Pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet, optical member

Abstract

To provide an adhesive composition excellent in reworkability, transparency and impact resistance, an adhesive sheet, an optical member and a display device.SOLUTION: A (meth) acryl-based polymer (A) having a reactive functional group, a (meth) acryl-based polymer (B) having a glass transition temperature higher than a glass transition temperature of the (meth) acryl-based polymer (A) by 85 °C or more, and a crosslinking agent, in which when a pressure-sensitive adhesive layer is formed, a half-value width H °C of a peak of a loss tangent of the pressure-sensitive adhesive layer, a content CA parts by mass of the (meth) acryl-based polymer (A), and a content CB parts by mass of the (meth) acryl-based polymer (B) satisfy a relationship of the following Expression (X), and applications thereof. 14.8 ≤ H * CA / (CA + CB) <21.0 (X) SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet, an optical member, and a display device. [Background technology]

[0002] A liquid crystal display device generally includes a liquid crystal cell in which a liquid crystal component aligned in a predetermined direction is sandwiched between two support substrates, and optical films such as a polarizing plate, a retardation film, and a brightness enhancement film. When a liquid crystal display device is manufactured by laminating a liquid crystal cell and an optical film, or by laminating optical films together, these components are bonded together via a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition. In liquid crystal display devices, (meth)acrylic pressure-sensitive adhesive compositions are often used to ensure visibility.

[0003] For example, Patent Document 1 discloses a pressure-sensitive adhesive composition for polarizing films, characterized by containing 100 parts by mass of a high-molecular-weight acrylic polymer (a) containing a functional group and having a weight-average molecular weight of 1,000,000 to 2,500,000, 10 parts by mass to 100 parts by mass of a low-molecular-weight acrylic polymer (b) having a glass transition point of 0°C to -80°C and having a weight-average molecular weight of 30,000 to 100,000, and 0.001 parts by mass to 10 parts by mass of a polyfunctional compound (c) containing two or more functional groups capable of reacting with the reactive functional group of (a) to form a crosslinked structure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-121521 Summary of the Invention [Problem to be solved by the invention]

[0005] Optical films, such as polarizing plates, used in liquid crystal display devices are used with a pressure-sensitive adhesive layer attached. Generally, when a pressure-sensitive adhesive-attached optical film is attached to a liquid crystal cell, if foreign matter gets caught between the pressure-sensitive adhesive layer and the liquid crystal cell or if misalignment occurs due to incorrect attachment, the film is peeled off from the liquid crystal cell and reattached. Because the liquid crystal cell is reused after peeling the pressure-sensitive adhesive-attached optical film, the pressure-sensitive adhesive layer is required to have excellent reworkability, i.e., to easily peel the film from the liquid crystal cell without damaging the liquid crystal cell or leaving adhesive residue on the attachment surface. Furthermore, the peeling operation is not necessarily performed immediately after attachment, but may be performed long after attachment. Therefore, the pressure-sensitive adhesive layer is required to have excellent reworkability, allowing the film to be easily peeled off without any problems even long after attachment of the polarizing plate to the liquid crystal cell. Furthermore, with the recent increase in display size, the surface area of ​​optical films, such as polarizing plates, has increased, making it more difficult to peel the optical film from the display. This has led to a trend toward requiring pressure-sensitive adhesive layers with better reworkability than before.

[0006] In recent years, as displays have become thinner, there has been a trend toward thinner optical films. When the optical film becomes thinner, if the optical film is subjected to an external impact, the pressure-sensitive adhesive layer may not be able to withstand the impact, resulting in defects such as foaming. Therefore, the pressure-sensitive adhesive layer is required to have excellent impact resistance, i.e., to be less likely to generate bubbles even when subjected to an external impact.

[0007] One method for improving the reworkability of a pressure-sensitive adhesive layer is to add a low-molecular-weight resin with a low glass transition temperature to a high-molecular-weight base resin, as described in Patent Document 1. However, this method makes it difficult to improve the impact resistance of the pressure-sensitive adhesive layer because the low-molecular-weight resin has a low glass transition temperature. Thus, it has traditionally been difficult to form a pressure-sensitive adhesive layer that combines high levels of reworkability and impact resistance.

[0008] Moreover, pressure-sensitive adhesive compositions used in optical films are generally required to be capable of forming pressure-sensitive adhesive layers with excellent transparency.

[0009] The present disclosure has been made in light of the above-mentioned circumstances. An object of one embodiment of the present disclosure is to provide a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer that is excellent in reworkability, transparency, and impact resistance. Another problem to be solved by another embodiment of the present disclosure is to provide a pressure-sensitive adhesive sheet, an optical member, and a display device that include a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition. [Means for solving the problem]

[0010] Specific means for solving the problems include the following aspects. <1> a (meth)acrylic polymer (A) having a reactive functional group; a (meth)acrylic polymer (B) having a glass transition temperature higher by 85° C. or more than the glass transition temperature of the (meth)acrylic polymer (A); a cross-linking agent; Including, When a pressure-sensitive adhesive layer is formed, the half width H°C of the loss tangent peak of the pressure-sensitive adhesive layer, the content C of the (meth)acrylic polymer (A), A parts by mass, and the content C of the (meth)acrylic polymer (B) B A pressure-sensitive adhesive composition in which the parts by mass satisfy the relationship of the following formula (X): 14.8≦|H×C A / (C A +C B )|<21.0 (X) <2> The reactive functional group contains at least one of a carboxy group and a hydroxyl group. <1> The pressure-sensitive adhesive composition according to claim 1. <3> The content of the (meth)acrylic polymer (B) is 1 part by mass or more and 40 parts by mass or less per 100 parts by mass of the (meth)acrylic polymer (A). <1> or <2> The pressure-sensitive adhesive composition according to claim 1. <4> The (meth)acrylic polymer (B) contains at least one of a structural unit derived from t-butyl methacrylate and a structural unit derived from methyl methacrylate. <1> ~ <3> The pressure-sensitive adhesive composition according to any one of the above. <5> The (meth)acrylic polymer (B) has a glass transition temperature of 40°C or higher and 150°C or lower. <1> ~ <4> The pressure-sensitive adhesive composition according to any one of the above. <6> <1> ~ <5> 1. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of the above items. <7> An optical film; provided on at least one surface of the optical film, and <1> ~ <5> a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of the above items; An adhesive sheet comprising: <8> The optical film is a polarizing plate. <7> The adhesive sheet according to claim 1. <9> A glass substrate; <1> ~ <5> a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of the above items; An optical film; An optical element comprising the above in this order. <10> <9> A display device comprising the optical member according to claim 1. [Effects of the Invention]

[0011] According to one embodiment of the present disclosure, there is provided a pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive layer that is excellent in reworkability, transparency, and impact resistance. According to another embodiment of the present disclosure, there are provided a pressure-sensitive adhesive sheet, an optical member, and a display device, each comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition. DETAILED DESCRIPTION OF THE INVENTION

[0012] The pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet, optical member, and display device of the present disclosure are described in detail below. The following description of the requirements may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments and can be implemented with appropriate modifications within the scope of the object of the present disclosure.

[0013] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits, respectively. In the numerical ranges described in stages in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.

[0014] In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0015] In the present disclosure, when the PSA composition contains a plurality of substances corresponding to each component, the amount of each component in the PSA composition means the total amount of the plurality of substances present in the PSA composition, unless otherwise specified.

[0016] In the present disclosure, unless otherwise specified, "solid content" means components other than the solvent contained in the composition, and "solvent" means water and organic solvents. For example, when the only solvent contained in the composition is water, the solid content refers to the components other than water contained in the composition; when the only solvent contained in the composition is an organic solvent, the solid content refers to the components other than the organic solvent contained in the composition; and when the solvents contained in the composition are water and an organic solvent, the solid content refers to the components other than water and the organic solvent contained in the composition.

[0017] In the present disclosure, "(meth)acrylic polymer" means a polymer that contains structural units derived from (meth)acrylic monomers and in which the proportion of structural units derived from (meth)acrylic monomers is 50 mass % or more. In the present disclosure, the term "(meth)acrylic monomer" means a monomer having a (meth)acryloyl group.

[0018] In the present disclosure, "(meth)acrylic" is a term that encompasses both "acrylic" and "methacrylic," "(meth)acrylate" is a term that encompasses both "acrylate" and "methacrylate," and "(meth)acryloyl" is a term that encompasses both "acryloyl" and "methacryloyl."

[0019] In this disclosure, "n-" means normal, "i-" means iso, "s-" means secondary, and "t-" means tertiary.

[0020] In the present disclosure, the terms "monomer" and "monomer compound" are synonymous, and the terms "polymer" and "polymeric compound" are synonymous.

[0021] In the present disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous.

[0022] In the present disclosure, the term "structural unit derived from a monomer" refers to a structural unit formed by addition polymerization of a monomer.

[0023] In the present disclosure, the term "process" includes not only an independent process but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

[0024] [Adhesive composition] The pressure-sensitive adhesive composition of the present disclosure comprises a (meth)acrylic polymer (A) having a reactive functional group, a (meth)acrylic polymer (B) having a glass transition temperature 85°C or higher than the glass transition temperature of the (meth)acrylic polymer (A), and a crosslinking agent, and when a pressure-sensitive adhesive layer is formed, the pressure-sensitive adhesive layer has a half-width H°C of the loss tangent peak, a content C of the (meth)acrylic polymer (A), and a crosslinking agent. A parts by mass, and the content C of the (meth)acrylic polymer (B) B The parts by mass satisfy the relationship of the following formula (X). 14.8≦|H×C A / (C A +C B )|<21.0 (X)

[0025] According to the pressure-sensitive adhesive composition of the present disclosure, a pressure-sensitive adhesive layer having excellent reworkability, transparency, and impact resistance can be formed. The reason why the PSA composition of the present disclosure can exhibit such effects is unclear, but the present inventors speculate as follows: However, the following speculation is not intended to limit the PSA composition of the present disclosure, but is provided as an example.

[0026] The (meth)acrylic polymer (A) contained in the pressure-sensitive adhesive composition of the present disclosure has reactive functional groups, and thus forms a crosslinked structure by reaction of the reactive functional groups with a crosslinking agent. The formation of the crosslinked structure imparts cohesive strength to the pressure-sensitive adhesive layer, which tends to improve the impact resistance of the pressure-sensitive adhesive layer. Furthermore, it is presumed that the moderate increase in cohesive strength of the pressure-sensitive adhesive layer makes the pressure-sensitive adhesive layer less susceptible to cohesive failure, thereby improving the reworkability of the pressure-sensitive adhesive layer. The pressure-sensitive adhesive composition of the present disclosure contains, in addition to a (meth)acrylic polymer (A), a (meth)acrylic polymer (B) having a glass transition temperature that is at least 85°C higher than the glass transition temperature of the (meth)acrylic polymer (A). In general, a pressure-sensitive adhesive layer formed using a pressure-sensitive adhesive composition containing two polymers with significantly different glass transition temperatures tends to have increased cohesive strength throughout the pressure-sensitive adhesive layer. It is presumed that increased overall cohesive strength improves the pressure-sensitive adhesive layer's adhesion to the adherend, thereby improving impact resistance.

[0027] In a pressure-sensitive adhesive layer formed using a pressure-sensitive adhesive composition containing two polymers with significantly different glass transition temperatures, the polymers may not be compatible with each other, forming a phase-separated structure. The present inventors focused on controlling the compatibility of the two polymers contained in the pressure-sensitive adhesive composition as a means for realizing the formation of a pressure-sensitive adhesive layer excellent in reworkability, transparency, and impact resistance. The degree of compatibility of the two polymers contained in the pressure-sensitive adhesive composition can be determined by defining the half-width of the peak of the loss tangent (tanδ) of the pressure-sensitive adhesive layer as H°C and the content of the (meth)acrylic polymer (A) as C°. A The content of the (meth)acrylic polymer (B) is expressed as C parts by mass. B When expressed as parts by mass, H × C A / (C A +C B ) can be expressed as the absolute value of

[0028] It is known that the loss tangent of a pressure-sensitive adhesive layer is maximized near the glass transition temperature of the polymer contained in the pressure-sensitive adhesive layer. When a pressure-sensitive adhesive composition contains one type of polymer, the peak of the viscoelastic spectrum of the pressure-sensitive adhesive layer is sharp and the half-width is small. On the other hand, when a pressure-sensitive adhesive composition contains two types of polymers with significantly different glass transition temperatures, the interaction between the two polymers is strong. Therefore, the better the compatibility of the two polymers, the broader the peak shape of the viscoelastic spectrum of the pressure-sensitive adhesive layer and the larger the half-width. On the other hand, the worse the compatibility of the two polymers, the sharper the peak shape of the viscoelastic spectrum of the pressure-sensitive adhesive layer and the smaller the half-width. Furthermore, when the content ratio of one of the two types with significantly different glass transition temperatures is high, the peak shape of the viscoelastic spectrum of the pressure-sensitive adhesive layer tends to be broader and the half-width to be large due to the influence of the polymer contained in the higher proportion. As described above, the degree of compatibility between two polymers contained in a pressure-sensitive adhesive composition is affected by the strength of the interaction between the two polymers and the content ratio of the two polymers, and therefore it is thought that it can be expressed as the absolute value of the product of the half-width, which indicates the degree of interaction between the two polymers, and the coefficient, which indicates the content ratio of the two polymers.

[0029] The pressure-sensitive adhesive composition of the present disclosure has a viscosity of 14.8≦|H×C when a pressure-sensitive adhesive layer is formed. A / (C A +C B )| relationship is satisfied. 14.8≦|H×C A / (C A +C B In a pressure-sensitive adhesive layer that satisfies the relationship of ||, the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) are in a state of suitably high compatibility, which is presumably why the pressure-sensitive adhesive layer has excellent transparency. Furthermore, the pressure-sensitive adhesive composition of the present disclosure, when a pressure-sensitive adhesive layer is formed, exhibits a viscosity of |H×C A / (C A +C B )|<21.0. |H×C A / (C A +C B In a pressure-sensitive adhesive layer that satisfies the relationship )|<21.0, the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) are said to be in a moderately immiscible state. Therefore, it is thought that a phase-separated structure is formed in the pressure-sensitive adhesive layer, in which the (meth)acrylic polymer (B) is locally present in the (meth)acrylic polymer (A). When such a phase-separated structure is formed, the stress generated when peeling from the adherend is moderately alleviated, and it is presumed that the reworkability of the pressure-sensitive adhesive layer is improved.

[0030] From the above, it is presumed that the pressure-sensitive adhesive composition of the present disclosure can realize the formation of a pressure-sensitive adhesive layer that is excellent in reworkability, transparency, and impact resistance.

[0031] In the present disclosure, the "(meth)acrylic polymer (A) having a reactive functional group" is also referred to as the "specific (meth)acrylic polymer (A)." In addition, in the present disclosure, the "(meth)acrylic polymer (B) having a glass transition temperature higher than the glass transition temperature of the specific (meth)acrylic polymer (A) by 85° C. or more" is also referred to as the "specific (meth)acrylic polymer (B)." In the present disclosure, the "specific (meth)acrylic polymer (A) and the specific (meth)acrylic polymer (B)" may be collectively referred to as the "specific (meth)acrylic polymer."

[0032] [Formula (X)] The pressure-sensitive adhesive composition of the present disclosure, when forming a pressure-sensitive adhesive layer, has a half-width H°C of the loss tangent peak of the pressure-sensitive adhesive layer, a content C of the (meth)acrylic polymer (A) of the (meth)acrylic polymer (A), and a A Parts by mass, and the content C of the (meth)acrylic polymer (B) B The parts by mass satisfy the relationship of the following formula (X). 14.8≦|H×C A / (C A +C B )|<21.0 (X)

[0033] In formula (X), H represents the half-width (unit: °C) of the peak of the loss tangent of the pressure-sensitive adhesive layer. The "half-width H" is the peak height ("h") of the value corresponding to half the peak top value of the loss tangent (tan δ) of the pressure-sensitive adhesive layer. 1 / 2 ").

[0034] In this disclosure, |H×C A / (C A +C B )| is an index showing the degree of compatibility between the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B). A / (C A +C B The larger the value of |H×C|, the higher the compatibility between the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B), and A / (C A +C B )| value is smaller, the compatibility between the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) is lower.

[0035] 14.8≦|H×C A / (C A +C B In a pressure-sensitive adhesive layer that satisfies the relationship of ||, the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) are in a state of suitably high compatibility, and therefore the pressure-sensitive adhesive layer tends to have excellent transparency. |H×C A / (C A +C BIn a pressure-sensitive adhesive layer that satisfies the relationship of ||<21.0, the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) are in a moderately immiscible state. Therefore, it is believed that a phase-separated structure is formed in the pressure-sensitive adhesive layer, in which the (meth)acrylic polymer (B) is locally present in the (meth)acrylic polymer (A). When such a phase-separated structure is formed, the stress generated when the pressure-sensitive adhesive layer is peeled from the adherend is moderately alleviated, and the pressure-sensitive adhesive layer tends to have excellent reworkability. The pressure-sensitive adhesive composition of the present disclosure, when forming a pressure-sensitive adhesive layer, has a half-width H°C of the loss tangent peak of the pressure-sensitive adhesive layer, a content C of the (meth)acrylic polymer (A) of the (meth)acrylic polymer (A), and a A Parts by mass, and the content C of the (meth)acrylic polymer (B) B The parts by mass preferably satisfy the relationship of the following formula (X-1), more preferably the relationship of the following formula (X-2), and even more preferably the relationship of the following formula (X-3). 14.8≦|H×C A / (C A +C B )|≦20.6 (X-1) 15.1≦|H×C A / (C A +C B )|≦20.6 (X-2) 15.1≦|H×C A / (C A +C B )|≦16.8 (X-3)

[0036] The half width H can be controlled by the structures, weight average molecular weights, etc. of the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B). The half width H can be increased, for example, by decreasing the weight average molecular weight of the (meth)acrylic polymer (B), thereby increasing the difference in weight average molecular weight between the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B), or by making the structures of the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) have affinity for each other; and the half width H can be decreased by increasing the weight average molecular weight of the (meth)acrylic polymer (B), thereby decreasing the difference in weight average molecular weight between the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B), or by making the structures of the (meth)acrylic polymer (A) and the (meth)acrylic polymer (B) have no affinity for each other.

[0037] In the present disclosure, the half-value width H is determined by the following method. A pressure-sensitive adhesive composition is applied to the easy-release treated surface of a release film to form a coating film. The formed coating film is then dried to form a 25 μm thick adhesive film on the release film. Next, the exposed surface of the adhesive film formed on the release film is laminated to the easy-release treated surface of a separately prepared release film, and the adhesive film is then cured. In this manner, a substrate-free type adhesive sheet (composition: release film / adhesive layer / release film) is produced. Next, the release film of the substrate-free type adhesive sheet is peeled off, and the resulting adhesive layers are laminated together to obtain a 400 μm thick adhesive layer. Next, the viscoelasticity spectrum of the resulting adhesive layer is measured using a dynamic viscoelasticity measuring device according to JIS K 7244-1:1998 [temperature range: -60°C to 60°C, heating rate: 8.6°C / min, frequency: 1 Hz, jig used: parallel plate 8 mmφ (PB-08)]. From the obtained viscoelasticity spectrum, the half-width H (unit: °C) of the peak of the loss tangent [loss modulus (G'') / storage modulus (G')] in the measurement range of -50°C to 20°C is determined. In the obtained viscoelasticity spectrum, the vertical axis represents the loss tangent and the horizontal axis represents the temperature. The half-width H is the value of the peak h of the loss tangent. 1 / 2The temperature is determined by drawing a line parallel to the temperature axis at the position and measuring the temperature width between the intersections of this line with the left and right peaks. As the dynamic viscoelasticity measuring device, for example, a dynamic viscoelasticity measuring device manufactured by Anton Paar (trade name: Physica MCR301) can be suitably used, but the dynamic viscoelasticity measuring device is not limited to this.

[0038] [Specific (meth)acrylic polymer (A)] The pressure-sensitive adhesive composition of the present disclosure contains a (meth)acrylic polymer (A) having a reactive functional group (ie, a specific (meth)acrylic polymer (A)). The pressure-sensitive adhesive composition of the present disclosure may contain one type of specific (meth)acrylic polymer (A) alone, or may contain two or more types.

[0039] The specific (meth)acrylic polymer (A) may be a homopolymer or a copolymer. The specific (meth)acrylic polymer (A) may be, for example, a homopolymer or copolymer of a (meth)acrylic monomer having no reactive functional group into which a reactive functional group has been introduced by substitution, or a copolymer of a (meth)acrylic monomer having no reactive functional group and a monomer having no reactive functional group but other than the (meth)acrylic monomer, into which a reactive functional group has been introduced by substitution. The specific (meth)acrylic polymer (A) may be, for example, a copolymer of a (meth)acrylic monomer having a reactive functional group and a (meth)acrylic monomer not having a reactive functional group, a copolymer of a (meth)acrylic monomer having a reactive functional group and a monomer not having a reactive functional group but a monomer other than the (meth)acrylic monomer, or a copolymer of a (meth)acrylic monomer not having a reactive functional group and a monomer having a reactive functional group but a monomer other than the (meth)acrylic monomer.

[0040] The specific (meth)acrylic polymer (A) has a reactive functional group. In the present disclosure, the term "reactive functional group" refers to a functional group that can react with a crosslinking agent to form a crosslinked structure. The specific (meth)acrylic polymer (A) has reactive functional groups, and thus forms a crosslinked structure by reaction of the reactive functional groups with a crosslinking agent described below. The formation of the crosslinked structure imparts cohesive strength to the pressure-sensitive adhesive layer, improving the impact resistance of the pressure-sensitive adhesive layer. Furthermore, when the cohesive strength of the pressure-sensitive adhesive layer is appropriately increased, the pressure-sensitive adhesive layer is less likely to undergo cohesive failure, and adhesive residue is less likely to be left on the adherend when the pressure-sensitive adhesive layer is peeled off, improving the reworkability of the pressure-sensitive adhesive layer. Specific examples of reactive functional groups include a hydroxyl group, a carboxyl group, and an amino group. In the present disclosure, the term "amino group" encompasses primary amino groups, secondary amino groups, and tertiary amino groups. The reactive functional group preferably contains at least one of a hydroxyl group and a carboxyl group, and more preferably contains both a hydroxyl group and a carboxyl group.

[0041] A preferred embodiment of the specific (meth)acrylic polymer (A) is an embodiment in which the specific (meth)acrylic polymer (A) has a reactive functional group by containing a structural unit derived from a monomer having a reactive functional group, which will be described later.

[0042] <Structural Units Derived from Monomers Having Reactive Functional Groups> The type of the monomer having a reactive functional group is not particularly limited. Examples of the monomer having a reactive functional group include a monomer having at least one reactive functional group and an ethylenically unsaturated group in one molecule. Specific examples of the reactive functional group are as described above. Examples of the ethylenically unsaturated group include a vinyl group, an allyl group, a vinylphenyl group, and a (meth)acryloyl group.

[0043] Examples of the monomer having a reactive functional group include a monomer having a carboxy group, a monomer having a hydroxyl group, and a monomer having an amino group.

[0044] The type of the monomer having a carboxy group is not particularly limited. Specific examples of the monomer having a carboxy group include (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone mono(meth)acrylate [e.g., ω-carboxy-polycaprolactone (n≒2) monoacrylate], and succinic acid derivatives (e.g., 2-acryloyloxyethyl-succinic acid). The monomer having a carboxy group preferably includes acrylic acid, and more preferably is acrylic acid.

[0045] The type of the hydroxyl group-containing monomer is not particularly limited. Specific examples of monomers having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, 3-methyl-3-hydroxybutyl (meth)acrylate, 1,1-dimethyl-3-hydroxybutyl (meth)acrylate, 1,3-dimethyl-3-hydroxybutyl (meth)acrylate, 2,2,4-trimethyl-3-hydroxypentyl (meth)acrylate, 2-ethyl-3-hydroxyhexyl (meth)acrylate, glycerin mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, and poly(ethylene glycol-propylene glycol) mono(meth)acrylate. The monomer having a hydroxyl group preferably includes a hydroxyalkyl (meth)acrylate, more preferably includes 2-hydroxyethyl (meth)acrylate, even more preferably includes 2-hydroxyethyl acrylate, and particularly preferably includes 2-hydroxyethyl acrylate.

[0046] The type of the monomer having an amino group is not particularly limited. Specific examples of the monomer having an amino group include 2-dimethylaminoethyl (meth)acrylate, 2-diethylaminoethyl (meth)acrylate, 2-diisopropylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylamide.

[0047] The monomer having a reactive functional group preferably includes at least one of a monomer having a carboxy group and a monomer having a hydroxyl group, and more preferably includes a monomer having a carboxy group.

[0048] When the specific (meth)acrylic polymer (A) contains a structural unit derived from a monomer having a reactive functional group, it may contain one type of structural unit derived from a monomer having a reactive functional group alone, or may contain two or more types of structural units derived from a monomer having a reactive functional group.

[0049] When the specific (meth)acrylic polymer (A) contains a structural unit derived from a monomer having a reactive functional group, the content of the structural unit derived from the monomer having a reactive functional group in the specific (meth)acrylic polymer (A) is not particularly limited, but, for example, from the viewpoint of further improving the reworkability and impact resistance of the pressure-sensitive adhesive layer, it is preferably from 0.5% by mass to 9% by mass, more preferably from 1% by mass to 7% by mass, and even more preferably from 2% by mass to 7% by mass, relative to all structural units of the specific (meth)acrylic polymer (A).

[0050] <Structural Units Derived from (Meth)acrylic Acid Alkyl Ester Monomers> The specific (meth)acrylic polymer (A) preferably contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer. The type of (meth)acrylic acid alkyl ester monomer is not particularly limited. The (meth)acrylic acid alkyl ester monomer may be an acrylic acid alkyl ester monomer or a methacrylic acid alkyl ester monomer. The alkyl group contained in the (meth)acrylic acid alkyl ester monomer may be unsubstituted or may have a substituent (excluding reactive functional groups), but is preferably unsubstituted. The alkyl group contained in the (meth)acrylic acid alkyl ester monomer may be linear, branched, or cyclic. The alkyl moiety of the (meth)acrylic acid alkyl ester monomer preferably has 1 to 18 carbon atoms, more preferably 1 to 12 carbon atoms, further preferably 1 to 8 carbon atoms, and particularly preferably 1 to 4 carbon atoms.

[0051] Specific examples of the (meth)acrylic acid alkyl ester monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl (meth)acrylate. The (meth)acrylic acid alkyl ester monomer preferably contains at least one of n-butyl acrylate and methyl methacrylate, more preferably contains n-butyl acrylate, and further preferably is n-butyl acrylate.

[0052] When the specific (meth)acrylic polymer (A) contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer, it may contain one type of structural unit derived from a (meth)acrylic acid alkyl ester monomer alone, or may contain two or more types of structural units derived from a (meth)acrylic acid alkyl ester monomer.

[0053] When the specific (meth)acrylic polymer (A) contains structural units derived from a (meth)acrylic acid alkyl ester monomer, the content of the structural units derived from a (meth)acrylic acid alkyl ester monomer in the specific (meth)acrylic polymer (A) is not particularly limited, but, for example, is preferably 50 mass% or more, more preferably 50 mass% or more and 99.5 mass% or less, even more preferably 60 mass% or more and 99.0 mass% or less, and particularly preferably 70 mass% or more and 98.0 mass% or less, relative to all structural units of the specific (meth)acrylic polymer (A). The content of structural units derived from (meth)acrylic acid alkyl ester monomers in the specific (meth)acrylic polymer (A) being 50 mass% or more relative to all structural units of the specific (meth)acrylic polymer (A) means that structural units derived from (meth)acrylic acid alkyl ester monomers are contained as a main component of the structural units of the specific (meth)acrylic polymer (A).

[0054] <Constituent units derived from other monomers> The specific (meth)acrylic polymer (A) may contain a structural unit derived from a monomer (so-called other monomer) that does not fall into either the category of a monomer having a reactive functional group or a (meth)acrylic acid alkyl ester monomer.

[0055] Examples of structural units derived from other monomers include structural units derived from (meth)acrylates having an aromatic ring, such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; structural units derived from alkoxyalkyl (meth)acrylates, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; structural units derived from aromatic monovinyls, such as styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; structural units derived from vinyl cyanides, such as acrylonitrile and methacrylonitrile; and structural units derived from vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate.

[0056] From the viewpoint of suppressing white spots, the specific (meth)acrylic polymer (A) preferably contains, as a constituent unit derived from another monomer, a constituent unit derived from a (meth)acrylate having an aromatic ring, more preferably at least one selected from the group consisting of benzyl (meth)acrylate and phenoxyethyl (meth)acrylate, even more preferably a constituent unit derived from phenoxyethyl (meth)acrylate, and particularly preferably a constituent unit derived from phenoxyethyl acrylate. Here, "white spots" refers to, for example, a phenomenon in which light leakage occurs in a liquid crystal display device, resulting in a white appearance.

[0057] When the specific (meth)acrylic polymer (A) contains a structural unit derived from another monomer, it may contain one type of structural unit derived from the other monomer alone, or may contain two or more types of structural units derived from the other monomer.

[0058] When the specific (meth)acrylic polymer (A) contains a structural unit derived from another monomer, the content of the structural unit derived from the other monomer in the specific (meth)acrylic polymer (A) can be appropriately set within a range that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0059] <<Glass transition temperature of specific (meth)acrylic polymer (A)>> The glass transition temperature (also referred to as "Tg") of the specific (meth)acrylic polymer (A) is not particularly limited as long as it is at least 85°C lower than the glass transition temperature of the specific (meth)acrylic polymer (B). The glass transition temperature of the specific (meth)acrylic polymer (A) is, for example, preferably −60° C. or higher and −30° C. or lower, more preferably −55° C. or higher and −35° C. or lower, and even more preferably −50° C. or higher and −40° C. or lower, from the viewpoint of further improving the reworkability and transparency of the pressure-sensitive adhesive layer.

[0060] The glass transition temperature of the specific (meth)acrylic polymer (A) is a value obtained by converting the absolute temperature (unit: K) calculated from the following formula 1 into Celsius temperature (unit: ° C.). 1 / Tg=m1 / Tg1+m2 / Tg2+ +m(k-1) / Tg(k-1)+mk / Tgk (Formula 1)

[0061] In formula 1, Tg1, Tg2, . . . , Tg(k-1), and Tgk respectively represent the glass transition temperatures expressed as absolute temperatures when each monomer constituting the specific (meth)acrylic polymer (A) is made into a homopolymer. m1, m2, . . . , m(k-1), and mk respectively represent the molar fractions of each monomer constituting the specific (meth)acrylic polymer (A), and the equation is m1 + m2 + . . . + m(k-1) + mk = 1. Note that absolute temperatures can be converted to Celsius degrees by subtracting 273 from the absolute temperature, and Celsius degrees can be converted to absolute temperatures by adding 273 to the Celsius degrees.

[0062] In the present disclosure, the "glass transition temperature when converted into a homopolymer" refers to a value described in a publicly known document or a value measured using a differential scanning calorimeter (DSC). The specific value to be used is as follows:

[0063] For the "glass transition temperature when made into a homopolymer" of the monomers shown below, the value in parentheses is used. Methyl acrylate (10°C), methyl methacrylate (105°C), ethyl acrylate (-22°C), ethyl methacrylate (65°C), n-butyl acrylate (-54°C), n-butyl methacrylate (20°C), i-butyl methacrylate (53°C), t-butyl acrylate (43°C), t-butyl methacrylate (118°C), 2-ethylhexyl acrylate (-70°C), 2-ethylhexyl methacrylate (-10°C), n-octyl acrylate (-65°C), stearyl acrylate (30°C), stearyl methacrylate (38°C), lauryl acrylate (-3°C), lauryl methacrylate (-65°C), Cyclohexyl methacrylate (104°C), isobornyl acrylate (94°C), isobornyl methacrylate (180°C), benzyl acrylate (6°C), phenoxyethyl acrylate (-22°C), 2-methoxyethyl acrylate (-50°C), glycidyl methacrylate (74°C), 2-hydroxyethyl acrylate (-15°C), 2-hydroxyethyl methacrylate (85°C), 4-hydroxybutyl acrylate (-80°C), acrylic acid (106°C), methacrylic acid (228°C), dimethylaminoethyl methacrylate (18°C), ω-carboxy-polycaprolactone (n≒2) monoacrylate (-30°C).

[0064] Regarding the "glass transition temperature when made into a homopolymer" of a monomer other than the above-mentioned monomers, the value described in the Polymer Handbook (4th edition, Wiley-Interscience; the same applies hereinafter) is adopted. If there is no description in the Polymer Handbook, the value of the glass transition temperature of the homopolymer obtained by the following measurement method is adopted.

[0065] Specifically, a differential scanning calorimeter (DSC) is used to measure 10 mg of a measurement sample (i.e., homopolymer) in a nitrogen gas flow at a temperature increase rate of 10°C / min, and the inflection point of the obtained DSC curve is taken as the glass transition temperature of the homopolymer. As a differential scanning calorimeter, for example, a differential scanning calorimeter (trade name: Discovery DSC 2500) manufactured by TA Instruments Japan Co., Ltd. can be suitably used. However, the differential scanning calorimeter is not limited to this.

[0066] The glass transition temperature of the specific (meth)acrylic polymer (A) can be adjusted to a desired value, for example, by appropriately selecting the types and ratios of the monomers that are polymerization components of the specific (meth)acrylic polymer (A).

[0067] <<Weight-average molecular weight of specific (meth)acrylic polymer (A)>> The weight average molecular weight (also referred to as "Mw") of the specific (meth)acrylic polymer (A) is not particularly limited, but is preferably, for example, 600,000 or more and 2,000,000 or less, more preferably 750,000 or more and 1,900,000 or less, and even more preferably 800,000 or more and 1,500,000 or less. When the weight-average molecular weight of the specific (meth)acrylic polymer (A) is 600,000 or more, when a pressure-sensitive adhesive layer is formed, the specific (meth)acrylic polymer (B) is less likely to segregate at the interface of the pressure-sensitive adhesive layer, and therefore the transparency of the pressure-sensitive adhesive layer tends not to be impaired. When the weight average molecular weight of the specific (meth)acrylic polymer (A) is 2,000,000 or less, the viscosity of the pressure-sensitive adhesive composition does not increase excessively, and therefore the coatability of the pressure-sensitive adhesive composition tends not to be impaired.

[0068] The weight average molecular weight of the specific (meth)acrylic polymer (A) is a value measured by the following method, specifically, according to the following (1) to (3). (1) A solution of the specific (meth)acrylic polymer (A) is applied to a release paper and then dried at 100° C. for 1 minute to obtain a film of the specific (meth)acrylic polymer (A). (2) Using the film-like specific (meth)acrylic polymer (A) obtained in (1) above and tetrahydrofuran, a sample solution having a solids concentration of 0.2% by mass is obtained. Here, the "solids concentration" refers to the mass proportion of the specific (meth)acrylic polymer (A) in the sample solution. (3) The weight average molecular weight of the specific (meth)acrylic polymer (A) is determined as a standard polystyrene equivalent value by gel permeation chromatography (GPC) under the following conditions.

[0069] ~Conditions~ Measurement equipment: High-speed GPC [Model: HLC-8420 GPC, manufactured by Tosoh Corporation] Detector: Differential refractometer (RI) [built into HLC-8420, manufactured by Tosoh Corporation] Column: TSKgel GMH XL Two Tosoh products are used. Column temperature: 40℃ Eluent: tetrahydrofuran Sample solution injection volume: 100 μL Flow rate: 0.8mL / min

[0070] The weight average molecular weight of the specific (meth)acrylic polymer (A) can be adjusted to a desired value by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, etc. when polymerizing the monomers.

[0071] <<Content of specific (meth)acrylic polymer (A)>> The content of the specific (meth)acrylic polymer (A) in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, as long as formula (X) is satisfied. The content of the specific (meth)acrylic polymer (A) in the pressure-sensitive adhesive composition of the present disclosure is, for example, preferably 73.5% by mass to 99.0% by mass, more preferably 75.5% by mass to 98.0% by mass, and even more preferably 76.0% by mass to 97.0% by mass, relative to the total solid content in the pressure-sensitive adhesive composition.

[0072] [Specific (meth)acrylic polymer (B)] The pressure-sensitive adhesive composition of the present disclosure contains a (meth)acrylic polymer (B) [i.e., specific (meth)acrylic polymer (B)] having a glass transition temperature that is 85°C or more higher than the glass transition temperature of the specific (meth)acrylic polymer (A). The pressure-sensitive adhesive composition of the present disclosure may contain one type of specific (meth)acrylic polymer (B) alone, or may contain two or more types.

[0073] The specific (meth)acrylic polymer (B) may be a homopolymer or a copolymer, but is preferably a copolymer from the viewpoint of, for example, facilitating control of the glass transition temperature.

[0074] <Structural Units Derived from (Meth)acrylic Acid Alkyl Ester Monomers> The specific (meth)acrylic polymer (B) preferably contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer. The type of (meth)acrylic acid alkyl ester monomer is not particularly limited. The (meth)acrylic acid alkyl ester monomer may be an acrylic acid alkyl ester monomer or a methacrylic acid alkyl ester monomer, but is preferably a methacrylic acid alkyl ester monomer. The alkyl group contained in the (meth)acrylic acid alkyl ester monomer may be unsubstituted or may have a substituent, but is preferably unsubstituted. The alkyl group contained in the (meth)acrylic acid alkyl ester monomer may be linear, branched, or cyclic. The alkyl moiety of the (meth)acrylic acid alkyl ester monomer preferably has 1 to 18 carbon atoms, more preferably 1 to 12 carbon atoms, further preferably 1 to 8 carbon atoms, and particularly preferably 1 to 4 carbon atoms.

[0075] Specific examples of the (meth)acrylic acid alkyl ester monomer are the same as those explained in the specific (meth)acrylic polymer (A). The (meth)acrylic acid alkyl ester monomer preferably contains at least one of methyl methacrylate and t-butyl methacrylate, and more preferably at least one of methyl methacrylate and t-butyl methacrylate.

[0076] When the specific (meth)acrylic polymer (B) contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer, it may contain one type of structural unit derived from a (meth)acrylic acid alkyl ester monomer alone, or may contain two or more types of structural units derived from a (meth)acrylic acid alkyl ester monomer.

[0077] When the specific (meth)acrylic polymer (B) contains a structural unit derived from a (meth)acrylic acid alkyl ester monomer, the content of the structural unit derived from a (meth)acrylic acid alkyl ester monomer in the specific (meth)acrylic polymer (B) is not particularly limited, but is, for example, preferably from 80% by mass to 100% by mass, more preferably from 90% by mass to 100% by mass, and even more preferably from 95% by mass to 100% by mass, relative to all structural units of the specific (meth)acrylic polymer (B).

[0078] <Constituent units derived from other monomers> The specific (meth)acrylic polymer (B) may contain a structural unit derived from a monomer that does not fall under the category of a (meth)acrylic acid alkyl ester monomer (so-called other monomer).

[0079] Examples of structural units derived from other monomers include structural units derived from monomers having a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; structural units derived from monomers having a carboxy group, such as (meth)acrylic acid; structural units derived from (meth)acrylates having an aromatic ring, such as benzyl (meth)acrylate and phenoxyethyl (meth)acrylate; structural units derived from alkoxyalkyl (meth)acrylates, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; structural units derived from aromatic monovinyls, such as styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; structural units derived from vinyl cyanide, such as acrylonitrile and methacrylonitrile; and structural units derived from vinyl esters, such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl versatate.

[0080] When the specific (meth)acrylic polymer (B) contains a structural unit derived from another monomer, it may contain one type of structural unit derived from the other monomer alone, or may contain two or more types of structural units derived from the other monomer.

[0081] When the specific (meth)acrylic polymer (B) contains a structural unit derived from another monomer, the content of the structural unit derived from another monomer in the specific (meth)acrylic polymer (B) can be appropriately set within a range that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0082] <<Glass transition temperature of specific (meth)acrylic polymer (B)>> The glass transition temperature (Tg) of the specific (meth)acrylic polymer (B) is not particularly limited as long as it is at least 85° C. higher than the glass transition temperature of the specific (meth)acrylic polymer (A). When the glass transition temperature of the specific (meth)acrylic polymer (B) is at least 85°C higher than the glass transition temperature of the specific (meth)acrylic polymer (A), the cohesive strength of the pressure-sensitive adhesive layer formed increases, and the adhesion between the pressure-sensitive adhesive layer and the adherend can be improved, which tends to result in excellent impact resistance of the pressure-sensitive adhesive layer.

[0083] The glass transition temperature of the specific (meth)acrylic polymer (B) is, for example, preferably 40°C or higher and 150°C or lower, more preferably 107°C or higher and 140°C or lower, and even more preferably 109°C or higher and 130°C or lower, from the viewpoint of further improving the impact resistance and transparency of the pressure-sensitive adhesive layer.

[0084] The glass transition temperature of the specific (meth)acrylic polymer (B) is determined by the same method as that for determining the glass transition temperature of the specific (meth)acrylic polymer (A) described above.

[0085] The glass transition temperature of the specific (meth)acrylic polymer (B) can be adjusted to a desired value, for example, by appropriately selecting the types and ratios of the monomers that are polymerization components of the specific (meth)acrylic polymer (B).

[0086] <<Weight-average molecular weight of specific (meth)acrylic polymer (B)>> The weight average molecular weight (Mw) of the specific (meth)acrylic polymer (B) is not particularly limited, but from the viewpoint of further improving the reworkability and impact resistance of the pressure-sensitive adhesive layer, it is preferably from 10,000 to 500,000, more preferably from 100,000 to 500,000, and even more preferably from 100,000 to 400,000.

[0087] The weight average molecular weight of the specific (meth)acrylic polymer (B) is measured by the same method as the method for measuring the weight average molecular weight of the specific (meth)acrylic polymer (A) described above.

[0088] The weight average molecular weight of the specific (meth)acrylic polymer (B) can be adjusted to a desired value by adjusting the polymerization temperature, polymerization time, amount of organic solvent used, type of polymerization initiator, amount of polymerization initiator used, etc. when polymerizing the monomers.

[0089] <<Content of specific (meth)acrylic polymer (B)>> The content of the specific (meth)acrylic polymer (B) in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, but is, for example, preferably 1 part by mass or more and 40 parts by mass or less, more preferably 3 parts by mass or more and 35 parts by mass or less, and even more preferably 3 parts by mass or more and 30 parts by mass or less, relative to 100 parts by mass of the specific (meth)acrylic polymer (A). When the content of the specific (meth)acrylic polymer (B) in the pressure-sensitive adhesive composition of the present disclosure is 1 part by mass or more per 100 parts by mass of the specific (meth)acrylic polymer (A), the impact resistance of the pressure-sensitive adhesive layer tends to be further improved. When the content of the specific (meth)acrylic polymer (B) in the pressure-sensitive adhesive composition of the present disclosure is 40 parts by mass or less per 100 parts by mass of the specific (meth)acrylic polymer (A), the reworkability of the pressure-sensitive adhesive layer tends to be further improved.

[0090] In the present disclosure, the "total solid content in the PSA composition" means the total mass of the PSA composition when the PSA composition does not contain a solvent, and means the mass of the residue remaining after removing the solvent from the PSA composition when the PSA composition contains a solvent.

[0091] [Method for producing specific (meth)acrylic polymer] The method for producing the specific (meth)acrylic polymer (A) and the specific (meth)acrylic polymer (B) (i.e., the specific (meth)acrylic polymer) is not particularly limited. The specific (meth)acrylic polymer can be produced by polymerizing the above-mentioned monomers by a known polymerization method, such as solution polymerization, emulsion polymerization, suspension polymerization, or bulk polymerization. As the polymerization method, solution polymerization is preferred because the processing steps are relatively simple and can be completed in a short time when preparing the pressure-sensitive adhesive composition of the present disclosure after production.

[0092] In the solution polymerization method, a predetermined organic solvent, a monomer, a polymerization initiator, and an optional chain transfer agent are generally charged into a polymerization vessel, and the mixture is heated and reacted for several hours with stirring, for example, at the reflux temperature of the organic solvent. In this case, at least a portion of the organic solvent, the monomer, the polymerization initiator, and the optional chain transfer agent may be added sequentially. Alternatively, the reaction may be carried out in a nitrogen gas stream.

[0093] Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds, aliphatic hydrocarbon compounds, alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, and alcohol compounds. More specifically, examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds such as benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha; aliphatic or alicyclic hydrocarbon compounds such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and turpentine; ester compounds such as methyl acetate, ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate; acetone; Examples of the alcohol compounds include ketone compounds typified by ethyl ketone, methyl-i-butyl ketone, isophorone, cyclohexanone, and methylcyclohexanone; glycol ether compounds typified by ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; and alcohol compounds typified by methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol.

[0094] In producing the specific (meth)acrylic polymer, it is preferable to use an organic solvent that is unlikely to cause chain transfer during the polymerization reaction, such as an aromatic hydrocarbon compound, an ester compound, or a ketone compound. In particular, it is preferable to use methyl acetate and ethyl acetate from the viewpoints of the solubility of the specific (meth)acrylic polymer, ease of the polymerization reaction, etc.

[0095] During the polymerization reaction, one type of organic solvent may be used alone, or two or more types may be used.

[0096] Examples of the polymerization initiator include organic peroxides and azo compounds that are used in ordinary solution polymerization methods. Specific examples of organic peroxides include t-butyl peroxy-2-ethylhexanoate, t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 2,2-bis(4,4-di-t-butylperoxysilane), peroxycyclohexyl)propane, 2,2-bis(4,4-di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane. Specific examples of azo compounds include 2,2'-azobisisobutyronitrile [AIBN], 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN], 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), and 2,2'-azobis(isobutyrate) dimethyl.

[0097] During the polymerization reaction, one type of polymerization initiator may be used alone, or two or more types may be used.

[0098] The amount of the polymerization initiator used is not particularly limited and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic polymer.

[0099] In producing the specific (meth)acrylic polymer, a chain transfer agent may be used as needed. Examples of the chain transfer agent include cyanoacetic acid, alkyl ester compounds of cyanoacetic acid having 1 to 8 carbon atoms, bromoacetic acid, alkyl ester compounds of bromoacetic acid having 1 to 8 carbon atoms, α-methylstyrene, aromatic compounds such as anthracene, phenanthrene, fluorene, and 9-phenylfluorene, p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, aromatic nitro compounds such as p-nitrophenol and p-nitrotoluene, benzoquinone derivatives such as benzoquinone and 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives such as tributylborane, carbon tetrabromide, ... Examples of suitable mercaptan compounds include halogenated hydrocarbon compounds such as carbon chloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene, aldehyde compounds such as chloral and furaldehyde, alkyl mercaptan compounds having 1 to 18 carbon atoms, aromatic mercaptan compounds such as thiophenol and toluene mercaptan, mercaptoacetic acid, alkyl ester compounds of mercaptoacetic acid having 1 to 10 carbon atoms, hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms, and terpene compounds such as pinene and terpinolene.

[0100] When a chain transfer agent is used in producing the specific (meth)acrylic polymer, the amount of the chain transfer agent used is not particularly limited and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic polymer.

[0101] The polymerization temperature is not particularly limited and can be appropriately set depending on, for example, the molecular weight of the target specific (meth)acrylic polymer.

[0102] [Crosslinking agent] The pressure-sensitive adhesive composition of the present disclosure contains a crosslinking agent. The type of crosslinking agent is not particularly limited. Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, a metal chelate-based crosslinking agent, and an aziridine-based crosslinking agent.

[0103] In this disclosure, "isocyanate-based crosslinking agent" refers to a compound having two or more isocyanate groups in one molecule (so-called polyisocyanate-based compound). Also, "epoxy-based crosslinking agent" refers to a compound having two or more epoxy groups in one molecule (so-called bifunctional or higher epoxy-based compound). Also, "metal chelate-based crosslinking agent" refers to a metal chelate-based compound that functions as a crosslinking agent. Also, "aziridine-based crosslinking agent" refers to a compound having two or more aziridine groups in one molecule (so-called polyaziridine-based compound).

[0104] The crosslinking agent preferably contains at least one selected from the group consisting of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent, more preferably contains an isocyanate-based crosslinking agent, and even more preferably is an isocyanate-based crosslinking agent.

[0105] Examples of the isocyanate crosslinking agent include aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, and aromatic polyisocyanate compounds. "Aliphatic polyisocyanate compounds" include, for example, aliphatic polyisocyanate compounds, polymers of aliphatic polyisocyanate compounds, adducts of aliphatic polyisocyanate compounds and polyol compounds (e.g., trimethylolpropane (TMP); the same applies hereinafter), and biuret compounds of aliphatic polyisocyanate compounds. Specific examples of aliphatic polyisocyanate compounds include hexamethylene diisocyanate (HDI), pentamethylene diisocyanate (PDI), tetramethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate. The "alicyclic polyisocyanate compound" includes, for example, an alicyclic polyisocyanate compound, a polymer of an alicyclic polyisocyanate compound, an adduct of an alicyclic polyisocyanate compound and a polyol compound, and a biuret of an alicyclic polyisocyanate compound. Specific examples of the alicyclic polyisocyanate compound include isophorone diisocyanate (IPDI), hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate. The "aromatic polyisocyanate compound" includes, for example, an aromatic polyisocyanate compound, a polymer of an aromatic polyisocyanate compound, an adduct of an aromatic polyisocyanate compound and a polyol compound, and a biuret of an aromatic polyisocyanate compound. Specific examples of the aromatic polyisocyanate compound include tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), and 4,4'-diphenylmethane diisocyanate.

[0106] The isocyanate-based crosslinking agent is preferably an aromatic polyisocyanate-based compound, more preferably at least one selected from the group consisting of tolylene diisocyanate-based compounds and xylylene diisocyanate-based compounds, and even more preferably a tolylene diisocyanate-based compound. The "tolylene diisocyanate compound" includes, for example, TDI, TDI polymers, adducts of TDI and polyol compounds, and biuret compounds of TDI. As the tolylene diisocyanate compound, an adduct of TDI and TMP is preferred. The "xylylene diisocyanate compound" includes, for example, XDI, XDI polymers, adducts of XDI and polyol compounds, and biuret compounds of XDI. The xylylene diisocyanate compound is preferably an adduct of XDI and TMP.

[0107] As the isocyanate-based crosslinking agent, commercially available products can be used. Examples of commercially available isocyanate crosslinking agents include "Coronate HX," "Coronate HK," "Coronate HL," "Coronate HL-S," "Coronate 2031," "Coronate 2037," "Coronate 2234," "Coronate 2770," "Coronate 2785," "Coronate 2793," "Aquanate 200," and "Aquanate 210" (all manufactured by Tosoh Corporation), "Sumidur N75," "Sumidur N3300," "Desmodur N75 MPA / X," "Desmodur N100," "Desmodur N3200," and "Desmodur N3400" (all manufactured by Sumika Covestro Urethane Co., Ltd.), "Duranate D201," "Duranate E405-70B," "Duranate E405-80T," "Duranate AE700-100," and "Duranate 24A-100," "Duranate TSE-100," and "Duranate TMA-100" (all manufactured by Asahi Kasei Corporation), as well as "Takenate D-101E," "Takenate D-110N," "Takenate D-120N," "Takenate D-140N," "Takenate D-160N," "Takenate D-172N," "Takenate M-631N," "MT-Olestar NP1200," and "Stabio XD-340N" (all manufactured by Mitsui Chemicals, Inc.). The above-mentioned "Coronate," "Aquanate," "Sumidur," "Desmodur," "Duranate," "Takenate," "Olestar," and "Stabio" are all registered trademarks.

[0108] Examples of bifunctional or higher functional epoxy compounds include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, and resol. Examples of suitable glycidyl ethers include lucine diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris(glycidyl)isocyanurate, tris(glycidoxyethyl)isocyanurate, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-1,3-benzenedi(methanamine), and 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate.

[0109] As the epoxy-based crosslinking agent, commercially available products can be used. Examples of commercially available epoxy crosslinking agents include "TETRAD-X" and "TETRAD-C" (both manufactured by Mitsubishi Gas Chemical Company, Inc.), "Denacol EX-201" and "Denacol EX-931" (both manufactured by Nagase ChemteX Corporation), and Celloxide 2021P (manufactured by Daicel Corporation). The above "TETRAD," "Denacol," and "Celloxide" are all registered trademarks.

[0110] The pressure-sensitive adhesive composition of the present disclosure may contain one type of crosslinking agent alone, or may contain two or more types of crosslinking agents.

[0111] The content of the crosslinking agent in the pressure-sensitive adhesive composition of the present disclosure is not particularly limited, but is, for example, preferably 0.05 to 15 parts by mass, more preferably 0.07 to 10 parts by mass, and even more preferably 0.1 to 8 parts by mass, relative to 100 parts by mass of the specific (meth)acrylic polymer (A). The content of the crosslinking agent in the pressure-sensitive adhesive composition of the present disclosure being 0.05 parts by mass or more relative to 100 parts by mass of the specific (meth)acrylic polymer (A) means that the pressure-sensitive adhesive composition of the present disclosure actively contains a crosslinking agent. When the pressure-sensitive adhesive composition of the present disclosure contains a crosslinking agent, a crosslinked structure is formed by reaction between the reactive functional groups of the specific (meth)acrylic polymer (A) and the crosslinking agent. The formation of the crosslinked structure imparts cohesive strength to the pressure-sensitive adhesive layer, which tends to improve the impact resistance of the pressure-sensitive adhesive layer. Furthermore, an appropriate increase in the cohesive strength of the pressure-sensitive adhesive layer makes the pressure-sensitive adhesive layer less susceptible to cohesive failure, which tends to improve the reworkability of the pressure-sensitive adhesive layer. When the content of the crosslinking agent in the pressure-sensitive adhesive composition of the present disclosure is 15 parts by mass or less per 100 parts by mass of the specific (meth)acrylic polymer (A), a decrease in transparency due to excess crosslinking agent tends to be less likely to occur.

[0112] [Organic solvent] The pressure-sensitive adhesive composition of the present disclosure may contain an organic solvent. When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, the coating properties can be improved. Examples of the organic solvent include the same organic solvents as those used in the polymerization reaction of the above-mentioned specific (meth)acrylic polymer.

[0113] When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, it may contain only one type of organic solvent, or may contain two or more types of organic solvents.

[0114] When the pressure-sensitive adhesive composition of the present disclosure contains an organic solvent, the content of the organic solvent is not particularly limited and can be set appropriately depending on the purpose.

[0115] [Other ingredients] The pressure-sensitive adhesive composition of the present disclosure may contain components other than the components described above (so-called other components) as needed, provided that the effects of the composition are not impaired. Examples of other components include various additives such as polymers other than the specific (meth)acrylic polymer, silane coupling agents, release adjusters (e.g., silicone oils), crosslinking catalysts, antioxidants, colorants (e.g., dyes and pigments), light stabilizers (e.g., ultraviolet absorbers), and antistatic agents.

[0116] When the pressure-sensitive adhesive composition of the present disclosure contains other components, the content of the other components can be set appropriately within a range that does not impair the effects of the pressure-sensitive adhesive composition of the present disclosure.

[0117] <<Applications of adhesive compositions>> The use of the pressure-sensitive adhesive composition of the present disclosure is not particularly limited. The pressure-sensitive adhesive composition of the present disclosure can form a pressure-sensitive adhesive layer that has excellent reworkability, transparency, and impact resistance, and is therefore suitable, for example, as a pressure-sensitive adhesive composition to be used in optical films (i.e., a pressure-sensitive adhesive composition for optical films), and is particularly suitable as a pressure-sensitive adhesive composition to be used in polarizing plates among optical films (i.e., a pressure-sensitive adhesive composition for polarizing plates). Specific applications of the pressure-sensitive adhesive composition of the present disclosure include applications for bonding a polarizing plate to a glass substrate (for example, a glass substrate of a liquid crystal cell) and applications for bonding optical films together.

[0118] [Adhesive sheet] The pressure-sensitive adhesive sheet of the present disclosure includes a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure. The pressure-sensitive adhesive sheet of the present disclosure also includes a sheet-like pressure-sensitive adhesive layer itself formed from the pressure-sensitive adhesive composition of the present disclosure. The pressure-sensitive adhesive layer provided in the pressure-sensitive adhesive sheet of the present disclosure contains a cured product of the pressure-sensitive adhesive composition of the present disclosure. The cured product includes, for example, a crosslinked product of the specific (meth)acrylic polymer (A) obtained by crosslinking and curing with a crosslinking agent. The pressure-sensitive adhesive sheet of the present disclosure includes a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure, and therefore tends to have excellent reworkability, transparency, and impact resistance.

[0119] The thickness of the pressure-sensitive adhesive layer provided in the pressure-sensitive adhesive sheet of the present disclosure is not particularly limited. The thickness of the pressure-sensitive adhesive layer is generally 1 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm.

[0120] In the present disclosure, the "thickness of the pressure-sensitive adhesive layer" refers to the average thickness of the pressure-sensitive adhesive layer. The average thickness of the pressure-sensitive adhesive layer is a value determined by the following method. The thickness of the adhesive layer is measured at 10 randomly selected locations in the thickness direction using a film thickness meter. The arithmetic mean of the measured values ​​is calculated and this value is taken as the average thickness of the adhesive layer.

[0121] The pressure-sensitive adhesive sheet of the present disclosure may be a substrate-free pressure-sensitive adhesive sheet that does not have a substrate, or may be a substrate-containing pressure-sensitive adhesive sheet that has a pressure-sensitive adhesive layer on one or both sides of a substrate. When the pressure-sensitive adhesive sheet of the present disclosure is a substrate-free type pressure-sensitive adhesive sheet that does not have a substrate, or when it is a substrate-containing type pressure-sensitive adhesive sheet that has a pressure-sensitive adhesive layer on one side of a substrate, the exposed surface of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of the present disclosure may be protected by a release sheet. Generally, the release sheet protects the surface of the pressure-sensitive adhesive layer until the pressure-sensitive adhesive sheet is put to practical use, and is peeled off at the time of use.

[0122] The release sheet is not particularly limited as long as it can be easily peeled off from the pressure-sensitive adhesive layer. Examples of release sheets include resin films, paper, synthetic paper, and composite sheets made by laminating two or more of these, each of which has been surface-treated with a release agent on one or both sides (so-called easy-release treatment). In the present disclosure, a release sheet in an embodiment in which one or both sides of a resin film have been surface-treated with a release treatment agent (so-called easy-release treatment) is also referred to as a "release film." Examples of release agents include silicone-based release agents (such as silicone), wax-based release agents (such as paraffin wax), and fluorine-based release agents (such as fluorine-based resins). Examples of resin films include polyester films such as polyethylene terephthalate (PET) films. Examples of paper include fine paper and coated paper. The thickness of the release sheet is not particularly limited, and is generally 20 μm to 180 μm.

[0123] When the pressure-sensitive adhesive sheet of the present disclosure includes a substrate, the substrate is not particularly limited as long as a pressure-sensitive adhesive layer can be formed thereon. Examples of the substrate include films containing resins such as polyolefin resins (e.g., polyethylene (PE) and polypropylene (PP)), polyester resins (e.g., polyethylene terephthalate (PET)), acetate resins (e.g., triacetyl cellulose), polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyurethane resins, (meth)acrylic resins, vinyl chloride resins, ABS (Acrylonitrile Butadiene Styrene) resins, and fluorine-based resins.

[0124] The surface of the substrate on which the adhesive layer is provided may be subjected to a surface treatment such as corona discharge treatment or plasma discharge treatment (so-called easy-adhesion treatment) in order to improve the adhesion between the substrate and the adhesive layer.

[0125] The substrate may contain various additives such as plasticizers, colorants (eg, dyes and pigments), heat stabilizers, light stabilizers, antistatic agents, flame retardants, antioxidants, fillers, and the like. The substrate may be partially or entirely patterned.

[0126] When the pressure-sensitive adhesive sheet of the present disclosure includes a substrate, the substrate is preferably an optical film. In this case, a preferred embodiment of the pressure-sensitive adhesive sheet of the present disclosure includes an optical film and a pressure-sensitive adhesive layer provided on at least one surface of the optical film and formed from the pressure-sensitive adhesive composition of the present disclosure.

[0127] The type of optical film is not particularly limited. Specific examples of optical films include polarizing plates, AG (Anti-Glare) polarizing plates, wave plates (e.g., half-wave plates and quarter-wave plates), retardation films including the wave plates, viewing angle compensation films, optical compensation films, brightness enhancement films, light guide plates, reflective films, anti-reflection films, prism sheets, lens sheets, diffusion plates, and transparent conductive films.

[0128] The optical film is preferably a polarizing plate (so-called polarizing film). The polarizing plate is configured to include at least a polarizer, and may be a polarizer alone or a laminate of a polarizer and a protective film. That is, the polarizing plate may have a single-layer structure with a polarizer alone, a two-layer structure with a protective film provided on one side of the polarizer, or a three-layer structure with protective films provided on both sides of the polarizer.

[0129] When the pressure-sensitive adhesive sheet of the present disclosure includes a substrate and the substrate is a polarizing plate, examples of the layer configuration include pressure-sensitive adhesive layer / polarizing plate [protective film / polarizer], pressure-sensitive adhesive layer / polarizing plate [protective film / polarizer / protective film], pressure-sensitive adhesive layer / polarizing plate [retardation film / polarizer], pressure-sensitive adhesive layer / polarizing plate [retardation film / polarizer / protective film], pressure-sensitive adhesive layer / polarizing plate [retardation film / protective film / polarizer / protective film], pressure-sensitive adhesive layer / polarizing plate [polarizer / brightness-enhancing film], pressure-sensitive adhesive layer / polarizing plate [protective film / polarizer / brightness-enhancing film], pressure-sensitive adhesive layer / polarizing plate [polarizer / protective film / brightness-enhancing film], and pressure-sensitive adhesive layer / polarizing plate [protective film / polarizer / protective film / brightness-enhancing film].

[0130] The protective film may be a film containing a resin such as triacetyl cellulose (TAC), polycycloolefin (COP), polyethylene terephthalate (PET), or polymethyl methacrylate (PMMA). The polarizer may be, for example, a stretched film of polyvinyl alcohol (PVA) impregnated with iodine. The retardation film may be a film containing a resin such as polycycloolefin (COP).

[0131] The thickness of the substrate (preferably, the optical film) is not particularly limited, but is, for example, preferably 10 μm to 300 μm, more preferably 10 μm to 200 μm, and even more preferably 10 μm to 100 μm.

[0132] In this disclosure, "thickness of the substrate" means the average thickness of the substrate. The average thickness of the substrate is a value determined by the following method. The thickness of the substrate is measured at 10 randomly selected locations in the thickness direction using a film thickness meter. The arithmetic mean of the measured values ​​is calculated and this value is taken as the average thickness of the substrate.

[0133] [How to make adhesive sheets] The method for producing the pressure-sensitive adhesive sheet of the present disclosure is not particularly limited. The pressure-sensitive adhesive sheet of the present disclosure can be produced by a known method. The pressure-sensitive adhesive sheet of the present disclosure can be produced, for example, by the following method.

[0134] When the pressure-sensitive adhesive sheet of the present disclosure is a substrate-free type pressure-sensitive adhesive sheet, first, the pressure-sensitive adhesive composition of the present disclosure is applied to the easily peelable surface of the release sheet to form a coating film on the release sheet. The formed coating film is then dried to form an adhesive film on the release sheet. Next, the exposed surface of the formed adhesive film is laminated onto the easily peelable surface of a separately prepared release sheet, and then cured as necessary, thereby producing a pressure-sensitive adhesive sheet of the present disclosure having a laminated structure of release sheet / pressure-sensitive adhesive layer / release sheet.

[0135] When the pressure-sensitive adhesive sheet of the present disclosure is a substrate-type pressure-sensitive adhesive sheet, first, the pressure-sensitive adhesive composition of the present disclosure is applied to one surface of the substrate (preferably the surface treated for easy adhesion) to form a coating film on the substrate. The formed coating film is then dried to form a pressure-sensitive adhesive film on the substrate. Next, the exposed surface of the formed pressure-sensitive adhesive film is laminated onto the surface of a release sheet treated for easy release, and then cured as necessary to produce a pressure-sensitive adhesive sheet of the present disclosure having a laminate structure of substrate / pressure-sensitive adhesive layer / release sheet.

[0136] When the pressure-sensitive adhesive sheet of the present disclosure is a substrate-containing pressure-sensitive adhesive sheet, another method may be mentioned, for example, as follows. The pressure-sensitive adhesive composition of the present disclosure is applied to the easy-release treated surface of a release sheet to form a coating film on the release sheet. The formed coating film is then dried to form a pressure-sensitive adhesive film on the release sheet. Next, the exposed surface of the formed pressure-sensitive adhesive film is laminated to one surface of the substrate (preferably the easy-adhesion treated surface), and then cured as necessary, thereby producing a pressure-sensitive adhesive sheet of the present disclosure having a laminated structure of substrate / pressure-sensitive adhesive layer / release sheet.

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

[0138] The method for drying the coating film is not particularly limited. Examples of methods for drying the coating film include natural drying, heat drying, hot air drying, and vacuum drying. The drying temperature and drying time of the coating film are not particularly limited, and are set appropriately depending on the thickness of the coating film, the amount of solvent contained in the coating film, and the like. Drying conditions include, for example, using a hot air circulation dryer to blow air at 60°C to 130°C at a speed of 3 m / sec to 5 m / sec for 30 seconds to 300 seconds.

[0139] The curing method may involve leaving the product to stand for 2 to 7 days in an environment with an ambient temperature of 20°C to 35°C and a relative humidity of 45% to 65%, for example.

[0140] [Optical components] The optical member of the present disclosure includes, in this order, a glass substrate, a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present disclosure, and an optical film. In the optical member of the present disclosure, the pressure-sensitive adhesive layer is less likely to cause a decrease in transparency. Furthermore, in the optical member of the present disclosure, the optical film can be easily peeled off from the glass substrate without leaving any adhesive residue. Furthermore, in the optical member of the present disclosure, air bubbles are less likely to be generated by external impact.

[0141] The thickness of the glass substrate is not particularly limited, but is generally 0.3 mm to 0.7 mm, and preferably 0.3 mm to 0.5 mm.

[0142] Examples of the glass substrate include a soda glass plate, an alkali-free glass plate, and an ITO (Indium Tin Oxide) film-coated glass plate.

[0143] The pressure-sensitive adhesive layer and optical film in the optical member of the present disclosure have the same meaning as the pressure-sensitive adhesive layer and optical film in the pressure-sensitive adhesive sheet of the present disclosure, and preferred embodiments are also the same, so description thereof will be omitted here.

[0144] The optical member of the present disclosure can be suitably used, for example, as a member of a display device. Examples of display devices include liquid crystal displays and organic EL (Electro-Luminescence) displays.

[0145] The method for producing the optical member of the present disclosure is not particularly limited. The optical member of the present disclosure can be produced, for example, by using an optical film as a substrate, preparing a pressure-sensitive adhesive sheet of the present disclosure by the method described above, and then bonding the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet to a glass substrate.

[0146] [Display device] The display device of the present disclosure includes the optical member of the present disclosure. In the display device of the present disclosure, the pressure-sensitive adhesive layer is less likely to cause a decrease in transparency, and air bubbles are less likely to be generated by external impact.

[0147] Specific examples of the display device are as described above. [Example]

[0148] The pressure-sensitive adhesive composition of the present disclosure will be described in more detail below with reference to examples. The present disclosure is not limited to the following examples as long as they do not depart from the gist of the disclosure.

[0149] [Production of (meth)acrylic polymer (A)] [Manufacturing example A-1] A reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser was charged with 77.7 parts by weight of n-butyl acrylate (n-BA), 18.0 parts by weight of phenoxyethyl acrylate (PHEA), 1.5 parts by weight of acrylic acid (AA), 2.8 parts by weight of 2-hydroxyethyl acrylate (2HEA), 110.0 parts by weight of ethyl acetate (organic solvent), and 20.0 parts by weight of methyl acetate (organic solvent). The mixture was then mixed and purged with nitrogen. The mixture in the reactor was then heated to 70°C while stirring. Next, 0.01 parts by weight of 2,2'-azobis(2,4-dimethylvaleronitrile) (ABVN; polymerization initiator) and 30.0 parts by weight of ethyl acetate were sequentially added to the mixture in the reactor, and the mixture was then maintained for 6 hours to complete the polymerization reaction. Next, the solution obtained upon completion of the polymerization reaction was diluted with ethyl acetate to a solid content concentration of 25.0% by mass, and then cooled to obtain a solution of (meth)acrylic polymer A-1.

[0150] The term "solid content concentration" used herein refers to the mass proportion of the (meth)acrylic polymer A-1 in the solution of the (meth)acrylic polymer A-1. The same applies to the solutions of the (meth)acrylic polymers A-2 to A-7 produced below.

[0151] [Production Examples A-2 and A-3] In Production Examples A-2 and A-3, the same operations as in Production Example A-1 were carried out, except that at least one of the amount of the organic solvent used and the amount of the polymerization initiator used was adjusted to make the weight average molecular weight of the (meth)acrylic polymer (A) the weight average molecular weight shown in Table 1, to obtain solutions of (meth)acrylic polymers A-2 and A-3 each having a solid content concentration of 25.0 mass%.

[0152] [Manufacturing examples A-4 to A-7] In Production Examples A-4 to A-7, the monomer composition of the (meth)acrylic polymer (A) was changed to the monomer composition shown in Table 1, and at least one of the amount of organic solvent used and the amount of polymerization initiator used was adjusted to make the weight average molecular weight of the (meth)acrylic polymer (A) the weight average molecular weight shown in Table 1. Solutions of (meth)acrylic polymers A-4 to A-7, each with a solids concentration of 25.0 mass%, were obtained by the same operation as in Production Example A-1.

[0153] Table 1 shows the monomer compositions (unit: mass %), glass transition temperatures (denoted as "Tg"), and weight average molecular weights (denoted as "Mw") of the (meth)acrylic polymers A-1 to A-7. The glass transition temperatures of the (meth)acrylic polymers A-1 to A-7 were determined by the same method as that for determining the glass transition temperature of the specific (meth)acrylic polymer (A) described above. The weight average molecular weights of the (meth)acrylic polymers A-1 to A-7 were measured by the same method as the method for measuring the weight average molecular weight of the specific (meth)acrylic polymer (A) described above.

[0154] Among the (meth)acrylic polymers A-1 to A-7, the (meth)acrylic polymers A-1 to A-6 correspond to the specific (meth)acrylic polymer (A) in the present disclosure.

[0155] [Table 1]

[0156] Details of each monomer listed in Table 1 are as follows: <Monomers having reactive functional groups> "AA": acrylic acid (reactive functional group: carboxyl group) "2HEA": 2-hydroxyethyl acrylate (reactive functional group: hydroxyl group) <(Meth)acrylic acid alkyl ester monomer> "n-BA": n-butyl acrylate "MMA": Methyl methacrylate <Other monomers> "PHEA": Phenoxyethyl acrylate

[0157] In Table 1, "-" in the column of monomer composition means that the monomer in that column was not used.

[0158] [Production of (meth)acrylic polymer (B)] [Manufacturing example B-2] A reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser was charged with 15.9 parts by mass of t-butyl methacrylate (t-BMA), 4.0 parts by mass of methyl methacrylate (MMA), 0.08 parts by mass of 2-hydroxyethyl methacrylate (2HEMA), 0.01 parts by mass of 2,2'-azobisisobutyronitrile (AIBN; polymerization initiator), 25.0 parts by mass of ethyl acetate (organic solvent), and 2.5 parts by mass of methyl acetate (organic solvent), and mixed to obtain a mixture. The atmosphere in the reactor was then replaced with nitrogen. The mixture in the reactor was then heated to 70°C while stirring. Next, 63.7 parts by mass of t-butyl methacrylate (t-BMA), 16.0 parts by mass of methyl methacrylate (MMA), 0.32 parts by mass of 2-hydroxyethyl methacrylate (2HEMA), 0.1 parts by mass of 2,2'-azobisisobutyronitrile (AIBN; polymerization initiator), 90.0 parts by mass of ethyl acetate (organic solvent), and 10.0 parts by mass of methyl acetate (organic solvent) were successively added to the mixture in the reactor, and the mixture was maintained for 6 hours to complete the polymerization reaction. Next, the solution obtained by the completion of the polymerization reaction was diluted with ethyl acetate to a solids concentration of 35.0% by mass, and then cooled to obtain a solution of (meth)acrylic polymer B-2.

[0159] The term "solid content" as used herein refers to the mass proportion of the (meth)acrylic polymer B-2 in the solution of the (meth)acrylic polymer B-2. The same applies to the solutions of the (meth)acrylic polymers B-1 and B-3 to B-12 produced below.

[0160] [Production Examples B-1 and B-3 to B-7] In Production Examples B-1 and B-3 to B-7, the same operations as in Production Example B-2 were carried out except that the monomer composition of the (meth)acrylic polymer (B) was changed to the monomer composition shown in Table 2, and solutions of (meth)acrylic polymers B-1 and B-3 to B-7 each having a solids concentration of 35.0 mass% were obtained.

[0161] [Manufacturing examples B-8 to B-12] In Production Examples B-8 to B-12, the monomer composition of the (meth)acrylic polymer (B) was changed to the monomer composition shown in Table 2, and at least one of the amount of organic solvent used and the amount of polymerization initiator used was adjusted to make the weight average molecular weight of the (meth)acrylic polymer (B) the weight average molecular weight shown in Table 2. Except for this, the same operation as in Production Example B-2 was performed to obtain solutions of (meth)acrylic polymers B-8 to B-12 each having a solids concentration of 35.0 mass%.

[0162] Table 2 shows the monomer compositions (unit: mass %), glass transition temperatures (denoted as "Tg"), and weight average molecular weights (denoted as "Mw") of the (meth)acrylic polymers B-1 to B-12. The glass transition temperatures of the (meth)acrylic polymers B-1 to B-12 were determined by the same method as that for determining the glass transition temperature of the specific (meth)acrylic polymer (A) described above. The weight average molecular weights of the (meth)acrylic polymers B-1 to B-12 were measured by the same method as the method for measuring the weight average molecular weight of the specific (meth)acrylic polymer (A) described above.

[0163] [Table 2]

[0164] Details of each monomer listed in Table 2 are as follows: "MMA": Methyl methacrylate "n-BMA": n-butyl methacrylate "t-BMA": t-butyl methacrylate "2HEMA": 2-hydroxyethyl methacrylate

[0165] In Table 2, "-" in the column of monomer composition means that the monomer in that column was not used.

[0166] [Preparation of Pressure-Sensitive Adhesive Composition] Example 1 A pressure-sensitive adhesive composition of Example 1 was obtained by thoroughly mixing 400.00 parts by mass (100 parts by mass as solids) of the solution of (meth)acrylic polymer A-1, 25.71 parts by mass (9 parts by mass as solids) of the solution of (meth)acrylic polymer B-2, 0.44 parts by mass (0.20 parts by mass as solids) of Takenate (registered trademark) D-101E (trade name, isocyanate-based crosslinking agent, solids concentration: 45% by mass, manufactured by Mitsui Chemicals, Inc.) as a crosslinking agent, and an appropriate amount of ethyl acetate (organic solvent).

[0167] Examples 2 to 21 In Examples 2 to 21, the same procedure as in Example 1 was carried out except that the formulation of the adhesive composition was changed to the formulation shown in Table 3, to obtain each of the adhesive compositions of Examples 2 to 21.

[0168] Comparative Examples 1 to 6 In Comparative Examples 1 to 6, the same procedure as in Example 1 was carried out except that the formulation of the adhesive composition was changed to the formulation shown in Table 4, to obtain each of the adhesive compositions of Comparative Examples 1 to 6.

[0169] [Preparation of polarizing plate with adhesive layer] The pressure-sensitive adhesive composition prepared above was applied to the easily peelable surface of a release film (type: MRF, thickness: 38 μm, manufactured by Mitsubishi Chemical Corporation) that had been surface-treated with a silicone-based release agent (so-called easily peelable treatment) to form a coating film. The amount of pressure-sensitive adhesive composition applied was such that the thickness of the adhesive film described below would be 20 μm. Next, the formed coating film was dried by blowing 100°C air at a wind speed of 3 m / s for 60 seconds using a hot air circulation dryer (product name: automatic discharge dryer, model: ATO-101, manufactured by Tojo Netsugaku Co., Ltd.), forming a 20 μm-thick adhesive film on the release film. Next, the exposed surface of the adhesive film formed on the release film was laminated to one of the TAC layer surfaces of a polarizing plate (thickness: 100 μm) having a triacetyl cellulose (TAC) layer / iodine-containing polyvinyl alcohol (PVA) layer / TAC layer configuration. Next, the laminate obtained by lamination was left to stand for 7 days (so-called curing period) in an environment of an atmospheric temperature of 23°C and 50% RH to cure the adhesive film. In this way, a polarizing plate with an adhesive layer having a structure of release film / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer) was produced.

[0170] [Measurement and Evaluation]

[0171] 1. Measurement of the half-width H of the loss tangent peak and calculation of the X value 1-1. Measurement of half-width H of loss tangent peak The pressure-sensitive adhesive composition prepared above was applied to the easily peelable surface of a release film (trade name: Film Byna (registered trademark) 100E-0010 No. 23, thickness: 100 μm, manufactured by Fujimori Kogyo Co., Ltd.) that had been surface-treated with a silicone-based release agent (so-called easy-peeling treatment) to form a coating film. The amount of pressure-sensitive adhesive composition applied was such that the thickness of the adhesive film described below would be 25 μm. Next, the formed coating film was dried by blowing 100°C air at a wind speed of 3 m / s for 60 seconds using a hot air circulation dryer (trade name: automatic discharge dryer, model: ATO-101, manufactured by Tojo Netsugaku Co., Ltd.). This formed a 25 μm-thick adhesive film on the release film. Next, the exposed surface of the adhesive film formed on the release film was laminated to the easy-release-treated surface of a separately prepared release film (product name: Film Byna (registered trademark) 100E-0010 No. 23, thickness: 100 μm, manufactured by Fujimori Kogyo Co., Ltd.). The laminate obtained by lamination was then left to stand in an environment of an atmospheric temperature of 25°C and 50% RH for 7 days (the so-called curing period) to allow the adhesive film to cure. In this way, a substrate-free adhesive sheet having a release film / adhesive layer / release film configuration was produced. Next, the release film of the substrate-free pressure-sensitive adhesive sheet was peeled off, and the resulting pressure-sensitive adhesive layer was laminated to obtain a 400 μm thick pressure-sensitive adhesive layer. The viscoelastic spectrum of the resulting pressure-sensitive adhesive layer was measured using a dynamic viscoelasticity measuring device (trade name: Physica MCR301, manufactured by Anton Paar) according to the dynamic viscoelasticity measurement method in accordance with JIS K 7244-1:1998 [temperature range: -60°C to 60°C, heating rate: 8.6°C / min, frequency: 1 Hz, jig used: parallel plate 8 mmφ (PB-08)], and the half-width H (unit: °C) of the peak of the loss tangent [loss modulus (G'') / storage modulus (G')] in the measurement range of -50°C to 20°C was determined. The half-width H is the h of the peak of the loss tangent. 1 / 2 A line parallel to the temperature axis was drawn at the position, and the temperature width between the intersections of this line with the left and right peaks was measured.

[0172] 1-2.Calculation of X value The half-value width H (unit: °C) of the loss tangent peak of the pressure-sensitive adhesive layer obtained above, and the content C of the (meth)acrylic polymer (A) A (unit: parts by mass), and the content C of the (meth)acrylic polymer (B) B The X value was calculated from the results (unit: parts by mass) based on the following formula. The X values ​​are shown in Tables 3 and 4. X value = |H × C A / (C A +C B )|

[0173] 2. Reworkability 2-1. Preparation of samples for reworkability evaluation The polarizing plate with the adhesive layer prepared above was cut to prepare a test piece X1 measuring 25 mm (short side) × 75 mm (long side). Next, the release film was peeled off from the cut test piece X1 [structure: release film / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer)] to obtain a test piece X2 [structure: adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer)]. Next, the exposed adhesive layer surface of test piece X2 was placed on one side of a soda glass plate (manufactured by Matsunami Glass Industry Co., Ltd.) as an adherend, and then pressure-bonded using a laminator. In this manner, a sample for evaluating reworkability was prepared, having a structure of adherend (soda glass plate) / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer).

[0174] 2-2.Evaluation test The reworkability evaluation sample prepared above was treated at a temperature of 50°C and a pressure of 5 kg / cm 2The specimens were autoclaved for 20 minutes under the following conditions: The autoclaved reworkability evaluation samples were then left to stand for 5 hours in an 80°C ambient temperature environment, followed by 30 minutes in an 23°C ambient temperature and 50% RH environment to obtain test specimens. The adhesive strength (unit: N / 25 mm) of the test specimens was measured when test specimen X2 was peeled from the adherend (soda glass plate) at a 90° angle along the long side (75 mm) using a single-column materials testing machine (model number: STA-1225, manufactured by A&D Co., Ltd.) at an ambient temperature of 23°C and 50% RH at a peel speed of 0.3 m / min. Evaluation was then performed according to the following criteria: The measured adhesive strength and evaluation results are shown in Tables 3 and 4. In the following evaluation criteria, "A," "B," and "C" are practically acceptable levels, with "A" being the most preferable.

[0175] -Evaluation criteria- A: The adhesive strength is less than 13N / 25mm. B: The adhesive strength is 13N / 25mm or more and less than 15N / 25mm. C: The adhesive strength is 15N / 25mm or more and less than 17.5N / 25mm. D: The adhesive strength is 17.5 N / 25 mm or more, or adhesive residue is observed on the adherend.

[0176] 3.Transparency 3-1. Preparation of samples for transparency evaluation The pressure-sensitive adhesive composition prepared above was applied to the easily peelable surface of a release film (type: MRF, thickness: 38 μm, manufactured by Mitsubishi Chemical Corporation) that had been surface-treated with a silicone-based release agent (so-called easy-peeling treatment) to form a coating film. The amount of pressure-sensitive adhesive composition applied was such that the thickness of the adhesive film described below would be 40 μm. Next, the formed coating film was dried by blowing 100°C air at a wind speed of 3 m / s for 60 seconds using a hot air circulation dryer (product name: automatic discharge dryer, model: ATO-101, manufactured by Tojo Netsugaku Co., Ltd.), forming a 40 μm-thick adhesive film on the release film. Next, the exposed surface of the adhesive film formed on the release film was laminated to one side of a PET film (product name: COSMOSHINE (registered trademark) A4100, thickness: 100 μm, manufactured by Toyobo Co., Ltd.). Next, the laminate obtained by lamination was left to stand in an environment of an atmospheric temperature of 23°C and 50% RH for 7 days (so-called curing period) to cure the adhesive film. In this manner, a sample for evaluating transparency having a structure of release film / adhesive layer / PET film was prepared.

[0177] 3-2.Evaluation test (1) Rating 1 (Transparency) The transparency evaluation sample prepared above was cut to prepare an evaluation adhesive sheet piece measuring 100 mm (short side) × 150 mm (long side). The release film was peeled off from this evaluation adhesive sheet piece to prepare a test piece. The haze was measured at five randomly selected points on the test piece using a haze meter (model: NDH 5000SP, manufactured by Nippon Denshoku Industries Co., Ltd.). The obtained values ​​were arithmetically averaged to obtain the haze value. Evaluation was then performed according to the following evaluation criteria. The haze values ​​and the evaluation results are shown in Tables 3 and 4. In the following evaluation criteria, "A," "B," and "C" are practically acceptable levels, with "A" being the most preferable.

[0178] -Evaluation criteria- A: The haze value is less than 1.0%. B: The haze value is 1.0% or more and less than 3.0%. C: The haze value is 3.0% or more and less than 6.0%. D: The haze value is 6.0% or more.

[0179] (2) Rating 2 The transparency evaluation sample prepared above was cut to prepare a 100 mm (short side) × 150 mm (long side) adhesive sheet strip for evaluation. The release film was peeled off from this prepared adhesive sheet strip for evaluation to prepare a test piece. The haze at 10 randomly selected locations on the test piece was measured using a haze meter (model: NDH 5000SP, manufactured by Nippon Denshoku Industries Co., Ltd.). The obtained values ​​were divided into two groups: Group X, which contained the top five values ​​counting from the largest value, and Group Y, which contained the top five values ​​counting from the smallest value. The five values ​​in Group X and the five values ​​in Group Y were then arithmetically averaged to obtain the haze value (X) and the haze value (Y). The difference in haze value (Z) was calculated from the haze value (X) and the haze value (Y) according to the following formula. Evaluation was then performed according to the following evaluation criteria. The difference in haze value (Z) and the evaluation results are shown in Tables 3 and 4. In the following evaluation criteria, "A," "B," and "C" are practically acceptable levels, with "A" being the most preferable.

[0180] Haze difference (Z) = [Haze value (X) - Haze value (Y)]

[0181] -Evaluation criteria- A: The difference in haze value (Z) is less than 1.0%. B: The difference (Z) in haze value is 1.0% or more and less than 3.0%. C: The difference (Z) in haze value is 3.0% or more and less than 6.0%. D: The difference in haze value (Z) is 6.0% or more.

[0182] In the transparency evaluation test, when the results of the above evaluations 1 and 2 were both "A," "B," or "C," the pressure-sensitive adhesive layer was determined to have excellent transparency.

[0183] 4. Shock resistance 4-1. Preparation of impact resistance evaluation samples The polarizing plate with the adhesive layer prepared above was cut to prepare a test piece Y1 measuring 30 mm x 30 mm. Next, the release film was peeled off from the cut test piece Y1 [structure: release film / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer)] to obtain test piece Y2 [structure: adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer)]. Next, the exposed adhesive layer surface of test piece Y2 was placed on one side of a soda glass plate (manufactured by Matsunami Glass Industry Co., Ltd.) as an adherend, and then pressure-bonded using a laminator. In this manner, a sample for evaluating impact resistance was prepared, having a structure of adherend (soda glass plate) / adhesive layer / polarizing plate (TAC layer / PVA layer / TAC layer).

[0184] 4-2.Evaluation test The impact resistance evaluation sample prepared above was placed in an environment with an ambient temperature of 23°C and 50% RH. Next, an evaluation pen (trade name: gel ink ballpoint pen, ball diameter: 0.5 mm, manufactured by ZEBRA Corporation) was held with the pen tip facing downward at a height of 15 cm from the outermost surface of the impact resistance evaluation sample on the polarizing plate side. The evaluation pen was then dropped from the held position. The impact resistance evaluation sample that had been hit by the pen tip of the evaluation pen was visually observed and evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 3 and 4. In the following evaluation criteria, "A" and "B" are practically acceptable levels, with "A" being the most preferable.

[0185] -Evaluation criteria- A: No bubbles are generated, or the size of the bubbles that are generated is less than 50 μm. B: The size of the generated bubbles is 50 μm or more and less than 100 μm. C: The size of the generated bubbles is 100 μm or more.

[0186] [Table 3]

[0187] [Table 4]

[0188] Details of the components listed in Tables 3 and 4 are as follows: <Crosslinking agent> "D-101E" (trade name: Takenate (registered trademark) D-101E, isocyanate-based crosslinking agent, tolylene diisocyanate (TDI) trimethylolpropane (TMP) adduct, solid content: 45% by mass, manufactured by Mitsui Chemicals, Inc.) "D-110N" (trade name: Takenate (registered trademark) D-110N, isocyanate-based crosslinking agent, adduct of xylylene diisocyanate (XDI) and trimethylolpropane (TMP), solid content: 75% by mass, manufactured by Mitsui Chemicals, Inc.) "2021P" (product name: CELLOXIDE (registered trademark) 2021P, epoxy crosslinking agent, 3',4'-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, solid content: 100% by mass, manufactured by Daicel Corporation) <Other ingredients> "X-41-1810" (product name, silane coupling agent, thiol group-containing silane compound, solid content: 100% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.) "KF-859" (product name, release modifier, silicone oil, amino group-containing silane compound, solid content: 100% by mass, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0189] In Tables 3 and 4, the values ​​shown in the "blending amount" column are all solid content converted values. In Tables 3 and 4, "-" in the column for the composition of the adhesive composition means that the component in that column was not blended. In Table 4, the "Not rated" in the reworkability column means that the pressure-sensitive adhesive layer was destroyed when peeling it from the adherend, making it impossible to evaluate.

[0190] As shown in Table 3, it was confirmed that the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive compositions of the Examples were excellent in reworkability, transparency and impact resistance. On the other hand, as shown in Table 4, it was confirmed that the adhesive layer formed using the adhesive composition of the comparative example was inferior to the adhesive layer formed using the adhesive composition of the example in at least one of the evaluation items of reworkability, transparency, and impact resistance.

Claims

1. a (meth)acrylic polymer (A) having a reactive functional group; a (meth)acrylic polymer (B) having a glass transition temperature higher by 85° C. or more than the glass transition temperature of the (meth)acrylic polymer (A); a cross-linking agent; Including, When a pressure-sensitive adhesive layer is formed, the half width H°C of the loss tangent peak of the pressure-sensitive adhesive layer, the content C of the (meth)acrylic polymer (A), Ａ parts by mass, and the content C of the (meth)acrylic polymer (B) Ｂ A pressure-sensitive adhesive composition in which the parts by mass satisfy the relationship of the following formula (X): 14.8≦|H×C Ａ / (C Ａ +C Ｂ )|<21.0 (X)

2. The pressure-sensitive adhesive composition according to claim 1 , wherein the reactive functional group includes at least one of a carboxy group and a hydroxyl group.

3. The pressure-sensitive adhesive composition according to claim 1, wherein the content of the (meth)acrylic polymer (B) is 1 part by mass or more and 40 parts by mass or less per 100 parts by mass of the (meth)acrylic polymer (A).

4. 2. The pressure-sensitive adhesive composition according to claim 1, wherein the (meth)acrylic polymer (B) contains at least one of a structural unit derived from t-butyl methacrylate and a structural unit derived from methyl methacrylate.

5. The pressure-sensitive adhesive composition according to claim 1, wherein the (meth)acrylic polymer (B) has a glass transition temperature of 40°C or higher and 150°C or lower.

6. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 5.

7. An optical film; a pressure-sensitive adhesive layer provided on at least one surface of the optical film and formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 5; An adhesive sheet comprising:

8. The pressure-sensitive adhesive sheet according to claim 7 , wherein the optical film is a polarizing plate.

9. A glass substrate; A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of claims 1 to 5; An optical film; An optical element comprising the above in this order.

10. A display device comprising the optical member according to claim 9 .

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