Pressure-sensitive adhesive sheet laminate

Abstract

Provided is a pressure-sensitive adhesive sheet laminate that is less prone to appearance defects regardless of being provided with a pressure-sensitive adhesive layer having a high storage elastic modulus and a large thickness.　The pressure-sensitive adhesive sheet laminate according to the present invention comprises a pressure-sensitive adhesive layer and a release sheet A. The release sheet A is bonded so as to be in contact with at least one surface of the pressure-sensitive adhesive layer. The thickness of the release sheet A is 0.25 times or more the thickness of the pressure-sensitive adhesive layer. The 180° peeling force Sa between the release sheet A and the pressure-sensitive adhesive layer is 0.2-0.5 N / 50 mm. The storage elastic modulus of the pressure-sensitive adhesive layer at 23°C is 5×104 Pa or greater. The thickness of the pressure-sensitive adhesive layer is 120 μm or greater. T (minutes) measured according to the separator creep test is T>40.

Description

Adhesive sheet laminate

[0001] The present invention relates to a pressure-sensitive adhesive sheet laminate.

[0002] Conventionally, input devices used in combination with display devices such as liquid crystal displays (LCDs) and display devices such as touch panels have been widely used. In these display devices and input devices, transparent pressure-sensitive adhesive sheets are used to bond optical members, and pressure-sensitive adhesive sheets are also used to bond the display devices and input devices.

[0003] A pressure-sensitive adhesive sheet typically includes a pressure-sensitive adhesive layer. If the pressure-sensitive adhesive layer is exposed, it may deteriorate during storage or transportation, or may stick to other materials. For this reason, pressure-sensitive adhesive sheets are generally stored and transported with the pressure-sensitive adhesive layer protected by a release sheet. A release sheet is, for example, a component formed by providing a release layer on a substrate, and is sometimes referred to as a separator. A release sheet is used, for example, by directly adhering it to the pressure-sensitive adhesive layer. Hereinafter, a laminate in which a release sheet is adhered to a pressure-sensitive adhesive layer will be referred to as a "pressure-sensitive adhesive sheet laminate." Furthermore, the term "pressure-sensitive adhesive sheet" refers to a pressure-sensitive adhesive layer without a release sheet, and particularly refers to the pressure-sensitive adhesive layer alone.

[0004] In the lamination process of components using pressure-sensitive adhesive sheets, a low peel force when peeling the separator from the pressure-sensitive adhesive layer is important for improving the efficiency of the lamination process. If the release sheet is heavy (i.e., if the force required for peeling is large), measures such as slowing down the peeling speed are necessary, which reduces the efficiency of the lamination process. From this perspective, technologies for improving the releasability of release sheets have been widely studied. For example, Patent Document 1 discloses a pressure-sensitive adhesive film that has excellent releasability of the separator film and good workability.

[0005] JP 2009-242767 A

[0006] On the other hand, during the manufacturing process, pressure-sensitive adhesive sheets are subjected to bending stress due to sheet bending caused by the conveying roll path, curling caused by product winding, etc. In pressure-sensitive adhesive sheets in which the storage modulus of the pressure-sensitive adhesive layer is high and the thickness is large (for example, a pressure-sensitive adhesive layer having a thickness of 120 μm or more), if the release strength of the release sheet in the pressure-sensitive adhesive sheet laminate is low, this can cause misalignment between the release sheet and the pressure-sensitive adhesive layer, resulting in the problem of floating (poor appearance) in the pressure-sensitive adhesive sheet.

[0007] That is, in a pressure-sensitive adhesive sheet laminate in which the pressure-sensitive adhesive layer has a high storage modulus and a large thickness, simply reducing the peel force of the release sheet to improve releasability has tended to result in problems with poor appearance (a pressure-sensitive adhesive sheet with a low storage modulus follows deformation even when bent, so peel lifting is less likely to occur). This means that in a pressure-sensitive adhesive sheet laminate with a release sheet, the releasability of the release sheet and the suppression of poor appearance are in a trade-off relationship. In particular, in a pressure-sensitive adhesive sheet laminate having a pressure-sensitive adhesive layer with a high storage modulus and a large thickness, it is difficult to achieve both improved releasability and the suppression of poor appearance. However, depending on the type of application, a pressure-sensitive adhesive sheet with a high storage modulus and a large thickness may be required, so it is extremely important to establish a technology that improves the releasability of the release sheet and suppresses poor appearance, even in a pressure-sensitive adhesive sheet laminate having a pressure-sensitive adhesive layer with a high storage modulus and a large thickness.

[0008] The present invention has been made in view of the above, and has an object to provide a pressure-sensitive adhesive sheet laminate that is less likely to suffer from poor appearance despite having a pressure-sensitive adhesive layer with a high storage modulus and a large thickness.

[0009] As a result of extensive research to achieve the above-mentioned object, the inventors discovered that the above-mentioned object can be achieved by combining an adhesive layer having predetermined properties with a release sheet, and thus completed the present invention.

[0010] That is, the present invention encompasses, for example, the subject matter described in the following items: Item 1: A pressure-sensitive adhesive sheet laminate comprising a pressure-sensitive adhesive layer and a release sheet A, wherein the release sheet A is attached so as to be in contact with at least one surface of the pressure-sensitive adhesive layer, the thickness of the release sheet A is 0.25 times or more the thickness of the pressure-sensitive adhesive layer, the 180° peel force Sa between the release sheet A and the pressure-sensitive adhesive layer is 0.2 to 0.5 N / 50 mm, and the storage modulus at 23°C of the pressure-sensitive adhesive layer is 5×10 ４ A pressure-sensitive adhesive sheet laminate having a viscosity of 100 Pa or more, a thickness of the pressure-sensitive adhesive layer of 120 μm or more, and T (minutes), measured in accordance with the separator creep test described below, is greater than 40. <Separator Creep Test> A film is attached to the surface of the pressure-sensitive adhesive layer opposite to the release sheet A to prepare a pressure-sensitive adhesive sheet laminate (25 mm wide x 25 mm long), and the film side of this pressure-sensitive adhesive sheet laminate is fixed to a SUS304 plate with double-sided tape to prepare a test sample. That is, a test sample is prepared in which the release sheet A, the pressure-sensitive adhesive layer, the film, the double-sided tape, and the SUS304 plate are laminated in this order. For this test sample, a shear load of 9.8 N is applied to release sheet A at 23°C, and the time required for release sheet A and the pressure-sensitive adhesive layer to peel is measured, and this time is designated T (minutes). Item 2. The pressure-sensitive adhesive sheet laminate according to Item 1, wherein a release sheet B is attached to the surface of the pressure-sensitive adhesive layer opposite to the surface to which the release sheet A is attached, the thickness of the release sheet B is 0.2 times or more the thickness of the pressure-sensitive adhesive layer, and the 180° peel force Sb between the release sheet B and the pressure-sensitive adhesive layer is 1.5 times or more the peel force Sa. Item 3. The pressure-sensitive adhesive sheet laminate according to Item 1 or 2, wherein the pressure-sensitive adhesive layer is a cured product of an active energy ray-curable pressure-sensitive adhesive.

[0011] The pressure-sensitive adhesive sheet laminate of the present invention is less likely to suffer from poor appearance despite having a pressure-sensitive adhesive layer with a high storage modulus and a large thickness.

[0012] FIG. 1 is a schematic diagram illustrating a separator creep test.

[0013]

[0023] In the present specification, the terms "contain" and "comprise" include the concepts of "contain," "comprise," "consist essentially of," and "consist only of."

[0014] The pressure-sensitive adhesive sheet laminate of the present invention includes a pressure-sensitive adhesive layer and a release sheet A. In the pressure-sensitive adhesive sheet laminate of the present invention, the release sheet A is bonded to at least one surface of the pressure-sensitive adhesive layer so as to be in contact with the pressure-sensitive adhesive layer, the thickness of the release sheet A is 0.25 times or more the thickness of the pressure-sensitive adhesive layer, and the 180° peel force Sa between the release sheet A and the pressure-sensitive adhesive layer is 0.2 to 0.5 N / 50 mm.

[0015] In the pressure-sensitive adhesive sheet laminate of the present invention, the pressure-sensitive adhesive layer has a storage modulus of 5×10 at 23° C. ４ The pressure-sensitive adhesive layer has a thickness of 120 μm or more. Furthermore, the pressure-sensitive adhesive sheet laminate of the present invention has a T (minutes) measured in accordance with a predetermined separator creep test of T>40.

[0016] The pressure-sensitive adhesive sheet laminate of the present invention is less likely to suffer from poor appearance despite having a pressure-sensitive adhesive layer with a high storage modulus and a large thickness. In particular, the pressure-sensitive adhesive sheet laminate of the present invention has a 180° peel strength Sa of 0.2 to 0.5 N / 50 mm, which allows for easy peeling and excellent lamination efficiency. In other words, the pressure-sensitive adhesive sheet laminate of the present invention is less likely to suffer from poor appearance while providing excellent peelability despite having a pressure-sensitive adhesive layer with a high storage modulus and a large thickness.

[0017] In this specification, the term "adhesive sheet laminate of the present invention" means a laminate in which a release sheet A is bonded to an adhesive layer, and the term "adhesive sheet" means an adhesive layer without a release sheet, and in particular means only the adhesive layer.

[0018] (Adhesive Layer) In the adhesive sheet laminate of the present invention, the adhesive layer has a storage modulus at 23°C of 5 × 10 ４ The type of the material is not particularly limited as long as the material has a modulus of at least 100 Pa and a thickness of at least 120 μm.

[0019] For example, the pressure-sensitive adhesive layer preferably contains an acrylic polymer, and more preferably has a crosslinked structure. Therefore, the pressure-sensitive adhesive layer is preferably formed from various pressure-sensitive adhesive compositions containing an acrylic polymer. In particular, the pressure-sensitive adhesive layer is preferably a cured product of an active energy ray-curable pressure-sensitive adhesive composition in order to provide thickness.

[0020] The pressure-sensitive adhesive composition contains at least a base agent containing an acrylic polymer, and also contains a crosslinking agent, a polyfunctional monomer, a photopolymerization initiator, and the like, which will be described later.

[0021] The type of acrylic polymer contained in the base material is not particularly limited, and examples thereof include a wide range of known acrylic polymers that are widely used in conventional pressure-sensitive adhesive sheets.

[0022] The type of the acrylic polymer is not particularly limited as long as it is a polymer composed of, for example, (meth)acrylic monomer units. Note that the (meth)acrylic monomer units refer to structural units formed by polymerization of (meth)acrylic monomers.

[0023] An example of the (meth)acrylic monomer unit is a (meth)acrylic acid ester unit. Examples of the (meth)acrylic acid ester include a (meth)acrylate having a linear, branched, or cyclic alkyl group, and a (meth)acrylate having an aromatic ring. When the (meth)acrylate has a linear, branched, or cyclic alkyl group, the number of carbon atoms therein can be, for example, 1 to 20, preferably 1 to 15, and more preferably 2 to 10. When the (meth)acrylate has an aromatic ring, the number of carbon atoms therein can be, for example, 5 to 20, preferably 6 to 10. Specific examples of the (meth)acrylic acid ester monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, isopropyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, and benzyl (meth)acrylate.

[0024] The (meth)acrylic monomer units may include, in addition to the (meth)acrylic acid ester units, monomer units having a carboxy group and monomer units having a hydroxy group. Examples of monomers having a carboxy group include (meth)acrylic acid. Examples of monomers having a hydroxy group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2,2-dimethyl-2-hydroxyethyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate.

[0025] The (meth)acrylic monomer unit constituting the acrylic polymer may be one type alone or two or more types. That is, the acrylic polymer may be a homopolymer or a copolymer, and a copolymer is more preferable. For example, the acrylic polymer may be a copolymer of one or more types of (meth)acrylic acid esters and one or more types of monomers having a carboxy group.

[0026] When the acrylic polymer contains a monomer unit having a carboxy group and / or a monomer unit having a hydroxyl group, the total content thereof is preferably 0.1 to 40% by mass, more preferably 0.5 to 35% by mass, in the acrylic polymer. The acrylic polymer preferably contains 40% by mass or more of the (meth)acrylic acid ester units, more preferably 50% by mass or more, even more preferably 55% by mass or more, and particularly preferably 60% by mass or more.

[0027] The weight-average molecular weight of the acrylic polymer is not particularly limited, and from the viewpoint of preventing a decrease in adhesive strength in the pressure-sensitive adhesive sheet, it can be, for example, 100,000 to 2,000,000, and more preferably 200,000 to 1,000,000. Note that the weight-average molecular weight referred to in the present invention refers to the weight-average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC).

[0028] There are no particular limitations on the GPC apparatus used in the GPC method, and commercially available GPC measuring instruments, such as the LC-2000Plus series manufactured by JASCO Corporation, and detectors such as RI-2031Plus and UV-2075Plus, can be used. In this case, for example, a GPC column consisting of four columns connected together, namely, "Shodex KF801," "Shodex KF803L," "Shodex KF800L," and "Shodex KF800D" manufactured by Showa Denko K.K., can be used. The column temperature can be set to 40°C. Tetrahydrofuran is used as the eluent, and measurements are performed at a flow rate of 1.0 ml / min. Typically, a calibration curve is prepared using standard polystyrene, and the weight average molecular weight (Mw) can be obtained in polystyrene equivalent terms.

[0029] The acrylic polymer can be produced, for example, by polymerizing a monomer mixture for forming each structural unit by a known polymerization method. Examples of the polymerization method that can be used include solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization. The ratio of each structural unit in the acrylic polymer corresponds to the ratio of each monomer used during polymerization. The types of solvent and polymerization initiator used in the polymerization are not particularly limited, and for example, solvents and polymerization initiators used in the production of known acrylic polymers can be used.

[0030] In the pressure-sensitive adhesive composition, the base agent may further contain a monofunctional monomer in addition to the acrylic polymer described above. In this case, the base agent may be in the form of a solution (syrup) in which the acrylic polymer is dissolved in the monofunctional monomer, or in the form in which a monofunctional monomer solution is partially bulk-polymerized by heat or light. When the acrylic polymer is a copolymer, the monofunctional monomer contained in the base agent may be a mixture of the same monomers as the monomers constituting the acrylic polymer. In this case, the ratio of each monomer in the mixture may be the same as the ratio of each monomer constituting the acrylic polymer, but is not limited to this.

[0031] When the base resin is a partial bulk polymer obtained by partial bulk polymerization, the polymer fraction is not particularly limited. The polymer fraction is the content (mass %) of the resin component relative to the total mass of the resin component (e.g., acrylic polymer) and the monomer. The polymer fraction can be, for example, 1 to 80 mass %, and preferably 5 to 50 mass %.

[0032] The base material preferably consists of only an acrylic polymer and a monofunctional monomer.

[0033] The pressure-sensitive adhesive composition may contain a crosslinking agent. Examples of crosslinking agents include functional group reactive crosslinking agents and polyfunctional monomers. Examples of functional group reactive crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, chelate-based crosslinking agents, and carbodiimide-based crosslinking agents. Examples of polyfunctional monomers include compounds having two or more polymerizable double bonds in the molecule. The polyfunctional monomer has two or more polymerizable double bonds, preferably two or more but less than five, and more preferably two or more but less than four.

[0034] The type of isocyanate crosslinking agent is not particularly limited, and a wide variety of known compounds can be used. Examples of isocyanate crosslinking agents include polyisocyanates such as tolylene 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. The isocyanate crosslinking agents can be used alone or in combination of two or more different types. It is more preferable to use trifunctional derivatives, such as adducts, nurates, and biurets, obtained from the above-mentioned diisocyanates as the isocyanate crosslinking agent.

[0035] The type of epoxy crosslinking agent is not particularly limited, and a wide variety of known compounds can be used. Examples of epoxy crosslinking agents 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-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexanone, trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, and sorbitol polyglycidyl ether.

[0036] The type of chelate crosslinking agent is not particularly limited, and examples thereof include aluminum chelate, titanium chelate, and zirconium chelate.

[0037] The carbodiimide crosslinking agent is not particularly limited as long as it is a compound having a carbodiimide group in the molecule, and examples thereof include monocarbodiimide and polycarbodiimide.

[0038] Examples of polyfunctional monomers include bifunctional monomers (monomers having two polymerizable double bonds), such as polyethylene glycol diacrylate, polypropylene diacrylate, alkyl diacrylate, polytetramethylene glycol diacrylate, polypropylene glycol diacrylate, dioxane diacrylate, tricyclodecanol diacrylate, and fluorene diacrylate. Examples of polyfunctional monomers include trifunctional or higher functional monomers, such as alkoxylated trimethylolpropane triacrylate, alkoxylated glycerin triacrylate, caprolactone-modified isocyanurate triacrylate, pentaerythritol acrylate, alkoxylated pentaerythritol acrylate, (alkoxylated) pentaerythritol acrylate, (alkoxylated) ditrimethylolpropane acrylate, (alkoxylated) dipentaerythritol acrylate, and (ethoxylated) polyglycerin acrylate.

[0039] The polyfunctional monomer may have a bisphenol skeleton in one molecule, such as a diacrylate of bisphenol A diglycidyl ether, a diacrylate of propoxylated bisphenol A, or a diacrylate of bisphenol F diglycidyl ether.

[0040] The polyfunctional monomer may be, for example, a commercially available product. Examples of commercially available products include "A-200" (polyethylene glycol #200 diacrylate) and "A-400" (polyethylene glycol #400 diacrylate) from the NK Ester series, which are bifunctional polyethylene glycol acrylates manufactured by Shin-Nakamura Chemical Co., Ltd., trifunctional monomer M310 (trimethylolpropane PO-modified triacrylate) and trifunctional monomer M321 (trimethylolpropane propylene oxide-modified triacrylate) manufactured by Toagosei Co., Ltd., and bifunctional monomer M211B (bisphenol A EO-modified diacrylate) manufactured by Toagosei Co., Ltd.

[0041] When the pressure-sensitive adhesive composition contains a polyfunctional monomer, the main agent can form a crosslinked structure by curing the pressure-sensitive adhesive composition with active energy rays, which makes the pressure-sensitive adhesive sheet more likely to have excellent adhesive strength.

[0042] The content of the crosslinking agent in the pressure-sensitive adhesive composition is not particularly limited, and for example, the pressure-sensitive adhesive composition may contain 10 parts by mass or less, and more preferably 5 parts by mass or less, of the crosslinking agent per 100 parts by mass of the main agent. Furthermore, the pressure-sensitive adhesive composition preferably contains 0.01 parts by mass or more, and more preferably 0.05 parts by mass or more, of the crosslinking agent per 100 parts by mass of the main agent. When the pressure-sensitive adhesive composition contains a crosslinking agent, one type of crosslinking agent may be used alone, or two or more types of crosslinking agents may be used in combination.

[0043] (Photopolymerization initiator) The pressure-sensitive adhesive composition may contain a photopolymerization initiator. As the photopolymerization initiator, for example, a wide variety of known photopolymerization initiators can be used, and among them, an acetophenone-based photopolymerization initiator or an acylphosphine oxide-based photopolymerization initiator is preferred.

[0044] Specific examples of acetophenone-based initiators include diethoxyacetophenone, benzyl dimethyl ketal, oligo(2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenylpropanone], 2,2-dimethoxy-2-phenylacetophenone, (1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, etc. Specific examples of benzoin ether-based initiators include benzoin and benzoin methyl ether.

[0045] Specific examples of the acylphosphine oxide initiator include phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0046] Other examples of the photopolymerization initiator include benzoin ether initiators, benzophenone initiators, hydroxyalkylphenone initiators, thioxanthone initiators, and amine initiators.

[0047] The content of the photopolymerization initiator in the pressure-sensitive adhesive composition is not particularly limited, and may be, for example, 0.01 to 5 parts by mass, and more preferably 0.05 to 1 part by mass, of the photopolymerization initiator per 100 parts by mass of the pressure-sensitive adhesive composition. When the pressure-sensitive adhesive composition contains a photopolymerization initiator, one type of photopolymerization initiator may be used alone, or two or more types of photopolymerization initiators may be used in combination.

[0048] The pressure-sensitive adhesive composition preferably contains a base agent containing the acrylic polymer and the monofunctional monomer, a crosslinking agent, and a photopolymerization initiator. In addition, the pressure-sensitive adhesive composition may contain a silane coupling agent, a solvent, etc., and may also contain a dye or pigment for coloring.

[0049] The method for forming the pressure-sensitive adhesive layer is not particularly limited, and for example, a wide variety of known methods can be employed. When forming a pressure-sensitive adhesive layer using the above-mentioned pressure-sensitive adhesive composition, for example, the pressure-sensitive adhesive layer can be formed by curing the pressure-sensitive adhesive composition using a known method. Such a pressure-sensitive adhesive layer is a cured product of the pressure-sensitive adhesive composition. Specifically, the method can include a step of applying the pressure-sensitive adhesive composition to a substrate to form a coating film, and a step of irradiating the coating film with active energy rays to obtain a cured product of the pressure-sensitive adhesive composition. This allows the pressure-sensitive adhesive layer to be formed by curing the pressure-sensitive adhesive composition.

[0050] The PSA composition can be applied using a known coating device, such as a blade coater, air knife coater, roll coater, bar coater, gravure coater, microgravure coater, rod blade coater, lip coater, die coater, or curtain coater.

[0051] The substrate onto which the pressure-sensitive adhesive composition is applied can be various substrates, such as a resin substrate or a glass substrate. In particular, in the present invention, the substrate can be a release sheet A or a release sheet B described below. By sandwiching the pressure-sensitive adhesive layer between a pair of release sheets, a double-sided pressure-sensitive adhesive sheet laminate can be easily produced. Furthermore, instead of the release sheet, a film that has not been release-treated, such as a film of polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, polyarylate, or other polyester, can also be used.

[0052] The thickness of the pressure-sensitive adhesive composition after coating can be appropriately set depending on the desired thickness of the pressure-sensitive adhesive layer. After forming the coating film, the coating film may be subjected to a heat treatment or a drying treatment, if necessary.

[0053] The step of irradiating the coating film with active energy rays can be, for example, a step similar to a known method. In this step, the photopolymerization initiator in the pressure-sensitive adhesive composition generates radicals due to the active energy rays, and the polymerizable components in the pressure-sensitive adhesive composition (e.g., monomers, polyfunctional monomers, etc. in the pressure-sensitive adhesive composition) initiate and progress a polymerization reaction due to the generated radicals, thereby forming a polymerized and cured product. This allows the formation of a pressure-sensitive adhesive layer and also improves adhesive strength.

[0054] Examples of active energy rays include ultraviolet rays, electron beams, visible light, X-rays, and ion beams, and can be appropriately selected depending on the photopolymerization initiator contained in the pressure-sensitive adhesive layer. Among these, ultraviolet rays or electron beams are preferred from the viewpoint of versatility, and ultraviolet rays are particularly preferred. Examples of light sources that can be used for ultraviolet rays include chemical lamps, LEDs, high-pressure mercury lamps, low-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, carbon arcs, xenon arcs, and electrodeless ultraviolet lamps. The irradiation output of ultraviolet rays is such that the cumulative light amount is 100 to 10,000 mJ / cm. ２ It is preferable to set the value to 200 to 5000 mJ / cm ２ It is more preferable to set it so that:

[0055] The thickness of the pressure-sensitive adhesive layer can be appropriately set depending on the application as long as it is 120 μm or more, and is, for example, preferably 125 μm or more, more preferably 150 μm or more, and is preferably 1000 μm or less.

[0056] The pressure-sensitive adhesive layer may have either a single-layer structure or a multilayer structure, and preferably has a single-layer structure.

[0057] The pressure-sensitive adhesive layer has a storage modulus of 5×10 at 23° C. ４ The storage modulus of the pressure-sensitive adhesive layer at 23°C is 5 x 10 Pa or more. ４ If the storage modulus is less than 5×10 Pa, the pressure-sensitive adhesive sheet may not have sufficient hardness, which may limit its applications. ４ Pa or more, and ４ Pa or more, and 1 × 10 ７ It is preferable that the pressure is 0.05 Pa or less.

[0058] (Release Sheet A) The release sheet A can be, for example, a substrate on which a release treatment layer is formed. Examples of the substrate include a resin film and paper. Examples of the resin film include polyethylene terephthalate, polybutylene terephthalate, polyethylene, polypropylene, polyarylate, polyester, etc. Examples of the paper include polyethylene-laminated paper, polypropylene-laminated paper, clay-coated paper, resin-coated paper, glassine paper, etc.

[0059] The release treatment layer can be formed from various resins, such as silicone-based resins, long-chain alkyl-based resins, and fluorine-based resins.

[0060] The release treatment layer used in the release sheet is preferably a silicone-based release agent. The silicone release layer is cured by either a thermal condensation type, a thermal addition type, or an ultraviolet curing type. Examples of the thermal condensation type include a reaction between polydimethylsiloxane and polymethylhydrosiloxane using an organotin catalyst, etc., and examples of the thermal addition type include a reaction between vinyl-group-containing polydimethylsiloxane and polymethylhydrogensiloxane using a platinum catalyst, etc. Examples of ultraviolet curing release agents include those obtained by polymerizing epoxy-group-containing modified silicones by photocationic polymerization. To adjust the release properties, MQ resins, vinyl-group-containing silicone resins, silicone oils, silane coupling agents, leveling agents, etc. may be added to the silicone-based release agent. Furthermore, the thickness may be adjusted to adjust the release force.

[0061] The base material of the release sheet A is preferably polyethylene terephthalate, and the release treatment layer is preferably a silicone-based release agent. This combination tends to bring both the 180° peel force Sa and T measured according to the separator creep test into the desired range.

[0062] Commercially available release sheets A can be used, such as "75E-KF" manufactured by Fujimori Kogyo Co., Ltd., "50-TKA (09)" manufactured by Toray Industries, Inc., "75-J02" manufactured by Nippa Corporation, and "NS-75-SUM" manufactured by Nakamoto Packs Co., Ltd.

[0063] The thickness of release sheet A is at least 0.25 times the thickness of the pressure-sensitive adhesive layer. By setting the thickness at this level, the appearance of the pressure-sensitive adhesive sheet laminate is suppressed. Specifically, even if curling occurs due to sheet bending or product winding during the pressure-sensitive adhesive sheet manufacturing process, misalignment between the release sheet and the pressure-sensitive adhesive layer is unlikely to occur, and the occurrence of lifting in the pressure-sensitive adhesive sheet is suppressed. If the thickness of release sheet A is less than 0.25 times the thickness of the pressure-sensitive adhesive layer, misalignment between the release sheet and the pressure-sensitive adhesive layer is likely to occur, causing lifting in the pressure-sensitive adhesive sheet and resulting in a poor appearance.

[0064] The thickness of the release sheet A is preferably 0.25 times or more, more preferably 0.28 times or more, and preferably 1 time or less, the thickness of the pressure-sensitive adhesive layer.

[0065] (Adhesive Sheet Laminate) The adhesive sheet laminate of the present invention comprises at least an adhesive layer and a release sheet A, and the release sheet A is attached so as to be in contact with at least one surface of the adhesive layer. More specifically, the release sheet A is attached directly to one surface of the adhesive layer.

[0066] In the pressure-sensitive adhesive sheet laminate, the 180° peel force Sa between the release sheet A and the pressure-sensitive adhesive layer is 0.2 to 0.5 N / 50 mm (i.e., 0.2 N / 50 mm or more and 0.5 N / 50 mm or less). If the 180° peel force Sa is less than 0.2 N / 50 mm, the release sheet A may be unintentionally peeled off or shifted, or if the pressure-sensitive adhesive sheet is curved, the release sheet A may be easily shifted, which may result in poor appearance. If the 180° peel force Sa exceeds 0.5 N / 50 mm, the peel force is too strong, making it difficult to peel off the release sheet A and reducing the efficiency of the lamination operation using the pressure-sensitive adhesive sheet.

[0067] The 180° peel force Sa between the release sheet A and the pressure-sensitive adhesive layer can be measured as follows. A film is attached to the surface of the pressure-sensitive adhesive layer opposite the release sheet A to prepare a pressure-sensitive adhesive sheet laminate (50 mm wide x 50 mm long), and the film side of this pressure-sensitive adhesive sheet laminate is fixed to a SUS304 plate with double-sided tape to prepare a test sample. That is, a test sample is prepared by laminating the release sheet A, the pressure-sensitive adhesive layer, the film, the double-sided tape, and the SUS304 plate in this order. Thereafter, the test sample is left to stand for one day under an environment of atmospheric pressure, temperature 23°C, and humidity 50%, and then the release sheet A is peeled at 180° at a rate of 0.3 m / min using a Shimadzu AGX-500NX, and the peel force at this time is recorded as the 180° peel force Sa (N / 50 mm). The type of film used in measuring the 180° peel force Sa is not particularly limited; for example, the same type of film as that contained in the test sample S used in the separator creep test described below can be used.

[0068] The pressure-sensitive adhesive sheet laminate of the present invention has a T (minutes) measured according to a separator creep test of >40. The separator creep test is performed by the following method. <Separator Creep Test> A film is attached to the surface of the pressure-sensitive adhesive layer opposite the release sheet A to prepare a pressure-sensitive adhesive sheet laminate (25 mm wide x 25 mm long), and the film side of this pressure-sensitive adhesive sheet laminate is fixed to a SUS304 plate with double-sided tape to prepare a test sample. That is, a test sample is prepared in which the release sheet A, the pressure-sensitive adhesive layer, the film, the double-sided tape, and the SUS304 plate are laminated in this order. A shear load of 9.8 N is applied to the release sheet A at 23°C in this test sample, and the time required for the release sheet A and the pressure-sensitive adhesive layer to peel is measured, and this time is designated as T (minutes). A more detailed measurement procedure for the separator creep test is described with reference to FIG. 1.

[0069] FIG. 1 is a schematic diagram illustrating how a separator creep test is performed. The separator creep test is performed by preparing a test sample S shown in FIG. 1 . The test sample S can be prepared, for example, by the following procedure. First, a pressure-sensitive adhesive sheet laminate consisting of a release sheet A, a pressure-sensitive adhesive layer 1, and a film 2 is prepared and cut into a size of 25 mm x 90 mm. After that, the release sheet A is slowly peeled from the interface of the pressure-sensitive adhesive layer from one end in the longitudinal direction, and the film 2 and the pressure-sensitive adhesive layer 1 are cut out so that a 25 mm x 25 mm portion of the film 2 and the pressure-sensitive adhesive layer 1 remain from the other end (the 25 mm x 90 mm portion of the release sheet A is left). A metal ring (not shown) is attached to a portion C (end portion) of the release sheet A where the film 2 and the pressure-sensitive adhesive layer 1 are not bonded. A triangular ring with a side length of 35 mm is prepared as the metal ring by folding SUS304 stainless steel with a diameter of 3 mm. This is wrapped around the side edge of the release sheet A and secured in place with a stapler.

[0070] Separately, a SUS304 plate (labeled "SUS304" in FIG. 1 ) measuring 1 mm thick, 30 mm wide, and 50 mm long and having a hole H drilled in the upper portion was prepared. Double-sided tape 3 was attached to the SUS304 plate so as not to block the hole H. The film 2 side of the pressure-sensitive adhesive sheet laminate (25 mm x 25 mm) was then attached to the double-sided tape 3 and adhered with a roller to prepare a test sample S. This test sample S was hung on a hook via the hole H in the SUS304 plate, and a 1 kg weight G was hung from the metal ring at 23°C to apply a shear load of 9.8 N to the release sheet A in the vertical direction. The time required for the release sheet A and the pressure-sensitive adhesive layer 1 to peel was measured. This time was designated T (minutes), as measured in accordance with the separator creep test. Therefore, T (minutes) refers to the time from immediately after the 1 kg weight G was hung from the metal ring until the release sheet A and the pressure-sensitive adhesive layer 1 were completely peeled off.

[0071] The type of film 2 used to prepare the test sample S is not particularly limited, and may be, for example, a release sheet, or a material other than a release sheet, such as a resin sheet. When film 2 is a release sheet, such a release sheet may be the same as release sheet A, may be a different type of release sheet, or may be release sheet B described below. The type of resin sheet is also not particularly limited, and a wide variety of known resin sheets, such as polyethylene terephthalate (PET), can be used.

[0072] When the T of the pressure-sensitive adhesive sheet laminate of the present invention is 40 minutes or less, the pressure-sensitive adhesive sheet laminate is likely to have poor appearance. That is, when the T is 40 minutes or less, the release sheet A may be unintentionally peeled off or shifted, or when the pressure-sensitive adhesive sheet is curved, the release sheet A is likely to shift, which is likely to cause poor appearance.

[0073] In the pressure-sensitive adhesive sheet laminate of the present invention, the T is preferably 41 minutes or more, more preferably 43 minutes or more, even more preferably 60 minutes or more, even more preferably 90 minutes or more, and particularly preferably 120 minutes or more. In addition, in the pressure-sensitive adhesive sheet laminate of the present invention, the T is preferably 2880 minutes or less. The T may be 1200 minutes or less.

[0074] The pressure-sensitive adhesive sheet laminate of the present invention may have other layers as long as it includes a pressure-sensitive adhesive layer and a release sheet A. For example, the pressure-sensitive adhesive sheet laminate of the present invention may have a release sheet B bonded to the surface of the pressure-sensitive adhesive layer opposite to the release sheet A. That is, the pressure-sensitive adhesive sheet laminate of the present invention may have a structure in which the release sheet A is bonded to one surface of the pressure-sensitive adhesive layer and the release sheet B is bonded to the other surface. The release sheets A and B may be the same or different.

[0075] A preferred embodiment of the pressure-sensitive adhesive sheet laminate of the present invention is one in which a release sheet B is bonded to the surface of the pressure-sensitive adhesive layer opposite to the surface to which the release sheet A is bonded, the thickness of the release sheet B is at least 0.2 times the thickness of the pressure-sensitive adhesive layer, and the 180° peel force Sb between the release sheet B and the pressure-sensitive adhesive layer is at least 1.5 times the peel force Sa.

[0076] As with release sheet A, a substrate having a release treatment layer formed thereon can be used as release sheet B. Commercially available release sheets can be used as release sheets B, and examples thereof include "MRV#50V04," "MRV#100 V06T," "MRV#75V06," and "MRF#75," all manufactured by Mitsubishi Chemical Corporation.

[0077] By making the thickness of release sheet B at least 0.2 times the thickness of the adhesive layer, it becomes easier to suppress poor appearance of the adhesive sheet laminate, and it also becomes easier to selectively peel off only one of the release sheets when peeling them off, which makes it easier to prevent the so-called ``disconnection phenomenon.''

[0078] The thickness of the release sheet B is preferably 0.2 times or more, more preferably 0.25 times or more, and preferably 2 times or less, the thickness of the adhesive layer.

[0079] The phenomenon of tearing apart can be more easily suppressed when the 180° peel strength Sb between the release sheet B and the pressure-sensitive adhesive layer is 1.5 times or more the peel strength Sa. The 180° peel strength Sb between the release sheet B and the pressure-sensitive adhesive layer is preferably 1.7 times or more, more preferably 2 times or more, the peel strength Sa, and is preferably 20 times or less, more preferably 10 times or less.

[0080] The method for measuring the 180° peel strength Sb between the release sheet B and the pressure-sensitive adhesive layer is the same as the method for measuring the 180° peel strength Sa.

[0081] When the pressure-sensitive adhesive sheet laminate of the present invention has a release sheet A on one side of the pressure-sensitive adhesive layer and a release sheet B on the other side, release sheet A functions as a light separator film and release sheet B functions as a heavy separator film. Therefore, when using such a pressure-sensitive adhesive sheet laminate, first, release sheet A is peeled off to expose the pressure-sensitive adhesive layer, and the exposed pressure-sensitive adhesive layer is attached to an object. Next, release sheet B is peeled off to expose the pressure-sensitive adhesive layer, and another member can be attached to this exposed surface.

[0082] The pressure-sensitive adhesive sheet laminate of the present invention can provide a thick pressure-sensitive adhesive sheet with a high storage modulus. In particular, since the adhesive strength between the release sheet A and the pressure-sensitive adhesive layer is within a predetermined range, the release sheet can be easily peeled off, resulting in efficient lamination work. Furthermore, even if shear stress occurs in the pressure-sensitive adhesive sheet laminate due to bending or slippage, the release sheet A is less likely to slip or peel off, resulting in reduced appearance defects.

[0083] Furthermore, since the 180° peel strength Sa is 0.2 to 0.5 N / 50 mm, peeling is easy and the efficiency of the lamination work is also excellent.

[0084] As described above, the pressure-sensitive adhesive sheet laminate of the present invention has excellent releasability and is less likely to cause defects in appearance, despite being provided with a pressure-sensitive adhesive layer having a high storage modulus and a large thickness.

[0085] The pressure-sensitive adhesive sheet laminate of the present invention can be used for bonding to an adherend. For example, the adherend can be various optical members, such as glass, polycarbonate, polyethylene terephthalate, polymethyl methacrylate (PMMA), polyethylene naphthalate, cycloolefin polymer, triacetyl cellulose, polyimide, cellulose acylate, etc. Among these, it is particularly preferable that the adherend contains at least one selected from glass, polycarbonate, and PMMA.

[0086] Further examples of optical components include components such as touch panels and image display devices. Examples of components for touch panels include ITO films in which an ITO film is provided on a transparent resin film, ITO glass in which an ITO film is provided on the surface of a glass plate, transparent conductive films in which a transparent resin film is coated with a conductive polymer, hard coat films, and fingerprint-resistant films. Examples of components for image display devices include anti-reflection films, alignment films, polarizing films, retardation films, and brightness-enhancing films used in liquid crystal display devices. The pressure-sensitive adhesive sheet laminate of the present invention may also be used to bond modules such as a liquid crystal module and a touch panel module together.

[0087] In specifying the inventions included in the present disclosure, the components (properties, structures, functions, etc.) described in each embodiment of the present disclosure may be combined in any manner. In other words, the present disclosure includes all subject matter consisting of all combinations of the components that can be combined as described in this specification.

[0088] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0089] (Production Example 1) 600 g of 2-ethylhexyl acrylate, 100 g of cyclohexyl methacrylate, 300 g of 4-hydroxybutyl acrylate, and 0.1 g of n-dodecyl mercaptan were added to a 2 L flask equipped with a stirrer, a nitrogen inlet tube, a condenser, and a thermometer, followed by the addition of 0.15 g of AIBN. The mixture was allowed to react for 30 minutes while controlling the heat generation, and then cooled to room temperature. Additional monomers were added to the flask to achieve the aforementioned monomer ratio, and the solid content was adjusted to 30%. In this manner, a syrup (main component) containing an acrylic polymer with a solid content of 20% by mass and a weight-average molecular weight of approximately 800,000 was obtained.

[0090] (Production Example 2) 600 g of butyl acrylate, 100 g of isobutyl methacrylate, 400 g of 4-hydroxybutyl acrylate, and 0.2 g of n-dodecyl mercaptan were added to a 2 L flask equipped with a stirrer, a nitrogen inlet tube, a condenser, and a thermometer, and 0.2 g of AIBN was then added. The mixture was allowed to react for 30 minutes while controlling the heat generation, and then cooled to room temperature. Additional monomers were added to the flask to achieve the aforementioned monomer ratio, and the solid content was adjusted to 20%. In this manner, a syrup (main component) containing an acrylic polymer with a solid content of 30% by mass and a weight-average molecular weight of approximately 600,000 was obtained.

[0091] Example 1 100 parts by mass of the syrup obtained in Production Example 1 were mixed with 0.3 parts by mass of "A-200: polyethylene glycol #200 diacrylate" manufactured by Shin-Nakamura Chemical Co., Ltd. as a crosslinking agent and 0.4 parts by mass of "Omniard 651" manufactured by IGMresin as a photopolymerization initiator by planetary stirring to prepare a pressure-sensitive adhesive composition. This pressure-sensitive adhesive composition was applied to release sheet B ("MRV#50V04" manufactured by Mitsubishi Chemical Corporation, thickness 50 μm) so as to have a thickness of 200 μm, a width of 150 mm, and a length of 250 mm to form a coating film, and release sheet A ("75E-KF" manufactured by Fujimori Kogyo Co., Ltd., thickness 75 μm) was further superimposed thereon to obtain a laminate. This laminate was exposed to 5 mW / cm irradiated with a chemical lamp. ２ The cumulative light intensity is 240 mJ / cm ２ After irradiating the sample with a high-pressure mercury lamp at 150 mW / cm ２ The cumulative light intensity is 2000 mJ / cm ２As a result, the pressure-sensitive adhesive layer had a thickness of 200 μm and a storage modulus at 23° C. of 9.1×10 ４ A pressure-sensitive adhesive sheet laminate of Pa was obtained.

[0092] Example 2 A pressure-sensitive adhesive composition was prepared by mixing 0.5 parts by mass of "A-400: polyethylene glycol #400 diacrylate" manufactured by Shin-Nakamura Chemical Co., Ltd. as a crosslinking agent and 0.4 parts by mass of "Omniard 651" manufactured by IGMresin as a photopolymerization initiator using planetary stirring. The pressure-sensitive adhesive composition was prepared in the same manner as in Example 1, except that the release sheet A was changed to "50-TKA(09)" (thickness: 50 μm) manufactured by Toray Industries, Inc. and the release sheet B was changed to "MRV#100V06T" (thickness: 100 μm) manufactured by Mitsubishi Chemical Corporation. The thickness of the pressure-sensitive adhesive layer was 150 μm and the storage modulus at 23° C. was 1.5×10 ５ A pressure-sensitive adhesive sheet laminate of Pa was obtained.

[0093] (Example 3) A pressure-sensitive adhesive layer having a thickness of 200 μm and a storage modulus at 23° C. of 9.1×10 was prepared in the same manner as in Example 1, except that adhesive / release sheet A was changed to "J02" (thickness 75 μm) manufactured by Nippa Corporation and release sheet B was changed to "MRF#75" (thickness 75 μm) manufactured by Mitsubishi Chemical Corporation. ４ A pressure-sensitive adhesive sheet laminate of Pa was obtained.

[0094] (Example 4) A storage modulus of 1.5 × 10 at 23°C was obtained in the same manner as in Example 2, except that the adhesive / release sheet A was changed to "NS-75-SUM" (thickness 75 μm) manufactured by Nakamoto Pax Co., Ltd., and the release sheet B was changed to "MRV#100V06" (thickness 100 μm) manufactured by Mitsubishi Chemical Corporation, and the thickness of the adhesive layer was changed to 250 μm. ５ A pressure-sensitive adhesive sheet laminate of Pa was obtained.

[0095] Comparative Example 1 A pressure-sensitive adhesive layer having a thickness of 200 μm and a storage modulus at 23° C. of 9.1×10 was prepared in the same manner as in Example 1, except that the adhesive / release sheet A was changed to "J01" (thickness 75 μm) manufactured by Nippa Corporation and the release sheet B was changed to "MRV#100V06T" (thickness 100 μm) manufactured by Mitsubishi Chemical Corporation. ４ A pressure-sensitive adhesive sheet laminate of Pa was obtained.

[0096] Comparative Example 2 A pressure-sensitive adhesive layer having a thickness of 200 μm and a storage modulus at 23° C. of 9.1×10 was prepared in the same manner as in Example 1, except that the adhesive / release sheet A was changed to "MRQ#75" (thickness 75 μm) manufactured by Mitsubishi Chemical Corporation and the release sheet B was changed to "MRV#100V06" (thickness 100 μm) manufactured by Mitsubishi Chemical Corporation. ４ A pressure-sensitive adhesive sheet laminate of Pa was obtained.

[0097] Comparative Example 3 A pressure-sensitive adhesive layer having a thickness of 150 μm and a storage modulus at 23° C. of 1.5×10 was prepared in the same manner as in Example 1, except that the syrup was changed to the syrup obtained in Production Example 2, the release sheet A was changed to "NS-50-TA" (thickness 50 μm) manufactured by Nakamoto Pax Co., Ltd., and the release sheet B was changed to "MRV#100V06T" (thickness 100 μm) manufactured by Mitsubishi Chemical Corporation. ５ A pressure-sensitive adhesive sheet laminate of Pa was obtained.

[0098] Comparative Example 4 A pressure-sensitive adhesive layer having a thickness of 175 μm and a storage modulus at 23° C. of 9.1×10 was prepared in the same manner as in Example 1, except that the syrup was changed to the syrup obtained in Production Example 1, the release sheet A was changed to "TKA(07)" (thickness 38 μm) manufactured by Toray Industries, Inc., and the release sheet B was changed to "MRV#100V06T" (thickness 100 μm) manufactured by Mitsubishi Chemical Corporation. ４ A pressure-sensitive adhesive sheet laminate of Pa was obtained.

[0099] Comparative Example 5 A pressure-sensitive adhesive layer having a thickness of 200 μm and a storage modulus at 23° C. of 9.1×10 was prepared in the same manner as in Example 1, except that the adhesive release sheet A was changed to "MFAS" (thickness 38 μm) manufactured by Toray Industries, Inc., and the release sheet B was changed to "MRF#75" (thickness 75 μm) manufactured by Mitsubishi Chemical Corporation. ４ A pressure-sensitive adhesive sheet laminate of Pa was obtained.

[0100] (Evaluation Method) <Storage Modulus> The storage modulus of the pressure-sensitive adhesive layer at 23°C was measured using a dynamic viscoelasticity apparatus (product name: MCR301) manufactured by Anton Paar Japan Co., Ltd. The pressure-sensitive adhesive layer was laminated to a thickness of 1 mm and punched out to a diameter of 8 mm, and the resulting sample was attached to a fixture. The temperature was raised from -70°C to 120°C at a frequency of 1 Hz and a heating rate of 5°C / min, and the storage modulus G' of the pressure-sensitive adhesive layer at 23°C was read.

[0101] <180° Peel Force Sa> The surface of release sheet B of the pressure-sensitive adhesive sheet laminate comprising release sheet A, a pressure-sensitive adhesive layer, and release sheet B obtained in the examples was attached to a SUS304 plate with a width of 50 mm and a length of 50 mm using double-sided tape, and then pressed with a roller. The plate was then left to stand for one day under atmospheric pressure, a temperature of 23°C, and a humidity of 50%. The measurement sample thus obtained was subjected to 180° peeling of release sheet A at a rate of 0.3 m / min using a Shimadzu AGX-500NX, and the peel force at this time was recorded as the 180° peel force Sa (N / 50 mm).

[0102] <180° Peel Force Sb> Release sheet A of the adhesive sheet laminate comprising release sheet A, adhesive layer, and release sheet B obtained in the Examples was peeled from the adhesive layer, and the adhesive layer surface was attached to a SUS304 plate with a width of 50 mm and a length of 50 mm, and then pressed with a roller. This was then left to stand for one day under atmospheric pressure, a temperature of 23°C, and a humidity of 50%. The measurement sample thus obtained was subjected to 180° peeling of release sheet B at a rate of 0.3 m / min using a Shimadzu AGX-500NX, and the peel force at this time was recorded as the 180° peel force Sb (N / 50 mm).

[0103] <Separator Creep Test> A separator creep test was carried out using test sample S shown in Figure 1. Test sample S was prepared using the same procedure as described above. This test sample S was hung on a hook through a hole in an SUS304 plate, and a 1 kg weight was hung from the metal ring at 23°C to apply a shear load of 9.8 N in the vertical direction to release sheet A, and the time required for release sheet A to peel from pressure-sensitive adhesive layer 1 was measured. This time was taken as T (minutes), measured in accordance with the separator creep test.

[0104] <Appearance> Immediately after preparation, the pressure-sensitive adhesive sheet laminates prepared in the Examples and Comparative Examples were placed on a table, and a weight of 30 mm diameter, 130 mm length, and 1 kg weight was placed next to them so that it was perpendicular to the longitudinal direction of the laminate. The end of the laminate parallel to the weight was then grasped with both hands, and the weight and the laminate were lifted 100 mm from the table. The left and right ends of the laminate were then moved up and down ten times, taking care not to cause the weight on the bent laminate to move significantly left and right. This operation was performed on both sides of the laminate, and then the laminate was left to stand at room temperature for one day with the weight removed. The appearance was then observed, and if wrinkles, folds, or lifting due to peeling from the pressure-sensitive adhesive layer were observed, the appearance was rated as poor (×), and if no such conditions were observed, the appearance was rated as good (◯).

[0105] <Sad Separation> The pressure-sensitive adhesive sheet laminates produced in the Examples and Comparative Examples were cut into 100 mm x 100 mm pieces using a cutter, and then the release sheet was slowly peeled off from the side of release sheet A of the cut sheet. When peeling off release sheet A, if the pressure-sensitive adhesive sheet was peeled off by 5 mm or more from the edge of release sheet B, it was rated as poor (×), and if it did not peel off it was rated as good (◯).

[0106]

[0107] Table 1 shows the structure of the pressure-sensitive adhesive sheet laminates obtained in the examples and comparative examples, as well as the results of the storage modulus, Sa value, and Sb value, and also shows the results of the appearance evaluation and tear-off evaluation of the pressure-sensitive adhesive sheet laminates.

[0108] No appearance defects were observed in the pressure-sensitive adhesive sheet laminates obtained in Examples 1 to 4, whereas all of the pressure-sensitive adhesive sheet laminates obtained in Comparative Examples exhibited appearance defects. Thus, the pressure-sensitive adhesive sheet laminates including the specified release sheet A were less likely to exhibit appearance defects, despite being provided with a pressure-sensitive adhesive layer having a high storage modulus and a large thickness.

[0109] S: Test sample A: Release sheet 1: Adhesive layer 2: Film H: Hole 3: Double-sided tape 3 G: Weight

Claims

1. A pressure-sensitive adhesive sheet laminate comprising a pressure-sensitive adhesive layer and a release sheet A, wherein the release sheet A is attached to at least one surface of the pressure-sensitive adhesive layer so as to be in contact with the pressure-sensitive adhesive layer, the thickness of the release sheet A is 0.25 times or more the thickness of the pressure-sensitive adhesive layer, the 180° peel strength Sa between the release sheet A and the pressure-sensitive adhesive layer is 0.2 to 0.5 N / 50 mm, and the storage modulus of the pressure-sensitive adhesive layer at 23° C. is 5×10 ４ Pa or more, the thickness of the adhesive layer is 120 μm or more, and T (min) measured according to the separator creep test described below is T>40. <Separator creep test> A film is attached to the surface of the adhesive layer opposite to the release sheet A to prepare an adhesive sheet laminate (width 25 mm x length 25 mm), and the film side surface of this adhesive sheet laminate is fixed to a SUS304 plate with double-sided tape to prepare a test sample. That is, a test sample is prepared in which the release sheet A, the adhesive layer, the film, the double-sided tape, and the SUS304 plate are laminated in this order. In this test sample, a shear load of 9.8 N is applied to the release sheet A at 23° C., and the time required for the release sheet A and the adhesive layer to peel off is measured, and this time is defined as T (min).

2. The adhesive sheet laminate of claim 1, wherein a release sheet B is attached to the surface of the adhesive layer opposite to the surface to which the release sheet A is attached, the thickness of the release sheet B is at least 0.2 times the thickness of the adhesive layer, and the 180° peel force Sb between the release sheet B and the adhesive layer is at least 1.5 times the peel force Sa.

3. The adhesive sheet laminate according to claim 1 or 2, wherein the adhesive layer is a cured product of an active energy ray-curable adhesive.

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