laminate

Abstract

This invention addresses the problem of providing a laminate which has good indentation recovery characteristics and bending resistance. As a means for solving this problem, provided is a laminate having: a resin layer; a hard coat layer having a thickness of more than 10 μm on the resin layer; and, if necessary, a backing layer below the resin layer. The absolute value of the difference between the indentation elastic modulus of the surface of the hard coat layer of the laminate and the indentation elastic modulus of the surface of only the resin layer, which are respectively measured by a nanoindentation method, is 1.0 GPa or less.

Description

Laminate

[0001] The present invention relates to a laminate useful as a material applied to the surface of various display elements such as flexible displays, etc. In particular, the present invention relates to a laminate having good indentation recovery properties and flex resistance.

[0002] Many electronic devices, such as televisions, mobile phones, game consoles, and other electrical devices, as well as communication devices, office equipment, entertainment devices, medical devices, and lifestyle devices, are provided with touch panel displays using liquid crystal display elements or OLED display elements that can be operated with a human finger. These touch panel displays use a hard coat film, which is a transparent plastic film substrate and has a scratch-resistant hard coat layer on the outermost surface of the display to prevent scratches on the display surface caused by fingernails or the like when the display is operated with a human finger.

[0003] For example, Patent Document 1 proposes an invention relating to a hard coat film in which the surface hardness is increased to prevent scratches by incorporating a compound having a silsesquioxane structure into the hard coat layer.

[0004] Meanwhile, apart from hard-coated films with a hard-coat layer that achieves scratch resistance by increasing the surface hardness to prevent scratches, self-repairing materials have been reported that achieve scratch resistance by repairing scratches on the surface through deformation within the elastic recovery range of the surface layer material.

[0005] However, while hard-coated films with a hard-coat layer are resistant to scratches even when rubbed with a high-hardness material, repeated rubbing with a soft cloth can cause fine scratches on the surface, causing the surface to become cloudy. On the other hand, self-repairing materials with a repairable surface layer are hardly scratched when rubbed repeatedly with a soft cloth, but may not recover and scratches may remain when rubbed with a high-hardness material or when rubbed under a high load.

[0006] To solve this problem, Patent Document 2 proposes an invention relating to a laminate film in which the elastic modulus of a surface layer, consisting of one or more layers provided on a supporting substrate, is designed to increase toward the supporting substrate, thereby improving the scratch resistance and indentation resistance of the surface layer. However, no studies have been conducted so far on a laminate having a hard coat layer that has good indentation recovery properties and flex resistance.

[0007] International Publication No. 2020 / 110966 Japanese Patent Application Laid-Open No. 2016-028888

[0008] An object of the present invention is to provide a laminate having good indentation recovery properties and flex resistance.

[0009] As a result of extensive research into achieving the above-mentioned object, the present inventors have found that a laminate comprising a resin layer, a hard coat layer having a thickness of more than 10 μm on the resin layer, and optionally a backing layer below the resin layer, wherein the absolute value of the difference between the indentation modulus of the hard coat layer surface of the laminate and the indentation modulus of the surface of the resin layer alone, measured by nanoindentation, is 1.0 GPa or less, has good recovery properties and flex resistance, and have completed the present invention.

[0010] A first aspect of the present invention is a laminate comprising a resin layer, a hard coat layer having a thickness of more than 10 μm on the resin layer, and optionally a backing layer below the resin layer, wherein the absolute value of the difference between the indentation elastic modulus of the surface of the hard coat layer of the laminate and the indentation elastic modulus of the surface of the resin layer alone, both measured by nanoindentation, is 1.0 GPa or less.

[0011] The resin layer is, for example, a polyimide layer.

[0012] The absolute value of the difference between the indentation elastic modulus of the surface of the hard coat layer of the laminate and the indentation elastic modulus of the surface of only the resin layer is, for example, 0.6 GPa or less.

[0013] The hard coat layer is, for example, a cured product of a curable composition containing a polyfunctional (meth)acrylate having no urethane bond, a surface modifier, and a polymerization initiator.

[0014] The curable composition further contains, for example, a polyfunctional urethane (meth)acrylate.

[0015] A second aspect of the present invention is a flexible substrate having a supporting substrate, an adhesive layer provided on the supporting substrate, and the laminate provided so that the resin layer or the backing layer is in contact with the adhesive layer.

[0016] According to the present invention, a laminate having good recovery properties and flex resistance can be provided. Furthermore, according to the present invention, a flexible substrate having the laminate can be provided, and a flexible substrate having good recovery properties and flex resistance can be provided.

[0017] <Laminate> The laminate of the present invention is a laminate having a resin layer, a hard coat layer having a thickness of more than 10 μm on the resin layer, and optionally a backing layer below the resin layer, wherein the absolute value of the difference between the indentation modulus of the hard coat layer surface of the laminate and the indentation modulus of the resin layer alone, measured by nanoindentation, is 1.0 GPa or less. When the absolute value of the difference between the indentation modulus of the hard coat layer surface of the laminate and the indentation modulus of the resin layer alone is within the above range, the laminate has good recovery properties and flex resistance. The absolute value of the difference between the indentation modulus of the hard coat layer surface of the laminate and the indentation modulus of the resin layer alone is preferably 0.6 GPa or less.

[0018] Examples of indenters used in nanoindentation include a triangular pyramidal indenter (Berkovich type), a square pyramidal indenter (Vickers type), a conical indenter, a spherical indenter, etc. Among these indenters, the triangular pyramidal indenter (Berkovich type) is preferred because it allows for more accurate control in a shallow indentation depth range.

[0019] The absolute value of the difference between the indentation elastic modulus of the hard coat layer surface of the laminate and the indentation elastic modulus of the resin layer alone is determined, for example, by the following method. That is, a triangular pyramidal indenter (Berkovich type) is placed in contact with the surface of the hard coat layer or the surface of the resin layer alone of the laminate, and the triangular pyramidal indenter (Berkovich type) is pressed at 23°C using a nanoindenter (iNano nanoindenter manufactured by Toyo Corporation) with a load holding time of 1 second until a maximum indentation load of 50 mN or a maximum indentation depth of 1500 nm is reached. A load-unloading curve (force curve) is measured, and the indentation elastic modulus of the hard coat layer surface of the laminate and the indentation elastic modulus of the resin layer alone are determined based on ISO 14577. The absolute value of the difference between the obtained values ​​of the indentation elastic modulus of the hard coat layer surface of the laminate and the indentation elastic modulus of the resin layer alone is then calculated.

[0020] [Resin Layer] The resin layer may be, for example, a film or sheet made of various transparent resins that can be used for optical applications. Preferred resin layers include those made of polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), polyurethane, thermoplastic polyurethane (TPU), polycarbonate, polymethacrylate, polystyrene, polyolefin, polyamide, polyimide, triacetyl cellulose (TAC), and the like. Among these, polyimide layers are preferred.

[0021] The resin layer may be formed by laminating a plurality of layers. For example, a layer different from the resin layer, such as a primer layer, an ultraviolet absorbing layer, an infrared absorbing layer, a near-infrared absorbing layer, an electromagnetic wave absorbing layer, a color correction layer, a refractive index adjusting layer, a weather-resistant layer, an anti-reflection layer, an antistatic layer, a discoloration prevention layer, a gas barrier layer, a water vapor barrier layer, a light scattering layer, or an electrode layer, may be laminated on the surface of the resin layer as an underlayer of the hard coat layer, or a plurality of underlayers of the hard coat layer may be laminated. The layer laminated on the surface of the resin layer is not particularly limited as long as it does not impair the effects of the present invention.

[0022] The thickness of the resin layer in the present invention is not particularly limited as long as it does not impair the effects of the present invention, but specifically, it can be, for example, about 10 μm or more and 100 μm or less.

[0023] [Hard Coating Layer] The hard coat layer provided in the laminate of the present invention is a cured product of a curable composition containing a polyfunctional (meth)acrylate having no urethane bond, a surface modifier, and a polymerization initiator. The hard coat layer has a thickness of more than 10 μm, for example, 15 μm or more. When the thickness of the hard coat layer satisfies the above range, there is an advantage in that a laminate can be produced that has excellent hardness while maintaining flexibility, making it advantageous for application to flexible substrates. The thickness of the hard coat layer may refer to either the thickness before or after curing. The upper limit of the thickness of the hard coat layer is not limited as long as the effects of the present invention are achieved. However, for example, from an economical standpoint, it may be approximately 50 μm or less.

[0024] [Polyfunctional (meth)acrylate without urethane bond] The polyfunctional (meth)acrylate without urethane bond that can be used as a curable composition for forming the hard coat layer of the laminate of the present invention is a monomer compound or oligomer compound having two or more (meth)acryloyloxy groups in one molecule of the polyfunctional (meth)acrylate. The polyfunctional (meth)acrylate undergoes a polymerization reaction and hardens when irradiated with active energy rays such as ultraviolet light. In the present invention, the (meth)acrylate compound includes both an acrylate compound and a methacrylate compound, and for example, (meth)acrylic acid includes acrylic acid and methacrylic acid.

[0025]

[0023] Preferred examples of the polyfunctional (meth)acrylate having no urethane bond in the curable composition for forming the hard coat layer of the laminate of the present invention include a monomer selected from the group consisting of polyfunctional (meth)acrylate compounds having no urethane bond described below, and a monomer selected from the group consisting of lactone-modified polyfunctional (meth)acrylate compounds described below. In the present invention, one type selected from the group consisting of the polyfunctional (meth)acrylate compounds described above can be used alone, or two or more types can be used in combination, as the polyfunctional (meth)acrylate having no urethane bond.

[0026] The polyfunctional (meth)acrylate not having a urethane bond may be an oxyalkylene-modified polyfunctional (meth)acrylate, and examples of the oxyalkylene-modified polyfunctional (meth)acrylate include oxymethylene-modified, oxyethylene-modified (also referred to as EO-modified), and oxypropylene-modified. The oxyalkylene-modified polyfunctional (meth)acrylate may be an oxyalkylene-modified polyfunctional (meth)acrylate compound. The oxyalkylene-modified polyfunctional (meth)acrylate may be used alone or in combination of two or more.

[0027] In addition, preferred examples of the polyfunctional (meth)acrylate having no urethane bond in the present invention include a polyfunctional (meth)acrylate having at least three (meth)acryloyl groups in one molecule, for example, at least four (meth)acryloyl groups in one molecule. In the present invention, examples of the polyfunctional (meth)acrylate having no urethane bond in the present invention include a monomer selected from the group consisting of oxyalkylene-modified polyfunctional (meth)acrylate compounds having at least three (meth)acryloyl groups in one molecule.

[0028] Examples of polyfunctional (meth)acrylate compounds not having a urethane bond include trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, glycerin tri(meth)acrylate, 1,3-propanediol di(meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate. , 2-methyl-1,8-octanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, bis(2-hydroxyethyl)isocyanurate di(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, tricyclo[5.2.1.0 ２，６] decanedimethanol di(meth)acrylate, dioxane glycol di(meth)acrylate, 2-hydroxy-1-acryloyloxy-3-methacryloyloxypropane, 2-hydroxy-1,3-di(meth)acryloyloxypropane, 9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene, bis[4-(meth)acryloylthiophenyl]sulfide, bis[2-(meth)acryloylthioethyl]sulfide, 1,3-adamantanediol di(meth)acrylate, 1,3-adamantanedimethanol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate can be mentioned. Among these, preferred polyfunctional (meth)acrylate compounds not having a urethane bond include pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0029] Examples of the oxyalkylene-modified polyfunctional (meth)acrylate compound include (meth)acrylate compounds of polyols modified with oxyalkylene. Examples of the polyols include glycerin, diglycerin, triglycerin, tetraglycerin, pentaglycerin, hexaglycerin, decaglycerin, polyglycerin, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, and bisphenol A. Examples of the oxyalkylene-modified polyol (meth)acrylate compound include EO-modified trimethylolpropane tri(meth)acrylate, EO-modified pentaerythritol tetra(meth)acrylate, EO-modified dipentaerythritol hexa(meth)acrylate, EO-modified glycerin tri(meth)acrylate, EO-modified diglycerin (meth)acrylate, and EO-modified bisphenol A di(meth)acrylate.

[0030] The polyfunctional (meth)acrylate having no urethane bond may be a lactone-modified polyfunctional (meth)acrylate compound, and the modifying lactone is preferably ε-caprolactone. Examples of the lactone-modified polyfunctional (meth)acrylate compound include ε-caprolactone-modified pentaerythritol tri(meth)acrylate, ε-caprolactone-modified pentaerythritol tetra(meth)acrylate, ε-caprolactone-modified dipentaerythritol penta(meth)acrylate, and ε-caprolactone-modified dipentaerythritol hexa(meth)acrylate.

[0031] Among the polyfunctional (meth)acrylates not having a urethane bond, particularly preferred polyfunctional (meth)acrylates not having a urethane bond include pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, EO-modified pentaerythritol tetra(meth)acrylate, EO-modified dipentaerythritol hexa(meth)acrylate, and EO-modified diglycerin (meth)acrylate. By using these particularly preferred polyfunctional (meth)acrylate compounds, more satisfactory recovery properties and flex resistance can be simultaneously exhibited.

[0032] [Surface Modifier] The surface modifier usable in the curable composition for forming the hard coat layer of the laminate of the present invention is preferably a perfluoropolyether having an active energy ray-polymerizable group at the end of a molecular chain containing a poly(oxyperfluoroalkylene) group, and this perfluoropolyether will hereinafter also be referred to simply as "perfluoropolyether". The ends of the molecular chain containing the poly(oxyperfluoroalkylene) group having an active energy ray-polymerizable group may be all or some of the ends of the molecular chain. When the molecular chain is linear, all or some of the ends of the molecular chain are both ends and one end of the linear molecular chain, respectively. The perfluoropolyether preferably has an active energy ray-polymerizable group at the end of the molecular chain containing the poly(oxyperfluoroalkylene) group via a urethane bond. As such a perfluoropolyether, a perfluoropolyether having at least two (meth)acryloyloxy groups at the end of a molecular chain containing a poly(oxyperfluoroalkylene) group represented by the following formula [1] via a urethane bond is preferred. (In the formula [1], PFPE is a repeating unit -(CF ２ CF ２ O)- and repeating units -(CF ２ and represents a poly(oxyperfluoroalkylene) group having at least one of the repeating units of —O)—, and these repeating units are bonded together by block bonds, random bonds, or block bonds and random bonds, and * represents the bond between the —O— group and the urethane bond.

[0033] From the viewpoint of obtaining a hard coat layer having good abrasion resistance and scratch resistance, the poly(oxyperfluoroalkylene) group is -[CF ２ O]-(oxyperfluoromethylene group) and -[CF ２ CF ２ In this case, the bond between these oxyperfluoroalkylene groups may be either a block bond or a random bond.

[0034] The perfluoropolyether more preferably contains a perfluoropolyether having a group represented by the following formula [A1] or [A2] bonded via the urethane bond to each end of a molecular chain containing a poly(oxyperfluoroalkylene) group represented by the formula [1]: (In the formula [A1] and formula [A2], R １ and R ２ each independently represents a hydrogen atom or a methyl group, and the black dot represents a bond to the —NH— group of the urethane bond.)

[0035] From the viewpoint of obtaining a hard coat layer with good abrasion resistance and scratch resistance, perfluoropolyether is more preferably one having active energy ray polymerizable groups at both ends of molecular chain containing poly(oxyperfluoroalkylene) group, and more preferably one having a large number of active energy ray polymerizable groups in one molecule.The number of said polymerizable groups is preferably 2 or more, more preferably 3 or more, at each end of molecular chain containing poly(oxyperfluoroalkylene) group.

[0036] The content of the surface modifier usable in the curable composition for forming the hard coat layer of the laminate of the present invention is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, and even more preferably 0.1 to 3 parts by mass, relative to 100 parts by mass of the polyfunctional (meth)acrylate not having a urethane bond. When the content of the surface modifier is 0.05 parts by mass or more, sufficient abrasion resistance and scratch resistance can be imparted to the hard coat layer, and when the content of the surface modifier is 10 parts by mass or less, the surface modifier is sufficiently compatible with the polyfunctional (meth)acrylate not having a urethane bond, and a hard coat layer with little cloudiness can be obtained.

[0037] The surface modifier may be used alone or in combination of two or more. When two or more types are combined, a perfluoropolyether having an active energy ray polymerizable group via a urethane bond at one end (one end) of a molecular chain containing a poly(oxyperfluoroalkylene) group and a hydroxy group at the other end (the other end) of the molecular chain may be included.

[0038] [Polymerization initiator] A preferred polymerization initiator in the curable composition for forming the hard coat layer of the laminate of the present invention is a polymerization initiator that generates radicals by irradiation with active energy rays such as electron beams, ultraviolet rays, and X-rays, particularly ultraviolet rays.

[0039] Examples of the polymerization initiator include benzoins, alkylphenones, thioxanthones, azo compounds, azides, diazo compounds, o-quinonediazides, acylphosphine oxides, oxime esters, organic peroxides, benzophenones, biscoumarins, bisimidazoles, titanocene compounds, thiols, halogenated hydrocarbons, trichloromethyltriazines, and onium salts such as iodonium salts and sulfonium salts. These may be used alone or in combination of two or more. In the present invention, from the viewpoints of transparency, surface curability, internal curability, and thin-film curability, it is preferable to use alkylphenones or acylphosphine oxides as the polymerization initiator, either alone or in combination of two or more. The use of alkylphenones or acylphosphine oxides makes it possible to obtain a hard coat layer with improved abrasion resistance.

[0040] Examples of the alkylphenones include α-hydroxyalkylphenones such as 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-hydroxy-1-(4-(2-hydroxyethoxy)phenyl)-2-methylpropan-1-one, and 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropan-1-one; α-aminoalkylphenones such as 2-methyl-1-(4-(methylthio)phenyl)-2-morpholinopropan-1-one and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one; 2,2-dimethoxy-1,2-diphenylethan-1-one; and methyl phenylglyoxylate.

[0041] Examples of the acylphosphine oxides include diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and the like.

[0042] The content of the polymerization initiator in the curable composition for forming the hard coat layer of the laminate of the present invention is preferably 1 to 20 parts by mass, more preferably 2 to 10 parts by mass, relative to 100 parts by mass of the polyfunctional (meth)acrylate not having a urethane bond. By having the content of the polymerization initiator be 1 to 20 parts by mass, the hard coat layer can be imparted with sufficient indentation recovery properties and flex resistance.

[0043] [Multifunctional Urethane (Meth)acrylate] The curable composition for forming the hard coat layer of the laminate of the present invention may further contain a multifunctional urethane (meth)acrylate in addition to the multifunctional (meth)acrylate not having a urethane bond, the surface modifier, and the polymerization initiator. The multifunctional urethane (meth)acrylate is a compound having a plurality of acryloyl groups or methacryloyl groups in one molecule and having one or more urethane bonds [—NHC(═O)O—], and may further contain a urea bond [—NHC(═O)NH—]. Examples of the multifunctional urethane (meth)acrylate include a compound obtained by reacting a multifunctional isocyanate with a (meth)acrylate having a hydroxy group, and a compound obtained by reacting a multifunctional isocyanate with a (meth)acrylate having a hydroxy group, and a polyol. However, the multifunctional urethane (meth)acrylate usable in the present invention is not limited to these examples.

[0044] Examples of the polyfunctional isocyanate include tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and hexamethylene diisocyanate. Examples of the (meth)acrylate having a hydroxy group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, and tripentaerythritol hepta(meth)acrylate. Examples of the polyol include diols such as ethylene glycol, propylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, and dipropylene glycol; polyester polyols that are reaction products of these diols with aliphatic dicarboxylic acids or dicarboxylic acid anhydrides such as succinic acid, maleic acid, and adipic acid; polyether polyols; and polycarbonate diols.

[0045] When the curable composition for forming the hard coat layer of the laminate of the present invention contains a polyfunctional urethane (meth)acrylate, the content of the polyfunctional urethane (meth)acrylate is preferably 0.001 parts by mass or more and less than 50 parts by mass per 100 parts by mass of the total of the polyfunctional (meth)acrylate not having a urethane bond and the polyfunctional urethane (meth)acrylate. When the content of the polyfunctional urethane (meth)acrylate is in this range, the hard coat layer can be imparted with sufficient indentation recovery properties and flex resistance.

[0046] [Solvent] The curable composition for forming the hard coat layer of the laminate of the present invention may further contain a solvent. The solvent may be appropriately selected in consideration of dissolving or uniformly dispersing the polyfunctional (meth)acrylate having no urethane bond, the surface modifier, and the polymerization initiator, as well as workability during coating for forming the hard coat layer and drying properties before and after curing. For example, aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, tetralin, etc.; aliphatic or alicyclic hydrocarbons such as n-hexane, n-heptane, mineral spirits, cyclohexane, etc.; halides such as methyl chloride, methyl bromide, methyl iodide, dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, perchloroethylene, o-dichlorobenzene, etc.; esters or ester ethers such as ethyl acetate, propyl acetate, butyl acetate, methoxybutyl acetate, methyl cellosolve acetate, ethyl cellosolve acetate, propylene glycol monomethyl ether acetate (PGMEA), etc.; diethyl ether, tetrahydrofuran (THF), 1,4-dioxane, methyl cellosolve, ethyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether, etc. ethers such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), di-n-butyl ketone, cyclopentanone, cyclohexanone, etc.; alcohols such as methanol, ethanol, n-propanol, isopropyl alcohol, n-butanol, isobutyl alcohol, tert-butyl alcohol, 2-ethylhexyl alcohol, benzyl alcohol, ethylene glycol, etc.; amides such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), etc.; sulfoxides such as dimethyl sulfoxide (DMSO), etc., and mixtures of two or more of these solvents.

[0047] The amount of solvent used in the curable composition for forming the hard coat layer of the laminate of the present invention is not particularly limited, but for example, the solvent is used at a concentration such that the solid content concentration in the curable composition for forming the hard coat layer of the present invention is 1% by mass to 70% by mass, preferably 5% by mass to 50% by mass. Here, the solid content concentration (also referred to as non-volatile content concentration) represents the content of solids (all components excluding solvent components) relative to the total mass (total mass) of the polyfunctional (meth)acrylate not having a urethane bond, the surface modifier, and the polymerization initiator (and, if desired, the polyfunctional urethane (meth)acrylate and other additives) in the curable composition for forming the hard coat layer of the present invention.

[0048] Furthermore, the curable composition for forming the hard coat layer included in the laminate of the present invention may contain, as needed, an additive that is generally added, such as a polymerization accelerator, a polymerization inhibitor, a photosensitizer, a leveling agent, a surfactant, an adhesion imparting agent, a plasticizer, an ultraviolet absorber, a light stabilizer, an antioxidant, a storage stabilizer, a conductive aid, an inorganic filler, a light diffusing agent, a pigment, a dye, an antifoaming agent, or a defoaming agent, as long as the effect of the present invention is not impaired.

[0049] The hard coat layer in the laminate of the present invention can be formed, for example, by a method including a step of applying the above-mentioned curable composition onto a resin layer to form a coating film, a step of removing the solvent by heating as necessary, and a step of irradiating the coating film with active energy rays such as ultraviolet rays to cure the coating film.

[0050] The method for applying the composition onto the resin layer can be appropriately selected from cast coating, spin coating, blade coating, dip coating, roll coating, spray coating, bar coating, die coating, inkjet printing, printing methods (relief printing, intaglio printing, lithographic printing, screen printing, etc.), and among these, roll-to-roll methods can be used. From the viewpoint of thin-film application, relief printing, particularly gravure coating, is preferred. It is preferable to filter the curable composition before application using a filter having a pore size of approximately 0.2 μm to 5 μm. When applying the composition, a solvent may be added to the curable composition as needed to form a varnish. Examples of the solvent include the various solvents mentioned above.

[0051] After applying a curable composition to the resin layer to form a coating film, the coating film is pre-dried as needed using a heating means such as a hot plate or oven to remove the solvent (solvent removal step). The heat drying conditions are preferably, for example, 40°C to 120°C for about 30 seconds to 10 minutes. After drying, the coating film is cured by irradiating it with active energy rays such as ultraviolet light. Examples of active energy rays include ultraviolet light, electron beams, and X-rays, with ultraviolet light being particularly preferred. Examples of light sources that can be used for ultraviolet irradiation include sunlight, chemical lamps, low-pressure mercury lamps, high-pressure mercury lamps, metal halide lamps, xenon lamps, UV-LEDs, and electrodeless lamps. The polymerization may then be completed by post-baking, specifically by heating using a heating means such as a hot plate or oven.

[0052] [Backing Layer] The laminate of the present invention may have a backing layer below the resin layer. The backing layer may be made of the same material as the hard coat layer.

[0053] The thickness of the backing layer in the present invention can be appropriately adjusted depending on the use of the laminate of the present invention, the thickness of the resin layer and the hard coat layer, etc., and is not particularly limited, but it is preferable that the thickness be such that the provision of the backing layer can impart better indentation recovery properties and bending resistance.

[0054] The specific thickness of the backing layer in the present invention is preferably, for example, in the range of 1.0 μm to 20.0 μm, and more preferably in the range of 4.0 μm to 15.0 μm. By having the thickness of the backing layer in the present invention within this range, the laminate of the present invention can be imparted with better indentation recovery properties and bending resistance. Furthermore, when the laminate of the present invention is used in a flexible substrate described below, it becomes easier to bend freely, and peeling and cracking of the backing layer due to bending can be effectively suppressed.

[0055] <Flexible Substrate> Using the laminate of the present invention, a flexible substrate can be produced that has a supporting substrate, an adhesive layer provided on the supporting substrate, and the laminate provided so that the resin layer or the backing layer is in contact with the adhesive layer. The flexible substrate is also a target of the present invention, and the flexible substrate is suitably used for protecting the surfaces of various display panels such as touch panels and liquid crystal displays.

[0056] [Supporting substrate] The material of the supporting substrate is not particularly limited as long as it is flexible, and any inorganic material such as ultra-thin glass (UTG), metal film, etc., or organic material such as plastic, etc. can be used. Depending on the application of the flexible substrate, a plate, sheet, film, thin film, or any other shape, or a composite of these, can be used, but from the viewpoint of protecting the surface of various display panels such as touch panels and liquid crystal displays, it is particularly preferable to use a sheet, film, thin film, etc. that is flexible and has excellent continuous productivity. Examples of flexible materials that have flexibility include amorphous thermoplastic resins such as polymethyl methacrylate resin, polycarbonate resin, polystyrene resin, cycloolefin resin (COP), cross-linked polyethylene resin, polyvinyl chloride resin, polyacrylate resin, polyphenylene ether resin, modified polyphenylene ether resin, polyetherimide resin, polyethersulfone resin, polysulfone resin, and polyetherketone resin, as well as crystalline thermoplastic resins such as polyethylene terephthalate (PET) resin, polyethylene naphthalate resin, polyethylene resin, polypropylene resin, polybutylene terephthalate resin, aromatic polyester resin, polyacetal resin, and polyamide resin, as well as ultraviolet (UV) curable resins such as acrylic, epoxy, and urethane resins, thermosetting resins such as polyimide resin, and triacetyl cellulose (TAC). Furthermore, the support substrate can be constructed by combining ultraviolet curable resins or thermosetting resins with inorganic substrates such as glass, the thermoplastic resins, and triacetyl cellulose, or by using them alone.

[0057] [Adhesive layer] Examples of the adhesive composition constituting the adhesive layer in the present invention include acrylic adhesives, rubber adhesives, vinyl alkyl ether adhesives, silicone adhesives, polyester adhesives, polyamide adhesives, urethane adhesives, fluorine-based adhesives, epoxy adhesives, and polyether adhesives. The adhesives constituting the adhesive layer may be used alone or in combination of two or more. Among these adhesives, acrylic adhesives are preferred in terms of transparency, processability, durability, adhesion, and flex resistance.

[0058] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. In the examples, the apparatus and conditions used for sample preparation and physical property analysis are as follows:

[0059] (1) Bar Coating Apparatus: Automatic Film Applicator AB3125 manufactured by TQC Sheen Co., Ltd. Bar 1 (bar1): A-Bar OSP-22 manufactured by OSG System Products Co., Ltd., maximum wet film thickness 22 μm (equivalent to wire bar #9) Bar 2 (bar2): A-Bar OSP-42 manufactured by OSG System Products Co., Ltd., maximum wet film thickness 42 μm (equivalent to wire bar #16) Bar 3 (bar3): A-Bar OSP-52 manufactured by OSG System Products Co., Ltd., maximum wet film thickness 52 μm (equivalent to wire bar #20) Bar 4 (bar4): A-Bar OSP-80 manufactured by OSG System Products Co., Ltd., maximum wet film thickness 80 μm (equivalent to wire bar #30) (1) Measurement of film thickness: 100μm (equivalent to wire bar #37) (2) Oven: Two-layer clean oven (top and bottom type) PO-250-45-D manufactured by Sanki Keiso Co., Ltd. (3) UV irradiation: CV-110QC-G manufactured by Heraeus Corporation Lamp: High-pressure mercury lamp H-bulb manufactured by Heraeus Corporation (4) Film thickness: Digital length measuring machine Digimicro MH-15M + Counter TC-101A manufactured by Nikon Corporation (5) Indentation recovery: Electric pencil scratch hardness tester No. manufactured by Yasuda Seiki Seisakusho Co., Ltd. 553-M Load: 500 g Pencil: Uni (registered trademark) manufactured by Mitsubishi Pencil Co., Ltd. Measurement temperature: 23 ° C. (6) Indentation elastic modulus Apparatus: Nanoindenter iNano manufactured by Toyo Corporation Indenter: Berkovich triangular pyramid indenter Measurement temperature: 23 ° C. Maximum indentation load: 50 mN Maximum indentation depth: 1500 nm Load holding time: 1 second (7) Resin layer Material: Transparent polyimide film [manufactured by Mitsubishi Gas Chemical Co., Ltd.] Thickness: 50 μm or 60 μm (8) Adhesive layer Material: OCA film [manufactured by Nitto Denko Corporation LUCIACS (registered trademark) CS9862UA] Thickness: 50 μm (9) Supporting substrate Material: Polyimide film [manufactured by DuPont-Toray Co., Ltd. Kapton (registered trademark) 300H] Thickness: 75 μm

[0060] The abbreviations have the following meanings: Ac1: a polyfunctional acrylate monomer not having a urethane bond [Aronix (registered trademark) MT-3010, manufactured by Toagosei Co., Ltd.] Ac2: a polyfunctional urethane acrylate oligomer [Art Resin (registered trademark) UN-906S, manufactured by Negami Chemical Industrial Co., Ltd.] Ac3: a polyfunctional urethane acrylate oligomer [RUA-051, manufactured by Asia Industries Co., Ltd.] Ac4: a 48% to 52% by mass polyfunctional urethane acrylate diluted in methyl ethyl ketone [AUP-2302, manufactured by Tokushiki Corporation] PFPE1: a perfluoropolyether having the following structure, which has two hydroxy groups at each end of a molecular chain containing a poly(oxyperfluoroalkylene) group, without an intervening poly(oxyalkylene) group, and which has two hydroxy groups at each end without an intervening poly(oxyalkylene) group [Fomblin (registered trademark) T4, manufactured by Solvay Specialty Polymers] (In the above formula, m represents a repeating unit -(CF ２ CF ２ O)-, and n is the number of repeating units -(CF ２ 0)-, satisfying 5≦(m+n)≦40, and m and n each independently represent an integer of 0 or greater. BEI: 1,1-bis(acryloyloxymethyl)ethyl isocyanate [Karenz (registered trademark) BEI, manufactured by Resonac Corporation] DOTDD: dioctyltin dineodecanoate [Neostan (registered trademark) U-830, manufactured by Nitto Kasei Co., Ltd.] O2959: 2-hydroxy-1-(4-(2-hydroxyethoxy)phenyl)-2-methylpropan-1-one [Omnirad (registered trademark) 2959, manufactured by IGM Resins] O819: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide [Omnirad (registered trademark) 819, manufactured by IGM Resins] R-40: [Megafac (registered trademark) R-40, manufactured by DIC Corporation] CYH: cyclohexanone PGME: propylene glycol monomethyl ether

[0061] [Production Example 1] Production of perfluoropolyether (S1) having four acryloyl groups via urethane bonds at each end of a molecular chain containing a poly(oxyperfluoroalkylene) group. 1.19 g (0.5 mmol) of PFPE1, 0.52 g (2.2 mmol) of BEI, 0.017 g of DOTDD (0.01 times the total mass of PFPE1 and BEI), and 1.67 g of PGMEA were charged into a screw tube. This mixture was stirred at room temperature (approximately 23 ° C.) for 24 hours using a stirrer tip to obtain a 50 wt% PGMEA solution of the target compound S1. The weight average molecular weight (Mw) of the obtained S1 measured in polystyrene equivalent by GPC was 2,300, and the dispersity (Mw (weight average molecular weight) / Mn (number average molecular weight)) was 1.0.

[0062] [Production Example 2] Preparation of leveling material L1 Leveling material L1 was prepared by adding PGME to 1.00 g of R-40 and diluting it to a solid content concentration of 8.0 mass %.

[0063] [Production Examples 3-1 to 3-5] Preparation of Curable Compositions (for Hard Coat Layer) The following components were mixed according to the description in Table 1 to prepare curable compositions (HC1 to HC5) with a solid content concentration of 35% by mass. Note that the solid content here refers to components other than the solvent. In the table, [parts] represents [parts by mass], and [%] represents [% by mass]. (1) Polyfunctional (meth)acrylate not having a urethane bond: Polyfunctional (meth)acrylate listed in Table 1 (1') Polyfunctional urethane (meth)acrylate: Polyfunctional urethane (meth)acrylate listed in Table 1 A total of 100 parts by mass of (1) and (1') (2) Surface modifier: Surface modifier listed in Table 1 0.4 parts by mass (solid content equivalent) (3) Polymerization initiator: O2959 2.5 parts by mass (4) Solvent: PGME Amount listed in Table 1

[0064] [Production Examples 3-6 and 3-7] Preparation of Curable Compositions (for Backing Layer) The following components were mixed according to the description in Table 1 to prepare curable compositions (BC1 to BC2) with solid content concentrations of 32% by mass or 26% by mass. Here, the solid content refers to the components other than the solvent. In Table 1, [parts] represents [parts by mass], and [%] represents [% by mass]. (1) Multifunctional urethane (meth)acrylate: 100 parts by mass of the multifunctional urethane (meth)acrylate listed in Table 1. (2) Leveling material: 0.1 part by mass (solid content equivalent) of the leveling material listed in Table 1. (3) Polymerization initiator: 5.0 parts by mass of O819. (4) Solvent: PGME and / or CYH in the amounts listed in Table 1. *L1 was calculated as an 8.0% by mass PGME solution, and the solid content was calculated.

[0065]

[0066] [Examples 1 to 3 and 5 to 7 and Comparative Examples 1 to 3 and 5] The curable compositions (for hard coat layer) obtained in Production Examples 3-1 to 3-5 were applied to the resin layer using a bar coater to obtain a coating film. The coating film was dried in an oven at 60°C for 3 minutes to remove the solvent. The obtained film was then exposed to light at an exposure dose of 700 mJ / cm under a nitrogen atmosphere. ２ A laminate having a hard coat layer (cured film) with a film thickness shown in Table 2 was produced by irradiating and exposing the laminate with UV light of 1000 nm to 1000 nm. Subsequently, the curable compositions (for backing layer) obtained in Production Examples 3-6 and 3-7 were applied with a bar coater to the surface of the resin layer opposite the hard coat layer of the produced laminate, to obtain a coating film. This coating film was dried in an oven at 60°C for 3 minutes to remove the solvent. The obtained film was then exposed to UV light of 700 mJ / cm under a nitrogen atmosphere. ２ This was exposed to UV light of 1000 W at 1000 W to produce a laminate having a backing layer (cured film) with a thickness shown in Table 2. This laminate was attached to the supporting substrate using the adhesive layer so that the hard coat layer was on the surface, thereby producing a flexible substrate.

[0067] [Example 4 and Comparative Examples 4 and 6] The curable compositions (for hard coat layer) obtained in Production Examples 3-1, 3-4, and 3-5 were applied to the resin layer using a bar coater to obtain a coating film. The coating film was dried in an oven at 60°C for 3 minutes to remove the solvent. The obtained film was then exposed to light at an exposure dose of 700 mJ / cm under a nitrogen atmosphere. ２ A laminate having a hard coat layer (cured film) with a thickness shown in Table 2 was produced by irradiating and exposing the laminate to UV light of 1000 kJ / cm2 with UV light of 1000 kJ / cm2 to produce a laminate having a hard coat layer (cured film) with a thickness shown in Table 2. This laminate was attached to the supporting substrate using the pressure-sensitive adhesive layer without forming a backing layer, so that the hard coat layer was on the surface, to produce a flexible substrate.

[0068] The obtained laminate and flexible substrate were evaluated for indentation modulus and indentation recovery. The procedure for evaluating indentation modulus and pencil hardness is shown below. The results are also shown in Table 2. [Indentation modulus] Using the nanoindenter, the indentation modulus E of the surface of (a) the entire laminate (the hard coat layer, resin layer, and backing layer if a backing layer is present, or the hard coat layer and resin layer if no backing layer is present) of the flexible substrate was measured. ＩＴ a, and (b) the indentation elastic modulus E of the surface of the resin layer alone ＩＴ The measurement was carried out before the laminate was attached to the supporting substrate using the adhesive layer, and in (a) the measurement was carried out from the hard coat layer side. ＩＴ is E ＩＴ a and E ＩＴ The absolute value of the difference between b is expressed as the difference between the hardness and the hardness. [Indentation recovery property] The indentation recovery property of the flexible substrate was evaluated using the electric pencil scratch hardness tester. A load was applied to a pencil having a hardness of 4B, and the pencil was slid across the surface of the hard coat layer, and the presence or absence of a pencil indentation mark after 1 hour of testing was visually determined. If no indentation mark was left, or if an indentation mark was left but the mark recovered within 1 hour, the evaluation was given as "○", and if an indentation mark was left but the mark did not recover within 1 hour, the evaluation was given as "×".

[0069]

[0070] As shown in Table 2, the laminate is composed of a hard coat layer having a thickness of more than 10 μm, a resin layer, and a backing layer, or a hard coat layer having a thickness of more than 10 μm, and a resin layer, and the indentation elastic modulus E ＩＴ a and the indentation elastic modulus E of the resin layer alone ＩＴ The absolute value of the difference between b (ΔE ＩＴ It was shown that flexible substrates (Examples 1 to 7) having a laminate with a modulus of elasticity of 1 GPa or less were excellent in recovering pencil indentations. This is thought to be because the total thickness of the laminate and the film thickness of the hard coat layer were thick to a certain extent, which allowed stress relaxation of the load when used as a flexible substrate, and made it easy to recover from deformation of the soft adhesive layer provided between the laminate and the supporting substrate.

[0071] On the other hand, the laminate is composed of a hard coat layer having a thickness of more than 10 μm, a resin layer and a backing layer, or a hard coat layer having a thickness of more than 10 μm and a resin layer, but ΔE ＩＴ It was found that the flexible substrates (Comparative Examples 1 to 4) having an indentation modulus of elasticity of 1 GPa or more recovered more slowly from pencil indentations than the flexible substrates of Examples 1 to 7. In Comparative Examples 1 to 4, the total thickness of the laminate was thick, almost the same as in Examples 1 to 7, but the indentation modulus E ＩＴ It can be seen that the hardness of the hard coat layer alone is improved, as a is higher compared to Examples 1 to 7. However, it is thought that simply improving the hardness of the hard coat layer alone is not enough to fully relieve the stress of the load when used as a flexible substrate, and plastic deformation occurs in the soft adhesive layer provided between the laminate and the supporting substrate.

[0072] The laminate is composed of a hard coat layer having a thickness of 10 μm or less, a resin layer, and a backing layer. ＩＴIt was found that the flexible substrate (Comparative Example 5) having a compressive strength of 1 GPa or less had poor recovery from pencil indentations, leaving clear marks, compared to the flexible substrates of Examples 1 to 7. In Comparative Example 5, the total thickness of the laminate was as thick as in Examples 1 to 7, but the film thickness of the hard coat layer was thinner than in Examples 1 to 7. Therefore, it is thought that when made into a flexible substrate, the load could not be fully relaxed, and plastic deformation occurred in the soft adhesive layer provided between the laminate and the supporting substrate.

[0073] Furthermore, the laminate is composed of a hard coat layer having a thickness of 10 μm or less and a resin layer, and ΔE ＩＴ It was found that the flexible substrate having a compressive strength of 1 GPa or more (Comparative Example 6) had poor recovery from pencil indentations, leaving clear marks, compared to the flexible substrates of Examples 1 to 7. In Comparative Example 6, the total thickness of the laminate was thinner than in Examples 1 to 7, and the film thickness of the hard coat layer was also thinner than in Examples 1 to 7. Therefore, it is thought that when made into a flexible substrate, stress relaxation of the load was not sufficient, and plastic deformation occurred in the soft adhesive layer provided between the laminate and the supporting substrate.

Claims

1. A laminate having a resin layer, a hard coat layer having a thickness of more than 10 μm on the resin layer, and optionally a backing layer below the resin layer, in which the absolute value of the difference between the indentation elasticity of the hard coat layer surface of the laminate and the indentation elasticity of the surface of the resin layer alone, each measured by nanoindentation method, is 1.0 GPa or less.

2. The laminate according to claim 1, wherein the resin layer is a polyimide layer.

3. The laminate according to claim 1, wherein the absolute value of the difference between the indentation elastic modulus of the surface of the hard coat layer of the laminate and the indentation elastic modulus of the surface of only the resin layer is 0.6 GPa or less.

4. The laminate according to claim 1, wherein the hard coat layer is a cured product of a curable composition containing a polyfunctional (meth)acrylate having no urethane bond, a surface modifier and a polymerization initiator.

5. The laminate according to claim 4, wherein the curable composition further comprises a multifunctional urethane (meth)acrylate.

6. A flexible substrate having a supporting substrate, an adhesive layer provided on the supporting substrate, and a laminate according to any one of claims 1 to 5, the resin layer or the backing layer being provided so as to be in contact with the adhesive layer.

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