Method for manufacturing laminated thin films

Abstract

The present invention aims to provide a method for manufacturing a laminated film that protects the surface of the product film and achieves a product film with excellent appearance. As a solution, the method for manufacturing a laminated film according to an embodiment of the present invention includes a lamination step. In the lamination step, a protective film and a product film are laminated between a first lamination roller and a second lamination roller using an adhesive layer. The storage modulus of elasticity of the adhesive layer at 25°C and 55%RH is 1.0 × 10³ Pa to 9.9 × 10⁵ Pa. The thickness of the adhesive layer is 5 µm or more. The thickness T1 of the protective film is greater than 1.0 relative to the thickness T2 of the adhesive layer. At 25°C, the hardness R2 of the second lamination roller on the product film side is greater than 1.0 relative to the hardness R1 of the first lamination roller on the protective film side.

Description

Method for manufacturing laminated film The present invention relates to a method for manufacturing a laminated film. In the past, resin films have been widely used in various industrial products. One example of the resin film is an optical film that can be used in image display devices. Optical films require more stringent standards for scratches and dirt than resin films used for other purposes (such as packaging films). Therefore, it is known that when transporting an optical film, a protective film is temporarily adhered to the surface of the optical film to suppress scratches and dirt on the surface of the optical film. Regarding the protective film, for example, it has been proposed to use a polyester film with excellent mechanical strength and transparency (for example, refer to Patent Document 1). Prior Art Documents Patent Documents Patent Document 1: Japanese Patent Application Laid-Open No. 2006-176685 Problems to be Solved by the Invention In recent years, new uses of image display devices have been continuously developed. Depending on the use of the image display device, sometimes a resin film (typically an optical film) is required to have an appearance that is significantly better than before. In particular, poor appearance at a level that has not caused any problems so far may have a substantial adverse effect on the performance of the image display device. The present invention is made to solve the above-mentioned previous problems, and its main purpose is to provide a method for manufacturing a laminated film, which can protect the surface of the product film and can achieve a product film with excellent appearance. Means for solving the problem [1] The method for manufacturing a laminated film according to an embodiment of the present invention includes a laminating step. In the laminating step, the protective film and the product film are passed between a first laminating roller and a second laminating roller and laminated by an adhesive layer. In the laminating step, the first laminating roller is located on the opposite side of the product film relative to the protective film, and the second laminating roller is located on the opposite side of the product film relative to the protective film. The storage elastic modulus of the adhesive layer at 25°C and a relative humidity of 55% is 1.0×10 3 Pa~9.9×10 5 Pa. The thickness T1 of the adhesive layer is greater than 5µm. The thickness T1 of the adhesive layer relative to the thickness T2 of the protective film is less than 1.0. At 25°C, the hardness R2 of the second laminating roller relative to the hardness R1 of the first laminating roller is greater than 1.0. Effects of the Invention According to the embodiments of the present invention, the surface of a product film can be protected and a product film having an excellent appearance can be realized. The following describes embodiments of the present invention, but the present invention is not limited to these embodiments. In addition, in order to more clearly illustrate the drawings, the width, thickness, shape, etc. of various parts are shown schematically compared to the embodiments, but this is only an example and is not intended to limit the interpretation of the present invention. (Definition of terms and symbols) The definitions of terms and symbols in this specification are as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction where the in-plane refractive index reaches the maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane phase difference measured at 23°C with light of a wavelength of λnm. For example, "Re(550)" is the in-plane phase difference measured at 23°C with light of a wavelength of 550nm. Re(λ) can be obtained by the formula: Re(λ)=(nx-ny)×d when the thickness of the layer (film) is d(nm). A. Overview of the Method for Producing a Laminated Film FIG. 1 is a schematic diagram for explaining a method for producing a laminated film according to one embodiment of the present invention. A method for manufacturing a laminated film according to one embodiment includes a laminating step. In the laminating step, a protective film 1 and a product film 2 are passed between a first laminating roller 3a and a second laminating roller 3b and are laminated by an adhesive layer 5. In the laminating step, the first laminating roller 3a is located on the opposite side of the product film 2 relative to the protective film 1, and the second laminating roller 3b is located on the opposite side of the protective film 1 relative to the product film 2. The storage elastic modulus of the adhesive layer 5 at 25°C and 55% RH (relative humidity) is 1.0×10 3 Pa~9.9×10 5Pa. The thickness T1 of the adhesive layer 5 is greater than or equal to 5µm. The thickness T1 of the adhesive layer 5 relative to the thickness T2 of the protective film 1 (T1 / T2) is less than or equal to 1.0. At 25°C, the hardness R2 of the second laminating roller 3b relative to the hardness R1 of the first laminating roller 3a (R2 / R1) is greater than 1.0. The inventors have discovered that if the first laminating roller and the second laminating roller are used to laminate the product film and the protective film, dents may be formed on the product film. Therefore, the inventors have actively studied the formation of dents on the product film, and as a result, it has been inferred that the dents on the product film are formed when the appearance defects of the protective film (such as fish eyes, burns, and wrinkles) are transferred to the product film during the laminating step. The inventors of the present invention have further studied this view and found that if the thickness of the adhesive layer used to attach the product film and the protective film is in a specific relationship with the hardness of the first laminating roller and the second laminating roller, even if the protective film is attached to the product film using the first laminating roller and the second laminating roller, dents in the product film can still be suppressed. Specifically, if the thickness T1 of the adhesive layer is greater than 5µm, and the hardness R2 of the second laminating roller relative to the hardness R1 of the first laminating roller (R2 / R1) is greater than 1.0, the poor appearance of the protective film can be suppressed from being transferred to the product film. Therefore, dents in the product film can be suppressed. In addition, according to one embodiment, the thickness T1 of the adhesive layer relative to the thickness T2 of the protective film (T1 / T2) is less than 1.0, and the storage elastic modulus of the adhesive layer is 1.0×10 3 Pa or higher, wrinkles on the product film can be suppressed during transport of the laminated film, and peeling of the protective film from the product film can be suppressed. As a result, the protective film can be attached to the product film to protect the surface of the product film, while also achieving a product film with excellent appearance. The storage elastic modulus of the adhesive layer 5 at 25°C and 55% RH is preferably 1.0×10 3 Pa~9.0×10 5 Pa, preferably 8.0×10 4 Pa~1.2×10 5 Pa. If the storage modulus of the adhesive layer is within this range, peeling of the protective film from the product film can be stably suppressed. The storage modulus of the adhesive layer is measured, for example, in shear mode at a constant temperature of 25°C and a frequency of 1 Hz in accordance with JIS K 6868. The thickness T1 of the adhesive layer 5 relative to the thickness T2 of the protective film 1 (T1 / T2) is preferably 0.90 or less, more preferably 0.80 or less, and even more preferably 0.50 or less. If the thickness ratio (T1 / T2) between the protective film and the adhesive layer is in the above relationship, the generation of wrinkles in the product film during transport of the laminated film can be stably suppressed, thereby improving the transportability of the laminated film. On the other hand, the thickness T1 of the adhesive layer 5 relative to the thickness T2 of the protective film 1 (T1 / T2) is, for example, 0.10 or more, preferably 0.20 or more, and more preferably 0.30 or more. If the thickness ratio (T1 / T2) between the protective film and the adhesive layer is in the above relationship, the generation of dents in the product film can be stably suppressed. The thickness T1 of the adhesive layer 5 is preferably 8µm or greater, more preferably 10µm or greater. This thickness can more reliably suppress the formation of dents in the finished film. Alternatively, the thickness T1 of the adhesive layer 5 is, for example, 50µm or less, preferably 40µm or less, and more preferably 35µm or less. This thickness can more reliably suppress the formation of wrinkles in the finished film during transport of the laminated film. The thickness T2 of the protective film 1 is, for example, 7 µm or greater, preferably 10 µm or greater, more preferably 20 µm or greater, and even more preferably 25 µm or greater. On the other hand, the thickness T2 of the protective film 1 is, for example, 80 µm or less, preferably 60 µm or less, and more preferably 40 µm or less. When the protective film has the aforementioned thickness, the thickness ratio (T1 / T2) between the protective film and the adhesive layer can be stably adjusted within the aforementioned range. At 25°C, the hardness R2 of the second laminating roller 3b relative to the hardness R1 of the first laminating roller 3a (R2 / R1) is preferably 1.01 or greater, more preferably 1.05 or greater, and even more preferably 1.08 or greater. When the hardness ratio (R2 / R1) between the first laminating roller and the second laminating roller is in this relationship, sink marks in the product film can be more stably suppressed. Meanwhile, at 25°C, the hardness R2 of the second laminating roller 3b relative to the hardness R1 of the first laminating roller 3a (R2 / R1) is, for example, 2.0 or less, preferably 1.8 or less, and even more preferably 1.60 or less. The first laminating roller 3a on the protective film 1 side is typically softer than the second laminating roller 3b on the product film 2 side. The hardness R1 of the first laminating roller 3a at 25°C is, for example, 30-120, preferably 50-90, and more preferably 60-80. The hardness R2 of the second laminating roller 3b at 25°C is, for example, 50-130, preferably 70-110, and more preferably 85-95. The hardness of the laminating roller is a durometer hardness, measured, for example, in accordance with JIS K 6253. At 25°C, the ratio of the indentation elastic modulus E2 of the product film 2 to the indentation elastic modulus E1 of the protective film 1 (E2 / E1) is, for example, 0.30 or greater, preferably 0.50 or greater, and more preferably 0.60 or greater. Meanwhile, at 25°C, the ratio of the indentation elastic modulus E2 of the product film 2 to the indentation elastic modulus E1 of the protective film 1 (E2 / E1) is, for example, 1.40 or less, further example, 1.20 or less, further example, 1.00 or less, and further example, 0.80 or less. Even with the above-described relationship between the indentation elastic modulus ratio (E2 / E1) between the protective film and the product film, the above-described embodiment can still stably achieve a product film having an excellent appearance. The protective film 1 may be softer or harder than the product film 2. In one embodiment, the protective film 1 is harder than the product film 2. The indentation elastic modulus E1 of the protective film 1 at 25°C is, for example, 0.5 GPa to 6.0 GPa, preferably 1.5 GPa to 4.5 GPa, and more preferably 2.0 GPa to 4.0 GPa. The indentation elastic modulus E2 of the product film 2 at 25°C is, for example, 1.0 GPa to 5.0 GPa, preferably 1.0 GPa to 4.0 GPa, more preferably 2.5 GPa to 3.5 GPa, and particularly preferably 2.0 GPa to 3.2 GPa. The indentation elastic modulus of the film is measured, for example, in accordance with ISO 14577. B. Details of the Method for Producing a Laminated Film The following describes the details of the method for producing a laminated film. In one embodiment of the method for producing a laminated film, a protective film 1 and a product film 2 are first prepared. B-1. Product Film: Product film 2 can have any suitable structure. Product film 2 typically has an elongated strip shape. Product film 2 can have a single-layer structure or a laminated structure comprising two or more layers. In the illustrated example, product film 2 has a single-layer structure. The thickness of product film 2 is, for example, 10 µm to 100 µm, preferably 15 µm to 80 µm. The product film 2 is typically formed from any suitable resin material. Examples of the resin material forming the product film 2 include polycarbonate (PC) resins, polyvinyl acetal resins, cycloolefin (COP) resins, (meth)acrylic resins, cellulose ester resins, cellulose resins, polyester resins, polyester carbonate resins, olefin resins, and polyurethane resins. Furthermore, (meth)acrylic resins refer to acrylic resins and / or methacrylic resins. These resin materials may be used alone or in combination. Among the resin materials constituting the product film 2, PC resins, COP resins, and (meth)acrylic resins are more preferred, with PC resins being more preferred. If the product film is composed of these resin materials, sink marks on the product film can be stably suppressed. Examples of the PC-based resin include PC-based resins containing structural units derived from dihydroxy compounds. Specific examples of the dihydroxy compound include 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 9,9-bis(4-hydroxy-3-ethylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-propylphenyl)fluorene, 9,9-bis(4-hydroxy-3-isopropylphenyl)fluorene, 9,9-bis(4-hydroxy-3-n-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-sec-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-tert-butylphenyl)fluorene, 9,9-bis(4-hydroxy-3-cyclohexylphenyl)fluorene, 9,9-bis(4-hydroxy-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, )-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl)fluorene, 9,9-bis(4-(3-hydroxy-2,2-dimethylpropyloxy)phenyl)fluorene. In addition to the structural units derived from the above-mentioned dihydroxy compounds, PC-based resins may also contain structural units derived from dihydroxy compounds such as isosorbide, anhydromannitol, iditol, spiroglycerol, dialkylene glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol (CHDM), tricyclodecanedimethanol (TCDDM), and bisphenols. The details of the PC-based resin are described in, for example, Japanese Patent Application Laid-Open No. 2012-67300 and Japanese Patent No. 3325560. The descriptions of these patent documents are incorporated herein by reference. The product film 2 may be, for example, an optical film such as a retardation film, and preferably a retardation film. The retardation film is typically formed by stretching a resin film made of the aforementioned resin material in a predetermined direction. Any suitable stretching method may be employed. The retardation film typically has a slow axis in the stretching direction. In one embodiment, the refractive index of the retardation film exhibits the relationship nx>ny. The retardation film can also function as a λ / 4 plate. When the retardation film functions as a λ / 4 plate, the in-plane retardation Re(550) of the retardation film is, for example, 100 nm to 180 nm, preferably 135 nm to 155 nm. Furthermore, the retardation film can also function as a λ / 2 plate. When the retardation film functions as a λ / 2 plate, the in-plane retardation Re(550) of the retardation film is, for example, 230 nm to 310 nm, preferably 250 nm to 290 nm. B-2. Protective Film: Protective film 1 is attached to product film 2 to protect the surface of product film 2. Protective film 1 can have any suitable structure. Typically, protective film 1 has a long strip shape. Protective film 1 can have a single-layer structure or a laminated structure comprising two or more layers. In the illustrated example, protective film 1 has a single-layer structure. The protective film 1 is typically formed from any suitable resin material. Examples of the resin material forming the protective film 1 include olefin resins, COP resins, polyester resins, cellulose resins, PC resins, (meth)acrylic resins, polyvinyl acetal resins, polyamide resins, polyimide resins, polyether sulfide resins, polysulfide resins, polystyrene resins, acetate resins, thermosetting resins, and UV curing resins. These resin materials may be used alone or in combination. Among the resin materials constituting the protective film 1, COP resins and polyester resins are more preferably mentioned, and polyethylene terephthalate (PET) is more preferably mentioned. If the protective film is composed of the above resin materials, the surface of the product film can be stably protected by the protective film. B-3. ​​Adhesive Layer In one embodiment, an adhesive layer 5 is pre-laminated on the protective film 1 and / or the product film 2. In the illustrated example, the adhesive layer 5 is laminated on the protective film 1 and not on the product film 2. Hereinafter, the protective film 1 laminated with the adhesive layer 5 may be referred to as a protective film 6 with an adhesive layer. The adhesive layer 5 can be laminated using any appropriate method. The adhesive layer 5 can be formed by direct printing onto the surface of the film (protective film 1 and / or product film 2) or by transfer printing. In direct printing, the adhesive composition is applied directly to the surface of the film to form the adhesive layer 5. In transfer printing, the adhesive composition is applied to the surface of a release liner to form the adhesive layer 5, which is then attached to the film. The adhesive layer 5 can be composed of any appropriate adhesive. Examples of the adhesive include (meth) acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, quantity, combination, and blending ratio of the monomers forming the base resin of the adhesive, as well as the blending amount, reaction temperature, and reaction time of the cross-linking agent, an adhesive having the desired properties that meet the purpose can be formulated. The base resin of the adhesive can be used alone or in combination of two or more. Among the adhesives, (meth) acrylic adhesives ((meth) acrylic adhesive compositions) can also be cited. The (meth)acrylic adhesive composition typically contains a (meth)acrylic polymer as a main component. The content of the (meth)acrylic polymer in the solids content of the adhesive composition is, for example, 50% by mass or greater, preferably 70% by mass or greater, and more preferably 90% by mass or greater. On the other hand, the upper limit of the content of the (meth)acrylic polymer in the solids content of the adhesive composition is typically 100% by mass. The (meth)acrylic polymer contains an alkyl (meth)acrylate as a main component in terms of monomer units. In the (meth)acrylic polymer, the content of structural units derived from the alkyl (meth)acrylate is, for example, 70% by mass or more, preferably 80% by mass or more, and more preferably 85% by mass or more. On the other hand, the content of structural units derived from the alkyl (meth)acrylate is, for example, 98% by mass or less, and preferably 95% by mass or less. The alkyl group of the alkyl (meth)acrylate can be, for example, a linear or branched alkyl group having 1 to 18 carbon atoms. The average carbon number of the alkyl group is preferably 3 to 9, more preferably 3 to 6. Among the alkyl (meth)acrylates, butyl acrylate is another preferred example. In addition to alkyl (meth)acrylates, monomers (comonomers) that constitute (meth)acrylic acid polymers may include carboxyl-containing monomers, hydroxyl-containing monomers, amide-containing monomers, aromatic ring-containing (meth)acrylates, and heterocyclic vinyl-containing monomers. Representative examples of comonomers include acrylic acid, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, benzyl acrylate, phenoxyethyl acrylate, and N-vinyl-2-pyrrolidone. Comonomers may be used alone or in combination. Preferred comonomers include acrylic acid, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, and benzyl acrylate. More preferred comonomers include acrylic acid and 2-hydroxyethyl acrylate, and even more preferred are acrylic acid and 2-hydroxyethyl acrylate. In the (meth)acrylic acid polymer, the content of structural units derived from the comonomers is, for example, 30% by mass or less, preferably 20% by mass or less, and more preferably 15% by mass or less. On the other hand, the content of structural units derived from the comonomers is, for example, 0% by mass or greater, and another example is 3% by mass or greater. The weight average molecular weight Mw of the (meth)acrylic polymer is, for example, 200,000 to 3,000,000, preferably 1,000,000 to 2,500,000, more preferably 1,200,000 to 2,500,000, and even more preferably 1,500,000 to 2,500,000. The weight average molecular weight Mw can be calculated, for example, from the results of GPC measurement by converting to styrene. If the weight average molecular weight Mw is within the above range, an adhesive layer with excellent durability (especially heat resistance) can be obtained. The weight average molecular weight Mw of the (meth)acrylic polymer relative to the number average molecular weight Mn (Mw / Mn) is, for example, 1.0 or more, preferably 2.0 or more, and for example, 5.0 or less, preferably 4.0 or less. The acrylic adhesive composition preferably contains a silane coupling agent and / or a crosslinking agent. Examples of the silane coupling agent include epoxy-containing silane coupling agents. The content of the silane coupling agent is, for example, 0.001 parts by mass to 5 parts by mass per 100 parts by mass of the (meth)acrylic polymer. Examples of crosslinking agents include isocyanate crosslinking agents and peroxide crosslinking agents. The crosslinking agents can be used alone or in combination. Among the crosslinking agents, isocyanate crosslinking agents are more preferably used. The content of the crosslinking agent relative to 100 parts by mass of the (meth)acrylic polymer is, for example, 0.01 parts by mass or more, preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more. On the other hand, the content of the crosslinking agent is, for example, 15 parts by mass or less, preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and particularly preferably 1.0 parts by mass or less. B-4. First Laminating Roller and Second Laminating Roller: The first laminating roller 3a may have any suitable configuration. The first laminating roller 3a generally has a cylindrical shape extending in a predetermined direction. The outer diameter of the first laminating roller 3a is, for example, 100 mm to 500 mm, preferably 150 mm to 300 mm. The outer circumference of the first laminating roller 3a is softer than the outer circumference of the second laminating roller 3b. The outer circumference of the first laminating roller 3a has the aforementioned hardness R1. The first laminating roller 3a is made of any suitable material. Examples of the material of the first laminating roller 3a include metal, semi-metal, and rubber, preferably rubber. Examples of the rubber include silicone rubber, butyl rubber, and SEBS, and more preferably silicone rubber. In one embodiment, the first laminating roller 3a comprises a cylindrical roller body and a shaft inserted into the roller body. The roller body is typically made of the aforementioned rubber. The outer diameter of the roller body is typically within the same range as the outer diameter of the first laminating roller. The outer circumference of the roller body is softer than the outer circumference of the second laminating roller 3b. The outer circumference of the roller body has the aforementioned hardness R1. The shaft is typically made of the aforementioned metal. When the shaft is inserted into the roller body, both ends of the shaft protrude from the roller body. The second laminating roller 3b may have any suitable structure. The second laminating roller 3b is generally cylindrical and extends in a predetermined direction. The outer diameter of the second laminating roller 3b is, for example, 100 mm to 500 mm, preferably 150 mm to 300 mm. The outer circumferential surface of the second laminating roller 3b has the aforementioned hardness R2. The second laminating roller 3b is made of any suitable material. Examples of the material of the second laminating roller 3b include metals and semi-metals, preferably metals. Examples of metals include iron, copper, aluminum, chromium, nickel, and alloys thereof. Among the metals, iron is particularly preferred. In one embodiment, the second laminating roller 3b comprises a cylindrical shaft and a plated film applied to the outer circumference of the shaft. The shaft is typically composed of the aforementioned metal. The plated film is typically composed of an alloy of the aforementioned metals. In one embodiment, the plated film is applied to the entire outer circumference of the shaft. The thickness of the plated film is arbitrarily adjusted so that the hardness R2 of the outer circumference of the second laminating roller 3b is within the aforementioned range. The second laminating roller 3b is arranged to face the first laminating roller 3a in the diametrical direction. The outer circumference of the first laminating roller 3a and the outer circumference of the second laminating roller 3b are in contact with each other before the protective film 1 and the product film 2 are supplied therebetween. In one embodiment, either the first laminating roller 3a or the second laminating roller 3b is pressed in either direction. Thus, the first laminating roller 3a and the second laminating roller 3b together form a nip roller N. The nip pressure (pressing force of the laminating rollers) is, for example, 1 MPa to 100 MPa, preferably 5 MPa to 50 MPa. B-5. Details of the Laminating Step In the laminating step, the protective film 1 and the product film 2 are fed through a nip roller N. In one embodiment, the protective film 6 with an adhesive layer and the product film 2 are fed through a nip roller N. In the illustrated example, the protective film 1 (protective film 6 with an adhesive layer) is fed between the first laminating roller 3a and the second laminating roller 3b via a first conveyor roller 41. Furthermore, the product film 2 is fed between the first laminating roller 3a and the second laminating roller 3b via a second conveyor roller 42. The first conveyor roller 41 and the second conveyor roller 42 are each movable relative to the first laminating roller 3a. During the laminating step, the tension applied to the protective film 1 is, for example, 50 N / m to 500 N / m, preferably 100 N / m to 300 N / m. If the tension applied to the protective film during the laminating step is within this range, the protective film and the product film can be smoothly laminated, and the formation of dents in the product film can be more reliably suppressed. The tension of the protective film 1 can be appropriately adjusted by moving the first transport roller 41 relative to the first laminating roller 3a. During the laminating step, the tension applied to the product film 2 is, for example, 50 N / m to 500 N / m, preferably 100 N / m to 300 N / m. If the tension applied to the product film during the laminating step is within this range, the protective film and product film can be laminarized more smoothly, and the formation of dents in the product film can be more reliably suppressed. The tension of the product film 2 can be appropriately adjusted by moving the second transport roller 42 relative to the first laminating roller 3a. The feeding speed (line speed) of each of the protective film 1 and the product film 2 in the laminating step is, for example, 5 m / min to 50 m / min, preferably 15 m / min to 30 m / min. When the protective film 1 passes between the first laminating roller 3a and the second laminating roller 3b (nip roller N), it comes into contact with the outer circumference of the first laminating roller 3a. Similarly, when the product film 2 passes between the first laminating roller 3a and the second laminating roller 3b (nip roller N), it comes into contact with the outer circumference of the second laminating roller 3b. At this point, the protective film 1 and the product film 2 are appropriately pressed by the first laminating roller 3a and the second laminating roller 3b. This creates a pressure bond between the protective film 1 and the product film 2 via the adhesive layer 5. The long laminated film 100 is manufactured in the above manner. In the illustrated example, the laminated film 100 is wound up as needed after passing through the third transport roller 43. The third transport roller 43 can also move relative to the first laminating roller 3a. C. Laminated Film The laminated film 100 shown in the figure comprises a protective film 1, an adhesive layer 5, and a product film 2 in this order. The laminated film 100 can be used for any appropriate purpose. The product film 2 can be used in a state with the protective film 1 attached (i.e., in the state of the laminated film 100), or it can be used after the protective film 1 and the adhesive layer 5 are peeled off. The product film 2 is preferably used after the protective film 1 and the adhesive layer 5 (the protective film 6 with the adhesive layer attached) are peeled off. The product film 2 can be used for optical purposes such as image display devices. In particular, the product film 2 has significantly suppressed scratches and dirt and has an excellent appearance, so it is suitable for use in image display devices such as smartphones and tablet PCs. The present invention is further illustrated by examples below, but the present invention is not limited to these examples. The methods for measuring various properties are described below. In addition, unless otherwise noted, "parts" and "%" in the Examples and Comparative Examples are by mass. Furthermore, the methods for measuring various properties in the Examples and Comparative Examples are described below. (1) Determination of the indentation elastic modulus of each of the protective film and the product film In accordance with ISO14577, the indentation elastic modulus of each of the protective film and the product film used in the examples and comparative examples was measured using the nanoindentation method under the following measurement conditions. The indentation elastic modulus E1 of the protective film, the indentation elastic modulus E2 of the product film, and E2 / E1 are shown in Table 1. Apparatus: Nanoindentation tester (manufactured by nanomechanics) Sample size: 10×10 mm Indenter: Square pyramid indenter Measurement temperature: 25°C Measurement humidity: 55% RH Maximum indentation load: 25 mN Indentation speed: 100 nm / s Holding time: 2 seconds Load unloading speed: 2.5 mN / s Calculation method: Based on ISO14577 (2) Determination of Storage Elastic Modulus of Adhesive Layer The storage elastic modulus of the adhesive layer used in the Examples and Comparative Examples was measured under the following measurement conditions in accordance with JIS K 6868. The storage elastic modulus of the adhesive layer is shown in Table 1. Measurement temperature: 25°C (constant temperature) Measurement humidity: 55% RH Measurement mode: Shear frequency: 1 Hz (3) Measurement of Hardness of the First and Second Laminating Rollers The hardness of the first and second laminating rollers used in Examples and Comparative Examples was measured in accordance with JIS K 6253. The hardness R1 of the first laminating roller, the hardness R2 of the second laminating roller, and R2 / R1 are shown in Table 1. (4) Evaluation of Laminated Film Appearance: The laminated films prepared in Examples and Comparative Examples were integrated with polarizing plates, attached to aluminum reflectors, and then translucently observed under fluorescent light. The appearance was evaluated according to the following criteria. The results are shown in Table 1. ○: No visible dents. ×: Observable dents. (5) Evaluation of Laminated Film Transportability The transportability of the laminated films prepared in the Examples and Comparative Examples was evaluated based on the following criteria, including contamination of the production line and the presence of film breakage. The results are shown in Table 1. ○: No process contamination or film breakage. ×: Process contamination and / or film breakage. <<Preparation of Adhesive>> <Preparation Example 1> 94.9 parts by mass of butyl acrylate, 5 parts by mass of acrylic acid, 0.1 part by mass of 2-hydroxyethyl acrylate, and diphenylformyl peroxide were added together with 0.3 parts by mass of ethyl acetate relative to 100 parts by mass of the total amount of the aforementioned monomers (solid content) to a reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer, and a stirring device. After reacting at 60°C under a nitrogen flow for 7 hours, ethyl acetate was added to the reaction solution to obtain a solution containing an acrylic polymer having a weight-average molecular weight of 2.2 million and a dispersion ratio of 3.9 (solid content concentration 30% by mass). For every 100 parts by mass of the solid content of the solution containing the acrylic polymer, 0.6 parts by mass of trimethylolpropane diisocyanate toluene (manufactured by Nippon Polyurethane Industry Co., Ltd.: Coronate L) and 0.075 parts by mass of γ-glycidoxypropyl methoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.: KBM-403) were mixed to obtain an adhesive solution. The above solution was diluted with ethyl acetate to a solid content concentration of 15% by mass to prepare an adhesive coating liquid. The prepared adhesive coating liquid was applied to one side of a 38µm polyethylene terephthalate (PET) film (manufactured by Mitsubishi Polyester Film Co., Ltd., MRF38) treated with polysiloxane using a spray die coater so that the coating thickness was 134.0µm. Subsequently, it was dried at 155°C for 1 minute to obtain a storage elastic modulus of 1.13×10 5 The adhesive layer of Pa. The thickness T1 of the adhesive layer is 15µm. <Preparation Example 2> 89.9 parts by mass of butyl acrylate, 10 parts by mass of acrylic acid, 0.1 parts by mass of 2-hydroxyethyl acrylate, and diphenylformyl peroxide were added together with 0.3 parts by mass of ethyl acetate relative to 100 parts by mass of the total amount of the above monomers (solid content), and reacted at 60°C under a nitrogen stream for 6 hours. Ethyl acetate was then added to the reaction solution to obtain a solution (solid content concentration of 30% by mass) containing an acrylic polymer having a weight average molecular weight of 1.7 million and a dispersion ratio of 3.9. A storage elastic modulus of 1.13×10 3 The adhesive layer of Pa. The thickness T1 of the adhesive layer is 38µm. <Preparation Example 3> An adhesive layer was obtained in the same manner as in Preparation Example 1 except that the thickness T1 was changed to 10 μm. <Preparation Example 4> An adhesive layer was obtained in the same manner as in Preparation Example 1 except that the thickness T1 was changed to 50 μm. <Preparation Example 5> An adhesive layer was obtained in the same manner as in Preparation Example 1 except that the thickness T1 was changed to 3 μm. <Preparation Example 6> 92.9 parts by mass of butyl acrylate, 7 parts by mass of acrylic acid, 0.1 parts by mass of 2-hydroxyethyl acrylate, and diphenylformyl peroxide were added together with 0.3 parts by mass of ethyl acetate relative to 100 parts by mass of the total amount of the above monomers (solid content), and reacted at 60°C for 7 hours under a nitrogen stream. Ethyl acetate was then added to the reaction solution to obtain a solution (solid content concentration of 30% by mass) containing an acrylic polymer (B) having a weight average molecular weight of 2,000,000 and a dispersion ratio of 3.9. A solution having an elastic modulus of 8.86×10 4 The adhesive layer of Pa. The thickness T1 of the adhesive layer is 10µm. <Preparation Example 7> 89.9 parts by mass of butyl acrylate, 10 parts by mass of acrylic acid, 0.1 parts by mass of 2-hydroxyethyl acrylate, and diphenylformyl peroxide were added together with 0.3 parts by mass of ethyl acetate relative to 100 parts by mass of the total amount of the above monomers (solid content), and reacted at 60°C for 4 hours under a nitrogen stream. Ethyl acetate was then added to the reaction solution to obtain a solution (solid content concentration of 30% by mass) containing an acrylic polymer having a weight average molecular weight of 1.2 million and a dispersion ratio of 3.9. A solution having an elastic modulus of 8.86×10 2 The adhesive layer of Pa. The thickness T1 of the adhesive layer is 10µm. <<Preparation of a Protective Film with an Adhesive Layer>> <Preparation Example 8> The adhesive layer obtained in Preparation Example 1 was laminated onto a polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Co., model "DIAFOIL") as a protective film to prepare a protective film with an adhesive layer. The thickness T2 of the protective film was 38 µm. The ratio of the protective film thickness T2 to the adhesive layer thickness T1 (T1 / T2) is shown in Table 1. <Preparation Example 9> The adhesive layer obtained in Preparation Example 2 was laminated on the surface of a PET film (manufactured by Mitsubishi Chemical Co., model number "DIAFOIL") as a protective film to prepare a protective film with an adhesive layer. <Preparation Example 10> The adhesive layer obtained in Preparation Example 3 was laminated on the surface of a PET film (manufactured by Mitsubishi Chemical Co., model "DIAFOIL") as a protective film to prepare a protective film with an adhesive layer. The thickness T2 of the protective film was 30 μm. <Preparation Example 11> The adhesive layer obtained in Preparation Example 6 was laminated onto a cycloolefin (COP) resin film (ZEON Corporation, Model "ZF-14") as a protective film to prepare a protective film with an adhesive layer. The thickness T2 of the protective film was 13 μm. <Preparation Example 12> The adhesive layer obtained in Preparation Example 4 was laminated on the surface of a PET film (manufactured by Mitsubishi Chemical Co., model number "DIAFOIL") as a protective film to prepare a protective film with an adhesive layer. <Preparation Example 13> The adhesive layer obtained in Preparation Example 5 was laminated on the surface of a COP-based resin film (manufactured by ZEON Corporation, model "ZF-14") as a protective film to prepare a protective film with an adhesive layer. <Preparation Example 14> The adhesive layer obtained in Preparation Example 7 was laminated onto the surface of a COP resin film (ZEON Corporation, Model "ZF-14") as a protective film to prepare a protective film with an adhesive layer. The thickness T2 of the protective film was 25 μm. <<Preparation of Product Film>> <Preparation Example 15> A resin film composed of a PC-based resin was prepared in the same manner as in Production Example 9 of Japanese Patent Application Laid-Open No. 2022-150732. The resin film had a long strip shape and a thickness of 130µm. Next, the resin film was subjected to fixed-end transverse uniaxial stretching at a stretching temperature of 150°C and a stretching ratio of 2.8 times to prepare a phase difference film as a product film. The phase difference film had a long strip shape. The thickness of the phase difference film was 47µm. The in-plane phase difference Re(550) of the phase difference film was 140nm. Preparation Example 16: A COP-based resin film (ZEON Corporation, Japan, Model "ZF16") was subjected to fixed-end transverse uniaxial stretching at a stretching temperature of 170°C and a stretching ratio of 2.8x to prepare a retardation film as a finished film. The retardation film had a long strip shape and a thickness of 40 µm. The in-plane retardation Re(550) of the retardation film was 140 nm. <Preparation Example 17> An acrylic resin film (manufactured by Kaneka Corporation, product name "HTX-Z") was subjected to fixed-end simultaneous biaxial stretching at a stretching temperature of 125°C and a stretching ratio of 4 to prepare an optical film as a product film. The optical film had a long strip shape. The thickness of the optical film was 40 µm. The in-plane retardation Re(550) of the optical film was 0.5 nm. [Examples 1-4, Comparative Examples 1-3] A first laminating roller and a second laminating roller were prepared. The first laminating roller had a roller body made of silicone rubber (Si rubber) and a metal shaft. The outer diameter of the roller body was 250 mm. The second laminating roller had a shaft made of iron (Fe) and a chromium-plated coating. The outer diameter of the second laminating roller was 250 mm. Next, the first and second laminating rollers were positioned opposite each other so that they were in contact with each other in the diametrical direction. Furthermore, both ends of the second laminating roller were pressed toward the first laminating roller at 10 MPa using an air cylinder. The first and second laminating rollers were then rotated. Next, the protective film with an adhesive layer obtained in the preparation examples shown in Table 1 and the product film were fed between the first and second laminating rolls, respectively. The feed speed (line speed) of the protective film with an adhesive layer and the product film was 15 m / min. The protective film was in contact with the outer circumference of the first laminating roll (roller body), while the product film was in contact with the outer circumference of the second laminating roll (plated film). As the protective film and product film pass between the first and second laminating rollers, they are pressed against the first and second laminating rollers and bonded together via the adhesive layer. This produces a laminated film consisting of a protective film / adhesive layer / product film (retardation film). [Comparative Example 4] The protective film with an adhesive layer of Modulation Example 8 is changed to the protective film with an adhesive layer of Modulation Example 10, the product film of Modulation Example 16 is changed to the product film of Modulation Example 15, and the first laminating roller and the second laminating roller are replaced, so that the laminating roller having an axis composed of Fe is in contact with the protective film, and the laminating roller having a roller body composed of Si rubber is in contact with the product film. Otherwise, a laminated film is obtained in the same manner as in Example 1. [Table 1] [Evaluation] It is clear from Table 1 that if the storage elastic modulus of the adhesive layer is 1.0×10 3 Pa~9.9×10 5 If the thickness of the adhesive layer T1 is greater than 5µm, the thickness of the adhesive layer T1 / the thickness of the protective film T2 is less than 1.0, and the hardness of the second laminating roller R2 / the hardness of the first laminating roller R1 is greater than 1.0, a product film with excellent appearance can be achieved. Industrial Applicability The method for producing a laminated film of the present invention can be used to produce product films that can be used in various industrial products, and is particularly suitable for producing optical films (specifically, retardation films). 1: Protective film 2: Product film 3a: First laminating roller 3b: Second laminating roller 5: Adhesive layer 6: Protective film with adhesive layer 41: First conveyor roller 42: Second conveyor roller 43: Third conveyor roller 100: Laminated film N: Nip roller FIG1 is a schematic structural diagram for explaining a method for manufacturing a laminated film according to one embodiment of the present invention. 1: Protective film 2: Product film 3a: 1st laminating roller 3b: 2nd laminating roller 5: Adhesive layer 6: Protective film with adhesive layer 41: 1st conveyor roller 42: 2nd conveyor roller 43: 3rd conveyor roller 100: Laminated film N:Pinch roller

Claims

1. A method for manufacturing a laminated film, comprising a lamination step, wherein a protective film and a product film are laminated between a first lamination roller and a second lamination roller using an adhesive layer; wherein, in the lamination step, the first lamination roller is located on the opposite side of the product film relative to the protective film, and the second lamination roller is located on the opposite side of the protective film relative to the product film; the adhesive layer has a storage modulus of elasticity of 1.0 × 10³ Pa to 9.9 × 10⁵ Pa at 25°C and 55% relative humidity; the thickness T1 of the adhesive layer is 5 µm or more, and is 0.10 or more and 1.0 or less relative to the thickness T2 of the protective film; at 25°C, the hardness R2 of the second lamination roller is 1.01 or more and 2.0 or less relative to the hardness R1 of the first lamination roller.

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