Release film and adhesive tape with release film

Abstract

Provided is a non-fluorine-based release film having favorable releasability from an adhesive tape. This release film comprises a polyester film and a release layer, wherein: the polyester film contains titanium oxide; and the release layer is a cured layer of an active energy ray-curable composition that contains a compound having an alkyl group having at least 8 carbon atoms.

Description

Release film and adhesive tape with release film

[0001] The present invention relates to a release film and an adhesive tape with a release film.

[0002] Release films are used, for example, to protect the surface of adhesive tapes. Adhesive tapes are generally supplied with a release film attached, and the release film is peeled off from the adhesive tape when the adhesive tape is used.

[0003] Silicone adhesives are commonly used as adhesives for pressure-sensitive adhesive tapes, and release films made of fluorine-based release agents have been well known as release films for use in silicone pressure-sensitive adhesive tapes (see, for example, Patent Documents 1 to 3).

[0004] Japanese Patent No. 3025262 International Publication No. 2019 / 208141 Japanese Patent Application Laid-Open No. 2024-6000

[0005] However, fluorine-containing release agents are expensive in terms of material costs and have been criticized for their environmental impact. Therefore, an object of the present invention is to provide a non-fluorine-containing release film that exhibits good releasability from pressure-sensitive adhesive tape.

[0006] The above-mentioned objects of the present invention have been achieved by the following inventions. [1] A release film comprising a polyester film and a release layer, wherein the polyester film contains titanium oxide, and the release layer is a cured layer of an active energy ray-curable composition containing a compound having an alkyl group having 8 or more carbon atoms. [2] The release film according to [1], wherein the polyester film contains 1% by mass or more of titanium oxide relative to 100% by mass of the total solid content of the polyester film. [3] The release film according to [1] or [2], wherein the polyester film has a whiteness index of 75 or more. [4] The release film according to any one of [1] to [3], wherein the polyester film has an optical density of 0.5 or more. [5] The release film according to any one of [1] to [4], wherein the polyester film has a haze value of 30% or more. [6] The release film according to any one of [1] to [5], wherein the polyester film has a thermal conductivity of 0.075 W / (m·K) or more. [7] The release film according to any one of [1] to [6], wherein the arithmetic mean height Ra of the roughness curve defined in JIS B0601 on the surface of the release layer side of the polyester film is 0.07 μm or more and 0.70 μm or less. [8] The release film according to any one of [1] to [7], wherein the thickness of the polyester film is less than 100 μm. [9] The release film according to any one of [1] to [8], wherein the compound having an alkyl group having 8 or more carbon atoms has an ethylenically unsaturated group.

[10] The release film according to any one of [1] to [9], wherein the alkyl group in the compound having an alkyl group having 8 or more carbon atoms is a linear alkyl group.

[11] The release film according to any one of [1] to

[10] , wherein the active energy ray-curable composition further contains a compound having an ethylenically unsaturated group and not having an alkyl group having 8 or more carbon atoms in the molecule (hereinafter referred to as polymerizable compound (c)).

[12] The release film according to

[11] , wherein the polymerizable compound (c) contains a compound having two or more ethylenically unsaturated groups in the molecule.

[13] The release film according to

[11] or

[12] , wherein the content of the polymerizable compound (c) in the active energy ray-curable composition is 10% by mass or more and 95% by mass or less, based on 100% by mass of the total solids content of the active energy ray-curable composition.

[14] The release film according to any one of [1] to

[13] , wherein the content of the compound having an alkyl group having 8 or more carbon atoms in the active energy ray-curable composition is 1% by mass or more and 70% by mass or less, based on 100% by mass of the total solids content of the active energy ray-curable composition.

[15] The release film according to any one of

[11] to

[14] , wherein the mass ratio of the content of the polymerizable compound (c) to the content of the compound having an alkyl group having 8 or more carbon atoms in the active energy ray-curable composition (content of polymerizable compound (c) / content of the compound having an alkyl group having 8 or more carbon atoms) is 1.0 to 11.0.

[16] The release film according to any one of [1] to

[15] , wherein the surface free energy of the release layer is 17 mN / m or more and less than 40 mN / m.

[17] The release film according to any one of [1] to

[16] , wherein the surface free energy of the surface of the polyester film facing the release layer is higher than the surface free energy of the release layer.

[18] The release film according to any one of [1] to

[17] , wherein the thickness of the release layer is 50 nm or more and less than 600 nm.

[19] A pressure-sensitive adhesive tape with a release film, comprising a silicone pressure-sensitive adhesive tape having a silicone pressure-sensitive adhesive layer and the release film according to any one of [1] to

[18] bonded to the silicone pressure-sensitive adhesive layer.

[0007] According to the present invention, a non-fluorine-containing release film that exhibits good releasability from an adhesive tape can be provided.

[0008] 1 is a schematic side view showing an example of a production apparatus for a release film of the present invention.

[0009] The release film of the present invention comprises a polyester film and a release layer. The polyester film contains titanium oxide, and the release layer is a cured layer of an active energy ray-curable composition containing a compound having an alkyl group having 8 or more carbon atoms.

[0010] The combination of the polyester film containing titanium oxide and the release layer being a cured layer of an active energy ray-curable composition containing a compound having an alkyl group having 8 or more carbon atoms improves the releasability from the adhesive tape. In particular, the releasability from silicone-based adhesive tapes is improved. Hereinafter, the releasability between the adhesive tape and the release film will be simply referred to as "releasability."

[0011] Although the mechanism by which the release film of the present invention has improved releasability is not clear, it is presumed that the inclusion of titanium oxide in the polyester film increases the thermal conductivity, which contributes to the improved releasability of the release layer comprising a cured layer of an active energy ray-curable composition containing a compound having an alkyl group having 8 or more carbon atoms. Details will be described later.

[0012] [Polyester Film] Polyester is a general term for polymer compounds having ester bonds as the main bonds in the main chain, and can usually be obtained by polycondensation reaction of a dicarboxylic acid component and a diol component.

[0013] Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid, etc. Examples of the diol component include ethylene glycol, trimethylene glycol, tetramethylene glycol, 1,4-butanediol, cyclohexanedimethanol, etc.

[0014] Specific examples of polyesters include polymethylene terephthalate, polyethylene terephthalate, polytetramethylene terephthalate, polybutylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene naphthalate (polyethylene-2,6-naphthalenedicarboxylate), etc. Among these, polyethylene terephthalate and polyethylene naphthalate are preferred, with polyethylene terephthalate being particularly preferred.

[0015] The polyester film of the present invention preferably does not substantially contain thermoplastic resins other than polyester, such as polyolefins such as polyethylene, polypropylene, polymethylpentene, and polymethylbutene, polystyrene, polycarbonate, and polyphenylene sulfide. Here, "substantially not containing thermoplastic resins other than polyester" means that the content of thermoplastic resins other than polyester is less than 5 parts by mass per 100 parts by mass of polyester. The content of thermoplastic resins other than polyester is preferably less than 4 parts by mass, more preferably less than 3 parts by mass, even more preferably less than 1 part by mass, and particularly preferably 0 part by mass per 100 parts by mass of polyester.

[0016] If the polyester film contains a thermoplastic resin other than polyester, fine bubbles may be formed in the polyester film, which may reduce the thermal conductivity.

[0017] From the viewpoint of ensuring good thermal conductivity, the polyester film in the present invention preferably does not contain microbubbles.

[0018] The means for incorporating titanium oxide into the polyester composition is not particularly limited, and titanium oxide may be added during the polymerization process of the polyester composition, or pellets of the polyester composition and titanium oxide may be kneaded together. Kneading is preferred for dispersing titanium oxide at a high concentration.

[0019] The polyester film may be any of an unstretched film, a uniaxially stretched film, and a biaxially stretched film, but a biaxially stretched film is preferred from the viewpoints of heat resistance, dimensional stability, etc. That is, the polyester film is particularly preferably a biaxially stretched polyethylene terephthalate film.

[0020] Titanium dioxide is preferred as the titanium oxide contained in the polyester film. Rutile, anatase, and brookite types of titanium dioxide are known, and any of them can be used. Among them, rutile titanium dioxide is preferred from the viewpoint of excellent whiteness and light-shielding properties.

[0021] The average particle size of titanium oxide is preferably 0.05 μm or more, more preferably 0.07 μm or more, and particularly preferably 0.1 μm or more, and the upper limit is preferably 5 μm or less, more preferably 3 μm or less, and particularly preferably 2 μm or less.

[0022] The content of titanium oxide is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and particularly preferably 10% by mass or more, relative to 100% by mass of the total solid content of the polyester film, from the viewpoint of improving thermal conductivity, while from the viewpoint of film strength and film formability, it is preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, and particularly preferably 20% by mass or less.

[0023] The thermal conductivity of the polyester film is preferably 0.075 W / (m K) or more, more preferably 0.080 W / (m K) or more, even more preferably 0.083 W / (m K) or more, and particularly preferably 0.085 W / (m K) or more. The upper limit is preferably 0.3 W / (m K) or less.

[0024] Conventionally, release paper made of paper has generally been used for pressure-sensitive adhesive tapes. When the release film of the present invention is used as a substitute for this release paper, from the viewpoint of achieving a texture similar to that of the release paper, the whiteness of the polyester film is preferably 75 or more, more preferably 80 or more, and particularly preferably 85 or more. Moreover, the whiteness is preferably 110 or less, more preferably 105 or less, and particularly preferably 100 or less.

[0025] From the same viewpoint as above, it is preferable that the polyester film has a relatively high light-shielding property. The light-shielding property can be expressed by optical density. That is, the optical density of the polyester film is preferably 0.5 or more, more preferably 0.6 or more, and particularly preferably 0.7 or more. Moreover, the optical density is preferably 1.1 or less, more preferably 1.0 or less, and particularly preferably 0.95 or less.

[0026] From the same viewpoint as above, the haze value of the polyester film is preferably 30% or more, more preferably 50% or more, even more preferably 80% or more, and particularly preferably 90% or more, with the upper limit being 100%.

[0027] The above-mentioned whiteness, optical density and haze value can be obtained by adjusting the content of titanium oxide within the above-mentioned ranges.

[0028] The surface free energy of the release layer side of the polyester film, i.e., the surface on which the release layer is formed of the polyester film, is preferably greater than the surface free energy of the release layer described below, from the viewpoints of adhesion to the release layer and coatability of the release layer. For example, the difference in surface free energy between the polyester film and the release layer is preferably 5 mN / m or more, more preferably 10 mN / m or more, even more preferably 15 mN / m or more, and particularly preferably 20 mN / m or more. The upper limit is preferably 40 mN / m or less.

[0029] The surface free energy of the polyester film is preferably 40 mN / m or more, more preferably 43 mN / m or more, and particularly preferably 45 mN / m or more. The upper limit is preferably 60 mN / m or less. Here, the surface free energy can be measured using a contact angle meter, for example, "Drop Master DM501" manufactured by Kyowa Interface Science Co., Ltd. Details will be described later.

[0030] In addition, from the viewpoint of the adhesion between the polyester film and the release layer and the coatability of the release layer, the arithmetic mean height Ra of the roughness curve of the surface of the polyester film on the release layer side is preferably 0.07 μm or more, more preferably 0.10 μm or more, and particularly preferably 0.15 μm or more. Moreover, the Ra is preferably 0.70 μm or less, more preferably 0.50 μm or less, and particularly preferably 0.40 μm or less. The method for measuring the Ra will be described later.

[0031] The thickness of the polyester film is preferably less than 100 μm, more preferably less than 80 μm, and particularly preferably less than 60 μm from the viewpoint of thermal conductivity, while it is preferably 20 μm or more, more preferably 25 μm or more, and particularly preferably 35 μm or more from the viewpoint of processability and handleability of the release film.

[0032] The polyester film may have an easy-adhesion layer for improving adhesion with the release layer. When the easy-adhesion layer is provided on the polyester film, as described above, the thickness thereof is preferably an extremely thin film so as not to inhibit the thermal conductivity effect of the polyester film containing titanium oxide. From this viewpoint, the thickness of the easy-adhesion layer is preferably 500 nm or less, more preferably 350 nm or less, even more preferably 200 nm or less, and particularly preferably 150 nm or less. The lower limit of the thickness is preferably 10 nm or more.

[0033] As the polyester film containing titanium oxide, commercially available products can be used, such as "Lumirror (registered trademark)" models E20, E22, E28G, and E315 from Toray Industries, Inc.

[0034] [Release Layer] The release layer is a cured layer of an active energy ray-curable composition containing a compound having an alkyl group having 8 or more carbon atoms. Here, the cured layer of the active energy ray-curable composition refers to a layer cured by irradiation with active energy rays.

[0035] Specifically, it is a layer obtained by irradiating an active energy ray-curable composition coated on a polyester film with active energy rays and curing the composition. Examples of active energy rays include ultraviolet rays, visible light, infrared rays, electron beams, α rays, β rays, and γ rays. Among these, ultraviolet rays and electron beams are preferred, and ultraviolet rays are particularly preferred.

[0036] Hereinafter, an alkyl group having 8 or more carbon atoms may be referred to as a "long-chain alkyl group," and a compound having an alkyl group having 8 or more carbon atoms may be referred to as a "long-chain alkyl compound." The long-chain alkyl group preferably has 10 or more carbon atoms, more preferably 12 or more carbon atoms, and particularly preferably 14 or more carbon atoms. The long-chain alkyl group preferably has 30 or less carbon atoms, more preferably 28 or less carbon atoms, even more preferably 25 or less carbon atoms, and particularly preferably 23 or less carbon atoms. The long-chain alkyl group may be a linear alkyl group or a branched alkyl group, but is preferably a linear alkyl group. A linear alkyl group having 8 or more carbon atoms is more likely to orient and crystallize on the surface of the release layer than a branched alkyl group, thereby improving the releasability of the release layer.

[0037] The active energy ray-curable composition contains a compound that polymerizes and cures when exposed to active energy rays (hereinafter, sometimes referred to as a "polymerizable compound"). Examples of such polymerizable compounds include compounds (monomers and oligomers) having at least one ethylenically unsaturated group in the molecule. Preferred examples of the ethylenically unsaturated group include an acryloyl group, a methacryloyl group, an acryloyloxy group, a methacryloyloxy group, an allyl group, and a vinyl group.

[0038] The long-chain alkyl compound may or may not be a polymerizable compound, but is preferably a polymerizable compound. That is, the long-chain alkyl compound is preferably a compound containing a long-chain alkyl group and an ethylenically unsaturated group in the molecule. Hereinafter, a compound containing a long-chain alkyl group and an ethylenically unsaturated group in the molecule may be referred to as a "polymerizable long-chain alkyl compound (a)." Furthermore, a long-chain alkyl compound that is not a polymerizable compound may be referred to as a "non-polymerizable long-chain alkyl compound (b)." Examples of such non-polymerizable long-chain alkyl compounds (b) that can be preferably used include long-chain alkyl group-containing polyvinyl resins, long-chain alkyl group-containing acrylic resins, long-chain alkyl group-containing polyester resins, long-chain alkyl group-containing alkyd resins, long-chain alkyl group-containing ether compounds, and long-chain alkyl group-containing amine compounds.

[0039] It is preferable that the active energy ray-curable composition further contains a compound that does not have an alkyl group having 8 or more carbon atoms (long-chain alkyl group) in the molecule and has an ethylenically unsaturated group (hereinafter, may be referred to as “polymerizable compound (c)”).

[0040] When the active energy ray-curable composition contains only the non-polymerizable long-chain alkyl compound (b) as the long-chain alkyl compound, it preferably contains a polymerizable compound (c). The polymerizable compound (c) will be described in detail later.

[0041] In the present invention, preferred active energy ray-curable compositions include, for example, the following compositions: (I) a composition containing a polymerizable long-chain alkyl compound (a), (II) a composition containing a polymerizable long-chain alkyl compound (a) and a non-polymerizable long-chain alkyl compound (b), (III) a composition containing a polymerizable long-chain alkyl compound (a) and a polymerizable compound (c), (IV) a composition containing a non-polymerizable long-chain alkyl compound (b) and a polymerizable compound (c), and (V) a composition containing a polymerizable long-chain alkyl compound (a), a non-polymerizable long-chain alkyl compound (b), and a polymerizable compound (c).

[0042] Among the above compositions, (III), (IV) and (V) are preferred, and (III) is particularly preferred. That is, it is particularly preferred that the active energy ray-curable composition contains at least the polymerizable long-chain alkyl compound (a) and the polymerizable compound (c).

[0043] Examples of the polymerizable long-chain alkyl compound (a) are shown below, but the present invention is not limited to these. In the following description, "(meth)acrylate" is a general term for "acrylate" and "methacrylate," and "(meth)acryloyl" is a general term for "acryloyl group" and "methacryloyl."

[0044] Examples of the polymerizable long-chain alkyl compound (a) include octyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

[0045] In particular, the following polymerizable long-chain alkyl compound (a) is preferably used: For example, a compound obtained by reacting a (meth)acrylate compound (d) having one or more (meth)acryloyl groups and one or more hydroxyl groups in the molecule, a polyisocyanate compound (e) having two or more isocyanate groups in the molecule, and a higher alcohol (f) having 8 or more carbon atoms.

[0046] Examples of the (meth)acrylate compound (d) include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycerin mono(meth)acrylate, glycerin di(meth)acrylate, 2-hydroxy-3-acryloyloxypropyl methacrylate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, 2-(meth)acryloyloxyethyl acid phosphate, and epoxy compounds. Examples of the alkyleneoxy group include di(meth)acrylate, pentaerythritol mono(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol mono(meth)acrylate, dipentaerythritol di(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and (meth)acrylates having 2 to 30 alkyleneoxy groups (e.g., ethyleneoxy groups, propyleneoxy groups, butyleneoxy groups, etc.) in the molecule.

[0047] Among the above (meth)acrylate compounds (d), 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and (meth)acrylates having 2 to 30 alkyleneoxy groups in the molecule are preferably used from the viewpoint of releasability.

[0048] Examples of the polyisocyanate compound (e) include known diisocyanate compounds such as hexamethylene diisocyanate, lysine diisocyanate, naphthalene diisocyanate, diphenylmethane diisocyanate, tolidine diisocyanate, tolylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and hydrogenated xylylene diisocyanate, as well as biuret polyisocyanate compounds obtained by reacting these various diisocyanate compounds with water, adduct polyisocyanate compounds obtained by reacting various diisocyanate compounds with polyhydric alcohols such as trimethylolpropane, and polymers obtained by isocyanurating various compounds.

[0049] Among the polyisocyanate compounds (e), compounds having a molecular weight of 50 to 500 are preferred, compounds having a molecular weight of 100 to 400 are more preferred, and compounds having a molecular weight of 130 to 300 are particularly preferred. For example, hexamethylene diisocyanate (molecular weight 168) and diphenylmethane diisocyanate (molecular weight 250) are exemplified as preferred compounds. Further, compounds having an arylene group, such as naphthalene diisocyanate and diphenylmethane diisocyanate, are also preferred.

[0050] Examples of the higher alcohol (f) include linear higher alcohols such as octyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, cetanol, cetostearyl alcohol, stearyl alcohol, and behenyl alcohol; linear unsaturated higher alcohols such as oleyl alcohol; and branched higher alcohols such as 2-hexyldecanol, 2-octyldodecanol, and 2-decyltetradodecanol.

[0051] Commercially available products can be used as the higher alcohol (f). For example, examples of linear saturated higher alcohols include "Conol (registered trademark)" 10WS, "Conol (registered trademark)" 1098, "Conol (registered trademark)" 1275, "Conol (registered trademark)" 20F, "Conol (registered trademark)" 20P, "Conol (registered trademark)" 1495, "Conol (registered trademark)" 1670, "Conol (registered trademark)" 1695, "Conol (registered trademark)" 30CK, "Conol (registered trademark)" 30OC, "Conol (registered trademark)" 30RC, "Conol (registered trademark)" 30F, and "Conol (registered trademark)" 30S. , "Conol (registered trademark)" 30SS, "Conol (registered trademark)" 30T, "Conol (registered trademark)" 2265, "Conol (registered trademark)" 2280 (trade names of New Japan Chemical Co., Ltd.), "Kalcol (registered trademark)" 0898, "Kalcol (registered trademark)" 0880, "Kalcol (registered trademark)" 1098, "Kalcol (registered trademark)" 2098, "Kalcol (registered trademark)" 4098, "Kalcol (registered trademark)" 6098, "Kalcol (registered trademark)" 8098, "Kalcol (registered trademark)" 200GD, "Kalcol (registered trademark) "Kalcol (registered trademark)" 2475, "Kalcol (registered trademark)" 2474, "Kalcol (registered trademark)" 2473, "Kalcol (registered trademark)" 2463, "Kalcol (registered trademark)" 2455, "Kalcol (registered trademark)" 2450, "Kalcol (registered trademark)" 4250, "Kalcol (registered trademark)" 6870, "Kalcol (registered trademark)" 6850, "Kalcol (registered trademark)" 8688, "Kalcol (registered trademark)" 8665, "Kalcol (registered trademark)" 220-80 (trade names of Kao Corporation), and linear unsaturated higher alcohols include "Rika Coal (registered trademark) 60B, Rikacol (registered trademark) 70B, Rikacol (registered trademark) 75BJ, Rikacol (registered trademark) 85BJ, Rikacol (registered trademark) 90B, Rikacol (registered trademark) 90BR, Rikacol (registered trademark) 90BHR, Rikacol (registered trademark) 110BJ, Angecol (registered trademark) 50A, Angecol (registered trademark) 60AN, Angecol (registered trademark) 70AN, Angecol (registered trademark) 80AN, Angecol (registered trademark) 85AN,Examples of branched higher alcohols include "N-Jecol (registered trademark)" 90AN, "N-Jecol (registered trademark)" 90NR, and "N-Jecol (registered trademark)" 90NHR (trade names of New Japan Chemical Co., Ltd.). Examples of branched higher alcohols include "N-Jecol (registered trademark)" 160BR, "N-Jecol (registered trademark)" 200A, and "N-Jecol (registered trademark)" 240A (trade names of New Japan Chemical Co., Ltd.). The carbon number of the long-chain alkyl group contained in the higher alcohol (f) having 8 or more carbon atoms is preferably 10 or more, more preferably 12 or more, and particularly preferably 14 or more. The carbon number is preferably 30 or less, more preferably 28 or less, even more preferably 25 or less, and particularly preferably 23 or less. The long-chain alkyl group may be a linear alkyl group or a branched alkyl group, but is preferably a linear alkyl group.

[0052] Examples of the polymerizable compound (c) include methyl (meth)acrylate, ethyl diethylene glycol (meth)acrylate, ethoxy diethylene glycol (meth)acrylate, methoxy triethylene glycol (meth)acrylate, ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerin propoxy tri(meth)acrylate, (meth)acrylate, pentaerythritol mono(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol mono(meth)acrylate, dipentaerythritol di(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, Examples of the urethane copolymer include dipentaerythritol hexa(meth)acrylate, tripentaerythritol tri(meth)acrylate, tripentaerythritol hexa(meth)acrylate, pentaerythritol tri(meth)acrylate hexamethylene diisocyanate urethane pre-oligomer, pentaerythritol tri(meth)acrylate-toluene diisocyanate urethane oligomer, and pentaerythritol tri(meth)acrylate-isophorone diisocyanate urethane oligomer.

[0053] The polymerizable compound (c) preferably contains at least the following compounds. The compound is preferably a compound having two or more ethylenically unsaturated groups in the molecule, more preferably a compound having three or more ethylenically unsaturated groups, even more preferably a compound having four or more ethylenically unsaturated groups, and particularly preferably a compound having five or more ethylenically unsaturated groups. The number of ethylenically unsaturated groups contained in one molecule is preferably 10 or less, more preferably 7 or less, and particularly preferably 6 or less.

[0054] Furthermore, the polymerizable compound (c) preferably includes a compound having a theoretical number-average molecular weight of 400 or more but less than 1,000 and 5 to 6 ethylenically unsaturated groups. Representative examples of this compound include, but are not limited to, dipentaerythritol penta(meth)acrylate and dipentaerythritol hexa(meth)acrylate. Here, the theoretical number-average molecular weight is calculated from the molecular formula structure. For commercially available products, the theoretical number-average molecular weight is the number-average molecular weight listed in a catalog or the like, or is calculated from the listed molecular formula structure.

[0055] From the viewpoint of improving releasability, the content of the long-chain alkyl compound in the active energy ray-curable composition (the total amount of the polymerizable long-chain alkyl compound (a) and the non-polymerizable long-chain alkyl compound (b)) is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 7% by mass or more, and particularly preferably 10% by mass or more, relative to 100% by mass of the total solids content of the active energy ray-curable composition. On the other hand, if the content of the long-chain alkyl compound is too high, the strength (hardness) of the release layer may decrease, and the solvent resistance and heat resistance may also decrease. Therefore, the content of the long-chain alkyl compound is preferably 70% by mass or less, more preferably 50% by mass or less, even more preferably 35% by mass or less, and particularly preferably 30% by mass or less.

[0056] From the viewpoint of increasing the strength (hardness) of the release layer, the content of the polymerizable compound (c) in the active energy ray-curable composition is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and particularly preferably 50% by mass or more, relative to 100% by mass of the total solid content of the active energy ray-curable composition. On the other hand, from the viewpoint of ensuring good releasability, the content of the polymerizable compound (c) is preferably 95% by mass or less, more preferably 90% by mass or less, even more preferably 85% by mass or less, and particularly preferably 80% by mass or less.

[0057] The mass ratio of the content of the polymerizable compound (c) to the content of the long-chain alkyl compound in the active energy ray-curable composition (content of polymerizable compound (c) / content of long-chain alkyl compound) is preferably 1.0 or more, more preferably 1.5 or more, even more preferably 2.0 or more, and particularly preferably 2.5 or more. This mass ratio is preferably 11.0 or less, more preferably 10.0 or less, even more preferably 9.0 or less, and particularly preferably 7.0 or less. By containing the long-chain alkyl compound and the polymerizable compound (c) at such a ratio, the strength of the release layer and good releasability can be achieved. From the viewpoint of improving releasability, the total content of the long-chain alkyl compound and the polymerizable compound (c) is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more, relative to 100% by mass of the total solids content of the active energy ray-curable composition. The content is preferably 100% by mass or less, more preferably 98% by mass or less, and particularly preferably 95% by mass or less.

[0058] The active energy ray-curable composition preferably further contains a photopolymerization initiator. Specific examples of such photopolymerization initiators include carbonyl compounds such as acetophenone, 2,2-diethoxyacetophenone, p-dimethylacetophenone, p-dimethylaminopropiophenone, benzophenone, 2-chlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bisdiethylaminobenzophenone, Michler's ketone, benzil, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, methylbenzoyl formate, p-isopropyl-α-hydroxyisobutylphenone, α-hydroxyisobutylphenone, 2,2-dimethoxy-2-phenylacetophenone, and 1-hydroxycyclohexyl phenyl ketone; and sulfur compounds such as tetramethylthiuram monosulfide, tetramethylthiuram disulfide, thioxanthone, 2-chlorothioxanthone, and 2-methylthioxanthone. These photopolymerization initiators may be used alone or in combination of two or more.

[0059] The photopolymerization initiator is generally commercially available, and these can be used. For example, "Irgacure (registered trademark)" 184, "Irgacure (registered trademark)" 907, "Irgacure (registered trademark)" 379, "Irgacure (registered trademark)" 819, "Irgacure (registered trademark)" 127, "Irgacure (registered trademark)" 500, "Irgacure (registered trademark)" 754, "Irgacure (registered trademark)" 250, "Irgacure (registered trademark)" 1800, "Irgacure (registered trademark)" 1870, "Irgacure (registered trademark)" OXE01, and "DAROCUR (registered trademark)" manufactured by Ciba Specialty Chemicals Co., Ltd. TPO, "DAROCUR (registered trademark)" 1173, etc., manufactured by Nippon SiberHegner Co., Ltd., "Speedcure (registered trademark)" MBB, "Speedcure (registered trademark)" PBZ, "Speedcure (registered trademark)" ITX, "Speedcure (registered trademark)" CTX, "Speedcure (registered trademark)" EDB, "Esacure (registered trademark)" ONE, "Esacure (registered trademark)" KIP150, "Esacure (registered trademark)" KTO46, etc., manufactured by Nippon Kayaku Co., Ltd., "KAYACURE (registered trademark)" DETX-S, "KAYACURE (registered trademark)" CTX, "KAYACURE (registered trademark)" BMS, "KAYACURE (registered trademark)" DMBI and the like.

[0060] The content of the photopolymerization initiator is preferably 0.1% by mass or more, and more preferably 0.5% by mass or more, relative to 100% by mass of the total solid content of the active energy ray-curable composition, and the upper limit is preferably 15% by mass or less, more preferably 10% by mass or less, and particularly preferably 8% by mass or less.

[0061] It is most preferable that the release layer does not contain a fluorine-based compound. In other words, it is most preferable that the active energy ray-curable composition does not contain a fluorine-based compound. Even when a fluorine-based compound is contained, the content thereof is preferably 3% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less, relative to 100% by mass of the total solid content of the active energy ray-curable composition.

[0062] In addition, from the viewpoint of releasability from a silicone-based pressure-sensitive adhesive tape, it is preferable that the release layer does not substantially contain a conventionally known silicone-based release agent. Here, "substantially does not contain" means that the content is 3% by mass or less relative to 100% by mass of the total solid content of the active energy ray-curable composition. The content is preferably 2% by mass or less, more preferably 1% by mass or less, and most preferably 0% by mass.

[0063] From the viewpoint of releasability, it is preferable that the surface free energy of the release layer is small. The surface free energy of the release layer is preferably less than 40 mN / m, more preferably less than 35 mN / m, even more preferably less than 30 mN / m, and particularly preferably less than 27 mN / m. The lower limit is preferably 17 mN / m or more. The method for measuring the surface free energy of the release layer will be described later.

[0064] From the viewpoint of releasability, the thickness of the release layer is preferably 50 nm or more, more preferably 80 nm or more, even more preferably 100 nm or more, and particularly preferably 150 nm or more, while from the viewpoints of production efficiency and processability, the thickness is preferably less than 600 nm, more preferably less than 500 nm, even more preferably less than 400 nm, and particularly preferably less than 350 nm.

[0065] In the release film of the present invention, it is preferable that no layer, such as a printed layer such as a logo, a decorative layer, or a concealing layer, is interposed between the titanium oxide-containing polyester film and the release layer. Such layers generally have a thickness of more than 500 nm, and if such a layer is present, as described above, the thermal conductivity effect of the titanium oxide-containing polyester film is inhibited, and the releasability may not be sufficiently improved.

[0066] On the other hand, as described above, the titanium oxide-containing polyester film may have an easy-adhesion layer having a thickness of 500 nm or less, and a release layer may be laminated on the easy-adhesion layer. As described above, the smaller the thickness of the easy-adhesion layer, the more preferable it is.

[0067] In the release film of the present invention, it is most preferable that the release layer is laminated directly on the titanium oxide-containing polyester film without any other layer interposed therebetween.

[0068] [Method for producing release film] The release film of the present invention is preferably obtained, for example, by applying an active energy ray-curable composition to a polyester film containing titanium oxide, drying the composition, and irradiating the composition with active energy rays to cure the composition, thereby forming a release layer.

[0069] That is, the method for producing a release film of the present invention includes, in this order, a step of applying an active energy ray-curable composition containing a compound having an alkyl group having 8 or more carbon atoms onto a polyester film containing titanium oxide, a step of drying the composition, and a step of irradiating the composition with active energy rays to cure the composition.

[0070] Preferred examples of the coating method include reverse coating, spray coating, bar coating, gravure coating, rod coating, die coating, spin coating, extrusion coating, and curtain coating.

[0071] As for the active energy rays, as described in the description of the release layer, ultraviolet rays are most preferable.

[0072] The light source for irradiating ultraviolet light is not particularly limited, and examples thereof include ultraviolet fluorescent lamps, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, carbon arc lamps, metal halide lamps, and xenon lamps. ArF excimer lasers, KrF excimer lasers, excimer lamps, and synchrotron radiation may also be used. Among these, ultra-high-pressure mercury lamps, high-pressure mercury lamps, low-pressure mercury lamps, carbon arc lamps, xenon arc lamps, and metal halide lamps are preferably used. Furthermore, when irradiating ultraviolet light, it is preferable to perform irradiation in an atmosphere with a low oxygen concentration, for example, an atmosphere with an oxygen concentration of 500 ppm or less, since this allows for efficient curing.

[0073] The ultraviolet light intensity was 50 mJ / cm ２ More than 100 mJ / cm is preferable. ２More preferably, 150 mJ / cm or more is particularly preferable. ２ The irradiation dose of ultraviolet light is preferably 2000 mJ / cm or more. ２ Preferably, 1000 mJ / cm or less ２ The following is more preferred:

[0074] When a composition is irradiated with active energy rays, the temperature of the composition rises due to the heat of reaction or the heat of the light source. When the temperature of a cured layer of an active energy ray-curable composition containing a compound having an alkyl group having 8 or more carbon atoms rises during curing, it becomes difficult for the alkyl group having 8 or more carbon atoms to be oriented on the surface of the cured layer (release layer), and this is presumed to hinder improvement in releasability.

[0075] Therefore, it is speculated that by using a polyester film containing titanium oxide as the substrate of the release film, the thermal conductivity is higher than that of conventional substrates, making it easier for the heat of the composition to diffuse through the substrate, suppressing the temperature rise of the composition, and as a result, achieving good releasability.

[0076] Furthermore, in the production of ultraviolet-curable resin coatings such as hard coat layers, in order to suppress temperature rise during ultraviolet irradiation, for example, a cooling function or temperature control function is added to the conveying roller of the ultraviolet irradiation device. For example, see JP-B No. 62-25429, Japanese Patent No. 2523574, Japanese Patent No. 4360396, and Japanese Patent Laid-Open No. 2005-255957. Such ultraviolet irradiation devices can also be applied to the production of the release film of the present invention.

[0077] By using the ultraviolet irradiation device described above, since the polyester film containing titanium oxide has a relatively high thermal conductivity, the cooling or temperature control effect from the conveying rollers is easily transmitted to the composition, and an effect of suppressing the temperature rise of the composition can be expected.

[0078] An example of an apparatus for producing the release film of the present invention is shown in Figure 1. However, the present invention is not limited to this.

[0079] The polyester film 10 is unwound from the unwinding device 20 and conveyed, and an active energy ray-curable composition (not shown) is applied to the polyester film 10 by the coating device 30. The solvent in the composition is evaporated and dried in the drying device 40 to form a release layer precursor (not shown) on the polyester film 10. This release layer precursor is irradiated with ultraviolet light by the ultraviolet irradiation device 50 and cured to form a release layer, becoming the release film 11, which is then wound into a roll by the winding device 60.

[0080] In the ultraviolet irradiation device 50, the polyester film 10 on which the release layer precursor has been formed is wound around a transport roller 51 and transported while being irradiated with ultraviolet rays from an ultraviolet generator 52. The transport roller is of a water-cooled type or a type that is temperature-controlled to 20 to 50°C.

[0081] [Adhesive Tape with Release Film] The release film of the present invention is preferably applied to an adhesive tape. In particular, it is preferably applied to a silicone-based adhesive tape. That is, an adhesive tape with a release film is preferred, in which the release film of the present invention is bonded to the silicone adhesive layer of a silicone adhesive tape having a silicone adhesive layer.

[0082] The release film of the present invention has good releasability from a silicone pressure-sensitive adhesive tape. For example, the peel strength between the silicone pressure-sensitive adhesive tape and the release film is preferably less than 1.7 N / 50 mm, more preferably less than 1.2 N / 50 mm, even more preferably less than 1.0 N / 50 mm, and particularly preferably less than 0.8 N / 50 mm. The lower limit of the peel strength is preferably 0.1 N / 50 mm or more. The above peel strength is the peel strength when "Kapton (registered trademark)" tape No. 650S #25 manufactured by Teraoka Seisakusho Co., Ltd. is used as the silicone pressure-sensitive adhesive tape. Details of the measurement method will be shown in the examples below.

[0083] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0084] [Measurement and Evaluation Methods] (1) Measurement of Surface Free Energy of Release Layer and Polyester Film Using water, diiodomethane, and 1-bromonaphthalene as three types of liquids whose surface free energy and the values ​​of its components (dispersion force, polar force, and hydrogen bonding force) are known, the contact angle of each liquid on the release layer (or polyester film) was measured at 23°C and 65% RH using a contact angle meter DropMaster DM501 (manufactured by Kyowa Interface Science Co., Ltd.). Five measurements were taken for one measurement surface, and the average value was taken as the contact angle (θ). From this contact angle (θ) value and the known values ​​for each liquid (Panzer's Method IV (described in the Journal of the Japan Adhesion Association, Vol. 15, No. 3, p. 96)), the values ​​for each component were calculated using the following formula, derived from the Kitazaki-Hata formula: (γSd γLd)1 / 2 + (γSp γLp)1 / 2 + (γSh γLh)1 / 2 = γL(1 + cos θ) / 2.

[0085] Here, γLd, γLp, and γLh respectively represent the dispersion force, polar force, and hydrogen bonding force components of the test liquid, θ represents the contact angle of the test liquid on the test surface, γSd, γSp, and γSh respectively represent the dispersion force, polar force, and hydrogen bonding force components of the layer surface, and γL represents the surface energy of each liquid. The values ​​of the three components of the test surface (release layer surface) were determined by solving the simultaneous equations obtained by substituting the known values ​​and θ into the above formula.

[0086] The surface free energy (E) was calculated by adding the calculated dispersion force component, polar force component, and hydrogen bonding force component values ​​according to the following formula: E = γSd + γSp + γSh.

[0087] (2) Measurement of Release Layer Thickness A sample for cross-sectional observation of a release film was prepared by the FIB method using a microsampling system (Hitachi FB-2000A) (specifically, based on the method described in "Polymer Surface Processing Science" (by Akira Iwamori, published June 2005), pp. 118-119). The cross section of the sample for cross-sectional observation was observed using a transmission electron microscope (Hitachi H-9000UHRII) at an acceleration voltage of 300 kV, and the thickness of the release layer was measured. Measurements were taken at three points and averaged.

[0088] (3) Measurement of Thickness of Polyester Film The polyester film was cut into an A4 size sample, and the thickness was measured at any three points within the cut sample using a micrometer according to the micrometer method specified in JIS C2151 (2019). The average value of the obtained values ​​was taken as the thickness of the polyester film.

[0089] (4) Measurement of Thermal Conductivity of Polyester Film Polyester film was cut into a size of 20 mm x 20 mm to prepare a measurement sample, and measured using a thermal conductivity measuring device TCM1001 (manufactured by Rhesca Co., Ltd.) according to the unidirectional heat flow steady-state method under the following measurement conditions. Three measurements were taken and averaged. High temperature side: 80°C Low temperature side: 20°C Load: 800 N (5) Measurement of Whiteness of Polyester Film Whiteness was measured using a colorimetric color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., ZE2000) with standard illuminant C according to the Hunter method described in JIS Z 8722 (2000) and JIS L 1015 (2010). Values ​​expressed in the Lab color system were used to calculate using the following formula. Three measurements were taken and averaged. 100 - [(100 - L) ２ +a ２ +b ２ ] １／２ = Whiteness (%).

[0090] (6) Measurement of Optical Density of Polyester Film According to ISO 5-2, an optical densitometer (XRite 361T, manufactured by Nippon Heiban Kikai) was used to irradiate a sample with a perpendicular transmitted light beam, and the ratio to the state without the sample, expressed in log (logarithm), was taken as the optical density. The light beam width was a circle with a diameter of 1 mm or wider. Three points were measured and averaged.

[0091] (7) Measurement of Haze Value of Polyester Film The haze value was measured according to JIS K 7136 (2000) using a turbidity meter “NDH-4000” manufactured by Nippon Denshoku Industries Co., Ltd. Measurements were taken at three points and the average was calculated.

[0092] (8) Measurement of the arithmetic mean height Ra of the roughness profile of a polyester film. Measurement was carried out in accordance with JIS B0601 (2001) and ISO 4278 (1997) using a Surfcom SE500A manufactured by Kosaka Laboratory under the following conditions. Measurements were taken at three points and averaged. <Measurement conditions> - Needle radius: 2 μm - Cutoff: 0.8 mm - Measurement speed: 0.5 mm / sec - Measurement length: 4 mm.

[0093] (9) Evaluation of releasability The release film was cut into a size of 50 mm wide x 70 mm long to prepare a measurement sample. A silicone adhesive tape (Kapton Tape No. 650S #25 manufactured by Teraoka Seisakusho Co., Ltd.) was attached to the release layer surface of this measurement sample by pressing it back and forth with a rubber roller having a weight of 5 kg. After leaving it at room temperature (23±2°C) for 24 hours, the peel force was measured using a tensile tester when the adhesive tape side was peeled off at an angle of 180° at a speed of 300 mm / min. Five measurement samples were prepared, and the peel force was measured for each measurement sample and averaged. The smaller the peel force (N / 50 mm), the better the releasability.

[0094] [Polyester Film] <Polyester Film 1> A 50 μm-thick "Lumirror (registered trademark)" E20 manufactured by Toray Industries, Inc. was used as a titanium oxide-containing polyester film (polyethylene terephthalate film). This polyester film contained 16% by mass of titanium oxide. The polyester film had a whiteness of 93, an optical density of 0.90, a haze value of 99.6%, a surface free energy of 48 mN / m, an arithmetic mean height Ra of 0.21 μm, and a thermal conductivity of 0.090 W / (m·K).

[0095] <Polyester film 2> A 50 μm thick "Lumirror (registered trademark)" T60 manufactured by Toray Industries, Inc. was used as a titanium oxide-free polyester film (polyethylene terephthalate film). This polyester film had a haze value of 1.8%, a surface free energy of 44 mN / m, an arithmetic mean height Ra of 0.05 μm, and a thermal conductivity of 0.074 W / (m·K). Because this polyester film 2 is a transparent film that does not contain titanium oxide, the whiteness and optical density were not measured.

[0096] [Release Layer-Forming Composition] <Active Energy Ray-Curable Composition p1> 25 parts by mass of the polymerizable long-chain alkyl compound (a1) synthesized below, 75 parts by mass of dipentaerythritol hexaacrylate (trade name "DPHA" manufactured by Daicel Cytec Co., Ltd.) as the polymerizable compound (c), and 10 parts by mass of a photopolymerization initiator ("Irgacure" (registered trademark) 184 manufactured by Ciba Specialty Chemicals Co., Ltd.) were charged, heated to 100°C, and mixed for 1 hour. Further, a mixed solvent of toluene and isopropyl alcohol (IPA) (toluene:IPA = 3:1 (mass ratio)) was added so that the solids concentration became 4% by mass.

[0097] (Synthesis of Polymerizable Long-Chain Alkyl Compound (a1)) A flask equipped with a stirrer and a thermometer was charged with 100 parts by mass of 2-hydroxyethyl acrylate ("BHEA" manufactured by Nippon Shokubai Co., Ltd.) as a (meth)acrylate compound (d) having a hydroxyl group, 240 parts by mass of diphenylmethane diisocyanate ("Millionate" (registered trademark) MT manufactured by Nippon Polyurethane Co., Ltd.) as a polyisocyanate compound (e), and 25 parts by mass of hexadecanol ("1-Hexadecanol" manufactured by Tokyo Chemical Industry Co., Ltd.) as a higher alcohol (f), and the mixture was heated to 100°C and kept at that temperature for 7 hours to react. The reaction was terminated when it was confirmed by IR measurement that the isocyanate groups had disappeared.

[0098] <Active energy ray-curable composition p2> 25 parts by mass of the polymerizable long-chain alkyl compound (a2) synthesized as described below, 75 parts by mass of dipentaerythritol hexaacrylate (trade name "DPHA" manufactured by Daicel Cytec Co., Ltd.) as the polymerizable compound (c), and 10 parts by mass of a photopolymerization initiator ("Irgacure" (registered trademark) 184 manufactured by Ciba Specialty Chemicals Co., Ltd.) were charged, heated to 100°C, and mixed for 1 hour. Further, a mixed solvent of toluene and isopropyl alcohol (IPA) (toluene:IPA = 3:1 (mass ratio)) was added so that the solids concentration became 4 mass%.

[0099] (Synthesis of Polymerizable Long-Chain Alkyl Compound (a2)) A flask equipped with a stirrer and a thermometer was charged with 100 parts by mass of 2-hydroxyethyl acrylate ("BHEA" manufactured by Nippon Shokubai Co., Ltd.) as a (meth)acrylate compound (d) having a hydroxyl group, 240 parts by mass of diphenylmethane diisocyanate ("Millionate" (registered trademark) MT" manufactured by Nippon Polyurethane Co., Ltd.) as a polyisocyanate compound (e), and 26 parts by mass of stearyl alcohol ("Conol" (registered trademark) 30SS" manufactured by New Japan Chemical Co., Ltd.) as a higher alcohol (f), and the mixture was heated to 100°C and kept at that temperature for 7 hours to react. The reaction was terminated when it was confirmed by IR measurement that the isocyanate groups had disappeared.

[0100] <Active energy ray-curable composition p3> 15 parts by mass of the polymerizable long-chain alkyl compound (a3) ​​synthesized below, 85 parts by mass of dipentaerythritol hexaacrylate (trade name "DPHA" from Daicel Cytec Co., Ltd.) as the polymerizable compound (c), and 10 parts by mass of a photopolymerization initiator ("Irgacure" (registered trademark) 184 from Ciba Specialty Chemicals Co., Ltd.) were charged, heated to 100°C, and mixed for 1 hour to obtain an active energy ray-curable composition. This composition was then adjusted to a solids concentration of 4% by mass with a mixed solvent of toluene and isopropyl alcohol (toluene:IPA = 3:1 (mass ratio)).

[0101] (Synthesis of Polymerizable Long-Chain Alkyl Compound (a3)) A flask equipped with a stirrer and a thermometer was charged with 100 parts by mass of 2-hydroxyethyl acrylate (BHEA, available from Nippon Shokubai Co., Ltd.) as a (meth)acrylate compound (d) having a hydroxyl group, 86 parts by mass of hexamethylene diisocyanate (HDI, available from Nippon Polyurethane Co., Ltd.) as a polyisocyanate compound (e), and 46 parts by mass of stearyl alcohol (Conol (registered trademark) 30SS, available from New Japan Chemical Co., Ltd.) as a higher alcohol (f), and the mixture was heated to 100°C and kept at that temperature for 7 hours to react. The reaction was terminated when it was confirmed by IR measurement that the isocyanate groups had disappeared.

[0102] <Active energy ray-curable composition p4> 10 parts by mass of the non-polymerizable long-chain alkyl compound (b) synthesized as described below, 66 parts by mass of a urethane acrylate ("UA-306T" manufactured by Kyoeisha Chemical Co., Ltd., hexafunctional) as the polymerizable compound (c), 33 parts by mass of tricyclodecane dimethanol acrylate, and 3 parts by mass of a photopolymerization initiator ("Irgacure" (registered trademark) 184 manufactured by Ciba Specialty Chemicals Co., Ltd.) were mixed in a mixed solvent of toluene and isopropyl alcohol (toluene:IPA=3:1 (mass ratio)) to give a solids concentration of 4% by mass.

[0103] (Synthesis of Non-Polymerizable Long-Chain Alkyl Compound (b)) 50 parts by mass of octadecyl acrylate was added to a four-neck flask equipped with a stirrer, a nitrogen inlet tube, a condenser, and a rubber septum, and 1.2 parts by mass of 2,2'-bipyridine was then added to replace the atmosphere in the system with nitrogen. Under a nitrogen stream, 0.5 parts by mass of copper bromide was added, and the reaction system was heated to 90°C. 0.6 parts by mass of a polymerization initiator (ethyl 2-bromoisobutyrate) was added to initiate polymerization. Polymerization was carried out at 90°C for 10 hours under a nitrogen stream without adding a solvent. After confirming that the conversion was 85% by mass or higher, 33 parts by mass of 2-ethylhexyl acrylate was added through the rubber septum, and the mixture was heated at 110°C for 20 hours.

[0104] In this way, an A-B type diblock polymer of an octadecyl acrylate polymer block and a 2-ethylhexyl acrylate polymer block was obtained. This was heated to 60°C and centrifuged at a centrifugal force of 8,000 g for 30 minutes to obtain a supernatant polymer. 10 parts by mass of a sulfonic acid type ion exchange resin was added to 50 parts by mass of this polymer, and the mixture was stirred at 100°C for 1 hour. The ion exchange resin was then filtered off to obtain a long-chain alkyl compound (polymer) with a number average molecular weight of 25,000.

[0105] <Thermosetting composition q1> Long-chain alkyl compound: 10 parts by mass, in terms of solid content, of a mixture of a long-chain alkyl group-containing alkyd resin and a melamine-based crosslinking agent ("Tesfine" (registered trademark) 303, manufactured by Resonac Corporation); Acid catalyst: 0.3 parts by mass, in terms of solid content, of p-toluenesulfonic acid ("TAYCACURE" AC-707, manufactured by Tayca Corporation); Solvent: mixed solvent (toluene:methyl ethyl ketone:cyclohexanone=45:45:10 (mass ratio)) adjusted to a solid content concentration of 2.0% by mass.

[0106] <Thermosetting composition q2> Long-chain alkyl compound: 3 parts by mass of long-chain alkyl group-containing polyvinyl resin ("Peiroil" (registered trademark)) 1050 manufactured by Lion Specialty Chemicals Co., Ltd.) converted to solids Crosslinking agent: 70 parts by mass of melamine compound ("Yuvan" (registered trademark)) 28-60 manufactured by Mitsui Chemicals, Inc. Acid catalyst: 5 parts by mass of p-toluenesulfonic acid ("TAYCACURE" AC-707 manufactured by Teika Corporation) converted to solids Solvent: mixed solvent (toluene:methyl ethyl ketone:cyclohexanone = 45:45:10 (mass ratio)) adjusted to a solids concentration of 2.0 mass% <Thermosetting composition q3> Melamine compound ("ATOM BOND" RP-50 manufactured by Mitsuba Research Institute Co., Ltd.) converted to solids 10 parts by mass Acid catalyst: 2.0 parts by mass of an isocyanate compound (Washin Chemical Industry Co., Ltd., "PLUSCOAT" (registered trademark) ST" DEP Clear), converted to solids. Solvent: Mixed solvent (toluene:cyclohexanone:methanol = 50:40:10 (mass ratio)) adjusted to a solids concentration of 5.0 mass%. <Thermosetting composition q4> Silicone compound: 40 parts by mass of an addition reaction curable silicone resin (KS847H, manufactured by Shin-Etsu Chemical Co., Ltd.) converted to solids. Curing agent: 0.4 parts by mass of (PL-50T, manufactured by Shin-Etsu Chemical Co., Ltd.) converted to solids. Solvent: Mixed solvent (toluene:heptane = 1:1 (mass ratio)) adjusted to a solids concentration of 0.4 mass%.

[0107] Example 1 Using a production apparatus such as that shown in FIG. 1, an active energy ray-curable composition p1 was applied to one side of a polyester film 1 using a gravure coater, and the applied composition was dried at a temperature of 85° C. After that, the applied composition was irradiated with ultraviolet light at 300 mJ / cm while being conveyed by a water-cooled roller. ２The coating was irradiated and cured to form a release layer having a thickness of 200 nm, thereby producing a release film.

[0108] Examples 2 to 4 and Comparative Example 1 Release films were prepared in the same manner as in Example 1, except that the polyester film and the active energy ray-curable composition were changed as shown in Table 1.

[0109] [Comparative Examples 2 to 5] Each of thermosetting compositions q1 to q4 was applied to one side of polyester film 1 using a gravure coater, and the coated film was dried by heating at 160°C for 30 seconds to form a release layer, thereby producing a release film. The thickness of the release layer was 200 nm in each case.

[0110] [Evaluation] The surface free energy and releasability (peeling force) of the release layer of the release film prepared above were measured. The results are shown in Table 1. The smaller the peeling force, the better the releasability.

[0111]

[0112] REFERENCE SIGNS LIST 10 Polyester film 11 Release film 20 Unwinding device 30 Coating device 40 Drying device 50 Ultraviolet ray irradiation device 51 Conveying roller 52 Ultraviolet ray generating device 60 Winding device

Claims

1. A release film comprising a polyester film and a release layer, wherein the polyester film contains titanium oxide, and the release layer is a cured layer of an active energy ray-curable composition containing a compound having an alkyl group having 8 or more carbon atoms.

2. The release film according to claim 1, wherein the polyester film contains 1% by mass or more of titanium oxide relative to 100% by mass of the total solid content of the polyester film.

3. The release film according to claim 1, wherein the polyester film has a whiteness of 75 or more.

4. The release film of claim 1, wherein the optical density of said polyester film is 0.5 or greater.

5. The release film according to claim 1, wherein the haze value of said polyester film is 30% or more.

6. The release film according to claim 1, wherein the thermal conductivity of said polyester film is 0.075 W / (m·K) or more.

7. The release film according to claim 1, wherein the arithmetic mean height Ra of the roughness curve defined in JIS B0601 on the surface of the release layer side of the polyester film is 0.07 μm or more and 0.70 μm or less.

8. The release film of claim 1, wherein the polyester film has a thickness of less than 100 μm.

9. The release film according to claim 1, wherein the compound having an alkyl group having 8 or more carbon atoms has an ethylenically unsaturated group.

10. The release film according to claim 1, wherein the alkyl group in the compound having an alkyl group having 8 or more carbon atoms is a straight-chain alkyl group.

11. A release film according to claim 1, wherein the active energy ray-curable composition further contains a compound that does not have an alkyl group having 8 or more carbon atoms in the molecule and has an ethylenically unsaturated group (hereinafter referred to as polymerizable compound (c)).

12. The release film according to claim 11, wherein the polymerizable compound (c) comprises a compound having two or more ethylenically unsaturated groups in the molecule.

13. A release film according to claim 11, wherein the content of the polymerizable compound (c) in the active energy ray-curable composition is 10% by mass or more and 95% by mass or less, relative to 100% by mass of the total solid content of the active energy ray-curable composition.

14. A release film according to claim 1, wherein the content of the compound having an alkyl group having 8 or more carbon atoms in the active energy ray-curable composition is 1% by mass or more and 70% by mass or less, relative to 100% by mass of the total solid content of the active energy ray-curable composition.

15. A release film according to claim 11, wherein in the active energy ray-curable composition, the mass ratio of the content of the polymerizable compound (c) to the content of the compound having an alkyl group with 8 or more carbon atoms (content of the polymerizable compound (c) / content of the compound having an alkyl group with 8 or more carbon atoms) is 1.0 or more and 11.0 or less.

16. The release film according to claim 1, wherein the surface free energy of the release layer is 17 mN / m or more and less than 40 mN / m.

17. The release film according to claim 1, wherein the surface free energy of the surface of the polyester film facing the release layer is greater than the surface free energy of the release layer.

18. The release film according to claim 1, wherein the thickness of the release layer is 50 nm or more and less than 600 nm.

19. A pressure-sensitive adhesive tape with a release film, comprising a silicone pressure-sensitive adhesive tape having a silicone adhesive layer, and a release film according to any one of claims 1 to 18 bonded to the silicone adhesive layer.

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