Laminated film and method for producing laminated film

Abstract

To provide a laminated film capable of suppressing erroneous detection caused by the laminated film and accurately inspecting an adherend even when the laminated film is subjected to optical inspection in a state of being stuck to the adherend, and a method for manufacturing the laminated film.SOLUTION: A laminated film according to an embodiment of the present invention includes a base film formed of a resin material and a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer is laminated on the base film. The in-plane retardation Re (550) of the base film is 10nm or less. The number of defects having maximum Feret diameters of 30 μm or more in a unit area 10cm2 of the base film is 8 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] It is known that a laminate film having a base film and a pressure-sensitive adhesive layer is attached to the surface of various industrial products for various purposes. One purpose of attaching a laminate film is to protect 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] It has been considered to inspect an adherend with such a laminate film attached to the adherend, but when an adherend with a laminate film attached is subjected to optical inspection, false detection due to the laminate film may occur, making it impossible to inspect the adherend accurately. [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 laminate film and a method for manufacturing a laminate film that can suppress erroneous detection caused by the laminate film even when attached to an adherend and subjected to optical inspection, and can accurately inspect the adherend. [Means for solving the problem]

[0006] [1] A laminated film according to one embodiment of the present invention includes a substrate film and a pressure-sensitive adhesive layer. The substrate film is made of a resin material. The pressure-sensitive adhesive layer is laminated on the substrate film. The substrate film has an in-plane retardation Re(550) of 10 nm or less. The substrate film has a unit area of ​​10 cm. 2 The number of defects with a maximum Feret's diameter of 30 μm or more is eight or less. [2] In the laminated film described in [1] above, the peel force of the laminated film from the acrylic plate may be 3.0 N / 25 mm or less at a pulling speed of 30 m / min and a peel angle of 180°. [3] In the laminated film according to the above [1] or [2], the resin material may contain a polycarbonate resin and / or a cycloolefin resin. [4] A method for producing a laminated film according to another aspect of the present invention includes the steps of forming a substrate film made of a resin material and forming a pressure-sensitive adhesive layer on the substrate film, wherein the step of forming the substrate film includes the steps of melting the resin material, passing the molten resin material through a filter, and extrusion-molding the resin material after passing through the filter. [5] In the method for producing a laminated film according to the above item [4], the filter may be a screen mesh, in which case the openings of the screen mesh may be 0.035 mm to 0.070 mm. [Effects of the Invention]

[0007] According to an embodiment of the present invention, even when a laminated film is attached to an adherend and subjected to optical inspection, false detections caused by the laminated film can be suppressed, and the adherend can be inspected with high accuracy. [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. [Figure 2]FIG. 2 is a schematic cross-sectional view of an optical member with a laminate film including the laminate film of FIG. 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 in-plane retardation Re(550) of the base film 1 is 10 nm or less. The unit area of ​​the base film 1 is 10 cm. 2 The number of defects with a maximum Feret diameter of 30 μm or more (hereinafter referred to as D30 / 10 cm of the base film) 2 The number of defects is 8 or less. The method for measuring the number of defects will be explained in the examples below. In-plane retardation Re(550) of the substrate film and D30 / 10cm of the substrate film 2 With this combination, even if the laminate film is attached to an adherend and subjected to optical inspection, false detections due to the laminate film can be suppressed, and the adherend can be inspected with high accuracy. In other words, the results of inspecting the adherend with the laminate film attached can be consistent with the results of inspecting the adherend alone.

[0012] Defects in the base film 1 include, for example, foreign matter such as fibers mixed in the resin material, gel-like matter formed by thermal crosslinking of the resin material, and air bubbles formed due to moisture in the resin.

[0013] The in-plane retardation Re(550) of the base film 1 is preferably 5 nm or less, more preferably 3 nm or less. The lower limit of the in-plane retardation Re(550) of the base film 1 is typically 0 nm. When the in-plane retardation Re(550) of the base film is within this range, rainbow unevenness of the base film during optical inspection can be effectively suppressed, and as a result, the adherend can be inspected more accurately.

[0014] Base film D30 / 10cm 2 is preferably 5 or less, more preferably 3 or less, and even more preferably 1 or less. 2 The lower limit of D30 / 10cm of the base film is typically 0. 2If is within this range, it is possible to prevent defects in the base film from being erroneously detected in the optical inspection of the adherend, and as a result, it is possible to inspect the adherend with even greater accuracy.

[0015] In addition, the unit area of ​​the base film 1 is 10 cm 2 The number of defects having a maximum Feret's diameter of less than 30 μm is not particularly limited. Unit area 10cm 2 The number of defects having a maximum Feret's diameter of 10 μm or more but less than 30 μm is, for example, 15 or less, preferably 10 or less. 2 The lower limit of the number of defects having a maximum Feret diameter of less than 30 μm and 10 μm or more is typically 0.

[0016] The peel force of the laminate film 100 from the acrylic plate is, for example, 3.5 N / 25 mm or less, preferably 3.0 N / 25 mm or less, more preferably 2.5 N / 25 mm or less, and even more preferably 2.0 N / 25 mm or less, at a pulling speed of 30 m / min and a peel angle of 180°. If the laminate film has such a peel force, the laminate film can be smoothly peeled from the adherend after optical inspection. On the other hand, the peel strength of the laminate film 100 from an acrylic plate is, for example, 0.5 N / 25 mm or more, preferably 1.0 N / 25 mm or more, and preferably 1.2 N / 25 mm or more. If the laminate film has such a peel strength, the laminate film can stably conform to the surface of the adherend when attached to the adherend. The peel strength can be measured in accordance with JIS Z0237, and more specifically, can be measured by the peel strength test described below. (peel force test) The laminated film was cut into strips measuring 25 mm x 100 mm to prepare samples; the sample was roll-bonded to the surface of an acrylic plate using the adhesive layer at a pressure of 0.25 MPa and a feed rate of 0.3 m / min; the sample attached to the acrylic plate was left to stand in an environment with a temperature of 23°C and a relative humidity of 50% for 30 minutes, and then peeled at a peel angle of 180° and a tensile speed of 30 m / min under the same conditions to measure the peel force.

[0017] The components of the laminated film will be described below.

[0018] 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.

[0019] 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.

[0020] Of these resin materials, preferably, PC-based resins and COP-based resins are used, and more preferably, PC-based resins are used.

[0021] 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]

[0022] 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.

[0023] 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).

[0024] (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.

[0025] 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.

[0026] [ka]

[0027] [ka]

[0028] 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.

[0029] 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, and more preferably 60 mol% or more. On the other hand, the proportion of the structural units derived from the dihydroxy compound (A) is, 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, rainbow unevenness of the base film during optical inspection can be stably suppressed.

[0030] (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. The combined use of dihydroxy compounds (A) and (B) can more stably suppress rainbow unevenness in the substrate film during optical inspection.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] [ka]

[0036] The alicyclic dihydroxy compound represented by the general formula (I), tricyclodecane dimethanol or pentacyclopentadecanedimethanol, is a compound represented by the general formula (I), 1 The compound includes various isomers represented by the following general formula (Ib) (wherein n is 0 or 1).

[0037] [ka]

[0038] 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-decalindimethanol, 1,5-decalindimethanol, and 2,3-decalindimethanol.

[0039] [ka]

[0040] 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.

[0041] [ka]

[0042] Adamantane dimethanol, which is an alicyclic dihydroxy compound represented by general formula (I), is 1The general formula (Ie) includes various isomers represented by the following general formula (Ie): Specific example of such isomer is 1,3-adamantanedimethanol.

[0043] [ka]

[0044] 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.

[0045] [ka]

[0046] 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).

[0047] [ka]

[0048] 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 2is 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.

[0049] [ka]

[0050] 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.

[0051] [ka]

[0052] 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.

[0053] [ka]

[0054] 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.

[0055] 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. On the other hand, the proportion of the structural units derived from the dihydroxy compound (B) is, for example, 90 mol% or less, preferably 60 mol% or less, and more preferably 40 mol% or less.

[0056] 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.

[0057] 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, rainbow unevenness of the substrate film during optical inspection can be more stably suppressed. 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.

[0058] 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.

[0059] The thickness of the substrate film 1 is, for example, 30 μm or more, preferably 40 μm or more. On the other hand, the thickness of the substrate film 1 is, for example, 130 μm or less, preferably 120 μm or less. When the thickness of the substrate film is within this range, the substrate film can be given stiffness (elasticity) suitable for peeling the laminated film. Therefore, the substrate film can be smoothly peeled from the adherend. Furthermore, the in-plane retardation of the substrate film can be stably adjusted within the above range.

[0060] The trouser tear strength of the base film 1 is, for example, 0.09 N or more, preferably 0.10 N or more. The trouser tear strength of the base film 1 is, for example, 0.4 N or less, preferably 0.3 N or less. When the trouser tear strength of the base film is within this range, the laminate film can be smoothly peeled from the adherend, and tearing (ripping) of the laminate film can be suppressed when the laminate film is peeled from the adherend. The trouser tear strength can be measured, for example, in accordance with JIS K7128-1.

[0061] The base film 1 is typically optically isotropic. In this specification, "optically isotropic" means that the in-plane retardation Re(550) of the base film 1 is in the above-mentioned range, and the retardation Rth(550) in the thickness direction of the base film 1 is in the range of, for example, -10 nm to +10 nm, or in the range of, for example, -5 nm to +5 nm.

[0062] The total light transmittance of the substrate film 1 is, for example, 80% or more, preferably 85% or more, more preferably 90% or more, and even more preferably 95% or more. The haze value of the base film 1 is, for example, 2.0% or less, preferably 1.5% or less, more preferably 1.0% or less, even more preferably 0.7% or less, particularly preferably 0.5% or less, and particularly preferably 0.3% or less. The lower limit of the haze value of the base film 1 is typically 0.05%. If the total light transmittance and / or haze value of the base film is within such range, the base film can be endowed with excellent transparency, and as a result, the influence of the laminate film on optical inspection of the adherend can be reduced.

[0063] 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. The adhesive layer 2 is made of an adhesive (pressure-sensitive adhesive).

[0064] 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.

[0065] 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.

[0066] The (meth)acrylic pressure-sensitive adhesive composition typically contains a (meth)acrylic polymer as a main component. The content of the (meth)acrylic polymer in the solid content of the pressure-sensitive adhesive composition is, for example, 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more. On the other hand, the upper limit of the content of the (meth)acrylic polymer is typically 100% by mass.

[0067] The (meth)acrylic polymer contains structural units derived from alkyl (meth)acrylate. In the (meth)acrylic polymer, the content of the structural units derived from alkyl (meth)acrylate is, for example, 70% by mass or more, preferably 80% by mass or more. On the other hand, the upper limit of the content of the structural units derived from alkyl (meth)acrylate is typically 90% by mass. 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.

[0068] 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.

[0069] 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.

[0070] 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, whereas the content of the structural units derived from carboxyl group-containing monomers is, 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.

[0071] 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.

[0072] 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% by mass or more, preferably 1.0% by mass or more, more preferably 5.0% by mass or more, and even more preferably 8.0% by mass or more. The upper limit of the content of the structural units derived from hydroxyl group-containing monomers is typically 10% by mass.

[0073] 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.

[0074] 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.

[0075] The content of the crosslinking agent is, 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, relative to 100 parts by mass of the (meth)acrylic polymer. On the other hand, the content of the crosslinking agent is, 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 this range, the peel force of the laminated film can be stably adjusted within the above range.

[0076] 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.

[0077] The thickness of the pressure-sensitive adhesive layer 2 is typically 1 μm or more, preferably 5 μm or more, whereas the thickness of the pressure-sensitive adhesive layer 2 is, for example, 30 μm or less, preferably 15 μm or less.

[0078] The storage modulus of the pressure-sensitive adhesive layer 2 at 25°C is, for example, 5.0 × 10 4 Pa ~ 5.0 × 10 6 Pa, preferably 7.5 × 10 4 Pa~2.5×10 6 When the storage modulus of the pressure-sensitive adhesive layer is within this range, the adhesive layer has good wettability to the adherend and can have sufficient adhesive strength.

[0079] 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.

[0080] E. Manufacturing method of laminated film The laminated film 100 can be produced by any appropriate method. In one embodiment, the method for producing the laminated film includes a step of forming a base film 1 (film formation step) and a step of forming a pressure-sensitive adhesive layer 2 on the base film 1 (pressure-sensitive adhesive layer formation step).

[0081] The film-forming process typically includes a step of melting the resin material (melting step); a step of passing the molten resin material (hereinafter referred to as molten resin) through a filter (filtering step); and a step of extruding the molten resin after passing through the filter (extrusion step).

[0082] The resin material subjected to the melting step may have any suitable shape. In one embodiment, the resin material is pelletized in advance. The method for pelletizing the resin material is not particularly limited, and may be a strand cut method or a hot cut method. Details of the pellet preparation step are described, for example, in JP 2013-181105 A. The disclosure of this patent document is incorporated herein by reference.

[0083] In the melting step, the resin material (typically pellets) is heated and melted. Any appropriate heating temperature may be adopted depending on the resin material. This results in a molten resin in which the resin material is melted.

[0084] In the filtering step, the molten resin is passed through a filter, whereby foreign matter contained in the molten resin can be removed from the molten resin.

[0085] The filter may have any suitable configuration, and examples of the filter include a screen mesh and a disk filter, with a screen mesh being preferred. The opening of the screen mesh is, for example, 0.080 mm or less, preferably 0.070 mm or less, more preferably 0.055 mm or less. When the screen mesh has such openings, it is possible to prevent foreign matter having a maximum Feret diameter of 30 μm or more from being mixed into the substrate film to be formed. Therefore, defects in the substrate film (specifically, foreign matter) can be reduced, and the D30 / 10cm of the substrate film can be improved. 2 can be stably adjusted to fall within the above range. On the other hand, the opening of the screen mesh is, for example, 0.025 mm or more, preferably 0.035 mm or more. When the screen mesh has such openings, the molten resin can pass through the screen mesh smoothly. Therefore, the stagnation of the molten resin can be suppressed, and the molten resin can be prevented from being excessively heated. This can suppress the generation of gel-like matter due to thermal crosslinking of the molten resin. As a result, defects in the base film (specifically, gel-like matter) can be reduced, and the D30 / 10cm of the base film can be improved. 2 can be adjusted more stably within the above range.

[0086] In the extrusion molding step, the molten resin that has passed through the filter is typically extruded into a film shape using a die. This prepares the substrate film 1. Such a film-forming process can be carried out by any appropriate film-forming device.

[0087] Next, in the pressure-sensitive adhesive layer forming step, a pressure-sensitive adhesive layer 2 is formed on the obtained base film 1. Any appropriate means can be adopted as a method for forming the pressure-sensitive adhesive layer. To form the pressure-sensitive adhesive layer 2 on the base film 1, for example, the above-mentioned pressure-sensitive adhesive may be directly applied to the base film 1, or the pressure-sensitive adhesive may be applied to another base material to form a pressure-sensitive adhesive layer, which may then be transferred to the base film 1. In this way, the laminated film 100 is manufactured.

[0088] F. Applications of laminated film The laminated films described in the above items A to E are used by being attached to the surface of various adherends. Examples of adherends include optical components and electronic components, and optical components are preferred. Representative examples of optical components include polarizing plates, retardation films, optical laminates containing polarizing plates and / or retardation films, displays, imaging devices, lenses, and (half) mirrors.

[0089] In one embodiment, the laminate film 100 is a film with a pressure-sensitive adhesive layer and can be suitably used as a surface protection film. In this case, the laminate film 100 is attached to the surface of an adherend, and can protect the surface of the adherend during inspection, processing, and / or transportation of the adherend.

[0090] Fig. 2 is a schematic cross-sectional view of an optical member with a laminate film including the laminate film of Fig. 1. The illustrated optical member with a laminate film 200 includes an optical member 5 as an adherend and a laminate film 100 as a surface protective film. The laminate film 100 is attached to the surface of the optical member 5 by a pressure-sensitive adhesive layer 2.

[0091] In one embodiment, the optical member 5 included in the laminated film-attached optical member 200 is a polarizing plate. The thickness of the polarizing plate is, for example, 5 μm to 200 μm. The thickness of the base film 1 of the laminate film 100 is, for example, 0.1 to 1.05, and preferably 0.15 to 1.0, relative to the thickness of the adherend (optical member). If the thickness ratio between the base film and the adherend is within this range, the adherend (optical member) can be inspected with even greater accuracy even when optical inspection is performed with the laminate film attached to the adherend.

[0092] Such an optical member 200 with a laminated film is typically subjected to optical inspection. The optical inspection is not particularly limited, and examples thereof include automated optical inspection (AOI). Examples of automated optical inspection include foreign matter inspection to check for foreign matter contained in an optical component and air bubble inspection to check for air bubbles contained in an optical component. In such optical inspection, false detections due to the laminate film are sufficiently suppressed, so that the optical component can be inspected with high accuracy even when the laminate film is attached to the optical component.

[0093] Thereafter, the laminated film 100 can be peeled off and removed from the surface of the optical member 5 at a desired timing. [Example]

[0094] 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.

[0095] (1) Measuring the number of defects on the base film The substrate films used in the examples and comparative examples were measured using an optical microscope at a unit area of ​​10 cm 2 The number of defects with a maximum Feret's diameter of 30 μm or more was measured. The results are shown in Table 1.

[0096] (2) Rainbow unevenness on the base film The substrate film used in the examples and comparative examples was placed between two polarizing plates in a crossed Nicol configuration. The substrate film was placed so that the longitudinal direction of the substrate film was parallel to the transmission axis direction of one of the polarizing plates. In this state, fluorescent light was irradiated from below the lower polarizing plate, and the presence or absence of rainbow unevenness was visually observed. The results are shown in Table 1. Furthermore, when a laminate film including a substrate film that may cause rainbow unevenness is attached to an adherend and subjected to automated optical inspection (AOI), the accuracy of the optical inspection of the adherend may decrease.

[0097] (3) Automatic foreign body inspection The laminated films obtained in the examples and comparative examples were subjected to a count of the number of foreign objects contained in an area of ​​10 cm x 10 cm in the laminated film based on the method described in JP 2021-135219 A. Next, the results of the automatic foreign matter inspection were evaluated according to the following criteria. The results are shown in Table 1. 〇: Number of foreign objects 30μm or larger is 5 / 10cm 2 below ×: 6 foreign objects 30 μm or larger per 10 cm 2 End

[0098] <<Preparation Example 1: Adhesive Composition>> 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.

[0099] Ethyl acetate was added to a 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 a pressure-sensitive adhesive composition.

[0100] <<Preparation Example 2: 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 stirrer increased, the temperature was raised to 250°C in 8 minutes, and the pressure inside the reaction vessel was reduced to 0.200 kPa or less to remove the phenol that was generated. After the predetermined stirring torque was reached, the reaction was terminated and the reaction product was extruded into water to obtain pellets of PC resin.

[0101] [Example 1, Comparative Examples 2 and 3] The PC resin pellets obtained in Preparation Example 2 were vacuum dried at 100°C for 12 hours and then fed to a film-forming apparatus. The film-forming apparatus was equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder temperature setting: 250°C), a filter shown in Table 1, a T-die (width 1700 mm, temperature setting: 250°C), a cast roll (temperature setting: 60°C), and a winder. More specifically, the pellets were fed into a single-screw extruder and heated to melt. The molten PC resin was then extruded from the single-screw extruder and passed through a filter and a T-die in that order. This produced a PC resin film with a thickness of 40 μm. The PC resin film passed through a cast roll and was then wound up by a winder. Next, the pressure-sensitive adhesive composition of Preparation Example 1 was applied to the release-treated surface of a release liner (a 25 μm-thick biaxially oriented polyethylene terephthalate film with one side treated with silicone release agent) and heated at 130° C. for 20 seconds to form a 10 μm-thick pressure-sensitive adhesive layer. This pressure-sensitive adhesive layer was then bonded to the corona-treated surface of a PC resin film with one side corona-treated, to obtain a laminated film.

[0102] [Example 2] A laminated film was obtained in the same manner as in Example 1, except that the pellets of the PC resin obtained in Preparation Example 2 were changed to pellets of a COP resin.

[0103] [Comparative Example 1] A laminated film was obtained in the same manner as in Example 1, except that the PC resin pellets obtained in Preparation Example 2 were changed to PET pellets.

[0104] [Table 1]

[0105] [evaluation] As is clear from Table 1, when the in-plane retardation Re(550) of the base film and the number of defects of 30 μm or more in the base film are adjusted as described above, even when the laminate film is subjected to optical inspection while attached to an adherend, false detections caused by the laminate film can be suppressed, and the adherend can be inspected accurately. [Industrial Applicability]

[0106] The laminated film of the present invention can be applied to various industrial products, and can be particularly suitably used for optical products that are subjected to optical inspection. [Explanation of symbols]

[0107] 1. Base film 2. Adhesive layer 100 Laminated Film

Claims

[Claim 1] a base film made of a resin material; a pressure-sensitive adhesive layer laminated on the base film, The in-plane retardation Re(550) of the substrate film is 10 nm or less, Unit area of ​​the base film: 10 cm ２ The laminated film has eight or less defects having a maximum Feret's diameter of 30 μm or more.

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