Composition and radio wave control element

Abstract

The present invention addresses the problem of providing: a composition having a large refractive index anisotropy with respect to a radio wave, excellent melting point lowering properties, and a low melting point; and a radio wave control element.　This composition contains two or more liquid crystal compounds. The two or more liquid crystal compounds include a first liquid crystal compound and a second liquid crystal compound that satisfy a relationship in which the Tanimoto similarity is 0.75 or less. At least one of the first liquid crystal compound and the second liquid crystal compound has an asymmetric carbon atom, satisfies the relationship represented by formula (X), and satisfies the relationship represented by formula (Y).

Description

Composition, radio wave control element

[0001] The present invention relates to a composition and a radio wave control element.

[0002] Radio waves, such as the high-frequency radio waves (millimeter waves and terahertz waves) required for high-capacity wireless communication, tend to travel in a straight line. Therefore, elements are used to change the direction of radio waves. However, with a conventional reflector, for example, the direction of reflection of radio waves is fixed, and the reflection direction is specular, with the angle of incidence and the angle of emission being 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] As an element capable of bending the traveling direction of radio waves, a radio wave control element having a layer made of a liquid crystal composition having refractive index anisotropy is known. Patent Document 1 discloses a liquid crystal medium containing a pleochroic compound, a specific compound, and a polymerizable mesogenic compound, and an antenna element using the liquid crystal medium.

[0004] Special Publication No. 2019-512023

[0005] Thinner wave control devices and shorter operating times are desirable. To manufacture a wave control device exhibiting such characteristics using a composition containing a liquid crystal compound, the composition must be capable of forming a layer with a larger refractive index anisotropy (Δn) of radio waves. One way to improve the refractive index anisotropy Δn is to use a liquid crystal compound with a high polarization anisotropy (the ratio of molecular length to molecular width). For example, liquid crystal compounds with a large molecular weight and a long rigid π-electron conjugated core exhibit high polarization anisotropy. Meanwhile, wave control devices are expected to be used in a variety of external environments, such as outdoor antennas and in-vehicle sensors. Because these devices are expected to be used in a variety of temperature environments, it is preferable to use a composition with a low melting point and a wide temperature range in which a liquid crystal phase is expressed. It is known that mixing two or more liquid crystal compounds can sometimes lower the melting point of the resulting mixture. Herein, the property of the melting point of a mixture of two or more liquid crystal compounds being lower than the average melting point of each liquid crystal compound is referred to as "melting point depression."

[0006] The present inventors have studied the properties of a composition containing two or more liquid crystal compounds with reference to the liquid crystal medium described in Patent Document 1. As a result, it has been found that when a liquid crystal compound having high polarization anisotropy is used as at least one of the two or more liquid crystal compounds from the viewpoint of improving the refractive index anisotropy Δn, the melting point depression effect is small, and the desired decrease in melting point and expansion of the temperature range in which a liquid crystal phase is exhibited may not be achieved, and there is a possibility that further improvement is required.

[0007] In view of the above circumstances, an object of the present invention is to provide a composition having a large refractive index anisotropy with respect to radio waves, an excellent melting point lowering property, and a low melting point. Another object of the present invention is to provide a radio wave control element.

[0008] 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.

[0009] [1] A composition containing two or more liquid crystal compounds, the two or more liquid crystal compounds including a first liquid crystal compound and a second liquid crystal compound that satisfy a relationship in which the Tanimoto similarity is 0.75 or less, and at least one of the first liquid crystal compound and the second liquid crystal compound is a specific liquid crystal compound that has an asymmetric carbon atom, satisfies the relationship of formula (X) described below, and also satisfies the relationship of formula (Y) described below. [2] The composition according to [1], in which both the first liquid crystal compound and the second liquid crystal compound have an asymmetric carbon atom. [3] The composition according to [1] or [2], in which both the first liquid crystal compound and the second liquid crystal compound satisfy the relationship of formula (X). [4] The composition according to any one of [1] to [3], in which both the first liquid crystal compound and the second liquid crystal compound have an asymmetric carbon atom and also satisfy the relationship of formula (Y). [5] The composition according to any one of [1] to [4], in which both the first liquid crystal compound and the second liquid crystal compound have an asymmetric carbon atom, also satisfy the relationship of formula (X), and also satisfy the relationship of formula (Y). [6] The composition according to any one of [1] to [5], which is for use in a radio wave control element. [7] A radio wave control element having, in this order, a first electrode, a liquid crystal composition layer made of the composition according to any one of [1] to [6], and a second electrode.

[0010] According to the present invention, a composition having a large refractive index anisotropy with respect to radio waves, an excellent melting point lowering property, and a low melting point can be provided. Also, according to the present invention, a radio wave control element can be provided.

[0011] FIG. 1 is a diagram showing an example of a 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 conceptually showing the relationship between the applied voltage and the amount of phase delay of radio waves. FIG. 7 is a diagram conceptually showing another example of a radio wave control element. FIG. 8 is a diagram conceptually showing another example of a radio wave control element. FIG. 9 is a diagram conceptually showing another example of a radio wave control element.

[0012] 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.

[0013] 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.

[0014] In this specification, unless otherwise specified, each component may be a single substance corresponding to the component, or two or more substances may be used in combination. Here, when two or more substances are used in combination for each component, the content of that component refers to the total content of the substances used in combination, unless otherwise specified. In this specification, stereoisomers are considered to be the same type of compound, except when referring to a racemate.

[0015] 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."

[0016] [Composition] The composition of the present invention (hereinafter also simply referred to as "the composition") contains two or more liquid crystal compounds, the two or more liquid crystal compounds including a first liquid crystal compound and a second liquid crystal compound that satisfy the relationship that the Tanimoto similarity is 0.75 or less, and at least one of the first liquid crystal compound and the second liquid crystal compound has an asymmetric carbon atom and is a specific liquid crystal compound that satisfies the relationship of formula (X) and the relationship of formula (Y). (X) f×λ ２ / Mw≧700 (Y) Mw / n≦400 In formulas (X) and (Y), f represents the maximum oscillator strength of the specific liquid crystal compound, λ represents the wavelength (nm) of the maximum oscillator strength in the specific liquid crystal compound, Mw represents the molecular weight of the specific liquid crystal compound, and n represents the number of asymmetric carbon atoms in the specific liquid crystal compound. By virtue of having the above characteristics, the composition has the excellent effects of having a large refractive index anisotropy with respect to radio waves, an excellent melting point depression property, and a low melting point.

[0017] As used herein, "large refractive index anisotropy with respect to radio waves" means that when the liquid crystal compound in the composition is oriented, the oriented liquid crystal compound has large refractive index anisotropy with respect to radio waves. Furthermore, radio waves refer to electromagnetic waves with a frequency of 0.003 to 0.3 THz (3 to 300 GHz). Radio waves have a high frequency and therefore have a strong tendency to propagate in a straight line.

[0018] Although the details of the mechanism by which the composition exhibits the above-mentioned excellent effects due to the above-mentioned characteristics are unknown, the inventors speculate as follows. The inventors speculate that when a liquid crystal compound satisfies the above formula (X), the wavelength integral value of absorbance per unit molecular weight is large, thereby increasing the refractive index anisotropy of the composition with respect to radio waves. On the other hand, the inventors speculate that the reason why the melting point of a composition is high when a liquid crystal compound with large refractive index anisotropy is used is that such liquid crystal compounds often have large molecular weights and long rigid π-electron conjugated cores, which result in strong intermolecular interactions and make the melting point difficult to lower even when mixed with other liquid crystal compounds. In contrast, when at least one of the first liquid crystal compound and the second liquid crystal compound has an asymmetric carbon atom, the intermolecular interactions between the liquid crystal compounds are suppressed by the branched structure centered on the asymmetric carbon atom. In particular, when the liquid crystal compound having an asymmetric carbon atom satisfies the above formula (Y), the suppression of intermolecular interactions due to the branched structure is speculated to improve the melting point depression ability of the composition and lower the melting point. Furthermore, as will be described later, Tanimoto similarity is an index showing the structural similarity between two compounds, and when it is close to 0, it indicates that the similarity between the two compounds is low. If the structural similarity of the liquid crystal compounds contained in a composition is moderately low, mixed crystals (crystals in which different liquid crystal compounds are mixed) are unlikely to be formed when they are mixed, and it is presumed that by setting the structural similarity to 0.75 or less, the formation of mixed crystals (crystals in which different liquid crystal compounds are mixed) is suppressed and the melting point depression of the composition is not hindered.

[0019] The components and characteristics of this composition are described in detail below.

[0020] <Liquid Crystal Compound> The present composition contains two or more liquid crystal compounds. A liquid crystal compound is a compound that exhibits liquid crystallinity. "Exhibiting liquid crystallinity" refers to a compound that exhibits a liquid crystal phase (intermediate phase) between a crystalline phase (low temperature side) and an isotropic phase (high temperature side) when the temperature is changed. A specific method for observing the liquid crystal phase is to observe the compound using a polarizing microscope while heating or cooling, thereby confirming the optical anisotropy and fluidity derived from the liquid crystal phase. Since the present composition contains two or more liquid crystal compounds, including more liquid crystal compounds that are miscible in the liquid crystal phase but not miscible in the crystalline phase can further enhance the melting point depression, which is preferable. The present composition preferably contains 2 to 20 liquid crystal compounds, and more preferably 2 to 10 liquid crystal compounds.

[0021] <Tanimoto Similarity> The two or more liquid crystal compounds contained in the composition include a first liquid crystal compound and a second liquid crystal compound that satisfy a relationship in which the Tanimoto similarity is 0.75 or less. Tanimoto Similarity is an index used to quantitatively evaluate the structural similarity between compounds and is calculated by normalizing the number of common features between two data sets corresponding to the two compounds by the total number of features in the two data sets. Specifically, Tanimoto Similarity (T(A, B)) is calculated by dividing the number of common elements in Data Sets A and B (|A∩B|) by the sum of the number of unique elements contained in each data set (|A∪B|) minus the number of common elements. In the following formula, |A∩B| represents the number of common elements between Set A and Set B, |A∪B| represents the total number of elements in Set A and Set B, and T(A, B) represents the Tanimoto similarity. T(A, B) = (|A∩B|) / (|A∪B| - |A∩B|) Tanimoto similarity takes a value in the range from 0 to 1. When the Tanimoto similarity is close to 1, it indicates that the two compounds are highly similar, and when the Tanimoto similarity is close to 0, it indicates that the two compounds are less similar.

[0022] The Tanimoto similarity between two liquid crystal compounds is determined using the cheminformatics software library "RDKit." In this specification, a 2048-dimensional Morgan fingerprint is first generated from the molecular structure of each liquid crystal compound, and the Tanimoto similarity is calculated based on the generated fingerprint. A Morgan fingerprint is a fixed-length binary vector that reflects the connectivity of atoms within a molecule and information about surrounding atoms. In this specification, the Morgan fingerprint is generated with a radius of 2.

[0023] When the composition contains two liquid crystal compounds, the two liquid crystal compounds satisfy the relationship that the Tanimoto similarity is 0.75 or less. When the composition contains three or more liquid crystal compounds, it is sufficient that the Tanimoto similarity of any two liquid crystal compounds selected from the three or more liquid crystal compounds is 0.75 or less. In other words, when the composition contains three or more liquid crystal compounds, two liquid crystal compounds may be present that have a Tanimoto similarity of more than 0.75. It is preferable that the Tanimoto similarity of any two liquid crystal compounds selected from the three or more liquid crystal compounds contained in the composition is 0.75 or less.

[0024] The Tanimoto similarity of the first liquid crystal compound and the second liquid crystal compound is preferably 0.70 or less, more preferably 0.60 or less, and even more preferably 0.40 or less, in order to obtain a composition with better melting point depression properties and a lower melting point. There is no particular restriction on the lower limit of the Tanimoto similarity, but since it is preferable that the compounds are compatible with each other in the liquid crystal phase, it is preferable that it be 0.10 or more. When the composition contains three or more liquid crystal compounds, it is preferable that the Tanimoto similarity of any two liquid crystal compounds selected from the three or more liquid crystal compounds is within the above range, and it is more preferable that the Tanimoto similarity of both two liquid crystal compounds selected from the three or more liquid crystal compounds is within the above range.

[0025] <Specific Liquid Crystal Compound> At least one of the first liquid crystal compound and the second liquid crystal compound contained in the present composition is a specific liquid crystal compound that has an asymmetric carbon atom, satisfies the relationship of formula (X) described below, and satisfies the relationship of formula (Y) described below.

[0026] The specific liquid crystal compound contains one or more asymmetric carbon atoms. An asymmetric carbon atom refers to a carbon atom to which all four of the atoms or atomic groups to which it is bonded are different. The number of asymmetric carbon atoms contained in the specific liquid crystal compound is preferably two or more, since this provides a more excellent melting point lowering property and a lower melting point for the composition. There is no upper limit as long as the ability to develop a liquid crystal phase is not lost, but the number is often eight or less, and preferably seven or less.

[0027] The specific liquid crystal compound satisfies the relationship of formula (X): (X) f×λ ２ / Mw≧700 The meanings of f, λ, and Mw in formula (X) are as described above. ２ The value calculated from the formula "f × λ / Mw" is an index representing the wavelength integral value of absorbance per unit molecular weight of the liquid crystal compound in the main absorption band, and the present inventors have found that by adjusting this value within a predetermined range, a composition having a large refractive index anisotropy Δn for radio waves can be obtained. ２ / Mw is preferably 900 or more. There is no particular upper limit, but it is often 3000 or less, and preferably 2500 or less.

[0028] The maximum oscillator strength (f) and wavelength (λ) of the maximum oscillator strength (nm) of a liquid crystal compound are calculated using the quantum science calculation program Gaussian16 under the following conditions using density functional theory: Functional: CAM-B3LYP Basis function: 6-31+G(d,p) Solvent effect: Acetonitrile Other conditions: Default values ​​of Gaussian16 Based on the calculation model set above, an electronic excited state calculation from the ground state to an excited state is performed. This calculation uses a time-dependent method to determine the energy and oscillator strength of the electronic excited state. From the excitation energy and oscillator strength data of the liquid crystal compound obtained from the electronic excited state calculation, the electronic transition with the maximum oscillator strength is identified, and this value is taken as the maximum oscillator strength (f). The wavelength at which the maximum oscillator strength (f) is obtained is taken as the wavelength (λ).

[0029] The maximum oscillator strength f of a liquid crystal compound is proportional to the square of the transition moment (dipole strength), and increases as the overlap integral of the wave functions of the ground state and the transition state increases. Specifically, the higher the planarity of the π-bonded molecules due to aromatic rings or double-bond linking groups, etc., the greater the maximum oscillator strength f. Furthermore, the wavelength λ (nm) of the maximum oscillator strength in a liquid crystal compound increases as the energy difference between the ground state and the transition state decreases. Specifically, the longer the conjugation length of the π-bonded molecules due to aromatic rings or double-bond linking groups, etc., the longer the wavelength. The wavelength can also be increased by introducing a heteroatom or an electron-donating or electron-accepting substituent at a predetermined position.

[0030] The specific liquid crystal compound satisfies the relationship of formula (Y). (Y) Mw / n≦400 The meanings of Mw and n in formula (Y) are as described above. The inventors have found that by adjusting the value calculated from the formula "Mw / n" within a predetermined range, a composition having excellent melting point lowering properties and a low melting point can be obtained. In order to obtain a composition having excellent melting point lowering properties and a lower melting point, the Mw / n of the specific liquid crystal compound is preferably 380 or less. There is no particular lower limit, but it is often 50 or more, and preferably 100 or more.

[0031] One of the first and second liquid crystal compounds contained in the composition may be the specific liquid crystal compound and the other may be a liquid crystal compound other than the specific liquid crystal compound, or both the first and second liquid crystal compounds may be the specific liquid crystal compound. The contents of the first and second liquid crystal compounds are not particularly limited, but it is preferable that the content of one is 5 to 95% by mass and the content of the other is 95 to 5% by mass, and it is more preferable that the content of one is 10 to 90% by mass and the content of the other is 90 to 10% by mass, based on the total content of the first and second liquid crystal compounds.

[0032] In order to obtain a composition having a more excellent melting point lowering property and a lower melting point, it is preferable that both the first liquid crystal compound and the second liquid crystal compound have asymmetric carbon atoms. The preferred number of asymmetric carbon atoms is the same as the preferred number of asymmetric carbon atoms contained in the specific liquid crystal compound described above.

[0033] In order to increase the refractive index anisotropy Δn of the composition, it is preferable that both the first liquid crystal compound and the second liquid crystal compound satisfy the relationship of formula (X): ２ The preferred range of / Mw is the same as that of the specific liquid crystal compound described above.

[0034] In terms of achieving a more excellent melting point depressing property and a lower melting point of the composition, it is preferable that both the first liquid crystal compound and the second liquid crystal compound have an asymmetric carbon atom and satisfy the relationship of formula (Y). The preferred range of Mw / n of the liquid crystal compounds is the same as that of the specific liquid crystal compound described above.

[0035] It is more preferable that both the first liquid crystal compound and the second liquid crystal compound have an asymmetric carbon atom, satisfy the relationship of formula (X), and satisfy the relationship of formula (Y), in order to increase the refractive index anisotropy Δn of the composition, to improve the melting point depression property of the composition, and to lower the melting point of the composition.

[0036] It is preferable that both the first liquid crystal compound and the second liquid crystal compound contained in the composition are specific liquid crystal compounds. Of the two or more liquid crystal compounds contained in the composition, it is preferable that two or more are specific liquid crystal compounds, and it is more preferable that all of the liquid crystal compounds are specific liquid crystal compounds.

[0037] The specific liquid crystal compound may be a racemate. In this specification, the term "racemate" refers to a liquid crystal compound having n asymmetric carbon atoms (n is an integer of 1 or more), in which the number of R-form and S-form molecules at the ith (i=1 to n) asymmetric carbon atom 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. The specific liquid crystal compound is preferably a racemate. When the liquid crystal 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 liquid crystal compound can be more easily changed by application of an electric field.

[0038] The liquid crystal compound contained in the composition preferably exhibits dichroism. That is, a dichroic liquid crystal compound is preferred. Dichroism refers to the property of having different absorbance depending on the direction of polarization.

[0039] The two or more liquid crystal compounds contained in the present composition are selected and used so that the composition contains a first liquid crystal compound and a second liquid crystal compound that satisfy the Tanimoto similarity relationship described above, and further so that at least one of the first liquid crystal compound and the second liquid crystal compound is a specific liquid crystal compound.

[0040] Examples of the liquid crystal compound contained in the composition include a compound represented by the following 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 these represents the above alkyl group.

[0041] When the compound represented by formula (1) has an asymmetric carbon atom, R １ and R ２ At least one of R represents the above alkyl group having an asymmetric carbon atom. １ and R ２The total number of asymmetric carbon atoms contained in is preferably 2 or more.

[0042] -CH ２ The alkyl group in which - may be substituted with -O- or CO-O- preferably has an asymmetric carbon atom. 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.

[0043] The alkyl group is a group selected from the group consisting of —CH ２ - may be replaced by -O- or CO-O-. For example, the alkyl group may be *-CH ２ -CH ２ —O—CO—CH ２ -CH ３ may be.

[0044] 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). Formula (X) *-CH ２ -CH(CH ３ )-C ２ H ４ -* In formula (X), * represents the bonding position.

[0045] The alkyl group may be a group represented by formula (W): *-AL-C(R Ｗ１ ) (R Ｗ２ )-R Ｗ３ In formula (W), * represents the bonding position. AL represents an alkylene group having no asymmetric carbon atom. R Ｗ１ and R Ｗ２ each independently represents a hydrogen atom or an alkyl group having no asymmetric carbon atom; R Ｗ１ and R Ｗ２represent different groups. Ｗ３ represents an alkyl group.

[0046] 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.

[0047] 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.

[0048] R Ｗ３ The alkyl group represented by the formula (I) may have an asymmetric carbon atom. The alkyl group may be linear, branched, or cyclic, and is preferably linear or branched. The alkyl group preferably has 1 to 25 carbon atoms, more preferably 3 to 20 carbon atoms. The alkyl group is preferably an alkyl group containing an isopropyl group.

[0049] When the compound represented by formula (1) has an asymmetric carbon atom, R １ and R ２ At least one of R represents the above alkyl group having an asymmetric carbon atom. １ and R ２The total number of asymmetric carbon atoms in R is preferably 2 or more. １ and R ２ When 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 R and R represent the above alkyl group 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 replaced by -O- or CO-O-. １ and R ２ The total number of asymmetric carbon atoms contained in is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more. The upper limit is preferably 10 or less, and more preferably 8 or less.

[0050] 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. ３ represents an alkyl group which may have a substituent.

[0051] L １ and L ２ In each group represented by the formula (I), a part or all of the "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.

[0052] 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 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:

[0053] 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.

[0054] The aromatic ring and the aliphatic ring may be either a monocyclic or 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), an imidazooxazole ring (e.g., an imidazo[2,1-b]oxazole ring), Thienothiazole rings (for example, thieno[2,3-d]thiazole rings, etc.), benzothiadiazole rings, benzodithiophene rings (for example, benzo[1,2-b:4,5-b']dithiophene rings, etc.), thienothiophene rings (for example, thieno[3,2-b]thiophene rings, etc.), thiazolothiazole rings (for example, thiazolo[5,4-d]thiazole rings, etc.), naphthodithiophene rings (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.

[0055] 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 group), 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 phosphoric acid 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. Ｎ represents 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.

[0056] 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.

[0057] 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- is an example. 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-.

[0058] 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.

[0059] An example of a preferred embodiment of the compound represented by the formula (1) is shown below. The compound represented by the formula (1) preferably satisfies the requirement X and at least one of the requirements Y1 and Y2. The compound represented by the formula (1) preferably satisfies the requirement X and at least one of the requirements Z1 and Z2. Requirement X: In the 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.

[0060] The total content of the first liquid crystal compound and the second liquid crystal compound is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on the total solid content of the composition. There is no particular upper limit, and it may be 100% by mass or less. The preferred ranges for the content of the specific liquid crystal compound and the content of the compound represented by Formula (1) are the same as the preferred ranges for the total content of the first liquid crystal compound and the second liquid crystal compound.

[0061] The composition may contain a liquid crystal compound other than the above liquid crystal compound. The other liquid crystal compound that may be used in combination with the above liquid crystal compound is preferably a liquid crystal compound having a skeleton with a high Δn. Examples of skeletons with a high Δn include skeletons having multiple rings selected from aromatic hydrocarbon rings and aromatic heterocycles, and having triple bonds and / or double bonds as linking groups. The linking group is preferably tolane, ditolane, vinylene, or butadiene, and multiple of these linking groups may be present in one molecule. Furthermore, the other liquid crystal compound preferably has an electron-donating or electron-accepting substituent at its terminal. Examples of electron-donating substituents include alkoxy groups, thioalkoxy groups, and alkylamino groups. Examples of electron-accepting groups include cyano groups, nitro groups, isocyanate groups, isothiocyanate groups, cyanovinylene groups, and dicyanovinylene groups.

[0062] The total content of the liquid crystal compounds in the composition is preferably 30% by mass or more, more preferably 50% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, based on the total solid content of the composition. The upper limit is not particularly limited, but may be 100% by mass or less. This is because, when the total content of the liquid crystal compounds is within the above range, a liquid crystal composition layer made of the composition may exhibit a greater refractive index anisotropy with respect to radio waves. While the details of the reason for this are unclear, it is presumed that increasing the total content of the liquid crystal compounds in the liquid crystal composition layer increases the interaction between the liquid crystal compounds, thereby increasing the degree of orientational order of the absorption axes due to the absorbing skeletons in the liquid crystal compounds. As a result, the absorption anisotropy of the liquid crystal compounds affects the increase in refractive index anisotropy at wavelengths longer than the absorption wavelength.

[0063] <Other Components> The present composition may contain other components in addition to the liquid crystal compound. Examples of other components in addition to the liquid crystal compound include crystalline compounds that do not exhibit liquid crystallinity. The present composition preferably contains a crystalline compound, since the melting point of the crystalline compound contained in the present composition makes it easier to adjust the temperature range in which the composition exhibits a liquid crystal phase. When the present composition contains a crystalline compound, the content of the crystalline compound is, for example, 1 to 50% by mass, and preferably 5 to 30% by mass, based on the total solid content of the composition.

[0064] The present composition is preferably substantially free of solvent, meaning that the solvent content is 5% by mass or less, and preferably 1% by mass or less, relative to the total mass of the present composition.

[0065] [Radio wave control element] The present composition can be preferably used as a composition for a radio wave control element. That is, the present composition may be used for a radio wave control element. A radio wave control element is an element that acts on radio waves. Examples of radio waves include radio waves with a frequency of 0.003 to 0.3 THz. Radio waves in this frequency band RW are also called high-frequency radio waves (centimeter waves, millimeter waves, terahertz waves), and are capable of high-capacity wireless communication while also having high linearity.

[0066] 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, by applying a voltage between the first and second electrodes, the orientation state of the liquid crystal compound contained in the liquid crystal composition layer can be controlled, thereby adjusting the refractive index anisotropy of the liquid crystal composition layer and thereby adjusting the propagation direction of radio waves. The liquid crystal compound contained in the liquid crystal composition layer made of the present composition is likely to exhibit a property in which the orientation state of the liquid crystal compound changes with voltage. In the liquid crystal composition layer, by controlling the orientation state of the liquid crystal compound, a state exhibiting large refractive index anisotropy can be achieved. Typically, the response speed of a radio wave control element depends on the film thickness of the liquid crystal composition layer. Since the liquid crystal composition layer made of the present composition can exhibit 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.

[0067] 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 present invention 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 radiated 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.

[0068] 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, for example, a resonant circuit in which a coil and a capacitor are connected in series to resonate an alternating current. The phase of the incident radio wave RW changes due to the resonance 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.

[0069] The radio wave control element 10 mainly acts on radio waves RW with a frequency of 0.003 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 0.003 to 0.3 THz. The wavelength of radio waves RW with a frequency of 0.003 to 0.3 THz is 1 to 100 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.

[0070] 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 array 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.

[0071] 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.

[0072] Figure 4 conceptually shows an example of a more specific configuration of the radio wave control element of the present invention. The radio wave control element 10 shown in Figure 4 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 a 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 LD.

[0073] 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.

[0074] 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.

[0075] 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. A power supply 28 is connected to each microstructure 14 to apply 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," 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."

[0076] 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.

[0077] 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.

[0078] 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".

[0079] 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."

[0080] 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 .

[0081] 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 .

[0082] 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 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 this 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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 diverge. 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.

[0087] 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.

[0088] 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, trade name "Arton" manufactured by JSR Corporation, trade name "Zeonor" manufactured by Nippon Zeon Co., Ltd.), a resin film such as a polyethylene terephthalate (PET) film, a polycarbonate film, and a polyvinyl chloride film, and a glass plate.

[0089] 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.

[0090] In the radio wave control element according to the present invention, the support 16 of the metasurface structure 12 is not an essential component, and the support may be omitted. For example, if possible, the metasurface structure may be formed by arranging microstructures directly on the surface of the liquid crystal composition layer.

[0091] 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.

[0092] In the radio wave control element 10, 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 of the present invention. That is, in the radio wave control element of the present invention, there are no limitations on the shape and material of the microstructures, the arrangement of the microstructures, or the pitch between the microstructures. Furthermore, the metasurface structure can be designed using known methods depending on the wavelength of the radio wave RW to be controlled by the radio wave control element 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 used can be calculated using commercially available simulation software, and the arrangement of the microstructures can be set to achieve the desired distribution of phase modulation amounts. When a liquid crystal composition layer is used as in the present invention, phase modulation occurs due to the refractive index and the interaction between the refractive index and the microstructures, and the amount of phase modulation is determined by the resonance characteristics of the microstructures, which change depending on the refractive index.

[0093] The radio wave control element 10 controls radio waves RW with a frequency of, for example, 0.007 to 0.3 THz (7 to 300 GHz). Therefore, the metasurface structure 12 has the microstructures 14 selected so as to impart a desired phase difference to the radio waves RW of this frequency, and furthermore, the arrangement of the microstructures is set.

[0094] Although one unit cell UC basically has one microstructure 14, the present invention is not limited to this. That is, in the radio wave control element according to the present invention, one unit cell UC may have multiple microstructures as necessary depending on the reflection characteristics, the size, material and shape of the microstructures, and the size of the unit cell UC. In this case, one unit cell UC may have different microstructures. 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, the amount of phase modulation is determined for each unit cell UC.

[0095] The material for forming the microstructure 14 is not limited, 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. Composites consisting of metal particles and binders, and oxide semiconductors can also be used as materials for forming the microstructure 14. 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. 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.

[0096] 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. 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.

[0097] 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 direction in the XY plane, or in different directions. Furthermore, microstructures 14 of the same direction and those of different directions may be mixed. However, in the radio wave control element 10, it is preferable to use only one type of microstructure 14 and to arrange all of the microstructures 14 in the same direction.

[0098] As shown in FIG. 3 , the metasurface structure 12 preferably has identical microstructures 14, all of which have the same structure, arranged two-dimensionally at equal intervals in the mutually orthogonal X and Y directions. However, the present invention 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 plane direction of the support 16. However, considering the controllability of the reflection direction of radio waves 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 orthogonal X and Y directions.

[0099] 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.

[0100] 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 horizontal or vertical alignment, a change from 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.

[0101] The liquid crystal composition layer 20 may be formed by a known method, for example, on the surface of an alignment film described later. 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.

[0102] 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 used to form the main body.

[0103] 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.

[0104] There are no limitations on the first electrode layer 26, and a sheet-like object 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.

[0105] 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.

[0106] As described above, the radio wave control element 10 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 a 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.

[0107] In the radio wave control element 10, the refractive index anisotropy Δn 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 Δn 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 Δn 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.

[0108] Furthermore, there is no limitation on the thickness of the liquid crystal composition layer 20, and a thickness that can provide 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. 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.

[0109] Another example of a radio wave control element includes a temperature adjusting member that adjusts the temperature of the liquid crystal composition layer. In this embodiment, the alignment state of the liquid crystal compound in the liquid crystal composition layer can be fixed. This embodiment will be described in detail below. The radio wave control element 10B shown in FIG. 7 includes, from the bottom in the figure, a first electrode layer 26, a liquid crystal composition layer 20, and a 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 to completely cover the surface of the support 24 opposite the liquid crystal composition layer 20. Furthermore, a temperature adjusting member 30 is provided between the support 24 and the first electrode layer 26. The radio wave control element 10B shown in FIG. 7 has the same configuration as the radio wave control element 10 shown in FIG. 4, except for the temperature adjusting member 30. In the liquid crystal composition layer 20 shown in FIG. 7, when no voltage is applied, the liquid crystal compound LD is horizontally aligned. As the applied voltage increases, the liquid crystal compound LD is aligned in a vertically aligned direction.

[0110] The configuration of the temperature adjustment member 30 is not particularly limited as long as it is a member that adjusts the temperature of the liquid crystal composition layer 20. The location where the temperature adjustment member 30 is placed is also not limited as long as it can adjust the temperature of the liquid crystal composition layer 20. The temperature adjustment member 30 may also have a heating device that increases the temperature of the liquid crystal composition layer 20, a cooling device that decreases the temperature of the liquid crystal composition layer 20, or the like.

[0111] The procedure for fixing the alignment state of the liquid crystal compound LD in the liquid crystal composition layer 20 using the radio wave control element 10B is as follows. The liquid crystal compound LD contained in the liquid crystal composition layer 20 is a compound that exhibits liquid crystallinity when subjected to a heat treatment using the temperature adjustment member 30. Specifically, it is preferable to use the composition described above, which exhibits a nematic phase at any temperature between 50 and 150°C and a glassy or smectic phase at any temperature below 50°C. First, in the radio wave control element 10B, the liquid crystal composition layer 20 is heated using the temperature adjustment member 30 to transition to a liquid crystal phase. Next, while maintaining the heat treatment, a voltage is applied between the first electrode layer 26 and the microstructure 14 to control the alignment direction of the liquid crystal compound LD. In this case, as shown in FIG. 8 , the voltages applied to the first unit cell UC1 and the second unit cell UC2 may be different to cause the alignment state of the liquid crystal compound LD to differ. Thereafter, when the heat treatment and voltage application treatment are stopped, the temperature drops below the liquid crystal phase transition temperature, and the alignment state of the liquid crystal compound shown in FIG. 8 is fixed. In other words, the liquid crystal compound can maintain its aligned state without applying a voltage.

[0112] Furthermore, in radio wave control elements, a state with higher alignment can be created depending on the type of liquid crystal compound used. For example, if a liquid crystal compound exhibits both a nematic phase and a higher-order liquid crystal phase, such as a smectic phase, the higher-order liquid crystal phase can be fixed by rapidly cooling the radio wave control element. More specifically, the radio wave control element 10C shown in FIG. 9 has a configuration similar to the radio wave control element 10B shown in FIG. 7. However, in the radio wave control element 10C, the liquid crystal compound LD exhibits both a nematic phase and a smectic phase. Furthermore, in the liquid crystal composition layer 20 shown in FIG. 9, the liquid crystal compound LD is horizontally aligned when no voltage is applied, and as the applied voltage increases, the liquid crystal compound LD aligns in a direction toward vertical alignment. In such a radio wave control element 10C, the liquid crystal composition layer 20 is heated by the temperature adjustment member 30 as shown in FIG. 9 to align the liquid crystal compound LD and develop a nematic phase. Note that FIG. 9 corresponds to a mode in which no voltage is applied between the first electrode layer 26 and the microstructure 14, and the liquid crystal compound LD is horizontally aligned. As shown in Figure 9, although the liquid crystal compound LD is horizontally aligned, the degree of alignment of the nematic phase itself is not high, so the alignment direction of the liquid crystal compound LD is partially disturbed. Next, the heating treatment of the temperature adjustment member 30 is stopped and the liquid crystal composition layer 20 is rapidly cooled, so that the liquid crystal compound LD can be fixed in a state exhibiting a smectic phase. Specifically, as shown in Figure 10, the alignment of the liquid crystal compound LD is further improved. In other words, by performing the rapid cooling treatment, the liquid crystal compound can be fixed in a state with a higher degree of alignment.

[0113] Furthermore, the radio wave control element may have a layer between the first electrode and the second electrode whose refractive index does not change with voltage, or may have a gap between one of the first electrode and the second electrode and the liquid crystal composition layer. More specifically, the radio wave control element 10D shown in FIG. 11 has, from the bottom in the figure, a first electrode layer 26, a dielectric layer 32, a liquid crystal composition layer 20, and a metasurface structure 12, in this order. The radio wave control element 10D shown in FIG. 11 has the same configuration as the radio wave control element 10 shown in FIG. 4 except for the dielectric layer 32. In the liquid crystal composition layer 20 shown in FIG. 10, when no voltage is applied, the liquid crystal compound LD is horizontally aligned, and as the applied voltage is increased, the liquid crystal compound LD is aligned in a vertically aligned direction.

[0114] The dielectric layer 32 is a layer whose refractive index does not change with voltage. The material constituting the dielectric layer 32 is not particularly limited, as long as it has sufficient transparency to radio waves RW. Examples include semiconductors such as silicon, silicon oxide, germanium, and chalcogenide glass; polyacrylic resins such as polymethyl methacrylate; cellulose resins such as cellulose triacetate; resins such as cycloolefin polymers, polyethylene terephthalate (PET), polycarbonate, and polyvinyl chloride; and glass. The dielectric layer 32 may also be an alignment film for orienting the liquid crystal compound LD in a predetermined state. The thickness of the dielectric layer 32 is not particularly limited, but is preferably about the same as that of the liquid crystal composition layer 20. The difference between the thickness of the dielectric layer 32 and the thickness of the liquid crystal composition layer 20 is preferably 100 μm or less, more preferably 50 μm or less.

[0115] As in the radio wave control element 10D, by disposing a dielectric layer 32 between the first electrode layer 26 and the microstructures 14, the distance between the electrodes can be increased. This configuration reduces radio wave loss while maintaining the high response speed of the radio wave control element 10D. The location of the driving electrode that applies voltage to the liquid crystal composition layer is not particularly limited, and the electrode may be located between the first electrode layer 26 and the microstructures 14. Alternatively, an electrode may be provided between the dielectric layer 32 and the liquid crystal composition layer to efficiently apply voltage to the liquid crystal composition layer. In this case, a high-resistance electrode may be used to minimize the effect on radio waves. Furthermore, the electrodes may be positioned so as to sandwich the liquid crystal composition layer horizontally for driving with a transverse electric field. Furthermore, the dielectric constant of the material constituting the dielectric layer 32 with respect to the applied voltage is not particularly limited. When the liquid crystal composition layer and the dielectric layer are arranged in series between opposing planar electrodes, as in the case where the first electrode layer 26 and the microstructures 14 of the radio wave control element 10D are electrodes, a higher dielectric constant for the dielectric layer is preferred because it efficiently increases the electric field across the liquid crystal composition layer. In addition, when electrodes are positioned so as to sandwich the liquid crystal composition layer in the horizontal direction for driving by a transverse electric field, a low dielectric constant of the dielectric layer is preferable because the electric field of the liquid crystal composition layer can be efficiently increased. Furthermore, the dielectric layer may be patterned in the in-plane direction or the thickness direction, whereby the in-plane average effective value of the refractive index or the effective value distribution within the element can be adjusted, thereby adjusting the amount of radio wave control.

[0116] The radio wave control element may also have a light-shielding layer that blocks at least a portion of light in the wavelength range of 250 to 1000 nm. The position of the light-shielding layer in the radio wave control element is not particularly limited, but it is preferably located on the side of the liquid crystal composition layer where external light is incident. By having the light-shielding layer in the radio wave control element, light that can be absorbed by the liquid crystal compound can be prevented from reaching the liquid crystal compound, thereby suppressing decomposition of the liquid crystal compound.

[0117] The present invention will be described in more detail based on examples. The materials, amounts used, ratios, treatment contents, and treatment procedures shown in the following examples can be appropriately changed 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.

[0118] [Synthesis of Liquid Crystal Compound] [Synthesis Example 1] Liquid crystal compound LC-1 was synthesized according to the following scheme: In the following scheme, Ts represents a tosyl group.

[0119]

[0120] 3,7,11-Trimethyl-2,6,10-dodecatrien-1-ol (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 (23°C) for 6 hours. Next, the reaction solution was separated and washed with ethyl acetate and water. The organic layer was extracted, dried over magnesium sulfate, and then concentrated to obtain compound LC-1a (3.8 g) as a colorless liquid. 4-Nitrophenol (1.3 g), compound LC-1a (3.8 g), and potassium carbonate (1.4 g) were dissolved in N,N-dimethylacetamide (20 mL), and the solution was stirred at 95°C for 4 hours. Next, the reaction solution was cooled to room temperature and separated and washed with ethyl acetate and 10% aqueous ammonium chloride solution. The organic layer was extracted, dried over magnesium sulfate, and then concentrated to obtain compound LC-1b (2.5 g) as a colorless liquid. Next, compound LC-1b (2.5 g), palladium-carbon catalyst (0.03 g), and THF (20 mL) were mixed, and the mixture was stirred for 12 hours under a hydrogen atmosphere. The reaction solution was passed through Celite to remove the palladium-carbon catalyst, and then concentrated to obtain compound LC-1c (2.1 g) as a colorless liquid.

[0121] Separately, 2-aminothiophene was synthesized from 2-nitrothiophene according to the method described in Journal of Medicinal Chemistry, 2005, Vol. 48, p. 5794. Compound LC-1c (2.1 g) obtained above was added to a mixture of hydrochloric acid (2 g), pure water (5 mL), and tetrahydrofuran (THF) (10 mL), and the mixture was cooled to a temperature of 5°C or less. Next, a solution obtained by dissolving sodium nitrite (0.5 g) in pure water (2 mL) was added dropwise to the mixture. The mixture was stirred for 1 hour while maintaining the temperature at 5°C or less to prepare a diazonium solution.

[0122] Next, 2-aminothiophene hydrochloride Cp-1 (1 g) was dissolved in pure water (10 mL) and hydrochloric acid (2 g), and the diazonium solution prepared above was added dropwise to the resulting solution while maintaining the temperature at 0°C. After the temperature of the reaction solution was raised to room temperature, the reaction solution was stirred for 2 hours. The precipitated solid was filtered off and dried to obtain compound LC-1d (2.7 g) as a reddish-orange solid. Compound LC-1d (2.7 g) obtained above was suspended and dissolved in acetic acid (30 mL), and sodium thiocyanate (0.5 g) was added to the resulting solution at room temperature. The resulting solution was cooled with water to maintain the temperature at 20°C or below, and bromine (1 g) was added dropwise to the solution. The reaction solution was stirred at room temperature for 2 hours, and then pure water (20 mL) was added to the reaction solution. The resulting solid was filtered off and dried to obtain compound LC-1e (1.1 g) as an orange solid.

[0123] Separately, 2-(N-ethylanilino)ethanol (8.2 g) was dissolved in N,N-dimethylacetamide (DMAc) (50 mL), and the resulting solution was cooled to a temperature of 5°C or less. Next, propionic acid chloride (5.0 g) was added dropwise to the solution, and the mixture was stirred at room temperature for 2 hours. Water (50 mL) was added to the reaction solution, and then ethyl acetate (50 mL) was added, followed by a separation operation. The resulting organic layer was extracted, dried over magnesium sulfate, and filtered. The filtrate was concentrated to obtain compound Cp-2 (11 g).

[0124] Compound LC-1e (1.1 g) obtained above was added to hydrochloric acid (1 g) and acetic acid (2 mL). The resulting mixture was ice-cooled, and an aqueous solution (0.5 mL) of sodium nitrite (0.2 g) was added dropwise to the mixture at 0°C or below. The mixture was stirred for 1 hour, and then amidosulfuric acid (3 mg) was added to obtain a diazonium solution. Compound Cp-2 (0.5 g) was dissolved in methanol (3 mL) to obtain a methanol solution, and the diazonium solution was added dropwise to the methanol solution while maintaining the temperature at 0°C or below. The reaction solution was warmed to room temperature and stirred for 1 hour. Thereafter, pure water (5 mL) was added to the reaction solution, and the resulting solid was filtered to obtain liquid crystal compound LC-1 (0.8 g) as a black-purple solid.

[0125] Synthesis Example 2 A liquid crystal compound LC-2 was synthesized according to the following scheme.

[0126]

[0127] N-Ethylaniline (24.2 g), bromohexane (49.5 g), and potassium carbonate (82.9 g) were dissolved in N,N-dimethylacetamide (300 mL), and the solution was stirred at 95°C for 4 hours. The reaction solution was cooled to room temperature and washed with ethyl acetate and a 10% aqueous ammonium chloride solution. The organic layer was extracted, dried over magnesium sulfate, and then concentrated to obtain compound Cp-4 (32 g) as a colorless liquid.

[0128]

[0129] Compound LC-1e (0.8 g) obtained in Synthesis Example 1 was added to hydrochloric acid (1 g) and acetic acid (2 mL). The resulting mixture was ice-cooled, and an aqueous solution (0.5 mL) of sodium nitrite (0.2 g) was added dropwise to the mixture at 0°C or below. The mixture was stirred for 1 hour, and then amidosulfuric acid (3 mg) was added to obtain a diazonium solution. Compound Cp-4 (0.3 g) was dissolved in methanol (3 mL) to obtain a methanol solution, and the diazonium solution was added dropwise to the methanol solution while maintaining the temperature at 0°C or below. The reaction solution was warmed to room temperature and stirred for 1 hour. Thereafter, pure water (5 mL) was added to the reaction solution, and the resulting solid was filtered to obtain liquid crystal compound LC-2 (0.9 g) as a black-purple solid.

[0130] Synthesis Example 3 The following liquid crystal compound LC-3 was synthesized according to the method described in Example 4 of WO 2017 / 090668.

[0131]

[0132] [Synthesis Example 4] The following liquid crystal compound LC-4 was synthesized according to the following scheme with reference to the method described in

[0069] to

[0076] [Synthesis of dichroic dye compound] of WO 2017 / 154835. Note that in steps 1 to 3, propionyl chloride was used instead of acrylic acid chloride.

[0133]

[0134]

[0135] Compound Cp-5 used in Step 6 above was synthesized by the following method. N-ethylaniline (24.2 g), methyl 4-bromobutyrate (36.5 g), and potassium carbonate (82.9 g) were dissolved in N,N-dimethylacetamide (300 mL), and the solution was stirred at 95°C for 4 hours. The reaction solution was cooled to room temperature and washed with ethyl acetate and a 10% aqueous ammonium chloride solution. The organic layer was extracted, dried over magnesium sulfate, and concentrated to obtain compound Cp-5 (32 g) as a colorless liquid.

[0136] [Synthesis Example 5] The following liquid crystal compound LC-5 was synthesized according to the following scheme with reference to the method described in

[0069] to

[0076] [Synthesis of dichroic dye compound] of WO 2017 / 154835.

[0137]

[0138]

[0139] Compound Cp-6 used in Step 6 above was synthesized by the following method. N-ethylaniline (24.2 g), 3-chloropropanol (20.2 g), and potassium carbonate (82.9 g) were dissolved in N,N-dimethylacetamide (300 mL), and the solution was stirred at 95°C for 4 hours. The reaction solution was cooled to room temperature and washed with ethyl acetate and 10% aqueous ammonium chloride solution. The organic layer was extracted, dried over magnesium sulfate, and then concentrated. Ethyl acetate (300 mL) was added, and the mixture was cooled to 5°C. After that, acrylic acid chloride (22.1 g) and triethylamine (24.5 g) were added, and the mixture was stirred at room temperature (23°C) for 4 hours. Next, the reaction solution was washed with ethyl acetate and water. The organic layer was extracted, dried over magnesium sulfate, and then concentrated to obtain compound Cp-6 (32.5 g) as a colorless liquid.

[0140] [Synthesis Example 6] The following liquid crystal compound LC-6 was synthesized according to the following scheme with reference to the method described in

[0069] to

[0076] [Synthesis of dichroic dye compound] of WO 2017 / 154835.

[0141]

[0142]

[0143] Compound Cp-7 used in Step 6 above was synthesized by the following method. 2-(N-ethylanilino)ethanol (16.5 g) and triethylamine (12.5 g) were dissolved in ethyl acetate (200 mL) and cooled to 5°C. After that, a solution of acrylic acid chloride (9.1 g) was added and stirred at room temperature (23°C) for 4 hours. The reaction solution was then separated and washed with ethyl acetate and water. The organic layer was extracted, dried over magnesium sulfate, and concentrated to obtain compound Cp-7 (15.3 g) as a colorless liquid.

[0144] Synthesis Example 7 A liquid crystal compound LC-7 was synthesized according to the following scheme: In the following scheme, Ts represents a tosyl group, and Ac represents an acetyl group.

[0145]

[0146] Paraacetanilide (10 g) was dissolved in water (100 mL) and 12 mol / L hydrochloric acid (17 mL). The resulting solution was cooled in an ice bath, and sodium nitrite (4.6 g) was added and stirred for 30 minutes. Amidosulfuric acid (0.5 g) was further added to the solution, followed by m-toluidine (5.1 g), and the solution 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 compound LC-7a (14 g). Next, compound LC-7a (6.4 g) was mixed with methanol (50 mL), water (20 mL), and hydrochloric acid (10 mL), and the mixture was stirred while heating at 80°C for 8 hours. After the mixture was cooled to room temperature, the resulting solid was collected by suction filtration to obtain compound LC-7b (4.0 g). Compound LC-7b (3.5 g) was dissolved in water (35 mL) and hydrochloric acid (2.0 mL). The resulting solution was cooled in an ice bath, sodium nitrite (1.9 g) was added, and the mixture was stirred for 120 minutes. After adding amidosulfuric acid (0.5 g), a solution of phenol (2.5 g), 48% aqueous potassium hydroxide solution (4.0 g), and water (24 mL) was 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 compound LC-7c (4.2 g). Next, compound LC-7c (4.0 g), compound Cp-4a (6.5 g), and potassium carbonate (2.3 g) were dissolved in N,N-dimethylacetamide (DMAc) (50 mL), and the solution was stirred at 85°C for 8 hours. After stirring, hydrochloric acid (1.0 g), water (10 mL) and methanol (50 mL) were added to the reaction solution, and the resulting solid was filtered by suction to obtain liquid crystal compound LC-7 (4.5 g).

[0147] Synthesis Example 8 A liquid crystal compound LC-8 was synthesized according to the following scheme.

[0148]

[0149] Compound LC-7c (16 g), 2-ethylhexyl bromide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 18.4 g), and potassium carbonate (manufactured by Kanto Chemical, 13.2 g) were dissolved in DMAc (128 mL, dimethylacetamide), and the solution was stirred at 90°C for 5 hours. After stirring, water (300 mL) was added to the reaction solution to precipitate a solid. The precipitated solid was separated by suction filtration and purified by silica gel chromatography (eluent: chloroform + hexane), yielding liquid crystal compound LC-8 (19.0 g) as a yellow-orange solid.

[0150] [Synthesis Example 9] A liquid crystal compound was synthesized with reference to the method described in Synthesis Example 2 of WO 2019 / 225468. Specifically, the following liquid crystal compound LC-9 was synthesized in the same manner as the method described in Synthesis Example 2 above, except that N-methyl-N-(2-acryloyloxyethyl)aniline was used instead of N-ethyl-N-(2-acryloyloxyethyl)aniline. N-methyl-N-(2-acryloyloxyethyl)aniline was synthesized using N-methylaniline as a raw material according to U.S. Pat. No. 7,601,849 and known methods.

[0151]

[0152] Synthesis Example 10 Using a chiral separation column, only one isomer was separated and isolated from the liquid crystal compound LC-1 synthesized in Synthesis Example 1, and the isolated compound was designated as liquid crystal compound LC-10.

[0153] [Measurements of Liquid Crystal Compounds] The liquid crystal compounds LC-1 to LC-9 obtained in each synthesis example were measured for the following physical properties.

[0154] <Maximum oscillator strength f, wavelength λ> The maximum oscillator strength f and the wavelength λ of the maximum oscillator strength f of each liquid crystal compound were calculated by the density functional method using the quantum scientific calculation program Gaussian 16 according to the method described above.

[0155] <Melting Point Tm of Liquid Crystal Compound> Each liquid crystal compound was diluted with chloroform to a concentration of 1% by mass, and then heated and dried to obtain a solid. The obtained solid was placed on a glass plate, and the glass plate was set on a hot stage. While the set solid was heated from 30°C at a temperature increase rate of 20°C / min, the texture of the solid was observed using a polarizing microscope, and the temperature at which the texture of the solid transitioned to a nematic phase was observed was taken as the melting point Tm of each liquid crystal compound.

[0156] Molecular weight Mw of each liquid crystal compound, maximum oscillator strength f, wavelength λ, f×λ ２ The molecular weight distribution (Mw), the number of asymmetric carbon atoms n, Mw / n, and the melting point (Tm) are shown in Table 1 below. When a liquid crystal compound does not contain an asymmetric carbon atom, "-" is entered in the "Mw / n" column. The above physical properties of liquid crystal compound LC-10 were the same as those of liquid crystal compound LC-1.

[0157]

[0158] [Examples 1 to 5, Comparative Examples 1 to 4 (Preparation of Compositions)] The synthesized liquid crystal compounds were mixed to obtain the compositions shown in Table 2 below to prepare compositions 1 to 9 corresponding to Examples 1 to 5 and Comparative Examples 1 to 4. The mixing ratio of the liquid crystal compounds in each composition was selected so that the melting point Tm of the composition measured by the method described below was the lowest.

[0159] <Tanimoto Similarity> For each liquid crystal compound, a 2048-dimensional Morgan fingerprint representing the molecular structure of the compound was generated according to the method described above. Next, the Tanimoto similarity of the two liquid crystal compounds contained in each composition was calculated based on the generated fingerprints of each liquid crystal compound according to the method described above.

[0160] [Evaluation] <Melting Point Tm, Clearing Point Tc, and Melting Point Depression ΔT of Composition> The prepared composition was placed on a glass plate, and the glass plate was set on a hot stage. The set composition was heated from 30°C at a temperature increase rate of 20°C / min, while the texture of the composition was observed using a polarizing microscope. The temperature at which the texture of the composition was observed to transition to a nematic phase was taken as the melting point Tm (nematic minimum temperature), and the temperature at which the texture of the composition was observed to transition from a nematic phase to an isotropic phase was taken as the clearing point Tc (nematic maximum temperature).

[0161] For each composition, the melting points of the two liquid crystal compounds were divided by the mixing ratio of the liquid crystal compounds to calculate a theoretical melting point Tx of the composition. Specifically, the melting point and content (mass%) of one liquid crystal compound were designated Tm1 and M1, respectively, and the melting point and content (mass%) of the other liquid crystal compound were designated Tm2 and M2, respectively, and the melting point Tx was calculated using the following formula (X): Tx = {(Tm1 × M1) + (Tm2 × M2)} / (M1 + M2) (X). The value (Tx - Tm) obtained by subtracting the actual melting point Tm measured by the above method from the calculated Tx was used as the melting point depression ΔT (°C) of each composition.

[0162] <Refractive Index Anisotropy Δn> The refractive index anisotropy Δn of each composition at a frequency of 30 GHz was measured by the method described in Applied Optics, Vol. 44, No. 7, p. 1150 (2005). The refractive index anisotropy Δn was measured by filling a variable short-circuit waveguide with the composition and heating the waveguide with an external heater to adjust the temperature of the composition to 30°C lower than the clearing point Tc, thereby aligning the composition in a nematic state. Since the difference between the clearing point Tc and the melting point Tm of Compositions 2 and 6 was 30°C or less, the temperature of the composition was adjusted to 15°C lower than the clearing point Tc, thereby aligning the composition in a nematic state. Radio waves at a frequency of 30 GHz were input into the waveguide, and the amplitude ratio of the reflected wave to the incident wave was measured. The amplitude ratio was measured by changing the direction of the static magnetic field and the length of the shunt, the refractive indices ne and no were determined, and the refractive index anisotropy (Δn at a frequency of 30 GHz) was calculated from ne−no.

[0163] The refractive index anisotropy Δn of each composition was calculated and evaluated based on the following criteria: (Δn evaluation criteria) A: Δn is 0.40 or more. B: Δn is 0.35 or more and less than 0.40. C: Δn is less than 0.35.

[0164] Table 2 shows the physical properties, Tanimoto similarity, and evaluation results of each liquid crystal compound contained in the composition. In the table, the "Composition ratio (mass %)" column shows the mass ratio of the content of each liquid crystal compound to the total mass of the composition as a percentage. In the "Racemate" column, "A" indicates that the liquid crystal compound has an asymmetric carbon atom and is a racemate, and "B" indicates that the liquid crystal compound has an asymmetric carbon atom and is not a racemate. In the "Racemate" and "Mw / n (Formula (Y))" columns, "-" indicates that the liquid crystal compound does not have an asymmetric carbon atom.

[0165]

[0166] As shown in Table 2, when a composition contains a first liquid crystal compound and a second liquid crystal compound satisfying the relationship of a Tanimoto similarity of 0.75 or less, and at least one of the first liquid crystal compound and the second liquid crystal compound has an asymmetric carbon atom and is a specific liquid crystal compound satisfying formulas (X) and (Y), the composition has been confirmed to have excellent effects, such as a high refractive index anisotropy Δn with respect to radio waves, a large melting point depression ΔT, and a low melting point Tm. In contrast, the composition of Comparative Example 1, in which the Tanimoto similarity calculated using two liquid crystal compounds exceeds 0.75, and the composition of Comparative Example 2, in which neither of the two liquid crystal compounds has an asymmetric carbon atom, were confirmed to have a large melting point depression ΔT and a high melting point Tm. The composition of Comparative Example 4, in which the liquid crystal compound having an asymmetric carbon atom does not satisfy the relationship of formula (X), was confirmed to have a low refractive index anisotropy Δn with respect to radio waves. The composition of Comparative Example 5, in which the liquid crystal compound having an asymmetric carbon atom does not satisfy the relationship of formula (Y), was confirmed to have a high melting point Tm.

[0167] A comparison between Example 1 and Example 4 confirmed that when both the first liquid crystal compound and the second liquid crystal compound have an asymmetric carbon atom, the melting point depression ΔT was superior. A comparison between Example 3 and Example 4 confirmed that when both the first liquid crystal compound and the second liquid crystal compound satisfy the relationship of formula (X), the refractive index anisotropy Δn was superior. A comparison between Examples 1 and 2 and Examples 3 and 4 confirmed that when both the first liquid crystal compound and the second liquid crystal compound satisfy the relationship of formula (Y), the melting point depression ΔT and the melting point Tm were superior. A comparison between Examples 1 to 3 and Example 4 confirmed that when both the first liquid crystal compound and the second liquid crystal compound are specific compounds, the refractive index anisotropy Δn, the melting point depression ΔT, and the melting point Tm were well-balanced and superior.

[0168] [Fabrication of Radio Wave Control Element] Using each composition, a radio wave control element was fabricated according to the method described in B. Kang, et al., SID 2023 DIGEST (2023) p. 993. The fabricated radio wave control element had a metasurface structure consisting of circular microstructures arranged two-dimensionally at equal intervals along the mutually orthogonal X-Y directions. The fabricated radio wave control element also had a configuration in which the microstructure was sandwiched between two supports with the microstructures formed on one surface, facing the composition layer. Glass plates were used as the supports. Furthermore, an AC power source was connected to each of the microstructures constituting the electrode pair. The fabricated radio wave control element was equipped with a temperature control mechanism that abutted the entire surface of one of the supports. A Peltier element was used as the temperature control mechanism.

[0169] <Evaluation of Frequency Tunability (Tunability)> The prepared radio wave control element was heated using a temperature control mechanism to a temperature 5°C higher than the melting point Tm (nematic minimum temperature) of the composition. Next, while maintaining the temperature, a bias voltage was applied equally to each microstructure to change the alignment state of the liquid crystal compound. This operation was performed by varying the bias voltage from 0 to 25 V, and the frequency tunability (tunability) of each radio wave control element was measured using a horn antenna connected to a network analyzer according to the method described in B. Kang, et al., SID 2023 DIGEST (2023) p. 994.

[0170] As a result of the measurements, the radio wave control elements using the compositions of Examples 1 and 4 and Comparative Examples 2 and 4 had the highest frequency tunability, followed by the radio wave control elements of Examples 2 and 3 and Comparative Example 1, Comparative Example 3 was next highest, and Example 5 had the lowest. In Example 5, the liquid crystal compound was twistedly aligned rather than uniaxially aligned when no electric field was applied. It is presumed that the high enantiomeric excess of the liquid crystal compound contained in Example 5 caused twisted alignment, resulting in low frequency tunability. In all but Example 5, the liquid crystal compound was uniaxially aligned even when no electric field was applied.

[0171] The evaluation results of the frequency tunability of the radio wave control element confirmed that the greater the refractive index anisotropy Δn of the composition, the higher the frequency tunability of the radio wave control element, i.e., the wider the range of possible characteristic changes. The higher the frequency tunability, the wider the frequency range of radio waves that the radio wave control element can accommodate and the wider the phase range that can be moved, so the range of reflection angles of the radio wave control element can also be widened.

[0172] Example 6 A composition was prepared by replacing the liquid crystal compound LC-4 contained in composition 1 of Example 1 with the following compound in an amount equivalent to 5% by mass relative to the total content of liquid crystal compound LC-1 and liquid crystal compound LC-4, and designated composition 10 of Example 6. Composition 10 of Example 6 contained 65% by mass of liquid crystal compound LC-1, 30% by mass of liquid crystal compound LC-4, and 5% by mass of the following compound, based on the total solid content of the composition. The refractive index anisotropy Δn, melting point depression ΔT, and melting point Tm of the composition of Example 6 were evaluated according to the methods described above, and it was confirmed that all of these were comparable to those of Example 1. Furthermore, a radio wave control element was produced using the composition of Example 6 according to the methods described above, and the frequency tunability of the radio wave control element was evaluated, and it was confirmed that the frequency tunability of the radio wave control element was also comparable to that of Example 1.

[0173]

[0174] 2 Radio wave reflecting device 10, 10B, 10C, 10D Radio wave control element 12 Metasurface structure 14 Microstructure 16, 24 Support 20 Liquid crystal layer 26 First electrode layer 28 Power supply 30 Temperature adjustment member 32 Dielectric layer 34 Dielectric layer ANT Antenna AR1, AR2 Area BL Building LD Liquid crystal compound RW Radio wave UC Unit cell

Claims

1. A composition comprising two or more liquid crystal compounds, wherein the two or more liquid crystal compounds include a first liquid crystal compound and a second liquid crystal compound that satisfy the relationship that the Tanimoto similarity is 0.75 or less, and at least one of the first liquid crystal compound and the second liquid crystal compound has an asymmetric carbon atom, satisfies the relationship of formula (X), and is a specific liquid crystal compound that satisfies the relationship of formula (Y). (X) f×λ ２ / Mw≧700 (Y) Mw / n≦400 In the formulas (X) and (Y), f represents the value of the maximum oscillator strength of the specific liquid crystal compound, λ represents the wavelength (nm) of the maximum oscillator strength in the specific liquid crystal compound, Mw represents the molecular weight of the specific liquid crystal compound, and n represents the number of asymmetric carbon atoms in the specific liquid crystal compound.

2. The composition according to claim 1, wherein the first liquid crystal compound and the second liquid crystal compound both have an asymmetric carbon atom.

3. The composition according to claim 1 or 2, wherein the first liquid crystal compound and the second liquid crystal compound both satisfy the relationship of formula (X).

4. The composition according to claim 1 or 2, wherein the first liquid crystal compound and the second liquid crystal compound both have an asymmetric carbon atom and satisfy the relationship of formula (Y).

5. The composition according to claim 1 or 2, wherein the first liquid crystal compound and the second liquid crystal compound both have an asymmetric carbon atom, satisfy the relationship of formula (X), and satisfy the relationship of formula (Y).

6. The composition according to claim 1 or 2, which is used for a radio wave control element.

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

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