Light-modulating liquid crystal composition and light-modulating film

Abstract

To provide means capable of compatibly obtaining high transparency in a transparent state and a high reflection factor in a non-transparent state in a light controlling film with an optical state thereof changeable between the transparent state and non-transparent state.SOLUTION: A liquid crystal composition for light control includes: liquid crystal molecules; an optical active material including a photoisomerized material; a photopolymerizable monomer; and nano particles. Based on 100 mass pts. of the liquid crystal molecules, a content of the photopolymerizable monomer is 4.5 to 10.0 mass pts., a content of the nanoparticles is more than 0 and equal to or less than 1.4 mass pts., and a ratio of the nanoparticles to the total mass of the photopolymerizable monomer and the nanoparticles is 1 to 15 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a light-controlling liquid crystal composition and a light-controlling film. [Background technology]

[0002] 2. Description of the Related Art In recent years, technology has been developed for displaying images on transparent glass such as automobile windshields and building window glass.

[0003] In this regard, a display device is known that includes a screen whose optical state changes between a transmissive state and a scattering state in response to application of a voltage, and a projector that projects image light onto the screen to display an image. In such a display device, the screen, which is normally transparent, can be temporarily made opaque to display an image on the screen.

[0004] However, in such a display device, the control electrodes for applying voltage are arranged inside the screen, which causes surface reflection and absorption at the control electrodes, resulting in low transparency in the transparent state of the screen.

[0005] In response to this, Patent Document 1 discloses a display device that includes an image display having a display function layer whose light scattering properties increase when exposed to ultraviolet light and whose light scattering properties decrease when exposed to first visible light, in order to improve the transparency of the screen in its transparent state, and that projects second visible light onto the image display whose display function layer's light scattering properties have increased when exposed to ultraviolet light, thereby displaying an image on the image display. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-185511 Summary of the Invention [Problem to be solved by the invention]

[0007] The display device of Patent Document 1 can certainly improve the transparency in the transparent state of an image display element whose optical state changes between a transparent state and a non-transparent state. However, there is a demand for further improvement in the reflectance in the non-transparent state.

[0008] Therefore, the present invention aims to provide a means for achieving both high transparency in the transparent state and high reflectance in the non-transparent state in a light-control film whose optical state changes between a transparent state and a non-transparent state. [Means for solving the problem]

[0009] The present inventors have conducted extensive research to solve the above problems, and as a result have found that using a predetermined amount of nanoparticles makes it possible to achieve both high transparency in a transparent state and high reflectance in a non-transparent state, thereby completing the present invention.

[0010] That is, according to one aspect of the present invention, there is provided a light-modulating liquid crystal composition comprising liquid crystal molecules, an optically active material including a photoisomerizable material, a photopolymerizable monomer, and nanoparticles, characterized in that, relative to 100 parts by mass of the liquid crystal molecules, the content of the photopolymerizable monomer is 4.5 to 10.0 parts by mass, the content of the nanoparticles is more than 0 parts by mass and not more than 1.4 parts by mass, and the ratio of the nanoparticles to the total mass of the photopolymerizable monomer and the nanoparticles is 1 to 15% by mass. [Effects of the Invention]

[0011] According to the light-controlling liquid crystal composition of one embodiment of the present invention, in a light-controlling film whose optical state changes between a transparent state and a non-transparent state, it is possible to achieve both high transparency in the transparent state and high reflectance in the non-transparent state. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view showing a schematic configuration of a display device according to an embodiment of the present invention. [Figure 2A]1 is a cross-sectional view showing a schematic configuration of an embodiment of an image display. [Figure 2B] 1 is a cross-sectional view showing a schematic configuration of an embodiment of an image display. [Figure 3] FIG. 2 is a diagram for explaining the operation of the display device when displaying an image. [Figure 4] FIG. 10 is a diagram for explaining the operation of the display device when no image is displayed. DETAILED DESCRIPTION OF THE INVENTION

[0013] One embodiment of the present invention is a light-modulating liquid crystal composition comprising liquid crystal molecules, an optically active material including a photoisomerizable material, a photopolymerizable monomer, and nanoparticles, wherein the content of the photopolymerizable monomer is 4.5 to 10.0 parts by mass, the content of the nanoparticles is more than 0 parts by mass and not more than 1.4 parts by mass, relative to 100 parts by mass of the liquid crystal molecules, and the proportion of the nanoparticles to the total mass of the photopolymerizable monomer and the nanoparticles is 1 to 15% by mass.

[0014] According to the light-controlling liquid crystal composition of this embodiment, in a light-controlling film whose optical state changes between a transparent state and a non-transparent state, it is possible to achieve both high transparency in the transparent state and high reflectance in the non-transparent state.

[0015] An embodiment according to one aspect of the present invention will be described below. The present invention is not limited to the following embodiment. In this specification, the range "X to Y" means "X or more and Y or less." Unless otherwise specified, operations and measurements of physical properties are performed under conditions of room temperature (20 to 25°C) and relative humidity of 40 to 50% RH.

[0016] <Light-modulating liquid crystal composition> The light-modulating liquid crystal composition of this embodiment contains liquid crystal molecules, an optically active material including a photoisomerizable material, a photopolymerizable monomer, and nanoparticles.

[0017] (liquid crystal molecules) The liquid crystal molecules according to this embodiment are not particularly limited, and known nematic liquid crystal molecules can be used.

[0018] Liquid crystal molecules are compounds in which two to four ring 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 cyano groups, fluoro groups, alkyl groups, alkenyl groups, or alkoxy groups at their terminals. These compounds may be substituted with cyano groups, fluoro groups, alkyl groups, alkenyl groups, or alkoxy groups. Specifically, liquid crystal molecules that can be used include 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.

[0019] Examples of liquid crystal molecules 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.

[0020] The liquid crystal molecules can be used alone or as a mixture of two or more kinds.

[0021] The liquid crystal molecules can be either synthetic or commercially available, such as E44 (manufactured by Merck).

[0022] In the light-modulating liquid crystal composition of this embodiment, the content of the liquid crystal molecules is, for example, 60 to 95 mass %, preferably 70 to 90 mass %, and more preferably 80 to 85 mass %, relative to the total mass of the liquid crystal molecules, the optically active material including the photoisomerizable material, the photopolymerizable monomer, and the nanoparticles.

[0023] (Optical active materials including photoisomerizable materials) The optically active material according to this embodiment includes a photoisomerizable material. The photoisomerizable material refers to a compound that absorbs light and undergoes cis-trans isomerization. The photoisomerizable material according to this embodiment may be a compound whose structure changes from a trans isomer to a cis isomer when exposed to ultraviolet light and from a cis isomer to a trans isomer when exposed to visible light, or may be a compound whose structure changes from a cis isomer to a trans isomer when exposed to ultraviolet light and from a trans isomer to a cis isomer when exposed to visible light.

[0024] From the viewpoint of further exerting the effects of the present invention, the photoisomerizable material according to this embodiment is preferably a compound whose structure changes from a trans isomer to a cis isomer when exposed to ultraviolet light, and whose structure changes from a cis isomer to a trans isomer when exposed to visible light.

[0025] Examples of the photoisomerizable material according to this embodiment include azobenzene compounds, chalcone derivatives, sulfoxide compounds, fulgide compounds, and cinnamic acid compounds.

[0026] The azobenzene compound includes a compound represented by the following chemical formula (1).

[0027] [ka]

[0028] In the above chemical formula (1), R to R 10are 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.

[0029] 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, 1-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, 1-methylhexyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, 2,2-dimethylheptyl, 2,6-dimethyl-4-heptyl, 3,5,5-trimethylhexyl, 1-methyldecyl, and 1-hexylheptyl;

[0030] 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 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;

[0031] When the alkyl group and alkoxy group have a substituent, the introduced substituent is not particularly limited. Specific examples include a halogen group, an unsubstituted alkyl group, an unsubstituted alkoxy group, and combinations thereof.

[0032] A halogen group refers to a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br) or an iodo group (-I).

[0033] The azobenzene compound may be an ester of isosorbide or isomannide with the compound represented by the above chemical formula (1).

[0034] In a preferred embodiment, the azobenzene compound is selected from the compounds represented by the following chemical formulas (2) to (5).

[0035] [ka]

[0036] An example of a chalcone derivative is a compound represented by the following chemical formula (6).

[0037] [ka]

[0038] An example of the sulfoxide compound is a compound represented by the following chemical formula (7).

[0039] [ka]

[0040] An example of a fulgide compound is a compound represented by the following chemical formula (8).

[0041] [ka]

[0042] Examples of cinnamic acid compounds include compounds represented by the following chemical formulas (9) and (10).

[0043] [ka]

[0044] 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 (5), and even more preferably contains a compound represented by chemical formula (5).

[0045] The photoisomerizable material can be used alone or as a mixture of two or more kinds.

[0046] The method for synthesizing the photoisomerizable material is not particularly limited, and any conventionally known synthesis method can be applied. For example, the compounds represented by chemical formulas (2) to (5) can be synthesized according to the method described in Md. Z. Alam, T. Yoshioka, T. Ogata, T. Nonaka, and S. Kurihara, "Influence of Helical Twisting Power on Photoswitching Behavior of Chiral Azobenzene Compounds: Their Applications to High-Performance Switching Devices," Chem. Eur. J., 13, 2641-2647 (2007).

[0047] In a preferred embodiment, the optically active material further contains a non-photoresponsive chiral compound, from the viewpoint of further improving the transparency of the light control film in the transparent state.

[0048] The non-photoresponsive chiral compound can be a compound with a different optical rotation from that of the photoisomerizable material used. By using a photoisomerizable material in combination with a non-photoresponsive chiral compound, 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 disruption of the alignment of liquid crystal molecules caused by the twisting power of the trans-isomerizable material can be further suppressed. This increases the transparency of the light-control film in the transparent state. The helical twisting power can be determined using the Cano wedge method.

[0049] 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, (R)-1-phenyl-1,2-ethanediyl bis[4-(trans-4-pentylcyclohexyl)benzoate], and (S)-1-phenyl-1,2-ethanediyl bis[4-(trans-4-pentylcyclohexyl)benzoate].

[0050] The non-photoresponsive chiral compound may be either a commercially available product or a synthetic product. Commercially available products include R-811, S-811, CB15, C15, S-1011, and R-1011 (manufactured by Merck).

[0051] When an azobenzene compound is used as the photoisomerizable material, the non-photoresponsive chiral compound preferably includes a compound selected from (R)-2-octyl 4-[4-(hexyloxy)benzoyloxy]benzoate, 4'-[(S)-2-methylbutyl]-1,1'-biphenyl-4-carbonitrile, and (R)-1-phenyl-1,2-ethanediyl bis[4-(trans-4-pentylcyclohexyl)benzoate], and more preferably includes (R)-2-octyl 4-[4-(hexyloxy)benzoyloxy]benzoate.

[0052] In the light-modulating liquid crystal composition of this embodiment, the content of the optically active material including the photoisomerizable material is, for example, 5 to 20 parts by mass relative to 100 parts by mass of liquid crystal molecules, and from the viewpoint of being able to further exert the effects of the present invention, is preferably 7 to 15 parts by mass.

[0053] (Photopolymerizable monomer) Examples of the photopolymerizable monomer according to this embodiment include monomers having one or more general photopolymerizable groups in the molecule, such as an acryloyl group, a methacryloyl group, or a vinyl group.

[0054] 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 acrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, butyl ethyl 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;

[0055] From the viewpoint of further increasing the reflectance in a non-transparent state, the photopolymerizable monomer preferably includes at least one selected from a polyfunctional acrylate compound and a polyfunctional methacrylate compound, more preferably includes at least one selected from a liquid crystalline polyfunctional acrylate compound and a polyfunctional methacrylate compound, and even more preferably includes at least one selected from the group consisting of 4,4'-bis[6-(acryloyloxy)hexyloxy]biphenyl, 4,4'-bis[6-(methacryloyloxy)hexyloxy]biphenyl, 2-methyl-1,4-phenylenebis(4-3-(acryloyloxy)propoxy)benzoate), and 2-methyl-1,4-phenylenebis(4-3-(methacryloyloxy)propoxy)benzoate).

[0056] The photopolymerizable monomers may be used alone or in combination of two or more.

[0057] In the light-controlling liquid crystal composition of this embodiment, the content of the photopolymerizable monomer is 4.5 to 10.0 parts by mass relative to 100 parts by mass of liquid crystal molecules. If the content of the photopolymerizable monomer is less than 4.5 parts by mass relative to 100 parts by mass of liquid crystal molecules, it may be difficult to form a light-controlling film. If the content of the photopolymerizable monomer is more than 10.0 parts by mass relative to 100 parts by mass of liquid crystal molecules, it may be difficult to exhibit the function as a light-controlling film. From the viewpoint of being able to further exhibit the effects of the present invention, the content of the photopolymerizable monomer is preferably 7.0 to 9.5 parts by mass, more preferably 7.3 to 9.2 parts by mass, relative to 100 parts by mass of liquid crystal molecules.

[0058] (nanoparticles) The nanoparticles according to this embodiment are photopolymerizable nanoparticles, and are preferably nanoparticles made of metal oxides, from the viewpoint of being able to more effectively exhibit the effects of the present invention.

[0059] The metal species of the nanoparticles made of metal oxide is not particularly limited, and examples thereof include silicon, titanium, zirconia, barium, etc. From the viewpoint of further exhibiting the effects of the present invention, the metal oxide preferably contains at least one selected from the group consisting of silicon dioxide, titanium oxide, zirconium oxide, barium titanate, and barium zirconate.

[0060] The average particle size of the nanoparticles is not particularly limited as long as they are fine particles with a smaller particle size. The upper limit of the average particle size of the nanoparticles is preferably 50 nm or less, more preferably 40 nm or less, and even more preferably 25 nm or less. The lower limit of the average particle size of the nanoparticles is, for example, 1 nm or more. The average particle size of the nanoparticles can be measured by dynamic light scattering.

[0061] In the light control liquid crystal composition of this embodiment, the content of nanoparticles is more than 0 parts by mass and not more than 1.4 parts by mass per 100 parts by mass of liquid crystal molecules. If the content of nanoparticles is 0 parts by mass per 100 parts by mass of liquid crystal molecules, the reflectance of the light control film in the non-transparent state cannot be improved. If the content of nanoparticles is more than 1.4 parts by mass per 100 parts by mass of liquid crystal molecules, the transparency of the light control film in the transparent state cannot be ensured. From the viewpoint of being able to further exhibit the effects of the present invention, the content of nanoparticles is preferably 0.2 to 1.4 parts by mass, more preferably 0.3 to 1.3 parts by mass per 100 parts by mass of liquid crystal molecules.

[0062] In the light-modulating liquid crystal composition of this embodiment, the ratio of nanoparticles to the total mass of the photopolymerizable monomer and nanoparticles is 1.0 to 15.0% by mass. By setting the ratio of nanoparticles within this range, it is possible to achieve both high transparency in the transparent state and high reflectance in the non-transparent state. From the viewpoint of further exerting the effects of the present invention, the ratio of nanoparticles is preferably 3.2 to 15.0% by mass, and more preferably 3.4 to 15.0% by mass.

[0063] (Photopolymerization initiator) The light-modulating liquid crystal composition of this embodiment may contain a photopolymerization initiator.

[0064] The photopolymerization initiator according to the present embodiment is not particularly limited, and any conventionally known photopolymerization initiator can be used. The photopolymerization initiator can be appropriately selected depending on the photoisomerizable material used.

[0065] 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.

[0066] In this specification, "light of a wavelength different from the wavelength that promotes isomerization of a photoisomerizable material" means "light of a wavelength different from the wavelength that promotes isomerization of a photoisomerizable material from a trans isomer to a cis isomer" or "light of a wavelength different from the wavelength that promotes isomerization of a photoisomerizable material from a cis isomer to a trans isomer."

[0067] 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.

[0068] 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 or 1-methyl-2-pyrrolidone).

[0069] Examples of the photopolymerization initiator 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.

[0070] The photopolymerization initiator may be either a commercially available product or a synthetic product, such as IRGACURE 819, 784 (manufactured by IGM Resins BV) or DAROCUR (registered trademark) TPO (manufactured by BASF).

[0071] The photopolymerization initiator may be used alone or in combination of two or more kinds.

[0072] In the light modulating liquid crystal composition of this embodiment, the content of the photopolymerization initiator is, for example, 0.05 to 10% by mass, and more preferably 0.1 to 7% by mass, relative to the total mass of the light modulating liquid crystal composition.

[0073] (Other ingredients) The light-modulating liquid crystal composition of this embodiment may contain other components as long as the effects of the present invention are not impaired, such as dichroic dyes, photopolymerization initiators, dye sensitizers, solvents, and dispersion media.

[0074] Examples of dichroic dyes include acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, and anthraquinone dyes.

[0075] Examples of the photopolymerization initiator aid include methyldiethanolamine and 4-dimethylaminobenzoic acid.

[0076] 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 a photopolymerization initiator.

[0077] Examples of the dye sensitizer include coumarin dyes, rhodamine dyes, oxazine dyes, carbocyanine dyes, styryl dyes, xanthene dyes, merocyanine dyes, rhodacyanine dyes, porphyrin dyes, and acridine dyes.

[0078] A solvent or dispersion medium can be added to adjust the viscosity of the composition. There are no particular limitations on the solvent, so long as it is compatible with the liquid crystal molecules, optically active material, photopolymerizable monomer, and photopolymerization initiator. Examples of solvents or dispersion mediums include toluene, acetone, ethyl acetate, methyl ethyl ketone, and hexanediol diacrylate.

[0079] (Method of manufacturing a light-modulating liquid crystal composition) The method for preparing the light-modulating liquid crystal composition of this embodiment is not particularly limited, and examples thereof include a method of mixing liquid crystal molecules, an optically active material, a photopolymerizable monomer, nanoparticles, and, if necessary, a photopolymerization initiator and other components.

[0080] When a photoisomerizable material and a non-photoresponsive chiral compound are used as the optically active material, it is preferable to first mix the trans or cis photoisomerizable material and the non-photoresponsive chiral compound in a mass ratio that achieves a compensated state in which the helical induction forces of the two compounds cancel each other out, and then mix them with other components. This makes it possible to suppress the disorder of the alignment of liquid crystal molecules caused by the twisting force of the trans or cis photoisomerizable material in the step of aligning the liquid crystal molecules described below.

[0081] The conditions for mixing the light-modulating liquid crystal composition are not particularly limited, but when a photopolymerization initiator is used, it is preferable to mix the components in an environment that blocks wavelengths that the photopolymerization initiator absorbs. For example, the light-modulating liquid crystal composition may be mixed under orange light (wavelength 595 to 610 nm) or in a brown bottle.

[0082] <Light control film> One aspect of the present invention is a light control film obtained by curing the above-mentioned light control liquid crystal composition. The light control film of this aspect can achieve both high transparency in a transparent state and high reflectance in a non-transparent state.

[0083] The method for producing the light control film of this embodiment is not particularly limited, and conventionally known knowledge can be referred to as appropriate. In one embodiment, the method for producing the light control film of this embodiment includes: (1) a step of applying a light control liquid crystal composition containing liquid crystal molecules, an optically active material including a photoisomerizable material, a photopolymerizable monomer, nanoparticles, and a photopolymerization initiator to a substrate; (2) a step of aligning the liquid crystal molecules; and (3) a step of irradiating light to cure the light control liquid crystal composition to obtain a cured product.

[0084] In step (1), a light-modulating liquid crystal composition containing liquid crystal molecules, an optically active material including a photoisomerizable material, a photopolymerizable monomer, nanoparticles, and a photopolymerization initiator is applied to a substrate.

[0085] The substrate used in step (1) includes transparent substrates such as glass and resin.

[0086] Examples of glass include soda-lime glass, borosilicate glass, lead glass, quartz glass, and alkali-free glass.

[0087] Examples of resins include polymethyl methacrylate resin, polyacrylic resin, polyacrylonitrile resin, polycarbonate resin, polyester resin, polyether ether ketone resin, epoxy resin, norbornene resin, polysulfone resin, polyethersulfone resin, polymercaptoester resin, polyphenylene sulfide resin, polyimide resin, polyamide resin, polyolefin resin, polypropylene resin, polystyrene resin, polybutadiene resin, polymethylpentene, and vinyl chloride resin.

[0088] The substrate may be in the form of a sheet or film, or may be a cell (substrate) made of the above-mentioned glass or resin.

[0089] The method for applying the composition to the substrate is not particularly limited, and any conventionally known method can be used. When the substrate is in the form of a sheet or film, a dipping method, a bar coating method, a spin coating method, a printing method, etc. can be used. When the substrate is a cell, a vacuum injection method, a drop injection method, etc. can be used.

[0090] In step (2), the liquid crystal molecules are aligned.

[0091] The alignment of the liquid crystal molecules may be either homogeneous alignment (horizontal alignment) or homeotropic alignment (vertical alignment).

[0092] The liquid crystal molecules can be aligned by a conventional method. For example, a method of applying an alignment film treatment to a substrate, a method of applying a transparent conductive film to a substrate and applying a voltage, etc. Examples of the alignment film treatment include physical treatment such as rubbing, and mechanical surface treatment.

[0093] From the viewpoint of further improving the transparency of the light-control film in a transparent state, step (2) is preferably carried out in an environment that blocks ultraviolet light and wavelengths that the polymerization initiator used has absorption. For example, this step can be carried out under orange light (wavelength 595 to 610 nm).

[0094] In step (3), the light-controlling liquid crystal composition is irradiated with light to cure and obtain a cured product. At this time, the nanoparticles in the light-controlling liquid crystal composition are coated with a polymer of a photopolymerizable monomer. This increases the liquid crystal-resin interfacial surface area, thereby further improving the reflectance of the light-controlling film in its non-transparent state. Therefore, one embodiment of this aspect is a light-controlling film in which the surfaces of nanoparticles are coated with a polymer of a photopolymerizable monomer.

[0095] The wavelength of the irradiated light is preferably different from the wavelength that promotes the isomerization of the photoisomerizable material. This can prevent the trans or cis photoisomerizable material from isomerizing to the cis or trans form during polymerization, and can also prevent the alignment of the liquid crystal molecules from becoming distorted due to the isomerization of the photoisomerizable material. Therefore, a cured product with higher transparency can be obtained in the transparent state.

[0096] The wavelength of the light to be irradiated can be appropriately selected depending on the optically active material including the photoisomerizable material and the photopolymerization initiator used.

[0097] 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 430 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 cured product in the transparent state.

[0098] In the step (3), when irradiating with light, a filter that transmits only light in a specific wavelength range may be used, if necessary.

[0099] The amount of light to be irradiated is, for example, 1000 to 50,000 mJ / cm 2 The temperature condition during light irradiation is, for example, 10 to 40°C.

[0100] The orientation state of the liquid crystal molecules in the obtained cured product can be confirmed using a polarizing microscope, an ellipsometer, or the like.

[0101] The light control film of this embodiment may be in the form of a cured product (film-formed product) of the composition, or may be in the form including the above-mentioned substrate and the cured product.

[0102] The thickness of the light control film is, for example, 5 to 500 μm.

[0103] The use of the light control film of this embodiment is not particularly limited, but it is preferably applied to automobile glass, building window glass, etc. The light control film of this embodiment has high transparency in the transparent state and high reflectance in the non-transparent state. Therefore, the light control film of this embodiment is particularly advantageous when used on automobile windshields.

[0104] Therefore, one embodiment of the present invention relates to a display device for use in the above applications.

[0105] Hereinafter, with reference to the drawings, a display device having an image display, an ultraviolet light projector, and two visible light projectors (a first visible light projector and a second visible light projector) will be described as an example of a display device according to a preferred embodiment of the present invention, but the present invention is not limited to the following embodiment. Note that in the description of the drawings, identical elements are given the same reference numerals, and redundant description will be omitted. Also, the dimensional proportions in the drawings are exaggerated for the sake of explanation and may differ from the actual proportions.

[0106] 1 is a perspective view showing a schematic configuration of a display device 10 according to one embodiment of the present invention. The display device 10 of this embodiment includes an image display 100, a first projector 200, a second projector 300, a third projector 400, and a control unit 500.

[0107] 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.

[0108] 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.

[0109] 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, emitting first visible light with a wavelength of, for example, about 440 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.

[0110] The third projector 400 is a color projector and is disposed opposite the front surface 100a of the image display 100. The third projector 400 serves as a second visible light projector 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 100 in a non-transparent state, thereby displaying an image 600 on the image display 100.

[0111] The control unit 500 controls the operations of the first to third projectors 200 to 400. The control unit 500 switches the first and second projectors 200, 300 between projecting and not projecting light 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.

[0112] 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 100 by the second visible light is included inside the projection area 100c of the ultraviolet light on the image display 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 100.

[0113] Next, the image display element 100 of the display device 10 will be described in detail with reference to FIG. 2A.

[0114] 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 display function layer 110, a light control layer 120, and an ultraviolet light blocking layer 130. The display function layer 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 display function layer 110 and the ultraviolet light blocking layer 130.

[0115] The display function layer 110 is a film member whose optical state changes between a transparent state and a non-transparent state. The display function layer 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 display function layer 110 of this embodiment is the light control film according to one embodiment of the present invention described above.

[0116] The photochromic layer 120 is a transparent film member whose light absorbency increases when exposed to ultraviolet light. The photochromic layer 120 is made of a photochromic material and has the optical property of increasing its light absorbency and changing color from colorless to gray (or black) when exposed to ultraviolet light. The photochromic layer 120 has the optical property of decreasing its light absorbency and returning to colorless when exposed to no ultraviolet light or when exposed to blue or yellow visible light.

[0117] 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 display function layer 110 from the rear surface 100b of the display body 100.

[0118] 2B, the image display element 100 of the display device 10 may include a display function layer 110 and an ultraviolet light blocking layer 130. In this case, the display function layer 110 also serves as a light control layer.

[0119] Next, the operation of the display device 10 that displays an image on the image display 100 will be described with reference to FIGS.

[0120] 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.

[0121] 3 , when an image is displayed on the display device 100, the first projector 200 first projects ultraviolet light onto the front surface 100a of the display device 100. The ultraviolet light causes the display function layer 110 to become opaque, and the light control layer 120 to turn gray, causing the ultraviolet light projected region 100c on the display device 100 to change from a transparent state to a non-transparent state. The third projector 400 then projects second visible light onto the projected region 100c on the display device 100, which is in the non-transparent state, to display an image 600 on the display device 100.

[0122] 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 the trans isomer is converted to the cis isomer) is greater than the rate at which the photoisomerizable material is isomerized by the second visible light (e.g., the rate at which the cis isomer is converted to the trans isomer).

[0123] 4, when no image is displayed on the image display 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 100, thereby returning the ultraviolet light projected region 100c on the image display 100 from the non-transparent state to the transparent state.

[0124] 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. [Example]

[0125] The present invention will be explained in more detail below using examples and comparative examples, but it should be understood that the present invention is not limited to the following examples.

[0126] (Preparation of Optically Active Materials) An optically active material was prepared by mixing an azobenzene compound (a compound represented by the above chemical formula (5)) and (R)-2-octyl 4-[4-(hexyloxy)benzoyloxy]benzoate (R-811, manufactured by Merck) in a mass ratio of 5.1:4.9 so that the helical induction forces would cancel each other out.

[0127] Example 1 A light-modulating liquid crystal composition was prepared by mixing E44 (manufactured by Merck) as liquid crystal molecules, the optically active material prepared above, 4,4'-bis[6-(acryloyloxy)hexyloxy]biphenyl as a photopolymerizable monomer, a silica nanoparticle dispersion (particle content: 50 mass%, average particle size: 20 nm, manufactured by BYK) as a nanoparticle dispersion, and IRGACURE 819 (manufactured by IGM Resins BV) as a photopolymerization initiator in a mass ratio of 82.5:10:7:0.5:0.75.

[0128] A cell (substrate) was prepared by stacking and fixing two alignment-treated glass substrates with spacers between them so that the alignment direction was horizontal and the thickness of the cured product was 10 μm. The light-modulating liquid crystal composition prepared above was injected into the cell.

[0129] The above steps were carried out in an environment where light with a wavelength of 500 nm or less was blocked.

[0130] Thereafter, an LED light source (M450LKP1, manufactured by THORLABS) was used as the light source, and light with a wavelength of 440 nm was irradiated (10 mW / cm 2 , 30 minutes) to cure the light-control liquid crystal composition, thereby producing a light-control film.

[0131] (Examples 2 to 6, Comparative Examples 3 to 4) A light-control film was produced in the same manner as in Example 1, except that a zirconia nanoparticle dispersion (particle content: 70% by mass, average particle diameter: 11 nm, manufactured by Nippon Shokubai Co., Ltd.) was used as the nanoparticle dispersion instead of a silica nanoparticle dispersion, and the materials were mixed to obtain the composition shown in Table 1 below.

[0132] (Comparative Example 1) A light-controlling film was produced in the same manner as in Example 1, except that a light-controlling liquid crystal composition was prepared by mixing E44 (manufactured by Merck) as liquid crystal molecules, the optically active material prepared above, 4,4'-bis[6-(acryloyloxy)hexyloxy]biphenyl as a photopolymerizable monomer, and IRGACURE 819 (manufactured by IGM Resins BV) as a photopolymerization initiator in a mass ratio of 82.5:10:7.5:0.75.

[0133] (Comparative Example 2) A light-controlling film was produced in the same manner as in Example 1, except that a light-controlling liquid crystal composition was prepared by mixing E44 (manufactured by Merck) as liquid crystal molecules, the optically active material prepared above, 4,4'-bis[6-(acryloyloxy)hexyloxy]biphenyl as a photopolymerizable monomer, silica nanoparticle dispersion (particle content: 50 mass%, manufactured by BYK) as a nanoparticle dispersion, and IRGACURE 819 (manufactured by IGM Resins BV) as a photopolymerization initiator in a mass ratio of 82.5:10:5:2.5:0.75.

[0134] (Haze measurement) The light-control films obtained in Examples 1 to 6 and Comparative Examples 1 to 4 were irradiated with UV light and then with visible light under the following conditions: UV light: wavelength 365nm, 10mW / cm 2 , 60sec Visible light: wavelength 440nm, 60mW / cm 2 .

[0135] Using a haze meter HM-65W (manufactured by Murakami Color Research Laboratory Co., Ltd.), the haze of the light control film in a transparent state after irradiation with visible light was measured in accordance with JIS K 7136:2000.

[0136] The results are shown in Table 1.

[0137] (Measurement of diffuse reflectance) The diffuse reflectance in the visible light region was measured using a spectrophotometer U-4000 model (manufactured by Hitachi, Ltd.) for the light control films obtained in Examples 1 to 6 and Comparative Examples 1 to 4. The measurement was carried out using an integrating sphere unit.

[0138] The results are shown in Table 1.

[0139] [Table 1]

[0140] As shown in Table 1, the light control films of the examples have low haze in the transparent state and high diffuse reflectance in the diffuse state.

[0141] On the other hand, the light control film of Comparative Example 1 does not contain nanoparticles, so it has a low reflectance in the non-transparent state. Also, the light control films of Comparative Examples 2 to 4 have a high haze in the transparent state because the proportion of nanoparticles exceeds 15 mass%. [Explanation of symbols]

[0142] 10 display device; 100 image display body, 100a front, 100b back, 100c Light projection area, 120 photochromic layer, 130 Ultraviolet light shielding layer, 200 first projector (ultraviolet light projection unit), 300 second projector (first visible light projection unit), 400 third projector (second visible light projection unit), 500 control section, 600 images.

Claims

1. The optically active material includes liquid crystal molecules, a photoisomerizable material, and a non-photoresponsive chiral compound, a photopolymerizable monomer, and nanoparticles; the content of the photopolymerizable monomer is 4.5 to 10.0 parts by mass, and the content of the nanoparticles is more than 0 parts by mass and 1.4 parts by mass or less, relative to 100 parts by mass of the liquid crystal molecules; The light-modulating liquid crystal composition has a ratio of the nanoparticles to the total mass of the photopolymerizable monomer and the nanoparticles of 1 to 15% by mass.

2. The light-modulating liquid crystal composition according to claim 1 , wherein the nanoparticles are nanoparticles made of a metal oxide.

3. 3. The light-modulating liquid crystal composition according to claim 2, wherein the metal oxide comprises at least one selected from the group consisting of silicon dioxide, titanium oxide, zirconium oxide, barium titanate, and barium zirconate.

4. A light-controlling film obtained by curing the light-controlling liquid crystal composition according to any one of claims 1 to 3.

5. The light control film according to claim 4 , wherein the surface of the nanoparticles is coated with a polymer of the photopolymerizable monomer.

Images