JP2024051532A - Cover film with protective film - Google Patents

Abstract

[Problem] To provide a cover film with a protective film, which has high adhesion between the antifouling treated surface of the cover film and the first protective film, does not lose antifouling properties after peeling, and does not peel off the first protective film when peeling off the second protective film. [Solution] The cover film with a protective film has an antifouling layer with a water contact angle of 100° or more with the base film, the front side is an antifouling treated surface and the back side is a non-antifouling treated surface, a first adhesive layer of the first protective film is bonded to the antifouling treated surface, and a second adhesive layer of the second protective film is bonded to the non-antifouling treated surface, and the peeling force (P1) of the first adhesive layer against the antifouling treated surface and the peeling force (P2) of the second adhesive layer against the non-antifouling treated surface satisfy the relationship P1>P2. The first adhesive layer is also characterized in that it is a cured product of an adhesive composition containing a (meth)acrylic copolymer with a molecular weight distribution (Mw/Mn) of 3.0 or less and a crosslinking agent in a predetermined ratio. [Selected Figure] Figure 1

Description

The present invention relates to a cover film that is placed on the surface of a display and has protective films attached to both sides.

A cover window made of a glass substrate or a plastic substrate is placed on the outermost surface of the image display device. In addition, displays of smartphones, tablet terminals, and the like are provided with touch panels, and when the display surface is handled, dirt such as fingerprints and sweat may adhere to the display surface. For this reason, an anti-fouling layer may be provided on the cover window to prevent dirt from adhering and to make it easier to wipe off dirt.

In addition, a peelable protective film is attached to the cover window to prevent dirt from adhering to the cover window or to prevent scratches during transportation. However, when a cover window is formed with an anti-stain layer, the protective film has low adhesion due to the characteristics of the anti-stain layer, and the protective film is easily peeled off. Therefore, technology has been proposed to improve the adhesion of the protective film to the anti-stain layer.

For example, Patent Document 1 discloses an optical film with a protective film, which includes an optical film having an antifouling layer provided as an outermost layer on the first main surface of a first film substrate, and a surface protective film temporarily attached to the antifouling layer of the optical film, the surface protective film having an adhesive layer on a second film substrate, the adhesive layer having a thickness of 16 μm or more, the antifouling layer having a water contact angle of 100° or more, the antifouling layer being in contact with the adhesive layer, and the adhesive strength between the antifouling layer of the optical film and the adhesive layer of the surface protective film being less than 0.07 N/50 mm (see Patent Document 1 (Claim 1)).

JP 2020-52221 A

In recent years, in the field of image display devices, flexible displays that can maintain their display function even when bent and can be repeatedly bent and used have been attracting attention. Known examples of flexible displays include foldable displays that can be folded and rollable displays that can be rolled into a cylindrical shape. For the cover window of such flexible displays, a cover film made of an easily bendable plastic film is used instead of glass as the base.

The cover film, with the protective film attached, is subjected to processes such as printing, punching, lamination to the display surface, and inspection. During these processes, the protective film may peel off from the anti-fouling layer. In particular, when used in flexible displays, there is a problem that the protective film is easily peeled off from the anti-fouling layer when the cover film is bent and stretched. However, when the adhesion of the protective film to the anti-fouling layer is increased, glue residue occurs due to cohesive failure of the adhesive layer, and the cover film surface is contaminated due to migration of low molecular weight components, which tends to impair the anti-fouling performance.

In addition, because plastic films are more easily scratched than glass, in the case of a cover film, not only is the surface on which the anti-stain layer is provided protected by a first protective film, but the surface on which the anti-stain layer is not provided may also be protected by a second protective film. In this case, it is necessary to peel off the second protective film immediately before printing on the cover film or bonding it to a display, but there is a problem in that when attempting to peel off the second protective film, the first protective film bonded to the anti-stain layer peels off first.

The present invention has been made in consideration of the above circumstances, and aims to provide a cover film with protective film, which includes a cover film having an antifouling treated surface and a non-antifouling treated surface, a first protective film bonded to the antifouling treated surface, and a second protective film bonded to the non-antifouling treated surface, in which the first protective film has appropriate adhesion to the antifouling treated surface, does not impair the antifouling properties of the antifouling treated surface even after being peeled off, and in which peeling of the first protective film is suppressed when the second protective film is peeled off.

The cover film with protective film of the present invention, which has been able to solve the above problems, comprises a cover film having an antifouling treated surface on the front side and a non-antifouling treated surface on the back side, a first protective film arranged on the antifouling treated surface side of the cover film, and a second protective film arranged on the non-antifouling treated surface side of the cover film, the cover film comprising a substrate film and an antifouling layer arranged on the frontmost side and having a water contact angle of 100° or more, the first protective film comprising a first substrate and a first adhesive layer, the first adhesive layer being bonded to the antifouling treated surface, the second protective film comprising a second substrate and a second adhesive layer, the second adhesive layer being bonded to the non-antifouling treated surface, and the peel strength (P1) of the first adhesive layer against the antifouling treated surface at 23°C and the peel strength (P2) of the second adhesive layer against the non-antifouling treated surface at 23°C satisfy the relationship P1>P2. Furthermore, the first adhesive layer is a cured product of an adhesive composition containing a (meth)acrylic copolymer having a first reactive group and a crosslinking agent having a second reactive group that reacts with the first reactive group, the molecular weight distribution (Mw/Mn) of the (meth)acrylic copolymer having the first reactive group is 3.0 or less, and the molar ratio of the second reactive group of the crosslinking agent to the first reactive group of the (meth)acrylic copolymer having the first reactive group (molar amount of second reactive group/molar amount of first reactive group) is 0.01 to 0.30.

In the cover film with protective film of the present invention, the first protective film has a suitable adhesion to the antifouling treated surface of the cover film, and peeling of the first protective film is suppressed even when the cover film is bent and stretched, and the deterioration of the antifouling properties of the antifouling treated surface after peeling of the first protective film is suppressed. Furthermore, in the cover film with protective film of the present invention, the second protective film attached to the non-antifouling treated surface can be peeled off without peeling or lifting of the first protective film. Therefore, while protecting the non-antifouling treated surface of the cover film, the antifouling treated surface can also be reliably protected.

1 is a schematic cross-sectional view showing one embodiment of a cover film with a protective film of the present invention. FIG. 2 is a schematic cross-sectional view showing a test piece for a second protective film peeling test.

<Cover film with protective film>
The cover film with protective film of the present invention has a cover film having an anti-fouling treated surface on the front side and a non-anti-fouling treated surface on the back side, a first protective film arranged on the anti-fouling treated surface side of the cover film, and a second protective film arranged on the non-anti-fouling treated surface side of the cover film.

Figure 1 shows one embodiment of the cover film with protective film of the present invention. As shown in Figure 1, the cover film with protective film 1 according to one embodiment of the present invention has a cover film 10, a first protective film 20 arranged on the stain-resistant surface side of the cover film 10, and a second protective film 30 arranged on the non-stain-resistant surface side of the cover film 10.

The cover film 10 has at least a base film 11 and an antifouling layer 12 arranged on the outermost surface side, the antifouling layer 12 having a water contact angle of 100° or more. The outer surface side of the cover film becomes the outer surface side when the cover film is installed in a display. The surface of the cover film 10 on which the antifouling layer 12 is provided is the antifouling treated surface, and the surface on which the antifouling layer 12 is not provided is the non-antifouling treated surface.

The first protective film 20 has a first substrate 21 and a first adhesive layer 22, and the first adhesive layer 22 is bonded to the stain-resistant surface (stain-resistant layer 12) of the cover film 10. The second protective film 30 has a second substrate 31 and a second adhesive layer 32, and the second adhesive layer 32 is bonded to the non-stain-resistant surface of the cover film 10.

The cover film with protective film 1 of the present invention is characterized in that the peel strength (P1) of the first adhesive layer 22 against the stain-resistant surface at 23°C and the peel strength (P2) of the second adhesive layer 32 against the non-stain-resistant surface at 23°C satisfy the relationship P1>P2.

If the peeling force (P1) and the peeling force (P2) satisfy the relationship P1>P2, the second protective film 30 can be peeled off while preventing the first protective film 20 from lifting or peeling off during processes such as printing on the non-soiling-resistant surface of the cover film 10 and attaching the cover film to a display or the like.

The difference (P1-P2) between the peel strength (P1) of the first adhesive layer against the stain-resistant surface at 23°C and the peel strength (P2) of the second adhesive layer against the non-stain-resistant surface at 23°C is preferably 10 mN/25 mm or more, more preferably 20 mN/25 mm or more, even more preferably 30 mN/25 mm or more, and is preferably 370 mN/25 mm or less, more preferably 360 mN/25 mm or less, even more preferably 350 mN/25 mm or less. If the difference (P1-P2) is 10 mN/25 mm or more, the second protective film can be peeled off while suppressing lifting or peeling of the first protective film, and if it is 370 mN/25 mm or less, the first protective film and the second protective film can be easily peeled off from the cover film, and handling is easy in processes such as printing and lamination to a display.

The peeling force (P1) is preferably 30 mN/25 mm or more, more preferably 50 mN/25 mm or more, and even more preferably 70 mN/25 mm or more, and is preferably 380 mN/25 mm or less, more preferably 300 mN/25 mm or less, and even more preferably 200 mN/25 mm or less. If the peeling force (P1) is 30 mN/25 mm or more, the adhesion to the antifouling treated surface is further improved, and unexpected peeling is suppressed in the printing process following the attachment of the first protective film, and if it is 380 mN/25 mm or less, the first protective film can be peeled off from the antifouling treated surface more easily without leaving any adhesive residue.

The peeling force (P2) is preferably 10 mN/25 mm or more, more preferably 20 mN/25 mm or more, and even more preferably 40 mN/25 mm or more, and is preferably 300 mN/25 mm or less, more preferably 200 mN/25 mm or less, and even more preferably 100 mN/25 mm or less. If the peeling force (P2) is 10 mN/25 mm or more, peeling of the second protective film is further suppressed, and if it is 300 mN/25 mm or less, lifting of the first protective film when peeling the second protective film is further suppressed.

The cover film 1 with the protective film can be produced by attaching a first protective film 20 to the antifouling treated surface of the cover film 10 and a second protective film 30 to the non-antifouling treated surface. The order in which the first protective film 20 and the second protective film 30 are attached to the cover film 10 is not particularly limited. The second protective film 30 may be attached to the non-antifouling treated surface before the antifouling layer 12 is formed on the base film 11. In addition, since it is easy to inspect the appearance quality of the antifouling layer 12, it is preferable to attach the second protective film 30 to the non-antifouling treated surface after the antifouling layer 12 is formed on the base film 11.

The cover film with protective film of the present invention can be used for the cover window of an image display device. In particular, the cover film with protective film of the present invention can be suitably used as a cover filter for flexible displays because peeling of the first protective film is suppressed when the cover film is bent and stretched.

Below, we will explain each component that makes up the cover film with protective film of the present invention.

[Cover film]
The cover film 10 has at least a base film 11 and an antifouling layer 12 disposed on the outermost surface side. The surface of the cover film 10 on which the antifouling layer 12 is disposed is an antifouling treated surface, and the surface on which the antifouling layer 12 is not disposed is a non-antifouling treated surface.

(Base film)
Examples of the base film 11 include polymer films and glass films, and films having flexibility are preferred. Examples of polymer materials constituting the polymer film include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene, polyethylene, polycycloolefins and cycloolefin copolymers, cellulose-based resins such as triacetyl cellulose and diacetyl cellulose, polycarbonate, polyacrylate, polymethacrylate, polystyrene, polyamide, polyimide, polyacrylonitrile, polyphenylene sulfide, polyvinyl chloride, polyvinylidene chloride, and polyvinyl alcohol. The polymer film may be made of only one type of polymer material, or may be made of a combination of two or more types.

From the viewpoint of mechanical strength and heat resistance, the polymer film preferably contains, as a constituent component, at least one polymer component selected from the group consisting of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polymethyl methacrylate (PMMA), polycarbonate (PC), polyamide (PA), and polyphenylene sulfide (PPS).

The polymer film is more preferably a polyimide-based film containing polyimide as a constituent component. In this case, in order to fully exhibit the physical properties of polyimide, the content of polyimide in 100% by mass of the polymer material contained in the polyimide-based film is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. It is particularly preferable that the polyimide-based film contains only polyimide as the polymer material.

The polyimide-based film has flexibility that can withstand repeated bending, and is therefore suitable as a base film for a cover film for a flexible display that is repeatedly bent. In addition, the polyimide-based film has excellent surface hardness, and is therefore suitable as a base film for a cover film having excellent pencil hardness. By using a polyimide-based film as a base film, the pencil hardness of the hard coat layer surface when a hard coat layer is laminated thereon can be ensured. For example, depending on the configuration of the hard coat layer, the pencil hardness of the hard coat layer surface when a hard coat layer is laminated thereon can be 3H or more. In addition, the polyimide-based film also has excellent heat resistance.

In addition to the polymer material, the polymer film may contain additives such as antioxidants, UV absorbers, light stabilizers, nucleating agents, fillers, surfactants, and antistatic agents.

The substrate film 11 is preferably colorless and transparent. Colorless and transparent means that the total light transmittance in the visible light wavelength region measured in accordance with JIS K7361-1 (1997) is 50% or more, and the yellowness index (YI value) measured in accordance with JIS K 7373 (2006) is 20 or less. The total light transmittance is more preferably 70% or more, and even more preferably 85% or more. The yellowness index (YI value) is more preferably 10 or less, and even more preferably 5 or less. If the substrate film 11 is colorless and transparent, a display that displays images with high transparency and high color reproducibility can be obtained.

The thickness of the base film 11 is not particularly limited, but from the viewpoints of ease of handling, colorless transparency, etc., it is preferably 12 μm or more, more preferably 25 μm or more, even more preferably 40 μm or more, and is preferably 200 μm or less, more preferably 100 μm or less, even more preferably 80 μm or less. Note that "film" generally refers to a film having a thickness of less than 0.25 mm, but even if the thickness is 0.25 mm or more, if it can be wound into a roll, it is considered to be included in the "film".

(Anti-stain layer)
The antifouling layer 12 is disposed on the outermost surface of the cover film 10, and the side on which the antifouling layer 12 is disposed is the antifouling treatment surface. The antifouling layer 12 suppresses adhesion of dirt and fingerprints, and can easily remove the attached dirt and fingerprints, and further improves the finger slipperiness on the cover film. The antifouling layer 12 is formed directly on the surface side of the substrate film 11 or via an optical functional layer. Examples of the optical functional layer include an antireflection layer, an antiglare layer, a polarizing layer, and a hard coat layer. The optical functional layer may be provided with an antifouling function by blending an antifouling resin therein to form an antifouling layer.

The water contact angle of the antifouling layer 12 is 100° or more, preferably 102° or more, more preferably 105° or more, and is preferably 130° or less, more preferably 125° or less, and even more preferably 120° or less. If the water contact angle is 100° or more, adhesion of dirt and fingerprints is suppressed and adhesion of dirt and fingerprints can be easily removed, and if it is 130° or less, the adhesion of the first protective film is further improved.

The dynamic friction coefficient of the antifouling layer 12 is preferably 0.14 or less, more preferably 0.13 or less, even more preferably 0.11 or less, and particularly preferably 0.10 or less. If the dynamic friction coefficient is 0.14 or less, smooth sliding can be maintained when sliding a finger on the display surface.

The material of the antifouling layer 12 is preferably a fluorine-containing compound. The fluorine-containing compound not only imparts antifouling properties but also contributes to a lower refractive index. The fluorine-containing compound is preferably a fluorine-based polymer containing a perfluoropolyether skeleton. If a fluorine-based polymer containing a perfluoropolyether skeleton is used, the water repellency of the antifouling layer is further improved, and the antifouling properties are further improved.

The perfluoropolyether skeleton is preferably a perfluoroalkylene oxide which may have a branched chain having 1 to 4 carbon atoms, such as perfluoromethylene oxide (-CF ₂ O-), perfluoroethylene oxide (-CF ₂ CF ₂ O-), perfluoropropylene oxide (-CF ₂ CF ₂ CF ₂ O-), perfluoroisopropylene oxide (-CF(CF ₃ )CF ₂ O-), etc.

The anti-stain layer 12 can be formed by a wet method such as reverse coating, die coating, or gravure coating, or a dry method such as CVD (Chemical Vapor Deposition). The thickness of the anti-stain layer is about 2 nm to 50 nm.

(Anti-stain hard coat layer)
The antifouling layer 12 is preferably a hard coat layer having antifouling properties. By forming the antifouling layer 12 as an antifouling hard coat layer, it is possible to effectively impart antifouling properties, pencil hardness, and scratch resistance to the cover film.

The pencil hardness of the antifouling layer 12 is preferably 3H or more, and more preferably 4H or more. The pencil hardness of the antifouling layer 12 is the pencil hardness of the surface of the antifouling layer 12 formed on the substrate film 11. The pencil hardness of the antifouling layer 11 can be measured in accordance with JIS K 5600-5-4 (1999).

When the antifouling layer 12 is an antifouling hard coat layer, the thickness of the antifouling layer 12 is preferably 0.5 μm or more, more preferably 1.0 μm or more, and even more preferably 3.0 μm or more, and is preferably 10.0 μm or less, more preferably 8.0 μm or less, and even more preferably 6.0 μm or less. If the thickness of the antifouling layer 12 is 0.5 μm or more, the pencil hardness and scratch resistance of the antifouling layer are further improved, and if the thickness is 10.0 μm or less, the antifouling layer has flexibility that can withstand repeated bending, and curling of the cover film 10 caused by the difference in thermal shrinkage between the antifouling layer 12 and the base film 11 is suppressed. The thickness of the antifouling layer 12 is the thickness of the smooth part, and when the antifouling layer 12 contains particles, it is the thickness of the smooth part in the part without unevenness caused by the particles in the thickness direction.

When the antifouling layer 12 is an antifouling hard coat layer, it is preferable that the antifouling layer 12 be composed of a cured product of a curable composition containing an antifouling agent and an ultraviolet-curable compound, from the viewpoints of high hardness, high flexibility, productivity, etc.

The antifouling agent is preferably a fluorine-containing compound. The fluorine-containing compound can suppress adhesion of dirt and fingerprints and facilitate removal of dirt and fingerprints. Examples of the fluorine-containing compound include those containing a perfluoropolyether structure. As the structural unit of the main chain skeleton of the perfluoropolyether, a perfluoroalkylene oxide having 1 to 4 carbon atoms (which may have a branched chain) is preferable, and examples thereof include perfluoromethylene oxide (-CF ₂ O-), perfluoroethylene oxide (-CF ₂ CF ₂ O-), perfluoropropylene oxide (-CF ₂ CF ₂ CF ₂ O-), and perfluoroisopropylene oxide (-CF(CF ₃ )CF ₂ O-). In order to further enhance the antifouling property, the fluorine-containing compound may have a linear or cyclic polysiloxane structure.

The fluorine-containing compound preferably has an ethylenic carbon-carbon double bond. As a result, when the curable composition is cured, the ethylenic carbon-carbon double bond of the fluorine-containing compound copolymerizes with the ethylenic carbon-carbon double bond (e.g., a (meth)acryloyl group) of the ultraviolet-curable compound described below, and the antifouling agent is covalently bonded to the cured product of the curable composition. As a result, the antifouling properties of the cured product are further improved. Examples of commercially available products of such antifouling agents include Megafac (registered trademark) RS851, Megafac RS852, Megafac RS853, Megafac RS854 (manufactured by DIC Corporation), Opstar (registered trademark) TU2225, Opstar TU2224 (manufactured by Arakawa Chemical Industries Co., Ltd.), and KY-1203M (manufactured by Shin-Etsu Chemical Co., Ltd.).

The content of the fluorine-containing compound is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.2% by mass or more, and is preferably 15% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, based on 100% by mass of the solid content of the curable composition. If the content of the fluorine-containing compound is within the above range, the antifouling property, antifingerprint property, and scratch resistance of the antifouling layer are further improved. The solid content of the curable composition refers to the components other than the solvent contained in the curable composition.

The ultraviolet curable compound includes monomers, oligomers, prepolymers, etc. having a reactive group reactive to ultraviolet light. The ultraviolet reactive group includes radical polymerization type reactive groups having an ethylenically unsaturated bond such as (meth)acryloyl group, allyl group, vinyl group, etc., and cationic polymerization type reactive groups such as oxetanyl group. Among these, (meth)acryloyl group and oxetanyl group are more preferable, and (meth)acryloyl group is particularly preferable. That is, as the ultraviolet curable compound, (meth)acrylate-based monomers, oligomers, and polymers are particularly preferable. In this specification, "(meth)acrylate" means "at least one of acrylate and methacrylate". "(meth)acryloyl" means "at least one of acryloyl and methacryloyl". "(meth)acrylic" means "at least one of acrylic and methacrylic".

The (meth)acrylate monomers include monofunctional (meth)acrylates having one UV-reactive group in the molecule, and polyfunctional (meth)acrylates having two or more UV-reactive groups in the molecule.

The monofunctional (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, and deci aryl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, 2-ethyl-2-adamantyl (meth)acrylate, bornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, Cyclohexyl (meth)acrylate, benzyl (meth)acrylate, 1-naphthylmethyl (meth)acrylate, 2-naphthylmethyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxy-2-methylethyl (meth)acrylate, phenoxyethoxyethyl (meth)acrylate, 3-phenoxy-2-hydroxypropyl (meth)acrylate, 2-phenylphenoxyethyl (meth)acrylate, 4-phenylphenoxyethyl (meth)acrylate, 3-(2-phenylphenyl)-2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, methoxyethylene glycol (meth)acrylate, ethoxyethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, etc.

Examples of the polyfunctional (meth)acrylate include bifunctional (meth)acrylate, trifunctional (meth)acrylate, and tetrafunctional (meth)acrylate. More specifically, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate. , pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol tetra(meth)acrylate, tripentaerythritol penta(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol hepta(meth)acrylate, tripentaerythritol octa(meth)acrylate, etc.

Examples of the (meth)acrylate oligomers and polymers include urethane (meth)acrylates, silicone (meth)acrylates, and polymers of the above-mentioned monofunctional (meth)acrylates and/or polyfunctional (meth)acrylates.

The urethane (meth)acrylate is obtained by an addition reaction between a polyol, a polyisocyanate, and a (meth)acrylate having a hydroxyl group. The urethane (meth)acrylate is preferably a multifunctional urethane (meth)acrylate having two or more ultraviolet-reactive reactive groups in the molecule.

Examples of the polyol include polyether polyol, polyester polyol, and polycarbonate polyol, and can be appropriately selected from the viewpoints of flexibility, heat resistance, chemical resistance, and the like.
Examples of the polyisocyanate that can be used include aromatic diisocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate, xylylene diisocyanate (XDI), and tetramethylxylylene diisocyanate (TMXDI); and alicyclic diisocyanates such as 1,4-cyclohexane diisocyanate (CDI), isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), methylcyclohexane diisocyanate, isopropylidenedicyclohexyl-4,4'-diisocyanate, 1,3-diisocyanatomethylcyclohexane (hydrogenated XDI), and 4-methyl-1,3-cyclohexylene diisocyanate (hydrogenated TDI).
Examples of the (meth)acrylate having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate.

As the ultraviolet-curable compound, a polyfunctional (meth)acrylate monomer, a polyfunctional (meth)acrylate oligomer, or a polyfunctional (meth)acrylate polymer is preferred. In particular, urethane (meth)acrylate is particularly preferred from the viewpoint of being relatively flexible and improving the flexibility of the cover film 10, and it is preferable to include a polyfunctional urethane (meth)acrylate.

The curable composition may contain a photopolymerization initiator. Examples of the photopolymerization initiator include alkylphenone-based, acylphosphine oxide-based, and oxime ester-based photopolymerization initiators. Examples of alkylphenone-based photopolymerization initiators include 2,2'-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, and the like. Examples of the acylphosphine oxide photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, etc. Examples of the acylphosphine oxide photopolymerization initiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, etc. Examples of oxime ester photopolymerization initiators include 1,2-octanedione, 1-[4-(phenylthio)phenyl]-2-(O-benzoyloxime), ethanone-1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime), etc. Photopolymerization initiators may be used alone or in combination of two or more.

When the photopolymerization initiator is contained, the content of the photopolymerization initiator is preferably 0.1% by mass or more, more preferably 1% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, based on 100% by mass of the solid content of the curable composition.

The curable composition may contain a non-UV curable resin in addition to the UV curable compound. Examples of the non-UV curable resin include thermoplastic resins and thermosetting resins. Examples of the thermoplastic resin include polyester resins, polyether resins, polyolefin resins, and polyamide resins. Examples of the thermosetting resin include unsaturated polyester resins, epoxy resins, alkyd resins, and phenolic resins.

The curable composition may also contain additives as necessary. Examples of the additives include inorganic particles, resin particles, dispersants, leveling agents, defoamers, thixotropic agents, antibacterial agents, flame retardants, and slip agents.

The inorganic particles and resin particles are added for purposes such as preventing blocking in the antifouling hard coat layer, improving the hardness of the antifouling hard coat layer, and imparting antiglare properties.

Examples of the inorganic particles include metal oxide particles made of oxides of metals such as silica, titanium, zirconium, tin, zinc, silicon, niobium, aluminum, chromium, magnesium, germanium, gallium, antimony, and platinum. The inorganic particles may be used alone or in combination of two or more types. Titanium oxide, zirconium oxide, and tin oxide are particularly preferred inorganic particles from the viewpoint of achieving both high hardness and transparency.

The resin particles include, for example, resin particles made of resins such as (meth)acrylic resin, styrene resin, styrene-(meth)acrylic resin, urethane resin, polyamide resin, silicone resin, epoxy resin, phenolic resin, polyethylene resin, and cellulose. The resin particles may be used alone or in combination of two or more kinds.

The curable composition may contain a solvent as necessary. Examples of the solvent for the curable composition include alcohol-based solvents such as ethanol, isopropyl alcohol, n-butyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, propylene glycol monomethyl ether, and diethylene glycol monobutyl ether; ketone-based solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and acetone; aromatic solvents such as toluene and xylene; ester-based solvents such as ethyl acetate (EtAc), propyl acetate, isopropyl acetate, and butyl acetate (BuAc); and amide-based solvents such as N-methylpyrrolidone, acetamide, and dimethylformamide. These solvents may be used alone or in combination of two or more.

The solids concentration of the curable composition (concentration of components other than the solvent) is not particularly limited and may be appropriately determined taking into consideration the coatability, film thickness, etc. The solids concentration is, for example, preferably 1.0% by mass or more, more preferably 1.5% by mass or more, and even more preferably 2.0% by mass or more, and is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

[First protective film]
The first protective film 20 has a first substrate 21 and a first adhesive layer 22 , and the first adhesive layer 22 is attached to the stain-resistant surface of the cover film 10 .

The first protective film 20 prevents the surface of the antifouling treatment surface (antifouling layer 12) from being scratched during handling, such as continuous processing in a roll process or bonding the cover film 10 to a flexible display.

The first protective film 20 is peeled off from the stain-resistant surface (stain-resistant layer 12) of the cover film after the cover film 10 is attached to a display or the like. Therefore, the adhesive strength between the first substrate 21 and the first adhesive layer 22 is stronger than the adhesive strength between the stain-resistant surface of the cover film and the first adhesive layer 22, and the adhesive strength is adjusted to allow interfacial peeling between the stain-resistant surface and the first adhesive layer 22.

(First substrate)
The material constituting the first base material 21 is not particularly limited, and examples thereof include polymeric materials. Examples of polymeric materials include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene, polyethylene, polycycloolefins, and cycloolefin copolymers, polycarbonate, polyacrylate, polymethacrylate, polystyrene, polyamide, polyimide, polyacrylonitrile, polyphenylene sulfide, polyvinyl chloride, polyvinylidene chloride, and polyvinyl alcohol. The polymeric materials may be used alone or in combination of two or more. Among these, polyethylene terephthalate, polyimide, polycarbonate, polyacrylate, polymethacrylate, polycycloolefin, and cycloolefin copolymer are more preferable from the viewpoint of durability.

The first substrate 21 may be composed of a single layer containing one or more of the above polymeric materials, or may be composed of two or more layers, such as a layer containing one or more of the above polymeric materials and a layer containing one or more of a different polymeric material.

The thickness of the first substrate 21 is not particularly limited, but from the viewpoints of ease of handling during processing and material costs, it is preferably 19 μm or more, more preferably 22 μm or more, and even more preferably 25 μm or more, and is preferably 200 μm or less, more preferably 100 μm or less, and even more preferably 75 μm or less.

(First adhesive layer)
The first adhesive layer 22 is a cured product of an adhesive composition containing a (meth)acrylic copolymer having a first reactive group and a crosslinking agent having a second reactive group that reacts with the first reactive group. The adhesive composition contains (A) a (meth)acrylic copolymer having a first reactive group and (B) a crosslinking agent.

The thickness of the first adhesive layer 22 is not particularly limited and may be adjusted as appropriate depending on the adhesion to the antifouling surface. The thickness of the first adhesive layer is preferably 5 μm or more, more preferably 10 μm or more, and is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 30 μm or less, and particularly preferably 15 μm or less. If the thickness is within the above range, the adhesion to the antifouling surface is further improved, and stop marks caused by zipping (slip-stick phenomenon) can be suppressed.

(A) (Meth)acrylic Copolymer Having First Reactive Group The (A) (meth)acrylic copolymer having a first reactive group (hereinafter, may be simply referred to as "copolymer (A)") is a (meth)acrylic copolymer having a first reactive group and having a molecular weight distribution (Mw/Mn) of 3.0 or less.

The (meth)acrylic copolymer may be any copolymer that contains structural units derived from (meth)acrylic monomers as the main component (50% by mass or more), and may contain structural units derived from vinyl monomers other than (meth)acrylic monomers. The content of structural units derived from (meth)acrylic monomers in the (A) copolymer is preferably 80% by mass or more, more preferably 90% by mass or more, based on 100% by mass of the entire copolymer. The (A) copolymer may be composed only of structural units derived from (meth)acrylic monomers.

The (A) copolymer is preferably a (meth)acrylate-based copolymer. The (meth)acrylate-based copolymer may be any copolymer that contains structural units derived from (meth)acrylate as the main component (50% by mass or more), and may contain structural units derived from vinyl monomers other than (meth)acrylate. The (meth)acrylate is an ester compound in which the hydrogen atom of the carboxyl group of (meth)acrylic acid is substituted with an organic group. The content of structural units derived from (meth)acrylate in the (A) copolymer is preferably 80% by mass or more, more preferably 90% by mass or more, based on 100% by mass of the entire copolymer.

The copolymer (A) has a first reactive group. The first reactive group is a functional group that can react with a second reactive group possessed by the crosslinking agent (B) described below. The first reactive group may be, for example, one or more types selected from the group consisting of a hydroxy group, a carboxy group, and an epoxy group, and is preferably a hydroxy group and/or a carboxy group.

Preferred combinations of the first reactive group of the copolymer (A) and the second reactive group of the crosslinking agent (B) are (1) a combination in which the first reactive group is a hydroxy group and the second reactive group is an isocyanate group; and (2) a combination in which the first reactive group is a carboxy group and the second reactive group is an epoxy group.

The amount of the first reactive group per 100 g of the copolymer (A) is preferably 0.5 mmol/100 g or more, more preferably 5 mmol/100 g or more, even more preferably 10 mmol/100 g or more, and particularly preferably 15 mmol/100 g or more, and is preferably 150 mmol/100 g or less, more preferably 100 mmol/100 g or less, and even more preferably 70 mmol/100 g or less. If the amount of the first reactive group is 0.5 mmol/100 g or more, the durability of the first adhesive layer is excellent, and if it is 150 mmol/100 g or less, the adhesion of the first adhesive layer to the antifouling treated surface of the cover film is excellent.

When the (A) copolymer has a carboxy group, the amount of carboxy groups per 100 g of the (A) copolymer is preferably 0.5 mmol/100 g or more, more preferably 5 mmol/100 g or more, even more preferably 10 mmol/100 g or more, and particularly preferably 15 mmol/100 g or more, and is preferably 150 mmol/100 g or less, more preferably 100 mmol/100 g or less, and even more preferably 70 mol/100 g or less.

When the (A) copolymer has hydroxy groups, the amount of hydroxy groups per 100 g of the (A) copolymer is preferably 0.5 mmol/100 g or more, more preferably 5 mmol/100 g or more, even more preferably 10 mmol/100 g or more, particularly preferably 15 mmol/100 g or more, and is preferably 150 mmol/100 g or less, more preferably 100 mmol/100 g or less, even more preferably 70 mmol/100 g or less.

The (A) copolymer has a first reactive group. That is, the (A) copolymer contains a structural unit (a-1) having a first reactive group in its structure. The structural unit (a-1) having the first reactive group may be only one type, or may have two or more types. The first reactive group may be in a structural unit derived from a (meth)acrylic monomer (preferably a (meth)acrylate monomer and/or (meth)acrylic acid) or in a structural unit derived from a vinyl monomer other than a (meth)acrylic monomer. That is, the structural unit (a-1) having the first reactive group may be a structural unit derived from a (meth)acrylic monomer (preferably a (meth)acrylate monomer and/or (meth)acrylic acid) having a first reactive group, or a structural unit derived from a vinyl monomer other than a (meth)acrylic monomer having a first reactive group.

The content of the structural unit (structural unit (a-1) having a first reactive group) derived from a vinyl monomer having a first reactive group in the copolymer (A) is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, particularly preferably 3% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 8% by mass or less, based on 100% by mass of the entire copolymer. If the content of the structural unit (a-1) is within the above range, an adhesive layer having an excellent balance of adhesion to an antifouling treated surface and durability can be obtained. The vinyl monomer having a first reactive group includes a (meth)acrylic monomer having a first reactive group and a vinyl monomer other than a (meth)acrylic monomer having a first reactive group.

The (meth)acrylic monomer includes (b1) a (meth)acrylic monomer that does not have a functional group that can become a first reactive group, and (b2) a (meth)acrylic monomer that has a functional group that can become a first reactive group. These monomers may be used alone or in combination of two or more. The (b1) (meth)acrylic monomer is preferably (b1-1) a (meth)acrylate monomer that does not have a functional group that can become a first reactive group. The (b2) (meth)acrylic monomer includes (b2-1) a (meth)acrylate monomer that has a functional group that can become a first reactive group, and (meth)acrylic acid.

The (b1) (meth)acrylic monomer may be, for example, a (meth)acrylate having a linear alkyl group, a (meth)acrylate having a branched alkyl group, a (meth)acrylate having an alkoxy group, a (meth)acrylate having a polyalkylene glycol structural unit, a (meth)acrylate having an alicyclic hydrocarbon group, a (meth)acrylate having an aromatic group, a (meth)acrylate having a tertiary amino group, or a (meth)acrylamide. Among these, at least one selected from the group consisting of a (meth)acrylate having a linear alkyl group, a (meth)acrylate having a branched alkyl group, a (meth)acrylate having an alicyclic hydrocarbon group, a (meth)acrylate having an aromatic group, or a (meth)acrylamide is preferred.

As the (meth)acrylate having a linear alkyl group, a (meth)acrylate having a linear alkyl group with a carbon number of 1 to 20 is preferred, and a (meth)acrylate having a linear alkyl group with a carbon number of 1 to 10 is more preferred. Examples of the (meth)acrylate having a linear alkyl group include linear alkyl esters of (meth)acrylic acid such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-lauryl (meth)acrylate, and n-stearyl (meth)acrylate.

As the (meth)acrylate having a branched alkyl group, a (meth)acrylate having a branched alkyl group with a carbon number of 3 to 20 is preferred, and a (meth)acrylate having a branched alkyl group with a carbon number of 3 to 10 is preferred. Examples of the (meth)acrylate having a branched alkyl group include (meth)acrylic acid branched alkyl esters such as isopropyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isononyl (meth)acrylate, and isodecyl (meth)acrylate.

Examples of the (meth)acrylate having an alkoxy group include (meth)acrylic acid alkoxyalkyl esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate.

Examples of the (meth)acrylate having a polyalkylene glycol structural unit include (meth)acrylates having a polyethylene glycol structural unit such as polyethylene glycol (degree of polymerization = 2-10) methyl ether (meth)acrylate, polyethylene glycol (degree of polymerization = 2-10) ethyl ether (meth)acrylate, polyethylene glycol (degree of polymerization = 2-10) propyl ether (meth)acrylate, and polyethylene glycol (degree of polymerization = 2-10) phenyl ether (meth)acrylate; and (meth)acrylates having a polypropylene glycol structural unit such as polypropylene glycol (degree of polymerization = 2-10) methyl ether (meth)acrylate, polypropylene glycol (degree of polymerization = 2-10) ethyl ether (meth)acrylate, polypropylene glycol (degree of polymerization = 2-10) propyl ether (meth)acrylate, and polypropylene glycol (degree of polymerization = 2-10) phenyl ether (meth)acrylate.

The (meth)acrylate having an alicyclic hydrocarbon group includes a (meth)acrylate having a cyclic alkyl group and a (meth)acrylate having a polycyclic structure. The (meth)acrylate having a cyclic alkyl group is preferably a (meth)acrylate having a cyclic alkyl group with 6 to 12 carbon atoms. The cyclic alkyl group may include a cyclic alkyl group having a monocyclic structure (e.g., a cycloalkyl group), which may also have a chain portion. Specific examples of (meth)acrylates having a cyclic alkyl group with a monocyclic structure include (meth)acrylic acid cyclic alkyl esters such as cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, and cyclododecyl (meth)acrylate.

The (meth)acrylate having a polycyclic structure is preferably a (meth)acrylate having a polycyclic structure with 6 to 12 carbon atoms. Examples of the polycyclic structure include cyclic alkyl groups having a bridged ring structure (e.g., adamantyl group, norbornyl group, isobornyl group), and may also have a chain portion. Specific examples of (meth)acrylates having a polycyclic structure include bornyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, 2-ethyl-2-adamantyl (meth)acrylate, norbornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, etc.

The (meth)acrylate having an aromatic group is preferably a (meth)acrylate having an aromatic group with 6 to 12 carbon atoms. Examples of the aromatic group include an aryl group, and may also have a chain portion such as an alkylaryl group, an aralkyl group, or an aryloxyalkyl group. Examples of the (meth)acrylate having an aromatic group include a compound in which an aryl group is directly bonded to a (meth)acryloyloxy group, a compound in which an aralkyl group is directly bonded to a (meth)acryloyloxy group, and a compound in which an alkylaryl group is directly bonded to a (meth)acryloyloxy group. The number of carbon atoms of the aryl group is preferably 6 to 12. The number of carbon atoms of the aralkyl group is preferably 6 to 12. The number of carbon atoms of the alkylaryl group is preferably 6 to 12. Examples of the (meth)acrylate having an aromatic group include benzyl (meth)acrylate, phenyl (meth)acrylate, and phenoxyethyl (meth)acrylate.

Examples of the (meth)acrylate having a tertiary amino group include 2-(dimethylamino)ethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, etc.

Examples of the (meth)acrylamides include N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-tert-butyl(meth)acrylamide, N-octyl(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-ethoxymethyl(meth)acrylamide, N-propoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide, diacetoneacrylamide, and N-(meth)acryloylmorpholine. The (meth)acrylamides are (meth)acrylic monomers, but are not included in (meth)acrylate monomers.

Examples of monomers that can be the (meth)acrylic monomer (b2) include (meth)acrylic monomers having a hydroxy group (preferably (meth)acrylate monomers), (meth)acrylic monomers having a carboxy group (preferably (meth)acrylic acid), and (meth)acrylic monomers having an epoxy group (preferably (meth)acrylate monomers). Among these, (meth)acrylic monomers having a hydroxy group and/or (meth)acrylic monomers having a carboxy group are preferred.

Examples of the (meth)acrylic monomer having a hydroxy group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate; hydroxyalkyl cycloalkane (meth)acrylates such as (4-hydroxymethylcyclohexyl)methyl (meth)acrylate; and caprolactone adducts of hydroxyalkyl (meth)acrylates. Among these, hydroxyalkyl (meth)acrylates are preferred, and (meth)acrylates having a hydroxyalkyl group having 1 to 5 carbon atoms are more preferred.

Examples of the (meth)acrylic monomer having a carboxy group include monomers obtained by reacting (meth)acrylates having a hydroxy group, such as carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl maleate, and 2-(meth)acryloyloxyethyl phthalate, with acid anhydrides, such as maleic anhydride, succinic anhydride, and phthalic anhydride, and (meth)acrylic acid. Among these, (meth)acrylic acid is preferred.

Examples of the (meth)acrylic acid ester having an epoxy group include glycidyl (meth)acrylate and 3,4-epoxycyclohexylmethyl (meth)acrylate.

Examples of the vinyl monomer other than the (meth)acrylic monomer include (b3) a vinyl monomer other than the (meth)acrylic monomer that does not have a functional group that can become a first reactive group, and (b4) a vinyl monomer other than the (meth)acrylic monomer that has a functional group that can become a first reactive group. These monomers may be used alone or in combination of two or more.

Examples of the vinyl monomer (b3) include aromatic vinyl monomers, vinyl monomers containing a heterocycle, vinyl carboxylates, vinyl monomers containing a tertiary amino group, vinyl monomers containing a quaternary ammonium base, vinyl amides, α-olefins, dienes, and halogenated vinyl monomers.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, 4-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methoxystyrene, 2-hydroxymethylstyrene, and 1-vinylnaphthalene.
Examples of the vinyl monomer containing a heterocycle include 2-vinylthiophene, N-methyl-2-vinylpyrrole, 2-vinylpyridine, and 4-vinylpyridine.
Examples of the vinyl carboxylate include vinyl acetate, vinyl pivalate, and vinyl benzoate.
The vinyl monomer containing a tertiary amino group includes N,N-dimethylallylamine.
Examples of the vinyl monomer containing a quaternary ammonium base include N-methacryloylaminoethyl-N,N,N-dimethylbenzyl ammonium chloride.
Examples of the vinyl amides include N-vinylformamide, N-vinylacetamide, 1-vinyl-2-pyrrolidone, and N-vinyl-ε-caprolactam.
Examples of the α-olefin include 1-hexene, 1-octene, and 1-decene.
Examples of the dienes include butadiene, isoprene, 4-methyl-1,4-hexadiene, and 7-methyl-1,6-octadiene.
Examples of the halogenated vinyl monomer include vinyl fluoride, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, tetrafluoropropylene, vinylidene chloride, vinyl chloride, 1-chloro-1-fluoroethylene, and 1,2-dichloro-1,2-difluoroethylene.

Examples of the vinyl monomer (b4) include vinyl monomers having a hydroxy group, vinyl monomers having a carboxy group, and vinyl monomers containing an epoxy group.

Examples of the vinyl monomer having a hydroxy group include p-hydroxystyrene and allyl alcohol.
Examples of the vinyl monomer having a carboxy group include crotonic acid, maleic acid, itaconic acid, citraconic acid, and cinnamic acid.
Examples of the vinyl monomer containing an epoxy group include 2-allyloxirane, glycidyl vinyl ether, and 3,4-epoxycyclohexyl vinyl ether.

The copolymer (A) may be a random copolymer, a block copolymer, or a graft copolymer, and is preferably a random copolymer.

The weight average molecular weight (Mw) of the copolymer (A) is preferably 200,000 or more, more preferably 400,000 or more, even more preferably 500,000 or more, and preferably 2,000,000 or less, more preferably 1,500,000 or less, even more preferably 1,200,000 or less, and particularly preferably 1,000,000 or less. If the Mw of the copolymer (A) is 200,000 or more, the cohesive force is increased and the heat resistance of the adhesive layer is improved, and if it is 2,000,000 or less, the coating workability of the adhesive composition is improved. The method for measuring the weight average molecular weight (Mw) will be described later.

The molecular weight distribution (Mw/Mn) of the copolymer (A) is 3.0 or less, preferably 2.5 or less, more preferably 2.3 or less, and particularly preferably 2.0 or less. The smaller the molecular weight distribution, the narrower the molecular weight distribution width, resulting in a copolymer with a uniform molecular weight, and when the value is 1.0, the molecular weight distribution width is the narrowest. If the molecular weight distribution is 3.0 or less, the content of small and large molecular weights is low compared to the molecular weight of the designed copolymer, and an adhesive layer with little adhesive residue is obtained. In the present invention, the molecular weight distribution is a value calculated by (weight average molecular weight (Mw))/(number average molecular weight (Mn)), and the measurement method of Mw and Mn will be described later.

The glass transition temperature (Tg) of the copolymer (A) is preferably -80°C or higher, more preferably -75°C or higher, and is preferably 0°C or lower, more preferably -20°C or lower, and even more preferably -50°C or lower. If the glass transition temperature is -80°C or higher, sufficient cohesive strength is imparted to the adhesive, improving the durability of the adhesive, and if the glass transition temperature is 0°C or lower, appropriate adhesion to the antifouling layer is obtained, and zipping can be suppressed.

The glass transition temperature (Tg) of the copolymer (A) is a value calculated by the following FOX formula (Formula (1)). In Formula (1), Tg represents the glass transition temperature (°C) of the copolymer. Tgi represents the glass transition temperature (°C) when vinyl monomer i forms a homopolymer. Wi represents the mass ratio of vinyl monomer i to all vinyl monomers forming the copolymer, and ΣWi = 1. i is a natural number from 1 to n.

The glass transition temperatures of representative homopolymers are shown in Table 1.

The copolymer (A) is produced by polymerizing a vinyl monomer. In particular, the copolymer (A) is preferably polymerized by living radical polymerization. The living radical polymerization method maintains the simplicity and versatility of conventional radical polymerization methods, while being less susceptible to termination reactions and chain transfer, and allows growth without being hindered by side reactions that deactivate the growing ends, making it easy to precisely control the molecular weight distribution and produce polymers with uniform composition.

Living radical polymerization methods include a method using a compound capable of generating a nitroxide radical (nitroxide method; NMP method) depending on the method of stabilizing the polymerization growth end; a method using a metal complex such as copper or ruthenium to polymerize a halogenated compound as a polymerization initiator compound in a living manner from the polymerization initiator compound (ATRP method); a method using a dithiocarboxylic acid ester or a xanthate compound (RAFT method); a method using an organic tellurium compound (TERP method); a method using an organic iodine compound (ITP method); a method using an iodine compound as a polymerization initiator compound and an organic compound such as a phosphorus compound, a nitrogen compound, an oxygen compound, or a hydrocarbon as a catalyst (reversible transfer catalyst polymerization; RTCP method, reversible catalyst-mediated polymerization; RCMP method), etc. Among these methods, the TERP method is preferable from the viewpoint of the diversity of monomers that can be used, molecular weight control in the polymer region, uniform composition, or coloring.

The TERP method is a method of polymerizing a radically polymerizable compound (vinyl monomer) using an organic tellurium compound as a chain transfer agent, and is a method described, for example, in WO 2004/14848, WO 2004/14962, WO 2004/072126, and WO 2004/096870.

Specific polymerization methods of the TERP method include the following (a) to (d).
(a) A method of polymerizing a vinyl monomer using an organotellurium compound represented by formula (1).
(b) A method of polymerizing a vinyl monomer using a mixture of an organotellurium compound represented by formula (1) and an azo-based polymerization initiator.
(c) A method of polymerizing a vinyl monomer using a mixture of an organotellurium compound represented by formula (1) and an organic ditelluride compound represented by formula (2).
(d) A method of polymerizing a vinyl monomer using a mixture of an organotellurium compound represented by formula (1), an azo-based polymerization initiator, and an organic ditelluride compound represented by formula (2).

［式（１）において、Ｒ¹は、炭素数１～８のアルキル基、アリール基または芳香族ヘテロ環基である。Ｒ²およびＲ³は、それぞれ独立に、水素原子または炭素数１～８のアルキル基である。Ｒ⁴は、炭素数１～８のアルキル基、アリール基、置換アリール基、芳香族ヘテロ環基、アルコキシ基、アシル基、アミド基、オキシカルボニル基、シアノ基、アリル基またはプロパルギル基である。
式（２）において、Ｒ¹は、炭素数１～８のアルキル基、アリール基または芳香族ヘテロ環基である。］

In formula (1), R ¹ is an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group. R ² and R ³ are each independently a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. R ⁴ is an alkyl group having 1 to 8 carbon atoms, an aryl group, a substituted aryl group, an aromatic heterocyclic group, an alkoxy group, an acyl group, an amido group, an oxycarbonyl group, a cyano group, an allyl group, or a propargyl group.
In formula (2), R ¹ is an alkyl group having 1 to 8 carbon atoms, an aryl group, or an aromatic heterocyclic group.

Specific examples of the organic tellurium compound represented by formula (1) include ethyl 2-methyl-2-n-butyltellanyl propionate, ethyl 2-n-butyltellanyl propionate, (2-hydroxyethyl) 2-methyl-methyltellanyl propionate, and the organic tellurium compounds described in WO 2004/14848, WO 2004/14962, WO 2004/072126, and WO 2004/096870. Specific examples of the organic ditelluride compound represented by formula (2) include dimethyl ditelluride and dibutyl ditelluride. The azo polymerization initiator can be any azo polymerization initiator used in normal radical polymerization without any particular restrictions, such as 2,2'-azobis(isobutyronitrile) (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ADVN), 1,1'-azobis(1-cyclohexanecarbonitrile) (ACHN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70), etc.

In the polymerization process, a vinyl monomer and an organic tellurium compound of formula (1) are mixed in a vessel purged with an inert gas, and an azo-based polymerization initiator and/or an organic ditelluride compound of formula (2) are further mixed for the purpose of promoting the reaction and controlling the molecular weight and molecular weight distribution depending on the type of vinyl monomer. Examples of the inert gas include nitrogen, argon, and helium. Argon and nitrogen are preferable. The amount of the vinyl monomer used in (a), (b), (c), and (d) may be appropriately adjusted depending on the physical properties of the desired copolymer.

The polymerization reaction can be carried out without a solvent, but may be carried out by stirring the mixture using an aprotic or protic solvent generally used in radical polymerization. Examples of aprotic solvents that can be used include anisole, benzene, toluene, propylene glycol monomethyl ether acetate, ethyl acetate, and tetrahydrofuran (THF). Examples of protic solvents include water, methanol, and 1-methoxy-2-propanol. Solvents may be used alone or in combination of two or more. The amount of solvent used may be adjusted appropriately, and is preferably 0.01 ml to 50 ml per 1 g of vinyl monomer. The reaction temperature and reaction time may be adjusted appropriately depending on the molecular weight or molecular weight distribution of the resulting copolymer, but the mixture is usually stirred at 0°C to 150°C for 1 minute to 100 hours. After the polymerization reaction is completed, the solvent used and remaining vinyl monomers are removed from the resulting reaction mixture by ordinary separation and purification means, and the desired copolymer can be separated.

The growing end of the copolymer obtained by the polymerization reaction is in the form of -TeR ¹ (wherein R ¹ is the same as above) derived from the tellurium compound, and is deactivated by operation in air after the polymerization reaction is completed, but tellurium atoms may remain. Since a copolymer with tellurium atoms remaining at the end is colored or has poor thermal stability, it is preferable to remove the tellurium atoms. Methods for removing tellurium atoms include a radical reduction method; a method of adsorption with activated carbon or the like; a method of adsorbing metal with an ion exchange resin or the like, and these methods can also be used in combination. The other end of the copolymer obtained by the polymerization reaction (the end opposite to the growing end) is in the form of -CR ² R ³ R ⁴ (wherein R ² , R ³ and R ⁴ are the same as R ² , R ³ and R ⁴ in formula (1)) derived from the tellurium compound.

((B) Crosslinking Agent)
The adhesive composition contains a crosslinking agent (B). The crosslinking agent (B) is a compound having two or more second reactive groups in one molecule that can react with the first reactive group of the copolymer (A). The crosslinking agent (B) is not particularly limited, and examples thereof include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, metal chelate-type crosslinking agents, melamine resin-based crosslinking agents, and urea resin-based crosslinking agents. Among these, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and aziridine-based crosslinking agents are preferred, and isocyanate-based crosslinking agents or epoxy-based crosslinking agents are more preferred from the viewpoints of easily controlling the degree of progress of the crosslinking reaction and suppressing the migration of adhesive components to the antifouling layer.

(Isocyanate-based crosslinking agent)
The isocyanate crosslinking agent is a compound having two or more isocyanate groups (including isocyanate regenerating functional groups in which the isocyanate groups are temporarily protected by a blocking agent or oligomerization) in one molecule as second reactive groups. The isocyanate crosslinking agent may be used alone or in combination of two or more kinds.

Examples of the isocyanate-based crosslinking agents include aromatic polyisocyanates, alicyclic polyisocyanates, aliphatic polyisocyanates, as well as adducts of these with various polyols, and polyisocyanates that have been multifunctionalized with isocyanurate bonds, biuret bonds, allophanate bonds, etc. More specifically, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic polyisocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane; 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, polymethylene One or more selected from aromatic polyisocyanates such as polyphenyl isocyanate; isocyanate adducts such as trimethylolpropane/tolylene diisocyanate trimer adduct, trimethylolpropane/hexamethylene diisocyanate trimer adduct, and isocyanurate of hexamethylene diisocyanate; trimethylolpropane adduct of xylylene diisocyanate; trimethylolpropane adduct of hexamethylene diisocyanate; polyether polyisocyanate, polyester polyisocyanate, and adducts of these with various polyols, polyisocyanates multifunctionalized with isocyanurate bonds, biuret bonds, allophanate bonds, etc. can be used. Among these, it is preferable to use aliphatic polyisocyanates, and isocyanurates of aliphatic diisocyanates (e.g., isocyanurates of hexamethylene diisocyanate) are more preferable.

(Epoxy-based crosslinking agent)
The epoxy-based crosslinking agent is a compound having two or more epoxy groups as second reactive groups in one molecule. The epoxy-based crosslinking agents may be used alone or in combination of two or more kinds.

Examples of the epoxy crosslinking agent include bisphenol A, epichlorohydrin type epoxy resins, ethylene glycidyl ether, N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, diamine glycidylamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, Examples of such glycidyl ethers include glycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, and bisphenol-S-diglycidyl ether.

(Aziridine-based crosslinking agent)
The aziridine-based crosslinking agent is a compound having two or more aziridine groups as second reactive groups in one molecule. The aziridine-based crosslinking agents may be used alone or in combination of two or more kinds.

Examples of the aziridine-based crosslinking agent include tris-2,4,6-(1-aziridinyl)-1,3,5-triazine, tris[1-(2-methyl)-aziridinyl]phosphine oxide, and hexa[1-(2-methyl)-aziridinyl]triphosphatriazine.

The content of the second reactive group in the (B) crosslinking agent is preferably 0.5 mmol/g or more, more preferably 1.0 mmol/g or more, even more preferably 3.0 mmol/g or more, particularly preferably 5.0 mmol/g or more, and is preferably 20 mmol/g or less, more preferably 15.0 mmol/g or less, even more preferably 12.0 mmol/g or less. If the content of the second reactive group in the (B) crosslinking agent is within this range, the cohesive strength of the adhesive layer formed will be favorable, and adhesive residue and migration of the adhesive component to the antifouling layer can be suppressed.

The content of the (B) crosslinking agent in the adhesive composition is preferably 0.05 parts by mass or more, more preferably 0.06 parts by mass or more, even more preferably 0.08 parts by mass or more, and preferably 7 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less, relative to 100 parts by mass of the (A) copolymer. If the content of the (B) crosslinking agent is 0.05 parts by mass or more, the cohesive strength of the adhesive layer formed is favorable, and it is possible to suppress glue residue and migration of the adhesive component to the antifouling layer, and if it is 7 parts by mass or less, it is possible to obtain appropriate adhesion with the antifouling treated surface and suppress peeling of the first protective film.

In the adhesive composition, the molar ratio of the second reactive group of the crosslinking agent (B) to the first reactive group of the copolymer (A) (molar amount of the second reactive group/molar amount of the first reactive group) is 0.01 or more, preferably 0.02 or more, more preferably 0.08 or more, and 0.30 or less, preferably 0.25 or less, more preferably 0.20 or less. If the molar ratio is 0.01 or more, the cohesive strength of the first adhesive layer formed is good, and the adhesive residue and migration of the adhesive component to the antifouling treated surface during peeling can be suppressed, and if it is 0.30 or less, appropriate adhesion to the antifouling treated surface can be obtained, and peeling of the protective film can be suppressed.

(Other additives)
The adhesive composition may contain additives other than the copolymer (A) and the crosslinking agent (B). Examples of the additives include crosslinking accelerators, crosslinking retarders, tackifiers, plasticizers, softeners, peeling aids, dyes, pigments, dyestuffs, fluorescent brighteners, antistatic agents, wetting agents, surfactants, thickeners, antifungal agents, preservatives, oxygen absorbers, ultraviolet absorbers, antioxidants, near-infrared absorbers, water-soluble quenchers, fragrances, metal deactivators, nucleating agents, alkylating agents, flame retardants, lubricants, and processing aids.

(Crosslinking Accelerator)
The adhesive composition may contain a crosslinking accelerator as necessary. Examples of the crosslinking accelerator include an organic tin compound and a metal chelate compound. The crosslinking accelerator may be used alone or in combination of two or more kinds.

The organotin compounds include dibutyltin dilaurate, dioctyltn dilaurate, dibutyltin dioctylate, etc. The metal chelate compounds are complexes in which a ligand having two or more coordinating atoms forms a ring and is bonded to a central metal.

When the adhesive composition contains a crosslinking accelerator, the content of the crosslinking accelerator is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, even more preferably 0.04 parts by mass or more, and is preferably 0.5 parts by mass or less, more preferably 0.4 parts by mass or less, even more preferably 0.3 parts by mass or less, relative to 100 parts by mass of the copolymer (A). When the content of the crosslinking accelerator is within the above range, it is possible to obtain an excellent crosslinking promotion effect.

(Crosslinking Retarder)
The adhesive composition may contain a crosslinking retarder as necessary. The crosslinking retarder is a compound that can suppress an excessive increase in viscosity of an adhesive composition containing a crosslinking agent by blocking a functional group of the crosslinking agent. The type of crosslinking retarder is not particularly limited, and examples thereof include β-diketones such as acetylacetone, hexane-2,4-dione, heptane-2,4-dione, and octane-2,4-dione; β-ketoesters such as methyl acetoacetate, ethyl acetoacetate, propyl acetoacetate, butyl acetoacetate, octyl acetoacetate, oleyl acetoacetate, lauryl acetoacetate, and stearyl acetoacetate; and benzoylacetone. As the crosslinking retarder, those that can act as a chelating agent are preferred, and β-diketones and β-ketoesters are preferred.

When the adhesive composition contains a crosslinking retarder, the content of the crosslinking retarder is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, even more preferably 0.5 parts by mass or more, and is preferably 4.0 parts by mass or less, more preferably 3.0 parts by mass or less, even more preferably 1.5 parts by mass or less, relative to 100 parts by mass of the (A) copolymer. If the content of the crosslinking retarder is within the above range, excessive viscosity increase and gelation of the adhesive composition can be suppressed after the (B) crosslinking agent is blended into the adhesive composition, and the storage stability (pot life) of the adhesive composition can be extended.

(Tackifier)
The pressure-sensitive adhesive composition may contain a tackifier other than the copolymer (A) as necessary. The tackifier is not particularly limited, but examples thereof include rosin-based tackifier resins, terpene-based tackifier resins, phenol-based tackifier resins, and hydrocarbon-based tackifier resins.

Examples of the rosin-based tackifying resin include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin, modified rosins obtained by modifying these unmodified rosins through polymerization, disproportionation, hydrogenation, etc. (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, other chemically modified rosins, etc.), and various rosin derivatives.

Examples of the rosin derivatives include rosin phenol-based resins obtained by adding phenol to rosins (unmodified rosin, modified rosin) using an acid catalyst and thermally polymerizing the rosin; rosin ester-based resins such as rosin ester compounds (unmodified rosin esters) obtained by esterifying unmodified rosin with alcohols, and modified rosin ester compounds (polymerized rosin ester, stabilized rosin ester, disproportionated rosin ester, fully hydrogenated rosin ester, partially hydrogenated rosin ester, etc.) obtained by esterifying modified rosin with alcohols; unsaturated fatty acid modified rosin-based resins obtained by modifying unmodified rosin or modified rosin with unsaturated fatty acid; unsaturated fatty acid modified rosin ester-based resins obtained by modifying rosin ester-based resins with unsaturated fatty acid; rosin alcohol-based resins obtained by reducing the carboxyl groups in unmodified rosin, modified rosin, unsaturated fatty acid modified rosin-based resins, and unsaturated fatty acid modified rosin ester-based resins; and metal salts of rosin-based resins (particularly rosin ester-based resins) such as unmodified rosin and modified rosin.

Examples of the terpene-based tackifying resin include terpene-based resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers, and modified terpene-based resins obtained by modifying these terpene-based resins (phenol-modified, aromatic-modified, hydrogenated, hydrocarbon-modified, etc.) (e.g., terpene-phenolic resins, styrene-modified terpene resins, aromatic-modified terpene resins, and hydrogenated terpene resins).

Examples of the phenol-based tackifying resin include condensates of various phenols (e.g., phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcin) with formaldehyde (e.g., alkylphenol resins, xylene formaldehyde resins), resols obtained by addition reaction of the phenols with formaldehyde using an alkaline catalyst, and novolacs obtained by condensation reaction of the phenols with formaldehyde using an acid catalyst.

Examples of the hydrocarbon-based tackifying resin (petroleum-based tackifying resin) include aliphatic hydrocarbon resins [polymers of aliphatic hydrocarbons such as olefins and dienes having 4 to 5 carbon atoms (olefins such as butene-1, isobutylene, and pentene-1; dienes such as butadiene, 1,3-pentadiene, and isoprene)], aliphatic cyclic hydrocarbon resins [alicyclic hydrocarbon resins obtained by cyclizing and dimerizing so-called "C4 petroleum fractions" and "C5 petroleum fractions" and then polymerizing them, cyclic diene compounds (cyclopentadiene, dicyclopentadiene, ethylidene norbornene, dipentene, etc.) or their hydrogenated products, alicyclic hydrocarbon resins obtained by hydrogenating the aromatic rings of the aromatic hydrocarbon resins and aliphatic/aromatic petroleum resins listed below], aromatic hydrocarbon resins [polymers of vinyl group-containing aromatic hydrocarbons having 8 to 10 carbon atoms (styrene, vinyltoluene, α-methylstyrene, indene, methylindene, etc.)], aliphatic/aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic/alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, coumarone-indene resins, etc.

When the adhesive composition contains a tackifier, the content of the tackifier is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, even more preferably 5 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, relative to 100 parts by mass of copolymer (A). By adjusting the content of the tackifier within the above range, sufficient adhesion to the adherend can be ensured and peeling can be suppressed.

(Method for producing adhesive composition)
The adhesive composition can be produced by mixing the copolymer (A), the crosslinking agent (B), and other additives used as necessary. The adhesive composition may contain a solvent derived from the production of the copolymer (A), or may be diluted with a suitable solvent to have a viscosity suitable for forming an adhesive layer.

Examples of the solvent include aliphatic hydrocarbons such as hexane and heptane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; cellosolve-based solvents such as ethyl cellosolve; and glycol ether-based solvents such as propylene glycol monomethyl ether. These solvents may be used alone or in combination of two or more.

There are no particular limitations on the amount of the solvent used, and it may be adjusted appropriately so that the adhesive composition has a viscosity suitable for coating. From the viewpoint of coatability, the content of the solvent in the adhesive composition is, for example, preferably 1% by mass to 90% by mass, more preferably 10% by mass to 80% by mass, and even more preferably 20% by mass to 70% by mass.

(Formation of the first adhesive layer)
Methods for forming the first adhesive layer include a method of directly applying an adhesive composition onto one side of the first substrate; a method of applying an adhesive composition onto a surface of a release film to form a first adhesive layer, and then transferring the layer onto one side of the first substrate; a method of applying an adhesive composition onto a surface of a first release film to form a first adhesive layer, and then laminating a second release film, peeling off one of the release films, and transferring the layer onto one side of the first substrate.

The adhesive composition can be applied by various coating methods such as reverse gravure coating, direct gravure coating, die coating, bar coating, wire bar coating, roll coating, spin coating, dip coating, spray coating, knife coating, and kiss coating, or by various printing methods such as inkjet printing, offset printing, screen printing, and flexographic printing.

The conditions for drying the coating film and curing the composition are not particularly limited, as long as the solvent contained in the adhesive composition can be removed and curing can be achieved. As for the conditions, for example, it is preferable to perform heat treatment at a temperature of 60°C to 150°C for about 20 to 300 seconds. In particular, the drying temperature is preferably 100°C to 130°C.

[Second Protective Film]
The second protective film 30 has a second substrate 31 and a second adhesive layer 32 , and the second adhesive layer 32 is attached to the non-antifouling treated surface of the cover film 10 .

The second protective film 30 prevents the non-antifouling treated surface of the cover film 10 from being scratched, for example, during continuous processing or storage in a roll process or the like. The second protective film 30 is peeled off from the non-antifouling treated surface of the cover film 10 before a printing process on the non-antifouling treated surface of the cover film 10 or before the cover film 10 is attached to a display or the like. Therefore, the adhesive strength between the second substrate 31 and the second adhesive layer 32 is stronger than the adhesive strength between the non-antifouling treated surface of the cover film 10 and the second adhesive layer 32, and the adhesive strength is adjusted to allow interfacial peeling between the non-antifouling treated surface and the second adhesive layer 32.

The material constituting the second substrate 31 is not particularly limited, but examples thereof include polymeric materials. Examples of polymeric materials include polyesters such as polyethylene terephthalate and polyethylene naphthalate, polyolefins such as polypropylene, polyethylene, polycycloolefins, and cycloolefin copolymers, polycarbonate, polyacrylate, polymethacrylate, polystyrene, polyamide, polyimide, polyacrylonitrile, polyphenylene sulfide, polyvinyl chloride, polyvinylidene chloride, and polyvinyl alcohol. The polymeric materials may be used alone or in combination of two or more. Among these, polyethylene terephthalate, polypropylene, and polyethylene are more preferable from the viewpoints of mechanical properties and material costs, and polyethylene terephthalate is particularly preferable from the viewpoints of transparency and mechanical strength.

The second substrate 31 may be composed of a single layer containing one or more of the above polymeric materials, or may be composed of two or more layers, such as a layer containing one or more of the above polymeric materials and a layer containing one or more of a different polymeric material.

The thickness of the second substrate 31 is not particularly limited, but from the viewpoint of ease of handling, etc., it is preferably 19 μm or more, more preferably 22 μm or more, even more preferably 25 μm or more, and is preferably 200 μm or less, more preferably 150 μm or less, even more preferably 125 μm or less.

(Second adhesive layer)
The second adhesive layer 32 is for attaching the second protective film 30 to the non-soil-resistant surface of the cover film 10 .

The thickness of the second adhesive layer 32 is not particularly limited, but is preferably 1 μm or more, more preferably 2 μm or more, and is preferably 10 μm or less, more preferably 7 μm or less.

The present invention will be described in more detail below based on specific examples. The present invention is not limited to the following examples, and can be modified as appropriate within the scope of the present invention. The polymerization rate of the polymer composition, the weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn) of the polymer component, the thickness of each layer, the water contact angle of the antifouling layer, and the peel strength of the protective film were evaluated according to the following methods.

The meanings of the abbreviations are as follows:
EHA: 2-ethylhexyl acrylate BA: n-butyl acrylate AA: acrylic acid HEA: 2-hydroxyethyl acrylate HBA: 4-hydroxybutyl acrylate BTEE: ethyl 2-methyl-2-n-butyltellanyl-propionate V-70: 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile)
AIBN: Azobisisobutyronitrile AcOEt: Ethyl acetate

[Evaluation method]
(Polymerization rate)
^1H -NMR was measured (solvent: _CDCl3 , internal standard: trimethylsilane (TMS)) using a nuclear magnetic resonance (NMR) measurement device (Bruker Biospin, model: AVANCE500 (frequency 500 MHz)). From the obtained NMR spectrum, the integral ratio of the signal derived from the monomer to the signal derived from the polymer was obtained, and the polymerization rate of the monomer was calculated.

(Weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn))
The molecular weight was determined by gel permeation chromatography (GPC) using a high performance liquid chromatograph (Tosoh Corporation, model HLC-8320GPC). Two TSKgel Super Multipore HZ-H (Tosoh Corporation) columns were used, a tetrahydrofuran solution was used as the mobile phase, and a differential refractometer was used as the detector. The measurement conditions were a column temperature of 40°C, a sample concentration of 10 mg/mL, a sample injection amount of 10 μm, and a flow rate of 0.2 mL/min. A calibration curve was created using polystyrene (molecular weights 2,890,000, 1,090,000, 775,000, 427,000, 190,000, 96,400, 37,900, 10,200, 2,630, and 440) as a standard substance, and the weight average molecular weight (Mw) and number average molecular weight (Mn) were measured. From the measured values, the molecular weight distribution (Mw/Mn) was calculated.

(Thickness of each layer)
The thicknesses of the antifouling layer and the adhesive layer were measured by a spectral interference method using a film thickness measurement system (manufactured by Filmetrics, "Filmetrics F20").

(Water Contact Angle)
The water contact angle of the antifouling layer was measured using a contact angle meter (DropMaster DMo-502, manufactured by Kyowa Interface Science Co., Ltd.). Specifically, 4 μL of pure water was dropped onto the surface of the antifouling layer in an atmosphere of room temperature 23° C. and relative humidity 50%, and the water contact angle was measured 60 seconds after the drop.

(Evaluation of peel strength and adhesive residue of first adhesive layer from antifouling layer)
The release film of the first protective film was peeled off from the first adhesive layer, attached to the antifouling layer of the cover film, and cut into a size of 25 mm wide and 100 mm long. Then, a 2 kg roller was reciprocated twice to press the film, and the film was left to stand for 240 hours in a constant temperature and humidity layer at a temperature of 65°C and a relative humidity of 95%. Next, the peel force of the first adhesive layer was measured under the conditions of a peel speed of 300 mm/min and a peel angle of 180° under an atmosphere of room temperature of 23°C and a relative humidity of 50% using a precision universal testing machine (manufactured by Shimadzu Corporation, "AUTOGRAPH (registered trademark) AGS-1kNX, 50N load cell").
The adhesive residue was evaluated based on the difference (θ1-θ2) between the water contact angle (θ1) of the antifouling layer before the first adhesive layer was attached and the water contact angle (θ2) of the antifouling layer after the attached first adhesive layer was peeled off. The evaluation was made as "good" when the difference (θ1-θ2) was less than 2°, and "poor" when it was 2° or more.

(Peeling Force of Second Adhesive Layer from Cover Film Substrate)
The release film of the second protective film was peeled off from the second adhesive layer, attached to the base material of the cover film, and cut into a size of 25 mm wide and 100 mm long. Then, a 2 kg roller was reciprocated twice to press the film, and the film was left to stand for 240 hours in a constant temperature and humidity layer at a temperature of 65°C and a relative humidity of 95%. Next, the peel force of the second adhesive layer was measured under the conditions of a peel speed of 300 mm/min and a peel angle of 180° under an atmosphere of room temperature of 23°C and a relative humidity of 50% using a precision universal testing machine (manufactured by Shimadzu Corporation, "AUTOGRAPH (registered trademark) AGS-1kNX, 50N load cell").

(Peel test of second protective film)
The cover film with protective film was cut out to a size of 25 mm wide and 150 mm long. As shown in FIG. 2, the adhesive surface of half of the cellophane tape (registered trademark, made by Nichiban, width 25 mm) 40 cut to a length of 30 mm was attached to each of the first protective film 20 and the second protective film 30 of the cut-out cover film with protective film 1 so as to face each other with the cover film with protective film 1 sandwiched between them. The parts of the cellophane tape 40 that were not attached were fixed to a precision universal testing machine (manufactured by Shimadzu Corporation, "AUTOGRAPH (registered trademark) AGS-1kNX, 50N load cell") and peeled under the conditions of a peeling speed of 300 mm/min and a peeling angle of 90°. Then, the case where the first protective film 20 could be peeled off the second protective film 30 without peeling off the cover film 10 was evaluated as "○", and the case where the first protective film 20 peeled off or floated off the cover film 10 was evaluated as "×".

<Preparation of cover film>
(Preparation of Antifouling Hard Coat Layer Composition)
A fluorine-containing compound (Shin-Etsu Chemical Co., Ltd., "KY-1203", perfluoroalkyl group-containing (meth)acrylate, active ingredient 20% by mass) was added to an ultraviolet-curable resin composition (manufactured by Aica Corporation, "Z-735-3L", formulation: modified acrylate, photopolymerization initiator, solvent (methyl ethyl ketone, ethyl acetate), solids concentration 50% by mass) in an amount of 0.1% by mass relative to the total solids content of the composition for forming an antifouling hard coat layer, and propylene glycol monomethyl ether (PGM) was used to adjust the solids concentration to 37% by mass, thereby preparing a composition for forming an antifouling hard coat layer.

(Production of antifouling hard coat film)
The composition for antifouling hard coat layer was applied to a polyimide film (KOLON INDUSTRIES, "KOLON CPI (registered trademark) C_80_O", thickness 80 μm) so that the thickness after formation of the antifouling layer (antifouling hard coat layer) would be 4 μm, and dried at 80° C. for 60 seconds. Thereafter, an electrodeless (microwave type) lamp was used to irradiate ultraviolet light with a light intensity of 110 mJ/cm ² to produce an antifouling hard coat film. The contact angle of water on the surface of the antifouling layer was 111°.

<Preparation of First Protective Film>
(Preparation of Copolymer)
Synthesis Example 1: Copolymer No. A
In a flask equipped with an argon gas inlet tube and a stirrer, BA (570.0 g), HBA (30.0 g), and AcOEt (452.6 g) were charged, and after replacing with argon, BTEE (171.7 μL) and V-70 (76.3 mg) were added, and the reaction was carried out at 33° C. for 24 hours to polymerize. The polymerization rate was 85%.

After performing the polymerization termination operation, AcOEt was added to the obtained solution to obtain a copolymer solution containing Copolymer No. A. The obtained Copolymer No. A had a weight average molecular weight (Mw) of 670,000 and a molecular weight distribution (Mw/Mn) of 1.79.

Synthesis Examples 2 to 4: Copolymer Nos. B to D
Copolymers B to D were produced in the same manner as in the production of copolymer No. A. Table 2 shows the raw material monomers, organotellurium compounds, azo-based polymerization initiators, solvents, reaction conditions, etc. The polymerization rate, weight average molecular weight, molecular weight distribution, and glass transition temperature are shown. The content of each functional group in the copolymer was calculated from the charge ratio of the monomers used in the polymerization reaction.

(Production of First Protective Film)
First protective film No. 1
To 100 parts by mass of the copolymer component of Copolymer No. A obtained in Synthesis Example 1, 0.1 parts by mass of Duranate (registered trademark) TPA-100 was added, and butyl acetate was added so that the solid content concentration became 17% by mass, to obtain an adhesive composition for the first adhesive layer.

Next, the adhesive composition for the first adhesive layer was applied to the corona-treated surface of a polyethylene terephthalate film (Toyobo Ester (registered trademark) film E5101, manufactured by Toyobo, corona-treated on one side, thickness 50 μm) using a Baker-type film applicator to the thickness shown in Table 3, and heated at 120°C for 1 minute to form a first adhesive layer. Next, the release surface of a release film (PET film with a release-treated surface, Clean Sepa (registered trademark) HY-S10, manufactured by Higashiyama Film, thickness 38 μm) was attached to the surface of the first adhesive layer that was not covered with the polyethylene terephthalate film. This was then cured at 40°C for 3 days to produce first protective film No. 1.

First protective film No. 2 to 7
First protective films No. 2 to 7 were produced in the same manner as first protective film No. 1, except that the composition of the adhesive composition was changed as shown in Table 3.

The peel strength of the first protective film produced against the stain-resistant layer of the cover film was measured, and the amount of adhesive remaining after peeling was evaluated. The results are shown in Table 3.

粘着組成物の製造に用いた材料は、以下のとおりである。
ＴＰＡ－１００：旭化成社製、デュラネート（登録商標）ＴＰＡ－１００（ヘキサメチレンジイソシアネートのイソシアヌレート体、イソシアネート基量；５．５０ｍｍｏｌ／ｇ）
Ｔ－Ｃ：三菱ガス化学社製、ＴＥＴＲＡＤ（登録商標）－Ｃ（１，３－ビス（Ｎ，Ｎ－ジグリシジルアミノエチル）シクロヘキサン、エポキシ基量；９．７６ｍｍｏｌ／ｇ）

The materials used in producing the adhesive composition are as follows.
TPA-100: Duranate (registered trademark) TPA-100 (isocyanurate of hexamethylene diisocyanate, amount of isocyanate groups: 5.50 mmol/g), manufactured by Asahi Kasei Corporation
TC: TETRAD (registered trademark)-C (1,3-bis(N,N-diglycidylaminoethyl)cyclohexane, epoxy group amount: 9.76 mmol/g), manufactured by Mitsubishi Gas Chemical Company, Inc.

In the first protective film Nos. 1 to 4, the first adhesive layer is a cured product of an adhesive composition containing a (meth)acrylic copolymer having a first reactive group and a crosslinking agent having a second reactive group that reacts with the first reactive group, and the molecular weight distribution (Mw/Mn) of the (meth)acrylic copolymer having the first reactive group is 3.0 or less, and the molar ratio (molar amount of second reactive group/molar amount of first reactive group) is 0.01 to 0.30. These first protective films Nos. 1 to 4 have a high peeling force (P1) against the antifouling layer (antifouling treated surface) of the cover film, excellent adhesion, and also suppressed adhesive residue after peeling.

The first protective film No. 5 is a case where the molar ratio (molar amount of the second reactive group/molar amount of the first reactive group) in the adhesive composition forming the first adhesive layer is more than 0.30. In this first protective film No. 5, the adhesive residue after peeling was suppressed, but the peel force (P1) against the antifouling layer (antifouling treated surface) of the cover film was low.
The first protective film No. 6 is a case where the molar ratio (molar amount of the second reactive group/molar amount of the first reactive group) in the adhesive composition forming the first adhesive layer is less than 0.01. This first protective film No. 6 has a high peel strength (P1) against the antifouling layer (antifouling treated surface) of the cover film, but adhesive residue occurs after peeling.
The first protective film No. 7 is a case where the molecular weight distribution (Mw/Mn) of the (meth)acrylic copolymer having the first reactive group in the adhesive composition forming the first adhesive layer is more than 3.0. This first protective film No. 7 has a low peel strength (P1) against the antifouling layer (antifouling treated surface) of the cover film, and adhesive residue occurs after peeling.

<Preparation of second protective film>
As the second protective film, the following film was prepared.
Second protective film No. 1: HPF01 (manufactured by Higashiyama Film Co., Ltd., base material: polyester film (thickness 38 μm), adhesive layer: thickness 5 μm, peeling force against polyimide film 20 mN/25 mm)
Second protective film No. 2: MU masking (manufactured by Higashiyama Film Co., Ltd., base material: polyester film (thickness 50 μm), adhesive layer: thickness 10 μm, peeling force against polyimide film 40 mN/25 mm)
Second protective film No. 3: The first protective film No. 5 prepared above (peel strength from polyimide film: 100 mN/25 mm) was used.
Second protective film No. 4: HPF18 (manufactured by Higashiyama Film Co., Ltd., base material: polyester film (thickness 38 μm), adhesive layer: thickness 10 μm, peel strength against polyimide film 300 mN/25 mm)

<Preparation of cover film with protective film>
The release film of the first protective film was peeled off from the first adhesive layer, the first adhesive layer was attached to the antifouling layer (antifouling treatment surface) of the cover film, and a 2 kg roller was rolled back and forth twice to bond the film. The release film of the second protective film was peeled off from the second adhesive layer, the second adhesive layer was attached to the substrate surface (non-antifouling treatment surface) opposite to the surface of the cover film to which the first protective film was attached, and a 2 kg roller was rolled back and forth twice to bond the film. The cover film to which the first protective film and the second protective film were attached was left to stand for 240 hours in a constant temperature and humidity layer at a temperature of 65 ° C. and a relative humidity of 95%, to prepare a cover film with a protective film. The first protective film and the second protective film were used as shown in Table 4. A second protective film peeling test was performed on the obtained cover film with a protective film, and the results are shown in Table 4.

In the cover films with protective film Nos. 1 to 6, 9 to 11, 13 and 14, the peel strength (P1) and the peel strength (P2) satisfy the relationship P1>P2, and the first adhesive layer is a cured product of an adhesive composition containing a (meth)acrylic copolymer having a first reactive group and a crosslinking agent having a second reactive group that reacts with the first reactive group, and the molecular weight distribution (Mw/Mn) of the (meth)acrylic copolymer having the first reactive group is 3.0 or less, and the molar ratio (molar amount of second reactive group/molar amount of first reactive group) is 0.01 to 0.30. These cover films with protective film Nos. 1 to 6, 9 to 11, 13 and 14 have a high peel strength (P1) against the antifouling layer (antifouling treated surface) of the cover film, excellent adhesion, and the adhesive residue after peeling was suppressed. Furthermore, the second protective film could be peeled off without peeling or lifting of the first protective film.

The present invention includes the following embodiments.
(Embodiment 1)
A cover film having a front surface treated with an antifouling treatment and a back surface not treated with an antifouling treatment, a first protective film disposed on the antifouling treatment side of the cover film, and a second protective film disposed on the non-antifouling treatment side of the cover film,
the cover film has a base film and an antifouling layer disposed on the outermost surface side and having a water contact angle of 100° or more;
the first protective film has a first substrate and a first adhesive layer, and the first adhesive layer is attached to the antifouling treatment surface;
the second protective film has a second substrate and a second adhesive layer, and the second adhesive layer is attached to the non-antifouling treated surface;
a peel strength (P1) of the first adhesive layer from the antifouling treated surface at 23° C. and a peel strength (P2) of the second adhesive layer from the non-antifouling treated surface at 23° C. satisfy the relationship P1>P2;
the first adhesive layer is a cured product of an adhesive composition containing a (meth)acrylic copolymer having a first reactive group and a crosslinking agent having a second reactive group that reacts with the first reactive group;
the (meth)acrylic copolymer having a first reactive group has a molecular weight distribution (Mw/Mn) of 3.0 or less;
A cover film with a protective film, characterized in that the molar ratio of the second reactive group of the crosslinking agent to the first reactive group of the (meth)acrylic copolymer having the first reactive group (molar amount of second reactive group/molar amount of first reactive group) is 0.01 to 0.30.

(Embodiment 2)
A cover film with a protective film as described in claim 1, wherein the difference (P1-P2) between the peel strength (P1) of the first adhesive layer against the antifouling treated surface at 23°C and the peel strength (P2) of the second adhesive layer against the non-antifouling treated surface at 23°C is 10 mN/25 mm or more.

(Embodiment 3)
The peel strength (P1) of the first adhesive layer from the antifouling treated surface at 23° C. is 30 mN/25 mm to 380 mN/25 mm;
A cover film with a protective film according to claim 1 or 2, wherein the peel strength (P2) of the second adhesive layer from the non-stain-resistant surface at 23°C is 10 mN/25 mm to 300 mN/25 mm.

(Embodiment 4)
The cover film with a protective film according to any one of claims 1 to 3, wherein the base film of the cover film is a polyimide-based film.

(Embodiment 5)
5. The cover film with a protective film according to any one of claims 1 to 4, wherein the antifouling layer of the cover film is an antifouling hard coat layer.

(Embodiment 6)
The cover film with a protective film according to any one of claims 1 to 5, wherein the (meth)acrylic copolymer having the first reactive group is obtained by living radical polymerization.

The cover film with protective film of the present invention can be used as a cover window for an image display device.

1: Cover film with protective film, 10: Cover film, 11: Base material, 12: Antifouling layer, 20: First protective film, 21: First base material, 22: First adhesive layer, 30: Second protective film, 31: Second base material, 32: Second adhesive layer, 40: Cellophane tape

Claims (6)

A cover film having a front surface treated with an antifouling treatment and a back surface not treated with an antifouling treatment, a first protective film disposed on the antifouling treatment side of the cover film, and a second protective film disposed on the non-antifouling treatment side of the cover film,
the cover film has a base film and an antifouling layer disposed on the outermost surface side and having a water contact angle of 100° or more;
the first protective film has a first substrate and a first adhesive layer, and the first adhesive layer is attached to the antifouling treatment surface;
the second protective film has a second substrate and a second adhesive layer, and the second adhesive layer is attached to the non-antifouling treated surface;
a peel strength (P1) of the first adhesive layer from the antifouling treated surface at 23° C. and a peel strength (P2) of the second adhesive layer from the non-antifouling treated surface at 23° C. satisfy the relationship P1>P2;
the first adhesive layer is a cured product of an adhesive composition containing a (meth)acrylic copolymer having a first reactive group and a crosslinking agent having a second reactive group that reacts with the first reactive group;
the (meth)acrylic copolymer having a first reactive group has a molecular weight distribution (Mw/Mn) of 3.0 or less;
A cover film with a protective film, characterized in that the molar ratio of the second reactive group of the crosslinking agent to the first reactive group of the (meth)acrylic copolymer having the first reactive group (molar amount of second reactive group/molar amount of first reactive group) is 0.01 to 0.30. The cover film with protective film according to claim 1, wherein the difference (P1-P2) between the peel strength (P1) of the first adhesive layer against the stain-resistant surface at 23°C and the peel strength (P2) of the second adhesive layer against the non-stain-resistant surface at 23°C is 10 mN/25 mm or more. The peel strength (P1) of the first adhesive layer from the antifouling treated surface at 23° C. is 30 mN/25 mm to 380 mN/25 mm;
3. A cover film with a protective film according to claim 1 or 2, wherein the peel strength (P2) of the second adhesive layer from the non-stain-resistant surface at 23° C. is 10 mN/25 mm to 300 mN/25 mm. The cover film with protective film according to claim 1 or 2, wherein the base film of the cover film is a polyimide-based film. The cover film with protective film according to claim 1 or 2, wherein the antifouling layer of the cover film is an antifouling hard coat layer. The cover film with protective film according to claim 1 or 2, wherein the (meth)acrylic copolymer having the first reactive group is obtained by living radical polymerization.

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