TWI838427B - Adhesive sheet - Google Patents

Abstract

The present invention provides an adhesive sheet including an adhesive layer. The adhesive layer contains: polymer A, which is a polymer of monomer raw material A; and polymer B, which is a polymer of monomer raw material B including a monomer having a polyorganosiloxane skeleton and a (meth)acrylic monomer. The Mw of the polymer B is 7×10 ⁴ or more. The relationship between the adhesive force N ₅₀ of the adhesive sheet measured at 23°C after being bonded to a stainless steel plate and kept at 50°C for 30 minutes and the adhesive force N ₈₀ measured at 23°C after being bonded to a stainless steel plate and heated at 80°C for 5 minutes satisfies the following formula: (N ₈₀ /N ₅₀ )≧3.

Description

Adhesive sheet

The present invention relates to an adhesive sheet. This application claims priority based on Japanese Patent Application No. 2018-225412 filed on November 30, 2018, and the entire contents of the application are incorporated into this specification as a reference.

Adhesive sheets are used for purposes such as bonding adherends to each other, fixing an object to an adherend, and reinforcing an adherend by firmly adhering to the adherend. Previously, for such purposes, adhesive sheets that exhibited relatively high adhesive force from the initial stage of attachment were used. Moreover, recently, as shown in patent documents 1 to 3, an adhesive sheet has been proposed that exhibits relatively low adhesive force at the initial stage of attachment to an adherend and then significantly increases the adhesive force. According to an adhesive sheet having such characteristics, before the adhesive force increases, the re-adhesiveness (secondary processing property) useful for suppressing the reduction in yield caused by mis-attachment or failure of the female adhesive sheet can be exhibited, and after the adhesive force increases, the strong adhesiveness suitable for the original purpose of the adhesive sheet can be exhibited. Prior art documents Patent documents

Patent document 1: Japanese patent application publication No. 2014-224227 Patent document 2: Japanese patent publication No. 5890596 Patent document 3: Japanese patent publication No. 5951153

[The problem the invention is trying to solve]

However, depending on the usage of the adhesive sheet, after attachment, after proceeding to the subsequent steps, secondary processing may be required due to judgment of incorrect or damaged attachment, or positional displacement caused by the influence of subsequent steps, etc. In this case, during the period when the adhesive sheet attached to the adherend is required to be secondary processed, for example, due to the influence of heat generated by the operation of the equipment used in the manufacturing process (transport equipment, inspection equipment, other various processing equipment, etc.), or the exhaust heat from the adjacent equipment, the temperature rise of the manufacturing environment, and other accidental factors, the above-mentioned adhesive sheet may be subjected to a temperature of about 40℃ to 50℃. Therefore, the purpose of the present invention is to provide an adhesive sheet that can maintain secondary processability even when a temperature of about 50°C is applied at the initial stage of attachment to an adherend, and can significantly increase the adhesive force thereafter. [Technical means for solving the problem]

According to the present specification, an adhesive sheet including an adhesive layer is provided. The adhesive layer contains a polymer A as a polymer of a monomer raw material A, and a polymer B as a polymer of a monomer raw material B. The monomer raw material B contains a monomer having a polyorganosiloxane skeleton and a (meth)acrylic monomer. That is, the polymer B is a copolymer of the monomer having a polyorganosiloxane skeleton and the (meth)acrylic monomer. The weight average molecular weight (Mw) of the polymer B is 7×10 ⁴ or more. The relationship between the adhesive force _N50 measured at 23°C after the adhesive sheet is attached to a stainless steel plate and kept at 50°C for 30 minutes and the adhesive force N80 measured at 23°C after the adhesive sheet is attached to a stainless steel plate and heated at ₈₀ °C for 5 minutes satisfies the following formula: ( _N80 / _N50 )≧3.

The adhesive sheet of this structure can increase the adhesive force _N80 (hereinafter also referred to as "adhesive force after heating") to more than 3 times the adhesive force _N50 by containing a polymer B having an Mw of 7× ¹⁰⁴ or more. As a result, good secondary processability can be exhibited even in a usage state where a temperature of about 50°C may be applied at the initial stage of attachment, and the adhesive force can be greatly increased by subsequent heating.

Regarding the adhesive sheets of some aspects, the relationship between the above-mentioned adhesive force _N50 and the adhesive force _N23 measured at 23°C after being attached to a stainless steel plate and placed at 23°C for 30 minutes satisfies the following formula: ( _N50 / _N23 ) < 10. This kind of adhesive sheet is better in terms of workability or ease of step management because the difference in adhesive force (and thus secondary processability) between the case where the adhesive sheet is maintained at room temperature at the initial stage of attachment and the case where the adhesive sheet is exposed to a temperature of about 50°C is small.

The adhesive sheet disclosed herein preferably has a relationship between the above-mentioned adhesive force _N80 and the adhesive force _NH measured at 80°C after being attached to a stainless steel plate and kept in an environment of 80°C for 30 minutes, which satisfies the following formula: ( _NH / _N80 )≧15%. Such an adhesive sheet has superior heat resistance compared to adhesive sheets with a smaller ( _NH / _N80 ).

The (meth) acrylic monomer contained in the monomer raw material B is preferably a monomer M2 having a homopolymer glass transition temperature (Tg) of 50°C or higher. The polymer B formed from the monomer raw material B including a monomer having a polyorganosiloxane skeleton and the (meth) acrylic monomer M2 having a Tg of 50°C or higher can easily obtain an adhesive sheet satisfying one or two or more of the above relationship equations. As the monomer M2, an alkyl (meth) acrylate having a homopolymer Tg of 50°C or higher can be preferably used.

In some embodiments, the content of the polymer B in the adhesive layer is, for example, in the range of 0.5 to 50 parts by weight relative to 100 parts by weight of the polymer A. With the content in the above range, it is easy to obtain an adhesive sheet with lower initial adhesion and higher adhesion after heating.

The polymer A is preferably an acrylic polymer. The adhesive layer containing the polymer A as an acrylic polymer and the polymer B as a copolymer of a monomer having a polyorganosiloxane skeleton and a (meth)acrylic monomer can easily obtain an adhesive sheet having low initial adhesion and high adhesion after heating.

In some embodiments, the monomer raw material A is preferably a monomer containing a ring containing a nitrogen atom. By combining a polymer A (e.g., an acrylic polymer) obtained from the monomer raw material A containing a monomer containing a ring containing a nitrogen atom with a polymer B having a Mw of 7×10 ⁴ or more, an adhesive sheet having a lower initial adhesion and a higher adhesion after heating can be easily obtained.

In some embodiments, the adhesive layer may contain a crosslinking agent in an amount of more than 0 parts by weight and less than 10 parts by weight relative to 100 parts by weight of the polymer A. By using a crosslinking agent, the adhesive force at the initial stage of attachment can be effectively adjusted in a temperature range of about 50°C. Thereby, it is easy to obtain an adhesive sheet that takes into account both good secondary processability at the initial stage of attachment and strong adhesiveness after the adhesive force increases.

The adhesive sheet disclosed herein can be implemented in the form of a support substrate having a first surface and a second surface and having the above-mentioned adhesive layer on at least the above-mentioned first surface area of the support substrate, that is, a substrate-attached adhesive sheet. Such a substrate-attached adhesive sheet can be good in handling and processing. As the above-mentioned support substrate, for example, a resin film with a thickness of 30 μm or more can be preferably used.

Furthermore, appropriate combinations of the above-mentioned elements may also be included in the scope of the invention claimed by this Japanese patent application.

The following describes the preferred implementation of the present invention. With regard to matters other than those specifically mentioned in this specification and required for the implementation of the present invention, the industry can understand them based on the instructions on the implementation of the invention recorded in this specification and the technical common sense at the time of application. The present invention can be implemented based on the contents disclosed in this specification and the technical common sense in the field. Furthermore, in the following figures, there are cases where components and parts that play the same role are marked with the same symbols for description, and there are cases where repeated descriptions are omitted or simplified. In addition, the implementation forms recorded in the figures are modeled for the purpose of clearly explaining the present invention, and may not accurately represent the size or scale of the product actually provided.

Furthermore, in this specification, "acrylic polymer" refers to a polymer containing monomer units derived from (meth)acrylic monomers in the polymer structure, and typically refers to a polymer containing monomer units derived from (meth)acrylic monomers at a ratio of more than 50% by weight. Furthermore, a (meth)acrylic monomer refers to a monomer having at least one (meth)acryl group in one molecule. Here, "(meth)acryl" includes the meanings of acryl and methacryl. Therefore, the concept of the so-called (meth)acrylic monomer here may include both monomers having an acryl group (acrylic monomer) and monomers having a methacryl group (methacrylic monomer). Similarly, in this specification, "(meth)acrylic acid" includes the meanings of acrylic acid and methacrylic acid, and "(meth)acrylate" includes the meanings of acrylate and methacrylate.

<Structure example of adhesive sheet> The adhesive sheet disclosed herein is composed of an adhesive layer. The adhesive sheet disclosed herein may be in the form of an adhesive sheet with a substrate having the adhesive layer laminated on one or both sides of a supporting substrate, or in the form of an adhesive sheet without a supporting substrate. Hereinafter, the supporting substrate may also be referred to as a "substrate".

The structure of an adhesive sheet of an embodiment is schematically shown in FIG1. The adhesive sheet 1 is a single-sided adhesive sheet with a substrate having a sheet-shaped supporting substrate 10 having a first surface 10A and a second surface 10B, and an adhesive layer 21 provided on the first surface 10A side. The adhesive layer 21 is fixed to the first surface 10A side of the supporting substrate 10. The adhesive sheet 1 is used by attaching the adhesive layer 21 to an adherend. As shown in FIG. 1 , the adhesive sheet 1 before use (i.e. before being attached to an adherend) may be a constituent element of an adhesive sheet 100 with a peeling liner in which a surface (adhesive surface) 21A of an adhesive layer 21 abuts against a peeling liner 31 whose side opposite to the adhesive layer 21 becomes a peeling surface (peeling surface). As the peeling liner 31, for example, a peeling liner formed by providing a peeling layer formed by a peeling treatment agent on one side of a sheet-like substrate (liner substrate) so that the single side becomes a peeling surface can be preferably used. Alternatively, the peeling pad 31 may be omitted, and the second surface 10B of the supporting substrate 10 may be used as the peeling surface. The adhesive sheet 1 may be rolled up so that the adhesive surface 21A contacts the second surface 10B of the supporting substrate 10 (rolled form). When the adhesive sheet 1 is attached to an adherend, the peeling pad 31 or the second surface 10B of the supporting substrate 10 is peeled off from the adhesive surface 21A, and the exposed adhesive surface 21A is pressed against the adherend.

The structure of an adhesive sheet of another embodiment is schematically shown in FIG2. The adhesive sheet 2 is a double-sided adhesive sheet with a substrate, which includes a sheet-shaped supporting substrate 10 having a first surface 10A and a second surface 10B, an adhesive layer 21 disposed on the first surface 10A side, and an adhesive layer 22 disposed on the second surface 10B side. The adhesive layer (first adhesive layer) 21 is fixed to the first surface 10A of the supporting substrate 10, and the adhesive layer (second adhesive layer) 22 is fixed to the second surface 10B of the supporting substrate 10. The adhesive sheet 2 is used by attaching the adhesive layers 21 and 22 to different parts of an adherend. The locations where the adhesive layers 21 and 22 are attached may be locations of different components or different locations within a single component. As shown in FIG2 , the adhesive sheet 2 before use may be a component of an adhesive sheet 200 with a peeling liner attached in which the surface (first adhesive surface) 21A of the adhesive layer 21 and the surface (second adhesive surface) 22A of the adhesive layer 22 are in contact with the peeling liner 31 and 32 that are at least opposite to the adhesive layers 21 and 22 and serve as peeling surfaces. As the peeling pads 31 and 32, for example, a peeling layer formed by a peeling agent is provided on one side of a sheet-like substrate (pad substrate) so that the single side becomes a peeling surface. Alternatively, the peeling pad 32 may be omitted, and a peeling pad 31 having both sides as peeling surfaces may be used, and an adhesive sheet with a peeling pad attached may be formed in a form (roll form) in which the second adhesive surface 22A abuts against the back side of the peeling pad 31 by overlapping the peeling pad 32 and rolling the peeling pad 31 into a spiral shape.

The structure of another embodiment of the adhesive sheet is schematically shown in FIG3. The adhesive sheet 3 is constructed as a double-sided adhesive sheet without a substrate including an adhesive layer 21. The adhesive sheet 3 is used by attaching a first adhesive surface 21A including one surface (first surface) of the adhesive layer 21 and a second adhesive surface 21B including the other surface (second surface) of the adhesive layer 21 to different parts of the adherend. As shown in FIG3, the adhesive sheet 3 before use can be a constituent element of an adhesive sheet 300 with a peel-off liner in the form of a first adhesive surface 21A and a second adhesive surface 21B abutting against peel-off liner 31, 32 which respectively serve as peel-off surfaces on at least the sides opposite to the adhesive layer 21. Alternatively, the peeling pad 32 may be omitted and a peeling pad 31 having two peeling surfaces may be used, and the peeling pad 31 may be overlapped with the adhesive sheet 3 and rolled into a spiral shape to form an adhesive sheet with a peeling pad attached in a form in which the second adhesive surface 21B abuts against the back surface of the peeling pad 31 (roll shape).

Furthermore, the concept of adhesive sheet herein may include adhesive tape, adhesive film, adhesive label, etc. The adhesive sheet may be in the form of a roll, a single sheet, or may be cut into appropriate shapes or punched according to the purpose or usage. The adhesive layer in the technology disclosed herein is typically formed continuously, but is not limited thereto, and may be formed into regular or irregular patterns such as dots or strips.

<Adhesive layer> The adhesive sheet disclosed herein has an adhesive layer, which contains a polymer A as a polymer of a monomer raw material A, and a polymer B as a copolymer of a monomer having a polyorganosiloxane skeleton and a (meth)acrylic monomer. Such an adhesive layer can be formed by an adhesive composition containing a polymer A as a complete polymer or a partial polymer of the monomer raw material A, and a polymer B. The form of the adhesive composition is not particularly limited, and can be, for example, a solvent type, a water-dispersible type, a hot melt type, an active energy line curing type (e.g., a light curing type), and the like.

(Polymer A) As polymer A, one or more of various polymers that show rubber elasticity in the room temperature region, such as acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, polysilicone polymers, polyamide polymers, and fluorine polymers, which are well known in the field of adhesives, can be used. In the adhesive sheet disclosed herein, polymer A is typically the main component of the polymer components contained in the adhesive layer, that is, the component that accounts for more than 50% by weight, for example, it can be a component that accounts for more than 75% by weight of the above-mentioned polymer components. In some embodiments, the above-mentioned polymer A is a component that accounts for more than 50% by weight of the entire adhesive layer, and can also be a component that accounts for more than 70% by weight.

The glass transition temperature _TA of polymer A is not particularly limited, and can be selected in a manner that allows for better properties in the adhesive sheet disclosed herein. In some embodiments, polymer A having a _{TA of} less than 0°C can be preferably used. An adhesive containing such a polymer A exhibits moderate fluidity (e.g., the mobility of the polymer chains contained in the adhesive), and is therefore suitable for achieving an adhesive sheet having both low initial adhesion and strong adhesion after heating. The adhesive sheet disclosed herein can be well implemented using polymer _A having a TA of less than -10°C, less than -20°C, less than -30°C, or less than -35°C. In some embodiments, _TA may be less than -40°C, or less than -50°C. The lower limit of _TA is not particularly limited. From the viewpoint of easy material acquisition and improved cohesive force of the adhesive layer, a polymer A having a _TA of -80°C or higher, -70°C or higher, or -65°C or higher is generally preferably used. From the viewpoint of suppressing an increase in _N50 , in some aspects, _TA may be, for example, -63°C or higher, -55°C or higher, -50°C or higher, or -45°C or higher.

Here, in this specification, the glass transition temperature (Tg) of a polymer refers to a nominal value described in a literature or catalog, or a Tg calculated according to the Fox formula based on the composition of the monomer raw materials used to prepare the polymer. The Fox formula refers to a relationship between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below. 1/Tg＝Σ(Wi/Tgi) In the above Fox formula, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio based on weight), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K). When the polymer specified by Tg is a homopolymer, the Tg of the homopolymer is consistent with the Tg of the target polymer.

As the glass transition temperature of the homopolymer used to calculate Tg, the value recorded in the known data is used. Specifically, the value in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be cited. For monomers for which multiple values are recorded in the above polymer handbook, the highest value is adopted.

As the glass transition temperature of the homopolymer of the monomer not listed in the above polymer manual, the value obtained by the following measurement method is used. Specifically, 100 parts by weight of the monomer, 0.2 parts by weight of 2,2'-azobisisobutyronitrile and 200 parts by weight of ethyl acetate as a polymerization solvent are added to a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux cooling tube, and stirred for 1 hour while circulating nitrogen. After removing oxygen in the polymerization system in this way, the temperature is raised to 63°C and allowed to react for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution with a solid content concentration of 33% by weight. Next, the homopolymer solution was cast on a release pad and dried to prepare a test sample (sheet-shaped homopolymer) with a thickness of about 2 mm. The test sample was punched into a disc with a diameter of 7.9 mm and sandwiched between parallel plates. A viscoelasticity tester (manufactured by TA Instruments Japan, model name "ARES") was used to apply a shear strain of 1 Hz. The viscoelasticity was measured in a shear mode at a temperature range of -70°C to 150°C at a heating rate of 5°C/min. The temperature equivalent to the peak temperature of tanδ was set as the Tg of the homopolymer.

The weight average molecular weight (Mw) of polymer A is usually preferably about 20×10 ⁴ or more, but is not particularly limited. With polymer A of this Mw, an adhesive showing good cohesion can be easily obtained. From the viewpoint of obtaining higher cohesion, in several embodiments, the Mw of polymer A can be, for example, 30×10 ⁴ or more, 40×10 ⁴ or more, 50×10 ⁴ or more, 60×10 ⁴ or more, or 80×10 ⁴ or more. In addition, the Mw of polymer A is usually preferably about 500×10 ⁴ or less. Polymer A of this Mw can easily form an adhesive showing moderate fluidity (mobility of polymer chains), and is therefore suitable for achieving an adhesive sheet with lower adhesion in the initial stage of attachment and higher adhesion after heating. It is also preferred that the Mw of polymer A is not too high from the viewpoint of improving the compatibility with polymer B. In some aspects, the Mw of polymer A may be, for example, 250×10 ⁴ or less, 200×10 ⁴ or less, or 150×10 ⁴ or less.

In this specification, the Mw of polymer A and polymer B can be determined by polystyrene conversion by gel permeation chromatography (GPC). More specifically, Mw can be measured according to the method and conditions described in the following examples.

As polymer A in the adhesive sheet disclosed herein, an acrylic polymer can be preferably used. If an acrylic polymer is used as polymer A, it tends to be easy to obtain good compatibility with polymer B. Good compatibility between polymer A and polymer B can help reduce initial adhesion and increase adhesion after heating by improving the mobility of polymer B in the adhesive layer, so it is preferred.

The acrylic polymer may be, for example, a polymer containing 50% by weight or more of monomer units derived from an alkyl (meth)acrylate, i.e., a polymer in which 50% by weight or more of the total amount of monomer components (monomer raw material A) used to prepare the acrylic polymer is an alkyl (meth)acrylate. As the alkyl (meth)acrylate, an alkyl (meth)acrylate having a linear or branched alkyl group with a carbon number of 1 to 20 (i.e., _C1-20 ) can be preferably used. In terms of facilitating the balance of properties, the ratio of the _{C1-20 alkyl (meth)acrylate in the monomer raw material A may be, for example, 50% by weight or more, 60% by weight or more, or 70% by weight or more. For the same reason, the ratio of the C1-20 alkyl} (meth)acrylate in the monomer raw material A may be, for example, 99.9% by weight or less, 98% by weight or less, or 95% by weight or less. In some aspects, the ratio of C _1-20 alkyl (meth)acrylate in the monomer raw material A may be, for example, 90 wt % or less, 85 wt % or less, or 80 wt % or less.

Specific non-limiting examples of _C1-20 alkyl (meth)acrylates 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, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate. , nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc.

Among them, it is preferred to use at least C _1-18 alkyl (meth)acrylate, and more preferably at least C _1-14 alkyl (meth)acrylate. In some aspects, the acrylic polymer may contain at least one selected from C _4-12 alkyl (meth)acrylate (preferably C _4-10 alkyl acrylate, such as C _6-10 alkyl acrylate) as a monomer unit. For example, it is preferred to use an acrylic polymer containing one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA), and it is particularly preferred to use an acrylic polymer containing at least 2EHA. As examples of other C _1-18 alkyl (meth)acrylates that can be used well, there can be listed: methyl acrylate, methyl methacrylate (MMA), n-butyl methacrylate (BMA), 2-ethylhexyl methacrylate (2EHMA), isostearyl acrylate (ISTA), etc.

The monomer raw material A may also contain an alkyl (meth)acrylate as a main component and, if necessary, other monomers (copolymerizable monomers) that can be copolymerized with the alkyl (meth)acrylate. As copolymerizable monomers, monomers having polar groups (e.g., carboxyl groups, hydroxyl groups, rings containing nitrogen atoms, etc.) can be preferably used. Monomers having polar groups can help introduce crosslinking points into acrylic polymers or improve the cohesive force of acrylic polymers. Copolymerizable monomers can be used alone or in combination of two or more.

As non-limiting specific examples of copolymerizable monomers, the following can be cited. Hydroxyl group-containing monomers: for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, hydroxyalkyl (meth)acrylates such as (4-hydroxymethylcyclohexyl)methyl (meth)acrylate, and the like. Monomers having a ring containing a nitrogen atom: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperidone, N-vinylpyrrolidone, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(methyl)acryloyl-2-pyrrolidone, N-(methyl)acryloylpiperidine, N-(methyl)acryloylpyrrolidine, N-vinylpyrimidine, Phosphine, N-vinyl-3- Linocarbyl ketone, N-vinyl-2-caprolactam, N-vinyl-1,3-dimethoxy-2-one, N-vinyl-3,5- 1-(2-(meth)acryloxymethylenediamine, N-(meth)acryl-6-oxyhexamethylenediamine, N-(meth)acryl-8-oxyhexamethylenediamine; For example, citric acid imides such as N-cyclohexyl citric acid imide, N-isopropyl citric acid imide, N-lauryl citric acid imide, and N-phenyl citric acid imide; and iconimides such as N-methyl iconimide, N-ethyl iconimide, N-butyl iconimide, N-octyl iconimide, N-2-ethylhexyl iconimide, N-cyclohexyl iconimide, and N-lauryl iconimide. Carboxyl group-containing monomers: for example, acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, citric acid, fumaric acid, crotonic acid, isobutyric acid, and the like. Anhydride-containing monomers: for example, maleic anhydride and itaconic anhydride. Epoxy-containing monomers: for example, (meth)acrylate glycidyl ester or (meth)acrylate-2-ethyl glycidyl ether and other epoxy-containing acrylates, allyl glycidyl ether, (meth)acrylate glycidyl ether, etc. Cyano-containing monomers: for example, acrylonitrile and methacrylonitrile, etc. Isocyanate-containing monomers: for example, (meth)acrylate 2-isocyanatoethyl ester, etc. Amide group-containing monomers: for example (meth)acrylamide; N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-dipropyl (meth)acrylamide, N,N-diisopropyl (meth)acrylamide, N,N-di(n-butyl) (meth)acrylamide, N,N-di(tert-butyl) (meth)acrylamide and the like N,N-dialkyl (meth)acrylamide; N-ethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-butyl (meth)acrylamide, N-n-butyl (meth)acrylamide and the like N-alkyl (meth)acrylamide; N-vinylcarboxylic acid amides such as N-vinylacetamide; monomers having hydroxyl and amide groups, for example N-(2-hydroxyethyl) ( N-(2-hydroxypropyl)(meth)acrylamide, N-(1-hydroxypropyl)(meth)acrylamide, N-(3-hydroxypropyl)(meth)acrylamide, N-(2-hydroxybutyl)(meth)acrylamide, N-(3-hydroxybutyl)(meth)acrylamide, N-(4-hydroxybutyl)(meth)acrylamide and the like N-hydroxyalkyl(meth)acrylamide; monomers having an alkoxy group and an amide group, for example, N-methoxymethyl(meth)acrylamide, N-methoxyethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide and the like N-alkoxyalkyl(meth)acrylamide; in addition, N,N-dimethylaminopropyl(meth)acrylamide, N-(meth)acrylamide Phosphine, etc. (Meth) acrylate aminoalkyl esters: for example, (meth) acrylate aminoethyl, (meth) acrylate N, N-dimethylaminoethyl, (meth) acrylate N, N-diethylaminoethyl, (meth) acrylate tert-butylaminoethyl. Alkoxy-containing monomers: for example, (meth) acrylate 2-methoxyethyl, (meth) acrylate 3-methoxypropyl, (meth) acrylate 2-ethoxyethyl, (meth) acrylate propoxyethyl, (meth) acrylate butoxyethyl, (meth) acrylate ethoxypropyl and other (meth) acrylate alkoxyalkyl esters; (meth) acrylate alkoxyalkylene glycol esters such as (meth) acrylate methoxyethylene glycol, (meth) acrylate methoxypolypropylene glycol and other (meth) acrylate. Monomers containing sulfonic acid groups or phosphate groups: for example, styrene sulfonic acid, allyl sulfonic acid, sodium vinyl sulfonate, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamide propanesulfonic acid, (meth)acrylate sulfopropyl, (meth)acryloyloxynaphthalenesulfonic acid, 2-hydroxyethylacryloyl phosphate, etc. (Meth)acrylates having alicyclic hydrocarbon groups: for example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobutyl (meth)acrylate, dicyclopentyl (meth)acrylate, etc. (Meth)acrylates having aromatic hydrocarbon groups: for example, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, etc. Vinyl ethers: for example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether. Vinyl esters: for example, vinyl acetate, vinyl propionate, etc. Aromatic vinyl compounds: such as styrene, α-methylstyrene, vinyltoluene, etc. Olefins: such as ethylene, butadiene, isoprene, isobutylene, etc. In addition, heterocyclic (meth)acrylates such as tetrahydrofuranyl (meth)acrylate, halogen-containing (meth)acrylates such as vinyl chloride or fluorine-containing (meth)acrylates, silicon-containing (meth)acrylates such as polysiloxane (meth)acrylates, and (meth)acrylates obtained from terpene compound derivative alcohols.

When such a copolymerizable monomer is used, its usage amount is not particularly limited, and is usually appropriately set to 0.01% by weight or more of the monomer raw material A. From the perspective of better exerting the effect produced by the use of the copolymerizable monomer, the usage amount of the copolymerizable monomer can be set to 0.1% by weight or more of the monomer raw material A, and can also be set to 1% by weight or more. In addition, the usage amount of the copolymerizable monomer can be set to 50% by weight or less of the monomer raw material A, preferably 45% by weight or less. In this way, the cohesive force of the adhesive can be prevented from becoming too high, and the stickiness at room temperature (25°C) can be improved. In some embodiments, the usage amount of the copolymerizable monomer can be 40% by weight or less of the monomer raw material A, and can also be 35% by weight or less.

In some embodiments, the monomer raw material A may include a monomer having a ring containing a nitrogen atom. By using a monomer having a ring containing a nitrogen atom, the cohesion or polarity of the adhesive can be adjusted to increase the adhesion after heating. As disclosed herein, in an embodiment where the Mw of polymer B is as high as a certain level (typically 7×10 ⁴ or more, preferably 8×10 ⁴ or more, for example, more than 10×10 ⁴ ), it is particularly meaningful to include a monomer having a ring containing a nitrogen atom in the monomer raw material A. Thereby, there is a tendency to increase the compatibility between the polymer A formed by the above-mentioned monomer raw material A and the above-mentioned polymer B. Thereby, it is easy to obtain an adhesive sheet that can maintain secondary processability even when a temperature of about 50°C is applied at the initial stage of attachment to the adherend and then greatly increases the adhesion. The polymer B having a high Mw to a certain extent has improved solubility in the adhesive layer, which is also preferred from the viewpoint of improving the heat resistance of the adhesive sheet.

The monomer having a ring containing a nitrogen atom can be appropriately selected from the above examples, and one type can be used alone or in combination of two or more types. In some aspects, the monomer raw material A preferably contains at least one monomer selected from the group consisting of N-vinyl cyclic amides represented by the following general formula (M1) as the monomer having a ring containing a nitrogen atom. The monomer raw material A may contain only one type or two or more types of the N-vinyl cyclic amides as the monomer having a ring containing a nitrogen atom.

[Chemistry 1] Here, ^R1 in the above general formula (M1) is a divalent organic group.

Specific examples of N-vinyl cyclic amides include N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-3- Linocarbyl ketone, N-vinyl-2-caprolactam, N-vinyl-1,3-dimethoxy-2-one, N-vinyl-3,5- Particularly preferred are N-vinyl-2-pyrrolidone and N-vinyl-2-caprolactam.

The amount of the monomer having a ring containing a nitrogen atom is not particularly limited, and is usually preferably set to 0.01% by weight or more (preferably 0.1% by weight or more, for example 0.5% by weight or more) of the monomer raw material A. In some embodiments, the amount of the monomer having a ring containing a nitrogen atom can be set to 1% by weight or more of the monomer raw material A, can be set to 5% by weight or more, can be set to 10% by weight or more, and can also be set to 12% by weight or more. In addition, from the perspective of improving the stickiness at room temperature (25°C) or improving the softness at low temperatures, the amount of the monomer having a ring containing a nitrogen atom is usually preferably set to 40% by weight or less of the monomer raw material A, can be set to 30% by weight or less, can be set to 20% by weight or less, and can also be set to 18% by weight or less.

By using hydroxyl-containing monomers, the cohesive force or polarity of the adhesive can be adjusted to improve the adhesion after heating. In addition, the hydroxyl-containing monomers provide reaction sites with the following crosslinking agents (such as isocyanate crosslinking agents), which can improve the cohesive force of the adhesive through crosslinking reactions.

As the hydroxyl group-containing monomer, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, N-(2-hydroxyethyl) (meth)acrylamide, etc. can be preferably used. Among them, 2-hydroxyethyl acrylate (HEA), 4-hydroxybutyl acrylate (4HBA), and N-(2-hydroxyethyl)acrylamide (HEAA) can be cited as preferred examples.

The amount of the hydroxyl-containing monomer used is not particularly limited, and is usually preferably set to 0.01% by weight or more (preferably 0.1% by weight or more, for example 0.5% by weight or more) of the monomer raw material A. In some embodiments, the amount of the hydroxyl-containing monomer used can be set to 1% by weight or more of the monomer raw material A, can be set to 5% by weight or more, and can also be set to 10% by weight or more. In addition, from the perspective of improving the stickiness at room temperature (25°C) or the softness at low temperatures, the amount of the hydroxyl-containing monomer used is usually preferably set to 40% by weight or less of the monomer raw material A, can be set to 30% by weight or less, can be set to 20% by weight or less, and can also be set to 10% by weight or less or 5% by weight.

In some aspects, a monomer having a ring containing a nitrogen atom (e.g., N-vinyl cycloamide) and a hydroxyl-containing monomer may be used together as a copolymerizable monomer. In this case, the total amount of the monomer having a ring containing a nitrogen atom and the hydroxyl-containing monomer may be, for example, 0.1% by weight or more of the monomer raw material A, 1% by weight or more, 5% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, or 25% by weight or more. In addition, the total amount of the monomer having a ring containing a nitrogen atom and the hydroxyl-containing monomer may be, for example, 50% by weight or less of the monomer raw material A, preferably 40% by weight or less.

In the aspect that the monomer raw material A contains a combination of a monomer having a nitrogen atom-containing ring and a hydroxyl group-containing monomer, the relationship (weight basis) between the content of the monomer having a nitrogen atom-containing ring (W _N ) and the content of the hydroxyl group-containing monomer (W _OH ) in the monomer raw material A is not particularly limited. W _N /W _OH may be, for example, 0.01 or more, usually preferably 0.05 or more, 0.1 or more, 0.2 or more, 0.5 or more, or 0.7 or more. In addition, W _N /W _OH may be, for example, 100 or less, usually preferably 20 or less, 10 or less, 5 or less, 2 or less, or 1.5 or less.

In some embodiments, the monomer raw material A preferably does not contain a monomer having a polysiloxane skeleton (monomer S1) which can be well used as a constituent component of the monomer raw material B described below, or the content of the monomer is less than 10% by weight of the monomer raw material A (more preferably less than 5% by weight, for example less than 2% by weight). With such a composition of the monomer raw material A, an adhesive sheet that takes into account both initial secondary processability and strong adhesion after the adhesion force increases can be well realized. For the same reason, in other embodiments, the monomer raw material A preferably does not contain the monomer S1, or when it contains the monomer S1, its content (weight basis) is lower than the content of the monomer S1 in the monomer raw material B.

The method for obtaining polymer A is not particularly limited, and various polymerization methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization can be appropriately adopted. In some aspects, solution polymerization can be preferably 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.

The initiator used for the polymerization can be appropriately selected from conventionally known thermal polymerization initiators or photopolymerization initiators, etc., depending on the polymerization method. The polymerization initiator can be used alone or in combination of two or more.

Examples of the thermal polymerization initiator include: azo-based polymerization initiators (e.g., 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid) dimethyl ester, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methylpropionic acid)] -2-imidazoline-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine) dihydrochloride, etc.); persulfates such as potassium persulfate; peroxide-based polymerization initiators (such as dibenzoyl peroxide, tert-butyl peroxymaleic acid, lauryl peroxide, etc.); redox-based polymerization initiators, etc. The amount of the thermal polymerization initiator used is not particularly limited. For example, the amount can be set to 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, relative to 100 parts by weight of the monomer component (monomer raw material A) used in the preparation of the acrylic polymer.

The photopolymerization initiator is not particularly limited, and for example, benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, 9-oxysulfide-based photopolymerization initiators, and the like can be used. The amount of the photopolymerization initiator used is not particularly limited, for example, relative to 100 parts by weight of the monomer raw material A, it can be set to 0.01 parts by weight to 5 parts by weight, preferably 0.05 parts by weight to 3 parts by weight.

In some embodiments, the polymer A can be contained in the adhesive composition for forming the adhesive layer in the form of a partial polymer (polymer slurry) obtained by irradiating a mixture obtained by mixing a polymerization initiator in the monomer raw material A as described above with ultraviolet rays (UV) to polymerize a part of the monomer component. The adhesive composition containing the polymer slurry can be applied to a prescribed coated object and irradiated with ultraviolet rays to complete the polymerization. That is, the above-mentioned polymer slurry can be solved as a precursor of polymer A. The adhesive layer disclosed here can be formed, for example, using an adhesive composition containing the above-mentioned polymer slurry and polymer B.

(Polymer B) The polymer B in the technology disclosed herein is a copolymer of a monomer having a polyorganosiloxane skeleton (hereinafter also referred to as "monomer S1") and a (meth)acrylic monomer. Polymer B can function as an adhesion delay agent that suppresses the initial adhesion to the adherend by the low polarity and mobility of the polyorganosiloxane structure derived from monomer S1, and increases the adhesion to the adherend by heating to a temperature higher than 50°C or over time. There is no particular limitation as monomer S1, and any monomer containing a polyorganosiloxane skeleton can be used. The monomer S1 promotes the polymer B to lean toward the surface of the adhesive layer in the adhesive sheet before use (before being attached to the adherend) due to the low polarity of its structure, and exhibits light peeling property (low adhesion) in the initial stage of bonding. As monomer S1, a structure having a polymerizable reactive group at one end can be well used. By copolymerizing such monomer S1 with a (meth) acrylic monomer, a polymer B having a polyorganosiloxane skeleton in the side chain is formed. The polymer B of this structure is easy to become a polymer with low initial adhesion and high adhesion after heating due to the mobility and ease of movement of the side chain. In addition, in some embodiments, as monomer S1, a structure having a polymerizable reactive group at one end and not having a functional group at the other end that produces a cross-linking reaction with polymer A can be well used. The polymer B obtained by copolymerizing the monomer S1 having such a structure tends to have a lower initial adhesion and a higher adhesion after heating due to the mobility of the polyorganosiloxane structure derived from the monomer S1.

As the monomer S1, for example, a compound represented by the following general formula (1) or (2) can be used. More specifically, as single-terminal reactive polysiloxane oils manufactured by Shin-Etsu Chemical Co., Ltd., there can be exemplified X-22-174ASX, X-22-2426, X-22-2475, KF-2012, etc. The monomer S1 can be used alone or in combination of two or more. [Chemistry 2] [Chemistry 3] Here, in the above general formulae (1) and (2), R ³ is hydrogen or methyl, R ⁴ is methyl or a monovalent organic group, and m and n are integers greater than 0.

The functional group equivalent of the monomer S1 can be an appropriate value within the range in which the monomer S1 is used to exert the desired effect, and is not limited to a specific range. From the perspective of easily suppressing the initial adhesion, the functional group equivalent can be, for example, 140 g/mol or more, or 200 g/mol or more, usually preferably 300 g/mol or more (e.g., 500 g/mol or more), preferably 700 g/mol or more, 800 g/mol or more, 850 g/mol or more, 1000 g/mol or more, or 1500 g/mol or more. The technology disclosed herein can also be implemented in the state where the functional group equivalent is 2500 g/mol or more, 3000 g/mol or more, 4500 g/mol or more, 6000 g/mol or more, 9000 g/mol or more, 12000 g/mol or more, 15000 g/mol or more, or 16000 g/mol or more. In addition, the functional group equivalent of monomer S1 can be, for example, 50000 g/mol or less. From the perspective of improving the adhesion after heating, it is usually advantageous to be 30000 g/mol or less, preferably 20000 g/mol or less. From this perspective, the functional group equivalent can be, for example, less than 18000 g/mol, less than 15000 g/mol, less than 10000 g/mol, less than 6000 g/mol, or less than 5000 g/mol. In some aspects, the functional group equivalent weight of monomer S1 is preferably 700 g/mol or more and less than 15000 g/mol, more preferably 800 g/mol or more and less than 10000 g/mol, further preferably 850 g/mol or more and less than 6000 g/mol, and particularly preferably 1500 g/mol or more and less than 5000 g/mol. If the functional group equivalent weight of monomer S1 is within the above range, it is easy to adjust the compatibility (e.g., compatibility with polymer A) or mobility in the adhesive layer within an appropriate range, and it is easy to achieve an adhesive sheet that takes into account both low initial adhesion and strong adhesion after the adhesion force increases at a high level.

Here, "functional group equivalent" refers to the weight of the main skeleton (e.g., polydimethylsiloxane) bonded to each functional group. The unit of g/mol is converted to 1 mol of functional group. The functional group equivalent of monomer S1 can be calculated, for example, based on the spectral intensity of ¹ H-NMR (proton NMR) based on nuclear magnetic resonance (NMR). The calculation of the functional group equivalent (g/mol) of monomer S1 based on the spectral intensity of ¹ H-NMR can be based on the general structural analysis method related to ¹ H-NMR spectrum analysis, and can refer to the description of Japanese Patent Gazette No. 5951153 as needed.

Furthermore, when two or more monomers having different functional group equivalents are used as monomer S1, the arithmetic mean value can be used as the functional group equivalent of monomer S1. That is, the functional group equivalent of monomer S1 including n monomers having different functional group equivalents (monomer S1 ₁ , monomer S1 ₂ ... monomer S1 _n ) can be calculated by the following formula. Functional group equivalent of monomer S1 (g/mol) = (functional group equivalent of monomer S1 ₁ × blended amount of monomer S1 ₁ + functional group equivalent of monomer S1 ₂ × blended amount of monomer S1 ₂ + ... + functional group equivalent of monomer S1 _n × blended amount of monomer S1 _n ) / (blended amount of monomer S1 ₁ + blended amount of monomer S1 ₂ + ... + blended amount of monomer S1 _n )

The amount of monomer S1 used can be an appropriate value within the range in which the desired effect is exerted by using the monomer S1, and is not limited to a specific range. In some embodiments, the amount of monomer S1 in the total amount of monomer components (monomer raw material B) used to prepare polymer B can be, for example, 5% by weight or more from the perspective of easily suppressing the initial adhesion, and from the perspective of better exerting the effect as an adhesion increase delay agent, it is preferably set to 10% by weight or more, can be set to 15% by weight or more, and can also be set to 20% by weight or more. In addition, the content of monomer S1 in monomer raw material B can be, for example, 80% by weight or less from the perspective of polymerization reactivity or compatibility, and from the perspective of improving the adhesion after heating, it is usually appropriately set to 60% by weight or less, can be set to 50% by weight or less, can be set to 40% by weight or less, and can also be set to 30% by weight or less. From the perspective of easily and well taking into account both the suppression of initial adhesion and the increase in adhesion by heating, the technology disclosed herein can be implemented in a state where the content of monomer S1 in monomer raw material B is, for example, greater than 5 weight % and less than 50 weight %, preferably greater than 10 weight % and less than 40 weight %, and more preferably greater than 15 weight % and less than 30 weight %.

In addition to monomer S1, monomer raw material B also includes a (meth) acrylic monomer that can copolymerize with monomer S1. By copolymerizing one or more (meth) acrylic monomers with monomer S1, the mobility of polymer B in the adhesive layer can be well adjusted. Copolymerizing monomer S1 with a (meth) acrylic monomer can also help improve the compatibility of polymer B with polymer A (e.g., acrylic polymer).

As the (meth)acrylic monomer that can be used for the monomer raw material B, for example, alkyl (meth)acrylates can be listed. For example, one or two or more of the monomers exemplified above as alkyl (meth)acrylates that can be used when the polymer A is an acrylic polymer can be used as a constituent of the monomer raw material B. In some embodiments, the monomer raw material B can contain at least one C _4-12 alkyl (meth)acrylate (preferably C _4-10 alkyl (meth)acrylate, such as C _6-10 alkyl (meth)acrylate). In other embodiments, the monomer raw material B can contain at least one C _1-18 alkyl methacrylate (preferably C _1-14 alkyl methacrylate, such as C _1-10 alkyl methacrylate). The monomer raw material B can include, for example, one or two or more selected from MMA, BMA and 2EHMA as the (meth)acrylic monomer.

As other examples of the (meth)acrylic monomer, (meth)acrylic acid esters having alicyclic alkyl groups can be cited. For example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobutyl (meth)acrylate, dicyclopentyl (meth)acrylate, 1-adamantyl (meth)acrylate, etc. can be used. In some embodiments, the monomer raw material B can contain at least one selected from dicyclopentyl methacrylate, isobutyl methacrylate, and cyclohexyl methacrylate as the (meth)acrylic monomer.

The content of the above-mentioned alkyl (meth)acrylate and the above-mentioned (meth)acrylate having an alicyclic alkyl group in the monomer raw material B may be, for example, 10% by weight to 95% by weight, 20% by weight to 95% by weight, 30% by weight to 90% by weight, 40% by weight to 90% by weight, or 50% by weight to 85% by weight. From the perspective of the ease of increasing the adhesive force generated by heating to a temperature higher than 50° C., the use of alkyl (meth)acrylate may be advantageous. In some aspects, the content of the (meth)acrylate having an alicyclic alkyl group may be less than 50% by weight of the monomer raw material B, less than 30% by weight, less than 15% by weight, less than 10% by weight, or less than 5% by weight. It is also possible not to use the (meth)acrylate having an alicyclic alkyl group.

In some preferred embodiments, the (meth)acrylic monomer as a constituent of the monomer raw material B may include a monomer M2 having a homopolymer Tg of 50°C or higher. In polymer B having an Mw of a certain degree or higher (e.g., 7×10 ⁴ or higher, 8×10 ⁴ or higher, or even more than 10×10 ⁴ ), by copolymerizing monomer S1 with monomer M2, N ₅₀ /N ₂₃ tends to be suppressed. This is believed to be because the repeating units derived from the monomer M2 can effectively suppress the increase in mobility or mobility of the polyorganosiloxane structure portion accompanying the temperature rise from room temperature to about 50°C, and the low adhesion due to the presence of the polyorganosiloxane structure portion can be better maintained. From the viewpoint of improving the effect of suppressing N ₅₀ /N ₂₃ , in some aspects, the Tg of the homopolymer of the monomer M2 may be 60°C or higher, 70°C or higher, 80°C or higher, or 90°C or higher. The upper limit of the Tg of the homopolymer of the monomer M2 is not particularly limited, but is usually preferably 200°C or lower from the viewpoint of the ease of synthesis of the polymer B. In some aspects, the Tg of the homopolymer of the monomer M2 may be, for example, 180°C or lower, 150°C or lower, or 120°C or lower.

As the monomer M2, for example, one whose homopolymer Tg satisfies the conditions can be used from the (meth)acrylic monomers exemplified above. For example, one or more monomers selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid esters having alicyclic alkyl groups can be used. As the (meth)acrylic acid alkyl ester, methacrylic acid alkyl esters having an alkyl group with 1 to 4 carbon atoms can be preferably used.

In the aspect that the monomer raw material B includes the monomer M2, the content of the monomer M2 may be, for example, 5% by weight or more of the monomer raw material B, 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, or 30% by weight or more. In some aspects, the content of the above-mentioned monomer M2 may be 35% by weight or more of the monomer raw material B, 40% by weight or more, 45% by weight or more, 50% by weight or more, or 55% by weight or more. In addition, the content of the above-mentioned monomer M2 may be, for example, 90% by weight or less. From the perspective of improving _N80 / _N50 , it is usually suitable to be 80% by weight or less, preferably 75% by weight or less, 70% by weight or less, 65% by weight or less, or 60% by weight or less. The content of the above-mentioned monomer M2 can be well applied, for example, to an aspect in which the monomer M2 includes one or more monomers selected from the group consisting of (meth)acrylic acid alkyl esters and the above-mentioned (meth)acrylic acid esters having alicyclic alkyl groups, or an aspect in which the monomer M2 includes one or more monomers selected from (meth)acrylic acid alkyl esters (e.g., methacrylic acid alkyl esters). As a preferred example of this aspect, an aspect in which the above-mentioned monomer M2 includes MMA can be cited.

In some aspects, the (meth)acrylic monomer may include a monomer M3 whose homopolymer Tg is less than 50°C (typically, -20°C or higher and less than 50°C). By using the monomer M3, it is easy to obtain an adhesive sheet that balances the adhesive force and the cohesive force after the adhesive force increases. From the perspective of easily exerting this effect, the monomer M3 is preferably used in combination with the monomer M2.

As the monomer M3, for example, one having a homopolymer Tg satisfying the conditions can be used from the (meth)acrylic monomers exemplified above. For example, one or two or more monomers selected from the group consisting of alkyl (meth)acrylates can be used.

In the aspect that the monomer raw material B includes the monomer M3, the content of the monomer M3 may be, for example, 5% by weight or more of the monomer raw material B, 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, 30% by weight or more, or 35% by weight or more. In addition, the content of the monomer M3 is usually preferably set to 70% by weight or less of the monomer raw material B, 60% by weight or less, or 50% by weight or less. The above-mentioned content of the monomer M3 can be well applied to the aspect that the monomer M3 includes one or more monomers selected from (meth) alkyl acrylates (e.g., methacrylate alkyl esters).

In the several aspects of the adhesive sheet disclosed herein, the monomer raw material B is preferably a homopolymer having a Tg higher than 170°C and the content of the monomer is 30% by weight or less. Here, when the content of the monomer in this specification is X% by weight or less, unless otherwise specified, the concept includes an aspect in which the content of the monomer is 0% by weight, that is, an aspect in which the monomer is substantially not contained. Moreover, the so-called substantially not containing means that the above-mentioned monomer is at least not intentionally used. If the copolymerization ratio of the monomer having a homopolymer having a Tg higher than 170°C increases, the mobility of the polymer B may be insufficient, making it difficult to increase the adhesive force generated by heating to a temperature range higher than 50°C. By setting the copolymerization ratio of the monomer having a homopolymer Tg higher than 170°C to less than 30 wt %, at least one of the effects of increasing _N80 and increasing _N50 / _N80 can be achieved.

In some embodiments, the monomer raw material B preferably contains at least MMA as a (meth) acrylic monomer. By copolymerizing the polymer B with MMA, it is easy to obtain an adhesive sheet with a larger _N80 / _N50 . The ratio of MMA contained in the monomer raw material B to the total amount of (meth) acrylic monomers can be, for example, 5% by weight or more, 10% by weight or more, 20% by weight or more, 30% by weight or more, or 40% by weight or more. In some embodiments, the ratio of MMA to the total amount of the above-mentioned (meth) acrylic monomers can be, for example, more than 50% by weight, more than 55% by weight, more than 60% by weight, more than 65% by weight, or more than 70% by weight. In addition, the ratio of MMA to the total amount of the above-mentioned (meth) acrylic monomers is usually preferably less than 95% by weight, less than 90% by weight, or less than 85% by weight.

As other examples of monomers that can be contained together with the monomer S1 in the monomer units constituting the polymer B, the monomers that can be used when the polymer A is an acrylic polymer include the carboxyl group-containing monomers, acid anhydride group-containing monomers, hydroxyl group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, isocyanate group-containing monomers, amide group-containing monomers, monomers having a ring containing a nitrogen atom (N-vinyl ring) exemplified above. The present invention relates to (meth)acrylates of the present invention and the like. The present invention relates to (meth)acrylates of the present invention and the like. The present invention relates to (meth)acrylates of the present invention and the like.

As further examples of monomers that can be contained together with the monomer S1 in the monomer units constituting the polymer B, there can be listed: ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate and the like alkylene oxide di(meth)acrylate; monomers having a polyalkylene oxide skeleton, for example, polyalkylene oxides such as polyethylene glycol or polypropylene glycol; A polymerizable polyoxyalkylene ether having a polymerizable functional group such as (meth)acryl, vinyl, or allyl at one end of the chain and an ether structure (alkyl ether, aromatic ether, or aromatic alkyl ether, etc.) at the other end; an alkoxyalkyl (meth)acrylate such as methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, or ethoxypropyl (meth)acrylate; a salt such as a metal (meth)acrylate; a poly(meth)acrylate such as trihydroxymethylpropane tri(meth)acrylate; Meth) acrylic acid esters: halogenated vinyl compounds such as vinylidene chloride and 2-chloroethyl (meth)acrylate; monomers containing oxazoline groups such as 2-vinyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, and 2-isopropenyl-2-oxazoline; monomers containing aziridine groups such as (meth)acryloylaziridine and 2-aziridineethyl (meth)acrylate; monomers containing aziridine groups such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and addition products of lactones and 2-hydroxyethyl (meth)acrylate; Hydroxyl vinyl monomers; fluorine-containing vinyl monomers such as fluorine-substituted (meth) alkyl acrylates; 2-chloroethyl vinyl ether, vinyl monochloroacetate and other reactive halogen-containing vinyl monomers; vinyl monomers containing organic silicon such as vinyl trimethoxysilane, γ-(meth)acryloyloxypropyl trimethoxysilane, allyl trimethoxysilane, trimethoxysilyl propyl allylamine, 2-methoxyethoxy trimethoxysilane; in addition, macromonomers having a free radical polymerizable vinyl group at the end of the monomer that polymerizes the vinyl group, etc. These monomers can be copolymerized with the monomer S1 alone or in combination of two or more.

In some embodiments, as polymer B, a polymer that does not have a functional group that crosslinks with polymer A can be preferably used. In other words, polymer B is preferably contained in the adhesive layer in a form that is not chemically bonded to polymer A. Regarding the adhesive layer containing polymer B in this form, the mobility of polymer B when heated is good, which is suitable for improving the adhesion increase ratio. The functional group that crosslinks with polymer A may vary depending on the type of functional group possessed by the polymer A, for example, it may be an epoxy group, an isocyanate group, a carboxyl group, an alkoxysilane group, an amine group, etc.

The adhesive sheet disclosed herein contains a polymer B having an Mw of 7×10 ⁴ or more. The adhesive sheet comprising a polymer B having an Mw higher than a certain level as described above and configured in a manner satisfying (N ₈₀ /N ₅₀ ) ≧ 3 can also show good secondary processability in a usage state where a temperature of about 50°C may be applied at the initial stage of attachment, and the adhesive force is greatly increased by subsequent heating, etc. In some aspects, the Mw of polymer B can be, for example, 7.5×10 ⁴ or more, and can also be 8×10 ⁴ or more from the viewpoint of easily achieving a higher N ₈₀ /N ₅₀ . In some aspects, the Mw of polymer B may be, for example, 10×10 ⁴ or more, more than 10×10 4 , 12×10 ⁴ or more, or 15×10 ⁴ or more, from the ^viewpoint of improving _heat resistance (e.g., it can be evaluated based on the increase in NH, the increase in _NH / _N80 , etc.). Increasing the Mw of polymer B may also be advantageous from the viewpoint of improving the cohesiveness of the adhesive and suppressing cohesive failure during secondary processing.

Furthermore, the Mw of polymer B may be less than 50×10 ⁴ , and from the viewpoint of suppressing the initial adhesive force and improving the secondary processing workability, it is advantageous to be less than 40×10 ⁴ , less than 35×10 ⁴ , or less than 30×10 ⁴ . If the Mw of polymer B is within the range of any of the upper and lower limits mentioned above, it is easy to adjust the compatibility or mobility in the adhesive layer to an appropriate range, and it is easy to realize an adhesive sheet that takes into account both good secondary processing properties at the initial stage of attachment and strong adhesiveness after the adhesive force is increased at a high level.

In some preferred embodiments, the Mw of polymer B is preferably lower than the Mw of polymer A. In this way, it is easy to achieve an adhesive sheet that takes into account both good secondary processability at the initial stage of attachment and strong adhesion after the adhesion force increases at a high level. The Mw of polymer B can be, for example, 0.8 times or less, 0.75 times or less, 0.5 times or less, or 0.3 times or less of the Mw of polymer A. In addition, the Mw of polymer B is, for example, suitably 10×10 ⁴ or more lower than the Mw of polymer A, preferably 20×10 ⁴ or more lower, and more preferably 30×10 ⁴ or more lower.

The polymer B can be produced by polymerizing the above-mentioned monomers by a known method such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, or photopolymerization.

In order to adjust the molecular weight of polymer B, a chain transfer agent may be used as needed. Examples of the chain transfer agent include compounds having a hydroxyl group such as octyl mercaptan, lauryl mercaptan, tert-nonyl mercaptan, tert-dodecyl mercaptan, hydroxyethanol, α-thioglycerol, etc.; thioglycolic acid, methyl thioglycolate, ethyl thioglycolate, propyl thioglycolate, butyl thioglycolate, tert-butyl thioglycolate, 2-ethylhexyl thioglycolate, octyl thioglycolate, isooctyl thioglycolate, decyl thioglycolate, dodecyl thioglycolate, thioglycolate of ethylene glycol, thioglycolate of neopentyl glycol, thioglycolate of pentaerythritol, etc.; α-methylstyrene dimer, etc.

The amount of the chain transfer agent used is not particularly limited, but is generally 0.05 to 20 parts by weight, preferably 0.1 to 15 parts by weight, and more preferably 0.2 to 10 parts by weight, relative to 100 parts by weight of the monomer. By adjusting the amount of the chain transfer agent added, a polymer B with a better molecular weight can be obtained. The chain transfer agent can be used alone or in combination of two or more.

As a method for adjusting the molecular weight of polymer B, various previously known methods including the use of the above-mentioned chain transfer agent can be used alone or in appropriate combination. The same is true for the molecular weight of polymer A. Non-limiting examples of such methods include the selection of polymerization method, the selection of the type or amount of polymerization initiator, the selection of polymerization temperature, the selection of the type or amount of polymerization solvent in solution polymerization, the selection of light irradiation intensity in photopolymerization, etc. The industry can understand how to obtain a polymer with a desired molecular weight based on the description of the present invention including the following specific examples and the technical common sense at the time of application of the present invention.

In the adhesive sheet disclosed herein, the amount of polymer B used can be set to, for example, 0.1 parts by weight or more relative to 100 parts by weight of polymer A. From the perspective of obtaining a higher effect, it can be set to 0.5 parts by weight or more, 1 part by weight or more, or 2 parts by weight or more. In some embodiments, from the perspective of improving secondary processability, the amount of polymer B used can be set to, for example, 3 parts by weight or more, 4 parts by weight or more, or 5 parts by weight or more. In addition, the amount of polymer B used can be set to, for example, 75 parts by weight or less, 60 parts by weight or less, or 50 parts by weight or less relative to 100 parts by weight of polymer A. From the perspective of avoiding excessive reduction in the cohesive force of the adhesive layer, in some embodiments, the amount of polymer B used can be set to, for example, 40 parts by weight or less, 35 parts by weight or less, 30 parts by weight or less, or 25 parts by weight or less relative to 100 parts by weight of polymer A. From the perspective of obtaining higher adhesion after heating, in some embodiments, the amount of polymer B used can be set to 20 parts by weight or less, 17 parts by weight or less, 15 parts by weight or less, 12 parts by weight or less, or 10 parts by weight or less.

The adhesive layer may contain polymers other than polymer A and polymer B (arbitrary polymers) as needed, within the range that the adhesive sheet disclosed herein will not be significantly damaged. The amount of such arbitrary polymers used is usually preferably set to less than 20% by weight of the total polymer components contained in the adhesive layer, and may be less than 15% by weight, or less than 10% by weight. In some embodiments, the amount of the arbitrary polymer used may be less than 5% by weight of the total polymer components, and may be less than 3% by weight, or may be less than 1% by weight. It may also be an adhesive layer that does not substantially contain polymers other than polymer A and polymer B.

(Crosslinking agent) In the adhesive layer, a crosslinking agent may be used as needed for the purpose of adjusting the cohesive force, etc. As the crosslinking agent, a crosslinking agent known in the field of adhesives may be used, for example: epoxy crosslinking agents, isocyanate crosslinking agents, polysiloxane crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, silane crosslinking agents, alkyl etherified melamine crosslinking agents, metal chelate crosslinking agents, etc. The crosslinking agent may be used alone or in combination of two or more. Examples of crosslinking agents that can be used well include epoxy crosslinking agents, isocyanate crosslinking agents, silane crosslinking agents, alkyl etherified melamine crosslinking agents, and metal chelate crosslinking agents. Examples of particularly preferred crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, and metal chelate crosslinking agents.

Specifically, examples of isocyanate crosslinking agents include: toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, polymethylene polyphenyl isocyanate, and adducts of these with polyols such as trihydroxymethylpropane. Alternatively, a compound having at least one isocyanate group and one or more unsaturated bonds in one molecule, specifically 2-isocyanatoethyl (meth)acrylate, etc. can also be used as an isocyanate crosslinking agent. These may be used alone or in combination of two or more.

Examples of epoxy crosslinking agents include bisphenol A, epichlorohydrin epoxy resins, ethyl glycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol glycidyl ether, trihydroxymethylpropane triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N,N,N',N'-tetraglycidyl meta-xylylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, etc. These can be used alone or in combination of two or more.

As for the metal chelate compound which can be used as the metal chelate crosslinking agent, as the metal component, aluminum, iron, tin, titanium, nickel, etc. can be listed, as the chelate component, acetylene, methyl acetylacetate, ethyl lactate, etc. can be listed. These can be used alone or in combination of two or more.

The amount used when using a crosslinking agent is not particularly limited, for example, it can be set to an amount exceeding 0 weight part relative to 100 weight parts of polymer A. In addition, the amount of the crosslinking agent used can be set to, for example, more than 0.01 weight part relative to 100 weight parts of polymer A, and preferably more than 0.05 weight part. By increasing the amount of the crosslinking agent used, there is a tendency to suppress the adhesion in the initial stage of attachment and improve secondary processing properties. In several embodiments, the amount of the crosslinking agent used can be more than 0.1 weight part, more than 0.5 weight part, or more than 1 weight part relative to 100 weight parts of polymer A. On the other hand, from the viewpoint of avoiding the decrease in viscosity caused by excessive cohesive force, the amount of the crosslinking agent used is usually appropriately set to less than 15 weight parts relative to 100 weight parts of polymer A, can be set to less than 10 weight parts, and can also be set to less than 5 weight parts. It may also be beneficial from the viewpoint of easily achieving an adhesive sheet with a higher _N80 / _N50 if the amount of the crosslinking agent used is not too large.

The technology disclosed herein can be well implemented in the form of at least using an isocyanate crosslinking agent as a crosslinking agent. From the perspective of easily achieving an adhesive sheet having both good secondary processability at the initial stage of attachment and strong adhesion after the adhesion strength increases, in some forms, the amount of the isocyanate crosslinking agent used can be set to, for example, 0.1 to 5 parts by weight, 0.3 to 4 parts by weight, or 0.5 to 3 parts by weight relative to 100 parts by weight of the polymer A.

When an isocyanate crosslinking agent is used in a structure in which the adhesive layer contains a hydroxyl-containing monomer as a monomer unit, the amount of the hydroxyl-containing monomer used W _OH relative to the amount of the isocyanate crosslinking agent used W _NCO can be set to an amount that W _OH /W _NCO is 2 or more, but there is no particular limitation. By increasing the amount of the hydroxyl-containing monomer used relative to the isocyanate crosslinking agent in this way, a crosslinking structure suitable for significantly increasing the adhesion after heating relative to the adhesion at the initial stage of attachment can be formed. In several aspects, W _OH /W _NCO can be 3 or more, 5 or more, 10 or more, 20 or more, 30 or more, or 50 or more. There is no particular limitation on the upper limit of W _OH /W _NCO . W _OH /W _NCO may be, for example, 500 or less, 200 or less, or 100 or less.

In order to make any of the above crosslinking reactions more effective, a crosslinking catalyst may be used. As a crosslinking catalyst, for example, a tin catalyst (especially dioctyltin dilaurate) can be used well. The amount of the crosslinking catalyst used is not particularly limited, for example, it can be set to about 0.0001 to 1 parts by weight relative to 100 parts by weight of polymer A.

A multifunctional monomer can be used in the adhesive layer as needed. The multifunctional monomer can be used to achieve the purpose of adjusting the cohesive force by replacing the crosslinking agent as described above or using it in combination with the crosslinking agent. For example, the multifunctional monomer can be used well in the adhesive layer formed by the photocurable adhesive composition. Examples of the polyfunctional monomer include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trihydroxymethylpropane tri(meth)acrylate, tetrahydroxymethylmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butanediol (meth)acrylate, hexanediol di(meth)acrylate, and the like. Among them, trihydroxymethylpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate can be preferably used. The polyfunctional monomer can be used alone or in combination of two or more.

The amount of the multifunctional monomer used varies according to its molecular weight or functional group, etc., and is usually appropriately set to a range of about 0.01 to 3.0 parts by weight relative to 100 parts by weight of polymer A. In some embodiments, the amount of the multifunctional monomer used relative to 100 parts by weight of polymer A may be, for example, 0.02 parts by weight or more, or 0.03 parts by weight or more. By increasing the amount of the multifunctional monomer used, there is a tendency to suppress the adhesion in the initial stage of attachment and improve the secondary processability. On the other hand, from the perspective of avoiding a decrease in viscosity due to excessive cohesive force, the amount of the multifunctional monomer used relative to 100 parts by weight of polymer A may be 2.0 parts by weight or less, 1.0 parts by weight or less, or 0.5 parts by weight or less. It may also be beneficial from the perspective of easily achieving an adhesive sheet with a higher _N80 / _N50 if the amount of the multifunctional monomer used is not too much.

(Adhesive resin) The adhesive layer may contain an adhesive resin as needed. There are no particular restrictions on the adhesive resin, and examples thereof include rosin-based adhesive resins, terpene-based adhesive resins, phenol-based adhesive resins, hydrocarbon-based adhesive resins, ketone-based adhesive resins, polyamide-based adhesive resins, epoxy-based adhesive resins, and elastic-based adhesive resins. The adhesive resin may be used alone or in combination of two or more.

Examples of rosin-based adhesive imparting resins include: unmodified rosins (raw rosins) such as rosin gum, wood rosin, and tall oil rosin, or modified rosins (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, or other chemically modified rosins) obtained by modifying such unmodified rosins by polymerization, disproportionation, and hydrogenation, etc. In addition, various rosin derivatives can also be listed. As the above-mentioned rosin derivatives, for example, there can be listed: Rosin phenol resins obtained by adding phenol to rosins (unmodified rosin, modified rosin or various rosin derivatives, etc.) in an acid catalyst and then thermally polymerizing them; Rosin ester resins obtained by esterifying unmodified rosin with alcohols (unmodified rosin esters), or ester compounds of modified rosin (polymerized rosin esters, stabilized rosin esters, disproportionated rosin esters, fully hydrogenated rosin esters, partially hydrogenated rosin esters, etc.) obtained by esterifying modified rosins such as polymerized rosin, stabilized rosin, disproportionated rosin esters, fully hydrogenated rosin esters, partially hydrogenated rosin esters, etc.) with alcohols; Rosin ester resins obtained by esterifying unmodified rosin or modified rosin with unsaturated fatty acids. Unsaturated fatty acid modified rosin resins modified with (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, etc.); Unsaturated fatty acid modified rosin ester resins modified with unsaturated fatty acids; Rosin alcohol resins obtained by reducing the carboxyl groups in unmodified rosin, modified rosin (polymerized rosin, stabilized rosin, disproportionated rosin, fully hydrogenated rosin, partially hydrogenated rosin, etc.), unsaturated fatty acid modified rosin resins or unsaturated fatty acid modified rosin ester resins; Metal salts of rosin resins (especially rosin ester resins) such as unmodified rosin, modified rosin, or various rosin derivatives.

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

Examples of the phenolic adhesive imparting resin include: condensates of various phenols (e.g., phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcinol, etc.) and formaldehyde (e.g., alkylphenol resins, xylene formaldehyde resins, etc.), soluble phenolic resins obtained by an addition reaction of the above phenols with formaldehyde using an alkaline catalyst, or phenolic varnish resins obtained by a condensation reaction of the above phenols with formaldehyde using an acid catalyst, etc.

Examples of hydrocarbon adhesive-imparting resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic-aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic-aliphatic cyclopentane petroleum resins, hydrogenated hydrocarbon resins, lavender resins, lavender indene resins and the like.

Examples of commercially available polymerized rosin esters that can be preferably used include "Pensel D-125", "Pensel D-135", "Pensel D-160", "Pensel KK", and "Pensel C" manufactured by Arakawa Chemical Industries, Ltd., but the present invention is not limited to these.

Examples of commercially available terpene phenol resins that can be preferably used include "YS Polystar S-145", "YS Polystar G-125", "YS Polystar N125", and "YS Polystar U-115" manufactured by Yasuhara Chemical Co., Ltd., "Tamanol 803L" and "Tamanol 901" manufactured by Arakawa Chemical Industries, Ltd., and "Sumilite resin PR-12603" manufactured by Sumitomo Bakelite Co., Ltd., but are not limited to these.

The content of the tackifier resin is not particularly limited and can be set so as to exert appropriate adhesive properties according to the purpose or use. The content of the tackifier resin relative to 100 parts by weight of the polymer A (the total amount of the tackifier resins when two or more tackifier resins are contained) can be set to about 5 to 500 parts by weight, for example.

As the tackifier resin, a resin having a softening point (softening temperature) of about 80°C or more (preferably about 100°C or more, for example, about 120°C or more) can be preferably used. According to the tackifier resin having a softening point above the above lower limit, it is easy to obtain an adhesive sheet satisfying _N80 / _N50 ≧5. There is no particular upper limit to the softening point, for example, it can be about 200°C or less (typically 180°C or less). Furthermore, the softening point of the tackifier resin can be measured based on the softening point test method (global method) specified in JIS K2207.

In addition, the adhesive layer in the technology disclosed herein may also contain leveling agents, plasticizers, softeners, coloring agents (dyes, pigments, etc.), fillers, antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, light stabilizers, preservatives, etc., which are known additives that can be used in adhesives, within the scope that does not significantly hinder the effects of the present invention.

The adhesive layer constituting the adhesive sheet disclosed herein may be a hardening layer of an adhesive composition. That is, the adhesive layer may be formed by applying (e.g., coating) a water-dispersible, solvent-based, light-hardening, hot-melt-based adhesive composition to an appropriate surface and then appropriately performing a hardening treatment. When two or more hardening treatments (drying, crosslinking, polymerization, cooling, etc.) are performed, they may be performed simultaneously or in multiple stages. In an adhesive composition using a partial polymer (polymer slurry) of a monomer raw material, typically, a final copolymerization reaction is performed as the above-mentioned hardening treatment. That is, a partial polymer is subjected to a further copolymerization reaction to form a complete polymer. For example, if it is a photocurable adhesive composition, light irradiation is performed. If necessary, curing treatments such as crosslinking and drying may be performed. For example, when drying is required with a photocurable adhesive composition, photocuring may be performed after drying. In adhesive compositions using a complete polymer, typically, as the above-mentioned curing treatment, drying (heat drying), crosslinking, etc. may be performed as necessary.

The adhesive composition can be applied by using a commonly used coating machine such as a gravure roll coater, a reverse roll coater, a contact roll coater, a dip roll coater, a rod coater, a doctor blade coater, or a spray coater.

The thickness of the adhesive layer is not particularly limited, and can be set to 1 μm or more, for example. In some embodiments, the thickness of the adhesive layer can be, for example, 3 μm or more, 5 μm or more, 8 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. By increasing the thickness of the adhesive layer, the adhesive force tends to increase after heating. In addition, in some embodiments, the thickness of the adhesive layer can be, for example, 300 μm or less, 200 μm or less, 150 μm or less, 100 μm or less, 70 μm or less, 50 μm or less, or 40 μm or less. The thickness of the adhesive layer is not too large, which may be beneficial from the viewpoints of thinning the adhesive sheet or preventing the coagulation and destruction of the adhesive layer. Furthermore, in the case of an adhesive sheet having a first adhesive layer and a second adhesive layer on the first and second surfaces of a substrate, the thickness of the above-mentioned adhesive layer can at least be applied to the thickness of the first adhesive layer. The thickness of the second adhesive layer can also be selected from the same range. In addition, in the case of an adhesive sheet without a substrate, the thickness of the adhesive sheet is consistent with the thickness of the adhesive layer.

The gel fraction of the adhesive constituting the adhesive layer is usually preferably in the range of 20.0% to 99.0%, and preferably in the range of 30.0% to 90.0%, but there is no particular limitation. By setting the gel fraction in the above range, it is easy to realize an adhesive sheet that takes into account both secondary processability at the initial stage of attachment and strong adhesiveness after the adhesive force increases at a high level. The gel fraction is measured by the following method.

[Determination of gel fraction] About 0.1 g of adhesive sample (weight Wg ₁ ) is wrapped in a purse shape using a porous polytetrafluoroethylene membrane (weight Wg ₂ ) with an average pore size of 0.2 μm, and the mouth is tied with a kite line (weight Wg ₃ ). As the porous polytetrafluoroethylene membrane, the trade name "Nitoflon (registered trademark) NTF1122" (Nitto Denko Co., Ltd., average pore size 0.2 μm, porosity 75%, thickness 85 μm) or its equivalent is used. The package is immersed in 50 mL of ethyl acetate and kept at room temperature (typically 23°C) for 7 days to allow the sol component (ethyl acetate soluble component) in the adhesive to dissolve out of the above membrane. Next, the package was taken out, the ethyl acetate attached to the outer surface was wiped off, and the package was dried at 130°C for 2 hours, and the weight of the package (Wg ₄ ) was measured. By substituting each value into the following formula, the gel fraction _GC of the adhesive can be calculated. Gel fraction _GC (%) = [(Wg ₄ -Wg ₂ -Wg ₃ )/Wg ₁ ] × 100

<Supporting substrate> Some types of adhesive sheets may be in the form of an adhesive sheet with an adhesive layer on one or both sides of a supporting substrate. The material of the supporting substrate is not particularly limited and can be appropriately selected according to the purpose of use or usage of the adhesive sheet. As non-limiting examples of usable substrates, there can be cited: plastic films such as polyolefin films with polyolefin as the main component, such as polypropylene or ethylene-propylene copolymer, polyester films with polyester as the main component, such as polyethylene terephthalate or polybutylene terephthalate, and polyvinyl chloride films with polyvinyl chloride as the main component; foam sheets containing foams, such as polyurethane foam, polyethylene foam, and polychloroprene foam; woven fabrics and non-woven fabrics formed by single bodies or blends of various fibrous materials (which may be natural fibers such as linen and cotton, synthetic fibers such as polyester and vinyl, and semi-synthetic fibers such as acetate); papers such as Japanese paper, wood-free paper, kraft paper, and wrinkled paper; metal foils such as aluminum foil and copper foil, etc. It may also be a substrate having a structure of a composite of these. Examples of such a composite substrate include a substrate having a structure of a metal foil and the above-mentioned plastic film laminated thereon, and a plastic substrate such as glass cloth reinforced with inorganic fibers.

As the substrate of the adhesive sheet disclosed herein, various film substrates can be used well. The above-mentioned film substrate can be a porous substrate such as a foam film or a non-woven fabric sheet, a non-porous substrate, or a substrate having a structure in which a porous layer and a non-porous layer are layered. In some aspects, as the above-mentioned film substrate, a resin film that can independently maintain its shape (self-supporting or non-related) as a base film can be used well. The "resin film" here refers to a non-porous structure, and typically refers to a resin film that does not substantially contain bubbles (pores). Therefore, the concept of the above-mentioned resin film is different from that of a foam film or a non-woven fabric. As the above-mentioned resin film, a (self-supporting or non-related) resin film that can independently maintain its shape can be used well. The resin film may be a single-layer structure or a multi-layer structure of two or more layers (eg, a three-layer structure).

Examples of the resin material constituting the resin film include polyester, polyolefin, nylon 6, nylon 66, partially aromatic polyamides such as polyamide (PA), polyimide (PI), polyamide imide (PAI), polyetheretherketone (PEEK), polyethersulfone (PES), polyphenylene sulfide (PPS), polycarbonate (PC), polyurethane (PU), ethylene-vinyl acetate copolymer (EVA), polytetrafluoroethylene (PTFE) and other fluororesins, acrylic resins, polyacrylates, polystyrene, polyvinyl chloride, polyvinylidene chloride and the like. The resin film may be formed using a resin material containing only one of these resins, or may be formed using a resin material blended with two or more of these resins. The resin film may be unstretched or stretched (for example, uniaxially stretched or biaxially stretched).

Preferred examples of resin materials constituting the resin film include polyester resins, PPS resins, and polyolefin resins. Here, the polyester resin refers to a resin containing polyester at a ratio of more than 50% by weight. Similarly, the PPS resin refers to a resin containing PPS at a ratio of more than 50% by weight, and the polyolefin resin refers to a resin containing polyolefin at a ratio of more than 50% by weight.

As the polyester resin, a polyester resin containing as a main component a polyester obtained by polycondensing a dicarboxylic acid and a diol is typically used.

Examples of the dicarboxylic acid constituting the polyester include phthalic acid, isophthalic acid, terephthalic acid, 2-methylterephthalic acid, 5-sulfoisophthalic acid, 4,4'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 4,4'-diphenyl ketone dicarboxylic acid, 4,4'-diphenoxyethane dicarboxylic acid, 4,4'-diphenylsulfone dicarboxylic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 2,7 -Aromatic dicarboxylic acids such as naphthalene dicarboxylic acid; alicyclic dicarboxylic acids such as 1,2-cyclohexane dicarboxylic acid, 1,3-cyclohexane dicarboxylic acid, 1,4-cyclohexane dicarboxylic acid; aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanoic acid; unsaturated dicarboxylic acids such as maleic acid, maleic anhydride, fumaric acid; derivatives thereof (e.g., lower alkyl esters of the above dicarboxylic acids such as terephthalic acid, etc.). These can be used alone or in combination of two or more. From the viewpoint of strength, aromatic dicarboxylic acids are preferred. Among them, terephthalic acid and 2,6-naphthalene dicarboxylic acid can be listed as preferred dicarboxylic acids. For example, it is preferred that 50% by weight or more (e.g., 80% by weight or more, typically 95% by weight or more) of the dicarboxylic acid constituting the above polyester is terephthalic acid, 2,6-naphthalenedicarboxylic acid, or a combination thereof. The above dicarboxylic acid may be substantially composed of terephthalic acid, substantially composed of 2,6-naphthalenedicarboxylic acid, or substantially composed of terephthalic acid and 2,6-naphthalenedicarboxylic acid.

Examples of the diol constituting the polyester include aliphatic diols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, 1,3-propanediol, 1,5-pentanediol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, and polyoxytetramethylene glycol; alicyclic diols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol; aromatic diols such as benzyl alcohol, 4,4'-dihydroxybiphenyl, 2,2-bis(4'-hydroxyphenyl)propane, and bis(4-hydroxyphenyl)sulfone. These diols may be used alone or in combination of two or more. Among them, from the viewpoint of transparency, aliphatic diols are preferred, and ethylene glycol is particularly preferred. The proportion of aliphatic diols (preferably ethylene glycol) in the diols constituting the above-mentioned polyester is preferably 50% by weight or more (e.g., 80% by weight or more, typically 95% by weight or more). The above-mentioned diol may also be substantially composed of ethylene glycol only.

Specific examples of polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and polybutylene naphthalate.

As the polyolefin resin, one kind of polyolefin may be used alone or two or more kinds of polyolefins may be used in combination. The polyolefin may be, for example, a homopolymer of α-olefin, a copolymer of two or more kinds of α-olefins, a copolymer of one or more kinds of α-olefins and other vinyl monomers, etc. As specific examples, there may be listed: polyethylene (PE), polypropylene (PP), poly-1-butene, poly-4-methyl-1-pentene, ethylene propylene rubber (EPR), ethylene-propylene copolymer, ethylene-propylene-butene copolymer, ethylene-butene copolymer, ethylene-vinyl alcohol copolymer, ethylene-ethyl acrylate copolymer, etc. Any of low-density (LD) polyolefin and high-density (HD) polyolefin may be used. Examples of polyolefin resin films include: unoriented polypropylene (CPP) film, biaxially oriented polypropylene (OPP) film, low-density polyethylene (LDPE) film, linear low-density polyethylene (LLDPE) film, medium-density polyethylene (MDPE) film, high-density polyethylene (HDPE) film, polyethylene (PE) film blended with two or more polyethylene (PE), PP/PE blended film blended with polypropylene (PP) and polyethylene (PE), etc.

Specific examples of resin films that can be used well as the base film of the adhesive sheet disclosed herein include PET film, PEN film, PPS film, PEEK film, CPP film, and OPP film. Examples of preferred base films from the viewpoint of strength or dimensional stability include PET film, PEN film, PPS film, and PEEK film. From the viewpoint of ease of obtaining the base material, PET film and PPS film are particularly preferred, and PET film is preferred.

In the resin film, known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, lubricants, and anti-adhesive agents may be added as needed within the range that does not significantly hinder the effects of the present invention. The amount of additives added is not particularly limited and can be appropriately set according to the purpose of the adhesive sheet.

The method for producing the resin film is not particularly limited. For example, a conventionally known general resin film forming method such as extrusion forming, inflation forming, T-die die casting, calender roll forming, etc. may be appropriately adopted.

The substrate may substantially include such a base film. Alternatively, the substrate may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include: an optical property adjustment layer (e.g., a coloring layer, an anti-reflection layer), a printing layer or a lamination layer for giving the substrate a desired appearance, an antistatic layer, a primer layer, a peeling layer, and other surface treatment layers.

The thickness of the substrate is not particularly limited and can be selected according to the purpose or usage of the adhesive sheet. The thickness of the substrate can be, for example, 1000 μm or less. In some embodiments, from the perspective of operability or processability of the adhesive sheet, the thickness of the substrate can be, for example, 500 μm or less, 300 μm or less, 250 μm or less, or 200 μm or less. From the perspective of miniaturization or lightweight of products using the adhesive sheet, in some embodiments, the thickness of the substrate can be, for example, 160 μm or less, 130 μm or less, 100 μm or less, 90 μm or less, 80 μm or less, 60 μm or less, 50 μm or less, 25 μm or less, 10 μm or less, or 5 μm or less. If the thickness of the substrate becomes smaller, the softness of the adhesive sheet or the ability to follow the surface shape of the adherend tends to be improved. In addition, from the perspective of operability or processability, the thickness of the substrate can be, for example, 2 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, or 25 μm or more. In several embodiments, the thickness of the substrate can be, for example, 30 μm or more, 35 μm or more, 55 μm or more, 70 μm or more, 75 μm or more, 90 μm or more, or 120 μm or more. For example, in an adhesive sheet that can be used for the purpose of reinforcing, supporting, and impact mitigating the adherend, a substrate with a thickness of 30 μm or more can be well used.

If necessary, the first side of the substrate may be subjected to previously known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkaline treatment, and forming a primer layer by coating with a primer. Such surface treatments may be used to improve the grip of the adhesive layer on the substrate. For example, in an adhesive sheet having a substrate containing a resin film as a base film, a substrate subjected to the grip-improving treatment may be well used. The above-mentioned surface treatments may be applied alone or in combination. The composition of the primer used to form the primer layer is not particularly limited and may be appropriately selected from the known ones. The thickness of the base coating layer is not particularly limited, and is usually preferably about 0.01 μm to 1 μm, preferably about 0.1 μm to 1 μm. Other treatments that may be performed on the first surface of the substrate as needed include antistatic layer formation treatment, coloring layer formation treatment, printing treatment, etc.

When the adhesive sheet disclosed herein is a single-sided adhesive sheet having an adhesive layer only on the first side of the substrate, the second side of the substrate may be subjected to a previously known surface treatment such as a peeling treatment or an antistatic treatment as required. For example, the unwinding force of the adhesive sheet wound into a roll may be reduced by performing a surface treatment on the back side of the substrate using a peeling treatment agent (typically, by providing a peeling layer formed by the peeling treatment agent). As the stripping agent, a polysilicone stripping agent, a long-chain alkyl stripping agent, an olefin stripping agent, a fluorine stripping agent, a fatty acid amide stripping agent, molybdenum sulfide, silicon dioxide powder, etc. can be used. In addition, the second side of the substrate can be subjected to a treatment such as a corona discharge treatment, a plasma treatment, an ultraviolet irradiation treatment, an acid treatment, an alkali treatment, etc. for the purpose of improving the printing property, reducing the light reflectivity, and improving the lamination adhesion. In addition, in the case of a double-sided adhesive sheet, the second side of the substrate can be subjected to the same surface treatment as the surface treatment that can be applied to the first side of the substrate as exemplified above, as necessary. Furthermore, the surface treatment applied to the first side of the substrate may be the same as or different from the surface treatment applied to the second side.

<Adhesive sheet> (Adhesive sheet characteristics, etc.) The adhesive sheet disclosed herein has a ratio of adhesive force N ₈₀ [N/25 mm] to adhesive force N ₅₀ [N/25 mm], i.e., an adhesive force increase ratio N ₈₀ /N ₅₀ of 3 or more, and therefore can show good secondary processability even in a usage state where a temperature of about 50°C may be applied at the initial stage of attachment, and the adhesive force is greatly increased by subsequent heating, etc. From the viewpoint of obtaining a higher effect, in some states, N ₈₀ /N ₅₀ can be, for example, 3.5 or more, 4.5 or more, 5.0 or more, 5.5 or more, or 6.0 or more. The upper limit of _N80 / _N50 is not particularly limited. From the viewpoint of ease of manufacturing or economy of the adhesive sheet, in several aspects, it may be, for example, 50 or less, 30 or less, 20 or less, or 10 or less. The adhesive sheet disclosed herein may be well implemented in an aspect in which _N80 / _N50 is, for example, 3.0 or more and 50 or less, 3.5 or more and 50 or more, or 5.0 or more and 30 or less.

In some aspects, the ratio of the adhesive force N ₅₀ [N/25 mm] to the adhesive force N ₂₃ [N/25 mm], i.e., the adhesive force increase ratio N ₅₀ /N ₂₃ is preferably less than 10, more preferably less than 7.0, and may be less than 6.0, less than 5.5, less than 5.0, or less than 5.0. An adhesive sheet with a smaller N ₅₀ /N ₂₃ tends to exhibit good secondary processability in a usage aspect where a temperature of about 50°C may be applied at the initial stage of attachment. The lower limit of N ₅₀ /N ₂₃ is not particularly limited, and is usually greater than 1.0, typically exceeds 1.0, and may be greater than 1.2. From the viewpoint of easily achieving a higher N ₈₀ /N ₅₀ , in some aspects, N ₅₀ /N ₂₃ may be, for example, 1.5 or more, 2.0 or more, or 2.5 or more.

In some aspects, the ratio of the adhesive force N ₈₀ [N/25 mm] to the adhesive force N ₂₃ [N/25 mm], i.e., the adhesive force increase ratio N ₈₀ /N ₂₃ , can be, for example, 5 or more, 7 or more, or 10 or more. According to the adhesive sheet with a larger N ₈₀ /N ₂₃ , the low adhesiveness at the initial stage of attachment and the strong adhesiveness after the adhesive force increases can be exerted at a higher level. The adhesive sheet disclosed herein can also be well implemented in an aspect where N ₈₀ /N ₂₃ is, for example, 15 or more, 20 or more, or 25 or more. The upper limit of N ₈₀ /N ₂₃ is not particularly limited. From the perspective of the ease of manufacturing or economy of the adhesive sheet, it can be, for example, 100 or less, 80 or less, 60 or less, or 50 or less.

Here, the adhesion force N ₂₃ [N/25 mm] is obtained by measuring the 180° peel adhesion under the conditions of a peel angle of 180 degrees and a tensile speed of 300 mm/min in an environment of 23°C, 50% RH for 30 minutes after being pressed onto a stainless steel (SUS) plate as an adherend. Adhesion force _N50 [N/25 mm] is obtained by pressing the adherend to a SUS plate at 50°C for 30 minutes, then placing it at 23°C and 50% RH for 30 minutes, and then measuring the 180° peel adhesion at a peel angle of 180 degrees and a tensile speed of 300 mm/min. Adhesion force _N80 [N/25 mm] is obtained by pressing on a SUS plate as an adherend and heating at 80°C for 5 minutes, then placing it in an environment of 23°C and 50%RH for 30 minutes, and then measuring the 180° peeling adhesion under the conditions of a peeling angle of 180 degrees and a tensile speed of 300 mm/min. As the adherend, SUS304BA plate is used in the measurement of any of the adhesion forces _N23 , _N50 , and _N80 . During the measurement, a suitable backing material (e.g., a PET film with a thickness of about 25 μm) is attached to the adhesive sheet of the measurement object as needed for reinforcement. More specifically, the adhesion forces N ₂₃ , N ₅₀ , and N ₈₀ can be measured according to the method described in the following examples.

In some embodiments, the adhesion force _N23 may be, for example, 3 N/25 mm or less, preferably 2.5 N/25 mm or less, more preferably less than 2 N/25 mm, and may be 1.5 N/25 mm or less, 1.2 N/25 mm or less, or 1 N/25 mm or less. A lower adhesion force _N23 is better from the perspective of secondary processability. There is no particular restriction on the lower limit of the adhesion force _N23 , and for example, it may be 0.01 N/25 mm or more. From the perspective of adhesion workability to the adherend or preventing positional deviation before the adhesion force rises, the adhesion force _N23 is usually preferably 0.1 N/25 mm or more. From the viewpoint of improving the adhesion after heating, in some aspects, the adhesion _N23 can be, for example, greater than 0.2 N/25 mm, greater than 0.3 N/25 mm, greater than 0.4 N/25 mm, or greater than 0.5 N/25 mm.

In some aspects, the adhesion force _N50 may be, for example, 8 N/25 mm or less, preferably 7 N/25 mm or less, more preferably 5 N/25 mm or less, 4.5 N/25 mm or less, 4 N/25 mm or less, or less than 4 N/25 mm. A lower adhesion force _N50 is preferred from the viewpoint of good secondary processability even in a use aspect where a temperature of about 50°C may be applied at the initial stage of attachment. The lower limit of the adhesion force _N50 is not particularly limited, and may be, for example, 0.05 N/25 mm or more. From the viewpoint of preventing positional deviation before the adhesion force rises, the adhesion force _N50 is usually preferably 0.1 N/25 mm or more. From the perspective of improving the adhesion after heating, in some aspects, the adhesion _N50 may be, for example, greater than 0.5 N/25 mm, greater than 1 N/25 mm, or greater than 1.5 N/25 mm.

In some embodiments, the adhesive force _N80 (adhesive force after heating) can be, for example, 5 N/25 mm or more, 7 N/25 mm or more, 10 N/25 mm or more, 13 N/25 mm or more, 15 N/25 mm or more, or 17 N/25 mm or more. There is no particular upper limit to the adhesive force after heating. From the perspective of ease of manufacturing or economy of the adhesive sheet, in some embodiments, the adhesive force after heating can be, for example, 70 N/25 mm or less, 50 N/25 mm or less, or 40 N/25 mm or less.

Furthermore, the adhesive force of the adhesive sheet disclosed here after heating represents a characteristic of the adhesive sheet, and does not limit the usage of the adhesive sheet. In other words, the usage of the adhesive sheet disclosed here is not limited to the usage of 80°C for 5 minutes. For example, it can also be used for the usage of the adhesive sheet without being heated to the room temperature area (usually 20°C to 30°C, typically 23°C to 25°C) or above. In this usage, the adhesive force can also be increased for a long time to achieve a strong bond. In addition, the adhesive sheet disclosed here can be heated at a temperature higher than 50°C at any time after attachment to promote the increase of the adhesive force. The heating temperature in the heat treatment is not particularly limited and can be set in consideration of workability, economy, heat resistance of the substrate of the adhesive sheet or the adherend, etc. The above-mentioned heating temperature may be, for example, less than 150°C, may be below 120°C, may be below 100°C, may be below 80°C, or may be below 70°C. Furthermore, the above-mentioned heating temperature may be, for example, above 55°C, above 60°C, or above 70°C, may be above 80°C, or may be above 100°C. By a higher heating temperature, the adhesion can be increased by a shorter treatment time. The heating time is not particularly limited, for example, it may be less than 1 hour, may be less than 30 minutes, may be less than 10 minutes, or may be less than 5 minutes. Furthermore, the heating time may be, for example, more than 1 minute, may be more than 3 minutes, may be more than 7 minutes, or may be more than 15 minutes. Alternatively, a longer heating treatment may be performed within the limit that no significant thermal degradation occurs to the adhesive sheet or the adherend. Furthermore, the heat treatment may be performed once or in multiple times.

The adhesive sheet disclosed herein exhibits low initial adhesion and strong adhesion after the adhesion increases in the room temperature range (e.g., 23°C) by making the Mw of polymer B greater than 7×10 ⁴ (preferably greater than 8×10 ⁴ , more preferably greater than 10×10 ⁴ , for example, greater than 10×10 ⁴ ). Moreover, after the adhesion increases, it is easy to improve the maintenance rate of the adhesion in the high temperature range (e.g., 80°C) relative to the adhesion N ₈₀ in the room temperature range. In some aspects, the ratio of the adhesive force _NH [N/25 mm] to the adhesive force _N50 [N/25 mm] at 80°C, i.e., _NH / _N80 (hereinafter also referred to as "heat-resistant adhesive force maintenance ratio") is advantageously higher than 10%, preferably higher than 12%, more preferably higher than 15%, may be higher than 17%, and may be higher than 20%. From the viewpoint of the heat resistance of the adhesive sheet, the higher _NH / _N80 , the better. Therefore, the upper limit of _NH / _N80 is not particularly limited, and is typically lower than 100%.

Here, the adhesion _NH (hereinafter, also referred to as 80°C adhesion) is obtained by measuring the 180° peeling adhesion under the conditions of a peeling angle of 180 degrees and a tensile speed of 300 mm/min in the environment (i.e., at 80°C) after being pressed onto a SUS plate as an adherend and kept in an environment of 80°C for 30 minutes. As the adherend, a SUS304BA plate is used in the same manner as in the measurement of the adhesion _N23 . During the measurement, a suitable backing material (e.g., a PET film with a thickness of about 25 μm) may be attached to the adhesive sheet of the measurement object as needed for reinforcement. More specifically, the adhesion _NH may be measured according to the method described in the following embodiment.

In some embodiments, the adhesion _NH may be, for example, 3 N/25 mm or more, 3.5 N/25 mm or more, or 4 N/25 mm or more. A higher adhesion _NH means that after the adhesion increases, a more reliable bond can be maintained even in a high temperature region. There is no particular upper limit to the adhesion _NH . From the perspective of heat resistance, the higher the better. However, typically, it is 40 N/25 mm or less. From the perspective of taking into account the initial low adhesion, it may be 30 N/25 mm or less, or 20 N/25 mm or less.

(Adhesive sheet attached to substrate) When the adhesive sheet disclosed here is in the form of an adhesive sheet attached to substrate, the thickness of the adhesive sheet may be, for example, less than 1000 μm, less than 600 μm, less than 350 μm, or less than 250 μm. From the perspective of miniaturization, lightness, and thinness of products to which the adhesive sheet is applied, in some embodiments, the thickness of the adhesive sheet may be, for example, less than 200 μm, less than 175 μm, less than 140 μm, less than 120 μm, or less than 100 μm (for example, less than 100 μm). In addition, from the perspective of operability, the thickness of the adhesive sheet may be, for example, more than 5 μm, more than 10 μm, more than 15 μm, more than 20 μm, more than 25 μm, or more than 30 μm. In some embodiments, the thickness of the adhesive sheet can be, for example, 50 μm or more, 60 μm or more, 80 μm or more, 100 μm or more, or 120 μm or more. The upper limit of the thickness of the adhesive sheet is not particularly limited. Furthermore, the thickness of the adhesive sheet refers to the thickness of the portion attached to the adherend. For example, in the adhesive sheet 1 of the structure shown in FIG. 1, it refers to the thickness from the adhesive surface 21A of the adhesive sheet 1 to the second surface 10B of the substrate 10, excluding the thickness of the peeling pad 31.

The adhesive sheet disclosed herein can be well implemented in a state where the thickness Ts of the supporting substrate is greater than the thickness Ta of the adhesive layer, that is, in a state where Ts/Ta is greater than 1. Ts/Ta can be, for example, greater than 1.1, greater than 1.2, greater than 1.5, or greater than 1.7, but is not particularly limited. For example, in an adhesive sheet that can be used for purposes such as reinforcement, support, and impact relief of an adherend, by increasing Ts/Ta, there is a tendency that a good effect can be easily exerted even if the adhesive sheet is thinned. In several aspects, Ts/Ta can be greater than 2 (for example, greater than 2), greater than 2.5, or greater than 2.8. In addition, Ts/Ta can be, for example, less than 50, or less than 20. From the viewpoint of being able to easily exert a higher adhesive force after heating even when the adhesive sheet is thinned, Ts/Ta may be, for example, 10 or less, 8 or less, or 5 or less.

The above-mentioned adhesive layer is preferably fixed to the supporting substrate. The fixing mentioned here means that in the adhesive sheet whose adhesive force increases after being attached to the adherend, the adhesive layer shows sufficient grip to the supporting substrate to the extent that the interface between the adhesive layer and the supporting substrate does not peel when the adhesive sheet is peeled off from the adherend. By fixing the adhesive layer to the supporting substrate, the adherend and the supporting substrate can be firmly integrated. As a better example of an adhesive sheet in which the adhesive layer is fixed to the substrate, there can be cited an adhesive sheet in which no peeling (grip failure) occurs between the adhesive layer and the supporting substrate during the above-mentioned measurement of the adhesive force after heating. An adhesive sheet having a post-heating adhesion of 15 N/25 mm or more and which does not cause gripping and damage when measuring the post-heating adhesion is a preferred example of an adhesive sheet having an adhesive layer fixed on a substrate.

The adhesive sheet disclosed herein can be well manufactured, for example, by a method including the following steps in sequence: bringing a liquid adhesive composition into contact with a first surface of a substrate; and hardening the adhesive composition on the first surface to form an adhesive layer. The hardening of the adhesive composition may be accompanied by one or more of drying, crosslinking, polymerization, cooling, etc. of the adhesive composition. According to the method of hardening the liquid adhesive composition on the first surface of the substrate to form an adhesive layer, the grip of the adhesive layer on the substrate can be improved compared to the method of arranging the adhesive layer on the first surface by attaching the hardened adhesive layer to the first surface of the substrate. By utilizing this situation, an adhesive sheet in which the adhesive layer is fixed to the substrate can be well manufactured.

In some embodiments, as a method of bringing a liquid adhesive composition into contact with the first surface of a substrate, a method of directly applying the adhesive composition to the first surface of the substrate can be adopted. By bringing the first surface (adhesive surface) of the adhesive layer hardened on the first surface of the substrate into contact with the peeling surface, an adhesive sheet can be obtained in which the second surface of the adhesive layer is fixed to the first surface of the substrate and the first surface of the adhesive layer is in contact with the peeling surface. As the above-mentioned peeling surface, the surface of a peeling pad or the back surface of a substrate subjected to peeling treatment can be used.

Furthermore, for example, in the case of using a light-curing adhesive composition of a partial polymer (polymer slurry) of a monomer raw material, after the adhesive composition is applied to the peeling surface, the applied adhesive composition is coated on the first surface of the substrate, thereby making the first surface of the substrate contact with the uncured adhesive composition. In this state, the adhesive composition sandwiched between the first surface of the substrate and the peeling surface is irradiated with light to cure it, thereby forming an adhesive layer.

Furthermore, the method exemplified above is not limited to the method for manufacturing the adhesive sheet disclosed herein. When manufacturing the adhesive sheet disclosed herein, one or a combination of two or more appropriate methods that can fix the adhesive layer to the first surface of the substrate can be used. Examples of such methods include: a method of hardening a liquid adhesive composition on the first surface of the substrate to form an adhesive layer as described above, or a method of performing a surface treatment on the first surface of the substrate to improve the grip of the adhesive layer, etc. For example, in a situation where the grip of the adhesive layer on the substrate can be sufficiently improved by providing a primer layer on the first surface of the substrate, the adhesive sheet can also be manufactured by a method of attaching the hardened adhesive layer to the first surface of the substrate. Furthermore, the grip of the adhesive layer on the substrate can be improved by selecting the material of the substrate or the composition of the adhesive. Furthermore, the grip of the adhesive layer on the substrate can be improved by applying a temperature higher than room temperature to the adhesive sheet having the adhesive layer on the first surface of the substrate. The temperature for improving the grip can be, for example, about 35°C to 80°C, about 40°C to 70°C or above, or about 45°C to 60°C.

In the case where the adhesive sheet disclosed herein is in the form of an adhesive sheet having a first adhesive layer disposed on the first surface of a substrate and a second adhesive layer disposed on the second surface of the substrate (i.e., a double-sided adhesive sheet attached to a substrate), the first adhesive layer and the second adhesive layer may be of the same composition or of different compositions. In the case where the first adhesive layer and the second adhesive layer have different compositions, the difference may be, for example, a difference in composition or a difference in structure (thickness, surface roughness, formation range, formation pattern, etc.). For example, the second adhesive layer may also be an adhesive layer that does not contain polymer B. In addition, regarding the surface of the second adhesive layer (second adhesive surface), N ₈₀ /N ₅₀ may be less than 3, less than 2, less than 1.5, or less than 1.

<Adhesive sheet with peel-off liner> The adhesive sheet disclosed herein can be in the form of an adhesive product in which the surface (adhesive surface) of the adhesive layer abuts against the peel-off surface of the peel-off liner. Therefore, this specification can provide an adhesive sheet with peel-off liner (adhesive product) comprising any adhesive sheet disclosed herein and a peel-off liner having a peel-off surface abutting against the adhesive surface of the adhesive sheet.

The thickness of the peeling pad is not particularly limited, and is generally preferably about 5 μm to 200 μm. If the thickness of the peeling pad is within the above range, the bonding workability of the adhesive layer and the peeling workability of the self-adhesive layer are excellent, so it is preferred. In some embodiments, the thickness of the peeling pad can be, for example, 10 μm or more, 20 μm or more, 30 μm or more, or 40 μm or more. In addition, from the perspective of facilitating the peeling of the self-adhesive layer, the thickness of the peeling pad can be, for example, 100 μm or less, or 80 μm or less. If necessary, the release pad may be subjected to known antistatic treatment such as coating type, kneading type, and evaporation type.

The peeling pad is not particularly limited, and can be used, for example, a peeling pad having a peeling layer on the surface of a pad base material such as a resin film or paper (which may be a paper laminated with a resin such as polyethylene), or a peeling pad including a resin film formed using a low-adhesion material such as a fluorine-based polymer (polytetrafluoroethylene, etc.) or a polyolefin-based resin (polyethylene, polypropylene, etc.). In terms of excellent surface smoothness, it can be well used as a peeling pad having a peeling layer on the surface of a resin film as a pad base material, or a peeling pad including a resin film formed using a low-adhesion material. The resin film is not particularly limited as long as it can protect the adhesive layer, and examples thereof include polyethylene film, polypropylene film, polybutylene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyester film (PET film, PBT film, etc.), polyurethane film, ethylene-vinyl acetate copolymer film, etc. The above-mentioned release layer can be formed by, for example, using a known release agent such as a polysilicone release agent, a long-chain alkyl release agent, an olefin release agent, a fluorine release agent, a fatty acid amide release agent, molybdenum sulfide, and silica powder. It is particularly preferred to use a polysilicone release agent.

The thickness of the release layer is not particularly limited, and is usually about 0.01 μm to 1 μm, preferably about 0.1 μm to 1 μm. The method for forming the release layer is not particularly limited, and a known method corresponding to the type of release treatment agent used can be appropriately adopted.

<Application> The adhesive sheet provided by this specification, for example, after being attached to an adherend, can suppress the adhesive force to a relatively low level in a short period of time in a temperature range from room temperature to about 50°C (for example, 20°C to 50°C), during which it can exhibit good secondary processability, thereby contributing to suppressing yield reduction or improving the quality of products containing the adhesive sheet. Moreover, the adhesive force of the above-mentioned adhesive sheet can be greatly increased by aging (which can be heating to a temperature higher than 50°C, over time, or a combination of the above). For example, by heating at the desired time, the adhesive sheet can be firmly attached to the adherend. Utilizing this feature, the adhesive sheet disclosed herein can be well used in various fields for the purposes of fixing, joining, forming, decorating, protecting, reinforcing, supporting, and impact mitigating components contained in various products.

The adhesive sheet disclosed herein can be used as a reinforcing film that is attached to an adherend to reinforce the adherend, for example, in the form of an adhesive sheet with an adhesive layer provided on at least the first surface of a film-like substrate having a first surface and a second surface. In the reinforcing film, as the above-mentioned film substrate, a base film containing a resin film can be used. In addition, from the viewpoint of improving the reinforcing performance, the above-mentioned adhesive layer is preferably fixed to the first surface of the film-like substrate. For example, with respect to optical components used in optical products or electronic components used in electronic products, the high degree of integration, miniaturization, lightness, and thinness are constantly developing, and multiple thinner optical components/electronic components with different linear expansion coefficients or thicknesses can be layered. By attaching the reinforcing film as described above to such a component, the optical component/electronic component can be given appropriate rigidity. In this way, in the manufacturing process and/or the product after manufacturing, the curling or bending caused by the stress that may be generated between multiple components with different linear expansion coefficients or thicknesses can be suppressed. In addition, in the manufacturing process of optical products/electronic products, when the thinner optical components/electronic components are subjected to shape processing such as cutting processing as described above, by attaching a reinforcing film to the component and processing it, the stress concentration on the local part of the optical component/electronic component accompanying the processing can be alleviated, and the risks of cracking, rupture, and peeling of the laminated components can be reduced. Attaching a reinforcing member to an optical component/electronic component can also help to relieve local stress concentration during the transportation, lamination, and rotation of the component, or suppress bending or curvature caused by the weight of the component. Furthermore, when optical products or electronic products including the above-mentioned reinforcing film are used by consumers on the market, even if the device is dropped, placed under a heavy object, or hit by a flying object, the stress applied to the device can be relieved by including the reinforcing film. Therefore, by including the reinforcing film in the above-mentioned device, the durability of the device can be improved.

In addition, the adhesive sheet disclosed herein can be used well by being attached to components constituting various portable devices (portable devices). The term "portable" herein does not simply mean being able to be carried, but means having a degree of portability that an individual (standard adult) can carry relatively easily. Furthermore, examples of portable devices herein may include: mobile phones, smart phones, tablet personal computers, laptop personal computers, various portable devices, digital cameras, digital video recorders, audio equipment (portable music players, recorders, etc.), calculators (calculators, etc.), portable gaming equipment, electronic dictionaries, electronic notepads, electronic books, in-vehicle information equipment, portable radios, portable televisions, portable printers, portable scanners, portable modems, and other portable electronic devices. In addition, they may also include mechanical watches or pocket watches, flashlights, magnifying glasses, and the like. Examples of components constituting the above-mentioned portable electronic devices may include optical films or display panels used in image display devices such as thin-film displays such as liquid crystal displays or film-type displays. The adhesive sheet disclosed herein can also be used in a state of being attached to various components in automobiles, home appliances, etc.

The matters disclosed in this specification include the following. (1) An adhesive sheet comprising an adhesive layer, wherein the adhesive layer comprises a polymer A as a polymer of a monomer raw material A and a polymer B as a polymer of a monomer raw material B, wherein the monomer raw material B comprises a monomer having a polyorganosiloxane skeleton and a (meth)acrylic monomer, wherein the weight average molecular weight of the polymer B is 7×10 ⁴ or more, and wherein the relationship between the adhesive force N 50 of the adhesive sheet measured at 23°C after being bonded to a stainless steel plate and kept at 50°C for 30 minutes and the adhesive force N ₈₀ of the adhesive sheet measured at 23°C after being bonded to a stainless steel plate and heated at ₈₀ °C for 5 minutes satisfies the following formula: (N ₈₀ /N ₅₀ )≧3. (2) The adhesive sheet as described in (1) above, wherein the relationship between the adhesive force _N50 and the adhesive force _N23 measured at 23°C after being attached to a stainless steel plate and placed at 23°C for 30 minutes satisfies the following formula: ( _N50 / _N23 ) < 10. (3) The adhesive sheet as described in (1) or (2) above, wherein the relationship between the adhesive force _N80 and the adhesive force NH measured at 80°C after being attached to a stainless steel plate and placed in an environment of 80°C for 30 minutes satisfies the following formula: ( _NH / _N80 ) ≧ 15%. (4) The adhesive sheet as described in any one of (1) to (3) above, wherein the relationship between the adhesive force N50 and the adhesive force _N23 measured at 23°C after being attached to a stainless steel plate and placed at 80°C for 30 minutes satisfies the following formula: ( _N80 / _N23 ) ≧ 15. (5) The adhesive sheet as described in any one of (1) to (4) above, wherein the adhesive force _N23 is 2 N/25 mm or less. (6) The adhesive sheet as described in any one of (1) to (5) above, wherein the adhesive force _N50 is 8 N/25 mm or less. (7) The adhesive sheet as described in any one of (1) to (6) above, wherein the adhesive force _N80 is 15 N/25 mm or more. (8) The adhesive sheet as described in any one of (1) to (7) above, wherein the adhesive force NH is 3 N/25 mm or more.

(9) An adhesive sheet as described in any one of (1) to (8) above, wherein the functional group equivalent of the monomer having a polysiloxane skeleton is 700 g/mol or more and less than 15,000 g/mol. (10) An adhesive sheet as described in any one of (1) to (9) above, wherein the content of the monomer having a polysiloxane skeleton in the monomer raw material B is 10% by weight or more and 60% by weight or less. (11) An adhesive sheet as described in any one of (1) to (10) above, wherein the (meth)acrylic monomer contained in the monomer raw material B includes a monomer M2 whose homopolymer has a glass transition temperature of 50° C. or more. (12) An adhesive sheet as described in (11) above, wherein the monomer M2 comprises one or more monomers selected from the group consisting of (meth)acrylates and (meth)acrylates having alicyclic hydrocarbon groups. (13) An adhesive sheet as described in (11) above, wherein the monomer M2 comprises one or more (meth)acrylates. (14) An adhesive sheet as described in any one of (11) to (13) above, wherein the content of the monomer M2 in the monomer raw material B is 5 wt % to 80 wt %. (15) An adhesive sheet as described in any one of (1) to (14) above, wherein the (meth)acrylic monomer contained in the monomer raw material B comprises a monomer M3 having a homopolymer glass transition temperature of not less than -20°C and not more than 50°C. (16) The adhesive sheet as described in (14) above, wherein the content of the monomer M3 in the monomer raw material B is 5% by weight or more and 70% by weight or less. (17) The adhesive sheet as described in any one of (1) to (16) above, wherein the weight average molecular weight of the polymer B is 8×10 ⁴ or more and less than 40×10 ^4. (18) The adhesive sheet as described in any one of (1) to (17) above, wherein the content of the polymer B in the adhesive layer is 0.5 parts by weight or more and 50 parts by weight or less relative to 100 parts by weight of the polymer A.

(19) An adhesive sheet as described in any one of (1) to (18) above, wherein the weight average molecular weight of the polymer A is 40×10 ⁴ or more. (20) An adhesive sheet as described in any one of (1) to (19) above, wherein the polymer A is an acrylic polymer. (21) An adhesive sheet as described in any one of (1) to (20) above, wherein the monomer raw material A contains a monomer having a ring containing a nitrogen atom. (22) An adhesive sheet as described in (21) above, wherein the monomer having a ring containing a nitrogen atom is N-vinyl cyclic amide. (23) An adhesive sheet as described in (20) above, wherein the monomer raw material A contains a hydroxyl-containing monomer. (24) An adhesive sheet as described in (20) above, wherein the monomer raw material A contains N-vinyl cyclic amide and a hydroxyl-containing monomer. (25) The adhesive sheet as described in any one of (1) to (24) above, wherein the adhesive layer contains more than 0 parts by weight and less than 10 parts by weight of a crosslinking agent relative to 100 parts by weight of the polymer A. (26) The adhesive sheet as described in (25) above, wherein the crosslinking agent comprises an isocyanate crosslinking agent.

(27) An adhesive sheet as described in any one of (1) to (26) above, wherein the thickness of the adhesive layer is not less than 3 μm and not more than 100 μm. (28) An adhesive sheet as described in any one of (1) to (27) above, which has a supporting substrate having a first surface and a second surface, and the adhesive layer is laminated on at least the first surface of the supporting substrate. (29) An adhesive sheet with a release pad, comprising: an adhesive sheet as described in any one of (1) to (28) above, and a release pad having a release surface abutting against the adhesive surface of the adhesive sheet. (30) An adhesive sheet with a peel-off liner as described in (29) above, wherein the peelable surface is a surface of a peeling layer formed by a polysilicone-based peeling treatment agent. Example

Hereinafter, several embodiments of the present invention will be described, but it is not intended to limit the present invention to the specific embodiments. Furthermore, "parts" and "%" in the following description are by weight unless otherwise specified.

(Preparation of polymer A1) In a reaction vessel equipped with a stirring blade, a thermometer, a nitrogen inlet tube and a cooler, 60 parts of 2-ethylhexyl acrylate (2EHA), 15 parts of N-vinyl-2-pyrrolidone (NVP), 10 parts of methyl methacrylate (MMA), 15 parts of 2-hydroxyethyl acrylate (HEA), and 200 parts of ethyl acetate as a polymerization solvent were added, and stirred at 60°C in a nitrogen environment for 2 hours. Then, 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) as a thermal polymerization initiator was added, and the reaction was carried out at 60°C for 6 hours to obtain a solution of polymer A1. The Mw of the polymer A1 is 1.1 million.

(Preparation of polymer B1) In a reaction vessel equipped with a stirring blade, a thermometer, a nitrogen inlet tube and a cooler, 40 parts of MMA, 20 parts of n-butyl methacrylate (BMA), 20 parts of 2-ethylhexyl methacrylate (2EHMA), 8.7 parts of a methacrylate monomer containing a polyorganosiloxane skeleton with a functional group equivalent of 900 g/mol (trade name: X-22-174ASX, manufactured by Shin-Etsu Chemical Co., Ltd.), and 4600 parts of a methacrylate monomer with a functional group equivalent of 4600 g/mol were added. 11.3 parts of methacrylate monomer containing polyorganosiloxane skeleton (trade name: KF-2012, manufactured by Shin-Etsu Chemical Co., Ltd.) with a weight of 0.05 g/mol, 100 parts of ethyl acetate, and 0.5 parts of thioglycerol as a chain transfer agent were stirred at 70°C in a nitrogen environment for 1 hour, and then 0.2 parts of AIBN as a thermal polymerization initiator were added. After reacting at 70°C for 2 hours, 0.1 parts by weight of AIBN as a thermal polymerization initiator was added, and then reacted at 80°C for 5 hours. In this way, a solution of polymer B1 was obtained. The Mw of the polymer B1 was 2.2×10 ⁴ .

(Preparation of Polymer B2) A solution of Polymer B2 having a Mw of 7.5×10 ⁴ was obtained in the same manner as in the preparation of Polymer B1 except that the amount of thioglycerol used was changed to 0.1 part.

(Preparation of polymer B3) A solution of polymer B3 having a Mw of 16.5×10 ⁴ was obtained in the same manner as in the preparation of polymer B1 except that thioglycerol was not used.

(Preparation of polymer B4) In a reaction vessel equipped with a stirring blade, a thermometer, a nitrogen inlet tube and a cooler, 40 parts of MMA, 20 parts of BMA, 20 parts of 2EHMA, 8.7 parts of a methacrylate monomer containing a polyorganosiloxane skeleton with a functional group equivalent of 900 g/mol (trade name: X-22-174ASX, manufactured by Shin-Etsu Chemical Co., Ltd.), 11.3 parts of a methacrylate monomer containing a polyorganosiloxane skeleton with a functional group equivalent of 4600 g/mol (trade name: KF-2012, manufactured by Shin-Etsu Chemical Co., Ltd.) and 82 parts of ethyl acetate were added. After stirring at 65°C in a nitrogen atmosphere for 1 hour, 0.2 parts of AIBN was added. After reacting at 65°C for 4 hours, AIBN was added. 0.1 parts by weight, followed by reaction at 80°C for 4 hours. Thus, a solution of polymer B4 with a Mw of 23.4×10 ⁴ was obtained.

(Preparation of Polymer B5) A solution of Polymer B5 having a Mw of 29.6×10 ⁴ was obtained in the same manner as in the preparation of Polymer B4 except that the amount of ethyl acetate used was changed to 67 parts.

The weight average molecular weight of each polymer was measured using a GPC device (manufactured by Tosoh, HLC-8220GPC) under the following conditions and was obtained by conversion to polystyrene. [GPC conditions] ・Sample concentration: 0.2 wt% (tetrahydrofuran (THF) solution) ・Sample injection volume: 10 μl ・Eluent: THF, flow rate: 0.6 ml/min ・Measurement temperature: 40°C ・Column: Sample column: TSKguardcolumn SuperHZ-H (1 column) + TSKgel SuperHZM-H (2 columns) Reference column: TSKgel SuperH-RC (1 column) ・Detector: Differential refractometer (RI)

<Preparation of adhesive sheet> (Example 1) In a solution of polymer A1, 5 parts of polymer B1 and 2.5 parts of an isocyanate crosslinking agent (trade name: Takenate D110N, trihydroxymethylpropane benzyl diisocyanate, manufactured by Mitsui Chemicals Co., Ltd.) were added to 100 parts of polymer A1 contained in the solution, and the mixture was uniformly mixed to prepare an adhesive composition C1. The adhesive composition C1 was directly applied to the first surface of a 75 μm thick polyethylene terephthalate (PET) film (manufactured by Toray Co., Ltd., trade name "Lumirror") as a supporting substrate, and dried by heating at 110°C for 2 minutes to form an adhesive layer with a thickness of 25 μm. The peeling surface of the peeling liner is attached to the surface (adhesive surface) of the adhesive layer. As the peeling liner, MRQ25T100 manufactured by Mitsubishi Chemical Corporation (a peeling liner having a peeling layer formed by a silicone-based peeling treatment agent on one side of a polyester film, with a thickness of 25 μm) is used. In this way, the peeling liner-attached adhesive sheet of Example 1 is obtained in which the peeling surface of the peeling liner is abutted on the adhesive surface.

(Examples 2 to 8) The type and amount of polymer B were changed as shown in Table 1, and adhesive compositions C2 to C8 were prepared in the same manner as adhesive composition C1. The adhesive compositions C2 to C11 were used respectively, and in the same manner as the adhesive sheet of Example 1, the adhesive sheets of Examples 2 to 8 were obtained in the form of adhesive sheets with a peeling liner on their adhesive surfaces.

<Measurement of Adhesion (23°C)> The adhesive sheets of each example were cut into 25 mm width together with the peeling pad, and the same was used as test pieces. The SUS plate (SUS304BA plate) cleaned with toluene was used as the adherend, and the adhesion _N23 , adhesion _N50 and adhesion _N80 were measured according to the following procedure. (Measurement of Adhesion _N23 ) In a standard environment of 23°C and 50%RH, the peeling pad covering the adhesive surface of each test piece was peeled off, and the exposed adhesive surface was pressed against the adherend by moving a 2 kg roller back and forth once. After the test piece pressed against the adherend was placed in the above standard environment for 30 minutes, the 180° peeling adhesion (relative to the above stretching resistance) was measured using a universal tensile compression tester (device name "tensile compression tester, TCM-1kNB" manufactured by Minebea) according to JIS Z0237 at a peeling angle of 180 degrees and a stretching speed of 300 mm/min. The measurement was performed 3 times, and the average value was shown in Table 1 as the adhesion N ₂₃ [N/25 mm]. (Measurement of Adhesion N ₅₀ ) The test piece pressed onto the adherend in the same manner as the above-mentioned Adhesion N ₂₃ was kept in an environment of 50°C for 30 minutes, and then placed in the above-mentioned standard environment for 30 minutes, and then the 180° peel adhesion was measured in the same manner. The measurement was performed 3 times, and the average value thereof was shown in Table 1 as Adhesion N ₅₀ [N/25 mm]. (Measurement of Adhesion N ₈₀ ) The test piece pressed onto the adherend in the same manner as the above-mentioned Adhesion N ₂₃ was heated at 80°C for 5 minutes, and then placed in the above-mentioned standard environment for 30 minutes, and then the 180° peel adhesion was measured in the same manner. The measurement was performed three times, and the average value thereof was shown as the adhesion force N ₈₀ [N/25 mm] in Table 1. Furthermore, it was confirmed that the adhesive sheets of Examples 1 to 11 did not suffer from grip failure during the measurement of the adhesion force N ₈₀ .

<Measurement of 80℃ Adhesion _NH > After the test piece pressed to the adherend in the same manner as the above-mentioned adhesion _N23 was kept in an environment at 80℃ for 30 minutes, the 180° peel adhesion was measured in the same environment as above. The measurement was performed 3 times, and the average value thereof was shown in Table 1 as the 80℃ adhesion _NH [N/25 mm]. Based on the adhesion measurement results, the adhesion increase ratio _N80 / _N50 and _N50 / _N23 and the heat-resistant adhesion maintenance rate _NH / _N80 were calculated. The results are shown in Table 1.

[Table 1] Table 1 example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Polymer B Type B3 B4 B5 B2 B1 Mw(×10 ⁴ ) 16.5 23.4 29.6 7.5 2.2 Amount ¹⁾ [parts by weight] 5 7.5 7.5 7.5 5 7.5 5 7.5 Adhesion (23℃) [N/25 mm] N ₂₃ 0.8 1.0 0.9 0.6 1.0 0.8 0.7 0.5 N ₅₀ 3.8 2.8 3.8 3.0 8.0 7.0 12.0 7.8 N ₈₀ 23.0 20.8 23.8 23.4 24.5 22.2 22.2 19.8 Adhesion force increase ratio N ₈₀ /N ₅₀ 6.1 7.4 6.3 7.8 3.1 3.2 1.8 2.5 _N50 / _N23 4.8 2.8 4.2 5.0 8.0 8.8 17.1 15.5 80℃ Adhesion strength [N/25 mm] N _H 4.5 5.0 4.0 6.0 3.0 3.0 2.2 2.8 Heat-resistant adhesion retention rate (%) _NH /N ₈₀ 20% twenty four% 17% 26% 12% 14% 10% 14% 1) The amount of polymer B used relative to 100 parts by weight of polymer A

As shown in Table 1, Examples 1 to 6 using polymer B having an Mw of 7×10 ⁴ or more were confirmed to have a N ₈₀ /N ₅₀ of 3 or more, and thus maintained low tack suitable for secondary processing even at a temperature of about 50°C at the initial stage of attachment, and the adhesive force could be significantly increased by heating at 80°C for 5 minutes. The adhesive sheets of Examples 1 to 4 obtained particularly good results.

The specific examples of the present invention are described in detail above, but these are only examples and do not limit the scope of the patent application. The technology described in the scope of the patent application includes various changes and modifications of the specific examples described above.

1: Adhesive sheet 2: Adhesive sheet 3: Adhesive sheet 10: Support substrate 10A: First side 10B: Second side 21: Adhesive layer (first adhesive layer) 21A: Adhesive surface (first adhesive surface) 21B: Adhesive surface (second adhesive surface) 22: Adhesive layer (second adhesive layer) 22A: Adhesive surface (second adhesive surface) 31: Peel-off pad 32: Peel-off pad 100: Adhesive sheet with peel-off pad (adhesive product) 200: Adhesive sheet with peel-off pad (adhesive product) 300: Adhesive sheet with peel-off pad (adhesive product)

FIG. 1 is a cross-sectional view schematically showing the structure of an adhesive sheet in one embodiment. FIG. 2 is a cross-sectional view schematically showing the structure of an adhesive sheet in another embodiment. FIG. 3 is a cross-sectional view schematically showing the structure of an adhesive sheet in another embodiment.

1: Adhesive sheet

10: Support substrate

10A: First side

10B: Second side

21: Adhesive layer (first adhesive layer)

21A: Adhesive surface (first adhesive surface)

31: Peel off the liner

100: Adhesive sheet with peel-off liner (adhesive product)

Claims (8)

An adhesive sheet includes an adhesive layer, wherein the adhesive layer contains a polymer A as a monomer raw material A and a polymer B as a monomer raw material B, wherein the monomer raw material A contains a (meth) acrylate alkyl ester as a main component, and the monomer raw material B contains a monomer having a polyorganosiloxane skeleton and a (meth) acrylic monomer, wherein the weight average molecular weight of the polymer B is 7×10 ⁴ or more, and the amount of the polymer B used is more than 5 parts by weight relative to 100 parts by weight of the polymer A used, and the relationship between the adhesive force N ₅₀ measured at 23° C. after the adhesive sheet is attached to a stainless steel plate and kept at 50° C. for 30 minutes and the adhesive force N 80 measured at 23° C. after the adhesive sheet is attached to a stainless steel plate and heated at ₈₀ ° C. for 5 minutes satisfies the following formula: (N ₈₀ /N ₅₀ )≧3, the relationship between the above-mentioned adhesion N ₅₀ and the adhesion N ₂₃ measured at 23°C after being bonded to a stainless steel plate and placed at 23°C for 30 minutes satisfies the following formula: (N ₅₀ /N ₂₃ )<7. The adhesive sheet of claim 1, wherein the relationship between the adhesive force _N80 and the adhesive force _NH measured at 80°C after being bonded to a stainless steel plate and kept in an environment of 80°C for 30 minutes satisfies the following formula: ( _NH / _N80 )≧15%. As in the adhesive sheet of claim 1 or 2, the (meth) acrylic monomer contained in the monomer raw material B includes a monomer M2 whose homopolymer has a glass transition temperature of 50°C or above. As in claim 3, the adhesive sheet, wherein the monomer M2 comprises alkyl (meth)acrylate. As in the adhesive sheet of claim 1 or 2, the content of the polymer B in the adhesive layer is less than 50 parts by weight relative to 100 parts by weight of the polymer A. As in the adhesive sheet of claim 1 or 2, wherein the monomer raw material A comprises a monomer having a ring containing a nitrogen atom. As in the adhesive sheet of claim 1 or 2, the adhesive layer contains more than 0 weight parts and less than 10 weight parts of a crosslinking agent relative to 100 weight parts of the polymer A. The adhesive sheet of claim 1 or 2 has a supporting substrate having a first surface and a second surface, and the adhesive layer is laminated on at least the first surface of the supporting substrate.