general formula (1), as a specific structure of the mesogen group represented by M, for example, the structure described in paragraph [0086] of JP-A-2007-279688 can be mentioned.

In the general formula (1), the mesogen group represented by M is a group containing at least one cyclic structure selected from the group consisting of aromatic hydrocarbon groups, heterocyclic groups, and alicyclic hydrocarbon groups. It is preferably a group containing an aromatic hydrocarbon group, and more preferably a group containing an aromatic hydrocarbon group.

In the general formula (1), the mesogen group represented by M is preferably a group containing 2 to 5 aromatic hydrocarbon groups, and is a group containing 3 to 5 aromatic hydrocarbon groups. Is more preferable.

In the general formula (1), the mesogen group represented by M is preferably a group containing 3 to 5 phenylene groups and the phenylene groups are linked to each other by -CO-O-.

In the general formula (1), the cyclic structure (for example, aromatic hydrocarbon group, heterocyclic group, and alicyclic hydrocarbon group) contained in the mesogen group represented by M may have a substituent. Good. Examples of the substituent include an alkyl group having 1 to 10 carbon atoms (for example, a methyl group).

Specific examples of the compound represented by the general formula (1) are shown below. However, the compound represented by the general formula (1) is not limited to the compounds shown below. In the chemical structure of the compounds shown below, "-Me" represents a methyl group.

Specific examples of the rod-shaped thermotropic liquid crystal compound are shown below. However, the rod-shaped thermotropic liquid crystal compound is not limited to the compounds shown below.

The liquid crystal compound may be a synthetic product synthesized by a known method or a commercially available product. Commercially available liquid crystal compounds are available from, for example, Tokyo Chemical Industry Co., Ltd. and Merck & Co., Inc.

The composition may contain one kind alone or two or more kinds of liquid crystal compounds.

From the viewpoint of heat resistance, the content of the liquid crystal compound is preferably 70% by mass or more, more preferably 80% by mass or more, and 90% by mass or more with respect to the solid content mass of the composition. It is particularly preferable to have. The upper limit of the content of the liquid crystal compound may be determined according to the content of the chiral agent. The content of the liquid crystal compound may be determined in the range of, for example, less than 100% by mass with respect to the solid content mass of the composition. The content of the liquid crystal compound may be 99% by mass or less, or 96% by mass or less, based on the solid content mass of the composition. The content of the liquid crystal compound is preferably 70% by mass or more and less than 100% by mass, more preferably 80% by mass or more and less than 100% by mass, and 90% by mass, based on the solid content mass of the composition. It is particularly preferable that it is more than 100% by mass.

-Chiral agent-
The composition comprises a chiral agent whose spiral-inducing force changes upon light irradiation.

In the present disclosure, "the spiral-inducing force changes by light irradiation" means that there is a difference between the spiral-inducing force before light irradiation and the spiral-inducing force after light irradiation. The spiral-inducing force (HTP) is known as an index showing the spiral-forming ability of a chiral agent. The spiral inducing force is generally expressed as the reciprocal of the product of the length of one cycle of the spiral axis and the concentration of the chiral auxiliary. The spiral inducing force depends, for example, on the type of chiral auxiliary and the concentration of the chiral agent.

The type of chiral agent is not limited as long as it is a chiral agent whose spiral-inducing force changes with light irradiation. The type of chiral agent may be determined, for example, according to the inclination angle of the target spiral shaft.

The chiral agent may be a liquid crystal or non-liquid crystal chiral agent.

Most chiral agents contain asymmetric carbon atoms. However, the chiral agent is not limited to compounds containing an asymmetric carbon atom. Examples of the chiral agent include an axial asymmetric compound containing no asymmetric carbon atom and a planar asymmetric compound.

The chiral agent may have a polymerizable group. The chiral agent may have one kind alone or two or more kinds of polymerizable groups. The chiral agent may have two or more homogeneous polymerizable groups. Examples of the polymerizable group in the chiral agent include the polymerizable group described in the above section "Liquid crystal compound". A preferred embodiment of the polymerizable group in the chiral agent is the same as that of the polymerizable group described in the above section "Liquid crystal compound".

Examples of the chiral agent include a photoreactive chiral agent. A photoreactive chiral agent is a compound having a chiral site (a site that causes chirality; the same applies hereinafter) and a photoreactive site whose structure changes due to light irradiation. The photoreactive chiral agent, for example, greatly changes the twisted structure of the liquid crystal compound according to the amount of irradiation light.

Examples of the chiral site include the asymmetric carbon described in "Hiroyuki Nohira, Review of Chemistry, No. 22 Chemistry of Liquid Crystal, 73p: 1994".

Photochemical sites whose structure changes due to light irradiation include, for example, "photochromic compounds" (Kingo Uchida, Masahiro Irie, Chemical Industry, vol.64, 640p, 1999, Kingo Uchida, Masahiro Irie, Fine Chemicals, vol.28 (9), 15p, 1999). Examples of the structural change due to light irradiation include decomposition, addition reaction, isomerization, and dimerization reaction. The structural change due to light irradiation may be reversible or irreversible.

Examples of the photoreactive chiral agent include the photoreactive chiral agents described in paragraphs [0044] to [0047] of JP-A-2001-159709, paragraphs [0019] to paragraphs of JP-A-2002-179669. The optically active compound described in Japanese Patent Application Laid-Open No. 2002-179633, paragraphs [0020] to paragraph [0044] of JP-A-2002-179633, paragraphs [0016] to paragraph [0040] of JP-A-2002-179670. ], The optically active compounds described in JP-A-2002-179668, paragraphs [0017] to paragraph [0050], and the optically active compounds described in JP-A-2002-180051, paragraphs [0018] to paragraphs [0044]. The optically active compound described, the optically active compound described in paragraphs [0016] to paragraph [0055] of JP-A-2002-338575, and paragraphs [0020] to paragraph [0049] of JP-A-2002-179682. Optically active compounds of.

The chiral agent is preferably a chiral agent that causes photoisomerization from the viewpoint that the spiral-inducing force is easily changed by light irradiation. The chiral agent that causes photoisomerization is a chiral agent having a photoisomerization site. The photoisomerization site is one of the above photoreaction sites. From the viewpoint that the photoisomerization site absorbs less visible light, is prone to photoisomerization, and has a large difference in spiral-inducing force before and after light irradiation, the cinnamoyl site, coumarin site, azobenzene site, stilbene site, or It is preferably a coumarin moiety, more preferably a cinnamoyl moiety or a chalcone moiety.

The chiral agent preferably has an isosorbide skeleton, an isomannide skeleton, or a binaphthol skeleton, more preferably an isosorbide skeleton, or an isosorbide skeleton, from the viewpoint of a large difference in spiral-inducing force before and after light irradiation. It is particularly preferable to have.

The chiral agent shall be at least one selected from the group consisting of a chiral agent that induces a right-handed helical structure with respect to a liquid crystal compound and a chiral agent that induces a left-handed helical structure with respect to a liquid crystal compound. Is preferable. Depending on the type of chiral agent as described above, a spiral structure having a desired winding direction can be formed. For example, a right-handed helical structure can be formed by using a chiral agent that induces a right-handed helical structure with respect to a liquid crystal compound. Further, as will be described later, by using a chiral agent that induces a right-handed spiral structure for a liquid crystal compound and a chiral agent that induces a left-handed spiral structure for a liquid crystal compound, a spiral-inducing force ( It is also possible to adjust the amount of change in the spiral-inducing force before and after the step (C).

The chiral agent may include a chiral agent that induces a right-handed helical structure with respect to the liquid crystal compound, and a chiral agent that induces a left-handed helical structure with respect to the liquid crystal compound. By using the above two kinds of chiral agents in combination, the spiral-inducing force (including the amount of change in the spiral-inducing force before and after the step (C). The same shall apply hereinafter in this paragraph) can be adjusted. When the above two types of chiral agents are used in combination, for example, the spiral-inducing force can be adjusted by adjusting the content of each chiral agent.

The composition may contain one kind alone or two or more kinds of chiral agents.

The content of chiral auxiliary is not limited. The content of the chiral agent may be determined, for example, according to the target spiral pitch. The content of the chiral agent is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, based on the solid content mass of the composition, from the viewpoint of the spiral orientation regulating force. It is particularly preferably 0.1% by mass or more. From the viewpoint of heat resistance, the content of the chiral agent is preferably 20% by mass or less, more preferably 10% by mass or less, and 5% by mass or less, based on the solid content mass of the composition. Is particularly preferred. The content of the chiral agent is preferably 0.01% by mass to 20% by mass, more preferably 0.05% by mass to 10% by mass, and 0. It is particularly preferably 1% by mass to 5% by mass.

In the composition, the ratio of the content of the chiral agent to the content of the liquid crystal compound is preferably 0.01 or more, preferably 0.05 or more, based on the mass, from the viewpoint of the spiral orientation regulating force. More preferably, it is particularly preferably 0.1 or more. In the composition, the ratio of the content of the chiral auxiliary to the content of the liquid crystal compound is preferably 20 or less, more preferably 10 or less, and 5 or less, on a mass basis, from the viewpoint of heat resistance. Is particularly preferable. The ratio of the content of the chiral agent to the content of the liquid crystal compound is preferably 0.01 to 20, more preferably 0.05 to 20, and 0.1 to 20 on a mass basis. Is particularly preferred. Further, the ratio of the content of the chiral agent to the content of the liquid crystal compound is preferably 0.1 to 10 and more preferably 0.1 to 5 on a mass basis.

-Other ingredients-
The composition may contain components other than the above-mentioned components (hereinafter, referred to as "other components"). Examples of other components include a solvent, an orientation regulator, a polymerization initiator, a leveling agent, an orientation auxiliary, a photopolymerization inhibitor, a sensitizer, and a chiral agent whose spiral-inducing force does not change by light irradiation.

The composition preferably contains a solvent. The composition contains a solvent, and the coatability of the composition can be improved.

As the solvent, an organic solvent is preferable. Examples of the organic solvent include an amide solvent (for example, N, N-dimethylformamide), a sulfoxide solvent (for example, dimethyl sulfoxide), a heterocyclic compound (for example, pyridine), a hydrocarbon solvent (for example, benzene, and hexane), and the like. Alkyl halide solvents (eg chloroform, dichloromethane), ester solvents (eg methyl acetate and butyl acetate), ketone solvents (eg acetone, methyl ethyl ketone, and cyclohexanone), and ether solvents (eg tetrahydrofuran, and 1, 2 -Dimethoxyethane). The organic solvent is preferably at least one selected from the group consisting of an alkyl halide solvent and a ketone solvent, and more preferably a ketone solvent.

The composition may contain one kind alone or two or more kinds of solvents.

The content of the solid content in the composition is preferably 25% by mass to 40% by mass, more preferably 25% by mass to 35% by mass, based on the total mass of the composition.

Examples of the orientation control agent include the compounds described in paragraphs [0012] to [0030] of JP2012-2011306A, and paragraphs [0037] to [0044] of JP2012-101999. The compound, the fluorine-containing (meth) acrylate polymer described in paragraphs [0018] to [0043] of JP-A-2007-272185, and JP-A-2005-099258, which are described in detail together with the synthesis method. Examples include compounds. A polymer containing the polymerization unit of the fluoroaliphatic group-containing monomer in an amount of more than 50% by mass of the total polymerization unit described in JP-A-2004-331812 may be used as the orientation control agent.

A vertical alignment agent can also be mentioned as an orientation control agent. Examples of the vertical alignment agent include a boronic acid compound and / or an onium salt described in JP-A-2015-38598, and an onium salt described in JP-A-2008-26730.

The composition may contain one kind alone or two or more kinds of orientation control agents.

When the composition contains an orientation control agent, the content of the orientation control agent is preferably more than 0% by mass and 5.0% by mass or less, preferably 0.3% by mass, based on the solid content mass of the composition. More preferably, it is% to 2.0% by mass.

The composition preferably contains a polymerization initiator. When the composition contains a polymerization initiator, the curability of the composition can be improved.

Examples of the polymerization initiator include a photopolymerization initiator and a thermal polymerization initiator.

The polymerization initiator is preferably a photopolymerization initiator from the viewpoint of suppressing deformation of the base material due to heat and deterioration of the composition. Examples of the photopolymerization initiator include an α-carbonyl compound (for example, the compound described in US Pat. No. 2,376,661 or US Pat. No. 2,376,670) and an acyloin ether (for example, US Pat. No. 2,448,828). Compounds described in the specification), α-hydrogen-substituted aromatic acidoine compounds (eg, compounds described in US Pat. No. 2,725,212), polynuclear quinone compounds (eg, US Pat. No. 3,46127, or A compound described in US Pat. No. 2,951,758), a combination of a triarylimidazole dimer and a p-aminophenyl ketone (eg, a compound described in US Pat. No. 3,549,637), an acridin compound (eg, special treatment). Kaisho 60-105667, or a compound described in US Pat. No. 4,239,850), a phenazine compound (for example, JP-A-60-105667, or a compound described in US Pat. No. 4,239,850). ), Oxaziazole compounds (for example, the compounds described in US Pat. No. 4,212,970), and acylphosphine oxide compounds (for example, Japanese Patent Application Laid-Open No. 63-40799, Japanese Patent Application Laid-Open No. 5-29234, JP-A-10- Examples thereof include compounds described in Japanese Patent Application Laid-Open No. 95788 or JP-A-10-29997).

It is preferable that the ultraviolet absorption wavelength of the polymerization initiator is different from the ultraviolet absorption wavelength of the chiral agent. Since the ultraviolet absorption wavelength of the polymerization initiator is different from the ultraviolet absorption wavelength of the chiral agent, in step (C), the spiral inducing force of the chiral agent contained in the composition can be changed while suppressing the curing of the composition. it can. As a result of the above, the controllability of the inclination angle of the spiral shaft is further improved.

The composition may contain one kind alone or two or more kinds of polymerization initiators.

When the composition contains a polymerization initiator, the content of the polymerization initiator is preferably 0.5% by mass to 5.0% by mass, and 1.0% by mass, based on the solid content mass of the composition. It is more preferably about 4.0% by mass.

The composition may contain a chiral agent whose spiral-inducing force does not change due to light irradiation (hereinafter, may be referred to as a "second chiral agent"). For example, the spiral inducing force is increased by light irradiation due to the action of the first chiral agent whose spiral inducing force is reduced by light irradiation and the second chiral agent whose winding direction is different from that of the first chiral agent. The tilt angle can be reduced. The above-mentioned first chiral agent is one kind of chiral agent whose spiral-inducing force changes by light irradiation.

The second chiral agent is a chiral agent other than the chiral agent whose spiral-inducing force changes by light irradiation. Examples of the second chiral agent include chiral agents that do not have a photoreactive site whose structure changes due to light irradiation. The photoreactive site whose structure changes due to light irradiation is as described in the above section "Chiral agent".

The second chiral agent is described in, for example, "Liquid Crystal Device Handbook, Chapter 3, Section 4-3, Chiral Auxiliary for TN, STN, p. 199, Japan Society for the Promotion of Science, 42nd Committee, 1989". You may choose from agents.

The second chiral agent may have a polymerizable group. The second chiral agent may have one kind alone or two or more kinds of polymerizable groups. The second chiral agent may have two or more homogeneous polymerizable groups. Examples of the polymerizable group in the second chiral agent include the polymerizable group described in the above section "Liquid crystal compound". A preferred embodiment of the polymerizable group in the second chiral agent is the same as that of the polymerizable group described in the above section "Liquid crystal compound".

The second chiral agent preferably has an isosorbide skeleton, an isomannide skeleton, or a binaphthol skeleton, more preferably has an isosorbide skeleton or an isomannide skeleton, and particularly preferably has an isosorbide skeleton.

The second chiral agent may be a chiral agent that induces a right-handed helical structure with respect to a liquid crystal compound, or a chiral agent that induces a left-handed helical structure with respect to a liquid crystal compound. When the second chiral agent is a chiral agent that induces a right-handed spiral structure with respect to the liquid crystal compound, the chiral agent whose spiral-inducing force changes by light irradiation is a left-handed spiral with respect to the liquid crystal compound. It is preferably a chiral agent that induces a structure. On the other hand, when the second chiral agent is a chiral agent that induces a left-handed spiral structure with respect to the liquid crystal compound, the chiral agent whose spiral-inducing force changes by light irradiation is right-handed with respect to the liquid crystal compound. It is preferably a chiral agent that induces a helical structure. As explained in the section of "chiral agent" above, by using a chiral agent that induces a right-handed spiral structure and a chiral agent that induces a left-handed spiral structure in combination, a spiral-inducing force (before and after step (C)). Includes the amount of change in the spiral-inducing force in.).

-Composition manufacturing method-
The method for producing the composition is not limited. Examples of the method for producing the composition include a method of mixing the above-mentioned components. As the mixing method, a known mixing method can be used. In the method for producing the composition, after mixing each of the above components, the obtained mixture may be filtered.

(Applying method)
The method of applying the composition is not limited. Examples of the coating method of the composition include an extrusion die coater method, a curtain coating method, a dip coating method, a spin coating method, a print coating method, a spray coating method, a slot coating method, a roll coating method, a slide coating method, and a blade coating method. , Gravure coating method, and wire bar method.

(Applying amount)
The amount of the composition applied is not limited. The coating amount of the composition is determined according to, for example, the thickness of the target cholesteric liquid crystal layer or the thickness of the composition before the shearing force described in the section "Step (B)" below is applied. Just do it.

[Step (B)]
In the step (B), a shearing force is applied to the surface of the composition applied on the base material. Hereinafter, the step (B) will be specifically described.

-Direction to apply shear force-
In step (B), the shear force is preferably applied in one direction along the surface of the composition. By applying the shearing force in one direction along the surface of the composition, it is possible to further reduce the variation in the orientation of the spiral axis.

-Means to apply shear force-
Means for applying shear forces include, for example, blades, air knives, bars, and applicators. In the step (B), it is preferable to apply a shearing force to the surface of the composition by using a blade or an air knife, and it is more preferable to apply a shearing force to the surface of the composition by using a blade.

In the method of applying a shearing force to the surface of the composition using a blade, it is preferable to scrape the surface of the composition with the blade. In the above method, the thickness of the composition may change before and after the application of the shearing force. The thickness of the composition after the shearing force is applied by the blade may be 1/2 or less or 1/3 or less of the thickness of the composition before the shearing force is applied. The thickness of the composition after the shearing force is applied by the blade is preferably 1/4 or more of the thickness of the composition before the shearing force is applied.

The material of the blade is not limited. Examples of the blade material include metals (eg, stainless steel) and resins (eg, Teflon® and polyetheretherketone (PEEK)).

The shape of the blade is not limited. Examples of the shape of the blade include a plate shape.

The blade is preferably a metal plate-shaped member from the viewpoint of easily applying a shearing force to the composition.

The thickness of the tip of the blade in contact with the composition is preferably 0.1 mm or more, and more preferably 1 mm or more, from the viewpoint of easily applying a shearing force to the composition. There is no upper limit to the thickness of the blade. The thickness of the blade may be determined in the range of, for example, 10 mm or less.

In the method of applying a shearing force to the surface of the composition using an air knife, the shearing force is applied to the surface of the composition by blowing compressed air on the surface of the composition with the air knife. The shear rate applied to the composition can be adjusted according to the rate at which the compressed air is blown (that is, the flow velocity).

The direction in which the compressed air is blown by the air knife may be the same direction or the opposite direction to the transport direction of the composition. The direction in which the compressed air is blown by the air knife should be the same as the transport direction of the composition from the viewpoint of preventing the fragments of the composition scraped by the compressed air from adhering to the composition remaining on the substrate. Is preferable.

-Shear velocity-
The higher the shear rate in the step (B), the higher the orientation accuracy (meaning that there is less variation in the orientation of the spiral axis. The same applies hereinafter). The cholesteric liquid crystal layer can be formed. The shear rate is ^{preferably 1,000 seconds-1} or more, more preferably 10,000 seconds- ¹ or more, and ^{particularly preferably 30,000 seconds-1} or more. The upper limit of shear rate is not limited. Shear rate, for example, may be determined in the range of 1.0 × 10 ⁶ sec ^-1 or less.

The method of obtaining the shear rate will be explained below. For example, when a shear force is applied using a blade, the shear rate is such that the shortest distance between the blade and the base material is "d" and the transfer speed of the composition in contact with the blade (that is, relative to the composition and the blade). When (velocity) is set to "V", it is obtained by "V / d". Further, for example, when a shear force is applied using an air knife, the shear rate is such that the thickness of the composition after applying shear is "h" and the relative speed between the composition surface and the substrate surface is "V". Then, it is obtained by "V / 2h".

-Surface temperature of the composition-
The surface temperature of the composition when the shearing force is applied may be determined according to the phase transition temperature of the liquid crystal compound contained in the composition. The surface temperature of the composition when the shearing force is applied is preferably 50 ° C. to 120 ° C., more preferably 60 ° C. to 100 ° C. By adjusting the surface temperature of the composition within the above range, a cholesteric liquid crystal layer having high orientation accuracy can be obtained. The surface temperature of the composition is measured using a radiation thermometer whose emissivity is calibrated by the temperature value measured by a non-contact thermometer. The surface temperature of the composition is measured within 10 cm from the surface on the side opposite to the measurement surface (that is, the back side) in the absence of reflectors.

-Composition thickness-
The thickness of the composition before the shearing force is applied is preferably in the range of 30 μm or less, more preferably in the range of 1 μm to 25 μm, from the viewpoint of forming a cholesteric liquid crystal layer having high orientation accuracy. It is particularly preferably in the range of 3 μm to 25 μm.

The thickness of the composition after the shearing force is applied is preferably in the range of 20 μm or less, and more preferably in the range of 10 μm or less, from the viewpoint of forming a cholesteric liquid crystal layer having high orientation accuracy. The lower limit of the thickness of the composition after the shear force is applied is not limited. The thickness of the composition after the shearing force is applied is preferably in the range of 0.5 μm or more.

[Step (C)]
In the step (C), the composition to which the shearing force is applied is irradiated with ultraviolet rays having a wavelength that changes the spiral-inducing force of the chiral agent. Hereinafter, the step (C) will be specifically described.

The wavelength of ultraviolet rays is not limited as long as it includes a wavelength that changes the spiral-inducing force of the chiral auxiliary. Whether or not the wavelength of ultraviolet rays includes a wavelength that changes the spiral-inducing force of the chiral auxiliary is confirmed based on the change in the inclination angle of the spiral axis before and after the step (C). When the tilt angle of the spiral shaft after the step (C) is increased or decreased as compared with the tilt angle of the spiral shaft before the step (C), the wavelength of the ultraviolet ray changes the spiral-inducing force of the chiral auxiliary. It is considered to include the wavelength to be caused.

The wavelength at which the spiral inducing force is changed may be determined, for example, according to the type of chiral agent. The wavelength for changing the spiral inducing force is preferably in the range of 180 nm to 400 nm, more preferably in the range of 200 nm to 380 nm, and particularly preferably in the range of 300 nm to 370 nm.

When the composition contains a polymerization initiator (particularly when the ultraviolet absorption wavelength of the polymerization initiator overlaps with the ultraviolet absorption wavelength of the chiral agent), the wavelength of the ultraviolet rays irradiated in the step (C) is the polymerization initiator. It is preferable not to include the ultraviolet absorption wavelength of. Since the wavelength of the ultraviolet rays irradiated in the step (C) does not include the ultraviolet absorption wavelength of the polymerization initiator, it is possible to change the spiral-inducing force of the chiral agent contained in the composition while suppressing the curing of the composition. it can. As a result of the above, the controllability of the inclination angle of the spiral shaft is further improved. The phrase "does not contain the UV absorption wavelength of the polymerization initiator" is not limited to the fact that the UV absorption wavelength of the polymerization initiator is not contained at all, and the polymerization initiator is used to suppress the curing of the composition caused by the polymerization initiator. Includes as little UV absorption wavelength as possible. For example, by using a long wavelength cut filter described later or an LED (light emitting diode) ultraviolet irradiator having a narrow irradiation wavelength band, the composition can be irradiated with ultraviolet rays that do not include the ultraviolet absorption wavelength of the polymerization initiator.

In step (C), a member that selectively transmits or shields a specific wavelength (hereinafter, referred to as "member having wavelength selectivity") may be used. For example, by irradiating the composition with ultraviolet rays through a member having wavelength selectivity, the wavelength range of the ultraviolet rays reaching the composition can be adjusted. Examples of the member having wavelength selectivity include a long wavelength cut filter (Asahi Spectroscopy Co., Ltd., SH0325), a short wavelength cut filter, and a bandpass filter.

The exposure amount of ultraviolet rays (also referred to as integrated light amount) is not limited. For example, the amount of change in the spiral-inducing force of the chiral agent can be adjusted according to the amount of exposure to ultraviolet rays. As the amount of exposure to ultraviolet rays increases, the amount of change in the spiral-inducing force of the chiral agent tends to increase. As the amount of exposure to ultraviolet rays decreases, the amount of change in the spiral-inducing force of the chiral agent tends to decrease. Exposure of ultraviolet rays, for ^example, may be determined in the range of 1mJ / cm 2 ~ 1,000mJ / cm 2.

Examples of the light source of ultraviolet rays include lamps (for example, tungsten lamps, halogen lamps, xenon lamps, xenon flash lamps, mercury lamps, mercury xenon lamps, LED lamps, LED-UV (ultraviolet) lamps, and carbon arc lamps) and lasers. (For example, semiconductor laser, helium neon laser, argon ion laser, helium cadmium laser, and YAG (Ytrium Aluminum Garnet) laser), light emitting diode, and cathode line tube.

(Other processes)
The method for producing a cholesteric liquid crystal layer according to the present disclosure may include steps other than the above-mentioned steps (hereinafter, referred to as "other steps" in this paragraph), if necessary. Hereinafter, other steps will be specifically described. However, the other steps are not limited to the steps shown below.

-Process (D)-
The method for producing a cholesteric liquid crystal layer according to the present disclosure includes a step of forming an orientation layer on a base material (hereinafter, may be referred to as "step (D)") before the step (A). May be good. The alignment layer can give an orientation regulating force to the liquid crystal compound.

The method of forming the oriented layer is not limited. As a method for forming the alignment layer, a known method can be used. Examples of the method for forming the oriented layer include rubbing treatment of an organic compound (preferably a polymer), oblique vapor deposition of an inorganic compound, and formation of a layer having microgrooves.

(Step (E))
When the composition contains a solvent, the method for producing a cholesteric liquid crystal layer according to the present disclosure determines the content of the solvent in the composition applied on the substrate between the steps (A) and (B). It may have a step (hereinafter, may be referred to as “step (E)”) of adjusting to a range of 50% by mass or less with respect to the total mass of the composition. By adjusting the content of the solvent in the composition to a range of 50% by mass or less, a cholesteric liquid crystal layer having high orientation accuracy can be formed.

In the step (E), the content of the solvent in the composition is preferably 40% by mass or less, more preferably 30% by mass or less, based on the total mass of the composition. The lower limit of the solvent content in the applied composition is not limited. The content of the solvent in the applied composition may be 0% by mass or more than 0% by mass with respect to the total mass of the composition. The content of the solvent in the applied composition is preferably 10% by mass or more from the viewpoint of easily suppressing deterioration of the surface condition of the applied composition.

The content of the solvent in the composition is measured by the absolute drying method. Hereinafter, a specific procedure of the measurement method will be described. The sample collected from the composition is dried at 60 ° C. for 24 hours, and then the mass change of the sample before and after drying (that is, the difference between the mass of the sample after drying and the mass of the sample before drying) is determined. The content of the solvent in the sample is determined based on the mass change of the sample before and after drying. The arithmetic mean of the values obtained by performing the above operation three times is taken as the solvent content.

Examples of the method for adjusting the content of the solvent in the applied composition in the step (E) include drying.

As a means for drying the composition, a known drying means can be used. Drying means include, for example, ovens, hot air blowers, and infrared (IR) heaters.

In drying using a warm air blower, warm air may be directly applied to the composition, or warm air may be applied to the surface opposite to the surface on which the composition of the base material is arranged. Further, a diffusion plate may be installed in order to prevent the surface of the composition from flowing due to warm air.

Drying may be done by inhalation. In drying by intake air, for example, a decompression chamber having an exhaust mechanism can be used. By inhaling the gas around the composition, the content of the solvent in the composition can be reduced.

The drying conditions are not limited as long as the content of the solvent in the composition can be adjusted in the range of 50% by mass or less. The drying conditions may be determined, for example, according to the components contained in the composition, the coating amount of the composition, and the transport speed.

(Step (F))
The method for producing a cholesteric liquid crystal layer according to the present disclosure may include a step (hereinafter, may be referred to as "step (F)") of curing the composition irradiated with ultraviolet rays after the step (C). Good. By curing the composition in step (F), the molecular arrangement of the liquid crystal compound can be fixed.

Examples of the method for curing the composition include heating and irradiation with active energy rays. The method for curing the composition is preferably irradiation with active energy rays from the viewpoint of production suitability.

Examples of active energy rays include α-rays, γ-rays, X-rays, ultraviolet rays, infrared rays, visible rays, and electron beams. The active energy ray is preferably ultraviolet rays from the viewpoint of curing sensitivity and availability of the apparatus.

Examples of the light source of ultraviolet rays include the light source described in the above section "Step (C)".

The peak wavelength of ultraviolet rays emitted from the light source of ultraviolet rays is preferably 200 nm to 400 nm.

The exposure amount of ultraviolet rays (also referred to as integrated light amount) is preferably ^{100 mJ / cm 2} to 500 mJ / cm ^2.

(Manufacturing method)
The method for producing a cholesteric liquid crystal layer according to the present disclosure may be carried out by a roll-to-roll method. In the roll-to-roll method, for example, each step is carried out while continuously transporting a long base material. The method for producing a cholesteric liquid crystal layer according to the present disclosure may be carried out using a base material that is conveyed one by one.

Hereinafter, the present disclosure will be described in detail by way of examples. However, the present disclosure is not limited to the following examples.

<Example 1>
An orientation layer and a cholesteric liquid crystal layer were sequentially formed on the substrate by the following procedure.

[Preparation of base material]
As a base material, a triacetyl cellulose (TAC) film (FUJIFILM Corporation, refractive index: 1.48, thickness: 40 μm, length: 300 mm, width: 200 mm) was prepared.

[Formation of Orientation Layer: Step (D)]
A composition for forming an orientation layer was prepared by stirring a mixture containing pure water (96 parts by mass) and PVA-205 (Kuraray Co., Ltd., polyvinyl alcohol) in a container kept warm at 80 ° C. Using a bar (bar count: 6), the composition for forming an orientation layer was applied onto a substrate (triacetyl cellulose film), and then dried in an oven at 100 ° C. for 10 minutes. By the above procedure, an orientation layer (thickness: 2 μm) was formed on the base material.

[Formation of cholesteric liquid crystal layer]
A cholesteric liquid crystal layer (thickness: 10 μm) was formed on the oriented layer by the following procedure.

(Preparation of coating liquid (1) for forming a liquid crystal layer)
After mixing each of the components shown below, a coating liquid (1) for forming a liquid crystal layer was prepared by filtering using a polypropylene filter (pore diameter: 0.2 μm).

-component-
(1) Rod-shaped thermotropic liquid crystal compound (compound (A) below): 100 parts by mass (2) Chiral agent (compound (B) below): 1 part by mass (3) Photopolymerization initiator (PM758, Nippon Kayaku Co., Ltd.) Company): 3 parts by mass (4) Photopolymerization inhibitor (IRGANOX (registered trademark) 1010, BASF): 1 part by mass (5) Orientation inhibitor (compound (C) below): 0.5 parts by mass (6) Solvent (methyl ethyl ketone): 184 parts by mass (7) Solvent (cyclohexanone): 31 parts by mass

Compound (A) is a mixture of the following three compounds. The content of each compound in the mixture is 84% by mass, 14% by mass, and 2% by mass in this order from the top.

The chemical structure of compound (B) is shown below. Compound (B) has an isosorbide skeleton. Compound (B) is a chiral agent that induces a right-handed helical structure. The spiral-inducing force of compound (B) is changed by light irradiation (specifically, first ultraviolet irradiation described later).

The chemical structure of compound (C) is shown below.

(Application: Step (A))
The base material having the alignment layer was heated at 70 ° C., and then the liquid crystal layer forming coating liquid (1) was applied onto the alignment layer using a bar (bar count: 18).

(Drying: Step (E))
A coating film (thickness: 10 μm) was formed by drying the liquid crystal layer forming coating liquid (1) coated on the alignment layer in an oven at 70 ° C. for 1 minute. The content of the solvent in the coating film was 1% by mass or less with respect to the total mass of the coating film.

(Applying shear force: step (B))
With the coating film heated to 70 ° C., a stainless steel blade heated to 70 ° C. is brought into contact with the coating film, and then the blade is moved at a speed of 1.5 m / min while still in contact with the coating film. As a result, a shearing force was applied to the coating film. The length of the contact portion of the blade with the coating film was 30 mm. The shear rate was 2,500 seconds ^-1 .

(First ultraviolet irradiation (change in spiral-inducing force of chiral agent): step (C))
A chiral agent contained in the coating film by irradiating the coating film to which shearing force is applied with ultraviolet rays (exposure amount: 5 mJ / cm ^{2) using an ultra-high pressure mercury lamp (HOYA Corporation, UL750).} Was denatured. In the above method, the coating film was irradiated with ultraviolet rays via a long wavelength cut filter (Asahi Spectroscopy Co., Ltd., SH0325). The ultraviolet rays applied to the coating film include a wavelength (for example, 315 nm) that changes the spiral-inducing force of the chiral agent whose spiral-inducing force is changed by light irradiation.

(Second UV irradiation (curing): Step (F))
After the first irradiation with ultraviolet rays, the coating film was cured by irradiating the coating film with ultraviolet rays (exposure amount: 500 mJ / cm ^{2) using a metal halide lamp.}

<Example 2>
The alignment layer and the cholesteric liquid crystal layer were sequentially formed on the substrate by the same procedure as in Example 1 except that the exposure amount in the first ultraviolet irradiation ^{was changed to 10 mJ / cm 2.}

<Example 3>
The chiral agent (compound (B)) was changed to the components shown below, the amount of photopolymerization initiator (PM758) added was changed to 1 part by mass, and the exposure amount in the first ultraviolet irradiation was 750 mJ / cm. ^The alignment layer and the cholesteric liquid crystal layer were sequentially formed on the substrate by the same procedure as in Example 1 except that the change was changed to 2.

-component-
(1) Chiral agent (compound (D) below, Palocolor® LC756, BASF): 2.4 parts by mass (2) Chiral agent (compound (E) below): 1.7 parts by mass

The chemical structure of compound (D) is shown below. Compound (D) has an isosorbide skeleton. Compound (D) is a chiral agent that induces a right-handed helical structure. However, the spiral-inducing force of compound (D) does not change with light irradiation.

The chemical structure of compound (E) is shown below. Compound (E) has an isomannide skeleton. Compound (E) is a chiral agent that induces a left-handed helical structure. The spiral-inducing force of compound (E) changes with light irradiation.

<Comparative example 1>
The alignment layer and the cholesteric liquid crystal layer were sequentially formed on the substrate by the same procedure as in Example 1 except that the first ultraviolet irradiation was not performed.

<Comparative example 2>
The alignment layer and the cholesteric liquid crystal layer were sequentially formed on the substrate by the same procedure as in Example 3 except that the first ultraviolet irradiation was not performed.

<Comparative example 3>
The procedure was the same as in Example 1 except that the chiral agent (compound (B)) was changed to the chiral agent (compound (D), 1.2 parts by mass) and the first ultraviolet irradiation was not performed. An oriented layer and a cholesteric liquid crystal layer were sequentially formed on the substrate.

<Comparative example 4>
An orientation layer and a cholesteric liquid crystal were placed on the substrate by the same procedure as in Example 1 except that the chiral agent (compound (B)) was changed to the chiral agent (compound (D), 1.2 parts by mass). The layers were formed in sequence.

<Inclination angle of spiral axis>
The cross section of each cholesteric liquid crystal layer in the thickness direction was observed with a polarizing microscope (NV100LPOL manufactured by Nikon Corporation, magnification of objective lens: 100 times). In the cross-sectional image of each cholesteric liquid crystal layer, the angle formed by the five spiral axes and the straight line orthogonal to the main surface of the cholesteric liquid crystal layer was measured, and the inclination angle of the spiral axis was calculated by arithmetically averaging the measured values. The measurement results are shown in Table 1.

In Table 1, the alphabets listed in the "chiral agent" column are the alphabets attached to the compounds used as chiral agents.

In Table 1, "-" described in the column of "first ultraviolet irradiation" means that the first ultraviolet irradiation was not performed.

The results shown in Table 1 show that the composition containing the liquid crystal compound and the chiral agent whose spiral-inducing force is changed by light irradiation is irradiated with ultraviolet rays having a wavelength that changes the spiral-inducing force of the chiral agent. By doing so, it is shown that the controllability of the tilt angle of the spiral axis is improved. For example, comparing Examples 1 and 2 and Comparative Example 1, the inclination angle of the spiral axis was increased by performing the first ultraviolet irradiation. Comparing Example 3 and Comparative Example 2, the inclination angle of the spiral axis was reduced by performing the first ultraviolet irradiation. On the other hand, in Comparative Examples 3 to 4 in which only the chiral agent (that is, compound (D)) whose spiral-inducing force does not change by light irradiation was used as the chiral agent, the spiral shaft in Comparative Example 4 in which the first ultraviolet irradiation was performed. The tilt angle of the spiral axis was the same as the tilt angle of the spiral axis in Comparative Example 3 in which the first ultraviolet irradiation was not performed.

The disclosure of Japanese Patent Application No. 2019-237297 filed on December 26, 2019 is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are to the same extent as if the individual documents, patent applications, and technical standards were specifically and individually stated to be incorporated by reference. Incorporated herein by reference.

Claims (12)

1. A step of applying a composition containing a liquid crystal compound and a chiral agent whose spiral-inducing force changes by light irradiation on a base material.
   A step of applying a shearing force to the surface of the composition applied on the base material, and
   A step of irradiating the composition to which the shearing force is applied with ultraviolet rays having a wavelength that changes the spiral-inducing force of the chiral agent whose spiral-inducing force is changed by the light irradiation.
   A method for manufacturing a cholesteric liquid crystal layer including.
2. The method for producing a cholesteric liquid crystal layer according to claim 1, which comprises a step of curing the composition irradiated with ultraviolet rays.
3. The method for producing a cholesteric liquid crystal layer according to claim 1 or 2, wherein the shear rate in the step of applying a shearing force to the surface of the composition is 1,000 seconds- ^{1 or more.}
4. The method for producing a cholesteric liquid crystal layer according to any one of claims 1 to 3, wherein in the step of applying a shearing force to the surface of the composition, a shearing force is applied to the surface of the composition by using a blade. ..
5. The method for producing a cholesteric liquid crystal layer according to any one of claims 1 to 4, wherein the chiral agent whose spiral-inducing force is changed by light irradiation is a chiral agent that causes photoisomerization.
6. The method for producing a cholesteric liquid crystal layer according to any one of claims 1 to 5, wherein the chiral agent whose spiral-inducing force is changed by light irradiation has an isosorbide skeleton, an isomannide skeleton, or a binaphthol skeleton.
7. The method for producing a cholesteric liquid crystal layer according to any one of claims 1 to 6, wherein the wavelength for changing the spiral inducing force is in the range of 200 nm to 380 nm.
8. The chiral agent whose spiral-inducing force is changed by light irradiation is a chiral agent that induces a right-handed helical structure with respect to the liquid crystal compound, and a chiral agent that induces a left-handed helical structure with respect to the liquid crystal compound. The method for producing a cholesteric liquid crystal layer according to any one of claims 1 to 7, which is at least one selected from the group.
9. Claims 1 to 8 in which, in the composition, the ratio of the content of the chiral agent whose spiral-inducing force is changed by the light irradiation to the content of the liquid crystal compound is 0.1 to 20 on a mass basis. The method for producing a cholesteric liquid crystal layer according to any one of the above items.
10. The method for producing a cholesteric liquid crystal layer according to any one of claims 1 to 9, wherein the composition contains a polymerization initiator.
11. The method for producing a cholesteric liquid crystal layer according to any one of claims 1 to 10, wherein the composition contains a chiral agent whose spiral-inducing force does not change by light irradiation.
12. When the chiral agent whose spiral-inducing force does not change by light irradiation is a chiral agent that induces a right-handed spiral structure with respect to the liquid crystal compound, the chiral agent whose spiral-inducing force changes by light irradiation is the above-mentioned. A chiral agent that induces a left-handed helical structure with respect to a liquid crystal compound, or a chiral agent whose spiral-inducing force does not change with light irradiation is a chiral agent that induces a left-handed helical structure with respect to the liquid crystal compound. The method for producing a cholesteric liquid crystal layer according to claim 11, wherein the chiral agent whose spiral-inducing force is changed by light irradiation is a chiral agent that induces a right-handed spiral structure with respect to the liquid crystal compound.