Liquid crystal dimming element and method for manufacturing same

Abstract

The purpose of the present invention is to improve a response speed from a transparent state to a screen state in a liquid crystal dimming element in which light scattering is increased by receiving ultraviolet light and light scattering is reduced by receiving visible light.　A liquid crystal dimming element according to the present invention comprises: a pair of transparent substrates that each have a transparent electrode and an alignment function layer disposed on one surface of the transparent electrode, and that are disposed such that the alignment function layers face each other; and a liquid crystal layer that includes liquid crystal molecules, a photoresponsive material containing a photoisomerization material, and a polymer of a photopolymerizable monomer, and that is interposed between the pair of transparent substrates, wherein light scattering is increased by receiving ultraviolet light and light scattering is reduced by receiving visible light. The liquid crystal dimming element is characterized in that an angle ϴ [°], formed by an axial direction of an orientation force in which the alignment functional layer acts on the liquid crystal molecules and an axial direction of an orientation force in which the polymer of the photopolymerizable monomer acts on the liquid crystal molecules, satisfies 0<ϴ≤90.

Description

Liquid crystal light control element and its manufacturing method

[0001] The present invention relates to a liquid crystal light control element and a method for manufacturing the same.

[0002] In recent years, technologies have been developed for displaying images on transparent glass such as automobile windshields and building windowpanes. For example, a display device is known that includes an image display whose optical state changes between a light-transmitting state and a light-scattering state, and a projector that projects visible light onto the image display to display an image.

[0003] Specifically, Patent Document 1 discloses a display device that irradiates ultraviolet light onto an image display having a liquid crystal light control element as a display function layer, thereby increasing the light scattering property of the display function layer and changing the screen state from a transparent state to a cloudy white state. The liquid crystal light control element that constitutes this display function layer contains liquid crystal and azobenzene, and ultraviolet light changes the azobenzene molecules from trans to cis isomers, and the bent molecular structure of the cis azobenzene disrupts the alignment of the liquid crystal molecules, thereby increasing the light scattering property.

[0004] Japanese Patent Application Laid-Open No. 2018-185511

[0005] In a liquid crystal light control element mounted on an image display such as that described in Patent Document 1, the faster the response speed from the transparent state to the screen state, the better.

[0006] Therefore, the present invention aims to provide a means for improving the response speed from a transparent state to a screen state in a liquid crystal dimming element whose light scattering properties increase when exposed to ultraviolet light and decrease when exposed to visible light.

[0007] The present inventors conducted extensive research in light of the above-mentioned problems. As a result, they found that the above-mentioned problems can be solved by constructing a liquid crystal dimming device in which a liquid crystal layer interposed between a pair of transparent substrates having an alignment functional layer contains liquid crystal molecules, a photoresponsive material including a photoisomerizable material, and a polymer of a photopolymerizable monomer, and the angle θ (°) between the axial direction of the alignment force exerted on the liquid crystal molecules by the alignment functional layer and the axial direction of the alignment force exerted on the liquid crystal molecules by the polymer of the photopolymerizable monomer satisfies 0<θ≦90. They also found that such a liquid crystal dimming device can be manufactured by applying a predetermined electric field to a liquid crystal composition filled between a pair of transparent substrates having an alignment functional layer, the liquid crystal composition including liquid crystal molecules, a photoresponsive material including a photoisomerizable material, a photopolymerizable monomer, and a photopolymerization initiator, to polymerize the photopolymerizable monomer. Based on these findings, the present inventors have completed the present invention.

[0008] That is, one aspect of the present invention relates to a liquid crystal light control device comprising a pair of transparent substrates each having a transparent electrode and an alignment functional layer disposed on one surface of the transparent electrode such that the alignment functional layers face each other, and a liquid crystal layer interposed between the pair of transparent substrates, the liquid crystal layer including liquid crystal molecules, a photoresponsive material including a photoisomerizable material, and a polymer of a photopolymerizable monomer, the liquid crystal layer increasing light scattering properties upon exposure to ultraviolet light and decreasing light scattering properties upon exposure to visible light. The liquid crystal light control device is characterized in that the angle θ [°] between the axial direction of the alignment force exerted on the liquid crystal molecules by the alignment functional layer and the axial direction of the alignment force exerted on the liquid crystal molecules by the polymer of the photopolymerizable monomer satisfies 0<θ≦90.

[0009] FIG. 1 is a perspective view showing a schematic configuration of a display device according to an embodiment of the liquid crystal light control element of the present invention. FIG. 2A is a cross-sectional view showing a schematic configuration of an image display. FIG. 2B is a modified example of the image display shown in FIG. 2A. FIG. 3 is a diagram illustrating the operation of the display device 10 when an image is displayed. FIG. 4 is a diagram illustrating the operation of the display device 10 when an image is not displayed. FIG. 5 is a layout diagram of a measuring device for measuring the transmittance of a liquid crystal light control element. FIG. 6 is a graph showing the change over time in visible light transmittance after ultraviolet light irradiation for Comparative Example 1 and Example 1. FIG. 7 is a graph showing the change over time in visible light transmittance after ultraviolet light irradiation for Examples 2 and 3. FIG. 8 is a graph showing the change over time in visible light transmittance after ultraviolet light irradiation for Examples 4 to 6 and Comparative Examples 3 and 4.

[0010] One aspect of the present invention is a liquid crystal dimming device comprising: a pair of transparent substrates each having a transparent electrode and an alignment functional layer disposed on one surface of the transparent electrode, the alignment functional layers arranged so that the alignment functional layers face each other; and a liquid crystal layer interposed between the pair of transparent substrates, the liquid crystal layer including liquid crystal molecules, a photoresponsive material including a photoisomerizable material, and a polymer of a photopolymerizable monomer, wherein the angle θ [°] between the axial direction of the alignment force exerted on the liquid crystal molecules by the alignment functional layer and the axial direction of the alignment force exerted on the liquid crystal molecules by the polymer of the photopolymerizable monomer satisfies 0 < θ ≦ 90, and wherein light scattering increases upon exposure to ultraviolet light and decreases upon exposure to visible light. The liquid crystal dimming device according to the present invention achieves an improved response speed when switching from a transparent state to a screen state.

[0011] Hereinafter, the embodiments of the liquid crystal light control element according to the present invention will be described with reference to the drawings. However, the technical scope of the present invention should be determined based on the claims and is not limited to the following embodiments. Note that the dimensional ratios in the drawings are exaggerated for the convenience of explanation and may differ from the actual ratios.

[0012] 1 is a perspective view showing a schematic configuration of a display device 10 according to an embodiment of the liquid crystal light control element of the present invention. The display device 10 of this embodiment includes an image display body 100, a first projector 200, a second projector 300, a third projector 400, and a control unit 500.

[0013] The image display 100 is a thin plate-like member whose optical state changes between a transparent state and a non-transparent state, and has a front surface 100a facing the first to third projectors 200 to 400, and a back surface 100b opposite the front surface 100a. The image display 100 changes from a transparent state to a non-transparent state when exposed to ultraviolet light, and changes from a non-transparent state to a transparent state when exposed to first visible light. The image display 100 is attached to, for example, the windshield of an automobile. A detailed description of the image display 100 will be given later.

[0014] The first projector 200 is a projector that emits ultraviolet light and is disposed opposite the front surface 100a of the image display body 100. The first projector 200 serves as an ultraviolet light projecting unit and emits ultraviolet light with a wavelength of, for example, 365 nm. The first projector 200 projects the ultraviolet light onto the front surface 100a of the image display body 100, changing the ultraviolet light projected region 100c on the image display body 100 from a transparent state to a non-transparent state.

[0015] The second projector 300 is a projector that emits visible light of a specific wavelength and is disposed opposite the front surface 100a of the image display body 100. The second projector 300 serves as a first visible light projector, and emits first visible light having a wavelength of, for example, about 450 nm. The second projector 300 projects the first visible light onto the image display body 100, which is in a non-transparent state, and changes the ultraviolet light projected region 100c on the image display body 100 from a non-transparent state to a transparent state.

[0016] The third projector 400 is a color projector and is disposed opposite the front surface 100a of the image display body 100. The third projector 400 serves as a second visible light projecting unit and emits second visible light, which is light of one of three colors: blue (wavelength 450 nm), green (wavelength 532 nm), and red (wavelength 640 nm), or a combination of two or more colors. The third projector 400 projects the second visible light onto the image display body 100 in a non-transparent state, thereby displaying an image 600 on the image display body 100.

[0017] The control unit 500 controls the operations of the first to third projectors 200 to 400. The control unit 500 switches between light projection and non-light projection of the first and second projectors 200, 300 while communicating with a higher-level control device (not shown). The control unit 500 also sends image information to the third projector 400 while communicating with the higher-level control device.

[0018] The first and third projectors 200 and 400 respectively project the ultraviolet light and the second visible light so that the image 600 displayed on the image display body 100 by the second visible light is included inside the projection area 100c of the ultraviolet light on the image display body 100. The second projector 300 projects the first visible light so that the projection area 100c of the ultraviolet light is included in the projection area of ​​the first visible light on the image display body 100.

[0019] Next, the image display member 100 of the display device 10 will be described in detail with reference to Fig. 2A. Fig. 2A is a cross-sectional view showing a schematic configuration of the image display member 100. The image display member 100 of this embodiment includes a liquid crystal light control element 110, a light control layer 120, and an ultraviolet light blocking layer 130. The liquid crystal light control element 110 is disposed on the front surface 100a side of the image display member 100, and the ultraviolet light blocking layer 130 is disposed on the back surface 100b side of the image display member 100. The light control layer 120 is disposed between the liquid crystal light control element 110 and the ultraviolet light blocking layer 130.

[0020] The liquid crystal light control element 110 is a film member whose optical state changes between a transparent state and a non-transparent state. The liquid crystal light control element 110 has the optical property that, when exposed to ultraviolet light, its light scattering property increases and it becomes cloudy, and when exposed to first visible light, its light scattering property decreases and it returns to a transparent state. The liquid crystal light control element 110 also has the function of displaying an image on the image display 100.

[0021] The ultraviolet light-shielding layer 130 is a transparent film member that blocks ultraviolet light. The ultraviolet light-shielding layer 130 is made of a transparent resin containing an ultraviolet light reflector or ultraviolet light absorber, and reflects or absorbs light in a wavelength region near ultraviolet light to block it. The ultraviolet light-shielding layer 130 is disposed on the rear surface 100b side of the display body 100, and prevents ultraviolet light from entering the liquid crystal light control element 110 from the rear surface 100b of the display body 100.

[0022] 2B, the image display element 100 of the display device 10 may include a liquid crystal light control element 110 and an ultraviolet light blocking layer 130. In this case, the liquid crystal light control element 110 also serves as a light control layer.

[0023] <<Liquid Crystal Light Control Element>> Components of a liquid crystal light control element according to one embodiment of the present invention will be described below.

[0024] [Transparent Substrate] The liquid crystal light control element includes a pair of transparent substrates. Each transparent substrate has a transparent electrode and an alignment layer disposed on one surface of the transparent electrode. The pair of transparent substrates are disposed so that the alignment layers face each other, and a liquid crystal layer (described later) is disposed in the gap between the transparent substrates. Here, a transparent substrate such as a glass substrate or a resin substrate can be used as the transparent substrate. Furthermore, an ITO film, for example, can be used as the transparent electrode.

[0025] The alignment functional layer may be a conventionally known layer, such as a polyimide film subjected to an alignment film treatment. Examples of alignment film treatment include physical treatments such as rubbing, and mechanical surface treatments. It is also possible to use an alignment functional layer that has been oriented by other means. The alignment functional layer may be one that aligns liquid crystal molecules homogeneously (horizontally) or homeotropically (vertically). However, in the liquid crystal dimming element according to this embodiment, the axial direction of the alignment force exerted by the alignment functional layer on the liquid crystal molecules must satisfy a predetermined relationship with the alignment force exerted by the polymer of the photopolymerizable monomer described below.

[0026] There is no particular limitation on the thickness of the gap (cell gap; equal to the thickness of the liquid crystal layer) between the pair of transparent substrates, but from the viewpoint of sufficiently reducing the transmittance in the screen state after ultraviolet light irradiation and achieving a better response speed, the thickness is preferably more than 2 μm, more preferably 3 μm or more, even more preferably 4 μm or more, still more preferably 5 μm or more, particularly preferably 8 μm or more, and most preferably 10 μm or more.

[0027] [Liquid Crystal Layer] The liquid crystal layer is a layer that essentially contains liquid crystal molecules, a photoresponsive material including a photoisomerizable material, and a polymer of a photopolymerizable monomer.

[0028] (Liquid Crystal Molecules) The liquid crystal molecules are not particularly limited, and known nematic liquid crystal molecules can be used. The liquid crystal molecules are compounds in which two to four cyclic compounds, such as benzene rings, cyclohexane rings, cyclohexene rings, pyrimidine rings, dioxane rings, and pyridine rings, are bonded by single bonds, ester bonds, acetylene bonds, ethane bonds, ethylene bonds, azo bonds, or the like, and have a cyano group, a fluoro group, an alkyl group, an alkenyl group, or an alkoxy group at their terminals. These compounds may be substituted with a cyano group, a fluoro group, an alkyl group, an alkenyl group, an alkoxy group, or the like. Specifically, liquid crystal molecules such as biphenyl-based, biphenylcyclohexane-based, terphenyl-based, phenylcyclohexane-based, Schiff base-based, azo-based, azoxy-based, benzoate ester-based, cyclohexanecarboxylic acid ester-based, pyrimidine-based, dioxane-based, cyclohexylcyclohexane ester-based, cyclohexylethane-based, cyclohexene-based, fluorine-based, and tolan-based liquid crystal molecules can be used. Examples of the liquid crystal molecule include 4-cyano-4'-ethylbiphenyl, 4-cyano-4'-pentylbiphenyl, 4-cyano-4'-propylbiphenyl, 4-cyano-4"-p-terphenyl, 4-cyano-4'-propoxy-1,1'-biphenyl, 4-cyano-4'-(4-pentylcyclohexyl)biphenyl, 4-hexyl-4'-cyanophenylpyridine, 4-hexyl-4'-propylphenylcyclohexane, 4-methyl-4'-propyldicyclohexane, and 4-hexyl-4'-methoxydicyclohexane. The liquid crystal molecule can be used alone or as a mixture of two or more types. Either synthesized or commercially available liquid crystal molecules can be used.

[0029] The content of liquid crystal molecules in the liquid crystal layer is, for example, 60 to 95 mass %, preferably 65 to 90 mass %, more preferably 70 to 85 mass %, and particularly preferably 75 to 80 mass %, relative to the total mass of the liquid crystal molecules, the photoresponsive material including the photoisomerizable material, and the polymer of the photopolymerizable monomer.

[0030] (Photoresponsive Material) The photoresponsive material includes a photoisomerizable material. A photoisomerizable material refers to a compound in which structural changes such as bond rearrangement are induced by absorption of light, for example, cis-trans isomerization occurs upon absorbing light. The photoisomerizable material according to this embodiment changes its structure from a trans isomer to a cis isomer upon exposure to ultraviolet light, and the liquid crystal helical induction power changes reversibly in accordance with the structural change.

[0031] Examples of photoisomerizable materials include azobenzene compounds, chalcone derivatives, sulfoxide compounds, fulgide compounds, and cinnamic acid compounds.

[0032] The azobenzene compound includes a compound represented by the following chemical formula (1).

[0033]

[0034] In the above chemical formula (1), R １ ~R １０ are each independently a group selected from the group consisting of a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a halogen group, a hydroxy group, a carboxyl group, an ester group (—COOR′), and combinations thereof, and R′ is a group selected from the group consisting of a substituted or unsubstituted alkyl group and a substituted or unsubstituted alkoxy group.

[0035] Examples of the alkyl group include linear alkyl groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, and n-hexadecyl; and isopropyl, isobutyl, sec-butyl, tert-butyl, isoamyl, and tert-pentyl groups. , branched alkyl groups such as neopentyl group, 1-methylpentyl group, 4-methyl-2-pentyl group, 3,3-dimethylbutyl group, 2-ethylbutyl group, 1-methylhexyl group, tert-octyl group, 1-methylheptyl group, 2-ethylhexyl group, 2-propylpentyl group, 2,2-dimethylheptyl group, 2,6-dimethyl-4-heptyl group, 3,5,5-trimethylhexyl group, 1-methyldecyl group, and 1-hexylheptyl group.

[0036] Examples of the alkoxy group include linear alkoxy groups such as a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, an n-pentyloxy group, an n-hexyloxy group, an n-heptyloxy group, an n-octyloxy group, an n-nonyloxy group, an n-decyloxy group, an n-undecyloxy group, an n-dodecyloxy group, an n-tridecyloxy group, an n-tetradecyloxy group, an n-pentadecyloxy group, and an n-hexadecyloxy group; an isopropoxy group, a tert-butoxy group, a 1-methylpentyloxy group, and the like. branched alkoxy groups such as a silyl group, a 4-methyl-2-pentyloxy group, a 3,3-dimethylbutyloxy group, a 2-ethylbutyloxy group, a 1-methylhexyloxy group, a tert-octyloxy group, a 1-methylheptyloxy group, a 2-ethylhexyloxy group, a 2-propylpentyloxy group, a 2,2-dimethylheptyloxy group, a 2,6-dimethyl-4-heptyloxy group, a 3,5,5-trimethylhexyloxy group, a 1-methyldecyloxy group, and a 1-hexylheptyloxy group.

[0037] When the alkyl group and alkoxy group have a substituent, the substituent to be introduced is not particularly limited. Specific examples include a halogen group, an unsubstituted alkyl group, an unsubstituted alkoxy group, and combinations thereof. The halogen group refers to a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br), or an iodo group (-I).

[0038] The azobenzene compound may be an ester of isosorbide or isomannide with the compound represented by the above chemical formula (1).

[0039] In a preferred embodiment, the azobenzene compound is selected from the compounds represented by the following chemical formulas (2) to (6).

[0040]

[0041] An example of the chalcone derivative is a compound represented by the following chemical formula (7).

[0042]

[0043] An example of the sulfoxide compound is a compound represented by the following chemical formula (8).

[0044]

[0045] An example of the fulgide compound is a compound represented by the following chemical formula (9).

[0046]

[0047] Examples of cinnamic acid compounds include compounds represented by the following chemical formulas (10) and (11).

[0048]

[0049] From the viewpoint of a fast photoisomerization reaction rate, the photoisomerizable material preferably contains an azobenzene compound, more preferably contains a compound represented by chemical formulas (2) to (6), and even more preferably contains a compound represented by chemical formula (5) or (6). The photoisomerizable material can be used alone or as a mixture of two or more types. There are no particular limitations on the synthesis method of the photoisomerizable material, and conventionally known synthesis methods can be applied.

[0050] In a preferred embodiment, the photoresponsive material further contains a non-photoresponsive chiral compound, from the viewpoint of canceling the helical induction force of the photoisomerizable material and further improving the transparency of the light control film in the transparent state.

[0051] The non-photoresponsive chiral compound can be a compound having an optical rotation different from that of the photoisomerizable material used. By using a photoisomerizable material and a non-photoresponsive chiral compound in combination, a compensated state can be achieved in which the helical twisting power (HTP) of the photoisomerizable material and the non-photoresponsive chiral compound cancel each other out. In other words, the disorder of the alignment and phase change of the liquid crystal molecules caused by the twisting power of the trans-isomerizable material can be further suppressed. Therefore, the transparency of the liquid crystal dimming element in the transparent state can be further increased. The helical twisting power can be determined by the Cano wedge method.

[0052] Examples of non-photoresponsive chiral compounds include (R)-2-octyl 4-[4-(hexyloxy)benzoyloxy]benzoate, (S)-2-octyl 4-[4-(hexyloxy)benzoyloxy]benzoate, 4'-[(S)-2-methylbutyl]-1,1'-biphenyl-4-carbonitrile, bis[4-(trans-4-pentylcyclohexyl)benzoate](R)-1-phenyl-1,2-ethanediyl, bis[4-(trans-4-pentylcyclohexyl)benzoate](S)-1-phenyl-1,2-ethanediyl, bis[4-(4-pentyloxyphenyl)benzoate](aS)-1,1'-binaphthalene-2,2'-diyl, etc. Either commercially available or synthesized non-photoresponsive chiral compounds may be used.

[0053] When an azobenzene compound is used as the photoisomerizable material, the non-photoresponsive chiral compound preferably comprises a compound selected from (R)-2-octyl 4-[4-(hexyloxy)benzoyloxy]benzoate, 4'-[(S)-2-methylbutyl]-1,1'-biphenyl-4-carbonitrile, (R)-1-phenyl-1,2-ethanediyl bis[4-(trans-4-pentylcyclohexyl)benzoate] and (aS)-1,1'-binaphthalene-2,2'-diyl bis[4-(4-pentyloxyphenyl)benzoate], and more preferably comprises (R)-2-octyl 4-[4-(hexyloxy)benzoyloxy]benzoate or (aS)-1,1'-binaphthalene-2,2'-diyl bis[4-(4-pentyloxyphenyl)benzoate].

[0054] The content of the photoresponsive material including the photoisomerizable material in the liquid crystal layer is, for example, 5 to 20 parts by mass per 100 parts by mass of liquid crystal molecules, and from the viewpoint of being able to more effectively exhibit the effects of the present invention, it is preferably 7 to 15 parts by mass.

[0055] (Photopolymerizable Monomer Polymer) A photopolymerizable monomer polymer is a polymer formed by polymerizing a photopolymerizable monomer by light irradiation in the presence of a photopolymerization initiator. Details of the polymerization method will be described later, but here, the photopolymerizable monomer and the photopolymerization initiator, which are raw materials for the photopolymerizable monomer polymer, will be described.

[0056] Examples of the photopolymerizable monomer include monomers having one or more general photopolymerizable groups in the molecule, such as an acryloyl group, a methacryloyl group, or a vinyl group.

[0057] Examples of the photopolymerizable monomer include monofunctional acrylate compounds such as methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, butyl ethyl acrylate, butoxyethyl acrylate, 2-cyanoethyl acrylate, benzyl acrylate, cyclohexyl acrylate, 2-hydroxypropyl acrylate, 2-ethoxyethyl acrylate, N,N-diethylaminoethyl acrylate, N,N-dimethylaminoethyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, glycidyl acrylate, tetrahydrofurfuryl acrylate, isobornyl acrylate, isodecyl acrylate, lauryl acrylate, morpholine acrylate, phenoxyethyl acrylate, and phenoxydiethylene glycol acrylate; monofunctional methacrylate compounds such as tetrahydrofuran, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, butylethyl methacrylate, butoxyethyl methacrylate, 2-cyanoethyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, 2-hydroxypropyl methacrylate, 2-ethoxyethyl acrylate, N,N-diethylaminoethyl methacrylate, N,N-dimethylaminoethyl methacrylate, dicyclopentanyl methacrylate, dicyclopentenyl methacrylate, glycidyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl methacrylate, isodecyl methacrylate, lauryl methacrylate, morpholine methacrylate, phenoxyethyl methacrylate, and phenoxydiethylene glycol methacrylate;Polyfunctional acrylate compounds such as 4,4'-bis[6-(acryloyloxy)hexyloxy]biphenyl, 2-methyl-1,4-phenylenebis(4-3-(acryloyloxy)propoxy)benzoate), diethylene glycol diacrylate, 1,4-butanediol diacrylate, 1,3-butylene glycol diacrylate, dicyclopentanyl diacrylate, glycerol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tetraethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, ditrimethylolpropane tetraacrylate, dipentaerythritol hexaacrylate, and dipentaerythritol monohydroxypentaacrylate; 4,4'-bis[6- (methacryloyloxy)hexyloxy]biphenyl, 2-methyl-1,4-phenylenebis(4-3-(methacryloyloxy)propoxy)benzoate), diethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,3-butylene glycol dimethacrylate, dicyclopentyl dimethacrylate glycerol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, tetraethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, pentaerythritol trimethacrylate, ditrimethylolpropane tetramethacrylate, dipentaerythritol hexamethacrylate, dipentaerythritol monohydroxypentamethacrylate, and other polyfunctional methacrylate compounds;

[0058] From the viewpoint of further increasing the reflectance in a non-transparent state, the photopolymerizable monomer preferably contains at least one selected from a polyfunctional acrylate compound and a polyfunctional methacrylate compound, more preferably contains at least one selected from a liquid crystalline polyfunctional acrylate compound and a polyfunctional methacrylate compound, and even more preferably contains at least one selected from the group consisting of 4,4'-bis[6-(acryloyloxy)hexyloxy]biphenyl, 4,4'-bis[6-(methacryloyloxy)hexyloxy]biphenyl, bis[4-[3-(acryloyloxy)propoxy]benzoic acid]2-methyl-1,4-phenylene, 2-methyl-1,4-phenylenebis(4-3-(methacryloyloxy)propoxy)benzoate), and acrylic acid = 6-(4'-cyano-1,1'-biphenyl-4-yloxy)hexyl. Note that the photopolymerizable monomer may be used alone or in combination of two or more types.

[0059] The photopolymerization initiator is not particularly limited, and conventionally known photopolymerization initiators can be used. The photopolymerization initiator can be appropriately selected depending on the photoisomerizable material used. However, from the viewpoint of transparency in a transparent state, the photopolymerization initiator is preferably one that can generate radicals that can initiate polymerization of the photopolymerizable monomer by exposure to light of a wavelength different from the wavelength that promotes isomerization of the photoisomerizable material. In this specification, "light of a wavelength different from the wavelength that promotes isomerization of the photoisomerizable material" means "light of a wavelength different from the wavelength that promotes isomerization of the photoisomerizable material from the trans isomer to the cis isomer" or "light of a wavelength different from the wavelength that promotes isomerization of the photoisomerizable material from the cis isomer to the trans isomer."

[0060] From the viewpoint of curability, the photopolymerization initiator preferably has absorbance at wavelengths of visible light, more preferably at wavelengths in the range of 400 to 500 nm. Furthermore, from the viewpoint of curability, the photopolymerization initiator preferably has an absorbance of 0.5 or more, more preferably 1.0 or more, at a concentration of 0.1% by mass, an optical path length of 1 cm, and a wavelength of 400 nm. The upper limit of the absorbance is not particularly limited, and is, for example, 3.0 or less.

[0061] The absorbance of the photopolymerization initiator can be measured using a spectrophotometer (UV-2550, manufactured by Shimadzu Corporation) in accordance with JIS K0115: 2004. The measurement sample is prepared by dissolving the photopolymerization initiator at a concentration of 0.1% by mass in a solvent that does not absorb light in the wavelength range of 400 to 500 nm (e.g., acetonitrile, 1-methyl-2-pyrrolidone).

[0062] Examples of photopolymerization initiators include phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,4-cyclopentadienyl)bis[2,6-difluoro-3-(1-pyrryl)phenyl]titanium(IV), (benzene)tricarbonylchromium, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(dimethylamino)benzophenone, 2-chlorothioxanthen-9-one, 4-(dimethylamino)benzophenone, phenanthrenequinone, and thioxanthen-9-one. The photopolymerization initiator may be either a commercially available product or a synthetic product. Examples of commercially available products include IRGACURE 819 and 784 (manufactured by IGM Resins B.V.) and DAROCUR (registered trademark) TPO (manufactured by BASF). The photopolymerization initiator may be used alone or in combination of two or more kinds.

[0063] The content of the photopolymerizable monomer polymer in the liquid crystal layer is preferably 5 to 30 parts by mass, more preferably 8 to 25 parts by mass, and even more preferably 10 to 18 parts by mass, per 100 parts by mass of liquid crystal molecules.

[0064] (Other Components) The liquid crystal layer may contain other components as long as the effects of the present invention are not impaired. Examples of other components include nanoparticles, dichroic dyes, photopolymerization initiation aids, and dye sensitizers.

[0065] Examples of nanoparticles include nanoparticles made of oxides of metals such as silicon, titanium, zirconium, and barium.

[0066] Examples of dichroic dyes include acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, and anthraquinone dyes.

[0067] Examples of the photopolymerization initiator aid include methyldiethanolamine and 4-dimethylaminobenzoic acid.

[0068] The dye sensitizer is not particularly limited as long as it is a dye that can be excited by light irradiation and transfer energy to the photopolymerization initiator. Examples of the dye sensitizer include coumarin-based dyes, rhodamine-based dyes, oxazine-based dyes, carbocyanine-based dyes, styryl-based dyes, xanthene-based dyes, merocyanine-based dyes, rhodacyanine-based dyes, porphyrin-based dyes, and acridine-based dyes.

[0069] [Characteristics of Liquid Crystal Light Control Device] As described above with reference to the drawings, the liquid crystal light control device according to this embodiment has the property that light scattering increases when exposed to ultraviolet light and decreases when exposed to visible light. Here, the liquid crystal light control device according to this embodiment preferably has a higher visible light transmittance in the transparent state (state in which light scattering is reduced). Specifically, the visible light transmittance (transmittance for light with a wavelength of 650 nm) of the liquid crystal light control device in the transparent state is preferably 65% ​​or more, more preferably 70% or more, even more preferably 75% or more, and particularly preferably 80% or more. On the other hand, the liquid crystal light control device according to this embodiment preferably has a lower visible light transmittance in the screen state (state in which light scattering is increased). Specifically, the visible light transmittance (transmittance for light with a wavelength of 650 nm) of the liquid crystal light control device in the screen state is preferably 30% or less, more preferably 20% or less, even more preferably 10% or less, and particularly preferably 5% or less.

[0070] The liquid crystal dimming element according to this embodiment also has the characteristic that the angle θ [°] formed between the axial direction of the alignment force exerted on the liquid crystal molecules contained in the liquid crystal layer by an alignment functional layer (for example, an alignment film) mounted on the transparent substrate and the axial direction of the alignment force exerted on the liquid crystal molecules by a polymer of a photopolymerizable monomer also contained in the liquid crystal layer satisfies 0<θ≦90 (i.e., θ is not 0 [°] (the angle formed is not parallel)). This characteristic will be described below.

[0071] First, the liquid crystal molecules in the liquid crystal layer near the alignment layer are subjected to the alignment force of the alignment layer, and are aligned in the direction of the alignment layer. On the other hand, the liquid crystal molecules farther from the alignment layer are subjected to the alignment force of the polymer (polymer) of the photopolymerizable monomer, and are aligned in the direction of the polymer.

[0072] In contrast, in the liquid crystal light control device of this embodiment, the axial direction of the aligning force exerted by the alignment functional layer on the liquid crystal molecules is not parallel to the axial direction of the aligning force exerted by the polymer of the photopolymerizable monomer on the liquid crystal molecules. Instead, the angle θ [°] between these axial directions is 0<θ≦90°. An electric field is applied during polymerization to constrain the alignment of the liquid crystal molecules, and the photopolymerizable monomer is polymerized in this state, thereby controlling the direction of the aligning force exerted by the polymer on the liquid crystal molecules. This allows the alignment direction of the liquid crystal molecules to change rapidly when the liquid crystal light control device receives ultraviolet light, thereby improving the response speed from the transparent state to the screen state. Note that, from the perspective of more significantly exhibiting the effects of the present invention, the aligning force exerted by the alignment functional layer on the liquid crystal molecules is preferably in the direction that homeotropically aligns the liquid crystal molecules (vertical alignment). That is, when the alignment functional layer employs an alignment film, the alignment film is preferably a vertical alignment film.

[0073] Whether or not θ is in the range of 0<θ≦90 can be determined by observing using a polarizing microscope as described in the Examples section below, and determining whether or not an image with a color tone different from both the image observed when liquid crystal is sealed in a horizontal alignment film and the image observed when liquid crystal is sealed in a vertical alignment film.

[0074] <<Method for Manufacturing Liquid Crystal Light Control Element>> The method for manufacturing the liquid crystal light control element according to the embodiment of the present invention is not particularly limited, and conventionally known knowledge can be referred to as appropriate. However, according to another embodiment of the present invention, a preferred method for manufacturing the liquid crystal light control element according to the embodiment of the present invention is provided.

[0075] This manufacturing method includes a pair of transparent substrates having a transparent electrode and an alignment functional layer disposed on one surface of the transparent electrode, the alignment functional layers facing each other, and a liquid crystal composition containing liquid crystal molecules, a photoresponsive material including a photoisomerizable material, a photopolymerizable monomer, and a photopolymerization initiator, filled between the pair of transparent substrates. The liquid crystal composition polymerizes the photopolymerizable monomer while applying an electric field to the liquid crystal composition (hereinafter also referred to as a "polymerization step"). This manufacturing method is also suitable for a liquid crystal display device in which the absolute value of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field (|Δε×E|) is 2.1×10 ７ The feature of this method is that the electric field is applied in such a manner as described above.

[0076] The liquid crystal composition is a composition before the liquid crystal layer is photopolymerized and contains the components of the liquid crystal layer described above, and further contains a solvent as needed. The solvent is not particularly limited as long as it is compatible with the liquid crystal molecules, the photoresponsive material, the photopolymerizable monomer, and the photopolymerization initiator. Examples of the solvent include toluene, acetone, ethyl acetate, methyl ethyl ketone, and hexanediol diacrylate.

[0077] In the polymerization step, first, the liquid crystal composition is filled between a pair of transparent substrates having a transparent electrode and an alignment functional layer disposed on one surface of the transparent electrode, the alignment functional layers being arranged so as to face each other. There are no particular limitations on the method for filling the liquid crystal composition.

[0078] Next, the photopolymerizable monomer is polymerized while applying an electric field to the liquid crystal composition. To polymerize the photopolymerizable monomer, light of a wavelength absorbed by the photopolymerization initiator used may be irradiated. Here, from the viewpoint of further improving the transparency of the liquid crystal dimming element in its transparent state, it is preferable to perform this process in an environment that blocks ultraviolet light and wavelengths absorbed by the polymerization initiator used. For example, this process may be performed under orange light (wavelength 595 to 610 nm). Furthermore, the wavelength of the light irradiated here is preferably different from the wavelength that promotes isomerization of the photoisomerizable material. This prevents the trans- or cis-isomerized photoisomerizable material from being isomerized to the cis- or trans-isomer during polymerization, and also prevents the alignment of liquid crystal molecules from being disturbed by the isomerization of the photoisomerizable material. Therefore, a liquid crystal layer with higher transparency in the transparent state can be obtained. The wavelength of the light irradiated can be appropriately selected depending on the photoresponsive material, including the photoisomerizable material, and the photopolymerization initiator used.

[0079] In one embodiment, from the viewpoint of further suppressing the disorder of the alignment of the liquid crystal molecules, irradiation with visible light is preferred, and irradiation with light having a wavelength in the range of 400 to 500 nm and / or irradiation with light having an emission peak wavelength in the range of 420 to 460 nm is more preferred. In particular, when the above-mentioned azobenzene compound is used as the photoisomerizable material, irradiation with light having a wavelength in this range can improve the transparency of the liquid crystal layer in the transparent state. Note that when irradiating with light, a filter that transmits only a specific wavelength range may be used as necessary. The amount of light to be irradiated is, for example, 1,000 to 50,000 mJ / cm. ２ The temperature condition during light irradiation is, for example, 10 to 40°C.

[0080] In the polymerization step, an electric field is applied to the filled liquid crystal composition simultaneously with the polymerization of the photopolymerizable monomer by the above-mentioned light irradiation. This electric field may be applied along the lamination direction of the transparent substrate and the liquid crystal layer. Furthermore, the period of light irradiation for polymerization of the photopolymerizable monomer and the period of electric field application do not need to be completely the same, as long as there is at least a period during which light irradiation and electric field application are carried out simultaneously. However, it is preferable that the electric field be applied to the liquid crystal composition throughout the entire light irradiation period.

[0081] The electric field applied to the liquid crystal composition may be a DC electric field or an AC electric field. The frequency of the AC electric field is usually about 40 to 80 Hz. As described above, in the manufacturing method according to this embodiment, the electric field is applied such that the absolute value of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field (|Δε×E|) is 2.1×10 ７ By applying an electric field so as to satisfy this requirement, the orientation force exerted by the polymer of the photopolymerizable monomer on the liquid crystal molecules becomes sufficiently large, and the liquid crystal molecules are sufficiently oriented. As a result, the visible light transmittance in the transparent state can be sufficiently increased. There is no particular upper limit to the absolute value of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field (|Δε×E|), but it is preferable that the upper limit be 6.2×10 ７ It is preferable that the value is not more than 2.1×10. If the value is within this range, the effect of improving the response speed can be particularly remarkable. In addition, the visible light transmittance, which has decreased after receiving ultraviolet light, is prevented from increasing again. That is, in a preferred embodiment, the electric field is set so that the absolute value (|Δε×E|) of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field is 2.1×10 ７ ~6.2 x 10 ７ The magnitude E of the electric field can be controlled by appropriately adjusting the value of the applied voltage and the value of the cell gap based on the relational expression E=V / d.

[0082] <<Operation of Display Device>> Next, the operation of the display device 10 that displays an image on the image display body 100 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 is a diagram for explaining the operation of the display device 10 when an image is displayed, and Fig. 4 is a diagram for explaining the operation of the display device 10 when an image is not displayed.

[0083] 3 , when an image is displayed on the image display body 100, the first projector 200 first projects ultraviolet light onto the front surface 100a of the image display body 100. The ultraviolet light projected area 100c on the image display body 100 changes from a transparent state to a non-transparent state. Then, the third projector 400 projects second visible light onto the light projected area 100c on the image display body 100, which is in the non-transparent state, to display an image 600 on the image display body 100.

[0084] While the image 600 is displayed on the image display 100, in order to prevent the image display 100 from returning from a non-transparent state to a transparent state due to receiving the second visible light, the first projector 200 continues to project ultraviolet light onto the image display 100. Specifically, the first projector 200 continues to project ultraviolet light with an output such that the rate at which the photoisomerizable material is isomerized by the ultraviolet light (e.g., the rate at which trans isomers are converted to cis isomers) is greater than the rate at which the photoisomerizable material is isomerized by the second visible light (e.g., the rate at which cis isomers are converted to trans isomers).

[0085] 4 , when no image is displayed on the image display body 100 (when the image is erased), the first and third projectors 200, 400 first stop projecting the ultraviolet light and the second visible light, respectively. Then, the second projector 300 projects the first visible light onto the front surface 100a of the image display body 100, thereby returning the ultraviolet light-projected region 100c on the image display body 100 from the non-transparent state to the transparent state. At this time, it is also possible to return to the transparent state (erasing the image) in a short time by applying a voltage between the transparent electrodes of the liquid crystal light control element included in the display device 10.

[0086] As described above, the display device 10 of this embodiment switches between the transparent state and the non-transparent state of the image display body 100 by switching between emitting and not emitting ultraviolet light and the first visible light. Then, the second visible light is emitted onto the image display body 100 in the non-transparent state, thereby displaying the image 600 on the image display body 100 in the non-transparent state. With this configuration, the image display body 100, which is normally in the transparent state, can be temporarily made non-transparent, thereby displaying the image 600 on the image display body 100.

[0087] Although the above embodiments have been described using the liquid crystal light control element as an example of its application to a display device, the application of the liquid crystal light control element is not limited to this. The liquid crystal light control element can also be used, for example, in a shading device for suppressing temperature increases in greenhouses or indoor living spaces due to sunlight. In any of these applications, the improved response speed of the element as it transitions from the transparent state to the screen state is extremely advantageous.

[0088] The following embodiments are also included within the scope of the present invention: the liquid crystal light control device according to claim 1 having the features of claim 2; the liquid crystal light control device according to claim 1 or 2 having the features of claim 3; the liquid crystal light control device according to any one of claims 1 to 3 having the features of claim 4; the liquid crystal light control device according to any one of claims 1 to 4 having the features of claim 5; the liquid crystal light control device according to any one of claims 1 to 5 having the features of claim 6; a method for manufacturing the liquid crystal light control device according to any one of claims 1 to 6, the method having the features of claim 7; the manufacturing method according to claim 7 having the features of claim 8; a display device using the liquid crystal light control device according to any one of claims 1 to 6; and a shading device using the liquid crystal light control device according to any one of claims 1 to 6.

[0089] The present invention will be described in more detail below with reference to examples. However, the technical scope of the present invention is not limited to the following examples. Unless otherwise specified, the following operations were carried out in an environment of 25°C and 50% RH.

[0090] <<Preparation of Liquid Crystal Light Control Device>> Liquid crystal light control devices of Examples and Comparative Examples were prepared using the following method: The specifications and preparation conditions of the liquid crystal light control devices prepared in this manner are shown in Table 1 below.

[0091] Example 1 The liquid crystal molecules used were p-type liquid crystal Sb-826010 (Δε=12.6, manufactured by Shanben), the photoisomerization material was an azobenzene compound BN-OCO-Ph-8, the non-photoresponsive chiral compound (S)-BN-OCO (bis[4-(4-pentyloxyphenyl)benzoic acid](aS)-1,1′-binaphthalene-2,2′-diyl), the photopolymerizable monomers were acrylic acid=6-(4′-cyano-1,1′-biphenyl-4-yloxy)hexyl (CB6) and bis[4-[3-(acryloyloxy)propoxy]benzoic acid]2-methyl-1,4-phenylene (RM257), and the photopolymerization initiator was IRGACURE 819 (IGM Resins). A liquid crystal composition was prepared by mixing these components (manufactured by BV Co.) in a mass ratio of 76.85:5.0:3.0:13.5:1.5:0.15.

[0092] The liquid crystal composition prepared above was heated to 100°C on a hot plate and poured into a glass cell for liquid crystal evaluation placed on the same hot plate. The glass cell for liquid crystal evaluation used was a horizontally aligned liquid crystal evaluation glass cell (cell gap 10 μm, manufactured by EHC Corporation; equipped with a pair of transparent substrates with a horizontal alignment film disposed on the surface of a transparent electrode as an alignment functional layer) using a polyimide film (AL63201, manufactured by JSR Corporation). After pouring the liquid crystal composition, the glass cell for evaluation was allowed to cool at room temperature. The above process was carried out in an environment that blocked light with wavelengths of 500 nm or less.

[0093] Thereafter, an AC electric field of 30 V and 50 Hz was applied to the evaluation glass cell, while irradiating it with light of 420 nm wavelength at 30 mW / cm ２ The liquid crystal composition was cured by irradiating the liquid crystal layer with light of an intensity of 1.0×10 for 20 minutes to form a liquid crystal layer. ６ The absolute value of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field (|Δε×E|) was 3.78×10 ７ It was.

[0094] Example 2 Instead of Sb-826010, n-type liquid crystal MLC2179 (Δε = -4.3, manufactured by Merck) was used as the liquid crystal molecule, and 4,4'-bis[6-(acryloyloxy)hexyloxy]biphenyl (BAB6) was used instead of RM257 as the photopolymerizable monomer. Furthermore, a glass cell for evaluating vertically aligned liquid crystals (cell gap 5 μm, manufactured by EHC Corporation; equipped with a pair of transparent substrates on which a vertical alignment film was disposed as an alignment functional layer on the surface of a transparent electrode) using a polyimide film (AL63201, manufactured by JSR Corporation) was used as the glass cell for evaluating liquid crystals. Furthermore, the voltage of the AC electric field applied when curing the liquid crystal composition was changed to 25 V. Apart from these changes, the liquid crystal dimming element of this example was fabricated using the same method as in Example 1 described above. In this case, the magnitude of the electric field calculated from the applied voltage and cell gap was 5.0 × 10 ６ The absolute value of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field (|Δε×E|) was 2.15×10 ７ It was.

[0095] [Example 3] The cell gap of the glass cell for evaluating vertically aligned liquid crystal was changed to 10 μm. In addition, the voltage of the AC electric field applied when curing the liquid crystal composition was changed to 50 V. Apart from these changes, the liquid crystal light control element of this example was fabricated using the same method as in Example 2 described above. In this case, the magnitude of the electric field calculated from the applied voltage and cell gap was 5.0 × 10 ６ The absolute value of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field (|Δε×E|) was 2.15×10 ７ It was.

[0096] Example 4 4,4'-bis[6-(acryloyloxy)hexyloxy]biphenyl (BAB6) was used instead of the photopolymerizable monomer RM257. In addition, the voltage of the AC electric field applied when curing the liquid crystal composition was changed to 20 V. Other than these changes, the liquid crystal light control element of this example was fabricated using the same method as in Example 1 described above. In this case, the magnitude of the electric field calculated from the applied voltage and cell gap was 2.0 × 10 ６The absolute value of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field (|Δε×E|) was 2.52×10 ７ It was.

[0097] Example 5 A liquid crystal light control device of this example was fabricated using the same method as in Example 4, except that the voltage of the AC electric field applied when curing the liquid crystal composition was changed to 30 V. In this case, the magnitude of the electric field calculated from the applied voltage and cell gap was 3.0 × 10 ６ The absolute value of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field (|Δε×E|) was 3.78×10 ７ It was.

[0098] Example 6 A liquid crystal light control device of this example was fabricated using the same method as in Example 4, except that the voltage of the AC electric field applied when curing the liquid crystal composition was changed to 50 V. In this case, the magnitude of the electric field calculated from the applied voltage and cell gap was 5.0 × 10 ６ The absolute value of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field (|Δε×E|) was 6.30×10 ７ It was.

[0099] [Comparative Example 1] A liquid crystal dimming element of this comparative example was fabricated using the same method as in Example 1, except that a glass cell for evaluating vertically aligned liquid crystals (cell gap 5 μm, manufactured by EHC Corporation) using a polyimide film (AL63201, manufactured by JSR Corporation) was used as the glass cell for evaluating liquid crystals. In this case, the magnitude of the electric field calculated from the applied voltage and the cell gap was 3.0 × 10 ６ The absolute value of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field (|Δε×E|) was 3.78×10 ７ It was.

[0100] [Comparative Example 2] A liquid crystal dimming element of this comparative example was fabricated using the same method as in Example 2, except that a glass cell for evaluating horizontally aligned liquid crystals (cell gap 5 μm, manufactured by EHC Corporation) using a polyimide film (AL63201, manufactured by JSR Corporation) was used as the glass cell for evaluating liquid crystals. In this case, the magnitude of the electric field calculated from the applied voltage and the cell gap was 5.0 × 10 ６ The absolute value of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field (|Δε×E|) was 2.15×10 ７ It was.

[0101] [Comparative Example 3] A liquid crystal light control element of this comparative example was fabricated using the same method as in Comparative Example 1, except that 4,4'-bis[6-(acryloyloxy)hexyloxy]biphenyl (BAB6) was used instead of the photopolymerizable monomer RM257. In this case, the magnitude of the electric field calculated from the applied voltage and cell gap was 3.0 × 10 ６ The absolute value of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field (|Δε×E|) was 3.78×10 ７ It was.

[0102] Comparative Example 4 A liquid crystal light control device of this example was fabricated using the same method as in Example 4, except that the voltage of the AC electric field applied when curing the liquid crystal composition was changed to 10 V. In this case, the magnitude of the electric field calculated from the applied voltage and cell gap was 1.0×10 ６ The absolute value of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field (|Δε×E|) was 1.26×10 ７ It was.

[0103]

[0104] <Confirmation of the Orientation of the Liquid Crystal Layer in the Liquid Crystal Light Control Device> The liquid crystal light control devices fabricated in Examples 1 to 6 and Comparative Examples 1 to 4 above were observed using a polarizing microscope in the stacking direction from the side of one of the transparent substrates. The two polarizers were arranged so that their polarization directions were perpendicular to each other. The liquid crystal light control device was then positioned so that the angle between the rubbing direction of the alignment film and each polarizer was 45°. During this observation, an observed image of light corresponding to the orientation direction of the liquid crystal molecules contained in the liquid crystal layer was obtained.

[0105] As a result of the above observations, the liquid crystal light control elements of Examples 1 to 6 and Comparative Example 4 obtained observation images with different color tones from both the observation images obtained when liquid crystals were sealed in a horizontal alignment film and the observation images obtained when liquid crystals were sealed in a vertical alignment film. These results confirmed that, in the liquid crystal light control elements of Examples 1 to 6 and Comparative Example 4, the angle θ [°] between the axial direction of the alignment force exerted on the liquid crystal molecules by the alignment functional layer (alignment film) and the axial direction of the alignment force exerted on the liquid crystal molecules by the polymerized product of the photopolymerizable monomer satisfied the condition 0 < θ ≦ 90. In contrast, the liquid crystal light control element of Comparative Example 2 obtained an observation image identical to the observation image obtained when liquid crystals were sealed in a horizontal alignment film. Furthermore, the liquid crystal light control elements of Comparative Examples 1 and 3 obtained an observation image identical to the observation image obtained when liquid crystals were sealed in a vertical alignment film. Therefore, it was confirmed that, in the liquid crystal light control elements of Comparative Examples 1 to 3, the angle θ [°] was 0 (i.e., the axial directions of the two alignment forces were the same).

[0106] <<Measurement of Transmittance of Liquid Crystal Light Control Element>> Using the measurement device shown in FIG. 5, the initial transmittance and time change of the transmittance for visible light of the liquid crystal light control elements fabricated in Examples 1 to 6 and Comparative Examples 1 to 4 were measured. FIG. 5 is a layout diagram of the measurement device used to measure the transmittance of the liquid crystal light control element. In the measurement device shown in FIG. 5, the liquid crystal light control element 110 is placed between a laser diode that emits laser light with a wavelength λ of 650 nm and a photodiode that receives the laser light. The distance between the liquid crystal light control element and the photodiode was set to approximately 8 cm, and the distance between the ultraviolet light source (or visible light source) and the liquid crystal light control element was set to approximately 20 cm. Ultraviolet light (wavelength λ of 365 nm) was projected from the ultraviolet light source onto the liquid crystal light control element 110. The photodiode receives the laser light that has passed through the liquid crystal light control element 110, converts the intensity of the received laser light into the intensity of a current, and outputs the current to an oscilloscope.

[0107] The model names of the devices used to measure the transmittance of the liquid crystal light control element 110 are as follows: Laser diode: THORLAB HANDHELD LASER SOURCE Photodiode: HAMAMATSU Photodiode module C10439 Ultraviolet light source: THORLAB M365LP1-C1 Oscilloscope: Tektronix TBS 1052B Digital Oscilloscope.

[0108] [Measurement of Initial Transmittance and Time-Varying Transmittance] Using the measurement device shown in FIG. 5, ultraviolet light (wavelength λ: 365 [nm], output: 20 [mW / cm 2 ]) was started to be irradiated onto the liquid crystal light control element 110, and the time change in the visible light transmittance of the liquid crystal light control element 110 during the ultraviolet light irradiation was measured. The visible light transmittance at the start of the measurement was defined as the initial transmittance. The transmittance of the liquid crystal light control element 110 before the ultraviolet light irradiation (transparent state) was defined as T ０ and the transmittance T of the liquid crystal light adjusting element 110 is T=T ０ The time required for the transmittance to reach / e (e is Napier's constant (base of natural logarithm)) was measured as the response time. The results of the initial transmittance and response time thus measured are shown in Table 2 below.

[0109] 6 is a graph showing the change over time in visible light transmittance after ultraviolet light irradiation for Comparative Example 1 and Example 1. FIG. 7 is a graph showing the change over time in visible light transmittance after ultraviolet light irradiation for Examples 2 and 3. FIG. 8 is a graph showing the change over time in visible light transmittance after ultraviolet light irradiation for Examples 4 to 6 and Comparative Examples 3 and 4.

[0110]

[0111] From the results shown in Table 2 and Figures 6 to 8, the liquid crystal light control elements of Examples 1 to 6 have high initial transmittance and respond to irradiation with ultraviolet light, which indicates that light scattering increases upon exposure to ultraviolet light and decreases upon exposure to visible light. In contrast, the liquid crystal light control element of Comparative Example 4 has low initial transmittance, which indicates that light scattering increases upon exposure to ultraviolet light and decreases upon exposure to visible light. The reason for the low initial transmittance of the liquid crystal light control element of Comparative Example 4 is thought to be that the absolute value (|Δε × E|) of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude of the electric field E when the liquid crystal composition is cured to prepare the liquid crystal layer is too small.

[0112] Furthermore, the liquid crystal light control element of the above example exhibited an extremely short response time compared to the liquid crystal light control elements of Comparative Examples 1 to 3. This indicates that the liquid crystal light control element according to the present invention can improve the response speed from the transparent state to the screen state. This is thought to be because, in the liquid crystal display element of the above example, the angle θ [°] formed between the axial direction of the alignment force exerted on the liquid crystal molecules by the alignment functional layer (alignment film) and the axial direction of the alignment force exerted on the liquid crystal molecules by the polymer of the photopolymerizable monomer satisfies 0<θ≦90.

[0113] REFERENCE SIGNS LIST 10 display device, 100 image display body, 100a front surface, 100b rear surface, 100c light projection area, 110 liquid crystal dimming element, 120 dimming layer, 130 ultraviolet light blocking layer, 200 first projector, 300 second projector, 400 third projector, 500 control unit, 600 image.

Claims

1. A liquid crystal dimming element comprising: a pair of transparent substrates each having a transparent electrode and an alignment functional layer disposed on one surface of the transparent electrode, the alignment functional layers arranged so that the alignment functional layers face each other; and a liquid crystal layer interposed between the pair of transparent substrates, the liquid crystal layer containing liquid crystal molecules, a photoresponsive material including a photoisomerizable material, and a polymer of a photopolymerizable monomer, wherein the angle θ [°] between the axial direction of the alignment force exerted on the liquid crystal molecules by the alignment functional layer and the axial direction of the alignment force exerted on the liquid crystal molecules by the polymer of the photopolymerizable monomer satisfies 0 < θ ≦ 90; and wherein light scattering increases when exposed to ultraviolet light and decreases when exposed to visible light.

2. The liquid crystal light control device according to claim 1, wherein the alignment force exerted by the alignment functional layer on the liquid crystal molecules acts in a direction in which the liquid crystal molecules are homeotropically aligned.

3. The liquid crystal light control element according to claim 1 or 2, wherein the cell gap between the pair of transparent substrates is 5 μm or more.

4. The liquid crystal light control element according to claim 1 or 2, which has a transmittance of 65% or more for light with a wavelength of 650 nm in a state where the light scattering property is reduced.

5. The liquid crystal light control element according to claim 1 or 2, wherein the photopolymerizable monomer comprises at least one selected from the group consisting of 4,4'-bis[6-(acryloyloxy)hexyloxy]biphenyl, 4,4'-bis[6-(methacryloyloxy)hexyloxy]biphenyl, bis[4-[3-(acryloyloxy)propoxy]benzoic acid]2-methyl-1,4-phenylene, 2-methyl-1,4-phenylenebis(4-3-(methacryloyloxy)propoxy)benzoate), and acrylic acid=6-(4'-cyano-1,1'-biphenyl-4-yloxy)hexyl.

6. The liquid crystal light control device according to claim 1 or 2, wherein the photoresponsive material further comprises a non-photoresponsive chiral compound.

7. A method for producing a liquid crystal display device comprising: a pair of transparent substrates having a transparent electrode and an alignment functional layer disposed on one surface of the transparent electrode, the alignment functional layers facing each other; a liquid crystal composition containing liquid crystal molecules, a photoresponsive material including a photoisomerizable material, a photopolymerizable monomer, and a photopolymerization initiator, the liquid crystal composition being filled between the pair of transparent substrates; and polymerizing the photopolymerizable monomer while applying an electric field to the liquid crystal composition; wherein the absolute value of the product of the dielectric anisotropy Δε of the liquid crystal molecules and the magnitude E of the electric field (|Δε×E|) is 2.1×10 ７ The method for producing a liquid crystal light control element according to claim 1 or 2, wherein the electric field is applied so as to satisfy the above.

8. The absolute value (|Δε×E|) is 2.1×10 ７ ~6.2 x 10 ７ The method of claim 7 , wherein the electric field is applied such that:

9. A display device using the liquid crystal light control element according to claim 1 or 2.

10. A light-shielding device using the liquid crystal light-adjusting element according to claim 1 or 2.

Images