JP7142167B2 - multilayer film - Google Patents

Description

The present invention relates to multilayer films.

BACKGROUND ART Conventionally, hard-coated films have been used as surface protective films for optical members such as liquid crystal panels. However, although it is possible to make the film less likely to be scratched by increasing the surface hardness of the film, once the film is scratched, it cannot be repaired.
Therefore, materials having self-healing properties have been studied, and for example, a film in which a polyester-based urethane resin is laminated on a transparent base material such as polyamide, polycarbonate, or polyimide has been proposed (see, for example, Patent Document 1).
However, conventional techniques, including the multilayer film described in Patent Document 1, have the problem that the scratch recovery time is long and the scratch resistance is not sufficient under conditions where fine scratches are likely to occur. Moreover, the conventional technique also has a problem that the bending resistance is not sufficient.

Japanese Patent Publication No. 2019-511386

The present invention has been made in view of the above problems, and an object of the present invention is to provide a film which is excellent in scratch resistance and also excellent in flex resistance.

The present inventors arrived at the present invention as a result of intensive studies to solve the above problems.
That is, the present invention provides a multilayer film having a base layer and a surface layer formed on the base layer, wherein the surface layer contains a compound (a1) having a polyorganosiloxane group and an active hydrogen group as an essential component. It contains a polyurethane resin (U1) consisting of a component (A1) and an isocyanate component (B1), the elastic recovery rate of the polyurethane resin (U1) at 100% elongation is 50 to 100%, and the base layer has an active containing a polyurethane resin (U2) consisting of a hydrogen component (A2) and an isocyanate component (B2), wherein the active hydrogen component (A2) does not contain a compound (a1) having a polyorganosiloxane group and an active hydrogen group, It is an active hydrogen component containing a polymer polyol (a2) as an essential component, and is a multilayer film having an elastic recovery rate of 80 to 100% at 100% elongation of the polyurethane resin (U2).

The multilayer film of the present invention has excellent scratch resistance and also excellent flex resistance.

The multilayer film of the present invention is a multilayer film having a base layer and a surface layer formed on the base layer.
Then, the surface layer contains a polyurethane resin (U1) composed of an active hydrogen component (A1) containing a compound (a1) having a polyorganosiloxane group and an active hydrogen group as an essential component and an isocyanate component (B1), The polyurethane resin (U1) has an elastic recovery rate of 50 to 100% at 100% elongation, and the base layer contains a polyurethane resin (U2) consisting of an active hydrogen component (A2) and an isocyanate component (B2), The active hydrogen component (A2) is an active hydrogen component that does not contain the compound (a1) having a polyorganosiloxane group and an active hydrogen group and contains a polymer polyol (a2) as an essential component, and the polyurethane resin (U2 ) has an elastic recovery rate of 80 to 100% at 100% elongation.

A polyurethane resin (U1) consisting of an active hydrogen component (A1) containing a compound (a1) having a polyorganosiloxane group and an active hydrogen group in the surface layer and an isocyanate component (B1) as essential components, and the polyurethane resin ( U1) having an elastic recovery rate of 50 to 100% at 100% elongation improves scratch resistance.
Further, the base layer contains a polyurethane resin (U2) composed of an active hydrogen component (A2) and an isocyanate component (B2), and the active hydrogen component (A2) is a compound having the polyorganosiloxane group and the active hydrogen group ( It is an active hydrogen component that does not contain a1) and contains the polymer polyol (a2) as an essential component, and the elastic recovery rate at 100% elongation of the polyurethane resin (U2) is 80 to 100%. A film having excellent scratch resistance and bending resistance can be obtained.
In general, the polyurethane resin (U2) used for the base layer in the present invention is excellent in scratch resistance and flex resistance, but often causes tack on the surface. It is possible to suppress the occurrence of tack on the surface of the film.

[surface]
The polyurethane resin (U1), which is the main component of the surface layer, reacts the active hydrogen component (A1) containing the compound (a1) having a polyorganosiloxane group and an active hydrogen group as an essential component with the isocyanate component (B1). It is a polyurethane resin obtained by

The active hydrogen component (A1) in the polyurethane resin (U1) includes a compound (a1) having a polyorganosiloxane group and an active hydrogen group as essential components and a polymer polyol (a2) and chain extender (a3) as optional components. ) and a reaction terminator (a4).

As the compound (a1) having a polyorganosiloxane group and an active hydrogen group, a compound having a polyorganosiloxane group represented by general formula (1) is preferable from the viewpoint of scratch resistance and haze.

R ¹ to R ⁶ in general formula (1) each independently represent a hydrocarbon group having 1 to 6 carbon atoms. From the viewpoint of scratch resistance, R ¹ to R ⁶ are preferably alkyl groups having 1 to 3 carbon atoms, more preferably methyl groups.

n in the general formula (1) is an integer of 1 to 100, preferably 10 to 70, more preferably 15 to 50, from the viewpoint of scratch resistance and haze.

Examples of the active hydrogen group of the compound (a1) having a polyorganosiloxane group and an active hydrogen group [hereinafter abbreviated as (a1)] include a hydroxyl group, an amino group and a carboxyl group.
Since (a1) generally has low compatibility with other constituent monomers of the polyurethane resin (U1), the haze of (U1) is increased by uniformly introducing (a1) into the polyurethane resin (U1). From the viewpoint of suppression, it is preferable to use (a1) having a hydroxyl group and an amino group as active hydrogen groups. (a1) may be used alone or in combination of two or more.

Among (a1), as the compound (a11) having a hydroxyl group, a commercially available product can be used. ” (functional group equivalent weight 1,600 g / mol), “KF-6003” (functional group equivalent weight 2,550 g / mol), “X-22-1821” having phenolic hydroxyl groups at both ends (functional group equivalent weight 1,470 g / mol) (manufactured by Shin-Etsu Chemical Co., Ltd.), "BY-16-752A" (functional group equivalent 1,500 g / mol) (manufactured by Dow Corning Toray Co., Ltd.), having a hydroxyl group at one end "X-22-170BX" (functional group equivalent weight 2,800 g / mol), "X-22-170DX" (functional group equivalent weight 4,670 g / mol), "X-22-176DX" (functional group equivalent weight 1,600 g / mol), “X-22-176F” (functional group equivalent 6,300 g / mol) (manufactured by Shin-Etsu Chemical Co., Ltd.), “X-22-4039” having a hydroxyl group in the side chain (functional group equivalent 970 g / mol) “X-22-4015” (functional group equivalent 1,870 g / mol) (manufactured by Shin-Etsu Chemical Co., Ltd.), “SF8427” having hydroxyl groups in both terminal polyethers (functional group equivalent 930 g / mol , Dow Corning Toray Co., Ltd.), "X-22-4952" (functional group equivalent 1,100 g / mol, manufactured by Shin-Etsu Chemical Co., Ltd.); "FZ-2162" having a hydroxyl group in the side chain polyether ( functional group equivalent 750) and "SH3773M" (functional group equivalent 800 g/mol) (manufactured by Dow Corning Toray Co., Ltd.).

Among (a1), as the compound (a12) having an amino group, a commercially available product can be used. -22-161A" (functional group equivalent weight 800 g/mol), "X-22-161B" (functional group equivalent weight 1,500 g/mol), "KF-8012" (functional group equivalent weight 2,200 g/mol), "KF -8008” (functional group equivalent weight 5,700 g/mol), “X-22-9409” (functional group equivalent weight 700 g/mol), “X-22-1660B-3” (functional group equivalent weight 2,200 g/mol) ( Above, manufactured by Shin-Etsu Chemical Co., Ltd.), "BY-16-853U" (functional group equivalent 460 g / mol), "BY-16-853" (functional group equivalent 650 g / mol), "BY-16-853B" ( functional group equivalent 2,200 g / mol) (manufactured by Dow Corning Toray Co., Ltd.), "KF-868" having an amino group in the side chain (functional group equivalent 8,800 g / mol), "KF-865" ( functional group equivalent 5,000 g / mol), "KF-864" (functional group equivalent 3,800), "KF-880" (functional group equivalent 1,800 g / mol), "KF-8004" (functional group equivalent 1 , 500 g/mol) (manufactured by Shin-Etsu Chemical Co., Ltd.).

Among (a1), as the compound (a13) having a carboxyl group, a commercially available product can be used. ), “X-22-3710” having a carboxyl group at one end (functional group equivalent 1,450 g / mol) and “X-22-3701E” having a carboxyl group in the side chain (functional group equivalent 4,000 g / mol) (manufactured by Shin-Etsu Chemical Co., Ltd.).

The weight of the compound (a1) having a polyorganosiloxane group and an active hydrogen group in the polyurethane resin (U1) is based on the weight of the polyurethane resin (U1) as a constituent component from the viewpoint of scratch resistance, tack-free property and haze. , preferably 0.5 to 5% by weight, more preferably 1 to 4% by weight.

The polymer polyol (a2) is preferably a polymer polyol having a number average molecular weight (hereinafter abbreviated as Mn) of 500 or more. Specifically, polyester polyol (a21), polyether polyol (a22) and polyether and ester polyol (a23). The polymer polyol (a2) may be used alone or in combination of two or more.

Polyester polyols (a21) include condensation type polyester polyols, polylactone polyols, polycarbonate polyols, and the like.

As the condensation-type polyester polyol, Mn or a polyol having a chemical formula weight of less than 500, a polycarboxylic acid having 2 to 20 carbon atoms or an ester-forming derivative thereof [acid anhydride, lower (1 to 4 carbon atoms) alkyl ester and acid halides, etc.].

Polyols having Mn or a chemical formula weight of less than 500 include polyhydric alcohols having 2 to 20 carbon atoms; alkylene oxides having 2 to 12 carbon atoms (hereinafter abbreviated as AO) adducts of polyhydric alcohols having 2 to 20 carbon atoms. Mn or those having a chemical formula weight of less than 500; AO adducts having 2 to 12 carbon atoms of bisphenol (bisphenol A, bisphenol S, bisphenol F, etc.) having Mn or a chemical formula weight of less than 500; bis( 2-Hydroxyethyl)terephthalate and its C2-C12 AO adducts having Mn or a chemical formula weight of less than 500, and the like.

Examples of AO having 2 to 12 carbon atoms include ethylene oxide, 1,2- or 1,3-propylene oxide, 1,2-, 1,3- or 2,3-butylene oxide, tetrahydrofuran, 3-methyltetrahydrofuran, Examples include styrene oxide, α-olefin oxide and epichlorohydrin.

Examples of the polyhydric alcohol having 2 to 20 carbon atoms include linear or branched aliphatic dihydric alcohols having 2 to 12 carbon atoms [ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5 - such as pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-dodecanediol, diethylene glycol, triethylene glycol and tetraethylene glycol; Linear alcohol; 1,2-, 1,3- or 2,3-butanediol, 2-methyl-1,4-butanediol, neopentyl glycol, 2,2-diethyl-1,3-propanediol, 2 -methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,6-hexanediol, 3-methyl-1,6-hexanediol, 2-methyl-1,7 -heptanediol, 3-methyl-1,7-heptanediol, 4-methyl-1,7-heptanediol, 2-methyl-1,8-octanediol, 3-methyl-1,8-octanediol and 4- branched alcohols such as methyloctanediol]; alicyclic dihydric alcohols having 6 to 20 carbon atoms [1,4-cyclohexanediol, 1,3- or 1,4-cyclohexanedimethanol, 1,3-cyclopentanediol , 1,4-cycloheptanediol, 2,5-bis(hydroxymethyl)-1,4-dioxane, 2,7-norbornanediol, tetrahydrofurandimethanol, 1,4-bis(hydroxyethoxy)cyclohexane, 1,4 -bis(hydroxymethyl)cyclohexane and 2,2-bis(4-hydroxycyclohexyl)propane, etc.]; araliphatic dihydric alcohols having 8 to 20 carbon atoms [m- or p-xylylenediol, bis(hydroxyethyl) Benzene and bis(hydroxyethoxy)benzene, etc.]; trihydric alcohols having 3 to 20 carbon atoms [aliphatic triols (glycerin, trimethylolpropane, etc.), etc.]; tetrahydric to octahydric alcohols having 5 to 20 carbon atoms [aliphatic polyols (pentaerythritol, sorbitol, mannitol, sorbitan, diglycerin, dipentaerythritol, etc.); sugars (sucrose, glucose, mannose, fructose, methylglucoside and derivatives thereof)];

Examples of the polyvalent carboxylic acid having 2 to 20 carbon atoms or an ester-forming derivative thereof include aliphatic dicarboxylic acids (succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, octadecanedicarboxylic acid, decylsuccinic acid, fumaric acid, and maleic acid, etc.), alicyclic dicarboxylic acids (dimer acid, etc.), aromatic dicarboxylic acids (terephthalic acid, isophthalic acid, phthalic acid, t-butyl isophthalic acid, 2,6-naphthalenedicarboxylic acid and 4,4′- biphenyldicarboxylic acid, etc.), trivalent or higher polycarboxylic acids (trimellitic acid, pyromellitic acid, etc.), anhydrides thereof (succinic anhydride, maleic anhydride, phthalic anhydride, trimellitic anhydride, etc.) , acid halides thereof (adipic acid dichloride, etc.), low-molecular-weight alkyl esters thereof (dimethyl succinate, dimethyl phthalate, etc.), and combinations thereof.

As the polylactone polyol, lactone monomers having 3 to 12 carbon atoms (β-propiolactone, γ-butyrolactone, γ-valerolactone, ε-caprolactone, η -caprylolactone, 11-undecanolactone, 12-tridecanoid, etc.), and the like, by ring-opening polymerization. Lactone monomers may be used alone or in combination of two or more.

As the polycarbonate polyol, one or more (preferably 2 to 4 types), and low-molecular-weight carbonate compounds (for example, dialkyl carbonates having an alkyl group with 1 to 6 carbon atoms, alkylene carbonates having an alkylene group having 2 to 6 carbon atoms, and diaryl having an aryl group having 6 to 9 carbon atoms. carbonate) by condensation with dealcoholization reaction.

Examples of the polyether polyol (a22) include compounds obtained by adding AO having 2 to 12 carbon atoms to the above Mn or polyol having a chemical formula weight of less than 500. AO may be used alone or in combination of two or more. In the latter case, block addition (chip type, balance type, active secondary type, etc.), random addition, or a combination of these may be used.

The addition of AO to the above Mn or polyol having a chemical formula weight of less than 500 can be performed, for example, without a catalyst or in the presence of a catalyst (alkali catalyst, amine-based catalyst, acidic catalyst, etc.) (especially in the latter half of the AO addition). It is carried out in one stage or in multiple stages under pressure or under pressure.

Specific examples of the polyether polyol (a22) include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly(oxy-3-methyltetramethylene) glycol, tetrahydrofuran/ethylene oxide copolymer diol and tetrahydrofuran/3-methyltetrahydrofuran co- Polymerized diols and the like can be mentioned.

As the polyether ester polyol (a23), one or more of the above polyether polyols and one or more of the polycarboxylic acids having 2 to 20 carbon atoms or ester-forming derivatives thereof exemplified as raw materials for the condensation-type polyester polyols. and the like obtained by condensation polymerization.

Of the polymer polyols (a2) in the polyurethane resin (U1), polycarbonate polyols are particularly preferred from the viewpoint of scratch resistance, tack-free properties and chemical resistance.

Mn of the polymer polyol (a2) is preferably 500 or more, more preferably 500 to 5000, particularly preferably 800 to 3000, from the viewpoint of scratch resistance.

The Mn of the polymer polyol (a2) in the present invention can be measured by gel permeation chromatography under the following conditions, for example.
Apparatus: "Waters Alliance 2695" [manufactured by Waters]
Column: "Guardcolumn Super HL" (1 piece), "TSKgel SuperH2000, TSKgel SuperH3000, TSKgel SuperH4000 (all manufactured by Tosoh Corporation) each connected"
Sample solution: 0.25% by weight tetrahydrofuran solution Injection amount: 10 μl
Flow rate: 0.6 ml/min Measurement temperature: 40°C
Detection device: refractive index detector Reference material: standard polyethylene glycol

From the standpoint of scratch resistance and tack-free property, the weight of the polymer polyol (a2) in the polyurethane resin (U1) is preferably 50 to 90% by weight, based on the weight of the polyurethane resin (U1), as a constituent component. More preferably 60 to 80% by weight.

Examples of the chain extender (a3) include water, polyols having Mn or chemical formula weight of less than 500 and polyamine compounds having Mn or chemical formula weight of less than 500, and the like.

Examples of the polyol having Mn or chemical formula weight of less than 500 include the same polyols having Mn or chemical formula weight of less than 500 that constitute the condensation type polyester polyol.

Examples of polyamine compounds having Mn or a chemical formula weight of less than 500 include aliphatic polyamines having 2 to 36 carbon atoms [alkylenediamines such as ethylenediamine and hexamethylenediamine; diethylenetriamine, dipropylenetriamine, dihexylenetriamine, triethylenetetramine, tetraethylene Poly (n = 2-6) alkylene groups (carbon number 2-6) poly (n = 3-7) amines such as pentamine, pentaethylenehexamine and hexaethyleneheptamine], C 6-20 lipids Cyclic polyamines (1,3- or 1,4-diaminocyclohexane, 4,4'- or 2,4'-dicyclohexylmethanediamine and isophoronediamine, etc.), aromatic polyamines having 6 to 20 carbon atoms (1,3- or 1,4-phenylenediamine, 2,4- or 2,6-tolylenediamine, 4,4'- or 2,4'-methylenebisaniline, etc.), araliphatic polyamines having 8 to 20 carbon atoms [1 , 3- or 1,4-xylylenediamine, bis(aminoethyl)benzene, bis(aminopropyl)benzene and bis(aminobutyl)benzene, etc.], heterocyclic polyamines having 3 to 20 carbon atoms [2,4- diamino-1,3,5-triazine, piperazine and N-(2-aminoethyl)piperazine], hydrazine or its derivatives (dibasic acid dihydrazide such as adipic acid dihydrazide, etc.) and aminoalcohols having 2 to 20 carbon atoms ( Examples include ethanolamine, diethanolamine, 2-amino-2-methylpropanol and triethanolamine).

Among the chain extenders (a3), water, ethylene glycol, 1,4-butanediol and trimethylolpropane are preferred from the viewpoint of scratch resistance and tack-free properties.

The weight of the chain extender (a3) in the polyurethane resin (U1) is preferably 0.5 to 10 wt. %, more preferably 1 to 5% by weight.

The reaction terminator (a4) includes monoalcohols having 1 to 20 carbon atoms (methanol, ethanol, butanol, octanol, decanol, dodecyl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, etc.), monoamines having 1 to 20 carbon atoms. (mono- or dialkylamines such as monomethylamine, monoethylamine, monobutylamine, dibutylamine and monooctylamine; and mono- or dialkanolamines such as monoethanolamine, diethanolamine and diisopropanolamine).

Of the reaction terminator (a4), monoethanolamine and diethanolamine are preferred from the viewpoint of scratch resistance and tack-free properties.

The polyisocyanate component (B1) includes an aromatic polyisocyanate (b1) having 8 to 26 carbon atoms and having 2 to 3 or more isocyanate groups, an aliphatic polyisocyanate (b2) having 4 to 22 carbon atoms, carbon Examples include alicyclic polyisocyanates (b3) having 8 to 18 carbon atoms, araliphatic polyisocyanates (b4) having 10 to 18 carbon atoms, and modified products (b5) of these organic polyisocyanates.

Examples of the aromatic polyisocyanate (b1) having 8 to 26 carbon atoms [hereinafter abbreviated as (b1)] include 1,3- or 1,4-phenylene diisocyanate and 2,4- or 2,6-tolylene diisocyanate. (hereinafter, tolylene diisocyanate is abbreviated as TDI), crude TDI, 4,4′- or 2,4′-diphenylmethane diisocyanate (hereinafter, diphenylmethane diisocyanate is abbreviated as MDI), crude MDI, polyarylpolyisocyanate, 4,4 '-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatobiphenyl, 3,3'-dimethyl-4,4'-diisocyanatodiphenylmethane, 1,5-naphthylene diisocyanate, 4 ,4′,4″-triphenylmethane triisocyanate and m- or p-isocyanatophenylsulfonyl isocyanate.

Examples of the aliphatic polyisocyanate (b2) having 4 to 22 carbon atoms [hereinafter abbreviated as (b2)] include ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (hereinafter abbreviated as HDI), dodecamethylene diisocyanate, 1, 6,11-undecane triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,6-diisocyanatomethylcaproate, bis(2-isocyanatoethyl) fumarate, bis(2-isocyanatoethyl) ) carbonates and 2-isocyanatoethyl-2,6-diisocyanatohexanoate.

The alicyclic polyisocyanate (b3) having 8 to 18 carbon atoms [hereinafter abbreviated as (b3)] includes, for example, isophorone diisocyanate (hereinafter abbreviated as IPDI), 4,4′-dicyclohexylmethane diisocyanate (hereinafter abbreviated as hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, bis(2-isocyanatoethyl)-4-cyclohexene-1,2-dicarboxylate and 2,5- or 2,6-norbornane diisocyanate.

Examples of the araliphatic polyisocyanate (b4) having 10 to 18 carbon atoms [hereinafter abbreviated as (b4)] include m- or p-xylylene diisocyanate and α,α,α',α'-tetramethylxylylene diisocyanate Isocyanates can be mentioned.

As the modified organic polyisocyanate (b5) of (b1) to (b4), the urethane group, carbodiimide group, allohanate group, urea group, biuret group, uretdione group, uretimine group, isocyanurate group, or oxazolidone of the above polyisocyanate Group-containing modified products [for example, modified MDI (urethane-modified MDI, carbodiimide-modified MDI, trihydrocarbyl phosphate-modified MDI, etc.), urethane-modified TDI, biuret-modified HDI, isocyanurate-modified HDI and isocyanurate-modified IPDI] can be mentioned.

Among the isocyanate components (B1) in the polyurethane resin (U1), from the viewpoint of scratch resistance, aromatic polyisocyanates (b1) having 8 to 26 carbon atoms are preferred, and aromatic polyisocyanates having 8 to 26 carbon atoms are more preferred. Diisocyanates, particularly preferred is MDI.
The isocyanate component (B1) may be used alone or in combination of two or more.

The weight of the isocyanate component (B1) in the polyurethane resin (U1) is preferably 10 to 50% by weight, based on the weight of the polyurethane resin (U1), as a constituent component, from the viewpoint of scratch resistance and tack-free property. It is preferably 20 to 40% by weight.

The glass transition point (Tg) of the polymer polyol (a2) used in the polyurethane resin (U1), the concentration of cross-linking points in the polyurethane resin (U1), and the urethane group concentration and urea group concentration in the polyurethane resin (U1) are adjusted. By doing so, the elastic recovery rate of the polyurethane resin (U1) can be kept within a predetermined range.
The Tg of the polymer polyol (a2) used in the polyurethane resin (U1) is preferably −20° C. or lower, and the concentration of cross-linking points in the polyurethane resin (U1) is preferably 0.03 to 0.25 mmol/g. ) (the total concentration of urethane groups and urea groups when urea groups are present) is preferably 1.5 to 2.5 mmol/g.
The concentration (unit: mmol/g) of cross-linking points in the polyurethane resin (U1) in the present invention is trifunctional, where F is the number of functional groups of the trifunctional or higher constituent monomer used in the polyurethane resin (U1). Values calculated by calculating (F-2)×{number of millimoles in 1 g of polyurethane resin (U2) of tri- or higher-functional constituent monomers} for each of the constituent monomers above, and summing the values. is.

The method for producing the polyurethane resin (U1) in the present invention is not particularly limited, and a urethane prepolymer is produced in advance using the active hydrogen component (A1), the isocyanate component (B1) and, if necessary, an organic solvent. Examples include a method of reacting with a chain extender, a method of charging an active hydrogen component (A1), an isocyanate component (B1) and, if necessary, an organic solvent all at once in a batch reaction tank, and heating and reacting.
The method for producing the urethane prepolymer is not particularly limited, but for example, a method in which the active hydrogen component (A1) and the isocyanate component (B1) are mixed in a kneader in the absence of a solvent and heated to react; in the presence or absence of an organic solvent, the active hydrogen component (A1) and the isocyanate component (B1) are mixed and heated to react.

In the method for producing the polyurethane resin (U1), an organic solvent can be used in any production step. The organic solvent is not particularly limited, and includes ketone solvents with 3 to 10 carbon atoms (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.), ester solvents with 2 to 10 carbon atoms (ethyl acetate, butyl acetate, γ-butyrolactone, etc.). , C4-10 ether solvents (dioxane, tetrahydrofuran, ethyl cellosolve and diethylene glycol dimethyl ether), C3-10 amide solvents (N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl -2-pyrrolidone and N-methylcaprolactam, etc.), sulfoxide solvents with 2 to 10 carbon atoms (dimethylsulfoxide, etc.), alcohol solvents with 1 to 8 carbon atoms (methanol, ethanol, isopropyl alcohol, octanol, etc.) and carbon numbers 4 to 10 hydrocarbon solvents (cyclohexane, toluene, xylene, etc.) and the like. An organic solvent may be used individually by 1 type, or may use 2 or more types together.

Among these, methyl ethyl ketone and toluene are preferred from the viewpoint of solubility.

When an organic solvent is used, the amount used is preferably such that the concentration of the polyurethane resin (U1) is 10 to 70% by weight, more preferably 15 to 50% by weight.

In addition, a catalyst may be contained, if necessary, in order to promote the reaction during the production of the polyurethane resin (U1). Specific examples of catalysts include organometallic compounds (dibutyltin dilaurate, dioctyltin dilaurate, bismuth carboxylate, bismuth alkoxide, chelate compounds of bismuth with a compound having a dicarbonyl group, etc.), inorganic metal compounds (bismuth oxide, hydroxide bismuth, bismuth halide, etc.); amines (triethylamine, triethylenediamine, 1,8-diazabicyclo[5.4.0]-7-undecene, etc.) and combinations of two or more thereof.

The surface layer contains polyurethane resin (U1) as an essential component, but if necessary, additives such as antioxidants, ultraviolet absorbers, light stabilizers, plasticizers, adsorbents, fillers, release agents and flame retardants ( D) can be contained.

Antioxidants include hindered phenol compounds [pentaerythyl-tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-t -butyl-4-hydroxyphenyl)propionate, etc.], phosphorus compounds [tris(2,4-di-t-butylphenyl)phosphite, etc.], sulfur compounds [pentaerythyl-tetrakis(3-laurylthiopropionate) , dilauryl-3,3′-thiodipropionate, etc.] and the like.

Examples of UV absorbers include benzotriazole compounds [2-(3,5-di-t-amyl-2-hydroxyphenyl)benzotriazole, 2-(5-methyl-2-hydroxyphenyl)benzotriazole, etc.]. be done.

Light stabilizers include hindered amine compounds [(bis-2,2,6,6-tetramethyl-4-piperidyl) sebacate, etc.] and the like.

Plasticizers include phthalates (dibutyl phthalate, dioctyl phthalate, dibutyl benzyl phthalate, diisodecyl phthalate, etc.); aliphatic dibasic acid esters (di-2-ethylhexyl adipate, 2-ethylhexyl sebacate, etc.); ); trimellitate esters (tri-2-ethylhexyl trimellitate and trioctyl trimellitate, etc.); fatty acid esters (butyl oleate, etc.); aliphatic phosphate esters (trimethyl phosphate, triethyl phosphate, tributyl phosphate, tri- 2-ethylhexyl phosphate and tributoxy phosphate, etc.); 2,6-dimethylphenyl)phosphate, etc.]; Halogen aliphatic phosphate [tris(chloroethyl)phosphate, tris(β-chloropropyl)phosphate, tris(dichloropropyl)phosphate and tris(tribromoneopentyl)phosphate, etc.] ; and the like.

Adsorbents include alumina, silica gel, molecular sieves, and the like.

Fillers include kaolin, talc, silica, titanium oxide, calcium carbonate, bentonite, mica, sericite, glass flakes, glass fiber, graphite, magnesium hydroxide, aluminum hydroxide, antimony trioxide, barium sulfate, and zinc borate. , alumina, magnesia, wollastonite, xonotlite, whiskers and metal powders.

As the release agent, a known release agent or the like can be used, and a fluorine compound type release agent [triperfluoroalkyl phosphate (carbon number 8-20) ester (triperfluorooctyl phosphate, triperfluorododecyl phosphate, etc.) ]; silicone compound type release agent (dimethylpolysiloxane, amino-modified dimethylpolysiloxane and carboxyl-modified dimethylpolysiloxane, etc.); fatty acid ester type release agent [mono- or polyhydric alcohol ester of fatty acid having 10 to 24 carbon atoms (butyl stearate, hydrogenated castor oil, ethylene glycol monostearate, etc.)]; fatty acid amide release agents [mono- or bisamides of fatty acids having 8 to 24 carbon atoms (oleic acid amide, palmitic acid amide, stearic acid amide and ethylenediamine metal soaps (magnesium stearate, zinc stearate, etc.); natural or synthetic waxes (paraffin wax, microcrystalline wax, polyethylene wax, polypropylene wax, etc.);

Flame retardants include halogen-containing flame retardants, phosphorus-containing flame retardants, antimony-containing flame retardants, metal hydroxide-containing flame retardants, and the like.

The elastic recovery rate of the polyurethane resin (U1) used for the surface layer measured by the method described below is 50 to 100%, more preferably 60 to 100%. If the elastic recovery rate of the polyurethane resin (U1) is less than 50%, the scratch resistance and flex resistance are poor.
With such a configuration, the polyurethane resin (U1) can be adjusted to have a predetermined elastic recovery rate, and can be imparted with scratch resistance and flex resistance.

[Base layer]
In the present invention, the base layer contains a polyurethane resin (U2) composed of an active hydrogen component (A2) and an isocyanate component (B2), and the active hydrogen component (A2) is a compound having a polyorganosiloxane group and an active hydrogen group. It is an active hydrogen component that does not contain (a1) and contains the polymer polyol (a2) as an essential component, and the elastic recovery rate of the polyurethane resin (U2) at 100% elongation is 80 to 100%.

The active hydrogen component (A2) in the polyurethane resin (U2) does not contain the compound (a1) having a polyorganosiloxane group and an active hydrogen group, and contains the polymer polyol (a2) as an essential component.
The polyurethane resin (U2) is excellent in transparency because it does not contain the compound (a1) having an active hydrogen group, and can be adjusted to a predetermined elastic recovery rate by containing the polymer polyol (a2) as an essential component. It is possible to impart scratch resistance and flex resistance.
The compound (a1) having a polyorganosiloxane group and an active hydrogen group and the polymer polyol (a2) are the compound (a1) having a polyorganosiloxane group and an active hydrogen group described in the polyurethane resin (U1), Molecular polyol (a2) is meant.

The polymer polyol (a2) preferably contains a polyether polyol (a22) from the viewpoint of adjusting the elastic recovery rate to a predetermined range and suitably imparting scratch resistance and flex resistance, and polytetramethylene glycol , poly(oxy-3-methyltetramethylene)glycol and tetrahydrofuran/3-methyltetrahydrofuran copolymerized diol, and particularly preferably polytetramethylene glycol.

Mn of the polymer polyol (a2) is preferably 500 or more, more preferably 500 to 5000, particularly preferably 800 to 4000, from the viewpoint of scratch resistance.

The weight of the polymer polyol (a2) in the polyurethane resin (U2) is preferably 60 to 90% by weight, based on the weight of the polyurethane resin (U2), as a constituent component, from the viewpoint of scratch resistance and flex resistance. More preferably 70 to 85% by weight.

The active hydrogen component (A2) may optionally contain a chain extender and a reaction terminator.
As the chain extender, the chain extender (a3) described for the polyurethane resin (U1) can be appropriately selected and used.
As the reaction terminator, the reaction terminator (a4) described for the polyurethane resin (U1) can be appropriately selected and used.

The weight of the chain extender (a3) in the polyurethane resin (U2) is preferably 0.5 to 20 weight as a constituent component based on the weight of the polyurethane resin (U2) from the viewpoint of scratch resistance and flex resistance. %, more preferably 1 to 10% by weight.

As the polyisocyanate component (B2), the polyisocyanate component (B1) described for the polyurethane resin (U1) can be appropriately selected and used.
Among them, from the viewpoint of scratch resistance, aromatic polyisocyanate (b1) having 8 to 26 carbon atoms is preferable, aromatic diisocyanate having 8 to 26 carbon atoms is more preferable, and MDI is particularly preferable.

The weight of the polyisocyanate component (B2) in the polyurethane resin (U2) is preferably 5 to 40% by weight, based on the weight of the polyurethane resin (U2), as a constituent component, from the viewpoint of scratch resistance and flex resistance. More preferably 10 to 30% by weight.

The glass transition point (Tg) of the polymer polyol (a2) used in the polyurethane resin (U2), the concentration of cross-linking points in the polyurethane resin (U2), and the urethane group concentration and urea group concentration in the polyurethane resin (U2) are adjusted. By doing so, the elastic recovery rate of the polyurethane resin (U2) can be kept within a predetermined range.
The Tg of the polymer polyol (a2) used in the polyurethane resin (U2) is preferably −20° C. or less, and the concentration of cross-linking points in the polyurethane resin (U2) is preferably 0.05 to 0.25 mmol/g. ) (the total concentration of urethane groups and urea groups when urea groups are present) is preferably 1.0 to 2.0 mmol/g.
Incidentally, the concentration (unit: mmol/g) of the cross-linking points of the polyurethane resin (U2) in the present invention is trifunctional, where F is the number of functional groups of the tri- or higher functional constituent monomer used in the polyurethane resin (U2). Values calculated by calculating (F-2)×{number of millimoles in 1 g of polyurethane resin (U2) of tri- or higher functional monomers} for each of the constituent monomers above, and summing the values. is.

The method for producing the polyurethane resin (U2) in the present invention is not particularly limited, and the same method as the method for producing the polyurethane resin (U1) may be used except that the active hydrogen component (A2) and the isocyanate component (B2) are contained. can be done.

Further, in the production of the polyurethane resin (U2), the above-mentioned catalyst used in the production method of the polyurethane resin (U1) may be contained if necessary for promoting the reaction.

The base layer contains the polyurethane resin (U2) as an essential component, and if necessary, may contain the additive (D) used in the method for producing the polyurethane resin (U1).

The polyurethane resin (U2) used in the base layer has the function of quickly recovering the deformation of the multilayer film due to external pressure in the multilayer film of the present invention, so the elastic recovery rate at 100% elongation is 80 to 80. Must be 100%. The elastic recovery rate of the polyurethane resin (U2) is preferably 85-100%, more preferably 90-100%, particularly preferably 95-100%. If the elastic recovery rate at 100% elongation is less than 80%, sufficient scratch resistance and flexibility are not imparted.

The elastic recovery rate at 100% elongation in the present invention is measured by the following method.
<Method for measuring elastic recovery rate at 100% elongation>
(1) A strip-shaped test piece of 100 mm long×5 mm wide is cut out from a sheet having a film thickness of about 2 mm, and marked lines are attached so that the distance between the marked lines becomes 50 mm.
(2) Set this test piece on the chuck of an Instron type tensile tester (Autograph manufactured by Shimadzu Corporation), and set the distance between the gauge lines to 100% at a constant speed of 500 mm / min in an atmosphere of 25 ° C. After extending until it becomes , immediately perform the operation of returning to the distance between the chucks before extension at the same speed.
(3) The stress at 50% elongation (M ₁ ) in the elongation process during this operation and the stress at 50% elongation (M ₂ ) in the return process are measured, and the elastic recovery rate is obtained from the following equation.
Elastic recovery rate (%) = _M2 /M1 x ₁₀₀

[Multilayer film]
The multilayer film of the present invention has a base layer and a surface layer formed on the base layer.
The film thickness of the surface layer is preferably 1 to 50 μm, more preferably 5 to 25 μm from the viewpoint of scratch resistance and tack suppression.
The film thickness of the base layer is preferably 100 to 1,000 μm, more preferably 300 to 600 μm, from the viewpoint of scratch resistance and bending resistance.

The multilayer film of the present invention is preferably used as a surface protection film for optical members. An adhesive layer may be provided on the base layer side as necessary to impart adhesiveness to the optical member. As the adhesive layer, a known one can be appropriately selected and used.

The method for producing the multilayer film of the present invention is not particularly limited, and it can be produced, for example, by the following method.
(1) Process for producing urethane prepolymer for polyurethane resin (U1) used for surface layer A compound (a1) having a polyorganosiloxane group and an active hydrogen group, a polymer polyol (a2), and an isocyanate component (B1) are combined in an organic solvent if necessary. A urethane prepolymer for a polyurethane resin (U1) having an isocyanate group at the terminal is produced by reacting in the reaction medium.
(2) Production process of urethane prepolymer for polyurethane resin (U2) used in base layer The polymer polyol (a2) and the isocyanate component (B2) are reacted in an organic solvent if necessary to obtain a polyurethane resin (U2) having terminal isocyanate groups. ) to manufacture urethane prepolymers.
(3) Step of Forming Surface Layer A urethane prepolymer for polyurethane resin (U1) or an organic solvent solution thereof is mixed with, if necessary, a polymer polyol (a2) and/or a chain extender (a3), and the mold is released. It is coated on the film so as to have a predetermined film thickness. In addition, when an organic solvent is used, the organic solvent is dried.
(4) Base Layer Forming Step A urethane prepolymer for polyurethane resin (U2) or an organic solvent solution thereof is mixed with a chain extender (a3) to obtain a predetermined film thickness on the surface layer obtained in (3). A base layer is formed by coating and heat curing. Incidentally, when an organic solvent is used, it is dried at the same time as it is cured.
Through the above steps (1) to (4), a multilayer film having a surface layer and a base layer on the release film is formed.

The temperature of the urethane prepolymerization reaction in the above steps (1) and (2) is not particularly limited, but is preferably 50 to 140°C, more preferably 70 to 100°C, and the reaction time is not particularly limited. is preferably 1 to 10 hours, more preferably 2 to 8 hours.

Although the drying temperature in the step (3) is not particularly limited, it is preferably 30 to 80° C., more preferably 40 to 60° C. The drying time is not particularly limited, but is preferably 10 seconds to 5 minutes, more preferably 10 seconds to 5 minutes. is 20-60 seconds.
The curing temperature in the step (4) is not particularly limited, but is preferably 60 to 150° C., more preferably 80 to 120° C. The curing time is not particularly limited, but is preferably 1 to 8 hours, more preferably 2 to 6 hours. Incidentally, the drying of the organic solvent in the step (4), which is performed as necessary, is performed together with the curing.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples. In addition, a part represents a weight part below.

<Production Example 1> [Production of urethane prepolymer for polyurethane resin (U1-1) used for surface layer]
Compound (a1) having polyorganosiloxane groups and active hydrogen in the types and amounts (parts by weight) shown in Table 1, polymer polyol (a2), and aromatic polyisocyanate (b1) are placed in a container equipped with a stirring device and a temperature control device. , modified organic polyisocyanate (b5) and an organic solvent were charged and allowed to react at 80° C. for 3 hours to obtain a urethane prepolymer for polyurethane resin (U1-1). The NCO content of the resulting urethane prepolymer was 1.46%.

<Production Examples 2-6 and Comparative Production Examples 1-2> [Urethane prepolymers for polyurethane resins (U1-2) to (U1-5) and Manufacturing]
Urethane resins for polyurethane resins (U1-2) to (U1-6) used for the surface layer were prepared in the same manner as in Production Example 1 except that the raw materials used and the amounts used (parts by weight) were changed to those shown in Table 1. A polymer and urethane prepolymers for polyurethane resins (U1'-1) to (U1'-2) for comparison were obtained.

[Measurement of elastic recovery rate of polyurethane resin (U1-1) used for surface layer]
The urethane prepolymer for (U1-1) obtained in Production Example 1 and the chain extender (a3) were blended according to the formulation shown in Table 1 in a polypropylene beaker. The obtained blended solution was poured into an 11×17.5 cm polypropylene tray so that the thickness after drying was 200 μm, and dried overnight at room temperature. After drying, it was cured at 120° C. for 2 hours to obtain a sheet of polyurethane resin (U1-1) used for the surface layer.
Using this sheet, the elastic recovery rate was measured based on the above-described method for measuring the elastic recovery rate at 100% elongation. Table 1 shows the results.

[Measurement of elastic recovery rate of polyurethane resins (U1-2) to (U1-6) used for the surface layer and polyurethane resins (U1′-1) to (U1′-2) for comparison]
Polyurethane resin (U1-2 ) to (U1-6) and polyurethane resin sheets (U1′-1) to (U1′-2) for comparison were obtained.
Using this sheet, the elastic recovery rate was measured based on the above-described method for measuring the elastic recovery rate at 100% elongation. Table 1 shows the results.

The contents of various raw materials described in Table 1 are as follows.
<Material of urethane prepolymer for polyurethane resin>
[Compound (a1) having a polyorganosiloxane group and an active hydrogen group]
・X-22-161A: Shin-Etsu Chemical Co., Ltd. amino group-modified silicone oil [Mn = 1600, R ¹ to R ⁶ = methyl group in general formula (1), n = 22]
・KF-6003: Hydroxy-modified silicone oil manufactured by Shin-Etsu Chemical Co., Ltd. [Mn = 5100, R ¹ to R ⁶ = methyl group in general formula (1), n = 68]
[Polymer polyol (a2)]
・Kuraray Polyol C1090: Polycarbonate polyol manufactured by Kuraray Co., Ltd. (Mn: 1000)
[Aromatic polyisocyanate (b1)]
・ 4,4'-MDI: "Millionate MT" manufactured by Tosoh Corporation
[Modified product of organic polyisocyanate (b5)]
・Coronate 2793: Allophanate group-containing polyisocyanate manufactured by Tosoh Corporation (average number of functional groups = 5.1)
[Organic solvent]
・Toluene <Material for chain extension reaction of urethane prepolymer>
[Chain extender (a3)]
・1,4-Butanediol・Trimethylolpropane [organic solvent]
· Methyl ethyl ketone In addition, in the column of "Materials for chain elongation reaction of urethane prepolymer" in Table 1, the materials used for chain elongation of each prepolymer used in the examples described later and the amounts thereof are described.

<Production Example 7> [Production of urethane prepolymer for polyurethane resin (U2-1) used for base layer]
Polymer polyol (a2) and aromatic polyisocyanate (b1) of the types and amounts (parts by weight) shown in Table 2 are placed in a container equipped with a stirring device and a temperature control device, and reacted at 80° C. for 3 hours to obtain a polyurethane resin ( A urethane prepolymer for U2-1) was obtained. The NCO content of the resulting urethane prepolymer was 3.36%.

[Production of urethane prepolymers for polyurethane resins (U2-2) to (U2-8) and (U2'-1) to (U2'-2) used for base layer]
Polyurethane resins (U2-2) to (U2-8) used for the surface layer were prepared in the same manner as in Production Example 7, except that the urethane prepolymer used and the amount (parts by weight) thereof used were changed to those shown in Table 2. ) and urethane prepolymers for comparative polyurethane resins (U2′-1) to (U2′-2) were obtained.

The contents of various raw materials represented by symbols or trade names in Table 2 are as follows.
<Material of urethane prepolymer for polyurethane resin>
[Polymer polyol (a2)]
・ PTMG-1000: Polytetramethylene glycol (Mn = 1000) manufactured by Mitsubishi Chemical Corporation
・ PTMG-2000: Polytetramethylene glycol (Mn = 2000) manufactured by Mitsubishi Chemical Corporation
・ PTMG-3000: Polytetramethylene glycol (Mn = 3000) manufactured by Mitsubishi Chemical Corporation
・ PLAXEL 220: polycaprolactone diol (Mn = 2000) manufactured by Daicel Corporation
[Polyol with Mn less than 500]
・ Sannics PP-400: Sanyo Chemical Industries, Ltd. polypropylene glycol (Mn = 400)
[Aromatic polyisocyanate (b1)]
・ 4,4'-MDI: "Millionate MT" manufactured by Tosoh Corporation
<Material for chain elongation reaction of urethane prepolymer>
[Chain extender (a3)]
・1,4-Butanediol ・Trimethylolpropane In addition, in the column of "Materials for chain extension reaction of urethane prepolymer" in Table 2, when chain extension of each prepolymer used in the test examples and examples described later The material used and the amount used were described.

[Measurement of elastic recovery rate of polyurethane resin (U2-1) used for base layer]
The urethane prepolymer for the polyurethane resin (U2) obtained in Production Example 7 and the chain extender (a3), which had been temperature-controlled in advance at 80°C, were blended in a polypropylene beaker according to the formulation shown in Table 2, After stirring and mixing with an agitator for 1 minute, defoaming was performed for 2 minutes under reduced pressure. The resulting mixture was cast into a SUS mold with a gap of 2 mm and cured at 120° C. for 2 hours to obtain a sheet of polyurethane resin (U2-1) used for the base layer.
Table 2 shows the cross-linking point concentration and urethane group concentration of the polyurethane resin (U2-1).
Using this sheet, the elastic recovery rate was measured based on the above-described method for measuring the elastic recovery rate at 100% elongation. Table 2 shows the results.

[Measurement of elastic recovery rate of polyurethane resins (U2-2) to (U2-8) used for base layer and polyurethane resins (U2'-1) to (U2'-2) for comparison]
Polyurethane resin (U2-2 ) to (U2-8) and polyurethane resin sheets (U2′-1) to (U2′-2) for comparison were obtained.
Table 2 shows the cross-linking point concentrations and urethane group concentrations of the polyurethane resins (U2-2) to (U2-8) and the comparative polyurethane resins (U2'-1) to (U2'-2).
Using these sheets, the elastic recovery rate was measured based on the above-described method for measuring the elastic recovery rate at 100% elongation. Table 2 shows the results.

[Measurement of Elastic Recovery Rate of Comparative Polyurethane Resin (U2′-3) Used for Base Layer]
In a container equipped with a stirrer and a temperature controller charged with 350 parts of toluene, 150 parts of polyether-based thermoplastic urethane elastomer "Elastollan 1180A" (manufactured by BASF Japan Ltd.) are charged under stirring, and the temperature is raised to 80 ° C. to dissolve. The obtained blended solution was poured into an 11×17.5 cm polypropylene tray so that the thickness after drying was 400 μm, and dried overnight at room temperature. Further, it was dried in a vacuum dryer at 100° C. for 2 hours to obtain a sheet of polyurethane resin (U2′-3) for comparison to be used for the base layer.
Using this sheet, the elastic recovery rate was measured based on the above-described method for measuring the elastic recovery rate at 100% elongation. Table 2 shows the results.

<Example 1> [Production of multilayer film]
496.1 parts of the urethane prepolymer for the surface layer polyurethane resin (U1-1) obtained in Production Example 1 (the total amount of the urethane prepolymer materials listed in Table 1) and the corresponding urethane listed in Table 1 A mixture of 7.6 parts of 1,4-butanediol and 496.3 parts of methyl ethyl ketone as a material for the chain extension reaction of the prepolymer was coated on the release film so that the film thickness after drying was 10 μm, It was dried for 30 seconds in a circulating air dryer at 50° C. to volatilize the solvent to prepare a surface layer polyurethane resin.
The urethane prepolymer for the polyurethane resin (U2-1) obtained in Production Example 7 and the chain extender (a3) were blended according to the formulation shown in Table 2, and the film thickness on the polyurethane resin for the surface layer was 400 μm. After curing at 120° C. for 2 hours, the release film was peeled off to obtain a multi-layer film having a surface layer of polyurethane resin (U1-1) and a base layer of polyurethane resin (U2-1).

<Examples 2 to 19 and Comparative Examples 1 to 4>
Multilayer films of Examples 2 to 19 and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1, except that the combination of the polyurethane resin for the surface layer and the polyurethane resin for the base layer was changed to the combination shown in Table 3. .

<Comparative Example 5>
A urethane prepolymer for the surface layer polyurethane resin (U1-1) obtained in the same manner as in Example 1 was added to a polyurethane resin (U2'-3) having a thickness of 400 μm obtained in the same manner as in Comparative Test Example 5. on the sheet of Comparative Example 5 so that the film thickness after drying is 10 μm, dried in a circulating air dryer at 50 ° C. for 30 seconds, and further cured at 120 ° C. for 2 hours to obtain a multilayer film of Comparative Example 5. Obtained.

Table 3 shows the results of evaluating the scratch resistance of the obtained multilayer film by the following evaluation method.

[Scratch resistance evaluation method]
Steel wool (No. 0000) manufactured by Nippon Steel Wool Co., Ltd. was attached to a steel wool fixing jig of "Tribogear TYPE: 40" manufactured by Shinto Scientific Co., Ltd., and a load of 100 g per 1 cm ² was applied. When the surface layer side of the multilayer film obtained in 1. was rubbed repeatedly over a length of 5 cm, the number of reciprocations at which scratches occurred was observed and evaluated based on the following criteria. The results are shown in Table 3.
<Evaluation Criteria>
⊚: No scratch occurs after 500 reciprocations or more.
◯: Scratches occurred after 300 reciprocations or more and less than 500 reciprocations.
x: Scratches occurred in less than 300 reciprocations.

[Evaluation method for bending resistance]
A sample having a size of 50 mm in the width direction (folded portion direction)×100 mm in the flow direction (bending direction) is prepared for the multilayer films obtained in Examples and Comparative Examples. Using a no-load U-shaped stretching tester (manufactured by Yuasa System Co., Ltd., DLDMLH-FS), a bending radius of 3 mm was set, and bending was performed 50,000 times at a speed of 1 time/second. At that time, the sample was fixed at 10 mm on both ends on the long side, and the bent portion was 50 mm×80 mm. After the bending process was completed, the samples were placed on a flat surface with the inside of the bend facing down and visually inspected.
<Evaluation Criteria>
⊚: No deformation of the sample, or even if the sample is deformed, the maximum floating height is less than 3 mm when placed horizontally.
◯: The sample was deformed, and when placed horizontally, the maximum floating height was 3 mm or more and less than 5 mm.
x: The sample has creases or has a maximum floating height of 5 mm or more when placed horizontally.

Since the polyurethane resin of the present invention is excellent in abrasion resistance and also excellent in flex resistance, it is suitable for surface protective films for optical members, particularly for touch-type devices.

Claims (6)

A multilayer film having a base layer and a surface layer formed on the base layer,
The surface layer contains a polyurethane resin (U1) composed of an active hydrogen component (A1) containing a compound (a1) having a polyorganosiloxane group and an active hydrogen group as essential components and an isocyanate component (B1), and the polyurethane The elastic recovery rate of the resin (U1) at 100% elongation is 50 to 100%,
The base layer contains a polyurethane resin (U2) consisting of an active hydrogen component (A2) and an isocyanate component (B2), and the active hydrogen component (A2) is a compound having the polyorganosiloxane group and an active hydrogen group ( It is an active hydrogen component that does not contain a1) and contains a polymer polyol (a2) as an essential component, and the elastic recovery rate of the polyurethane resin (U2) at 100% elongation is 80 to 100% ,
The film thickness of the surface layer is 1 to 50 μm, and the film thickness of the base layer is 100 to 1,000 μm.
multilayer film. 2. The multi-layer film according to claim 1, wherein said polyorganosiloxane group is a polyorganosiloxane group represented by general formula (1).

[In the formula, R ¹ to R ⁶ each independently represent a hydrocarbon group having 1 to 6 carbon atoms, and n is an integer of 1 to 100. ] 3. The weight of the compound (a1) having a polyorganosiloxane group and an active hydrogen group is 0.5 to 5% by weight based on the weight of the polyurethane resin (U1) as a constituent component according to claim 1 or 2. multi-layer film. The multilayer film according to any one of claims 1 to 3, wherein the polymer polyol (a2) is a polymer polyol containing polytetramethylene glycol. The concentration of the cross-linking points of the polyurethane resin (U2) is 0.05 to 0.25 mmol/g, and the urethane group concentration of the polyurethane resin (U2) (when urea groups are present, the sum of the urethane groups and the urea groups is concentration) is 1.0 to 2.0 mmol/g, the multilayer film according to any one of claims 1 to 4. The multilayer film according to any one of claims 1 to 5 , which is used as a surface protection film for optical members.