Reinforcing films, optical and electronic components

Abstract

To provide a reinforcing film that shows light peelability at first after stuck to an adherend and allows, thereafter, the adhesion to be increased greatly, and has flex recoverability and flex holding power.SOLUTION: There is provided a reinforcing film having an adhesive layer. The adhesive layer includes a polymer (A) and a polymer (B). The polymer (B) includes a monomer unit having a polyorganosiloxane skeleton and a (meth)acrylic monomer unit. The monomer unit having the polyorganosiloxane skeleton is derived from a polyorganosiloxane skeleton-containing monomer S1, and the polyorganosiloxane skeleton-containing monomer S1 has a functional group equivalent of 2000-7000 g / mol. The adhesive layer has a surface elastic modulus of 1-20 kPa at 23°C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a reinforcing film, and an optical member and an electronic member to which the reinforcing film is attached. [Background technology]

[0002] Pressure-sensitive adhesives in the form of pressure-sensitive adhesive sheets are widely used in various applications in portable electronic devices such as mobile phones, smartphones, and tablet computers, as well as other electronic devices, for purposes such as bonding adherends together or fixing articles to adherends. For example, pressure-sensitive adhesive sheets are used as reinforcing materials (reinforcing films) that impart rigidity and impact resistance to optical components, electronic components, and the like that make up the above-mentioned devices. Patent Documents 1 and 2 disclose prior art of this type.

[0003] Furthermore, in recent years, portable electronic devices that can be bent or rolled have been attracting attention, and the development of adhesive sheets that can be used to fix flexible devices (typically image display devices such as organic electroluminescence (EL) and liquid crystal display devices) built into such electronic devices is progressing (Patent Documents 3 to 6).

[0004] Meanwhile, looking at the performance of adhesives, recently, a pressure-sensitive adhesive sheet has been proposed that exhibits low adhesive strength when initially attached to an adherend, but can subsequently increase significantly in adhesive strength (Patent Document 7). Pressure-sensitive adhesive sheets with such properties exhibit reworkability (reworkability), which is useful for preventing yield losses due to incorrect or failed application of the pressure-sensitive adhesive sheet, before their adhesive strength increases, and can exhibit strong adhesive strength suitable for the intended use of the pressure-sensitive adhesive sheet after their adhesive strength increases. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6366199 [Patent Document 2] Patent No. 6366200 [Patent Document 3] Patent No. 6376271 [Patent Document 4] Japanese Patent Application Laid-Open No. 2016-108555 [Patent Document 5] Japanese Patent Application Publication No. 2017-095657 [Patent Document 6] Japanese Patent Application Publication No. 2017-095659 [Patent Document 7] Patent No. 6373458 Summary of the Invention [Problem to be solved by the invention]

[0006] The reinforcing film can also be used in the flexible device. For example, in the manufacture of the flexible device, since the components constituting the device are often thin, it is desirable to reinforce the device by attaching a pressure-sensitive adhesive sheet as a reinforcing film to prevent defects caused by deformation and improve handleability. Since flexible devices can be repeatedly folded or bent, the reinforcing film used in the flexible device is required to have the property of recovering its shape normally even after repeated bending (flexion recovery) and the property of preventing defects such as peeling (flexion retention). A reinforcing film having such flex recovery and flexion retention can be used in various applications, including flexible devices, and is therefore useful with few limitations on its range of application.

[0007] For example, even for adhesives that exhibit low adhesive strength initially after application but subsequently increase significantly, as proposed in Patent Document 7, it is desirable for them to have flex recovery and flex retention when used as a reinforcing film. One method for improving flex retention is to appropriately set the storage modulus of the adhesive. However, for adhesives designed to increase in adhesive strength as described above, changing the storage modulus affects both the initial low adhesive strength and the adhesive strength after increase. Furthermore, when considering flex recovery in addition to flex retention, it is not easy to satisfy all of these properties. It would be practically useful to be able to improve flex recovery and flex retention for adhesives that exhibit low adhesive strength initially after application but subsequently increase significantly in adhesive strength.

[0008] The present invention has been made in view of the above circumstances, and aims to provide a reinforcing film that exhibits easy peelability in the early stages after being attached to an adherend, and that is capable of significantly increasing its adhesive strength thereafter, and that also has flex recovery and flex retention. Another aim of the present invention is to provide optical components and electronic components to which the reinforcing film is attached. [Means for solving the problem]

[0009] According to the present specification, there is provided a reinforcing film including a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer includes a polymer (A) and a polymer (B). The polymer (B) includes a monomer unit having a polyorganosiloxane skeleton and a (meth)acrylic monomer unit. The monomer unit having a polyorganosiloxane skeleton included in the polymer (B) is derived from a polyorganosiloxane skeleton-containing monomer S1. The polyorganosiloxane skeleton-containing monomer S1 has a functional group equivalent of 2000 to 7000 g / mol. The pressure-sensitive adhesive layer has a surface elastic modulus at 23°C of 1 to 20 kPa.

[0010] According to the above configuration, the pressure-sensitive adhesive layer contains a polymer (A) and a polymer (B) containing a monomer unit having a polyorganosiloxane skeleton. This allows the layer to exhibit easy peelability initially after application to an adherend, and subsequently significantly increase its adhesive strength. Furthermore, when the functional group equivalent of the polyorganosiloxane skeleton-containing monomer S1 is 2000 g / mol or more, the layer tends to exhibit excellent easy peelability initially after application. When the functional group equivalent is 7000 g / mol or less, the layer tends to exhibit excellent increased adhesive strength. Furthermore, the reinforcing film has flex recovery and flex retention. Specifically, a reinforcing film having a surface modulus at 23°C (23°C surface modulus) of 1 kPa or more of the pressure-sensitive adhesive layer exhibits the above-mentioned adhesive properties while also exhibiting good flex recovery. Furthermore, when the surface modulus at 23°C of the pressure-sensitive adhesive layer is 20 kPa or less, the layer exhibits the above-mentioned adhesive properties while also exhibiting good flex retention. Therefore, even when the layer is used in a manner that requires repeated folding, problems such as peeling are unlikely to occur.

[0011] In some preferred embodiments of the technology disclosed herein (including reinforcing films, optical components, and electronic components; the same applies hereinafter), the pressure-sensitive adhesive layer has a bulk modulus G' at 23°C. 23 The bulk modulus G' in this range is 10 to 200 kPa. 23 The adhesive having the formula (I) tends to have an initial adhesive strength within a suitable range that provides excellent easy peelability, and also has excellent processability and generally tends to achieve both strain relaxation and flex recovery at room temperature.

[0012] In some preferred embodiments, the pressure-sensitive adhesive layer has a bulk modulus G' at 80°C 80 The bulk modulus G' in this range is 5 to 100 kPa. 80 Generally, a pressure-sensitive adhesive having the above structure can easily achieve both flex recovery and flex retention. For example, even when used under high temperature conditions of around 80°C, the pressure-sensitive adhesive can have an elasticity suitable for flex recovery and an adhesive retention that realizes flex retention.

[0013] In some preferred embodiments, the pressure-sensitive adhesive layer has a tan δ80 is 0.10 to 0.60. 80 (Loss modulus G″ at 80℃ 80 / Storage modulus G' at 80°C 80 ) is 0.10 or more, the adhesive is likely to exhibit adhesive strength suitable for bending and maintaining. 80 By making the ratio 0.60 or less, plastic deformation of the adhesive is suppressed, and good flex recovery is easily obtained. In addition, even when the reinforcing film is kept in a bent state for a long time, it is easy to exhibit a holding power (flexion holding power) that does not cause peeling from the adherend.

[0014] The polymer (A) is preferably an acrylic polymer. The effects of the technology disclosed herein are preferably achieved by a pressure-sensitive adhesive layer containing the polymer (A), which is an acrylic polymer, and the polymer (B), which contains a monomer unit having a polyorganosiloxane skeleton.

[0015] In some preferred embodiments, the content of the polymer (B) in the pressure-sensitive adhesive layer is 0.5 to 5 parts by weight per 100 parts by weight of the polymer (A). By setting the amount of polymer (B) to 0.5 parts by weight or more per 100 parts by weight of polymer (A), easy peelability at the initial stage of application is easily achieved. By setting the amount of polymer (B) to 5 parts by weight or less, the desired increase in adhesive strength is easily achieved. Furthermore, by setting the amount of polymer (B) used within the above range, good flex recovery and flex retention are easily achieved.

[0016] In some preferred embodiments, the molar ratio ([NCO] / [OH]) of isocyanate groups to hydroxyl groups contained in the pressure-sensitive adhesive layer is 0.002 to 0.03. A pressure-sensitive adhesive layer having the molar ratio ([NCO] / [OH]) of 0.002 or more tends to have excellent flex recovery and excellent processability. Furthermore, by setting the molar ratio ([NCO] / [OH]) to 0.03 or less, a suitable increase in adhesive strength tends to be easily achieved. Note that in the pressure-sensitive adhesive layer, at least a portion of the isocyanate groups and hydroxyl groups may be present in a chemically bonded (crosslinked) state. The pressure-sensitive adhesive layer may contain, for example, a crosslinking agent, and in such a configuration, the isocyanate groups may be, for example, part of the crosslinking agent, and the hydroxyl groups may be, for example, part of the polymer (A).

[0017] The reinforcing film disclosed herein is suitable as a reinforcing film that imparts rigidity and impact resistance to optical members such as polarizing plates, wavelength plates, etc. during processing or transport of the optical members. Therefore, this specification provides an optical member to which any of the reinforcing films disclosed herein is attached.

[0018] The reinforcing film disclosed herein is also suitable as a reinforcing film for electronic components of devices such as portable electronic devices, etc. Therefore, according to the present specification, there is provided an electronic component to which any of the reinforcing films disclosed herein is attached. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view schematically illustrating a configuration of a reinforcing film according to an embodiment. [Figure 2] FIG. 10 is a cross-sectional view schematically showing the configuration of a reinforcing film according to another embodiment. [Figure 3] FIG. 10 is a cross-sectional view schematically showing the configuration of a reinforcing film according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] Preferred embodiments of the present invention will be described below. Matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings on carrying out the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. In the following drawings, components and parts having the same function may be denoted by the same reference numerals, and redundant explanations may be omitted or simplified. The embodiments shown in the drawings are schematic in order to clearly explain the present invention, and do not necessarily accurately represent the size or scale of the actual product.

[0021] Furthermore, in this specification, the term "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 more than 50% by weight of monomer units derived from (meth)acrylic monomers. Furthermore, the term "(meth)acrylic monomer" refers to a monomer having at least one (meth)acryloyl group per molecule. Here, the term "(meth)acryloyl group" refers to both acryloyl and methacryloyl groups. Therefore, the term "(meth)acrylic monomer" as used herein encompasses both monomers having an acryloyl group (acrylic monomers) and monomers having a methacryloyl group (methacrylic monomers). Similarly, in this specification, the term "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid, and the term "(meth)acrylate" refers to both acrylate and methacrylate.

[0022] <Structural example of reinforcing film> The reinforcing film disclosed herein has the form of a pressure-sensitive adhesive sheet having an adhesive surface formed by a pressure-sensitive adhesive. The pressure-sensitive adhesive sheet used as the reinforcing film is configured to include a pressure-sensitive adhesive layer. The reinforcing film disclosed herein may be in the form of a substrate-attached pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer is laminated on one or both sides of a supporting substrate, or may be in the form of a substrate-less pressure-sensitive adhesive sheet that does not have a supporting substrate. Hereinafter, the supporting substrate may also be simply referred to as the "substrate." In this specification, the term "reinforcing film" refers to a pressure-sensitive adhesive sheet (reinforcing pressure-sensitive adhesive film) used to reinforce an adherend, as described below. The reinforcing film can be in the form of, for example, a substrate-less pressure-sensitive adhesive sheet, with a support material or the like attached to one adhesive surface, and then the other adhesive surface can be attached to the adherend to be reinforced, so it is not limited to the form of a substrate-attached pressure-sensitive adhesive sheet. In this respect, it can be understood as a broader concept than the "reinforcing film" described below, which has the form of a substrate-attached pressure-sensitive adhesive sheet.

[0023] The structure of a reinforcing film according to one embodiment is shown schematically in FIG. 1. This reinforcing film 1 is configured as a substrate-attached single-sided pressure-sensitive adhesive sheet including a sheet-like supporting substrate 10 having a first side 10A and a second side 10B, and a pressure-sensitive adhesive layer 21 provided on the first side 10A. The pressure-sensitive adhesive layer 21 is fixed to the first side 10A of the supporting substrate 10. The reinforcing film 1 is used by attaching the pressure-sensitive adhesive layer 21 to an adherend. Before use (i.e., before being attached to an adherend), the reinforcing film 1 can be a component of a release-liner-attached reinforcing film 100 in which the surface (adhesive surface) 21A of the pressure-sensitive adhesive layer 21 is in contact with a release liner 31, at least the side facing the pressure-sensitive adhesive layer 21 being a releasable surface (release surface), as shown in FIG. 1. The release liner 31 can be, for example, a sheet-like substrate (liner substrate) configured so that one side serves as a release surface by providing a release layer made of a release treatment agent on that surface. Alternatively, the release liner 31 may be omitted, and a supporting substrate 10 having a release surface on its second surface 10B may be used, with the reinforcing film 1 rolled up so that the adhesive surface 21A is in contact with the second surface 10B of the supporting substrate 10. When attaching the reinforcing film 1 to an adherend, the release liner 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.

[0024] The structure of a reinforcing film according to another embodiment is shown schematically in FIG. 2. This reinforcing film 2 is configured as a substrate-attached double-sided pressure-sensitive adhesive sheet including a sheet-like support substrate 10 having a first surface 10A and a second surface 10B, a pressure-sensitive adhesive layer 21 provided on the first surface 10A side, and a pressure-sensitive adhesive layer 22 provided on the second surface 10B side. The pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer) 21 is adhered to the first surface 10A of the support substrate 10, and the pressure-sensitive adhesive layer (second pressure-sensitive adhesive layer) 22 is adhered to the second surface 10B of the support substrate 10. The reinforcing film 2 is used by adhering the pressure-sensitive adhesive layers 21 and 22 to different locations on an adherend. The locations to which the pressure-sensitive adhesive layers 21 and 22 are adhered may be locations on different members, or may be different locations on a single member. As shown in Fig. 2, the reinforcing film 2 before use can be a component of a release-liner-attached reinforcing film 200 in which the surface (first adhesive surface) 21A of the pressure-sensitive adhesive layer 21 and the surface (second adhesive surface) 22A of the pressure-sensitive adhesive layer 22 are in contact with release liners 31, 32, each of which has a release surface on at least the side facing the pressure-sensitive adhesive layers 21, 22. As the release liners 31, 32, for example, a sheet-like substrate (liner substrate) configured such that one side serves as a release surface by providing a release layer made of a release treatment agent on that surface can be preferably used. Alternatively, the release liner 32 can be omitted, and a release liner 31 having release surfaces on both sides can be used. This can be superimposed on the reinforcing film 2 and wound spirally to form a reinforcing film with a release liner in a roll form in which the second adhesive surface 22A is in contact with the back surface of the release liner 31.

[0025] The structure of a reinforcing film according to yet another embodiment is shown schematically in FIG. 3. This reinforcing film 3 is configured as a substrate-less double-sided pressure-sensitive adhesive sheet made of a pressure-sensitive adhesive layer 21. The reinforcing film 3 is used by attaching a first adhesive surface 21A, which is one surface (first surface) of the pressure-sensitive adhesive layer 21, and a second adhesive surface 21B, which is the other surface (second surface) of the pressure-sensitive adhesive layer 21, to different locations on an adherend. Before use, the reinforcing film 3 may be a component of a release-liner-attached reinforcing film 300, as shown in FIG. 3, in which the first adhesive surface 21A and the second adhesive surface 21B are in contact with release liners 31 and 32, each of which has a release surface on at least the side facing the pressure-sensitive adhesive layer 21. Alternatively, the release liner 32 may be omitted, and a release liner 31 having release surfaces on both sides may be used. This may be superimposed on the reinforcing film 3 and wound into a spiral shape to form a reinforcing film with a release liner in a form in which the second adhesive surface 21B is in contact with the back surface of the release liner 31 (in a roll form).

[0026] The reinforcing film may be in the form of a roll or a sheet, and may be cut, punched, or otherwise processed into an appropriate shape depending on the application or mode of use. The pressure-sensitive adhesive layer in the technology disclosed herein is typically formed continuously, but is not limited thereto, and may be formed in a regular or random pattern such as a dotted or striped pattern.

[0027] <Adhesive layer> The reinforcing film disclosed herein includes a pressure-sensitive adhesive layer containing a polymer (A) and a polymer (B). Such a pressure-sensitive adhesive layer may be formed from a pressure-sensitive adhesive composition containing a polymer (A) that is a complete or partial polymer of a monomer raw material A, and a polymer (B). The form of the pressure-sensitive adhesive composition is not particularly limited, and may be in various forms, such as a solvent-based, water-dispersible, hot-melt, or active energy ray-curable (e.g., photocurable) form.

[0028] (Surface elasticity at 23°C) The pressure-sensitive adhesive layer disclosed herein is characterized in that its surface (adhesive surface) has a surface modulus at 23°C (23°C surface modulus) in the range of 1 to 20 kPa. When the 23°C surface modulus is 1 kPa or more, the pressure-sensitive adhesive layer can have good flex recovery while realizing the adhesive properties based on the inclusion of polymer (A) and polymer (B). Furthermore, when the surface modulus is 20 kPa or less, the pressure-sensitive adhesive layer can exhibit good flex retention while realizing the adhesive properties.

[0029] From the viewpoint of improving flex recovery, the 23°C surface elastic modulus is preferably 2 kPa or more, more preferably 3 kPa or more, and even more preferably 4 kPa or more (e.g., 5 kPa or more), and may be 8 kPa or more, 10 kPa or more, or 12 kPa or more (e.g., 14 kPa or more). The higher the surface elastic modulus, the better the initial easy peelability tends to be. Furthermore, from the viewpoint of achieving both good flex recovery and flex retention while preferably exhibiting increased adhesive strength, the 23°C surface elastic modulus is suitably 15 kPa or less, preferably 12 kPa or less, more preferably 9 kPa or less, and even more preferably 7 kPa or less (e.g., 6 kPa or less), and may be 4 kPa or less.

[0030] The surface elastic modulus at 23°C of the pressure-sensitive adhesive layer can be adjusted by the type and characteristics (molecular weight, glass transition temperature, molecular structure, etc.) of polymer (A), the type (chemical structure, etc.) and characteristics (molecular weight, glass transition temperature, etc.) and amount used of polymer (B), the type and amount used of crosslinking agent, etc. The surface elastic modulus at 23°C of the pressure-sensitive adhesive layer is measured by the method described in the Examples below.

[0031] (23℃ bulk modulus G' 23 ) Bulk elastic modulus G' of adhesive layer at 23°C 23 (23℃ bulk modulus G' 23 ) is appropriately set within a range that satisfies the above-mentioned range of the surface elastic modulus at 23°C, and is not limited to a specific range. In some embodiments, the bulk elastic modulus G' of the PSA layer at 23°C 23 The bulk elastic modulus G' is preferably 10 kPa or more.23 By setting the bulk modulus G' to a predetermined value or more, the adhesive strength at the initial stage of application tends to fall within a suitable range that provides excellent peelability. In addition, the adhesive tends to have excellent processability and generally also excellent flex recovery at room temperature. 23 In some other embodiments, the bulk modulus G' is preferably 15 kPa or more, more preferably 20 kPa or more, even more preferably 25 kPa or more, and particularly preferably 30 kPa or more. 23 The pressure may be 50 kPa or more, 80 kPa or more, or 100 kPa or more.

[0032] In some embodiments, the 23°C bulk modulus G' of the adhesive layer 23 The bulk elastic modulus G' is preferably 200 kPa or less. 23 A pressure-sensitive adhesive having a bulk modulus G' of not more than a predetermined value generally tends to have excellent strain relaxation properties at room temperature and is also likely to exhibit increased adhesive strength. 23 In some preferred embodiments, the bulk modulus G' is preferably 150 kPa or less, more preferably 90 kPa or less. 23 The pressure may be 60 kPa or less, or 40 kPa or less (for example, 35 kPa or less).

[0033] (80℃ bulk modulus G' 80 ) Bulk elastic modulus G' of adhesive layer at 80℃ 80 (80℃ bulk modulus G' 80 ) is appropriately set within a range that satisfies the above-mentioned range of the surface elastic modulus at 23°C, and is not limited to a specific range. In some embodiments, the 80°C bulk elastic modulus G' of the PSA layer 80 The bulk elastic modulus G' is preferably 5 kPa or more. 80 By setting the bulk elastic modulus G' to a predetermined value or more, the flex recovery is generally improved, and the fiber can have elasticity suitable for flex recovery even when used under high temperature conditions. 80In some other embodiments, the bulk modulus G' may be 7 kPa or more, 9 kPa or more, or 10 kPa or more. 80 The pressure may be 15 kPa or more, 30 kPa or more, or 50 kPa or more.

[0034] In some embodiments, the 80°C bulk modulus G' of the adhesive layer 80 The bulk elastic modulus G' is preferably 100 kPa or less. 80 By limiting the bulk elastic modulus G' to a predetermined value or less, it is generally easy to obtain good bending retention and to achieve both bending recovery and bending retention. For example, it is possible to obtain a material that has elasticity suitable for bending recovery and adhesive retention that realizes bending retention in various environments, including high-temperature conditions. 80 In some embodiments, the bulk modulus G' is preferably 90 kPa or less, and more preferably 60 kPa or less. 80 The pressure may be 20 kPa or less, 16 kPa or less, or 14 kPa or less (for example, 12 kPa or less).

[0035] (80℃ tanδ 80 ) Tan δ of adhesive layer at 80℃ 80 (80℃ tanδ 80 ) is appropriately set within a range that satisfies the above-mentioned range of the surface elastic modulus at 23°C, and is not limited to a particular range. 80 It is appropriate that tan δ is 0.10 or more. 80 The higher the tan δ, the more likely the adhesive will exhibit adhesive strength suitable for bending and maintaining the adhesive strength. 80 is preferably 0.20 or more. 80 may be 0.30 or more, 0.40 or more, or 0.45 or more.

[0036] In some embodiments, the 80°C tanδ of the adhesive layer 80 is preferably 0.60 or less.80 By being 0.60 or less, plastic deformation of the adhesive is suppressed, and good flex recovery is easily obtained. In addition, even when the reinforcing film is kept in a bent state for a long time, it is easy to exhibit holding power that does not cause peeling from the adherend. Furthermore, the increase in adhesive strength is also likely to be in a suitable range. 80 In some other embodiments, the 80°C tan δ may be 0.55 or less. 80 may be 0.50 or less, or may be 0.35 or less.

[0037] Bulk elastic modulus G' of adhesive layer at 23°C 23 , 80℃ bulk modulus G′ 80 and 80℃ tanδ 80 The bulk modulus G' of the pressure-sensitive adhesive layer at 23°C can be adjusted by the type and characteristics (molecular weight, glass transition temperature, molecular structure, etc.) of polymer (A), the type (chemical structure, etc.) and characteristics (molecular weight, glass transition temperature, etc.) of polymer (B), the amount used, and the type and amount used of the crosslinking agent. 23 , 80℃ bulk modulus G′ 80 and 80℃ tanδ 80 is measured by the method described in the Examples below.

[0038] (Polymer (A)) The polymer (A) can be one or more of various polymers known in the field of pressure-sensitive adhesives that exhibit rubber elasticity at room temperature, such as acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine-containing polymers. In the reinforcing film disclosed herein, the polymer (A) is typically the main component of the polymer components contained in the pressure-sensitive adhesive layer, i.e., a component that accounts for more than 50% by weight, and can be a component that accounts for, for example, 75% by weight or more of the above polymer components. In some embodiments, the polymer (A) accounts for more than 50% by weight of the entire pressure-sensitive adhesive layer, and may also be a component that accounts for 70% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more (e.g., 97% by weight or more).

[0039] Glass transition temperature T of polymer (A) A is not particularly limited and can be selected to obtain desirable properties in the reinforcing film disclosed herein. A A polymer (A) having a temperature of less than 0°C can be preferably used. A pressure-sensitive adhesive containing such a polymer (A) exhibits appropriate fluidity (for example, mobility of the polymer chains contained in the pressure-sensitive adhesive), and is therefore suitable for realizing a reinforcing film whose adhesive strength increases to a predetermined value or more upon heating. The reinforcing film disclosed herein has a temperature of T A may be preferably carried out using polymer (A) at a temperature of less than -10°C, less than -20°C, less than -30°C or less than -35°C. A may be below −40° C. or below −50° C. In some preferred embodiments, T A is -55°C or lower, more preferably -58°C or lower, even more preferably -62°C or lower, and may be -65°C or lower (for example, -66°C or lower). A There is no particular restriction on the lower limit of T. From the viewpoint of material availability and improving the cohesive strength of the adhesive layer, it is usually A Preferably, the polymer (A) has a temperature of -80°C or higher, or -70°C or higher. A may be, for example, -63°C or higher, -55°C or higher, -50°C or higher, or -45°C or higher.

[0040] In this specification, the glass transition temperature (Tg) of polymers including polymer (A) and polymer (B) described below refers to a nominal value described in literature, catalogs, etc., or a Tg calculated by the Fox equation based on the composition of the monomer raw materials used to prepare the polymer. The Fox equation, as shown below, is 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. 1 / Tg=Σ(Wi / Tgi) In the above Fox formula, Tg represents the glass transition temperature (unit: K) of the copolymer, Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi represents the glass transition temperature (unit: K) of a homopolymer of monomer i. When the target polymer for specifying Tg is a homopolymer, the Tg of the homopolymer and the Tg of the target polymer will be the same.

[0041] The glass transition temperature of a homopolymer used to calculate Tg is a value listed in a publicly available document. Specifically, values ​​are listed in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989). For monomers for which multiple values ​​are listed in the Polymer Handbook, the highest value is used.

[0042] As the glass transition temperature of a homopolymer of a monomer not described in the Polymer Handbook, a value obtained by the following measurement method is used. Specifically, 100 parts by weight of monomer, 0.2 parts by weight of 2,2'-azobisisobutyronitrile, and 200 parts by weight of ethyl acetate as a polymerization solvent were added to a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, and the mixture was stirred for 1 hour while passing nitrogen gas through. After removing oxygen from the polymerization system in this way, the temperature was raised to 63°C and the reaction was continued for 10 hours. The mixture was then cooled to room temperature, yielding a homopolymer solution with a solids concentration of 33% by weight. This homopolymer solution was then cast onto a release liner and dried to prepare a test sample (sheet-like homopolymer) approximately 2 mm thick. This test sample was punched out into a disk with a diameter of 7.9 mm, sandwiched between parallel plates, and the viscoelasticity was measured in shear mode using a viscoelasticity tester (TA Instruments Japan, model name "ARES") while applying a shear strain of 1 Hz over a temperature range of -70°C to 150°C at a heating rate of 5°C / min. The temperature corresponding to the peak top temperature of tan δ was taken as the Tg of the homopolymer.

[0043] Although not particularly limited, the weight average molecular weight (Mw) of the polymer (A) is usually about 20 × 10 4 It is suitable that the Mw of the polymer (A) is 30×10 or more. A PSA exhibiting good cohesive properties is easily obtained by using the polymer (A) having such an Mw. From the viewpoint of obtaining higher cohesive strength, in some preferred embodiments, the Mw of the polymer (A) is, for example, 30×10 4 It may be 40 x 10 or more. 4 More than 50 x 10 4 More than 60 x 10 4 More than 80 x 10 4 The Mw of the polymer (A) is usually about 500×10 4 It is appropriate that the Mw of the polymer (A) is not too high. A polymer (A) having such an Mw is likely to form an adhesive that exhibits appropriate fluidity (mobility of polymer chains), and is therefore suitable for realizing a reinforcing film that has low initial adhesive strength after application and a large increase in adhesive strength. It is also preferable from the viewpoint of improving compatibility with the polymer (B) that the Mw of the polymer (A) is not too high. In some preferred embodiments, the Mw of the polymer (A) is, for example, 250 × 10 4 may be less than or equal to 200 x 10 4 Less than 150 x 10 4 Less than 100 x 10 4 Less than 70 x 10 is fine. 4 The following is also acceptable.

[0044] In this specification, the Mw of polymer (A) and polymer (B) described later can be determined in terms of polystyrene by gel permeation chromatography (GPC). More specifically, the Mw can be measured according to the method and conditions described in the examples described later.

[0045] An acrylic polymer can be preferably used as the polymer (A) in the reinforcing film disclosed herein. When an acrylic polymer is used as the polymer (A), good compatibility with the polymer (B) tends to be easily obtained. Good compatibility between the polymer (A) and the polymer (B) is preferable because it can contribute to reducing the initial adhesive strength and improving the adhesive strength after heating by improving the mobility of the polymer (B) within the adhesive layer. Furthermore, acrylic polymers, which have a high degree of freedom in molecular design, are suitable as adhesive materials that can improve adhesive properties, flex recovery, and flex retention in a balanced manner.

[0046] The acrylic polymer may be, for example, a polymer containing 50% by weight or more of monomer units derived from (meth)acrylic acid alkyl esters, i.e., a polymer in which 50% by weight or more of the total amount of the monomer components (monomer raw material A) for preparing the acrylic polymer is a (meth)acrylic acid alkyl ester. The (meth)acrylic acid alkyl ester may be a (meth)acrylic acid alkyl ester having 1 to 20 carbon atoms (i.e., C 1-20 (Meth)acrylic acid alkyl esters having a linear or branched alkyl group are preferably used. Among the monomer raw materials A, (meth)acrylic acid C is preferred because it is easy to balance the properties. 1-20 The proportion of alkyl ester may be, for example, 50% by weight or more, or 60% by weight or more. In some preferred embodiments, the proportion of (meth)acrylic acid C in the monomer raw material A is 50% by weight or more, or 60% by weight or more. 1-20 The proportion of alkyl ester is 70% by weight or more, more preferably 80% by weight or more, even more preferably 85% by weight or more, and particularly preferably 90% by weight or more. By using an acrylic polymer with such a monomer composition, it is easy to obtain a pressure-sensitive adhesive that achieves a good balance between increased adhesive strength, flex recovery, and flex retention. In addition, (meth)acrylic acid C in the monomer raw material A is 1-20 The proportion of alkyl ester may be, for example, 99.9% by weight or less, 98% by weight or less, or 95% by weight or less. 1-20The proportion of alkyl ester may be, for example, 90% by weight or less, 85% by weight or less, or 80% by weight or less.

[0047] (Meth)acrylic acid C 1-20 Non-limiting examples of alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isopropyl (meth)acrylate. Examples of the acrylate include 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, and eicosyl (meth)acrylate.

[0048] Among these, at least (meth)acrylic acid C 1-18 It is preferable to use alkyl esters, and at least (meth)acrylic acid C 1-14 It is more preferred to use alkyl esters. In some embodiments, the acrylic polymer is (meth)acrylic acid C 4-12 Alkyl ester (preferably acrylic acid C 4-10 Alkyl esters, such as acrylic acid C 6-10 The acrylic polymer may contain at least one selected from n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) as a monomer unit. For example, an acrylic polymer containing one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) is preferred, and an acrylic polymer containing at least 2EHA is particularly preferred.

[0049] In some preferred embodiments, acrylic acid C is used as the monomer raw material A for preparing the acrylic polymer. 6-10 Alkyl ester (preferably acrylic acid C 8-9 The proportion of alkyl ester (typically 2EHA) is 70% by weight or more, more preferably 80% by weight or more, even more preferably 85% by weight or more, and particularly preferably 90% by weight or more. An acrylic polymer having such a monomer composition is particularly suitable for realizing the effects of the technology disclosed herein. In addition, the proportion of acrylic acid C in the monomer raw material A is 70% by weight or more, more preferably 80% by weight or more, even more preferably 85% by weight or more, and particularly preferably 90% by weight or more. An acrylic polymer having such a monomer composition is particularly suitable for realizing the effects of the technology disclosed herein. 6-10 Alkyl ester (preferably acrylic acid C 8-9 The proportion of alkyl ester (typically 2EHA) may be, for example, 99.9% by weight or less, and from the viewpoint of low initial adhesion, flex recovery, etc., it may be 98% by weight or less, or 95% by weight or less.

[0050] In some preferred embodiments, the monomer raw material A for preparing the acrylic polymer contains (meth)acrylic acid C 1-3 It is preferred that the proportion of alkyl esters (e.g., (meth)acrylic acid C1 alkyl esters, typically methyl methacrylate (MMA)) is limited. 1-3 Alkyl esters (e.g., (meth)acrylic acid C1 alkyl esters, typically MMA) tend to have a relatively high Tg, and PSA containing an acrylic polymer using the above monomer component tends to have high cohesiveness. 1-3 By limiting the amount of alkyl ester used, the cohesive strength of the adhesive can be appropriately reduced, and an elastic modulus (typically a surface elastic modulus) suitable for achieving both bending retention and increased adhesive strength can be preferably achieved. From this viewpoint, (meth)acrylic acid C of the above-mentioned monomer raw material A is preferably used. 1-3 The proportion of alkyl ester (e.g., (meth)acrylic acid C1 alkyl ester, typically MMA) is suitably 8% by weight or less, preferably 6% by weight or less, more preferably 3% by weight or less, and even more preferably 1% by weight or less (e.g., 0 to 0.3% by weight).

[0051] Monomer raw material A may contain, in addition to the (meth)acrylic acid alkyl ester as the main component, other monomers (copolymerizable monomers) copolymerizable with the (meth)acrylic acid alkyl ester, as necessary. Monomers having polar groups (e.g., carboxy groups, hydroxyl groups, nitrogen atom-containing rings, etc.) can be suitably used as the copolymerizable monomers. Monomers having polar groups can be useful for introducing crosslinking points into the acrylic polymer or for increasing the cohesive strength of the acrylic polymer. The copolymerizable monomers can be used alone or in combination of two or more.

[0052] Non-limiting examples of copolymerizable monomers include the following: Hydroxyl group-containing monomers: for example, hydroxyalkyl (meth)acrylates such as 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, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylmorpholine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, N-vinylpyridazine, etc.; For example, monomers having a succinimide skeleton, such as N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, and N-(meth)acryloyl-8-oxyhexamethylene succinimide; Maleimides, such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; and For example, itaconimides such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide. Carboxy group-containing monomers: for example, acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, etc. Acid anhydride group-containing monomers: for example, maleic anhydride, itaconic anhydride. Epoxy group-containing monomers: for example, epoxy group-containing acrylates such as glycidyl (meth)acrylate and 2-ethyl (meth)acrylate glycidyl ether, allyl glycidyl ether, glycidyl (meth)acrylate, etc. Cyano group-containing monomers: for example, acrylonitrile, methacrylonitrile, etc. Isocyanate group-containing monomers: for example, 2-isocyanatoethyl (meth)acrylate. Amide group-containing monomers: for example, (meth)acrylamide; N,N-dialkyl(meth)acrylamides such as 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, and N,N-di(t-butyl)(meth)acrylamide; N-alkyl(meth)acrylamides such as N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, and Nn-butyl(meth)acrylamide; N-vinylcarboxylic acid amides such as N-vinylacetamide; monomers having a hydroxyl group and an amide group, for example, N-(2-hydroxyethyl)( N-hydroxyalkyl(meth)acrylamides such as N-(meth)acrylamide, 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, and N-(4-hydroxybutyl)(meth)acrylamide; monomers having an alkoxy group and an amide group, for example, N-alkoxyalkyl(meth)acrylamides such as N-methoxymethyl(meth)acrylamide, N-methoxyethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide; and others such as N,N-dimethylaminopropyl(meth)acrylamide. Aminoalkyl (meth)acrylates: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate. Alkoxy group-containing monomers: for example, alkoxyalkyl (meth)acrylates such as 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, and ethoxypropyl (meth)acrylate; and alkoxyalkylene (meth)acrylates such as methoxyethylene glycol (meth)acrylate and methoxypolypropylene glycol (meth)acrylate. Monomers containing a sulfonic acid group or a phosphoric acid group: for example, styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, 2-hydroxyethyl acryloylphosphate, etc. (Meth)acrylic acid esters having an alicyclic hydrocarbon group: for example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and the like. (Meth)acrylic acid esters having an aromatic hydrocarbon group: for example, phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, etc. Vinyl ethers: for example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether. Vinyl esters: for example, vinyl acetate, vinyl propionate, etc. Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyltoluene, etc. Olefins: for example, ethylene, butadiene, isoprene, isobutylene, etc. Other examples include heterocyclic ring-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing (meth)acrylates such as vinyl chloride and fluorine atom-containing (meth)acrylates, silicon atom-containing (meth)acrylates such as silicone (meth)acrylate, and (meth)acrylic acid esters obtained from terpene compound derivative alcohols.

[0053] When such a copolymerizable monomer is used, its amount is not particularly limited, but is usually appropriate to be 0.01 wt% or more of the monomer raw material A. From the viewpoint of better exerting the effect of using the copolymerizable monomer, the amount of the copolymerizable monomer used may be 0.1 wt% or more, or even 1 wt% or more of the monomer raw material A. In some preferred embodiments, the content of the copolymerizable monomer in the monomer raw material A is 3 wt% or more, more preferably 5 wt% or more, and even more preferably 7 wt% or more (e.g., 8 wt% or more). The greater the amount of the copolymerizable monomer used, the higher the cohesiveness and the improved flex recovery tend to be. Furthermore, the amount of the copolymerizable monomer used can be 50 wt% or less of the monomer raw material A, and preferably 30 wt% or less. This can prevent the cohesive strength of the PSA from becoming too high and improve the tackiness at room temperature (25°C). In some preferred embodiments, the amount of the copolymerizable monomer used is 20 wt% or less of the monomer raw material A, more preferably 15 wt% or less (e.g., 12 wt% or less), and may be 10 wt% or less. By limiting the amount of copolymerizable monomer used, the cohesive strength of the adhesive is reduced, the modulus of elasticity (typically the surface modulus of elasticity) falls within a suitable range, making it easier to obtain excellent bending retention and increase adhesive strength.

[0054] In some embodiments, the monomer raw material A may contain a monomer having a nitrogen atom-containing ring. The use of a monomer having a nitrogen atom-containing ring can adjust the cohesive strength and polarity of the adhesive, thereby favorably improving the adhesive strength after heating. By including a monomer having a nitrogen atom-containing ring in the monomer raw material A, the compatibility between the polymer (A) formed from the monomer raw material A and the polymer (B) tends to be improved. This makes it easier to obtain a reinforcing film whose adhesive strength can be significantly increased by heating.

[0055] The monomer having a nitrogen atom-containing ring can be selected from the above examples, and used alone or in combination of two or more. In some embodiments, the monomer raw material A preferably contains, as the monomer having a nitrogen atom-containing ring, at least one monomer selected from the group consisting of N-vinyl cyclic amides and cyclic amides having a (meth)acryloyl group.

[0056] Specific examples of N-vinyl cyclic amides include N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, etc. Particularly preferred are N-vinyl-2-pyrrolidone and N-vinyl-2-caprolactam. Specific examples of cyclic amides having a (meth)acryloyl group include N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-(meth)acryloylmorpholine, etc. A suitable example is N-acryloylmorpholine (ACMO).

[0057] The amount of the monomer having a nitrogen atom-containing ring used is not particularly limited, and is typically 40% by weight or less of the monomer starting material A, and may be 30% by weight or less, 20% by weight or less, or 10% by weight or less. In some preferred embodiments, from the viewpoint of reducing cohesive strength and elastic modulus (typically surface elastic modulus), the content of the monomer having a nitrogen atom-containing ring in the monomer starting material A is 7% by weight or less, more preferably 5% by weight or less, and even more preferably 3% by weight or less (e.g., 1.5% by weight or less). Furthermore, the amount of the monomer having a nitrogen atom-containing ring used is typically 0.01% by weight or more of the monomer starting material A (preferably 0.1% by weight or more, e.g., 0.5% by weight or more). In some embodiments, from the viewpoint of obtaining appropriate cohesive strength and elastic modulus, the amount of the monomer having a nitrogen atom-containing ring used may be 0.8% by weight or more of the monomer starting material A, or may be 1.0% by weight or more.

[0058] In some preferred embodiments, the monomer raw material A includes a hydroxyl group-containing monomer. The use of a hydroxyl group-containing monomer adjusts the cohesive strength and polarity of the PSA, and thus the modulus of elasticity (typically the surface modulus of elasticity), thereby enabling the effects of the technology disclosed herein to be preferably realized. In addition, the hydroxyl group-containing monomer provides a reactive site with a crosslinking agent (e.g., an isocyanate-based crosslinking agent) described below, and can increase the cohesive strength of the PSA through a crosslinking reaction.

[0059] Suitable hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and N-(2-hydroxyethyl)(meth)acrylamide. Among these, preferred examples include 2-hydroxyethyl acrylate (HEA), 4-hydroxybutyl acrylate (4HBA), and N-(2-hydroxyethyl)acrylamide (HEAA). 4HBA is particularly preferred from the viewpoint of obtaining cohesive strength suitable for flex recovery and flex retention.

[0060] The amount of hydroxyl-containing monomer used is not particularly limited, and is usually suitably 40% by weight or less of the monomer raw material A, and may be 30% by weight or less, or may be 20% by weight or less. In some preferred embodiments, from the viewpoint of reducing cohesive strength and, in turn, elastic modulus (typically, surface elastic modulus), the content of hydroxyl-containing monomer in the monomer raw material A is 15% by weight or less, more preferably 12% by weight or less (e.g., 10% by weight or less). By limiting the amount of hydroxyl-containing monomer used, the mobility of polymer (B) within the adhesive layer is improved, making it easier to achieve increased adhesive strength. In other embodiments, the content of hydroxyl-containing monomer may be 5% by weight or less of the monomer raw material A. Furthermore, the amount of hydroxyl-containing monomer used is suitably 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). From the viewpoint of obtaining an appropriate cohesive strength and elastic modulus, in some preferred embodiments, the amount of the hydroxyl group-containing monomer used is 1% by weight or more of the monomer raw material A, more preferably 3% by weight or more, even more preferably 5% by weight or more, and particularly preferably 7% by weight or more (e.g., 8% by weight or more).

[0061] In some embodiments, a monomer having a nitrogen atom-containing ring and a hydroxyl group-containing monomer can be used in combination as copolymerizable monomers. In this case, the total amount of the monomer having a nitrogen atom-containing ring and the hydroxyl group-containing monomer can be, for example, 0.1% by weight or more of the monomer starting material A, preferably 1% by weight or more, more preferably 3% by weight or more, even more preferably 5% by weight or more, and particularly preferably 7% by weight or more (e.g., 9% by weight or more), and may be 10% by weight or more, 15% by weight or more, 20% by weight or more, or even 25% by weight or more. Furthermore, the total amount of the monomer having a nitrogen atom-containing ring and the hydroxyl group-containing monomer can be, for example, 50% by weight or less of the monomer starting material A, and preferably 30% by weight or less. In some preferred embodiments, the total amount of the monomer having a nitrogen atom-containing ring and the hydroxyl group-containing monomer is 20% by weight or less of the monomer starting material A, more preferably 15% by weight or less (e.g., 12% by weight or less).

[0062] In an embodiment in which the monomer raw material A contains a combination of a monomer having a nitrogen atom-containing ring and a hydroxyl group-containing monomer, the content of the monomer having a nitrogen atom-containing ring in the monomer raw material A (W N ) and the content of hydroxyl group-containing monomers (W OH The relationship (weight basis) between W and W is not particularly limited. N / W OH may be, for example, 0.01 or more, and usually 0.05 or more is appropriate, and may be 0.10 or more, or 0.12 or more. N / W OH may be, for example, 10 or less, and is usually suitably 1 or less, and is preferably 0.50 or less, or may be 0.30 or less, or may be 0.20 or less, or may be 0.15 or less.

[0063] In some embodiments, it is preferable that monomer raw material A does not contain a monomer having a polyorganosiloxane skeleton (monomer S1), which is preferably used as a constituent component of monomer raw material B described below, or that the content of this monomer is less than 10% by weight (more preferably less than 5% by weight, e.g., less than 2% by weight) of monomer raw material A. Monomer raw material A having such a composition can suitably realize a reinforcing film that satisfies both initial reworkability and strong adhesion after adhesive strength has increased. For the same reason, in other embodiments, it is preferable that monomer raw material A does not contain monomer S1, or if it contains monomer S1, its content (by weight) is lower than the content of monomer S1 in monomer raw material B.

[0064] The method for obtaining the polymer (A) is not particularly limited, and various polymerization methods can be appropriately used, such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization. In some embodiments, solution polymerization can be preferably used. The polymerization temperature during solution polymerization can be appropriately selected depending on the types of monomers and solvents used, the type of polymerization initiator, and the like, and can be, for example, about 20°C to 170°C (typically about 40°C to 140°C).

[0065] The initiator used for polymerization can be appropriately selected from conventionally known thermal polymerization initiators, photopolymerization initiators, etc., depending on the polymerization method. The polymerization initiators can be used alone or in combination of two or more.

[0066] 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, 4,4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2 Examples of suitable thermal polymerization initiators include 2,2'-azobis(N,N'-imidazolin-2-yl)propane dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine) dihydrochloride, etc.; persulfates such as potassium persulfate; peroxide polymerization initiators (e.g., dibenzoyl peroxide, t-butyl permaleate, lauroyl peroxide, etc.); and redox polymerization initiators. The amount of the thermal polymerization initiator used is not particularly limited, but can be, for example, 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, per 100 parts by weight of the monomer component (monomer raw material A) used in preparing the acrylic polymer.

[0067] The photopolymerization initiator is not particularly limited, but examples thereof include 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, thioxanthone-based photopolymerization initiators, and acylphosphine oxide-based photopolymerization initiators. The amount of the photopolymerization initiator used is not particularly limited, but can be, for example, 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, per 100 parts by weight of the monomer raw material A.

[0068] In some embodiments, the polymer (A) may be contained in the PSA composition for forming a PSA layer in the form of a partially polymerized product (polymer syrup) obtained by irradiating a mixture of the monomer raw material A and a polymerization initiator with ultraviolet (UV) light to polymerize a portion of the monomer component. The PSA composition containing such a polymer syrup can be applied to a predetermined substrate and then irradiated with ultraviolet light to complete the polymerization. In other words, the polymer syrup can be considered a precursor of the polymer (A). The PSA layer disclosed herein can be formed, for example, using a PSA composition containing the polymer syrup and polymer (B).

[0069] (Polymer (B)) The polymer (B) in the technology disclosed herein is a polymer of a monomer component (monomer raw material B) containing a monomer having a polyorganosiloxane skeleton (hereinafter also referred to as "monomer S1") and a (meth)acrylic monomer. Polymer (B) can be considered a copolymer of monomer S1 and a (meth)acrylic monomer. Polymer (B) can be used singly or in combination of two or more. Due to the low polarity and mobility of the polyorganosiloxane structure derived from monomer S1, polymer (B) suppresses the initial adhesive strength after application to an adherend and can function as an adhesive strength increase retarder that increases the adhesive strength to the adherend upon heating. Monomer S1 is not particularly limited, and any monomer containing a polyorganosiloxane skeleton can be used. Due to the low polarity derived from its structure, monomer S1 promotes uneven distribution of polymer (B) on the surface of the adhesive layer of the reinforcing film before use (before application to an adherend), thereby achieving easy peelability (low adhesive strength) during the initial application. Monomer S1 preferably has a structure having a polymerizable reactive group at one end. A composition containing such monomer S1 units and (meth)acrylic monomer units results in the formation of a polymer (B) having a polyorganosiloxane skeleton in the side chain. Polymer (B) with such a structure tends to have low initial adhesive strength and high adhesive strength after heating due to the mobility and ease of movement of the side chain. Furthermore, in some embodiments, monomer S1 preferably has a polymerizable reactive group at one end and does not have a functional group at the other end that undergoes a crosslinking reaction with polymer (A). Polymer (B) copolymerized with monomer S1 of such a structure tends to have low initial adhesive strength and high adhesive strength after heating due to the mobility of the polyorganosiloxane structure derived from monomer S1.

[0070] As the monomer S1, for example, a compound represented by the following general formula (1) or (2) can be used. More specifically, examples of the single-end reactive silicone oils manufactured by Shin-Etsu Chemical Co., Ltd. include X-22-174ASX, X-22-2426, X-22-2475, and KF-2012. The monomer S1 can be used alone or in combination of two or more. [ka] [ka] Here, R in the above general formulas (1) and (2) 3 is hydrogen or methyl, and R 4 is a methyl group or a monovalent organic group, and m and n are integers of 0 or greater.

[0071] The functional group equivalent of the monomer S1 can be any appropriate value within the range in which the desired effect is achieved using the monomer S1, and is not limited to a specific range. From the viewpoint of sufficiently suppressing the initial adhesive strength, the functional group equivalent is, for example, 100 g / mol or more, or 200 g / mol or more, and suitably 300 g / mol or more (e.g., 500 g / mol or more), preferably 800 g / mol or more, and more preferably 1500 g / mol or more. In a particularly preferred embodiment, from the viewpoint of achieving both low adhesive strength at the initial stage of application and increased adhesive strength after heating, the functional group equivalent is 2000 g / mol or more, more particularly preferably 2500 g / mol or more, or even 3000 g / mol or more, 4000 g / mol or more, or 5000 g / mol or more. In some other embodiments, the functional group equivalent may be 9000 g / mol or more, 12000 g / mol or more, or 15000 g / mol or more.

[0072] From the viewpoint of sufficiently increasing adhesive strength, the functional group equivalent weight is suitably, for example, 30,000 g / mol or less, and may be 20,000 g / mol or less, less than 15,000 g / mol, or less than 10,000 g / mol. In some preferred embodiments, the functional group equivalent weight of monomer S1 is 7,000 g / mol or less, more preferably 5,500 g / mol or less, even more preferably 4,500 g / mol or less, and may be 4,200 g / mol or less, or may be 3,500 g / mol or less. When the functional group equivalent weight of monomer S1 is within the above range, compatibility within the adhesive layer (e.g., compatibility with the base polymer) tends to be good, the mobility of the polyorganosiloxane skeleton (chain) of polymer (B) is good, and the mobility of polymer (B) can be easily adjusted within an appropriate range, making it easier to realize an adhesive layer that combines low initial adhesive strength with increased adhesive strength after heating.

[0073] Here, "functional group equivalent" means the weight of the main skeleton (e.g., polydimethylsiloxane) bonded to one functional group. The unit g / mol is calculated as 1 mol of functional group. The functional group equivalent of the monomer S1 can be calculated, for example, by nuclear magnetic resonance (NMR) analysis. 1 It can be calculated from the spectral intensity of H-NMR (proton NMR). 1 The functional group equivalent weight (g / mol) of monomer S1 was calculated based on the H-NMR spectrum intensity: 1 This can be done based on a general structural analysis method involving H-NMR spectrum analysis, and if necessary, by referring to the description in Japanese Patent No. 5951153. In the functional group equivalent of the monomer S1, the functional group refers to a polymerizable functional group (for example, an ethylenically unsaturated group such as a (meth)acryloyl group, a vinyl group, or an allyl group).

[0074] When two or more monomers having different functional group equivalents are used as the monomer S1, the arithmetic mean value can be used as the functional group equivalent of the monomer S1. That is, when n types of monomers (monomer S11, monomer S12, ..., monomer S1) having different functional group equivalents are used, the arithmetic mean value can be used as the functional group equivalent of the monomer S1. nThe functional group equivalent weight of the monomer S1 consisting of (a) can be calculated by the following formula: Functional group equivalent of monomer S1 (g / mol) = (functional group equivalent of monomer S11 × amount of monomer S11 + functional group equivalent of monomer S12 × amount of monomer S12 + + monomer S1 n Functional group equivalent weight × monomer S1 n (amount of monomer S11 + amount of monomer S12 + + monomer S1 n (amount of blend)

[0075] The content of monomer S1 can be any appropriate value within the range in which the desired effect is achieved using the monomer S1, and is not limited to a specific range. From the viewpoint of sufficiently suppressing the initial adhesive strength, in some embodiments, the content of monomer S1 relative to the total amount of monomer components (monomer starting material B) used to prepare polymer (B) may be, for example, 5% by weight or more. From the viewpoint of better exerting the effect as an adhesive strength increase retarder, it is preferably 10% by weight or more, more preferably 12% by weight or more, even more preferably 15% by weight or more, particularly preferably 18% by weight or more, and may even be 20% by weight or more. Furthermore, from the viewpoint of polymerization reactivity and compatibility, the content of monomer S1 in monomer starting material B may be, for example, 80% by weight or less, and suitably 60% by weight or less, preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 30% by weight or less. By setting the polymerization ratio of monomer S1 within an appropriate range, an increase in adhesive strength can be suitably achieved.

[0076] In addition to the monomer S1, the monomer raw material B contains a (meth)acrylic monomer copolymerizable with the monomer S1. The use of one or more (meth)acrylic monomers can favorably adjust the mobility of the polymer (B) within the pressure-sensitive adhesive layer. This can also help improve the compatibility between the polymer (B) and the polymer (A). The polymer (B) containing a (meth)acrylic monomer unit has good compatibility with the acrylic polymer, which improves the mobility of the polymer (B) within the pressure-sensitive adhesive layer, thereby easily achieving a reduction in the initial adhesive strength and an improvement in the adhesive strength after heating.

[0077] In the polymer (B) used in the technology disclosed herein, the composition of the (meth)acrylic monomer contained in the monomer raw material B is such that the glass transition temperature T B1 is the glass transition temperature T of polymer (A). A It is preferable that the value is set higher than T B1 can be set to be higher than 0° C. Here, the glass transition temperature T B1 means the Tg calculated by the Fox equation based on the composition of only the (meth)acrylic monomers among the monomer components used in the preparation of polymer (B). B1 The glass transition temperature T can be calculated from the glass transition temperature of the homopolymer of each (meth)acrylic monomer and the weight fraction of each (meth)acrylic monomer in the total amount of the (meth)acrylic monomers by applying the above-mentioned Fox equation to only the (meth)acrylic monomers among the monomer components used in preparing the polymer (B). B1 The polymer (B) has a relatively high temperature (typically higher than 0°C), which tends to suppress the initial adhesive strength. B1 A polymer (B) having a relatively high Tc (typically higher than 0° C.) tends to provide a reinforcing film with a large adhesive strength increase ratio.

[0078] In some preferred embodiments, T B1 is 10°C or higher, more preferably 30°C or higher, even more preferably 40°C or higher, and may be 45°C or higher. B1 As T increases, the initial adhesive strength tends to be better suppressed. B1This is thought to be because, when the polymer (B) has a temperature of at least a predetermined temperature, the increase in the mobility and mobility of the polyorganosiloxane structural portion that accompanies a rise in temperature to room temperature or a region somewhat higher than room temperature is effectively suppressed by the monomer units derived from the (meth)acrylic monomer contained in the polymer (B), and the low adhesiveness resulting from the presence of the polyorganosiloxane structural portion can be better maintained. From the viewpoint of more stably maintaining the low adhesiveness at the initial stage of application, in some embodiments, T B1 may be, for example, 50°C or higher, 55°C or higher, or 60°C or higher. B1 For example, T may be 120°C or less, or may be 100°C or less. B1 When T is lower, the adhesive strength tends to increase more easily by heating. B1 is, for example, 90°C or lower, more preferably 70°C or lower, even more preferably 60°C or lower, and particularly preferably 55°C or lower (for example, 50°C or lower).

[0079] T B1 From the viewpoint of making it easier to exert the effect of appropriately setting the above, the total amount of the monomer S1 and the (meth)acrylic monomer in all the monomer components for preparing the polymer (B) may be, for example, 50% by weight or more, 70% by weight or more, 85% by weight or more, 90% by weight or more, 95% by weight or more, or even substantially 100% by weight.

[0080] Glass transition temperature T of polymer (B) B is not particularly limited and can be selected so as to obtain desirable properties in the reinforcing film disclosed herein. B The T of the polymer (B) may be, for example, less than 50°C, 30°C or less, 20°C or less, 15°C or less, or 10°C or less. B When the T of the polymer (B) is lowered, the mobility (typically temperature-sensitive mobility) of the polymer (B) is improved, and the adhesive strength can be significantly increased. In some preferred embodiments, the T of the polymer (B) Bis 5° C. or less, and may be less than 0° C., may be −5° C. or less, or may be −10° C. or less. In some embodiments, the T B For example, T may be −40° C. or higher, or may be −30° C. or higher. B The higher the T of the polymer (B), the more the polymer (B) unevenly distributed on the surface side of the pressure-sensitive adhesive layer when attached to an adherend contributes to a decrease in the initial adhesive strength, and the easier peelability at the initial stage of attachment tends to be excellent. B is -20°C or higher, and may be -15°C or higher. B By setting this within an appropriate range, it is possible to control the easy peelability at the initial stage of application and the increase in adhesive strength after heating within a preferred range.

[0081] In some embodiments, the composition of the monomer components for preparing polymer (B) is T B1 T B To be higher, i.e., T B1 -T B can be set so that the temperature is greater than 0° C. With such a composition, the effect of adjusting the mobility of the polymer (B) is easily achieved by the composition of the (meth)acrylic monomer contained in the monomer component. T B1 -T B For example, T may be about 40°C to 100°C, or about 50°C to 90°C. B1 -T B is 45° C. or higher, more preferably 50° C. or higher, and even more preferably 55° C. or higher (for example, 58° C. or higher). B1 -T B is preferably 80°C or lower, more preferably 70°C or lower, and even more preferably 65°C or lower (for example, 62°C or lower).

[0082] In order to facilitate control of the mobility of the polymer (B) in the pressure-sensitive adhesive layer, in some embodiments, the composition of the monomer components for preparing the polymer (B) is selected so as to have a temperature higher than the glass transition temperature T A In relation to T BT A 20°C higher than T B -T A In some preferred embodiments, T B -T A is, for example, 30° C. or higher, more preferably 40° C. or higher, and even more preferably 50° C. or higher, and may be 60° C. or higher, or may be 70° C. or higher. B -T A For example, the temperature may be 130°C or lower, 120°C or lower, preferably 100°C or lower, more preferably 80°C or lower, and even more preferably 65°C or lower, and may be 55°C or lower, or 45°C or lower.

[0083] Examples of (meth)acrylic monomers that can be used for the monomer raw material B include (meth)acrylic acid alkyl esters. The term "alkyl" used here refers to a chain (including linear and branched) alkyl (group) and does not include the alicyclic hydrocarbon group described below. For example, one or more of the monomers exemplified above as (meth)acrylic acid alkyl esters that can be used for the polymer (A) can be used as constituents of the monomer raw material B. In some embodiments, the monomer raw material B is (meth)acrylic acid C 4-12 Alkyl ester (preferably (meth)acrylic acid C 4-10 Alkyl esters, such as (meth)acrylic acid C 6-10 In some other embodiments, the monomer feedstock B may contain at least one of methacrylic acid C 1-18 Alkyl ester (preferably methacrylic acid C 1-14 Alkyl esters, such as methacrylic acid C 1-10 Monomer raw material B may contain, as a (meth)acrylic monomer, one or more selected from the group consisting of MMA, n-butyl methacrylate (BMA), and 2-ethylhexyl methacrylate (2EHMA).

[0084] Other examples of the (meth)acrylic monomer include (meth)acrylic acid esters having an alicyclic hydrocarbon group. For example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, etc. can be used. In some embodiments, the monomer raw material B may contain at least one (meth)acrylic monomer selected from dicyclopentanyl methacrylate, isobornyl methacrylate, and cyclohexyl methacrylate.

[0085] The content of the (meth)acrylic acid alkyl ester and the (meth)acrylic acid ester having an alicyclic hydrocarbon 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 viewpoint of ease of increasing adhesive strength by heating, the use of a (meth)acrylic acid alkyl ester may be advantageous. In some embodiments, the content of the (meth)acrylic acid ester having an alicyclic hydrocarbon group may be less than 50% by weight, less than 30% by weight, less than 15% by weight, less than 10% by weight, or less than 5% by weight of the monomer raw material B. The (meth)acrylic acid ester having an alicyclic hydrocarbon group need not be used.

[0086] In some preferred embodiments, the (meth)acrylic monomer constituting the monomer raw material B may include a monomer M2 having a homopolymer Tg of 50°C or higher. By copolymerizing the monomer S1 and the monomer M2 in the polymer (B), the mobility and movability of the polyorganosiloxane structural moiety with increasing temperature are favorably controlled, making it easier to achieve both easy initial releasability (reworkability) and increased adhesive strength after heating. In some embodiments, the Tg of the homopolymer of the monomer M2 may be 60°C or higher, 70°C or higher, 80°C or higher, or 90°C or higher. While there is no particular upper limit for the Tg of the homopolymer of the monomer M2, it is generally appropriate that it be 200°C or lower from the viewpoint of ease of synthesis of the polymer (B). In some embodiments, the Tg of the homopolymer of the monomer M2 may be, for example, 180°C or lower, 150°C or lower, or 120°C or lower.

[0087] As the monomer M2, for example, from among the (meth)acrylic monomers exemplified above, those whose homopolymer Tg satisfies the conditions can be used. For example, one or more monomers selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid esters having an alicyclic hydrocarbon group can be used. As the (meth)acrylic acid alkyl ester, a methacrylic acid alkyl ester having an alkyl group with 1 to 4 carbon atoms can be preferably used.

[0088] In embodiments in which the monomer starting material B contains the monomer M2, the content of the monomer M2 may be, for example, 5% by weight or more, 10% by weight or more, 15% by weight or more, 20% by weight or more, 25% by weight or more, or 30% by weight or more of the monomer starting material B. In some embodiments, the content of the monomer M2 may be 35% by weight or more, 40% by weight or more, 45% by weight or more, 50% by weight or more, or 55% by weight or more of the monomer starting material B. The content of the monomer M2 may be, for example, 90% by weight or less, typically 80% by weight or less, preferably 75% by weight or less, or may be 70% by weight or less, or may be 65% by weight or less. In some preferred embodiments, the content of the monomer M2 is 60% by weight or less (e.g., 50% by weight or less, typically 42% by weight or less). By limiting the copolymerization ratio of monomer M2 with a Tg of 50° C. or higher in polymer (B) to a predetermined value or less, it is possible to preferably achieve an increase in adhesive strength after heating based on the mobility of polymer (B) at around 50° C. From the same viewpoint, the content of monomer M2 in monomer raw material B may be 35% by weight or less, 25% by weight or less, or 15% by weight or less (e.g., 5% by weight or less).

[0089] The content of the monomer M2 is preferably, for example, in an embodiment in which the monomer M2 is composed of one or more monomers selected from the group consisting of (meth)acrylic acid alkyl esters and the (meth)acrylic acid esters having an alicyclic hydrocarbon group, or in an embodiment in which the monomer M2 is composed of one or more monomers selected from (meth)acrylic acid alkyl esters (e.g., methacrylic acid alkyl esters). One preferred example of such an embodiment is an embodiment in which the monomer M2 is composed of MMA.

[0090] In some embodiments, the (meth)acrylic monomer may contain a monomer M3 having a homopolymer Tg of less than 50°C (typically -20°C or more and less than 50°C). Use of the monomer M3 makes it easier to obtain a reinforcing film that has a good balance between adhesive strength and cohesive strength after the adhesive strength is increased. From the viewpoint of making it easier to exert such effects, it is preferable to use the monomer M3 in combination with the monomer M2.

[0091] The monomer M3 may be, for example, one of the (meth)acrylic monomers listed above, whose homopolymer Tg satisfies the conditions. For example, one or more monomers selected from the group consisting of (meth)acrylic acid alkyl esters may be used.

[0092] In an embodiment in which monomer raw material B contains monomer M3, the content of monomer M3 may be, for example, 5% by weight or more, 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 of monomer raw material B. The content of monomer M3 is usually suitably 70% by weight or less, 60% by weight or less, or 50% by weight or less of monomer raw material B. The above content of monomer M3 is preferably applied, for example, to an embodiment in which monomer M3 is composed of one or more monomers selected from (meth)acrylic acid alkyl esters (e.g., methacrylic acid alkyl esters).

[0093] In some embodiments of the reinforcing film disclosed herein, the monomer raw material B preferably contains 30% by weight or less of a monomer whose homopolymer Tg is higher than 170°C. Herein, unless otherwise specified, the term "a monomer content of X% by weight or less" refers to an embodiment in which the content of the monomer is 0% by weight, i.e., an embodiment in which the monomer is substantially not contained. Furthermore, "substantially not contained" means that the monomer is not used, at least intentionally. If the copolymerization ratio of a monomer whose homopolymer Tg is higher than 170°C is high, the mobility of polymer (B) tends to be insufficient, and it may be difficult to increase the adhesive strength by heating to a temperature range higher than 50°C.

[0094] In some embodiments, the monomer raw material B preferably contains at least MMA as a (meth)acrylic monomer. Polymer (B) copolymerized with MMA facilitates the production of a reinforcing film with high adhesive strength after heating. The proportion of MMA in the total amount of (meth)acrylic monomers contained in the monomer raw material B may 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. Furthermore, the proportion of MMA in the total amount of the monomer raw material B is typically 95% by weight or less. In some preferred embodiments, the proportion of MMA in the total amount of the monomer raw material B may be 75% by weight or less, 65% by weight or less, 60% by weight or less, or 55% by weight or less (e.g., 50% by weight or less) from the viewpoint of increasing adhesive strength after heating.

[0095] Other examples of monomers that can be contained together with monomer S1 as a monomer unit constituting polymer (B) 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 nitrogen atom-containing ring (N-vinyl cyclic amides, cyclic amides having a (meth)acryloyl group, monomers having a succinimide skeleton, maleimides, itaconimides, etc.), aminoalkyl (meth)acrylates, vinyl esters, vinyl ethers, olefins, (meth)acrylic acid esters having an aromatic hydrocarbon group, heterocyclic ring-containing (meth)acrylates, halogen atom-containing (meth)acrylates, and (meth)acrylic acid esters obtained from terpene compound-derived alcohols, all of which are exemplified above as monomers that can be used in polymer (A).

[0096] Further examples of monomers that can be contained together with the monomer S1 as a monomer unit constituting the polymer (B) include oxyalkylene di(meth)acrylates such as 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, and tripropylene glycol di(meth)acrylate; monomers having a polyoxyalkylene skeleton, such as polyethylene glycol and polypropylene glycol, polymerizable polyoxyalkylene ethers having a polymerizable functional group such as a (meth)acryloyl group, a vinyl group, or an allyl group at one end of the polyoxyalkylene chain and an ether structure (alkyl ether, aryl ether, aryl alkyl ether, or the like) at the other end; methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, and propoxyethyl (meth)acrylate. alkoxyalkyl (meth)acrylates such as butoxyethyl (meth)acrylate and ethoxypropyl (meth)acrylate; salts such as alkali metal (meth)acrylate salts; polyvalent (meth)acrylates such as trimethylolpropane tri(meth)acrylate; halogenated vinyl compounds such as vinylidene chloride and 2-chloroethyl (meth)acrylate; oxazoline group-containing monomers such as 2-vinyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, and 2-isopropenyl-2-oxazoline; aziridine group-containing monomers such as (meth)acryloylaziridine and 2-aziridinylethyl (meth)acrylate; hydroxyl group-containing vinyl monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and adducts of lactones and 2-hydroxyethyl (meth)acrylate; fluorine-containing vinyl monomers such as fluorine-substituted alkyl (meth)acrylates; reactive halogen-containing vinyl monomers such as 2-chloroethyl vinyl ether and vinyl monochloroacetate;Examples of suitable vinyl monomers include organosilicon-containing vinyl monomers such as vinyltrimethoxysilane, γ-(meth)acryloxypropyltrimethoxysilane, allyltrimethoxysilane, trimethoxysilylpropylallylamine, and 2-methoxyethoxytrimethoxysilane; and macromonomers having a radically polymerizable vinyl group at the end of a monomer formed by polymerizing a vinyl group. These may be copolymerized with monomer S1 either alone or in combination of two or more.

[0097] In some embodiments, the polymer (B) preferably does not have a functional group that undergoes a crosslinking reaction with the polymer (A). In other words, the polymer (B) is preferably contained in the pressure-sensitive adhesive layer in a form that is not chemically bonded to the polymer (A). A pressure-sensitive adhesive layer containing the polymer (B) in such a form exhibits good mobility of the polymer (B) upon heating, and is suitable for improving the adhesive strength increase ratio. The functional group that undergoes a crosslinking reaction with the polymer (A) may vary depending on the type of functional group possessed by the polymer (A), and may be, for example, an epoxy group, an isocyanate group, a carboxy group, an alkoxysilyl group, an amino group, etc.

[0098] The Mw of polymer (B) is not particularly limited. The Mw of polymer (B) may be, for example, 1,000 or more, or 5,000 or more. In some preferred embodiments, from the viewpoint of favorably exhibiting an increase in adhesive strength after heating, the Mw of polymer (B) is 10,000 or more, more preferably 12,000 or more, 15,000 or more, 20,000 or more, 22,000 or more, or 25,000 or more. In other embodiments, the Mw of polymer (B) may be 30,000 or more, 50,000 or more, or 70,000 or more. The upper limit of the Mw of polymer (B) is, for example, 500,000 or less, 350,000 or less, 200,000 or less, or 150,000 or less. From the viewpoint of adjusting the compatibility and mobility within the pressure-sensitive adhesive layer within an appropriate range and suitably exhibiting low adhesiveness in the initial stage of application, in some preferred embodiments, the Mw of polymer (B) is 100,000 or less, more preferably 80,000 or less, even more preferably 60,000 or less, particularly preferably 40,000 or less (e.g., 30,000 or less), and may be 25,000 or less, or even 20,000 or less. By setting the Mw of polymer (B) within an appropriate range, a pressure-sensitive adhesive that is excellent in both easy peelability and increased adhesive strength in the initial stage of application can be easily obtained.

[0099] In some preferred embodiments, the Mw of polymer (B) is preferably lower than the Mw of polymer (A). This makes it easier to realize a reinforcing film that has both good reworkability at the initial stage of application and increased adhesive strength after heating. In some embodiments, the Mw of polymer (B) may be, for example, 0.8 times or less, 0.75 times or less, 0.5 times or less, or 0.3 times or less of the Mw of polymer (A). In some preferred embodiments, the Mw of polymer (B) may be, for example, 0.8 times or less, 0.75 times or less, 0.5 times or less, or 0.3 times or less of the Mw of polymer (A). A Mw of polymer (B) B Ratio (Mw B / Mw A ) is 0.3 or less, more preferably 0.2 or less, even more preferably 0.1 or less, and particularly preferably 0.06 or less (for example, 0.05 or less). B / MwA ) is suitably, for example, 0.010 or more, preferably 0.020 or more, more preferably 0.03 or more, and even more preferably 0.04 or more. By setting the Mw of polymer (A) and the Mw of polymer (B) within appropriate ranges, the effects of the technology disclosed herein can be more effectively achieved. In some other embodiments, the Mw of polymer (B) may be 0.03 times or less (e.g., 0.02 times or less) the Mw of polymer (A).

[0100] The polymer (B) can be prepared, for example, by polymerizing the above-mentioned monomers by a known method such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, or photopolymerization.

[0101] A chain transfer agent can be used as needed to adjust the molecular weight of the polymer (B). Examples of the chain transfer agent include compounds having a mercapto group, such as octyl mercaptan, lauryl mercaptan, t-nonyl mercaptan, t-dodecyl mercaptan, mercaptoethanol, and α-thioglycerol; thioglycolic acid esters, such as thioglycolic acid, methyl thioglycolate, ethyl thioglycolate, propyl thioglycolate, butyl thioglycolate, t-butyl thioglycolate, 2-ethylhexyl thioglycolate, octyl thioglycolate, isooctyl thioglycolate, decyl thioglycolate, dodecyl thioglycolate, ethylene glycol thioglycolate, neopentyl glycol thioglycolate, and pentaerythritol thioglycolate; and α-methylstyrene dimer.

[0102] The amount of chain transfer agent used is not particularly limited, but is usually 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, of the chain transfer agent per 100 parts by weight of the monomer. By adjusting the amount of chain transfer agent added in this manner, a polymer (B) with a suitable molecular weight can be obtained. The chain transfer agents can be used alone or in combination of two or more.

[0103] As a means for adjusting the molecular weight of polymer (B), various conventionally known means, including the use of the chain transfer agent, can be used alone or in appropriate combination. The same applies to the molecular weight of polymer (A). Non-limiting examples of such means include selection of the polymerization method, selection of the type and amount of polymerization initiator used, selection of the polymerization temperature, selection of the type and amount of polymerization solvent used in solution polymerization, and selection of the light irradiation intensity in photopolymerization. Those skilled in the art will understand how to obtain a polymer having a desired molecular weight based on the description of the present specification, including the specific examples described below, and the common general technical knowledge at the time of filing of this application.

[0104] In the reinforcing film disclosed herein, the amount of polymer (B) used relative to 100 parts by weight of polymer (A) can be, for example, 0.1 parts by weight or more. From the viewpoint of obtaining a higher effect (preferably, easy peelability at the initial stage of application), it is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, even more preferably 1.5 parts by weight or more, and may be 2 parts by weight or more. In some embodiments, from the viewpoint of improving reworkability, the amount of polymer (B) used can be, for example, 3 parts by weight or more, or even 4 parts by weight or more, or even 5 parts by weight or more. Furthermore, the amount of polymer (B) used relative to 100 parts by weight of polymer (A) can be, for example, 75 parts by weight or less, 30 parts by weight or less, 10 parts by weight or less, or 8 parts by weight or less. From the viewpoint of suitably achieving the desired increase in adhesive strength, in some preferred embodiments, the amount of polymer (B) used relative to 100 parts by weight of polymer (A) is 5 parts by weight or less, more preferably 4 parts by weight or less, even more preferably 3 parts by weight or less, and particularly preferably 2.5 parts by weight or less. In some other preferred embodiments, the amount of polymer (B) used per 100 parts by weight of polymer (A) is 1.5 parts by weight or less (e.g., 1.2 parts by weight or less). By using the amount of polymer (B) within the above range, it is easy to achieve good flex recovery and flex retention. In addition, it is possible to better achieve both easy peeling properties and increased adhesive strength at the initial stage of application.

[0105] The pressure-sensitive adhesive layer may contain a polymer (optional polymer) other than polymer (A) and polymer (B) as needed, provided that the performance of the reinforcing film disclosed herein is not significantly impaired. The amount of such optional polymer used is typically 20% by weight or less of the total polymer components contained in the pressure-sensitive adhesive layer, and may be 15% by weight or less, or 10% by weight or less. In some embodiments, the amount of the optional polymer used may be 5% by weight or less, 3% by weight or less, or 1% by weight or less of the total polymer components. The pressure-sensitive adhesive layer may also be substantially free of polymers other than polymer (A) and polymer (B).

[0106] (Crosslinking agent) A crosslinking agent may be used in the pressure-sensitive adhesive layer as needed for purposes such as adjusting cohesive strength. Examples of crosslinking agents that can be used include crosslinking agents known in the field of pressure-sensitive adhesives, such as epoxy-based crosslinking agents, isocyanate-based crosslinking agents, silicone-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, silane-based crosslinking agents, alkyl etherified melamine-based crosslinking agents, and metal chelate-based crosslinking agents. Isocyanate-based crosslinking agents, epoxy-based crosslinking agents, and metal chelate-based crosslinking agents are preferably used. An isocyanate-based crosslinking agent is preferably used as a crosslinking agent that satisfies both flex recovery and flex retention. The crosslinking agents can be used alone or in combination of two or more.

[0107] As the isocyanate-based crosslinking agent, a polyfunctional isocyanate (which refers to a compound having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. The isocyanate-based crosslinking agent can be used alone or in combination of two or more.

[0108] Examples of polyfunctional isocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates. Specific examples of aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; hexamethylene diisocyanates such as 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

[0109] Specific examples of alicyclic polyisocyanates include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0110] Specific examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, Examples of the diisocyanate include 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, and xylylene-1,3-diisocyanate.

[0111] A preferred example of the polyfunctional isocyanate is one having an average of three or more isocyanate groups per molecule. Such a trifunctional or higher isocyanate may be a multimer (e.g., a dimer or trimer) of a bifunctional or trifunctional or higher isocyanate, a derivative (e.g., an addition reaction product of a polyhydric alcohol with two or more molecules of a polyfunctional isocyanate), a polymer, or the like. Examples of the isocyanate include dimers and trimers of diphenylmethane diisocyanate, isocyanurates of hexamethylene diisocyanate (trimer adducts with an isocyanurate structure), reaction products of trimethylolpropane and tolylene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, trimethylolpropane adducts of xylylene diisocyanate, trimethylolpropane adducts of isophorone diisocyanate, trimethylolpropane adducts of hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, and adducts of these with various polyols, and polyfunctional isocyanates such as polyisocyanates multifunctionalized with isocyanurate bonds, biuret bonds, allophanate bonds, etc.

[0112] Commercially available products of the polyfunctional isocyanate include those manufactured by Asahi Kasei Chemicals Corporation under the trade name "Duranate TPA-100," those manufactured by Tosoh Corporation under the trade names "Coronate L," "Coronate HL," "Coronate HK," "Coronate HX," and "Coronate 2096," and those manufactured by Mitsui Chemicals, Inc. under the trade names "Takenate D110N," "Takenate D120N," "Takenate D140N," and "Takenate D160N."

[0113] Examples of epoxy crosslinking agents include bisphenol A, epichlorohydrin-type epoxy resins, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diamine glycidylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane. These may be used alone or in combination of two or more.

[0114] Examples of metal chelate compounds include aluminum, iron, tin, titanium, nickel, etc. as metal components, and acetylene, methyl acetoacetate, ethyl lactate, etc. as chelate components. These can be used alone or in combination of two or more.

[0115] When a crosslinking agent is used, the amount used is not particularly limited and can be, for example, an amount greater than 0 parts by weight per 100 parts by weight of polymer (A). The amount of crosslinking agent used can be, for example, 0.01 parts by weight or more, preferably 0.05 parts by weight or more, per 100 parts by weight of polymer (A). Increasing the amount of crosslinking agent used tends to suppress initial adhesive strength after application and improve reworkability. It also tends to provide excellent flex recovery and processability. In some embodiments, the amount of crosslinking agent used per 100 parts by weight of polymer (A) may be 0.1 parts by weight or more, 0.5 parts by weight or more, or even 0.8 parts by weight or more. On the other hand, from the viewpoint of allowing a moderate degree of mobility of polymer (B) and achieving increased adhesive strength after heating, the amount of crosslinking agent used per 100 parts by weight of polymer (A) is typically 15 parts by weight or less, and may be 10 parts by weight or less, or may be 5 parts by weight or less.

[0116] The technology disclosed herein can be preferably implemented in an embodiment using at least an isocyanate-based crosslinking agent as a crosslinking agent. From the viewpoint of achieving both good reworkability at the initial stage of application and increased adhesive strength after heating, in some embodiments, the amount of isocyanate-based crosslinking agent used per 100 parts by weight of polymer (A) can be, for example, 0.01 parts by weight or more, preferably 0.05 parts by weight or more, more preferably 0.07 parts by weight or more, and may be 0.10 parts by weight or more, or even 0.15 parts by weight or more (e.g., 0.20 parts by weight or more). Increasing the amount of isocyanate-based crosslinking agent used tends to provide appropriate cohesive strength and elastic modulus, and also to provide excellent flex recovery and processability. Furthermore, the amount of isocyanate-based crosslinking agent used per 100 parts by weight of polymer (A) can be, for example, 5 parts by weight or less, preferably less than 1.0 parts by weight, more preferably less than 0.5 parts by weight, even more preferably less than 0.3 parts by weight, and particularly preferably less than 0.2 parts by weight (e.g., 0.15 parts by weight or less). This appropriately reduces the cohesive strength of the adhesive and hence the modulus of elasticity (typically the surface modulus of elasticity), resulting in good bending retention and also making it easier to obtain an increase in adhesive strength after heating.

[0117] Although not particularly limited, when an isocyanate-based crosslinking agent is used in a configuration in which the pressure-sensitive adhesive layer contains a hydroxyl group-containing monomer as a monomer unit, the molar ratio of the isocyanate group to the hydroxyl group contained in the pressure-sensitive adhesive layer ([NCO] / [OH]) can be, for example, 0.001 or more. By increasing the amount of isocyanate-based crosslinking agent used relative to the hydroxyl group-containing monomer in this way, the elastic modulus (typically the surface elastic modulus) of the pressure-sensitive adhesive falls within a suitable range, and flex recovery tends to be improved. Furthermore, processability also tends to be excellent. In some preferred embodiments, the molar ratio ([NCO] / [OH]) is 0.002 or more, more preferably 0.004 or more, even more preferably 0.006 or more (e.g., 0.007 or more), and may be 0.010 or more, 0.020 or more, or 0.030 or more. Furthermore, the molar ratio ([NCO] / [OH]) can be, for example, 1.0 or less, or may be 0.10 or less. By limiting the molar ratio to a predetermined value or less, a crosslinked structure suitable for significantly increasing the adhesive strength after heating relative to the adhesive strength at the initial stage of application can be preferably formed. In some preferred embodiments, the molar ratio ([NCO] / [OH]) is 0.030 or less, more preferably 0.015 or less, even more preferably 0.012 or less (e.g., 0.009 or less), and may be 0.005 or less. In the adhesive layer, at least a portion of the isocyanate groups and hydroxyl groups may exist in a chemically bonded (crosslinked) state. More specifically, the isocyanate groups may exist in a chemically bonded (crosslinked) state with the hydroxyl groups. Meanwhile, some of the hydroxyl groups may exist chemically bonded to the isocyanate groups, while the other portion may exist in a state not chemically bonded (crosslinked) to the isocyanate groups.

[0118] In some preferred embodiments, the pressure-sensitive adhesive layer contains a catalyst. The catalyst may be added to promote curing of the pressure-sensitive adhesive layer during formation, typically to more effectively promote any of the crosslinking reactions described above. Therefore, the catalyst is also referred to as a curing catalyst or a crosslinking catalyst. Adding a catalyst promotes initial curing and suppresses side reactions that can cause bubbles on the surface of the pressure-sensitive adhesive layer. Examples of catalysts include organometallic compounds such as iron-based catalysts, tin-based catalysts, titanium-based catalysts, zirconium-based catalysts, lead-based catalysts, cobalt-based catalysts, and zinc-based catalysts, as well as tertiary amine compounds. These may be used alone or in combination. Among these, iron-based catalysts and tin-based catalysts are preferred from the standpoint of balance between reaction rate and pot life, with iron-based catalysts being particularly preferred.

[0119] Examples of iron-based catalysts include iron acetylacetonate, iron 2-ethylhexanoate, etc. The iron-based catalysts may be used alone or in combination of two or more.

[0120] Examples of tin-based catalysts include dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin maleate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin sulfide, tributyltin methoxide, tributyltin acetate, triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, dioctyltin dilaurate, tributyltin chloride, tributyltin trichloroacetate, tin 2-ethylhexanoate, etc. The tin-based catalysts can be used alone or in combination of two or more.

[0121] The amount of catalyst used is not particularly limited and can be, for example, 0.0001 parts by weight or more, preferably 0.001 parts by weight or more, more preferably 0.003 parts by weight or more, even more preferably 0.006 parts by weight or more, and particularly preferably 0.008 parts by weight or more, per 100 parts by weight of polymer (A). Using an appropriate amount of catalyst can suppress the generation of bubbles from the adhesive layer, making it easier to obtain a smooth adhesive surface. Furthermore, the amount of catalyst used per 100 parts by weight of polymer (A) can be, for example, 1 part by weight or less, and may be 0.1 parts by weight or less. In some preferred embodiments, the amount of catalyst used per 100 parts by weight of polymer (A) is 0.03 parts by weight or less, more preferably 0.02 parts by weight or less, even more preferably 0.01 parts by weight or less, and may be 0.005 parts by weight or less. By appropriately limiting the amount of catalyst used per 100 parts by weight of polymer (A), it is easy to achieve a suitable increase in adhesive strength.

[0122] Although not particularly limited, when a catalyst is used in a configuration in which the pressure-sensitive adhesive layer contains a hydroxyl group-containing monomer as a monomer unit, the amount of catalyst used is, for example, 1.0 × 10 -6 The amount can be set to 1.0×10 or more, preferably 1.0×10 -5 More preferably, 1.0 × 10 -4 More preferably, 2.0 × 10 -4 More preferably, 3.0 × 10 -4 By using an appropriate amount of catalyst, the generation of bubbles from the adhesive layer is suppressed, and a smooth adhesive surface is easily obtained. In addition, the molar ratio ([catalyst] / [OH]) is, for example, 5.0 × 10 -2 It can be 5.0 x 10 -3 In some preferred embodiments, the molar ratio ([catalyst] / [OH]) is 3.0×10 or less. -3 or less, and more preferably 1.0 × 10 -3 or less, more preferably 5.0 × 10 -4 is less than or equal to 3.0 x 10 -4 By appropriately limiting the catalyst content, it is easy to achieve a suitable increase in adhesive strength.

[0123] (tackifying resin) The pressure-sensitive adhesive layer may contain a tackifying resin as needed. The tackifying resin is not particularly limited, but examples thereof include rosin-based tackifying resins, terpene-based tackifying resins, phenol-based tackifying resins, hydrocarbon-based tackifying resins, ketone-based tackifying resins, polyamide-based tackifying resins, epoxy-based tackifying resins, and elastomer-based tackifying resins. The tackifying resins may be used alone or in combination of two or more.

[0124] The content of the tackifier resin is not particularly limited and can be set so as to exhibit appropriate adhesive performance depending on the purpose and application. The content of the tackifier resin (when two or more types of tackifier resins are included, the total amount thereof) per 100 parts by weight of polymer (A) can be, for example, about 5 to 500 parts by weight. The technology disclosed herein can also be preferably implemented in an embodiment in which the amount of tackifier resin used is limited. For example, the content of the tackifier resin per 100 parts by weight of polymer (A) can be less than 20 parts by weight, or even less than 10 parts by weight, or even less than 3 parts by weight, or even less than 1 part by weight (0 parts by weight to less than 1 part by weight). In some embodiments, the pressure-sensitive adhesive layer is substantially free of tackifier resin.

[0125] In addition, the adhesive layer in the technology disclosed herein may contain, as needed, known additives that can be used in adhesives, such as leveling agents, plasticizers, softeners, colorants (dyes, pigments, etc.), fillers, antistatic agents, antioxidants, UV absorbers, antioxidants, light stabilizers, and preservatives, as long as the effects of the present invention are not significantly impaired.

[0126] The pressure-sensitive adhesive layer constituting the reinforcing film disclosed herein may be a cured layer of a pressure-sensitive adhesive composition. That is, the pressure-sensitive adhesive layer can be formed by applying (e.g., coating) a water-dispersible, solvent-based, photocurable, hot-melt, or other pressure-sensitive adhesive composition to a suitable surface, followed by an appropriate curing treatment. When two or more curing treatments (drying, crosslinking, polymerization, cooling, etc.) are performed, these can be performed simultaneously or in multiple stages. For pressure-sensitive adhesive compositions using a partially polymerized product (polymer syrup) of a monomer raw material, the curing treatment typically involves a final copolymerization reaction. That is, the partially polymerized product is subjected to a further copolymerization reaction to form a fully polymerized product. For example, in the case of a photocurable pressure-sensitive adhesive composition, light irradiation is performed. Curing treatments such as crosslinking and drying may be performed as needed. For example, if a photocurable pressure-sensitive adhesive composition requires drying, photocuring may be performed after drying. For pressure-sensitive adhesive compositions using a fully polymerized product, the curing treatment typically involves drying (heat drying), crosslinking, or other treatments as needed.

[0127] The pressure-sensitive adhesive composition can be applied using a conventional coater such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater or spray coater.

[0128] The thickness of the pressure-sensitive adhesive layer is not particularly limited and can be, for example, 6 μm or more. In some embodiments, the thickness of the pressure-sensitive adhesive layer may be 8 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more or more than 20 μm. Increasing the thickness of the pressure-sensitive adhesive layer tends to increase the adhesive strength after heating. In some embodiments, the thickness of the pressure-sensitive adhesive layer may 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. Not having an excessively thick pressure-sensitive adhesive layer can be advantageous from the perspective of reducing the thickness of the reinforcing film and preventing cohesive failure of the pressure-sensitive adhesive layer. A reinforcing film having a pressure-sensitive adhesive layer with a thickness within the above-mentioned range can have a well-balanced adhesive properties such as adhesive strength, flex recovery, and flex retention. In the case of a reinforcing film having a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer on the first and second surfaces of a substrate, the thickness of the pressure-sensitive adhesive layer described above can be applied to at least the thickness of the first pressure-sensitive adhesive layer. The thickness of the second pressure-sensitive adhesive layer can also be selected from a similar range. In the case of a reinforcing film without a substrate, the thickness of the reinforcing film is the same as the thickness of the pressure-sensitive adhesive layer.

[0129] <Supporting base material> The reinforcing film according to some embodiments may be in the form of a substrate-attached pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one or both sides of a support substrate. The material of the support substrate is not particularly limited and can be appropriately selected depending on the intended use and manner of use of the reinforcing film. Non-limiting examples of substrates that can be used include resin films such as plastic films; foam sheets made of foams such as polyurethane foam, polyethylene foam, and polychloroprene foam; woven and nonwoven fabrics made by single or mixed spinning of various fibrous materials (natural fibers such as hemp and cotton, synthetic fibers such as polyester and vinylon, semi-synthetic fibers such as acetate, etc.); paper such as Japanese paper, fine paper, kraft paper, and crepe paper; and metal foils such as aluminum foil and copper foil. Substrates having a composite structure of these may also be used. Examples of such composite substrates include substrates having a structure in which metal foil and the above-mentioned plastic film are laminated, and plastic substrates reinforced with inorganic fibers such as glass cloth.

[0130] Various film substrates can be preferably used as the substrate of the reinforcing film disclosed herein. The film substrate may be a porous substrate such as a foam film or a nonwoven fabric sheet, a nonporous substrate, or a substrate having a structure in which a porous layer and a nonporous layer are laminated. In some embodiments, the film substrate preferably includes a base film that is an independently shape-retaining (self-supporting or independent) resin film. Here, the term "resin film" refers to a resin film that has a nonporous structure and typically contains substantially no air bubbles (void-free). Therefore, the resin film is a concept that is distinct from foam films and nonwoven fabrics. The resin film preferably includes an independently shape-retaining (self-supporting or independent) resin film. The resin film may have a single-layer structure or a multi-layer structure of two or more layers (e.g., a three-layer structure).

[0131] Examples of resin materials that can be used to form the resin film include polyester, polyolefin, polyamide (PA) such as nylon 6, nylon 66, and partially aromatic polyamide, polyimide (PI), polyamideimide (PAI), polyetheretherketone (PEEK), polyethersulfone (PES), polyphenylene sulfide (PPS), polycarbonate (PC), polyurethane (PU), ethylene-vinyl acetate copolymer (EVA), fluororesin such as polytetrafluoroethylene (PTFE), acrylic resin, polyacrylate, polystyrene, polyvinyl chloride, and polyvinylidene chloride. The resin film may be formed using a resin material containing only one of these resins, or may be formed using a resin material containing a blend of two or more of these resins. The resin film may be unstretched or stretched (for example, uniaxially or biaxially stretched).

[0132] Suitable examples of resin materials constituting the resin film include polyimide-based resins, polyester-based resins, PPS resins, and polyolefin-based resins. Here, polyimide-based resins refer to resins containing more than 50% by weight of polyimide. Similarly, polyester-based resins refer to resins containing more than 50% by weight of polyester, PPS resins refer to resins containing more than 50% by weight of PPS, and polyolefin-based resins refer to resins containing more than 50% by weight of polyolefin.

[0133] Specific examples of polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and polybutylene naphthalate.

[0134] The polyolefin resin can be a single polyolefin or a combination of two or more polyolefins. The polyolefin can be, for example, an α-olefin homopolymer, a copolymer of two or more α-olefins, or a copolymer of one or more α-olefins with other vinyl monomers. Specific examples include polyethylene (PE), polypropylene (PP), poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymers such as ethylene-propylene rubber (EPR), ethylene-propylene-butene copolymers, ethylene-butene copolymers, ethylene-vinyl alcohol copolymers, and ethylene-ethyl acrylate copolymers. Both low-density (LD) and high-density (HD) polyolefins can 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 made by blending two or more types of polyethylene (PE), and PP / PE blend film made by blending polypropylene (PP) and polyethylene (PE).

[0135] Specific examples of resin films that can be preferably used as the base film of the reinforcing film disclosed herein include PI film, PET film, PEN film, PPS film, PEEK film, CPP film and OPP film.

[0136] The resin film may contain known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slip agents, antiblocking agents, etc., as needed, provided that the effects of the present invention are not significantly impaired. The amount of additives added is not particularly limited and can be appropriately determined depending on the purpose, etc.

[0137] The method for producing the resin film is not particularly limited, and any conventionally known resin film forming method such as extrusion molding, inflation molding, T-die casting, or calendar roll molding can be appropriately used.

[0138] The substrate may be substantially composed of 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 adjusting layer (e.g., a coloring layer, an anti-reflection layer), a printed layer or a laminate layer for imparting a desired appearance to the substrate, an antistatic layer, an undercoat layer, a release layer, or other surface treatment layer.

[0139] The thickness of the substrate is not particularly limited and can be selected depending on the purpose and mode of use of the reinforcing film. The thickness of the substrate can be, for example, 1000 μm or less. In some embodiments, from the viewpoint of the handleability and processability of the reinforcing film, 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. In some embodiments, from the viewpoint of miniaturization and weight reduction of the product to which the reinforcing film is applied, 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. As the thickness of the substrate decreases, the flexibility of the reinforcing film and its ability to conform to the surface shape of the adherend tend to improve. Furthermore, from the viewpoint of handleability and processability, the thickness of the substrate may be, for example, 2 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, 25 μm or more, or more than 25 μm. In some embodiments, the thickness of the substrate may 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 a reinforcing film that can be used for purposes such as reinforcing, supporting, and shock absorption of an adherend, a substrate having a thickness of 30 μm or more may be preferably used.

[0140] The first surface of the substrate may be subjected to a conventional surface treatment, such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or formation of an undercoat layer by applying a primer, as needed. Such a surface treatment may be intended to improve the anchoring ability of the pressure-sensitive adhesive layer to the substrate. For example, a substrate that has been subjected to such an anchoring ability-improving treatment may be preferably used in a reinforcing film having a substrate containing a resin film as a base film. The above surface treatments may be applied alone or in combination. The composition of the primer used to form the undercoat layer is not particularly limited and may be appropriately selected from known primers. The thickness of the undercoat layer is not particularly limited, but is typically approximately 0.01 μm to 1 μm, preferably approximately 0.1 μm to 1 μm. Other treatments that may be applied to the first surface of the substrate as needed include antistatic layer formation, colored layer formation, printing, etc.

[0141] When the reinforcing film disclosed herein is in the form of a single-sided PSA sheet having a PSA layer only on the first surface of the substrate, the second surface of the substrate may be subjected to a conventional surface treatment, such as a release treatment or an antistatic treatment, as needed. For example, by surface treating the back surface of the substrate with a release agent (typically by providing a release layer made of a release agent), the unwinding force of the reinforcing film wound into a roll can be reduced. Examples of release agents that can be used include silicone-based release agents, long-chain alkyl-based release agents, olefin-based release agents, fluorine-based release agents, fatty acid amide-based release agents, molybdenum sulfide, and silica powder. Furthermore, for purposes such as improving printability, reducing light reflectivity, and improving overlapping properties, the second surface of the substrate may be subjected to a corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or the like. Furthermore, in the case of a double-sided PSA sheet, the second surface of the substrate may be subjected to a surface treatment similar to the examples given above for the surface treatment that can be applied to the first surface of the substrate, as needed. The surface treatments applied to the first surface and the second surface of the substrate may be the same or different.

[0142] <Characteristics of the reinforcing film> The reinforcing film disclosed herein has an initial adhesive strength N measured after being attached to a stainless steel plate and kept at 23°C for 30 minutes. 23 In some embodiments, the adhesive force N 23 is, for example, preferably less than 500 gf / 25 mm, more preferably less than 400 gf / 25 mm, even more preferably less than 300 gf / 25 mm, particularly preferably 250 gf / 25 mm or less (for example, 200 gf / 25 mm or less), and may be 150 gf / 25 mm or less. 23 A low adhesive strength (N) is desirable from the viewpoint of reworkability. 23 The lower limit of the adhesive strength N is not particularly limited, and may be, for example, 0.1 gf / 25 mm or more. 23 In order to improve the adhesive strength after heating, it is usually appropriate that the adhesive strength N 23 may be, for example, 20 gf / 25 mm or more, 50 gf / 25 mm or more, 80 gf / 25 mm or more, or 100 gf / 25 mm or more (for example, 150 gf / 25 mm or more).

[0143] Adhesive force N 23 [gf / 25mm] is determined by pressing the film onto a stainless steel (SUS) plate as the adherend, leaving it in an environment of 23°C and 50% RH for 30 minutes, and then measuring the 180° peel adhesive strength in the same environment (i.e., at 23°C) under conditions of a peel angle of 180° and a pulling speed of 300mm / min. SUS304BA plate is used as the adherend. When measuring, if necessary, the reinforcing film to be measured can be reinforced by attaching an appropriate backing material (for example, a PET film with a thickness of about 25μm). Adhesion strength N 23 More specifically, the initial adhesive strength can be measured in accordance with the method for measuring the initial adhesive strength described in the Examples below.

[0144] The reinforcing film disclosed herein has an adhesive strength that increases when heated, and for example, has an adhesive strength of N 60 That is, the adhesive strength measured at 23°C after being attached to a stainless steel plate and kept at 60°C for 60 minutes may be 300 gf / 25 mm or more. 60 The adhesive strength is 400 gf / 25 mm or more, and suitably 500 gf / 25 mm or more. A reinforcing film that satisfies these characteristics will have its adhesive strength increased to a predetermined value or more by heating after being attached to an adherend. The technology disclosed herein makes it possible to obtain strong adhesive strength by heating. In some preferred embodiments, the adhesive strength N 60 is 600 gf / 25 mm or more, more preferably 700 gf / 25 mm or more, may be 800 gf / 25 mm or more, or may be 900 gf / 25 mm or more. 60 There is no particular upper limit to the adhesive strength N. In some embodiments, from the viewpoint of ease of production of the reinforcing film and economic efficiency, 60 may be, for example, 3000 gf / 25 mm or less, 1500 gf / 25 mm or less, or 1000 gf / 25 mm or less.

[0145] Adhesive force N 60 [gf / 25mm] is determined by pressing the adhesive onto a SUS plate as the adherend, keeping it in a 60°C environment for 60 minutes, then leaving it in a 23°C, 50% RH environment for 30 minutes, and then measuring the 180° peel adhesive strength in the same environment at a peel angle of 180° and a pulling speed of 300mm / min. 23 As in the previous example, a SUS304BA plate is used. When making measurements, if necessary, the reinforcing film to be measured can be reinforced by attaching an appropriate backing material (for example, a PET film with a thickness of about 25 μm). Adhesion strength N 60 More specifically, the adhesive strength after heating can be measured in accordance with the method for measuring the adhesive strength after heating described in the examples below.

[0146] Adhesive force N 23 Adhesion strength N against [gf / 25mm] 60[gf / 25mm] ratio, i.e., adhesive strength increase ratio N 60 / N 23 is not particularly limited. In some embodiments, N 60 / N 23 is suitably 1.5 or more, preferably 2.0 or more, more preferably 2.5 or more, and further preferably 3.0 or more. 60 / N 23 A reinforcing film having a large N exhibits good reworkability in the initial stage of application, and can significantly increase adhesive strength by subsequent heating or the like. 60 / N 23 may be 3.5 or more, 4.0 or more, 5.0 or more, 5.5 or more, more than 6.0, or more than 7.0. 60 / N 23 The upper limit of N is not particularly limited, and is usually 100 or less, and from the viewpoint of ease of production of the reinforcing film and economic efficiency, it may be 30 or less, 15 or less, or 10 or less. 60 / N 23 may be, for example, 5 or less, 3 or less, or 2 or less.

[0147] The adhesive strength after heating of the reinforcing film disclosed herein represents one characteristic of the reinforcing film and does not limit the use of the reinforcing film. In other words, the use of the reinforcing film disclosed herein is not limited to heating at 60°C for 60 minutes. For example, the reinforcing film can also be used in a mode in which heating to a temperature above room temperature (usually 20°C to 30°C, typically 23°C to 25°C) is not particularly performed. Even in such a mode of use, the adhesive strength increases over the long term, achieving strong bonding. Furthermore, the reinforcing film disclosed herein can be subjected to a heat treatment at a temperature above 30°C (e.g., approximately 50 to 70°C) or above 60°C at any time after application, thereby promoting an increase in adhesive strength. The heating temperature in such a heat treatment is not particularly limited and can be set taking into consideration workability, economy, the heat resistance of the substrate of the reinforcing film, the adherend, and the like. The heating temperature may be, for example, less than 150°C, 120°C or less, 100°C or less, 80°C or less, or 70°C or less. The heating temperature can be, for example, 40°C or higher, 45°C or higher, 50°C or higher, 55°C or higher, 60°C or higher, or 70°C or higher, or may be 80°C or higher, or 100°C or higher. The heating time is not particularly limited and may be, for example, 3 hours or less, 1 hour or less, 30 minutes or less, or 10 minutes or less. The heating time may be, for example, 1 minute or more, 15 minutes or more, 30 minutes or more, or 1 hour or more. Alternatively, the heating treatment may be performed for a longer period of time as long as significant thermal degradation does not occur in the reinforcing film or the adherend. The heating treatment may be performed all at once or in multiple steps.

[0148] <Reinforcing film with substrate> When the reinforcing film disclosed herein is in the form of a substrate-attached pressure-sensitive adhesive sheet, the thickness of the reinforcing film may be, for example, 1000 μm or less, 600 μm or less, 350 μm or less, or 250 μm or less. From the viewpoint of miniaturization, weight reduction, thinning, etc. of products to which the reinforcing film is applied, in some embodiments, the thickness of the reinforcing film may be, for example, 200 μm or less, 175 μm or less, 140 μm or less, 120 μm or less, or 100 μm or less (e.g., less than 100 μm). Furthermore, from the viewpoint of handleability, etc., the thickness of the reinforcing film may be, for example, 5 μm or more, 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, or 30 μm or more. In some embodiments, the thickness of the reinforcing film may 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 reinforcing film is not particularly limited. The thickness of the reinforcing film refers to the thickness of the portion attached to the adherend. For example, in the case of the reinforcing film 1 having the configuration shown in Fig. 1, the thickness refers to the thickness from the adhesive surface 21A of the reinforcing film 1 to the second surface 10B of the substrate 10, and does not include the thickness of the release liner 31.

[0149] The reinforcing film disclosed herein can be suitably implemented, for example, in an embodiment in which the thickness Ts of the support substrate is greater than the thickness Ta of the pressure-sensitive adhesive layer, i.e., in an embodiment in which Ts / Ta is greater than 1. Although not particularly limited, Ts / Ta may be, for example, 1.1 or greater, 1.2 or greater, 1.5 or greater, or 1.7 or greater. For example, an increase in Ts / Ta tends to make it easier to achieve good effects even when the reinforcing film is made thinner. In some embodiments, Ts / Ta may be 2 or greater (e.g., greater than 2), 2.5 or greater, or 2.8 or greater. Furthermore, Ts / Ta may be, for example, 50 or less, or 20 or less. From the viewpoint of making it easier for the reinforcing film to exhibit high post-heat adhesive strength even when made thinner, Ts / Ta may be, for example, 10 or less, 8 or less, or 5 or less.

[0150] The pressure-sensitive adhesive layer is preferably adhered to the supporting substrate. Here, "adhesion" refers to a state in which, in a reinforcing film whose adhesive strength has increased after application to an adherend, the adhesive layer exhibits sufficient anchoring properties to the supporting substrate to such an extent that peeling does not occur at the interface between the adhesive layer and the supporting substrate when the reinforcing film is peeled from the adherend. A substrate-attached reinforcing film in which the adhesive layer is adhered to the supporting substrate can firmly integrate the adherend and the supporting substrate. A preferred example of a reinforcing film in which the adhesive layer is adhered to the substrate is a reinforcing film in which peeling (anchor failure) does not occur between the adhesive layer and the supporting substrate when measuring the adhesive strength after heating as described above. A reinforcing film in which anchor failure does not occur when measuring the adhesive strength after heating is a preferred example of a reinforcing film in which the adhesive layer is adhered to the substrate.

[0151] The reinforcing film disclosed herein can be preferably produced, for example, by a method comprising, in this order, contacting a liquid pressure-sensitive adhesive composition with a first surface of a substrate and curing the pressure-sensitive adhesive composition on the first surface to form a pressure-sensitive adhesive layer. Curing the pressure-sensitive adhesive composition may involve one or more of the following processes: drying, crosslinking, polymerization, and cooling of the pressure-sensitive adhesive composition. This method of curing a liquid pressure-sensitive adhesive composition on the first surface of a substrate to form a pressure-sensitive adhesive layer can enhance the anchoring ability of the pressure-sensitive adhesive layer to the substrate compared to a method in which the cured pressure-sensitive adhesive layer is attached to the first surface of the substrate, thereby disposing the pressure-sensitive adhesive layer on the first surface. Taking advantage of this, a reinforcing film in which a pressure-sensitive adhesive layer is fixed to a substrate can be preferably produced.

[0152] In some embodiments, the method for contacting the liquid PSA composition with the first surface of the substrate can involve directly applying the PSA composition to the first surface of the substrate. By contacting the first surface (adhesive surface) of the PSA layer cured on the first surface of the substrate with a release surface, a reinforcing film can be obtained in which the second surface of the PSA layer is fixed to the first surface of the substrate and the first surface of the PSA layer is in contact with the release surface. The release surface can be the surface of a release liner, the back surface of a release-treated substrate, or the like.

[0153] Furthermore, for example, in the case of a photocurable pressure-sensitive adhesive composition using a partial polymer (polymer syrup) of a monomer raw material, the pressure-sensitive adhesive composition may be applied to a release surface, and then the first surface of a substrate may be placed over the applied pressure-sensitive adhesive composition to bring the uncured pressure-sensitive adhesive composition into contact with the first surface of the substrate, and in this state, the pressure-sensitive adhesive composition sandwiched between the first surface of the substrate and the release surface may be irradiated with light to cure it, thereby forming a pressure-sensitive adhesive layer.

[0154] The methods exemplified above do not limit the manufacturing method of the reinforcing film disclosed herein. In manufacturing the reinforcing film disclosed herein, any suitable method capable of adhering a pressure-sensitive adhesive layer to the first surface of a substrate can be used, either alone or in combination. Examples of such methods include the method of forming a pressure-sensitive adhesive layer by curing a liquid pressure-sensitive adhesive composition on the first surface of a substrate, as described above, or a method of applying a surface treatment to the first surface of a substrate to enhance the anchoring ability of the pressure-sensitive adhesive layer. For example, if the anchoring ability of the pressure-sensitive adhesive layer to the substrate can be sufficiently improved by providing an undercoat layer on the first surface of the substrate, the reinforcing film may be manufactured by laminating the cured pressure-sensitive adhesive layer to the first surface of the substrate. The anchoring ability of the pressure-sensitive adhesive layer to the substrate can also be improved by selecting the material of the substrate and the composition of the pressure-sensitive adhesive. Furthermore, applying a temperature higher than room temperature to a reinforcing film having a pressure-sensitive adhesive layer on the first surface of the substrate can enhance the anchoring ability of the pressure-sensitive adhesive layer to the substrate. The temperature applied to enhance the anchoring property may be, for example, about 35°C to 80°C, about 40°C to 70°C or higher, or about 45°C to 60°C.

[0155] When the reinforcing film disclosed herein is in the form of a pressure-sensitive adhesive sheet having a first pressure-sensitive adhesive layer provided on a first surface of a substrate and a second pressure-sensitive adhesive layer provided on a second surface of the substrate (i.e., a double-sided, substrate-attached pressure-sensitive adhesive sheet), the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may have the same configuration or different configurations. When the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer have different configurations, the difference may be, for example, a difference in composition or structure (thickness, surface roughness, formation area, formation pattern, etc.). For example, the second pressure-sensitive adhesive layer may be a pressure-sensitive adhesive layer that does not contain polymer (B). Furthermore, the surface elasticity of the surface of the second pressure-sensitive adhesive layer (second pressure-sensitive adhesive surface) at 23°C may be outside the range of 1 to 20 kPa (e.g., greater than 20 kPa), or may be 30 kPa or greater.

[0156] <Reinforcing film with release liner> The reinforcing film disclosed herein can be in the form of a pressure-sensitive adhesive product in which the surface (adhesive surface) of the pressure-sensitive adhesive layer is in contact with the release surface of a release liner. Thus, this specification can provide a reinforcing film with a release liner (adhesive product) that includes any of the reinforcing films disclosed herein and a release liner having a release surface that contacts the adhesive surface of the pressure-sensitive adhesive sheet.

[0157] The thickness of the release liner is not particularly limited, but a thickness of approximately 5 μm to 200 μm is usually appropriate. A release liner having a thickness within the above range is preferred because it provides excellent workability in bonding to the pressure-sensitive adhesive layer and in peeling from the pressure-sensitive adhesive layer. In some embodiments, the thickness of the release liner may be, for example, 10 μm or more, 20 μm or more, 30 μm or more, or 40 μm or more. Furthermore, from the viewpoint of facilitating peeling from the pressure-sensitive adhesive layer, the thickness of the release liner may be, for example, 100 μm or less, or 80 μm or less. The release liner may be subjected to a known antistatic treatment, such as a coating type, a kneading type, or a vapor deposition type, as needed.

[0158] The release liner is not particularly limited, and examples thereof include a release liner having a release layer on the surface of a liner substrate such as a resin film or paper (which may be paper laminated with a resin such as polyethylene), and a release liner made of a resin film formed from a low-adhesion material such as a fluorine-based polymer (such as polytetrafluoroethylene) or a polyolefin resin (such as polyethylene or polypropylene). Because of their excellent surface smoothness, release liners having a release layer on the surface of a resin film as a liner substrate and release liners made of a resin film formed from a low-adhesion material are preferably used. The resin film is not particularly limited as long as it is a film that can protect the pressure-sensitive adhesive layer, and examples thereof include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyester film (such as PET film or PBT film), polyurethane film, and ethylene-vinyl acetate copolymer film. The release layer can be formed using known release treatment agents, such as silicone-based release treatment agents, long-chain alkyl-based release treatment agents, olefin-based release treatment agents, fluorine-based release treatment agents, fatty acid amide-based release treatment agents, molybdenum sulfide, silica powder, etc. Silicone-based release treatment agents are particularly preferred.

[0159] The thickness of the release layer is not particularly limited, but is usually about 0.01 μm to 1 μm, and preferably about 0.1 μm to 1 μm. The method for forming the release layer is not particularly limited, and any known method can be appropriately adopted depending on the type of release treatment agent used, etc.

[0160] <Application> The reinforcing film provided by this specification can exhibit good reworkability, for example, initially after being attached to an adherend, thereby contributing to suppressing yield declines and improving the quality of products containing the reinforcing film. Furthermore, after being attached to an adherend, the adhesive strength of the reinforcing film can be significantly increased by aging or heating. For example, by heating at an appropriate time after attachment to the adherend, the reinforcing film can be firmly adhered to the adherend. Taking advantage of these characteristics, the reinforcing film disclosed herein can be preferably used in various fields to reinforce components included in various products.

[0161] The reinforcing film disclosed herein can be preferably used as a reinforcing film that is attached to an adherend to reinforce the adherend, for example, in the form of a substrate-attached pressure-sensitive adhesive sheet having a film-like substrate having a first side and a second side and a pressure-sensitive adhesive layer provided on at least the first side of the substrate. In such a reinforcing film, the film substrate can preferably be one that includes a resin film as a base film. Furthermore, from the viewpoint of improving reinforcing performance, it is preferable that the pressure-sensitive adhesive layer be fixed to the first side of the film-like substrate. For example, optical components used in optical products and electronic components used in electronic products are becoming increasingly integrated, smaller, lighter, and thinner, and multiple thin optical / electronic components with different linear expansion coefficients and thicknesses may be stacked. By attaching the above-described reinforcing film to such components, appropriate rigidity can be imparted to the optical / electronic components. This can suppress curling and bending due to stress that may occur between multiple components with different linear expansion coefficients and thicknesses during the manufacturing process and / or in the manufactured product. Furthermore, in the manufacturing process of optical / electronic products, when thin optical / electronic components are subjected to shaping processes such as cutting as described above, attaching a reinforcing film to the components before processing can alleviate local stress concentrations on the optical / electronic components that accompany processing, thereby reducing the risk of cracks, breakage, peeling of laminated components, etc. Attaching a reinforcing film to optical / electronic components before handling can also be useful for alleviating local stress concentrations during transportation, stacking, rotation, etc. of the components, and for preventing bending or bending of the components due to their own weight. Furthermore, when devices such as optical products and electronic products including the above-mentioned reinforced film are used by consumers in the market, even if the device is subjected to unintentional stress such as when it is dropped, placed under a heavy object, hit by a flying object, etc., the inclusion of the reinforced film in the device can alleviate stress on the device. Therefore, the inclusion of the reinforced film in the device can improve the durability of the device.

[0162] The reinforcing film disclosed herein can be preferably used, for example, in a manner in which it is attached to components constituting various portable devices (portable devices). Here, "portable" does not simply mean being portable, but rather means having a level of portability that allows an individual (average adult) to carry it relatively easily. Examples of portable devices referred to herein include mobile phones, smartphones, tablet PCs, laptop PCs, various wearable devices, digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game consoles, electronic dictionaries, electronic organizers, e-books, in-car information devices, portable radios, portable televisions, portable printers, portable scanners, and portable modems, as well as mechanical wristwatches, pocket watches, flashlights, and hand mirrors. Examples of components constituting the portable electronic devices include optical films and display panels used in image display devices such as thin-film displays (e.g., liquid crystal displays) and film-type displays. The reinforcing film disclosed herein can also be preferably used in a manner in which it is attached to various components in automobiles, home appliances, and the like.

[0163] Furthermore, the reinforcing film disclosed herein has flex recovery and flex retention, and thus can be preferably used by taking advantage of these characteristics in a mode in which it is attached to a component constituting a device having a bendable element (for example, a flexible device such as a flexible display, which may also be called a rollable device or a foldable device). Examples of such devices include the various mobile devices (portable devices) described above. Examples of components constituting the above-mentioned mobile electronic devices include optical films and display panels used in image display devices such as liquid crystal displays and organic EL (electroluminescence) displays. The reinforcing film disclosed herein can be preferably used in such mobile electronic devices to reinforce components constituting the device (typically, image display devices called flexible devices or foldable devices, etc.).

[0164] The reinforcing film disclosed herein is suitable for applications such as reinforcing optical members during the production or transportation of optical members used as components of liquid crystal display panels, plasma display panels (PDPs), organic EL displays, etc. It is useful as a reinforcing film applied to optical members such as polarizing plates (polarizing films), wave plates, retardation plates, optical compensation films, brightness enhancement films, light diffusion sheets, and reflective sheets for liquid crystal display panels.

[0165] The uses of the reinforcing film disclosed herein are not particularly limited, and the film can be used in various applications for the purpose of imparting rigidity, impact resistance, etc. The reinforcing film disclosed herein can be preferably used not only for flexible device applications as described above, but also for applications other than flexible devices. The fact that the reinforcing film has flex recovery and flex retention means that there are fewer restrictions on the range of application of the reinforcing film, which has great practical advantages. [Example]

[0166] Several examples of the present invention will be described below, but it is not intended that the present invention be limited to these specific examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

[0167] [Synthesis of polymer (A)] (Synthesis Example A1) A four-neck flask equipped with a stirring blade, thermometer, nitrogen gas inlet tube, and condenser was charged with 90.2 parts of 2-ethylhexyl acrylate (2EHA), 8.6 parts of 4-hydroxybutyl acrylate (4HBA), 1.2 parts of N-acryloylmorpholine (ACMO), 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and ethyl acetate as a polymerization solvent. Nitrogen gas was introduced while gently stirring, and the liquid temperature in the flask was maintained at around 65°C for 6 hours to prepare an acrylic polymer A1 solution with a polymer concentration of 35%. The weight-average molecular weight (Mw) of the acrylic polymer A1 was 540,000.

[0168] (Synthesis example A2) A solution of acrylic polymer A2 was obtained by solution polymerization in the same manner as in Synthesis Example A1, except that the monomer composition was changed to 2EHA / 4HBA / ACMO / n-butyl acrylate (BA) = 86.1 parts / 9.7 parts / 1.8 parts / 2.4 parts.

[0169] (Synthesis example A3) A solution of acrylic polymer A3 was obtained by carrying out solution polymerization in the same manner as in Synthesis Example A1, except that the monomer composition was changed to BA / 4HBA=96 parts / 4 parts.

[0170] (Synthesis example A4) A solution of acrylic polymer A4 was obtained by solution polymerization in the same manner as in Synthesis Example A1, except that the monomer composition was changed to 2EHA / 2-hydroxyethyl acrylate (HEA) / methyl methacrylate (MMA) / N-vinyl-2-pyrrolidone (NVP) = 65 parts / 15 parts / 7 parts / 13 parts.

[0171] [Synthesis of polymer (B)] (Synthesis Example B1) 101.15 parts of ethyl acetate, 40 parts of MMA, 20 parts of n-butyl methacrylate (BMA), 20 parts of 2-ethylhexyl methacrylate (2EHMA), 8.7 parts of a polyorganosiloxane skeleton-containing methacrylate monomer having a functional group equivalent of 900 g / mol (trade name: X-22-174ASX, manufactured by Shin-Etsu Chemical Co., Ltd.), 11.3 parts of a polyorganosiloxane skeleton-containing methacrylate monomer having a functional group equivalent of 4600 g / mol (trade name: KF-2012, manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.8 parts of thioglycerol as a chain transfer agent were added to a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, a condenser, and a dropping funnel. Then, after stirring for 30 minutes under a nitrogen atmosphere at 70 ° C, 0.2 parts of AIBN were added as a thermal polymerization initiator, and the mixture was allowed to react at 70 ° C for 3 hours. After stirring at 80°C for 30 minutes, 0.1 parts of AIBN was added and the mixture was reacted at 80°C for 2 hours. 0.05 parts of AIBN was then added and the mixture was reacted at 80°C for 2 hours to obtain polymer B1. The Mw of the obtained polymer B1 was 20,000. The functional group equivalent weight of monomer S1 used in the synthesis of polymer B1 was 2,991 g / mol.

[0172] (Synthesis examples B2 to B7) Polymers B2 to B7 were prepared in the same manner as for polymer B1, except that the composition of the monomer components was changed as shown in Table 1. In Table 1, X-22-174ASX represents a polyorganosiloxane skeleton-containing methacrylate monomer (trade name: X-22-174ASX, manufactured by Shin-Etsu Chemical Co., Ltd., functional group equivalent: 900 g / mol), KF-2012 represents a polyorganosiloxane skeleton-containing methacrylate monomer (trade name: KF-2012, manufactured by Shin-Etsu Chemical Co., Ltd., functional group equivalent: 4600 g / mol), and X-22-2426 represents a polyorganosiloxane skeleton-containing methacrylate monomer (trade name: X-22-2426, manufactured by Shin-Etsu Chemical Co., Ltd., functional group equivalent: 12000 g / mol).

[0173] Table 1 shows the compositions of the monomer components used in the preparation of polymers B1 to B7 and the functional group equivalent weight of the monomer S1 used in the synthesis of each polymer (B).

[0174] [Table 1]

[0175] The Mw of each of the above polymers was measured under the following conditions using a GPC device (HLC-8220GPC, manufactured by Tosoh Corporation) and calculated in terms of polystyrene. [GPC conditions] Sample concentration: 0.2 wt% (tetrahydrofuran (THF) solution) Sample injection volume: 10 μL ·Eluent: THF ·Flow rate: 0.6mL / min ·Measurement temperature: 40℃ ·column: Sample column: TSKguardcolumn SuperHZ-H (1 column) + TSKgel SuperHZM-H (2 columns) Reference column: TSKgel SuperH-RC (1 column) Detector: Differential refractometer (RI)

[0176] [Preparation of reinforcing film] Example 1 100 parts of acrylic polymer A1, 2.0 parts of polymer B1, and 0.10 parts in solids of isocyanate compound C1 (trade name "Coronate HX", manufactured by Tosoh Corporation) as a crosslinking agent were added, and the mixture was diluted with ethyl acetate so that the total solids content was 30%, thereby obtaining an acrylic adhesive solution according to this example. A release liner (trade name "Diafoil MRF75", manufactured by Mitsubishi Chemical Corporation) made of polyester resin and 75 μm thick with one side silicone-treated was prepared, and the acrylic adhesive solution obtained above was applied to the silicone-treated surface, followed by drying at 130°C for 1 minute to form an adhesive layer 25 μm thick. Next, a 50 μm thick polyimide substrate (trade name "Upilex 50S", manufactured by Ube Industries, Ltd.) was attached to the surface of the obtained pressure-sensitive adhesive layer to obtain a reinforcing film according to this example. This reinforcing film has a pressure-sensitive adhesive layer on one side of the substrate, and is in the form of a pressure-sensitive adhesive sheet with a release liner, in which the release surface of a release liner is in contact with the pressure-sensitive adhesive layer on the adhesive surface. For the reinforcing film of this example, the molar ratio ([NCO] / [OH]) was calculated from the OH amount (the number of moles of hydroxyl groups in the acrylic polymer A1) and the NCO amount (the number of moles of isocyanate groups in the isocyanate compound) in the adhesive layer, and was found to be 0.008.

[0177] <Examples 2 to 5> Except for using polymer B2 (Example 2), polymer B3 (Example 3), polymer B4 (Example 4), or polymer B5 (Example 5) instead of polymer B1, an acrylic pressure-sensitive adhesive solution according to each example was obtained in the same manner as in Example 1. Except for using each of these acrylic pressure-sensitive adhesive solutions, a reinforcing film according to each example was produced in the same manner as in the production of the reinforcing film according to Example 1.

[0178] <Examples 6 to 9> Acrylic pressure-sensitive adhesive solutions of each example were obtained in the same manner as in Example 1, except that the amount of isocyanate compound C1 used was changed to 0.015 parts (Example 6), 0.05 parts (Example 7), 0.20 parts (Example 8), or 0.60 parts (Example 9) relative to 100 parts of acrylic polymer A1, as shown in Table 2. Reinforcing films of each example were prepared in the same manner as in the preparation of the reinforcing film of Example 1, except that these acrylic pressure-sensitive adhesive solutions were used, respectively.

[0179] <Examples 10 to 12> Acrylic pressure-sensitive adhesive solutions of each example were obtained in the same manner as in Example 1, except that the amount of polymer B1 used was changed to 1.0 part (Example 10), 3.0 parts (Example 11), or 6.0 parts (Example 12) per 100 parts of acrylic polymer A1, as shown in Table 2. Reinforcing films of each example were prepared in the same manner as in the preparation of the reinforcing film of Example 1, except that these acrylic pressure-sensitive adhesive solutions were used, respectively.

[0180] Example 13 Except for using acrylic polymer A2 instead of acrylic polymer A1, an acrylic pressure-sensitive adhesive solution according to this example was obtained in the same manner as in Example 1. Except for using the obtained acrylic pressure-sensitive adhesive solution, a reinforcing film according to this example was produced in the same manner as in the production of the reinforcing film according to Example 1.

[0181] Example 14 An acrylic pressure-sensitive adhesive solution according to this example was obtained in the same manner as in Example 1, except that acrylic polymer A3 was used instead of acrylic polymer A1 and 0.07 parts, in terms of solid content, of isocyanate compound C2 (trade name "Takenate D110N", manufactured by Mitsui Chemicals, Inc.) was used as the crosslinking agent per 100 parts of acrylic polymer A3. A reinforcing film according to this example was produced in the same manner as in Example 1, except that the obtained acrylic pressure-sensitive adhesive solution was used.

[0182] <Examples 15 and 16> Acrylic pressure-sensitive adhesive solutions of each example were obtained in the same manner as in Example 14, except that the amount of isocyanate compound C2 used was changed to 0.09 parts (Example 15) or 0.395 parts (Example 16) in terms of solid content relative to 100 parts of acrylic polymer A3, as shown in Table 2. Reinforcing films of each example were prepared in the same manner as in the preparation of the reinforcing film of Example 1, except that these acrylic pressure-sensitive adhesive solutions were used, respectively.

[0183] <Comparative Examples 1 and 2> Except for using polymer B6 (Comparative Example 1) or polymer B7 (Comparative Example 2) instead of polymer B1, an acrylic pressure-sensitive adhesive solution according to each example was obtained in the same manner as in Example 1. Except for using these acrylic pressure-sensitive adhesive solutions, a reinforcing film according to each example was produced in the same manner as in the production of the reinforcing film according to Example 1.

[0184] <Comparative Example 3> An acrylic pressure-sensitive adhesive solution according to this example was obtained in the same manner as in Example 1, except that acrylic polymer A4 was used instead of acrylic polymer A1 and 0.50 parts, in terms of solid content, of isocyanate compound C2 (trade name "Takenate D110N", manufactured by Mitsui Chemicals, Inc.) was used as the crosslinking agent per 100 parts of acrylic polymer A4. A reinforcing film according to this example was produced in the same manner as in the production of the reinforcing film according to Example 1, except that the obtained acrylic pressure-sensitive adhesive solution was used.

[0185] <Comparative Examples 4 and 5> Acrylic pressure-sensitive adhesive solutions of each example were obtained in the same manner as in Comparative Example 3, except that the amount of isocyanate compound C2 used was changed to 1.10 parts (Comparative Example 4) or 2.50 parts (Comparative Example 5) in terms of solid content per 100 parts of acrylic polymer A4, as shown in Table 2. Reinforcing films of each example were prepared in the same manner as in the preparation of the reinforcing film of Example 1, except that these acrylic pressure-sensitive adhesive solutions were used, respectively.

[0186] <Evaluation> [Surface elastic modulus] The reinforcing film according to each example was aged for one day at 50°C, and the surface elastic modulus was measured. The release liner protecting the adhesive surface was peeled off, and a nanoindenter (Triboindenter manufactured by Hysitron Inc.) was used to press an indenter into the surface of the adhesive layer to a depth of 6 µm. The maximum load (Pmax) [GPa / mm 2 This is expressed as the formula: Surface hardness [GPa] = Pmax / A The surface hardness was calculated by substituting the above formula, and the surface hardness was converted into [kPa] units and recorded as the surface elastic modulus at 23°C (23°C surface elastic modulus). The measurement conditions are as follows: In the above formula, A is the contact projected area of ​​the indenter [mm 2 ]. (Measurement conditions) Indenter approach speed: 5 μm / s Maximum displacement: 6 μm Pushing speed: 5μm / s Pulling speed: 5μm / s Indenter used: Conical (spherical indenter: radius of curvature 10μm) Measurement method: Single indentation measurement Measurement temperature: room temperature (23℃)

[0187] [Bulk elastic modulus G' and tanδ] A release liner R1 (trade name "Diafoil MRF75", manufactured by Mitsubishi Chemical Corporation) made of a 75 μm thick polyester resin with one side silicone-treated was prepared, and the acrylic adhesive solution according to each example was applied to the silicone-treated surface, followed by drying at 130°C for 1 minute to form a 25 μm thick adhesive layer. Next, the surface of the resulting adhesive layer was covered with a release liner R2 (trade name "Diafoil MRE75", manufactured by Mitsubishi Chemical Corporation) made of a 75 μm thick polyester resin with one side silicone-treated, with the silicone-treated surface facing the adhesive layer, and aging was carried out at 50°C for 1 day. Only the resulting adhesive layer was taken out, laminated to a thickness of about 1 mm, and punched out to a diameter of 8 mm to prepare a cylindrical pellet, which was used as a measurement sample. The above measurement sample was fixed to a φ8 mm parallel plate jig, and the storage modulus G', loss modulus G'', and loss tangent tanδ were measured under the following conditions using a dynamic viscoelasticity measuring device (TA Instruments "ARES"), and the storage modulus G' at 23°C was 23 [kPa], storage modulus G' at 80°C 80 [kPa] and tan δ at 80°C (loss modulus G″ at 80°C) 80 / Storage modulus G' at 80°C 80 ) was sought. Measurement mode: Shear mode Temperature range: -70℃~200℃ Heating rate: 5℃ / min Frequency: 1Hz The storage modulus G' corresponds to the portion of elastic energy stored when a material is deformed, and is an index that indicates the degree of hardness. The loss modulus G'' corresponds to the portion of energy lost due to internal friction when a material is deformed, and indicates the degree of viscosity.

[0188] [Initial adhesive strength] The reinforcing film for each example was aged at 50°C for one day and then cut to a 25 mm wide x 140 mm long sample, including the release liner. The release liner was removed from the sample to expose the adhesive surface, which was then pressed against a stainless steel plate (SUS304BA plate) using a 2 kg hand roller, with one stroke. The sample thus pressed against the adherend was then left at 23°C for 30 minutes. The load required to peel the reinforcing film from the adherend was measured using a tensile tester (Shimadzu Corporation, trade name "Autograph AG-Xplus HS 6000 mm / min High-Speed ​​Model (AG-50NX plus)") at a peel angle of 180° and a peel speed (tensile speed) of 300 mm / min. The average load during the measurement was recorded as the initial adhesive strength [gf / 25 mm].

[0189] [Adhesive strength after heating] For each reinforcing film according to the present invention, a measurement sample was prepared and pressure-bonded to an adherend in the same manner as in the initial adhesive strength measurement. The pressure-bonded measurement sample was then heated at an ambient temperature of 60°C for 60 minutes. The sample was then left at an ambient temperature of 23°C for 30 minutes. Using a tensile tester (Shimadzu Corporation, product name "Autograph AG-Xplus HS 6000mm / min High-Speed ​​Model (AG-50NX plus)"), the load when the reinforcing film was peeled from the adherend was measured at a peel angle of 180° and a peel speed (tensile speed) of 300mm / min. The average load during the measurement was recorded as the post-heat adhesive strength [gf / 25mm].

[0190] [Bending retention test] The reinforcing film of each example was aged at 50°C for 1 day, after which the release liner was peeled off. A 25 μm-thick polyimide substrate (trade name "Upilex 25S" manufactured by Ube Industries, Ltd.) was bonded to the exposed adhesive surface and heated at 60°C for 60 minutes for adhesion. The resulting measurement sample (laminate) was then folded with the 25 μm substrate side facing inward to a diameter of 6 mm and heated at 80°C for 15 hours. The sample was then left at room temperature (23°C) and allowed to cool sufficiently. The folded sample was then released from its fixed position. Within 10 minutes of release, the bend angle [°] of the bent sample was measured using a protractor to evaluate its flex recovery. The bend angle was the opening angle of the measurement sample (the angle at which the measurement sample opens from its folded state). The closer the bend angle was to 180°, the better the flex recovery; the closer the bend angle was to 0°, the poorer the flex recovery. Next, to evaluate the bending retention, the presence or absence of "peeling" at the bent portion of the measurement sample was visually checked, and if no "peeling" was observed, it was rated as "G (Good)", and if "peeling" was observed, it was rated as "P (Poor)".

[0191] The evaluation results for the reinforcing film of each example are shown in Table 2. Table 2 also shows an outline of the composition of the pressure-sensitive adhesive layer of each example.

[0192] [Table 2]

[0193] As shown in Table 2, the reinforcing films of Examples 1 to 16 comprised a pressure-sensitive adhesive layer containing a polymer (A) and a polymer (B) having a functional group equivalent of monomer S1 of 2000 to 7000 g / mol, and the surface elastic modulus at 23°C of the pressure-sensitive adhesive layer was in the range of 1 to 20 kPa. These reinforcing films initially exhibited low adhesive strength, but after the adhesive strength increased, they exhibited sufficient adhesive strength suitable for flexion retention, and both flex recovery and flexion retention were good. On the other hand, the reinforcing films of Comparative Examples 1 to 5, in which either the functional group equivalent of monomer S1 or the 23°C surface elastic modulus of the adhesive layer was outside the above range, were unable to achieve both initial easy peelability, increased adhesive strength upon heating, and flexion retention. The reinforcing film of Comparative Example 1 had high initial adhesive strength, while the reinforcing film of Comparative Example 2 had low adhesive strength after heating, and the reinforcing films of Comparative Examples 3 to 5 exhibited peeling during the flexion retention test.

[0194] More specifically, by comparing Examples 1 to 5 and Comparative Examples 1 and 2, in which the functional group equivalent of the monomer S1 used in the synthesis of the polymer (B) was different, it was found that Examples 1 to 5, in which the polymer (B) had a functional group equivalent of 2000 to 7000 g / mol, had a low initial adhesive strength and a high adhesive strength increase ratio (N 60 / N 23 ) was 3.2 to 6.3, indicating excellent initial easy peelability and adhesive strength increase upon heating. When the functional group equivalent was below the above range (Comparative Example 1), the initial easy peelability decreased, and when it was above the above range (Comparative Example 2), the adhesive strength after heating decreased. Comparative Examples 1 and 2 all had smaller adhesive strength increase ratios than Examples 1 to 5. The reinforcing films of Examples 1 to 5 and Comparative Examples 1 and 2 all had adhesive layer surface moduli at 23°C in the range of 1 to 20 kPa, and exhibited good flex recovery and flex retention. Furthermore, a comparison of Examples 1 to 5 revealed that the higher the functional group equivalent within the range of 2000 to 7000 g / mol, the more suppressed the initial adhesive strength, while the lower the functional group equivalent, the higher the adhesive strength after heating. In particular, Examples 1 to 3, which had functional group equivalents in the range of 2000 to 4500 g / mol, exhibited high post-heat adhesive strength, demonstrating favorable properties as a reinforcing film.

[0195] Furthermore, a comparison of Examples 6 to 9 showed that the higher the 23°C surface elasticity of the adhesive layer in the range of 1 to 20 kPa, the more improved the flex recovery, and the lower the initial adhesive strength and post-heat adhesive strength. Examples 7 to 9 were superior to Example 6 in flex recovery, with a 23°C surface elasticity of 2 kPa or more and a tanδ 80 In Example 9, both the surface elastic modulus and bulk elastic modulus were high, and the adhesive strength after heating was relatively low compared to Examples 6 to 8. In Examples 6 to 8, the bulk elastic modulus G' at 23°C of the adhesive layer was 23 No difference was observed. With regard to Examples 6 to 8, it can be said that the 23°C surface modulus had a higher correlation with flex recovery than the 23°C bulk modulus. In Examples 6 to 9, the molar ratio of isocyanate groups to hydroxyl groups ([NCO] / [OH]) in the pressure-sensitive adhesive layers of Examples 7 and 8, which showed better balanced improvements in initial adhesive strength, adhesive strength after heating, flex recovery, and flex retention, was within the range of 0.002 to 0.03.

[0196] Furthermore, a comparison of Examples 10 to 12 confirmed that the initial adhesive strength tended to decrease as the amount of polymer (B) used increased. In Examples 10 to 11, in which the amount of polymer (B) used was within the range of 0.5 to 5 parts per 100 parts of polymer (A), the initial adhesive strength was less than 400 gf / 25 mm and the adhesive strength after heating was 500 gf / 25 mm or more, thereby achieving a good balance between easy peelability at the initial stage of application and subsequent increase in adhesive strength. Furthermore, as the amount of polymer (B) used increased, the surface modulus at 23°C tended to increase and flex recovery tended to decrease. Furthermore, the results of Examples 13 to 16 confirmed that the desired effects could be achieved even if the type of polymer (A) or crosslinking agent in the adhesive was changed.

[0197] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. [Explanation of symbols]

[0198] 1,2,3 Reinforcement film 10 Supporting base material 10A front page 10B Second side 21 Adhesive layer (first adhesive layer) 21A Adhesive surface (first adhesive surface) 21B Adhesive surface (second adhesive surface) 22 Adhesive layer (second adhesive layer) 22A Adhesive surface (second adhesive surface) 31,32 Release liner 100,200,300 Reinforcement film with release liner

Claims

1. A reinforcing film having a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer contains a polymer (A) and a polymer (B), the polymer (A) is an acrylic polymer, and the acrylic polymer contains a monomer unit derived from a hydroxyl group-containing monomer, The glass transition temperature T Ａ is greater than or equal to -80°C and less than -35°C, The polymer (B) contains a monomer unit having a polyorganosiloxane skeleton and a (meth)acrylic monomer unit, the monomer unit having a polyorganosiloxane skeleton is derived from a polyorganosiloxane skeleton-containing monomer S1, and the functional group equivalent of the polyorganosiloxane skeleton-containing monomer S1 is 2000 to 7000 g / mol; the content of the polymer (B) in the pressure-sensitive adhesive layer is 0.1 to 30 parts by weight based on 100 parts by weight of the polymer (A); The pressure-sensitive adhesive layer contains an isocyanate-based crosslinking agent, the molar ratio ([NCO] / [OH]) of the isocyanate group to the hydroxyl group contained in the pressure-sensitive adhesive layer is 0.002 to 0.03; the pressure-sensitive adhesive layer has a surface elastic modulus of 1 to 20 kPa at 23°C; The reinforcing film has an initial adhesive strength of N ２３ A reinforcing film having a strength of 10 gf / 25 mm or more.

2. The pressure-sensitive adhesive layer has a bulk modulus G' at 23°C ２３ is 10 to 200 kPa, and the bulk modulus G' at 80 ° C. ８０ is 5 to 100 kPa, and tan δ at 80°C ８０ The reinforcing film according to claim 1, wherein is 0.10 to 0.

60.

3. 3. The reinforcing film according to claim 1, wherein the content of the polymer (B) in the pressure-sensitive adhesive layer is 0.5 to 5 parts by weight per 100 parts by weight of the polymer (A).

4. An optical member having the reinforcing film according to any one of claims 1 to 3 attached thereto.

5. An electronic component to which the reinforcing film according to any one of claims 1 to 3 is attached.

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