Liquid crystal composition for radio wave control element, radio wave control element, and compound

Abstract

The present invention provides a liquid crystal composition for a radio wave control element that is a material having large refractive index anisotropy to a radio wave and has high melting point depression. A liquid crystal composition for a radio wave control element according to the present invention contains two or more types of liquid crystal compounds. At least one of the two or more types of liquid crystal compounds is a compound represented by formula (1).　Formula (1): R1-L1-A1-(Z1-B1)n-L2-R2

Description

Liquid crystal composition for radio wave control element, radio wave control element, compound

[0001] The present invention relates to a liquid crystal composition for a radio wave control device, a radio wave control device, and a compound.

[0002] High-frequency radio waves (e.g., millimeter waves and terahertz waves) required for high-capacity wireless communication have a tendency to propagate in a straight line. Therefore, a radio wave control element that can bend the direction of radio waves in any direction is required. However, for example, a typical reflector reflects radio waves in a fixed direction, and the reflection direction is a specular reflection in which the incident angle and the outgoing angle are equal. This significantly limits the range in which the direction of radio waves can be changed, making it difficult to deliver radio waves to the desired destination.

[0003] Patent Document 1 discloses a radio wave control element using a liquid crystal composition for a radio wave control element, and discloses a predetermined polychromatic compound as the liquid crystal compound.

[0004] Special table number 2019-512023

[0005] On the other hand, radio wave control elements using liquid crystal compositions for radio wave control elements are desired to be thinner and have shorter operating times. To achieve such characteristics, a liquid crystal composition for radio wave control elements that exhibits a greater refractive index anisotropy with respect to radio waves is required. Furthermore, a liquid crystal composition for radio wave control elements with a high melting point depression ability is also desired. A high melting point depression ability refers to a large difference between the melting point of a single liquid crystal compound and the melting point of a liquid crystal composition containing two or more liquid crystal compounds. In this specification, the term "melting point" refers to the temperature at which a solid state changes to a liquid state or a liquid crystal state (e.g., a nematic phase, a smectite phase, etc.). The present inventors evaluated the properties of liquid crystal compositions for radio wave control elements containing the liquid crystal compounds described in Patent Document 1 and found that it was difficult to achieve both refractive index anisotropy with respect to radio waves and melting point depression ability.

[0006] In view of the above circumstances, an object of the present invention is to provide a liquid crystal composition for a radio wave control device, which is a material having a large refractive index anisotropy with respect to radio waves and a high melting point lowering property.Another object of the present invention is to provide a radio wave control device and a compound.

[0007] As a result of extensive research into solving the above problems, the present inventors have found that the problems can be solved by the following configuration.

[0008] [1] A liquid crystal composition for a radio wave control element, comprising two or more liquid crystal compounds, wherein at least one of the two or more liquid crystal compounds is a compound represented by formula (1) described below. [2] The liquid crystal composition for a radio wave control element according to [1], wherein the content of the compound represented by formula (1) is 30% by mass or more relative to the total solid content of the liquid crystal composition for a radio wave control element. [3] Z １ [4] The liquid crystal composition for a radio wave control element according to [1] or [2], wherein at least one of R １ and R ２ [5] The liquid crystal composition for a radio wave control element according to [3], wherein at least one of the above is the alkyl group having a partial structure represented by formula (X) described below. １ and B １ [6] The liquid crystal composition for a radio wave control element according to [3] or [4], wherein R is each independently an aromatic hydrocarbon ring, and n is an integer of 2 to 4. １ and R ２ are the same groups, and L １ and L ２ is —CH═CH—, —O—, or —NR ３ [7] The liquid crystal composition for a radio wave control element according to [5], wherein A １ and B １ The liquid crystal composition for a radio wave control element according to [3] or [4], wherein at least one of the above is an aromatic heterocycle, and n is an integer of 1 to 3. [8] A １ and B １ [7] The liquid crystal composition for a radio wave control element according to [7], wherein at least one of the following is a thienothiazole ring. [9] The liquid crystal composition for a radio wave control element according to any one of [1] to [8], wherein the compound represented by formula (1) is a racemate.

[10] A radio wave control element having, in this order: a first electrode; a liquid crystal composition layer made of the liquid crystal composition for a radio wave control element according to any one of [1] to [9]; and a second electrode.

[11] A compound represented by formula (1) described later.

[12] R１ and R ２

[13] The compound according to

[11] , wherein at least one of A is the alkyl group having two or more asymmetric carbon atoms. １ and B １

[14] The compound according to

[11] or

[12] , wherein R is each independently an aromatic hydrocarbon ring, and n is an integer of 2 to 4. １ and R ２ are the same group, and L １ and L ２ is —CH═CH—, —O—, or —NR ３

[15] The compound according to

[13] , wherein A is -. １ and B １ The compound according to

[11] or

[12] , wherein at least one of A is an aromatic heterocycle, and n is an integer of 1 to 3. １ and B １

[17] The compound according to any one of

[11] to

[16] , wherein the compound represented by formula (1) is a racemate.

[0009] According to the present invention, it is possible to provide a liquid crystal composition for a radio wave control element, which is a material having a large refractive index anisotropy with respect to radio waves and a high melting point lowering property. Also, according to the present invention, it is possible to provide a radio wave control element and a compound.

[0010] FIG. 1 is a diagram showing an example of the use of a radio wave control element. FIG. 2 is a diagram showing an example of a metasurface structure used in a radio wave control element. FIG. 3 is a diagram explaining the mechanism by which the emission direction of radio waves is changed in a radio wave control element. FIG. 4 is a diagram conceptually showing an example of a radio wave control element. FIG. 5 is a diagram conceptually showing an example of a liquid crystal orientation pattern in a radio wave control element. FIG. 6 is a diagram showing the relationship between the applied voltage and the amount of phase delay of the radio waves. FIG. 7 is a diagram showing an example of the results of melting point measurement.

[0011] The present invention will be described in detail below. The following description of the constituent elements may be based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0012] In this specification, parallel and perpendicular do not mean parallel and perpendicular in the strict sense, but mean a range of parallel ±5° and a range of perpendicular ±5°, respectively.

[0013] In this specification, each component may be a single substance corresponding to the component, or two or more substances may be used in combination. When two or more substances are used in combination for each component, the content of the component means the total content of the substances used in combination, unless otherwise specified.

[0014] In this specification, the bonding direction of a divalent group (e.g., -CO-O-, etc.) is not limited unless otherwise specified. For example, when Y is -CO-O- in a compound represented by the formula "X-Y-Z," the compound may be either "X-O-CO-Z" or "X-CO-O-Z."

[0015] <Liquid crystal composition for radio wave control element> The liquid crystal composition for radio wave control element of the present invention (hereinafter also simply referred to as "the composition") is a liquid crystal composition for radio wave control element containing two or more liquid crystal compounds, at least one of which is a compound represented by formula (1) described below (hereinafter also referred to as "specific compound").

[0016] Although the mechanism by which the present composition becomes a material with large refractive index anisotropy with respect to radio waves and high melting point depression is unclear, the inventors speculate as follows. Among the two or more liquid crystal compounds contained in the present composition, at least one liquid crystal compound is a specific compound. Because the specific compound has a structure in which multiple ring structures are linked via linking groups, the resulting material is likely to have large refractive index anisotropy with respect to radio waves. Meanwhile, compounds with such linked structures generally tend to have a high melting point, which can result in an elevated phase transition temperature to the liquid crystal phase. For example, one method for further lowering the melting point of a single liquid crystal compound is to mix it with a liquid crystal compound with an even lower melting point. However, depending on the type of liquid crystal compound, this method fails to meet the current melting point depression requirements, and further improvement is needed. In contrast, the present composition is presumed to have excellent melting point depression properties because the specific compound has multiple asymmetric carbon atoms at specific positions. Hereinafter, superiority in at least one of the effects of refractive index anisotropy with respect to radio waves and the effect of melting point depression is also referred to as "excellent effects of the present invention."

[0017] (Two or more liquid crystal compounds) The present composition contains two or more liquid crystal compounds, and at least one of the two or more liquid crystal compounds is a specific compound. For example, the present composition may contain two or more specific compounds, or may contain one or more specific compounds and one or more liquid crystal compounds other than the specific compounds. Hereinafter, the liquid crystal compounds other than the specific compounds will also be simply referred to as "other liquid crystal compounds."

[0018] The specific compound is a compound represented by formula (1).

[0019] Formula (1) R １ -L １ -A １ -(Z １ -B １ ) ｎ -L ２ -R ２

[0020] In formula (1), R １ and R ２ are each independently —CH ２- represents an alkyl group which may be substituted with -O- or -CO-O-, a cyano group, a halogen atom, -N=C=S, or -N=C=Se, provided that R １ and R ２ At least one of R represents the above alkyl group having an asymmetric carbon atom, １ and R ２ The total number of asymmetric carbon atoms contained in is 2 or more.

[0021] -CH ２ The alkyl group in which - may be substituted with -O- or -CO-O- preferably has an asymmetric carbon atom. An asymmetric carbon atom refers to a carbon atom in which all four of the atoms or atomic groups to which it is bonded are different. The number of asymmetric carbon atoms in the alkyl group is preferably 1 or more, more preferably 1 to 10, and even more preferably 1 to 5. The alkyl group may be linear, branched, or cyclic, and is preferably linear or branched. Furthermore, when the alkyl group has an asymmetric carbon atom, the alkyl group is preferably branched. The number of carbon atoms in the alkyl group is preferably 1 to 30, more preferably 1 to 25, and even more preferably 3 to 25.

[0022] The alkyl group is a group selected from the group consisting of —CH ２ - may be substituted with -O- or -CO-O-. For example, the alkyl group may be *-CH ２ -CH ２ —O—CO—CH ２ -CH ３ may be.

[0023] When the alkyl group has an asymmetric carbon atom, the alkyl group is preferably an alkyl group having a structure represented by formula (X). The alkyl group may have one or more structures represented by formula (X).

[0024] Formula (X) *-CH ２ -CH(CH ３ )-C ２ H ４ -*

[0025] In formula (X), * represents a bonding position.

[0026] The alkyl group may be a group represented by formula (W).

[0027] Formula (W) *-AL-C(R Ｗ１ ) (R Ｗ２ )-R Ｗ３

[0028] In formula (W), * represents a bonding position, and AL represents an alkylene group having no asymmetric carbon atom. Ｗ１ and R Ｗ２ each independently represents a hydrogen atom or an alkyl group having no asymmetric carbon atom; R Ｗ１ and R Ｗ２ represent different groups. Ｗ３ represents an alkyl group.

[0029] The alkylene group having no asymmetric carbon atom represented by AL may be linear, branched, or cyclic, and is preferably linear. The alkylene group preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms.

[0030] R Ｗ１ and R Ｗ２ The alkyl group having no asymmetric carbon atom represented by the formula (I) may be linear, branched, or cyclic, and is preferably linear. The number of carbon atoms in the alkyl group is preferably 1 to 10, and more preferably 1 to 3. Ｗ１ and R Ｗ２ represent different groups. Ｗ１ When represents a hydrogen atom, R Ｗ２ represents an alkyl group having no asymmetric carbon atom. Ｗ１ and R Ｗ２ may be the same group as long as they are different groups. For example, R Ｗ１ When represents a methyl group, R Ｗ２ R may be an alkyl group other than a methyl group that does not have an asymmetric carbon atom (for example, an ethyl group). Ｗ１ and R Ｗ２ Preferably, one of these represents a hydrogen atom, and the other represents an alkyl group having no asymmetric carbon atom.

[0031] R Ｗ３The alkyl group represented by may have an asymmetric carbon atom. The alkyl group may be linear, branched, or cyclic, and is preferably linear or branched. The number of carbon atoms in the alkyl group is preferably 1 to 25, more preferably 3 to 20. The alkyl group is preferably an alkyl group containing an isopropyl group. R Ｗ３ is R Ｗ１ and R Ｗ２ It is preferable that the ion exchange rate is different from any of the above.

[0032] However, R １ and R ２ At least one of R represents the above alkyl group having an asymmetric carbon atom, １ and R ２ The total number of asymmetric carbon atoms in R is 2 or more. １ and R ２ As long as at least one of R is the alkyl group having an asymmetric carbon atom, the other is not particularly limited, and R １ and R ２ Among them, R １ and R ２ Preferably, both of R and R represent the above alkyl groups having an asymmetric carbon atom. １ and R ２ It is also preferable that the alkyl groups having an asymmetric carbon atom are the same as those of the above-mentioned R １ and R ２ In the same manner as the alkyl group represented by the formula (I), —CH ２ - may be substituted with -O- or -CO-O-. １ and R ２ The total number of asymmetric carbon atoms contained in is 2 or more, preferably 3 or more, and more preferably 4 or more. The upper limit is preferably 10 or less, and more preferably 8 or less.

[0033] In formula (1), L １ and L ２ each independently represents a single bond, —O—, —CO—, —CO—O—, —O—CO—O—, or —NR ３ - or -CH=CH-, and O may be substituted with S. ３represents an alkyl group which may have a substituent.

[0034] L １ and L ２ In each group represented by the formula (I), "O (oxygen atom)" may be substituted with "S (sulfur atom)". １ and L ２ There are no particular limitations on the groups represented by the formula, but examples thereof include -S-, -CS-, -CO-S-, and -S-CO-O-. １ and L ２ is a single bond, —CH═CH—, —O—, —CO—O—, or —NR ３ - is preferred.

[0035] R ３ The alkyl group represented by the formula (I) may be linear, branched, or cyclic, with linear being preferred. The number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 5, and even more preferably 1 to 3. The alkyl group may have an asymmetric carbon atom, but preferably does not have an asymmetric carbon atom. Examples of the substituent that the alkyl group may have include, for example, the groups represented by the formula (I) (I) (I) (I). １ and B １ Examples of the substituents that can be possessed by the group represented by the formula:

[0036] In formula (1), A １ and B １ each independently represents an aromatic ring which may have a substituent or an aliphatic ring which may have a substituent. １ If there are multiple B １ They may be the same or different.

[0037] The aromatic ring and the aliphatic ring may be either a monocyclic ring or a polycyclic ring, or may be a fused ring. Examples of the aromatic ring include an aromatic hydrocarbon ring and an aromatic heterocyclic ring. Examples of the aromatic hydrocarbon ring include a benzene ring, a naphthalene ring, an anthracene ring, a pyrene ring, a phenanthrene ring, and a fluorene ring, with a benzene ring or a naphthalene ring being preferred. The aromatic heterocyclic ring is preferably an aromatic heterocyclic ring having at least one atom selected from the group consisting of a nitrogen atom and a sulfur atom as a ring member atom. Examples of the aromatic heterocycle include a pyridine ring, a pyrimidine ring, a pyridazine ring, a pyrazine ring, a triazine ring (e.g., a 1,2,3-triazine ring, a 1,2,4-triazine ring, and a 1,3,5-triazine ring), a tetrazine ring (e.g., a 1,2,4,5-tetrazine ring), a quinoxaline ring, a pyrrole ring, a furan ring, a thiophene ring, an imidazole ring, an oxazole ring, a thiazole ring, a benzopyrrole ring, a benzofuran ring, a benzothiophene ring, a benzimidazole ring, a benzoxazole ring, a benzothiazole ring, a naphthopyrrole ring, a naphthofuran ring, a naphthothiophene ring, a naphthoimidazole ring, a naphthoxazole ring, a pyrroloimidazole ring (e.g., a 5H-pyrrolo[1,2-a]imidazole ring), and an imidazooxazole ring (e.g., an imidazo[2,1-b]oxazole ring). , thienothiazole ring (for example, thieno[2,3-d]thiazole ring, etc.), benzothiadiazole ring, benzodithiophene ring (for example, benzo[1,2-b:4,5-b']dithiophene ring, etc.), thienothiophene ring (for example, thieno[3,2-b]thiophene ring, etc.), thiazolothiazole ring (for example, thiazolo[5,4-d]thiazole ring, etc.), naphthodithiophene ring (for example, naphtho[2,3- b:6,7-b']dithiophene ring, naphtho[2,1-b:6,5-b']dithiophene ring, naphtho[1,2-b:5,6-b']dithiophene ring, 1,8-dithiadicyclopenta[b,g]naphthalene ring, etc.), benzothienobenzothiophene ring, dithieno[3,2-b:2',3'-d]thiophene ring, and 3,4,7,8-tetrathiadicyclopenta[a,e]pentalene ring.Among these, the aromatic heterocycle is preferably a pyridine ring, a pyrimidine ring, a thiophene ring, a thiazole ring, or a fused ring formed by condensing two or more of these rings, and more preferably a pyrimidine ring or a thienothiazole ring.

[0038] Examples of the substituent that the aromatic ring and the aliphatic ring may have include halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc.), hydrocarbon groups (alkyl groups (including cycloalkyl groups, bicycloalkyl groups, and tricycloalkyl groups), alkenyl groups (including cycloalkenyl groups and bicycloalkenyl groups), alkynyl groups, and aryl groups), heterocyclic groups, cyano groups, isothiocyanate groups, nitro groups, alkoxy groups, aryloxy groups, silyl groups, silyloxy groups, heterocyclic oxy groups, acyloxy groups, carbamoyloxy groups, alkoxycarbonyloxy groups, aryloxy groups, and the like. Examples of the substituent include a carbonyloxy group, a primary, secondary, or tertiary amino group (including anilino), an alkylthio group, an arylthio group, a heterocyclic thio group, an alkyl or arylsulfinyl group, an alkyl or arylsulfonyl group, an acyl group, an aryloxycarbonyl group, an alkoxycarbonyl group, an aryl or heterocyclic azo group, an imido group, a phosphino group, a phosphinyl group, a phosphinyloxy group, a phosphinylamino group, a phosphono group, a carboxy group, a phosphate group, a sulfonic acid group, a hydroxy group, a thiol group, an acylamino group, a carbamoyl group, a ureido group, a boronic acid group, and a combination thereof. Among these, the substituent is preferably an alkyl group which may have an oxygen atom, a nitrogen atom, or a sulfur atom, an alkoxy group which may have an oxygen atom, a nitrogen atom, or a sulfur atom, a halogen atom, a cyano group, or an isothiocyanate group, and more preferably an alkyl group or a halogen atom. The alkyl group and the alkoxy group may have an oxygen atom, a nitrogen atom, or a sulfur atom. For example, the alkyl group and the alkyl group in the alkoxy group may be —CH ２ - is -O-, -S-, -CO-, -CS-, -CO-O-, -CO-NR Ｎ -, -NR Ｎ -, or a combination thereof. Ｎrepresents a hydrogen atom or an alkyl group. The alkyl group and the alkoxy group preferably have 1 to 10 carbon atoms, and more preferably have 1 to 6 carbon atoms.

[0039] In formula (1), Z １ represents a single bond, —O—, —CO—, —CO—O—, —O—CO—O—, —CR Ｚ =CR Ｚ -, -C≡C-, -N=N-, -CR Ｚ =CR Ｚ -CR Ｚ =CR Ｚ -, -C≡C-C≡C-, -CR Ｚ =CR Ｚ -CO- or -CR Ｚ =CR Ｚ represents —CO—O—, where O may be substituted with S. Ｚ each independently represents a hydrogen atom or a fluorine atom. １ If there are multiple Z １ They may be the same or different.

[0040] Z １ In each group represented by the formula (I), "O (oxygen atom)" may be substituted with "S (sulfur atom)". Z substituted with "S (sulfur atom)" １ Although there is no particular limitation on each group represented by the formula (I), examples thereof include -S-, -CS-, -CO-S-, -S-CO-O-, -CR Ｚ =CR Ｚ -CS- and -CR Ｚ =CR Ｚ -CO-S-. １ is preferably a single bond, —O—, —CO—O—, —C≡C— or —N═N—, more preferably a single bond, —C≡C— or —N═N—, and still more preferably —N═N—. １ It is also preferred that at least one of Z is -N=N-. １ More preferably, all of are -N=N-.

[0041] In formula (1), n ​​represents an integer of 1 to 4. n is preferably an integer of 1 to 3 or an integer of 2 to 4.

[0042] An example of a preferred embodiment of the specific compound is shown below. The specific compound preferably satisfies requirement X and at least one of requirements Y1 and Y2. Furthermore, the specific compound preferably satisfies requirement X and at least one of requirements Z1 and Z2. Requirement X: In formula (1), Z １ At least one of R is -N=N-. １ and R ２ At least one of the above is an alkyl group having a partial structure represented by the above formula (X). １ and B １ are each independently an aromatic hydrocarbon ring, and n is an integer of 2 to 4. Requirement Y2: In formula (1), R １ and R ２ are the same group, and L １ and L ２ is —CH═CH—, —O—, or —NR ３ Requirement Z1: In formula (1), A １ and B １ At least one of A is an aromatic heterocycle, and n is an integer of 1 to 3. Requirement Z2: In formula (1), A １ and B １ At least one of the groups is a thienothiazole ring.

[0043] The specific compound is preferably a racemate, i.e., a so-called racemic mixture. In this specification, the term "racemate" refers to a specific compound having an asymmetric carbon atom, in which, when the specific compound has n asymmetric carbon atoms (n is an integer of 2 or more), the number of R-form molecules and S-form molecules at the ith asymmetric carbon atom (i=1 to n) is N. Ｒｉ , N Ｓｉ When N Ｒｉ / (N Ｒｉ +N Ｓｉ ) means that it is 0.4 to 0.6. Ｒｉ / (N Ｒｉ +N Ｓｉ) is preferably 0.45 to 0.55, and more preferably 0.5. When the specific compound having an asymmetric carbon is a racemate containing equal amounts of chiral isomers, twisted orientation is less likely to occur in a layer formed using the composition, and the refractive index of the specific compound can be more easily changed by application of an electric field.

[0044] The specific compound may be used alone or in combination of two or more. The content of the specific compound is preferably 1% by mass or more, more preferably 10% by mass or more, and even more preferably 30% by mass or more, based on the total solid content of the liquid crystal composition for radio wave control elements. The upper limit is preferably less than 100% by mass, more preferably 80% by mass or less, and even more preferably 60% by mass or less, based on the total solid content of the liquid crystal composition for radio wave control elements. The solid content refers to components excluding the solvent, and components other than the solvent are considered to be solids even if they are in a liquid state.

[0045] The other liquid crystal compounds are not particularly limited as long as they are liquid crystal compounds other than the specific compound. Generally, liquid crystal compounds can be classified into rod-shaped and discotic types based on their shape. Each type can further be divided into low-molecular-weight and high-molecular-weight types. The high-molecular-weight type generally refers to a compound with a degree of polymerization of 100 or more (see "Polymer Physics: Phase Transition Dynamics," by Masao Doi, p. 2, Iwanami Shoten, 1992).

[0046] The other liquid crystal compound is preferably a rod-shaped liquid crystal compound or a discotic liquid crystal compound (discotic liquid crystal compound). The other liquid crystal compound may be any of two or more rod-shaped liquid crystal compounds, two or more discotic liquid crystal compounds, or a mixture of a rod-shaped liquid crystal compound and a discotic liquid crystal compound. The other liquid crystal compound may have either forward wavelength dispersion or reverse wavelength dispersion.

[0047] The other liquid crystal compound may be a liquid crystal compound having a polymerizable group (polymerizable liquid crystal compound). The polymerizable liquid crystal compound is preferably at least one polymerizable liquid crystal compound selected from the group consisting of polymerizable rod-shaped liquid crystal compounds and polymerizable discotic liquid crystal compounds. Examples of the polymerizable group include an acryloyl group, a methacryloyl group, an epoxy group, and a vinyl group. The orientation of the liquid crystal compound can be fixed by polymerizing the polymerizable liquid crystal compound. It is not necessary for the liquid crystal compound to exhibit liquid crystallinity after being fixed by polymerization.

[0048] Examples of rod-shaped liquid crystal compounds include those described in claim 1 of JP-A No. 11-513019 and paragraphs

[0026] to

[0098] of JP-A No. 2005-289980. Examples of discotic liquid crystal compounds include those described in paragraphs

[0020] to

[0067] of JP-A No. 2007-108732 and paragraphs

[0013] to

[0108] of JP-A No. 2010-244038.

[0049] As the other liquid crystal compound, a compound represented by formula (2) is preferred. ３ -L １ -A １ -(Z １ -B １ ) ｎ -L ２ -R ４ L in formula (2) １ , L ２ , A １ , B １ , Z １ The definitions and preferred embodiments of R and n are the same as those of each group in formula (1). ３ and R ４ is -CH ２ - represents an alkyl group which may be substituted with -O- or -CO-O-, a cyano group, a halogen atom, -N=C=S, or -N=C=Se, provided that R ３ and R ４ The total number of asymmetric carbon atoms in R is 0 or 1. ３ and R ４ Represented by -CH ２The alkyl group in which - may be substituted with -O- or -CO-O- preferably has no asymmetric carbon atom or one asymmetric carbon atom, and more preferably has no asymmetric carbon atom. ３ and R ４ are preferably the above alkyl groups each having no asymmetric carbon atom. The alkyl groups may be linear, branched, or cyclic, and are preferably linear or branched. The number of carbon atoms in the alkyl groups is preferably 1 to 30, more preferably 1 to 25, and even more preferably 3 to 25.

[0050] The other liquid crystal compounds may be used alone or in combination of two or more. The content of the other liquid crystal compounds is preferably 99% by mass or less, more preferably 90% by mass or less, and even more preferably 70% by mass or less, based on the total solid content of the liquid crystal composition for radio wave control elements. The lower limit is preferably 0% by mass or more, more preferably 20% by mass or more, and even more preferably 60% by mass or more, based on the total solid content of the liquid crystal composition for radio wave control elements.

[0051] The present composition preferably contains substantially no solvent, which means that the solvent content is 5% by mass or less, and preferably 3% by mass or less, based on the total mass of the liquid crystal composition for radio wave control elements.

[0052] <Radio wave control element> The composition can be applied to a radio wave control element. The radio wave control element acts on radio waves. Examples of radio waves include radio waves with a frequency of 0.007 to 0.3 THz. Radio waves in this frequency band (RW) are called high-frequency radio waves (centimeter waves, millimeter waves, terahertz waves, etc.), and are capable of high-capacity wireless communication while also having a high degree of directional propagation.

[0053] An example of a radio wave control element is a radio wave control element having, in this order, a first electrode, a liquid crystal composition layer made of the present composition, and a second electrode. In the radio wave control element, applying a voltage between the first and second electrodes controls the orientation of the liquid crystal compounds (specific compounds and other liquid crystal compounds) contained in the liquid crystal composition layer, thereby adjusting the refractive index anisotropy of the liquid crystal composition layer and thereby adjusting the propagation direction of radio waves. In a liquid crystal composition layer made of the present composition, the orientation state of the liquid crystal compound can be changed by applying a voltage. This characteristic is particularly likely to be exhibited when the liquid crystal compound exhibits liquid crystallinity. In a liquid crystal composition layer made of the present composition, controlling the orientation state of the liquid crystal compound can result in a state exhibiting large refractive index anisotropy. Generally, the response speed of a radio wave control element depends on the film thickness of the liquid crystal composition layer. Because a liquid crystal composition layer made of the present composition can assume a state exhibiting large refractive index anisotropy, the film thickness of the liquid crystal composition layer can be reduced, resulting in improved response speed. Therefore, the reflection direction of incident radio waves can be switched in a short time.

[0054] Specific examples of radio wave control elements will be described below with reference to the drawings. A radio wave control element 10 according to the technology of the present disclosure is used in a radio wave reflecting device 2 shown in FIG. 1 . The radio wave reflecting device 2 is capable of reflecting highly directional radio waves RW emitted from an antenna ANT located behind a building BL toward an area AR1 in front of the building BL, which is in the shadow of the antenna ANT. The radio wave reflecting device 2 is also capable of changing the reflection direction of the radio waves RW to different directions in multiple areas AR1 and AR2. For example, the area where many users are present may change depending on the time of day, such as when many wireless communication users are present in area AR1 during the daytime and in area AR2 during the nighttime. In such cases, the radio wave reflecting device 2 can change the area to which the radio waves RW are supplied by changing the reflection direction of the radio waves RW depending on the time of day.

[0055] As shown in FIG. 2 , the radio wave control element 10 has a metasurface structure 12 and is a reflective radio wave control element that reflects the propagation direction of radio waves RW in a desired direction. The metasurface structure 12 is a structure that uses metamaterials. Metamaterials are artificial materials that exhibit properties not found in natural materials, such as a negative refractive index for radio waves. The radio wave control element 10 is configured with a plurality of unit cells UC arranged two-dimensionally, and the two-dimensional plane formed by the arrangement of the plurality of unit cells UC serves as a reflection surface for the radio waves RW. Each unit cell UC includes a microstructure 14 as a metamaterial, and constitutes the smallest unit on the reflection surface that can actively change the phase of the radio waves RW. The microstructure 14 is made of metal, for example. The microstructure 14 is sized on the order of the wavelength of the incident radio waves RW or less and functions as a resonator that resonates through interaction with the incident radio waves RW. Electrically, the microstructure 14 can be considered equivalent to a resonant circuit, for example, a coil and a capacitor connected in series to resonate an alternating current. The phase of the incident radio wave RW changes due to the resonance action of the microstructure 14. Furthermore, by actively changing the resonance conditions of the microstructure 14 using various methods, it is also possible to control the amount of phase delay of the radio wave RW.

[0056] The radio wave control element 10 mainly acts on radio waves RW with a frequency of 0.007 to 0.3 THz. In the radio wave control element 10, the metasurface structure 12 is configured to act on radio waves RW with a frequency of 0.1 to 0.3 THz. The wavelength of radio waves RW with a frequency of 0.1 to 0.3 THz is 1 to 3 mm, and the size of the microstructures 14 that make up the metasurface structure 12 is, for example, on the order of about half the wavelength. By making the size of the microstructures 14 equal to or less than the wavelength of the radio waves RW, the microstructures 14 resonate with the radio waves RW that pass through them, and function as a phase modulation element that modulates the phase of the radio waves RW.

[0057] As shown in FIG. 3 by the incident direction IN and the outgoing direction OUT, the overall traveling direction of the radio wave RW can be considered as the normal direction to the line connecting the wavefronts of the multiple radio waves RW. In the radio wave control element 10, for example, consider gradually increasing the phase delay of the radio wave RW incident on and reflected from each of the multiple unit cells UC arranged in a one-dimensional manner from the right-hand unit cell UC to the left-hand unit cell UC. In this case, even if the line connecting the wavefronts of the individual incident radio waves RW is parallel to the reflecting surface, the line connecting the wavefronts of the individual radio waves RW reflected by each unit cell UC is inclined with respect to the reflecting surface. In other words, the outgoing direction OUT, which is the traveling direction of the radio wave RW emitted from the reflecting surface, changes by an angle θ with respect to the incident direction IN of the radio wave RW. In this way, the traveling direction of the radio wave RW can be controlled by performing phase modulation, i.e., controlling the phase delay, for each unit cell UC.

[0058] As a result, while a normal reflector can only change the direction of propagation of the radio wave RW in the direction of specular reflection, the radio wave reflecting device 2 can change the direction of propagation of the radio wave RW in a direction other than specular reflection by using the metasurface structure 12. In addition, by actively changing the amount of phase delay in each unit cell UC, it becomes possible to actively change the direction of propagation of the radio wave RW.

[0059] As an example, as conceptually shown in Figure 4, a radio wave control element 10 uses a liquid crystal composition layer 20 as an element that actively changes the resonance conditions of the microstructures 14 of the metasurface structure 12. The radio wave control element 10 has, from the bottom in the figure, a first electrode layer 26, a liquid crystal composition layer 20, and the metasurface structure 12, in this order. The liquid crystal composition layer 20 is provided on a support 24. Furthermore, the first electrode layer 26 is provided so as to entirely cover the surface of the support 24 opposite to the liquid crystal composition layer 20. The liquid crystal composition layer 20 contains a liquid crystal compound (liquid crystal compound LD).

[0060] Each unit cell UC is configured to include a microstructure 14, a liquid crystal composition layer 20, and a first electrode layer 26. Of these, the microstructure 14 is provided individually for each unit cell UC. The remaining components, the support 16, the liquid crystal composition layer 20, the support 24, and the first electrode layer 26, are not independent components for each unit cell UC, but are integrally formed in regions corresponding to a plurality of unit cells UC.

[0061] In the radio wave control element 10, the first electrode layer 26 and the support 24, and the liquid crystal composition layer 20 and the support 16 are attached using an adhesive (pressure-sensitive adhesive or adhesive) as necessary. There are no limitations on the attachment method, and various known methods that are permeable to the radio waves that the radio wave control element 10 targets, such as a method that uses an OCA (Optical Clear Adhesive) that is permeable to the radio waves that the radio wave control element 10 targets, can be used.

[0062] As an example, the microstructure 14 is formed of a conductive material and doubles as an electrode that forms an electrode pair with the first electrode layer 26. Furthermore, a power supply 28 is connected to each microstructure 14 for applying a voltage between the microstructure 14 and the first electrode layer 26. This makes it possible to control the magnitude of the voltage applied to each unit cell UC. The first electrode layer 26 is a common electrode shared by each unit cell UC, and the microstructure 14 of each unit cell UC functions as an individual electrode. The first electrode layer 26 functioning as a common electrode is an example of a "first electrode" according to the technology of the present disclosure, and the individual electrode shared by the microstructure 14 is an example of a "second electrode." The microstructure 14 as the second electrode and the first electrode layer 26 as the first electrode are an example of an "electrode pair for applying a voltage."

[0063] The radio wave control element 10 is of a reflective type, and the first electrode layer 26 also serves as a reflective layer that reflects the radio wave RW.

[0064] In the liquid crystal composition layer 20, the orientation state (hereinafter also referred to as the orientation pattern) of the liquid crystal compound changes upon application of a voltage. The alignment direction of the microstructures 14 of each unit cell UC is a direction (X direction or Y direction in the figure) perpendicular to the thickness direction of the liquid crystal composition layer 20 (Z direction in the figure). Here, the microstructures 14 and the first electrode layer 26 are disposed on both sides of the thickness direction of the liquid crystal composition layer 20. By supplying power from a power source 28, a voltage is applied between the microstructures 14 and the first electrode layer 26 of each unit cell UC. The application of the voltage generates an electric field in the thickness direction of the liquid crystal composition layer 20, changing the orientation state of the liquid crystal compound LD in each unit cell UC. Furthermore, the orientation state of the liquid crystal compound LD in each unit cell UC can be adjusted by adjusting the voltage applied to each unit cell UC.

[0065] As shown in Fig. 5, the liquid crystal compound LD has a cross section of a substantially elliptical shape having a major axis and a minor axis. As an example, when no voltage is applied between the microstructure 14 and the first electrode layer 26, which function as an electrode pair, no electric field is generated in the liquid crystal composition layer 20. In this state, as conceptually shown in the upper part of Fig. 5, the liquid crystal compound LD is aligned such that its major axis is aligned in the thickness direction of the liquid crystal composition layer 20. In the following description, this alignment state will also be referred to as "vertical alignment".

[0066] When a voltage is applied between the microstructures 14 and the first electrode layer 26 from this state, an electric field is generated in the liquid crystal composition layer 20, and the alignment state of the liquid crystal compound LD changes. Specifically, as conceptually shown in the lower part of Figure 5, the alignment state of the liquid crystal compound LD in the region corresponding to the microstructures 14 changes depending on the magnitude of the applied voltage, and the liquid crystal compound LD is tilted with respect to the thickness direction of the liquid crystal composition layer 20. The example shown in the lower part of Figure 5 shows a state in which the tilt angle of the liquid crystal compound LD is maximum. When the tilt angle is maximum, the liquid crystal compound LD is aligned so that its major axis is aligned in a direction perpendicular to the thickness direction of the liquid crystal composition layer 20. In the following description, the alignment state in which the tilt angle is maximum is also referred to as "horizontal alignment."

[0067] The refractive index of the liquid crystal composition layer 20 increases as the tilt of the liquid crystal compound LD increases, i.e., as the angle of the long axis of the liquid crystal compound LD approaches the principal surface direction of the liquid crystal composition layer 20 (the X or Y direction in FIG. 5 ). Conversely, the refractive index of the liquid crystal composition layer 20 decreases as the tilt of the liquid crystal compound LD decreases, i.e., as the angle of the long axis of the liquid crystal compound LD approaches the thickness direction of the liquid crystal composition layer 20 (the Z direction in the figure). Such a change in the refractive index of the liquid crystal composition layer 20 of each unit cell UC changes the resonance condition of the microstructure 14, thereby changing the amount of phase delay of the incident radio wave RW. In this example, the amount of phase delay of the unit cell UC in the lower row of FIG. 5 is greater than that of the unit cell UC in the upper row of FIG. 5 .

[0068] That is, when the alignment state of the liquid crystal compound LD in the liquid crystal composition layer 20 located around the microstructures 14 of each unit cell UC changes, the refractive index of the liquid crystal composition layer 20 changes with respect to the radio wave RW transmitted through each unit cell UC. Because the refractive index and the dielectric constant are positively correlated, a change in the refractive index of the liquid crystal composition layer 20 changes the resonance conditions of the microstructures 14, which function as a resonator. The change in the resonance conditions of the microstructures 14 manifests as a change in the phase delay of the radio wave RW. Therefore, changing the refractive index of the liquid crystal composition layer 20 can change the phase delay of the radio wave RW. Furthermore, a change in the refractive index of the liquid crystal composition layer 20 itself also causes a change in the phase delay of the radio wave RW. Because the refractive index of the liquid crystal composition layer 20 of each unit cell UC changes depending on the voltage V applied to each unit cell UC, the relationship between the voltage V and the phase delay of the radio wave RW is, for example, as shown in FIG. 6 .

[0069] As shown in FIG. 3 , when a radio wave RW is incident on the radio wave control element 10 from the microstructure 14 side, the radio wave RW passes through the microstructure 14 and the liquid crystal composition layer 20 in this order. Furthermore, the radio wave RW is reflected by the first electrode layer 26, which also serves as a reflective layer, and again passes through the liquid crystal composition layer 20 and the microstructure 14 in this order before exiting the radio wave control element 10. The radio wave RW is reflected along this incident / exit path. Along the incident / exit path, the radio wave RW passing through each unit cell UC is phase-modulated by resonance with the microstructure 14 and also phase-modulated by passing through the liquid crystal composition layer 20. More specifically, in each unit cell UC, the resonance condition of the microstructure 14 is determined according to the refractive index of the liquid crystal composition layer 20, and the phase modulation of the radio wave RW occurs due to resonance according to the condition. In addition, the phase modulation of the radio wave RW also occurs according to the magnitude of the refractive index of the liquid crystal composition layer 20.

[0070] Based on the relationship shown in FIG. 6, the reflection direction of the radio wave RW reflected at the radio wave control element 10 is controlled by controlling the amount of phase delay of the radio wave RW for each unit cell UC through the applied voltage V.

[0071] 3, while a normal reflector can only change the direction of propagation of the radio wave RW in the direction of specular reflection, the radio wave control element 10 can change the direction of propagation of the radio wave RW in a direction other than specular reflection by using the metasurface structure 12. In addition, by actively changing the amount of phase delay in each unit cell UC, it is possible to actively change the direction of propagation of the radio wave RW.

[0072] Furthermore, various examples of controlling the traveling direction of the radio wave RW emitted from the radio wave control element 10 are possible other than controlling the reflected radio wave RW so that it travels straight in one direction as a whole as in the example shown in Figure 3. For example, the radio wave RW emitted from the radio wave control element 10 may be made to converge toward a single focal point, or conversely, may be made to diverge. The traveling direction of the emitted radio wave RW can be controlled by adjusting the voltage applied to each unit cell UC, thereby adjusting the amount of phase delay of the radio wave RW for each unit cell UC.

[0073] For example, in the case of a plurality of unit cells UC arranged in one direction as shown in FIG. 3 , consider increasing the phase delay of the central unit cell UC and decreasing the phase delay toward both sides. In this case, connecting the wavefronts of the radio waves RW passing through each unit cell UC forms a V-shape, allowing the emitted radio waves RW to be focused. Conversely, consider decreasing the phase delay of the central unit cell UC and increasing the phase delay toward both sides. In this case, connecting the wavefronts of the radio waves RW passing through each unit cell UC forms a mountain-like shape (inverted V-shape), allowing the emitted radio waves RW to be diverged. The degree of such focusing and divergence can also be adjusted by controlling the phase delay of the radio waves RW passing through each unit cell UC through adjusting the magnitude of the applied voltage.

[0074] Similar to known metasurface structures, the metasurface structure 12 is formed by two-dimensionally arranging microstructures 14, which are metamaterials, on a support 16. In the illustrated metasurface structure 12, as shown in Fig. 2, the microstructures 14 are two-dimensionally arranged at equal intervals in the X and Y directions, which are orthogonal to each other. In this metasurface structure 12, all of the microstructures 14 are, for example, the same.

[0075] There are no limitations on the support 16, and various known sheet-like materials can be used as long as they can support the microstructure 14 and can transmit radio waves RW of 0.007 to 0.3 THz, which is the frequency targeted by the radio wave control element 10. Examples of the support 16 include a metal substrate having an oxide insulating layer such as a silicon substrate having silicon oxide, a support made of an oxide such as silicon oxide, a support made of a semiconductor such as germanium and chalcogenide glass, a polyacrylic resin film such as polymethyl methacrylate, a cellulose resin film such as cellulose triacetate, a cycloolefin polymer film (for example, a product under the trade name "Arton" manufactured by JSR Corporation, or a product under the trade name "Zeonor" manufactured by Zeon Corporation), a resin film such as a polyethylene terephthalate (PET) film, a polycarbonate film, and a polyvinyl chloride film, and a glass plate.

[0076] There is no limitation on the thickness of the support 16, as long as it can support the microstructure 14, has sufficient transparency to radio waves RW with a frequency of 0.007 to 0.3 THz, and further has sufficient strength depending on the application of the radio wave control element 10. The thickness of the support 16 is set appropriately depending on the material from which the support 16 is made so as to satisfy these conditions.

[0077] In the radio wave control element 10 according to the technology of the present disclosure, the support 16 is not an essential component of the metasurface structure 12, and the support 16 may be omitted. For example, if possible, the metasurface structure 12 may be formed by arranging the microstructures 14 directly on the surface of the liquid crystal composition layer 20.

[0078] As described above, the metasurface structure 12 is composed of microstructures 14, which are metamaterials, spaced apart and arranged two-dimensionally on a plane, and more specifically, is composed of an arrangement of unit cells UC, each of which basically consists of one microstructure 14 and the space surrounding the microstructure 14.

[0079] In the radio wave control element 10 according to the technology of the present disclosure, the shape of the metasurface structure is basically the same as that of known metasurface structures. Therefore, various known metasurface structures can be used in the radio wave control element 10 according to the technology of the present disclosure. That is, in the technology of the present disclosure, there are no limitations on the shape and material of the microstructures 14, the arrangement of the microstructures 14, or the pitch between the microstructures 14. Furthermore, the metasurface structure 12 may be designed using known methods depending on the wavelength of the radio wave RW to be controlled by the radio wave control element 10 and the target reflection characteristics (e.g., the range of controllable reflection directions). As an example, the amplitude and phase of the radio wave RW reflected by the microstructures 14 used may be calculated using commercially available simulation software, and the arrangement of the microstructures 14 may be set to achieve the desired distribution of phase modulation amounts. When a liquid crystal composition layer 20 is used as in this example, phase modulation occurs due to the refractive index and the interaction between the refractive index and the microstructures 14. The amount of phase modulation is determined by the resonance characteristics of the microstructures 14, which change depending on the refractive index.

[0080] The radio wave control element 10 according to the technology of the present disclosure is intended to control radio waves RW with frequencies of 0.007 to 0.3 THz. Therefore, the metasurface structure 12 has microstructures 14 selected so as to impart a desired phase difference to the radio waves RW of this frequency, and the arrangement of the microstructures is also set. Specifically, when radio waves RW with frequencies of 0.1 to 0.3 THz are to be controlled, the wavelength range of the radio waves RW is approximately 1 to 3 mm, so the size of the microstructures 14 is selected to be equal to or smaller than this wavelength range.

[0081] Although one unit cell UC basically has one microstructure 14, the technology of the present disclosure is not limited to this. That is, in the radio wave control element according to the technology of the present disclosure, one unit cell UC may have multiple microstructures 14 as necessary depending on the reflection characteristics, the size, material and shape of the microstructures 14, and the size of the unit cell UC. In this case, one unit cell UC may have different microstructures 14. However, because the unit cell UC is the smallest unit capable of actively changing the phase of the radio wave RW, even when one unit cell UC has multiple microstructures 14, the amount of phase modulation is determined for each unit cell UC.

[0082] Furthermore, there are no limitations on the material for forming the microstructure 14, and various materials used as microstructures in known metasurface structures can be used. Examples of materials for forming the microstructure 14 include metals and dielectrics. In the case of metals, copper, gold, and silver are preferred due to their low optical loss. In addition, composites consisting of metal particles and binders and oxide semiconductors can also be used as materials for forming the microstructure 14. On the other hand, in the case of dielectrics, silicon, titanium oxide, and germanium are preferred due to their high refractive index and the ability to increase the amount of phase modulation. Note that, as shown in FIG. 4 , when the microstructure 14 also serves as an electrode that forms an electrode pair with the first electrode layer 26, the microstructure 14 is formed from a conductor.

[0083] Similarly, the shape of the microstructure 14 is not limited, and various shapes used as microstructures in known metasurface structures can be used. Examples include a cross-shaped solid like a crossed rectangular parallelepiped, a rectangular parallelepiped, a cylindrical shape, a V-shaped solid like a rectangular parallelepiped connected at its ends as shown in JP 2018-046395 A, an approximately H-shaped solid like an H-beam, and an approximately C-shaped solid like a C-channel. Furthermore, as shown in JP 2018-046395 A, various shapes can be used for the V-shaped solid and the cross-shaped solid by adjusting the angle between the two rectangular parallelepipeds. Other shapes, such as those shown in Figure 5 of "Appl. Sci. 2018, 8(9), 1689; https: / / doi.org / 10.3390 / app8091689," can also be used.

[0084] In the metasurface structure 12, the microstructures 14 may be of the same type, or multiple types may be used in combination. Furthermore, the same microstructures 14 may be arranged in the same orientation in the XY plane, or in different orientations. Furthermore, microstructures 14 of the same orientation and those of different orientations may be mixed. However, in the radio wave control element 10 according to the technology of the present disclosure, it is preferable to use only one type of microstructure 14 and to arrange all of the microstructures 14 in the same orientation.

[0085] 3, a preferred embodiment of the metasurface structure 12 is one in which the same microstructures 14, all of which have the same structure, are arranged two-dimensionally at equal intervals in the X and Y directions, which are orthogonal to each other. However, the technology of the present disclosure is not limited to this, and multiple types of microstructures may be used in combination as described above. Furthermore, the arrangement intervals and arrangement of the microstructures 14 may also differ in the surface direction of the support 16. However, considering the controllability of the reflection direction of the radio wave RW when a voltage is applied to the liquid crystal composition layer 20, it is preferable that the metasurface structure 12 use all the same microstructures 14. Furthermore, it is more preferable that the microstructures 14 in the metasurface structure 12 are spaced at equal intervals, and even more preferably at equal intervals in both the X and Y directions, which are orthogonal to each other.

[0086] The liquid crystal composition layer 20 is a layer in which the liquid crystal compound LD is aligned in a preset state, and as described above, the alignment state of the liquid crystal compound LD changes when a voltage is applied.

[0087] In the liquid crystal composition layer 20 illustrated in Fig. 4, the liquid crystal compound LD is vertically aligned when no voltage is applied. When a voltage is applied to the liquid crystal composition layer 20, the liquid crystal compound LD is aligned at an angle relative to the thickness direction in response to the applied voltage, and reaches a maximum horizontal alignment. In the radio wave control element 10, the change in alignment of the liquid crystal compound LD is not limited to a change from vertical alignment to horizontal alignment or vice versa, but may be a change from a state tilted relative to the thickness direction to a horizontal or vertical alignment, a change from a horizontal or vertical alignment to a state tilted relative to the thickness direction, or a change at an angle from a state tilted relative to the thickness direction to a state tilted relative to the thickness direction.

[0088] The liquid crystal composition layer 20 may be formed, for example, on the surface of an alignment film described later by a known method. In the radio wave control element 10, the liquid crystal composition layer 20 is formed on a support 24. The support 24 is basically the same as the support 16 described above.

[0089] Here, the support 24 on which the liquid crystal composition layer 20 is formed may further include an alignment film for aligning the liquid crystal compound LD in a predetermined state on the surface of the support 16 described above, which serves as the main body, on which the liquid crystal composition layer 20 is formed. Various known alignment films can be used. Examples include rubbed films made of organic compounds such as polymers, obliquely evaporated films of inorganic compounds, films with microgrooves, and films formed by accumulating LB (Langmuir-Blodgett) films made by the Langmuir-Blodgett method using organic compounds such as ω-tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearate. Furthermore, so-called photoalignment films, which are formed by irradiating a photoalignable material with polarized or unpolarized light, can also be used as the alignment film. These alignment films can be formed by known methods depending on the material forming the main body.

[0090] The surface of the support 24 on which the liquid crystal composition layer 20 is formed, opposite to the liquid crystal composition layer 20, is entirely covered with a first electrode layer 26. The first electrode layer 26 is an electrode that changes the orientation of the liquid crystal compound LD in the liquid crystal composition layer 20, and also functions as a reflective layer that reflects radio waves RW with a frequency of 0.007 to 0.3 THz that are incident from the metasurface structure 12 side, as described above.

[0091] There are no limitations on the first electrode layer 26, and a sheet-like material made of various known materials can be used as long as it has sufficient conductivity and is capable of reflecting radio waves RW. Examples of the first electrode layer 26 include metal layers such as copper, aluminum, gold, and silver; inorganic conductive materials such as ITO (tin-doped indium oxide); organic conductive materials such as polythiophenes, typified by PEDOT (poly 3,4-ethylenedioxythiophene); and graphene. Inorganic conductive materials, organic conductive materials, and graphene are transparent to visible light, but act as reflective layers for radio waves of the above frequencies.

[0092] There is no limitation on the thickness of the first electrode layer 26, and the thickness may be set appropriately depending on the material from which the first electrode layer 26 is made so that the target radio waves can be reflected with the required reflectivity.

[0093] As described above, the radio wave control element 10 according to the technology of the present disclosure is a reflective radio wave control element having a metasurface structure 12 and a liquid crystal composition layer 20. In the radio wave control element 10, power is supplied to each microstructure 14 to change the alignment state of the liquid crystal compound LD in the corresponding region of the liquid crystal composition layer 20, thereby forming regions with different refractive indices for each unit cell UC, thereby reflecting the radio wave RW in the desired direction. Furthermore, by changing the power supplied to each microstructure 14, i.e., the voltage applied to the liquid crystal composition layer 20, the reflection direction of the incident radio wave RW can be switched.

[0094] In the radio wave control element 10 according to the technology of the present disclosure, the refractive index anisotropy of the liquid crystal composition layer 20 with respect to radio waves is not limited, but is preferably large. Here, in the reflective radio wave control element 10 of this example, the refractive index anisotropy of the liquid crystal composition layer 20 with respect to radio waves of 100 GHz is preferably 0.35 or more. By making the refractive index anisotropy of the liquid crystal composition layer 20 with respect to radio waves of 100 GHz 0.35 or more, the liquid crystal composition layer 20 can be made thinner, which is preferable in that the reflection direction of the radio waves RW can be switched more quickly.

[0095] Furthermore, there is no limitation on the thickness of the liquid crystal composition layer 20, and a thickness that provides the necessary phase difference for the radio wave RW may be appropriately set depending on the material for forming the liquid crystal composition layer 20. As described above, in the radio wave control element 10 according to the technology of the present disclosure, the liquid crystal composition layer 20 is made of the present composition containing a predetermined amount of liquid crystal compound, and therefore the liquid crystal composition layer 20 can be made thin. In consideration of this point, the thickness of the liquid crystal composition layer 20 is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less. Setting the thickness of the liquid crystal composition layer 20 to 200 μm or less is preferable in that the reflection direction of the radio wave RW can be switched more quickly, for example.

[0096] <Compound> The compound of the present invention is not particularly limited as long as it is the above-mentioned specific compound. As the specific compound, a compound represented by the following formula (1) is preferred. Compound represented by formula (1). Formula (1) R １ -L １ -A １ -(Z １-B １ ) ｎ -L ２ -R ２ In formula (1), R １ and R ２ are each independently —CH ２ - represents an alkyl group which may be substituted with -O- or -CO-O-, a cyano group, a halogen atom, -N=C=S, or -N=C=Se, provided that R １ and R ２ at least one of R represents the alkyl group having a partial structure represented by formula (X); １ and R ２ The total number of asymmetric carbon atoms contained in L is 2 or more. １ and L ２ each independently represents a single bond, —O—, —CO—, —CO—O—, —O—CO—O—, or —NR ３ - or -CH=CH-, and O may be substituted with S. ３ represents an alkyl group which may have a substituent. １ and B １ each independently represents an aromatic ring or an aliphatic ring. １ represents a single bond, —O—, —CO—, —CO—O—, —O—CO—O—, —CR Ｚ =CR Ｚ -, -C≡C-, -N=N-, -CR Ｚ =CR Ｚ -CR Ｚ =CR Ｚ -, -C≡C-C≡C-, -CR Ｚ =CR Ｚ -CO- or -CR Ｚ =CR Ｚ represents —CO—O—; Z １ At least one of R represents -N=N-, and O may be substituted with S. Ｚ represents a hydrogen atom or a fluorine atom, and n represents an integer of 1 to 4. Formula (X) *-CH ２ -CH(CH ３ )-C ２ H ４ -* In formula (X), * represents a bonding position. The definition and preferred embodiments of each symbol are the same as those for the specific compound described above.

[0097] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[0098] <Specific Compound> Specific compound A-1 was synthesized according to the following procedure.

[0099]

[0100] 3,7-Dimethyl-1-octanol (8 g), tosyl chloride (10 g), and triethylamine (5 g) were dissolved in ethyl acetate (50 mL) and stirred at room temperature for 6 hours. The mixture was separated and washed with ethyl acetate and water. The organic phase was dried over magnesium sulfate and then concentrated to obtain colorless liquid compound Cp-1a (15 g). Next, 6-bromo-2-naphthol (4.5 g), compound Cp-1a (6.3 g) obtained by the method described above, and potassium carbonate (2.8 g) were dissolved in N,N-dimethylacetamide (DMAc) (50 mL) and stirred at 85°C for 8 hours. After stirring, the mixture was separated and washed with ethyl acetate and water. The organic phase was dried over magnesium sulfate and then concentrated to obtain colorless liquid compound A-1a (6.8 g). Next, under a nitrogen atmosphere, A-1a (6.0 g), trimethylsilylacetylene (3.2 g), tetrakis(triphenylphosphine)palladium (1.0 g), copper(I) iodide (0.3 g), and triethylamine (80 mL) were dissolved in tetrahydrofuran (THF, 100 mL) and heated with stirring at 60°C for 8 hours. After stirring, the mixture was separated and washed with ethyl acetate and water. The organic phase was dried over magnesium sulfate, concentrated, and then purified by silica gel chromatography to obtain A-1b (3.2 g). Next, A-1b (3.0 g) and a 70-75% aqueous solution of tetrabutylammonium fluoride (5.5 g) were dissolved in THF (100 mL) and stirred at room temperature for 3 hours. After stirring, the mixture was separated and washed with ethyl acetate and water. The organic phase was dried over magnesium sulfate, concentrated, and then purified by silica gel chromatography to obtain A-1c (2.2 g). Next, under a nitrogen atmosphere, A-1c (2.0 g), 1,4-dibromo-2-ethylbenzene (0.5 g), tetrakis(triphenylphosphine)palladium (0.5 g), copper(I) iodide (0.1 g), and triethylamine (40 mL) were dissolved in THF (50 mL) and heated with stirring at 60°C for 8 hours. After stirring, the mixture was separated and washed with ethyl acetate and water. The organic phase was dried over magnesium sulfate, concentrated, and then purified by silica gel chromatography to obtain Specific Compound A-1 (0.6 g).

[0101] Specific Compound A-2 was synthesized by the following procedure with reference to the synthesis method of Specific Compound A-1.

[0102]

[0103] Specific compound A-3 was synthesized according to the following procedure.

[0104]

[0105] 3,7-Dimethyl-1-octanol (8 g), tosyl chloride (10 g), and triethylamine (5 g) were dissolved in ethyl acetate (50 mL) and stirred at room temperature for 6 hours. The mixture was separated and washed with ethyl acetate and water. The organic phase was dried over magnesium sulfate and then concentrated to obtain colorless liquid compound Cp-1a (15 g). N-Methylaniline (5 g), compound Cp-1a (15 g), and potassium carbonate (7 g) were dissolved in N,N-dimethylacetamide (50 mL) and stirred at an external temperature of 95°C for 4 hours. The mixture was cooled to room temperature and separated and washed with ethyl acetate and a 10% by mass aqueous ammonium chloride solution. The organic phase was dried over magnesium sulfate and then concentrated to obtain colorless liquid compound Cp-1 (12 g).

[0106] Paraacetanilide (10 g) was dissolved in water (100 mL) and 12 mol / L hydrochloric acid (17 mL) and cooled in an ice bath. Sodium nitrite (4.6 g) was added and the mixture was stirred for 30 minutes. After further addition of amidosulfuric acid (0.5 g), compound Cp-1 (16.5 g), potassium acetate (20 g), and methanol (100 mL) were added and stirred at room temperature for 1 hour. After stirring, the mixture was neutralized with hydrochloric acid, and the resulting solid was collected by suction filtration to obtain compound A-3a (20 g). Next, compound A-3a (20 g) was mixed with methanol (100 mL), water (20 mL), and hydrochloric acid (10 mL) and heated at 80°C for 8 hours. After cooling to room temperature, the resulting solid was collected by suction filtration to obtain compound A-3b (15 g). Next, compound A-3b (4.0 g) was dissolved in water (35 mL) and hydrochloric acid (3.1 g) and cooled in an ice bath. Sodium nitrite (0.7 g) was added and the mixture was stirred for 120 minutes. After amidosulfuric acid (0.5 g) was further added, compound Cp-1 (2.5 g), potassium acetate (4 g), and methanol (20 mL) were added and the mixture was stirred at room temperature for 1 hour. After stirring, the mixture was neutralized with hydrochloric acid, and the resulting solid was collected by suction filtration to obtain specific compound A-3 (4.3 g).

[0107] Specific compound A-4 was synthesized according to the following procedure.

[0108]

[0109] Paraacetanilide (10 g) was dissolved in water (100 mL) and 12 mol / L (liter) hydrochloric acid (17 mL) and cooled in an ice bath. Sodium nitrite (4.6 g) was added and the mixture was stirred for 30 minutes. Furthermore, amidosulfuric acid (0.5 g) was added, followed by m-toluidine (5.1 g) and stirring at room temperature for 1 hour. After stirring, the mixture was neutralized with hydrochloric acid, and the resulting solid was collected by suction filtration to obtain compound A-4a (14 g). Next, compound A-4a (6.4 g) was mixed with methanol (50 mL), water (20 mL), and hydrochloric acid (10 mL), and the mixture was heated and stirred at 80°C for 8 hours. After cooling to room temperature, the resulting solid was collected by suction filtration to obtain compound A-4b (4.0 g). Furthermore, compound A-4b (3.5 g) was dissolved in water (35 mL) and hydrochloric acid (2.0 mL) and cooled in an ice bath, and sodium nitrite (1.9 g) and water (5 mL) were added and stirred for 120 minutes. Furthermore, after adding amidosulfuric acid (0.5 g), a solution of compound Cp-1 (5.8 g) obtained by the above method, potassium acetate (6 g), and methanol (30 mL) was added and stirred at room temperature for 1 hour. After stirring, the obtained solid was collected by suction filtration to obtain specific compound A-4 (5.0 g).

[0110] Specific compound A-5 was synthesized according to the following procedure.

[0111]

[0112] Compound A-4b (3.5 g) obtained by the method described above was dissolved in water (35 mL) and hydrochloric acid (2.0 mL) and cooled in an ice bath. Sodium nitrite (1.9 g) was added and the mixture was stirred for 120 minutes. Furthermore, amidosulfuric acid (0.5 g) was added, and a solution of 3-fluorophenol (2.7 g), 48% by mass aqueous potassium hydroxide solution (4.0 g), and water (24 mL) was added and stirred at room temperature for 1 hour. After stirring, the mixture was neutralized with hydrochloric acid, and the resulting solid was collected by suction filtration to obtain compound A-5c (4.4 g). Next, compound A-5c (4.0 g), compound Cp-4a (6.5 g) obtained by the method described above, and potassium carbonate (2.3 g) were dissolved in N,N-dimethylacetamide (DMAc) (50 mL) and stirred at 85°C for 8 hours. After stirring, hydrochloric acid (1.0 g), water (10 mL), and methanol (50 mL) were added, and the resulting solid was suction filtered to obtain Specific Compound A-5 (4.5 g).

[0113] Specific compound A-6 was synthesized according to the following procedure.

[0114]

[0115]

[0116] 3,7,11-Trimethyl-2,6,10-dodecatrien-1-ol (isomer mixture) (isomer mixture, 2.2 g), tosyl chloride (2.1 g), and triethylamine (1.1 g) were dissolved in ethyl acetate (20 mL) and stirred at room temperature for 6 hours. The mixture was separated and washed with ethyl acetate and water. The organic phase was dried over magnesium sulfate and then concentrated to obtain colorless liquid compound A-6a (3.8 g). 4-Nitrophenol (1.3 g), compound A-6a (3.8 g), and potassium carbonate (1.4 g) were dissolved in N,N-dimethylacetamide (20 mL) and stirred at an external temperature of 95°C for 4 hours. The temperature was lowered to room temperature, and the mixture was separated and washed with ethyl acetate and a 10% by mass aqueous ammonium chloride solution. The organic phase was dried over magnesium sulfate and then concentrated to obtain colorless liquid compound A-6b (2.5 g). Next, colorless liquid compound A-6b (2.5 g), Pd / C (0.03 g), and THF (20 mL) were mixed and stirred under a hydrogen atmosphere for 12 hours. The reaction solution was filtered through Celite to remove the Pd / C, and then concentrated to obtain colorless liquid compound A-6c (2.1 g). Separately, 2-aminothiophene was synthesized from 2-nitrothiophene according to a method described in the literature (Journal of Medicinal Chemistry, 2005, Vol. 48, p. 5794). Compound A-6c (2.1 g) obtained by the above method was added to a mixture of hydrochloric acid (2 g), pure water (5 mL), and THF (10 mL). The mixture was cooled to an internal temperature of 5°C or below, and sodium nitrite (0.5 g) dissolved in pure water (2 mL) was added dropwise. The mixture was stirred at an internal temperature of 5°C or below for 1 hour to prepare a diazonium solution. Next, 2-aminothiophene hydrochloride Cp-2 (1 g) was dissolved in pure water (10 mL) and hydrochloric acid (2 g), and the diazonium solution prepared above was added dropwise at an internal temperature of 0°C. The reaction solution was allowed to warm to room temperature and stirred for 2 hours. The precipitated solid was filtered off and dried to obtain a reddish-orange solid A-6d (2.7 g). The reddish-orange solid A-6d (2.7 g) obtained above was suspended and dissolved in acetic acid (30 mL), and sodium thiocyanate (0.5 g) was added at room temperature. The mixture was cooled with water and bromine (1 g) was added dropwise while maintaining the internal temperature at 20°C or below. After stirring at room temperature for 2 hours, pure water (20 mL) was added, and the resulting solid was filtered off and dried to obtain an orange solid A-6e (1.1 g).2-(N-ethylanilino)ethanol (8.2 g) was dissolved in N,N-dimethylacetamide (DMAc) (50 mL), cooled to an internal temperature of 5°C or below, and propionic acid chloride (5.0 g) was added dropwise and stirred at room temperature for 2 hours. Water (50 mL) was added, followed by ethyl acetate (50 mL). The mixture was separated, and the resulting organic layer was dried over magnesium sulfate, filtered, and the filtrate was concentrated to obtain compound Cp-3 (11 g). The orange solid A-6e (1.1 g) obtained above was added to hydrochloric acid (1 g) and acetic acid (2 mL). Under ice-cooling, an aqueous solution (0.5 mL) of sodium nitrite (0.2 g) was added dropwise at 0°C or below. After stirring for 1 hour, amidosulfuric acid (3 mg) was added to obtain a diazonium solution. The diazonium solution was added dropwise to a methanol solution (3 mL) of compound Cp-3 (0.5 g) while maintaining the temperature at 0°C or below. The mixture was allowed to warm to room temperature and stirred for 1 hour, after which pure water (5 mL) was added and the resulting solid was filtered off to obtain Specific Compound A-6 (0.8 g) as a blackish purple solid.

[0117] Specific compound A-7 was synthesized according to the following procedure.

[0118]

[0119]

[0120] N,N-dimethyl-1,4-phenylenediamine dihydrochloride (2.1 g) was added to a mixture of hydrochloric acid (3 g), purified water (5 mL), and THF (10 mL). The mixture was cooled to an internal temperature of 5°C or below, and sodium nitrite (0.7 g) dissolved in purified water (2 mL) was added dropwise. The mixture was stirred at an internal temperature of 5°C or below for 1 hour to prepare a diazonium solution. Next, 2-aminothiophene hydrochloride Cp-2 (1.5 g) was dissolved in purified water (10 mL) and hydrochloric acid (2 g), and the diazonium solution prepared above was added dropwise at an internal temperature of 0°C. The reaction solution was allowed to warm to room temperature and stirred for 2 hours. The precipitated solid was filtered off and dried to obtain reddish-orange solid compound A-7a (2.5 g). The reddish-orange solid Compound A-7a (2.5 g) obtained above was suspended and dissolved in acetic acid (30 mL), and sodium thiocyanate (0.7 g) was added at room temperature. The mixture was cooled with water and bromine (1.4 g) was added dropwise while maintaining the internal temperature at 20°C or below. After stirring at room temperature for 2 hours, purified water (20 mL) was added, and the resulting solid was filtered and dried to obtain orange solid A-7b (1.1 g). 3,7,11-trimethyl-1-dodecanol (11 g), tosyl chloride (10 g), and triethylamine (5 g) were dissolved in ethyl acetate (50 mL) and stirred at room temperature for 6 hours. The mixture was separated and washed with ethyl acetate and water. The organic phase was dried over magnesium sulfate and then concentrated to obtain colorless liquid Compound Cp-4a (19 g). Next, N-methylaniline (5 g), compound Cp-4a (19 g), and potassium carbonate (7 g) were dissolved in N,N-dimethylacetamide (50 mL) and stirred at an external temperature of 95°C for 4 hours. The temperature was lowered to room temperature, and the mixture was separated and washed with ethyl acetate and a 10% aqueous ammonium chloride solution. The organic phase was dried over magnesium sulfate and then concentrated to obtain colorless liquid compound Cp-4 (16 g). The orange solid A-7b (1.1 g) obtained above was added to hydrochloric acid (1.1 g) and acetic acid (2 mL), and an aqueous solution (0.5 mL) of sodium nitrite (0.2 g) was added dropwise at 0°C or below under ice cooling. After stirring for 1 hour, amidosulfuric acid (3 mg) was added to obtain a diazonium solution. The diazonium solution was added dropwise to a methanol solution (3 mL) of compound Cp-4 (1.1 g) while maintaining the temperature at 0°C or below. The mixture was warmed to room temperature and stirred for 1 hour, and then purified water (5 mL) was added thereto. The resulting solid was filtered off to obtain Specific Compound A-7 (1.1 g) as a blackish purple solid.

[0121] Specific Compound A-8 was synthesized with reference to the synthesis method of Specific Compound A-6.

[0122]

[0123] All of the specific compounds A-1 to A-8 are racemates (racemic mixtures), and N Ｒｉ / (N Ｒｉ +N Ｓｉ ) was 0.5.

[0124] Compounds C-1 to C-4 were synthesized with reference to the synthesis procedures for each of the specific compounds described above.

[0125]

[0126] <Other Liquid Crystal Compounds> Another liquid crystal compound B-1 was synthesized under known conditions according to the following scheme.

[0127]

[0128] <Evaluation> Next, each measurement composition having a different composition ratio of Component A and Component B was prepared by mixing components to obtain the composition shown in Table 1 below. In each example and comparative example, the compounds used as Component A and Component B were as shown in Table 2. Specifically, in Example 1, specific compound A-1 was mixed as Component A, other liquid crystal compound B-1 as Component B, and chloroform were mixed to prepare measurement composition 1, and measurement compositions 2 to 7 were prepared by changing the contents of Component A and Component B using the same procedure.

[0129]

[0130] (Melting Point Depression Property) Each measurement composition in each Example and Comparative Example was heated and observed under a polarizing microscope equipped with a hot stage, and the melting point of each measurement composition was measured. ΔT / T' (%) was calculated according to the following formula, and evaluation was performed according to the following evaluation criteria. The melting point was defined as the temperature at which the solid state changes to the liquid crystal state. ΔT / T' (%) = 100 × (T' - Tmix) / T' T' (°C): {[Melting point of component A alone (°C) × composition ratio (mass%) of component A in the measurement composition that exhibited Tmix] + [Melting point of component B alone (°C) × composition ratio (mass%) of component B in the measurement composition that exhibited Tmix]} / 100 Tmix (°C): The smallest melting point among the melting points of each measurement composition.

[0131] The melting point depressing ability will be described in detail below using an example of the melting point measurement results of each test composition shown in FIG. 7. Note that the measurement results shown in FIG. 7 are illustrative examples. In FIG. 7, when the melting point of component A alone is TA (°C) and the melting point of component B alone is TB (°C), if the composition ratio of the test composition containing components A and B is changed, the melting point of the test composition will exhibit a melting point different from both the melting point TA and the melting point TB. When the composition ratio of the test composition is changed in this way, the minimum melting point exhibited by the test composition is Tmix (°C), and the composition ratio of component B in the test composition exhibiting Tmix is ​​the composition ratio XB (mass%), and the composition ratio of component A is the composition ratio XA (mass%) (not shown). Furthermore, T' is a value calculated by the above-mentioned method using the composition ratios XA and XB and the respective melting points TA and TB. Next, ΔT is calculated by subtracting Tmin from T' (°C), and the ratio (percentage) of ΔT to T' is ΔT / T'. Excellent melting point depressant ability (large ΔT / T') means that the difference between T' and Tmix is ​​large and the amount of melting point depression relative to T' is large.

[0132] "A": ΔT / T' is 15% or more. "B": ΔT / T' is 10% or more but less than 15%. "C": ΔT / T' is less than 10%.

[0133] (Refractive index anisotropy (Δn)) The refractive index anisotropy at 100 GHz radio waves was measured by the method disclosed in Applied Optics, Vol. 44, No. 7, p. 1150 (2005). The refractive index anisotropy was measured by filling a variable short-circuit waveguide with a measurement composition showing Tmix, orienting the liquid crystal compound in the measurement composition, inputting a radio wave of 100 GHz into the waveguide, and measuring the amplitude ratio of the reflected wave to the incident wave. Measurements were made by changing the direction of the static magnetic field and the length of the short-circuit tube, and the refractive indices ne and no were determined. The refractive index anisotropy was calculated from ne - no.

[0134] "A": Δn is 0.5 or more; "B": Δn is 0.3 or more and less than 0.5; "C": Δn is less than 0.3

[0135] In Table 2, the "number of asymmetric carbon atoms" indicates the number of R １ and R ２ indicates the total number of asymmetric carbon atoms contained in "A １ B １ The "thienothiazole ring" is A in formula (1). １ and B １ When at least one of the groups is a thienothiazole ring, it is designated as "A", and when it is not, it is designated as "B". As described above, "XA [mass %]" indicates the composition ratio XA (mass %) of component A in the measurement composition showing Tmix. Note that the composition ratio XB of component B in each example is [100 - XA (mass %) in the table].

[0136]

[0137] As shown in Table 2, it was confirmed that the present composition exhibited the desired effects. From the comparison of Examples 6 to 8 with Examples 1 to 5, A １ and B １ It was confirmed that the effects of the present invention are more excellent when at least one of the asymmetric carbon atoms is a thienothiazole ring. From a comparison between Example 5 and Example 4, it was confirmed that the effects of the present invention are more excellent when the number of asymmetric carbon atoms is 3 or more.

[0138] 2 Radio wave reflecting device 10 Radio wave control element 12 Metasurface structure 14 Microstructure 16, 24 Support 20 Liquid crystal layer 26 First electrode layer 28 Power supply ANT Antenna AR1, AR2 Area BL Building LD Liquid crystal compound RW Radio wave UC Unit cell

Claims

1. A liquid crystal composition for a radio wave control element, comprising two or more liquid crystal compounds, wherein at least one of the two or more liquid crystal compounds is a compound represented by formula (1). Formula (1) R １ -L １ -A １ -(Z １ -B １ ) ｎ -L ２ -R ２ In formula (1), R １ and R ２ are each independently —CH ２ - represents an alkyl group which may be substituted with -O- or -CO-O-, a cyano group, a halogen atom, -N=C=S, or -N=C=Se, provided that R １ and R ２ At least one of R represents the alkyl group having an asymmetric carbon atom; １ and R ２ The total number of asymmetric carbon atoms contained in L is 2 or more. １ and L ２ each independently represents a single bond, —O—, —CO—, —CO—O—, —O—CO—O—, or —NR ３ - or -CH=CH-, and O may be substituted with S. ３ represents an alkyl group which may have a substituent. １ and B １ each independently represents an aromatic ring which may have a substituent or an aliphatic ring which may have a substituent. １ represents a single bond, —O—, —CO—, —CO—O—, —O—CO—O—, —CR Ｚ =CR Ｚ -, -C≡C-, -N=N-, -CR Ｚ =CR Ｚ -CR Ｚ =CR Ｚ -, -C≡C-C≡C-, -CR Ｚ =CR Ｚ -CO- or -CR Ｚ =CR Ｚ represents —CO—O—, where O may be substituted with S. Ｚ each independently represents a hydrogen atom or a fluorine atom, and n represents an integer of 1 to 4.

2. A liquid crystal composition for a radio wave control element according to claim 1, wherein the content of the compound represented by formula (1) is 30% by mass or more based on the total solid content of the liquid crystal composition for a radio wave control element.

3. Z １ 3. The liquid crystal composition for a radio wave control element according to claim 1, wherein at least one of the above is -N=N-.

4. R １ and R ２ The liquid crystal composition for a radio wave control element according to claim 3, wherein at least one of the above is an alkyl group having a partial structure represented by formula (X): ２ -CH(CH ３ )-C ２ H ４ -* In formula (X), * represents the bonding position.

5. A １ and B １ 4. The liquid crystal composition for a radio wave control element according to claim 3, wherein each independently represents an aromatic hydrocarbon ring, and n is an integer of 2 to 4.

6. R １ and R ２ are the same group, and L １ and L ２ is —CH═CH—, —O—, or —NR ３ 6. The liquid crystal composition for a radio wave control element according to claim 5, wherein:

7. A １ and B １ 4. The liquid crystal composition for radio wave control devices according to claim 3, wherein at least one of the above is an aromatic heterocycle, and n is an integer of 1 to 3.

8. A １ and B １ 8. The liquid crystal composition for a radio wave control element according to claim 7, wherein at least one of the above is a thienothiazole ring.

9. The liquid crystal composition for radio wave control devices according to claim 1 or 2, wherein the compound represented by formula (1) is a racemate.

10. A radio wave control element having, in this order: a first electrode; a liquid crystal composition layer comprising the liquid crystal composition for radio wave control elements according to claim 1 or 2; and a second electrode.

11. A compound represented by formula (1). Formula (1) R １ -L １ -A １ -(Z １ -B １ ) ｎ -L ２ -R ２ In formula (1), R １ and R ２ are each independently —CH ２ - represents an alkyl group which may be substituted with -O- or -CO-O-, a cyano group, a halogen atom, -N=C=S, or -N=C=Se, provided that R １ and R ２ at least one of R represents the alkyl group having a partial structure represented by formula (X); １ and R ２ The total number of asymmetric carbon atoms contained in L is 2 or more. １ and L ２ each independently represents a single bond, —O—, —CO—, —CO—O—, —O—CO—O—, or —NR ３ - or -CH=CH-, and O may be substituted with S. ３ represents an alkyl group which may have a substituent. １ and B １ each independently represents an aromatic ring which may have a substituent or an aliphatic ring which may have a substituent. １ represents a single bond, —O—, —CO—, —CO—O—, —O—CO—O—, —CR Ｚ =CR Ｚ -, -C≡C-, -N=N-, -CR Ｚ =CR Ｚ -CR Ｚ =CR Ｚ -, -C≡C-C≡C-, -CR Ｚ =CR Ｚ -CO- or -CR Ｚ =CR Ｚ represents —CO—O—; Z １ At least one of R represents -N=N-, and O may be substituted with S. Ｚ represents a hydrogen atom or a fluorine atom, and n represents an integer of 1 to 4. Formula (X) *-CH ２ -CH(CH ３ )-C ２ H ４ -* In formula (X), * represents the bonding position.

12. R １ and R ２ The compound according to claim 11, wherein at least one of the following is an alkyl group having two or more asymmetric carbon atoms:

13. A １ and B １ are each independently an aromatic hydrocarbon ring, and n is an integer of 2 to 4.

14. R １ and R ２ are the same groups, and L １ and L ２ is —CH═CH—, —O—, or —NR ３ The compound according to claim 13, wherein 15. A １ and B １ and n is an integer of 1 to 3.

16. A １ and B １ The compound of claim 15, wherein at least one of is a thienothiazole ring.

17. The compound according to claim 11 or 12, wherein the compound represented by formula (1) is a racemate.

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