Method for manufacturing aligned liquid crystal films

Abstract

To provide a manufacturing method of an alignment liquid crystal film that bonds an alignment liquid crystal layer and an optical layer, interposing an active energy ray-curable type adhesive agent, by a roll-to-roll method, the manufacturing method of an alignment liquid crystal film capable of manufacturing an alignment liquid crystal film with less change in optical characteristics even when exposed to a high temperature environment for a long period of time.SOLUTION: A manufacturing method of an alignment liquid crystal film includes a bonding process of bonding an alignment liquid crystal layer and an optical layer, interposing an active energy ray-curable type adhesive agent, by a roll-to-roll method. The bonding process includes a coating process and an irradiation process. In the coating process, an adhesive agent before curing of temperature 0°C to 45°C is applied onto a surface of at least one of the alignment liquid crystal layer and the optical layer. In the irradiation process, a laminate in which an alignment liquid crystal layer and an optical layer is laminated interposing an adhesive agent before curing is irradiated with an active energy ray, under a state where a tensile force of 70 N / 1000 mm width to 550 N / 1000 mm width is applied in a direction of transporting the laminate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing an oriented liquid crystal film comprising an oriented liquid crystal layer in which liquid crystal compounds are oriented. [Background technology]

[0002] As an optical film having functions such as optical compensation for liquid crystal displays and anti-reflective coating for organic EL displays, liquid crystal films (aligned liquid crystal films) equipped with an oriented liquid crystal layer in which liquid crystal compounds are oriented in a predetermined direction are used. Because oriented liquid crystal films have a larger birefringence Δn compared to stretched polymer films, they are advantageous for thinning and lightening image display devices (more specifically, liquid crystal displays, organic EL displays, etc.). In image display devices, the oriented liquid crystal film is laminated to an organic EL panel or liquid crystal display panel as a laminate in which it is integrally laminated with a polarizer, etc., via an adhesive or bonding agent (see, for example, Patent Document 1).

[0003] Liquid crystal compounds can be oriented in a predetermined direction by shear force applied when coating them onto a substrate or by the orientation-regulating force of the orientation film. By oriented liquid crystal compounds, oriented liquid crystal films with various optical anisotropies can be obtained. For example, a homogeneous oriented liquid crystal layer in which nematic liquid crystal molecules with positive refractive index anisotropy are oriented parallel to the substrate surface can be used as a positive A plate with refractive index anisotropy nx>ny=nz.

[0004] When using thermotropic liquid crystals, a solution containing a liquid crystal compound (liquid crystal composition) is applied to a substrate, and the liquid crystal compound in the composition is heated to orient it into a liquid crystal state. If the liquid crystal composition contains a photopolymerizable liquid crystal compound (liquid crystal monomer), the orientation is fixed by curing the liquid crystal composition by light irradiation after orienting the liquid crystal compound. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2015-7700 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Image display devices are increasingly required to have higher durability, and the optical components that make up these devices are required to exhibit minimal changes in optical properties (more specifically, retardation, etc.) even when exposed to high-temperature environments for extended periods.

[0007] On the other hand, the optical properties of the oriented liquid crystal film may change in high-temperature environments due to the influence of layers positioned adjacent to the oriented liquid crystal layer. For example, when the oriented liquid crystal layer and the optical layer (more specifically, a polarizer, transparent film, or other oriented liquid crystal layer) are bonded together via an adhesive layer, there is almost no change in retardation in high-temperature environments. In contrast, when the oriented liquid crystal layer and the optical layer are bonded together via an active energy ray curing adhesive, retardation tends to increase in high-temperature environments.

[0008] Furthermore, our investigations have revealed that the tendency for retardation to increase under the high-temperature environment described above is particularly pronounced when the oriented liquid crystal layer and the optical layer are bonded together using 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 manufacturing 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 using an active energy ray curable adhesive, and which enables the production of an oriented liquid crystal film that exhibits little change in optical properties even when exposed to a high-temperature environment for a long period of time. [Means for solving the problem]

[0010] The manufacturing method of the aligned liquid crystal film according to the present invention is a manufacturing method of an aligned liquid crystal film including an aligned liquid crystal layer in which a liquid crystal compound is aligned, and has a bonding step of bonding the aligned liquid crystal layer and an optical layer by a roll-to-roll method through an active energy ray curable adhesive. The bonding step includes a coating step and an irradiation step. In the coating step, the adhesive before curing and at a temperature of 0°C or higher and 45°C or lower is applied to at least one surface of the aligned liquid crystal layer and the optical layer. In the irradiation step, active energy rays are irradiated to the laminate in which the aligned liquid crystal layer and the optical layer are laminated through the adhesive before curing, with a tension of 70 N / 1000 mm width or more and 550 N / 1000 mm width or less applied in the conveyance direction of the laminate.

[0011] In one embodiment of the manufacturing method of the aligned liquid crystal film according to the present invention, in the irradiation step, with respect to the laminate, the active energy rays are irradiated under the condition that the integrated light quantity is 450 mJ / cm 2 or more and 1200 mJ / cm 2 or less.

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

[0013] In one embodiment of the manufacturing method of the aligned 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 manufacturing method of the aligned liquid crystal film according to the present invention, in the aligned liquid crystal layer, the liquid crystal compound is homogeneously aligned.

[0015] In one embodiment of the manufacturing method of the aligned liquid crystal film according to the present invention, the birefringence Δn of the aligned liquid crystal layer after the bonding step is 0.03 or more.

[0016] In one embodiment of the manufacturing method of the aligned liquid crystal film according to the present invention, the optical layer is a polarizer, a transparent film, or another aligned liquid crystal layer.

Advantages of the Invention

[0017] According to the method for manufacturing an aligned liquid crystal film according to the present invention, while having a bonding step of bonding an aligned liquid crystal layer and an optical layer by a roll-to-roll method through an active energy ray-curable adhesive, an aligned liquid crystal film with small changes in optical properties can be manufactured even when exposed to a high-temperature environment for a long time.

Brief Description of the Drawings

[0018] [Figure 1] It is an explanatory drawing for explaining an example of the method for manufacturing an aligned liquid crystal film according to the present invention. [Figure 2] It is a cross-sectional view showing an example of an aligned liquid crystal film in which an aligned liquid crystal layer and an optical layer are laminated via an adhesive. [Figure 3] A, B, C, and D are cross-sectional views of steps showing an example of the method for manufacturing the aligned liquid crystal film shown in FIG. 2. [Figure 4] It is a cross-sectional view showing an example of an aligned liquid crystal film in which an aligned liquid crystal layer and an optical layer are laminated via an adhesive. [Figure 5] It is a cross-sectional view showing an example of an aligned liquid crystal film provided with an adhesive layer. [Figure 6] It is a cross-sectional view showing an example of an aligned liquid crystal film in which an aligned liquid crystal layer and an optical layer are laminated via an adhesive. [Figure 7] It is a cross-sectional view showing an example of the layer configuration of an image display device.

Embodiments for Carrying Out the Invention

[0019] Hereinafter, preferred embodiments of the present invention will be described. 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 composed of the adhesive after irradiation with active energy rays (after curing) (hereinafter, may be simply referred to as the "adhesive layer") are obtained by observing a cross-section obtained by cutting the layer in the thickness direction with a transmission electron microscope (TEM), randomly selecting 10 measurement points from the cross-sectional image, and measuring the thickness of the selected 10 measurement points, and is the arithmetic mean value of the 10 measured values.

[0020] In the following, the compound name may be followed by "system" to refer to the compound and its derivatives collectively. When "system" is followed by a compound name to represent a polymer name, it means that the repeating unit of the polymer originates 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 for manufacturing aligned liquid crystal film> The method for manufacturing an oriented liquid crystal film according to this embodiment is a method for manufacturing an oriented liquid crystal film comprising an oriented liquid crystal layer in which liquid crystal compounds are oriented, and comprises a bonding step of bonding the oriented liquid crystal layer and an optical layer by a roll-to-roll method using an active energy ray curable adhesive. The bonding step comprises a coating step and an irradiation step. In the coating step, an adhesive that is not yet cured and is heated to a temperature of 0°C to 45°C is applied to the surface of at least one of the oriented liquid crystal layer and the optical layer. In the irradiation step, an active energy ray is irradiated onto the 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.

[0022] The method for manufacturing an oriented liquid crystal film according to this embodiment includes a bonding step in which an oriented liquid crystal layer and an optical layer are bonded together using an active energy ray curable adhesive in a roll-to-roll manner, while still producing an oriented liquid crystal film that exhibits minimal changes in optical properties even when exposed to high-temperature environments for extended periods. The reason for this is presumed to be as follows.

[0023] Generally, when manufacturing film products from film materials using a roll-to-roll method, the film material is processed under tension in the transport direction in order to transport it. As a result, film products manufactured using the roll-to-roll method tend to exhibit anisotropy in shrinkage stress between the longitudinal direction (transport direction during manufacturing) and the width direction, making them prone to residual stress. Consequently, film products manufactured using the roll-to-roll method tend to exhibit changes in optical properties (e.g., retardation) under high-temperature conditions. This tendency is particularly pronounced when the oriented liquid crystal layer and the optical layer are bonded together using a roll-to-roll method via an active energy ray curable adhesive, as described above.

[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 also set within a specific range, thereby suppressing the volume change (curing shrinkage) of the adhesive during curing. As a result, the generation of residual stress caused by the curing shrinkage of the adhesive is suppressed, making it possible to manufacture an oriented liquid crystal film that exhibits minimal changes in optical properties even when exposed to high-temperature environments for extended periods (hereinafter sometimes referred to as having "excellent heat resistance").

[0025] The embodiment will be described in detail below with reference to the drawings. Figures 1 to 7, for ease of understanding, schematically show the main components, and the size, number, shape, etc., of each component shown may differ from the actual dimensions due to the limitations of drawing creation. Furthermore, for the sake of explanation, in the drawings described later, components identical to those described earlier may be denoted by the same reference numerals, and their descriptions may be omitted.

[0026] Figure 1 is an explanatory diagram illustrating an example of a method for manufacturing an oriented liquid crystal film according to this embodiment. As shown in Figure 1, an adhesive is applied by a coating device 11 to the surface of an oriented liquid crystal layer-containing film 10 that is conveyed by a roll-to-roll method (more specifically, the surface of the oriented liquid crystal layer in the oriented liquid crystal layer-containing film 10) to form a coated layer 12 (coating process). In Figure 1, a die coater is used as the coating device 11, but in the present invention, the coating device is not limited, and a gravure coater, reverse coater, bar coater, or other coating device can be appropriately used depending on the viscosity of the adhesive, etc.

[0027] Next, the optical layer-containing film 13 and the alignment liquid crystal layer-containing film 10 are guided by the guide roll 14 and transported between the first lamination roll 15 and the second lamination roll 16, and as they pass through this space, they are laminated via the coating layer 12 to form a laminate 17. At this time, the optical layer in the optical layer-containing film 13 is in contact with the coating layer 12 when the laminate 17 is formed.

[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). During the irradiation step, the adhesive in the coating layer 12 hardens, forming an adhesive layer 19, and an oriented liquid crystal film 100 is obtained in which the oriented liquid crystal layer-containing film 10 and the optical layer-containing film 13 are bonded together via the adhesive layer 19. Examples of light sources for active energy rays include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, LEDs, black lights, chemical lamps, etc. The illuminance of the active energy ray light source is, for example, 100 mW / cm². 2 More than 1000mW / cm 2 The following, preferably 400 mW / cm² 2 More than 800mW / cm 2The following is the case. The active energy ray can be irradiated onto the surface on the side of the film 10 containing the aligned liquid crystal layer, the surface on the side of the film 13 containing the optical layer, or both surfaces of the laminate 17 according to the active energy ray transmittance of the film 10 containing the aligned liquid crystal layer and the film 13 containing the optical layer to be used.

[0029] In order to manufacture an aligned liquid crystal film excellent in heat resistance to heating, the thickness of the adhesive layer 19 is preferably 3.0 μm or less, more preferably 2.8 μm or less. Further, in order to manufacture an aligned liquid crystal film excellent in adhesion reliability, the thickness of the adhesive layer 19 is preferably 0.1 μm or more, more preferably 0.5 μm or more. In order to manufacture an aligned liquid crystal film excellent in heat resistance to heating while ensuring adhesion reliability, the thickness of the adhesive layer 19 is preferably 0.1 μm or more and 3.0 μm or less, 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 laminating step described with reference to FIG. 1, tension is applied to the film 10 containing the aligned liquid crystal layer, the film 13 containing the optical layer, and the laminate 17 by, for example, a dancer roll (not shown). The direction in which the tension is applied is the conveyance direction for any of the film 10 containing the aligned liquid crystal layer, the film 13 containing the optical layer, and the laminate 17.

[0031] In order to manufacture an aligned liquid crystal film excellent in heat resistance to heating while stably conveying 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 manufacture an aligned liquid crystal film excellent in heat resistance to heating, it is preferable to irradiate the laminate 17 with active energy rays under the conditions of an integrated light amount of 450 mJ / cm 2 or more and 1200 mJ / cm 2 or less, and it is more preferable to irradiate with an integrated light amount of 450 mJ / cm 2 or more and 1100 mJ / cm 2It is more preferable to irradiate with active energy rays under the following conditions, with an integrated light intensity of 450 mJ / cm². 2 More than 800mJ / cm 2 It is even more preferable to irradiate with active energy rays under the following conditions, with an integrated light intensity of 450 mJ / cm². 2 More than 600mJ / cm 2 It is even more preferable to irradiate with active energy rays under the following conditions.

[0033] To manufacture an oriented liquid crystal film with superior heat resistance, the temperature of the adhesive applied in the coating process is preferably between 0°C and 25°C, and more preferably between 0°C and 10°C.

[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 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 between the application of adhesive to the oriented liquid crystal layer-containing film 10 in the coating process and the irradiation of the laminate 17 with active energy rays in the irradiation process is, for example, 0 seconds or more and 300 seconds or less.

[0036] In order to manufacture an oriented liquid crystal film with even better heat resistance, it is preferable to satisfy condition 1 below, more preferably condition 2 below, even more preferably condition 3 below, and even more preferably condition 4 below. Condition 1: The temperature of the adhesive applied in the coating process is between 0°C and 25°C, and the integrated light intensity for the laminate 17 in the irradiation process is 450 mJ / cm². 2 More than 1200mJ / cm 2 The activated energy rays are irradiated under the following conditions. Condition 2: The temperature of the adhesive applied in the coating process is 0°C or higher and 25°C or lower, and the integrated light intensity for the laminate 17 in the irradiation process is 450 mJ / cm². 2 More than 800mJ / cm 2The activated energy rays are irradiated under the following conditions. Condition 3: The temperature of the adhesive applied in the coating process is 0°C or higher and 10°C or lower, and the integrated light intensity for the laminate 17 in the irradiation process is 450 mJ / cm². 2 More than 1200mJ / cm 2 The activated energy rays are irradiated under the following conditions. Condition 4: The temperature of the adhesive applied in the coating process is 0°C or higher and 10°C or lower, and in the irradiation process, the integrated light intensity for the laminate 17 is 450 mJ / cm². 2 More than 800mJ / cm 2 The activated energy rays are irradiated under the following conditions.

[0037] An example of a method for manufacturing an oriented liquid crystal film according to this embodiment has been described above with reference to Figure 1, but the present invention is not limited to the above example. For example, in the above example, an adhesive was applied to the oriented liquid crystal layer, but in the present invention, the adhesive may be applied to the optical layer, or the adhesive may be applied to both the oriented liquid crystal layer and the optical layer.

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

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

[0040] An example of a manufacturing method for the oriented liquid crystal film 101 shown in Figure 2 will be explained with reference to Figures 1 and 3A to 3D. Figures 3A to 3D are cross-sectional views showing the process steps of an example of a manufacturing method for the oriented liquid crystal film 101 shown in Figure 2.

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

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

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

[0044] Next, the laminate 17 is irradiated with active energy rays using the active energy ray irradiation device 18 (see Figure 1) to cure the adhesive in the coating layer 12 and form the adhesive layer 19, after which the support substrate 23 is peeled off from the optical layer 22. Through these steps, the oriented liquid crystal film 101 shown in Figure 3D is obtained. Alternatively, the oriented liquid crystal film may be used with the support substrate 23 attached to the optical layer 22 without peeling it off.

[0045] To manufacture an oriented liquid crystal film with superior heat resistance, it is preferable that the absolute value of the difference between the retardation of the oriented liquid crystal layer 21 in Figure 3A and the retardation of the oriented liquid crystal layer 21 in Figure 3D is 3.2 nm or less. There is no particular lower limit to the absolute value of the above difference, and it may be 0 nm, but from the viewpoint of reducing manufacturing costs, it is preferable that the absolute value of the above difference is 1.5 nm or more. The absolute value of the above difference can be adjusted, for example, by changing at least one of the following: the temperature of the adhesive applied in the coating process, the tension applied to the laminate 17 in the irradiation process, and the integrated amount of active energy rays irradiated onto the laminate 17 in the irradiation process.

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

[0047] The adhesive constituting the adhesive layer 30 is not particularly limited, and can be appropriately selected and used from acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, fluoropolymers, rubber polymers, etc., which are used as base polymers. In particular, adhesives such as acrylic adhesives and rubber adhesives that have excellent transparency, exhibit appropriate wettability, cohesiveness and adhesion, and have excellent weather resistance and heat resistance are preferred. The thickness of the adhesive layer 30 is appropriately set according to the type of substrate, etc., for example, 5 μm to 500 μm.

[0048] The adhesive layer 30 is laminated onto the alignment liquid crystal layer 21 by, for example, bonding a pre-formed sheet of adhesive to the surface of the alignment liquid crystal layer 21. Alternatively, the adhesive composition may be applied to the alignment liquid crystal layer 21, followed by solvent drying, crosslinking, photocuring, etc., to form the adhesive layer 30. To enhance the adhesion (anchoring force) between the alignment liquid crystal layer 21 and the adhesive layer 30, the surface of the alignment liquid crystal layer 21 may be subjected to surface treatment such as corona treatment or plasma treatment, or an easy-adhesion layer may be formed before laminating the adhesive layer 30.

[0049] As shown in Figure 5, it is preferable that a separator 31 is temporarily attached to the surface of the adhesive layer 30. The separator 31 protects the surface of the adhesive layer 30, for example, until the adhesive-coated oriented liquid crystal film 103 is bonded to the image display cell 50 (see Figure 7), which will be described later. As the constituent material of the separator 31, a plastic film formed from acrylic, polyolefin, cyclic polyolefin, polyester, etc. is preferably used. The thickness of the separator 31 is, for example, 5 μm to 200 μm. It is preferable that the surface of the separator 31 is subjected to a release treatment. Examples of release agents used in the release treatment include silicone-based materials, fluorine-based materials, long-chain alkyl-based materials, fatty acid amide-based materials, etc.

[0050] When manufacturing the alignment liquid crystal film 104 shown in Figure 6, the alignment liquid crystal layer 21 and the optical layer 22 may be bonded together with an adhesive, and then the alignment liquid crystal layer 21 and the optical layer 41 may be bonded together with an adhesive, or the alignment liquid crystal layer 21 and the optical layer 41 may be bonded together with an adhesive, and then the alignment liquid crystal layer 21 and the optical layer 22 may be bonded together with an adhesive. Alternatively, the alignment liquid crystal layer 21 and the optical layer 22, and the alignment liquid crystal layer 21 and the optical layer 41 may be bonded together with an adhesive simultaneously. An adhesive layer (not shown) may be further laminated on the optical layer 22 or the optical layer 41, and a separator (not shown) may be temporarily attached to the surface of the adhesive layer.

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

[0052] [Liquid crystal composition] Examples of liquid crystal compounds included in the liquid crystal composition include rod-shaped liquid crystal compounds and disc-shaped liquid crystal compounds. Rod-shaped liquid crystal compounds are preferred as liquid crystal compounds because they are easily homogeneously oriented due to the orientation-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 type liquid crystal polymer, a side-chain type liquid crystal polymer, etc.), or a polymer of a polymerizable liquid crystal compound. If the liquid crystal compound (monomer) before polymerization exhibits liquid crystal properties, it may not exhibit liquid crystal properties after polymerization.

[0053] The liquid crystal compound is preferably a thermotropic liquid crystal that exhibits liquid crystal properties upon heating. Thermotropic liquid crystals undergo a phase transition between the crystalline phase, the liquid crystal phase, and the isotropic phase in response to temperature changes. The liquid crystal compound included in the liquid crystal composition may be a nematic liquid crystal, a smectic liquid crystal, or a cholesteric liquid crystal. A chiral agent may be added to the nematic liquid crystal to give it cholesteric orientation.

[0054] Examples of rod-shaped liquid crystal compounds that exhibit thermotropic properties include azomethine compounds, azoxy compounds, cyanobiphenyl compounds, cyanophenyl ester compounds, benzoic acid ester compounds, cyclohexanecarboxylic acid phenyl ester compounds, cyanophenylcyclohexane compounds, cyanosubstituted phenylpyrimidine compounds, alkoxysubstituted phenylpyrimidine compounds, phenyldioxane compounds, tran compounds, and alkenylcyclohexylbenzonitrile compounds.

[0055] Examples of polymerizable liquid crystal compounds include polymerizable liquid crystal compounds in which the orientation state of a rod-shaped liquid crystal compound can be fixed using a polymer binder, and polymerizable liquid crystal compounds having polymerizable functional groups that allow the orientation state of the liquid crystal compound to be fixed by polymerization. Among these, photopolymerizable liquid crystal compounds having photopolymerizable functional groups are preferred.

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

[0057] Examples of mesogenic groups for liquid crystal monomers include cyclic structures such as biphenyl groups, phenylbenzoate groups, phenylcyclohexane groups, azoxybenzene groups, azobenzene groups, phenylpyrimidine groups, diphenylacetylene groups, diphenylbenzoate groups, bicyclohexane groups, cyclohexylbenzene groups, and terphenyl groups. The ends of these cyclic units may be substituted with cyano groups, alkyl groups, alkoxy groups, halogen groups, etc.

[0058] Examples of photopolymerizable functional groups include (meth)acryloyl groups, epoxy groups, and vinyl ether groups. Among these, (meth)acryloyl groups are preferred. Liquid crystal monomers that have two or more photopolymerizable functional groups in one molecule are preferred. By using liquid crystal monomers 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] Any suitable liquid crystal monomer can be used as the liquid crystal monomer. For example, see International Publication No. 00 / 37585, U.S. Patent No. 5211877, U.S. Patent No. 4388453, International Publication No. 93 / 22397, European Patent No. 0261712, German Patent No. 19504224, German Patent No. 4408171, British Patent No. 2280445, Japanese Patent Publication No. 2017-206460, International Publication No. 2014 / 126113, International Publication No. 2016 / 114348, International Publication No. 2014 / 010325, Japanese Patent Publication No. 2015-2008 Compounds described in Japanese Patent Publication No. 77, Japanese Patent Publication No. 2010-31223, International Publication No. 2011 / 050896, Japanese Patent Publication No. 2011-207765, Japanese Patent Publication No. 2010-31223, Japanese Patent Publication No. 2010-270108, International Publication No. 2008 / 119427, Japanese Patent Publication No. 2008-107767, Japanese Patent Publication No. 2008-273925, International Publication No. 2016 / 125839, Japanese Patent Publication No. 2008-273925, etc., can be used as liquid crystal monomers. By selecting the liquid crystal monomer, it is also possible to adjust the birefringence and the wavelength dispersion of retardation.

[0060] In addition to liquid crystal monomers, the liquid crystal composition may also contain compounds (orientation control agents) that control the orientation of the liquid crystal monomers in a predetermined direction. For example, by including a side-chain type liquid crystal polymer in the liquid crystal composition, the liquid crystal compound (monomer) can be homeotropically oriented. Alternatively, by adding a chiral agent to the liquid crystal composition, the liquid crystal compound can be cholesterically oriented.

[0061] The liquid crystalline composition may contain a photopolymerization initiator. When curing liquid crystal monomers by ultraviolet irradiation, it is preferable that the liquid crystalline composition contains a photoradical polymerization initiator (photoradical generator) that generates radicals upon light irradiation 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 photopolymerization initiator used is, for example, 0.01 parts by weight or more and 10 parts by weight or less per 100 parts by weight of liquid crystal monomer. In addition to the photopolymerization initiator, sensitizers and the like may also be used.

[0062] A liquid crystalline composition can be prepared by mixing liquid crystal monomers with various orientation control agents, polymerization initiators, etc., as needed, in a solvent. The solvent is not particularly limited as long as it can dissolve the liquid crystal monomers and does not erode (or has low erosive properties) the support substrate 20, and includes 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, and N-methyl- Examples of solvents 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 mixture of two or more solvents may also be used.

[0063] The solid content concentration of the liquid crystalline composition is, for example, 5% by weight or more and 60% by weight or less. The liquid crystalline composition may contain additives such as surfactants and leveling agents.

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

[0065] The resin material constituting the resin film substrate is not particularly limited as long as it does not dissolve in the solvent of the liquid crystalline composition and has heat resistance when heated to orient the liquid crystalline composition. Examples include polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cyclic polyolefins such as norbornene polymers; cellulosic polymers such as diacetylcellulose and triacetylcellulose; acrylic polymers; styrene polymers; polycarbonate; polyamide; and polyimide.

[0066] The support substrate 20 may have orientation capabilities for aligning 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 orient the liquid crystal compound along its stretching direction. The stretching ratio of the stretched film only needs to be sufficient to exhibit orientation capabilities, for example, 1.1 times or more and 5 times or less. The stretched film may also be a biaxially oriented film. Even with a biaxially oriented film, if the stretching ratios in the longitudinal and transverse directions are different, the liquid crystal compound can be oriented along the direction with the larger stretching ratio. The stretched film may also 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 or widthwise direction of the support substrate 20.

[0067] The support substrate 20 may have an alignment film on its first main surface. The alignment film should be appropriately selected depending on the type of liquid crystal compound and the material of the support substrate 20. 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 rubbed is preferably used. Alternatively, a photo-alignment film may be used. Alternatively, the resin film used as the support substrate 20 may be rubbed 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 a homeotropically oriented alignment film (vertical alignment film) include lecithin, stearic acid, hexadecyltrimethylammonium bromide, octadecylamine hydrochloride, monobasic chromium carboxylate complex, organosilane (more specifically, silane coupling agents, siloxane compounds, etc.), perfluorodimethylcyclohexane, tetrafluoroethylene, polytetrafluoroethylene, and the like.

[0069] [Aligned liquid crystal layer] If the liquid crystal compound is a thermotropic liquid crystal, the liquid crystal composition is applied to the first main surface of the support 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 support substrate 20 is not particularly limited, and methods such as spin coating, die coating, kiss roll coating, gravure coating, reverse coating, spray coating, Meyer bar coating, knife roll coating, and air knife coating can be used. After applying the liquid crystalline composition, the solvent is removed to form a liquid crystalline composition layer on the support substrate 20. Preferably, the thickness of the coating layer formed by applying the liquid crystalline composition is adjusted so that the thickness of the liquid crystalline composition layer after solvent removal is 0.1 μm or more and 20 μm or less.

[0071] By heating the liquid crystalline composition layer formed on the support substrate 20 to convert it into a liquid crystal phase, the liquid crystal compounds are oriented, and an oriented liquid crystal layer 21 is formed. Specifically, after coating the liquid crystalline composition onto the support substrate 20, the composition is heated to a temperature above the N (nematic phase)-I (isotropic liquid phase) transition temperature to convert it into an isotropic liquid state. From there, it is slowly cooled as needed to induce the nematic phase. At this time, it is desirable to maintain the temperature at which the liquid crystal phase is exhibited and grow the liquid crystal phase domains to form monodomains. Alternatively, after coating the liquid crystalline composition onto the support substrate 20, the temperature may be maintained for a certain period of time within the temperature range at which the nematic phase is expressed to orient the liquid crystal compounds in a predetermined direction.

[0072] The heating temperature for orienting the liquid crystal compound in a predetermined direction can be appropriately selected depending on the type of liquid crystal composition, for example, between 40°C and 200°C. 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 orientation defects may increase. The heating time should be adjusted so that the liquid crystal phase domains grow sufficiently, for example, between 30 seconds and 30 minutes.

[0073] It is preferable to cool the liquid crystal compound to a temperature below its glass transition temperature after aligning it by heating. The cooling method is not particularly limited; for example, it may be removed from the heating atmosphere to room temperature. Forced cooling such as air cooling or water cooling may also be performed.

[0074] By irradiating an oriented photopolymerizable liquid crystal compound with light, the photopolymerizable liquid crystal compound (liquid crystal monomer) is photocured while exhibiting liquid crystal regularity. The irradiation light can be any light capable of polymerizing the photopolymerizable liquid crystal compound, and typically ultraviolet light or visible light with a wavelength of 250 nm to 450 nm is used. If the liquid crystal composition contains a photopolymerization initiator, light with a wavelength to which the photopolymerization initiator is sensitive should be selected. Suitable irradiation sources include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, LEDs, black lights, chemical lamps, etc. To promote the photocuring reaction, it is preferable to perform the light irradiation under an inert gas atmosphere such as nitrogen gas.

[0075] During the photocuring of the liquid crystalline composition, the liquid crystal compound can be oriented in a predetermined direction by utilizing polarization in a predetermined direction. As described above, when the liquid crystal compound is oriented by the orientation restricting force of the support substrate 20, the irradiation light may be unpolarized (natural light).

[0076] The irradiation intensity of the light can be appropriately adjusted according to the composition of the liquid crystalline composition and the amount of photopolymerization initiator added. The irradiation energy (integrated light amount) can be, for example, 20 mJ / cm². 2 More than 10000mJ / cm 2 The following is true: 50 mJ / cm 2 More than 5000mJ / cm 2 Preferably, it is 100 mJ / cm². 2 More than 800mJ / cm 2 The following is more preferable: Light irradiation may be carried out under heating conditions to accelerate the photocuring reaction.

[0077] The polymer obtained after photocuring liquid crystal monomers by light irradiation is non-liquidental and does not undergo a phase transition due to temperature changes. Therefore, a liquid crystal layer photocured with liquid crystal monomers oriented in a predetermined direction is usually less prone to changes in molecular orientation. Furthermore, since the birefringence Δn of an oriented liquid crystal film is significantly larger than that of a film made of a non-liquid crystal material, the thickness of an optically anisotropic element having the desired retardation can be significantly reduced. The thickness of the oriented liquid crystal layer 21 can be set according to the desired retardation value, etc., and for example, it is preferably 0.1 μm to 20 μm, preferably 0.2 μm to 10 μm, and more preferably 0.5 μm to 7 μm.

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

[0079] When the liquid crystal compound is homogeneously oriented in the oriented liquid crystal layer 21, it is preferable that the birefringence Δn of the oriented liquid crystal layer 21 after the lamination process be 0.03 or more in order to reduce the thickness of the optically anisotropic element. Furthermore, when the liquid crystal compound is homogeneously oriented in the oriented liquid crystal layer 21, it is preferable that the birefringence Δn of the oriented liquid crystal layer 21 after the lamination process be 0.5 or less in order to facilitate the adjustment of the in-plane retardation of the oriented liquid crystal layer 21. The birefringence Δn of the oriented liquid crystal layer 21 can be adjusted, for example, by changing the type of liquid crystal compound used to form the oriented liquid crystal layer 21.

[0080] [Optical layer] The optical layers 22 and 41 are not particularly limited. For example, commonly used optical isotropic or optical anisotropic optical films can be used without restriction as optical layers 22 and 41. Specific examples of optical layers 22 and 41 include transparent films (more specifically, phase difference films, polarizer protective films, etc.) and functional films (more specifically, polarizers, viewing angle expanding films, viewing angle limiting (anti-peeping) films, brightness enhancing films, etc.). The optical layers 22 and 41 may be single layers or laminates. The optical layers 22 and 41 may also be alignment liquid crystal layers (other alignment liquid crystal layers). Furthermore, the optical layer 22 may be a polarizer plate in which a transparent protective film is laminated to one or both sides of a polarizer. When the polarizer plate has a transparent protective film on one side, the polarizer may be laminated to the alignment liquid crystal layer 21, or the transparent protective film may be laminated to the alignment liquid crystal layer 21. Optical layer 22 and optical layer 41 may be composed of the same material or of different materials. The thickness of optical layer 22 and optical layer 41 are adjusted as appropriate according to the required optical performance, but are, for example, 0.1 μm or more and 1000 μm or less, preferably 0.1 μm or more and 100 μm or less. The thickness of optical layer 22 and optical layer 41 may be the same or different.

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

[0082] Active energy ray curing adhesives are adhesives that can undergo radical polymerization, cationic polymerization, or anionic polymerization by irradiation with active energy rays such as electron beams or ultraviolet rays. Among these, photo-radical polymerizable adhesives, photo-cationic polymerizable adhesives, or hybrid adhesives that use both photo-cationic polymerization and photo-radical polymerization are preferred because they can be cured at low energy.

[0083] Examples of monomers for photoradical polymerizable adhesives include compounds having a (meth)acryloyl group and compounds having a vinyl group. Among these, compounds having a (meth)acryloyl group are preferred. Examples of compounds having a (meth)acryloyl group include C 1-20 Examples 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 also contain nitrogen-containing monomers 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 also contain polyfunctional monomers as crosslinking components, such as tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecanedimethanol diacrylate, cyclic trimethylolpropaneformal acrylate, dioxane glycol diacrylate, and polyoxyethylene glycol diacrylate.

[0084] Examples of curing components for photocationic polymerizable adhesives include compounds having epoxy groups or oxetanyl groups. Compounds having epoxy groups are not particularly limited as long as they have at least two epoxy groups in their molecule, and various generally known curable epoxy compounds can be used. Preferred epoxy compounds include compounds having at least two epoxy groups and at least one aromatic ring in their molecule (aromatic epoxy compounds), and compounds having at least two epoxy groups in their molecule, at least one of which is formed between two adjacent carbon atoms constituting an alicyclic ring (alicyclic epoxy compounds). By incorporating radical polymerizable compounds such as compounds having (meth)acryloyl groups into the cationic polymerizable adhesive, a hybrid adhesive can also be created.

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

[0086] Furthermore, even if the adhesive before curing contains oligomers with a weight-average molecular weight of 1000 or more, an adhesive with a low curing shrinkage rate can be obtained. Examples of oligomers with a weight-average molecular weight of 1000 or more (hereinafter sometimes referred to as "specific oligomers") include oligomers formed from monomers having (meth)acryloyl groups (acrylic oligomers). Acrylic oligomers may also have cationic polymerizable functional groups (e.g., epoxy groups).

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

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

[0089] Photocurable adhesives preferably contain a photopolymerization initiator. The photopolymerization initiator can be appropriately selected depending on the reaction species. For example, in photoradical polymerizable adhesives, it is preferable to include a photoradical polymerization initiator that generates radicals upon light irradiation. In photocationic polymerizable adhesives, it is preferable to include a photocationic polymerization initiator (photoacid generator) that generates cationic species or Lewis acids upon light irradiation. In hybrid adhesives, it is preferable to include both 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, per 100 parts by weight of monomer. A photosensitizer may also be added to the photocurable adhesive as needed. The amount of 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, per 100 parts by weight of monomer.

[0091] The adhesive may contain appropriate additives as needed. Examples of additives include coupling agents such as silane coupling agents and titanium coupling agents, adhesion promoters such as ethylene oxide, UV absorbers, degradation inhibitors, dyes, processing aids, ion trapping agents, antioxidants, tackifiers, fillers, plasticizers, leveling agents, foam inhibitors, antistatic agents, heat stabilizers, hydrolysis stabilizers, and the like.

[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 aimed at improving visibility.

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

[0094] A polarizing plate may consist of only one polarizer layer, or, as described above, a transparent protective film may be laminated to one or both sides of the polarizer. Examples of polarizers include hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based 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 or dehydrochlorinated polyvinyl chloride.

[0095] Among these, polyvinyl alcohol (PVA) polarizers are preferred because they have a high degree of polarization. These polarizers are made by adsorbing dichroic substances such as iodine or dichroic dyes onto a polyvinyl alcohol-based film, such as polyvinyl alcohol or partially formalized polyvinyl alcohol, and oriented them in a predetermined direction. For example, a PVA polarizer can be obtained by iodine dyeing and stretching a polyvinyl alcohol-based film. Alternatively, a PVA-based resin layer may be formed on a resin substrate, and iodine dyeing and stretching may be performed on the laminated structure.

[0096] In a circular polarizer, it is preferable that at least one oriented liquid crystal layer has liquid crystal compounds that are homogeneously oriented. In a circular polarizer, the orientation direction of the liquid crystal compounds in the oriented liquid crystal layer, where the liquid crystal compounds are homogeneously oriented, is neither parallel nor orthogonal to the absorption axis direction of the polarizer.

[0097] When a circular polarizer has only one aligning liquid crystal layer, for example, the aligning liquid crystal layer 21 is a quarter-wave plate, and the angle between the absorption axis direction of the polarizer as the optical layer 22 and the orientation direction of the liquid crystal compound (generally the slow phase axis direction) is set to 45°. The angle between the absorption axis direction of the polarizer and the orientation 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 optical layer 22 and a quarter-wave plate as aligning liquid crystal layer 21 are laminated such that the angle between their optical axes is 45°, an aligning liquid crystal layer in which the liquid crystal compound is homeotropically oriented may be further provided as optical layer 41 (see Figure 6). By sequentially laminating the aligning liquid crystal layer 21 as a quarter-wave plate and the optical layer 41 which functions as a positive C plate on the polarizing plate, a circular polarizing plate capable of shielding reflected light even from ambient light coming from an oblique direction can be formed. Alternatively, a homeotropically oriented liquid crystal layer (positive C plate) and a homogeneously oriented liquid crystal layer (a quarter-wave plate which is a positive A plate) may be sequentially laminated on the polarizing plate.

[0099] In the case where the alignment liquid crystal film 104 shown in Figure 6 is a circular polarizer in which an alignment liquid crystal layer 21 and an alignment liquid crystal layer 41 are sequentially laminated on a polarizer as an optical layer 22, both the alignment liquid crystal layer 21 and the optical layer 41 may be homogeneous alignment liquid crystal layers. In this case, it is preferable that the alignment liquid crystal layer 21 located closer to the optical layer 22 is a half-wave plate, and the optical layer 41 located further away from the optical layer 22 is a quarter-wave plate. In this layer configuration, it is preferable 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 with such a layer configuration functions as a circular polarizer over a wide wavelength range of visible light, thus reducing the coloration of reflected light.

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

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

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

[0103] <Preparation of Adhesive A-1> The UV-curing adhesive A-1 was prepared by blending each component shown in Table 1 in the proportions shown in Table 1. Note that in Table 1, each percentage represents the proportion of the total adhesive volume.

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

[0105] [Table 1]

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

[0107] A transversely oriented film (Zeonor Film® ZT12-50135, manufactured by Zeon Corporation, with a thickness of 52 μm and an in-plane retardation of 50 nm) was used as the film substrate. The above liquid crystalline composition was applied to the surface of the film substrate using a bar coater to a thickness of 1.4 μm after heating, and the film was heated at 100°C for 3 minutes to orient the liquid crystalline compounds. Next, the liquid crystalline composition on the film substrate was cooled to room temperature (25°C), and then exposed to a nitrogen atmosphere with an integrated light intensity of 400 mJ / cm². 2 The liquid crystalline composition was irradiated with ultraviolet light to perform photocuring, and a laminate L-1 was obtained in which a homogeneous oriented liquid crystal layer was formed on a film substrate.

[0108] The in-plane retardation of the oriented liquid crystal layer in the obtained laminate L-1 was measured. Specifically, first, a 15 μm thick acrylic adhesive sheet was bonded to the surface of the oriented liquid crystal layer of laminate L-1, and then the adhesive sheet was bonded 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 sample for measurement. Then, the in-plane retardation of the sample (oriented liquid crystal layer) at a wavelength of 590 nm was measured using a phase difference meter (KOBRA® 21-ADH, manufactured by Oji Instruments Co., Ltd.). Hereafter, the in-plane retardation measured here will be referred to as Re1. Re1 was 140 nm.

[0109] <Fabrication of Aligned Liquid Crystal Films> [Fabrication of the oriented liquid crystal film of Example 1] A film (manufactured by Dai Nippon Printing Co., Ltd., "MCP-N(100)", hereinafter referred to as "laminated L-2") was prepared on a substrate, with a homeotropically oriented liquid crystal layer (thickness: 3 μm, in-plane retardation: 0 nm) as an optical layer. Laminated L-1 was also fabricated using the method described above.

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

[0111] Next, mimicking a roll-to-roll bonding process, the adhesive A-1 in laminate L-3 was photocured while tension was applied to the laminate L-3. Specifically, under an atmosphere of 25°C, a tension of 538 N / 1000 mm width was applied to laminate L-3 in a direction perpendicular to the orientation direction of the homogeneous oriented liquid crystal layer in laminate L-1, and the illuminance was 600 mW / cm². 2 Using a high-pressure mercury lamp, the cumulative light intensity is 600 mJ / cm². 2 Adhesive A-1 was photocured by irradiating it with ultraviolet light under the specified conditions. The ultraviolet irradiation was performed from the laminate L-2 side. The orientation direction of the homogeneous oriented liquid crystal layer in laminate L-1 is the stretching direction of the film substrate (transversely stretched film) of laminate L-1. Therefore, in the roll-to-roll lamination process, the direction perpendicular in plane to the orientation direction of the homogeneous oriented liquid crystal layer is the transport direction of laminate L-3. Next, the substrate of laminate L-2 was peeled from laminate L-3 to obtain the oriented liquid crystal film of Example 1.

[0112] [Fabrication of Aligned Liquid Crystal Films in Examples 2-4] Except for changing the cumulative amount of light used to light-cur the adhesive as shown in Table 2 below, the oriented liquid crystal films of Examples 2 to 4 were each prepared using the same method as in Example 1.

[0113] [Preparation of oriented liquid crystal films in Examples 5-7 and Comparative Example 1] Except for changing the temperature of the adhesive when applying it, as shown in Table 3 below, the oriented liquid crystal films of Examples 5-7 and Comparative Example 1 were prepared using the same method as in Example 1. For reference, Table 3 also includes the details of Example 1 described above.

[0114] [Preparation of oriented liquid crystal films in Examples 8, 9 and Comparative Example 2] Except for changing the tension applied to the laminate L-3 as shown in Table 4 below, the oriented liquid crystal films of Example 8, Example 9, and Comparative Example 2 were prepared using the same method as in Example 1. For reference, Table 4 also includes the details of Example 1 described above.

[0115] <Rating> [Changes in lettering before and after bonding] A 15 μm thick acrylic adhesive sheet was bonded to the surface of the homeotropic oriented liquid crystal layer of the oriented liquid crystal film to be evaluated (any of the oriented liquid crystal films of Examples 1-9, Comparative Example 1, and Comparative Example 2). Then, the adhesive sheet was bonded 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 an evaluation sample. Then, the in-plane retardation at a wavelength of 590 nm of the evaluation sample (homogeneous oriented liquid crystal layer) was measured using a phase difference meter (KOBRA® 21-ADH, manufactured by Oji Instruments Co., Ltd.). Hereafter, the in-plane retardation measured here will be referred to as Re2. The change in retardation before and after bonding (unit: nm) was calculated according to the formula "Change in retardation before and after bonding = |Re2 - Re1|". Note that |Re2 - Re1| represents the absolute value of the difference between Re2 and Re1. If the retardation change before and after adhesion was 3.2 nm or less, it was evaluated as "the retardation change before and after adhesion has been suppressed." On the other hand, if the retardation change before and after adhesion exceeded 3.2 nm, it was evaluated as "the retardation change before and after adhesion has not been suppressed."

[0116] Furthermore, for the oriented liquid crystal film of Example 1, the birefringence Δn was calculated from Re2 and the thickness of the homogeneous oriented liquid crystal layer according to the formula "birefringence Δn = Re2 / thickness of the homogeneous oriented liquid crystal layer". The result was that the birefringence Δn of the homogeneous oriented liquid crystal layer was 0.10.

[0117] [Retrograde change rate before and after heat resistance test] The evaluation samples used to evaluate the above [regression change before and after bonding] were placed in an air-circulating constant-temperature oven at 85°C for 120 hours. After removing the evaluation samples from the oven, the in-plane retardation at a wavelength of 590 nm of the evaluation sample (homogeneous oriented liquid crystal layer) was measured using a phase difference meter (KOBRA® 21-ADH, manufactured by Oji Instruments Co., Ltd.). Hereafter, the in-plane retardation measured here will be referred to as Re3. The rate of change in retardation (in %) before and after the heat durability test was calculated according to the formula "Rate of change in retardation before and after heat durability test = 100 × |Re3 - Re2| / Re2". Note that |Re3 - Re2| represents the absolute value of the difference between Re3 and Re2. If the rate of change in retardation 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, if the rate of retardation change before and after the heat durability test exceeded 3.5%, it was evaluated as "failure to suppress changes in optical properties when exposed to high-temperature environments for extended periods."

[0118] Furthermore, none of the evaluation samples after the heat durability test showed any delamination, demonstrating the reliability of the adhesion.

[0119] Tables 2-4 show the retardation changes before and after bonding and the rate of retardation change before and after the heat durability test for each of the above examples and comparative examples, along with the manufacturing conditions. In Tables 2-4, "ΔRe" indicates the retardation change before and after bonding, and "Re change rate" indicates the rate of retardation change 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 applied was between 0°C and 45°C, and the tension applied to the laminate L-3 was between 70N / 1000mm width and 550N / 1000mm width. In Examples 1 to 9, the rate of retardation change before and after the heat durability test was 3.5% or less. Therefore, the oriented liquid crystal films of Examples 1 to 9 were able to suppress changes in optical properties even when exposed to high-temperature environments for a long time.

[0124] In Comparative Example 1, the temperature of the adhesive during application 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 rate of retardation change before and after the heat durability test exceeded 3.5%. Therefore, the oriented liquid crystal films of Comparative Examples 1 and 2 failed to suppress changes in optical properties when exposed to high-temperature environments for extended periods.

[0125] The results above demonstrate that the method for manufacturing an oriented liquid crystal film according to the present invention makes it possible to produce an oriented liquid crystal film that exhibits minimal changes in optical properties even when exposed to high-temperature environments for extended periods. [Explanation of Symbols]

[0126] 17 Laminate 19, 40 Adhesive layer 21 Aligned liquid crystal layer 22, 41 optical layer 100, 101, 102, 103, 104 Aligned 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 10°C, to 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. A method for manufacturing an oriented liquid crystal film having the following characteristics.

2. In the aforementioned irradiation step, the laminate is subjected to an integrated light intensity of 450 mJ / cm². ２ More than 1200mJ / cm ２ A method for manufacturing an oriented liquid crystal film according to claim 1, wherein the activated energy ray is irradiated under the following conditions.

3. A method for manufacturing an oriented liquid crystal film according to claim 1 or 2, 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. A method for producing an oriented liquid crystal film according to any one of claims 1 to 3, wherein the liquid crystal compound in the oriented liquid crystal layer is homogeneously oriented.

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

6. A method for manufacturing an oriented liquid crystal film according to any one of claims 1 to 5, wherein the optical layer is a polarizer, a transparent film, or another oriented liquid crystal layer.

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