Method for producing laminated film

Abstract

Provided is a method for producing a laminated film, which can protect the surface of a product film and can achieve a product film having an excellent appearance. 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 by the adhesive layer. The adhesive layer has a storage elastic modulus of 1.0 * 10 < 3 > Pa to 9.9 * 10 < 5 > Pa at 25 DEG C and 55% RH. The adhesive layer has a thickness of 5 [mu] m or more. The thickness T1 of the protective film is greater than 1.0 with respect to the thickness T2 of the adhesive layer. At 25 DEG C, the hardness R2 of the second bonding roller on the product film side is more than 1.0 with respect to the hardness R1 of the first bonding roller on the protective film side.

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 (typically an optical film) is required to have an appearance that is much more excellent than before. In particular, appearance defects at levels that have 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-described 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 can realize a product film having an excellent appearance.

[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 using an adhesive layer. 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. The storage elastic modulus of the adhesive layer at 25 °C and a relative humidity of 55% is 1.0×10 3 Pa to 9.9×10 5Pa. The thickness T1 of the adhesive layer is 5 μm or more. The thickness T1 of the adhesive layer is 1.0 or less with respect to the thickness T2 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.

[0012] Advantages of the Invention

[0013] According to the embodiment of the present invention, the surface of the product film can be protected, and a product film with excellent appearance can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic configuration diagram for explaining the manufacturing method of the laminated film according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] 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 in the description, compared with the embodiments, the width, thickness, shape, etc. of each part are sometimes shown schematically in the drawings, but this is only an example and does not limit the interpretation of the present invention.

[0016] (Definition of Terms and Symbols)

[0017] The definitions of the terms and symbols in this specification are as follows.

[0018] (1) Refractive Index (nx, ny, nz)

[0019] "nx" is the refractive index in the direction in which the in-plane refractive index 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.

[0020] (2) In-Plane Phase Difference (Re)

[0021] "Re(λ)" is the in-plane phase difference measured by light with a wavelength of λ nm at 23°C. For example, "Re(550)" is the in-plane phase difference measured by light with a wavelength of 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.

[0022] A. Outline of the Manufacturing Method of the Laminated Film

[0023] Figure 1 It is a schematic configuration diagram for explaining the manufacturing method of the laminated film according to one embodiment of the present invention.

[0024] The manufacturing method of the laminated film according to 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 using the adhesive layer 5. 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. The storage elastic modulus of the adhesive layer 5 at 25°C and 55% RH (relative humidity) is 1.0×10 3 Pa to 9.9×10 5 Pa. The thickness T1 of the adhesive layer 5 is 5 μm or more. The thickness T1 of the adhesive layer 5 with respect to the thickness T2 of the protective film 1 (T1 / T2) is 1.0 or less. 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.

[0025] 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, indentations are sometimes formed in the product film. Therefore, an in-depth study 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 are formed by transferring the appearance defects (e.g., shrinkage holes, burns, wrinkles) of the protective film during the laminating step.

[0026] The present inventors further studied this finding and found that if the thickness of the adhesive layer for attaching the product film and the protective film and the hardness of each 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.

[0027] Specifically, if the thickness T1 of the adhesive layer is 5 μm or more 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 indentations in the product film can be suppressed.

[0028] In addition, according to one embodiment, since the thickness T1 of the adhesive layer with respect to the thickness T2 of the protective film (T1 / T2) is 1.0 or less and the storage elastic modulus of the adhesive layer is 1.0×10 3 Pa or more, wrinkles can be suppressed from being generated in the product film during the conveyance of the laminated film, and the peeling of the protective film from the product film can be suppressed.

[0029] As a result, the surface of the product film can be protected by attaching the protective film to the product film, and a product film with excellent appearance can be realized.

[0030] The storage elastic modulus of the adhesive layer 5 at 25°C and 55% RH is preferably 1.0×10 3 Pa to 9.0×105 Pa, more preferably 8.0×10 4 Pa to 1.2×10 5 Pa. If the storage elastic modulus of the adhesive layer is within such a range, peeling of the protective film from the product film can be stably suppressed.

[0031] It should be noted that the storage elastic modulus of the adhesive layer is measured, for example, in a shear mode, at a constant temperature of 25°C, a frequency of 1 Hz, and in accordance with JIS K 6868.

[0032] 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 further preferably 0.50 or less. If the thickness ratio (T1 / T2) of the protective film to the adhesive layer is in such a relationship, wrinkles generated in the product film during conveyance of the laminated film can be stably suppressed, and improvement in the conveyance property of the laminated film can be achieved.

[0033] 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) of the protective film to the adhesive layer is in such a relationship, scratches in the product film can be stably suppressed.

[0034] The thickness T1 of the adhesive layer 5 is preferably 8 μm or more, more preferably 10 μm or more. If the adhesive layer has such a thickness, scratches in the product film can be more stably suppressed.

[0035] On the other hand, the thickness T1 of the adhesive layer 5 is, for example, 50 μm or less, preferably 40 μm or less, and more preferably 35 μm or less. If the adhesive layer has such a thickness, wrinkles generated in the product film during conveyance of the laminated film can be more stably suppressed.

[0036] The thickness T2 of the protective film 1 is, for example, 7 μm or more, preferably 10 μm or more, more preferably 20 μm or more, and further preferably 25 μm or more. 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. If the protective film has such a thickness, the thickness ratio (T1 / T2) of the protective film to the adhesive layer can be stably adjusted within the above-mentioned range.

[0037] At 25°C, the hardness R2 of the second laminating roll 3b relative to the hardness R1 of the first laminating roll 3a (R2 / R1) is preferably 1.01 or more, more preferably 1.05 or more, and further preferably 1.08 or more. If the hardness ratio (R2 / R1) of the first laminating roll to the second laminating roll is in such a relationship, scratches in the product film can be more stably suppressed.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] It should be noted that the hardness of the laminating roller is the hardness measured by a Durometer rebound hardness tester and is measured, for example, in accordance with JIS K 6253.

[0043] At 25°C, the indentation modulus of elasticity E2 of the product film 2 relative to the indentation modulus of elasticity E1 of the protective film 1 (E2 / E1) is, for example, 0.30 or more, preferably 0.50 or more, and more preferably 0.60 or more. On the other hand, at 25°C, the indentation modulus of elasticity E2 of the product film 2 relative to the indentation modulus of elasticity E1 of the protective film 1 (E2 / E1) is, for example, 1.40 or less, and furthermore, for example, 1.20 or less, furthermore, for example, 1.00 or less, and furthermore, for example, 0.80 or less. Even if the ratio of the indentation modulus of elasticity of the protective film to the product film (E2 / E1) is such a relationship, according to the above-described embodiments, a product film having excellent appearance can be stably obtained.

[0044] The protective film 1 may be softer than the product film 2 or may be harder than the product film 2. In one embodiment, the protective film 1 is harder than the product film 2.

[0045] The indentation modulus of elasticity 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.

[0046] The indentation modulus of elasticity 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.

[0047] It should be noted that the indentation modulus of elasticity of the film is measured, for example, in accordance with ISO 14577.

[0048] B. Details of the method for manufacturing the laminated film

[0049] Hereinafter, the details of the method for manufacturing the laminated film will be described.

[0050] In the method for manufacturing a laminated film according to one embodiment, first, a protective film 1 and a product film 2 are prepared.

[0051] B-1. Product film

[0052] The product film 2 can have any suitable configuration. The product film 2 is typically strip-shaped. 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.

[0053] The thickness of the product film 2 is, for example, 10 μm to 100 μm, preferably 15 μm to 80 μm.

[0054] The product film 2 is typically 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-based resins, cellulose ester-based resins, cellulose-based resins, polyester-based resins, polyester carbonate-based resins, olefin-based resins, and polyurethane-based resins. Note that the (meth)acrylic-based resin refers to an acrylic-based resin and / or a methacrylic-based resin. These resin materials can be used alone or in combination.

[0055] Among the resin materials constituting the product film 2, PC-based resins, COP-based resins, and (meth)acrylic-based resins are preferably listed, and PC-based resins are more preferably listed. If the product film is made of such resin materials, scratches in the product film can be stably suppressed.

[0056] As the PC-based resin, for example, a PC-based resin containing a structural unit derived from a dihydroxy compound can be mentioned. 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), bisphenols, etc.

[0057] Details of the above PC-based resin are described, for example, in Japanese Unexamined Patent Application Publication No. 2012-67300 and Japanese Patent No. 3325560. The descriptions of this patent document are incorporated herein by reference.

[0058] As the article film 2, for example, an optical film such as a retardation film can be mentioned, and a retardation film is preferably mentioned.

[0059] Typically, the retardation film is prepared by stretching a resin film made of the above resin material in a predetermined direction. Any suitable stretching method can be adopted.

[0060] Typically, the retardation film has a slow axis in the stretching direction. In one embodiment, the refractive index of the retardation film shows a relationship of nx > ny.

[0061] 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.

[0062] 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.

[0063] B-2. Protective film

[0064] The protective film 1 can protect the surface of the product film 2 by adhering to the product film 2. The protective film 1 can have any suitable constitution. Representatively, the protective film 1 has a 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.

[0065] Representatively, 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.

[0066] Among the resin materials constituting the protective film 1, preferably, COP resins and polyester resins are exemplified, and more preferably, polyethylene terephthalate (PET) is exemplified. If the protective film is made of such a resin material, the surface of the product film can be stably protected by the protective film.

[0067] B-3. Adhesive layer

[0068] 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 laminated on the product film 2. Hereinafter, the protective film 1 laminated with the adhesive layer 5 is sometimes referred to as a protective film with an adhesive layer 6.

[0069] 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 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.

[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 type, number, combination, and mixing ratio 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 characteristics 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, preferred examples include (meth)acrylic adhesives ((meth)acrylic adhesive compositions).

[0071] The (meth)acrylic adhesive composition typically contains a (meth)acrylic polymer as a main component. The content ratio of the (meth)acrylic polymer in the solid content 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 polymer in the solid content of the adhesive composition is typically 100% by mass.

[0072] The (meth)acrylic polymer contains (meth)acrylic alkyl ester as a main component as a monomer unit. In the (meth)acrylic polymer, the content ratio of the structural unit derived from the (meth)acrylic alkyl ester 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 structural unit derived from the (meth)acrylic alkyl ester is, for example, 98% by mass or less, preferably 95% by mass or less.

[0073] Examples of the alkyl group of the (meth)acrylic 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 alkyl esters, butyl acrylate is preferred.

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

[0075] In the (meth)acrylic polymer, the content ratio of the structural unit derived from the comonomer is, for example, 30% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less. On the other hand, the content ratio of the structural unit derived from the comonomer is, for example, 0% by mass or more, and for example, 3% by mass or more.

[0076] 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 further preferably 1,500,000 to 2,500,000. The weight average molecular weight Mw is calculated, for example, by styrene conversion from the result 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, an epoxy group-containing silane coupling agent can be cited. The content of the silane coupling agent is, for example, 0.001 part by mass or more and 5 parts by mass or less relative to 100 parts by mass of the (meth)acrylic polymer.

[0079] As a crosslinking agent, for example, an isocyanate-based crosslinking agent and a peroxide-based crosslinking agent can be mentioned. The crosslinking agent can be used alone or in combination. Among the crosslinking agents, an isocyanate-based crosslinking agent is preferably mentioned. The content of the crosslinking agent is, for example, 0.01 part by mass or more, preferably 0.1 part by mass or more, more preferably 0.5 part by mass or more, with respect 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, further preferably 3.0 parts by mass or less, and particularly preferably 1.0 part by mass or less.

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

[0081] The first laminating roll 3a has an arbitrary suitable configuration. The first laminating roll 3a typically has a cylindrical shape extending in a specified direction. The outer diameter of the first laminating roll 3a is, for example, 100 mm to 500 mm, 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.

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

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

[0084] 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 above-mentioned first laminating roll. 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.

[0085] The shaft is typically made of the above-mentioned metal. 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 laminating roll 3b has an arbitrary suitable configuration. The second laminating roll 3b typically has a cylindrical shape extending in a specified direction. The outer diameter of the second laminating roll 3b is, for example, 100 mm to 500 mm, preferably 150 mm to 300 mm. The outer peripheral surface of the second laminating roll 3b has the above-mentioned hardness R2.

[0087] The second laminating roller 3b is made of any suitable material. Examples of the material for the second laminating roller 3b include metals and semi-metals, and metals are preferably cited. Examples of metals include iron, copper, aluminum, chromium, nickel, and their alloys. Iron is preferably cited among the metals.

[0088] In one embodiment, the second laminating roller 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 above-mentioned metal. The plating film is typically made of an alloy of the above-mentioned metal. 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 appropriately so that the hardness R2 of the outer peripheral surface of the second laminating roller 3b falls within the above-mentioned range.

[0090] The second laminating roller 3b is arranged to be radially opposed to the first laminating roller 3a. The outer peripheral surfaces of the first laminating roller 3a and the second laminating roller 3b typically contact each other before the protective film 1 and the product film 2 are supplied therebetween.

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

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

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

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

[0095] In the illustrated example, the protective film 1 (the 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, and 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 scratches generated in the product film can be more stably suppressed.

[0097] The tension applied to the protective film 1 can be appropriately adjusted by relatively 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 relatively moving the second conveying roller 42 relative to the first laminating roller 3a.

[0100] The supply speeds (linear speeds) of the protective film 1 and the product film 2 in the laminating process are, 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 contacts 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 contacts 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 crimped using the adhesive layer 5.

[0103] Through the above, a long 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 relatively movable relative 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 preferably used after the protective film 1 and the adhesive layer 5 (the protective film 6 with an adhesive layer) are peeled off. The product film 2 can typically be used for optical applications such as image display devices. In particular, since the product film 2 can significantly suppress scratches and stains and has excellent appearance, 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 of each property 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 of each property 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] Apparatus: 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: According to ISO14577

[0120] (2) Measurement of the storage elastic modulus of the adhesive layer

[0121] According to JIS K 6868, the storage elastic modulus of the adhesive layer used in the examples and comparative examples was measured under the following measurement conditions. The storage elastic modulus of the adhesive layer is shown in Table 1.

[0122] Measurement temperature: 25 °C (constant temperature)

[0123] Measurement humidity: 55% RH

[0124] Measurement mode: Shear

[0125] Frequency: 1 Hz

[0126] (3) Measurement of the hardness of each of the first laminating roll and the second laminating roll

[0127] 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. The hardness R1 of the first laminating roll, the hardness R2 of the second laminating roll, and R2 / R1 are shown in Table 1.

[0128] (4) Appearance judgment of the laminated film

[0129] After being integrated with the polarizing plate and laminated with the aluminum reflector, the appearance of the laminated films prepared in the examples and comparative examples was confirmed by the appearance reflected by the fluorescent lamp, and evaluated according to the following criteria. The results are shown in Table 1.

[0130] 〇: No indentation shape was visually confirmed.

[0131] ×: An indentation shape was visually confirmed.

[0132] (5) Evaluation of the transportability of the laminated film

[0133] The transportability of the laminated films prepared in the examples and comparative examples was confirmed by the presence or absence of contamination of the production line or film breakage, and evaluated according to the following criteria. The results are shown in Table 1.

[0134] 〇: There was no process contamination and no film breakage.

[0135] ×: There was process contamination and / or film breakage.

[0136] <<Preparation of the adhesive>>

[0137] <Preparation Example 1>

[0138] Into a reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer and a stirring device, 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 0.3 part by mass of benzoyl peroxide based on 100 parts by mass of the total of the above monomers (solid content) were added together with ethyl acetate. After reacting for 7 hours under a nitrogen stream at 60 °C, ethyl acetate was added to the reaction solution to obtain a solution (solid content concentration: 30 mass%) containing an acrylic polymer having a weight average molecular weight of 2.2 million and a dispersion ratio of 3.9. For every 100 parts by mass of the solid content of the solution containing the above acrylic polymer, 0.6 part by mass of trimethylolpropane tolylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd.: CORONATE L) and 0.075 part by mass of γ-glycidoxypropylmethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.: KBM-403) were blended to obtain a solution of the adhesive. The above solution was diluted with ethyl acetate so that the solid content concentration became 15 mass% to prepare an adhesive coating solution. The adhesive coating solution prepared above was coated on one side of a 38 μm organosilicon-treated polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical polyester film Co., Ltd., MRF38) so that the coating thickness became 134.0 μm using a jet die coater. Then, it was dried at 155 °C for 1 minute to obtain an adhesive layer having a storage elastic modulus of 1.13×10 5 Pa. The thickness T1 of the adhesive layer was 15 μm.

[0139] <Preparation Example 2>

[0140] 89.9 parts by mass of butyl acrylate, 10 parts by mass of acrylic acid, 0.1 part by mass of 2-hydroxyethyl acrylate, and 0.3 part by mass of benzoyl peroxide based on 100 parts by mass of the total of the above monomers (solid content) were added together with ethyl acetate. After reacting for 6 hours under a nitrogen stream at 60 °C, ethyl acetate was added to the reaction solution to obtain a solution (solid content concentration: 30 mass%) containing an acrylic polymer having a weight average molecular weight of 1.7 million and a dispersion ratio of 3.9. Except for this, the same operations as in Preparation Example 1 were carried out to obtain an adhesive layer having a storage elastic modulus of 1.13×10 3 Pa. The thickness T1 of the adhesive layer was 38 μm.

[0141] <Preparation Example 3>

[0142] An adhesive layer was obtained by carrying out the same operations as in Preparation Example 1 except that the thickness T1 was changed to 10 μm.

[0143] <Preparation Example 4>

[0144] An adhesive layer was obtained by operating in the same manner as in Preparation Example 1 except that the thickness T1 was changed to 50 μm.

[0145] <Preparation Example 5>

[0146] An adhesive layer was obtained by operating in the same manner as in Preparation Example 1 except that the thickness T1 was changed to 3 μm.

[0147] <Preparation Example 6>

[0148] 92.9 parts by mass of butyl acrylate, 7 parts by mass of acrylic acid, 0.1 part by mass of 2-hydroxyethyl acrylate, and 0.3 part by mass of benzoyl peroxide with respect to 100 parts by mass of the total of the above monomers (solid content) were added together with ethyl acetate. After reacting at 60 °C for 7 hours under a nitrogen stream, ethyl acetate was added to the reaction solution to obtain a solution (solid content concentration: 30 mass%) containing an acrylic polymer (B) having a weight average molecular weight of 2 million and a dispersion ratio of 3.9. Except for this, the operation was the same as in Adjustment Example 1 to obtain an adhesive layer having an elastic modulus of 8.86×10 4 Pa. The thickness T1 of the adhesive layer was 10 μm.

[0149] <Preparation Example 7>

[0150] 89.9 parts by mass of butyl acrylate, 10 parts by mass of acrylic acid, 0.1 part by mass of 2-hydroxyethyl acrylate, and 0.3 part by mass of benzoyl peroxide with respect to 100 parts by mass of the total of the above monomers (solid content) were added together with ethyl acetate. After reacting at 60 °C for 4 hours under a nitrogen stream, ethyl acetate was added to the reaction solution to obtain a solution (solid content concentration: 30 mass%) containing an acrylic polymer having a weight average molecular weight of 1.2 million and a dispersion ratio of 3.9. Except for this, the operation was the same as in Adjustment Example 1 to obtain an adhesive layer having an elastic modulus of 8.86×10 2 Pa. The thickness T1 of the adhesive layer was 10 μm.

[0151] <<Preparation of Protective Film with Adhesive Layer>>

[0152] <Preparation Example 8>

[0153] An adhesive layer obtained in Preparation Example 1 was laminated on the surface of a polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Corporation, part number “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 thickness T2 of the protective film to the thickness T1 of the adhesive layer (T1 / T2) is shown in Table 1.

[0154] <Preparation Example 9>

[0155] On the surface of a PET film (manufactured by Mitsubishi Chemical Corporation, part number "DIAFOIL") used as a protective film, the adhesive layer obtained in Preparation Example 2 was laminated to prepare a protective film with an adhesive layer.

[0156] <Preparation Example 10>

[0157] On the surface of a PET film (manufactured by Mitsubishi Chemical Corporation, part number "DIAFOIL") used as a protective film, the adhesive layer obtained in Preparation Example 3 was laminated to prepare a protective film with an adhesive layer. The thickness T2 of the protective film was 30 μm.

[0158] <Preparation Example 11>

[0159] On the surface of a cycloolefin (COP) - based resin film (manufactured by Zeon Corporation, part number "ZF - 14") used as a protective film, the adhesive layer obtained in Preparation Example 6 was laminated to prepare a protective film with an adhesive layer. The thickness T2 of the protective film was 13 μm.

[0160] <Preparation Example 12>

[0161] On the surface of a PET film (manufactured by Mitsubishi Chemical Corporation, part number "DIAFOIL") used as a protective film, the adhesive layer obtained in Preparation Example 4 was laminated to prepare a protective film with an adhesive layer.

[0162] <Preparation Example 13>

[0163] On the surface of a COP - based resin film (manufactured by Zeon Corporation, part number "ZF - 14") used as a protective film, the adhesive layer obtained in Preparation Example 5 was laminated to prepare a protective film with an adhesive layer.

[0164] <Preparation Example 14>

[0165] On the surface of a COP - based resin film (manufactured by Zeon Corporation, part number "ZF - 14") used as a protective film, the adhesive layer obtained in Preparation Example 7 was laminated to prepare a protective film with an adhesive layer. The thickness T2 of the protective film was 25 μm.

[0166] <<Preparation of Product Film>>

[0167] <Preparation Example 15>

[0168] In the same manner as in Production Example 9 of Japanese Unexamined Patent Application Publication No. 2022 - 150732, a resin film made of a PC - based resin was prepared. The resin film had a long - strip shape, and the thickness of the resin film was 130 μm.

[0169] Next, the resin film was subjected to fixed-end lateral uniaxial stretching 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 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.

[0170] <Preparation Example 16>

[0171] A resin film made of a COP-based resin (manufactured by Zeon Corporation, part number "ZF16") was subjected to fixed-end lateral uniaxial stretching 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 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.

[0172] <Preparation Example 17>

[0173] 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.

[0174] [Examples 1 to 4, Comparative Examples 1 to 3]

[0175] Prepare a first laminating roll and a second laminating roll.

[0176] 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.

[0177] 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.

[0178] 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 with a roller at 10 MPa. Further, the first laminating roll and the second laminating roll were rotated respectively.

[0179] 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 roll and the second laminating roll. The supply speed (linear speed) of each of the protective film with an adhesive layer and the product film is 15 m / min. The protective film is in contact with the outer peripheral surface of the first laminating roll (roll body), and the product film is in contact with the outer peripheral surface (plating film) of the second laminating roll.

[0180] When the protective film and the product film pass between the first laminating roller and the second laminating roller, they are pressed by the first laminating roller and the second laminating roller and laminated using the adhesive layer.

[0181] Through the above, a laminated film having a structure of protective film / adhesive layer / product film (phase difference film) is obtained.

[0182] [Comparative Example 4]

[0183] The protective film with an adhesive layer of Preparation Example 8 was changed to the protective film with an adhesive layer of Preparation Example 10, the product film of Preparation Example 16 was changed to the product film of Preparation Example 15, and the first laminating roller and the second laminating roller were replaced so that the laminating roller having a shaft made of Fe contacted the protective film and the laminating roller having a roller body made of Si rubber contacted the product film. Otherwise, the operation was the same as in Example 1 to obtain a laminated film.

[0184] [Table 1]

[0185]

[0186] [Evaluation]

[0187] As shown in Table 1, it was found that if the storage elastic modulus of the adhesive layer is 1.0×10 3 Pa to 9.9×10 5 Pa, the thickness T1 of the adhesive layer is 5 μm or more, the ratio of the thickness T1 of the adhesive layer to the thickness T2 of the protective film is 1.0 or less, and the ratio of the hardness R2 of the second laminating roller to the hardness R1 of the first laminating roller exceeds 1.0, then a product film with excellent appearance can be achieved.

[0188] Industrial Applicability

[0189] The manufacturing method of 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).

[0190] Explanation of Symbols

[0191] 1 Protective film

[0192] 2 Product film

[0193] 3a First laminating roller

[0194] 3b Second laminating roller

[0195] 5 Adhesive layer

[0196] 100 Laminated film

Claims

1. A method for manufacturing a laminated film, which includes a laminating step of passing a protective film and a product film between a first laminating roller and a second laminating roller and laminating them using an adhesive layer, 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, The storage elastic modulus of the adhesive layer at 25 °C and a relative humidity of 55% is 1.0×10 3 Pa to 9.9×10 5 Pa, The thickness T1 of the adhesive layer is 5 μm or more and 1.0 or less with respect to the thickness T2 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.

Images