Laminated Film

Abstract

To provide a laminated film capable of suppressing generation of wrinkles and floating from a curved surface even when the laminated film is stuck to the curved surface having a curvature radius of 5 cm or less, and capable of being smoothly peeled from the curved surface.SOLUTION: A laminated film according to an embodiment of the invention includes a base film made of a resin material and an adhesive layer. The adhesive layer is laminated on the base film. The heat shrinkage rate of the base film at the glass transition temperature±10°C of the resin material of the base film is 0.20% or less. The peel force of the laminated film with respect to the acrylic plate is 1.0 N / 25 mm or more and 3.0 N / 25 mm or less at a tensile speed of 30 m / min and a peel angle of 180°.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] It is known that laminate films comprising a base film and a pressure-sensitive adhesive layer are attached to the surfaces of various industrial products for various purposes. Examples of purposes for attaching laminate films include imparting a desired design to the adherend using a laminate film further comprising a printing layer, and protecting the surface of the adherend. For example, a surface protection film for polarizing plates has been proposed as such a laminate film, which has a support film and a pressure-sensitive adhesive layer formed on one or both sides of the support film (see Patent Document 1).

[0003] In recent years, the applications of laminate films have become more diverse, and laminate films are sometimes attached to curved surfaces. However, when laminate films are attached to curved surfaces with a curvature radius of 5 cm or less, wrinkles may form in the laminate film, adversely affecting the adherend, or the laminate film may lift off (partially peel off) from the curved surface. Furthermore, laminate films may be required to be peeled off from the curved surface at a desired time depending on the application of the adherend. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2017-32768 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made to solve the above-mentioned conventional problems, and its main object is to provide a laminated film that can suppress the occurrence of wrinkles and lifting from the curved surface even when the laminated film is attached to a curved surface with a curvature radius of 5 cm or less, and can be smoothly peeled off from the curved surface. [Means for solving the problem]

[0006] [1] A laminated film according to one embodiment of the present invention includes a base film and a pressure-sensitive adhesive layer. The base film is made of a resin material. The pressure-sensitive adhesive layer is laminated on the base film. The base film has a heat shrinkage of 0.20% or less at a temperature within ±10°C of the glass transition temperature of the resin material. The peel force of the laminated film from an acrylic plate is 1.0 N / 25 mm or more and 3.0 N / 25 mm or less at a pulling speed of 30 m / min and a peel angle of 180°. [2] In the laminated film described in [1] above, the glass transition temperature of the resin material may be 125° C. or higher. [3] In the laminated film according to the above [1] or [2], the resin material may be amorphous. [4] In the laminated film according to any one of the above [1] to [3], the resin material may contain a polycarbonate resin and / or a cycloolefin resin. [5] In the laminate film according to any one of the above [1] to [4], the pressure-sensitive adhesive layer may be made of a (meth)acrylic pressure-sensitive adhesive. [Effects of the Invention]

[0007] According to an embodiment of the present invention, a laminated film can be realized that is able to be smoothly peeled off from a curved surface, while suppressing the occurrence of wrinkles and lifting from the curved surface, even when attached to a curved surface with a curvature radius of 5 cm or less. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view of a laminated film according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] Representative embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. In addition, in order to clarify the explanation, the width, thickness, shape, etc. of each part may be shown schematically in the drawings compared to the embodiments, but these are merely examples and do not limit the interpretation of the present invention.

[0010] (Definition of terms and symbols) The definitions of terms and symbols used in this specification are as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction in which the in-plane refractive index is greatest (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane retardation measured with light of wavelength λ nm at 23°C. For example, "Re(550)" is the in-plane retardation measured with light of wavelength 550 nm at 23°C. Re(λ) is calculated by the formula: Re(λ)=(nx-ny)×d, where d (nm) is the thickness of the layer (film). (3) Retardation in the thickness direction (Rth) "Rth(λ)" is the retardation in the thickness direction measured with light of wavelength λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction measured with light of wavelength 550 nm at 23°C. Rth(λ) is calculated by the formula: Rth(λ) = (nx - nz) × d, where d (nm) is the thickness of the layer (film).

[0011] A. Overall structure of laminated film FIG. 1 is a schematic cross-sectional view of a laminated film according to one embodiment of the present invention. The illustrated laminated film 100 includes a base film 1 and a pressure-sensitive adhesive layer 2. The base film 1 is made of a resin material. The pressure-sensitive adhesive layer 2 is laminated on the base film 1. The heat shrinkage of the base film 1 is 0.20% or less, preferably 0.18% or less, and more preferably 0.15% or less at the glass transition temperature of the resin material constituting the base film 1 ±10°C. The lower limit of the heat shrinkage of the base film is typically 0.001%. The peel force of the laminated film 100 from the acrylic plate is 1.0 N / 25 mm or more, preferably 1.2 N / 25 mm or more, and 3.0 N / 25 mm or less, preferably 2.5 N / 25 mm or less, more preferably 2.0 N / 25 mm or less, and even more preferably 1.8 N / 25 mm or less, at a pulling speed of 30 m / min and a peel angle of 180°. When the heat shrinkage rate of the base film is equal to or less than the upper limit and the peel strength of the laminate film is equal to or greater than the lower limit, even when the laminate film is attached to a curved surface with a curvature radius of 5 cm or less, the laminate film can be prevented from wrinkling and from lifting (partially peeling) from the curved surface. Therefore, the laminate film can be stably maintained in a state conforming to the curved surface while suppressing the influence of the laminate film on the adherend. Furthermore, because the peel strength of the laminate film is equal to or less than the upper limit, the laminate film can be smoothly peeled from the curved surface.

[0012] The glass transition temperature (hereinafter sometimes referred to as Tg) of the resin material constituting the base film 1 is, for example, 80°C or higher, preferably 125°C or higher. If the Tg of the resin material is equal to or higher than the above lower limit, the formation of wrinkles in the laminate film can be stably suppressed when the laminate film is attached to a curved surface with a curvature radius of 5 cm or less. The upper limit of the Tg of the base film is typically 180°C. The glass transition temperature can be measured using any appropriate simultaneous thermogravimetry-differential thermal analyzer (TG-DTA).

[0013] The components of the laminated film will be described below.

[0014] B. Base film The base film 1 contains a resin material as its main component. Specific examples of the resin material include transparent resins such as cycloolefin (COP) resins (e.g., polynorbornene resins), polyester resins (e.g., polyethylene terephthalate (PET) resins), cellulose resins (e.g., triacetyl cellulose (TAC)), polycarbonate (PC) resins, (meth)acrylic resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyethersulfone resins, polysulfone resins, polystyrene resins, polyolefin resins, and acetate resins. Also included are thermosetting or ultraviolet-curable resins such as (meth)acrylic resins, urethane resins, (meth)acrylic urethane resins, epoxy resins, and silicone resins. The term "(meth)acrylic resin" refers to acrylic resins and / or methacrylic resins. Other examples include glassy polymers such as siloxane polymers. The polymer films described in JP 2001-343529 A (WO 01 / 37007) can also be used. Examples of materials for this film include resin compositions containing a thermoplastic resin with substituted or unsubstituted imide groups in its side chains and a thermoplastic resin with substituted or unsubstituted phenyl and nitrile groups in its side chains. Examples include a resin composition containing an alternating copolymer of isobutene and N-methylmaleimide and an acrylonitrile-styrene copolymer. The polymer film can be, for example, an extrusion molded product of the above resin composition. The resin film materials can be used alone or in combination.

[0015] In one embodiment, the resin material of the base film 1 is amorphous. When the base film is made of an amorphous resin material, excellent transparency can be imparted to the laminate film.

[0016] Of these resin materials, preferably, PC-based resin and / or COP-based resin is used, and more preferably, PC-based resin is used.

[0017] PC resins contain at least structural units derived from dihydroxy compounds having a bond structure represented by the following structural formula (1), and are produced by reacting a dihydroxy compound containing at least one dihydroxy compound having at least one -CH2-O- bond in the molecule with a carbonate diester in the presence of a polymerization catalyst. In other words, PC resins contain structural units derived from dihydroxy compounds and carbonate groups derived from carbonate diesters. [ka]

[0018] Here, the dihydroxy compound having the bond structure represented by structural formula (1) can be any compound having any structure, as long as it has two alcoholic hydroxyl groups, contains a structure having a linking group -CH-O- in the molecule, and is capable of reacting with a carbonate diester in the presence of a polymerization catalyst to produce a polycarbonate, and multiple types may be used in combination.

[0019] Furthermore, a dihydroxy compound not having the bond structure represented by the structural formula (1) may be used in combination with the dihydroxy compound used in the PC resin. Hereinafter, a dihydroxy compound having the bond structure represented by the structural formula (1) may be abbreviated as dihydroxy compound (A), and a dihydroxy compound not having the bond structure represented by the structural formula (1) may be abbreviated as dihydroxy compound (B).

[0020] (Dihydroxy compound (A)) The "linking group -CH2-O-" in the dihydroxy compound (A) means a structure in which atoms other than hydrogen atoms are bonded to form a molecule. In this linking group, the atom to which at least an oxygen atom can be bonded or the atom to which both a carbon atom and an oxygen atom can be bonded is preferably a carbon atom. The number of "linking groups -CH2-O-" in the dihydroxy compound (A) is preferably 1 or more, more preferably 2 to 4.

[0021] Specific examples of the dihydroxy compound (A) include 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, and 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene. a compound having an aromatic group in a side chain and an ether group bonded to the aromatic group in the main chain, such as 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, or 9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene;Bis[4-(2-hydroxyethoxy)phenyl]methane, bis[4-(2-hydroxyethoxy)phenyl]diphenylmethane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]ethane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]-1-phenylethane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, 2,2-bis[4-(2-hydroxyethoxy)-3-methylphenyl]propane, 2,2-bis[3,5-dimethyl-4-(2-hydroxyethoxy)phenyl]propane 1,1-bis[4-(2-hydroxyethoxy)phenyl]propane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]-3,3,5-trimethylcyclohexane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,4-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,3-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 2,2-bis[4-(2-hydroxyethoxy)-3-phenylphenyl]propane, 2,2-bis[(2-hydroxyethoxy)-3- isopropylphenyl]propane, 2,2-bis[3-tert-butyl-4-(2-hydroxyethoxy)phenyl]propane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]butane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]-4-methylpentane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]octane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]decane, 2,2-bis[3-bromo-4-(2-hydroxyethoxy)phenyl]propane bis(hydroxyalkoxyaryl)alkanes, such as 2,2-bis[3-cyclohexyl-4-(2-hydroxyethoxy)phenyl]propane; bis(hydroxyalkoxyaryl)cycloalkanes, such as 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,1-bis[3-cyclohexyl-4-(2-hydroxyethoxy)phenyl]cyclohexane, and 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclopentane;Dihydroxyalkoxy diaryl ethers, such as 4,4'-bis(2-hydroxyethoxy)diphenyl ether and 4,4'-bis(2-hydroxyethoxy)-3,3'-dimethyldiphenyl ether; bishydroxyalkoxy aryl sulfides, such as 4,4'-bis(2-hydroxyethoxyphenyl) sulfide and 4,4'-bis[4-(2-dihydroxyethoxy)-3-methylphenyl] sulfide; bishydroxyalkoxy aryl sulfoxides, such as 4,4'-bis(2-hydroxyethoxyphenyl) sulfoxide and 4,4'-bis[4-(2-dihydroxyethoxy)-3-methylphenyl] sulfoxide; 4,4'-bis(2-hydroxyethoxyphenyl) sulfone, 4,4'-bis[4-(2- Examples of the dihydroxy compound (A) include bishydroxyalkoxyarylsulfones, such as 1,4-bishydroxyethoxybenzene; bishydroxyalkoxybenzenes, such as 1,4-bishydroxyethoxybenzene; 1,3-bis[2-[4-(2-hydroxyethoxy)phenyl]propyl]benzene; 1,4-bis[2-[4-(2-hydroxyethoxy)phenyl]propyl]benzene; 4,4'-bis(2-hydroxyethoxy)biphenyl; 1,3-bis[4-(2-hydroxyethoxy)phenyl]-5,7-dimethyladamantane; anhydrosugar alcohols, such as the dihydroxy compound represented by the following formula (2); and compounds having a cyclic ether structure, such as the spiroglycol represented by the following general formula (3). The dihydroxy compound (A) may be used alone or in combination.

[0022] [ka]

[0023] [ka]

[0024] Of these dihydroxy compounds (A), preferred is the dihydroxy compound represented by the above formula (2). Examples of the dihydroxy compound represented by the above formula (2) include isosorbide, isomannide, and isoidet, which are stereoisomers, and these may be used alone or in combination of two or more. Among the dihydroxy compounds (A), isosorbide, which is obtained by dehydration condensation of sorbitol produced from various starches that are abundant and easily available as resources, is most preferred in terms of availability, ease of production, optical properties, and moldability.

[0025] The proportion of the structural units derived from the dihydroxy compound (A) relative to all structural units derived from dihydroxy compounds contained in the PC resin is, for example, 10 mol% or more, preferably 40 mol% or more, more preferably 60 mol% or more, and for example, 100 mol% or less, preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mol% or less. When the proportion of the dihydroxy compound (A) is within the above range, the heat shrinkability of the base film can be suitably adjusted.

[0026] (Dihydroxy compound (B)) As the dihydroxy compound that forms the structural unit of the PC resin, dihydroxy compound (A) and dihydroxy compound (B) can be used together. By using dihydroxy compounds (A) and (B) in combination, the heat shrinkability of the base film can be more suitably adjusted.

[0027] The dihydroxy compound (B) is typically a dihydroxy compound other than the dihydroxy compound (A). Examples of the dihydroxy compound (B) include alicyclic dihydroxy compounds, aliphatic dihydroxy compounds, oxyalkylene glycols, aromatic dihydroxy compounds, and diols having a cyclic ether structure. The dihydroxy compounds (B) may be used alone or in combination. Of the dihydroxy compounds (B), preferred are alicyclic dihydroxy compounds.

[0028] The alicyclic dihydroxy compound is not particularly limited, but preferably includes a compound having a five-membered ring structure or a six-membered ring structure. The six-membered ring structure may be fixed in a chair or boat shape by a covalent bond. The five-membered or six-membered ring structure of the alicyclic dihydroxy compound can improve the heat resistance of the resulting PC resin. The number of carbon atoms contained in the alicyclic dihydroxy compound is, for example, 70 or less, preferably 50 or less, and more preferably 30 or less.

[0029] Specific examples of the alicyclic dihydroxy compound containing a 5-membered ring structure or a 6-membered ring structure include alicyclic dihydroxy compounds represented by the following general formula (I) or (II). HOCH2-R 1 -CH2OH (I) HO-R 2 -OH (II) (In formulas (I) and (II), R 1 and R 2 Each of the represents a cycloalkylene group having 4 to 20 carbon atoms.

[0030] Cyclohexanedimethanol, which is an alicyclic dihydroxy compound represented by the general formula (I), is a compound represented by the general formula (I) in which R 1 is represented by the following general formula (Ia) (wherein R 3 represents an alkyl group having 1 to 12 carbon atoms or a hydrogen atom. Specific examples of such isomers include 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol.

[0031] [ka]

[0032] The alicyclic dihydroxy compound represented by the general formula (I), tricyclodecane dimethanol or pentacyclopentadecanedimethanol, is a compound represented by the general formula (I), 1The compound includes various isomers represented by the following general formula (Ib) (wherein n is 0 or 1).

[0033] [ka]

[0034] Decalin dimethanol or tricyclotetradecane dimethanol, which is an alicyclic dihydroxy compound represented by the above general formula (I), is a compound represented by the general formula (I) in which R 1 is represented by the following general formula (Ic) (wherein m is 0 or 1). Specific examples of such isomers include 2,6-decalin dimethanol, 1,5-decalin dimethanol, and 2,3-decalin dimethanol.

[0035] [ka]

[0036] Norbornane dimethanol, which is an alicyclic dihydroxy compound represented by the above general formula (I), is a compound represented by the general formula (I) in which R 1 The isomers include various isomers represented by the following general formula (Id): Specific examples of such isomers include 2,3-norbornane dimethanol and 2,5-norbornane dimethanol.

[0037] [ka]

[0038] Adamantane dimethanol, which is an alicyclic dihydroxy compound represented by general formula (I), is 1 The general formula (Ie) includes various isomers represented by the following general formula (Ie): Specific example of such isomer is 1,3-adamantanedimethanol.

[0039] [ka]

[0040] The cyclohexanediol, which is an alicyclic dihydroxy compound represented by the general formula (II), is a compound represented by the general formula (II) in which R 2 is represented by the following general formula (IIa) (wherein R 3 represents an alkyl group having 1 to 12 carbon atoms or a hydrogen atom. Specific examples of such isomers include 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, and 2-methyl-1,4-cyclohexanediol.

[0041] [ka]

[0042] The alicyclic dihydroxy compound represented by the general formula (II), tricyclodecanediol or pentacyclopentadecanediol, is a compound represented by the general formula (II), 2 includes various isomers represented by the following general formula (IIb) (wherein n is 0 or 1).

[0043] [ka]

[0044] Decalindiol or tricyclotetradecanediol, which is an alicyclic dihydroxy compound represented by the above general formula (II), is a compound represented by the general formula (II) in which R 2 is represented by the following general formula (IIc) (wherein m represents 0 or 1). Specific examples of such isomers include 2,6-decalindiol, 1,5-decalindiol, and 2,3-decalindiol.

[0045] [ka]

[0046] Norbornanediol, which is an alicyclic dihydroxy compound represented by the above general formula (II), is 2 The isomers include various isomers represented by the following general formula (IId): Specific examples of such isomers include 2,3-norbornanediol and 2,5-norbornanediol.

[0047] [ka]

[0048] Adamantanediol, which is an alicyclic dihydroxy compound represented by the general formula (II), is a compound represented by the general formula (II) in which R 2 These include various isomers represented by the following general formula (IIe): Specific examples of such isomers include 1,3-adamantanediol.

[0049] [ka]

[0050] Among the specific examples of the alicyclic dihydroxy compound described above, preferred are cyclohexanedimethanols, tricyclodecane dimethanols, adamantanediols, and pentacyclopentadecanedimethanols. From the viewpoints of availability and ease of handling, more preferred are 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, and tricyclodecane dimethanol, and even more preferred is tricyclodecane dimethanol.

[0051] The proportion of the structural units derived from the dihydroxy compound (B) relative to all structural units derived from dihydroxy compounds contained in the PC resin is, for example, 0 mol% or more, preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more, and is, for example, 90 mol% or less, preferably 60 mol% or less, and more preferably 40 mol% or less.

[0052] Details of these PC resins are described, for example, in JP 2012-31370 A (Patent No. 5448264), the disclosure of which is incorporated herein by reference.

[0053] In one embodiment, the PC resin contains a structural unit derived from the dihydroxy compound (A) represented by the above formula (2), a structural unit derived from the alicyclic dihydroxy compound (B) represented by the above general formula (I), and a carbonate group linking them. When a PC resin containing these structural units is used in a substrate film, the heat shrinkability of the substrate film can be more suitably adjusted. In such a PC resin, the molar ratio (A:B) of the structural units derived from the dihydroxy compound (A) represented by the above formula (2) to the structural units derived from the alicyclic dihydroxy compound (B) represented by the above general formula (I) is, for example, 5:5 to 9:1, and preferably 6:4 to 8:2. In such a PC resin, the combination of the dihydroxy compound (A) represented by the above formula (2) and the alicyclic dihydroxy compound (B) represented by the above general formula (I) is preferably a combination of isosorbide and tricyclodecane dimethanol.

[0054] In addition to the resin material described above, the substrate film 1 may contain any appropriate additive. Examples of additives include antioxidants, UV absorbers, light stabilizers, nucleating agents, fillers, pigments, surfactants, and antistatic agents. Any appropriate surface treatment layer may be provided on the surface of the substrate film 1 (the surface opposite the pressure-sensitive adhesive layer 2). Examples of surface treatment layers include an easy-adhesion layer, an easy-slip layer, an antiblocking layer, an antistatic layer, an antireflection layer, and an anti-oligomer layer.

[0055] The thickness of the substrate film 1 is, for example, 5 μm or more, preferably 20 μm or more, and for example, 200 μm or less, preferably 100 μm or less.

[0056] The in-plane retardation Re(550) of the base film 1 is, for example, 100 nm or less, preferably 50 nm or less, more preferably 30 nm or less, even more preferably 20 nm or less, particularly preferably 10 nm or less, and particularly preferably 5 nm or less. The lower limit of the in-plane retardation Re(550) of the base film 1 is typically 0 nm.

[0057] The thickness direction retardation Rth(550) of the substrate film 1 is, for example, 100 nm or less, preferably 50 nm or less, more preferably 30 nm or less, still more preferably 20 nm or less, particularly preferably 10 nm or less, and particularly preferably 5 nm or less. The lower limit of Rth(550) of the substrate film 1 is typically 0 nm.

[0058] The haze value of the base film 1 is, for example, 2% or less, preferably 1.5% or less, more preferably 0.4% or less, and typically 0.05% or more.

[0059] C. Adhesive layer The adhesive layer 2 is provided on the surface of the base film 1 in order to attach the laminate film 100 to the surface of an adherend, particularly a curved surface with a curvature radius of 5 cm or less. The adhesive layer 2 is made of an adhesive (pressure-sensitive adhesive).

[0060] Examples of adhesives that can be used to form the adhesive layer 2 include (meth)acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, number, combination, and compounding ratio of the monomers that form the base resin of the adhesive, as well as the amount of crosslinking agent, reaction temperature, reaction time, etc., it is possible to prepare an adhesive having the desired properties depending on the purpose. The base resin of the adhesive may be used alone or in combination of two or more types.

[0061] In one embodiment, the pressure-sensitive adhesive layer 2 is composed of a (meth)acrylic pressure-sensitive adhesive (a (meth)acrylic pressure-sensitive adhesive composition). When the pressure-sensitive adhesive layer is composed of a (meth)acrylic pressure-sensitive adhesive, the peel strength of the laminated film can be stably adjusted to within the above-mentioned range.

[0062] The (meth)acrylic pressure-sensitive adhesive composition typically contains a (meth)acrylic polymer as a main component, and the content of the (meth)acrylic polymer in the solid content of the pressure-sensitive adhesive composition is, for example, 50% by mass or more, preferably 70% by mass or more, more preferably 90% by mass or more, and for example, 100% by mass or less.

[0063] The (meth)acrylic polymer contains structural units derived from alkyl (meth)acrylate. The content of the structural units derived from alkyl (meth)acrylate in the (meth)acrylic polymer is, for example, 70% by mass or more, preferably 80% by mass or more, and for example, 90% by mass or less. Examples of the alkyl group of the alkyl (meth)acrylate include linear or branched alkyl groups having 1 to 18 carbon atoms. The average number of carbon atoms in the alkyl group is preferably 3 to 12, and more preferably 3 to 8. Among the alkyl (meth)acrylates, preferred are butyl acrylate and 2-ethylhexyl acrylate, and more preferred is 2-ethylhexyl acrylate.

[0064] The (meth)acrylic polymer may contain, in addition to the structural unit derived from the alkyl (meth)acrylate, a structural unit derived from a copolymerizable monomer polymerizable with the alkyl (meth)acrylate. Examples of the copolymerizable monomer include a carboxyl group-containing monomer, a hydroxyl group-containing monomer, an amide group-containing monomer, an aromatic ring-containing (meth)acrylate, and a heterocycle-containing vinyl monomer. The copolymerizable monomers can be used alone or in combination. Of the copolymerizable monomers, preferred are carboxyl group-containing monomers and hydroxyl group-containing monomers. In one embodiment, the (meth)acrylic polymer contains structural units derived from an alkyl (meth)acrylate, structural units derived from a carboxyl group-containing monomer, and structural units derived from a hydroxyl group-containing monomer.

[0065] The carboxyl group-containing monomer is a compound that contains a carboxyl group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of the carboxyl group-containing monomer include (meth)acrylic acid, carboxyethyl (meth)acrylate, maleic acid, fumaric acid, and crotonic acid, and preferably (meth)acrylic acid. When the (meth)acrylic polymer contains a structural unit derived from the carboxyl group-containing monomer, the adhesive properties of the pressure-sensitive adhesive layer can be improved.

[0066] When the (meth)acrylic polymer contains structural units derived from carboxyl group-containing monomers, the content of the structural units derived from carboxyl group-containing monomers is, for example, 0.01% by mass or more, preferably 0.10% by mass or more, and for example, 10% by mass or less, preferably 5.0% by mass or less, more preferably 1.0% by mass or less, and even more preferably 0.5% by mass or less.

[0067] The hydroxyl group-containing monomer is a compound that contains a hydroxyl group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. Preferred examples include 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate, and more preferred examples include 4-hydroxybutyl (meth)acrylate. When the (meth)acrylic polymer contains a structural unit derived from the hydroxyl group-containing monomer, the durability of the pressure-sensitive adhesive layer can be improved.

[0068] When the (meth)acrylic polymer contains structural units derived from hydroxyl group-containing monomers, the content of the structural units derived from hydroxyl group-containing monomers is, for example, 0.01 mass% or more, preferably 1.0 mass% or more, more preferably 5.0 mass% or more, and even more preferably 8.0 mass% or more, and for example, 10 mass% or less.

[0069] The weight average molecular weight Mw of the (meth)acrylic polymer is, for example, 100,000 to 2,000,000, and preferably 200,000 to 1,000,000. The weight average molecular weight Mw can be calculated, for example, from the results of GPC measurement in terms of styrene.

[0070] The (meth)acrylic adhesive may also contain a crosslinking agent. Typical examples of the crosslinking agent include organic crosslinking agents and polyfunctional metal chelates, and preferably organic crosslinking agents. Examples of the organic crosslinking agent include isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, and imine crosslinking agents, and more preferably isocyanate crosslinking agents.

[0071] The content of the crosslinking agent is, relative to 100 parts by mass of the (meth)acrylic polymer, for example, 0.01 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1.2 parts by mass or more, and for example, 10 parts by mass or less, preferably 5 parts by mass or less, more preferably 2.5 parts by mass or less, and even more preferably 2.0 parts by mass or less. When the content of the crosslinking agent is within the above range, the peel force of the laminated film can be stably adjusted within the above range.

[0072] Furthermore, the (meth)acrylic pressure-sensitive adhesive may contain various additives (for example, a silane coupling agent, a polymerization initiator, a solvent, a crosslinking catalyst) in an appropriate ratio. Details of these adhesives are described, for example, in JP 2006-183022 A, JP 2015-199942 A, JP 2018-053114 A, JP 2016-190996 A, and WO 2018 / 008712 A, the disclosures of which are incorporated herein by reference.

[0073] The thickness of the pressure-sensitive adhesive layer 2 is typically 1 μm or more, preferably 5 μm or more, and typically 30 μm or less, preferably 15 μm or less.

[0074] D. Release liner The laminate film 100 may further include a release liner 3 in addition to the base film 1 and the pressure-sensitive adhesive layer 2. The release liner 3 is typically temporarily attached to the pressure-sensitive adhesive layer 2 until the laminate film is attached to an adherend, and is peeled off from the pressure-sensitive adhesive layer 2 when the laminate film is attached. The release liner 3 is formed of any appropriate resin film that can be used as a release liner. A release-treated layer may be provided on the surface of the release liner 3 that comes into contact with the pressure-sensitive adhesive layer 2.

[0075] E. Applications of laminated film The laminated films described in the above items A to D are used by being attached to the surface of various adherends. More specifically, the laminated film 100 is attached to the surface of the adherend (particularly a curved surface with a curvature radius of 5 cm or less) by the pressure-sensitive adhesive layer 2. Examples of the adherend include optical components and electronic components, preferably optical components. Typical examples of the optical components include polarizing plates, retardation films, optical laminates containing polarizing plates and / or retardation films, displays, imaging devices, lenses, and (half) mirrors. The radius of curvature of the curved surface of the adherend is, for example, 5 cm or less, or, for example, 3 cm or less, and, for example, 0.5 cm or more.

[0076] In one embodiment, the laminate film 100 is a decorative film. When the laminate film 100 is a decorative film, the laminate film 100 has a printed layer (not shown) in addition to the base film 1 and the pressure-sensitive adhesive layer 2. The printed layer is provided on the surface of the pressure-sensitive adhesive layer 2 opposite to the base film 1. Such decorative films are attached to the surface of an adherend (typically a curved surface with a radius of curvature of 5 cm or less) so that the printed layer is in contact with the adherend. They are then heated as needed and peeled off from the surface of the adherend. The printed layer is then transferred to the surface of the adherend (particularly a curved surface with a radius of curvature of 5 cm or less), imparting a desired design to the adherend.

[0077] In another embodiment, the laminated film 100 is a film with a pressure-sensitive adhesive layer, and can be suitably used as a surface protection film. Such a surface protection film is attached to the surface of an adherend (typically a curved surface with a radius of curvature of 5 cm or less). This can protect the surface of the adherend during processing and / or transportation of the adherend. The surface protection film is then peeled off and removed from the surface of the adherend at the desired time. [Example]

[0078] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring each property are as follows.

[0079] (1) Glass transition temperature (Tg) of the base film The glass transition temperatures of the resin materials constituting the substrate films used in the examples and comparative examples were measured using a differential scanning calorimeter (DSC6220) manufactured by SII NanoTechnology. More specifically, approximately 10 mg of resin sample was placed in an aluminum pan manufactured by SII NanoTechnology, sealed, and heated from 30°C to 200°C at a heating rate of 20°C / min under a 50 mL / min nitrogen flow. After holding the temperature for 3 minutes, the sample was cooled to 30°C at a rate of 20°C / min. The sample was then held at 30°C for 3 minutes and again heated to 200°C at a rate of 20°C / min. From the DSC data obtained during the second heating run, the extrapolated glass transition onset temperature (Tg) was determined. This temperature was the intersection of a line extending the low-temperature baseline toward the high-temperature side and a tangent drawn at the point where the gradient of the stepwise change in the glass transition curve is greatest. This was designated the glass transition temperature (Tg). The results are shown in Table 1.

[0080] (2) Measurement of heat shrinkage of base film The substrate film used in the examples and comparative examples was attached to a 1 mm thick glass plate via an adhesive layer to prepare a measurement sample, and the four corners of the film were marked. The length L0 between the marks at the four corners of the film was measured using a Mitutoyo Quick Vision image measuring device. The measured sample was placed in a heating oven at ±10°C of the glass transition temperature (Tg) of the resin material for 120 hours, and then the length L500 between the marks at the four corners of the polarizing film was measured again. The dimensional change rate was calculated using the following formula. The results are shown in Table 1. Dimensional change rate (%) = {(L500-L0) / L0} x 100

[0081] (3) Peel strength measurement of laminated film The laminated films obtained in the Examples and Comparative Examples were cut into 25 mm x 100 mm strips to prepare samples. The samples were then roll-bonded to the surface of an acrylic plate ("Acrylite" manufactured by Mitsubishi Chemical Corporation, thickness: 2 mm, width: 70 mm, length: 100 mm) via the adhesive layer at a pressure of 0.25 MPa and a feed rate of 0.3 m / min. The samples were then left to stand for 30 minutes in an environment at 23°C and 50% relative humidity. Then, a peel test was conducted in the same environment at a peel angle of 180° and a pulling rate of 30 m / min to measure the peel force. The evaluation results are shown in Table 1.

[0082] (4) Evaluation of curved surface workability An adherend with a curved surface with a radius of curvature of 3 cm was prepared. Next, the laminated films obtained in the Examples and Comparative Examples were attached to the curved surface of the adherend using the adhesive layer. The laminated films were then visually and microscopically inspected for wrinkles and for any lifting from the adherend. The results are shown in Table 1. The laminated film was then visually inspected for peeling from the adherend. The results are shown in Table 1.

[0083] <<Preparation Example 1: Adhesive Composition A>> A reaction vessel equipped with a thermometer, stirrer, condenser, and nitrogen gas inlet tube was charged with 100 parts by weight of 2-ethylhexyl acrylate (2EHA), 10 parts by weight of 4-hydroxybutyl acrylate (4HBA), 0.02 parts by weight of acrylic acid (AA), and 0.2 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, along with 157 parts by weight of ethyl acetate. Nitrogen gas was introduced while gently stirring at 23°C to perform nitrogen substitution. The liquid temperature was then maintained at around 65°C, and a polymerization reaction was carried out for 6 hours to prepare a solution of (meth)acrylic polymer A (concentration 40% by weight). The weight-average molecular weight of acrylic polymer A was 540,000.

[0084] Ethyl acetate was added to the solution of acrylic polymer A to dilute it to a concentration of 20% by mass. To 500 parts by mass of this solution (solid content 100 parts by mass), 1.5 parts by mass of an isocyanurate of hexamethylene diisocyanate ("Coronate HX" manufactured by Tosoh Corporation) as a crosslinking agent and 3 parts by mass (solid content 0.03 parts by mass) of dibutyltin dilaurate (1% by mass ethyl acetate solution) as a crosslinking catalyst were added and stirred to prepare PSA composition A.

[0085] <<Preparation Example 2: Adhesive Composition B>> A pressure-sensitive adhesive composition B was prepared in the same manner as in Preparation Example 1, except that the amount of the isocyanurate of hexamethylene diisocyanate added as the crosslinking agent was changed to 3.0 parts by mass.

[0086] <<Preparation Example 3: Adhesive Composition C>> A pressure-sensitive adhesive composition C was prepared in the same manner as in Preparation Example 1, except that the amount of the isocyanurate of hexamethylene diisocyanate added as the crosslinking agent was changed to 0.3 parts by mass.

[0087] <<Preparation Example 4: Preparation of PC resin film>> 81.98 parts by mass of isosorbide (ISB), 47.19 parts by mass of tricyclodecane dimethanol (TCDDM), 175.1 parts by mass of diphenyl carbonate (DPC), and 0.979 parts by mass of a 0.2% by mass aqueous solution of cesium carbonate as a catalyst were charged into a reaction vessel. Under a nitrogen atmosphere, the heating vessel temperature was heated to 150°C as the first step of the reaction, and the raw materials were dissolved (approximately 15 minutes) with stirring as necessary. Next, the pressure was increased from atmospheric pressure to 13.3 kPa, and the heating vessel temperature was raised to 190°C over 1 hour, while the generated phenol was withdrawn from the reaction vessel. After the entire reaction vessel was held at 190°C for 15 minutes, the pressure inside the reaction vessel was increased to 6.67 kPa, and the heating vessel temperature was raised to 230°C over 15 minutes as the second step, and the generated phenol was withdrawn from the reaction vessel. As the stirring torque of the mixer increased, the temperature was raised to 250°C in 8 minutes. Furthermore, the pressure inside the reactor was reduced to 0.200 kPa or less to remove the phenol generated. After reaching the predetermined stirring torque, the reaction was terminated, and the resulting reaction product was extruded into water to obtain PC resin pellets. The resulting PC resin was vacuum-dried at 100°C for 12 hours, and then a 20 μm-thick PC resin film was produced using a film-making device equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder temperature setting: 250°C), a T-die (width: 1700 mm, temperature setting: 250°C), a cast roll (temperature setting: 60°C), and a winder.

[0088] [Example 1] The pressure-sensitive adhesive composition A of Preparation Example 1 was applied to the surface of the PC resin film (substrate film) of Preparation Example 4, and then dried to form a pressure-sensitive adhesive layer with a thickness of 15 μm. In this way, a laminate film was obtained.

[0089] [Example 2] A laminated film was obtained in the same manner as in Example 1, except that the PC resin film in Preparation Example 4 was changed to a COP resin film (manufactured by Nippon Zeon Co., Ltd., product number ZF16).

[0090] [Comparative Example 1] A laminated film was obtained in the same manner as in Example 1, except that the PC resin film in Preparation Example 4 was changed to a PET film (manufactured by Toray Industries, Inc., product number "50U48").

[0091] Comparative Example 2 A laminated film was obtained in the same manner as in Example 1, except that the PC resin film of Preparation Example 4 was changed to an acrylic resin film (manufactured by Kaneka Corporation, product name "HTX-Z").

[0092] Comparative Example 3 A laminated film was obtained in the same manner as in Example 1, except that the pressure-sensitive adhesive composition A in Preparation Example 1 was changed to the pressure-sensitive adhesive composition B in Preparation Example 2.

[0093] Comparative Example 4 A laminated film was obtained in the same manner as in Example 1, except that the pressure-sensitive adhesive composition A in Preparation Example 1 was changed to the pressure-sensitive adhesive composition C in Preparation Example 3.

[0094] [Table 1]

[0095] [evaluation] As is clear from Table 1, when the heat shrinkage rate of the base film is equal to or less than the upper limit and the peel strength of the laminate film is equal to or greater than the lower limit, the laminate film can be prevented from wrinkling and from lifting off from the adherend even when attached to a curved surface with a curvature radius of 5 cm or less via the pressure-sensitive adhesive layer. Furthermore, when the peel strength of the laminate film is equal to or less than the upper limit, the laminate film can be smoothly peeled off from the adherend. [Industrial Applicability]

[0096] The laminated film of the present invention can be used in the production of various industrial products, and can be particularly suitably used in the production of industrial products having curved surfaces. [Explanation of symbols]

[0097] 1. Base film 2. Adhesive layer 100 Laminated Film

Claims

1. a base film made of a resin material; a pressure-sensitive adhesive layer laminated on the base film, the pressure-sensitive adhesive layer is made of a (meth)acrylic pressure-sensitive adhesive containing a (meth)acrylic polymer, the (meth)acrylic polymer contains a structural unit derived from an alkyl(meth)acrylate, a structural unit derived from a carboxyl group-containing monomer, and a structural unit derived from a hydroxyl group-containing monomer; the (meth)acrylic polymer has a content of structural units derived from the carboxyl group-containing monomer of 0.01% by mass or more and 5.0% by mass or less, and a content of structural units derived from the hydroxyl group-containing monomer of 5.0% by mass or more and 10% by mass or less; the (meth)acrylic pressure-sensitive adhesive contains a crosslinking agent, the content of the crosslinking agent is 0.5 parts by mass or more and 2.5 parts by mass or less relative to 100 parts by mass of the (meth)acrylic polymer, the heat shrinkage rate of the base film at a glass transition temperature of the resin material ±10°C is 0.20% or less, A laminated film having a peel strength from an acrylic plate of 1.0 N / 25 mm or more and 3.0 N / 25 mm or less at a pulling speed of 30 m / min and a peel angle of 180°.

2. The laminated film according to claim 1 , wherein the resin material has a glass transition temperature of 125° C. or higher.

3. The laminated film according to claim 1 or 2, wherein the resin material is amorphous.

4. The laminated film according to claim 1 or 2, wherein the resin material contains a polycarbonate-based resin and / or a cycloolefin-based resin.

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