Liquid crystal optical elements

Abstract

This liquid crystal optical element comprises an optical functional layer sandwiched by two transparent substrates, wherein the optical functional layer contains liquid crystal molecules and a photoisomerization material, and the state of the optical functional layer is switched between a light transmission state and a light scattering state according to the orientation state of the liquid crystal molecules.　As the optical functional layer holds the liquid crystal molecules and the photoisomerization material within a network structure formed by an aggregate of resin particles, light can be strongly scattered in a screen state and a high-contrast image is obtained when visible light is projected.

Description

[Technical Field]

[0001] The present invention relates to a liquid crystal optical element, and more particularly to a liquid crystal optical element that switches between a transparent state that transmits light and a screen state that scatters light. [Background technology]

[0002] Liquid crystal optical elements are known whose optical state can be switched between a transparent state that transmits light and a screen state that scatters light, and visible images are displayed by projecting visible light onto a liquid crystal optical element in the screen state.

[0003] Patent Document 1 discloses that by providing multiple resin columns standing in the thickness direction of a liquid crystal optical element and reducing the area occupied by these resin columns at the center in the thickness direction, deformation of the resin columns can be prevented even when an impact is applied to the liquid crystal optical element, and clouding in the transparent state can be suppressed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2011-154388 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the case of the product described in Patent Document 1, the surface of the columnar resin is smooth and the interface area with the liquid crystal molecules is small, so that light scattering in the screen state is weak and a large amount of light is transmitted. Therefore, in an environment with a large amount of external light, a high-contrast image cannot be obtained even when visible light is projected, and use as a screen is limited.

[0006] The present invention has been made in view of the problems associated with the prior art, and its object is to provide a liquid crystal optical element that can be suitably used for a screen, by which a high-contrast image can be obtained by projecting visible light even in an environment with a large amount of external light. [Means for solving the problem]

[0007] As a result of extensive research into achieving the above-mentioned objective, the inventors discovered that by forming the network structure that holds the liquid crystal molecules from a resin with surface irregularities, it is possible to strongly scatter light in the screen state, thereby achieving the above-mentioned objective, and thus completed the present invention.

[0008] That is, the liquid crystal optical element of the present invention is an optical element that is composed of two transparent substrates and an optical functional layer sandwiched between them, the optical functional layer containing liquid crystal molecules and a photoisomerizable material, and that switches between a light-transmitting state and a light-scattering state depending on the orientation state of the liquid crystal molecules. the optical functional layer holds the liquid crystal molecules and the photoisomerizable material in a network structure formed by an aggregate of resin particles, The resin particles are 4,4'-bis[4-{6-(acryloyloxy)hexyloxy}benzoate]-1,1'-biphenylene having moieties derived from at least two types of photopolymerizable monomers, including It is characterized by: [Effects of the Invention]

[0009] According to the present invention, liquid crystal molecules are held in a mesh structure formed by an aggregate of resin particles and having a surface irregularity, thereby providing a liquid crystal optical element that can strongly scatter light when in screen state and can produce high-contrast images when visible light is projected. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B are diagrams illustrating a mechanism by which a liquid crystal optical element switches between a light-transmitting state and a light-scattering state. [Figure 2]1 is an SEM image of the network structure of the liquid crystal optical element of Example 1. [Figure 3] 1 is an SEM image of the network structure of the liquid crystal optical element of Example 2. [Figure 4] 1 is an SEM image of the network structure of the liquid crystal optical element of Comparative Example 1. [Figure 5] 1 is a graph showing the diffuse reflectance of liquid crystal optical elements of an example and a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0011] The liquid crystal optical element of the present invention will now be described in detail. The liquid crystal optical element of the present invention comprises an optical functional layer sandwiched between two transparent substrates, the optical functional layer being capable of changing between a transparent state that transmits light and a cloudy screen state that scatters light. The optical functional layer contains liquid crystal molecules and a photoisomerizable material, which are held within a network structure formed by an aggregate of resin particles.

[0012] First, the mechanism by which the optical functional layer changes from a transparent state to a cloudy screen state due to light scattering will be described.

[0013] The liquid crystal molecules are nematic liquid crystals that have a rigid mesogenic skeleton and a flexible long-chain alkyl group, and have optical anisotropy and dielectric anisotropy. In the absence of an external voltage, the rod-shaped liquid crystal molecules associate with each other and align in a substantially uniform direction.

[0014] The photoisomerizable material is a compound that absorbs light such as ultraviolet light and undergoes cis-trans isomerization. In the liquid crystal optical element of the present invention, the material undergoes a structural change upon isomerization, disorganizing the liquid crystal molecules and randomly aligning them. For example, a compound having an azobenzene structure in which two benzene rings are bonded by an azo group (hereinafter sometimes referred to as an azobenzene compound) can be used. Other examples of photoisomerizable materials include chalcone derivatives, sulfoxide compounds, fulgide compounds, and cinnamic acid compounds.

[0015] The azobenzene compound includes a compound represented by the following chemical formula (1).

[0016] [ka]

[0017] In the above chemical formula (1), R to 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.

[0018] 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;

[0019] 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;

[0020] 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.

[0021] A halogen group refers to a fluoro group (-F), a chloro group (-Cl), a bromo group (-Br) or an iodo group (-I).

[0022] The azobenzene compound may be an ester of isosorbide or isomannide with the compound represented by the above chemical formula (1).

[0023] In a preferred embodiment, the azobenzene compound is selected from the compounds represented by the following chemical formulas (2) to (5).

[0024] [ka]

[0025] [ka]

[0026] [ka]

[0027] [ka]

[0028] An example of a chalcone derivative is a compound represented by the following chemical formula (6).

[0029] [ka]

[0030] An example of the sulfoxide compound is a compound represented by the following chemical formula (7).

[0031] [ka]

[0032] An example of a fulgide compound is a compound represented by the following chemical formula (8).

[0033] [ka]

[0034] Examples of cinnamic acid compounds include compounds represented by the following chemical formulas (9) and (10).

[0035] [ka]

[0036] [ka]

[0037] 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).

[0038] The photoisomerizable material can be used alone or as a mixture of two or more kinds.

[0039] 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).

[0040] In a preferred embodiment, the photoisomerizable material and the non-photoresponsive chiral compound constitute an optically active material. Such an optically active material is preferably used from the viewpoint of further improving the transparency of the light control film in the transparent state.

[0041] 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.

[0042] 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].

[0043] 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).

[0044] 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.

[0045] When exposed to ultraviolet light, the azobenzene undergoes a structural change from a trans isomer to a cis isomer. The trans isomer of azobenzene has a planar structure, whereas the cis isomer has a curved, three-dimensional structure. In FIG. 1, trans azobenzene is shown as a straight line, and cis azobenzene is shown as an L-shape, and the network structure formed by the aggregation of resin particles is omitted.

[0046] When the optical functional layer is not exposed to ultraviolet light, the azobenzene is in a planar trans isomer, and the liquid crystal molecules form a nematic phase with directional order, as shown on the left side of Figure 1. The liquid crystal molecules in this nematic phase are aligned in a direction perpendicular to the vertical alignment film by the vertical alignment film, so the optical functional layer is in a transparent state that allows light to pass through.

[0047] When the optical function layer is irradiated with ultraviolet light, the azobenzene isomerizes to a cis form. As the azobenzene changes from a planar structure to a curved structure, the alignment of the liquid crystal molecules becomes disordered and they become oriented in random directions, as shown on the right side of Figure 1. As a result, the light incident on the optical function layer is reflected and scattered by the liquid crystal molecules, resulting in a cloudy white screen.

[0048] At this time, the liquid crystal molecules are held within the mesh structure of the resin particle aggregate, so in addition to scattering due to reflection of the liquid crystal molecules, geometric scattering occurs at the contact interface between the liquid crystal molecules and the resin particles due to the difference in refractive index between the liquid crystal molecules and the resin particles, causing light to be scattered in all directions.

[0049] In the liquid crystal optical element of the present invention, the above-mentioned network structure is formed by an aggregate of resin particles, and the surface of the resin aggregate has unevenness, so the area of the liquid crystal molecule-resin interface where geometric scattering occurs is large, thereby improving the scattering intensity.

[0050] As described above, the liquid crystal optical element of the present invention has a high scattering intensity and scatters incident light approximately isotropically, so that the amount of incident light that passes through the optical functional layer and exits to the opposite side is reduced.

[0051] In this way, the liquid crystal optical element of the present invention can reduce the amount of light transmitted to the side opposite to the optical functional layer, so that when visible light is projected onto the liquid crystal optical element, the amount of light transmitted to the side opposite to the projection side is reduced and the amount of light reflected to the projection side is increased, thereby increasing the light intensity of the image viewed from the projection side.

[0052] Furthermore, in a bright environment, light incident from the opposite side to the side onto which the visible light is projected is also less likely to pass through to the projected side, and the intensity of the background light as seen from the projected side is reduced. As a result, the influence of the brightness of the environment is reduced, and a projected image with high contrast [= (image light intensity + background light intensity) / background light intensity] can be formed even in a bright environment.

[0053] The cis azobenzene isomer returns to the trans isomer when left under or exposed to visible light, so the liquid crystal molecules also return to their original alignment state, and the optical functional layer can return to its transparent state. The optical functional layer of the present invention returns to a transparent state when irradiated with visible light, and can be quickly returned to a transparent state by applying an electric field to the optical functional layer.

[0054] The optical functional layer can be produced by mixing liquid crystal molecules, a photoisomerizable material, and a photopolymerizable monomer having a biphenyl structure, and adding a polymerization initiator to polymerize the photopolymerizable monomer having a phenyl structure.

[0055] Examples of the photopolymerizable monomer that can be used include liquid crystal resins such as 4,4'-bis[4-{6-(acryloyloxy)hexyloxy}benzoate]-1,1'-biphenylene, 4,4'-bis[6-(acryloyloxy)hexyloxy]biphenyl, and 6-[{4'-cyano-(1,1'-biphenyl)-4-yl}oxy]hexyl acrylate. Also usable are monomers made of resin nanoparticles whose surfaces are coated with a non-liquid crystal resin, such as NOA65 (manufactured by Norland).

[0056] 4,4'-Bis[6-(acryloyloxy)hexyloxy]biphenyl has a biphenyl structure and has a high affinity with liquid crystal molecules. Therefore, even when mixed with liquid crystal molecules, it does not undergo phase separation but polymerizes while remaining mixed to form a network structure of resin particles. This allows the formation of an optically functional layer that encapsulates and holds liquid crystal molecules within the network structure.

[0057] The average particle size of the resin particles is preferably 1 μm or less, and more preferably 0.7 μm or less. Since the particle size of the resin particles is approximately the same size as the wavelength of visible light, in addition to scattering due to reflection by the liquid crystal molecules and geometric scattering due to the refractive index difference, diffraction scattering also occurs, and since this diffraction scattering occurs multiple times due to the aggregation of resin particles, the scattering intensity is further increased, making it possible to form a high-contrast visible light projection image.

[0058] If the particle size of the resin particles is small, they will scatter light, so there is no particular lower limit to the average particle size, but the practical lower limit is about 0.1 μm.

[0059] The resin particles preferably have refractive index anisotropy. The polymer molecules that make up resin particles are each nano-sized, string-like. In a disordered (amorphous) state, the polymer molecules are bent and coiled, lacking directionality and acting as a uniform medium for light. However, when the molecular structure contains planar functional groups, as exemplified by the biphenyl structure described below, the polymer molecules align, or orient, along the planar structure. In this oriented state, the refractive index n / / for linearly polarized light polarized in the direction of orientation differs from the refractive index n⊥ for linearly polarized light polarized perpendicular to the direction of orientation. This property of refractive index varying depending on the plane of polarization is called refractive index anisotropy, or birefringence, and the magnitude of birefringence is expressed as Δn = n / / - n⊥. Because the resin particles have refractive index anisotropy, the refractive index in the in-plane direction of the optical functional layer differs from the refractive index in the thickness direction of the optical functional layer, and the difference in refractive index between the liquid crystal molecules in the in-plane direction is greater than the refractive index between the liquid crystal molecules in the thickness direction.As a result, in the screen state, the scattering intensity at the liquid crystal molecule-resin interface is increased, and in the transparent state, the scattering intensity at the liquid crystal molecule-resin interface is reduced, making it easier for light to transmit, thereby improving transparency.

[0060] In addition, 4,4'-bis[6-(acryloyloxy)hexyloxy]biphenyl has a biphenyl structure in its molecular structure, which is a structure in which two planar phenyl groups are bonded together, and since it has refractive index anisotropy when oriented in a direction along this planar structure, a polymer containing this biphenyl structure also has refractive index anisotropy.

[0061] As the polymerization initiator, IRGACURE 819 (manufactured by IGM Resins BV) can be used.

[0062] The transparent substrate may be made of glass or resin, and an ITO film or the like may be used as the transparent electrode when an electric field is applied to the optical functional layer.

[0063] Furthermore, the liquid crystal optical element of the present invention may have an ultraviolet light blocking layer, if necessary. The ultraviolet light-shielding layer is a layer that blocks ultraviolet light incident from the rear side of the optical functional layer, and is a transparent film that contains an ultraviolet absorber and an ultraviolet light diffuser.

[0064] As the ultraviolet absorber, a conventionally known ultraviolet absorber that absorbs ultraviolet light having a wavelength of 400 nm or less, does not absorb visible light, and has little coloring can be used, such as benzophenone derivatives, salicylic acid ester derivatives, triazole derivatives, and acrylonitrile derivatives. Furthermore, as an ultraviolet light diffuser, titanium oxide, zinc oxide, etc. can be used.

[0065] The liquid crystal optical element of the present invention can be used, for example, in automobile windshields or show windows, and can be switched between a screen state in which a visible light image can be projected and displayed, and a transparent state in which the other side can be seen. [Example]

[0066] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0067] [Example 1] A liquid crystal composition was prepared by mixing 83.8 parts by mass of liquid crystal molecules (nematic liquid crystal: E44, manufactured by Merck), 8 parts by mass of an optically active material obtained by mixing an azobenzene compound (photoisomerizable material) represented by structural formula (5) above and (R)-2-octyl 4-[4-(hexyloxy)benzoyloxy]benzoate (R-811, manufactured by Merck, a non-photoresponsive chiral compound) in a mass ratio of 5.1:4.9, 7.5 parts by mass of a photopolymerizable monomer (liquid crystal resin 4,4′-bis[4-{6-(acryloyloxy)hexyloxy}benzoate]-1,1′-biphenylene), and 0.7 parts by mass of a photopolymerization initiator (IRGACURE 819, manufactured by IGM Resins BV).

[0068] A vertical alignment film (polyimide) was formed on the entire surface of one side of a transparent glass, and two transparent substrates were arranged with the vertical alignment film on the inside. The liquid crystal composition was poured between the two transparent substrates while heating, and ultraviolet light was irradiated to polymerize the photopolymerizable monomer, obtaining a liquid crystal optical element. Note that an AC voltage of 50 V was applied between the transparent substrates during polymerization, so that the photopolymerizable monomer and liquid crystal molecules were aligned in the direction of the applied voltage. It should be noted that Example 1 is a reference example.

[0069] [Example 2] A liquid crystal composition was prepared by mixing 85.4 parts by mass of the liquid crystal molecules of Example 1, 8 parts by mass of the optically active material of Example 1, 5 parts by mass of the photopolymerizable monomer (liquid crystal resin) of Example 1, 1 part by mass of NOA65 (manufactured by Norland) as a photopolymerizable monomer (non-liquid crystal resin), and 0.6 parts by mass of the photopolymerization initiator of Example 1. Except for using this liquid crystal composition, a liquid crystal optical element was obtained in the same manner as in Example 1.

[0070] [Example 3] A liquid crystal composition was prepared by mixing 86.4 parts by mass of the liquid crystal molecules of Example 1, 8 parts by mass of the optically active material of Example 1, 2 parts by mass of 4,4'-bis[4-{6-(acryloyloxy)hexyloxy}benzoate]-1,1'-biphenylene of Example 1 and 3 parts by mass of 4,4'-bis[6-(acryloyloxy)hexyloxy]biphenyl as photopolymerizable monomers (liquid crystal resins), totaling 5 parts by mass, and 0.6 parts by mass of the photopolymerization initiator of Example 1. A liquid crystal composition was prepared, and a liquid crystal optical element was obtained in the same manner as in Example 1, except for using this liquid crystal composition.

[0071] [Example 4] A liquid crystal composition was prepared by mixing 86.4 parts by mass of the liquid crystal molecules of Example 1, 8 parts by mass of the optically active material of Example 1, 4.5 parts by mass of 4,4'-bis[4-{6-(acryloyloxy)hexyloxy}benzoate]-1,1'-biphenylene of Example 1 and 0.5 parts by mass of 6-[{4'-cyano-(1,1'-biphenyl)-4-yl}oxy]hexyl acrylate as photopolymerizable monomers (liquid crystal resins), totaling 5 parts by mass, and 0.6 parts by mass of the photopolymerization initiator of Example 1. A liquid crystal composition was prepared, and a liquid crystal optical element was obtained in the same manner as in Example 1, except for using this liquid crystal composition.

[0072] [Comparative Example] The photopolymerizable monomer was changed to 2,3,5,6-tetrafluoro-1,4-phenylene-bis[4-{6-(acryloyloxy)hexyloxy}benzoate], and a liquid crystal composition was prepared by mixing 83.8 parts by mass of the liquid crystal molecules of Example 1, 8 parts by mass of the optically active material of Example 1, 7.5 parts by mass of the photopolymerizable monomer, and 0.7 parts by mass of the photopolymerization initiator of Example 1. Except for using this liquid crystal composition, a liquid crystal optical element was obtained in the same manner as in Example 1.

[0073] <Evaluation> (Measurement of the average particle size of resin particles) The network structure of the liquid crystal optical element was observed by SEM, and the average particle size of the resin particles was measured. SEM images of Examples 1 and 2 and the Comparative Example are shown in FIGS. Table 1 shows the configurations of Examples 1 to 4 and the comparative example, and Table 2 shows the results of observation and measurement.

[0074] In Examples 1 and 2, a three-dimensional network structure was formed by an aggregate of resin particles, and the average particle size of the resin particles was 1 μm in Example 1 and 0.5 μm in Example 2. As a result of similar observations for Examples 3 and 4, the average particle size of the resin particles was found to be 0.5 μm. In the comparative example, the network structure was formed of rod-shaped resin, the surface of the network structure was smooth, and no resin particles were observed.

[0075] (Measurement of diffuse reflectance) The diffuse reflectance SCE in the visible light region was measured using a branch colorimeter CM3600A (manufactured by Konica Minolta). The relationship between the wavelength of light and the diffuse reflectance for Examples 1 and 2 and the Comparative Example is shown in Figure 5. The diffuse reflectance for visible light of 550 nm for Examples 1 to 4 and the Comparative Example was 11.3%, 15.3%, 15.0%, 15.0%, and 8.0%, respectively. When the diffuse reflectance in the visible light region increases, light incident from the side opposite to the side onto which the visible light is projected (i.e., background light) also becomes less likely to transmit to the side onto which the visible light is projected, and the intensity of the background light as seen from the side onto which the visible light is projected decreases. As a result, the influence of the brightness of the environment is reduced, and it becomes possible to form a visible image with high contrast [= (image light intensity + background light intensity) / background light intensity] even in a bright environment.

[0076] It can be seen from FIG. 5 that the liquid crystal optical element of the present invention has a high diffuse reflectance in the visible light region and can form a visible image with high contrast.

[0077] [Table 1]

[0078] [Table 2] [Explanation of symbols]

[0079] 1 Liquid crystal optical elements 2 Optical functional layer 21 Liquid crystal molecules 22 Azobenzene 23 Vertical alignment film 3 Transparent substrate

Claims

1. The optical function layer is sandwiched between two transparent substrates. the optical functional layer contains liquid crystal molecules and a photoisomerizable material, A liquid crystal optical element that switches between a light-transmitting state and a light-scattering state depending on the orientation state of the liquid crystal molecules, the optical functional layer holds the liquid crystal molecules and the photoisomerizable material within a network structure formed by an aggregate of resin particles, The liquid crystal optical element is characterized in that the resin particles have moieties derived from at least two kinds of photopolymerizable monomers including 4,4'-bis[4-{6-(acryloyloxy)hexyloxy}benzoate]-1,1'-biphenylene.

2. A liquid crystal optical element as described in Claim 1, characterized in that the resin particles have portions derived from at least two types of liquid crystal resins including 4,4'-bis[4-{6-(acryloyloxy)hexyloxy}benzoate]-1,1'-biphenylene.

3. A liquid crystal optical element as described in claim 1, characterized in that the resin particles have a portion derived from 4,4'-bis[4-{6-(acryloyloxy)hexyloxy}benzoate]-1,1'-biphenylene and a portion derived from a non-liquid crystal resin.

4. 4. The liquid crystal optical element according to claim 1, wherein the resin particles have an average particle size of 1 μm or less.

5. 5. The liquid crystal optical element according to claim 1, wherein the resin particles have an average particle size of 0.7 μm or less.

6. 4. The liquid crystal optical element according to claim 1, wherein the resin particles have a refractive index anisotropy.

7. 7. The liquid crystal optical element according to claim 1, wherein the resin particles have a biphenyl structure in their molecular structure.

Images