TWI879969B - Liquid crystal composition for liquid crystal dimming element and its use, liquid crystal dimming element, dimming window, smart window - Google Patents

Abstract

The present invention provides a liquid crystal composition for a guest-host type liquid crystal dimming element, which fully satisfies at least one of the following characteristics: high upper temperature limit, low lower temperature limit, low viscosity, large optical anisotropy, large positive dielectric anisotropy, large specific resistance, high light stability, high thermal stability, large elastic constant, small helical pitch, excellent storage stability, or has a proper balance between at least two of these characteristics, and the present invention provides a use of the composition, a liquid crystal dimming element, a dimming window, and a smart window. The present invention uses a liquid crystal composition for a liquid crystal dimming element, which contains a liquid crystal composition with positive and large dielectric anisotropy, an optically active compound with an octahydrobinaphthyl structure, and a specific type of dichroic pigment.

Description

Liquid crystal composition for liquid crystal dimming element and its use, liquid crystal dimming element, dimming window, smart window

The present invention mainly relates to a liquid crystal dimming element. More specifically, the present invention relates to a liquid crystal dimming element having a liquid crystal composition for a liquid crystal dimming element, wherein the liquid crystal composition for a liquid crystal dimming element is a combination of a liquid crystal composition having positive dielectric anisotropy, an optically active compound and a dichroic pigment.

Liquid crystal materials are not only used in various display elements that display text, images, and videos, such as televisions (TV) and smartphones, but are also being used as dimming elements that adjust the transmittance of light. Among them, when a "guest host (GH) type liquid crystal composition" is used, which is formed by adding a dichroic pigment to a liquid crystal composition as a host, a polarizing plate is not required, so a dimming element with high transmittance is expected to be obtained at a low cost. Research has been conducted on GH type liquid crystal compositions in the past, and attempts have been made to develop liquid crystal display elements or dimming elements having useful element performance (for example, a large dichroic ratio, a high contrast, high solubility in liquid crystal compositions, excellent light resistance, excellent ultraviolet resistance (UV), and excellent heat resistance) (see Patent Document 1). In addition, in recent years, a method of using a twisted nematic liquid crystal medium has been proposed as an element for expanding the switching range in a smart window (see Patent Document 2).

On the other hand, among the liquid crystal compositions containing dichroic dyes, some are not suitable for use in liquid crystal display elements or dimming elements depending on their constituent components, and further improvement of performance is required. For example, in order to obtain a large dichroic ratio, it is necessary to make the liquid crystal composition contain a large amount of dichroic dyes, and there is a problem of solubility of the composition where the dichroic dye or liquid crystal compound precipitates. In particular, in order to be used as a dimming element, a nematic liquid crystal phase must be presented in a wide temperature range, but since the molecular weight of the dye is larger than that of the liquid crystal compound, there is a problem in solubility at low temperatures.

As a liquid crystal composition having a twisted nematic phase, a liquid crystal composition having a positive dielectric anisotropy characterized by containing an optically active compound having an octahydrobinaphthyl skeleton or a binaphthyl skeleton has been proposed (see Patent Document 3). Although there are suggestions related to mixed dichroic dyes in the above document, there is no disclosure as a liquid crystal dimming element, and research as a liquid crystal dimming element is insufficient. [Prior Art Document] [Patent Document]

[Patent Document 1] International Publication No. 1997/17415 [Patent Document 2] Japanese Patent Publication No. 2016-536634 [Patent Document 3] Japanese Patent Publication No. 2018-95668

[Problems to be solved by the invention] The subject of the present invention is to provide a guest-host type liquid crystal dimming element suitable for dimming by combining an optically active compound having a specific structure with a dichroic pigment in a liquid crystal composition. Another subject is to provide a liquid crystal dimming element suitable for dimming containing a guest-host type liquid crystal dimming element, wherein the guest-host type liquid crystal dimming element fully satisfies at least one of the following characteristics: a high upper temperature limit of the nematic phase, a low lower temperature limit of the nematic phase, low viscosity, large optical anisotropy, large positive dielectric anisotropy, large specific resistance, high light stability, high thermal stability, large elastic constant, and small helical pitch. Another topic is to provide a liquid crystal dimming element that contains a liquid crystal composition for a liquid crystal dimming element and is suitable for dimming, wherein the liquid crystal composition for the liquid crystal dimming element has an appropriate balance between at least two of these characteristics. Another topic is to provide a liquid crystal dimming element that has the characteristics of short response time, high voltage retention rate, low threshold voltage, small haze rate (few bright spot defects), not easy to produce precipitation in low temperature environment, good storage stability, high weather resistance, long life, etc.

[Technical means for solving the problem] A liquid crystal composition for a liquid crystal dimming element comprises a liquid crystal composition, an optically active compound and a dichroic dye, wherein the liquid crystal composition comprises at least one liquid crystal compound selected from the compounds represented by formula (1) as component A, the optically active compound comprises at least one compound selected from the group of compounds having an octahydronaphthyl structure represented by formula (K1) and formula (K2), and the dichroic dye comprises at least one compound selected from the group consisting of azo compounds, benzothiadiazoles, and diketopyrrolopyrroles, and at least one compound selected from the group consisting of anthraquinones. Here, the definitions of the symbols of each formula are described below. A liquid crystal composition for a liquid crystal dimming element comprises a liquid crystal composition, an optically active compound and a dichroic dye, wherein the liquid crystal composition comprises at least one liquid crystal compound selected from the compounds represented by formula (1) as component A, the optically active compound comprises at least one compound selected from the group of compounds represented by formula (K1) and formula (K2), and the dichroic dye comprises at least one compound selected from the group consisting of azo compounds, benzothiadiazoles, diketopyrrolopyrroles and at least one compound selected from the group consisting of anthraquinones. In formula (1), ^R1 is an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an alkenyl group having 2 to 12 carbon atoms; Ring A is 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene, pyrimidine-2,5-diyl, 1,3-dioxane-2,5-diyl, or tetrahydropyran-2,5-diyl; ^Z1 is a single bond, ethylene, ethenylene, ethynylene, methyleneoxy, carbonyloxy, or difluoromethyleneoxy; ^X1 and ^X2 are hydrogen or fluorine; Y ¹ is fluorine, chlorine, cyano, an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine or chlorine, an alkoxy group having 1 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine or chlorine, or an alkenyloxy group having 2 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine or chlorine; a is 1, 2, 3 or 4; In formula (K1) and formula (K2), R ^K is hydrogen, a halogen, -C≡N, -N=C=O, -N=C=S or an alkyl group having 1 to 12 ^carbon atoms, in which at least one -CH ₂ - may be substituted by -O-, -S-, -COO- or -OCO-, at least one -CH ₂ -CH ₂ - may be substituted by -CH=CH-, -CF=CF- or -C≡C-, and at least one hydrogen may be substituted by fluorine or chlorine; A ^K is an aromatic 6- to 8-membered ring, a non-aromatic 3- to 8-membered ring, or a condensed ring with 9 or more carbon atoms. In A ^K , at least one hydrogen can be substituted by a halogen, an alkyl group or a halogenated alkyl group with 1 to 3 carbon atoms, _-CH2- can be substituted by -O-, -S- or -NH-, and -CH= can be substituted by -N=; Z ^K is a single bond, an alkylene group with 1 to 8 carbon atoms. In Z ^K , at least one _-CH2- can be substituted by -O-, -S-, -COO-, -OCO-, -CSO-, -OCS-, -N=N-, -CH=N- or -N=CH-, at least one -CH2 _{- CH2-} can be substituted by -CH=CH-, -CF=CF- or -C≡C-, and at least one hydrogen can be substituted by a halogen; X ^K is a single bond, -COO-, -OCO-, -CH ₂ O-, -OCH ₂ -, -CF ₂ O-, -OCF ₂ - or -CH ₂ CH ₂ -; mK is an integer from 1 to 3. A liquid crystal dimming element, wherein the dimming layer is the liquid crystal composition for liquid crystal dimming element, the dimming layer is sandwiched by a pair of transparent substrates, and the transparent substrates have transparent electrodes. A dimming window, which uses the liquid crystal dimming element. A smart window, which uses the liquid crystal dimming element. A use of the liquid crystal composition for liquid crystal dimming element, wherein the liquid crystal composition for liquid crystal dimming element is the liquid crystal composition for liquid crystal dimming element, which is used in a liquid crystal dimming element whose transparent substrate is a plastic film. A use of the liquid crystal composition for liquid crystal dimming element, wherein the liquid crystal composition for liquid crystal dimming element is the liquid crystal composition for liquid crystal dimming element, which is used in a dimming window. A use of a liquid crystal composition for a liquid crystal dimming element, wherein the liquid crystal composition for a liquid crystal dimming element is the liquid crystal composition for a liquid crystal dimming element, and is used in a smart window.

[Effect of the invention] The advantage of the present invention is that a liquid crystal composition for a liquid crystal dimming element suitable for dimming is provided by combining an optically active compound of a specific structure with a specific dichroic pigment in a liquid crystal composition. Another advantage is that a liquid crystal dimming element containing a liquid crystal composition for a liquid crystal dimming element and suitable for dimming is provided, wherein the liquid crystal composition for a liquid crystal dimming element fully satisfies at least one of the following characteristics: a high upper temperature limit of the nematic phase, a low lower temperature limit of the nematic phase, a low viscosity, a large optical anisotropy, a large positive dielectric anisotropy, a large specific resistance, a high light stability, a high heat stability, a large elastic constant, and a small helical pitch. Another advantage is that a liquid crystal dimming element containing a liquid crystal composition for a liquid crystal dimming element and suitable for dimming is provided, wherein the liquid crystal composition for a liquid crystal dimming element has an appropriate balance between at least two of these characteristics. Another advantage is to provide a liquid crystal dimming element with characteristics such as short response time, high voltage retention rate, low threshold voltage, low haze rate (few alignment defects), not easy to produce precipitation in low temperature environment, good storage stability, high weather resistance, and long life.

In this specification, the terms "liquid crystal compound", "liquid crystal composition", "optically active compound", "dichroic pigment", "liquid crystal dimming element" and the like are used. "Liquid crystal compound" is a general term for compounds having liquid crystal phases such as nematic phase and smectic phase, and compounds that do not have a liquid crystal phase but are added to the composition for the purpose of adjusting the temperature range, viscosity, dielectric anisotropy and other properties of the nematic phase. For example, the compound has a six-membered ring such as 1,4-cyclohexylene or 1,4-phenylene, and its molecule (liquid crystal molecule) is rod-like.

"Liquid crystal composition" is prepared by mixing a plurality of liquid crystal compounds. Additives such as optically active compounds, antioxidants, ultraviolet absorbers, matting agents, dichroic pigments, defoaming agents, polar compounds, etc. are added to the liquid crystal composition as needed to prepare a liquid crystal composition for a liquid crystal dimming element. Even when additives are added, the proportion of the liquid crystal compound is expressed as a mass percentage (mass %) based on the liquid crystal composition not containing the additive. The proportion of the additive is expressed as a mass percentage based on the liquid crystal composition not containing the additive. That is, the proportion of the liquid crystal compound or the additive is calculated based on the total amount of the liquid crystal compound. Furthermore, the "mass" in "mass %" is sometimes omitted.

The "liquid crystal composition for liquid crystal dimming element" is produced by the above-mentioned preparation process. The "liquid crystal dimming element" is an element having the liquid crystal composition for liquid crystal dimming element, and is a general term for liquid crystal panels and liquid crystal modules used for dimming.

Sometimes, the "upper limit temperature of the nematic phase" is referred to as the "upper limit temperature". Sometimes, the "lower limit temperature of the nematic phase" is referred to as the "lower limit temperature". The expression "increasing dielectric anisotropy" means that its value increases positively in the case of a composition with positive dielectric anisotropy, and that its value increases negatively in the case of a composition with negative dielectric anisotropy. "High voltage retention rate" means that the element has a high voltage retention rate not only at room temperature but also at a temperature close to the upper limit temperature in the initial stage, and that after long-term use, the element has a high voltage retention rate not only at room temperature but also at a temperature close to the upper limit temperature. The characteristics of a composition or element are sometimes studied by time change tests.

The compound (1z) is used as an example for explanation. In formula (1z), the symbols α and β surrounded by a hexagon correspond to ring α and ring β, respectively, and represent a ring such as a six-membered ring or a fused ring. When the subscript 'x' is 2, there are two rings α. The two groups represented by the two rings α may be the same or different. The above rule applies to any two rings α when the subscript 'x' is greater than 2. The above rule also applies to other symbols such as the bonding group Z. The slash that crosses one side of the ring β indicates that any hydrogen on the ring β can be substituted by a substituent (-Sp-P). The subscript 'y' indicates the number of substituted substituents. When the subscript 'y' is 0, there is no such substitution. When the subscript 'y' is 2 or more, there are multiple substituents (-Sp-P) on ring β. In this case, the rule of "may be the same or different" also applies. Furthermore, the above rule also applies to the case where the symbol of Ra is used in multiple compounds.

In formula (1z), for example, the expression "Ra and Rb are alkyl, alkoxy or alkenyl" means that Ra and Rb are independently selected from the group consisting of alkyl, alkoxy and alkenyl. That is, the group represented by Ra and the group represented by Rb may be the same or different.

At least one compound selected from the compounds represented by formula (1z) is sometimes referred to as "compound (1z)". "Compound (1z)" refers to one compound, a mixture of two compounds, or a mixture of three or more compounds represented by formula (1z). The same applies to compounds represented by other formulae. The expression "at least one compound selected from the compounds represented by formula (1z) and formula (2z)" refers to at least one compound selected from the group of compound (1z) and compound (2z).

"Main component" refers to the component that accounts for the largest proportion in a mixture or composition. For example, in a mixture of 40% compound (1z), 35% compound (2z), and 25% compound (3z), the main component is compound (1z). When the component is only compound (1z), compound (1z) is also called the main component. When compound (1z) is a single compound, the compound is also called the main component.

The expression "at least one 'A'" means that the number of 'A' is arbitrary. The expression "at least one 'A' may be substituted by 'B'" means that when the number of 'A' is one, the position of 'A' is arbitrary, and when the number of 'A' is two or more, their positions can also be selected without limitation. The expression "at least one -CH ₂ - may be substituted by -O-" is sometimes used. In such a case, -CH ₂ -CH ₂ -CH ₂ - may be converted to -O-CH ₂ -O- by replacing a non-adjacent -CH ₂ - with -O-. However, there is no case where an adjacent -CH ₂ - is substituted by -O-. The reason is that -OO-CH ₂ - (peroxide) is generated in such substitution.

The alkyl group of the liquid crystal compound is linear or branched, and does not include cyclic alkyl groups. Linear alkyl groups are preferred over branched alkyl groups. This also applies to terminal groups such as alkoxy and alkenyl groups. In order to increase the upper limit temperature, the stereo configuration associated with 1,4-cyclohexylene is preferred to the trans configuration over the cis configuration. Since 2-fluoro-1,4-phenylene is asymmetric, there are left-facing (L) and right-facing (R). The same applies to divalent groups such as tetrahydropyran-2,5-diyl and the like. The same applies to bonding groups such as carbonyloxy (-COO- or -OCO-).

The present invention includes the following items, etc.

Item 1. A liquid crystal composition for a liquid crystal dimming element, comprising a liquid crystal composition, an optically active compound and a dichroic dye, wherein the liquid crystal composition comprises at least one liquid crystal compound selected from the compounds represented by formula (1) as component A, the optically active compound comprises at least one compound selected from the group of compounds represented by formula (K1) and formula (K2), and the dichroic dye comprises at least one compound selected from the group consisting of azo compounds, benzothiadiazoles, and diketopyrrolopyrroles, and at least one compound selected from the group consisting of anthraquinones. In formula (1), ^R1 is an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an alkenyl group having 2 to 12 carbon atoms; Ring A is 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene, pyrimidine-2,5-diyl, 1,3-dioxane-2,5-diyl, or tetrahydropyran-2,5-diyl; ^Z1 is a single bond, ethylene, ethenylene, ethynylene, methyleneoxy, carbonyloxy, or difluoromethyleneoxy; ^X1 and ^X2 are hydrogen or fluorine; Y ¹ is fluorine, chlorine, cyano, an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine or chlorine, an alkoxy group having 1 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine or chlorine, or an alkenyloxy group having 2 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine or chlorine; a is 1, 2, 3 or 4; In formula (K1) and formula (K2), R ^K is hydrogen, a halogen, -C≡N, -N=C=O, -N=C=S or an alkyl group having 1 to 12 ^carbon atoms, in which at least one -CH ₂ - may be substituted by -O-, -S-, -COO- or -OCO-, at least one -CH ₂ -CH ₂ - may be substituted by -CH=CH-, -CF=CF- or -C≡C-, and at least one hydrogen may be substituted by fluorine or chlorine; A ^K is an aromatic 6- to 8-membered ring, a non-aromatic 3- to 8-membered ring, or a condensed ring with 9 or more carbon atoms. In A ^K , at least one hydrogen can be substituted by a halogen, an alkyl group or a halogenated alkyl group with 1 to 3 carbon atoms, _-CH2- can be substituted by -O-, -S- or -NH-, and -CH= can be substituted by -N=; Z ^K is a single bond, an alkylene group with 1 to 8 carbon atoms. In Z ^K , at least one _-CH2- can be substituted by -O-, -S-, -COO-, -OCO-, -CSO-, -OCS-, -N=N-, -CH=N- or -N=CH-, at least one -CH2 _{- CH2-} can be substituted by -CH=CH-, -CF=CF- or -C≡C-, and at least one hydrogen can be substituted by a halogen; X ^K is a single bond, -COO-, -OCO-, -CH ₂ O-, -OCH ₂ -, -CF ₂ O-, -OCF ₂ - or -CH ₂ CH ₂ -; mK is an integer of 1 to 3.

Item 2. The liquid crystal composition for a liquid crystal light modulating element according to Item 1, wherein the liquid crystal composition contains, as component A, at least one compound selected from the group consisting of compounds represented by formula (1-1) to formula (1-47). In formula (1-1) to formula (1-47), ^R1 is an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an alkenyl group having 2 to 12 carbon atoms; ^X1 and ^X2 are hydrogen or fluorine; ^Y1 is fluorine, chlorine, cyano, an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen atom is substituted with fluorine or chlorine, an alkoxy group having 1 to 12 carbon atoms in which at least one hydrogen atom is substituted with fluorine or chlorine, or an alkenyloxy group having 2 to 12 carbon atoms in which at least one hydrogen atom is substituted with fluorine or chlorine.

Item 3. The liquid crystal composition for a liquid crystal dimming element according to Item 1 or Item 2, wherein the proportion of component A is in the range of 5% to 90% based on the total amount of the liquid crystal composition.

Item 4. The liquid crystal composition for a liquid crystal light modulating element according to any one of Items 1 to 3, wherein the liquid crystal composition contains, as component B, at least one compound selected from the compounds represented by formula (2). In formula (2), ^R2 and ^R3 are alkyl groups having 1 to 12 carbon atoms, alkoxy groups having 1 to 12 carbon atoms, alkenyl groups having 2 to 12 carbon atoms, or alkenyl groups having 2 to 12 carbon atoms in which at least one hydrogen atom is substituted with fluorine or chlorine; Ring B and Ring C are 1,4-cyclohexylene, 1,3-phenylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 2,5-difluoro-1,4-phenylene or pyrimidine-2,5-diyl; ^Z2 is a single bond, ethylene, ethenylene, ethynylene, methyleneoxy or carbonyloxy; and b is 1, 2, 3 or 4.

Item 5. The liquid crystal composition for a liquid crystal light modulating element according to any one of Items 1 to 4, wherein the liquid crystal composition contains, as component B, at least one compound selected from the group consisting of compounds represented by Formula (2-1) to Formula (2-25). In formula (2-1) to formula (2-25), ^R2 and ^R3 are alkyl groups having 1 to 12 carbon atoms, alkoxy groups having 1 to 12 carbon atoms, alkenyl groups having 2 to 12 carbon atoms, or alkenyl groups having 2 to 12 carbon atoms in which at least one hydrogen atom is substituted with fluorine or chlorine.

Item 6. The liquid crystal composition for a liquid crystal dimming element according to Item 4 or Item 5, wherein the proportion of component B is in the range of 5% to 90% based on the total amount of the liquid crystal composition.

Item 7. The liquid crystal composition for a liquid crystal light modulating element according to any one of Items 1 to 6, wherein the liquid crystal composition contains, as component C, at least one compound selected from the compounds represented by formula (3). In formula (3), ^R4 and ^R5 are hydrogen, alkyl having 1 to 12 carbon atoms, alkoxy having 1 to 12 carbon atoms, alkenyl having 2 to 12 carbon atoms, or alkenyloxy having 2 to 12 carbon atoms; Ring D and Ring F are 1,4-cyclohexylene, 1,4-cyclohexenyl, tetrahydropyran-2,5-diyl, 1,4-phenylene, 1,4-phenylene in which at least one hydrogen atom is substituted with fluorine or chlorine, naphthalene-2,6-diyl, naphthalene-2,6-diyl in which at least one hydrogen atom is substituted with fluorine or chlorine, chromane-2,6-diyl, or chromane-2,6-diyl in which at least one hydrogen atom is substituted with fluorine or chlorine. ,6-diyl; Ring E is 2,3-difluoro-1,4-phenylene, 2-chloro-3-fluoro-1,4-phenylene, 2,3-difluoro-5-methyl-1,4-phenylene, 3,4,5-trifluoronaphthalene-2,6-diyl, 7,8-difluorochromane-2,6-diyl, 3,4,5,6-tetrafluorofluorene-2,7-diyl, 4,6-difluorodibenzofuran-3,7-diyl, 4,6-difluorodibenzothiophene-3,7-diyl or 1,1,6,7-tetrafluoroindan-2,5-diyl; Z ³ and Z ⁴ are a single bond, ethylene, ethenylene, methyleneoxy or carbonyloxy; c is 0, 1, 2 or 3, d is 0 or 1, and the sum of c and d is 3 or less.

Item 8. The liquid crystal composition for a liquid crystal light modulating element according to any one of Items 1 to 7, wherein the liquid crystal composition contains, as component C, at least one compound selected from the group consisting of compounds represented by Formula (3-1) to Formula (3-35). In formula (3-1) to formula (3-35), ^R4 and ^R5 are hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an alkenyloxy group having 2 to 12 carbon atoms.

Item 9. The liquid crystal composition for a liquid crystal dimming element according to Item 7 or Item 8, wherein the proportion of component C is in the range of 3% to 25% based on the total amount of the liquid crystal composition.

Item 10. The liquid crystal composition for a liquid crystal dimming element according to any one of Items 1 to 9, comprising at least one compound selected from the optically active compounds represented by Formula (K1-1) to Formula (K1-7) and Formula (K2-1) to Formula (K2-4). R ^K is hydrogen or an alkyl group having 1 to 12 carbon atoms. In said R ^K , at least one -CH ₂ - may be substituted by -O-, -S-, -COO- or -OCO-, at least one -CH ₂ -CH ₂ - may be substituted by -CH=CH-, -CF=CF- or -C≡C-, and at least one hydrogen may be substituted by fluorine or chlorine.

Item 11. The liquid crystal composition for a liquid crystal dimming element according to any one of Items 1 to 10, wherein the ratio of the optically active compound is in the range of 0.01 parts by weight to 5 parts by weight based on the total amount of the liquid crystal composition.

Item 12. The liquid crystal composition for a liquid crystal light modulating element according to any one of Items 1 to 11, wherein the helical pitch is in the range of 2 μm to 20 μm.

Item 13. The liquid crystal composition for a liquid crystal light modulating element according to any one of Items 1 to 12, wherein the dichroic dye comprises at least one compound selected from azo compounds and at least one compound selected from anthraquinones.

Item 14. The liquid crystal composition for a liquid crystal dimming element according to any one of Items 1 to 13, wherein the ratio of the dichroic pigment is in the range of 0.01 parts by weight to 25 parts by weight based on the total amount of the liquid crystal composition.

Item 15. A liquid crystal dimming element, wherein the dimming layer is the liquid crystal composition for the liquid crystal dimming element according to any one of items 1 to 14, and the dimming layer is sandwiched by a pair of transparent substrates, and the transparent substrates have transparent electrodes.

Item 16. A liquid crystal dimming element according to Item 15, wherein the transparent substrate is a glass plate or an acrylic plate.

Item 17. A liquid crystal dimming element according to Item 15, wherein the transparent substrate is a plastic film.

Item 18. A dimming window using a liquid crystal dimming element according to any one of items 15 to 17.

Item 19. A smart window using a liquid crystal dimming element according to any one of items 15 to 17.

Item 20. Use of a liquid crystal composition for a liquid crystal dimming element, wherein the liquid crystal composition for a liquid crystal dimming element is the liquid crystal composition for a liquid crystal dimming element according to any one of items 1 to 14, and is used in a liquid crystal dimming element whose transparent substrate is a plastic film.

Item 21. A use of a liquid crystal composition for a liquid crystal dimming element, wherein the liquid crystal composition for a liquid crystal dimming element is the liquid crystal composition for a liquid crystal dimming element according to any one of items 1 to 14, and is used in a dimming window.

Item 22. A use of a liquid crystal composition for a liquid crystal dimming element, wherein the liquid crystal composition for a liquid crystal dimming element is the liquid crystal composition for a liquid crystal dimming element according to any one of items 1 to 14, and is used in a smart window.

The present invention also includes the following items. (a) The liquid crystal composition for a liquid crystal light-adjusting element, wherein the liquid crystal composition contains as component (A) at least one compound in which ^Y1 is fluorine among the compounds (1) described in item 1. (b) The liquid crystal composition for a liquid crystal light-adjusting element, wherein the liquid crystal composition contains as component (A) at least one compound in which ^Y1 is cyano among the compounds (1) described in item 1.

The present invention also includes the following item: (c) the liquid crystal composition for a liquid crystal light-adjusting element, wherein the liquid crystal composition contains at least one compound selected from the group consisting of compound (1-1), compound (1-2), compound (1-3), compound (1-7), compound (1-9), compound (1-13), compound (1-14), compound (1-15), compound (1-16), compound (1-17), compound (1-21), compound (1-22), compound (1-23), compound (1-24), compound (1-27), compound (1-28), compound (1-29), compound (1-30), compound (1-33), compound (1-34), compound (1-36), compound (1-41), compound (1-42), compound (1-43) and compound (1-44) described in item 2 as component (A).

The present invention also includes the following item: (d) the liquid crystal composition for a liquid crystal light-adjusting element, wherein the liquid crystal composition contains at least one compound selected from the group consisting of compound (2-1), compound (2-2), compound (2-3), compound (2-4), compound (2-6), compound (2-8), compound (2-9), compound (2-10), compound (2-11), compound (2-12), compound (2-13), compound (2-14), compound (2-16), compound (2-17), compound (2-19), compound (2-21), compound (2-24) and compound (2-25) described in item 5 as component (B).

The present invention also includes the following items: (e) the liquid crystal composition for a liquid crystal light-adjusting element, wherein the liquid crystal composition contains at least one compound selected from the group consisting of compound (3-1), compound (3-5), compound (3-6), compound (3-7), compound (3-8), compound (3-12), compound (3-14), compound (3-19) and compound (3-34) described in item 8 as component (C).

We have attempted to improve the properties of a liquid crystal composition for a liquid crystal dimming element. In order to improve the properties of a liquid crystal composition for a liquid crystal dimming element, we considered an approach of using a liquid crystal composition for a liquid crystal dimming element having a specific type of dichroic dye in a chiral nematic liquid crystal composition formed by mixing an optically active compound having an octahydronaphthyl structure and a liquid crystal composition. The reason is that a liquid crystal composition for a liquid crystal dimming element, which is a mixture of a nematic liquid crystal composition, an optically active compound having an octahydronaphthyl structure, and a specific type of dichroic dye, can be expected to have both good compatibility and high weather resistance, and therefore it is considered that it can be used in a liquid crystal dimming element. We have studied the above possibility and completed the present invention.

The present invention relates to a liquid crystal composition for a liquid crystal dimming element containing a specific type of dichroic pigment and a liquid crystal composition having a chiral nematic phase, and a liquid crystal dimming element having the liquid crystal composition for a liquid crystal dimming element. In order to be suitable for a dimming element, an optically active compound (chiral agent) is added to the nematic liquid crystal composition. The chiral nematic liquid crystal composition is prepared in the following manner. The liquid crystal composition for a liquid crystal dimming element contains a chiral nematic liquid crystal composition and a dichroic pigment. We have found that the specific liquid crystal composition for a liquid crystal dimming element has excellent compatibility, exhibits a focal conic state, a planar state, a homeotropic state, etc. depending on the conditions, and is suitable for a dimming element. The present invention is described below.

First, the liquid crystal composition is described. The composition contains a plurality of liquid crystal compounds. The composition may also contain additives. The additives are optically active compounds, antioxidants, ultraviolet absorbers, extinction agents, dichroic pigments, defoaming agents, polar compounds, and the like. From the perspective of the liquid crystal compounds, the composition is classified into composition A and composition B. Composition A not only contains a liquid crystal compound selected from compound (1), compound (2) and compound (3), but may also further contain other liquid crystal compounds, additives, and the like. "Other liquid crystal compounds" are liquid crystal compounds different from compound (1), compound (2) and compound (3). Such compounds are mixed into the composition for the purpose of further adjusting the properties.

The composition B substantially contains only a liquid crystal compound selected from the group consisting of compound (1), compound (2) and compound (3). "Substantially" means that although the composition B may contain additives, it does not contain other liquid crystal compounds. The number of components of the composition B is smaller than that of the composition A. From the perspective of cost reduction, the composition B is superior to the composition A. From the perspective of further adjusting the properties by mixing other liquid crystal compounds, the composition A is superior to the composition B.

Second, the main characteristics of liquid crystal compounds and the main effects of the compounds on liquid crystal compositions or devices are described. The main characteristics of the component compounds are summarized in Table 1. In the symbols in Table 1, L means large or high, M means medium, and S means small or low. The symbols L, M, and S are classifications based on qualitative comparisons between the component compounds, and 0 (zero) means extremely small.

Table 1. Characteristics of liquid crystal compounds       Compounds Compound (1) Compound (2) Compound (3) Upper limit temperature S～L S～L S～L Viscosity M～L S～M M～L Optical anisotropy M～L S～L M～L Dielectric anisotropy S～L 0 M～L ^{1 ）} Specific resistance L L L 1) The value of dielectric anisotropy is negative, and the sign indicates the magnitude of the absolute value  

The main effects of the component compounds on the properties of the composition are as follows. Compound (1) increases dielectric anisotropy. Compound (2) increases the upper limit temperature or decreases the lower limit temperature. Compound (3) increases the dielectric constant in the short axis direction of the liquid crystal molecules.

Third, the combination or preferred ratio of liquid crystal compounds is described. The preferred combination is component A + component B, component A + component C, or component A + component B + component C. Further preferred combinations are component A + component B, or component A + component B + component C. It is also possible to combine a specific one or two compounds selected from component A with component B (or component C). The same applies to component B or component C.

In order to improve the dielectric anisotropy, the preferred ratio of component A is about 5% or more, and in order to reduce the minimum temperature, the preferred ratio of component A is about 90% or less. Further preferred ratios are in the range of about 10% to about 85%. The particularly preferred ratio is in the range of about 20% to about 80%.

In order to increase the upper temperature limit or reduce the lower temperature limit, the preferred ratio of component B is about 5% or more, and in order to increase the dielectric anisotropy, the preferred ratio of component B is about 90% or less. Further preferred ratios are in the range of about 10% to about 85%. Particularly preferred ratios are in the range of about 20% to about 80%.

In order to increase the dielectric constant of the liquid crystal molecules in the short axis direction, the preferred ratio of component C is about 3% or more, and in order to reduce the minimum temperature, the preferred ratio of component C is about 25% or less. Further preferred ratio is in the range of about 5% to about 20%. The particularly preferred ratio is in the range of about 5% to about 15%.

Fourth, the preferred form of the liquid crystal compound is described. In formula (1), formula (2) and formula (3), ^R1 is an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms or an alkenyl group having 2 to 12 carbon atoms. In order to improve the stability to light or heat, the preferred ^R1 is an alkyl group having 1 to 12 carbon atoms.

^R2 and ^R3 are alkyl groups having 1 to 12 carbon atoms, alkoxy groups having 1 to 12 carbon atoms, alkenyl groups having 2 to 12 carbon atoms, or alkenyl groups having 2 to 12 carbon atoms in which at least one hydrogen atom is substituted by fluorine or chlorine. In order to increase the upper temperature limit or lower the lower temperature limit, preferably ^R2 or ^R3 is an alkenyl group having 2 to 12 carbon atoms, and in order to increase the stability to light or heat, preferably ^R2 or ^R3 is an alkyl group having 1 to 12 carbon atoms.

^R4 and ^R5 are hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an alkenyloxy group having 2 to 12 carbon atoms. In order to improve the stability to light or heat, preferably ^R4 or ^R5 is an alkyl group having 1 to 12 carbon atoms, and in order to improve the dielectric constant in the short axis direction of the liquid crystal molecule, preferably ^R4 or ^R5 is an alkoxy group having 1 to 12 carbon atoms.

Preferred alkyl groups are methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl or octyl. In order to reduce the viscosity, further preferred alkyl groups are methyl, ethyl, propyl, butyl or pentyl.

Preferred alkoxy groups are methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy or heptyloxy. In order to reduce the viscosity, further preferred alkoxy groups are methoxy or ethoxy.

Preferred alkenyl groups are vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 4-hexenyl or 5-hexenyl. In order to reduce viscosity, further preferred alkenyl groups are vinyl, 1-propenyl, 3-butenyl or 3-pentenyl. The preferred stereo configuration of -CH=CH- in these alkenyl groups depends on the position of the double bond. In order to reduce viscosity and other reasons, trans configuration is preferred in alkenyl groups such as 1-propenyl, 1-butenyl, 1-pentenyl, 1-hexenyl, 3-pentenyl, 3-hexenyl. In alkenyl groups such as 2-butenyl, 2-pentenyl, 2-hexenyl and the like, the cis configuration is preferred.

Preferred alkenyloxy groups are vinyloxy, allyloxy, 3-butenyloxy, 3-pentenyloxy or 4-pentenyloxy. In order to reduce the viscosity, further preferred alkenyloxy groups are allyloxy or 3-butenyloxy.

Preferred examples of the alkyl group in which at least one hydrogen is substituted with fluorine or chlorine are fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl, 7-fluoroheptyl or 8-fluorooctyl. In order to improve the dielectric anisotropy, further preferred examples are 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl or 5-fluoropentyl.

Preferred examples of the alkenyl group in which at least one hydrogen is substituted with fluorine or chlorine are 2,2-difluorovinyl, 3,3-difluoro-2-propenyl, 4,4-difluoro-3-butenyl, 5,5-difluoro-4-pentenyl or 6,6-difluoro-5-hexenyl. Further preferred examples are 2,2-difluorovinyl or 4,4-difluoro-3-butenyl in order to reduce the viscosity.

Ring A is 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene, pyrimidine-2,5-diyl, 1,3-dioxane-2,5-diyl or tetrahydropyran-2,5-diyl. In order to improve the optical anisotropy, the preferred ring A is 1,4-phenylene or 2-fluoro-1,4-phenylene. In order to increase the upper limit temperature, the stereo configuration associated with 1,4-cyclohexylene is the trans configuration is better than the cis configuration. Tetrahydropyran-2,5-diyl is or , preferably .

Ring B and Ring C are 1,4-cyclohexylene, 1,3-phenylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 2,5-difluoro-1,4-phenylene or pyrimidine-2,5-diyl. In order to increase the upper limit temperature or to lower the lower limit temperature, the preferred ring B or ring C is 1,4-cyclohexylene, and in order to lower the lower limit temperature, the preferred ring B or ring C is 1,4-phenylene. In order to improve the stability to light or heat, the preferred ring B or ring C is 1,4-phenylene.

Ring D and Ring F are 1,4-cyclohexylene, 1,4-cyclohexenyl, tetrahydropyran-2,5-diyl, 1,4-phenylene, 1,4-phenylene in which at least one hydrogen is substituted by fluorine or chlorine, naphthalene-2,6-diyl, naphthalene-2,6-diyl in which at least one hydrogen is substituted by fluorine or chlorine, chromane-2,6-diyl, or chromane-2,6-diyl in which at least one hydrogen is substituted by fluorine or chlorine. In order to lower the lower limit temperature or to increase the upper limit temperature, the preferred ring D or ring F is 1,4-cyclohexylene, and in order to lower the lower limit temperature, the preferred ring D or ring F is 1,4-phenylene.

Ring E is 2,3-difluoro-1,4-phenylene, 2-chloro-3-fluoro-1,4-phenylene, 2,3-difluoro-5-methyl-1,4-phenylene, 3,4,5-trifluoronaphthalene-2,6-diyl, 7,8-difluorochromane-2,6-diyl, 3,4,5,6-tetrafluorofluorene-2,7-diyl (FLF4), 4,6-difluorodibenzofuran-3,7-diyl (DBFF2), 4,6-difluorodibenzothiophene-3,7-diyl (DBTF2) or 1,1,6,7-tetrafluoroindan-2,5-diyl (InF4). In order to reduce the viscosity, the preferred ring E is 2,3-difluoro-1,4-phenylene, and in order to increase the dielectric constant of the liquid crystal molecule in the short axis direction, the preferred ring E is 4,6-difluorodibenzothiophene-3,7-diyl.

Z ¹ is a single bond, an ethyl group, a vinyl group, an ethynyl group, a methyleneoxy group, a carbonyloxy group or a difluoromethyleneoxy group. In order to increase the upper limit temperature, Z ¹ is preferably a single bond, and in order to increase the dielectric anisotropy, Z ¹ is preferably a difluoromethyleneoxy group. Particularly preferably Z ¹ is a single bond. ^{Z 2} is a single bond, an ethyl group, a vinyl group, an ethynyl group, a methyleneoxy group or a carbonyloxy group. In order to improve the stability to light or heat, preferably Z ² is a single bond. Z ³ and Z ⁴ are a single bond, an ethyl group, a vinyl group, a methyleneoxy group or a carbonyloxy group. In order to reduce the lower limit temperature, preferably Z ³ or Z ⁴ is a single bond or an ethyl group, and in order to increase the dielectric constant in the short axis direction of the liquid crystal molecule, preferably Z ³ or Z ⁴ is a methyleneoxy group. Especially preferred is the Z ³ or Z ⁴ for single keys.

Bivalent groups such as methyleneoxy groups are not bilaterally symmetrical. In methyleneoxy groups, -CH ₂ O- is preferred to -OCH ₂ -. In carbonyloxy groups, -COO- is preferred to -OCO-. In difluoromethyleneoxy groups, -CF ₂ O- is preferred to -OCF ₂ -.

a is 1, 2, 3 or 4. In order to reduce the lower limit temperature, the preferred a is 2, and in order to increase the dielectric anisotropy, the preferred a is 3. b is 1, 2, 3 or 4. In order to reduce the lower limit temperature, the preferred b is 1, and in order to increase the upper limit temperature, the preferred b is 2 or 3. In order to improve the stability to light or heat, the preferred b is 3 or 4. c is 0, 1, 2 or 3, d is 0 or 1, and the sum of c and d is 3 or less. In order to reduce the lower limit temperature, the preferred c is 1, and in order to increase the upper limit temperature, the preferred c is 2 or 3. In order to increase the dielectric constant in the short axis direction of the liquid crystal molecule, the preferred d is 0, and in order to reduce the lower limit temperature, the preferred d is 1.

^X1 and ^X2 are hydrogen or fluorine. In order to increase the upper limit temperature, preferably ^X1 or ^X2 is hydrogen, and in order to increase the dielectric anisotropy, preferably ^X1 or ^X2 is fluorine.

^Y1 is fluorine, chlorine, cyano, an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine or chlorine, an alkoxy group having 1 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine or chlorine, or an alkenyloxy group having 2 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine or chlorine. In order to reduce the viscosity, ^Y1 is preferably fluorine, and in order to increase the dielectric anisotropy, ^Y1 is preferably cyano.

A preferred example of the alkyl group in which at least one hydrogen is substituted by fluorine or chlorine is trifluoromethyl. A preferred example of the alkoxy group in which at least one hydrogen is substituted by fluorine or chlorine is trifluoromethoxy. A preferred example of the alkenyloxy group in which at least one hydrogen is substituted by fluorine or chlorine is trifluorovinyloxy.

Fifth, preferred liquid crystal compounds are shown. Preferred compounds (1) are compounds (1-1) to (1-47) described in item 2. Among these compounds, at least one of the preferred components A is compound (1-1), compound (1-2), compound (1-7), compound (1-9), compound (1-13), compound (1-14), compound (1-15), compound (1-16), compound (1-17), compound (1-22), compound (1-23), compound (1-24), compound (1-28), compound (1-29), compound (1-30), compound (1-33), compound (1-34), compound (1-41), compound (1-42), compound (1-43) or compound (1-44). Preferably, at least two of the components A are a combination of Compound (1-1) and Compound (1-2), Compound (1-1) and Compound (1-9), Compound (1-2) and Compound (1-9), Compound (1-1) and Compound (1-16), Compound (1-2) and Compound (1-16), Compound (1-9) and Compound (1-16), Compound (1-9) and Compound (1-24), Compound (1-16) and Compound (1-24), Compound (1-9) and Compound (1-41), Compound (1-16) and Compound (1-41), Compound (1-9) and Compound (1-41), Compound (1-16) and Compound (1-42), or Compound (1-28) and Compound (1-42).

Preferred compounds (2) are compounds (2-1) to (2-25) described in item 5. Among these compounds, at least one of component B is preferably Compound (2-1), compound (2-2), compound (2-3), compound (2-4), compound (2-6), compound (2-8), compound (2-9), compound (2-10), compound (2-11), compound (2-12), compound (2-13), compound (2-16), compound (2-19), compound (2-20), compound (2-21), compound (2-24) or compound (2-25). Preferably, at least two of the components B are a combination of Compound (2-1) and compound (2-2), Compound (2-1) and compound (2-9), Compound (2-2) and compound (2-9), Compound (2-2) and compound (2-10), Compound (2-2) and compound (2-12), Compound (2-2) and compound (2-19), Compound (2-4) and compound (2-9), Compound (2-4) and compound (2-19), Compound (2-9) and compound (2-10), Compound (2-9) and compound (2-12), or Compound (2-10) and compound (2-12).

Preferred compounds (3) are compounds (3-1) to (3-35) described in item 8. Among these compounds, at least one of component C is preferably compound (3-1), compound (3-3), compound (3-6), compound (3-8), compound (3-10), compound (3-14) or compound (3-34). Preferred components C are at least two of the following: compound (3-1) and compound (3-8), compound (3-1) and compound (3-14), compound (3-3) and compound (3-8), compound (3-3) and compound (3-14), compound (3-3) and compound (3-34), compound (3-6) and compound (3-8), compound (3-6) and compound (3-10) or compound (3-6) and compound (3-14).

Sixth, the preferred form of the optically active compound and an example thereof are described. The optically active compound can also be used, for example, in a twisted nematic (TN) mode liquid crystal display element. In the mode, two substrates have an alignment film. The substrates are configured by rotating the rubbing direction by 90 degrees. The optically active compound is added to twist the arrangement of the liquid crystal molecules by 90 degrees between the substrates. In order to obtain a higher contrast, it is preferred to apply a super twisted nematic (STN) mode liquid crystal display element to twist the arrangement of the liquid crystal molecules by 180 degrees, and further preferably twist by 240 degrees, 250 degrees, 260 degrees, 270 degrees, or 360 degrees or more. The spiral pitch of the liquid crystal composition for the liquid crystal dimming element is preferably 1 μm to 20 μm. By increasing the amount of the optically active compound, the helical pitch becomes smaller. Therefore, the optically active compound preferably has high compatibility with the liquid crystal composition. On the other hand, the dimming layer in the liquid crystal dimming element is obtained by making the substrates face each other with the transparent electrode layer becoming the inner side, and at this time, adjusting the spacing of the substrates through the spacer. The thickness of the obtained dimming layer is preferably adjusted to 1 μm to 100 μm. Further preferably, it is 1.5 μm to 10 μm. When using a polarizing plate, it is preferably to adjust the product of the refractive index anisotropy Δn of the liquid crystal and the unit thickness d to maximize the contrast.

Preferred optically active compounds are compound (K1) or compound (K2), preferably compound (K1-1) to compound (K1-7) or compound (K2-1) to compound (K2-4). The structures of these compounds are similar to those of compounds having liquid crystal properties. These compounds have an octahydronaphthyl structure and therefore have a low melting point and high compatibility with liquid crystal compositions. In addition, since the helical twisting force (helical torsion) is large, they are preferred from the viewpoint of easily forming a small helical pitch. These optically active compounds have axial asymmetry.

In formula (K1), formula (K2), compounds (K1-1) to (K1-7) or compounds (K2-1) to (K2-4), R ^K is hydrogen, a halogen, -C≡N, -N=C=O, -N=C=S or an alkyl group having 1 to 12 carbon atoms, at least one -CH ₂ - in R ^K may be substituted by -O-, -S-, -COO- or -OCO-, at least one -CH ₂ -CH ₂ - in R ^K may be substituted by -CH=CH-, -CF=CF- or -C≡C-, and at least one hydrogen in R ^K may be substituted by fluorine or chlorine. Preferred R ^K is hydrogen or an alkyl group having 1 to 12 carbon atoms. At least one -CH ₂ - in R ^K may be substituted by -O-, -S-, -COO- or -OCO-. At least one -CH ₂ -CH ₂ - in R ^K may be substituted by -CH=CH-, -CF=CF- or -C≡C-. At least one hydrogen in R ^K may be substituted by fluorine or chlorine. ^AK is an aromatic 6- to 8-membered ring, a non-aromatic 3- to 8-membered ring or a condensed ring having 9 or more carbon atoms. At least one hydrogen in these rings may be substituted by a halogen, an alkyl group having 1 to 3 carbon atoms or a halogenated alkyl group. The -CH ₂ - in the ring may be substituted by -O-, -S- or -NH-. -CH= may be substituted by -N=. Z ^K is a single bond, an alkylene group having 1 to 8 carbon atoms, at least one -CH ₂ - in Z ^K may be substituted by -O-, -S-, -COO-, -OCO-, -CSO-, -OCS-, -N=N-, -CH=N- or -N=CH-, at least one -CH ₂ -CH ₂ - in Z ^K may be substituted by -CH=CH-, -CF=CF- or -C≡C-, at least one hydrogen in Z ^K may be substituted by a halogen. X ^K is a single bond, -COO-, -OCO-, -CH ₂ O-, -OCH ₂ -, -CF ₂ O-, -OCF ₂ - or -CH ₂ CH ₂ -. mK is an integer from 1 to 3.

Based on the total amount of the liquid crystal composition, the preferred ratio of the optically active compound is in the range of about 0.01 parts by weight to about 5 parts by weight. A further preferred ratio is in the range of about 0.03 parts by weight to about 3 parts by weight. A particularly preferred ratio is in the range of about 0.05 parts by weight to about 2 parts by weight. The preferred helical pitch in the liquid crystal composition for the liquid crystal dimming element is 10 μm or less. A further preferred helical pitch is 5 μm or less. A particularly preferred helical pitch is 3 μm or less. In order to reduce or adjust the temperature dependence of the helical pitch, a plurality of optically active compounds may be mixed and used. At this time, from the perspective of the amount of addition, in order not to cancel out the helical torsion, it is preferred to combine optically active compounds having the same twisting direction.

Examples of the compound (K1) and the compound (K2) are as follows.

Seventh, the preferred form of dichroic dye and an example thereof are described. In order to be suitable for a guest host (GH) mode element, a dichroic dye is added to the composition. Liquid crystal dimming elements are sometimes used as room partitions or building windows, vehicle sun roofs, etc. In this case, a dichroic dye is added to the liquid crystal composition for the purpose of absorbing specific light. A variety of dichroic dyes can be added. Liquid crystal dimming elements are sometimes used to block sunlight. In this case, a black (or blackish) dichroic dye is added to the liquid crystal composition. Black is prepared by mixing cyan, magenta, and yellow dichroic dyes. For example, Example 42 of Japanese Patent Publication No. 2006-193742 describes a black dichroic pigment. The pigment is prepared by mixing an azo compound with three anthraquinones. In addition, Example 2 of Japanese Patent Publication No. 2000-313881 describes a black dichroic pigment. It can be prepared by mixing five azo compounds with three anthraquinones. By using azo compounds and anthraquinones together, a dichroic pigment that achieves both weather resistance and compatibility with liquid crystal compounds can be prepared.

Examples of dichroic pigments are benzothiadiazoles, diketopyrrolopyrroles, azo compounds, azomethine compounds, methine compounds, anthraquinones, merocyanines, naphthoquinones, tetrazines, pyrromethenes, squaraines, and perylenes or rylenes such as terrylenes and quaterrylenes.

This dichroic dye has at least some of the following characteristics. a) The dye molecule is linear. b) A skeleton unique to dichroic dyes such as a benzothiadiazole ring or a diketopyrrolopyrrole ring exists in the center of the molecule. c) The benzene ring or thiophene ring constituting the molecule together with the unique skeleton is located on the same plane. d) The side chain is an alkyl group or an alkoxy group. e) There is a conjugated double bond in the center.

Preferred dichroic pigments are benzothiadiazoles, diketopyrrolopyrroles, azo compounds, anthraquinones, and perylenes. The skeletons of the five pigments are shown below. For example, benzothiadiazoles refer to dichroic pigments having a benzothiadiazole ring.

Examples of commercially available dichroic pigments are G-207, G-241, G-305, G-470, G-471, G-472, LSB-278, LSB-335, NKX-1366, NKX-3538, NKX-3540, NKX-3622, NKX-3739, NKX-3742, NKX-3773, NKX-4010, and NKX-4033 manufactured by Nagase Sangyo; and S-428, SI-426, SI-486, M-412, and M-483 manufactured by Mitsui Fine Chemicals.

Based on the total amount of the liquid crystal composition, the preferred ratio of the dichroic pigment is in the range of about 0.01 parts by weight to about 25 parts by weight, further preferred ratio is in the range of about 0.1 parts by weight to about 23 parts by weight, and particularly preferred ratio is in the range of about 0.5 parts by weight to about 18 parts by weight.

Eighth, the synthesis method of the component compounds is described. These compounds can be synthesized using known methods. The synthesis method is illustrated. Compounds (1-9) and (1-16) are synthesized using the method described in Japanese Patent Laid-Open No. 2-233626. Compound (2-1) is synthesized using the method described in Japanese Patent Laid-Open No. 59-176221. Compound (3-1) is synthesized using the method described in Japanese Patent Laid-Open No. 2-503441. Antioxidants are already commercially available. Optically active compounds (K1) and optically active compounds (K2) are synthesized using the method described in International Publication No. 2018/025996. The compound (11-1) described later can be obtained from Sigma-Aldrich Corporation. Compound (11-2) and the like are synthesized by the method described in the specification of U.S. Patent No. 3,660,505. The polymerizable compound is commercially available or can be synthesized by a known method.

Compounds for which no synthesis method is described can be synthesized by methods described in books such as Organic Syntheses (John Wiley & Sons, Inc.), Organic Reactions (John Wiley & Sons, Inc.), Comprehensive Organic Synthesis (Pergamon Press), and New Experimental Chemistry Lectures (Maruzen). Compositions are prepared from compounds obtained in the above manner by known methods. For example, the component compounds are mixed and then dissolved in each other by heating.

Ninth, the additives that can be added to the liquid crystal composition for the liquid crystal dimming element are described. Such additives are optically active compounds other than (K1) and (K2), antioxidants, ultraviolet absorbers, matting agents, defoaming agents, polar compounds, etc. The additives can also be added to the liquid crystal composition instead of being added to the liquid crystal composition for the liquid crystal dimming element.

Examples of optically active compounds other than (K1) and (K2) are as follows.

In order to prevent the decrease in specific resistance caused by heating in the atmosphere or to maintain a large voltage retention rate not only at room temperature but also at a temperature close to the upper limit temperature after the element is used for a long time, an antioxidant such as compound (11-1) to compound (11-3) may be added to the composition.

Compound (11-2) or compound (11-3) is preferred because of its low volatility, and is effective in maintaining a high voltage retention rate not only at room temperature but also at a temperature close to the upper limit temperature after the device is used for a long time. In order to obtain the above effect, the preferred ratio of the antioxidant is about 50 ppm or more, and in order not to lower the upper limit temperature or to not increase the lower limit temperature, the preferred ratio of the antioxidant is about 600 ppm or less. Further, the preferred ratio is in the range of about 100 ppm to about 300 ppm.

Preferred examples of ultraviolet absorbers are benzophenone derivatives, benzoate derivatives, triazole derivatives, and the like. Light stabilizers such as sterically hindered amines are also preferred. Preferred examples of light stabilizers are compounds (12-1) to (12-16), and the like. In order to obtain the above-mentioned effect, the preferred ratio of these absorbers or stabilizers is about 50 ppm or more, and in order not to lower the upper limit temperature or to not increase the lower limit temperature, the preferred ratio of these absorbers or stabilizers is about 10,000 ppm or less. Furthermore, the preferred ratio is in the range of about 100 ppm to about 10,000 ppm.

The matting agent is a compound that prevents the decomposition of the liquid crystal compound by accepting the light energy absorbed by the liquid crystal compound and converting it into heat energy. Preferred examples of the matting agent are compounds (13-1) to (13-7) and the like. In order to obtain the above effect, the preferred ratio of these matting agents is about 50 ppm or more, and in order not to increase the lower limit temperature, the preferred ratio of these matting agents is about 20000 ppm or less. Furthermore, the preferred ratio is in the range of about 100 ppm to about 10000 ppm.

In order to prevent foaming, a defoaming agent such as dimethyl silicone oil or methylphenyl silicone oil is added to the composition. In order to obtain the above effect, the preferred ratio of the defoaming agent is about 1 ppm or more, and in order to prevent display defects, the preferred ratio of the defoaming agent is about 1000 ppm or less. Furthermore, the preferred ratio is in the range of about 1 ppm to about 500 ppm.

Polar compounds are organic compounds with polarity. This does not include compounds with ionic bonds. Atoms such as oxygen, sulfur, and nitrogen are negatively charged and tend to have partial negative charges. Carbon and hydrogen are neutral or tend to have partial positive charges. Polarity is caused by the uneven distribution of partial charges between different types of atoms in the compound. For example, polar compounds have at least one of the partial structures such as -OH, -COOH, -SH, _-NH2 , >NH, >N-.

The polar group has a non-covalent bonding interaction with the surface of a glass substrate, a metal oxide film, etc. The compound is adsorbed on the surface of the substrate by the action of the polar group and controls the alignment of the liquid crystal molecules.

Finally, the liquid crystal dimming element is explained. Nematic compositions are mixtures of rod-shaped liquid crystal compounds. Chiral nematic compositions are prepared by adding optically active compounds (chiral agents) to the nematic compositions. Liquid crystal molecules are given right or left twists by the action of optically active compounds, thereby becoming focal conic states. In microscopic regions, liquid crystal molecules are arranged in layers, and the directions of liquid crystal molecules in each layer are twisted in a spiral shape. The axis of twist in the spiral structure is called the spiral axis. The length corresponding to one period in the spiral structure is called the spiral pitch. The focal conic state is a collection of such microscopic regions, and the direction of the spiral axis is random. The focal conic state becomes a planar state on the alignment film after horizontal alignment treatment.

Prepare the liquid crystal composition for the dimming element of the present invention, and place the composition in the element for display. The upper and lower substrates in the element have transparent electrodes such as ITO on the dimming layer side. In addition, an absorption-type polarizing plate or a reflection-type polarizing plate can be attached to either of the upper and lower substrates. In addition, a well-known polyimide-based horizontal alignment film is provided on the two transparent electrodes. By means of the horizontal alignment film, the liquid crystal molecules have a pre-tilt angle of 1° to 10° relative to the alignment film surface, preferably a pre-tilt angle of 2° to 9°, and more preferably a pre-tilt angle of 3° to 8°. The orientation treatment direction (e.g., rubbing direction) of the orientation film in the upper and lower substrates is preferably an angle of 30° to 270°, preferably an angle of 100° to 260°, more preferably an angle of 160° to 255°, and particularly preferably an angle of 230° to 250°. The horizontal orientation treatment film can also be obtained by polarized light exposure treatment (photo-orientation method). The element has a horizontal orientation film on the upper and lower substrates, so the liquid crystal molecules are twisted (planar state) by the action of the orientation film. In the state, the dichroic dye adopts the same orientation as the liquid crystal molecules, so the light passing through the element is absorbed by the dichroic dye and the transmittance is reduced. By applying a voltage to the element, the liquid crystal molecules are transformed into a homeotropic state, and the dichroic dye also becomes the same orientation state. At this time, the light passing through the element is not easily absorbed by the dichroic pigment, so the transmittance increases. By removing the voltage, the vertical state returns to the twisted alignment state. On the other hand, the element is transparent regardless of the presence or absence of voltage. In the element, in order to suppress alignment defects such as reverse twist spherical or stripe spherical, the relationship between the twist pitch (p) and the unit thickness d, i.e., the d/p value, is preferably 0.5 to 2.2. For example, in the case of a twist of 240°, the optimal d/p value is in the range of 0.45 to 0.66. It is better to observe the spherical by visual observation or a microscope, and adjust it in a way that does not produce alignment defects.

If the device is used for a long time, flicker may occur on the display screen. It is speculated that the flicker is related to the image burn-in, and when the device is driven by AC, the flicker is generated due to the difference between the potential of the positive frame and the potential of the negative frame. The flicker rate (%) can be expressed by (|brightness when positive voltage is applied - brightness when negative voltage is applied|)/(average brightness)×100. The flicker rate of the device is preferably in the range of 0% to 1%.

When the device is used for a long time, the brightness may decrease partially. One example of such display failure is line streaking. This is a phenomenon in which the brightness between two adjacent electrodes decreases in a striped manner due to repeated application of different voltages to the two adjacent electrodes. It is speculated that the phenomenon is caused by the accumulation of ionic impurities contained in the liquid crystal composition on the alignment film near the electrode.

This dimming element has a dimming layer sandwiched by a pair of transparent substrates having transparent electrodes. An example of the substrate is a material that is not easily deformed, such as a glass plate, a quartz plate, or an acrylic plate. Another example is a flexible transparent plastic film, such as an acrylic film or a polycarbonate film. Depending on the application, one of the substrates may also be an opaque material such as silicone. The substrate may also have a transparent electrode thereon. Examples of transparent electrodes are indium tin oxide (tin-doped indium oxide (ITO)) or a conductive polymer. The substrate may also have an alignment film on the transparent electrode.

For the alignment film, a film such as polyimide or polyvinyl alcohol is suitable. For example, the polyimide alignment film can be obtained by applying a polyimide resin composition on a transparent substrate, heat-curing it at a temperature above about 180°C, and optionally rubbing it with cotton cloth or rayon cloth, or photo-aligning it by irradiating it with polarized ultraviolet light.

A pair of substrates are placed facing each other with the transparent electrode layer on the inner side. Spacers may be placed to make the thickness between the substrates uniform. Examples of spacers are glass particles, plastic particles, aluminum oxide particles, photo spacers, etc. The preferred thickness of the dimming layer is about 1 μm to about 100 μm, more preferably about 1.5 μm to about 20 μm, and further preferably about 1.5 μm to about 10 μm. When bonding a pair of substrates, a commonly used sealant may be used. An example of a sealant is an epoxy-based thermosetting composition.

In such an element, a linear polarizer or a light absorbing layer or a diffuse reflector may be arranged on the back of the element as required. Functions such as mirror reflection, diffuse reflection, complex reflection, and holographic reflection may also be added.

This element has the function of being a dimming film or dimming glass. When the element is in the form of a film, it can be attached to an existing window, or laminated glass can be made by sandwiching a pair of glass plates. This element is used for windows installed on the outer wall, partitions between conference rooms and corridors, skylights for vehicles, or dimming sunglasses. That is, there are uses such as electronic blinds, dimming windows, smart windows, and smart glass. Furthermore, the function of being a light switch can be used in liquid crystal shutters, etc. [Example]

The present invention is further described in detail by way of examples. The present invention is not limited to these examples. In the examples, composition (M1), composition (M2), etc. are described. In the examples, a mixture of composition (M1) and composition (M2) is not described. However, the mixture is deemed to be disclosed. A mixture of at least two compositions selected from the examples is deemed to be disclosed. The synthesized compound is identified by methods such as nuclear magnetic resonance (NMR) analysis. The properties of the compound, composition, and element are measured by the following methods.

NMR analysis: DRX-500 manufactured by Bruker BioSpin was used for the measurement. In the ¹ H-NMR measurement, the sample was dissolved in a deuterated solvent such as CDCl ₃ , and the measurement was performed at room temperature at 500 MHz and 16 cumulative times. Tetramethylsilane was used as an internal standard. In the ¹⁹ F-NMR measurement, CFCl ₃ was used as an internal standard and the measurement was performed at 24 cumulative times. In the description of nuclear magnetic resonance spectra, s refers to singlet, d refers to doublet, t refers to triplet, q refers to quartet, quin refers to quintet, sex refers to sextet, m refers to multiplet, and br refers to broad peak.

Gas chromatography analysis: A GC-14B gas chromatograph manufactured by Shimadzu Corporation was used for the measurement. The carrier gas was helium (2 mL/min). The sample vaporization chamber was set to 280°C, and the detector (flame ionization detector (FID)) was set to 300°C. When separating the component compounds, a capillary column DB-1 (length 30 m, inner diameter 0.32 mm, film thickness 0.25 μm; stationary liquid phase is dimethyl polysiloxane; non-polar) manufactured by Agilent Technologies Inc. was used. After the column was kept at 200°C for 2 minutes, the temperature was raised to 280°C at a rate of 5°C/min. After the sample was prepared as an acetone solution (0.1%), 1 μL of it was injected into the sample vaporization chamber. The recording instrument is a C-R5A chromatograph unit (Chromatopac) manufactured by Shimadzu Corporation or its equivalent. The obtained gas chromatogram shows the retention time and peak area of the peak corresponding to the component compound.

The solvent used to dilute the sample can be chloroform, hexane, etc. To separate the component compounds, the following capillary columns can be used. HP-1 manufactured by Agilent Technologies (length 30 m, inner diameter 0.32 mm, film thickness 0.25 μm), Rtx-1 manufactured by Restek Corporation (length 30 m, inner diameter 0.32 mm, film thickness 0.25 μm), BP-1 manufactured by SGE International Pty. Ltd. (length 30 m, inner diameter 0.32 mm, film thickness 0.25 μm). To prevent the overlap of compound peaks, the capillary column CBP1-M50-025 manufactured by Shimadzu Corporation (length 50 m, inner diameter 0.25 mm, film thickness 0.25 μm) can be used.

The ratio of the liquid crystal compound contained in the composition can be calculated by the method described below. The mixture of liquid crystal compounds is analyzed by gas chromatography (FID). The area ratio of the peaks in the gas chromatogram is equivalent to the ratio of the liquid crystal compound. When using the capillary column described above, the correction factor of each liquid crystal compound can be regarded as 1. Therefore, the ratio of the liquid crystal compound can be calculated based on the area ratio of the peak.

Measurement sample: When measuring the characteristics of a liquid crystal composition, a liquid crystal composition for a dimming element, or an element having these compositions, the liquid crystal composition or the liquid crystal composition for a dimming element is directly used as a sample. When measuring the characteristics of a compound, a sample for measurement is prepared by mixing the compound (15%) with a mother liquid crystal (85%). Based on the value obtained by the measurement, the characteristic value of the compound is calculated by extrapolation. (Extrapolated value) = {(measured value of the sample) - 0.85 × (measured value of the mother liquid crystal)} / 0.15. When a smectic phase (or crystal) precipitates at 25°C under the above ratio, the ratio of the compound to the mother liquid crystal is changed in the order of 10%: 90%, 5%: 95%, and 1%: 99%. The above extrapolation method is used to obtain the values of the upper temperature, optical anisotropy, viscosity, and dielectric anisotropy related to the compound.

The following mother liquid crystals were used.

Measurement method: The characteristics are measured using the following methods. Most of these methods are methods described in the JEITA standard (JEITA ED-2521B) reviewed and established by the Japan Electronics and Information Technology Industries Association (JEITA) or modified methods. The twisted nematic (TN) element used for measurement does not have a thin film transistor (TFT) installed.

(1) Upper limit temperature of the nematic phase (NI; °C): Place the sample on a hot plate of a melting point measuring device equipped with a polarizing microscope and heat it at a rate of 1 °C/min. Measure the temperature at which a portion of the sample changes from the nematic phase to an isotropic liquid. The upper limit temperature of the nematic phase is sometimes referred to as the "upper limit temperature".

(2) Lower limit temperature of nematic phase (T _C ; ℃): A sample with nematic phase was placed in a glass bottle and stored in a freezer at 0℃, -10℃, -20℃, -30℃ and -40℃ for 10 days, and the liquid crystal phase was observed. For example, when the sample remains in the nematic phase at -20℃ and changes to a crystalline or smectic phase at -30℃, T _C is recorded as <-20℃. The lower limit temperature of the nematic phase is sometimes referred to as the "lower limit temperature".

(3) Viscosity (volume viscosity; η; measured at 20°C; mPa·s): The measurement was performed using an E-type rotational viscometer manufactured by Tokyo Keiki Co., Ltd.

(4) Viscosity (rotational viscosity; γ1; measured at 25°C; mPa·s): Measured according to the method described in M. Imai et al., Molecular Crystals and Liquid Crystals, Vol. 259, p. 37 (1995). The sample was placed in a TN device with a torsion angle of 0° and a distance between two glass substrates (cell gap) of 5 μm. A voltage was applied to the device in steps of 0.5 V in the range of 16 V to 19.5 V. After no voltage was applied for 0.2 seconds, a rectangular wave (rectangular pulse; 0.2 seconds) and no voltage were applied (2 seconds) repeatedly. The peak current and peak time of the transient current generated by the application are measured. The rotational viscosity value is obtained based on these measured values and the calculation formula (10) described on page 40 of the paper by M. Imai et al. The value of the dielectric anisotropy required for the calculation is obtained by using the element for measuring the rotational viscosity and the method described below.

(5) Optical anisotropy (refractive index anisotropy; Δn; measured at 25°C): Measured using an Abbe refractometer with a polarizing plate mounted on the eyepiece, using light with a wavelength of 589 nm. After rubbing the surface of the main prism in one direction, the sample is dropped onto the main prism. The refractive index n∥ is measured when the direction of polarization is parallel to the direction of rubbing. The refractive index n⊥ is measured when the direction of polarization is perpendicular to the direction of rubbing. The value of optical anisotropy is calculated using the formula Δn=n∥-n⊥.

(6) Dielectric anisotropy (Δε; measured at 25°C): A sample was placed in a TN device with a distance (cell gap) of 9 μm between two glass substrates and a twist angle of 80 degrees. A sine wave (10 V, 1 kHz) was applied to the device, and after 2 seconds, the dielectric constant (ε∥) of the long axis of the liquid crystal molecules was measured. A sine wave (0.5 V, 1 kHz) was applied to the device, and after 2 seconds, the dielectric constant (ε⊥) of the short axis of the liquid crystal molecules was measured. The value of dielectric anisotropy is calculated using the formula Δε=ε∥-ε⊥.

(7) Threshold voltage (Vth; measured at 25°C; V): The measurement was performed using an LCD5100 luminance meter manufactured by Otsuka Electronics Co., Ltd. The light source was a halogen lamp. The sample was placed in a normally white mode TN element in which the distance between the two glass substrates (cell gap) was 0.45/Δn (μm) and the twist angle was 80 degrees. The voltage applied to the element (32 Hz, rectangular wave) was increased stepwise from 0 V to 10 V in units of 0.02 V. At this time, light was irradiated from the vertical direction to measure the amount of light passing through the element. A voltage-transmittance curve was prepared in which the transmittance was 100% when the light amount reached the maximum and the transmittance was 0% when the light amount reached the minimum. The threshold voltage is expressed as the voltage when the transmittance reaches 90%.

(8) Voltage retention ratio (VHR; measured at 25°C; %): The TN element used in the measurement has a polyimide alignment film and the distance between the two glass substrates (cell gap) is 5 μm. A sample is placed in the TN element and sealed using an adhesive that cures with ultraviolet light. The TN element is placed in a constant temperature bath at 60°C and charged by applying a pulse voltage (1 V, 60 microseconds, 3 Hz). The attenuated voltage is measured using a high-speed voltmeter during 166.6 milliseconds, and the area A between the voltage curve and the horizontal axis per unit cycle is calculated. Area B is the area when there is no attenuation. The voltage retention ratio is expressed as a percentage of area A relative to area B.

(9) Voltage holding ratio (UV-VHR; measured at 25°C; %): A TN element containing a sample is irradiated with 5 mW ultraviolet light for 166.6 minutes using a black light as a light source. The voltage holding ratio is measured to evaluate the stability to ultraviolet light. The structure of the TN element or the method for measuring the voltage holding ratio is described in measurement (8). A composition having a large UV-VHR has a large stability to ultraviolet light. The UV-VHR is preferably 90% or more, and more preferably 95% or more.

(10) Voltage holding ratio (heating VHR; measured at 25°C; %): After heating a TN element containing a sample in a constant temperature bath at 120°C for 20 hours, the voltage holding ratio is measured to evaluate thermal stability. The structure of the TN element or the method for measuring the voltage holding ratio is described in measurement (8). A composition having a large heating VHR has great thermal stability. The heating VHR is preferably 90% or more, and more preferably 95% or more.

(11) Response time (τ; measured at 25°C; ms): The measurement was performed using an LCD5100 luminance meter manufactured by Otsuka Electronics Co., Ltd. The light source was a halogen lamp. The low-pass filter was set to 5 kHz. The sample was placed in a normally white mode TN element with a distance (cell gap) of 8.8 μm between two glass substrates and a twist angle of 80 degrees. A rectangular wave (60 Hz, 5 V, 0.5 seconds) was applied to the element. At this time, light was irradiated to the element from a vertical direction, and the amount of light passing through the element was measured. When the light amount reached a maximum, the transmittance was considered to be 100%, and when the light amount was a minimum, the transmittance was considered to be 0%. The rise time (τr: rise time; milliseconds) is the time required for the transmittance to change from 90% to 10%. The fall time (τf: fall time; milliseconds) is the time required for the transmittance to change from 10% to 90%. The response time is represented by the sum of the rise time and the fall time obtained in the above manner. In the present invention, when the response time is 70 ms or less, it is assumed to have a good response time.

(12) Elastic constant (K; measured at 25°C; pN): The measurement was performed using an HP4284A inductance capacitance resistance (LCR) meter manufactured by Yokogawa-Hewlett-Packard Co., Ltd. A sample was placed in a horizontally aligned element in which the distance between two glass substrates (unit gap) was 20 μm. A charge of 0 V to 20 V was applied to the element, and the electrostatic capacitance and applied voltage were measured. The measured electrostatic capacitance (C) and applied voltage (V) values were fitted using equations (2.98) and (2.101) in the Liquid Crystal Element Handbook (Nikkan Kogyo Shimbun, p. 75), and the values of K11 and K33 were obtained from equation (2.99). Next, K22 is calculated using the previously determined values of K11 and K33 in formula (3.18) on page 171 of the Liquid Crystal Element Handbook (Nikkan Kogyo Shimbun Co., Ltd.). The elastic constant is represented by the average value of K11, K22, and K33 determined in the above manner.

(13) Specific resistance (ρ; measured at 25°C; Ωcm): 1.0 mL of sample is placed in a container including electrodes. A DC voltage (10 V) is applied to the container, and the DC current is measured after 10 seconds. The specific resistance is calculated by the following formula. (Specific resistance) = {(voltage) × (capacitance of container)}/{(DC current) × (dielectric constant of vacuum)}

(14) Helical pitch (P; measured at room temperature; μm): The helical pitch is measured using the wedge method. See "Liquid Crystal Handbook" page 196 (published in 2000, Maruzen). Place the sample in a wedge unit and leave it at room temperature for 2 hours. Then, observe the interval (d2-d1) of the disclination lines using a polarizing microscope (Nikon Co., Ltd., trade name MM40/60 series). The helical pitch (P) is calculated using the following formula, where the angle of the wedge unit is represented by θ. P = 2×(d2-d1)×tanθ.

(15) Dielectric constant in the short axis direction (ε⊥; measured at 25°C): A sample was placed in a TN device with a distance between two glass substrates (cell gap) of 9 μm and a twist angle of 80 degrees. A sine wave (0.5 V, 1 kHz) was applied to the device, and after 2 seconds, the dielectric constant (ε⊥) in the short axis direction of the liquid crystal molecules was measured.

(16) Pre-tilt angle (degrees): The pre-tilt angle was measured using a spectroscopic ellipsometer M-2000U (manufactured by J. A. Woollam Co., Inc.).

(17) Alignment stability (liquid crystal alignment axis stability): Evaluate the change in the liquid crystal alignment axis on the electrode side of the fringe field switching (FFS) element. Measure the liquid crystal alignment angle ϕ on the electrode side before stress is applied (before), then apply a rectangular wave of 4.5 V, 60 Hz to the element for 20 minutes, buffer for 1 second, and measure the liquid crystal alignment angle ϕ on the electrode side again after 1 second and 5 minutes (after). Calculate the change in the liquid crystal alignment angle (Δϕ; degrees) after 1 second and 5 minutes using the following formula from these values. Δϕ(degree)=ϕ(after)-ϕ(before) These measurements were made with reference to J. Hilfiker, B. Johs, C. Herzinger, J. F. Elman, E. Montbach, D. Bryant and P. J. Bos, Thin Solid Films, 455-456 (2004) 596-600. It can be said that the smaller Δϕ is, the smaller the change rate of the liquid crystal alignment axis is, and the liquid crystal molecules are further stabilized.

(18) Flicker rate (measured at 25°C; %): The measurement was performed using a multimedia display tester 3298F manufactured by Yokogawa Electric Co., Ltd. The light source was a light emitting diode (LED). The sample was placed in a normally black mode element in which the distance between two glass substrates (cell gap) was 3.5 μm and the rubbing directions were antiparallel. The element was sealed using an adhesive that was cured by ultraviolet light. A voltage was applied to the element, and the voltage at which the amount of light passing through the element reached a maximum was measured. While the voltage was applied to the element, the sensor unit was brought close to the element and the displayed flicker rate was read.

(19) Line Image Sticking Parameter (LISP); %): Line image sticking is generated by applying electrical stress to the device. The brightness of the area where the line image sticking exists and the brightness of the rest of the area (reference area) are measured. The ratio of the brightness reduction caused by the line image sticking is calculated, and the size of the line image sticking is expressed by the ratio.

19a) Measurement of brightness: An imaging colorimeter (PM-1433F-0, manufactured by Radiant Zemax) was used to capture images of the device. The image was analyzed using software (Prometric 9.1, manufactured by Radiant Imaging) to calculate the brightness of each region of the device. The light source used was an LED backlight with an average brightness of 3500 cd/ ^m2 .

19b) Setting of stress voltage: A sample was placed in an FFS element (16 elements of 4 vertical elements x 4 horizontal elements) with an array structure and a cell gap of 3.5 μm, and the element was sealed with an adhesive that cures with ultraviolet light. Polarizing plates were arranged on the top and bottom of the element so that the polarization axes were orthogonal. The element was irradiated with light and a voltage was applied (rectangular wave, 60 Hz). The voltage was increased stepwise in units of 0.1 V in the range of 0 V to 7.5 V, and the brightness of the transmitted light at each voltage was measured. The voltage at which the brightness reached the maximum was abbreviated as V255. The voltage at which the brightness reached 21.6% of V255 (i.e., 127 gray levels) was abbreviated as V127.

19c) Stress conditions: V255 (rectangular wave, 30 Hz) was applied to the stress area at 60°C for 23 hours, and 0.5 V (rectangular wave, 30 Hz) was applied to the reference area to display a checkerboard pattern. Then, V127 (rectangular wave, 0.25 Hz) was applied, and the brightness was measured with an exposure time of 4000 milliseconds.

19d) Calculation of line residual images: 4 units in the central part of the 16 units are used for calculation (2 units in the vertical direction × 2 units in the horizontal direction). The 4 units are divided into 25 areas (5 units in the vertical direction × 5 units in the horizontal direction). The average brightness of the 4 areas located at the four corners (2 units in the vertical direction × 2 units in the horizontal direction) is referred to as brightness A. The area formed by removing the areas at the four corners from the 25 areas is a cross shape. In the 4 areas formed by removing the central intersection area from the cross-shaped area, the minimum brightness is referred to as brightness B. The line residual image is calculated by the following formula. (Line residual image) = (Brightness A-Brightness B)/Brightness A×100. The line residual image is preferably smaller.

(20) Face Image Sticking Parameter (FISP); %): A face image sticking is generated by applying electrical stress to the device. The brightness of the area where the face image sticks and the brightness of the rest of the area are measured at 25°C. The ratio of the brightness change caused by the face image sticking is calculated, and the size of the face image sticking is expressed by the ratio.

20a) "Brightness measurement", "Stress voltage setting", and "Stress conditions" shall be in the order described in the "Line residual image" section.

20b) The facial imperfection is calculated by the following formula. (Facial imperfection) = (Brightness C - Brightness D) / Brightness D × 100. Here, Brightness C is the average brightness of 8 units with V255 applied, and Brightness D is the average brightness of 8 units with 0.5V applied. The facial imperfection is preferably smaller. When the dielectric anisotropy of the liquid crystal composition is positive, the facial imperfection is represented by P-FISP. When the dielectric anisotropy of the liquid crystal composition is negative, the facial imperfection is represented by N-FISP.

(21) Haze rate (%): A haze meter NDH5000 (manufactured by Nippon Denshoku Industries Co., Ltd.) was used to measure the haze rate.

(22) Fog change rate (%): The component is subjected to a weather resistance test. The fog rate is measured before and after the test, and the fog change rate is calculated. The test is conducted in accordance with Japanese Industrial Standards (JIS) K5600-7-7, accelerated weather resistance and accelerated light resistance (xenon lamp method). The measurement is performed using a super xenon weather meter SX75 manufactured by Suga Test Instruments Co., Ltd. The measurement conditions are illumination (UVA; 180 W/m ² ), irradiation time (100 hours), blackboard temperature (63°C ± 2°C), tank temperature (35°C), and tank relative humidity (40% RH). UVA refers to ultraviolet A.

(23) Transmittance measurement: The transmittance of the element was measured using an LCD5100 luminance meter manufactured by Otsuka Electronics Co., Ltd. The light source was a halogen lamp. The measurement was performed at 25°C. The polarizing plate was not attached to the element. Transmittance (off): The transmittance (%) when the applied voltage was 0 (V) when the electro-optical characteristics of the element injected with the dimming liquid crystal composition were evaluated using the device. Transmittance (on): The transmittance (%) when the applied voltage was 50 (V) when the electro-optical characteristics of the element injected with the dimming liquid crystal composition were evaluated using the device. In the present invention, when the transmittance (off) is 2% or less and the transmittance (on) is 28% or more, it is considered to have good electro-optical characteristics.

(24) Characteristics of liquid crystal dimming elements When measuring the characteristics of liquid crystal dimming elements, elements with glass substrates having transparent electrodes are usually used. In addition, in liquid crystal dimming elements, plastic films are sometimes used as substrates. Therefore, elements with polycarbonate substrates are made and characteristics such as threshold voltage and response time are measured. The measured values are compared with those of elements with glass substrates. As a result, the measured values of the two are roughly the same. Therefore, the characteristics are measured using elements with glass substrates and the results are recorded.

The following are examples of compositions. Liquid crystal compounds are represented by symbols based on the definitions in Table 3 below. In Table 3, the stereo configuration associated with 1,4-cyclohexylene is trans. The numbers in parentheses after the marked compounds represent the chemical formula to which the compounds belong. The symbol (-) refers to other liquid crystal compounds. Finally, the characteristic values of the compositions are summarized.

The following compositions were used in the examples.

[Composition (M1)] 5-HB-CL (1-1) 12% 3-BB(F)B(F,F)-F (1-24) 6% 3-BB(F,F)XB(F,F)-F (1-28) 20% 3-BB(F)B(F,F)XB(F,F)-F (1-41) 4% 4-BB(F)B(F,F)XB(F,F)-F (1-41) 4% 3-BB(F,F)XB(F)B(F,F)-F (1-42) 13% 1-BB-3 (2-3) 10% V-HHB-1 (2-9) 8% 1-BB(F)B-2V (2-12) 3% 2-BB(F)B-2V (2-12) 4% 3-BB(F)B-2V (2-12) 4% 5-HBB(F)B-2 (2-21) 6% 5-HBB(F)B-3 (2-21) 6% NI=79.2℃; Tc＜-20℃; η=39.2 mPa·s; Δn=0.179; Δε=13.2; Vth=1.46 V.

[Composition (M2)] 3-HB-C (1-1) 10% 3-HB(F)-C (1-1) 15% 3-HHB-F (1-9) 4% 2-HHB(F)-F (1-9) 11% 3-HHB(F)-F (1-9) 11% 5-HHB(F)-F (1-9) 10% 3-HHB(F)-C (1-9) 8% 3-BB(F,F)XB(F,F)-F (1-28) 1% 3-HB-O2 (2-2) 10% 3-HHB-1 (2-9) 8% 3-HHB-3 (2-9) 8% 3-HHB-O1 (2-9) 4% NI=95.5℃; Tc＜-20℃; η=22.3 mPa·s; Δn=0.100; Δε=8.1; Vth=1.50 V.

[Composition (M3)] 2-HHB(F)-F             (1-9)          12% 3-HHB(F)-F            (1-9)          12% 5-HHB(F)-F            (1-9)          11% 3-HHB(F,F)-F              (1-9)          10% 3-HHXB(F,F)-F            (1-13)        1% 2-HBB(F)-F            (1-16)        4.5% 3-HBB(F)-F            (1-16)        4.5% 5-HBB(F)-F            (1-16)        9% 3-HBB(F,F)-F (1-16) 18% 3-HB-O2 (2-2) 5% 3-HHB-1 (2-9) 8% 3-HHB-O1 (2-9) 5% NI=101.8℃; Tc＜-20℃; η=24.5 mPa·s; Δn=0.105; Δε=6.1; Vth=1.76 V.

[Composition (M4)] 3-BB(F,F)XB(F,F)-F (1-28) 15% 3-BB(F,F)XB(F)B(F,F)-F (1-42) 12% 3-HB-O2 (2-2) 15% 3-HHB-1 (2-9) 8% 3-HHB-3 (2-9) 10% 3-HHB-O1 (2-9) 5% 3-HBB-2 (2-10) 12% 2-BB(F)B-5 (2-12) 8% 3-BB(F)B-5 (2-12) 8% 3-BB(2F,5F)B-3 (2-13) 7% NI=100.5℃; Tc＜-20℃; η=32.3 mPa·s; Δn=0.162; Δε=6.2; Vth=2.28 V.

[Composition (M5)] 3-HB-CL (1-1) 3% 5-HXB(F,F)-F (1-7) 3% 3-HHB-OCF3 (1-9) 3% 3-HHXB(F,F)-F (1-13) 6% 3-HGB(F,F)-F (1-14) 3% 3-HB(F)B(F,F)-F (1-17) 5% 3-BB(F,F)XB(F,F)-F (1-28) 6% 3-HHBB(F,F)-F (1-29) 6% 5-BB(F)B(F,F)XB(F)B(F,F)-F (1-43) 2% 3-BB(2F,3F)XB(F,F)-F (1-44) 4% 3-HHB(F,F)XB(F,F)-F (1) 4% 3-HBB(2F,3F)XB(F,F)-F (1) 5% 3-HH-V (2-1) 22% 3-HH-V1 (2-1) 10% 5-HB-O2 (2-2) 5% 3-HHEH-3 (2-8) 3% 3-HBB-2 (2-10) 7% 5-B(F)BB-3 (2-11) 3% NI=77.2℃; Tc＜-20℃; Δn=0.101; Δε=5.8; Vth=1.88 V; η=13.7 mPa·s; γ1=61.3 mPa·s.

[Composition (M6)] 2-HB(F)-C               （1-1）          9% 3-HB(F)-C               （1-1）          10% 3-HHB-F                （1-9）          4% 2-HHB(F)-F            （1-9）          6% 3-HHB(F)-F            （1-9）          6% 5-HHB(F)-F            （1-9）          6% 2-HHB(F)-C            （1-9）          6% 3-HHB(F)-C           （1-9）          6% 3-HEB-O4                 （2-4）         6% 4-HEB-O2 (2-4) 4% 5-HEB-O1 (2-4) 4% 3-HEB-O2 (2-4) 3% 5-HEB-O2 (2-4) 3% 2-HHB-1 (2-9) 5% 3-HHB-1 (2-9) 8% 3-HHB-3 (2-9) 10% 3-HHB-O1 (2-9) 4% NI=102.2℃; Tc＜-20℃; Δn=0.098; Δε=7.1; Vth=1.53 V; η=25.7 mPa·s; γ1=139.6 mPa·s.

[Composition (M7)] 2-HB(F)-C               （1-1）          15% 3-HB(F)-C               （1-1）          15% 3-HHB-F                （1-9）          5% 2-HHB(F)-F            （1-9）          3% 3-HHB(F)-F            （1-9）          3% 5-HHB(F)-F            （1-9）          4% 2-HHB(F)-C           （1-9）          13% 3-HHB(F)-C           （1-9）          12% 3-HEB-O4                 （2-4）         5% 4-HEB-O2 (2-4) 4% 5-HEB-O1 (2-4) 4% 3-HEB-O2 (2-4) 3% 5-HEB-O2 (2-4) 2% 3-HHEBH-3 (2-19) 4% 3-HHEBH-4 (2-19) 4% 3-HHEBH-5 (2-19) 4% NI=103.4℃; Tc＜-20℃; Δn=0.105; Δε=11.4; Vth=1.18 V; η=37.1 mPa·s

[Composition (M8)] 2-HHB(F)-F (1-9) 9% 3-HHB(F)-F (1-9) 9% 3-HHB(F)-F (1-9) 9% 3-HHB-F (1-9) 5% 1-HHB(F,F)-F (1-9) 5% 2-HHB(F,F)-F (1-9) 5% 3-HHB(F,F)-F (1-9) 5% 3-HBB(F)-F (1-16) 7% 3-HBB(F,F)-F (1-16) 18% 2-HHBB(F,F)-F (1-29) 4% 3-HHBB(F,F)-F (1-29) 5% 3-HH-4 (2-1) 9% 3-HHB-3 (2-9) 10% NI=106.5℃; Tc＜-20℃; Δn=0.098; Δε=6.22; Vth=1.52 V; η=24.2 mPa·s

[Composition (M9)] 3-HHB(F,F)-F                （1-9）          8% 2-HHB(F)-F            （1-9）          15% 3-HHB(F)-F            （1-9）          15% 5-HHB(F)-F            （1-9）          15% 3-HHB-F                （1-9）          5% 3-HH-4             （2-1）          12% 3-HB-O2                （2-2）          10% 3-HHEBH-3             （2-19）        7% 3-HHEBH-4             （2-19）        7% 3-HHEBH-5 (2-19) 6% NI=139.7℃; Tc＜-20℃; Δn=0.081; Δε=2.90; Vth=2.55 V; η=24.5 mPa·s

[Composition (M10)] 2-HB(F)-C              （1-1）          6% 3-HB(F)-C              （1-1）          12% 2-HHB(F)-C           （1-9）          10% 3-HHB(F)-C           （1-9）          11% 3-HHB(F)-F            （1-9）          3% 2-HHB(F,F)-F               （1-9）          8% 3-HHB(F,F)-F              （1-9）          10% 3-HHXB(F,F)-F            （1-13）        17% 3-GB(F,F)XB(F,F)-F (1-22) 5% 5-HHBB(F,F)-F (1-29) 3% 3-HHEBH-3 (2-19) 3% 3-HHEBH-4 (2-19) 6% 3-HHEBH-5 (2-19) 6% NI=124.5℃; Tc＜-20℃; Δn=0.100; Δε=14.4; Vth=0.95 V; η=43 mPa·s

[Composition (M11)] 2-HHB(F)-F (1-9) 9% 3-HHB(F)-F (1-9) 9% 5-HHB(F)-F (1-9) 9% 3-HHB-F (1-9) 5% 1-HHB(F,F)-F (1-9) 5% 2-HHB(F,F)-F (1-9) 5% 3-HHB(F,F)-F (1-9) 10% 2-HBB(F)-F (1-16) 2% 3-HBB(F)-F (1-16) 2% 5-HBB(F)-F (1-16) 4% 3-HBB-F (1-16) 3% 5-HBB-F (1-16) 3% 3-HBB(F,F)-F (1-16) 15% 5-HBB(F,F)-F (1-16) 8% 2-HHBB(F,F)-F (1-29) 3% 3-HHBB(F,F)-F (1-29) 5% 5-BB(2F)BBm-2 (2-24) 3% NI=102.0℃; Tc＜-20℃; Δn=0.120; Δε=7.5; Vth=1.58 V; η=32.8 mPa·s

[Composition (M12)] 3-HHB(F,F)-F (1-9) 10% 3-HHXB(F,F)-F (1-13) 2% 3-GHB(F,F)-F (1-15) 4% 3-BB(F)B(F,F)-F (1-24) 7% 3-BB(F,F)XB(F,F)-F (1-28) 14% 4-BB(F)B(F,F)XB(F,F)-F (1-41) 10% 5-BB(F)B(F,F)XB(F,F)-F (1-41) 6% 3-HH-V (2-1) 18% 3-HH-4 (2-1) 11% 5-HB-O2 (2-2) 2% 3-HHB-1 (2-9) 5% 3-HHB-3 (2-9) 5% 3-HHB-O1 (2-9) 6% NI=78.4℃; Tc＜-20℃; Δn=0.108; Δε=10.4; Vth=1.35 V; η=17.8 mPa·s; γ1=80 mPa·s.

[Composition (M13)] 2-HHB(F)-F (1-9) 9% 3-HHB(F)-F (1-9) 9% 5-HHB(F)-F (1-9) 9% 3-HHB-F (1-9) 5% 1-HHB(F,F)-F (1-9) 5% 2-HHB(F,F)-F (1-9) 5% 3-HHB(F,F)-F (1-9) 10% 2-HBB(F)-F (1-16) 2% 3-HBB(F)-F (1-16) 2% 5-HBB(F)-F (1-16) 4% 3-HBB-F (1-16) 3% 5-HBB-F (1-16) 3% 3-HBB(F,F)-F (1-16) 15% 5-HBB(F,F)-F (1-16) 8% 2-HHBB(F,F)-F (1-29) 3% 3-HHBB(F,F)-F (1-29) 5% 5-HBB(F)BB-2 (2-25) 3% NI=108.0℃; Tc＜-20℃; Δn=0.123; Δε=7.5; Vth=1.65 V; η=35.1 mPa·s

The following optically active compounds were used in the Examples.

[Example 1] (1) Preparation of a liquid crystal dimming element The liquid crystal composition (M6) has a positive dielectric anisotropy. Based on the total amount of the liquid crystal composition (M6), an optically active compound (K1-7-1) is added at a ratio of 0.4 parts by weight. Furthermore, a mixture of azo pigments and anthraquinone pigments disclosed in Example 2 of Japanese Patent Publication No. 2000-313881, i.e., a black pigment (pigment composition-II), is mixed at a ratio of 15 parts by weight as a dichroic pigment relative to the total amount of the liquid crystal composition (M6), and the mixture is heated and mixed at 120°C to prepare a liquid crystal composition for a dimming element. The helical pitch of the liquid crystal composition for a dimming element is 3.0 μm. The liquid crystal composition for a dimming element is injected into an element having a spacing (unit gap) of 8.8 μm between two glass substrates to prepare a liquid crystal dimming element. A horizontally aligned film is formed on the upper and lower substrates of the device, and the alignment direction between the upper and lower substrates is set to be twisted 80°.

(2) Electro-optical properties of liquid crystal dimming element The transmittance was measured by applying a voltage in the range of 0 V to 50 V to the liquid crystal dimming element. Transmittance (off): 1.6%, transmittance (on): 29.2%, so it can be seen that it is a liquid crystal dimming element with good electro-optical properties. In addition, the response time is 62 ms, which shows that it has a good response time.

(3) Low-temperature storage stability of the liquid crystal composition for liquid crystal dimming elements The liquid crystal dimming element was stored at -20°C for 7 days. As a result, no foreign matter such as crystals was observed and the liquid crystal composition was transparent. Therefore, it was judged that the storage stability of the liquid crystal composition for liquid crystal dimming elements was good.

[Comparative Example 1] (1) Preparation of a liquid crystal dimming element Based on the total amount of the liquid crystal composition (M6), an optically active compound represented by formula (L-1) was added in a ratio of 6.4 parts by weight instead of the optically active compound (K1-7-1) used in Example 1. Then, a liquid crystal composition for a dimming element was prepared by the same method as in Example 1. The helical pitch of the liquid crystal composition for a dimming element was 3.0 μm. A liquid crystal dimming element was obtained by using the liquid crystal composition for a dimming element and the same method as in Example 1.

(2) Electro-optical properties of liquid crystal dimming element The transmittance was measured by applying a voltage in the range of 0 V to 50 V to the liquid crystal dimming element. Transmittance (off): 1.8%, transmittance (on): 28.5%, so it can be seen that it is a liquid crystal dimming element with good electro-optical properties. On the other hand, the response time is 84 ms, which is an insufficient response time.

(3) Low-temperature storage stability of the liquid crystal composition for liquid crystal dimming elements The liquid crystal composition for liquid crystal dimming elements was stored at -20°C for 7 days. As a result, no foreign matter such as crystals was observed and the liquid crystal composition was transparent. Therefore, it was judged that the storage stability of the liquid crystal composition for liquid crystal dimming elements was good.

[Comparative Example 2] (1) Preparation of a liquid crystal dimming element A liquid crystal composition for a dimming element was prepared in the same manner as in Example 1, except that 7 parts by weight of a dichroic dye comprising three azo compounds disclosed in paragraph 0189 of Japanese Patent Re-publication No. WO2018/159303 and Example 1 (azo dye (A): azo dye (B): azo dye (C) = 0.86:0.52:1.43 (weight ratio)) was added instead of the dichroic dye used in Example 1. A liquid crystal dimming element was obtained by adding a liquid crystal composition for a dimming element in the same manner as in Example 1.

(2) Electro-optical characteristics of liquid crystal dimming element A voltage in the range of 0 V to 50 V was applied to the liquid crystal dimming element to measure the transmittance. Transmittance (off): 1.4%, transmittance (on): 26.5%, so it can be seen that the electro-optical characteristics are insufficient. On the other hand, the response time is 38 ms, which shows that it has a good response time.

(3) Low-temperature storage stability of the liquid crystal composition for liquid crystal dimming elements The liquid crystal composition for liquid crystal dimming elements was stored at -20°C for 7 days. As a result, crystalline foreign matter and scattering were observed. Therefore, it was determined that the storage stability of the liquid crystal composition for liquid crystal dimming elements was insufficient.

According to the above results, the liquid crystal dimming element of the present invention has good electro-optical properties (high contrast) and good response speed. In addition, it can be seen that the liquid crystal composition used in the liquid crystal dimming element shows good compatibility with the dichroic dye and has high storage stability at low temperatures. Even if a liquid crystal composition other than the liquid crystal composition (M6) is used, the same effect can be expected. Therefore, we have come to the following conclusion: The guest-host (GH) type liquid crystal composition composed of a specific chiral nematic liquid crystal composition and a specific dichroic dye can be suitably used in a liquid crystal dimming element. [Industrial Applicability]

The liquid crystal dimming element having the liquid crystal composition for liquid crystal dimming element of the present invention can be used in dimming windows, smart windows, smart glass, sunroofs for vehicles, etc.

without

without

Claims (22)

A liquid crystal composition for a liquid crystal dimming element, comprising a liquid crystal composition, an optically active compound and a dichroic dye, wherein the liquid crystal composition comprises at least one liquid crystal compound selected from the compounds represented by formula (1) as component A, the optically active compound comprises at least one compound selected from the group of compounds represented by formula (K1) and formula (K2), and the dichroic dye comprises at least one compound selected from the group consisting of azo compounds, benzothiadiazoles, and diketopyrrolopyrroles, and at least one compound selected from the group consisting of anthraquinones; In formula (1), ^R1 is an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an alkenyl group having 2 to 12 carbon atoms; Ring A is 1,4-cyclohexylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, 2,6-difluoro-1,4-phenylene, pyrimidine-2,5-diyl, 1,3-dioxane-2,5-diyl, or tetrahydropyran-2,5-diyl; ^Z1 is a single bond, ethylene, ethenylene, ethynylene, methyleneoxy, carbonyloxy, or difluoromethyleneoxy; ^X1 and ^X2 are hydrogen or fluorine; Y ¹ is fluorine, chlorine, cyano, an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine or chlorine, an alkoxy group having 1 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine or chlorine, or an alkenyloxy group having 2 to 12 carbon atoms in which at least one hydrogen is substituted by fluorine or chlorine; a is 1, 2, 3 or 4; In formula (K1) and formula (K2), R ^K is hydrogen, a halogen, -C≡N, -N=C=O, -N=C=S or an alkyl group having 1 to 12 ^carbon atoms, in which at least one -CH ₂ - may be substituted by -O-, -S-, -COO- or -OCO-, at least one -CH ₂ -CH ₂ - may be substituted by -CH=CH-, -CF=CF- or -C≡C-, and at least one hydrogen may be substituted by fluorine or chlorine; A ^K is an aromatic 6- to 8-membered ring, a non-aromatic 3- to 8-membered ring, or a condensed ring with 9 or more carbon atoms. In A ^K , at least one hydrogen can be substituted by a halogen, an alkyl group or a halogenated alkyl group with 1 to 3 carbon atoms, _-CH2- can be substituted by -O-, -S- or -NH-, and -CH= can be substituted by -N=; Z ^K is a single bond, an alkylene group with 1 to 8 carbon atoms. In Z ^K , at least one _-CH2- can be substituted by -O-, -S-, -COO-, -OCO-, -CSO-, -OCS-, -N=N-, -CH=N- or -N=CH-, at least one -CH2 _{- CH2-} can be substituted by -CH=CH-, -CF=CF- or -C≡C-, and at least one hydrogen can be substituted by a halogen; X ^K is a single bond, -COO-, -OCO-, -CH ₂ O-, -OCH ₂ -, -CF ₂ O-, -OCF ₂ - or -CH ₂ CH ₂ -; mK is an integer of 1 to 3. The liquid crystal composition for a liquid crystal light modulating element according to claim 1, wherein the liquid crystal composition contains at least one compound selected from the compounds represented by formula (1-1) to formula (1-47) as component A; In formula (1-1) to formula (1-47), ^R1 is an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an alkenyl group having 2 to 12 carbon atoms; ^X1 and ^X2 are hydrogen or fluorine; ^Y1 is fluorine, chlorine, cyano, an alkyl group having 1 to 12 carbon atoms in which at least one hydrogen atom is substituted with fluorine or chlorine, an alkoxy group having 1 to 12 carbon atoms in which at least one hydrogen atom is substituted with fluorine or chlorine, or an alkenyloxy group having 2 to 12 carbon atoms in which at least one hydrogen atom is substituted with fluorine or chlorine. A liquid crystal composition for a liquid crystal dimming element as described in claim 1 or claim 2, wherein the proportion of component A is in the range of 5% to 90% based on the total amount of the liquid crystal composition. The liquid crystal composition for a liquid crystal light modulating element as claimed in claim 1 or claim 2, wherein the liquid crystal composition contains at least one compound selected from the compounds represented by formula (2) as component B; In formula (2), ^R2 and ^R3 are alkyl groups having 1 to 12 carbon atoms, alkoxy groups having 1 to 12 carbon atoms, alkenyl groups having 2 to 12 carbon atoms, or alkenyl groups having 2 to 12 carbon atoms in which at least one hydrogen atom is substituted with fluorine or chlorine; Ring B and Ring C are 1,4-cyclohexylene, 1,3-phenylene, 1,4-phenylene, 2-fluoro-1,4-phenylene, 2,5-difluoro-1,4-phenylene or pyrimidine-2,5-diyl; ^Z2 is a single bond, ethylene, ethenylene, ethynylene, methyleneoxy or carbonyloxy; and b is 1, 2, 3 or 4. The liquid crystal composition for a liquid crystal light modulating element according to claim 1 or claim 2, wherein the liquid crystal composition contains at least one compound selected from the compounds represented by formula (2-1) to formula (2-25) as component B; In formula (2-1) to formula (2-25), ^R2 and ^R3 are alkyl groups having 1 to 12 carbon atoms, alkoxy groups having 1 to 12 carbon atoms, alkenyl groups having 2 to 12 carbon atoms, or alkenyl groups having 2 to 12 carbon atoms in which at least one hydrogen atom is substituted with fluorine or chlorine. A liquid crystal composition for a liquid crystal dimming element as described in claim 4, wherein the proportion of component B is in the range of 5% to 90% based on the total amount of the liquid crystal composition. The liquid crystal composition for a liquid crystal light modulating element as claimed in claim 1 or claim 2, wherein the liquid crystal composition contains at least one compound selected from the compounds represented by formula (3) as component C; In formula (3), ^R4 and ^R5 are hydrogen, alkyl having 1 to 12 carbon atoms, alkoxy having 1 to 12 carbon atoms, alkenyl having 2 to 12 carbon atoms, or alkenyloxy having 2 to 12 carbon atoms; Ring D and Ring F are 1,4-cyclohexylene, 1,4-cyclohexenyl, tetrahydropyran-2,5-diyl, 1,4-phenylene, 1,4-phenylene in which at least one hydrogen atom is substituted with fluorine or chlorine, naphthalene-2,6-diyl, naphthalene-2,6-diyl in which at least one hydrogen atom is substituted with fluorine or chlorine, chromane-2,6-diyl, or chromane-2,6-diyl in which at least one hydrogen atom is substituted with fluorine or chlorine. ,6-diyl; Ring E is 2,3-difluoro-1,4-phenylene, 2-chloro-3-fluoro-1,4-phenylene, 2,3-difluoro-5-methyl-1,4-phenylene, 3,4,5-trifluoronaphthalene-2,6-diyl, 7,8-difluorochromane-2,6-diyl, 3,4,5,6-tetrafluorofluorene-2,7-diyl, 4,6-difluorodibenzofuran-3,7-diyl, 4,6-difluorodibenzothiophene-3,7-diyl or 1,1,6,7-tetrafluoroindan-2,5-diyl; Z ³ and Z ⁴ are a single bond, ethylene, ethenylene, methyleneoxy or carbonyloxy; c is 0, 1, 2 or 3, d is 0 or 1, and the sum of c and d is 3 or less. The liquid crystal composition for a liquid crystal light modulating element according to claim 1 or claim 2, wherein the liquid crystal composition contains at least one compound selected from the compounds represented by formula (3-1) to formula (3-35) as component C; In formula (3-1) to formula (3-35), ^R4 and ^R5 are hydrogen, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an alkenyl group having 2 to 12 carbon atoms, or an alkenyloxy group having 2 to 12 carbon atoms. A liquid crystal composition for a liquid crystal dimming element as described in claim 7, wherein the proportion of component C is in the range of 3% to 25% based on the total amount of the liquid crystal composition. The liquid crystal composition for a liquid crystal light-adjusting element as described in claim 1 or claim 2, which contains at least one compound selected from the compounds represented by formula (K1-1) to formula (K1-7) and formula (K2-1) to formula (K2-4) as an optically active compound; R ^K is hydrogen or an alkyl group having 1 to 12 carbon atoms. In said R ^K , at least one -CH ₂ - may be substituted by -O-, -S-, -COO- or -OCO-, at least one -CH ₂ -CH ₂ - may be substituted by -CH=CH-, -CF=CF- or -C≡C-, and at least one hydrogen may be substituted by fluorine or chlorine. In the liquid crystal composition for a liquid crystal dimming element as described in claim 1 or claim 2, the ratio of the optically active compound is in the range of 0.01 parts by weight to 5 parts by weight based on the total amount of the liquid crystal composition. The liquid crystal composition for a liquid crystal light modulating element as described in claim 1 or claim 2, wherein the helical pitch is in the range of 2 μm to 20 μm. The liquid crystal composition for a liquid crystal light modulating element as described in claim 1 or claim 2, wherein the dichroic dye contains at least one compound selected from azo compounds and at least one compound selected from anthraquinones. The liquid crystal composition for a liquid crystal dimming element as described in claim 1 or claim 2, wherein the ratio of the dichroic pigment is in the range of 0.01 parts by weight to 25 parts by weight based on the total amount of the liquid crystal composition. A liquid crystal dimming element, wherein the dimming layer is the liquid crystal composition for the liquid crystal dimming element as described in any one of claim 1 to claim 14, and the dimming layer is sandwiched by a pair of transparent substrates, and the transparent substrates have transparent electrodes. A liquid crystal dimming element as described in claim 15, wherein the transparent substrate is a glass plate or an acrylic plate. A liquid crystal dimming element as described in claim 15, wherein the transparent substrate is a plastic film. A dimming window using a liquid crystal dimming element as described in any one of claim 15 to claim 17. A smart window using a liquid crystal dimming element as described in any one of claim 15 to claim 17. A use of a liquid crystal composition for a liquid crystal dimming element, wherein the liquid crystal composition for a liquid crystal dimming element is the liquid crystal composition for a liquid crystal dimming element as described in any one of claim 1 to claim 14, and is used in a liquid crystal dimming element whose transparent substrate is a plastic film. A use of a liquid crystal composition for a liquid crystal dimming element, wherein the liquid crystal composition for a liquid crystal dimming element is the liquid crystal composition for a liquid crystal dimming element as described in any one of claim 1 to claim 14, and is used in a dimming window. A use of a liquid crystal composition for a liquid crystal dimming element, wherein the liquid crystal composition for a liquid crystal dimming element is the liquid crystal composition for a liquid crystal dimming element as described in any one of claim 1 to claim 14, and is used in a smart window.