Adhesive compositions, adhesives, adhesive sheets, and laminates

Abstract

Provided is a pressure-sensitive adhesive composition containing: a (meth)acrylic ester polymer (A) including, as a monomer unit forming the polymer, an ethylene-carbonate-containing monomer having the ethylene carbonate structure represented by formula (1); an ionic compound (B); and an active-energy-ray-curable component (C). A pressure-sensitive adhesive, pressure-sensitive adhesive sheet, and laminate obtained from said pressure-sensitive adhesive composition have excellent conformability to unevenness and make it possible to suppress the occurrence of optical irregularities.

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition, adhesive, adhesive sheet, and laminate suitable for use in display devices and the like. [Background technology]

[0002] In recent years, various mobile electronic devices such as smartphones and tablet devices are equipped with displays using display modules that have liquid crystal elements, light-emitting diodes (LED elements), organic electroluminescent (OLED) elements, etc., and these displays are increasingly becoming touch panels.

[0003] In displays like the one described above, a protective panel is typically provided on the surface side of the display module. With the trend towards thinner and lighter electronic devices, these protective panels are increasingly being replaced from traditional glass plates to plastic plates such as acrylic or polycarbonate.

[0004] Here, a gap is provided between the protective panel and the display module to prevent the deformed protective panel from colliding with the display module even if the protective panel is deformed by an external force.

[0005] However, the presence of such gaps, or air layers, leads to a problem where the difference in refractive index between the protective panel and the air layer, and the difference in refractive index between the air layer and the display module, results in significant light reflection loss, thus degrading the display's image quality.

[0006] Therefore, it has been proposed to improve the image quality of the display by filling the gap between the protective panel and the display module with an adhesive layer. For example, Patent Document 1 describes an adhesive layer for filling the gap between the protective panel and the display module, wherein the shear storage modulus (G') at 25°C and 1 Hz is 1.0 × 10⁻⁶. 5 The disclosure provides an adhesive layer having a Pa value of 0.5 or less and a gel fraction of 40% or more. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2010-97070 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] Patent Document 1 attempts to improve step-following ability by lowering the storage modulus at room temperature in the adhesive layer. However, lowering the storage modulus at room temperature as described above causes the storage modulus at high temperatures to decrease excessively, leading to problems under durability conditions. For example, bubbles may form near steps when subjected to high temperature and high humidity conditions. In addition, conventional adhesive layers may exhibit optical irregularities such as visual distortion near steps.

[0009] This invention has been made in view of the above circumstances, and aims to provide an adhesive composition, adhesive, adhesive sheet, and laminate that have excellent step-following properties and can suppress the occurrence of optical unevenness. [Means for solving the problem]

[0010] To achieve the above objective, firstly, the present invention provides the following formula (1) as the monomer unit constituting the polymer [ka] The present invention provides an adhesive composition characterized by containing an ethylene carbonate-containing monomer having an ethylene carbonate structure as shown in (A), an ionic compound (B), and an active energy ray-curable component (C).

[0011] In the above invention (Invention 1), by containing the above components, the obtained adhesive can exhibit good cohesive force even without containing a crosslinking agent, and has excellent handling properties (for example, workability when using an adhesive sheet, etc.). Further, together with the cohesive force, excellent stress relaxation properties are exhibited, and by curing by irradiation with active energy rays, it has excellent step-following properties under initial to high temperature and high humidity (severe durability conditions). Furthermore, due to the above excellent stress relaxation properties, the occurrence of optical unevenness (such as optical distortion) is suppressed. And since the above adhesive composition does not need to contain a crosslinking agent, in obtaining the adhesive, an aging period is not required, and the productivity of the adhesive sheet can be improved.

[0012] In the above invention (Invention 1), it is preferable that the (meth)acrylate polymer (A) contains 0.5% by mass or more and 40% by mass or less of the ethylene carbonate-containing monomer as a monomer unit constituting the polymer (Invention 2).

[0013] In the above invention (Inventions 1 and 2), it is preferable that the ionic compound (B) is an alkali metal salt (Invention 3).

[0014] In the above invention (Inventions 1 to 3), it is preferable that the content of the ionic compound (B) in the adhesive composition is 0.1 part by mass or more and 2 parts by mass or less with respect to 100 parts by mass of the (meth)acrylate polymer (A) (Invention 4).

[0015] In the above invention (Inventions 1 to 4), it is preferable that the content of the crosslinking agent in the adhesive composition is 0.1 part by mass or less with respect to 100 parts by mass of the (meth)acrylate polymer (A) (Invention 5).

[0016] Second, the present invention provides an adhesive obtained by crosslinking the above adhesive composition (Inventions 1 to 5) (Invention 6).

[0017] Thirdly, the present invention provides an adhesive sheet comprising at least an adhesive layer, wherein the adhesive layer is made of the adhesive (Invention 6) (Invention 7).

[0018] Fourthly, the present invention relates to an adhesive sheet comprising at least an adhesive layer, wherein the adhesive constituting the adhesive layer is an active energy ray curable adhesive, the strain amount of the adhesive constituting the adhesive layer 1210 seconds after a stress of 7950 Pa is applied to the adhesive at 25°C is 30% or more and 1500% or less, the ratio of the strain amount of the cured adhesive obtained by curing the adhesive constituting the adhesive layer with active energy rays to the strain amount 1210 seconds after a stress of 7950 Pa is applied to the cured adhesive at 25°C is less than 1, and the maximum relaxation modulus of elasticity measured when the adhesive constituting the adhesive layer is strained by 10% according to JIS K7244-1 is the maximum relaxation modulus of elasticity G(t) max (MPa) and the maximum relaxation modulus G(t) max The adhesive is subjected to a 10% strain for 3757 seconds after the measurement is taken, and the minimum relaxation modulus value measured during that time is defined as the minimum relaxation modulus G(t). min The invention provides an adhesive sheet characterized in that the relaxation modulus variation value ΔlogG(t), calculated from the following formula (X), is 1.2 or more and 3 or less, with a pressure of (MPa). ΔlogG(t)=logG(t) max -logG(t) min …(X)

[0019] In the above invention (Invention 8), it is preferable that the amount of strain of the cured adhesive, which is obtained by curing the adhesive constituting the adhesive layer with active energy rays, 1210 seconds after a stress of 7950 Pa is applied to the cured adhesive at 25°C is 50% or more and 600% or less (Invention 9).

[0020] In the above invention (Inventions 8 and 9), the maximum relaxation elastic modulus value measured when the cured adhesive obtained by curing the adhesive constituting the adhesive layer with active energy rays is stretched by 10% in accordance with JIS K7244-1 is defined as the maximum relaxation elastic modulus G(t) max (MPa), and the cured adhesive is continuously stretched by 10% until 3757 seconds after the maximum relaxation elastic modulus G(t) max is measured, and the minimum relaxation elastic modulus value measured during that time is defined as the minimum relaxation elastic modulus G(t) min (MPa). It is preferable that the relaxation elastic modulus variation value ΔlogG(t) calculated from the above formula (X) is 1.2 or more and 3 or less (Invention 10).

[0021] In the above invention (Inventions 7 to 10), it is preferable that the adhesive sheet includes two release sheets, and the adhesive layer is sandwiched between the release sheets so as to be in contact with the release surfaces of the two release sheets (Invention 11).

[0022] Fifth, the present invention provides a laminate including one display body component member, another display body component member, and a cured adhesive layer that bonds the one display body component member and the other display body component member to each other, wherein the cured adhesive layer is a cured adhesive layer obtained by curing the adhesive layer of the adhesive sheet (Inventions 7 to 11) with active energy rays (Invention 12).

[0023] In the above invention (Invention 12), it is preferable that at least one of the one display body component member and the other display body component member has a step on the surface on the side bonded by the adhesive layer (Invention 13).

Effect of the Invention

[0024] The adhesive composition, adhesive, adhesive sheet, and laminate according to the present invention are excellent in step following properties and can suppress the occurrence of optical unevenness.

Brief Description of the Drawings

[0025] [Figure 1] This is a cross-sectional view of an adhesive sheet according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view of a laminate according to one embodiment of the present invention. [Modes for carrying out the invention]

[0026] Embodiments of the present invention will be described below. [Adhesive composition] An adhesive composition according to one embodiment of the present invention (hereinafter sometimes referred to as "adhesive composition P") has the following formula (1) as the monomer unit constituting the polymer [ka] It is preferable to contain a (meth)acrylic acid ester polymer (A) containing an ethylene carbonate-containing monomer having the ethylene carbonate structure shown in [figure], and an ionic compound (B). In this specification, (meth)acrylic acid means both acrylic acid and methacrylic acid. The same applies to other similar terms. Furthermore, the concept of "polymer" is also included in the concept of "copolymer".

[0027] Since the (meth)acrylic acid ester polymer (A) is composed of the above-mentioned ethylene carbonate-containing monomer, the adhesive composition P according to this embodiment contains an ethylene carbonate structure as a side chain of the (meth)acrylic acid ester polymer (A). When the (meth)acrylic acid ester polymer (A) contains an ethylene carbonate structure as a side chain, the interaction between the side chains becomes stronger, and the glass transition temperature (Tg) of the (meth)acrylic acid ester polymer (A) becomes relatively high. As a result, the cohesive force of the resulting adhesive becomes stronger. In addition, the ethylene carbonate structure contains two carbonyl dipoles. As a result, the ethylene carbonate structure as a side chain of the (meth)acrylic acid ester polymer (A) and the ionic compound (B) bond through interaction, forming a pseudo-crosslinked structure. By including such a crosslinked structure, the resulting adhesive exhibits good cohesive force even without containing a crosslinking agent and has excellent handling properties (for example, workability when using adhesive sheets). Furthermore, from the standpoint of the polarity of the ethylene carbonate structure, the resulting adhesive exhibits high adhesive strength, particularly to glass. On the other hand, when a predetermined pressure (and heat) is applied to the adhesive, the above-mentioned cross-linked structure unravels, exhibiting excellent stress relaxation properties. For example, if there are steps or other irregularities on the object to which the adhesive is applied, it becomes easier to conform to the shape of such steps or irregularities. Subsequently, even after the predetermined pressure (and heat) is removed, a pseudo-cross-linked structure is formed again while maintaining a state of good conformity to the shape of steps or irregularities. In such cases, the stress in the adhesive when conforming to the shape of steps or irregularities is less likely to remain, so the force that causes the adhesive to return to its pre-conformation state can be kept small, and a state of good conformity to the shape of steps or irregularities can be maintained. In addition, the adhesive's cohesive strength is further improved and the film strength is increased by curing by active energy ray irradiation (after application to the object). Due to these effects, the adhesive sheet obtained using this adhesive exhibits excellent step-conformity from the initial stage to high temperature and high humidity conditions (severe durability conditions). Note that the term "initial period" as used here excludes the period immediately after application.Furthermore, the residual stress of general adhesives is particularly noticeable near steps and other uneven surfaces. For example, even when the adhesive exhibits excellent step-following properties from the initial stage to high temperature and humidity (i.e., no bubbles, lifting, or peeling occur near steps and other uneven surfaces), optical irregularities (optical distortion, etc.) may occur near steps and other uneven surfaces due to distortion of the adhesive caused by the force of the adhesive trying to return to its pre-following state. However, adhesive sheets obtained using the adhesive obtained from the adhesive composition P according to this embodiment can suppress the force of the adhesive trying to return to its pre-following state, resulting in excellent suppression of optical irregularities near steps and other uneven surfaces. For example, this can improve the image quality and appearance of displays. Moreover, since the adhesive composition according to this embodiment does not need to contain a crosslinking agent, a curing period (aging) is not required to obtain the adhesive, thereby improving the productivity of adhesive sheets. In this specification, "crosslinking" includes not only general crosslinking by covalent bonds, but also pseudo-crosslinking by interactions (including, but not limited to, coordination bonds, ionic bonds, intermolecular forces, etc.).

[0028] (1) Components of the adhesive composition (1-1)(meth)acrylic acid ester polymer (A) The ethylene carbonate-containing monomer containing the ethylene carbonate structure shown in formula (1) above is not particularly limited as long as it contains an ethylene carbonate structure and can undergo polymerization reactions with other monomers constituting the (meth)acrylic acid ester polymer (A).

[0029] A preferred example of an ethylene carbonate-containing monomer is a (meth)acrylic acid ester having a structure in which an organic group having an ethylene carbonate structure is bonded to a (meth)acryloyloxy group. An example of such a (meth)acrylic acid ester is the following formula (2): [ka] Acrylic acid esters represented by the following formula (3) [ka] Examples include methacrylic acid esters represented by the formulas (2) and (3). In both formulas (2) and (3), n represents an integer of 0 or more. Among the (meth)acrylic acid esters represented by the formulas (2) and (3) above, (meth)acrylic acid esters in which n is 1 or more are preferred, and (meth)acrylic acid esters in which n is 2 or more are preferred. When n is 1 or more, the ethylene carbonate group as a side chain of the (meth)acrylic acid ester polymer (A) is located relatively far from the main chain, increasing the probability that the ethylene carbonate structures present in the resulting adhesive will overlap with each other. As a result, stacking interactions between the ethylene carbonate structures come into play, making it easier to favorably exhibit the mechanical properties (strain amount, relaxation modulus fluctuation value, storage modulus) and adhesive strength described later. In addition, interactions between the ethylene carbonate structure and the ionic compound (B) are more likely to occur, making it easier to form pseudo-crosslinked structures and increasing the cohesive force. Due to these effects, the resulting adhesive has superior step-following ability. Furthermore, it exhibits excellent suppression of optical unevenness and also has excellent handling properties. The upper limit of n is not particularly limited, but from the viewpoint of polymerization, it is preferably 10 or less, more preferably 6 or less, particularly preferably 4 or less, and even more preferably 3 or less. Among these, (meth)acrylic acid esters with n=2 are preferred from the viewpoint of easily improving the mechanical properties (strain amount, relaxation modulus fluctuation value, storage modulus) and adhesive strength of the resulting adhesive, and having superior step-following properties, and in particular (2-oxo-1,3-dioxolan-4-yl)methyl methacrylic acid with n=2 in formula (3) are preferred. Note that one type of ethylene carbonate-containing monomer may be used alone, or two or more types may be used in combination.

[0030] The (meth)acrylic acid ester polymer (A) preferably contains 0.5% by mass or more, more preferably 1% by mass or more, particularly preferably 5% by mass or more, and even more preferably 10% by mass or more, of the above-mentioned ethylene carbonate-containing monomer as a monomer unit constituting the polymer. This allows stacking interactions between the ethylene carbonate structures to work, making it easier to favorably exhibit the mechanical properties (strain amount, relaxation modulus fluctuation value, storage modulus) and adhesive strength described later. In addition, interactions between the ethylene carbonate structure and the ionic compound (B) are made easier to exhibit, making it easier to form a pseudo-crosslinked structure and increasing the cohesive force. Due to these effects, the resulting adhesive has superior step-following ability. It also has excellent suppression of optical unevenness and excellent handling properties. Furthermore, from the viewpoint of polarity, the adhesive strength of the adhesive, especially the adhesive strength to glass, is high.

[0031] On the other hand, the (meth)acrylic acid ester polymer (A) preferably contains 40% by mass or less of the above-mentioned ethylene carbonate-containing monomer as monomer units constituting the polymer, more preferably 30% by mass or less, particularly preferably 25% by mass or less, and even more preferably 20% by mass or less. This makes it easier to satisfy the mechanical properties (strain amount, relaxation modulus fluctuation value, storage modulus) described later, resulting in superior step-following ability.

[0032] In this embodiment, the (meth)acrylic acid ester polymer (A) preferably contains an alkyl (meth)acrylic acid ester as a monomer unit constituting the polymer. This allows the resulting adhesive to exhibit good tackiness. The alkyl group may be linear or branched.

[0033] From the viewpoint of adhesiveness, alkyl (meth)acrylate esters with 1 to 20 carbon atoms in the alkyl group are preferred. Examples of alkyl (meth)acrylate esters with 1 to 20 carbon atoms in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate.

[0034] Among the above, alkyl (meth)acrylates with 2 to 12 C atoms in the alkyl group are more preferred, and alkyl (meth)acrylates with 4 to 10 C atoms in the alkyl group are particularly preferred, from the viewpoint of providing good tackiness. Specifically, n-butyl (meth)acrylate is preferred, and n-butyl acrylate is particularly preferred. These may be used alone or in combination of two or more.

[0035] From the viewpoint of imparting good tackiness, the (meth)acrylic acid ester polymer (A) preferably contains 50% by mass or more of alkyl (meth)acrylate as monomer units constituting the polymer, more preferably 60% by mass or more, particularly preferably 70% by mass or more, and even more preferably 80% by mass or more. Furthermore, from the viewpoint of ensuring the content of other monomers (especially ethylene carbonate-containing monomers), it is preferable that the polymer contains 99.5% by mass or less of alkyl (meth)acrylate, more preferably 99% by mass or less, particularly preferably 95% by mass or less, and even more preferably 90% by mass or less.

[0036] The (meth)acrylic acid ester polymer (A) may also preferably contain a reactive functional group-containing monomer as a monomer constituting the polymer, which has a reactive functional group within its molecule. By containing a reactive functional group-containing monomer, the interaction between the (meth)acrylic acid ester polymer (A) and the ionic compound (B) is more easily exhibited, and a pseudo-crosslinked structure is more easily formed. As a result, the resulting adhesive has higher cohesive force, and the mechanical properties (strain amount, relaxation modulus fluctuation value, storage modulus) described later are more easily satisfied, resulting in better step-following ability.

[0037] Preferred examples of the above-mentioned reactive functional group-containing monomers include monomers having a hydroxyl group in the molecule (hydroxyl group-containing monomers), monomers having a carboxyl group in the molecule (carboxyl group-containing monomers), and monomers having an amino group in the molecule (amino group-containing monomers). Among these, hydroxyl group-containing monomers are preferred from the viewpoint of easily forming the above-mentioned pseudo-crosslinking structure. These reactive functional group-containing monomers may be used individually or in combination of two or more.

[0038] Examples of hydroxyl group-containing monomers include hydroxyalkyl esters of (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Among these, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred from the viewpoint of easily forming the above-mentioned pseudo-crosslinking structure, and 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are particularly preferred. These may be used individually or in combination of two or more.

[0039] Examples of carboxyl group-containing monomers include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. These may be used individually or in combination of two or more.

[0040] Examples of amino group-containing monomers include aminoethyl (meth)acrylate and n-butylaminoethyl (meth)acrylate. These may be used individually or in combination of two or more.

[0041] The (meth)acrylic acid ester polymer (A) preferably contains 0.1 to 10% by mass of a reactive functional group-containing monomer as a monomer constituting the polymer, more preferably 0.4 to 8% by mass, particularly preferably 0.8 to 6% by mass, and even more preferably 1 to 3% by mass. When the reactive functional group-containing monomer is contained within the above range, the pseudo-crosslinked structure described above is more easily formed. As a result, the resulting adhesive has higher cohesive strength, and the mechanical properties (strain amount, relaxation modulus fluctuation value, storage modulus) described later are more easily satisfied, resulting in superior step-following ability. In addition, it exhibits excellent suppression of optical unevenness and also has excellent handling properties.

[0042] The (meth)acrylic acid ester polymer (A) in this embodiment may further contain other monomers as monomers constituting the polymer. Examples of such other monomers include alicyclic structure-containing (meth)acrylic acid esters such as dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate; alkoxyalkyl (meth)acrylate esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; non-crosslinked acrylamides such as acrylamide and methacrylamide; non-crosslinked (meth)acrylic acid esters having a tertiary amino group such as N,N-dimethylaminoethyl (meth)acrylate and N,N-dimethylaminopropyl (meth)acrylate; vinyl acetate; and styrene. These may be used individually or in combination of two or more.

[0043] The polymerization method of the (meth)acrylic acid ester polymer (A) in this embodiment may be random polymerization or block polymerization. Furthermore, the (meth)acrylic acid ester polymer (A) can be obtained by polymerizing each of the above-mentioned monomers by conventional methods. For example, it can be prepared by polymerization using emulsion polymerization, solution polymerization, suspension polymerization, bulk polymerization, aqueous solution polymerization, etc. Among these, from the viewpoint of stability during polymerization and ease of handling during use, it is preferable to prepare it by solution polymerization carried out in an organic solvent.

[0044] The weight-average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 100,000 to 2,000,000, more preferably 300,000 to 1,500,000, particularly preferably 500,000 to 1,000,000, and even more preferably 650,000 to 800,000. This makes it easier for the resulting adhesive to satisfy the mechanical properties (strain amount, relaxation modulus fluctuation value, storage modulus) described later, resulting in superior step-following ability. It also exhibits excellent suppression of optical unevenness and superior handling properties. Note that the weight-average molecular weight in this specification is the value on a standard polystyrene basis measured by gel permeation chromatography (GPC).

[0045] The adhesive composition P according to this embodiment may contain one of the above-described (meth)acrylic acid ester polymers (A), or it may contain two or more. Furthermore, the adhesive composition P according to this embodiment may contain another (meth)acrylic acid ester polymer along with the above-described (meth)acrylic acid ester polymer (A).

[0046] (1-2) Ionic compounds (B) In this specification, an ionic compound refers to a compound in which a cation and anion are bonded primarily by electrostatic attraction. In this embodiment, the ionic compound (B) may be a liquid (ionic liquid) or a solid (ionic solid) at room temperature.

[0047] Examples of ionic compound (B) include alkali metal salts, alkaline earth metal salts, nitrogen-containing onium salts, sulfur-containing onium salts, and phosphorus-containing onium salts. Among these, alkali metal salts or alkaline earth metal salts are preferred, and alkali metal salts are particularly preferred, from the viewpoint of easily forming the above-mentioned pseudo-crosslinking structure with the (meth)acrylic acid ester polymer (A). Ionic compound (B) can be used alone or in combination of two or more types.

[0048] Specific examples of alkali metal salts include potassium bis(fluorosulfonyl)imide, lithium bis(fluorosulfonyl)imide, potassium bis(fluoromethanesulfonyl)imide, lithium bis(fluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide. Among these, lithium bis(trifluoromethanesulfonyl)imide is preferred from the viewpoint of easily forming the pseudo-crosslinked structure described above.

[0049] The content of the ionic compound (B) in the adhesive composition is preferably 0.1 to 2 parts by mass, more preferably 0.2 to 1.5 parts by mass, particularly preferably 0.3 to 1 part by mass, and even more preferably 0.4 to 0.7 parts by mass, per 100 parts by mass of the (meth)acrylic acid ester polymer (A). Having the ionic compound (B) content within the above range results in an appropriate degree of pseudo-crosslinking. This makes the resulting adhesive more readily satisfies the mechanical properties (strain, relaxation modulus fluctuation, storage modulus) described later, resulting in superior step-following ability. Furthermore, it exhibits excellent suppression of optical unevenness and superior handling properties.

[0050] (1-3) Active energy ray curing component (C) The adhesive obtained from the adhesive composition P containing the active energy ray curable component (C) readily exhibits a plastic effect when a predetermined pressure (and heat) is applied during adhesion to the substrate (before curing with active energy rays). For example, if there are steps or other uneven surfaces on the substrate to which the adhesive is applied, it becomes easier to conform to the shape of such steps or uneven surfaces. This results in excellent initial step-following ability. Furthermore, it is presumed that curing by irradiation with active energy rays after adhesion to the substrate causes the active energy ray curable component (C) to polymerize with each other, and that the polymerized active energy ray curable component (C) becomes entangled in the pseudo-crosslinked structure of the (meth)acrylic acid ester polymer (A). The cured adhesive having such a higher-order structure exhibits high cohesive force and high film strength, resulting in superior step-following ability under high temperature and high humidity conditions (severe durability conditions).

[0051] The active energy ray curable component (C) is not particularly limited as long as it is a component that hardens upon irradiation with active energy rays and produces the above-mentioned effects, and may be a monomer, oligomer, or polymer, or a mixture thereof. Among these, polyfunctional acrylate monomers that have excellent compatibility with (meth)acrylic acid ester polymers (A) etc. are particularly preferred.

[0052] Examples of polyfunctional acrylate monomers include bifunctional types such as 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, hydroxypivalate neopentyl glycol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, caprolactone-modified dicyclopentenyl di(meth)acrylate, ethylene oxide-modified phosphate di(meth)acrylate, di(acryloxyethyl) isocyanurate, ethoxylated isocyanurate di(meth)acrylate, allylated cyclohexyl di(meth)acrylate, ethoxylated bisphenol A diacrylate, and 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene; trimethylol Examples include trifunctional types such as tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, ethoxylated isocyanurate tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, tris(acryloxyethyl) isocyanurate, and ε-caprolactone-modified tris-(2-(meth)acryloxyethyl) isocyanurate; tetrafunctional types such as diglycerin tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; pentafunctional types such as propionic acid-modified dipentaerythritol penta(meth)acrylate; and hexafunctional types such as dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate. These may be used individually or in combination of two or more. Furthermore, from the viewpoint of compatibility with (meth)acrylic acid ester polymer (A), polyfunctional acrylate monomers with a molecular weight of less than 1000 are preferred.

[0053] Among the above, polyfunctional acrylate monomers containing an isocyanurate structure in the molecule are preferred from the viewpoint of the step-following ability of the resulting cured adhesive under high temperature and high humidity conditions. Ethoxylated polyfunctional acrylate monomers containing an isocyanurate structure in the molecule are preferred, and it is particularly preferred to use at least one of ethoxylated isocyanuric acid di(meth)acrylate and ethoxylated isocyanuric acid tri(meth)acrylate, and even more preferably to use both ethoxylated isocyanuric acid di(meth)acrylate and ethoxylated isocyanuric acid tri(meth)acrylate.

[0054] As the active energy ray curable component (C), an active energy ray curable acrylate oligomer can also be used. Examples of such acrylate oligomers include polyester acrylates, epoxy acrylates, urethane acrylates, polyether acrylates, polybutadiene acrylates, and silicone acrylates.

[0055] The weight-average molecular weight of the above acrylate oligomers is preferably 50,000 or less, particularly preferably 1,000 to 50,000, and even more preferably 3,000 to 40,000. These acrylate oligomers may be used individually or in combination of two or more.

[0056] Furthermore, as the active energy ray curable component (C), an adduct acrylate polymer in which a group having a (meth)acryloyl group is introduced into the side chain can also be used. Such an adduct acrylate polymer can be obtained by using a copolymer of a (meth)acrylic acid ester and a monomer having a crosslinkable functional group in the molecule, and reacting a compound having a (meth)acryloyl group and a group that reacts with the crosslinkable functional group with a portion of the crosslinkable functional group of the copolymer.

[0057] The weight-average molecular weight of the above adduct acrylate polymer is preferably around 50,000 to 900,000, and particularly preferably around 100,000 to 500,000.

[0058] The active energy ray curable component (C) can be selected from the aforementioned polyfunctional acrylate monomers, acrylate oligomers, and adduct acrylate polymers, or it can be used in combination with two or more of these, or it can be used in combination with other active energy ray curable components.

[0059] The content of the active energy ray curable component (C) in the adhesive composition P is preferably at a lower limit of 1 part by mass or more, more preferably at a lower limit of 2 parts by mass or more, and particularly preferably at a lower limit of 3 parts by mass or more, per 100 parts by mass of (meth)acrylic acid ester polymer (A), from the viewpoint of improving initial step-following ability and improving the cohesive force of the resulting cured adhesive, thereby providing excellent step-following ability under high temperature and high humidity conditions. On the other hand, the content is preferably at an upper limit of 12 parts by mass or less, more preferably at a lower limit of 8 parts by mass or less, and particularly preferably at a lower limit of 6 parts by mass or less, from the viewpoint of preventing phase separation of the active energy ray curable component (C) from the (meth)acrylic acid ester polymer (A).

[0060] (1-4) Photopolymerization initiator (D) When ultraviolet light is used as the active energy ray to cure the adhesive obtained from the adhesive composition P, it is preferable that the adhesive composition P further contains a photopolymerization initiator (D). By including the photopolymerization initiator (D) in this way, the active energy ray curable component (C) can be polymerized efficiently, and the polymerization curing time and the amount of active energy ray irradiation can be reduced.

[0061] Examples of such photopolymerization initiators (D) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)ketone, benzophenone, p-phenylbenzophenone, Examples include 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyldimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoic acid ester, oligo[2-hydroxy-2-methyl-1[4-(1-methylvinyl)phenyl]propanone], 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, etc. These may be used individually or in combination of two or more.

[0062] The content of the photopolymerization initiator (D) in the adhesive composition P is preferably 0.1 to 30 parts by mass, particularly preferably 1 to 20 parts by mass, and even more preferably 5 to 12 parts by mass, per 100 parts by mass of the active energy ray curable component (C). As a result, the resulting adhesive is more likely to satisfy the mechanical properties (strain amount, relaxation modulus fluctuation value, storage modulus) described later, and will have superior step-following ability.

[0063] (1-5) Various additives The adhesive composition P may optionally contain various additives commonly used in acrylic adhesives, such as crosslinking agents, silane coupling agents, rust inhibitors, ultraviolet absorbers, antistatic agents, tackifiers, antioxidants, light stabilizers, softeners, and refractive index modifiers. The polymerization solvent and diluent described later are not included in the additives constituting the adhesive composition P.

[0064] As mentioned above, the adhesive composition P forms a pseudo-crosslinked structure and therefore does not require a crosslinking agent. As a result, aging is unnecessary when obtaining the adhesive. From this viewpoint, it is preferable that the adhesive composition P does not contain a crosslinking agent.

[0065] However, this does not exclude adhesive compositions P that contain a crosslinking agent. If the adhesive composition P contains a crosslinking agent, the amount of the crosslinking agent is preferably 0.1 parts by mass or less, and particularly preferably 0.01 parts by mass or less, per 100 parts by mass of the (meth)acrylic acid ester polymer (A). The crosslinking agent referred to herein is a crosslinking agent that forms a covalent bond with the (meth)acrylic acid ester polymer (A), such as an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an amine-based crosslinking agent, and so on.

[0066] (2) Preparation of adhesive composition The adhesive composition P can be prepared by preparing a (meth)acrylic acid ester polymer (A), mixing the obtained (meth)acrylic acid ester polymer (A) with an ionic compound (B) and an active energy ray curable component (C), and optionally adding a photopolymerization initiator (D), additives, etc.

[0067] (Meth)acrylic acid ester polymer (A) can be prepared by polymerizing a mixture of monomers constituting the polymer using a conventional radical polymerization method. Polymerization of (meth)acrylic acid ester polymer (A) is preferably carried out by solution polymerization using a polymerization initiator if desired. However, the present invention is not limited thereto, and polymerization may also be carried out without a solvent. Examples of polymerization solvents include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, etc., and two or more types may be used in combination.

[0068] Examples of polymerization initiators include azo compounds and organic peroxides, and two or more may be used in combination. Examples of azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane1-carbonitride), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), and 2,2'-azobis[2-(2-imidazolin-2-yl)propane].

[0069] Examples of organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl) peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, and diacetyl peroxide.

[0070] Furthermore, in the polymerization process described above, the weight-average molecular weight of the resulting polymer can be adjusted by incorporating a chain transfer agent such as 2-mercaptoethanol.

[0071] Once the (meth)acrylic acid ester polymer (A) is obtained, an ionic compound (B), an active energy ray curable component (C), and optionally a photopolymerization initiator (D), a diluent, an additive, etc. are added to the solution of the (meth)acrylic acid ester polymer (A), and thoroughly mixed to obtain a solvent-diluted adhesive composition P (coating solution). If any of the above components are used in solid form, or if precipitation occurs when mixed with other components in an undiluted state, that component may be dissolved or diluted in the diluent beforehand before mixing with the other components.

[0072] Examples of the diluent solvents used include aliphatic hydrocarbons such as hexane, heptane, and cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as methylene chloride and ethylene chloride; alcohols such as methanol, ethanol, propanol, butanol, and 1-methoxy-2-propanol; ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone, and cyclohexanone; esters such as ethyl acetate and butyl acetate; and cellosolve solvents such as ethyl cellosolve.

[0073] The concentration and viscosity of the coating solution prepared in this manner can be any value within the coating range and can be appropriately selected depending on the situation. For example, the adhesive composition P may be diluted to a concentration of 10 to 60% by mass. Note that the addition of a diluent is not a necessary condition when obtaining the coating solution; if the adhesive composition P has a coating viscosity, a diluent may not be added. In this case, the adhesive composition P becomes a coating solution where the polymerization solvent of the (meth)acrylic acid ester polymer (A) is used directly as the diluent.

[0074] [Adhesive] An adhesive according to one embodiment of the present invention is obtained from the adhesive composition P according to the above embodiment, and more specifically, is obtained by crosslinking (pseudo-crosslinking) the adhesive composition P described above.

[0075] Crosslinking of the adhesive composition P can usually be achieved by heat treatment. This heat treatment can also be combined with the drying process used to volatilize the diluent solvent, etc., from the coating of the adhesive composition P applied to the desired object.

[0076] The heating temperature for the heat treatment is preferably 50 to 150°C, and the heating time is preferably 10 seconds to 10 minutes.

[0077] When the adhesive composition P contains a crosslinking agent, it is desirable to allow a curing period after the heat treatment described above to complete the crosslinking reaction. However, the adhesive composition P according to this embodiment does not need to contain a crosslinking agent, and in that case, a curing period is unnecessary. This makes it possible to improve the productivity of adhesive sheets.

[0078] [Adhesive sheet] An adhesive sheet according to one embodiment of the present invention comprises at least an adhesive layer, and preferably an adhesive sheet having a release sheet laminated on one or both sides of the adhesive layer.

[0079] The adhesive sheet according to this embodiment is preferably used to bond one member to another member, and is particularly preferably used when at least one of the members has a step on at least the side facing the adhesive layer. A display component is a preferred example of the above member, and therefore, the adhesive sheet according to this embodiment is preferably used in optical applications, but is not limited thereto.

[0080] An adhesive sheet according to one embodiment of the present invention is characterized in that the adhesive layer is made of the adhesive described above. Preferably, the adhesive layer or the adhesive constituting the adhesive layer has the physical properties described below.

[0081] Adhesive sheets according to other embodiments of the present invention preferably have the following physical properties. Specifically, the strain amount (pre-curing strain) of the adhesive constituting the adhesive layer, 1210 seconds after applying a stress of 7950 Pa at 25°C, is preferably 30% or more and 1500% or less. Furthermore, the ratio of the strain amount (post-curing strain) of the cured adhesive, obtained by curing the adhesive constituting the adhesive layer with active energy rays, 1210 seconds after applying a stress of 7950 Pa at 25°C, to the pre-curing strain is preferably less than 1. In addition, the maximum relaxation modulus of elasticity G(t) of the adhesive constituting the adhesive layer, measured when the adhesive is strained by 10% according to JIS K7244-1, is specified as the maximum relaxation modulus of elasticity G(t). max (MPa) and the maximum relaxation modulus G(t) max The adhesive is subjected to a 10% strain for 3757 seconds after the measurement is taken, and the minimum relaxation modulus value measured during that time is defined as the minimum relaxation modulus G(t). min (MPa) is used, and it is preferable that the relaxation modulus variation value ΔlogG(t), calculated from the following formula (X), is between 1.2 and 3. ΔlogG(t)=logG(t) max -logG(t) min …(X)

[0082] The details of the measurement method for strain (%) and the relaxation modulus G(t) are shown in the test examples described later. Furthermore, "when a stress of 7950 Pa is applied to the adhesive" refers to the point in time when the stress applied to the adhesive reaches 7950 Pa.

[0083] In this embodiment, the adhesive sheet has the above-described physical properties of the adhesive layer, which allows the adhesive layer to deform easily and exhibits excellent stress relaxation properties, resulting in excellent step-following ability from the initial stage to high temperature and high humidity conditions. Furthermore, it exhibits excellent suppression of optical unevenness and excellent handling properties.

[0084] In particular, when the above strain amount is 30% or more, when an external force is applied to the adhesive layer, a moderate strain is generated and deformation is easily achieved, resulting in excellent step-following ability both initially and after autoclave treatment. Furthermore, when the above strain amount is 120% or more, the stress relaxation rate fluctuation value ΔlogG(t) tends to increase, making it easier to satisfy the desired range. From this viewpoint, the above strain amount is preferably 120% or more, more preferably 220% or more, particularly preferably 320% or more, and even more preferably 420% or more.

[0085] Furthermore, when the above-mentioned strain amount is 1500% or less, the adhesive exhibits high cohesiveness and excellent step-following properties even under high temperature and high humidity conditions. In addition, cohesive failure of the adhesive is less likely to occur, and the generation of adhesive residue when peeling the adhesive sheet from the adherend can be suppressed. Moreover, the resulting adhesive sheet has excellent handling properties. From this viewpoint, the above-mentioned strain amount is more preferably 1200% or less, particularly preferably 1000% or less, and even more preferably 900% or less.

[0086] Furthermore, when the ratio of strain amounts is less than 1, the cured adhesive layer exhibits high cohesiveness and tackiness, resulting in excellent step-following ability under high temperature and high humidity conditions. From this viewpoint, the ratio of strain amounts is preferably 0.9 or less, more preferably 0.8 or less, particularly preferably 0.7 or less, and even more preferably 0.6 or less. The lower limit of the ratio of strain amounts is preferably 0.1 or more, particularly preferably 0.2 or more, and even more preferably 0.3 or more, from the viewpoint of preventing the cured adhesive layer from becoming too hard and thus deteriorating its step-following ability under high temperature and high humidity conditions.

[0087] Furthermore, if the relaxation modulus fluctuation value ΔlogG(t) is 1.2 or higher, the material exhibits excellent stress relaxation properties. Therefore, after the adhesive sheet is applied to a step in the substrate, stress relaxation within the adhesive proceeds easily, and residual stress near the step is particularly easily relieved. As a result, even under high temperature and high humidity conditions, the occurrence of lifting and peeling induced by residual stress at the time of application to the step is suppressed, and excellent step-following properties are exhibited. From this viewpoint, the relaxation modulus fluctuation value ΔlogG(t) is more preferably 1.4 or higher, particularly preferably 1.5 or higher, and even more preferably 1.6 or higher.

[0088] Furthermore, when the relaxation modulus fluctuation value ΔlogG(t) is 3 or less, the adhesive is more likely to exhibit appropriate stress relaxation properties. From this viewpoint, the relaxation modulus fluctuation value ΔlogG(t) is more preferably 2.5 or less, particularly preferably 2.2 or less, and even more preferably 1.9 or less.

[0089] Preferably, the amount of strain of the cured adhesive, which is obtained by curing the adhesive constituting the above adhesive layer with active energy rays, 1210 seconds after applying a stress of 7950 Pa at 25°C, is 50% or more and 600% or less. Furthermore, the maximum relaxation modulus of elasticity measured when the cured adhesive is strained by 10% in accordance with JIS K7244-1 is defined as the maximum relaxation modulus of elasticity G(t). max (MPa) and the maximum relaxation modulus G(t) max The cured adhesive is subjected to a 10% strain for 3757 seconds after the measurement is taken, and the minimum relaxation modulus value measured during that time is defined as the minimum relaxation modulus G(t). min (MPa) is used, and the relaxation modulus variation value ΔlogG(t) calculated from the aforementioned formula (X) is preferably 1.2 or more and 3 or less.

[0090] Because the cured adhesive possesses the above-mentioned physical properties, the cured adhesive layer easily exhibits excellent cohesiveness and adhesion, resulting in particularly superior step-following capabilities under harsh conditions of high temperature and high humidity. It also exhibits excellent suppression of optical unevenness.

[0091] In particular, when the strain amount of the cured adhesive described above is 50% or more, it is easier to maintain good adhesion to the adherend (especially near steps), and it exhibits excellent step-following properties even under harsh high-temperature and high-humidity conditions. Furthermore, the stress relaxation rate fluctuation value ΔlogG(t) tends to increase, making it easier to satisfy the desired range. From this viewpoint, the strain amount of the cured adhesive described above is more preferably 120% or more, particularly preferably 180% or more, and even more preferably 240% or more.

[0092] Furthermore, if the strain amount of the cured adhesive is 600% or less, the adhesive exhibits high cohesiveness and excellent step-following ability even under harsh high-temperature and high-humidity conditions. In addition, cohesive failure of the adhesive is less likely to occur, and the generation of adhesive residue when peeling the adhesive sheet from the adherend can be suppressed. From this viewpoint, the strain amount of the cured adhesive is more preferably 500% or less, particularly preferably 400% or less, and even more preferably 300% or less.

[0093] On the other hand, if the relaxation modulus variation value ΔlogG(t) of the cured adhesive is 1.2 or higher, it exhibits excellent stress relaxation properties. Therefore, after the adhesive sheet is applied to a step in the substrate, stress relaxation within the adhesive proceeds easily, and residual stress near the step is particularly easily relieved. As a result, even under high temperature and high humidity conditions, the occurrence of lifting and peeling induced by residual stress at the time of application to the step is suppressed, and excellent step-following properties are exhibited. From this viewpoint, the relaxation modulus variation value ΔlogG(t) of the cured adhesive is more preferably 1.3 or higher, particularly preferably 1.4 or higher, and even more preferably 1.5 or higher.

[0094] Furthermore, if the relaxation modulus variation value ΔlogG(t) of the cured adhesive is 3 or less, the adhesive is more likely to exhibit appropriate stress relaxation properties. From this viewpoint, the relaxation modulus variation value ΔlogG(t) is more preferably 2.5 or less, particularly preferably 2 or less, and even more preferably 1.8 or less.

[0095] The gel fraction of the adhesive constituting the above adhesive layer is preferably 0% or more and 60% or less. Having the gel fraction within this range makes it easier to adjust the strain amount and the relaxation modulus variation value ΔlogG(t) to the aforementioned range. From this viewpoint, the gel fraction is more preferably 1 to 40%, particularly preferably 2 to 20%, even more preferably 2.5 to 10%, and most preferably 3 to 6% or less. In particular, having a gel fraction of 10% or less allows the adhesive to be said to be pseudo-crosslinked, resulting in superior initial step-following ability. The method for measuring the gel fraction of the adhesive is as shown in the test examples described later.

[0096] The gel fraction of the cured adhesive, obtained by curing the adhesive constituting the above adhesive layer with active energy rays, is preferably 10% or more as a lower limit, more preferably 20% or more, particularly preferably 30% or more, and even more preferably 35% or more. This makes it easier to obtain high cohesive force and high film strength, and results in superior step-following ability under harsh conditions of high temperature and high humidity. Furthermore, the gel fraction is preferably 90% or less as an upper limit, more preferably 75% or less, particularly preferably 65% ​​or less, and even more preferably 55% or less. This makes it easier to satisfy the strain amount mentioned above.

[0097] The storage modulus (G') of the adhesive constituting the above adhesive layer at 25°C is preferably 0.01 MPa or higher as a lower limit, more preferably 0.04 MPa or higher, particularly preferably 0.06 MPa or higher, and even more preferably 0.08 MPa or higher. As a result, the resulting adhesive is more likely to satisfy the aforementioned ranges for strain amount and relaxation modulus fluctuation value ΔlogG(t), resulting in better step-following ability under high temperature and high humidity conditions, and the adhesive sheet equipped with this adhesive has excellent handling properties. Furthermore, it is easier to satisfy the adhesive strength described later. The test method for the storage modulus (G') is as shown in the test example described later.

[0098] On the other hand, the storage modulus (G') of the adhesive constituting the adhesive layer at 25°C is preferably 1 MPa or less, more preferably 0.5 MPa or less, particularly preferably 0.3 MPa or less, and even more preferably 0.15 MPa or less. As a result, the resulting adhesive is more likely to satisfy the aforementioned strain amount and relaxation modulus fluctuation value ΔlogG(t), and will have better initial step-following ability. It will also be easier to satisfy the adhesive strength described later.

[0099] The storage modulus (G') of the adhesive constituting the above adhesive layer at 50°C is preferably 0.01 MPa or higher as a lower limit, more preferably 0.02 MPa or higher, particularly preferably 0.03 MPa or higher, and even more preferably 0.04 MPa or higher. As a result, the resulting adhesive is more likely to satisfy the aforementioned strain amount and relaxation modulus fluctuation value ΔlogG(t), and will have better step-following ability under high temperature and high humidity conditions. It will also be easier to satisfy the adhesive strength described later.

[0100] On the other hand, the storage modulus (G') of the adhesive constituting the adhesive layer at 50°C is preferably 1 MPa or less, more preferably 0.5 MPa or less, particularly preferably 0.3 MPa or less, and even more preferably 0.1 MPa or less. As a result, the resulting adhesive is more likely to satisfy the aforementioned ranges for strain amount and relaxation modulus fluctuation value ΔlogG(t), and will have better initial step-following ability, especially step-following ability after lamination by autoclaving, etc. It will also be easier to satisfy the adhesive strength described later.

[0101] The storage modulus (G') of the adhesive constituting the above adhesive layer at 85°C is preferably 0.01 MPa or higher as a lower limit, particularly preferably 0.015 MPa or higher, and even more preferably 0.02 MPa or higher. As a result, the resulting adhesive is more likely to satisfy the aforementioned strain amount and relaxation modulus fluctuation value ΔlogG(t), and will have better step-following ability under high temperature and high humidity conditions. It will also be easier to satisfy the adhesive strength described later.

[0102] On the other hand, the storage modulus (G') of the adhesive constituting the adhesive layer at 85°C is preferably 1 MPa or less, more preferably 0.5 MPa or less, particularly preferably 0.1 MPa or less, and even more preferably 0.03 MPa or less. As a result, the resulting adhesive is more likely to satisfy the aforementioned strain amount and relaxation modulus fluctuation value ΔlogG(t), and will have better step-following ability under high temperature and high humidity conditions. It will also be easier to satisfy the adhesive strength described later.

[0103] The storage modulus (G') at 25°C of the cured adhesive, obtained by curing the adhesive constituting the above adhesive layer with active energy rays, is preferably 0.02 MPa or higher as a lower limit, more preferably 0.08 MPa or higher, particularly preferably 0.1 MPa or higher, and even more preferably 0.12 MPa or higher. As a result, the cured adhesive is more likely to satisfy the aforementioned strain amount and relaxation modulus fluctuation value ΔlogG(t), and will have better step-following ability under high temperature and high humidity conditions. It will also be easier to satisfy the adhesive strength described later.

[0104] On the other hand, the storage modulus (G') of the cured adhesive at 25°C is preferably 2 MPa or less, more preferably 1 MPa or less, particularly preferably 0.6 MPa or less, and even more preferably 0.4 MPa or less. This makes it easier for the cured adhesive to satisfy the aforementioned strain amount and relaxation modulus fluctuation value ΔlogG(t), and also to satisfy the adhesive strength described later.

[0105] The storage modulus (G') at 50°C of the cured adhesive, obtained by curing the adhesive constituting the above adhesive layer with active energy rays, is preferably 0.02 MPa or higher as a lower limit, particularly preferably 0.03 MPa or higher, and even more preferably 0.04 MPa or higher. As a result, the cured adhesive is more likely to satisfy the aforementioned strain amount and relaxation modulus fluctuation value ΔlogG(t), and will have better step-following ability under high temperature and high humidity conditions. It will also be easier to satisfy the adhesive strength described later.

[0106] On the other hand, the storage modulus (G') of the cured adhesive at 50°C is preferably 2 MPa or less, more preferably 1 MPa or less, particularly preferably 0.5 MPa or less, and even more preferably 0.2 MPa or less. This makes it easier for the cured adhesive to satisfy the aforementioned strain amount and relaxation modulus fluctuation value ΔlogG(t), and also to satisfy the adhesive strength described later.

[0107] The storage modulus (G') at 85°C of the cured adhesive, obtained by curing the adhesive constituting the above adhesive layer with active energy rays, is preferably 0.01 MPa or higher as a lower limit, particularly preferably 0.02 MPa or higher, and even more preferably 0.03 MPa or higher. As a result, the cured adhesive is more likely to satisfy the aforementioned strain amount and relaxation modulus fluctuation value ΔlogG(t), and will have better step-following ability under high temperature and high humidity conditions. It will also be easier to satisfy the adhesive strength described later.

[0108] On the other hand, the storage modulus (G') of the cured adhesive at 85°C is preferably 2 MPa or less, more preferably 1 MPa or less, particularly preferably 0.1 MPa or less, and even more preferably 0.06 MPa or less. As a result, the cured adhesive is more likely to satisfy the aforementioned strain amount and relaxation modulus fluctuation value ΔlogG(t), resulting in better step-following ability under high temperature and high humidity conditions. It is also more likely to satisfy the adhesive strength described later.

[0109] The adhesive strength of the adhesive sheet according to this embodiment to soda-lime glass is preferably greater than 1 N / 25 mm, more preferably 10 N / 25 mm or more, particularly preferably 20 N / 25 mm or more, and even more preferably 24 N / 25 mm or more. Furthermore, the adhesive strength of the adhesive sheet according to this embodiment to alkali-free glass is preferably greater than 1 N / 25 mm, more preferably 10 N / 25 mm or more, particularly preferably 18 N / 25 mm or more, and even more preferably 22 N / 25 mm or more. When the lower limit of the adhesive strength to soda-lime glass or alkali-free glass is as described above, the ability to follow steps under high temperature and high humidity conditions is further improved. On the other hand, while there is no particular upper limit to the adhesive strength to the soda-lime glass or alkali-free glass, considering cases where reworkability is required, it is preferably 100 N / 25 mm or less, more preferably 60 N / 25 mm or less, particularly preferably 40 N / 25 mm or less, and even more preferably 30 N / 25 mm or less.

[0110] The adhesive strength mentioned above basically refers to the adhesive strength measured by the 180-degree peel method in accordance with JIS Z0237:2009, and the specific test method is as shown in the test examples described later.

[0111] After attaching the adhesive sheet according to this embodiment to soda-lime glass, the adhesive strength of the cured adhesive layer to the soda-lime glass, obtained by curing the adhesive layer with active energy rays, is preferably greater than 1 N / 25 mm, more preferably 10 N / 25 mm or more, particularly preferably 20 N / 25 mm or more, and even more preferably 26 N / 25 mm or more. Similarly, after attaching the adhesive sheet according to this embodiment to alkali-free glass, the adhesive strength of the cured adhesive layer to the alkali-free glass, obtained by curing the adhesive layer with active energy rays, is preferably greater than 1 N / 25 mm, more preferably 10 N / 25 mm or more, particularly preferably 20 N / 25 mm or more, and even more preferably 24 N / 25 mm or more. On the other hand, the upper limit of the adhesive strength to the soda-lime glass or alkali-free glass is preferably 100 N / 25 mm or less, more preferably 60 N / 25 mm or less, particularly preferably 40 N / 25 mm or less, and even more preferably 30 N / 25 mm or less. When the lower and upper limits of the adhesive strength of the cured adhesive layer to soda-lime glass or alkali-free glass are as described above, the ability to follow steps under high temperature and high humidity conditions is improved.

[0112] In this embodiment, the haze value of the adhesive layer in the adhesive sheet (a value measured in accordance with JIS K7136:2000) is preferably 1% or less, particularly preferably 0.8% or less, and even more preferably 0.6% or less, from the viewpoint of high transparency and suitability for optical applications. The lower limit of the haze value is usually 0% or more, preferably 0.1% or more, more preferably 0.2% or more, and particularly preferably 0.3% or more.

[0113] In this embodiment, the total light transmittance of the adhesive layer in the adhesive sheet (a value measured in accordance with JIS K7361-1:1997) is preferably 80% or more, more preferably 90% or more, particularly preferably 95% or more, and even more preferably 99% or more, from the viewpoint of ensuring good visibility of the display and suitability for optical applications. The upper limit of this total light transmittance is usually 100% or less.

[0114] Adhesives or adhesive layers having the above physical properties can preferably be obtained by the aforementioned adhesive composition P, but are not limited thereto.

[0115] Here, Figure 1 shows a specific configuration as an example of an adhesive sheet according to this embodiment. As shown in Figure 1, the adhesive sheet 1 according to one embodiment consists of two release sheets 12a and 12b, and an active energy ray curable adhesive layer 11 sandwiched between the two release sheets 12a and 12b so as to be in contact with the release surfaces of the two release sheets 12a and 12b. In this specification, the release surface of a release sheet refers to the surface of the release sheet that has release properties, and includes both surfaces that have undergone a release treatment and surfaces that exhibit release properties even without a release treatment.

[0116] 1. Each component 1-1. Adhesive layer The adhesive layer 11 of the adhesive sheet 1 according to this embodiment has the composition or physical properties described above.

[0117] In this embodiment, the thickness of the adhesive layer 11 (a value measured in accordance with JIS K7130) is preferably 1 μm or more, more preferably 5 μm or more, particularly preferably 10 μm or more, and even more preferably 20 μm or more. This makes it easier to exhibit the aforementioned adhesive strength and improves the ability to follow steps. Furthermore, the thickness of the adhesive layer 11 is preferably 500 μm or less, more preferably 200 μm or less, particularly preferably 100 μm or less, even more preferably 50 μm or less, and most preferably 30 μm or less. This suppresses appearance defects such as indentations and dents on the adhesive layer 11. It also makes it possible to make the laminate (display, etc.) obtained using the adhesive sheet 1 thinner. The adhesive layer 11 may be formed as a single layer or as multiple layers laminated together.

[0118] 1-2. Release sheet The release sheets 12a and 12b protect the adhesive layer 11 until the adhesive sheet 1 is used, and are peeled off when the adhesive sheet 1 (adhesive layer 11) is used. In the adhesive sheet 1 according to this embodiment, one or both of the release sheets 12a and 12b are not necessarily required.

[0119] Examples of release sheets 12a and 12b include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene-(meth)acrylic acid polymer film, ethylene-(meth)acrylic acid ester polymer film, polystyrene film, polycarbonate film, polyimide film, fluororesin film, etc. Crosslinked films of these can also be used. Furthermore, laminated films of these may also be used.

[0120] It is preferable that the release surfaces of the above-mentioned release sheets 12a and 12b are subjected to a release treatment. Examples of release agents used in the release treatment include alkyd, silicone, fluorine, unsaturated polyester, polyolefin, and wax-based release agents.

[0121] There are no particular restrictions on the thickness of the release sheets 12a and 12b, but they are usually around 20 to 200 μm.

[0122] 2. Manufacturing of adhesive sheets One example of manufacturing the adhesive sheet 1 involves applying a coating solution of the adhesive composition P to the release surface of one release sheet 12a (or 12b), performing a heat treatment to crosslink the adhesive composition P and form an adhesive layer 11, and then overlapping the release surface of the other release sheet 12b (or 12a) onto the adhesive layer 11. This yields the adhesive sheet 1. The heat treatment conditions are as described above. By using the adhesive composition P to form the adhesive layer 11, the adhesive sheet 1 can be manufactured without aging.

[0123] Another manufacturing example of the adhesive sheet 1 involves applying a coating solution of the adhesive composition P to the release surface of one release sheet 12a, performing a heat treatment to crosslink the adhesive composition P, and forming an adhesive layer to obtain a release sheet 12a with an adhesive layer. Similarly, applying a coating solution of the adhesive composition P to the release surface of the other release sheet 12b, performing a heat treatment to crosslink the adhesive composition P, and forming an adhesive layer to obtain a release sheet 12b with an adhesive layer. Then, the release sheets 12a and 12b with adhesive layers are bonded together so that both adhesive layers are in contact with each other to form an adhesive layer 11. This yields the adhesive sheet 1. According to this manufacturing example, stable production is possible even when the adhesive layer 11 is thick.

[0124] Methods for applying the coating solution of the above-mentioned adhesive composition P include, for example, bar coating, knife coating, roll coating, blade coating, die coating, and gravure coating.

[0125] [Laminate] A laminate according to one embodiment of the present invention comprises one display component, another display component, and a cured adhesive layer that bonds these display components together. The cured adhesive layer is obtained by curing the adhesive layer of the aforementioned adhesive sheet with active energy rays. This laminate is a display (display panel) or one of its components.

[0126] Preferably, at least one of the above-mentioned display component and the other display component has a step on the side to which it is bonded by the adhesive layer, and preferably, the step is a step caused by the printed layer. The cured adhesive layer has excellent step-following properties under high temperature and high humidity conditions (severe durability conditions), so even when the laminate is placed under severe high temperature and high humidity conditions (for example, 85°C, 85%RH, 500 hours), the occurrence of bubbles, lifting, peeling, etc. near the step is suppressed. Furthermore, the cured adhesive layer also has excellent optical unevenness suppression properties, so the occurrence of optical unevenness near the step is also suppressed.

[0127] Figure 2 shows a specific configuration as an example of a laminate according to this embodiment. As shown in Figure 2, the laminate 2 according to this embodiment is composed of a first display component 21, a second display component 22, and a cured adhesive layer 11' located between them and sandwiched between the first display component 21 and the second display component 22. Furthermore, in the laminate 2 according to this embodiment, the first display component 21 has a step on the side facing the cured adhesive layer 11', specifically, a step due to the presence or absence of the printed layer 3.

[0128] The laminate 2 may be, for example, a component that constitutes part of a display such as a liquid crystal (LCD) display, a light-emitting diode (LED) display, an organic electroluminescent (OLED) display, or electronic paper, or it may be the display itself. The display may be a touch panel or a flexible display that can be repeatedly bent.

[0129] The cured adhesive layer 11' in the laminate 2 described above is obtained by curing the adhesive layer 11 of the adhesive sheet 1 described above by irradiation with active energy rays. If the adhesive constituting the adhesive layer 11 is a crosslinked adhesive composition P, it is presumed that in the adhesive constituting this cured adhesive layer 11', polymerized active energy ray curable component (C) is entangled with a pseudo-crosslinked structure composed of a (meth)acrylic acid ester polymer (A) and an ionic compound (B), forming a higher-order structure.

[0130] The first display component 21 and the second display component 22 are not particularly limited as long as they can be bonded to the cured adhesive layer 11'. Furthermore, the first display component 21 and the second display component 22 may be made of the same material or different materials.

[0131] The first display component 21 is preferably a protective panel made of a glass plate, a plastic plate, or a laminate containing these materials. In this case, the printed layer 3 is generally formed in a frame-like shape on the side of the cured adhesive layer 11' of the first display component 21.

[0132] The above-mentioned glass plates are not particularly limited, but include, for example, chemically strengthened glass, alkali-free glass, quartz glass, soda-lime glass, barium-strontium-containing glass, aluminosilicate glass, lead glass, borosilicate glass, barium-borosilicate glass, etc. The thickness of the glass plate is not particularly limited, but is usually 0.1 to 5 mm, and preferably 0.2 to 2 mm.

[0133] The above-mentioned plastic sheet is not particularly limited, but examples include acrylic sheets, polycarbonate sheets, etc. The thickness of the plastic sheet is not particularly limited, but is usually 0.2 to 5 mm, preferably 0.4 to 3 mm, particularly preferably 0.6 to 2.5 mm, and even more preferably 0.8 to 2.1 mm.

[0134] Furthermore, various functional layers (such as transparent conductive films, metal layers, silica layers, hard coat layers, and anti-glare layers) may be provided on one or both sides of the above-mentioned glass or plastic plates, or optical components may be laminated on them. In addition, the transparent conductive films and metal layers may be patterned.

[0135] The second display component 22 is preferably an optical component to be attached to the first display component 21, a display module (for example, a liquid crystal (LCD) module, a light-emitting diode (LED) module, an organic electroluminescent (OLED) module, etc.), an optical component as part of a display module, or a laminate including a display module.

[0136] Examples of the optical components mentioned above include shatterproof films, polarizing plates (polarizing films), polarizers, phase difference plates (phase difference films), viewing angle compensation films, brightness enhancement films, contrast enhancement films, liquid crystal polymer films, diffusion films, semi-transparent reflective films, and transparent conductive films. Examples of shatterproof films include hard-coat films in which a hard-coat layer is formed on one side of a base film.

[0137] The material constituting the printed layer 3 is not particularly limited, and known printing materials can be used. The lower limit of the thickness of the printed layer 3, i.e., the height of the step, is preferably 3 μm or more, more preferably 5 μm or more, particularly preferably 7 μm or more, and most preferably 10 μm or more. By setting the lower limit as described above, sufficient concealment, such as making electrical wiring invisible to the viewer, can be ensured. Furthermore, the upper limit is preferably thinner than the thickness of the cured adhesive layer 11', preferably 80 μm or less, more preferably 50 μm or less, particularly preferably 25 μm or less, and even more preferably 20 μm or less. By setting the upper limit as described above, deterioration of the step-following ability of the cured adhesive layer 11' to the printed layer 3 can be prevented. In addition, it becomes possible to make the resulting laminate 2 thinner.

[0138] To manufacture the laminate 2 described above, one example is to peel off one of the release sheets 12a of the adhesive sheet 1 and adhere the exposed adhesive layer 11 of the adhesive sheet 1 to the side of the first display component 21 where the printed layer 3 is located. At this time, since the adhesive layer 11 has excellent step-following properties, the occurrence of gaps or lifting near the step caused by the printed layer 3 is suppressed. In addition, since the adhesive layer 11 also has excellent optical unevenness suppression properties, the occurrence of optical unevenness near the step is also suppressed.

[0139] Subsequently, the release sheet 12b is peeled off from the adhesive layer 11 of the adhesive sheet 1, and the exposed adhesive layer 11 of the adhesive sheet 1 is bonded to the second display component 22. Alternatively, the bonding order of the first display component 21 and the second display component 22 may be reversed.

[0140] In the above bonding process, autoclaving may be performed to ensure that the adhesive layer 11 adheres tightly to the first display component 21 and the second display component 22. Since the adhesive layer 11 has excellent step-following properties, the occurrence of air bubbles, lifting, etc., near the step is suppressed even at this stage. Autoclaving can be performed by conventional methods, and it is preferable to perform the process at a temperature of 40 to 80°C and a pressure of 0.3 to 1 MPa for 5 to 60 minutes.

[0141] After the bonding described above, the adhesive layer 11 in the laminate is irradiated with active energy rays. This irradiation of active energy rays hardens the adhesive layer 11, resulting in a hardened adhesive layer 11'. This yields the laminate 2 described above.

[0142] The irradiation of the adhesive layer 11 with energy rays is usually performed through either the first display component 21 or the second display component 22, preferably through the first display component 21 which serves as a protective panel.

[0143] Active energy rays refer to electromagnetic waves or charged particle beams that possess energy quanta, specifically including ultraviolet rays and electron beams. Among active energy rays, ultraviolet rays are particularly preferred because they are easy to handle.

[0144] Ultraviolet irradiation can be performed using high-pressure mercury lamps, fusion H lamps, xenon lamps, etc., with an illuminance of 50 to 1000 mW / cm². 2 It is preferable that the level be around 100-500 mW / cm². 2 It is preferable that the light intensity be around 50 to 10,000 mJ / cm². 2 Preferably, the concentration is 200-7000 mJ / cm². 2 It is more preferable that the concentration be 500-3000 mJ / cm². 2 It is particularly preferable that this is the case. On the other hand, electron beam irradiation can be performed by an electron beam accelerator or the like, and the electron beam irradiation dose is preferably about 10 to 1000 krad.

[0145] In the laminate 2 described above, the cured adhesive layer 11' has excellent step-following properties, so even when the laminate 2 is placed under severe high temperature and high humidity conditions (e.g., 85°C, 85%RH, 500 hours), the occurrence of bubbles, lifting, peeling, etc. near steps is suppressed. Furthermore, the cured adhesive layer 11' also has excellent optical unevenness suppression properties, so the occurrence of optical unevenness near steps is also suppressed.

[0146] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Accordingly, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0147] For example, either one or both of the release sheets 12a and 12b in the adhesive sheet 1 may be omitted, and a desired optical element may be laminated in place of the release sheets 12a and / or 12b. Furthermore, the first display component 21 does not have to have a printed layer 3 (step), or it may have a step other than the printed layer 3. Moreover, not only the first display component 21, but also the second display component 22 may have a step on the side of the cured adhesive layer 11'.

[0148] In this specification, when "X~Y" (where X and Y are any numbers) is written, unless otherwise specified, it includes the meaning of "greater than or equal to X and less than or equal to Y," as well as "preferably greater than X" or "preferably less than Y." Similarly, when "greater than or equal to X" (where X is any number) is written, unless otherwise specified, it includes the meaning of "preferably greater than X," and when "less than or equal to Y" (where Y is any number) is written, unless otherwise specified, it also includes the meaning of "preferably less than Y." [Examples]

[0149] The present invention will be described in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0150] [Example 1] 1. Preparation of (meth)acrylic acid ester polymer (A) (Meth)acrylic acid ester polymer (A) was prepared by copolymerizing 84 parts by mass of n-butyl acrylate, 15 parts by mass of (2-oxo-1,3-dioxolan-4-yl)methyl methacrylic acid as an ethylene carbonate-containing monomer, and 1 part by mass of 4-hydroxybutyl acrylate by solution polymerization. The molecular weight of this (meth)acrylic acid ester polymer (A) was measured by the method described later and found to be a weight-average molecular weight (Mw) of 750,000.

[0151] 2. Preparation of adhesive composition 100 parts by mass (on a solid content basis; the same applies hereinafter) of the (meth)acrylic acid ester polymer (A) obtained in step 1 above, 0.5 parts by mass of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) diluted with methyl ethyl ketone as an ionic compound (B), 3 parts by mass of a mixture of ethoxylated isocyanuric acid diacrylate and ethoxylated isocyanuric acid triacrylate (manufactured by Toagosei Co., Ltd., product name "M-315") as an active energy ray curable component (C), and 0.3 parts by mass of a mixture of benzophenone and 1-hydroxycyclohexyl phenyl ketone in a 1:1 mass ratio as a photopolymerization initiator (D) were mixed, stirred thoroughly, and diluted with methyl ethyl ketone to obtain a coating solution for the adhesive composition.

[0152] 3. Preparation of adhesive sheets The adhesive composition coating solution obtained in step 2 above was applied using a knife coater to the release surface of a heavy-release type release sheet (Lintec Corporation, product name "SP-PET382150"), which had one side of a polyethylene terephthalate film released with a silicone-based release agent. The coated layer was then heat-treated at 90°C for 1 minute to form an adhesive layer.

[0153] Next, the adhesive layer on the heavy-peel release sheet obtained above and a light-peel release sheet (Lintec Corporation, product name "SP-PET381130"), which was obtained by peeling one side of a polyethylene terephthalate film with a silicone-based release agent, were bonded together so that the peeled surface of the light-peel release sheet was in contact with the adhesive layer, thereby producing an adhesive sheet consisting of a heavy-peel release sheet / adhesive layer (thickness: 25 μm) / light-peel release sheet.

[0154] The thickness of the adhesive layer was measured in accordance with JIS K7130 using a constant-pressure thickness measuring instrument (TECLOCK Co., Ltd., product name "PG-02").

[0155] Here, Table 1 shows the respective formulations (solid content equivalent) of the adhesive composition when (meth)acrylic acid ester polymer (A) is present in 100 parts by mass (solid content equivalent). Details of the abbreviations and other terms listed in Table 1 are as follows. [(meth)acrylic acid ester polymer (A)] BA: n-butyl acrylate CARBOM: Methyl methacrylate (2-oxo-1,3-dioxolan-4-yl) 4HBA: 4-hydroxybutyl acrylate [Ionic compounds (B)] Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) [Activated energy ray-curing component (C)] A mixture of ethoxylated isocyanuric acid diacrylate and ethoxylated isocyanuric acid triacrylate (manufactured by Toagosei Co., Ltd., product name "M-315") [Photopolymerization initiator (D)] A mixture of benzophenone and 1-hydroxycyclohexyl phenyl ketone in a 1:1 mass ratio. [Crosslinking agent] Trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name "TD-75")

[0156] [Example 2, Comparative Examples 1-2] An adhesive sheet was prepared in the same manner as in Example 1, except that the amounts of ionic compound (B), active energy ray curable component (C), and photopolymerization initiator (D) were changed as shown in Table 1.

[0157] [Comparative Example 3] 100 parts by mass of the (meth)acrylic acid ester polymer (A) obtained in step 1 of Example 1 and 0.22 parts by mass of trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name "TD-75") as a crosslinking agent were mixed, thoroughly stirred, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.

[0158] The coating solution of the obtained adhesive composition was applied using a knife coater to the peeled surface of a heavy-peel release sheet (Lintec Corporation, product name "SP-PET382150"), which was obtained by peeling one side of a polyethylene terephthalate film with a silicone-based release agent. Then, the coating film was heat-treated at 90°C for 1 minute to form a coating layer.

[0159] Next, the coating layer on the heavy-peel release sheet obtained above and a light-peel release sheet (Lintec Corporation, product name "SP-PET381130"), which was obtained by peeling one side of a polyethylene terephthalate film with a silicone-based release agent, were bonded together so that the peeled surface of the light-peel release sheet was in contact with the coating layer. By curing under conditions of 23°C and 50% RH for 7 days, an adhesive sheet consisting of a heavy-peel release sheet / adhesive layer (thickness: 25 μm) / light-peel release sheet was produced.

[0160] [Comparative Example 4] 1. Preparation of (meth)acrylic acid ester polymer (A) (Meth)acrylic acid ester polymer (A) was prepared by copolymerizing 99 parts by mass of n-butyl acrylate and 1 part by mass of 4-hydroxybutyl acrylate by solution polymerization. The molecular weight of this (meth)acrylic acid ester polymer (A) was measured by the method described later and found to be 750,000.

[0161] 2. Preparation of adhesive composition 100 parts by mass of the (meth)acrylic acid ester polymer (A) obtained in step 1 above and 0.5 parts by mass of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) diluted with methyl ethyl ketone as the ionic compound (B) were mixed, stirred thoroughly, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.

[0162] 3. Manufacturing of adhesive sheets Using the coating solution of the adhesive composition obtained in step 2 above, an adhesive sheet was prepared in the same manner as in Example 1.

[0163] [Comparative Example 5] 100 parts by mass of the (meth)acrylic acid ester polymer (A) obtained in step 1 of Comparative Example 4 and 0.22 parts by mass of trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name "TD-75") as a crosslinking agent were mixed, thoroughly stirred, and diluted with methyl ethyl ketone to obtain a coating solution of the adhesive composition.

[0164] Using the coating solution of the obtained adhesive composition, an adhesive sheet was prepared in the same manner as in Comparative Example 3.

[0165] [Comparative Example 6] In Comparative Example 4, 100 parts by mass of the (meth)acrylic acid ester polymer (A) obtained in Step 1 was mixed with 0.5 parts by mass of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) diluted with methyl ethyl ketone as the ionic compound (B), and 0.22 parts by mass of trimethylolpropane-modified xylylene diisocyanate (manufactured by Soken Chemical Co., Ltd., product name "TD-75") as a crosslinking agent. The mixture was thoroughly stirred and then diluted with methyl ethyl ketone to obtain a coating solution for the adhesive composition.

[0166] Using the coating solution of the obtained adhesive composition, an adhesive sheet was prepared in the same manner as in Comparative Example 3.

[0167] The weight-average molecular weight (Mw) mentioned above is the weight-average molecular weight in polystyrene terms, measured using gel permeation chromatography (GPC) under the following conditions (GPC measurement). <Measurement conditions> • GPC measuring device: Tosoh Corporation, HLC-8020 • GPC column (passes through in the following order): Manufactured by Tosoh Corporation TSK Guard Column HXL-H TSK gel GMHXL (x2) TSK gel G2000HXL • Measurement solvent: tetrahydrofuran ·Measurement temperature: 40℃

[0168] [Test Example 1] (Measurement of gel fraction) The adhesive sheets prepared in the examples and comparative examples were cut to a size of 80 mm x 80 mm, and the adhesive layer was wrapped in a polyester mesh (mesh size 200). The mass was weighed using a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. This mass was denoted as M1.

[0169] Next, the adhesive wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23°C) for 24 hours. The adhesive was then removed and air-dried for 24 hours at 23°C and 50% relative humidity, followed by 12 hours of drying in an oven at 80°C. After drying, its mass was measured using a precision balance, and the mass of the adhesive alone was calculated by subtracting the mass of the mesh alone. This mass was denoted as M2. The gel fraction (%) is expressed as (M2 / M1) × 100. This allowed for the derivation of the gel fraction of the adhesive (before UV exposure). The results are shown in Table 2.

[0170] Furthermore, the adhesive layer of the adhesive sheet prepared in the example was irradiated with active energy rays (ultraviolet light; UV) through a light-peel release sheet under the following conditions to cure the adhesive layer and obtain a cured adhesive layer. The gel fraction (after UV) of the adhesive in this cured adhesive layer was derived in the same manner as described above. The results are shown in Table 2.

[0171] <Activated energy ray irradiation conditions> • Use of high-pressure mercury lamps ·Illuminance 200mW / cm 2 , light intensity 1000mJ / cm 2 • The UV irradiance / light intensity meter used is the "UVPF-A1" manufactured by iGraphics Co., Ltd.

[0172] [Test Example 2] (Measurement of Storage Modulus) Multiple layers of adhesive sheets prepared in the examples and comparative examples were laminated to form a laminate with a thickness of 0.8 mm. From the resulting laminate of adhesive layers, a cylindrical object with a diameter of 8 mm (height 0.8 mm) was punched out and used as a sample.

[0173] For the above samples, dynamic viscoelasticity was measured using the torsional shear method with a viscoelasticity measuring device (Anton Paar, product name "MCR302") in accordance with JIS K7244-1, under the following conditions, and the storage modulus (G') (before UV; MPa) at 25°C, 50°C, and 85°C was measured. The results are shown in Table 2. Measurement frequency: 1Hz Measurement temperature range: -20℃ to 150℃ Heating rate: 3°C / min

[0174] Furthermore, the adhesive sheets prepared in the examples were irradiated with active energy rays (ultraviolet light; UV) under the same conditions as in Test Example 1 to cure the adhesive, thereby obtaining samples after active energy ray irradiation. The storage modulus (after UV; MPa) at 23°C was measured for the obtained samples after active energy ray irradiation in the same manner as for the samples before active energy ray irradiation. The results are shown in Table 2.

[0175] [Test Example 3] (Measurement of Relaxation Modulus Fluctuation Value) Multiple adhesive layers from the adhesive sheets prepared in the examples and comparative examples were laminated to form a 0.8 mm thick laminate. From the resulting laminate of adhesive layers, a cylindrical object with a diameter of 8 mm (height 0.8 mm) was punched out and used as a sample.

[0176] For the above sample, in accordance with JIS K7244-1, the relaxation modulus of elasticity G(t)(MPa) was measured by continuously straining the adhesive by 10% under the following conditions using a viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR302"). From the measurement results, the maximum relaxation modulus of elasticity G(t) was determined. max (MPa) is derived, and the maximum relaxation modulus G(t) is also derived. max The minimum relaxing modulus of elasticity G(t) measured within 3757 seconds after the measurement was taken. min The value (MPa) was derived. Measurement temperature: 25℃ Measurement points: 1000 points (logarithmic plot)

[0177] The obtained maximum relaxation modulus G(t) max (MPa) and minimum relaxation modulus G(t) min The relaxation modulus variation value ΔlogG(t)(before UV) was calculated from (MPa) based on the following equation (X). The results are shown in Table 2. ΔlogG(t)=logG(t) max -logG(t) min …(X)

[0178] Furthermore, for the adhesive sheets prepared in the examples, samples were irradiated with active energy rays (ultraviolet light; UV) under the same conditions as in Test Example 1 to cure the adhesive, thereby obtaining samples after active energy ray irradiation. For the obtained samples after active energy ray irradiation, the relaxation modulus change value ΔlogG(t)(after UV) was calculated in the same manner as for the samples before active energy ray irradiation. The results are shown in Table 2.

[0179] [Test Example 4] (Measurement of Strain Amount) Multiple adhesive layers from the adhesive sheets prepared in the examples and comparative examples were laminated to form a laminate with a thickness of 0.2 mm. From the resulting laminate of adhesive layers, a 15 mm x 15 mm rectangular parallelepiped (height 0.2 mm) was punched out and used as a sample.

[0180] For the above samples, in accordance with JIS K7244-1, a viscoelasticity measuring device (manufactured by Anton Paar, product name "MCR302") was used to continuously apply a constant stress to the samples under the following conditions, and the amount of strain (before UV exposure; %) was measured 1210 seconds after the start of stress application. The results are shown in Table 2. Measurement temperature: 25℃ Number of measurement points: 321 Stress: 7950 Pa

[0181] Furthermore, for the adhesive sheets prepared in the examples, samples were irradiated with active energy rays (ultraviolet light; UV) under the same conditions as in Test Example 1 to cure the adhesive, thereby obtaining samples after active energy ray irradiation. The amount of strain (after UV; %) was measured for the obtained samples after active energy ray irradiation in the same manner as for the samples before active energy ray irradiation. The results are shown in Table 2.

[0182] Furthermore, the ratio (post-UV / pre-UV) of the strain after UV exposure (strain after curing) to the strain before UV exposure (strain before curing) obtained from the above measurements was calculated. The results are shown in Table 2.

[0183] [Test Example 5] (Measurement of haze value) The adhesive layers of the adhesive sheets prepared in the examples and comparative examples were bonded to glass to serve as measurement samples. After background measurements were performed on the glass, the haze value (%) of the measurement samples was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "SH-7000") in accordance with JIS K7136:2000. The results are shown in Table 2. For the adhesive sheets prepared in the examples, the adhesive layer was cured by irradiation with active energy rays under the same conditions as in Test Example 1, and then the above measurements were performed.

[0184] [Test Example 6] (Measurement of total light transmittance) The adhesive layers of the adhesive sheets prepared in the examples and comparative examples were bonded to glass to serve as measurement samples. After background measurements were performed on the glass, the total light transmittance (%) of the measurement samples was measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., product name "SH-7000") in accordance with JIS K7361-1:1997. The results are shown in Table 2. For the adhesive sheets prepared in the examples, the adhesive layer was cured by irradiation with active energy rays under the same conditions as in Test Example 1, and then the above measurements were performed.

[0185] [Test Example 7] (Measurement of Adhesion) In the examples and comparative examples, the light-peel release sheet was peeled off from the adhesive sheets, and the exposed adhesive layer was laminated to the easy-adhesion layer of a polyethylene terephthalate (PET) film (Toyobo Co., Ltd., product name "PET TA063", thickness: 100 μm) to obtain a laminate of heavy-peel release sheet / adhesive layer / PET film. In Comparative Example 3, an adhesive sheet consisting of a heavy-peel release sheet / adhesive layer (thickness: 25 μm) was prepared without using a light-peel release sheet during the manufacturing of the adhesive sheet, and the easy-adhesion layer of a PET film (Toyobo Co., Ltd., product name "PET TA063", thickness: 100 μm) was laminated to the exposed adhesive layer to obtain a laminate of heavy-peel release sheet / adhesive layer / PET film. The laminate obtained as described above was cut to a width of 25 mm and a length of 100 mm.

[0186] Under conditions of 23°C and 50%RH, the heavy-peel release sheet was peeled from the laminate, and the exposed adhesive layer was attached to the following two types of substrates. The substrates were then pressurized at 0.5 MPa and 50°C for 20 minutes in an autoclave manufactured by Kurihara Seisakusho Co., Ltd. After leaving the substrates at 23°C and 50%RH for 24 hours, the adhesive strength (before UV testing; N / 25mm) of the laminate of PET film and adhesive layer was measured when it was peeled from the substrate using a tensile testing machine (Tensilon, manufactured by Orientec Co., Ltd.) under conditions of a peeling speed of 300 mm / min and a peeling angle of 180 degrees. Measurements other than those described herein were performed in accordance with JIS Z0237:2009. The results are shown in Table 2. In the table, "CF" indicates that cohesive failure occurred in the adhesive layer. <Adherend> • Soda-lime glass sheet (manufactured by Nippon Sheet Glass Co., Ltd., product name "Soda-lime Glass", thickness: 1.1 mm) • Alkali-free glass plate (manufactured by Nippon Sheet Glass Co., Ltd., product name "Eagle-X", thickness: 1.1 mm)

[0187] Furthermore, for the adhesive sheets prepared in the examples, the adhesive layer was attached to the substrate in the same manner as described above, autoclaved, and left for 24 hours under conditions of 23°C and 50% RH. Then, the adhesive layer was cured by irradiating it with active energy rays through a PET film under the same conditions as in Test Example 1. The adhesive strength (after UV; N / 25mm) of the cured adhesive layer was measured in the same manner as described above. The results are shown in Table 2.

[0188] [Test Example 8] (Evaluation of Handling) When peeling the light-peel release sheet from the adhesive sheets prepared in the examples and comparative examples, the handling properties (ease of handling the adhesive sheet) were evaluated based on the following criteria. The results are shown in Table 2. ◎: When peeling, the adhesive layer did not deform, string, or undergo cohesive failure, allowing the easy-peel release sheet to be easily removed. ○: During peeling, the adhesive layer deformed, but it was possible to peel off the light-peel type release sheet without stringing or cohesive failure. ×: When peeling, the adhesive layer deformed significantly, stringing occurred, and cohesive failure occurred, making it difficult to peel off the light-peel type release sheet.

[0189] [Test Example 9] (Evaluation of step-following ability) A glass plate (NSG Precision Co., Ltd., product name "Corning Glass Eagle XG", 90mm high x 50mm wide x 0.5mm thick) was screen-printed with UV-curing ink (Teikoku Ink Co., Ltd., product name "POS-911 Sumi") in a frame-like pattern (outer dimensions: 90mm high x 50mm wide, 5mm thick). Then, it was irradiated with ultraviolet light (80W / cm²). 2 Using two metal halide lamps (lamp height 15 cm, belt speed 10-15 m / min), the printed UV-curable ink was cured to produce stepped glass plates with raised edges (height of raised edges: 5 μm, 10 μm, 15 μm).

[0190] The light-peel release liner was peeled off the adhesive sheets manufactured in the examples and comparative examples, and the exposed adhesive layer was laminated to the easy-adhesion layer of a polyethylene terephthalate (PET) film (Toyobo Co., Ltd., product name "PET TA063", thickness: 100 μm) having an easy-adhesion layer. Next, the heavy-peel release liner was peeled off to expose the adhesive layer, and using a laminator (Fujipla Co., Ltd., product name "LPD3214"), the adhesive layer was laminated to each stepped glass plate so that it covered the entire printed surface in a frame-like manner, and these were used as samples. At this stage, the step-following ability after lamination (immediately after application) was evaluated based on the following criteria. The results are shown in Table 2. <Adjustability to follow uneven surfaces after lamination> A: No air bubbles, lifting, or peeling were observed near the step. B: Air bubbles with a diameter of 0.2 mm or less were observed near the step, but no lifting or peeling was observed. C: Bubbles, lifting, and peeling with a diameter of 0.2 mm or more were observed near the step.

[0191] Subsequently, the above samples were autoclaved at 50°C and 0.5 MPa for 20 minutes, and then left at atmospheric pressure, 23°C, and 50% RH for 24 hours. At this stage, the step-following ability (initial step-following ability) after autoclaving was evaluated based on the following criteria. The results are shown in Table 2. <Step-following ability after autoclave treatment> A: No air bubbles, lifting, or peeling were observed near the step. B: Air bubbles with a diameter of 0.2 mm or less were observed near the step, but no lifting or peeling was observed. C: Bubbles, lifting, and peeling with a diameter of 0.2 mm or more were observed near the step.

[0192] Next, the example samples were cured by irradiating them with active energy rays through a PET film under the same conditions as in Test Example 1. After the curing of the adhesive layer in the example samples, and after the autoclave treatment described above in the comparative example samples, the samples were stored for 96 hours and 500 hours under high temperature and high humidity conditions of 85°C and 85%RH (durability test). After the durability test, the samples were removed to an environment of 23°C and 50%RH, and the cured adhesive layer and the adhesive layer (especially near the step caused by the printed layer) were visually inspected. The step-following ability after high temperature and high humidity conditions was evaluated based on the following criteria. The results are shown in Table 2. <Step-following ability under high temperature and high humidity conditions> A: No air bubbles, lifting, or peeling were observed near the step. B: Air bubbles with a diameter of 0.2 mm or less were observed near the step, but no lifting or peeling was observed. C: Bubbles larger than 0.2 mm in diameter, or lifting / peeling, were observed near the step.

[0193] [Test Example 10] (Evaluation of Optical Unevenness) A glass plate (NSG Precision Co., Ltd., product name "Corning Glass Eagle XG", 90mm high x 50mm wide x 0.5mm thick) was screen-printed with UV-curing ink (Teikoku Ink Co., Ltd., product name "POS-911 Sumi") in a frame-like pattern (outer dimensions: 90mm high x 50mm wide, 5mm thick). Then, it was irradiated with ultraviolet light (80W / cm²). 2 Using two metal halide lamps (lamp height 15 cm, belt speed 10-15 m / min), the printed UV-curable ink was cured to produce a stepped glass plate with a step (step height: 15 μm) created by the printing.

[0194] The light-peel release liner was peeled off the adhesive sheets prepared in the examples and comparative examples, and the exposed adhesive layer was laminated to the easy-adhesion layer of a polyethylene terephthalate (PET) film (Toyobo Co., Ltd., product name "PET TA063", thickness: 100 μm) having an easy-adhesion layer. Next, the heavy-peel release liner was peeled off to expose the adhesive layer, and it was laminated to each stepped glass plate using a laminator (Fujipla Co., Ltd., product name "LPD3214") so that the adhesive layer covered the entire printed surface in a frame-like manner. After that, it was autoclaved for 20 minutes under conditions of 50°C and 0.5 MPa, and left for 24 hours at atmospheric pressure, 23°C, and 50% RH. In the comparative example, this was used as a sample. On the other hand, in the examples, the adhesive layer was cured by irradiating it with active energy rays through the PET film under the same conditions as in Test Example 1, and this was used as a sample.

[0195] For the above samples, the vicinity of the step caused by the printed layer was visually inspected, and optical uniformity was evaluated based on the following criteria. The results are shown in Table 2. <Presence or absence of optical irregularities> ○: No optical irregularities were observed near the step. ×: Optical irregularities were observed near the step.

[0196] In Comparative Example 4, due to poor handling and the difficulty in preparing samples for Test Examples 2, 3, 4, and 9, Test Examples 2, 3, 4, and 9 were not performed.

[0197] [Table 1]

[0198] [Table 2]

[0199] As can be seen from Table 2, the adhesive sheets produced in the examples exhibited excellent step-following ability after autoclave treatment (initial step-following ability) and step-following ability after high temperature and high humidity conditions (85°C, 85%RH, 500 hours), as well as excellent suppression of optical unevenness. Furthermore, the adhesive sheets produced in the examples exhibited excellent optical properties, high adhesive strength, and excellent handling properties. [Industrial applicability]

[0200] The adhesive sheet according to the present invention can be suitably used, for example, for bonding a protective panel having a step to a desired display component. [Explanation of Symbols]

[0201] 1…Adhesive sheet 11…Adhesive layer 12a, 12b… Release sheets 2…Laminate 11'…Adhesive layer after curing 21...First display component 22...Second display component 3...Printing layer

Claims

1. The monomer units that make up the polymer are as follows: (1) 【Chemistry 1】 A (meth)acrylic acid ester polymer (A) containing an ethylene carbonate-containing monomer having the ethylene carbonate structure shown, At least one ionic compound (B) selected from the group consisting of potassium bis(fluorosulfonyl)imide, lithium bis(fluorosulfonyl)imide, potassium bis(fluoromethanesulfonyl)imide, lithium bis(fluoromethanesulfonyl)imide, potassium bis(trifluoromethanesulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide, Active energy ray curing component (C) and An adhesive composition characterized by containing [a certain substance].

2. The adhesive composition according to claim 1, characterized in that the (meth)acrylic acid ester polymer (A) contains 0.5% by mass or more and 40% by mass or less of the ethylene carbonate-containing monomer as monomer units constituting the polymer.

3. The adhesive composition according to claim 1, characterized in that the content of the ionic compound (B) in the adhesive composition is 0.1 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the (meth)acrylic acid ester polymer (A).

4. The adhesive composition according to claim 1, characterized in that the amount of crosslinking agent in the adhesive composition is 0.1 parts by mass or less per 100 parts by mass of the (meth)acrylic acid polymer (A).

5. An adhesive obtained by crosslinking the adhesive composition described in claim 1.

6. An adhesive sheet having at least an adhesive layer, The adhesive layer comprises the adhesive described in claim 5. An adhesive sheet characterized by the following features.

7. The amount of strain of the adhesive constituting the adhesive layer, 1210 seconds after a stress of 7950 Pa is applied to the adhesive at 25°C, is 30% or more and 1500% or less. The ratio of the strain amount to the amount of strain of the cured adhesive, which is obtained by curing the adhesive constituting the adhesive layer with active energy rays, at 25°C, 1210 seconds after a stress of 7950 Pa is applied to the cured adhesive, is less than 1. The maximum relaxation modulus of elasticity of the adhesive constituting the adhesive layer, measured when the adhesive is strained by 10%, according to JIS K7244-1, is defined as the maximum relaxation modulus of elasticity G(t). ｍａｘ (MPa) and the maximum relaxation modulus G(t) ｍａｘ The adhesive is subjected to a 10% strain for 3757 seconds after the measurement is taken, and the minimum relaxation modulus value measured during that time is defined as the minimum relaxation modulus G(t). ｍｉｎ The adhesive sheet according to claim 6, characterized in that the relaxation modulus variation value ΔlogG(t), calculated from the following formula (X), is 1.2 or more and 3 or less, where (MPa) is the coefficient of elasticity. ΔlogG(t)=logG(t) ｍａｘ -logG(t) ｍｉｎ …(X)

8. The adhesive sheet according to claim 7, characterized in that the amount of strain of the cured adhesive, which is obtained by curing the adhesive constituting the adhesive layer with active energy rays, 1210 seconds after a stress of 7950 Pa is applied to the cured adhesive at 25°C is 50% or more and 600% or less.

9. The maximum relaxation modulus of elasticity G(t) of the cured adhesive obtained by curing the adhesive constituting the adhesive layer with active energy rays, according to JIS K7244-1, is measured when the cured adhesive is strained by 10%. ｍａｘ (MPa) and the maximum relaxation modulus G(t) ｍａｘ The cured adhesive is subjected to a 10% strain for 3757 seconds after the measurement is taken, and the minimum relaxation modulus value measured during that time is defined as the minimum relaxation modulus G(t). ｍｉｎ The adhesive sheet according to claim 7, characterized in that the relaxation modulus variation value ΔlogG(t) calculated from formula (X) is 1.2 or more and 3 or less, where (MPa) is the coefficient of elasticity.

10. The adhesive sheet comprises two release sheets. The adhesive layer is sandwiched between the two release sheets so as to be in contact with the release surfaces of the two release sheets. The adhesive sheet according to any one of claims 6 to 9, characterized by the features described herein.

11. One display component, Other display component members, A cured adhesive layer that bonds the first display component and the other display component to each other. A laminate comprising, The cured adhesive layer is a cured adhesive layer obtained by curing the adhesive layer of the adhesive sheet described in any one of claims 6 to 9 using active energy rays. A laminate characterized by the following features.

12. The laminate according to claim 11, characterized in that at least one of the one display element component and the other display element component has a step on the side to which it is bonded by the adhesive layer.

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