Laminate and production method therefor

Abstract

Provided is a laminate roll which is obtained by winding a laminate (3), in which a transparent film (1) and a protective film (2) with an adhesive layer are laminated, into a roll shape. The transparent film may be a film that contains a polyimide-based resin. The protective film with an adhesive layer may be a film that has an adhesive layer on one surface of a polyester-based film. The number of periodic dents in the laminate is preferably 2.0 / m2 or less. In a process for obtaining a laminate by sandwiching and laminating the components between a metal roll (6) and a rubber roll (7), the occurrence of periodic dents can be suppressed by executing a metal roll cleaning step in which a cloth (95) is brought into contact with the surface of the metal roll and rigid members (91, 92) are pressed against the metal roll, with the cloth being interposed therebetween, in a state in which the metal roll is driven and rotated.

Description

Laminate and manufacturing method thereof

[0001] The present invention relates to a laminate and a method for producing the same.

[0002] Glass plates have traditionally been used as cover windows placed on the surfaces of mobile devices, such as smartphones, but from the viewpoint of reducing the weight and increasing the flexibility of devices, resin films such as transparent polyimide have begun to be used (see, for example, Patent Document 1). Patent Documents 2 and 3 disclose hard coating treatments to impart scratch resistance to transparent films used for cover windows.

[0003] A protective film such as a polyester film having an adhesive layer is attached to a transparent film used as a cover window for the purpose of preventing scratches during storage and handling until mounting on a device. Patent Documents 2 and 3 propose attaching a protective film to the surface of a transparent film for the purpose of suppressing curling of a transparent film having a hard coat layer and improving processability during hard coat treatment.

[0004] JP 2019-151093 A International Publication No. 2018 / 207914 International Publication No. 2021 / 172201

[0005] The cover window placed on the viewing side of the display is prone to visible deformations such as scratches and dents, and even minute defects are easily visible, especially in mobile devices where the user holds the display close to their eyes. A laminate in which a protective film is bonded to the surface of a transparent film tends to have a greater number of minute dents than a transparent film alone, posing the issue of lower yields due to the dents.

[0006] Although Patent Document 1 proposes a method for producing a transparent polyimide film that is less likely to develop micro-scratches, it does not specifically mention reducing dents in laminates. The present invention aims to reduce dents in laminates in which a protective film with an adhesive layer is bonded to a transparent film.

[0007] The present invention relates to a laminate in which a transparent film and a protective film with an adhesive layer are laminated and wound into a roll, and a method for manufacturing the same. The transparent film may have a thickness of 30 μm or more, and the protective film with an adhesive layer may have a thickness of 50 μm or more.

[0008] In one embodiment, the transparent film is a film containing a polyimide resin, and the adhesive-layered protective film is a film having an adhesive layer on one side of a polyester film. The polyimide-based transparent film may contain a polyimide resin and a resin other than the polyimide resin (e.g., an acrylic resin).

[0009] The number of periodic dents in the laminate is 2.0 / m ２ The following is preferable: Dents are irregularities with a major axis of 100 μm or more and 10,000 μm or less that are visible at the same position from both sides of the laminate, and are defined as periodic dents when two or more dents exist at the same position (within 3 mm) in the width direction perpendicular to the length direction within a range of 2 m along the length direction of the laminate (flow direction during manufacturing).

[0010] The transparent film and the adhesive-layered protective film are sandwiched between a driven metal roll and a driven rubber roll while being conveyed, thereby laminating them, and a laminate in which the transparent film and the adhesive-layered protective film are laminated is obtained. By winding up this laminate downstream, a roll of the laminate in which the adhesive-layered protective film is bonded to the transparent film is obtained.

[0011] In one embodiment of the present invention, a metal roll cleaning step is carried out in which a cloth is brought into contact with the surface of the metal roll while the metal roll is being driven to rotate, and a rigid member is pressed against the cloth. The timing of carrying out the metal roll cleaning step is not particularly limited. For example, the metal roll cleaning step may be carried out while the transparent film and the adhesive layer-equipped protective film are being sandwiched between the metal roll and the rubber roll and laminated while being transported.

[0012] The cloth used in the metal roll cleaning process may be one whose main fiber is polyester-based fiber. The rigid member used in the metal roll cleaning process may be a plate-shaped member or a rod-shaped member. The rigid member may be made of a resin such as a polyamide resin, or may be a resin rod.

[0013] The metal roll cleaning step may be performed by pressing a metal roll cleaning jig, which has a cloth stretched across two rod-shaped members (corresponding to the above-mentioned "rigid members") arranged parallel to and spaced apart from each other, against the metal roll. The metal roll cleaning jig may have two sides of a cloth wrapped around and fixed to the two rods. The rod-shaped members of the metal roll cleaning jig may be rods made of resin such as polyamide resin.

[0014] According to the present invention, a laminate having few dents and excellent appearance characteristics can be obtained. The transparent film of this laminate can be suitably used as a cover window material for displays, and since there are few defects due to dents, the yield can be improved.

[0015] It is a cross-sectional view of a laminate of one embodiment. It is a diagram showing a state in which a transparent film and a protective film are laminated. It is a cross-sectional view of a roll cleaning jig. It is a schematic perspective view of a roll cleaning jig. It is a diagram showing a state in which a metal roll cleaning step is performed.

[0016] 1 is a cross-sectional view of a laminate according to one embodiment of the present invention. The laminate 3 has a configuration in which a protective film 2 is laminated on one surface of a transparent film 1. The protective film 2 has an adhesive layer 22 on one surface of a substrate 21, and the adhesive layer 22 is attached to the transparent film 1.

[0017] By laminating the protective film 2 on the surface of the transparent film 1, it is possible to prevent scratches and foreign matter from adhering to the transparent film 1. The laminate 3 in which the protective film 2 is laminated on one surface of the transparent film 1 is thicker and has greater bending elasticity than the transparent film 1 alone. Therefore, the laminate 3 in which the protective film 2 is laminated on one surface of the transparent film 1 is prevented from wrinkling or curling, and is easy to handle, and also easy to process when performing surface treatment on the other surface of the transparent film 1 or forming a functional layer such as a hard coat layer.

[0018] The adhesive strength between the transparent film 1 and the protective film 2 in the laminate 3 is preferably 1 to 20 gf / 25 mm, more preferably 3 to 15 gf / 25 mm, and even more preferably 5 to 10 gf / 25 mm, in a 180° peel test in accordance with JIS Z 0237. If the adhesive strength is less than 1 gf / 25 mm, the adhesion may be insufficient, and if it is more than 20 gf / 25 mm, deformation of the transparent film 1 may occur during peeling.

[0019] The laminate of the present invention may have protective films on both sides of the transparent film 1. From the viewpoint of achieving both strength and ease of handling, the total thickness of the laminate is preferably 80 to 300 μm, and may be 120 to 250 μm or 150 to 200 μm.

[0020] [Transparent Film] The transparent film 1 is suitable for use as a display material, and is particularly suitable for use as a cover window material for a display.

[0021] The total light transmittance of the transparent film 1 is preferably 85% or more, more preferably 86% or more, even more preferably 87% or more, and may be 88% or more, 89% or more, 90% or more, or 91% or more. The haze of the transparent film is preferably 10% or less, more preferably 5% or less, even more preferably 4% or less, and may be 3% or less, 2% or less, or 1% or less.

[0022] From the viewpoint of providing self-supporting properties and strength applicable as a cover window material, the thickness of the transparent film 1 is preferably 30 μm or more, and may be 35 μm or more, or 40 μm or more. From the viewpoint of ensuring bendability (flexibility) applicable to foldable devices, the thickness of the transparent film 1 is preferably 100 μm or less, more preferably 80 μm or less, and may be 70 μm or less, 60 μm or less, or 50 μm or less.

[0023] From the viewpoint of ensuring the strength required as a cover window material, the tensile modulus of the transparent film 1 is preferably 2.0 GPa or more, more preferably 2.5 GPa or more, and may be 3.0 GPa or more or 3.5 GPa or more.

[0024] The transparent film 1 may be made of any suitable material, as long as it has the above-described transparency and strength. In one embodiment of the present invention, the transparent film 1 is a film containing one or more polyimide-based resins selected from the group consisting of polyimide and polyamide-imide. Polyimide-based resins have high mechanical strength and are suitable as materials for cover windows.

[0025] The polyimide-based resin-containing film may be a blended resin film containing a polyimide-based resin and a resin other than a polyimide-based resin. By containing a polyimide-based resin and another resin, the transparency of the film tends to be improved.

[0026] <Polyimide Resin> Polyimide is obtained by cyclodehydration of polyamic acid obtained by the reaction of tetracarboxylic dianhydride with diamine. Polyamideimide is obtained by replacing a part of the tetracarboxylic dianhydride of polyimide with a dicarboxylic acid derivative such as dicarboxylic acid dichloride.

[0027] The composition of the polyimide resin is not particularly limited as long as it is transparent. Examples of transparent polyimides include those containing a fluorine atom-containing aromatic diamine as a diamine component and one or more tetracarboxylic acid dianhydride components selected from the group consisting of a fluorine atom-containing aromatic tetracarboxylic acid dianhydride, an alicyclic tetracarboxylic acid dianhydride, a bis(trimellitic anhydride) ester, a tetracarboxylic acid dianhydride having an ether bond, a tetracarboxylic acid dianhydride having a fluorene structure, and a tetracarboxylic acid dianhydride having a xanthene structure.

[0028] The fluorine atom-containing aromatic diamines include those having a fluorine group, a perfluoroalkyl group such as a trifluoromethyl group, or a CF ３ -O-, -(CF ２ -O) ｎ -, -O-(CF ２ -CF ２ -O) ｎ From the viewpoint of transparency of the polyimide resin, preferred are those in which functional groups containing fluorine atoms are bonded to the 2- and 2'-positions of biphenyl, and 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 2,2'-bis(trifluoromethoxy)benzidine (TFMOB) are particularly preferred.

[0029] The amount of the fluorine atom-containing aromatic diamine relative to the total amount of the diamine components of the polyimide resin is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, and may be 80 mol% or more, 85 mol% or more, or 90 mol% or more. A high content of the fluorine atom-containing aromatic diamine tends to suppress coloration of the film and increase mechanical strength such as pencil hardness and elastic modulus.

[0030] The polyimide resin may contain, as a diamine component, a diamine other than the fluorine atom-containing aromatic diamine. From the viewpoint of transparency, the diamine other than the fluorine atom-containing aromatic diamine preferably has one or more selected from the group consisting of a sulfone group, a fluorene structure, and an alicyclic structure.

[0031] Examples of the fluorine-containing aromatic tetracarboxylic acid dianhydride include 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride and 2,2-bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}-1,1,1,3,3,3-hexafluoropropane dianhydride.

[0032] The alicyclic tetracarboxylic acid dianhydride may have at least one alicyclic structure, and may have both an alicyclic ring and an aromatic ring in one molecule. The alicyclic ring may be polycyclic or may have a spiro structure. From the viewpoints of the transparency of the polyimide resin and compatibility with other resins, the alicyclic tetracarboxylic acid dianhydride is preferably one that does not have an aromatic ring. Specific examples thereof include 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA), 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride (CPDA), 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride (H-PMDA), and 1,1'-bicyclohexane-3,3',4,4'tetracarboxylic acid-3,4:3',4'-dianhydride (H-BPDA). Of these, CBDA is particularly preferred.

[0033] From the viewpoint of improving the compatibility of the polyimide-based resin with other resins, the amount of the alicyclic tetracarboxylic acid dianhydride relative to the total amount of tetracarboxylic acid dianhydride components in the polyimide-based resin is preferably 1 to 80 mol%, more preferably 3 to 60 mol%, still more preferably 5 to 50 mol%, and may be 8 to 45 mol%, 10 to 40 mol%, or 15 to 35 mol%.

[0034] Examples of bis(trimellitic anhydride) esters include bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-2,2',3,3',5,5'-hexamethylbiphenyl-4,4'diyl (abbreviation: TAHMBP).

[0035] Examples of acid dianhydrides having an ether bond include 3,4'-oxydiphthalic anhydride (a-ODPA), 4,4'-oxydiphthalic anhydride (s-ODPA), 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride (BPADA), etc. Among these, BPADA is particularly preferred.

[0036] Examples of acid dianhydrides having a fluorene structure include 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride (BPF-PPA), N,N'-(9H-fluoren-9-ylidene-4,1-phenylene)bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxamide] (FDA-ATA), and 5,5'-(9H-fluoren-9-ylidenebis(2-methyl-4,1-phenylene)bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate] (TBIS.MPN). Among these, BPAF and BPF-PPA are particularly preferred.

[0037] Examples of acid dianhydrides having a xanthene structure include 5,5'-spiro[9H-fluorene-9,9'-[9H]xanthene]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate (TBIS.RXN), spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone (SFDA), and the like.

[0038] From the viewpoints of transparency and compatibility with other resins, the total amount of the fluorine atom-containing aromatic tetracarboxylic acid dianhydride, the alicyclic tetracarboxylic acid dianhydride, the bis(trimellitic anhydride) ester, the tetracarboxylic acid dianhydride having an ether bond, the tetracarboxylic acid dianhydride having a fluorene structure, and the tetracarboxylic acid dianhydride having a xanthene structure relative to the total amount of tetracarboxylic acid dianhydride components in the polyimide-based resin is preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 65 mol% or more, and may be 70 mol% or more, 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, or 95 mol% or more.

[0039] When the polyimide resin is a polyamideimide, examples of the dicarboxylic acid component include aliphatic dicarboxylic acids such as adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-oxybisbenzoic acid, 4,4'-biphenyldicarboxylic acid, and 2-fluoroterephthalic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-hexahydroterephthalic acid, hexahydroisophthalic acid, 1,3-cyclopentanedicarboxylic acid, and bi(cyclohexyl)-4,4'-dicarboxylic acid; and heterocyclic dicarboxylic acids such as 2,5-thiophenedicarboxylic acid and 2,5-furandicarboxylic acid. Among these, terephthalic acid and isophthalic acid are preferred, and terephthalic acid is particularly preferred.

[0040] Examples of dicarboxylic acid derivatives used as raw material monomers for polyamide-imide include dicarboxylic acid dichlorides, dicarboxylic acid esters, and dicarboxylic acid anhydrides. Among these, dicarboxylic acid dichlorides are preferred due to their high reactivity. Tricarboxylic acid derivatives such as trimellitic anhydride chloride may also be used as raw material monomers for polyamide-imide.

[0041] When the polyimide resin is a polyamideimide, the ratio of the dicarboxylic acid component to the total of the tetracarboxylic dianhydride component and the dicarboxylic acid component is preferably 40 mol % or less, more preferably 35 mol % or less, and even more preferably 30 mol % or less.

[0042] The method for synthesizing the polyimide-based resin is not particularly limited. Generally, a polyamic acid as a poly(amide)imide precursor is obtained by reacting a tetracarboxylic dianhydride (and a dicarboxylic acid derivative) with a diamine, and a poly(amide)imide is obtained by cyclodehydration (imidization) of the polyamic acid. A polyamic acid solution can be formed into a film, which can then be imidized to obtain a film containing the polyimide-based resin.

[0043] The molecular weight of the polyimide resin (weight average molecular weight in terms of polyethylene oxide measured by gel permeation chromatography (GPC)) is preferably 10,000 to 300,000, more preferably 20,000 to 250,000, and even more preferably 40,000 to 200,000. If the molecular weight is too small, the strength of the film may be insufficient. If the molecular weight is too large, the compatibility with other resins may be poor.

[0044] <Other Resins> As described above, the transparent film may contain, in addition to the polyimide resin, a resin other than the polyimide resin ("other resin"). Transparent films containing a polyimide resin and other resins are disclosed in, for example, WO2021 / 132279, WO2023 / 026982, WO2023 / 100806, WO2023 / 132310, WO2023 / 249079, etc.

[0045] When the transparent resin film contains a polyimide-based resin and another resin, the mixing ratio (weight ratio) of the polyimide-based resin to the other resin is preferably 98:2 to 2:98, and may be 95:5 to 10:90, 90:10 to 15:85, or 65:35 to 50:50. The higher the ratio of the polyimide-based resin, the higher the tensile modulus and pencil hardness of the film, and the more excellent the mechanical strength. The higher the ratio of the other resin, the less coloring the film tends to have and the more transparent it tends to be.

[0046] The other resin may be a solvent-soluble resin. Examples of the other resin include acrylic resins, polycarbonate resins, polyester resins, polyamide resins, polyether resins, cellulose resins, silicone resins, and cyclic olefin resins. A plurality of these resins may be used. Acrylic resins are particularly preferred as the other resin because they have high compatibility with polyimide resins, a low refractive index, and are easily formed into a high-hardness film.

[0047] Examples of acrylic resins include poly(meth)acrylic acid esters such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymers, methyl methacrylate-(meth)acrylic acid ester copolymers, methyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymers, methyl (meth)acrylate-styrene copolymers, etc. The acrylic resins may be modified to introduce glutarimide structural units or lactone ring structural units.

[0048] From the viewpoints of transparency, compatibility with polyimide resins, and mechanical strength, the acrylic resin preferably has methyl methacrylate as its main structural unit. The amount of methyl methacrylate relative to the total amount of monomer components in the acrylic resin is preferably 60% by weight or more, and may be 70% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. The acrylic resin may be a homopolymer of methyl methacrylate. Alternatively, the acrylic resin may be an acrylic polymer having a methyl methacrylate content within the above range, into which a glutarimide structure or a lactone ring structure has been introduced.

[0049] From the viewpoint of heat resistance of the transparent film, the glass transition temperature of the acrylic resin is preferably 100°C or higher, more preferably 110°C or higher, and may be 115°C or higher or 120°C or higher.

[0050] From the viewpoints of solubility in organic solvents, compatibility with polyimide resins, and film strength, the weight average molecular weight (polystyrene equivalent) of the acrylic resin is preferably 5,000 to 500,000, more preferably 10,000 to 300,000, and even more preferably 15,000 to 200,000.

[0051] <Preparation of Transparent Film> The method for producing the transparent film is not particularly limited, and known solution methods and melting methods can be applied. When the transparent film contains a polyimide-based resin, as described above, a polyamic acid may be formed into a film and then imidized.

[0052] In addition to the resin component, the transparent film may contain additives such as fillers, bluing agents, ultraviolet absorbers, flame retardants, stabilizers, crosslinking agents, surfactants, leveling agents, plasticizers, and fine particles.

[0053] The transparent film may be a stretched film. Stretching the film may improve its strength and flex resistance, thereby enhancing its applicability to foldable displays. The transparent film may also include functional layers such as a color-adjusting layer, an anti-reflection layer, an adhesive layer, and a hard coat layer.

[0054] [Protective Film] The protective film 2 is an adhesive layer-attached film that includes an adhesive layer 22 on one surface of a substrate 21. From the viewpoints of suppressing wrinkles and curling in the laminate 3 and suppressing the occurrence of dents when the transparent film 1 and the protective film 2 are bonded together, the thickness of the protective film 2 is preferably 50 μm or more, more preferably 80 μm or more, and even more preferably 100 μm or more. On the other hand, from the viewpoint of transportability in a roll-to-roll system, the thickness of the protective film 2 is preferably 200 μm or less.

[0055] <Substrate> The substrate 21 of the protective film 2 is a resin film. From the viewpoints of suppressing wrinkles and curls in the laminate 3 and suppressing the occurrence of dents when the transparent film 1 and the protective film 2 are bonded together, the thickness of the substrate 21 is preferably 49 μm or more, more preferably 79 μm or more, and even more preferably 99 μm or more. On the other hand, from the viewpoint of transportability in a roll-to-roll system, the thickness of the substrate 21 is preferably 199 μm or less. From the viewpoint of suppressing the occurrence of dents, the tensile modulus of elasticity of the substrate 21 is preferably 3.0 GPa or more, more preferably 3.5 GPa or more, and particularly preferably 4.0 GPa or more.

[0056] The material of the substrate 21 is not particularly limited, and examples thereof include polyesters such as polyethylene terephthalate, polyolefins such as polyethylene and polypropylene, etc. The substrate 21 is preferably a polyester film, since it has few fisheyes, has excellent flatness, and can suppress the occurrence of dents during lamination.

[0057] The polyester film contains 51% by weight or more of a polyester resin. The polyester resin is a polymer having a polyester structure in the main chain, such as polyethylene terephthalate, polyethylene naphthalate, or polybutylene terephthalate. From the viewpoints of smoothness, mechanical strength, cost, etc., polyethylene terephthalate is preferred. The polyester film may contain two or more types of polyester resins. The polyester film may also contain a resin other than the polyester resin in the range of 0 to 49% by weight.

[0058] The substrate may be a single layer of resin film, or may have a resin film on which functions such as an oligomer blocking layer, an antistatic layer, an abrasion-resistant layer, a color tone adjusting layer, a lubricating layer, or an antireflection layer are provided.

[0059] <Adhesive Layer> The adhesive layer 22 is composed of an adhesive that has adhesiveness to the transparent film 1. The type of adhesive is not particularly limited, and examples include acrylic adhesives, rubber adhesives, olefin adhesives, epoxy adhesives, urethane adhesives, silicone adhesives, etc. Among these, acrylic adhesives are preferred because they leave little adhesive residue and are less likely to contaminate the transparent film.

[0060] From the viewpoint of adhesive strength, the thickness of the adhesive layer is preferably 1 μm or more, more preferably 5 μm or more, more preferably 8 μm or more, and may be 10 μm or more. On the other hand, from the viewpoint of the flatness of the adhesive layer surface and removability from the transparent film, the thickness of the adhesive layer is preferably 20 μm or less, more preferably 15 μm or less.

[0061] [Method for Producing Laminate] The laminate of the present invention is provided as a roll of a wound long film. The roll of the laminate is obtained by laminating the transparent film 1 and the protective film 2 by a roll-to-roll method.

[0062] 2 shows how a transparent film and a protective film are laminated using a roll-to-roll method. While conveying, the transparent film 1 and the protective film 2 are passed between a pair of nip rolls consisting of a metal roll 6 that is driven to rotate and a rubber roll 7 that rotates in response to the rotation of the metal roll 6, and a laminate is formed by pressing the adhesive layer 22 of the protective film 2 onto the surface of the transparent film 1. The laminated laminate is conveyed downstream and wound around a winding roll (not shown) to obtain a roll of the laminate.

[0063] The metal roll 6 is not particularly limited as long as it is a driven metal roll. The material of the metal roll 6 can be selected from various metals such as stainless steel, aluminum, and iron, with stainless steel being preferred from the viewpoint of durability. The metal roll 6 may be surface-treated. Examples of surface treatments include various plating treatments such as chrome plating and zinc plating, and diamond-like carbon treatment. From the viewpoint of durability, a chrome-plated metal roll is preferred.

[0064] From the viewpoint of suppressing the occurrence of dents due to protrusions on the metal roll surface, it is preferable that the surface of the metal roll 6 is smooth. The maximum roughness of the metal roll 6 measured in accordance with JIS B 0601:2001 is preferably 10 μm or less, and may be 5 μm or less, 1 μm or less, or 0.5 μm or less. From the viewpoint of suppressing deflection, it is preferable that the diameter of the metal roll 6 is 50 mm or more. From the viewpoint of providing movement tracking ability to the driving source, it is preferable that the diameter of the metal roll 6 is 500 mm or less, and may be 400 mm or less.

[0065] The rubber roll 7 is a roll whose surface is coated with a rubber material such as NBR, EPDM, silicone, Hypalon, fluororubber, or ACM. The hardness of the rubber roll 7 is not particularly limited, but from the viewpoint of preventing blocking with the film, the Shore A hardness is preferably 30° or more, more preferably 50° or more, and may be 60° or more. From the viewpoint of restoring ability from deformation due to foreign matter, the Shore A hardness is preferably 90° or less.

[0066] In Figures 2 and 5, the diameter of the rubber roll 7 is shown to be smaller than the diameter of the metal roll 6, but the diameter of the rubber roll 7 is not particularly limited and may be the same as the diameter of the metal roll 7 or larger than the diameter of the metal roll 7.

[0067] 2 and 5, lamination is performed with the protective film 2 in contact with the metal roll 6 and the transparent film 1 in contact with the rubber roll 7, but the surface that contacts the metal roll 6 may be either the transparent film side or the protective film side. From the viewpoint of suppressing the occurrence of dents in the transparent film 1 or reducing dents in the transparent film 1, it may be preferable to arrange the protective film so that it is in contact with the metal roll.

[0068] <Explanation (Definition) of Dents> The laminate of the present invention preferably has few dents. If dents are present in the laminate, when the transparent film 1 obtained by peeling and removing the protective film 2 from the laminate 3 is applied to the cover window of a display, the displayed image may be distorted at the position of the dent, resulting in a defect.

[0069] Dents are irregular deformations formed by localized pressure on the surface of a film during the film manufacturing process or handling. Because dents are formed by pressure from one side of the film, they appear concave when viewed from one side and convex when viewed from the other side.

[0070] The dents formed in the laminate 3 during or after lamination of the transparent film 1 and the protective film 2 are visible in the same position whether observed from the transparent film 1 side or the protective film 2 side, and when the surface on the transparent film 1 side is convex, the surface on the protective film 2 side is concave, and when the surface on the transparent film 1 side is concave, the surface on the protective film 2 side is convex.

[0071] The presence or absence of dents in the laminate was confirmed by placing the laminate on a horizontal black table, irradiating it with light from a straight-tube three-band fluorescent lamp, and visually observing the reflected image of the straight-tube three-band fluorescent lamp reflected on the surface of the laminate from an angle of 30° relative to the horizontal. On a smooth surface without dents, the edges of the reflected image of the straight-tube three-band fluorescent lamp are linear, whereas in areas where convex or concave dents are present, the edges of the reflected image of the straight-tube three-band fluorescent lamp appear V-curved. The shallower the angle at which observation is made relative to the horizontal plane (the surface of the laminate), the easier it is to detect even the smallest dents; the above method detects dents with a major diameter of approximately 100 μm or more.

[0072] The size of the dent can be measured using a white light interference microscope. Specifically, a white light interference microscope (ZYGO NEWVIEW7300 manufactured by ZYGO) is used to observe the dent area from both the transparent film side and the protective film side with a 2.5x objective lens (measurement range: 5.65 mm × 4.24 mm), and the longest distance between the points where the slope of a linear profile passing through the peak top of the concave or convex shape of the dent gradually decreases on both sides including the peak top and the slope becomes zero (points where the slope becomes parallel to the reference line) is taken as the longest diameter of the dent.

[0073] In order to eliminate the influence of minute roughness due to fillers, etc., the following filter conditions are applied during measurement: Filter: Low Pass Filter Type: Gauss Spline Filter Low Wavelength: Not set Filter High Wavelength: 100.00000 μm

[0074] Dents can be classified into periodic dents and non-periodic dents. Periodic dents are dents that appear consecutively at regular intervals in the machine direction (MD) of a long film at the same position in the width direction (TD). Non-periodic dents are isolated dents that do not appear at regular intervals in the machine direction (MD) of a roll film.

[0075] "Dents at the same position in the TD" refers to dents where the difference in the TD position of each dent (the coordinates of the center of the dent measured using a JIS Class 1 steel ruler) is within 3 mm. The film is observed over a 2 m length in the MD direction to determine whether the dents are periodic. This method can determine whether there are periodic dents with a period of 1 m or less.

[0076] Periodic dents often occur over a wide area or over the entire length in the machine direction (MD), causing a decrease in yield and significantly reducing commercial value. In particular, dents with small periods occur frequently, reducing the commercial value of the entire length of the film (laminate).

[0077] The number of periodic dents in the laminate of the present invention is 2.0 / m ２ Preferably, the number is 1.0 or less per m ２ More preferably, 0.5 pieces / m or less ２ The following is particularly preferred: The number of periodic dents is ideally 0 / m ２ The fewer periodic dents, the higher the yield when the transparent film 1 is applied to a display material such as a cover window.

[0078] <Reduction of Periodic Dents> As mentioned above, dents are uneven deformations formed by localized pressure on the surface of a film. If foreign matter adheres to the surface of a roll that constitutes the film transport path, the foreign matter adhered to the roll surface locally presses the film surface as the film travels over the roll, forming concave dents on the contact surface with the roll. These dents have a period corresponding to the outer circumferential diameter of the roll.

[0079] As shown in Figure 2, a laminate formed by sandwiching and laminating a transparent film 1 and a protective film 2 between a metal roll 6 and a rubber roll 7 may have periodic dents with a period corresponding to the outer diameter of the metal roll 6. Because foreign matter that causes dents tends to adhere to the surface of the metal roll, and because the metal roll is hard and presses strongly against the film surface with nip pressure, the metal roll that constitutes the nip roll is thought to be more susceptible to dents than a rubber roll or other conveying rolls.

[0080] As a method for reducing dents caused by foreign matter adhering to the roll surface, it is known to contact an adhesive roll with the roll surface to remove the foreign matter, but this method alone was not able to reduce minute dents of about 100 μm that can be seen at a viewing angle of 30°.

[0081] In one embodiment of the present invention, a process (metal roll cleaning process) is carried out in which a cloth is brought into contact with the surface of the metal roll while the metal roll is being driven to rotate, and a rigid member is pressed against the cloth from above. By pressing the rigid member against the cloth, the contact pressure of the cloth against the metal roll increases, making it possible to efficiently wipe off foreign matter adhering to the metal roll surface with the cloth and remove it, thereby reducing the occurrence of periodic dents caused by the metal roll.

[0082] Metal roll cleaning may be performed by pressing a rigid rod wrapped with cloth against the metal roll. Alternatively, metal roll cleaning may be performed by pressing multiple rigid members against the cloth. For example, a metal roll cleaning jig, which is made of two rod-shaped members with cloth stretched across them, may be pressed against the metal roll, thereby causing multiple rigid members to be pressed against the cloth.

[0083] 3 is a cross-sectional view showing an example of the configuration of a metal roll cleaning jig 9. This metal roll cleaning jig 9 includes two rods 91 and 92 and a cloth 95 fixed to the rods 91 and 92. The two rods 91 and 92 may be connected via a connecting portion 97 as necessary.

[0084] Fig. 4 is a schematic perspective view showing the positional relationship between the two rods 91 and 92 of the metal roll cleaning jig 9 and the cloth 95. Fig. 5 is a view showing the state in which the metal roll cleaning step is carried out by pressing the cloth portion of the metal roll cleaning jig 9 against the metal roll 6.

[0085] 4, two rods 91 and 92 extend in the x direction and are connected via a connecting portion (not shown) so that they are arranged parallel to each other with a distance L between them. One end 951 of cloth 95 is fixed to rod 91, and the other end 952 is fixed to rod 92, so that a central portion 950 of cloth 95 is stretched between the two rods 91 and 92. In other words, both ends (two opposing sides) of cloth 95 are fixed portions 951 and 952 fixed to rods 91 and 92, and the portion of cloth between these fixed portions constitutes a stretching portion 950 stretched between the two rods.

[0086] 5 , the extension direction (x direction) of the rods 91 and 92 is parallel to the extension direction (TD direction) of the metal roll 6, and the cloth 95 is positioned so as to abut against the metal roll 6. In this state, the metal roll cleaning jig 9 is pressed against the metal roll 6, thereby cleaning the metal roll. The areas of the cloth 95 near the fixing portions 951 and 952 are pressed against the metal roll 6 by the force of the rods 91 and 92, and the stretched portion 950 of the cloth 95 deforms in accordance with the curvature of the metal roll 6. Because the cloth 95 is in planar contact with the metal roll 6, foreign matter adhering to the surface of the metal roll 6 can be efficiently wiped off and removed by the cloth 95, and periodic dents caused by the metal roll 6 can be reduced.

[0087] The material of the cloth 95 is not particularly limited as long as it can wipe off and remove foreign matter adhering to the surface of the metal roll, and various fibers and nonwoven fabrics such as polyester, polyamide, cellulose, polypropylene, polyethylene, acrylic, and urethane can be used. Among these, those with low dust generation and excellent strength are preferred, and commercially available clean wipers are preferably used. As the cloth, those containing polyester fibers are sometimes preferred, and for example, the "Toraysee" series manufactured by Toray Industries, etc. are preferably used.

[0088] The rods 91, 92 may be made of any material, including metal, ceramics, resin, etc., as long as they are rigid enough to transmit the force required to press the cloth 95 against the metal roll 6. To prevent damage to the metal roll due to contact between the rods and the metal roll, the rods 91, 92 are preferably softer than the metal roll, and resin is preferred. Among resins, polyacetal, polyamide, polyester, polypropylene, polyethylene, acrylic, etc. are preferred from the standpoint of strength (rigidity). Among these, polyacetal and polyamide are preferred from the standpoint of strength and abrasion resistance, and polyamide is particularly preferred from the standpoint of processability and cost.

[0089] The cross-sectional shape of the rods 91, 92 is not particularly limited and may be circular, elliptical, polygonal, irregular, etc. From the viewpoint of efficiently pressing the cloth 95 against the metal roll, it is preferable that the portion that presses against the metal roll via the cloth has a curved surface, and the cross-sectional shape of the rods 91, 92 is preferably circular or elliptical. If the cross-sectional shape is polygonal or irregular, it is preferable that the portion that presses against the metal roll via the cloth be chamfered.

[0090] The length of the rods 91 and 92 is not particularly limited. The longer the rods, the faster the cleaning of the entire width direction of the metal roll 6 can be performed. The length of the rods 91 and 92 may be 100 mm or more, 500 mm or more, or 1000 mm or more, and may be the same length as the width of the laminate or the same length as the metal roll 6. On the other hand, if the rods are excessively long, it becomes difficult to apply a uniform force across the entire width direction (the extension direction of the rods) when pressing the metal roll cleaning jig 9 against the metal roll 6, which may result in localized areas of insufficient cleaning. Therefore, the length of the rods 91 and 92 may be shorter than the length of the metal roll 6, or may be 50% or less, 40% or less, 35% or less, or 30% or less of the length of the metal roll 6.

[0091] The distance L between the two rods 91, 92 is not particularly limited as long as it is smaller than the diameter of the metal roll 6. From the viewpoint of efficiently transmitting the force pressing the metal roll cleaning jig 9 to the surface of the metal roll 6 and improving the ability to wipe off foreign matter, the distance L is preferably 80% or less of the diameter of the metal roll 6, more preferably 60% or less, even more preferably 50% or less, and may be 40% or less, 30% or less, or 25% or less. If the distance L between the two rods 91, 92 is excessively small, the area of ​​contact between the cloth 95 and the metal roll 6 may be small, and the ability to wipe off foreign matter may be reduced. Therefore, the distance L is preferably 3% or more of the diameter of the metal roll 6, more preferably 5% or more, and may be 7% or more, 10% or more, 12% or more, or 15% or more. The distance L may be 5 mm or more, 10 mm or more, 15 mm or more, 20 mm or more, 25 mm or more, 30 mm or more, 35 mm or more, or 40 mm or more, or may be 500 mm or less, 400 mm or less, 300 mm or less, 250 mm or less, 200 mm or less, 150 mm or less, or 100 mm or less.

[0092] As shown in FIG. 3 , the two rods 91 and 92 may be connected via a connecting portion 97. Connecting and fixing the two rods via the connecting portion 97 fixes their relative positions and allows them to be maintained parallel. Therefore, when the metal roll cleaning jig 9 is pressed against the metal roll 6, contact points with the metal roll 6 can be ensured along the entire length of the rods 91 and 92 in the x direction, improving the efficiency of removing foreign matter adhering to the surface of the metal roll 6. The rods 91 and 92 may be connected by connecting members at two or more locations in the length direction (x direction). Connecting the rods at two or more locations facilitates maintaining their parallel relationship. The parallel relationship between the two rods 91 and 92 may be maintained by forming the connecting members constituting the connecting portion 97 to extend in the x direction.

[0093] 4, in order to simply explain the positional relationship between the rods 91, 92 and the cloth 95, the length of the cloth 95 in the x direction is shown to be smaller than the lengths of the rods 91, 92, but the cloth 95 may be arranged to cover the entire length of the rods 91, 92 in the x direction. In order to prevent the metal roll 6 from being damaged due to contact between the rods 91, 92 and the metal roll 6, it is preferable that the length of the cloth 95 in the x direction is equal to or greater than the length of the rods 91, 92 in the x direction, and that the entire portions of the rods 91, 92 facing the metal roll 6 are covered by the cloth 95 (fixing portions 951, 952).

[0094] The method for fixing the fixing portions 951, 952 at both ends of the cloth 95 to the rods 91, 92 is not particularly limited, and various fixing means may be used, such as an adhesive such as double-sided tape, fusion, pins, screws, clamps, etc. When the metal roll cleaning jig 9 is pressed against the metal roll 6 that is being driven to rotate, a force that pulls the cloth 95 acts in the direction of rotation of the metal roll 6. Therefore, it is preferable to fix the cloth 95 so that it is not pulled off the rods 91, 92 by this force.

[0095] On the other hand, when repeatedly cleaning the metal roll surface, the cloth 95 must be replaced when it becomes contaminated or worn, so it is preferable that the cloth 95 be detachable from the rods 91 and 92. As shown in Figures 3 and 4, by wrapping and fixing the fixing portions 951 and 952 on two opposing sides of the cloth 95 around the rods 91 and 92, the force pulling the cloth 95 in the rotational direction of the metal roll 6 is reduced. Therefore, even if the cloth 95 is fixed with a small force that allows it to be detached from the rods 91 and 92, it is possible to prevent the cloth 95 from being pulled off the rods 91 and 92 during cleaning of the metal roll.

[0096] From the viewpoint of preventing the cloth 95 from being peeled off when cleaning the metal rolls, the amount of wrapping of the cloth 95 (fixing portions 951, 952) around the rods 91, 92 is preferably 25% or more (90° or more) of the circumference of the rod, more preferably 30% or more (108° or more), and may be 33% or more (120° or more), or 50% or more (180° or more). The cloth 95 may be wrapped around the entire circumference (360°) of the rods 91, 92, or may be wrapped around two or more times.

[0097] 3 to 5, an embodiment of the metal roll cleaning process is described in which a metal roll cleaning jig 9 having a cloth stretched between two rod-shaped members is pressed against a metal roll 6. However, a single rod-shaped member wrapped in cloth may also be pressed against the metal roll. Furthermore, three or more rod-shaped members may be pressed against a cloth placed in contact with the surface of the metal roll. The rigid member pressed against the cloth is not limited to a rod shape and may be, for example, a plate-shaped member. By pressing a plate-shaped member shaped to match the curvature of the metal roll against the cloth placed in contact with the surface of the metal roll, the cloth can be pressed against the surface of the metal roll over a wide area. Therefore, foreign matter adhering to the surface of the metal roll can be efficiently wiped off and removed, similar to the case of using a metal roll cleaning jig having a cloth stretched between two rod-shaped members.

[0098] In the metal roll cleaning step, the time for which the cloth is pressed against the surface of the metal roll is not particularly limited as long as it is sufficient to remove foreign matter adhering to the surface of the metal roll, but it is preferable that the cloth be pressed against the entire outer periphery of the metal roll at least once in the entire area through which the film passes on the metal roll 6. If the length of the rigid members such as rods 91 and 92 is smaller than the width of the area through which the film passes on the metal roll 6 (the width of the laminate 3), it is preferable to clean the entire area in the width direction by changing the position of the metal roll cleaning jig in the width direction, for example, while the metal roll is rotating or is stopped from rotating.

[0099] In the manufacturing process of a laminate in which a transparent film and a protective film with an adhesive layer are laminated, the timing of performing the above-mentioned metal roll cleaning step is not particularly limited. For example, the metal roll cleaning step may be performed before starting lamination of the transparent film 1 and the protective film 2, with the nip roll composed of the metal roll 6 and the rubber roll 7 in a closed or open state. Furthermore, when laminating the transparent film 1 and the protective film 2 with the nip roll closed, the metal roll cleaning step may be performed simultaneously with or after the start of lamination, or at any timing after the start of lamination. The metal roll cleaning step may be performed continuously while the metal roll is being driven to rotate, or may be performed continuously after the start of film lamination.

[0100] Before laminating the transparent film and the protective film, the previous lot of film and lead film are present on the pass line (film transport path) of the roll-to-roll laminator, and the product (lot) changeover is performed by connecting these films to the transparent film and / or protective film with adhesive tape, etc. During this changeover operation or when the film joint passes over the nip roll, foreign matter may adhere to the surface of the metal roll.

[0101] In order to remove foreign matter adhering to the surface of the metal roll when changing over such products (lots) and to suppress the occurrence of periodic dents during lamination, it is preferable to carry out a metal roll cleaning process while the transparent film 1 and the protective film 2 are being conveyed and laminated by being sandwiched between nip rolls consisting of a metal roll 6 and a rubber roll 7.

[0102] In a long laminate, the portion laminated before the metal roll cleaning process (or before the completion of the metal roll cleaning process) may have more periodic dents than the portion laminated after the metal roll cleaning process. After the portion laminated after the metal roll cleaning process reaches the take-up roll, the laminate is wound on the take-up roll to obtain a roll of laminate, thereby selectively commercializing only the non-defective portion with fewer periodic dents. Alternatively, the portion laminated before the metal roll cleaning process and the portion laminated after the metal roll cleaning process may be continuously wound to obtain a roll of laminate, and the former portion wound closer to the core (inner circumference) may be distinguished from the non-defective portion by being treated as a "B-grade" or excluded from the effective length of the product.

[0103] After the metal roll cleaning step is performed, while the transparent film 1 and the protective film 2 are being conveyed and sandwiched between the metal roll 6 and the rubber roll 7 to be laminated, an adhesive roll 8 may be pressed against the metal roll 6 (see the dashed line in Figure 5). By performing the metal roll cleaning step, foreign matter adhered to the surface of the metal roll 6 can be efficiently removed, but after the metal roll cleaning step is performed, foreign matter may accidentally adhere to the rotating metal roll 6 during lamination (when a laminate product is obtained).

[0104] During lamination, pressing the adhesive roll 8 against the rotating metal roll 6 may remove foreign matter accidentally adhering to the surface of the metal roll 6, and periodic dents caused by the metal roll may be reduced. An adhesive roll (not shown) may also be pressed against the driven rotating rubber roll 7. Pressing the adhesive roll against the rubber roll 7 during lamination may reduce periodic dents caused by the rubber roll.

[0105] As described above, according to the present invention, a laminate with few periodic dents can be obtained, and improvements in the appearance quality and yield of the film can be expected. In one embodiment of the present invention, a laminate is obtained in which a transparent film containing a polyimide resin and a protective film with an adhesive layer having an adhesive layer on one side of a polyester film are laminated and wound into a roll, and the periodic dents (dents that are irregularities with a major axis of 100 μm to 10,000 μm and that are visible at the same position from both sides of the laminate and that occur at two or more positions (within 3 mm) in the TD direction) occur at a rate of 2.0 / m. ２ A laminate is provided which is:

[0106] The present invention will be described in more detail below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0107] [Preparation of Transparent Film] A polyimide resin having a monomer composition of 70 parts by mole of 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride (6FDA) and 30 parts by mole of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA) as tetracarboxylic dianhydrides, and 100 parts by mole of 2,2′-bis(trifluoromethyl)benzidine (TFMB) as a diamine was prepared. This polyimide resin and a commercially available acrylic resin ("Parapet G" manufactured by Kuraray; a copolymer of methyl methacrylate / methyl acrylate (monomer ratio 87 / 13), glass transition temperature 109°C, acid value 0.0 mmol / g) were dissolved in methylene chloride in a weight ratio of 55:45, and 5.6 parts by weight of a triazine-based ultraviolet absorber ("ADEKA STAB LA-31RG" manufactured by ADEKA) was added per 100 parts by weight of the resins to prepare a solution with a solids concentration of 15% by weight.

[0108] This solution was applied to a PET film ("Lumirror U40" manufactured by Toray Industries, Inc.) as a support using a roll-to-roll coating and drying facility, and the film was passed through a drying oven whose temperature was set to increase stepwise from 30°C to 45°C to obtain a primary dried film with a residual solvent content of 10 to 15% by weight. The primary dried film was peeled from the support, and the primary dried film was passed through a drying oven whose temperature was set to increase stepwise from 90°C to 150°C to perform secondary drying, obtaining a film with a residual solvent content of approximately 1% by weight and a thickness of 110 μm.

[0109] The obtained film was transversely stretched (fixed-end uniaxial stretching) using a tenter-type stretching machine at a temperature of 215°C and a stretch ratio of 120% (TD length 2.20 times that of the film before stretching) to obtain a transparent film with a thickness of 50 μm and a width of 1.3 m.

[0110] The transparent film had a total light transmittance of 91.4% and a haze of 0.5%, demonstrating good transparency. The transparent film showed no cracks or breaks after a 200,000-cycle repeated bending test, demonstrating good bending resistance.

[0111] [Protective film] A polyester protective film with an adhesive layer (Sanae Chemical's "SAT PAD01", width 1.3 m) was prepared, which had an acrylic adhesive layer (thickness 10 μm) on one side of a polyethylene terephthalate film (thickness 125 μm) with an antistatic layer.

[0112] [Preparation of Laminate] Comparative Example 1 The transparent film and protective film were each conveyed at a conveying speed of 4 m / min, and laminated at a nip pressure of 0.35 MPa between a rotating metal roll (surface chrome-plated, surface roughness 0.8 μm) with a diameter of 300 mm and a driven rubber roll (made of silicone rubber, Shore A hardness 80°) to obtain a laminate in which the adhesive layer side of the protective film was bonded to the surface of the transparent film. The protective film was positioned so that the polyethylene terephthalate film side was in contact with the metal roll, and the transparent film was in contact with the rubber roll. During lamination, a vinyl chloride adhesive roll was constantly pressed against the metal roll to remove foreign matter adhering to the surface of the metal roll. The obtained laminate was wound into a roll downstream to obtain a roll-shaped laminate.

[0113] Example 1 Two cylindrical rods made of polyamide resin, each 10 mm in diameter and 100 mm in length, were fixed in a parallel position with a 50 mm gap between them, and both ends of a polyester cloth wiper for clean rooms ("Toraysee MK" manufactured by Toray) were wrapped around and fixed to the rods, thereby producing a metal roll cleaning jig in which the cloth wiper was stretched across the surface between the two polyamide resin rods.

[0114] While the transparent film and the protective film were being transported and laminated with the driven rubber roll and the driven metal roll, the portion of the cleaning jig around which the cloth wiper was wrapped was pressed against the metal roll with a force of about 1 kg and held there while the metal roll made one rotation. Thereafter, the position of the cleaning jig was moved 100 mm in the width direction, and the same operation was repeated to clean the surface of the metal roll over the entire width direction (the entire portion in contact with the transparent film) with the cleaning jig.

[0115] After cleaning the metal roll, the laminated laminate was taken up in a roll on the downstream side to obtain a roll-shaped laminate of Example 1. As in the above-mentioned Comparative Example 1, during lamination, an adhesive roll was constantly pressed against the metal roll to remove foreign matter adhering to the surface of the metal roll.

[0116] Example 2 The same procedure as in Example 1 was carried out, except that the payout positions of the transparent film and the protective film were swapped so that the transparent film was in contact with the metal roll and the protective film was in contact with the rubber roll during lamination. After cleaning the metal roll, the laminated laminate was taken up into a roll on the downstream side, thereby obtaining a roll-shaped laminate of Example 2.

[0117] [Evaluation of Laminates] <Peel Strength> The laminate was cut into a 25 mm wide strip, the transparent film surface was attached to a stainless steel plate with 25 μm thick double-sided tape, the protective film was peeled off at 180° at 300 mm / min, and the peel strength was determined by averaging the peel strength measurements over a 50 mm period extending from 25 mm after the start of peeling. The peel strength of the laminates of Comparative Example 1 and Examples 1 and 2 was 6 gf / 25 mm.

[0118] <Dents> A laminate measuring 2.0 m in the MD direction and 1.3 m in the TD direction was placed on a horizontal black table, and the image of a straight-tube three-wavelength fluorescent lamp reflected on the surface of the laminate was visually observed at an angle of 30° to the horizontal plane, and dents were detected from the shape of the edges of the reflected image. When the dents were observed using a white light interference microscope (ZYGO NEWVIEW7300, manufactured by ZYGO), all of the detected dents were irregular deformations with a major axis of 100 μm to 10,000 μm.

[0119] The center position of the dent was taken as the dent occurrence position, and the occurrence positions of all detected dents in the TD direction were measured using a JIS Class 1 steel ruler, and the presence or absence of periodicity (presence or absence of dents with a difference in coordinates in the TD direction of 3 mm or less) was confirmed. ２ On the other hand, the laminates of Examples 1 and 2 had no periodic dents (0.0 dents / m ２ ).

[0120] A comparison of Comparative Example 1 with Examples 1 and 2 shows that the occurrence of periodic dents can be suppressed and a laminate with a good appearance can be obtained by performing a metal roll cleaning step in which a cleaning jig is pressed against the metal roll. A comparison of Examples 1 and 2 shows that the occurrence of periodic dents can be suppressed by performing the metal roll cleaning step regardless of whether the transparent film or the protective film comes into contact with the metal roll.

[0121] REFERENCE SIGNS LIST 1 transparent film 2 protective film 21 substrate 22 adhesive layer 3 laminate 6 metal roll 7 rubber roll 8 adhesive roll 9 metal roll cleaning jig 91, 92 rod 97 connecting portion 95 cloth 950 stretching portion 951, 952 fixing portion

Claims

1. A method for manufacturing a laminate in which a transparent film and an adhesive-layered protective film are conveyed, sandwiched between a rotating metal roll and a driven rubber roll, laminated, and then wound up downstream to obtain a roll of laminate in which the adhesive-layered protective film is bonded to the transparent film, the method comprising a metal roll cleaning step in which, while the metal roll is being driven to rotate, a cloth is brought into contact with the surface of the metal roll and a rigid member is pressed against the cloth.

2. The method for producing a laminate according to claim 1, wherein the transparent film is a film containing a polyimide resin, and the protective film with an adhesive layer is a film having an adhesive layer on one side of a polyester film.

3. The method for manufacturing a laminate according to claim 1, wherein the rigid members are two rod-shaped members arranged parallel to each other at a distance from each other, and in the metal roll cleaning step, a metal roll cleaning jig having a cloth stretched across the two rod-shaped members is pressed against the metal roll.

4. The method for producing a laminate according to claim 3, wherein the rod-shaped member is a resin rod.

5. The method for producing a laminate according to claim 3, wherein the rod-shaped member is a rod made of polyamide resin.

6. The method for manufacturing a laminate according to claim 3, wherein in the metal roll cleaning jig, two sides of the cloth are wound around and fixed to the two rods.

7. The method for producing a laminate according to any one of claims 1 to 6, wherein the main fibers constituting the fabric are polyester fibers.

8. A method for producing a laminate described in any one of claims 1 to 6, wherein the metal roll cleaning step is carried out while the transparent film and the adhesive layer-attached protective film are being conveyed and sandwiched between the metal roll and the driven rubber roll to be laminated.

9. A method for manufacturing a laminate described in any one of claims 1 to 6, wherein after the metal roll cleaning step is performed, an adhesive roll is pressed against the metal roll while the transparent film and the adhesive layer-equipped protective film are sandwiched between the metal roll and the driven rubber roll and laminated together while being transported.

10. The method for producing a laminate according to any one of claims 1 to 6, wherein the transparent film has a thickness of 30 μm or more, and the adhesive-layered protective film has a thickness of 50 μm or more.

11. The number of periodic dents in the laminate is 2.0 / m ２ The method for producing a laminate according to any one of claims 1 to 6, wherein:

12. A laminate in which a transparent film containing a polyimide resin and a protective film with an adhesive layer having an adhesive layer on one side of a polyester film are laminated and wound into a roll, and the number of periodic dents is 2.0 / m ２ The laminate is as follows:

13. The laminate according to claim 12, wherein the transparent film has a thickness of 30 μm or more, and the adhesive-layered protective film has a thickness of 50 μm or more.

14. The laminate according to claim 12 or 13, wherein the transparent film contains the polyimide resin and a resin other than a polyimide resin.

15. The laminate according to claim 14, wherein the resin other than the polyimide resin is an acrylic resin.

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