Adhesive sheet with release sheet

Abstract

The invention provides an adhesive sheet with a non-silicone release sheet. The adhesive sheet has release sheet peelability which is not inferior to that of a silicone release sheet. The present invention provides an adhesive sheet with a release sheet, which comprises an adhesive sheet having an adhesive layer and a non-silicone release sheet disposed on the surface of the adhesive layer. The adhesive layer contains an acrylic polymer. Furthermore, the acrylic polymer is a polymer of a monomer component including an alkyl (meth) acrylate (m1) having an alkyl group having 6-17 carbon atoms at an ester terminal, where the alkyl group having 6-17 carbon atoms is a linear alkyl group or a branched alkyl group having 1 carbon atoms.

Description

Technical Field

[0001] The present invention relates to an adhesive sheet with a release sheet.

[0002] This application claims priority based on Japanese Patent Application No. 2022-190773 filed on November 29, 2022, and the entire content of this application is incorporated into this specification by reference. Background Art

[0003] Generally, an adhesive (also referred to as a pressure-sensitive adhesive. The same applies hereinafter) is in a soft solid (viscoelastic body) state in a temperature region near room temperature and has the property of simply adhering to an adherend by pressure. Making effective use of such a property, adhesives are widely used in the form of adhesive sheets for purposes such as joining of components and surface protection. For example, an adhesive sheet having an adhesive layer on one surface of a substrate is preferably used as a surface protection sheet that prevents damage (scratches, dirt, corrosion, etc.) to the surface of various articles during processing or handling. Such an adhesive sheet can be circulated, stored, and processed in a form in which the adhesive surface is protected by a release sheet before use. As a prior art document disclosing such prior art, Patent Document 1 can be cited.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-224811 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] As a release sheet for an adhesive sheet, a silicone-based release sheet having excellent light release properties (for example, Patent Document 1) is widely used. However, depending on the usage scenario, application site, etc. of the adhesive sheet, it is sometimes not desirable to use a silicone-based release sheet. For example, in a scenario where an adhesive sheet is used to protect the surface of an optical member, the silicone material contained in the silicone-based release sheet is transferred from the release surface of the release sheet to the adhesive surface and then to the adherend, so that after the adhesive sheet is peeled off, the surface characteristics of the adherend surface may change. In addition, depending on the application site of the adhesive sheet such as inside a precision machine, it is sometimes desirable to avoid using a silicone material that can generate siloxane gas. In such a case, a non-silicone-based release sheet such as a release sheet having a release treatment layer formed of a release treatment agent other than a silicone material (non-silicone-based release treatment agent) is used, but compared with the silicone-based release sheet, it is difficult to obtain light release properties (release sheet releasability) from the adhesive surface, and there is a tendency for the releasability to decrease.

[0009] The present invention has been created in view of the above circumstances, and an object thereof is to provide an adhesive sheet with a non-silicone release sheet having release sheet releasability comparable to that in the case of using a silicone release sheet.

[0010] Means for Solving the Problem

[0011] According to the present specification, there is provided an adhesive sheet with a release sheet, which includes an adhesive sheet having an adhesive layer and a non-silicone release sheet disposed on the surface of the adhesive layer. The adhesive layer contains an acrylic polymer. Further, the acrylic polymer is a polymer of monomer components, and the monomer components include an alkyl (meth)acrylate (m1) having an alkyl group with 6 to 17 carbon atoms at the ester terminal. Among them, the alkyl group with 6 to 17 carbon atoms is a straight-chain alkyl group or a branched alkyl group with 1 carbon atom in the branch. By using an adhesive containing an acrylic polymer having the above structure, in the case of using a non-silicone release sheet, an adhesive sheet having release sheet releasability comparable to that in the case of using a silicone release sheet can also be obtained.

[0012] In some preferred embodiments, the alkyl (meth)acrylate (m1) includes at least one selected from n-heptyl acrylate and n-octyl acrylate. By using at least one selected from n-heptyl acrylate and n-octyl acrylate as the monomer component of the acrylic polymer, the effects brought by the technology disclosed herein are preferably exerted.

[0013] In some embodiments, the monomer components include a monomer (m2) having a hydroxyl group. By using a monomer having a hydroxyl group, the side chain of the acrylic polymer has a hydroxyl group. This hydroxyl group can become a crosslinking point, for example, in the case of using a crosslinking agent such as an isocyanate-based or epoxy-based crosslinking agent.

[0014] In some preferred embodiments, the adhesive layer contains an isocyanate-based crosslinking agent. In the embodiment of using an isocyanate-based crosslinking agent as the crosslinking agent, the technology disclosed herein is preferably implemented.

[0015] In some embodiments, the adhesive layer contains a zirconium-containing compound. By using a zirconium-containing compound as a catalyst, it is easy to balance the progress of curing (typically, crosslinking reaction) of the adhesive layer and the pot life. From the aspect of reducing the environmental load, it is also desirable to use a zirconium-based catalyst. Further, by using a zirconium-containing compound as a catalyst, it is easy to form a non-colored adhesive. This can be an advantageous feature when the adhesive sheet is used for optical applications.

[0016] In some preferred embodiments, the above non-silicone release sheet has a release sheet substrate and a non-silicone release treatment layer provided on at least one surface of the release sheet substrate. The above non-silicone release treatment layer is formed of a material containing a long-chain alkyl-based release treatment agent. In the embodiment where a release sheet having a release treatment layer containing a long-chain alkyl-based release treatment agent is used as the non-silicone release sheet, the desired light releasability can be preferably obtained.

[0017] In some embodiments, the above adhesive sheet has a substrate and the above adhesive layer disposed on at least one surface of the substrate. The processability, operability, etc. of the adhesive sheet with the substrate are excellent, and for example, it can be preferably used as a surface protective film that is removed (peeled off) from the adherend after use.

[0018] Since the adhesive surface of the adhesive sheet disclosed herein is protected by the release sheet, the adhesive surface can be kept smooth and adhered to the adherend evenly. In addition, by using a non-silicone release sheet as the release sheet, contamination of the adherend caused by silicone materials will not occur. This can be an advantageous advantage, for example, in optical applications that require specified optical properties. Therefore, the adhesive sheet disclosed herein is preferably used in optical applications, specifically, in the embodiment of being attached to an optical member.

[0019] In addition, the adhesive sheet disclosed herein is suitable as a surface protective film, for example. After the surface protective film is attached to the object to be protected, when its protection purpose is achieved, it is usually peeled off (re-peeled) from the object to be protected. For such a surface protective film, it is required not to deteriorate the object to be protected before and after the protection, so it is advantageous to use an adhesive sheet with a non-silicone release sheet that does not cause contamination of silicone materials on the protected surface after peeling off. Description of the Drawings

[0020] Figure 1 It is a cross-sectional view schematically showing the configuration of an adhesive sheet with a release sheet according to an embodiment. Detailed Embodiments

[0021] Hereinafter, preferred embodiments of the present invention will be described. Regarding matters other than those specifically mentioned in this specification and required for the implementation of the present invention, those skilled in the art can understand based on the teachings related to the implementation of the invention described in this specification and the common general knowledge in the art at the time of application. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in the art.

[0022] It should be noted that in the following drawings, sometimes components / parts that perform the same function are marked with the same reference numerals for description, and repeated descriptions are sometimes omitted or simplified. In addition, the embodiments described in the drawings are schematized for clearly explaining the present invention and do not necessarily accurately represent the dimensions and scales of the actually provided products.

[0023] In this specification, the "adhesive" refers to, as described above, a material that is in a soft solid (viscoelastic body) state in the temperature range near room temperature and has the property of simply adhering to the adherend by pressure. The adhesive mentioned here, as defined in "C.A. Dahlquist, 'Adhesion: Fundamentals and Practice', McLaren & Sons (1966), p. 143", generally can be a material having a complex tensile elastic modulus E ＊ (1 Hz) < 10 7 dyne / cm 2 of the property (typically, a material having the above property at 25°C).

[0024] In this specification, carbon derived from biomass refers to carbon (renewable carbon) derived from biomass materials, that is, materials derived from renewable organic resources. The above biomass materials typically refer to materials derived from biological resources (typically, photosynthetic plants) that can be continuously reproduced as long as sunlight, water, and carbon dioxide exist. Therefore, materials derived from fossil resources (fossil resource-based materials) that are depleted after mining are excluded from the concept of the biomass materials mentioned here. The biomass carbon ratio of the adhesive (layer) and the adhesive sheet, that is, the proportion of carbon derived from biomass contained in the adhesive (layer) and the adhesive sheet in all carbon, can be estimated based on the carbon isotope content of mass number 14 measured according to ASTM D6866.

[0025] <Configuration Example of Adhesive Sheet with Release Sheet>

[0026] The adhesive sheet with a release sheet disclosed here includes an adhesive sheet having an adhesive layer and a non-silicone release sheet disposed on the surface of the adhesive layer. The adhesive sheet can be a substrate-bearing adhesive sheet in a form having the above adhesive layer on one or both sides of a non-peeling substrate (support substrate), or can be a substrate-free adhesive sheet in a form in which the adhesive layer is held by a release sheet (that is, an adhesive sheet that does not have a non-peeling substrate). Hereinafter, the support substrate is sometimes simply referred to as the "substrate". It should be noted that the concept of the adhesive sheet mentioned here can include those called adhesive tapes, adhesive labels, adhesive films, etc. The adhesive sheet can be in a roll form or in a single sheet form. In addition, it can also be an adhesive sheet in a form processed into various shapes.

[0027] Figure 1 Schematically shows the structure of an adhesive sheet with a release sheet according to an embodiment. The adhesive sheet 100 with a release sheet includes: an adhesive sheet 1 having an adhesive layer 21, and a release sheet 31 laminated on the surface (adhesive surface) 21A of the adhesive layer 21. The adhesive sheet 1 is configured as a single-sided adhesive sheet with a substrate, and this single-sided adhesive sheet with a substrate includes: a sheet-like support substrate (such as a resin film) 10 having a first surface 10A and a second surface 10B; and an adhesive layer 21 provided on the first surface 10A side of the support substrate 10. The adhesive layer 21 is fixedly provided, that is, not intended to be separated from the support substrate 10, on the first surface 10A side of the support substrate 10. Such a single-sided adhesive adhesive sheet 1 is preferably used as a surface protection film by attaching its adhesive surface to the surface of an adherend (a protected object, such as an optical member like a polarizing plate). Before use, the adhesive sheet 1 has the form of an adhesive sheet 100 with a release sheet, and the surface (adhesive surface) 21A of the adhesive layer 21 is protected by a release sheet 31 whose at least the side facing the adhesive layer 21 is a release surface.

[0028] <Adhesive layer>

[0029] (Acrylic polymer)

[0030] The adhesive layer disclosed herein contains an acrylic polymer. The above-mentioned adhesive layer is typically an adhesive layer based on an acrylic polymer. Such an adhesive layer is also referred to as an acrylic adhesive layer. It should be noted that the base polymer refers to the main component of the rubber-like polymer (a polymer that exhibits rubber elasticity in the temperature region near room temperature) contained in the adhesive layer. In addition, in this specification, unless otherwise specified, "main component" means a component containing more than 50% by weight. In addition, the following descriptions related to the components that can be included in the adhesive and the adhesive layer can also be applied to the adhesive composition used to form the adhesive (layer) as long as not otherwise specified.

[0031] In this specification, "acrylic polymer" refers to a polymer derived from a monomer component containing more than 50% by weight of (meth)acrylic monomers. The content of (meth)acrylic monomers in the monomer component is preferably 70% by weight or more, and can also be 80% by weight or more. In some embodiments, the content of (meth)acrylic monomers in the monomer component can be 90% by weight or more, can also be 95% by weight or more, or can be 100%. On the other hand, considering the balance of adhesion characteristics, in some embodiments, the proportion of (meth)acrylic monomers in the entire monomer component can be, for example, less than 99% by weight, can also be less than 95% by weight, or can also be less than 93% by weight.

[0032] In addition, in this specification, the "(meth)acrylic monomer" refers to a monomer having at least one (meth)acryloyl group in one molecule. Herein, the "(meth)acryloyl group" generically refers to an acryloyl group and a methacryloyl group. Similarly, the "(meth)acrylate" generically refers to an acrylate and a methacrylate, and the "(meth)acrylic acid" generically refers to acrylic acid and methacrylic acid. Therefore, the concept of the (meth)acrylic monomer as described herein can include both a monomer having an acryloyl group (acrylic monomer) and a monomer having a methacryloyl group (methacrylic monomer).

[0033] As the above acrylic polymer, typically a polymer of monomer raw materials is used, which contains one or more (meth)acrylic linear alkyl esters as main monomers, and further may contain one or more comonomers copolymerizable with the main monomers. The above main monomer refers to a component accounting for more than 50% by weight of the total monomer components. In addition, the (meth)acrylic linear alkyl ester refers to an (meth)acrylic alkyl ester having a linear alkyl group at the ester terminal. The above linear alkyl group is a concept including linear and branched alkyl groups, and does not include a cyclic alkyl group called alicyclic. In addition, the above comonomer refers to monomer components other than the (meth)acrylic linear alkyl esters used as main monomers, and includes functional group-containing monomers such as the following hydroxyl group-containing monomers and carboxyl group-containing monomers, and other copolymerizable monomers. In this specification, the comonomer refers to monomer components other than the (meth)acrylic alkyl ester (m1) and other (meth)acrylic linear alkyl esters.

[0034] The acrylic polymer used in the technology disclosed herein contains an alkyl (meth)acrylate (m1) having a specific chemical structure as a monomer component. Specifically, the alkyl (meth)acrylate (m1) is an alkyl (meth)acrylate having an alkyl group with 6 to 17 carbon atoms at the ester terminal, and the alkyl group with 6 to 17 carbon atoms is a straight-chain alkyl group, or a branched alkyl group with 1 carbon atom (also referred to as a branch or branched group). According to the adhesive of the acrylic polymer containing the above structure, in the case of using a non-silicone release sheet, a release sheet peelability comparable to that in the case of using a silicone release sheet can also be obtained. Although the reason is not specifically and limitatively explained, according to the results of the following examples, the acrylic polymer synthesized using the above alkyl (meth)acrylate (m1) as a monomer component has a long straight chain or a low degree of branching alkyl group in the side chain of the acrylic polymer. It is considered that this side-chain alkyl group contributes to achieving the light peelability of the non-silicone release sheet. The above alkyl (meth)acrylate (m1) is included as at least a part of the main monomer ((meth)acrylic acid linear alkyl ester) in the monomer component of the acrylic polymer. Hereinafter, the (meth)acrylic acid linear alkyl ester having a linear alkyl group with X carbon atoms at the ester terminal is sometimes referred to as (meth)acrylic acid C X alkyl ester (for example, in the case of a (meth)acrylic acid linear alkyl ester having a linear alkyl group with 6 to 17 carbon atoms at the ester terminal, it is (meth)acrylic acid C 6－17 alkyl ester).

[0035] The above alkyl (meth)acrylate (m1) can also be represented by the following formula (1).

[0036] CH2=C(R 1 )COOR 2 (1)

[0037] Here, R 1 in the above formula (1) is a hydrogen atom or a methyl group. In addition, R 2 is an alkyl group with 6 to 17 carbon atoms, which is a straight-chain alkyl group or a branched alkyl group with 1 carbon atom. From the viewpoint of the light peelability of the non-silicone release sheet, the number of carbon atoms of the alkyl group of the alkyl (meth)acrylate (m1) is preferably 7 or more, can be 8 or more, can be 9 or more, can be 10 or more, and can be 12 or more. The more the number of carbon atoms of the alkyl group, the easier it is to effectively exhibit the functions and characteristics of the alkyl group as a long chain. In addition, from the viewpoints of adhesive formability, adhesion characteristics, curing speed, etc., the above number of carbon atoms is preferably 14 or less, more preferably 12 or less, further preferably 10 or less, and particularly preferably 8 or less (for example, 7 or 8).

[0038] As the (meth)acrylic acid C used as the alkyl (meth)acrylate (m1)6－17 Specific examples of the linear alkyl esters include: n-hexyl (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-decyl (meth)acrylate, n-undecyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, n-pentadecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-heptadecyl (meth)acrylate. Regarding the (meth)acrylic acid C as the (meth)acrylic alkyl ester (m1) 6－17 Specific examples of the branched alkyl esters include: 2-octyl (meth)acrylate, isooctyl acrylate, etc., methylheptyl (meth)acrylate, methyloctyl (meth)acrylate, methylnonyl (meth)acrylate, methyldecyl (meth)acrylate, methyldodecyl (meth)acrylate, methyltridecyl (meth)acrylate, methyltetradecyl (meth)acrylate, methylpentadecyl (meth)acrylate, methylhexadecyl (meth)acrylate. The (meth)acrylic alkyl ester (m1) can be used alone or in combination of two or more. Although not particularly limited, in some embodiments, an acrylic alkyl ester is preferably used as the (meth)acrylic alkyl ester (m1).

[0039] In some embodiments, a (meth)acrylic acid C 6－17 linear alkyl ester is preferably used. Among them, as the (meth)acrylic alkyl ester (m1), n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, n-dodecyl (meth)acrylate are more preferred, and n-heptyl (meth)acrylate and n-octyl (meth)acrylate are further preferred.

[0040] As the (meth)acrylic acid C 6－17 branched alkyl ester, any of the (meth)acrylic acid isoalkyl esters having an isoalkyl group with a methyl branched on the first carbon from the end of the branched alkyl chain, and the (meth)acrylic acid branched alkyl esters having a non-iso branched alkyl chain with a methyl branched on two or more carbons from the end of the branched alkyl chain such as 2-octyl (meth)acrylate can be used. However, in some embodiments, a (meth)acrylic acid branched alkyl ester having a non-iso branched alkyl chain with a relatively long linear alkyl chain at the side chain end of the acrylic polymer is preferably used. For example, a (meth)acrylic acid C branched alkyl ester in which the branched group of the branched alkyl is (meth)bonded to the first or second carbon from the ester end side can be preferably used. 6－17 branched alkyl ester.

[0041] The proportion of the alkyl (meth)acrylate (m1) in the whole monomer components is set according to its intended use, required properties, and the like. In some embodiments, the proportion of the alkyl (meth)acrylate (m1) in the whole monomer components can be, for example, 10% by weight or more, suitably 30% by weight or more, in some preferred embodiments, 50% by weight or more (e.g., more than 50% by weight), more preferably 70% by weight or more, further preferably 80% by weight or more, can be 85% by weight or more, particularly preferably 90% by weight or more, can be 92% by weight or more, and can also be 95% by weight or more. By increasing the usage amount of the alkyl (meth)acrylate (m1), the properties based on the alkyl (meth)acrylate (m1) can be effectively exhibited. On the other hand, from the viewpoint of copolymerizing a functional group-containing monomer that becomes a crosslinking point, etc., the proportion of the alkyl (meth)acrylate (m1) in the whole monomer components can be, for example, less than 99% by weight, can also be less than 98% by weight, and can also be less than 97% by weight. In other embodiments, from the viewpoint of obtaining the usage effect of other monomers, the upper limit of the proportion of the alkyl (meth)acrylate (m1) in the whole monomer components can be 95% by weight or less, can also be 75% by weight or less, can also be 60% by weight or less, and can also be 50% by weight or less (e.g., less than 50% by weight).

[0042] In some embodiments, the proportion of the alkyl (meth)acrylate (m1) in the whole alkyl (meth)acrylate chain esters contained in the monomer components of the above acrylic polymer can be, for example, 10% by weight or more, suitably 30% by weight or more, in some preferred embodiments, 50% by weight or more (e.g., more than 50% by weight), more preferably 70% by weight or more, further preferably 80% by weight or more, particularly preferably 90% by weight or more, can be 95% by weight or more, and can also be 99% by weight or more. By increasing the usage amount of the alkyl (meth)acrylate (m1), the properties based on the alkyl (meth)acrylate (m1) can be effectively exhibited. In some embodiments, as the alkyl (meth)acrylate chain ester, an acrylic polymer composed of a monomer containing only the alkyl (meth)acrylate (m1) is used. Therefore, the upper limit of the proportion of the alkyl (meth)acrylate (m1) in the whole alkyl (meth)acrylate chain esters is 100% by weight. In other embodiments, from the viewpoint of obtaining the usage effect of the alkyl (meth)acrylate chain ester other than the alkyl (meth)acrylate (m1), the proportion of the alkyl (meth)acrylate (m1) in the whole alkyl (meth)acrylate chain esters can be 95% by weight or less, can also be 75% by weight or less, can also be 60% by weight or less, and can also be 50% by weight or less (e.g., less than 50% by weight).

[0043] In some preferred embodiments, as the (meth)acrylic acid alkyl ester (m1), a C 7－12 linear alkyl ester is used. Among them, it is more preferred to use a C 7－8 linear alkyl ester. The proportion of the C 7－12 linear alkyl ester (more preferably the C 7－8 linear alkyl ester) in the total monomer components can be, for example, 10% by weight or more, suitably 30% by weight or more, in some preferred embodiments, 50% by weight or more (e.g., more than 50% by weight), more preferably 70% by weight or more, further preferably 80% by weight or more, can be 85% by weight or more, particularly preferably 90% by weight or more, can be 92% by weight or more, and can also be 95% by weight or more. In addition, the proportion of the C 7－12 linear alkyl ester (more preferably the C 7－8 linear alkyl ester) in the total monomer components can be, for example, less than 99% by weight, can also be less than 98% by weight, and can also be less than 97% by weight. In other embodiments, from the viewpoint of obtaining the use effects of other monomers, the upper limit of the proportion of the C 7－12 linear alkyl ester (more preferably the C 7－8 linear alkyl ester) in the total monomer components can be 95% by weight or less, can also be 75% by weight or less, can also be 60% by weight or less, and can also be 50% by weight or less (e.g., less than 50% by weight).

[0044] In some preferred embodiments, as the (meth)acrylic acid alkyl ester (m1), n-heptyl (meth)acrylate is used. By using n-heptyl (meth)acrylate, the effects brought by the technology disclosed herein can be particularly preferably exerted. Among them, from the viewpoint of adhesion characteristics, n-heptyl acrylate is particularly preferred.

[0045] The proportion of n-heptyl (meth)acrylate in the whole monomer component is set according to its intended use, required properties, etc. In some embodiments, the proportion of n-heptyl (meth)acrylate in the whole monomer component can be, for example, 10% by weight or more, suitably 30% by weight or more, in some preferred embodiments, 50% by weight or more (e.g., more than 50% by weight), more preferably 70% by weight or more, further preferably 80% by weight or more, can be 85% by weight or more, particularly preferably 90% by weight or more, can be 92% by weight or more, and can also be 95% by weight or more. By increasing the amount of n-heptyl (meth)acrylate used, its usage effect can be effectively exhibited. On the other hand, from the viewpoint of copolymerizing a functional group-containing monomer or the like that becomes a crosslinking point, the proportion of n-heptyl (meth)acrylate in the whole monomer component can be, for example, less than 99% by weight, can also be less than 98% by weight, and can also be less than 97% by weight. In other embodiments, from the viewpoint of obtaining the usage effects of various monomers other than n-heptyl (meth)acrylate, the proportion of n-heptyl (meth)acrylate in the above-mentioned whole monomer component can be 95% by weight or less, can also be 75% by weight or less, can also be 60% by weight or less, and can also be 50% by weight or less (e.g., less than 50% by weight).

[0046] In some embodiments, the proportion of n-heptyl (meth)acrylate in the whole linear alkyl (meth)acrylate of the acrylic polymer in the above-mentioned monomer component can be, for example, 10% by weight or more, suitably 30% by weight or more, in some preferred embodiments, 50% by weight or more (e.g., more than 50% by weight), more preferably 70% by weight or more, further preferably 80% by weight or more, particularly preferably 90% by weight or more, can be 95% by weight or more, and can also be 99% by weight or more. By increasing the amount of n-heptyl (meth)acrylate used, its usage effect can be effectively exhibited. The technology disclosed herein can be preferably implemented in an embodiment of using an acrylic polymer having a monomer composition containing only n-heptyl (meth)acrylate as the above-mentioned linear alkyl (meth)acrylate. Therefore, the upper limit of the proportion of n-heptyl (meth)acrylate in the whole linear alkyl (meth)acrylate is 100% by weight. In other embodiments, from the viewpoint of obtaining the usage effects of other linear alkyl (meth)acrylates, the proportion of n-heptyl (meth)acrylate in the whole linear alkyl (meth)acrylate can be 95% by weight or less, can also be 75% by weight or less, can also be 60% by weight or less, and can also be 50% by weight or less (e.g., less than 50% by weight).

[0047] In some embodiments, the monomer components constituting the acrylic polymer may also contain (meth)acrylic linear alkyl esters that do not belong to the (meth)acrylic alkyl ester (m1) within a range that does not significantly impair the effects of the invention. As the (meth)acrylic linear alkyl esters other than the (meth)acrylic alkyl ester (m1), examples include: (meth)acrylic C 1－5 alkyl esters, (meth)acrylic C 18+ alkyl esters in which the alkyl group has 18 or more carbon atoms, (meth)acrylic C 6－17 branched alkyl esters in which the branched group in the alkyl group has 2 or more carbon atoms. They may be used alone or in combination of two or more. As specific examples of the (meth)acrylic C 1－5 alkyl esters, examples include: methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate. As specific examples of the (meth)acrylic C 18+ alkyl esters, examples include: octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate. As specific examples of the above (meth)acrylic C 6－17 branched alkyl esters, examples include 2-ethylhexyl (meth)acrylate, etc.

[0048] The proportion of the (meth)acrylic linear alkyl esters other than the (meth)acrylic alkyl ester (m1) in the monomer components is not particularly limited. For example, it may be approximately 50% by weight or less (e.g., less than 50% by weight), may be 30% by weight or less, may be 10% by weight or less, or may be 1% by weight or less. The technology disclosed herein can be preferably implemented in an embodiment where the monomer components substantially do not contain (meth)acrylic linear alkyl esters other than the (meth)acrylic alkyl ester (m1). In the embodiment where the above monomer components contain (meth)acrylic linear alkyl esters other than the (meth)acrylic alkyl ester (m1), the proportion of the (meth)acrylic linear alkyl esters other than the (meth)acrylic alkyl ester (m1) in the monomer components may be, for example, 1% by weight or more, may be 10% by weight or more, or may be 30% by weight or more.

[0049] It should be noted that in this specification, the monomer components substantially do not contain monomer A (e.g., (meth)acrylic linear alkyl esters other than the above (meth)acrylic alkyl ester (m1)) means that the monomer A is at least not intentionally used, and it is allowed that the monomer A is, for example, unintentionally contained at about 0.1% by weight or less.

[0050] In some embodiments, the above monomer components may include an alkyl (meth)acrylate having a biomass-derived alkyl group at the ester terminal (hereinafter, also referred to as “biomass-derived linear alkyl (meth)acrylate”) as the above linear alkyl (meth)acrylate. In recent years, environmental problems such as global warming have been taken seriously, and it is desired to reduce the use of fossil resource-based materials such as petroleum. In such a situation, reducing the use of fossil resource-based materials is also required in the field of adhesives. By using biomass-derived linear alkyl (meth)acrylate, an acrylic adhesive composition that takes into account the suppression of dependence on fossil resource-based materials can be appropriately achieved.

[0051] (Meth)acrylate biomass-derived linear alkyl esters are not particularly limited. For example, they are esters of biomass-derived alkanols and (meth)acrylic acid derived from biomass or non-biomass. Examples of biomass-derived alkanols include biomass ethanol; alkanols derived from plant raw materials such as palm oil, palm kernel oil, coconut oil, and castor oil; etc. When the number of carbon atoms of the biomass-derived alkanol is 3 or more, the alkanol can be linear or branched. In some embodiments, as the (meth)acrylate biomass-derived linear alkyl ester for synthesizing an acrylic polymer, an ester of a biomass-derived alkanol and non-biomass-derived (meth)acrylic acid is used. In this (meth)acrylate biomass-derived linear alkyl ester, the larger the number of carbon atoms of the alkanol, the higher the proportion of biomass-derived carbon atoms in the total number of carbon atoms contained in the (meth)acrylate biomass-derived linear alkyl ester, that is, the higher the biomass carbon ratio of the linear alkyl (meth)acrylate. Therefore, in the above (meth)acrylate biomass-derived linear alkyl ester, in terms of reducing the dependence on fossil resource-based materials, it is desirable that the number of carbon atoms of the biomass-derived linear alkyl group is large. On the other hand, if the number of carbon atoms of the linear alkyl group constituting the linear alkyl (meth)acrylate is too large, there is a tendency that adhesive properties such as adhesion are difficult to obtain, and in addition, it may be disadvantageous in terms of productivity such as synthesis, operability, and cost. In the embodiment where an ester of a biomass-derived alkanol and non-biomass-derived (meth)acrylic acid is used as the (meth)acrylate biomass-derived linear alkyl ester, it is desirable to use a material that well balances adhesive properties and reduction of dependence on fossil resource-based materials (more specifically, the biomass carbon ratio of the above linear alkyl (meth)acrylate).

[0052] In the technology disclosed herein, any of the above-mentioned (meth)acrylic acid alkyl esters (m1) and the linear chain (meth)acrylic acid alkyl esters other than the (meth)acrylic acid alkyl esters (m1) can be a (meth)acrylic acid biomass linear chain alkyl ester. In a scheme where two or more compounds are used as the linear chain (meth)acrylic acid alkyl esters for synthesizing an acrylic polymer, at least a part thereof (for example, one or two, or all, i.e., all types) can be a (meth)acrylic acid biomass linear chain alkyl ester. In some preferred schemes, by using a (meth)acrylic acid biomass linear chain alkyl ester as the (meth)acrylic acid alkyl ester (m1), the dependence on fossil resource-based materials is reduced, and preferably the effects brought about by the technology disclosed herein are achieved.

[0053] From the viewpoints of binder formability, adhesion properties, and curing speed, the number of carbon atoms of the alkyl group in the (meth)acrylic acid biomass linear chain alkyl ester is preferably 14 or less, more preferably 12 or less, further preferably 10 or less, and particularly preferably 8 or less (for example, 7 or 8). In addition, the above-mentioned number of carbon atoms is preferably 7 or more. For example, in a scheme where an alkanol derived from biomass and a (meth)acrylic acid ester derived from non-biomass are used as the (meth)acrylic acid biomass linear chain alkyl ester, by increasing the number of carbon atoms of the alkyl group, the biomass carbon ratio of the synthesized acrylic polymer can be increased.

[0054] In some preferred schemes, as the (meth)acrylic acid alkyl ester (m1), n-heptyl (meth)acrylate having a n-heptyl group derived from biomass (hereinafter, also referred to as "(meth)acrylic acid biomass heptyl ester") is used. By using the (meth)acrylic acid biomass heptyl ester, the dependence on fossil resource-based materials can be reduced, and particularly preferably the effects brought about by the technology disclosed herein can be exerted. Among them, from the viewpoint of adhesion properties, acrylic acid biomass heptyl ester is particularly preferred.

[0055] In some embodiments, the proportion of the biomass linear alkyl (meth)acrylate (e.g., biomass n-heptyl (meth)acrylate) in the total linear alkyl (meth)acrylate used as the monomer component of the above acrylic polymer may be, for example, 1% by weight or more, suitably 10% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more (e.g., more than 50% by weight), may be 70% by weight or more, may be 80% by weight or more, may be 90% by weight or more, may be 95% by weight or more, or may be 99% by weight or more. By increasing the proportion of the biomass linear alkyl (meth)acrylate used, the biomass carbon ratio of the acrylic polymer can be increased, and its usage effect can be effectively demonstrated. The technology disclosed herein can be preferably implemented by using an acrylic polymer composed of only the biomass linear alkyl (meth)acrylate as the linear alkyl (meth)acrylate. Therefore, the upper limit of the proportion of the biomass linear alkyl (meth)acrylate in the total linear alkyl (meth)acrylate is 100% by weight. In other embodiments, the proportion of the biomass linear alkyl (meth)acrylate in the total linear alkyl (meth)acrylate may be 95% by weight or less, may be 70% by weight or less, may be 50% by weight or less (e.g., less than 50% by weight), may be 30% by weight or less, may be 10% by weight or less, or may be 1% by weight or less.

[0056] In some embodiments, the monomer component of the acrylic polymer preferably contains a monomer (m2) having a hydroxyl group. The hydroxyl group-containing monomer (m2) is included in the monomer component in the form of the above co-monomer. By using the hydroxyl group-containing monomer (m2), the side chain of the acrylic polymer has a hydroxyl group. This hydroxyl group can become a crosslinking point, for example, when a crosslinking agent such as an isocyanate-based or epoxy-based crosslinking agent is used. The hydroxyl group-containing monomer (m2) may be used alone or in combination of two or more.

[0057] In the hydroxyl group-containing monomer (m2), the length of the side chain having a hydroxyl group is not particularly limited. The number of carbon atoms in the hydroxyl group-containing side chain of the hydroxyl group-containing monomer (m2) can be, for example, 2 or more, preferably 3 or more. Here, regarding the side chain having a hydroxyl group in the hydroxyl group-containing monomer (m2), for example, in the case of a hydroxyl group-containing (meth)acrylic monomer, it refers to the chain structure bonded to the (meth)acryloyl group. It is considered that by using the hydroxyl group-containing monomer (m2) having a hydroxyl group in a side chain with a longer number of carbon atoms, the hydroxyl group serving as a crosslinking point approaches the crosslinking agent, and curing (crosslinking reaction) proceeds rapidly. In addition, based on the relationship with the chain length of the alkyl group of the (meth)acrylic acid alkyl ester (m1), the length of the side chain of the hydroxyl group-containing monomer (m2) is appropriately set, whereby the crosslinking reaction can be moderately controlled, and thus the progress of the crosslinking reaction and the practical pot life can be preferably balanced. The hydroxyl group-containing monomer (m2) can be derived from biomass or non-biomass.

[0058] As the hydroxyl group-containing monomer (m2), a hydroxyl group-containing (meth)acrylic monomer is preferably used. Specific examples of the above-mentioned hydroxyl group-containing (meth)acrylic monomer include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate and other (meth)acrylic acid hydroxyalkyl esters; N-hydroxypropyl (meth)acrylamide, N-hydroxybutyl (meth)acrylamide and other hydroxyalkyl (meth)acrylamides. Among them, (meth)acrylic acid hydroxyalkyl esters are preferred, and 4-hydroxybutyl (meth)acrylate is more preferred. The above-mentioned hydroxyl group-containing (meth)acrylic monomers can be used alone or in combination of two or more.

[0059] In some preferred embodiments, as the hydroxyl group-containing (meth)acrylic monomer, a (meth)acrylic monomer having a hydroxyalkyl group with 3 or more carbon atoms is used. Among them, a (meth)acrylic acid hydroxyalkyl ester having a hydroxyalkyl group with 3 or more carbon atoms at the ester terminal is more preferred, and among them, a compound in which the alkyl group constituting the hydroxyalkyl group is linear is further preferred. The number of carbon atoms in the hydroxyalkyl group of the (meth)acrylic acid hydroxyalkyl ester is, for example, 3 to 10, preferably 4 to 10, can be 4 to 8, or can be 4 to 6.

[0060] In the case of using a hydroxyl group-containing monomer (m2), the content of the hydroxyl group-containing monomer (m2) in the monomer component can be appropriately set according to the purpose of use, required properties, etc. In some cases, the content of the hydroxyl group-containing monomer (m2) is, for example, 0.01% by weight or more of the entire monomer component, can be 0.1% by weight or more, appropriately more than 0.5% by weight, and in some preferred cases, can be 1% by weight or more (e.g., more than 1% by weight), can also be 2% by weight or more, and can also be 3% by weight or more. In addition, in some cases, the content of the hydroxyl group-containing monomer (m2) in the entire monomer component can be, for example, less than 15% by weight, appropriately set to 10% by weight or less, and in some preferred cases, can be 8% by weight or less, can also be 6% by weight or less, and can also be 5% by weight or less. By using an appropriate amount of the hydroxyl group-containing monomer (m2) within the above range, the cohesive force is increased, and it is easy to adjust to a good adhesive force that can be re-peeled. For example, it is easy to form an adhesive suitable for surface protection applications that can be re-peeled.

[0061] Although not particularly limited, in some cases, from the viewpoint of effectively exerting the effect of copolymerizing the hydroxyl group-containing monomer (m2), the proportion of the hydroxyl group-containing monomer (m2) in the comonomers used as the monomer component of the acrylic polymer is appropriately 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, further preferably 80% by weight or more, particularly preferably 90% by weight or more. For example, it can be 95% by weight or more, can also be 97% by weight or more, can also be 98% by weight or more, and can also be 99% by weight or more (e.g., 99.9% by weight or more). The upper limit of the proportion of the hydroxyl group-containing monomer (m2) in all the above copolymerizable monomers is 100% by weight, and it can be, for example, 95% by weight or less.

[0062] In addition, in some cases, the monomer component of the acrylic polymer may also contain a carboxyl group-containing monomer as a comonomer. By using the carboxyl group-containing monomer, the side chain of the acrylic polymer has a carboxyl group. This carboxyl group can become a crosslinking point, for example, when using a crosslinking agent such as an epoxy-based crosslinking agent. By using the carboxyl group-containing monomer, it is easy to obtain an adhesive having appropriate cohesive force. The carboxyl group-containing monomer can be used alone or in combination of two or more.

[0063] As the carboxyl group-containing monomer, for example, the following can be mentioned: acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, 2-(meth)acryloyloxyethyl maleate, carboxyl-terminated polycaprolactone mono(meth)acrylate, 2-(meth)acryloyloxyethyl tetrahydrophthalate, crotonic acid, isocrotonic acid and other ethylenically unsaturated monocarboxylic acids; maleic acid, fumaric acid, itaconic acid, citraconic acid and other ethylenically unsaturated dicarboxylic acids. In addition, the carboxyl group-containing monomer may also be a monomer having a metal salt (e.g., an alkali metal salt) of a carboxyl group. As the carboxyl group-containing monomer, a carboxyl group-containing (meth)acrylic monomer is preferably used. The above-mentioned carboxyl group-containing (meth)acrylic monomers may be used alone or in combination of two or more.

[0064] In a scheme using a carboxyl group-containing monomer, the length of the side chain having a carboxyl group in the monomer is not particularly limited. The number of carbon atoms of the carboxyl group-containing side chain of the carboxyl group-containing monomer may be, for example, 1 or more, may be 2 or more, and is preferably 3 or more. For example, one or more carboxyl group-containing (meth)acrylic monomers having 3 or more carbon atoms can be selected from the Light ester series or the Light acrylate series available from Kyoeisha Chemical Co., Ltd. As specific examples, for example, the following can be mentioned: the product name "Light ester HO-MS(N)" (2-methacryloyloxyethyl succinate), or "HOA-MPE(N)" (2-acryloyloxyethyl-2-hydroxyethyl phthalate), etc.

[0065] In some schemes, the usage amount of the carboxyl group-containing monomer in the monomer component forming the acrylic polymer is, for example, less than 10% by weight, may be less than 8% by weight, may be less than 5% by weight, may be less than 3% by weight, may be less than 1% by weight, may be less than 0.5% by weight, may be less than 0.3% by weight, or may be less than 0.1% by weight. The technology disclosed herein can be preferably implemented in a scheme where the monomer component substantially does not contain a carboxyl group-containing monomer. By restricting the usage amount of the carboxyl group-containing monomer or not using the carboxyl group-containing monomer, it is easy to adjust the adhesive force to an appropriate range for re-peeling, for example, it is easy to form an adhesive suitable for surface protection applications for re-peeling.

[0066] The monomer components forming the acrylic polymer may also include other copolymerizable monomers capable of copolymerizing with the above-mentioned (meth)acrylic acid alkyl ester (m1). Other copolymerizable monomers are defined as copolymerizable monomers different from the above-mentioned (meth)acrylic acid alkyl ester (m1), (meth)acrylic acid linear alkyl esters other than the above-mentioned (meth)acrylic acid alkyl ester (m1), the above-mentioned hydroxyl group-containing monomer (m2), and the above-mentioned carboxyl group-containing monomer. As non-limiting examples of other copolymerizable monomers, the following can be cited: acid anhydride group-containing monomers; monomers containing a sulfonic acid group or a phosphoric acid group; epoxy group-containing monomers; cyano group-containing monomers; (meth)acrylamide, amide group-containing monomers such as N,N-dimethyl(meth)acrylamide; amino group-containing monomers such as (meth)acrylic acid aminoethyl ester, N,N-dimethylaminoethyl (meth)acrylate; monomers having a nitrogen atom-containing ring such as N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine; functional group-containing monomers such as imide group-containing monomers; vinyl ester-based monomers such as vinyl acetate; aromatic vinyl compounds such as styrene; (meth)acrylic acid cycloalkyl esters such as (meth)acrylic acid cyclohexyl ester, (meth)acrylic acid cyclopentyl ester, (meth)acrylic acid isobornyl ester; (meth)acrylic acid aryl esters (e.g., (meth)acrylic acid phenyl ester), (meth)acrylic acid aryloxyalkyl esters (e.g., (meth)acrylic acid phenoxyethyl ester), (meth)acrylic acid aralkyl esters (e.g., (meth)acrylic acid benzyl ester), etc., (meth)acrylic acid esters containing an aromatic ring; olefin-based monomers; chlorine-containing monomers; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxy group-containing monomers such as (meth)acrylic acid methoxyethyl ester, (meth)acrylic acid ethoxyethyl ester; vinyl ether-based monomers such as methyl vinyl ether, ethyl vinyl ether, etc. The other copolymerizable monomers may be used alone or in combination of two or more.

[0067] The monomer components constituting the acrylic polymer may or may not include the above-mentioned other copolymerizable monomers. In addition, the amount of the above-mentioned other copolymerizable monomers may be appropriately selected according to the purpose and use, and there is no particular limitation. The content of the other copolymerizable monomers in the above monomer components is, for example, appropriately set to be less than 30% by weight, preferably less than 10% by weight, may be set to be less than 8% by weight, more preferably less than 5% by weight, and may also be set to be less than 3% by weight (e.g., less than 1% by weight). The technology disclosed herein can be preferably implemented in a scheme where the monomer components are substantially free of other copolymerizable monomers.

[0068] The biomass carbon ratio of the monomer components constituting the above acrylic polymer (biomass carbon ratio of the acrylic polymer) can be, for example, 1% or more, suitably 10% or more, preferably 30% or more, more preferably 50% or more (e.g., exceeding 50%), can also be 70% or more, can also be 80% or more, and can also be 90% to 100%. By designing in this way, an acrylic adhesive that takes into account the suppression of dependence on fossil resource-based materials can be obtained.

[0069] The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as synthesis methods of acrylic polymers such as solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, photopolymerization method, etc. can be suitably adopted. For example, the solution polymerization method can be preferably adopted. From the viewpoints of transparency, adhesive properties, etc., the solution polymerization method can be advantageous. As the monomer supply method during solution polymerization, a one-time charging method of supplying all monomer raw materials at once, a continuous supply (dropwise addition) method, a batch supply (dropwise addition) method, etc. can be suitably adopted. The polymerization temperature during solution polymerization can be appropriately selected according to the types of monomers and solvents used, the types of polymerization initiators, etc., and can be set to about 20°C to 170°C (typically about 40°C to 140°C), for example.

[0070] The solvent for solution polymerization (polymerization solvent) can be appropriately selected from conventionally known organic solvents (such as toluene, ethyl acetate, etc.). The polymerization initiator can be appropriately selected from conventionally known polymerization initiators (such as azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN), peroxide-based initiators, etc.) according to the type of polymerization method. The usage amount of the polymerization initiator can be the usual usage amount, and can be selected, for example, from the range of approximately 0.005 to 1 part by weight (typically approximately 0.01 to 1 part by weight) relative to 100 parts by weight of the monomer components.

[0071] The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, but is usually suitably approximately 10×10 4 or more. Based on the acrylic polymer with this Mw, it is easy to obtain an adhesive that exhibits good cohesion. In some embodiments, from the viewpoints of re-peelable adhesive force, cohesion, etc., the Mw of the acrylic polymer is, for example, suitably 30×10 4 or more, preferably 50×10 4 or more, and can be 70×10 4 or more. By setting the Mw of the acrylic polymer to a specified value or more, the cohesion of the adhesive is improved, and it is easy to prevent residual glue from being generated on the surface of the adherend. In addition, from the viewpoint of the adhesion to the adherend, the Mw of the acrylic polymer is usually suitably approximately 500×10 4Hereinafter, it may also be 300×10 4 Hereinafter, it may also be 100×10 4 Hereinafter (for example, less than 100×10 4 ). By setting Mw to be below a specified value, the adhesive has appropriate fluidity and tends to easily obtain wettability (adhesion) to the adherend. By having good wettability, for example, in surface protection applications, the surface protective film will not peel off from the adherend during use, and its protection function can be preferably completed. In the acrylic polymer obtained by solution polymerization, it is particularly meaningful that its Mw is within the above-mentioned preferred range.

[0072] The Mw of the acrylic polymer can be measured by gel permeation chromatography (GPC) and obtained in the form of values converted to standard polystyrene. Specifically, a GPC measuring device with the trade name "HLC-8220GPC" (manufactured by Tosoh Corporation) can be used, and the measurement can be carried out under the following conditions to obtain the result. The same applies to the following examples.

[0073] [GPC Measurement Conditions]

[0074] Sample concentration: 0.2 wt% (tetrahydrofuran solution).

[0075] Sample injection volume: 10 μL.

[0076] Eluent: Tetrahydrofuran (THF).

[0077] Flow rate: 0.6 mL / minute.

[0078] Column temperature (measurement temperature): 40 °C.

[0079] Column:

[0080] Sample column: One column with the trade name "TSKguardcolumn SuperHZ-H" + two columns with the trade name "TSKgel SuperHZM-H" (manufactured by Tosoh Corporation).

[0081] Reference column: One column with the trade name "TSKgel SuperH-RC" (manufactured by Tosoh Corporation).

[0082] Detector: Differential refractometer (RI).

[0083] Standard sample: Polystyrene.

[0084] (Crosslinking agent)

[0085] In some embodiments, the adhesive layer contains a crosslinking agent. The crosslinking agent can be used to improve the cohesion of the adhesive. The crosslinking agent can be selected from various crosslinking agents known in the field of adhesives. As examples of such crosslinking agents, there may be mentioned: isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, amine-based crosslinking agents, etc. The crosslinking agent can be used alone or in combination of two or more. The crosslinking agent can be derived from biomass or from non-biomass.

[0086] The amount of the crosslinking agent used is not particularly limited. The amount of the crosslinking agent used can be selected from the range of, for example, 0.1 to 20 parts by weight relative to 100 parts by weight of the acrylic polymer. From the viewpoint of achieving a good balance between improving the cohesion and the adhesion to the adherend, the amount of the crosslinking agent used relative to 100 parts by weight of the acrylic polymer is usually preferably set to 10 parts by weight or less, can be 8 parts by weight or less, and can also be 6 parts by weight or less. In addition, it is appropriately set to 0.5 parts by weight or more and can also be 1 part by weight or more. By setting the amount of the crosslinking agent used within an appropriate range, the cohesion of the adhesive can be improved, the residual glue on the adherend can be prevented, and in addition, the adhesion to the adherend can be obtained.

[0087] In some embodiments, the adhesive layer preferably contains an isocyanate-based crosslinking agent. The isocyanate-based crosslinking agent can be used alone or in combination of two or more. The isocyanate-based crosslinking agent can be derived from biomass or from non-biomass. In addition, the isocyanate-based crosslinking agent can be used in combination with other crosslinking agents, such as epoxy-based crosslinking agents.

[0088] As the isocyanate-based crosslinking agent, a polyisocyanate-based crosslinking agent having two or more isocyanate groups per molecule is preferably used. The number of isocyanate groups in each molecule of the polyisocyanate-based crosslinking agent is preferably 2 to 10, for example, 2 to 4, and typically 2 or 3. Examples of the polyisocyanate-based crosslinking agent include aromatic polyisocyanates such as toluene diisocyanate and xylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; and aliphatic polyisocyanates such as hexamethylene diisocyanate. More specifically, for example, lower aliphatic polyisocyanates such as butylene diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate; alicyclic polyisocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; aromatic diisocyanates such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and polymethylene polyphenyl diisocyanate; isocyanate adducts such as trimethylolpropane / toluene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate L"), trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate HL"), isocyanurate of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name "Coronate HX"), isocyanurate of pentamethylene diisocyanate (manufactured by Mitsui Chemicals, Inc., trade name "STABiO D-370N"); polyisocyanates such as polyether polyisocyanate and polyester polyisocyanate; adducts of these polyisocyanates and polyols; and polyisocyanates polyfunctionalized by isocyanurate bonds, biuret bonds, urethane bonds, etc.; and the like. For example, in applications where transparency is required for the adhesive, aliphatic diisocyanates such as pentamethylene diisocyanate and hexamethylene diisocyanate, and isocyanurates of such aliphatic diisocyanates are preferably used. In the case of using an isocyanate-based crosslinking agent, the proportion of aliphatic polyisocyanates (aliphatic diisocyanates, isocyanurates of aliphatic diisocyanates, etc.) in the total amount of the isocyanate-based crosslinking agent is preferably set to more than 50% by weight, for example, 70% by weight or more, or 90% by weight or more (for example, 95 to 100% by weight).

[0089] With respect to 100 parts by weight of the acrylic polymer, the amount of the isocyanate-based crosslinking agent used can be, for example, approximately 0.1 part by weight or more, 0.5 part by weight or more, 1.0 part by weight or more, or more than 1.5 parts by weight. From the viewpoint of obtaining a higher usage effect, in some preferred embodiments, the amount of the isocyanate-based crosslinking agent used with respect to 100 parts by weight of the acrylic polymer is, for example, 2.0 parts by weight or more (e.g., more than 2.0 parts by weight), more preferably 2.5 parts by weight or more, can be 3.0 parts by weight or more, or 3.5 parts by weight or more. In addition, the amount of the isocyanate-based crosslinking agent used with respect to 100 parts by weight of the acrylic polymer is usually appropriately set to 20 parts by weight or less, can be 10 parts by weight or less, 8 parts by weight or less, or 6 parts by weight or less. In some preferred embodiments, the amount of the above isocyanate-based crosslinking agent used is 5 parts by weight or less (e.g., less than 5 parts by weight), or can be 4.5 parts by weight or less (e.g., less than 4.0 parts by weight). By setting the amount of the isocyanate-based crosslinking agent used within an appropriate range, the cohesion of the adhesive can be improved, the residual glue on the adherend can be prevented, and in addition, the adhesion to the adherend can be obtained. In addition, by restricting the amount of the isocyanate-based crosslinking agent used, it is easy to form a transparent adhesive.

[0090] Although not particularly limited, the technology disclosed herein can be preferably implemented in an embodiment having an adhesive layer containing an acrylic polymer and a crosslinking agent. In some embodiments, the total amount (total) of the acrylic polymer and the crosslinking agent in the adhesive layer is appropriately approximately 85% by weight or more and 100% by weight or less, preferably approximately 90% by weight or more (e.g., more than 90% by weight), can be approximately 95% by weight or more, approximately 98% by weight or more, or approximately 99% by weight or more (e.g., more than 99% by weight). In the above adhesive composition, the amount of any additive used is restricted. This is preferably from the viewpoint of preventing contamination of the adherend caused by any additive (e.g., low molecular weight components).

[0091] (Catalyst)

[0092] In addition, the adhesive layer preferably contains a catalyst. By using a catalyst, the curing reaction of the adhesive composition (typically, the crosslinking reaction of the above crosslinking agent) can be efficiently carried out, and stable adhesion can be easily achieved from an earlier stage after the production of the adhesive sheet. The catalyst is also called a crosslinking catalyst. Examples of the catalyst include: tin (Sn)-containing compounds (tin-based catalysts), zirconium (Zr)-containing compounds (zirconium-based catalysts), titanium (Ti)-containing compounds (titanium-based catalysts), hafnium (Hf)-containing compounds (hafnium-based catalysts), iron (Fe)-containing compounds (iron-based catalysts), aluminum (Al)-containing compounds (aluminum-based catalysts), zinc (Zn)-containing compounds (zinc-based catalysts), bismuth (Bi)-containing compounds (bismuth-based catalysts), and the like. Typically, they are organic compounds having a metal at the active center and are also called organometallic catalysts. The catalysts can be used alone or in combination of two or more.

[0093] In some preferred embodiments, a compound containing a Group IVB element is used as the catalyst. By using a compound containing a Group IVB element as the catalyst, rapid curing and a sufficient pot life can be achieved. By using a compound containing a Group IVB element, a good catalyst addition effect can be obtained without using a widely used tin-based catalyst due to its high catalyst activity, and thus an adhesive considering environmental impact and safety can be obtained. In addition, compared with other catalysts such as iron-based catalysts, the compound containing a Group IVB element has a tendency of less hue change such as coloring. Therefore, for example, in applications where transparency and optical properties are required for the adhesive, it is preferred to use a compound containing a Group IVB element as the catalyst. Furthermore, by using an appropriate compound containing a Group IVB element, contamination of the surface of the adherend can be highly suppressed. The compound containing a Group IVB element can be used alone or in combination of two or more. As the compound containing a Group IVB element, any of a zirconium-containing compound (zirconium-based catalyst), a titanium-containing compound (titanium-based catalyst), and a hafnium-containing compound (hafnium-based catalyst) can be used, and among them, a zirconium-containing compound is preferred. By using a zirconium-containing compound, an adhesive having excellent transparency can be preferably obtained.

[0094] The zirconium-containing compound (organo-zirconium compound) as a preferred example of the catalyst is not particularly limited, and examples thereof include zirconium tetraacetylacetonate, monoacetylacetonate zirconium, zirconium ethyl acetoacetate, zirconium octoate compound, etc. More specifically, examples include alkoxyzirconiums such as zirconium tetraethoxide, zirconium tetra-n-propoxide, zirconium tetraisopropoxide, zirconium tetra-n-butoxide (n-butyl zirconate), zirconium tetra-isobutoxide, zirconium tetra-sec-butoxide, zirconium tetra-tert-butoxide; triethoxymono(acetylacetonate)zirconium, tri-n-propoxymono(acetylacetonate)zirconium, triisopropoxymono(acetylacetonate)zirconium, tri-n-butoxymono(acetylacetonate)zirconium, tri-sec-butoxymono(acetylacetonate)zirconium, tri-tert-butoxymono(acetylacetonate)zirconium, diethoxybis(acetylacetonate)zirconium, di-n-propoxybis(acetylacetonate)zirconium, diisopropoxybis(acetylacetonate)zirconium, di-n-butoxybis(acetylacetonate)zirconium, di-sec-butoxybis(acetylacetonate)zirconium, di-tert-butoxybis(acetylacetonate)zirconium, monoethoxytri(acetylacetonate)zirconium, mono-n-propoxytri(acetylacetonate)zirconium, monoisopropoxytri(acetylacetonate)zirconium, mono-n-butoxytri(acetylacetonate)zirconium, mono-sec-butoxytri(acetylacetonate)zirconium, mono-tert-butoxytri(acetylacetonate)zirconium, zirconium tetra(acetylacetonate), triethoxymono(ethyl acetoacetate)zirconium, tri-n-propoxymono(ethyl acetoacetate)zirconium, triisopropoxymono(ethyl acetoacetate)zirconium, tri-n-butoxymono(ethyl acetoacetate)zirconium, tri-sec-butoxymono(ethyl acetoacetate)zirconium, tri-tert-butoxymono(ethyl acetoacetate)zirconium, diethoxybis(ethyl acetoacetate)zirconium, di-n-propoxybis(ethyl acetoacetate)zirconium, diisopropoxybis(ethyl acetoacetate)zirconium, di-n-butoxybis(ethyl acetoacetate)zirconium, di-sec-butoxybis(ethyl acetoacetate)zirconium, di-tert-butoxybis(ethyl acetoacetate)zirconium, monoethoxytri(ethyl acetoacetate)zirconium, mono-n-propoxytri(ethyl acetoacetate)zirconium, monoisopropoxytri(ethyl acetoacetate)zirconium, mono-n-butoxytri(ethyl acetoacetate)zirconium, mono-sec-butoxytri(ethyl acetoacetate)zirconium, mono-tert-butoxytri(ethyl acetoacetate)zirconium, zirconium tetra(ethyl acetoacetate), mono(acetylacetonate)tri(ethyl acetoacetate)zirconium, bis(acetylacetonate)bis(ethyl acetoacetate)zirconium, tris(acetylacetonate)mono(ethyl acetoacetate)zirconium and other zirconium chelates; etc. The above zirconium-containing compounds can be used alone or in combination of two or more.

[0095] As the titanium-containing compound (organotitanium compound), there is no particular limitation, and examples thereof include: tetra-isopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetra-octyl titanate, titanium acetylacetonate, tetra-acetylacetonate titanium, titanium ethyl acetoacetate, etc. More specifically, examples include: tetra-ethoxy titanium, tetra-n-propoxy titanium, tetra-isopropoxy titanium, tetra-n-butoxy titanium, tetra-n-butoxy titanium dimer, tetra-iso-butoxy titanium, tetra-sec-butoxy titanium, tetra-tert-butoxy titanium, di-2-ethylhexoxy bis(2-ethyl-3-hydroxyhexyl oxide) titanium, titanium lactate, ammonium salt of titanium lactate, titanium diisopropoxy bis(triethanolaminate), tetra(2-ethylhexoxy) titanium, titanium isopropoxy octanediol, titanium diisopropoxy bis(acetylacetonate), propane dioxy titanium bis(ethyl acetoacetate), tri-n-butoxy titanium monostearate, titanium diisopropoxy distearate, titanium stearate, titanium diisopropoxy diisostearate, (2-n-butoxycarbonylbenzoyloxy) tributoxy titanium, titanium dibutoxy bis(triethanolamine), triethoxy mono(acetylacetonate) titanium, tri-n-propoxy mono(acetylacetonate) titanium, triisopropoxy mono(acetylacetonate) titanium, tri-n-butoxy mono(acetylacetonate) titanium, tri-sec-butoxy mono(acetylacetonate) titanium, tri-tert-butoxy mono(acetylacetonate) titanium, diethoxy bis(acetylacetonate) titanium, di-n-propoxy bis(acetylacetonate) titanium, di-n-butoxy bis(acetylacetonate) titanium, di-sec-butoxy bis(acetylacetonate) titanium, di-tert-butoxy bis(acetylacetonate) titanium, monoethoxy tris(acetylacetonate) titanium, mono-n-propoxy tris(acetylacetonate) titanium, mono-isopropoxy tris(acetylacetonate) titanium, mono-n-butoxy tris(acetylacetonate) titanium, mono-sec-butoxy tris(acetylacetonate) titanium, mono-tert-butoxy tris(acetylacetonate) titanium, tetra(acetylacetonate) titanium, triethoxy mono(ethyl acetoacetate) titanium, tri-n-propoxy mono(ethyl acetoacetate) titanium, triisopropoxy mono(ethyl acetoacetate) titanium, tri-n-butoxy mono(ethyl acetoacetate) titanium, tri-sec-butoxy mono(ethyl acetoacetate) titanium, tri-tert-butoxy mono(ethyl acetoacetate) titanium, diethoxy bis(ethyl acetoacetate) titanium, di-n-propoxy bis(ethyl acetoacetate) titanium, diisopropoxy bis(ethyl acetoacetate) titanium, di-n-butoxy bis(ethyl acetoacetate) titanium, di-sec-butoxy bis(ethyl acetoacetate) titanium, di-tert-butoxy bis(ethyl acetoacetate) titanium, monoethoxy tris(ethyl acetoacetate) titanium, mono-n-propoxy tris(ethyl acetoacetate) titanium, mono-isopropoxy tris(ethyl acetoacetate) titanium, mono-n-butoxy tris(ethyl acetoacetate) titanium, mono-sec-butoxy tris(ethyl acetoacetate) titanium, mono-tert-butoxy tris(ethyl acetoacetate) titanium, tetra(ethyl acetoacetate) titanium, mono(acetylacetonate) tris(ethyl acetoacetate) titanium, bis(acetylacetonate) bis(ethyl acetoacetate) titanium, tris(acetylacetonate) mono(ethyl acetoacetate) titanium, etc. The above titanium-containing compounds can be used alone or in combination of two or more.

[0096] As the hafnium compound (organic hafnium compound), a compound obtained by substituting zirconium or titanium in the above zirconium compound and titanium compound with hafnium is used. For example, the following can be cited: hafnium tetraacetylacetonate; hafnium pivalate; hafnium alkoxides such as hafnium tetramethoxide, hafnium tetraethoxide, hafnium tetrabutoxide, hafnium tetrapentoxide, etc. The above hafnium compounds can be used alone or in combination of two or more.

[0097] As other examples of the catalyst, the following can be cited: tin compounds (organic tin compounds) such as dioctyltin dilaurate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin diacetylacetonate, tetra-n-butyltin, trimethyltin hydroxide, butyltin oxide, etc.; aluminum compounds (organic aluminum compounds) such as aluminum sec-butoxide, aluminum triacetylacetonate, aluminum bis(acetoacetate) ethyl ester, aluminum tri(acetoacetate) ethyl ester, etc.; iron compounds (organic iron compounds) such as iron triacetylacetonate, etc.

[0098] In some embodiments, the catalyst used in the adhesive layer does not contain a tin compound. The technology disclosed herein does not exclude the use of tin-based catalysts, but it is possible to achieve the desired catalyst addition effect (rapid curing and sufficient pot life) without using the widely used tin-based catalysts due to their high catalyst activity. By controlling the use of tin-based catalysts, an adhesive considering environmental impact and safety can be obtained.

[0099] The amount of the catalyst used is not particularly limited. With respect to 100 parts by weight of the acrylic polymer, the amount of the catalyst used can be set, for example, to be approximately 0.0001 part by weight or more, suitably approximately 0.001 part by weight or more, and can be approximately 0.005 part by weight or more (for example, 0.01 part by weight or more). In some preferred embodiments, the amount of the catalyst used with respect to 100 parts by weight of the acrylic polymer is approximately 0.02 part by weight or more, and can be approximately 0.03 part by weight or more. By using the catalyst within the above range, there is a tendency to easily form an adhesive with good peelability of the release sheet. In addition, with respect to 100 parts by weight of the acrylic polymer, the amount of the catalyst used can be set, for example, to be approximately 1 part by weight or less, or can be set to be approximately 0.5 part by weight or less, suitably approximately 0.1 part by weight or less, and can be approximately 0.05 part by weight or less. By using an appropriate amount of the catalyst, the crosslinking reaction rate can be adjusted. In addition, by limiting the amount of the catalyst used, contamination of the adherend caused by the catalyst can be suppressed.

[0100] (Other components)

[0101] In addition, the adhesive composition for forming the adhesive layer may contain, as a crosslinking retarder, a compound that generates keto-enol tautomerism, if desired. For example, a compound that generates keto-enol tautomerism may preferably be used in an adhesive composition containing an isocyanate-based crosslinking agent. Thereby, the effect of extending the pot life of the adhesive composition can be exhibited. As the compound that generates keto-enol tautomerism, various β-dicarbonyl compounds can be used. As specific examples, β-diketones such as acetylacetone and 2,4-hexanedione can be mentioned; acetoacetates such as methyl acetoacetate and ethyl acetoacetate; propionates such as ethyl propionylacetate; isobutyrylacetates such as ethyl isobutyrylacetate; malonates such as methyl malonate and ethyl malonate, etc. Among them, as suitable compounds, acetylacetone and acetoacetates can be mentioned. The compound that generates keto-enol tautomerism may be used alone or in combination of two or more kinds.

[0102] With respect to 100 parts by weight of the acrylic polymer contained in the adhesive composition, the amount of the compound that generates keto-enol tautomerism used may be, for example, 1 part by weight or more, suitably set to 5 parts by weight or more, and may be set to 15 parts by weight or more, for example. In some embodiments, from the viewpoint of obtaining a sufficient pot life, with respect to 100 parts by weight of the acrylic polymer contained in the adhesive composition, the amount of the above-mentioned compound that generates keto-enol tautomerism used may be, for example, 30 parts by weight or more, may be 60 parts by weight or more, and may be 120 parts by weight or more. In addition, the above-mentioned amount used may be, for example, 200 parts by weight or less, suitably set to 180 parts by weight or less, may be set to 160 parts by weight or less, and may be set to 140 parts by weight or less.

[0103] In the above-mentioned adhesive layer, various additives known in the past can be further incorporated as needed. Examples of such additives include: surface lubricants, leveling agents, tackifying resins, peel adjustment agents (such as surfactants), plasticizers, softening agents, fillers, colorants (such as pigments and dyes), antistatic agents, antioxidants, preservatives, light stabilizers, ultraviolet absorbers, polymerization inhibitors, silane coupling agents, etc. The content of these additives as optional components can be appropriately set according to the intended use. With respect to 100 parts by weight of the acrylic polymer, the usage amount of the above-mentioned optional additive is, for example, less than 10 parts by weight, preferably set to approximately 3 parts by weight or less, and in some preferred embodiments, it is approximately 1 part by weight or less (e.g., less than 1 part by weight), and can be 0.5 part by weight or less, or 0.3 part by weight or less, or 0.1 part by weight or less (e.g., less than 0.1 part by weight). By restricting the usage amount of the optional additive (especially low-molecular-weight components such as peel adjustment agents and antistatic agents), contamination of the adherend caused by the optional additive can be suppressed. From the same viewpoint, the proportion of the acrylic polymer in the adhesive layer is appropriately 80% by weight or more, preferably 85% by weight or more, more preferably 90% by weight or more (e.g., 90% by weight or more and 99.9% by weight or less), and can be 95% by weight or more.

[0104] (Method for forming the adhesive layer)

[0105] The form of the adhesive composition for forming the adhesive layer is not particularly limited, and an aqueous adhesive composition, a solvent-based adhesive composition, etc. are preferred. Here, the aqueous adhesive composition refers to an adhesive composition in a form in which an adhesive (an adhesive layer-forming component) is contained in a solvent (aqueous solvent) mainly composed of water, and as a typical example, a water-dispersed adhesive composition in a form in which the adhesive is dispersed in water can be cited. In addition, the solvent-based adhesive composition refers to an adhesive composition in a form in which an adhesive is contained in an organic solvent. As the organic solvent contained in the solvent-based adhesive composition, one or more of the organic solvents (such as toluene and ethyl acetate) that can be used in the above-mentioned solution polymerization can be used without particular limitation. From the viewpoints of adhesion characteristics, etc., the technology disclosed herein can be preferably implemented in an embodiment having an adhesive layer formed from a solvent-based adhesive composition. In an embodiment having a solvent-based adhesive layer formed from a solvent-based adhesive composition, the effects brought about by the technology disclosed herein will be preferably achieved.

[0106] The formation of an adhesive (layer) from an adhesive composition can be carried out by methods known in the art. For example, in the case of a substrate-free double-sided adhesive sheet, the adhesive sheet can be formed as follows: after applying the adhesive composition to a surface with peelability (peel surface), the adhesive composition is cured, thereby forming an adhesive layer (layer formed from the adhesive) on this surface. In addition, in the case of an adhesive sheet with a substrate, the following method (direct method) can preferably be used: the adhesive composition is directly applied (typically coated) to the substrate and cured, thereby forming an adhesive layer. In addition, the following method (transfer method) can also be used: the adhesive composition is applied to a surface with peelability (peel surface), cured, thereby forming an adhesive layer on this surface, and the adhesive layer is transferred to the substrate. As the above-mentioned peel surface, the surface of a release sheet, the back surface of a substrate subjected to a peeling treatment, etc. can be used. In addition, the curing of the adhesive composition can be carried out by performing curing treatments such as drying, crosslinking, polymerization, and cooling on the adhesive composition. Two or more curing treatments can also be carried out simultaneously or stepwise.

[0107] The coating of the adhesive composition can be carried out, for example, using known or conventional coating machines such as a gravure coater, a reverse roll coater, a roll kiss coater, a dip roll coater, a die coater, a bar coater, a knife coater, a spray coater, etc. Alternatively, the adhesive composition can also be coated by impregnation, curtain coating method, etc.

[0108] From the viewpoints of promoting the crosslinking reaction and improving the manufacturing efficiency, etc., the drying of the adhesive composition is preferably carried out under heating. The drying temperature can be set, for example, to about 40 to 150 °C, and is usually preferably set to about 60 to 130 °C. After drying the adhesive composition, aging can also be carried out for purposes such as adjustment of the component transfer in the adhesive layer, progress of the crosslinking reaction, and relaxation of the strain that may exist in the substrate or the adhesive layer.

[0109] (Thickness)

[0110] The thickness of the adhesive layer is not particularly limited, but is, for example, appropriately at least about 1 μm, preferably at least about 3 μm (for example, at least about 5 μm). From the viewpoints of adhesiveness to the adherend, etc., the above thickness is preferably at least about 10 μm, more preferably at least about 14 μm, and further preferably at least about 17 μm. In addition, the above thickness can be set, for example, to at most about 100 μm, appropriately at most about 50 μm (for example, at most about 30 μm), and preferably at most about 25 μm. The adhesive layer having the above thickness is preferably used as an adhesive layer for the purpose of a surface protective film.

[0111] (Gel fraction)

[0112] Although the gel fraction of the adhesive layer is not particularly limited, it is preferably 70% or more. An adhesive having a gel fraction of 70% or more is, for example, less likely to be deformed or damaged, such as dents caused by external forces during manufacturing, and is less likely to change in appearance. Such an adhesive is likely to become an adhesive sheet having a smooth surface. For example, when formed into a transparent adhesive sheet and the adherend is inspected through the adhesive sheet, high-precision inspection can be performed, so it is preferred. In addition, by setting the gel fraction high, it is easy to form an adhesive having excellent peelability. From this point of view, the above gel fraction is more preferably greater than 80%, may be greater than 85% (for example, 90% or more), may be 92% or more, or may be 94% or more (for example, 95% or more). The above gel fraction may be 100%, but from the viewpoint of adhesion to the adherend, it may be less than 99%, for example, or may be less than 95% (for example, 94% or less).

[0113] The gel fraction of the adhesive layer is measured by the following method. Take out an amount of W1 (g) from the adhesive layer, wrap it in a porous PTFE (polytetrafluoroethylene) sheet to make a sample. Put the sample into a glass bottle, immerse it in an ethyl acetate solution and let it stand for 7 days, then take out the sample and dry it at 130°C for 2 hours. Weigh the dried sample, subtract the weight of the porous PTFE sheet from it, and obtain the weight W2 (g) of the dried adhesive. Substitute W1 and W2 into the following formula to calculate the gel fraction [%].

[0114] Gel fraction [%] = (W2 / W1) × 100

[0115] As the porous PTFE sheet, a product named "TEMISH" manufactured by Nitto Denko Corporation or its equivalent can be used.

[0116] (Biomass carbon ratio)

[0117] In some embodiments, the adhesive layer contains a biomass-derived material, and its biomass carbon ratio can be above a specified value. The biomass carbon ratio of the adhesive layer is, for example, 1% or more, can be 10% or more, preferably 30% or more, and more preferably 50% or more. A high biomass carbon ratio of the adhesive means that the usage amount of fossil resource-based materials represented by petroleum and the like is small. In terms of this view, the higher the biomass carbon ratio of the adhesive, the more preferable. For example, the biomass carbon ratio of the adhesive layer can be 55% or more, can be 60% or more, can be 70% or more, can be 75% or more, can be 80% or more, or can be greater than 80%. The upper limit of the biomass carbon ratio is 100% by definition, can be 99% or less, and from the view of easy availability of materials, can be 95% or less, or can be 90% or less. From the view of easily exhibiting good adhesive properties, in some embodiments, the biomass carbon ratio of the adhesive layer can be, for example, 90% or less, can be 85% or less, or can be 80% or less.

[0118] <Substrate>

[0119] The material of the support substrate used as the support for the adhesive sheet disclosed herein is not particularly limited. For example, a resin film can be preferably used. The above resin film can be a film formed by shaping various resin materials into a film shape. As the above resin materials, materials that can preferably form a resin film having excellent properties in one or more of transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. are preferred. For example, a resin film composed of the following resin materials can be preferably used as the above substrate: polyester-based materials such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate; cellulose-based materials such as cellulose diacetate, cellulose triacetate; polycarbonate-based materials; acrylic polymer-based materials such as polymethyl methacrylate; etc. as the main component (i.e., containing more than 50% by weight of the component). Other examples of the resin materials constituting the above resin film include: styrene polymer-based materials such as polystyrene, acrylonitrile-styrene copolymer; polyolefins (e.g., polyethylene, polypropylene, cyclic or polyolefins having a norbornene structure, ethylene-propylene copolymer, etc.); polyvinyl chloride-based materials; polyamide-based materials such as nylon 6, nylon 6,6, aromatic polyamide; etc. Alternatively, a resin film composed of the following resin materials can also be used for the substrate: resin materials having polyimide-based materials, polysulfone-based materials, polyethersulfone-based materials, polyetheretherketone-based materials, polyphenylene sulfide-based materials, fluorine-based resins, polyvinyl alcohol-based materials, polyvinyl acetate-based materials, polyvinylidene chloride-based materials, polyvinyl butyral-based materials, polyarylate-based materials, polyoxymethylene-based materials, epoxy resin-based materials; etc. as the main component. The resin materials constituting the above resin film can be a blend of two or more of them.

[0120] It should be noted that in this specification, the "resin film" refers to a resin film having a non-porous structure, typically substantially free of air bubbles (void-free). Therefore, the above-mentioned resin film is a concept that is distinguished from a foamed film, a non-woven fabric, and a woven fabric.

[0121] Other examples of the base material include: a foamed sheet formed of a foamed material such as polyurethane foam, polyethylene foam, and polychloroprene foam; a woven fabric and a non-woven fabric obtained by individually or blending various fibrous materials (which may be natural fibers such as hemp and cotton; synthetic fibers such as polyester and vinylon; semi-synthetic fibers such as acetate fiber, etc.); papers such as Japanese paper, high-quality paper, kraft paper, and crepe paper; metal foils such as aluminum foil and copper foil; glass, etc. It may also be a base material formed by laminating them. Examples of the base material having such a composite structure include, for example, a base material having a structure in which a metal foil and the above-mentioned plastic film are laminated, a plastic sheet reinforced with an inorganic fiber such as a glass cloth, etc.

[0122] The base material can be formed of a material derived from biomass or a material derived from non-biomass. From the viewpoint of manufacturing an adhesive sheet considering suppressing the dependence on fossil resource-based materials, it is preferable to use a base material material (typically a resin film) derived from biomass.

[0123] In addition, the base material can also be formed using recyclable materials and recycled materials (also referred to as recycled materials). As the recycled material, it is preferable to use a resin film. A resin film (such as a polyester film such as a PET film) can be recycled. Therefore, regardless of whether a plant-derived material is used, by reusing the used resin film, continuous reproduction can be achieved, and the environmental load can be reduced. Such a recyclable resin film and a recycled resin film are also referred to as recycled films. The above-mentioned recycled materials (such as recycled films) can be formed of a material derived from biomass or a material derived from non-biomass.

[0124] In some preferred embodiments, as the above-mentioned base material, a resin film (a polyester resin film) formed by molding a resin (a polyester resin) having polyester as a main component (including more than 50% by weight of the component) into a film shape is used. For example, a resin film (PET film) in which the above-mentioned polyester is mainly PET, a resin film (PEN film) in which the above-mentioned polyester is mainly PEN, etc. can be preferably used.

[0125] The base material can be a single-layer structure or can have a multilayer structure. Therefore, the resin film that can be used as the base material can also be a single-layer structure or a multilayer structure of two or more layers (for example, a three-layer structure). It is possible to preferably use a single-layer resin film as the base material.

[0126] In the above-mentioned base material (typically a resin film), various additives such as antioxidants, anti-aging agents, heat stabilizers, light stabilizers, ultraviolet absorbers, antistatic components, plasticizers, colorants (pigments, dyes, etc.), and fillers can also be incorporated as needed.

[0127] Surface treatments such as chromic acid treatment, ozone exposure, flame exposure, high-voltage electric shock exposure, and ionizing radiation treatment can also be performed on the surface of the adhesive layer side of the base material. Such surface treatments can be, for example, treatments for improving the adhesion between the base material and the adhesive layer. In some embodiments, a primer treatment can also be performed on the surface of the adhesive layer side of the base material. In some embodiments, a hard coat treatment can also be performed on the back surface of the base material. As a result, the scratch resistance of the back surface of the base material is improved, and when the adhesive sheet is used as a protective sheet, more excellent protective performance can be exhibited. In addition, in other embodiments, from the viewpoint of suppressing static electricity generation, the base material can also be subjected to an antistatic treatment. In addition, the base material can be subjected to various treatments such as antifouling, fingerprint adhesion prevention, antiglare, and antireflection.

[0128] The thickness of the base material can be appropriately selected in consideration of the use, purpose, and usage form of the adhesive sheet. From the viewpoints of strength, workability, etc., a base material with a thickness of approximately 10 μm or more is suitable, and its thickness is preferably approximately 20 μm or more, more preferably approximately 30 μm or more (for example, 35 μm or more). In addition, from the viewpoints of cost, etc., the thickness of the base material is appropriately approximately 200 μm or less, preferably approximately 150 μm or less, more preferably approximately 100 μm or less, and further preferably approximately 75 μm or less (for example, 50 μm or less). A base material having the above thickness is preferably used as the base material of a surface protective film, for example.

[0129] <Release sheet>

[0130] The release sheet used in the adhesive sheet with a release sheet disclosed herein is a non-silicone release sheet. The non-silicone release sheet is used to protect the adhesive surface during the circulation, storage, processing, etc. of the adhesive sheet before use in applications where silicone release sheets are not desired, and can also be used to form the adhesive layer and manufacture the adhesive sheet. It should be noted that in this specification, the "release sheet" is also referred to as a release sheet and includes objects called release films and release liners. In addition, the "non-silicone release sheet" refers to a release sheet in which at least the surface (release surface) on the adhesive sheet side is made of a material that does not contain a silicone material, and can be, for example, a release sheet in which the entire release sheet is made of a material that does not contain a silicone material. As the non-silicone release sheet, for example, a release sheet having a release treatment layer formed by a release treatment agent other than a silicone material (non-silicone release treatment agent) can be cited.

[0131] As a non-silicone release sheet, for example, a release sheet having a release treatment layer on the surface of a substrate such as a resin film or paper, a fluorine-based release sheet having a single-layer structure or a multi-layer structure formed of a fluorine-based polymer (polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, chlorofluoroethylene-vinylidene fluoride copolymer, etc.), a polyolefin-based release sheet having a single-layer structure or a multi-layer structure formed of a polyolefin-based resin (polyethylene, polypropylene, etc.), etc. can be used.

[0132] In some embodiments, the non-silicone release sheet has a release sheet substrate and a non-silicone release treatment layer provided on at least one surface of the release sheet substrate. Herein, the "release sheet substrate" refers to the substrate used to form the release sheet, that is, the substrate for the release sheet, and is used for the purpose of distinguishing from the above-mentioned adhesive sheet substrate. Other than this, there is no particular limitation. As the release sheet substrate, various plastic films can be used. In this specification, the plastic film is typically a non-porous sheet, for example, a concept that is distinguished from a non-woven fabric (that is, does not contain a non-woven fabric). As the above-mentioned substrate, a non-porous structure can be preferably used, typically a resin film that is substantially free of air bubbles (void-free). The above-mentioned resin film can be a single-layer structure or a multi-layer structure of two or more layers (for example, a three-layer structure).

[0133] Examples of the material of the above-mentioned plastic film include: polyolefin-based resins such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, and ethylene-butene copolymer; polyester-based resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT); polyvinyl chloride-based resins; polyvinylidene chloride-based resins; polyvinyl alcohol-based resins; ethylene-vinyl acetate copolymer resins; ethylene-vinyl alcohol copolymer resins; cellulose resins such as triacetate cellulose; acetate-based resins; polycarbonate-based resins; polyamide-based resins; etc. A release sheet substrate formed of any one or a mixture of two or more of these resins can also be used. Among them, as a preferred release sheet substrate, a polyester-based resin film (for example, a PET film) formed of a polyester-based resin can be cited. As the release sheet substrate, similar to the substrate of the adhesive sheet, a material formed using a biomass-derived material and a recycled material (recycled film, etc.) can be preferably used.

[0134] The plastic film used as the substrate of the release sheet can be any of a non-stretched film, a uniaxially stretched film, and a biaxially stretched film. In addition, the above-mentioned plastic film can have a single-layer structure or a multi-layer structure including two or more sub-layers. In the above-mentioned plastic film, known additives that can be used in the substrate, such as antioxidants, anti-aging agents, heat stabilizers, light stabilizers, ultraviolet absorbers, colorants such as pigments and dyes, lubricants, fillers, plasticizers, antistatic agents, slip agents, anti-blocking agents, and nucleating agents, can be incorporated. In the plastic film with a multi-layer structure, each additive can be incorporated in all sub-layers or only in a part of the sub-layers.

[0135] In some embodiments, the non-silicone-based release treatment layer disposed on the substrate of the release sheet is a release treatment layer that does not contain silicone materials. For example, it can be a release treatment layer formed from non-silicone-based release treatment agents such as long-chain alkyl-based release treatment agents, aliphatic carboxylic acid ester-based release treatment agents, fluorine-based release treatment agents, and molybdenum disulfide release treatment agents. Although not particularly limited, from the aspect of easily forming a release treatment layer without coating unevenness and whitening, as the non-silicone-based release treatment layer, a release treatment layer formed from at least one selected from long-chain alkyl-based release treatment agents and aliphatic carboxylic acid ester-based release treatment agents is preferred. Among them, from the aspect of easily obtaining excellent light release properties, a release treatment layer formed from a material containing a long-chain alkyl-based release treatment agent is particularly preferred.

[0136] As the long-chain alkyl-based release treatment agent, a release treatment agent containing a long-chain alkyl-containing compound having a straight-chain or branched-chain alkyl with 6 or more carbon atoms can be used. The number of carbon atoms of the alkyl in the long-chain alkyl-containing compound is preferably 8 or more, more preferably 12 or more. Examples of the above-mentioned alkyl include octyl, decyl, lauryl, octadecyl, behenyl, etc. Examples of the long-chain alkyl-containing compound include various long-chain alkyl-containing polymer compounds, long-chain alkyl-containing amine compounds, long-chain alkyl-containing ether compounds, long-chain alkyl-containing quaternary ammonium salts, etc. From the viewpoints of heat resistance and contamination, long-chain alkyl-containing polymer compounds are preferred. In addition, from the viewpoint of using a small amount and effectively obtaining hydrophobicity, a polymer compound having a long-chain alkyl in the side chain is more preferred. The long-chain alkyl-containing compound can be used alone or in combination of two or more.

[0137] Examples of the polymer compound having a long-chain alkyl group in the side chain include: an acrylic polymer obtained by polymerizing a monomer component containing an alkyl (meth)acrylate having an alkyl group with 6 or more carbon atoms, a polymer obtained by reacting a polymer having a reactive group with an alkyl group-containing compound capable of reacting with the reactive group, and the like. Examples of the above reactive group include: a hydroxyl group, an amino group, a carboxyl group, an acid anhydride, and the like. Examples of the polymer having these reactive groups include: an acrylic polymer, polyvinyl alcohol, butyral resin, ethylene-vinyl alcohol resin, polyethyleneimine, polyvinylamine, a polyester resin containing a reactive group, a poly(meth)acrylic resin containing a reactive group, and the like. Among them, from the viewpoints of easy peelability and handleability, as the above polymer, an acrylic polymer, polyvinyl alcohol, butyral resin, or ethylene-vinyl alcohol resin is preferably used.

[0138] Examples of the alkyl group-containing compound capable of reacting with the above reactive group and used for the reaction with the polymer having the above reactive group include: long-chain alkyl group-containing isocyanates such as octyl isocyanate, decyl isocyanate, lauryl isocyanate, octadecyl isocyanate, behenyl isocyanate; long-chain alkyl group-containing acid chlorides such as chlorooctane, chlorodecane, chlorododecane, chlorooctadecane, chlorodocosane; long-chain alkyl group-containing amines; long-chain alkyl group-containing alcohols; and the like. Among them, from the viewpoints of easy peelability and handleability, long-chain alkyl group-containing isocyanates are preferred, and octadecyl isocyanate is particularly preferred.

[0139] The amount of the alkyl group-containing compound capable of reacting with the above reactive group used is preferably set to an appropriate amount that can achieve the target peelability, does not cause transfer to the adhesive surface, and further does not cause contamination of the adherend. Although not particularly limited, the above alkyl group-containing compound is appropriately 100 parts by weight or more (for example, 200 parts by weight or more, and further 300 parts by weight or more) with respect to 100 parts by weight of the polymer having a reactive group. In addition, the amount of the above alkyl group-containing compound used is appropriately set to 1000 parts by weight or less (for example, 800 parts by weight or less, and further 700 parts by weight or less) with respect to 100 parts by weight of the polymer having a reactive group.

[0140] In addition, as the aliphatic carboxylic acid ester that can be contained in the stripping agent, an aliphatic carboxylic acid ester obtained by reacting an aliphatic carboxylic acid with an alcohol can be used. As the aliphatic carboxylic acid component, a monocarboxylic acid or dicarboxylic acid having 6 to 36 carbon atoms is preferred, and an aliphatic saturated monocarboxylic acid having 6 to 36 carbon atoms is more preferred. Specific examples of the aliphatic carboxylic acid include palmitic acid, stearic acid, valeric acid, caproic acid, capric acid, lauric acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, melissic acid, pentanedioic acid, hexanedioic acid, azelaic acid, etc. The aliphatic carboxylic acid can be used alone or in combination of two or more. As the alcohol used for generating the aliphatic carboxylic acid ester, saturated or unsaturated monohydric alcohols or polyhydric alcohols, etc. can be cited. The above-mentioned alcohol can also have substituents such as fluorine atoms and aryl groups. For example, a saturated alcohol having 30 or less carbon atoms is preferably used, and an aliphatic saturated alcohol having 30 or less carbon atoms is more preferably used. It should be noted that the above-mentioned aliphatic alcohol includes alicyclic alcohols. Specific examples of the above-mentioned alcohol include octanol, decanol, dodecanol, stearyl alcohol, behenyl alcohol, ethylene glycol, diethylene glycol, glycerol, pentaerythritol, 2,2-dihydroxyperfluoropropanol, neopentyl glycol, di-trimethylolpropane, dipentaerythritol, etc. The alcohol can be used alone or in combination of two or more.

[0141] Specific examples of the above-mentioned aliphatic carboxylic acid ester include beeswax (a mixture mainly composed of myricyl palmitate), stearyl stearate, behenyl behenate, octyldodecyl behenate, glyceryl monopalmitate, glyceryl monostearate, glyceryl distearate, glyceryl tristearate, pentaerythritol monopalmitate, pentaerythritol monostearate, pentaerythritol distearate, pentaerythritol tristearate, pentaerythritol tetrastearate, etc. The aliphatic carboxylic acid ester can be used alone or in combination of two or more.

[0142] Although not particularly limited, the non-silicone-based stripping treatment layer usually contains 70% by weight or more of the above-mentioned long-chain alkyl-containing compound, stripping treatment agents such as aliphatic carboxylic acid esters, and the content of the stripping treatment agent in the above-mentioned stripping treatment layer can be 80% by weight or more, or can be 90% by weight or more. The upper limit of the content of the above-mentioned stripping treatment agent can be, for example, 99% by weight or less.

[0143] The stripping treatment layer can optionally contain known additives such as antistatic agents, colorants, surfactants, plasticizers, tackifiers, low molecular weight polymers, surface lubricants, leveling agents, antioxidants, corrosion inhibitors, light stabilizers, ultraviolet absorbers, polymerization inhibitors, fillers, etc.

[0144] The non-silicone release sheet can be produced by a known method or obtained as a commercially available non-silicone release sheet for use. For example, a release sheet having a non-silicone release treatment layer on a release sheet substrate can be produced as follows: A solution (release treatment agent composition) containing a non-silicone release treatment agent is applied to the surface of the release sheet substrate using an appropriate coater (such as a gravure roll coater), and the solvent etc. is removed by drying etc., and curing is appropriately performed.

[0145] The thickness of the release treatment layer is not particularly limited and is set to an appropriate thickness that can achieve the desired peelability. The thickness of the release treatment layer is, for example, appropriately 1 nm or more, preferably 5 nm or more, more preferably 10 nm or more. In addition, for example, it is appropriately set to about 200 nm or less, preferably 100 nm or less, and can be 50 nm or less.

[0146] The thickness of the entire release sheet is not particularly limited. From the viewpoints of the strength and dimensional stability of the release sheet, it is appropriately 5 μm or more, preferably 10 μm or more, and can be 20 μm or more. By using a release sheet with a sufficient thickness to protect the adhesive surface, it is easy to maintain the smoothness of the adhesive surface. In addition, from the viewpoints of the operability of the release sheet (such as ease of winding), etc., the thickness of the release sheet is appropriately 300 μm or less, preferably 200 μm or less, more preferably 100 μm or less, and can be 75 μm or less, can also be 50 μm or less, and can also be 35 μm or less. By setting the thickness of the release sheet to a value below the specified value, it is easy to peel smoothly from the adhesive sheet.

[0147] <Adhesive sheet characteristics>

[0148] The adhesive sheet with a release sheet disclosed herein has a light releasability such that the release force (release sheet release force) when peeling the non-silicone release sheet of the adhesive sheet with the release sheet is not inferior to that in the case of using a silicone release sheet. Although not particularly limited, in some embodiments, the release sheet release force is, for example, less than 0.50 N / 50 mm, suitably 0.30 N / 50 mm or less, may be 0.20 N / 50 mm or less, and may also be 0.10 N / 50 mm or less. The lower the release sheet release force, the more likely the release operation property is to be improved. In some preferred embodiments, the release sheet release force is less than 0.07 N / 50 mm, more preferably 0.05 N / 50 mm or less, may be 0.04 N / 50 mm or less, may also be 0.03 N / 50 mm or less, and may also be 0.02 N / 50 mm or less. According to the technology disclosed herein, the above-described light releasability can be achieved for the non-silicone release sheet. The lower limit value of the release sheet release force may be, for example, 0.01 N / 50 mm or more. By making the release sheet release force a specified value or more, the adhesive surface can be well protected by the release sheet. The release sheet release force is measured under the conditions of a temperature of 23°C, a relative humidity of 50%, a tensile speed of 0.3 m / minute, and a peeling angle of 180°. Specifically, it is measured by the method described in the examples below.

[0149] The adhesive force of the adhesive sheet can be appropriately set according to the purpose of use and the application site, and thus is not limited to a specific range. In some embodiments, the adhesive force of the adhesive sheet (preferably a surface protective film) to a glass plate (initial adhesive force to glass) measured under the conditions of a temperature of 23°C, a relative humidity of 50%, a peeling angle of 180°, and a tensile speed of 0.3 m / minute is preferably 2.0 N / 25 mm or less. Since the release force when peeling from an adherend (e.g., a protected object) of the adhesive sheet (preferably a surface protective film) satisfying this property is suppressed to be low, it is easily peeled off. From the viewpoint of release operation property, the initial adhesive force to glass is more preferably 1.0 N / 25 mm or less, further preferably 0.5 N / 25 mm or less, and particularly preferably 0.1 N / 25 mm or less (e.g., less than 0.1 N / 25 mm). From the viewpoints of adhesion to the adherend and protection of the adherend, etc., the initial adhesive force to glass is suitably 0.01 N / 25 mm or more, may be 0.03 N / 25 mm or more, and may also be 0.05 N / 25 mm or more. Specifically, the initial adhesive force to glass is measured by the method described in the examples below.

[0150] In some embodiments, the adhesive sheet preferably has a transparency with a total light transmittance of approximately 50% or more. More preferably, the total light transmittance is 80% or more (e.g., 85% or more) for the transparent adhesive sheet. In applications where transparency is required, the upper limit of the total light transmittance can be around 99% or less (e.g., 95% or less). The adhesive sheet having such transparency is preferred, for example, in the case of inspecting an adherend through the adhesive sheet, high-precision inspection can be performed. This adhesive sheet is preferably used as an optical surface protective film. As the value of the total light transmittance, the value measured according to JIS K 7361-1 can be adopted.

[0151] <Usage>

[0152] The adhesive sheet disclosed herein can be used for various applications. The adhesive sheet disclosed herein is preferably used, for example, as a surface protective film that is usually peeled off (re-peeled) from the protected object when the protection purpose is achieved after being attached to the protected object. Generally, for a surface protective film, it is required not to deteriorate the protected object before and after protecting the protected object. Therefore, it is advantageous to use an adhesive sheet with a non-silicone release sheet that does not cause contamination such as silicone material contamination on the protected surface after peeling off. The protected object of the above surface protective film is not particularly limited, and it can be used as a protective film for various products, components, etc. In addition, the adhesive sheet with a non-silicone release sheet disclosed herein does not cause contamination of the adherend caused by silicone material, and thus is particularly suitable for optical applications that require specified optical characteristics. For example, the adhesive sheet disclosed herein is particularly preferably used as an optical surface protective film that protects the surface of an optical member (e.g., an optical member such as a polarizer, a wave plate, etc. used as a component of a liquid crystal display panel) during processing and transportation. More specifically, the surface protective film is suitable for protecting the optical member during the manufacture and transportation of optical members used as components of a liquid crystal display panel, a plasma display panel (PDP), an organic electroluminescence (EL) display, etc. In particular, it is useful as a surface protective film for optical members such as polarizers (polarization films, e.g., reflective polarization films), wave plates, retardation plates, optical compensation films, brightness enhancement films, light diffusion sheets, and reflective sheets for liquid crystal display panels.

[0153] In addition, in some embodiments, the adhesive disclosed herein may contain an acrylic polymer with a high biomass carbon ratio. Therefore, by using it as a substitute for the conventional general acrylic adhesive (i.e., an acrylic adhesive with a low biomass carbon ratio) in various applications, it can help to reduce the dependence on fossil resource-based materials. The adhesive sheet disclosed herein can typically be preferably used as an adhesive sheet (e.g., a surface protective film) that reduces the dependence on fossil resource-based materials.

[0154] The matters disclosed in this specification include the following.

[0155] 〔1〕An adhesive sheet with a release sheet, which includes an adhesive sheet having an adhesive layer and a non-silicone release sheet disposed on the surface of the adhesive layer. The adhesive layer contains an acrylic polymer, and the acrylic polymer is a polymer of monomer components. The monomer components include an alkyl (meth)acrylate (m1) having an alkyl group with 6 to 17 carbon atoms at the ester terminal, where the alkyl group with 6 to 17 carbon atoms is a straight-chain alkyl group or a branched alkyl group with 1 carbon atom in the branch.

[0156] 〔2〕The adhesive sheet with a release sheet according to the above 〔1〕, wherein the alkyl (meth)acrylate (m1) includes at least one selected from n-heptyl acrylate and n-octyl acrylate.

[0157] 〔3〕The adhesive sheet with a release sheet according to the above 〔1〕 or 〔2〕, wherein the monomer components include a monomer (m2) having a hydroxyl group.

[0158] 〔4〕The adhesive sheet with a release sheet according to any one of the above 〔1〕 to 〔3〕, wherein the adhesive layer includes an isocyanate-based crosslinking agent.

[0159] 〔5〕The adhesive sheet with a release sheet according to any one of the above 〔1〕 to 〔4〕, wherein the adhesive layer contains a zirconium-containing compound.

[0160] 〔6〕The adhesive sheet with a release sheet according to any one of the above 〔1〕 to 〔5〕, wherein the non-silicone release sheet has a release sheet substrate and a non-silicone release treatment layer provided on at least one surface of the release sheet substrate, and the non-silicone release treatment layer is formed of a material containing a long-chain alkyl-based release treatment agent.

[0161] 〔7〕The adhesive sheet with a release sheet according to any one of the above 〔1〕 to 〔6〕, wherein the adhesive sheet has a substrate and the adhesive layer disposed on at least one surface of the substrate.

[0162] 〔8〕The adhesive sheet with a release sheet according to any one of the above 〔1〕 to 〔7〕, wherein the adhesive sheet is used by being attached to an optical member.

[0163] 〔9〕The adhesive sheet with a release sheet according to any one of the above 〔1〕 to 〔8〕, wherein the adhesive sheet is used as a surface protective film.

[0164] Examples

[0165] Hereinafter, some examples related to the present invention will be described, but it is not intended to limit the present invention to the content shown in these examples. It should be noted that "parts" in the following description are based on weight unless otherwise specified.

[0166] <Preparation Example>

[0167] (Preparation of Acrylic Polymer (A1))

[0168] 96 parts of n-heptyl acrylate (HpA), 4 parts of 4-hydroxybutyl acrylate (4HBA), and ethyl acetate (polymerization solvent) were charged into a flask equipped with a reflux condenser, a stirrer, a nitrogen inlet tube, and a thermometer so that the solid component concentration became 36%. Further, 0.3 part of azobisisobutyronitrile (AIBN) as a polymerization initiator was added. Nitrogen was introduced while slowly stirring, and the liquid temperature in the flask was maintained at around 60 °C. Polymerization reaction was carried out for 4 hours, and then it was aged at 70 °C for 4 hours to obtain a solution of acrylic polymer (A1). The weight-average molecular weight (Mw) of the obtained acrylic polymer (A1) was 760,000. It should be noted that the above HpA is a compound synthesized using biomass-derived heptanol and having a biomass-derived heptyl group at the ester terminal.

[0169] (Preparation of Acrylic Polymer (A2))

[0170] 96 parts of lauryl acrylate (LA), 4 parts of 4HBA, and ethyl acetate (polymerization solvent) were charged into a flask equipped with a reflux condenser, a stirrer, a nitrogen inlet tube, and a thermometer so that the solid component concentration became 30%. Further, 0.2 part of AIBN as a polymerization initiator was added. Nitrogen was introduced while slowly stirring, and the liquid temperature in the flask was maintained at around 60 °C. Polymerization reaction was carried out for 5 hours, and then it was aged at 70 °C for 2 hours to obtain a solution of acrylic polymer (A2). The Mw of the obtained acrylic polymer (A2) was 570,000.

[0171] (Preparation of Acrylic Polymer (A3))

[0172] As a monomer component, n-octyl acrylate (n-OcA) was used instead of LA. Otherwise, a solution of acrylic polymer (A3) was obtained by the same method as the preparation of acrylic polymer (A2). The Mw of the obtained acrylic polymer (A3) was 800,000.

[0173] (Preparation of Acrylic Polymer (A4))

[0174] As a monomer component, 2-ethylhexyl acrylate (2EHA) was used instead of HpA. Otherwise, a solution of acrylic polymer (A4) was obtained by the same method as the preparation of acrylic polymer (A1). The Mw of the obtained acrylic polymer (A4) was 410,000.

[0175] (Preparation of Acrylic Polymer (A5))

[0176] Into a flask equipped with a reflux condenser, a stirrer, a nitrogen inlet tube, and a thermometer, 96 parts of n-pentyl acrylate (n-PnA) as a monomer component, 4 parts of 4HBA, and ethyl acetate (polymerization solvent) were charged so that the solid component concentration became 30%. Further, 0.2 part of AIBN as a polymerization initiator was added. While slowly stirring, nitrogen was introduced, and the liquid temperature in the flask was maintained at around 60°C. Polymerization reaction was carried out for 6 hours, and then it was aged at 70°C for 2 hours to obtain a solution of acrylic polymer (A5). The Mw of the obtained acrylic polymer (A5) was 770,000.

[0177] (Preparation of acrylic polymer (A6))

[0178] As the monomer component, isostearyl acrylate (i-StA) was used instead of LA. Except for this, a solution of acrylic polymer (A6) was obtained by the same method as the preparation of acrylic polymer (A2). The Mw of the obtained acrylic polymer (A6) was 49,000.

[0179] <Example 1>

[0180] (Preparation of adhesive composition)

[0181] The solution of the acrylic polymer (A1) obtained above was diluted with ethyl acetate so that the solid component concentration became 30%. To this solution, an isocyanate-based crosslinking agent (trade name “Coronate HX”, isocyanurate of hexamethylene diisocyanate, manufactured by Tosoh Corporation) in an amount of 3.5 parts (solid component) based on 100 parts of the solid component of the solution, and a zirconium catalyst (trade name “ZC-150”, zirconium tetraacetylacetonate, manufactured by Matsumoto Fine Chemical Co., Ltd.) in an amount of 0.035 part (solid component) based on 100 parts of the solid component of the solution were added. Further, acetylacetone was added in an amount to be 8% of the diluted polymer solution and stirred to obtain the acrylic adhesive composition of this example.

[0182] (Production of adhesive sheet)

[0183] The above-prepared acrylic adhesive composition was coated on a polyethylene terephthalate (PET) film (manufactured by Mitsubishi Chemical Corporation, product name "DIAFOIL T100C38", thickness 38 μm), and dried at 130 °C for 20 seconds to remove the solvent, thereby forming an adhesive layer (thickness 21 μm). Thereafter, the surface of the adhesive layer was covered with a non-silicone release sheet (manufactured by Mitsubishi Chemical Corporation, product name "DIAFOIL T100H25[UH18]", thickness 25 μm), and left standing at room temperature (23 °C) for 4 days to obtain the adhesive sheet with a release sheet of this example. The above non-silicone release sheet has a release treatment layer formed of a release treatment agent containing pentaerythritol fatty acid ester and octadecyl isocyanate on the surface of the polyester film substrate.

[0184] <Examples 2 to 12 and Comparative Examples 1 to 6>

[0185] The type of acrylic polymer, the amount of crosslinking agent used (solid content), the type and amount of catalyst used (solid content), and the type of release sheet were changed as shown in Table 1. Otherwise, the adhesive sheets with release sheets of each example were obtained by the same method as in Example 1.

[0186] In the example of using a tin catalyst, as the tin catalyst, dioctyltin dilaurate (manufactured by Tokyo Fine Chemical Co., Ltd., trade name "EMBILIZER OL-1") at 0.015 parts (solid content) relative to 100 parts of the solid content of the acrylic polymer solution was used, and acetylacetone was added in such a manner that the diluted polymer solution became 3%.

[0187] As the silicone release sheet, a silicone release sheet produced by the following method was used. 3.3 parts of a silicone curing catalyst (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "CAT-PL-50T") was added to 100 parts of a silicone release agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KS-847T"), and diluted to a concentration of 0.3% with a mixed solvent containing toluene, n-hexane, and methyl ethyl ketone in a weight ratio of 1:2:1 to obtain a silicone release treatment agent composition. The release treatment agent composition was coated on a polyester film (manufactured by Mitsubishi Chemical Corporation, product name "DIAFOIL T100-25") with a thickness of 25 μm and dried at 130 °C for 1 minute, thereby producing a silicone release sheet having a silicone release treatment layer with a dried thickness of 20 nm on the above polyester film.

[0188] (Initial adhesion to glass)

[0189] The adhesive sheet was cut into a size of 25 mm in width and 80 mm in length. A clean sodium glass plate was obtained by reciprocally wiping it 10 times with a cleaning cloth impregnated with ethanol and then washing it. It was pressed onto the obtained clean sodium glass plate by rolling a 2-kg roller once back and forth to produce a sample for evaluating the adhesive strength. After leaving the above-mentioned evaluation sample at room temperature for 30 minutes, the adhesive strength [N / 25 mm] was measured at a peeling angle of 180° and a tensile speed of 0.3 m / minute in an environment of 23°C and 50% RH using a tensile testing machine (manufactured by Shimadzu Corporation, product name "Autograph AG-50NX"). Each example was measured twice (n = 2), and the average value was set as the initial adhesive strength to glass [N / 25 mm]. As the glass plate as the adherend, a sodium glass plate (product number "S200423") manufactured by Matsunami Glass Industry Co., Ltd. or its equivalent was used.

[0190] (Contamination)

[0191] In a dark room, the surface of the adherend (the adhesive sheet removal surface of the glass plate) after measuring the initial adhesive strength to glass was reflected under a fluorescent lamp and visually observed. If no change was observed in the surface state of the adherend, it was judged as qualified.

[0192] (Peeling force of the release sheet)

[0193] The adhesive sheet was cut into a size of 50 mm in width and 80 mm in length. The back surface of the adhesive sheet was fixed to an acrylic plate using a double-sided tape (manufactured by Nitto Denko Corporation, product name "No. 5000NS"). In an environment of 23°C and 50% RH, the release sheet was peeled from the adhesive surface of the adhesive sheet at a peeling angle of 180° and a tensile speed of 0.3 m / minute using a tensile testing machine (manufactured by Shimadzu Corporation, product name "Autograph AG-50NX"), and the peeling force [N / 50 mm] at this time was measured. Each example was measured twice (n = 2), and the maximum value among them was set as the peeling force of the release sheet [N / 50 mm].

[0194] (Water contact angle of the glass plate surface after peeling the adhesive sheet)

[0195] An evaluation sample was prepared by pressing an adhesive sheet onto a glass substrate using a method of rolling a 2-kg roller back and forth once. After leaving the above evaluation sample at room temperature for 30 minutes, the adhesive sheet was peeled off from the glass substrate at a certain angle and speed, and the water contact angle [°] of the glass substrate surface was measured in an atmosphere of 23°C and 50% RH. The contact angle was measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name “CA-X”) and implemented by the droplet method (θ / 2 method). The droplet volume of distilled water was set to 2 μL, and the standing time from contacting the liquid to measurement was set to 2000 milliseconds. Five measurements (n = 5) were performed for each case, and the average value was used. As the glass plate as the adherend, a soda lime glass plate (product number “S1214”) manufactured by Matsunami Glass Industry Co., Ltd. or its equivalent was used.

[0196] The outline and evaluation results of each case are shown in Table 1.

[0197] [Table 1]

[0198]

[0199] As shown in Table 1, in the case of using an adhesive containing an acrylic polymer synthesized using 2EHA (a branched alkyl group having 8 carbon atoms and 2 branched carbon atoms) as a (meth)acrylic acid linear alkyl ester, in Comparative Example 1 using a silicone release sheet, the release force of the release sheet was as low as 0.02 N / 50 mm, and the release property of the release sheet was excellent. However, in Comparative Example 2 using a non-silicone release sheet, the release force of the release sheet increased to 0.07 N / 50 mm, and a tendency of a decrease in the release property of the release sheet was observed. On the other hand, in the case of using HpA (a linear alkyl group having 7 carbon atoms) as a monomer component of the acrylic polymer contained in the adhesive, in Comparative Example 4 using a silicone release sheet, the initial adhesion to glass was 0.06 N / 25 mm, and the release force of the release sheet was 0.02 N / 50 mm. In contrast, in Example 1 using a non-silicone release sheet, the initial adhesion to glass was 0.05 N / 25 mm, and the release force of the release sheet was 0.03 N / 50 mm. It was confirmed that even when using a non-silicone release sheet, the release property of the release sheet was not inferior to the case of using a silicone release sheet. In Examples 2 to 4 in which the same acrylic polymer as in Example 1 was used and the amount of crosslinking agent used and the type of catalyst were changed, good release properties of the release sheet were also confirmed.

[0200] In addition, in Examples 5 to 12 of the adhesive using an acrylic polymer synthesized using an (alkyl) acrylate (specifically, LA or n-OcA) in which the number of carbon atoms in the alkyl group is in the range of 6 to 17 and the alkyl group is a straight-chain alkyl group or a branched alkyl group with 1 carbon atom in the branch as a monomer component, good release sheet releasability was also confirmed. On the other hand, even if the alkyl group of the (alkyl) acrylate used as the monomer component is a straight-chain alkyl group, if the number of carbon atoms in the alkyl group is 5 (Comparative Example 5: using n-PnA), there is a tendency for the release force of the release sheet to increase, and good release sheet releasability cannot be obtained. In addition, in Comparative Example 6 using i-StA with 18 carbon atoms in the alkyl group as the (alkyl) acrylate chain alkyl ester, since the viscosity is too low, an adhesive layer with a uniform film thickness cannot be formed, and the evaluation of the adhesive sheet cannot be carried out.

[0201] It should be noted that the water contact angle of the glass plate surface after the adhesive sheet was peeled off was measured. As a result, it was 16° in Example 1, 41° in Comparative Example 1, 43° in Comparative Example 2, and 20° in Comparative Example 4. In Example 1, the water contact angle did not increase before and after the adhesive sheet was attached. In addition, based on the comparison between Comparative Example 1 and Comparative Example 2, and the comparison between Example 1 and Comparative Example 4, in the case of using a silicone-based release sheet, compared with the case of using a non-silicone-based release sheet, it was observed that the water contact angle of the surface of the adherend increased through short-term attachment. It is considered that the reason is that the silicone material of the release sheet is transferred to the adherend. It should be noted that it is considered that the difference in the water contact angle between Example 1, Comparative Example 4 and Comparative Examples 1 to 2 is due to the different types of catalysts. In addition, Examples 1 to 12 and Comparative Examples 1 to 5 were evaluated for contamination, and as a result, all passed at the visual level (no change in the surface state was observed).

[0202] From the above results, it can be seen that by using an adhesive of an acrylic polymer containing a polymer as a monomer component, in the case of using a non-silicone-based release sheet, release sheet releasability comparable to that of using a silicone-based release sheet can also be achieved. The monomer component contains an (alkyl) acrylate (m1) having an alkyl group with 6 to 17 carbon atoms at the ester terminal, and the alkyl group with 6 to 17 carbon atoms is a straight-chain alkyl group or a branched alkyl group with 1 carbon atom in the branch.

[0203] The above has described the specific examples of the present invention in detail, but these are only examples and do not limit the claims. The technologies described in the claims include various modifications and changes of the specific examples exemplified above.

[0204] Explanation of reference numerals

[0205] 1: Adhesive sheet; 10: Substrate (support substrate); 10A: First side; 10B: Second side (back side); 21: Adhesive layer; 21A: Adhesive surface; 31: Release sheet; 100: Adhesive sheet with release sheet.

Claims

1. An adhesive sheet with a release sheet, which comprises an adhesive sheet having an adhesive layer, and a non-silicone release sheet disposed on the surface of the adhesive layer. The adhesive layer contains an acrylic polymer. The acrylic polymer is a polymer of monomer components, and the monomer components include an alkyl (meth)acrylate m1 having an alkyl group with 6 to 17 carbon atoms at the ester terminal. Among them, The alkyl group having 6 to 17 carbon atoms is a straight-chain alkyl group or a branched alkyl group having 1 carbon atom in the branch.

2. The adhesive sheet with a release sheet according to claim 1, wherein the (meth)acrylic acid alkyl ester m1 includes at least one selected from n-heptyl acrylate and n-octyl acrylate.

3. The adhesive sheet with a release sheet according to claim 1 or 2, wherein the monomer component contains a monomer m2 having a hydroxyl group.

4. The adhesive sheet with a release sheet according to claim 1 or 2, wherein the adhesive layer contains an isocyanate-based crosslinking agent.

5. The adhesive sheet with a release sheet according to claim 1 or 2, wherein the adhesive layer contains a zirconium-containing compound.

6. The adhesive sheet with a release sheet according to claim 1 or 2, wherein the non-silicone release sheet has a release sheet substrate and a non-silicone release treatment layer provided on at least one surface of the release sheet substrate. The non-silicone release treatment layer is formed of a material containing a long-chain alkyl-based release treatment agent.

7. The adhesive sheet with a release sheet according to claim 1 or 2, wherein the adhesive sheet has a substrate and the adhesive layer disposed on at least one surface of the substrate.

8. The adhesive sheet with a release sheet according to claim 1 or 2, wherein the adhesive sheet is used by being attached to an optical member.

9. The adhesive sheet with a release sheet according to claim 1 or 2, wherein the adhesive sheet is used as a surface protection film.

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