Liquid crystal composition and liquid crystal light control element

Abstract

To provide a guest-host type liquid crystal composition having a stable driving voltage in a wide temperature range, and a liquid crystal light control element.SOLUTION: A liquid crystal composition contains a liquid crystal compound, a chiral dopant and a dichroic dye, where the liquid crystal compound shows a nematic phase, and a temperature change rate (X1) of a chiral pitch length expressed by the following formula (1) is -0.0006 to 0.0006. Temperature change rate (X1)=[(P2-P1) / (T2-T1)] / P0 (1) (in the formula (1), P0 denotes a chiral pitch length (μm) at 20°C, P1 denotes a chiral pitch length (μm) at 0°C, P2 denotes a chiral pitch length (μm) at 60°C, T1 denotes 0°C and T2 denotes 60°C).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a liquid crystal composition and a liquid crystal light control device. [Background technology]

[0002] In recent years, the use of glass has become increasingly common in trains, automobiles, business buildings, hospitals, and other buildings, including windows, doors, and partitions. In addition, liquid crystal dimming elements are used as dimming shutters for the purposes of design and privacy protection. Many of these prior art technologies are based on polymer-dispersed liquid crystal elements, known as PDLC. It is used (Patent Document 1) In this method, the transparent state and the scattering state are electrically switched, so all light rays There were issues such as poor transparency change. Therefore, in order to improve the brightness change and design, In recent years, a guest-host liquid crystal light-control device has been investigated, in which a dichroic dye is added to the liquid crystal material. In particular, the liquid crystals using chiral nematic liquid crystals as the host liquid crystal material of guest-host type liquid crystal materials. The dynamic range of the device when electrically switching between the bright and dark states is It has attracted attention because it has advantages such as a wider viewing angle than those without the addition of polarizing plates and no need for polarizing plates. (Patent Document 2).

[0003] However, in order to obtain a large dynamic range in a liquid crystal composition containing a dichroic dye, In order to achieve this, it is necessary to include a large amount of a dichroic dye in the liquid crystal composition. It is difficult to obtain an element with a stable driving voltage (threshold) over a wide temperature range. Further improvements in performance were required. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-42213 [Patent Document 2] Japanese Patent Application Publication No. 2019-85581 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides a guest-host liquid crystal composition having a stable driving voltage over a wide temperature range, and An object of the present invention is to provide a liquid crystal light control element. [Means for solving the problem]

[0006] As a result of extensive research to solve the above problems, the present inventors have discovered a liquid crystal compound exhibiting a nematic phase. A liquid crystal composition containing a chiral dopant and a dichroic dye, The above-mentioned problems can be solved by using a liquid crystal composition having a temperature change rate within a predetermined range. This discovery led to the present invention.

[0007] That is, the gist of the present invention is as follows. [1] A liquid crystal composition comprising a liquid crystal compound, a chiral dopant, and a dichroic dye, The liquid crystal compound is a liquid crystal compound exhibiting a nematic phase, and is a chiral compound represented by the following formula (1): A liquid crystal composition having a temperature coefficient of change (X1) of pitch length of −0.0006 to 0.0006. Temperature change rate (X1) = [(P2 - P1) / (T2 - T1)] / P0 (1) P0: Chiral pitch length (μm) at 20°C P1: Chiral pitch length at 0°C (μm) P2: Chiral pitch length at 60°C (μm) T1:0℃ T2: 60℃ [2] The temperature change rate (X2) of the chiral pitch length expressed by the following formula (2) is -0.000 The liquid crystal composition according to [1], wherein the δ is 0.6 to 0.0006. Temperature change rate (X2) = [(P2 - P1) / (T2 - T1)] / P0 (2) P0: Chiral pitch length (μm) at 20°C P1: Chiral pitch length at 0°C (μm) P3: Chiral pitch length at 80°C (μm) T1:0℃ T3: 80℃ [3] The temperature dependence of the chiral pitch length of the dichroic dye in the liquid crystal composition is negative. [1 ] or [2]. The liquid crystal composition according to [4] The dichroic dye is at least one selected from the group consisting of anthraquinone dyes. The liquid crystal composition according to any one of [1] to [3], comprising: [5] The content of the dichroic dye relative to 100% by mass of the liquid crystal composition is 5% by mass or more. The liquid crystal composition according to any one of [1] to [4], wherein the content is 25% by mass or less. [6] A liquid crystal light-controlling element comprising a layer made of the liquid crystal composition according to any one of [1] to [5]. child. [7] A pair of substrates with transparent electrodes arranged so that the transparent electrodes face each other, and The liquid crystal light control method according to [6], wherein a layer of a liquid crystal composition is sandwiched between substrates with a light electrode. element. [8] The liquid crystal light control element according to [6], which is for use in automobiles. [9] The liquid crystal light control element according to [6], which is used as a building material.

[10] A light control window comprising the liquid crystal light control element described in [6]. [Effects of the Invention]

[0008] According to the present invention, deterioration of quality due to changes in ambient temperature is suppressed, and the driving voltage and optical quality are improved. Furthermore, it is possible to provide an improved liquid crystal composition. It is possible to provide a liquid crystal light control element and a light control window equipped with the liquid crystal light control element of the present invention. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a graph showing the chiral pitch lengths of the liquid crystal composition prepared in Example 1 at temperatures of 0 to 90°C, normalized by the chiral pitch length (P0) at 20°C. [Figure 2] FIG. 2 is a graph showing the chiral pitch lengths of the liquid crystal composition prepared in Comparative Example 1 at temperatures of 0 to 90°C, normalized by the chiral pitch length (P0) at 20°C. [Figure 3] FIG. 3 is a graph showing the chiral pitch lengths of the liquid crystal composition prepared in Comparative Example 2 at temperatures of 0 to 90°C, normalized by the chiral pitch length (P0) at 20°C. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below, but the following description is an example of an embodiment of the present invention. The present invention is not limited to the following description as long as it does not deviate from the gist of the present invention. The invention can be implemented in any modified form without departing from the spirit of the invention. In the present invention, when it is written as "x to y" (x and y are arbitrary numbers), unless otherwise specified, Unless otherwise specified, "greater than x and less than y" is used in conjunction with "preferably greater than x" or "preferably It also includes the meaning of "smaller than y." Also, when "x or more" (x is any number) is written, it means "preferred" unless otherwise specified. "is greater than x" is included, and "is less than y" (where y is any number) is included. Unless otherwise specified, the meaning of "preferably smaller than y" is also included. In the present invention, the numerical ranges described in stages are not necessarily the upper limit of the numerical range of a certain stage. The upper or lower limit may be arbitrarily combined with the upper or lower limit of a numerical range of another stage. In addition, in the numerical ranges described in the present invention, the upper or lower values ​​of the numerical ranges can be The limit values ​​may be replaced with values ​​shown in the Examples or Production Examples. Furthermore, "x and / or y (x and y are optional configurations)" means at least one of x and y. It means three things: x only, y only, and x and y.

[0011] Liquid Crystal Composition The liquid crystal composition of the present invention comprises a liquid crystal compound exhibiting a nematic phase, a chiral dopant, and The liquid crystal composition contains a dichroic dye. Each component of the liquid crystal composition will be described in detail below.

[0012] (1) Liquid crystal compound The liquid crystal compound contained in the liquid crystal composition of the present invention is a liquid crystal compound that exhibits a nematic phase. By using the above liquid crystal compound, when a liquid crystal light control element is produced, the liquid crystal molecules are oriented perpendicular to the substrate. The orientation can be When a known liquid crystalline substance is used as the liquid crystal compound of the present invention, for example, "Liquid Crystal Device Handbook," Japan Industrial Newspaper (1989), Vol. 1 Pages 52-192, edited by the Liquid Crystal Handbook Editorial Committee; "Liquid Crystal Handbook" Maruzen Co., Ltd. (2000) Biphenyls, phenylcyclohexylsulfones, etc., as described on pages 260 to 330 Various low molecular weight compounds such as cyclohexane, cyclohexylcyclohexane, halogenated alkyl, and tolan A series of compounds or mixtures can be used.

[0013] In the present invention, the nematic isotropic phase transition temperature (Tni) of the liquid crystal compound is 6 The phase transition temperature is preferably 0°C or higher, and more preferably 80°C or higher. If (Tni) is less than the lower limit, the usable temperature range will be narrowed and the dimming function will not work in the high temperature range. On the other hand, although there is no particular upper limit, if it is too high, the viscosity at room temperature will increase, From the viewpoint that driving at high temperatures tends to be difficult, a temperature of 140° C. or less is preferable. The phase transition temperature can be measured using, for example, a polarizing microscope equipped with a temperature control stage or a differential scanning calorimeter. The measurement can be performed using a differential scanning calorimetry (DSC), a thermogravimetric differential thermal analyzer (TG-DTA), or the like.

[0014] In the present invention, the value of the dielectric anisotropy (Δε) of the liquid crystal compound may be either positive or negative. However, from the viewpoint of reducing the driving voltage of the light-control element, the absolute value is preferably 3 or more, and 5 More preferably, it is equal to or greater than this.

[0015] (2) Chiral dopants The liquid crystal composition of the present invention contains a chiral dopant, which induces helical structure in the liquid crystal compound. This allows the orientation of the liquid crystal to be changed. The chiral dopant in the present invention is not particularly limited, and known dopants can be used. In particular, chiral dopants with a positive temperature dependence of the rotational power are preferred. By using a combination of the panto and a dichroic dye described later, the chirality of the liquid crystal composition can be improved. This makes it easier to adjust the temperature dependency of the switch length. The term "positive temperature dependence of rotation ability" means that the chiral pitch length increases with increasing temperature. This means that...

[0016] Commercially available chiral dopants include, for example, CB-15 (CAS RN: 63 799-11-1), S-1011(CASRN:165660-09-3), R-10 11(CASRN:154102-21-3), S-2011(CASRN:18520 7-90-3), R-2011(CASRN:159077-75-5), S-5011 (CASRN:693227-30-4), R-5011(CASRN:944537- 61-5) and others. As a chiral dopant with a positive temperature dependence of the rotational power, for example, JOURNAL OF APPLIED PHYSICS” VOL.28, No.1, 1989, pp. L121-L124. An example of a preferred chiral dopant is S-811 (CAS RN: 8732 1-20-8), product name R-811 (CAS RN:133676-09-2), product name S-5011(CAS RN:693227-30-4), Product name R-5011(CAS RN:944537-61-5).

[0017] The amount of chiral dopant in the liquid crystal composition is set to 100% when the chiral pitch length is 1 to 50%. It is preferable that the concentration be such that the chiral pitch in the liquid crystal light control element is It is preferable that the d / p value, which is the relationship between the length (p) and the element thickness (d), satisfies 1 to 5.

[0018] (3) Dichroic dyes In the present invention, the dichroic dye is not particularly limited, but may be a dichroic dye that changes the temperature of the rotation ability of the chiral dopant. It is preferable to contain a dichroic dye that has an effect opposite to the intensity dependency. When a compound with a positive temperature dependence of rotational power is used as a dopant, the temperature dependence of rotational power is It is preferable to use a dichroic dye that has a negative dependence. When a compound with a negative temperature dependence is used, a dichroic dye that makes the temperature dependence of the rotation ability positive is used. It is preferable to use: Among them, the temperature dependence of the rotational power is positive, and the effect of the dopant on the liquid crystal composition is It is preferable to use a dichroic dye having a negative temperature dependency of rotational power in combination with the liquid crystal composition. The chiral dopant and dichroic dye contained in the composition are in the above combination, The temperature dependence of the helical pitch length of the crystal composition can be easily adjusted, and as a result, it is possible to It is possible to obtain a liquid crystal light control element with a stable driving voltage (threshold voltage) over a wide range. The "negative temperature dependence of the rotational power" means that the chiral pitch length (p) shortens with increasing temperature. It means to shrink.

[0019] The reason why the driving voltage (threshold) is stabilized by the present composition is thought to be as follows. Guest-host chiral nematic liquid crystal compositions are nematic liquid crystal materials, nematic Optically active substances (chiral dopants) that exhibit the ability to rotate into a cholesteric phase when added to liquid crystals The liquid crystal light control element using this composition exhibits excellent luminance without voltage application. The liquid crystal changes from a cholesteric phase (twisted planar alignment) to a nematic phase (twisted planar alignment) when a voltage is applied. This is a liquid crystal element of the so-called phase transition mode, in which the liquid crystal transitions to a homeotropic alignment (a state where the liquid crystal molecules are dissociated). The driving voltage (phase transition voltage: Vc) in this liquid crystal element is expressed by the following formula (3): It depends on the element thickness (d) and the chiral pitch length (p).

number

[0020] On the other hand, the chiral pitch length (p) of chiral nematic liquid crystal compositions is elongated by temperature changes. The chiral pitch length can be controlled by temperature by optimizing the type and composition of the chiral dopant. Many studies have been reported on suppressing temperature-dependent changes and improving driving voltage and optical quality (particularly Kaihei 7-258641 etc.).

[0021] However, the present inventors have investigated chiral nematics to which various chiral dopants have been added. Guest-host chiral nematic liquid crystal compositions induced by adding dichroic dyes to chiral liquid crystals As a result of investigating the temperature dependence of the chiral pitch length of the compound, it was found that the compound has optical activity in the molecule. Although the dichroic dyes that are not present have almost no rotational ability in the chiral nematic phase, By combining the chiral dopant and the dichroic dye, the chiral pitch of the liquid crystal composition can be controlled. It was found that this significantly changes the temperature dependence of the length. Therefore, in the liquid crystal composition containing the dichroic dye, the chiral Even if a dopant is used, the temperature dependency increases depending on the combination with the dichroic dye, making it difficult to adjust. In some cases, the resulting material is not suitable for use in optical elements. The above-mentioned prior art does not include a dichroic dye or is a liquid crystal composition that assumes the addition of a very small amount of the dye. The disclosure only concerns compositions for liquid crystal light control devices containing a large amount of dichroic dyes. This did not improve the temperature dependence of the chiral pitch length. Therefore, a high concentration of dichroic dye was blended to achieve the optical characteristics required for liquid crystal dimming elements. It was necessary to improve the temperature dependency of the chiral pitch length of the liquid crystal composition. The present inventors have been working diligently to optimize the combination of chiral dopants and dichroic dyes. As a result of careful investigation, the temperature dependence of the rotation ability was positive (the chiral pitch length increases with increasing temperature). ) and the chiral pitch length is negatively dependent on the temperature of the rotational ability (as the temperature rises) The liquid crystal obtained by blending a dichroic dye that The temperature dependence of the helical pitch length of the composition is adjusted, thereby reducing the temperature dependence of the driving power. I discovered that it was possible. When the liquid crystal composition of the present invention contains two or more dichroic dyes, The rotation ability imparted to the liquid crystal composition means the rotation ability exhibited as a mixture of dichroic dyes.

[0022] Specific examples of the dichroic dyes in the present composition include those described in " Liquid Crystal Device Handbook, Japan Industrial Newspaper (1989), p. 728, JP 61-9 azo dyes such as those described in Japanese Patent Application Laid-Open No. 8768 and Japanese Patent Application Laid-Open No. 61-145285; Quinophthalone dyes such as those described in JP-A-61-53361, Perylene dye compounds such as those described in Patent Publication No. 63377, or mixtures thereof Among these, the properties that make the temperature dependence of rotational power negative are easily obtained, and heat resistance is From the viewpoint of high durability such as light resistance, anthraquinone dyes are preferred.

[0023] Preferred examples of anthraquinone dyes include dyes represented by the following general formula (Ia) and Examples of the dyes include those represented by the general formula (I).

[0024] [ka]

[0025] In formula (Ia), R 12 represents a linear or branched alkyl group having 1 to 5 carbon atoms, or It represents a cycloalkyl group having a linear alkyl group having 1 to 6 carbon atoms as a substituent. R2 a , R 3 a , R 4 a , R 5 a , R 6 a , and R 7 a are each independently a hydrogen atom, a carbon atom, Linear alkyl groups with 1 to 5 prime numbers, linear or branched alkyl groups with 1 to 6 carbon atoms a phenylthio group, a pyridylthio group, or a group having 1 to 6 carbon atoms, which may have as a substituent The formula represents a cyclohexylcarboxy group having a linear alkyl group of the formula (I) as a substituent.

[0026] In the above formula (Ia), from the viewpoint of light-blocking property in a dark state and solubility in the host liquid crystal, et al., R 12 is an ethyl group, a propyl group, an n-butyl group, a t-butyl group, a 4-methylcyclohexane group, R is preferably an aryl group or a 4-n-butylcyclohexyl group. 3 a is a hydrogen atom, R is preferably a thio group, a 4-methylphenylthio group, or a pyridylthio group. 2 a , R 4 a , R 5 a , R 6 a and R 7 a is preferably a hydrogen atom.

[0027] Specific examples of suitable anthraquinone dyes represented by the general formula (Ia) include: The following are some examples:

[0028] [ka]

[0029] The dye represented by the following general formula (I) is an anthraquinone dye having four or less aromatic rings. It is a mixture.

[0030] [ka]

[0031] In formula (I), R 1 -NHR 8 , or -SR 9 indicates R 2 , R 3 and R 4 Each is unique In other words, a hydrogen atom, -NHR 8 , -SR 9 , or -OR 10 Indicates R 8 ~R 10 are each Independently, hydrogen atom, linear or branched alkyl group, optionally substituted silyl group, a cycloalkyl group, an optionally substituted aryl group, or an optionally substituted aryl group Indicates a heterocyclic residue. However, R 1 ~R 4 If one of them is -NH2, the other three are not -NH2. Also, R 8 ~R 10 The substituents of the cycloalkyl group, aryl group, and heterocyclic residue of It does not contain a linked ring structure. R 5 , R 6 and R 7 are each independently a hydrogen atom, a halogen atom, a straight-chain or branched-chain alkyl groups which may have a substituent; aryl groups which may have a substituent; -SR 9 (R 9 is the same as above.) or -COYR 11 (Y is oxygen atom, sulfur atom, or -NHR 8 (R 8is the same as above.) R 11 is hydrogen atom, a linear or branched alkyl group, or a cycloalkyl group which may have a substituent an aralkyl group which may have a substituent, an aryl group which may have a substituent, or The heterocyclic residue may have a substituent. However, R 1 ~R 4 If one of the groups is -NH2, then R 5 ~R 7 At least one of It is not a hydrogen atom. 5 ~R 7 does not have a linked ring structure of three or more rings.

[0032] In the above formula (I), in view of light-blocking properties in a dark state and solubility in the host liquid crystal, , R 1 represents an amino group which may have a substituent, or a phenyl group which may have a substituent. A thio group is preferred, and R 2 , R 3 and R 4 are each independently a hydrogen atom, a hydroxyl group, or a substituted An amino group which may have one or more substituents, or a phenylthio group which may have one or more substituents is preferred. Yes. R 5 , R 6 and R 7 are each independently a hydrogen atom, a carbonyl group which may have a substituent, A carboxyl group or an optionally substituted carboxyl group is preferred.

[0033] In the anthraquinone dye represented by the general formula (I) and having four or less aromatic rings, More preferred dyes are those represented by the following general formulas (Ib), (Ic), and (Id): Examples include:

[0034] [ka]

[0035] In formula (Ib), R 2 b is a hydrogen atom, a hydroxyl group, a linear or A phenylthio group having a branched alkyl group as a substituent, or a linear alkyl group having 1 to 8 carbon atoms A phenylthio group having a cyclohexyl group as a substituent, which has an alkyl group as a substituent. Shows. R 5 b has a linear or branched alkyl group having 1 to 8 carbon atoms as a substituent. Cyclohexyl having a carboxyl group or a linear alkyl group having 1 to 8 carbon atoms as a substituent Phenyl carboxylates having a carboxyl group or a linear alkyl group having 1 to 8 carbon atoms as a substituent and a phenoxy group having a substituted oxy group or a linear alkyl group having 1 to 8 carbon atoms. vinegar. R 7 b is a group having a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms as a substituent. a cycloalkyl group having a carboxyl group as a substituent, and a linear alkyl group having 1 to 8 carbon atoms as a substituent; phenylene having a phenyl group having a 2-methyl-2-isopropyl ... a cycloalkyl group having a substituted arylcarboxy group or a linear alkyl group having 1 to 8 carbon atoms; This represents a phenylcarboxy group having a hexyl group as a substituent.

[0036] In the above formula (Ib), from the viewpoint of light-blocking property in a dark state and solubility in the host liquid crystal, et al., R 2 b is preferably a phenylthio group having a hydroxy group or a methyl group as a substituent. K, R 5 b is a phenylcarboxylate having a linear alkyl group having 1 to 8 carbon atoms as a substituent. A silyl group is preferred. 7 b is substituted with a hydrogen atom or a linear alkyl group having 1 to 8 carbon atoms. A cyclohexylcarboxy group having the formula (I) is preferred.

[0037] [ka]

[0038] In formula (Ic), R 13 is a methyl group, a linear or branched alkyl group having 1 to 8 carbon atoms, a cyclohexyl group having a linear alkyl group having 1 to 8 carbon atoms as a substituent; indicates R 14 represents a phenyl group having a linear alkyl group having 1 to 8 carbon atoms as a substituent, or a cyclohexylphenyl group having a linear alkyl group having 1 to 8 carbon atoms as a substituent. Shows.

[0039] In the above formula (Ic), from the viewpoint of light-blocking property in a dark state and solubility in the host liquid crystal, et al., R 13 is preferably a cyclohexyl group having a linear alkyl group having 1 to 8 carbon atoms, R 14 is preferably a phenyl group having a linear alkyl group having 1 to 8 carbon atoms as a substituent. .

[0040] [ka]

[0041] In formula (Id), R 15 , R 16 , R 17 and R 18 are each independently a hydrogen atom, the number of carbon atoms a linear or branched alkyl group having 1 to 8 carbon atoms, or a linear alkyl group having 1 to 8 carbon atoms The cyclohexyl group contained as a substituent is shown.

[0042] In the above formula (Id), in view of light-blocking properties in a dark state and solubility in the host liquid crystal, , R 15 , R 16 , R 17 and R 18 each independently represents a hydrogen atom, a methyl group, a propyl group, A pentyl group or a t-butyl group is preferred.

[0043] Suitable anthraquinone dyes represented by the general formulas (Ib), (Ic) and (Id) include: Specifically, the following are listed as examples:

[0044] [ka]

[0045] In the anthraquinone dye represented by the general formula (II) and having four or less aromatic rings, More preferred dyes include those represented by the following general formula (Ie):

[0046] [ka]

[0047] In formula (Ie), R 2 e represents an amino group, a linear alkylthio group having 1 to 8 carbon atoms, a phenylamino group having 1 to 8 linear alkyl groups or fluorine atoms as a substituent, or a phenylthio group having a linear alkyl group having 1 to 8 carbon atoms as a substituent, and R 3 e , R 4 e , and R 7 e are each independently a hydrogen atom, a hydroxyl group, or a group having 1 to 8 carbon atoms. A linear alkylthio group or a linear or branched alkyl group having 1 to 13 carbon atoms is substituted. R represents a phenylthio group having as a substituent. 5 e is a hydrogen atom, a straight chain with 1 to 8 carbon atoms Or a carboxyl group having a branched alkyl group as a substituent, a straight chain having 1 to 8 carbon atoms a cyclohexylcarboxy group having a cyclic alkyl group as a substituent, or a cyclohexylcarboxy group having 1 to 8 carbon atoms represents a linear alkyl group or a phenylcarboxy group having a fluorine atom as a substituent, R 19 represents a hydrogen atom, a linear or branched alkyl group having 1 to 8 carbon atoms, or a fluorine atom It represents a phenyl group having a phenyl or chlorine atom as a substituent.

[0048] In the above formula (Ie), from the viewpoint of light-blocking properties in a dark state and solubility in the host liquid crystal, et al., R 2 e is an amino group, a linear alkylthio group having 1 to 8 carbon atoms, a linear alkylthio group having 1 to 8 carbon atoms, a phenylamino group having a chain alkyl group or a fluorine atom as a substituent, or a phenylamino group having 1 to 10 carbon atoms A phenylthio group having a linear alkyl group of R 3 e is a hydrogen atom R is preferably a straight-chain alkylthio group having 1 to 8 carbon atoms. 4 e , R 7 e and R 19 teeth A hydrogen atom is preferred, and R 5 e represents a linear alkyl group having 1 to 8 carbon atoms or a fluorine atom Phenylcarboxyl group as a substituent, linear alkyl group having 1 to 8 carbon atoms as a substituent A cyclohexylcarboxy group having the formula (I) is preferred.

[0049] Specific examples of suitable anthraquinone dyes represented by the general formula (Ie) include: The following are some examples:

[0050] [ka]

[0051] In the present invention, in order to obtain a wide dimming dynamic range, the above-mentioned anthraquino It is more preferable to use at least two or more kinds of dyes in combination.

[0052] Anthraquinone dyes are disclosed in, for example, JP-A-56-55479 and JP-A-58-53 The compound can be synthesized by combining known methods such as those described in US Pat. No. 6,9544. In addition, if necessary, other dyes than anthraquinones, such as ultraviolet absorbing dyes and near-infrared absorbing dyes, may be used. The pigment may also contain the following dye.

[0053] The amount of dichroic dye blended is determined based on the liquid crystal composition from the viewpoint of achieving high light blocking properties and a dynamic range. The content is preferably 8% by mass or more, and more preferably 10% by mass or more, relative to 100% by mass of the composition. The upper limit of the thickness is set to 25°C to prevent the decrease in response speed due to the precipitation of the dichroic dye and the increase in viscosity. It is preferably 100% by mass or less, and more preferably 22% by mass or less. When the liquid crystal composition of the present invention contains two or more dichroic dyes, the above blending amounts are The mass of the dichroic dye is the ratio of the total mass of the dichroic dye to 100% by mass of the composition.

[0054] The liquid crystal composition of the present invention comprises (1) a liquid crystal compound, (2) a chiral dopant, and (3) a dichroic In addition to the pigment, other additives may be contained as necessary.

[0055] The liquid crystal composition of the present invention comprises (1) a liquid crystal compound, (2) a chiral dopant, and (3) a divalent metal compound. The liquid crystal composition can be prepared by mixing the coloring dyes by a known method. Specifically, (1) liquid crystal compounds, (2) chiral dopants, (3) dichroic dyes, and It can be prepared by shaking and mixing the container containing other additives to be added as needed. Cut.

[0056] <Liquid crystal dimming element> The liquid crystal light control device of the present invention comprises a layer made of the liquid crystal composition of the present invention, and a pair of substrates with transparent electrodes arranged so that the electrodes face each other; It is preferable that the liquid crystal display device has a structure in which a layer made of the liquid crystal composition of the present invention is sandwiched between the liquid crystal display device and the liquid crystal display device.

[0057] The operating temperature range of the light-adjusting element of the present invention is preferably 0°C to 60°C, more preferably -10°C to 80°C. preferable. The transmittance of the dimming element from visible light to near-infrared light (wavelength 380 to 780 nm) varies depending on the drive voltage. It is preferable that the visible light transmittance can be arbitrarily adjusted, and the range is preferably 1% to 40%. The haze is preferably 10% or less, more preferably 5% or less. These device characteristics depend on the physical properties of the liquid crystal components used in the liquid crystal composition, the cell thickness of the light-adjusting device, and the It can be appropriately selected depending on the number of stacked elements, etc.

[0058] The substrate of the transparent electrode of the light-adjusting element of the present invention is not particularly limited, but may be a glass plate, an acrylic plate, or the like. Various synthetic resin plates such as polyethylene terephthalate resin, polycarbonate resin, etc. The transparent electrode layer formed on the substrate is preferably, but not limited to, an oxide film. Materials made of metal oxides such as indium and indium tin oxide (ITO, IZO) and PE A conductive polymer such as DOT / PSS is preferably used. The surface of the transparent electrode layer that comes into contact with the liquid crystal may be subjected to an alignment treatment, if necessary. As a treatment method, for example, octadecyldimethyl [3-(trimethoxysilyl)propionate ammonium chloride, etc., is applied to form vertical alignment, and polyimide is applied to form parallel alignment. Known methods such as alignment methods, photo-alignment films, etc. can be used appropriately. The two electrode-equipped substrates are arranged so that the alignment-treated surfaces face each other, and are held together by a spacer or the like. By integrating the two electrode-attached substrates, the gap between the two electrode-attached substrates is, for example, 1 to 30 μm, preferably An element (cell) is formed with a space of 3 to 10 μm, and liquid crystal is sealed in this space. Enter.

[0059] <<Dimming elements, dimming windows>> The use of the light control element of the present invention is not particularly limited, but it is possible to efficiently control visible light. Therefore, it can be suitably used as a light control window or smart window for automobiles and buildings. The light-controlling element of the present invention is disclosed in Japanese Patent Application Laid-Open No. 6-18856 and Japanese Patent Application Laid-Open No. 2007-102210. and JP-A-2020-126240. It can be processed into dimming windows such as curved glass and smart windows. [Example]

[0060] The present invention will be described in detail below with reference to examples. The following examples are not intended to be limiting.

[0061] [Example 1] As a liquid crystal compound, a nematic liquid crystal product manufactured by EHC, O1-104 (Tni= 100℃) 1g, and as a chiral dopant, 4-[4-(hexyloxy) )benzoyloxy]benzoic acid (S)-2-octyl (CAS: 87321-20-8) 30 mg, and as a dichroic dye component, 25 mg of a dichroic dye represented by the following general formula (1),

[0062] [ka]

[0063] 9 mg of a dichroic dye represented by the following general formula (2),

[0064] [ka] In the formula (*), each R independently represents a hydrogen atom or a tert-butyl group.

[0065] 38 mg of a dichroic dye represented by the following general formula (3),

[0066] [ka]

[0067] 60 mg of a dichroic dye represented by the following general formula (4),

[0068] [ka]

[0069] A total of four dichroic dyes were mixed and dissolved to prepare liquid crystal composition-I.

[0070] This liquid crystal composition I was injected into a wedge cell manufactured by EHC, and the liquid crystal composition I was then mixed with the liquid crystal composition I prepared by the method described in the publication of "Okamura Nobuhiko / Ichinose Hideo" (2004). , Journal of the Japanese Liquid Crystal Society "Liquid Crystal", Vol.6 No.3, p41 (2002) Liquid Crystal Science Experiment Course The method of "4. Pitch length" described in "Part 3: Measurement techniques for liquid crystal material properties (1)" The temperature dependence of the pitch length was measured using the method described above. The results are shown in Table 1. The chiral pitch length (P0) at 20°C is 3.854 μm, and the chiral pitch at 0°C is The chiral pitch length (P1) is 3.900 μm, and the chiral pitch length (P2) at 60°C is 3.89 The chiral pitch length (P3) at 7 μm and 80° C. was 3.969 μm. From the chiral pitch length at each temperature obtained by measurement, the temperature 0℃ expressed by the following formula (1) The temperature change rate (X1) at 60°C was calculated as -0.0 0001, and the change in chiral pitch length due to temperature was very small. Temperature change rate (X1) = [(P2 - P1) / (T2 - T1)] / P0 (1) P0: Chiral pitch length (μm) at 20°C P1: Chiral pitch length at 0°C (μm) P2: Chiral pitch length at 60°C (μm) T1:0℃ T2: 60℃

[0071] In addition, the temperature change rate (X2) from 0°C to 80°C is calculated using the following formula (2). As a result, the temperature change rate (X2) was 0.00022, and the change in pitch length due to temperature It was very minute. Temperature change rate (X2) = [(P3 - P1) / (T3 - T1)] / P0 (2) P0: Chiral pitch length (μm) at 20°C P1: Chiral pitch length at 0°C (μm) P3: Chiral pitch length at 80°C (μm) T1:0℃ T3: 80℃

[0072] On the other hand, liquid crystal composition-I was coated with a polyimide resin, cured, and then rubbed to obtain a homogeneous alignment. The alignment-treated surfaces of the glass plates are opposed to each other. The liquid crystal was sealed in a cell with a gap of 12 μm to prepare liquid crystal light control device-I. After attaching a lead wire for applying voltage to the fabricated liquid crystal light control element, the liquid crystal light control element was used for a microscope. The liquid crystal display was set on a cooling and heating stage, and the change in driving characteristics due to temperature was observed under a microscope. The optical element showed no abnormalities in threshold voltage with temperature changes from 0°C to 80°C, demonstrating good drive quality. and optical quality.

[0073] As a liquid crystal composition not containing the dichroic dye component of the liquid crystal composition-I, Nematic liquid crystal product name O1-104 1g, chiral dopant, Tokyo Chemical Industry Co., Ltd. -[4-(Hexyloxy)benzoyloxy]benzoic acid (S)-2-octyl ester 30m The liquid crystal composition II was prepared by mixing and dissolving g, and the temperature dependence of the chiral pitch length was measured. Ta. The chiral pitch length (P0) of this liquid crystal composition II at 20°C was 3.144 μm. The chiral pitch length (P1) at 0°C is 3.144 μm, and the chiral pitch at 60°C is The chiral pitch length P2 is 3.236 μm, and the chiral pitch length (P3) at 80°C is 3.320 μm It was. From the chiral pitch length at each temperature obtained by measurement, the calculated The temperature change rate (X1) at temperatures from 0°C to 80°C is 0.00070. 2) is 0.00049, which is larger than the value of liquid crystal composition I containing a dichroic dye component. It was a success.

[0074] The pitch lengths of liquid crystal compositions I and II at each temperature were measured using chiral spectroscopy at 20°C. The temperature dependence of the chiral pitch length normalized by the chiral pitch length (P0) is shown in Figure 1. As shown in this figure, the liquid crystal composition I, which is a mixture of chiral dopant and nematic liquid crystal, I has a positive temperature dependence in which the chiral pitch length increases with increasing temperature, whereas In addition, the temperature dependence (P / P0) of the liquid crystal composition I containing the dichroic dye was reduced. Therefore, in the present liquid crystal composition, the dichroic dye has the effect of suppressing the temperature change of the chiral pitch length. That is, the dichroic dye in Example 1 had the rotation ability imparted to the liquid crystal composition. The temperature dependence was negative.

[0075] [Example 2] As the dichroic dye component, 30 mg of the dichroic dye of general formula (4) in Example 1 was used. Liquid crystal composition-VII was prepared in the same manner as liquid crystal composition-I described in Example 1, except for the above. Ta. The chiral pitch of the present liquid crystal composition VII at each temperature was determined in the same manner as in Example 1. The chiral pitch length (P0) at 20°C is 3.270 μm, and the temperature change rate is The chiral pitch length (P1) at 60°C is 3.267 μm, and the chiral pitch length ( P2) is 3.335 μm, and the chiral pitch length at 80°C (P3) is 3.442 μm. there were. Liquid crystal composition VII and a liquid crystal composition not containing a dichroic dye component of liquid crystal composition VII The temperature change rate (X1) of each of the liquid crystal compositions II described in Example 1 is 0.0 The dichroic dye exhibits chiral pitches of 0.0035 and 0.00070 at temperatures between 0°C and 60°C. That is, the dichroic dye in Example 2 had the effect of suppressing the temperature change of the film. The temperature dependence of the rotation power given to the liquid crystal composition was negative.

[0076] [Example 3] The liquid crystal compound was EHC's nematic liquid crystal product E-7 (Tni = 60°C ) 1g, and Sigma-Aldrich 5-((1s,4r)-4 -propylcyclohexyl)-5,6-dihydro-4H-dinaphtho[2,1-f:1', 2'-h][1,5]dioxonine (CAS: 944537-61-5) 2.0 mg, As the dichroic dye component, 25 mg of the dichroic dye of the general formula (1) used in Example 1, 5 mg of dichroic dye of formula (2), 35 mg of dichroic dye of formula (3), 60 mg of a dichroic dye, and 40 mg of a dichroic dye represented by the following general formula (5),

[0077] [ka] Liquid crystal composition-VIII was prepared in the same manner as in Example 1, except that a total of five dichroic dyes were used. Ta.

[0078] The chiral pitch of the liquid crystal composition VIII at each temperature was determined in the same manner as in Example 1. The chiral pitch length and temperature change rate are as follows: the chiral pitch length (P0) at 20°C is 5.533 μm, The chiral pitch length (P1) at 60°C is 5.533 μm. (P2) was 5.711 μm.

[0079] Furthermore, as a liquid crystal composition not containing a dichroic dye component of this liquid crystal composition-VIII, Liquid crystal composition IX was prepared in the same manner as in Example 1. The chiral pitch length and temperature change rate of The chiral pitch length (P1) at 0°C is 4.144 μm, and the chiral pitch length (P1) at 60°C is 4.144 μm. The radial pitch length (P2) was 4.320 μm. The present liquid crystal composition-VIII and the liquid crystal composition-IX containing no dichroic dye component are The temperature change rate (X1) is 0.00054 and 0.00070, and the ... The dichroic dye had the effect of suppressing the temperature change of the chiral pitch length. The dichroic dye in Example 3 had a negative temperature dependency of the rotation power it imparted to the liquid crystal composition.

[0080] [Comparative Example 1] As a chiral dopant, bis(trimethylsilyl) benzophenone (Bis(trimethylsilyl)) manufactured by SYNTHON Chemicals GmbH was used. (S)-1-phenyl-[4-(trans-4-pentylcyclohexyl)benzoic acid] Except for using 7.5 mg of 1,2-ethanediyl (CAS: 165660-09-3), Liquid crystal composition III was prepared in the same manner as in the preparation of liquid crystal composition I described in Example 1.

[0081] The chiral pitch of the liquid crystal composition III at each temperature was determined in the same manner as in Example 1. The chiral pitch length (P0) at 20°C is 4.541 μm, and the temperature change rate is The chiral pitch length (P1) at 60°C is 4.663 μm, and the chiral pitch length ( P2) is 4.350 μm, and the chiral pitch length at 80°C (P3) is 4.350 μm. The temperature change rate (X1) from 0°C to 60°C is -0.00115. The temperature change rate (X2) from 0°C to 80°C was -0.00086.

[0082] Furthermore, as a liquid crystal composition not containing the dichroic dye component of this liquid crystal composition-III, Example Liquid crystal composition IV was prepared in the same manner as in Example 1. The chiral pitch length and temperature change rate are as follows: the chiral pitch length (P0) at 20°C is 3.60 The chiral pitch length (P1) at 2 μm and 0°C is 3.702 μm, and the chiral pitch length (P1) at 60°C is The chiral pitch length (P2) is 3.534 μm, and the chiral pitch length (P3) at 80°C is 3 0.557μm, the temperature change rate (X1) from 0℃ to 60℃ is -0.00078, The temperature change rate (X2) from 0°C to 80°C was -0.00050.

[0083] The pitch lengths of liquid crystal compositions III and IV at various temperatures were measured at 20°C. Figure 2 shows the temperature dependence of the chiral pitch length normalized by the chiral pitch length (P0). As shown in this figure, the chiral dopant of this comparative example, the nematic liquid crystal, and the dichroic color Liquid crystal composition III, which is a mixture of the dichroic dye components, is a liquid crystal composition IV, which does not contain a dichroic dye component. In comparison, the change in chiral pitch length due to temperature change is large. The dichroic dye enhanced the temperature dependence of the chiral pitch length.

[0084] Comparative Example 2 As the chiral dopant, 5-((1s,4r)-4-promoter (Sigma-Aldrich) was used. (2,1-f:1',2'-phenylcyclohexyl)-5,6-dihydro-4H-dinaphtho[ h][1,5]dioxonine (CAS: 944537-61-5) 2.0 mg was used. Liquid crystal composition-V was prepared in the same manner as liquid crystal composition-I described in Example 1, except for the above.

[0085] The chiral pitch length of the liquid crystal composition V at each temperature was determined in the same manner as in Example 1. The temperature change rate is as follows: the chiral pitch length (P0) at 20°C is 4.980 μm, and at 0°C The chiral pitch length (P1) at 60°C is 4.885 μm, and the chiral pitch length (P2 ) is 5.161 μm, and the chiral pitch length (P3) at 80°C is 5.333 μm. The temperature change rate (X1) from 0°C to 60°C is 0.00093, and the temperature change rate (X2) from 0°C to 80°C is 0.00093. The temperature change rate (X2) in °C was 0.00113.

[0086] Furthermore, as a liquid crystal composition not containing a dichroic dye component of this liquid crystal composition-V, Example 1 and Liquid crystal composition VI was prepared in the same manner. The chiral pitch length and temperature change rate are as follows: The chiral pitch length (P0) at 20°C is 4.778μm. m, the chiral pitch length (P1) at 0°C is 4.785 μm, and the chiral pitch at 60°C is The pitch length (P2) is 4.900 μm, and the chiral pitch length (P3) at 80°C is 5.1 06μm, the temperature change rate (X1) from 0℃ to 60℃ is 0.00040, The temperature change rate (X2) from 0 to 80°C was 0.00084. The pitch lengths of liquid crystal compositions V and VI at each temperature were measured using chiral spectroscopy at 20°C. The temperature dependence of the chiral pitch length normalized by the chiral pitch length (P0) is shown in Figure 3. As shown in this figure, the chiral dopant, nematic liquid crystal, and dichroic dye of this comparative example The liquid crystal composition V, which is a mixture, has the following characteristics compared to the liquid crystal composition VI, which does not contain a dichroic dye component: The chiral pitch length changed significantly with temperature change, and the negative temperature dependence increased.

[0087] [Table 1]

Claims

1. A liquid crystal composition comprising a liquid crystal compound, a chiral dopant, and a dichroic dye, the liquid crystal compound is a liquid crystal compound exhibiting a nematic phase, The temperature change rate (X1) of the chiral pitch length represented by the following formula (1) is -0.0006 to 0. 0006. A liquid crystal composition. Temperature change rate (X1) = [(P2 - P1) / (T2 - T1)] / P0 (1) P0: Chiral pitch length (μm) at 20°C P1: Chiral pitch length at 0°C (µm) P2: Chiral pitch length (μm) at 60°C T1: 0°C T2: 60°C

2. The temperature change rate (X2) of the chiral pitch length of the liquid crystal composition, which is represented by the following formula (2), is - 2. The liquid crystal composition according to claim 1, wherein the δ is 0.0006 to 0.0006. Temperature change rate (X2) = [(P2 - P1) / (T2 - T1)] / P0 (2) P0: Chiral pitch length (μm) at 20°C P1: Chiral pitch length at 0°C (µm) P3: Chiral pitch length (μm) at 80°C T1: 0°C T3: 80°C

3. 2. The dichroic dye according to claim 1, wherein the temperature dependence of the rotational power imparted to the liquid crystal composition is negative.

3. The liquid crystal composition according to claim 2.

4. The dichroic dye contains at least one selected from the group consisting of anthraquinone dyes. The liquid crystal composition according to claim 1 or 2, comprising:

5. The content of the dichroic dye relative to 100% by mass of the liquid crystal composition is 5% by mass or more and 25% by mass or less.

3. The liquid crystal composition according to claim 1, wherein the amount of the crystalline solid is 0.1% or less.

6. A liquid crystal light control device comprising a layer made of the liquid crystal composition according to any one of claims 1 to 5.

7. a pair of substrates with transparent electrodes arranged so that the transparent electrodes face each other; 7. The liquid crystal light control element according to claim 6, wherein a layer of a liquid crystal composition is sandwiched between the attached substrates. 。

8. The liquid crystal light control device according to claim 6, which is for use in an automobile.

9. The liquid crystal light control device according to claim 6, which is used as a building material.

10. A light control window comprising the liquid crystal light control element according to claim 6.

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