JP7552694B2 - Film, film roll, and method for producing film - Google Patents

Description

The present invention relates to a film, a film roll and a method for producing a film.

In recent years, as devices have become lighter and more flexible, the films used in the devices have become thinner. For example, thin optical films are used in devices such as displays and touch sensors (for example, Patent Document 1).

JP 2017-100372 A

However, making the film thinner can lead to winding problems when forming a film roll, which can impair the quality of the film. For example, if there is too little air between the films, this can lead to winding problems such as sticking between the films.

Therefore, the present invention aims to provide a film, a film roll, and a film manufacturing method that can suppress the occurrence of winding defects.

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

A film having a first end and a second end in a width direction intersecting the longitudinal direction, a central portion between the first end and the second end, a convex position where the thickness Te1 of at least the first end of the first end and the second end is smaller than the thickness Tc of the central portion, and a concave position that is disposed at a position different from the convex position in the longitudinal direction and where the thickness Te1 of the first end is greater than the thickness Tc of the central portion.

According to the present invention, the film has a convex position where the thickness Te1 of the first end is smaller than the thickness Tc of the central portion, and a concave position where the thickness Te1 of the first end is larger than the thickness Tc of the central portion, so that it is easy to control the amount of air between the film when forming a film roll. This makes it possible to suppress the occurrence of winding defects.

FIG. 2 is a schematic diagram illustrating an example of a configuration of a film roll according to an embodiment of the present invention. FIG. 2 is a plan view illustrating an example of a configuration of the film illustrated in FIG. 1 . 3A is a diagram illustrating a cross-sectional configuration of a convex region shown in FIG. 2, and FIG. 3B is a diagram illustrating a cross-sectional configuration of a concave region shown in FIG. 2. FIG. 4 is a diagram illustrating another example of the cross-sectional configuration of the end portion of the film illustrated in FIGS. 3 is a diagram illustrating an example of the relationship between the position in the longitudinal direction of the film shown in FIG. 2 and a difference ratio D between the thicknesses of the end portions and the central portion. FIG. 5B is a diagram illustrating another example of the relationship between the position in the longitudinal direction of the film and the difference ratio D shown in FIG. 5A. 5B is a diagram illustrating another example of the relationship between the position in the longitudinal direction of the film and the difference ratio D shown in FIG. 5A. 5B is a diagram illustrating another example of the relationship between the position in the longitudinal direction of the film and the difference ratio D shown in FIG. 5A. 5B is a diagram illustrating another example of the relationship between the position in the longitudinal direction of the film and the difference ratio D shown in FIG. 5A. 1 is a flow chart illustrating an example of a method for producing a film. FIG. 8 is a diagram illustrating a configuration of a clip tenter used in step S102 shown in FIG. 7. FIG. 13 is a diagram illustrating an example of the relationship between the longitudinal position of a film and a difference ratio D in a comparative example. 9B is a diagram illustrating another example of the relationship between the longitudinal position of the film and the difference ratio D shown in FIG. 9A. 9B is a diagram illustrating another example of the relationship between the longitudinal position of the film and the difference ratio D shown in FIG. 9A. 2 is a diagram illustrating an example of a configuration of an end surface of the film roll illustrated in FIG. 1 . FIG. 13 is a diagram illustrating an example of a cross-sectional configuration of a film according to a modified example.

The following describes preferred embodiments of the present invention. In this specification, the range "X to Y" means "X or more and Y or less." Furthermore, unless otherwise specified, the operation and physical properties are measured under the conditions of room temperature (20 to 25°C) and relative humidity of 40 to 50% RH.

In addition, the dimensional proportions in the drawings have been exaggerated for the purposes of explanation and may differ from the actual proportions.

Figure 1 shows a schematic configuration of a film roll 1 according to one embodiment. This film roll 1 is formed by winding an optical film 11 in a roll shape around a winding 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 winding core 12 has, for example, a cylindrical shape and a predetermined length (the size in the X direction in Figure 1). The optical film 11 is wound in the circumferential direction of this winding core 12. The total winding length of the film roll 1 is, for example, 500 m to 20,000 m.

Figure 2 shows an example of the planar configuration of optical film 11. Optical film 11 is wound around winding core 12 along its longitudinal direction. In the following description, the longitudinal direction of optical film 11 may be referred to as the Y direction, the width direction intersecting the longitudinal direction as the X direction, and the thickness direction as the Z direction. Here, the width direction of optical film 11 is approximately perpendicular to the longitudinal direction. The longitudinal size of optical film 11 is, for example, 500 m to 20,000 m, and the width direction of optical film 11 is, for example, 100 mm to 3,000 mm.

The optical film 11 has a pair of ends e1, e2 in the width direction and a central portion c between the pair of ends e1, e2. The pair of ends e1, e2 and the central portion c are each, for example, portions having about 10% of the entire size of the optical film 11 in the width direction, with the end e1 including one end of the optical film 11 in the width direction, the end e2 including the other end of the optical film 11 in the width direction, and the central portion c including the center of the optical film 11 in the width direction. Here, the end e1 corresponds to a specific example of the first end of the present invention, and the end e2 corresponds to a specific example of the second end of the present invention.

This optical film 11 has convex regions R1 and concave regions R2 aligned in the Y direction. For example, the optical film 11 is provided with a plurality of convex regions R1 and concave regions R2, and the convex regions R1 and concave regions R2 are arranged alternately in the Y direction.

3A shows the XZ cross section of the convex region R1, and FIG. 3B shows the XZ cross section of the concave region R2. In the convex region R1, the thickness Te1 of the end e1 and the thickness Te2 of the end e2 are smaller than the thickness Tc of the central portion c, and in the concave region R2, the thickness Te1 of the end e1 and the thickness Te2 of the end e2 are larger than the thickness Tc of the central portion c. That is, in the convex region R1, the thicknesses Te1, Te2, and Tc preferably satisfy the following formulas (1) and (2), and in the concave region R2, the thicknesses Te1, Te2, and Tc preferably satisfy the following formulas (3) and (4).

In other words, it is preferable that at the convex position P1 provided in the convex region R1, the thicknesses Te1, Te2, and Tc satisfy the formulas (1) and (2), and at the concave position P2 provided in the concave region R2, the thicknesses Te1, Te2, and Tc satisfy the formulas (3) and (4). The convex position P1 may be any position within the convex region R1, and the concave position P2 may be any position within the concave region R2.

Although details will be described later, in this embodiment, the optical film 11 has such convex positions P1 and concave positions P2, more specifically, convex regions R1 and concave regions R2, so that when forming the film roll 1, it is easy to control the amount of air between the overlapping optical films 11. This makes it possible to suppress the occurrence of winding defects.

At the convex position P1 and the convex region R1, the thickness Te1 of the end e1 needs to be smaller than the thickness Tc of the central portion c, and at this time, at the concave position P2 and the concave region R2, the thickness Te1 of the end e1 needs to be larger than the thickness Tc of the central portion c. That is, at the convex position P1 and the convex region R1, the thicknesses Te1 and Tc need to at least satisfy formula (1), and at this time, at the concave position P2 and the concave region R2, the thicknesses Te1 and Tc need to at least satisfy formula (3).

In the optical film 11, it is preferable that the thicknesses Te1, Te2, and Tc at the convex position P1 and the convex region R1 satisfy the formula (1) and the formula (2), and that the thicknesses Te1, Te2, and Tc at the concave position P2 and the concave region R2 satisfy the formula (3) and the formula (4). This can more effectively suppress the occurrence of winding defects. For example, at a predetermined position in the Y direction, the thickness Te1 of the end e1 and the thickness Te2 of the end e2 are almost the same. The average thickness of the entire optical film 11 is, for example, about 10 μm to 40 μm. The size in the Y direction of each of the convex region R1 and the concave region R2 is preferably 100 m to 500 m, and more preferably 250 m or more. This can more effectively suppress the occurrence of winding defects. The size in the Y direction of the convex region R1 and the concave region R2 is, for example, almost the same. The sizes of the convex region R1 and the concave region R2 in the Y direction may be different from each other.

Figure 4 shows another example of the cross-sectional configuration of the optical film 11 shown in Figure 3. The optical film 11 may have an embossed portion E. The embossed portion E is a portion that has been embossed, and for example, has unevenness on its surface. The embossed portion E is provided, for example, on ends e1 and e2. In this case, the thicknesses Te1 and Te2 of the ends e1 and e2 are, for example, the thicknesses of the convex portions of the embossed portion E.

In the optical film 11, the difference between the thicknesses Te1, Te2 of the ends e1, e2 and the thickness Tc of the center c at a predetermined position in the Y direction (for example, the convex position P1, the concave position P2) can be expressed by the difference ratio D1 and the difference ratio D2. The difference ratio D1 and the difference ratio D2 are the difference between the thicknesses Te1, Te2 and the thickness Tc with respect to the average thickness Ta of the optical film 11, and can be expressed by the following formulas (5) and (6). In the convex region R1, the difference ratio D1 and the difference ratio D2 are positive values, and in the concave region R2, the difference ratio D1 and the difference ratio D2 are negative values. The absolute values of the difference ratio D1 and the difference ratio D2 (hereinafter, represented as |D1| and |D2|) are, for example, 10% or less, and more preferably 5% or less. By setting |D1| and |D2| to 5% or less, the occurrence of winding defects can be more effectively suppressed.

For example, the difference ratio D1 and the difference ratio D2 at a predetermined position in the Y direction are approximately the same. In the following description, when the difference ratio D1 and the difference ratio D2 at a predetermined position in the Y direction are approximately the same, the difference ratio D1 and the difference ratio D2 are collectively referred to as the difference ratio D. In Figures 5A to 6B and Figures 8A to 8C described below, the difference ratio D1 and the difference ratio D2 at a predetermined position in the Y direction are approximately the same, and the difference ratio D is used.

Figures 5A, 5B and 5C show an example of the relationship between the Y-direction position of the optical film 11 and the differential ratio D. The optical film 11 has, for example, constant portions C1 and C2 in the convex region R1 and the concave region R2, respectively, where the differential ratio D is constant. For example, in the convex region R1, the absolute value of the differential ratio D (hereinafter referred to as |D|) is largest in the constant portion C1, and in the concave region R2, |D| is largest in the constant portion C2. It is preferable that |D| of the constant portions C1 and C2, i.e., the maximum value of |D| of the convex region R1 and the concave region R2, is 10% or less, and more preferably 5% or less.

It is preferable that the optical film 11 has a sloping portion S between the constant portion C1 and the constant portion C2 (FIGS. 5A and 5B). This sloping portion S is a portion in which the difference ratio D (%) changes continuously along the longitudinal direction. In other words, in the sloping portion S, at least one of the thicknesses Te1, Te2 of the ends e1, e2 and the thickness Tc of the central portion c changes continuously along the longitudinal direction. By having such a sloping portion S, the optical film 11 can effectively suppress the occurrence of winding defects compared to the case in which the sloping portion S is not present (FIG. 5C). By making the Y-direction size of the sloping portion S 5 m or more, it is possible to more effectively suppress the occurrence of winding defects. In the sloping portion S, the change in |D| per 100 m of the Y-direction size, i.e., the slope of the sloping portion S, is preferably, for example, 0.03% to 10.0%, more preferably 0.05% to 7.5%, and even more preferably 2.0% to 5.0%. This makes it possible to more effectively prevent winding defects from occurring.

Figures 6A and 6B show other examples of the relationship between the Y-direction position of the optical film 11 and the differential ratio D. In this way, the change in the differential ratio D in the Y direction may be nonlinear. Within the convex region R1 or the concave region R2, the differential ratio D may have multiple maximum values (Figure 6B). Within the convex region R1 or the concave region R2, an inflection point of the differential ratio D may be provided. The relationship between the Y-direction position of the optical film 11 and the differential ratio D is not limited to the examples shown in Figures 5A to 6B.

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

Among the above resins, it is preferable to use cycloolefin resins from the viewpoints of transparency, mechanical strength, etc. Examples of cycloolefin resins include (co)polymers having structural units derived from the following structures:

In the formula, R ¹ to R ⁴ are each independently a hydrogen atom, a hydrocarbon group, a halogen atom, a hydroxy group, an ester group, an alkoxy group, a cyano group, an amide group, an imide group, a silyl group, or a hydrocarbon group substituted with a polar group (i.e., a halogen atom, a hydroxy group, an ester group, an alkoxy group, a cyano group, an amide group, an imide group, or a silyl group). However, two or more of R ¹ to R ⁴ may be bonded to each other to form an unsaturated bond, a monocycle, or a polycycle, and this monocycle or polycycle may have a double bond or form an aromatic ring. R ¹ and R ² , or R ³ and R ⁴ , may together form an alkylidene group. p and m are each independently an integer of 0 or more.

In the above general formula, R ¹ and R ³ are preferably a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, more preferably a hydrocarbon group having 1 to 4 carbon atoms, and particularly preferably a hydrocarbon group having 1 to 2 carbon atoms. ^{R 2} and R ⁴ are preferably a hydrogen atom or a monovalent organic group, and at least one of R ² and R ⁴ is preferably a polar group having polarity other than a hydrogen atom or a hydrocarbon group. m is preferably an integer of 0 to 3, p is preferably an integer of 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. A specific monomer in which m=1 and p=0 is preferred in that the glass transition temperature of the resulting cycloolefin resin is high and the mechanical strength is also excellent.

The polar group of the specific monomer may be carboxyl group, hydroxyl group, alkoxycarbonyl group, allyloxycarbonyl group, amino group, amide group, cyano group, etc., and these polar groups may be bonded via a linking group such as methylene group.In addition, the polar group may be a hydrocarbon group to which a polar divalent organic group such as carbonyl group, ether group, silyl ether group, thioether group, imino group, etc. is bonded as a linking group.Among these, carboxyl group, hydroxyl group, alkoxycarbonyl group, or allyloxycarbonyl group is preferred, and particularly alkoxycarbonyl group or allyloxycarbonyl group is preferred.

Furthermore, a monomer in which at least one of ^R2 and ^R4 is a polar group represented by the formula -( _CH2 ) _nCOOR is preferred in that the resulting cycloolefin resin has a high glass transition temperature, low moisture absorption, and excellent adhesion to various materials. In the formula relating to the specific polar group above, R is preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, and particularly preferably an alkyl group having 1 to 2 carbon atoms. n is an integer of 0 or more.

When the above structural units have a polar group, specific examples of other copolymerizable monomers include cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, dicyclopentadiene, and norbornene.

The number of carbon atoms of the cycloolefin as a copolymerizable monomer is not particularly limited, but is preferably 4 to 20, and more preferably 5 to 12.

The cycloolefin resin contained in the optical film 11 may be one type or two or more types.

The cycloolefin resin contained in the optical film 11 has an intrinsic viscosity [ηinh] of preferably 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. The number average molecular weight (Mn) in terms of polystyrene measured 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, and the weight average molecular weight (Mw) is preferably in the range of 20,000 to 300,000, more preferably 30,000 to 250,000, and even more preferably 40,000 to 200,000.

By having the intrinsic viscosity [ηinh], number average molecular weight, and weight average molecular weight within the above ranges, the cycloolefin resin has good heat resistance, water resistance, chemical resistance, mechanical properties, and moldability as a cycloolefin film. The intrinsic viscosity [ηinh] value is the viscosity of a solution in which the cycloolefin resin is dissolved in chloroform, measured at a temperature of 30°C. Viscosity measurements are performed on three or more solutions each with a different concentration of cycloolefin resin. An Ubbelohde viscometer is used for the measurements.

The glass transition temperature (Tg) of the cycloolefin resin contained in the optical film 11 is, for example, preferably 110°C or higher, more preferably 110 to 350°C, even more preferably 120 to 250°C, and particularly preferably 120 to 220°C. If the Tg is 110°C or higher, deformation due to use under high temperature conditions or secondary processing such as coating and printing can be suppressed. On the other hand, if the Tg is 350°C or lower, molding processing becomes easy and deterioration of the resin due to heat during molding processing can be prevented. For the glass transition temperature (Tg), the midpoint glass transition temperature value obtained according to JIS K7121 (1987) by performing thermal analysis of the cycloolefin resin at a heating rate of 20°C/min is adopted. For the thermal analysis, a differential scanning calorimeter DSC220 manufactured by Seiko Instruments Inc. is used.

The optical film 11 preferably contains 50% by mass or more, and more preferably 70 to 90% by mass or more of a cycloolefin resin.

The optical film 11 may contain known hydrocarbon resins, thermoplastic resins, thermoplastic elastomers, rubbery polymers, organic particles, or inorganic particles, as described in, for example, JP-A-9-221577 and JP-A-10-287732, within the scope of not impairing the effects of this embodiment. The optical film 11 may contain additives such as a specific wavelength dispersion agent, a sugar ester compound (also simply called sugar ester), an antioxidant, a peeling promoter, rubber particles, or a plasticizer.

The cycloolefin resin contained in the optical film 11 may be a commercially available product or a synthetic product. Examples of commercially available products include SANUQI (registered trademark) from Konica Minolta, Inc., ARTON (registered trademark, the same applies below) G, ARTON F, ARTON R, and ARTON RX from JSR Corporation, and ZEONOR (registered trademark) ZF14, ZF16, ZEONEX (registered trademark, the same applies below) 250, or ZEONEX 280 from Zeon Corporation.

<Method of Manufacturing Optical Film>
7 is a flow chart showing 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 original film (for example, an original film 11f in FIG. 8 described later) and then forming the convex region R1 and the concave region R2 in the original film. More preferably, the optical film 11 is manufactured, for example, by forming an original film (step S101) and then forming the convex region R1 and the concave region R2 in the original film (step S102). The manufacturing method of the optical film 11 will be described below.

In step S101, the original film may be prepared in advance or may be newly formed. In step S101, for example, an original film having a width direction and a length direction is formed.

The method of forming the raw film is not particularly limited, and known methods can be used. Among these, from the viewpoint of productivity, it is preferable to manufacture by the solution casting method or the melt casting method, and from the viewpoint of transparency, transportability, and flexibility, it is more preferable to manufacture by the solution casting method. Here, the solution casting method is generally a method in which a solution in which a resin and other components that may be optionally contained are dissolved is cast onto a support, dried on the support, and then a film-like material (web) is peeled off, and the web is further dried after peeling to form a film. On the other hand, the melt casting method is generally a method in which a resin and other components that may be optionally contained are melt-kneaded to manufacture a film, and the mixture is heated to a temperature at which it exhibits fluidity and melted, and then cast as a fluid molten material to form a film.

In addition, when the solution casting method is used, the raw film of the present invention may be a membrane-like material (web) or a film obtained by further drying the web after peeling.

The amount of residual solvent when peeling the web from the support is not particularly limited as long as it is an amount that provides sufficient self-supporting properties to enable peeling. However, from the viewpoint of ensuring that the original film exhibits good flatness, 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.

The residual solvent content of the web or film is defined by the following formula:
Residual Solvent Amount (% by mass)={(M−N)/N}×100
Here, M is the mass of a sample taken at any time during or after the production of the web or film, and N is the mass of M after heating at 115° C. for 1 hour.

The amount of residual solvent in the film obtained by further drying the web after peeling is preferably 1% by mass or less, more preferably 0.1% by mass or less, and particularly preferably in the range of 0 to 0.01% by mass.

For example, it is preferable to form the original film as follows. In the solution casting method, first, a dope containing a resin and a solvent is prepared. Then, this dope is cast onto a support. The casting is performed while moving the support. Next, the cast film formed on the support is peeled off from the support. Thereafter, the cast film is dried as necessary to form an original film containing a resin. As mentioned above, the original film may be a so-called web.

Solvents used in the dope are not particularly limited, but include, for example, chlorine-based solvents such as chloroform and dichloromethane (methylene chloride); aromatic solvents such as toluene, xylene, benzene, and mixed solvents thereof; alcohol-based solvents such as methanol, ethanol, isopropanol, n-butanol, and 2-butanol; methyl cellosolve, ethyl cellosolve, butyl cellosolve, ethylene glycol monomethyl ether, dimethylformamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), ethyl acetate, diethyl ether, and the like.

The solids concentration of the dope is not particularly limited, but is preferably 10 to 35% by mass, and more preferably 15 to 35% by mass.

The support is not particularly limited, but a mirror-finished surface is preferred, and a stainless steel belt (stainless steel belt) or a cast drum with a plated surface is preferably used.

In step S102, for example, the original film is stretched in the width direction while the end portions of the original film in the width direction are heated to form convex regions R1 and concave regions R2 in the original film. The thickness of the original film is generally reduced by stretching compared to before stretching, but the thickness is less likely to be reduced near the ends held by clips or the like compared to the central portion. By heating the ends of this original film, the thicknesses Te1 and Te2 of the ends e1 and e2 of the film 11 are adjusted.

It is possible to control the thicknesses Te1, Te2 of the ends e1, e2 by adjusting the temperature, conveying speed and equipment when stretching the raw film (see, for example, SEN-I GAKKAISHI (Textiles and Industry), Vol. 41, No. 9, pp. 290-301, 1985), and any method may be used for the stretching technique.

Figure 8 shows an example of the configuration of a clip tenter 50 used to stretch the original film (original film 11f) in the width direction. In the clip tenter 50, the original film 11f is stretched in the width direction while being transported along the longitudinal direction. The clip tenter 50 is provided with a first relaxation area 50A before stretching, a stretching area 50B, a second relaxation area 50C after stretching, and a cooling area 50D, arranged in this order. The original film 11f is transported by passing through the first relaxation area 50A, the stretching area 50B, the second relaxation area 50C, and the cooling area 50D, in this order.

For example, a heating member 51 for heating both ends of the original film 11f is disposed in each of the first relaxation area 50A, the stretching area 50B, and the second relaxation area 50C of the clip tenter 50 (see, for example, JP 2011-115985 A). The heating member 51 is disposed in each of the first relaxation area 50A, the stretching area 50B, and the second relaxation area 50C. The heating member 51 may be disposed in at least one of the first relaxation area 50A, the stretching area 50B, and the second relaxation area 50C. The heating member 51 may be capable of adjusting the temperature depending on the position in the X direction. For example, a plurality of heating members 51 may be disposed in the X direction, and the temperature of the heating members 51 may be changed in the X direction. The temperature of the heating members 51 is controlled by a control unit 52.

The heating member 51 is, for example, an infrared ray irradiating member that irradiates infrared rays toward the end of the original film 11f in the width direction. The heating member 51 may be a blowing member that blows high-temperature air or inert gas toward the end of the original film 11f in the width direction, or may be a heating wire and a heating roll. The heating member 51 is, for example, arranged in the front, back, top, or bottom of the original film 11f, or in a plurality of these locations. The position of the heating member 51 in the X direction is preferably 10 mm to 500 mm away from the portion where both ends of the film 11 in the width direction are formed, and more preferably 20 mm to 400 mm away. This makes it easier to control the thicknesses Te1 and Te2 of the ends e1 and e2. The both ends of the film 11 in the width direction are formed, for example, by slitting the portion (ends in the width direction) held by the clip from the original film 11f after stretching.

A clip tenter 50 having a heating member 51 in each of the first relaxation area 50A, the stretching area 50B and the second relaxation area 50C is used to form a convex region R1 and a concave region R2 in the original film 11f, for example, as follows.

First, both ends of the original film 11f in the width direction are gripped with clips or the like. Then, the transport of the original film 11f is started. As a result, the original film 11f passes through the first relaxation area 50A, the stretching area 50B, the second relaxation area 50C, and the cooling area 50D in order, and is stretched in the width direction. The transport speed of the original film 11f is not particularly limited, but is preferably 3 m/min to 100 m/min, and 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, it becomes easier to adjust the amount of air between the films 11, and it is also possible to reduce the transport time and reduce costs. By setting the transport speed to 100 m/min or less, more preferably 50 m/min or less, it is possible to prevent the heating member 51 for providing sufficient heat to the target range from becoming large, and to reduce equipment costs.

In the first relaxation area 50A, the stretching area 50B, and the second relaxation area 50C, it is preferable that the temperature of both ends in the width direction of the original film 11f is about 0°C to 50°C higher than the temperature of the center. Here, the temperature of the heating member 51 is changed over time by the control unit 52, so that the temperature difference between both ends and the center of the part forming the convex region R1 in the original film 11f is made larger than the temperature difference between both ends and the center of the part forming the concave region R2. As a result, the thicknesses Te1 and Te2 of the ends e1 and e2 of the convex region R1 become 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 original film 11f. For example, in the portion where the convex region R1 is formed, the temperature difference between both ends and the center of the original film 11f is set to 20°C to 30°C, and in the portion where the concave region R2 is formed, the temperature difference between both ends and the center of the original film 11f is set to 0°C to 10°C.

For example, the magnitude of |D| can be controlled by adjusting the temperature difference between both ends and the center of the original film 11f. In the portion forming the convex region R1, the greater the temperature difference between the ends and the center, the greater |D|, and in the portion forming the concave region R2, the smaller the temperature difference between the ends and the center, the greater |D|.

For example, the rate of change in |D| per 100 m in the Y direction can be controlled by adjusting the rate of temperature rise and fall of both ends of the original film 11f (or the heating member 51). The faster the rate of temperature rise or fall of both ends, the greater the rate of change in |D| per 100 m in the Y direction.

It is preferable that the temperature difference between both ends of the original film 11f and the temperature at the center is 50°C or less. This suppresses softening of the ends e1 and e2 of the film 11, and makes it possible to adjust the thicknesses Te1 and Te2 of the ends e1 and e2 with high accuracy. In the portion forming the convex region R1, it is preferable that the temperature difference between both ends and the center of the original film 11f is 3°C or more. This makes it possible to sufficiently reduce the thicknesses Te1 and Te2 of the ends e1 and e2 in a relatively short time without enlarging the equipment. In addition, the temperatures at both ends of the original film 11f may be different from each other, but it is preferable that they are approximately the same.

The temperatures of both ends and the center of the original film 11f are measured from below the direction of gravity using, for example, a thermal non-contact temperature sensor (MT150 manufactured by Raytec Corporation). The temperatures of both ends of the original film 11f are measured, for example, at a position overlapping near the center of the heating member 51, and the average value is used over a range of 50 mm in the width direction. The temperature of the center of the original film 11f is measured, for example, at a position midway between both ends, and the average value is used over a range of 100 mm in the width direction.

The stretching ratio in the width 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 the thicknesses Te1 and Te2 of the ends e1 and e2 to be effectively adjusted by heating the ends e1 and e2. In addition, the stretching ratio in the width direction is preferably 1000% or less. This allows stretching to be performed without enlarging the stretching equipment, making it possible to reduce equipment costs. The stretching ratio in the width direction can be adjusted by the distance between the clips of the clip tenter 50. The stretching ratio in the width direction can be evaluated by comparing the width of the film before and after stretching. The above-mentioned stretching ratio and temperature are examples, and are appropriately adjusted to obtain the desired orientation, physical properties, and surface state of the film 11. For stretching in the width direction, any method can be used, not limited to the clip tenter 50, but for example, a pin tenter or the like may be used.

The stretching ratio in the conveying direction is not particularly limited. Any method can be used for stretching in the conveying direction, for example, the pantograph method, the roll-to-roll draw method, the float method, etc.

The convex region R1 and the concave region R2 may be formed using other methods. For example, the convex region R1 and the concave region R2 may be formed by controlling the amount of dope cast when casting. For example, the amount of dope cast may be adjusted using a choke bar (also called a die bolt) or the like (see, for example, JP 2016-190344 A) to form the convex region R1 and the concave region R2. The dope for forming the central portion c and the ends e1 and e2 may be independently controlled and supplied to adjust the amount of dope cast (see, for example, JP 2009-78371 A) to form the convex region R1 and the concave region R2. For example, when the thicknesses Te1 and Te2 of the ends e1 and e2 are to be increased, the flow rate of the dope for forming the ends e1 and e2 may be increased, and when the thicknesses Te1 and Te2 of the ends e1 and e2 are to be decreased, the flow rate of the dope for forming the ends e1 and e2 may be decreased.

Alternatively, the convex region R1 and the concave region R2 may be formed by controlling the presence or absence and size of an embossed portion (for example, embossed portion E in FIG. 4) (see, for example, JP 2009-73154 A). The convex region R1 and the concave region R2 may be formed by combining a plurality of these methods.

For example, in this manner, an optical film 11 having a convex region R1 and a concave region R2 can be manufactured. The optical film 11 is wound around a core 12, for example, using a winding machine, to form a film roll 1.

<Actions and Effects of Optical Film and Film Roll>
The optical film 11 of this embodiment has a convex region R1 (or a convex position P1) where the thicknesses Te1, Te2 of the ends e1, e2 are smaller than the thickness Tc of the central portion c, and a concave region R2 (or a concave position P2) where the thicknesses Te1, Te2 of the ends e1, e2 are larger than the thickness Tc of the central portion c, so that when forming the film roll 1, it becomes easy to control the amount of air between the optical films 11. Therefore, it becomes possible to suppress the occurrence of winding defects. The effect of this will be described in detail below.

9A, 9B, and 9C each show the relationship between the position in the Y direction (longitudinal direction) of the optical film according to the comparative example and the difference ratio D. Each of these optical films according to the comparative examples has only one of the convex region R1 and the concave region R2. The optical film shown in FIG. 9A and the optical film shown in FIG. 9C have only the convex region R1, and the thickness of the end portion is smaller than the thickness of the central portion at all positions in the longitudinal direction (difference ratio D>0). The optical film shown in FIG. 9B has only the concave region R2, and the thickness of the end portion is larger than the thickness of the central portion at all positions in the longitudinal direction (difference ratio D<0). In such an optical film according to the comparative example, when forming a film roll, it is difficult to control the amount of air between the overlapping optical films, and winding defects are likely to occur.

For example, in the optical film shown in FIG. 9A and the optical film shown in FIG. 9C, the amount of air between the overlapping optical films is relatively small, and strong adhesion is likely to occur in the thicker central portion. This adhesion between the optical films may cause black bands in the film roll. In black bands, expansion and contraction occurs between the central portion, where adhesion is strong, and the ends, where adhesion is weak, causing deformation of the optical film. In addition, tiny air particles caught between the films may grow as the film is wound up, forming dents.

On the other hand, in the optical film shown in Figure 9B, the amount of air between the overlapping optical films is relatively large, making it possible to prevent winding problems caused by sticking between the optical films. However, with this optical film, after the film roll is formed, the air between the optical films escapes over time, making it difficult to maintain the shape. There is a risk of the optical film deforming due to this air escape.

Deterioration of the optical film caused by such winding defects also affects devices that use the optical film, such as displays and touch sensors. For example, in displays, image visibility decreases, and in touch sensors, resistance values fluctuate, reducing sensor function.

Unlike the optical films of these comparative examples, the optical film 11 of this embodiment has both convex regions R1 and concave regions R2, so that the amount of air between overlapping optical films 11 can be controlled.

Figure 10 shows 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 each other, so that adhesion between the optical films 11 is suppressed and the shape is maintained. In other words, the occurrence of black bands and dents is suppressed, and deformation of the optical film 11 over time can be suppressed.

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

When such an optical film 11 is used in devices such as displays and touch sensors, it is possible to improve the performance of the devices.

In addition, this optical film 11 can be made thinner because the occurrence of winding defects is suppressed. Furthermore, low-elasticity materials can also be suitably used for the optical film 11. In addition, even when manufacturing a long optical film 11, a decrease 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 more effectively suppressed.

<Modification>
The film roll 1 may be formed by winding up a laminate of a plurality of films. This laminate may have, for example, an optical film 11 and a protective film (protective film 21 in FIG. 11 described below). Here, the optical film 11 corresponds to a specific example of the functional film of the present invention.

Figure 11 shows an example of the cross-sectional configuration of a laminate of an optical film 11 and a protective film 21. The protective film 21 is for protecting the optical film 11 and is configured to be peelable from the optical film 11. The protective film 21 contains, for example, 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, polyarylate resins, polystyrene resins, polyvinyl alcohol resins, epoxy resins, and mixtures thereof.

For example, a protective film 21 is laminated onto an optical film 11, and then the laminate is wound up to form a film roll 1.

<Other Modifications>
A transparent conductive film may be laminated on the optical film 11. Examples of materials used to form the transparent conductive film include metals such as Sn, In, Ti, Pb, Au, Pt, and Ag, and oxides thereof. Examples of the oxides include indium tin oxide (ITO), aluminum oxide, silicon oxide, titanium oxide, zinc oxide, and tungsten oxide. The transparent conductive film may be formed using aluminum nitride, silicon nitride, titanium nitride, cadmium sulfide, zinc sulfide, zinc selenide, or the like.

An adhesive layer and an anchor coat layer may be provided between the optical film 11 and the transparent conductive film. The adhesive layer can be formed using a heat-resistant resin such as an epoxy resin, polyimide, polybutadiene, phenolic resin, or polyether ether ketone. The anchor coat layer can be formed by using an anchor coat agent containing an acrylic prepolymer such as epoxy diacrylate, urethane diacrylate, or polyester diacrylate, and curing the agent by a known curing method such as UV curing or heat curing.

An adhesive layer may be provided between the optical film 11 and the transparent conductive film in order to improve the smoothness of the film and its adhesion to the transparent conductive film. This adhesive layer can be obtained, for example, by applying a resin varnish and then drying it to remove the solvent.

The laminate including 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. Usable inorganic materials include silicon oxide, aluminum oxide, indium oxide, etc., and usable organic materials include polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyamide, etc. Furthermore, a protective coating layer for protecting the gas barrier layer may be laminated on the gas barrier layer.

<Application Examples>
The optical film 11 is, for example, a substrate for a color filter, a light guide plate, a protective film, a polarizing film, a retardation film, a touch panel, a transparent electrode substrate, a compact disc (CD), a mini disc (MD), a digital versatile disc (DVD), etc.
The film can be suitably used as an optical recording substrate such as a thin film transistor (TFT) substrate, a liquid crystal display substrate and an organic electroluminescence (EL) display substrate, or an optical component such as an optical transmission waveguide and an optical element sealant. In particular, the film can be suitably used as a display element member, specifically, a color filter substrate, a light guide plate, a protective film, a polarizing film, a retardation film, a touch sensor, a transparent electrode substrate, a TFT substrate, a liquid crystal display substrate, an organic EL display substrate, etc.

For example, a color filter can be obtained by laminating a color filter layer on a color filter substrate including the optical film 11. This lamination method can be a known pigment dispersion method, dyeing method, electrodeposition method, printing method, transfer method, etc. This color filter can be used as a color filter for a liquid crystal display device, and can also be used as a part of a color display, liquid crystal display device, etc.

In addition to optical components, the optical film 11 can also be used for electrical insulation components, electrical and electronic components, electronic component sealants, medical equipment, and packaging materials. In particular, the optical film 11 containing cycloolefin resin has excellent heat resistance and electrical properties, and exhibits little dimensional change even when subjected to high-temperature treatment or chemical treatment, making it ideal as an electrical insulation component. Examples of electrical insulation components include coating materials for electric wires and cables, insulating materials for office equipment such as computers, printers, and copiers, and insulating components for flexible printed circuit boards, but it is particularly suitable for use as a flexible printed circuit board.

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

The touch sensor including the optical film 11 is, for example, a transparent electrode type touch sensor. In the transparent electrode type touch sensor, for example, a transparent electrode is formed by coating the optical film 11 with a metal oxide, and a position is sensed by a contact point with the transparent electrode. For example, indium tin oxide (ITO) is used as the metal oxide. For example, the optical film 11 is coated with the metal oxide by vacuum deposition or sputtering.

The optical film 11 used in such a touch sensor preferably has high heat resistance. Heat resistance can be evaluated, for example, by the glass transition temperature, and the optical film 11 preferably has a high glass transition temperature equal to or higher than the sputtering temperature and high mechanical strength.

In addition, it is preferable that the optical film 11 used in the touch sensor also has transparency in the visible light range, and for example, it is preferable that it has a light transmittance of 90% or more for visible light.

The optical film 11 containing cycloolefin resin has a high glass transition temperature and high heat resistance, as well as high optical transmittance to visible light, making it suitable for use in touch sensors.

The effects of the present invention will be explained using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples.

Example 1
First, a raw film was prepared as follows.

(Preparation of Dope)
PET resin (Toyobo Ester Film E7002, manufactured by Toyobo Co., Ltd.) 100 parts by weight Dichloromethane 200 parts by weight Ethanol 10 parts by weight First, the above components were charged into a sealed container, and the PET resin was dissolved under stirring to prepare a dope.

(Film formation)
Next, the dope was uniformly cast on a stainless steel belt support at a temperature of 31° C. and a width of 1800 mm using an endless belt casting apparatus to form a casting film. The temperature of the stainless steel belt was controlled at 28° C. Next, the solvent was evaporated on the stainless steel belt support until the amount of residual solvent in the casting film was 30%. Next, the casting film was peeled off from the stainless steel belt support at a peeling tension of 128 N/m, and then the casting film was stretched 1.15 times in the width direction under the condition of 160° C. The residual solvent at the start of stretching was 5% by mass. Next, the casting film was dried while being conveyed by a number of rollers. Next, the parts of the casting film that were clamped by the tenter clips (both ends) were slit by a laser cutter, and then the casting film was wound up. As a result, a raw film having a thickness of 33 μm was produced.

Next, the original film was stretched in the width direction using a clip tenter while holding both ends in the width direction of the original film with clips. At this time, both ends in the width direction of the original film were heated in the stretching area (stretching area 50B in FIG. 8) to form convex regions R1 and concave regions R2. An infrared irradiation member was used as the heating member. The heating member was disposed at a distance of 150 mm or less from the position where both ends in the width direction of the film roll were formed. The central part of the original film was heated to 130° C. and both ends were heated to 160° C. to form convex regions, and both the central part and both ends of the original film were heated to 130° C. to form concave regions. The stretch ratio in the width direction of both the convex region R1 and the concave region R2 was 30%.

Using an in-line thickness gauge, the average thickness of the film prepared above, the difference ratio D of each of the convex region R1 and the concave region R2 where |D| is maximum, and the longitudinal size of each of the convex region R1 and the concave region R2 were measured. In addition, using an in-line thickness gauge and an encoder (length measuring device), the change in the difference ratio D of the inclined portion per 100 m of longitudinal size was measured (see Figures 5A and 5B). The average thickness of the prepared film was 25 μm, and the difference ratio D of each of the convex region and the concave region where |D| is maximum was 7.5% and -7.5%. The longitudinal size of the convex region R1 and the longitudinal size of the concave region R2 were the same, 250 m. The change in the difference ratio D per 100 m at the inclined portion was 7.5%. In addition, the glass transition temperature of this film was 80 ° C. After this, the prepared film was wound around a winding core to prepare a film roll. The total length of the roll was 4000 m.

Example 2
First, a raw film was prepared as follows.

(Preparation of Rubber Particle Dispersion)
A solution containing 10 parts by mass of rubber particles (Kane Ace (registered trademark) M210 manufactured by Kaneka Corporation, average primary particle size R: 200 nm) and 90 parts by mass of ME16 (a mixed solvent of methylene chloride and ethanol in a mass ratio of 84:16) was stirred and mixed with a dissolver for 50 minutes. After that, the solution was dispersed using a Milder disperser (manufactured by Pacific Machinery Works, Ltd.) under a condition of 1500 rpm to obtain a rubber particle dispersion.

(Preparation of Silica Particle Dispersion)
A mixture of 20 parts by mass of silica particles (Aerosil (registered trademark) R812, manufactured by Nippon Aerosil Co., Ltd., hydrophobic fumed silica, average primary particle size Rs1: 7 nm, specific surface area: 260±30 ^m2 /g) and 80 parts by mass of ME50 (a mixed solvent of methylene chloride and ethanol in a mass ratio of 50:50) was stirred and mixed in a dissolver for 50 minutes. After this, the mixture was dispersed in a Manton-Gaulin to obtain an additive solution.

Next, 10 parts by mass of the additive solution was slowly added to 90 parts by mass of ME16 that had been thoroughly stirred in a dissolution tank. The additive solution added to ME16 was then dispersed using an attritor. This was then filtered using Finemet NF manufactured by Nippon Seisen Co., Ltd. to obtain a silica particle dispersion.

(Preparation of Dope)
Next, a dope having the following composition was prepared. First, 90 parts by mass of methylene chloride and 10 parts by mass of ethanol were added to a pressurized dissolution tank. Next, 80 parts by mass of acrylic resin (MR1000, manufactured by Nippon Shokubai Co., Ltd., lactone acrylic resin) was added to the pressurized dissolution tank while stirring. Next, the rubber particle dispersion liquid prepared above was added to the pressurized dissolution tank, and then stirring was performed to dissolve the acrylic resin. This acrylic resin solution was filtered using SHP150 (manufactured by Roki Techno Co., Ltd.) to obtain a dope.

(Film formation)
Next, the above dope was used to form a membrane. Specifically, the dope was uniformly cast on a stainless steel belt supporter at a temperature of 30° C. and a width of 1800 mm using an endless belt casting apparatus to form a cast membrane. The temperature of the stainless steel belt was controlled at 28° C.

The solvent was evaporated on the stainless steel belt support until the residual solvent amount in the casting film was 30% by mass. Then, the casting film was peeled off from the stainless steel belt support at a peeling tension of 128 N/m. The residual solvent amount in the casting film after peeling was 30% by mass.

Next, the peeled cast film was stretched 50% in the width direction in a tenter at 140°C while being transported by multiple rollers. The cast film was then dried at 105°C while being transported by rolls. Next, the parts of the cast film that were clamped by the tenter clips (both end parts) were slit, and the cast film was then wound up. This resulted in a raw film with a thickness of 33 μm.

Next, the original film was stretched in the width direction using a clip tenter while holding both ends in the width direction with clips. A film roll was produced in the same manner as the stretching of the original film described in Example 1 above, except that the temperatures of the center and both ends of the original film were changed. Specifically, the center of the original film was heated to 140°C and both ends to 170°C to form a convex region, and both the center and both ends of the original film were heated to 140°C to form a concave region. The stretch ratio in the width direction was 30% for both the convex region R1 and the concave region R2.

Example 3
First, a raw film was prepared as follows.

(Preparation of Microparticle Dispersion)
11.3 parts by mass of fine particles (Aerosil (registered trademark) R812, manufactured by Nippon Aerosil Co., Ltd.) and 84 parts by mass of ethanol were mixed and stirred for 50 minutes using a dissolver, and then the mixture was dispersed using a Manton-Gaulin mixer to obtain a fine particle dispersion.

Five parts by mass of the microparticle dispersion liquid was slowly added to methylene chloride (100 parts by mass) that was being thoroughly stirred in a dissolution tank. The microparticle dispersion liquid added to the methylene chloride was then dispersed in an attritor so that the secondary particles had a predetermined particle size. This was then filtered through Finemet NF manufactured by Nippon Seisen Co., Ltd. to prepare a microparticle-added liquid.

(Preparation of Dope)
A dope having the following composition was prepared. First, 200 parts by mass of dichloromethane and 10 parts by mass of ethanol were added to a pressurized dissolution tank. Next, 100 parts by mass of cycloolefin resin (ARTON (registered trademark) F4520, manufactured by JSR Corporation), 5 parts by mass of ultraviolet absorber (Tinuvin (registered trademark) 477, manufactured by BASF Japan Co., Ltd.), and 3 parts by mass of the above-mentioned fine particle additive solution were added to the pressurized dissolution tank containing the mixed solution of dichloromethane and ethanol while stirring. Next, the mixture was heated and the cycloolefin resin was dissolved while stirring. Next, the cycloolefin resin solution was filtered using Azumi Filter Paper No. 244 manufactured by Azumi Filter Paper Co., Ltd. to prepare a dope.

ARTON (registered trademark) F4520 is a polymer having the structural unit of the following structure.

(Film formation)
Next, the dope was uniformly cast on a stainless steel belt support at a temperature of 31° C. and a width of 1800 mm using an endless belt casting apparatus to form a casting film. The temperature of the stainless steel belt was controlled at 28° C. Next, the solvent was evaporated on the stainless steel belt support until the residual solvent amount in the casting film was 30% by mass. Next, the casting film was peeled off from the stainless steel belt support at a peeling tension of 128 N/m. Next, the peeled casting film was stretched 1.15 times in the width direction under the condition of 160° C. The residual solvent amount in the casting film at the start of stretching was 5% by mass. Next, the casting film was dried while being conveyed by a number of rollers. Next, the parts of the casting film that were clamped by the tenter clips (both ends) were slit by a laser cutter, and then the casting film was wound up. As a result, a raw film having a thickness of 33 μm was obtained.

Next, the original film was stretched in the width direction using a clip tenter while holding both ends in the width direction with clips. A film roll was produced in the same manner as the stretching of the original film described in Example 1 above, except that the temperatures of the center and both ends of the original film were changed. Specifically, the center of the original film was heated to 180°C and both ends to 210°C to form a convex region, and both the center and both ends of the original film were heated to 180°C to form a concave region. The stretch ratio in the width direction was 30% for both the convex region R1 and the concave region R2.

Example 4
A film roll was produced in the same manner as in the production of the film roll of Example 3, except that the temperatures of the center and both ends of the original film when stretching the original film in the width direction were changed. Specifically, the center of the original film was heated to 180°C and both ends were heated to 200°C to form a convex region, and the center of the original film was heated to 180°C and both ends were heated to 190°C to form a concave region. As a result, the maximum values of |D| of the convex region R1 and the concave region R2 were changed from the film roll of Example 3.

Example 5
A film roll was produced in the same manner as in the production of the film roll of Example 3, except that the temperature increase and decrease rates at both ends of the original film were changed. Specifically, the temperature increase and decrease rates at both ends of the original film were slowed down by 2.1 times compared to Example 3. As a result, the change in the difference ratio D per 100 m at the inclined portion was changed from that of the film roll of Example 3.

Example 6
A film roll was produced in the same manner as in Example 4, except that the temperature increase and decrease rates at both ends of the raw film were changed.
As a result, the amount of change in the difference ratio D per 100 m in the inclined portion was changed from that of the film roll in Example 4.

Example 7
A film roll was produced in the same manner as in Example 6, except that the total wound length was changed.

Example 8
A film roll was produced in the same manner as in the production of the film roll of Example 4, except that the period of temperature change at both ends of the original film was changed. Specifically, the period of temperature change of the heating member was made shorter than that in the production of the film roll of Example 4. As a result, the longitudinal sizes of the convex region R1 and the concave region R2 were changed from those of the film roll of Example 4.

<Example 9>
A film roll was produced in the same manner as in the production of the film roll of Example 6, except that the method of forming the convex regions R1 and the concave regions R2 was changed. Specifically, a plurality of heat bolts were arranged in the width direction of the casting die, and the value of the voltage applied to the heat bolts was changed depending on the position in the width direction. As a result, the dope casting amount at both ends of the casting die and the dope casting amount at the center of the casting die were adjusted, respectively, to form the convex regions R1 and the concave regions R2. Specifically, the casting gap at both ends in the width direction was changed by -2.5% to 2.5% with respect to the casting gap at the center in the width direction.

Example 10
A film roll was produced in the same manner as in the production of the film roll of Example 6, except that the method of forming the convex regions R1 and the concave regions R2 was changed. Specifically, the temperature of the embossing ring was changed from 180°C to 200°C under a constant pressure. This adjusted the height of the embossed portions, and formed the convex regions R1 and the concave regions R2.

Example 11
In the preparation of the film roll of Example 1, the temperatures of the central portion and both ends of the original film when the original film was stretched in the width direction, and the temperature increase rate and temperature decrease rate of the both ends of the original film were changed. Except for this, the film roll was prepared in the same manner as in Example 1. As a result, the maximum values of |D| in the convex region R1 and the concave region R2, and the change in the difference ratio D per 100 m in the inclined portion were changed from those of the film roll of Example 1.

Example 12
A film roll was produced in the same manner as in Example 6, except that the temperatures at both ends of the original film were changed nonlinearly, causing the difference ratio D to change sinusoidally along the longitudinal direction.

Example 13
A film roll was produced in the same manner as in Example 6, except that the total wound length was changed.

<Example 14>
A film roll was produced in the same manner as in Example 6, except that the total wound length was changed.

Example 15
A film roll was produced in the same manner as in the production of the film roll of Example 4, except that the period of temperature change at both ends of the original film was changed. Specifically, the period of temperature change of the heating member was made longer than that in the production of the film roll of Example 4. As a result, the longitudinal sizes of the convex region R1 and the concave region R2 were changed from those of the film roll of Example 4.

<Comparative Example 1>
A film roll was produced in the same manner as in the production of the film roll of Example 3, except that the temperatures of the center and both ends of the original film when stretching the original film in the width direction were changed. Specifically, the original film was stretched in the width direction while maintaining the center of the original film at 180° C. and both ends at 210° C. As a result, only convex regions were formed in the film roll.

<Comparative Example 2>
A film roll was produced in the same manner as in the production of the film roll of Example 3, except that the temperatures of the center and both ends of the original film when stretching the original film in the width direction were changed. Specifically, the original film was stretched in the width direction while maintaining the center of the original film at 180° C. and both ends at 190° C. As a result, only concave regions were formed in the film roll.

<Comparative Example 3>
In the preparation of the film roll of Comparative Example 1, except that the temperatures of the center and both ends of the original film when stretching the original film in the width direction were changed, the film roll was prepared in the same manner. Specifically, the center of the original film was heated to 180°C and both ends were heated to 210°C to form a first convex region, and the center of the original film was heated to 180°C and both ends were heated to 200°C to form a second convex region. As a result, two convex regions (first convex region and second convex region) having different values of the difference ratio D were formed.

The characteristics of the film rolls prepared in this manner for Examples 1 to 15 and Comparative Examples 1 to 3 are summarized in Table 1 below.

<Evaluation of Film Roll>
(Black band rating)
Immediately after the film roll was produced, the color of the film surface was observed by visually observing the film roll surface in the direction of the core under a white fluorescent lamp. The observation was performed over the entire width of the film roll, for one revolution of the film roll. At this time, the presence or absence of a part where the color of the core was visible and the color looked different from the surroundings was confirmed. A specified limit sample was used for this color confirmation. If there was a part where the color looked different, the presence or absence of deformation of the film was confirmed for this part. Specifically, the film was placed on a table arranged approximately horizontally against black rag paper, and the presence or absence of deformation of the film was confirmed by the reflected light of the light irradiated to the film. The light was irradiated to the film using a fluorescent lamp of 2500 lux or more, and the fluorescent lamp was placed within 2 m from the film. In this way, the black band of the film roll was evaluated according to the following evaluation criteria. The results are shown in Table 1 below;
Evaluation Criteria
A: There are no areas on the film roll that look different in color.
B: There are some areas on the film roll that appear to be different colors, but no deformation of the film is observed.
C: Deformation of the film was observed.

(Evaluation of changes over time)
Immediately after the film roll was produced, the surface of the black core was visually observed from the outside to confirm whether or not there were any parts that looked different in color. Next, the film roll was left for 500 hours under conditions of 23°C and 90% RH, and the surface of the black core was visually observed from the outside again to confirm whether or not there were any parts that looked different in color. If there were any parts that looked different in color immediately after the film roll was produced and after 500 hours had passed, the presence or absence of deformation of the film in these parts was confirmed. In this way, the change over time of the film roll was evaluated according to the following evaluation criteria. The results are shown in Table 1 below;
Evaluation Criteria
A: Even after 500 hours, there was no increase in the number of areas on the film roll that looked different in color.
B: After 500 hours, the film roll has more and more areas that look different in color, but no deformation of the film is observed in these areas.
C: After 500 hours, new deformation of the film was observed.

The film and film roll according to the present invention have convex positions (or convex regions) where the thickness of the ends in the width direction is smaller than the thickness of the center, and concave positions (or concave regions) where the thickness of the ends is larger than the thickness of the center. From the results in Table 1, it was confirmed that the films according to the examples of the present invention are superior in terms of black bands and changes over time, and suppress the occurrence of winding defects, compared to films having only either convex positions or concave positions.

This application is based on a Japanese patent application (Patent Application No. 2020-116621) filed on July 6, 2020, the disclosure of which is hereby incorporated by reference in its entirety.

Claims (16)

a first end portion and a second end portion in a width direction intersecting with the longitudinal direction;
a central portion between the first end and the second end;
a convex position in which a thickness Te1 of at least the first end of the first end and the second end is smaller than a thickness Tc of the central portion;
a concave position disposed at a position different from the convex position in the longitudinal direction, the concave position having a thickness Te1 of the first end portion greater than a thickness Tc of the central portion. At the convex position, the thickness Te2 of the second end portion is smaller than the thickness Tc of the central portion,
The film of claim 1 , wherein at the concave position, the thickness Te2 of the second end is greater than the thickness Tc of the central portion. a convex region in which the convex position is provided and a thickness Te1 of at least the first end of the first end and the second end is smaller than a thickness Tc of the central portion;
The film of claim 1 or 2, further comprising a recessed region in which the recessed position is provided and the thickness Te1 of the first end is greater than the thickness Tc of the central portion. The film of claim 3, having a plurality of alternating convex and concave regions along the longitudinal direction. A film as described in claim 3 or 4, wherein the longitudinal size of the convex regions and the concave regions is 100 m or more and 500 m or less. a difference between a thickness Te1 of the first end portion at the convex position and a thickness Tc of the central portion is 10% or less of an average thickness of the film at the convex position;
The film according to any one of claims 1 to 5, wherein the difference between the thickness Te1 of the first end portion at the concave position and the thickness Tc of the central portion is 10% or less of the average thickness of the film at the concave position. a difference between a thickness Te1 of the first end portion at the convex position and a thickness Tc of the central portion is 5% or less of an average thickness of the film at the convex position;
The film according to any one of claims 1 to 6, wherein the difference between the thickness Te1 of the first end portion at the concave position and the thickness Tc of the central portion is 5% or less of the average thickness of the film at the concave position. A film as described in any one of claims 1 to 7, further comprising an inclined portion between the convex position and the concave position, in which at least one of the thickness Te1 of the first end portion and the thickness Tc of the central portion changes continuously. The film described in claim 8, wherein the longitudinal dimension of the inclined portion is 5 m or more. The film according to any one of claims 1 to 9, comprising a polymer containing an alicyclic structure. A film according to any one of claims 1 to 10, having an optical function. A film according to any one of claims 1 to 11, used in a touch sensor. A film according to any one of claims 1 to 12,
A laminate having a protective film laminated on the film. A core;
The film according to any one of claims 1 to 12 or the laminate according to claim 13 wound around the core;
A film roll comprising: Providing or forming a web of film;
forming a convex portion and a concave portion at different positions in a longitudinal direction of the raw film;
Including,
The convex position is formed by making a thickness Te1 of at least the first end of the first end and a second end of the original film in a width direction intersecting the longitudinal direction smaller than a thickness Tc of a central portion between the first end and the second end,
The method for manufacturing a film, wherein the recessed position is formed by making a thickness Te1 of the first end portion greater than a thickness Tc of the central portion. In forming the convex portion and the concave portion, at least the first end portion of the first end portion and the second end portion is heated while the raw film is stretched in the width direction;
The method for manufacturing a film according to claim 15 , wherein the temperature difference between the first end and the central portion when the convex position is formed is made larger than the temperature difference between the first end and the central portion when the concave position is formed.