Method for producing laminated film

Abstract

The invention provides a method for manufacturing a laminated film, which can protect the surface of a product film and can restrain marks in the product film. A method for manufacturing a laminated film according to an embodiment of the present invention includes a bonding step. In the bonding step, the protective film and the product film pass between the first bonding roller and the second bonding roller and are bonded. In the bonding step, the first bonding roller is located on the opposite side of the product film with respect to the protective film, and the second bonding roller is located on the opposite side of the product film with respect to the protective film. At 25 DEG C, the press-in elastic modulus E2 of the product film is greater than 1.0 with respect to the press-in elastic modulus E1 (E2 / E1) of the protective film. At 25 DEG C, the hardness R2 of the second bonding roller is greater than 1.0 with respect to the hardness R1 (R2 / R1) of the first bonding roller.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a laminated film. Background Art

[0002] Conventionally, resin films have been widely used in various industrial products. As an example of such a resin film, an optical film used in an image display device can be cited. The optical film is required to have stricter standards regarding scratches and stains than resin films used in other applications (for example, 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 stains on the surface of the optical film.

[0003] As such a protective film, for example, a polyester film having excellent mechanical strength and transparency has been proposed (for example, refer to Patent Document 1).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-176685 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] In recent years, the development of new uses for image display devices has progressed. Depending on the use of the image display device, sometimes a resin film (representatively an optical film) is required to have an appearance that is much more excellent than before. In particular, scratches at a level that has not been a problem so far may have a substantial adverse effect on the performance of the image display device.

[0009] 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 a product film and suppress scratches in the product film.

[0010] Means for Solving the Problems

[0011] [1] The method for manufacturing a laminated film according to an embodiment of the present invention includes a laminating step. In this laminating step, a protective film and a product film are passed between a first laminating roll and a second laminating roll and laminated. In this laminating step, the first laminating roll is located on the side opposite to the product film with respect to the protective film, and the second laminating roll is located on the side opposite to the protective film with respect to the product film. At 25°C, the indentation modulus of elasticity E2 of the product film is more than 1.0 with respect to the indentation modulus of elasticity E1 of the protective film. At 25°C, the hardness R2 of the second laminating roll is more than 1.0 with respect to the hardness R1 of the first laminating roll.

[0012] [2]According to the method for manufacturing a laminated film described in [1] above, the protective film and the product film may also be adhered using an adhesive layer.

[0013] [3]According to the method for manufacturing a laminated film described in [2] above, the thickness of the adhesive layer may also be less than 5 μm.

[0014] Advantages of the Invention

[0015] According to an embodiment of the present invention, the surface of the product film can be protected, and scratches in the product film can be suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic configuration diagram for explaining the method for manufacturing a laminated film according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments. In addition, for the sake of clarity, compared with the embodiments, the width, thickness, shape, etc. of each part may be schematically shown in the drawings, but this is only an example and does not limit the interpretation of the present invention.

[0018] (Definition of Terms and Symbols)

[0019] The terms and symbols in this specification are defined as follows.

[0020] (1) Refractive Index (nx, ny, nz)

[0021] "nx" is the refractive index in the direction in which the refractive index in the plane is the largest (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.

[0022] (2) In-Plane Phase Difference (Re)

[0023] "Re(λ)" is the in-plane phase difference measured by light of wavelength λ nm at 23°C. For example, "Re(550)" is the in-plane phase difference measured by light of wavelength 550 nm at 23°C. When the thickness of the layer (film) is set to d (nm), Re(λ) is obtained by the formula: Re(λ) = (nx - ny) × d.

[0024] A. Outline of the Method for Manufacturing a Laminated Film

[0025] Figure 1 It is a schematic configuration diagram for explaining the method for manufacturing a laminated film according to one embodiment of the present invention.

[0026] The manufacturing method of the laminated film of one embodiment includes a laminating step. In the laminating step, the protective film 1 and the product film 2 are passed between the first laminating roller 3a and the second laminating roller 3b and laminated. In the laminating step, the first laminating roller 3a is located on the side opposite to the product film 2 with respect to the protective film 1, and the second laminating roller 3b is located on the side opposite to the protective film 1 with respect to the product film 2. At 25 °C, the indentation modulus of elasticity E2 of the product film 2 with respect to the indentation modulus of elasticity E1 of the protective film 1 (E2 / E1) is more than 1.0. At 25 °C, the hardness R2 of the second laminating roller 3b with respect to the hardness R1 of the first laminating roller 3a (R2 / R1) is more than 1.0.

[0027] The present inventors found that: when the product film and the protective film are laminated using the first laminating roller and the second laminating roller, sometimes indentations are formed in the product film. Thus, in-depth research was conducted on the formation of indentations in the product film, and as a result, it was presumed that the indentations in the product film transfer the appearance defects (e.g., shrinkage holes, burns, wrinkles) of the protective film and are formed in the product film during the laminating step.

[0028] The present inventors further studied this insight and found that: if the indentation moduli of elasticity of the protective film and the product film and the hardnesses of the first laminating roller and the second laminating roller are set to a specific relationship, even if the protective film is attached to the product film using the first laminating roller and the second laminating roller, the indentations in the product film can be suppressed.

[0029] Specifically, if the indentation modulus of elasticity E2 of the product film with respect to the indentation modulus of elasticity E1 of the protective film (E2 / E1) is more than 1.0 and the hardness R2 of the second laminating roller with respect to the hardness R1 of the first laminating roller (R2 / R1) is more than 1.0, the transfer of the appearance defects of the protective film to the product film can be suppressed. Therefore, the protective film can be attached to the product film to protect the surface of the product film, and the indentations in the product film can be suppressed.

[0030] At 25 °C, the indentation modulus of elasticity E2 of the product film 2 with respect to the indentation modulus of elasticity E1 of the protective film 1 (E2 / E1) is preferably 1.10 or more, more preferably 1.20 or more, and further preferably 1.30 or more. If the ratio of the indentation moduli of elasticity of the protective film and the product film is in such a relationship, the indentations in the product film can be stably suppressed.

[0031] On the other hand, at 25 °C, the upper limit of the indentation modulus of elasticity E2 of the product film 2 with respect to the indentation modulus of elasticity E1 of the protective film 1 (E2 / E1) is typically 1.70 or less.

[0032] Typically, the protective film 1 is softer than the product film 2.

[0033] 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.

[0034] The indentation elastic 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.

[0035] It should be noted that the indentation elastic modulus of the film is measured, for example, in accordance with ISO14577.

[0036] 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 more, more preferably 1.10 or more, and further preferably 1.30 or more. If the hardness ratio of the first laminating roller to the second laminating roller is in such a relationship, scratches in the product film can be more stably suppressed.

[0037] On the other hand, 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 more preferably 1.60 or less.

[0038] Typically, the first laminating roller 3a on the side of the protective film 1 is softer than the second laminating roller 3b on the side of the product film 2.

[0039] The hardness R1 of the first laminating roller 3a at 25°C is, for example, 30 to 120, preferably 50 to 90, and more preferably 60 to 80.

[0040] The hardness R2 of the second laminating roller 3b at 25°C is, for example, 50 to 130, preferably 70 to 110, and more preferably 85 to 95.

[0041] It should be noted that the hardness of the laminating roller is the hardness measured by a durometer, and is measured, for example, in accordance with JISK 6253.

[0042] In the laminating process, the protective film 1 and the product film 2 can be laminated using an adhesive layer or a bonding agent layer. In one embodiment, the protective film 1 and the product film 2 are laminated using the adhesive layer 5.

[0043] B. Details of the manufacturing method of the laminated film

[0044] Hereinafter, the details of the manufacturing method of the laminated film will be described.

[0045] In the manufacturing method of the laminated film according to one embodiment, first, the protective film 1 and the product film 2 are prepared.

[0046] B-1. Product film

[0047] The product film 2 can have any suitable constitution. Representatively, the product film 2 has an elongated shape. The product film 2 can have a single-layer structure or a laminated structure formed by laminating two or more layers. In the illustrated example, the product film 2 has a single-layer structure.

[0048] The thickness of the product film 2 is, for example, 10 μm to 100 μm, preferably 25 μm to 70 μm.

[0049] Representatively, the product film 2 is made of any suitable resin material. Examples of the resin material constituting the product film 2 include polycarbonate (PC)-based resins, polyvinyl acetal-based resins, cycloolefin (COP)-based resins, (meth)acrylic acid-based resins, cellulose ester-based resins, cellulose-based resins, polyester-based resins, polyester carbonate-based resins, olefin-based resins, and polyurethane-based resins. It should be noted that the (meth)acrylic acid-based resin refers to an acrylic acid-based resin and / or a methacrylic acid-based resin. These resin materials can be used alone or in combination.

[0050] Among the resin materials constituting the product film 2, preferably, PC-based resins, COP-based resins, and (meth)acrylic acid-based resins can be mentioned, and more preferably, PC-based resins can be mentioned. If the product film is made of such resin materials, the indentation elastic modulus of the product film can be stably adjusted within the above range.

[0051] As the PC-based resin, for example, a PC-based resin containing a structural unit derived from a dihydroxy compound can be cited. 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)-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-dimethylpropoxy)phenyl)fluorene. In addition to the structural unit derived from the above dihydroxy compound, the PC-based resin may further contain a structural unit derived from a dihydroxy compound such as isosorbide, isomannitol, isoidide, spirodiol, dioxanediol, diethylene glycol (DEG), triethylene glycol (TEG), polyethylene glycol (PEG), cyclohexanedimethanol (CHDM), tricyclodecanedimethanol (TCDDM), and bisphenols.

[0052] Details of the above PC-based resin are described, for example, in Japanese Patent Application Laid-Open No. 2012-67300 and Japanese Patent No. 3325560. The descriptions in these patent documents are incorporated herein by reference.

[0053] As the article film 2, for example, an optical film such as a retardation film can be cited, and preferably a retardation film can be cited.

[0054] Typically, the retardation film is prepared by stretching a resin film made of the above resin material in a specified direction. Any suitable stretching method can be adopted.

[0055] Typically, the retardation film has a slow axis in the stretching direction. In one embodiment, the refractive indices of the retardation film show the relationship of nx > ny.

[0056] 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.

[0057] In addition, 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.

[0058] B-2. Protective film

[0059] By attaching to the product film 2, the protective film 1 can protect the surface of the product film 2. The protective film 1 can have any suitable constitution. Typically, the protective film 1 has a long strip shape. The protective film 1 can have a single-layer structure or a laminated structure formed by laminating two or more layers. In the illustrated example, the protective film 1 has a single-layer structure.

[0060] The thickness of the protective film 1 is, for example, 10 μm to 80 μm, preferably 30 μm to 60 μm.

[0061] Typically, the protective film 1 is made of any suitable resin material. Examples of the resin material constituting 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, polyethersulfone resins, polysulfone resins, polystyrene resins, acetate resins, thermosetting resins, and ultraviolet curable resins. These resin materials can be used alone or in combination.

[0062] Among the resin materials constituting the protective film 1, olefin resins are preferably exemplified. Examples of olefin resins include polyethylene (PE) and polypropylene (PP). If the protective film is made of such a resin material, the indentation modulus of the protective film can be stably adjusted within the above range.

[0063] B-3. Adhesive layer

[0064] 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 is sometimes referred to as the protective film 6 with an adhesive layer.

[0065] As a method for laminating the adhesive layer 5, any suitable method can be adopted. The adhesive layer 5 can be formed on the surface of the film (protective film 1 and / or product film 2) by direct printing, or can be formed by transfer printing. In the case of direct printing, the adhesive composition is directly coated on the surface of the film to form the adhesive layer 5. In the case of transfer printing, the adhesive composition is coated on the surface of the release liner to form the adhesive layer 5, and then the adhesive layer 5 is attached to the film.

[0066] The storage elastic modulus of the adhesive layer 5 at 25°C is, for example, 1.0×10 3 Pa to 9.0×10 6 Pa, preferably 1.0×10 4 Pa to 9.0×10 5 Pa. If the storage elastic modulus of the adhesive layer is in such a range, the indentation in the product film can be stably suppressed.

[0067] It should be noted that the storage elastic modulus of the adhesive layer is measured, for example, in shear mode, at a constant temperature (25°C), a frequency of 1 Hz, and in accordance with JIS K 6868.

[0068] The thickness of the adhesive layer 5 is, for example, 10 μm or less, preferably 5 μm or less, more preferably less than 5 μm, and further preferably 4 μm or less. Even if the thickness of the adhesive layer is in such a range, due to the relationship between the indentation elastic modulus ratio (E2 / E1) of the film and the hardness ratio (R2 / R1) of the laminating roll as described above, the indentation in the product film can be sufficiently suppressed. In addition, the thickness reduction of the laminated film can be achieved.

[0069] On the other hand, the lower limit of the thickness of the adhesive layer 5 is typically 1 μm.

[0070] The adhesive layer 5 can be composed of any suitable 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 types, numbers, combinations, and mixing ratios of the monomers of the base resin forming the adhesive, as well as the mixing amount of the crosslinking agent, reaction temperature, reaction time, etc., an adhesive having desired properties corresponding to the purpose can be prepared. The base resin of the adhesive can be used alone or in combination of two or more. Among such adhesives, (meth)acrylic adhesives ((meth)acrylic adhesive compositions) are preferably listed.

[0071] (Meth)acrylic acid-based adhesive compositions typically contain a (meth)acrylic acid-based polymer as a main component. The content ratio of the (meth)acrylic acid-based polymer in the solid components of the 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 ratio of the (meth)acrylic acid-based polymer in the solid components of the adhesive composition is typically 100% by mass.

[0072] (Meth)acrylic acid-based polymers contain (meth)acrylic acid alkyl esters as a main component as monomer units. In the (meth)acrylic acid-based polymer, the content ratio of the constituent units derived from (meth)acrylic acid alkyl esters 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 ratio of the constituent units derived from (meth)acrylic acid alkyl esters is, for example, 98% by mass or less, further for example 95% by mass or less, or for example 90% by mass or less.

[0073] Examples of the alkyl group of the (meth)acrylic acid alkyl ester include linear or branched alkyl groups having 1 to 18 carbon atoms. The average carbon number of the alkyl group is preferably 3 to 9, and more preferably 3 to 6. Among the (meth)acrylic acid alkyl esters, butyl acrylate is preferably mentioned.

[0074] As monomers (comonomers) constituting the (meth)acrylic acid-based polymer, in addition to (meth)acrylic acid alkyl esters, carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, (meth)acrylic esters containing an aromatic ring, heterocyclic ring-containing vinyl monomers, etc. can be mentioned. As representative examples of the comonomers, acrylic acid, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, benzyl acrylate, phenoxyethyl acrylate, N-vinyl-2-pyrrolidone can be mentioned. The comonomers can be used alone or in combination. Among the comonomers, acrylic acid, 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, benzyl acrylate are preferably mentioned.

[0075] In the (meth)acrylic acid-based polymer, the content ratio of the constituent 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 ratio of the constituent units derived from the comonomers is, for example, 0% by mass or more, further for example 3% by mass or more, or for example 10% by mass or more.

[0076] The weight-average molecular weight Mw of the (meth)acrylic polymer is, for example, from 200,000 to 3,000,000, preferably from 1,000,000 to 2,500,000, more preferably from 1,200,000 to 2,500,000, and still more preferably from 1,500,000 to 2,500,000. The weight-average molecular weight Mw is calculated, for example, by styrene conversion based on the results measured by GPC. If the weight-average molecular weight Mw is in such a range, an adhesive layer excellent in durability (especially heat resistance) can be obtained.

[0077] 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, for example, 5.0 or less, preferably 4.0 or less.

[0078] The acrylic adhesive composition preferably contains a silane coupling agent and / or a crosslinking agent. As the silane coupling agent, for example, a silane coupling agent containing an epoxy group can be cited. The content of the silane coupling agent is, for example, 0.001 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the (meth)acrylic polymer.

[0079] As the crosslinking agent, for example, an isocyanate-based crosslinking agent and a peroxide-based crosslinking agent can be cited. The crosslinking agent can be used alone or in combination. Among the crosslinking agents, an isocyanate-based crosslinking agent is preferably cited. 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, still more preferably 3.0 parts by mass or less, and particularly preferably 1.0 parts by mass or less.

[0080] B-4. The first laminating roll and the second laminating roll

[0081] The first laminating roll 3a has any suitable configuration. Representatively, the first laminating roll 3a has a cylindrical shape extending in a predetermined direction. The outer diameter of the first laminating roll 3a is, for example, from 100 mm to 500 mm, preferably from 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.

[0082] The first laminating roll 3a is made of any suitable material. As the material of the first laminating roll 3a, for example, metal, semi-metal, and rubber can be cited, and rubber is preferably cited. As the rubber, silicone rubber, butyl rubber, and SEBS are preferably cited, and silicone rubber is more preferably cited.

[0083] In one embodiment, the first laminating roll 3a includes a roll main body having a cylindrical shape and a shaft inserted into the roll main body.

[0084] The roll body is typically made of the rubber described above. The range of the outer diameter of the roll body is typically the same as the range of the outer diameter of the first bonding roll described above. The outer peripheral surface of the roll body is softer than the outer peripheral surface of the second bonding roll 3b. The outer peripheral surface of the roll body has the hardness R1 described above.

[0085] The shaft is typically made of the metal described above. In a state where the shaft is inserted into the roll body, both end portions of the shaft protrude from the roll body.

[0086] The second bonding roll 3b has any suitable configuration. The second bonding roll 3b typically has a cylindrical shape extending in a predetermined direction. The outer diameter of the second bonding roll 3b is, for example, 100 mm to 500 mm, preferably 150 mm to 300 mm. The outer peripheral surface of the second bonding roll 3b has the hardness R2 described above.

[0087] The second bonding roll 3b is made of any suitable material. Examples of the material of the second bonding roll 3b include metal and semi-metal, and preferably metal. Examples of the metal include iron, copper, aluminum, chromium, nickel, and alloys thereof. Iron is preferably used among the metals.

[0088] In one embodiment, the second bonding roll 3b includes a shaft having a cylindrical shape and a plating film provided on the outer peripheral surface of the shaft.

[0089] The shaft is typically made of the metal described above. The plating film is typically made of an alloy of the metal described above. In one embodiment, the plating film is provided over the entire outer peripheral surface of the shaft. The thickness of the plating film is adjusted arbitrarily and suitably so that the hardness R2 of the outer peripheral surface of the second bonding roll 3b falls within the above range.

[0090] The second bonding roll 3b is arranged to be radially opposed to the first bonding roll 3a. The outer peripheral surface of the first bonding roll 3a and the outer peripheral surface of the second bonding roll 3b typically come into contact with each other before the protective film 1 and the product film 2 are supplied therebetween.

[0091] In one embodiment, either the first bonding roll 3a or the second bonding roll 3b is pressed against the other. Thus, a nip N is typically formed between the first bonding roll 3a and the second bonding roll 3b.

[0092] The nip pressure (pressing force of the bonding roll) is, for example, 1 MPa to 100 MPa, preferably 5 MPa to 50 MPa.

[0093] B-5. Details of the bonding process

[0094] In the laminating process, the protective film 1 and the product film 2 are supplied in such a manner as to pass through the clamp N. In one embodiment, the protective film 6 with an adhesive layer and the product film 2 are supplied in such a manner as to pass through the clamp N.

[0095] In the illustrated example, the protective film 1 (protective film 6 with an adhesive layer) is supplied between the first laminating roller 3a and the second laminating roller 3b via the first conveying roller 41. In addition, the product film 2 is supplied between the first laminating roller 3a and the second laminating roller 3b via the second conveying roller 42. Each of the first conveying roller 41 and the second conveying roller 42 can move relative to the first laminating roller 3a.

[0096] In the laminating process, 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. In the laminating process, if the tension applied to the protective film is within such a range, the protective film and the product film can be laminated smoothly, and the generation of scratches in the product film can be more stably suppressed.

[0097] The tension applied to the protective film 1 can be appropriately adjusted by moving the first conveying roller 41 relative to the first laminating roller 3a.

[0098] In the laminating process, 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. In the laminating process, if the tension applied to the product film is within such a range, the protective film and the product film can be laminated more smoothly, and the generation of scratches in the product film can be further stably suppressed.

[0099] The tension applied to the product film 2 can be appropriately adjusted by moving the second conveying roller 42 relative to the first laminating roller 3a.

[0100] The supply speed (linear speed) of each of the protective film 1 and the product film 2 in the laminating process is, for example, 5 m / min to 50 m / min, preferably 15 m / min to 30 m / min.

[0101] When the protective film 1 passes between the first laminating roller 3a and the second laminating roller 3b (clamp N), it typically comes into contact with the outer peripheral surface of the first laminating roller 3a. In addition, when the product film 2 passes between the first laminating roller 3a and the second laminating roller 3b (clamp N), it typically comes into contact with the outer peripheral surface of the second laminating roller 3b.

[0102] At this time, the protective film 1 and the product film 2 are appropriately pressed by the first laminating roller 3a and the second laminating roller 3b. Thus, the protective film 1 and the product film 2 are typically crimped using the adhesive layer 5.

[0103] Through the above, a strip-shaped laminated film 100 is manufactured. In the illustrated example, the laminated film 100 is wound up as needed after passing through the third conveying roller 43. The third conveying roller 43 can also be capable of relative movement with respect to the first laminating roller 3a.

[0104] C. Laminated film

[0105] The laminated film 100 in the illustrated example sequentially includes a protective film 1, an adhesive layer 5, and a product film 2. Such a laminated film 100 can be used for any suitable purpose. The product film 2 can be used in a state where the protective film 1 is attached (i.e., in the state of the laminated film 100), or can be used after the protective film 1 and the adhesive layer 5 are peeled off. The product film 2 is typically used for optical applications such as image display devices. In particular, since the product film 2 significantly suppresses scratches, stains, and indentations, it can be suitably used for image display devices such as smartphones and tablet PCs.

[0106] Examples

[0107] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The measurement methods for each characteristic are as follows. It should be noted that unless otherwise specified, "parts" and "%" in the examples and comparative examples are based on mass. In addition, the measurement methods for each characteristic in the examples and comparative examples are as follows.

[0108] (1) Measurement of the indentation elastic modulus of each of the protective film and the product film

[0109] According to ISO14577, the indentation elastic modulus of each of the protective film and the product film used in the examples and comparative examples was measured by 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.

[0110] Device: Nanoindentation instrument (manufactured by nanomechanics)

[0111] Sample size: 10×10 mm

[0112] Indenter: Square pyramid indenter

[0113] Measurement temperature: 25°C

[0114] Measurement humidity: 55% RH

[0115] Maximum indentation load: 25 mN

[0116] Indentation speed: 100 nm / second

[0117] Holding time: 2 seconds

[0118] Load unloading speed: 2.5 mN / second

[0119] Calculation method: Based on ISO14577

[0120] (2) Measurement of the hardness of the first laminating roller and the second laminating roller respectively

[0121] The hardness of the first laminating roller and the second laminating roller used in the examples and comparative examples was measured according to 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.

[0122] (3) Scratch determination of the laminated film

[0123] After being integrated with the polarizing plate and adhered to the aluminum reflector, the scratches of the laminated films prepared in the examples and comparative examples were confirmed through the appearance reflected by the fluorescent lamp, and evaluated according to the following criteria. The results are shown in Table 1.

[0124] 〇: No scratch shape was visually confirmed.

[0125] ×: A scratch shape was visually confirmed.

[0126] <<Preparation of the product film>>

[0127] <Preparation Example 1>

[0128] The resin film made of a PC-based resin was prepared in the same manner as in Production Example 9 of Japanese Unexamined Patent Application Publication No. 2022-150732. The resin film has a long strip shape, and the thickness of the resin film is 130 μm.

[0129] 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 retardation film as the product film. The retardation film has a long strip shape. The thickness of the retardation film is 47 μm. The in-plane retardation Re(550) of the retardation film is 140 nm.

[0130] <Preparation Example 2>

[0131] The resin film made of a COP-based resin (manufactured by Zeon Corporation, part number "ZF16") was subjected to fixed-end transverse uniaxial stretching at a stretching temperature of 170 °C and a stretching ratio of 2.8 times to prepare a retardation film as the product film. The retardation film has a long strip shape. The thickness of the retardation film is 40 μm. The in-plane retardation Re(550) of the retardation film is 140 nm.

[0132] <Preparation Example 3>

[0133] A resin film made of an acrylic resin (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 times to prepare an optical film as a product film. The optical film has a long strip shape. The thickness of the optical film is 40 μm. The in-plane retardation Re(550) of the optical film is 0.5 nm.

[0134] <<Preparation of a Protective Film with an Adhesive Layer>>

[0135] <Preparation Example 4>

[0136] An acrylic adhesive layer was laminated on the surface of a polyethylene (PE) film as a protective film to prepare a protective film with an adhesive layer. The thickness of the PE film is 30 μm. The thickness of the acrylic adhesive layer is 3 μm.

[0137] <Preparation Example 5>

[0138] 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 is 30 μm. The thickness of the acrylic adhesive layer is 3 μm.

[0139] <Preparation Example 6>

[0140] 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 is 50 μm. The thickness of the acrylic adhesive layer is 3 μm.

[0141] [Examples 1 to 4, Comparative Examples 1 to 4]

[0142] Prepare a first laminating roll and a second laminating roll.

[0143] The first laminating roll includes a roll body made of silicone rubber (Si rubber) and a shaft made of metal. The outer diameter of the roll body is 250 mm.

[0144] The second laminating roll includes a shaft made of iron (Fe) and a plating film made of chromium. The outer diameter of the second laminating roll is 250 mm.

[0145] Next, the first laminating roll and the second laminating roll were relatively arranged in such a manner that they were in contact with each other in the radial direction. In addition, both ends of the second laminating roll were pressed against the first laminating roll at 10 MPa using a roller. Furthermore, the first laminating roll and the second laminating roll were rotated respectively.

[0146] Next, the protective film with an adhesive layer and the product film obtained in the preparation examples shown in Table 1 were respectively supplied between the first laminating roller and the second laminating roller. The supply speed (linear speed) of each 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 peripheral surface of the first laminating roller (roller body), and the product film was in contact with the outer peripheral surface (coated film) of the second laminating roller.

[0147] When the protective film and the product film passed between the first laminating roller and the second laminating roller, they were pressed by the first laminating roller and the second laminating roller and adhered using the adhesive layer.

[0148] Through the above, a laminated film having a structure of protective film / adhesive layer / product film (phase difference film) was obtained.

[0149] [Comparative Example 5]

[0150] The first laminating roller and the second laminating roller were replaced so that the laminating roller having a shaft made of Fe was in contact with the protective film, and the laminating roller having a roller body made of Si rubber was in contact with the product film. Otherwise, the operation was the same as in Example 1, and a laminated film was obtained.

[0151] Table 1

[0152]

[0153] [Evaluation]

[0154] As shown in Table 1, it was found that if the indentation elastic modulus E2 of the product film / the indentation elastic modulus E1 of the protective film exceeded 1.0 and the hardness R2 of the second laminating roller / the hardness R1 of the first laminating roller exceeded 1.0, scratches in the product film could be sufficiently suppressed.

[0155] Industrial Applicability

[0156] The method for manufacturing the laminated film of the present invention is used for manufacturing product films that can be used in various industrial products, and is particularly suitable for manufacturing optical films (specifically, phase difference films).

[0157] Explanation of Symbols

[0158] 1 Protective film

[0159] 2 Product film

[0160] 3a First laminating roller

[0161] 3b Second laminating roller

[0162] 5 Adhesive layer

[0163] 100 Laminated film

Claims

1. A method for manufacturing a laminated film, which includes a laminating step of passing and laminating a protective film and a product film between a first laminating roller and a second laminating roller, In the laminating step, the first laminating roller is located on the side opposite to the product film with respect to the protective film, and the second laminating roller is located on the side opposite to the protective film with respect to the product film, At 25 °C, the indentation elastic modulus E2 of the product film is more than 1.0 with respect to the indentation elastic modulus E1 of the protective film, At 25 °C, the hardness R2 of the second laminating roller is more than 1.0 with respect to the hardness R1 of the first laminating roller.

2. The manufacturing method of the laminated film according to claim 1, wherein, The protective film and the product film are laminated by an adhesive layer.

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

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