Manufacturing method of laminate film

Abstract

To provide a manufacturing method of a laminate film capable of preventing a bruise on a product film while protecting a surface of a product film.SOLUTION: The manufacturing method of a laminate film includes a bonding process. In the bonding process, a protective film and a product film are passed between a first bonding roller and a second bonding roller and are bonded together. In the bonding process, the first bonding roller is positioned on a side opposite to the product film with regard to the protective film, and the second bonding roller is positioned on a side opposite to the protective film with regard to the product film. At 25°C, an indentation elastic modulus E2 of the product film to an indentation elastic modulus E1 of the protective film (E2 / E1) exceeds 1.0. At 25°C, hardness R2 of the second bonding roller to hardness R1 of the first bonding roller (R2 / R1) exceeds 1.0.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a laminated film. [Background technology]

[0002] Resin films have been widely used in various industrial products. One example of such a resin film is an optical film used in an image display device. Optical films are required to meet stricter standards for scratches and stains than resin films used for other purposes (e.g., packaging films). Therefore, it is known that a protective film is temporarily attached to the surface of the optical film during transportation to prevent scratches and stains on the surface of the optical film. As such a protective film, for example, it has been proposed to use a polyester film that is excellent in mechanical strength and transparency (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-176685 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, new applications for image display devices have been developed. Depending on the application of the image display device, resin films (typically optical films) may be required to have significantly better appearances than before. In particular, dents at a level that was not previously considered a problem may have a substantial adverse effect on the performance of the image display device. The present invention has been made to solve the above-mentioned conventional problems, and its main object is to provide a method for manufacturing a laminated film that can protect the surface of the product film and suppress dents in the product film. [Means for solving the problem]

[0005] [1] A method for manufacturing a laminated film according to an embodiment of the present invention includes a laminating step. In the laminating step, a protective film and a product film are laminated by passing them between a first laminating roll and a second laminating roll. In the laminating step, the first laminating roll is located on the opposite side of the protective film from the product film, and the second laminating roll is located on the opposite side of the product film from the protective film. At 25°C, the ratio of the indentation elastic modulus E2 of the product film to the indentation elastic modulus E1 of the protective film exceeds 1.0. At 25°C, the ratio of the hardness R2 of the second laminating roll to the hardness R1 of the first laminating roll exceeds 1.0. [2] In the method for producing a laminated film described in [1] above, the protective film and the product film may be bonded together with a pressure-sensitive adhesive layer. [3] In the method for producing a laminated film according to the above [2], the pressure-sensitive adhesive layer may have a thickness of less than 5 μm. [Effects of the Invention]

[0006] According to an embodiment of the present invention, the surface of the product film can be protected and dents in the product film can be suppressed. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram illustrating a method for producing a laminated film according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments. In addition, in order to clarify the explanation, the width, thickness, shape, etc. of each part may be shown schematically in the drawings compared to the embodiments, but this is merely an example and does not limit the interpretation of the present invention.

[0009] (Definition of terms and symbols) The definitions of terms and symbols used in this specification are as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction in which the in-plane refractive index is greatest (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular 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 retardation measured with light of wavelength λ nm at 23°C. For example, "Re(550)" is the in-plane retardation measured with light of wavelength 550 nm at 23°C. Re(λ) is calculated by the formula: Re(λ)=(nx-ny)×d, where d (nm) is the thickness of the layer (film).

[0010] A. Overview of laminated film manufacturing method FIG. 1 is a schematic diagram illustrating a method for producing a laminated film according to one embodiment of the present invention.

[0011] A method for manufacturing a laminated film according to one embodiment includes a laminating step. In the laminating step, the protective film 1 and the product film 2 are laminated by passing them between a first laminating roll 3a and a second laminating roll 3b. In the laminating step, the first laminating roll 3a is located on the opposite side of the protective film 1 from the product film 2, and the second laminating roll 3b is located on the opposite side of the product film 2 from the protective film 1. 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) exceeds 1.0. At 25°C, the ratio of the hardness R2 of the second laminating roll 3b to the hardness R1 of the first laminating roll 3a (R2 / R1) exceeds 1.0. The present inventors have discovered that when a product film and a protective film are bonded together using a first laminating roll and a second laminating roll, dents may be formed in the product film. As a result of extensive research into the formation of dents in the product film, they have deduced that the dents in the product film are formed when defects in the appearance of the protective film (for example, fisheyes, fading, or wrinkles) are transferred to the product film during the bonding process. The inventor further studied this finding and found that if the indentation elastic modulus of each of the protective film and the product film and the hardness of each of the first laminating roll and the second laminating roll are in a specific relationship, dents in the product film can be suppressed even when the protective film is attached to the product film using the first laminating roll and the second laminating roll. Specifically, when the ratio of the indentation elastic modulus E2 of the product film to the indentation elastic modulus E1 of the protective film (E2 / E1) exceeds 1.0 and the ratio of the hardness R2 of the second lamination roll to the hardness R1 of the first lamination roll (R2 / R1) exceeds 1.0, the transfer of defects in the appearance of the protective film to the product film can be suppressed. Therefore, by attaching the protective film to the product film, the surface of the product film can be protected and dents in the product film can be suppressed.

[0012] 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 preferably 1.10 or greater, more preferably 1.20 or greater, and even more preferably 1.30 or greater. When the ratio of the indentation elastic moduli of the protective film and the product film satisfies this relationship, dents in the product film can be stably suppressed. On the other hand, at 25° C., the upper limit of the ratio of the indentation elastic modulus E2 of the product film 2 to the indentation elastic modulus E1 of the protection film 1 (E2 / E1) is typically 1.70 or less.

[0013] The protective film 1 is typically softer 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 3.0 GPa, preferably 1.5 GPa to 2.5 GPa, and more preferably 1.8 GPa to 2.3 GPa. The indentation modulus E2 of the product film 2 at 25°C is, for example, 1.0 GPa to 5.0 GPa, preferably 2.0 GPa to 4.0 GPa, more preferably 2.5 GPa to 3.5 GPa, and particularly preferably 2.8 GPa to 3.2 GPa. The indentation modulus of the film is measured in accordance with, for example, ISO14577.

[0014] At 25°C, the ratio R2 (R2 / R1) of the hardness of the second laminating roll 3b to the hardness R1 of the first laminating roll 3a is preferably 1.01 or more, more preferably 1.10 or more, and even more preferably 1.30 or more. When the hardness ratio between the first laminating roll and the second laminating roll has such a relationship, dents in the product film can be more stably suppressed. On the other hand, at 25° C., the ratio of the hardness R2 of the second laminating roll 3b to the hardness R1 of the first laminating roll 3a (R2 / R1) is, for example, 2.0 or less, preferably 1.8 or less, and more preferably 1.60 or less.

[0015] The first laminating roll 3a on the protective film 1 side is typically softer than the second laminating roll 3b on the product film 2 side. The hardness R1 of the first laminating roll 3a at 25°C is, for example, 30-120, preferably 50-90, and more preferably 60-80. The hardness R2 of the second laminating roll 3b at 25°C is, for example, 50 to 130, preferably 70 to 110, and more preferably 85 to 95. The hardness of the laminating roll is a durometer hardness, and is measured in accordance with JIS K 6253, for example.

[0016] In the bonding step, the protective film 1 and the product film 2 may be bonded together using an adhesive layer or a pressure-sensitive adhesive layer. In one embodiment, the protective film 1 and the product film 2 are bonded together using a pressure-sensitive adhesive layer 5.

[0017] B. Details of the manufacturing method of the laminated film The method for producing the laminated film will be described in detail below. In a method for producing a laminated film according to one embodiment, first, a protective film 1 and a product film 2 are prepared.

[0018] B-1.Product film The product film 2 may have any appropriate configuration. The product film 2 is typically long. The product film 2 may have a single-layer structure or a laminated structure in which two or more layers are laminated. In the illustrated example, the product film 2 has a single-layer structure. The thickness of the product film 2 is, for example, 10 μm to 100 μm, and preferably 25 μm to 70 μm.

[0019] The product film 2 is typically made of any appropriate resin material. Examples of resin materials that can be used to make 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. Note that (meth)acrylic resins refer to acrylic resins and / or methacrylic resins. These resin materials can be used alone or in combination.

[0020] Among the resin materials constituting the product film 2, PC resin, COP resin, and (meth)acrylic resin are preferred, and PC resin is more preferred. When the product film is made of such a resin material, the indentation modulus of the product film can be stably adjusted to fall within the above-mentioned range.

[0021] Examples of PC resins include PC resins containing structural units derived from dihydroxy compounds. Specific examples of dihydroxy compounds 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, and 9,9-bis( 4-(2-hydroxyethoxy)-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-cyclohexyl phenyl)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, and 9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene.In addition to the structural units derived from the above dihydroxy compounds, the PC resin may also contain structural units derived from dihydroxy compounds such as isosorbide, isomannide, isoidet, spiroglycol, dioxane glycol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol (CHDM), tricyclodecanedimethanol (TCDDM), and bisphenols.

[0022] Details of the above-mentioned PC resins are described, for example, in JP-A No. 2012-67300 and Japanese Patent No. 3325560. The descriptions in these patent documents are incorporated herein by reference.

[0023] The product film 2 may be, for example, an optical film such as a retardation film, and preferably a retardation film.

[0024] The retardation film is typically prepared by stretching a resin film made of the above-mentioned resin material in a predetermined direction. Any appropriate stretching method can be adopted. The retardation film typically has a slow axis in the stretching direction. In one embodiment, the refractive index of the retardation film satisfies the relationship nx>ny.

[0025] The retardation film may 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, and preferably 135 nm to 155 nm. The retardation film may 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, and preferably 250 nm to 290 nm.

[0026] B-2. Protective film The protective film 1 can protect the surface of the product film 2 by being attached to the product film 2. The protective film 1 can have any appropriate configuration. The protective film 1 is typically long. The protective film 1 may have a single-layer structure or a laminated structure in which two or more layers are laminated. In the illustrated example, the protective film 1 has a single-layer structure. The thickness of the protective film 1 is, for example, 10 μm to 80 μm, and preferably 30 μm to 60 μm.

[0027] The protective film 1 is typically made of any appropriate resin material. Examples of resin materials that make up the protective film 1 include olefin-based resins, COP-based resins, polyester-based resins, cellulose-based resins, PC-based resins, (meth)acrylic resins, polyvinyl acetal-based resins, polyamide-based resins, polyimide-based resins, polyethersulfone-based resins, polysulfone-based resins, polystyrene-based resins, acetate-based resins, thermosetting resins, and ultraviolet-setting resins. These resin materials may be used alone or in combination.

[0028] Among the resin materials constituting the protective film 1, preferred is an olefin-based resin. Examples of olefin-based resins include polyethylene (PE) and polypropylene (PP). When the protective film is made of such a resin material, the indentation modulus of the protective film can be stably adjusted to fall within the above-mentioned range.

[0029] 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, but not on the product film 2. Hereinafter, the protective film 1 laminated with the adhesive layer 5 may be referred to as an adhesive layer-attached protective film 6.

[0030] Any appropriate method can be used as a method for laminating the pressure-sensitive adhesive layer 5. The pressure-sensitive adhesive layer 5 may be formed on the surface of the film (protective film 1 and / or product film 2) by direct printing or by transfer printing. In the case of direct printing, the pressure-sensitive adhesive composition is applied directly to the surface of the film to form the pressure-sensitive adhesive layer 5. In the case of transfer printing, the pressure-sensitive adhesive composition is applied to the surface of a release liner to form the pressure-sensitive adhesive layer 5, and then the pressure-sensitive adhesive layer 5 is attached to the film.

[0031] The storage modulus of the pressure-sensitive adhesive layer 5 at 25°C is, for example, 1.0 × 10 3 Pa ~ 9.0 × 10 6 Pa, preferably 1.0×10 4 Pa ~ 9.0 × 10 5 When the storage modulus of the pressure-sensitive adhesive layer is within this range, dents on the product film can be stably suppressed. The storage modulus of the pressure-sensitive adhesive layer is measured, for example, in a shear mode at a constant temperature (25° C.) and a frequency of 1 Hz in accordance with JIS K 6868.

[0032] The thickness of the pressure-sensitive adhesive layer 5 is, for example, 10 μm or less, preferably 5 μm or less, more preferably less than 5 μm, and even more preferably 4 μm or less. Even when the thickness of the pressure-sensitive adhesive layer is within this range, the indentation elastic modulus ratio (E2 / E1) of the film and the hardness ratio (R2 / R1) of the lamination roll satisfy the above-mentioned relationship, so that dents in the product film can be sufficiently suppressed. Furthermore, a thinner laminated film can be achieved. On the other hand, the lower limit of the thickness of the pressure-sensitive adhesive layer 5 is typically 1 μm.

[0033] The pressure-sensitive adhesive layer 5 may be composed of any appropriate pressure-sensitive adhesive. Examples of pressure-sensitive adhesives include (meth)acrylic pressure-sensitive adhesives, rubber pressure-sensitive adhesives, silicone pressure-sensitive adhesives, polyester pressure-sensitive adhesives, urethane pressure-sensitive adhesives, epoxy pressure-sensitive adhesives, and polyether pressure-sensitive adhesives. By adjusting the type, number, combination, and compounding ratio of monomers forming the base resin of the pressure-sensitive adhesive, as well as the amount of cross-linking agent, reaction temperature, reaction time, etc., a pressure-sensitive adhesive having desired properties depending on the purpose can be prepared. The base resin of the pressure-sensitive adhesive may be used alone or in combination of two or more types. Among such pressure-sensitive adhesives, a (meth)acrylic pressure-sensitive adhesive (a (meth)acrylic pressure-sensitive adhesive composition) is preferable.

[0034] A (meth)acrylic pressure-sensitive adhesive composition typically contains a (meth)acrylic polymer as a main component. The content of the (meth)acrylic polymer in the solid content of the pressure-sensitive adhesive composition is, for example, 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more. On the other hand, the upper limit of the content of the (meth)acrylic polymer in the solid content of the pressure-sensitive adhesive composition is typically 100% by mass.

[0035] The (meth)acrylic polymer contains alkyl (meth)acrylate as a monomer unit as a main component. In the (meth)acrylic polymer, the content of the structural units derived from 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 the structural units derived from alkyl (meth)acrylate is, for example, 98% by mass or less, for example, 95% by mass or less, or for example, 90% by mass or less. Examples of the alkyl group of the alkyl (meth)acrylate include linear or branched alkyl groups having 1 to 18 carbon atoms. The average number of carbon atoms in the alkyl group is preferably 3 to 9, and more preferably 3 to 6. Of the alkyl (meth)acrylates, butyl acrylate is preferred.

[0036] Examples of monomers (comonomers) constituting the (meth)acrylic polymer include, in addition to alkyl (meth)acrylates, carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, and heterocyclic ring-containing vinyl monomers. Representative examples of copolymerizable monomers include acrylic acid, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, benzyl acrylate, phenoxyethyl acrylate, and N-vinyl-2-pyrrolidone. The copolymerizable monomers may be used alone or in combination. Among the copolymerizable monomers, preferred are acrylic acid, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, and benzyl acrylate. In the (meth)acrylic polymer, the content of the structural units derived from the copolymerization monomer is, for example, 30% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less, whereas the content of the structural units derived from the copolymerization monomer is, for example, 0% by mass or more, for example, 3% by mass or more, or for example, 10% by mass or more.

[0037] 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 in terms of styrene. If the weight-average molecular weight Mw is within this range, a pressure-sensitive adhesive layer with excellent durability (particularly heat resistance) can be obtained. The weight average molecular weight Mw (Mw / Mn) of the (meth)acrylic polymer relative to the number average molecular weight 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.

[0038] The acrylic pressure-sensitive adhesive composition preferably contains a silane coupling agent and / or a crosslinking agent. Examples of the silane coupling agent include an epoxy group-containing silane coupling agent. The content of the silane coupling agent is, for example, 0.001 to 5 parts by mass per 100 parts by mass of the (meth)acrylic polymer.

[0039] Examples of crosslinking agents include isocyanate-based crosslinking agents and peroxide-based crosslinking agents. The crosslinking agents may be used alone or in combination. Among the crosslinking agents, isocyanate-based crosslinking agents are preferred. The content of the crosslinking agent is, for example, 0.01 parts by mass or more, preferably 0.1 parts by mass or more, and more preferably 0.5 parts by mass or more, relative to 100 parts by mass of the (meth)acrylic polymer. 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, even more preferably 3.0 parts by mass or less, and particularly preferably 1.0 part by mass or less.

[0040] B-4. First laminating roll and second laminating roll The first laminating roll 3a has any appropriate configuration. The first laminating roll 3a typically has a cylindrical shape extending in a predetermined direction. The outer diameter of the first laminating roll 3a is, for example, 100 mm to 500 mm, and preferably 150 mm to 300 mm. The outer peripheral surface of the first laminating roll 3a is softer than the outer peripheral surface of the second laminating roll 3b. The outer peripheral surface of the first laminating roll 3a has the above-mentioned hardness R1.

[0041] The first laminating roll 3a is made of any suitable material. Examples of the material of the first laminating roll 3a include metal, semi-metal, and rubber, and preferably rubber. Examples of rubber include silicone rubber, butyl rubber, and SEBS, and more preferably silicone rubber.

[0042] In one embodiment, the first laminating roll 3a includes a roll body having a cylindrical shape and a shaft inserted into the roll body. The roll body is typically made of the above-mentioned rubber. The range of the outer diameter of the roll body is typically the same as the range of the outer diameter of the first laminating roll described above. The outer peripheral surface of the roll body is softer than the outer peripheral surface of the second laminating roll 3b. The outer peripheral surface of the roll body has the above-mentioned hardness R1. The shaft is typically made of the above-mentioned metals, and when the shaft is inserted into the roll body, both ends of the shaft are exposed from the roll body.

[0043] The second laminating roll 3b has any appropriate configuration. The second laminating roll 3b typically has a cylindrical shape extending in a predetermined direction. The outer diameter of the second laminating roll 3b is, for example, 100 mm to 500 mm, and preferably 150 mm to 300 mm. The outer peripheral surface of the second laminating roll 3b has the above-mentioned hardness R2.

[0044] The second laminating roll 3b is made of any suitable material. Examples of the material of the second laminating roll 3b include metals and semi-metals, and preferably metals. Examples of metals include iron, copper, aluminum, chromium, nickel, and alloys thereof. Of the metals, iron is preferred.

[0045] In one embodiment, the second laminating roll 3b includes a cylindrical shaft and a plated coating provided on the outer circumferential surface of the shaft. The shaft is typically made of the metals listed above. The plated coating is typically made of an alloy of the metals listed above. In one embodiment, the plated coating is provided over the entire outer circumferential surface of the shaft. The thickness of the plated coating is arbitrarily and appropriately adjusted so that the hardness R2 of the outer circumferential surface of the second laminating roll 3b falls within the above-mentioned range.

[0046] The second laminating roll 3b is disposed radially opposite the first laminating roll 3a. The outer circumferential surfaces of the first laminating roll 3a and the second laminating roll 3b typically contact each other before the protective film 1 and the product film 2 are fed between them.

[0047] In one embodiment, one of the first laminating roll 3a and the second laminating roll 3b is pressed toward the other, whereby the first laminating roll 3a and the second laminating roll 3b typically form a nip N. The nip pressure (pressing force of the laminating roll) is, for example, 1 MPa to 100 MPa, and preferably 5 MPa to 50 MPa.

[0048] B-5. Details of the lamination process In the laminating step, the protective film 1 and the product film 2 are supplied to pass through the nip N. In one embodiment, the pressure-sensitive adhesive layer-attached protective film 6 and the product film 2 are supplied to pass through the nip N. In the illustrated example, the protective film 1 (adhesive layer-attached protective film 6) passes through a first transport roller 41 and is supplied between the first laminating roll 3a and the second laminating roll 3b. The product film 2 passes through a second transport roller 42 and is supplied between the first laminating roll 3a and the second laminating roll 3b. Each of the first transport roller 41 and the second transport roller 42 is movable relative to the first laminating roll 3a.

[0049] In the lamination step, the tension applied to the protective film 1 is, for example, 50 N / m to 500 N / m, and preferably 100 N / m to 300 N / m. When the tension applied to the protective film in the lamination step is in this range, the protective film and the product film can be smoothly laminated together, and the occurrence of dents in the product film can be more stably prevented. The tension applied to the protective film 1 can be adjusted appropriately by moving the first transport roller 41 relative to the first laminating roll 3a.

[0050] In the lamination step, the tension applied to the product film 2 is, for example, 50 N / m to 500 N / m, and preferably 100 N / m to 300 N / m. When the tension applied to the product film in this range in the lamination step, the protective film and the product film can be more smoothly laminated together, and the occurrence of dents in the product film can be more reliably prevented. The tension applied to the product film 2 can be adjusted appropriately by moving the second transport roller 42 relative to the first laminating roll 3a.

[0051] The supply 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, and preferably 15 m / min to 30 m / min.

[0052] When the protective film 1 passes between the first laminating roll 3a and the second laminating roll 3b (nip N), it typically comes into contact with the outer peripheral surface of the first laminating roll 3a. When the product film 2 passes between the first laminating roll 3a and the second laminating roll 3b (nip N), it typically comes into contact with the outer peripheral surface of the second laminating roll 3b. At this time, the protective film 1 and the product film 2 are appropriately pressed by the first laminating roll 3a and the second laminating roll 3b, whereby the protective film 1 and the product film 2 are pressure-bonded together, typically by the pressure-sensitive adhesive layer 5.

[0053] In this way, a long laminate film 100 is manufactured. In the illustrated example, the laminate film 100 is taken up as needed after passing under the third conveyor roller 43. The third conveyor roller 43 may be movable relative to the first laminating roll 3a.

[0054] C. Laminated film The laminate film 100 shown in the figure comprises a protective film 1, a pressure-sensitive adhesive layer 5, and a product film 2, in this order. Such a laminate film 100 can be used for any appropriate application. The product film 2 may be used with the protective film 1 attached (i.e., the laminate film 100 itself), or may be used after the protective film 1 and the pressure-sensitive adhesive layer 5 have been peeled off. The product film 2 can be used, typically, for optical applications such as image display devices. In particular, the product film 2 is significantly less susceptible to scratches, stains, and dents, and therefore can be suitably used for image display devices such as smartphones and tablet PCs. [Example]

[0055] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring each property are as follows. Unless otherwise specified, "parts" and "%" in the examples and comparative examples are based on mass. The methods for measuring each property in the examples and comparative examples are as follows.

[0056] (1) Measurement of the indentation elastic modulus of the protective film and the product film The indentation modulus of each of the protective films and product films used in the examples and comparative examples was measured under the following measurement conditions using a nanoindenter method in accordance with ISO 14577. The indentation modulus of the protective film, E1, the indentation modulus of the product film, E2, and E2 / E1 are shown in Table 1. Equipment: Nanoindenter (manufactured by nanomechanics) Sample size: 10 x 10 mm Indenter: square pyramid indenter Measurement temperature: 25℃ Measurement humidity: 55%RH Maximum pressing force: 25mN Indentation speed: 100nm / sec Hold time: 2 seconds Load unloading speed: 2.5mN / sec Calculation method: Compliant with ISO14577

[0057] (2) Measurement of the hardness of the first laminating roll and the second laminating roll The hardness of each of the first laminating roll and the second laminating roll used in the examples and comparative examples was measured in accordance with JIS K 6253. Table 1 shows the hardness R1 of the first laminating roll, the hardness R2 of the second laminating roll, and R2 / R1.

[0058] (3) Identifying dents on laminated film The laminated films prepared in the examples and comparative examples were integrated with a polarizing plate and then attached to an aluminum reflector, and the appearance of the films was checked by fluorescent light reflection and evaluated according to the following criteria. The results are shown in Table 1. ◯: No visible dent shape. ×: The shape of the dent is visible.

[0059] <<Product Film Preparation>> <Preparation Example 1> A resin film composed of a PC resin was prepared in the same manner as in Production Example 9 of JP 2022-150732 A. The resin film had a long shape and a thickness of 130 μm. Next, the resin film was uniaxially stretched with fixed ends in the transverse direction at a stretching temperature of 150°C and a stretching ratio of 2.8 times to prepare a retardation film as a product film. The retardation film had a long shape. The thickness of the retardation film was 47 μm. The in-plane retardation Re(550) of the retardation film was 140 nm.

[0060] <Preparation Example 2> A resin film composed of a COP resin (manufactured by Zeon Corporation, product number "ZF16") was uniaxially stretched in the transverse direction with fixed ends at a stretching temperature of 170°C and a stretching ratio of 2.8 times to prepare a retardation film as a product film. The retardation film had a long shape. The thickness of the retardation film was 40 μm. The in-plane retardation Re(550) of the retardation film was 140 nm.

[0061] <Preparation Example 3> An optical film was prepared as a product film by simultaneously biaxially stretching an acrylic resin film (manufactured by Kaneka Corporation, product name "HTX-Z") at a stretching temperature of 125°C and a stretching ratio of 4 times, with fixed ends. The optical film had a long shape. The thickness of the optical film was 40 μm. The in-plane retardation Re(550) of the optical film was 0.5 nm.

[0062] <<Preparation of protective film with adhesive layer>> <Preparation Example 4> An acrylic adhesive layer was laminated on the surface of a polyethylene (PE) film used as a protective film to prepare a protective film with an adhesive layer. The thickness of the PE film was 30 μm. The thickness of the acrylic adhesive layer was 3 μm.

[0063] <Preparation Example 5> An acrylic adhesive layer was formed on the surface of a polypropylene (PP) film as a protective film to prepare a protective film with an adhesive layer. The thickness of the PP film was 30 μm. The thickness of the acrylic adhesive layer was 3 μm.

[0064] <Preparation Example 6> An acrylic adhesive layer was formed on the surface of a polyethylene terephthalate (PET) film as a protective film to prepare a protective film with an adhesive layer. The thickness of the PET film was 50 μm. The thickness of the acrylic adhesive layer was 3 μm.

[0065] [Examples 1 to 4, Comparative Examples 1 to 4] A first laminating roll and a second laminating roll were prepared. The first laminating roll had a roll body made of silicone rubber (Si rubber) and a shaft made of metal. The outer diameter of the roll body was 250 mm. The second laminating roll had a shaft made of iron (Fe) and a plated coating made of chromium, and the outer diameter of the second laminating roll was 250 mm.

[0066] Next, the first laminating roll and the second laminating roll were arranged facing each other so that they were in contact with each other in the radial direction. Furthermore, both ends of the second laminating roll were pressed against the first laminating roll at 10 MPa by a cylinder. Furthermore, the first laminating roll and the second laminating roll were each rotated.

[0067] Next, the pressure-sensitive adhesive layer-attached protective film and the product film obtained in the preparation examples shown in Table 1 were each supplied between the first laminating roll and the second laminating roll. The supply speed (line speed) of the pressure-sensitive adhesive layer-attached protective film and the product film was 15 m / min. The protective film contacted the outer peripheral surface of the first laminating roll (roll body), and the product film contacted the outer peripheral surface (plated coating) of the second laminating roll.

[0068] When passing between the first laminating roll and the second laminating roll, the protective film and the product film were pressed by the first laminating roll and the second laminating roll, and were bonded together by the pressure-sensitive adhesive layer. As a result of the above, a laminated film having a structure of protective film / adhesive layer / product film (retardation film) was obtained.

[0069] Comparative Example 5 A laminated film was obtained in the same manner as in Example 1, except that the first laminating roll and the second laminating roll were swapped so that the laminating roll with a shaft made of Fe was in contact with the protective film and the laminating roll with a roller body made of Si rubber was in contact with the product film.

[0070] [Table 1]

[0071] [evaluation] As is clear from Table 1, when the indentation elastic modulus E2 of the product film / the indentation elastic modulus E1 of the protective film exceeds 1.0 and the hardness R2 of the second laminating roll / the hardness R1 of the first laminating roll exceeds 1.0, dents in the product film can be sufficiently suppressed. [Industrial Applicability]

[0072] The method for producing a laminated film of the present invention is used to produce product films that can be used in various industrial products, and is particularly suitable for producing optical films (specifically, retardation films). [Explanation of symbols]

[0073] 1 protective film 2. Product film 3a First laminating roll 3b Second laminating roll 5. Adhesive layer 100 Laminated Film

Claims

1. The method includes a lamination step of laminating the protective film and the product film by passing them between a first lamination roll and a second lamination roll, In the laminating step, the first laminating roll is located on the opposite side of the protective film from the product film, and the second laminating roll is located on the opposite side of the product film from the protective film, At 25°C, the indentation elastic modulus E2 of the product film relative to the indentation elastic modulus E1 of the protective film exceeds 1.0; A method for producing a laminated film, wherein at 25°C, a hardness R2 of the second laminating roll relative to a hardness R1 of the first laminating roll exceeds 1.

0.

2. The method for producing a laminated film according to claim 1 , wherein the protective film and the product film are bonded together by an adhesive layer.

3. The method for producing a laminated film according to claim 2 , wherein the thickness of the pressure-sensitive adhesive layer is less than 5 μm.

Images