Manufacturing method of aligned liquid crystal film

Abstract

To provide a manufacturing method of aligned liquid crystal film for bonding an aligned liquid crystal layer and an optical layer with activation energy ray curable adhesive agent using a roll-to-roll method, capable of manufacturing an alignment liquid crystal film optical characteristics of which less changes even after being exposed to a high temperature environment for a long time.SOLUTION: The manufacturing method of aligned liquid crystal film includes a bonding step of bonding an aligned liquid crystal layer and an optical layer with activation energy ray curable adhesive agent using a roll-to-roll method. The bonding step includes a coating step and an irradiation step. In the coating step, at least one surface of the aligned liquid crystal layer and the optical layer is coated with uncured adhesive agent with temperature of 0°C or higher and 45°C or lower. In the irradiation step, a laminate obtained by laminating the aligned liquid crystal layer and the optical layer with the uncured adhesive agent therebetween is irradiated with activation energy ray while the laminate is subjected to a tensile force of 70 N / 1000 mm width or more and 550 N / 1000 mm width or less in the conveyance direction of the laminate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing an oriented liquid crystal film having an oriented liquid crystal layer in which a liquid crystal compound is oriented. [Background technology]

[0002] A liquid crystal film (oriented liquid crystal film) having an oriented liquid crystal layer in which liquid crystal compounds are oriented in a predetermined direction is used as an optical film (optically anisotropic element) having functions such as optical compensation for liquid crystal display devices and anti-reflection of external light for organic electroluminescence display devices. Since an oriented liquid crystal film has a larger birefringence Δn than a stretched polymer film, it is advantageous for making image display devices (more specifically, liquid crystal display devices, organic electroluminescence display devices, etc.) thinner and lighter. In image display devices, an oriented liquid crystal film is laminated with a polarizer or the like via a pressure sensitive adhesive or adhesive to form a laminate, which is attached to an organic electroluminescence panel or a liquid crystal display panel (see, for example, Patent Document 1).

[0003] The liquid crystal compound can be aligned in a predetermined direction by the shear force when applied to the substrate or the alignment force of the alignment film, and aligned liquid crystal films with various optical anisotropies can be obtained by orienting the liquid crystal compound. For example, a homogeneously aligned liquid crystal layer in which nematic liquid crystal molecules with positive refractive index anisotropy are aligned parallel to the substrate surface can be used as a positive A plate with a refractive index anisotropy of nx>ny=nz.

[0004] When using thermotropic liquid crystal, a solution containing a liquid crystal compound (liquid crystal composition) is applied onto a substrate, and the liquid crystal compound contained in the composition is heated to be in a liquid crystal state, thereby aligning the liquid crystal compound. When the liquid crystal composition contains a photopolymerizable liquid crystal compound (liquid crystal monomer), the liquid crystal compound is aligned, and then the alignment state is fixed by curing the liquid crystal composition by light irradiation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-7700 A Summary of the Invention [Problem to be solved by the invention]

[0006] Image display devices are now required to have higher durability, and the optical members constituting the image display devices are required to show small changes in their optical properties (more specifically, retardation, etc.) even when exposed to high-temperature environments for long periods of time.

[0007] On the other hand, the optical properties of the oriented liquid crystal film may change in a high-temperature environment due to the influence of a layer disposed adjacent to the oriented liquid crystal layer. For example, when an oriented liquid crystal layer and an optical layer (more specifically, a polarizer, a transparent film, another oriented liquid crystal layer, etc.) are bonded together via a pressure-sensitive adhesive layer, there is almost no change in retardation in a high-temperature environment, whereas when an oriented liquid crystal layer and an optical layer are bonded together via an active energy ray-curable adhesive, there is a tendency for the retardation to increase in a high-temperature environment.

[0008] Furthermore, the inventors have found through their investigations that the tendency for retardation to increase in the above-mentioned high temperature environment is particularly pronounced when the aligned liquid crystal layer and the optical layer are bonded together by a roll-to-roll method via an active energy ray-curable adhesive.

[0009] In view of these problems, the present invention aims to provide a method for producing an oriented liquid crystal film in which an oriented liquid crystal layer and an optical layer are bonded together by a roll-to-roll method via an active energy ray-curable adhesive, which can produce an oriented liquid crystal film whose optical properties change little even when exposed to a high-temperature environment for a long period of time. [Means for solving the problem]

[0010] The method for producing an oriented liquid crystal film according to the present invention is a method for producing an oriented liquid crystal film having an oriented liquid crystal layer in which a liquid crystal compound is oriented, and includes a lamination step of laminating the oriented liquid crystal layer and the optical layer by a roll-to-roll method via an active energy ray curable adhesive. The lamination step includes a coating step and an irradiation step. In the coating step, the adhesive is applied to at least one surface of the oriented liquid crystal layer and the optical layer before curing and at a temperature of 0°C to 45°C. In the irradiation step, active energy rays are irradiated to a laminate in which the oriented liquid crystal layer and the optical layer are laminated via the uncured adhesive while applying a tension of 70 N / 1000 mm width to 550 N / 1000 mm width in the transport direction of the laminate.

[0011] In one embodiment of the method for producing an oriented liquid crystal film according to the present invention, in the irradiation step, an integrated light amount of 450 mJ / cm 2 is applied to the laminate. 2 More than 1200mJ / cm 2 The active energy rays are irradiated under the following conditions.

[0012] In one embodiment of the method for producing an aligned liquid crystal film according to the present invention, in the coating step, the adhesive is applied to the surface at a temperature of 0° C. or more and 10° C. or less.

[0013] In one embodiment of the method for producing an oriented liquid crystal film according to the present invention, the thickness of the layer made of the adhesive after the irradiation step is 0.1 μm or more and 3.0 μm or less.

[0014] In one embodiment of the method for producing an aligned liquid crystal film according to the present invention, the liquid crystal compound is homogeneously aligned in the aligned liquid crystal layer.

[0015] In one embodiment of the method for producing an aligned liquid crystal film according to the present invention, the aligned liquid crystal layer has a birefringence Δn of 0.03 or more after the laminating step.

[0016] In one embodiment of the method for producing an oriented liquid crystal film according to the present invention, the optical layer is a polarizer, a transparent film, or another oriented liquid crystal layer. Effect of the Invention

[0017] According to the method for producing an oriented liquid crystal film of the present invention, an oriented liquid crystal film can be produced that exhibits minimal change in optical properties even when exposed to a high-temperature environment for a long period of time, while including a lamination process in which an oriented liquid crystal layer and an optical layer are laminated together by a roll-to-roll method via an active energy ray-curable adhesive. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is an explanatory diagram for explaining an example of a method for producing an oriented liquid crystal film according to the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of an oriented liquid crystal film in which an oriented liquid crystal layer and an optical layer are laminated via an adhesive. [Diagram 3] 3A, 3B, 3C and 3D are cross-sectional views illustrating steps in one example of a method for producing the aligned liquid crystal film shown in FIG. 2. [Figure 4] FIG. 2 is a cross-sectional view showing an example of an oriented liquid crystal film in which an oriented liquid crystal layer and an optical layer are laminated via an adhesive. [Diagram 5] FIG. 2 is a cross-sectional view showing an example of an oriented liquid crystal film having a pressure-sensitive adhesive layer. [Figure 6] FIG. 2 is a cross-sectional view showing an example of an oriented liquid crystal film in which an oriented liquid crystal layer and an optical layer are laminated via an adhesive. [Figure 7] FIG. 2 is a cross-sectional view showing an example of a layer structure of an image display device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] A preferred embodiment of the present invention will be described below. First, the terms used in this specification will be described. The thickness of the aligned liquid crystal layer, the thickness of the optical layer, and the thickness of the layer made of the adhesive after irradiation with active energy rays (after curing) (hereinafter, may be simply referred to as "adhesive layer") are the arithmetic average values ​​of 10 measured values ​​obtained by observing a cross section cut in the thickness direction of the layer with a transmission electron microscope (TEM), randomly selecting 10 measurement points from the cross section image, and measuring the thicknesses of the selected 10 measurement points.

[0020] Hereinafter, the compound and its derivatives may be collectively referred to by adding "based" after the compound name. When the polymer name is expressed by adding "based" after the compound name, it means that the repeating unit of the polymer is derived from the compound or its derivative. Acrylic and methacrylic may be collectively referred to as "(meth)acrylic". Acrylate and methacrylate may be collectively referred to as "(meth)acrylate". Acryloyl and methacryloyl may be collectively referred to as "(meth)acryloyl".

[0021] <Method of manufacturing oriented liquid crystal film> The method for producing an oriented liquid crystal film according to the present embodiment is a method for producing an oriented liquid crystal film having an oriented liquid crystal layer in which a liquid crystal compound is oriented, and includes a lamination process in which the oriented liquid crystal layer and the optical layer are laminated together by a roll-to-roll method via an active energy ray curable adhesive. The lamination process includes a coating process and an irradiation process. In the coating process, an adhesive that has not yet been cured and is at a temperature of 0°C or more and 45°C or less is applied to at least one surface of the oriented liquid crystal layer and the optical layer. In the irradiation process, an active energy ray is irradiated to a laminate in which the oriented liquid crystal layer and the optical layer are laminated via the uncured adhesive while applying a tension of 70N / 1000mm width or more and 550N / 1000mm width or less in the transport direction of the laminate.

[0022] According to the method for producing an aligned liquid crystal film according to the present embodiment, an aligned liquid crystal film that exhibits little change in optical properties even when exposed to a high-temperature environment for a long period of time can be produced while having a lamination process in which an aligned liquid crystal layer and an optical layer are laminated together by a roll-to-roll method via an active energy ray-curable adhesive. The reason for this is presumed to be as follows.

[0023] In general, when a film product is manufactured from a film material by the roll-to-roll method, the film material is processed while tension is applied to the film material in the transport direction in order to transport the film material. Therefore, in a film product manufactured by the roll-to-roll method, anisotropy occurs in the shrinkage stress between the longitudinal direction (the transport direction during manufacturing) and the width direction, and residual stress tends to occur. Therefore, in a film product manufactured by the roll-to-roll method, optical properties (e.g., retardation, etc.) tend to change easily in a high-temperature environment. As described above, this tendency is particularly noticeable when an aligned liquid crystal layer and an optical layer are bonded together by the roll-to-roll method via an active energy ray curable adhesive.

[0024] In contrast, in this embodiment, the temperature of the adhesive in the coating process is set within a specific range, and the tension applied to the laminate in the irradiation process is set within a specific range, thereby suppressing the volume change (curing shrinkage) of the adhesive when curing. As a result, the generation of residual stress caused by the curing shrinkage of the adhesive is suppressed, and an oriented liquid crystal film with small changes in optical properties even when exposed to a high-temperature environment for a long period of time (hereinafter, sometimes described as "excellent heat durability") can be manufactured.

[0025] Hereinafter, this embodiment will be described in detail with reference to the drawings. Note that, for ease of understanding, Figs. 1 to 7 are mainly schematic illustrations of each component, and the size, number, shape, etc. of each component shown in the drawings may differ from the actual size, number, shape, etc. of each component shown in the drawings. For convenience of explanation, in the drawings described later, the same components as those in the drawings described earlier may be given the same reference numerals, and explanations thereof may be omitted.

[0026] Fig. 1 is an explanatory diagram for explaining an example of a method for producing an aligned liquid crystal film according to the present embodiment. As shown in Fig. 1, an adhesive is applied by a coating device 11 to the surface of an aligned liquid crystal layer-containing film 10 (specifically, the surface of the aligned liquid crystal layer in the aligned liquid crystal layer-containing film 10) transported by a roll-to-roll method to form a coating layer 12 (coating step). In Fig. 1, a die coater is used as the coating device 11, but the coating device is not limited in the present invention, and a coating device such as a gravure coater, a reverse coater, or a bar coater can be appropriately used depending on the viscosity of the adhesive, etc.

[0027] Next, the optical layer-containing film 13 and the aligned liquid crystal layer-containing film 10 are guided by the guide roll 14 and transported to between the first laminating roll 15 and the second laminating roll 16, and are laminated via the coating layer 12 by passing through the gap to form a laminate 17. At this time, the laminate 17 is formed in a state where the optical layer in the optical layer-containing film 13 is in contact with the coating layer 12.

[0028] Next, the laminate 17 is irradiated with active energy rays (more specifically, ultraviolet rays, electron beams, etc.) by the active energy ray irradiation device 18 (irradiation step). In the irradiation step, the adhesive in the coating layer 12 is cured to form an adhesive layer 19, and an aligned liquid crystal film 100 is obtained in which the aligned liquid crystal layer-containing film 10 and the optical layer-containing film 13 are bonded together via the adhesive layer 19. Examples of the light source of the active energy rays include a low pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, an LED, a black light, a chemical lamp, etc. The illuminance of the light source of the active energy rays is, for example, 100 mW / cm. 2 More than 1000mW / cm 2 less than or equal to 400 mW / cm 2 More than 800mW / cm 2The active energy rays can be irradiated onto the surface of the aligned liquid crystal layer-containing film 10, the surface of the optical layer-containing film 13, or both surfaces of the laminate 17, depending on the active energy ray transmittance of the aligned liquid crystal layer-containing film 10 and the optical layer-containing film 13 used.

[0029] In order to produce an oriented liquid crystal film having superior heat durability, the thickness of the adhesive layer 19 is preferably 3.0 μm or less, and more preferably 2.8 μm or less. In order to produce an oriented liquid crystal film having superior adhesion reliability, the thickness of the adhesive layer 19 is preferably 0.1 μm or more, and more preferably 0.5 μm or more. In order to produce an oriented liquid crystal film having superior heat durability while ensuring adhesion reliability, the thickness of the adhesive layer 19 is preferably 0.1 μm or more and 3.0 μm or less, and more preferably 0.5 μm or more and 2.8 μm or less. The thickness of the adhesive layer 19 can be adjusted by changing the thickness of the coating layer 12.

[0030] In the lamination step described with reference to Fig. 1, tension is applied to the aligned liquid crystal layer-containing film 10, the optical layer-containing film 13, and the laminate 17, for example, by a dancer roll (not shown). The direction in which tension is applied is the transport direction for all of the aligned liquid crystal layer-containing film 10, the optical layer-containing film 13, and the laminate 17.

[0031] In order to produce an oriented liquid crystal film having excellent heat durability while stably transporting the laminate 17, it is preferable to irradiate the laminate 17 with active energy rays while applying a tension of 77 N / 1000 mm width or more and 550 N / 1000 mm width or less.

[0032] In order to produce an oriented liquid crystal film having superior heat resistance, the laminate 17 is exposed to an integrated light amount of 450 mJ / cm. 2 More than 1200mJ / cm 2 It is preferable to irradiate with active energy rays under the following conditions: cumulative light dose 450 mJ / cm 2 More than 1100mJ / cm 2It is more preferable to irradiate the active energy rays under the following conditions: 2 More than 800mJ / cm 2 It is more preferable to irradiate the active energy rays under the following conditions: 2 More than 600mJ / cm 2 It is even more preferable to irradiate with active energy rays under the following conditions.

[0033] In order to produce an oriented liquid crystal film having excellent heat durability, the temperature of the adhesive applied in the application step is preferably 0°C or higher and 25°C or lower, more preferably 0°C or higher and 10°C or lower.

[0034] In order to stably transport the oriented liquid crystal layer-containing film 10, the optical layer-containing film 13, and the laminate 17, the transport speed thereof is preferably 1 m / min or more and 100 m / min or less, and more preferably 5 m / min or more and 50 m / min or less.

[0035] The time from when the adhesive is applied to the aligned liquid crystal layer-containing film 10 in the application step until when the laminate 17 is irradiated with active energy rays in the irradiation step is, for example, from 0 seconds to 300 seconds.

[0036] In order to produce an oriented liquid crystal film having even better heat durability, it is preferable to satisfy the following condition 1, it is more preferable to satisfy the following condition 2, it is even more preferable to satisfy the following condition 3, and it is even more preferable to satisfy the following condition 4. Condition 1: The temperature of the adhesive applied in the application step is 0° C. or higher and 25° C. or lower, and the integrated light amount for the laminate 17 in the irradiation step is 450 mJ / cm 2 2 More than 1200mJ / cm 2 The active energy rays are irradiated under the following conditions. Condition 2: The temperature of the adhesive applied in the application step is 0° C. or higher and 25° C. or lower, and the integrated light amount for the laminate 17 in the irradiation step is 450 mJ / cm 2 2 More than 800mJ / cm 2The active energy rays are irradiated under the following conditions. Condition 3: The temperature of the adhesive applied in the application step is 0° C. or higher and 10° C. or lower, and the integrated light amount for the laminate 17 in the irradiation step is 450 mJ / cm 2 More than 1200mJ / cm 2 The active energy rays are irradiated under the following conditions. Condition 4: The temperature of the adhesive applied in the application step is 0° C. or higher and 10° C. or lower, and the integrated light amount for the laminate 17 in the irradiation step is 450 mJ / cm 2 2 More than 800mJ / cm 2 The active energy rays are irradiated under the following conditions.

[0037] Although an example of the method for producing an aligned liquid crystal film according to the present embodiment has been described above with reference to Fig. 1, the present invention is not limited to the above example. For example, in the above example, an adhesive is applied to the aligned liquid crystal layer, but in the present invention, an adhesive may be applied to the optical layer, or an adhesive may be applied to both the aligned liquid crystal layer and the optical layer.

[0038] Next, a configuration example of an oriented liquid crystal film obtained by the manufacturing method according to this embodiment will be described.

[0039] Fig. 2 is a cross-sectional view showing an example of an aligned liquid crystal film obtained by the manufacturing method according to the present embodiment. The aligned liquid crystal film 101 shown in Fig. 2 includes a supporting substrate 20, an aligned liquid crystal layer 21 laminated on the supporting substrate 20, and an optical layer 22 laminated on the aligned liquid crystal layer 21 via an adhesive layer 19.

[0040] An example of a method for producing the aligned liquid crystal film 101 shown in Fig. 2 will be described with reference to Fig. 1 and Figs. 3A to D. Figs. 3A to D are cross-sectional views illustrating steps in an example of a method for producing the aligned liquid crystal film 101 shown in Fig. 2.

[0041] First, an aligned liquid crystal layer-containing film 10 is prepared in which an aligned liquid crystal layer 21 is laminated on a supporting substrate 20 (FIG. 3A). The aligned liquid crystal layer-containing film 10 is obtained, for example, by applying a liquid crystal composition containing a liquid crystal compound onto the supporting substrate 20, aligning the liquid crystal compound in a predetermined direction, and then fixing the aligned state.

[0042] Next, an adhesive is applied to the surface of the aligned liquid crystal layer 21 by a coating device 11 (see FIG. 1) to form a coating layer 12 (FIG. 3B).

[0043] Next, between the first laminating roll 15 and the second laminating roll 16 (see FIG. 1), the aligned liquid crystal layer-containing film 10 and the optical layer-containing film 13 including the support substrate 23 and the optical layer 22 are laminated via the coating layer 12 to form the laminate 17 (FIG. 3C). At this time, the laminate 17 is formed in a state where the optical layer 22 is in contact with the coating layer 12.

[0044] Next, active energy rays are irradiated to the laminate 17 by an active energy ray irradiation device 18 (see FIG. 1) to cure the adhesive in the coating layer 12 and form an adhesive layer 19, and then the support substrate 23 is peeled off from the optical layer 22. Through the above steps, an oriented liquid crystal film 101 shown in FIG. 3D is obtained. Note that the support substrate 23 may not be peeled off and may be used as an oriented liquid crystal film while remaining attached to the optical layer 22.

[0045] In order to produce an oriented liquid crystal film having superior heat durability, the absolute value of the difference between the retardation of the oriented liquid crystal layer 21 in FIG. 3A and the retardation of the oriented liquid crystal layer 21 in FIG. 3D is preferably 3.2 nm or less. There is no particular preferable lower limit of the absolute value of the difference, and it may be 0 nm, but from the viewpoint of reducing manufacturing costs, the absolute value of the difference is preferably 1.5 nm or more. The absolute value of the difference can be adjusted, for example, by changing at least one of the temperature of the adhesive applied in the application step, the tension applied to the laminate 17 in the irradiation step, and the integrated light amount of the active energy rays irradiated to the laminate 17 in the irradiation step.

[0046] The oriented liquid crystal film 101 may be used as an optical component as it is. In this case, the supporting substrate 20 constitutes a part of the oriented liquid crystal film 101. Alternatively, the supporting substrate 20 may be peeled off from the oriented liquid crystal layer 21 as in the oriented liquid crystal film 102 shown in FIG. 4. On the surface of the oriented liquid crystal layer 21 exposed by peeling off the supporting substrate 20, an appropriate adhesive layer 30 may be laminated as in the oriented liquid crystal film 103 shown in FIG. 5, or an optical layer 41 may be laminated via an adhesive layer 40 as in the oriented liquid crystal film 104 shown in FIG. 6.

[0047] The adhesive constituting the adhesive layer 30 is not particularly limited, and an adhesive having an acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based polymer, a rubber-based polymer, or the like as a base polymer can be appropriately selected and used. In particular, adhesives such as acrylic adhesives and rubber-based adhesives that have excellent transparency, moderate wettability, cohesiveness, and adhesiveness, and excellent weather resistance and heat resistance are preferred. The thickness of the adhesive layer 30 is appropriately set depending on the type of adherend, and is, for example, 5 μm or more and 500 μm or less.

[0048] The adhesive layer 30 is laminated on the aligned liquid crystal layer 21, for example, by laminating an adhesive formed in advance into a sheet shape onto the surface of the aligned liquid crystal layer 21. Alternatively, the adhesive layer 30 may be formed by applying an adhesive composition onto the aligned liquid crystal layer 21, followed by drying of the solvent, crosslinking, photocuring, or the like. In order to increase the adhesive strength (anchor strength) between the aligned liquid crystal layer 21 and the adhesive layer 30, the surface of the aligned liquid crystal layer 21 may be subjected to a surface treatment such as a corona treatment or a plasma treatment, or an easy-adhesion layer may be formed, and then the adhesive layer 30 may be laminated.

[0049] As shown in Fig. 5, a release liner 31 is preferably temporarily attached to the surface of the adhesive layer 30. The release liner 31 protects the surface of the adhesive layer 30, for example, until the adhesive-attached aligned liquid crystal film 103 is bonded to an image display cell 50 (see Fig. 7) described below. The release liner 31 is preferably made of a plastic film made of acrylic, polyolefin, cyclic polyolefin, polyester, or the like. The release liner 31 has a thickness of, for example, 5 µm or more and 200 µm or less. The surface of the release liner 31 is preferably subjected to a release treatment. Examples of the release agent used in the release treatment include silicone-based materials, fluorine-based materials, long-chain alkyl-based materials, and fatty acid amide-based materials.

[0050] 6, the aligned liquid crystal film 104 may be manufactured by first adhering the aligned liquid crystal layer 21 and the optical layer 22 with an adhesive, and then adhering the aligned liquid crystal layer 21 and the optical layer 41 with an adhesive, or the aligned liquid crystal layer 21 and the optical layer 41 may be adhering the aligned liquid crystal layer 21 and the optical layer 22 with an adhesive. The aligned liquid crystal layer 21 and the optical layer 22, and the aligned liquid crystal layer 21 and the optical layer 41 may be simultaneously adhering with an adhesive. An adhesive layer (not shown) may be further laminated on the optical layer 22 or the optical layer 41, and a release liner (not shown) may be temporarily attached to the surface of the adhesive layer.

[0051] Next, materials used in the method for producing an oriented liquid crystal film according to this embodiment will be described.

[0052] [Liquid crystal composition] Examples of the liquid crystal compound contained in the liquid crystal composition include rod-shaped liquid crystal compounds and discotic liquid crystal compounds. A rod-shaped liquid crystal compound is preferable as the liquid crystal compound because it is easy to achieve homogeneous alignment due to the alignment regulating force of the support substrate 20. The rod-shaped liquid crystal compound may be a polymer. For example, the rod-shaped liquid crystal compound may be a liquid crystal polymer (more specifically, a main-chain liquid crystal polymer, a side-chain liquid crystal polymer, etc.) or a polymerized product of a polymerizable liquid crystal compound. As long as the liquid crystal compound (monomer) before polymerization exhibits liquid crystallinity, it may not exhibit liquid crystallinity after polymerization.

[0053] The liquid crystal compound is preferably a thermotropic liquid crystal that exhibits liquid crystallinity upon heating. Thermotropic liquid crystals undergo phase transition between a crystal phase, a liquid crystal phase, and an isotropic phase with a change in temperature. The liquid crystal compound contained in the liquid crystal composition may be any of nematic liquid crystals, smectic liquid crystals, and cholesteric liquid crystals. Nematic liquid crystals may be provided with cholesteric alignment by adding a chiral agent.

[0054] Examples of rod-shaped liquid crystal compounds exhibiting thermotropic properties include azomethine compounds, azoxy compounds, cyanobiphenyl compounds, cyanophenyl ester compounds, benzoate compounds, cyclohexanecarboxylic acid phenyl ester compounds, cyanophenylcyclohexane compounds, cyano-substituted phenylpyrimidine compounds, alkoxy-substituted phenylpyrimidine compounds, phenyldioxane compounds, tolane compounds, and alkenylcyclohexylbenzonitrile compounds.

[0055] Examples of the polymerizable liquid crystal compound include a polymerizable liquid crystal compound in which the alignment state of a rod-shaped liquid crystal compound can be fixed by using a polymer binder, a polymerizable liquid crystal compound having a polymerizable functional group in which the alignment state of a liquid crystal compound can be fixed by polymerization, etc. Among these, a photopolymerizable liquid crystal compound having a photopolymerizable functional group is preferred.

[0056] The photopolymerizable liquid crystal compound (liquid crystal monomer) has a mesogen group and at least one photopolymerizable functional group in one molecule. The temperature at which the liquid crystal monomer exhibits liquid crystallinity (liquid crystal phase transition temperature) is preferably 40°C or higher and 200°C or lower, more preferably 50°C or higher and 150°C or lower, and even more preferably 55°C or higher and 100°C or lower.

[0057] Examples of the mesogenic group of the liquid crystal monomer include cyclic structures such as a biphenyl group, a phenylbenzoate group, a phenylcyclohexane group, an azoxybenzene group, an azobenzene group, a phenylpyrimidine group, a diphenylacetylene group, a diphenylbenzoate group, a bicyclohexane group, a cyclohexylbenzene group, a terphenyl group, etc. The terminals of these cyclic units may be substituted with a cyano group, an alkyl group, an alkoxy group, a halogen group, etc.

[0058] Examples of photopolymerizable functional groups include (meth)acryloyl groups, epoxy groups, vinyl ether groups, and the like. Among them, (meth)acryloyl groups are preferred. The liquid crystal monomer preferably has two or more photopolymerizable functional groups in one molecule. By using a liquid crystal monomer containing two or more photopolymerizable functional groups, a crosslinked structure is introduced into the liquid crystal layer after photocuring, which tends to improve the durability of the oriented liquid crystal film.

[0059] As the liquid crystal monomer, any suitable liquid crystal monomer may be adopted. For example, WO 00 / 37585, U.S. Pat. No. 5,211,877, U.S. Pat. No. 4,388,453, WO 93 / 22397, EP 0261712, DE 19504224, DE 4408171, UK 2280445, JP 2017-206460 A, WO 2014 / 126113 A, WO 2016 / 114348 A, WO 2014 / 010325 A, JP 2015-2008 A, Compounds described in JP-A-77, JP-A-2010-31223, WO-2011 / 050896, JP-A-2011-207765, JP-A-2010-31223, JP-A-2010-270108, WO-2008 / 119427, JP-A-2008-107767, JP-A-2008-273925, WO-2016 / 125839, JP-A-2008-273925, etc. can be used as liquid crystal monomers. By selecting the liquid crystal monomer, it is also possible to adjust the expression of birefringence and the wavelength dispersion of retardation.

[0060] In addition to the liquid crystal monomer, the liquid crystal composition may contain a compound (alignment control agent) that controls the alignment of the liquid crystal monomer in a predetermined direction. For example, by including a side-chain liquid crystal polymer in the liquid crystal composition, the liquid crystal compound (monomer) can be aligned homeotropically. In addition, by adding a chiral agent to the liquid crystal composition, the liquid crystal compound can be aligned cholesterically.

[0061] The liquid crystal composition may contain a photopolymerization initiator. When the liquid crystal monomer is cured by irradiation with ultraviolet light, the liquid crystal composition preferably contains a photoradical polymerization initiator (photoradical generator) that generates radicals by irradiation with light in order to promote photocuring. Depending on the type of liquid crystal monomer (type of photopolymerizable functional group), a photocation generator or a photoanion generator may be used. The amount of the photopolymerization initiator used is, for example, 0.01 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the liquid crystal monomer. In addition to the photopolymerization initiator, a sensitizer or the like may be used.

[0062] A liquid crystal composition can be prepared by mixing the liquid crystal monomer and, if necessary, various alignment control agents, polymerization initiators, etc., with a solvent. The solvent is not particularly limited as long as it can dissolve the liquid crystal monomer and does not corrode (or has low corrosive properties) the support substrate 20, and examples of the solvent include halogenated hydrocarbon compounds such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and orthodichlorobenzene; phenolic compounds such as phenol and parachlorophenol; aromatic hydrocarbon compounds such as benzene, toluene, xylene, methoxybenzene, and 1,2-dimethoxybenzene; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, N-methyl- Examples of the solvent include ketone solvents such as 2-pyrrolidone, ester solvents such as ethyl acetate and butyl acetate, alcohol solvents such as t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, and 2-methyl-2,4-pentanediol, amide solvents such as dimethylformamide and dimethylacetamide, nitrile solvents such as acetonitrile and butyronitrile, ether solvents such as diethyl ether, dibutyl ether, and tetrahydrofuran, and cellosolve solvents such as ethyl cellosolve and butyl cellosolve. A mixed solvent of two or more solvents may be used.

[0063] The solid content of the liquid crystal composition is, for example, 5% by weight to 60% by weight. The liquid crystal composition may contain additives such as a surfactant and a leveling agent.

[0064] [Supporting base material] The supporting substrate 20 and the supporting substrate 23 are not particularly limited as long as they are substrates that can be transported by a roll-to-roll method, but from the viewpoint of ease of transport, a film substrate (more specifically, a resin film substrate, etc.) is preferred. The supporting substrate 20 and the supporting substrate 23 may be made of the same type of material, or may be made of different types of materials. The thickness of the supporting substrate 20 and the supporting substrate 23 are not particularly limited, but are, for example, 1 μm or more and 500 μm or less. The thickness of the supporting substrate 20 and the supporting substrate 23 may be the same or different. The supporting substrate 20 has a first main surface and a second main surface, and a liquid crystal composition is applied onto the first main surface.

[0065] The resin material constituting the resin film substrate is not particularly limited as long as it is insoluble in the solvent of the liquid crystal composition and has heat resistance when heated to align the liquid crystal composition, and examples of the resin material include polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cyclic polyolefins such as norbornene-based polymers; cellulose-based polymers such as diacetyl cellulose and triacetyl cellulose; acrylic polymers; styrene-based polymers; polycarbonates; polyamides; polyimides, etc.

[0066] The support substrate 20 may have an orientation ability for orienting the liquid crystal compound in a predetermined direction. For example, by using a stretched film as the support substrate 20, it is possible to homogeneously align the liquid crystal compound along the stretching direction. The stretching ratio of the stretched film may be such that it can exert its orientation ability, for example, 1.1 times or more and 5 times or less. The stretched film may be a biaxially stretched film. Even if a biaxially stretched film is used, if the stretching ratios in the longitudinal direction and the transverse direction are different, the liquid crystal compound can be oriented along the direction with the larger stretching ratio. The stretched film may be an obliquely stretched film. By using an obliquely stretched film as the support substrate 20, the liquid crystal compound can be oriented in a direction that is not parallel to either the longitudinal direction or the transverse direction of the support substrate 20.

[0067] The support substrate 20 may have an alignment film on the first main surface. An appropriate alignment film may be selected depending on the type of liquid crystal compound, the material of the support substrate 20, and the like. As an alignment film for homogeneously aligning the liquid crystal compound in a predetermined direction, a polyimide-based or polyvinyl alcohol-based alignment film that has been subjected to a rubbing treatment is preferably used. A photo-alignment film may also be used. A resin film serving as the support substrate 20 may be subjected to a rubbing treatment without providing an alignment film.

[0068] The support substrate 20 may include an alignment film for homeotropically aligning the liquid crystal compound. Examples of alignment agents for forming an alignment film (vertical alignment film) with homeotropic alignment include lecithin, stearic acid, hexadecyltrimethylammonium bromide, octadecylamine hydrochloride, monobasic carboxylate chromium complex, organic silane (more specifically, silane coupling agent, siloxane compound, etc.), perfluorodimethylcyclohexane, tetrafluoroethylene, polytetrafluoroethylene, etc.

[0069] [Alignment liquid crystal layer] When the liquid crystal compound is a thermotropic liquid crystal, a liquid crystalline composition is applied onto the first main surface of the supporting substrate 20, and the liquid crystal compound is oriented in a liquid crystal state by heating.

[0070] The method for applying the liquid crystalline composition onto the supporting substrate 20 is not particularly limited, and may be spin coating, die coating, kiss roll coating, gravure coating, reverse coating, spray coating, Mayer bar coating, knife roll coating, air knife coating, etc. After applying the liquid crystalline composition, the solvent is removed to form a liquid crystalline composition layer on the supporting substrate 20. The thickness of the applied layer formed by applying the liquid crystalline composition is preferably adjusted so that the thickness of the liquid crystalline composition layer after the solvent removal is 0.1 μm or more and 20 μm or less.

[0071] The liquid crystal composition layer formed on the support substrate 20 is heated to a liquid crystal phase, whereby the liquid crystal compound is aligned, and an aligned liquid crystal layer 21 is formed. Specifically, after the liquid crystal composition is applied onto the support substrate 20, the liquid crystal composition is heated to a temperature equal to or higher than the N (nematic phase)-I (isotropic liquid phase) transition temperature of the liquid crystal composition to make the liquid crystal composition into an isotropic liquid state. From there, the liquid crystal composition is gradually cooled as necessary to express the nematic phase. At this time, it is desirable to hold the temperature at which the liquid crystal phase is exhibited once, and grow the liquid crystal phase domain to form a monodomain. Alternatively, after the liquid crystal composition is applied onto the support substrate 20, the temperature may be held for a certain period of time within the temperature range at which the nematic phase is expressed, to align the liquid crystal compound in a predetermined direction.

[0072] The heating temperature for aligning the liquid crystal compound in a predetermined direction may be appropriately selected depending on the type of liquid crystal composition, and is, for example, 40°C or more and 200°C or less. If the heating temperature is too low, the transition to the liquid crystal phase tends to be insufficient, and if the heating temperature is too high, the alignment defects may increase. The heating time may be adjusted so that the liquid crystal phase domain grows sufficiently, and is, for example, 30 seconds or more and 30 minutes or less.

[0073] After the liquid crystal compound is oriented by heating, it is preferable to cool the liquid crystal compound to a temperature equal to or lower than the glass transition temperature. The cooling method is not particularly limited, and for example, the liquid crystal compound may be taken out from the heated atmosphere to room temperature. Forced cooling such as air cooling or water cooling may also be performed.

[0074] By irradiating the aligned photopolymerizable liquid crystal compound with light, the photopolymerizable liquid crystal compound (liquid crystal monomer) is photocured in a state of having liquid crystal regularity. The irradiated light may be any light capable of polymerizing the photopolymerizable liquid crystal compound, and typically, ultraviolet light or visible light having a wavelength of 250 nm or more and 450 nm or less is used. When the liquid crystal composition contains a photopolymerization initiator, light having a wavelength to which the photopolymerization initiator is sensitive may be selected. As the irradiation light source, a low pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a metal halide lamp, a xenon lamp, an LED, a black light, a chemical lamp, or the like is used. In order to promote the photocuring reaction, it is preferable to perform the light irradiation under an inert gas atmosphere such as nitrogen gas.

[0075] When the liquid crystal composition is photocured, the liquid crystal compound can be aligned in a predetermined direction by using polarized light in a predetermined direction. As described above, when the liquid crystal compound is aligned by the alignment regulating force of the support substrate 20, the irradiated light may be unpolarized (natural light).

[0076] The irradiation intensity of the irradiation light may be appropriately adjusted depending on the composition of the liquid crystal composition, the amount of the photopolymerization initiator added, etc. The irradiation energy (integral light amount) is, for example, 20 mJ / cm 2 More than 10000mJ / cm 2 Less than 50 mJ / cm 2 More than 5000mJ / cm 2 It is preferable that the concentration is less than 100 mJ / cm 2 More than 800mJ / cm 2 It is more preferable that the photocuring reaction is performed under heating conditions.

[0077] The polymerized product after the liquid crystal monomer is photocured by irradiation with light is non-liquid crystal, and no phase transition occurs due to temperature change. Therefore, the liquid crystal layer photocured in a state in which the liquid crystal monomer is oriented in a predetermined direction is usually unlikely to undergo change in molecular orientation. In addition, since the oriented liquid crystal film has a significantly larger birefringence Δn than a film made of a non-liquid crystal material, the thickness of the optically anisotropic element having the desired retardation can be significantly reduced. The thickness of the oriented liquid crystal layer 21 may be set according to the desired retardation value, for example, from 0.1 μm to 20 μm, preferably from 0.2 μm to 10 μm, and more preferably from 0.5 μm to 7 μm.

[0078] The optical properties of the aligned liquid crystal layer 21 are not particularly limited. The in-plane retardation and thickness direction retardation of the aligned liquid crystal layer 21 may be appropriately set according to the application. When the liquid crystal compound is homogeneously aligned in the aligned liquid crystal layer 21, the in-plane retardation of the aligned liquid crystal layer 21 is, for example, 20 nm or more and 1000 nm or less. When the aligned liquid crystal layer 21 is a quarter-wave plate, the in-plane retardation is preferably 100 nm or more and 180 nm or less, and more preferably 120 nm or more and 150 nm or less. When the aligned liquid crystal layer 21 is a half-wave plate, the in-plane retardation is preferably 200 nm or more and 340 nm or less, and more preferably 240 nm or more and 300 nm or less. When the liquid crystal compound in the aligned liquid crystal layer 21 is homeotropically aligned, the in-plane retardation of the aligned liquid crystal layer 21 is approximately 0 (for example, 5 nm or less, preferably 3 nm or less), and the absolute value of the thickness direction retardation is, for example, 30 nm or more and 500 nm or less.

[0079] When the liquid crystal compound is homogeneously aligned in the aligned liquid crystal layer 21, the birefringence Δn of the aligned liquid crystal layer 21 after the lamination step is preferably 0.03 or more in order to reduce the thickness of the optically anisotropic element. When the liquid crystal compound is homogeneously aligned in the aligned liquid crystal layer 21, the birefringence Δn of the aligned liquid crystal layer 21 after the lamination step is preferably 0.5 or less in order to easily adjust the in-plane retardation of the aligned liquid crystal layer 21. The birefringence Δn of the aligned liquid crystal layer 21 can be adjusted, for example, by changing the type of liquid crystal compound used to form the aligned liquid crystal layer 21.

[0080] [Optical layer] The optical layer 22 and the optical layer 41 are not particularly limited. For example, a commonly used optically isotropic or optically anisotropic optical film can be used as the optical layer 22 and the optical layer 41 without any restrictions. Specific examples of the optical layer 22 and the optical layer 41 include a transparent film (more specifically, a retardation film, a polarizer protective film, etc.), a functional film (more specifically, a polarizer, a viewing angle widening film, a viewing angle limiting (peeping prevention) film, a brightness improving film, etc.). The optical layer 22 and the optical layer 41 may be a single layer or a laminate. The optical layer 22 and the optical layer 41 may be an aligned liquid crystal layer (another aligned liquid crystal layer). In addition, the optical layer 22 may be a polarizing plate in which a transparent protective film is attached to one or both sides of a polarizer. When the polarizing plate has a transparent protective film on one side, the polarizer and the aligned liquid crystal layer 21 may be attached to each other, or the transparent protective film and the aligned liquid crystal layer 21 may be attached to each other. The optical layer 22 and the optical layer 41 may be made of the same type of material or different types of materials. The thickness of the optical layer 22 and the optical layer 41 is appropriately adjusted according to the required optical performance, and is, for example, 0.1 μm or more and 1000 μm or less, and preferably 0.1 μm or more and 100 μm or less. The thickness of the optical layer 22 and the optical layer 41 may be the same or different.

[0081] [Adhesive layer] The adhesive constituting the adhesive layer 19 and the adhesive layer 40 is not particularly limited as long as it is active energy ray curable and optically transparent, and examples thereof include epoxy resin adhesives, silicone resin adhesives, acrylic resin adhesives, polyurethane adhesives, polyamide adhesives, polyether adhesives, etc. The adhesive layer 19 and the adhesive layer 40 may be composed of the same type of adhesive, or may be composed of different types of adhesives. The preferred range of the thickness of the adhesive layer 40 is the same as the preferred range of the thickness of the adhesive layer 19 described above. The thickness of the adhesive layer 19 and the thickness of the adhesive layer 40 may be the same or different.

[0082] The active energy ray curable adhesive is an adhesive that can be radically polymerized, cationic polymerized, or anionically polymerized by irradiation with active energy rays such as electron beams or ultraviolet rays. Among them, a photoradical polymerizable adhesive, a photocationic polymerizable adhesive, or a hybrid adhesive that uses both photocationic polymerization and photoradical polymerization, in which polymerization is initiated by ultraviolet irradiation, is preferred because they can be cured with low energy.

[0083] Examples of monomers for photo-radical polymerizable adhesives include compounds having a (meth)acryloyl group and compounds having a vinyl group. Among them, compounds having a (meth)acryloyl group are preferable. Examples of compounds having a (meth)acryloyl group include C 1-20 Examples of the photo-radical polymerizable adhesive include alkyl (meth)acrylates such as linear alkyl (meth)acrylates, alicyclic alkyl (meth)acrylates, and polycyclic alkyl (meth)acrylates; hydroxyl group-containing (meth)acrylates; and epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate. The photo-radical polymerizable adhesive may contain a nitrogen-containing monomer such as hydroxyethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, (meth)acrylamide, and (meth)acryloylmorpholine. The photo-radical polymerizable adhesive may contain a polyfunctional monomer such as tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, dioxane glycol diacrylate, and polyoxyethylene glycol diacrylate as a crosslinking component.

[0084] Examples of the curable component of the photo-cationically polymerizable adhesive include compounds having an epoxy group or an oxetanyl group. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in the molecule, and various commonly known curable epoxy compounds are used. Examples of preferred epoxy compounds include compounds having at least two epoxy groups and at least one aromatic ring in the molecule (aromatic epoxy compounds), compounds having at least two epoxy groups in the molecule, at least one of which is formed between two adjacent carbon atoms constituting an alicyclic ring (alicyclic epoxy compounds), and the like. A hybrid adhesive can also be made by adding a radically polymerizable compound such as a compound having a (meth)acryloyl group to the cationic polymerizable adhesive.

[0085] In order to obtain an adhesive with a small cure shrinkage rate, it is preferable to adjust the formulation of the adhesive so that the number of bonds formed when the adhesive is cured is reduced. In order to reduce the number of bonds formed, it is preferable to use a monomer with a high molecular weight per reactive functional group (e.g., (meth)acryloyl group, etc.). Examples of monomers with a high molecular weight per reactive functional group include alkyl (meth)acrylates (e.g., isostearyl acrylate, etc.) having an alkyl group with 10 or more, 12 or more, 14 or more, 16 or more, or 18 or more carbon atoms, and polyoxyethylene glycol diacrylates with 5 or more, 7 or more, or 9 or more oxyethylene groups per molecule.

[0086] In addition, when the adhesive before curing contains an oligomer having a weight average molecular weight of 1000 or more, an adhesive having a small cure shrinkage rate can be obtained. Examples of the oligomer having a weight average molecular weight of 1000 or more (hereinafter, sometimes referred to as "specific oligomer") include an oligomer (acrylic oligomer) formed from a monomer having a (meth)acryloyl group. The acrylic oligomer may have a cationic polymerizable functional group (e.g., an epoxy group, etc.).

[0087] The weight average molecular weight of the specific oligomer can be measured by gel permeation chromatography (GPC). In this specification, the weight average molecular weight of the specific oligomer is a standard polystyrene equivalent value measured under the following conditions unless otherwise specified.

[0088] (Molecular weight measurement conditions) GPC measuring device: Tosoh Corporation "HLC-8120GPC" Sample concentration: 2.0g / L (tetrahydrofuran solution) Sample injection volume: 20 μL Column: Tosoh Corporation "TSKgel, SuperAWM-H + superAW4000 + superAW2500" Column size: 6.0mm I.D. x 150mm Eluent: Tetrahydrofuran Flow rate: 0.4mL / min Detector: Differential refractometer (RI) Column temperature (measurement temperature): 40℃

[0089] The photocurable adhesive preferably contains a photopolymerization initiator. The photopolymerization initiator may be appropriately selected depending on the reactive species. For example, the photoradical polymerizable adhesive preferably contains a photoradical polymerization initiator that generates radicals upon light irradiation as the photopolymerization initiator. The photocationic polymerizable adhesive preferably contains a photocationic polymerization initiator (photoacid generator) that generates cationic species or Lewis acid upon light irradiation as the photopolymerization initiator. The hybrid adhesive preferably contains a photocationic polymerization initiator and a photoradical polymerization initiator.

[0090] The content of the photopolymerization initiator is, for example, 0.1 parts by weight to 10 parts by weight, preferably 0.5 parts by weight to 3 parts by weight, relative to 100 parts by weight of the monomer. If necessary, a photosensitizer can also be blended into the photocurable adhesive. The amount of the photosensitizer used is, for example, 0.001 parts by weight to 10 parts by weight, preferably 0.01 parts by weight to 3 parts by weight, relative to 100 parts by weight of the monomer.

[0091] The adhesive may contain appropriate additives as necessary, such as coupling agents, such as silane coupling agents and titanium coupling agents, adhesion promoters, such as ethylene oxide, ultraviolet absorbers, deterioration inhibitors, dyes, processing aids, ion trapping agents, antioxidants, tackifiers, fillers, plasticizers, leveling agents, foaming inhibitors, antistatic agents, heat stabilizers, and hydrolysis stabilizers.

[0092] [Application] The oriented liquid crystal film obtained by the manufacturing method according to this embodiment can be used, for example, as an optical film for displays for the purpose of improving visibility.

[0093] The oriented liquid crystal film obtained by the manufacturing method according to this embodiment may be a circular polarizing plate in which a polarizing plate as an optical layer 22 is bonded to one surface of the oriented liquid crystal layer 21 via an adhesive layer 19. The circular polarizing plate may include two or more oriented liquid crystal layers.

[0094] The polarizing plate may be composed of only one layer of polarizer, or may have a transparent protective film attached to one or both sides of the polarizer as described above. Examples of polarizers include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, which are uniaxially stretched after adsorbing dichroic substances such as iodine or dichroic dyes, and polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride.

[0095] Among them, polyvinyl alcohol (PVA) polarizers are preferred because they have a high polarization degree, and are prepared by adsorbing a dichroic substance such as iodine or a dichroic dye onto a polyvinyl alcohol film such as polyvinyl alcohol or partially formalized polyvinyl alcohol, and aligning the film in a predetermined direction. For example, a PVA polarizer can be obtained by dyeing a polyvinyl alcohol film with iodine and stretching the film. A PVA resin layer may be formed on a resin substrate, and the laminate may be dyed with iodine and stretched.

[0096] In a circular polarizing plate, it is preferable that at least one aligned liquid crystal layer has a liquid crystal compound aligned homogeneously. In the circular polarizing plate, the alignment direction of the liquid crystal compound in the aligned liquid crystal layer in which the liquid crystal compound is aligned homogeneously is neither parallel nor perpendicular to the absorption axis direction of the polarizer.

[0097] When the circular polarizer has only one aligned liquid crystal layer, for example, aligned liquid crystal layer 21 is a quarter-wave plate, and the angle between the absorption axis direction of the polarizer as optical layer 22 and the alignment direction of the liquid crystal compound (generally the slow axis direction) is set to 45°. The angle between the absorption axis direction of the polarizer and the alignment direction of the liquid crystal compound may be 35° or more and 55° or less, 40° or more and 50° or less, or 43° or more and 47° or less.

[0098] In a configuration in which a polarizing plate as the optical layer 22 and a quarter-wave plate as the aligned liquid crystal layer 21 are laminated so that the angle between the optical axes of the two is 45°, an aligned liquid crystal layer in which the liquid crystal compound is homeotropically aligned may be further provided as the optical layer 41 (see FIG. 6). By laminating the aligned liquid crystal layer 21 as the quarter-wave plate and the optical layer 41 functioning as a positive C plate in this order on the polarizing plate, a circular polarizing plate capable of blocking reflected light even from external light coming from an oblique direction can be formed. A homeotropically aligned liquid crystal layer (positive C plate) and a homogeneously aligned liquid crystal layer (quarter-wave plate as a positive A plate) may be laminated in this order on the polarizing plate.

[0099] When the oriented liquid crystal film 104 shown in FIG. 6 is a circular polarizer in which an oriented liquid crystal layer 21 and an oriented liquid crystal layer 41 are sequentially laminated on a polarizer as the optical layer 22, both the oriented liquid crystal layer 21 and the optical layer 41 may be homogeneously oriented liquid crystal layers. In this case, it is preferable that the oriented liquid crystal layer 21 arranged closer to the optical layer 22 is a half-wave plate, and the optical layer 41 arranged farther from the optical layer 22 is a quarter-wave plate. In this layer structure, it is preferable to arrange the half-wave plate so that the angle between the slow axis direction of the half-wave plate and the absorption axis direction of the polarizer is 75°±5°, and the angle between the slow axis direction of the quarter-wave plate and the absorption axis direction of the polarizer is 15°±5°. A circular polarizer having such a layer structure functions as a circular polarizer over a wide wavelength range of visible light, and thus can reduce coloring of reflected light.

[0100] <Image display device> 7 is a cross-sectional view showing an example of the layer structure of an image display device, in which an oriented liquid crystal film (obtained by the manufacturing method according to the present embodiment) having an oriented liquid crystal layer 21 is bonded to the surface of an image display cell 50 via an adhesive layer 30. The oriented liquid crystal film may have two or more oriented liquid crystal layers. Examples of the image display cell 50 include a liquid crystal cell and an organic EL cell.

[0101] As described above, the aligned liquid crystal film obtained by the manufacturing method according to the present embodiment has improved heat durability of the aligned liquid crystal layer 21. Therefore, the image display device 200 shown in Fig. 7 has little change in visibility and excellent heat durability because the retardation of the aligned liquid crystal layer 21 changes little even when exposed to a high-temperature environment for a long period of time. EXAMPLES

[0102] The present invention will be described in more detail below with reference to examples of preparing oriented liquid crystal films, but the present invention is not limited to the following examples.

[0103] <Preparation of Adhesive A-1> An ultraviolet-curing adhesive A-1 was prepared by mixing the components shown in Table 1 in the content ratios shown in Table 1. In Table 1, each value of the content ratio is the content ratio relative to the total amount of the adhesive.

[0104] The meaning of each term in Table 1 is as follows: HEAA: Hydroxyethylacrylamide ("HEAA (registered trademark)" manufactured by KJ Chemicals) M-5700: Acrylate monomer ("Aronix (registered trademark) M-5700" manufactured by Toagosei Co., Ltd.) P2H-A: Phenoxydiethylene glycol acrylate (Kyoeisha Chemical Co., Ltd. "Light Acrylate (registered trademark) P2H-A") M-220: Acrylate monomer ("Aronix (registered trademark) M-220" manufactured by Toagosei Co., Ltd.) 1,9ND-A: 1,9-nonanediol diacrylate ("Light Acrylate (registered trademark) 1,9ND-A" manufactured by Kyoeisha Chemical Co., Ltd.) UP-1190: Acrylic oligomer ("ARUFON (registered trademark) UP-1190" manufactured by Toagosei Co., Ltd., weight average molecular weight: 1700) Omnirad 907: Photoradical polymerization initiator (IGM Resins "Omnirad (registered trademark) 907") DETX-S: Photoradical polymerization initiator ("KAYACURE (registered trademark) DETX-S" manufactured by Nippon Kayaku Co., Ltd.)

[0105] [Table 1]

[0106] <Preparation of Laminate L-1> A photopolymerizable liquid crystal compound exhibiting a nematic liquid crystal phase (BASF's "Paliocolor (registered trademark) LC242") was dissolved in cyclopentanone to prepare a solution with a solid content concentration of 30% by weight. A surfactant (BYK Japan's "BYK (registered trademark)-360") and a photopolymerization initiator (IGM Resins' "Omnirad (registered trademark) 907") were added to this solution to prepare a liquid crystal composition. The amounts of the surfactant and photopolymerization initiator added were 0.01 parts by weight and 3 parts by weight, respectively, relative to 100 parts by weight of the photopolymerizable liquid crystal compound.

[0107] A laterally stretched film (ZEONORFILM® ZT12-50135, manufactured by ZEON Corporation, thickness: 52 μm, in-plane retardation: 50 nm) was used as the film substrate. The above liquid crystal composition was applied to the surface of the film substrate using a bar coater so that the thickness after heating would be 1.4 μm, and the liquid crystal compound was aligned by heating at a temperature of 100° C. for 3 minutes. Next, the liquid crystal composition on the film substrate was cooled to room temperature (25° C.), and then exposed to an accumulated light amount of 400 mJ / cm under a nitrogen atmosphere. 2 The liquid crystalline composition was irradiated with ultraviolet light to perform photocuring, thereby obtaining a laminate L-1 in which a homogeneously aligned liquid crystal layer was formed on the film substrate.

[0108] The in-plane retardation of the aligned liquid crystal layer in the obtained laminate L-1 was measured. In detail, first, an acrylic adhesive sheet having a thickness of 15 μm was attached to the surface of the aligned liquid crystal layer of the laminate L-1, and then the adhesive sheet was attached to a glass plate to obtain a laminate with a glass plate. Next, the film substrate was peeled off from the laminate with the glass plate to obtain a measurement sample. Next, the in-plane retardation of the measurement sample (aligned liquid crystal layer) at a wavelength of 590 nm was measured using a retardation meter (Oji Scientific Instruments Co., Ltd.'s "KOBRA (registered trademark) 21-ADH"). Hereinafter, the in-plane retardation measured here is referred to as Re1. Re1 was 140 nm.

[0109] <Preparation of oriented liquid crystal film> [Preparation of Aligned Liquid Crystal Film of Example 1] A film ("MCP-N(100)" manufactured by Dai Nippon Printing Co., Ltd., hereinafter referred to as "Laminate L-2") having a homeotropic alignment liquid crystal layer (thickness: 3 μm, in-plane retardation: 0 nm) as an optical layer on a substrate was prepared. Also, laminate L-1 was produced by the above-mentioned method.

[0110] The above-mentioned adhesive A-1 (temperature: 25°C) was applied to the surface of the aligned liquid crystal layer of the laminate L-1 so that the thickness of the layer (adhesive layer) made of the adhesive A-1 after curing was 1.0 μm. Next, the surface of the aligned liquid crystal layer side of the laminate L-2 was attached to the coating layer made of the adhesive A-1 to obtain the laminate L-3.

[0111] Next, in imitation of a lamination process by a roll-to-roll method, the adhesive A-1 in the laminate L-3 was photocured while tension was applied to the laminate L-3. In detail, in an atmosphere at a temperature of 25° C., a tension of 538 N / 1000 mm width was applied to the laminate L-3 in a direction perpendicular to the alignment direction of the homogeneously aligned liquid crystal layer in the laminate L-1, and an illuminance of 600 mW / cm 2 A high-pressure mercury lamp is used, with an integrated light output of 600 mJ / cm 2 The adhesive A-1 was photocured by irradiating ultraviolet rays under the conditions above. The ultraviolet irradiation was performed from the laminate L-2 side. The orientation direction of the homogeneously aligned liquid crystal layer in the laminate L-1 is the stretching direction of the film substrate (laterally stretched film) of the laminate L-1. Therefore, in the lamination process by the roll-to-roll method, the direction perpendicular to the orientation direction of the homogeneously aligned liquid crystal layer in the plane is the transport direction of the laminate L-3. Next, the substrate of the laminate L-2 was peeled off from the laminate L-3 to obtain the aligned liquid crystal film of Example 1.

[0112] [Preparation of Aligned Liquid Crystal Films in Examples 2 to 4] The aligned liquid crystal films of Examples 2 to 4 were each produced in the same manner as in Example 1, except that the integrated amount of light used to photo-cure the adhesive was changed as shown in Table 2 below.

[0113] [Preparation of Aligned Liquid Crystal Films in Examples 5 to 7 and Comparative Example 1] The aligned liquid crystal films of Examples 5 to 7 and Comparative Example 1 were each produced in the same manner as in Example 1, except that the temperature of the adhesive when applying the adhesive was changed as shown in Table 3 below. For reference, Table 3 also shows the details of Example 1 described above.

[0114] [Preparation of Aligned Liquid Crystal Films in Example 8, Example 9, and Comparative Example 2] The oriented liquid crystal films of Example 8, Example 9, and Comparative Example 2 were each produced in the same manner as Example 1, except that the tension applied to the laminate L-3 was changed as shown in Table 4 described below. For reference, Table 4 also shows the details of Example 1 described above.

[0115] <Evaluation> [Change in retardation before and after adhesion] An acrylic adhesive sheet having a thickness of 15 μm was attached to the surface of the homeotropic aligned liquid crystal layer of the aligned liquid crystal film to be evaluated (any of the aligned liquid crystal films of Examples 1 to 9, Comparative Example 1, and Comparative Example 2), and then the adhesive sheet was attached to a glass plate to obtain a laminate with the glass plate. Next, the film substrate was peeled off from the laminate with the glass plate to obtain an evaluation sample. Next, the in-plane retardation of the evaluation sample (homogeneously aligned liquid crystal layer) at a wavelength of 590 nm was measured using a retardation meter (Oji Scientific Instruments Co., Ltd.'s "KOBRA (registered trademark) 21-ADH"). Hereinafter, the in-plane retardation measured here is referred to as Re2. Then, the retardation change (unit: nm) before and after adhesion was calculated according to the formula "retardation change before and after adhesion = |Re2-Re1|". Here, |Re2-Re1| represents the absolute value of the difference between Re2 and Re1. When the retardation change before and after adhesion was 3.2 nm or less, it was evaluated as "the retardation change before and after adhesion was suppressed." On the other hand, when the retardation change before and after adhesion was more than 3.2 nm, it was evaluated as "the retardation change before and after adhesion was not suppressed."

[0116] In addition, for the oriented liquid crystal film of Example 1, the birefringence Δn was calculated from Re2 and the thickness of the homogeneously aligned liquid crystal layer according to the formula "birefringence Δn = Re2 / thickness of homogeneously aligned liquid crystal layer", and the birefringence Δn of the homogeneously aligned liquid crystal layer was 0.10.

[0117] [Retardation change rate before and after heat durability test] The evaluation sample used in the evaluation of [Change in retardation before and after adhesion] was placed in an air-circulating thermostatic oven at 85°C for 120 hours. Next, the evaluation sample was removed from the oven, and the in-plane retardation of the evaluation sample (homogeneously aligned liquid crystal layer) at a wavelength of 590 nm was measured using a retardation meter (Oji Scientific Instruments' "KOBRA (registered trademark) 21-ADH"). Hereinafter, the in-plane retardation measured here is referred to as Re3. The retardation change rate (unit: %) before and after the heat durability test was calculated according to the formula "Retardation change rate before and after heat durability test = 100 x |Re3-Re2| / Re2". Note that |Re3-Re2| represents the absolute value of the difference between Re3 and Re2. When the retardation change rate before and after the heat durability test was 3.5% or less, it was evaluated as "the change in optical properties can be suppressed even when exposed to a high temperature environment for a long time." On the other hand, when the retardation change rate before and after the heat durability test exceeded 3.5%, it was evaluated as "not being able to suppress the change in optical properties when exposed to a high-temperature environment for a long period of time."

[0118] After the heat durability test, no delamination occurred in any of the evaluation samples, and adhesion reliability was ensured.

[0119] For each of the above-mentioned Examples and Comparative Examples, the retardation change before and after adhesion and the retardation change rate before and after the heat durability test are shown together with the preparation conditions, etc. in Tables 2 to 4. In Tables 2 to 4, "ΔRe" indicates the retardation change before and after adhesion, and "Re change rate" indicates the retardation change rate before and after the heat durability test.

[0120] [Table 2]

[0121] [Table 3]

[0122] [Table 4]

[0123] In Examples 1 to 9, the temperature of the adhesive when applied was 0°C or higher and 45°C or lower, and the tension applied to the laminate L-3 was 70N / 1000mm width or higher and 550N / 1000mm width or lower. In Examples 1 to 9, the retardation change rate before and after the heat durability test was 3.5% or lower. Therefore, the oriented liquid crystal films of Examples 1 to 9 were able to suppress changes in optical properties even when exposed to a high-temperature environment for a long period of time.

[0124] In Comparative Example 1, the temperature of the adhesive when applied exceeded 45°C. In Comparative Example 2, the tension applied to the laminate L-3 exceeded 550N / 1000mm width. In Comparative Examples 1 and 2, the retardation change rate before and after the heat durability test exceeded 3.5%. Thus, the oriented liquid crystal films of Comparative Examples 1 and 2 could not suppress the change in optical properties when exposed to a high-temperature environment for a long time.

[0125] The above results show that the method for producing an aligned liquid crystal film according to the present invention makes it possible to produce an aligned liquid crystal film whose optical properties change little even when exposed to a high-temperature environment for a long period of time. [Explanation of symbols]

[0126] 17 Laminate 19, 40 Adhesive layer 21 Alignment liquid crystal layer 22, 41 optical layer 100, 101, 102, 103, 104 Oriented liquid crystal film

Claims

1. A method for manufacturing an oriented liquid crystal film comprising an oriented liquid crystal layer in which liquid crystal compounds are oriented, The process includes a bonding step in which an oriented liquid crystal layer and an optical layer are bonded together using an active energy ray curing adhesive in a roll-to-roll manner. The aforementioned bonding process is, A coating step of applying the adhesive, which is uncured and at a temperature of 0°C to 45°C, to the surface of at least one of the oriented liquid crystal layer and the optical layer, An irradiation step in which an active energy ray is irradiated onto a laminate in which the oriented liquid crystal layer and the optical layer are laminated via the adhesive before curing, while applying a tension of 70 N / 1000 mm width or more and 550 N / 1000 mm width or less in the transport direction of the laminate. It has, A method for manufacturing an oriented liquid crystal film, wherein the liquid crystal compound in the oriented liquid crystal layer is homogeneously oriented.

2. The method for manufacturing an oriented liquid crystal film according to Claim 1, wherein in the irradiation step, the laminate is irradiated with the active energy ray under the condition of an integrated light amount of 450 mJ / cm² or more and 1200 mJ / cm² or less.

3. The method for manufacturing an oriented liquid crystal film according to Claim 1, wherein the thickness of the layer made of the adhesive after the irradiation step is 0.1 μm or more and 3.0 μm or less.

4. The method for manufacturing an oriented liquid crystal film according to Claim 1, wherein the birefringence Δn of the oriented liquid crystal layer after the lamination step is 0.03 or more.

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