Optical laminate

Abstract

An optical laminate is characterized by comprising a support substrate made of polyethylene terephthalate and a protective layer peelably laminated on at least one side of the support substrate, wherein the thickness of the protective layer is 1.0 μm or more and 7.0 μm or less, the peeling force when peeling the protective layer from the support substrate is 0.030 N / 25 mm or more and 0.150 N / 25 mm or less, and the pure water contact angle on the peeling side of the protective layer is 50 degrees or more and 85 degrees or less. Furthermore, the surface free energy of the laminated protective layer on the support substrate may be specific, or the puncture force of the protective layer may be specific, etc.

Description

Optical layered bodies The present invention relates to an optical laminate having a peelable laminated hardened film that can be used as a protective film for a polarizing plate. Polarizing plates are generally made of a polyvinyl alcohol (PVA) film and a dichroic dye such as iodine, with polarizer protective films attached to both sides using a polyethylene (polyvinyl) adhesive. With the recent trend toward thinner and lighter displays, there is also a demand for thinner polarizing plates and the polarizer protective films used therein. Conventionally, polarizer protective films have used laminated films consisting of a functional layer with a hard coat layer laminated onto a transparent substrate such as triacetyl cellulose (TAC) film. However, the demand for thinner polarizer protective films has necessitated thinner transparent substrates. The transparent substrate used in polarizer protective films has a certain thickness, so even attempts to reduce the thickness of the film have limitations. Furthermore, as the transparent substrate becomes thinner, it becomes difficult to achieve the required properties of polarizer protective films, such as hardness, durability, and UV absorption. Therefore, as one of the methods for reducing the thickness of polarizing plates, the technology of using a polarizer protective film without a substrate such as a TAC film has been reviewed (for example, see Patent Documents 1 to 3). In Patent Documents 1 to 3, a laminate having a protective layer formed on one side of a supporting substrate (release film) in a releasable manner is produced, and the protective layer peeled from the supporting substrate is used as a polarizer protective film. In the case of such a polarizer protective film without a substrate, the desired function can also be obtained by adding additives to the protective layer formed on the supporting substrate. [Prior Art Document] [Patent Document] [Patent Document 1] International Publication No. 2019 / 054405 [Patent Document 2] Japanese Patent Application Publication No. 2018-169513 [Patent Document 3] Japanese Patent Application Publication No. 2017-65017 [Problem to be Solved by the Invention] When a protective layer is releasably laminated on a supporting substrate, the wettability of the protective layer (the release surface) after peeling may sometimes deteriorate, which may cause poor adhesion during the subsequent bonding step with other components. Furthermore, in recent years, the demand for thinner and more flexible display devices has increased. Even when thinning the polarizer protective film to, for example, 1 to 7 μm, it is necessary to achieve both hard coating properties and flexibility, and to exhibit stable peeling properties without zipping or breakage. Therefore, an object of the present invention is to provide an optical layered product having excellent wettability on the peeling surface of the protective layer even after peeling from the supporting substrate, and having good hard coating properties, flexibility, and peelability from the supporting substrate even when the protective layer is thinned. [Means for Solving the Problems] The optical layered product of the present invention is characterized by comprising a support substrate made of polyethylene terephthalate and a protective layer releasably laminated on at least one surface of the support substrate, wherein the protective layer has a thickness of 1.0 μm to 7.0 μm, a peel force when peeling the protective layer from the support substrate of 0.030 N / 25 mm to 0.150 N / 25 mm, and a pure water contact angle of 50 degrees to 85 degrees on the peeling surface of the protective layer. [Effects of the Invention] According to the present invention, an optical layered product can be provided in which the wettability of the release surface of the protective layer is excellent even after being peeled from the supporting substrate, and the hard coating properties, flexibility, and releasability from the supporting substrate are good even when the protective layer is thinned. [Embodiments for Implementing the Invention] Figure 1 is a schematic cross-sectional view of an optical layered structure according to an embodiment. The optical layered product 1 comprises a support substrate 2 and a protective layer 3 laminated on one surface of the support substrate 2. In the following description, of the two surfaces of the protective layer 3, the surface that forms the interface with air in the optical layered product 1 (the upper surface in FIG. 1 ) is referred to as the "air surface," and the surface that contacts the support substrate 2 in the optical layered product 1 (the lower surface in FIG. 1 ) is referred to as the "release surface." The support substrate 2 is a thin film that becomes a support when the protective layer 3 used as a protective film of the polarizer is formed into a film. As the support substrate 2, a polyethylene terephthalate (PET) film can be suitably used due to its excellent heat resistance and mechanical strength. The arithmetic average roughness Ra of one side of the support substrate 2 (the side on which the protective layer 3 is laminated) is preferably less than 20 nm, and the maximum height Rz is preferably less than 100 nm. When the arithmetic average roughness Ra and the maximum height Rz of one side of the support substrate 2 are within these ranges, the pure water contact angle of the peeling surface of the protective layer 3 can be made within the preferred range described later, which can improve the adhesion with the polarizer or other films. Moreover, if it is a film having a surface with an arithmetic average roughness Ra and a maximum height Rz within the above ranges, a resin film other than PET can also be used as the support substrate 2. The thickness of the support substrate 2 is preferably 75 μm or more. If the thickness of the support substrate 2 is less than 75 μm, the hardness of the protective layer 3 in the indentation direction before being peeled from the support substrate 2 may be insufficient, potentially reducing the shelf life of the optical layered product 1. This is undesirable. However, as long as the hardness is sufficiently maintained by adjusting the composition of the protective layer 3, a thickness less than 75 μm is acceptable, for example, 50 μm or greater. While there is no particular upper limit on the thickness of the support substrate 2, a thickness too thick increases material costs, so it is preferably 125 μm or less. The pure water contact angle of one surface of the support substrate 2 (the surface on which the protective layer 3 is deposited) is preferably 50 degrees or more and 95 degrees or less. Furthermore, the hexadecane contact angle is preferably 1 degree or more and 30 degrees or less. The diiodomethane contact angle is preferably 3 degrees or more and 63 degrees or less. When the contact angles of the above solvents on the support substrate 2 are within these ranges, the wettability of the support substrate 2 is improved, the coating properties of the protective layer-forming coating solution described later are enhanced, and the releasability of the protective layer 3 is improved. The surface free energy of one side of the support substrate 2 (the side on which the protective layer 3 is laminated) is preferably 30 mJ / m 2 Above 85mJ / m 2 If the surface free energy of the supporting substrate 2 is 30 mJ / m 2 Above, the wettability becomes good, and the coating property of the protective layer forming coating liquid described later is improved, preferably 32mJ / m 2 Furthermore, if it is 85mJ / m 2 The following is preferable because tearing noise and breakage are less likely to occur when peeling the protective layer 3. The surface free energy can be calculated for three solvents (water, hexadecane, and diiodomethane) using the known surface free energy and contact angle of each solvent. The protective layer 3 is a thin film that is releasably laminated on one side of the supporting substrate 2 and is used as a protective film for the polarizer in a state that it has been peeled off from the supporting substrate 2. The thickness of the protective layer 3 is preferably not less than 1.0 μm and not more than 7.0 μm. The lower limit can be exemplified by not less than 1.0 μm, not less than 1.5 μm, not less than 2.0 μm, etc., and the upper limit can be exemplified by not more than 7.0 μm, not more than 4.0 μm, etc. When the thickness of the protective layer 3 is less than 1.0 μm, when the protective layer 3 is used alone as a protective film for the polarizer, the hard coating required of the protective film becomes insufficient, and there is a possibility of tearing sound or breakage during peeling due to insufficient strength. When the thickness of the protective layer 3 exceeds 7.0 μm, it is not conducive to the thinning of the polarizing plate and the image display device, and is therefore not suitable. In the state where the protective layer 3 has been peeled off from the supporting substrate 2, the pure water contact angle of the peeling surface of the protective layer 3 is preferably not less than 50 degrees and not more than 85 degrees, and the lower limit can be exemplified by not less than 50 degrees, not less than 53 degrees, not less than 59 degrees, etc., and the upper limit can be exemplified by not more than 85 degrees, not more than 83 degrees, not more than 79 degrees, etc. In addition, the pure water contact angle of the air surface of the protective layer 3 is preferably not less than 50 degrees and not more than 85 degrees, and can also be not less than 53 degrees and not more than 83 degrees. When the pure water contact angles of the peeling surface and the air surface of the protective layer 3 are within these ranges, the wettability of each surface is good, and the adhesion is good in the subsequent steps of laminating to other films, etc., and poor adhesion is reduced, so it can be expected that the quality and yield rate will be improved. In addition, the surface free energy of the surface of the supporting substrate 2 on which the protective layer 3 is laminated is 30mJ / m 2 Above 85mJ / m 2 In the following cases, if the pure water contact angles of the peeling surface and the air surface of the protective layer 3 are within these ranges, troubles are less likely to occur when peeling the protective layer 3, which is preferred. The puncture force of the protective layer 3 is preferably 0.25 N or more, more preferably 0.30 N or more, from the perspective of excellent hard coating properties even when the protective layer is made into a thin film as described above. The upper limit is not particularly limited, but from the perspective of excellent hardness in the direction perpendicular to the surface of the protective layer, examples include 2.00 N or less, 1.00 N or less, 0.70 N or less, 0.50 N or less, etc. In order to exert flexibility, the puncture elongation of the protective layer 3 is preferably 1.0 mm or more, more preferably 1.4 mm or more, and particularly preferably 1.5 mm or more. The upper limit is not particularly limited, but from the perspective of balancing softness and strength, examples include 5.0 mm or less, 4.0 mm or less, 3.0 mm or less, 2.0 mm or less, 1.7 mm or less, etc. Furthermore, from the perspective of achieving both hard coating properties and flexibility while improving peelability, the protective layer 3 preferably has a puncture modulus of elasticity of 0.15 N / mm or greater, more preferably 0.16 N / mm or greater, particularly preferably 0.18 N / mm or greater, and even more preferably 0.20 N / mm or greater. The upper limit is not particularly limited, but examples thereof include 0.70 N / mm or less, 0.60 N / mm or less, 0.50 N / mm or less, 0.40 N / mm or less, and 0.30 N / mm or less. Furthermore, in this specification, the puncture force, puncture elongation, and puncture modulus of elasticity can be evaluated using a universal testing machine (STB-1225L, A&D) in accordance with JIS Z 1707. The protective layer 3 can be formed by applying a coating solution containing a UV-curable compound, a photopolymerization initiator, and a solvent onto the support substrate 2, drying the solution, and then curing the coating by UV irradiation. The protective layer 3 has the hard coating properties required for a protective film and is typically formed as a hard coat layer. As UV-curable compounds, for example, monofunctional, bifunctional, or trifunctional or higher-functional (meth)acrylate monomers can be used. Furthermore, in this specification, "(meth)acrylate" is a general term for both acrylate and methacrylate, and "(meth)acryl" is a general term for both acryl and methacryl. Examples of the monofunctional (meth)acrylate compound include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, glycidyl (meth)acrylate, acryl Phosphine, N-vinyl pyrrolidone, tetrahydrofurfuryl acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, octadecyl (meth)acrylate, benzyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phosphoric acid (meth)acrylate, ethylene oxide modified phosphoric acid (meth)acrylate, phenoxy (meth)acrylate, ethylene oxide modified phenoxy (meth)acrylate, propylene oxide modified phenoxy (meth)acrylate, b-phenol (meth)acrylate, ethylene oxide modified nonylphenol (meth)acrylate, propylene oxide modified nonylphenol (meth)acrylate, methoxydiethylene glycol (meth)acrylate

[0014] Examples of the present invention include: 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hexahydro hydrogen phthalate, 2-(meth)acryloyloxypropyl tetrahydro hydrogen phthalate, dimethylaminoethyl (meth)acrylate, trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropropyl (meth)acrylate, and adamantane derivative mono(meth)acrylates such as adamantane acrylate having a monovalent mono(meth)acrylate derived from 2-adamantane or adamantanediol. Examples of bifunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, ethoxylated hexanediol di(meth)acrylate, propoxylated hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethoxylated neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and hydroxypivalate neopentyl glycol di(meth)acrylate. Examples of trifunctional or higher-functional (meth)acrylates include trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, 2-hydroxyethyl isocyanurate tri(meth)acrylate, glycerol tri(meth)acrylate, and pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, and the like. Ester compounds, or trifunctional or higher-functional (meth)acrylate compounds such as pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrimethylolpropane penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and ditrimethylolpropane hexa(meth)acrylate, or multifunctional (meth)acrylate compounds in which a portion of these (meth)acrylates is substituted with an alkyl group or ε-caprolactone. Furthermore, urethane (meth)acrylates can also be used as polyfunctional monomers. Examples of urethane (meth)acrylates include those obtained by reacting a product obtained by reacting an isocyanate monomer or prepolymer with a polyester polyol with a (meth)acrylate monomer having a hydroxyl group. Examples of the urethane (meth)acrylate include pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate toluene diisocyanate urethane prepolymer, pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, and dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymer. As UV-curable compounds, (meth)acrylates containing an alicyclic structure can be used. Examples of (meth)acrylates containing an alicyclic structure include esters having one or more of the following structures: cyclopentane, dicyclopentane, cyclohexane, cyclodecane, tricyclodecane, isobornyl, and adamantane. By incorporating these compounds into the protective layer-forming coating liquid, hydrophobicity can be imparted to the protective layer 3, thereby reducing the moisture permeability required for the polarizer protective film. Specific examples of the (meth)acrylate containing an alicyclic structure include monofunctional (meth)acrylates such as cyclohexyl (meth)acrylate, cyclohexanedimethanol mono(meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexanol (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentadienyl (meth)acrylate, 2-dicyclopentenyloxyethyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, bornyl (meth)acrylate, isobornyl (meth)acrylate, tricyclodecyl (meth)acrylate, tricyclodecane dimethanol mono(meth)acrylate, and adamantyl (meth)acrylate, or cyclohexanedimethanol di(meth)acrylate, dicyclopentyl di(meth)acrylate, dicyclopentenyl Multifunctional (meth)acrylates such as pentenyl di(meth)acrylate, dicyclopentadienyl di(meth)acrylate, bornyl di(meth)acrylate, isobornyl di(meth)acrylate, tricyclodecyl di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, adamantyl di(meth)acrylate, adamantane dimethanol di(meth)acrylate, adamantane diethanol di(meth)acrylate, dihydroxymethyldicyclopentane di(meth)acrylate, norbornane dihydroxymethyl di(meth)acrylate, cyclohexanedimethanol tri(meth)acrylate, adamantyl tri(meth)acrylate, adamantane trimethanol tri(meth)acrylate, norbornane trihydroxymethyl tri(meth)acrylate, tricyclodecane trimethanol tri(meth)acrylate, and perhydro-1,4,5,8-dimethylnaphthalene-2,3,7-(oxymethyl) tri(meth)acrylate. These (meth)acrylates containing an alicyclic structure may be used alone or in combination of two or more. The above-mentioned ultraviolet curable compound may be used alone or in combination of two or more. The above-mentioned ultraviolet curable compound may be a monomer or a partially polymerized oligomer in the composition. The double bond equivalent weight of the UV-curable compound is preferably 90 g / mol or more and 140 g / mol or less. Examples of lower limits include 90 g / mol or more, 99 g / mol or more, and 109 g / mol or more. Examples of upper limits include 140 g / mol or less and 138 g / mol or less. When the double bond equivalent weight of the UV-curable compound is within this range, the hardness and flexibility of the cured protective layer 3 are balanced, and peelability from the support substrate 2 is also improved. When the double bond equivalent weight of the UV-curable compound is outside this range, the adhesion strength between the protective layer 3 and the support substrate 2 increases, and peelability deteriorates, making this undesirable. Furthermore, when the double bond equivalent weight of the UV-curable compound is less than 90 g / mol, the number of polymerizable double bonds relative to the mass of the UV-curable compound increases, resulting in a higher hardness of the protective layer 3 but lower flex resistance, making it unsuitable for applications in bendable display devices. When the double bond equivalent of the ultraviolet curable compound exceeds 140 g / mol, the curability of the protective layer 3 decreases, and the surface hardness and scratch resistance may be deteriorated. Examples of the photopolymerization initiator include free radical polymerization initiators such as acetophenone, benzophenone, thioxanthone, benzoin, benzoin methyl ether, and acylphosphine oxide. Examples of the photopolymerization initiator include 2,4,6-trimethylbenzyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzyl)phenylphosphine oxide, 2,2-diethoxyacetophenone, 1-hydroxycyclohexylphenyl ketone, 2,2-dimethoxyphenylacetophenone, dibenzodione, benzoin, benzoin methyl ether, benzoin ethyl ether, p-chlorobenzophenone, p-methoxybenzophenone, Michler's ketone, acetophenone, 2-chlorothioxanthone, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropane-1-one, and 2-benzyl-2-(dimethylamino)-4'- Linobutylphenone, etc. These may be used alone or in combination of two or more. The amount of the photopolymerization initiator blended is preferably 3.0% to 6.0% by mass of the protective layer-forming coating solution. The lower limit may be 3.0% to 3.6% by mass, and the upper limit may be 6.0% to 5.2% by mass. When the amount of the photopolymerization initiator blended is less than 3.0% by mass of the protective layer-forming coating solution, the peeling strength of the protective layer 3 from the supporting substrate 2 increases, and the peeling property may deteriorate, so it is not suitable. When the amount of the photopolymerization initiator blended exceeds 6.0% by mass of the protective layer-forming coating solution, the solubility of the photopolymerization initiator deteriorates, so it is not suitable. Moreover, when the total solid content of the protective layer-forming coating solution is used as a reference, the amount of the photopolymerization initiator blended is preferably 9.0% to 13.0% by mass of the total solid content. As the solvent, one or a mixture of two or more of the following can be used: alcohols such as methanol, ethanol, 1-propanol, 2-propanol, butanol, isopropanol, and isobutanol; ketones such as acetone, methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone; ketoalcohols such as diacetone alcohol; aromatic hydrocarbons such as benzene, toluene, and xylene; glycols such as ethylene glycol, propylene glycol, and hexylene glycol; glycol ethers such as ethyl cellulose, butyl cellulose, ethyl carbitol, butyl carbitol, diethyl cellulose, diethyl carbitol, and propylene glycol monomethyl ether; esters such as dimethyl carbonate, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, butyl acetate, and amyl acetate; ethers such as dimethyl ether and diethyl ether; N-methylpyrrolidone; and dimethylformamide. In the coating solution for forming the protective layer, inorganic fine particles may be added to improve the mechanical strength or surface strength (pencil strength) of the protective layer 3. As the inorganic fine particles, silicon dioxide fine particles (SiO 2) or metal oxide particles. As metal oxide particles, antimony-doped tin oxide (ATO), phosphorus-doped tin oxide (PTO), gallium-doped tin oxide (GTO), zirconium oxide (ZrO 2) and titanium oxide (TiO 2) can be used. The inorganic microparticles can be surface-modified by bonding with a silane coupling agent. Silane coupling agents having one or more functional groups selected from vinyl, acryl, and methacryl groups can be used. Furthermore, various additives such as antistatic agents, defoaming agents, antioxidants, ultraviolet absorbers, infrared absorbers, colorants, light stabilizers, polymerization inhibitors, photosensitizers, antifouling agents, leveling agents, oil repellents, water repellents, and fingerprint inhibitors may be added to the protective layer-forming coating liquid as needed. By appropriately adding these additives, various functions can be imparted to the protective layer 3. Furthermore, to enhance the hydrophobicity of the protective layer 3, a hydrophobic material such as a cycloolefin polymer may be incorporated. The coating method of the protective layer-forming coating liquid is not particularly limited. For example, a spin coater, a roll coater, a reverse roll coater, a gravure coater, a micro gravure coater, a knife coater, a rod coater, a wire bar coater, a die coater, a dip coater, a spray coater, an applicator, etc. can be used for coating. The cumulative amount of ultraviolet light when curing the protective layer 3 is preferably set to 60 mJ / cm 2 Above 300mJ / cm 2 Below. The cumulative amount of ultraviolet light is less than 60mJ / cm 2 When , the peel strength of the protective layer 3 may become higher. After the formation of the optical layered body 1, the peeling force when peeling the protective layer 3 from the supporting substrate 2 is preferably not less than 0.030N / 25mm and not more than 0.150N / 25mm. In addition, from the perspective of excellent peelability, it can be not less than 0.030N / 25mm and not more than 0.100N / 25mm. Moreover, the peeling force is a value measured by a 180° peeling test in accordance with JIS K 6854-2. When the peeling force when peeling the protective layer 3 from the supporting substrate 2 is within this range, the occurrence of breakage or tearing sounds during peeling or the undesirable situation of being unable to peel can be reduced. If the pure water contact angle between the peeling surface and the air surface of the protective layer 3 is not less than 50 degrees and not more than 85 degrees, even if peeling is performed with a peeling force within the aforementioned range, it is less likely to cause an undesirable situation on the peeling surface, and therefore it is more preferable. The protective layer 3 of the optical laminate 1 of this embodiment can be used as a protective film for the polarizer in a state in which it has been peeled off from the supporting substrate 2. The surface that becomes the interface with the polarizer can be either the air surface or the peeling surface, but it is preferable to set the air surface as the interface with the polarizer. The polarizer and the protective layer 3 can be bonded together using an adhesive to make them adhere closely. Alternatively, a polarizer that adheres closely to the protective layer 3 can be formed by applying a coating liquid of a PVA resin containing a dichroic pigment on the protective layer 3. The other side of the protective layer 3 can be bonded to other components such as a resin film or a phase difference plate via an adhesive or the like. The peeling of the protective layer 3 from the supporting substrate 2 can be performed before bonding with the polarizer or after bonding with the polarizer. As described above, the optical layered product 1 of this embodiment comprises a support substrate 2 made of polyethylene terephthalate and a protective layer 3 releasably laminated on at least one surface of the support substrate 2. The protective layer 3 has a thickness of 1.0 μm to 7.0 μm, a peeling force when peeling the protective layer 3 from the support substrate 2 of 0.030 N / 25 mm to 0.150 N / 25 mm, and a pure water contact angle of 50 degrees to 85 degrees on the peeling surface of the protective layer 3. This embodiment provides an optical layered product 1 having excellent wettability on the peeling surface of the protective layer 3 even after peeling from the support substrate 2. Even when the protective layer 3 is thinned to a thickness of 1.0 to 7.0 μm, the optical layered product 1 exhibits excellent hard coating properties, flexibility, and releasability from the support substrate 2. In addition, another optical layered body 1 of this embodiment is laminated with a support substrate 2 made of polyethylene terephthalate and a protective layer 3 laminated on at least one side of the support substrate 2 in a releasable manner. The film thickness of the protective layer 3 is 1.0 μm or more and 7.0 μm or less. The surface free energy of the surface of the support substrate 2 on which the protective layer is laminated is 30 mJ / m 2 Above 85mJ / m 2The pure water contact angle on the release surface of the protective layer 3 is 50° to 85°, the pencil hardness of the protective layer is F or higher, and the minimum diameter of a cylinder that can be wound with the protective layer facing outward without cracking is 2 mm or less. This embodiment provides an optical layered product 1 having excellent wettability on the release surface of the protective layer 3 even after being peeled from the support substrate 2. Even when the protective layer 3 is thinned to a thickness of 1.0 to 7.0 μm, the optical layered product 1 exhibits excellent hard coating properties, flexibility, and releasability from the support substrate 2. Another optical layered product 1 of this embodiment comprises a support substrate 2 made of polyethylene terephthalate and a protective layer 3 releasably laminated on at least one surface of the support substrate 2. The protective layer 3 exhibits a puncture force of 0.25 N or greater, a puncture elongation of 1.0 mm or greater, and a puncture elastic modulus of 0.15 N / mm or greater. The peel force when peeling the protective layer 3 from the support substrate 2 is 0.030 N / 25 mm or greater and 0.150 N / 25 mm or less. The pure water contact angle on the peeled surface of the protective layer 3 is 50 degrees or greater and 85 degrees or less. This embodiment provides an optical layered product 1 having excellent wettability on the peeled surface of the protective layer 3 even after peeling from the support substrate 2. Even when the protective layer 3 is thinned to a thickness of 1.0 to 7.0 μm, the optical layered product 1 exhibits excellent hard coating properties, flexibility, and releasability from the support substrate 2. Another optical layered body 1 of this embodiment is laminated with a support substrate 2 made of polyethylene terephthalate and a protective layer 3 laminated on at least one side of the support substrate 2 in a releasable manner. The surface free energy of the surface of the support substrate 2 on which the protective layer is laminated is 30 mJ / m 2 Above 85mJ / m 2 The puncture force of the protective layer 3 is 0.25 N or more, the puncture elongation is 1.0 mm or more, the puncture elastic modulus is 0.15 N / mm or more, and the pure water contact angle on the peeling surface of the protective layer 3 is 50 degrees or more and 85 degrees or less. According to this embodiment, an optical layered body 1 is achieved in which the peeling surface of the protective layer 3 has excellent wettability even after being peeled from the supporting substrate 2. Even when the protective layer 3 is thinned to a thickness of 1.0 to 7.0 μm, the hard coating properties, flexibility, and peelability from the supporting substrate 2 are excellent. [Example] Hereinafter, embodiments for specifically implementing the present invention will be described. (Example 1) A coating liquid for forming a protective layer having the composition described in Table 1 was prepared and applied to one side of a 75 μm thick PET substrate (T60, Toray Industries, Inc.) by bar coating to a cured film thickness of 2.0 μm. The film was then dried at 70°C for 30 seconds. After drying, a metal halide lamp was used to provide a cumulative light intensity of 122 mJ / cm 2The coating film is cured by irradiating ultraviolet rays in a manner to obtain an optical laminate having a protective layer laminated on a supporting substrate. (Examples 2 to 5) Optical layered products were obtained under the same conditions as in Example 1 except that the composition of the protective layer-forming coating liquid was changed as described in Table 1. (Example 6) An optical layered body was obtained under the same conditions as in Example 1 except that the coating liquid was applied so that the cured film thickness of the protective layer would be 7.0 μm. (Example 7) An optical layered body was obtained under the same conditions as in Example 1 except that the coating liquid was applied so that the cured film thickness of the protective layer would be 1.5 μm. (Example 8) An optical layered product was obtained under the same conditions as in Example 1, except that a PET substrate (O324H50 [H39E], Mitsubishi Chemical Corporation) with a thickness of 50 μm and the surface roughness and surface free energy shown in Table 2 was used and the composition of the coating liquid for forming the protective layer was changed to that described in Table 2. Comparative Example 1 An optical layered product was obtained under the same conditions as in Example 1 except that a PET substrate (S100H, thickness 23 μm, Mitsubishi Chemical Corporation) having the surface roughness and surface free energy shown in Table 3 was used as the supporting substrate. (Comparative Examples 2 to 5) Optical layered products were obtained under the same conditions as in Example 1 except that the composition of the protective layer-forming coating liquid was changed as shown in Table 3. (Comparative Example 6) An optical layered body was obtained under the same conditions as in Example 1, except that the coating liquid was applied so that the cured film thickness of the protective layer would be 0.9 μm. Comparative Example 7 An optical layered product was obtained under the same conditions as in Example 1 except that a 38 μm thick PET substrate (Toray, 38-SY) having the surface roughness and surface free energy shown in Table 4 was used as the supporting substrate. (Comparative Example 8) An optical layered product was obtained under the same conditions as in Example 1 except that a 75 μm thick PET substrate (Toyobo, TN200) having the surface roughness and surface free energy shown in Table 4 was used as the supporting substrate. (Comparative Example 9) An optical layered product was obtained under the same conditions as in Example 1 except that the composition of the protective layer-forming coating liquid was changed as described in Table 4. The following is a detailed description of the compounds shown in Tables 1 to 4. 1. UV-curable compounds (monomers) (1) NK Ester A-TMM-3L (trade name), Shin-Nakamura Chemical Industry Co., Ltd., pentaerythritol triacrylate and pentaerythritol tetraacrylate (2) LIGHTACRYLATE (registered trademark) 3EG-A (trade name), Kyoeisha Chemical Co., Ltd., triethylene glycol diacrylate (3) LIGHTACRYLATE 9EG-A (trade name), Kyoeisha Chemical Co., Ltd., PEG400 diacrylate (4) LIGHTACRYLATE DPE-6A (trade name), Kyoeisha Chemical Co., Ltd., dipentaerythritol hexaacrylate 2. Photopolymerization initiator (1) Omnirad (registered trademark) 184 (trade name), IGM Resins BV, 1-hydroxycyclohexyl-phenyl ketone (2) Omnirad TPO (trade name), IGM Resins BV, 2,4,6-trimethylbenzyl-diphenylphosphine oxide (3) Omnirad 127 (trade name), IGM Resins BV, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)-2-methylpropane-1-one (4) Omnirad 369 (trade name), IGM Resins BV, 2-benzyl-2-(dimethylamino)-4'- Linobutylphenone 3. Additives (1) GRANDIC PC4300, manufactured by DIC Corporation, leveling agent (2) BYK-3566, manufactured by BYK Corporation, leveling agent 4.Solvent (1) Dimethyl carbonate (2) MIBK (methyl isobutyl ketone) The optical layered bodies of the examples and comparative examples were evaluated by the following methods. [Arithmetic Mean Roughness Ra, Maximum Height Rz] The surface shape of the evaluation surface (the surface on which the protective layer was deposited) was observed using a white interference microscope (ECLIPSE LV150N, NIKON Co., Ltd.), and the average Ra and Rz were calculated from the surface shape data at 6 locations. [Peel Force] Peel force was measured using a 180° peel test in accordance with JIS K 6854-2. Specifically, a test sample was prepared with the protective layer of the optical laminate attached to a glass plate using adhesive tape (TD06A, Tomoe Paper Co., Ltd.). Using a Tensilon single-column material testing machine (STB-1225L, A&D Co., Ltd.), the support substrate was stretched 180° and peeled from the protective layer using a load cell of 50 N and a peel speed of 500 mm / min. The load was measured while the support substrate was peeled from the protective layer. The peel force was calculated from the resulting peel curve (load-displacement). [Pure Water Contact Angle of Protective Layer] A contact angle meter (Drop Master 300, Kyowa Interface Science Co., Ltd.) was used, with the value measured 5 seconds after the pure water droplet landed on the measurement surface. The pure water contact angle of the air side of the protective layer was measured without peeling the protective layer from the supporting substrate. The peeled side was measured by attaching the protective layer of the optical laminate to a glass plate with adhesive tape (TD06A, Tomotagawa Paper Co., Ltd.), peeling the supporting substrate from the protective layer, and attaching the protective layer to the glass plate with the adhesive tape. [Pencil Hardness] Pencil hardness is evaluated in accordance with JIS K5400-1900. The pencil hardness of the protective layer surface is measured using a pencil (uni, Mitsubishi Pencil Co., Ltd.) and a Clemens scratch tester (HA-301, Tester Industries, Ltd.). Repeat the test while varying the pencil hardness. Visually observe changes in appearance due to damage. The maximum hardness at which no damage is observed is the evaluation value. For pencil hardness, a score of F or higher is considered acceptable. In Tables 1-4, "<B" indicates a pencil hardness lower than B, and ">H" indicates a pencil hardness higher than H. [Scratch Resistance] A 50mm x 170mm sample was cut from the optical laminate and fixed to a stand with transparent tape. A 20mm x 20mm piece of steel wool (BONSTAR #0000) was placed in contact with the air side of the protective layer and a test load of 1,000g / 4cm was applied. 2 After making the scratch length of more than 80mm, move back and forth 10 times, and visually count the scratches within the center 30mm of the scratch length. 10 or fewer scratches are considered acceptable. [Bending Resistance (Mandrel Test)] Bending resistance is evaluated using a mandrel test in accordance with JIS K 5600-1. A sample of the optical layered product is wound around a metal cylinder with a diameter of 1 to 3 mm, with the protective layer facing outward. The diameter of the smallest cylinder without cracks in the protective layer is used as the evaluation value. A minimum cylinder diameter of 2 mm or less is considered acceptable. [Contact Angle of Supporting Substrate] A contact angle meter (Drop Master 300, Kyowa Interface Science Co., Ltd.) was used to measure the value 5 seconds after each solvent (pure water, hexadecane, diiodomethane) was dropped onto the measurement surface. [Surface free energy of the supporting substrate] Formula (3) is derived from the following formulas (1) and (2). The contact angles of the solvents (pure water, hexadecane, and diiodomethane) obtained above are introduced into Formula (3), and the surface free energy is calculated by simultaneously solving three linear equations. Young-Dupre formula: Expanding Fowkes' formula: W A : Adhesion work between substrate and solvent γ SL : Surface free energy γ between substrate and solvent S : Surface free energy γ of substrate L : The known surface free energy γ of the solvent S d : Dispersion force component γ of the surface free energy of the substrate S p : Polar force component γ of the surface free energy of the substrate S H : Hydrogen bonding component γ of the surface free energy of the substrate L d : The dispersion force component γ of the known surface free energy of the solvent L p : The polar force component γ of the known surface free energy of the solvent L H : The known hydrogen bonding component of the solvent's surface free energy [Puncture Strength (Puncture Test)] Evaluated using a universal testing machine (STB-1225L, A&D) in accordance with JIS Z 1707. The protective layer is transferred to a base paper with a hole of 10 mm in diameter. The puncture force (N) and puncture elongation (mm) are measured when a needle (1.0 mm in diameter, semicircular with a 0.5 mm radius at the tip) is vertically punctured at a rate of 50 mm / min through the portion overlapping the hole. The puncture force is divided by the puncture elongation to determine the puncture modulus (N / mm). The average value of five measurements is used as the evaluation value. A puncture force of 0.25 N or greater, a puncture elongation of 1.0 mm or greater, and a puncture modulus of 0.15 N / mm or greater are considered acceptable. Tables 1 to 4 show the configuration (coating liquid composition) and evaluation results of the optical layered bodies of each Example and each Comparative Example. [Table 1] [Table 2] [Table 3] [Table 4] ※1: Due to poor adhesion between the support substrate and the protective layer, measurement is impossible. ※2: Since the protective layer cannot be peeled off, measurement or calculation is impossible. As shown in Table 1, the optical layered products of Examples 1-6 all exhibit excellent wettability (pure water contact angle), and good releasability is maintained even when the protective layer is thinned to a thickness of 2.0-7.0 μm. Furthermore, as shown by the evaluation results of pencil hardness, scratch resistance, and flex resistance, the protective layer systems of the optical layered products of Examples 1-6 exhibit excellent surface hardness and good flex resistance. In other words, the optical layered systems of Examples 1-6 exhibit excellent performance across all aspects: wettability of the release surface of the protective layer, hard coating properties, flexibility, and releasability from the supporting substrate. While Example 7 utilizes the same protective layer composition as Example 1, further reducing the thickness to 1.5 μm, the protective layer maintains its strength while also exhibiting good peelability, excellent surface hardness, and excellent flex resistance. Compared to the other examples, Example 8, despite utilizing a support substrate with a smaller surface irregularity and lower surface free energy, exhibits no issues with the coating properties of the protective layer. Even with a thin film thickness of 2.0 μm, peelability remains good, and the surface hardness and flex resistance are excellent. In contrast, the optical layered product of Comparative Example 1 uses a PET substrate with a rougher surface than that of Examples 1-6 as its support substrate, resulting in a lower pure water contact angle on the release surface of the protective layer. Consequently, the release surface of the protective layer exhibits poorer wettability than that of Examples 1-6, potentially leading to reduced adhesion when laminating to other components. The optical layered products of Comparative Examples 2 and 3 both used a monomer with a double bond equivalent weight exceeding 140 g / mol as the UV-curable compound for forming the protective layer. Consequently, the peel strength of the protective layer was excessively high, resulting in poor peelability. Furthermore, the optical layered products of Comparative Examples 2 and 3 had a low number of polymerizable double bonds relative to the weight of the monomer, resulting in insufficient hardening of the protective layer. As shown by the pencil hardness and scratch resistance evaluation results, the hard coating properties were insufficient. The optical layered products of Comparative Examples 4 and 5 both used a monomer with a double bond equivalent weight of less than 90 g / mol as the UV-curable compound for forming the protective layer. Consequently, the peel strength of the protective layer was excessively high, resulting in poor releasability. Furthermore, the optical layered products of Comparative Examples 4 and 5 exhibited excellent hard-coating properties due to the high number of polymerizable double bonds relative to the weight of the monomer. However, the hardness of the protective layer was excessively high, resulting in poor flex resistance. Comparative Example 6 is a film in which the thickness of the protective layer is reduced to 0.9μm. Although it has excellent bending resistance, the surface hardness and the strength of the film itself are poor, and it lacks practicality. Compared with Examples 1 to 6, the support substrate of Comparative Example 7 also has low affinity for any of the solvents of pure water, hexadecane, and diiodomethane, so the coating properties of the coating liquid for forming the protective layer are deteriorated, and since the pure water contact angle of the peeling surface is poor, there is a possibility of reduced adhesion when bonding with other components. Comparative Example 8 has an excessively large surface free energy of the support substrate, so it is difficult to peel off the protective layer, and it is difficult to form a peelable film. Comparative Example 9 uses the same support substrate as Examples 1 to 6. Although the peelability is good, the protective layer formed is not sufficiently hardened, and the surface hardness and the strength of the film itself are poor. [Possibility of Industrial Utilization] The present invention can be used as an optical laminate that releasably supports a protective layer that can be used as a protective film for a polarizing plate. 1: Optical laminate 2: Support substrate 3: Protective layer FIG1 is a schematic cross-sectional view of an optical layered product according to an embodiment. 1: Optical laminate 2: Support substrate 3: Protective layer

Claims

1. An optical laminate, characterized by comprising: a support substrate made of polyethylene terephthalate, and a protective layer peelably laminated on at least one side of the support substrate; wherein the thickness of the protective layer is 1.0 μm or more and 7.0 μm or less, the peeling force when peeling the protective layer from the support substrate is 0.030 N / 25 mm or more and 0.150 N / 25 mm or less, and the pure water contact angle on the peeling side of the protective layer is 50 degrees or more and 85 degrees or less.

2. An optical laminate, characterized by comprising: a support substrate made of polyethylene terephthalate, and a protective layer peelably laminated on at least one side of the support substrate; wherein the surface free energy of the side of the support substrate on which the protective layer is laminated is 30 mJ / m² to 85 mJ / m², the film thickness of the protective layer is 1.0 μm to 7.0 μm, the pure water contact angle of the peelable side of the protective layer is 50 degrees to 85 degrees, the pencil hardness of the protective layer is F or higher, and the minimum diameter of the cylinder that can be wound around the protective layer without cracking is 2 mm or less.

3. An optical laminate, characterized by comprising: a support substrate made of polyethylene terephthalate, and a protective layer peelably laminated on at least one side of the support substrate; wherein the protective layer has a puncture force of 0.25 N or more, a puncture elongation of 1.0 mm or more, and a puncture modulus of elasticity of 0.15 N / mm or more, a peel force when peeling the protective layer from the support substrate of 0.030 N / 25 mm or more and 0.150 N / 25 mm or less, and a pure water contact angle of the peel surface side of the protective layer of 50 degrees or more and 85 degrees or less.

4. An optical laminate, characterized by comprising: a support substrate made of polyethylene terephthalate, and a protective layer peelably laminated on at least one side of the support substrate; wherein the surface free energy of the side of the support substrate on which the protective layer is laminated is 30 mJ / m² or more and 85 mJ / m² or less, the puncture force of the protective layer is 0.25 N or more, the puncture elongation is 1.0 mm or more, and the puncture modulus is 0.15 N / mm or more, and the pure water contact angle of the peelable side of the protective layer is 50 degrees or more and 85 degrees or less.

5. An optical laminate as claimed in any of claims 1 to 4, wherein the arithmetic mean roughness Ra of the surface on which the protective layer is laminated on the supporting substrate is less than 20 nm and the maximum height Rz is less than 100 nm.

6. An optical laminate as claimed in any one of claims 1 to 4, wherein the protective layer is formed of a hardened film of a coating liquid comprising an ultraviolet-curable compound, a photopolymerization initiator and a solvent, wherein the photopolymerization initiator is 3.0% by mass or more and 6.0% by mass or less in the coating liquid, and the double bond equivalent of the ultraviolet-curable compound is 90 g / mol or more and 140 g / mol or less.

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