Dielectric Materials and Capacitors

Abstract

A dielectric material according to the present invention, which contains a nematic liquid crystal compound that has dielectric anisotropy and an azo compound that exists as a trans-isomer in the ground state, wherein the azo compound is transformed into a cis-isomer upon absorption of light that has a first wavelength, while being transformed into a trans-isomer upon absorption of light that has a second wavelength which is longer than the first wavelength.

Description

[Technical field]

[0001] The present invention relates to dielectric materials and capacitors. [Background technology]

[0002] Conventional dielectric materials are used as the dielectric of capacitors, etc., by utilizing the property that the capacitance changes. As such a dielectric material, for example, one using a ferroelectric material such as barium titanate is known (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-55745 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a dielectric material having a large change in dielectric constant. [Means for solving the problem]

[0005] A dielectric material according to one embodiment of the present invention contains a nematic liquid crystal compound having dielectric anisotropy and an azo compound which is a trans isomer in a ground state, and the azo compound is converted to a cis isomer when it absorbs light of a first wavelength, and is converted to the trans isomer when it absorbs light of a second wavelength longer than the first wavelength. Effect of the Invention

[0006] According to one aspect of the present invention, a dielectric material having a large change in dielectric constant can be provided. [Brief description of the drawings]

[0007] [Figure 1] A general formula for nematic liquid crystal compounds contained in dielectric materials. [Diagram 2] Chemical formulas of the substituents in the general formula in Figure 1. [Diagram 3] Specific examples of nematic liquid crystal compounds are shown in the following general formula. [Figure 4] A chemical formula showing an example of a nematic liquid crystal compound. [Diagram 5] 1 is a chemical formula showing another example of a nematic liquid crystal compound. [Figure 6] Chemical formula showing an example of an azo compound (trans isomer) contained in a dielectric material. [Figure 7] Chemical formula showing an example of an azo compound (cis isomer) contained in a dielectric material. [Figure 8] Chemical formula showing another example of an azo compound (heteroarene type azo compound). [Figure 9] Chemical formula showing another example of an azo compound (dihalogenoborane coordination type azo compound). [Figure 10] FIG. 1 shows an evaluation cell for evaluating the performance of a dielectric material. [Figure 11] FIG. 11 shows the state in which the evaluation cell of FIG. 10 is filled with a dielectric material. [Figure 12] FIG. 12 shows an evaluation cell filled with the dielectric material in FIG. 11 . [Figure 13] FIG. 13 is a diagram showing a state in which the evaluation cell in FIG. 12 is irradiated with ultraviolet light. [Figure 14] FIG. 14 is a diagram showing the state in which the evaluation cell in FIG. 13 is irradiated with visible light after being irradiated with ultraviolet light. [Figure 15] FIG. 1 is a diagram showing an evaluation system for evaluating the performance of a dielectric material. [Figure 16] Graph showing the relationship between absorption wavelength and absorbance in a nematic liquid crystal compound and an azo compound (trans isomer). [Figure 17] 1 is a graph showing the relationship between the absorption wavelength and absorbance of a dielectric material, for a dielectric material initially (before irradiation with ultraviolet and visible light), after irradiation with ultraviolet light, and after irradiation with visible light. [Figure 18] 1 is a graph showing the relationship between temperature and relative dielectric constant in a dielectric material and a nematic liquid crystal compound. [Figure 19]1 is a graph showing the relationship between frequency and dielectric constant of a dielectric material initially (after exposure to visible light but not UV light), after exposure to UV light, and after re-exposure to visible light. [Figure 20] Polarized light microscope image showing the initial (before UV and visible light exposure) structure of the dielectric material. [Figure 21] Polarized light microscope image showing the structure of a dielectric material after UV irradiation. [Figure 22] Polarized light microscope image showing the structure of a dielectric material after exposure to visible light. [Diagram 23] 1 is a graph showing the relationship between the irradiation time and the capacitance when a dielectric material is irradiated with ultraviolet light. [Figure 24] 1 is a graph showing the relationship between the irradiation time and the oscillation frequency when a dielectric material is irradiated with ultraviolet light. [Diagram 25] 1 is a graph showing the relationship between the exposure time and the capacitance when a dielectric material is exposed to visible light. [Figure 26] 1 is a graph showing the relationship between the irradiation time and the oscillation frequency when a dielectric material is irradiated with visible light. [Figure 27] 1 is a graph showing the relationship between ultraviolet irradiation intensity and relative dielectric constant in a dielectric material. [Figure 28] 1 is a graph showing the relationship between the irradiation intensity of visible light and the relative dielectric constant of a dielectric material. [Figure 29] 6 is a graph showing the change over time of a dielectric material after being irradiated with ultraviolet light. [Diagram 30] 1 is a graph showing the change over time of a dielectric material (when the azo compound is BDMAB) after ultraviolet irradiation. [Diagram 31] 1 is a graph showing the relationship between frequency and dielectric constant of a dielectric material (when the azo compound is BDMAB) at the initial stage (after exposure to visible light but not UV light), after exposure to UV light, and after exposure to visible light. [Diagram 32] 1 is a graph showing the relationship between ultraviolet irradiation intensity and relative dielectric constant in a dielectric material (when the azo compound is BDMAB). [Diagram 33] 1 is a graph showing the relationship between the irradiation intensity of visible light and the relative dielectric constant of a dielectric material (when the azo compound is BDMAB). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In addition, common parts in the drawings may be denoted by the same or corresponding reference numerals, and description thereof may be omitted.

[0009] The dielectric material according to this embodiment contains a nematic liquid crystal compound having dielectric anisotropy and an azo compound which is a trans isomer in the ground state, and the azo compound is converted to a cis isomer when it absorbs light of a first wavelength, and is converted to the trans isomer when it absorbs light of a second wavelength which is longer than the first wavelength.

[0010] In this specification, the dielectric material is an example of the dielectric material according to the present embodiment. The dielectric material is a substance that generates dielectric polarization and is separated into a positively charged portion and a negatively charged portion. The dielectric material contains a nematic liquid crystal compound and an azo compound.

[0011] A nematic liquid crystal compound is a fluid liquid-like substance in which the constituent molecules have an orientational order but no three-dimensional positional order. In this embodiment, the nematic liquid crystal compound has a dielectric anisotropy. Here, the dielectric anisotropy indicates anisotropy in the ease of polarization.

[0012] The relative dielectric constant of a nematic liquid crystal compound having dielectric anisotropy is not particularly limited, but is preferably 1000 or more, more preferably 5000 or more and 20000 or less, and further preferably 8000 or more and 15000 or less. In this specification, the relative dielectric constant is defined as the ratio of the dielectric constant of a medium to the dielectric constant of a vacuum (ε / ε 0 =ε r ) is shown.

[0013] The nematic liquid crystal compound component is not particularly limited, but is, for example, a compound represented by general formula (1) in FIG.

[0014] In equation (1) of Figure 1, R 11 , P 11 -Sp 11-, hydrogen, or alkyl having 1 to 20 carbon atoms, and any -CH 2 - may be replaced by -O-, -S-, -COO-, -OCO-, -CH=CH-, -CF=CF-, or -C≡C-, and any hydrogen in the alkyl group may be replaced by a halogen. 11 represents a polymerizable group, Sp 11 represents a single bond or a spacer group.

[0015] R 11 is preferably an alkyl group having 1 to 7 carbon atoms, and any —CH 2 - may be replaced by -O-, -CH=CH-, or -C≡C-, and any hydrogen in the alkyl group may be replaced by halogen.

[0016] R 12 , P 12 -Sp 12 -, hydrogen, halogen, -CN, -N=C=O, -N=C=S, -CF 3 , -OCF 3 or alkyl having 1 to 3 carbon atoms. Any -CH 2 - may be replaced by -O-, -S-, -COO-, -OCO-, -CH=CH-, -CF=CF-, or -C≡C-, any hydrogen in this alkyl may be replaced by halogen, and -CH 3 may be replaced by -CN.

[0017] Here, P 12 represents a polymerizable group, Sp 12 represents a single bond or a spacer group. 12 are halogens, -CN, -N=C=S, -CF 3 , -OCF 3 or alkyl having 1 to 3 carbon atoms, any hydrogen of which may be replaced by halogen.

[0018] A 11 ~A 15are independently a 5- to 8-membered ring or a fused ring having 9 or more carbon atoms, and any hydrogen in these rings may be replaced by halogen, alkyl having 1 to 5 carbon atoms, or alkyl halide.

[0019] Any -CH of the alkyl or halogenated alkyl having 1 to 5 carbon atoms 2 - may be replaced by -O-, -S-, or -NH-, and -CH 2 - may be replaced by -O-, -S-, or -NH-, and -CH= in the ring may be replaced by -N=.

[0020] Preferably, A 11 ~A 14 is a ring selected from the group consisting of (A-1) to (A-5) shown in FIG. 15 is a ring selected from the group consisting of (A-1) to (A-3) shown in FIG.

[0021] Z 11 ~Z 14 are independently a single bond or an alkylene having 1 to 8 carbon atoms, and any -CH 2 - may be replaced by -O-, -S-, -COO-, -OCO-, -CSO-, -OCS-, -N=N-, -CH=N-, -N=CH-, -N(O)=N-, -N=N(O)-, -CH=CH-, -CF=CF-, or -C≡C-, and any hydrogen may be replaced by halogen.

[0022] Preferably, Z 11 ~Z 14 are independently a single bond, -COO-, or -CF 2 More preferably, Z 11 ~Z 14 At least one of the groups is -COO- or -CF 2 It is O-.

[0023] And n 11 ~n 13 is independently 0 or 1, but preferably, n 11 ~n 13 The sum of (n11 +n 12 +n 13 ) is 2 or 3.

[0024] The nematic liquid crystal compound may contain at least one compound selected from the group consisting of compounds represented by formulas (2) and (3) shown in Fig. 3. The nematic liquid crystal compound may contain 60% by weight or more, preferably 80% by weight or more, of the compounds represented by these chemical formulas.

[0025] In equation (2) of Figure 3, R 21 is alkyl having 1 to 12 carbon atoms, alkenyl having 2 to 12 carbon atoms, or alkoxy having 1 to 11 carbon atoms; Z 21 and Z 22 are independently a single bond, -COO-, or -CF 2 O- and X 21 is fluorine, chlorine, -CF 3 , or -OCF 3 And L 21 ~L 23 is independently hydrogen or fluorine.

[0026] In addition, in equation (3) of FIG. 3, R 31 is an alkyl group having 1 to 12 carbon atoms or an alkoxyalkyl group having 1 to 11 carbon atoms; Z 31 and Z 32 are independently a single bond, -COO-, or -CF 2 O- and X 31 is fluorine, chlorine, -CF 3 , or -OCF 3 And L 31 ~L 34 is independently hydrogen or fluorine.

[0027] Of these, the nematic liquid crystal compound is preferably the compound represented by the above formula (3), and more preferably the compound represented by the above formula (3) R 31 is an alkyl group having 3 carbon atoms, and L 33 is hydrogen and Z 32 is a single bond, and L 31 , L 32 , L34 , and X 31 is fluorine and Z 31 is an ester compound of a halogenobiphenyl and a halogenophenyldioxane derivative (hereinafter referred to as DIO), represented by the following formula (4) in FIG. 4, in which —COO— is present.

[0028] 4 (an ester compound of a halogenobiphenyl and a halogenophenyldioxane derivative) is known as a nematic liquid crystal compound having a dielectric anisotropy with a relative dielectric constant of 10000 or more. Therefore, this DIO is suitable as a nematic liquid crystal compound (a nematic liquid crystal compound having a dielectric anisotropy with a relative dielectric constant of 1000 or more) to be used in the dielectric material of this embodiment.

[0029] In addition to DIO, 4-[(4-nitrophenoxy)carbonyl]phenyl 2,4-dimethoxybenzoic acid (hereinafter referred to as RM734) shown in Fig. 5 is known as a nematic liquid crystal compound having a dielectric anisotropy with a relative dielectric constant of 1000 or more. Therefore, it is considered that RM734 can be used as a nematic liquid crystal compound (a nematic liquid crystal compound having a dielectric anisotropy with a relative dielectric constant of 1000 or more) in addition to DIO for use in the dielectric material of this embodiment.

[0030] The nematic liquid crystal compound of the present invention may be a composite material of at least one of the compounds represented by the above formulas (1) to (4) and a polymer compound, for example, a polymer network may be formed within the nematic liquid crystal compound.

[0031] Azo compounds are trans isomers in the ground state. In this specification, an azo compound refers to an organic compound having an azo group (-N=N-). The ground state refers to the state with the lowest energy. A trans isomer refers to an isomer in which an azo group has two different substituents on both sides of the azo group, and the substituents are bonded to opposite sides of the double bond of the azo group as an axis. Hereinafter, a trans isomer may be referred to as a trans form or a trans type.

[0032] In addition, when an azo compound absorbs light of the first wavelength, it is converted into a cis isomer. In this specification, a cis isomer refers to an isomer in which an azo group has two different substituents on both sides of the azo group, and the substituents are bonded to the same side of the double bond of the azo group as an axis. Hereinafter, a cis isomer may be referred to as a cis form or a cis type. Here, light of the first wavelength refers to electromagnetic waves having a given wavelength (e.g., ultraviolet light, visible light, infrared light).

[0033] The length of the first wavelength is not particularly limited, and is, for example, 300 nm or more and 390 nm or less, preferably 310 nm or more and 380 nm or less, and more preferably 320 nm or more and 370 nm or less. Note that light (electromagnetic waves) having a wavelength of 300 nm or more and 390 nm or less has the properties of ultraviolet light (ultraviolet rays).

[0034] Furthermore, the azo compound is converted to a trans isomer when it absorbs light of a second wavelength, which is longer than the first wavelength. Here, the light of the second wavelength refers to electromagnetic waves having a wavelength longer than the first wavelength. For example, when the electromagnetic wave of the first wavelength is ultraviolet light (UV), the electromagnetic wave of the second wavelength is visible light (VIS) or infrared light (IR).

[0035] The length of the second wavelength is not particularly limited, and is, for example, 400 nm or more and 490 nm or less, preferably 410 nm or more and 480 nm or less, and more preferably 420 nm or more and 470 nm or less. Note that light (electromagnetic waves) having a wavelength of 400 nm or more and 490 nm or less has the properties of visible light (visible light rays).

[0036] The azo compound is not particularly limited, but is preferably an azobenzene derivative from the viewpoint of having the above-mentioned optical properties. Azobenzene has a structure (C 6 H 5 -N=NC 6 H 5 ), and an azobenzene dielectric is such a dielectric of azobenzene.

[0037] From the viewpoint of having the above-mentioned optical properties, the azobenzene dielectric preferably has cis-trans isomers as shown in Figures 6 and 7. As such an azobenzene dielectric, for example, an azobenzene compound in which at least one of both ends of the azobenzene skeleton is substituted with an alkyl group or an alkoxy group and the other end is substituted with an alkyl group, an alkoxy group, a cyano group, a methoxy group, a halogeno group, or the like can be used.

[0038] Of these, the azobenzene dielectric is preferably an alkylalkoxyazobenzene compound in which one end of the azobenzene skeleton is substituted with an alkyl group and the other end is substituted with an alkoxy group.

[0039] Specific examples of alkylalkoxyazobenzene compounds include 4-butyl-4'-methoxyazobenzene (hereinafter referred to as BMAB) in which R is a hydrogen atom in the alkylalkoxyazobenzene compound represented by formula (6) in FIG. 6, and 4-butyl-2,5-dimethyl-4'-methoxyazobenzene (hereinafter referred to as BDMAB) in which R is a methyl group.

[0040] The azobenzene compound shown in formula (6) in Fig. 6 is a trans isomer, specifically a trans isomer in the ground state, or a trans isomer converted from a cis isomer by absorbing light of the second wavelength. The azobenzene compound shown in formula (7) in Fig. 7 is a cis isomer with respect to the azobenzene compound shown in formula (6) in Fig. 6, specifically a cis isomer converted from a trans isomer by absorbing light of the first wavelength.

[0041] In addition, examples of azo compounds contained in the dielectric material of this embodiment (azo compounds that are trans isomers in the ground state, are converted to cis isomers when they absorb light of a first wavelength, and are converted to trans isomers when they absorb light of a second wavelength longer than the first wavelength) include heteroarene-type azo compounds represented by formulas (8-1) to (8-12) in FIG. 8, and dihalogenoborane coordination-type azo compounds represented by formula (9) in FIG. 9, in addition to BMAB and BDMAB.

[0042] Here, in the equation (8-1) showing FIG. 8, R 1 is a methyl group, R 2 is hydrogen or a methyl group, R 3 is hydrogen, R 4 is hydrogen or a methyl group. In formula (8-2), R 1 is a methyl group, R 2 is a methyl group, R 3 is a methyl group, and R4 is a hydrogen or a methyl group. In formula (8-3), R 1 is hydrogen or a methyl group, R 2 is a methyl group, R 3 is hydrogen or a methyl group. In formula (8-4), R 1 is hydrogen or a methyl group, R 2 is a methyl group, R 3 is hydrogen or a methyl group. In formula (8-5), R 1 is a methyl group, R 2 is hydrogen, R 3 is hydrogen or a methyl group. In formula (8-6), R 1 is a methyl group, R 2 is hydrogen, R 3 is hydrogen. In formula (8-7), R 1 is hydrogen, R 2 is a methyl group, R 3 is hydrogen. In formula (8-8), R 1 is a methyl group, R 2 is hydrogen, R 3 is hydrogen. In formula (8-9), R 1 is hydrogen, R 2 is a trityl group, R 3 is hydrogen. In formula (8-10), R 1 is a methyl group, R 2 is hydrogen, R 3 is hydrogen. In formula (8-11), R 1 is a methyl group, R 2 is hydrogen. In formula (8-12), R 1 is a nitrodimethylsulfone group, R 2 is hydrogen, R 3 is hydrogen.

[0043] In addition, in equation (9) of Figure 9, R 1 is hydrogen, R 2is hydrogen, a methoxy group, a nitrodimethyl group, a pyrrolidinyl group, a piperidinyl group, a methylpiperazinyl group, or a morpholinyl group; R 3 is hydrogen, R 4 is hydrogen or a methoxy group.

[0044] Therefore, as the azo compound used in the dielectric material of this embodiment (azo compound that is a trans isomer in the ground state, is converted to a cis isomer when it absorbs light of a first wavelength, and is converted to the trans isomer when it absorbs light of a second wavelength longer than the first wavelength), in addition to BMAB and BDMAB, it is considered that the heteroarene type azo compound shown in FIG. 8 or the dihalogenoborane coordination type azo compound shown in FIG. 9 can be applied.

[0045] The content of the nematic liquid crystal compound and the azo compound in the dielectric material is arbitrary, but preferably the content of the azo compound is 0.1% by weight or more and 10% by weight or less, preferably 0.5% by weight or more and 5% by weight or less, and more preferably 1% by weight or more and 4% by weight or less, relative to 100% by weight of the nematic liquid crystal compound.

[0046] The dielectric material can be produced by any method. For example, 100% by weight of a nematic liquid crystal compound and 2% by weight of an azo compound are stirred in an organic solvent at room temperature to produce a mixed solution of the nematic liquid crystal compound and the azo compound, which is then distilled under reduced pressure while heating and solidified at room temperature to obtain the dielectric material.

[0047] The dielectric material of the present embodiment may contain other components within the range that does not impair the effect of the dielectric material. For example, the nematic liquid crystal compound contained in the dielectric material may contain a polymer having no mesogens and / or a polymer having mesogens. In addition, the polymer having mesogens may be a polymer having R at the terminal. 11 As P 11 -Sp 11 The compound may include a polymer obtained by polymerization of a compound represented by general formula (1) having -.

[0048] Polymerizable group P 11is, for example, an acrylic group, a methacrylic group, a vinyl group, an isocyanate group, an isothiocyanate group, an epoxy group, an aziridine group, an azlactone group, etc. The polymer may contain a polymerization initiator, a curing agent, a catalyst, a stabilizer, a dichroic dye, a photochromic compound, etc., within a range that does not impair the effect of the dielectric material.

[0049] Furthermore, by using a compound containing a polymerizable group or another polymerizable compound, the dielectric material of this embodiment can form a plastic member having the properties (characteristics such as high dielectric constant) of a nematic liquid crystal compound having dielectric anisotropy contained in the dielectric material.

[0050] Furthermore, the dielectric material of the present embodiment may contain a filler to the extent that the effect of the dielectric material is not impaired. As the filler, for example, a light-transmitting material is preferable.

[0051] Examples of light-transmitting materials that can be used include various resin materials such as acrylic resins, methacrylic resins, polycarbonate, polystyrene, cyclic ether resins such as epoxy resins and oxetane resins, and cyclic olefin resins such as polyamide, polyimide, polybenzoxazole, polysilane, polysilazane, benzocyclobutene resins and norbornene resins, as well as various glass materials such as quartz glass and borosilicate glass, and various crystal materials such as sapphire and quartz. Among these, it is preferable to use a filler having flexibility.

[0052] The capacitor according to the present embodiment uses the above-mentioned dielectric material as a dielectric constituting the capacitor. In the capacitor according to the present embodiment, the dielectric material may be applied in any manner, and may be disposed between the electrodes of the capacitor by a known method.

[0053] The effects of the embodiment will be described below. As described above, the dielectric material of the embodiment contains a nematic liquid crystal compound having dielectric anisotropy and an azo compound that is a trans isomer in the ground state, converts to a cis isomer when it absorbs light of a first wavelength, and converts to a trans isomer when it absorbs light of a second wavelength longer than the first wavelength. This makes it possible to obtain a dielectric material with a large change in dielectric constant.

[0054] Specifically, when a dielectric material absorbs light of a first wavelength, the azo compound contained in the dielectric material is converted from a trans isomer (Figure 6) to a cis isomer (Figure 7), causing the azo compound to bend (or twist) within the dielectric material.

[0055] Then, the action of the bent cis-type azo compound or the electric polarization generated in the azo compound causes disturbances in the nematic liquid crystal compound (Figure 3) contained in the dielectric material, which is thought to cause the orientation structure of the nematic liquid crystal compound in the dielectric material to collapse, significantly reducing the dielectric constant of the dielectric material.

[0056] Furthermore, when the dielectric material absorbs light of the second wavelength, the azo compound contained in the dielectric material is converted from a cis isomer (Fig. 7) to a trans isomer (Fig. 6), and the azo compound returns to its original state in the dielectric material (Fig. 6). This eliminates the bent or polarized state of the azo compound, and the disturbance of the nematic liquid crystal compound (Fig. 4) contained in the dielectric material is eliminated.

[0057] It is believed that this causes the orientation structure of the nematic liquid crystal compound in the dielectric material to return to its original state (or a state close to its original state), and the dielectric constant of the dielectric material increases significantly, causing it to exhibit the original dielectric constant (or a dielectric constant close to its original state).

[0058] Furthermore, by alternately absorbing light of the first wavelength and light of the second wavelength, the dielectric material of this embodiment can reversibly convert between cis and trans isomers. In this way, the dielectric material of this embodiment can repeatedly greatly increase and decrease the dielectric constant by alternately absorbing two types of light of different wavelengths. Therefore, the dielectric material of this embodiment can control the dielectric constant by light irradiation, and can increase the amount of change in the dielectric constant.

[0059] As described above, the dielectric material of this embodiment can be used as a dielectric material disposed between electrodes of a capacitor because the amount of change in dielectric constant can be greatly controlled by light irradiation.

[0060] In addition, as described above, the dielectric material of the present embodiment contains a nematic liquid crystal compound and an azo compound, and since both the nematic liquid crystal compound and the azo compound are organic compounds having flexibility, a flexible dielectric material can be formed. Therefore, the dielectric material of the present embodiment can be used in devices that require flexibility, such as wearable devices.

[0061] In this embodiment, as described above, the upper limit of the change in dielectric constant can be increased by using a nematic liquid crystal compound having a relative dielectric constant of 1000 or more as the nematic liquid crystal compound contained in the dielectric material. As a result, according to this embodiment, the amount of change in the dielectric constant in the dielectric material can be further increased.

[0062] As described above, the dielectric material of this embodiment uses DIO (an ester compound of a halogenobiphenyl and a halogenophenyldioxane derivative) as the nematic liquid crystal compound contained in the dielectric material. Since DIO has a relative dielectric constant of more than 10,000, a dielectric material containing a nematic liquid crystal compound having a relative dielectric constant of 1,000 or more can be realized with high precision.

[0063] In this embodiment, the range of the first wavelength is adjusted to 300 nm or more and 390 nm or less, so that the azo compound can be irradiated with ultraviolet light. Since ultraviolet light has a high energy intensity among electromagnetic waves, an azo compound in a ground state with a low energy state is likely to become in an excited state with a high energy state by absorbing such ultraviolet light.

[0064] Therefore, in this embodiment, by irradiating the dielectric material with the first wavelength corresponding to ultraviolet light, the azo compound in the dielectric material is easily converted from a trans isomer to a cis isomer, which in this embodiment makes it easier for disturbances to occur in the nematic liquid crystal compound contained in the dielectric material, causing the orientation structure of the nematic liquid crystal compound in the dielectric material to collapse, thereby achieving a large reduction in the dielectric constant of the dielectric material with high precision.

[0065] In this embodiment, the range of the second wavelength is adjusted to 400 nm or more and 490 nm or less, so that the azo compound can be irradiated with visible light. Since visible light has a lower energy intensity than ultraviolet light, an azo compound in an excited state with a high energy state is likely to return to a ground state with a low energy state by absorbing such visible light.

[0066] Therefore, in this embodiment, the azo compound in the dielectric material is easily converted from a cis form to a trans form by irradiating the dielectric material with the second wavelength corresponding to visible light. As a result, in this embodiment, the disturbance of the nematic liquid crystal compound contained in the dielectric material is easily eliminated, the orientation structure of the nematic liquid crystal compound in the dielectric material returns to the original state, and a large increase in the dielectric constant of the dielectric material can be realized with high precision.

[0067] In this embodiment, as described above, by using an azobenzene derivative as the azo compound contained in the dielectric material, since the azobenzene derivative undergoes a large bending or twisting when being converted from a trans isomer to a cis isomer, or since the cis isomer has a large electric polarization, the action of the azobenzene derivative in the dielectric material can cause a large disturbance in the nematic liquid crystal compound.

[0068] Therefore, the orientation structure of the nematic liquid crystal compound in the dielectric material can be significantly disrupted, and the decrease in the dielectric constant of the dielectric material can be further increased.

[0069] In this embodiment, as described above, by using a dimethylbutylazobenzene compound among azobenzene derivatives as the azo compound contained in the dielectric material, the dimethylbutylazobenzene compound is very stable in bending or twisting when converted from a trans isomer to a cis isomer, and therefore, the disturbance generated in the nematic liquid crystal compound due to the action of the bent azobenzene derivative in the dielectric material can be induced more stably.

[0070] Therefore, the orientation structure of the nematic liquid crystal compound in the dielectric material can be disrupted for a longer period of time, and the reduced state of the dielectric constant of the dielectric material can be maintained for a long period of time.

[0071] As described above, the capacitor of this embodiment uses the dielectric material of this embodiment, making it possible to configure a capacitor that has not been seen in the past, which can modulate the dielectric constant (capacitance) by photoresponse. In addition, since such a capacitor can increase the amount of change in the dielectric constant (capacitance), it is possible to realize a capacitor capable of large-capacity charging and discharging, a capacitor capable of rapid charging and discharging, and the like.

[0072] In addition, the capacitor of this embodiment uses a flexible dielectric material as the dielectric constituting the capacitor as described above, and therefore the capacitor of this embodiment can be used in devices that require flexibility, such as wearable devices. EXAMPLES

[0073] The present embodiment will be described in detail below with reference to examples, but the present embodiment is not limited to these examples. Various tests and evaluations were performed according to the following methods. The dielectric constant means the relative dielectric constant.

[0074] <Sample> A sample of the dielectric material was prepared by pipetting 100% by weight of DIO (an ester compound of halogenobiphenyl and halogenophenyldioxane derivative) represented by the following formula (4) in Fig. 4 as a nematic liquid crystal compound, and 2% by weight of BMAB (4-butyl-4'-methoxyazobenzene) represented by the formula (6) in Fig. 6 or 2% by weight of BDMAB (4-butyl-2,5-dimethyl-4'-methoxyazobenzene) as an azo compound in an aluminum pan at 120°C for 5 minutes to prepare a mixed solution.

[0075] This was cooled at room temperature to obtain a solid sample. Hereinafter, the dielectric material containing DIO and BMAB is referred to as BMAB / DIO, and the dielectric material containing DIO and BDMAB is referred to as BDMAB / DIO.

[0076] <Evaluation cell> An evaluation cell 10 was created to evaluate the performance of a dielectric material. As shown in Fig. 10, the evaluation cell 10 includes a cell 11, an electrode 12, current collectors 13 and 14, wiring 15 and 16, and lead wires 17 and 18. The cell 11 is a 50 mm2 cell made of ITO (indium tin oxide). 2 The upper and lower surfaces are sandwiched between a space of 14 μm and an opening (not shown).

[0077] Electrodes 12 are formed on the lower surface side within the space of cell 11, and constitute positive and negative electrodes for detecting the charge of the sample. Current collectors 13 and 14 are connected to the positive and negative electrodes of electrode 12, wiring 15 and 16 are disposed between electrode 12 and current collectors 13 and 14, and lead wires 17 and 18 are connected to current collectors 13 and 14, and are electrically connected to the outside (FIG. 10).

[0078] A sample of the dielectric material (the content of the azo compound in the nematic liquid crystal compound is 2% by weight) is filled into the space of the cell 11 through the opening of the cell 11 (FIG. 11), completing the evaluation cell 10 filled with the sample 20 (FIG. 12). Note that evaluation cell 10 was also prepared in which the nematic liquid crystal compound and the azo compound contained in the dielectric material were each filled alone.

[0079] These evaluation cells 10 are irradiated with ultraviolet light and visible light from an ultraviolet-visible LED light source 30, which will be described later. When irradiating ultraviolet light, the ultraviolet-visible LED light source 30 constitutes an ultraviolet light source 31, and when irradiating visible light, it constitutes a visible light source 32 (FIGS. 13 and 14).

[0080] <Evaluation System> An evaluation system for evaluating the performance of dielectric materials was constructed. As shown in Fig. 15, the evaluation system includes an ultraviolet-visible LED light source 30, a polarizing microscope 40, a temperature control device 50, an impedance analyzer 60, an audio amplifier 70, and a computer 80.

[0081] The ultraviolet-visible LED light source 30 is connected to a polarizing microscope 40 described below, and constitutes a light source for the polarizing microscope 40. The ultraviolet-visible LED light source 30 can irradiate ultraviolet light and visible light. In this embodiment, the ultraviolet-visible LED light source 30 irradiates ultraviolet light (wavelength 365 nm, intensity 2.3 mW / cm 2 ), visible light (wavelength 450nm, intensity 3.0mW / cm 2 ) was irradiated onto the evaluation cell 10.

[0082] A mercury lamp may be used instead of the ultraviolet-visible LED light source 30. In the case of a mercury lamp, it is preferable to combine it with bandpass filters around 365 nm and 450 nm.

[0083] The polarizing microscope (POM) 40 includes at least a stage 41, a lens barrel 42, an objective lens 43, and an eyepiece 44, and captures a polarizing microscopic image.

[0084] The above-mentioned evaluation cell 10 is fixed as a preparation on a stage 41 of a polarizing microscope 40. An objective lens 43 and an eyepiece lens 44 are provided on a lens barrel 42. An ultraviolet-visible LED light source 30 is further connected to the lens barrel 42, and irradiates the fixed evaluation cell 10 with ultraviolet light and visible light.

[0085] The temperature control device 50 is connected to the stage 41 of the polarizing microscope 40, and controls the temperature of the stage 41, thereby adjusting the temperature of the evaluation cell 10 fixed as a preparation. In this embodiment, the temperature of the stage 41 was adjusted to 55.6°C.

[0086] The impedance analyzer 60 includes an interface 61, a main body 62, a memory 63, and a display 64, and is connected to the stage 41 of the polarizing microscope 40 via the interface 61. The impedance analyzer 60 measures the impedance of the evaluation cell 10 at a measurement frequency of 1 MHz to 1 Hz and an AC voltage of 0.1 mV, and calculates the apparent relative dielectric constant (ε') from the values ​​of the real and imaginary parts of the obtained impedance.

[0087] The audio amplifier 70 includes a main body 71, a DC stabilized power supply 72, and an oscilloscope 73, and is connected to the stage 41 of the polarizing microscope 40 via the main body 71. The main body 71 of the audio amplifier 70 includes an audio oscillator circuit (not shown), and is operated in accordance with the relationship 1 / T=1.44 / (R A +2R B ) C measures the frequency (waveform).

[0088] In this equation, C is the capacitance, T is the period (time), and R A , R B In this embodiment, the resistance value is R A = 200Ω, R B =20 kΩ. By appropriately changing these resistance values, the modulation frequency can be expanded. The oscilloscope 73 displays the measured frequency (waveform).

[0089] The computer 80 includes a central processing unit (CPU) 81 and a display 82. The central processing unit (CPU) 81 controls the operations of the ultraviolet-visible LED light source 30, the polarizing microscope 40, the temperature control device 50, the impedance analyzer 60, and the audio amplifier 70 that constitute the evaluation system. The display 82 displays each operation of the evaluation system in a visualized form.

[0090] [Example 1] The absorption wavelengths of the nematic liquid crystal compound (DIO) and the trans-type azo compound (BMAB) were measured, and the results are shown in Figure 16.

[0091] Figure 16 is a graph showing the relationship between the absorption wavelength and absorbance in a nematic liquid crystal compound and a trans-type azo compound. According to Figure 16, the absorption wavelength of the nematic liquid crystal compound (DIO) shows a peak at about 245 nm, and the absorption wavelength of the trans-type azo compound (BMAB) shows a peak at about 350 nm. In other words, it was confirmed that the absorption wavelength peaks of the nematic liquid crystal compound (DIO) and the trans-type azo compound (BMAB) do not overlap.

[0092] From this, it is considered that when electromagnetic waves of 300 nm or longer are irradiated to a dielectric material containing a nematic liquid crystal compound (DIO) and a trans-type azo compound (BMAB), the nematic liquid crystal compound (DIO) will not be excited in the dielectric material, and only the trans-type azo compound (BMAB) will be excited (converted into a cis-type azo compound).

[0093] [Example 2] The peak absorption wavelength (nm) of the dielectric material (BMAB / DIO) was measured initially (before irradiation with UV and visible light), after 10 minutes of UV irradiation, and after 10 minutes of visible light irradiation. The results are shown in Figure 17.

[0094] Fig. 17 is a graph showing the relationship between the absorption wavelength and absorbance in a dielectric material initially (before irradiation with ultraviolet and visible light), after 10 minutes of irradiation with ultraviolet light, and after 10 minutes of irradiation with visible light. According to Fig. 17, the absorption wavelength of the dielectric material (BMAB / DIO) initially (before irradiation with ultraviolet and visible light) and after 10 minutes of irradiation with visible light showed a peak near 350 nm, and the dielectric material (BMAB / DIO) after 10 minutes of irradiation with ultraviolet light showed a peak near 445 nm.

[0095] In other words, it was confirmed that the dielectric material (BMAB / DIO) has two absorption wavelengths whose peaks do not overlap depending on the state. From this, it is thought that the state of the dielectric material (BMAB / DIO) changes when it is irradiated with electromagnetic waves (ultraviolet rays) around 350 nm and electromagnetic waves (visible light) around 445 nm.

[0096] [Example 3] The dielectric constant as a function of temperature was measured for the dielectric material (BMAB / DIO) of this embodiment and the nematic liquid crystal compound (DIO) alone. The results are shown in FIG.

[0097] FIG. 18 is a graph showing the relationship between temperature and relative dielectric constant for the dielectric material (BMAB / DIO) and the nematic liquid crystal compound (DIO) alone.

[0098] 18, it was confirmed that the relative dielectric constant of the nematic liquid crystal compound (DIO) alone changes from approximately 14,000 to almost 0 in the range of approximately 60°C to 70°C, and the relative dielectric constant of the dielectric material (BMAB / DIO) changes from approximately 13,800 to almost 0 in the range of approximately 50°C to 60°C. This shows that the nematic liquid crystal compound (DIO) exhibits an extremely high relative dielectric constant (10,000 or more) in the low temperature region (below 100°C).

[0099] It was also found that the nematic liquid crystal compound (DIO) can significantly reduce its high relative dielectric constant (10,000 or more) in the low temperature range (below 100°C). Furthermore, it was found that the nematic liquid crystal compound (DIO) maintains its characteristic of exhibiting a high relative dielectric constant (10,000 or more) in the low temperature range (below 100°C) even in the state of a dielectric material (BMAB / DIO), and of significantly reducing the relative dielectric constant (10,000 or more).

[0100] [Example 4] The dielectric constant of the dielectric material (BMAB / DIO) was measured at various frequencies (1 MHz to 1 Hz, AC voltage 0.1 V) at the initial stage (after 5 minutes of visible light irradiation without UV irradiation), after 5 minutes of UV irradiation, and after 5 minutes of visible light irradiation again. The results are shown in Figure 19.

[0101] Fig. 19 is a graph showing the relationship between frequency (logf) and dielectric constant of a dielectric material (BMAB / DIO) at an initial stage (after exposure to visible light without exposure to UV light), after exposure to UV light, and after re-exposure to visible light. According to Fig. 19, when comparing the initial stage (after exposure to visible light for 5 minutes without exposure to UV light) and the 5 minutes exposure to UV light of the dielectric material (BMAB / DIO) at around 1000 Hz (logf=3), it was confirmed that a difference of 10,000 or more occurred in the dielectric constant.

[0102] In addition, when comparing the dielectric constant of the dielectric material (BMAB / DIO) after 5 minutes of UV irradiation with the initial state (after 5 minutes of visible light irradiation without UV irradiation) and after 5 minutes of visible light irradiation at around 1000 Hz (logf = 3), it was confirmed that there was a difference of more than 10,000 in the dielectric constant.

[0103] This difference (change) in relative dielectric constant corresponds to a change in capacitance of 7 nF to 0.34 μF. This suggests that the dielectric constant (capacitance) of the dielectric material (BMAB / DIO) can be significantly increased or decreased by alternately irradiating it with ultraviolet light and visible light, making it possible to control the relative dielectric constant (capacitance) by optical modulation.

[0104] [Example 5] Polarizing microscope images of the dielectric material (BMAB / DIO) were taken at an initial stage (before irradiation with ultraviolet light and visible light), after 5 minutes of irradiation with ultraviolet light, and after 5 minutes of irradiation with visible light at a temperature of 55.6° C. The results are shown in FIGS.

[0105] FIG. 20 is a polarizing microscope image showing the initial structure of the dielectric material (before irradiation with UV and visible light), FIG. 21 is a polarizing microscope image showing the structure of the dielectric material after 5 minutes of irradiation with UV light, and FIG. 22 is a microscope image showing the structure of the dielectric material after 5 minutes of irradiation with visible light.

[0106] 20 and 22, the initial structure (before irradiation with UV and visible light) and the structure of the dielectric material (BMAB / DIO) after 5 minutes of irradiation with visible light show regular layer structure. Also, according to Fig. 21, the structure of the dielectric material (BMAB / DIO) after 5 minutes of UV irradiation shows irregular sand-like structure.

[0107] From this, it was found that the structure of the dielectric material (BMAB / DIO) changes when it is irradiated with electromagnetic waves (ultraviolet rays) around 350 nm and electromagnetic waves (visible light) around 445 nm. This change in structure is considered to correspond to the change in the dielectric constant.

[0108] [Example 6] The change in capacitance and the change in oscillation frequency due to ultraviolet irradiation were measured for the dielectric material (BMAB / DIO). Specifically, the relationship between the irradiation time and the capacitance when a sample 20 of the dielectric material (BMAB / DIO) was irradiated with ultraviolet light having a wavelength of 365 nm for 120 seconds was confirmed by an impedance analyzer 60, and the relationship between the irradiation time and the oscillation frequency was confirmed by an audio amplifier 70 (oscilloscope 73). The results are shown in Figures 23 and 24.

[0109] FIG. 23 is a graph showing the relationship between the exposure time when a dielectric material is irradiated with ultraviolet rays and the capacitance, and FIG. 24 is a graph showing the relationship between the exposure time when a dielectric material is irradiated with ultraviolet rays and the oscillation frequency.

[0110] It was confirmed from Fig. 23 that the capacitance of the dielectric material (BMAB / DIO) exponentially decreased with the passage of time of ultraviolet irradiation, and from Fig. 24 that the oscillation frequency of the dielectric material (BMAB / DIO) became higher in pitch with the passage of time of ultraviolet irradiation.

[0111] From this, it was found that the capacitance and oscillation frequency of the dielectric material (BMAB / DIO) can be controlled by irradiating it with ultraviolet light (wavelength 365 nm).

[0112] [Example 7] The change in capacitance and the change in oscillation frequency of the dielectric material (BMAB / DIO) due to the irradiation of visible light after ultraviolet irradiation were measured. Specifically, when a sample 20 of the dielectric material (BMAB / DIO) was irradiated with visible light having a wavelength of 450 nm for 65 seconds, the relationship between the irradiation time and the capacitance was confirmed by an impedance analyzer 60, and the relationship between the irradiation time and the oscillation frequency was confirmed by an audio amplifier 70 (oscilloscope 73). The results are shown in Figures 25 and 26.

[0113] FIG. 25 is a graph showing the relationship between the exposure time when a dielectric material is irradiated with visible light and the capacitance, and FIG. 26 is a graph showing the relationship between the exposure time when a dielectric material is irradiated with visible light and the oscillation frequency.

[0114] It was confirmed from Fig. 25 that the capacitance of the dielectric material (BMAB / DIO) exponentially increases with the lapse of time of visible light irradiation, and from Fig. 26 that the oscillation frequency of the dielectric material (BMAB / DIO) becomes lower in pitch with the lapse of time of visible light irradiation.

[0115] This indicates that the capacitance and oscillation frequency of the dielectric material (BMAB / DIO) may be controllable by irradiating it with visible light (wavelength 365 nm).

[0116] [Example 8] For dielectric material (BMAB / DIO), the temperature is 55.6℃, the frequency is 1kHz, and the irradiation intensity of ultraviolet light (wavelength 365nm) is I UV The relative dielectric constant was measured when the dielectric constant was set to 2.3, 1.0, 0.36, and 0.15. The results are shown in Figure 27.

[0117] Fig. 27 is a graph showing the relationship between the irradiation intensity of ultraviolet light and the relative dielectric constant of a dielectric material. According to Fig. 27, the irradiation intensity I UV When the irradiation intensity I is 2.3 or 1.0, the relative dielectric constant decreases rapidly within about 0.2 minutes of ultraviolet irradiation. UV When is 0.36, the UV irradiation time is limited to about 1 minute, and the irradiation intensity IUV When the value was 0.15, it was confirmed that the ultraviolet light exposure time gradually decreased within about 2 minutes.

[0118] This indicates that it is possible to control the rate at which the dielectric constant of the dielectric material (BMAB / DIO) decreases by changing the intensity of ultraviolet light irradiation.

[0119] [Example 9] For dielectric material (BMAB / DIO), the temperature is 55.6℃, the frequency is 1kHz, and the irradiation intensity of visible light (wavelength 450nm) is I VIS The relative dielectric constant was measured when the dielectric constant was set to 3.0, 1.7, 0.6, and 0.2. The results are shown in Figure 28.

[0120] Fig. 28 is a graph showing the relationship between the irradiation intensity of visible light and the relative dielectric constant of a dielectric material. According to Fig. 28, the irradiation intensity I VIS When the irradiation intensity I is 3.0 or 1.7, the relative dielectric constant increases rapidly within about 0.4 minutes of visible light irradiation. VIS When is 0.6, the exposure time of visible light increases within about 1 minute, and the exposure intensity I VIS When the value was 0.2, it was confirmed that the exposure time of visible light increased gradually within about 3 minutes.

[0121] This indicates that it is possible to control the rate at which the dielectric constant of the dielectric material (BMAB / DIO) increases by changing the intensity of visible light irradiation.

[0122] [Example 10] The dielectric material (BMAB / DIO) was irradiated with ultraviolet light (wavelength 365 nm, intensity 2.3) for a sufficient amount of time, then the temperature was fixed at 55.6°C and the material was left in a dark room. The change in the relative dielectric constant over time was confirmed. The results are shown in Figure 29.

[0123] Fig. 29 is a graph showing the change over time of the dielectric material (BMAB / DIO) after UV irradiation. According to Fig. 29, it was confirmed that the relative dielectric constant of the dielectric material (BMAB / DIO) remained almost 0 for about 10 minutes after UV irradiation was stopped, increased to about 8000 after about 16 minutes, and increased to the original value of about 14000 after about 24 minutes. This shows that the low dielectric constant was maintained for about 16 minutes even after UV irradiation was stopped.

[0124] [Example 11] Measurements were performed in the same manner as in Example 10, except that the change in relative dielectric constant over time was confirmed for the dielectric material (BDMAB / DIO) instead of the dielectric material (BMAB / DIO). The results are shown in FIG.

[0125] Figure 30 is a graph showing the change over time of the dielectric material (BDMAB / DIO) after UV irradiation. According to Figure 30, it was confirmed that the relative dielectric constant of the dielectric material (BDMAB / DIO) is maintained close to 0 for about 8 hours after UV irradiation is stopped, increases to about 9000 after about 10 hours, and increases to about 13000 after about 12 hours. This shows that a low dielectric constant is maintained for about 10 hours even after UV irradiation is stopped.

[0126] [Example 12] The measurement was performed in the same manner as in Example 5, except that the dielectric constant as a function of temperature was measured for the dielectric material (BDMAB / DIO) instead of the dielectric material (BMAB / DIO). The results are shown in FIG.

[0127] Fig. 18 is also a graph showing the relationship between temperature and dielectric constant in the dielectric material (BDMAB / DIO). According to Fig. 18, it was confirmed that the dielectric constant of the dielectric material (BDMAB / DIO) changes from approximately 12,800 to almost 0 in the range of approximately 55°C to 65°C. From this, it was found that the nematic liquid crystal compound (DIO) exhibits a high dielectric constant (10,000 or more) in the low temperature region (100°C or less) even in the state of the dielectric material (BMAB / DIO), and maintains the characteristic of a significant decrease in the dielectric constant (10,000 or more).

[0128] [Example 13] Measurements were performed in the same manner as in Example 4, except that the dielectric constant at a frequency (1 MHz to 1 Hz, AC voltage 0.1 V) was measured for the dielectric material (BDMAB / DIO) instead of the dielectric material (BMAB / DIO). The results are shown in FIG.

[0129] Fig. 31 is a graph showing the relationship between frequency and dielectric constant of a dielectric material (BDMAB / DIO) at an initial stage (after exposure to visible light without exposure to UV light), after exposure to UV light, and after exposure to visible light. According to Fig. 31, when comparing the initial stage (after exposure to visible light for 5 minutes without exposure to UV light) and the 5 minutes exposure to UV light of the dielectric material (BDMAB / DIO) at around 1000 Hz, it was confirmed that there was a difference of 10,000 or more in the dielectric constant.

[0130] In addition, when comparing the dielectric material (BDMAB / DIO) after 5 minutes of UV irradiation with the initial state (after 5 minutes of visible light irradiation without UV irradiation) and after 5 minutes of visible light irradiation at around 1000 Hz, it was confirmed that there was a difference in the relative dielectric constant of more than 10,000. This difference (change) in relative dielectric constant is equivalent to a change in capacitance from 7 nF to 0.34 μF.

[0131] From this, it is believed that the dielectric constant (capacitance) of the dielectric material (BDMAB / DIO) can be significantly increased or decreased by alternating irradiation with ultraviolet light and visible light, making it possible to control the dielectric constant (capacitance) by light modulation.

[0132] [Example 14] For the dielectric material (BDMAB / DIO) instead of the dielectric material (BMAB / DIO), the ultraviolet light (wavelength 365 nm) was irradiated at each intensity I UV The measurement was performed in the same manner as in Example 8, except that the relative dielectric constant at was measured. The results are shown in FIG.

[0133] FIG. 32 is a graph showing the relationship between the ultraviolet irradiation intensity and the relative dielectric constant of a dielectric material (BDMAB / DIO).

[0134] According to Figure 32, the irradiation intensity I of ultraviolet light (wavelength 365 nm) UV When the irradiation intensity I is 2.3 or 1.0, the relative dielectric constant decreases rapidly within about 0.2 minutes of ultraviolet irradiation. UV When is 0.36, the UV irradiation time is limited to about 1 minute, and the irradiation intensity I UV When the value was 0.15, it was confirmed that the ultraviolet light exposure time gradually decreased within about 2 minutes.

[0135] This suggests that the rate at which the dielectric constant of the dielectric material (BDMAB / DIO) decreases may be controllable by changing the intensity of ultraviolet light irradiation.

[0136] [Example 15] For the dielectric material (BDMAB / DIO) instead of the dielectric material (BMAB / DIO), each irradiation intensity I of visible light (wavelength 450 nm) VIS The measurements were performed in the same manner as in Example 9, except that the relative dielectric constant was measured at 100° C. The results are shown in FIG.

[0137] FIG. 33 is a graph showing the relationship between the irradiation intensity of visible light and the relative dielectric constant of a dielectric material (BDMAB / DIO).

[0138] According to Figure 33, the irradiation intensity I of visible light (wavelength 450 nm) VIS When the irradiation intensity I is 3.0 or 1.7, the relative dielectric constant increases rapidly within about 0.4 minutes of visible light irradiation. VIS When is 0.6, the exposure time of visible light increases rapidly within about 1.4 minutes, and the exposure intensity I VIS When the value was 0.2, it was confirmed that the exposure time of visible light increased gradually within about 3 minutes.

[0139] This suggests that it may be possible to control the rate at which the dielectric constant of the dielectric material (BDMAB / DIO) increases by changing the intensity of visible light irradiation.

[0140] It was found that the dielectric material of this embodiment can repeatedly and significantly increase and decrease the dielectric constant by alternately absorbing two types of light with different wavelengths. Therefore, the dielectric constant of the dielectric material of this embodiment can be controlled by irradiation with light of different wavelengths, and the amount of change in the dielectric constant can be increased.

[0141] The dielectric material of this embodiment can be used as a dielectric material disposed between electrodes of a capacitor because the amount of change in dielectric constant can be greatly controlled by light irradiation.

[0142] In addition, since the dielectric material of this embodiment contains organic compounds (nematic liquid crystal compounds and azo compounds) having flexibility, a flexible dielectric material can be formed and used in devices that require flexibility, such as wearable devices.

[0143] Although an embodiment of the present invention has been described above, the present invention is not limited to a specific embodiment, and various modifications and changes are possible within the scope of the invention described in the claims.

[0144] This application claims priority to Japanese Patent Application No. 2020-137063, filed on August 14, 2020, the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0145] 10 Evaluation Cell 11 Cell 12 electrodes 13, 14 Current collector 15, 16 Wiring 17, 18 Lead wire 20 Samples 30 UV-visible LED light source 31 Ultraviolet light source 32 Visible light source 40 Polarizing Microscope 41 Stage 42 Telescope tube 43 Objective Lens 44 Eyepiece 50 Temperature control device 60 Impedance Analyzer 61 Interface 62 Main Body 70 Audio Amplifier 71 Main unit 72 DC stabilized power supply 73 Oscilloscope 80 Computer 81 Central Processing Unit (CPU) 82 Display

Claims

1. A nematic liquid crystal compound having a dielectric anisotropy; An azo compound which is a trans isomer in the ground state; Contains The azo compound is When it absorbs the first wavelength of light, it is converted to the cis isomer. is converted to the trans isomer upon absorption of light at a second wavelength that is longer than the first wavelength; Dielectric material.

2. The dielectric material of claim 1 , wherein the nematic liquid crystal compound has a relative dielectric constant of 1000 or more.

3. 3. The dielectric material according to claim 1, wherein the nematic liquid crystal compound is an ester compound of a halogenobiphenyl and a halogenophenyldioxane derivative.

4. The dielectric material according to claim 1 , wherein the first wavelength is not less than 300 nm and not more than 390 nm.

5. The dielectric material according to claim 1 , wherein the second wavelength is not less than 400 nm and not more than 490 nm.

6. The dielectric material according to claim 1 , wherein the azo compound is an azobenzene derivative.

7. The dielectric material of claim 6 , wherein the azobenzene derivative is a dimethylbutylazobenzene compound.

8. A capacitor using the dielectric material according to any one of claims 1 to 7.

Images