Pressure-sensitive adhesive composition, pressure-sensitive adhesive layer, and

Abstract

To provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer which facilitates a re-sticking process when a decorative film is stuck to an adherend and hardly leaves an adhesive on the adherend when the decorative film stuck to the adherend is re-stuck, and to provide the pressure-sensitive adhesive layer.SOLUTION: A pressure sensitive adhesive composition comprising a (meth) acrylic copolymer and an epoxy-based crosslinking agent, wherein a loss tangent tan δ A at 23 °C. after aging is 1.00 or more and 1.68 or less, a difference between the loss tangent tan δ A at 23 °C. after aging and a loss tangent tan δ A ' at 80 °C. after aging is 1.25 or less, and a gel fraction after aging is 75% by mass or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive layer, and a decorative film including the pressure-sensitive adhesive layer. [Background technology]

[0002] In recent years, decorative films have been used instead of paint as a means of decorating the exterior of automobiles, in order to reduce solvent usage and shorten construction times in line with the reduction of CO2 emissions in line with SDGs. Polyvinyl chloride is widely used as the resin material for decorative films for the exterior of automobiles due to its high formability, durability, and economical efficiency. However, polyvinyl chloride is prone to deterioration over time, and measures to improve weather resistance are required.

[0003] Patent Document 1 describes a synthetic resin skin material having a skin layer containing a fluororesin-containing layer on the surface of a base layer containing a polyvinyl chloride resin and a colorant. Patent Document 2 describes a decorative film for vehicle exteriors that includes a resin layer containing at least one resin selected from polyurethane resin, polyolefin resin, and polyester resin. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-137612 [Patent Document 2] Japanese Patent Publication No. 2020-84106 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in synthetic resin skin materials that include a polyvinyl chloride resin-containing layer and a fluororesin-containing layer, although the weather resistance of the polyvinyl chloride is greatly improved, the fluororesin-containing layer is hard, so the synthetic resin skin material as a whole is also hard. Therefore, when applied to a curved surface such as the exterior of an automobile, the synthetic resin skin material may peel off and float over time.

[0006] Decorative films for vehicle exteriors that contain a resin layer containing a polyurethane resin or the like are more flexible than films that contain a fluororesin-containing layer, and therefore tend to be able to conform to the surface of an adherend that has a curved surface, such as the exterior of an automobile.

[0007] However, while flexible decorative films have excellent curved surface conformability, they also have low overall rigidity (rubber elastic modulus), making them susceptible to distortion even from small external forces. Therefore, when decorating an adherend using a decorative film containing a pressure-sensitive adhesive layer with low holding power, the decorative film may peel off and float from the automobile exterior over time due to shrinkage caused by residual stress in the decorative film.

[0008] On the other hand, even when an adherend is decorated using a decorative film containing a highly retentive adhesive layer, the adhesive layer may leave adhesive residue on the exterior surface of the adherend when the decorative film is replaced due to deterioration over time. Applying the decorative film with adhesive residue on the exterior of the adherend results in poor appearance. Therefore, when a flexible decorative film is used, the adhesive layer that bonds the decorative film to the adherend must have high retentive strength and be able to be peeled off without leaving adhesive residue on the exterior of the adherend, not only at the initial stage of bonding but also over time.

[0009] Furthermore, if the adhesive strength of the decorative film is too high at the initial stage of application, it may be difficult to remove the decorative film from the adherend during the reapplication process, which may result in poor application properties. Therefore, the decorative film is also required to be easy to reapplication when applied to the adherend.

[0010] Therefore, one aspect of the present invention aims to provide an adhesive composition and an adhesive layer that facilitate the re-application process when adhering a decorative film to an adherend (easy application), and that can form an adhesive layer that is less likely to leave adhesive residue on the adherend when re-adhering a decorative film that has been adhered to the adherend. [Means for solving the problem]

[0011] The present invention includes the following aspects.

[0012] [1] A (meth)acrylic copolymer and an epoxy crosslinking agent, The loss tangent tanδA at 23°C after curing is 1.00 or more and 1.68 or less, The difference between the loss tangent tanδA at 23°C after curing and the loss tangent tanδA' at 80°C after curing is 1.25 or less, for example, 0.50 or more and 1.25 or less, A pressure-sensitive adhesive composition having a gel fraction after curing of 75% by mass or less, for example, 40.0% by mass or less and 75.0% by mass or less.

[0013] [2] The pressure-sensitive adhesive composition according to [1], wherein the (meth)acrylic copolymer comprises a (meth)acrylic copolymer (A) having a glass transition temperature of −49° C. or higher and −13° C. or lower and a (meth)acrylic copolymer (B) having a glass transition temperature of 75° C. or higher and 115° C. or lower.

[0014] [3] The pressure-sensitive adhesive composition according to [2], wherein the content of the (meth)acrylic copolymer (B) is 5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the (meth)acrylic copolymer (A).

[0015] [4] The pressure-sensitive adhesive composition according to [2] or [3], wherein the (meth)acrylic copolymer (A) contains a structural unit (a1) derived from a monomer having an acidic functional group, and the content of the structural unit (a1) is 1% by mass or more and 6% by mass or less based on all structural units contained in the (meth)acrylic copolymer (A).

[0016] [5] A pressure-sensitive adhesive composition comprising a (meth)acrylic copolymer and an epoxy-based crosslinking agent, The loss tangent tanδA at 23°C is 1.00 or more and 1.68 or less, The difference between the loss tangent tanδA at 23°C and the loss tangent tanδA' at 80°C is 1.25 or less, for example, 0.50 or more and 1.25 or less, A pressure-sensitive adhesive layer having a gel fraction of 75% by mass or less, for example, 40.0% by mass or more and 75.0% by mass or less.

[0017] [6] The pressure-sensitive adhesive layer according to [5], wherein the ratio of the loss tangent tanδB at 23°C after storage for 168 hours in an 80°C environment to the loss tangent tanδA at 23°C is 0.95 or more and 1.05 or less.

[0018] [7] The pressure-sensitive adhesive layer according to [5] or [6], which has a glass transition temperature of 15°C or lower, for example, 0.0°C or higher and 15.0°C or lower.

[0019] [8] The pressure-sensitive adhesive layer according to any one of [5] to [7], which is for use in a decorative film for a vehicle coating surface.

[0020] [9] A decorative film comprising the pressure-sensitive adhesive layer according to any one of [5] to [7]. [Effects of the Invention]

[0021] According to one aspect of the present invention, it is possible to provide an adhesive composition and an adhesive layer that can form an adhesive layer that is easy to reapply when attaching a decorative film to an adherend (easy application) and that is less likely to leave adhesive residue on the adherend when reapplying a decorative film that has been attached to the adherend. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described in detail. Note that the scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without departing from the spirit of the present invention. The upper and lower limits of the numerical ranges described in this specification can be determined by arbitrarily selecting and combining the numerical values ​​exemplified as numerical ranges to obtain a suitable numerical range. Furthermore, in this specification, the content of each component in each layer of the pressure-sensitive adhesive composition or pressure-sensitive adhesive layer, etc., means the total amount of the multiple substances present in the pressure-sensitive adhesive composition or each layer, unless otherwise specified, when multiple substances corresponding to each component are present in the pressure-sensitive adhesive composition or each layer.

[0023] [Adhesive composition] The pressure-sensitive adhesive composition may contain a (meth)acrylic copolymer and an epoxy-based crosslinking agent. The pressure-sensitive adhesive composition may have a loss tangent tanδA at 23°C after aging (hereinafter also simply referred to as "tanδA") of 1.00 or more and 1.68 or less. The pressure-sensitive adhesive composition may have a difference of 1.25 or less between tanδA and a loss tangent at 80°C after aging (hereinafter also simply referred to as "tanδA'"). The pressure-sensitive adhesive composition may have a gel fraction of 75 mass% or less after aging. In this specification, (meth)acrylic is a general term for acrylic and methacrylic, and represents either or both of them.

[0024] In this specification, the loss tangent and gel fraction after aging refer to the loss tangent and gel fraction of a pressure-sensitive adhesive composition after aging. The pressure-sensitive adhesive composition after aging may be a pressure-sensitive adhesive composition obtained by drying a coating film of the pressure-sensitive adhesive composition under drying conditions of a drying temperature of 100°C and a drying time of 1 minute, and then allowing the coating film to stand for 168 hours in an environment of an atmospheric temperature of 40°C and 50% RH, and the thickness of the coating film after drying may be 40 μm.

[0025] Regarding adhesive residue on an adherend, we will explain the case where a decorative film including a substrate film and an adhesive layer formed from a pressure-sensitive adhesive composition is attached to an adherend. In this case, the adherend to which the decorative film is attached has a laminated structure of "substrate film / adhesive layer / adherend." When peeling the decorative film from the adherend, if peeling occurs only at the interface between the adhesive layer and the adherend, no adhesive residue will be left on the adherend.

[0026] However, if the adhesive strength between the pressure-sensitive adhesive layer and the adherend is higher than the adhesive strength between the base film and the pressure-sensitive adhesive layer, peeling occurs not at the interface between the pressure-sensitive adhesive layer and the adherend but at the interface between the base film and the pressure-sensitive adhesive layer, resulting in part or all of the pressure-sensitive adhesive layer remaining on the adherend, causing adhesive residue.

[0027] Furthermore, if the cohesive strength of the pressure-sensitive adhesive layer is low, the pressure-sensitive adhesive layer will break during peeling, and peeling will occur with the pressure-sensitive adhesive layer adhering to both the substrate and the adherend, resulting in part of the pressure-sensitive adhesive layer remaining on the adherend and causing adhesive residue.

[0028] Therefore, in order to prevent adhesive residue on the adherend, it is necessary to make the adhesive strength between the adhesive layer and the adherend lower than the adhesive strength between the adhesive layer and the base film so that peeling occurs only at the interface between the adhesive layer and the adherend when the decorative film is peeled off from the adherend, and to ensure that the cohesive strength of the adhesive layer is sufficient to prevent rupture of the adhesive layer.

[0029] Here, when a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is exposed to high temperatures during storage or use in a usage environment, it softens and its wettability to an adherend increases, and when the adhesive strength is measured in a room temperature environment, the adhesive strength to the adherend tends to be higher than that of a pressure-sensitive adhesive layer stored in a room temperature environment. For example, decorative films to be attached to the exterior of automobiles, etc., are heated to about 80°C, so the adhesive strength between the adherend and the pressure-sensitive adhesive layer tends to increase over time from the initial stage of attachment.

[0030] Furthermore, when the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is heated, the balance of viscoelasticity is lost, and the viscosity becomes more influential than the elasticity, which tends to reduce the cohesive strength. As a result, cohesive failure may occur when the decorative film is replaced due to deterioration over time.

[0031] Therefore, in order to create an adhesive layer that is less likely to leave adhesive residue on the adherend when the decorative film attached to the adherend is replaced, it is necessary to make the adhesive strength between the adhesive layer and the adherend lower than the adhesive strength between the adhesive layer and the base film, not only at the initial stage of attachment but also after storage or use in the usage environment and exposure to high temperatures, and to ensure that the cohesive strength of the adhesive layer is sufficient to prevent the adhesive layer from breaking.

[0032] The loss tangent tanδ is expressed as the ratio of the loss modulus to the storage modulus (loss modulus / storage modulus), and is an index of the balance between the viscous and elastic components. When the loss tangent tanδ is greater than 1, the influence of viscosity becomes stronger, and when the loss tangent tanδ is less than 1, the influence of elasticity becomes stronger.

[0033] In one embodiment of the pressure-sensitive adhesive composition of the present invention, the loss tangent tanδA at 23°C after aging is within a predetermined range, for example, from 1.00 to 1.68, and the gel fraction after aging is a specific value or less, for example, 75 mass% or less, so that adhesive residue at the initial stage of bonding can be suppressed. Therefore, a pressure-sensitive adhesive layer can be formed that is easy to re-bond when bonding the decorative film to an adherend.

[0034] More specifically, since the loss tangent tanδA at 23°C after curing is a specific value or more, for example, 1.00 or more, it is easy to ensure the adhesive strength at the interface between the pressure-sensitive adhesive layer and the base film, and in addition, the elasticity of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition does not become excessively high, making it less likely that adhesive residue will occur due to interfacial peeling between the pressure-sensitive adhesive layer and the base film. Furthermore, since the loss tangent tanδA at 23°C after curing is a specific value or less, for example, 1.68 or less, the influence of the viscosity of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition does not become excessively high, the cohesive strength of the pressure-sensitive adhesive layer can be ensured, and adhesive residue will not occur due to rupture of the pressure-sensitive adhesive layer.

[0035] When tan δA is within a predetermined range, for example, not less than 1.00 and not more than 1.68, a pressure-sensitive adhesive layer having a suitably high initial holding power can be formed.

[0036] Furthermore, since the gel fraction after curing is a specific value or less, for example, 75 mass% or less, the cohesive force of the pressure-sensitive adhesive layer does not become excessively large, the adhesive strength at the interface between the base film and the pressure-sensitive adhesive layer can be ensured, and adhesive residue due to interfacial peeling between the base film and the pressure-sensitive adhesive layer can be suppressed.

[0037] In one embodiment of the pressure-sensitive adhesive composition of the present invention, the difference between the loss tangent tanδA at 23°C after curing and the loss tangent tanδA' at 80°C after curing is a specific value or less, for example, 1.25 or less. Therefore, if adhesive residue at the initial stage of lamination can be suppressed, adhesive residue after storage or use in the usage environment and exposure to high temperatures can also be suppressed.

[0038] The tan δA of the PSA composition after aging is an index corresponding to the loss tangent at 23°C of the PSA layer formed from the PSA composition, i.e., the loss tangent of the PSA layer before heating. The tan δA' of the PSA composition after aging is an index corresponding to the loss tangent at 80°C of the PSA layer formed from the PSA composition, i.e., the loss tangent of the PSA layer when heated to 80°C. Therefore, the smaller the difference between the loss tangent tan δA of the PSA composition at 23°C after aging and the loss tangent tan δA' at 80°C after aging, the smaller the rate of change in the loss tangent of the PSA layer formed from the PSA composition before and after heating.

[0039] In one embodiment of the pressure-sensitive adhesive composition of the present invention, the difference between the loss tangent tanδA at 23°C after aging and the loss tangent tanδA' at 80°C after aging is a specific value or less, for example, 1.25 or less, so that the viscoelastic properties of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition do not change significantly before and after heating. Therefore, if adhesive residue can be suppressed at the initial stage of application, adhesive residue can also be suppressed after storage or use in the usage environment and exposure to high temperatures. Therefore, a pressure-sensitive adhesive layer that is less likely to leave adhesive residue on the adherend when the decorative film attached to the adherend is replaced can be formed.

[0040] The PSA composition may have a loss tangent tanδA at 23°C after aging of, for example, 1.00 or more and 1.68 or less, preferably 1.02 or more and 1.68 or less, and more preferably 1.04 or more and 1.68 or less. When the tanδA is at least the above-mentioned lower limit, the adhesive strength at the interface between the PSA layer and the base film is easily ensured, and in addition, the elasticity of the PSA layer formed from the PSA composition does not become excessively high, so that adhesive residue due to peeling at the interface between the PSA layer and the base film tends to be less likely to occur. Furthermore, when the tanδA is at most the above-mentioned upper limit, the influence of the viscosity of the PSA layer formed from the PSA composition does not become excessively high, so that the cohesive strength of the PSA layer can be ensured, and adhesive residue due to breakage of the PSA layer tends to be less likely to occur.

[0041] The PSA composition may have a loss tangent tanδA' at 80°C after aging of, for example, 0.30 or more and 0.55 or less, preferably 0.31 or more and 0.50 or less, and more preferably 0.32 or more and 0.45 or less. When the tanδA' is equal to or greater than the lower limit, even when the PSA layer is stored or used in an environment where it is exposed to high temperatures, it is possible to prevent an excessive decrease in the cohesive strength of the PSA layer, and adhesive residue tends to be easily suppressed. On the other hand, when the tanδA' is equal to or less than the upper limit, even when the PSA layer is stored or used in an environment where it is exposed to high temperatures, it is possible to prevent an excessive increase in adhesion between the PSA layer and the adherend, and it tends to be easy to suppress the occurrence of adhesive residue due to interfacial peeling between the PSA layer and the substrate film.

[0042] The pressure-sensitive adhesive composition may have a difference (tanδA - tanδA') between the loss tangent tanδA at 23°C after aging and the loss tangent tanδA' at 80°C after aging of, for example, 0.50 or more and 1.25 or less, preferably 0.55 or more and 1.25 or less, more preferably 0.60 or more and 1.25 or less, and even more preferably 0.62 or more and 1.24 or less. When the difference between tanδA and tanδA' is within the above range, particularly below the upper limit, the viscoelastic properties of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition do not change significantly before and after heating. Therefore, if adhesive residue is unlikely to occur at the initial stage of lamination, adhesive residue can be suppressed even after lamination and storage or use in the usage environment and exposure to high temperatures.

[0043] The PSA composition may have a loss tangent tan δB (hereinafter simply referred to as "tan δB") at 23°C after 168 hours of storage in an 80°C environment after curing, for example, of 0.88 to 1.67, preferably 0.90 to 1.65, more preferably 0.92 to 1.63, and even more preferably 0.95 to 1.61. The tan δB can be said to be an index corresponding to the loss tangent at 23°C of a PSA layer formed from the PSA composition after 168 hours of storage in an 80°C environment, i.e., the loss tangent of the PSA layer when replacing a decorative film attached to an adherend. When the tan δB is at or above the lower limit, adhesive residue due to interfacial peeling between the PSA layer and the substrate film tends to be more easily suppressed, even after storage or use in a usage environment and exposure to high temperatures. Furthermore, when the tan δB is equal to or less than the upper limit, the adhesive strength between the pressure-sensitive adhesive and the adherend does not increase excessively after storage or use in a usage environment and exposure to high temperatures, and there is a tendency that the occurrence of adhesive residue due to peeling at the interface between the pressure-sensitive adhesive layer and the base film can be suppressed.

[0044] The PSA composition may have a ratio (tan δB / tan δA) of the loss tangent tan δB at 23°C after storage for 168 hours in an 80°C environment after curing to the loss tangent tan δA at 23°C after curing, of, for example, 0.95 or more and 1.05 or less, preferably 0.95 or more and 1.04 or less, and more preferably 0.95 or more and 1.03 or less. The closer the value of tan δB / tan δA is to 1, the smaller the difference in viscoelastic properties of the PSA layer formed from the PSA composition before and after heating. Therefore, when the value of tan δB / tan δA is within the above range, adhesive residue after exposure to high temperatures during storage or use in an environment after lamination tends to be more easily suppressed.

[0045] The loss tangents tanδA and tanδA' of the pressure-sensitive adhesive composition after aging are measured using Sample A prepared by drying a coating of the pressure-sensitive adhesive composition formed to a thickness of 40 μm after drying under drying conditions of a drying temperature of 100°C and a drying time of 1 minute, and then leaving it to stand in an environment of an ambient temperature of 40°C and 50% RH for 168 hours and aging it.

[0046] The loss tangent tanδB of the pressure-sensitive adhesive composition after aging is measured using Sample B, which is prepared by further storing Sample A in an environment of 23°C and 50% humidity for 24 hours, then storing it in an environment of 80°C for 168 hours, and then leaving it to stand in an environment of 23°C for 24 hours.

[0047] Each loss tangent tanδ can be measured by measuring the dynamic viscoelasticity using a dynamic viscoelasticity measuring device (for example, Reogel-E4000 manufactured by UBM Corporation) under conditions of a test temperature of −50 to 130° C., a heating rate of 5° C. / min, a vibration frequency of 10 Hz, and a tensile length of 10 mm, and more specifically, by the method described in the examples.

[0048] Each loss tangent tanδ of the pressure-sensitive adhesive composition after aging can be adjusted by the type and content of the (meth)acrylic copolymer contained in the pressure-sensitive adhesive composition, the type and content of the crosslinking agent, the glass transition temperature of the pressure-sensitive adhesive composition, the type and content of the structural unit constituting the (meth)acrylic copolymer, etc.

[0049] The pressure-sensitive adhesive composition may have a gel fraction after curing of, for example, 40.0% by mass or more and 75.0% by mass or less, preferably 43.0% by mass or more and 73.5% by mass or less, more preferably 45.0% by mass or more and 72.0% by mass or less, and even more preferably 48.0% by mass or more and 71.5% by mass or less. When the gel fraction is equal to or less than the upper limit, the adhesiveness to the adherend is good, and adhesive strength to the adherend can be ensured at the initial stage of lamination. When the gel fraction is equal to or greater than the lower limit, the cohesive strength of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is likely to be ensured, and adhesive residue due to breakage of the pressure-sensitive adhesive layer tends to be easily suppressed. The gel fraction can be adjusted, for example, by adjusting the degree of crosslinking by adjusting the content of a monomer having an acidic functional group or the amount of crosslinking agent, as described below.

[0050] In this specification, the gel fraction of the PSA composition after aging and the gel fraction of the PSA layer described below are the proportion of solvent-insoluble matter measured using ethyl acetate as an extraction solvent. Specifically, the gel fraction can be measured according to the following (1) to (4). (1) After accurately measuring the mass (X) of a 250-mesh wire net (100 mm × 100 mm) using a precision balance, approximately 0.15 g of the cured adhesive composition or adhesive layer is attached, and the wire net is folded five times with the cured adhesive composition or adhesive layer facing inward to prevent leakage of the gel, thereby obtaining a sample. Thereafter, the mass (Y) is measured using a precision balance. (2) The obtained sample is immersed in 80 mL of ethyl acetate for 3 days. (3) The sample is taken out, washed with a small amount of ethyl acetate, and dried at 120°C for 24 hours. Then, the mass (Z) is measured using a precision balance. (4) Calculate the gel fraction using the following formula. Gel fraction (unit: mass%) = (ZX) / (YX) × ​​100 where X is the mass of the wire mesh (unit: g), Y is the mass of the wire mesh to which the cured adhesive composition or adhesive layer is attached (unit: g) before immersion, and Z is the mass of the wire mesh to which the cured adhesive composition or adhesive layer is attached, after immersion and drying (unit: g).

[0051] The pressure-sensitive adhesive composition may have a glass transition temperature after aging of 0.0° C. or more and 15.0° C. or less, preferably 0.5° C. or more and 14.7° C. or less, more preferably 1.0° C. or more and 14.5° C. or less, and even more preferably 1.5° C. or more and 14.3° C. or less. When the glass transition temperature is at least the above lower limit, reworkability during the attachment operation of the pressure-sensitive adhesive layer to the adherend at 23° C. is likely to be improved, and when the glass transition temperature is at most the above upper limit, adhesive strength between the adherend and the pressure-sensitive adhesive layer at 23° C. is likely to be ensured.

[0052] The glass transition temperature of the PSA composition after aging can be measured using a dynamic viscoelasticity measuring device, more specifically, by the method described in the Examples. In this specification, the glass transition temperature of the PSA composition after aging is defined as the temperature at which the loss tangent tanδ shows a peak top in the dynamic viscoelasticity measurement.

[0053] The pressure-sensitive adhesive composition may contain a (meth)acrylic copolymer.

[0054] The (meth)acrylic copolymer may contain a (meth)acrylic copolymer (A). The glass transition temperature of the (meth)acrylic copolymer (A) may be −49.0° C. or higher and −13.0° C. or lower, preferably −47.0° C. or higher and −13.3° C. or lower, more preferably −46.0° C. or higher and −13.6° C. or lower, and even more preferably −45.0° C. or higher and −13.9° C. or lower. When the glass transition temperature is above the lower limit, adhesive residue is easily suppressed even when exposed to high temperatures during storage or use in a usage environment. When the glass transition temperature is below the upper limit, wettability to the adherend is increased, making it easier to ensure adhesive strength to the adherend at the initial stage of lamination.

[0055] In this specification, the glass transition temperature (Tg) of the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) described later is a glass transition temperature calculated from the following formula 1 (Fox's formula), and is a value obtained by converting absolute temperature (unit: K; the same applies hereinafter) to Celsius temperature (unit: °C; the same applies hereinafter). 1 / Tg=m1 / Tg1+m2 / Tg2+ +m(k-1) / Tg(k-1)+mk / Tgk (Formula 1)

[0056] In formula 1, Tg1, Tg2, . . . , Tg(k-1), and Tgk represent the glass transition temperatures expressed as absolute temperatures when each monomer constituting the (meth)acrylic copolymer is made into a homopolymer. m1, m2, . . . , m(k-1), and mk represent the mole fractions of each monomer constituting the (meth)acrylic copolymer, respectively, and the equation is m1 + m2 + . . . + m(k-1) + mk = 1.

[0057] For homopolymers not listed in the Polymer Handbook, the glass transition temperature is measured using a differential scanning calorimeter (DSC) (Model: EXSTAR6000, Seiko Instruments Inc.) in a nitrogen gas flow with 10 mg of sample at a heating rate of 10°C / min, and the inflection point of the obtained DSC curve is taken as the glass transition temperature of the homopolymer. However, in this specification, the glass transition temperatures of the following monomers are referred to by the following values:

[0058] The glass transition temperatures of homopolymers of representative monomers are as follows: 2-ethylhexyl acrylate (2EHA): -70°C, 2-ethylhexyl methacrylate (2EHMA): -10°C, n-butyl acrylate (n-BA): -54°C, n-butyl methacrylate (n-BMA): 20°C, t-butyl acrylate (t-BA): 43°C, t-butyl methacrylate (t-BMA): 118°C, i-butyl methacrylate (i-BMA): 53°C, methyl acrylate (MA): 10°C, methyl methacrylate (MMA): 105°C, isobornyl methacrylate (IBXMA): 180°C, isobornyl acrylate (IBXA): 94°C, ethyl acrylate (IBXA): 100°C, methyl acrylate (MA): 100°C, methyl methacrylate (MMA): 105°C, isobornyl methacrylate (IBXA): 100°C, isobornyl ... Acrylate (EA): -22°C, methacrylic acid: 228°C, 4-hydroxybutyl acrylate (4HBA): -80°C, 2-hydroxyethyl acrylate (2HEA): -15°C, 2-hydroxyethyl methacrylate (2HEMA): 85°C, 2-hydroxypropyl acrylate (2HPA): -7°C, acrylic acid (AA): 106°C, i-octyl acrylate (i-OA): -65°C, dimethylaminoethyl methacrylate (DM): 18°C, ω-carboxy-polycaprolactone (n≒2) monoacrylate: -30°C, 2-acryloyloxyethyl-succinic acid: -40°C.

[0059] The glass transition temperature of the (meth)acrylic copolymer can be appropriately adjusted, for example, by using two or more monomers having different glass transition temperatures when made into a homopolymer. For example, by combining a monomer having a high glass transition temperature (high Tg monomer) with a monomer having a low glass transition temperature (low Tg monomer) to make a polymer, the glass transition temperature of the polymer can be adjusted to be between the glass transition temperatures of the high Tg monomer and the low Tg monomer used.

[0060] The (meth)acrylic copolymer (A) may contain a structural unit (a1) derived from a monomer having an acidic functional group, and may be a (meth)acrylic copolymer in which a monomer having an acidic functional group and a (meth)acrylate are polymerized. When the pressure-sensitive adhesive composition contains the (meth)acrylic copolymer (A) containing the structural unit (a1), the degree of crosslinking is easily adjusted, and therefore the gel fraction is easily adjusted.

[0061] The (meth)acrylic copolymer (A) may contain a structural unit (a1) derived from a monomer having an acidic functional group and a structural unit (a2) derived from a (meth)acrylate. In addition to the structural unit (a1) and the structural unit (a2), the (meth)acrylic copolymer (A) may also contain a structural unit (a3) ​​derived from another monomer.

[0062] The (meth)acrylic copolymer (A) may contain a structural unit (a1) derived from a monomer having an acidic functional group. Examples of the acidic functional group include a carboxy group, a sulfonic acid group, and a phosphoric acid group. The monomer having an acidic functional group may be a monomer having an acidic functional group and an unsaturated double bond group.

[0063] Examples of the monomer having a carboxy group include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone mono(meth)acrylate [e.g., ω-carboxy-polycaprolactone (n≒2) monoacrylate], and succinic acid ester [e.g., 2-acryloyloxyethyl-succinic acid].

[0064] Examples of monomers having a sulfonic acid group include (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, vinylsulfonic acid, styrenesulfonic acid, allylsulfonic acid, and 2-(meth)acrylamido-2-methylpropanesulfonic acid.

[0065] Examples of the monomer having a phosphate group include 2-methacryloyloxyethyl acid phosphate.

[0066] In one embodiment, the monomer having an acidic functional group is preferably a monomer having a carboxy group, and more preferably at least one of acrylic acid (AA) and methacrylic acid (MAA).

[0067] The (meth)acrylic copolymer (A) may contain only one type of structural unit (a1), or may contain two or more types.

[0068] In the (meth)acrylic copolymer (A), the content of the structural unit (a1) may be, for example, from 1 to 6% by mass, preferably from 2 to 5.5% by mass, and more preferably from 3 to 5% by mass, relative to all structural units (100.0% by mass) contained in the (meth)acrylic copolymer (A). When the content of the structural unit (a1) is within the above range, it is easy to adjust the degree of crosslinking, and therefore the gel fraction.

[0069] The (meth)acrylic copolymer (A) may contain a structural unit (a2) derived from a (meth)acrylate. A (meth)acrylate is an ester of an alcohol and (meth)acrylic acid. Examples of the alcohol include linear, branched, or cyclic alkyl alcohols, alkoxyalkyl alcohols, and alcohols having an aromatic ring. The number of carbon atoms in the alkyl alcohol may be, for example, 1 to 18, preferably 1 to 12, and more preferably 1 to 8.

[0070] Examples of (meth)acrylates include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate; alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; and (meth)acrylates having an aromatic ring such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate.

[0071] The (meth)acrylic copolymer (A) may contain only one type of structural unit (a2), or may contain two or more types. When the (meth)acrylic copolymer (A) contains, for example, two or more types of structural unit (a2), it is easy to adjust the glass transition temperature of the (meth)acrylic copolymer (A) to within the aforementioned range.

[0072] In one embodiment, the (meth)acrylate constituting the structural unit (a2) is preferably an alkyl (meth)acrylate, more preferably at least one selected from the group consisting of methyl acrylate (MA), n-butyl acrylate (n-BA), and 2-ethylhexyl acrylate (2EHA), and even more preferably a combination of at least one of n-BA and 2EHA with MA.

[0073] In the (meth)acrylic copolymer (A), the content of the structural unit (a2) may be, for example, from 94.0 to 99.0 mass%, preferably from 93.0 to 99.0 mass%, more preferably from 92.0 to 99.0 mass%, and even more preferably from 91.0 to 99.0 mass%, based on the total structural units (100.0 mass%) contained in the (meth)acrylic copolymer (A). When the content of the structural unit (a2) is within the above range, the content of the structural unit (a1) can be adjusted to the above range, making it easy to adjust the degree of crosslinking and therefore the gel fraction.

[0074] The (meth)acrylic copolymer (A) may contain a structural unit (a3) ​​derived from a monomer (other monomer) other than a (meth)acrylate and a monomer having an acidic functional group.

[0075] Other monomers include, for example, aromatic monovinyls such as styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate, and various derivatives of these monomers.

[0076] The content of the structural unit (a3) ​​in the (meth)acrylic copolymer (A) is not particularly limited as long as it is within a range that does not impair the effects of the present invention. In one embodiment of the present invention, the (meth)acrylic copolymer (A) does not need to contain the structural unit (a3).

[0077] In the (meth)acrylic copolymer (A), the content of the structural unit (a3) ​​may be, for example, 0.010% by mass or more and 10.0% by mass or less, preferably 5.0% by mass or less, and more preferably 3.0% by mass or less, relative to all structural units contained in the (meth)acrylic copolymer (A) (100.0% by mass).

[0078] In the pressure-sensitive adhesive composition, the content of the (meth)acrylic copolymer (A) may be, for example, 75.0% by mass or more and 97.0% by mass or less, preferably 80.0% by mass or more and 96.0% by mass or less, and more preferably 82.0% by mass or more and 96.0% by mass or less, calculated as solid content. When the content of the (meth)acrylic copolymer (A) is within the above range, there are many crosslinkable components, and the degree of crosslinking is easily adjusted, so that the gel fraction is easily adjusted.

[0079] The method for producing the (meth)acrylic copolymer (A) and the (meth)acrylic copolymer (B) described below is not particularly limited, and they can be produced by polymerizing monomers corresponding to the respective structural units of the (meth)acrylic copolymer (A) and the (meth)acrylic copolymer (B) described below using a known polymerization method typified by solution polymerization, emulsion polymerization, suspension polymerization, and bulk polymerization. As the polymerization method, solution polymerization is preferred because the processing steps required for preparing the pressure-sensitive adhesive composition after production are relatively simple and can be completed in a short time.

[0080] The (meth)acrylic copolymer may contain a (meth)acrylic copolymer (B). The glass transition temperature of the (meth)acrylic copolymer (B) may be 75.0°C or higher and 115.0°C or lower, preferably 75.3°C or higher and 114.7°C or lower, and more preferably 75.5°C or higher and 114.3°C or lower. If the glass transition temperature is above the lower limit, after exposure to high temperatures during storage or use in a usage environment, the adhesive strength between the pressure-sensitive adhesive layer and the adherend is unlikely to be excessively improved, and the occurrence of adhesive residue due to peeling at the interface between the pressure-sensitive adhesive layer and the base film tends to be easily suppressed. If the glass transition temperature is below the upper limit, cohesive strength is easily secured, and adhesive residue due to rupture of the pressure-sensitive adhesive layer tends to be less likely to occur.

[0081] The (meth)acrylic copolymer (B) may contain a structural unit (b1) derived from a monomer having a polar group other than an acidic functional group (hereinafter simply referred to as a "polar group"), and may be a (meth)acrylic copolymer in which a monomer having a polar group is polymerized with a (meth)acrylate. The (meth)acrylic copolymer (B) preferably does not contain a structural unit derived from a monomer having an acidic functional group. By including a (meth)acrylic copolymer (B) in the pressure-sensitive adhesive composition that does not substantially undergo a crosslinking reaction with a crosslinking agent, the cohesive strength of the pressure-sensitive adhesive layer is increased, and lifting of the decorative film can be prevented.

[0082] The (meth)acrylic copolymer (B) may contain a structural unit (b1) derived from a monomer having a polar group and a structural unit (b2) derived from a (meth)acrylate. In addition to the structural unit (b1) and the structural unit (b2), the (meth)acrylic copolymer (B) may also contain a structural unit (b3) derived from another monomer.

[0083] The (meth)acrylic copolymer (B) may contain a structural unit (b1) derived from a monomer having a polar group. The monomer having a polar group is not particularly limited, but from the viewpoint of compatibility, a (meth)acrylate having a polar group is preferred. The polar group is not particularly limited as long as it is a polar group other than an acidic functional group. Specific examples of the polar group include, for example, a hydroxyl group containing a methylol group, an amide group, an amino group, and the like. Among these, the polar group is preferably a hydroxyl group, and more preferably an alcoholic hydroxyl group. When the polar group is a hydroxyl group, the affinity of the pressure-sensitive adhesive layer to the adherend is further increased, and lifting of the decorative film can be more effectively prevented.

[0084] Examples of monomers having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,1-dimethyl-3-hydroxybutyl (meth)acrylate, 1,3-dimethyl-3-hydroxybutyl (meth)acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth)acrylate, 2-ethyl-3-hydroxyhexyl (meth)acrylate, N-hydroxyethyl (meth)acrylamide, glycerin mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, and poly(ethylene glycol-propylene glycol) mono(meth)acrylate.

[0085] Among these monomers having a hydroxyl group, hydroxyalkyl (meth)acrylates are preferred, hydroxyalkyl (meth)acrylates having a hydroxyalkyl group having 1 to 4 carbon atoms are more preferred, at least one selected from the group consisting of 2-hydroxyethyl methacrylate (2HEMA), 2-hydroxyethyl acrylate (2HEA), and 4-hydroxybutyl acrylate (4HBA) is even more preferred, and 2-hydroxyethyl methacrylate (2HEMA) is particularly preferred.

[0086] Examples of the monomer having an amide group include N,N-dimethyl(meth)acrylamide, N,N-diethylacrylamide, N-ethyl,N-methyl(meth)acrylamide, and N-isopropyl(meth)acrylamide.

[0087] Examples of the monomer having an amino group include 2-aminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate (2-(diethylamino)ethyl (meth)acrylate), dimethylaminoethyl (meth)acrylate (2-(dimethylamino)ethyl (meth)acrylate), and 3-(dimethylamino)propyl (meth)acrylate.

[0088] Among these monomers having an amino group, dimethylaminoethyl (meth)acrylate is preferred, and dimethylaminoethyl methacrylate is more preferred.

[0089] The (meth)acrylic copolymer (B) may contain only one type of structural unit (b1), or may contain two or more types.

[0090] In the (meth)acrylic copolymer (B), the content of the structural unit (b1) may be, for example, 4.0% by mass or more and 12.0% by mass or less, preferably 5.0% by mass or more and 11.0% by mass or less, and more preferably 6.0% by mass or more and 10.0% by mass or less, relative to the total structural units (100.0% by mass) contained in the (meth)acrylic copolymer (B). When the content of the structural unit (b1) is equal to or greater than the lower limit, the adhesive layer has an increased affinity to the adherend, preventing lifting of the decorative film. When the content of the structural unit (b1) is equal to or less than the upper limit, the adhesive layer has an increased affinity to the adherend, improving reapplication workability.

[0091] The (meth)acrylic copolymer (B) may contain, in addition to the structural unit (b1), a structural unit (b2) derived from a (meth)acrylate that does not have a polar group.

[0092] Examples of (meth)acrylates that do not have a polar group include alkyl (meth)acrylates derived from the structural unit (a2) in the above-mentioned (meth)acrylic copolymer (A). The alkyl alcohol that constitutes the alkyl (meth)acrylate may have, for example, 1 to 18 carbon atoms, preferably 1 to 12, and more preferably 1 to 8 carbon atoms.

[0093] The (meth)acrylate having no polar group is preferably at least one selected from the group consisting of methyl methacrylate (MMA), ethyl acrylate (EA) and t-butyl (meth)acrylate, among alkyl (meth)acrylates.

[0094] The (meth)acrylic copolymer (B) may contain only one type of structural unit (b2), or may contain two or more types.

[0095] In the (meth)acrylic copolymer (B), the content of the structural unit (b2) may be, for example, 60.0 mass% or more and 96.0 mass% or less, preferably 70.0 mass% or more and 95.0 mass% or less, and more preferably 80.0 mass% or more and 94.0 mass% or less, relative to all structural units contained in the (meth)acrylic copolymer (B) (100.0 mass%).

[0096] The (meth)acrylic copolymer (B) may contain a structural unit (b3) derived from a monomer having a polar group and a monomer (other monomer) other than (meth)acrylate that does not have a polar group. Examples of the other monomer in the (meth)acrylic copolymer (B) include the same monomers as the other monomers in the (meth)acrylic copolymer (A).

[0097] The content of the structural unit (b3) in the (meth)acrylic copolymer (B) is not particularly limited as long as it is within a range that does not impair the effects of the present invention. In one embodiment of the present invention, the (meth)acrylic copolymer (B) does not need to contain the structural unit (b3).

[0098] In the (meth)acrylic copolymer (B), the content of the structural unit (b3) may be, for example, from 0.010% by mass to 10.0% by mass, preferably from 0.010% by mass to 5.0% by mass, and more preferably from 0.010% by mass to 3.0% by mass, relative to all structural units (100.0% by mass) contained in the (meth)acrylic copolymer (B).

[0099] In the pressure-sensitive adhesive composition, the content of the (meth)acrylic copolymer (B) may be, for example, 3.0% by mass or more and 20.0% by mass or less, preferably 4.0% by mass or more and 18.0% by mass or less, and more preferably 4.5% by mass or more and 17.0% by mass or less, calculated as solid content. When the content of the (meth)acrylic copolymer (B) is within the above range, the cohesive strength of the pressure-sensitive adhesive layer is increased, and lifting of the decorative film can be prevented.

[0100] The content of the (meth)acrylic copolymer (B) in the pressure-sensitive adhesive composition may be, for example, 3 to 25 parts by mass, preferably 4 to 23 parts by mass, and more preferably 5 to 20 parts by mass, relative to 100 parts by mass of the (meth)acrylic copolymer (A). When the pressure-sensitive adhesive composition contains the (meth)acrylic copolymer (B), which contains the structural unit (b1) and does not substantially undergo a crosslinking reaction with a crosslinking agent, within the above range, the cohesive strength of the pressure-sensitive adhesive layer is increased, and lifting of the decorative film can be prevented.

[0101] The (meth)acrylic copolymer may have functional groups on its side chains modified with additives such as silicone, but is preferably not modified with additives such as silicone.

[0102] The pressure-sensitive adhesive composition may contain an epoxy-based crosslinking agent. The epoxy-based crosslinking agent crosslinks the (meth)acrylic copolymer (A) by reacting with the acidic functional group. By using an epoxy-based crosslinking agent as the crosslinking agent, the adhesive strength between the pressure-sensitive adhesive layer and the adherend does not increase excessively after storage or use under the usage environment and exposure to high temperatures, and the occurrence of adhesive residue due to peeling at the interface between the pressure-sensitive adhesive layer and the substrate film can be suppressed.

[0103] The epoxy crosslinking agent may be any compound having two or more epoxy groups. Examples of the epoxy crosslinking agent include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, resorcinol diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, adipic acid diglycidyl ester, and fluororesin diglycidyl ether. and epoxy compounds having three or more epoxy groups, such as glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, tris(glycidyl)isocyanurate, tris(glycidoxyethyl)isocyanurate, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidyl-1,3-benzenedi(methanamine). Among these, epoxy compounds having three or more epoxy groups are preferred.

[0104] The pressure-sensitive adhesive composition may contain only one type of epoxy crosslinking agent, or may contain two or more types.

[0105] Examples of commercially available epoxy crosslinking agents include "TETRAD (registered trademark)-X" and "TETRAD (registered trademark)-C" (both manufactured by Mitsubishi Gas Chemical Company, Inc.), and "Denacol (registered trademark) EX-201" and "Denacol (registered trademark) EX-931" (both manufactured by Nagase ChemteX Corporation).

[0106] The content of the epoxy-based crosslinking agent in the pressure-sensitive adhesive composition may be, for example, from 0.05 to 0.18 parts by mass, preferably from 0.06 to 0.17 parts by mass, more preferably from 0.07 to 0.16 parts by mass, and even more preferably from 0.08 to 0.15 parts by mass, relative to 100 parts by mass of the (meth)acrylic copolymer (A). When the content of the epoxy-based crosslinking agent is above the above-mentioned lower limit, the degree of crosslinking of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is sufficiently increased, making it easier to ensure cohesive strength, and therefore adhesive residue due to breakage of the pressure-sensitive adhesive layer tends to be less likely to occur. Furthermore, when the content of the epoxy-based crosslinking agent is below the above-mentioned upper limit, the degree of crosslinking of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is prevented from becoming excessively high, preventing a decrease in adhesive strength between the pressure-sensitive adhesive layer and the adherend, and preventing lifting of the decorative film.

[0107] The pressure-sensitive adhesive composition may or may not contain a crosslinking agent other than an epoxy-based crosslinking agent, such as a metal chelate-based crosslinking agent or an isocyanate-based crosslinking agent. In one embodiment, the pressure-sensitive adhesive composition preferably does not contain a crosslinking agent other than an epoxy-based crosslinking agent, such as a metal chelate-based crosslinking agent or an isocyanate-based crosslinking agent. The content of the crosslinking agent other than an epoxy-based crosslinking agent in the pressure-sensitive adhesive composition may be, for example, 0.05 parts by mass or less, preferably 0.01 parts by mass or less, per 100 parts by mass of the (meth)acrylic copolymer (A).

[0108] The pressure-sensitive adhesive composition may or may not contain additives such as ultraviolet absorbers, light stabilizers, antioxidants, etc., as long as the effects of the present invention are not impaired.

[0109] When the pressure-sensitive adhesive composition contains an additive, the content of the additive may be, for example, 0.01 parts by mass or more and 5 parts by mass or less, preferably 0.01 parts by mass or more and 3 parts by mass or less, more preferably 0.01 parts by mass or more and 1 part by mass or less, and even more preferably 0.01 parts by mass or more and 0.1 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic copolymer (A).

[0110] [Adhesive layer] In one aspect, the present invention includes a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer (hereinafter also referred to as a "first pressure-sensitive adhesive layer") may be a layer formed from a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer and an epoxy-based crosslinking agent. That is, the pressure-sensitive adhesive layer may be a layer derived from a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer and an epoxy-based crosslinking agent.

[0111] The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer may be the pressure-sensitive adhesive composition described above in the section [Pressure-sensitive adhesive composition]. When the (meth)acrylic copolymer contained in the pressure-sensitive adhesive composition contains a (meth)acrylic copolymer (A) and a (meth)acrylic copolymer (B), the pressure-sensitive adhesive layer contains a component derived from the (meth)acrylic copolymer (A) and a component derived from the (meth)acrylic copolymer (B), and at least a portion of the component derived from the (meth)acrylic copolymer (A) may be linked by a partial structure derived from an epoxy-based crosslinking agent.

[0112] The pressure-sensitive adhesive layer may have a loss tangent tanδA at 23°C of, for example, 1.00 or more and 1.68 or less, preferably 1.02 or more and 1.68 or less, and more preferably 1.04 or more and 1.68 or less. When the tanδA is equal to or greater than the lower limit, the adhesive strength at the interface between the pressure-sensitive adhesive layer and the base film is easily ensured, and the elasticity of the pressure-sensitive adhesive layer does not become excessively high, so adhesive residue due to peeling at the interface between the pressure-sensitive adhesive layer and the base film tends to be less likely to occur. Furthermore, when the tanδA is equal to or less than the upper limit, the influence of the viscosity of the pressure-sensitive adhesive layer does not become excessively high, the cohesive strength of the pressure-sensitive adhesive layer can be ensured, and adhesive residue due to rupture of the pressure-sensitive adhesive layer tends to be less likely to occur.

[0113] The pressure-sensitive adhesive layer may have a loss tangent tanδA' at 80°C of, for example, 0.30 or more and 0.55 or less, preferably 0.31 or more and 0.50 or less, and more preferably 0.32 or more and 0.45 or less. When the tanδA' is equal to or greater than the lower limit, even when the pressure-sensitive adhesive layer is stored or used in an environment where it is exposed to high temperatures, it is possible to prevent an excessive decrease in the cohesive strength of the pressure-sensitive adhesive layer, and adhesive residue tends to be easily suppressed. Furthermore, when the tanδA' is equal to or less than the upper limit, even when the pressure-sensitive adhesive layer is stored or used in an environment where it is exposed to high temperatures, it is possible to prevent an excessive increase in adhesion between the pressure-sensitive adhesive layer and the adherend, and it tends to be easy to suppress the occurrence of adhesive residue due to interfacial peeling between the pressure-sensitive adhesive layer and the substrate film.

[0114] The pressure-sensitive adhesive layer may have a difference (tanδA-tanδA') between the loss tangent tanδA at 23°C and the loss tangent tanδA' at 80°C of, for example, 0.50 or more and 1.25 or less, preferably 0.55 or more and 1.25 or less, more preferably 0.60 or more and 1.25 or less, and even more preferably 0.62 or more and 1.24 or less. When the difference between tanδA and tanδA' is within the above range, particularly below the upper limit, the viscoelastic properties of the pressure-sensitive adhesive layer do not change significantly before and after heating. Therefore, if adhesive residue is unlikely to occur at the initial stage of lamination, adhesive residue can be suppressed even after lamination and exposure to high temperatures during storage or use in the usage environment.

[0115] The PSA layer may have a loss tangent tanδB at 23°C after storage for 168 hours in an 80°C environment of, for example, 0.88 to 1.67, preferably 0.90 to 1.65, more preferably 0.92 to 1.63, and even more preferably 0.95 to 1.61. The tanδB can be considered an index corresponding to the loss tangent at 23°C after storage for 168 hours in an 80°C environment, i.e., the loss tangent of the PSA layer when replacing a decorative film attached to an adherend. When the tanδB is equal to or greater than the lower limit, adhesive residue due to interfacial peeling between the PSA layer and the substrate film tends to be suppressed even after storage or use in a usage environment and exposure to high temperatures. Furthermore, when the tanδB is equal to or less than the upper limit, the adhesive strength between the PSA and the adherend does not increase excessively after storage or use in a usage environment and exposure to high temperatures, and adhesive residue due to interfacial peeling between the PSA layer and the substrate film tends to be suppressed. The loss tangent tanδB at 23°C after storage for 168 hours in an 80°C environment can be measured using a pressure-sensitive adhesive layer that has been stored for 24 hours in an environment of 23°C and 50% humidity, further stored in an 80°C environment for 168 hours, and then left to stand in an environment of 23°C for 24 hours.

[0116] The pressure-sensitive adhesive layer may have a ratio (tanδB / tanδA) of the loss tangent tanδB at 23°C after 168 hours of storage in an 80°C environment to the loss tangent tanδA at 23°C of, for example, 0.95 or more and 1.05 or less, preferably 0.95 or more and 1.04 or less, and more preferably 0.95 or more and 1.03 or less. The closer the value of tanδB / tanδA is to 1, the smaller the viscoelastic properties of the pressure-sensitive adhesive layer before and after heating. Therefore, when the value of tanδB / tanδA is within the above range, adhesive residue after exposure to high temperatures during storage or use in a usage environment tends to be more easily suppressed.

[0117] Each loss modulus of the pressure-sensitive adhesive layer can be measured by cutting the pressure-sensitive adhesive layer into a size of 25 mm wide and 150 mm long, rolling the sample into a cylindrical shape, and measuring the dynamic viscoelasticity using a dynamic viscoelasticity measuring device (e.g., Reogel-E4000 manufactured by UBM Corporation) under conditions of a test temperature of -50 to 130°C, a heating rate of 5°C / min, a vibration frequency of 10 Hz, and a tensile length of 10 mm; more specifically, the measurement can be performed by the method described in the examples.

[0118] The loss tangent tanδ of each pressure-sensitive adhesive layer can be adjusted by the type and content of the (meth)acrylic copolymer contained in the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer, the type and content of the crosslinking agent, the glass transition temperature of the pressure-sensitive adhesive composition, the type and content of the structural unit constituting the (meth)acrylic copolymer, etc.

[0119] The pressure-sensitive adhesive layer may have a gel fraction of, for example, 40.0% by mass to 75.0% by mass or less, preferably 43.0% by mass to 73.5% by mass or less, more preferably 45.0% by mass to 72.0% by mass or less, and even more preferably 48.0% by mass to 71.5% by mass or less. When the gel fraction is equal to or less than the upper limit, the adhesive layer has good wettability to the adherend, ensuring adhesive strength to the adherend at the initial stage of lamination. When the gel fraction is equal to or greater than the lower limit, the adhesive layer tends to have a high cohesive strength and to be less susceptible to adhesive residue caused by breakage of the adhesive layer. The gel fraction can be adjusted, for example, by adjusting the crosslinking degree by adjusting the content of the monomer having an acidic functional group or the amount of the crosslinking agent.

[0120] The pressure-sensitive adhesive layer may have a glass transition temperature of 0.0° C. or higher and 15.0° C. or lower, preferably 0.5° C. or higher and 14.7° C. or lower, more preferably 1.0° C. or higher and 14.5° C. or lower, and even more preferably 1.5° C. or higher and 14.3° C. or lower. When the glass transition temperature is equal to or higher than the above lower limit, reworkability during attachment of the pressure-sensitive adhesive to the adherend at 23° C. is likely to be improved, and when the glass transition temperature is equal to or lower than the above upper limit, adhesive strength between the adherend and the pressure-sensitive adhesive at 23° C. is likely to be ensured.

[0121] The glass transition temperature of the pressure-sensitive adhesive layer can be measured using a dynamic viscoelasticity measuring device, more specifically, by the method described in the Examples. In this specification, the glass transition temperature of the pressure-sensitive adhesive layer is defined as the temperature at which the loss tangent δ reaches its peak in the dynamic viscoelasticity measurement.

[0122] The thickness of the adhesive layer may be, for example, 20 μm or more and 60 μm or less, preferably 22 μm or more and 55 μm or less, and more preferably 25 μm or more and 50 μm or less. When the thickness of the adhesive layer is equal to or greater than the lower limit, re-application workability and adhesiveness when adhering the decorative film to an adherend are more likely to be improved, and lifting of the decorative film can be prevented. When the thickness of the adhesive layer is equal to or less than the upper limit, breakage of the adhesive layer during re-application work is more likely to be suppressed.

[0123] The thickness of the adhesive layer is measured with a micrometer and calculated as the arithmetic mean of the measurements taken at five points. The thickness of the adhesive layer may be calculated by directly measuring the adhesive layer with a micrometer, or by subtracting the thickness of the two films from the total thickness when the adhesive layer is sandwiched between two films of specified thickness.

[0124] The adhesive strength of the pressure-sensitive adhesive layer after application to an adherend and storage for 1 hour at 23°C and 50% humidity (hereinafter also referred to as "adhesion strength after 1 hour at 23°C") may be, for example, 3.5 N / 10 mm or more and 8.0 N / 10 mm or less, preferably 3.6 N / 10 mm or more and 7.8 N / 10 mm or less, more preferably 3.7 N / 10 mm or more and 7.6 N / 10 mm or less, and even more preferably 3.8 N / 10 mm or more and 7.4 N / 10 mm or less. When the adhesive strength after 1 hour at 23°C is equal to or greater than the lower limit, lifting after application can be prevented, and when it is equal to or less than the upper limit, reapplication can be facilitated.

[0125] The adhesive strength of the pressure-sensitive adhesive layer after application to an adherend and storage for 168 hours at 23°C and 50% humidity (hereinafter also referred to as "adhesion strength of product stored at 23°C") may be, for example, 3.5 N / 10 mm to 9.0 N / 10 mm, preferably 3.9 N / 10 mm to 8.8 N / 10 mm, more preferably 4.2 N / 10 mm to 8.6 N / 10 mm, and even more preferably 4.5 N / 10 mm to 8.4 N / 10 mm. If the adhesive strength of the product stored at 23°C is above the above lower limit, lifting after application can be prevented. If the adhesive strength is below the above upper limit, the adhesive strength between the pressure-sensitive adhesive and the adherend does not increase excessively after storage or use in an environment where it is exposed to high temperatures, and adhesive residue due to peeling at the interface between the pressure-sensitive adhesive layer and the substrate film can be suppressed.

[0126] The adhesive strength of the pressure-sensitive adhesive layer, after being attached to an adherend and stored in an environment at 23°C and 50% humidity for 24 hours, then stored in an environment at 80°C for 168 hours, and then allowed to stand in an environment at 23°C for a further 24 hours (hereinafter also referred to as "adhesion strength of product stored at 80°C") may be, for example, 4.6 N / 10 mm or more and 10.5 N / 10 mm or less, preferably 4.8 N / 10 mm or more and 10.3 N / 10 mm or less, more preferably 5.0 N / 10 mm or more and 10.2 N / 10 mm or less, and even more preferably 5.2 N / 10 mm or more and 10.0 N / 10 mm or less. If the adhesive strength of the product stored at 80°C is equal to or greater than the above lower limit, lifting after application can be prevented, and if it is equal to or less than the above upper limit, the adhesive strength between the pressure-sensitive adhesive layer and the adherend does not increase excessively after exposure to high temperatures during storage or use in the usage environment, and adhesive residue due to peeling at the interface between the pressure-sensitive adhesive layer and the base film can be suppressed.

[0127] The adhesive strength of the pressure-sensitive adhesive layer to an adherend can be measured using a Tensilon universal testing machine or the like, by peeling at a peel speed of 200 mm / min, a peel angle of 180°, and a measurement temperature of 23°C, more specifically, by the method described in the Examples. Measurement of the adhesive strength of the pressure-sensitive adhesive layer to an adherend may be carried out by using a sample piece of a film obtained by laminating the pressure-sensitive adhesive layer to a substrate film having an upper yield point load of 17.4 N / 10 mm at 20°C. The pressure-sensitive adhesive layer may be attached to the adherend by applying a load twice back and forth using a 2 kg roller.

[0128] The method for forming the pressure-sensitive adhesive layer is not particularly limited, and a commonly used method can be used. In one embodiment, the decorative film including the pressure-sensitive adhesive layer has the pressure-sensitive adhesive layer laminated on a base film. Hereinafter, a method for forming the pressure-sensitive adhesive layer on the base film will be described.

[0129] One method for forming a pressure-sensitive adhesive layer on a substrate film is as follows. The pressure-sensitive adhesive composition is applied to the substrate film as is, or diluted with a solvent as necessary, to form a coating film. The formed coating film is then dried to form a pressure-sensitive adhesive film on the substrate film. The pressure-sensitive adhesive film formed on the substrate film is then cured, thereby forming a pressure-sensitive adhesive layer on the substrate film.

[0130] Other methods for forming a pressure-sensitive adhesive layer on a substrate film include the following. The pressure-sensitive adhesive composition, either as is or diluted with a solvent as necessary, is applied to a release film such as paper or a resin film that has been surface-treated with a release agent, to form a coating film on the release film. The formed coating film is then dried to form a pressure-sensitive adhesive film on the release film. Thereafter, the exposed surface of the formed pressure-sensitive adhesive film is brought into contact with the substrate film and pressure is applied, and the pressure-sensitive adhesive film is transferred to the substrate film, thereby forming a pressure-sensitive adhesive film on the substrate film. Finally, the formed pressure-sensitive adhesive film is cured, thereby forming a pressure-sensitive adhesive layer on the substrate film.

[0131] Examples of solvents for diluting the PSA composition include aromatic hydrocarbon compounds such as benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha; aliphatic or alicyclic hydrocarbon compounds such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and turpentine oil; ester compounds such as ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate; acetone, methyl ethyl ketone, methyl ... Examples of dilution solvents include ketone compounds such as ethyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohexanone; glycol ether compounds such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; and alcohol compounds such as methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol. The dilution solvent may be used alone or in combination of two or more.

[0132] Among these solvents, aromatic hydrocarbon compounds, ester compounds and ketone compounds are preferred, and from the viewpoint of the solubility of the (meth)acrylic copolymer, ethyl acetate is more preferred.

[0133] When the PSA composition is diluted with a solvent, the solid content of the diluted PSA composition is, from the viewpoint of coatability, preferably 15% by mass to 40% by mass, more preferably 20% by mass to 35% by mass, and even more preferably 25% by mass to 30% by mass, relative to the total amount of the diluted PSA composition. The solid content of the PSA composition refers to all components of the diluted PSA composition excluding the liquid medium such as the solvent.

[0134] The release film is not particularly limited as long as it can be easily peeled from the pressure-sensitive adhesive layer, and examples include resin films that have been surface-treated with a release agent on one or both sides (so-called easy-release treatment).

[0135] Examples of resin films include polyester films such as polyethylene terephthalate (PET) films, and examples of release agents include fluorine-based resins, paraffin wax, silicone, and long-chain alkyl group compounds.

[0136] The exposed pressure-sensitive adhesive layer may be protected by a release film. When the pressure-sensitive adhesive layer is protected by a release film, the release film is peeled off when the decorative film is applied.

[0137] The method for applying the pressure-sensitive adhesive composition onto the substrate film or the release film is not particularly limited, and examples thereof include known methods using a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, knife coater, spray coater, bar coater, applicator, etc. The amount of the pressure-sensitive adhesive composition to be applied is appropriately determined depending on the thickness of the pressure-sensitive adhesive layer to be formed.

[0138] The method for drying the coating film formed on the substrate film or release film is not particularly limited, and examples thereof include natural drying, heat drying, hot air drying, and vacuum drying.

[0139] The drying temperature and drying time of the coating film are not particularly limited and are appropriately set depending on the thickness of the coating film, the amount of organic solvent in the coating film, etc. An example of the drying conditions is drying using a hot air dryer at 70°C to 120°C for 1 minute to 3 minutes.

[0140] The curing may be carried out for 4 to 7 days in an environment of 20 to 40° C. By curing, a pressure-sensitive adhesive layer is formed from the pressure-sensitive adhesive composition.

[0141] The adhesive layer may be an adhesive layer for a decorative film (an adhesive layer for a decorative film on a vehicle's paint surface) that is attached to an object to be decorated such as a vehicle to decorate the object to be decorated, or an adhesive layer for a protective film for a vehicle's paint surface that protects the vehicle from external factors to prevent scratches, dirt, etc. from being attached to the painted surface of the vehicle.

[0142] [Decorative film] In one aspect, the present invention includes a decorative film including a first pressure-sensitive adhesive layer. The decorative film may include the first pressure-sensitive adhesive layer and a base film, and the first pressure-sensitive adhesive layer may be laminated on the base film.

[0143] The base film may include a surface protective layer and a colored layer, and in this case, the decorative film includes a first pressure-sensitive adhesive layer on the colored layer side of the base film.

[0144] The surface protective layer may contain a polyurethane resin. Examples of polyurethane resins include polycarbonate-based urethane resins, polycaprolactone-based urethane resins, polyether-based urethane resins, polyester-based urethane resins, and polyolefin-based urethane resins. These polyurethane resins have a main chain of polycarbonate, polycaprolactone, polyether, polyester, polyolefin, or the like, and a urethane structure. Here, the urethane structure is preferably a urethane structure derived from an aliphatic isocyanate or an alicyclic isocyanate. The polyurethane resin is preferably at least one selected from the group consisting of polycarbonate-based urethane resins and polycaprolactone-based urethane resins, and more preferably a polycarbonate-based urethane resin.

[0145] The polyurethane resin is produced by synthesizing monomers that can constitute the polyurethane resin by a known synthesis method.

[0146] Examples of commercially available polyurethane resins include Rezamin (registered trademark) NE-8836, NE-8850, and NE-8811 (all manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), Miractoran (registered trademark) E580, E585, E590, E595, E598, E980, E985, E990, E995, and E998 (all manufactured by Nippon Miractoran Co., Ltd.), NY88A10F, NY993-10HB4, and NY585N11A (manufactured by FCI Corporation), and Crisvon (registered trademark) NY-393, NY-331, and NY-328FTR (manufactured by DIC Corporation).

[0147] The surface protective layer may further contain other components in addition to the polyurethane resin. Examples of the other components include ultraviolet absorbers, light stabilizers, plasticizers, extender pigments, matting agents, etc. Examples of ultraviolet absorbers include benzotriazole-based compounds, benzophenone-based compounds, cyanoacrylate-based compounds, ultrafine zinc oxide, titanium oxide, etc. Examples of light stabilizers include hindered amine-based compounds, etc.

[0148] When the surface protection layer contains other components, the content of the other components may be, for example, 0.01 parts by mass or more and 10 parts by mass or less, preferably 0.1 parts by mass or more and 8 parts by mass or less, more preferably 0.5 parts by mass or more and 5 parts by mass or less, and even more preferably 1 part by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the polyurethane resin.

[0149] The surface protective layer may have an upper yield point load at 20°C of, for example, 3.5 N / 10 mm or more and 9.0 N / 10 mm or less, preferably 4.0 N / 10 mm or more and 7.5 N / 10 mm or less, and more preferably 4.4 N / 10 mm or more and 6.5 N / 10 mm or less. When the upper yield point load of the surface protective layer is above the above-mentioned lower limit, the application of the decorative film tends to be improved and the occurrence of wrinkles during application of the decorative film tends to be easily suppressed. Furthermore, when the upper yield point load of the surface protective layer is below the above-mentioned upper limit, the curved surface conformability of the decorative film tends to be improved and the occurrence of lifting after application tends to be easily suppressed. In this specification, "curved surface conformability" refers to the property of a decorative film that is less likely to lift when applied to a curved portion such as an uneven portion.

[0150] In this specification, the upper yield point load refers to the load at the upper yield point of a sample observed in a tensile test. Since this load is measured using a 10 mm wide sample, its unit is expressed as "N / 10 mm." The upper yield point load can be determined by measuring a 10 mm wide sample using a known measuring device such as a Tensilon universal testing machine. Specifically, a rectangular sample measuring 10 mm wide and 150 mm long is prepared, and the sample is stretched at a constant rate of 300 mm / min at 20°C using a TENSILON (registered trademark, manufacturer: A&D, model RTG-1310) with a chuck distance of 100 mm. The tensile load during stretching is measured. When the elastic limit of the hook is exceeded, the sample increases nonlinearly, reaching the upper yield point, and simultaneously necking occurs. Therefore, the load at the upper yield point can be considered the upper yield point load.

[0151] The thickness of the surface protective layer may be, for example, 15 μm to 60 μm, preferably 18 μm to 50 μm, more preferably 20 μm to 40 μm, and even more preferably 25 μm to 30 μm. From the viewpoint of protecting the colored layer with a sufficient thickness, the thickness of the surface protective layer is preferably equal to or greater than the above lower limit. The thickness of the surface protective layer can be measured with a micrometer and calculated as the arithmetic average of the measurements at five points.

[0152] The surface protective layer can be produced, for example, by preparing a dispersion containing a polyurethane resin, other components, and an organic solvent, casting the dispersion to form a coating film, and then solidifying or curing the coating film.

[0153] The colored layer may contain an acrylic resin and a colorant. For example, the colored layer may be a layer in which a colorant is dispersed in an acrylic resin matrix resin. Note that "acrylic resin" is a general term for acrylic resin and methacrylic resin.

[0154] The acrylic resin contained in the colored layer may be one type of resin, or may be a combination of two or more types of resins with different hardnesses. Examples of hard resins with relatively high hardness in the combination include hard acrylic resins used in films, sheets, and the like formed by melt extrusion. Examples of soft acrylic resins with relatively low hardness in the combination include resins for adjusting fluidity and resins for soft materials. From the viewpoint of adjusting the mechanical properties of the decorative film and achieving the physical properties described below, the acrylic resin preferably includes a hard acrylic resin and a soft acrylic resin.

[0155] In this specification, the term "hard acrylic resin" refers to an acrylic resin that, when formed into a sheet material having a thickness of 100 μm and a width of 10 mm, has an upper yield point load of 10.0 N / 10 mm or more at 20° C. The upper yield point load can be measured using a known measuring device such as a Tensilon universal testing machine.

[0156] When the upper yield point load of a hard acrylic resin is a specified value or more, the application properties of the decorative film (reduction of wrinkles during application) may be improved, and when the upper yield point load is less than the specified value, the curved surface conformability of the decorative film may be improved.

[0157] The upper yield point load of the rigid acrylic resin may be, for example, 10.0 N / 10 mm or more and 35.0 N / 10 mm or less. From the viewpoint of further improving the application property of the decorative film, the lower limit of the upper yield point load of the rigid acrylic resin may be preferably 15.0 N / 10 mm or more, more preferably 16.0 N / 10 mm or more. From the viewpoint of further improving the curved surface conformability of the decorative film, the upper limit of the upper yield point load of the rigid acrylic resin may be preferably 30.0 N / 10 mm or less, more preferably 28.0 N / 10 mm or less.

[0158] The hard acrylic resin can be prepared by radical polymerization of known monomers that can constitute an acrylic resin. Examples of hard acrylic resins include polymethyl methacrylate and methyl methacrylate-styrene copolymer.

[0159] The hard acrylic resin may be an acrylic resin having a Shore A hardness of greater than 90. The "Shore A hardness" is measured, for example, using a durometer GS-706N manufactured by Teclock Corporation, and is the maximum value when a Type A sensor is pressed perpendicularly against the surface of the object to be measured with a load of 1 kg.

[0160] As the hard acrylic resin, for example, it is preferable to first select an acrylic resin having a Shore A hardness of greater than 90 as a standard, and then select from the selected acrylic resins a resin that will give a molded sheet material having an upper yield point load of 10.0 N / 10 mm or more. The hard acrylic resin may be a commercially available product, examples of which include Parapet (registered trademark) GR-F1000P (Kuraray Co., Ltd.), Kane Ace (registered trademark) MC-732 (Kaneka Corporation), Dianale LP-3202, 3207, 3130, and 3121 (all Mitsubishi Chemical Corporation), and Delpet (Asahi Kasei Corporation).

[0161] In this specification, the term "soft acrylic resin" refers to an acrylic resin that, when made into a sheet material of the above-mentioned size, has an upper yield point load of less than 10.0 N / 10 mm at 20°C.

[0162] When the upper yield point load of a soft acrylic resin is a specified value or higher, the application properties of the decorative film (reduction of wrinkles during application) tend to be improved, and when the upper yield point load is less than the specified value, the curved surface conformability of the decorative film tends to be improved.

[0163] The upper yield point load of the soft acrylic resin may be, for example, 2.0 N / 10 mm or more and less than 10.0 N / 10 mm. From the viewpoint of further improving the application property of the decorative film, the lower limit of the upper yield point load of the soft acrylic resin may be preferably 3.0 N / 10 mm or more, more preferably 3.5 N / 10 mm or more. Furthermore, from the viewpoint of further improving the curved surface conformability of the decorative film, the upper limit of the upper yield point load of the soft acrylic resin may be preferably 7.0 N / 10 mm or less, more preferably 5.0 N / 10 mm or less, and even more preferably 4.5 N / 10 mm or less.

[0164] The soft acrylic resin can be prepared by radical polymerization of known monomers that can constitute acrylic resins. Examples of the soft acrylic resin include polymethyl methacrylate and methyl methacrylate-styrene copolymer.

[0165] The soft acrylic resin may be an acrylic resin having a Shore A hardness of 70 or more and 90 or less.

[0166] As the soft acrylic resin, for example, it is preferable to first select an acrylic resin having a Shore A hardness of 70 or more and 90 or less, and then select from the selected acrylic resins a resin that will give a molded product, which is a predetermined sheet material, with an upper yield point load of less than 10.0 N / 10 mm. The soft acrylic resin may be a commercially available product, an example of which is Parapet (registered trademark) SA-F1000P (Kuraray Co., Ltd.).

[0167] When a mixture of hard acrylic resin and soft acrylic resin is used as the acrylic resin, the mass ratio of the soft acrylic resin to the hard acrylic resin may be, for example, 0.4 or more and 1.4 or less.

[0168] At least one of the hard acrylic resin and the soft acrylic resin may be formed from a resin composition containing core-shell particles in which core particles having rubber elasticity are coated with an acrylic resin. Core-shell particles in which core particles having rubber elasticity are coated with an acrylic resin may be formed by polymerizing a monomer mixture containing core particles, a (meth)acrylic acid ester, and, if necessary, a polyfunctional monomer copolymerizable therewith and other monofunctional monomers. At least one of the hard acrylic resin and the soft acrylic resin may be a thermoplastic elastomer. Note that "(meth)acrylic acid" is a general term for acrylic acid and methacrylic acid, and refers to either or both of them.

[0169] Examples of (meth)acrylic acid esters include esters of (meth)acrylic acid and saturated aliphatic alcohols having 1 to 22 carbon atoms; esters of (meth)acrylic acid and alicyclic alcohols having 5 or 6 carbon atoms; and esters of (meth)acrylic acid and phenols or aromatic alcohols.

[0170] More specifically, examples of (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, and benzyl (meth)acrylate. Note that "(meth)acrylate" is a general term for acrylate and methacrylate, and refers to either or both of them.

[0171] Examples of polyfunctional monomers include esters of unsaturated monocarboxylic acids and unsaturated alcohols; diesters of unsaturated monocarboxylic acids and glycols; aromatic divinyl monomers; diesters of dicarboxylic acids and unsaturated alcohols; and conjugated diene monomers.

[0172] Examples of unsaturated monocarboxylic acids include (meth)acrylic acid and cinnamic acid. Examples of unsaturated alcohols include allyl alcohol and methallyl alcohol. Examples of glycols include ethylene glycol, propanediol, butanediol, and hexanediol. Examples of aromatic divinyl monomers include divinylbenzene. Examples of dicarboxylic acids include phthalic acid, terephthalic acid, isophthalic acid, and maleic acid.

[0173] Examples of conjugated diene monomers include butadiene, isoprene, 2,3-dimethylbutadiene, 2-methyl-3-ethylbutadiene, 1,3-pentadiene, 3-methyl-1,3-pentadiene, 2-ethyl-1,3-pentadiene, 1,3-hexadiene, 2-methyl-1,3-hexadiene, 3,4-dimethyl-1,3-hexadiene, 1,3-heptadiene, 3-methyl-1,3-heptadiene, 1,3-octadiene, cyclopentadiene, chloroprene, and myrcene.

[0174] More specifically, examples of the polyfunctional monomer include allyl (meth)acrylate, methallyl (meth)acrylate, allyl cinnamate, methallyl cinnamate, diallyl maleate, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, divinylbenzene, ethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, and hexanediol di(meth)acrylate.

[0175] Examples of other monofunctional monomers include aromatic vinyl monomers and vinyl cyanide monomers.

[0176] Examples of aromatic vinyl monomers include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-(phenylbutyl)styrene, and halogenated styrenes.

[0177] Examples of vinyl cyanide monomers include acrylonitrile and methacrylonitrile.

[0178] The colorant contained in the colored layer may be a known pigment or dye used in paints for printing on resin films. The colorant may be a single type or a combination of two or more types. The colorant is used in an amount according to the desired color to be expressed in the decorative film.

[0179] Examples of white colorants include titanium oxide and barium sulfate.

[0180] Examples of black colorants include iron black, carbon black, and aniline black.

[0181] Examples of yellow colorants include cadmium yellow and oil yellow 2G.

[0182] Examples of orange colorants include chrome vermilion and cadmium orange.

[0183] Examples of red colorants include cadmium red, permanent red 4R, and oil red.

[0184] Examples of purple colorants include cobalt violet and anthraquinone violet.

[0185] Examples of blue colorants include ultramarine, Prussian blue, and cobalt blue.

[0186] Examples of green colorants include phthalocyanine green and chrome green.

[0187] The content of the colorant in the colored layer may be, for example, 10 parts by mass or more and 30 parts by mass or less, and preferably 15 parts by mass or more or 25 parts by mass or less, relative to 100 parts by mass of the acrylic resin.

[0188] The colored layer may further contain other components in addition to the acrylic resin and colorant. Examples of the other components include ultraviolet absorbers, light stabilizers, plasticizers, extender pigments, and matting agents. Examples of ultraviolet absorbers include benzotriazole compounds, benzophenone compounds, cyanoacrylate compounds, ultrafine zinc oxide, and titanium oxide. Examples of light stabilizers include hindered amine compounds.

[0189] When the colored layer contains other components, the content of the other components may be, for example, 0.01 parts by mass or more and 10 parts by mass or less, preferably 0.1 parts by mass or more and 8 parts by mass or less, more preferably 0.3 parts by mass or more and 5 parts by mass or less, and even more preferably 0.3 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the acrylic resin.

[0190] The thickness of the colored layer may be, for example, 60 μm or more and 150 μm or less. From the viewpoint of fully expressing the desired chromaticity, the lower limit of the thickness of the colored layer may be preferably 80 μm or more, more preferably 100 μm or more. The upper limit of the thickness of the colored layer can be determined appropriately from the above viewpoint, and may be preferably 130 μm or less, more preferably 110 μm or less. The thickness of the colored layer can be measured with a micrometer and calculated as the arithmetic average of the measurements at five points.

[0191] The colored layer may have an upper yield point load at 20°C of, for example, 7.5 N / 10 mm or more and 18.0 N / 10 mm or less. The lower limit of the upper yield point load of the colored layer at 20°C may be preferably 8.0 N / 10 mm or more, more preferably 9.0 N / 10 mm or more, and even more preferably 10.0 N / 10 mm or more, from the viewpoint of improving application ease. The upper limit of the upper yield point load of the colored layer at 20°C may be preferably 15.0 N / 10 mm or less, more preferably 14.0 N / 10 mm or less, and even more preferably 13.5 N / 10 mm or less, from the viewpoint of improving curved surface conformability. When the upper yield point load of the colored layer at 20°C is equal to or greater than the lower limit, the occurrence of wrinkles during application of the decorative film tends to be easily suppressed. Furthermore, when the upper yield point load of the colored layer at 20°C is equal to or less than the upper limit, the occurrence of lifting after application tends to be easily suppressed. The upper yield point load of the colored layer can be adjusted by using (meth)acrylic resins having different upper yield point loads in combination in an appropriate amount ratio.

[0192] The colored layer can be produced by mixing the components contained in the colored layer, such as an acrylic resin, a colorant, and other components, and molding the resulting mixture into a film. The film formation of the colored layer may be carried out by, for example, extrusion molding, calendar molding, etc.

[0193] The base film may further include layers other than the surface protective layer and the colored layer. Examples of such layers include a second pressure-sensitive adhesive layer interposed between the surface protective layer and the colored layer to bond the two layers together. In one embodiment, the second pressure-sensitive adhesive layer may be disposed between the surface protective layer and the colored layer. That is, in one embodiment, the decorative film may be a laminate in which the surface protective layer, the second pressure-sensitive adhesive layer, the colored layer, and the first pressure-sensitive adhesive layer are laminated in this order.

[0194] The second pressure-sensitive adhesive layer can be made of various known pressure-sensitive adhesives such as rubber-based pressure-sensitive adhesives, acrylic-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, polyvinyl ether-based pressure-sensitive adhesives, etc. The second pressure-sensitive adhesive layer may also be formed using the pressure-sensitive adhesive composition that forms the first pressure-sensitive adhesive layer.

[0195] The thickness of the second pressure-sensitive adhesive layer may be appropriately set depending on the type of pressure-sensitive adhesive layer and the object to be adhered, for example, from 3 μm to 70 μm, preferably 10 μm to 50 μm, more preferably 15 μm to 45 μm, and even more preferably 20 μm to 40 μm. The thickness of the second pressure-sensitive adhesive layer can be measured with a micrometer and calculated as the arithmetic mean of measurements at five points.

[0196] The thickness of the base film is expressed, for example, as the sum of the thickness of the surface protective layer, the thickness of the colored layer, and the thickness of the second pressure-sensitive adhesive layer. From the viewpoint of the ease of application of the decorative film and its ability to conform to curved surfaces, the thickness of the base film may be, for example, 100 μm to 200 μm, preferably 120 μm to 180 μm, and more preferably 140 μm to 170 μm.

[0197] The upper yield point load of the substrate film at 20° C. may be, for example, 10.0 N / 10 mm or more and 45.0 N / 10 mm or less, preferably 13.7 N / 10 mm or more and 30.0 N / 10 mm or less, more preferably 15.0 N / 10 mm or more and 25.0 N / 10 mm or less, and even more preferably 17.0 N / 10 mm or more and 20.0 N / 10 mm or less. When the upper yield point load of the substrate film at 20° C. is equal to or more than the above lower limit, the application property of the decorative film is easily improved, and when it is equal to or less than the above upper limit, the curved surface conformability of the decorative film is easily improved.

[0198] The stress relaxation rate of the base film at 20° C. may be, for example, 50% or more and 63% or less, preferably 53% or more and 60% or less, and more preferably 55% or more and 58% or less. When the stress relaxation rate of the base film at 20° C. is equal to or more than the above-mentioned lower limit, the application property of the decorative film is easily improved, and when it is equal to or less than the above-mentioned upper limit, the curved surface conformability of the decorative film is easily improved.

[0199] In this specification, the stress relaxation rate of a base film at 20°C is the rate of change in tensile load before and after stretching when a tensile load is applied to the decorative film for 5 minutes at a stretching rate of 300 mm / min to stretch it by 5% (to 105% of its length). The temperature of the base film when measuring the stress relaxation rate is 20°C. The stress relaxation rate of the base film can be calculated using the following formula, where x is the tensile load immediately after 5% stretching and y is the tensile load 5 minutes after 5% stretching.

[0200] Stress relaxation rate z[%]={(xy) / x}×100

[0201] The stress relaxation rate of the substrate film can be determined by measuring the tensile load using a known measuring device such as a Tensilon universal testing machine. The stress relaxation rate of the substrate film can also be adjusted by the material resins of the surface protective layer, colored layer, and the like that constitute the substrate film, or the thickness of the layers.

[0202] In this specification, unless otherwise specified, when the base film is a laminate having a laminate structure, the upper yield point load and stress relaxation rate of the base film refer to the upper yield point load and stress relaxation rate of the laminate. For example, when the base film is a laminate having a surface protective layer and a colored layer, the upper yield point load and stress relaxation rate of the base film refer to the upper yield point load and stress relaxation rate of the laminate of the surface protective layer and the colored layer. Furthermore, when the base film is a laminate further having a second pressure-sensitive adhesive layer, the upper yield point load and stress relaxation rate of the base film refer to the upper yield point load and stress relaxation rate of the laminate formed by stacking the surface protective layer, the second pressure-sensitive adhesive layer, and the colored layer in this order.

[0203] The substrate film can be produced by a method that allows the surface protective layer and the colored layer to be stacked in this order, for example.

[0204] For example, the substrate film can be produced by a method including the steps of preparing a surface protective layer, preparing a colored layer, and attaching the surface protective layer to the colored layer.

[0205] The surface protective layer and the colored layer may be prepared by the methods described above.

[0206] The step of attaching the surface protective layer to the colored layer may be, for example, a step of directly bonding the colored layer and the surface protective layer by heat fusion or the like. Alternatively, the step of attaching the surface protective layer to the colored layer may be a step of supplying the material of the other layer in a layer form onto one surface of a previously prepared colored layer or surface protective layer, and bonding the other layer onto the one layer. Furthermore, the step of attaching the surface protective layer to the colored layer may be a step of applying a second adhesive layer to one surface of the colored layer and attaching the surface protective layer to the second adhesive layer obtained. Attaching the colored layer and the surface protective layer via the second adhesive layer is advantageous from the viewpoint of increasing the degree of freedom in the material design of both layers.

[0207] The thickness of the decorative film is represented by the sum of the thickness of the base film and the thickness of the pressure-sensitive adhesive layer, and may be, for example, from 100 μm to 300 μm, preferably from 150 μm to 250 μm, and more preferably from 180 μm to 220 μm.

[0208] The decorative film is preferably used for purposes of adhering to an object to be decorated to decorate the object. The decorative film is preferably used as a vehicle exterior film that is adhered to an exterior part of a vehicle. Examples of the substrate to which the decorative film is attached include a urethane-coated plate, a melamine-coated plate, an aluminum plate, and a stainless steel plate.

[0209] The decorative film can be produced by forming a first pressure-sensitive adhesive layer on a substrate film by the above-mentioned method. When the substrate film includes a surface protective layer and a colored layer, the first pressure-sensitive adhesive layer is formed on the colored layer side of the substrate film.

[0210] The present invention will be explained in more detail by the following examples, but the present invention is not limited to these examples. [Example]

[0211] [Synthesis of (meth)acrylic copolymer] The (meth)acrylic copolymers (A1) to (A6) and the (meth)acrylic copolymers (B1) to (B3) were synthesized as follows.

[0212] Each (meth)acrylic copolymer was synthesized by solution polymerization. More specifically, ethyl acetate was used as the solvent, and 0.026 parts by mass of 2,2'-azobisisobutyronitrile (AIBN; polymerization initiator) was added to 20 parts by mass of the monomer mixture under reflux temperature conditions. 80 parts by mass of the monomer mixture was then added dropwise over 120 minutes, and after the dropwise addition was completed, the reaction was continued for another 30 minutes. The mixture was then diluted with ethyl acetate to a solids concentration of 35.0% by mass, yielding a solution of each (meth)acrylic copolymer.

[0213] In the synthesis of (meth)acrylic copolymer (B3), 0.05 parts by mass of silicone (polydimethylsiloxane) was added to the (meth)acrylic copolymer synthesis product after the completion of the reaction in the above-mentioned method, and then diluted with ethyl acetate to a solid content of 35.0% by mass to obtain a solution of (meth)acrylic copolymer (B3).

[0214] The compositions of the structural units derived from the monomers in the obtained (meth)acrylic copolymers (A) and (B), the contents of the structural units (a1), (b1), and glass transition temperatures are shown in Tables 1 and 2 below.

[0215] [Table 1]

[0216] [Table 2]

[0217] The abbreviations in Tables 1 and 2 are as follows: BA: n-butyl acrylate, 2EHA: 2-ethylhexyl acrylate, MA: methyl acrylate, AA: acrylic acid, t-BMA: t-butyl methacrylate, 2HEMA: 2-hydroxyethyl methacrylate, MMA: methyl methacrylate, EA: ethyl acrylate, DM: dimethylaminoethyl methacrylate, silicone: polydimethylsiloxane

[0218] The glass transition temperature of the (meth)acrylic copolymer was calculated from Formula 1 (Fox's formula). The glass transition temperatures of the homopolymers of the respective monomers used to calculate the glass transition temperatures are as follows:

[0219] n-Butyl acrylate (n-BA): -54°C, 2-ethylhexyl acrylate (2EHA): -70°C, methyl acrylate (MA): 10°C, acrylic acid (AA): 106°C, t-butyl acrylate (t-BA): 43°C, 2-hydroxyethyl methacrylate (2HEMA): 85°C, methyl methacrylate (MMA): 105°C, ethyl acrylate (EA): -22°C, dimethylaminoethyl methacrylate (DM): 18°C.

[0220] [Preparation of Pressure-Sensitive Adhesive Composition] The crosslinking agents used in the pressure-sensitive adhesive compositions are as follows. (Crosslinking agent) EP: TETRAD-X (epoxy crosslinking agent, manufactured by Mitsubishi Gas Chemical Company, Inc.) MC: Aluminum Chelate A (metal chelate crosslinking agent, manufactured by Kawaken Fine Chemicals Co., Ltd.) ICN: Coronate (registered trademark) L45 (isocyanate-based crosslinking agent, manufactured by Tosoh Corporation)

[0221] (Adhesive composition AD1) To an acrylic copolymer (A1) (solid content: 100 parts by mass), a methacrylic copolymer (B1) (solid content: 10 parts by mass) and 0.08 parts by mass of EP (crosslinking agent) were added, and a pressure-sensitive adhesive composition AD1 was prepared using ethyl acetate as a diluting solvent to give a solid content of 27% by mass.

[0222] (Adhesive compositions AD2 to AD18) According to the compositions shown in Tables 3 and 4 below, adhesive compositions AD2 to AD18 were prepared in the same manner as adhesive composition AD1 by adding methacrylic copolymer (B) and a crosslinking agent to acrylic copolymer (A).

[0223] [Preparation of adhesive layer] The pressure-sensitive adhesive composition was applied to the easily peelable surface of a release film (trade name: Film Byna (registered trademark) 100E-0010 No. 23, thickness: 100 μm, manufactured by Fujimori Kogyo Co., Ltd.) that had been treated with a silicone-based release agent to provide an easy-release treatment, so that the coating film would have a thickness of 40 μm after drying. The formed coating film was then dried using a hot air circulation dryer at a drying temperature of 100°C for 1 minute, forming an adhesive film on the release film. The exposed surface of the adhesive film was then laminated to the easily peelable surface of a separately prepared release film (trade name: Film Byna (registered trademark) 100E-0010 No. 23, thickness: 100 μm, manufactured by Fujimori Kogyo Co., Ltd.) that had been treated with a silicone-based release agent, and the resulting mixture was left to stand for 168 hours in an environment with an ambient temperature of 40°C and 50% RH to allow the adhesive film to age, thereby producing a substrate-free adhesive sheet. The pressure-sensitive adhesive sheet thus produced has a laminated structure of release film / pressure-sensitive adhesive layer / release film.

[0224] [Loss tangent and glass transition temperature of adhesive layer] Using the pressure-sensitive adhesive layer peeled from the pressure-sensitive adhesive sheet after curing, the dynamic viscoelasticity of the pressure-sensitive adhesive layer was measured according to the following procedure, and each loss tangent and glass transition temperature of the pressure-sensitive adhesive layer was determined.

[0225] The pressure-sensitive adhesive layer was cut into a size of 25 mm wide and 150 mm long and rolled into a cylindrical sample. Dynamic viscoelasticity was measured using a Reogel-E4000 (manufactured by UBM Corporation) under the following conditions: test temperature -50 to 130°C, heating rate 5°C / min, vibration frequency 10 Hz, and tensile length 10 mm. The loss tangent tanδA at 23°C and the loss tangent tanδA' at 80°C were determined. The difference between tanδA and tanδA' (tanδA - tanδA') was calculated from the obtained values ​​of tanδA and tanδA'. Here, the glass transition temperature of the pressure-sensitive adhesive layer was defined as the temperature at which the loss tangent tanδ, which is the ratio of the storage modulus to the loss modulus, shows its peak.

[0226] The aged pressure-sensitive adhesive sheet was then stored for 24 hours in an environment at 23°C and 50% humidity, followed by 168 hours in an environment at 80°C. After leaving the pressure-sensitive adhesive sheet at rest for 24 hours in an environment at 23°C, the pressure-sensitive adhesive layer was cut into a size of 25 mm wide and 150 mm long and rolled into a cylindrical shape. Using a Reogel-E4000 (manufactured by UBM Corporation), dynamic viscoelasticity was measured at a test temperature of -50 to 130°C, a heating rate of 5°C / min, a vibration frequency of 10 Hz, and a tensile length of 10 mm. The loss tangent tanδB at 23°C after 168 hours of storage in an environment at 80°C was then determined. The ratio of tanδB to tanδA (tanδB / tanδA) was calculated from the obtained values ​​of tanδA and tanδB.

[0227] [Gel fraction of adhesive layer] The pressure-sensitive adhesive layer was peeled off from the prepared pressure-sensitive adhesive sheet, and the gel fraction of the pressure-sensitive adhesive layer was measured according to the following (1) to (4).

[0228] (1) The mass (X) of a 250-mesh wire mesh (100 mm × 100 mm) was measured using a precision balance. Approximately 0.15 g of an adhesive layer was attached to the wire mesh, and the wire mesh was folded five times with the attached adhesive layer facing inward to prevent leakage of the gel, to prepare a sample. Thereafter, the mass (Y) of the wire mesh with the adhesive layer attached before immersion was measured using a precision balance. (2) The obtained sample was immersed in 80 mL of ethyl acetate for 3 days. (3) The sample was taken out, washed with a small amount of ethyl acetate, and dried for 24 hours at 120° C. Thereafter, the mass (Z) of the immersed and dried wire mesh with the adhesive layer attached was measured using a precision balance. (4) The gel fraction was calculated using the following formula. Gel fraction (unit: mass%) = (ZX) / (YX) × ​​100 where X is the mass of the wire mesh (unit: g), Y is the mass of the wire mesh with the adhesive layer attached (unit: g) before immersion, and Z is the mass of the wire mesh with the adhesive layer attached after immersion and drying (unit: g).

[0229] [Preparation of base film] <Material> The materials used are listed below.

[0230] (Polyurethane resin) Polyurethane resin 1: Lezamin (registered trademark) NE-8836 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd., polycarbonate type)

[0231] (acrylic resin) Acrylic resin 1 (hard acrylic resin) Parapet (registered trademark) GR-F1000P (manufactured by Kuraray Co., Ltd., upper yield point load at 20°C when film thickness is 100 μm is 27.1 N / 10 mm, Shore A hardness 100) Acrylic resin 2 (soft acrylic resin) Parapet (registered trademark) SA-F1000P (manufactured by Kuraray Co., Ltd., upper yield point load at 20°C when film thickness is 100 μm is 3.9 N / 10 mm, Shore A hardness 70)

[0232] (adhesive) Adhesive 0 Tg = -37.4°C, adhesive made by crosslinking acrylic resin with a BA / AA composition ratio of 90:10 with Aluminum Chelate A (manufactured by Kawaken Fine Chemicals Co., Ltd.)

[0233] (additives) Additive 1: Tinuvin® 234 (manufactured by BASF Japan Ltd., ultraviolet absorber) Additive 2: Tinuvin® 213 (manufactured by BASF Japan Ltd., ultraviolet absorber)

[0234] <Preparation of Colored Layer> The following components were dry-blended in the amounts shown below, then kneaded in a Henschel mixer, and then formed into a 100 μm thick film using a calendar molding machine set at 180°C to produce colored layer 1. The carbon black shown below is a carbon black pigment (product name "W-8012-G5") manufactured by Nichiko Bix Co., Ltd., and is coated with an acrylic resin. The upper yield point load of the obtained colored layer 1 was measured, and the upper yield point load of colored layer 1 at 20°C was 10.6 N / 10 mm. Acrylic resin 1 50 parts by mass Acrylic resin 2 50 parts by mass Carbon black 19 parts by mass Additive 1 0.3 parts by mass

[0235] <Creating a surface protective layer> A dispersion of 100 parts by mass of polyurethane resin 1 in a 1:1 IPA:toluene solution, containing 25% solids by mass, was mixed with 1.2 parts by mass of additive 2 and then cast. The mixture was then dried at 80°C for 3 minutes and then at 140°C for 3 minutes to form a film with a thickness of 30 μm. Surface protective layer 1 was thus produced. The upper yield point load of surface protective layer 1 at 20°C was 5.9 N / 10 mm.

[0236] <Adhesion between colored layer and surface protective layer> Surface protective layer 1 was overlaid on a coating of adhesive 0 formed by applying adhesive 0 to one surface of colored layer 1, and surface protective layer 1 was adhered to colored layer 1. In this way, substrate film 1 was produced, in which colored layer 1, adhesive layer 0 made of adhesive 0, and surface protective layer 1 were overlaid in this order. The thickness of adhesive layer 1 was 30 μm. The upper yield point load of the obtained substrate film 1 at 20° C. was 17.4 N / 10 mm.

[0237] [Creating decorative film] Example 1 The adhesive composition AD1 was applied to the release-treated surface of a release paper (product name: AirXLiner™, thickness: 180 μm, manufactured by Mondi) that had been treated with a silicone release agent to achieve an easy-release treatment, to form a coating film with a dry thickness of 40 μm. The coating film was then dried using a hot air circulation dryer at a drying temperature of 100°C for 1 minute to form an adhesive film on the release film. The exposed surface of the adhesive film was then laminated to the colored layer 1 side of the base film 1, and the film was then left to stand for 168 hours in an environment with an ambient temperature of 40°C and 50% RH to allow the adhesive film to age, thereby producing a decorative film including an adhesive layer AD1 formed from the adhesive composition AD1 on the release paper. The resulting decorative film had a laminate structure of surface protective layer 1 / adhesive layer 1 / colored layer 1 / adhesive layer AD1.

[0238] <Examples 2 to 10 and Comparative Examples 1 to 8> Decorative films were produced in the same manner as in Example 1, except that adhesive compositions AD2 to AD18 were used instead of adhesive composition AD1.

[0239] [Evaluation of adhesive strength and adhesive residue] The decorative films obtained in the Examples and Comparative Examples were cut to a width of 10 mm and a tensile length of 100 mm. The release paper was peeled from the cut decorative film, and the decorative film was attached to a urethane-coated plate prepared as an adherend using a 2 kg roller, with a load applied twice back and forth, to produce a sample piece. The prepared sample piece was stored in an environment of 23°C and 50% humidity for 1 hour after application. The adhesive strength of this to the urethane-coated plate was measured using a Tensilon (registered trademark) (manufactured by A&D Co., Ltd.) at a peel rate of 200 mm / min, a peel angle of 180°, and a measurement temperature of 23°C. The adhesive strength after 1 hour at 23°C was measured. An adhesive strength of 8.0 N / 10 mm or less after 1 hour at 23°C indicates a pressure-sensitive adhesive layer that is easy to reapply when attaching the decorative film to an adherend.

[0240] The prepared sample pieces were stored in an environment of 23°C and 50% humidity for 168 hours after application, and the adhesive strength of these samples to a urethane-coated plate was measured using Tensilon (registered trademark) (manufactured by A&D Co., Ltd.) at a peel speed of 200 mm / min, a peel angle of 180°, and a measurement temperature of 23°C.

[0241] Furthermore, the prepared sample pieces were stored in an environment of 23°C and 50% humidity for 24 hours, and then placed in an environment of 80°C for 168 hours. After leaving them to stand in the 23°C environment for 24 hours, the adhesive strength to a urethane-coated plate was measured using Tensilon (registered trademark) (manufactured by A&D Corporation) at a peel rate of 200 mm / min, a peel angle of 180°, and a measurement temperature of 23°C, and the adhesive strength of the product stored at 80°C was measured.

[0242] Furthermore, for each sample piece, the state of the adherend was observed when the adhesive strength was measured for the samples stored at 23°C and 80°C, and the presence or absence of adhesive residue was visually confirmed.

[0243] The measurement results and evaluation results of the pressure-sensitive adhesive layer are shown in Tables 3 and 4.

[0244] [Table 3]

[0245] [Table 4]

Claims

1. Contains a (meth)acrylic copolymer and an epoxy crosslinking agent, The loss tangent tanδA at 23 ° C after aging is 1.00 or more and 1.68 or less, the difference between the loss tangent tanδA at 23°C after curing and the loss tangent tanδA' at 80°C after curing is 1.25 or less; A pressure-sensitive adhesive composition having a gel fraction of 75 mass% or less after curing.

2. The pressure-sensitive adhesive composition according to claim 1, wherein the (meth)acrylic copolymer comprises a (meth)acrylic copolymer (A) having a glass transition temperature of −49° C. or higher and −13° C. or lower, and a (meth)acrylic copolymer (B) having a glass transition temperature of 75° C. or higher and 115° C. or lower.

3. The pressure-sensitive adhesive composition according to claim 2, wherein the content of the (meth)acrylic copolymer (B) is 5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the (meth)acrylic copolymer (A).

4. 3. The pressure-sensitive adhesive composition according to claim 2, wherein the (meth)acrylic copolymer (A) contains a structural unit (a1) derived from a monomer having an acidic functional group, and the content of the structural unit (a1) is 1% by mass or more and 6% by mass or less, based on all structural units contained in the (meth)acrylic copolymer (A).

5. The adhesive layer is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic copolymer and an epoxy-based crosslinking agent, a loss tangent tanδA at 23°C of 1.00 or more and 1.68 or less; the difference between the loss tangent tanδA at 23°C and the loss tangent tanδA' at 80°C is 1.25 or less; A pressure-sensitive adhesive layer having a gel fraction of 75% by mass or less.

6. The pressure-sensitive adhesive layer according to claim 5, wherein the ratio of loss tangent tanδB at 23°C after storage in an 80°C environment for 168 hours to loss tangent tanδA at 23°C is 0.95 or more and 1.05 or less.

7. The pressure-sensitive adhesive layer according to claim 5 , which has a glass transition temperature of 15° C. or lower.

8. The pressure-sensitive adhesive layer according to any one of claims 5 to 7, which is used for a coating surface decoration film for a vehicle.

9. A decorative film comprising the pressure-sensitive adhesive layer according to any one of claims 5 to 7.

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