Film, film roll, and method for manufacturing film

Abstract

Provided is a film, a film roll, and a film manufacturing method that can suppress the occurrence of winding defects. The film includes: a first end portion and a second end portion in a width direction that intersects a long direction; a central portion between the first end portion and the second end portion; a convex position in which a thickness Te1 of at least the first end portion is smaller than a thickness Tc of the central portion; and a concave position that is disposed at a position different from the convex position in the long direction and in which the thickness Te1 of the first end portion is greater than the thickness Tc of the central portion.

Description

Technical Field

[0001] This invention relates to a membrane, a membrane roll, and a method for manufacturing the membrane. Background Technology

[0002] In recent years, with the trend towards lighter and more flexible devices, the thinning of membranes used in devices has been developing. For example, thin-film optical films can be used in devices such as displays and touch sensors (e.g., Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-100372 Summary of the Invention

[0006] However, if the membrane is made thinner, poor winding can easily occur during membrane roll formation, potentially damaging the membrane quality. For example, if the amount of air between the membranes becomes too small, poor winding, such as poor adhesion between the membranes, can occur.

[0007] Therefore, the object of the present invention is to provide a film, a film roll, and a method for manufacturing the film that can suppress the generation of winding defects.

[0008] The above-mentioned problems of the present invention are solved by the following means.

[0009] A membrane comprising: a first end and a second end intersecting in a wide side direction along a long side direction; a central portion between the first end and the second end; a convex position where the thickness Te1 of at least one of the first end and the second end is smaller than the thickness Tc of the central portion; and a concave position disposed in the long side direction at a position different from the convex position, wherein the thickness Te1 of the first end is larger than the thickness Tc of the central portion.

[0010] According to the present invention, since the membrane has a convex position where the thickness Te1 at the first end is smaller than the thickness Tc at the center, and a concave position where the thickness Te1 at the first end is larger than the thickness Tc at the center, the amount of air between the membranes can be easily controlled during membrane roll formation. Therefore, the occurrence of winding defects can be suppressed. Attached Figure Description

[0011] Figure 1 This is a schematic diagram illustrating an example of the structure of a film roll according to one embodiment of the present invention.

[0012] Figure 2 It means Figure 1 A top view showing an example of the structure of a membrane.

[0013] Figure 3 (A) represents Figure 2 The diagram (B) shows the cross-section of the convex region. Figure 2 The diagram shows the cross-section of the concave region.

[0014] Figure 4 It means Figure 3 Figures (A) and (B) show other examples of membrane end sections forming cross-sections.

[0015] Figure 5A It means Figure 2 This is a diagram illustrating an example of the relationship between the position of the membrane along its long side and the difference ratio D of the thickness at the ends and the center.

[0016] Figure 5B It means Figure 5A The figure shows other examples of the relationship between the position of the membrane along its long side and the difference ratio D.

[0017] Figure 5C It means Figure 5A The figure shows other examples of the relationship between the position of the membrane along its long side and the difference ratio D.

[0018] Figure 6A It means Figure 5A The figure shows other examples of the relationship between the position of the membrane along its long side and the difference ratio D.

[0019] Figure 6B It means Figure 5A The figure shows other examples of the relationship between the position of the membrane along its long side and the difference ratio D.

[0020] Figure 7 This is a flowchart illustrating an example of a membrane manufacturing method.

[0021] Figure 8 It means Figure 7 The diagram shows the configuration of the tenter frame used in step S102.

[0022] Figure 9A This is a diagram illustrating an example of the relationship between the position of the membrane along its long side and the difference ratio D in the comparative example.

[0023] Figure 9B It means Figure 9A The figure shows other examples of the relationship between the position of the membrane along its long side and the difference ratio D.

[0024] Figure 9C It means Figure 9A The figure shows other examples of the relationship between the position of the membrane along its long side and the difference ratio D.

[0025] Figure 10 It means Figure 1 A diagram showing an example of the configuration of the end face of the membrane roll.

[0026] Figure 11 This is a diagram illustrating an example of the cross-sectional structure of the membrane involved in the modified example. Detailed Implementation

[0027] Hereinafter, preferred embodiments of the present invention will be described. In this specification, the range “X~Y” indicates “X or more and Y or less”. Furthermore, unless otherwise specified, operation and physical properties are measured under conditions of room temperature (20~25°C) and relative humidity 40~50%RH.

[0028] In addition, the dimensions in the attached drawings are exaggerated for ease of explanation and differ from the actual dimensions.

[0029] Figure 1 This illustrates the configuration of a film roll 1 according to one embodiment. The film roll 1 is formed by winding an optical film 11 in a roller shape onto a core 12. The optical film 11 has optical functions such as light transmission, reflection, diffusion, and absorption, and is used, for example, in displays and touch sensors. The core 12, for example, has a cylindrical shape and a predetermined length (…). Figure 1 (The size in the X direction). An optical film 11 is wound circumferentially around the core 12. The total winding length of the film roll 1 is, for example, 500m to 20000m.

[0030] Figure 2 This is an example of the planar configuration of the optical film 11. The optical film 11 is wound around the core 12 along its long side direction. In the following description, the long side direction of the optical film 11 may be referred to as the Y direction, the wide side direction intersecting the long side direction may be referred to as the X direction, and the thickness direction may be referred to as the Z direction. Here, the wide side direction of the optical film 11 is almost orthogonal to the long side direction. The length of the long side direction of the optical film 11 is, for example, 500 μm to 20000 μm, and the length of the wide side direction of the optical film 11 is, for example, 100 mm to 3000 mm.

[0031] The optical film 11 has a pair of ends e1 and e2 in the wide-side direction and a central portion c between the pair of ends e1 and e2. The pair of ends e1 and e2 and the central portion c are, for example, portions each having approximately 10% of the overall size of the optical film 11 in the wide-side direction. End e1 is one end of the optical film 11 in the wide-side direction, end e2 is the other end of the optical film 11 in the wide-side direction, and the central portion c respectively includes the center of the optical film 11 in the wide-side direction. Here, end e1 corresponds to a specific example of the first end of the present invention, and end e2 corresponds to a specific example of the second end of the present invention.

[0032] The optical film 11 has convex regions R1 and concave regions R2 arranged side by side in the Y direction. For example, multiple convex regions R1 and concave regions R2 are provided in the optical film 11, and the convex regions R1 and concave regions R2 are alternately arranged in the Y direction.

[0033] Figure 3 (A) represents the XZ section of the convex region R1. Figure 3 (B) represents the XZ section of the concave region R2. In the convex region R1, the thickness Te1 of end e1 and the thickness Te2 of end e2 are smaller than the thickness Tc of the central part c. In the concave region R2, the thickness Te1 of end e1 and the thickness Te2 of end e2 are larger than the thickness Tc of the central part c. That is, in the convex region R1, the thicknesses Te1, Te2, and Tc satisfy the following mathematical formulas (1) and (2), and in the concave region R2, the thicknesses Te1, Te2, and Tc preferably satisfy the following mathematical formulas (3) and (4).

[0034] [Mathematical Expression 1]

[0035] Te1<Tc (1)

[0036] Te2<Tc (2)

[0037] [Mathematical Expression 2]

[0038] Te1>Tc (3)

[0039] Te2>Tc (4)

[0040] In other words, at the convex position P1 within the convex region R1, the thicknesses Tel, Te2, and Tc satisfy mathematical formulas (1) and (2), and at the concave position P2 within the concave region R2, the thicknesses Tel, Te2, and Tc preferably satisfy mathematical formulas (3) and (4). The convex position P1 can be any position within the convex region R1, and the concave position P2 can be any position within the concave region R2.

[0041] The details are described below, but in this embodiment, the optical film 11 has a convex position P1 and a concave position P2, and more specifically, a convex region R1 and a concave region R2. Therefore, when forming the film roll 1, it is easy to control the amount of air between the overlapping optical films 11. Thus, the occurrence of winding defects can be suppressed.

[0042] In the convex position P1 and the convex region R1, the thickness Tel of the end e1 is less than the thickness Tc of the central part c. In the concave position P2 and the concave region R2, the thickness Tel of the end e1 is greater than the thickness Tc of the central part c. That is, in the convex position P1 and the convex region R1, the thickness Tel and Tc must at least satisfy mathematical formula (1). In the concave position P2 and the concave region R2, the thickness Te1 and Tc must at least satisfy mathematical formula (3).

[0043] In the optical film 11, at the convex position P1 and the convex region R1, the thicknesses Te1, Te2, and Tc satisfy mathematical formulas (1) and (2), and at the concave position P2 and the concave region R2, the thicknesses Te1, Te2, and Tc preferably satisfy mathematical formulas (3) and (4). This allows for more effective suppression of winding defects. For example, at a specified position in the Y direction, the thickness Te1 of end e1 and the thickness Te2 of end e2 are almost the same. The overall average thickness of the optical film 11 is, for example, about 10 μm to 40 μm. The respective sizes of the convex region R1 and the concave region R2 in the Y direction are preferably 100 μm to 500 μm, more preferably 250 μm or more. This allows for more effective suppression of winding defects. The sizes of the convex region R1 and the concave region R2 in the Y direction are, for example, almost the same. The sizes of the convex region R1 and the concave region R2 in the Y direction can be different from each other.

[0044] Figure 4 express Figure 3 Other examples of the cross-sectional configuration of the optical film 11 shown. The optical film 11 may have an embossed portion E. The embossed portion E is a portion that has undergone embossing processing, for example, having irregularities on its surface. The embossed portion E is provided, for example, at the ends e1 and e2. In this case, the thicknesses Te1 and Te2 of the ends e1 and e2 are, for example, the thickness of the protrusion of the embossed portion E.

[0045] In the optical film 11, the difference between the thickness Te1, Te2 of the ends e1, e2 at predetermined positions in the Y direction (e.g., convex position P1, concave position P2) and the thickness Tc of the central portion c is expressed using differential ratios D1 and D2. These differential ratios D1 and D2 are the differences between the thickness Te1, Te2 and the thickness Tc relative to the average thickness Ta of the optical film 11, and can be expressed by the following mathematical formulas (5) and (6). In the convex region R1, the differential ratios D1 and D2 are positive, and in the concave region R2, they are negative. The absolute values ​​of the differential ratios D1 and D2 (hereinafter denoted as |D1|, |D2|) are preferably, for example, 10% or less and 5% or less. By setting |D1| and |D2| to 5% or less, the generation of winding defects can be suppressed more effectively.

[0046] [Mathematical Expression 3]

[0047] Difference ratio D1(%) = [(Tc-Te1) / Ta]×100 (5)

[0048] Difference ratio D2(%) = [(Tc-Te2) / Ta]×100 (6)

[0049] Where Ta is the average thickness of the optical film 11 at a predetermined position in the Y direction.

[0050] For example, the difference ratios D1 and D2 for the specified positions in the Y direction are almost identical. In the following explanation, when the difference ratios D1 and D2 for the specified positions in the Y direction are almost identical, they will be collectively represented as difference ratio D. This will be explained below. Figures 5A to 6B and Figure 8 A~ Figure 8 In C, the difference ratios D1 and D2 for the specified positions in the Y direction are almost the same, so difference ratio D is used.

[0051] Figure 5A , Figure 5B and Figure 5C Here is an example illustrating the relationship between the position of the optical film 11 in the Y direction and the difference ratio D. For example, the optical film 11 has constant portions C1 and C2 in the convex region R1 and the concave region R2, respectively, where the difference ratio D is constant. For instance, in the convex region R1, the absolute value of the difference ratio D (hereinafter denoted as |D|) is largest in the constant portion C1, and in the concave region R2, |D| is largest in the constant portion C2. Preferably, the maximum value of |D| in these constant portions C1 and C2, i.e., the maximum value of |D| in the convex region R1 and the concave region R2, is 10% or less, more preferably 5% or less.

[0052] Optical film 11 preferably has an inclined portion S between the constant portion C1 and the constant portion C2. Figure 5A , Figure 5B The inclined portion S is the portion where the differential ratio D (%) changes continuously along the long side direction. In other words, in the inclined portion S, at least one of the thicknesses Te1, Te2 of the ends e1 and e2 and the thickness Tc of the central portion c changes continuously along the long side direction. The optical film 11, by having such an inclined portion S, differs from the case without the inclined portion S ( Figure 5CCompared to other methods, this method can effectively suppress the occurrence of winding defects. By setting the Y-direction size of the inclined portion S to 5m or more, the occurrence of winding defects can be suppressed more effectively. The change in |D| in 100m units of the Y-direction size in the inclined portion S, i.e., the slope of the inclined portion S, is preferably 0.03% to 10.0%, more preferably 0.05% to 7.5%, and even more preferably 2.0% to 5.0%. As a result, the occurrence of winding defects can be suppressed more effectively.

[0053] Figure 6A and Figure 6B Other examples illustrating the relationship between the position of the optical film 11 in the Y direction and the difference ratio D. Thus, the variation of the difference ratio D in the Y direction can be nonlinear. Within the convex region R1 or the concave region R2, the difference ratio D can have multiple maxima ( Figure 6B Within the convex region R1 or the concave region R2, curvature points of the difference ratio D can be provided. The relationship between the position of the optical film 11 in the Y direction and the difference ratio D is not limited to... Figures 5A to 6B The example shown.

[0054] Such an optical film 11 is, for example, made of a resin that is transparent to the desired wavelength. Examples of such resins include polymers containing an alicyclic structure, such as cyclic olefin resins (COP). The optical film 11 can be composed of acrylic resins, cellulose ester resins, polycarbonate resins, polyethersulfone resins, polyethylene terephthalate (PET) resins, polyimide resins, polymethyl methacrylate resins, polysulfone resins, polyarylate resins, polyethylene resins, and polyvinyl chloride resins, etc.

[0055] Of the resins mentioned above, cyclic olefin resins are preferred from the viewpoints of transparency and mechanical strength. Examples of cyclic olefin resins include (copolymers) having structural units derived from the following structures.

[0056] [Chemical Formula 1]

[0057]

[0058] In the formula, R 1 ~R 4 These are hydrocarbon groups that are independently substituted by a hydrogen atom, a hydrocarbon group, a halogen atom, a hydroxyl group, an ester group, an alkoxy group, a cyano group, an amide group, an imino group, a silyl group, or a polar group (i.e., a halogen atom, a hydroxyl group, an ester group, an alkoxy group, a cyano group, an amide group, an imino group, or a silyl group). Among them, R... 1 ~R 4 Two or more can combine to form unsaturated bonds, monocyclic or polycyclic rings, which may have double bonds or form aromatic rings. It can be formed by R... 1 and R2 , or R 3 and R 4 , forming alkylene groups. p and m are each an independent integer greater than or equal to 0.

[0059] In the above general formula, R 1 and R 3 Preferably, it is a hydrocarbon group with 1 to 10 carbon atoms, more preferably a hydrocarbon group with 1 to 4 carbon atoms, and particularly preferably a hydrocarbon group with 1 to 2 carbon atoms. 2 and R 4 Preferably, it is a hydrogen atom or a monovalent organic group, R 2 and R 4 At least one of the monomers is preferably a polar group other than a hydrogen atom and a hydrocarbon group. Preferably, m is an integer from 0 to 3, and p is an integer from 0 to 3; more preferably, m+p = 0 to 4; even more preferably, m+p = 0 to 2; and particularly preferably, m = 1 and p = 0. Specific monomers with m = 1 and p = 0 are preferred from the viewpoint that the resulting cycloolefin resin has a high glass transition temperature and excellent mechanical strength.

[0060] Examples of polar groups for the aforementioned specific monomers include carboxyl, hydroxyl, alkoxycarbonyl, allyloxycarbonyl, amino, amide, and cyano groups, which can be linked by a linking group such as a methylene group. Additionally, examples of polar groups include carbonyl, ether, silyl ether, thioether, and imino groups, which are linked by a hydrocarbon group. Among these compounds, carboxyl, hydroxyl, alkoxycarbonyl, or aryloxycarbonyl groups are preferred, with alkoxycarbonyl or aryloxycarbonyl groups being particularly preferred.

[0061] Additionally, R 2 and R 4 At least one of them is derived from formula – (CH2) n The monomer representing the polar group COOR is preferred from the viewpoint that the resulting cyclic olefin resin exhibits high glass transition temperature, low hygroscopicity, and excellent adhesion to various materials. In the formula for the specific polar group described above, R is preferably an alkyl group with 1 to 12 carbon atoms, more preferably an alkyl group with 1 to 4 carbon atoms, and particularly preferably an alkyl group with 1 to 2 carbon atoms. n is an integer of 0 or more.

[0062] When the above-mentioned structural unit has a polar group, other specific examples of monomers that can be copolymerized include cyclobutene, cyclopentene, cycloheptene, cyclooctene, dicyclopentadiene, norbornene, and other cycloolefins.

[0063] The number of carbon atoms in the cycloolefin, which is a monomer capable of copolymerization, is not particularly limited, but is preferably 4 to 20, and more preferably 5 to 12.

[0064] The optical film 11 may contain one type of cyclic olefin resin, or two or more types.

[0065] The cyclic olefin resin contained in the optical film 11 preferably has an intrinsic viscosity [ηinh] of 0.2 to 5 dL / g, more preferably 0.3 to 3 dL / g, and even more preferably 0.4 to 1.5 dL / g. Furthermore, the number-average molecular weight (Mn) of the polystyrene, as determined by gel permeation chromatography (GPC), is preferably 8,000 to 100,000, more preferably 10,000 to 80,000, and even more preferably 12,000 to 50,000; the weight-average molecular weight (Mw) is preferably 20,000 to 300,000, more preferably 30,000 to 250,000, and even more preferably in the range of 40,000 to 200,000.

[0066] By ensuring that the intrinsic viscosity (ηinh), number-average molecular weight, and weight-average molecular weight are within the aforementioned ranges, the cyclic olefin resin exhibits good heat resistance, water resistance, chemical resistance, mechanical properties, and processability as a cyclic olefin film. The intrinsic viscosity (ηinh) is measured at 30°C using a solution of the cyclic olefin resin dissolved in chloroform. Viscosity measurements are performed on three or more solutions with different concentrations of the cyclic olefin resin. An Ubbelohde viscometer is used for the measurements.

[0067] The glass transition temperature (Tg) of the cyclic olefin resin contained in the optical film 11 is preferably 110°C or higher, more preferably 110–350°C, even more preferably 120–250°C, and particularly preferably 120–220°C. If the Tg is 110°C or higher, deformation caused by use under high-temperature conditions or by secondary processing such as coating or printing can be suppressed. On the other hand, if the Tg is 350°C or lower, molding processing becomes easier, and resin deterioration due to heat during molding processing can be prevented. The glass transition temperature (Tg) value is obtained by thermal analysis of the cyclic olefin resin at a heating rate of 20°C / min, and the value of the intermediate glass transition temperature is determined according to JIS K7121 (1987). The thermal analysis was performed using a differential scanning calorimeter DSC220 manufactured by Seiko Instruments Co., Ltd.

[0068] The optical film 11 contains preferably 50% or more by mass, more preferably 70 to 90% or more by mass of a cyclic olefin resin.

[0069] In the optical film 11, without impairing the effects of this embodiment, for example, hydrocarbon resins, thermoplastic resins, thermoplastic elastomers, rubber polymers, organic microparticles, or inorganic microparticles known as described in Japanese Patent Application Publication Nos. 9-221577 and 10-287732 may be incorporated. The optical film 11 may contain specific wavelength dispersants, sugar ester compounds (also simply sugar esters), antioxidants, peel accelerators, rubber particles, or plasticizers, etc.

[0070] The cyclic olefin resin contained in the optical film 11 can be a commercially available product or a synthetic product. Examples of commercially available products include SANUQI (registered trademark) of Konica Minolta Co., Ltd., ARTON (registered trademark, hereinafter the same) G, ARTONF, ARTONR and ARTONRX of JSR Co., Ltd., ZEONOR (registered trademark) ZF14, ZF16, ZEONEX (registered trademark, hereinafter the same) 250 or ZEONEX 280 of Zeon Co., Ltd. of Japan.

[0071] <Methods for Manufacturing Optical Films>

[0072] Figure 7 This is a flowchart illustrating an example of a method for manufacturing the optical film 11. The optical film 11 is preferably manufactured, for example, by preparing or forming an initial film (e.g., as described later). Figure 8 After forming the initial film 11f, a convex region R1 and a concave region R2 are formed on the initial film. Alternatively, the optical film 11 is more preferably manufactured, for example, by forming the convex region R1 and the concave region R2 on the initial film after forming the initial film (step S101) (step S102). The manufacturing method of this optical film 11 will be described below.

[0073] In step S101, the initial membrane can be a pre-formed membrane or a newly formed membrane. For example, in step S101, an initial membrane having a wide side direction and a long side direction is formed.

[0074] There are no particular limitations on the method for forming the initial film, and known methods can be used. Among these methods, from the viewpoint of productivity, solution casting or melt casting is preferred, and from the viewpoint of transparency, transportability, and flexibility, solution casting is more preferred. Here, solution casting generally involves casting a solution of resin and other components (which may be dissolved in the resin) onto a support, drying it on the support, peeling off a thin film (net), and further drying the net after peeling to form a film. On the other hand, melt casting generally involves melting and mixing resin and other components (which may be dissolved in the resin) to produce a film, which involves heating the mixture to a fluid temperature and casting it as a fluid melt to form a film.

[0075] It should be noted that when using the solution casting method, the initial film involved in this invention can be a thin film (net) or a film obtained by further drying the net after peeling.

[0076] The amount of residual solvent when peeling the mesh from the support is not particularly limited if it is a self-supporting amount sufficient for peeling. However, from the viewpoint of exhibiting good planarity of the initial film, it is preferably in the range of 10 to 50% by mass, more preferably in the range of 15 to 40% by mass, and even more preferably in the range of 20 to 30% by mass.

[0077] The amount of residual solvent in a mesh or membrane is defined by the following formula;

[0078] Residual solvent content (mass%) = {(M - N) / N} × 100

[0079] It should be noted that M is the mass of a sample of the web or membrane taken at any time during or after manufacturing, and N is the mass of M after heating it at 115°C for 1 hour.

[0080] The residual solvent content of the film obtained after further drying the mesh after peeling is preferably less than 1% by mass, more preferably less than 0.1% by mass, and particularly preferably in the range of 0 to 0.01% by mass.

[0081] For example, the initial film is preferably formed as follows. In the solution casting method, firstly, a coating comprising resin and solvent is prepared. Next, the coating is cast onto a support. Casting is performed while the support is being moved. Next, the cast film formed on the support is peeled off from the support. Subsequently, the cast film is dried as needed to form an initial film containing resin. As mentioned above, the initial film can be a so-called mesh.

[0082] There are no particular limitations on solvents used in coatings. Examples include chlorinated solvents such as chloroform and methylene chloride; aromatic solvents such as toluene, xylene, benzene, and their mixtures; alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, and 2-butanol; and solvents such as methyl cellosolve, ethyl cellosolve, butyl cellosolve, ethylene glycol monomethyl ether, dimethylformamide, and dimethyl sulfoxide. Alkane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), ethyl acetate, diethyl ether; etc.

[0083] There is no particular limitation on the concentration of solid components in the coating, but it is preferably 10-35% by mass, more preferably 15-35% by mass.

[0084] There are no particular restrictions on the support body, but it is preferable to have a mirror finish on the surface, and it is even more preferable to use a roller with a surface finish made by plating stainless steel strip (stainless steel strip) or casting.

[0085] In step S102, for example, while stretching the initial film in the wide-side direction, the ends of the initial film in the wide-side direction are heated, thereby forming a convex region R1 and a concave region R2 in the initial film. Through stretching, the thickness of the initial film decreases overall compared to before stretching, but near the ends held by clamps or the like, the thickness is difficult to decrease compared to the central portion. By heating the ends of the initial film, the thicknesses Te1 and Te2 of the ends e1 and e2 of the film 11 are adjusted.

[0086] It should be noted that the thicknesses Te1 and Te2 of the ends e1 and e2 can be controlled depending on the temperature, transport speed, and equipment used to initially stretch the membrane (for example, refer to SEN-I GAKKAISHI (Fiber and Industry), Vol. 41, No. 9, 1985, pp. 290-301), and any method can be used in the stretching technique.

[0087] Figure 8 This is an example of the configuration of a tenter frame 50 used for stretching the initial film (initial film 11f) in the wide-side direction. In the tenter frame 50, the initial film 11f is stretched in the wide-side direction while being transported along its long side. The tenter frame 50 includes a first tempering region 50A before stretching, a stretching region 50B, a second tempering region 50C after stretching, and a cooling region 50D arranged sequentially side-by-side. The initial film 11f is transported sequentially through the first tempering region 50A, the stretching region 50B, the second tempering region 50C, and the cooling region 50D.

[0088] For example, heating elements 51 for heating both ends of the initial film 11f are respectively arranged in the first tempering region 50A, the stretching region 50B, and the second tempering region 50C of the tenter frame 50 (see, for example, Japanese Patent Application Publication No. 2011-115985). The heating elements 51 are arranged, for example, in the first tempering region 50A, the stretching region 50B, and the second tempering region 50C. The heating elements 51 can be arranged in at least one of the first tempering region 50A, the stretching region 50B, and the second tempering region 50C. The temperature in the X-direction can be adjusted by the heating elements 51. For example, multiple heating elements 51 can be arranged side-by-side in the X-direction, and the temperature of the heating elements 51 can be varied in the X-direction. The temperature of the heating elements 51 is controlled by a control unit 52.

[0089] The heating element 51 may be, for example, an infrared irradiation element that irradiates infrared rays at its end facing the wide side of the initial film 11f. The heating element 51 may be a blowing element that blows high-temperature air or inactive gas at its end facing the wide side of the initial film 11f, or it may utilize electric heating wires and heating rollers. The heating element 51 may be disposed at any of the front, back, top, and bottom surfaces of the initial film 11f, or at multiple locations therein. The position of the heating element 51 in the X direction is preferably located at a distance of 10 mm to 500 mm from the portions at both ends of the film 11 formed in the wide side direction, more preferably 20 mm to 400 mm. This facilitates control of the thicknesses Te1 and Te2 of the ends e1 and e2. The two ends of the film 11 in the wide side direction are formed, for example, by cutting the portions (ends in the wide side direction) held by clamps from the stretched initial film 11f.

[0090] Using a tenter frame 50 in which heating elements 51 are respectively provided in the first tempering region 50A, the stretching region 50B and the second tempering region 50C, a convex region R1 and a concave region R2 are formed in the initial film 11f, as described below.

[0091] First, the two ends of the initial membrane 11f in the wide side direction are clamped using clamps or the like. Then, the initial membrane 11f is transported. Thus, the initial membrane 11f is stretched in the wide side direction by sequentially passing through a first tempering region 50A, a stretching region 50B, a second tempering region 50C, and a cooling region 50D. The transport speed of the initial membrane 11f is not particularly limited, but is preferably 3 m / min to 100 m / min, more preferably 5 m / min to 50 m / min. By setting the transport speed to 3 m / min or more, more preferably 5 m / min or more, the air volume between the membranes 11 can be easily adjusted, and the transport time can be shortened, thus reducing costs. By setting the transport speed to 100 m / min or less, more preferably 50 m / min or less, the large size of the heating element 51 used to apply sufficient heat to the target area can be prevented, thus reducing equipment costs.

[0092] In the first tempering region 50A, the stretching region 50B, and the second tempering region 50C, it is preferable that the temperature at both ends of the initial film 11f in the wide side direction is approximately 0°C to 50°C higher than the temperature at the center. Here, by using the control unit 52 to change the temperature of the heating member 51 over time, the temperature difference between the two ends and the center of the portion forming the convex region R1 in the initial film 11f is greater than the temperature difference between the two ends and the center of the portion forming the concave region R2. As a result, the thicknesses Te1 and Te2 of the ends e1 and e2 of the convex region R1 are smaller than the thicknesses Te1 and Te2 of the ends e1 and e2 of the concave region R2, and the convex region R1 and the concave region R2 are formed in the initial film 11f. For example, in the portion forming the convex region R1, the temperature difference between the two ends and the center of the initial film 11f is set to 20°C to 30°C, and in the portion forming the concave region R2, the temperature difference between the two ends and the center of the initial film 11f is set to 0°C to 10°C.

[0093] For example, by adjusting the temperature difference between the two ends and the center of the initial membrane 11f, the size of |D| can be controlled. In the part forming the convex region R1, the greater the temperature difference between the ends and the center, the larger |D| is; in the part forming the concave region R2, the smaller the temperature difference between the ends and the center, the larger |D| is.

[0094] For example, by adjusting the heating and cooling rates of the two ends (or heating element 51) of the initial membrane 11f, the change in |D| within a 100m unit in the Y direction can be controlled. The faster the heating or cooling rate of the two ends is increased, the greater the change in |D| within a 100m unit in the Y direction.

[0095] The temperature difference between the two ends and the central portion of the initial membrane 11f is preferably 50°C or less. This suppresses softening at the ends e1 and e2 of the membrane 11, allowing for precise adjustment of the thicknesses Te1 and Te2 at the ends e1 and e2. In the portion forming the convex region R1, the temperature difference between the two ends and the central portion of the initial membrane 11f is preferably 3°C or more. This allows for sufficient reduction of the thicknesses Te1 and Te2 at the ends e1 and e2 in a shorter time without requiring a large-scale device. Furthermore, the temperatures at the two ends of the initial membrane 11f can be different, but are preferably almost identical.

[0096] The temperatures at both ends and the center of the initial membrane 11f are measured, for example, using a thermal non-contact temperature sensor (RAYTECH MT150) from the downward side of the initial membrane 11f in the direction of gravity. The temperatures at both ends of the initial membrane 11f are measured, for example, at a position coinciding with the center of the heating element 51, and the average value over a width of 50 mm is used. The temperature at the center of the initial membrane 11f is measured, for example, at a position between the two ends, and the average value over a width of 100 mm is used.

[0097] The stretching ratio in the wide-side direction is not particularly limited, but is preferably 5% or more, more preferably 10% or more, and even more preferably 15% or more. This allows for effective adjustment of the thicknesses Te1 and Te2 of the ends e1 and e2 by heating the ends e1 and e2. Furthermore, the stretching ratio in the wide-side direction is preferably 1000% or less. This allows for stretching without increasing the size of the stretching equipment, thus reducing equipment costs. The stretching ratio in the wide-side direction can be adjusted by the distance between the slits in the tenter frame 50. The stretching ratio in the wide-side direction can be evaluated by comparing the width of the film before and after stretching. The stretching ratio and temperature described above are just examples; appropriate adjustments are made to obtain the desired orientation, physical properties, and surface condition of the film 11. Stretching in the wide-side direction is not limited to the tenter frame 50; any method can be used, such as a needle tenter frame.

[0098] There are no particular restrictions on the stretching ratio in the transport direction. Stretching in the transport direction can be performed using any method, such as shrinkage stretching, roller stretching, or floating stretching.

[0099] The convex region R1 and the concave region R2 can be formed using other methods. For example, the convex region R1 and the concave region R2 can be formed by controlling the amount of paint being cast. For example, the convex region R1 and the concave region R2 can be formed by adjusting the amount of paint being cast using an adjusting rod (also called a mold base) (see, for example, Japanese Patent Application Publication No. 2016-190344). The convex region R1 and the concave region R2 can be formed by independently controlling the supply of paint used to form the central portion c and the ends e1 and e2, thereby adjusting the amount of paint being cast (see, for example, Japanese Patent Application Publication No. 2009-78371). For example, when increasing the thickness Te1 and Te2 of the ends e1 and e2, the flow rate of paint used to form the ends e1 and e2 can be increased; when decreasing the thickness Te1 and Te2 of the ends e1 and e2, the flow rate of paint used to form the ends e1 and e2 can be decreased.

[0100] Or by controlling the embossing part (e.g.) Figure 4 The presence, absence, and size of the embossed portion E can be adjusted to form a convex region R1 and a concave region R2 (see, for example, Japanese Patent Application Publication No. 2009-73154). By combining multiple methods from these approaches, a convex region R1 and a concave region R2 can be formed.

[0101] For example, an optical film 11 having a convex region R1 and a concave region R2 can be manufactured in this way. By winding the optical film 11 onto a core 12, for example, using a winding machine, a film roll 1 is formed.

[0102] <The Functions and Effects of Optical Films and Film Rolls>

[0103] Because the optical film 11 in this embodiment has a convex region R1 (or convex position P1) where the thickness Te1 and Te2 of the ends e1 and e2 are smaller than the thickness Tc of the central portion c, and a concave region R2 (or concave position P2) where the thickness Te1 and Te2 of the ends e1 and e2 are larger than the thickness Tc of the central portion c, the amount of air between the optical films 11 can be easily controlled when forming the film roll 1. Therefore, the occurrence of winding defects can be suppressed. The effects of this operation will be explained in detail below.

[0104] Figure 9A , Figure 9B as well as Figure 9C The numbers represent the relationship between the position of the optical film in the Y direction (long side direction) and the difference ratio D in the comparative examples. The optical films in these comparative examples each have only one of the convex region R1 and the concave region R2. Figure 9A The optical film shown and Figure 9C The optical film shown has only a convex region R1, and the thickness at the ends is smaller than that at the center at all locations along the long side (difference ratio D > 0). Figure 9B The optical film shown only has a concave region R2, and the thickness at the ends is greater than the thickness at the center at all locations along the long side (difference ratio D < 0). In optical films involved in such comparative examples, it is difficult to control the amount of air between overlapping optical films during film roll formation, making it less likely to produce winding defects.

[0105] For example, Figure 9A The optical film shown and Figure 9C In the optical films shown, the amount of air between the overlapping optical films is relatively small, and strong adhesion easily occurs in the thicker central portion. This adhesion between the optical films may cause black bands to form on the film roll. Within these black bands, stretching occurs between the centrally adhered portion and the weakly adhered end, causing deformation of the optical film. Furthermore, tiny air particles trapped between the films entangle and grow, resulting in indentations (depressions).

[0106] on the other hand, Figure 9B In the optical film shown, the amount of air between the overlapping optical films is relatively large, thus suppressing the occurrence of winding defects caused by the adhesion between the optical films. However, in this optical film, after the film roll is formed, the air between the optical films is removed over time, making it difficult to maintain its shape. The removal of this air may cause deformation of the optical film.

[0107] Such poor winding leading to optical film degradation can affect devices such as displays or touch sensors that use the optical film. For example, in displays, image visibility decreases, and in touch sensors, changes in resistance value lead to reduced sensor functionality.

[0108] Compared to the optical films involved in these comparative examples, the optical film 11 of this embodiment has both a convex region R1 and a concave region R2, thus enabling control over the amount of air between the overlapping optical films 11.

[0109] Figure 10 This is an example of the configuration of the end face of the film roll 1. In the film roll 1, for example, convex regions R1 and concave regions R2 overlap alternately, thus suppressing adhesion between optical films 11 and maintaining their shape. That is, it can suppress the formation of black bands and indentations, and it can suppress the deformation of the optical films 11 due to the passage of time.

[0110] As shown above, in the optical film 11 and film roll 1 of this embodiment, since the optical film 11 has a convex position P1 where the thickness Te1 and Te2 of the ends e1 and e2 are smaller than the thickness Tc of the central portion c, and a concave position P2 where the thickness Te1 and Te2 of the ends e1 and e2 are larger than the thickness Tc of the central portion c, it is easy to control the amount of air between the optical films 11 when forming the film roll 1. Therefore, it is possible to suppress the occurrence of winding defects.

[0111] If such an optical film 11 is used in devices such as displays and touch sensors, the performance of the devices can be improved.

[0112] Furthermore, the optical film 11 can suppress the occurrence of winding defects, thus enabling thin-film production. Also, the optical film 11 can be suitably made of a low-elasticity material. Moreover, when manufacturing long optical films 11, the reduction in productivity can be suppressed. When the total winding length of the film roll 1 is 1000 m or more, preferably 4000 m or more, the occurrence of winding defects can be suppressed more effectively.

[0113] <Variation Example>

[0114] The film roll 1 can be formed by winding a stack of multiple films. This stack can, for example, have an optical film 11 and a protective film (described later). Figure 11 (Protective film 21). Here, optical film 11 corresponds to a specific example of the functional film of the present invention.

[0115] Figure 11 This is an example of the cross-sectional configuration of the laminate of the optical film 11 and the protective film 21. The protective film 21 is used to protect the optical film 11 and can be peeled off from the optical film 11. The protective film 21 may, for example, contain polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins such as polymethyl methacrylate, polyaryl ester compound resins, polystyrene resins, polyvinyl alcohol resins, epoxy resins, and mixtures thereof.

[0116] For example, after a protective film 21 is laminated onto an optical film 11, a film roll 1 is formed by winding the laminated body.

[0117] <Other variations>

[0118] A transparent conductive film can be stacked on top of the optical film 11. Materials used to form the transparent conductive film include, for example, metals such as Sn, In, Ti, Pb, Au, Pt, and Ag, or their oxides. The oxides can be, for example, indium tin oxide (ITO), aluminum oxide, silicon oxide, titanium oxide, zinc oxide, and tungsten oxide. The transparent conductive film can be formed using aluminum nitride, silicon nitride, titanium nitride, cadmium sulfide, zinc sulfide, or zinc selenide.

[0119] An adhesive layer and an anchoring coating layer can be provided between the optical film 11 and the transparent conductive film. The adhesive layer can be formed using heat-resistant resins such as epoxy resin, polyimide, polybutadiene, phenolic resin, and polyetheretherketone. The anchoring coating layer can be formed using an anchoring coating agent such as an acrylic prepolymer containing epoxy diacrylate, urethane diacrylate, and polyester diacrylate, cured by a known curing method, such as UV curing or heat curing.

[0120] An adhesive layer may be provided between the optical film 11 and the transparent conductive film to improve the smoothness of the film and the adhesion of the transparent conductive film. This adhesive layer is obtained, for example, by applying a resin varnish and removing the solvent by drying.

[0121] The laminate comprising the optical film 11 and the transparent conductive film may have a gas barrier layer on the side opposite to the transparent conductive film. The gas barrier layer may be formed of an inorganic material or an organic material. Examples of usable inorganic materials include silicon oxide, aluminum oxide, and indium oxide; examples of organic materials include polyvinyl alcohol, ethylene-vinyl alcohol copolymers, and polyamides. Furthermore, a protective coating layer for protecting the gas barrier layer may be laminated on top of it.

[0122] <Application Examples>

[0123] Optical film 11 is suitable for use in optical components such as color filter substrates, light guide plates, protective films, polarizing films, retardation films, touch panels, transparent electrode substrates, optical recording substrates such as CD (Compact Disc), MD (Mini Disc), and DVD (Digital Versatile Disc), TFT (Thin Film Transistor) substrates, liquid crystal display substrates, and organic EL (Electroluminescence) display substrates, or waveguides for light transmission and sealing materials for optical elements. Specifically, it can be used in display element components, including color filter substrates, light guide plates, protective films, polarizing films, retardation films, touch sensors, transparent electrode substrates, TFT substrates, liquid crystal display substrates, and organic EL display substrates.

[0124] For example, a color filter can be obtained by laminating a color filter layer on a color filter substrate containing an optical film 11. Known methods such as pigment dispersion, dyeing, plating, printing, and transfer can be used for this lamination. This color filter can be used as a color filter in a liquid crystal display device, and can also be used as part of components such as a color display, a liquid crystal display device, etc.

[0125] Besides optical components, the optical film 11 can also be used as an electrical insulating component, electrical and electronic component, electronic component sealant, medical device, and packaging material. In particular, the optical film 11 containing cyclic olefin resin exhibits excellent heat resistance and electrical properties. Since its dimensional changes are minimal even after high-temperature processing or pharmaceutical treatment, it is optimal as an electrical insulating component. Examples of electrical insulating components include sheathing materials for wires and cables, insulating materials for OA equipment such as computers, printers, and copiers, and insulating components for flexible printed circuit boards. It is particularly suitable for use as a flexible printed circuit board.

[0126] The optical film 11 can also be used, for example, in a touch sensor (claim 12). A touch sensor is, for example, a device mounted on the surface of a display device that converts physical contact, such as a stylus pen, with a user's finger into an electrical signal and outputs it. The display device is, for example, a liquid crystal display device, a plasma display device, and an EL display device.

[0127] The touch sensor including the optical film 11 is, for example, a transparent electrode type touch sensor. In a transparent electrode type touch sensor, for example, a transparent electrode is formed by coating the optical film 11 with a metal oxide, and position is sensed using the contact of the transparent electrode. The metal oxide can be, for example, indium tin oxide (ITO). The metal oxide is coated on the optical film 11, for example, by vacuum evaporation or sputtering.

[0128] The optical film 11 used for such a touch sensor is preferably highly heat-resistant. Heat resistance can be evaluated, for example, by the glass transition temperature, and the optical film 11 preferably has a high glass transition temperature above the sputtering temperature and high mechanical strength.

[0129] In addition, the optical film 11 used for the touch sensor preferably also has transparency in the visible light region, for example, preferably has a transmittance of more than 90% for visible light.

[0130] The optical film 11 containing cyclic olefin resin is suitable for use as a touch sensor due to its high glass transition temperature, high heat resistance, and high transmittance to visible light.

[0131] Example

[0132] The effects of the present invention will be illustrated using the following examples and comparative examples. However, the scope of the present invention is not limited to the following examples.

[0133] <Example 1>

[0134] First, the initial membrane is prepared as follows.

[0135] (Preparation of coatings)

[0136] PET resin (Toyobo Ester Film E7002 manufactured by Toyobo Corporation)

[0137] 100 portions

[0138] 200 parts by weight of dichloromethane

[0139] 10 parts by weight of ethanol

[0140] First, put the above-mentioned components into a closed container and dissolve the PET resin while stirring to prepare the coating.

[0141] (Membrane fabrication)

[0142] Next, the coating was uniformly cast (cast) on a stainless steel strip support at a temperature of 31°C and a width of 1800 mm using an endless tape casting device to form a cast film. The temperature of the stainless steel strip was controlled at 28°C. Next, the amount of solvent remaining in the cast film after evaporation was reduced to 30% on the stainless steel strip support. Then, the cast film was peeled from the stainless steel strip support at a peel tension of 128 N / m and stretched 1.15 times its original width at 160°C. The residual solvent at the start of stretching was 5% by mass. Next, the cast film was dried while being transported by multiple rollers. Then, the portion held by the tenter frame (both ends) was cut using a laser cutter, and the cast film was wound. This produced an initial film with a thickness of 33 μm.

[0143] Next, while clamping both ends of the initial film along its wide side using fabric clamps, the initial film is stretched along its wide side using a fabric clamp tenter. At this time, by stretching both ends of the initial film along its wide side in the stretching region (… Figure 8 The stretched region 50B is heated to form a convex region R1 and a concave region R2. An infrared irradiation element is used for the heating. The heating element is positioned within 150 mm of both ends of the film roll in the wide-side direction. The initial film is heated to 130°C at the center and 160°C at both ends to form the convex region; concave regions are formed by simultaneously heating the initial film to 130°C at both the center and both ends. The stretching ratio of both convex region R1 and concave region R2 in the wide-side direction is 30%.

[0144] Using an online thickness gauge, the average thickness of the film prepared above, the differential ratio D of the convex region R1 and the concave region R2 where |D| is the largest, and the magnitude of each long side direction of the convex region R1 and the concave region R2 were measured. Additionally, using an online thickness gauge and an encoder (length gauge), the change in the differential ratio D of the inclined portion within a 100m unit dimension along the long side direction was measured (refer to...). Figure 5A , Figure 5BThe average thickness of the fabricated film is 25 μm. |D| represents the largest difference ratio D in the convex and concave regions, which are 7.5% and -7.5% respectively. The long side dimensions of the convex region R1 and the concave region R2 are the same, both being 250 μm. The variation in the difference ratio D within a 100 μm unit of the inclined portion is 7.5%. Furthermore, the glass transition temperature of the film is 80 °C. Subsequently, the fabricated film is wound onto a core to form a film roll. The total winding length is 4000 μm.

[0145] <Example 2>

[0146] First, the initial membrane is prepared as shown below.

[0147] (Preparation of rubber particle dispersion)

[0148] A solution containing 10 parts by mass of rubber particles (Kaneace M210 manufactured by KANEKA Co., Ltd., with an average primary particle size R of 200 nm) and 90 parts by mass of ME16 (a mixed solvent of dichloromethane and ethanol in a mass ratio of 84:16) was stirred in a dissolver for 50 minutes. The solution was then dispersed at 1500 rpm using an emulsifying disperser (manufactured by Tairao Kiko Co., Ltd.) to obtain a rubber particle dispersion.

[0149] (Preparation of silica particle dispersion)

[0150] 20 parts by weight of silica particles (Aerosil (registered trademark) R812, manufactured by Aerosil Corporation of Japan, hydrophobic fumed silica, average primary particle size Rs1: 7 nm, specific surface area: 260 ± 30 m²) 2 A mixture of (g / g) and 80 parts by mass of ME50 (a mixed solvent of dichloromethane and ethanol in a 50:50 mass ratio) was stirred in a dissolver for 50 minutes. The mixture was then dispersed using a high-pressure emulsifier to obtain the additive solution.

[0151] Next, 10 parts by mass of the above-mentioned additive solution were slowly added to 90 parts by mass of ME16, which was thoroughly stirred in a dissolving tank. The additive solution added to ME16 was then dispersed in a mill. The mixture was then filtered using a FINEMET NF filter manufactured by Nippon Seiki Co., Ltd., to obtain a silica particle dispersion.

[0152] (Preparation of coatings)

[0153] Next, a coating with the following composition was prepared. First, 90 parts by weight of dichloromethane and 10 parts by weight of ethanol were added to a pressurized dissolving vessel. Then, 80 parts by weight of acrylic resin (MR1000, manufactured by Nippon Shokubai Co., Ltd., lactone acrylic resin) was added while stirring in the pressurized dissolving vessel. Next, the rubber particle dispersion prepared above was added to the pressurized dissolving vessel and stirred to dissolve the acrylic resin. The acrylic resin solution was filtered using an SHP150 filter (manufactured by ROKI TECHNO Co., Ltd.) to obtain the coating.

[0154] (Membrane fabrication)

[0155] Next, a film was formed using the aforementioned coating. Specifically, an endless tape casting apparatus was used to uniformly cast the coating onto a stainless steel strip support at a temperature of 30°C and a width of 1800 mm to form a cast film. The temperature of the stainless steel strip was controlled at 28°C.

[0156] On a stainless steel strip support, the solvent is evaporated to a residual solvent content of 30% by mass in the cast film. Then, the cast film is peeled from the stainless steel strip support at a peel tension of 128 N / m. The residual solvent content of the peeled cast film is 30% by mass.

[0157] Next, while the peeled cast film is transported using multiple rollers, it is stretched by 50% in the wide direction at 140°C using a tenter frame. Then, the cast film is dried at 105°C while being transported by rollers. Next, the portion of the cast film held by the tenter frame (both ends) is cut open, and the cast film is wound. This yields an initial film with a thickness of 33 μm.

[0158] Next, while holding both ends of the initial film in the wide-side direction with clamps, the initial film is stretched in the wide-side direction using a tenter frame. The temperature of the central portion and both ends of the initial film is varied, but otherwise, a film roll is produced in the same manner as the stretching of the initial film described in Example 1 above. Specifically, the central portion of the initial film is set to 140°C, and the two ends are set to 170°C to form a convex region; the central portion and both ends of the initial film are simultaneously set to 140°C to form a concave region. The stretch ratio in the wide-side direction of both the convex region R1 and the concave region R2 is 30%.

[0159] <Example 3>

[0160] First, the initial membrane is prepared as follows.

[0161] (Preparation of particulate dispersion)

[0162] 11.3 parts by weight of microparticles (Aerosil (registered trademark) R812, manufactured by Aerosil Co., Ltd., Japan) and 84 parts by weight of ethanol were mixed in a dissolver for 50 minutes, and then the mixture was dispersed using a high-pressure emulsifier. This yielded a microparticle dispersion.

[0163] In a dissolving tank, 5 parts by mass of a particulate dispersion are slowly added to 100 parts by mass of thoroughly stirred dichloromethane. The particulate dispersion added to the dichloromethane is then dispersed using a mill to ensure that the secondary particles have the specified particle size. The mixture is then filtered through a FINEMET NF filter manufactured by Nippon Seiki Co., Ltd. to prepare the particulate additive solution.

[0164] (Preparation of coatings)

[0165] A coating with the following composition was prepared. First, 200 parts by weight of dichloromethane and 10 parts by weight of ethanol were added to a pressure dissolving vessel. Next, in the pressure dissolving vessel containing the mixed solution of dichloromethane and ethanol, 100 parts by weight of cyclic olefin resin (ARTON (registered trademark) F4520, manufactured by JSR Corporation), 5 parts by weight of ultraviolet absorber (Tinuvin (registered trademark) 477, manufactured by BASF JAPAN Corporation), and 3 parts by weight of the above-mentioned particulate additive solution were added while stirring. Then, the mixture was heated, and the cyclic olefin resin was dissolved while stirring. Next, the cyclic olefin resin solution was filtered using Anji Filter Paper No. 244 manufactured by Anji Filter Paper Co., Ltd., to prepare the coating.

[0166] It should be noted that ARTON (registered trademark) F4520 is a polymer of structural units having the following structure.

[0167]

[0168] (Membrane fabrication)

[0169] Next, using an endless tape casting apparatus, the coating is uniformly cast onto a stainless steel strip support at a temperature of 31°C and a width of 1800 mm to form a cast film. The temperature of the stainless steel strip is controlled at 28°C. Next, the residual solvent in the cast film is evaporated from the stainless steel strip support to 30% by mass. Then, the cast film is peeled off from the stainless steel strip support at a peel tension of 128 N / m. Next, the peeled cast film is stretched 1.15 times its original length in the width direction at 160°C. The residual solvent in the cast film at the start of stretching is 5% by mass. Next, the cast film is dried while being transported using multiple rollers. Next, the portion of the cast film held by a tenter frame (both ends) is cut with a laser cutter, and then the cast film is wound. This yields an initial film with a thickness of 33 μm.

[0170] Next, while holding both ends of the initial film in the wide-side direction with clamps, a tenter frame is used to stretch the initial film in the wide-side direction. The temperature of the central portion and both ends of the initial film is varied, but otherwise, a film roll is produced in the same manner as the initial film stretching described in Example 1 above. Specifically, the central portion of the initial film is set to 180°C, and the two ends are set to 210°C to form a convex region; the central portion and both ends of the initial film are simultaneously set to 180°C to form a concave region. The stretching ratio of both the convex region R1 and the concave region R2 in the wide-side direction is 30%.

[0171] <Example 4>

[0172] In the fabrication of the film roll in Embodiment 3 above, the temperature of the central portion and both ends of the initial film when it is stretched in the wide-side direction is changed, but the film roll is fabricated in the same manner. Specifically, the central portion of the initial film is set to 180°C and the two ends are set to 200°C to form a convex region, and the central portion of the initial film is set to 180°C and the two ends are set to 190°C to form a concave region. Thus, the maximum value of |D| of each of the convex region R1 and the concave region R2 is changed from the film roll of Embodiment 3 above.

[0173] <Example 5>

[0174] In the fabrication of the membrane roll in Example 3 above, the heating and cooling rates at both ends of the initial membrane were changed, but the membrane roll was fabricated in the same manner. Specifically, compared to Example 3, the heating and cooling rates at both ends of the initial membrane were delayed by a factor of 2.1. As a result, the amount of change in the differential ratio D within 100m units of the inclined portion was changed in the membrane roll of Example 3 above.

[0175] <Example 6>

[0176] In the fabrication of the membrane roll in Example 4 above, the heating and cooling rates at both ends of the initial membrane were changed, but the membrane roll was fabricated in the same manner. Specifically, compared to Example 4, the heating and cooling rates at both ends of the initial membrane were delayed by a factor of 2.1. As a result, the amount of change in the differential ratio D per 100m unit in the inclined portion of the membrane roll in Example 4 was changed.

[0177] <Example 7>

[0178] In the fabrication of the film roll in Example 6 above, the length of the total winding length is changed, but the film roll is fabricated in the same manner otherwise.

[0179] <Example 8>

[0180] In the fabrication of the film roll in Embodiment 4 above, the temperature change period at both ends of the initial film is changed, but the film roll is fabricated in the same manner. Specifically, the temperature change period of the heating element is shortened compared to the fabrication of the film roll in Embodiment 4. As a result, the size of the long side direction of the convex region R1 and the concave region R2 is changed in the film roll of Embodiment 4 above.

[0181] <Example 9>

[0182] In the fabrication of the film roll in Embodiment 6 described above, the method for forming the convex region R1 and the concave region R2 is changed, but the film roll is fabricated in the same manner. Specifically, multiple heating bolts are arranged in the wide-side direction of the casting die, and the voltage applied to the heating bolts is varied according to their positions in the wide-side direction. As a result, the amount of coating material cast at both ends of the casting die and the amount of coating material cast at the center of the casting die are adjusted respectively, forming the convex region R1 and the concave region R2. Specifically, the casting gap at both ends in the wide-side direction is varied from the casting gap at the center in the wide-side direction to between -2.5% and 2.5%.

[0183] <Example 10>

[0184] In the fabrication of the film roll in Example 6 above, the method for forming the convex region R1 and the concave region R2 was changed, but the film roll was fabricated in the same manner. Specifically, under a certain extrusion, the temperature of the embossing ring was varied between 180°C and 200°C. As a result, the height of the embossing was adjusted to form the convex region R1 and the concave region R2.

[0185] <Example 11>

[0186] In the fabrication of the membrane roll in Example 1 above, the temperatures of the central portion and both ends of the initial membrane when it is stretched in the wide-side direction, the heating rate of the temperature at both ends of the initial membrane, and the cooling rate are changed. Otherwise, the membrane roll is fabricated in the same manner as in Example 1 above. Thus, the maximum values ​​of |D| for the convex region R1 and the concave region R2, and the change in the difference ratio D per 100m unit on the inclined portion are changed from those in the membrane roll of Example 1 above.

[0187] <Example 12>

[0188] In the fabrication of the membrane roll in Example 6 above, the temperature at both ends of the initial membrane is varied nonlinearly, and the membrane roll is fabricated in the same manner otherwise. As a result, the differential ratio D varies in a sine curve along the long side direction.

[0189] <Example 13>

[0190] In the fabrication of the film roll in Example 6 above, the length of the total winding length is changed, but the film roll is fabricated in the same manner otherwise.

[0191] <Example 14>

[0192] In the fabrication of the film roll in Example 6 above, the length of the total winding length is changed, but the film roll is fabricated in the same manner otherwise.

[0193] <Example 15>

[0194] In the fabrication of the film roll in Embodiment 4 above, the period of temperature change at both ends of the initial film is changed, but the film roll is fabricated in the same manner. Specifically, compared with the fabrication of the film roll in Embodiment 4, the period of temperature change of the heating element is extended. As a result, the size of the long side direction of the convex region R1 and the concave region R2 is changed in the film roll of Embodiment 4 above.

[0195] <Comparative Example 1>

[0196] In the fabrication of the film roll in Example 3 described above, the temperature of the central portion and both ends of the initial film when it is stretched in the wide-side direction is changed, but the film roll is fabricated in the same manner. Specifically, the initial film is stretched in the wide-side direction while maintaining the central portion at 180°C and both ends at 210°C. As a result, only convex regions are formed in the film roll.

[0197] <Comparative Example 2>

[0198] In the fabrication of the film roll in Example 3 described above, the temperature of the central portion and both ends of the initial film when it is stretched in the wide-side direction is changed, but the film roll is fabricated in the same manner. Specifically, the initial film is stretched in the wide-side direction while maintaining the central portion at 180°C and both ends at 190°C. As a result, only concave regions are formed in the film roll.

[0199] <Comparative Example 3>

[0200] In the fabrication of the film roll in Comparative Example 1 above, the temperature of the central portion and both ends of the initial film when it is stretched in the wide-side direction was changed, but the film roll was fabricated in the same manner. Specifically, the central portion of the initial film was set to 180°C and the two ends were set to 210°C to form a first convex region, and the central portion of the initial film was set to 180°C and the two ends were set to 200°C to form a second convex region. Thus, two convex regions (the first convex region and the second convex region) with different differential ratios D were formed.

[0201] The characteristics of the film rolls produced in Examples 1-15 and Comparative Examples 1-3 are summarized in Table 1 below.

[0202] <Evaluation of the membrane roll>

[0203] (Black belt's evaluation)

[0204] After the membrane roll is manufactured, under a white fluorescent lamp, visually observe the color of the membrane surface from the core direction. The observation covers the entire width of the membrane roll, performing the observation around the entire circumference. At this time, clearly observe the color of the core and confirm whether there are any areas where the color differs from the surrounding area. This color confirmation uses a specified boundary sample. If there are areas where the color differs, check for membrane deformation in those areas. Specifically, place the membrane on a table with black sandpaper set slightly horizontally, and use the reflected light from the illuminated membrane to confirm the presence or absence of membrane deformation. Irradiation of the membrane is performed using a fluorescent lamp with a light output of 2500 lux or higher, positioned within 2 meters of the membrane. The black band of the membrane roll is then evaluated based on the following evaluation criteria. The results are shown in Table 1 below.

[0205] Evaluation Criteria

[0206] A: There are no parts in the membrane roll that appear to be different colors.

[0207] B: There are parts of the membrane roll that appear to be different colors, but no membrane deformation has been confirmed.

[0208] C: The deformation of the membrane has been confirmed.

[0209] (Evaluation of changes relative to time)

[0210] After the membrane roll is manufactured, the surface of the black core is visually inspected to check for any areas that appear to be a different color. Next, the membrane roll is placed at 23°C and 90% RH for 500 hours, and the surface of the black core is visually inspected again to check for any areas that appear to be a different color. If areas appearing to be a different color are found both immediately after manufacturing and after 500 hours, these areas are checked for membrane deformation. The change in the membrane roll over time is evaluated based on the following evaluation criteria. The results are shown in Table 1 below.

[0211] Evaluation Criteria

[0212] A: Even after 500 hours, the film roll does not show any areas that appear to have different colors.

[0213] B: After 500 hours, a section with a different color was added to the membrane roll, but no membrane deformation was detected in that section.

[0214] C: After 500 hours, the deformation of the membrane was newly confirmed.

[0215] Table 1

[0216]

[0217] The membrane and membrane roll involved in this invention have convex positions (or convex regions) where the thickness at the ends in the wide side direction is smaller than the thickness at the center, and concave positions (or concave regions) where the thickness at the ends is larger than the thickness at the center. Based on the results in Table 1, it is confirmed that the membranes involved in the embodiments of this invention are preferred from the viewpoint of black bands and changes over time, compared to membranes having only convex or concave positions, and can suppress the generation of winding defects.

[0218] This application is based on Japanese Patent Application No. 2020-116621, filed on July 6, 2020, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A film, comprising: a first end portion and a second end portion in a width direction intersecting a long direction; a central portion between the first end portion and the second end portion; a convex position in which at least the first end portion has a thickness Tei smaller than a thickness Tc of the central portion; and a concave position disposed at a position different from the convex position in the long direction and in which the first end portion has a thickness Tei larger than the thickness Tc of the central portion.

2. The film according to claim 1, wherein: in the convex position, the second end portion has a thickness Te2 smaller than the thickness Tc of the central portion, and in the concave position, the second end portion has a thickness Te2 larger than the thickness Tc of the central portion. Further comprising: a convex region provided with the convex position and in which at least the first end portion has a thickness Tei smaller than the thickness Tc of the central portion; and a concave region provided with the concave position and in which the first end portion has a thickness Tei larger than the thickness Tc of the central portion. The convex region and the concave region have a size in the long direction of 100 m to 500 m. The difference between the thickness Tei of the first end portion and the thickness Tc of the central portion in the convex position is 10% or less relative to an average thickness of the film in the convex position, The difference between the thickness Tei of the first end portion and the thickness Tc of the central portion in the concave position is 10% or less relative to an average thickness of the film in the concave position. The difference between the thickness Tei of the first end portion and the thickness Tc of the central portion in the convex position is 5% or less relative to an average thickness of the film in the convex position, The difference between the thickness Tei of the first end portion and the thickness Tc of the central portion in the concave position is 5% or less relative to an average thickness of the film in the concave position.

3. The film according to claim 1 or 2, wherein, Between the convex position and the concave position, there is further provided a slope portion in which at least one of the thickness Tei of the first end portion and the thickness Tc of the central portion continuously changes. The size in the long direction of the slope portion is 5 m or more. The film contains a polymer containing an alicyclic structure.

11. The film according to claim 1 or 2, having an optical function.

4. The film of claim 3, wherein, 12. The film according to claim 1 or 2, used for a touch sensor.

5. The film of claim 3, wherein, 13. A laminate, comprising: the film according to any one of claims 1 to 12, and a protective film laminated to the film.

6. The film according to claim 1 or 2, wherein, 14. A film roll, comprising: a core, and the film according to any one of claims 1 to 12 or the laminate according to claim 13 wound around the core.

15. A method for manufacturing a film, comprising: a step of preparing or forming an initial film, and a step of forming a convex position and a concave position at mutually different positions in a long direction of the initial film.

7. The film according to claim 1 or 2, wherein, ​ ​ 8. The film according to claim 1 or 2, wherein, ​ 9. The film of claim 8, wherein, ​ 10. The film of claim 1 or 2, wherein, ​ ​ ​ ​ ​ ​ ​ ​ the convex position is formed so that the thickness Te1 of the first end portion is smaller than the thickness Tc of the central portion between the first end portion and the second end portion, the concave position is formed so that the thickness Te1 of the first end portion is larger than the thickness Tc of the central portion.

16. The method of manufacturing a film according to claim 15, wherein, in forming the convex position and the concave position, at least the first end portion of the first end portion and the second end portion is heated while the initial film is stretched in the width direction, the temperature difference between the first end portion and the central portion when forming the convex position is set to be larger than the temperature difference between the first end portion and the central portion when forming the concave position.

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