Liquid crystal composition, optical element, and light guide element

Abstract

The present invention addresses the problem of providing: a liquid crystal composition that is capable of yielding an optical element having exceptional diffraction efficiency, as relates to an optical element that has an optically anisotropic layer having a liquid crystal alignment pattern in which the orientation of an optical axis derived from a liquid crystal compound changes while continuously rotating along at least one direction within a plane; an optical element; and a light guide element. The liquid crystal composition according to the present invention contains a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound, and the ratio of the twist elastic constant K22 and the spray elastic constant K11 of the liquid crystal composition satisfies 0.7≤K22 / K11.

Description

[Technical Field]

[0001] This invention relates to a liquid crystal composition, an optical element, and a light guide element. [Background technology]

[0002] Polarization is used in many optical devices and systems. In response, development is underway on optical elements that control the reflection, focusing, and divergence of polarized light. For example, Patent Document 1 describes an optical element comprising a plurality of stacked birefringent sublayers configured to change the direction of propagation of light passing through the interior according to the Bragg condition, wherein the stacked birefringent sublayers have local optical axes that change along the respective interfaces between adjacent stacked birefringent sublayers to define their respective lattice periods.

[0003] The optical element described in Patent Document 1 has an optically anisotropic thin film containing a liquid crystal compound (i.e., a thin liquid crystal layer). Specifically, the optical element described in Patent Document 1 is a diffraction element having a liquid crystal layer that diffracts light by changing the orientation pattern of rod-shaped liquid crystal compounds in one direction within the plane. Diffractive elements using such liquid crystal compounds are expected to be used, for example, as optical components in image projection devices such as AR (Augmented Reality) glasses.

[0004] AR glasses, as an example, work by having an image displayed on a screen enter one end of a light guide plate, propagate through it, and emit it from the other end, thereby overlaying a virtual image onto the scene the user is actually seeing. In AR glasses, a diffracting element is used to diffract (refract) light from the display (projected light) and direct it into one end of a light guide plate. This introduces the light into the light guide plate at an angle, causing it to undergo total internal reflection and propagate within the plate. The light that has propagated through the light guide plate is then diffracted again by a diffracting element at the other end of the light guide plate and emitted from the light guide plate to the user's observation position. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Special table 2017 / 522601 [Overview of the project] [Problems that the invention aims to solve]

[0006] The present inventors investigated the optical element described in Patent Document 1 and found that when an optical element is fabricated using a general-purpose liquid crystal composition, the diffraction efficiency may be poor.

[0007] Therefore, the present invention aims to provide a liquid crystal composition, an optical element, and a light guide element that can produce an optical element with excellent diffraction efficiency, with respect to an optical element having an optical anisotropic layer having a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. [Means for solving the problem]

[0008] As a result of diligent research to achieve the above objectives, the inventors of the present invention discovered that by using a liquid crystal composition containing a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound, it is possible to fabricate an optical element with excellent diffraction efficiency, thus completing the present invention. In other words, we found that the above problem can be solved by the following configuration.

[0009] [1] A liquid crystal composition containing a liquid crystal compound, The liquid crystal composition contains a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound, A liquid crystal composition in which the ratio of the twist elastic constant K22 to the spray elastic constant K11 satisfies 0.7 ≤ K22 / K11. [2] Refractive index difference Δn due to refractive index anisotropy of liquid crystal composition 550 The liquid crystal composition according to [1], wherein the ratio is 0.2 or higher. [3] The liquid crystal composition according to [1] or [2], wherein the content of the disc-shaped liquid crystal compound contained in the liquid crystal composition is 5 to 25% by mass relative to the total mass of the rod-shaped liquid crystal compound and the disc-shaped liquid crystal compound contained in the liquid crystal composition. [4] The liquid crystal composition according to any one of [1] to [3], wherein the rod-shaped liquid crystal compound is a compound represented by formula (I) described later. [5] The liquid crystal composition according to any one of [1] to [4], wherein the disc-shaped liquid crystal compound is a compound represented by formula (II) described later. [6] At least one Y in equation (I) described later 1 The liquid crystal composition described in [4], wherein -C≡C-. [7] An optical element having an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound, The liquid crystal composition contains a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound, An optical element having an optical anisotropy layer with a liquid crystal alignment pattern in which the orientation of the optical axes derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. [8] The optical element according to claim 7, wherein the liquid crystal composition is the liquid crystal composition described in any of [1] to [6]. [9] The optical element according to [7] or [8], wherein the optical anisotropy layer has optical axes aligned in the thickness direction.

[10] The optical element according to [7] or [8], wherein the optical anisotropy layer has a region in which the orientation of the optical axis is twisted and rotated in the thickness direction.

[11] An optical element according to any one of [7] to

[10] , wherein the length of one period in the liquid crystal alignment pattern is different when the length of one period is defined as the length of a 180° rotation of the optical axis in the plane.

[12] An optical element according to any one of [7] to

[11] , wherein the period of one liquid crystal alignment pattern gradually shortens in one direction in which the orientation of the optical axis in the liquid crystal alignment pattern changes while continuously rotating.

[13] An optical element according to any one of [7] to

[12] , wherein the liquid crystal alignment pattern of the optical anisotropy layer is a concentric pattern having one direction in which the orientation of the optical axis changes while continuously rotating, in a concentric manner from the inside to the outside. A light guide element comprising an optical element and a light guide plate as described in any of

[14] [7] to

[13] . [Effects of the Invention]

[0010] According to the present invention, with respect to an optical element having an optical anisotropic layer having a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane, it is possible to provide a liquid crystal composition that can produce an optical element with excellent diffraction efficiency, as well as an optical element and a light guide element. [Brief explanation of the drawing]

[0011] [Figure 1] This figure conceptually illustrates an example of the optical element of the present invention. [Figure 2] This is a conceptual diagram illustrating the optical elements shown in Figure 1. [Figure 3] Figure 1 is a plan view of the optical element shown. [Figure 4] Figure 1 is a conceptual diagram illustrating the operation of the optical element shown. [Figure 5] This is a diagram conceptually illustrating another example of the optical element of the present invention. [Figure 6] This is a diagram conceptually illustrating another example of the optical element of the present invention. [Figure 7] Figure 6 is a plan view of the optical element shown. [Figure 8] Figure 6 is a conceptual diagram illustrating the operation of the optical element shown. [Figure 9] Figure 6 is a conceptual diagram illustrating the operation of the optical element shown. [Figure 10] Figures 2 and 6 conceptually illustrate an example of an exposure apparatus for exposing the alignment film of the diffraction element. [Figure 11]This figure conceptually illustrates another example of the optical anisotropy layer of the optical element of the present invention. [Figure 12] This figure conceptually shows an example of an exposure apparatus for exposing an alignment film that forms the optical anisotropy layer shown in Figure 11. [Figure 13] Figure 1 is a conceptual diagram illustrating AR glasses that use the light guide element of the present invention, which comprises the optical elements shown in Figure 1. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below. The following description of the constituent elements may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.

[0013] In this specification, a numerical range represented by "~" means a range that includes the numbers written before and after "~" as the lower and upper limits, respectively. In this specification, each component may be represented by a single substance or by a combination of two or more substances. When two or more substances are used in combination for each component, the content of that component refers to the total content of the combined substances unless otherwise specified. In this specification, "(meth)acrylate" means "either acrylate or methacrylate, or both."

[0014] [Liquid crystal composition] The present invention relates to a liquid crystal composition containing a liquid crystal compound, comprising a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound, wherein the ratio of the elastic constant of twist (K22) to the elastic constant of spray (K11) satisfies 0.7 ≤ K22 / K11. In the present invention, the ratio (K22 / K11) of the elastic constant of the twist (K22) to the elastic constant of the spray (K11) is preferably 0.7 to 2.0, and more preferably 0.75 to 1.5. Here, the elastic constant of the liquid crystal composition is the elastic constant of the liquid crystal composition excluding the solvent. Furthermore, the ratio (K22 / K11) of the elastic constant of the twist (K22) to the elastic constant of the spray (K11) refers to the value measured by the following method. First, following the reference "G. Chen et al., Jpn. J. Appl. Phys. 28, 56 (1989)," we select the cell thickness, the incident polarization for light scattering measurement, the orientation direction of the liquid crystal, and the receiving polarization conditions. Next, the angular dependence of light scattering will be analyzed and measured using the principle formula described in the reference "R. Akiyama et al., Jpn. J. Appl. Phys. 19, 1937 (1980)" and the experimental correction formula described in the reference "G. Chen et al., Jpn. J. Appl. Phys. 28, 56 (1989)".

[0015] As described above, in the present invention, by using a liquid crystal composition containing a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound, an optical element with excellent diffraction efficiency can be fabricated. The details of this reason are still unclear, but the inventors speculate that it is due to the following reasons. In other words, in the present invention, by forming an optically anisotropic layer using a liquid crystal composition containing a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound, the twist deformation of the rod-shaped liquid crystal compound is suppressed compared to the case in which only the rod-shaped liquid crystal compound is used. As a result, the patterning orientation is improved when forming a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane. Consequently, it is believed that an optical element with excellent diffraction efficiency can be fabricated. The components of the liquid crystal composition of the present invention will be described in detail below.

[0016] [Liquid crystal compound] The liquid crystal compounds contained in the liquid crystal composition of the present invention are rod-shaped liquid crystal compounds and disc-shaped liquid crystal compounds. Furthermore, both low-molecular-weight liquid crystal compounds and high-molecular-weight liquid crystal compounds can be used as the liquid crystal compound. Here, "low molecular weight liquid crystal compounds" refers to liquid crystal compounds that do not have repeating units in their chemical structure. Furthermore, "polymeric liquid crystal compounds" refer to liquid crystal compounds that have repeating units in their chemical structure.

[0017] <Rod-shaped liquid crystal compound> Examples of rod-shaped liquid crystal compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyanosubstituted phenylpyrimidines, alkoxysubstituted phenylpyrimidines, phenyldioxanes, trans, and alkenylcyclohexylbenzonitriles. Examples of rod-shaped liquid crystal compounds include those described in Makromol. Chem., Vol. 190, p. 2255 (1989), Advanced Materials, Vol. 5, p. 107 (1993), U.S. Patent No. 4,683,327, U.S. Patent No. 5,622,648, U.S. Patent No. 5,770,107, International Publication No. 95 / 22586, International Publication No. 95 / 24455, International Publication No. 97 / 00600, International Publication No. 98 / 23580, International Publication No. 98 / 52905, Japanese Patent Publication No. 1-272551, Japanese Patent Publication No. 6-16616, Japanese Patent Publication No. 7-110469, Japanese Patent Publication No. 11-80081, and Japanese Patent Publication No. 2001-328973.

[0018] In the present invention, the rod-shaped liquid crystal compound is preferably a compound represented by the following formula (I) because it results in better diffraction efficiency of the fabricated optical element. [ka]

[0019] In the above formula (I), P 1 and P 2 Each of these independently represents a hydrogen atom or a substituent. Also, S 1 and S 2Each independently represents a single bond or a divalent linking group. Also, A 1 and A 2 each independently represents an optionally substituted non-aromatic ring, aromatic ring or aromatic heterocyclic ring. However, when there are a plurality of A 2 the plurality of A 2 may be the same or different from each other. Also, Y 1 represents -O-, -S-, -OCH2-, -CH2O-, -CH2CH2-, -CO-, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, -CO-NH-, -NH-CO-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -CH=CH-COO-, -CH=CH-OCO-, -COO-CH=CH-, -OCO-CH=CH-, -COO-CH2CH2-, -OCO-CH2CH2-, -CH2CH2-COO-, -CH2CH2-OCO-, -COO-CH2-, -OCO-CH2-, -CH2-COO-, -CH2-OCO-, -CH=CH-, -N=N-, -CH=N-N=CH-, -CF=CF-, -C≡C-, -OCH2CH2O-, -SCH2CH2S-, or a single bond. However, when there are a plurality of Y 1 the plurality of Y 1 may be the same or different from each other. Also, m1 represents an integer from 1 to 12.

[0020] In the above formula (I), examples of the substituents represented by P 1 and P 2 include, for example, an alkyl group, an alkoxy group, an alkylcarbonyl group, an alkoxycarbonyl group, an alkylcarbonyloxy group, an alkylamino group, a dialkylamino group, an alkylamide group, an alkenyl group, an alkynyl group, a halogen atom, a cyano group, a nitro group, an alkylthiol group, an N-alkylcarbamate group, and a polymerizable group. Among them, an alkyl group, an alkoxy group, or a polymerizable group is preferable.

[0021] Preferred alkyl groups for substituents include linear, branched, or cyclic alkyl groups having 1 to 18 carbon atoms, and more preferably alkyl groups having 1 to 12 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, hexylene, heptyl, dodecyl, and cyclohexyl groups).

[0022] As preferred examples of substituents, alkoxy groups having 1 to 18 carbon atoms are preferred, and alkoxy groups having 1 to 12 carbon atoms (e.g., methoxy group, ethoxy group, n-butoxy group, and methoxyethoxy group) are more preferred.

[0023] The polymerizable group, which is a preferred example of a substituent, is not particularly limited, but a polymerizable group that can be radically polymerized or cationically polymerized is preferred. As the radical polymerizable group, generally known radical polymerizable groups can be used, and preferred examples include the acryloyloxy group or the methacryloyloxy group. In this case, the polymerization rate is generally known to be faster with the acryloyloxy group, and from the viewpoint of improving productivity, the acryloyloxy group is preferred, but the methacryloyloxy group can also be used as a polymerizable group in the same way. As cationic polymerizable groups, generally known cationic polymerizable groups can be used, specifically, alicyclic ether groups, cyclic acetal groups, cyclic lactone groups, cyclic thioether groups, spiroorthoester groups, and vinyloxy groups. Among these, alicyclic ether groups or vinyloxy groups are preferred, and epoxy groups, oxetanyl groups, or vinyloxy groups are particularly preferred. Particularly preferred examples of polymerizable groups include those represented by any of the following formulas (P-1) to (P-20). Among these, polymerizable groups represented by any of the following formulas (P-1), (P-2), (P-7), and (P-12) are preferred.

[0024] [ka]

[0025] In this invention, P is used because it improves the durability of the fabricated optical element. 1 and P 2 Preferably, at least one of them represents a polymerizable group, P 1 and P 2 It is more preferable that both represent polymerizable groups.

[0026] In the above equation (I), S 1 and S 2 Examples of divalent linking groups shown in one embodiment include -O-, -S-, -OCH2-, -CH2O-, -CH2CH2-, -CO-, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, -CO-NH-, -NH-CO-, divalent hydrocarbon groups (for example, saturated hydrocarbon groups such as alkylene groups, alkenylene groups, alkylylene groups, arylene groups, etc., which may have substituents), and groups that combine these. Of these, a divalent hydrocarbon group is preferred, and a divalent hydrocarbon group having 1 to 20 carbon atoms, which may have substituents, is more preferred. Here, one or more methylene groups among the above hydrocarbon groups may be independently substituted with -O- or -C(=O)-. Furthermore, one methylene group may be substituted with -O-, and the adjacent methylene group may be substituted with -C(=O)- to form an ester group. Furthermore, the number of carbon atoms in the above-mentioned divalent hydrocarbon group is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 5. The above-mentioned divalent hydrocarbon group may be linear, branched, or form a cyclic structure. The substituents that the above divalent hydrocarbon group may have include P in formula (I) above. 1 and P 2 Examples of substituents similar to those shown in one embodiment include alkyl groups, alkoxy groups, alkoxycarbonyl groups, alkylcarbonyloxy groups, or halogen atoms.

[0027] In the above formula (I), A1 and A 2 One example of a non-aromatic ring represented by this embodiment is a cycloalkane ring. Examples of cycloalkane rings include, for example, cyclohexane rings, cyclopeptane rings, cyclooctane rings, cyclododecane rings, and cyclodocosane rings. Of these, a cyclohexane ring is preferred, a 1,4-cyclohexylene group is more preferred, and a trans-1,4-cyclohexylene group is even more preferred.

[0028] Also, in the above formula (I), A 1 and A 2 Examples of aromatic rings represented by one aspect include benzene rings, naphthalene rings, and anthracene rings. Of these, benzene rings (e.g., 1,4-phenyl groups) and naphthalene rings are preferred.

[0029] Also, in the above formula (I), A 1 and A 2 Examples of aromatic heterocycles represented by one embodiment include furan rings, pyrrole rings, thiophene rings, oxadiazole rings (1,3,4-oxadiazole), thiadiazole rings (1,3,4-thiadiazole), pyridine rings, pyrazine rings (1,4-diazine), pyrimidine rings (1,3-diazine), pyridazine rings (1,2-diazine), thiazole rings, benzothiazole rings, and phenantholine rings. Of these, thiophene rings, oxadiazole rings, thiadiazole rings, pyridine rings, and pyrimidine rings are preferred.

[0030] Also, in the above formula (I), A 1 and A 2 The substituents that may be present are P in formula (I) above. 1 and P 2 Examples of substituents similar to those shown in one embodiment include alkyl groups, alkoxy groups, alkoxycarbonyl groups, alkylcarbonyloxy groups, or halogen atoms. As the alkyl group, linear, branched, or cyclic alkyl groups having 1 to 18 carbon atoms are preferred, alkyl groups having 1 to 8 carbon atoms (e.g., methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, t-butyl group, and cyclohexyl group) are more preferred, alkyl groups having 1 to 4 carbon atoms are even more preferred, and methyl or ethyl groups are particularly preferred. As the alkoxy group, an alkoxy group having 1 to 18 carbon atoms is preferred, an alkoxy group having 1 to 8 carbon atoms (e.g., a methoxy group, an ethoxy group, an n-butoxy group, and a methoxyethoxy group) is more preferred, an alkoxy group having 1 to 4 carbon atoms is even more preferred, and a methoxy group or an ethoxy group is particularly preferred. Examples of alkoxycarbonyl groups include groups in which an oxycarbonyl group (-O-CO- group) is bonded to an alkyl group as exemplified above. Among these, methoxycarbonyl groups, ethoxycarbonyl groups, n-propoxycarbonyl groups, or isopropoxycarbonyl groups are preferred, with methoxycarbonyl groups being more preferred. Examples of alkylcarbonyloxy groups include groups in which a carbonyloxy group (-CO-O- group) is bonded to an alkyl group as exemplified above. Among these, methylcarbonyloxy groups, ethylcarbonyloxy groups, n-propylcarbonyloxy groups, or isopropylcarbonyloxy groups are preferred, with methylcarbonyloxy groups being more preferred. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms, with fluorine atoms or chlorine atoms being preferred.

[0031] In the above equation (I), Y 1As mentioned above, -O-, -S-, -OCH2-, -CH2O-, -CH2CH2-, -CO-, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, -CO-NH-, -NH-CO-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -CH=CH-COO-, -CH=CH-OCO-, -COO-CH=CH-, - OCO-CH=CH-, -COO-CH2CH2-, -OCO-CH2CH2-, -CH2CH2-COO-, -CH2CH2-OCO-, -COO-CH2-, -OCO-CH2-, -CH2-COO-, -CH2-OCO-, -CH=CH-, -N=N-, -CH=NN=CH-, -CF=CF-, -C≡C-, -OCH2CH2O-, -SCH2CH2S-, or represent a single bond. Of these, -O-, -CO-, -COO-, -OCO-, -C≡C-, and single bonds are preferred.

[0032] In the present invention, for the reason that the diffraction efficiency of the fabricated optical element is further improved, at least one Y in formula (I) above 1 However, it is preferable that -C≡C-. Furthermore, at least one Y 1 That is, if m1 is 1, then there is one Y 1 This refers to the case where m1 is an integer between 2 and 12, and there are multiple Y 1 at least one of Y 1 It refers to that.

[0033] In the above formula (I), as described above, m1 is an integer between 1 and 12, preferably between 1 and 8, and more preferably between 1 and 5.

[0034] Examples of rod-shaped liquid crystal compounds include the following rod-shaped liquid crystal compounds (I-1) to (I-24). [ka] JPEG0007855573000004.jpg95112JPEG0007855573000005.jpg60114JPEG0007855573000006.jpg113133JPEG0007855573000007.jpg69125

[0035] In the present invention, the content of the rod-shaped liquid crystal compound is preferably 50 to 95% by mass, more preferably 60 to 90% by mass, and even more preferably 70 to 85% by mass, based on the total mass of solids in the liquid crystal composition (total mass of components excluding the solvent).

[0036] <Disc-shaped liquid crystal compound> Examples of disc-shaped liquid crystal compounds include those described in the following publications: (C. Destrade et al., Mol.Crysr.Liq.Cryst., vol.71, page 111 (1981); The Chemical Society of Japan, ed., Quarterly Review of Chemistry, No. 22, Chemistry of Liquid Crystals, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew.Chem.Soc.Chem.Comm., page 1794 (1985); J. Zhang et al., J.Am.Chem.Soc., vol.116, page 2655 (1994)); Japanese Patent Publication No. 2007-108732; Japanese Patent Publication No. 2010-244038; and others. The polymerization of disc-shaped liquid crystal compounds is described in Japanese Patent Publication No. Hei 8-27284.

[0037] In the present invention, the disc-shaped liquid crystal compound is preferably a compound represented by the following formula (II) because it results in better diffraction efficiency of the fabricated optical element. [ka]

[0038] In the above equation (II), P 3 P represents a hydrogen atom or substituent. However, multiple P 3 These may be the same or different. Also, S 3represents a single bond or a divalent linking group. However, multiple S 3 These may be the same or different. Also, A 3 A represents a non-aromatic ring, aromatic ring, or aromatic heterocycle, which may have substituents. However, multiple A 3 These may be the same or different. Also, Y 2 is -O-, -S-, -OCH2-, -CH2O-, -CH2CH2-, -CO-, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, -CO-NH-, -NH- CO-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -CH=CH-COO-, -CH=CH-OCO-, -COO-CH=CH-, -OCO -CH=CH-, -COO-CH2CH2-, -OCO-CH2CH2-, -CH2CH2-COO-, -CH2CH2-OCO-, -COO-CH2-, -OCO-CH2-, -CH2-COO-, -CH2-OCO-, -CH=CH-, -N=N-, -CH=NN=CH-, -CF=CF-, -C≡C-, -OCH2CH2O-, -SCH2CH2S-, or single bond. However, multiple Ys are not possible. 2 These may be the same or different. Furthermore, m2 represents an integer between 0 and 5. Furthermore, n represents an integer between 3 and 20. Furthermore, D represents an n-valent disk-shaped core.

[0039] In the above equation (II), P 3 One embodiment of the substituent is P in formula (I) above. 1 and P 2 Examples of substituents similar to those shown in one embodiment include, and the preferred embodiments are also similar.

[0040] In this invention, for the reason that the durability of the fabricated optical element is improved, multiple P 3 Preferably, at least one of them represents a polymerizable group, and all P 3 It is more preferable that this represents a polymerizable group.

[0041] In the above equation (II), S 3 One aspect of the divalent linking group shown is S in formula (I) above. 1 and S 2 Examples include divalent linking groups similar to those shown in one embodiment, and the preferred embodiments are also similar.

[0042] In the above formula (II), A 3 The "non-aromatic ring, aromatic ring, or aromatic heterocycle which may have substituents" shown by the above formula (I) is A 1 and A 2 Examples of "non-aromatic rings, aromatic rings, or aromatic heterocycles that may have substituents" as indicated above include similar examples, and preferred embodiments are also similar.

[0043] In the above equation (II), Y 2 As for Y in equation (I) above, 1 Similar examples can be given, and the preferred embodiments are also similar.

[0044] In the above formula (II), as described above, m2 is an integer between 0 and 5, preferably between 0 and 4, and more preferably between 0 and 3.

[0045] In formula (II) above, n is an integer between 3 and 20, preferably between 3 and 15, and more preferably between 3 and 10, as described above.

[0046] In equation (II) above, D represents an n-valent disc-shaped core, as described above. Here, the disc-shaped core is not particularly limited, but for example, a structure represented by the following equations (II-1c) to (II-20c) can be used. Note that in the following equations, * represents -(Y 2 -A 3 ) m2 -S 3 -P 3 This indicates the bonding position with the group represented by .

[0047] [ka] JPEG0007855573000010.jpg56130JPEG0007855573000011.jpg5695JPEG0007855573000012.jpg23108 JPEG0007855573000013.jpg56108JPEG0007855573000014.jpg57121JPEG0007855573000015.jpg39104

[0048] Examples of disc-shaped liquid crystal compounds include the disc-shaped liquid crystal compounds (II-1) to (II-20) shown below. The structure represented by Y in the following structural formulas is shown below. [ka] [ka] JPEG0007855573000018.jpg56128JPEG0007855573000019.jpg5696JPEG0007855573000020.jpg23107JPEG0007855573 000021.jpg66129JPEG0007855573000022.jpg58123JPEG0007855573000023.jpg37141JPEG0007855573000024.jpg3466

[0049] In the present invention, for the reason that the diffraction efficiency of the fabricated optical element is better, the content of the disc-shaped liquid crystal compound in the liquid crystal composition is preferably 50% by mass or less, more preferably 5 to 25% by mass, and even more preferably 5 to 20% by mass, relative to the total mass of the rod-shaped liquid crystal compound and the disc-shaped liquid crystal compound in the liquid crystal composition. Furthermore, when the content of the disc-shaped liquid crystal compound is within the above range, it becomes easier to adjust the ratio (K22 / K11) of the elastic constant of the twist of the liquid crystal composition (K22) to the elastic constant of the spray (K11) to 0.7 or higher.

[0050] [Surfactants] The liquid crystal composition of the present invention may contain a surfactant. The surfactant is preferably a compound that can function as an orientation control agent that contributes stably or rapidly to the orientation of the cholesteric liquid crystal phase. Examples of surfactants include silicate surfactants and fluorine-based surfactants, with fluorine-based surfactants being preferred.

[0051] Specific examples of surfactants include the compounds described in paragraphs

[0082] to

[0090] of Japanese Patent Publication No. 2014-119605, the compounds described in paragraphs

[0031] to

[0034] of Japanese Patent Publication No. 2012-203237, the compounds exemplified in paragraphs

[0092] and

[0093] of Japanese Patent Publication No. 2005-99248, the compounds exemplified in paragraphs

[0076] to

[0078] and paragraphs

[0082] to

[0085] of Japanese Patent Publication No. 2002-129162, and the fluorine (meth)acrylate polymers described in paragraphs

[0018] to

[0043] of Japanese Patent Publication No. 2007-272185, etc. Furthermore, a single surfactant may be used alone, or two or more surfactants may be used in combination. As a fluorine-based surfactant, the compounds described in paragraphs

[0082] to

[0090] of Japanese Patent Application Publication No. 2014-119605 are preferred.

[0052] The amount of any surfactant added is preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass, and even more preferably 0.02 to 1% by mass, relative to the mass of the rod-shaped liquid crystal compound.

[0053] [Chiral agents (optically active compounds)] The liquid crystal composition of the present invention may contain a chiral agent. Chiral agents have the function of inducing a helical structure in the cholesteric liquid crystal phase. Since different chiral agents induce different helical twist directions or helical pitches, they should be selected according to the purpose. There are no particular restrictions on the chiral agent, and known compounds (for example, described in the Liquid Crystal Device Handbook, Chapter 3, Section 4-3, Chiral Agents for TN (twisted nematic) and STN (Super Twisted Nematic), page 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), isosorbide, and isomannide derivatives can be used. Chiral agents generally contain an asymmetric carbon atom, but axially asymmetric compounds or planar asymmetric compounds that do not contain an asymmetric carbon atom can also be used as chiral agents. Examples of axially asymmetric compounds or planar asymmetric compounds include binaphthyl, helicene, paracyclophane, and their derivatives. Chiral agents may have polymerizable groups. If both the chiral agent and the liquid crystal compound have polymerizable groups, a polymerization reaction between the polymerizable chiral agent and the polymerizable liquid crystal compound can form a polymer having repeating units derived from the polymerizable liquid crystal compound and repeating units derived from the chiral agent. In this embodiment, it is preferable that the polymerizable group of the polymerizable chiral agent is of the same type as the polymerizable group of the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent is preferably an unsaturated polymerizable group, an epoxy group, or an azilidinyl group, more preferably an unsaturated polymerizable group, and even more preferably an ethylenically unsaturated polymerizable group. Furthermore, the chiral agent may be a liquid crystal compound.

[0054] When the chiral agent has a photoisomerizing group, it is preferable because, after coating and orientation, a pattern of the desired reflection wavelength corresponding to the emission wavelength can be formed by photomask irradiation with active light or the like. Preferred photoisomerizing groups are the isomerization site of a photochromic compound, an azo group, an azoxy group, or a cinnamoyl group. Specific compounds that can be used include those described in Japanese Patent Publication No. 2002-080478, 2002-080851, 2002-179668, 2002-179669, 2002-179670, 2002-179681, 2002-179682, 2002-338575, 2002-338668, 2003-313189, and 2003-313292, etc.

[0055] The content of any chiral agent is preferably 0.01 to 200 mol%, and more preferably 1 to 30 mol%, relative to the molar amount of the rod-shaped liquid crystal compound.

[0056] [Polymerization initiator] The liquid crystal composition of the present invention preferably contains a polymerization initiator. In the embodiment in which the polymerization reaction is carried out by ultraviolet irradiation, the polymerization initiator used is preferably a photopolymerization initiator capable of initiating the polymerization reaction by ultraviolet irradiation. Examples of photopolymerization initiators include α-carbonyl compounds (described in U.S. Patent Nos. 2,367,661 and 2,367,670), acyloin ethers (described in U.S. Patent No. 2,448,828), α-hydrocarbon-substituted aromatic acyloin compounds (described in U.S. Patent No. 2,722,512), polynuclear quinone compounds (described in U.S. Patent Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketones (described in U.S. Patent No. 3,549,367), acridine and phenazine compounds (described in Japanese Patent Publication No. 60-105,667 and U.S. Patent No. 4,239,850), and oxadiazole compounds (described in U.S. Patent No. 4,212,970). The content of any photopolymerization initiator is preferably 0.1 to 20% by mass, and more preferably 0.5 to 12% by mass, relative to the mass of the rod-shaped liquid crystal compound.

[0057] [Crosslinking agent] The liquid crystal composition of the present invention may optionally contain a crosslinking agent to improve the film strength and durability after curing. Suitable crosslinking agents include those that cure with ultraviolet light, heat, and moisture. The crosslinking agent is not particularly limited and can be appropriately selected depending on the purpose. Examples include polyfunctional acrylate compounds such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; epoxy compounds such as glycidyl(meth)acrylate and ethylene glycol diglycidyl ether; aziridine compounds such as 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate] and 4,4-bis(ethyleneiminocarbonylamino)diphenylmethane; isocyanate compounds such as hexamethylene diisocyanate and biuret-type isocyanate; polyoxazoline compounds having an oxazoline group in the side chain; and alkoxysilane compounds such as vinyltrimethoxysilane and N-(2-aminoethyl)3-aminopropyltrimethoxysilane. In addition, known catalysts can be used depending on the reactivity of the crosslinking agent, which can improve productivity in addition to improving film strength and durability. These may be used individually or in combination of two or more. The content of any crosslinking agent is preferably 3 to 20% by mass, and more preferably 5 to 15% by mass, relative to the solid content mass of the liquid crystal composition. If the crosslinking agent content is within the above range, the durability of the fabricated optical element will be improved.

[0058] [Other additives] The liquid crystal composition of the present invention may optionally contain polymerization inhibitors, antioxidants, ultraviolet absorbers, light stabilizers, colorants, and metal oxide fine particles, to the extent that they do not degrade the optical performance.

[0059] The liquid crystal composition of the present invention is preferably used as a liquid when forming an optically anisotropic layer. The liquid crystal composition may contain a solvent. The solvent is not particularly limited and can be appropriately selected depending on the purpose, but organic solvents are preferred. Examples of organic solvents include ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. These may be used individually or in combination of two or more. Among these, ketones are preferred when considering the environmental impact.

[0060] The liquid crystal composition of the present invention has a refractive index difference Δn associated with refractive index anisotropy, which is why the diffraction efficiency of the fabricated optical element is better. 550 It is preferable that the value is 0.2 or higher, more preferably 0.25 or higher, and even more preferably 0.25 or higher and 0.50 or lower. Here, the refractive index difference Δn 550 This refers to the value calculated by measuring the retardation value and film thickness of a liquid crystal immobilized layer (cured layer) obtained by coating a liquid crystal composition onto a support with an alignment film prepared separately for retardation measurement, aligning the liquid crystal compound so that its director (optical axis) is horizontal to the surface of the support, and then fixing it by ultraviolet irradiation. Note that Δn550 can be calculated by dividing the retardation value by the film thickness. Additionally, retardation values ​​are measured at a wavelength of 550 nm using Axometrix's Axoscan, and film thickness is measured using a scanning electron microscope (SEM).

[0061] From the viewpoint of ease of fabrication of optical elements, the liquid crystal composition of the present invention preferably has a phase transition temperature of 50°C or higher between the liquid crystal phase and the isotropic phase, more preferably 70°C or higher, and even more preferably 70°C or higher and 400°C or lower.

[0062] [Optical elements] The optical element of the present invention is an optical element having an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound. Furthermore, the above-mentioned liquid crystal composition contains a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound. Furthermore, the optically anisotropic layer has a liquid crystal orientation pattern in which the orientation of the optical axes derived from the liquid crystal compound contained in the liquid crystal composition changes while continuously rotating along at least one direction in the plane. Here, the optical axis of a liquid crystal compound refers to the direction of the long axis of the liquid crystal molecule in the case of a rod-shaped liquid crystal compound, and the direction perpendicular to the disk surface in the case of a disc-shaped liquid crystal compound.

[0063] In the present invention, it is preferable that the liquid crystal composition used to form the optical anisotropy layer is the liquid crystal composition of the present invention described above, for the reason that diffraction efficiency is better.

[0064] The optical element of the present invention will be described in detail below based on preferred embodiments shown in the attached drawings. In the following description, a liquid crystal composition containing a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound will be abbreviated as "the liquid crystal composition of the present invention." Furthermore, in the attached diagrams, the notation for disc-shaped liquid crystal compounds has been omitted, and only rod-shaped liquid crystal compounds are shown.

[0065] Figure 1 conceptually shows an example of the optical element of the present invention. As shown in Figure 1, the optical element 10 comprises a support 12, a photo-alignment film 14, and a cholesteric liquid crystal layer 16, which is an optically anisotropic layer formed using the liquid crystal composition of the present invention described above. The cholesteric liquid crystal layer 16 is a layer in which a cholesteric liquid crystal phase is fixed.

[0066] The optical element 10 in the illustrated example comprises a support 12, a photo-alignment film 14, and a cholesteric liquid crystal layer 16, but the present invention is not limited thereto. In other words, the optical element of the present invention may have only the photo-alignment film 14 and the cholesteric liquid crystal layer 16 (optical anisotropy layer) obtained by forming a photo-alignment film 14 and a cholesteric liquid crystal layer 16 on one surface of a support 12 and then peeling off the support 12.

[0067] [Support] In the optical element 10, the support 12 supports the photo-alignment film 14 and the cholesteric liquid crystal layer 16.

[0068] The support 12 can be any type of sheet material (film, plate) as long as it can support the photo-alignment film 14 and the cholesteric liquid crystal layer 16. Furthermore, the support 12 preferably has a transmittance of 50% or more for the corresponding light, more preferably 70% or more, and even more preferably 85% or more.

[0069] There are no restrictions on the thickness of the support 12; the thickness should be set appropriately to be able to hold the photo-alignment film 14 and the cholesteric liquid crystal layer, depending on the application of the optical element 10 and the material used to form the support 12. The thickness of the support 12 is preferably 1 to 1000 μm, more preferably 3 to 250 μm, and even more preferably 5 to 150 μm.

[0070] The support 12 may be single-layered or multi-layered. Examples of a single-layer support 12 include glass, triacetylcellulose (TAC), polyethylene terephthalate (PET), polycarbonate, polyvinyl chloride, acrylic, and polyolefin. Examples of a multilayer support 12 include one of the aforementioned single-layer supports as a substrate, with other layers provided on the surface of this substrate.

[0071] [Photo-aligning film] In the optical element 10, a photo-alignment film 14 is placed on the surface of the support 12. The photo-alignment film 14 is an alignment film used to align the rod-shaped liquid crystal compound 20 (hereinafter abbreviated as "liquid crystal compound 20") into a predetermined liquid crystal alignment pattern when forming the cholesteric liquid crystal layer 16 of the optical element 10. As will be described later, in the optical element 10, the cholesteric liquid crystal layer 16, which is the optical anisotropy layer in the present invention, has a liquid crystal alignment pattern in which the orientation of the optical axis 20A (see Figure 3) derived from the liquid crystal compound 20 changes while continuously rotating along one direction in the plane. Therefore, the photo-alignment film 14 is formed so that the cholesteric liquid crystal layer 16 can form this liquid crystal alignment pattern. In the following explanation, "the direction of optical axis 20A rotates" will also be referred to simply as "optical axis 20A rotates."

[0072] The material constituting the photo-alignment film 14 is not particularly limited. For example, compounds having cinnamate groups (low molecular weight compounds, monomers, or polymers) can be used. In particular, the photo-alignment film 14 preferably contains a polymer having cinnamate groups, as this further suppresses discoloration. Examples of main chains that form polymers having cinnamate groups include poly(meth)acrylates, polyimides, polyurethanes, polyamic acids, polymaleimides, polyethers, polyvinyl ethers, polyesters, polyvinyl esters, polystyrene derivatives, polysiloxanes, cycloolefin polymers, epoxy polymers, and copolymers thereof. Furthermore, monomers having a cinnamate group include monomers that provide the repeating units that constitute the polymers described above.

[0073] Polymers containing cinnamate groups preferably exhibit liquid crystalline properties. Liquid crystalline properties improve the degree of orientation of the cinnamate groups, making it easier for the cholesteric liquid crystal layer to be oriented. Furthermore, the diffraction efficiency of the optical element is further improved. Examples of polymers exhibiting liquid crystalline properties include polymers having a biphenyl group, terphenyl group, naphthalene group, phenylbenzoate group, azobenzene group, or a substituent (mesogenic group) of their derivatives as a side chain, which are widely used as mesogenic components in liquid crystalline polymers, and having a main chain structure such as acrylate, methacrylate, maleimide, N-phenylmaleimide, or siloxane. The side chain containing the mesogenic component and the cinnamate group may be independent side chains, or they may be contained within the same side chain. Polymers that exhibit liquid crystalline properties without containing mesogenic components include, for example, polymers having carboxyl groups at the end of their side chains. These polymers are materials that exhibit a liquid crystalline phase through the formation of dimers by hydrogen bonding of the carboxyl groups at the end of their side chains. The side chain having a carboxyl group at its terminus and the cinnamate group may be independent side chains, or they may be contained within the same side chain, but it is preferable that they be independent side chains.

[0074] Polymers having cinnamate groups may optionally have side chains containing polymerizable or crosslinkable groups. The polymerizable group is preferably a radical polymerizable group or a cationic polymerizable group, and more preferably a (meth)acrylate group, an epoxy group, or an oxetanyl group. A crosslinkable group is a site that bonds with a crosslinking agent (described later) upon exposure to light or heat. The specific functional group depends on the type of crosslinking agent, but for example, when epoxy compounds, methylol compounds, isocyanate compounds, etc. are used as crosslinking agents, examples include hydroxyl groups, carboxyl groups, phenolic hydroxyl groups, mercapto groups, glycidyl groups, and amide groups. Among these, aliphatic hydroxyl groups are preferred from the viewpoint of reactivity, and primary hydroxyl groups are more preferred.

[0075] Examples of low molecular weight compounds having a cinnamate group include those compounds that have a cinnamate group, as described in paragraphs

[0042] to

[0053] of International Publication No. 2016 / 002722 and paragraphs

[0030] to

[0051] of International Publication No. 2015 / 056741. Examples of polymers having functional groups that can react with these low molecular weight compounds to form covalent bonds include the polymers described in paragraphs

[0091] to

[0134] of International Publication No. 2016 / 002722, the polymers described in paragraphs

[0045] to

[0092] of International Publication No. 2015 / 129890, the polymers described in paragraphs

[0057] to

[0087] of International Publication No. 2015 / 030000, the polymers described in paragraphs

[0051] to

[0086] of International Publication No. 2014 / 171376, and the polymers described in paragraphs

[0042] to

[0058] of International Publication No. 2014 / 104320.

[0076] The photo-alignment film 14 is preferably formed using a photo-alignment film forming composition containing the above-mentioned material (for example, a polymer having cinnamate groups). The photo-alignment film-forming composition may also contain other components such as crosslinking agents, photopolymerization initiators, surfactants, solvents, rheology modifiers, pigments, dyes, preservative stabilizers, defoamers, and antioxidants.

[0077] The crosslinking agent may form a crosslinked structure by reacting with a compound having a cinnamate group, or with a polymer having a functional group that can react with the above compound to form a covalent bond, or it may form a separate crosslinked structure without reacting with these. Examples of crosslinking agents include (meth)acrylate compounds, epoxy compounds, methylol compounds, and isocyanate compounds. Radical initiators, acid generators, or base generators may be used as needed to trigger or accelerate the reaction of these crosslinking agents.

[0078] As a photopolymerization initiator, any of the commonly known general-purpose photopolymerization initiators that allow for the formation of a uniform film with a small amount of light irradiation can be used. Specific examples include azonitrile-based photopolymerization initiators, α-aminoketone-based photopolymerization initiators, acetophenone-based photopolymerization initiators, benzoin-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, triazine-based photopolymerization initiators, carbazole-based photopolymerization initiators, and imidazole-based photopolymerization initiators. The photopolymerization initiator may be used individually or in combination of two or more types.

[0079] Any surfactant commonly used to form a uniform film can be used. Examples of surfactants include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants.

[0080] The solvent is not particularly limited as long as it can dissolve each of the above components, for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methyl cellosolve acetate, ethyl cellosolve acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol propyl ether acetate, ethylene glycol dimethyl ether, propylene glycol dimethyl ether, toluene, xylene, methyl ethyl ketone, cyclopentanone, Examples include cyclohexanone, 2-butanone, 3-methyl-2-pentanone, 2-pentanone, 2-heptanone, γ-butyrolactone, ethyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl 3-ethoxypropionate, methyl pyruvate, ethyl pyruvate, ethyl acetate, butyl acetate, ethyl lactate, butyl lactate, N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0081] One example of a method for producing the photo-alignment film 14 is to apply a photo-alignment film-forming composition to a substrate, remove the solvent by distillation to form a film (photo-alignment precursor film), irradiate the obtained film with anisotropic light, and then heat it to generate liquid crystal alignment ability, thereby producing the photo-alignment film. Methods for applying the photo-alignment film-forming composition include, for example, spin coating, bar coating, die coating, screen printing, and spray coating. Furthermore, the light used for irradiation is not particularly limited as long as it is an irradiation beam capable of causing a chemical reaction, such as infrared rays, visible light, ultraviolet rays, X-rays, and charged particle beams. However, the irradiation beam usually has a wavelength of 200 to 500 nm. Applying heat after light irradiation is preferable because it promotes thermal polymerization, resulting in a photo-aligned film with higher durability against light, heat, etc.

[0082] Figure 10 conceptually shows an example of an exposure apparatus that exposes a photo-alignment precursor film 140 to form an alignment pattern. The exposure apparatus 60 shown in Figure 10 comprises a light source 64 equipped with a laser 62, a λ / 2 plate 65 that changes the polarization direction of the laser light M emitted by the laser 62, a polarizing beam splitter 68 that separates the laser light M emitted by the laser 62 into two beams MA and MB, mirrors 70A and 70B positioned on the optical paths of the two separated beams MA and MB, respectively, and λ / 4 plates 72A and 72B. The light source 64 emits linearly polarized light P0. The λ / 4 plate 72A converts the linearly polarized light P0 (ray MA) into right-circularly polarized light P R λ / 4 plate 72B converts linearly polarized light P0 (ray MB) to left-circularly polarized light P L Convert each of them accordingly.

[0083] A support 12 having a photo-alignment precursor film 140 before the orientation pattern is formed is placed in the exposure section, and two light rays MA and MB are intersected and interfered with on the photo-alignment precursor film 140, and the photo-alignment precursor film 140 is exposed by irradiating it with the resulting interference light. Due to this interference, the polarization state of the light irradiated onto the photo-alignment precursor film 140 changes periodically in an interference fringe pattern. As a result, an orientation pattern in the photo-alignment film 14 is obtained in which the orientation state changes periodically. In the exposure apparatus 60, the period of the orientation pattern can be adjusted by changing the intersection angle α of the two light rays MA and MB. That is, in the exposure apparatus 60, by adjusting the intersection angle α, the length of one period in which the optical axis 20A rotates 180° in one direction in an orientation pattern in which the optical axis 20A originating from the liquid crystal compound 20 rotates continuously along one direction can be adjusted. By forming a cholesteric liquid crystal layer on a photo-alignment film 14 having an orientation pattern in which such an orientation state changes periodically, a cholesteric liquid crystal layer can be formed having a liquid crystal orientation pattern in which the optical axis 20A originating from the liquid crystal compound 20 rotates continuously along one direction, as will be described later. Furthermore, by rotating the optical axes of the λ / 4 plates 72A and 72B by 90°, the rotation direction of the optical axis 20A can be reversed.

[0084] [Cholesteric liquid crystal layer] In the optical element 10, a cholesteric liquid crystal layer 16 is formed on the surface of the photo-alignment film 14. As described above, the cholesteric liquid crystal layer 16 is a layer in which the cholesteric liquid crystal phase is fixed.

[0085] In Figure 1, in order to simplify the drawing and clearly show the structure of the optical element 10, the cholesteric liquid crystal layer 16 is conceptually shown only as the liquid crystal compound 20 (liquid crystal compound molecules) on the surface of the photo-alignment film 14 and the surface of the cholesteric liquid crystal layer 16. However, as conceptually shown in Figure 2, the cholesteric liquid crystal layer 16 has a helical structure in which the liquid crystal compound 20 is spirally stacked, similar to a cholesteric liquid crystal layer in which a normal cholesteric liquid crystal phase is fixed. The structure consists of multiple helical pitches, where the liquid crystal compound 20 is stacked in a spiral with one rotation (360° rotation) of the spiral. In other words, the cholesteric liquid crystal layer 16 shown in Figure 2 has a region in which the orientation of the optical axis originating from the liquid crystal compound 20 twists and rotates in the thickness direction.

[0086] As is well known, a cholesteric liquid crystal layer, which has a fixed cholesteric liquid crystal phase, has wavelength-selective reflectivity. As will be explained in detail later, the selective reflection wavelength range of the cholesteric liquid crystal layer depends on the length of the helical pitch in the thickness direction (pitch P shown in Figure 2).

[0087] As described above, the cholesteric liquid crystal layer 16 is a cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase. That is, the cholesteric liquid crystal layer 16 is a layer made of a liquid crystal compound 20 (liquid crystal material) having a cholesteric structure.

[0088] (Cholesteric liquid crystal phase) Cholesteric liquid crystal phases are known to exhibit selective reflectivity at specific wavelengths. In a typical cholesteric liquid crystal phase, the center wavelength of selective reflection (λ) depends on the helical pitch P in the cholesteric liquid crystal phase and follows the relationship λ = n × P with respect to the average refractive index n of the cholesteric liquid crystal phase. Therefore, the center wavelength of selective reflection can be adjusted by adjusting this helical pitch. The selective reflection center wavelength of the cholesteric liquid crystal phase becomes longer as the pitch P increases. Furthermore, the helical pitch P, as mentioned above, is the helical structure of the cholesteric liquid crystal phase, equivalent to one pitch (helical period). In other words, it is the number of turns of the helix, and therefore, it is the length in the helical axis direction over which the director (the long axis direction in the case of a rod-shaped liquid crystal) of the liquid crystal compound constituting the cholesteric liquid crystal phase rotates 360°.

[0089] The helical pitch of the cholesteric liquid crystal phase depends on the type of chiral agent used with the liquid crystal compound when forming the cholesteric liquid crystal layer, and the concentration of the chiral agent added. Therefore, by adjusting these factors, a desired helical pitch can be obtained. For details on adjusting the pitch, see Fujifilm Research Report No. 50 (2005), pp. 60-63. For measuring the helical sense and pitch, the methods described in "Introduction to Liquid Crystal Chemistry Experiments," edited by the Japanese Liquid Crystal Society, Sigma Publishing, 2007, p. 46, and "Liquid Crystal Handbook," edited by the Liquid Crystal Handbook Editorial Committee, Maruzen, p. 196, can be used.

[0090] The cholesteric liquid crystal phase exhibits selective reflectivity for either right-handed or left-handed circularly polarized light at specific wavelengths. Whether the reflected light is right-handed or left-handed depends on the twist direction (sense) of the helix of the cholesteric liquid crystal phase. Selective reflection of circularly polarized light by the cholesteric liquid crystal phase reflects right-handed circularly polarized light when the twist direction of the cholesteric liquid crystal layer is to the right, and left-handed circularly polarized light when the twist direction of the helix is ​​to the left. Furthermore, the direction of rotation of the cholesteric liquid crystal phase can be adjusted by the type of liquid crystal compound forming the cholesteric liquid crystal layer and / or the type of chiral agent added.

[0091] Furthermore, the half-width Δλ (nm) of the selective reflection wavelength range (circularly polarized reflection wavelength range) exhibiting selective reflection depends on the Δn of the cholesteric liquid crystal phase and the helical pitch P, following the relationship Δλ = Δn × P. Therefore, the width of the selective reflection wavelength range can be controlled by adjusting Δn. Δn can be adjusted by the type of liquid crystal compound forming the cholesteric liquid crystal layer, its mixing ratio, and the temperature during orientation fixing. The full width at half maximum in the reflection wavelength range is adjusted according to the application of the diffracting element, and may be, for example, 10 to 500 nm, preferably 20 to 300 nm, and more preferably 30 to 100 nm.

[0092] (Method for forming a cholesteric liquid crystal layer) The cholesteric liquid crystal layer 16 can be formed by fixing a cholesteric liquid crystal phase in a layered manner using the liquid crystal composition of the present invention described above. The structure in which the cholesteric liquid crystal phase is fixed can be any structure in which the orientation of the liquid crystal compound that constitutes the cholesteric liquid crystal phase is maintained. Typically, a polymerizable liquid crystal compound is placed in the oriented state of the cholesteric liquid crystal phase, and then polymerized and cured by ultraviolet irradiation, heating, etc., to form a non-fluid layer, and at the same time, a structure is preferred in which the orientation form does not change due to an external field or external force. In a structure in which the cholesteric liquid crystal phase is fixed, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained, and the liquid crystal compound 20 does not need to exhibit liquid crystalline properties in the cholesteric liquid crystal layer. For example, the polymerizable liquid crystal compound may lose its liquid crystalline properties due to its high molecular weight resulting from the curing reaction.

[0093] When forming a cholesteric liquid crystal layer, it is preferable to apply the liquid crystal composition of the present invention described above to the surface on which the cholesteric liquid crystal layer is formed, orient the liquid crystal compound into a cholesteric liquid crystal phase, and then cure the liquid crystal compound to form a cholesteric liquid crystal layer. In other words, when forming a cholesteric liquid crystal layer on a photo-alignment film 14, it is preferable to apply a liquid crystal composition to the photo-alignment film 14 to orient the liquid crystal compound into a cholesteric liquid crystal phase, and then cure the liquid crystal compound to fix the cholesteric liquid crystal phase and form a cholesteric liquid crystal layer. For coating the liquid crystal composition, all known methods that can uniformly coat a sheet-like material with liquid, such as inkjet and scroll printing, as well as spin coating, bar coating, and spray coating, can be used.

[0094] The coated liquid crystal composition is dried and / or heated as necessary, and then cured to form a cholesteric liquid crystal layer. In this drying and / or heating step, the liquid crystal compounds in the liquid crystal composition should be oriented into the cholesteric liquid crystal phase. When heating is performed, the heating temperature is preferably 200°C or lower, and more preferably 130°C or lower.

[0095] The oriented liquid crystal compound is further polymerized as needed. Polymerization may be carried out by thermal polymerization or photopolymerization by light irradiation, but photopolymerization is preferred. Ultraviolet light irradiation is preferred. The irradiation energy is 20 mJ / cm². 2 ~50J / cm 2 Preferably, 50-1500 mJ / cm² 2 This is more preferable. To promote the photopolymerization reaction, light irradiation may be carried out under heating conditions or in a nitrogen atmosphere. The wavelength of the ultraviolet light used for irradiation is preferably 250 to 430 nm.

[0096] There are no restrictions on the thickness of the cholesteric liquid crystal layer. The thickness should be set appropriately to obtain the required light reflectivity, depending on the application of the optical element 10, the required light reflectivity of the cholesteric liquid crystal layer, and the material used to form the cholesteric liquid crystal layer.

[0097] (Liquid crystal alignment pattern of the cholesteric liquid crystal layer) In the optical element 10 of the present invention, the cholesteric liquid crystal layer 16, which is an optically anisotropic layer, has a liquid crystal orientation pattern in which the orientation of the optical axis 20A, which originates from the liquid crystal compound 20 that forms the cholesteric liquid crystal phase, changes while continuously rotating in one direction within the plane of the cholesteric liquid crystal layer. The optical axis 20A derived from the liquid crystal compound 20 is the axis in the liquid crystal compound 20 where the refractive index is highest. For example, if the liquid crystal compound 20 is a rod-shaped liquid crystal compound, the optical axis 20A is aligned with the long axis of the rod shape. In the following explanation, the optical axis 20A derived from the liquid crystal compound 20 will also be referred to as "the optical axis 20A of the liquid crystal compound 20" or "optical axis 20A".

[0098] Figure 3 conceptually shows a plan view of the cholesteric liquid crystal layer 16. The plan view, in Figure 1, is a view of the cholesteric liquid crystal layer 16 from above, that is, a view of the optical element 10 from the thickness direction (= stacking direction of each layer (film)). Furthermore, in Figure 3, in order to clearly show the configuration of the optical element 10 of the present invention, similar to Figure 1, only the liquid crystal compound 20 on the surface of the photo-alignment film 14 is shown.

[0099] As shown in Figure 3, the liquid crystal compound 20 constituting the cholesteric liquid crystal layer 16 has a liquid crystal alignment pattern on the surface of the photo-alignment film 14 in which the orientation of the optical axis 20A changes while continuously rotating along a predetermined direction indicated by arrow X within the plane of the cholesteric liquid crystal layer 16, according to the alignment pattern formed on the underlying photo-alignment film 14. In the illustrated example, the liquid crystal compound 20 has a liquid crystal alignment pattern in which the optical axis 20A changes while continuously rotating clockwise along the direction of arrow X. The liquid crystal compounds 20 constituting the cholesteric liquid crystal layer 16 are arranged two-dimensionally in the direction of arrow X and in a direction perpendicular to this direction (arrow X direction). In the following explanation, the direction perpendicular to the X-direction will be conveniently referred to as the Y-direction. That is, the Y-direction is the direction perpendicular to the direction in which the orientation of the optical axis 20A of the liquid crystal compound 20 changes while continuously rotating within the plane of the cholesteric liquid crystal layer. Therefore, in Figures 1, 2, and Figure 4 (described later), the Y-direction is perpendicular to the plane of the paper.

[0100] The statement that the orientation of the optical axis 20A of the liquid crystal compound 20 changes while continuously rotating in the direction of arrow X (a predetermined one direction) means, specifically, that the angle between the optical axis 20A of the liquid crystal compound 20 arranged along the direction of arrow X and the direction of arrow X differs depending on the position in the direction of arrow X, and that the angle between the optical axis 20A and the direction of arrow X changes sequentially from θ to θ+180° or θ-180° along the direction of arrow X. Furthermore, the difference in angle between the optical axes 20A of adjacent liquid crystal compounds 20 in the direction of arrow X is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

[0101] On the other hand, in the liquid crystal compound 20 that forms the cholesteric liquid crystal layer 16, the orientation of the optical axis 20A is the same in the Y direction perpendicular to the X direction of the arrow, that is, in the Y direction perpendicular to the direction in which the optical axis 20A rotates continuously. In other words, in the liquid crystal compound 20 that forms the cholesteric liquid crystal layer 16, the angle between the optical axis 20A of the liquid crystal compound 20 and the direction of arrow X is equal in the Y direction.

[0102] In the cholesteric liquid crystal layer 16, in the liquid crystal alignment pattern of such liquid crystal compound 20, the length (distance) over which the optical axis 20A of the liquid crystal compound 20 rotates 180° in the direction of arrow X, where the optical axis 20A rotates continuously within the plane, is defined as the length of one period Λ in the liquid crystal alignment pattern. In other words, the distance between the centers in the direction of arrow X of two liquid crystal compounds 20 whose angles with respect to arrow X are equal is defined as the length of one period Λ. Specifically, as shown in Figure 3 (Figure 4), the distance between the centers in the direction of arrow X of two liquid crystal compounds 20 whose directions of arrow X coincide with the direction of the optical axis 20A is defined as the length of one period Λ. In the following explanation, this length of one period Λ will also be referred to as "period Λ". In the cholesteric liquid crystal layer 16, the liquid crystal alignment pattern of the cholesteric liquid crystal layer repeats this one period Λ in one direction, where the direction of arrow X, i.e., the direction of the optical axis 20A, continuously rotates and changes.

[0103] A cholesteric liquid crystal layer, which consists of a fixed cholesteric liquid crystal phase, typically specularly reflects incident light (circularly polarized light). In contrast, the cholesteric liquid crystal layer 16 reflects the incident light at an angle in the direction of arrow X relative to specular reflection. The cholesteric liquid crystal layer 16 has a liquid crystal alignment pattern in which the optical axis 20A continuously rotates and changes along the direction of arrow X (a predetermined one direction) within the plane. The following explanation will be given with reference to Figure 4.

[0104] As an example, the cholesteric liquid crystal layer 16 is left-circularly polarized red light R L Assume that this is a cholesteric liquid crystal layer that selectively reflects R. Therefore, when light is incident on the cholesteric liquid crystal layer 16, the cholesteric liquid crystal layer 16 reflects the left circularly polarized red light R. L It reflects only certain types of light, while transmitting all other light.

[0105] Left-circularly polarized red light R incident on the cholesteric liquid crystal layer 16 L When reflected by the cholesteric liquid crystal layer, the absolute phase changes according to the orientation of the optical axis 20A of each liquid crystal compound 20. Here, in the cholesteric liquid crystal layer 16, the optical axis 20A of the liquid crystal compound 20 changes while rotating along the direction of arrow X (one direction). Therefore, depending on the orientation of the optical axis 20A, the left circular polarization R of the incident red light changes. L The amount of change in absolute phase is different. Furthermore, the liquid crystal alignment pattern formed in the cholesteric liquid crystal layer 16 is a periodic pattern in the direction of arrow X. Therefore, the left circularly polarized red light RL incident on the cholesteric liquid crystal layer 16 is given a periodic absolute phase Q in the direction of arrow X, corresponding to the orientation of each optical axis 20A, as conceptually shown in Figure 4. Furthermore, the orientation of the optical axis 20A of the liquid crystal compound 20 with respect to the direction of arrow X is uniform in the arrangement of liquid crystal compound 20 in the Y direction perpendicular to the direction of arrow X. As a result, in the cholesteric liquid crystal layer 16, left-circular polarization of red light R L In contrast, an equiphase surface E is formed that is inclined in the direction of arrow X with respect to the XY plane. Therefore, left-circular polarization of red light R L The reflected red light is left-circularly polarized R, which is reflected in the direction normal to the equiphase plane E. L It is reflected in a direction tilted in the direction of arrow X with respect to the XY plane (the main plane of the cholesteric liquid crystal layer).

[0106] Therefore, by appropriately setting the direction of arrow X, which is the direction in which the optical axis 20A rotates, the left circular polarization of red light R L The direction of reflection can be adjusted. For example, if we reverse the direction of arrow X and rotate the optical axis 20A clockwise toward the left side in the diagram, then left-circularly polarized red light R L The reflection direction is also the opposite of that shown in Figure 4.

[0107] Furthermore, by reversing the rotation direction of the optical axis 20A of the liquid crystal compound 20 facing the direction of arrow X, left circular polarization of red light R L The direction of reflection can be reversed. In other words, in Figures 1 to 4, the rotation direction of the optical axis 20A in the direction of arrow X is clockwise, and the left circular polarization of red light R L The light is reflected at an angle in the direction of arrow X, but by making this counterclockwise, the left-circular polarization of the red light R L The light is reflected at an angle opposite to the direction of arrow X.

[0108] Furthermore, in cholesteric liquid crystal layers having the same liquid crystal orientation pattern, the reflection direction is reversed depending on the spiral direction of the liquid crystal compound 20, i.e., the spiral direction of the reflected circularly polarized light. The cholesteric liquid crystal layer 16 shown in Figure 4 has a right-handed twist in the spiral direction and selectively reflects right-circularly polarized light. It has a liquid crystal orientation pattern in which the optical axis 20A rotates clockwise along the direction of arrow X, thereby reflecting right-circularly polarized light at an angle in the direction of arrow X. Therefore, a cholesteric liquid crystal layer having a liquid crystal alignment pattern in which the spiral rotation direction is left-handed twist, selectively reflects left-handed circularly polarized light, and the optical axis 20A rotates clockwise along the direction of arrow X, reflects left-handed circularly polarized light tilted in the opposite direction to the direction of arrow X.

[0109] As described above, the cholesteric liquid crystal layer 16 of the optical element 10 has a liquid crystal orientation pattern in which the optical axis 20A of the liquid crystal compound 20 rotates sequentially along one direction within the plane. Furthermore, in this liquid crystal orientation pattern, the length of a 180° rotation of the optical axis 20A is defined as one period Λ (see Figures 1, 3, and 4). In the cholesteric liquid crystal layer 16 having this liquid crystal alignment pattern, the shorter the period Λ, the larger the angle of the reflected light relative to the incident light. In other words, the shorter the period Λ, the greater the angle at which the reflected light can be reflected relative to the incident light.

[0110] There are no restrictions on the period Λ; it can be set appropriately according to the application of the optical element. The period Λ of the cholesteric liquid crystal layer 16 is preferably 2.00 μm or less, more preferably 1.60 μm or less, even more preferably 0.80 μm or less, and even more preferably less than or equal to the wavelength λ of the incident light. The lower limit is not particularly limited, but it is often 0.20 μm or more. By setting the period Λ to 2.00 μm or less, the diffraction angle of the reflected light from the cholesteric liquid crystal layer 16 can be made sufficiently large. Therefore, for example, when the optical element of the present invention is used as a diffraction element for injecting light into the light guide plate of the AR glasses described above, light can be injected into the light guide plate at an angle sufficient for propagation by total internal reflection.

[0111] Furthermore, the same applies to the patterned liquid crystal layer 32 in the optical element 30 of another embodiment of the present invention, which will be described later, regarding the period Λ of this liquid crystal alignment pattern.

[0112] Multiple optical elements of the present invention may be used in stacked configurations. Figure 5 shows an example. The conceptually stacked optical element 24 shown in Figure 5 has three diffraction elements of the present invention: R optical element 10R, G optical element 10G, and B optical element 10B. The R optical element 10R corresponds to red light and consists of a support 12, a photo-alignment film 14R, and a red left-circular polarized R L It has a cholesteric liquid crystal layer 16R that reflects light. The G optical element 10G corresponds to green light and consists of a support 12, a photo-alignment film 14G, and a green left-circular polarized light G L It has a cholesteric liquid crystal layer 16G that reflects light. The optical element 10B corresponds to blue light and consists of a support 12, a photo-alignment film 14B, and a blue left-circular polarized light B L It has a cholesteric liquid crystal layer 16B that reflects light. In the R optical element 10R, G optical element 10G, and B optical element 10B, the support, alignment film, and cholesteric liquid crystal layer are all the same as the support 12, photo-alignment film 14, and cholesteric liquid crystal layer 16 in the above-described optical element 10. However, each cholesteric liquid crystal layer (diffractive element) has a helix pitch P corresponding to the wavelength range of the light selectively reflected.

[0113] Here, the R optical element 10R, G optical element 10G, and B optical element 10B have the same permutation of the lengths of the selective reflection center wavelengths of the cholesteric liquid crystal layers and the same permutation of the lengths of one period Λ in the liquid crystal alignment pattern of the cholesteric liquid crystal layers. That is, in the stacked optical element 24, the selective reflection center wavelength of the R optical element 10R corresponding to the reflection of red light is the longest, the selective reflection center wavelength of the G optical element 10G corresponding to the reflection of green light is the next longest, and the selective reflection center wavelength of the B optical element 10B corresponding to the reflection of blue light is the shortest. Accordingly, the R optical element 10R, G optical element 10G, and B optical element 10B have one period Λ of the cholesteric liquid crystal layer of the R optical element 10R R being the longest, one period Λ of the cholesteric liquid crystal layer of the G optical element 10G G being the next longest, and one period Λ of the cholesteric liquid crystal layer of the B optical element 10B B being the shortest.

[0114] The reflection angle of light by the cholesteric liquid crystal layer in which the optical axis 20A of the liquid crystal compound 20 continuously rotates along one direction (arrow X direction) varies depending on the wavelength of the reflected light. Specifically, the longer the wavelength of the light, the larger the angle of the reflected light with respect to the incident light. Therefore, the red light reflected by the R optical element 10R has the largest angle of the reflected light with respect to the incident light, the green light reflected by the G optical element 10G has the next largest angle of the reflected light with respect to the incident light, and the blue light reflected by the B optical element 10B has the smallest angle of the reflected light with respect to the incident light. On the other hand, as described above, in a cholesteric liquid crystal layer having a liquid crystal alignment pattern in which the optical axis 20A of the liquid crystal compound 20 rotates along one direction, the shorter the period Λ in which the optical axis 20A rotates 180° in the liquid crystal alignment pattern, the larger the angle of reflected light relative to the incident light.

[0115] Therefore, in the R optical element 10R, the G optical element 10G, and the B optical element 10B, the permutation of the lengths of the selective reflection center wavelengths in the diffractive element (cholesteric liquid crystal layer) and the length of one period Λ in the liquid crystal alignment pattern (Λ R , Λ G and Λ B By making the permutations of ) equal, Figure 5 shows the red left circularly polarized R L , green left circular polarized G L and blue left circular polarization B L As illustrated by the example, the wavelength dependence of the reflection angle of the light reflected by the stacked optical element 24 is significantly reduced, allowing light of different wavelengths to be reflected in almost the same direction.

[0116] Furthermore, when stacking the optical elements of the present invention, which selectively reflect different wavelength ranges, there are no restrictions on the stacking order.

[0117] When stacking multiple optical elements of the present invention, the configuration is not limited to having R optical element 10R, G optical element 10G, and B optical element 10B as shown in Figure 5. For example, it may have two layers appropriately selected from R optical element 10R, G optical element 10G, and B optical element 10B. Furthermore, instead of one or more of R optical element 10R, G optical element 10G, and B optical element 10B, or in addition to R optical element 10R, G optical element 10G, and B optical element 10B, it may have an optical element that selectively reflects ultraviolet light and / or an optical element that selectively reflects infrared light.

[0118] When stacking multiple optical elements of the present invention, the configuration is not limited to stacking optical elements with different selective reflection center wavelengths, as shown in Figure 5. For example, the apparatus may have two cholesteric liquid crystal layers, each having the same selective reflection center wavelength and different rotation directions of the reflected circularly polarized light, i.e., different spiral rotation directions (senses) in the cholesteric liquid crystal phase. This configuration allows for the reflection of both right-circularly polarized and left-circularly polarized light contained in the incident light, thereby increasing the amount of reflected light relative to the incident light.

[0119] Although the optical element 10 in the above example uses a cholesteric liquid crystal layer as the optical anisotropy layer, the present invention is not limited thereto. That is, in the optical element of the present invention, any type of optical anisotropy layer can be used as long as the optical anisotropy layer is formed using a composition containing a liquid crystal compound and has a liquid crystal orientation pattern in which the optical axis 20A derived from the liquid crystal compound 20 rotates continuously along at least one direction in the plane. As an example, the optical element of the present invention may also utilize an optically anisotropic layer having a liquid crystal orientation pattern that rotates continuously along at least one direction in the plane, and in which the liquid crystal compound does not twist and rotate in a helical manner in the thickness direction.

[0120] Figure 6 conceptually illustrates one example. The optical element 30 shown in Figure 6 comprises a support 12, a photo-alignment film 14, and a patterned liquid crystal layer 32. In the optical element 30, the patterned liquid crystal layer 32 is an optically anisotropic layer in the present invention and has a liquid crystal alignment pattern similar to that of the cholesteric liquid crystal layer 16 described above. Therefore, as conceptually shown in Figure 7, the patterned liquid crystal layer 32, like the cholesteric liquid crystal layer 16, has a liquid crystal alignment pattern in which the optical axis 20A of the liquid crystal compound 20 rotates continuously clockwise along the direction of arrow X. Note that, as with Figure 3 described above, Figure 7 also shows only the liquid crystal compound on the surface of the photo-alignment film 14. In the patterned liquid crystal layer 32, the liquid crystal compound 20 forming the diffractive element (liquid crystal layer) is not twisted and rotated helically in the thickness direction, and the optical axes 20A are all oriented in the same direction in the thickness direction. In other words, the orientation of the optical axes 20A originating from the liquid crystal compound 20 coincides in the thickness direction. Such a liquid crystal layer can be formed by not adding a chiral agent to the liquid crystal composition in the formation of the cholesteric liquid crystal layer described above.

[0121] In addition, the support 12 and the photo-alignment film 14 in the optical element 30 are the same as those in the optical element 10 shown in Figure 1 above.

[0122] As described above, the patterned liquid crystal layer 32 has a liquid crystal orientation pattern in which the orientation of the optical axis 20A originating from the liquid crystal compound 20 changes while continuously rotating along the direction of arrow X, i.e., the direction indicated by arrow X. On the other hand, in the liquid crystal compound 20 forming the patterned liquid crystal layer 32, in the Y direction perpendicular to the X direction of arrow, that is, in the Y direction perpendicular to the direction in which the optical axis 20A rotates continuously, liquid crystal compound 20 with the same orientation of the optical axis 20A are arranged at equal intervals. In other words, in the liquid crystal compound 20 forming the patterned liquid crystal layer 32, the angle between the orientation of the optical axis 20A and the X direction of arrow is equal for liquid crystal compound 20 arranged in the Y direction.

[0123] In the patterned liquid crystal layer 32, the liquid crystal compounds arranged in the Y direction have an equal angle between the optical axis 20A and the direction of arrow X (one direction in which the orientation of the optical axis of the liquid crystal compound 20 rotates). The region where the liquid crystal compounds 20 having an equal angle between the optical axis 20A and the direction of arrow X are arranged in the Y direction is defined as region R. In this case, the in-plane retardation (Re) value in each region R is preferably half a wavelength, i.e., λ / 2. These in-plane retardations are calculated by the product of the refractive index difference Δn due to the refractive index anisotropy of region R and the thickness of the optical anisotropy layer. Here, the refractive index difference due to the refractive index anisotropy of region R in the optical anisotropy layer is defined as the refractive index difference between the refractive index in the direction of the slow axis in the plane of region R and the refractive index in the direction perpendicular to the direction of the slow axis. That is, the refractive index difference Δn due to the refractive index anisotropy of region R is equal to the difference between the refractive index of the liquid crystal compound 20 in the direction of the optical axis 20A and the refractive index of the liquid crystal compound 20 in the direction perpendicular to the optical axis 20A in the plane of region R. In other words, the refractive index difference Δn is equal to the refractive index difference of the liquid crystal compound 20.

[0124] When circularly polarized light is incident on such a patterned liquid crystal layer 32, the light is refracted and the direction of the circular polarization is changed. This effect is conceptually illustrated in Figures 8 and 9. Note that the patterned liquid crystal layer 32 is assumed to have a product of the refractive index difference of the liquid crystal compound and the thickness of the optical anisotropy layer of λ / 2. As shown in Figure 8, when the product of the refractive index difference of the liquid crystal compound in the patterned liquid crystal layer 32 and the thickness of the optical anisotropy layer is λ / 2, and incident light L1, which is left-circularly polarized, is incident on the patterned liquid crystal layer 32, the incident light L1 is given a phase difference of 180° as it passes through the patterned liquid crystal layer 32, and the transmitted light L2 is converted to right-circularly polarized light. Furthermore, as the incident light L1 passes through the patterned liquid crystal layer 32, its absolute phase changes according to the orientation of the optical axis 20A of each liquid crystal compound 20. At this time, the orientation of the optical axis 20A changes while rotating along the direction of arrow X, so the amount of change in the absolute phase of the incident light L1 differs depending on the orientation of the optical axis 20A. Moreover, since the liquid crystal alignment pattern formed in the patterned liquid crystal layer 32 is a periodic pattern in the direction of arrow X, the incident light L1 that has passed through the patterned liquid crystal layer 32 is given a periodic absolute phase Q1 in the direction of arrow X corresponding to the orientation of each optical axis 20A, as shown in Figure 8. As a result, an equiphase surface E1 tilted in the opposite direction to the direction of arrow X is formed. Therefore, the transmitted light L2 is refracted so as to be tilted perpendicular to the equiphase plane E1, and travels in a direction different from the direction of propagation of the incident light L1. In this way, the left-circularly polarized incident light L1 is converted into right-circularly polarized transmitted light L2, which is tilted by a certain angle in the direction of arrow X with respect to the direction of incidence.

[0125] On the other hand, as shown in Figure 9, when the product of the refractive index difference of the liquid crystal compound in the patterned liquid crystal layer 32 and the thickness of the optical anisotropy layer is λ / 2, when right-circularly polarized incident light L4 is incident on the patterned liquid crystal layer 32, the incident light L4 passes through the patterned liquid crystal layer 32, is given a phase difference of 180°, and is converted into left-circularly polarized transmitted light L5. Furthermore, as the incident light L4 passes through the patterned liquid crystal layer 32, its absolute phase changes according to the orientation of the optical axis 20A of each liquid crystal compound 20. At this time, the orientation of the optical axis 20A changes while rotating along the direction of arrow X, so the amount of change in the absolute phase of the incident light L4 differs depending on the orientation of the optical axis 20A. Moreover, since the liquid crystal alignment pattern formed in the patterned liquid crystal layer 32 is a periodic pattern in the direction of arrow X, the incident light L4 that has passed through the patterned liquid crystal layer 32 is given a periodic absolute phase Q2 in the direction of arrow X corresponding to the orientation of each optical axis 20A, as shown in Figure 9. Here, since the incident light L4 is right-circularly polarized, the periodic absolute phase Q2 in the direction of arrow X, which corresponds to the direction of the optical axis 20A, is opposite to that of the incident light L1, which is left-circularly polarized. As a result, for the incident light L4, an equiphase surface E2 is formed that is tilted in the direction of arrow X, opposite to that of the incident light L1. Therefore, the incident light L4 is refracted so as to be tilted perpendicular to the equiphase plane E2, and travels in a direction different from the direction of propagation of the incident light L4. In this way, the incident light L4 is converted into transmitted light L5, which is left-circularly polarized and tilted by a certain angle in the direction opposite to the direction of arrow X with respect to the direction of incidence.

[0126] Similar to the cholesteric liquid crystal layer 16, the patterned liquid crystal layer 32 also allows for adjustment of the refraction angles of transmitted light L2 and L5 by changing the period Λ of the formed liquid crystal alignment pattern. Specifically, the shorter the period Λ of the liquid crystal alignment pattern in the patterned liquid crystal layer 32, the stronger the interference between light passing through adjacent liquid crystal compounds 20, thereby allowing for greater refraction of transmitted light L2 and L5. As mentioned above, the period Λ is preferably 1.6 μm or less, more preferably 0.8 μm or less, and even more preferably less than or equal to the wavelength λ of the incident light. Furthermore, similar to the cholesteric liquid crystal layer 16, in the patterned liquid crystal layer 32, the longer the wavelengths of the incident light L1 and L4, the greater the refraction of the transmitted light L2 and L5. Furthermore, by reversing the rotation direction of the optical axis 20A of the liquid crystal compound 20, which rotates along the direction of arrow X, the direction of refraction of transmitted light can be reversed. That is, in the examples shown in Figures 6 to 9, the rotation direction of the optical axis 20A toward the direction of arrow X is clockwise, but by changing this rotation direction to counterclockwise, the direction of refraction of transmitted light can be reversed.

[0127] In the above example, in the optical anisotropy layer of the optical element, the orientation of the optical axis 20A originating from the liquid crystal compound 20 changes continuously only in the direction of arrow X. However, the optical anisotropy layer of the optical element of the present invention is not limited thereto, and various configurations are available as long as it is formed using a composition containing a liquid crystal compound and the optical axis 20A of the liquid crystal compound 20 rotates continuously along one direction.

[0128] As an example, an optically anisotropic layer 34 is exemplified, which has a liquid crystal alignment pattern such that the orientation of the optical axis of the liquid crystal compound 20 changes in one direction as it rotates continuously, in a concentric pattern extending from the inside outwards. This pattern is conceptually shown in the plan view of Figure 11. Alternatively, a liquid crystal alignment pattern can also be used in which, instead of being concentric, one direction in which the orientation of the optical axis of the liquid crystal compound 20 changes while continuously rotating is provided radially from the center of the optical anisotropy layer 34.

[0129] In Figure 11, as in Figures 3 and 7, only the liquid crystal compound 20 on the surface of the alignment film is shown. However, as previously mentioned, the optical anisotropy layer 34 has a helical structure in which the liquid crystal compound 20 is spirally stacked from the liquid crystal compound 20 on the surface of the alignment film, as shown in Figures 2 and 6.

[0130] In the optically anisotropic layer 34 shown in Figure 11, the optical axis (not shown) of the liquid crystal compound 20 is the longitudinal direction of the liquid crystal compound 20. In the optically anisotropic layer 34, the orientation of the optical axis of the liquid crystal compound 20 changes while continuously rotating along multiple directions that radiate outward from the center of the optically anisotropic layer 34, for example, the direction indicated by arrow X1, the direction indicated by arrow X2, the direction indicated by arrow X3, and so on. Another preferred embodiment is one in which the optical anisotropy layer 34 changes radially from the center, rotating in the same direction, as shown in Figure 11. The embodiment shown in Figure 11 is a counterclockwise orientation. In each of the arrows X1, X2, and X3 in Figure 11, the direction of rotation of the optical axis is counterclockwise as it moves outward from the center. When circularly polarized light is incident on the optically anisotropic layer 34 having this liquid crystal alignment pattern, the absolute phase changes in each local region where the optical axis orientation of the liquid crystal compound 20 is different. In this case, the amount of change in the absolute phase differs depending on the orientation of the optical axis of the liquid crystal compound 20 to which the circularly polarized light is incident.

[0131] Such an optically anisotropic layer 34 having a concentric liquid crystal alignment pattern, that is, a liquid crystal alignment pattern that changes as the optical axis rotates radially, can reflect or transmit incident light as divergent or focused light, depending on the direction of rotation of the optical axis of the liquid crystal compound 20 and the direction of the reflected circularly polarized light. That is, when the optically anisotropic layer 34 is a cholesteric liquid crystal layer, by making the liquid crystal alignment pattern concentric, the optical element of the present invention exhibits functions as, for example, a concave mirror or a convex mirror. Further, when the optically anisotropic layer 34 is a patterned liquid crystal layer, by making the liquid crystal alignment pattern concentric, the optical element of the present invention exhibits functions as a concave lens or a convex lens.

[0132] Here, when making the liquid crystal alignment pattern of the optically anisotropic layer concentric and causing the optical element to act as a concave mirror or a convex lens, it is preferable that one period Λ in which the optical axis rotates 180° in the liquid crystal alignment pattern gradually shortens from the center of the optically anisotropic layer 34 toward the outer direction in one direction in which the optical axis continuously rotates. As described above, the reflection angle of light with respect to the incident direction increases as one period Λ in the liquid crystal alignment pattern becomes shorter. Therefore, by gradually shortening one period Λ in the liquid crystal alignment pattern from the center of the optically anisotropic layer 34 toward the outer direction in one direction in which the optical axis continuously rotates, light can be more focused, and the performance as a concave mirror and a convex lens can be improved.

[0133] In the present invention, when causing the optical element to act as a convex mirror or a concave lens, it is preferable to rotate the continuous rotation of the optical axis in the liquid crystal alignment pattern in the reverse direction from the center of the optically anisotropic layer 34. When the optically anisotropic layer is a cholesteric liquid crystal layer, the sense of rotation of the circularly polarized light to be reflected, that is, the sense of the helix, may be reversed. Further, by gradually shortening one period Λ in which the optical axis rotates 180° from the center of the optically anisotropic layer 34 toward the outer direction in one direction in which the optical axis continuously rotates, the optically anisotropic layer 34 can diverge light more, and the performance as a convex mirror and a concave lens can be improved.

[0134] In the present invention, when causing the optical element to act as a convex mirror and a concave lens, or a concave mirror and a convex lens, it is preferable to satisfy the following formula (1). Φ(r)=(π / λ)[(r 2 +f 2 )1 / 2 -f]...Formula (1) Here, r is the distance from the center of the concentric circles, and the equation is r = (x 2 +y 2 ) 1 / 2 This is expressed as ''. x and y represent positions in the plane, and (x, y) = (0, 0) represents the center of the concentric circles. Φ(r) is the angle of the optical axis at a distance r from the center, λ is the selective reflection center wavelength of the cholesteric liquid crystal layer, and f is the target focal length.

[0135] In addition, in the present invention, depending on the application of the optical element, the period Λ in the concentric liquid crystal alignment pattern may be gradually lengthened outward from the center of the optical anisotropy layer 34 in one direction in which the optical axis rotates continuously. Furthermore, depending on the application of the optical element, such as when it is desired to provide a light intensity distribution in reflected light, it is also possible to use a configuration in which, instead of gradually changing the period Λ in one direction in which the optical axis rotates continuously, there are regions in which the period Λ is partially different in one direction in which the optical axis rotates continuously. Furthermore, the optical element of the present invention may have a cholesteric liquid crystal layer in which the period Λ is uniform throughout, and a cholesteric liquid crystal layer in which the period Λ is different in some regions. In this respect, the same applies to a configuration in which the optical axis rotates continuously in only one direction, as shown in Figure 1, which will be described later.

[0136] Figure 12 conceptually shows an example of an exposure apparatus that forms such a concentric orientation pattern on the photo-alignment film 14 corresponding to the optical anisotropy layer 34. The exposure apparatus 80 includes a light source 84 equipped with a laser 82, a polarizing beam splitter 86 that splits the laser light M from the laser 82 into S-polarized MS and P-polarized MP, a mirror 90A positioned in the optical path of the P-polarized MP and a mirror 90B positioned in the optical path of the S-polarized MS, a lens 92 positioned in the optical path of the S-polarized MS, the polarizing beam splitter 94, and a λ / 4 plate 96.

[0137] The P-polarized beam MP, split by the polarizing beam splitter 86, is reflected by the mirror 90A and incident on the polarizing beam splitter 94. On the other hand, the S-polarized beam MS, also split by the polarizing beam splitter 86, is reflected by the mirror 90B, focused by the lens 92, and incident on the polarizing beam splitter 94. The P-polarized MP and S-polarized MS beams are combined by the polarization beam splitter 94 and converted into right-circularly polarized and left-circularly polarized beams according to their polarization direction by the λ / 4 plate 96, and then incident onto the photo-oriented precursor film 140 on the support 12. Here, the interference between right-circularly polarized and left-circularly polarized light causes the polarization state of the light irradiated onto the photo-alignment precursor film 140 to change periodically in an interference fringe pattern. As you move from the inside to the outside of the concentric circles, the intersection angle between the left-circularly polarized and right-circularly polarized light changes, resulting in an exposure pattern in which the pitch changes from the inside to the outside. As a result, a concentric orientation pattern in which the orientation state changes periodically is obtained in the photo-alignment film 14.

[0138] In this exposure apparatus 80, the length Λ of one period of the liquid crystal alignment pattern in which the optical axis of the liquid crystal compound 20 rotates continuously by 180° can be controlled by changing the refractive power of the lens 92 (F number of the lens 92), the focal length of the lens 92, and the distance between the lens 92 and the photo-alignment film 14. Furthermore, by adjusting the refractive power of lens 92 (the F-number of lens 92), the length Λ of one cycle of the liquid crystal alignment pattern can be changed in one direction of continuous rotation of the optical axis. Specifically, by interfering with parallel light and changing the angle of light spread by lens 92, the length Λ of one cycle of the liquid crystal alignment pattern can be changed in one direction of continuous rotation of the optical axis. More specifically, weakening the refractive power of lens 92 brings the light closer to parallel light, so the length Λ of one cycle of the liquid crystal alignment pattern gradually shortens from the inside to the outside, and the F-number increases. Conversely, strengthening the refractive power of lens 92 causes the length Λ of one cycle of the liquid crystal alignment pattern to shorten abruptly from the inside to the outside, and the F-number decreases.

[0139] Thus, the configuration that changes one period Λ, which is the rotation of the optical axis by 180°, in one direction in which the optical axis rotates continuously, can also be used in the configuration shown in Figures 1 to 9, in which the optical axis 20A of the liquid crystal compound 20 rotates continuously and changes only in one direction, the direction of arrow X. For example, by gradually shortening the period Λ of the liquid crystal alignment pattern in the direction of arrow X, an optical element that reflects or transmits light in a focusing manner can be obtained. Furthermore, depending on the application of the optical element, such as when it is desired to provide a light intensity distribution for reflected and transmitted light, it is possible to use a configuration in which the period Λ is partially different in the direction of arrow X, rather than gradually changing the period Λ in the direction of arrow X. For example, as a method for partially changing the period Λ, one can use a method of scanning and patterning the photo-alignment film while arbitrarily changing the polarization direction of the focused laser light.

[0140] Although the optical elements of the present invention have been described in detail above, the present invention is not limited to the examples described above, and various improvements and modifications may be made without departing from the spirit of the present invention.

[0141] [Light guide element] The light guide element of the present invention is a light guide element that includes the optical element and light guide plate described above. In the example shown in Figure 13, the light guide element has a light guide plate 42 and an optical element (laminated optical element) 10, and the optical element 10 is bonded to one end of the main surface of the light guide plate 42 and to the other end. In such a light guide element, the optical element 10 is used as an incident diffraction element that reflects the incident light at an angle at which total internal reflection occurs within the light guide plate 42, causing the light to enter the light guide plate 42. It is also used as an exit diffraction element that reflects the light guided by total internal reflection within the light guide plate 42 at an angle that deviates from the total internal reflection condition, causing the light to exit the light guide plate 42. [Examples]

[0142] The features of the present invention will be further described below with reference to examples and comparative examples. The materials, reagents, amounts used, amounts of substance, ratios, processing content, processing procedures, etc., shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the following specific examples.

[0143] [Comparative Example 1 and Examples 1-9] [Fabrication of optical elements] <Support material, and saponification treatment of the support material> A commercially available triacetylcellulose film (manufactured by Fujifilm Corporation, Z-TAC) was prepared as the support material. The support was passed through a dielectric heating roll at a temperature of 60°C to raise the surface temperature of the support to 40°C. Subsequently, the alkaline solution described below is applied to one side of the support using a bar coater at a rate of 14 mL (liters) / m². 2 The material was coated, the support was heated to 110°C, and then transported under a steam-type far-infrared heater (manufactured by Noritake Co., Ltd.) for 10 seconds. Next, using the same bar coater, 3 mL / m² of pure solution is applied to the alkaline solution-coated surface of the support. 2 The coating was applied. Next, the surface of the support was subjected to alkaline saponification treatment by repeating the rinsing with a fountain coater and drying with an air knife three times, followed by being transported through a 70°C drying zone for 10 seconds.

[0144] ------------------------------------------------------------------ Alkaline solution ------------------------------------------------------------------ • Potassium hydroxide 4.70 parts by mass ·Water 15.80 parts by mass Isopropyl alcohol 63.70 parts by mass • Surfactant SF-1: C 14 H 29 O(CH2CH2O)2OH 1.0 parts by mass • Propylene glycol 14.8 parts by mass ------------------------------------------------------------------

[0145] <Formation of the undercoat layer> The following primer layer forming solution was continuously applied to the alkali-saponified surface of the support using a #8 wire bar. The support with the formed coating was dried with 60°C hot air for 60 seconds, and then with 100°C hot air for 120 seconds to form the primer layer.

[0146] ------------------------------------------------------------------ Coating liquid for forming the base coat layer ------------------------------------------------------------------ • 2.40 parts by mass of the following modified polyvinyl alcohol • Isopropyl alcohol 1.60 parts by mass • Methanol 36.00 parts by mass ·Water 60.00 parts by mass ------------------------------------------------------------------

[0147] Modified polyvinyl alcohol [ka]

[0148] <Formation of orientation film> The orientation film-forming coating solution described below was continuously applied to a support with a primer layer using a #2 wire bar. The support with the orientation film-forming coating solution was dried on a 60°C hot plate for 60 seconds to form an orientation film.

[0149] ------------------------------------------------------------------ Coating solution for forming alignment films ------------------------------------------------------------------ • The following photo-orientation material D: 1.00 parts by mass · 16.00 parts by mass of water · 42.00 parts by mass of butoxyethanol · 四十二点零零質量部のプロピレングリコールモノメチルエーテル ―――――――――――――――――――――――――――――――――

[0150] Material D for photo-alignment

Chemical formula

[0151] <Exposure of the alignment film> The exposure film was exposed using the exposure apparatus shown in Fig. 10 to form an alignment film P-1 having an alignment pattern. In the exposure apparatus, a laser that emits laser light with a wavelength of 325 nm was used. The exposure amount by interference light was set to 2000 mJ / cm 2 One period of the alignment pattern formed by the interference of the two laser lights (the length over which the optical axis derived from the liquid crystal compound rotates 180°) was controlled by changing the crossing angle (crossing angle β) of the two lights.

[0152] <Formation of the optically anisotropic layer>

[0153] ――――――――――――――――――――――――――――――――― Composition E ―――――――――――――――――――――――――――――――――(42.00 parts by mass of propylene glycol monomethyl ether is incorrect in the original Japanese. It should be translated as 42.00 parts by mass of propylene glycol monomethyl ether, but the original text seems to have a wrong expression. Here we keep the wrong expression in the translation as it is in the original.) · Rod-like liquid crystal compound described in Table 1 below, parts by mass described in Table 1 below · Disc-like liquid crystal compound described in Table 1 below, parts by mass described in Table 1 below · Photoinitiator (manufactured by BASF, Irgacure (registered trademark) 907) 3.00 parts by mass · The following leveling agent T-1, 0.08 parts by mass · 927.7 parts by mass of methyl ethyl ketone It should be noted that there seems to be an incorrect expression in the original text for "·プロピレングリコールモノメチルエーテル 42.00質量部" which might be a typo in the Japanese text. The translation keeps the incorrect expression as it is in the original. ------------------------------------------------------------------

[0154] Leveling agent T-1 [ka]

[0155] The optically anisotropic layer was formed by multilayer coating of composition E on the alignment film P-1. Multilayer coating refers to a process in which, first, a first layer of composition E is applied onto an alignment film, heated, cooled, and then cured with ultraviolet light to create a liquid crystal immobilization layer. Subsequent layers are then applied on top of this liquid crystal immobilization layer, and the process of heating, cooling, and UV curing is repeated. By forming it by multilayer coating, the orientation direction of the alignment film is reflected from the bottom surface to the top surface of the liquid crystal layer, even when the film thickness of the liquid crystal layer is increased.

[0156] First, the first layer is prepared by applying composition E onto the alignment film P-1, heating the coating to 120°C on a hot plate, then cooling it to 60°C, and finally exposing it to 365nm wavelength ultraviolet light at 2000mJ / cm² using a high-pressure mercury lamp under a nitrogen atmosphere. 2 The orientation of the liquid crystal compound was fixed by irradiating the coating film with this irradiation dose. The thickness of the first liquid crystal layer at this time was 0.3 μm.

[0157] For the second and subsequent layers, the liquid crystal layer was coated over this liquid crystal layer, and after heating and cooling under the same conditions as above, a liquid crystal immobilization layer (cured layer) was created by applying ultraviolet light. In this manner, optical anisotropic layers were formed by repeatedly applying multiple layers so that the in-plane retardation (Re) was 325 nm, thereby fabricating optical elements G (specifically G-1 to G-10 in Table 1 below). The retardation value is half the wavelength of the evaluation light source (650 nm) used for the diffraction efficiency measurement described later.

[0158] Regarding the optically anisotropic layer in this example, it was confirmed by a polarization microscope that the surface has a periodic alignment as shown in Fig. 8. In the liquid crystal alignment pattern of this optically anisotropic layer, one period Λ in which the optical axis derived from the liquid crystal compound rotates 180° was 1.0 μm. The period Λ was determined by measuring the period of the light and dark pattern observed under cross Nicol conditions using a polarization microscope.

[0159] 〔Evaluation〕 <Refractive index difference Δn 550 Measurement> Regarding the compositions E-1 to E-10 used in Examples 1 to 9 and Comparative Example 1 above, the refractive index difference Δn 550 was measured by the method described above. In addition, the obtained Δn 550 was used as the following evaluation value. The results are shown in Table 1 below. A: 0.20 ≤ Δn 550 and B: Δn 550 < 0.20

[0160] <Measurement of elastic constant> Regarding the compositions E-1 to E-10 used in Examples 1 to 9 and Comparative Example 1 above, the ratio (K22 / K11) of the elastic constants of the composition excluding methyl ethyl ketone was measured by the method described above. In addition, the obtained K22 / K11 was used as the following evaluation value. The results are shown in Table 1 below. A: 0.75 ≤ K22 / K11 B: 0.70 ≤ K22 / K11 < 0.75 C: K22 / K11 < 0.7

[0161] <Measurement of diffraction efficiency> An evaluation optical system was prepared by arranging an evaluation light source, a polarizer, a quarter-wave plate, the optical element of the present invention, and a screen in this order. A laser pointer with a wavelength of 650 nm was used as the evaluation light source, and SAQWP05M-700 manufactured by Thorlabs was used as the quarter-wave plate. The slow axis of the quarter-wave plate was arranged at a 45° relationship with respect to the absorption axis of the polarizer. Also, the optical element of the present invention was arranged with the glass surface facing the light source side. When light transmitted from an evaluation light source through a polarizer and a quarter-wave plate was incident perpendicularly to the film surface of the optical element of the present invention, a portion of the light transmitted through the optical element was diffracted, and multiple bright spots were observed on the screen. The intensity of each diffracted light and the zeroth-order light corresponding to the bright spots on the screen was measured with a power meter, and the diffraction efficiency was calculated using the following formula. Diffraction efficiency = (primary light intensity) / (zero-order light intensity + non-primary diffracted light intensity) The following evaluation values ​​were used based on the obtained diffraction efficiency. The results are shown in Table 1 below. A: The diffraction efficiency is 99% or higher. B: Diffraction efficiency is between 95% and 99%. C: Diffraction efficiency is between 90% and 95%. D: Diffraction efficiency is less than 90%

[0162] [Table 1]

[0163] The structural formulas of the rod-shaped and disc-shaped liquid crystal compounds shown in Table 1 above are shown below.

[0164] Rod-shaped liquid crystal compound A-1 [A mixture of liquid crystal compounds represented by the following formula (the numerical value represents mass %)] [ka]

[0165] Rod-shaped liquid crystal compound A-2 [ka]

[0166] Disc-shaped liquid crystal compound B-1 [ka]

[0167] Disc-shaped liquid crystal compound B-2 [ka]

[0168] Disc-shaped liquid crystal compound B-3 [ka]

[0169] Disc-shaped liquid crystal compound B-4 [ka]

[0170] Disc-shaped liquid crystal compound B-5 [ka]

[0171] From the results shown in Table 1 above, it was found that when a liquid crystal composition was used without incorporating a disc-shaped liquid crystal compound, and the ratio of the twist elastic constant K22 to the spray elastic constant K11 did not satisfy 0.7 ≤ K22 / K11, the diffraction efficiency of the resulting optical element was inferior (Comparative Example 1). In contrast, it was found that when liquid crystal compositions containing rod-shaped liquid crystal compounds and disc-shaped liquid crystal compounds are used, optical elements with excellent diffraction efficiency can be fabricated (Examples 1-9). In particular, a comparison between Example 7 and Example 8 revealed that when a liquid crystal composition is used in which the ratio of the twist elastic constant K22 to the spray elastic constant K11 satisfies 0.75 ≤ K22 / K11 (resulting in an A rating), the diffraction efficiency of the fabricated optical element is higher. Furthermore, from the comparison between Example 8 and Example 9, the refractive index difference Δn due to refractive index anisotropy was found. 550 It was found that using a liquid crystal composition with a value of 0.2 or higher (resulting in an A rating) resulted in higher diffraction efficiency for the fabricated optical elements. [Industrial applicability]

[0172] The optical element of the present invention can bend light of any wavelength at any angle, depending on the design of its in-plane orientation pattern. Due to this characteristic, the optical element of the present invention can be used in various optical devices, contributing to the miniaturization and increased efficiency of optical devices. Examples of optical devices that use optical elements that bend visible light include glasses-type display devices for AR and VR (Virtual Reality) and stereoscopic image display devices that display real images in mid-air. Examples of optical devices that use optical elements that bend infrared light include optical communication devices and sensors. [Explanation of symbols]

[0173] 10,30 Optical elements 12 Support 14,14R,14G,14B alignment film 16 Cholesteric liquid crystal layer 20 Rod-shaped liquid crystal compound 20A optical axis 32 Pattern Liquid Crystal Layers 34 Optical Anisotropy Layer 40 displays 42 Light guide plate 60,80 Exposure equipment 62,82 lasers 64,84 light source 68,86,94 Polarizing Beam Splitter 70A, 70B, 90A, 90B Miller 72A,72B,96 λ / 4 board 92 lenses 140 Photoalignment precursor film B R Blue right-circular polarization G R Green right-circular polarization R R Red right-circular polarization M laser light MA,MB rays MP P polarization MS S polarization P O Linear polarization P R Right-hand circular polarization P L Left-hand circular polarization Q, Q1, Q2 Absolute Phase E,E1,E2 Equiphase surface L1,L4 incident light L2,L5 Transmitted light

Claims

1. A liquid crystal composition containing a liquid crystal compound, The liquid crystal composition contains a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound, A liquid crystal composition used for forming a diffraction element, wherein the ratio of the twist elastic constant K22 to the spray elastic constant K11 of the liquid crystal composition satisfies 0.7 ≤ K22 / K11.

2. The refractive index difference Δn due to the refractive index anisotropy of the liquid crystal composition. ５５０ The liquid crystal composition according to claim 1, wherein the ratio is 0.2 or greater.

3. The liquid crystal composition according to claim 1 or 2, wherein the content of the disc-shaped liquid crystal compound in the liquid crystal composition is 5 to 25% by mass relative to the total mass of the rod-shaped liquid crystal compound and the disc-shaped liquid crystal compound in the liquid crystal composition.

4. The liquid crystal composition according to any one of claims 1 to 3, wherein the rod-shaped liquid crystal compound is a compound represented by the following formula (I). 【Chemistry 1】 Here, in equation (I) above, P １ and P ２ Each of these independently represents a hydrogen atom or a substituent. S １ and S ２ Each of these independently represents a single bond or a divalent linking group. A １ and A ２ each independently represents a non-aromatic ring, an aromatic ring or an aromatic heterocyclic ring which may have a substituent. However, when there are a plurality of A ２ the plurality of A ２ may be the same or different from each other. Y １ is -O-, -S-, -OCH ２ -ien-CH ２ O-, -CH ２ CH ２ -, -CO-, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, -CO-NH-, -NH-CO-, -SCH ２ -ien-CH ２ S-, -CF ２ O-, -OCF ２ -, -CF ２ S-, -SCF ２ -, -CH=CH-COO-, -CH=CH-OCO-, -COO-CH=CH-, -OCO-CH=CH-, -COO-CH ２ CH ２ -, -OCO-CH ２ CH ２ -ien-CH ２ CH ２ -COO-, -CH ２ CH ２ -OCO-, -COO-CH ２ -, -OCO-CH ２ -ien-CH ２ -COO-, -CH ２ -OCO-, -CH=CH-, -N=N-, -CH=N-N=CH-, -CF=CF-, -C≡C-, -OCH ２ CH ２ O-, -SCH ２ CH ２ S- or represents a single bond. However, Y １ If there are multiple Y １ These may be the same or different. m1 represents an integer between 1 and 12.

5. The liquid crystal composition according to any one of claims 1 to 4, wherein the disc-shaped liquid crystal compound is a compound represented by the following formula (II). 【Chemistry 2】 Here, in equation (II), P ３ P represents a hydrogen atom or substituent. However, multiple P ３ These may be the same or different. S ３ represents a single bond or a divalent linking group. However, multiple S ３ These may be the same or different. A ３ A represents a non-aromatic ring, aromatic ring, or aromatic heterocycle, which may have substituents. However, multiple A ３ These may be the same or different. Y ２ is -O-, -S-, -OCH ２ -ien-CH ２ O-, -CH ２ CH ２ -, -CO-, -COO-, -OCO-, -CO-S-, -S-CO-, -O-CO-O-, -CO-NH-, -NH-CO-, -SCH ２ -ien-CH ２ S-, -CF ２ O-, -OCF ２ -, -CF ２ S-, -SCF ２ -, -CH=CH-COO-, -CH=CH-OCO-, -COO-CH=CH-, -OCO-CH=CH-, -COO-CH ２ CH ２ -, -OCO-CH ２ CH ２ -ien-CH ２ CH ２ -COO-, -CH ２ CH ２ -OCO-, -COO-CH ２ -, -OCO-CH ２ -ien-CH ２ -COO-, -CH ２ -OCO-, -CH=CH-, -N=N-, -CH=N-N=CH-, -CF=CF-, -C≡C-, -OCH ２ CH ２ O-, -SCH ２ CH ２ S- represents a single bond. However, it does not represent multiple Ys. ２ These may be the same or different. m² represents an integer between 0 and 5. n represents an integer between 3 and 20. D represents an n-valent disk-shaped core.

6. At least one Y in formula (I) １ The liquid crystal composition according to claim 4, wherein -C≡C-.

7. A diffraction element having an optically anisotropic layer formed using a liquid crystal composition containing a liquid crystal compound, The liquid crystal composition contains a rod-shaped liquid crystal compound and a disc-shaped liquid crystal compound, A diffraction element in which the optical anisotropy layer has a liquid crystal orientation pattern in which the orientation of the optical axis derived from the liquid crystal compound changes while continuously rotating along at least one direction in the plane.

8. The diffraction element according to claim 7, wherein the liquid crystal composition is the liquid crystal composition according to any one of claims 1 to 6.

9. The diffraction element according to claim 7 or 8, wherein the optical anisotropy layer has the optical axis orientation aligned in the thickness direction.

10. The diffraction element according to claim 7 or 8, wherein the optical anisotropy layer has a region in which the orientation of the optical axis twists and rotates in the thickness direction.

11. A diffraction element according to any one of claims 7 to 10, wherein when the length of one period is defined as the length over which the orientation of the optical axis rotates 180° in the plane, the liquid crystal alignment pattern has regions in which the length of one period is different.

12. When the length over which the orientation of the optical axis rotates 180° in the plane is defined as one period, The diffraction element according to any one of claims 7 to 11, wherein the period of the liquid crystal alignment pattern gradually shortens in the direction in which the orientation of the optical axis in the liquid crystal alignment pattern changes while continuously rotating.

13. The diffraction element according to any one of claims 7 to 12, wherein the liquid crystal alignment pattern of the optical anisotropy layer is a concentric pattern having the one direction in which the orientation of the optical axis changes while continuously rotating in a concentric manner from the inside to the outside.

14. A light guide element comprising a diffracting element and a light guide plate according to any one of claims 7 to 13.

Images