Adhesive films, laminates, and methods of using adhesive films

Abstract

This invention provides an adhesive film that, when annealing a resin film while it is temporarily fixed, does not hinder the elimination of residual stress or strain in the resin film. Furthermore, it is not easily peeled off from the resin film, and therefore, no residue remains after annealing, allowing for easy peeling. The adhesive film is characterized by having a substrate and an adhesive layer disposed on at least one side of the substrate. The adhesive layer has a temperature region in the range of 70°C to 100°C where the loss tangent tanδ is 0.8 or higher, and can be peeled off by irradiation with an active energy line.

Description

Technical Field

[0001] The present invention relates to an adhesive film that is preferably used for conveying or surface protection of resin films that require annealing, such as optical films. Prior Technology

[0002] Industrial films are used in various fields such as displays, electronics, batteries or energy, and automotive (vehicles) to impart or perform desired functions. For example, optical films such as polarizing films or retardation films used in the display field are used as components of image display devices such as liquid crystal displays (LCDs) or organic electroluminescence (EL) displays mounted on electronic terminals such as smartphones or tablets.

[0003] In various stages of manufacturing, processing, handling, and inspection of articles in various fields, adhesive films are applied to the surface of industrial films for the purpose of handling and assembling them into the articles or for protecting surfaces from damage or contamination. The adhesive film is removed from the industrial film at a stage where it is no longer needed. For example, Patent Document 1 discloses an adhesive film for surface protection or handling of optical films during the manufacturing process of display devices. Depending on its method of use, such adhesive films are sometimes referred to as, for example, protective films, engineering films, etc. [Existing Technical Documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2013-216738 Summary of the Invention

[0005] [The problem that the invention aims to solve] Resin films used in industrial applications are typically annealed to remove residual stress or strain generated during the forming process. However, these resin films suffer from the following problem: while removing residual stress or strain is accompanied by deformation, annealing occurs when the adhesive film is pre-attached to the resin film. The adhesive film constrains this deformation, preventing sufficient elimination of residual stress or strain even after annealing, leading to adverse conditions in subsequent processing steps.

[0006] Furthermore, the heating temperature or processing time during the annealing process is set according to the glass transfer temperature of the resin film. It is required that the adhesive film bonded to the resin film is not easily peeled off even under the annealing conditions of the resin film, and can be easily peeled off from the resin film after annealing.

[0007] That is, the problem to be solved by the present invention is to provide an adhesive film that, when the resin film is annealed while it is temporarily fixed, does not hinder the elimination of residual stress or strain of the resin film, and is not easily peeled off from the resin film, so that no paste remains after annealing and can be easily peeled off. [Methods for solving problems]

[0008] The present invention includes the following forms. [1] An adhesive film, characterized in that it has a substrate and an adhesive layer disposed on at least one side of the substrate, the adhesive layer having a temperature region in the range of 70°C to 100°C where the loss tangent tanδ at a frequency of 1 Hz is 0.8 or higher, and can be peeled off by irradiation with an active energy line.

[0009] [2] An adhesive film, characterized in that it has a substrate and an adhesive layer disposed on at least one side of the substrate, the adhesive layer being formed of an adhesive composition comprising an acrylic copolymer and an active energy line curing compound, and having a temperature region in which the loss tangent tanδ at a frequency of 1 Hz is 0.8 or higher in the range of 70°C to 100°C.

[0010] [3] The adhesive film as described in [1] or [2], wherein the gel fraction of the adhesive layer is less than 50% by mass.

[0011] [4] The adhesive film as described in any one of [1] to [3], wherein the substrate has a 100% elongation stress of 5 MPa to 60 MPa at 150°C.

[0012] [5] The adhesive film as described in any one of [1] to [4] is used by adhering it to the resin film.

[0013] [6] The adhesive film as described in any one of [1] to [5] is used for surface protection purposes.

[0014] [7] The adhesive film as described in any one of [1] to [6] is used for the conveying step.

[0015] [8] A laminate, characterized in that it comprises: an adhesive film as described in any one of [1] to [7], and a resin film disposed on the adhesive layer of the adhesive film.

[0016] [9] The laminate as described in [8], wherein the resin film is an optical film.

[0017]

[10] A method of using an adhesive film, comprising the steps of: bonding a resin film to the adhesive layer of the adhesive film as described in any one of [1] to [7] to obtain a laminate; annealing the resin film of the laminate; and irradiating the laminate after the annealing step with an active energy line to peel the adhesive film off from the resin film. Simple Explanation of the Diagram

[0018] Figure 1 is a schematic cross-sectional view showing an example of the adhesive film of the present invention. Figure 2 is a schematic cross-sectional view showing an example of the laminate of the present invention. Figures 3(a) to (c) are explanatory diagrams illustrating the curling test methods in the embodiments and comparative examples. Figure 4 is an explanatory diagram illustrating the thermoforming test method in the embodiments and comparative examples. Figure 5 is an explanatory diagram illustrating the thermoforming test method in the embodiments and comparative examples. Figure 6 is an explanatory diagram illustrating the thermoforming test method in the embodiments and comparative examples. Implementation

[0019] In this invention, "(meth)acrylic acid" refers to acrylic acid or methacrylic acid. Additionally, "(meth)acrylate" refers to acrylate or methacrylate. Furthermore, the loss tangent tanδ is sometimes simply expressed as tanδ.

[0020] 1. Adhesive membrane The adhesive film of the present invention is characterized in that it has a substrate and an adhesive layer disposed on at least one side of the substrate, the adhesive layer having a temperature region in the range of 70°C to 100°C where the loss tangent tanδ is 0.8 or higher, and can be peeled off by irradiation with an active energy line.

[0021] In other words, the adhesive film of the present invention is characterized by having a substrate and an adhesive layer disposed on at least one side of the substrate, the adhesive layer being formed of an adhesive composition comprising an acrylic copolymer and an active energy line curing compound, and having a temperature region in which the loss tangent tanδ is 0.8 or higher in the range of 70°C to 100°C.

[0022] Figure 1 is a schematic cross-sectional view showing an example of the adhesive film of the present invention, having a substrate 1 and an adhesive layer 2 disposed on one side of the substrate 1. The adhesive layer 2 has a temperature region in the range of 70°C to 100°C where the loss tangent tanδ is 0.8 or higher. Furthermore, the adhesive layer 2 can be peeled off by irradiation with an active energy line. In other words, the adhesive layer 2 is a layer formed of an adhesive composition comprising an acrylic copolymer and an active energy line curing compound.

[0023] The heating temperature or time to be set in the annealing process is selected based on the type or properties of the resin (e.g., the glass transition temperature of the resin). For resin films used in optical films, annealing is performed at around 100°C to prevent damage to the resin film's function due to the heat of the annealing process. However, if annealing is performed with an adhesive film attached, the following problem arises: the resin film is constrained by the adhesive film, and residual stress or strain cannot be fully eliminated, thus affecting the processability or optical properties of the annealed resin film.

[0024] In contrast, according to the adhesive film of the present invention, the adhesive layer has a temperature range in which the loss tangent tanδ is 0.8 or higher within the range of 70°C to 100°C. Therefore, in the temperature environment during the annealing treatment of the resin film, the adhesive layer can exhibit softness and fluidity, and the adhesive layer will not hinder the deformation of the resin film generated during the annealing treatment. When the adhesive film is attached, the residual stress or strain of the resin film can be fully eliminated.

[0025] In addition, the adhesive film of the present invention exhibits excellent adhesion before being irradiated with active energy lines. Therefore, it is not easy to peel off from the resin film even when exposed to a hot environment after annealing. When peeled off from the resin film after annealing, it can be easily peeled off by irradiating with active energy lines without leaving any paste residue.

[0026] The adhesive film of the present invention possesses the aforementioned physical properties through its adhesive layer. Whether the resin film is annealed at a temperature range of around 100°C, for example, between 70°C and 100°C (sometimes designated as a low-temperature range), or at a temperature range exceeding 100°C (sometimes designated as a high-temperature range), the adhesive layer exhibits the aforementioned functions. Therefore, it does not hinder the deformation of the resin film accompanied by the elimination of residual stress or strain. Furthermore, before irradiation with the active energy line, the adhesion between the resin film and the adhesive film can be maintained, and good peelability is achieved by irradiation with the active energy line. Therefore, by annealing a functional resin film, such as an optical film, in a low-temperature range while the adhesive film of the present invention is adhered to, surface protection or transport can be performed while preventing damage to the function of the resin film and eliminating residual stress or strain in the resin film while the adhesive film is adhered to.

[0027] In this invention, unless otherwise specified, the tanδ of the adhesive layer refers to the tanδ of the adhesive layer before the resin film is annealed and before it is cured (before irradiation by the active energy line). Similarly, the properties of the adhesive layer other than tanδ also refer to the properties of the adhesive layer before the resin film is annealed and before it is cured (before irradiation by the active energy line) unless otherwise specified.

[0028] [Adhesive layer] In this invention, the adhesive layer is disposed on a substrate and at least one side of the substrate. The adhesive layer can be directly disposed on the surface of the substrate, or it can be disposed on the surface of the substrate through other layers.

[0029] Furthermore, the adhesive layer in this invention exhibits a lower adhesion strength after irradiation with the active energy line than before irradiation. The adhesive layer in this invention is characterized by: exhibiting excellent adhesion strength before irradiation with the active energy line; and, on the other hand, decreasing adhesion strength due to a curing reaction caused by irradiation with the active energy line. That is, the adhesive layer in this invention is formed from an adhesive composition that is cured by the active energy line (sometimes described as an active energy line-cured adhesive composition).

[0030] The active energy beam can be any light source capable of hardening the adhesive layer, such as far-ultraviolet, ultraviolet, near-ultraviolet, infrared, electromagnetic waves such as X-rays and gamma rays, electron beams, proton beams, neutron beams, etc. Among these, ultraviolet light is preferred in terms of fast hardening speed and ease of operation or device.

[0031] The adhesive layer of this invention has a temperature range within which the loss tangent (tanδ) is 0.8 or higher, within the range of 70°C to 100°C. Because the adhesive layer has a temperature range exhibiting a predetermined tanδ within this temperature range, when the resin film is annealed while being bonded to the adhesive film, the adhesive layer exhibits high flexibility and fluidity under the annealing environment. Therefore, the adhesive layer does not hinder the deformation of the resin film generated during the annealing process, and residual stress or strain in the resin film can be sufficiently eliminated while it is bonded to the adhesive film.

[0032] The adhesive layer requires only a temperature range of tanδ of 0.8 or higher within the range of 70°C to 100°C. Preferably, this range is within 80°C to 100°C, more preferably within 85°C to 100°C, and even more preferably within 90°C to 100°C. By having a temperature range of tanδ of 0.8 or higher within this range, the deformation of the resin film during annealing, which is accompanied by the elimination of residual stress or strain, can be prevented from being hindered by the adhesive layer, and the shape retention of the adhesive layer can be ensured.

[0033] The adhesive layer in this invention has a temperature range of 70°C to 100°C where tanδ is 0.8 or higher, and even in temperature ranges exceeding 100°C, tanδ remains above 0.8. Therefore, whether the resin film is annealed in a temperature range below 100°C or in a temperature range exceeding 100°C, the adhesive layer does not hinder the deformation of the resin film that accompanies the elimination of residual stress or strain, thus eliminating the residual stress or strain of the resin film.

[0034] Furthermore, the adhesive layer only needs to have a temperature range of tanδ of 0.80 or higher within the range of 70°C to 100°C, preferably a temperature range of tanδ of 0.80 or higher, more preferably a temperature range of tanδ of 0.87 or higher, more preferably a temperature range of tanδ of 0.93 or higher, and even more preferably a temperature range of tanδ of 1.0 or higher. The reason for this is that, under the annealing treatment environment of the resin film, the adhesive layer can exhibit higher flexibility and fluidity, and the adhesive layer will not hinder the elimination of residual stress or strain of the resin film, but can eliminate the residual stress or strain of the resin film. Regarding the upper limit of tanδ of the adhesive layer in the range of 70℃~100℃, there is no particular limitation as long as the softness and fluidity of the adhesive layer and its shape retention as an adhesive layer can be taken into account in the annealing treatment environment of the resin film. For example, the tanδ can be set to 2.0 or less. In terms of eliminating residual stress or strain of the resin film and improving the processing adaptability or shape retention of the adhesive film, it is preferred to be 1.5 or less, and it can be set to 1.3 or less.

[0035] In the annealing process of the resin film adhering to the adhesive film of the present invention, from the viewpoint of balancing the softness and flowability of the adhesive layer with the shape retention of the adhesive layer, for the adhesive layer, in the temperature range of 75°C to 100°C, tanδ is preferably 0.80 or higher, more preferably 0.87 or higher, more preferably 0.93 or higher, and even more preferably 1.0 or higher. In addition, tanδ is preferably 2.0 or lower, more preferably 1.5 or lower.

[0036] As another preferred embodiment, for the adhesive layer, in the temperature range of 80°C to 100°C, tanδ is preferably 0.80 or higher, more preferably 0.87 or higher, more preferably 0.93 or higher, and even more preferably 1.0 or higher. In addition, tanδ is preferably 2.0 or lower, more preferably 1.5 or lower, and even more preferably 1.3 or lower.

[0037] As another preferred embodiment, for the adhesive layer, in the temperature range of 85°C to 100°C, tanδ is preferably 0.80 or higher, more preferably 0.87 or higher, more preferably 0.93 or higher, and even more preferably 1.0 or higher. In addition, tanδ is preferably 2.0 or lower, more preferably 1.5 or lower, and even more preferably 1.3 or lower.

[0038] As another preferred embodiment, for the adhesive layer, in the temperature range of 90°C to 100°C, tanδ is preferably 0.80 or higher, more preferably 0.87 or higher, more preferably 0.93 or higher, and even more preferably 1.0 or higher. In addition, tanδ is preferably 2.0 or lower, more preferably 1.5 or lower, and even more preferably 1.3 or lower.

[0039] As a preferred form of the adhesive layer, more specifically, the loss tangent tanδ (90°C) at 90°C is preferably 0.8 or higher, more preferably 0.80 or higher, more preferably 0.87 or higher, and even more preferably 0.93 or higher. This is because the adhesive layer exhibits excellent shape retention even at the ambient temperature of the resin film annealing treatment, and at the ambient temperature of the resin film annealing treatment, the adhesive layer can exhibit high flexibility and fluidity, which can suppress the adhesive layer from hindering the elimination of residual stress or strain of the resin film.

[0040] The maximum loss tangent tanδ of the adhesive layer in the temperature range of 50°C to 70°C is preferably 1.5 or less, more preferably 1.3 or less, and even more preferably 1.0 or less. This is because it prevents the adhesive layer from exhibiting excessive fluidity and compromising its shape stability as a layer under the annealing temperature conditions of the resin film bonded to the adhesive film.

[0041] The loss tangent tanδ of the adhesive layer can be adjusted, for example, by adjusting the gel fraction of the adhesive composition constituting the adhesive layer, adjusting the crosslinking dosage, reducing the weight average molecular weight of the acrylic copolymer contained in the adhesive composition, and increasing the content of active energy linear polymerizable compounds (e.g., urethane (meth)acrylate) contained in the adhesive composition.

[0042] The loss tangent tanδ of the adhesive layer refers to the ratio of the loss elastic coefficient G'' of the adhesive composition used to form the adhesive layer to the storage elastic coefficient G', that is, tanδ=G'' / G'. Regarding the loss tangent tanδ of the adhesive layer, the adhesive composition used to form the adhesive layer can be applied to the surface of the release liner. The layer is heated in an oven at 85°C for 5 minutes to create an adhesive layer a with a thickness of 50 μm. The obtained adhesive layers a are then overlapped to create an adhesive layer A with a total thickness of 2 mm. This adhesive layer A is then cut into a circle with a diameter of 8 mm and used as a test piece. Using a viscoelastic testing machine (manufactured by Rheometrics, trade name: Ares 2KSTD), the test piece is clamped between the measuring section (parallel discs) of the testing machine. In shear stress measurement mode, at a heating rate of 2.0°C / min and a temperature range of -40°C to 150°C, the storage elastic coefficient (G') and loss elastic coefficient (G'') at a frequency of 1 Hz are measured. The loss tangent tanδ at each temperature is calculated based on G' and G''.

[0043] Furthermore, the gel fraction of the adhesive layer relative to toluene (gel fraction before irradiation with the active energy line) is preferably 50% by mass or less, more preferably in the range of 10% to 40% by mass, and even more preferably in the range of 15% to 35% by mass. By keeping the gel fraction of the adhesive layer within this range, the adhesion to the resin film is excellent under both room temperature and annealing conditions before irradiation with the active energy line. In addition, by keeping the gel fraction of the adhesive layer within this range, the adhesive layer will not hinder the deformation of the resin film generated during the annealing process, and residual stress or strain of the resin film can be sufficiently eliminated while the adhesive film is in place.

[0044] The gel fraction of the adhesive layer and the adhesive composition constituting the adhesive layer refers to the value determined using the method shown below. (Determination Method) For a release liner, the adhesive composition is applied to the release surface with a dried thickness of 10 μm. It is dried at 85°C for 5 minutes, followed by aging at 40°C for 2 days to form an adhesive layer. This adhesive layer is then cut into squares of 50 mm in length and 50 mm in width, and used as test pieces. After determining the mass (G1) of the test piece, it is immersed in toluene at 23°C for 24 hours. After immersion, the mixture of the test piece and toluene is filtered through a 300-mesh metal mesh to extract the insoluble components in toluene. The mass (G2) of the insoluble components obtained by drying at 110°C for 1 hour is then determined. Based on the mass (G1), mass (G2), and the following formula, the gel fraction is calculated. Gel fraction (mass%) = (G2 / G1) × 100

[0045] Furthermore, for the adhesive layer, the gel fraction relative to toluene after irradiation with the active energy line is preferably 80% by mass or more, more preferably 80% by mass or more and 98% by mass or less, and even more preferably 85% by mass or more and 98% by mass or less. By ensuring that the gel fraction of the adhesive layer after irradiation with the active energy line is within the aforementioned range, it can be easily peeled off under light load.

[0046] Regarding the gel fraction of the adhesive layer after irradiation with active energy lines, in the method for determining the gel fraction, after the adhesive layer is formed, the adhesive layer is irradiated with active energy lines under the following conditions. The adhesive layer after irradiation with active energy lines is cut into squares with a length of 50 mm and a width of 50 mm, and used as a test piece. Otherwise, the determination can be carried out in the same way as described above. (Irradiation conditions of active energy lines) Light source: Electrodeless bulb manufactured by Heraeus (D bulb) Illuminance: 90 mW / cm² Light intensity: 180 mJ / cm² Illuminance-Photometer: ORC UV-M10 photometer manufactured by ORC Corporation.

[0047] The adhesive layer in this invention is formed from an active energy line-curing adhesive composition containing various components for constituting the adhesive layer. The adhesive composition constituting the adhesive layer in this invention is not particularly limited as long as it exhibits adequate adhesion before irradiation with the active energy line and hardens upon irradiation, thereby reducing or eliminating adhesion; however, it is preferably an adhesive composition with an adhesive resin as its main component. Furthermore, the main component of the adhesive composition refers to the component with the highest proportion among the various components contained in the adhesive composition.

[0048] To achieve the function of reducing / disappearing adhesion upon irradiation with an active energy line, the adhesive composition may comprise an adhesive resin and an active energy line curing compound, or it may be a composition in which the adhesive resin itself possesses active energy line curing properties. Furthermore, even when the adhesive resin itself possesses active energy line curing properties, the adhesive composition may comprise an adhesive resin with active energy line curing properties, and other active energy line curing compounds. Preferably, the adhesive composition comprises an adhesive resin and an active energy line curing compound because, before irradiation with the active energy line, the adhesive resin exhibits appropriate adhesion, and after irradiation, the adhesion is sufficiently reduced through curing by the active energy line curing compound, allowing for peeling and easily achieving the desired physical properties before and after irradiation.

[0049] When the adhesive resin itself possesses active energy line curing properties, active energy line polymerizable groups are introduced into the adhesive resin. Preferably, the active energy line polymerizable groups are introduced into the main chain or side chain of the adhesive resin. Furthermore, to distinguish it from adhesive resins without active energy line polymerizable groups, adhesive resins containing active energy line polymerizable groups are sometimes referred to as active energy line curing adhesive resins.

[0050] <Adhesive resin> The adhesive resin is a component used to ensure the adhesion of the adhesive layer. There are no particular limitations on the adhesive resin; examples include copolymers (polymers) such as acrylic copolymers, polyurethanes, rubber polymers, polyolefin polymers, and silicones. Among these, acrylic copolymers are preferred. That is, the adhesive layer is preferably formed from an active energy line-curing adhesive composition containing an acrylic copolymer.

[0051] Acrylic copolymers are obtained by copolymerizing monomer components containing alkyl (meth)acrylates as the main monomer. Preferably, the alkyl (meth)acrylate has 1 to 20 carbon atoms, with the alkyl group preferably having 1 to 12 carbon atoms, more preferably 1 to 9, and even more preferably 4 to 9. If the alkyl group has too many carbon atoms, the adhered material may easily become contaminated due to residual paste during the peeling process after irradiation with active energy lines. Furthermore, the alkyl group can be linear or branched.

[0052] As alkyl methacrylates, examples include, for instance, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tributyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, isononyl methacrylate, cyclohexyl methacrylate, and 2-ethylhexyl methacrylate. These monomers can be used alone or in combination. From the viewpoint of copolymerization or adhesive properties, methyl methacrylate, n-butyl methacrylate, and 2-ethylhexyl methacrylate are preferred.

[0053] The content of alkyl (meth)acrylate in the acrylic copolymer is preferably 10% to 99% by mass, more preferably 30% to 99% by mass, more preferably 50% to 99% by mass, more preferably 80% to 98.5% by mass, and more preferably 90% to 98.5% by mass. By keeping the content of alkyl (meth)acrylate within the aforementioned range, the adhesion before irradiation by the active energy line can be prevented from becoming too low or too high, thereby ensuring good adhesion to the resin film.

[0054] Alternatively, the acrylic copolymer may also be a copolymer of (meth)acrylate alkyl ester and a highly polar monomer. Examples of highly polar monomers copolymerized with (meth)acrylate alkyl ester include monomers with hydroxyl groups, monomers with carboxyl groups, and monomers with amino groups; these may be used individually or in combination of two or more.

[0055] As monomers containing hydroxyl groups, hydroxyl-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate are preferred. These can be used alone or in combination of two or more. Among them, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred in terms of reactivity with crosslinking agents.

[0056] The content of hydroxyl-containing monomers in the acrylic copolymer is preferably 0.1% to 40% by mass, more preferably 0.2% to 30% by mass, and more preferably 0.5% to 30% by mass. By keeping the content of hydroxyl-containing monomers within the aforementioned range, contamination of the resin film caused by residual paste or the like can be prevented during the peeling of the adhesive film after irradiation with active energy lines.

[0057] As monomers containing carboxyl groups, (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, (meth)acrylic acid dimer, crotonic acid, ethylene oxide-modified succinic acid acrylate, etc., can be used. These can be used alone or in combination of two or more. Among them, from the point of view of copolymerization, acrylic acid and methacrylic acid are preferred.

[0058] In the monomer components constituting the acrylic copolymer, the content of carboxyl-containing monomers is preferably 10% by weight or less, more preferably 5% by weight or less, more preferably 1% by weight or less, and particularly preferably 0.3% by weight or less. Furthermore, in the monomer components constituting the acrylic copolymer, the content of carboxyl-containing monomers is preferably 0.01% by weight or more, more preferably 0.03% by weight or more, and more preferably 0.05% by weight or more. By ensuring that the content of carboxyl-containing monomers is within the aforementioned range, deterioration of the resin film or surface contamination of the resin film caused by residual paste or the like during peeling off the adhesive film after irradiation with active energy lines can be prevented.

[0059] Examples of monomers containing amide groups include: N-vinylpyrrolidone, N-vinylcaprolactone, acrylamide, acrylamide, and N,N-dimethylacrylamide.

[0060] Other highly polar vinyl monomers include: vinyl acetate, ethylene oxide-modified succinic acid acrylate, sulfonic acid-containing monomers such as 2-acrylamide-2-methylpropanesulfonic acid, and terminal alkoxy-modified (meth)acrylates such as (meth)acrylate 2-methoxyethyl ester and (meth)acrylate 2-phenoxyethyl ester.

[0061] Acrylic copolymers can be obtained by copolymerizing monomers using known polymerization methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization. Among these methods, solution polymerization or bulk polymerization is preferred for the water resistance of the adhesive composition.

[0062] In the preparation of acrylic copolymers using the solution polymerization method, for example, it is sufficient to mix or dropwise add monomer components containing alkyl (meth)acrylate and polymerization initiators in an organic solvent, and polymerize in reflux or at a temperature of 50°C to 98°C for about 0.1 to 20 hours.

[0063] Examples of organic solvents used in the polymerization reaction include: aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as hexane; esters such as ethyl acetate and butyl acetate; aliphatic alcohols such as n-propanol and isopropanol; and ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

[0064] As the polymerization initiator, common free radical polymerization initiators can be used. Specifically, examples include: azo-based polymerization initiators such as azobisisobutyronitrile and azobisdimethylvalerate; and peroxide-based polymerization initiators such as benzoyl peroxide, lauryl peroxide, di-tert-butyl peroxide, and cumene hydroperoxide.

[0065] The weight average molecular weight of the acrylic copolymer is preferably above 100,000 and below 1,000,000. If the weight average molecular weight of the acrylic copolymer is too small, surface contamination of the resin film caused by residual paste may occur when peeling off the adhesive film after irradiation with active energy lines. If it is too large, the coatability may be reduced.

[0066] Here, the molecular weight determination using gel permeation chromatography (GPC) is based on the standard polystyrene conversion value determined using a GPC apparatus (HLC-8329GPC) manufactured by Tosoh Corporation, under the following conditions. Sample concentration: 0.5% by mass (tetrahydrofuran (THF) solution) Sample injection volume: 100 μL Elution buffer: THF Flow rate: 1.0 mL / min Measurement temperature: 40℃ Main column: TSKgel GMHHR-H(20) 2 columns Protection string: TSKgel HXL-H Detector: Differential refractometer Standard polystyrene molecular weight: 10,000~20,000,000 (manufactured by Tosoh Corporation)

[0067] When the adhesive resin itself has active energy line curing properties, an active energy line curing adhesive resin in which active energy line polymerizable groups are introduced into the adhesive resin can be used.

[0068] Examples of polymerizable groups with active energy lines include groups containing carbon-carbon double bonds, specifically (meth)acrylonitrile groups. These polymerizable groups can be bonded to the adhesive resin via alkyl groups, alkoxy groups, or polyalkoxy groups.

[0069] There is no particular limitation on the active energy line curable adhesive resin, and examples of adhesive resins in which active energy line polymerizable groups are introduced can be listed. Among them, acrylic resins in which active energy line polymerizable groups are introduced can be preferred.

[0070] Acrylic resins incorporating active energy line polymerizable groups can be obtained by reacting acrylic copolymers containing functional groups such as hydroxyl, carboxyl, amine, substituted amine, and epoxy groups with compounds containing polymerizable groups. These polymerizable compounds have substituents that react with the functional groups and have 1 to 5 active energy line polymerizable carbon-carbon double bonds in each molecule. Examples of such polymerizable compounds include: (meth)acrylic oxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate, (meth)acrylic oxyisocyanate, allyl isocyanate, glycidyl (meth)acrylate, and (meth)acrylic acid.

[0071] <Active Energy Line Polymerization Compounds> The active energy line polymerizable compound contained in the adhesive composition is not particularly limited as long as it is a compound that can polymerize upon irradiation by an active energy line, and examples include compounds having active energy line polymerizable groups (monofunctional or polyfunctional monomers and oligomers). Examples of such active energy line polymerizable compounds include active energy line polymerizable compounds containing two or more ethylene unsaturated groups (i.e., ethylene unsaturated compounds).

[0072] Specifically, examples of polymerizable compounds with active energy lines include: urethane (meth)acrylate compounds, epoxy (meth)acrylate compounds, polyester (meth)acrylate compounds, polyether (meth)acrylate compounds, and polyfunctional vinyl unsaturated monomers other than these acrylate compounds, which have two or more vinyl unsaturated groups in one molecule. These can be used alone or in combination of two or more.

[0073] In terms of excellent reactivity or exfoliation properties after irradiation based on the active energy line irradiation, the active energy line polymerizable compound is preferably a carbamate (meth) acrylate compound or a polyfunctional vinyl unsaturated monomer.

[0074] The weight-average molecular weight of the active energy line polymerizable compound also depends on the type of active energy line polymerizable compound, preferably below 10,000, more preferably below 5,000, and even more preferably below 1,000. Furthermore, the weight-average molecular weight of the active energy line polymerizable compound is preferably above 100, more preferably above 300, and even more preferably above 500.

[0075] Regarding the number of vinyl unsaturated groups in the active energy line polymerizable compound, as long as there are two or more per molecule, it can be appropriately selected according to the type of active energy line polymerizable compound. Preferably, there are three or more vinyl unsaturated groups, more preferably three to 60, and even more preferably three to 40. If the number of vinyl unsaturated groups is too small, even with active energy line irradiation, the adhesive force will be difficult to reduce, and sometimes the peelability will decrease.

[0076] The content of the active energy line polymerizable compound in the adhesive composition is not particularly limited, as long as the adhesive layer exhibits excellent adhesion before irradiation with the active energy line and the adhesion of the adhesive layer is sufficiently reduced or eliminated by irradiation with the active energy line. For example, it is preferably 5 parts by weight or more, more preferably 10 parts by weight or more, and even more preferably 20 parts by weight or more, relative to 100 parts by weight of adhesive resin. In addition, the content of the active energy line polymerizable compound is preferably 200 parts by weight or less, more preferably 100 parts by weight or less, and even more preferably 80 parts by weight or less, relative to 100 parts by weight of adhesive resin. By keeping the content of the active energy line polymerizable compound in the adhesive composition within the above range, the adhesive film can be easily peeled off by reducing the adhesion in a short time by irradiation with the active energy line. In addition, surface contamination of the resin film caused by residual paste or the like can be prevented during peeling.

[0077] (Aminocarbamate (meth)acrylate compounds) Aminocarbamate (meth)acrylate compounds are compounds containing an aminocarbamate bond and a (meth)acrylic group at the end. Aminocarbamate (meth)acrylate compounds exhibit active energy line hardening properties due to the action of the (meth)acrylic group.

[0078] As the aforementioned urethane (meth)acrylate compound, the reaction product of a hydroxyl-containing (meth)acrylate and a polyvalent isocyanate compound can be used. Alternatively, the reaction product of a hydroxyl-containing (meth)acrylate, a polyvalent isocyanate compound, and a polyol compound can also be used as the aforementioned urethane (meth)acrylate compound. Among these, the use of an urethane (meth)acrylate compound that is the reaction product of a hydroxyl-containing (meth)acrylate compound and a polyvalent isocyanate compound is preferred, as it provides better peelability after irradiation with an active energy line.

[0079] Examples of hydroxyl-containing (meth)acrylates include: 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 2-(meth)acryloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-(meth)acryloxypropyl (meth)acrylate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, and pentaerythritol tri(meth)propyl... Acrylates, pentaerythritol penta(meth)acrylate, pentaerythritol hexa(meth)acrylate, caprolactone-modified pentaerythritol penta(meth)acrylate, caprolactone-modified pentaerythritol tri(meth)acrylate, caprolactone-modified pentaerythritol tetra(meth)acrylate, caprolactone-modified pentaerythritol hexa(meth)acrylate, ethylene oxide-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified pentaerythritol penta(meth)acrylate, ethylene oxide-modified pentaerythritol hexa(meth)acrylate, etc.

[0080] Among these, (meth)acrylates containing three or more acrylonitrile groups and having hydroxyl groups are preferred. Specifically, examples include dipentaerythritol penta(meth)acrylate and dipentaerythritol hexa(meth)acrylate. Furthermore, one or more of these can be used in combination.

[0081] Examples of such polyisocyanate compounds include: aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, modified diphenylmethane diisocyanate, xylene diisocyanate, tetramethylxylene diisocyanate, phenyl diisocyanate, and naphthalene diisocyanate; aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, and lysine triisocyanate; alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate, hydrogenated xylene diisocyanate, isophorone diisocyanate, and norbornene diisocyanate; isocyanurate or polymeric compounds of these polyisocyanates, urea-formate type polyisocyanates, biuret type polyisocyanates, and water-dispersible polyisocyanates. From a reactivity point of view, aliphatic diisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate, as well as alicyclic diisocyanates such as hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and norbornene diisocyanate are preferred.

[0082] Examples of such polyol compounds include: ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butanediol, polybutanediol, 1,6-hexanediol, neopentyl glycol, cyclohexanediol, hydrogenated bisphenol A, polycaprolactone, trimethylolethane, trimethylolpropane, polytrimethylolpropane, pentaerythritol, polypentaerythritol, sorbitol, mannitol, glycerol, polyglycerol, polytetramethylene glycol, etc.; polyether polyols having at least one structure of block or random copolymerization of polyethylene oxide, polypropylene oxide, or ethylene oxide / propylene oxide; and polyols or polyether polyols combined with maleic anhydride, maleic acid, fumaric acid, itaconic anhydride, etc. Polyester polyols containing condensates of polybasic acids such as itaconic acid, adipic acid, and isophthalic acid; caprolactone-modified polyols such as caprolactone-modified polytetramethylene polyol; polyolefin polyols; polybutadiene polyols such as hydrogenated polybutadiene polyol; polycarboxyl-containing polyols such as 2,2-bis(hydroxymethyl)butyric acid, tartaric acid, 2,4-dihydroxybenzoic acid, 3,5-dihydroxybenzoic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxyethyl)propionic acid, 2,2-bis(hydroxypropyl)propionic acid, dihydroxymethylacetic acid, bis(4-hydroxyphenyl)acetic acid, 4,4-bis(4-hydroxyphenyl)valerate, and homogentisic acid; and polyols containing sulfonic acid groups or sulfonate groups such as sodium 1,4-butanediol sulfonate.

[0083] There are no particular limitations on the method for manufacturing methacrylate compounds, and known methods can be used. For example, hydroxyl-containing methacrylates, polyisocyanate compounds, and, if desired, the polyol compound can be mixed in an inert gas environment and subjected to an aminocarbamate reaction using known reaction methods. Alternatively, when using the polyol compound, a method can be used in which the polyisocyanate compound is reacted with the polyol compound before reacting with the hydroxyl-containing methacrylate.

[0084] The weight average molecular weight of the urethane (meth)acrylate compound is preferably in the range of 500 to 10,000, more preferably in the range of 750 to 5,000, and even more preferably in the range of 1,000 to 4,000. It exhibits excellent compatibility with adhesive resins, particularly with acrylic resins when using acrylic copolymers as adhesive resins. Furthermore, it prevents the exudation of the self-adhesive layer, thereby suppressing surface contamination of the resin film caused by residual paste or the like during peeling after irradiation with active energy lines.

[0085] Relative to 100 parts by weight of the adhesive resin, the content of the urethane (meth)acrylate compound in the adhesive composition can be in the range of 5 parts by weight to 100 parts by weight, preferably in the range of 10 parts by weight to 90 parts by weight, and more preferably in the range of 12 parts by weight to 80 parts by weight. By ensuring that the content of the urethane (meth)acrylate compound in the adhesive composition is within the aforementioned range, an adhesive layer with excellent peelability after irradiation by active energy lines can be formed.

[0086] (Ethylene-unsaturated compounds) The ethylene unsaturated compound is a compound having two or more ethylene unsaturated groups in one molecule. The number of ethylene unsaturated groups in the ethylene unsaturated compound only needs to be two or more, preferably two to ten, more preferably three to nine, and even more preferably four to eight. By ensuring that the number of ethylene unsaturated groups is within the aforementioned range, the adhesive layer after irradiation with active energy lines will not leave any paste residue and can be easily peeled off from the resin film.

[0087] As for the ethylene unsaturated compound, there is no particular limitation as long as it is a compound having an ethylene unsaturated group, but (meth)acrylate compounds are preferred. Examples of ethylene unsaturated (meth)acrylate compounds include: ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide modified bisphenol A type di(meth)acrylate, and propylene oxide modified bisphenol A type di(meth)acrylate. Ester, Cyclohexanediethanol di(meth)acrylate, Ethoxylated cyclohexanediethanol di(meth)acrylate, Dihydroxymethyldicyclopentanedi(meth)acrylate, Tricyclodecanediethanol di(meth)acrylate, 1,6-Hexanediol di(meth)acrylate, Glyceryl di(meth)acrylate, Pentaerythritol di(meth)acrylate, Ethylene glycol diglycidyl ether di(meth)acrylate, Diethylene glycol diglycidyl ether di(meth)acrylate, Phthalic acid diglycidyl ester di(meth)acrylate, Hydroxypentanoic acid modified neopentyl glycol di(meth)acrylate Compounds containing two vinyl unsaturated groups, such as (meth)acrylates and ethylene oxide-modified diacrylates of isocyanuric acid; compounds containing three vinyl unsaturated groups, such as trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, tri(meth)acryloxyethoxytrimethylolpropane, ethylene oxide-modified triacrylates of isocyanuric acid, caprolactone-modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified pentaerythritol tri(meth)acrylate, and ethoxylated glycerol triacrylate; and pentaerythritol tetra(meth)acrylates, Compounds containing four or more vinyl unsaturated groups, such as dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, glycerol polyglycidyl ether poly(meth)acrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, caprolactone-modified pentaerythritol tetra(meth)acrylate, ethylene oxide-modified dipentaerythritol penta(meth)acrylate, ethylene oxide-modified dipentaerythritol hexa(meth)acrylate, and ethylene oxide-modified pentaerythritol tetra(meth)acrylate.

[0088] In addition, as the vinyl unsaturated (meth)acrylate compounds, Michael adducts of (meth)acrylate such as (meth)acrylate dimers, (meth)acrylate trimers, and (meth)acrylate tetramers can also be used; 2-(meth)acrylate acetoethyl succinate monoesters, 2-(meth)acrylate acetoethyl phthalate monoesters, 2-(meth)acrylate acetoethyl hexahydrophthalate monoesters, and other 2-(meth)acrylate acetoethyl dicarboxylic acid monoesters can also be used.

[0089] The ethylene unsaturated compound can be used alone or in combination with two or more.

[0090] Relative to 100 parts by weight of the adhesive resin, the content of the vinyl unsaturated compound in the adhesive composition is preferably 5 parts by weight or more and 100 parts by weight or less, more preferably 10 parts by weight or more and 80 parts by weight or less, and even more preferably 20 parts by weight or more and 60 parts by weight or less. By ensuring that the content of the vinyl unsaturated compound in the adhesive composition is within the aforementioned range, an adhesive layer with excellent peelability and stain resistance after irradiation by active energy lines can be formed.

[0091] Crosslinking agent The adhesive composition preferably contains a crosslinking agent to form an adhesive layer with excellent cohesiveness by adjusting the loss tangent of the adhesive layer within a specified temperature range to a specified range. Examples of such crosslinking agents include: isocyanate-based crosslinking agents, epoxy-based crosslinking agents, metal chelate-based crosslinking agents, aziridine-based crosslinking agents, oxazoline-based crosslinking agents, melamine-based crosslinking agents, aldehyde-based crosslinking agents, and amine-based crosslinking agents. These crosslinking agents can be used alone or in combination of two or more. From the viewpoint of reactivity with the adhesive resin and the active energy line polymerizable compound, or adhesion to the substrate, isocyanate-based crosslinking agents and epoxy-based crosslinking agents are more preferred.

[0092] As the isocyanate-based crosslinking agent, known materials can be used, such as: 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated xylene diisocyanate, hexamethylene diisocyanate, diphenylmethane-4,4-diisocyanate, isophorone diisocyanate, 1,3-bis(isocyanomethyl)cyclohexane, tetramethylxylyl diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, and adducts of these polyisocyanate compounds with polyol compounds such as trimethylolpropane, biuret forms or isocyanurates of these polyisocyanate compounds, etc.

[0093] As the epoxy crosslinking agent, known materials can be used, such as: bisphenol A-epiochlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl erythritol, diglycerol polyglycidyl ether, 1,3'-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylenediamine, etc.

[0094] The amount of the crosslinking agent in the adhesive composition can be appropriately selected to make the adhesive layer and the adhesive composition within the range of tanδ.

[0095] <Other Ingredients> In addition to the aforementioned components, the adhesive composition may also contain a photopolymerization initiator. As a photopolymerization initiator, any compound that generates free radicals upon irradiation with an active energy line is acceptable; known photopolymerization initiators such as acetophenones, benzoin compounds, benzophenones, thioxanones, and phosphine oxides can be used. These can be used alone or in combination of two or more. The content of the photopolymerization initiator in the adhesive composition is not particularly limited; it can be appropriately set to an amount sufficient to allow the adhesive composition to harden sufficiently upon irradiation with the active energy line. For example, relative to 100 parts by weight of the adhesive resin and the polymerizable compound of the active energy line, it can be set to 0.1 parts by weight or more and 20 parts by weight or less.

[0096] In addition to the aforementioned components, the adhesive composition may also contain an adhesive-improving resin to achieve an adhesive layer with superior peel adhesion. Examples of such adhesive-improving resins include rosin-based adhesive-improving resins, polymerized rosin-based adhesive-improving resins, polymerized rosin ester-based adhesive-improving resins, rosin phenol-based adhesive-improving resins, stabilized rosin ester-based adhesive-improving resins, disproportionated rosin ester-based adhesive-improving resins, hydrogenated rosin ester-based adhesive-improving resins, terpene-based adhesive-improving resins, terpene phenol-based adhesive-improving resins, petroleum resin-based adhesive-improving resins, and (meth)acrylate resin-based adhesive-improving resins. These can be used alone or in combination of two or more.

[0097] Furthermore, in addition to the aforementioned components, the adhesive composition may also contain colorants such as pigments or dyes, anti-deterioration agents, antistatic agents, flame retardants, silicone compounds, chain transfer agents, plasticizers, softeners, fillers such as glass or plastic fibers / beads, metals, metal oxides, and metal nitrides, as well as additives such as leveling agents, thickeners, hydrophobic agents, and defoamers.

[0098] <Adhesive layer> The thickness of the adhesive layer in this invention is preferably 200 μm or less, more preferably 1 μm or more and 150 μm or less, and even more preferably 5 μm or more and 100 μm or less. This is because by keeping the thickness of the adhesive layer within this range, good adhesion to the resin film can be achieved before irradiation by the active energy line. Furthermore, the active energy line can be fully transmitted, allowing the curing reaction to proceed.

[0099] [Substrate] The substrate in this invention is a component that supports the adhesive layer. Preferably, the substrate has strength capable of conveying or protecting the resin film and heat resistance sufficient to withstand the annealing temperature of the resin film. Furthermore, the substrate preferably has physical properties suitable for processing corresponding to the intended use of the resin film; for example, it preferably exhibits excellent forming stability when the shape of the resin film changes during molding processing.

[0100] The substrate can be a substrate that transmits active energy lines or a substrate that does not transmit active energy lines, but in terms of the ability to peel off the adhesive film by irradiating the adhesive layer with active energy lines through the substrate, it is preferable to be a substrate that transmits active energy lines. As long as the active energy lines can be sufficiently transmitted, the total light transmittance of the substrate is not particularly limited, but it is preferably 80% or more, more preferably 85% or more, more preferably 90% or more, and particularly preferably 95% or more.

[0101] Examples of substrates include resin films, metal foils, paper, fabrics, and non-woven fabrics. Among these, resin films are preferred from the viewpoint of operability and permeability of active energy lines. Examples of resin films include: polyester-based resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PET), and polyethylene naphthalate (PET); polyolefin-based resin films such as polyethylene, polypropylene, and polymethylpentene; cyclic olefin-based resin films such as cyclic olefin polymers or polymers with a norbornene structure; fluoropolymer films such as polyvinyl fluoride, polyvinylidene fluoride, and polyfluoroethylene; polyamide-based resin films such as nylon 6 and nylon 6,6; polyamide-based resin films such as polyetherimide; and polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride / vinyl acetate copolymer, ethylene-vinyl acetate copolymer, and ethylene-vinyl alcohol. Vinyl polymer resin films such as vinyl alcohol copolymers, polyvinyl alcohol, and vinylon; cellulose resin films such as diacetyl cellulose, triacetyl cellulose, acetyl cellulose butyrate, and celluloid; acrylic resin films such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate; polyurethane resin films such as polyurethane film and polyether ether ether ketone film; polystyrene resin films; polycarbonate resin films; polymethylpentene films; and polyether ether ketone films. Among these, polyester resin films, acrylic resin films, and polycarbonate resin films are preferred in terms of both processability with heat-assisted forming and appropriate tensile strength that allows for non-fracture peeling after processing; polyethylene terephthalate films are even more preferred.

[0102] The substrate can be a single-layer structure consisting of only one layer, or a laminated structure consisting of two or more laminated layers. When the substrate is composed of two or more laminated layers, the layers can be the same or different.

[0103] To improve adhesion to the adhesive layer, the substrate may have an easy-adhesion layer on its surface, or it may undergo surface treatment. Examples of surface treatments include: surface roughening treatment using sandblasting or solvent treatment, corona discharge treatment, chromic acid treatment, flame treatment, hot air treatment, ozone treatment, ultraviolet irradiation treatment, and other oxidation treatments.

[0104] When the resin film is subjected to thermal forming processes such as shaping, bending, or three-dimensional forming, the surface of the resin film can be protected during the forming process by integrally forming the resin film and the adhesive film by attaching the adhesive film of the present invention to the resin film.

[0105] The stress at 100% elongation of the substrate at 150°C is not particularly limited and can be appropriately set according to the physical properties required by the adhesive film. From the viewpoint of the processability of the adhesive film, the stress at 100% elongation at 150°C is preferably 5 MPa or more and 60 MPa or less, more preferably 10 MPa or more and 50 MPa or less, more preferably 15 MPa or more and 45 MPa or less, and even more preferably 15 MPa or more and 40 MPa or less. If it is within the range, when the resin film is thermoformed while being bonded to the adhesive film, the adhesive film can easily follow the processing shape, preventing processing defects such as wrinkles, and exhibiting excellent forming stability.

[0106] The elongation at break at 150°C of the substrate is not particularly limited and can be appropriately set according to the physical properties required by the adhesive film. However, from the viewpoint of the processability of the adhesive film, the elongation at break at 150°C is preferably 500% or less, more preferably 100% or more and 400% or less, further preferably 120% or more and 300% or less, and particularly preferably 120% or more and 250% or less. When the resin film is thermoformed while it is bonded to the adhesive film, the adhesive film easily follows the processing shape of the resin film. In addition, deformation or breakage of the substrate caused by heat application can be prevented.

[0107] The stress at 100% elongation and the elongation at break at 150°C of the substrate can be determined using the following methods. First, a rectangle 150 mm long × 10 mm wide is cut from the substrate and used as a sample. A tensile testing machine (Tensilon RTG-1310 manufactured by A&D Corporation) is used, with the initial chuck distance set to 50 mm and the tensile speed set to 200 mm / min. The sample is placed in a preheated temperature chamber at 150°C, and the tensile test is performed after 90 seconds of preheating. The load applied to the sample at 100% elongation (with a chuck distance of 100 mm) is read and divided by the sample's cross-sectional area before the test (substrate thickness × 10 mm). The resulting value is taken as the stress at 100% elongation. Additionally, the elongation at break is taken as the elongation at break. Each measurement is performed five times, and the average value is used for evaluation.

[0108] The thermal shrinkage rate of the substrate at 150°C is preferably 25% or less, more preferably 15% or less, and even more preferably 5% or less. By ensuring that the thermal shrinkage rate of the substrate is within this range, when the resin film is annealed with the adhesive film attached, the substrate is less likely to shrink due to the temperature of the annealing environment, thus preventing the adhesive film from peeling off from the resin film before irradiation by the active energy line. Furthermore, it prevents the removal of residual stress or the elimination of strain in the resin film from being hindered by the thermal shrinkage of the substrate.

[0109] The heat shrinkage rate of the substrate at 150°C was determined as follows. First, markings for measuring the distance between the markings (L0 and T0) were made along the length and width directions of a square substrate cut out to be 120 mm × 120 mm, and the distance between the markings was measured. Second, the substrate was left to stand at 150°C for 30 minutes, and the distance between the markings (L and T) in the length and width directions was measured again at 23°C and 50%RH. The heat shrinkage rate was calculated according to the following formula. Thermal shrinkage rate along length = [(L0 - L) / L0] × 100 (unit: %) Thermal shrinkage rate in the width direction = [(T0-T) / T0] × 100 (unit: %) (L0 and T0: Distance between markings before the test (mm)) L and T: Distance between marks after heating (mm)

[0110] The thickness of the substrate is not particularly limited, but it is preferably 12 μm or more and 250 μm or less, more preferably 25 μm or more and 100 μm or less, and even more preferably 38 μm or more and 75 μm or less. By keeping the thickness of the substrate within the aforementioned range, the adherend can exhibit good peel resistance or conformability under high-temperature environments such as annealing treatment, as well as good peelability after irradiation with active energy lines.

[0111] [Release pad] The adhesive film of the present invention may have a release liner on the side of the adhesive layer opposite to the substrate. The release liner is not particularly limited, but examples include: release liners on at least one side of substrates such as polyethylene film, polypropylene film, polyester film, paper, nonwoven fabric, cloth, foamed sheets, metal foil, and laminates thereof, which have undergone release treatments such as silicone-based treatment, long-chain alkyl-based treatment, or fluorine-based treatment to improve the peelability of the self-adhesive.

[0112] [Adhesive membrane] The adhesive film of the present invention only needs to have an adhesive layer on at least one side of the substrate. It can be a single-sided adhesive film with an adhesive layer on one side of the substrate, or a double-sided adhesive film with adhesive layers on both sides of the substrate. From the viewpoint of functioning as an engineering film or a protective film, it is preferred to be a single-sided adhesive film with an adhesive layer on one side of the substrate. In the case that the adhesive film of the present invention is a double-sided adhesive film, it is sufficient to have an adhesive layer with a specified tanδ on at least one side of the substrate, or an adhesive layer with a specified tanδ on both sides of the substrate.

[0113] The thickness of the adhesive film of the present invention is not particularly limited, but from the viewpoint of maintaining stable processability in the annealing process or thermoforming process, an appropriate thickness is preferred. Specifically, the total thickness of the adhesive film of the present invention is preferably 200 μm or less, and more preferably 175 μm or less. Furthermore, the lower limit of the total thickness of the adhesive film of the present invention is not particularly limited, but is preferably 40 μm or more, and more preferably 50 μm or more. Furthermore, the total thickness of the adhesive film is assumed to exclude the thickness of the release liner.

[0114] In order to enable the active energy lines to pass through sufficiently, the adhesive film of the present invention, as well as each layer of the adhesive layer and the substrate constituting the adhesive film, is preferably transparent. However, if the resin film bonded to the adhesive film is transparent and the active energy lines can be irradiated from the resin film side to the adhesive film, the substrate of the adhesive film may be transparent or not.

[0115] [Method for manufacturing adhesive films] The adhesive film of the present invention can be manufactured, for example, by applying an adhesive composition for forming an adhesive layer to at least one side of a substrate using a coater, roller coater, gravure printing coater, reverse coater, spray coater, air knife coater, die coater, etc., and then drying it.

[0116] In addition, the adhesive film of the present invention can be manufactured by the following transfer method: the adhesive composition is applied to the surface of the release liner using a doctor blade coater, roller coater or die coater, etc., and dried to form an adhesive layer, and then the adhesive layer is bonded to at least one side of the substrate.

[0117] When applying the adhesive composition, to achieve good workability, the viscosity is adjusted by dissolving or dispersing the adhesive composition in an organic solvent. Examples of solvents include toluene, xylene, ethyl acetate, butyl acetate, acetone, methyl ethyl ketone, and hexane. Furthermore, in the case of preparing an aqueous adhesive, water or a water-based solvent can be used.

[0118] The adhesive layer is preferably formed by drying the adhesive composition film at 50°C to 140°C for 30 seconds to 10 minutes. Alternatively, to promote the curing reaction after drying, the adhesive film can be further aged at 30°C to 50°C after drying.

[0119] [use] The adhesive film of the present invention is preferably used as an engineering film for temporarily fixing and transporting resin films or as a surface protective film for protecting the surface of resin films. Resin films typically require annealing, but for resin films that do not require annealing, the adhesive film of the present invention can also be used for transporting or surface protection purposes.

[0120] The resin constituting the resin film is not particularly limited and can be selected appropriately according to the intended use or function of the resin film. Examples include: polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate; polyolefin resins such as polyethylene (PE), polypropylene (PP), polybutene-1, poly-4-methylpentene, and ethylene-propylene copolymer; acrylic resins; polycarbonate, polyamide, polyimide, triacetyl cellulose (TAC), and cyclic olefin polymers. In the laminate, the resin film is preferably before annealing, but it can also be after annealing.

[0121] The glass transfer temperature of the resin film is not particularly limited as long as it falls within the temperature range described later for annealing, and can be appropriately set according to the type of resin. Furthermore, other physical properties of the resin film are also not particularly limited and can be appropriately set according to the type of resin.

[0122] Examples of resin films include industrial films used in applications such as display components, electronic components, and automotive components. Preferably, the resin film is an optical film because it allows for surface protection and transport via the bonded adhesive film, and annealing treatment achieves the high dimensional accuracy or optical performance required for optical films. Examples of optical films include polarizing films, retardation films, anti-reflective films, antiglare films, ultraviolet absorption films, infrared absorption films, optical compensation films, brightness enhancement films, diffusers, or prisms.

[0123] Furthermore, the adhesive film of the present invention can be preferably used as an engineering film or surface protection film for bonding with a resin film as described above, but it is not limited thereto, and can also be used as an engineering film or surface protection film for components other than resin films.

[0124] [How to use adhesive film] As an example of the method of using the adhesive film of the present invention, the following method of using the adhesive film can be listed, which sequentially includes: a step of bonding a resin film to the adhesive layer of the adhesive film of the present invention to obtain a laminate; a step of annealing the resin film of the laminate; and a step of irradiating the laminate after the annealing step with an active energy line to peel the adhesive film off from the resin film.

[0125] In the laminated body, it is preferable that the resin film is directly bonded to the adhesive layer.

[0126] The annealing environment of the resin film can be appropriately set according to the type or material of the resin film, and can be set to a temperature of 70°C or higher, preferably 70°C or higher and 350°C or lower, more preferably 70°C or higher and 150°C or lower, and even more preferably 70°C or higher and 100°C or lower. Furthermore, as long as the strain of the resin film can be eliminated, the annealing time is not particularly limited, and can be set to 5 minutes or more and 1 hour or less, preferably 10 minutes or more and 40 minutes or less.

[0127] When irradiating an adhesive layer of a resin film bonded to an adhesive film with active energy lines, the irradiation can be performed from the resin film side of the laminate or from the side opposite to the resin film.

[0128] Furthermore, the irradiation conditions for irradiating the active energy lines can be appropriately set according to the composition of the adhesive layer, for example, preferably an illuminance of 50 mW / cm² or more and 2000 mW / cm² or less, and a light intensity of 50 mJ / cm² or more and 3000 mJ / cm² or less. The light source can be appropriately selected according to the type of active energy lines.

[0129] 2. Laminated body The laminate of the present invention has an adhesive film as described in item "1. Adhesive film" and a resin film disposed on the adhesive layer of the adhesive film.

[0130] Figure 2 is a schematic cross-sectional view showing an example of the laminate of the present invention, in which a resin film 11 is disposed on the adhesive layer 2 of the adhesive film 10. In the laminate, the resin film is disposed in direct contact (adhered to the adhesive layer) with the adhesive layer of the adhesive film.

[0131] In the laminate of the present invention, the adhesive film bonded to the resin film has an adhesive layer. This adhesive layer has a temperature range within which the loss tangent (tanδ) is 0.8 or higher, within the range of 70°C to 100°C, and can be peeled off by irradiation with an active energy line. Therefore, the laminate can undergo resin film annealing while maintaining its original state, and can also be used for resin film surface protection or transport.

[0132] The details regarding the adhesive film in the laminate of the present invention are the same as those described in section "1. Adhesive Film [Application]", so they are omitted here. Furthermore, the resin film described in section "1. Adhesive Film" can be used as the resin film in the laminate of the present invention; however, for applications requiring high dimensional accuracy, the resin film is preferably an optical film.

[0133] 3. Manufacturing methods for optical films The method for manufacturing the optical film of the present invention is as follows, characterized by comprising the following steps: obtaining a laminate having an optical film on an adhesive layer of an adhesive film, wherein the adhesive film has the adhesive layer on one side of a substrate; annealing the optical film of the laminate; and irradiating the laminate after the annealing step with an active energy line to peel the optical film off from the adhesive film, wherein the adhesive layer has a temperature region in the range of 70°C to 100°C where the loss tangent tanδ is 0.8 or higher.

[0134] The adhesive film used in the manufacturing method of the optical film may be the adhesive film described in section "1. Adhesive Film". Details regarding the optical film and adhesive film in the manufacturing method of the optical film, the conditions of the annealing environment, the irradiation surface and irradiation conditions when irradiating the adhesive film with active energy lines, may be set to be the same as those already described in section "1. Adhesive Film".

[0135] This invention is not limited to the embodiments described herein. The embodiments are illustrative, and any manner having a structure substantially the same as the technical concept described in the claims of this invention and performing the same effect is included within the technical scope of this invention. [Example]

[0136] The present invention will be described in more detail below by way of examples and comparative examples. Furthermore, the thermal shrinkage rates in the length and width directions of the polyethylene terephthalate films used in the examples and comparative examples were measured at 150°C according to the method described in section "1. Adhesive Film". The stress at 100% elongation and the elongation at break were measured at 150°C according to the method described in section "1. Adhesive Film".

[0137] [Adjustment Example 1] In a reaction vessel including a stirrer, reflux cooler, nitrogen inlet pipe, and thermometer, 100 parts by weight of ethyl acetate, 10 parts by weight of toluene, and 0.03 parts by weight of azobisisobutyronitrile (AIBN) were added. The mixture was stirred and heated to 95°C and then refluxed. 100 parts by weight of n-butyl acrylate, 38 parts by weight of methyl methacrylate, and 3.8 parts by weight of methacrylic acid were mixed and added dropwise over 2 hours. One hour after the addition was complete, 0.03 parts by weight of azobisisobutyronitrile (AIBN) and 4 parts by weight of toluene were added, and the reaction was allowed to proceed for 2 hours. The mixture was then filtered through a 200-mesh metal screen to obtain a solution of acrylic copolymer (A-1) with a weight average molecular weight of 380,000 (50% by mass of non-volatile components).

[0138] [Adjustment Example 2] In a reaction vessel including a stirrer, reflux cooler, nitrogen inlet pipe, and thermometer, 146 parts by weight of ethyl acetate, 15 parts by weight of toluene, and 0.04 parts by weight of azobisisobutyronitrile (AIBN) were added. The mixture was stirred and heated to 95°C and then refluxed. 100 parts by weight of methyl acrylate and 61 parts by weight of 2-ethylhexyl acrylate were mixed and added dropwise over 2 hours. One hour after the addition was complete, 0.04 parts by weight of azobisisobutyronitrile (AIBN) and 6 parts by weight of toluene were added, and the reaction was allowed to proceed for 2 hours. The mixture was then filtered through a 200-mesh metal screen to obtain a solution of acrylic copolymer (A-2) with a weight average molecular weight of 250,000 (50% by weight of non-volatile components).

[0139] [Comparison and Adjustment Example 1] In a reaction vessel including a stirrer, reflux cooler, nitrogen inlet pipe, and thermometer, 146 parts by weight of ethyl acetate, 15 parts by weight of toluene, and 0.04 parts by weight of azobisisobutyronitrile (AIBN) were added. The mixture was stirred and heated to 95°C and then refluxed. 100 parts by weight of methyl acrylate and 61 parts by weight of 2-ethylhexyl acrylate were mixed and added dropwise over 2 hours. One hour after the addition was complete, 0.04 parts by weight of azobisisobutyronitrile (AIBN) and 6 parts by weight of toluene were added, and the reaction was allowed to proceed for 2 hours. The mixture was then filtered through a 200-mesh metal screen to obtain a solution of acrylic copolymer (B-1) with a weight average molecular weight of 250,000 (50% by weight of non-volatile components).

[0140] [Comparison and Adjustment Example 2] In a reaction vessel including a stirrer, reflux cooler, nitrogen inlet pipe, and thermometer, 138 parts by weight of ethyl acetate, 14 parts by weight of toluene, and 0.04 parts by weight of azobisisobutyronitrile (AIBN) were added. The mixture was stirred and heated to 95°C and then refluxed. 100 parts by weight of n-butyl acrylate and 52 parts by weight of methyl acrylate were mixed and added dropwise over 2 hours. One hour after the addition was complete, 0.04 parts by weight of azobisisobutyronitrile (AIBN) and 6 parts by weight of toluene were added, and the reaction was allowed to proceed for 2 hours. The mixture was then filtered through a 200-mesh metal screen to obtain a solution of acrylic copolymer (B-2) with a weight average molecular weight of 150,000 (50% by weight of non-volatile components).

[0141] [Comparison and Adjustment Example 3] In a reaction vessel including a stirrer, reflux cooler, nitrogen inlet pipe, and thermometer, 82 parts by weight of 2-ethylhexyl acrylate, 14 parts by weight of methyl acrylate, 4 parts by weight of 2-hydroxyethyl acrylate, and 200 parts by weight of ethyl acetate were added. The mixture was stirred at 72°C for 4 hours, and then at 75°C for 5 hours. Next, 2 parts by weight (0.1% by weight of solids) of azobisisobutyronitrile (AIBN) solution pre-dissolved in ethyl acetate were added to the initial mixture. The mixture was stirred at 72°C for 4 hours, and then at 75°C for 5 hours. Finally, ethyl acetate was added to the initial mixture and mixed thoroughly. The mixture was then filtered through a 200-mesh metal mesh to obtain an acrylic copolymer (B-3) solution with a weight average molecular weight of 880,000 (34% by weight of non-volatile components).

[0142] Synthesis of active energy line polymerizable compound (C) In a reaction vessel including a stirrer, reflux cooler, nitrogen inlet pipe, and thermometer, 7.1 parts by weight of isophorone diisocyanate, 100 parts by weight of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (hydroxyl value 48 mgKOH / g), 0.06 parts by weight of 2,6-di-tert-butylcresol as a polymerization inhibitor, and 0.02 parts by weight of dibutyltin dilaurate as a reaction catalyst were added. The reaction was carried out at 60°C, and the reaction was terminated when the residual isocyanate groups reached below 0.3%, yielding an vinyl unsaturated compound (urethane (meth)acrylate) as an active energy linear polymerizable compound. The obtained vinyl unsaturated compound has 10 unsaturated groups per molecule.

[0143] [Example 1] 100 parts by weight of the acrylic copolymer (A-1) solution, 50 parts by weight of the active energy linear polymerizable compound (C), 1 part by weight of 1-hydroxycyclohexylphenyl ketone (manufactured by Omnirad 184: IGM Resins BV) as photopolymerization initiator (D), and an adduct of toluene diisocyanate and trimethylolpropane with a gel fraction of 25% by weight (BURNOCK D-40 manufactured by DIC Corporation, hereinafter referred to as "D-40") as crosslinking agent (E) were placed in a light-proof container equipped with a stirrer and stirred for 2 hours to dissolve, thereby obtaining the adhesive composition (P-1).

[0144] The obtained adhesive composition (P-1) was applied to the release treatment surface of the release liner (a 50 μm thick polyethylene terephthalate film with a single-sided release treatment) with a dried adhesive layer thickness of 50 μm, and dried at 85°C for 5 minutes to form an adhesive layer with a thickness of 50 μm.

[0145] Secondly, at 23°C, the 50 μm thick adhesive layer is attached to one side of a 75 μm thick polyethylene terephthalate film (with a length heat shrinkage rate of 1.5%, a width heat shrinkage rate of 0.9%, a stress of 20 MPa at 100% elongation in the length direction, and a length break point elongation of 235%), and then laminated from the upper surface of the release liner using a roller with a linear pressure of 5 kg / cm.

[0146] Then, it was cured at 40°C for 48 hours to obtain an adhesive film with a thickness of 125 μm (T-1).

[0147] [Example 2] The obtained adhesive composition (P-1) was applied to the release treatment surface of the release liner (a 50 μm thick polyethylene terephthalate film with a single-sided release treatment) with a dried adhesive layer thickness of 25 μm, and dried at 85°C for 5 minutes to create an adhesive layer with a thickness of 25 μm.

[0148] Secondly, at 23°C, the 25 μm thick adhesive layer is attached to one side of a 75 μm thick polyethylene terephthalate film (with a length direction heat shrinkage rate of 1.5%, a width direction heat shrinkage rate of 0.9%, a stress of 20 MPa at 100% elongation in the length direction, and a length direction breakage elongation rate of 235%), and then laminated from the upper surface of the release liner using a roller with a linear pressure of 5 kg / cm.

[0149] Then, it was cured at 40°C for 48 hours to obtain an adhesive film with a thickness of 100 μm (T-2).

[0150] [Example 3] The acrylic copolymer (A-1) solution of Example 1 was replaced with the acrylic copolymer (A-2) solution, and the crosslinking agent (E) was prepared in such a way that the gel fraction was 15% by mass. Otherwise, the same procedure as in Example 1 was followed to obtain the adhesive composition (P-2).

[0151] The obtained adhesive composition (P-2) was applied to the release treatment surface of the release liner (a 50 μm thick polyethylene terephthalate film with a single-sided release treatment) with a dried adhesive layer thickness of 50 μm, and dried at 85°C for 5 minutes to create an adhesive layer with a thickness of 50 μm.

[0152] Secondly, at 23°C, the 50 μm thick adhesive layer is attached to one side of a 75 μm thick polyethylene terephthalate film (with a length heat shrinkage rate of 1.5%, a width heat shrinkage rate of 0.9%, a stress of 20 MPa at 100% elongation in the length direction, and a length break point elongation of 235%), and then laminated from the upper surface of the release liner using a roller with a linear pressure of 5 kg / cm.

[0153] Then, it was cured at 40°C for 48 hours to obtain an adhesive film with a thickness of 125 μm (T-3).

[0154] [Example 4] Crosslinking agent (E) was formulated in the acrylic copolymer (A-1) solution of Example 1 with a gel fraction of 35% by mass. Otherwise, the same procedure as in Example 1 was followed to obtain adhesive composition (P-3).

[0155] The obtained adhesive composition (P-3) was applied to the release treatment surface of the release liner (a 50 μm thick polyethylene terephthalate film with a single-sided release treatment) with a dried adhesive layer thickness of 50 μm, and dried at 85°C for 5 minutes to create an adhesive layer with a thickness of 50 μm.

[0156] Secondly, at 23°C, the 50 μm thick adhesive layer is attached to one side of a 75 μm thick polyethylene terephthalate film (with a length heat shrinkage rate of 1.5%, a width heat shrinkage rate of 0.9%, a stress of 20 MPa at 100% elongation in the length direction, and a length break point elongation of 235%), and then laminated from the upper surface of the release liner using a roller with a linear pressure of 5 kg / cm.

[0157] Then, it was cured at 40°C for 48 hours to obtain an adhesive film with a thickness of 125 μm (T-4).

[0158] [Example 5] The crosslinking agent (E) was formulated in the acrylic copolymer (A-1) solution of Example 1 with a gel fraction of 40% by mass. Otherwise, the same procedure as in Example 1 was followed to obtain the adhesive composition (P-4).

[0159] The obtained adhesive composition (P-4) was applied to the release treatment surface of the release liner (a 50 μm thick polyethylene terephthalate film with a single-sided release treatment) with a dried adhesive layer thickness of 50 μm, and dried at 85°C for 5 minutes to create an adhesive layer with a thickness of 50 μm.

[0160] Secondly, at 23°C, the 50 μm thick adhesive layer is attached to one side of a 75 μm thick polyethylene terephthalate film (with a length heat shrinkage rate of 1.5%, a width heat shrinkage rate of 0.9%, a stress of 20 MPa at 100% elongation in the length direction, and a length break point elongation of 235%), and then laminated from the upper surface of the release liner using a roller with a linear pressure of 5 kg / cm.

[0161] Then, it was cured at 40°C for 48 hours to obtain an adhesive film with a thickness of 125 μm (T-5).

[0162] [Example 6] The adhesive composition (P-1) was applied to the release liner (a 50 μm thick polyethylene terephthalate film with a single-sided release treatment) with a dried adhesive layer thickness of 50 μm, and dried at 85°C for 5 minutes to create an adhesive layer with a thickness of 50 μm.

[0163] Secondly, at 23°C, the 50 μm thick adhesive layer is attached to one side of a 75 μm thick polyethylene terephthalate film (with a length direction heat shrinkage rate of 1.5%, a width direction heat shrinkage rate of 0.9%, a stress of 37 MPa at 100% elongation in the length direction, and a length direction breakage elongation rate of 231%), and then laminated from the upper surface of the release liner using a roller with a linear pressure of 5 kg / cm.

[0164] Then, it was cured at 40°C for 48 hours to obtain an adhesive film with a thickness of 125 μm (T-6).

[0165] [Example 7] The adhesive composition (P-1) was applied to the release liner (a 50 μm thick polyethylene terephthalate film with a single-sided release treatment) with a dried adhesive layer thickness of 50 μm, and dried at 85°C for 5 minutes to create an adhesive layer with a thickness of 50 μm.

[0166] Secondly, at 23°C, an adhesive layer of 50 μm thickness is applied to one side of a polyethylene terephthalate film (with a thermal shrinkage rate of 0.4% in the length direction, 0.0% in the width direction, a stress of 70 MPa at 100% elongation in the length direction, and an elongation at the break point in the length direction of 266%), and then laminated from the upper surface of the release liner using a roller with a linear pressure of 5 kg / cm.

[0167] Then, it was cured at 40°C for 48 hours to obtain an adhesive film with a thickness of 100 μm (T-7).

[0168] [Comparative Example 1] The acrylic copolymer (A-1) solution of Example 1 was replaced with the acrylic copolymer (B-1) solution, and the crosslinking agent (E) was prepared in such a way that the gel fraction was 30% by mass. Otherwise, the same procedure as in Example 1 was followed to obtain the adhesive composition (Q-1).

[0169] The obtained adhesive composition (Q-1) was applied to the release treatment surface of the release liner (a polyethylene terephthalate film with a thickness of 50 μm after single-sided release treatment) with the dried adhesive layer thickness of 50 μm, and dried at 85°C for 5 minutes to form an adhesive layer with a thickness of 50 μm.

[0170] Secondly, at 23°C, the 50 μm thick adhesive layer is attached to one side of a 75 μm thick polyethylene terephthalate film (with a length heat shrinkage rate of 1.5%, a width heat shrinkage rate of 0.9%, a stress of 20 MPa at 100% elongation in the length direction, and a length break point elongation of 235%), and then laminated from the upper surface of the release liner using a roller with a linear pressure of 5 kg / cm.

[0171] Then, it was cured at 40°C for 48 hours to obtain an adhesive film (U-1) with a thickness of 125 μm.

[0172] [Comparative Example 2] The acrylic copolymer (A-1) solution of Example 1 was replaced with the acrylic copolymer (B-2) solution, and the crosslinking agent (E) was prepared in such a way that the gel fraction was 50% by mass. Otherwise, the same procedure as in Example 1 was followed to obtain the adhesive composition (Q-2).

[0173] The obtained adhesive composition (Q-2) was applied to the release treatment surface of the release liner (a 50 μm thick polyethylene terephthalate film with a single-sided release treatment) with a dried adhesive layer thickness of 50 μm, and dried at 85°C for 5 minutes to create an adhesive layer with a thickness of 50 μm.

[0174] Secondly, at 23°C, the 50 μm thick adhesive layer is attached to one side of a 75 μm thick polyethylene terephthalate film (with a length heat shrinkage rate of 1.5%, a width heat shrinkage rate of 0.9%, a stress of 20 MPa at 100% elongation in the length direction, and a length break point elongation of 235%), and then laminated from the upper surface of the release liner using a roller with a linear pressure of 5 kg / cm.

[0175] Then, it was cured at 40°C for 48 hours to obtain an adhesive film (U-2) with a thickness of 125 μm.

[0176] [Comparative Example 3] In the acrylic copolymer (B-3) solution, D-40 was formulated with a gel fraction of 80% by mass to obtain adhesive composition (Q-3). Furthermore, adhesive composition (Q-3) does not contain any active energy line curing compounds, and its adhesion and peel strength are the same before and after active energy line irradiation.

[0177] The obtained adhesive composition (Q-3) was applied to the release treatment surface of the release liner (a 50 μm thick polyethylene terephthalate film with a single-sided release treatment) with a dried adhesive layer thickness of 5 μm, and dried at 85°C for 5 minutes to create an adhesive layer with a thickness of 5 μm.

[0178] Secondly, at 23°C, a 5 μm thick adhesive layer is attached to one side of a 75 μm thick polyethylene terephthalate film (with a length direction heat shrinkage rate of 1.5%, a width direction heat shrinkage rate of 0.9%, a stress of 20 MPa at 100% elongation in the length direction, and a length direction breakage elongation rate of 235%), and then laminated from the upper surface of the release liner using a roller with a linear pressure of 5 kg / cm.

[0179] Then, it was cured at 40°C for 48 hours to obtain an adhesive film (U-3) with a thickness of 55 μm.

[0180] [Comparative Example 4] The adhesive composition (Q-3) was applied to the release treatment side of the release liner (a 50 μm thick polyethylene terephthalate film with a single-sided release treatment) to a thickness of 5 μm after drying, and dried at 85°C for 5 minutes to create an adhesive layer with a thickness of 5 μm.

[0181] Secondly, at 23°C, a 5 μm thick adhesive layer is attached to one side of a 50 μm thick polyethylene terephthalate film (with a length direction heat shrinkage rate of 0.4%, a width direction heat shrinkage rate of 0.0%, a stress of 37 MPa at 100% elongation in the length direction, and a length direction breakage elongation rate of 266%), and then laminated from the upper surface of the release liner using a roller with a linear pressure of 5 kg / cm.

[0182] Then, it was cured at 40°C for 48 hours to obtain an adhesive film (U-4) with a thickness of 55 μm.

[0183] <Evaluation> The adhesive films obtained in the Examples and Comparative Examples were evaluated as follows. The results of each evaluation are shown in Tables 1 and 2. Furthermore, the optical film (resin film) used in the 180° peel adhesion and curling tests in the following evaluations was an optical polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name "Lumirror 100U46", glass transfer temperature 120°C, thickness 100 μm). The optical film (resin film) used in the thermoforming tests was an optical acrylic resin film (manufactured by Mitsubishi Chemical Corporation, product name "Acryplen HBA007P", glass transfer temperature 92°C, thickness 75 μm).

[0184] [Method for determining the loss tangent (tanδ) of the adhesive layer] The obtained adhesive components were applied to the surface of the release liner and heated in an oven at 85°C for 5 minutes to create an adhesive layer with a thickness of 50 μm. These adhesive layers were then overlapped to create an adhesive layer with a thickness of 2 mm. Next, the adhesive layer was cut into circles with a diameter of 8 mm and used as test pieces. Then, using a viscoelasticity testing machine (manufactured by Rheometrics, trade name: Ares 2KSTD), the test pieces were clamped between the measuring sections (parallel discs) of the machine. Under shear stress measurement mode, at a heating rate of 2.0°C / min and a frequency of 1 Hz, the storage elastic coefficient (G') and loss elastic coefficient (G'') were measured within a temperature range of -40°C to 150°C. The loss tangent (tanδ) was calculated from G' and G''. The results are shown in the table below.

[0185] [180° peel adhesion of adhesive film] The 180° peel adhesion of the adhesive films of the examples and comparative examples was measured using the following method. The results are shown in Table 2. (1) The adhesive film is applied to the optical film by pressing it with a 2 kg roller once at 23°C and 50%RH. (2) After standing for 1 hour at 23°C and 50%RH, the strength of the adhesive film when peeled off from the optical film in the 180-degree direction at a tensile speed of 300 mm / min at 23°C and 50%RH is measured (unit: N / 25 mm).

[0186] [Peelability: 180° peel adhesion of the adhesive film after irradiation with active energy lines] The 180° peel adhesion of the adhesive films of the Examples and Comparative Examples after irradiation with active energy lines was measured using the following method. The results are shown in Table 2. (1) The adhesive film is applied to the optical film by pressing it with a 2 kg roller once at 23°C and 50%RH. (2) After standing at 23℃ and 50%RH for 1 hour, the product was heated at 90℃ for 20 minutes and then annealed. A 90 mW electrodeless lamp from Heraeus was used to irradiate the product with ultraviolet light from a height of 8 cm at a transmission speed of 6.5 m / min (cumulative irradiation dose of 180 mJ / cm2). (3) The strength of the adhesive film when it is peeled off from the optical film in a 180-degree direction at a tensile speed of 300 mm / min at 23°C and 50%RH is measured (unit: N / 25 mm). (4) Visual evaluation of peelability. The evaluation criteria are as follows. (Benchmark) ◎: Peel off the adhesive film without deforming or damaging the optical film. ○: Although it has resistance to peeling, it peels off the adhesive film without deforming or damaging the optical film. ×: Cannot be peeled off, optical film damaged. -: Since it does not contain compounds that harden with active energy lines, no changes in physical properties caused by irradiation with active energy lines have been identified. (5) Visually evaluate residual paste. The evaluation criteria are as follows. (Benchmark) ○: No adhesive residue is present. ×: Adhesive residue remains on the optical film. -: Since it does not contain compounds that harden with active energy lines, no changes in physical properties caused by irradiation with active energy lines have been identified.

[0187] [The property of not hindering the relief of residual stress or strain in the resin film during annealing: curling test] To evaluate the performance of the resin film in eliminating residual stress or strain during annealing, a curling test was conducted on optical films with adhesive films of the examples and comparative examples bonded together using the following method. Figures 3(a) to 3(c) are explanatory diagrams illustrating the curling test method. The results are shown in Table 2. (1) At 23℃ and 50%RH, the adhesive layer of the adhesive film was attached to one side of the optical film and cut into 150 mm squares to make sample 20 (laminated body 20). (2) Place the sample 20 with the optical film side surface 20a facing down on the horizontal surface 30. At 23°C and 50%RH, measure the floating distance (L1) of the four corners of the sample 20 from the horizontal surface 30 (see Figure 3(a)). (3) Next, the sample 20 is heated in an oven at 90°C for 20 minutes and the optical film is annealed. Then it is placed at room temperature and the annealed sample 20' is restored to room temperature. (4) The annealed sample 20' is placed on a horizontal surface 30 with the optical film side surface 20'a facing down. At 23°C and 50%RH, the floating distance (L2) of the four corners of the sample 20' from the horizontal surface 30 is measured (see Figure 3(b)). Furthermore, as shown in Figure 3(c), when the annealed sample 20' is bent with the optical film side surface 20'a as the inner surface, the adhesive film side surface 20'b of the sample 20' is arranged to be in contact with the horizontal surface 30. The length from the horizontal surface 30 to the four corners of the sample 20' is taken as the floating distance (L2), and expressed as a negative value. (5) Calculate the buoyancy distance Δ(L) of each angle using the following formula. The buoyancy distance Δ(L) = buoyancy distance after heating (L2) - buoyancy distance before heating (L1) Furthermore, (6) Calculate the average value of each Δ(L) at the four corners, and use it as the floating distance aveΔ(L) of the adhered object. Deformation adaptability is judged based on the floating distance ave(L) of the adhered object. Deformation adaptability is judged according to the following criteria. For the reasons described below, the smaller the absolute value of the floating distance aveΔ(L), the more the residual stress or strain of the resin film is eliminated. (Benchmark) ◎: -5 mm < buoyancy distance aveΔ(L) < 5 mm ○: -9 mm < float distance aveΔ(L) ≦ -5 mm, 5 mm ≦ float distance aveΔ(L) < 9 mm ×: Buoyancy distance aveΔ(L) ≦ -9 mm, 9 mm ≦ buoyancy distance aveΔ(L)

[0188] [Forming Stability: Thermoforming Test] To evaluate the ease of shape tracking when thermoforming optical films into a curved shape, thermoforming tests were conducted on optical films with adhesive films from the examples and comparative examples bonded together using the following method. Figure 4 is an explanatory diagram illustrating the thermoforming test method. The results are shown in Table 2. (1) A spring 42 is placed at the center of a rectangular metal plate 41 with a thickness of 8 mm and dimensions of 50 mm × 130 mm, and an iron ball 43 with a diameter of 20 mm is fixed on the spring 42. Furthermore, a metal cylinder 44 is placed at the center of the metal plate 41 with the spring 42 located inside. A rectangular metal plate 45 with a diameter of 25 mm and a thickness of 4 mm and dimensions of 50 mm × 130 mm is placed on the cylinder 44 with the spring 42 and the iron ball 43 protruding from the hole in the metal plate 45 (see Figure 4). (2) The adhesive layer of the adhesive film is attached to one side of the optical film and cut into 50 mm × 60 mm pieces to form sample 46 (laminated body 46). A rectangular metal plate 47 with a diameter of 25 mm and a thickness of 25 mm and 50 mm × 100 mm is formed by opening a hole in the center and fixing sample 46 to cover the hole in the center. At this time, the optical film surface 46a of sample 46 is fixed to the metal plate 47 in contact with it. (See Figure 5). (3) The metal plate 47, on which the sample 46 is fixed, is overlapped on the metal plate 45. At this time, the holes in the center of the metal plate 45 and the center of the metal plate 47 are aligned. Then, a 2 kg weight 48 is placed on the metal plate 47 to fix it in place (see Figure 6). Here, the iron ball 43 is pressed into the sample 46 from the substrate surface 46b, thereby stretching the sample 46 into a bent shape. At this time, the spring 42 is adjusted so that a force of 12 N is applied to the sample 46 by the iron ball 43. The entire test fixture manufactured in the above steps is used as the test fixture 40. (4) Heat the test fixture 40 in an oven at 90°C for 20 minutes to conduct a thermoforming test. (5) Remove the test fixture 40 from the oven after the thermoforming test and place it at room temperature to allow the sample 46 to return to room temperature. Visually observe the appearance of the sample 46 and evaluate its forming stability according to the following criteria. The less wrinkles appear in the stretched sample 46 due to thermoforming, the better its forming stability. (Benchmark) ○: The sample after the test has no wrinkles, or there are wrinkles around the periphery of the stretched and bent part, but no wrinkles in the stretched and bent part. ×: Wrinkles exist in the stretched and bent portion.

[0189] [Table 1] Adhesive composition P-1 P-2 P-3 P-4 Q-1 Q-2 Q-3 The temperature range where tanδ becomes 0.8 or higher is within the range of 70℃ to 100℃. Above 78℃ Above 70℃ (Above 53℃) Above 85℃ Above 90℃ none none none tanδ@90℃ 0.99 1.07 0.87 0.80 0.69 0.32 0.11

[0190] [Table 2] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Adhesive membrane T-1 T-2 T-3 T-4 T-5 T-6 T-7 Adhesive layer Adhesive composition P-1 P-1 P-2 P-3 P-4 P-1 P-1 Thickness [μm] 50 25 50 50 50 50 50 Gel fraction [%] 25 25 15 35 40 25 25 tanδ90℃ 0.99 0.99 1.07 0.87 0.80 0.99 0.99 Substrate layer Stress at 100% elongation [MPa] 20 20 20 20 20 37 70 Before irradiation with active energy lines 180° peel adhesion [N / 25mm] twenty three 20 15 twenty two twenty three twenty three 17 After irradiation with active energy lines 180° peel adhesion [N / 25mm] 0.24 0.15 0.09 0.28 0.26 0.24 0.40 Easy to peel ◎ ◎ ◎ ◎ ◎ ◎ ◎ Residual paste 〇 〇 〇 〇 〇 〇 〇 Annealing does not impede the ability of the resin film to relieve residual stress or strain. The buoyancy distance aveΔ(L) [mm] during the curling test 1.8 1.6 -0.1 7.3 8.0 1.8 -0.6 Deformation adaptability ◎ ◎ ◎ 〇 〇 ◎ ◎ Forming stability Thermoforming test Proper processing 〇 〇 〇 〇 〇 〇 ×

[0191] [Table 3] Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4 Adhesive membrane U-1 U-2 U-3 U-4 Adhesive layer Adhesive composition Q-1 Q-2 Q-3 Q-3 Thickness [μm] 50 50 5 5 Gel fraction [%] 30 50 80 80 tanδ90℃ 0.69 0.32 0.11 0.11 Substrate layer Stress at 100% elongation [MPa] 20 20 20 70 Before irradiation with active energy lines 180° peel adhesion [N / 25mm] 12 14 1 1 After irradiation with active energy lines 180° peel adhesion [N / 25mm] 0.09 0.15 - Easy to peel ◎ ◎ - - Residual paste 〇 〇 - - Annealing does not impede the ability of the resin film to relieve residual stress or strain. The buoyancy distance aveΔ(L) [mm] during the curling test 12.8 18.4 22.6 -9.0 Deformation adaptability × × × × Forming stability Thermoforming test Proper processing 〇 〇 〇 ×

[0192] According to the results, the adhesive films of Examples 1 to 7 suppressed the curling of the optical film in the curling test, while the adhesive films of Comparative Examples 1 to 4 showed greater curling of the optical film in the curling test. These results indicate that the adhesive film of the present invention does not easily hinder the elimination of residual stress or strain of the resin film by annealing at a temperature of about 100°C.

[0193] The relationship between the results of the curling test and the performance of the resin film in eliminating residual stress or strain during annealing is as follows. Specifically, when the resin film is annealed with an adhesive film attached, the resin film (optical film) undergoes thermal shrinkage while maintaining the bonded state. At this time, the adhesive layer of the adhesive film bonded to the resin film experiences strain. However, it is speculated that the adhesive films of Examples 1 to 7, by ensuring the adhesive layer meets the specified physical properties (tanδ), exhibit softness and fluidity in the annealing environment, thus dissipating the strain generated within the layer. As a result, curling in the shrinkage direction is less likely, therefore, it is speculated that the absolute value of aveΔ(L) decreases in the curling test. Since the adhesive layer, which can dissipate the strain generated within the layer, does not hinder the deformation of the resin film during annealing accompanied by the elimination of residual stress or strain, it can be said that even when the adhesive film and the resin film are bonded, the residual stress or strain of the resin film can be sufficiently eliminated. On the other hand, regarding the adhesive films of Comparative Examples 1 to 4, since the adhesive layer does not meet the specified physical properties, the strain generated in the adhesive layer is retained internally, causing curling in the shrinkage direction. Therefore, it is speculated that the absolute value of aveΔ(L) increases in the curling test. The adhesive layer, which retains the strain generated internally, restricts the deformation of the resin film during annealing, which is accompanied by the elimination of residual stress or strain. Therefore, it can be said that the residual stress or strain inside the resin film cannot be sufficiently eliminated.

[0194] In addition, the adhesive films of Examples 1 to 7 showed high adhesion before being irradiated with active energy lines. After the resin film (optical film) was annealed, the adhesion was greatly reduced by irradiating with active energy lines, and there was no residual paste, thus showing easy peelability.

[0195] In addition, in Examples 1 to 7, the adhesive films of Examples 1 to 6 fully followed the curved processing shape in the thermoforming test, suppressing the generation of wrinkles, and thus showing forming stability.

[0196] 1: Substrate 2: Adhesive layer 10: Adhesive membrane 11: Resin film 20: Laminated body (sample) 20': Sample after annealing 20a, 20'a, 20'b, 46a, 46b: Surface 30: Horizontal plane / surface 40: Test fixture 41, 45, 47: Metal plates 42: Spring 43: Iron Ball 44: Tube 46: Sample (Laminated Form) 48: Heavy objects L1, L2: Floating distance

Claims

1. An adhesive film, characterized in that it has a substrate and an adhesive layer disposed on at least one side of the substrate, the adhesive layer having a temperature region in the range of 70°C to 100°C where the loss tangent tanδ at a frequency of 1 Hz is 0.87 or higher, and being peelable by irradiation with an active energy line.

2. An adhesive film, characterized in that it has a substrate and an adhesive layer disposed on at least one side of the substrate, the adhesive layer being formed of an adhesive composition comprising an acrylic copolymer and an active energy line curing compound, and having a temperature region in which the loss tangent tanδ at a frequency of 1 Hz is 0.87 or higher within a temperature range of 70°C to 100°C.

3. The adhesive film as claimed in claim 1 or claim 2, wherein the gel fraction of the adhesive layer is less than 50% by mass.

4. The adhesive film as claimed in claim 1 or claim 2, wherein the substrate has a 100% elongation stress of 5 MPa to 60 MPa at 150°C.

5. The adhesive film as described in claim 1 or claim 2, for use in conjunction with a resin film.

6. The adhesive film as described in claim 1 or claim 2, for surface protection purposes.

7. The adhesive film as described in claim 1 or claim 2, for use in the conveying step.

8. A laminate, characterized in that it comprises: an adhesive film as described in claim 1 or claim 2, and a resin film disposed on the adhesive layer of the adhesive film.

9. The laminate as claimed in claim 8, wherein the resin film is an optical film.

10. A method of using an adhesive film, comprising, in sequence: The step of obtaining a laminate by bonding the adhesive layer of the adhesive film as described in claim 1 or claim 2 to the resin film; The steps include annealing the resin film of the laminate; and irradiating the laminate after the annealing step with active energy lines to peel the adhesive film off from the resin film.

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