Adhesive sheet, laminate, and method of using adhesive sheet

Abstract

To provide an adhesive sheet which is suitable as an adhesive for forming a laminate of a resin plate and a film base material, and is especially suitable as an adhesive for forming a laminate that is less likely to cause warpage and stickiness on the end even if the resin plate and the film base material in the laminate are worked at the same time.SOLUTION: An adhesive sheet includes an adhesive layer for bonding a resin plate and a film base material, wherein the adhesive layer contains a crosslinked body of an acrylic high molecular weight polymer (A) having a mass average molecular weight of 500,000 or more and 2,000,000 or less, and an acrylic low molecular weight polymer (B) having a mass average molecular weight of 3,000 or more and 50,000 or less, and the adhesive layer has a storage elastic modulus at 25°C of 0.2-2 MPa.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an adhesive sheet, a laminate, and a method of using an adhesive sheet.

Background Art

[0002] Conventionally, display devices such as liquid crystal displays (LCDs) and input devices such as touch panels used in combination with display devices have been widely used. For these input devices such as touch panels, for the purpose of improving their visibility, a cover panel such as a resin plate is bonded to the surface of a functional film (film base material) constituting the touch panel. An adhesive sheet is used to bond the functional film and the cover panel.

[0003] When bonding a functional film and a cover panel with an adhesive film, for example, Patent Document 1 discloses a method using a so-called after-cure process. In this method, after bonding the functional film and the cover panel with an adhesive film, after-cure, that is, irradiating ultraviolet rays, can firmly bond the functional film and the cover panel.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, laminates obtained by bonding a functional film and a cover panel using ultraviolet light were prone to warping and cracking during processing. Furthermore, because the functional film and cover panel required an after-curing process using ultraviolet light to bond them, processing the laminate also required a separate after-curing process after lamination, resulting in a large number of steps.

[0006] The present invention has been made in view of the above, and aims to provide an adhesive sheet suitable as an adhesive for forming a laminate of a resin plate and a film substrate, and in particular suitable as an adhesive for forming a laminate that is less prone to warping and stickiness at the edges even when the resin plate and film substrate in the laminate are processed simultaneously, as well as a laminate equipped with the adhesive sheet and a method for manufacturing the adhesive sheet. [Means for solving the problem]

[0007] The inventors of this invention conducted extensive research to achieve the above objectives and, as a result, discovered that these objectives can be achieved by using an adhesive layer formed from specific components, thus completing the present invention.

[0008] In other words, the present invention encompasses, for example, the subject matter described in the following sections. Item 1 An adhesive sheet comprising an adhesive layer for bonding a resin plate and a film substrate, The adhesive layer contains a crosslinked acrylic high molecular weight polymer (A) with a mass-average molecular weight of 500,000 or more and 2,000,000 or less, and an acrylic low molecular weight polymer (B) with a mass-average molecular weight of 3,000 or more and 50,000 or less. The adhesive layer is an adhesive sheet having a storage modulus of 0.2 to 2 MPa at 25°C. Section 2 The adhesive sheet according to item 1, wherein the gel fraction of the adhesive layer is 60% or more. Section 3 The adhesive sheet according to item 1 or 2, wherein the adhesive strength of the adhesive layer against glass is 10 N / 25 mm or more. Section 4 The adhesive sheet according to any one of claims 1 to 3, wherein the thickness of the adhesive layer is 5 to 50 μm. Section 5 The adhesive sheet according to any one of claims 1 to 4, wherein the amount of carboxyl group-containing monomer units is 3 to 20 parts by mass per 100 parts by mass of the total mass of structural units in the acrylic high molecular weight polymer (A). Section 6 The adhesive sheet according to any one of claims 1 to 5, wherein the Tg of the acrylic low molecular weight polymer (B) is 80°C or higher. Section 7 A laminate comprising an adhesive sheet as described in any one of items 1 to 6 and a resin plate. Section 8 A method of using an adhesive sheet as described in any one of items 1 to 6, A step of bonding the adhesive sheet and the film substrate to obtain an adhesive-coated film, A lamination process to obtain a laminate by bonding the adhesive-coated film and the resin plate, A step of subjecting the laminate to machining, A method for using an adhesive sheet, comprising the following features. [Effects of the Invention]

[0009] The adhesive sheet of the present invention is suitable as an adhesive for forming a laminate of a resin plate and a film substrate, and is particularly suitable as an adhesive for forming a laminate that is less prone to warping and stickiness at the edges, even when the resin plate and film substrate in the laminate are processed simultaneously. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below. In this specification, the expressions "containing" and "including" include the concepts of "containing," "including," "substantially consisting of," and "consisting only of."

[0011] 1. Adhesive sheet The adhesive sheet of the present invention includes an adhesive layer for bonding a resin plate and a film substrate. The adhesive layer contains a crosslinked body of an acrylic high molecular weight polymer (A) having a mass average molecular weight of 500,000 or more and 2,000,000 or less, and an acrylic low molecular weight polymer (B) having a mass average molecular weight of 3,000 or more and 50,000 or less. The adhesive layer has a storage elastic modulus at 25°C of 0.2 to 2 MPa.

[0012] The adhesive sheet of the present invention is suitable for bonding a resin plate and a film substrate, that is, it is suitable as an adhesive for forming a laminate of a resin plate and a film substrate. Further, in the laminate obtained by using the adhesive sheet of the present invention, the resin plate and the film substrate constituting the laminate can be processed simultaneously, and even if the processing is performed simultaneously, the laminate is less likely to warp and the edges are less sticky. Therefore, the adhesive sheet of the present invention is suitable as an adhesive for forming a laminate that is less likely to warp and the edges are less sticky even when the resin plate and the film substrate are processed simultaneously.

[0013] In this specification, the simultaneous processing of the laminated resin plate and film substrate by the adhesive sheet may also be referred to as "multi-layer simultaneous processing" in this specification.

[0014] Further, the adhesive sheet of the present invention is suitable as an adhesive for forming a laminate that is less likely to warp and the edges are less sticky.

[0015] As described above, according to the adhesive sheet of the present invention, it is suitable for multi-layer simultaneous processing of a resin plate and a film substrate, and the laminate obtained by such processing is less likely to warp and the edges are less sticky.

[0016] The adhesive sheet of the present invention includes an adhesive layer. The adhesive layer is a layer for bonding a resin plate and a film substrate. The adhesive layer is, for example, an acrylic adhesive layer.

[0017] As described above, the adhesive layer contains a crosslinked acrylic high molecular weight polymer (A) and an acrylic low molecular weight polymer (B).

[0018] <Acrylic high molecular weight polymer (A)> Acrylic high molecular weight polymer (A) has a mass-average molecular weight of 500,000 to 2,000,000. This allows the adhesive sheet to exhibit excellent adhesive performance and facilitates the formation of laminates that are less prone to warping and less likely to develop stickiness at the edges.

[0019] The mass-average molecular weight of the acrylic high molecular weight polymer (A) is preferably 600,000 or more, more preferably 700,000 or more, even more preferably 800,000 or more, and particularly preferably 900,000 or more. Furthermore, there is no particular upper limit to the mass-average molecular weight of the acrylic high molecular weight polymer (A), but from an economic standpoint and from the viewpoint of easily obtaining good coating properties, it is preferably 1,800,000 or less, more preferably 1,600,000 or less, even more preferably 1,500,000 or less, and particularly preferably 1,300,000 or less.

[0020] The mass-average molecular weight of the high-molecular-weight acrylic polymer (A) and the mass-average molecular weight of the low-molecular-weight acrylic polymer (B), described below, were measured by gel permeation chromatography (GPC) and the values ​​were obtained in terms of standard polystyrene equivalents. The measurement conditions for gel permeation chromatography (GPC) are as follows. Solvent: tetrahydrofuran Columns: Shodex KF801, KF803L, KF800L, KF800D (four columns manufactured by Showa Denko K.K. are connected together for use) Column temperature: 40℃ Sample concentration: 0.5% by mass Detector: RI-2031plus (manufactured by JASCO) Pump: RI-2080plus (made by JASCO) Flow rate (flow rate): 0.8ml / min Injection volume: 10μL Calibration curve: A calibration curve is used based on 10 samples of standard polystyrene (Shodex standard polystyrene, manufactured by Showa Denko) with Mw values ​​ranging from 1320 to 2,500,000.

[0021] The acrylic high molecular weight polymer (A) is not particularly limited in type as long as its mass-average molecular weight is within the above range, and can broadly include (meth)acrylic copolymers used in conventional adhesive layers. In this specification, "(meth)acrylic" means "acrylic" or "methacrylic," "(meth)acrylate" means "acrylate" or "methacrylate," and "(meth)allyl" means "allyl" or "methallyl."

[0022] The acrylic high molecular weight polymer (A) may, for example, have (meth)acrylate alkyl ester units. In this specification, "unit" refers to a repeating structural unit (also called a monomer unit) that constitutes a polymer. The (meth)acrylate alkyl ester units are derived from (meth)acrylate alkyl esters. Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-undecyl (meth)acrylate, n-dodecyl (meth)acrylate, stearyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and isobolonyl (meth)acrylate. The alkyl (meth)acrylate units contained in the high molecular weight acrylic polymer (A) can consist of one type alone, or may contain two or more types of units.

[0023] Among the alkyl (meth)acrylate esters listed above, at least one selected from the group consisting of methyl (meth)acrylate, n-butyl (meth)acrylate, and isobolonyl (meth)acrylate is preferred because it provides high adhesiveness.

[0024] The acrylic high molecular weight polymer (A) may contain other acrylic monomer units besides the (meth)acrylate alkyl ester unit. Examples of other acrylic monomer units include monomer units having crosslinkable functional groups, such as hydroxyl group-containing monomer units and carboxyl group-containing monomer units. The acrylic high molecular weight polymer (A) may contain one or more of these monomer units.

[0025] Hydroxyl group-containing acrylic monomer units are derived from hydroxy group-containing acrylic monomers. Examples of hydroxy group-containing acrylic monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxypropyl (meth)acrylate; (meth)acrylic acids [(mono, di, or poly)alkylene glycols] such as mono(diethylene glycol) (meth)acrylate; and (meth)acrylic acid lactones such as monocaprolactone (meth)acrylate.

[0026] Examples of carboxyl group-containing acrylic monomer units include acrylic acid and methacrylic acid.

[0027] The acrylic high molecular weight polymer (A) preferably contains acrylic monomer units having crosslinkable functional groups, more preferably contains hydroxyl group-containing acrylic monomer units and / or carboxyl group-containing acrylic monomer units, even more preferably contains carboxyl group-containing acrylic monomer units, and particularly preferably does not contain hydroxyl group-containing acrylic monomer units but contains carboxyl group-containing acrylic monomer units. When the acrylic high molecular weight polymer (A) contains carboxyl group-containing acrylic monomer units, it can exhibit better adhesive performance and easily form laminates that are less prone to warping and less likely to develop stickiness at the edges.

[0028] When the acrylic high molecular weight polymer (A) contains acrylic monomer units having crosslinkable functional groups, the content is preferably, for example, 3 to 20 parts by mass of acrylic monomer units having crosslinkable functional groups per 100 parts by mass of the total mass of structural units in the acrylic high molecular weight polymer (A). This makes it easier to form laminates that are less prone to warping and less likely to develop stickiness at the edges. Preferably, the content of acrylic monomer units having crosslinkable functional groups is 5 to 15 parts by mass per 100 parts by mass of the total mass of structural units in the acrylic high molecular weight polymer (A).

[0029] In particular, it is preferable that the acrylic high molecular weight polymer (A) has carboxyl group-containing monomer units, and when the amount of carboxyl group-containing monomer units is 3 to 20 parts by mass per 100 parts by mass of the total mass of structural units in the acrylic high molecular weight polymer (A), it is particularly easy to form a laminate that is less prone to warping and less prone to stickiness at the edges. The amount of carboxyl group-containing monomer units per 100 parts by mass of the total mass of structural units in the acrylic high molecular weight polymer (A) is preferably 5 parts by mass or more, more preferably 6 parts by mass or more, preferably 18 parts by mass or less, and even more preferably 15 parts by mass or less.

[0030] The acrylic high molecular weight polymer (A) may also contain monomer units other than (meth)acrylate alkyl ester units and acrylic monomer units having crosslinkable functional groups (e.g., carboxyl group-containing monomer units). The content of other monomer units is preferably 20% by mass or less, and more preferably 10% by mass, relative to the total mass of the (meth)acrylic copolymer. The acrylic high molecular weight polymer (A) may be formed only of (meth)acrylate alkyl ester units and acrylic monomer units having crosslinkable functional groups, or only of (meth)acrylate alkyl ester units, hydroxyl group-containing monomer units and carboxyl group-containing monomer units, or only of (meth)acrylate alkyl ester units and carboxyl group-containing monomer units.

[0031] The glass transition temperature (Tg) of the acrylic high molecular weight polymer (A) is not particularly limited. For example, the Tg of the acrylic high molecular weight polymer (A) can be -40°C or higher. In this case, the adhesive sheet can exhibit excellent adhesive performance, and it is easy to form a laminate that is less prone to warping and less likely to develop stickiness at the edges. The Tg of the acrylic high molecular weight polymer (A) is preferably -38°C or higher, more preferably -36°C or higher, and even more preferably -35°C or higher. The Tg of the acrylic high molecular weight polymer (A) is preferably 10°C or lower, more preferably 0°C or lower, and even more preferably -10°C or lower.

[0032] In the present invention, the Tg (glass transition temperature) of the acrylic high molecular weight polymer (A) and the acrylic low molecular weight polymer (B) described below refers to the Tg determined by the following Fox formula based on the composition of the monomers used in the synthesis of the polymer. Fox's formula: 1 / Tg = (W1 / Tg1) + (W2 / Tg2) + ... + (Wm / Tgm ) Here, W1 + W2 + ... + Wm = 1 In the formula, Tg is the glass transition temperature (unit: K) of the crosslinkable acrylic copolymer (A), Tg1, Tg2, ..., Tgm are the glass transition temperatures of the respective homopolymers of m types of monomers (m is an integer) that constitute the crosslinkable acrylic copolymer (A), and W1, W2, ..., Wm are the mass fractions of each constituent unit in the crosslinkable acrylic copolymer (A). Note that Tg1 and W1 are in a corresponding relationship; that is, the monomer constituting the homopolymer exhibiting the glass transition temperature of Tg1 is the same monomer that forms the constituent unit with mass fraction W1. Similarly, Tg2 and W2, ..., Tgm and Wm are in a corresponding relationship.

[0033] As for the glass transition temperature of the homopolymer mentioned above, the value listed in, for example, the Polymer Handbook 4th Edition (Wiley-Interscience 2003) can be used. If it is not listed in such a handbook, the glass transition temperature of the homopolymer can be measured by, for example, a differential scanning calorimeter (DSC). The DSC measurement conditions are as follows: 5 mg of sample, under a nitrogen atmosphere, the temperature is raised from -100°C to 200°C at a heating rate of 5°C / min in the first measurement (1st RUN), then cooled to -100°C at a cooling rate of 5°C / min, and then the temperature is raised again from -100°C to 200°C at a heating rate of 5°C / min in the second measurement (2nd RUN). Here, the glass transition temperature is defined as the point where, in the region where the baseline of the DSC curve measured when the temperature is increased from -100°C to 200°C in the 2nd RUN changes in a sigmoid shape in the endothermic direction, the extension of the baseline on the lower temperature side of the region where the curve changes in a sigmoid shape intersects with the tangent line to the inflection point in the sigmoid curve.

[0034] Acrylic high molecular weight polymer (A) can be produced, for example, by known methods, such as by polymerization of (meth)acrylic monomers. In this case, various polymerization methods can be employed, such as solution polymerization, emulsion polymerization, and suspension polymerization.

[0035] <Crosslinked acrylic high molecular weight polymer (A)> In the adhesive sheet of the present invention, the adhesive layer contains a crosslinked acrylic high molecular weight polymer (A) as described above. A crosslinked acrylic high molecular weight polymer (A) means that the acrylic high molecular weight polymer (A) has a structure that is crosslinked with a crosslinking agent, for example.

[0036] The aforementioned crosslinking agent can be broadly defined as a component that can promote the crosslinking reaction of the acrylic high molecular weight polymer (A). In particular, the crosslinking agent can be broadly defined as a component that can react with carboxyl groups or hydroxyl groups in the acrylic high molecular weight polymer (A). The crosslinking agent is preferably bifunctional, and preferably trifunctional or more.

[0037] Such crosslinking agents can be selected from known crosslinking agents such as isocyanate compounds, epoxy compounds, oxazoline compounds, aziridine compounds, metal chelate compounds, and butylated melamine compounds.

[0038] Examples of isocyanate compounds include polyisocyanates such as tolylene diisocyanate, isophorone diisocyanate, chlorophenylene diisocyanate, diphenylmethane diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and xylylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate and cyclohexylene diisocyanate; and aromatic isocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and 4,4'-diphenylmethane diisocyanate. Isocyanate compounds can be used individually or in combination of two or more different types. Examples of commercially available products include tolylene diisocyanate compounds (Coronate L, manufactured by Nippon Polyurethane Industries Co., Ltd.) and xylylene diisocyanate compounds (Takenate D-110N, manufactured by Mitsui Chemicals, Inc.).

[0039] Examples of epoxy compounds include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerin diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexanone, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, and sorbitol polyglycidyl ether. Examples of commercially available epoxy compounds include TETRAD-C (manufactured by Mitsubishi Gas Chemical Co., Ltd.) and TETRAD-X (manufactured by Mitsubishi Gas Chemical Co., Ltd.).

[0040] In particular, the crosslinking agent is preferably an isocyanate compound and / or an epoxy compound, and more preferably an epoxy compound. That is, the crosslinked acrylic high molecular weight polymer (A) preferably has a structure derived from the epoxy crosslinking agent.

[0041] <Acrylic low molecular weight polymer (B)> Acrylic low molecular weight polymer (B) has a mass-average molecular weight of 3,000 or more and 50,000 or less. Acrylic low molecular weight polymer (B) can function as a so-called tackifier in the adhesive layer. As a result, the adhesive sheet can exhibit excellent adhesive performance, and when combined with acrylic high molecular weight polymer (A), it is easy to form a laminate that is less prone to warping and less likely to develop stickiness at the edges.

[0042] The mass-average molecular weight of the acrylic low molecular weight polymer (B) is preferably 3500 or more, more preferably 4000 or more, even more preferably 4500 or more, and particularly preferably 5000 or more. Furthermore, the mass-average molecular weight of the acrylic low molecular weight polymer (B) is preferably 40000 or less, more preferably 30000 or less, even more preferably 20000 or less, and particularly preferably 12000 or less.

[0043] The acrylic low molecular weight polymer (B) is not particularly limited in type, as long as its mass-average molecular weight is within the above range. For example, it can broadly include acrylic polymers that are conventionally used as tackifiers.

[0044] The low molecular weight acrylic polymer (B) may, for example, have alkyl (meth)acrylate units, similar to the high molecular weight acrylic polymer (A). Therefore, as mentioned above, examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-undecyl (meth)acrylate, n-dodecyl (meth)acrylate, stearyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobolonyl (meth)acrylate, etc. The alkyl (meth)acrylate units contained in the acrylic low molecular weight polymer (B) can consist of one type alone, or may contain two or more types of units.

[0045] Among the alkyl (meth)acrylate esters mentioned above, the acrylic low molecular weight polymer (B) preferably contains at least one selected from the group consisting of methyl (meth)acrylate units, n-butyl (meth)acrylate units, and isobolonyl (meth)acrylate units, and more preferably contains at least one selected from the group consisting of methyl (meth)acrylate units and isobolonyl (meth)acrylate units, as this results in higher adhesiveness.

[0046] The acrylic low molecular weight polymer (B) may contain other acrylic monomer units besides (meth)acrylate alkyl ester units, but it is preferable that it does not contain the aforementioned hydroxyl group-containing monomer units and carboxyl group-containing monomer units, and more preferably that it does not contain any units other than (meth)acrylate alkyl ester units, in order to enhance its performance as a tackifier. In other words, it is preferable that the acrylic low molecular weight polymer (B) is formed only of (meth)acrylate alkyl ester units. If the acrylic low molecular weight polymer (B) contains units other than (meth)acrylate alkyl ester units, the content thereof is preferably 10% by mass or less, more preferably 5% by mass, and even more preferably 1% by mass, based on the total mass of the acrylic low molecular weight polymer (B).

[0047] The Tg of the acrylic low molecular weight polymer (B) is not particularly limited. For example, the Tg of the acrylic low molecular weight polymer (B) is preferably 80°C or higher. In this case, the adhesive sheet can exhibit excellent adhesive performance and easily form a laminate that is less prone to warping and less likely to develop stickiness at the edges. The Tg of the acrylic low molecular weight polymer (B) is preferably 90°C or higher, more preferably 100°C or higher, and even more preferably 105°C or higher. The Tg of the acrylic low molecular weight polymer (B) is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower.

[0048] Acrylic low molecular weight polymer (B) can be produced, for example, by known methods, such as by polymerization of (meth)acrylic monomers. In this case, various polymerization methods can be employed, such as solution polymerization, emulsion polymerization, and suspension polymerization.

[0049] <Adhesive layer> The adhesive layer contains an acrylic high molecular weight polymer (A) and an acrylic low molecular weight polymer (B). The content ratio of the acrylic high molecular weight polymer (A) and the acrylic low molecular weight polymer (B) is not particularly limited. For example, the adhesive layer preferably contains 0.5 to 50 parts by mass of acrylic low molecular weight polymer (B) per 100 parts by mass of acrylic high molecular weight polymer (A), more preferably 1 to 30 parts by mass, even more preferably 2 to 20 parts by mass, and particularly preferably 3 to 10 parts by mass of acrylic low molecular weight polymer (B).

[0050] The adhesive layer contains an acrylic high molecular weight polymer (A) and an acrylic low molecular weight polymer (B), and may also contain other components as long as they do not hinder the effects of the present invention. So-called after-cure adhesive sheets contain photopolymerization initiators and monofunctional or polyfunctional monomers to impart after-cure properties, but the adhesive layer of the present invention preferably does not contain photopolymerization initiators, monofunctional monomers, and polyfunctional monomers in order to achieve the aforementioned simultaneous multilayer processing.

[0051] The adhesive layer may contain various adhesive additives other than those mentioned above, as long as they do not impair the effects of the present invention. Such additives can be selected as needed from, for example, silane coupling agents, plasticizers, antioxidants, metal corrosion inhibitors, ultraviolet absorbers, and light stabilizers such as hindered amine compounds. Dyes and pigments may also be added for coloring purposes.

[0052] The adhesive layer has a storage modulus of 0.2 to 2 MPa at 25°C. If the storage modulus falls below 0.2 MPa, the ability to process multiple layers simultaneously decreases, and the laminate formed using the adhesive sheet becomes sticky at the edges. If the storage modulus exceeds 2 MPa, the ability to process multiple layers simultaneously decreases, and the laminate formed using the adhesive sheet warps.

[0053] The adhesive layer preferably has a storage modulus of 0.25 MPa or higher at 25°C, more preferably 0.3 MPa or higher, more preferably 1.8 MPa or lower, more preferably 1.6 MPa or lower, even more preferably 1.4 MPa or lower, and particularly preferably 1.2 MPa or lower.

[0054] The gel fraction of the adhesive layer is preferably 60% or more. This allows the adhesive sheet to have excellent tackiness and also improves the ability to process multiple layers simultaneously.

[0055] The gel fraction of the adhesive layer was measured using the following method. First, approximately 0.1 g of the adhesive sheet (adhesive layer) was placed in a sample bottle, 30 ml of ethyl acetate was added, and the sample was shaken for 24 hours. Then, the contents of the sample bottle were filtered through a 150-mesh stainless steel mesh, and the residue on the mesh was dried at 120°C for 1 hour to measure the dry mass (g). From the obtained dry mass, the following formula 1 was used. Gel fraction (mass%) = (dry mass / mass of adhesive layer sampled) × 100 ... Equation 1 The gel fraction can be determined by this method.

[0056] The thickness of the adhesive layer can be set appropriately depending on the application and is not particularly limited. For example, the thickness of the adhesive layer is preferably 5 to 50 μm. In this case, the simultaneous processing of multiple layers is easily improved, and it is easier to form a laminate that is less prone to warping and less likely to become sticky at the edges. The thickness of the adhesive layer is more preferably 10 to 40 μm. Note that the thickness of the adhesive layer refers to the total thickness of each layer if the adhesive layer has a multilayer laminated structure.

[0057] The adhesive strength of the adhesive layer against glass is, for example, 10 N / 25 mm or more. The adhesive strength of the adhesive sheet against glass is measured in accordance with the adhesive strength measurement method described in JIS Z 0237, and the details of the measurement conditions are as described in the examples.

[0058] The adhesive layer can have a single-layer structure, or it can have a multilayer structure in which multiple single-layer adhesive layers are stacked.

[0059] The method for manufacturing the adhesive layer is not particularly limited; for example, the adhesive layer can be formed in a manner similar to that of known adhesive sheets. Specifically, the adhesive layer can be formed using an adhesive composition for forming the adhesive layer.

[0060] The adhesive composition comprises at least the acrylic high molecular weight polymer (A), the crosslinking agent, and the acrylic low molecular weight polymer (B). The adhesive composition, by containing the crosslinking agent, can form a crosslinked body of the acrylic high molecular weight polymer (A).

[0061] The adhesive composition preferably contains 0.5 to 50 parts by mass, more preferably 1 to 30 parts by mass, even more preferably 2 to 20 parts by mass, and particularly preferably 3 to 10 parts by mass of the acrylic low molecular weight polymer (B) per 100 parts by mass of the acrylic high molecular weight polymer (A).

[0062] The adhesive composition preferably contains 0.005 to 5 parts by mass of the crosslinking agent per 100 parts by mass of the acrylic high molecular weight polymer (A), more preferably 0.01 to 3 parts by mass, even more preferably 0.02 to 1 part by mass, and particularly preferably 0.03 to 1 part by mass of the crosslinking agent.

[0063] The adhesive composition may contain other components as long as they do not hinder the effects of the present invention. For example, the adhesive composition may optionally contain a solvent. The inclusion of a solvent in the adhesive composition improves its coatability and facilitates the formation of adhesive sheets.

[0064] Examples of the aforementioned solvents include hydrocarbons such as hexane, heptane, octane, toluene, xylene, ethylbenzene, cyclohexane, and methylcyclohexane; halogenated hydrocarbons such as dichloromethane, trichloroethane, trichloroethylene, tetrachloroethylene, and dichloropropane; alcohols such as methanol, ethanol, propanol, isopropyl alcohol, butanol, isobutyl alcohol, and diacetone alcohol; ethers such as diethyl ether, diisopropyl ether, dioxane, and tetrahydrofuran; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, amyl acetate, and ethyl butyrate; and polyols and their derivatives such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether acetate, and propylene glycol monomethyl ether acetate.

[0065] The solvent content in the adhesive composition is not particularly limited, but is preferably 25 to 500 parts by mass, and more preferably 30 to 400 parts by mass, per 100 parts by mass of the acrylic high molecular weight polymer (A). In addition, the solvent content relative to the total mass of the adhesive composition is preferably 10 to 90% by mass, and more preferably 20 to 80% by mass. The solvent contained in the adhesive composition may be a single type or two or more types.

[0066] The adhesive composition may also contain other components not mentioned above, as long as they do not impair the effects of the present invention. Other components can be selected as needed from, for example, silane coupling agents, plasticizers, antioxidants, metal corrosion inhibitors, ultraviolet absorbers, and light stabilizers such as hindered amine compounds. Dyes and pigments may also be added for coloring purposes.

[0067] In addition, when obtaining a so-called after-cure type adhesive sheet, the adhesive composition contains a photopolymerization initiator and monofunctional or polyfunctional monomers in order to impart after-cure properties. However, in the present invention, in order to achieve the aforementioned simultaneous multilayer processing, it is preferable that the adhesive composition does not contain a photopolymerization initiator, monofunctional monomers, or polyfunctional monomers.

[0068] The method for preparing the above-mentioned adhesive composition is not particularly limited, and for example, a wide range of known methods for preparing adhesive compositions can be employed.

[0069] <Adhesive sheet> The adhesive sheet of the present invention comprises the adhesive layer. The adhesive sheet may consist of, for example, only the adhesive layer. Alternatively, the adhesive sheet may have layers other than the adhesive layer, as long as the effects of the present invention are not hindered.

[0070] The adhesive sheet of the present invention may be a single-sided adhesive sheet or a double-sided adhesive sheet, but a double-sided adhesive sheet is preferable in that it forms a laminate as described later.

[0071] The adhesive sheet of the present invention may be an adhesive sheet with a release liner. The release liner may be directly attached to one or both sides of the adhesive sheet.

[0072] As the release sheet, a wide range of known release sheets can be applied. For example, a release-compatible laminated sheet can be made in which a release agent layer is formed on one side of a release sheet substrate. The release agent constituting the release agent layer is also not limited. For example, general-purpose addition-type or condensation-type silicone-based release agents or long-chain alkyl group-containing compounds can be used. Release-compatible laminated sheets can also be obtained from the market. For example, heavy separator films, which are release-treated polyethylene terephthalate films manufactured by Toyobo Co., Ltd., and light separator films, which are release-treated polyethylene terephthalate films manufactured by Toyobo Co., Ltd., can be used.

[0073] An adhesive sheet with a release liner may also have a pair of release liner sheets on both surfaces of the adhesive sheet, each with a different release strength.

[0074] The method for manufacturing the adhesive sheet is not particularly limited, and for example, known manufacturing methods can be widely applied. In particular, it is preferable to form the adhesive sheet by a manufacturing method that includes the steps of applying the above-mentioned adhesive composition onto a release sheet to form a coating film and heating this coating film. In such a manufacturing method, if the adhesive composition contains a solvent, the solvent is removed in the heating step, and at the same time, the reaction between the acrylic high molecular weight polymer (A) and the crosslinking agent proceeds to form a cured product. Specifically, the crosslinkable functional group (e.g., carboxyl group) of the acrylic high molecular weight polymer (A) reacts with the crosslinking agent to form a crosslinked body of the acrylic high molecular weight polymer (A). The adhesive composition hardens upon heating, and the resulting cured product is the adhesive layer of the adhesive sheet.

[0075] The adhesive composition can be coated using known coating equipment. Examples of coating equipment include applicators, blade coaters, air knife coaters, roll coaters, bar coaters, gravure coaters, microgravure coaters, rod blade coaters, lip coaters, die coaters, and curtain coaters.

[0076] The substrate used for coating the adhesive composition is not particularly limited. For example, the adhesive composition can be coated onto various substrates such as resin substrates and glass substrates. For example, when obtaining an adhesive sheet with a release liner, a release liner can be selected as the substrate. The adhesive composition can also be directly coated onto the components to be bonded.

[0077] The thickness of the adhesive composition after coating is not particularly limited and can be set appropriately according to the desired thickness of the adhesive layer.

[0078] In the step of heating the coating film, the heating temperature is not particularly limited, but is preferably 50 to 150°C. The heating time can be appropriately adjusted depending on the heating temperature, the thickness of the coating film, and the solvent content of the adhesive composition, and can be, for example, 1 to 60 minutes. Known heating devices such as heating furnaces and infrared lamps can be used to heat the coating film. Furthermore, after heating, it is preferable to perform an aging treatment in which the adhesive sheet is left to stand at a constant temperature for a certain period of time. The aging treatment can be performed, for example, by leaving it to stand at 23°C for 7 days.

[0079] The adhesive sheet of the present invention is suitable for bonding resin plates and film substrates, that is, it is suitable as an adhesive for forming laminates of resin plates and film substrates, and is therefore suitable as an adhesive for panels used in various display devices. Furthermore, the adhesive sheet of the present invention is suitable for bonding optical components used in optical devices and the like.

[0080] 2. Laminate The laminate of the present invention comprises the aforementioned adhesive sheet of the present invention and a resin plate. If the adhesive sheet is formed only of an adhesive layer, the laminate of the present invention comprises an adhesive layer and a resin plate. In the laminate of the present invention, the resin plate is directly bonded to, for example, both sides or one side of the adhesive sheet. In the laminate of the present invention, the adhesive sheet (adhesive layer) is a layer bonded to at least one side of the resin plate and is a layer that exhibits adhesive function.

[0081] The laminate of the present invention may also include a film substrate in addition to the resin plate. In this case, for example, the laminate may have a resin plate directly bonded to one side of an adhesive sheet and a film substrate directly bonded to the other side.

[0082] In the laminate of the present invention, the resin plate can be a wide variety of resin plates that can be applied to display devices such as liquid crystal displays (LCDs) for touch panels and car navigation panels.

[0083] The resin sheet is not particularly limited, and for example, known transparent or translucent resin sheets can be used. Examples include polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polyethylene naphthalate, cycloolefin polymer, triacetylcellulose, polyimide, and cellulose acylate. Among these, acrylic resin sheets and polycarbonate resin sheets are particularly preferred because they have good optical properties and heat resistance, as well as excellent mechanical strength, dimensional stability, weather resistance, and cost-effectiveness. Alternatively, laminates of acrylic resin sheets and polycarbonate resin sheets may be used, and two-layer or two-layer sheets may also be used.

[0084] The thickness of the resin plate is not particularly limited, and for example, a thickness similar to that of cover panels that can be applied to conventional input devices such as touch panels can be adopted. The thickness of the resin plate can be, for example, 200 to 10000 μm, and from the viewpoint of the strength of the resin plate and processability during machining, it is preferable to be in the range of 400 to 5000 μm, and more preferably in the range of 400 to 2000 μm.

[0085] The type of film substrate is not particularly limited, and for example, a wide range of known films can be applied. Examples of film substrates include films that are laminated to cover panels that can be applied to input devices such as touch panels. Examples of such film substrates include various resin films, and specifically, general films used in the optical field such as polyethylene terephthalate film, acrylic film, polycarbonate film, polyolefin film, triacetylcellulose film, and cycloolefin polymer film are widely exemplified. Furthermore, an easy-adhesion layer may be provided on the surface to which the adhesive layer of the film is laminated. In addition, a functional layer such as a hard coat layer, anti-reflective layer, anti-fouling layer, or ultraviolet absorbing layer may be provided on the surface of the film substrate opposite to the adhesive layer.

[0086] The thickness of the film substrate is not particularly limited; for example, it can be the same thickness as the film used to bond to cover panels that can be applied to conventional input devices such as touch panels. The thickness of the film substrate can be, for example, 10 to 200 μm.

[0087] The laminate of the present invention can be applied to various uses, and can be suitably used in optical devices, image display devices, and the like. In particular, since the laminate of the present invention is formed by bonding together highly transparent adhesive sheets, the design and visibility of images can be further improved when applied to optical devices, image display devices, and the like.

[0088] Since the laminate of the present invention includes the aforementioned adhesive sheet of the present invention, it is less prone to warping and less likely to become sticky at the edges. Therefore, the laminate of the present invention can be suitably used for cover panels of touch panels and car navigation systems. In particular, even when a functional film (film substrate) to be bonded to improve visibility and the cover panel are processed simultaneously, the laminate is less prone to warping and less likely to become sticky at the edges. The laminate of the present invention can improve the design of display devices and the like, as well as improve the overall visibility of the screen.

[0089] The method for manufacturing the laminate of the present invention is not particularly limited, and for example, known methods for manufacturing laminates can be widely employed. For example, the method may include a step 1 of bonding the adhesive sheet of the present invention and a functional film to obtain an adhesive-coated film, and a lamination step 2 of bonding the adhesive-coated film and a resin plate to obtain a laminate. Step 1 may be performed before or after step 2.

[0090] The laminate obtained as described above can also be subjected to machining, thereby allowing the laminate to be molded into an appropriate shape.

[0091] 3. How to use the adhesive sheet The adhesive sheet of the present invention is suitable for use in the above-mentioned laminate, and can be used to laminate a functional film and a cover panel. In such a laminate, even when the functional film and the cover panel are processed simultaneously, the laminate is less prone to warping and less likely to become sticky at the edges.

[0092] Therefore, the method of using the adhesive sheet of the present invention preferably comprises a step 1 of laminating the adhesive sheet and a functional film to obtain an adhesive-coated film, a lamination step 2 of laminating the adhesive-coated film and a resin plate to obtain a laminate, and a step 3 of processing the laminate by machining.

[0093] The machining method in step 3 is not particularly limited, and known machining methods can be widely adopted in this invention. Examples of machining methods include punching and cutting. Among these, cutting is preferred because it allows for shaping to a desired size and form. [Examples]

[0094] The present invention will be described more specifically below with reference to examples, but the present invention is not limited to the embodiments of these examples.

[0095] (Manufacturing Example 1-1; Acrylic high molecular weight polymer (A-1)) In a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, 100 parts by mass of a mixed monomer having a mass ratio of methyl acrylate (MA), butyl acrylate (BA), and acrylic acid (AA) of 20:70:10 was polymerized by heating to 65°C in 120 parts by mass of ethyl acetate, a polymerization solvent, in the presence of 0.3 parts by mass of (ABVN (azobisdimethylvaleronitrile)). This yielded a solution of acrylic high molecular weight polymer (A-1) (indicated as "A-1" in Table 1) with a solid content concentration of 23% by mass. The obtained acrylic high molecular weight polymer (A-1) had a mass-average molecular weight of 1,000,000 and a glass transition temperature of -32°C.

[0096] (Manufacturing Example 1-2; Acrylic high molecular weight polymer (A-2)) The mixed monomers have a mass ratio of BA, isobolonyl acrylate (IBXA), and AA of 82. A solution of acrylic high molecular weight polymer (A-2) (indicated as "A-2" in Table 1) with a solid content of 23% by mass was obtained by the same method as in Production Example 1-1, except that the mixed monomer was changed to a :10:8 ratio and the amounts of ABVN and ethyl acetate added were adjusted. The obtained acrylic high molecular weight polymer (A-2) had a mass-average molecular weight of 1 million and a glass transition temperature of -35°C.

[0097] (Manufacturing Examples 1-3; Acrylic high molecular weight polymer (A-3)) A solution of acrylic high molecular weight polymer (A-3) (indicated as "A-3" in Table 1) with a solid content of 23% by mass was obtained in the same manner as in Production Example 1-1, except that the mixed monomer was changed to a mixed monomer with a mass ratio of MA, BA, hydroxylethyl acrylate (HEA), and AA of 10:74:10:6, and the amounts of ABVN and ethyl acetate added were adjusted. The obtained acrylic high molecular weight polymer (A-3) had a mass-average molecular weight of 1,000,000 and a glass transition temperature of -32°C.

[0098] (Manufacturing Examples 1-4; Acrylic high molecular weight polymer (A-4)) A solution of acrylic high molecular weight polymer (A-4) (indicated as "A-4" in Table 1) with a solid content of 40% by mass was obtained in the same manner as in Production Example 1-1, except that the mixed monomer was changed to a mixed monomer with a mass ratio of BA and AA of 90:10, and the amounts of ABVN and ethyl acetate added were adjusted. The obtained acrylic high molecular weight polymer (A-4) had a mass-average molecular weight of 600,000 and a glass transition temperature of -42°C.

[0099] (Manufacturing Examples 1-5; Acrylic high molecular weight polymer (A-5)) A solution of acrylic high molecular weight polymer (A-5) (indicated as "A-5" in Table 1) with a solid content of 40% by mass was obtained by the same method as in Production Example 1-1, except that the mixed monomer was changed to a mixed monomer in which the mass ratio of 2-ethylhexyl acrylate (2EHA) and HEA was 80:20, and the amounts of ABVN and ethyl acetate added were adjusted. The obtained acrylic high molecular weight polymer (A-5) had a mass-average molecular weight of 600,000 and a glass transition temperature of -46°C.

[0100] (Manufacturing Example 2-1; Acrylic Low Molecular Weight Polymer (B-1)) In a reaction apparatus equipped with a stirrer, reflux condenser, sequential dropper, and thermometer, 50 parts by mass of ethyl acetate and 20 parts by mass of toluene were added and heated, and maintained at reflux temperature for 10 minutes. Then, under reflux temperature conditions, a mixture of 300 parts by mass of a mixed monomer having a mass ratio of methyl methacrylate (MMA) and isobolonyl methacrylate (IBXMA) of 90:10, 15 parts by mass of ethyl acetate, 10 parts by mass of toluene, and 5 parts by mass of dimethyl 2,2-azobis(2-methylpropionate) (V-601, manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator was sequentially added dropwise over 180 minutes. After the addition was complete, the polymerization reaction was carried out for another 180 minutes. After the reaction was complete, the mixture was diluted with ethyl acetate to a solid content concentration of 40% by mass to obtain a solution of acrylic low molecular weight polymer (B-1) (indicated as "B-1" in Table 1). The obtained acrylic low molecular weight polymer (B-1) had a mass-average molecular weight of 5000 and a glass transition temperature of 111°C.

[0101] (Manufacturing Example 2-2; Acrylic Low Molecular Weight Polymer (B-2)) A solution of acrylic low molecular weight polymer (B-2) (indicated as "B-2" in Table 1) with a solid content of 30% by mass was obtained using the same method as in Production Example 2-1, except that the mixed monomer was changed to a monomer consisting solely of MMA, and the weight-average molecular weight was adjusted by changing the amounts of polymerization initiator and organic solvent. The obtained acrylic low molecular weight polymer (B-2) had a weight-average molecular weight of 8000 and a glass transition temperature of 105°C.

[0102] (Example 1) A raw material containing 100 parts by mass of acrylic high molecular weight polymer (A-1), 5 parts by mass of acrylic low molecular weight polymer (B-1), and 0.1 parts by mass of an epoxy compound (Tetrad X, manufactured by Mitsubishi Gas Chemical Co., Ltd., indicated as "Crosslinking Agent 1" in Table 1) as a crosslinking agent was added to ethyl acetate to a concentration of 20% by mass of the raw material, and the mixture was stirred to prepare an adhesive composition. This adhesive composition was uniformly applied with an applicator to the surface of a 50 μm thick polyethylene terephthalate film (first release sheet, manufactured by Oji F-Tex Co., Ltd., 50RL-07(2)) equipped with a release agent layer treated with a silicone-based release agent to form a coating film. This coating film was dried in an air-circulating constant temperature oven at 100°C for 3 minutes to form an adhesive layer (adhesive sheet) with a thickness of 15 μm on the surface of the first release sheet. Next, a second release sheet (manufactured by Oji F-Tex Co., Ltd., 38RL-07(L)) with a thickness of 38 μm and a different release strength from the first release sheet was laminated to the surface of the adhesive layer, and cured for 7 days at 23°C and 50% relative humidity. As a result, an adhesive sheet with a release sheet was obtained, having a configuration of first release sheet / adhesive sheet / second release sheet, in which the adhesive layer (adhesive sheet) is sandwiched between a pair of release sheets with different release strengths.

[0103] (Example 2) An adhesive sheet with a release liner was obtained in the same manner as in Example 1, except that acrylic high molecular weight polymer (A-2) was used instead of acrylic high molecular weight polymer (A-1).

[0104] (Example 3) An adhesive sheet with a release liner was obtained in the same manner as in Example 1, except that acrylic high molecular weight polymer (A-3) was used instead of acrylic high molecular weight polymer (A-1), and the amount of crosslinking agent was changed to 0.05 parts by mass.

[0105] (Example 4) An adhesive sheet with a release liner was obtained in the same manner as in Example 1, except that acrylic low molecular weight polymer (B-2) was used instead of acrylic low molecular weight polymer (B-1), and the amount of crosslinking agent was changed to 0.2 parts by mass.

[0106] (Example 5) An adhesive sheet with a release liner was obtained in the same manner as in Example 1, except that the thickness of the adhesive layer was changed to 8 μm.

[0107] (Example 6) An adhesive sheet with a release liner was obtained in the same manner as in Example 1, except that the thickness of the adhesive layer was changed to 35 μm.

[0108] (Comparative Example 1) An adhesive sheet with a release liner was obtained in the same manner as in Example 1, except that acrylic high molecular weight polymer (A-4) was used instead of acrylic high molecular weight polymer (A-1), the amount of crosslinking agent was changed to 0.05 parts by mass, and the thickness of the adhesive layer was changed to 25 μm.

[0109] (Comparative Example 2) An adhesive sheet with a release liner was obtained in the same manner as in Example 1, except that acrylic high molecular weight polymer (A-5) was used instead of acrylic high molecular weight polymer (A-1), the crosslinking agent was changed to an isocyanate compound (Coronate L-55, manufactured by Tosoh Corporation, indicated as "Crosslinking Agent 2" in Table 1), and the thickness of the adhesive layer was changed to 25 μm.

[0110] (Comparative Example 3) An adhesive sheet with a release liner was obtained in the same manner as in Example 1, except that the acrylic low molecular weight polymer (B-1) was not used and the amount of crosslinking agent was changed to 0.2 parts by mass.

[0111] (Comparative Example 4) An adhesive composition was prepared by adding ethyl acetate to 100 parts by mass of acrylic high molecular weight polymer (A-4), 0.25 parts by mass of epoxy compound (Tetrad X, manufactured by Mitsubishi Gas Chemical Co., Ltd.) as a crosslinking agent, 1.5 parts by mass of IGM Resin's "Omnirad TPO" as a photopolymerization initiator, and 15 parts by mass of A-9300 (A-9300 from Shin Nakamura Chemical Industry's "NK Ester" series) as an ultraviolet curing component, to a raw material to which the raw material concentration was 25% by mass, and stirring. This adhesive composition was uniformly coated with an applicator onto the surface of a 50 μm thick polyethylene terephthalate film (first release sheet, manufactured by Oji F-Tex Co., Ltd., 50RL-07(2)) equipped with a release agent layer treated with a silicone-based release agent to form a coating film. The coating film was dried in an air-circulating constant-temperature oven at 100°C for 3 minutes to form an adhesive layer (adhesive sheet) with a thickness of 15 μm on the surface of the first release sheet. Next, a second release sheet (manufactured by Oji F-Tex Co., Ltd., 38RL-07(L)) with a thickness of 38 μm and a different release strength from the first release sheet was laminated to the surface of the adhesive layer, and cured for 14 days at 23°C and 50% relative humidity. As a result, an adhesive sheet with a release sheet was obtained, having a structure of first release sheet / adhesive sheet / second release sheet, in which the adhesive layer (adhesive sheet) is sandwiched between a pair of release sheets with different release strengths.

[0112] <Gel fraction> From the double-sided adhesive sheets with release sheets obtained in the examples and comparative examples, the adhesive sheets were peeled off, and approximately 0.1 g of the adhesive sheet (adhesive layer only) was taken into a sample bottle. 30 ml of ethyl acetate was added and the sample was shaken for 24 hours. The contents of the sample bottle were then filtered through a 150-mesh stainless steel mesh, and the residue on the mesh was dried at 100°C for 1 hour to measure the dry weight W (g). From the obtained dry weight, the following formula was used: Gel fraction (%) = (Dry mass W / Mass of adhesive sheet sampled) × 100 The value calculated from this was taken as the gel fraction of the adhesive sheet. In Comparative Example 4, the double-sided adhesive sheet with a release sheet was obtained with an illuminance of 200 mW / cm² from the second release sheet side. 2 Using a UV LED lamp (365nm), the integrated light intensity is 2000 mJ / cm².2 Approximately 0.1g of the adhesive sheet, which had been post-cured by light irradiation in such a manner, was taken into a sample bottle, and the gel fraction was measured using the same method as described above.

[0113] <Storage modulus> The adhesive layer of the double-sided adhesive sheets with release sheets obtained in the examples and comparative examples was peeled from the release sheet, and the sheets were laminated to a thickness of 1000 μm. The laminated adhesive sheets were then pressurized in an autoclave at 30°C, 0.5 MPa for 10 minutes to obtain measurement samples. The storage modulus G' of the measurement samples was measured using a dynamic viscoelastic analyzer MCR301 (manufactured by Anton Paar) with a probe diameter of 8 mm, a temperature range of 20 to 120°C, a heating rate of 5°C / min, a strain of 0.1%, and a frequency of 1 Hz. In the case of the double-sided adhesive sheet with release sheet obtained in Comparative Example 4, the illuminance was 200 mW / cm² from the second release sheet side. 2 Using a UV LED lamp (365nm), the integrated light intensity is 3000 mJ / cm². 2 The storage modulus was measured using the same method as described above, with an adhesive layer obtained by post-curing an adhesive sheet by irradiating it with light in such a manner.

[0114] <Adhesion to glass> The method for measuring adhesive strength was followed according to JIS Z 0237. First, the release liner on the easily peelable side of the adhesive sheet with a release liner was peeled off and bonded to 100 μm PET (Toyobo Co., Ltd. / product number: Cosmoshine A4300) to obtain a test piece with a width of 25 mm and a length of 50 mm. Next, the release liner on the other side of this test piece was peeled off, and the adhesive layer was bonded to soda glass (Hiraoka Special Glass Manufacturing Co., Ltd., with the bonding surface being the opposite side of the tin float) using a 2 kg roller. In this case, except for the use of soda glass as the test plate, the measurement sample was prepared according to the method for measuring 180° peel adhesive strength described in JIS Z 0237. Then, 24 hours after bonding, the adhesive strength was measured at a peeling speed of 300 mm / min, and this adhesive strength was defined as the adhesive strength to glass.

[0115] (Fabrication of laminates) In the examples and comparative examples, the release liner on the lightly peeled side of the adhesive layer of the double-sided adhesive sheet with release liner obtained was peeled off and laminated to a 100 μm PET film (Toyobo Co., Ltd. / product number: Cosmoshine A4300). Furthermore, the release liner on the heavily peeled side was peeled off and laminated to a 100 mm x 300 mm polycarbonate resin plate (Teijin Corporation / product number: Panlight PC-1151 / thickness 0.5 mm). After that, it was treated in an autoclave at a temperature of 30°C and a pressure of 0.5 MPa for 30 minutes to obtain a laminate. In Comparative Example 4, after obtaining the above test piece, the illuminance was 200 mW / cm from the 100 μm PET side. 2 Using a UV LED lamp (365nm), the integrated light intensity is 3000 mJ / cm². 2 It was cured by irradiating it with light in this manner.

[0116] (Multi-layer simultaneous processability) Using a guillotine cutter, the laminate was cut vertically from the PET film side of the laminate at a position 50 mm from the short side, obtaining a processed product measuring 100 mm x 250 mm. The simultaneous multilayer processing capability was evaluated by microscopic observation of the cut surface formed at this time, according to the following criteria. ○: There were no air bubbles on the cut surface, and the peeling distance was less than 0.05 mm. △: No air bubbles were present on the cut surface, and the peeling distance was 0.05 mm or more and less than 0.1 mm. ×: There were air bubbles on the cut surface, or the peeling distance was 0.1 mm or more.

[0117] (Evaluation of warping of processed products) The laminate was placed horizontally on the 250mm long side, the maximum amount of warping was measured, and the warping of the processed product was evaluated according to the following criteria. ○: The maximum amount of warping was within 5 mm, indicating that warping was suppressed. ×: The maximum warp was 5mm or more, indicating warping.

[0118] (Sticky end surface) A sample for cutting was prepared by stacking 50 double-sided adhesive sheets with release liner obtained in the A4-sized examples and comparative examples. In the double-sided adhesive sheet with release liner obtained in Comparative Example 4, the illuminance from the second release liner side was 200 mW / cm². 2 Using a UV LED lamp (365nm), the integrated light intensity is 3000 mJ / cm². 2 Light was irradiated to achieve the desired result. The guillotine blade and the cut surface (edge) of the sample used for cutting were visually inspected using a guillotine cutter, and the stickiness of the edge (end) was determined according to the following criteria. ○: There was no excess adhesive from the cut edges of the adhesive sheet, and there was no stickiness on the guillotine blade or the cut edges, indicating good performance. △: There was a slight excess of adhesive from the cut edges of the adhesive sheet, and there was some stickiness on the guillotine blade and the cut edges, but it was at a level that did not pose any practical problems. ×: The adhesive oozed excessively from the cut edges of the adhesive sheet, and the stickiness of the guillotine blade and the cut edges was at a level that posed practical problems.

[0119] (comprehensive evaluation) The overall evaluation of multi-layer simultaneous machining capability, workpiece warpage, and end face stickiness was judged according to the following criteria. ◎: Received a good rating in all of the above evaluations. ○: While some aspects of the evaluation are not perfect, they are at a level that does not pose any practical problems. ×: There were problems with some aspects of the evaluation, to the point where they posed practical problems.

[0120] [Table 1]

[0121] Table 1 shows the component ratios of the adhesive composition used to manufacture the adhesive sheet, and the evaluation results of the obtained adhesive sheet. The laminates formed from the adhesive sheets obtained in each example were less prone to warping and stickiness at the edges, even when the resin plate and film substrate in the laminate were processed simultaneously. Therefore, it was found that the adhesive sheet of the present invention is suitable as an adhesive for forming laminates of resin plates and film substrates.

Claims

1. An adhesive sheet comprising an adhesive layer for bonding a resin plate and a film substrate, The adhesive layer contains a crosslinked acrylic high molecular weight polymer (A) with a mass average molecular weight of 500,000 or more and 2,000,000 or less, and an acrylic low molecular weight polymer (B) with a mass average molecular weight of 3,000 or more and 50,000 or less. In the acrylic high molecular weight polymer (A), the amount of carboxyl group-containing monomer units is 6 parts by mass or more per 100 parts by mass of the total mass of structural units, The acrylic low molecular weight polymer (B) contains alkyl (meth)acrylate units, and the content of units other than alkyl (meth)acrylate units is 1% by mass or less with respect to the total mass of the acrylic low molecular weight polymer (B). The Tg of the aforementioned acrylic low molecular weight polymer (B) is 80°C or higher. The adhesive layer is an adhesive sheet having a storage modulus of 0.2 to 2 MPa at 25°C.

2. The adhesive sheet according to claim 1, wherein the gel fraction of the adhesive layer is 60% or more.

3. The adhesive sheet according to claim 1 or 2, wherein the adhesive strength of the adhesive layer against glass is 10 N / 25 mm or more.

4. The adhesive sheet according to any one of claims 1 to 3, wherein the thickness of the adhesive layer is 5 to 50 μm.

5. The adhesive sheet according to any one of claims 1 to 4, wherein the amount of carboxyl group-containing monomer units is 20 parts by mass or less per 100 parts by mass of the total mass of structural units in the acrylic high molecular weight polymer (A).

6. A laminate comprising an adhesive sheet according to any one of claims 1 to 5 and a resin plate.

7. A method for using an adhesive sheet according to any one of claims 1 to 5, A step of bonding the adhesive sheet and the film substrate to obtain an adhesive-coated film, A lamination process to obtain a laminate by bonding the adhesive-coated film and the resin plate, A step of subjecting the laminate to machining, A method for using an adhesive sheet, comprising the following features.

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