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

Abstract

To provide an anthraquinone compound that is a dichroic dye having a novel structure.SOLUTION: The present invention relates to an anthraquinone compound represented by formula (1) (where R1 represents a C3-C14 branched alkyl group, or the like; R2 represents a hydrogen atom, a C1-C16 linear or branched alkyl group, or the like; and n represents a carbon number of 1 to 3).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 control element.

Background Art

[0002] In vehicles such as trains and automobiles, and in the windows, doors, partitions, etc. of buildings such as business buildings and hospitals, for the purpose of protecting privacy, etc., a film obtained by dispersing liquid crystal in a polymer, or a composition containing a photocurable compound and liquid crystal is used. It has become common to use a film or the like in which a light control layer is formed by utilizing the property that a liquid crystal substance phase-separates during photocuring as a light control panel instead of a blind. Usually, in such a light control panel, it is possible to control the transmission and scattering of light by applying or not applying a voltage to block the field of view, but it is not possible to block light, and glare tends to increase due to light scattering. Therefore, attempts have been made to use a dye as a material for the light control panel for the purpose of reducing glare and improving contrast. For example, when such a light control panel is used for the window glass of an automobile, in addition to having no fogging and good visibility when transparent and obtaining high contrast, even when irradiated with light for a long time at a high temperature due to the influence of long-term exposure during outdoor use, light resistance that does not cause a decrease in transmittance is also required. In addition, the demand for black light control elements that can block visible light is also increasing from the viewpoints of practicality and design.

[0003] In order to meet the above market demands, various liquid crystal display elements called GH (guest-host) type using a liquid crystal composition containing a dye have been proposed. These liquid crystal display elements having characteristics such as viewing angle and brightness have also been put into practical use in in-vehicle applications and light control element applications.

[0004] The dichroic dyes generally used in liquid crystal compositions for dimming elements are required to have high contrast when used as elements, as well as light resistance, UV resistance, heat resistance, and compatibility (solubility) of the dichroic dye with the components of the liquid crystal composition. Also, from the viewpoints of practicality and design, those that can lower the transmittance during light shielding and block more visible light are required. Generally, to lower the transmittance during light shielding, it is necessary to increase the amount of dye added. However, when the amount of dye increases, the solubility decreases, or the contrast becomes difficult to obtain when made into an element. To increase the light shielding property with a smaller amount of dye, the coloring power of the dye itself is important. For example, Patent Documents 4 and 5 disclose dichroic dyes having a maximum absorption wavelength in the range of 500 to 550 nm. However, the dyes in these documents have high coloring properties but insufficient contrast, or sufficient contrast but insufficient coloring properties. No dichroic dye has been found that has a maximum absorption wavelength in the above range, has high coloring power of the dye itself, and at the same time has excellent contrast of the element.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0006] One object of the present invention is to provide an anthraquinone compound which is a dichroic dye having a novel structure. A further object of the present invention is to provide an anthraquinone compound which is a dichroic dye having a maximum absorption wavelength in a specific wavelength region and having an excellent coloring property and a novel structure. A still further object of the present invention is to provide a liquid crystal composition containing an anthraquinone compound which is a dichroic dye having a maximum absorption wavelength in a specific wavelength region and having an excellent coloring property and a novel structure, and a light control element having excellent contrast containing the composition.

Means for Solving the Problems

[0007] As a result of intensive studies, the present inventors have succeeded in developing a novel anthraquinone compound having a specific structure. Further, the present inventors have found that the above problems can be solved by using the anthraquinone compound, and have completed the present invention. That is, aspects or embodiments of the present invention are as follows. [1]. The following formula (1)

[0008]

Chemical formula

[0009] (In the formula, R1 represents a branched alkyl group having 3 to 14 carbon atoms or a branched alkoxy group having 3 to 14 carbon atoms. R2 represents a hydrogen atom, a linear or branched alkyl group having 1 to 16 carbon atoms, or a linear or branched alkoxy group having 1 to 16 carbon atoms. n represents 1 to 3 carbon atoms.) An anthraquinone compound represented by the formula. [2]. The anthraquinone compound according to the above item [1], wherein R1 is a branched alkyl group having 3 to 8 carbon atoms. [3]. The anthraquinone compound according to the above item [2], wherein R1 is a branched alkyl group having 3 to 6 carbon atoms. [4]. The anthraquinone compound according to the above item [1], wherein R1 is a branched alkoxy group having 3 to 8 carbon atoms. [5]. The anthraquinone compound according to the above item [1], wherein R2 is a linear or branched alkyl group having 1 to 10 carbon atoms. [6]. The anthraquinone compound according to the preceding item [1], wherein R2 is a linear or branched alkoxy group having 1 to 10 carbon atoms. [7]. The anthraquinone compound according to any one of the preceding items [1] to [6], having a maximum absorption wavelength at 500 to 550 nm. [8]. A dimming liquid crystal composition containing the anthraquinone compound according to any one of the preceding items [1] to [7] and a liquid crystal material. [9]. The dimming liquid crystal composition according to the preceding item [8], further containing a dye compound other than the anthraquinone compound represented by the formula (1).

[10] . A dimming element formed by sandwiching the dimming liquid crystal composition according to the preceding item [8] or [9] between a pair of substrates arranged opposite to each other, at least one of which is a transparent substrate having a transparent electrode.

Advantages of the Invention

[0010] The anthraquinone compound of the present invention having a maximum absorption wavelength in a specific wavelength region has high color developability, and by using the dimming liquid crystal composition containing the anthraquinone compound, a dimming element excellent in contrast can be obtained.

Embodiments for Carrying Out the Invention

[0011] The present invention will be described in detail below. The anthraquinone compound of the present invention is represented by the following formula (1).

[0012]

Chemical formula

[0013] In the formula (1), R1 represents a branched alkyl group having 3 to 14 carbon atoms or a branched alkoxy group having 3 to 14 carbon atoms. The alkyl group having 3 to 14 carbon atoms represented by R1 in the formula (1) preferably has a branched chain. Specific examples thereof include an iso-propyl group, an iso-butyl group, a sec-butyl group, a t-butyl group, an iso-pentyl group, a neo-pentyl group, a t-pentyl group, a 2-ethylhexyl group, a 2-propylhexyl group, a 2-butylhexyl group, a 2-pentylhexyl group, a 2-pentylheptyl group, and a 2-pentylnonyl group. Among these, the alkyl group having a branched chain preferably has 3 to 6 carbon atoms, more preferably 3 or 4 carbon atoms.

[0014] The alkoxy group having 3 to 14 carbon atoms represented by R1 in the formula (1) preferably has a branched chain. Specific examples thereof include an iso-propoxy group, an iso-butoxy group, a sec-butoxy group, a t-butoxy group, an iso-pentyloxy group, a neo-pentyloxy group, a t-pentyloxy group, a 2-ethylhexyloxy group, a 2-propylhexyloxy group, a 2-butylhexyloxy group, a 2-pentylhexyloxy group, a 2-pentylheptyloxy group, and a 2-pentylnonyloxy group. Among these, the alkoxy group having a branched chain and having 3 to 8 carbon atoms is preferable, and the branched alkoxy group having 3 to 6 carbon atoms is more preferable.

[0015] As R1 in the formula (1), an alkyl group having a branched chain and having 3 to 6 carbon atoms or an alkoxy group having a branched chain and having 3 to 8 carbon atoms is preferable, and an alkyl group having a branched chain and having 3 or 4 carbon atoms or an alkoxy group having a branched chain and having 3 to 6 carbon atoms is more preferable.

[0016] In the formula (1), R2 represents a hydrogen atom, a linear or branched alkyl group having 1 to 16 carbon atoms, or a linear or branched alkoxy group having 1 to 16 carbon atoms.

[0017] The alkyl group having 1 to 16 carbon atoms represented by R2 in the formula (1) may be either linear or branched. Specific examples thereof include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, t-butyl group, n-pentyl group, iso-pentyl group, neo-pentyl group, t-pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, 2-ethylhexyl group, 2-propylhexyl group, 2-butylhexyl group, 2-pentylhexyl group, 2-pentylheptyl group, 2-heptylnonyl group and the like. A linear or branched alkyl group having 1 to 10 carbon atoms is preferred, a linear alkyl group having 2 to 8 carbon atoms is more preferred, and a linear alkyl group having 4 to 7 carbon atoms is still more preferred.

[0018] The alkoxy group having 1 to 16 carbon atoms represented by R2 in the formula (1) may be either linear or branched. Specific examples thereof include methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n-butoxy group, iso-butoxy group, sec-butoxy group, t-butoxy group, n-pentyloxy group, iso-pentyloxy group, neo-pentyloxy group, t-pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group, nonyloxy group, decyloxy group, undecyloxy group, dodecyloxy group, tridecyloxy group, tetradecyloxy group, pentadecyloxy group, hexadecyloxy group, 2-ethylhexyloxy group, 2-propylhexyloxy group, 2-butylhexyloxy group, 2-pentylhexyloxy group, 2-pentylheptyloxy group, 2-heptylnonyloxy group and the like. A linear alkoxy group having 2 to 8 carbon atoms is more preferred.

[0019] As R2 in the formula (1), a linear or branched alkyl group having 1 to 10 carbon atoms is preferred, a linear alkyl group or alkoxy group having 2 to 8 carbon atoms is more preferred, and a linear alkyl group having 4 to 7 carbon atoms is still more preferred.

[0020] In formula (1), n represents 1 to 3 carbon atoms, and 1 carbon atom is more preferred.

[0021] Preferable specific examples of the compound represented by the formula (1) include the following, but the present invention is not limited thereto.

[0022]

Chemical formula

[0023] The compound represented by the formula (1) can be synthesized by a conventionally known method described in, for example, WO2023 / 100848A1 and WO2023 / 096111A1. Specifically, for example, an anthraquinone compound represented by the following formula (A) and an aniline derivative represented by the following formula (B) are reacted in a solvent such as xylene at 110 to 120 °C under basic conditions such as tripotassium phosphate in the presence of a catalyst such as palladium or copper powder to obtain a compound represented by the following formula (C). Incidentally, R2 in the following formulas (B) and (C) represents the same meaning as R2 in the formula (1).

[0024]

Chemical formula

[0025] By brominating the obtained compound represented by the above formula (C), a compound represented by the following formula (D) can be obtained. Then, the compound represented by the following formula (D) and the compound represented by the following formula (E) are reacted in a solvent such as 1,4-dioxane at 80 to 90 °C under basic conditions such as potassium carbonate in the presence of a palladium catalyst such as palladium acetate to obtain an anthraquinone compound represented by the formula (1). Incidentally, R1, R2, and n in the following formulas (D) and (E) represent the same meaning as R1, R2, and n in the formula (1). Also, B in the following formula (E) pin represents a pinacolborol group.

[0026]

Chem.

[0027] 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 formula (1) and a liquid crystal material.

[0028] The content ratio of the anthraquinone compound represented by formula (1) in the liquid crystal composition is not particularly limited, but it is preferably 0.5 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, based on 100 parts by mass of the liquid crystal material. When a dichroic dye (described later) other than the compound represented by formula (1) is used in combination, the total content of the anthraquinone compound represented by formula (1) and the dichroic dye other than the compound represented by formula (1) is preferably within the above range (0.5 to 10 parts by mass based on 100 parts by mass of the liquid crystal material).

[0029] The liquid crystal material contained in the liquid crystal composition of the present invention is not particularly limited as long as it is a material having liquid crystallinity (a compound having liquid crystallinity) such as nematic liquid crystal, cholesteric liquid crystal, smectic liquid crystal, etc. Examples of the compound having liquid crystallinity include liquid crystal compounds described on pages 154 to 192 and pages 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).

[0030] The liquid crystal composition of the present invention may contain a dichroic dye other than the anthraquinone compound represented by formula (1), an optically active substance that exhibits or does not exhibit a liquid crystal phase such as cholesteryl nonanoate, various additives such as an ultraviolet absorber and an antioxidant, a photocurable compound, a photopolymerization initiator, and the like.

[0031] In the composition of the present invention, the anthraquinone compound represented by formula (1) and a dichroic dye other than the anthraquinone compound represented by formula (1) can be used in combination. The dichroic dyes that can be used in combination with the anthraquinone compound represented by formula (1) are not particularly limited. For example, they may be selected from 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. Specifically, those described in "Dichroic dyes for Liquid Crystal Display" (written by A.V. Ivashchenko, CRC Press, 1994) and the like can be mentioned. Among these, it is preferable to use an azo dye, an anthraquinone dye, a perylene dye or a quinophthalone dye in combination with the anthraquinone compound represented by formula (1), and it is more preferable to use an azo dye and an anthraquinone dye in combination.

[0032] When the anthraquinone compound represented by formula (1) is used in combination with a dichroic dye other than the anthraquinone compound represented by formula (1), the content of the anthraquinone compound represented by formula (1) in all the dichroic dyes is not particularly limited as long as the effects of the present invention are not impaired, but 1 to 90% by mass is preferable, 5 to 70% by mass is more preferable, and 10 to 50% by mass is still more preferable.

[0033] The composition of the present invention may further contain, if necessary, other additives, such as light stabilizers such as benzotriazole-based, benzophenone-based and hindered amine-based ones, antioxidants such as phosphite-based and hindered phenol-based ones, thermal polymerization inhibitors, thiol compounds, photosensitizers, photosensitizers, chain transfer inhibitors, polymerization inhibitors, adhesion-imparting agents, defoaming agents, crosslinking agents, surfactants, thermal curing accelerators, thermoplastic resins, thermosetting resins, thickeners such as urethane diacrylate, and the like. In addition, in order to control the cell gap as a light control element, spherical or cylindrical spacers such as silica, glass, plastic, and ceramic may be added. The cell gap of the light control element can usually be set in the range of 2 to 100 μm.

[0034] The dimming element of the present invention is formed by sandwiching a layer of the liquid crystal composition or its photocured product between a pair of substrates in which at least one of the substrates is a transparent substrate having a transparent electrode and the substrates are arranged opposite to each other. Here, examples of the substrate include inorganic transparent materials such as glass and quartz, metals, metal oxides, semiconductors, ceramics, plastic plates, plastic films, etc., which are colorless transparent, colored transparent, or opaque. The electrode is formed on the substrate by, for example, depositing a thin film of a metal oxide, metal, semiconductor, organic conductive substance, etc. over the entire surface or partially of the substrate by a known coating method, printing method, vapor deposition method such as sputtering, etc. In particular, in order to obtain a large-area dimming element, from the viewpoints of productivity and processability, it is desirable to use an electrode substrate formed by depositing an ITO (indium oxide, tin oxide) electrode on a transparent polymer film such as PET using a vapor deposition method such as sputtering or a printing method. Incidentally, wiring for connecting between electrodes or between the electrode and the outside may be provided on the substrate. For example, an electrode substrate for segment driving, an electrode substrate for matrix driving, an electrode substrate for active matrix driving, etc. may be used. Further, the surface of the electrode provided on the substrate may be entirely or partially covered with a protective film or an alignment film formed from an organic compound such as polyimide, polyamide, silicone, cyanide compound, etc., an inorganic compound such as SiO2, TiO2, ZrO2, etc., or a mixture thereof.

[0035] By using a plastic film as a substrate, a flexible and lightweight light control element can be obtained. Therefore, the light control element can be sandwiched and used between a pair of planar or curved glass, hard plastic, etc. via an adhesive layer such as polyvinyl butyral, vinyl acetate ester, double-sided tape, or an adhesive. Alternatively, the light control element can be attached to the surface of a single planar or curved glass, hard plastic, etc. with double-sided tape, an adhesive, or the like. Also, the light control element may be sandwiched between soft plastics or attached to one or both sides. Further, a protective layer such as a hard coat, an ultraviolet cut layer, an infrared cut layer, or a half mirror may be provided on the substrate surface on the side opposite to the electrode surface of the light control element. A color filter may be laminated on the light control element, or a polarizer filter may be attached. Also, an electroluminescence display element, a light-emitting diode display element, an electrochromic display element, or other liquid crystal display elements may be laminated on the light control element.

[0036] As a driving device for applying a voltage to the light control element of the present invention, a device capable of applying a DC voltage of 2 to 100 V or an AC voltage of 10 to 1000 Hz is sufficient as long as it opens or short-circuits the electrodes when no voltage is applied. Further, this driving device may be provided with a voltage application circuit for segment driving, a voltage application circuit for matrix driving, a voltage application circuit for active matrix, and the like.

[0037] The anthraquinone compound represented by formula (1) of the present invention has high color developability, and a light control element using this compound can achieve a high-contrast display. Therefore, this light control element is suitable for building materials such as windows, partitions, and doors, in-vehicle materials such as windows and sunroofs, displays for displaying characters, numbers, etc., and materials for exhibits such as show windows.

Example

[0038] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In the text, "parts" and "%" are based on mass unless otherwise specified. The maximum absorption wavelength in the examples was measured with a spectrophotometer "UV-3150" manufactured by Shimadzu Corporation.

[0039] Example 1 (Synthesis of the anthraquinone compound of the present invention represented by Specific Example No. 4) (Step 1-1) Synthesis of an intermediate compound represented by the following formula (3) To 80 parts of xylene were added 0.6 part of 2,2-bis(diphenylphosphino)-1,1-binaphthyl and 0.22 part of palladium acetate, and the mixture was stirred at 80°C for 10 minutes under a nitrogen atmosphere. Then, 8.0 parts of the compound represented by the following formula (2), 8.2 parts of tripotassium phosphate, 5.8 parts of 4-n-butylaniline, and 32 parts of N-methyl-2-pyrrolidone were added, and the mixture was stirred at 120°C for 2 hours. After the reaction solution was cooled to 45°C, 160 parts of methanol were added, and the mixture was stirred for 30 minutes. The reaction product was collected by filtration, washed with methanol, and then dried in a hot air dryer at 80°C for 24 hours to obtain 9.1 parts of the intermediate compound represented by the following formula (3).

[0040]

Chemical formula

[0041] (Step 1-2) Synthesis of an intermediate compound represented by the following formula (4) To 65.1 parts of methanol were added 6.51 parts of the compound represented by the above formula (3). After stirring for 10 minutes, 2.9 parts of 49% hydrobromic acid and 1.71 parts of 35% hydrogen peroxide were added, and the mixture was stirred at 25°C for 3 hours. The reaction product was collected by filtration, washed with methanol, and then dried in a hot air dryer at 80°C for 24 hours to obtain 5.55 parts of the intermediate compound represented by the following formula (4).

[0042]

Chemical formula

[0043] (Step 1-3) Synthesis of the compound represented by No. 4 of the specific example To 80 parts of 1,4 - dioxane and 17 parts of water, 1.9 parts of the compound represented by the above formula (4), 0.7 part of potassium carbonate, 1.9 parts of the compound represented by the following formula (5), and 0.49 part of tetrakis(triphenylphosphine)palladium were added, and the mixture was stirred at 80 °C for 3 hours. After the reaction solution was cooled to 30 °C, 80 parts of methanol was added and stirred for 30 minutes. The reaction product was collected by filtration, washed with methanol, and then dried in a hot air dryer at 80 °C for 24 hours to obtain 0.7 part of the compound represented by No. 4 of the specific example. The maximum absorption wavelength of this compound in toluene was 515.8 nm.

[0044]

Chemical formula

[0045] Example 2 (Synthesis of the anthraquinone compound of the present invention represented by Specific Example No. 12) Except for using 1.8 parts of the following formula (6) instead of the above formula (5), in the same manner as in Example 1, 0.5 part of the compound represented by No. 12 of the above specific example was obtained. The maximum absorption wavelength of this compound in toluene was 515.5 nm.

[0046]

Chemical formula

[0047] Example 3 (Synthesis of the anthraquinone compound of the present invention represented by Specific Example No. 5) 0.7 part of the compound represented by Specific Example No. 5 above was obtained in the same manner as in Example 1, except that 7.4 parts of 4-n-heptylaniline was used instead of 4-n-butylaniline in Step 1-1. The maximum wavelength of this compound in toluene was 516.0 nm.

[0048] Example 4 (Synthesis of the anthraquinone compound of the present invention represented by Specific Example No. 9) Except for using 2.1 parts of the following formula (7) instead of the above formula (5), in the same manner as in Example 1, 0.6 part of the compound represented by No. 9 of the above specific example was obtained. The maximum absorption wavelength of this compound in toluene was 515.0 nm.

[0049]

Chemical formula

[0050] Example 5 (Synthesis of the anthraquinone compound of the present invention represented by Specific Example No. 10) In Engineering 1-1, 9.1 parts of 4-n-decylaniline were used instead of 4-n-butylaniline, and 2.3 parts of the following formula (8) were used instead of the above formula (5). Otherwise, in the same manner as in Example 1, 0.4 part of the compound represented by No. 10 of the above specific examples was obtained. The maximum absorption wavelength of this compound in toluene was 515.5 nm.

[0051]

Chemical formula

[0052] Example 6 (Synthesis of the anthraquinone compound of the present invention represented by No. 11 of the specific examples) In Engineering 1-1, 3.6 parts of aniline were used instead of 4-n-butylaniline. Otherwise, in the same manner as in Example 1, 0.5 part of the compound represented by No. 11 of the above specific examples was obtained. The maximum wavelength of this compound in toluene was 515.5 nm.

[0053] Synthesis Example 1 (Synthesis of a comparative example compound) The compound represented by the following formula (X) corresponding to No. 37 shown in Table 1 of JP-A-04-264193 was synthesized according to the description in paragraph

[0031] of the said document.

[0054]

Chemical formula

[0055] Synthesis Example 2 (Synthesis of a comparative example compound) The compound represented by the following formula (Y) corresponding to the general formula (II) described in paragraphs

[0045] to

[0046] of JP-A-2011-190314 was synthesized according to the description in paragraph

[0054] of the said document.

[0056]

Chemical formula

[0057] Example 7 (Preparation of the liquid crystal composition of the present invention) 0.012 part of the compound represented by No. 4 of the specific example obtained in Example 1, 0.306 part of 1-cyano-4'-n-pentylbiphenyl, 0.15 part of 1-cyano-4'-n-heptylbiphenyl, 0.096 part of 1-cyano-4'-n-octyloxybiphenyl, and 0.048 part of 1-cyano-4''-n-pentylterphenyl were mixed at room temperature to obtain the liquid crystal composition of the present invention.

[0058] Examples 8 to 12 and Comparative Examples 1 to 2 (Preparation of the liquid crystal composition of the present invention and a comparative liquid crystal composition) The liquid crystal compositions of the present invention and the comparative liquid crystal compositions were obtained according to Example 7, except that the compound represented by No. 4 obtained in Example 1 was changed to the compounds obtained in Examples 2 to 6, the compound represented by the formula (X) obtained in Synthesis Example 1, and the compound represented by the formula (Y) obtained in Synthesis Example 2, respectively.

[0059] Example 13 (Fabrication of the light control element of the present invention) The liquid crystal composition obtained in Example 7 was encapsulated in an element with a gap of 15 μm between two glass substrates having transparent electrodes and subjected to a homogeneous alignment treatment by rubbing a polyamide resin on the surface in contact with the liquid crystal. In the element thus obtained, the liquid crystal took a homogeneous alignment state when no voltage was applied, and the dye molecules (anthraquinone compound obtained in Example 1) also took a similar alignment according to the liquid crystal.

[0060] Examples 14 to 18 and Comparative Examples 3 to 4 (Fabrication of the light control element of the present invention and a comparative light control element) The light control elements of the present invention and the comparative light control elements were produced according to Example 16, except that the liquid crystal composition obtained in Example 7 was changed to the liquid crystal compositions obtained in Examples 8 to 12 and Comparative Examples 1 to 2, respectively. For the obtained light control elements, the transmittance (Kz) with respect to linearly polarized light parallel to the alignment direction, the transmittance (Ky) with respect to polarized light perpendicular to the alignment direction, and the dichroic ratio (Rd) were measured. At the same dye concentration, the smaller the value of the transmittance (Kz), the higher the color development property, and the larger the value of the dichroic ratio (Rd), the better the contrast.

[0061] As shown in Table 1 below, the dimming elements of Examples 13 to 16 and 18 had the same transmittance (Kz) as the dimming element of Comparative Example 3, but showed a high dichroic ratio (Rd). Also, the dimming element of Example 17 had the same dichroic ratio (Rd) as the dimming element of Comparative Example 4, but the value of the transmittance (Kz) was small, indicating that it had high color-developing properties. From these results, it can be seen that the dimming elements of Examples 13 to 18 achieved both high color-developing properties and high contrast.

[0062]

Table 1

Industrial Applicability

[0063] By using the dimming liquid crystal composition containing the anthraquinone compound of the present invention having a maximum absorption wavelength in a specific wavelength region and having high color-developing properties and a high dichroic ratio, a dimming element excellent in contrast can be obtained. The dimming element of the present invention can be suitably used for building materials such as windows, partitions, and doors, in-vehicle materials such as windows and sunroofs, displays for displaying characters and numbers, materials for exhibits such as show windows, and the like.

Claims

1. An anthraquinone compound represented by the following formula (1). 【Chemical Formula 1】 (In the formula, R １ represents a branched alkyl group having 3 to 14 carbon atoms or a branched alkoxy group having 3 to 14 carbon atoms. R ２ represents a hydrogen atom, a linear or branched alkyl group having 1 to 16 carbon atoms, or a linear or branched alkoxy group having 1 to 16 carbon atoms. n represents 1 to 3 carbon atoms.)

2. R １ The anthraquinone compound according to claim 1, wherein R is a branched alkyl group having 3 to 8 carbon atoms.

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

4. R １ The anthraquinone compound according to claim 1, wherein R is a branched alkoxy group having 3 to 8 carbon atoms.

5. R ２ The anthraquinone compound according to claim 1, wherein R is a linear or branched alkyl group having 1 to 10 carbon atoms.

6. R ２ The anthraquinone compound according to claim 1, wherein R is a linear or branched alkoxy group having 1 to 10 carbon atoms.

7. The anthraquinone compound according to any one of Claims 1 to 6, having a maximum absorption wavelength at 500 to 550 nm.

8. A dimming liquid crystal composition containing the anthraquinone compound according to any one of Claims 1 to 6 and a liquid crystal material.

9. A dimming liquid crystal composition containing the anthraquinone compound according to Claim 7 and a liquid crystal material.

10. The dimming liquid crystal composition according to Claim 8, further containing a dye compound other than the anthraquinone compound represented by formula (1).

11. The dimming liquid crystal composition according to Claim 9, further containing a dye compound other than the anthraquinone compound represented by formula (1).

12. A dimming element formed by sandwiching the dimming liquid crystal composition according to Claim 8 between a pair of substrates arranged opposite to each other, at least one of which is a transparent substrate having a transparent electrode.

13. A dimming element formed by sandwiching the dimming liquid crystal composition according to Claim 9 between a pair of substrates arranged opposite to each other, at least one of which is a transparent substrate having a transparent electrode.

14. A dimming element formed by sandwiching the dimming liquid crystal composition according to Claim 10 between a pair of substrates arranged opposite to each other, at least one of which is a transparent substrate having a transparent electrode.

15. A dimming element formed by sandwiching the dimming liquid crystal composition according to Claim 11 between a pair of substrates arranged opposite to each other, at least one of which is a transparent substrate having a transparent electrode.

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