Anthraquinone compound, liquid crystal composition containing the compound, and light control element

Abstract

To provide an anthraquinone compound suitable as a dichroic dye employed in a liquid crystal composition and a light control element having high contrast.SOLUTION: An anthraquinone compound represented by formula (A). (In the formula, R1 denotes a linear alkyl group having 1 to 8 carbons, R2 denotes a linear alkyl group having 1 to 13 carbons, and R3 and R4 denote a hydrogen atom and the like, provided that the carbon number of R2 is greater than or equal to the carbon number of R1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a novel anthraquinone compound, a liquid crystal composition containing the compound, and a light-adjusting element. [Background technology]

[0002] Various proposals have been made for light-controlling films that control the transmission of external light for purposes such as protecting privacy in windows, doors, and partitions in vehicles such as trains and automobiles, and in buildings such as business buildings and hospitals (Patent Documents 1 and 2). One such light-controlling film uses liquid crystal. Typically, liquid crystal light-controlling films can block the view by controlling the transmission and scattering of light depending on whether or not a voltage is applied, but they cannot block light itself, so light scattering tends to increase glare. Therefore, attempts have been made to use dyes as materials for light-controlling panels with the aim of reducing glare and improving contrast (Patent Document 3). When such light-controlling panels are used in automobile windows, they are required to provide clear visibility without fogging when transparent, as well as a deep color when blocking light.

[0003] Dichroic dyes are generally used as dyes in liquid crystal light control films. GH (guest-host) type light control elements using liquid crystal compositions containing dichroic dyes are known, and various dichroic dyes have been proposed (Patent Documents 4 to 6).

[0004] Such dichroic dyes are required to have not only high contrast when used in a display device, but also light resistance and heat resistance, and efforts are being made to improve these properties. On the other hand, in liquid crystal compositions containing dichroic dyes, a large amount of the dichroic dye must be incorporated into the liquid crystal composition to achieve high contrast. However, if the compatibility (solubility) of the dichroic dye with the components of the liquid crystal composition is low, the dichroic dye will precipitate at room temperature or low temperatures, resulting in a decrease in contrast and insufficient performance as a light-adjusting device. For example, Patent Documents 4 to 6 disclose dyes with excellent order parameters, but the dyes in these documents have insufficient compatibility with the components of the liquid crystal composition, resulting in a problem of reduced contrast in the light-adjusting device. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 63-501512 [Patent Document 2] Patent Publication No. 03-47392 [Patent Document 3] Patent Publication No. 2018-205746 [Patent Document 4] WO2022 / 220212 [Patent Document 5] Patent Publication No. 10-316970 [Patent Document 6] EP59036A1 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a dichroic dye that has sufficient solubility in a liquid crystal composition, coloring power, and excellent contrast, and a light-controlling device that includes a light-controlling liquid crystal composition containing the dichroic dye. [Means for solving the problem]

[0007] As a result of extensive research into solving the above problems, the present inventors have found that the above problems can be solved by using an anthraquinone compound having a specific structure, and have thus completed the present invention. That is, the present invention is [1] An anthraquinone compound represented by the following formula (A):

[0008] [ka]

[0009] (Wherein R1 is a linear alkyl group having 1 to 8 carbon atoms, R2 is a linear alkyl group having 1 to 13 carbon atoms, R 3、 Each R4 independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or a linear or branched alkoxy group having 1 to 8 carbon atoms, provided that the number of carbon atoms in R2 is greater than or equal to the number of carbon atoms in R1. [2] The anthraquinone compound according to [1], wherein R1 is a linear alkyl group having 1 to 6 carbon atoms, and R2 is a linear alkyl group having 1 to 8 carbon atoms. [3] The anthraquinone compound according to [2], wherein R1 is a linear alkyl group having 2 to 4 carbon atoms, and R2 is a linear alkyl group having 2 to 6 carbon atoms. [4] The anthraquinone compound according to [3], wherein R1 is a linear alkyl group having 2 to 3 carbon atoms, and R2 is a linear alkyl group having 2 to 4 carbon atoms. [5] The anthraquinone compound according to [1], wherein R4 is a hydrogen atom. [6] The anthraquinone compound according to [5], wherein R3 is a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or a linear or branched alkoxy group having 1 to 4 carbon atoms. [7] The anthraquinone compound according to [6], wherein R3 is a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms. [8] A liquid crystal composition containing the anthraquinone compound according to [1] and a liquid crystal material. [9] The liquid crystal composition according to [8], which contains a dichroic dye other than the anthraquinone compound represented by formula (A).

[10] A light-adjusting element comprising a pair of opposing substrates, at least one of which is a transparent substrate having a transparent electrode, and the liquid crystal composition according to [8] or [9] sandwiched between the pair of substrates.

[11] The light-adjusting element according to

[10] , wherein both of the pair of substrates are transparent substrates having transparent electrodes. [Effects of the Invention]

[0010] The anthraquinone compounds of the present invention are useful as dichroic dyes for liquid crystal light control devices. By using a liquid crystal composition containing these dichroic dyes, a light control device with excellent contrast can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below. The compound of the present invention (anthraquinone compound) is represented by the following formula (A).

[0012] [ka]

[0013] In formula (A), R1 represents a linear alkyl group having 1 to 8 carbon atoms. Specific examples of the linear alkyl group having 1 to 8 carbon atoms represented by R1 in formula (A) include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, and an n-octyl group, of which a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, and an n-hexyl group are preferred, an ethyl group, an n-propyl group, and an n-butyl group are more preferred, and an ethyl group and an n-propyl group are particularly preferred.

[0014] In formula (A), R2 represents a linear alkyl group having 1 to 13 carbon atoms. Specific examples of the linear alkyl group having 1 to 13 carbon atoms represented by R2 in Formula (A) include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-undecyl group, an n-dodecyl group, and an n-tridecyl group; a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, and an n-octyl group are preferred; an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, and an n-hexyl group are more preferred; and an ethyl group, an n-propyl group, and an n-butyl group are particularly preferred.

[0015] In formula (A), R3 represents a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or a linear or branched alkoxy group having 1 to 8 carbon atoms, provided that the branched alkyl group does not include a cyclic alkyl group. Specific examples of the linear alkyl group having 1 to 8 carbon atoms represented by R in Formula (A) include the same as those described in the section on specific examples of the alkyl group having 1 to 8 carbon atoms represented by R in Formula (A). A straight-chain alkyl group having 1 to 4 carbon atoms is preferred, with a methyl group and an ethyl group being particularly preferred. Specific examples of the branched alkyl group having 1 to 8 carbon atoms include an isopropyl group, an isobutyl group, a sec-butyl group, a t-butyl group, an isopentyl group, an isohexyl group, a t-pentyl group, a 2-methylpentyl group, a 2-methylhexyl group, a 2-methylheptyl group, a 3-methylbutyl group, a 3-methylpentyl group, a 3-methylhexyl group, a 3-methylheptyl group, a 2-ethylpropyl group, a 2-ethylbutyl group, a 2-ethylhexyl group, and a t-butyl group, and an isopropyl group and a t-butyl group are preferred.

[0016] Specific examples of the linear or branched alkoxy group having 1 to 8 carbon atoms represented by R3 in Formula (A) include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an iso-propoxy group, an n-butoxy group, an iso-butoxy group, a sec-butoxy group, a t-butoxy group, an n-pentyloxy group, an iso-pentyloxy group, a neo-pentyloxy group, a t-pentyloxy group, a hexyloxy group, a heptyloxy group, and an octyloxy group. A linear or branched alkoxy group having 1 to 4 carbon atoms is preferred, and a linear alkoxy group having 1 to 4 carbon atoms is more preferred.

[0017] In formula (A), R3 is preferably a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or a linear alkoxy group having 1 to 8 carbon atoms, more preferably a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or a linear or branched alkoxy group having 1 to 4 carbon atoms, even more preferably a hydrogen atom, a linear alkoxy group having 1 to 4 carbon atoms, or a linear or branched alkyl group having 1 to 4 carbon atoms, still more preferably a hydrogen atom, or a linear alkyl group having 1 to 4 carbon atoms, and particularly preferably a methyl group or an ethyl group.

[0018] In formula (A), each R4 independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or a linear or branched alkoxy group having 1 to 8 carbon atoms, provided that branched alkyl groups do not include cyclic alkyl groups. Specific examples of the linear and branched alkyl group having 1 to 8 carbon atoms represented by R4 in Formula (A) include the same as those described in the section on specific examples of the alkyl group having 1 to 8 carbon atoms represented by R3 in Formula (A), and are preferably linear or branched alkyl groups having 1 to 4 carbon atoms, and particularly preferably a methyl group or an ethyl group.

[0019] Specific examples of the linear or branched alkoxy group having 1 to 8 carbon atoms represented by R4 in Formula (A) include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an iso-propoxy group, an n-butoxy group, an iso-butoxy group, a sec-butoxy group, a t-butoxy group, an n-pentyloxy group, an iso-pentyloxy group, a neo-pentyloxy group, a t-pentyloxy group, a hexyloxy group, a heptyloxy group, and an octyloxy group. A linear or branched alkoxy group having 1 to 4 carbon atoms is preferred, and a linear alkoxy group having 1 to 4 carbon atoms is more preferred.

[0020] R4 in formula (A) is preferably a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or a linear alkoxy group having 1 to 8 carbon atoms, more preferably a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or a linear or branched alkoxy group having 1 to 4 carbon atoms, still more preferably a hydrogen atom, or a linear alkyl group having 1 to 4 carbon atoms, still more preferably a hydrogen atom, a methyl group, or an ethyl group, and particularly preferably a hydrogen atom.

[0021] Regarding the combination of R1 and R2 in formula (A), when R1 is a linear alkyl group having 1 to 8 carbon atoms, R2 is preferably a linear alkyl group having 1 to 13 carbon atoms; when R1 is a linear alkyl group having 1 to 6 carbon atoms, R2 is more preferably a linear alkyl group having 1 to 8 carbon atoms; when R1 is a linear alkyl group having 2 to 4 carbon atoms, R2 is still more preferably a linear alkyl group having 2 to 6 carbon atoms; and when R1 is a linear alkyl group having 2 to 3 carbon atoms, R2 is particularly preferably a linear alkyl group having 2 to 4 carbon atoms.

[0022] Specific examples of suitable compounds represented by the formula (A) include the following.

[0023] [ka] TIFF2025117559000004.tif187170TIFF2025117559000005.tif188170TIFF2025117559000006.tif232170TIFF2025117559000007.tif53170

[0024] The compound represented by the above formula (A) can be synthesized by a conventionally known method, for example, as described in JP-A-2017-518413.

[0025] The liquid crystal composition of the present invention (hereinafter also simply referred to as "the composition of the present invention") contains an anthraquinone compound represented by the above formula (A) and a liquid crystal material.

[0026] The content of the anthraquinone compound represented by formula (A) in the liquid crystal composition is not particularly limited, but is preferably 0.5 to 5 parts by mass per 100 parts by mass of the liquid crystal material. When a dichroic dye (described later) other than the compound represented by formula (A) is used in combination, the total content of the anthraquinone compound represented by formula (A) and the dichroic dye other than the compound represented by formula (A) is preferably within the above range (0.5 to 5% by mass).

[0027] The liquid crystal material contained in the composition of the present invention is not particularly limited as long as it is a material (compound having liquid crystal properties) having liquid crystal properties such as nematic liquid crystal, cholesteric liquid crystal, smectic liquid crystal, etc. Examples of the compound having liquid crystal properties include the liquid crystal compounds described in pages 154 to 192 and 715 to 722 of "Liquid Crystal Device Handbook" (edited by the 142nd Committee of the Japan Society for the Promotion of Science, Nikkan Kogyo Shimbun, Ltd., 1989).

[0028] The liquid crystal composition of the present invention may contain an optically active substance that exhibits or does not exhibit a liquid crystal phase, such as a dichroic dye other than the anthraquinone compound represented by the above formula (A) or cholesteryl noenoate, various additives such as an ultraviolet absorber and an antioxidant, a photocurable compound, a photopolymerization initiator, etc.

[0029] By using a dichroic dye other than the compound represented by the above formula (A) in the composition of the present invention in combination, the contrast of the light-controlling element when light is blocked can be improved. The dichroic dye that can be used in combination is not particularly limited, and may be selected from, for example, azo dyes, anthraquinone dyes, perylene dyes, quinophthalone dyes, merocyanine dyes, azomethine dyes, phthaloperylene dyes, indigo dyes, azulene dyes, dioxazine dyes, polythiophene dyes, and the like. Specific examples include those described in "Dichroic dyes for Liquid Crystal Display" (AVI Vashchenko, CRC, 1994). Among these, it is preferable to use an azo dye, an anthraquinone dye, a perylene dye or a quinophthalone dye in combination, and it is more preferable to use an azo dye or an anthraquinone dye in combination.

[0030] When a dichroic dye other than the compound represented by Formula (A) is used in combination, the content of the compound represented by Formula (A) in the total dichroic dyes is not particularly limited as long as it is within a range that does not impair the effects of the present invention, but is preferably 1 to 80 mass %, more preferably 10 to 70 mass %, and even more preferably 20 to 55 mass %.

[0031] The composition of the present invention may further contain in combination a benzotriazole-based, benzophenone-based, hindered amine-based, or other light stabilizer, a phosphite-based, hindered phenol-based, or other antioxidant, a thermal polymerization inhibitor, a thiol compound, a photosensitizer, a photosensitizer, a chain transfer inhibitor, a polymerization inhibitor, an adhesion promoter, an antifoaming agent, a crosslinking agent, a surfactant, a heat curing accelerator, a thermoplastic resin, a thermosetting resin, a thickener such as urethane diacrylate, or the like.

[0032] The light control device of the present invention comprises a pair of substrates, at least one of which is a transparent substrate having a transparent electrode, sandwiched between the layer of the light control liquid crystal composition. Examples of the substrate include inorganic transparent materials such as glass and quartz, and colorless, transparent, or opaque materials such as metals, metal oxides, semiconductors, ceramics, and plastic plates and films. The electrodes are formed on the substrates by coating, printing, or vapor deposition such as sputtering with a thin film of a metal oxide, metal, semiconductor, or organic conductive material over the entire surface or in part of the substrate using a known coating method, printing method, or vapor deposition method such as sputtering. To obtain a particularly large-area light control device, it is desirable to use an electrode substrate in which an ITO (indium oxide, tin oxide) electrode is formed on a transparent polymer film such as PET using a vapor deposition method such as sputtering or a printing method, from the standpoints of productivity and processability. The substrate may also have electrodes or wiring for connecting the electrodes to the outside. For example, the substrate may be a segment drive electrode substrate, a matrix drive electrode substrate, or an active matrix drive electrode substrate. Furthermore, the electrode surface provided on the substrate may be covered entirely or partially with a protective film or alignment film made of organic compounds such as polyimide, polyamide, silicon, and cyanide compounds, inorganic compounds such as SiO2, TiO2, and ZrO2, or mixtures thereof.

[0033] The use of a plastic film as a substrate allows for a flexible and lightweight photochromic element. Therefore, the photochromic element can be sandwiched between a pair of flat or curved glass or hard plastic substrates via an adhesive layer such as polyvinyl butyral, vinyl acetate ester, double-sided tape, or adhesive. Alternatively, the photochromic element can be attached to the surface of a single flat or curved glass or hard plastic substrate using double-sided tape or adhesive. The photochromic element can also be sandwiched between soft plastic substrates or attached to one or both sides. A protective layer such as a hard coat, an ultraviolet-blocking layer, an infrared-blocking layer, or a half mirror may be provided on the substrate surface opposite the electrode surface of the photochromic element. A color filter or a polarizer filter may also be laminated. The photochromic element may also be laminated as an electroluminescent display element, a light-emitting diode display element, an electrochromic display element, or another liquid crystal display element.

[0034] The driving device for applying a voltage to the dimming element of the present invention is a device that can apply a DC voltage of 2 to 100 V or an AC voltage of 10 to 1000 Hz, and that opens or shorts the electrodes when no voltage is applied. This driving device may also be equipped with a voltage application circuit for segment driving, a voltage application circuit for matrix driving, a voltage application circuit for active matrix driving, etc.

[0035] The above-mentioned light-adjusting element has a neutral color, exhibits little color leakage in the visible light region when no voltage is applied, and has excellent contrast, making it ideal for use in vehicles or as a building material. [Example]

[0036] The present invention will be described in more detail below with reference to examples, but these are illustrative and do not limit the present invention in any way. In the text, "parts" and "%" are by mass unless otherwise specified. The maximum absorption wavelength in the examples is a value measured using a spectrophotometer "UV-3150 manufactured by Shimadzu Corporation."

[0037] Example 1 (Synthesis of a specific example of a compound represented by formula (10)) (Step 1) Synthesis of intermediate compound represented by formula (42) To 120 parts of DMF were added 10.0 parts of 1,5-dichloroanthraquinone, 7.3 parts of potassium carbonate, and 6.0 parts of 4-hydroxybenzenethiol, and the mixture was stirred at 60°C for 4 hours. After the reaction solution was cooled to 25°C, 240 parts of methanol was added and the mixture was stirred for 1 hour. The reaction product was collected by filtration and dried in a hot air dryer at 80°C for 24 hours to obtain 6.3 parts of an intermediate compound represented by the following formula (42).

[0038] [ka]

[0039] (Step 2) Synthesis of intermediate compound represented by formula (43) To 70 parts of DMF, 6.3 parts of the intermediate compound represented by formula (42) obtained in step 1, 3.6 parts of potassium carbonate, and 4.3 parts of 4-t-butylbenzenethiol were added, and the mixture was stirred at 60°C for 2 hours. After the reaction solution was cooled to 25°C, 140 parts of methanol was added and the mixture was stirred for 1 hour. The reaction product was collected by filtration, washed with toluene, and then dried in a hot air dryer at 80°C for 24 hours to obtain 5.1 parts of the intermediate compound represented by formula (43):

[0040] [ka]

[0041] (Step 3) Synthesis of the compound of the present invention represented by formula (10) To 70 parts of N-methylpyrrolidone, 5.1 parts of the intermediate compound represented by formula (43) obtained in step 2, 2.5 parts of 1-bromo-2-ethylbutane, and 2.8 parts of potassium carbonate were added and stirred at 80-90°C for 2 hours. The reaction solution was then cooled to 25°C, and 140 parts of methanol was added and stirred for 1 hour. The reaction product was collected by filtration, washed with water, and then dried in a hot air dryer at 80°C for 24 hours. The resulting crude product was dissolved in toluene and purified using a column chromatography column with toluene as the developing solvent. The solvent was removed from the purified solution by distillation under reduced pressure, and the solution was dried in a hot air dryer at 80°C for 24 hours to obtain 4.2 parts of the compound represented by formula (10) as an orange solid. The maximum absorption wavelength of this compound in toluene solution was 450 nm.

[0042] Example 2 (Synthesis of a specific example of a compound represented by formula (16)) (Step 4) The compound represented by the above formula (16) was obtained as an orange solid (4.4 parts) in the same manner as in Example 1, except that 2.5 parts of 1-bromo-2-ethylbutane was replaced with 3.0 parts of 1-bromo-2-ethylhexane in step 3. The maximum wavelength of the toluene solution of this compound was 450 nm.

[0043] Example 3 (Synthesis of a specific example of a compound represented by formula (13)) (Step 5) The compound represented by the above formula (13) was obtained in an orange solid form in an amount of 2.8 parts in the same manner as in Example 1, except that 4.3 parts of 4-t-butylbenzenethiol was replaced with 3.2 parts of 4-methylbenzenethiol in step 2, and 2.5 parts of 1-bromo-2-ethylbutane was replaced with 3.0 parts of 1-bromo-2-ethylhexane in step 3. The maximum absorption wavelength of a toluene solution of this compound was 449 nm.

[0044] Example 4 (Synthesis of a specific example of a compound represented by formula (15)) (Step 6) The compound represented by the above formula (15) was obtained in an orange solid form in an amount of 2.4 parts in the same manner as in Example 1, except that 4.3 parts of 4-t-butylbenzenethiol was replaced with 3.2 parts of 2-methylbenzenethiol in step 2, and 2.5 parts of 1-bromo-2-ethylbutane was replaced with 3.0 parts of 1-bromo-2-ethylhexane in step 3. The maximum absorption wavelength of a toluene solution of this compound was 449 nm.

[0045] Example 5 (Synthesis of a specific example of a compound represented by formula (40)) (Step 7) The compound represented by the above formula (15) was obtained as an orange solid (2.6 parts) in the same manner as in Example 1, except that 4.3 parts of 4-t-butylbenzenethiol was replaced with 3.2 parts of 3-methylbenzenethiol in step 2, and 2.5 parts of 1-bromo-2-ethylbutane was replaced with 3.0 parts of 1-bromo-2-ethylhexane in step 3. The maximum absorption wavelength of a toluene solution of this compound was 449 nm.

[0046] Example 6 (Synthesis of a specific example of a compound represented by formula (41)) (Step 8) The compound represented by the above formula (15) was obtained in an orange solid form in an amount of 2.9 parts in the same manner as in Example 1, except that 4.3 parts of 4-t-butylbenzenethiol was replaced with 4.7 parts of 4-butoxybenzenethiol in step 2, and 2.5 parts of 1-bromo-2-ethylbutane was replaced with 3.0 parts of 1-bromo-2-ethylhexane. The maximum absorption wavelength of a toluene solution of this compound was 449 nm.

[0047] Comparative Example 1 (Synthesis of Comparative Compound) By the same synthesis method as in Example 1, a compound represented by the following formula (B) was obtained.

[0048] [ka]

[0049] Comparative Example 2 (Synthesis of Comparative Compound) The compound represented by the following formula (C) was obtained by the same synthesis method as in Example 1.

[0050] [ka]

[0051] Comparative Example 3 (Synthesis of Comparative Compound) A compound represented by the following formula (D) was obtained by the same synthesis method as in Example 1.

[0052] [ka]

[0053] Comparative Example 4 (Synthesis of Comparative Compound) By the same synthesis method as in Example 1, a compound represented by the following formula (E) was obtained.

[0054] [ka]

[0055] Example 7 (Preparation of Liquid Crystal Composition of the Present Invention) A liquid crystal composition of the present invention was prepared by mixing 0.003 parts of the compound represented by formula (10) obtained in Example 1, 0.306 parts of 1-cyano-4'-n-pentylbiphenyl, 0.15 parts of 1-cyano-4'-n-heptylbiphenyl, 0.096 parts of 1-cyano-4'-n-octyloxybiphenyl, and 0.048 parts of 1-cyano-4'-n-pentylterphenyl at room temperature.

[0056] Examples 8 to 12 and Comparative Examples 5 to 8 (Preparation of Liquid Crystal Compositions of the Present Invention and Comparative Examples) Liquid crystal compositions of the present invention and comparative liquid crystal compositions were prepared as shown in Table 1 below in accordance with Example 4, except that the compound represented by formula (10) obtained in Example 1 was changed to the compound represented by formula (16) obtained in Example 2, the compound represented by formula (13) obtained in Example 3, the compound represented by formula (15) obtained in Example 4, the compound represented by formula (40) obtained in Example 5, the compound represented by formula (41) obtained in Example 6, the compound represented by formula (B) obtained in Comparative Example 1, the compound represented by formula (C) obtained in Comparative Example 2, the compound represented by formula (D) obtained in Comparative Example 3, and the compound represented by formula (E) obtained in Comparative Example 4, respectively.

[0057] [Table 1]

[0058] Example 13 (Evaluation of solubility of the compound of the present invention in liquid crystal materials) To the composition obtained in Example 7, 0.003 parts of the compound represented by formula (10) was added, and the mixture was stirred at room temperature for 1 hour. The composition's appearance was then visually inspected. If a uniform composition free of insoluble matter was obtained, 0.003 parts of the compound represented by formula (10) was added, and the mixture was stirred at room temperature for 1 hour. The procedure was repeated, and the solubility of the compound represented by formula (10) in the liquid crystal material was evaluated based on the maximum amount of compound added that resulted in a uniform composition free of insoluble matter. The results are shown in Table 2. The amount of the compound represented by formula (10) dissolved in the liquid crystal material in Example 7 and the amount of the compound represented by formula (10) dissolved in the liquid crystal material after further adding the compound represented by formula (10) are as follows:

[0059] Dissolution amount of the compound represented by formula (10) in Example 7: about 0.5% by mass Amount dissolved after adding 0.003 parts in total: Approximately 1.0% by mass Amount dissolved after adding 0.006 parts in total: Approximately 1.5% by mass Amount dissolved after adding 0.009 parts in total: Approximately 2.0% by mass Amount dissolved after adding 0.012 parts in total: Approximately 2.5% by mass Amount dissolved after adding 0.015 parts in total: Approximately 3.0% by mass Amount dissolved after adding 0.018 parts in total: Approximately 3.5% by mass Amount dissolved after adding 0.021 parts in total: Approximately 4.0% by mass (Supplementary Note) For example, if a homogeneous composition without insoluble matter was obtained after adding a total of 0.009 parts of a compound and stirring, and if insoluble matter remained after adding another 0.003 parts of a compound and stirring, the maximum dissolution amount was determined to be 2.0% by mass.

[0060] Examples 14 to 18 and Comparative Examples 9 to 12 (Evaluation of Solubility of the Compounds of the Present Invention and Comparative Compounds in Liquid Crystal Materials) Instead of using the compound represented by formula (10) in the composition obtained in Example 7, the compounds represented by formulas (16), (13), (15), (40), (41) and (B), (C), (D) and (E) were used in the compositions obtained in Examples 9 to 12 and Comparative Examples 5 to 8, respectively, and the solubility in liquid crystal materials was evaluated in the same manner as above. The results are shown in Table 2 below.

[0061] [Table 2]

[0062] Examples 19 to 24 and Comparative Examples 13 to 16 (Preparation of light-controlling elements of the present invention and comparative examples) The liquid crystal compositions obtained in Examples 13 to 18 and Comparative Examples 9 to 12 were sealed in devices with a gap of 15 μm between the substrates, each of which had a transparent electrode and was made of two glass substrates, one on top of the other, that had been subjected to a homogeneous alignment treatment by rubbing a polyamide resin on the surface that came into contact with the liquid crystal. In the device, when no voltage was applied, the liquid crystal was in a homogeneous alignment state, and the dye molecules were also in a similar alignment state according to the liquid crystal.

[0063] (Contrast Evaluation of the Composition of the Present Invention and the Comparative Composition) The transmittance (Kz) of linearly polarized light parallel to the alignment direction and the transmittance (Ky) of linearly polarized light perpendicular to the alignment direction of the elements filled with the compositions obtained in Examples 19 to 24 and Comparative Examples 13 to 16 that were uniform and had the maximum dissolution amount without insoluble content were measured, and the contrast (CR) at the absorption peak (λmax) was calculated using the following formula (i). The results are shown in Table 3. CR=Ky / Kz Equation (i)

[0064] [Table 3]

[0065] As shown in Tables 2 and 3, the compounds of the present invention have higher solubility in liquid crystals than the compounds of the comparative examples, and can increase the content of the dye compound (dichroic dye) in the liquid crystal composition for dimming. Therefore, the contrast of the dimming element obtained using the composition of the present invention can be increased compared to the dimming elements of the comparative examples, and it is clear that the compounds of the present invention are superior as dimming elements.

[0066] Example 25 (Preparation of black photochromic element) A black light-controlling element was produced in the same manner as in Examples 10 to 12 using a light-controlling liquid crystal composition of the present invention prepared in the same manner as in Example 7, except that 0.0105 parts of the compound represented by formula (10) obtained in Example 1, 0.0074 parts of a compound represented by formula (F) below, and 0.0038 parts of a compound represented by formula (G) below were added. The average contrast of the obtained black light-controlling element in the range from 400 to 700 nm was 25, which was high.

[0067] [ka] [Industrial Applicability]

[0068] The light-controlling liquid crystal composition of the present invention can stably maintain a high dye concentration, and by using the composition, a light-controlling device excellent in solubility and contrast can be obtained. The light-controlling device obtained by the present invention can be used for construction materials such as windows, partitions, and doors, automotive materials such as windows and sunroofs, displays that show letters and numbers, and materials for exhibits such as show windows.

Claims

1. An anthraquinone compound represented by the following formula (A): 【Chemical 1】 (In the formula, R １ is a linear alkyl group having 1 to 8 carbon atoms; R ２ is a linear alkyl group having 1 to 13 carbon atoms; R ３、 R ４ each independently represents a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or a linear or branched alkoxy group having 1 to 8 carbon atoms. ２ Number of carbon atoms ≧ R １ The number of carbon atoms is

2. R １ is a linear alkyl group having 1 to 6 carbon atoms, R ２ 2. The anthraquinone compound according to claim 1, wherein is a linear alkyl group having 1 to 8 carbon atoms.

3. R １ is a linear alkyl group having 2 to 4 carbon atoms, R ２ 3. The anthraquinone compound according to claim 2, wherein is a linear alkyl group having 2 to 6 carbon atoms.

4. R １ is a linear alkyl group having 2 to 3 carbon atoms, R ２ 4. The anthraquinone compound according to claim 3, wherein is a linear alkyl group having 2 to 4 carbon atoms.

5. R ４ The anthraquinone compound according to claim 1, wherein is a hydrogen atom.

6. R ３ 6. The anthraquinone compound according to claim 5, wherein is a hydrogen atom, a linear or branched alkyl group having 1 to 4 carbon atoms, or a linear or branched alkoxy group having 1 to 4 carbon atoms.

7. R ３ 7. The anthraquinone compound according to claim 6, wherein is a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms.

8. A liquid crystal composition comprising the anthraquinone compound according to claim 1 and a liquid crystal material.

9. 9. The liquid crystal composition according to claim 8, which contains a dichroic dye other than the anthraquinone compound represented by formula (A).

10. A light-adjusting element comprising a pair of opposing substrates, at least one of which is a transparent substrate having a transparent electrode, and the liquid crystal composition according to claim 8 sandwiched between the pair of substrates.

11. 11. The light-adjusting element according to claim 10, wherein both of the pair of substrates are transparent substrates having transparent electrodes.

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