JP2018187785A - Production method of multilayer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a multilayer film, with which wrinkling and peeling of the multilayer film are scarcely produced just after bonding and wrinkling and peeling thereof are scarcely produced even after the lapse of time.SOLUTION: A production method of a multilayer film has a step to bond a substrate film with a Young's modulus of 1,000 MPa or more and a protective film with a Young's modulus less than 1,000 MPa, in which the ratio (ε2/ε1) of the distortion index ε2(2) of the protective film to the distortion index ε1(1) of the substrate film in the bonding step is more than 7 and is equal to or less than 15. ε1=T1/(t1×Y1)...(1), ε2=T2/(t2×Y2)...(2), (T1 is tension [N] applied to the substrate film in bonding, t1 is thickness [mm] of the substrate film, Y1 is the Young's modulus [MPa] of the substrate film, T2 is tension [N] applied to the protective film in bonding, t2 is thickness [mm] of the protective film, and Y2 is the Young's modulus [MPa] of the protective film).SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a multilayer film.

  A base film made of a resin having a low surface hardness such as a (meth) acrylic resin is easily damaged during transportation or storage. In order to reduce the damage of the base film, it is proposed in Patent Document 1 to bond a surface protective film to the optical film. Moreover, in patent document 2, it is a roll-shaped winding body formed by winding the multilayer film provided with an optical film and the protective film which can be peeled from an optical film in roll shape, Comprising: The tensile elasticity modulus of a protective film is 100 Mpa or more and 400 Mpa The following roll-shaped winding bodies have been proposed.

JP 2005-125659 A JP 2011-112945 A

  When a protective film is bonded to a base film to form a multilayer film, even if there is no problem immediately after the bonding, when the time elapses after bonding, the resulting multilayer film is wrinkled. May occur or a part of the protective film may be peeled off. When wrinkles are generated in the multilayer film, the substrate film is damaged and the appearance is deteriorated, and further, defects such as printing omission occur in subsequent processes such as printing and metal deposition. Moreover, when a protective film peels even partially from a base film, a base film may be damaged or a multilayer film may fracture | rupture from the part peeled off during conveyance of a multilayer film.

  The present invention has been made in consideration of the above-mentioned problems, and its purpose is to prevent wrinkles and peeling immediately after bonding, and to prevent wrinkles and peeling even after a lapse of time after bonding. It is providing the manufacturing method of a multilayer film.

  That is, the present invention relates to the following [1] to [16].

[1] A bonding step of bonding a base film having a Young's modulus of 1000 MPa or more and a protective film having a Young's modulus of less than 1000 MPa,
When the index ε1 of the base film distortion in the bonding step is represented by the following formula (1), and the strain index ε2 of the protective film in the bonding step is represented by the following formula (2), the ratio of ε2 to ε1 The manufacturing method of the multilayer film which makes ((epsilon) 2 / (epsilon) 1) 7 more than 15 or less.
ε1 = T1 / (t1 × Y1) (1)
ε2 = T2 / (t2 × Y2) (2)
(However, T1 is the tension [N] applied to the base film when the base film and the protective film are bonded, t1 is the thickness [mm] of the base film, and Y1 is the Young's modulus of the base film [ T2 is the tension [N] applied to the protective film when the base film and the protective film are bonded, t2 is the thickness [mm] of the protective film, and Y2 is the Young's modulus of the protective film. [MPa].)
[2] The production method of [1], wherein the peel strength between the base film and the protective film is 0.05 to 1.0 N / 25 mm.
[3] The method according to [1] or [2], wherein the haze of the multilayer film is 15% or less.
[4] The method according to any one of [1] to [3], wherein a ratio (t2 / t1) of the thickness t2 of the protective film to the thickness t1 of the base film is 0.1-1.
[5] The method according to any one of [1] to [4], wherein a ratio (T2 / T1) of the tension T2 of the protective film to the tension T1 of the base film is 0.1 to 1.0.
[6] The method according to any one of [1] to [5], wherein a distortion index ε1 [mm] of the base film is 1.0 or less.
[7] The method according to any one of [1] to [6], wherein the base film is a thermoplastic resin film.
[8] The method according to [7], wherein the thermoplastic resin constituting the thermoplastic resin film is a (meth) acrylic resin.
[9] The method according to [8], wherein the (meth) acrylic resin is a composition containing a hard methacrylic resin and an elastomer.
[10] The method according to [9], wherein the elastomer is a (meth) acrylic elastomer.
[11] The method according to any one of [1] to [10], wherein the protective film has an adhesive layer and a back layer.
[12] The method according to [11], wherein the adhesive layer contains an ethylene-vinyl acetate copolymer.
[13] The method according to [11] or [12], wherein the back layer is a polyolefin resin film.
[14] The method according to [13], wherein the polyolefin resin constituting the polyolefin resin film is polyethylene.
[15] The method according to any one of [1] to [14], wherein the base film is a decorative film.
[16] The method according to any one of [1] to [14], wherein the base film is an optical film.

  By the method for producing a multilayer film of the present invention, it is possible to provide a multilayer film that is unlikely to be wrinkled and peeled immediately after pasting, and is less likely to be wrinkled and peeled even after a lapse of time after pasting.

  In the manufacturing method of the multilayer film of this invention, it has the bonding process of bonding the base film whose Young's modulus is 1000 Mpa or more, and the protective film whose Young's modulus is less than 1000 Mpa.

[Base film]
The Young's modulus Y1 of the base film is 1000 MPa or more, preferably 1500 MPa or more, more preferably 2000 MPa or more, because a base film having high strength can be obtained. Moreover, Preferably it is 5000 MPa or less, More preferably, it is 3000 MPa or less. The Young's modulus Y1 of the base film can be determined according to JIS K7127 using a test piece of 15 mm × 150 mm, and specifically can be determined by the method described later in the examples.

  There is no restriction | limiting in particular in the kind of base film, For example, a thermoplastic resin film, a thermosetting resin film, etc. are mentioned. Examples of the thermoplastic resin constituting the thermoplastic resin film include polycarbonate resins such as bisphenol A polycarbonate; aromatics such as polystyrene, styrene-acrylonitrile resin, styrene-maleic anhydride resin, styrene-maleimide resin, and styrene thermoplastic elastomer Group-based vinyl resin or hydrogenated product thereof; amorphous polyolefin, transparent polyolefin with a refined crystal phase, polyolefin resin such as ethylene-methyl methacrylate resin; polymethyl methacrylate, styrene-methyl methacrylate resin, etc. (Meth) acrylic resins: Polyesters such as polyethylene terephthalate, polyethylene naphthalate and polyarylate partially modified with polyethylene terephthalate, cyclohexanedimethanol and isophthalic acid Resin; polyamide resin; polyimide resins; polyether sulfone-based resins; cellulose resin such as triacetyl cellulose resins; and polyphenylene oxide resins. In this specification, (meth) acrylic resin refers to methacrylic resin and / or acrylic resin. The (meth) acrylic resin may be a heat resistant (meth) acrylic resin modified by imide cyclization, lactone cyclization, methacrylic acid modification or the like. Examples of the thermosetting resin constituting the thermosetting resin film include phenolic resins, urea resins, melamine resins, epoxy resins, silicon resins, and polyurethane resins. These resins constituting the base film may be used alone or in combination of two or more. The total content of the thermoplastic resin and the thermosetting resin in the base film is preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more. 100 mass%.

  From the viewpoint of transparency and moldability, the substrate film is preferably a thermoplastic resin film, and more preferably the thermoplastic resin constituting the thermoplastic resin film is a (meth) acrylic resin. From the viewpoint of impact resistance, the (meth) acrylic resin preferably contains an elastomer. Examples of such a (meth) acrylic resin include a composition containing a hard methacrylic resin and an elastomer. . When the (meth) acrylic resin is a composition containing a hard methacrylic resin and an elastomer, the total content of the hard methacrylic resin and the elastomer in the composition is preferably 80% by mass or more. 90% by mass or more, more preferably 95% by mass or more, and may be 100% by mass.

  The proportion of the structural units derived from methyl methacrylate in the hard methacrylic resin is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and still more. Preferably it is 99 mass% or more, Most preferably, it is 100 mass%. That is, the proportion of structural units derived from monomers other than methyl methacrylate is preferably 20% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less, and even more. This is preferably 1% by mass or less, particularly preferably 0% by mass.

  Examples of the monomer other than methyl methacrylate include, for example, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, and acrylic acid. tert-butyl, amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, phenyl acrylate, benzyl acrylate, phenoxyethyl acrylate, acrylic acid Acrylic esters such as 2-hydroxyethyl, 2-ethoxyethyl acrylate, glycidyl acrylate, allyl acrylate, cyclohexyl acrylate, norbornyl acrylate, isobornyl acrylate; ethyl methacrylate, methacrylate N-propyl acid, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-methacrylic acid 2- Ethylhexyl, pentadecyl methacrylate, dodecyl methacrylate, phenyl methacrylate, benzyl methacrylate, phenoxyethyl methacrylate, 2-hydroxyethyl methacrylate, 2-ethoxyethyl methacrylate, glycidyl methacrylate, allyl methacrylate, cyclomethacrylate Methacrylic acid esters other than methyl methacrylate such as hexyl, norbornyl methacrylate, isobornyl methacrylate; acrylic acid, methacrylic acid, maleic anhydride, maleic acid, Unsaturated carboxylic acids such as taconic acid; olefins such as ethene, propylene, 1-butene, isobutene and 1-octene; conjugated dienes such as butadiene, isoprene and myrcene; styrene, α-methylstyrene, p-methylstyrene, m- Aromatic vinyl compounds such as methylstyrene; acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl pyridine, vinyl ketone, vinyl chloride, vinylidene chloride, vinylidene fluoride, and the like. These monomers may be used individually by 1 type, and may use 2 or more types together.

  The production method of the hard methacrylic resin is not particularly limited, and can be obtained by polymerizing one or more monomers containing preferably 80% by mass or more of methyl methacrylate under suitable conditions.

  Examples of the elastomer include (meth) acrylic elastomers; silicone elastomers; styrene thermoplastic elastomers such as SEPS, SEBS, and SIS; and olefin elastomers such as IR, EPR, and EPDM. Of these, (meth) acrylic elastomers are preferred from the viewpoints of transparency and toughness.

  There is no restriction | limiting in particular in the kind of (meth) acrylic-type elastomer, For example, the acrylic-type elastic polymer which contains as a main component the structural unit derived from an acrylic-acid acyclic alkylester is mentioned. In the acrylic elastic polymer, the content of the structural unit derived from the acrylic acid acyclic alkyl ester is preferably 50 to 100% by mass, more preferably 70 to 99.8% by mass. The acyclic alkyl group in the acyclic alkyl ester of acrylic acid has 4 to 8 carbon atoms, specifically, for example, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n -Octyl groups and their isomer groups are preferred. The acrylic elastic polymer may contain a structural unit derived from a monomer other than the acrylic acid acyclic alkyl ester. Examples of such a monomer include methyl methacrylate and ethyl methacrylate. Methacrylic acid alkyl esters such as styrene; styrene monomers such as styrene and alkyl styrene; unsaturated nitriles such as acrylonitrile and methacrylonitrile; 2-chloroethyl vinyl ether; ethylene glycol (meth) acrylate, ethoxy-diethylene glycol acrylate, methoxy -Triethylene glycol acrylate, 2-ethylhexyl-diglycol acrylate, methoxy-polyethylene glycol acrylate, methoxydipropylene glycol acrylate, phenoxydiethylene glycol acrylate, Phenoxy - polyethylene glycol acrylate, alkylene glycol (meth) acrylates such as nonylphenol ethylene oxide adduct acrylate.

  The acrylic elastic polymer may have a structural unit derived from the above-mentioned acrylic acid acyclic alkyl ester and a structural unit derived from a crosslinkable monomer at random. Examples of the crosslinkable monomer include allyl (meth) acrylate, methallyl (meth) acrylate, diallyl maleate, triethylene glycol diacrylate, polyethylene glycol diacrylate, 1.6-hexanediol diacrylate, 1 , 9-nonanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, and the like. The content of the structural unit derived from the crosslinkable monomer in the acrylic elastic polymer is preferably 0.2 to 30% by mass from the viewpoint of toughness.

  Further, since the effects of the present invention are more remarkably exhibited, the (meth) acrylic elastomer is composed of (meth) acrylic elastic particles (A), acrylate polymer block (b1) and methacrylic. It is preferable that the acid ester polymer block (b2) is at least one selected from the group consisting of a (meth) acrylic block copolymer (B) bonded to the acid ester polymer block (b2).

The (meth) acrylic elastic particles (A) may be particles made of a single polymer, or may be particles in which at least two layers of polymers having different elastic moduli are formed. The (meth) acrylic elastic particles (A) include a layer containing the above-mentioned acrylic elastic polymer (a polymer containing a structural unit derived from an acrylic non-cyclic alkyl ester as a main component) and another polymer. Core-shell particles having a multilayer structure composed of a layer containing them, and core-shell particles having a two-layer structure comprising a layer containing an acrylic elastic polymer and a layer containing a methacrylic polymer covering the outside, or And a core-shell particle having a three-layer structure comprising a layer containing a methacrylic polymer, a layer containing an acrylic elastic polymer covering the outer side, and a layer containing a methacrylic polymer covering the outer side. The core-shell particles having a three-layer structure are more preferable.
The methacrylic polymer constituting the core-shell particles is preferably a polymer containing as a main component a structural unit derived from methacrylic acid acyclic alkyl ester. In the methacrylic polymer, the content of the structural unit derived from the methacrylic acid acyclic alkyl ester is preferably 50 to 100% by mass, and more preferably 80 to 100% by mass. The methacrylic acid acyclic alkyl ester is preferably methyl methacrylate, and the methacrylic polymer constituting the core-shell particles may contain 80 to 100% by mass of a methyl methacrylate unit as a hard methacrylic polymer. Most preferable from the viewpoint of miscibility.

  The number average particle diameter of the (meth) acrylic elastic particles (A) is preferably 150 to 350 nm, more preferably 200 to 300 nm, from the viewpoints of transparency, toughness, and adhesiveness. The number average particle diameter of the (meth) acrylic elastic particles (A) is determined by dyeing a sample obtained by melting and kneading the (meth) acrylic elastic particles (A) into a hard methacrylic resin with ruthenium oxide. It is determined based on the observed micrograph. Here, ruthenium oxide dyes the layer containing the acrylic elastic polymer, but does not dye the layer containing the methacrylic polymer. Therefore, the number of the core-shell particles having the two-layer structure or the core-shell particles having the three-layer structure described above. The average particle diameter is estimated to correspond to a value not including the thickness of the outermost layer containing the methacrylic polymer.

  There is no restriction | limiting in particular in the manufacturing method of (meth) acrylic-type elastic body particle | grains (A), It can manufacture by the method according to a well-known method (For example, international publication 2016/121868 grade | etc.,).

  Hard methacrylic resin and (meth) acrylic elastic particles (A) when the (meth) acrylic resin is a composition comprising a hard methacrylic resin and (meth) acrylic elastic particles (A) Is a total of 100 of the hard methacrylic resin and the (meth) acrylic elastic particles (A) from the viewpoints of transparency, hardness, melt viscosity, toughness, slipperiness, and adhesion to the protective film. The content of the (meth) acrylic elastic particles (A) with respect to parts by mass is preferably 1 to 30 parts by mass, more preferably 10 to 25 parts by mass, and even more preferably 15 to 20 parts by mass.

In the (meth) acrylic block copolymer (B), the bonding state of the polymer block (b1) and the polymer block (b2) is not particularly limited. For example, a diblock represented by (b1)-(b2) A copolymer; a triblock copolymer represented by (b1)-(b2)-(b1) or (b2)-(b1)-(b2); (b1)-((b2)-(b1)) _n , (b1)-((b2)-(b1)) _n- (b2), (b2)-((b1)-(b2)) _n (n is an integer); ((B1)-(b2)) _n- X, ((b2)-(b1)) Star block copolymers represented by _n- X (X is a coupling residue), etc. are mentioned. From the viewpoint of productivity, the diblock copolymer represented by (b1)-(b2), (b2)-(b1)-(b2) or (b1)-(b2)-(b1) A triblock copolymer is preferable, and from the viewpoint of fluidity of the resin composition at the time of melting, surface smoothness and haze of the base film, the triblock copolymer represented by (b2)-(b1)-(b2) A polymer is more preferred. In this case, the two polymer blocks (b2) bonded to both ends of the polymer block (b1) are composed of the types of monomers constituting them, the proportion of structural units derived from methacrylic acid esters, the weight average molecular weight and the stereoregulation. Each sex may be independently the same or different. The (meth) acrylic block copolymer (B) may further contain other polymer blocks.

  The polymer block (b1) constituting the (meth) acrylic block copolymer (B) is mainly composed of a structural unit derived from an acrylate ester. The proportion of the structural unit derived from the acrylate ester in the polymer block (b1) is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and particularly preferably. Is 100% by mass.

  Examples of the acrylate ester include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, and acrylic. Amyl acid, Isoamyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, pentadecyl acrylate, dodecyl acrylate, isobornyl acrylate, phenyl acrylate, benzyl acrylate, phenoxyethyl acrylate, acrylic acid Examples include 2-hydroxyethyl, 2-methoxyethyl acrylate, glycidyl acrylate, and allyl acrylate. A polymer block (b1) can be formed by polymerizing these acrylic acid esters singly or in combination of two or more. Among these, from the viewpoints of economy and impact resistance, the polymer block (b1) is preferably one obtained by polymerizing n-butyl acrylate alone.

  The polymer block (b1) may contain a structural unit derived from a monomer other than the acrylate ester, and the proportion thereof is preferably 50% by mass or less, more preferably 30% by mass or less, and still more preferably. It is 10 mass% or less, Most preferably, it is 0 mass%.

  Examples of the monomer other than the acrylic ester include, for example, methacrylic ester, unsaturated carboxylic acid, aromatic vinyl compound, olefin, conjugated diene, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl pyridine, Examples thereof include vinyl ketone, vinyl chloride, vinylidene chloride, and vinylidene fluoride. A polymer block (b1) can be formed by copolymerizing with the above-mentioned acrylic ester by using these monomers other than acrylic ester alone or in combination of two or more.

  The polymer block (b2) constituting the (meth) acrylic block copolymer (B) is mainly composed of a structural unit derived from a methacrylic acid ester. The proportion of the structural unit derived from the methacrylic acid ester in the polymer block (b2) is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably. Is 100% by mass.

  Examples of the methacrylic acid ester include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, methacrylic acid. Amyl acid, isoamyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, pentadecyl methacrylate, dodecyl methacrylate, isobornyl methacrylate, phenyl methacrylate, benzyl methacrylate, phenoxyethyl methacrylate, methacrylic acid Examples include 2-hydroxyethyl, 2-methoxyethyl methacrylate, glycidyl methacrylate, and allyl methacrylate. Among these, from the viewpoint of improving transparency and heat resistance, methacrylic acid such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, cyclohexyl methacrylate, and isobornyl methacrylate. Alkyl esters are preferred, and methyl methacrylate is more preferred. A polymer block (b2) can be formed by polymerizing these methacrylic acid esters singly or in combination of two or more.

  The polymer block (b2) may contain a structural unit derived from a monomer other than the methacrylic acid ester, and the ratio is preferably 20% by mass or less, more preferably 10% by mass or less, and still more preferably. It is 5 mass% or less, Most preferably, it is 0 mass%.

  Examples of the monomer other than the methacrylic acid ester include, for example, acrylic acid ester, unsaturated carboxylic acid, aromatic vinyl compound, olefin, conjugated diene, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl acetate, vinyl pyridine, Examples thereof include vinyl ketone, vinyl chloride, vinylidene chloride, and vinylidene fluoride. A polymer block (b2) can be formed by copolymerizing these monomers other than methacrylic acid esters alone or in combination of two or more with the above methacrylic acid esters.

  The ratio of the polymer block (b2) in the (meth) acrylic block copolymer (B) is determined from the viewpoints of transparency, surface hardness, molding processability, surface smoothness, and impact resistance. And the polymer block (b2) is preferably 40% by mass or more, more preferably 43% by mass or more, and still more preferably 47% by mass or more with respect to 100% by mass in total. Moreover, it is 70 mass% or less preferably, More preferably, it is 65 mass% or less, More preferably, it is 60 mass% or less.

  The method for producing the (meth) acrylic block copolymer (B) is not particularly limited, and a method according to a known method (for example, International Publication No. 2016/121868) can be employed. For example, a method of living polymerizing monomers constituting each polymer block is generally used, and an organic alkali metal compound is used as a polymerization initiator in the presence of a mineral salt such as an alkali metal salt or an alkaline earth metal salt. Anionic polymerization using an organic alkali metal compound as a polymerization initiator, an anionic polymerization in the presence of an organoaluminum compound, a polymerization using an organic rare earth metal complex as a polymerization initiator, an α-halogenated ester compound And a method of radical polymerization in the presence of a copper compound. Moreover, the method of polymerizing the monomer which comprises each block using a polyvalent radical polymerization initiator or a polyvalent radical chain transfer agent, and manufacturing as a mixture containing a (meth) acrylic block copolymer (B), etc. Also mentioned.

  Hard methacrylic resin and (meth) acrylic block copolymer (B) when the (meth) acrylic resin is a composition comprising a hard methacrylic resin and a (meth) acrylic block copolymer (B) ) Is a (meth) acrylic block copolymer based on a total of 100 parts by mass of the hard methacrylic resin and the (meth) acrylic block copolymer (B) from the viewpoint of surface hardness and impact resistance. The content of (B) is preferably 1 to 35 parts by mass, more preferably 8 to 25 parts by mass, and still more preferably 12 to 21 parts by mass.

  The base film is various additives as necessary, for example, polymer processing aids, light stabilizers, ultraviolet absorbers, antioxidants, heat stabilizers, lubricants, electrification, as long as the effects of the present invention are not impaired. Inhibitors, pigments, dyes, fillers, impact resistance aids and the like may be included. An additive may be used individually by 1 type and may use 2 or more types together by arbitrary ratios. In view of the mechanical properties and surface hardness of the base film, it is preferable not to contain a large amount of a foaming agent, a filler, a matting agent, a light diffusing agent, a softening agent and a plasticizer. The content of the additive in the base film is preferably 20% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less, and even 0% by mass. Good.

  There is no particular limitation on the method for preparing the material of the base film, and examples thereof include a method of melt-kneading the above-described thermoplastic resin or thermosetting resin, or the above-described various additives added as necessary. It is done. Examples of the apparatus for kneading include a kneader ruder, a twin screw extruder, a single screw extruder, a mixing roll, and a Banbury mixer. Among these, a twin screw extruder is preferable from the viewpoint of kneading properties, and a vented twin screw extruder is more preferable from the viewpoint of suppressing coloring. The vented twin screw extruder is preferably operated under reduced pressure or nitrogen. The shear rate during melt kneading is preferably 10 to 1000 / sec. The temperature at the time of kneading becomes like this. Preferably it is 110-300 degreeC, More preferably, it is 180-300 degreeC, More preferably, it is 230-270 degreeC. The resin composition melt-kneaded by an extruder is extruded into a strand shape, and can be cut into pellets by a pelletizer or the like.

  The base film is obtained by molding the above-mentioned base film material. The molding method is not particularly limited. For example, known molding methods such as extrusion molding (T-die method, etc.), injection molding, compression molding, inflation molding, blow molding, calendar molding, cast molding, and vacuum molding can be employed, and the extrusion molding method is preferably employed. The According to the extrusion molding method, particularly the T-die method, a base film having improved toughness, excellent handleability, and excellent balance between toughness, surface hardness and rigidity can be obtained. The extruder used for the extrusion method, particularly the T-die method, preferably has a single screw or a twin screw. Moreover, it is preferable to melt-extrude under reduced pressure using a vent from a viewpoint of suppressing coloring of a base film. Further, from the viewpoint of obtaining a base film having a uniform thickness, it is preferable that a gear pump is connected to the extruder and melt extrusion is performed through a polymer filter in order to reduce fish eye defects. Furthermore, from the viewpoint of suppressing oxidative degradation, it is preferable to perform melt extrusion under a nitrogen stream. The temperature of the material discharged from the extruder is preferably 230 to 290 ° C, more preferably 240 to 280 ° C.

  From the viewpoint of the surface smoothness and thickness uniformity of the base film, it is preferable that the extruded film-like molten resin is taken and sandwiched between mirror rolls or mirror belts. Both the mirror roll and the mirror belt are preferably made of metal. From the viewpoint of surface smoothness, the linear pressure between the mirror roll or the mirror belt is preferably 10 N / mm or more, and more preferably 30 N / mm or more. The surface temperature of the mirror roll or mirror belt is preferably 60 ° C. or higher, more preferably 70 ° C. or higher, from the viewpoint of surface smoothness, haze, appearance, and the like. Moreover, Preferably it is 130 degrees C or less, More preferably, it is 100 degrees C or less.

  The base film may be formed into a film and then stretched. The mechanical strength of the base film is improved by the stretching treatment, and it is difficult to crack. The stretching method is not particularly limited, and examples thereof include a simultaneous biaxial stretching method, a sequential biaxial stretching method, a tuber stretching method, and a rolling method. The temperature at the time of stretching is preferably not less than 5 ° C. higher than the glass transition temperature of the material, and preferably not more than 40 ° C. higher than the glass transition temperature of the material. When the material has a plurality of glass transition temperatures, the highest value is adopted as the reference for the stretching temperature. The stretching speed is preferably 100 to 5000% / min. The stretching treatment preferably has a heat setting step after the stretching step. A base film with little heat shrinkage can be obtained by heat setting.

  The base film may be colored. As a coloring method, for example, the material itself for forming the base film is made to contain a pigment or a dye to color the material itself before film formation; the base film is immersed in a liquid in which the dye is dispersed and colored. Examples include dyeing methods.

  The base film may be printed on at least one surface. Patterns and colors such as pictures, characters and figures are added by printing. The pattern may be chromatic or achromatic.

  The base film may be a laminated film in which other layers such as a layer made of a metal and / or a metal oxide and another thermoplastic resin layer are laminated on at least one surface. The method for laminating other layers is not particularly limited, and the layers can be joined directly or via an adhesive layer. As the other layer, one layer or a plurality of layers can be laminated.

  Examples of the thermoplastic resin constituting the other thermoplastic resin layer include polycarbonate resin, polyethylene terephthalate resin, polyamide resin, polyethylene resin, polypropylene resin, polystyrene resin, polyvinyl chloride resin, and others. (Meth) acrylic resin, ABS (acrylonitrile-butadiene-styrene copolymer), ethylene vinyl alcohol resin, polyvinyl butyral resin, polyvinyl acetal resin, styrene thermoplastic elastomer, olefin thermoplastic elastomer, acrylic heat Examples thereof include plastic elastomers.

  The thickness t1 [unit: mm] of the base film (in the case where the base film is a laminated film in which other layers are laminated) is preferably 0.010 or more, more preferably It is 0.030 or more, More preferably, it is 0.050 or more. Moreover, it is preferably 1.0 or less, more preferably 0.50 or less, still more preferably 0.30 or less, and still more preferably 0.20 or less.

〔Protective film〕
The protective film is typically laminated on at least one side of the base film, and can be stored, transported and / or used in a post-process in the state of a multilayer film laminated with the base film. When the base film is used for decorating the adherend or when it is incorporated as a member, the protective film may be peeled off from the base film. From such a viewpoint, the protective film can be peeled off from the base film. Are preferably used.

  Since Young's modulus Y2 of a protective film can suppress the curvature at the time of bonding with a base film, it is less than 1000 MPa, Preferably it is 500 MPa or less, More preferably, it is 300 MPa or less. Moreover, Preferably it is 50 MPa or more, More preferably, it is 80 MPa or more. The Young's modulus Y2 of the protective film can be determined according to JIS K7127 using a test piece of 15 mm × 150 mm, and specifically can be determined by the method described later in the examples.

  The protective film may be a single-layer film composed of only one layer, but is preferably a laminated film having two or more layers. Examples of such a protective film include a film having an adhesive layer and a back layer. Examples of the film having an adhesive layer and a back layer include a film having an adhesive layer, an intermediate layer, and a back layer in this order, in addition to a film having a two-layer structure of an adhesive layer and a back layer.

  If an adhesive layer is arrange | positioned on the surface at the side of the base film of a protective film, a protective film can be made to adhere to a base film by the said adhesive layer. The pressure-sensitive adhesive layer is formed including a pressure-sensitive adhesive, and the protective film can be fixed to the base film by the pressure-sensitive adhesive force. Examples of the adhesive include ethylene-vinyl acetate adhesive, rubber adhesive, acrylic adhesive, polyvinyl ether adhesive, urethane adhesive, silicone adhesive, and the like. From the viewpoint of peelability, an ethylene-vinyl acetate adhesive is preferred. The ethylene-vinyl acetate adhesive is made of an ethylene-vinyl acetate copolymer. In addition, an adhesive may be used individually by 1 type and may use 2 or more types together by arbitrary ratios.

  In the adhesive layer, various additives such as a softening agent, a polymer processing aid, a light stabilizer, an ultraviolet absorber, an antioxidant, and a heat stabilizer are added as necessary within the range not impairing the effects of the present invention. , Lubricants, antistatic agents, pigments, dyes, fillers, impact resistance aids, and the like. An additive may be used individually by 1 type and may use 2 or more types together by arbitrary ratios. Examples of the softening agent include process oil, liquid rubber, and plasticizer. Examples of the filler include barium sulfate, talc, calcium carbonate, mica, silica, and titanium oxide.

  The thickness of the adhesive layer is usually 0.0010 mm or more, preferably 0.0020 mm or more, and usually 0.050 mm or less, preferably 0.030 mm or less. When the thickness of the pressure-sensitive adhesive layer is within the range, the handleability of the protective film is improved, the protective film can be prevented from being lifted or peeled off, and wrinkles and scratches are less likely to occur when bonded to the base film.

  The back layer is usually located on the surface of the protective film opposite to the base film (that is, the back surface). Usually, the back layer is formed of a resin. The polymer contained in the resin forming the back layer may be a homopolymer or a copolymer. Preferable examples include polyolefin resins and polyester resins.

  When the back layer is a polyolefin resin film, examples of the polyolefin resin constituting the polyolefin resin film include polyethylene, polypropylene, ethylene-propylene copolymer, propylene-α-olefin copolymer, ethylene- α-olefin copolymer, ethylene-ethyl (meth) acrylate copolymer, ethylene-methyl (meth) acrylate copolymer, ethylene-n-butyl (meth) acrylate copolymer, ethylene-vinyl acetate copolymer, etc. Is mentioned. Here, examples of the polyethylene include low density polyethylene, medium density polyethylene, high density polyethylene, and linear low density polyethylene. Examples of the ethylene-propylene copolymer include a random copolymer and a block copolymer. Furthermore, examples of the α-olefin include butene-1, hexene-1, 4-methylpentene-1, octene-1, pentene-1, and heptene-1. Among these polyolefin resins, at least one polymer selected from the group consisting of polyethylene, polypropylene, ethylene-propylene copolymer, and propylene-α-olefin copolymer is preferable, polyethylene or polypropylene is more preferable, and polyethylene Is more preferable. One type of polyolefin resin may be used alone, or two or more types may be used in combination at any ratio.

  The back layer may contain additives such as fillers, lubricants, antioxidants, ultraviolet absorbers, light stabilizers, heat stabilizers, pigments, dyes, antistatic agents, and nucleating agents. In addition, an additive may be used individually by 1 type and may use 2 or more types together by arbitrary ratios.

  The ratio of the thickness of the adhesive layer to the thickness of the back layer (the thickness of the adhesive layer / the thickness of the back layer) is usually 1/40 or more, preferably 1/20 or more, and usually 1/1 or less, preferably Is 1/2 or less. The ratio of the thickness of the adhesive layer to the thickness of the back layer is within this range, so that the fish eyes of the protective film can be suppressed, and the generation of wrinkles and scratches can be further suppressed when the protective film and the base film are bonded. It becomes easy.

  The thickness t2 [unit: mm] of the protective film (the total thickness when the protective film is a film having a laminated structure such as a film having an adhesive layer and a back layer) is the thickness of the base film. Although it varies depending on the thickness and the required quality level, it is preferably from 0.010 to 0.10, more preferably from 0.020 to 0.070, from the viewpoint of moldability and handleability.

  There is no restriction | limiting in the manufacturing method of a protective film, As long as the protective film mentioned above is obtained, arbitrary methods are employable. Examples of the production method of the protective film are: (i) a method of co-extrusion of the material of the adhesive layer and the material of the back layer, and the material of the intermediate layer as required, (ii) preparing a back layer or an intermediate layer. And a method of forming an adhesive layer by applying an adhesive to the prepared layer. Further, (iii) a method in which an adhesive layer and a back layer, and an intermediate layer are separately prepared as necessary, and the prepared layers are bonded and integrated may be adopted.

  Among the exemplified production methods, the production method (i) by the coextrusion molding method is such that the adhesive layer and the back layer or the intermediate layer are firmly adhered, and the adhesive residue on the base film (after the protective film is peeled off) The phenomenon that the adhesive remains in the material film) is less likely to occur, and it is preferable from the viewpoint of low cost.

[Multilayer film]
The multilayer film obtained by the manufacturing method of this invention is equipped with the base film and protective film which were mentioned above. The multilayer film should just be provided with the protective film on at least one surface of the base film, and may be provided with the protective film on both surfaces of the base film. The multilayer film may be a multilayer film having a total of three or more layers having two or more of one or both of the base film and the protective film.

  The multilayer film may have other layers besides the base film and the protective film. The other layers may be one layer or two or more layers. Moreover, each layer may be the same or different. The positions of other layers can be set arbitrarily.

  In the multilayer film, the ratio (t2 / t1) of the thickness t2 of the protective film to the thickness t1 of the base film is preferably 0.1 to 1, more preferably 0.2 to 0.8. More preferably, it is 0.3-0.7. When the ratio (t2 / t1) is 0.1 or more, wrinkles at the time of bonding of the base film and the protective film can be more effectively suppressed, and when it is 1 or less, wrinkles after being left standing are more effective. Can be suppressed.

  The haze of the multilayer film is preferably 15% or less, more preferably 13% or less, and further preferably 12% or less. Since the haze of the multilayer film is 15% or less, it is possible to observe defects and wrinkles using a light transmission type defect inspection machine in the state of the multilayer film without peeling off the protective film. Increased film productivity. Moreover, a multilayer film is excellent in transparency, and can be preferably used for an optical use. The haze of the multilayer film can be determined according to JIS K7136 using a haze meter, and specifically can be determined by the method described later in the examples.

  In the multilayer film, the peel strength between the base film and the protective film is preferably 0.01 to 1.0 N / 25 mm, more preferably 0.05 to 0.80 N / 25 mm, and still more preferably 0.00. 10 to 0.50 N / 25 mm. When the peel strength is 0.01 N / 25 mm or more, peeling and wrinkles of the base film and the protective film can be more effectively suppressed during and after the production of the multilayer film. Moreover, when the peel strength is 1.0 N / 25 mm or less, adhesive residue can be suppressed when the protective film is peeled off from the base film. The said peeling strength can be calculated | required by the 90 degree peeling test based on JIS-K6854-2 (1999), and can be specifically calculated | required by the method mentioned later in an Example.

  The manufacturing process of a base film or a protective film and the bonding process (manufacturing process of a multilayer film) of a base film and a protective film may be different or may be included in one process continuously. . In one embodiment, the base film and the protective film are separately manufactured in advance to form film rolls, and the films are unwound from these film rolls and used for the bonding step.

In this specification, the index | exponent (epsilon) [unit: mm] of the distortion | strain of the base film in a bonding process is represented by following formula (1).
ε1 = T1 / (t1 × Y1) (1)
However, T1 is the tension [unit: N] applied to the base film when the base film and the protective film are bonded, t1 is the thickness [unit: mm] of the base film, and Y1 is the base film. Young's modulus [unit: MPa].

Moreover, in this specification, the parameter | index (epsilon) 2 [unit: mm] of distortion of the protective film in a bonding process is represented by following formula (2).
ε2 = T2 / (t2 × Y2) (2)
However, T2 is the tension [unit: N] applied to the protective film when the base film and the protective film are bonded, t2 is the thickness [unit: mm] of the protective film, and Y2 is the Young's modulus of the protective film [ Unit: MPa].

  In the production method of the present invention, the ratio (ε2 / ε1) of the strain index ε2 of the protective film to the strain index ε1 of the base film is set to more than 7 and 15 or less. The ratio (ε2 / ε1) is preferably 13 or less, more preferably 12 or less, and even more preferably 10 or less. By setting the ratio (ε2 / ε1) to 15 or less, wrinkles and peeling do not occur even after a lapse of time after bonding, and a multilayer film that is particularly difficult to cause wrinkles can be obtained. Further, the ratio (ε2 / ε1) is preferably 7.5 or more, more preferably 8.0 or more, and further preferably 9.0 or more. By setting the ratio (ε2 / ε1) to more than 7, it is possible to obtain a multilayer film that is unlikely to be wrinkled and peeled even after a lapse of time, and particularly difficult to peel. When the film is stored as a film roll, breakage of the base film can be reduced when the multilayer film is unwound from the film roll.

  Ε1 [unit: mm] of the base film is preferably 1.0 or less, more preferably 0.95 or less, still more preferably 0.90 or less, and even more preferably 0.80 or less. Yes, particularly preferably 0.70 or less. When ε1 is 1.0 or less, breakage of the base film can be reduced. Moreover, from a viewpoint of productivity, Preferably it is 0.10 or more, More preferably, it is 0.30 or more, More preferably, it is 0.50 or more.

  Ε2 [unit: mm] of the protective film is preferably 12 or less, more preferably 8.0 or less, and even more preferably 7.0 or less. When ε2 is 12 or less, breakage of the protective film can be reduced. Moreover, from a viewpoint of productivity, Preferably it is 1.0 or more, More preferably, it is 3.0 or more, More preferably, it is 5.0 or more.

  50-200 are preferable, as for tension | tensile_strength T1 [unit: N] concerning a base film at the time of bonding of a base film and a protective film, 80-150 are more preferable, and 90-130 are more preferable. When the tension T1 of the base film is within the range, warpage is unlikely to occur even if the obtained multilayer film is stored for a long period of time, and when the multilayer film is stored as a film roll, the film roll has excellent winding quality. . In addition, when unwinding a base film from a film roll and bonding with a protective film, the tension | tensile_strength T1 can employ | adopt the value of the unwinding tension | tensile_strength of a base film. For example, the tension T1 can be adjusted by adjusting the torque for unwinding the base film from the film roll using a powder clutch, powder brake, or motor, or by adjusting the unwinding speed of the base film using a dancer roll. Can be controlled.

  10-200 are preferable, as for tension | tensile_strength T2 [unit: N] concerning a protective film at the time of bonding of a base film and a protective film, 15-100 are more preferable, and 20-60 are more preferable. If the tension T2 of the protective film is within the range, deformation of the multilayer film due to shrinkage can be suppressed. In addition, when unwinding a protective film from a film roll and bonding with a base film, the tension | tensile_strength T2 can employ | adopt the value of the unwinding tension | tensile_strength of a protective film. As a method for controlling the tension T2, the same method as that for the tension T1 described above can be employed.

  The ratio (T2 / T1) of the protective film tension T2 to the substrate film tension T1 is preferably 0.1 to 1.0, more preferably 0.2 to 0.8, and 0.3 to 0.5. Further preferred. By setting the ratio (T2 / T1) in such a range, peeling immediately after pasting can be more effectively reduced.

  The method for pasting the base film and the protective film is not particularly limited, and a known method can be adopted, for example, a method of sandwiching with two rolls. Such two rolls may be rolls of the same material or structure, or may be rolls of different materials or structures. Examples of such rolls include a metal rigid roll, a metal elastic roll, and a rubber roll. Moreover, the pressure (contact pressure) applied in the film thickness direction when the base film and the protective film are bonded, and the speed at which the base film, the protective film, and the multilayer film flow are the base film and the protective film. It can be determined appropriately in consideration of the strength of the material.

[Usage]
The use of the multilayer film obtained by the production method of the present invention is not particularly limited. For example, vehicle decorative parts such as vehicle exteriors and vehicle interiors; building material parts such as wall materials, window films, window frames, bathroom wall materials; Daily miscellaneous goods such as tableware, toys and musical instruments; home appliance decoration parts such as vacuum cleaner housings, television housings and air conditioner housings; interior members such as kitchen door cover materials; ship members; touch panel cover materials, personal computer housings, mobile phone housings Electronic communication equipment such as: LCD protective plates, light guide plates, light guide films, polarizer protective films, polarizing plate protective films, retardation films, front plates and cover materials for various displays, diffuser plates and other optical components; solar cells Or photovoltaic power generation members, such as a panel covering material for photovoltaic power generation, are mentioned.

  Among them, members used for display devices such as liquid crystal display devices, for example, polarizer protective films, polarizing plate protective films, retardation films, brightness enhancement films, liquid crystal substrates, light diffusion sheets, prism sheets, etc. In particular, it can be suitably used for a polarizing plate protective film and a retardation film.

  Moreover, the multilayer film obtained by the manufacturing method of this invention can be used suitably also for a decoration use. The decoration method is not particularly limited, and a known method can be used.

  In each use of the multilayer film, the protective film constituting the multilayer film can be appropriately peeled off from the base film as described above. For example, when the multilayer film is used for optical applications, the multilayer film is used. The substrate film constituting the multilayer film can be used as an optical film, and when the multilayer film is used for decorating purposes, the substrate film constituting the multilayer film can be used as a decorative film.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited thereto. In addition, the measurement or evaluation of the physical-property value in an Example and a comparative example was performed with the following method.

(Young's modulus)
A base film or a protective film is cut out to 15 mm × 150 mm to obtain a test piece, and tensile Young's modulus [MPa] in accordance with JIS K7127 using an autograph (manufactured by Shimadzu Corporation, precision universal testing machine AG-IS 5 kN). Was measured.

(Haze)
The multilayer film was cut out to 50 mm × 50 mm to obtain a test piece, and the haze was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., SH7000) according to JIS K7136.

(Peel strength)
The multilayer film was cut into a size of 10 mm × 50 mm to obtain a test piece, which was allowed to stand for 24 hours in an environment having a temperature of 23 ° C. and a relative humidity of 50%. Necessary when using a small tensile tester to peel off the base film and protective film of the test piece at an angle of 90 degrees at a tensile speed of 30 mm / min in accordance with JIS-K6854-2 (1999). The average load [N] per unit width (25 mm) was measured.

(Peeling immediately after bonding)
The multilayer film immediately after being obtained was placed on a black cloth (manufactured by Kawashima Textile Cellcon Co., Ltd.), the appearance was visually observed under a fluorescent lamp (200 lux), and evaluated as follows.
A: No air layer is observed between the base film and the protective film on the entire surface of the multilayer film.
B: A part of the multilayer film, and an air layer is seen between the base film and the protective film.
C: On the entire surface of the multilayer film, an air layer is seen between the base film and the protective film.

(Peeling after leaving)
Seven days after obtaining the multilayer film, the multilayer film according to the same method as the peeling immediately after bonding was observed again and evaluated on the same basis as the peeling immediately after bonding.

(Wrinkles immediately after bonding)
The multilayer film immediately after obtained was placed on a black cloth (manufactured by Kawashima Textile Cellcon), the appearance was visually observed under a fluorescent lamp (200 lux), and the presence or absence of wrinkles was evaluated as follows.
A: Wrinkles are not seen on the entire surface of the multilayer film.
B: Wrinkles are seen in a part of the multilayer film.
C: Wrinkles are observed on the entire surface of the multilayer film.

(Wrinkles after leaving)
Seven days after obtaining the multilayer film, the multilayer film according to the same method as the wrinkle immediately after bonding was observed again and evaluated according to the same criteria as the wrinkle immediately after bonding.

<Production Example 1>
(Base film (1-1))
80 parts by mass of a methacrylic polymer (weight average molecular weight 30000) obtained by referring to Synthesis Example 4 of International Publication No. 2016/121868, and a (meth) acryl having a three-layer structure obtained by referring to Synthesis Example 8 20 parts by mass of elastic particles are supplied to a hopper of a vented single screw extruder, melt kneaded at 260 ° C., discharged from a T die, and sandwiched between a metal elastic roll having a mirror surface and a metal rigid body roll having a mirror surface. A base film (1-1) made of a methacrylic resin and having a thickness of 75 μm and a width of 1400 mm was prepared and wound into a roll to obtain a film roll. The Young's modulus of the base film (1-1) was 2300 MPa.

<Production Example 2>
(Base film (1-2))
85 parts by mass of a methacrylic polymer (weight average molecular weight 30000) obtained by referring to Synthesis Example 4 of International Publication No. 2016/121868, and a (meth) acrylic triblock structure obtained by referring to Synthesis Example 6 15 parts by mass of the block copolymer is supplied to a hopper of a vented single-screw extruder, melt-kneaded at 260 ° C., discharged from a T die, and sandwiched between a metal elastic roll having a mirror surface and a metal rigid roll having a mirror surface Then, a base film (1-2) made of a methacrylic resin and having a thickness of 75 μm and a width of 1400 mm was prepared and wound into a roll to obtain a film roll. The Young's modulus of the base film (1-2) was 2600 MPa.

The film used as a protective film is shown below.
Protective film (2-1): Protective film with adhesive layer (manufactured by Sanei Kaken Co., Ltd., trade name “PAC3-60T”. Adhesive layer is made of ethylene-vinyl acetate copolymer, back layer is made of polyethylene, Young's modulus Is 90 MPa and has a thickness of 60 μm.)
Protective film (2-2): Protective film with adhesive layer (trade name “Tretec 7H52” manufactured by Toray Industries, Inc. The adhesive layer is made of an ethylene-vinyl acetate copolymer, the back layer is made of polypropylene, and the Young's modulus is 270 MPa. And the thickness is 30 μm.)

[Example 1]
The base film (1-1) was unwound from the film roll with an unwinding tension of 100N. Further, the protective film (2-1) was unwound from the film roll with an unwinding tension of 30N. The unrolled base film (1-1) and the protective film (2-1) are in a state where the respective unwinding tensions are applied, and a metal roll and a rubber roll through the adhesive layer of the protective film (2-1). Then, the film was bonded at a contact pressure of 0.2 MPa while being sandwiched between, and a multilayer film was produced at a speed of 15 m / min. At this time, the distortion index ε1 [mm] of the base film (1-1) was 0.58, and the distortion index ε2 [mm] of the protective film (2-1) was 5.6. The evaluation results of the obtained multilayer film are shown in Table 1.

[Examples 2-3, Comparative Examples 1-3]
In Example 1, a multilayer film was produced in the same manner as in Example 1 except that the used film and production conditions were changed as shown in Table 1. The evaluation results of the obtained multilayer film are shown in Table 1.

  From the results of Table 1, the multilayer film obtained by the production method of the present invention is less likely to be wrinkled and peeled immediately after bonding, and is less likely to be wrinkled and peeled even after a lapse of time after bonding. I understand. Therefore, the multilayer film obtained by the production method of the present invention can maintain a beautiful appearance without damaging the base film, and can further suppress defects such as printing omission in a subsequent process such as printing or metal deposition, Breakage of the multilayer film during conveyance can be suppressed.

Claims (16)

Having a bonding step of bonding a base film having a Young's modulus of 1000 MPa or more and a protective film having a Young's modulus of less than 1000 MPa;
When the index ε1 of the base film distortion in the bonding step is represented by the following formula (1), and the strain index ε2 of the protective film in the bonding step is represented by the following formula (2), the ratio of ε2 to ε1 The manufacturing method of the multilayer film which makes ((epsilon) 2 / (epsilon) 1) 7 more than 15 or less.
ε1 = T1 / (t1 × Y1) (1)
ε2 = T2 / (t2 × Y2) (2)
(However, T1 is the tension [N] applied to the base film when the base film and the protective film are bonded, t1 is the thickness [mm] of the base film, and Y1 is the Young's modulus of the base film [ T2 is the tension [N] applied to the protective film when the base film and the protective film are bonded, t2 is the thickness [mm] of the protective film, and Y2 is the Young's modulus of the protective film. [MPa].)   The manufacturing method of Claim 1 whose peeling strength of the said base film and the said protective film is 0.05-1.0N / 25mm.   The manufacturing method of Claim 1 or 2 whose haze of the said multilayer film is 15% or less.   The manufacturing method in any one of Claims 1-3 whose ratio (t2 / t1) of thickness t2 of the protective film with respect to thickness t1 of the said base film is 0.1-1.   The manufacturing method in any one of Claims 1-4 whose ratio (T2 / T1) of the tension | tensile_strength T2 of the said protective film with respect to tension | tensile_strength T1 of the said base film is 0.1-1.0.   The manufacturing method in any one of Claims 1-5 whose parameter | index (epsilon) 1 [mm] of distortion of the said base film is 1.0 or less.   The manufacturing method in any one of Claims 1-6 whose said base film is a thermoplastic resin film.   The manufacturing method of Claim 7 whose thermoplastic resin which comprises the said thermoplastic resin film is (meth) acrylic-type resin.   The manufacturing method according to claim 8, wherein the (meth) acrylic resin is a composition containing a hard methacrylic resin and an elastomer.   The manufacturing method according to claim 9, wherein the elastomer is a (meth) acrylic elastomer.   The manufacturing method in any one of Claims 1-10 in which the said protective film has an adhesion layer and a back layer.   The manufacturing method of Claim 11 with which the said adhesion layer contains an ethylene-vinyl acetate copolymer.   The manufacturing method according to claim 11 or 12, wherein the back layer is a polyolefin resin film.   The manufacturing method of Claim 13 whose polyolefin resin which comprises the said polyolefin resin film is polyethylene.   The manufacturing method in any one of Claims 1-14 whose said base film is a decorating film.   The manufacturing method in any one of Claims 1-14 whose said base film is an optical film.