TWI843788B - Adhesive Sheet - Google Patents

Abstract

The present invention provides a novel adhesive sheet that can show good secondary processability in the initial stage of being attached to an adherend, and can subsequently significantly increase the adhesive force in a short time by gentle heating at about 50°C. The present invention provides an adhesive sheet comprising an adhesive layer. The above-mentioned adhesive layer comprises polymer A and polymer B, and the polymer B is a copolymer of a monomer having a polysiloxane skeleton and a (meth) acrylic monomer. The adhesive sheet shows an adhesive force _N50 of more than 5 N/25 mm. Here, the adhesive force _N50 refers to the adhesive force measured at 23°C after being attached to a stainless steel plate and kept at 50°C for 15 minutes.

Description

Adhesive Sheet

The present invention relates to an adhesive sheet. This application claims priority based on Japanese Patent Application No. 2019-001349 filed on January 8, 2019, 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 objects to adherends, and reinforcing adherends by firmly adhering to them. Previously, for such purposes, adhesive sheets that exhibited high adhesive force from the initial stage of attachment were used. Moreover, recently, as shown in patent documents 1 to 3, an adhesive sheet that exhibits low adhesive force at the initial stage of attachment to an adherend and then greatly increases the adhesive force has been proposed. According to an adhesive sheet having such characteristics, before the adhesive force increases, the re-adhesiveness (secondary processing property) that is useful for suppressing the reduction in yield caused by the wrong 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 literature Patent literature

Patent document 1: Japanese Patent Application Publication No. 2014-224227 Patent document 2: Japanese Patent No. 5890596 Patent document 3: Japanese Patent No. 5951153

[The problem the invention is trying to solve]

The adhesive sheet described in the above-mentioned prior art document has a structure that shows low adhesion at the initial stage of attachment, and the adhesion increases to a specified value or more by being exposed to a high temperature of about 80°C or being placed for about 2 days. In this way, the increase in adhesion is reliably controlled. In addition, the use of such adhesive sheets includes the use in the manufacturing process of products, etc. In such uses, from the perspective of improving the efficiency (production efficiency) in the manufacturing process, it may be beneficial to increase the adhesion with a simpler process. For example, if an adhesive sheet is provided that can increase the adhesion in a short time by heating closer to room temperature (mild heating), the adhesion increase process can be effectively and uniformly implemented, which may be beneficial in terms of improving production efficiency. Adhesive sheets with such characteristics can be applied to adherends that are not suitable for exposure to high temperatures, and thus new applications can be expected. Therefore, the purpose of the present invention is to provide a novel adhesive sheet that can show good secondary processing properties at the initial stage of attachment to the adherend, and can then be heated gently at about 50°C to significantly increase the adhesive force in a short time. [Technical means to solve the problem]

According to the present specification, an adhesive sheet including an adhesive layer is provided. The adhesive layer includes polymer A and polymer B, and the polymer B is a copolymer of a monomer having a polyorganosiloxane skeleton and a (meth) acrylic monomer. The adhesive sheet exhibits an adhesive force _N50 of 5 N/25 mm or more. Here, the adhesive force _N50 refers to the adhesive force measured at 23°C after being attached to a stainless steel plate and kept at 50°C for 15 minutes.

The adhesive sheet of the above structure can show good secondary processing properties at the initial stage of attachment due to the effect of the polymer B having a polyorganosiloxane skeleton. Thereafter, the adhesive strength can be increased to a predetermined value or above by gentle heating at about 50°C.

The adhesive force _N23 of several better adhesive sheets after being bonded to a stainless steel plate and kept at 23°C for 30 minutes is less than 3 N/25 mm. The adhesive sheet meeting this characteristic has a relatively low adhesive force at the initial stage of bonding, thus showing good secondary processability. That is, it is able to take into account both the initial light peelability (secondary processability) and the increase in adhesive force after mild heating.

Regarding some preferred adhesive sheets, the above-mentioned adhesive force _N50 is 5 times or more of the adhesive force _N23 measured after being attached to a stainless steel plate and kept at 23°C for 30 minutes. According to the adhesive sheet whose adhesive force _N50 is 5 times or more of the adhesive force _N23 ( _N50 / _N23 ≧5) as described above, good secondary processability can be exhibited at the initial stage of attachment, and the adhesive force can be greatly increased by subsequent heating or the like.

The adhesive force _N80 of some types of adhesive sheets measured at 23°C after being attached to a stainless steel plate and kept at 80°C for 5 minutes can be less than 2 times the above-mentioned adhesive force _N50 (i.e., _N80 / _N50 ≦2). The adhesive sheet satisfying this characteristic can sufficiently increase its adhesive force by gentle heating at about 50°C, so it is not necessary to expose it to a further high temperature (specifically, heating at about 80°C) in order to obtain strong adhesive force. According to the adhesive sheet satisfying this characteristic, the adhesive force can be efficiently increased to the required level than before.

In addition, the storage elastic modulus G'(150°C) of the adhesive layer at 150°C is preferably not less than 10,000 Pa and not more than 90,000 Pa. The adhesive layer satisfying the above storage elastic modulus at 150°C can easily exert good adhesive properties and polymer B can easily move in the adhesive layer, so based on its mobility, the adhesive force can be well increased after mild heating.

In the technology disclosed herein, the polymer A contained in the adhesive layer is typically chemically cross-linked. Thereby, the adhesive sheet can exhibit good adhesive properties. Moreover, in a structure in which the degree of cross-linking is limited in such a manner that the storage elastic modulus G'(150°C) becomes below a specified value, an increase in adhesion after mild heating can be well achieved based on the mobility of polymer B in the adhesive layer. In some embodiments, the adhesive layer may contain a cross-linking agent 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 cross-linking agent, chemical cross-linking that satisfies the required properties can be well achieved, and the storage elastic modulus G'(150°C) within the specified range can be well achieved.

In some aspects, the weight average molecular weight of the polymer B can be 100,000 or more. In the aspect using a polymer B having an Mw above the specified value, the effects of the technology disclosed herein can also be well achieved.

In some preferred embodiments, the weight average molecular weight of the polymer B may be less than 80,000. By using a polymer B having an Mw value less than the specified value, the adhesion after mild heating can be well improved.

In some aspects, the content of the polymer B in the adhesive layer can be set to, for example, 0.5 parts by weight or more and 50 parts by weight or less relative to 100 parts by weight of the polymer A. If the content is within the above range, the adhesion after mild heating can be well achieved.

The polymer A is preferably an acrylic polymer. The adhesive layer comprising the polymer A which is an acrylic polymer and the polymer B which is a copolymer of a monomer having a polyorganosiloxane skeleton and a (meth)acrylic monomer can well achieve an increase in adhesiveness after mild heating.

In some embodiments, the acrylic polymer preferably comprises a monomer having a ring containing a nitrogen atom as its monomer unit. The polymer A comprising a monomer having a ring containing a nitrogen atom can achieve good adhesion increase after mild heating by using it in combination with the polymer B.

In some preferred embodiments, the monomer components used to prepare the polymer B include a monomer having a homopolymer glass transition temperature of 50°C or higher as the (meth) acrylic monomer (monomer M2) at a ratio of 60 wt% or lower. In the polymer B, by limiting the copolymerization ratio of the monomer M2 having a Tg of 50°C or higher to a prescribed value or lower, it is possible to achieve a good increase in adhesion after mild heating based on the mobility of the polymer B around 50°C. As the monomer M2, an alkyl (meth)acrylate having a homopolymer Tg of 50°C or higher can be preferably used.

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

Furthermore, according to the present specification, an adhesive sheet including an adhesive layer is provided. The adhesive layer includes polymer A and polymer B, and the polymer B is a copolymer of a monomer having a polyorganosiloxane skeleton and a (meth) acrylic monomer. Moreover, the storage elastic modulus G'(150°C) of the adhesive layer at 150°C is greater than 10,000 Pa and less than 90,000 Pa. The adhesive sheet having an adhesive layer satisfying the above-mentioned storage elastic modulus at 150°C can show good secondary processability based on the effect of polymer B, and the adhesive force can be increased by gentle heating at about 50°C thereafter.

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 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, which includes 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 peelable 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 peelable liner 31 and 32 that are at least opposite to the adhesive layers 21 and 22 and serve as peelable 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 it 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 an 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 at least a peel-off liner 31, 32 on the side opposite to the adhesive layer 21, which respectively serves as a peel-off surface. Alternatively, the peeling pad 32 may be omitted and a peeling pad 31 with 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 random patterns such as dots or strips.

<Adhesive layer> The adhesive sheet disclosed herein has an adhesive layer comprising a polymer A and a polymer B, wherein the polymer B is 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 which is 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 obtains better properties in the adhesive sheet disclosed herein. In some aspects, polymer A having a _{TA of} less than 0°C can be well used. The adhesive containing such polymer A exhibits moderate fluidity (e.g., the mobility of the polymer chains contained in the adhesive), and is therefore suitable for realizing an adhesive sheet whose adhesive force is increased to a value above a specified value by gentle 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 aspects, _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 preferred. In some embodiments, _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 having a lower adhesion in the initial stage of attachment and a higher adhesion after mild 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 described later 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. Hydroxy-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, (4-hydroxymethylcyclohexyl)methyl (meth)acrylate and other hydroxyalkyl (meth)acrylates, etc. 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-vinyloxaline, N-vinyl-3-oxaline, N-vinyl-2-caprolactam, N-vinyl-1,3-oxaline 2-oxo-1,4-dione, N-vinyl-3,5-oxo-1,4-dione, N-vinylpyrazole, N-vinylisothiazole, N-vinylthiazole, N-vinylisothiazole, N-vinylpyrazole, etc.; Monomers having a succinimide skeleton such as N-(methyl)acryloxymethylenesuccinimide, N-(methyl)acryl-6-oxyhexamethylenesuccinimide, and N-(methyl)acryl-8-oxyhexamethylenesuccinimide; For example, citric acid imides such as N-cyclohexyl citric acid imide, N-isopropyl citric acid imide, N-lauryl citric acid imide, N-phenyl citric acid imide, etc.; and Iconimides such as N-methyliconimide, N-ethyliconimide, N-butyliconimide, N-octyliconimide, N-2-ethylhexyliconimide, N-cyclohexyliconimide, N-lauryliconimide, etc. Carboxyl group-containing monomers: such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, citric acid, fumaric acid, butyric acid, isobutyric acid, etc. 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, 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-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, etc. -dialkyl (meth) acrylamide; N-alkyl (meth) acrylamide such as N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, N-n-butyl (meth) acrylamide; N-vinyl carboxylic acid amides such as N-vinyl acetamide; monomers having hydroxyl and amide groups, such as N-(2-hydroxyethyl) (methyl 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 (Meth)acrylamide; monomers having alkoxy and amide groups, such as N-methoxymethyl (meth)acrylamide, N-methoxyethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide and other N-alkoxyalkyl (meth)acrylamide; in addition, N,N-dimethylaminopropyl (meth)acrylamide, N-(meth)acrylamide, etc. (Meth)acrylic acid aminoalkyl esters: such as (meth)acrylic acid aminoethyl ester, (meth)acrylic acid N,N-dimethylaminoethyl ester, (meth)acrylic acid N,N-diethylaminoethyl ester, (meth)acrylic acid tert-butylaminoethyl ester. Alkoxy-containing monomers: for example, 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxypropyl (meth)acrylate, and other (meth)acrylate alkoxyalkyl esters; (meth)acrylate methoxyethylene glycol, (meth)acrylate methoxypolypropylene glycol, and other (meth)acrylate alkoxyalkylene glycol esters. Monomers containing sulfonic acid or phosphoric acid groups: for example, styrene sulfonic acid, allyl sulfonic acid, sodium vinyl sulfonate, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamide propanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, 2-hydroxyethylacryloyl phosphate, and the like. (Meth)acrylates with alicyclic hydrocarbon groups: for example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobutyl (meth)acrylate, dicyclopentyl (meth)acrylate, etc. (Meth)acrylates with 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 or ethyl vinyl ether. Vinyl esters: for example, vinyl acetate, vinyl propionate, etc. Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyl toluene, etc. Olefins: for example, ethylene, butadiene, isoprene, isobutylene, etc. In addition, heterocyclic (meth)acrylates such as tetrahydrofuranyl (meth)acrylate, halogen atom-containing (meth)acrylates such as vinyl chloride or fluorine atom-containing (meth)acrylates, silicon atom-containing (meth)acrylates such as polysiloxane (meth)acrylate, and (meth)acrylates obtained from terpene compound derivative alcohols may be used.

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 cohesive force or polarity of the adhesive can be adjusted, and the adhesive force after mild heating can be improved. By making the monomer raw material A contain a monomer having a ring containing a nitrogen atom, there is a tendency for the compatibility between the polymer A formed from the above monomer raw material A and the above polymer B to be improved. In this way, it is easy to obtain an adhesive sheet whose adhesive force can be greatly increased by mild heating.

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-oxo-1-olactone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxo-2-olactam, and N-vinyl-3,5-oxo-1-olactam. 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.

In some preferred embodiments, the monomer raw material A contains a hydroxyl-containing monomer. By using a hydroxyl-containing monomer, the cohesive force or polarity of the adhesive can be adjusted, and the adhesion after mild heating can be improved. In addition, the hydroxyl-containing monomer provides a reaction point with the following crosslinking agent (for example, an isocyanate crosslinking agent), and the cohesive force of the adhesive can be improved by a crosslinking reaction.

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 appropriately set to 0.01% by weight or more of the monomer raw material A (preferably 0.1% by weight or more, for example 0.5% by weight or more). 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 mobility of polymer B in the adhesive layer, or improving the stickiness at room temperature (25°C) and the softness at low temperatures, the amount of the hydroxyl-containing monomer used is usually appropriately 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 or less.

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, due to the low polarity and mobility of the polyorganosiloxane structure of monomer S1, can function as an adhesion increase delay agent that suppresses the initial adhesion to the adherend and increases the adhesion to the adherend by heating. There is no particular limitation as monomer S1, and any monomer containing a polyorganosiloxane skeleton can be used. Monomer S1, due to the low polarity of its structure, promotes polymer B to lean toward the surface of the adhesive layer in the adhesive sheet before use (before attachment to the adherend), showing 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 preferably 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 with such a structure tends to have a lower initial adhesion and a higher adhesion after mild heating due to the mobility and ease of movement of the side chain. Moreover, 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 preferably used. The polymer B formed by copolymerizing the monomer S1 with 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 sufficiently suppressing the initial adhesion, the functional group equivalent is, for example, 100 g/mol or more, 200 g/mol or more, preferably 300 g/mol or more (for example, 500 g/mol or more), preferably 700 g/mol or more, more preferably 800 g/mol or more, further preferably 850 g/mol or more, and particularly preferably 1500 g/mol or more. In some aspects, from the perspective of both low adhesion at the initial stage of attachment and increased adhesion after mild heating, the functional group equivalent may be 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, or 15000 g/mol or more (e.g., 16000 g/mol or more). The functional group equivalent of monomer S1 may be, for example, 50000 g/mol or less. From the perspective of sufficiently increasing adhesion, the functional group equivalent is, for example, preferably 30000 g/mol or less, and more preferably 20000 g/mol or less. In some aspects, the functional group equivalent weight of monomer S1 may be 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. 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 the base polymer) or mobility in the adhesive layer to an appropriate range, and it is easy to achieve an adhesive layer that takes into account both low initial adhesion and increased adhesion after mild heating.

Non-limiting examples of preferred ranges of the functional group equivalent weight of monomer S1 include: 700 g/mol to 50,000 g/mol, 700 g/mol to 30,000 g/mol, 700 g/mol to 20,000 g/mol, 700 g/mol to 18,000 g/mol, 700 g/mol to 15,000 g/mol, 800 g/mol to 10,000 g/mol, 850 g/mol to 6,000 g/mol, and 1,500 g/mol to 5,000 g/mol. In some embodiments, the functional group equivalent weight of monomer S1 is preferably in a range of 3000 g/mol to 50000 g/mol, 6000 g/mol to 50000 g/mol, 12000 g/mol to 50000 g/mol, or 15000 g/mol to 50000 g/mol.

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 content of monomer S1 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, in the total amount of the monomer component (monomer raw material B) used to prepare the polymer B, for example, it can be set to 5% by weight or more. From the perspective of better exerting the effect as an adhesion increase delay agent, it is preferably set to 10% by weight or more, and can be set to 15% by weight or more, and can also be set to 20% by weight or more. In addition, from the perspective of polymerization reactivity or compatibility, the content of monomer S1 in the monomer raw material B can be, for example, 80% by weight or less, preferably 60% by weight or less, 50% by weight or less, 40% by weight or less, and 30% by weight or less. If the content of monomer S1 is less than 5% by weight, the initial adhesion may not be sufficiently suppressed. If the content of monomer S1 is more than 60 wt %, the increase in adhesion may become insufficient.

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 or more and 95% by weight or less, 20% by weight or more and 95% by weight or less, 30% by weight or more and 90% by weight or less, 40% by weight or more and 90% by weight or less, or 50% by weight or more and 85% by weight or less. From the perspective of the ease of increasing the adhesive force by gentle heating, 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 whose homopolymer Tg is 50°C or higher. In polymer B, by copolymerizing monomer S1 and monomer M2, it is easy to well control the mobility or mobility of the polyorganosiloxane structure portion accompanying the temperature rise, thereby achieving a balance between the initial light peelability (secondary processability) and the increase in adhesion after mild heating. In some embodiments, the Tg of the homopolymer of monomer M2 may be above 60°C, above 70°C, above 80°C, or above 90°C. In addition, there is no particular restriction on the upper limit of the Tg of the homopolymer of monomer M2. From the perspective of the ease of synthesis of polymer B, it is usually suitable to be below 200°C. In some aspects, the Tg of the homopolymer of the monomer M2 may be, for example, below 180° C., below 150° C., or below 120° C.

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 where the monomer raw material B includes the monomer M2, the content of the monomer M2 may be, for example, 5% or more of the monomer raw material B, 10% or more, 15% or more, 20% or more, 25% or more, or 30% or more. In some aspects, the content of the above-mentioned monomer M2 may be 35% or more of the monomer raw material B, 40% or more, 45% or more, 50% or more, or 55% or more. Furthermore, the content of the above-mentioned monomer M2 may be, for example, 90% or less, usually 80% or less, preferably 75% or less, 70% or less, or 65% or less. In some preferred aspects, the content of the monomer M2 is 60% or less (e.g., 50% or less, typically 42% or less). In polymer B, by limiting the copolymerization ratio of monomer M2 having a Tg of 50°C or higher to a prescribed value or lower, it is possible to achieve a good increase in adhesion after mild heating based on the mobility of polymer B near 50°C. From a similar point of view, the content of monomer M2 in monomer raw material B may be 35% by weight or lower, 25% by weight or lower, or 15% by weight or lower (e.g., 5% by weight or lower).

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 adhesiveness and cohesiveness after the adhesiveness 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 more monomers selected from the group consisting of (meth)acrylic acid alkyl esters 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 becomes higher, the mobility of the polymer B is likely to be insufficient and it may be difficult to increase the adhesion by heating to a temperature region higher than 50°C.

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, an adhesive sheet with a larger _N50 can be easily obtained. 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. In some preferred embodiments, the ratio of MMA to the total amount of the above-mentioned (meth) acrylic monomers can be 75 weight % or less, 65 weight % or less, 60 weight % or less, or 55 weight % or less (for example, 50 weight % or less) from the perspective of increasing adhesion after mild heating.

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 Mw of polymer B is not particularly limited. The Mw of polymer B may be, for example, 1000 or more, or 5000 or more. From the perspective of showing a good increase in adhesion after mild heating, the Mw of polymer B may be, for example, 10,000 or more, 12,000 or more, 15,000 or more, or 20,000 or more. In some embodiments, the Mw of polymer B may be 50,000 or more, 80,000 or more, 100,000 or more, or 120,000 or more (for example, 150,000 or more). The upper limit of the Mw of polymer B may be, for example, 500,000 or less, 350,000 or less, 350,000 or less, or less than 100,000. From the viewpoint of adjusting the compatibility or mobility in the adhesive layer to an appropriate range and showing a good increase in adhesion after mild heating, the Mw of polymer B may be less than 80,000, less than 70,000, less than 50,000, less than 40,000, less than 20,000, or even less than 10,000.

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 realize an adhesive sheet that takes into account both good secondary processability in the initial stage of attachment and increased adhesive force after mild heating. The Mw of polymer B can be, for example, 0.8 times or less, 0.75 times or less, 0.5 times or less, 0.3 times or less, 0.1 times or less, 0.05 times or less, or 0.03 times or less (e.g., 0.02 times or less) the Mw of polymer A.

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 viewpoint 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 viewpoint 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, 10 parts by weight or less, 8 parts by weight or less, 6 parts by weight or less, or 4 parts by weight or less (e.g., 3 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 above-mentioned arbitrary polymers 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 can 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 can 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. In particular, isocyanate crosslinking agents, epoxy crosslinking agents, and metal chelate crosslinking agents can be used well. The crosslinking agent can be used alone or in combination of two or more.

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, examples of the metal component include aluminum, iron, tin, titanium, nickel, etc., and examples of the chelate component include acetylene, methyl acetylacetate, ethyl lactate, etc. These may be used alone or in combination of two or more.

The amount of crosslinking agent used is not particularly limited, for example, it can be set to an amount exceeding 0 parts by weight relative to 100 parts by weight of polymer A. In addition, the amount of crosslinking agent used can be set to, for example, 0.01 parts by weight or more, preferably 0.05 parts by weight or more relative to 100 parts by weight of polymer A. By increasing the amount of crosslinking agent used, there is a tendency to suppress the adhesion in the initial stage of attachment and improve the secondary processability. In some embodiments, the amount of crosslinking agent used can be 0.1 parts by weight or more, 0.5 parts by weight or more, or 0.8 parts by weight or more relative to 100 parts by weight of polymer A. On the other hand, from the viewpoint of allowing the mobility of polymer B to be appropriate and obtaining an increase in adhesion after mild heating, the amount of the crosslinking agent used is usually appropriately set to 15 parts by weight or less, and can be set to 10 parts by weight or less, or can be set to 5 parts by weight or less, relative to 100 parts by weight of polymer A.

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 both good secondary processability at the initial stage of attachment and increased adhesion after mild heating, in some forms, the amount of the isocyanate crosslinking agent used can be, for example, 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.2 parts by weight or more (for example, 0.3 parts by weight or more), or, for example, 5 parts by weight or less, 3 parts by weight or less, 1.5 parts by weight or less, 1.2 parts by weight or less, or 0.8 parts by weight or less (for example, 0.6 parts by weight or less) relative to 100 parts by weight of 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 adhesive force after mild heating relative to the adhesive force 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. The upper limit of W _OH /W _NCO is not particularly limited. From the viewpoint of setting the crosslinking degree that allows the polymer B to move appropriately by mild heating, W _OH /W _NCO may be, for example, 500 or less, 200 or less, 100 or less, or 50 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 in the range of about 0.01 to 3.0 parts by weight relative to 100 parts by weight of polymer A. In some aspects, 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 initial adhesion and improve the secondary processability. On the other hand, from the perspective of ensuring the mobility of polymer B and controlling its movement with a cross-linked network to regulate the increase in adhesion after mild heating, 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.

(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 adhesive imparting 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. An adhesive sheet having a high adhesive force after heating can be easily obtained by using an adhesive imparting resin having a softening point above the above lower limit. The upper limit of the softening point is not particularly limited, and for example, it can be about 200°C or less (typically, 180°C or less). Furthermore, the softening point of the adhesive imparting 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 cohesion 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 storage modulus G'(150°C) of the adhesive layer at 150°C is appropriately set within a range where the adhesive force rises to a value above a specified value after mild heating, and is not limited to a specific range. In some embodiments, the storage modulus G'(150°C) of the adhesive layer can be set to 5000 Pa or more. From the perspective of obtaining good adhesive properties such as low adhesive force at the initial stage of attachment, it is preferably 10,000 Pa or more, more preferably 15,000 Pa or more, and further preferably 20,000 Pa or more (for example, 25,000 Pa or more), and can be 30,000 Pa or more, 40,000 Pa or more, and can also be 50,000 Pa or more. Furthermore, the storage elastic modulus G'(150°C) can be set to, for example, 300,000 Pa or less, 200,000 Pa or less, 150,000 Pa or less, or 100,000 Pa or less. In some preferred embodiments, the storage elastic modulus G'(150°C) is 90,000 Pa or less, 70,000 Pa or less, 50,000 Pa or less, 40,000 Pa or less, or 30,000 Pa or less, from the viewpoint of achieving a cross-linking degree that allows appropriate movement of the polymer B in the adhesive layer and thus improving the adhesive force after mild heating. The storage elastic modulus G'(150°C) of the adhesive layer can be adjusted according to the type or amount of the crosslinking agent, the molecular weight and molecular structure of the polymer A, etc. The storage elastic modulus G'(150°C) of the adhesive layer is measured by the method described in the examples described below.

The gel fraction of the adhesive constituting the adhesive layer is usually preferably in the range of 20.0% to 99.0%, preferably in the range of 30.0% to 90.0%, but is not particularly limited. By setting the gel fraction in the above range, the increase in adhesive force after mild heating can be well achieved. 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 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) can be used well as a base film. The "resin film" here refers to a non-porous structure, and typically refers to a resin film that does not substantially contain bubbles (no 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 resin film, those that can independently maintain their shape (free-standing type or non-correlated) can be preferably used. The resin film may be a single-layer structure or a multi-layer structure of two or more layers (for example, 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 substrate, 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 the 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-enhancing 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 in the form of 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 printability, reducing light reflectivity, and improving lamination adhesion. In addition, in the case of a double-sided adhesive sheet, the second side of the substrate can be subjected to a surface treatment similar to the surface treatment exemplified above as the surface treatment that can be applied to the first side of the substrate, if 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 properties, etc.) The adhesive sheet disclosed herein can show an adhesive force _N50 of 5 N/25 mm or more, i.e., the adhesive force measured at 23°C after being adhered to a stainless steel plate and kept at 50°C for 15 minutes. After the adhesive sheet meeting this property is adhered to the adherend, it is gently heated at about 50°C to increase the adhesive force to a value above the specified value. According to the technology disclosed herein, strong adhesion can be obtained by gentle heating, so the adhesion _N50 can be set to 7 N/25 mm or more, for example, it can be set to 10 N/25 mm or more, and further to 13 N/25 mm or more, 15 N/25 mm or more, 17 N/25 mm or more, 19 N/25 mm or more, 21 N/25 mm or more, 23 N/25 mm or more (for example, 25 N/25 mm or more). There is no particular limit to the upper limit of the adhesion _N50 . From the perspective of the ease of manufacturing or economy of the adhesive sheet, in some embodiments, the adhesion _N50 can be, for example, 70 N/25 mm or less, 50 N/25 mm or less, or 40 N/25 mm or less.

The adhesion N ₂₃ measured after being bonded to a stainless steel plate and kept at 23°C for 30 minutes is not particularly limited. In some embodiments, the adhesion N ₂₃ 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, 1.5 N/25 mm or less, 1.2 N/25 mm or less, or 1 N/25 mm or less. A lower adhesion N ₂₃ is better from the perspective of secondary processability. There is no particular limitation on the lower limit of the adhesion N ₂₃ , 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 increases, the adhesion N ₂₃ is usually preferably 0.1 N/25 mm or more. From the perspective of improving adhesion after heating, in some embodiments, the adhesion _N23 can be, for example, greater than 0.2 N/25 mm, greater than 0.5 N/25 mm, greater than 0.8 N/25 mm, or greater than 1.0 N/25 mm (e.g., greater than 1.5 N/25 mm).

The adhesive force _N80 measured at 23°C after being bonded to a stainless steel plate and kept at 80°C for 5 minutes is not particularly limited. In some embodiments, the adhesive force _N80 may 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, 17 N/25 mm or more, 20 N/25 mm or more, 25 N/25 mm or more, or 30 N/25 mm or more (for example, 35 N/25 mm or more). In addition, from the perspective of ease of manufacturing or economy of the adhesive sheet, in some embodiments, the adhesive force _N80 may be, for example, 70 N/25 mm or less, 50 N/25 mm or less, or 40 N/25 mm or less.

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 not particularly limited. In some aspects, N ₅₀ /N ₂₃ is preferably 2 or more (e.g., 3 or more), preferably 5 or more, more preferably 8 or more, 10 or more, 12 or more, 15 or more, 18 or more, or 20 or more. An adhesive sheet with a large N ₅₀ /N ₂₃ can show good secondary processability at the initial stage of attachment, and the adhesive force can be greatly increased by subsequent heating or the like. The upper limit of _N50 / _N23 is not particularly limited, and is usually 100 or less, 80 or less, 60 or less, or 50 or less. From the viewpoint of ease of manufacturing or economy of the adhesive sheet, it is typically 30 or less, or 20 or less. In some aspects, _N50 / _N23 may be, for example, 18 or less, 15 or less, or 12 or less.

The ratio of the adhesive force N ₈₀ [N/25 mm] to the adhesive force N ₅₀ [N/25 mm], i.e., the adhesive force increase ratio N ₈₀ /N ₅₀ is not particularly limited. In some embodiments, N ₈₀ /N ₅₀ is preferably 3 or less, preferably 2 or less, for example, 1.8 or less, or 1.5 or less (for example, 1.3 or less). According to the adhesive sheet satisfying this characteristic, the adhesive force can be sufficiently increased by gentle heating at about 50°C, and there is no need to expose to further high temperature (specifically, heating at about 80°C) to obtain the required adhesive force. The lower limit of N ₈₀ /N ₅₀ is not particularly limited, and from the viewpoint of ease of manufacturing the adhesive sheet or economy, in several aspects, it may be, for example, 1 or more, 1.2 or more, 1.4 or more, or 1.6 or more.

Here, the adhesion force N ₂₃ [N/25 mm] is determined 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, after being pressed onto a stainless steel (SUS) plate as an adherend for 30 minutes. Adhesion force _N50 [N/25 mm] is determined by pressing the adherend to a SUS plate at 50°C for 15 minutes, then placing it at 23°C and 50% RH for 30 minutes, and then measuring the 180° peeling adhesion at a peeling angle of 180 degrees and a tensile speed of 300 mm/min. Adhesion force _N80 [N/25 mm] is determined by pressing a SUS plate as an adherend and heating it 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.

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 50°C for 15 minutes. For example, it can also be used in the usage without special heating 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 connection. In addition, the adhesive sheet disclosed here can be heated at a temperature of more than 30°C (for example, 50°C) or higher than 50°C at any time after attachment to promote the increase of 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 40°C, above 45°C, above 50°C, above 55°C, above 60°C, or above 70°C, may be above 80°C, or may be above 100°C. The heating time is not particularly limited, and may be, for example, less than 1 hour, less than 30 minutes, less than 10 minutes, or less than 5 minutes. Furthermore, the heating time may be, for example, more than 1 minute, more than 3 minutes, more than 7 minutes, or more than 15 minutes. Alternatively, the heat treatment may be performed for a longer time within the limit that the adhesive sheet or the adherend does not suffer significant thermal degradation. Furthermore, the heat treatment may be performed once or in multiple times.

(Adhesive sheet with substrate) When the adhesive sheet disclosed here is in the form of an adhesive sheet with substrate, the thickness of the adhesive sheet can 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 using the adhesive sheet, in some embodiments, the thickness of the adhesive sheet can 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 can 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, 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, it is easy to exert a good effect 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 made thinner, 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 on the supporting substrate to the extent that no peeling of the interface between the adhesive layer and the supporting substrate occurs 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 preferred 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 an adhesive force after heating of 15 N/25 mm or more and which does not cause gripping and damage when measuring the adhesive force after heating 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 does not limit 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 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 have the same composition or 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. Furthermore, regarding the surface of the second adhesive layer (second adhesive surface), the adhesive force _N50 may be less than 5 N/25 mm, less than 3 N/25 mm, less than 1.5 N/25 mm, or less than 1 N/25 mm.

<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 release layer can be formed using, for example, 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 silicone-based stripping 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 can, for example, exhibit good secondary processing properties at the initial stage of being attached to the adherend, thereby contributing to the suppression of yield reduction or the improvement of the quality of products containing the adhesive sheet. Moreover, the adhesive sheet can significantly increase its adhesive force by aging (which can be gentle heating around 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, shaping, 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 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 as a base film. 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 equipment). 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 well used in the form of being attached to various components in automobiles, home appliances, etc. 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 16.5×10 ⁴ was obtained in the same manner as in the preparation of polymer B1 except that thioglycerol was not used.

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 polystyrene conversion. [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, 2 parts of polymer B1 and 0.5 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 15 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 4) The type of polymer B or the amount of crosslinking agent used was changed as shown in Table 1. Adhesive compositions C2 to C4 were prepared in the same manner as the adhesive composition C1. The adhesive compositions C2 to C4 were used respectively. In the same manner as the adhesive sheet of Example 1, adhesive sheets of Examples 2 to 4 were obtained in the form of adhesive sheets with a peeling liner on the peeling surface of the adhesive surface.

<Storage elastic modulus G'(150℃)> The storage elastic modulus G'(150℃) of the adhesive layer was obtained by dynamic viscoelasticity measurement. Specifically, the adhesive layer was formed on the peeling surface of the peeling pad instead of the PET film, and the adhesive layer was formed under the same conditions as in each example, and the adhesive layer was stacked in multiple layers to form an adhesive layer with a thickness of about 2 mm. The obtained adhesive layer is punched into a disc shape with a diameter of 7.9 mm as a sample, and the sample is clamped and fixed by a parallel plate. The dynamic viscoelasticity is measured under the following conditions by a viscoelasticity tester (such as "ARES" manufactured by TA Instruments, or an equivalent product) to obtain the storage elastic modulus G' (150°C). Furthermore, the adhesive layer as the object of measurement can also be formed by applying the corresponding adhesive composition in a layer on the peeling surface of the peeling pad and drying or curing it. ・Measurement mode: Shear mode ・Temperature range: -50℃～200℃ ・Heating speed: 5℃/min ・Measurement frequency: 1 Hz

<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 thus pressed against the adherend was placed in the above standard environment for 30 minutes, a universal tensile compression tester (device name "tensile compression tester, TCM-1kNB" manufactured by Minebea) was used to measure the 180° peeling adhesion (relative to the above stretching resistance) under the conditions of a peeling angle of 180 degrees and a stretching speed of 300 mm/min in accordance with JIS Z0237. The measurement was performed 3 times, and the average value thereof was shown in Table 1 as the adhesion N ₂₃ [N/25 mm]. (Measurement of Adhesion _N50 ) The test piece pressed onto the adherend in the same manner as in the measurement of Adhesion ₂₃ was kept in an environment of 50°C for 15 minutes, then placed in the above 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 _N50 [N/25 mm]. (Measurement of Adhesion _N80 ) The test piece pressed onto the adherend in the same manner as in the measurement of Adhesion ₂₃ was heated at 80°C for 5 minutes, then placed in the above 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 adhesive force N ₈₀ [N/25 mm] in Table 1. Furthermore, it was confirmed that the adhesive sheets of Examples 1 to 4 did not suffer from grip failure during the measurement of the adhesive force N ₈₀ .

Based on the adhesion measurement results, adhesion increase ratios N ₈₀ /N ₅₀ and N ₅₀ /N ₂₃ were calculated. The results are shown in Table 1.

[Table 1] Table 1 example 1 Example 2 Example 3 Example 4 Polymer A1 [parts] 100 100 100 100 Polymer B1 [parts] 2 - 2 2 Polymer B2 [parts] - 2 - - Crosslinking agent [parts] 0.5 0.5 1.1 2.5 G'(150℃)[Pa] 26,000 26,000 53,000 104,000 Adhesion force N ₂₃ [N/25 mm] 1.2 2.8 0.9 0.6 Adhesion force N ₅₀ [N/25 mm] 26.8 26.7 12.9 8.2 Adhesion force N ₈₀ [N/25 mm] 35.7 33.4 22.5 19.1 _N50 / _N23 22.3 9.5 14.3 13.7 N ₈₀ /N ₅₀ 1.3 1.3 1.7 2.3

As shown in Table 1, the adhesive sheets of Examples 1 to 4 have an adhesive layer including polymer A and polymer B, wherein polymer B is a copolymer of a monomer having a polyorganosiloxane skeleton and a (meth) acrylic monomer, and the adhesive sheets of Examples 1 to 4 all show an adhesive force _N50 of 5 N/25 mm or more. It can be seen that the adhesive sheets can show good secondary processing properties at the initial stage of attachment, and then the adhesive force can be increased to a value above the specified value by gentle heating at about 50°C. In addition, in Examples 1 to 3 using an adhesive layer having a storage elastic modulus G'(150°C) of 10,000 Pa or more and 90,000 Pa or less at 150°C, particularly good results can be obtained. Specifically, the adhesion force N ₂₃ corresponding to the initial stage of attachment can be suppressed to a lower level, and the adhesion force N ₅₀ can be further increased.

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 surface) Second adhesive layer) 22A: Adhesive surface (second adhesive surface) 31: Peel-off liner 32: Peel-off liner 100: Adhesive sheet with peel-off liner (adhesive product) 200: Adhesive sheet with peel-off liner (adhesive product) 300: Adhesive sheet with peel-off liner (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 (10)

An adhesive sheet includes an adhesive layer, wherein the adhesive layer includes a polymer A, a polymer B and a crosslinking agent, wherein the polymer B is a copolymer of a monomer having a polyorganosiloxane skeleton and a (meth) acrylic monomer, wherein the polymer A is an acrylic polymer having a glass transition temperature of less than 0°C, wherein the polymer B does not have a functional group that can produce a crosslinking reaction with the polymer A, and wherein the weight average molecular weight of the polymer B is lower than that of the polymer A. The weight average molecular weight of the polymer A is 0.1 to 75 parts by weight of the polymer B in the adhesive layer relative to 100 parts by weight of the polymer A. The storage elastic modulus G' (150°C) of the adhesive layer at 150°C is 10,000 Pa to 50,000 Pa. The adhesive sheet is bonded to a stainless steel plate and maintained at 50°C for 15 minutes and then measured at 23°C. The adhesive force _N50 is 5N/25mm or more, the ratio of the adhesive force _N50 to the adhesive force _N23 measured after being bonded to a stainless steel plate and kept at 23°C for 30 minutes ( _N50 / _N23 ) is 12 or less, and the ratio of the adhesive force _N80 to the adhesive force _N50 ( _N80 / _N50 ) is 1.5 or less, where the adhesive force _N80 is the adhesive force _N80 measured at 23°C after being bonded to a stainless steel plate and kept at 80°C for 5 minutes. The adhesive sheet of claim 1, wherein the adhesive force _N23 is less than 3N/25mm. The adhesive sheet according to claim 1 or 2, wherein the ratio (N ₅₀ /N ₂₃ ) is 5 or more. As in the adhesive sheet of claim 1 or 2, the polymer A contained in the adhesive layer is chemically cross-linked. As in the adhesive sheet of claim 1 or 2, wherein the weight average molecular weight of the polymer B is greater than 100,000. For example, in the adhesive sheet of claim 1 or 2, the weight average molecular weight of the polymer B is less than 80,000. As in the adhesive sheet of claim 1 or 2, 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. As in claim 1 or 2, the adhesive sheet, wherein the acrylic polymer contains a monomer having a ring containing a nitrogen atom as its monomer unit. As in the adhesive sheet of claim 1 or 2, the monomer component used to prepare the above-mentioned polymer B contains a monomer having a homopolymer glass transition temperature of 50°C or above as the above-mentioned (meth) acrylic monomer at a ratio of less than 60% by weight. 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.