Method of manufacturing an optical film

Abstract

The manufacturing method of the optical film of the present application rolls a laminate (8) in which a protective film (2) is peelably attached to a first main surface of a long film substrate (1) along the length direction to a peeling section (10) in which the protective film is peeled from the first main surface of the film substrate. During the period from when the film substrate after the protective film has been peeled is carried from the peeling section to a coating section (30), the roll does not contact the central portion in the width direction of the first main surface of the film substrate, and the film pressing mechanism (15) contacts both end portions in the width direction of the first main surface of the film substrate at least once. The film pressing mechanism does not contact the central portion in the width direction of the first main surface of the film substrate.

Description

Technical Field

[0001] This invention relates to a method for manufacturing an optical film having a liquid crystal layer. Background Technology

[0002] Optical films used for functions such as optical compensation in liquid crystal display devices and anti-reflection of organic EL elements employ a liquid crystal layer (aligned liquid crystal layer) in which the liquid crystal compound is aligned along a predetermined direction. The liquid crystal compound can be oriented along a predetermined direction by shear force during coating onto a substrate, orientation constraint force of the substrate, etc., resulting in aligned liquid crystal layers with various optical anisotropies. For example, a parallel-aligned liquid crystal film 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 refractive index anisotropy of nx > ny = nz.

[0003] In Patent Document 1, an alignment layer is formed by coating a liquid crystal composition onto an inclined stretched film substrate and aligning the liquid crystal compound parallel to the stretching direction (orientation direction) of the film substrate. By coating the liquid crystal composition onto the film substrate while simultaneously conveying the film substrate, a long strip of liquid crystal film can be formed. As described in Patent Document 1, if an inclined stretched film substrate is used, the liquid crystal molecules are aligned parallel to the orientation direction of the film substrate, thus enabling the fabrication of a long strip of liquid crystal film where the liquid crystal molecules are not aligned parallel to the conveying direction of the film substrate.

[0004] Furthermore, Patent Document 1 discloses a method for fabricating a circular polarizer as an antireflective film for an organic EL display device by laminating a liquid crystal film with the slow axis direction forming a 45° angle with the absorption axis direction of a linear polarizer. A long strip of liquid crystal film, in which the liquid crystal molecules are oriented non-parallel to the transport direction of the film substrate, and a polarizer having an absorption axis parallel to the transport direction are laminated in a roll-to-roll manner.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: WO2016 / 121856 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] Sometimes, liquid crystal layers formed by coating a liquid crystal composition while simultaneously transporting a film substrate exhibit defects due to poor alignment of liquid crystal molecules. In particular, in liquid crystal layers where the liquid crystal molecules are aligned non-parallel to the transport direction of the film substrate, the number of defects caused by misalignment tends to increase. The object of the present invention is to provide an optical film containing a liquid crystal layer with fewer misalignment defects.

[0010] means for solving problems

[0011] One embodiment of the present invention is a method for manufacturing a strip of optical film including a liquid crystal layer, wherein the liquid crystal layer is formed on the first main surface of a strip of film substrate having a first main surface and a second main surface. First, a laminate on which a protective film is peelably adhered to the first main surface of the strip of film substrate is prepared. The laminate is then rolled along the length direction of the film substrate to a peeling section (first conveying step), where the protective film is peeled off from the first main surface of the film substrate (protective film peeling step).

[0012] The film substrate after the protective film has been peeled off is transported from the peeling section to the coating section along the length of the film substrate (second transport step), and a liquid crystal composition is coated on the first main surface of the film substrate in the coating section (coating step).

[0013] During the process of conveying the film substrate, after the protective film has been peeled off, to the coating section, the roller does not contact the central portion of the first main surface of the film substrate in the width direction, and the film pressing mechanism contacts both ends of the first main surface of the film substrate at least once in the width direction. The film pressing mechanism does not contact the central portion of the first main surface of the film substrate in the width direction. The film pressing mechanism may be a pressing roller that only contacts both ends of the first main surface of the film substrate in the width direction.

[0014] During the process of conveying the film substrate after the protective film has been peeled off to the coating section, the conveying roller may come into contact with the second main surface of the film substrate. The conveying roller may make integral contact with the second main surface of the film substrate in the width direction.

[0015] When coating a liquid crystal composition onto a film substrate, the liquid crystal composition is coated on the inner side in the width direction, closer to the contact portion with the film pressing mechanism on the first main surface of the film substrate. At an appropriate time after coating the liquid crystal composition, the areas at both ends of the film substrate in the width direction that contact the film pressing mechanism can be cut off and removed by means of a cut or the like.

[0016] The film substrate for coating the liquid crystal composition can be a film substrate having an orientation limiting force that orients liquid crystal molecules along a predetermined direction. For example, the film substrate can be a stretched film in which the molecules are not parallel to the length direction, or it can be an inclined stretched film. The film substrate can also be a film substrate without an alignment film disposed on the first main surface.

[0017] Optical films can be optical films in which other optical layers are stacked on a liquid crystal layer in a roll-to-roll manner. The optical layers stacked on the liquid crystal layer may include polarizers. Optical films can also be circular polarizers formed by stacking liquid crystal layers and polarizers. Attached Figure Description

[0018] Figure 1 This is a cross-sectional view of an optical film with a liquid crystal layer on a film substrate.

[0019] Figure 2 This is a cross-sectional view of a laminate with a protective film temporarily attached to a membrane substrate.

[0020] Figure 3 This is a diagram showing an overview of the film-forming apparatus and film-forming process for forming a liquid crystal layer on a film substrate.

[0021] Figure 4 This is a schematic diagram of the conveying path of the film substrate from the peeling roller to the support roller.

[0022] Figure 5 This is a schematic diagram of the transport path of the membrane substrate in the comparative example.

[0023] Figure 6 This is a schematic diagram of the transport path of the membrane substrate in the comparative example.

[0024] Figure 7 This is a schematic diagram of the transport path of the membrane substrate in one embodiment.

[0025] Figure 8 This is a perspective view showing an example of the shape of the pressure roller.

[0026] Figure 9 This is a cross-sectional view of an optical film according to one embodiment.

[0027] Figure 10 This is a cross-sectional view of an optical film according to one embodiment.

[0028] Figure 11 This is a cross-sectional view of an optical film according to one embodiment.

[0029] Symbol Explanation

[0030] 1. Membrane substrate

[0031] 2. Protective film

[0032] 3. Liquid crystal layer

[0033] 4. Optical layer (polarizer)

[0034] 5. Adhesive layer

[0035] 6 Adhesive layer

[0036] 7. Isolation components

[0037] 8-layered structure

[0038] 9, 96, 97, 98 Laminated films (optical films)

[0039] 81. Winding Roller

[0040] 21, 91 Take-up rollers

[0041] 10. Peeling section

[0042] 11. Peeling Roller

[0043] 30 Coating Section

[0044] 31 Support Rollers

[0045] 33 Mold

[0046] 50 Heating section

[0047] 55 Heating Furnace

[0048] 60 Curing Department

[0049] 61 Light Source

[0050] 83, 85, 87 conveying roller

[0051] 13 Conveying roller

[0052] 15, 151 Pressing Rollers

[0053] 71, 73, 75, 77, 79 Conveying roller Detailed Implementation

[0054] This invention relates to a method for manufacturing an optical film comprising a liquid crystal layer. In one embodiment of the invention, a liquid crystal composition is coated onto a main surface of a strip of film substrate to form a liquid crystal layer. Figure 1 This is a cross-sectional view of an optical film 9 on the first main surface 1A of a film substrate 1, on which a liquid crystal layer 3 is disposed. Figure 2 This is a cross-sectional view of a laminate 8 on which a protective film 2 is peelably adhered to the first main surface 1A of the membrane substrate 1.

[0055] If there are scratches on one side (the liquid crystal layer forming side) of the liquid crystal composition on the coated film substrate, the liquid crystal molecules are prone to aligning along the extension direction of the scratches when the liquid crystal composition is coated on it, resulting in poor alignment defects. In particular, when the liquid crystal composition is coated while the film substrate is being transported in a roll-to-roll manner, scratches along the length direction are easily generated on the film substrate due to the contact and friction of the transport rollers.

[0056] In this embodiment, a protective film 2 is temporarily attached to the film substrate 1 just before the liquid crystal composition is coated on the first main surface 1A of the film substrate 1. By temporarily attaching the protective film 2, the first main surface 1A of the film substrate 1 does not come into contact with the conveying roller, thus preventing scratches on the film substrate 1 due to conveying and suppressing misalignment of liquid crystal molecules in the liquid crystal layer 3.

[0057] Figure 3This is a conceptual diagram showing an outline of a film-forming apparatus and process for forming a liquid crystal layer 3 on a film substrate 1. In the film-forming apparatus, the film is wound from a long strip of film wound on a take-up roller 81 and transported to a coating section 30. In the coating section 30, a liquid crystal composition is coated onto the film to form a liquid crystal layer, and a take-up roller 91 takes the film (optical film 9) with the liquid crystal layer to form a winding 90. Between the coating section 30 and the take-up roller 91, heating can be performed by a heating section 50, or photocuring of the liquid crystal monomers can be performed by a curing section 60.

[0058] exist Figure 3 In this process, a roll body 80, obtained by winding the long strip film of the laminate 8 into a roll shape, is wound onto a take-up roller 81. As described above, the laminate 8 has a protective film 2 that is peelably adhered to the first main surface of the film substrate 1.

[0059] The laminate 8, wound from the winding body 80, moves continuously to the downstream side of the transport path formed by the transport rollers 83, 85, and 87, and is transported to the peeling section 10 (first transport step). During the period from the unwinding roller 81 to reaching the peeling section 10, a protective film 2 is adhered to the first main surface 1A of the film substrate 1, so the first main surface 1A of the film substrate 1 will not come into direct contact with the transport roller 87. Therefore, it is possible to prevent scratches on the first main surface of the film substrate due to contact with the transport roller 87.

[0060] In the peeling section 10, the protective film 2 is peeled off from the first main surface of the film substrate 1 (peeling process). The peeling method for the protective film is not particularly limited; typically, peeling is performed on the peeling roller 11. As long as the downstream conveying rollers 13 and 23 of the peeling roller 11 are configured such that the angle of the protective film 2 relative to the peeling roller 11 is larger than the angle of the film substrate 1 relative to the peeling roller 11, the protective film 2 can be peeled off from the film substrate 1 on the peeling roller 11. The peeling roller can be a pair of clamping rollers that sandwich the laminate 8 between its upper and lower parts.

[0061] The protective film 2, after being peeled off from the first main surface of the film substrate 1, is conveyed along a conveying path based on conveying rollers 23 and 25, and wound into a winding body 20 by winding roller 21.

[0062] By peeling off the protective film 2, the first main surface 1A of the film substrate 1 is exposed. The film substrate 1, after the protective film has been peeled off, is transferred from the peeling section 10 to the coating section 30 (second transfer step). In the coating section 30, with the second main surface 1B of the film substrate 1 in contact with the support roller 31, the liquid crystal composition ejected from the mold 33 is coated on the first main surface 1A of the film substrate 1 (coating step).

[0063] In the second conveying process, the first main surface 1A of the film substrate 1 is exposed. Therefore, during the period when the film substrate 1 is conveyed from the peeling section 10 (peeling roller 11) to the coating section 30 (support roller 31), if the conveying roller comes into contact with the first main surface 1A of the film substrate 1, scratches will be generated on the contact portion of the first main surface with the conveying roller, resulting in poor liquid crystal alignment.

[0064] Figure 4 Viewed from the second main surface 1B side of the membrane substrate 1 Figure 3 This diagram illustrates the transport path of the film substrate 1 from the peeling roller 11 to the support roller 31 in the apparatus shown. Regions 38 and 39 at both ends of the film substrate 1 in the width direction are areas outside the product. Region 37 in the center of the film substrate 1 in the width direction is the product area. In the coating section, with the second main surface 1B of the film substrate 1 in contact with the support roller 31, the liquid crystal composition ejected from the mold 33 is coated on region 37 of the first main surface 1A of the film substrate 1. The liquid crystal composition is not coated on regions 38 and 39 at either end of the film substrate 1.

[0065] Figure 3 , 4 In the illustrated manner, during the process of conveying the film substrate 1 from the peeling roller 11 of the peeling section 10 to the support roller 31 of the coating section 30, the pressing rollers 15 (rollers 15A and 15B), which serve as the film pressing mechanism, contact the regions 38 and 39 at both ends of the first main surface 1A of the film substrate 1. During the conveying path from the peeling roller 11 to the support roller 31, the second main surface 1B of the film substrate 1 may contact the conveying roller 13.

[0066] Figure 5 This is a schematic diagram showing the transport path of the film substrate in the comparative example. In this example, no other rollers are arranged between the peeling roller 211 and the support roller 231. Therefore, the film substrate 201, after the protective film 202 is peeled off on the peeling roller 211, is transported to the support roller 231 without contacting other rollers and is coated with the liquid crystal composition ejected from the mold 233. After the protective film 202 is peeled off, the first main surface of the film substrate 201 is coated with the liquid crystal composition without contacting the rollers, thus preventing scratches caused by roller transport.

[0067] However, in this example, the peeling force applied when the protective film 202 is peeled from the film substrate 201 causes the film substrate between the peeling roller 11 and the support roller 231 to vibrate up and down, resulting in uneven coating. Specifically, the liquid crystal layer formed on the film substrate produces segmental thickness unevenness extending along the width direction, resulting in optical defects.

[0068] As a method for non-contact membrane transport, an aerial turning method is known. By employing an aerial turning method in the second transport step, scratches on the first main surface of the membrane substrate can be prevented. However, in the aerial turning method, the membrane substrate also vibrates, thus causing uneven coating as in the example described above.

[0069] like Figure 6 As shown, when a roller 213, which contacts the second main surface of the film substrate 201, is arranged between the peeling roller 211 and the support roller 231, the second main surface of the film substrate 201 (the upper side of the figure) is pressed downward by the roller 213, thus... Figure 4 Compared to the method shown, the vibration (shuffling of the membrane) tends to be suppressed in the membrane substrate 201. However, the peeling force of the protective film 202 acts in a way that stretches the membrane substrate 201 toward the first main surface side (the lower side of the figure), so even if the roller 213 is arranged to contact the second main surface of the membrane substrate 201, the vibration suppression effect of the membrane substrate 201 is limited.

[0070] On the other hand, if a conveying roller is configured to contact the first main surface of the film substrate 201, the vibration of the film substrate 201 can be effectively suppressed. However, since the conveying roller is in contact with the first main surface of the film substrate 201, scratches will be generated, resulting in poor alignment of the liquid crystal layer.

[0071] In embodiments of the present invention, such as Figure 4 As shown, by bringing the rollers 15A and 15B, which serve as the film pressing mechanism, into contact with the regions 38 and 39 at both ends of the first main surface of the film substrate 1 in the width direction, a force is applied to the film substrate 1 from the first main surface side (lower side in the figure) to the upper side in the figure. Therefore, vibration of the film substrate 1 caused by the peeling force of the protective film 2 can be reduced, thereby suppressing uneven coating of the liquid crystal layer.

[0072] In the region 37 at the center of the film substrate 1 in the width direction, the pressing roller 15 does not contact the first main surface 1A, and the other rollers also do not contact the first main surface 1A of the film substrate 1. Therefore, it is possible to prevent scratches on the film substrate 1 from occurring in the product area 37 where the liquid crystal composition is coated, thereby reducing alignment defects in the liquid crystal layer 3.

[0073] like Figure 3 and Figure 4 As shown, if a roller 13, which is in contact with the second main surface 1B of the film substrate 1, is arranged between the peeling roller 11 and the pressing roller 15, the film substrate 1 is also pressed from the second main surface 1B side, thus more effectively suppressing the vibration of the film substrate 1 caused by the peeling force of the protective film 2. A roller in contact with the second main surface of the film substrate 1 can be arranged between the pressing roller 15 and the support roller 31. Rollers in contact with the second main surface 1B of the film substrate 1 can be arranged both between the peeling roller 11 and the pressing roller 15 and between the pressing roller 15 and the support roller 31.

[0074] The roller 15, which is in contact with the second main surface 1B of the membrane substrate 1, may be in contact with only the two ends of the membrane substrate, or it may be as follows: Figure 4 As shown, the roller 15 is integrally connected to the second main surface of the membrane substrate in the width direction. From the viewpoint of membrane substrate transportability, it is preferable that the roller 15 is integrally connected to the second main surface of the membrane substrate in the width direction.

[0075] Two or more pressing rollers can be provided between the peeling roller 11 and the support roller 31, which are connected to the regions 38 and 39 at both ends of the first main surface 1A of the film substrate 1 in the width direction.

[0076] exist Figure 4 In the membrane substrate 1, pressing rollers 15A and 15B are arranged so as to extend beyond the outer sides of both ends of the membrane substrate 1, but the pressing rollers do not necessarily have to extend beyond the outer sides of the membrane substrate 1. For example, the pressing rollers can be arranged within 30cm, 20cm, 15cm, 10cm, 5cm, 3cm or 1cm from the end of the membrane substrate in the width direction.

[0077] In regions 38 and 39 at both ends of the film substrate, the width of the portion of the film substrate in contact with the pressure roller is, for example, 1 to 50 cm. When the width of the portion of the film substrate in contact with the pressure roller is too small, the vibration suppression effect of the film substrate may become insufficient, thus reducing the travelability of the film substrate. When the width of the portion of the film substrate in contact with the pressure roller is too large, the width of the non-product area of ​​the optical film is large, resulting in reduced production efficiency and yield. The width of the portion of the film substrate in contact with the pressure roller can be more than 2 cm, more than 3 cm, or more than 5 cm, or it can be less than 30 cm, less than 25 cm, less than 20 cm, less than 15 cm, or less than 10 cm.

[0078] like Figure 7 As shown, the pressing roller 15 can be paired with roller 16 to clamp the film substrate, and roller 16 is in contact with the second main surface 1B of the film substrate 1. Figure 6 In the manner shown, the roller 16, which is in contact with the second main surface of the membrane substrate 1, can be in contact with the central portion of the membrane substrate 1 in the width direction.

[0079] like Figure 4 As shown, the shape of the pressure roller 15 is not limited to two rollers 15A and 15B separately arranged at both ends in the width direction. For example, like Figure 8 As shown in the barbell-shaped roller 151, cylindrical rollers 15R and 15L can be provided at both ends, and the rollers 15R and 15L at both ends can be connected by a connecting shaft 15C with a diameter smaller than these rollers.

[0080] The film pressing mechanism disposed between the peeling section 10 and the coating section 30 does not necessarily have to be a rotating body. It is acceptable as long as it is a mechanism that can press both ends of the film substrate 1 from the first main surface side to suppress the vibration of the film substrate 1 caused by the peeling of the protective film 2. For example, the film pressing mechanism may be a pin or the like that presses the film substrate from the first main surface side (the lower side of the figure) to the second main surface side.

[0081] After the protective film 2 is peeled off from the first main surface 1A of the film substrate 1, the two ends of the film substrate can be held by a tenter frame clamp. In this case, without the rollers or the like contacting the central portion of the film substrate in the width direction, the regions 38 and 39 at both ends of the film substrate in the width direction are pressed from both sides of the first and second main surfaces, thereby suppressing the vibration of the film substrate 201 caused by the peeling off of the protective film 2. In this case, the lower clamp connected to the first main surface side of the film substrate functions as a film pressing mechanism.

[0082] As described above, in embodiments of the present invention, by temporarily attaching a protective film to the first main surface of the film substrate beforehand, scratches on the first main surface of the film substrate during the transport path until the protective film is peeled off can be prevented. After the protective film is peeled off at the peeling section, during the transport path of the film substrate until the liquid crystal composition is coated at the coating section, the roller does not contact the central portion in the width direction of the first main surface of the film substrate, thus preventing scratches from occurring in the area of ​​the film substrate where the liquid crystal composition is coated (product area). Therefore, it is possible to suppress the formation of alignment defects in the liquid crystal layer caused by scratches on the film substrate, resulting in an optical film with fewer optical defects.

[0083] Furthermore, during the transport path of the film substrate after the protective film is peeled off at the peeling section until the liquid crystal composition is coated at the coating section, a film pressing mechanism, such as a pressing roller, contacts both ends of the first main surface of the film substrate in the width direction. This suppresses vibration of the film substrate caused by the peeling off of the protective film and reduces uneven coating of the liquid crystal composition. In the area where the film pressing mechanism contacts the substrate, scratches may sometimes occur on the first main surface of the film substrate. However, this area is either not coated with liquid crystal composition or is a non-product area excluded during productization, and therefore does not affect the quality of the optical film.

[0084] The following examples illustrate the materials used to form optical films and the manufacturing methods of optical films.

[0085] <Membrane substrate>

[0086] By using a long strip of film substrate 1 as the substrate for coating the liquid crystal composition, a series of processes such as coating, alignment, and photocuring of the liquid crystal composition can be performed in a roll-to-roll manner. In addition, the liquid crystal layer 3 formed on the film substrate 1 can also be bonded to other substrates in a roll-to-roll manner, thereby improving the productivity of optical films.

[0087] The width of the film substrate 1 is preferably 30 cm or more, but can also be 50 cm or more, 80 cm or more, 100 cm or more, or 120 cm or more. From the viewpoint of the productivity of optical films, the wider the width of the film substrate 1, the better; it is usually less than 500 cm, but can also be less than 400 cm or less, or less than 300 cm. The length of the film substrate is preferably 100 m or more, but can also be more than 300 m, 500 m or more, 800 m or more, 1000 m or more, or more than 1200 m. There is no particular upper limit to the length of the film substrate 1; it is usually less than 10000 m, but can also be less than 7000 m or less, or less than 5000 m. The thickness of the film substrate 1 is preferably about 10 to 200 μm.

[0088] The resin material constituting the film substrate 1 is not particularly limited as long as it is not soluble in the solvent of the liquid crystal composition and has heat resistance when heated to orient the liquid crystal composition. Examples include: polyesters such as polyethylene terephthalate and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; cyclic polyolefins such as norbornene polymers; cellulose polymers such as cellulose diacetate and cellulose triacetate; acrylic polymers; styrene polymers; polycarbonate, polyamide, polyimide, etc.

[0089] The film substrate 1 may have an alignment restraint force for aligning liquid crystal molecules along a predetermined direction. For example, the film substrate 1 may have an alignment film on its first main surface. The alignment film can be appropriately selected depending on the type of liquid crystal compound, the material of the substrate, etc. Examples of alignment films for aligning liquid crystal molecules parallel along a predetermined direction include: alignment films obtained by grinding polyimide-based or polyvinyl alcohol-based alignment films. In addition, photo-alignment films may also be used. Alternatively, the resin film may be ground without the alignment film.

[0090] The film substrate 1 may also have an alignment film for aligning liquid crystal molecules vertically. Examples of alignment agents for forming vertically oriented alignment films include: lecithin, stearic acid, hexadecyltrimethylammonium bromide, octadecylamine hydrochloride, monocarboxylic acid chromium complex, silane coupling agents, organosilanes such as siloxane compounds, perfluorodimethylcyclohexane, tetrafluoroethylene, and polytetrafluoroethylene.

[0091] As the film substrate 1, a stretch film can be used. In a stretch film, the resin material (polymer) constituting the film is oriented along the stretching direction, which has the function of oriented liquid crystal molecules along the stretching direction. By using a stretch film, even without forming an alignment film on the film substrate, an orientation-restricting force can be provided to orient liquid crystal molecules along a predetermined direction. Since it is not necessary to form an alignment film, the manufacturing cost of the optical film can be reduced. In addition, by not providing an alignment film, contamination and poor alignment caused by grinding debris can be prevented.

[0092] The stretching direction (orientation direction of the polymer) of the stretched film is not particularly limited; it can be parallel to or non-parallel to the length direction of the film substrate. By using a stretched film in which the molecules are oriented non-parallel to the length direction, a liquid crystal layer in which the liquid crystal molecules are oriented non-parallel to the length direction can be formed.

[0093] The stretching ratio of the stretched film only needs to be sufficient to exert the orientation constraint force, for example, around 1.1 to 5 times. The stretched film can be a biaxially stretched film. Even with a biaxially stretched film, if the stretching ratios in the longitudinal and transverse directions are different, the liquid crystal molecules can be oriented along the direction with the larger stretching ratio.

[0094] The stretched film can also be an inclined stretched film. The inclined stretched film has an orientation axis along a direction that is neither parallel to nor orthogonal to the length direction (for example, a direction at 10 to 80° relative to the length direction). Therefore, by using the inclined stretched film as the film substrate 1, a liquid crystal layer in which liquid crystal molecules are oriented along a direction that is neither parallel to nor orthogonal to the length direction can be formed.

[0095] <Protective film>

[0096] The protective film 2, temporarily adhered to the first main surface 1A of the membrane substrate 1, is not particularly limited in material as long as it is flexible; metal foil, resin film, etc., can be used. The protective film 2 can be transparent or opaque. Resin film is preferred due to its low material cost and excellent processability. Specific examples of resin materials for the protective film 2 include the aforementioned resin materials used as resin materials for the membrane substrate 1. The protective film 2 can also be a stretch film. The thickness of the protective film 2 is not particularly limited. From the viewpoint of balancing self-support and flexibility, the thickness of the protective film 2 is preferably around 10 to 100 μm.

[0097] The protective film 2 preferably has an adhesive layer on the surface in contact with the film substrate 1. The adhesive layer can be bonded to the film substrate 1 and can be made of an adhesive used in common adhesive tapes, as long as it can be peeled off from the film substrate 1. As a protective film, a self-adhesive film obtained by integrally molding the resin material constituting the film and the resin material of the adhesive layer through multilayer extrusion can be used.

[0098] The method of laminating the protective film 2 onto the film substrate 1 is not particularly limited. For example, in the manufacturing process of the film substrate 1, the protective film 2 can be applied to the film substrate 1 in a roll-to-roll manner before the film substrate 1 is rolled into a roll. By continuously applying the protective film 2 in conjunction with the manufacturing process of the film substrate 1, the number of contacts between the roller and the first main surface 1A of the film substrate 1 can be reduced, thereby suppressing the formation of scratches.

[0099] When the membrane substrate 1 is a stretch membrane, it is preferable to apply the protective film 2 immediately after stretching. For example, by stretching the membrane by holding both ends, and then applying the protective film 2 before the first main surface 1A of the membrane substrate 1 comes into contact with the conveying roller, it is possible to prevent scratches from forming on the first main surface 1A of the membrane substrate 1.

[0100] The laminate 8 on which the protective film 2 is adhered to the first main surface 1A of the membrane substrate 1 can be temporarily wound into a roller-shaped coil 80. Alternatively, the laminate 8 can be directly transported to the peeling section 10 without being wound up, and the protective film 2 can be peeled off from the membrane substrate 1.

[0101] <Liquid crystal material>

[0102] The liquid crystal layer 3 formed on the film substrate 1 contains liquid crystal molecules. Preferably, the liquid crystal molecules in the liquid crystal layer 3 are oriented along a predetermined direction. For example, a liquid crystal layer 3 with liquid crystal molecules oriented along a predetermined direction is formed by coating a liquid crystal composition containing a liquid crystal compound onto the film substrate 1, aligning the liquid crystal compound along a predetermined direction, and then fixing the alignment state.

[0103] Examples of liquid crystal compounds include rod-shaped and disc-shaped liquid crystal compounds. Rod-shaped liquid crystal compounds are preferred because they are easily aligned in parallel due to the orientation constraint forces of the film substrate. Rod-shaped liquid crystal compounds can be either main-chain or side-chain liquid crystals. They can be liquid crystal polymers or polymers of polymerizable liquid crystal compounds. If the liquid crystal compound (monomer) exhibits liquid crystal properties before polymerization, it can remain non-liquid crystal properties after polymerization.

[0104] The liquid crystal compound is preferably a thermotropic liquid crystal that exhibits liquid crystal properties upon heating. Thermotropic liquid crystals undergo phase transitions between a crystalline phase, a liquid crystal phase, and an isotropic phase with temperature changes. The liquid crystal compound contained in the liquid crystal composition can be any liquid crystal selected from nematic liquid crystals, dished liquid crystals, and cholesteric liquid crystals. A chiral agent can also be added to the nematic liquid crystal to impart cholesteric orientation.

[0105] Examples of thermotropic rod-shaped liquid crystal compounds include: methylimine derivatives, azo derivatives, cyanobiphenyl derivatives, cyanophenyl esters, benzoic acid esters, cyclohexane carboxylic acid phenyl esters, cyanophenylcyclohexane derivatives, cyano-substituted phenylpyrimidine derivatives, alkoxy-substituted phenylpyrimidine derivatives, phenyldialkyl derivatives, diphenylacetylene derivatives, and alkenylcyclohexylbenzonitrile derivatives.

[0106] Examples of polymerizable liquid crystal compounds include those that allow the orientation of rod-shaped liquid crystal compounds to be fixed using polymer adhesives, and those that have polymerizable functional groups that allow the orientation of liquid crystal compounds to be fixed through polymerization. Among these, photocurable liquid crystal compounds having photocurable functional groups are preferred.

[0107] The photocurable liquid crystal compound (liquid crystal monomer) has a mesocrystalline group and at least one photocurable 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 to 200°C, more preferably 50 to 150°C, and even more preferably 55 to 100°C.

[0108] Examples of mesocrystalline groups that can serve as monomers for liquid crystals include: biphenyl, phenylbenzoate, phenylcyclohexyl, azophenyl, methylimino, azophenyl, phenylpyrimidinyl, diphenylethynyl, diphenylbenzoate, dicyclohexyl, cyclohexylphenyl, and terphenyl, among others. These cyclic units may have substituents such as cyano, alkyl, alkoxy, or halogenated groups at their ends.

[0109] Examples of photocurable functional groups include (meth)acryloyl, epoxy, and vinyl ether groups. Among these, (meth)acryloyl is preferred. The photocurable liquid crystal monomer preferably has two or more photocurable functional groups in one molecule. By using a liquid crystal monomer containing two or more photocurable functional groups, a cross-linking structure is introduced into the photocured liquid crystal layer, thus tending to improve the durability of the optical film.

[0110] As the photocurable liquid crystal monomer, any suitable liquid crystal monomer can be used. Examples include: International Patent Publication No. 00 / 37585, US Patent No. 5,211,877, US Patent No. 4,388,453, International Patent Publication No. 93 / 22,397, European Patent No. 0261,712, German Patent No. 19,504,224, German Patent No. 4,408,171, British Patent No. 2,280,445, Japanese Patent Application Publication No. 2017-206460, International Patent Publication No. 2014 / 126,113, International Patent Publication No. 2016 / 114,348, International Patent Publication No. 2014 / 010325, and Japanese Patent Application Publication No. 2015. The compounds described in Japanese Patent Application Publication No. 200877, Japanese Patent Application Publication No. 2010-31223, International Patent Application Publication No. 2011 / 050896, Japanese Patent Application Publication No. 2011-207765, Japanese Patent Application Publication No. 2010-31223, Japanese Patent Application Publication No. 2010-270108, International Patent Application Publication No. 2008 / 119427, Japanese Patent Application Publication No. 2008-107767, Japanese Patent Application Publication No. 2008-273925, International Patent Application Publication No. 2016 / 125839, and Japanese Patent Application Publication No. 2008-273925, etc., can have their birefringence manifestation and retardation wavelength dispersion adjusted by selecting the liquid crystal monomer.

[0111] In addition to liquid crystal monomers, liquid crystal compositions may also contain compounds that control the orientation of 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 vertically oriented. Furthermore, by adding a chiral agent to the liquid crystal composition, the liquid crystal compound can be cholesterically oriented.

[0112] 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 photopolymerization initiator (photoradical generator) that generates free radicals upon light irradiation to promote photocuring. Depending on the type of liquid crystal monomer (the type of photocurable functional group), photocation generators or photoanion generators can be used. The amount of photopolymerization initiator used is approximately 0.01 to 10 parts by weight relative to 100 parts by weight of the liquid crystal monomer. In addition to photopolymerization initiators, sensitizers, etc., may also be used.

[0113] Liquid crystal compositions can be prepared by mixing liquid crystal monomers with various orientation control agents, polymerization initiators, etc., as needed, and solvents. There are no particular limitations on the solvent, as long as it can dissolve the liquid crystal monomers and does not corrode the substrate (or has low corrosiveness). Examples include: halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and o-dichlorobenzene; phenols such as phenol and p-chlorophenol; aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, and 1,2-dimethoxybenzene; and acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, and 2-pyrrolidone. Ketone solvents such as N-methyl-2-pyrrolidone; ester solvents such as ethyl acetate and butyl acetate; alcohol solvents such as tert-butanol, glycerol, 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; ethyl cellosolve and butyl cellosolve, etc. Mixed solvents of two or more solvents may also be used.

[0114] The solid content concentration of liquid crystal compositions is typically around 5–60% by weight. Liquid crystal compositions may also contain additives such as surfactants and leveling agents.

[0115] <Formation of liquid crystal layer on film substrate>

[0116] A laminate 8 with a protective film 2 peelably attached to the first main surface 1A of the film substrate 1 is conveyed to the peeling section 10, and the protective film 2 is peeled off. The film substrate 1 with the protective film 2 peeled off is then conveyed to the coating section 30, where a liquid crystal composition is coated on the first main surface 1A of the film substrate 1. As described above, during the conveying path from the peeling section 10 to the coating section 30, the roller does not contact the region 37 at the center of the width direction of the first main surface 1A of the film substrate 1. Therefore, for region 37 of the first main surface 1A, fewer scratches caused by roller contact are possible, thus reducing liquid crystal alignment defects.

[0117] exist Figure 3 The figures show a method of coating a liquid crystal composition onto a mold 33 positioned opposite the support roller 31, but the method of coating the liquid crystal composition onto the film substrate 1 is not particularly limited. Besides mold coating, other coating methods include: roller coating, gravure coating, reverse coating, spray coating, Mayer rod coating, doctor blade roller coating, and air knife coating.

[0118] As described above, the central region 37 of the first main surface 1A of the film substrate 1 in the width direction does not come into contact with rollers or the like after the protective film 2 is peeled off. Therefore, by coating the liquid crystal composition in this region, alignment defects caused by scratches on the film substrate can be reduced. Furthermore, the liquid crystal composition can also be coated at both ends of the film substrate 1 in the width direction, in contact areas 38 and 39 with the film pressing mechanism. In this case, by methods such as punching the optical film or cutting the ends, the contact areas with the film pressing mechanism can be cut off from the product at an appropriate stage after coating the liquid crystal composition.

[0119] The coating thickness of the liquid crystal composition is preferably adjusted such that the thickness of the liquid crystal composition layer (the thickness of the liquid crystal layer 3) after solvent drying is approximately 0.1 to 20 μm. The film substrate 1 coated with the liquid crystal composition can be heated in the heating unit 50. The heating unit 50 includes, for example, a heating furnace 55, and the film substrate 1 and the liquid crystal composition coated thereon are heated during the transfer of the film substrate 1 into the heating furnace 55. For example, heating can remove the solvent contained in the liquid crystal composition.

[0120] When the liquid crystal compound contained in the liquid crystal composition is a thermotropic liquid crystal, a liquid crystal phase is formed by heating the liquid crystal composition layer, and the liquid crystal compound is oriented along a predetermined direction. Specifically, the liquid crystal composition coated on the film substrate is heated to above the N (nematic phase) - I (isotropic liquid phase) transition temperature to form an isotropic liquid state. Then, a nematic phase is revealed by slow cooling as needed. At this time, it is desirable to maintain a temperature that temporarily reveals the liquid crystal phase and allow liquid crystal phase domains to grow, thus forming a single domain. Alternatively, after coating the liquid crystal composition, the temperature can be maintained for a certain period of time within the temperature range where the nematic phase is revealed, thereby oriented the liquid crystal molecules along a predetermined direction.

[0121] The heating temperature for aligning the liquid crystal compound along a specified direction can be appropriately selected according to the type of liquid crystal composition, typically ranging from 40 to 200°C. If the heating temperature is too low, the transfer to the liquid crystal phase tends to be insufficient; if the heating temperature is too high, alignment defects tend to increase. The heating time can be adjusted to ensure sufficient growth of the liquid crystal phase domain, typically ranging from 30 seconds to 30 minutes.

[0122] Preferably, the liquid crystal compound is oriented by heating and then cooled to a temperature below the glass transition temperature. The cooling method is not particularly limited; for example, it can be removed from a heated atmosphere to room temperature. Forced cooling, such as air cooling or water cooling, can also be used.

[0123] When the liquid crystal compound has curable properties, curing is preferably performed in the curing section 60. For example, when the liquid crystal compound has photocurable properties, photocuring is performed when the photocurable liquid crystal compound (liquid crystal monomer) has liquid crystal regularity. The irradiation light from the light source 61 is sufficient to polymerize the photocurable liquid crystal compound; ultraviolet or visible light with a wavelength of 250–450 nm is typically used. When the liquid crystal composition contains a photopolymerization initiator, light with a wavelength to which the photopolymerization initiator has sensitivity is selected. As the irradiation light source, low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, xenon lamps, LEDs, black lights, chemical lamps, etc., are used. To promote the photocuring reaction, light irradiation is preferably performed in an inert gas atmosphere such as nitrogen.

[0124] During photocuring, the liquid crystal compound can be oriented along a predetermined direction by using polarized light in a specified direction. As described above, when the liquid crystal compound is oriented by the orientation constraint force of the film substrate 1, the irradiation light can also be unpolarized light (natural light).

[0125] The irradiation intensity can be adjusted appropriately based on the composition of the liquid crystal composition and the amount of photopolymerization initiator added. The irradiation energy (cumulative irradiation light intensity) is typically 20–10000 mJ / cm². 2 Around 50 to 5000 mJ / cm² 2 More preferably 100–800 mJ / cm 2 To promote the photocuring reaction, light irradiation can be applied under heating conditions.

[0126] The polymer after photocuring of liquid crystal monomers is non-liquid crystal, and no temperature-dependent phase transitions occur between the liquid crystal phase, glass phase, and crystalline phase. Therefore, when the liquid crystal monomers are aligned in a specified direction, the photocured liquid crystal layer is less prone to changes in molecular orientation due to temperature variations. Furthermore, the liquid crystal layer exhibits significantly higher birefringence compared to films formed from non-liquid crystal materials, thus enabling a substantial reduction in the thickness of optically anisotropic elements with desired delays.

[0127] The optical properties of the liquid crystal layer 3 are not particularly limited. The frontal retardation and thickness retardation of the liquid crystal layer 3 can be appropriately set according to the application and other factors. When the liquid crystal molecules are aligned in parallel, the frontal retardation of the liquid crystal layer 3 is, for example, about 20 to 1000 nm. When the liquid crystal layer 3 is a quarter-wave plate, the frontal retardation is preferably 100 to 180 nm, more preferably 120 to 150 nm. When the liquid crystal layer 3 is a half-wave plate, the frontal retardation is preferably 200 to 340 nm, more preferably 240 to 300 nm. When the liquid crystal is aligned vertically, the in-plane retardation of the liquid crystal layer 3 is about 0 (for example, 5 nm or less, preferably 3 nm or less), and the absolute value of the thickness retardation is about 30 to 500 nm.

[0128] The orientation direction of the liquid crystal molecules in the liquid crystal layer 3 can be parallel to or non-parallel to the length direction (roll-to-roll transport direction) of the film substrate 1. As described above, by utilizing the orientation-restricting force of an inclined stretching film or the like, a liquid crystal layer in which the liquid crystal molecules are oriented non-parallel to the length direction can be formed. When the liquid crystal molecules are oriented non-parallel to the length direction, if there are scratches along the length direction on the film substrate, the liquid crystal molecules of the liquid crystal layer formed thereon will align along the scratches in the length direction, thus resulting in poor alignment. By temporarily attaching a protective film to the film substrate 1 as described above and preventing it from contacting the roller after peeling off the protective film, it is possible to suppress the formation of scratches on the film substrate and reduce the poor alignment of the liquid crystal layer.

[0129] A long strip of optical film is obtained by winding a laminate 9 (optical film) on the first main surface 1A of the film substrate 1 with a winding roller 91. This laminate 9 can be used directly as an optical film. The regions 38 and 39 at both ends of the film substrate 1 in the width direction are non-product regions, and therefore it is preferable to cut them off by slits during the period from the formation of the liquid crystal layer 3 until winding with the winding roller 91, or at an appropriate stage after winding with the winding roller 91. Alternatively, the film can be punched to cut out single-piece products in a manner that excludes the regions 38 and 39 at both ends in the width direction.

[0130] <Lamination method of optical films>

[0131] The laminate 9, on the first main surface 1A of the film substrate 1, having the liquid crystal layer 3 formed thereon, can be used directly as an optical film, or the film substrate 1 can be peeled off and only the liquid crystal layer 3 can be used as an optical film. Alternatively, other layers can be laminated on the liquid crystal layer 3. For example, by bonding the optical layer 4 onto the liquid crystal layer 3 with an adhesive layer 5 in between, a... Figure 9 The layered structure shown is 96.

[0132] The optical layer 4, stacked on the liquid crystal layer 3, is not particularly limited and can be any optically isotropic or optically anisotropic film commonly used as an optical film. Specific examples of the optical layer 4 include transparent films such as retardation films and polarizer protective films, polarizers themselves, viewing angle widening films, viewing angle limiting (spyscreen) films, and brightness enhancing films. The optical layer 4 can be a single layer or a stack. The optical layer 4 can be a liquid crystal layer. For example, the optical layer 4 can be a polarizer with a transparent protective film attached to one or both sides of the polarizer. When one side of the polarizer has a transparent protective film, the polarizer can be attached to the liquid crystal layer, or the transparent protective film can be attached to the liquid crystal layer.

[0133] The adhesive constituting the adhesive layer 5 is not particularly limited in material as long as it is optically transparent; examples include epoxy resin, silicone resin, acrylic resin, polyurethane, polyamide, polyether, and polyvinyl alcohol. The thickness of the adhesive layer 5 is appropriately set according to the type of substrate being adhered to and the material of the adhesive. When using a curing adhesive that exhibits adhesion through a cross-linking reaction after coating, the thickness of the adhesive layer 5 is preferably 0.01–5 μm, more preferably 0.03–3 μm.

[0134] As an adhesive, various types of adhesives can be used, including water-based adhesives, solvent-based adhesives, hot-melt adhesives, and active energy radiation-cured adhesives. Among these, water-based adhesives or active energy radiation-cured adhesives are preferred because they can reduce the thickness of the adhesive layer.

[0135] The liquid crystal layer 3 and the optical layer 4 are laminated through an adhesive layer 5 by applying and curing an adhesive to either or both of the surfaces of the liquid crystal layer 3 and the optical layer 4. The curing method of the adhesive can be appropriately selected depending on the type of adhesive. For example, water-based adhesives can be cured by heating. Active energy ray-cured adhesives can be cured by irradiation with active energy rays such as ultraviolet light.

[0136] A laminate 96 in which the liquid crystal layer 3 is bonded to the optical layer 4 via the adhesive layer 5 on the film substrate 1 can also be directly used as an optical film. In this case, the film substrate 1 constitutes part of the optical film. Figure 10 As shown, the film substrate can be peeled off and removed from the liquid crystal layer 3. Figure 11 As shown, a suitable adhesive layer 6 can be laminated on the surface of the liquid crystal layer 3 exposed by peeling off the film substrate.

[0137] There are no particular limitations on the adhesive constituting adhesive layer 6. Adhesives with acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, fluoropolymers, rubber polymers, etc., as base polymers can be appropriately selected. Acrylic adhesives and rubber adhesives, which exhibit excellent transparency, moderate wetting, cohesiveness, and adhesion, as well as excellent weather resistance and heat resistance, are particularly preferred. The thickness of the adhesive layer can be appropriately set according to the type of substrate being adhered to, typically ranging from 5 to 500 μm.

[0138] The adhesive layer 6 is laminated onto the liquid crystal layer 3, for example, by bonding a pre-formed sheet-like adhesive to the surface of the liquid crystal layer 3. The adhesive layer 6 can be formed by drying, cross-linking, or photocuring a solvent after the adhesive composition is applied to the liquid crystal layer 3. To improve the adhesion (anchoring force) between the liquid crystal layer 3 and the adhesive layer 6, the adhesive layer 6 can be laminated after forming a surface treatment such as corona treatment or plasma treatment, or an easy-to-adhere layer, on the surface of the liquid crystal layer 3.

[0139] Preferably, a diaphragm 7 is temporarily adhered to the surface of the adhesive layer 6. The diaphragm 7 protects the surface of the adhesive layer 6 until the optical film is bonded to other components. As the constituent material of the diaphragm, suitable plastic films such as acrylic, polyolefin, cyclic polyolefin, and polyester can be used. The thickness of the diaphragm is typically around 5–200 μm. Preferably, a release agent is applied to the surface of the diaphragm. Examples of release agents include: silicon-based materials, fluorine-based materials, long-chain alkyl-based materials, and fatty acid amide-based materials.

[0140] Other optical layers can be stacked on the exposed surface of the liquid crystal layer 3 after the film substrate 1 has been peeled off, with a suitable adhesive layer or bonding agent layer in between. For example, other optical layers can be stacked on the liquid crystal layer 3 with a suitable adhesive layer in between, or an adhesive layer can be further stacked on it.

[0141] Optical films with liquid crystal layers can be used, for example, as optical films for image display devices. As an example of an optical film in which other optical layers 4 are bonded to a liquid crystal layer 3, a circular polarizer formed by stacking a liquid crystal layer 3 and a polarizer can be cited.

[0142] Polarizing films can be formed from a single polarizer, or, as described above, a transparent protective film can be laminated to one or both sides of the polarizer. Examples of polarizers include polarizers formed by uniaxially stretching hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, as well as polyene-based oriented films such as dehydrated polyvinyl alcohol products and dehydrochlorinated polyvinyl chloride products.

[0143] Polyvinyl alcohol (PVA) polarizers, obtained by adsorbing dichroic substances such as iodine or dichroic dyes onto a polyvinyl alcohol film or partially formalized polyvinyl alcohol and orienting it in a specified direction, are preferred due to their high polarization degree. For example, a PVA polarizer can be obtained by iodizing and stretching a polyvinyl alcohol film. Alternatively, a PVA resin layer can be formed on a resin substrate, and iodizing and stretching can be performed in a laminated state.

[0144] For a circular polarizer formed by stacking a polarizer and a liquid crystal layer, it is preferable that the liquid crystal molecules in at least one liquid crystal layer are aligned in parallel. In a circular polarizer, the liquid crystal molecules in the liquid crystal layer with parallel alignment are arranged in a manner that is neither parallel nor orthogonal to the absorption axis of the polarizer.

[0145] For example, in the case where the circular polarizer has only one liquid crystal layer, the liquid crystal layer 3 is a quarter-wave plate, and the angle between the absorption axis of the polarizer and the orientation direction of the liquid crystal molecules (usually the slow axis) is set to 45°. The angle between the absorption axis of the polarizer and the orientation direction of the liquid crystal molecules can be 35–55°, 40–50°, or 43–47°.

[0146] In a configuration where the optical axes of the polarizer 4 and the liquid crystal layer 3 (which serves as a quarter-wave plate) are stacked at an angle of 45°, a liquid crystal layer in which the liquid crystal molecules are vertically aligned with respect to the substrate surface (vertical alignment) can be further incorporated. By sequentially stacking the liquid crystal layer 3 (which serves as a quarter-wave plate) and the vertically aligned liquid crystal layer (which functions as a positive C-plate) on the polarizer, a circular polarizer capable of shielding reflected light from external light coming from an inclined direction can be formed. A vertically aligned liquid crystal layer (positive C-plate) and a parallel-aligned liquid crystal layer (a quarter-wave plate serving as a positive A-plate) can be sequentially stacked on the polarizer.

[0147] In a circular polarizer with multiple liquid crystal layers stacked on top of a polarizer, all liquid crystal layers can be parallel-aligned liquid crystal layers. In this case, it is preferable that the liquid crystal layer disposed near the polarizer 4 is a half-wave plate and the liquid crystal layer disposed away from the polarizer is a quarter-wave plate. This stacking configuration is preferably arranged such 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 stacking configuration functions as a circular polarizer over a wide wavelength range of visible light, thus reducing the coloration of reflected light.

[0148] As described above, the liquid crystal layer obtained by the embodiments of the present invention suppresses the formation of scratches on the first main surface (coating surface of the liquid crystal composition) of the film substrate. Therefore, even when the liquid crystal molecules are not aligned parallel to the length direction of the film substrate, there are few misalignment defects and good display characteristics can be achieved.

Claims

1. A method for manufacturing an optical film, comprising a strip of optical film including a liquid crystal layer, comprising the following steps: The process of preparing a laminate formed by peelably attaching a protective film to the first main surface of a strip of film substrate having a first main surface and a second main surface; The first conveying process involves conveying the laminated body rollers to the peeling section along the length of the film substrate. The protective film peeling process in which the protective film is peeled off from the first main surface of the film substrate at the peeling section; A second conveying process in which the membrane substrate, after the protective film has been peeled off, is conveyed from the peeling section to the coating section along the length direction of the membrane substrate; and The coating process of coating a liquid crystal composition onto the first main surface of the film substrate in the coating section. In the second conveying process, the roller does not contact the central portion of the first main surface of the film substrate in the width direction. The membrane pressing mechanism, which applies a force to the membrane substrate from the first main surface side to the second main surface side, contacts both ends of the first main surface of the membrane substrate at least once in the width direction, and the membrane pressing mechanism does not contact the central portion of the first main surface of the membrane substrate in the width direction.

2. The method for manufacturing the optical film according to claim 1, wherein, The membrane pressing mechanism is a pressing roller that contacts only the two ends of the first main surface of the membrane substrate in the width direction.

3. The method for manufacturing the optical film according to claim 1, wherein, In the second conveying process, the conveying roller contacts the second main surface of the film substrate at least once.

4. The method for manufacturing the optical film according to claim 3, wherein, The conveying roller is integrally connected to the second main surface of the film substrate in the width direction.

5. The method for manufacturing the optical film according to any one of claims 1 to 4, wherein, In the coating process, the liquid crystal composition is coated onto the inner side in the width direction of the contact portion with the film pressing mechanism on the first main surface of the film substrate.

6. The method for manufacturing an optical film according to any one of claims 1 to 4, wherein after the coating process, the method includes a step of cutting off and removing the regions at both ends of the film substrate in the width direction that are in contact with the film pressing mechanism.

7. The method for manufacturing the optical film according to any one of claims 1 to 4, wherein, The membrane substrate is a stretched membrane in which the molecules are oriented non-parallel to the length direction.

8. The method for manufacturing an optical film according to claim 7, wherein, The membrane substrate is an inclined stretch membrane.

9. The method for manufacturing the optical film according to any one of claims 1 to 4, wherein, An alignment film is not disposed on the first main surface of the film substrate.

10. The method for manufacturing the optical film according to any one of claims 1 to 4, wherein, The liquid crystal composition comprises a photocurable liquid crystal compound. The coating process is followed by a process of photocuring the liquid crystal compound.

11. A method for manufacturing an optical film according to any one of claims 1 to 4, comprising a step of laminating other optical layers on the liquid crystal layer in a roll-to-roll manner.

12. The method for manufacturing an optical film according to claim 11, wherein, The optical layer includes a polarizer.

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