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

Abstract

This invention provides a liquid crystal composition for use as a material with high refractive index anisotropy for radio waves and high melting point reduction in radio wave control elements. The liquid crystal composition for radio wave control elements of this invention comprises two or more liquid crystal compounds, wherein at least one of the two or more liquid crystal compounds is a compound represented by formula (1). Formula (1) R 1 -L 1 -A 1 - (Z) 1 -B 1 ) n -L 2 -R 2 .

Description

Technical Field

[0001] This invention relates to liquid crystal compositions for radio wave control elements, radio wave control elements, and compounds. Background Technology

[0002] High-frequency radio waves (e.g., millimeter waves and terahertz waves) required for high-capacity wireless communication exhibit strong linear propagation. Therefore, a radio wave control element is needed to bend the propagation direction of the radio waves to any direction. However, for example, ordinary reflectors reflect radio waves in a fixed direction, and the reflection direction is a specular reflection with equal incident and exit angles. Therefore, the range of possible changes to the propagation direction of the radio waves is significantly limited, making it difficult to transmit the radio waves to the desired location.

[0003] Patent Document 1 discloses a wave control element using a liquid crystal composition for wave control elements, and discloses a specified multicolor compound as a liquid crystal compound. Previous technical documents Patent documents

[0004] Patent Document 1: Japanese Patent Application Publication No. 2019-512023 Summary of the Invention The technical problem to be solved by the invention

[0005] On the other hand, in radio wave control elements using liquid crystal compositions for radio wave control elements, it is desirable to achieve thinner designs and shorter driving times. To obtain radio wave control elements exhibiting these characteristics, a liquid crystal composition for radio wave control elements is needed that can be used as a material with greater refractive index anisotropy to radio waves. Furthermore, a liquid crystal composition for radio wave control elements with high melting point reduction properties is also required. High melting point reduction means that the melting point of a single liquid crystal compound differs significantly from the melting point of a liquid crystal composition containing two or more liquid crystal compounds. Furthermore, in this specification, "melting point" refers to the temperature at which a liquid or liquid crystal state (e.g., nematic phase and smectic phase) changes from a solid state to a liquid or liquid crystal state. After evaluating the properties of a liquid crystal composition for a radio wave control element containing the liquid crystal compound described in Patent Document 1, the inventors found that it was difficult to simultaneously achieve both anisotropy of refractive index for radio waves and reduction of melting point.

[0006] In view of the above-mentioned actual situation, the objective of the present invention is to provide a liquid crystal composition for use as a material with large refractive index anisotropy to radio waves and high melting point reduction properties for radio wave control elements. Furthermore, the subject of this invention also lies in providing radio wave control elements and compounds. means for solving technical problems

[0007] In order to solve the above-mentioned technical problems, the inventors conducted in-depth research and found that the technical problems can be solved by the following configuration.

[0008] [1] A liquid crystal composition for an electromagnetic wave control element comprises two or more liquid crystal compounds, wherein, At least one of the two or more liquid crystal compounds mentioned above is a compound represented by formula (1) described later. [2] According to the liquid crystal composition for radio wave control elements described in [1], wherein, The content of the compound represented by the above formula (1) is 30% by mass or more relative to the total solid content of the liquid crystal composition for the above-mentioned radio wave control element. [3] According to the liquid crystal composition for the radio wave control element described in [1] or [2], wherein, Z 1 At least one of them is -N=N-. [4] According to the liquid crystal composition for radio wave control elements described in [3], wherein, R 1 and R 2 At least one of them is the aforementioned alkyl group having a partial structure represented by formula (X) described later. [5] According to the liquid crystal composition for the radio wave control element described in [3] or [4], wherein, A 1 and B 1 Each is an independent aromatic hydrocarbon ring, and n is an integer from 2 to 4. [6] According to the liquid crystal composition for radio wave control elements described in [5], wherein, R 1 and R 2 For the same group, L 1 and L 2 -CH=CH-, -O-, or -NR 3 - [7] According to the liquid crystal composition for the radio wave control element described in [3] or [4], wherein, A 1 and B 1 At least one of them is an aromatic heterocycle, and n is an integer from 1 to 3. [8] According to the liquid crystal composition for radio wave control elements described in [7], wherein, A 1 and B 1At least one of them is a thienothiazole ring. [9] The liquid crystal composition for a radio wave control element according to any one of [1] to [8], wherein, The compound represented by the above formula (1) is a racemic mixture.

[10] An electromagnetic wave control element, comprising, in sequence: Electrode 1; A liquid crystal composition layer comprising a liquid crystal composition for a radio wave control element as described in any one of [1] to [9]; and Second electrode.

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

[12] According to the compound described in

[11] , wherein, R 1 and R 2 At least one of them is the above-mentioned alkyl group having two or more asymmetric carbon atoms.

[13] According to the compound described in

[11] or

[12] , wherein, A 1 and B 1 Each is an independent aromatic hydrocarbon ring, and n is an integer from 2 to 4.

[14] According to the compound described in

[13] , wherein, R 1 and R 2 For the same group, L 1 and L 2 -CH=CH-, -O-, or -NR 3 -

[15] According to the compound described in

[11] or

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

[16] According to the compound described in

[15] , wherein, A 1 and B 1 At least one of them is a thienothiazole ring.

[17] The compound according to any one of

[11] to

[16] , wherein, The compound represented by the above formula (1) is a racemic mixture. Invention Effects

[0009] According to the present invention, a liquid crystal composition for use as a wave control element that can be used as a material with large refractive index anisotropy to electromagnetic waves and high melting point reduction is provided. Furthermore, according to the present invention, it is possible to provide radio wave control elements and compounds. Attached Figure Description

[0010] Figure 1 This is a diagram illustrating an example of the use of a radio wave control element. Figure 2 This is a diagram illustrating an example of a metasurface structure used in radio wave control elements. Figure 3 This diagram illustrates the mechanism by which the emission direction of radio waves changes in a radio wave control element. Figure 4 This is a diagram that conceptually illustrates an example of a radio wave control element. Figure 5 This is a diagram that conceptually illustrates an example of a liquid crystal alignment pattern in a radio wave control element. Figure 6 It is a graph showing the relationship between the applied voltage and the phase delay of the radio wave. Figure 7 This is a diagram showing an example of melting point determination results. Detailed Implementation

[0011] The present invention will now be described in detail. The following description of the constituent elements is sometimes based on representative embodiments of the present invention, but the present invention is not limited to such embodiments. In addition, in this specification, the numerical range indicated by “~” refers to the range including the values ​​recorded before and after “~” as the lower limit and upper limit.

[0012] In this specification, parallel and orthogonal refer to the range of parallel ±5° and orthogonal ±5°, respectively, rather than parallel and orthogonal in the strict sense.

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

[0014] In this specification, unless otherwise specified, the bonding direction of the divalent groups (e.g., -CO-O-, etc.) shown is not limited. For example, in the case of a compound represented by the formula "XYZ" where Y is -CO-O-, the compound can be either "XO-CO-Z" or "X-CO-OZ".

[0015] <Liquid Crystal Composition for Radio Wave Control Components> The liquid crystal composition for a radio wave control element of the present invention (hereinafter, also simply referred to as "the composition") is a liquid crystal composition for a radio wave control element comprising two or more liquid crystal compounds, wherein, At least one of the two or more liquid crystal compounds is a compound represented by formula (1) described below (hereinafter also referred to as "specific compound").

[0016] The mechanism by which this composition can be used as a material with a large anisotropy of refractive index for radio waves and a high melting point reduction is not yet clear, but the inventors speculate as follows. At least one of the two or more liquid crystal compounds contained in this composition is a specific compound. Because the specific compound has a structure in which multiple ring structures are continuously linked via linking groups, the resulting material tends to have increased anisotropy of refractive index to electromagnetic waves. On the other hand, for compounds with the aforementioned continuously linked structure, the melting point of the compound generally tends to be high, resulting in a possible increase in the phase transition temperature to the liquid crystal phase. For example, as a method to further lower the melting point of a single liquid crystal compound, one could cite mixing liquid crystal compounds with a lower melting point than the individual liquid crystal compound. However, depending on the type of liquid crystal compound, this method sometimes fails to meet the current performance requirements for melting point reduction, and therefore further improvement is still needed. In contrast, because the specific compound has multiple asymmetric carbon atoms at specific sites, it is presumed that this composition has excellent melting point reduction properties. Hereinafter, the case where at least one of the effects of the anisotropy of the refractive index of the radio waves and the effect of the melting point reduction is superior will also be referred to as "the effect of the present invention is superior".

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

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

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

[0020] In equation (1), R 1 and R 2 Each of these can be used independently to represent an alkyl group, cyano group, halogen atom, or -N=C=S or -N=C=Se that can be substituted by -O- or -CO-O-. However, R 1 and R 2 At least one of them represents the above-mentioned alkyl group having an asymmetric carbon atom, R 1 and R 2 The total number of asymmetric carbon atoms is more than 2.

[0021] Alkyl groups that can be substituted with -O- or -CO-O- preferably have asymmetric carbon atoms. An asymmetric carbon atom is a carbon atom to which all four atoms or groups of atoms bonded are different from each other. 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 can be any of the following: straight-chain, branched, and cyclic, preferably straight-chain or branched. Furthermore, when the alkyl group has an asymmetric carbon atom, the alkyl group is preferably branched. The number of carbon atoms in the alkyl group is preferably 1 to 30, more preferably 1 to 25, and even more preferably 3 to 25.

[0022] The -CH2- in the above alkyl group can be replaced by -O- or -CO-O-. For example, the above alkyl group can be... -CH2-CH2-O-CO-CH2-CH3.

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

[0024] Formula (X) -CH2-CH(CH3)-C2H4-

[0025] In formula (X), Indicates the bonding location.

[0026] Furthermore, the aforementioned alkyl group can be a group represented by formula (W).

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

[0028] In formula (W), Indicates the bonding location. AL indicates an alkylene group that does not have an asymmetric carbon atom. R W1 and R W2 R represents either a hydrogen atom or an alkyl group that does not have an asymmetric carbon atom, respectively. W1 and R W2 Indicates distinct groups. R W3 Indicates alkyl group.

[0029] The alkylene group represented by AL that does not have an asymmetric carbon atom can be any of the following: linear, branched, or cyclic, with linear being preferred. The number of carbon atoms in the aforementioned alkylene group is preferably 1 to 10, more preferably 1 to 5.

[0030] By R W1 and R W2 The alkyl group that does not have an asymmetric carbon atom can be any of the following: linear, branched, or cyclic, preferably linear. The number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 3. R W1 and R W2 This indicates distinct groups. In other words, for example, in R... W1 In the case of representing a hydrogen atom, R W2 This indicates an alkyl group that does not have an asymmetric carbon atom. Furthermore, R... W1 and R W2 As long as they are different groups, they can be the same type of group. For example, in R W1 In the case of methyl, R W2 It can be an alkyl group other than methyl (e.g., ethyl) that does not have an asymmetric carbon atom. R W1 and R W2 One of them preferably represents a hydrogen atom, and the other preferably represents an alkyl group that does not have an asymmetric carbon atom.

[0031] By R W3The alkyl group can have asymmetric carbon atoms. The alkyl group can be any one of straight-chain, branched, and cyclic, preferably straight-chain or branched. The number of carbon atoms in the alkyl group is preferably 1 to 25, more preferably 3 to 20. The alkyl group described above is preferably an alkyl group containing isopropyl. R W3 Preferred and R W1 and R W2 Each of them is different.

[0032] However, R 1 and R 2 At least one of them represents the above-mentioned alkyl group having an asymmetric carbon atom, R 1 and R 2 The total number of asymmetric carbon atoms is more than 2. As long as R 1 and R 2 At least one of them is an alkyl group having an asymmetric carbon atom, and the other is not particularly limited, as long as it is R. 1 and R 2 The exemplified groups are acceptable. Among them, R is particularly preferred. 1 and R 2 Both of these refer to the aforementioned alkyl groups having asymmetric carbon atoms. Furthermore, R 1 and R 2 It is also preferable to represent the same group. In addition, with the above R 1 and R 2 Similarly, the -CH2- in the alkyl group with asymmetric carbon atoms mentioned above can also be replaced by -O- or -CO-O-. R 1 and R 2 The total number of asymmetric carbon atoms is 2 or more, preferably 3 or more, and more preferably 4 or more. The upper limit is preferably 10 or less, and more preferably 8 or less.

[0033] In equation (1), L 1 and L 2 Each of these can be used independently to represent a single bond, -O-, -CO-, -CO-O-, -O-CO-O-, and -NR. 3 - or -CH=CH-, O can be replaced by S. R 3 This indicates an alkyl group that can have substituents.

[0034] By L 1 and L 2The "O" (oxygen atom) in each group can be replaced by "S" (sulfur atom). As for L... 1 and L 2 There are no particular restrictions on the groups in which "O (oxygen atom)" is replaced by "S (sulfur atom)". Examples include -S-, -CS-, -CO-S-, and -S-CO-O-. As L 1 and L 2 Preferably, it is a single bond, -CH=CH-, -O-, -CO-O-, or -NR. 3 -

[0035] By R 3 The alkyl group can be any of the following: straight-chain, branched, and cyclic, preferably straight-chain. 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 described above may have asymmetric carbon atoms, but preferably does not have asymmetric carbon atoms. As a substituent that the above-mentioned alkyl group may have, examples include A, which will be described later. 1 and B 1 The indicated group may have substituents.

[0036] In equation (1), A 1 and B 1 Each can be independently represented as an aromatic ring that may have substituents or an aliphatic ring that may have substituents. In B 1 In the case of multiple occurrences, B 1 They can be the same or different.

[0037] The aforementioned aromatic ring and aliphatic ring can be any of the monocyclic and polycyclic rings, or they can be fused rings. Examples of aromatic rings mentioned above include aromatic hydrocarbon rings and aromatic heterocycles. Examples of aromatic hydrocarbon rings include benzene rings, naphthalene rings, anthracene rings, pyrene rings, phenanthrene rings, and fluorene rings, with benzene rings or naphthalene rings being preferred. As the aforementioned aromatic heterocycle, it is preferable to be an aromatic heterocycle in which at least one atom selected from the group consisting of nitrogen and sulfur atoms is a ring member atom. Examples of aromatic heterocycles mentioned above include pyridine rings, pyrimidine rings, pyridazine rings, pyrazine rings, triazine rings (e.g., 1,2,3-triazine rings, 1,2,4-triazine rings, and 1,3,5-triazine rings), tetrazine rings (e.g., 1,2,4,5-tetraazine rings), quinoxaline rings, pyrrole rings, furan rings, thiophene rings, imidazole rings, oxazole rings, thiazole rings, benzopyrrole rings, benzofuran rings, benzothiophene rings, benzoimidazolium rings, benzoxazole rings, benzothiazole rings, benzoxazole rings, naphthopyrrole rings, naphthofuran rings, naphthothiophene rings, naphthoimidazolium rings, naphthooxazole rings, pyrroloimidazolium rings (e.g., 5H-pyrrolo[1,2-a]imidazolium rings), imidazoxazole rings (e.g., imidazo[2,1-b]oxazole rings), and thieno[2]thiazole rings (e.g., thieno[2]thiazole rings). [3-d]thiazole ring, etc.), benzothiadiazole ring, benzodithiophene ring (e.g., benzo[1,2-b:4,5-b']dithiophene ring, etc.), thieno[3,2-b]thiophene ring, etc., thiazo[5,4-d] ... Dithiophene ring, naphtho[2,1-b:6,5-b']dithiophene ring, naphtho[1,2-b:5,6-b']dithiophene ring and 1,8-dithiabicyclopenta[b,g]naphthyl ring, benzothiophene ring, dithiophene[3,2-b:2',3'-d]thiophene ring and 3,4,7,8-tetrathiabicyclopenta[a,e]cyclopentadiene ring. Among them, the aromatic heterocycle is particularly preferred to be a pyridine ring, a pyrimidine ring, a thiophene ring, a thiazole ring, or a fused ring formed by two or more of these rings, and more preferably a pyrimidine ring or a thiophene-thiazole ring.

[0038] Examples of substituents that can be present in the aforementioned aromatic rings and aliphatic rings include halogen atoms (e.g., fluorine, chlorine, bromine, and iodine atoms), hydrocarbon groups (alkyl (including cycloalkyl, bicycloalkyl, and tricycloalkyl), alkenyl (including cycloalkenyl and bicycloalkenyl), alkynyl, and aryl), heterocyclic groups, cyano, isothiocyanate groups, nitro, alkoxy, aryloxy, silyl, silanoxy, heterocyclic, acyloxy, carbamoyloxy, alkoxycarbonyloxy, and aromatic groups). The group consisting of alkyl carbonyl group, primary, secondary or tertiary amino group (including aniline group), alkyl thio group, aryl thio group, heterocyclic thio group, alkyl sulfinyl group or aryl sulfinyl group, alkyl sulfonyl group or aryl sulfonyl group, acyl group, aryloxy carbonyl group, alkoxy carbonyl group, aryl azo group or heterocyclic azo group, imide group, phosphinyl group, oxophosphinyl group, oxophosphinyloxy group, oxophosphinylamino group, phosphonyl group, carboxyl group, phosphate group, sulfonic acid group, hydroxyl group, thiol group, amide group, carbamoyl group, ureyl group, borate group and groups composed of these groups. Among them, the substituents mentioned above are particularly preferred to be alkyl groups that may have oxygen atoms, nitrogen atoms or sulfur atoms, alkoxy groups that may have oxygen atoms, nitrogen atoms or sulfur atoms, halogen atoms, cyano groups or isothiocyanate groups, and more preferably alkyl groups or halogen atoms. The alkyl group and the alkoxy group described above may have an oxygen atom, a nitrogen atom, or a sulfur atom. For example, in the alkyl group described above and the alkyl group constituting the alkoxy group described above, -CH2- can be -O-, -S-, -CO-, -CS-, -CO-O-, or -CO-NR. N -、-NR N -Or substitution by groups formed by combinations of these groups. R N It represents a hydrogen atom or an alkyl group. The number of carbon atoms in the alkyl group and the alkoxy group is preferably 1 to 10, more preferably 1 to 6.

[0039] In equation (1), Z 1 This indicates a single bond, -O-, -CO-, -CO-O-, -O-CO-O-, and -CR. Z =CR Z -、-C≡C-、-N=N-、-CR Z =CR Z -CR Z =CR Z -、-C≡CC≡C-、-CR Z =CR Z -CO- or -CR Z =CR Z -CO-O-, where O can be replaced by S. R Z They can be used to represent hydrogen atoms or fluorine atoms independently. In Z 1 In the case of multiple Z 1 They can be the same or different.

[0040] By Z 1 The "O (oxygen atom)" in each group can be replaced by "S (sulfur atom)". As a group composed of Z... 1 The groups represented by replacing "O (oxygen atom)" with "S (sulfur atom)" are not particularly limited; examples include -S-, -CS-, -CO-S-, -S-CO-O-, and -CR. Z =CR Z -CS- and -CR Z =CR Z -CO-S-. As Z 1Preferably, it is a single bond, -O-, -CO-O-, -C≡C- or -N=N-, more preferably a single bond, -C≡C- or -N=N-, and even more preferably -N=N-. Furthermore, Z is preferred. 1 At least one of them is -N=N-, more preferably Z. 1 All are -N=N-.

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

[0042] The following shows an example of a preferred method for a particular compound. The specific compound preferably satisfies requirement X and at least one of requirements Y1 and Y2. Furthermore, the specific compound preferably satisfies requirement X and at least one of requirements Z1 and Z2. ·Requirement X: In formula (1), Z 1 At least one of them is -N = N-. R 1 and R 2 At least one of them is an alkyl group having a partial structure represented by the above formula (X). • Requirement Y1: In formula (1), A 1 and B 1 Each is an independent aromatic hydrocarbon ring, and n is an integer from 2 to 4. ·Requirement Y2: In formula (1), R 1 and R 2 For the same group, L 1 and L 2 -CH=CH-, -O-, or -NR 3 - • Requirement Z1: In formula (1), A 1 and B 1 At least one of them is an aromatic heterocycle, and n is an integer from 1 to 3. • Requirement Z2: In formula (1), A 1 and B 1 At least one of them is a thienothiazole ring.

[0043] The specific compound is preferably a racemic mixture. A so-called racemic mixture is preferred. In this specification, "racemate" refers to a compound having n asymmetric carbon atoms (n being an integer greater than or equal to 2), where the number of molecules with the i-th (i=1 to n) asymmetric carbon atom as the R-body and the number of molecules as the S-body are respectively set as N. Ri N Si At that time, NRi / (N) Ri +N Si The value is 0.4–0.6. N Ri / (N) Ri +N Si The preferred value is 0.45 to 0.55, and more preferably 0.5. Since the specific compound with asymmetric carbon is a racemic mixture containing chiral isomers in approximately the same proportion, the orientation is less likely to be twisted in the layer formed using this composition, and the refractive index of the specific compound is more easily changed by applying an electric field.

[0044] A specific compound may be used alone or in two or more forms. The content of the specific compound relative to the total solid content of the liquid crystal composition for radio wave control elements is preferably 1% by mass or more, more preferably 10% by mass or more, and even more preferably 30% by mass or more. The upper limit relative to the total solid content of the liquid crystal composition for radio wave control elements is preferably less than 100% by mass, more preferably 80% by mass or less, and even more preferably 60% by mass or less. Solid components refer to components other than solvents. Any component other than a solvent, even if it is in a liquid state, is considered a solid component.

[0045] Other liquid crystal compounds are not subject to special restrictions as long as they are liquid crystal compounds other than the specific compounds. Liquid crystal compounds are generally classified into rod-shaped and disk-shaped types based on their shape. Furthermore, each type includes low-molecular-weight and high-molecular-weight types. High-molecular-weight types typically refer to substances with a degree of polymerization of 100 or higher. (Polymer Physics and Phase Transition Dynamics, Masao Doi, p. 2, Iwanami Shoten, 1992).

[0046] As other liquid crystal compounds, rod-shaped liquid crystal compounds or disk-shaped liquid crystal compounds (disc-shaped liquid crystal compounds) are preferred. Other liquid crystal compounds may be any one of two or more rod-shaped liquid crystal compounds, two or more disk-shaped liquid crystal compounds, or a mixture of rod-shaped liquid crystal compounds and disk-shaped liquid crystal compounds. Furthermore, other liquid crystal compounds can be either positive wavelength dispersion or negative wavelength dispersion.

[0047] Other liquid crystal compounds can be liquid crystal compounds with polymerizable groups (polymeric liquid crystal compounds). As a polymerizable liquid crystal compound, at least one polymerizable liquid crystal compound is preferably selected from the group consisting of polymerizable rod-shaped liquid crystal compounds and polymerizable disk-shaped liquid crystal compounds. Examples of polymerizable groups include acryloyl, methacryl, epoxy, and vinyl groups. By polymerizing the above-mentioned polymerizable liquid crystal compounds, the orientation of the liquid crystal compound can be fixed. Furthermore, the liquid crystal compound does not need to exhibit liquid crystal properties after being fixed by polymerization.

[0048] As rod-shaped liquid crystal compounds, examples include those described in claim 1 of Japanese Patent Application Publication No. 11-513019 and in paragraphs

[0026] to

[0098] of Japanese Patent Application Publication No. 2005-289980. As a disc-shaped liquid crystal compound, examples include the disc-shaped liquid crystal compounds described in paragraphs

[0020] to

[0067] of Japanese Patent Application Publication No. 2007-108732 and paragraphs

[0013] to

[0108] of Japanese Patent Application Publication No. 2010-244038.

[0049] As other liquid crystal compounds, compounds represented by formula (2) are preferred. Equation (2) R 3 -L 1 -A 1 -(Z 1 -B 1 ) n -L 2 -R 4 L in equation (2) 1 L 2 A 1 B 1 Z 1 The definition and preferred method of n are the same as the definition and preferred method of each group in formula (1). R 3 and R 4 This indicates that -CH2- can be replaced by alkyl, cyano, halogen atom, -N=C=S or -N=C=Se. However, R 3 and R 4 The total number of asymmetric carbon atoms is 0 or 1. By R 3 and R 4 The alkyl group represented, where -CH2- can be substituted with -O- or -CO-O-, preferably has no asymmetric carbon atom or has one asymmetric carbon atom, more preferably has no asymmetric carbon atom. That is, R 3 and R 4 Preferably, all of the above-mentioned alkyl groups are free of asymmetric carbon atoms. The alkyl group can be any one of straight-chain, branched, and cyclic, preferably straight-chain or 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.

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

[0051] This composition preferably contains no solvent. Essentially, "not containing solvent" means that the solvent content is 5% by mass or less, preferably 3% by mass or less, relative to the total mass of the liquid crystal composition for the radio wave control element.

[0052] <Radio Wave Control Components> This composition is suitable for use in radio wave control components. Radio wave control elements act on radio waves. Examples of radio waves include those with frequencies ranging from 0.007 to 0.3 THz. Radio waves in this frequency band (RW) are called high-frequency radio waves (centimeter waves, millimeter waves, terahertz waves, etc.), which are capable of high-capacity wireless communication and have strong line-of-sight propagation.

[0053] As an example of an electromagnetic wave control element, one can cite an element having a first electrode, a liquid crystal composition layer composed of the present composition, and a second electrode in sequence. In this electromagnetic wave control element, by applying a voltage between the first and second electrodes, the orientation state of the liquid crystal compounds (specific compounds and other liquid crystal compounds) contained in the liquid crystal composition layer is controlled, and the refractive index anisotropy of the liquid crystal composition layer is adjusted, thereby enabling the adjustment of the propagation direction of the electromagnetic wave. In the liquid crystal composition layer formed by this composition, the orientation state of the liquid crystal compound can be changed by applying a voltage. Especially when the liquid crystal compound exhibits liquid crystal properties, the above-mentioned characteristics are readily manifested. In the liquid crystal composition layer formed by this composition, a state with high refractive index anisotropy can be achieved by controlling the orientation state of the liquid crystal compound. Typically, in radio wave control devices, the response speed depends on the film thickness of the liquid crystal composition layer. Since the liquid crystal composition layer formed by this composition can exhibit a state with high refractive index anisotropy, the film thickness of the liquid crystal composition layer can be reduced, resulting in an improved response speed. Therefore, switching of the reflection direction of incident radio waves can be performed in a short time.

[0054] The following description uses accompanying drawings to illustrate specific examples of radio wave control elements. exist Figure 1 The radio wave reflecting device 2 shown uses the radio wave control element 10 involved in the technology of this invention. The radio wave reflecting device 2 is capable of reflecting radio waves RW, which have strong line propagation characteristics, radiated from the antenna ANT located behind the building BL, toward the area AR1 in front of the building BL, which is a shadowed area from the perspective of the antenna ANT due to the obstruction of the building BL. Furthermore, the radio wave reflecting device 2 can change the reflection direction of the radio wave RW between multiple different directions, such as the direction towards region AR1 and the direction towards region AR2. For example, if users utilizing wireless communication are mostly located in region AR1 during the daytime and mostly in region AR2 during the nighttime, the user concentration area may change with different time periods. In this case, the radio wave reflecting device 2 can change the area supplying the radio wave RW by changing the reflection direction of the radio wave RW according to the time period.

[0055] like Figure 2 As shown, 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 the radio wave RW in the desired direction. The metasurface structure 12 is a structure utilizing metamaterials. Metamaterials are artificial materials that exhibit properties not found in natural materials, such as a negative refractive index for electromagnetic waves. The electromagnetic wave control element 10 is a structure consisting of multiple unit cells UC arranged in a two-dimensional pattern, and the two-dimensional plane formed by the arrangement of the multiple unit cells UC becomes the reflecting surface of the electromagnetic wave RW. Each unit cell UC contains a microstructure 14, which is a metamaterial, and constitutes the smallest unit capable of actively changing the phase of the electromagnetic wave RW on the reflecting surface. As an example, the microstructure 14 is made of metal. The microstructure 14 has a size on the order of less than the wavelength of the incident electromagnetic wave RW, and functions as a resonator that resonates through interaction with the incident electromagnetic wave RW. Electrically, for example, the microstructure 14 can be considered equivalent to a resonant circuit in which an alternating current resonates by connecting a coil and a capacitor in series. Through the resonant action of the microstructure 14, the phase of the incident electromagnetic wave RW changes. Moreover, by actively changing the resonance conditions of the microstructure 14 through various methods, the phase delay of the radio wave RW can also be controlled.

[0056] The radio wave control element 10 mainly operates on radio waves RW with a frequency of 0.007 to 0.3 THz. In the radio wave control element 10, the metasurface structure 12 is configured to operate on a radio wave RW with a frequency of 0.1 to 0.3 THz. The wavelength of the radio wave RW with a frequency of 0.1 to 0.3 THz is 1 to 3 mm. As an example, the size of the microstructure 14 constituting the metasurface structure 12 is on the order of about half the wavelength. By setting the size of the microstructure 14 to be below the wavelength of the radio wave RW, the microstructure 14 resonates due to the transmitted radio wave RW and functions as a phase modulation element that modulates the phase of the radio wave RW.

[0057] exist Figure 3 In the above, as shown by the incident direction IN and the exit direction OUT, the overall propagation direction of the radio wave RW can be considered to be the normal direction relative to the straight line connecting the wavefronts of the multiple radio waves RW. Then, in the radio wave control element 10, for example, consider the case where the phase delay of the radio waves RW, which are respectively incident on and reflected from multiple unit cells UC arranged in a one-dimensional direction, gradually increases from the unit cells UC in the right direction towards the unit cells UC in the left direction. In this way, even when the straight line connecting the wavefronts of the individual incident radio waves RW is parallel to the reflecting surface, the straight line connecting the wavefronts of the individual radio waves RW reflected by each unit cell UC will be inclined relative to the reflecting surface. That is, the propagation direction of the radio wave RW exiting from the reflecting surface, i.e., the exit direction OUT, changes by an angle θ relative to the incident direction IN of the radio wave RW. Thus, by controlling the phase modulation, i.e., the phase delay, for each unit cell UC, the propagation direction of the radio wave RW can be controlled.

[0058] As a result, ordinary reflectors can only change the propagation direction of radio waves RW to the specular reflection direction, while the radio wave reflecting device 2, by using the metasurface structure 12, can change the propagation direction of radio waves RW to a direction other than the specular reflection direction. Furthermore, by actively changing the phase delay in each unit cell UC, the propagation direction of radio waves RW can be actively changed.

[0059] As an example, such as Figure 4 The diagram conceptually illustrates that the radio wave control element 10 uses a liquid crystal composition layer 20 as an element for actively changing the resonance conditions of the microstructure 14 of the metasurface structure 12. The radio wave control element 10, from bottom to top, includes a first electrode layer 26, a liquid crystal composition layer 20, and a metasurface structure 12. The liquid crystal composition layer 20 is disposed on a support 24. Furthermore, the first electrode layer 26 is configured to completely cover the side of the support 24 opposite to the liquid crystal composition layer 20. The liquid crystal composition layer 20 contains a liquid crystal compound (liquid crystal compound LD).

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

[0061] In the radio wave control element 10, the first electrode layer 26 and the support 24, and the liquid crystal composition layer 20 and the support 16, are bonded together as needed using an adhesive (binder or bonding agent). The bonding method is not limited; any known method that allows the radio waves targeted by the radio wave control element 10 to pass through can be used. For example, an OCA (Optical Clear Adhesive) method that allows the radio waves targeted by the radio wave control element 10 to pass through can be used.

[0062] As an example, the microstructure 14 is formed of a conductive material and also serves as an electrode that forms an electrode pair with the first electrode layer 26. Furthermore, a power supply 28 for applying voltage between the microstructure 14 and the first electrode layer 26 is connected to each microstructure 14. Therefore, the magnitude of the applied voltage can be controlled for each unit cell UC. The first electrode layer 26 is a common electrode shared by all unit cells UC, while the microstructure 14 of each unit cell UC functions as an independent electrode. The first electrode layer 26, functioning as a common electrode, is an example of the "first electrode" according to the technology of this invention, and the independent electrode, which is also a microstructure 14, is an example of the "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 voltage."

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

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

[0065] like Figure 5 As shown, the cross-section of the liquid crystal compound LD is approximately elliptical with a major axis and a minor axis. As an example, when no voltage is applied between the microstructure 14, which functions as an electrode pair, and the first electrode layer 26, no electric field is generated in the liquid crystal composition layer 20. In this state, as... Figure 5 As conceptually shown in the upper part, the liquid crystal compound LD is oriented with its long axis along the thickness direction of the liquid crystal composition layer 20. In the following description, this orientation state is also referred to as "vertical orientation".

[0066] In this state, if a voltage is applied between the microstructure 14 and the first electrode layer 26, an electric field is generated in the liquid crystal composition layer 20, and the orientation state of the liquid crystal compound LD changes. Specifically, as... Figure 5 As conceptually shown in the lower part, the orientation state of the liquid crystal compound LD in the region corresponding to the microstructure 14 changes according to the magnitude of the applied voltage and is tilted relative to the thickness direction of the liquid crystal composition layer 20. Figure 5 The example shown at the bottom illustrates the state where the tilt angle of the liquid crystal compound LD is at its maximum. In this maximum tilt angle state, the liquid crystal compound LD is oriented with its long axis perpendicular to the thickness direction of the liquid crystal composition layer 20. In the following description, the orientation state with the maximum tilt angle is also referred to as "horizontal orientation".

[0067] The greater the tilt of the liquid crystal compound LD, that is, the closer the long axis of the liquid crystal compound LD is to the main plane direction of the liquid crystal composition layer 20 ( Figure 5The greater the angle (X or Y direction) of the liquid crystal compound LD, the higher the refractive index of the liquid crystal composition layer 20. Conversely, the smaller the tilt of the liquid crystal compound LD, i.e., the closer the long axis of the liquid crystal compound LD is to the thickness direction of the liquid crystal composition layer 20 (Z direction in the figure), the lower the refractive index of the liquid crystal composition layer 20. Due to this change in the refractive index of the liquid crystal composition layer 20 in each unit cell UC, the resonance condition of the microstructure 14 changes, and the phase delay of the incident electromagnetic wave RW changes. In this example, Figure 5 The phase delay of the lower unit cell UC is greater than Figure 5 The upper unit cell UC is large.

[0068] That is, in the liquid crystal composition layer 20 surrounding the microstructure 14 of each unit cell UC, if the orientation state of the liquid crystal compound LD changes, the refractive index of the liquid crystal composition layer 20 relative to the electromagnetic wave RW transmitted through each unit cell UC changes. Furthermore, since the refractive index is positively correlated with the dielectric constant, when the refractive index of the liquid crystal composition layer 20 changes, the resonance condition of the microstructure 14, which functions as a resonator, also changes. The change in the resonance condition of the microstructure 14 manifests as a change in the phase retardation of the electromagnetic wave RW. Therefore, by changing the refractive index of the liquid crystal composition layer 20, the phase retardation of the electromagnetic wave RW can be changed. Moreover, the change in the refractive index of the liquid crystal composition layer 20 itself also causes a change in the phase retardation of the electromagnetic wave RW. The refractive index of the liquid crystal composition layer 20 of each unit cell UC changes according to the voltage V applied to each unit cell UC; therefore, as an example, the relationship between voltage V and the phase retardation of the electromagnetic wave RW is as follows: Figure 6 As shown.

[0069] like Figure 3 As shown, if radio wave RW is incident on radio wave control element 10 from the microstructure 14 side, the radio wave RW passes through microstructure 14 and liquid crystal composition layer 20 in sequence. Furthermore, the radio wave RW is reflected by the first electrode layer 26, which also serves as a reflective layer, and again passes through liquid crystal composition layer 20 and microstructure 14 in sequence before exiting radio wave control element 10. The radio wave RW is reflected through this incident-out incident path. In the incident-out incident path, for the radio wave RW passing through each unit cell UC, phase modulation caused by the resonance of microstructure 14 and phase modulation caused by the radio wave RW passing through liquid crystal composition layer 20 are generated. More specifically, in each unit cell UC, the resonance condition of microstructure 14 is determined according to the refractive index of liquid crystal composition layer 20, and phase modulation of radio wave RW is generated through resonance corresponding to this condition. In addition, phase modulation of radio wave RW corresponding to the magnitude of the refractive index of liquid crystal composition layer 20 is also generated.

[0070] according to Figure 6The relationship shown is that the phase delay of the radio wave RW is controlled by the applied voltage V for each unit cell UC, thereby controlling the reflection direction of the radio wave RW reflected by the radio wave control element 10.

[0071] like Figure 3 As shown, a conventional reflector can only change the propagation direction of radio wave RW to the specular reflection direction, while the radio wave control element 10, by using the metasurface structure 12, can change the propagation direction of radio wave RW to a direction other than the specular reflection direction. Furthermore, by actively changing the phase delay in each unit cell UC, the propagation direction of radio wave RW can be actively changed.

[0072] Furthermore, regarding the control of the propagation direction of the radio wave RW emitted from the radio wave control element 10, in addition to... Figure 3 In addition to controlling the reflected radio wave RW to propagate in a straight line in one direction as shown in the example, various other methods can be conceived. For example, the radio wave RW emitted from the radio wave control element 10 can be focused toward a certain focal point, or it can diverge in the opposite direction. By adjusting the applied voltage for each unit cell UC, and thus adjusting the phase delay of the radio wave RW in each unit cell UC, the propagation direction of the emitted radio wave RW can be controlled.

[0073] For example, consider the following situation: Figure 3 As shown, when multiple unit cells UC are arranged in one direction, the phase delay of the central unit cell UC is increased, and the phase delay gradually decreases from the center towards both sides. In this case, if the wavefronts connecting the radio waves RW passing through each unit cell UC form a V-shape, the emitted radio waves RW can be focused. Conversely, consider the case where the phase delay of the central unit cell UC is decreased, and the phase delay gradually increases from the center towards both sides. In this case, if the wavefronts connecting the radio waves RW passing through each unit cell UC form a mountain shape (inverted V-shape), the emitted radio waves RW can be diverged. The degree of focusing and divergence can also be adjusted by controlling the phase delay of the radio waves RW passing through each unit cell UC by adjusting the applied voltage.

[0074] The metasurface structure 12, like known metasurface structures, is formed by arranging microstructures 14, which are metamaterials, in a two-dimensional manner on a support 16. In the metasurface structure 12 illustrated in the figure, as... Figure 2 As shown, the microstructures 14 are arranged in a two-dimensional pattern at equal intervals along mutually orthogonal X and Y directions. Furthermore, in this metasurface structure 12, as an example, all the microstructures 14 are identical.

[0075] The support 16 is not limited; any known sheet material can be used as long as it can support the microstructure 14 and allow radio waves RW with a frequency of 0.007 to 0.3 THz targeted by the radio wave control element 10 to pass through. As an example, the support 16 can be a metal substrate with an oxide insulating layer, such as a silicon substrate with silicon oxide; a support made of oxides such as silicon oxide; a support made of semiconductors such as germanium and chalcogenide glass; a polyacrylic resin film such as polymethyl methacrylate; a cellulose resin film such as cellulose triacetate; a cyclic olefin polymer film (e.g., manufactured by JSR Corporation under the trade name "ARTON" and by Zeon Corporation under the trade name "ZEONOR"); a polyethylene terephthalate (PET) film; a polycarbonate film; a polyvinyl chloride film; and a glass plate.

[0076] The thickness of the support 16 is not limited, as long as it can support the microstructure 14, has sufficient transmittance to radio waves RW with a frequency of 0.007 to 0.3 THz, and has sufficient strength corresponding to the application of the radio wave control element 10. The thickness of the support 16 can be appropriately set according to the forming material of the support 16 to meet these conditions.

[0077] Furthermore, in the radio wave control element 10 according to the technology of the present invention, the support 16 is not a necessary component of the metasurface structure 12, and the support 16 can be omitted. For example, whenever possible, the metasurface structure 12 can also be formed by directly arranging microstructures 14 on the surface of the liquid crystal composition layer 20.

[0078] As described above, the metasurface structure 12 is formed by arranging microstructures 14, which are metamaterials, in a two-dimensional arrangement on a plane, spaced apart from each other. More specifically, the metasurface structure 12 is basically composed of unit cells UC, which are units of one microstructure 14 and the space surrounding the microstructure 14.

[0079] In the radio wave control element 10 according to the technology of the present invention, the morphology of the metasurface structure is substantially the same as that of known metasurface structures. Therefore, various known metasurface structures can be utilized in the radio wave control element 10 according to the technology of the present invention. That is, in the technology of the present invention, the shape and forming material of the microstructure 14, the arrangement of the microstructure 14, and the spacing of the microstructure 14 are not limited. Furthermore, the metasurface structure 12 can be designed using known methods based on the wavelength of the radio wave RW controlled by the radio wave control element 10 and the target reflection characteristics (e.g., the controllable range of reflection directions). For example, the amplitude and phase of the radio wave RW reflected by the microstructure 14 can be calculated using commercially available simulation software, and the arrangement of the microstructure 14 can be set in a manner that obtains the target phase modulation distribution. In the case where the liquid crystal composition layer 20 is used as in this example, the phase modulation is generated by the refractive index and the interaction between the refractive index and the microstructure 14, and the phase modulation amount is determined by the resonant characteristics of the microstructure 14 that vary with the refractive index.

[0080] The radio wave control element 10 according to the present invention controls radio waves RW with frequencies ranging from 0.007 to 0.3 THz. Therefore, for the metasurface structure 12, a microstructure 14 is selected to impart a desired phase difference to the radio waves RW at that frequency, and the arrangement of the microstructures is further configured. Specifically, when the radio waves RW with frequencies ranging from 0.1 to 0.3 THz are controlled, the wavelength range of the radio waves RW is approximately 1 to 3 mm; therefore, a microstructure 14 with a size within this wavelength range is selected.

[0081] While the number of microstructures 14 in a single unit cell UC is essentially one, the present invention is not limited to this. That is, in the radio wave control element involved in the present invention, a single unit cell UC can have multiple microstructures 14 as needed, depending on reflection characteristics, the size of the microstructures 14, the forming material and shape, and the size of the unit cell UC. In this case, a single unit cell UC can have different microstructures 14. However, the unit cell UC is the smallest unit capable of actively changing the phase of the radio wave RW; therefore, even when a single unit cell UC has multiple microstructures 14, the phase modulation amount is still determined separately for each unit cell UC.

[0082] Furthermore, the material used to form the microstructure 14 is not limited, and various materials used as microstructures in known metasurface structures can be utilized. Examples of materials for forming the microstructure 14 include metals and dielectrics. In the case of metals, copper, gold, and silver are preferred examples from the viewpoint of minimizing optical loss. Furthermore, composites composed of metal particles and binders, as well as oxide semiconductors, can also be used as materials for forming the microstructure 14. On the other hand, in the case of dielectrics, silicon, titanium oxide, and germanium are preferred examples considering their high refractive index and ability to increase phase modulation. Additionally, as... Figure 4As shown, when the microstructure 14 also serves as an electrode forming an electrode pair with the first electrode layer 26, the microstructure 14 is formed of a conductor.

[0083] Similarly, the shape of the microstructure 14 is not limited, and various shapes used as microstructures in known metasurface structures can be utilized. Examples include: a cross-shaped solid formed by intersecting cuboids, a cuboid shape, a cylindrical shape, a V-shaped solid formed by connecting cuboids at the ends, as shown in Japanese Patent Application Publication No. 2018-046395, a roughly H-shaped solid like an H-beam, and a roughly C-shaped solid like a C-channel. Furthermore, as shown in Japanese Patent Application Publication No. 2018-046395, various shapes obtained by adjusting the angle between two cuboids can be used for the V-shaped and cross-shaped solids. In addition, shapes with features such as those described in "Appl. Sci. 2018, 8(9), 1689; https: / / doi.org / 10.3390 / app8091689" can also be utilized. Figure 5 The solid shape shown is a base shape, etc.

[0084] In the metasurface structure 12, the microstructures 14 can be of the same type, or multiple microstructures can be combined. Furthermore, the same microstructures 14 can be arranged in the same orientation or in different orientations in the XY plane. Also, microstructures 14 with the same orientation and microstructures 14 with different orientations can coexist. However, in the radio wave control element 10 according to the technology of this invention, it is preferable to use only one type of microstructure 14 and arrange all microstructures 14 in the same orientation.

[0085] And, as Figure 3 As shown, the preferred embodiment of the metasurface structure 12 is as follows: all identical microstructures 14 having the same structure are arranged at equal intervals in a two-dimensional arrangement along mutually orthogonal X and Y directions. However, the technology of the present invention is not limited to this. As described above, various microstructures can be used in combination, and the arrangement interval and arrangement of the microstructures 14 can also differ in the in-plane direction of the support 16. However, considering the controllability of the reflection direction of the electromagnetic wave RW when a voltage is applied to the liquid crystal composition layer 20, it is preferable to use completely identical microstructures 14 for the metasurface structure 12. Moreover, it is more preferable that the microstructures 14 are evenly spaced from each other, and even more preferably that they are evenly spaced in the two orthogonal X and Y directions.

[0086] The liquid crystal composition layer 20 is a layer formed by aligning a liquid crystal compound LD in a predetermined state. As described above, the orientation state of the liquid crystal compound LD changes when a voltage is applied.

[0087] exist Figure 4 In the illustrated liquid crystal composition layer 20, the liquid crystal compound LD is vertically oriented when no voltage is applied. If a voltage is applied to the liquid crystal composition layer 20, the liquid crystal compound LD is oriented in a tilted manner relative to the thickness direction according to the magnitude of the voltage, and can be tilted up to a horizontal orientation. Furthermore, in the radio wave control element 10, the orientation change of the liquid crystal compound LD is not limited to changing from vertical orientation to horizontal orientation or from horizontal orientation to vertical orientation; it can also change from a state tilted relative to the thickness direction to a horizontal orientation or a vertical orientation, or from a horizontal orientation or a vertical orientation to a state tilted relative to the thickness direction; and the tilt angle can be changed between one state tilted relative to the thickness direction and another state tilted relative to the thickness direction.

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

[0089] Here, the support 24 forming the liquid crystal composition layer 20 can also be based on the aforementioned support 16, and have an alignment film on the surface of the liquid crystal composition layer 20 formed on this body for aligning the liquid crystal compound LD in a predetermined state. Various known alignment films can be used. Examples include a rubbing film made of organic compounds such as polymers, a tilted vapor-deposited film of inorganic compounds, a film with microgrooves, and a film formed by accumulating organic compounds such as ω-trisanoic acid, dioctadecylmethylammonium chloride, and methyl stearate using the Langmuir-Blodgett (LB) method. Furthermore, a so-called photoalignment film, formed by irradiating a photoalignment material with polarized or unpolarized light, can also be used as the alignment film. These alignment films can be formed using known methods corresponding to the forming material of the body.

[0090] The entire surface of the support 24 forming the liquid crystal composition layer 20 on the side opposite to the liquid crystal composition layer 20 is covered by the 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 as described above, it also functions as a reflective layer that reflects radio waves RW with a frequency of 0.007 to 0.3 THz incident from the metasurface structure 12 side.

[0091] The first electrode layer 26 is unrestricted; as long as it has sufficient conductivity and can reflect electromagnetic waves RW, it can be made of a sheet of various known materials. As an example of the first electrode layer 26, examples 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 polythiophene represented by PEDOT (poly(3,4-ethylenedioxythiophene)); and graphene. Inorganic conductive materials, organic conductive materials, and graphene are transparent to visible light, but function as reflective layers for electromagnetic waves of the aforementioned frequencies.

[0092] The thickness of the first electrode layer 26 is also not limited. Depending on the material in which the first electrode layer 26 is formed, the thickness can be appropriately set to reflect the target electromagnetic wave with the required reflectivity.

[0093] As described above, the radio wave control element 10 involved in the present invention 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, by supplying power to each microstructure 14, the orientation state of the liquid crystal compound LD in the corresponding region of the liquid crystal composition layer 20 is changed, and a region with a different refractive index is formed for each unit cell UC, thereby causing the radio wave RW to be reflected in the desired direction. Furthermore, by changing the power supplied to each microstructure 14, i.e., the voltage applied to the liquid crystal composition layer 20, the reflection direction of the incident radio wave RW can be switched.

[0094] In the radio wave control element 10 according to the technology of the present invention, the refractive index anisotropy of the liquid crystal composition layer 20 for radio waves is not limited, but is preferably relatively large. Here, in the reflective radio wave control element 10 of this example, the refractive index anisotropy of the liquid crystal composition layer 20 for 100GHz radio waves is preferably 0.35 or more. Setting the refractive index anisotropy of the liquid crystal composition layer 20 for 100GHz radio waves to 0.35 or more is preferred because it allows for a reduction in the thickness of the liquid crystal composition layer 20 and a more rapid switching of the reflection direction of the radio wave RW.

[0095] Furthermore, the thickness of the liquid crystal composition layer 20 is not limited; it can be appropriately set to impart the required phase difference to the radio wave RW, depending on the forming material of the liquid crystal composition layer 20. Here, as described above, in the radio wave control element 10 according to the technology of this invention, since the liquid crystal composition layer 20 is composed of this composition containing a predetermined amount of liquid crystal compound, the thickness of the liquid crystal composition layer 20 can be reduced. Considering this, 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 for more rapidly switching the reflection direction of the radio wave RW.

[0096] <Compound> The compounds of this invention are not particularly limited as long as they are the specific compounds described above. As a specific compound, it is preferred to be a compound represented by the following formula (1). The compound represented by formula (1). Equation (1) R 1 -L 1 -A 1 -(Z 1 -B 1 ) n -L 2 -R 2 In equation (1), R 1 and R 2 Each of these can be used independently to represent an alkyl group, cyano group, halogen atom, or -N=C=S or -N=C=Se that can be substituted by -O- or -CO-O-. However, R 1 and R 2 At least one of them represents the above-mentioned alkyl group having a partial structure represented by formula (X), R 1 and R 2 The total number of asymmetric carbon atoms is more than 2. L 1 and L 2 Each of these can be used independently to represent a single bond, -O-, -CO-, -CO-O-, -O-CO-O-, and -NR. 3 - or -CH=CH-, O can be replaced by S. R 3 This indicates an alkyl group that can have substituents. A 1 and B 1 Each can be used to represent an aromatic ring or an aliphatic ring independently. Z 1 This indicates a single bond, -O-, -CO-, -CO-O-, -O-CO-O-, and -CR. Z =CR Z -、-C≡C-、-N=N-、-CR Z =CR Z -CR Z =CR Z -、-C≡CC≡C-、-CR Z =CR Z -CO- or -CR Z =CR Z -CO-O-,Z 1 At least one of them represents -N=N-, and O can be replaced by S. R Z It represents a hydrogen atom or a fluorine atom. n represents an integer from 1 to 4. Formula (X) -CH2-CH(CH3)-C2H4- In formula (X), Indicates the bonding location. The definitions and preferred methods for each symbol are the same as those for the specific compounds mentioned above. Example

[0097] The present invention will now be described in further detail based on embodiments. The materials, amounts, proportions, processing contents, and processing steps shown in the following embodiments may be appropriately modified without departing from the spirit of the invention. Therefore, the scope of the present invention should not be construed as limited to the embodiments shown below.

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

[0099] [Chemical Formula 1]

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

[0101] Compound A-2 was synthesized following the steps described below, referring to the synthetic method for compound A-1.

[0102] [Chemical Formula 2]

[0103] The specific compound A-3 was synthesized according to the following steps.

[0104] [Chemical Formula 3]

[0105] 3,7-Dimethyl-1-octanol (8 g), p-toluenesulfonyl chloride (10 g), and triethylamine (5 g) were dissolved in ethyl acetate (50 mL) and stirred at room temperature for 6 hours. The mixture was washed separately with ethyl acetate and water. After drying the organic phase with magnesium sulfate, it was concentrated to give a colorless liquid compound Cp-1a (15 g). N-methylaniline (5 g), compound Cp-1a (15 g), and potassium carbonate (7 g) were dissolved in N,N-dimethylacetamide (50 mL) and stirred at 95 °C for 4 hours. The mixture was then cooled to room temperature and washed separately with ethyl acetate and a 10% (w / w) ammonium chloride aqueous solution. After drying the organic phase with magnesium sulfate, the solution was concentrated to obtain a colorless liquid compound Cp-1 (12 g).

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

[0107] The specific compound A-4 was synthesized according to the following steps.

[0108] [Chemical Formula 4]

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

[0110] The specific compound A-5 was synthesized according to the following steps.

[0111] [Chemical Formula 5]

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

[0113] The specific compound A-6 was synthesized according to the following steps.

[0114] [Chemical Formula 6]

[0115] [Chemical Formula 7]

[0116] 3,7,11-trimethyl-2,6,10-dodecanetrien-1-ol (a mixture of isomers, 2.2 g), p-toluenesulfonyl chloride (2.1 g), and triethylamine (1.1 g) were dissolved in ethyl acetate (20 mL) and stirred at room temperature for 6 hours. The mixture was washed separately with ethyl acetate and water. After drying the organic phase with magnesium sulfate, it was concentrated to give a colorless liquid compound A-6a (3.8 g). 4-Nitrophenol (1.3 g), compound A-6a (3.8 g), and potassium carbonate (1.4 g) were dissolved in N,N-dimethylacetamide (20 mL) and stirred at 95 °C for 4 hours. The mixture was cooled to room temperature and washed separately with ethyl acetate and a 10% (w / w) ammonium chloride aqueous solution. After drying the organic phase with magnesium sulfate, the solution was concentrated to obtain a colorless liquid compound A-6b (2.5 g). Next, the colorless liquid compound A-6b (2.5 g), Pd / C (0.03 g), and THF (20 mL) were mixed and stirred for 12 hours under a hydrogen atmosphere. The reaction solution was filtered through diatomaceous earth to remove Pd / C and then concentrated to obtain the colorless liquid compound A-6c (2.1 g). In addition, 2-aminothiophene was synthesized from 2-nitrothiophene according to the method described in the literature (Journal of Medicinal Chemistry, 2005, Vol. 48, p. 5794). Compound A-6c (2.1 g) obtained by the above method was added to a mixture of hydrochloric acid (2 g), pure water (5 mL), and THF (10 mL), and the mixture was cooled to below 5°C. Sodium nitrite (0.5 g) was dissolved in pure water (2 mL) and added dropwise. The mixture was stirred at below 5°C for 1 hour to prepare a diazonium salt solution. Next, 1 g of 2-aminothiophene hydrochloride Cp-2 was dissolved in 10 mL of pure water and 2 g of hydrochloric acid, and the diazonium salt solution prepared above was added dropwise at an internal temperature of 0 °C. The reaction solution was heated to room temperature and stirred for 2 hours. The precipitated solid was filtered off and dried to obtain 2.7 g of orange-red solid A-6d. The orange-red solid A-6d (2.7 g) obtained above was suspended and dissolved in acetic acid (30 mL), and sodium thiocyanate (0.5 g) was added at room temperature. The mixture was water-cooled and the internal temperature was maintained below 20 °C, and bromine (1 g) was added dropwise. After stirring at room temperature for 2 hours, pure water (20 mL) was added, the solid was filtered off and dried, and orange solid A-6e (1.1 g) was obtained. 2-(N-ethylaniline)ethanol (8.2 g) was dissolved in N,N-dimethylacetamide (DMAc) (50 mL), cooled to below 5 °C, and propionyl chloride (5.0 g) was added dropwise. The mixture was stirred at room temperature for 2 hours. Water (50 mL) was added, followed by ethyl acetate (50 mL). The mixture was separated, and the resulting organic layer was dried over magnesium sulfate, filtered, and the filtrate was concentrated to obtain compound Cp-3 (11 g). The orange solid A-6e (1.1 g) obtained above was added to hydrochloric acid (1 g) and acetic acid (2 mL). While cooling in an ice bath, an aqueous solution of sodium nitrite (0.2 g) (0.5 mL) was added dropwise below 0°C. After stirring for 1 hour, sulfamic acid (3 mg) was added to obtain a diazonium salt solution. A methanol solution of compound Cp-3 (0.5 g) (3 mL) was maintained below 0°C, and the diazonium salt solution was added dropwise. After heating to room temperature and stirring for 1 hour, pure water (5 mL) was added, and the obtained solid was filtered off to obtain the specific compound A-6 (0.8 g) as a blackish-purple solid.

[0117] The specific compound A-7 was synthesized according to the following steps.

[0118] [Chemical Formula 8]

[0119] [Chemical Formula 9]

[0120] 2.1 g of N,N-dimethyl-1,4-phenylenediamine dihydrochloride was added to a mixture of hydrochloric acid (3 g), pure water (5 mL), and THF (10 mL). The mixture was cooled to below 5 °C, and 0.7 g of sodium nitrite was dissolved in pure water (2 mL) and added dropwise. The mixture was stirred for 1 hour at an internal temperature below 5 °C to prepare a diazonium salt solution. Next, 1.5 g of 2-aminothiophene hydrochloride Cp-2 was dissolved in 10 mL of pure water and 2 g of hydrochloric acid, and the diazonium salt solution prepared above was added dropwise at an internal temperature of 0 °C. The reaction solution was heated to room temperature and stirred for 2 hours. The precipitated solid was filtered off and dried to obtain an orange-red solid compound A-7a (2.5 g). The orange-red solid compound A-7a (2.5 g) obtained above was suspended and dissolved in acetic acid (30 mL), and sodium thiocyanate (0.7 g) was added at room temperature. The mixture was water-cooled and the internal temperature was maintained below 20 °C, and bromine (1.4 g) was added dropwise. After stirring at room temperature for 2 hours, pure water (20 mL) was added, the solid was filtered off and dried to obtain orange solid A-7b (1.1 g). 3,7,11-trimethyl-1-dodecanool (11 g), p-toluenesulfonyl chloride (10 g), and triethylamine (5 g) were dissolved in ethyl acetate (50 mL) and stirred at room temperature for 6 hours. The mixture was washed with ethyl acetate and water. After drying the organic phase with magnesium sulfate, the solution was concentrated to give a colorless liquid compound Cp-4a (19 g). Next, N-methylaniline (5 g), compound Cp-4a (19 g), and potassium carbonate (7 g) were dissolved in N,N-dimethylacetamide (50 mL) and stirred at 95 °C for 4 hours. After cooling to room temperature, the mixture was washed with ethyl acetate and a 10% ammonium chloride aqueous solution. After drying the organic phase with magnesium sulfate, the solution was concentrated to give a colorless liquid compound Cp-4 (16 g). The orange solid A-7b (1.1 g) obtained above was added to hydrochloric acid (1.1 g) and acetic acid (2 mL). While cooling in an ice bath, an aqueous solution of sodium nitrite (0.2 g) (0.5 mL) was added dropwise below 0°C. After stirring for 1 hour, sulfamic acid (3 mg) was added to obtain a diazonium salt solution. A methanol solution (3 mL) of compound Cp-4 (1.1 g) was maintained below 0°C, and the diazonium salt solution was added dropwise. After heating to room temperature and stirring for 1 hour, pure water (5 mL) was added, and the obtained solid was filtered off to obtain the specific compound A-7 (1.1 g) as a blackish-purple solid.

[0121] Compound A-8 was synthesized using the same method as compound A-6.

[0122] [Chemical Formula 10]

[0123] In addition, specific compounds A-1 to A-8 are all racemic mixtures (racemic mixtures), N Ri / (N) Ri +N Si The value is 0.5.

[0124] Following the synthesis steps of the specific compounds described above, compounds C-1 to C-4 were synthesized.

[0125] [Chemical Formula 11]

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

[0127] [Chemical Formula 12]

[0128] <Evaluation> Next, compositions for determination with different ratios of component A and component B were prepared by mixing according to the compositions shown in Table 1 below. Furthermore, in each example and comparative example, components A and B were the compounds shown in Table 2. Specifically, in Example 1, a specific compound A-1 as component A, another liquid crystal compound B-1 as component B, and chloroform were mixed to prepare composition 1 for determination. Compositions 2 to 7 for determination were prepared by changing the contents of components A and B in the same manner.

[0129] [Table 1]

[0130] (Melting point lowering property) Using a polarizing microscope equipped with a heated stage, the test compositions of each example and each comparative example were observed while being heated, and the melting point of each test composition was measured. ΔT / T' (%) was calculated according to the following formula, and the results were evaluated according to the following evaluation criteria. The melting point was set as the temperature at which the solid state transitions to a liquid crystal state. ΔT / T'(%)=100×(T'-Tmix) / T' T' (°C): {[Melting point of component A alone (°C) × Composition ratio of component A in the composition used to determine Tmix (mass %)] + [Melting point of component B alone (°C) × Composition ratio of component B in the composition used to determine Tmix (mass %)]} / 100 Tmix (°C): The lowest melting point among the melting points of the various compositions used for testing.

[0131] The following uses Figure 7 An example of the melting point determination results for each of the test compositions is shown, providing a detailed explanation of the melting point lowering property. Furthermore, Figure 7 The measurement results shown are examples for illustration. exist Figure 7 In this study, the melting point of component A used alone is set as TA (°C), and the melting point of component B used alone is set as TB (°C). When the composition ratio of the assay composition containing components A and B is changed, the melting point of the assay composition will differ from both TA and TB. Thus, when the composition ratio of the assay composition is changed, the minimum melting point exhibited by the assay composition is Tmix (°C), where the composition ratio of component B in the assay composition of Tmix is ​​composition ratio XB (mass %), and the composition ratio of component A is composition ratio XA (mass %) (not shown). Furthermore, T' is the value calculated using the melting points TA and TB when using composition ratios XA and XB, and when components A and B are used individually, according to the above method. Next, subtract Tmin from T' (°C) to obtain ΔT. The ratio (percentage) of ΔT to T' is ΔT / T'. Excellent melting point reduction (large ΔT / T') means that the difference between T' and Tmin is large, and the reduction is large relative to T'.

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

[0133] (Refractive index anisotropy (Δn)) The refractive index anisotropy of the 100 GHz radio wave was determined using the method disclosed in Applied Optics, Vol. 44, No. 7, p. 1150 (2005). Regarding refractive index anisotropy, a measurement composition exhibiting Tmix was filled into a variable short-circuit waveguide, and the liquid crystal compound in the measurement composition was oriented. Then, a 100 GHz radio wave was input into the waveguide, and the amplitude ratio of the reflected wave to the incident wave was measured. The refractive indices ne and no were determined by varying the direction of the static magnetic field and the length of the short-circuit. The refractive index anisotropy was calculated from ne - no.

[0134] “A”: Δn is 0.5 or higher. "B": Δn is greater than 0.3 and less than 0.5 “C”: Δn is less than 0.3

[0135] In Table 2, the expression for "the number of asymmetric carbon atoms" in formula (1) is R. 1 and R 2 The total number of asymmetric carbon atoms present. Regarding "A" 1 B 1 Thiophene-thiazole ring", A in formula (1) 1 and B 1 The case where at least one of the rings is a thienothiazole ring is denoted as "A", and the other cases are denoted as "B". As described above, "XA [mass%]" indicates the composition ratio XA (mass%) of component A in the composition used for the determination of Tmix. Furthermore, the composition ratio XB of component B in each example is [100 - XA (mass%) in the table] .

[0136] [Table 2]

[0137] As shown in Table 2, the composition was confirmed to exhibit the desired effect. Based on comparisons of Examples 6-8 with Examples 1-5, etc., it was confirmed that in A 1 and B 1 The present invention is even more effective when at least one of the rings is a thienothiazole ring. Based on the comparison between Example 5 and Example 4, it was confirmed that the effect of the present invention is better when there are 3 or more asymmetric carbon atoms. Symbol Explanation

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

Claims

1. A liquid crystal composition for an electromagnetic wave control element, comprising two or more liquid crystal compounds, wherein, At least one of the two or more liquid crystal compounds is a compound represented by formula (1). Equation (1) R 1 -L 1 -A 1 -(Z 1 -B 1 ) n -L 2 -R 2 In equation (1), R 1 and R 2 Each of these can independently represent an alkyl group, cyano group, halogen atom, or -N=C=S or -N=C=Se that can be substituted by -O- or -CO-O-. However, R 1 and R 2 At least one of them represents the alkyl group having an asymmetric carbon atom, R 1 and R 2 The total number of asymmetric carbon atoms is 2 or more. L 1 and L 2 Each of these can be used independently to represent a single bond, -O-, -CO-, -CO-O-, -O-CO-O-, and -NR. 3 - or -CH=CH-, O can be replaced by S. R 3 This indicates an alkyl group that can have substituents. A 1 and B 1 Each can be independently represented as an aromatic ring that may have substituents or an aliphatic ring that may have substituents. Z 1 This indicates a single bond, -O-, -CO-, -CO-O-, -O-CO-O-, and -CR. Z =CR Z -、-C≡C-、-N=N-、-CR Z =CR Z -CR Z =CR Z -、-C≡CC≡C-、-CR Z =CR Z -CO- or -CR Z =CR Z -CO-O-, where O can be replaced by S. R Z Each can be used independently to represent a hydrogen atom or a fluorine atom. n represents an integer from 1 to 4.

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

3. The liquid crystal composition for a radio wave control element according to claim 1 or 2, wherein, Z 1 At least one of them is -N=N-.

4. The liquid crystal composition for a radio wave control element according to claim 3, wherein, R 1 and R 2 At least one of them is the alkyl group having a partial structure represented by formula (X), Formula (X) -CH2-CH(CH3)-C2H4- , In formula (X), Indicates the bonding location.

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

6. The liquid crystal composition for a radio wave control element according to claim 5, wherein, R 1 and R 2 For the same group, L 1 and L 2 -CH=CH-, -O-, or -NR 3 - 7. The liquid crystal composition for a radio wave control element according to claim 3, wherein, A 1 and B 1 At least one of them is an aromatic heterocycle, and n is an integer from 1 to 3.

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

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

10. A radio wave control element, comprising, in sequence: Electrode 1; A liquid crystal composition layer comprising a liquid crystal composition for a radio wave control element as described in claim 1 or 2; and Second electrode.

11. A compound represented by formula (1), Equation (1) R 1 -L 1 -A 1 -(Z 1 -B 1 ) n -L 2 -R 2 In equation (1), R 1 and R 2 Each of these can independently represent an alkyl group, cyano group, halogen atom, or -N=C=S or -N=C=Se that can be substituted by -O- or -CO-O-. However, R 1 and R 2 At least one of them represents the alkyl group having a partial structure represented by formula (X), R 1 and R 2 The total number of asymmetric carbon atoms is 2 or more. L 1 and L 2 Each of these can be used independently to represent a single bond, -O-, -CO-, -CO-O-, -O-CO-O-, and -NR. 3 - or -CH=CH-, O can be replaced by S. R 3 This indicates an alkyl group that can have substituents. A 1 and B 1 Each can be independently represented as an aromatic ring that may have substituents or an aliphatic ring that may have substituents. Z 1 This indicates a single bond, -O-, -CO-, -CO-O-, -O-CO-O-, and -CR. Z =CR Z -、-C≡C-、-N=N-、-CR Z =CR Z -CR Z =CR Z -、-C≡CC≡C-、-CR Z =CR Z -CO- or -CR Z =CR Z -CO-O-,Z 1 At least one of them represents -N=N-, and O can be replaced by S. R Z Represents a hydrogen atom or a fluorine atom. n represents an integer from 1 to 4. Formula (X) -CH2-CH(CH3)-C2H4- , In formula (X), Indicates the bonding location.

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

13. The compound according to claim 11 or 12, wherein, A 1 and B 1 Each is an independent aromatic hydrocarbon ring, and n is an integer from 2 to 4.

14. The compound according to claim 13, wherein, R 1 and R 2 For the same group, L 1 and L 2 -CH=CH-, -O-, or -NR 3 - 15. The compound according to claim 11 or 12, wherein, A 1 and B 1 At least one of them is an aromatic heterocycle, and n is an integer from 1 to 3.

16. The compound according to claim 15, wherein, A 1 and B 1 At least one of them is a thienothiazole ring.

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

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