Acrylic polymer release agents, release sheets, tapes, and double-sided tapes

Abstract

[Problem] To provide a long-chain alkyl-based release agent useful for producing a light release liner that can be used on the light release surface of an adhesive transfer tape. [Solution] An acrylic polymer release agent according to one embodiment comprises the polymerization product of a polymerizable precursor composition that contains an acrylate monomer having a branched alkyl group having 24 or more carbon atoms and an acrylic monomer having a benzophenone structure.

Description

[Technical field]

[0001] The present disclosure relates to acrylic polymer release agents, release sheets, tapes, and double-sided tapes. [Background technology]

[0002] Silicone-based release agents, fluorine-based release agents, and long-chain alkyl-based release agents are known as release agents used in release liners or release sheets of adhesive products such as adhesive tapes. Among these, long-chain alkyl-based release agents do not have the problem of silicone contamination that may occur with silicone-based release liners. Therefore, adhesive transfer tapes (ATTs) and double-sided or single-sided tapes having long-chain alkyl-based release liners are widely used in the electronics industry, such as for hard disk drive (HDD) applications.

[0003] Patent Document 1 (JP 2017-165818(A)) discloses a release agent composition containing a liquid polymer (A) and an acrylic polymer (B), in which the acrylic polymer (B) contains a constituent unit derived from a long-chain alkyl (meth)acrylate (b1) represented by formula (1) and a constituent unit derived from an alkyl (meth)acrylate (b2) represented by formula (2).

[0004] Patent Document 2 (JP 2001-240775(A)) discloses "a polymerizable composition for forming a release agent, which contains a first alkyl(meth)acrylate having an alkyl group having 12 to 30 carbon atoms, a second alkyl(meth)acrylate having an alkyl group having 1 to 12 carbon atoms, and a polymerization initiator for the first alkyl(meth)acrylate and the second alkyl(meth)acrylate."

[0005] Patent Document 3 (JP 2003-327945(A)) describes a method for producing a poly(meth)acrylic acid ester having a UV-active group, which exhibits a thermal conductivity of 1×10 at 20° C. and a frequency of 1 Hz. 2~3×10 6 The document discloses an acrylic release agent precursor having a storage modulus of 1.0 Pa, which, upon irradiation with ultraviolet light, has a contact angle of 15° or more with a mixed solution of methanol and water (volume ratio 90 / 10) having a wetting tension of 25.4 mN / m. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-165818 A [Patent Document 2] JP 2001-240775 A [Patent Document 3] JP 2003-327945 A Summary of the Invention [Problem to be solved by the invention]

[0007] To produce adhesive transfer tapes for use in the electronics industry, such as HDD applications, one surface of the adhesive layer (light release surface) is typically covered with a light release liner, and the other surface (heavy release surface) is covered with a heavy release liner. In order to peel the release liner from the adhesive layer in the correct order in the adhesive transfer tape and reliably apply the adhesive layer to the adherend, it is necessary that the release force ratio of the heavy release surface to the light release surface is equal to or greater than a certain value. On the other hand, it is desirable that the heavy release surface also be easily peeled off.

[0008] In such adhesive transfer tapes, long-chain alkyl release liners are generally used for the heavy release side, and fluorine-based release liners are used for the light release side. When the long-chain alkyl release liners of the related art are used for the light release side, it is difficult to sufficiently increase the release force ratio of the heavy release side to the light release side.

[0009] However, although fluorine-based materials can achieve light release, disposal must be considered, and they often require the use of fluorine-based solvents, so it is preferable to avoid their use as much as possible depending on the application.Therefore, there is a demand for non-silicone, non-fluorine (NSNF) release sheets that contain neither silicone compounds nor fluorine compounds, and tapes using the same.

[0010] The present disclosure provides a long-chain alkyl release agent useful for producing a light release liner that can be used on the light release surface of an adhesive transfer tape. The present disclosure also provides a release sheet, tape, and double-sided tape that use such a long-chain alkyl release agent. [Means for solving the problem]

[0011] According to a first embodiment, there is provided an acrylic polymer release agent comprising a polymerization product of a polymerizable precursor composition comprising an acrylate monomer having a branched alkyl group having 24 or more carbon atoms and an acrylic monomer having a benzophenone structure.

[0012] According to a second embodiment, there is provided an acrylic polymer release agent comprising a polymerization product of a polymerizable precursor composition comprising 99% by weight or more of an acrylate monomer having a branched alkyl group having 24 or more carbon atoms, based on the polymerizable component.

[0013] According to another embodiment, a release sheet is provided that includes a substrate and a release coating disposed on the substrate, the release coating including a cured product of an acrylic polymer release agent.

[0014] According to yet another embodiment, a tape is provided that includes a release sheet and an adhesive layer laminated onto the release coating of the release sheet.

[0015] According to yet another embodiment, there is provided a double-sided tape comprising, in that order, a release sheet, an adhesive layer, and a second release sheet, the second release sheet comprising a second substrate and a heavy release coating disposed on the second substrate, the heavy release coating comprising a cured product of a second acrylic polymer release agent, the second acrylic polymer release agent comprising a polymerization product of a second polymerizable precursor composition containing 50% or more by weight, based on the polymerizable component, of acrylate monomers having an alkyl group having less than 24 carbon atoms, and the release coating of the release sheet and the heavy release coating of the second release sheet are laminated together so as to be in contact with the adhesive layer. Effect of the Invention

[0016] The acrylic polymer release agent of the present disclosure is useful for producing a light release liner that can be used on the light release side of an adhesive transfer tape. The release sheet using the acrylic polymer release agent of the present disclosure can be particularly suitably used for NSNF adhesive transfer tape as a release sheet for tapes and double-sided tapes.

[0017] It should be noted that the above description is not intended to be construed as a complete disclosure of the embodiments of the present invention and advantages associated with the present invention. [Brief description of the drawings]

[0018] [Figure 1] 1 is a schematic cross-sectional view of a double-sided tape according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the present invention will be described in more detail with reference to the drawings in order to explain representative embodiments of the present invention, but the present invention is not limited to these embodiments.

[0020] In this disclosure, the term "(meth)acrylic" refers to acrylic or methacrylic, and the term "(meth)acrylate" refers to acrylate or methacrylate.

[0021] In this disclosure, "sheet" encompasses articles referred to as "films."

[0022] In this disclosure, "double-sided tape" also encompasses what is called "transfer tape" in certain applications.

[0023] In this disclosure, "pressure sensitive adhesion" refers to the property of a material or composition that adheres to a variety of surfaces with minimal pressure for a short period of time at a range of service temperatures, such as 0° C. to 50° C., and does not exhibit a phase change (liquid to solid). In this disclosure, "adhesion" is used interchangeably with "pressure sensitive adhesion."

[0024] In the present disclosure, "disposed on" refers not only to being directly disposed on, but also to being indirectly disposed on, i.e., being disposed on via another material or layer.

[0025] In this disclosure, "polymerizable component" refers to a component capable of radically polymerizing with an acrylate monomer having a branched alkyl group having 24 or more carbon atoms.

[0026] According to a first embodiment, the acrylic polymer release agent contains a polymerization product of a polymerizable precursor composition containing an acrylate monomer having a branched alkyl group with 24 or more carbon atoms and an acrylic monomer having a benzophenone structure. The acrylic polymer release agent containing such a polymerization product can be cured by exposure to radiation such as ultraviolet light or electron beam to form a release coating on a substrate that corresponds to a light release surface.

[0027] The polymerizable precursor composition contains an acrylate monomer having a branched alkyl group having 24 or more carbon atoms and an acrylic monomer having a benzophenone structure.

[0028] The long chain alkyl moiety of the branched alkyl group having 24 or more carbon atoms not only reduces the surface energy of the cured product of the acrylic polymer release agent, but also reduces the crystallinity of the cured product due to the branching, and the storage modulus of the cured product due to the branching of the alkyl group, which allows the formation of a release coating that exhibits a smooth (non-chattering) and light release force over a wide range of release speeds.

[0029] Examples of acrylate monomers having a branched alkyl group with 24 or more carbon atoms include 2-decyltetradecyl acrylate (24 carbon atoms), 2-dodecylhexadecyl acrylate (28 carbon atoms), and 2-tetradecyloctadecyl acrylate (32 carbon atoms). The acrylate monomers having a branched alkyl group with 24 or more carbon atoms can be used alone or in combination of two or more kinds.

[0030] Branched alkyl groups having 24 or more carbon atoms are preferably single-branched, so that the long chain alkyl portion of the branched alkyl group can be anchored to form a release coating that exhibits light release force.

[0031] The branching position of the branched alkyl group having 24 or more carbon atoms is preferably position 2 or 4. As a result, the crystallinity of the cured product can be effectively reduced, and smoother release properties can be obtained.

[0032] The number of carbon atoms in the branched chain of the branched alkyl group having 24 or more carbon atoms is preferably 8 or more, 10 or more, or 12 or more, so that multiple long chain alkyl moieties of the branched alkyl group can be attached to form a release coating that exhibits a lighter release force.

[0033] The content of the acrylate monomer having a branched alkyl group having 24 or more carbon atoms in the polymerizable precursor composition is preferably about 90% by weight or more, about 95% by weight or more, or about 99% by weight or more, based on the polymerizable components.

[0034] The benzophenone structure of the acrylic monomer having a benzophenone structure generates radicals when irradiated with radiation such as an electron beam or ultraviolet light. The generated radicals promote crosslinking of the polymerization product of the polymerizable precursor composition and bonding of the cured product obtained from the crosslinking to the substrate. As a result, the acrylic polymer release agent can be efficiently cured with a small radiation exposure dose, improving the cohesiveness of the cured product and the adhesion between the cured product and the substrate, and suppressing migration of the cured product to the adhesive. As a result of suppressing migration of the cured product to the adhesive, the residual adhesive strength of the adhesive can be maintained at a high level.

[0035] Examples of acrylic monomers having a benzophenone structure include 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy-4'-bromobenzophenone, and 4-acryloyloxyethoxy-4'-bromobenzophenone. The acrylic monomers having a benzophenone structure can be used alone or in combination of two or more.

[0036] The content of the acrylic monomer having a benzophenone structure in the polymerizable precursor composition is preferably about 1% by mass or less, about 0.8% by mass or less, or about 0.5% by mass or less, based on the polymerizable component. By making the content of the acrylic monomer having a benzophenone structure about 1% by mass or less, it is possible to suppress an increase in the peeling force. The content of the acrylic monomer having a benzophenone structure in the polymerizable precursor composition is preferably about 0.01% by mass or more, about 0.02% by mass or more, or about 0.05% by mass or more, based on the polymerizable component. By making the content of the acrylic monomer having a benzophenone structure about 0.01% by mass or more, it is possible to effectively promote crosslinking of the polymerization product and bonding of the cured product to the substrate.

[0037] The polymerizable precursor composition may contain an acrylate monomer having an alkyl group having from 4 to 20 carbon atoms. The alkyl group having from 4 to 20 carbon atoms may be linear or branched. Examples of acrylate monomers having an alkyl group having 4 to 20 carbon atoms include butyl acrylate (4 carbon atoms), hexyl acrylate (6 carbon atoms), octyl acrylate (8 carbon atoms), 2-ethylhexyl acrylate (8 carbon atoms), decyl acrylate (10 carbon atoms), 8-methylnonyl acrylate (10 carbon atoms), dodecyl acrylate (12 carbon atoms), tridecyl acrylate (13 carbon atoms), tetradecyl acrylate (14 carbon atoms), hexadecyl acrylate (16 carbon atoms), octadecyl acrylate (18 carbon atoms), isooctadecyl acrylate (18 carbon atoms), 2-hexyldodecyl acrylate (18 carbon atoms), 2-octyldecyl acrylate (18 carbon atoms), and icosyl acrylate (20 carbon atoms).

[0038] The content of the acrylate monomer having an alkyl group having 4 to 20 carbon atoms in the polymerizable precursor composition is preferably about 30% by mass or less, about 15% by mass or less, or about 8% by mass or less, based on the polymerizable component.

[0039] In one embodiment, the acrylate monomers having a branched alkyl group with 24 or more carbon atoms and the acrylate monomers having an alkyl group with 4 to 20 carbon atoms do not have a polar functional group such as a carboxy group, a hydroxyl group, an amino group, or an amide group on the alkyl group. In this embodiment, the cured product can maintain a light release force even after being exposed to high temperatures.

[0040] The polymerizable precursor composition generally contains a polymerization initiator. The use of the polymerization initiator can promote the initiation of the polymerization reaction of the polymerizable components in the polymerizable precursor composition, for example, an acrylate monomer having a branched alkyl group with 24 or more carbon atoms and an acrylic monomer having a benzophenone structure. As the polymerization initiator, a typical thermal polymerization initiator can be used. Examples of the thermal polymerization initiator include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 2,2-azobis(2,4-dimethylvaleronitrile), and dimethyl 2,2'-azobis(2-methylpropionate); and peroxides such as benzoyl peroxide and lauroyl peroxide.

[0041] The amount of the polymerization initiator used is preferably about 0.005 parts by mass or more and about 0.5 parts by mass or less based on 100 parts by mass of the polymerizable component. By using an amount of the polymerization initiator of about 0.005 parts by mass or more, a practical polymerization rate can be ensured. By using an amount of the polymerization initiator of about 0.5 parts by mass or less, the molecular weight of the polymerization product can be increased to a level sufficient for forming a coating.

[0042] By heating the polymerizable precursor composition in the presence of a polymerization initiator, a polymerization product of an acrylate monomer having a branched alkyl group with 24 or more carbon atoms, an acrylic monomer having a benzophenone structure, and optionally an acrylate monomer having an alkyl group with 4 to 20 carbon atoms can be obtained. The polymerization product contains a copolymer of an acrylate monomer having a branched alkyl group with 24 or more carbon atoms and an acrylic monomer having a benzophenone structure, and optionally contains a homopolymer of each polymerizable component, a copolymer of two or more polymerizable components, and / or an unreacted polymerizable component (unreacted monomer). The remaining unreacted monomer is polymerized by applying the acrylic polymer release agent to a substrate and irradiating it with radiation such as ultraviolet light or an electron beam, and is incorporated into the cured product of the acrylic polymer release agent.

[0043] Although the polymerization method may be various, solution polymerization, which is carried out by dissolving the polymerizable components in a solvent, is preferred because it produces a polymer with a high molecular weight that is advantageous for coating formation. When using solution polymerization, the solution of the polymerization product can be used as an acrylic polymer release agent as it is after the polymerization is completed. As the polymerization solvent, aliphatic hydrocarbons such as n-hexane and n-heptane, esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone and methyl isobutyl ketone, or mixed solvents thereof can be used. From the viewpoint of molecular weight control, chain transfer agents or chain extenders can also be used. Examples of chain transfer agents include thiol compounds such as 2-mercaptoethanol, 3-mercapto-2-butanol, 3-mercapto-2-propanol, 3-mercapto-1-propanol, dodecanethiol, isooctylthioglycolate, and 2-mercaptoethylamine. Examples of chain extenders include divalent acrylic monomers such as 1,6-hexanediol diacrylate, 1,9-nonanediol diacrylate, polyethylene glycol diacrylate, and polypropylene glycol diacrylate. The solution polymerization of the polymerizable precursor composition can be carried out in an atmosphere of an inert gas such as nitrogen gas at a reaction temperature of about 50° C. to about 100° C. for about 2 hours to about 100 hours.

[0044] The weight average molecular weight (Mw) of the polymerization product is preferably about 500,000 or more, more preferably about 800,000 or more, and even more preferably about 1,000,000 or more. By making the weight average molecular weight of the polymerization product about 500,000 or more, the peel force can be reduced, the film formability can be improved, and the residual adhesive force of the adhesive can be maintained. In the present disclosure, the "weight average molecular weight" is a molecular weight converted into a polystyrene standard by gel permeation chromatography (GPC) method.

[0045] The weight average molecular weight (Mw) of the polymerization product is preferably about 5,000,000 or less, more preferably about 4,000,000 or less, and even more preferably about 3,000,000 or less. By making the weight average molecular weight of the polymerization product about 5,000,000 or less, the acrylic polymer release agent can have a viscosity suitable for application, while the solid content of the acrylic polymer release agent can be increased, and the amount of the solvent used can be reduced.

[0046] According to the second embodiment, the acrylic polymer release agent contains a polymerization product of a polymerizable precursor composition containing 99% by mass or more of an acrylate monomer having a branched alkyl group with 24 or more carbon atoms based on the polymerizable component. In the second embodiment, unlike the first embodiment, the polymerizable precursor composition does not contain an acrylic monomer having a benzophenone structure as an essential component. However, in fields where time for photopolymerization can be guaranteed or in situations where equipment with high light intensity can be used, a release coating that shows a smooth and light release force at a wide range of release speeds can be formed by containing a large amount of 99% by mass or more of an acrylate monomer having a branched alkyl group with 24 or more carbon atoms based on the polymerizable component, as in the first embodiment.

[0047] The acrylate monomer having a branched alkyl group having 24 or more carbon atoms is as described in the first embodiment except for its content. The content of the acrylate monomer having a branched alkyl group having 24 or more carbon atoms in the polymerizable precursor composition is preferably about 99.5% by mass or more, about 99.8% by mass or more, or 100% by mass or more based on the polymerizable component.

[0048] The polymerizable precursor composition may contain an acrylate monomer having an alkyl group having 4 to 20 carbon atoms. The acrylate monomer having an alkyl group having 4 to 20 carbon atoms is as described in the first embodiment except for its content. The content of the acrylate monomer having an alkyl group having 4 to 20 carbon atoms in the polymerizable precursor composition is preferably about 1 mass % or less, about 0.5 mass % or less, or about 0.2 mass % or less based on the polymerizable component.

[0049] The polymerization initiator, the chain transfer agent, the chain extender, and the method for obtaining a polymerizable component by polymerizing the polymerizable precursor composition, as well as the weight average molecular weight of the obtained polymerizable component, are as described in the first embodiment.

[0050] The acrylic polymer release agent may contain a photopolymerization initiator. The use of the photopolymerization initiator can promote the formation of a cured product of the acrylic polymer release agent and the bonding of the cured product to a substrate. Examples of photopolymerization initiators include benzophenone, 4-methylbenzophenone, 4-phenylbenzophenone, 4,4'-bis(dimethylamino)benzophenone, and methyl 2-benzoylbenzoate. From the viewpoint of reducing organic contamination due to decomposition products of the photopolymerization initiator, it is advantageous for the acrylic polymer release agent to not contain a photopolymerization initiator.

[0051] In one embodiment, the acrylic polymer release agent is substantially free of silicone and fluorine compounds or does not contain any of them. The acrylic polymer release agent of this embodiment can provide NSNF release liners suitable for electronic components or electronic products such as HDDs, and NSNF double-sided tapes or adhesive transfer tapes manufactured using NSNF release liners. In this disclosure, "substantially free of silicone and fluorine compounds" means that the total amount of silicone and fluorine compounds contained in the acrylic polymer release agent is less than 1 part by weight, preferably less than 0.5 parts by weight, more preferably less than 0.1 parts by weight, based on 100 parts by weight of the solid content of the acrylic copolymer release agent.

[0052] A release sheet according to one embodiment includes a substrate and a release coating disposed on the substrate, the release coating including a cured product of an acrylic polymer release agent.

[0053] Examples of the substrate include plastic films such as polyester and polyolefin, paper, or paper substrates coated with such plastic materials. One example of the substrate may be a colored film. The colored film may be a mixture of dyes in plastic, colored paper, or a transparent film coated with colored ink. For example, an example of using a white film as the colored film will be described later. The use of a colored film makes it easier for the user to recognize the release sheet. Furthermore, the film may be printed with a logo, instructions on how to use, etc. The use of a colored film makes it easier for the user to see these printed characters, etc. The thickness of the substrate may vary depending on the application, and may be, for example, about 1 μm or more and about 300 μm or less.

[0054] The release sheet can be produced, for example, by the following procedure. The acrylic polymer release agent is diluted with an aliphatic hydrocarbon such as n-hexane and n-heptane, an aromatic hydrocarbon such as toluene and xylene, an ester such as ethyl acetate and butyl acetate, a ketone such as methyl ethyl ketone and methyl isobutyl ketone, or a halogenated hydrocarbon such as methylene chloride, or a mixture of these substances, as required. The resulting solution is then applied to a substrate of a predetermined thickness using a bar coater, a roll coater, a spray, or the like, and dried by heating as required to form a release precursor layer on the substrate. The dilution solvent may be the same as or different from the solvent used in carrying out the solution polymerization. The amount of acrylic polymer release agent applied may vary depending on the substrate. The acrylic polymer release agent is generally applied so that the dry thickness is about 0.01 μm or more and about 10 μm or less. When the substrate is a plastic film such as polyester or polyolefin, the dry thickness is generally about 0.05 μm or more and about 1 μm or less. When the substrate is a paper or the like having absorbency or low smoothness, the dry thickness is generally about 0.1 μm or more and about 5 μm or less.

[0055] The release precursor layer is then irradiated with radiation such as an electron beam or ultraviolet light to form a release coating on the substrate. The release coating adheres to the substrate by irradiation with radiation. In this manner, a release sheet can be obtained. In the case of irradiation with an electron beam, the amount of absorption depends on the thickness and composition of the release precursor layer, and is typically about 1 kGy to about 100 kGy. In the case of irradiation with ultraviolet light, the ultraviolet energy depends on the thickness and composition of the release precursor layer. The ultraviolet energy is typically about 10 mJ / cm 2 ~Approx. 3000mJ / cm 2 , preferably about 20 mJ / cm 2 ~about 500mJ / cm 2 Unlike electron beam irradiation, ultraviolet irradiation does not require a large-scale device, and therefore the release sheet can be produced at low cost and with high productivity.

[0056] Another embodiment of the release sheet includes a substrate having a first surface and a second surface opposite to the first surface, a first release coating disposed on the first surface of the substrate, and a second release coating disposed on the second surface of the substrate. The first release coating contains a cured product of an acrylic polymer release agent. The first release coating and the second release coating may be the same or different from each other. The second release coating may contain a cured product of an acrylic polymer release agent, or may be formed from another release agent. For example, when the release sheet of this embodiment is used for a double-sided tape that is distributed in a roll wound around a core, the release sheet can be arranged so that the outer peripheral surface side is the first release coating (light release coating) and the inner peripheral surface side is the second release coating (heavy release coating).

[0057] In one embodiment, the tape includes a substrate, a release sheet having a release coating containing a cured product of an acrylic polymer release agent disposed on the substrate, and an adhesive layer laminated onto the release coating of the release sheet, which may also be referred to as a transfer tape when used in an embodiment in which the adhesive layer is separated from the release sheet and adhered to an adherend.

[0058] The tape of this embodiment may further include a support substrate such as paper, a plastic film, a foam material such as acrylic or urethane, and a nonwoven fabric, laminated on the surface of the adhesive layer opposite the release sheet. In this embodiment, when the surface of the support substrate opposite the surface facing the adhesive layer has a second adhesive layer, the substrate is in the form of a so-called double-sided tape with substrate (including a transfer tape with substrate). When the surface of the support substrate opposite the surface facing the adhesive layer does not have an adhesive layer, the substrate is in the form of a so-called single-sided tape.

[0059] The adhesive layer can be formed by using an adhesive containing an adhesive polymer, such as, for example, an acrylic, polyolefin-based, polyurethane-based, polyester-based, or rubber-based polymer. Silicone-based adhesives are also applicable if the requirements meet the silicone specifications. The adhesive may be solvent-based, emulsion-based, or solvent-free. The adhesive may be a hot melt adhesive, a heat-curable adhesive, or an ultraviolet-curable adhesive. In one embodiment, the adhesive layer is formed using a solvent-based acrylic adhesive. The adhesive may be applied directly onto a release sheet to form an adhesive layer. The adhesive layer formed on the liner may be transferred and laminated onto a release sheet. The adhesive layer may or may not have a support made of paper, plastic film, nonwoven fabric, etc., inside it.

[0060] The thickness of the adhesive layer can typically be about 1 μm or more, about 5 μm or more, or about 10 μm or more, and about 100 μm or less, about 80 μm or less, or about 50 μm or less.

[0061] In one embodiment, the release sheet has a release force from the adhesive layer of less than 0.1 N / cm. Release sheets having a release force of less than 0.1 N / cm are suitable for use as light release liners for double-sided tapes or adhesive transfer tapes.

[0062] In one embodiment, the residual adhesion of the adhesive layer after the release sheet is removed is about 85% or more, about 90% or more, or about 95% or more of the residual adhesion of the adhesive layer without the release sheet applied.

[0063] In one embodiment, the double-sided tape includes a substrate, a release sheet having a release coating containing a cured product of an acrylic polymer release agent disposed on the substrate, an adhesive layer, and a second release sheet, in that order. The second release sheet is a heavy release sheet including a second substrate and a heavy release coating containing a cured product of a second acrylic polymer release agent disposed on the second substrate. The release coating of the release sheet and the heavy release coating of the second release sheet are laminated so as to be in contact with the adhesive layer.

[0064] 1 shows a schematic cross-sectional view of a double-sided tape according to one embodiment. The double-sided tape 100 is a laminate of a release sheet 10 (light release sheet) including a substrate 12 and a release coating 14 (light release coating) disposed on the substrate 12, an adhesive layer 20, and a second substrate 32 and a second release sheet 30 (heavy release sheet) including a gun release coating 34 disposed on the second substrate 32. The release coating 14 of the release sheet 10 and the heavy release coating 34 of the second release sheet 30 are in contact with the adhesive layer 20.

[0065] Another embodiment of the double-sided tape includes a substrate having a first surface and a second surface opposite the first surface, a release sheet including a first release coating disposed on the first surface of the substrate and a second release coating disposed on the second surface of the substrate, and an adhesive layer having a first surface and a second surface opposite the first surface, the double-sided tape being a wound roll, the first surface of the adhesive layer contacting the first release coating of the release sheet, and the second surface of the adhesive layer contacting the second release coating of the release sheet. The first release coating contains a cured product of an acrylic polymer release agent. The second release coating is a heavy release coating containing a cured product of a second acrylic polymer release agent. In this embodiment, the release sheet can be arranged so that the outer peripheral side of the double-sided tape is the first release coating (light release coating) and the inner peripheral side is the second release coating (heavy release coating).

[0066] The second acrylic polymer release agent comprises the polymerization product of a second polymerizable precursor composition that contains 50% by weight or more, based on the polymerizable component, of acrylate monomers having an alkyl group with less than 24 carbon atoms. Examples of acrylate monomers having an alkyl group with less than 24 carbon atoms include butyl acrylate (4 carbon atoms), hexyl acrylate (6 carbon atoms), octyl acrylate (8 carbon atoms), 2-ethylhexyl acrylate (8 carbon atoms), decyl acrylate (10 carbon atoms), 8-methylnonyl acrylate (10 carbon atoms), dodecyl acrylate (12 carbon atoms), tridecyl acrylate (13 carbon atoms), tetradecyl acrylate (14 carbon atoms), hexadecyl acrylate (16 carbon atoms), octadecyl acrylate (18 carbon atoms), isooctadecyl acrylate (18 carbon atoms), 2-hexyldodecyl acrylate (18 carbon atoms), 2-octyldecyl acrylate (18 carbon atoms), icosyl acrylate (20 carbon atoms), and docosyl acrylate (C22). The content of the acrylate monomer having an alkyl group with less than 24 carbon atoms in the second polymerizable precursor composition is preferably about 60% by weight or more, about 70% by weight or more, or about 80% by weight or more, based on the polymerizable components.

[0067] The remainder of the polymerizable components of the second polymerizable precursor composition may be an acrylate monomer having a linear or branched alkyl group having 24 or more carbon atoms, an acrylic monomer having a benzophenone structure, other radical polymerizable monomers, or a combination thereof. The acrylate monomer having a branched alkyl group having 24 or more carbon atoms and the acrylic monomer having a benzophenone structure are as described in the first embodiment. Examples of the acrylic monomer having a linear alkyl group having 24 or more carbon atoms include tetracosyl acrylate (C24), octacosyl acrylate (C28), and dotriacyl acrylate (C32). Examples of other radical polymerizable monomers include styrene, cyclohexyl acrylate, isobornyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, dicyclopentanyl acrylate, and dicyclopentenyl acrylate.

[0068] For the second polymerizable precursor composition, the polymerization initiator, the chain transfer agent, the chain extender, and the method for obtaining a polymerizable component by polymerizing the polymerizable precursor composition, as well as the weight average molecular weight of the obtained polymerizable component, are as described in the first embodiment.

[0069] The method of producing a second release sheet using the second acrylic polymer release agent is the same as that of the above-mentioned acrylic polymer release agent. The double-sided tape can be produced by laminating a second release sheet on the adhesive layer of the tape. The double-sided tape can also be produced by forming an adhesive layer on the second release sheet and laminating a release sheet thereon.

[0070] In one embodiment, the peel force between the second release sheet (heavy release sheet) and the adhesive layer is about 2.5 times or more, about 4 times or more, about 10 times or less, or about 5 times or less than the peel force between the release sheet (light release sheet) and the adhesive layer.

[0071] In one embodiment, the peel force between the second release sheet (heavy release sheet) and the adhesive layer is about 1 N / 10 mm or less, or about 0.5 N / 10 mm or less.

[0072] The acrylic polymer release agent, release sheet, tape, and double-sided tape of the present disclosure can be used in applications where very light release force is required.The release sheet using the acrylic polymer release agent of the present disclosure can be particularly suitably used for the light release surface of NSNF adhesive transfer tape (ATT). EXAMPLES

[0073] The following examples illustrate specific embodiments of the present disclosure, but the invention is not limited to these embodiments. All parts and percentages are by weight unless otherwise specified.

[0074] The materials used to prepare or manufacture the acrylic polymer release agents, release sheets, and tapes are shown in Table 1. [Table 1]

[0075] Synthesis Example 1 (iso-C20 acrylate) Using the reaction conditions and purification method disclosed in US Patent No. 8,137,807, page 13, Method 2, iso-C20 acrylate (2-octyldodecyl acrylate) was synthesized from the esterification reaction of 2-octyl-1-dodecanol (iso-C20 alcohol) with acryloyl chloride. The IR spectrum confirmed that iso-C20 acrylate was produced.

[0076] Synthesis Example 2 (iso-C28 acrylate) Using the reaction conditions and purification method disclosed in U.S. Pat. No. 8,137,807, page 13, Method 2, iso-C28 acrylate (2-dodecylhexadecyl acrylate) was synthesized from the esterification reaction of 2-dodecyl-1-hexadecanol (iso-C28 alcohol) with acryloyl chloride.

[0077] Synthesis Example 3 (iso-C32 acrylate) Using the reaction conditions and purification method disclosed in U.S. Pat. No. 8,137,807, page 13, Method 2, iso-C32 acrylate (2-tetradecyl octadecyl acrylate) was synthesized from the esterification reaction of 2-tetradecyl-1-octadecanol (iso-C32 alcohol) with acryloyl chloride.

[0078] The polymerization product contained in the acrylic polymer release agent (also referred to in this example as the "precursor polymer") was prepared by the following procedure, which involved solution polymerization of a polymerizable precursor composition.

[0079] Precursor polymer 1 100 parts by mass of iso-C16 acrylate and 0.2 parts by mass of AEBP were mixed to obtain a monomer mixture. The monomer mixture was diluted with a mixed solvent of ethyl acetate / n-heptane (50% by mass / 50% by mass) until the monomer concentration was 75% by mass. Furthermore, 0.1 parts by mass of V-601 was added as an initiator to 100 parts by mass of the monomer component to obtain a polymerizable precursor composition 1. The system containing the polymerizable precursor composition 1 was purged with nitrogen gas for 2 minutes, and then solution polymerization was carried out in a thermostatic bath at 65°C for 48 hours to obtain a transparent viscous solution. The weight average molecular weight (Mw) of the obtained polymerization product was about 1.80×10 6 In this example, the weight average molecular weight of the polymerization product was measured in chloroform solvent by gel permeation chromatography (GPC) and converted to polystyrene standard.

[0080] Precursor polymer 4 Precursor polymer 4 was prepared in the same manner as precursor polymer 1, except that iso-C16 acrylate was changed to iso-C24 acrylate, 0.2 parts by mass of V-601 was added per 100 parts by mass of the monomer components, and 0.1 parts by mass of NDDA was added per 100 parts by mass of the monomer components. The weight average molecular weight (Mw) of the obtained polymerization product was approximately 1.88 × 10 6 It was.

[0081] Precursor polymer 9 Precursor polymer 9 was prepared in the same manner as precursor polymer 1, except that iso-C16 acrylate was changed to iso-C24 acrylate, AEBP was changed to ABP, 0.2 parts by mass of V-601 was added per 100 parts by mass of the monomer components, and 0.1 parts by mass of NDDA was added per 100 parts by mass of the monomer components. The weight average molecular weight (Mw) of the obtained polymerization product was approximately 1.9 × 10 6 It was.

[0082] Precursor Polymer 10 Precursor polymer 10 was prepared in the same manner as precursor polymer 1, except that iso-C16 acrylate was changed to iso-C24 acrylate, AEBP was not used, 0.2 parts by mass of V-601 was added per 100 parts by mass of the monomer components, and 0.1 parts by mass of NDDA was added per 100 parts by mass of the monomer components. The weight average molecular weight (Mw) of the obtained polymerization product was approximately 1.74 × 10 6 It was.

[0083] Precursor Polymer 15 Precursor polymer 15 was prepared in the same manner as precursor polymer 1, except that the iso-C16 acrylate was changed to a 1:1 (mass ratio) mixture of linear C18 acrylate and linear C22 acrylate, 0.2 parts by mass of V-601 was added per 100 parts by mass of the monomer component, and the monomer concentration was 50% by mass. The weight average molecular weight (Mw) of the obtained polymerization product was approximately 1.27 × 10 6 It was.

[0084] Precursor Polymer 16 Precursor polymer 16 was prepared in the same manner as precursor polymer 1, except that iso-C16 acrylate was changed to iso-C12 acrylate, V-601 was changed to V-65, the solvent was changed to ethyl acetate, and the monomer concentration was set to 50% by mass. The weight average molecular weight (Mw) of the obtained polymerization product was approximately 1.89 × 10 6 It was.

[0085] Precursor polymers 2, 3, 5-8, and 11-14 Precursor polymers 2, 3, 5 to 8, and 11 to 14 were prepared in the same manner as precursor polymers 1, 4, and 9, except that the type of acrylate, other components and their amounts added, and monomer concentration were as shown in Table 2. The weight average molecular weights (Mw) of the obtained polymerization products are shown in Table 2.

[0086] Details of the precursor polymers are shown in Table 2. [Table 2]

[0087] Example 1 A release sheet was prepared by the following procedure. An acrylic polymer release agent was prepared by diluting precursor polymer 4 to 1% by weight using a mixed solvent (50% by weight / 50% by weight) of toluene / methyl ethyl ketone (MEK). The obtained acrylic polymer release agent was applied onto polyester film S-50 using a bar coater (#04). The solvent was evaporated to form a release precursor layer with a thickness of about 0.1 μm. A release sheet was produced by irradiating a polyester film having a release precursor layer with ultraviolet light in one pass at a line speed of 20 m / min in a nitrogen gas atmosphere using an ultraviolet irradiation device (F300, medium pressure mercury lamp (H bulb), Heraeus (Hanau, Hessen, Germany)) to harden the release precursor layer. During irradiation, the ultraviolet irradiation conditions per pass as measured by a UV POWER PUCK (trade name) available from EIT were 350 mJ / cm. 2 , UVA 168mJ / cm 2 , UVB 158mJ / cm 2 , and UVC 24mJ / cm 2 It was.

[0088] Examples 2 to 10, Comparative Examples 1 to 7, and Reference Example 1 A release sheet was produced in the same manner as in Example 1, except that the precursor polymer shown in Table 3 was used instead of precursor polymer 4. An acrylic polymer release agent was prepared by diluting Examples 3, 4, and 8 (precursor polymers 6, 7, and 12) to 1% by mass using a toluene / methyl ethyl ketone (MEK) / n-heptane mixed solvent (34% by mass / 33% by mass / 33% by mass) instead of a toluene / MEK mixed solvent (50% by mass / 50% by mass). In Example 9, a release sheet was produced in the same manner as in Example 8, except that the acrylic polymer release agent was applied to a white polyester film #75-E20 instead of a polyester film S-50. In Example 10, a release sheet was produced in the same manner as in Example 8, except that a 1.5% by mass diluted solution was used instead of a 1% by mass diluted solution, and that the white polyester film K1212-100 was applied instead of a polyester film S-50. In Example 4 (precursor polymer 7), irradiation was performed 8 passes under the same ultraviolet irradiation conditions per pass as in Example 1. In Examples 6 and 7 (precursor polymers 10 and 11), 10 passes of irradiation were carried out under the same ultraviolet irradiation conditions per pass as in Example 1. Reference Example 1 is a heavy release surface sheet.

[0089] Comparative Example 8 A silicone-coated polyester film, SP-PET (trade name) 38O1-BU, was used as a release sheet.

[0090] Details of the release sheet are shown in Table 3. [Table 3]

[0091] Simple peel test For preliminary evaluation of the peeling properties, 3M (trade name) #810 tape (width 18 mm, length 150 mm, 3M Japan Co., Ltd. (Shinagawa-ku, Tokyo, Japan)) was attached to the release sheet using a roller and left at 70°C for 3 days, and then left at room temperature overnight. The exposed surface (the back side of the surface having the release agent) of the release sheet S-50 (or #75-E20, K1212-100) was attached to a SUS plate using double-sided tape. The peeling force was measured when the #810 tape was peeled in the 180° direction at a peeling speed of 300 mm / min using a precision universal testing machine Autograph AG-X (Shimadzu Corporation, Kyoto City, Kyoto, Japan). The results are shown in Table 4. [Table 4]

[0092] The release sheet of Example 4 (Precursor Polymer 7) gave the same release force as Example 3 (Precursor Polymer 6) having the same acrylate.

[0093] Peel strength and residual adhesion The release strength and residual adhesion strength of tapes produced using a release sheet were evaluated for tapes produced by two methods: (1) a method in which an adhesive solution was applied directly onto a release sheet to produce a tape (direct application), and (2) a method in which a release sheet was bonded to an adhesive layer formed on a substrate to produce a tape (dry lamination).

[0094] (1) Direct application An adhesive solution was prepared by diluting 100 parts by weight of BPS 5127 with 20 parts by weight of toluene and mixing it with 0.67 parts by weight of Coronate L-45E. The adhesive solution was applied onto a release sheet and dried at 105°C for 3 minutes. The dried adhesive layer had a thickness of about 25 μm. A tape was produced by laminating a tape substrate (polyester film S-50) precoated with 3M Primer N-200 (3M Japan Co., Ltd., Shinagawa-ku, Tokyo, Japan) onto the adhesive layer and leaving it at 70°C for 3 days.

[0095] (2) Dry lamination An adhesive solution was prepared by diluting 100 parts by weight of BPS 5127 with 20 parts by weight of toluene and mixing it with 0.67 parts by weight of Coronate L-45E. The adhesive solution was applied onto a tape substrate (polyester film S-50) precoated with 3M Primer N-200 (3M Japan Co., Ltd., Shinagawa-ku, Tokyo, Japan) and dried at 105°C for 3 minutes. The dried adhesive layer had a thickness of about 25 μm. A release sheet was laminated onto the adhesive layer and left at 70°C for 3 days to produce a tape.

[0096] (3) Peel strength The exposed surface of the tape substrate (the side behind the adhesive surface) was attached to a SUS plate using double-sided tape. The peel force was measured when the release sheet was peeled off in a 180° direction at a peel speed of 300 mm / min using a precision universal testing machine Autograph AG-X (Shimadzu Corporation, Kyoto City, Kyoto Prefecture, Japan). The results are shown in Table 5.

[0097] (4) Residual adhesive strength After the peel strength test, the tape remaining on the SUS plate was peeled off from the double-sided tape, and the exposed adhesive layer was attached to a SUS304 (BA) plate. After leaving the plate at room temperature for 30 minutes, the adhesive strength was measured as the residual adhesive strength when the tape was peeled off in the 180° direction at a peel speed of 300 mm / min using a precision universal testing machine Autograph AG-X (Shimadzu Corporation, Kyoto City, Kyoto Prefecture, Japan). The results are shown in Table 5. [Table 5]

[0098] As shown in Table 5, the peel force ratios of the heavy release surface to the light release surface calculated from the peel forces of Examples 1 to 3 and 5 to 8 (light release surfaces) and Reference Example 1 (heavy release surface) were 2.9 to 3.8 (direct application) and 2.7 to 3.7 (dry laminate).

[0099] Peel strength and residual adhesion test-2 Preparation of acrylic PSA solution 90 parts by mass of IOA and 10 parts by mass of AA were mixed and diluted with a mixed solvent of ethyl acetate / methyl ethyl ketone (75% by mass / 25% by mass) until the monomer concentration was 40% by mass. Furthermore, 0.15 parts by mass of V-601 was added as an initiator to 100 parts by mass of the monomer component to obtain a polymerizable precursor composition. The system containing the polymerizable precursor composition was purged with nitrogen gas for 2 minutes, and then solution polymerization was carried out in a thermostatic bath at 65°C for 24 hours to obtain a transparent viscous solution. The weight average molecular weight (Mw) of the obtained polymerization product was about 9.1×10 5 In this example, the weight average molecular weight of the polymerization product was measured by gel permeation chromatography (GPC) in tetrahydrofuran solvent and converted to a polystyrene standard.

[0100] (1) Direct application 100 parts of the prepared polymer solution was first mixed with 0.48 parts of 1,1-isophthaloylbis(2-methylaziridine) solution (3% by weight in toluene). The mixed solution was then coated onto the prepared release sheet and dried at 120°C for 3.5 minutes. The dried adhesive layer had a thickness of about 50 μm. A tape was produced by laminating a tape substrate (polyester film S-50) precoated with 3M (trade name) Primer N-200 (3M Japan Co., Ltd., Shinagawa-ku, Tokyo, Japan) onto the adhesive layer and left at 70°C for 3 days.

[0101] (2) Dry lamination 100 parts of the prepared polymer solution was first mixed with 0.48 parts of 1,1-isophthaloylbis(2-methylaziridine) solution (3% by weight in toluene). The mixed solution was then applied onto a tape substrate (polyester film S-50) pre-coated with 3M Primer N-200 (3M Japan Co., Ltd., Shinagawa-ku, Tokyo, Japan) and dried for 3.5 minutes at 120°C. The dried adhesive layer had a thickness of about 50 μm. A release sheet was laminated onto the adhesive layer and left at 70°C for 3 days to produce a tape.

[0102] (3) Peel strength and residual adhesion The peel strength and residual adhesion were measured as described above, and the results are shown in Table 6. [Table 6]

[0103] Reference List 100 Double-sided tape 10 Release sheet 12 Base material 14 Release Coating 20 Adhesive layer 30-ply release sheet 32 Second substrate 34 Heavy Release Coating

Claims

1. An acrylic polymer release agent comprising the polymerization product of a polymerizable precursor composition containing an acrylate monomer having a branched alkyl group having 24 or more carbon atoms and an acrylic monomer having a benzophenone structure.

2. 2. The acrylic polymer release agent according to claim 1, wherein the polymerizable precursor composition contains 99% by weight or more of an acrylate monomer having a branched alkyl group having 24 or more carbon atoms, based on the polymerizable component.

3. 3. The acrylic polymer release agent according to claim 1, wherein the polymerizable precursor composition contains the acrylic monomer having a benzophenone structure in an amount of 1% by mass or less based on the polymerizable component.

4. A polymerization product of a polymerizable precursor composition containing 99% by weight or more of an acrylate monomer having a branched alkyl group having 24 or more carbon atoms based on the polymerizable component.

1. An acrylic polymer release agent comprising:

5. A substrate; and a release coating comprising the cured product of the acrylic polymer release agent of any one of claims 1 to 4 disposed on the substrate.

6. The release sheet of claim 5 , wherein the substrate comprises a white film.

7. A release sheet according to claim 5, and an adhesive layer laminated on the release coating of the release sheet; Including tape.

8. 8. The tape of claim 7, wherein the peel force of the release sheet from the adhesive layer is less than 0.1 N / cm.

9. A coating composition comprising, in this order, the release sheet according to claim 5, the adhesive layer, and a second release sheet; the second release sheet comprises a second substrate and a heavy release coating disposed on the second substrate, the heavy release coating comprising a cured product of a second acrylic polymer release agent; the second acrylic polymer release agent comprises a polymerization product of a second polymerizable precursor composition containing 50% by weight or more of an acrylate monomer having an alkyl group having less than 24 carbon atoms, based on the polymerizable component; the release coating of the release sheet and the heavy release coating of the second release sheet are laminated to contact the adhesive layer; 8. The tape of claim 7.

10. 10. The tape of claim 9, wherein the peel force between the second release sheet and the adhesive layer is at least 2.5 times the peel force between the release sheet and the adhesive layer.

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