Anthraquinone derivatives, dye compositions, and photochromic sheets

Abstract

The present invention provides anthraquinone derivatives having a broad absorption wavelength range, a dye composition, and a photochromic sheet. [Solution] An anthraquinone derivative represented by the following formula (1-1), wherein X and Y in formula (1-1) each independently have a structure represented by the following formula (1-2). [Formula 1] In formula (1-2) JPEG0007831679000031.jpg48169, R is a linear or branched alkyl group having 4 to 11 carbon atoms.

Description

[Technical Field]

[0001] This disclosure relates to anthraquinone derivatives, dye compositions, and photochromic sheets. [Background technology]

[0002] Development of dichroic dyes used in liquid crystal elements such as liquid crystal displays and dimming sheets is progressing. In particular, anthraquinone derivatives, which are compounds with an anthraquinone skeleton, tend to exhibit high resistance to light, heat, and temperature, and are therefore expected to be used not only in indoor applications but also in automotive liquid crystal elements. For this reason, a great deal of research has been conducted on the structure and properties of anthraquinone derivatives (see, for example, Patent Documents 1-3). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2008-106200 [Patent Document 2] Japanese Patent Publication No. 2018-154704 [Patent Document 3] International Publication No. 2023 / 100848 [Overview of the project] [Problems that the invention aims to solve]

[0004] When using dichroic dyes in liquid crystal elements for the purpose of light shielding, or when mixing multiple dichroic dyes to obtain black, it is preferable that the absorption wavelength range of the dichroic dye is wide. For example, in a dimmable sheet whose transparency changes with the application of voltage, it is preferable that the dichroic dye contained in the dimmable sheet absorbs light over a wide range of wavelengths in order to enhance the contrast between the transparent and opaque states. In particular, magenta-based dichroic dyes absorb light in wavelengths that have a significant impact on brightness, so expanding the absorption wavelength range of magenta-based dichroic dyes is effective in improving contrast.

[0005] Therefore, anthraquinone derivatives with a broad absorption wavelength range are needed as magenta-based dichroic dyes. [Means for solving the problem]

[0006] This paper describes embodiments of anthraquinone derivatives, dye compositions, and photochromic sheets for solving the above problems. [Aspect 1] An anthraquinone derivative represented by the following formula (1-1), wherein X and Y in formula (1-1) each independently have a structure represented by the following formula (1-2).

[0007] [ka] In formula (1-2), R is a linear or branched alkyl group having 4 to 11 carbon atoms.

[0008] According to the above configuration, the anthraquinone derivative has an NHR group at a position that does not form a hydrogen bond with the oxygen atom attached to the anthraquinone skeleton. As a result, inversion occurs at the NHR group, which allows for an expansion of the absorption wavelength range. Therefore, as a magenta-based dichroic dye, it is capable of absorbing light over a wide wavelength range.

[0009] [Aspect 2] An anthraquinone derivative represented by the following formula (2-1), wherein X in formula (2-1) has the structure represented by the following formula (2-2), and Y in formula (2-1) has the structure represented by the following formula (2-3).

[0010] [ka] In formula (2-2), R is a linear or branched alkyl group having 4 to 11 carbon atoms, and in formula (2-3), Z is an oxygen atom or a methylene group, and R' is a linear or branched alkyl group having 5 to 9 carbon atoms.

[0011] According to the above configuration, the anthraquinone derivative has an NHR group at one end portion of the molecular structure, which is a position where an oxygen atom bonded to the anthraquinone skeleton does not form a hydrogen bond, and a ZR' group at the other end portion of the molecular structure. Therefore, in addition to the absorption wavelength range when each of X and Y is an NHR group, light in a wavelength range including the absorption wavelength range when each of X and Y is a ZR' group can be absorbed. Thus, the absorption wavelength range can be further broadened.

[0012] [Aspect 3] The anthraquinone derivative according to [Aspect 1], wherein at least one of X and Y in the formula (1-1) has a branched alkyl group. According to the above configuration, high solubility can be obtained for each of the liquid crystal and the monomer.

[0013] [Aspect 4] The anthraquinone derivative according to [Aspect 2], wherein at least one of X and Y in the formula (2-1) has a branched alkyl group. According to the above configuration, high solubility can be obtained for each of the liquid crystal and the monomer.

[0014] [Aspect 5] A dye composition comprising the anthraquinone derivative according to any one of [Aspect 1] to [Aspect 4] and a liquid crystal compound. According to the above configuration, since an anthraquinone derivative having a wide absorption wavelength range is used, the dye composition can be suitably used for a liquid crystal element.

[0015] [Aspect 6] A dye composition comprising the anthraquinone derivative according to any one of [Aspect 1] to [Aspect 4], a liquid crystal compound, and a polymerizable compound. According to the above configuration, since an anthraquinone derivative having a wide absorption wavelength range is used, the dye composition can be suitably used for the production of a liquid crystal element provided with a liquid crystal layer including a transparent polymer layer.

[0016] A light-adjusting sheet comprising a light-adjusting layer containing an anthraquinone derivative and a liquid crystal compound as described in any one of [Aspect 7], [Aspect 1] to [Aspect 4], and a pair of transparent electrode layers sandwiching the light-adjusting layer.

[0017] According to the above configuration, since an anthraquinone derivative having a broad absorption wavelength range is used, it is possible to reduce the total light transmittance in the opaque state of the photochromic sheet, thereby increasing the contrast between the transparent and opaque states.

[0018] [Aspect 8] The light-adjusting sheet according to [Aspect 7], wherein the light-adjusting layer comprises a transparent polymer layer containing a plurality of voids, and a liquid crystal composition held in the voids, the liquid crystal composition containing the anthraquinone derivative and the liquid crystal compound.

[0019] According to the above configuration, since an anthraquinone derivative having a broad absorption wavelength range is used, it is possible to reduce the total light transmittance in the opaque state of the photochromic sheet, thereby increasing the contrast between the transparent and opaque states. [Effects of the Invention]

[0020] According to this disclosure, a wide absorption wavelength range can be obtained as a magenta-based dichroic dye. [Brief explanation of the drawing]

[0021] [Figure 1] Figure 1 shows the structure of a dimming sheet according to one embodiment. [Figure 2] Figure 2 is a table showing the structures and evaluation results of the anthraquinone derivatives of Examples 1 to 7. [Figure 3] Figure 3 is a table showing the structures and evaluation results of the anthraquinone derivatives of Examples 8 and 9 and Comparative Examples 1 to 5. [Modes for carrying out the invention]

[0022] The following describes one embodiment of an anthraquinone derivative, a dye composition, and a photochromic sheet. An anthraquinone derivative is a compound having a 9,10-anthraquinone skeleton.

[0023] [Anthraquinone derivatives] As examples of anthraquinone derivatives in this embodiment, the first example anthraquinone derivative and the second example anthraquinone derivative will be described separately.

[0024] The first example of an anthraquinone derivative is a compound represented by the following formula (1-1), wherein X and Y in formula (1-1) each independently have a structure represented by the following formula (1-2).

[0025] [ka] In formula (1-2), R is a linear or branched alkyl group having 4 to 11 carbon atoms.

[0026] The first example of an anthraquinone derivative has an NHR group in a position that does not form a hydrogen bond with the oxygen atom attached to the anthraquinone skeleton. In this structure, in addition to rotation occurring around the CN single bond between the phenylene group attached to the anthraquinone skeleton and the NHR group, an inversion, i.e., enantiomerization via a planar transition state, occurs at the NHR group. Therefore, compared to the case where inversion does not occur, the number of molecular vibration patterns increases, and consequently, the number of energy levels to which the anthraquinone derivative can transition increases. As a result, light of a wavelength corresponding to the energy level difference is absorbed for each energy level, thus broadening the absorption wavelength range of the anthraquinone derivative.

[0027] It is thought that when an oxygen atom bonded to the anthraquinone skeleton forms a hydrogen bond with an NHR group, inversion becomes less likely. However, in this embodiment, by introducing the NHR group at a position where no hydrogen bond is formed, it is possible to expand the absorption wavelength range.

[0028] The second example of an anthraquinone derivative is a compound represented by the following formula (2-1), wherein X in formula (2-1) has the structure represented by the following formula (2-2), and Y in formula (2-1) has the structure represented by the following formula (2-3).

[0029] [ka] In formula (2-2), R is a linear or branched alkyl group having 4 to 11 carbon atoms. In formula (2-3), Z is an oxygen atom or a methylene group (-CH2-), and R' is a linear or branched alkyl group having 5 to 9 carbon atoms.

[0030] The second example of an anthraquinone derivative has an NHR group at one end of its molecular structure, in a position that does not form a hydrogen bond with the oxygen atom attached to the anthraquinone skeleton, and a ZR' group at the other end of its molecular structure. When both ends of the molecular structure, i.e., X and Y, each have a ZR' group, it is possible to absorb light in a different wavelength range than the first example of anthraquinone derivative, although the absorption wavelength range is narrower.

[0031] In the second example of anthraquinone derivatives, since X is an NHR group and Y is a ZR' group, it is possible to absorb light in a wavelength range that includes not only the absorption wavelength range when X and Y are both NHR groups, but also the absorption wavelength range when X and Y are both ZR' groups. Therefore, compared to the first example, although the absorbance at the absorption maximum wavelength is reduced, the absorption wavelength range can be further broadened.

[0032] In these first and second examples of anthraquinone derivatives, the absorption maximum wavelength is obtained in the wavelength range of 470 nm to 600 nm, making them usable as magenta-based dyes. Furthermore, as mentioned above, the absorption wavelength range is broadened in the first and second examples of anthraquinone derivatives, allowing for broad absorption of light with wavelengths around 555 nm.

[0033] Furthermore, the anthraquinone derivatives of the first and second examples exhibit high lightfastness compared to dichroic dyes such as azo dyes. In particular, the anthraquinone derivative of the second example is prone to achieving high lightfastness. Therefore, even when anthraquinone derivatives are used in articles exposed to light, their absorption properties can be maintained for extended periods.

[0034] In the first and second examples of anthraquinone derivatives, it is preferable that at least one of X and Y has a branched alkyl group. In other words, in the first example of anthraquinone derivatives, it is preferable that R in formula (1-2) is a branched alkyl group having 4 to 11 carbon atoms in at least one of X and Y in formula (1-1). In the second example of anthraquinone derivatives, it is preferable that at least one of the following conditions is met: R in formula (2-2) is a branched alkyl group having 4 to 11 carbon atoms, and R' in formula (2-3) is a branched alkyl group having 5 to 9 carbon atoms.

[0035] In anthraquinone derivatives, if at least one of X and Y has a branched alkyl group, the alkyl chain is branched around the ends of the molecular structure, making it difficult for molecules to come into close proximity to each other. Therefore, aggregation of anthraquinone derivatives is suppressed, and the solubility of the anthraquinone derivative in both the liquid crystal and the monomer is increased.

[0036] Another method to increase solubility in liquid crystals is to introduce substituents containing structures that frequently appear as partial structures of liquid crystal molecules, such as fluorine-containing functional groups or cyclohexane rings, into the dichroic dye molecule, thereby increasing the affinity between the liquid crystal and the dichroic dye.

[0037] On the other hand, in this embodiment, by focusing on suppressing the aggregation of dichroic dye molecules and introducing a branched alkyl group, we discovered an anthraquinone derivative that exhibits high solubility in liquid crystals from a different perspective than the affinity between liquid crystals and dichroic dyes.

[0038] Since suppressing the aggregation of dichroic dye molecules to improve solubility is effective not only for liquid crystals but also for monomers, high solubility can be obtained for monomers by including a branched alkyl group in at least one of X and Y.

[0039] Generally, monomers have a lower structural affinity for anthraquinone derivatives than liquid crystals, so even anthraquinone derivatives that are highly soluble in liquid crystals may have insufficient solubility in monomers. In contrast, the branched alkyl group anthraquinone derivative of this embodiment exhibits high solubility in monomers as well, making it suitable for use in liquid crystal elements manufactured from a mixture of liquid crystal, monomer, and dichroic dye, such as dimmable sheets.

[0040] Furthermore, for use as a dichroic dye, a high dichroism ratio is preferable. Specifically, a dichroism ratio of 7 or higher is preferable. To improve the dichroism ratio, it is advantageous that the orientation of the dichroic dye can easily follow the orientation of the liquid crystal. Generally, an increase in the steric bulk of the dichroic dye molecule leads to an increase in steric repulsion with the liquid crystal molecule, which reduces the ability of the dichroic dye orientation to follow the liquid crystal and is therefore unfavorable for improving the dichroism ratio. However, with the anthraquinone derivative of this embodiment, even if it has a branched alkyl group, the introduced substituent has enough flexibility to keep the steric repulsion with the liquid crystal molecule within an acceptable range, thus enabling the expression of a high dichroism ratio. The dichroism ratio is the ratio of the absorbance of polarization parallel to the long axis of the dichroic dye to the absorbance of polarization perpendicular to the long axis of the dichroic dye.

[0041] The structure of the branched alkyl group included in at least one of X and Y will be described further. Preferably, the branched alkyl group has one branching point and one side chain. With such a structure, compounds used in the synthesis of anthraquinone derivatives can be easily obtained, reducing the burden required for synthesis. In addition, excessive bulk of the molecule can be suppressed. The branched alkyl group is represented by the general formula (3) below. In formula (3) below, n, m, and l are each independently integers of 1 or more. -C n H 2n-1 (C m H 2m+1 )C l H 2l+1 ...(3)

[0042] In formula (3) above, n is preferably an integer between 1 and 5. With such a structure, it is easier to lengthen the alkyl chain beyond the branching point within the preferred range of carbon atoms, thereby achieving a high level of suppression of molecular aggregation. From the viewpoint of further enhancing this effect, n is preferably 1. That is, in the NHR group, the carbon atom bonded to the nitrogen atom is the first carbon, and in the ZR' group, the carbon atom bonded to Z is the first carbon, and it is preferable that the first carbon is the carbon atom at the branching point, and that two carbon atoms are bonded to the first carbon.

[0043] In formula (3) above, it is preferable that m and l are each independently integers between 1 and 5. That is, the alkyl chain bonded to the carbon atom at the branching point, including the end of the molecule, preferably has 1 to 5 carbon atoms. With this structure, the bulkiness of the branched alkyl group is suppressed. For example, when R in the NHR group is a branched alkyl group, m and l may each independently be between 1 and 5. Also, when R' in the ZR' group is a branched alkyl group, m and l may each independently be between 1 and 4.

[0044] In the above formula (3), when n is 1 and m and l are equal, the branched alkyl group is -CH(C m H 2m+1It is represented by the general formula 2. With such a structure, compounds used in the synthesis of anthraquinone derivatives can be easily obtained, and the burden on synthesis can be reduced.

[0045] Furthermore, in the anthraquinone derivative of this embodiment, if X and Y are different from each other, the molecular structure is asymmetrical, which suppresses the high crystallinity of the anthraquinone derivative. High crystallinity makes it difficult for the molecular aggregate structure of the anthraquinone derivative to be dissolved in liquid, so lower crystallinity results in higher solubility of the anthraquinone derivative in both liquid crystals and monomers. Therefore, in a structure where X and Y are different from each other, the solubility in both liquid crystals and monomers is higher compared to a structure where X and Y are the same. In addition, lower crystallinity suppresses the precipitation of the anthraquinone derivative even when liquid crystal elements using the anthraquinone derivative are stored for a long period of time, thus improving the reliability of the liquid crystal elements.

[0046] The anthraquinone derivatives of this embodiment can be produced, for example, by introducing each substituent to the anthraquinone skeleton using antralphine as a starting material. Any known method can be used to introduce the substituents. For example, the desired substituent can be introduced to the precursor by reacting a precursor in which the 2,6 positions of antralphine are iodized with a boronic acid ester having the desired substituent. In such a production method, the precursor having an anthraquinone skeleton and the boronic acid ester having the desired substituent, which are intermediates used in the synthesis, can be synthesized separately in parallel. Therefore, compared to production methods in which functional groups constituting the dye are attached one by one, anthraquinone derivatives can be produced in a shorter time.

[0047] [Pigment composition] The dye composition of this embodiment is a composition containing a dichroic dye which is an anthraquinone derivative as described above. Specific examples of the dye composition are a liquid crystal composition or a monomer composition.

[0048] The liquid crystal composition comprises a dichroic dye, which is an anthraquinone derivative as described above, and a liquid crystal compound. The liquid crystal composition is used in the liquid crystal layer of liquid crystal elements such as liquid crystal display devices and dimming sheets. The monomer composition comprises a dichroic dye, which is an anthraquinone derivative as described above, a liquid crystal compound, and a polymerizable compound. That is, the monomer composition may be a mixture of the liquid crystal composition and the polymerizable compound. The monomer composition is used to manufacture a liquid crystal layer having a structure in which liquid crystals are dispersed within a polymer layer. An example of a liquid crystal element having such a liquid crystal layer is a light-adjustable sheet.

[0049] The liquid crystal compounds included in the liquid crystal composition preferably have a cyclic structure and side chains such as alkyl chains in their molecular structure. Furthermore, it is preferable that the liquid crystal composition contains multiple types of liquid crystal compounds. In order to achieve rapid switching of liquid crystal orientation in a liquid crystal element under typical operating conditions, it is preferable that the liquid crystal components included in the liquid crystal composition exhibit a nematic phase in a temperature range of -30°C to 130°C.

[0050] In order to exhibit the nematic phase within the above temperature range, the number of cyclic structures in the liquid crystal compound is preferably 2 to 4, and the number of carbon atoms in the alkyl side chains of the liquid crystal compound is preferably 1 to 7. The anthraquinone derivative of this embodiment has high solubility in liquid crystals composed of liquid crystal compounds with such structures.

[0051] Examples of liquid crystal compounds included in liquid crystal compositions include 4'-ethoxybenzylidene-4-butylaniline, 4-cyano-4'-pentylbiphenyl, 4-cyano-4''-pentyl-p-terphenyl, 4-aminophenyl aminobenzoate, 1,2-diphenylacetylene, 4-[trans-4-[(E)-1-propenyl]cyclohexyl]benzonitrile, 4-cyano-4'-pentylbiphenylcyclohexane, 4-fluoro-4'-(trans-4-propylcyclohexyl)biphenyl, and 1-fluoro-4-[4-(4-pentylcyclohexyl)phenyl]benzene.

[0052] The liquid crystal composition may contain liquid crystal compounds that include a structure in which two or more benzene rings are bonded. For example, the liquid crystal composition may contain a biphenyl-based liquid crystal compound. Furthermore, among the multiple types of liquid crystal compounds contained in the liquid crystal composition, the liquid crystal compound containing a structure in which two or more benzene rings are bonded may have the largest mass proportion. For example, the liquid crystal composition may contain a biphenyl-based liquid crystal as its main component. The main component is the liquid crystal compound that has the largest mass proportion among the liquid crystal compounds contained in the liquid crystal composition. Because liquid crystal compounds containing a structure in which two or more benzene rings are bonded have a high structural affinity with the anthraquinone derivative of this embodiment, the anthraquinone derivative of this embodiment has high solubility in liquid crystal compositions containing liquid crystal compounds of such a structure.

[0053] The liquid crystal composition may contain at least one of a liquid crystal compound having one benzene ring and a liquid crystal compound not having a benzene ring. For example, the liquid crystal composition may contain at least one of a monophenyl liquid crystal compound and a bicyclohexane-based liquid crystal compound. Furthermore, the largest mass proportion of the liquid crystal compounds in the liquid crystal composition may be the liquid crystal compound having one benzene ring and the liquid crystal compound not having a benzene ring. The anthraquinone derivative of this embodiment has good solubility even in liquid crystal compositions containing liquid crystal compounds of this structure.

[0054] The polymerizable compound contained in the monomer composition is preferably an ultraviolet-curable compound having a polymerizable functional group in its molecular structure. The polymerizable compound is preferably at least one selected from the group consisting of (meth)acrylates, thiols, and oligomers of each of these compounds. The (meth)acrylate is preferably at least one selected from the group consisting of monofunctional, difunctional, trifunctional, and tetrafunctional (meth)acrylates. The anthraquinone derivative of this embodiment has high solubility in liquids consisting of polymerizable compounds of such structures. Note that "(meth)acrylate" is a general term for acrylates and methacrylates.

[0055] Examples of (meth)acrylates contained in monomer compositions include methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, isobolonyl acrylate, methoxypolyethylene glycol acrylate, 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, dipropylene glycol diacrylate, polypropylene glycol diacrylate, neopentyl glycol hydroxypivalate diacrylate, 3-[2,2-dimethyl-3-[[1-oxo-6-(propenoyloxy)hexyl]oxy]propoxy]-2,2-dimethyl-3-oxopropyl 6-(propenoyloxy)hexanoate, trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, propoxylated pentaerythritol tetraacrylate, and the like. Examples of thiols contained in monomer compositions include 1,3-propanedithiol and 1,6-hexanedithiol.

[0056] The monomer composition may contain a (meth)acrylate having a first structure in which a saturated hydrocarbon group with 6 or fewer carbon atoms is bonded to a (meth)acryloyloxy group, and the mass proportion of the (meth)acrylate having the first structure may be the largest among the polymerizable compounds contained in the monomer composition. Because the molecular size of the (meth)acrylate having the first structure is not too large, it easily fits between the molecules of the anthraquinone derivative. Therefore, the anthraquinone derivative of this embodiment has good solubility in the monomer composition containing the (meth)acrylate having the first structure. Examples of (meth)acrylate having the first structure are ethyl acrylate and cyclohexyl acrylate.

[0057] Furthermore, the monomer composition may contain a (meth)acrylate having a second structure in which a chain-like saturated hydrocarbon group with 5 or fewer carbon atoms is bonded to a (meth)acryloyloxy group, and the mass proportion of the (meth)acrylate having the second structure may be the largest among the polymerizable compounds contained in the monomer composition. The molecular size of the (meth)acrylate having the second structure is smaller than that of the (meth)acrylate containing a cyclic saturated hydrocarbon group. Therefore, the anthraquinone derivative of this embodiment has high solubility in monomer compositions containing the (meth)acrylate having the second structure. An example of a (meth)acrylate having the second structure is ethyl acrylate.

[0058] The monomer composition may further contain one or more polymerization initiators. Examples of polymerization initiators include diketone compounds, acetophenone compounds, benzoin compounds, benzophenone compounds, thioxanthone compounds, and the like.

[0059] The dye composition may contain other dichroic dyes in addition to the anthraquinone derivative of this embodiment. Preferably, the content of dichroic dyes, including the anthraquinone derivative of this embodiment, in the dye composition is 0.5% by mass or more and 10% by mass or less. Within this range, good solubility of the anthraquinone derivative is possible. The dye composition may also contain various additives.

[0060] [Dimmable sheet] Referring to Figure 1, the configuration of the dimming sheet of this embodiment will be described. As shown in Figure 1, the dimming sheet 10 comprises a dimming layer 20, which is an example of a liquid crystal layer, a first transparent electrode layer 31, a second transparent electrode layer 32, a first transparent support layer 41, and a second transparent support layer 42. The dimming layer 20 is sandwiched between the first transparent electrode layer 31 and the second transparent electrode layer 32 and is in contact with these transparent electrode layers 31 and 32. The first transparent support layer 41 supports the first transparent electrode layer 31 on the side opposite to the dimming layer 20. The second transparent support layer 42 supports the second transparent electrode layer 32 on the side opposite to the dimming layer 20.

[0061] The light-adjusting layer 20 comprises a transparent polymer layer and the liquid crystal composition described above, and is formed from the monomer composition described above. That is, the transparent polymer layer is a polymer of the polymerizable compound contained in the monomer composition. The transparent polymer layer has a plurality of voids, and the liquid crystal composition fills these voids. The shape of the voids is spherical, ellipsoidal, or irregular.

[0062] The structure for holding the liquid crystal composition in the dimming layer 20 is either a polymer network type or a polymer dispersion type. The polymer network type dimming layer 20 comprises a polymer network having a three-dimensional mesh structure. The polymer network is an example of a transparent polymer layer, and the liquid crystal composition is held in the interconnected voids of the polymer network. The polymer dispersion type dimming layer 20 comprises a transparent polymer layer that partitions a number of isolated voids, and the liquid crystal composition is held in the voids dispersed in the transparent polymer layer.

[0063] The dielectric anisotropy of the liquid crystal compound contained in the liquid crystal composition is, for example, positive. The dichroic dye is oriented using a guest-host method with the liquid crystal compound as the host, and exhibits a predetermined color when its long axis is substantially perpendicular to the direction of incident light. In addition to the liquid crystal compound and dichroic dye, the liquid crystal composition may also contain viscosity reducers, defoamers, antioxidants, weather stabilizers, etc. Examples of weather stabilizers include ultraviolet absorbers and light stabilizers.

[0064] Furthermore, the light-adjusting layer 20 may include spacers dispersed throughout the transparent polymer layer. The spacers uniformize the thickness of the light-adjusting layer 20 by defining its thickness around the spacers. The spacers may be bead spacers or photospacers formed by exposure and development of the photoresist, as long as they are light-transmitting.

[0065] The spacer may be colorless and transparent, or colored and transparent. Preferably, the spacer is colored and transparent, and the color exhibited by the spacer is the same as the color exhibited by the dichroic dye of the light-adjusting layer 20, that is, the color of the opaque light-adjusting sheet 10. For example, the liquid crystal composition contains multiple types of dichroic dyes, thereby the opaque light-adjusting sheet 10 may exhibit a color that is black or close to black.

[0066] Each of the first transparent electrode layer 31 and the second transparent electrode layer 32 is conductive and transparent to visible light. The materials for the transparent electrode layers 31 and 32 include, for example, indium tin oxide, fluorine-doped tin oxide, tin oxide, zinc oxide, carbon nanotubes, poly(3,4-ethylenedioxythiophene), silver, and silver alloys.

[0067] Each of the first transparent support layer 41 and the second transparent support layer 42 is a substrate that is transparent to light in the visible region. The materials of the transparent support layers 41 and 42 are, for example, synthetic resins and inorganic compounds. Synthetic resins include, for example, polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyacrylates such as polymethyl methacrylate, polycarbonates, and polyolefins. Inorganic compounds include, for example, silicon dioxide, silicon oxynitride, and silicon nitride.

[0068] The transparent electrode layers 31 and 32 are electrically connected to the control unit 50 via wiring. The control unit 50 applies a drive voltage, which is an AC voltage for changing the orientation state of the liquid crystal compound, to the transparent electrode layers 31 and 32 via the wiring. The control unit 50 controls the potential difference between the transparent electrode layers 31 and 32 by controlling whether or not the voltage is applied and by controlling the magnitude of the applied voltage. The dimming device is composed of the dimming sheet 10 and the control unit 50.

[0069] The dimming sheet 10 switches between a transparent state and an opaque state based on a change in the orientation state of the liquid crystal compound. The transparent state is a state with relatively high light transmittance, and the opaque state is a state with relatively low light transmittance.

[0070] When no driving voltage is applied, the orientation of the liquid crystal compound along its long axis is irregular. As a result, due to the birefringence of the liquid crystal compound and the refractive index difference between the liquid crystal compound and the transparent polymer layer, light incident on the dimming sheet 10 is scattered in various directions by the dimming layer 20. At this time, since the orientation of the dichroic dye along its long axis is also disordered, at least a portion of the dichroic dye exhibits color. Therefore, the dimming sheet 10 becomes opaque when no driving voltage is applied. In the opaque state, the dimming sheet 10 appears in a color corresponding to the color exhibited by the dichroic dye.

[0071] When a driving voltage is applied, the liquid crystal compound, which has positive dielectric anisotropy, is oriented so that its long axis aligns with the direction of the electric field. In other words, the orientation of the liquid crystal compound changes so that its long axis aligns with the thickness direction of the dichroic layer 20. Consequently, the dichroic dye is also oriented so that its long axis aligns with the direction of the electric field. As a result, light scattering and absorption in the dichroic layer 20 are suppressed, and light is more easily transmitted through the dichroic sheet 10. Therefore, the dichroic sheet 10 becomes transparent when a driving voltage is applied.

[0072] By using the anthraquinone derivative of this embodiment as a dichroic dye, it is possible to absorb light across a wide wavelength range in the opaque state, thereby reducing the total light transmittance in the opaque state. Consequently, the contrast, which is the ratio of the total light transmittance in the transparent state to that in the opaque state, can be increased. For example, even if there is a large difference in transmittance at the absorption maximum wavelength of the dichroic dye between the transparent and opaque states, if the absorption wavelength range of the dichroic dye is narrow, the total light transmittance in the opaque state will not decrease significantly. In contrast, by using the anthraquinone derivative of this embodiment, it is possible to accurately reduce the total light transmittance, which has a large impact on the transparency of the light-adjusting sheet 10, in the opaque state, thereby suitably increasing the contrast.

[0073] The dimming sheet 10 may also include layers different from those described above. For example, the dimming sheet 10 may include a pair of alignment layers sandwiching the dimming layer 20 between the dimming layer 20 and the transparent electrode layers 31 and 32. The alignment layers are layers that control the orientation of the liquid crystal compound, and when no driving voltage is applied, they orient the liquid crystal compound in a predetermined direction. The material of the alignment layer may be, for example, an organic compound such as polyimide, polyamide, polyvinyl alcohol, or a cyanide compound, an inorganic compound such as silicon oxide or zirconium oxide, or silicone.

[0074] The alignment layer is, for example, a vertical alignment film, in which the liquid crystal compound is aligned perpendicular to the alignment layer. In this case, by using a compound having negative dielectric anisotropy as the liquid crystal compound, when a driving voltage is applied to the transparent electrode layers 31 and 32, the liquid crystal compound and dichroic dye are aligned parallel to the transparent electrode layers 31 and 32. As a result, when no driving voltage is applied to the transparent electrode layers 31 and 32, the dimming sheet 10 is transparent, and when a driving voltage is applied to the transparent electrode layers 31 and 32, the dimming sheet 10 is opaque.

[0075] The dielectric anisotropy of the liquid crystal compound can be appropriately selected according to the direction in which the orientation-regulating force of the orientation layer acts. Furthermore, whether the dimming sheet 10 becomes transparent or opaque when a driving voltage is applied can be changed by the presence or absence of an orientation layer, the direction in which the orientation-regulating force of the orientation layer acts, the sign of dielectric anisotropy in the liquid crystal compound, etc.

[0076] At least one of the front and back surfaces of the dimming sheet 10 is attached to a transparent plate made of glass, resin, or the like. The transparent plate is, for example, a windowpane in various buildings, a partition installed indoors, or a windowpane or windshield in a moving object such as a vehicle or aircraft. The surface of the transparent plate may be flat or curved.

[0077] [Manufacturing method for dimmable sheets] A method for manufacturing the dimming sheet 10 will now be described. First, a first transparent support layer 41 on which a first transparent electrode layer 31 is laminated, and a second transparent support layer 42 on which a second transparent electrode layer 32 is laminated are prepared. The transparent electrode layers 31 and 32 are formed by known film deposition methods such as sputtering.

[0078] Then, a coating film for forming a light-adjusting layer 20 is formed between the first transparent electrode layer 31 and the second transparent electrode layer 32. The coating film is formed by applying a coating liquid which is the monomer composition described above. The monomer composition includes a liquid crystal composition containing the anthraquinone derivative and liquid crystal compound of this embodiment, a polymerizable compound, and a polymerization initiator. The spacer may be dispersed in the coating film after its formation, or it may be dispersed in the coating film by being mixed with the coating liquid.

[0079] When light such as ultraviolet light is irradiated onto the laminate in which the coating film is sandwiched between transparent electrode layers 31 and 32, the polymerizable compound is polymerized, causing phase separation of the liquid crystal composition and forming the light-adjusting layer 20. This forms the light-adjusting sheet 10.

[0080] The applications of the anthraquinone derivative and dye composition of this embodiment are not limited to the light-adjusting sheet 10 described above. For example, the anthraquinone derivative of this embodiment may be used in a light-adjusting sheet having a light-adjusting layer that does not contain a transparent polymer layer, in the liquid crystal layer of a liquid crystal display device, or in a polarizing film.

[0081] [Examples] The anthraquinone derivatives and dye compositions described above will be explained using specific examples.

[0082] (Example 1) <Synthesis of precursor P1> As shown in the reaction scheme below, precursor P1 was obtained by introducing an iodine atom into the starting material, antralphine. A known method was used for introducing the iodine atom.

[0083] [ka]

[0084] <Synthesis of anthraquinone derivatives> Boronic acid ester A1 was obtained according to the reaction scheme shown below.

[0085] [ka]

[0086] The detailed procedure is described below. 4-aminophenylboronic acid pinacol ester and potassium carbonate (3.0 equivalents) were placed in a two-necked flask. Dimethylformamide was added to achieve a molar concentration of 4-aminophenylboronic acid pinacol ester of 0.2 mol / L, and then 1-bromobutane (1.2 equivalents) was added. The mixture was heated and stirred at 120°C. After 8 hours, the mixture was allowed to return to room temperature, and then liquid-liquid separation was performed using toluene and water. The resulting organic phase was washed with saturated brine and dried over sodium sulfate. The solvent was removed by vacuum distillation using an evaporator, and then the mixture was purified by silica gel column chromatography (developing solvent: hexane / acetone = 10 / 1) to obtain boronic acid ester A1. The yield of boronic acid ester A1 was 42%.

[0087] The dichroic dye D1, an anthraquinone derivative of Example 1, was obtained according to the reaction scheme described below.

[0088] [ka]

[0089] The detailed procedure is described below. In a two-necked flask, precursor P1, boronic acid ester A1 (2.8 equivalents), PdCl2 (dppf) (0.1 equivalent), and sodium carbonate (3.5 equivalents) were added, and a Liebig tube was attached to purge the flask with nitrogen. To this, toluene / ethanol / water (volume ratio: toluene / ethanol / water = 5 / 1.3 / 1) was added to achieve a molar concentration of precursor P1 of 0.05 mol / L, and the mixture was bubbling with nitrogen for 20 minutes. After that, the mixture was heated and stirred at 90°C for 4 hours. After cooling to room temperature, liquid-liquid separation was performed using chloroform and water, and the organic phase was dried with sodium sulfate. After filtering off the sodium sulfate and concentrating the solution, it was purified by silica gel column chromatography (developing solvent: chloroform only) to obtain the dichroic dye D1. The yield of dichroic dye D1 was 38%.

[0090] (Example 2) <Synthesis of anthraquinone derivatives> Boronic acid ester A2 was obtained according to the reaction scheme shown below.

[0091] [ka]

[0092] The detailed procedure is described below. 4-aminophenylboronic acid pinacol ester and potassium carbonate (3.0 equivalents) were placed in a two-necked flask. Dimethylformamide was added to achieve a molar concentration of 4-aminophenylboronic acid pinacol ester of 0.2 mol / L, and then 1-bromoheptane (1.2 equivalents) was added. The mixture was heated and stirred at 120°C. After 8 hours, the mixture was allowed to return to room temperature, and then liquid-liquid separation was performed using toluene and water. The resulting organic phase was washed with saturated brine and dried over sodium sulfate. The solvent was removed by vacuum distillation using an evaporator, and then the mixture was purified by silica gel column chromatography (developing solvent: hexane / acetone = 10 / 1) to obtain boronic acid ester A2. The yield of boronic acid ester A2 was 45%.

[0093] The dichroic dye D2, an anthraquinone derivative of Example 2, was obtained according to the reaction scheme described below.

[0094] [ka]

[0095] The detailed procedure is described below. In a two-necked flask, precursor P1, boronic acid ester A2 (2.8 equivalents), PdCl2 (dppf) (0.1 equivalent), and sodium carbonate (3.5 equivalents) were added, and a Liebig tube was attached to purge the flask with nitrogen. To this, toluene / ethanol / water (volume ratio: toluene / ethanol / water = 5 / 1.3 / 1) was added to achieve a molar concentration of precursor P1 of 0.05 mol / L, and the mixture was bubbling with nitrogen for 20 minutes. After that, the mixture was heated and stirred at 90°C for 4 hours. After cooling to room temperature, liquid-liquid separation was performed using chloroform and water, and the organic phase was dried with sodium sulfate. After filtering off the sodium sulfate and concentrating the solution, it was purified by silica gel column chromatography (developing solvent: chloroform only) to obtain the dichroic dye D2. The yield of dichroic dye D2 was 40%.

[0096] (Example 3) <Synthesis of anthraquinone derivatives> Boronic acid ester A3 was obtained according to the reaction scheme shown below.

[0097] [ka]

[0098] The detailed procedure is described below. 4-aminophenylboronic acid pinacol ester and potassium carbonate (3.0 equivalents) were placed in a two-necked flask. Dimethylformamide was added to achieve a molar concentration of 4-aminophenylboronic acid pinacol ester of 0.2 mol / L, and then 4-bromoheptane (3.0 equivalents) was added. The mixture was heated and stirred at 120°C. After 3 hours, 4-bromoheptane (3.0 equivalents) was added, and the mixture was heated and stirred for another hour. After returning to room temperature, the mixture was separated using toluene and water, and the resulting organic phase was washed with saturated brine and dried over sodium sulfate. The solvent was removed by vacuum distillation using an evaporator, and the mixture was purified by silica gel column chromatography (developing solvent: chloroform / hexane = 5 / 1, changed to chloroform only midway through the process) to obtain boronic acid ester A3. The yield of boronic acid ester A3 was 15%.

[0099] The dichroic dye D3, an anthraquinone derivative of Example 3, was obtained according to the reaction scheme described below.

[0100] [ka]

[0101] The detailed procedure is described below. In a two-necked flask, precursor P1, boronic acid ester A3 (2.3 equivalents), PdCl2 (dppf) (0.1 equivalent), and sodium carbonate (3.5 equivalents) were added, and a Liebig tube was attached to purge the flask with nitrogen. To this, toluene / ethanol / water (volume ratio: toluene / ethanol / water = 5 / 1.3 / 1) was added to achieve a molar concentration of precursor P1 of 0.04 mol / L, and the mixture was bubbling with nitrogen for 20 minutes. Then, the mixture was heated and stirred at 90°C for 4 hours. After cooling to room temperature, liquid-liquid separation was performed using chloroform and water, and the organic phase was dried with sodium sulfate. After filtering off the sodium sulfate and concentrating the solution, it was purified by preparative thin-layer chromatography (developing solvent: hexane / ethyl acetate = 10 / 1) to obtain the dichroic dye D3. The yield of dichroic dye D3 was 21%.

[0102] (Example 4) <Synthesis of anthraquinone derivatives> Boronic acid ester A4 was obtained according to the reaction scheme shown below.

[0103] [ka]

[0104] The detailed procedure is described below. Pinacol 4-aminophenylboronic acid and potassium carbonate (3.0 equivalents) were placed in a two-necked flask. Dimethylformamide was added to this mixture until the molar concentration of pinacol 4-aminophenylboronic acid was 0.2 mol / L, and then 6-bromoundecane (3.0 equivalents) was added. The mixture was heated and stirred at 120°C. After 3 hours, 6-bromoundecane (3.0 equivalents) was added, and the mixture was heated and stirred for another hour. After returning to room temperature, the mixture was separated using toluene and water, and the resulting organic phase was washed with saturated brine and dried over sodium sulfate. The solvent was removed by vacuum distillation using an evaporator, and the mixture was purified by silica gel column chromatography (developing solvent: chloroform / hexane = 5 / 1, changed to chloroform only midway through the process) to obtain boronic acid ester A4. The yield of boronic acid ester A4 was 13%.

[0105] The dichroic dye D4, an anthraquinone derivative of Example 4, was obtained according to the reaction scheme described below.

[0106] [ka]

[0107] The detailed procedure is described below. In a two-necked flask, precursor P1, boronic acid ester A4 (2.3 equivalents), PdCl2 (dppf) (0.1 equivalent), and sodium carbonate (3.5 equivalents) were added, and a Liebig tube was attached to purge the flask with nitrogen. To this, toluene / ethanol / water (volume ratio: toluene / ethanol / water = 5 / 1.3 / 1) was added to achieve a molar concentration of precursor P1 of 0.04 mol / L, and the mixture was bubbling with nitrogen for 20 minutes. Then, the mixture was heated and stirred at 90°C for 4 hours. After cooling to room temperature, liquid-liquid separation was performed using chloroform and water, and the organic phase was dried with sodium sulfate. After filtering off the sodium sulfate and concentrating the solution, it was purified by preparative thin-layer chromatography (developing solvent: hexane / ethyl acetate = 10 / 1) to obtain the dichroic dye D4. The yield of dichroic dye D4 was 22%.

[0108] (Example 5) <Synthesis of anthraquinone derivatives> The dichroic dye D5, an anthraquinone derivative of Example 5, was obtained according to the reaction scheme described below.

[0109] [ka]

[0110] The detailed procedure is described below. In a two-necked flask, precursor P1, boronic acid ester A2 (1.2 equivalents), boronic acid ester A3 (1.2 equivalents), PdCl2 (dppf) (0.1 equivalent), and sodium carbonate (3.5 equivalents) were added, and a Liebig tube was attached to purge the flask with nitrogen. To this, toluene / ethanol / water (volume ratio: toluene / ethanol / water = 5 / 1.3 / 1) was added to achieve a molar concentration of precursor P1 of 0.04 mol / L, and the mixture was bubbling with nitrogen for 20 minutes. Then, the mixture was heated and stirred at 90°C for 4 hours. After cooling to room temperature, liquid-liquid separation was performed using chloroform and water, and the organic phase was dried over sodium sulfate. After filtering off the sodium sulfate and concentrating the solution, it was purified by preparative thin-layer chromatography (developing solvent: hexane / ethyl acetate = 10 / 1) to obtain the dichroic dye D5. The yield of dichroic dye D5 was 13%.

[0111] (Example 6) <Synthesis of anthraquinone derivatives> Boronic acid ester A5 was obtained according to the reaction scheme shown below.

[0112] [ka]

[0113] The detailed procedure is described below. Boronic acid B1 and pinacol (1.0 equivalent) were added to a two-necked flask. Dichloromethane was added until the molar concentration of boronic acid B1 reached 0.2 mol / L, and the mixture was heated and stirred under reflux for 1 hour. The solvent was then removed by vacuum distillation using an evaporator, and the mixture was purified by silica gel column chromatography (solvent: chloroform / hexane = 2 / 1) to obtain boronic acid ester A5. The yield of boronic acid ester A5 was 80%.

[0114] The dichroic dye D6, an anthraquinone derivative of Example 6, was obtained according to the reaction scheme described below.

[0115] [ka]

[0116] The detailed procedure is described below. In a two-necked flask, precursor P1, boronic acid ester A2 (1.2 equivalents), boronic acid ester A5 (1.2 equivalents), PdCl2 (dppf) (0.1 equivalent), and sodium carbonate (3.5 equivalents) were added, and a Liebig tube was attached to purge the flask with nitrogen. To this, toluene / ethanol / water (volume ratio: toluene / ethanol / water = 5 / 1.3 / 1) was added to achieve a molar concentration of precursor P1 of 0.05 mol / L, and the mixture was bubbling with nitrogen for 20 minutes. Then, the mixture was heated and stirred at 90°C for 4 hours. After cooling to room temperature, liquid-liquid separation was performed using chloroform and water, and the organic phase was dried with sodium sulfate. After filtering off the sodium sulfate and concentrating the solution, it was purified twice by preparative thin-layer chromatography (developing solvent: chloroform / hexane = 2 / 1) to obtain the dichroic dye D6. The yield of dichroic dye D6 was 20%.

[0117] (Example 7) <Synthesis of anthraquinone derivatives> Boronic acid ester A6 was obtained according to the reaction scheme shown below.

[0118] [ka]

[0119] The detailed procedure is described below. Boronic acid B2 and pinacol (1.0 equivalent) were added to a two-necked flask. Dichloromethane was added until the molar concentration of boronic acid B2 reached 0.2 mol / L, and the mixture was heated and stirred under reflux for 1 hour. The solvent was then removed by vacuum distillation using an evaporator, and the mixture was purified by silica gel column chromatography (solvent: chloroform / hexane = 2 / 1) to obtain boronic acid ester A6. The yield of boronic acid ester A6 was 76%.

[0120] The dichroic dye D7, an anthraquinone derivative of Example 7, was obtained according to the reaction scheme described below.

[0121] [ka]

[0122] The detailed procedure is described below. In a two-necked flask, precursor P1, boronic acid ester A2 (1.2 equivalents), boronic acid ester A6 (1.2 equivalents), PdCl2 (dppf) (0.1 equivalent), and sodium carbonate (3.5 equivalents) were added, and a Liebig tube was attached to purge the flask with nitrogen. To this, toluene / ethanol / water (volume ratio: toluene / ethanol / water = 5 / 1.3 / 1) was added to achieve a molar concentration of precursor P1 of 0.05 mol / L, and the mixture was bubbling with nitrogen for 20 minutes. After that, the mixture was heated and stirred at 90°C for 4 hours. After cooling to room temperature, liquid-liquid separation was performed using chloroform and water, and the organic phase was dried with sodium sulfate. After filtering off the sodium sulfate and concentrating the solution, it was purified twice by preparative thin-layer chromatography (developing solvent: chloroform / hexane = 2 / 1) to obtain the dichroic dye D7. The yield of dichroic dye D7 was 24%.

[0123] (Example 8) <Synthesis of anthraquinone derivatives> The dichroic dye D8, an anthraquinone derivative of Example 8, was obtained according to the reaction scheme described below.

[0124] [ka]

[0125] The detailed procedure is described below. In a two-necked flask, precursor P1, boronic acid ester A3 (1.2 equivalents), boronic acid ester A6 (1.2 equivalents), PdCl2 (dppf) (0.1 equivalent), and sodium carbonate (3.5 equivalents) were added, and a Liebig tube was attached to purge the flask with nitrogen. To this, toluene / ethanol / water (volume ratio: toluene / ethanol / water = 5 / 1.3 / 1) was added to achieve a molar concentration of precursor P1 of 0.05 mol / L, and the mixture was bubbling with nitrogen for 20 minutes. Then, the mixture was heated and stirred at 90°C for 4 hours. After cooling to room temperature, liquid-liquid separation was performed using chloroform and water, and the organic phase was dried with sodium sulfate. After filtering off the sodium sulfate and concentrating the solution, it was purified twice by preparative thin-layer chromatography (developing solvent: dichloromethane / hexane = 1 / 1) to obtain the dichroic dye D8. The yield of dichroic dye D8 was 20%.

[0126] (Example 9) <Synthesis of anthraquinone derivatives> Boronic acid ester A7 was obtained according to the reaction scheme shown below.

[0127] [ka]

[0128] The detailed procedure is described below. Boronic acid B3 and pinacol (1.0 equivalent) were added to a two-necked flask. Dichloromethane was added until the molar concentration of boronic acid B3 reached 0.2 mol / L, and the mixture was heated and stirred under reflux for 1 hour. The solvent was then removed by vacuum distillation using an evaporator, and the mixture was purified by silica gel column chromatography (solvent: chloroform / hexane = 2 / 1) to obtain boronic acid ester A7. The yield of boronic acid ester A7 was 75%.

[0129] The dichroic dye D9, an anthraquinone derivative of Example 9, was obtained according to the reaction scheme described below.

[0130] [ka]

[0131] The detailed procedure is described below. In a two-necked flask, precursor P1, boronic acid ester A3 (1.2 equivalents), boronic acid ester A7 (1.2 equivalents), PdCl2 (dppf) (0.1 equivalent), and sodium carbonate (3.5 equivalents) were added, and a Liebig tube was attached to purge the flask with nitrogen. To this, toluene / ethanol / water (volume ratio: toluene / ethanol / water = 5 / 1.3 / 1) was added to achieve a molar concentration of precursor P1 of 0.05 mol / L, and the mixture was bubbling with nitrogen for 20 minutes. Then, the mixture was heated and stirred at 90°C for 4 hours. After cooling to room temperature, liquid-liquid separation was performed using chloroform and water, and the organic phase was dried with sodium sulfate. After filtering off the sodium sulfate and concentrating the solution, it was purified twice by preparative thin-layer chromatography (developing solvent: dichloromethane / hexane = 1 / 1) to obtain the dichroic dye D9. The yield of dichroic dye D9 was 22%.

[0132] (Comparative Example 1) <Synthesis of precursor P2> As shown in the reaction scheme below, precursor P2 was obtained by introducing an iodine atom into the starting material, 1,5-diaminoanthraquinone. A known method was used for introducing the iodine atom.

[0133] [ka]

[0134] <Synthesis of anthraquinone derivatives> According to the reaction scheme below, the dichroic dye D10, an anthraquinone derivative of Comparative Example 1, was obtained.

[0135] [ka]

[0136] The detailed procedure is described below. In a two-necked flask, precursor P2, boronic acid B1 (1.4 equivalents), boronic acid B4 (1.4 equivalents), Pd(PPh3)4 (0.01 equivalent), and sodium carbonate (3.5 equivalents) were added, and a Liebig tube was attached to purge the flask with nitrogen. To this, toluene / ethanol / water (volume ratio: toluene / ethanol / water = 5 / 1.3 / 1) was added to achieve a molar concentration of precursor P2 of 0.05 mol / L, and the mixture was bubbling with nitrogen for 20 minutes. After that, the mixture was heated and stirred at 90°C for 9 hours. After cooling to room temperature, liquid-liquid separation was performed using ethyl acetate and water, and the organic phase was dried with sodium sulfate. After filtering off the sodium sulfate and concentrating the solution, the resulting residue was purified twice by silica gel column chromatography (developing solvent: hexane / ethyl acetate = 10 / 1) to obtain the dichroic dye D10. The yield of dichroic dye D10 was 21%.

[0137] (Comparative Example 2) <Synthesis of anthraquinone derivatives> According to the reaction scheme below, the dichroic dye D11, an anthraquinone derivative of Comparative Example 2, was obtained.

[0138] [ka]

[0139] The detailed procedure is described below. Dichroic dye D10 and potassium carbonate (2.3 equivalents) were added to a two-necked flask, and dimethylformamide was added to bring the concentration of dichroic dye D10 to 0.2 mol / L. After stirring this mixture at room temperature for 15 minutes, a Liebig tube was attached, and iodomethane (2.3 equivalents) was added dropwise, and the mixture was heated and stirred at 90°C. Iodomethane was added in 2.3 equivalents at 1 hour and 4.5 hours after the start of heating, and then 4.6 equivalents at 12 hours and 14 hours after the start of heating. After heating for 18 hours, the mixture was allowed to cool to room temperature, and then liquid-liquid separation was performed using toluene and water, and the organic phase was dried over sodium sulfate. After filtering off the sodium sulfate and concentrating the solution, the resulting residue was purified twice by preparative thin-layer chromatography (developing solvent: toluene / hexane = 2 / 1) to obtain dichroic dye D11. The yield of the dichroic pigment D11 was 9%.

[0140] (Comparative Example 3) <Synthesis of anthraquinone derivatives> According to the reaction scheme below, the dichroic dye D12, an anthraquinone derivative of Comparative Example 3, was obtained.

[0141] [ka]

[0142] The detailed procedure is described below. Dichroic dye D10 was added to a two-necked flask, and dichloromethane was added to achieve a molar concentration of 0.25 mol / L of dichroic dye D10. Triethylamine (2.2 equivalents) and acetyl chloride (2.4 equivalents) were added to this mixture, and the mixture was stirred at room temperature for 3 hours. Subsequently, liquid-liquid separation was performed using ethyl acetate and water, and the organic phase was dried over sodium sulfate. After filtering off the sodium sulfate and concentrating the solution, the resulting residue was purified by preparative thin-layer chromatography (eluent: toluene / ethanol = 20 / 1) to obtain dichroic dye D12. The yield of dichroic dye D12 was 24%.

[0143] (Comparative Example 4) <Synthesis of anthraquinone derivatives> According to the reaction scheme below, the dichroic dye D13, an anthraquinone derivative of Comparative Example 4, was obtained.

[0144] [ka]

[0145] The detailed procedure is described below. In a two-necked flask, precursor P1, boronic acid B2 (2.8 equivalents), PdCl2 (dppf) (0.01 equivalent), and sodium carbonate (3.5 equivalents) were added, and a Liebig tube was attached to purge the flask with nitrogen. To this, toluene / ethanol / water (volume ratio: toluene / ethanol / water = 5 / 1.3 / 1) was added to achieve a molar concentration of precursor P1 of 0.05 mol / L, and the mixture was bubbling with nitrogen for 20 minutes. After that, the mixture was heated and stirred at 90°C for 4 hours. After cooling to room temperature, liquid-liquid separation was performed using ethyl acetate and water, and the organic phase was dried with sodium sulfate. After filtering off the sodium sulfate and concentrating the solution, it was purified by silica gel column chromatography (developing solvent: chloroform / hexane = 2 / 1) to obtain the dichroic dye D13. The yield of dichroic dye D13 was 89%.

[0146] (Comparative Example 5) <Synthesis of anthraquinone derivatives> According to the reaction scheme below, the dichroic dye D14, an anthraquinone derivative of Comparative Example 5, was obtained.

[0147] [ka]

[0148] The detailed procedure is described below. In a two-necked flask, precursor P1, boronic acid B5 (2.8 equivalents), PdCl2 (dppf) (0.01 equivalent), and sodium carbonate (3.5 equivalents) were added, and a Liebig tube was attached to purge the flask with nitrogen. To this, toluene / ethanol / water (volume ratio: toluene / ethanol / water = 5 / 1.3 / 1) was added to achieve a molar concentration of precursor P1 of 0.05 mol / L, and the mixture was then heated and stirred at 90°C for 4 hours. After cooling to room temperature, liquid-liquid separation was performed using ethyl acetate and water, and the organic phase was dried over sodium sulfate. After filtering off the sodium sulfate and concentrating the solution, it was purified by recrystallization (solvent: tetrahydrofuran / hexane) to obtain the dichroic dye D14. The yield of dichroic dye D14 was 27%.

[0149] (Evaluation method) <Solubility: Liquid crystal> The dichroic dyes of each example and comparative example were mixed with each of the following liquid crystal mixtures L1 to L4, and their solubility was evaluated. Each of the following liquid crystal mixtures L1 to L4 is a mixture of multiple liquid crystal compounds. In the liquid crystal mixtures L1 and L3, the largest mass proportion is that of a liquid crystal compound containing a structure with two or more benzene rings bonded together. In the liquid crystal mixtures L2 and L4, the largest mass proportion is that of a liquid crystal compound having one benzene ring and a liquid crystal compound not having a benzene ring combined. L1: JC-5259XX (manufactured by JNC) L2: JC-7156XX (manufactured by JNC) L3: JC-5261XX (manufactured by JNC) L4:JC-7157XX (manufactured by JNC)

[0150] In the solubility evaluation test, the dichroic dye and liquid crystal mixture were mixed to a mass percentage concentration of 15%, and the mixture was heated and stirred at 150°C for 10 minutes. After that, it was allowed to cool at room temperature for 5 minutes, and the presence or absence of dichroic dye precipitation was visually determined. If dichroic dye precipitation was observed, the liquid crystal mixture was added to a mass percentage concentration of 12% of the dichroic dye, and the mixture was heated, stirred, and cooled in the same manner as above, after which the presence or absence of dichroic dye precipitation was visually determined. The same procedure was repeated to decrease the mass percentage concentration of the dichroic dye in the order of 9%, 6%, 3%, and 1.5% until it was determined that no dichroic dye precipitation occurred, thereby determining the upper limit of the mass percentage concentration at which the dichroic dye could dissolve.

[0151] <Solubility: Monomer> The dichroic dyes from each example and comparative example were mixed with the polymerizable compounds M1 and M2 described below, and their solubility was evaluated. M1: Cyclohexyl acrylate M2: Ethyl acrylate

[0152] In the solubility evaluation test, the dichroic dye and polymerizable compound were mixed to a mass percentage concentration of 10% and stirred at room temperature for 10 minutes. After that, the presence or absence of precipitation of the dichroic dye was visually determined. If precipitation of the dichroic dye was observed, the polymerizable compound was added to a mass percentage concentration of 8% of the dichroic dye, and after stirring in the same manner as above, the presence or absence of precipitation of the dichroic dye was visually determined. The same procedure was repeated to decrease the mass percentage concentration of the dichroic dye in the order of 6%, 2%, 0.1%, and 0.05% until it was determined that no precipitation of the dichroic dye occurred, thereby determining the upper limit of the mass percentage concentration at which the dichroic dye could be dissolved.

[0153] <Liquid crystal cell> For each example and comparative example, the dichroic dye was mixed with the L3 liquid crystal mixture so that the mass percentage concentration of the dichroic dye was 1.5%, and the mixture was heated and stirred at 120°C for 10 minutes, after which it was allowed to cool to room temperature to prepare a liquid crystal composition. The L3 liquid crystal mixture contains a biphenyl-based liquid crystal compound and a cyanophenyl-based liquid crystal compound.

[0154] A liquid crystal cell was fabricated by injecting the prepared liquid crystal composition into an evaluation cell (manufactured by EHC). The evaluation cell has a structure in which two glass plates (0.7 mm thick) are placed facing each other and sealed with epoxy resin. Each glass plate has a transparent electrode layer made of indium tin oxide and an alignment layer made of polyimide laminated on it, and the glass plates are arranged so that the alignment layers face each other. The alignment layers are parallel aligned by a rubbing process. The cell gap is 10 μm.

[0155] The transmission spectra were measured for liquid crystal cells when linearly polarized light parallel to the orientation direction and linearly polarized light perpendicular to the orientation direction were incident on them. A spectrophotometer (U-4100, Hitachi High-Technologies) was used for the measurements. Linearly polarized light parallel to the orientation direction is extraordinary light, and linearly polarized light perpendicular to the orientation direction is ordinary light.

[0156] The transmission spectrum was converted to an absorption spectrum to obtain the absorption maximum wavelength λmax and the full width at half maximum of the peak at the absorption maximum wavelength λmax in the absorption spectrum of the anomalous light. Furthermore, the anomalous light absorbance and the ordinary light absorbance at the absorption maximum wavelength λmax were obtained, and the dichromatic ratio was calculated by determining the ratio of the anomalous light absorbance to the ordinary light absorbance.

[0157] <Dimming sheet> A monomer mixture was prepared by mixing the following materials. The mixing ratios of each material listed below represent the mass ratio of each material to the total monomer mixture. • Ethyl acrylate (manufactured by Fujifilm Wako Pure Chemical Industries) 48% • Isobolonyl acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) 22% • Methoxytriethylene glycol acrylate (Light Acrylate MTG-A, manufactured by Kyoeisha Chemical Co., Ltd.) 10% • Dipropylene glycol diacrylate (NK ester APG-100, manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) 5% • Trimethylolpropane triacrylate (NK ester A-TMPT, manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) 9% • Trifunctional secondary thiol (Callenz MT NR1, manufactured by Resonaq) 6%

[0158] For each example and comparative example, the dichroic dye was mixed with the liquid crystal mixture, the dichroic dye, the monomer mixture, and the polymerization initiator in the following proportions. Specifically, the liquid crystal mixture and the dichroic dye were mixed and heated and stirred at 120°C for 10 minutes. After returning to room temperature, the monomer mixture in which the polymerization initiator was dissolved was added and stirred at room temperature for 10 minutes. This yielded a monomer composition containing the liquid crystal compound, the dichroic dye, the polymerizable compound, and the polymerization initiator. The mixing ratios of each material listed below represent the mass ratio of each material to the total monomer composition. ·Liquid crystal mixture (JC-5261XX, manufactured by JNC) 54% • Dichroic pigment 2% • Monomer mixture 43% • Polymerization initiator (Omnirad 819, IGM Resins) 1%

[0159] When the monomer compositions were visually inspected for the presence or absence of dichroic pigment precipitation, no dichroic pigment precipitation was observed in Examples 3-5, 7-9 and Comparative Examples 1-4. For Examples 3-5, 7-9 and Comparative Examples 1-4, 1% by mass of spacer particles (particle size 20 μm) made of polymethyl methacrylate was added to the monomer composition, and the mixture was stirred at room temperature for 10 minutes to prepare a coating solution for forming a light-adjusting layer.

[0160] An electrode sheet in which a transparent electrode layer made of indium tin oxide is laminated on a transparent support layer made of polyethylene terephthalate is coated with the above coating liquid and laminated to produce a laminate in which a coating film made of the above coating liquid is sandwiched between the transparent electrode layers of two electrode sheets. Then, the above laminate is irradiated with ultraviolet light having a wavelength of 365 nm at an intensity of 12 mW / cm 2 for 120 seconds to form a light control layer and obtain a light control sheet.

[0161] An electrode for voltage application was arranged on the light control sheet so that a voltage could be applied between the two transparent electrode layers. Then, for each of the non-application of voltage and the application of a 100 V sinusoidal AC voltage, the total light transmittance was measured and the transmittance ratio was calculated. The transmittance ratio is the ratio of the total light transmittance in the transparent state to the total light transmittance in the opaque state. The non-application of voltage is the opaque state of the light control sheet, and the application of voltage is the transparent state of the light control sheet.

[0162] Also, an optically transparent adhesive film that cuts light having a wavelength of 395 nm or less was laminated on one side of the light control sheet, and further, blue plate glass was laminated on the optically transparent adhesive film. Then, using a light resistance tester (Eye Super UV Tester SUV-W161, manufactured by Iwasaki Electric Co., Ltd.), light was irradiated onto the light control sheet from the side where the blue plate glass was located to conduct a light resistance test. The test conditions are as follows. · Illuminance: 65 mW / cm 2 · Temperature: 63 °C · Humidity: 60 Rh% · Test time: 300 h

[0163] For each of the opaque state and the transparent state of the light control sheet, the transmittance spectra before and after the light resistance test were measured using a spectrophotometer (U-4100, manufactured by Hitachi High-Technologies Corporation) to obtain L * , a * , b * . Then, the color difference ΔEab of the light control sheet before and after the light resistance test was calculated.

[0164] (Evaluation results) Figures 2 and 3 show the structures of the anthraquinone derivatives for each example and comparative example, as well as the results of each evaluation. In Figures 2 and 3, X and Y correspond to X and Y in the following formula (I). In addition, Figures 2 and 3 show the upper limit of the mass percentage concentration at which the dichroic dye can dissolve, as an evaluation of the solubility for the liquid crystal and monomer, respectively. Regarding solubility for monomer, "<0.05%" indicates that precipitation of the dichroic dye was confirmed even at a concentration of 0.05%.

[0165] [ka]

[0166] As shown in Figures 2 and 3, in Examples 1-9, which correspond to the first or second example anthraquinone derivative, the full width at half maximum of the peaks in the absorption spectrum was larger than in Comparative Examples 1-5, confirming that the absorption wavelength range was broadened. Furthermore, in the light-adjusting sheets using the anthraquinone derivatives of the examples, the ratio of total light transmittance between the opaque and transparent states was higher than in the comparative examples.

[0167] Comparative Examples 1-3 are -NH2 and -NHR 1 Although these compounds contain amino groups, the amino groups are located close to the oxygen atoms of the anthraquinone skeleton. Therefore, hydrogen bonding between the oxygen atoms and the amino groups makes inversion difficult, and it is thought that the effect of expanding the absorption wavelength range has not been achieved. Furthermore, comparative examples 4 and 5 do not contain functional groups that cause inversion, such as amino groups, so it is thought that their absorption wavelength range is narrow.

[0168] Furthermore, in Examples 3-5, 7-9, where at least one of X and Y in the anthraquinone derivative structure is a branched alkyl group, the solubility for both liquid crystals and monomers is improved compared to Examples 1, 2, and 6, where neither X nor Y is a branched alkyl group. While sufficient solubility for practical use is obtained for liquid crystals in Examples 1, 2, and 6, Examples 3-5, 7-9 provide practically suitable solubility not only for liquid crystals but also for monomers.

[0169] Furthermore, Examples 3 and 5 suggest that structures in which X and Y are different from each other yield higher solubility for both the liquid crystal and the monomer than structures in which X and Y are identical.

[0170] Furthermore, in the examples, the anthraquinone derivatives tended to show higher solubility in the L1 and L3 liquid crystal mixtures, which had the highest mass proportion of liquid crystal compounds containing two or more benzene rings, compared to the L2 and L4 liquid crystal mixtures, which had the highest mass proportion of liquid crystal compounds containing one benzene ring and liquid crystal compounds without a benzene ring. In addition, they tended to show higher solubility in ethyl acrylate than in cyclohexyl acrylate.

[0171] Furthermore, in Examples 1 to 9, it was confirmed that the absorption maximum wavelength λmax in the wavelength range usable as a magenta-based dye could be obtained, as well as a high dichromatic ratio. Furthermore, regarding the evaluation of lightfastness, it was confirmed that in Examples 7-9, which correspond to the anthraquinone derivative of Example 2, the ΔEab in both the transparent and opaque states was smaller compared to Examples 3-5, which correspond to the anthraquinone derivative of Example 1, indicating that higher lightfastness was obtained.

[0172] As described above using the examples, the anthraquinone derivative, dye composition, and light-adjusting sheet of the above embodiment provide the following effects. [1] The first example of anthraquinone derivative represented by formulas (1-1) to (1-2) above has an NHR group at a position that does not form a hydrogen bond with the oxygen atom attached to the anthraquinone skeleton. Therefore, due to the inversion that occurs at the NHR group, it is possible to expand the absorption wavelength range, and as a magenta dichroic dye, it is possible to absorb light over a wide wavelength range.

[0173] [2] The second example of anthraquinone derivative represented by formulas (2-1) to (2-3) above has an NHR group at one end of the molecular structure, which is a position that does not form a hydrogen bond with the oxygen atom bonded to the anthraquinone skeleton, and a ZR' group at the other end of the molecular structure. Therefore, it is possible to absorb light in a wavelength range that includes not only the absorption wavelength range when X and Y are each NHR groups, but also the absorption wavelength range when X and Y are each ZR' groups. Thus, the absorption wavelength range can be further broadened compared to the first example.

[0174] [3] In the first or second example of anthraquinone derivatives, if at least one of X and Y has a branched alkyl group, high solubility can be obtained for both the liquid crystal and the monomer, respectively.

[0175] [4] A dye composition containing an anthraquinone derivative and a liquid crystal compound as in the first or second example is suitable for use in liquid crystal devices because it uses an anthraquinone derivative having a broad absorption wavelength range.

[0176] [5] A dye composition comprising an anthraquinone derivative, a liquid crystal compound, and a polymerizable compound as in the first or second example is suitable for use in the manufacture of liquid crystal elements having a liquid crystal layer including a transparent polymer layer, since an anthraquinone derivative having a broad absorption wavelength range is used.

[0177] [6] If a photochromic sheet is equipped with a photochromic layer containing an anthraquinone derivative of the first or second example, since an anthraquinone derivative having a broad absorption wavelength range is used, it is possible to reduce the total light transmittance in the opaque state, thereby increasing the contrast between the transparent state and the opaque state. [Explanation of symbols]

[0178] 10… Dimming sheet 20…Dimming layer 31,32...Transparent electrode layer 41,42...Transparent support layer 50…Control Unit

Claims

1. An anthraquinone derivative represented by the following formula (1-1), wherein X and Y in formula (1-1) each independently have a structure represented by the following formula (1-2). 【Chemistry 1】 In formula (1-2), R is a linear or branched alkyl group having 4 to 11 carbon atoms.

2. An anthraquinone derivative represented by the following formula (2-1), wherein X in formula (2-1) has the structure represented by the following formula (2-2), and Y in formula (2-1) has the structure represented by the following formula (2-3). 【Chemistry 2】 In formula (2-2), R is a linear or branched alkyl group having 4 to 11 carbon atoms, and in formula (2-3), Z is an oxygen atom or a methylene group, and R' is a linear or branched alkyl group having 5 to 9 carbon atoms.

3. In formula (1-1), at least one of X and Y has a branched alkyl group. The anthraquinone derivative according to claim 1.

4. In formula (2-1), at least one of X and Y has a branched alkyl group. The anthraquinone derivative according to claim 2.

5. An anthraquinone derivative according to any one of claims 1 to 4, Liquid crystal compounds, including A pigment composition.

6. An anthraquinone derivative according to any one of claims 1 to 4, Liquid crystal compounds and polymerizable compounds, A pigment composition.

7. A light-adjusting layer comprising an anthraquinone derivative and a liquid crystal compound according to any one of claims 1 to 4, The light-adjusting layer is sandwiched between a pair of transparent electrode layers. Dimming sheet.

8. The aforementioned dimming layer is A transparent polymer layer containing multiple voids, A liquid crystal composition held in the void, comprising the anthraquinone derivative and the liquid crystal compound. The dimming sheet according to claim 7.

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