Method for producing laminated film

Abstract

Provided is a method for producing a laminated film capable of suppressing the mixing of air bubbles. A method of manufacturing a laminated film according to an embodiment of the present invention includes a bonding step of bonding a first film and a second film with an adhesive. In the bonding step, the first film and the second film are bonded when passing between the first bonding roller and the second bonding roller. And the first laminating roller and the second laminating roller are respectively provided with an outer side rubber pipe and an inner side shaft. The outer rubber tube has a cylindrical shape. The inner shaft is disposed in the outer rubber tube. The inner shaft includes a support portion. The support portion supports the central portion of the outer rubber tube in the axial direction. At least one of the first film and the second film satisfies the relationship represented by formula (1). E*T < 100000... (1)

Description

Technical Field The present invention relates to a method for producing a laminated film. Background Art Laminated films have been widely used in various industrial products. Laminated films are produced by laminating multiple films. For example, a technique has been proposed in which an active energy ray-curable adhesive is applied to one side of a first film or one or both sides of a second film, and then the adhesive is passed between a pair of laminating rollers to laminate the first and second films. Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Laid-Open No. 2013-92764 Summary of the Invention Technical problem to be solved by the invention In recent years, as the applications of laminated films have expanded, the requirements for their composition and performance have also diversified. Consequently, films with relatively low rigidity are sometimes used in laminated films. However, using a relatively low-rigidity film in the method described in Patent Document 1 can introduce air bubbles into the resulting laminated film. The present invention aims to solve the above-mentioned conventional problems, and its main object is to provide a method for producing a laminated film that can suppress the incorporation of bubbles. Means for solving problems

[0001] One embodiment of the present invention is a method for manufacturing a laminated film, which includes a laminating process of laminating a first film and a second film using an adhesive. In the laminating process, the first film and the second film are laminated when passing between a first laminating roller and a second laminating roller. The first laminating roller and the second laminating roller respectively have an outer rubber tube and an inner shaft. The outer rubber tube has a cylindrical shape. The inner shaft is arranged in the outer rubber tube. The inner shaft includes a support portion and a small diameter portion that is smaller than the support portion. The support portion supports the central portion of the outer rubber tube in the axial direction. The small diameter portion is arranged on both sides of the support portion in the axial direction. At least one of the first film and the second film satisfies the relationship of the following formula (1). E×T< 100000···(1) (In formula (1), E represents the tensile modulus at 25°C, in MPa; T represents the thickness, in μm.)

[0002] In the method for producing a laminated film described in [1] above, both the first film and the second film may satisfy the relationship of the above formula (1).

[0003] In the method for producing a laminated film described in [1] or [2] above, the thickness of at least one of the first film and the second film may be 45 μm or less.

[0004] In the method for producing a laminated film according to any one of [1] to [3], in the laminating step, the tension applied to the first film and / or the second film may be 50 N / m to 400 N / m.

[0005] In the method for producing a laminated film according to any one of [1] to [4], a nip may be formed between the first laminating roll and the second laminating roll to sandwich the first film and the second film. The nip extends along the axial direction. The width of the nip may be 13 mm to 20 mm.

[0006] In the method for producing a laminated film according to any one of [1] to [5] above, the outer diameter of the central portion of the outer rubber tube in the axial direction may be less than or equal to the outer diameter of the end portions of the outer rubber tube in the axial direction.

[0007] In the method for producing a laminated film described in [6] above, the outer peripheral surface of the outer rubber tube of the first laminating roller may include a contact region with the first film during the laminating step. The center angle of the outer rubber tube corresponding to the contact region may be 45° to 90°.

[0008] In the method for producing a laminated film according to any one of [1] to [7], the first film may be a polarizing plate including a polarizer. Effects of the Invention According to the embodiment of the present invention, a laminated film in which inclusion of bubbles is suppressed can be produced. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 This is a schematic configuration diagram for explaining a method for producing a laminated film according to one embodiment of the present invention. Figure 2 yes Figure 1 A schematic cross-sectional view of the first laminating roller and the second laminating roller is shown. Figure 3 It is a schematic cross-sectional view of a first bonding roll and a second bonding roll according to another embodiment of the present invention. Figure 4 yes Figure 1 A schematic cross-sectional view of the first film is shown. Figure 5 yes Figure 1 A schematic cross-sectional view of the second film is shown. Figure 6 This is a schematic cross-sectional view of a laminated film produced by the method for producing a laminated film according to one embodiment of the present invention. DETAILED DESCRIPTION The following describes representative embodiments of the present invention, but the present invention is not limited to these embodiments. In addition, the drawings are for the purpose of more clearly explaining the present invention, and therefore, the width, thickness, shape, etc. of each part are sometimes schematically shown compared to the embodiments, but this is only an example and does not limit the interpretation of the present invention. A. Overview of the method for producing a laminated film Figure 1 This is a schematic diagram for explaining a method for producing a laminated film according to one embodiment of the present invention; Figure 2 yes Figure 1 A schematic cross-sectional view of the first laminating roller and the second laminating roller is shown. One embodiment of the present invention provides a method for producing a laminated film including a laminating step in which a first film 1 and a second film 2 are laminated with an adhesive. The first film 1 and the second film 2 are laminated while passing between a first laminating roller 3a and a second laminating roller 3b. At least one of the first film 1 and the second film 2 satisfies the relationship of the following formula (1). E×T<100000···(1) (In formula (1), E represents the tensile modulus at 25°C [unit: MPa]; T represents the thickness [Unit: μm]). like Figure 2 As shown, the first laminating roller 3a and the second laminating roller 3b each include an outer rubber tube 31 and an inner shaft 32. The outer rubber tube 31 has a cylindrical shape. Hereinafter, the direction in which the axis of the outer rubber tube 31 extends is referred to as the axial direction. The inner shaft 32 is disposed within the outer rubber tube 31. The inner shaft 32 includes a support portion 321 and two small-diameter portions 322. The support portion 321 supports the axial center portion of the outer rubber tube 31. In one embodiment, the support portion 321 contacts the axial center portion of the inner circumferential surface of the outer rubber tube 31. In the illustrated example, the support portion 321 has an axially extending cylindrical shape. The small-diameter portions 322 are arranged on both sides of the support portion 321 in the axial direction. For distinction, the small-diameter portion 322 arranged on one side of the support portion 321 in the axial direction may be referred to as the first small-diameter portion 322a, while the small-diameter portion 322 arranged on the other side of the support portion 321 in the axial direction may be referred to as the second small-diameter portion 322b. Both small-diameter portions 322 have a smaller diameter than the support portion 321. According to this configuration, even if at least one of the first film 1 and the second film 2 is a relatively low-rigidity film that satisfies the relationship of the above-mentioned formula (1), the first laminating roller and the second laminating roller each have the above-mentioned outer rubber tube and the above-mentioned inner shaft, thereby suppressing the mixing of bubbles between the first and second films during the laminating process. Therefore, a laminated film with reduced bubbles can be smoothly manufactured. In one embodiment, the inner shaft 32 further has a first end 323 and a second end 324 . The first end portion 323 is one end portion of the inner shaft 32 in the axial direction. The first end portion 323 is located on the opposite side of the support portion 321 relative to the first small-diameter portion 322a. The second end portion 324 is the other end portion of the inner shaft 32 in the axial direction. The second end portion 324 is located on the opposite side of the support portion 321 relative to the second small-diameter portion 322b. The first end portion 323 and the second end portion 324 may each protrude from the outer rubber tube 31 in the axial direction. This configuration allows the first and second ends of the inner shaft of either the first or second laminating roller to be smoothly pressed against the other laminating roller. Since the first and second laminating rollers each include a support portion, deflection of the central portion of the first and / or second laminating rollers in the axial direction can be sufficiently suppressed. This allows for a stable roll gap, described later. Consequently, during the laminating process, the incorporation of bubbles between the first and second films can be stably suppressed. The support portion 321 typically includes the axial center portion of the inner shaft 32. In the illustrated example, the outer circumference of the support portion 321 contacts the axial center portion of the inner circumference of the outer rubber tube 31. Alternatively, the support portion 321 may be bonded to the inner circumference of the outer rubber tube 31. The outer diameter of the support portion 321 is, for example, 170 mm to 250 mm, or preferably 180 mm to 200 mm. The dimension of the support portion 321 in the axial direction is, for example, 10% to 35%, preferably 15% to 30%, when the entire length (axial dimension) of the outer rubber tube 31 is 100%. The dimension of the support portion 321 in the axial direction is, for example, 200 mm to 550 mm, or preferably 250 mm to 450 mm. The first small-diameter portion 322a and the second small-diameter portion 322b each typically have a cylindrical shape extending along the axial direction. In one embodiment, the first small-diameter portion 322a and the second small-diameter portion 322b are each adjacent to the support portion 321 in the axial direction. In the illustrated example, the first small-diameter portion 322a, the support portion 321, and the second small-diameter portion 322b are continuous, sharing a common axis. The difference in outer diameter between the support portion 321 and the first small diameter portion 322a is, for example, 60 mm to 100 mm, preferably 70 mm to 90 mm. When the difference in outer diameter between the support portion and the first small diameter portion is within this range, deflection of the first and / or second laminating rollers can be more stably suppressed during the laminating process. The outer diameter of the first small-diameter portion 322 a is, for example, 90 mm to 130 mm, or preferably 100 mm to 120 mm. The dimension of the first small diameter portion 322a in the axial direction is, for example, 20% to 50%, preferably 30% to 40%, of the total length (axial dimension) of the inner shaft 32 as 100%. The dimension of the first small diameter portion 322 a in the axial direction is, for example, 30% to 45%, preferably 35% to 40%, of the total length (axial dimension) of the outer rubber tube 31 as 100%. The dimension of the first small-diameter portion 322 a in the axial direction is, for example, 480 mm to 720 mm, or preferably 540 mm to 640 mm. Typically, the outer diameter of the second small diameter portion 322b is within the same range as the outer diameter of the first small diameter portion 322a. In one embodiment, the outer diameter of the first small diameter portion 322a is substantially the same as the outer diameter of the second small diameter portion 322b. The axial dimension of the second small diameter portion 322b is typically the same as the axial dimension of the first small diameter portion 322a. In one embodiment, the axial dimension of the second small diameter portion 322b is substantially the same as the axial dimension of the first small diameter portion 322a. The first end portion 323 and the second end portion 324 each typically have a cylindrical shape with a smaller diameter than the small-diameter portion 322. In one embodiment, the first end portion 323 is adjacent to the first small-diameter portion 322a in the axial direction. In the illustrated example, the first end portion 323 and the first small-diameter portion 322a are continuous, sharing a common axis. The difference in outer diameter between the first end portion 323 and the first small-diameter portion 322 a is, for example, 50 mm to 80 mm, and preferably 60 mm to 70 mm. The outer diameter of the first end portion 323 is, for example, 30 mm to 60 mm, and preferably 40 mm to 50 mm. The dimension of the first end portion 323 in the axial direction is, for example, 7.5% to 15%, preferably 10% to 12.5%, of the inner shaft 32 (axial dimension) as 100%. The dimension of the first end portion 323 in the axial direction is, for example, 30 mm to 60 mm, preferably 40 mm to 50 mm. When the dimension of the first end portion in the axial direction is within such a range, in the bonding step, one bonding roller can be stably pressed toward the other bonding roller. In one embodiment, the second end portion 324 is adjacent to the second small diameter portion 322b in the axial direction. In the illustrated example, the second end portion 324 and the second small diameter portion 322b are continuous in a manner of sharing the same axis. In other words, in the illustrated example, the inner shaft 32 is a stepped shaft having, in the axial direction, a first end portion 323, a first small-diameter portion 322a, a support portion 321, a second small-diameter portion 322b, and a second end portion 324. Furthermore, the first end portion 323, the first small-diameter portion 322a, the support portion 321, the second small-diameter portion 322b, and the second end portion 324 share a common axis. Typically, the range of the difference in outer diameter between the second end portion 324 and the second small-diameter portion 322 b is the same as the range of the difference in outer diameter between the first end portion 323 and the first small-diameter portion 322 a described above. The outer diameter of the second end portion 324 is typically within the same range as the outer diameter of the first end portion 323. In one embodiment, the outer diameter of the second end portion 324 is substantially the same as the outer diameter of the first end portion 323. Typically, the range of the axial dimension of the second end portion 324 is the same as the range of the axial dimension of the first end portion 323. In one embodiment, the axial dimension of the second end portion 324 is substantially the same as the axial dimension of the first end portion 323. When the axial dimension of the second end portion is within this range, one laminating roller can be pressed against the other laminating roller more stably during the laminating process. Examples of the material of the inner shaft 32 include metals and carbon, with metals being preferred. Examples of the metal include iron, aluminum, magnesium, stainless steel, and alloys thereof. Among metals, stainless steel is preferred. The elastic modulus of the inner shaft 32 at 25° C. is, for example, 50 GPa to 250 GPa. The elastic modulus is obtained from the gradient of the tensile stress and strain line according to the metal material tensile testing method of JIS Z2241. The inner shaft 32 may have a solid structure or a hollow structure. Figure 3 As shown, in one embodiment, the inner shaft 32 has a hollow shape. This configuration can reduce the weight of the inner shaft. Furthermore, even if the inner shaft is hollow, if the inner shaft includes a support portion and a small-diameter portion, deflection of the laminating roller during the laminating process can be sufficiently suppressed. The inner shaft 32 of the first laminating roller 3a and the inner shaft 32 of the second laminating roller 3b may have the same structure or different structures. In one embodiment, the inner shaft 32 of the first laminating roller 3a and the inner shaft 32 of the second laminating roller 3b have the same structure. like Figure 2As shown, the inner shaft 32 is inserted into the outer rubber tube 31 . The arithmetic mean surface roughness Ra of the outer circumferential surface of the outer rubber tube 31 is, for example, 0.6 μm to 0.9 μm, preferably 0.7 μm to 0.8 μm. The arithmetic mean surface roughness Ra of the outer circumferential surface of the outer rubber tube is measured, for example, in accordance with JIS B0601. When the arithmetic mean surface roughness Ra of the outer circumferential surface of the outer rubber tube is within this range, the first film and / or the second film can be laminated without slipping during the lamination process, and the transfer of irregularities can be suppressed. As described above, the axially central portion of the inner circumferential surface of the outer rubber tube 31 contacts the support portion 321 of the inner shaft 32. In the illustrated example, the inner circumferential surface of the outer rubber tube 31, excluding the portion in contact with the support portion 321, faces the outer circumferential surface of the small-diameter portion 322 at a distance therefrom. The outer diameter of the outer rubber tube 31 may be substantially constant in the axial direction, or may be substantially variable in the axial direction. The outer diameter of the axial center portion of the outer rubber tube 31 is, for example, 1.05 to 0.95 times the outer diameter of the axial end portion of the outer rubber tube 31 , preferably 1 time or less, and more preferably less than 1 time. In other words, the outer rubber tube 31 may have a concave shape (inverted crown shape) in which the outer diameter of the central portion in the axial direction is less than 1 times the outer diameter of the end portion, or may have a crown shape in which the outer diameter of the central portion in the axial direction is more than 1 times the outer diameter of the end portion. In one embodiment, the outer rubber tube 31 has a concave shape. With this configuration, the outer diameter of the outer rubber tube decreases toward the inner side of the axial direction, resulting in a difference in circumferential velocity between the center and the ends of the outer rubber tube. This allows for stable expansion of the film in contact with the outer rubber tube, effectively suppressing film wrinkling. As a result, the incorporation of bubbles into the laminated film can be more stably suppressed. The inner diameter of the axial center portion of the outer rubber tube 31 is typically within the same range as the outer diameter of the support portion 321. The inner diameter of the axial end portions of the outer rubber tube 31 is, for example, 170 mm to 200 mm, preferably 180 mm to 190 mm. The outer diameter of the axial center portion of the outer rubber tube 31 is, for example, 180 mm to 220 mm, preferably 190 mm to 210 mm. The outer diameter of the axial end portions of the outer rubber tube 31 is, for example, 180 mm to 220 mm, preferably 190 mm to 210 mm. The thickness of the outer rubber tube 31 is, for example, 4 mm to 20 mm, or preferably 5 mm to 10 mm. The dimension of the outer rubber tube 31 in the axial direction is, for example, 75% to 90%, preferably 80% to 90%, of the total length (axial dimension) of the inner shaft 32 as 100%. The dimension of the outer rubber tube 31 in the axial direction is, for example, 1000 mm to 3000 mm, or preferably 1200 mm to 2000 mm. The outer rubber tube 31 is made of any appropriate rubber material, such as silicone rubber, nitrile rubber, ethylene-propylene rubber, butyl rubber, or polyurethane rubber, with silicone rubber being preferred. The hardness of the outer rubber tube 31 at 25° C. is, for example, 50 to 95, or preferably 60 to 90. The hardness of the outer rubber tube is measured using, for example, a D-type durometer. The compressive modulus of the outer rubber tube 31 at 25°C is, for example, 1 MPa to 30 MPa, preferably 10 MPa to 20 MPa. The compressive modulus of the outer rubber tube can be determined from the gradient of the stress and displacement (strain) applied to a rubber test piece when the test piece is compressed at a constant speed using, for example, the "Precision Universal Testing Machine AG-IS" manufactured by Shimadzu Corporation. The outer rubber tube 31 of the first laminating roller 3a and the outer rubber tube 31 of the second laminating roller 3b may have the same structure or different structures. In one embodiment, the outer rubber tube 31 of the first laminating roller 3a and the outer rubber tube 31 of the second laminating roller 3b have the same structure. In the above embodiment, the support portion 321 contacts the central portion of the inner peripheral surface of the outer rubber tube 31 in the axial direction, and supports the central portion of the outer rubber tube 31 . Alternatively, the support portion 321 may support the central portion of the outer rubber tube 31 via another component. In another embodiment, at least one of the first laminating roller 3a and the second laminating roller 3b may include a SUS sleeve in addition to the outer rubber tube 31 and the inner shaft 32. Typically, the SUS sleeve is positioned between the inner circumferential surface of the outer rubber tube 31 and the outer circumferential surface of the support portion 321. In this case, the support portion 321 supports the central portion of the outer rubber tube 31 in the axial direction via the SUS sleeve. In one embodiment, the first laminating roller 3a and the second laminating roller 3b form a nip N. In the nip N, the first film 1 and the second film 2 are sandwiched between the first laminating roller 3a (specifically, the outer rubber tube 31) and the second laminating roller 3b (specifically, the outer rubber tube 31). In other words, the nip N represents a region where the first film 1 and the second film 2 are sandwiched between the first laminating roller 3a and the second laminating roller 3b at a pressure greater than or equal to a predetermined pressure. The nip N extends in the axial direction. Typically, the size of the nip N in the axial direction is substantially the same as the entire length of the outer rubber tube 31 . The width of the nip N (in the direction perpendicular to the stretching direction) is, for example, 8 mm or greater, preferably 12 mm or greater, more preferably 13 mm or greater, and even more preferably 15 mm or greater. When the nip N has such a width, it is possible to more stably suppress the incorporation of bubbles between the first film and the second film, and to suppress the generation of streaks on the manufactured laminated film 100. On the other hand, the width of the nip N is, for example, 30 mm or less, preferably 20 mm or less. When the nip N has such a width, the first and second films can be prevented from being excessively clamped (wrinkled) by the first and second laminating rollers during the laminating process. As a result, the incorporation of bubbles between the first and second films can be more stably suppressed. In one embodiment, the width of the center of the nip N in the axial direction is greater than the width of the ends of the nip N in the axial direction. The difference between the width of the center of the nip N in the axial direction and the width of the ends of the nip N in the axial direction is, for example, 5 mm or less, preferably 2 mm or less. When the width difference between the center and the ends of the nip N is within this range, the first and second films can be uniformly pressed in the width direction during the lamination process, and the incorporation of bubbles therebetween can be further stably suppressed. B. Details of the method for producing the laminated film Hereinafter, a method for producing a laminated film according to one embodiment will be described in more detail. In one embodiment, the method for manufacturing the laminate film 100 sequentially includes: a first preparation step of preparing the first film 1 , a second preparation step of preparing the second film 2 , a coating step of coating the first film 1 and / or the second film 2 with an adhesive, and the above-mentioned lamination step. B-1. First preparation step like Figure 4 As shown, in the first preparation step, a first film 1 is prepared. The first film 1 can have any appropriate structure. The first film 1 typically has an elongated shape. The first film 1 can have a single-layer structure or a laminated structure with two or more layers. In the example shown, the first film 1 has a laminated structure. In one embodiment, the first film 1 satisfies the relationship of the above formula (1). The tensile modulus E of the first film 1 at 25° C. is, for example, 1000 MPa to 4000 MPa, or preferably 2000 MPa to 3000 MPa. The thickness of the first film 1 is, for example, 100 μm or less, or preferably 45 μm or less. On the other hand, the thickness of the first film 1 is, for example, 10 μm or more, or preferably 15 μm or more. Examples of the first film 1 include a polarizing plate, a protective film, a release film, and a retardation film, and a polarizing plate is preferred. B-1-1. Polarizing Plate The polarizing plate 11 includes a polarizer 111 . Any appropriate polarizer can be adopted as the polarizer 111. For example, the polarizer may be composed of a single-layer resin film, or a laminate of two or more layers may be used. Specific examples of polarizers composed of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially hydroxymethylated PVA films, and partially crosslinked ethylene-vinyl acetate copolymer films, which have been dyed with a dichroic substance such as iodine or a dichroic dye and then stretched, and polyene-based oriented films such as dehydrated PVA films and dehydrochlorinated polyvinyl chloride films. Preferably, a polarizer is used in which a PVA film dyed with iodine and stretched along one axis, due to its excellent optical properties. The dyeing using iodine is performed, for example, by immersing the PVA film in an iodine aqueous solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching can be performed after the dyeing treatment or while dyeing. In addition, the dyeing can be performed after the stretching. As needed, the PVA film can be subjected to swelling treatment, bridging treatment, cleaning treatment, drying treatment, etc. For example, by immersing the PVA film in water for washing before dyeing, not only can the dirt and anti-sticking agent on the surface of the PVA film be cleaned as much as possible, but the PVA film can also be swollen to prevent uneven dyeing. As a specific example of a polarizer obtained using a laminate, there can be cited a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating the resin substrate. The polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating the resin substrate is produced, for example, by the following steps: a PVA-based resin solution is applied to a resin substrate, dried to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; the laminate is stretched and dyed to make the PVA-based resin layer a polarizer. In one embodiment of the present invention, it is preferred that a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate. Stretching typically includes stretching the laminate by immersing it in a boric acid aqueous solution. Moreover, stretching, as needed, also includes stretching the laminate in the air at a high temperature (for example, above 95°C) before stretching in the boric acid aqueous solution. In addition, in one embodiment of the present invention, a drying shrinkage treatment is preferably performed in which the laminate is heated while being transported in the longitudinal direction, shrinking it by at least 2% in the width direction. Typically, the manufacturing method of this embodiment includes sequentially subjecting the laminate to: an in-flight auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment. The introduction of the auxiliary stretching treatment improves the crystallinity of the PVA, even when PVA is coated on a thermoplastic resin, enabling high optical properties. Furthermore, by simultaneously improving the orientation of the PVA, problems such as a decrease in orientation and dissolution of the PVA during subsequent immersion in water during the dyeing and stretching steps can be prevented, thereby achieving high optical properties. Furthermore, when the PVA-based resin layer is immersed in liquid, orientation disorder and a decrease in orientation of the polyvinyl alcohol molecules can be suppressed compared to a PVA-based resin layer that does not contain a halide. This improves the optical properties of the polarizer obtained through treatment steps such as dyeing and underwater stretching, where the laminate is immersed in liquid. Furthermore, shrinking the laminate in the width direction during the drying shrinkage treatment improves optical properties. The obtained resin substrate / polarizer laminate can be used as is (i.e., the resin substrate can be used as a protective layer for the polarizer), or the resin substrate can be peeled off from the resin substrate / polarizer laminate and a suitable protective layer corresponding to the purpose can be laminated on the peeled surface for use. Details of the method for manufacturing such a polarizer are described, for example, in Japanese Patent Application Publication No. 2012-73580 and Japanese Patent No. 6470455. The entire contents of these publications are incorporated herein by reference. The thickness of the polarizer is, for example, 1 μm to 80 μm, preferably 1 μm to 15 μm, more preferably 1 μm to 12 μm, further preferably 3 μm to 12 μm, and particularly preferably 3 μm to 8 μm. When the thickness of the polarizer is within this range, curling during heating can be effectively suppressed, and good appearance durability during heating can be achieved. The polarizer preferably exhibits absorption dichroism at any wavelength between 380 nm and 780 nm. The single-piece transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The polarization degree of the polarizer is preferably 97.0% or higher, more preferably 99.0% or higher, and even more preferably 99.9% or higher. The polarizing plate 11 may include a protective layer 112 in addition to the polarizer 111. The protective layer 112 is provided on at least one surface of the polarizer 111. Typically, the protective layer 112 is bonded to the polarizer 111 via any appropriate adhesive layer (not shown). The protective layer is formed by any appropriate film that can be used as a protective layer of a polarizer. As a specific example of the material of the main component of the film, cycloolefin (COP) systems such as polynorbornene systems, polyester systems such as polyethylene terephthalate (PET) systems, cellulose resins such as triacetyl cellulose (TAC), polycarbonate (PC) systems, (meth) acrylic acid systems, polyvinyl alcohol systems, polyamide systems, polyimide systems, polyether sulfone systems, polysulfone systems, polystyrene systems, polyolefin systems, acetate systems and other transparent resins can be listed. In addition, thermosetting resins or ultraviolet curing resins such as (meth) acrylic acid systems, polyurethane systems, (meth) acrylic polyurethane systems, epoxy systems, silicone systems can be listed. It should be noted that "(meth) acrylic acid resin" refers to acrylic resin and / or methacrylic resin. In addition, glassy polymers such as siloxane polymers can be listed. In addition, the polymer film described in Japanese Patent Publication No. 2001-343529 (WO01 / 37007) can be used. Materials for the film include, for example, thermoplastic resins having substituted or unsubstituted imide groups in their side chains, or resin compositions containing thermoplastic resins having substituted or unsubstituted phenyl and nitrile groups in their side chains. Examples include alternating copolymers of isobutylene and N-methylmaleimide, and acrylonitrile-styrene copolymers. The polymer film is, for example, an extrusion molded product of the above resin compositions. The materials for the resin film can be used alone or in combination. In addition, the protective layer 112 may also be subjected to surface treatments such as hard coating, anti-reflection treatment, anti-adhesion treatment, and anti-glare treatment as needed. Furthermore, / or, the protective layer 112 may also be subjected to treatments to improve visibility when viewed through polarized sunglasses as needed (representatively, imparting (elliptical) polarization function or imparting ultra-high phase difference). The thickness of the protective layer is typically 5 mm or less, preferably 1 mm or less, more preferably 1 μm to 500 μm, and even more preferably 5 μm to 150 μm. B-2. Second preparatory step like Figure 5 As shown, in the second preparation step, a second film 2 is prepared. The second film 2 can have any appropriate structure. The second film 2 typically has an elongated shape. The second film 2 can also have a single-layer structure or a laminated structure with two or more layers. In the example shown, the second film 2 has a single-layer structure. In one embodiment, the second film 2 satisfies the relationship of the above formula (1). The tensile modulus E of the second film 2 at 25° C. is, for example, 1500 MPa to 4000 MPa, or preferably 2000 MPa to 3000 MPa. The thickness of the second film 2 is, for example, 5 μm to 60 μm, or preferably 10 μm to 30 μm. Examples of the second film 2 include resin films, and more specifically, phase difference films, protective films, and surface protective films. Examples of the material of the resin film include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl butyral resins, polyarylate resins, cycloolefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and (meth)acrylic resins. These resins can be used alone or in combination. Among these resin films, (meth)acrylic resins are preferred. B-3. ​​Coating process In the coating step, typically, an adhesive is applied to the surface of the first film 1 and / or the second film 2 before the film is fed between the first laminating roller 3a and the second laminating roller 3b. In one embodiment, the adhesive is applied to the surface of both the first film 1 and the second film 2. In the illustrated example, the adhesive is applied to the surface of the polarizer 111 of the polarizing plate 11 and the surface of the second film 2. Any appropriate method can be adopted as a coating method for the adhesive, and examples of the coating method include gravure coating and slit coating, with gravure coating being preferred. The thickness of the adhesive coating film is, for example, 0.5 μm to 3.0 μm, or preferably 0.8 μm to 2.0 μm. Typically, a curable adhesive is used as the adhesive. Examples of curable adhesives include thermosetting adhesives and UV-curable adhesives, with UV-curable adhesives being preferred. Details of UV-curable adhesives are described, for example, in Japanese Patent Application Laid-Open No. 2013-92764. The entire disclosure of these publications is incorporated herein by reference. The curable adhesive is in a liquid state before curing. The viscosity of the curable adhesive at 25° C. is, for example, 10 m / Pa·s to 80 m / Pa·s, and preferably 25 m / Pa·s to 50 m / Pa·s. B-4. Lamination process like Figure 2 As shown, in the laminating step, the first film 1 and the second film 2 are supplied between a first laminating roll 3a and a second laminating roll 3b. During the lamination process, the tension applied to the first film 1 and / or the second film 2 is, for example, 50 N / m to 800 N / m, preferably 50 N / m to 500 N / m, more preferably 50 N / m to 400 N / m, and even more preferably 150 N / m to 250 N / m. Thus, during the lamination process, by applying an appropriate tension corresponding to the rigidity of the first film and / or the second film, wrinkles and curling of the first and second films can be suppressed, and the incorporation of bubbles between the first and second films can be more stably suppressed. The feeding speed (line speed) of each of the first film 1 and the second film 2 in the laminating step is, for example, 5 m / min to 30 m / min, or preferably 15 m / min to 25 m / min. The rotation speed of each of the first bonding roll and the second bonding roll in the bonding step is, for example, 7 rpm to 50 rpm, or preferably 23 rpm to 40 rpm. When the first film 1 passes between the first laminating roller 3a and the second laminating roller 3b (nip N), it contacts the outer circumferential surface of the outer rubber tube 31 of the first laminating roller 3a. In the illustrated example, the protective layer 112 of the polarizing plate 11 contacts the outer circumferential surface of the outer rubber tube 31 of the first laminating roller 3a. Hereinafter, the area where the outer circumferential surface of the outer rubber tube 31 contacts the first film 1 is referred to as the contact area. The central angle of the outer rubber tube 31 corresponding to the contact area is, for example, 30° to 90°, preferably 45° to 90°. When the outer rubber tube 31 of the first laminating roller 3a has the aforementioned concave shape, the center angle of the outer rubber tube 31 corresponding to the contact area is preferably between 45° and 90°. When the outer rubber tube 31 has a concave shape, wrinkles in the first film can be stably suppressed even when the center angle of the outer rubber tube corresponding to the contact area is within the aforementioned range. As a result, the first film can be stably conveyed and the generation of bubbles can be sufficiently suppressed. However, if the outer rubber tube 31 has a crown shape, setting the center angle of the outer rubber tube corresponding to the contact area to between 45° and 90° may cause wrinkles in the first film. When the second film 2 passes between the first laminating roller 3a and the second laminating roller 3b (nip N), it contacts the outer peripheral surface of the outer rubber tube 31 of the second laminating roller 3b. The range of the central angle of the outer rubber tube 31 corresponding to the contact area in the second laminating roller 3b is typically the same as the range of the central angle in the first laminating roller 3a. The first film 1 and the second film 2 are appropriately pressed by the first laminating roller 3a and the second laminating roller 3b while passing through the first laminating roller 3a and the second laminating roller 3b, that is, while passing through the nip N. As a result, the first laminating roller 3a and the second laminating roller 3b are bonded together using the adhesive. Thereafter, the adhesive is cured by any appropriate method. For example, when the adhesive comprises an ultraviolet curable adhesive, the ultraviolet curable adhesive between the first film 1 and the second film 2 is irradiated with ultraviolet rays. As described above, the laminated film 100 is manufactured. C. Laminated Film like Figure 6 As shown, the laminated film 100 includes a first film 1 , an adhesive layer 5 , and a second film 2 in this order. The adhesive layer 5 is composed of a cured product of the above-mentioned adhesive. The thickness of the adhesive layer 5 is, for example, 0.5 μm to 2.0 μm, or preferably 0.8 μm to 1.5 μm. The laminated film 100 can be used for any appropriate purpose. In particular, the laminated film 100 can be suitably used for optical applications such as image display devices because the inclusion of bubbles is significantly suppressed. Example Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited to these Examples. The measuring methods of various physical properties are as follows. <Measurement of the Nip Width of the First Laminating Roll and the Second Laminating Roll> Pressure-sensitive paper (manufactured by Fujifilm Corporation, trade name " Prescale"(Extremely low pressure), thickness 95μm). As a result, in the pressure-sensitive paper, the part with a pressure of more than 0.1MPa is colored. The colored part extends along the axial direction of the outer rubber tube. The maximum width of the colored part is the width of the roller gap between the first laminating roller and the second laminating roller, as shown in Table 1. <Thickness> In each Example and each Comparative Example, the thickness of the member to be measured was measured using a digital micrometer (product name "KC-351C" manufactured by Anritsu Co., Ltd.) The thickness T of each of the first film (polarizing plate) and the second film (acrylic resin film) is shown in Table 1. Dynamic Viscoelasticity Measurement (DMA) The tensile modulus of the first film (polarizing plate) and the second film (acrylic resin film) in each example and comparative example was measured under the following conditions. The tensile modulus E at 25° C. is shown in Table 1. The tensile modulus was measured using an automatic chart. In addition, the product (E×T) of the tensile modulus E at 25° C. and the thickness T was calculated for each of the first and second films. The results are shown in Table 1. <Tension Applied to the First and Second Films> In each of the Examples and Comparative Examples, the tension acting on the first film and the second film was measured using a tension sensor. The results are shown in Table 1. <Bubble Check> 1 m thick pieces were cut out from the laminated films obtained in each of the Examples and Comparative Examples. 2 The number of bubbles larger than 70 μm in the sample was visually measured. The results are shown in Table 1. 0:Not generated (0) △: More than one but less than five ×: 6 or more [Preparation Example 1] 1. Production of polarizing plates As the thermoplastic resin substrate, a longitudinal amorphous isophthalate copolymer polyethylene terephthalate film (thickness: 100 μm) having a Tg of approximately 75° C. was used, and one surface of the resin substrate was corona treated. To 100 parts by mass of a PVA-based resin prepared by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and ethyl acetate-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gohsefimer") in a ratio of 9:1, 13 parts by mass of potassium iodide was added and dissolved in water to prepare a PVA aqueous solution (coating solution). The corona-treated surface of the resin substrate was coated with the aforementioned PVA aqueous solution and dried at 60° C. to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched at a magnification of 2.4 times in the longitudinal direction (lengthwise direction) in an oven at 130° C. (in-flight auxiliary stretching treatment). Next, the laminate was immersed in an insolubilization bath (a boric acid aqueous solution prepared by mixing 4 parts by mass of boric acid with 100 parts by mass of water) at a liquid temperature of 40° C. for 30 seconds (insolubilization treatment). Next, the polarizer is immersed in a dyeing bath (an iodine aqueous solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 per 100 parts by mass of water) at a liquid temperature of 30°C for 60 seconds while adjusting the concentration so that the single-unit transmittance (Ts) of the resulting polarizer reaches the desired value (dyeing treatment). Next, the sample was immersed in a bridging bath (a boric acid aqueous solution prepared by blending 3 parts by mass of potassium iodide and 5 parts by mass of boric acid per 100 parts by mass of water) at a liquid temperature of 40° C. for 30 seconds (crosslinking treatment). Afterwards, the laminate is immersed in a boric acid aqueous solution (boric acid concentration 4 wt%, potassium iodide concentration 5 wt%) at a liquid temperature of 70°C, and is subjected to uniaxial stretching (underwater stretching treatment) in the longitudinal direction (length direction) between rollers with different peripheral speeds so that the total stretching ratio becomes 5.5 times. Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution prepared by mixing 4 parts by mass of potassium iodide with respect to 100 parts by mass of water) at a liquid temperature of 20° C. (cleaning treatment). Thereafter, the sheet was dried in an oven maintained at approximately 90° C. while being brought into contact with a SUS heating roller maintained at a surface temperature of approximately 75° C. (drying shrinkage treatment). In this manner, a polarizer having a thickness of about 5 μm was formed on the resin substrate, thereby obtaining a polarizing plate (first film) having a structure of resin substrate / polarizer. The polarizing plate had a longitudinal shape. [Example 1] As a second film, a longitudinal acrylic resin film (thickness: 20 μm, manufactured by Toyo Kohan Co., Ltd., trade name “Fine Cast Film”) was prepared. In addition, a first bonding roll and a second bonding roll are prepared. The first bonding roller includes an outer rubber tube and an inner shaft. The outer rubber tube is made of silicone rubber. Its hardness is 85. Its outer and inner diameters are constant along its axis. The outer diameter is 200 mm. The inner diameter is 192 mm. In other words, the thickness of the outer rubber tube is 8 mm. The inner shaft is a stepped shaft, axially arranged in the following order: a first end, a first reduced diameter portion, a support portion, a second reduced diameter portion, and a second end portion. The inner shaft is made of iron (SUS304). Its hardness is 70HR. The outer diameter of the support portion is 186mm. The outer diameters of the first and second reduced diameter portions are each 110mm. The outer diameters of the first and second ends are each 45mm. The axial dimension of the support portion is 400mm. The second laminating roller has the same configuration as that of the first laminating roller. Next, the first laminating roller and the second laminating roller were positioned opposite each other so that the outer rubber tube of the first laminating roller and the outer rubber tube of the second laminating roller were in radial contact with each other. Furthermore, both ends of the inner shaft of the first laminating roller were pressed against the second laminating roller using a cylinder so that the nip width was the value shown in Table 1. In addition, each of the 1st bonding roll and the 2nd bonding roll rotated at 32 rpm. Next, an acrylic ultraviolet curable adhesive was applied to the surface of the polarizer in the polarizing plate obtained in Preparation Example 1 and the surface of the acrylic resin film to form a coating film having a thickness of 1.5 μm. Next, the polarizing plate and acrylic resin film were fed between the first and second laminating rollers, with the coating on the polarizer in contact with the coating on the acrylic resin film. The polarizing plate and acrylic resin film were fed at a linear speed of 20 m / min. The outer circumference of the rubber tube outside the first laminating roller contacted the polarizing plate's protective layer in an area corresponding to a 45° center angle (wrapped angle). The polarizing plate and the acrylic resin film are bonded together while passing between the first bonding roll and the second bonding roll, and then irradiated with ultraviolet light to cure the ultraviolet curing adhesive. As described above, a laminated film having a structure of polarizing plate (first film) / adhesive layer / acrylic resin film (second film) was obtained. [Example 2] A laminated film was obtained in the same manner as in Example 1 except that the tension applied to the first film and the tension applied to the second film were changed as shown in Table 1. [Examples 3 and 4] Except having changed the nip width of the 1st laminating roll and the 2nd laminating roll as shown in Table 1, it carried out similarly to Example 1, and obtained the laminated film. [Comparative Example 1] A laminated film was obtained in the same manner as in Example 1 except that the inner shaft (stepped shaft) of the second laminating roll was changed to a normal shaft (non-stepped shaft) with a constant outer diameter, and the tension applied to the second film and the nip width were changed as shown in Table 1. In addition, the normal shaft (non-stepped shaft) is in contact with the entire inner peripheral surface of the outer rubber tube of the second laminating roller. Hereinafter, the laminating roller having a normal shaft may be referred to as a normal roller. [Comparative Example 2] A laminated film was obtained in the same manner as in Example 1 except that the outer rubber tube of the second laminating roll was replaced with an iron metal tube and the tension applied to the second film and the nip width were changed as shown in Table 1. [Reference Example 1] A laminated film was obtained in the same manner as in Example 4 except that the PET film serving as the protective layer was replaced with a cycloolefin film having a hard coating layer (thickness 30 μm, manufactured by Zeon Corporation of Japan, trade name Zeonor), the second film was replaced with a triacetyl cellulose (TAC) film, the first laminating roller and the second laminating roller were replaced with ordinary rollers, respectively, and the roller gap width was changed as shown in Table 1. Table 1 [evaluate] As shown in Reference Example 1, when the product of the tensile modulus E and the thickness T of the first and second films is 100,000 or more, the generation of bubbles can be suppressed even when the first and second films are bonded together using a normal roller. On the other hand, as shown in Comparative Example 1, when the product of the tensile modulus E and the thickness T of the first film and / or the second film is less than 100,000, bubbles are confirmed to be generated when the first film and the second film are bonded together using a normal roller. In this case, as shown in Examples 1 to 4, the generation of bubbles can be significantly suppressed by laminating the first film and the second film using the first laminating roll and the second laminating roll having a specific structure. Industrial Applicability The laminated film obtained by the method for producing a laminated film according to the embodiment of the present invention can be applied to various industrial products, particularly optical products such as image display devices. Description of Reference Numerals 1First Film 2 Second film 3a First laminating roller 3b Second laminating roller 31 outer rubber tube 32 medial shaft 321 support part 322 Trail Section 100 layers of laminated film

Claims

1. A method for producing a laminated film, characterized in that: The method comprises a step of laminating the first film and the second film using an adhesive, In the laminating step, the first film and the second film are laminated while passing between a first laminating roller and a second laminating roller. The first laminating roller and the second laminating roller each have: An outer rubber tube having a cylindrical shape; an inner shaft disposed within the outer rubber tube; The inner shaft has: a supporting portion for supporting a central portion of the outer rubber tube in the axial direction; Small-diameter portions arranged on both sides of the support portion in the axial direction, the small-diameter portions having a smaller diameter than the support portion; At least one of the first film and the second film satisfies the following formula (1): E×T<100000···(1) In formula (1), E represents the tensile modulus at 25° C., in MPa; T represents the thickness, in μm.

2. The method for producing a laminated film according to claim 1, wherein Both the first film and the second film satisfy the relationship of the above-mentioned formula (1).

3. The method for producing a laminated film according to claim 1 or 2, wherein: The thickness of at least one of the first film and the second film is 45 μm or less.

4. The method for producing a laminated film according to claim 1 or 2, wherein: In the laminating step, the tension applied to the first film and / or the second film is 50 N / m to 400 N / m.

5. The method for producing a laminated film according to claim 1 or 2, wherein: A nip is formed between the first laminating roller and the second laminating roller to sandwich the first film and the second film, and the nip extends along the axial direction. The width of the roller gap is 13 mm to 20 mm.

6. The method for producing a laminated film according to claim 1 or 2, wherein: The outer diameter of the central portion of the outer rubber tube in the axial direction is not more than 1 times the outer diameter of the end portions of the outer rubber tube in the axial direction.

7. The method for producing a laminated film according to claim 5, wherein: The outer peripheral surface of the outer rubber tube of the first laminating roller includes a contact area with the first film in the laminating step. A central angle of the outer rubber tube corresponding to the contact area is 45° to 90°.

8. The method for producing a laminated film according to claim 1 or 2, wherein: The first film is a polarizing plate including a polarizer.

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