Optical compensation element and optical system including the same

Abstract

To improve the light utilization efficiency of an optical system by controlling the travel direction of polarized light by using a thin-type optical compensation element.SOLUTION: An optical compensation element has the sheet-like shape, includes a liquid crystalline material in which a side chain having the liquid crystal property is tilt-aligned with respect to the sheet surface, and has the optical characteristics in which the refractive index becomes nx>nz>ny. By arranging an optical unit including the optical compensation element and other optical members in an optical system such as an image projection device, the emanation in the travel direction of polarized light is suppressed and light leakage of the optical system is reduced.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical compensation element, and more particularly to an optical compensation element having the optical characteristic that the refractive index satisfies nx>nz>ny, and an optical system including the optical compensation element. [Background technology]

[0002] Conventionally, image projection devices are equipped with an optical system that separates light emitted from a light source into three colors (RGB) using a dichroic mirror or the like, forms images of each color using a liquid crystal cell, and then synthesizes the three color images and projects them externally. These optical systems use polarizing beam splitters or cross dichroic mirrors depending on the optical design.

[0003] Optical systems that use dichroic mirrors and the like are designed on the assumption that light travels along an optical axis (main optical path axis). However, since light emitted from a light source is usually not completely parallel, components that compensate for this are incorporated into the optical system. For example, Patent Document 1 describes a projector that incorporates an integrator with a fly's-eye lens array between the light source and the polarization conversion optical system.

[0004] Techniques for forming optical compensation elements from polymer films are also known. For example, Patent Document 2 describes a method for producing a retardation film having the optical properties of a negative C plate or a retardation film having biaxial optical anisotropy by controlling the orientation of a photo-alignable liquid crystalline polymer material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 104000 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-106018 Summary of the Invention [Problem to be solved by the invention]

[0006] In image projection devices, cross dichroic prisms, polarizing beam splitters, and other devices are placed opposite the liquid crystal cell. However, if the direction of polarized light entering these devices deviates from the optical path axis, light leakage occurs, reducing the utilization efficiency of the incident light. The integrator exemplified in Patent Document 1 uses, for example, a lens array to divide a single light beam into multiple light beams, thereby adjusting the illumination direction and is often used to reduce illumination unevenness. However, complex processing is required to achieve the desired optical control, and a certain thickness is required for the structure, making it difficult to install in the narrow space between the liquid crystal panel and the opposing optical components.

[0007] Patent Document 2 describes an optical element having optical properties represented by a biaxial index ellipsoid, where the refractive index is, for example, nx>ny>nz. However, the optical element is intended for use as a depolarizing film for liquid crystal display devices, and does not describe anything that can adjust the direction of light propagation in place of an integrator.

[0008] The present invention aims to provide an optical compensation element that has a thin sheet structure, is less restricted in terms of installation space, and can control the direction of polarized light, and an optical system that is equipped with the same and has reduced light leakage. [Means for solving the problem]

[0009] The first configuration of the present invention is It has a sheet-like shape, a liquid crystalline material in which side chains having liquid crystallinity are inclined relative to the sheet surface; It has optical properties where the refractive index is nx>nz>ny. It is an optical compensation element.

[0010] The optical compensation element described above can convert the traveling direction of polarized light incident on the sheet at an angle to a direction close to the normal to the sheet surface, thereby improving the light utilization efficiency.

[0011] The second configuration of the present invention is the optical compensation element according to the first configuration; A liquid crystal cell; a polarizing beam splitter; The optical compensation element is disposed between the liquid crystal cell and the polarizing beam splitter, forming an optical unit.

[0012] According to the optical unit having the above configuration, the utilization efficiency of the light incident on the polarizing beam splitter from the liquid crystal cell can be improved, and the contrast of the image displayed using the liquid crystal cell can be improved.

[0013] A third aspect of the present invention is an image projection device including the optical unit described above. In this image projection device, the effect of the optical compensation element described above makes it possible to improve image contrast and reduce the size of the device. [Effects of the Invention]

[0014] According to the present invention, the direction of polarization can be adjusted along the optical path axis of the optical system by using a space-saving sheet-like optical compensation element that can be manufactured by a simple method, thereby improving the light utilization efficiency. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 2 is a schematic perspective view for explaining the function of an optical compensation element according to one embodiment of the present invention. [Figure 2] 1 is a schematic perspective view showing a configuration of an optical compensation element according to one embodiment of the present invention. [Figure 3] 1 is a schematic cross-sectional view showing a configuration of an optical unit according to one embodiment of the present invention. [Figure 4] 1 is a schematic plan view showing a part of an image projection device according to an embodiment of the present invention. [Figure 5] 1 is a schematic plan view showing the configuration of an image projection device according to an embodiment of the present invention. [Figure 6] FIG. 1 is a schematic perspective view showing a configuration used in examples to verify the function of an optical compensation element. DETAILED DESCRIPTION OF THE INVENTION

[0016] The optical compensation element of the present invention is a sheet-like optical compensation element that contains a liquid crystalline material in which mesogen groups are obliquely aligned with respect to the sheet surface, and has optical properties in which the refractive index satisfies nx>nz>ny. Hereinafter, this optical compensation element and an optical system including the same will be described with reference to the drawings. Note that all drawings are schematic diagrams for illustrative purposes and do not reflect the dimensional ratios of the respective parts.

[0017] FIG. 1 is a schematic perspective view illustrating the function of an optical compensation element. The optical compensation element 1 has a sheet-like (plate-like or film-like) shape. When polarized light is incident on this element, as shown in the figure, even if the incident light LI is a luminous flux that diverges radially within the vibration plane P, the output light LE that passes through the optical compensation element 1 is adjusted to a direction normal to the sheet or a direction close to this. Therefore, compared to an integrator that combines two or more lens arrays, the direction of light can be controlled in a small space.

[0018] FIG. 2 is a perspective view schematically illustrating the configuration of an optical compensation element 1. The optical compensation element 1 includes a film 1a containing a liquid crystalline material in which side chain LCs having liquid crystallinity are tilted, and optionally includes a substrate 1b for forming the film 1a. The side chain LCs are aligned at a fixed angle with respect to the normal to the film 1a. Even if the propagation direction of polarized light is dispersed, the vibration direction remains within a fixed plane. Therefore, by aligning the alignment direction of the side chain LCs within the same plane, the propagation direction of polarized light passing through the optical compensation element 1 can be adjusted.

[0019] 3 is a schematic cross-sectional view showing an optical unit 10 as one application form of the optical compensation element 1. This optical unit 10 includes a liquid crystal cell 2 and a polarizing beam splitter 3, with the optical compensation element 1 disposed between them. The liquid crystal cell 2 may be an active matrix type TFT liquid crystal cell (not shown) having a structure in which a liquid crystal layer is sandwiched between an element substrate and an opposing substrate. Alternatively, the liquid crystal cell 2 may include two polarizing plates (not shown), an analyzer and a polarizer, and emit polarized light.

[0020] The liquid crystal cell 2 may be a transmissive liquid crystal cell 2 that modulates light L1 incident from the rear and emits it from the front. In an active matrix type liquid crystal cell 2, the emitted light L2 is split into light beams for each pixel. If the emitted light L2 contains components that are not parallel to the optical axis A, this will cause light leakage when it passes through the polarizing beam splitter 3. However, light L3 that passes through the optical compensation element 1 becomes approximately parallel to the optical axis A, thereby suppressing light leakage. If the light L2 emitted from the liquid crystal cell 2 is polarized, the light L3 that passes through the optical compensation element 1 is also polarized, and the polarizing beam splitter 3 either emits the light in the transmission direction (upward in the figure) or reflects it in the reflection direction (toward the left in the figure).

[0021] In the optical unit 10 configured as described above, the optical compensation element 1 is a space-saving sheet-like member, so that other optical members (not shown), such as a polarizing plate or a retardation plate, can be disposed at appropriate positions between the liquid crystal cell 2 and the polarizing beam splitter 3, as needed. This allows the optical unit 10 to be incorporated into optical systems such as image projection devices having various optical designs.

[0022] FIG. 4 is a plan view showing one embodiment of an image projection device 100 equipped with the optical unit 10. In the image projection device 100, light from a light source is typically split into red (R), green (G), and blue (B) light, or light of each color (RGB) is emitted from multiple light sources, and images are formed in liquid crystal cells 2a and 2b corresponding to each color. Finally, the images from the multiple liquid crystal cells 2a and 2b are combined and projected. In this case, an S-wave image is emitted from one liquid crystal cell 2a, and a P-wave image is emitted from the other liquid crystal cell 2b. The combined images are then combined by a polarizing beam splitter 3, incident on a cross dichroic prism 4, and combined with other images by the cross dichroic prism 4. The combined image is then projected externally via a projection optical system 5. In this case, combining the P-wave and S-wave images via an optical compensation element 1 can reduce light leakage and improve image contrast.

[0023] FIG. 5 is a schematic plan view of an image projection device 100 according to another embodiment. The image projection device 100 includes liquid crystal cells 2R, 2G, and 2B corresponding to the three colors R, G, and B, a cross dichroic prism 4 that combines the images emitted from these cells, and a projection optical system 5 that projects the combined image. In this image projection device 100, light emitted from a light source 6 is converted into P-wave or S-wave by a polarization conversion member 7, and then separated into red light LR and green light LG by a dichroic mirror 8R that reflects red light LR and a dichroic mirror 8G that reflects green light LG, respectively. The separated red light LR and green light LG, together with the remaining blue light LB, enter the liquid crystal cells 2R, 2G, and 2B directly (LG) or via a reflecting mirror 9 (LR, LB), respectively. Condenser lenses, relay lenses, and other elements are also used, but are not shown for simplicity. In this embodiment, an optical compensation element 1 according to the present invention is disposed between each of the liquid crystal cells 2R, 2G, and 2B and the cross dichroic prism 4. The cross dichroic prism 4 may also function as a polarizing beam splitter. In this case, the cross dichroic prism 4, the three optical compensation elements 1, and the three liquid crystal cells 2R, 2G, and 2B may be considered as an optical unit 11 according to the present invention. By incorporating the optical compensation element according to the present invention into an image projection device 100 having a general configuration as shown in FIG. 5, the contrast of the projected image can be improved.

[0024] Note that optical systems including the optical compensation element 1 according to the present invention are not limited to the above-described embodiments. For example, the optical unit according to the present invention is not limited to the above configuration and can be a combination of the optical compensation element 1 and any other optical element. For example, an optical unit may be formed by combining a liquid crystal cell 2 and the optical compensation element 1, a combination of the optical compensation element 1 and a polarizing beam splitter 3, or a combination of the optical compensation element 1 and a cross dichroic prism 4. In this case, multiple optical compensation elements 1 may be used as necessary. Furthermore, the polarizing beam splitter 3 may be a cube-shaped one in which two prisms are arranged opposite each other and a dielectric multilayer film is formed on one side, or a plate-shaped one in which a dielectric multilayer film is formed. While FIG. 3 shows a schematic representation of a cube-shaped one, a plate-shaped polarizing beam splitter may also be combined with the optical compensation element 1. When the optical compensation element 1 is used in a liquid crystal display device, the liquid crystal cell 2 may be either a transmissive or reflective type. Furthermore, the optical compensation element 1 may be used in optical systems other than image projection devices.

[0025] [Optical compensation element] The optical compensation element 1 has a sheet-like shape, contains a liquid crystalline material in which the liquid crystalline side chains are tilted relative to the sheet surface, and has optical properties such that the refractive index satisfies nx>nz>ny. This optical compensation element preferably has an in-plane retardation of 200 to 300 nm and an inclination angle of the slow axis relative to the surface of 10 to 45°. This optical compensation element 1 can be formed by controlling the alignment of a coating film of a photo-alignable liquid crystalline material. Due to the tilted alignment of the liquid crystalline side chains, this optical compensation element 1 has optical anisotropy in which the index ellipsoid satisfies nx>nz>ny is tilted relative to the surface of the optical compensation element 1.

[0026] For example, the optical compensation element 1 is not particularly limited as long as the liquid crystalline side chains can be tilted. However, from the viewpoint of ease of tilted alignment, it is preferable that the optical compensation element 1 be a polymer film made of a liquid crystalline polymer having a photosensitive group and a side chain structure capable of forming a liquid crystal structure. In this case, the tilted alignment is induced by a photoreaction of the photosensitive group in the side chain. Examples of the photoreaction include a photodimerization reaction, a photoisomerization reaction, and a photo-Fries rearrangement reaction.

[0027] When the side chain of the liquid crystalline polymer is capable of forming a liquid crystal structure, the liquid crystallinity may be exhibited by having a mesogenic group, which is a rigid moiety that exhibits liquid crystallinity, in the side chain structure, or by having a structure that can form a dimer by hydrogen bonding with another polymer or another side chain of the same polymer, etc., and by forming a mesogenic structure through this dimerization, thereby exhibiting liquid crystallinity.

[0028] The mesogenic group or mesogenic structure is composed of two or more aromatic or aliphatic rings and a linking group connecting them, and the linking group may be a covalent bond or a hydrogen bond. Examples of aromatic rings include a benzene ring, a naphthalene ring, and heterocycles (for example, oxygen-containing heterocycles such as a furan ring and a pyran ring; nitrogen-containing heterocycles such as a pyrrole ring and an imidazole ring). Examples of aliphatic rings include a cyclohexane ring. These aromatic rings or aliphatic rings may have a substituent, and the substituent may be an alkyl group (for example, C 1-6 Alkyl groups, preferably C 1-4 alkyl groups), alkyloxy groups (e.g., C 1-6 Alkyloxy groups, preferably C 1-4 alkyloxy groups), alkenyl groups (e.g., C 1-6 Alkenyl groups, preferably C 1-4 alkenyl groups), alkynyl groups (e.g., C 1-6 Alkynyl groups, preferably C 1-4 alkynyl groups), halogen atoms, etc. Examples of the linking group, in the case of a covalent bond, include a single bond, -O-, -COO-, -OCO-, -N=N-, -NO=N-, -C=C-, -C≡C-, -CO-C=C-, -CH=N-, an alkylene group, etc. In the case of a hydrogen bond, examples include a side chain structure having a carboxy group at the end, in which case a hydrogen bond is formed between the carboxy groups.

[0029] The photosensitive group is not particularly limited as long as it is a functional group capable of undergoing a photoreaction by light energy, and examples thereof include a chalcone group, a coumarin group, a cinnamoyl group, a cinnamic acid group, a cinnamylidene acetate group, a biphenylacryloyl group, a furyl acryloyl group, a naphthylacryloyl group, an azobenzene group, a benzylideneaniline group, or derivatives thereof, and preferably a cinnamoyl group.

[0030] A liquid crystalline polymer has at least a side chain structure in a repeating unit that has both a photosensitive group and a structure capable of forming a liquid crystal structure, and the photosensitive group may exist independently of the mesogenic group or mesogenic structure in the side chain structure, or may exist in a composite manner by sharing a chemical structure. Preferably, the polymer film may be made of a liquid crystalline polymer containing photoreactive hydrogen-bonding side chains and non-photoreactive hydrogen-bonding side chains.

[0031] The photoreactive hydrogen-bonding side chain preferably has a structure represented by the following chemical formula 1. It is a liquid crystalline polymer having a photoreactive carboxyl group at the end of the side chain. This photoreactive polymer has a structure that exhibits a liquid crystal phase through dimerization due to hydrogen bonding of the carboxyl group at the end of the side chain.

[0032] [ka]

[0033] In the formula, k=0 or an integer of 1 to 12 (preferably an integer of 1 to 10, more preferably an integer of 1 to 8); l=0 or 1 (preferably 1); m=0 or 1; n=an integer of 1 to 3 (preferably an integer of 1 to 2); X is a direct bond, C 1-3 an alkylene group, -C=C-, -C≡C-, -O-, -N=N-, -COO-, or -OCO-; R1 and R2 are the same or different and each represent a hydrogen atom, an alkyl group, an alkyloxy group, an alkenyl group, an alkynyl group, or a halogen atom;

[0034] Furthermore, as the non-photoreactive hydrogen-bonding side chain, a side chain having a structure represented by Chemical Formula 2 is preferably used. This side chain also has a carboxyl group at the side chain terminal, and has a structure that exhibits a liquid crystal phase by dimerization due to hydrogen bonding of the carboxyl group at the side chain terminal.

[0035] [ka]

[0036] In the formula, a=0 or an integer of 1 to 12 (preferably an integer of 1 to 10, more preferably an integer of 1 to 8); b=0 or 1 (preferably 1); c=0 or 1; Y is a direct bond, C 1-3 an alkylene group, -C=C-, -C≡C-, -O-, -N=N-, -COO-, or -OCO-; R3 and R4 are the same or different and each represent a hydrogen atom, an alkyl group, an alkyloxy group, an alkenyl group, an alkynyl group, or a halogen atom;

[0037] In the above chemical formulas 1 and 2, the alkyl group may be a C group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, or a t-butyl group. 1-20 Alkyl groups, preferably C 1-10 alkyl group, more preferably C 1-5 Examples of the alkyloxy group include C 2 alkyl groups such as methoxy groups, ethoxy groups, butoxy groups, and t-butoxy groups. 1-20 Alkyloxy groups, preferably C 1-10 Alkyloxy groups, more preferably C1-5 Examples of the alkenyl group include C alkyloxy groups, vinyl groups, allyl groups, and 2-butenyl groups. 2-20 Alkenyl groups, preferably C 2-10 Alkenyl groups, more preferably C 2-5 Examples of the alkynyl group include C 1-substituted alkenyl groups, such as propargyl and 3-pentynyl groups. 2-20 Alkynyl groups, preferably C 2-10 Alkynyl groups, more preferably C 2-5 Examples of the halogen atom include a fluorine atom, a chlorine atom, and a bromine atom.

[0038] As the non-photoreactive hydrogen-bonding side chain, a monomer or polymer thereof derived from 4-hydroxybenzoic acid can be suitably used. Such non-photoreactive hydrogen-bonding side chains are also materials that exhibit a liquid crystal phase even without a mesogenic group in their structure. Because they do not contain a mesogenic group in their structure, they do not absorb light of wavelengths that promote the photoreaction of the photosensitive group, and therefore do not impair photoreactivity. Furthermore, because they are materials that exhibit liquid crystallinity, they do not impair alignment. Therefore, even when a relatively large amount of these non-photoreactive side chains is added, alignment control of polymer films can be achieved using the photoreactive side chains.

[0039] The liquid crystalline polymer may be a homopolymer consisting of the same repeating units containing the above-mentioned side chain structure, or a copolymer containing repeating units containing a different side chain structure in addition to the repeating units containing the above-mentioned side chain structure. Examples of the main chain structure include a structure formed by polymerization of hydrocarbon, acrylate, methacrylate, siloxane, maleimide, N-phenylmaleimide, etc. Furthermore, the liquid crystalline polymer may have a repeating unit that does not have a photosensitive group and / or a structure capable of forming a liquid crystal structure, as long as the tilt alignment is not hindered.

[0040] In particular, we have found that by appropriately controlling the ratio of photoreactive hydrogen-bonding side chains to non-photoreactive hydrogen-bonding side chains and controlling their orientation with light, optical properties can be obtained in which the refractive index satisfies the relationship nx>nz>ny. For example, the ratio of the photoreactive hydrogen-bonding side chains represented by Chemical Formula 1 to the non-photoreactive hydrogen-bonding side chains represented by Chemical Formula 2 may be 1:99 to 20:80, or 3:97 to 10:90. Reducing the amount of photoreactive hydrogen-bonding side chains improves the durability of the optical compensation element formed and extends the life of the optical compensation element as an optical component.

[0041] The birefringence-inducing material of the present invention may contain a low-molecular-weight compound together with the liquid-crystalline polymer to promote the alignment of the side chains of the liquid-crystalline polymer. The low-molecular-weight compound preferably has a substituent known as a mesogenic component, such as biphenyl, terphenyl, phenylbenzoate, or azobenzene, and is liquid-crystalline, having such a substituent and a functional group, such as allyl, acrylate, methacrylate, or cinnamic acid group (or a derivative thereof), bonded via a spacer (e.g., an (oxy)alkylene group having 1 to 15 carbon atoms (preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms)). These low-molecular-weight compounds may be used alone or in combination.

[0042] A crosslinking agent may be added to the above materials to improve heat resistance to the extent that liquid crystallinity is not impaired.

[0043] The manufacturing process of the optical compensation element includes the steps of applying a solution of the liquid crystalline material having the above-mentioned side chains exhibiting liquid crystallinity to a substrate, drying the coating film, irradiating the dried coating film with linearly polarized light, heating the polarized light-irradiated coating film, and slowly cooling the heated coating film. After irradiating with linearly polarized light, the coating film may be irradiated with non-polarized light.

[0044] The solution used to dissolve the liquid crystalline polymer may be a solvent containing an aprotic polar solvent, which may be at least one selected from the group consisting of tetrahydrofuran (THF), diethyl carbonate, propyl carbonate, N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO).

[0045] The concentration of the liquid crystalline polymer material in the solution is not particularly limited as long as it can be used to form a coating film. For example, it may be 5 to 50% by weight, or 8 to 40% by weight, and It may be up to 25% by weight.

[0046] The substrate used for applying the solution may be a glass substrate or a transparent film having low birefringence (preferably optically isotropic) optical properties. Alternatively, an optical film such as a polarizing film or a retardation film, or a laminate of multiple optical films may be used as the substrate, as long as the optical properties of the substrate are not impaired in the orientation control step described below. Preferred substrates may be, for example, polycarbonate films, cycloolefin polymer films, etc. The solution can be applied to the substrate by, for example, spin coating, casting, or other methods.

[0047] Next, to advance the orientation control by photoreaction, irradiation with light of a wavelength to which the photosensitive group can react is required. This wavelength is generally 200-500 nm, with 250-400 nm being particularly effective in many cases. Therefore, it is preferable that the irradiated light has a maximum intensity in the wavelength range of 200-500 nm, and ultraviolet light is more preferable. As the ultraviolet light, it is preferable to use ultraviolet light having a maximum intensity in the wavelength range of 200-400 nm, preferably in the wavelength range of 250-400 nm. For example, a high-pressure mercury lamp may be used as the light source. The irradiation dose is, for example, 5 mJ / cm. 2 ~100mJ / cm 2 About 8 mJ / cm 2 ~20mJ / cm 2 It may also be possible to use the following.

[0048] In the irradiation, linearly polarized light is first irradiated at a predetermined angle, for example, 45° to 70°, for example, 55° to 65°, relative to the normal to the coating film. , non Polarized light may also be used.

[0049] The heating temperature of the coating film after light irradiation is not particularly limited as long as the liquid crystal polymer in the film is oriented along the photoisomerized side chains in the film due to molecular motion, but it is preferably set to a temperature equal to or higher than the liquid crystal phase transition temperature and lower than the isotropic phase transition temperature of the material (photosensitive liquid crystal polymer) that forms the film itself. For example, it may be 50 to 200°C, preferably 60 to 160°C, and more preferably 80 to 140°C.

[0050] The heating time is not particularly limited as long as the liquid crystal polymer in the film is oriented along the side chains that have undergone photoisomerization in the film due to molecular motion, but can be appropriately set depending on the type of liquid crystal polymer, heating temperature, etc. For example, the heating time may be 1 minute or more, preferably 3 minutes or more, and more preferably 5 minutes or more. The upper limit is not particularly limited, but from an economical viewpoint, it may be about 60 minutes (preferably about 40 minutes, more preferably about 20 minutes).

[0051] In the optical compensation element formed as described above, the thickness of the film formed on the substrate can be 20 μm or less, preferably 0.1 to 15 μm, and more preferably 0.5 to 10 μm. [Example]

[0052] The results of examples carried out to verify the function of the optical compensation element according to the present invention will be described below.

[0053] (Monomer 1) 4-(6-hydroxyhexyloxy)cinnamic acid was synthesized by heating p-coumaric acid and 6-chloro-1-hexanol under alkaline conditions. This product was esterified with a large excess of methacrylic acid in the presence of p-toluenesulfonic acid to synthesize Monomer 1, shown in Chemical Formula 3 below. [ka]

[0054] (Monomer 2) 4-(6-hydroxyhexyloxy)benzoic acid was synthesized by heating p-hydroxybenzoic acid and 6-chloro-1-hexanol under alkaline conditions. This product was esterified with a large excess of methacrylic acid in the presence of p-toluenesulfonic acid to synthesize monomer 2, shown in chemical formula 4 below. [ka]

[0055] (Polymer 1) Monomer 1 and monomer 2 were dissolved in dioxane in a molar ratio of 5:95, and AIBN was added as a reaction initiator. Polymerization was carried out at 70°C for 24 hours to obtain photosensitive polymer 1. This polymer 1 exhibited liquid crystallinity.

[0056] Example 1 Polymer 1 was dissolved in THF to prepare a solution with a concentration of 15 wt %. This solution was applied to a glass substrate with a thickness of 5 μm using a spin coater and dried. Next, UV light (10 mJ / cm ) obtained by polarizing and converting light from a high-pressure mercury lamp was applied. 2 ) for 20 seconds, followed by unpolarized UV light 6 seconds , at an irradiation angle of 60° Subsequently, the film was heated to 130°C, held for 3 minutes, and then slowly cooled to induce orientation. The optical compensation element 1 thus produced had an in-plane retardation value of 243 nm , bend The refractive index was (nx: 1.588, ny: 1.532, nz: 1.559).

[0057] Next, to verify the functionality of the optical compensation element 1, we placed the wire-grid polarizer WGP, the optical compensation element 1, and the polarizing beam splitter 3 in this order, as shown in Figure 6, and irradiated the wire-grid polarizer WGP with illumination light from below. Here, the polarized light L emitted from the wire-grid polarizer WGP replaced the polarized light emitted from the liquid crystal cell. As shown by the spindle-shaped schematic diagram on the substrate, the liquid crystal side chains LC were tilted in a plane perpendicular to the reflecting surface 3a of the polarizing beam splitter 3. Observations revealed that no light leakage was observed when viewed from the front of the reflecting surface 3a of the polarizing beam splitter 3 (VE1), and that light leakage was reduced when viewed from an oblique angle (VE2).

[0058] Although the embodiments of the present invention have been described above, the disclosed embodiments are illustrative in all respects and are not limiting. The scope of the present invention is defined by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0059] 1 Optical compensation element 1a Film 1b Base material 2, 2a, 2b, 2R, 2B, 2G liquid crystal cells 3 Polarizing Beam Splitter 4 Cross Dichroic Prisms 5 Projection optical system 6 light source 7 Polarization conversion member 8R, 8G dichroic mirror 9 Reflective mirror 10,11 Optical unit 100 Image projection device

Claims

1. It has a sheet-like shape, a liquid crystalline material in which side chains having liquid crystallinity are inclined relative to the sheet surface; The refractive index has an optical property of nx>nz>ny, the inclination angle of the slow axis of the liquid crystal material with respect to the surface of the sheet is 10 to 45°; Optical compensation element. However, the liquid crystalline material contains photoreactive hydrogen-bonding side chains represented by the following chemical formula 1 and non-photoreactive hydrogen-bonding side chains represented by the following chemical formula 2 in a ratio of 1:99 to 20:

80. 【Chemistry 1】 【Chemistry 2】 In Chemical Formula 1, k is 0 or an integer of 1 to 12; l is 0 or 1; m is 0 or 1; n is an integer of 1 to 3; X is a direct bond, a C1-3 alkylene group, -C=C-, -C≡C-, -O-, -N=N-, -COO-, or -OCO-; R 1 and R 2 are the same or different and each represent a hydrogen atom, an alkyl group, an alkyloxy group, an alkenyl group, an alkynyl group, or a halogen atom; In Chemical Formula 2, a is 0 or an integer of 1 to 12; b is 0 or 1; c is 0 or 1; Y is a direct bond, a C1-3 alkylene group, -C=C-, -C≡C-, -O-, -N=N-, -COO-, or -OCO-; and R 3 and R 4 are the same or different and represent a hydrogen atom, an alkyl group, an alkyloxy group, an alkenyl group, an alkynyl group, or a halogen atom.

2. The optical compensation element according to claim 1; A liquid crystal cell; a polarizing beam splitter; The optical compensation element is disposed between the liquid crystal cell and the polarizing beam splitter. The optical unit.

3. An image projection device comprising the optical unit according to claim 2.

Images