Adhesive sheet, adhesive composition, and decorative molded body

Abstract

Provided is an adhesive sheet equipped with an adhesive layer, where the adhesive layer includes an acrylic adhesive polymer and a modified polymer that is at least one selected from the group consisting of modified polyolefins and modified polydienes, and the acrylic adhesive polymer and the modified polymer undergo phase separation in the surface layer portion of the adhesive layer to form an adhesive sheet. Also provided is an adhesive composition that contains an acrylic adhesive polymer and a modified polymer, where phase separation of the acrylic adhesive polymer and modified polymer occurs in the process of forming an adhesive layer on a base material by applying the adhesive composition to a base material and removing the solvent.

Description

Adhesive sheet, adhesive composition, and decorated molded article

[0001] [Cross-reference to related applications] This application claims priority to Japanese Patent Application No. 2023-101845, filed on June 21, 2023, the entire contents of which are incorporated herein by reference. The present disclosure relates to a pressure-sensitive adhesive sheet, a pressure-sensitive adhesive composition, and a decorated molded body, and more particularly to a technology for improving the adhesion of an acrylic pressure-sensitive adhesive to a low-polarity material.

[0002] Acrylic pressure-sensitive adhesives are processed into, for example, tapes and labels and are used in a wide range of applications. Acrylic pressure-sensitive adhesives are also applied to a wide range of materials, including plastics, paper, metals, glass, and ceramics. In recent years, decorative films have been applied or transferred to molded products, primarily automotive interior and exterior components and home appliances, for the purpose of improving design and addressing VOC (volatile organic compounds) emissions. Forming methods using decorative films include in-mold molding using injection molding, vacuum forming, and vacuum-pressure forming. Decorative films having a pressure-sensitive adhesive layer are known as decorative films to be applied to molded products.

[0003] Pressure-sensitive adhesives are generally required to exhibit high adhesion to adherends. On the other hand, acrylic pressure-sensitive adhesives generally exhibit poor adhesion to low-polarity materials such as polypropylene. Therefore, various techniques for improving the adhesion of acrylic pressure-sensitive adhesives to low-polarity materials have been proposed (see, for example, Patent Document 1). Patent Document 1 discloses a pressure-sensitive adhesive sheet having a layer containing a modified polyolefin on at least one side of a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition.

[0004] International Publication No. 2020 / 004355

[0005] Considering that adhesives are used in a wide range of applications, it is desirable for them to exhibit high adhesive properties over a wide temperature range. Furthermore, when adding a design to a molded product using a decorative film, the decorative film is sometimes stretched before being attached to the molded product. A decorative film attached to a molded product in a stretched state is prone to slippage, peeling, or lifting from the molded product at high temperatures, which can result in poor appearance. Therefore, adhesives are required to exhibit excellent adhesive properties not only at room temperature but also at high temperatures.

[0006] The present disclosure has been made in view of the above circumstances, and a main object thereof is to provide a pressure-sensitive adhesive sheet having excellent adhesiveness both at room temperature and at high temperatures, and a pressure-sensitive adhesive composition from which the pressure-sensitive adhesive sheet can be obtained.

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems, and have found that in a pressure-sensitive adhesive layer containing an acrylic adhesive polymer and a modified polyolefin and / or a modified polydiene, the above-mentioned problems can be solved by forming a specific structure in the acrylic adhesive polymer and the modified polyolefin and / or the modified polydiene. Specifically, the present disclosure provides the following pressure-sensitive adhesive sheet, pressure-sensitive adhesive composition, and decorated molded article.

[0008] [1] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer comprising an acrylic pressure-sensitive adhesive polymer and at least one modified polymer selected from the group consisting of modified polyolefins and modified polydiene, wherein the acrylic pressure-sensitive adhesive polymer and the modified polymer are phase-separated in a surface portion of the pressure-sensitive adhesive layer. [2] The pressure-sensitive adhesive sheet according to [1] above, wherein the concentration of the modified polymer in the surface portion of the pressure-sensitive adhesive layer is higher than the concentration of the modified polymer throughout the pressure-sensitive adhesive layer. [3] The pressure-sensitive adhesive sheet according to [1] or [2] above, wherein the concentration of the modified polymer in the surface portion of the pressure-sensitive adhesive layer, as determined by X-ray photoelectron spectroscopy, is 1.5 times or more the concentration of the modified polymer throughout the pressure-sensitive adhesive layer. [4] The pressure-sensitive adhesive sheet according to any one of [1] to [3] above, wherein the haze value of the pressure-sensitive adhesive layer is 3.0% or more when the thickness of the pressure-sensitive adhesive layer is 50 μm. [5] The pressure-sensitive adhesive sheet according to any one of [1] to [4] above, wherein the modified polymer is at least one selected from the group consisting of acid-modified polyolefins, chlorinated polyolefins, acid-modified chlorinated polyolefins, acrylic-modified polyolefins, and acrylic-modified chlorinated polyolefins. [6] The pressure-sensitive adhesive sheet according to any one of [1] to [5] above, wherein the modified polymer is modified with at least one selected from the group consisting of carboxylic acids, carboxylic acid anhydrides, and (meth)acrylic acid esters. [7] The pressure-sensitive adhesive sheet according to any one of [1] to [6] above, wherein the modified polymer has a modification rate of 80% or less. [8] The pressure-sensitive adhesive sheet according to any one of [1] to [7] above, wherein the modified polymer has a melting point of 20°C or higher and 130°C or lower. [9] The pressure-sensitive adhesive sheet according to any one of [1] to [8] above, wherein the pressure-sensitive adhesive is a decorative film.

[10] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer contains an acrylic adhesive polymer and a modified polymer that is at least one selected from the group consisting of modified polyolefins and modified polydiene, and wherein the pressure-sensitive adhesive layer has a haze value of 3.0% or more when the thickness of the pressure-sensitive adhesive layer is 50 μm.

[0009]

[11] A pressure-sensitive adhesive composition used for forming a pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition comprising an acrylic pressure-sensitive adhesive polymer, at least one modified polymer selected from the group consisting of modified polyolefins and modified polydiene, and a solvent, wherein phase separation between the acrylic pressure-sensitive adhesive polymer and the modified polymer occurs during the process of forming the pressure-sensitive adhesive layer on the substrate by applying the pressure-sensitive adhesive composition to the substrate and removing the solvent.

[12] The pressure-sensitive adhesive composition according to

[11] above, wherein the concentration of the modified polymer in the surface layer portion of the pressure-sensitive adhesive layer is higher than the concentration of the modified polymer throughout the pressure-sensitive adhesive layer.

[13] The pressure-sensitive adhesive composition according to

[11] or

[12] above, wherein the concentration of the modified polymer in the surface layer portion of the pressure-sensitive adhesive layer, as determined by X-ray photoelectron spectroscopy, is 1.5 times or more the concentration of the modified polymer throughout the pressure-sensitive adhesive layer.

[14] The pressure-sensitive adhesive composition according to any one of

[11] to

[13] above, wherein the haze value of the pressure-sensitive adhesive layer when the thickness of the pressure-sensitive adhesive layer is 3.0% or more when the thickness of the pressure-sensitive adhesive layer is 50 μm.

[15] The pressure-sensitive adhesive composition according to any one of

[11] to

[14] above, wherein the glass transition temperature of the acrylic pressure-sensitive adhesive polymer is −40° C. or higher.

[16] The pressure-sensitive adhesive composition according to any one of

[11] to

[15] above, wherein the weight-average molecular weight of the acrylic pressure-sensitive adhesive polymer is 450,000 or higher.

[0010]

[17] The pressure-sensitive adhesive composition according to any one of

[11] to

[16] above, wherein the acrylic pressure-sensitive adhesive polymer contains 30 mass% or more of structural units derived from at least one selected from the group consisting of (meth)acrylic acid alkyl esters having an alkyl group of 1 to 3 carbon atoms and (meth)acrylic acid alkoxyalkyl esters having an alkoxyalkyl group of 3 or 4 carbon atoms, relative to all structural units contained in the acrylic pressure-sensitive adhesive polymer.

[18] The pressure-sensitive adhesive composition according to any one of

[11] to

[17] above, wherein the proportion of structural units derived from an amino group-containing unsaturated compound in the acrylic pressure-sensitive adhesive polymer is 0.2 mass% or less, relative to all structural units contained in the acrylic pressure-sensitive adhesive polymer.

[19] The pressure-sensitive adhesive composition according to any one of

[11] to

[18] above, wherein the modified polymer is at least one selected from the group consisting of acid-modified polyolefins, chlorinated polyolefins, acid-modified chlorinated polyolefins, acrylic-modified polyolefins, and acrylic-modified chlorinated polyolefins.

[20] The pressure-sensitive adhesive composition according to any one of

[11] to

[19] above, further comprising a crosslinking agent.

[21] A solvent-based pressure-sensitive adhesive composition comprising an acrylic pressure-sensitive adhesive polymer, a modified polymer that is at least one selected from the group consisting of modified polyolefins and modified polydiene, and a solvent, wherein when the pressure-sensitive adhesive composition is applied to a substrate and the solvent is removed to form a pressure-sensitive adhesive layer having a thickness of 50 μm on the substrate, the pressure-sensitive adhesive layer has a haze value of 3.0% or more.

[22] A decorated molded article in which the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of [1] to

[10] above is attached to a molded article.

[0011] The pressure-sensitive adhesive sheet of the present disclosure can exhibit high adhesiveness over a wide temperature range, from room temperature to high temperatures, and the pressure-sensitive adhesive composition of the present disclosure can provide a pressure-sensitive adhesive layer that exhibits excellent adhesiveness at both room temperature and high temperatures.

[0012] Fig. 1 is an image of the surface portion of the pressure-sensitive adhesive layer of Example 13 observed with a scanning probe microscope. Fig. 2 is an image of the surface portion of the pressure-sensitive adhesive layer of Comparative Example 4 observed with a scanning probe microscope.

[0013] The present disclosure will be described in detail below. In this specification, "(meth)acrylic" means acrylic and / or methacrylic. "(meth)acrylo" means acrylo and / or methacrylo. "(meth)acrylate" means acrylate and / or methacrylate.

[0014] <Adhesive Composition and Adhesive Layer> The adhesive composition of the present disclosure (hereinafter also simply referred to as "the composition") is used for forming a pressure-sensitive adhesive layer, and contains an acrylic adhesive polymer, at least one modified polymer selected from the group consisting of modified polyolefins and modified polydienes, and a solvent. The composition is a liquid composition in which the acrylic adhesive polymer and the modified polymer are dissolved in a solvent, so that the acrylic adhesive polymer and the modified polymer are in a single phase.

[0015] In a first aspect of the present composition, phase separation occurs between the acrylic adhesive polymer and the modified polymer contained in the composition during the process of forming a pressure-sensitive adhesive layer on a substrate by applying the composition to the substrate and removing the solvent. In a second aspect of the present composition, when a 50 μm-thick pressure-sensitive adhesive layer is formed on the substrate by applying the composition to the substrate and removing the solvent, the haze value of the pressure-sensitive adhesive layer is 3.0% or more. The pressure-sensitive adhesive layer obtained from this composition exhibits high adhesion both at room temperature and at high temperatures due to a well-balanced expression of the adhesive properties of the acrylic adhesive polymer and the adhesive properties of the modified polymer. First, the pressure-sensitive adhesive layer formed from the present composition will be described below.

[0016] (Adhesive Layer) The adhesive layer of the present disclosure can be produced by applying the present composition to a substrate and removing the solvent from the present composition on the substrate. Resin films made of various resin materials can be used as the substrate to which the present composition is applied. Examples of resin materials include polyester resins such as polyethylene terephthalate, polyethersulfone resins, acetate resins, polycarbonate resins, and polyolefin resins. It is preferable that the surface of the substrate to which the present composition is applied has releasability that allows the adhesive layer to be peeled off. Such a substrate is called a separator or release film. The releasability of the coating surface may be imparted by a known release treatment or may be due to the material of the substrate.

[0017] The composition can be applied by a known coating method, specifically, for example, a method using various coating machines such as a bar coater, an applicator, a gravure coater, a knife coater, a slot die coater, a doctor blade, or a dip coater, or a method using various printing machines such as gravure printing, offset printing, screen printing, or inkjet printing.

[0018] The composition coated on the substrate is preferably subjected to a heat treatment from the viewpoint of causing phase separation between the acrylic adhesive polymer and the modified polymer. The heating temperature and heating time during the heat treatment can be appropriately set depending on the type of solvent in the composition, the solids concentration of the composition, etc. The composition may be heated under normal pressure or under reduced pressure. The composition coated on the substrate is preferably subjected to a heat treatment to remove the solvent, thereby forming a pressure-sensitive adhesive layer, thereby causing phase separation between the acrylic adhesive polymer and the modified polymer during the formation of the pressure-sensitive adhesive layer. The thickness of the pressure-sensitive adhesive layer formed in this manner is, for example, 2 to 200 μm.

[0019] The pressure-sensitive adhesive layer obtained as described above is in a state in which the acrylic pressure-sensitive adhesive polymer and the modified polymer are phase-separated in its surface layer portion. That is, in the pressure-sensitive adhesive layer produced from the present composition, a first phase mainly composed of the acrylic pressure-sensitive adhesive polymer and a second phase mainly composed of the modified polymer are formed due to phase separation between the acrylic polymer and the modified polymer that occurs in the process of forming the pressure-sensitive adhesive layer. In this specification, "phase separation" refers to the separation of the acrylic pressure-sensitive adhesive polymer, the modified polymer, and the solvent in a single phase into a phase mainly composed of the acrylic pressure-sensitive adhesive polymer, a phase mainly composed of the modified polymer, and the solvent (gas phase) in accordance with thermodynamic equilibrium conditions in the process of removing the solvent. In a state in which the acrylic pressure-sensitive adhesive polymer and the modified polymer are phase-separated in the surface layer portion of the pressure-sensitive adhesive layer, a sea-island structure is typically formed, but is not limited to this. Phase separation is a different concept from segregation (more specifically, surface segregation), which describes the localization of a second polymer relative to a first polymer in the outermost layer in the thickness direction of a pressure-sensitive adhesive layer containing different polymers (referred to as a first polymer and a second polymer).

[0020] Figure 1 shows an image of the surface of a pressure-sensitive adhesive layer formed on a substrate by applying and heating the composition, as observed with a scanning probe microscope. To form the pressure-sensitive adhesive layer shown in Figure 1, the composition (acrylic polymer: modified polyolefin = 100:7 (mass ratio), solvent: toluene / cyclohexane = 75 / 25 (mass ratio), solid content 20 mass%, corresponding to the pressure-sensitive adhesive composition of Example 13 described below) was applied to a polyethylene terephthalate (PET) substrate and heated at 80°C to remove the solvent, thereby forming a pressure-sensitive adhesive layer with a film thickness of 50 μm. In Figure 1, the light-colored areas represent a phase (first phase P1) mainly composed of a relatively soft acrylic adhesive polymer, and the dark-colored areas represent a phase (second phase P2) mainly composed of a relatively hard polymer, modified polyolefin. As shown in Figure 1, the surface layer of the pressure-sensitive adhesive layer contains a mixture of a first phase P1 mainly composed of an acrylic adhesive polymer and a second phase P2 mainly composed of a modified polyolefin, and it can be seen that phase separation has occurred between the acrylic adhesive polymer and the modified polyolefin.

[0021] In addition, to obtain a pressure-sensitive adhesive layer in which the acrylic adhesive polymer and the modified polymer are phase-separated, for example, it can be achieved by adjusting the degree of modification of the modified polymer contained in the pressure-sensitive adhesive composition, adjusting the molecular weight of the modified polymer, adding a crosslinking agent, or combining these. The lower the degree of modification of the modified polymer, the more likely the modified polymer is to undergo phase separation from the acrylic adhesive polymer. Furthermore, the more likely the molecular weight of the modified polymer polyolefin is to be increased and approached to the molecular weight of the acrylic adhesive polymer, the more likely the modified polymer is to undergo phase separation from the acrylic adhesive polymer.

[0022] In addition, the difference in SP value between the acrylic adhesive polymer and the modified polymer contained in the adhesive composition may be a predetermined value or more, thereby obtaining an adhesive layer in which the acrylic adhesive polymer and the modified polymer are phase-separated at the surface layer portion. Here, the SP value is a solubility parameter, and can be calculated, for example, by the calculation method (Fedors method) described in "Polymer Engineering and Science" 14 (2), 147 (1974) written by R. F. Fedors. From the viewpoint of causing phase separation between the acrylic adhesive polymer and the modified polymer, the difference (absolute value) in the SP value between the acrylic adhesive polymer and the modified polymer is, for example, 1.0 or more, preferably 1.5 or more, and more preferably 1.8 or more.

[0023] Furthermore, the phase separation between the acrylic adhesive polymer and the modified polymer can be easily observed by observing the structure of a pressure-sensitive adhesive layer obtained using a pressure-sensitive adhesive composition in which a polymer blend of the intended acrylic adhesive polymer and the modified polymer is dissolved in a solvent using an electron microscope, a scanning probe microscope (such as an atomic force microscope), or small-angle X-ray scattering.

[0024] In the pressure-sensitive adhesive layer formed using the present composition, the acrylic adhesive polymer and the modified polymer are phase-separated, and further, the concentration of the modified polymer in the surface layer portion of the pressure-sensitive adhesive layer is preferably higher than the concentration of the modified polymer in the entire pressure-sensitive adhesive layer. Thus, a pressure-sensitive adhesive layer in which the acrylic adhesive polymer and the modified polymer are phase-separated within the layer and the modified polymer concentration in the surface layer portion is relatively high is preferable in that it exhibits higher adhesion both at room temperature and at high temperatures. The relatively high concentration of the modified polymer in the surface layer of the pressure-sensitive adhesive layer is thought to be mainly due to the difference in polarity and molecular weight between the modified polymer and the acrylic adhesive polymer. Specifically, it is thought to be because modified polymers with lower polarity or smaller molecular weight tend to be more present on the low-surface-energy interface side in the thickness direction of the pressure-sensitive adhesive layer.

[0025] Specifically, in the pressure-sensitive adhesive layer, the concentration of the modified polymer in the surface portion of the pressure-sensitive adhesive layer obtained by X-ray photoelectron spectroscopy is preferably 1.5 times or more the concentration of the modified polymer in the entire pressure-sensitive adhesive layer. From the viewpoint of obtaining a pressure-sensitive adhesive layer that exhibits even higher adhesiveness both at room temperature and at high temperatures, the concentration of the modified polymer in the surface portion of the pressure-sensitive adhesive layer is more preferably 1.8 times or more, even more preferably 2.0 times or more, even more preferably 2.2 times or more, and even more preferably 2.5 times or more the concentration of the modified polymer in the entire pressure-sensitive adhesive layer. In the pressure-sensitive adhesive layer, there is no particular limitation on the upper limit of the concentration of the modified polymer in the surface portion relative to the concentration of the modified polymer in the entire layer.

[0026] Here, in this specification, "the concentration of the modified polymer in the entire pressure-sensitive adhesive layer" is a value calculated as the ratio of the mass of the modified polymer to the total mass of the acrylic adhesive polymer and the modified polymer in the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer. "The concentration of the modified polymer in the surface layer portion of the pressure-sensitive adhesive layer" is the composition ratio of the modified polymer in the surface layer portion of the pressure-sensitive adhesive layer obtained by X-ray photoelectron spectroscopy. Details of the calculation method follow the method described in the Examples below.

[0027] When only one of the two outermost surfaces in the thickness direction of the pressure-sensitive adhesive layer is on the low surface energy interface side, a pressure-sensitive adhesive layer can be obtained in which only the interface side contains a higher concentration of modified polymer. When both of the two outermost surfaces in the thickness direction of the pressure-sensitive adhesive layer are on the low surface energy interface side, a pressure-sensitive adhesive layer can be obtained in which each of the two outermost surfaces contains a higher concentration of modified polymer. In the latter case, the phrase "the concentration of modified polymer in the surface layer portion of the pressure-sensitive adhesive layer obtained by X-ray photoelectron spectroscopy analysis" is "X times or more the concentration of modified polymer in the entire pressure-sensitive adhesive layer" means that the concentration of modified polymer in each of the two outermost surfaces in the thickness direction is X times or more the concentration of modified polymer in the entire pressure-sensitive adhesive layer.

[0028] When the amount of modified polymer in the surface portion of the pressure-sensitive adhesive layer is expressed as a mass ratio relative to the amount of modified polymer in the entire pressure-sensitive adhesive layer, the amount of modified polymer in the surface portion of the pressure-sensitive adhesive layer obtained by X-ray photoelectron spectroscopy is preferably 15% by mass or more relative to the amount of modified polymer in the entire pressure-sensitive adhesive layer. From the viewpoint of obtaining a pressure-sensitive adhesive layer that exhibits even higher adhesiveness both at room temperature and at high temperatures, the amount of modified polymer in the surface portion of the pressure-sensitive adhesive layer is more preferably 20% by mass or more, even more preferably 25% by mass or more, and even more preferably 30% by mass or more relative to the amount of modified polymer in the entire pressure-sensitive adhesive layer. In the pressure-sensitive adhesive layer, the upper limit of the amount of modified polymer in the surface portion relative to the amount of modified polymer in the entire layer is not particularly limited, but from the viewpoint of ensuring adhesiveness, it is, for example, 95% by mass or less, preferably 90% by mass or less, and more preferably 85% by mass or less relative to the amount of modified polymer in the entire pressure-sensitive adhesive layer.

[0029] Here, when a pressure-sensitive adhesive layer is formed using a pressure-sensitive adhesive composition containing an acrylic pressure-sensitive adhesive polymer and a modified polymer, the composition ratio of the modified polymer in the surface layer portion of the pressure-sensitive adhesive layer (mass fraction W Ｂ The mass fraction W of the modified polymer in the surface layer of the pressure-sensitive adhesive layer can be determined by composition analysis using X-ray photoelectron spectroscopy. Ｂ ) is specifically expressed by the following formulas (1) and (2): ＢW = (mass of modified polymer) / (total mass of modified polymer and acrylic adhesive polymer) ... (1) B = 1 - W A ...(2) (In the formulas (1) and (2), W Ａ is the mass fraction of the acrylic adhesive polymer relative to the total mass of the modified polymer and the acrylic adhesive polymer in the surface layer portion of the adhesive layer, and W Ｂ is the mass fraction of the modified polymer relative to the total mass of the modified polymer and the acrylic adhesive polymer in the surface layer portion of the pressure-sensitive adhesive layer.

[0030] Mass fraction W of the modified polymer in the surface layer of the adhesive layer Ｂ is preferably a value of 10% or more when expressed as a percentage. Within this range, phase separation between the acrylic adhesive polymer and the modified polymer occurs in the pressure-sensitive adhesive layer, and the concentration of the modified polymer in the surface layer portion becomes relatively high, thereby making it possible to obtain a pressure-sensitive adhesive layer that exhibits high adhesiveness at room temperature and at high temperatures. The mass fraction W when expressed as a percentage is Ｂ is more preferably 15% or more, and even more preferably 20% or more.

[0031] Peel strength: From the viewpoint of preventing the adhesive layer from lifting or peeling off from the adherend under room temperature conditions, the peel strength of a 50 μm thick adhesive layer made of the composition from a polypropylene (PP) plate at 23° C. and a peeling rate of 300 mm / min is preferably 5 N / 25 mm or more. From the viewpoint of obtaining an adhesive layer with excellent adhesion, the peel strength of a 50 μm thick adhesive layer made of the composition from the composition at 23° C. is more preferably 10 N / 25 mm or more, even more preferably 15 N / 25 mm or more, and still more preferably 20 N / 25 mm or more.

[0032] Furthermore, the peel strength of a 50 μm thick pressure-sensitive adhesive layer made of this composition against a PP plate at 85°C and a peel rate of 300 mm / min is preferably 5 N / 25 mm or more, from the viewpoint of preventing the pressure-sensitive adhesive layer from lifting or peeling from the adherend at high temperatures and providing a highly heat-resistant pressure-sensitive adhesive layer. The peel strength of a 50 μm thick pressure-sensitive adhesive layer made of this composition at 85°C is more preferably 7 N / 25 mm or more, and even more preferably 10 N / 25 mm or more. In this specification, the peel strength of the pressure-sensitive adhesive layer is a value measured in accordance with JIS Z-0237. Details of the measurement method follow the measurement method described in the Examples below.

[0033] Haze Value The pressure-sensitive adhesive layer has a phase-separated structure between the acrylic adhesive polymer and the modified polymer, and therefore exhibits a relatively high haze value, which is an index of the degree of cloudiness. Specifically, the haze value of the pressure-sensitive adhesive layer is preferably 3.0% or more as measured by a haze meter after a 50 μm-thick pressure-sensitive adhesive layer is attached to a glass substrate and left to stand for one day under conditions of 23°C and 50% RH. From the viewpoint of exhibiting high adhesive strength at room temperature and high temperatures due to the formation of a phase-separated structure between the acrylic adhesive polymer and the modified polymer, the haze value of the pressure-sensitive adhesive layer under the above conditions is more preferably 3.5% or more, and even more preferably 4.0% or more. Furthermore, when applied to applications where transparency of the pressure-sensitive adhesive layer is not required, the haze value of the pressure-sensitive adhesive layer measured under the above conditions is preferably 15% or more, more preferably 20% or more, since a pressure-sensitive adhesive layer with higher adhesive strength can be obtained. There is no particular upper limit to the haze value of the pressure-sensitive adhesive layer measured under the above conditions. When the pressure-sensitive adhesive layer is used in applications requiring transparency, the haze value of the pressure-sensitive adhesive layer measured under the above conditions is preferably 30% or less, and more preferably 25% or less. Details of the method for measuring the haze value follow the method described in the Examples below.

[0034] In the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer of the present disclosure, the acrylic adhesive polymer and the modified polymer are homogeneous and have a single phase. During the process of forming a pressure-sensitive adhesive layer using such a homogeneous pressure-sensitive adhesive composition, phase separation between the acrylic adhesive polymer and the modified polymer occurs, resulting in a pressure-sensitive adhesive layer obtained using this composition exhibiting a relatively high haze value. Therefore, in a pressure-sensitive adhesive layer that contains an acrylic adhesive polymer and a modified polymer but has a sufficiently low haze value (e.g., 1.5% or less, e.g., less than 1.0%), it can be said that the acrylic adhesive polymer and the modified polymer are not phase-separated.

[0035] Gel Fraction When the composition contains a crosslinking agent, the gel fraction of the pressure-sensitive adhesive layer made of the composition is preferably 50% or more. A gel fraction of 50% or more can sufficiently enhance the heat resistance and durability against temperature changes of the pressure-sensitive adhesive layer, and can also provide a pressure-sensitive adhesive layer that exhibits high adhesiveness at high temperatures. The gel fraction of the pressure-sensitive adhesive layer is more preferably 55% or more, even more preferably 60% or more, and even more preferably 65% ​​or more. The upper limit of the gel fraction is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less. In this specification, the gel fraction of the pressure-sensitive adhesive layer is the ratio of the mass W2 of the pressure-sensitive adhesive layer remaining after solvent immersion to the initial mass W1 of the pressure-sensitive adhesive layer. Details are given in accordance with the measurement method described in the Examples below.

[0036] Glass Transition Temperature The pressure-sensitive adhesive layer preferably has a glass transition temperature (Tg). Specifically, the Tg of the entire pressure-sensitive adhesive layer is preferably 20°C or lower. When the Tg of the entire adhesive layer is 20°C or lower, a pressure-sensitive adhesive layer with better adhesion at room temperature can be obtained. From the viewpoint of obtaining a pressure-sensitive adhesive layer with higher adhesion at room temperature, the Tg of the entire pressure-sensitive adhesive layer is more preferably 10°C or lower, even more preferably 0°C or lower, and even more preferably -5°C or lower. The Tg of the entire pressure-sensitive adhesive layer is preferably -80°C or higher, more preferably -70°C or higher, and even more preferably -60°C or higher. The Tg of the entire adhesive layer is a value obtained using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min in a nitrogen atmosphere. Details of the measurement conditions are as described in the examples below.

[0037] (Adhesive Composition) Next, the adhesive composition for obtaining the adhesive layer will be described. This composition contains an acrylic adhesive polymer, a modified polymer, and a solvent.

[0038] Acrylic Adhesive Polymer The acrylic adhesive polymer is a polymer containing a (meth)acrylic compound as a main structural unit. The acrylic adhesive polymer preferably uses a structural unit (hereinafter also referred to as "structural unit UA") derived from at least one selected from the group consisting of (meth)acrylic acid alkyl esters having an alkyl group of 1 to 8 carbon atoms and (meth)acrylic acid alkoxyalkyl esters having an alkoxy group of 1 to 4 carbon atoms, since this allows for the production of a polymer with a relatively low Tg and sufficient adhesiveness. The monomers constituting the acrylic adhesive polymer can be used alone or in combination of two or more.

[0039] Specific examples of (meth)acrylic acid alkyl esters having an alkyl group having 1 to 8 carbon atoms, used in the production of acrylic adhesive polymers, include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc. Preferred monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0040] Specific examples of alkoxyalkyl (meth)acrylates having an alkoxy group having 1 to 4 carbon atoms, used in the production of acrylic adhesive polymers, include methoxyethyl (meth)acrylate, ethoxymethyl (meth)acrylate, ethoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxybutyl (meth)acrylate, ethoxybutyl (meth)acrylate, and butoxybutyl (meth)acrylate.

[0041] In the acrylic adhesive polymer, the content of the structural unit UA is more preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on all structural units contained in the acrylic adhesive polymer (i.e., the total amount of monomer units constituting the acrylic adhesive polymer). By making the content of the structural unit UA 50% by mass or more, the adhesive strength, initial adhesive strength (tack), and low-temperature adhesion of the adhesive layer can be sufficiently increased.

[0042] The acrylic adhesive polymer preferably contains a structural unit (hereinafter also referred to as "structural unit UA-1") derived from at least one selected from the group consisting of (meth)acrylic acid alkyl esters having an alkyl group of 1 to 4 carbon atoms and (meth)acrylic acid alkoxy esters having an alkoxyalkyl group of 3 or 4 carbon atoms, in that phase separation between the acrylic adhesive polymer and the modified polymer is likely to occur in the pressure-sensitive adhesive layer, the concentration of the modified polymer is likely to be relatively high in the surface layer portion, and adhesiveness at high temperatures can be improved. Furthermore, by using such a (meth)acrylic acid alkyl ester and / or an acrylic acid alkoxy ester in the production of the acrylic adhesive polymer, the elastic modulus of the acrylic adhesive polymer can be increased and is also effective in improving heat resistance. Among these, the structural unit UA-1 is preferably a structural unit derived from one selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and methoxyethyl (meth)acrylate. The content of the structural unit UA-1 in the acrylic adhesive polymer is preferably 50% by mass or more, more preferably 70% by mass or more, based on all structural units contained in the acrylic adhesive polymer.

[0043] In particular, from the viewpoint of obtaining a pressure-sensitive adhesive layer having higher adhesiveness at high temperatures, the acrylic adhesive polymer preferably contains 30 mass % or more, more preferably 35 mass % or more, and even more preferably 40 mass % or more of structural units derived from at least one selected from the group consisting of a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 3 carbon atoms and a (meth)acrylic acid alkoxy ester having an alkoxyalkyl group having 3 or 4 carbon atoms, relative to the total structural units contained in the acrylic adhesive polymer.

[0044] In producing the acrylic adhesive polymer, a monomer having a crosslinkable functional group (hereinafter also referred to as a "crosslinkable group-containing monomer") is used, thereby making it possible to give the acrylic adhesive polymer a structure having a crosslinkable structural unit. When the acrylic adhesive polymer has a crosslinkable structural unit, it is possible to further improve the adhesiveness of the pressure-sensitive adhesive layer at high temperatures.

[0045] The crosslinkable group-containing monomer used in the production of the acrylic adhesive polymer is not particularly limited. The crosslinkable group-containing monomer is preferably at least one selected from the group consisting of (meth)acrylic acid, a hydroxyalkyl (meth)acrylate compound, an epoxy group-containing (meth)acrylic acid ester compound, and a reactive silyl group-containing (meth)acrylic acid ester compound. Among these, at least one selected from the group consisting of (meth)acrylic acid and a hydroxyalkyl (meth)acrylate compound is preferred because it tends to increase the adhesive strength of the acrylic adhesive polymer. At least one selected from the group consisting of (meth)acrylic acid and a hydroxyalkyl (meth)acrylate compound having a hydroxyalkyl group of 2 to 8 carbon atoms is more preferred, and at least one selected from the group consisting of (meth)acrylic acid and a hydroxyalkyl (meth)acrylate compound having a hydroxyalkyl group of 2 to 4 carbon atoms is particularly preferred.

[0046] When the acrylic adhesive polymer has a crosslinkable structural unit, the content of the crosslinkable structural unit is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, relative to the total structural units of the acrylic adhesive polymer. By making the content of the crosslinkable structural unit in the acrylic adhesive polymer 0.1% by mass or more, a good crosslinked structure can be formed, and an adhesive polymer exhibiting higher heat resistance and durability can be obtained. The upper limit of the content of the crosslinkable structural unit is not particularly limited, but from the viewpoint of ensuring the flexibility of the obtained adhesive layer, it is preferably 30% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and particularly preferably 10% by mass or less, relative to the total structural units of the acrylic adhesive polymer. In addition, when producing the acrylic adhesive polymer, only one type of crosslinkable group-containing monomer may be used, or two or more types may be used.

[0047] In addition to the above, the acrylic adhesive polymer may have a structural unit derived from a monomer copolymerizable with the above monomer (hereinafter also referred to as "other monomer") within a range that does not impair adhesive performance. Examples of other monomers include alicyclic ester compounds of (meth)acrylic acid, aromatic ester compounds of (meth)acrylic acid, polyalkylene glycol mono(meth)acrylate compounds, aromatic vinyl compounds, imide group-containing vinyl compounds, amino group-containing unsaturated compounds, amide group-containing unsaturated compounds, and nitrile group-containing unsaturated compounds.

[0048] Specific examples of these include alicyclic ester compounds of (meth)acrylic acid, such as cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, tert-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentanyl (meth)acrylate.

[0049] Examples of aromatic ester compounds of (meth)acrylic acid include phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxymethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, and 3-phenoxypropyl (meth)acrylate.

[0050] Examples of the polyalkylene glycol mono(meth)acrylate compound include polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol-polypropylene glycol mono(meth)acrylate, polyethylene glycol-polybutylene glycol mono(meth)acrylate, methoxypolyethylene glycol mono(meth)acrylate, lauroxypolyethylene glycol mono(meth)acrylate, stearoxypolyethylene glycol mono(meth)acrylate, octoxypolyethylene glycol-polypropylene glycol mono(meth)acrylate, phenoxypolyethylene glycol mono(meth)acrylate, phenoxypolyethylene glycol-polypropylene glycol mono(meth)acrylate, nonylphenoxypolyethylene glycol mono(meth)acrylate, nonylphenoxypolypropylene glycol mono(meth)acrylate, and nonylphenoxypolyethylene glycol-polypropylene glycol mono(meth)acrylate.

[0051] Examples of aromatic vinyl compounds include styrene, α-methylstyrene, β-methylstyrene, vinylxylene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, p-n-butylstyrene, p-isobutylstyrene, p-t-butylstyrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, p-isopropenylphenol, m-isopropenylphenol, o-isopropenylphenol, o-vinylbenzoic acid, m-vinylbenzoic acid, p-vinylbenzoic acid, and styrene-based compounds such as divinylbenzene; vinylnaphthalene, and the like.

[0052] Examples of the imide group-containing vinyl compound include maleimide compounds such as maleimide and N-substituted maleimide compounds; itaconimide compounds such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide; N-methylcitraconimide, N-ethylcitraconimide, N-butylcitraconimide, N-octylcitraconimide, N-2-ethylhexylcitraconimide, and N-cyclohexylitaconimide; Examples of the imide group-containing vinyl compound include citraconic acid compounds such as cyclohexylcitraconimide and N-laurylcitraconimide; and (meth)acrylimide compounds such as N-(2-(meth)acryloyloxyethyl)succinimide, N-(2-(meth)acryloyloxyethyl)maleimide, N-(2-(meth)acryloyloxyethyl)phthalimide, N-(4-(meth)acryloyloxybutyl)succinimide, N-(4-(meth)acryloyloxybutyl)maleimide, and N-(4-(meth)acryloyloxybutyl)phthalimide. Of these, maleimide compounds are preferably used as the imide group-containing vinyl compound.

[0053] Examples of the amino group-containing unsaturated compound include dimethylaminomethyl (meth)acrylate, diethylaminomethyl (meth)acrylate, 2-dimethylaminoethyl (meth)acrylate, 2-diethylaminoethyl (meth)acrylate, 2-(di-n-propylamino)ethyl (meth)acrylate, 2-dimethylaminopropyl (meth)acrylate, 2-diethylaminopropyl (meth)acrylate, 2-(di-n-propylamino)propyl (meth)acrylate, 3-dimethylaminopropyl (meth)acrylate, 3-diethylaminopropyl (meth)acrylate, and 3-(di-n-propylamino)propyl (meth)acrylate.

[0054] Examples of the amide group-containing unsaturated compound include (meth)acrylamide, (meth)acrylamide derivatives, and N-vinylamide monomers. Specific examples of (meth)acrylamide derivatives include tert-butyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, and (meth)acryloylmorpholine. Specific examples of N-vinylamide monomers include N-vinylacetamide, N-vinylformamide, and N-vinylisobutylamide.

[0055] Examples of the nitrile group-containing unsaturated compound include cyanomethyl (meth)acrylate, 1-cyanoethyl (meth)acrylate, 2-cyanoethyl (meth)acrylate, 1-cyanopropyl (meth)acrylate, 2-cyanopropyl (meth)acrylate, 3-cyanopropyl (meth)acrylate, 4-cyanobutyl (meth)acrylate, 6-cyanohexyl (meth)acrylate, 2-ethyl-6-cyanohexyl (meth)acrylate, 8-cyanooctyl (meth)acrylate, (meth)acrylonitrile, α-ethylacrylonitrile, α-isopropylacrylonitrile, α-chloroacrylonitrile, and α-fluoroacrylonitrile.

[0056] The proportion of the other monomer constituting the acrylic adhesive polymer can be appropriately selected within a range that does not impair the effects of the present disclosure. As the other monomer, one type may be used alone, or two or more types may be used in combination.

[0057] From the viewpoint of improving the adhesiveness of the pressure-sensitive adhesive layer at high temperatures, the proportion of structural units derived from amino group-containing unsaturated compounds in the acrylic adhesive polymer is preferably 0.2 mass% or less relative to the total structural units of the acrylic adhesive polymer. If the acrylic adhesive polymer contains a relatively large amount of structural units derived from amino group-containing unsaturated compounds, the interaction between the acrylic adhesive polymer and the modified polymer will be strong, which may inhibit phase separation between the acrylic adhesive polymer and the modified polymer, resulting in a decrease in the adhesive performance of the pressure-sensitive adhesive layer. From this viewpoint, the proportion of structural units derived from amino group-containing unsaturated compounds is more preferably 0.1 mass% or less, and even more preferably 0.05 mass% or less relative to the total structural units of the acrylic adhesive polymer. Furthermore, it is particularly preferred that the acrylic adhesive polymer does not substantially contain structural units derived from amino group-containing unsaturated compounds.

[0058] - Production of acrylic adhesive polymer The production method of the acrylic adhesive polymer is not particularly limited, and it can be obtained by a known production method. For example, the acrylic adhesive polymer can be obtained by polymerizing the above-mentioned monomers using a known radical polymerization method such as solution polymerization, suspension polymerization, emulsion polymerization, or bulk polymerization.

[0059] For example, a production method using a solution polymerization method includes charging an organic solvent and monomers into a reactor, adding a polymerization initiator, and heating to 50 to 300° C. to polymerize. In this case, the method for charging each raw material including the monomer may be a batch-type initial lump-sum charging in which all raw materials are charged at once, a semi-continuous charging in which at least a portion of the raw materials are continuously fed into the reactor, or a continuous polymerization method in which all raw materials are continuously fed and, at the same time, the produced resin is continuously withdrawn from the reactor.

[0060] Examples of organic solvents used in solution polymerization include cyclic ethers such as tetrahydrofuran, tetrahydropyran, 4-methyltetrahydropyran, and dioxane; aromatic hydrocarbon compounds such as benzene, toluene, and xylene; hydrocarbon compounds such as cyclohexane, methylcyclohexane, and isooctane; esters such as ethyl acetate and butyl acetate; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; and alcohols such as methyl orthoformate, methyl orthoacetate, methanol, ethanol, and isopropanol. One or more of these organic solvents can be used. The amount of organic solvent used is such that the total amount of monomers used in polymerization is, for example, 1 to 50% by mass relative to the total amount of the organic solvent and the monomers. From the viewpoints of the polymerizability and solubility of the acrylic adhesive polymer and the ease of blending the modified polymer after production, cyclic ethers, aromatic hydrocarbon compounds, and ketones are preferred, and among these, toluene, xylene, ethyl acetate, and butyl acetate are more preferred.

[0061] The polymerization initiator may be any known radical polymerization initiator, such as an azo compound, an organic peroxide, or an inorganic peroxide, and is not particularly limited. Among these, an azo compound is preferred because it is easy to handle safely and is less likely to cause side reactions during radical polymerization. Alternatively, a redox polymerization initiator consisting of a known oxidizing agent and a known reducing agent may be used as the polymerization initiator. Furthermore, a known chain transfer agent may be used in combination with the polymerization initiator.

[0062] Specific examples of the polymerization initiator include azo compounds such as 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 4,4'-azobis(4-cyanovaleric acid), 2-(tert-butylazo)-2-cyanopropane, 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(2-methylpropane), and dimethyl 2,2'-azobis(2-methylpropionate).

[0063] Examples of organic peroxides include cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, diisopropylbenzene peroxide, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexane.

[0064] Examples of inorganic peroxides include potassium persulfate and sodium persulfate. Examples of redox polymerization initiators include those using sodium sulfite, sodium thiosulfate, sodium formaldehyde sulfoxylate, ascorbic acid, ferrous sulfate, or the like as a reducing agent, and potassium peroxodisulfate, hydrogen peroxide, tert-butyl hydroperoxide, or the like as an oxidizing agent. When producing an acrylic adhesive polymer, the amount of polymerization initiator used is, for example, 0.01 to 20 parts by mass per 100 parts by mass of all monomers used in the polymerization.

[0065] The glass transition temperature (Tg) of the acrylic adhesive polymer is preferably in the range of -70°C or higher and 10°C or lower. When the Tg of the acrylic adhesive polymer is -70°C or higher, the cohesive strength of the adhesive layer can be sufficiently increased, and adhesiveness can be sufficiently ensured, which is preferable. From the viewpoint of achieving better adhesiveness at high temperatures, the Tg of the acrylic adhesive polymer is more preferably -60°C or higher, even more preferably -50°C or higher, and still more preferably -40°C or higher.

[0066] On the other hand, when the Tg of the acrylic adhesive polymer is 10°C or less, the adhesiveness at room temperature can be improved, and the adhesive layer can have good conformability to the adherend, so that a adhesive layer having high adhesiveness even at high temperatures can be obtained. The upper limit of the Tg of the acrylic adhesive polymer is more preferably 5°C or less, even more preferably 0°C or less, still more preferably -5°C or less, and even more preferably -10°C or less.

[0067] In this specification, the Tg of a polymer is a value determined from the intersection of the baseline of a heat flux curve obtained using DSC and the tangent point at the inflection point. Details of the measurement conditions are as described in the Examples below. The Tg of a polymer can be set to a desired value by changing the type and composition of the constituent monomers, etc.

[0068] Molecular Weight Characteristics of Acrylic Adhesive Polymer The Mw of the acrylic adhesive polymer is preferably 100,000 or more from the viewpoint of obtaining a polymer that exhibits sufficient cohesive strength and good adhesiveness. By making the Mw of the acrylic adhesive polymer 100,000 or more, sufficient adhesiveness and solvent resistance can be ensured. The Mw of the acrylic adhesive polymer is more preferably 200,000 or more, even more preferably 300,000 or more, even more preferably 400,000 or more, and even more preferably 450,000 or more.

[0069] The upper limit of the Mw of the acrylic adhesive polymer is not particularly limited, but from the viewpoint of ensuring good coating properties and handleability when forming the adhesive layer and also ensuring ease of production, it is preferably 3 million or less, more preferably 2 million or less, and even more preferably 1.5 million or less. The Mw range of the acrylic adhesive polymer is preferably 100,000 or more and 3 million or less, more preferably 200,000 or more and 2 million or less, and even more preferably 400,000 or more and 1.5 million or less. In this specification, the molecular weight of the polymer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0070] The molecular weight distribution (Mw / Mn) of the acrylic adhesive polymer, which is expressed as the ratio of Mw to Mn, is preferably 10.0 or less, more preferably 9.0 or less, from the viewpoint of easily obtaining good adhesiveness and suppressing an increase in viscosity of the adhesive composition. The lower limit of Mw / Mn of the acrylic adhesive polymer is not particularly limited, and can be 1.0 or more.

[0071] The SP value of the acrylic adhesive polymer calculated by the Fedors method is preferably 9.95 or more, more preferably 10.00 or more, even more preferably 10.05 or more, and even more preferably 10.10 or more.When the SP value of the acrylic adhesive polymer is within the above range, a pressure-sensitive adhesive layer with higher adhesiveness can be obtained both at room temperature and at high temperatures.The SP value according to the Fedors method is specifically calculated by the following formula (3). δ: SP value ((cal / cm ３ ) １／２ ) ΔEvap: Molar heat of vaporization of each atomic group (cal / mol) V: Molar volume of each atomic group (cm ３ / mol)

[0072] From the viewpoint of ensuring sufficient adhesiveness in the PSA layer at room temperature and at high temperatures, the content of the acrylic adhesive polymer in the PSA composition is preferably 70% by mass or more relative to the total solid content of the composition (i.e., the mass of components other than the solvent in the PSA composition relative to the total mass of the PSA composition), more preferably 80% by mass or more, and even more preferably 85% by mass or more, relative to the total solid content of the PSA composition.

[0073] Modified Polymers: Modified polymers are polyolefins and / or polydiene polymers obtained by chemical modification, and contain a structure or functional group different from that of unsaturated hydrocarbon units within the same molecule. Among modified polymers, modified polyolefins are polyolefins obtained by chemical modification, and contain a structure or functional group different from that of olefin units within the same molecule. Examples of polyolefins and polydienes include polymers containing structural units derived from at least one monomer selected from the group consisting of α-olefins, conjugated dienes, and non-conjugated dienes having 2 to 20 carbon atoms. Specific examples include homopolymers of α-olefins, conjugated dienes, or non-conjugated dienes having 2 to 20 carbon atoms, and copolymers of two or more monomers selected from the group consisting of α-olefins, conjugated dienes, and non-conjugated dienes having 2 to 20 carbon atoms.

[0074] Specific examples of α-olefins having 2 to 20 carbon atoms include ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-heptene, 4-methyl-1-hexene, 1-octene, 4,4-dimethyl-1-hexene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, etc. Specific examples of conjugated or non-conjugated dienes having 2 to 20 carbon atoms include butadiene, 1,5-hexadiene, ethylidenenorbornene, dicyclopentadiene, etc.

[0075] The polyolefin constituting the modified polyolefin may be copolymerized with other unsaturated monomers in addition to the olefin. Examples of such unsaturated monomers include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, isocrotonic acid, and cinnamic acid; unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, chloromaleic acid, glutaconic acid, and itaconic acid; half esters or half amides of unsaturated dicarboxylic acids; unsaturated tricarboxylic acids such as trans-anicotic acid; maleic anhydride, citraconic anhydride, chloromaleic anhydride, itaconic anhydride, 3,4,5, Examples of suitable modified polydiene include carboxylic acid anhydrides such as 6-tetrahydrophthalic anhydride; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, and tert-butyl (meth)acrylate; oligomers of these unsaturated compounds having terminal unsaturated bonds; and conjugated or non-conjugated dienes such as butadiene, 1,5-hexadiene, ethylidene norbornene, and dicyclopentadiene. Similarly, the polydienes constituting the modified polydiene may be copolymerized with other unsaturated monomers in addition to conjugated and non-conjugated dienes. Examples of suitable polyolefins include ethylene / ethyl acrylate copolymers and ethylene / vinyl acetate copolymers. Examples of suitable polydienes include styrene / butadiene copolymers and styrene / isoprene copolymers. When a copolymer is used, a random copolymer, a block copolymer, or a graft copolymer can be appropriately selected.

[0076] Preferred examples of polyolefins include polypropylene, propylene / ethylene copolymer, propylene / 1-butene copolymer, propylene / ethylene / 1-butene copolymer, and propylene / ethylene / 1-octene copolymer. The polyolefin may also be a blend of these. When a propylene copolymer is used, the propylene content is preferably 50% by mass or more, more preferably 60% by mass or more, and even more preferably 75% by mass or more. Of the above, polypropylene or a propylene copolymer is preferred as the polyolefin.

[0077] Commercially available polyolefins may be used, and specific examples thereof include the "L-MODU" series manufactured by Idemitsu Kosan Co., Ltd., the "REXtac" series manufactured by LLC, the "Vestoplast" series manufactured by Evonik, the "Eastoflex" series and the "Aerafin" series manufactured by Eastman, the "Tafmer" series manufactured by Mitsui Chemicals, Inc., the "Prime TPO" series manufactured by Prime Polymer, the "Versify" series manufactured by Dow Chemical Company, the "Vistamaxx" series and the "Linxar" series manufactured by ExxonMobil, the "Licocene" series manufactured by Clariant, and the "Adflex" series manufactured by Basell.

[0078] Examples of the type of modification include acid modification, chlorination, (meth)acrylic acid ester modification (hereinafter also referred to as "acrylic modification"), carbodiimide modification, urea modification, and imine modification. The modified polyolefin may be one in which two or more types of modifications have been performed sequentially. Specific examples include acid-modified chlorinated polyolefin, acrylic-modified chlorinated polyolefin, and urethane-modified chlorinated polyolefin. Among these, modified polyolefins are preferred in terms of their high effect of improving adhesion at high temperatures and ease of availability, and at least one selected from the group consisting of acid-modified polyolefin, chlorinated polyolefin, acid-modified chlorinated polyolefin, acrylic-modified polyolefin, and acrylic-modified chlorinated polyolefin is more preferred. Among these, at least one selected from the group consisting of acid-modified polyolefin, acid-modified chlorinated polyolefin, acrylic-modified polyolefin and acrylic-modified chlorinated polyolefin is more preferred, and at least one selected from the group consisting of acid-modified polyolefin and acrylic-modified polyolefin is even more preferred, in that the difference in SP value with the acrylic adhesive polymer is larger and phase separation with the acrylic adhesive polymer is more likely to occur, and therefore a pressure-sensitive adhesive layer with further improved high-temperature adhesion can be obtained.

[0079] The acid-modified polyolefin and the acid-modified chlorinated polyolefin are preferably modified with at least one selected from the group consisting of carboxylic acids and carboxylic anhydrides (hereinafter also referred to as "specific acid modifier"). Such modified polyolefins can be obtained, for example, by graft copolymerizing a specific acid modifier with a polyolefin. The modification reaction can be carried out using a conventionally known method, such as a method of adding a specific acid modifier to a polyolefin melted using an extruder to copolymerize it, a method of adding a specific acid modifier to a polyolefin dissolved in a solvent to copolymerize it, or a method of adding a specific acid modifier to a polyolefin suspension in water to copolymerize it. The modified site of the polyolefin chain in the modified polyolefin may be one end of the molecular chain, both ends of the molecular chain, or in the middle of the molecular chain, or multiple of these locations.

[0080] Examples of the specific acid modifier used in the modification reaction include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, isocrotonic acid, and cinnamic acid; unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, chloromaleic acid, glutaconic acid, and itaconic acid; half esters or half amides of unsaturated dicarboxylic acids; unsaturated tricarboxylic acids such as trans-anicotic acid; and carboxylic acid anhydrides such as maleic anhydride, citraconic anhydride, chloromaleic anhydride, itaconic anhydride, and 3,4,5,6-tetrahydrophthalic anhydride. Among these, at least one selected from the group consisting of unsaturated monocarboxylic acids and carboxylic acid anhydrides is preferred, at least one selected from the group consisting of (meth)acrylic acid, maleic acid, and maleic anhydride is more preferred, and maleic anhydride is even more preferred.

[0081] The acid-modified polyolefin and acid-modified chlorinated polyolefin blended in the present composition may be further modified with a (meth)acrylic acid ester in addition to the acid modifier. In other words, in this specification, the term "acid-modified polyolefin" encompasses acid-modified polyolefins that have been acrylic-modified, and the term "acid-modified chlorinated polyolefin" encompasses acid-modified chlorinated polyolefins that have been acrylic-modified. Therefore, for example, acid-modified polyolefins include ethylene-acrylic acid ester-maleic anhydride 3D copolymers, ethylene-methacrylic acid ester-maleic anhydride 3D copolymers, propylene-acrylic acid ester-maleic anhydride 3D copolymers, and propylene-methacrylic acid ester-maleic anhydride 3D copolymers. Specific examples of (meth)acrylic acid esters for acrylic modification are the same as the compounds exemplified in the description of acrylic-modified polyolefins.

[0082] The acrylic-modified polyolefin and the acrylic-modified chlorinated polyolefin are preferably polymers in which a polyolefin is modified with a (meth)acrylic acid ester. The (meth)acrylic acid ester can preferably be at least one selected from the group consisting of (meth)acrylic acid alkyl esters and (meth)acrylic acid cycloalkyl esters. Specific examples thereof include (meth)acrylic acid alkyl esters having an alkyl group of 1 to 8 carbon atoms, as exemplified in the description of the acrylic adhesive polymer, and the (meth)acrylic acid alicyclic ester compounds exemplified in the description of other monomers, as well as (meth)acrylic acid alkyl esters having an alkyl group of 9 or more carbon atoms, such as nonyl (meth)acrylate, decyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, and stearyl (meth)acrylate.

[0083] The acid-modified polyolefin, acid-modified chlorinated polyolefin, acrylic-modified polyolefin, and acrylic-modified chlorinated polyolefin may be modified in combination with other modifiers, such as functional group-containing (meth)acrylic acid alkyl esters, aromatic vinyl compounds, and cyclohexyl vinyl ether.

[0084] Examples of functional group-containing (meth)acrylic acid alkyl esters include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate, and isocyanate-containing (meth)acrylic acid esters. Examples of aromatic vinyl compounds include benzyl (meth)acrylate, styrene, o-methylstyrene, p-methylstyrene, and α-methylstyrene. By using other modifiers in combination as a modifier, it is possible to improve the modification rate by the modifier and further improve adhesiveness.

[0085] The modification rate of the modified polymer is preferably 0.1% or more and 80% or less, in order to improve the high-temperature adhesion and room-temperature adhesion of the pressure-sensitive adhesive layer in a well-balanced manner. From the viewpoint of enhancing the interaction with the acrylic adhesive polymer and increasing the cohesive strength of the entire pressure-sensitive adhesive layer, the modification rate of the modified polymer is more preferably 0.5% or more, even more preferably 1.0% or more, and even more preferably 1.5% or more. The modification rate of the modified polymer may be 75% or less, or may be 70% or less. The modification rate of the modified polymer represents the mass proportion of the portion (modified portion) introduced by the modification reaction, when the mass of the entire modified polymer is taken as 100% by mass. The mass of the modified portion can be determined by Fourier transform infrared spectroscopy or nuclear magnetic resonance spectroscopy.

[0086] The weight-average molecular weight of the modified polymer measured by GPC is preferably 3,000 to 500,000. When the weight-average molecular weight of the modified polymer is 3,000 or more, the heat resistance of the pressure-sensitive adhesive layer is good, and when it is 500,000 or less, the solubility of the modified polymer in solvents is improved, which is preferable in terms of excellent handleability. From the above viewpoints, the weight-average molecular weight of the modified polymer is more preferably 5,000 or more, and even more preferably 10,000 or more. The upper limit of the weight-average molecular weight of the modified polymer is more preferably 250,000 or less, even more preferably 200,000 or less, and even more preferably 180,000 or less.

[0087] When the modified polymer has a melting point, the melting point of the modified polymer is preferably 20°C or higher, more preferably 30°C or higher, even more preferably 40°C or higher, and even more preferably 50°C or higher, from the viewpoint of obtaining a pressure-sensitive adhesive layer with excellent high-temperature adhesion. Furthermore, if the melting point of the modified polymer is too high, the wettability to the adherend decreases. From this viewpoint, the melting point of the modified polymer is preferably 130°C or lower, more preferably 120°C or lower, even more preferably 110°C or lower, and even more preferably 100°C or lower. The melting point of the modified polymer is a value obtained by a differential scanning calorimeter. Details of the measurement conditions are as described in the examples below.

[0088] The modified polymer may be a commercially available product, and examples thereof include those used in plastic surface modifiers, primers for automotive plastic substrates, primers for electronics substrates, primers for building materials, etc. Specific examples of acid-modified polyolefins include the "Admer" series and "Unistole" series manufactured by Mitsui Chemicals, Inc., the "Hardlen" series manufactured by Toyobo Co., Ltd. (e.g., PMA-LE, PMA-L, PMA-LH, PMA-KE, PMA-K, PMA-KH, PMA-TE, PMA-T, PMA-TH, PMA-TZ, PMA-F6, PMA-F2, PMA-F7), the "Umex" series manufactured by Sanyo Chemical Industry Co., Ltd., and the "Rexpearl" series manufactured by Japan Polyethylene Corporation.

[0089] Examples of chlorinated polyolefins include Superchlorine 814HA, 814HS, 390S, and 360T manufactured by Nippon Paper Industries Co., Ltd., and Hardlen 13-LP, 13-LLP, 14-LWP, 15-LP, 16-LP, DX-523, DX-523P, DX-526P, and DX-530P manufactured by Toyobo Co., Ltd.

[0090] Examples of acid-modified chlorinated polyolefins include Superchlorine 3228S and 2319S manufactured by Nippon Paper Industries Co., Ltd., and Hardlen HM-21P, M-28P, CY-9124P, CY-1321P, CY-2121P, CY-2129, F-225P, F-2P, F-6P, and F-7P manufactured by Toyobo Co., Ltd.

[0091] Examples of acrylic acid-modified chlorinated polyolefins include Superchlorine 224H and 240H manufactured by Nippon Paper Industries Co., Ltd. Examples of ethylene / acrylic acid / maleic anhydride terpolymers include the Bondine series manufactured by Arkema. Examples of acrylic-modified polyolefins include S-7083S and S-7098S manufactured by Nippon Paper Industries Co., Ltd., and Hardlen NP-3000, NP-3003, and NP-3002 manufactured by Toyobo Co., Ltd.

[0092] The content of the modified polymer in the composition is preferably 0.5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the acrylic adhesive polymer. By setting the content of the modified polymer within the above range, a pressure-sensitive adhesive layer with excellent adhesion at both room temperature and high temperatures can be obtained. From the viewpoint of obtaining a pressure-sensitive adhesive layer with higher high-temperature adhesion, the content of the modified polymer is more preferably 1 part by mass or more, even more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more per 100 parts by mass of the acrylic adhesive polymer. With regard to the upper limit of the content of the modified polymer, from the viewpoint of ensuring room-temperature adhesion, it is more preferably 45 parts by mass or less, even more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less per 100 parts by mass of the acrylic adhesive polymer. Note that the modified polymer may be used alone or in combination of two or more types.

[0093] Solvent: As the solvent, an organic solvent capable of dissolving the acrylic adhesive polymer and the modified polymer is preferably used. This allows a solvent-based pressure-sensitive adhesive composition to be obtained. Specific examples of the organic solvent include aprotic polar solvents, phenolic solvents, alcoholic solvents, ester solvents, ketone solvents, ether solvents, aromatic hydrocarbon solvents, and aliphatic hydrocarbon solvents. The organic solvent may be one of these, or a mixed solvent of two or more of these.

[0094] Among these, the solvent is preferably at least one selected from the group consisting of ester solvents, ketone solvents, aromatic hydrocarbon solvents, and aliphatic hydrocarbon solvents. For example, by dissolving an acrylic adhesive polymer and a modified polymer in an organic solvent containing one or more of ethyl acetate, butyl acetate, ethyl methyl ketone, cyclohexane, methylcyclohexane, cyclohexanone, 4-methyltetrahydropyran, tetrahydropyran, tetrahydrofuran, and toluene, a pressure-sensitive adhesive composition suitable for obtaining a pressure-sensitive adhesive layer having a phase-separated structure of the acrylic adhesive polymer and the modified polymer can be obtained.

[0095] The solids concentration in the composition (i.e., the ratio of the mass of components other than the solvent in the PSA composition to the total mass of the PSA composition) is not particularly limited, but is preferably 1 to 70 mass%. When the solids concentration is 1 mass% or more, a PSA layer with sufficient thickness can be formed. When the solids concentration is 70 mass% or less, good coatability can be ensured and a PSA layer with uniform thickness can be easily formed. The solids concentration in the composition is more preferably 5 to 50 mass%, and even more preferably 10 to 45 mass%.

[0096] - Other Components The present pressure-sensitive adhesive composition may further contain various components (hereinafter also referred to as "other components"), such as polymers other than the acrylic pressure-sensitive adhesive polymer and the modified polymer, and additives, as necessary. The other components are described below.

[0097] [Crosslinking Agent] When the acrylic adhesive polymer has a crosslinkable functional group, it is preferable to incorporate a crosslinking agent capable of reacting with the crosslinkable functional group into the adhesive composition, since this can further improve adhesion at high temperatures, heat resistance, and durability against temperature changes. It is also preferable because forming a crosslinked structure in the acrylic adhesive polymer makes it easier for phase separation to occur between the acrylic adhesive polymer and the modified polymer during the process of forming the adhesive layer.

[0098] Examples of the crosslinking agent (curing agent) include a glycidyl compound having two or more glycidyl groups, an isocyanate compound having two or more isocyanate groups, an aziridine compound having two or more aziridinyl groups, an oxazoline compound having an oxazoline group, a metal chelate compound, a butylated melamine compound, etc. Among these, an isocyanate compound is preferred because of its excellent adhesive properties under high temperature conditions.

[0099] Specific examples of the crosslinking agent include glycidyl compounds such as ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, tetraglycidylxylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and trimethylolpropane polyglycidyl ether.

[0100] As the isocyanate compound, various polyfunctional isocyanate compounds of aromatic, aliphatic and alicyclic types, as well as modified products (prepolymers, etc.) of these polyfunctional isocyanate compounds can be used. Specifically, aromatic isocyanate compounds such as diphenylmethane diisocyanate (MDI), tolylene diisocyanate (TDI), naphthalene diisocyanate (NDI), p-phenylene diisocyanate (PPDI), xylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), and tolidine diisocyanate (TODI); hexamethylene diisocyanate (HDI), and lysine diisocyanate (LDI); alicyclic isocyanate compounds such as isophorone diisocyanate (IPDI), cyclohexyl diisocyanate (CHDI), hydrogenated XDI (H6XDI), and hydrogenated MDI (H12MDI); and modified isocyanate compounds such as urethane-modified compounds, dimers, trimers, carbodiimide-modified compounds, urea-modified compounds, isocyanurate-modified compounds, oxazolidone-modified compounds, and isocyanate-terminated prepolymers.

[0101] Examples of the aziridine compound include 1,6-bis(1-aziridinylcarbonylamino)hexane, 1,1'-(methylene-di-p-phenylene)bis-3,3-aziridyl urea, ethylene bis-(2-aziridinyl propionate), 2,4,6-triaziridinyl-1,3,5-triazine, and trimethylolpropane-tris(2-aziridinyl propionate).

[0102] When a crosslinking agent is blended into the composition, the content of the crosslinking agent in the composition is not particularly limited and is usually 0.01 to 10 parts by mass, preferably 0.03 to 5 parts by mass, and more preferably 0.05 to 2 parts by mass, per 100 parts by mass of the acrylic adhesive polymer.

[0103] [Tackifier] The composition may contain a tackifier. Examples of tackifiers include rosin derivatives such as rosin ester, gum rosin, tall oil rosin, hydrogenated rosin ester, maleated rosin, and disproportionated rosin ester; terpene-phenolic resins, terpene-based resins mainly composed of α-pinene, β-pinene, or limonene; coumarone-indene resins, hydrogenated aromatic copolymers, phenolic resins, and vinyl polymers. One type of tackifier may be used alone, or two or more types may be used in combination. The content of the tackifier is typically 0 to 30 parts by mass, preferably 0 to 20 parts by mass, and more preferably 0 to 10 parts by mass, per 100 parts by mass of the acrylic adhesive polymer.

[0104] [Plasticizer] The composition may contain a plasticizer. Examples of the plasticizer include phthalates such as di-n-butyl phthalate, di-n-octyl phthalate, bis(2-ethylhexyl) phthalate, and di-n-decyl phthalate; adipates such as bis(2-ethylhexyl) adipate and di-n-octyl adipate; sebacates; azelaates; paraffins such as chlorinated paraffin; glycols such as polypropylene glycol; epoxy-modified vegetable oils such as epoxidized soybean oil and epoxidized linseed oil; phosphates such as trioctyl phosphate and triphenyl phosphate; phosphites such as triphenyl phosphite; ester oligomers such as esters of adipic acid and 1,3-butylene glycol; low-molecular-weight polymers such as low-molecular-weight polybutene, low-molecular-weight polyisobutylene, and low-molecular-weight polyisoprene; and oils such as process oil and naphthenic oil. The content of the plasticizer is preferably 0 to 20 parts by mass, more preferably 0 to 10 parts by mass, and even more preferably 0 to 5 parts by mass, relative to 100 parts by mass of the content of the acrylic adhesive polymer.

[0105] Examples of additives that may be blended into the composition include the above-mentioned crosslinking agents, tackifiers, and plasticizers, as well as antioxidants, ultraviolet absorbers, antiaging agents, flame retardants, mildew inhibitors, silane coupling agents, fillers, colorants, antistatic agents, etc. The content of the additives can be appropriately set depending on the various compounds within a range that does not impair the effects of the present disclosure.

[0106] <Adhesive Sheet and Decorative Film> The adhesive sheet of the present disclosure (hereinafter also referred to as "the sheet") comprises a pressure-sensitive adhesive layer formed using the composition of the present disclosure. As a result, the pressure-sensitive adhesive layer of the sheet has a surface layer in which the acrylic adhesive polymer and the modified polymer are phase-separated. The pressure-sensitive adhesive layer of the sheet and the pressure-sensitive adhesive composition for forming the layer are as described above. Therefore, after the pressure-sensitive adhesive layer of the sheet is attached to a molded body, the pressure-sensitive adhesive layer is unlikely to peel from the molded body under both room temperature and high temperature environments, and the sheet has excellent room-temperature adhesion and high-temperature adhesion.

[0107] The pressure-sensitive adhesive sheet may be in a so-called substrate-less form in which the pressure-sensitive adhesive layer is sandwiched between two separators, or may be one in which one of the objects to be joined serves as the substrate. In a substrate-less form, the peel strengths of the two separators may be the same or different. The shape of the pressure-sensitive adhesive sheet is also not particularly limited and is appropriately set depending on the usage situation. The pressure-sensitive adhesive sheet may be, for example, in the form of a sheet, a roll, or cut into strips. The thickness of the pressure-sensitive adhesive layer may be appropriately set depending on the type of objects to be joined, the area and shape of the joining location, etc. Furthermore, in order to achieve a desired thickness for the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet may be formed by laminating multiple pressure-sensitive adhesive layers.

[0108] The PSA sheet of the present disclosure thus obtained can be used as a PSA in a wide range of applications, specifically, for example, clothing (including clothing accessories), sports goods (e.g., sportswear, sports shoes, sports gloves, bat and racket grips, etc.), medical supplies (e.g., supports and corsets, etc.), automotive interior and exterior parts, outdoor goods, handicraft supplies, toys, lifestyle goods, household goods, furniture, etc.

[0109] One preferred embodiment of the sheet is a decorative film. Examples of decorative films include a single-layer film in which a decorative layer is formed by coloring a substrate layer, and a laminate film in which a decorative layer and a substrate layer are laminated in this order. Decorative films of this configuration are preferably used as decorative films for lamination, which are attached to an adherend to obtain a decorated molded article.

[0110] In the decorative film, after the adherend is decorated with the decorative film, the substrate layer is located as the outermost layer of the decorated adherend (i.e., the decorated molded body) and functions as a protective layer for the decorated molded body. The material constituting the substrate layer is preferably a flexible material, and preferably a resin material. More preferably, it is a thermoplastic resin. The thermoplastic resin is not particularly limited, but examples include polyvinyl chloride (PVC) resin, polyester resin, acrylic resin, acrylonitrile butadiene styrene (ABS) resin, polycarbonate resin, polypropylene resin, and polyethylene resin. Of these, the substrate layer is preferably formed from at least one selected from the group consisting of PVC resin, polyester resin, and ABS resin.

[0111] The thickness of the substrate layer is preferably 25 μm to 500 μm, more preferably 50 μm to 400 μm, and even more preferably 100 to 300 μm. When the thickness of the substrate layer is within the above range, the processability, shape conformability, and handleability are improved when the decorative molded body is produced by injection molding (also known as insert molding), vacuum molding, vacuum pressure molding, or the like.

[0112] The decorative layer is an ink layer onto which designs and patterns such as text, figures, and trademarks are printed or otherwise applied. This decorative layer imparts design properties to the decorative film. The designs and patterns of the decorative layer can be formed by known printing methods such as gravure printing using printing ink, offset printing, silk screen printing, transfer printing from a transfer sheet, sublimation transfer printing, and inkjet printing. The thickness of the decorative layer is preferably 1 to 40 μm, more preferably 1 to 30 μm. When the thickness of the decorative layer is within the above range, a sufficient thickness can be ensured to express complex designs such as gradations. A textured pattern may be applied to the surface layer of the decorative film. The textured pattern can be formed, for example, by transferring the textured pattern using an embossing roller. Furthermore, the base layer or adhesive layer can be imparted with decorative functionality by incorporating pigments, dyes, brighteners, etc. into the base layer or adhesive layer.

[0113] Before being attached to an adherend, the decorative film may further include a release layer on the outermost layer on the adhesive layer side, in addition to the adhesive layer. The release layer prevents unintended adhesion and is peeled off when the decorative film is attached to the adherend. The material constituting the release layer is not particularly limited, and examples that can be used include resin materials such as polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, polyolefins such as polypropylene and polyethylene, and paper materials such as glassine paper, kraft paper, and clay-coated paper. The thickness of the release layer can be approximately 10 to 400 μm.

[0114] Alternatively, the decorative film may be a film having a hard coat layer (protective layer) and a decorative layer on a release layer of a release film having a release layer before being attached to an adherend, and the film may be attached to an adherend via an adhesive layer provided on the decorative layer side. A decorative film of this configuration is suitable for use as a transfer film. With this decorative film, a decorated molded article can be obtained by a transfer method in which the hard coat layer and the adhesive layer are transferred to the adherend.

[0115] The hard coat layer is preferably composed of a material that can be cured and / or crosslinked by irradiation with active energy rays or the like after being transferred to an adherend. Examples of materials that can be used for the hard coat layer include polymers or oligomers having a (meth)acryloyl group, active energy ray-curable compositions that have been semi-cured by irradiating them with an appropriate amount of active energy rays, and active energy ray-curable resin compositions that have been blended with an isocyanate compound, a polyol resin, or the like and appropriately crosslinked. The thickness of the hard coat layer is not particularly limited and is, for example, about 1 to 50 μm.

[0116]

[0013] The present disclosure provides a decorative molded body in which the adhesive layer of the decorative film described above is attached to a molded body. The decorative molded body is decorated with a decorative film having an adhesive layer obtained using the present composition, and therefore the decorative film is less likely to lift or peel at both room temperature and high temperatures, and has excellent heat resistance and durability.

[0117] The molded article to which the decorative film is adhered is not particularly limited, and may be any article to which the decorative film can be adhered, such as a resin product, a metal product, a ceramic product, a glass product, etc. Specific examples include various home appliances such as household appliances, kitchen appliances, health appliances, and seasonal appliances; interior and exterior components of housing facilities such as toilets, bathrooms, doors, and walls; automobile interior and exterior components such as bumpers, dashboards, doors, roofs, and hoods; various miscellaneous goods such as household goods and daily necessities; electronic components; nursing and medical supplies; interior and exterior components of ships and aircraft; etc. When the adhesion surface of the molded article to which the decorative film is adhered is made of a low-polarity material, the properties of the pressure-sensitive adhesive layer of the present disclosure, i.e., the effect of exhibiting high adhesion both at room temperature and at high temperatures, can be more suitably exhibited, and the adhesive layer can be particularly preferably applied to molded articles whose adhesion surface is made of polypropylene.

[0118] The decorative molded body can be manufactured using methods such as vacuum forming, vacuum pressure forming, and injection molding. In the vacuum forming method, the decorative film is heated and softened while being stretched, and the space on the molded body side of the decorative film is depressurized, thereby forming and adhering the decorative film to the surface shape of the molded body. In the vacuum pressure forming method, after the forming process of the vacuum forming method, the space on the opposite side is further pressurized, thereby forming and adhering the decorative film to the surface shape of the molded body. Examples of vacuum pressure forming machines include the TFH series hot plate type vacuum coating molding machine manufactured by Asano Laboratory, the NGF series TOM molding machine manufactured by Fuse Vacuum, and the NATS air transfer machine manufactured by Navitas. In the injection molding method, the decorative film is placed in the mold cavity of the injection molding machine and injection molded, thereby adhering the decorative film to the surface shape of the molded body. These methods can be used to obtain the decorative molded body.

[0119] The present disclosure will be specifically described below using examples. However, the present disclosure is not limited to these examples. In the following, "parts" and "%" mean "parts by mass" and "% by mass", respectively, unless otherwise specified. The polymers used in each example were analyzed using the following methods.

[0120] <Molecular Weight Measurement> Using a gel permeation chromatograph (model "HLC-8320", manufactured by Tosoh Corporation), the weight average molecular weight (Mw) and number average molecular weight (Mn) in terms of polystyrene were obtained under the following conditions: Measurement conditions Column: 4 columns of TSKgel SuperMultiporeHZ-M manufactured by Tosoh Corporation Column temperature: 40°C Eluent: tetrahydrofuran Detector: RI Flow rate: 600 μL / min

[0121] <Measurement of Glass Transition Temperature (Tg)> The glass transition temperature (Tg) of a polymer was determined from the intersection of the baseline of a heat flux curve obtained using a differential scanning calorimeter (DSC) and the tangent at the inflection point. The heat flux curve was obtained by cooling approximately 10 mg of a sample to -100°C, holding it for 5 minutes, then heating it at 10°C / min to 300°C, subsequently cooling it to -100°C, holding it for 5 minutes, and then heating it at 10°C / min to 350°C. Measuring instrument: DSC6220 manufactured by SII Nanotechnology Inc. Measurement atmosphere: nitrogen atmosphere

[0122] <Measurement of Melting Point (Tm)> The melting point (Tm) of modified or unmodified polyolefin was determined as the melting peak top of a heat flux curve obtained using a differential scanning calorimeter (DSC). The heat flux curve was obtained by cooling approximately 5 mg of a sample to -70°C, holding it for 5 minutes, then heating it at 10°C / min to 150°C, subsequently cooling it to -70°C, holding it for 5 minutes, and then heating it at 10°C / min to 150°C. Measuring instrument: DSC6220 manufactured by SII Nanotechnology Inc. Measurement atmosphere: nitrogen atmosphere

[0123] <Calculation of Monomer Composition Ratio of Polymer> The monomer composition ratio of the obtained polymer was calculated from the charged amount and the amount of monomer consumed measured by gas chromatography (GC). <SP Value> The SP value of the polymer was calculated by the Fedors method. The unit is [cal / cm ３ ] １／２ is.

[0124] 1. Synthesis of Acrylic Adhesive Polymer [Synthesis Example 1] (Synthesis of Polymer A-1) Methyl acrylate (hereinafter also referred to as "MA") (60 parts by mass), butyl acrylate (hereinafter also referred to as "BA") (35 parts by mass), 2-hydroxyethyl acrylate (hereinafter also referred to as "HEA") (5 parts by mass), and ethyl acetate (150 parts) were charged into a four-neck flask, and the mixture was thoroughly degassed by bubbling with nitrogen gas, and the internal temperature of the mixture was raised to 75°C. 2,2'-azobis(2,4-dimethylbutyronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "V-65") (0.0252 parts by mass) was charged as an initiator, and polymerization was carried out for 5 hours. Ethyl acetate was added so that the solids concentration was 22%, to obtain an ethyl acetate solution of Polymer A-1. The obtained polymer consisted of 60% by mass of MA, 35% by mass of BA, and 5% by mass of HEA, and had Mn = 174,000, Mw = 806,000, and Mw / Mn = 4.6. The Tg was -7°C, and the SP value was 10.57. The composition (feed ratio), reaction conditions, and analysis results of Polymer A-1 are shown in Table 1. The monomer composition ratio of Polymer A-1 was equivalent to the feed ratio of the monomers.

[0125] [Synthesis Examples 2 to 12] (Synthesis of Polymers A-2 to A-12) Solutions containing Polymers A-2 to A-12 were obtained by the same operation as in Synthesis Example 1, except that the types and amounts of raw materials charged to the flask and the reaction conditions were changed as shown in Table 1. In Synthesis Examples 7, 10, 11, and 12, where the reaction conditions are indicated as "65°C 3 h → 75°C 5 h," the mixed solution was polymerized at 65°C for 3 hours, and then the temperature was raised to 75°C and the reaction was continued for 5 hours. The analysis results of the obtained polymers are shown in Table 1. For Polymers A-2 to A-12, the monomer composition ratio of each polymer was equivalent to the monomer charging ratio.

[0126]

[0127] The abbreviations of the monomers in Table 1 are as follows: MA: methyl acrylate BA: butyl acrylate MEA: 2-methoxyethyl acrylate HEA: 2-hydroxyethyl acrylate 4HBA: 4-hydroxybutyl acrylate AA: acrylic acid HEMA: 2-hydroxyethyl methacrylate

[0128] 2. Synthesis of Vinyl Polymer [Synthesis Example 13] (Synthesis of Polymer B-1) A 1-liter four-neck flask was charged with a mixed solution consisting of butyl acetate (200 parts by mass) and dimethyl-2,2'-azobis(2-methylpropionate) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "V-601", hereinafter also referred to as "V-601") (0.9 parts by mass). This mixed solution was thoroughly degassed by bubbling nitrogen gas, and the internal temperature of the mixed solution was raised to 90°C. Separately, a mixed solution consisting of methyl methacrylate (hereinafter also referred to as "MMA") (165 parts by mass), isobornyl methacrylate (hereinafter also referred to as "IBXMA") (44 parts by mass), V-601 (17 parts by mass), and butyl acetate (90 parts by mass) was added dropwise from a dropping funnel into the flask over 5 hours to carry out polymerization. After completion of the dropwise addition, the polymerization solution was added dropwise to a mixed solution of methanol (4,800 parts by mass) and distilled water (1,200 parts by mass), thereby isolating the vinyl polymer in the polymerization solution to obtain Polymer B-1. The composition ratio of the monomers constituting the obtained Polymer B-1 was calculated from the charged amounts and the monomer consumption amounts measured by GC, and as a result, it consisted of 80% by mass of MMA and 20% by mass of IBXMA, and the molecular weight characteristics of Polymer B-1 were Mw = 6,700. Tg was 108°C.

[0129] 3. Production of Modified or Unmodified Polyolefins [Synthesis Example 14] (Synthesis of Modified Polyolefin C-1) A 300 mL four-neck flask was charged with 100 parts of Tafmer XM-7090 (a polyolefin manufactured by Mitsui Chemicals, Inc.), 18.7 g of maleic anhydride, and 267 parts of t-butylbenzene. The flask was thoroughly degassed by bubbling nitrogen gas through the flask, and the internal temperature was raised to 128°C with stirring to dissolve the polyolefin. A t-butylbenzene solution (3%, 8 parts solids) of dicumyl peroxide (manufactured by NOF Corporation, trade name "Percumyl D") as a peroxide was added dropwise over 3 hours. After completion of the dropwise addition, the mixture was stirred for an additional 3 hours while maintaining the temperature. The reaction mixture was allowed to cool, then added to 1,000 parts of ethyl acetate, and the resulting white solid was filtered. The solid was suspended in 1,000 parts of acetone, and this filtration procedure was repeated twice to remove impurities. The obtained powder was vacuum dried at 60°C for 3 hours to obtain modified polyolefin C-1. GPC measurement of modified polyolefin C-1 revealed that Mn = 29,000, Mw = 54,000, and Mw / Mn = 1.9. The melting point of modified polyolefin C-1 was 98°C. In addition, nuclear magnetic resonance spectroscopy (measuring device: JNM-ECA400 manufactured by JEOL Ltd.) １ The degree of acid modification was determined by H-NMR and was found to be 2.0%.

[0130] [Synthesis Examples 15 to 27] Modified polyolefins C-2, C-3, C-5 to C-14 and unmodified polyolefin C-4 were obtained by the same operation as in Synthesis Example 14, except that the types and amounts of raw materials charged into the flask and the reaction conditions were changed as shown in Table 2. In Table 2, the numerical values ​​for maleic anhydride and peroxide represent the amount (parts by mass) of each compound used per 100 parts by mass of the polyolefin raw material.

[0131]

[0132] The abbreviations for the polyolefin raw materials and solvents in Table 2 are as follows: XM-7090: Tafmer XM-7090 (polyolefin manufactured by Mitsui Chemicals, Inc.) PMA-TE: Hardlen PMA-TE (maleic anhydride modified polyolefin manufactured by Mitsui Chemicals, Inc., modification rate 1.8%, melting point 90°C, Mw 60,000) L-MODU S901: polypropylene resin manufactured by Idemitsu Kosan Co., Ltd. Vistamaxx 3020FL: propylene elastomer manufactured by ExxonMobil Japan Co., Ltd. tBB: t-butylbenzene oDCB: o-dichlorobenzene

[0133] 4. Preparation of Pressure-Sensitive Adhesive Composition and Pressure-Sensitive Adhesive Sheet [Example 1] A polymer PO-1 solution with a solids concentration of 40% by mass, prepared by dissolving polymer PO-1 (360T manufactured by Nippon Paper Industries Co., Ltd., chlorinated polyolefin, modification rate 31%, melting point 60°C, Mw 0.5 to 20,000) in ethyl acetate, was mixed with a polymer A-1 solution to prepare a polymer solution with a solids content of 22% by mass containing polymer A-1 (100 parts by mass) and polymer PO-1 (30 parts by mass). 0.20 parts by mass of a trimethylolpropane adduct of metaxylylene diisocyanate (Takenate D-110N manufactured by Mitsui Chemicals, Inc., solids concentration 75% by mass, isocyanate group content 11.5%) as a crosslinking agent was mixed thereto to obtain a pressure-sensitive adhesive composition. The obtained pressure-sensitive adhesive composition was applied to a 50 μm-thick polyethylene terephthalate (hereinafter referred to as "PET") separator so that the thickness after drying would be 50 μm. The ethyl acetate was removed by drying the pressure-sensitive adhesive composition for 4 minutes at 80° C. A 38 μm thick PET separator with a different peel strength from the above separator was attached, and the resulting sheet was left to stand at 40° C. for 5 days for aging, thereby obtaining a pressure-sensitive adhesive sheet with a double-sided separator.

[0134] [Examples 2 to 43, Comparative Examples 1 to 6] Based on the compositions and solid content concentrations shown in Tables 3 to 8, pressure-sensitive adhesive compositions were produced in the same manner as in Example 1. Furthermore, using the obtained pressure-sensitive adhesive compositions, pressure-sensitive adhesive sheets with double-sided separators were obtained in the same manner as in Example 1. Note that with respect to the numerical values ​​in parentheses for the compositions of the pressure-sensitive adhesive compositions in Tables 3 to 8, the values ​​represent the amount of solid content (parts by mass) for the acrylic pressure-sensitive adhesive polymer (BP), modified or unmodified polyolefin (PO), tackifier, and vinyl polymer, and the values ​​represent the amount (parts by mass) including the solvent for the crosslinking agent.

[0135] 5. Evaluation The resulting pressure-sensitive adhesive sheets with double-sided separators (hereinafter referred to as "evaluation sheets") were subjected to various measurements and evaluations using the methods described below. The results are shown in Tables 3 to 8.

[0136] <Gel fraction> 0.2 g of pressure-sensitive adhesive was sampled from the evaluation sheet, and the initial mass of the pressure-sensitive adhesive was weighed. The pressure-sensitive adhesive was immersed in 50 g of ethyl acetate and allowed to stand at room temperature for 16 hours. Thereafter, the pressure-sensitive adhesive was filtered through a 200-mesh wire netting, and the residue remaining on the mesh was dried at 80°C for 3 hours and weighed. The gel fraction was calculated from the initial mass and the mass of the residue.

[0137] <Haze Value> The release film was peeled off from the evaluation sheet (adhesive layer thickness: 50 μm), transferred to a glass plate (thickness: 1 mm), and the other release film was peeled off. After leaving the sheet to stand for 1 day under conditions of 23°C and 50% RH, the haze value was measured using a haze meter "COH7700" (model name) manufactured by Nippon Denshoku Industries Co., Ltd.

[0138] <Tg of the entire pressure-sensitive adhesive layer> The Tg of the entire pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition was measured by DSC in accordance with JIS K7121 under the following conditions: Measuring device: (Q-100) manufactured by TA Instrument Heating rate: 10°C / min Measurement atmosphere: Nitrogen atmosphere

[0139] <Composition of the surface portion of the pressure-sensitive adhesive layer> From the peak area ratio of O1s and C1s measured by an X-ray photoelectron spectrometer (XPS) of a pressure-sensitive adhesive film sample, the mass fraction (W Ａand W Ｂ ) was calculated. In Comparative Example 6, unmodified polyolefin C-4 was used instead of the modified polyolefin, and the composition of the surface layer portion of the pressure-sensitive adhesive layer was calculated in the same manner. The XPS measurement was carried out under the following conditions. Apparatus: PHI5000 VersaProbe manufactured by ULVAC-PHI, Inc. X-ray: Al-Kα (1486.6 eV) X-ray incident angle to sample: 0° (angle with respect to the normal to the sample measurement surface) Photoelectron detection angle: 45° (angle with respect to the normal to the sample measurement surface)

[0140] A specific method for calculating the mass fraction is described below. The ratio of oxygen atoms to the total number of oxygen atoms and carbon atoms calculated from the peak area ratio of O1s and C1s by XPS measurement represents the ratio of oxygen atoms to the total number of oxygen atoms and carbon atoms present per unit area of ​​the surface layer of the pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition comprising an acrylic pressure-sensitive adhesive polymer and a modified polyolefin, as shown in the following formula (4):

[0141] Here, O Ａ＋Ｂ : the ratio of the number of oxygen atoms to the total number of carbon atoms and oxygen atoms, calculated from the peak area ratio of O1s and C1s determined by XPS measurement of the pressure-sensitive adhesive layer obtained by drying the pressure-sensitive adhesive composition; x: the volume fraction of the acrylic adhesive polymer in the surface layer of the pressure-sensitive adhesive layer; N ＯＡ N: The ratio of the number of oxygen atoms derived from the acrylic adhesive polymer to the total number of carbon atoms and oxygen atoms in a unit area of ​​the surface layer of the adhesive layer ＯＢ N: The ratio of the number of oxygen atoms derived from modified polyolefin to the total number of carbon atoms and oxygen atoms in the surface layer of the adhesive layer ｃ N: Number of carbon atoms per unit area of ​​the surface of the adhesive layer ｏ : Number of oxygen atoms per unit area of ​​the adhesive layer surface

[0142] Furthermore, the ratio of oxygen atoms to the total number of carbon atoms and oxygen atoms calculated from the peak area ratio of O1s and C1s determined by XPS measurement of films obtained by drying each of the acrylic adhesive polymer and modified polyolefin alone is expressed by the following formula (5) and formula (6), respectively. Here, O ＡN: The ratio of the number of oxygen atoms to the total number of carbon atoms and oxygen atoms, calculated from the peak area ratio of O1s and C1s obtained by XPS measurement of a film obtained by drying an acrylic adhesive polymer ＯＡ N: O1s peak area obtained by XPS measurement of a film obtained by drying an acrylic adhesive polymer ＣＡ : C1s peak area determined by XPS measurement of a film obtained by drying an acrylic adhesive polymer Here, O Ｂ N: The ratio of the number of oxygen atoms to the total number of carbon atoms and oxygen atoms, calculated from the peak area ratio of O1s and C1s determined by XPS measurement of a film obtained by drying the modified polyolefin ＯＢ N: O1s peak area determined by XPS measurement of a film obtained by drying the modified polyolefin ＣＢ : C1s peak area determined by XPS measurement of a film obtained by drying the modified polyolefin

[0143] The density of the acrylic adhesive polymer and modified polyolefin is close, Ｃ +N Ｏ = N ＣＡ +N ＯＡ = N ＣＢ +N ＯＢ x = W Ａ Based on this approximation, the following formula (7) is derived from the above formulas (4) to (6), and the mass fraction W of the acrylic adhesive polymer is calculated from this formula. A is calculated. Furthermore, the W calculated above Ａ From the value of and the following formula (8), the mass fraction of the modified polyolefin (W Ｂ ) is calculated. Ｂ = 1 - W Ａ ...(8) where W Ａ W: Mass fraction of acrylic adhesive polymer Ｂ : mass fraction of modified polyolefin

[0144] For Example 13, the elements in the above formula (7) are as follows: Ａ＋Ｂ : 10.1 (measured value) O Ａ : 31.5 (measured value) OＢ : 1.6 (measured value) By substituting these values ​​into the above formula (4), W Ａ = 0.284, W Ｂ = 0.716 was obtained.

[0145] <Modified polyolefin concentration in the entire pressure-sensitive adhesive layer and the modified polyolefin concentration in the surface layer portion of the pressure-sensitive adhesive layer> The ratio (unit: %) of the mass of the modified polyolefin to the total mass of the acrylic adhesive polymer and modified polyolefin used in preparing the pressure-sensitive adhesive composition was calculated, and this was taken as the modified polyolefin concentration in the entire pressure-sensitive adhesive layer (hereinafter also referred to as "PO concentration in the pressure-sensitive adhesive layer"). In addition, the W calculated from the XPS measurement results of the pressure-sensitive adhesive film sample was used as the modified polyolefin concentration in the surface layer portion of the pressure-sensitive adhesive layer. Ｂ The value expressed as a percentage was taken as the concentration of modified polyolefin in the surface portion of the PSA layer (hereinafter also referred to as "PO surface concentration"). Furthermore, the PO surface concentration was divided by the PSA layer PO concentration to calculate the ratio of the PO surface concentration to the PSA layer PO concentration (PO concentration ratio).

[0146] <Peel test> The evaluation sheet (adhesive layer thickness: 50 μm) was transferred to an easily adhesive treated PET film (125 μm) to obtain a peel test sheet. This peel test sheet was attached to a polypropylene (PP) plate (manufactured by Resonac, trade name PP-N-BN, 2 mm thick) and pressed for 20 seconds under conditions of 120 ° C. and 0.8 MPa using a precision heating and pressing device (manufactured by Shinto Kogyo Co., Ltd.) to obtain a peel test specimen. The peel test specimen was measured for 180° peel strength of the adhesive sheet using a thermostatic oven equipped tensile tester Strograph R type (manufactured by Toyo Seiki Co., Ltd.) at temperatures of 23 ° C. and 85 ° C. and a peel speed of 300 mm / min. in accordance with JIS Z-0237 "Test method for adhesive tapes and adhesive sheets," and the peel strength at each temperature was recorded.

[0147]

[0148]

[0149]

[0150]

[0151]

[0152]

[0153] The abbreviations for modified or unmodified polyolefins (PO), additives, and solvents in Tables 3 to 8 are as follows: "BP" represents acrylic adhesive polymers A-1 to A-12 obtained in Synthesis Examples 1 to 12. PO-1: Nippon Paper Industries Co., Ltd. 360T, chlorinated polyolefin, modification rate 31%, melting point 60°C, Mw 0.5-20,000) PO-2: Toyobo Co., Ltd. 14-WL-P, chlorinated polyolefin, modification rate 27%, melting point 80°C, Mw 40,000) PO-3: Nippon Paper Industries Co., Ltd. Superchlor 814HS, chlorinated polypropylene, modification rate 41%, melting point 60°C, Mw 10,000-30,000) PO-4: Toyobo Co., Ltd. DX-523P, chlorinated polyolefin, modification rate 23%, melting point 84°C, Mw 100,000) PO-5: Nippon Paper Industries Co., Ltd. S-7083S, acrylic-modified polyolefin, modification rate 20%, melting point 72°C, Mw 30,000) PO-6: Nippon Paper Industries Co., Ltd. S-7098S, acrylic modified polyolefin, modification rate 70%, melting point 62°C, Mw 60,000) PO-7: Toyobo Co., Ltd. HARDLEN HM-21P, maleic anhydride modified chlorinated polyolefin, modification rate: chlorination modification rate 21%, maleic anhydride modification rate 1.6%, melting point 85°C, Mw 45,000) PO-8: Nippon Paper Industries Co., Ltd. 3221S, chlorinated polyolefin, modification rate 21%, melting point 55°C, Mw 40,000) PO-9: Nippon Paper Industries Co., Ltd. 3228S, chlorinated polyolefin, modification rate 28%, melting point 61°C, Mw 40,000) PO-10: Toyobo Co., Ltd. CY-2321P, maleic anhydride modified chlorinated polyolefin, modification rate 21%, melting point 56°C, Mw 45,000) PO-11: Toyobo Co., Ltd. HARDLEN PMA-TE, maleic anhydride modified polyolefin, modification rate 1.8%, melting point 90°C, Mw 60,000) PO-12: Toyobo Co., Ltd., HARDLEN PMA-T, maleic anhydride modified polyolefin, modification rate 1.5%, melting point 90°C, Mw 75,000) PO-13: Toyobo Co., Ltd., HARDLEN PMA-TH, maleic anhydride modified polyolefin, modification rate 1.0%, melting point 90°C, Mw 90,000) PO-14: Toyobo Co., Ltd., HARDLEN PMA-TZ, maleic anhydride modified polyolefin, modification rate 1.4%, melting point 90°C, Mw 115,000) C-1 to C-14: Modified or unmodified polyolefins obtained in Synthesis Examples 14 to 27 Tackifiers KE-311: Product name "KE-311", rosin ester with a softening point of 90 to 100°C, manufactured by Arakawa Chemical Industries, Ltd.Vinyl polymer B-1: Vinyl polymer B-1 obtained in Synthesis Example 13 Crosslinking agent D-110N: Takenate D-110N manufactured by Mitsui Chemicals, Inc., a trimethylolpropane-modified meta-xylylene diisocyanate, solids concentration 75% by mass, NCO content 11.5% Crosslinking agent D-101E: Takenate D-101E manufactured by Mitsui Chemicals, Inc., a trimethylolpropane-modified tolylene diisocyanate, solids concentration 75% by mass, NCO content 13.3% Tol / CH: a mixed solvent of toluene and cyclohexane (mass ratio Tol / CH=75:25) Crosslinking agent Tetrad-C: TETRAD-C manufactured by Mitsubishi Gas Chemical Company, Inc., 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane Crosslinking agent Tetrad-X: TETRAD-X manufactured by Mitsubishi Gas Chemical Company, Inc., tetraglycidylxylene diamine

[0154] From the results of Tables 3 to 8, the pressure-sensitive adhesive sheets of Examples 1 to 43, which had a pressure-sensitive adhesive layer in which the acrylic pressure-sensitive adhesive polymer and the modified polyolefin were phase-separated, had high peel strengths at 23°C and 80°C against PP plates, and had good adhesion at room temperature and at high temperatures.

[0155] In contrast, the PSA sheets of Comparative Examples 1 to 6 had low haze values ​​of less than 1.0, indicating the absence of polymer phase separation in the PSA layer. Furthermore, looking at the evaluation results of the PSA sheets of Comparative Examples 1 to 6, Comparative Example 1, which did not contain a modified polyolefin and contained only an acrylic adhesive polymer, had low peel strengths at both room temperature and high temperatures. Furthermore, Comparative Example 2, which contained a tackifier instead of modified polyolefin, had a relatively high peel strength at room temperature, but a lower peel strength at high temperatures than Examples 1 to 43, indicating poor adhesion at high temperatures. Comparative Example 3, which contained vinyl polymer B-1 instead of modified polyolefin, had a relatively high peel strength at high temperatures, but a lower peel strength at room temperature than Examples 1 to 43, indicating poor adhesion at room temperature. The PSA sheets of Comparative Examples 4 and 5, which showed from the haze values ​​the absence of phase separation between the acrylic adhesive polymer and modified polyolefin in the PSA layer, had low peel strengths at both room temperature and high temperatures. Furthermore, the pressure-sensitive adhesive sheet of Comparative Example 6, in which unmodified polyolefin was blended instead of modified polyolefin, exhibited low peel strength both at room temperature and at high temperatures.

[0156] <Observation of the Surface of the Pressure-Sensitive Adhesive Layer with a Microscope> In order to confirm by images that the acrylic pressure-sensitive adhesive polymer and the modified polyolefin had been phase-separated in the pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets of Examples 1 to 43, the pressure-sensitive adhesive compositions of the examples were applied to a PET separator and heated at 80°C to remove the solvent, forming pressure-sensitive adhesive layers with a thickness of 50 µm, and the surfaces of the pressure-sensitive adhesive layers were observed with a scanning probe microscope. The image obtained with the scanning probe microscope for Example 13 is shown in Figure 1.

[0157] As shown in Figure 1, the surface layer of the pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition of Example 13 contained a mixture of phase P1 mainly composed of an acrylic adhesive polymer and phase P2 mainly composed of a modified polyolefin, confirming that the acrylic adhesive polymer and the modified polyolefin were phase-separated. On the other hand, when the surface layers of the pressure-sensitive adhesive sheets of Comparative Examples 1 to 6 were observed with a scanning probe microscope, it was confirmed that the acrylic adhesive polymer and the modified polyolefin were not phase-separated. For Comparative Example 4, an image obtained with a scanning probe microscope is shown in Figure 2.

[0158] From the above results, it became clear that a pressure-sensitive adhesive layer in which the acrylic pressure-sensitive adhesive polymer and the modified polyolefin are phase-separated can increase adhesiveness both at room temperature and at high temperatures.

[0159] The present invention is not limited to the above-described embodiments, and encompasses various modifications and equivalent modifications within the scope of the spirit of the present invention. Therefore, in light of the above teachings, various combinations and forms, as well as other combinations and forms including only one element, more than one element, or less than one element, are to be understood as falling within the scope and spirit of the present invention.

[0160] P1...first phase, P2...second phase

Claims

1. An adhesive sheet having an adhesive layer, the adhesive layer comprising an acrylic adhesive polymer and at least one modified polymer selected from the group consisting of modified polyolefins and modified polydienes, the acrylic adhesive polymer and the modified polymer being phase-separated in a surface portion of the adhesive layer.

2. The pressure-sensitive adhesive sheet according to claim 1, wherein the concentration of the modified polymer in the surface portion of the pressure-sensitive adhesive layer is higher than the concentration of the modified polymer in the entire pressure-sensitive adhesive layer.

3. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the concentration of the modified polymer in the surface portion of the pressure-sensitive adhesive layer obtained by X-ray photoelectron spectroscopy analysis is 1.5 times or more higher than the concentration of the modified polymer in the entire pressure-sensitive adhesive layer.

4. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the haze value of the pressure-sensitive adhesive layer is 3.0% or more when the thickness of the pressure-sensitive adhesive layer is 50 μm.

5. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the modified polymer is at least one selected from the group consisting of acid-modified polyolefins, chlorinated polyolefins, acid-modified chlorinated polyolefins, acrylic-modified polyolefins and acrylic-modified chlorinated polyolefins.

6. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the modified polymer is modified with at least one selected from the group consisting of carboxylic acids, carboxylic anhydrides and (meth)acrylic esters.

7. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the modification rate of the modified polymer is 80% or less.

8. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the melting point of the modified polymer is 20°C or higher and 130°C or lower.

9. The pressure-sensitive adhesive sheet according to claim 1 or 2, which is a decorative film.

10. An adhesive sheet having an adhesive layer, the adhesive layer comprising an acrylic adhesive polymer and at least one modified polymer selected from the group consisting of modified polyolefins and modified polydienes, and the adhesive layer having a haze value of 3.0% or more when the thickness of the adhesive layer is 50 μm.

11. A pressure-sensitive adhesive composition used for forming a pressure-sensitive adhesive layer, comprising an acrylic adhesive polymer, at least one modified polymer selected from the group consisting of modified polyolefins and modified polydienes, and a solvent, wherein the pressure-sensitive adhesive composition is applied to a substrate, and the solvent is removed to form the pressure-sensitive adhesive layer on the substrate, and in the process, phase separation occurs between the acrylic adhesive polymer and the modified polymer.

12. The pressure-sensitive adhesive composition according to claim 11, wherein the concentration of the modified polymer in the surface portion of the pressure-sensitive adhesive layer is higher than the concentration of the modified polymer in the entire pressure-sensitive adhesive layer.

13. The pressure-sensitive adhesive composition according to claim 11 or 12, wherein the concentration of the modified polymer in the surface portion of the pressure-sensitive adhesive layer obtained by X-ray photoelectron spectroscopy analysis is 1.5 times or more higher than the concentration of the modified polymer in the entire pressure-sensitive adhesive layer.

14. The pressure-sensitive adhesive composition according to claim 11 or 12, wherein the haze value of the pressure-sensitive adhesive layer is 3.0% or more when the thickness of the pressure-sensitive adhesive layer is 50 μm.

15. The pressure-sensitive adhesive composition according to claim 11 or 12, wherein the glass transition temperature of the acrylic pressure-sensitive adhesive polymer is -40°C or higher.

16. The pressure-sensitive adhesive composition according to claim 11 or 12, wherein the weight-average molecular weight of the acrylic pressure-sensitive adhesive polymer is 450,000 or more.

17. The pressure-sensitive adhesive composition according to claim 11 or 12, wherein the acrylic adhesive polymer contains 30 mass% or more of structural units derived from at least one selected from the group consisting of (meth)acrylic acid alkyl esters having an alkyl group having 1 to 3 carbon atoms and (meth)acrylic acid alkoxyalkyl esters having 3 or 4 carbon atoms, based on all structural units contained in the acrylic adhesive polymer.

18. The adhesive composition according to claim 11 or 12, wherein the proportion of structural units derived from an amino group-containing unsaturated compound in the acrylic adhesive polymer is 0.2 mass% or less relative to the total structural units possessed by the acrylic adhesive polymer.

19. The pressure-sensitive adhesive composition according to claim 11 or 12, wherein the modified polymer is at least one selected from the group consisting of acid-modified polyolefins, chlorinated polyolefins, acid-modified chlorinated polyolefins, acrylic-modified polyolefins, and acrylic-modified chlorinated polyolefins.

20. The pressure-sensitive adhesive composition according to claim 11 or 12, further comprising a crosslinking agent.

21. A solvent-based pressure-sensitive adhesive composition comprising an acrylic adhesive polymer, at least one modified polymer selected from the group consisting of modified polyolefins and modified polydienes, and a solvent, wherein the pressure-sensitive adhesive composition is applied to a substrate, and the solvent is removed to form a 50 μm-thick pressure-sensitive adhesive layer on the substrate, and the haze value of the pressure-sensitive adhesive layer is 3.0% or more.

22. A decorated molded article in which the adhesive layer of the adhesive sheet according to claim 1 or 2 is adhered to the molded article.

Images