TWI905243B - Reinforcing membranes, optical components and electronic components - Google Patents

Abstract

This invention provides a reinforcing film that exhibits slight peelability initially upon attachment to an adhesive, followed by a significant increase in adhesive strength, and possesses flexural resilience and flexural retention. The reinforcing film comprises an adhesive layer. The adhesive layer comprises polymer (A) and polymer (B). Polymer (B) comprises monomer units having a polysiloxane backbone and (meth)acrylate monomer units. Furthermore, the adhesive layer has a surface elastic modulus of 1–20 kPa at 23°C.

Description

Reinforcing membranes, optical components and electronic components

This invention relates to a reinforcing film, and optical and electronic components having the reinforcing film adhered thereto. This application claims priority to Japanese Patent Application No. 2020-134187, filed on August 6, 2020, the entire contents of which are incorporated herein by reference.

Adhesives are widely used in the form of adhesive sheets for various applications, such as bonding objects together or fixing articles to objects. These adhesives are intended to attach objects to each other or to fix articles to objects. For example, adhesive sheets are used as reinforcing materials (reinforcing films) to impart rigidity or impact resistance to optical or electronic components constituting such devices. Patents 1 and 2 are cited as examples of this prior art.

Furthermore, in recent years, portable electronic devices that can be bent or rolled have attracted attention, and the development of an adhesive sheet for fixing flexible devices (typically organic EL (Electroluminescence) or liquid crystal display devices and other image display devices) built into such electronic devices is underway (Patents 3-6).

On the other hand, focusing on the performance of adhesives, a type of adhesive sheet has recently been proposed that exhibits low adhesive force initially upon attachment to the substrate, followed by a significant increase in adhesive force (Patent 7). Based on this characteristic, the adhesive sheet can provide useful re-adhesion (secondary processing capability) before the adhesive force increases, which helps to suppress yield reduction caused by mis-application or poor application of the adhesive sheet, and after the adhesive force increases, it exhibits strong adhesion suitable for the original purpose of the adhesive sheet. Previous Art Documents Patent Documents

Patent Document 1: Japanese Patent No. 6366199 Patent Document 2: Japanese Patent No. 6366200 Patent Document 3: Japanese Patent No. 6376271 Patent Document 4: Japanese Patent Application Publication 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: Japanese Patent No. 6373458

[The problem that the invention aims to solve]

Reinforcing films can also be used in the aforementioned flexible devices. For example, in the manufacture of such flexible devices, the components constituting the device are often relatively thin. Therefore, it is ideal to attach an adhesive sheet as a reinforcing film to prevent adverse conditions caused by device deformation or to improve operability. Since flexible devices can be repeatedly bent or flexed, the reinforcing film used in flexible devices is required to have the characteristic of normally recovering its shape when repeatedly bent (bending recovery) and the characteristic of not peeling or other adverse conditions (bending retention). This type of reinforcing membrane, which has bending recovery and bending retention, is more useful because it can be used in a variety of applications, including flexible devices, and therefore has fewer limitations in its scope of application.

For example, an adhesive, as proposed in Patent 7, which exhibits low adhesion initially followed by a significant increase in adhesion, would ideally possess flexural resilience and flexural retention when used as a reinforcing film. One method to improve flexural retention is to appropriately set the storage elastic modulus of the adhesive. However, as described above, if the storage elastic modulus of an adhesive designed to increase adhesion is changed, both the initial low adhesion and the subsequent increased adhesion will be affected. Furthermore, in addition to flexural retention, flexural resilience must also be considered; satisfying all these characteristics is not easy. Adhesives that exhibit low adhesion initially but subsequently increase significantly are beneficial in practical applications as long as they improve flexural resilience and flexural holding power.

This invention was created in view of the above-mentioned circumstances, with the aim of providing a reinforcing film that exhibits easy peelability in the initial stage of attachment to an adhesive, followed by a significant increase in adhesive strength, and possesses flexural resilience and flexural holding force. Furthermore, another object of this invention is to provide an optical component and an electronic component having the aforementioned reinforcing film adhered to them. [Technical Means for Solving the Problem]

According to this specification, a reinforcing film having an adhesive layer is provided. The adhesive layer comprises polymer (A) and polymer (B). Polymer (B) comprises monomer units having a polysiloxane backbone and (meth)acrylate monomer units. Furthermore, the adhesive layer has a surface elastic modulus of 1–20 kPa at 23°C.

Based on the above composition, the adhesive layer, containing polymer (A) and polymer (B) with monomer units having a polysiloxane backbone, exhibits slight peelability in the initial stage of adhesion to the substrate, followed by a significant increase in adhesive strength. Furthermore, the aforementioned reinforcing film possesses flexural resilience and flexural holding power. Specifically, reinforcing films with an adhesive layer having a surface elastic modulus at 23°C (surface elastic modulus at 23°C) of 1 kPa or higher exhibit the aforementioned adhesive properties and good flexural resilience. Furthermore, by setting the surface elastic modulus of the adhesive layer to below 20 kPa at 23°C, the aforementioned adhesive properties are achieved, and it also exhibits good bending retention. Therefore, even when used in a repeatedly bent manner, it is not easy to experience peeling or other adverse conditions.

In several preferred embodiments of the technologies disclosed herein (including reinforcing films, optical components, and electronic components, hereinafter the same), the volumetric elastic modulus G' ₂₃ of the aforementioned adhesive layer at 23°C is 10–200 kPa. With an adhesive having an adhesive modulus G' ₂₃ within this range, the initial adhesion force easily becomes a suitable range with excellent easy peelability. Furthermore, it exhibits excellent processability and generally tends to easily balance strain mitigation and flexural resilience in the room temperature range.

In several preferred embodiments, the volumetric elastic modulus G' ₈₀ of the adhesive layer at 80°C is 5–100 kPa. Adhesives with a volumetric elastic modulus G' ₈₀ within this range generally readily balance flexural resilience and flexural holding force. For example, even when used under high-temperature conditions around 80°C, they can exhibit suitable elasticity for flexural resilience and subsequent holding force to achieve flexural holding force.

In several preferred samples, the tanδ ₈₀ of the adhesive layer at 80°C is 0.10 to 0.60. Adhesives with a tanδ ₈₀ (loss modulus of elasticity at 80°C G'' ₈₀ / storage modulus of elasticity at 80°C G' ₈₀ ) of 0.10 or higher readily exhibit adhesion forces suitable for maintaining flexibility. Furthermore, by setting the tanδ ₈₀ to 0.60 or lower, plastic deformation of the adhesive is easily suppressed, resulting in good bending recovery. Moreover, when the reinforcing film is kept in a bent state for an extended period, it readily exhibits a holding force (bending holding force) that prevents it from peeling off from the adhered body.

The polymer (A) mentioned above is preferably an acrylic polymer. The effects of the technology disclosed herein can be readily and well achieved by using an adhesive layer comprising polymer (A) as an acrylic polymer and polymer (B) containing monomer units having a polyorganosiloxane backbone.

In several preferred embodiments, the content of polymer (B) in the adhesive layer is 0.5 to 5 parts by weight relative to 100 parts by weight of polymer (A). By setting the amount of polymer (B) relative to 100 parts by weight of polymer (A) to 0.5 parts by weight or more, easy peeling during the initial application is readily achieved. By setting the amount of polymer (B) to 5 parts by weight or less, the target increase in adhesive force is readily achieved. Furthermore, by setting the amount of polymer (B) used within the above range, good flexural resilience and flexural holding power are readily achieved.

In several preferred embodiments, the molar ratio ([NCO]/[OH]) of the isocyanate groups to hydroxyl groups contained in the adhesive layer is 0.002 to 0.03. Adhesive layers with a molar ratio ([NCO]/[OH]) of 0.002 or higher tend to exhibit excellent flexibility and processability. Furthermore, by setting the molar ratio ([NCO]/[OH]) to 0.03 or lower, a suitable increase in adhesive force is easily achieved. Moreover, in the adhesive layer, the isocyanate groups and hydroxyl groups exist in a state where at least a portion of them are chemically bonded (cross-linked). The aforementioned adhesive layer may include, for example, a crosslinking agent. In this configuration, the aforementioned isocyanate group may be part of the crosslinking agent, and the aforementioned hydroxyl group may be part of the polymer (A).

In several preferred embodiments, the adhesive layer contains a catalyst. Furthermore, the molar ratio (catalyst/OH) of the catalyst to hydroxyl groups in the adhesive layer is 1.0 × ^10⁻⁶ to 5.0 × ^10⁻² . By including a catalyst at a level greater than or equal to the amount of hydroxyl groups in the adhesive layer, bubble formation in the adhesive layer can be suppressed, and a smooth adhesive surface can be easily obtained. Furthermore, by keeping the amount of catalyst used below a certain level relative to the amount of hydroxyl groups in the adhesive layer, a suitable increase in adhesive force can be easily achieved. The catalyst is preferably an iron-based catalyst, and the molar ratio ([catalyst]/[OH]) of the catalyst to the hydroxyl group contained in the adhesive layer is preferably 1.0× ^10⁻⁴ to 1.0× ^10⁻³ .

The reinforcing films disclosed herein are suitable, for example, for imparting rigidity or impact resistance to optical components such as polarizing plates or wavelength plates during processing or transport. Therefore, according to this specification, an optical component with any of the reinforcing films disclosed herein can be provided.

Furthermore, the reinforcing films disclosed herein are also suitable as reinforcing films for electronic components of portable electronic devices and other machines. Therefore, according to this specification, an electronic component with any of the reinforcing films disclosed herein can be provided.

The preferred embodiments of this invention are described below. For matters necessary to implement this invention other than those specifically mentioned in this specification, practitioners can understand them based on the instructions for implementation contained in this specification and the technical common sense used in the application. This invention can be implemented based on the content disclosed in this specification and the technical common sense in the field. Furthermore, in the following figures, sometimes the same symbols are used to indicate components or parts that perform the same function, and sometimes repeated descriptions are omitted or simplified. Also, the embodiments shown in the figures are stylized for the purpose of clearly illustrating this invention and may not accurately represent the dimensions or scale of the actual product provided.

Furthermore, in this specification, "acrylic polymer" refers to a polymer whose polymer structure contains monomer units derived from (meth)acrylic monomers, typically referring to polymers containing monomer units derived from (meth)acrylic monomers in a ratio exceeding 50% by weight. Also, a (meth)acrylic monomer refers to a monomer having at least one (meth)acrylic group in one molecule. Here, "(meth)acrylic group" includes both acrylonitrile and methacrylic group. Therefore, the concept of (meth)acrylic monomers here can include both monomers having an acrylonitrile group (acrylic monomers) and monomers having a methacrylic group (methacrylic monomers). Similarly, in this specification, "(meth)acrylic acid" includes both acrylic acid and methacrylic acid, and "(meth)acrylate" includes both acrylate and methacrylate.

<Structural Example of a Reinforcing Film> The reinforcing film disclosed herein has the form of an adhesive sheet having an adhesive surface formed by an adhesive. The adhesive sheet used as a reinforcing film comprises an adhesive layer. The reinforcing film disclosed herein may be a substrate-attached adhesive sheet having the aforementioned adhesive layer laminated on one or both sides of a supporting substrate, or it may be a substrate-free adhesive sheet without a supporting substrate. Hereinafter, the supporting substrate may sometimes be simply referred to as the "substrate". Furthermore, in this specification, "reinforcing film" refers to the adhesive sheet (reinforcing adhesive film) used to reinforce an adhered body as described below. Reinforcing films, for example, can be in the form of a substrate-free adhesive sheet. After attaching a support material to one adhesive side, the other adhesive side is attached to the adhered object for reinforcement. Therefore, they are not limited to the form of a substrate-attached adhesive sheet. In this respect, the term "reinforcing film" can be understood as a broader concept than simply having the form of a substrate-attached adhesive sheet.

Figure 1 schematically illustrates the structure of a reinforcing film according to one embodiment. The reinforcing film 1 is constructed as a single-sided adhesive sheet with a substrate, comprising a sheet-like support substrate 10 having a first side 10A and a second side 10B, and an adhesive layer 21 disposed on the first side 10A. The adhesive layer 21 is fixed to the first side 10A of the support substrate 10. The reinforcing film 1 is used by attaching the adhesive layer 21 to the substrate. As shown in Figure 1, the reinforcing film 1 before use (i.e. before being attached to the substrate) can be a component of the reinforcing film 100 for attaching a peelable pad. The reinforcing film 100 for attaching a peelable pad is in the form of a peelable pad 31 in which the surface (adhesive surface) 21A of the adhesive layer 21 abuts against at least the side opposite to the adhesive layer 21 to form a peelable surface (peelable surface). As a peeling pad 31, for example, it can be constructed by providing a peeling layer formed by a peeling treatment agent on one side of a sheet substrate (pad substrate), so that one side becomes the peeling surface. Alternatively, the peeling pad 31 can be omitted, and the support substrate 10 with the second side 10B as the peeling surface can be used, in which the adhesive side 21A abuts against the second side 10B of the support substrate 10 by winding the reinforcing film 1 (roll form). When attaching the reinforcing film 1 to the substrate, the second side 10B of the liner 31 or the supporting substrate 10 is peeled off from the adhesive side 21A, and the exposed adhesive side 21A is pressed onto the substrate.

Figure 2 schematically illustrates the structure of another embodiment of the reinforcing film. The reinforcing film 2 is constructed as a double-sided adhesive sheet attached to a substrate, comprising a sheet-like support substrate 10 having a first side 10A and a second side 10B, an adhesive layer 21 disposed on the first side 10A, and an adhesive layer 22 disposed on the second side 10B. The adhesive layer (first adhesive layer) 21 is fixed to the first side 10A of the support substrate 10, and the adhesive layer (second adhesive layer) 22 is fixed to the second side 10B of the support substrate 10. The reinforcing film 2 is used by attaching the adhesive layers 21 and 22 to different parts of the adhered object. The adhesive layers 21 and 22 can be attached to different parts of different components or different parts within a single component. As shown in Figure 2, the reinforcing film 2 before use can be a component of the reinforcing film 200 with a peelable liner. The reinforcing film 200 with a peelable liner has the adhesive layer 21 surface (first adhesive surface) 21A and the adhesive layer 22 surface (second adhesive surface) 22A abutting against the peelable liner 31 and 32, which are at least peelable surfaces on the sides opposite to the adhesive layers 21 and 22. As peeling pads 31 and 32, for example, a peeling layer formed by a peeling treatment agent can be provided on one side of a sheet substrate (pad substrate) so that the one side becomes the peeling surface. Alternatively, the peeling pad 32 can be omitted, and a peeling pad 31 with peeling surfaces on both sides can be used. This is achieved by overlapping it with the reinforcing film 2 and winding it into a vortex shape to form a second adhesive surface 22A that abuts against the back of the peeling pad 31 (roll shape).

Figure 3 schematically illustrates the structure of another embodiment of the reinforcing film. The reinforcing film 3 is constructed as a substrate-free double-sided adhesive sheet consisting of an adhesive layer 21. The reinforcing film 3 is used by attaching a first adhesive surface 21A containing one surface (first surface) of the adhesive layer 21 and a second adhesive surface 21B containing the other surface (second surface) of the adhesive layer 21 to different parts of the adhered body. As shown in Figure 3, the reinforcing film 3 before use can be a component of the reinforcing film 300 with a peelable liner. The reinforcing film 300 with a peelable liner is in the form of a first adhesive surface 21A and a second adhesive surface 21B abutting against peelable liner 31 and 32, which are peelable surfaces respectively on the side opposite to the adhesive layer 21. Alternatively, the peeling pad 32 can be omitted, and a peeling pad 31 with both sides as peeling surfaces can be used. The peeling pad 31 is formed by overlapping it with the reinforcing film 3 and rolling it into a vortex shape to form a second adhesive surface 21B that abuts against the back of the peeling pad 31 (roll shape).

Furthermore, the reinforcing film can be in roll form, in sheet form, or cut and punched into appropriate shapes according to its application or usage. The adhesive layer in the technology disclosed here is typically formed continuously, but is not limited to this; for example, it can also be formed into regular or irregular patterns such as dots or stripes.

<Adhesive Layer> The reinforcing film disclosed herein has an adhesive layer comprising polymer (A) and polymer (B). This adhesive layer can be formed from an adhesive composition containing polymer (A) as a complete or partial polymer of monomer raw material A, and polymer (B). The morphology of the adhesive composition is not particularly limited, and it can be various forms, such as solvent-based, water-dispersible, hot-melt, or active energy line-curing (e.g., photocuring).

(Surface Elastic Modulus at 23°C) The adhesive layer disclosed herein is characterized by its surface elastic modulus (23°C surface elastic modulus) being in the range of 1–20 kPa at 23°C. By achieving a surface elastic modulus at 23°C of 1 kPa or higher, adhesive properties based on polymers (A) and (B) can be achieved, along with good flexural resilience. Furthermore, by achieving a surface elastic modulus of 20 kPa or lower, the aforementioned adhesive properties can be achieved, along with good flexural holding power.

From the perspective of improving flexural resilience, the aforementioned surface elastic modulus at 23°C is preferably 2 kPa or higher, more preferably 3 kPa or higher, and even more preferably 4 kPa or higher (e.g., 5 kPa or higher), and can be 8 kPa or higher, 10 kPa or higher, or 12 kPa or higher (e.g., 14 kPa or higher). A higher surface elastic modulus tends to result in better initial easy peeling. Furthermore, from the perspective of balancing good flexural resilience and flexural holding force while also demonstrating a good increase in adhesive force, the aforementioned surface elastic modulus at 23°C is preferably 15 kPa or lower, preferably 12 kPa or lower, more preferably 9 kPa or lower, and even more preferably 7 kPa or lower (e.g., 6 kPa or lower), and can also be 4 kPa or lower.

The surface elastic modulus at 23°C of the adhesive layer can be adjusted by the type or properties of polymer (A) (molecular weight or glass transition temperature, molecular structure, etc.), the type or properties of polymer (B) (chemical structure, etc.) (molecular weight or glass transition temperature, etc.), the amount used, and the type or amount of crosslinking agent. The surface elastic modulus at 23°C of the adhesive layer was determined by the method described in the following embodiment.

(Volume Elastic Modulus G' ₂₃ at 23°C) The volume elastic modulus G' ₂₃ of the adhesive layer at 23°C can be appropriately set within a range that satisfies the aforementioned surface elastic modulus at 23°C, and is not limited to a specific range. In several samples, the volume elastic modulus G' ₂₃ of the adhesive layer at 23°C is preferably set to 10 kPa or higher. By setting the aforementioned volume elastic modulus G' ₂₃ to a specified value or higher, the initial adhesion force easily becomes a suitable range with excellent easy peeling properties. Furthermore, _it exhibits excellent processability and generally tends to have excellent flexural recovery in the room temperature range. The aforementioned volumetric elastic modulus G' ₂₃ is preferably 15 kPa or more, more preferably 20 kPa or more, further preferably 25 kPa or more, and even more preferably 30 kPa or more. In several other cases, the aforementioned volumetric elastic modulus G' ₂₃ may be 50 kPa or more, 80 kPa or more, or 100 kPa or more.

In several samples, the volumetric elastic modulus G' ₂₃ at 23°C is preferably set to 200 kPa or less. Adhesives with a volumetric elastic modulus G' ₂₃ below the specified value generally exhibit excellent strain mitigation in the room temperature range and tend to show an increase in adhesive force. The volumetric elastic modulus G' ₂₃ is preferably 150 kPa or less, more preferably 90 kPa or less. In several preferred samples, the volumetric elastic modulus G' ₂₃ may be 60 kPa or less, or may be 40 kPa or less (e.g., 35 kPa or less).

(80°C Volumetric Elastic Modulus G' ₈₀ ) The volumetric elastic modulus G' ₈₀ of the adhesive layer at 80°C is appropriately set within the range that satisfies the above-mentioned surface elastic modulus at 23°C, and is not limited to a specific range. In several samples, the 80°C volumetric elastic modulus G' ₈₀ of the adhesive layer is preferably 5 kPa or higher. By setting the above-mentioned volumetric elastic modulus G' ₈₀ to a specified value or higher, flexural resilience is generally easily improved, _and even when used under high-temperature conditions, it can have elasticity suitable for flexural resilience. In several preferred states, the volumetric elastic modulus G' ₈₀ may be 7 kPa or more, 9 kPa or more, or 10 kPa or more. In several other states, the volumetric elastic modulus G' ₈₀ may be 15 kPa or more, 30 kPa or more, or 50 kPa or more.

In several samples, the volumetric elastic modulus G' ₈₀ at 80°C is preferably set to 100 kPa or less. By limiting the aforementioned volumetric elastic modulus G' ₈₀ to a specified value or less, good flexural holding force is generally easily obtained, and flexural recovery and flexural holding force are easily balanced. For example, it can have elasticity suitable for flexural recovery and subsequent holding force to achieve flexural holding force in various environments, including high-temperature conditions. The aforementioned volumetric elastic modulus G' ₈₀ is preferably 90 kPa or less, and more preferably 60 kPa or less. In several cases, the volumetric elastic modulus G' ₈₀ may be less than 20 kPa, less than 16 kPa, or less than 14 kPa (e.g., less than 12 kPa).

The tanδ ₈₀ of the adhesive layer at 80 _° C is appropriately set within a range that satisfies the surface elastic modulus at 23°C mentioned above, and is not limited to a specific range. In several samples, the tanδ ₈₀ of the adhesive layer at 80°C is preferably set to 0.10 or higher. The higher the tanδ ₈₀ , the easier it is for the adhesive to exert adhesion suitable for flexural retention. The tanδ ₈₀ is preferably 0.20 or higher. In several preferred samples, the tanδ ₈₀ may be 0.30 or higher, 0.40 _or higher, or 0.45 or higher.

In several samples, the tanδ ₈₀ at 80°C is preferably 0.60 or less for the adhesive layer. By keeping the tanδ ₈₀ below 0.60, plastic deformation of the adhesive can be suppressed, and good bending recovery can be easily obtained. Furthermore, when the reinforcing film is kept in a bent state for a long time, it is easier to maintain its holding force and prevent it from peeling off from the adherend. Consequently, an increase in adhesive force can easily become within a suitable range. The aforementioned tanδ ₈₀ at 80°C can be 0.55 or less. In other samples, the aforementioned tanδ ₈₀ at 80°C can be 0.50 or less, or 0.35 or less.

The volumetric elastic modulus _G'23 at 23°C, the volumetric elastic modulus _G'80 at 80°C, and the tanδ ₈₀ at 80°C of the adhesive layer can be adjusted by the type or properties of polymer (A) (molecular weight or glass transition temperature, molecular structure, etc.), the type or properties of polymer (B) (chemical structure, etc.) (molecular weight or glass transition temperature, etc.), the amount used, and the type or amount of crosslinking agent. The volumetric elastic modulus _G'23 at 23°C, the volumetric elastic modulus _G'80 at 80°C, and the tanδ ₈₀ at 80°C of the adhesive layer are determined by the method described in the following embodiments.

(Polymer (A)) As polymer (A), one or more of various polymers known in the adhesive field that exhibit rubber elasticity in the room temperature range, such as acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, polysiloxane polymers, polyamide polymers, and fluoropolymers, can be used. In the reinforcing film disclosed herein, polymer (A) is typically the main component of the polymer composition contained in the adhesive layer, that is, the component accounting for more than 50% by weight, for example, the component accounting for more than 75% by weight of the aforementioned polymer composition. In several embodiments, the polymer (A) comprises more than 50% by weight of the total adhesive layer, and may comprise more than 70% by weight, more than 80% by weight, more than 90% by weight, or more than 95% by weight (e.g., more than 97% by weight).

The glass transition temperature _TA of polymer (A) is not particularly limited and can be selected in a manner that yields better properties in the reinforcing film disclosed herein. In several embodiments, polymer (A) with _TA not reaching 0°C is readily used. Adhesives containing such polymer (A) exhibit suitable flowability (e.g., the movement of polymer chains contained in the adhesive), making them suitable for realizing reinforcing films where the adhesive force increases above a specified value upon heating. The reinforcing film disclosed herein can be readily implemented using polymers (A) with _TA not reaching -10°C, -20°C, -30°C, or -35°C. In several embodiments, _TA may not reach -40°C or -50°C. In several preferred states, _TA is below -55°C, more preferably below -58°C, even more preferably below -62°C, and can also be below -65°C (e.g., below -66°C). There is no particular limitation on the lower limit of _TA . From the viewpoint of material availability or improving the cohesiveness of the adhesive layer, polymers (A) with _TA of -80°C or higher, or -70°C or higher, are generally preferred. In several states, _TA can, for example, be above -63°C, above -55°C, above -50°C, or above -45°C.

In this specification, the glass transition temperature (Tg) of a polymer (e.g., the glass transition temperature of polymer (A), polymer (B) below, etc.) refers to the nominal value recorded in literature or catalogues, or the Tg calculated according to Fox's formula based on the composition of the monomer raw materials used to prepare the polymer. Fox's formula is the relationship between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer obtained by homopolymerization of the monomers constituting the copolymer, as shown below. 1/Tg＝Σ(Wi/Tgi) In the above Fox's formula, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (weight-based copolymerization ratio), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K). When the target polymer with a specific Tg is a homopolymer, the Tg of the homopolymer is the same as that of the target polymer.

As the glass transition temperature (Tg) of homopolymers used to calculate the glass transition temperature, values recorded in known sources are used. Specifically, values from the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be cited as examples. For monomers for which multiple values are recorded in the aforementioned Polymer Handbook, the highest value is used.

The glass transition temperature of the homopolymer of monomers not recorded in the aforementioned polymer manual was determined using the value obtained by the following method. Specifically, 100 parts by weight of the monomer, 0.2 parts by weight of 2,2'-azobisisobutyronitrile, and 200 parts by weight of ethyl acetate as the polymerization solvent were added to a reactor equipped with a thermometer, a stirrer, a nitrogen inlet, and a reflux condenser. The mixture was stirred for 1 hour while nitrogen was flowing through it. After removing oxygen from the polymerization system in this manner, the temperature was raised to 63°C and the reaction was allowed to proceed for 10 hours. Subsequently, the mixture was cooled to room temperature to obtain a homopolymer solution with a solid content of 33% by weight. Next, the homopolymer solution was cast onto a release liner and dried to prepare a test sample (sheet-like homopolymer) approximately 2 mm thick. This test sample was punched into a disc shape with a diameter of 7.9 mm and sandwiched between parallel plates. While applying a shear strain at a frequency of 1 Hz using a viscoelasticity testing machine (manufactured by TA Instruments Japan, model "ARES"), the viscoelasticity was measured in shear mode within the temperature range of -70°C to 150°C at a heating rate of 5°C/min. The temperature corresponding to the peak temperature of tanδ was set as the Tg of the homopolymer.

The weight-average molecular weight (Mw) of polymer (A) is typically preferably above about 20 × ^10⁴ , but is not particularly limited. With polymer (A) of this Mw, it is easy to obtain an adhesive exhibiting good cohesiveness. From the viewpoint of obtaining even higher cohesiveness, in several preferred embodiments, the Mw of polymer (A) can be, for example, above 30 × ^10⁴ , above 40 × ^10⁴ , above 50 × ^10⁴ , above 60 × ^10⁴ , or above 80 × ^10⁴ . Furthermore, the Mw of polymer (A) is typically preferably below about 500 × ^10⁴ . Polymer (A) with this Mw readily forms an adhesive exhibiting moderate fluidity (mobility of the polymer chain), thus it is suitable for achieving reinforcing films with lower initial adhesion and greater adhesion rise. From the viewpoint of improving compatibility with polymer (B), it is also preferable that the Mw of polymer (A) is not too high. Among several preferred embodiments, the Mw of polymer (A) may be, for example, 250 × ^10⁴ or less, 200 × ^10⁴ or less, 150 × ^10⁴ or less, 100 × ^10⁴ or less, or 70 × ^10⁴ or less.

Furthermore, in this specification, the Mw of polymer (A) and polymer (B) described below can be determined by polystyrene conversion using gel osmosis chromatography (GPC). More specifically, Mw can be determined according to the methods and conditions described in the following embodiments.

As the polymer (A) in the reinforcing film disclosed herein, acrylic polymers are well-suited. Using an acrylic polymer as polymer (A) tends to readily achieve good compatibility with polymer (B). Good compatibility between polymer (A) and polymer (B) helps reduce initial adhesive force and increase post-heating adhesive force by improving the mobility of polymer (B) within the adhesive layer, which is therefore preferable. Furthermore, acrylic polymers, with their higher degree of molecular design freedom, are suitable as adhesive materials that can comprehensively improve adhesive properties, flexural resilience, and flexural holding power.

Acrylic polymers can be, for example, polymers containing 50% by weight or more of monomer units derived from alkyl methacrylates, that is, polymers in which 50% by weight or more of the total monomer components (monomer raw material A) used to prepare the acrylic polymer are alkyl methacrylates. Alkyl methacrylates having 1 to 20 carbon atoms (i.e., _C1-20 ) in a straight-chain or branched-chain manner are preferred as alkyl methacrylates. In terms of easily obtaining a balance of properties, the ratio of _C1-20 alkyl methacrylates in monomer raw material A can be, for example, 50% by weight or more, or 60% by weight or more. In several preferred embodiments, the ratio of _C1-20 alkyl methacrylates in monomer raw material A is 70% by weight or more, more preferably 80% by weight or more, further preferably 85% by weight or more, and most preferably 90% by weight or more. By using acrylic polymers composed of this monomer, adhesives that balance adhesive strength increase, flexural resilience, and flexural retention can be easily obtained. Furthermore, the proportion of (meth)acrylate _C1-20 alkyl esters in monomer raw material A can be, for example, 99.9% by weight or less, 98% by weight or less, or 95% by weight or less. In several embodiments, the proportion of (meth)acrylate _C1-20 alkyl esters in monomer raw material A can be, for example, 90% by weight or less, 85% by weight or less, or 80% by weight or less.

Examples of non-limiting _C1-20 alkyl esters of (meth)acrylate include: methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, dibutyl methacrylate, terbutyl methacrylate, amyl methacrylate, isoamyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate. Nonyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecanyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, stearyl methacrylate, isostearyl methacrylate, nonadecanyl methacrylate, eicosyl methacrylate, etc.

In these embodiments, it is preferred to use at least _C1-18 alkyl esters of (meth)acrylate, more preferably at least _C1-14 alkyl esters of (meth)acrylate. In several embodiments, the acrylic polymer may contain at least one of _C4-12 alkyl esters of (meth)acrylate (preferably _C4-10 alkyl esters of acrylate, such as _C6-10 alkyl esters of acrylate) as a monomer unit. For example, it is preferred to use an acrylic polymer containing one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA), and even more preferably an acrylic polymer containing at least 2EHA.

In several preferred embodiments, the proportion of _C6-10 alkyl acrylate (suitably _C8-9 alkyl acrylate, typically 2EHA) in monomer raw material A used to prepare acrylic polymers is 70% by weight or more, more preferably 80% by weight or more, further preferably 85% by weight or more, and even more preferably 90% by weight or more. Acrylic polymers composed of this monomer are particularly suitable for achieving the effects of the technology disclosed herein. Furthermore, the proportion of _C6-10 alkyl acrylate (suitably _C8-9 alkyl acrylate, typically 2EHA) in monomer raw material A can be, for example, 99.9% by weight or less, and from the viewpoints of initial low adhesion and flexural resilience, it can be 98% by weight or less, or even 95% by weight or less.

Furthermore, in several preferred embodiments, the proportion of (meth)acrylate _C1-3 alkyl esters (e.g., (meth)acrylate _C1 alkyl esters, typically methyl methacrylate (MMA)) in monomer raw material A used to prepare acrylic polymers is preferably limited. (Meth)acrylate _C1-3 alkyl esters (e.g., (meth)acrylate _C1 alkyl esters, typically MMA) tend to have a relatively high Tg, and the cohesiveness of adhesives in acrylic polymers containing the aforementioned monomer components tends to increase. By limiting the amount of (meth)acrylate _C1-3 alkyl esters used, the cohesiveness of the adhesive can be appropriately reduced, achieving a suitable elastic modulus (typically surface elastic modulus) that balances flexural strength or adhesive strength. From this perspective, the proportion of (meth)acrylate _C1-3 alkyl esters (e.g., (meth)acrylate _C1 alkyl esters, typically MMA) in the aforementioned monomer raw material A is preferably set to 8% by weight or less, more preferably 6% by weight or less, even more preferably 3% by weight or less, and even more preferably 1% by weight or less (e.g., 0 to 0.3% by weight).

Monomer raw material A may also include alkyl (meth)acrylate as the main component and, as needed, other monomers (copolymeric monomers) capable of copolymerizing with alkyl (meth)acrylate. As copolymeric monomers, monomers with polar groups (e.g., carboxyl, hydroxyl, nitrogen-containing rings, etc.) are preferred. Monomers with polar groups can help introduce crosslinking points into acrylic polymers or improve the cohesiveness of acrylic polymers. Copolymeric monomers may be used alone or in combination of two or more.

As non-limiting examples of copolymerizable monomers, the following can be cited: Hydroxy-containing monomers: for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, methyl (4-hydroxymethylcyclohexyl)acrylate, and other hydroxyalkyl (meth)acrylates. Monomers having a ring containing a nitrogen atom: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperidine, N-vinylpyrrole, N-vinylimidazolium, N-vinylpyrazole, N-vinylpyrazole, N-(meth)acryl-2-pyrrolidone, N-(meth)acrylpiperidine, N-(meth)acrylpyrrolidone, N-(meth)acrylpyrrolidone, N-vinylpyrrolidone, N-vinyl-3-pyrrolidone, N-vinyl-2-caprolactone, N-vinyl-1,3-vinyl-2-one, N-vinyl-3,5-pyrrolidone, N-vinylpyrazole, N-vinylisothiazole, N-vinylisothiazole, N-vinylpyrrolidone, etc.; Examples of monomers with a succinyldiphenyl succinyl ... Examples of isonia derivatives include N-methyl isoniaimine, N-ethyl isoniaimine, N-butyl isoniaimine, N-octyl isoniaimine, N-2-ethylhexyl isoniaimine, N-cyclohexyl isoniaimine, and N-lauryl isoniaimine. Carboxyl-containing monomers: Examples include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, isoniazid, maleic acid, fumaric acid, butenoic acid, and isobutenoic acid. Anhydride-containing monomers: Examples include maleic anhydride and isoniazid anhydride. Epoxy-containing monomers: Examples include epoxy acrylates such as (meth)acrylate or (meth)acrylate-2-ethyl glycidyl ether, allyl glycidyl ether, and (meth)acrylate glycidyl ether. Cyano-containing monomers: Examples include acrylonitrile and methacrylonitrile. Isocyanate-containing monomers: Examples include ethyl (2-isocyanate)acrylate. Amino-containing monomers: Examples include (meth)acrylamide; N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, N,N-dipropyl (meth)acrylamide, N,N-diisopropyl (meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, N,N-di(tert-butyl)(meth)acrylamide, etc. N,N-dialkyl(meth)acrylamide; N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-butyl(meth)acrylamide, N-n-butyl(meth)acrylamide, and other N-alkyl(meth)acrylamides; N-vinylacetamide and other N-vinylcarboxylate derivatives; monomers having hydroxyl and amide groups, such as N-(2-hydroxyl) N-hydroxyalkyl (meth)acrylamides include 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 alkoxy and acetylated groups, such as N-methoxymethyl (meth)acrylamide, N-methoxyethyl (meth)acrylamide, and N-butoxymethyl (meth)acrylamide; and N-alkoxyalkyl (meth)acrylamides, etc. Additionally, N,N-dimethylaminopropyl (meth)acrylamide, etc. (Meth)acrylate aminoalkyl esters: Examples include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, and tributylaminoethyl (meth)acrylate. Alkoxy-containing monomers: Examples include 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxypropyl (meth)acrylate, and other (meth)acrylate alkoxyalkyl esters; methoxyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, and other (meth)acrylate alkoxyalkyl glycol esters. Monomers containing sulfonic acid or phosphoric acid groups: Examples include styrene sulfonic acid, allyl sulfonic acid, sodium vinyl sulfonate, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamide propanesulfonic acid, (meth)acrylic acid sulfonyl propane, (meth)acryloxynaphthalene sulfonic acid, 2-hydroxyethylacrylamide phosphate, etc. (Meth)acrylates containing alicyclic hydrocarbon groups: Examples include cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isopropyl (meth)acrylate, dicyclopentyl (meth)acrylate, etc. (Meth)acrylates containing aromatic hydrocarbon groups: Examples include phenyl (meth)acrylate, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, etc. Vinyl ethers: Examples include vinylalkyl ethers such as methyl vinyl ether or ethyl vinyl ether. Vinyl esters: Examples include vinyl acetate, vinyl propionate, etc. Aromatic vinyl compounds: such as styrene, α-methylstyrene, vinyltoluene, etc. Alkenes: such as ethylene, butadiene, isoprene, isobutylene, etc. Furthermore, heterocyclic (meth)acrylates such as tetrahydrofuran methyl (meth)acrylate, halogenated (meth)acrylates such as vinyl chloride or fluorine-containing (meth)acrylates, silicon-containing (meth)acrylates such as polysiloxane (meth)acrylates, and (meth)acrylates obtained from terpene compound derivative alcohols, etc.

When using this copolymerizable monomer, there is no particular limitation on its amount used, but it is generally suitable to set it to 0.01% by weight or more of monomer raw material A. From the viewpoint of better utilizing the effects produced by using the copolymerizable monomer, the amount of copolymerizable monomer used can be set to 0.1% by weight or more of monomer raw material A, or even 1% by weight or more. In several preferred embodiments, the content of copolymerizable monomer in monomer raw material A is 3% by weight or more, more preferably 5% by weight or more, and even more preferably 7% by weight or more (e.g., 8% by weight or more). The higher the amount of copolymerizable monomer used, the higher the cohesiveness and the higher the flexural resilience. Furthermore, the amount of copolymerizable monomer used can be set to 50% by weight or less of monomer raw material A, preferably 30% by weight or less. This prevents the adhesive's cohesive strength from becoming excessive, improving tackiness at room temperature (25°C). In several preferred embodiments, the amount of copolymer used is less than 20% by weight of monomer raw material A, more preferably less than 15% by weight (e.g., less than 12% by weight), and can also be less than 10% by weight. By limiting the amount of copolymer used, the adhesive's cohesive strength is reduced, the elastic modulus (typically the surface elastic modulus) becomes within a suitable range, excellent flexural holding power is easily obtained, and an increase in adhesive strength is easily achieved.

In several embodiments, monomer raw material A may include monomers having a ring containing nitrogen atoms. By using monomers having a ring containing nitrogen atoms, the cohesive force or polarity of the adhesive can be adjusted, and the adhesive force after heating can be appropriately improved. By including monomers having a ring containing nitrogen atoms in monomer raw material A, there is a tendency to improve the compatibility between the polymer (A) formed from the above monomer raw material A and the above polymer (B). In this way, it is easy to obtain a reinforcing film that can significantly increase the adhesive force upon heating.

Monomers having a nitrogen-containing ring can be suitably selected from the examples above, used alone or in combination of two or more. In several embodiments, monomer raw material A is preferably a monomer containing at least one monomer selected from the group consisting of N-vinylcyclic amides and cyclic amides having (meth)acrylic acid groups as a monomer having a nitrogen-containing ring.

Specific examples of N-vinylcyclic amides include: N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-3-carboxylinone, N-vinyl-2-caprolactone, N-vinyl-1,3-carboxy-2-one, and N-vinyl-3,5-carboxylindione. N-vinyl-2-pyrrolidone and N-vinyl-2-caprolactone are particularly preferred. Specific examples of cyclic amides having a (meth)acrylic group include: N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, and N-(meth)acryloylcarboxylin. A better example is N-acryloylphosphazeneline (ACMO).

There is no particular limitation on the amount of monomers containing nitrogen-containing rings used, but it is generally suitable to be 40% by weight or less of monomer raw material A, and can be 30% by weight or less, 20% by weight or less, or 10% by weight or less. In several preferred embodiments, from the viewpoint of reducing cohesion and thus reducing the elastic modulus (typically the surface elastic modulus), the content of monomers containing nitrogen-containing rings in monomer raw 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 monomers containing nitrogen-containing rings used is generally suitable to be 0.01% by weight or more of monomer raw material A (preferably 0.1% by weight or more, e.g., 0.5% by weight or more). From the perspective of obtaining appropriate cohesion and elastic modulus, in several states, the amount of monomers with nitrogen-containing rings can be set to 0.8% by weight or more of monomer raw material A, or 1.0% by weight or more.

In several preferred embodiments, monomer material A comprises a hydroxyl-containing monomer. By using the hydroxyl-containing monomer, the cohesiveness or polarity of the adhesive can be adjusted, thereby adjusting the elastic modulus (typically the surface elastic modulus), effectively achieving the effects of the techniques disclosed herein. Furthermore, the hydroxyl-containing monomer provides a reaction site with crosslinking agents (e.g., isocyanate-based crosslinking agents), thereby enhancing the cohesiveness of the adhesive through crosslinking reactions.

As hydroxyl-containing monomers, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and N-(2-hydroxyethyl)(meth)acrylamide are suitable examples. Among these, 2-hydroxyethyl acrylate (HEA), 4-hydroxybutyl acrylate (4HBA), and N-(2-hydroxyethyl)acrylamide (HEAA) are preferred examples. From the viewpoint of obtaining cohesive strength suitable for bending recovery and bending retention, 4HBA is particularly preferred.

There is no particular limitation on the amount of hydroxyl-containing monomer used, but it is generally suitable to set it to 40% by weight or less of monomer raw material A, and it can be set to 30% by weight or less, or even 20% by weight or less. In some preferred embodiments, from the viewpoint of reducing cohesiveness and thus reducing elastic modulus (typically surface elastic modulus), the content of hydroxyl-containing monomer in 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 an increase in adhesive strength. In some other embodiments, the content of hydroxyl-containing monomer can also be set to 5% by weight or less of monomer raw material A. Furthermore, the amount of hydroxyl-containing monomer used is preferably set at 0.01% by weight or more of monomer raw material A (preferably 0.1% by weight or more, for example 0.5% by weight or more). From the viewpoint of obtaining suitable cohesiveness and elastic modulus, in several preferred states, the amount of hydroxyl-containing monomer used is 1% by weight or more of monomer raw material A, more preferably 3% by weight or more, further preferably 5% by weight or more, and even more preferably 7% by weight or more (for example 8% by weight or more).

In several formulations, monomers having a nitrogen-containing ring and hydroxyl-containing monomers can be used together as copolymers. In this case, the total amount of the monomer having a nitrogen-containing ring and the hydroxyl-containing monomer can be, for example, set to 0.1% by weight or more of monomer raw material A, preferably 1% by weight or more, more preferably 3% by weight or more, further preferably 5% by weight or more, particularly preferably 7% by weight or more (e.g., 9% by weight or more), can be set to 10% by weight or more, can be set to 15% by weight or more, can be set to 20% by weight or more, and can also be set to 25% by weight or more. Furthermore, the total amount of the monomer having a nitrogen-containing ring and the hydroxyl-containing monomer can be, for example, set to 50% by weight or less of monomer raw material A, preferably 30% by weight or less. In several preferred samples, the total amount of the monomer having a nitrogen-containing ring and the hydroxyl-containing monomer is 20% by weight or less, more preferably 15% by weight or less (e.g., 12% by weight or less) of monomer raw material A.

In monomer raw material A, which comprises a monomer having a nitrogen-containing ring and a hydroxyl-containing monomer, the relationship (by weight) between the content of the nitrogen-containing ring monomer (W _{_N}) and the content of the hydroxyl-containing monomer (W _{_OH}) in monomer raw material A is not particularly limited. W _{_N} /W_{_OH} can be, for example, 0.01 or more, typically 0.05 or more, 0.10 or more, or 0.12 or more. Furthermore, W _{_N} /W_{_OH} can be, for example, 10 or less, typically 1 or less, preferably 0.50 or less, 0.30 or less, 0.20 or less, or 0.15 or less.

In several embodiments, monomer raw material A is preferably free of monomer (single S1) having a polyorganosiloxane backbone, which can be well used as a constituent component of monomer raw material B described below, or the content of such monomer is less than 10% by weight of monomer raw material A (more preferably less than 5% by weight, for example less than 2% by weight). Monomer raw material A with this composition can effectively achieve a reinforcing film that balances initial secondary processingability with strong adhesion after the adhesion has increased. For the same reason, in several other embodiments, monomer raw material A is preferably free of 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.

There are no particular limitations on the method for obtaining polymer (A). For example, various polymerization methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization can be appropriately used. Solution polymerization is a good choice for several states. The polymerization temperature during solution polymerization can be appropriately selected according to the type of monomer and solvent used, as well as the type of polymerization initiator. For example, it can be set to around 20℃ to 170℃ (typically around 40℃ to 140℃).

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

Examples of thermal polymerization initiators include: azo-based polymerization initiators (e.g., 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid) dimethyl ester, 4,4'-azobis-4-cyanopentanoic acid, azobisisopentanone, 2,2'-azobis(2-amidinylpropane) dihydrochloride, 2,2'-azobis[2-(5-methyl... [-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropanediamine) disulfide, 2,2'-azobis(N,N'-dimethyleneisobutylammonium) dihydrochloride, etc.; persulfates such as potassium persulfate; peroxide-based polymerization initiators (e.g., benzoyl peroxide, tributyl peroxymonoacrylate, lauryl peroxide, etc.); redox-based polymerization initiators, etc. There are no particular restrictions on the amount of thermal polymerization initiator used. For example, relative to 100 parts by weight of the monomer component (monomer raw material A) used in the preparation of acrylic polymers, the amount can be set to 0.01 parts by weight to 5 parts by weight, preferably 0.05 parts by weight to 3 parts by weight.

There are no particular limitations on its use as a photopolymerization initiator. For example, benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-keto alcohol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketone-based photopolymerization initiators, and 9-oxosulfuron-methyl-2-ethylhexylene ... Photopolymerization initiators, such as phosphine oxide photopolymerization initiators, etc. There is no particular limitation on the amount of photopolymerization initiator used. For example, relative to 100 parts by weight of monomer raw material A, it can be set to a range of 0.01 parts by weight to 5 parts by weight, preferably 0.05 parts by weight to 3 parts by weight.

In several embodiments, polymer (A) can be contained in an adhesive composition for forming an adhesive layer. This is achieved by irradiating a mixture of monomer raw material A, which contains a polymer (polymer slurry), with ultraviolet light (UV) to polymerize a portion of the monomer component. The adhesive composition containing the polymer slurry can be applied to a specified substrate and irradiated with UV light to complete the polymerization. That is, the polymer slurry can be understood as a precursor of polymer (A). The adhesive layer disclosed herein can be formed, for example, using an adhesive composition containing the polymer slurry and polymer (B).

(Polymer (B)) The polymer (B) disclosed herein is a polymer comprising a monomer component (monomer raw material B) having a polyorganosiloxane backbone (hereinafter also referred to as "monomer S1") and a (meth)acrylate monomer. Polymer (B) may be referred to as a copolymer of monomer S1 and a (meth)acrylate monomer. Polymer (B) may be used alone or in combination with two or more monomers. Due to the low polarity and kinematic properties of the polyorganosiloxane structure derived from monomer S1, polymer (B) functions as an adhesion force retarder, suppressing initial adhesion to the substrate and increasing adhesion to the substrate upon heating. There is no particular limitation on monomer S1; any monomer containing a polyorganosiloxane backbone may be used. Monomer S1, due to its low polarity, promotes polymer (B) to favor the adhesive layer surface in the reinforcing film before application (before being attached to the substrate), exhibiting mild peelability (low adhesion) in the initial bonding stage. Monomer S1 is well-suited for structures with polymerizable reactive groups at single ends. By incorporating this monomer S1 unit and (meth)acrylate monomer units, a polymer (B) with a polyorganosiloxane backbone on the side chains is formed. This polymer (B) structure readily exhibits lower initial adhesion and higher adhesion after heating due to the mobility and ease of movement of the side chains. Furthermore, among several states, monomer S1 can readily adopt a functional group at one end that is polymerizable and reactive, while the other end lacks a functional group that would crosslink with polymer (A). Polymer (B) copolymerized from monomer S1 of this structure readily exhibits lower initial adhesion and higher adhesion upon heating due to the mobility of the polyorganosiloxane structure derived from monomer S1.

As monomer S1, compounds represented by the following general formula (1) or (2) can be used, for example. More specifically, examples of single-terminal reactive polysiloxane oils manufactured by Shin-Etsu Chemical Industry Co., Ltd. include X-22-174ASX, X-22-2426, X-22-2475, and KF-2012. Monomer S1 can be used alone or in combination with two or more. [Chemical 1] [Chemistry 2] Here, in the above general formulas (1) and (2), ^R3 is hydrogen or methyl, ^R4 is methyl or monovalent organic group, and m and n are integers greater than or equal to 0.

The functional group equivalent of monomer S1 can be an appropriate value within the range that allows the monomer S1 to achieve the desired effect, and is not limited to a specific range. From the viewpoint of sufficiently suppressing initial adhesion, the aforementioned functional group equivalent is, for example, 100 g/mol or more, or 200 g/mol or more, preferably 300 g/mol or more (e.g., 500 g/mol or more), more preferably 800 g/mol or more, and even more preferably 1500 g/mol or more. In the particularly preferred state, from the viewpoint of balancing low adhesion in the initial stage of adhesion and the increase in adhesion after heating, the aforementioned functional group equivalent is 2000 g/mol or more, more preferably 2500 g/mol or more, and can be 3000 g/mol or more, 4000 g/mol or more, or 5000 g/mol or more. In several other states, the equivalent of the above functional groups can be above 9000 g/mol, above 12000 g/mol, or above 15000 g/mol.

From the perspective of fully enhancing adhesion, the aforementioned functional group equivalent is preferably 30,000 g/mol or less, possibly 20,000 g/mol or less, possibly less than 15,000 g/mol or less than 10,000 g/mol. In several preferred states, the functional group equivalent 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, possibly 4,200 g/mol or less, or possibly 3,500 g/mol or less. If the functional group equivalent of monomer S1 is within the above range, the compatibility of the adhesive layer (e.g., compatibility with the base polymer) is easily improved. Furthermore, the polysiloxane backbone (chain) of polymer (B) has good mobility, which makes it easy to adjust the mobility of polymer (B) to an appropriate range, and easily achieve an adhesive layer that balances low initial tackiness with increased adhesive strength after heating.

Here, "functional group equivalent" refers to the weight of the backbone (e.g., polydimethylsiloxane) bonded to each functional group. The unit g/mol is converted to 1 mol of functional groups. The functional group equivalent of monomer S1 can be calculated, for example, based on the spectral intensity of ^1H -NMR (proton NMR) based on nuclear magnetic resonance (NMR). The calculation of the functional group equivalent (g/mol) of monomer S1 based on the spectral intensity of ^1H -NMR can be based on general structural analysis methods for ^1H -NMR spectral analysis, and may be performed as required by reference to the description in Japanese Patent No. 5951153. In the functional group equivalent of monomer S1, the aforementioned functional group refers to polymerizable functional groups (e.g., vinyl, allyl, and other vinyl unsaturated groups).

Furthermore, when using two or more monomers with different functional group equivalents as monomer S1, the functional group equivalent of monomer S1 can be expressed as an arithmetic mean. That is, the functional group equivalent of monomer S1, which includes n monomers (single _S11 , _S12 , ..., _S1n ) with different functional group equivalents, can be calculated using 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 + ... + Functional group equivalent of monomer S1n × Amount of monomer _S1n ) / (Amount of monomer _S11 + Amount of monomer _S12 + ... + Amount of monomer _S1n )

The content of monomer S1 can be appropriate within the range that allows the monomer S1 to exert the desired effect, and is not limited to a specific range. From the viewpoint of sufficiently suppressing initial adhesion, in several states, the content of monomer S1 in the total amount of the monomer component (monomer raw material B) used to prepare polymer (B) can be, for example, 5% by weight or more. From the viewpoint of better exerting the effect as an adhesion rise delayer, 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 also be 20% by weight or more. Furthermore, from the perspective of polymerization reactivity or compatibility, the content of monomer S1 in monomer raw material B can be, for example, 80% by weight or less, preferably 60% by weight or less, more preferably 50% by weight or less, even 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 force can be appropriately observed.

In addition to monomer S1, monomer raw material B also contains (meth)acrylate monomers that can copolymerize with monomer S1. By using one or more (meth)acrylate monomers, the mobility of polymer (B) within the adhesive layer can be appropriately adjusted. Furthermore, it can also help improve the compatibility between polymer (B) and polymer (A). Polymer (B) containing (meth)acrylate monomer units is well compatible with acrylic polymers, thus easily achieving a reduction in initial adhesive strength and an increase in adhesive strength after heating by improving the mobility of polymer (B) within the adhesive layer.

In the polymer (B) used in the technology disclosed herein, the composition of the (meth)acrylic monomers contained in monomer raw material B is preferably set such that the glass transition temperature _TB1 based on the composition of the (meth)acrylic monomers is higher than the glass transition temperature _TA of polymer (A). _TB1 can be set, for example, to be higher than 0°C. Here, the glass transition temperature _TB1 based on the composition of the (meth)acrylic monomers refers to Tg calculated by the Fox formula based solely on the composition of the (meth)acrylic monomers in the monomer composition used to prepare polymer (B). _TB1 can be calculated using only the (meth)acrylate monomers in the monomer composition used to prepare polymer (B). Applying the aforementioned Fox formula, it is determined based on the glass transition temperature of the homopolymer of each (meth)acrylate monomer and the weight fraction of each (meth)acrylate monomer in the total amount of that monomer. Polymers (B) with a relatively high glass transition temperature _TB1 (typically above 0°C) are more likely to suppress initial adhesion. Furthermore, polymers (B) with a relatively high glass transition temperature _TB1 (typically above 0°C) are more likely to produce reinforcing films with a greater increase in adhesion.

In several preferred conditions, _TB1 is above 10°C, more preferably above 30°C, and even more preferably above 40°C, and can also be above 45°C. If _TB1 is higher, there is a tendency for the initial adhesion force to be better suppressed. This is believed to be because, with _TB1 above the specified temperature for polymer (B), the increased mobility or displacement of the polyorganosiloxane structural portion caused by the temperature rising to room temperature or a certain degree above room temperature is effectively suppressed by the monomer units derived from (meth)acrylic acid monomers contained in polymer (B), thus better maintaining the low adhesion caused by the presence of the aforementioned polyorganosiloxane structural portion. From the perspective of better maintaining stability and low adhesion in the initial stage of adhesion, in several conditions, _TB1 can be, for example, above 50°C, above 55°C, or above 60°C. Furthermore, _TB1 can be, for example, below 120°C or below 100°C. If _TB1 is lower, there is a tendency for the adhesion force to increase due to heating to become easier. In several preferred conditions, _TB1 is, for example, below 90°C, more preferably below 70°C, further preferably below 60°C, and especially preferably below 55°C (e.g., below 50°C).

From the perspective of easily leveraging the effects produced by properly setting _TB1 , the ratio of the total amount of monomer S1 and (meth)acrylic monomers in the total monomer composition used to prepare polymer (B) can 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 practically 100% by weight.

The glass transition temperature _TB of polymer (B) is not particularly limited and can be selected in a manner that yields better properties in the reinforcing film disclosed herein. The _TB of polymer (B) may, for example, be below 50°C, below 30°C, below 20°C, below 15°C, or below 10°C. If the _TB of polymer (B) is lower, the mobility (typically temperature-sensitive mobility) of the polymer (B) increases, which can significantly increase the adhesive force. In several preferred states, the _TB of polymer (B) is below 5°C, may not reach 0°C, may be below -5°C, or below -10°C. Furthermore, in several states, the _TB of polymer (B) may, for example, be above -40°C or above -30°C. A higher T_{_B} indicates that the polymer (B) positioned closer to the adhesive layer surface when adhering to the substrate is more conducive to reducing initial tack and exhibits better initial easy peelability. In several preferred samples, the T_{_B} of polymer (B) is above -20°C, and can also be above -15°C. By setting the T_{_B} within an appropriate range, the initial easy peelability and the increase in tack after heating can be controlled within an optimal range.

In several states, the composition of the monomer components used to prepare polymer (B) can be set such that _TB1 is higher than _TB , i.e., _TB1 - _TB is greater than 0°C. Based on this composition, the effect of regulating the mobility of polymer (B) by utilizing the composition of (meth)acrylate monomers contained in the aforementioned monomer components can be readily and appropriately achieved. _TB1 - _TB can be, for example, around 40°C to 100°C, or around 50°C to 90°C. In several preferred states, _TB1 - _TB is 45°C or higher, more preferably 50°C or higher, and even more preferably 55°C or higher (e.g., 58°C or higher). Furthermore, from the viewpoint of appropriately exhibiting the effects of containing polymer (B), _TB1 - _TB is preferably below 80°C, more preferably below 70°C, and even more preferably below 65°C (e.g., below 62°C).

From the viewpoint of easily controlling the mobility of polymer (B) within the adhesive layer, in several states, the composition of the monomer components used to prepare polymer (B) can be set such that, in relation to the glass transition temperature _TA of polymer (A), _TB is at least 20°C higher than _TA , i.e., _TB - _TA is at least 20°C. In several preferred states, _TB - _TA is, for example, at least 30°C, more preferably at least 40°C, even more preferably at least 50°C, and can be at least 60°C or even at least 70°C. Furthermore, from the viewpoint of increasing adhesive strength, _TB - _TA can be, for example, below 130°C, or below 120°C, preferably below 100°C, even more preferably below 80°C, even more preferably below 65°C, and can be below 55°C or even below 45°C.

As a (meth)acrylic monomer that can be used in monomer raw material B, alkyl (meth)acrylates may be cited as an example. Here, "alkyl" refers to a chain-like (including linear and branched) alkyl group, excluding alicyclic hydrocarbons described below. For example, one or more of the monomers exemplified above regarding alkyl (meth)acrylates that can be used in polymer (A) may be used as constituents of monomer raw material B. In some embodiments, monomer raw material B may contain at least one of _C4-12 alkyl (meth)acrylates (preferably _C4-10 alkyl, such as _C6-10 alkyl). In other embodiments, monomer raw material B may contain at least one of _C1-18 alkyl methacrylates (preferably _C1-14 alkyl, such as _C1-10 alkyl). Monomer raw material B may include one or more of the following as (meth)acrylic monomers: for example, MMA, n-butyl methacrylate (BMA) and 2-ethylhexyl methacrylate (2EHMA).

Other examples of the above-mentioned (meth)acrylate monomers include (meth)acrylates having an alicyclic hydrocarbon group. For example, cyclopentyl methacrylate, cyclohexyl methacrylate, isopropyl methacrylate, dicyclopentyl methacrylate, and 1-dalcenic methacrylate can be used. In several embodiments, monomer raw material B may contain at least one selected from dicyclopentyl methacrylate, isopropyl methacrylate, and cyclohexyl methacrylate as a (meth)acrylate monomer.

The content of the aforementioned alkyl (meth)acrylate and the aforementioned (meth)acrylate containing alicyclic hydrocarbons in monomer raw material B can be, for example, 10% by weight or more and 95% by weight, 20% by weight or more and 95% by weight, 30% by weight or more and 90% by weight, 40% by weight or more and 90% by weight, or 50% by weight or more and 85% by weight. From the viewpoint of ease of increase in adhesive force upon heating, the use of alkyl (meth)acrylate becomes advantageous. In several formulations, the content of (meth)acrylate containing alicyclic hydrocarbons 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 monomer raw material B. Alternatively, (meth)acrylate containing alicyclic hydrocarbons may not be used.

In several preferred embodiments, the aforementioned (meth)acrylic acid monomers, which are components of monomer raw material B, may include monomer M2, whose homopolymer has a Tg of 50°C or higher. In polymer (B), by copolymerizing monomer S1 and monomer M2, the mobility or displacement of the polyorganosiloxane structural portion accompanying temperature rise can be easily and appropriately controlled, while simultaneously achieving initial easy peelability (secondary processing capability) and an increase in adhesion after heating. In several embodiments, the Tg of the homopolymer of monomer M2 can be 60°C or higher, 70°C or higher, 80°C or higher, or 90°C or higher. Furthermore, there is no particular upper limit to the Tg of the homopolymer of monomer M2; from the viewpoint of ease of synthesis of polymer (B), it is generally suitable to be below 200°C. In several states, the Tg of the homopolymer of monomer M2 can be, for example, below 180°C, below 150°C, or below 120°C.

As monomer M2, for example, homopolymers whose Tg meets the requirements can be used from the (meth)acrylic monomers exemplified above. For example, one or more monomers selected from the group consisting of alkyl (meth)acrylates and (meth)acrylates having alicyclic hydrocarbon groups can be used. As an alkyl (meth)acrylate, alkyl methacrylates with the alkyl group having 1 to 4 carbon atoms are preferred.

In a sample containing monomer M2, the content of 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 monomer B. In several samples, the content of 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 monomer B. Furthermore, the content of monomer M2 may be, for example, 90% by weight or less, typically 80% by weight or less, preferably 75% by weight or less, and may be 70% by weight or less, or 65% by weight or less. In several preferred samples, the content of monomer M2 is 60% by weight or less (e.g., 50% by weight or less, typically 42% by weight or less). In polymer (B), by limiting the copolymerization ratio of monomer M2 with a Tg of 50°C or higher to a specified value, the increase in adhesive force after heating can be effectively achieved based on the mobility of polymer (B) near 50°C. From the same perspective, the content of monomer M2 in monomer raw material B can be 35% by weight or less, 25% by weight or less, or 15% by weight or less (e.g., 5% by weight or less).

The aforementioned content of monomer M2 can be well applied, for example, to a state in which monomer M2 comprises one or more monomers selected from the group consisting of alkyl (meth)acrylates and (meth)acrylates having an alicyclic hydrocarbon group, or to a state in which monomer M2 comprises one or more monomers selected from alkyl (meth)acrylates (e.g., alkyl methacrylate). As a preferred example of such a state, a state in which monomer M2 comprises MMA can be exemplified.

In several formulations, the aforementioned (meth)acrylic acid monomers may also include monomer M3, whose homopolymer Tg is below 50°C (typically above -20°C and below 50°C). By using monomer M3, it is easy to obtain a reinforcing film that balances adhesiveness and cohesiveness evenly after the adhesiveness increases. From the viewpoint of easily achieving this effect, monomer M3 is preferably used in combination with monomer M2.

As monomer M3, for example, homopolymers whose Tg meets the conditions can be used from the (meth)acrylate monomers exemplified above. For example, one or more monomers selected from the group consisting of alkyl (meth)acrylates can be used.

In a sample containing monomer M3 as monomer raw material B, 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. Furthermore, the content of monomer M3 is generally suitable to be 70% by weight or less, 60% by weight or less, or 50% by weight or less of monomer raw material B. The above-mentioned content of monomer M3 is well applicable, for example, to samples in which monomer M3 contains one or more monomers selected from alkyl methacrylates (e.g., alkyl methacrylates).

In the various forms of reinforcing films disclosed herein, the monomer raw material B preferably comprises a homopolymer with a Tg higher than 170°C containing 30% by weight or less of the monomer. Here, unless otherwise specified, the term "monomer content of X% by weight or less" in this specification includes forms with a monomer content of 0% by weight, i.e., forms that substantially do not contain the monomer. Furthermore, "substantially do not contain" means that the aforementioned monomer is not intentionally used. If the copolymerization ratio of monomers with a Tg higher than 170°C in the homopolymer becomes high, the mobility of polymer (B) may be insufficient, making it difficult to increase adhesion by heating to a temperature range higher than 50°C.

In several embodiments, monomer raw material B preferably contains at least MMA as a (meth)acrylic monomer. The polymer (B) copolymerized from MMA readily yields a reinforcing film with strong adhesion after heating. The percentage of MMA in the total amount of (meth)acrylic monomers contained in monomer raw material B can be, for example, 5% by weight or more, 10% by weight or more, 20% by weight or more, 30% by weight or more, or 40% by weight or more. Furthermore, the percentage of MMA in the total amount of monomer raw material B is generally preferably 95% by weight or less. In several preferred embodiments, from the viewpoint of increased adhesion after heating, the percentage of MMA in the total amount of monomer raw material B can 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).

Other examples of monomers that can be contained together with monomer S1 in the monomer units constituting polymer (B) include: carboxyl-containing monomers, anhydride-containing monomers, hydroxyl-containing monomers, epoxy-containing monomers, cyano-containing monomers, isocyanate-containing monomers, amide-containing monomers, monomers having a nitrogen-containing ring (N-vinylcyclic amide, (meth)propylene) Cyclic amides with amide groups, monomers with a succinimide skeleton, cis-butenediamides, isocarboximides, etc., aminoalkyl esters of (meth)acrylates, vinyl esters, vinyl ethers, alkenes, (meth)acrylates with aromatic hydrocarbon groups, (meth)acrylates containing heterocyclic rings, (meth)acrylates containing halogen atoms, and (meth)acrylates obtained from terpene compound derivative alcohols, etc.

Other examples of monomers that may be contained together with monomer S1 as monomer units constituting polymer (B) include: ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and other oxyalkylene di(meth)acrylates; monomers having a polyoxyalkylene backbone, such as those in polyethylene glycol or polypropylene glycol. Polymerizable polyoxyalkyl ethers with polymerizable functional groups such as (meth)acrylic, vinyl, or allyl at one end of the chain and ether structures (alkyl ethers, aromatic ethers, arylalkyl ethers, etc.) at the other end; methoxyethyl acrylate, ethoxyethyl acrylate, propoxyethyl acrylate, butoxyethyl acrylate, ethoxypropyl acrylate, and other alkoxyalkyl acrylates; salts such as alkali metal salts of (meth)acrylate; and multi-component (e.g., trihydroxymethylpropane tri(meth)acrylate. Methacrylates: halogenated vinylidene chloride, 2-chloroethyl methacrylate, and other ethoxylated vinylidene chloride compounds; acezoline-containing monomers such as 2-vinyl-2-acezoline, 2-vinyl-5-methyl-2-acezoline, and 2-isopropenyl-2-acezoline; aziridinium-containing monomers such as aziridinium acrylate and aziridinium ethyl methacrylate; hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, lactones, and adducts of 2-hydroxyethyl methacrylate, etc. Vinyl monomers containing fluorinated groups; fluorinated vinyl monomers such as fluorinated (meth)acrylate alkyl esters; vinyl monomers containing reactive halogens such as 2-chloroethyl vinyl ether and vinyl monochloroacetate; vinyl monomers containing organosilicon such as vinyltrimethoxysilane, γ-(meth)acryloxypropyltrimethoxysilane, allyltrimethoxysilane, trimethoxysilylpropylallylamine, and 2-methoxyethoxytrimethoxysilane; and, for example, macromonomers with free radical polymerizable vinyl groups at the ends of the monomers obtained by polymerizing vinyl groups. These can be copolymerized with monomer S1 alone or in combination with two or more of them.

Among several states, polymer (B) is preferably one that does not possess functional groups that would cause cross-linking reactions with polymer (A). In other words, polymer (B) is preferably contained in the adhesive layer in a form that does not chemically bond with polymer (A). An adhesive layer containing polymer (B) in this form exhibits good mobility of polymer (B) upon heating, which is suitable for increasing the adhesive strength ratio. The functional groups that would cause cross-linking reactions with polymer (A) may vary depending on the types of functional groups possessed by polymer (A), and may be, for example, epoxy, isocyanate, carboxyl, alkoxysilyl, amino, etc.

The Mw of polymer (B) is not particularly limited. The Mw of polymer (B) may be, for example, 1000 or more, or 5000 or more. In several preferred embodiments, from the viewpoint of suitably exhibiting an increase in adhesive force after heating, the Mw of polymer (B) may be 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 several 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) may be, for example, 500,000 or less, 350,000 or less, 200,000 or less, or 150,000 or less. From the perspective of adjusting the compatibility or mobility within the adhesive layer to an appropriate range to suitably exhibit low adhesion in the initial stage of application, in several preferred embodiments, the Mw of polymer (B) is 100,000 or less, more preferably 80,000 or less, further preferably 60,000 or less, especially preferably 40,000 or less (e.g., 30,000 or less), and can be 25,000 or less, and can also be 20,000 or less. By setting the Mw of polymer (B) to an appropriate range, an adhesive that achieves an excellent balance between easy peeling and increased adhesion in the initial stage of application can be easily obtained.

In several preferred embodiments, the Mw of polymer (B) is preferably lower than that of polymer (A). This facilitates the creation of a reinforcing film that balances good secondary processing properties during initial application with increased adhesion after heating. In several preferred embodiments, the Mw of polymer (B) may be, for example, less than 0.8 times, less than 0.75 times, less than 0.5 times, or less than 0.3 times that of polymer (A). In several preferred embodiments, the ratio of _MwB of polymer (B) to _MwA of polymer (A) ( _MwB / _MwA ) is less than 0.3, more preferably less than 0.2, further preferably less than 0.1, and most preferably less than 0.06 (e.g., less than 0.05). Furthermore, the ratio (Mw _B / Mw _A ) is preferably 0.010 or higher, more preferably 0.020 or higher, even more preferably 0.03 or higher, and even more preferably 0.04 or higher. By setting the Mw of polymer (A) and the Mw of polymer (B) to suitable ranges, the effects of the technology disclosed herein can be better achieved. In several other embodiments, the Mw of polymer (B) may also be less than 0.03 times (e.g., less than 0.02 times) of the Mw of polymer (A).

Polymer (B) can be produced by polymerizing the aforementioned monomers using known methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization.

To adjust the molecular weight of polymer (B), chain transfer agents may be used as needed. Examples of chain transfer agents that may be used include: compounds with a pi group such as octylthiol, laurylthiol, nonylthiol, dodecylthiol, pi-ethanol, and α-thioglycerol; thioglycolic acid, methyl thioglycolate, ethyl thioglycolate, propyl thioglycolate, butyl thioglycolate, tributyl thioglycolate, 2-ethylhexyl thioglycolate, octyl thioglycolate, isooctyl thioglycolate, decyl thioglycolate, dodecyl thioglycolate, thioglycolates of ethylene glycol, neopentyl glycol, and pentaerythritol; and α-methylstyrene dimers, etc.

There are no particular restrictions on the amount of chain transfer agent used. Typically, it contains 0.05 to 20 parts by weight, preferably 0.1 to 15 parts by weight, and even more preferably 0.2 to 10 parts by weight, relative to 100 parts by weight of the monomer. By adjusting the amount of chain transfer agent added in this way, a polymer (B) with a better molecular weight can be obtained. The chain transfer agent can be used alone or in combination with two or more others.

As a method for adjusting the molecular weight of polymer (B), various previously known methods, including the use of the aforementioned chain transfer agent, may be used alone or in appropriate combinations. The same applies to the molecular weight of polymer (A). Non-limiting examples of such methods include the selection of the polymerization method, the type or amount of the polymerization initiator, the polymerization temperature, the type or amount of the polymerization solvent in solution polymerization, and the light intensity in photopolymerization. Operators can understand how to obtain a polymer with the desired molecular weight based on the description in this specification, including the specific examples below, and the technical knowledge at the time of this application.

In the reinforcing film disclosed herein, relative to 100 parts by weight of polymer (A), the amount of polymer (B) used can be, for example, 0.1 parts by weight or more. From the viewpoint of obtaining a higher effect (suitable for easy peeling in the initial stage of adhesion), it is preferably 0.5 parts by weight or more, more preferably 1 part by weight or more, and even more preferably 1.5 parts by weight or more, and can also be 2 parts by weight or more. In several embodiments, from the viewpoint of improving secondary processingability, the amount of polymer (B) used can be, for example, 3 parts by weight or more, 4 parts by weight or more, and can also be 5 parts by weight or more. Furthermore, relative to 100 parts by weight of polymer (A), the amount of polymer (B) used can be, for example, 75 parts by weight or less, 30 parts by weight or less, 10 parts by weight or less, and 8 parts by weight or less. From the perspective of achieving the desired increase in adhesive strength, in several 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, further preferably 3 parts by weight or less, and even more preferably 2.5 parts by weight or less. In several other preferred embodiments, the amount of polymer (B) used relative to 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 setting the amount of polymer (B) within the above range, good flexural resilience and flexural holding power can be easily achieved. Furthermore, it is possible to better balance easy peeling in the initial stage of adhesion with the increase in adhesive strength.

The adhesive layer may contain polymers other than polymers (A) and (B) (any polymer) as needed, within a range that does not significantly impair the performance of the reinforcing film disclosed herein. The amount of such arbitrary polymer used is typically suitable to be 20% by weight or less, 15% by weight or less, or 10% by weight or less of the total polymer component contained in the adhesive layer. In some embodiments, the amount of the aforementioned arbitrary polymer may be 5% by weight or less, 3% by weight or less, or 1% by weight or less of the total polymer component. An adhesive layer that substantially does not contain polymers other than polymers (A) and (B) may also be used.

(Crosslinking Agents) Crosslinking agents can be used in the adhesive layer as needed to adjust cohesion, etc. As crosslinking agents, those known in the field of adhesives can be used, such as: epoxy crosslinking agents, isocyanate crosslinking agents, polysiloxane crosslinking agents, aziridine crosslinking agents, silane crosslinking agents, alkyl etherified melamine crosslinking agents, and metal chelate crosslinking agents. Isocyanate crosslinking agents, epoxy crosslinking agents, and metal chelate crosslinking agents are particularly suitable. Isocyanate-based crosslinkers are suitable crosslinkers that balance flexural recovery and flexural retention. Crosslinkers can be used alone or in combination of two or more.

As an isocyanate crosslinking agent, it can be used well with polyfunctional isocyanates (meaning compounds with an average of more than two isocyanate groups per molecule, including those with isocyanurate structures). Isocyanate crosslinking agents can be used alone or in combination with two or more.

Examples of polyfunctional isocyanates include: aliphatic polyisocyanates, cycloaliphatic polyisocyanates, and aromatic polyisocyanates. Specific examples of aliphatic polyisocyanates include: 1,2-epenylethyl 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.

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 phenyl dimethyl diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

Specific examples of aromatic polyisocyanates include: 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, and 2,2'-diphenylpropane-4,4'-diisocyanate. Cyanides, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, isophenyl diisocyanate, terephthalic diisocyanate, naphthyl-1,4-diisocyanate, naphthyl-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, phenyldimethyl-1,4-diisocyanate, phenyldimethyl-1,3-diisocyanate, etc.

As preferred polyfunctional isocyanates, examples include polyfunctional isocyanates having an average of three or more isocyanate groups per molecule. These trifunctional or higher isocyanates can be polymers (e.g., dimers or trimers) of difunctional or trifunctional or higher isocyanates, derivatives (e.g., products of addition reactions of polyols with two or more molecules of polyfunctional isocyanates), polymers, etc. Examples include: dimers or trimers of diphenylmethane diisocyanate, isocyanurates of hexamethylene diisocyanate (trimeric adducts of isocyanurate structures), reaction products of trimethylolpropane and toluene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, trimethylolpropane adducts of phenyl diisocyanate, and isoflavones. Trimethylolpropane adduct of ketone diisocyanate, trimethylolpropane adduct of hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, and their adducts with various polyols, as well as polyisocyanates that are multifunctionalized by means of isocyanurate bonds, biuret bonds, urethane bonds, etc., are all polyfunctional isocyanates.

Examples of commercially available polyfunctional isocyanates include: Asahi Kasei Chemicals' "Duranate TPA-100"; Tosoh's "Coronate L", "Coronate HL", "Coronate HK", "Coronate HX", and "Coronate 2096"; and Mitsui Chemicals' "Takenate D110N", "Takenate D120N", "Takenate D140N", and "Takenate D160N".

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

Regarding metal chelate compounds, examples of metal components include aluminum, iron, tin, titanium, and nickel, while examples of chelate components include acetylene, methyl acetate, and ethyl lactate. These can be used alone or in combination of two or more.

There is no particular limitation on the amount of crosslinking agent used, for example, it can be more than 0 parts by weight relative to 100 parts by weight of polymer (A). Furthermore, the amount of crosslinking agent used relative to 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. By increasing the amount of crosslinking agent used, the initial adhesion force is suppressed, and there is a tendency to improve secondary processing properties. It also tends to have excellent flexibility and processability. In several samples, the amount of crosslinking agent used relative to 100 parts by weight of polymer (A) can be 0.1 parts by weight or more, 0.5 parts by weight or more, or 0.8 parts by weight or more. On the other hand, from the viewpoint of allowing appropriate mobility of polymer (B) to obtain an increase in adhesive force after heating, the amount of crosslinking agent used is usually appropriate to be set to 15 parts by weight or less, or 10 parts by weight or less, or 5 parts by weight or less, relative to 100 parts by weight of polymer (A).

The technique disclosed herein can be well implemented in at least the form using an isocyanate-based crosslinker as the crosslinking agent. From the viewpoint of balancing good secondary processability in the initial stage of adhesion with an increase in adhesion after heating, in several forms, the amount of isocyanate-based crosslinker used relative to 100 parts by weight of polymer (A) can be set to, 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 can be set to 0.10 parts by weight or more, or can be set to 0.15 parts by weight or more (e.g., 0.20 parts by weight or more). By increasing the amount of isocyanate-based crosslinker used, suitable cohesive strength and elastic modulus can be obtained, with a tendency for excellent flexural resilience and processability. Furthermore, relative to 100 parts by weight of polymer (A), the amount of isocyanate-based crosslinker used can be set to, for example, less than 5 parts by weight, preferably less than 1.0 parts by weight, more preferably less than 0.5 parts by weight, further preferably less than 0.3 parts by weight, and even more preferably less than 0.2 parts by weight (e.g., less than 0.15 parts by weight). This moderately reduces the cohesive force of the adhesive, and consequently its elastic modulus (typically surface elastic modulus), resulting in good flexural retention and easier attainment of increased adhesive force upon heating.

When an isocyanate-based crosslinker is used in an adhesive layer containing hydroxyl-containing monomers as monomer units, the molar ratio ([NCO]/[OH]) of the isocyanate groups to hydroxyl groups in the adhesive layer can be set to, for example, 0.001 or higher, but is not particularly limited. By increasing the amount of isocyanate-based crosslinker relative to the hydroxyl-containing monomers, the elastic modulus of the adhesive (typically the surface elastic modulus) becomes suitable, tending to improve flexural resilience. Furthermore, it tends to have excellent processability. In several preferred embodiments, the molar ratio ([NCO]/[OH]) is 0.002 or higher, more preferably 0.004 or higher, and even more preferably 0.006 or higher (e.g., 0.007 or higher), and may be 0.010 or higher, 0.020 or higher, or 0.030 or higher. Furthermore, the molar ratio ([NCO]/[OH]) may, for example, be 1.0 or lower, or 0.10 or lower. By limiting the molar ratio to a specified value or lower, a cross-linking structure suitable for significantly increasing the adhesive force after heating relative to the initial adhesive force can be well formed. In several preferred embodiments, the molar ratio ([NCO]/[OH]) is 0.030 or less, more preferably 0.015 or less, and even more preferably 0.012 or less (e.g., 0.009 or less), or 0.005 or less. Furthermore, in the adhesive layer, the isocyanate group and the hydroxyl group can be chemically bonded (cross-linked) in at least a portion of their respective states. More specifically, the isocyanate group can be chemically bonded (cross-linked) with the hydroxyl group. On the other hand, the hydroxyl group can exist in a state where a portion is chemically bonded to the isocyanate group, and the other portion is not chemically bonded (cross-linked) with the isocyanate group.

In several preferred embodiments, the adhesive layer contains a catalyst. The purpose of adding a catalyst is to promote the hardening of the adhesive layer during its formation, typically by making any of the aforementioned cross-linking reactions more efficient. Therefore, the aforementioned catalyst is also called a hardening catalyst or a cross-linking catalyst. By adding a catalyst, initial hardening can be promoted, and side reactions that cause bubble formation on the adhesive layer surface can be suppressed. Examples of catalysts include: iron-based catalysts, tin-based catalysts, titanium-based catalysts, zirconium-based catalysts, lead-based catalysts, cobalt-based catalysts, zinc-based catalysts, and other organometallic compounds, tertiary amine compounds, etc. These can be used alone or in combination of two or more. In terms of balancing reaction speed and service life, iron-based catalysts and tin-based catalysts are preferred, with iron-based catalysts being the most preferred.

Examples of iron-based catalysts include ferric acetopyruvate and ferric 2-ethylhexanoate. Iron-based catalysts can be used alone or in combination with two or more other catalysts.

Examples of tin-based catalysts include: dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin citrate, dibutyltin dilaurate, dibutyltin diacetate, dibutyltin sulfide, tributylmethanol tin, tributyltin acetate, triethylethanol tin, tributylethanol tin, dioctyltin oxide, dioctyltin dilaurate, tributyltin chloride, tributyltin trichloroacetic acid, and tin 2-ethylhexanoate. Tin-based catalysts can be used alone or in combination with two or more other catalysts.

There is no particular limitation on the amount of catalyst used. For example, it can be set to 0.0001 parts by weight or more, preferably 0.001 parts by weight or more, more preferably 0.003 parts by weight or more, further preferably 0.006 parts by weight or more, and most preferably 0.008 parts by weight or more, relative to 100 parts by weight of polymer (A). By using an appropriate amount of catalyst, the formation of bubbles in the adhesive layer can be suppressed, making it easier to obtain a smooth adhesive surface. Furthermore, the amount of catalyst used can be set to less than 1 part by weight, or even less than 0.1 parts by weight, relative to 100 parts by weight of polymer (A). In several preferred embodiments, the amount of catalyst used relative to 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 also 0.005 parts by weight or less. By appropriately limiting the amount of catalyst relative to 100 parts by weight of polymer (A), a suitable increase in adhesion can be easily achieved.

When a catalyst is used in an adhesive layer containing hydroxyl-containing monomers as monomer units, the amount of catalyst used can be set such that the molar ratio of the catalyst to the hydroxyl group in the adhesive layer ([catalyst]/[OH]) is, for example, 1.0 × ^10⁻⁶ or more. Preferably, the molar ratio is 1.0 × ^10⁻⁵ or more, more preferably 1.0 × ^10⁻⁴ or more, further preferably 2.0 × ^10⁻⁴ or more, and even more preferably 3.0 × ^10⁻⁴ or more, but there are no particular limitations. By using an appropriate amount of catalyst, the formation of bubbles in the adhesive layer can be suppressed, and a smooth adhesive surface can be easily obtained. Furthermore, the aforementioned molar ratio ([catalyst]/[OH]) can be set to 5.0 × ^10⁻² or less, or even 5.0 × ^10⁻³ or less. In several preferred embodiments, the aforementioned molar ratio ([catalyst]/[OH]) is 3.0 × ^10⁻³ or less, more preferably 1.0 × ^10⁻³ or less, and even more preferably 5.0 × ^10⁻⁴ or less, or even 3.0 × ^10⁻⁴ or less. By appropriately limiting the catalyst content, a suitable increase in adhesive force can be easily achieved.

(Adhesive-Enhancing Resins) Adhesive layers may contain adhesive-enhancing resins as needed. There are no particular limitations on the type of adhesive-enhancing resin; examples include: rosin-based adhesive-enhancing resins, terpene-based adhesive-enhancing resins, phenolic adhesive-enhancing resins, hydrocarbon-based adhesive-enhancing resins, ketone-based adhesive-enhancing resins, polyamide-based adhesive-enhancing resins, epoxy-based adhesive-enhancing resins, and elastomer-based adhesive-enhancing resins. Adhesive-enhancing resins can be used alone or in combination with two or more.

The content of adhesive resin is not particularly limited and can be set according to the purpose or application to achieve appropriate adhesive properties. The content of adhesive resin (total amount when two or more adhesive resins are present) relative to 100 parts by weight of polymer (A) can be set, for example, to approximately 5 to 500 parts by weight. Furthermore, the technology disclosed herein allows for the effective implementation of variations in the amount of adhesive resin used. For example, the content of adhesive resin relative to 100 parts by weight of polymer (A) can be set to less than 20 parts by weight, less than 10 parts by weight, less than 3 parts by weight, or less than 1 part by weight (0 parts by weight to less than 1 part by weight), in several variations where the adhesive layer substantially does not contain adhesive resin.

Furthermore, the adhesive layer in the technology disclosed herein may, as needed, contain leveling agents, plasticizers, softeners, colorants (dyes, pigments, etc.), fillers, antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, light stabilizers, preservatives, and other known additives that can be used as adhesives, to a extent that does not significantly impair the effect of the invention.

The adhesive layer constituting the reinforcing film disclosed herein can be a hardened layer of the adhesive composition. That is, the adhesive layer can be formed by applying (e.g., coating) a water-dispersible, solvent-based, photocurable, or hot-melt adhesive composition to a suitable surface and then performing a curing treatment. When two or more curing treatments (drying, crosslinking, polymerization, cooling, etc.) are performed, these can be carried out simultaneously or in multiple stages. In adhesive compositions using a portion of a polymer (polymer slurry) of monomeric raw materials, typically, as a curing treatment, a final copolymerization reaction is carried out. That is, a portion of the polymer is subjected to a further copolymerization reaction to form a complete polymer. For example, if it is a photocurable adhesive composition, light irradiation is performed. Crosslinking, drying, or other curing treatments may also be performed as needed. For example, when drying is necessary for a light-curing adhesive composition, light curing can be performed after drying. In adhesive compositions using complete polymers, typically, as a curing treatment, drying (heat drying), crosslinking, or other treatments are performed as needed.

The coating of adhesive compositions can be carried out using commonly used coating machines such as gravure roller coating machines, reverse roller coating machines, contact roller coating machines, dip roller coating machines, rod coating machines, scraper coating machines, and spray coating machines.

The thickness of the adhesive layer is not particularly limited; for example, it can be set to 6 μm or more. In several samples, the thickness of the adhesive layer can be 8 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. By increasing the thickness of the adhesive layer, there is a tendency for the adhesive force to increase after heating. Furthermore, in several samples, the thickness of the adhesive layer can be, for example, 300 μm or less, 200 μm or less, 150 μm or less, 100 μm or less, 70 μm or less, 50 μm or less, or 40 μm or less. A less excessively thick adhesive layer is advantageous from the perspectives of thinning the reinforcing film or preventing the adhesive layer from agglomerating and breaking down. A reinforcing film having an adhesive layer with a thickness within the aforementioned range can achieve a balance between adhesive properties such as adhesive strength and bending resilience and bending holding force. Furthermore, when a reinforcing film having a first adhesive layer and a second adhesive layer on both the first and second surfaces of a substrate is used, the thickness of the adhesive layer can be at least the same as the thickness of the first adhesive layer. The thickness of the second adhesive layer can also be selected from the same range. Moreover, in the case of a reinforcing film without a substrate, the thickness of the reinforcing film is the same as the thickness of the adhesive layer.

<Supporting Substrate> Several types of reinforcing films may be in the form of adhesive sheets for attaching to a supporting substrate, with adhesive layers prepared on one or both sides of the supporting substrate. The material of the supporting substrate is not particularly limited and can be appropriately selected according to the intended use or application of the reinforcing film. Non-limiting examples of usable substrates include: resin films such as plastic films; foam sheets composed of foams such as polyurethane foam, polyethylene foam, and polychloroprene foam; woven and non-woven fabrics formed from various fibrous materials (such as natural fibers like hemp and cotton, synthetic fibers like polyester and vinylon, and semi-synthetic fibers like acetate); paper types such as Japanese paper, woodfree paper, kraft paper, and wrinkled paper; and metal foils such as aluminum foil and copper foil. Substrates composed of composites of these materials are also possible. Examples of such composite substrates include: substrates with a structure consisting of a metal foil and the aforementioned plastic film, and plastic substrates reinforced with inorganic fibers, such as glass cloth.

Various membrane substrates can be used as the substrate for the reinforcing membrane disclosed herein. These membrane substrates can be porous substrates such as foamed membranes or non-woven sheets, non-porous substrates, or substrates with a structure consisting of both porous and non-porous layers. Among several embodiments, resin membranes capable of independently maintaining their shape (self-contained or independent) can be used as the base membrane as the aforementioned membrane substrate. Here, "resin membrane" refers to a non-porous structure, and typically refers to a resin membrane that is substantially bubble-free (non-porous). Therefore, the concept of a resin membrane differs from that of foamed membranes or non-woven fabrics. The resin film described above is well-suited for use as it can independently maintain its shape (either self-supporting or independent). The resin film can be a single-layer structure or a multi-layer structure with two or more layers (e.g., a three-layer structure).

Examples of resin materials constituting resin films include: polyester, polyolefins, nylon 6, nylon 66, polyamides (PA) such as some aromatic polyamides, polyimide (PI), polyamide-imide (PAI), polyetheretherketone (PEEK), polyether sulfide (PES), polyphenylene sulfide (PPS), polycarbonate (PC), polyurethane (PU), ethylene-vinyl acetate copolymer (EVA), polytetrafluoroethylene (PTFE) and other fluororesins, acrylic resins, polyacrylates, polystyrene, polyvinyl chloride, polyvinylidene chloride, and other resins. The aforementioned resin films can be formed using a resin material containing only one of these resins, or they can be formed using a mixture of two or more resin materials. The resin membrane may be unstretched or stretched (e.g., uniaxial or biaxial stretching).

Preferred examples of resin materials constituting resin films include polyimide resins, polyester resins, PPS resins, and polyolefin resins. Here, polyimide resins refer to resins containing polyimide in a ratio of more than 50% by weight. Similarly, polyester resins refer to resins containing polyester in a ratio of more than 50% by weight, PPS resins refer to resins containing PPS in a ratio of more than 50% by weight, and polyolefin resins refer to resins containing polyolefins in a ratio of more than 50% by weight.

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

As a polyolefin resin, a single polyolefin can be used alone, or a combination of two or more polyolefins can be used. The polyolefin can be, for example, a homopolymer of α-olefins, 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 rubber (EPR) and other ethylene-propylene copolymers, ethylene-propylene-butene copolymers, ethylene-butene copolymers, ethylene-vinyl alcohol copolymers, ethylene-ethyl acrylate copolymers, etc. Both low-density (LD) and high-density (HD) polyolefins can be used. Examples of polyolefin resin films include: unstretched polypropylene (CPP) film, biaxially stretched 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 containing two or more types of polyethylene (PE), and PP/PE composite film containing polypropylene (PP) and polyethylene (PE), etc.

Examples of resin films that can be well used as base films for the reinforcing films disclosed herein include PI films, PET films, PEN films, PPS films, PEEK films, CPP films and OPP films.

Within the resin film, known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, lubricants, and antiblocking agents can be added as needed, within a range that does not significantly impair the effects of the invention. The amount of additives added is not particularly limited and can be appropriately set according to the intended purpose.

There are no particular limitations on the manufacturing method of resin films. For example, commonly known resin film forming methods such as extrusion molding, blow molding, T-die casting, and burnishing roll forming can be appropriately adopted.

The aforementioned substrate may be substantially composed of such a base film. Alternatively, the aforementioned substrate may also include auxiliary layers in addition to the aforementioned base film. Examples of such auxiliary layers include: optical property adjustment layers (e.g., coloring layers, anti-reflective layers), printed layers or laminated layers used to impart the desired appearance to the substrate, antistatic layers, primer layers, release layers, and other surface treatment layers.

The thickness of the substrate is not particularly limited and can be selected according to the intended use or application of the reinforcing film. For example, the substrate thickness can be 1000 μm or less. In some applications, from the viewpoint of operability or processability of the reinforcing film, the substrate thickness can be, for example, 500 μm or less, 300 μm or less, 250 μm or less, or 200 μm or less. From the viewpoint of miniaturization or weight reduction of products using the reinforcing film, in some applications, the substrate thickness can be, for example, 160 μm or less, 130 μm or less, 100 μm or less, 90 μm or less, 80 μm or less, 60 μm or less, 50 μm or less, 25 μm or less, 10 μm or less, or 5 μm or less. If the thickness of the substrate decreases, the flexibility of the reinforcing film or its ability to follow the surface shape of the adherend tends to increase. Furthermore, from the viewpoint of operability or processability, the thickness of the substrate can be, for example, 2 μm or more, 5 μm or more, 10 μm or more, 20 μm or more, 25 μm or more, or even more than 25 μm. In several cases, the thickness of the substrate can be, for example, 30 μm or more, 35 μm or more, 55 μm or more, 70 μm or more, 75 μm or more, 90 μm or more, or even 120 μm or more. For example, a substrate with a thickness of 30 μm or more can be well used in reinforcing films.

As needed, previously known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and primer coating can also be applied to the first surface of the substrate. Such surface treatments can be used to improve the adhesion of the adhesive layer to the substrate. For example, in reinforcing films having a substrate containing a resin film as a base film, a substrate with this adhesion-enhancing treatment can be used effectively. The above surface treatments can be applied individually or in combination. The composition of the primer used to form the primer layer is not particularly limited and can be appropriately selected from those known to the public. There are no particular limitations on the thickness of the base coat, but it is usually suitable to be around 0.01 μm to 1 μm, and preferably around 0.1 μm to 1 μm. Other treatments that can be applied to the first surface of the substrate as needed include antistatic layer formation treatment, color layer formation treatment, and printing treatment.

When the reinforcing film disclosed herein is a single-sided adhesive sheet with an adhesive layer on the first side of the substrate, the second side of the substrate may also be subjected to previously known surface treatments such as peeling or antistatic treatment as needed. For example, by surface treating the back side of the substrate with a peeling agent (typically by providing a peeling layer formed by the peeling agent), the unwinding force of the reinforcing film wound into a roll shape can be reduced. As a peeling agent, polysiloxane-based peeling agents, long-chain alkyl-based peeling agents, olefin-based peeling agents, fluorinated peeling agents, fatty acid amide-based peeling agents, molybdenum sulfide, and silica powder can be used. Furthermore, to improve printability, reduce light reflectivity, and improve overlap adhesion, the second side of the substrate can be treated with corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, or alkali treatment. In the case of double-sided adhesive sheets, the second side of the substrate can also be treated with the same surface treatments as those exemplified above, which can be applied to the first side of the substrate, as needed. Furthermore, the surface treatment applied to the first surface of the substrate can be the same as or different from the surface treatment applied to the second surface.

<Characteristics of Reinforcing Films> The reinforcing films disclosed herein preferably have an initial adhesion strength N ₂₃ , measured after being bonded to a stainless steel sheet and held at 23°C for 30 minutes, limited to a specified value or lower. In several samples, the adhesion strength N ₂₃ is preferably less than 500 gf/25 mm, more preferably less than 400 gf/25 mm, further preferably less than 300 gf/25 mm, particularly preferably less than 250 gf/25 mm (e.g., less than 200 gf/25 mm), and may also be less than 150 gf/25 mm. Lower adhesion strength N ₂₃ is preferable from the viewpoint of secondary processing. There is no particular limitation on the lower limit of adhesion strength N ₂₃ , for example, it may be more than 1 gf/25 mm. From the perspective of ease of application to the substrate and prevention of positional shift before the adhesive force increases, an adhesive force N ₂₃ is generally suitable to be 10 gf/25 mm or more. From the perspective of improving the adhesive force after heating, in several cases, the adhesive force 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 (e.g., 150 gf/25 mm or more).

The adhesive force N ₂₃ [gf/25 mm] is obtained by pressing the material onto a stainless steel (SUS) sheet (the substrate) at 23°C and 50%RH for 30 minutes. Then, under the same conditions (23°C), the 180° peel adhesive force is measured at a peel angle of 180° and a tensile speed of 300 mm/min. The substrate can be a SUS304BA sheet. During measurement, a suitable backing material (e.g., a PET film approximately 25 μm thick) can be applied to the reinforcing film of the test object for reinforcement, if necessary. More specifically, the adhesive force N ₂₃ can be measured according to the initial adhesive force measurement method described in the following embodiments.

The reinforcing film disclosed herein increases its adhesive strength through heating. For example, it can achieve an adhesive strength _N60 , meaning that after being bonded to a stainless steel sheet and held at 60°C for 60 minutes, the adhesive strength measured at 23°C shows 300 gf/25 mm or higher. In some samples, the adhesive strength _N60 is 400 gf/25 mm or higher, and preferably 500 gf/25 mm or higher. The reinforcing film meeting this characteristic increases its adhesive strength to a specified value after being applied to the substrate through heating. According to the technology disclosed herein, strong adhesive strength can be obtained through heating. In several preferred embodiments, the adhesive strength N ₆₀ is 600 gf/25 mm or more, more preferably 700 gf/25 mm or more, and may be 800 gf/25 mm or more, or may be 900 gf/25 mm or more. There is no particular upper limit to the adhesive strength N _60. From the viewpoint of ease of manufacture or economy of reinforcing films, in several embodiments, the adhesive strength N ₆₀ may be, for example, 3000 gf/25 mm or less, 1500 gf/25 mm or less, or 1000 gf/25 mm or less.

The adhesion strength N ₆₀ [gf/25 mm] was obtained by pressing the material onto an SUS board (the substrate) and holding it at 60°C for 60 minutes, followed by placing it at 23°C and 50%RH for 30 minutes. Then, under the same conditions, the 180° peel adhesion strength was measured at a peel angle of 180° and a tensile speed of 300 mm/min. Similar to adhesion strength N ₂₃ , an SUS304BA board can be used as the substrate. During testing, a suitable backing material (e.g., a PET film approximately 25 μm thick) can be attached to the reinforcing film of the test object for reinforcement, if necessary. The adhesion force N ₆₀ can be specifically determined according to the method for determining the adhesion force after heating as described in the following embodiments.

The ratio of adhesive force _N60 [gf/25 mm] to adhesive force _N23 [gf/25 mm], i.e., the adhesive force increase ratio _N60 / _N23 , is not particularly limited. In several samples, _N60 / _N23 is preferably 1.5 or higher, more preferably 2.0 or higher, even more preferably 2.5 or higher, and even more preferably 3.0 or higher (e.g., 3.5 or higher), and can also exceed 5.0 (e.g., exceeding 7.0). With a reinforcing film having a higher _N60 / _N23 , good secondary processing properties can be exhibited in the initial stage of application, and the adhesive force can be significantly increased by subsequent heating, etc. There is no particular upper limit to N ₆₀ / N ₂₃ , which is usually below 100. From the perspective of ease of manufacturing or economy of reinforcing membranes, it can be below 30, below 15, or below 10. In some cases, N ₆₀ / N ₂₃ can be below 5, below 3, or below 2.

Furthermore, the adhesive strength of the reinforcing film disclosed herein after heating represents one characteristic of the reinforcing film and is not a limitation on its application. In other words, the application of the reinforcing film disclosed herein is not limited to a state of heating at 60°C for 60 minutes. For example, it can also be used in a state where it is not specifically heated to room temperature (typically 20°C to 30°C, and typically 23°C to 25°C). In this application state, the adhesive strength increases over a longer period, achieving a strong bond. Moreover, the adhesive strength of the reinforcing film disclosed herein can be increased by heating it at temperatures exceeding 30°C (e.g., around 50 to 70°C) or higher than 60°C at any time after application. The heating temperature in this heat treatment is not particularly limited and can be set considering factors such as workability, economy, and the heat resistance of the substrate of the reinforcing film or the adherend. For example, the heating temperature may be below 150°C, below 120°C, below 100°C, below 80°C, or below 70°C. Furthermore, the heating temperature may be set to above 40°C, 45°C, 50°C, 55°C, 60°C, or 70°C, above 80°C, or above 100°C. The heating time is not particularly limited; for example, it may be less than 3 hours, less than 1 hour, less than 30 minutes, or less than 10 minutes. Furthermore, the heating time may be more than 1 minute, more than 15 minutes, more than 30 minutes, or more than 1 hour. Alternatively, a longer heating treatment can be performed within the limit that no significant thermal degradation occurs in the reinforcing membrane or the adherend. Furthermore, the heating treatment can be performed in one go or in multiple stages.

<Reinforcing Film for Substrate> When the reinforcing film disclosed herein is in the form of an adhesive sheet for a substrate, 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, and thinning of products using the reinforcing film, in several 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 an operability perspective, the thickness of the reinforcing film can 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 can be, for example, 50 μm or more, 60 μm or more, 80 μm or more, 100 μm or more, or 120 μm or more. There is no particular upper limit to the thickness of the reinforcing film. Furthermore, the thickness of the reinforcing film refers to the thickness of the portion adhered to the substrate. For example, in the reinforcing film 1 configured as shown in Figure 1, it refers to the thickness from the adhesive surface 21A of the reinforcing film 1 to the second surface 10B of the substrate 10, excluding the thickness of the peel-off pad 31.

The reinforcing film disclosed herein is suitable for implementation in a configuration where the thickness Ts of the supporting substrate is greater than the thickness Ta of the adhesive layer, i.e., a Ts/Ta ratio greater than 1. Ts/Ta can be, for example, 1.1 or more, 1.2 or more, 1.5 or more, or 1.7 or more, but there is no particular limitation. For example, by increasing Ts/Ta, there is a tendency to achieve good results even when the reinforcing film is made thinner. In some configurations, Ts/Ta can be 2 or more (e.g., greater than 2), 2.5 or more, or 2.8 or more. Furthermore, Ts/Ta can be, for example, 50 or less, or 20 or less. From the viewpoint that higher post-heating adhesion is easily achieved even when the reinforcing film is made thinner, Ts/Ta can be, for example, 10 or less, 8 or less, or 5 or less.

Preferably, the adhesive layer is adhered to the supporting substrate. Here, "adhesion" refers to the adhesive layer exhibiting sufficient grip on the supporting substrate in a reinforcing film where the adhesive force increases after attachment to the adherend, ensuring that the interface between the adhesive layer and the supporting substrate does not separate when the reinforcing film is peeled off from the adherend. By using a reinforcing film with an adhesive layer adhered to the supporting substrate, the adherend and the supporting substrate can be firmly integrated. A preferred example of a reinforcing film with an adhesive layer adhered to the substrate is a reinforcing film in which the adhesive layer does not peel off (break down) from the supporting substrate when the adhesive force after heating is measured. A reinforcing film that does not break down when the adhesion is tested after heating is a better example of a reinforcing film in which the adhesive layer is fixed to the substrate.

The reinforcing film disclosed herein can be well manufactured, for example, by a method comprising the following steps in sequence: contacting a liquid adhesive composition with a first surface of a substrate; and hardening the adhesive composition on the first surface to form an adhesive layer. The hardening of the adhesive composition may be accompanied by one or more of the following: drying, crosslinking, polymerization, cooling, etc. Compared to a method of depositing an adhesive layer on the first surface of a substrate by bonding a hardened adhesive layer to the first surface of the substrate, the method of hardening the liquid adhesive composition on the first surface of the substrate to form an adhesive layer improves the adhesion of the adhesive layer to the substrate. This situation allows for the suitable manufacture of reinforcing films in which the adhesive layer is fixed to the substrate.

In several embodiments, as a method for contacting the liquid adhesive composition with the first surface of the substrate, a method of directly applying the adhesive composition to the first surface of the substrate can be adopted. By having the first surface (adhesive surface) of the adhesive layer hardened on the first surface of the substrate abut against the peeling surface, a reinforcing film can be obtained in which the second surface of the adhesive layer is fixed to the first surface of the substrate and the first surface of the adhesive layer abuts against the peeling surface. The peeling surface can be the surface of a peeling pad or the back surface of the substrate after peeling treatment.

Furthermore, in the case of photocurable adhesive compositions using a portion of a polymer (polymer slurry) of monomeric raw materials, for example, after the adhesive composition is applied to a peeling surface, the first surface of the substrate covered by the applied adhesive composition is brought into contact with the uncured adhesive composition. In this state, the adhesive composition sandwiched between the first surface of the substrate and the peeling surface is irradiated with light to cure it, thereby forming an adhesive layer.

Furthermore, the methods described above are not limited to the manufacturing method of the reinforcing film disclosed herein. In manufacturing the reinforcing film disclosed herein, one or more suitable methods for adhering the adhesive layer to the first surface of the substrate can be used alone. Examples of such methods include: a method described above for hardening a liquid adhesive composition on the first surface of the substrate to form an adhesive layer, or a method for performing a surface treatment on the first surface of the substrate to improve the adhesion of the adhesive layer. For example, when the adhesion of the adhesive layer to the substrate can be sufficiently improved by providing a primer layer on the first surface of the substrate, the reinforcing film can also be manufactured by bonding the hardened adhesive layer to the first surface of the substrate. Furthermore, the adhesion of the adhesive layer to the substrate can be improved by selecting the material of the substrate or the composition of the adhesive. Also, the adhesion of the adhesive layer to the substrate can be improved by applying a temperature higher than room temperature to the reinforcing film having an adhesive layer on the first surface of the substrate. Temperatures used to improve adhesion can be, for example, around 35°C to 80°C, above 40°C to 70°C, or around 45°C to 60°C.

When the reinforcing film disclosed herein is an adhesive sheet having a first adhesive layer disposed on a first side of a substrate and a second adhesive layer disposed on a second side of the substrate (i.e., an adhesive sheet with double-sided adhesion to the substrate), the first adhesive layer and the second adhesive layer may have the same or different compositions. When the first adhesive layer and the second adhesive layer have different compositions, the difference may be, for example, a difference in composition or a difference in structure (thickness, surface roughness, formation area, formation pattern, etc.). For example, the second adhesive layer may be an adhesive layer that does not contain polymer (B). Furthermore, the surface elastic modulus of the second adhesive layer (second adhesive surface) at 23°C can be in the range of 1 to 20 kPa (e.g., more than 20 kPa) or more than 30 kPa.

<Reinforcing Film for Attached Peel-Off Liner> The reinforcing film disclosed herein can be in the form of an adhesive article in which the surface (adhesive surface) of the adhesive layer abuts against the peel-off surface of the peel-off liner. Therefore, this specification provides a reinforcing film comprising any of the reinforcing films disclosed herein, and a peel-off liner having a peel-off surface abutting against the adhesive surface of the reinforcing film.

There is no particular limitation on the thickness of the peelable pad, but it is generally suitable to be around 5 μm to 200 μm. If the thickness of the peelable pad is within the above range, the adhesion and peelability of the adhesive layer are excellent, and therefore preferred. In some cases, the thickness of the peelable pad 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 the peeling of the self-adhesive layer, the thickness of the peelable pad may be, for example, 100 μm or less, or 80 μm or less. As needed, the peeling liner can also be treated with known antistatic treatments such as coating, mixing, or evaporation.

There are no particular limitations on the type of release liner. For example, it can be used as a release liner on the surface of a resin film or paper (which may be paper laminated with resins such as polyethylene), or as a release liner containing a resin film formed using a low-adhesion material such as a fluoropolymer (polytetrafluoroethylene) or polyolefin resin (polyethylene, polypropylene, etc.). In terms of excellent surface smoothness, it is well-suited for use as a release liner on the surface of a resin film serving as a liner substrate, or as a release liner containing a resin film formed using a low-adhesion material. As for the resin film, there are no particular limitations as long as it is a film that can protect the adhesive layer. Examples include: polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyester film (PET film, PBT film, etc.), polyurethane film, ethylene-vinyl acetate copolymer film, etc. The above-mentioned release layer can be formed using, for example, polysiloxane-based release agents, long-chain alkyl-based release agents, olefin-based release agents, fluorinated release agents, fatty acid amide-based release agents, molybdenum sulfide, silica powder, and other known release agents. It is especially advantageous to use polysiloxane-based peeling agents.

There are no particular limitations on the thickness of the exfoliation layer, which is usually suitable at around 0.01 μm to 1 μm, and preferably around 0.1 μm to 1 μm. There are no particular limitations on the method of forming the exfoliation layer, and known methods corresponding to the type of exfoliating agent used can be appropriately adopted.

<Applications> The reinforcing film provided in this specification exhibits excellent secondary processing properties during the initial application to the substrate, thus helping to prevent yield reduction and improve the quality of products containing the reinforcing film. Furthermore, the adhesive strength of the reinforcing film can be significantly increased by curing or heating after application to the substrate. For example, by heating at an appropriate time after application, the reinforcing film can be firmly bonded to the substrate. Utilizing these features, the reinforcing film disclosed herein can be effectively used in various fields to reinforce components in various products.

The reinforcing film disclosed herein can be, for example, an adhesive sheet having an adhesive layer disposed on at least the first side of a film-like substrate having a first side and a second side. It is well-suited as a reinforcing film for attaching to and reinforcing an adherend. In this reinforcing film, a resin film as the base film is well-suited as the film substrate. Furthermore, from the viewpoint of improving reinforcing performance, the adhesive layer is preferably adhered to the first side of the film-like substrate. For example, regarding optical components used in optical products, or electronic components used in electronic products, there is a continuous trend towards high integration, miniaturization, lightweighting, and thinning. Multiple thinner optical/electronic components with different coefficients of linear expansion or thicknesses can be laminated. By attaching the reinforcing film as described above to such components, appropriate rigidity can be imparted to the aforementioned optical/electronic components. This suppresses curling or bending caused by stresses that may arise between multiple components with different coefficients of linear expansion or thicknesses during the manufacturing process and/or in the finished product. Furthermore, during the manufacturing process of optical/electronic products, when performing shape processing such as cutting on thinner optical/electronic components as described above, attaching the reinforcing film to the component can mitigate the localized stress concentration in the optical/electronic component during processing, reducing the risk of cracking, breakage, and peeling of laminated components. Applying reinforcing components to optical/electronic components during operation can help alleviate localized stress concentrations during handling, lamination, and rotation, or suppress bending or flexing caused by the component's own weight. Furthermore, when optical or electronic products containing the aforementioned reinforcing film are marketed to consumers, even in cases of accidental stress such as drops, placement under heavy objects, or impacts from flying objects, the reinforcing film can mitigate the stress applied to the device. Therefore, by incorporating a reinforcing film into such devices, the durability of the devices can be improved.

Furthermore, the reinforcing film disclosed herein can be applied to components constituting various portable machines in a manner that works well. The term "portable" here does not simply mean the ability to carry, but rather the degree of portability that allows a person (standard adult) to move it relatively easily. Furthermore, examples of portable devices here may include: mobile phones, smartphones, tablet computers, laptop computers, various portable devices, digital cameras, digital video cameras, audio devices (portable music players, voice recorders, etc.), computers (calculators, etc.), portable game consoles, electronic dictionaries, electronic notebooks, electronic books, in-vehicle information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems, and other portable electronic devices. In addition, it may also include mechanical watches or pocket watches, flashlights, magnifying glasses, etc. Examples of components constituting the aforementioned portable electronic devices may include optical films or display panels used in image display devices such as liquid crystal displays or thin-film displays. The reinforcing films disclosed herein can also be applied to various components in automobiles, home appliances, etc., and are used effectively.

Furthermore, the reinforcing film disclosed herein, due to its flexibility and bending retention, can be effectively used to adhere to components of machines that constitute flexible elements (such as flexible devices like flexible displays; also referred to as rollable or foldable devices). Examples of such machines include the various portable machines described above. Examples of components constituting the aforementioned portable electronic machines include: optical films or display panels used in image display devices such as liquid crystal displays or organic EL (electroluminescent) displays. The reinforcing film disclosed herein can be well used in portable electronic devices for reinforcing components that make up the device (typically image display devices called flexible or foldable devices).

Furthermore, the reinforcing film disclosed herein is suitable for reinforcing optical components used as components of liquid crystal display panels, plasma display panels (PDP), organic EL displays, etc., during manufacturing and transportation. It is particularly useful as a reinforcing film for optical components such as polarizing plates (polarizing films), wavelength plates, retardation plates, optical compensation films, brightness enhancement films, light diffusing sheets, and reflective sheets used in liquid crystal display panels.

Furthermore, the applications of the reinforcing membrane disclosed herein are not particularly limited, and it can be used for various purposes, such as imparting rigidity or impact resistance. The reinforcing membrane disclosed herein is not only well-suited for flexible devices as described above, but also for other applications not involving flexible devices. The flexural resilience and flexural holding force of the reinforcing membrane indicate fewer limitations on its applicability and greater advantages in practical applications. [Example]

The following describes several embodiments of the present invention, but it is not intended to limit the present invention to the specific examples shown. Furthermore, unless otherwise specified, "parts" and "%" in the following description are by weight.

[Synthesis of Polymer (A)] (Synthesis Example A1) In a four-necked flask equipped with a stirrer, thermometer, nitrogen inlet tube, and condenser, 90.2 parts of 2-ethylhexyl acrylate (2EHA), 8.6 parts of 4-hydroxybutyl acrylate (4HBA), 1.2 parts of N-acryloyl terephthaloline (ACMO), 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and ethyl acetate as a polymerization solvent were added. Nitrogen gas was introduced while stirring slowly, and the liquid temperature in the flask was maintained at approximately 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 acrylic polymer A1 is 540,000.

(Synthesis Example A2) Except for changing the monomer composition to 2EHA/4HBA/ACMO/butyl acrylate (BA) = 86.1 parts/9.7 parts/1.8 parts/2.4 parts, solution polymerization was carried out in the same manner as in Synthesis Example A1 to obtain a solution of acrylic polymer A2.

(Synthesis Example A3) Except for changing the monomer composition to BA/4HBA = 96 parts/4 parts, solution polymerization was carried out in the same manner as in Synthesis Example A1 to obtain a solution of acrylic polymer A3.

(Synthesis Example A4) Except for changing the monomer composition to 65 parts/15 parts/7 parts/13 parts of 2EHA/2-hydroxyethyl acrylate (HEA)/methyl methacrylate (MMA)/N-vinyl-2-pyrrolidone (NVP)/, solution polymerization was carried out in the same manner as in Synthesis Example A1 to obtain a solution of acrylic polymer A4.

[Synthesis of Polymer (B)] 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 methacrylate monomer with a functional group equivalent of 900 g/mol containing a polyorganosiloxane backbone (trade name: X-22-174ASX, manufactured by Shin-Etsu Chemical Industry Co., Ltd.), 11.3 parts of a methacrylate monomer with a functional group equivalent of 4600 g/mol containing a polyorganosiloxane backbone (trade name: KF-2012, manufactured by Shin-Etsu Chemical Industry Co., Ltd.), and 0.8 parts of thioglycerol as a chain transfer agent were added to a four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet tube, condenser and dropping funnel. Then, after stirring at 70°C under a nitrogen atmosphere for 30 minutes, 0.2 parts of AIBN as a thermal polymerization initiator were added, and the reaction was carried out at 70°C for 3 hours. Next, after stirring at 80°C for 30 minutes, 0.1 parts of AIBN were added, and the reaction was carried out at 80°C for 2 hours. Subsequently, 0.05 parts of AIBN were added, and the reaction was carried out at 80°C for 2 hours to obtain polymer B. The Mw of the obtained polymer B is 20000.

Furthermore, the molecular weight (Mw) of each polymer was determined using a GPC apparatus (Tosoh, HLC-8220GPC) under the following conditions, and calculated using polystyrene conversion. [GPC Conditions] ・Sample concentration: 0.2 wt% (tetrahydrofuran (THF) solution) ・Sample injection volume: 10 μl ・Cutting solution: THF, flow rate: 0.6 ml/min ・Measurement temperature: 40℃ ・Columns: Sample column: TSKguardcolumn SuperHZ-H (1 column) + TSKgel SuperHZM-H (2 columns) Reference column: TSKgel SuperH-RC (1 column) ・Detector: Differential refractometer (RI)

[Preparation of Reinforcing Film] <Example 1> 100 parts of acrylic polymer A1, 2.0 parts of polymer B, and 0.015 parts of isocyanate compound C1 (trade name "Coronate HX", manufactured by Tosoh Corporation) as a crosslinking agent (based on solids content) were added. The mixture was diluted with ethyl acetate to a total solids content of 30% to obtain the acrylic adhesive solution of this example. A 75 μm thick release liner containing polyester resin (trade name "DIAFOIL MRF75", manufactured by Mitsubishi Chemical Co., Ltd.) with one side treated with polysiloxane was prepared. An acrylic adhesive solution obtained above was applied to the polysiloxane-treated surface and dried at 130°C for 1 minute to form an adhesive layer with a thickness of 25 μm. Subsequently, a 50 μm thick polyimide substrate (trade name "Upilex 50S", manufactured by Ube Industries, Ltd.) was laminated onto the surface of the adhesive layer to obtain the reinforcing film of this example. The reinforcing film has the form of an adhesive sheet with a release liner, that is, an adhesive layer is present on one side of the substrate, and the release liner is attached to the adhesive side. Furthermore, for the reinforcing film in this example, the molar ratio ([NCO]/[OH]) was calculated based on the amount of OH (the molar number of hydroxyl groups in the acrylic polymer A1) and the amount of NCO (the molar number of isocyanate groups in the isocyanate compound) in the adhesive layer, and the result is 0.001.

<Examples 2-5> The amount of isocyanate compound C1 used was changed to 0.05 parts (Example 2), 0.10 parts (Example 3), 0.20 parts (Example 4), and 0.60 parts (Example 5) relative to 100 parts of acrylic polymer A1, as calculated by solid content. Otherwise, the acrylic adhesive solutions of each example were obtained in the same manner as in Example 1. Except for the use of these acrylic adhesive solutions, the reinforcing films of each example were manufactured in the same manner as the reinforcing film of Example 1.

<Examples 6-9> The amount of polymer B used was varied as shown in Table 1 to be 0.4 parts (Example 6), 1.0 parts (Example 7), 3.0 parts (Example 8), and 6.0 parts (Example 9) relative to 100 parts of acrylic polymer A1. Otherwise, the acrylic adhesive solutions of each example were obtained in the same manner as in Example 3. Except for the use of these acrylic adhesive solutions, the reinforcing films of each example were manufactured in the same manner as the reinforcing film of Example 1.

<Example 10> The acrylic adhesive solution of this example is obtained in the same manner as in Example 3, except that acrylic polymer A2 is used instead of acrylic polymer A1. The reinforcing film of this example is manufactured in the same manner as the reinforcing film of Example 1, except that the obtained acrylic adhesive solution is used.

<Example 11> Acrylic polymer A3 is used instead of acrylic polymer A1, and isocyanate compound C2 (trade name "Takenate D110N", manufactured by Mitsui Chemicals Co., Ltd.) is used as the crosslinking agent. The isocyanate compound C2 accounts for 0.07 parts of 100 parts of acrylic polymer A3 based on solid content. Otherwise, the acrylic adhesive solution of this example is obtained in the same manner as in Example 1. Except for using the obtained acrylic adhesive solution, the reinforcing film of this example is manufactured in the same manner as the reinforcing film of Example 1.

<Examples 12-13> The amount of isocyanate compound C2 used was changed as shown in Table 1 to 0.09 parts (Example 12) and 0.395 parts (Example 13) of solids relative to 100 parts of acrylic polymer A3. Otherwise, the acrylic adhesive solutions of each example were obtained in the same manner as in Example 11. Except for the use of these acrylic adhesive solutions, the reinforcing films of each example were manufactured in the same manner as the reinforcing film of Example 1.

<Examples 14-18> In the preparation of the acrylic adhesive solution of Example 3, in addition to acrylic polymer A1, polymer B, and isocyanate compound C1, as shown in Table 1, an iron catalyst (ferric triacetone, manufactured by Nippon Kagaku Kogyo Co., Ltd.) was added in amounts equivalent to 100 parts of acrylic polymer A1, calculated as 0.001 parts (Example 14), 0.005 parts (Example 15), 0.010 parts (Example 16), 0.020 parts (Example 17), and 0.050 parts (Example 18) of solid content. The solution was diluted with ethyl acetate (98% of the solvent content) and acetone (2% of the solvent content) until the total solid content reached 30%, thus obtaining the acrylic adhesive solutions of each example. Except for using the acrylic adhesive solutions respectively, the reinforcing films of each example were prepared in the same manner as those of Example 1. Furthermore, Table 1 also shows the molar ratio ([catalyst]/[OH]) of the catalyst to hydroxyl groups contained in the adhesive layer. The above molar ratio ([catalyst]/[OH]) is a value calculated based on the amount of OH (the molar number of hydroxyl groups in the acrylic polymer A1) and the amount of catalyst (the molar number of the catalyst) in the adhesive layer.

<Examples 19-20> The amount of polymer B used was changed as shown in Table 1 to 1.0 part (Example 19) and 3.0 parts (Example 20) relative to 100 parts of acrylic polymer A1. Otherwise, the acrylic adhesive solutions of each example were obtained in the same manner as in Example 14. Except for the use of these acrylic adhesive solutions, the reinforcing films of each example were manufactured in the same manner as the reinforcing film of Example 1.

<Comparative Example 1> 100 parts of acrylic polymer A1 and 0.05 parts of isocyanate compound C1 (trade name "Coronate HX", manufactured by Tosoh Co., Ltd.) as a crosslinking agent were added, and diluted with ethyl acetate to a total solids content of 30% to obtain the acrylic adhesive solution of this example. Except for using the obtained acrylic adhesive solution, the reinforcing film of this example was prepared in the same manner as the reinforcing film of Example 1.

<Comparative Examples 2-3> The amount of isocyanate compound C1 used was changed as shown in Table 1 to 0.10 parts (Comparative Example 2) and 0.20 parts (Comparative Example 3) relative to 100 parts of acrylic polymer A1, calculated based on solid content. Otherwise, the acrylic adhesive solutions of each example were obtained in the same manner as in Comparative Example 1. Except for using these acrylic adhesive solutions, the reinforcing films of each example were manufactured in the same manner as the reinforcing film of Example 1.

<Comparative Example 4> Acrylic polymer A4 was used instead of acrylic polymer A1, and isocyanate compound C2 (trade name "Takenate D110N", manufactured by Mitsui Chemicals Co., Ltd.) was used as the crosslinking agent. The isocyanate compound C2 was present in 0.50 parts per 100 parts of acrylic polymer A4, calculated based on solid content. Otherwise, the acrylic adhesive solution of this example was obtained in the same manner as in Comparative Example 1. Except for using the obtained acrylic adhesive solution, the reinforcing film of this example was manufactured in the same manner as the reinforcing film of Example 1.

<Comparative Examples 5-6> The amount of isocyanate compound C2 used was changed as shown in Table 1 to 1.10 parts (Comparative Example 5) and 2.50 parts (Comparative Example 6) relative to 100 parts of acrylic polymer A4, calculated based on solid content. Otherwise, the acrylic adhesive solutions for each example were obtained in the same manner as in Comparative Example 4. Except for using these acrylic adhesive solutions, the reinforcing films for each example were prepared in the same manner as the reinforcing film of Example 1.

<Comparative Example 7> In the preparation of the acrylic adhesive solution, apart from acrylic polymer A4 and isocyanate compound C2, as shown in Table 1, polymer B was added in an amount of 2.0 parts per 100 parts of acrylic polymer A4. Otherwise, the acrylic adhesive solution of this example was obtained in the same manner as in Comparative Example 4. Except for using the obtained acrylic adhesive solution, the reinforcing film of this example was prepared in the same manner as the reinforcing film of Example 1.

<Comparative Examples 8-9> The amount of isocyanate compound C2 used was changed as shown in Table 1 to 1.10 parts (Comparative Example 8) and 2.50 parts (Comparative Example 9) relative to 100 parts of acrylic polymer A4, calculated based on solid content. Otherwise, the acrylic adhesive solutions for each example were obtained in the same manner as in Comparative Example 7. Except for using these acrylic adhesive solutions, the reinforcing films for each example were prepared in the same manner as the reinforcing film of Example 1.

<Evaluation> [Surface Elastic Modulus] For each example of reinforcing film, the surface elastic modulus was measured after curing at 50°C for 1 day. The protective adhesive pad was removed, and an indenter was pressed into the adhesive layer surface to a depth of 6 μm using a nano-indenter (Triboindenter manufactured by Hysitron Inc.). The maximum load (Pmax) [GPa/ ^mm² ] was obtained by measuring using the nano-indenter. Substituting this into the following formula, surface hardness [GPa] = Pmax/A, the surface hardness was calculated, converted to [kPa] units, and recorded as the surface elastic modulus at 23°C (surface elastic modulus at 23°C). The measurement conditions are described below. Furthermore, in the above formula, A is the contact projection area of the indenter [ ^mm² ]. (Measurement conditions) Indenter approach speed: 5 μm/s Maximum displacement: 6 μm Indentation speed: 5 μm/s Withdrawal speed: 5 μm/s Indenter used: Conical (spherical indenter: radius of curvature 10 μm) Measurement method: Single indentation measurement Measurement temperature: Room temperature (23℃)

[Volume elastic modulus G' and tanδ] A 75 μm thick release liner containing polyester resin (trade name "DIAFOIL MRF75", manufactured by Mitsubishi Chemical Co., Ltd.) with polysiloxane treatment on one side was prepared. An acrylic adhesive solution of various types was applied to the polysiloxane-treated side and dried at 130°C for 1 minute to form an adhesive layer with a thickness of 25 μm. Next, a 75 μm thick release liner containing polyester resin, labeled "DIAFOIL MRE75" (manufactured by Mitsubishi Chemical Corporation), with its polysiloxane-treated side facing the adhesive layer, was applied to the surface of the obtained adhesive layer and cured at 50°C for one day. Only the obtained adhesive layer was removed, laminated to a thickness of approximately 1 mm, and then die-cut. 8 mm diameter cylindrical particles were prepared as samples for testing. The above-mentioned test samples were fixed onto... A fixture with an 8 mm parallel plate was used to measure the storage elastic modulus G', loss elastic modulus G'', and loss tangent tanδ under the following conditions using a dynamic viscoelasticity measuring device (ARES manufactured by TA Instruments). The storage elastic modulus _G'23 [kPa] at 23℃, the storage elastic modulus _G'80 [kPa] at 80℃, and tanδ at 80℃ (loss elastic modulus G''80 at ₈₀ ℃ / storage elastic modulus G'80 at ₈₀ ℃) were calculated. • Measurement mode: Shear mode • Temperature range: -70℃～200℃ • Heating rate: 5℃/min • Frequency: 1 Hz Furthermore, the stored elastic modulus G' is equivalent to the portion of elastic energy stored during material deformation, and is an indicator of the degree of hardness. The dissipated elastic modulus G'' is equivalent to the portion of energy lost due to internal friction, etc., during material deformation, and indicates the degree of viscosity.

[Initial Adhesion] The reinforcing films for each example were cured at 50°C for one day and then cut together with the release liner into 25 mm wide x 140 mm long samples as test specimens. The release liner was then peeled off from the test specimens, exposing the adhesive surface. A 2 kg hand roller was used to press the film back and forth once to adhere it to the stainless steel plate (SUS304BA plate) used as the bonded object. After placing the test sample, thus pressed to the substrate, at an ambient temperature of 23°C for 30 minutes, a tensile testing machine (manufactured by Shimadzu Corporation, product name "Autograph AG-Xplus HS 6000 mm/min high-speed mode (AG-50NX plus)") was used to measure the load when the reinforcing film was peeled off from the substrate under the conditions of a peeling angle of 180 degrees and a peeling speed (tensile speed) of 300 mm/min. The average load at the time of measurement was recorded as the initial adhesive force [gf/25 mm].

[Post-Heat Adhesion] For each example of the reinforcing film, test samples were prepared in the same manner as the initial adhesion test described above, and pressed onto the substrate. Then, the test samples pressed onto the substrate were heated at 60°C for 60 minutes. Afterwards, they were placed at 23°C for 30 minutes, and using a tensile testing machine (Shimadzu Corporation, trade name "Autograph AG-Xplus HS 6000mm/min high-speed mode (AG-50NX plus)"), under conditions of a peeling angle of 180 degrees and a peeling speed (tensile speed) of 300 mm/min, the load when peeling the reinforcing film from the substrate was measured. The average load measured was recorded as the post-heat adhesion [gf/25 mm].

[Bending Retention Test] For each reinforcing film, after curing at 50°C for 1 day, the peel-off backing was removed, and a 25 μm thick polyimide substrate (trade name "Upilex 25S", manufactured by Ube Industries, Ltd.) was laminated onto the exposed adhesive surface. The substrate was then heated at 60°C for 60 minutes to ensure a tight bond. Subsequently, the obtained test sample (laminate) was bent with the 25 μm substrate side as the inside. The sample was fixed at 6 mm in this state and heated at 80°C for 15 hours. Then, it was placed at room temperature (23°C) and, after confirming sufficient cooling, the fixed bending state of the test sample was released. Within 10 minutes of releasing the fixation, the bending angle [°] of the bent test sample was measured using a scale to evaluate the bending recovery. Furthermore, the bending angle is the opening angle of the test sample (the angle of the test sample from the side opened from the bent state). The closer to 180°, the better the bending recovery; the closer the bending angle is to 0°, the worse the bending recovery. Next, as an evaluation of bending retention, the bending portion of the test sample was visually confirmed to see if there was any "peeling". If no "peeling" was confirmed, it was rated as "G (Good)" and if "peeling" was confirmed, it was rated as "P (Poor)".

[Bubble Generation Confirmation] For each reinforcing membrane, after curing at 50°C for one day, it was cut into 10 cm × 10 cm pieces. The peel-off liner was removed, and the amount of bubble generation per 10 cm square was visually confirmed. Evaluation was based on the following criteria: E (Excellent): No bubble generation confirmed. G (Good): Bubble generation confirmed, but the bubble generation area is less than 50% per 10 cm square. A (Acceptable): Bubble generation confirmed at an area of more than 50% per 10 cm square. This indicates no problems in actual application.

The evaluation results of the reinforcing films for each example are shown in Table 1. Table 1 also shows a general overview of the composition of the adhesive layer for each example.

[Table 1] Table 1 Polymer (A) [parts] Polymer (B) [parts] Cross-linking agent (per serving) Mörby [NCO]/[OH] Media [share] Catalyst Möllby [catalyst]/[OH] Surface elastic modulus 23℃ [kPa] Volumetric elastic modulus 23℃ [kPa] Volumetric elastic modulus 80℃ [kPa] tanδ 80℃ Initial adhesion [gf/25 mm] Adhesion strength after heating [gf/25 mm] Bending resilience [°] Bending retention force Bubble formation A1 A2 A3 A4 C1 C2 Implementation Example 1 100 - - - 2.0 0.015 - 0.001 - - 1.2 33 8 0.79 325 2144 35 G G Implementation Example 2 100 - - - 2.0 0.05 - 0.004 - - 2.7 33 11 0.60 368 877 50 G G Implementation Example 3 100 - - - 2.0 0.10 - 0.008 - - 5.1 33 11 0.51 256 821 90 G G Implementation Example 4 100 - - - 2.0 0.20 - 0.016 - - 6.9 33 14 0.41 209 607 90 G G Implementation Example 5 100 - - - 2.0 0.60 - 0.049 - - 10.8 41 twenty four 0.23 128 463 100 G A Implementation Example 6 100 - - - 0.4 0.10 - 0.008 - - 3.2 32 11 0.52 502 923 120 G G Implementation Example 7 100 - - - 1.0 0.10 - 0.008 - - 4.8 32 12 0.52 221 750 115 G G Implementation Example 8 100 - - - 3.0 0.10 - 0.008 - - 5.6 38 13 0.51 283 651 65 G G Implementation Example 9 100 - - - 6.0 0.10 - 0.008 - - 6.8 39 14 0.51 185 495 60 G G Implementation Example 10 - 100 - - 2.0 0.10 - 0.008 - - 5.3 34 12 0.51 262 832 90 G G Implementation Example 11 - - 100 - 2.0 - 0.07 0.028 - - 15.1 81 52 0.25 275 547 105 G G Implementation Example 12 - - 100 - 2.0 - 0.09 0.036 - - 15.5 96 63 0.24 245 404 105 G A Implementation Example 13 - - 100 - 2.0 - 0.395 0.160 - - 17.8 114 88 0.13 186 331 110 G A Implementation Example 14 100 - - - 2.0 0.10 - 0.008 0.001 4.6E-05 5.1 33 12 0.51 105 602 90 G E Implementation Example 15 100 - - - 2.0 0.10 - 0.008 0.005 2.3E-04 5.1 33 12 0.52 159 624 85 G E Implementation Example 16 100 - - - 2.0 0.10 - 0.008 0.010 4.6E-04 5.0 33 11 0.51 160 641 90 G E Implementation Example 17 100 - - - 2.0 0.10 - 0.008 0.020 9.2E-04 5.1 34 13 0.51 134 644 90 G E Implementation Example 18 100 - - - 2.0 0.10 - 0.008 0.050 2.3E-03 4.9 33 11 0.52 115 483 85 G E Implementation Example 19 100 - - - 1.0 0.10 - 0.008 0.010 4.6E-04 4.7 33 11 0.51 199 719 110 G E Implementation Example 20 100 - - - 3.0 0.10 - 0.008 0.010 4.6E-04 5.4 37 12 0.52 143 729 60 G E Comparative example 1 100 - - - - 0.05 - 0.004 - - 2.3 29 10 0.61 2585 - 35 G G Comparative example 2 100 - - - - 0.10 - 0.008 - - 2.6 31 11 0.54 1306 - 65 G G Comparative example 3 100 - - - - 0.20 - 0.016 - - 3.0 34 15 0.33 873 - 110 G G Comparative example 4 - - - 100 - - 0.50 0.013 - - 22.6 248 60 0.30 1210 - 90 P G Comparative example 5 - - - 100 - - 1.10 0.028 - - 24.1 246 75 0.22 940 - 105 P G Comparative example 6 - - - 100 - - 2.50 0.063 - - 34.2 313 111 0.11 923 - 120 P A Comparative example 7 - - - 100 2.0 - 0.50 0.013 - - 26.2 250 61 0.31 330 735 80 P G Comparative example 8 - - - 100 2.0 - 1.10 0.028 - - 28.1 251 73 0.24 92 1227 105 P G Comparative example 9 - - - 100 2.0 - 2.50 0.063 - - 36.0 316 115 0.13 57 796 110 P A

As shown in Table 1, the adhesives of Examples 1-20 contain polymers (A) and (B), and compared with Comparative Examples 1-6 which do not contain polymer (B), the initial adhesive force is suppressed to a lower degree. Furthermore, the adhesive force of the adhesives of Examples 1-20 increases significantly after heating. Moreover, the flexural recovery and flexural holding power of the adhesive layer of the reinforcing film of Examples 1-20 are also good within the range of 1-20 kPa at 23°C. On the other hand, in Comparative Examples 4-9, which are outside the range of 1-20 kPa at 23°C, peeling was confirmed in the flexural holding test.

More specifically, based on a comparison of Examples 1-5, the following trend was confirmed: the higher the surface elastic modulus of the adhesive layer at 23°C in the range of 1-20 kPa, the better the flexural resilience, and the lower the initial adhesion and the adhesion after heating. The flexural resilience of Examples 2-5 is better than that of Example 1, with a surface elastic modulus at 23°C of 2 or higher, and tanδ ₈₀ at 80°C in the range of 0.10-0.60. Furthermore, in Example 5, both the surface elastic modulus and the volume elastic modulus are relatively high, and the increase in adhesion after heating is relatively low compared to Examples 1-4. Also, compared to the other examples mentioned above, there is a tendency for more bubbles to be generated on the surface of the adhesive layer. In Examples 2-4, the initial adhesion, post-heating adhesion, flexural resilience, and flexural holding power were improved more evenly, and the molar ratio of isocyanate groups to hydroxyl groups in the adhesive layer ([NCO]/[OH]) was in the range of 0.002-0.03. Furthermore, in Examples 1-4, no difference was found in the volumetric elastic modulus _G'23 at 23°C for the adhesive layer. Also, regarding Examples 2-3, no difference was found in the volumetric elastic modulus G'80 _{at 80} °C. Regarding Examples 1-5, compared to the volumetric elastic modulus, the correlation between the surface elastic modulus at 23°C and flexural resilience was higher.

Furthermore, based on the comparison of Examples 6-9, it was confirmed that the more polymer (B) is used, the lower the adhesive strength tends to be. In Examples 7-8, where the amount of polymer (B) used is in the range of 0.5 to 5 parts per 100 parts of polymer (A), the initial adhesive strength does not reach 500 gf/25 mm, but the adhesive strength after heating is more than 500 gf/25 mm, thus better balancing the easy peeling at the initial stage of adhesion and the increase in adhesive strength after heating. Also, the more polymer (B) is used, the higher the surface elastic modulus at 23°C and the lower the flexural resilience tends to be. Furthermore, based on the results of Examples 10-13, it was confirmed that even if the type of polymer (A) or the type of crosslinking agent of the adhesive is changed, the desired effect can still be achieved. Compared with Examples 12-13, the increase in adhesive force after heating in Examples 10-11 is greater.

Furthermore, in Examples 14-20, the formation of bubbles was successfully prevented by using a catalyst. In Examples 14-17 and 19-20, the amount of iron-based catalyst used was such that the molar ratio of catalyst to hydroxyl group ([catalyst]/[OH]) in the adhesive layer was 4.6E-5 (4.6 × ^10⁻⁵ ) to 9.2E-4 (9.2 × ^10⁻⁴ ). Compared to the initial low adhesion, the adhesion increased significantly after heating. Example 19, in particular, showed the most balanced improvement in initial adhesion, adhesion after heating, flexural resilience, flexural holding power, and prevention of bubble formation.

The above provides a detailed description of specific examples of the present invention, but these are merely illustrative and do not limit the scope of the patent application. The technology described in the patent application includes various changes and modifications to the specific examples illustrated above.

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

Figure 1 is a cross-sectional view schematically showing the structure of a reinforcing membrane in one embodiment. Figure 2 is a cross-sectional view schematically showing the structure of a reinforcing membrane in another embodiment. Figure 3 is a cross-sectional view schematically showing the structure of a reinforcing membrane in yet another embodiment.

1: Reinforcing film 10: Supporting substrate 10A: First side 10B: Second side 21: Adhesive layer (first adhesive layer) 21A: Adhesive surface (first adhesive surface) 31: Peel-off pad 100: Reinforcing film with peel-off pad attached

Claims (8)

A reinforcing film comprising an adhesive layer comprising a polymer (A) and a polymer (B), wherein polymer (A) is an acrylic polymer comprising 1% to 20% by weight of monomer units derived from hydroxyl-containing monomers, and the glass transition temperature _TA of polymer (A) is -80°C or higher and not lower than -35°C; polymer (B) comprises monomer units having a polyorganosiloxane backbone and (meth)acrylic monomer units; the content of polymer (B) in the adhesive layer is 0.1 to 30 parts by weight relative to 100 parts by weight of polymer (A); and the adhesive layer comprises 0.015 parts by weight or higher and not more than 1.0 parts by weight relative to 100 parts by weight of polymer (A) of an isocyanate-based crosslinker. The surface elastic modulus of the above adhesive layer at 23°C is 1–20 kPa. For example, the reinforcing membrane of claim 1, wherein the volume elastic modulus G' ₂₃ of the adhesive layer is 10 to 200 kPa at 23°C, the volume elastic modulus G' ₈₀ is 5 to 100 kPa at 80°C, and the tanδ ₈₀ at 80°C is 0.10 to 0.60. For example, in the reinforcing film of claim 1 or 2, the content of the polymer (B) in the adhesive layer is 0.5 to 5 parts by weight relative to 100 parts by weight of the polymer (A). For example, in the reinforcing membrane of claim 1 or 2, the molar ratio ([NCO]/[OH]) of isocyanate groups to hydroxyl groups contained in the adhesive layer is 0.002 to 0.03. For example, in the reinforcing membrane of claim 1 or 2, the adhesive layer contains a catalyst, and the molar ratio ([catalyst]/[OH]) of the catalyst to the hydroxyl group contained in the adhesive layer is 1.0× ^10⁻⁶ to 5.0× ^10⁻² . For example, in the reinforcing membrane of claim 5, the catalyst is an iron-based catalyst, and the molar ratio ([catalyst]/[OH]) of the catalyst to hydroxyl group contained in the adhesive layer is 1.0× ^10⁻⁴ to 1.0× ^10⁻³ . An optical component having a reinforcing film as described in any of claims 1 to 6. An electronic component having a reinforcing film attached as described in any of claims 1 to 6.