Hot melt adhesive, adhesive sheets, items

Abstract

To provide hot melt adhesives, adhesive sheets, and articles that offer excellent coating properties, adhesive strength, and also satisfy heat resistance and moisture heat resistance requirements. [Solution] A hot melt adhesive comprising a thermoplastic resin (A), a tackifying resin (B), a plasticizer (C), and a photopolymerization initiator (D), characterized in that the adhesive layer, which is a photocured product of the hot melt adhesive, has a holding power of 72,000 seconds or more in accordance with JIS Z 0237:2009.

Description

Technical Field

[0001] The present invention relates to a hot melt adhesive, an adhesive sheet, and an article to which the adhesive sheet is attached.

Background Art

[0002] Generally, an adhesive exhibits a viscoelastic state in a temperature range near room temperature and has the property of easily adhering to an adherend by pressure. Taking advantage of such properties, adhesives are widely used as a joining means with good workability and high adhesion reliability in various industrial fields such as labels, seals, building materials, household appliances, automobiles, and electronic devices.

[0003] An adhesive is typically formed into a film shape using an adhesive composition and is used in the form of an adhesive sheet including the film-shaped adhesive (adhesive layer). In the production of an adhesive sheet having such a configuration, an adhesive composition in the form of a solvent solution such as ethyl acetate or a toluene solution is generally used, and the adhesive layer is formed by coating the solvent solution on an appropriate surface. However, in recent years, suppression of solvent use has been required for reducing environmental impact and protecting the health of workers, and the use of a hot melt adhesive composition that does not use a solvent has been considered even in the formation of an adhesive layer. As technical documents regarding such a hot melt type adhesive composition, Patent Documents 1 and 2 can be cited.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] On the other hand, while various adhesives have traditionally been used to fix components in the fields of labels, seals, building materials, home appliances, automobiles, and electronic equipment, the use of hot-melt compositions has been increasing in recent years because they do not require a drying process and have excellent adhesive stability.

[0006] In particular, when using hot melt compositions for automotive interior materials or electronic equipment, adhesive strength is required when bonding adherends. Furthermore, because use is anticipated in high-temperature environments such as extremely hot regions or under scorching sun, and low-temperature environments such as extremely cold regions, heat resistance and heat and humidity resistance are necessary to suppress the generation of air bubbles at the interface between the adhesive and the adherend after bonding, and to suppress lifting or peeling from the adherend.

[0007] In contrast, while conventional hot melt adhesives may have sufficient adhesive strength for practical use, they currently fail to adequately meet the aforementioned heat resistance and moisture resistance requirements.

[0008] The present invention aims to provide hot-melt adhesives, adhesive sheets, and articles that have excellent coating properties and adhesive strength, and further satisfy heat resistance and moisture heat resistance. [Means for solving the problem]

[0009] After diligent research by the inventors, it was found that the problems of the present invention can be solved in the following embodiment. We discovered this and completed the present invention. In other words, embodiments of the present invention are solved by a hot melt adhesive comprising a thermoplastic resin (A), a tackifying resin (B), a plasticizer (C), and a photopolymerization initiator (D), characterized in that the adhesive layer, which is a photocured product of the hot melt adhesive, has a holding power of 72,000 seconds or more in accordance with JIS Z 0237:2009.

[0010] Furthermore, an embodiment of the present invention is a hot melt adhesive characterized by containing 100 to 250 parts by mass of the tackifying resin (B) with respect to 100 parts by mass of the thermoplastic resin (A).

[0011] Furthermore, an embodiment of the present invention is the hot melt adhesive characterized in that the thermoplastic resin (A) is a diene-styrene thermoplastic resin.

[0012] Furthermore, an embodiment of the present invention is a hot melt adhesive characterized by having a melt viscosity of 2,000 to 15,000 mPa·s at 150°C.

[0013] Furthermore, an embodiment of the present invention is an adhesive sheet comprising an adhesive layer which is a photocured product of the hot melt adhesive described above.

[0014] Furthermore, an embodiment of the present invention is an article to which the above-mentioned adhesive sheet is attached. [Effects of the Invention]

[0015] The present invention provides hot-melt adhesives, adhesive sheets, and articles that offer excellent coating properties, adhesive strength, and also satisfy heat resistance and moisture heat resistance requirements. [Modes for carrying out the invention]

[0016] The following describes, but is not limited to, examples of the configuration of the hot melt adhesive, adhesive sheet, and article of the present invention.

[0017] This specification defines the terms used herein. A thermoplastic resin is a resin that becomes fluid when heated above its glass transition point or melting point, and solidifies when cooled below its glass transition point or melting point, thus exhibiting reversibility between its fluid and solidified states. In this invention, sheet, film, and tape are synonymous. Unless otherwise noted, each of the components mentioned herein may be used independently, individually, or in combination of two or more.

[0018] In this specification, numerical ranges specified using "~" include the numbers before and after "~" as the lower and upper limits.

[0019] "Hot melt adhesive" The hot melt adhesive of the present invention contains a thermoplastic resin (A), a tackifier resin (B), a plasticizer (C), and a photoinitiator (D), and is a hot melt adhesive characterized in that the holding power conforming to JIS Z0237:2009 is 72,000 seconds or more. In the adhesive of the present invention, the tackifier resin (B) is used for the purpose of imparting high adhesiveness. The plasticizer (C) is used for the purpose of imparting wettability to the adherend and reducing the melt viscosity during heating. The photoinitiator (D) is used for the purpose of functioning as a polymerization initiator.

[0020] <Thermoplastic resin (A)> The hot melt adhesive of the present invention contains a thermoplastic resin (A). The above thermoplastic resin (A) is not particularly limited. For example, diene-based thermoplastic resins, polyvinyl acetal-based thermoplastic resins such as polyvinyl butyral resin, polyolefin-based thermoplastic resins, polyamide-based thermoplastic resins, polyphenylene sulfide-based thermoplastic resins, diene-styrene-based thermoplastic resins, polycarbonate-based thermoplastic resins, (meth)acrylic-based thermoplastic resins, polyethylene terephthalate-based thermoplastic resins, ethylene vinyl acetate copolymers, ABS resins, PVC, etc. can be mentioned. Further, these thermoplastic resins (A) can be used alone or in combination of two or more. In particular, when it is necessary to adjust the melt viscosity when applying the hot melt adhesive, by using two or more of these in combination to adjust the melt viscosity, a significant decrease in physical properties can be suppressed. In diene-based thermoplastic resins and diene-styrene-based thermoplastic resins, the diene moiety becomes a photo radical polymerization site. In other thermoplastic resins, photo radical polymerization occurs by combining with a hydrogen abstraction type photoinitiator. Among these thermoplastic resins (A), diene-based thermoplastic resins and diene-styrene-based thermoplastic resins are preferable from the viewpoints of heat resistance and heat and humidity resistance, and diene-styrene-based thermoplastic resins are more preferable.

[0021] Examples of the diene-based thermoplastic resin include butadiene rubber (product examples: BR 01, BR T700, BR 730, manufactured by ENEOS MATERIALS), isoprene rubber (product examples: Nipol IR2200, Nipol IR2200L, manufactured by Nippon Zeon Co., Ltd.; LIR-30, LIR-390, manufactured by Kuraray Co., Ltd.), butyl rubber (product examples: Butyl065, Butyl268, manufactured by Nippon Butyl Co., Ltd.), acrylonitrile-butadiene rubber (product examples: Nipol DN003, Nipol DN401, Nipol DN401L, manufactured by Nippon Zeon Co., Ltd.), and the like.

[0022] Examples of the diene-styrene-based thermoplastic resin include styrene-butadiene rubber (product examples: Nipol NS116R, Nipol NS612, manufactured by Nippon Zeon Co., Ltd.), styrene-isoprene-styrene block copolymer (product examples: SIS 5002, SIS 5229, SIS 5403P, manufactured by ENEOS MATERIALS; Clayton D1111, Clayton D1117, manufactured by Clayton Polymer Japan Co., Ltd.), styrene-butadiene-styrene block copolymer (product examples: Clayton D1101, Clayton D1116, Clayton D1118, manufactured by Clayton Japan Co., Ltd.), styrene-ethylene / butylene-styrene block copolymer (product examples: Clayton G-1633, Clayton G-1651, Clayton G1657, manufactured by Clayton Japan Co., Ltd.), styrene-butadiene-butylene-styrene block copolymer (product examples: Taftec H1221, Taftec H1062, Taftec H1521, manufactured by Asahi Kasei Corporation), styrene-ethylene / propylene-styrene block copolymer (product examples: Septon 2002, Septon 2004F, Septon 2005, manufactured by Kuraray Co., Ltd.), styrene-ethylene-ethylene / propylene-styrene block copolymer (product examples: Septon 4030S, Septon 4033, Septon 4055, manufactured by Kuraray Co., Ltd.), and the like. Among these diene-styrene-based thermoplastic resins, styrene-butadiene-styrene block copolymer is preferred from the viewpoints of heat resistance and heat and moisture resistance.

[0023] The styrene-butadiene-styrene block copolymer is preferably present in an amount of 10 to 100% by mass, and more preferably 30 to 100% by mass, of 100% by mass of the thermoplastic resin (A). An amount of 10% by mass or more is preferable because it makes it easier to obtain sufficient cohesive force.

[0024] <Tackifying resin (B)> The hot-melt adhesive of the present invention contains a tackifying resin (B). The above-mentioned heat-tackifying resin (B) is not particularly limited, but examples include phenol resins, modified phenol resins, terpene resins, terpene phenol resins, xylene phenol resins, cyclopentadiene-phenol resins, xylene resins, hydrocarbon resins, hydrogenated hydrocarbon resins, phenol-modified petroleum resins, rosin resins, rosin ester resins, hydrogenated rosin resins, hydrogenated rosin ester resins, acid-modified rosin resins, and low molecular weight polystyrene resins. Furthermore, these tackifying resins (B) can be used alone or in combination of two or more types. Of these tackifying resins (B), hydrogenated hydrocarbon resins are preferred from the viewpoint of heat resistance and heat and humidity resistance.

[0025] Examples of the above-mentioned hydrogenated hydrocarbon resins include C5 hydrogenated petroleum resins (product examples: Easttack C100, Easttack C115W, manufactured by Eastman Chemical Co., Ltd.), C9 hydrogenated petroleum resins (product examples: Alcon P-90, Alcon P-100, Alcon P-125, Alcon P-140, Alcon M-90, Alcon M-100, Alcon M-115, Alcon M-135, manufactured by Arakawa Chemical Industries, Ltd.), and C5 / C9 hydrogenated petroleum resins (product examples: iMarb S-100, iMarb S-110, iMarb P-100, iMarb P-140, manufactured by Idemitsu Kosan Co., Ltd.). Examples of styrene-based hydrogenated petroleum resins include FTR6100, FTR6110, FTR6125, FTR7080, FTR7100, and FTR7125 (manufactured by Mitsui Chemicals, Inc.). Examples of hydrogenated terpene resins include Clearon P-105, Clearon P-125, Clearon M-105, Clearon P-115, and YS Polystar TH130 (manufactured by Yasuhara Chemical Co., Ltd.). Among these hydrogenated hydrocarbon resins, C9-type hydrogenated petroleum resins are preferred from the viewpoint of heat resistance and heat and humidity resistance.

[0026] The tackifying resin (B) is preferably present in an amount of 100 to 250 parts by mass, and more preferably 180 to 250 parts by mass, per 100 parts by mass of the thermoplastic resin (A). A content of 100 parts by mass or more makes it easier to obtain sufficient cohesive force. Furthermore, a content of 250 parts by mass or less is preferable because it makes it easier to achieve both cohesive force and adhesion to the adherend.

[0027] <Plasticizer (C)> The hot-melt adhesive of the present invention contains a plasticizer (C). The plasticizer (C) is not particularly limited, but examples include ester-based plasticizers, liquid rubber-based plasticizers, and oil-based plasticizers. These plasticizers (C) can be used alone or in combination of two or more types. Of these plasticizers (C), oil-based plasticizers are preferred from the viewpoint of adhesion to the substrate.

[0028] Examples of the above-mentioned oil-based plasticizers include paraffin oil (product examples: Diana Fresia P90, Diana Fresia P150, Diana Fresia W90, Diana Fresia K8, Diana Fresia S90, Diana Process Oil PW8, Diana Process Oil PW32, Diana Process Oil PW90, manufactured by Idemitsu Kosan Co., Ltd.), naphthenic oil (product examples: Diana Fresia G9, Diana Fresia NR9, Diana Fresia N90, Diana Fresia U46, Diana Fresia U75, Diana Process Oil NS28, Diana Process Oil NS90S, manufactured by Idemitsu Kosan Co., Ltd.), and mixtures of paraffin oil and naphthenic oil (product examples: Diana Process Oil NP24, Diana Process NP250, manufactured by Idemitsu Kosan Co., Ltd.; KN-4006, manufactured by Karamay Co., Ltd.). Among these oil-based plasticizers, naphthenic oil is preferred from the viewpoint of adhesion to the substrate and cohesive force.

[0029] The plasticizer (C) is preferably present in an amount of 50 to 200 parts by mass, and more preferably 100 to 200 parts by mass, per 100 parts by mass of the thermoplastic resin (A). A content of 50 parts by mass or more makes it easier to obtain sufficient adhesion to the adherend. Furthermore, a content of 200 parts by mass or less is preferable because it makes it easier to achieve both adhesion to the adherend and cohesive force.

[0030] <Photopolymerization initiator> The hot-melt adhesive of the present invention contains a photopolymerization initiator (D). Photopolymerization initiators (D) are classified into two types based on how they react after absorbing light: those that generate radicals through intramolecular cleavage (intramolecular cleavage type) and those that generate radicals through the exchange of hydrogen and electrons between two molecules (hydrogen abstraction type and electron-donating type). The choice between the two types should be made appropriately depending on the components used as thermoplastic resin (A), tackifying resin (B), and plasticizer (C).

[0031] The above-mentioned photopolymerization initiator (D) is not particularly limited, but examples include hydroxyketones, benzyldimethylketals, aminoketones, acylphosphine oxides, benzophenones, and trichloromethyl group-containing triazine derivatives. Furthermore, these photopolymerization initiators (D) can be used alone or in combination of two or more types. Of these photopolymerization initiators (D), acyl phosphine oxides are preferred from the viewpoint of curability.

[0032] Examples of the above-mentioned acylphosphine oxides include diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and 2,4,6-trimethylbenzoylethoxylphenylphosphine oxide.

[0033] The photopolymerization initiator (D) is preferably present in an amount of 0.3 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of thermoplastic resin (A). A content of 1 part by mass or more makes it easier to obtain sufficient curability. Furthermore, a content of 10 parts by mass or less is preferable because it reduces contamination of the adherend by the initiator.

[0034] <Other ingredients (E)> The hot-melt adhesive of the present invention may further contain other components (E) as long as they do not impair the effects of the present invention. Examples of other components (E) include colorants, anti-blocking agents, inorganic fillers, antioxidants, fillers, flame retardants, antistatic agents, light stabilizers, ultraviolet absorbers, and heavy metal deactivators. These components can be used individually or in combination of two or more.

[0035] The aforementioned coloring agent can be a commonly known coloring agent such as red, blue, green, or yellow. The agent can be any of pigments, dyes, or colorants, for example, monoazo, disazo, etc. These include zolake-based, benzimidazolon-based, perylene-based, diketopyrrolopyrrole-based, condensed azo-based, anthraquinone-based, quinacridone-based, phthalocyanine-based, and anthraquinone-based pigments. Pigments include pigments, perylene-based, monoazo-based, condensed azo-based, isoindolinone-based, titanium dioxide, and carbon.

[0036] The aforementioned anti-blocking agents include silicone, stearate, and oleate. Unsaturated fatty acids such as iodide, erucate amide, oleamide, and behenate amide Examples include Myodo.

[0037] Examples of the inorganic filler include metals, metal oxides, and metal hydroxides, in granular or fibrous form. Specifically, these include glass fibers, carbon fibers, calcium silicate, and calcium titanate. Aluminum borate fiber, flake glass, talc, kaolin, mica, hydro Talcite, calcium carbonate, zinc carbonate, zinc oxide, monocalcium phosphate, wollaston Examples include kite, silica, zeolite, alumina, boehmite, aluminum hydroxide, titanium dioxide, silicon dioxide, magnesium oxide, calcium silicate, sodium alumina silicate, magnesium silicate, carbon nanotubes, graphite, copper, silver, aluminum, nickel, iron, calcium fluoride, mica, montmorillonite, and apatite.

[0038] Examples of the aforementioned antioxidants include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearin-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10-tetraoxaspiro[5,5]undecane, and Examples include senzenpropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-,C7-C9 side-chain alkyl ester, 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol ester, 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-S-triazine-2,4,6-(1H,3H,5H)trione, tocopherol, etc. Antioxidants can be used to prevent thermal degradation and thermal decomposition.

[0039] The aforementioned fillers include wet silica, aluminum hydroxide, aluminum oxide, and magnesium oxide. Nesium, montmorillonite, mica, smectite, organic montmorillonite, organic Examples include mica and organic smectite.

[0040] The aforementioned flame retardants include phosphorus-containing compound flame retardants, halogen-containing compound flame retardants, and sulfones. Examples include metal acid salt-based flame retardants and silicon-containing compound-based flame retardants.

[0041] The aforementioned antistatic agent may be one that is commonly used as an antistatic agent for plastics, and specifically includes nonionic surfactants (e.g., fatty acid esters of polyhydric alcohols, ethylene oxide adducts of alkylamines, and fatty acid esters of ethylene oxide adducts of alkylamines), anionic surfactants (e.g., alkylbenzene sulfonates, higher alcohol sulfate salts), cationic surfactants (e.g., aliphatic amine salts, quaternary ammonium salts), and amphoteric surfactants (e.g., imidazoline type, betaine type).

[0042] Examples of the aforementioned light stabilizers include hindered amine compounds and benzoate compounds.

[0043] The aforementioned UV absorbers include benzophenone-based UV absorbers and triazine-based UV absorbers. Examples include benzotriazole-based UV absorbers.

[0044] The heavy metal deactivator may be a salicylic acid derivative, a hydrazide derivative, or an oxalic acid derivative. Examples include mido derivatives.

[0045] If other components (E) are included, their content is preferably 1 to 50 parts by mass, and more preferably 5 to 30 parts by mass, per 100 parts by mass of thermoplastic resin (A).

[0046] <Melting viscosity> The melt viscosity of hot-melt adhesives can be measured, for example, by a measurement method compliant with JIS K6833-1. Specific measurement methods are described in the Examples section.

[0047] The melt viscosity of the hot-melt adhesive of the present invention at 150°C is preferably 2,000 to 15,000 mPa·s, and more preferably 3,000 to 12,000 mPa·s. A melt viscosity of 2,000 mPa·s or higher can suppress winding misalignment during coating and winding, and a melt viscosity of 15,000 mPa·s or lower can suppress appearance defects caused by coating streaks during coating. When the melt viscosity is within the predetermined range, the coatability can be said to be good.

[0048] <Holding power> The holding power of the adhesive layer, which consists of a photocured hot-melt adhesive, can be measured using an adhesive sheet made from the hot-melt adhesive and substrate, with the adherend being stainless steel, the application area being 25 mm x 25 mm, and the test temperature being 80°C, according to the measurement method compliant with JIS Z 0237:2009. For example, the holding time in a measurement period of up to 86,400 seconds (24 hours) is preferably 72,000 seconds or more, and more preferably 79,000 seconds or more. If the holding time in the measurement is 72,000 seconds or more, sufficient cohesive force is observed even in high-temperature environments, and excellent heat resistance and heat and humidity resistance are demonstrated. The specific measurement method is described in the Examples section.

[0049] <Adhesive strength> The adhesive strength of an adhesive layer made from a photocured hot-melt adhesive can be measured by attaching an adhesive sheet made from a hot-melt adhesive and a substrate to various substrates, leaving it undisturbed for a specified time, and then peeling it off. Higher adhesive strength indicates higher adhesive reliability, while lower adhesive strength indicates lower adhesive reliability. Specific measurement methods are described in the Examples section.

[0050] <Heat resistance and moisture resistance> The heat resistance and humidity resistance of hot melt adhesives can be measured by attaching an adhesive sheet made from the hot melt adhesive and substrate to various substrates, leaving it undisturbed for a specified time, and then leaving it undisturbed in a specified temperature and humidity environment. If no bubbles are observed after measurement, and no lifting or peeling of the adhesive sheet is observed, it indicates that the adhesive has sufficient heat resistance and humidity resistance for practical use. If bubbles are observed, and no lifting or peeling of the adhesive sheet is observed, it indicates that problems such as cosmetic defects may occur for practical use. The specific measurement method is described in the Examples section.

[0051] <Manufacturing of hot melt adhesives> The hot melt adhesive of the present invention can be manufactured, for example, by melting a plasticizer (C) in a melting vessel equipped with a stirrer, mixing and dispersing a tackifying resin (B) in the mixture, and then adding and mixing a thermoplastic resin (A) and a photopolymerization initiator (D) after the tackifying resin (B) has dissolved. Alternatively, the hot melt adhesive of the present invention may be manufactured by mixing and dispersing the components in an extruder and extruding the molten mixture from a nozzle at the tip of the extruder.

[0052] The hot-melt adhesive of the present invention may be used by mixing the constituent components and molding them into a desired shape. Examples of desired shapes include granules, pellets, planar shapes, or block shapes. These methods can be known methods without limitation.

[0053] <Adhesive sheet> The adhesive sheet of the present invention has an adhesive layer (hereinafter sometimes simply referred to as "adhesive layer") made of the hot melt adhesive described above. The adhesive layer may be provided on a substrate, or an intermediate layer such as an ink layer or a hard coat layer may be provided between the substrate and the hot melt adhesive.

[0054] Various sheet-like substrates can be used as the base material for the adhesive sheet, such as resin film, paper, cloth, rubber sheet, foam sheet, metal foil, or composites thereof. The above-mentioned base material may be a single layer or a laminate of the same or different types of base materials. In this specification, a single layer refers to a layer having the same composition, and includes a form in which multiple layers having the same composition are laminated.

[0055] In one preferred embodiment, a substrate mainly composed of a resin film is used. Examples of resins constituting the substrate include polyolefin resins such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene, random copolymer polypropylene, block copolymer polypropylene, homopolypropylene, polybutene, polymethylpentene, ethylene-vinyl acetate copolymer (EVA), ionomer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester (random, alternating) copolymer, ethylene-butene copolymer, and ethylene-hexene copolymer; polyurethane; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT); polycarbonate; polyimide; polyether ether ketone; polyetherimide; polyamides such as aramid and fully aromatic polyamide; polyphenyl sulfide; fluororesin; polyvinyl chloride; polyvinylidene chloride; cellulose resin; and silicone resin. The above resins may be used individually or in combination of two or more to form all or part of a substrate (for example, any layer in a substrate with a laminated structure of two or more layers).

[0056] <Manufacturing of adhesive sheets> The adhesive sheet of the present invention can be manufactured according to a conventional method for manufacturing adhesive sheets. For example, it can be manufactured by applying a hot melt adhesive (hereinafter sometimes simply referred to as "hot melt adhesive") containing a thermoplastic resin (A), a tackifying resin (B), a plasticizer (C), and a photopolymerization initiator (D) to the release surface of a release film so that the thickness after coating is predetermined, irradiating with light to form a hot melt adhesive layer, and then attaching the release film. Alternatively, it can be manufactured by applying the hot melt adhesive to the release surfaces of two release films so that the thickness after coating is predetermined, irradiating with light to form two separate hot melt adhesive layers, and then attaching each hot melt adhesive layer.

[0057] The aforementioned light irradiation is performed by irradiating with light of a specific wavelength on which the added photopolymerization initiator acts. The amount of light irradiation can be set according to the formulation and thickness of the raw material composition, the type and amount of photopolymerization initiator added, for example, 200 to 3,000 mJ / cm². 2 It can be done this way.

[0058] The thickness of the hot melt adhesive layer is not particularly limited, but is preferably 1 to 500 μm, and more preferably 5 to 300 μm. A thickness of 1 to 500 μm for the hot melt adhesive layer is preferable because it makes it easier to obtain cohesive force and allows for sufficient heat resistance and heat and humidity resistance.

[0059] Adhesive sheets can be manufactured by known methods. For example, they can be manufactured by coating a substrate with a hot-melt adhesive and then cooling it. Examples of methods for coating a substrate with hot-melt adhesive include heating it to liquefy it and then forming it in layers using a coater. Examples of coaters include blade coaters, bar coaters, comma coaters, gravure coaters, roll coaters, reverse roll coaters, die coaters, and T-die coatings.

[0060] <Items with adhesive sheets attached> An article to which the adhesive sheet of the present invention is attached is a component made of glass, resin, or metal to which the adhesive sheet of the present invention is attached. Methods for attaching the adhesive sheet include heating the adhesive sheet and attaching it to the article, or, when in-mold molding resin components, setting the adhesive sheet in the mold beforehand and using the heat generated during molding to bond it to the component. The glass component of the present invention may be clear glass, brown glass, or colored glass such as blue, red, or green. Furthermore, the surface of the glass may be untreated or coated with a resin such as cold coating, hot coating, or polyethylene (PE) coating.

[0061] Examples of resins that are components of the present invention include polyolefin resins such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene, random copolymer polypropylene, block copolymer polypropylene, homopolypropylene, polybutene, polymethylpentene, ethylene-vinyl acetate copolymer (EVA), ionomer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester (random, alternating) copolymer, ethylene-butene copolymer, and ethylene-hexene copolymer; polyurethane; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT); polycarbonate; polyimide; polyetheretherketone; polyetherimide; polyamides such as aramid and fully aromatic polyamide; polyphenyl sulfide; fluororesin; polyvinyl chloride; polyvinylidene chloride; cellulose resin; and silicone resin. Furthermore, if a multilayer structure is possible, a foamed layer may be placed on one side of the component, and the same resin may be extruded without foaming to create a multilayer structure, for purposes such as improving the impact strength of the component.

[0062] Examples of metals that can be used as components in the present invention include copper, iron, aluminum, nickel, titanium, gold, silver, chromium, magnesium, steel, zinc alloy, copper alloy, aluminum alloy, nickel alloy, titanium alloy, magnesium alloy, stainless steel, bronze, and the like. These metals may be used individually or in combination of two or more to form the whole or a part of a component (for example, any layer in a component with a laminated structure of two or more layers). [Examples]

[0063] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In the examples, unless otherwise specified, "parts" refers to "parts by mass," "%" refers to "percentage by mass," and "RH" refers to relative humidity. Also, the amounts in the table are in parts by mass. A blank space in the table indicates that the ingredient was not included.

[0064] <Melting viscosity> The melt viscosity was measured in accordance with JIS K6833-1 using a Type B viscometer (manufactured by Tokyo Keiki Co., Ltd.) under the following conditions. Measurement temperature: 150℃ Rotor No: #3 or #2 Rotation speed: 12 rpm

[0065] (Example 1) <Examples of hot melt adhesive preparation> In a reaction vessel equipped with a stirrer, thermometer, and nitrogen inlet tube, 100 parts of Alcon P-90 (B-1) as the tackifying resin (B), 50 parts of Diana Fresia P90 (C-1) as the plasticizer (C), and 1 part of tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate] (E-1) as the antioxidant were charged, and the atmosphere in the reaction vessel was replaced with nitrogen gas. Then, the mixture was heated to 180°C under a nitrogen atmosphere, and after confirming that the charged raw materials had melted, 100 parts of Kraton D1101 (A-1) as the thermoplastic resin (A) were gradually added while stirring with a stirrer. After the thermoplastic resin was completely dissolved, 1 part of diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide (D-1) was added as a photopolymerization initiator, and the mixture was uniformly stirred to obtain the hot melt adhesive of Example 1.

[0066] <Manufacturing of adhesive sheets> The obtained hot melt adhesive was coated onto a 50 μm thick release film (polyethylene terephthalate (PET), "E7004", silicone-based release layer, manufactured by Toyobo Co., Ltd.) so that the thickness after coating was 25 μm, and then irradiated with light (wavelength: 365 nm, irradiation dose: 1000 mJ / cm²). 2 The material was cured using a solvent to form an adhesive layer. Next, one side of a 50 μm thick PET film (polyethylene terephthalate, "T60", manufactured by Toray Industries, Inc.) was laminated to this adhesive layer to obtain an adhesive sheet consisting of "release film / adhesive layer / PET film".

[0067] (Examples 2-10, Comparative Examples 1-4) As shown in Table 1, an adhesive sheet was obtained in the same manner as in Example 1, except that the type and amount (parts by mass) of the thermoplastic resin (A), tackifying resin (B), plasticizer (C), and photopolymerization initiator (D) were changed.

[0068] The symbols in the table are as follows: <Thermoplastic resin (A)> A-1: Kraton D1101 (styrene-butadiene-styrene block copolymer, manufactured by Kraton Polymers Japan) A-2: Kraton D1118 (styrene-butadiene-styrene block copolymer, manufactured by Kraton Polymers Japan) A-3: LIR-390 (Isoprene rubber, manufactured by Kuraray Co., Ltd.) A-4: LA3320 (Acrylic thermoplastic resin, manufactured by Kuraray Co., Ltd.) <Tackifying resin (B)> B-1: Alcon P-90 (C9 hydrogenated petroleum resin, manufactured by Arakawa Chemical Co., Ltd.) B-2: Easttack C100 (C5 hydrogenated petroleum resin, manufactured by Eastman Chemical Company) B-3: Ester gum AT (rosin ester resin, manufactured by Arakawa Chemical Co., Ltd.) <Plasticizer (C)> C-1: Diana Fresia P90 (paraffin oil, manufactured by Idemitsu Kosan Co., Ltd.) C-2: Diana Fresia N90 (naphthenic oil, manufactured by Idemitsu Kosan Co., Ltd.) C-3: ADEKA Plasticizer RS-735 (ester-based plasticizer, manufactured by ADEKA Corporation) <Photopolymerization initiator (D)> D-1: Diphenyl (2,4,6-trimethylbenzoyl)phosphine oxide (acylphosphine oxide photopolymerization initiator) D-2: Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (acyl phosphine oxide photopolymerization initiator) D-3: 4-methylbenzophenone (benzophenone initiator) <Other (E)> E-1: Tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate] (hindered phenol antioxidant)

[0069] <Holding power> The adhesive sheets produced in the examples and comparative examples were cut to a size of 25 mm wide x 100 mm long. The release film was peeled off the cut test adhesive sheets, and the exposed adhesive layer was attached to a stainless steel (SUS) plate (SUS304, 360 grit polished) at 25°C and 50% RH. At this time, the area of ​​the adhesive layer attached to the stainless steel plate was made to be 25 mm x 25 mm in size. Next, the stainless steel plate with the adhesive sheet attached was left to stand for 15 minutes at 23°C and 50% RH, and then set in a creep tester and left to stand for another 15 minutes. Then, a load of 9.8 N was applied to the adhesive sheet at 80°C, and the time until the adhesive sheet fell (maximum 86,400 seconds: 24 hours) was measured according to the holding force measurement method of JIS Z 0237:2009.

[0070] ≪Evaluation of hot melt adhesives and adhesive sheets≫ The melt viscosity of the obtained hot-melt adhesive was evaluated, and the adhesive strength, heat resistance, and moisture heat resistance were further evaluated using adhesive sheets. The results are shown in Table 1.

[0071] <Coating properties> The coating properties were evaluated by measuring the melt viscosity of the hot-melt adhesives prepared in the examples and comparative examples. A B-type viscometer (manufactured by Tokyo Keiki Co., Ltd.) with a #3 or #4 rotor was used, and measurements were taken at a temperature of 150°C and a rotation speed of 12 rpm. The evaluation criteria are as follows. [Evaluation Criteria] ○: Viscosity of 2,000-15,000 mPa·s indicates good coating properties. ×: Viscosity below 2,000 mPa·s or above 15,000 mPa·s results in poor coating properties.

[0072] <Adhesive strength> The adhesive sheets produced in the examples and comparative examples were cut to a size of 25 mm wide x 100 mm long. The release film was peeled off the cut test adhesive sheets, and the exposed adhesive layer was attached to the following two types of substrates under a 25°C, 50% RH atmosphere. During attachment, a 2 kg roller was passed back and forth once to press the adhesive sheet onto the substrate. After that, the samples were left for 24 hours under a 23°C, 50% RH environment and used as samples for adhesion strength measurement. Next, under conditions of 23°C and 50%RH, a tensile testing machine (manufactured by Orientec Co., Ltd.) was used. Using the product name "Tensilon," the adhesive strength (N / 25mm) was measured when a laminate consisting of a base film and an adhesive layer was peeled from the adherend in a sample for adhesion strength measurement under conditions of a peeling speed of 300 mm / min and a peeling angle of 180°. Measurements under conditions other than those described herein were performed in accordance with JIS Z0 237:2000. The evaluation criteria are as follows. [Evaluation Criteria] ◎: The adhesive strength is 15N / 25mm or higher, which poses no practical problems whatsoever. ○: The adhesive strength is 10N / 25mm or more and less than 15N / 25mm, so there are no practical problems. ×: The adhesive strength is less than 10N / 25mm, which poses a practical problem.

[0073] <Adherend> • Stainless steel (SUS) plate (SUS304, 360 grit polished) • Polypropylene (PP) sheet (manufactured by Yuko Shoji Co., Ltd., product name "PP(PP-N-BN) )」, thickness: 2mm)

[0074] <Heat resistance and moisture resistance> The adhesive sheets produced in the examples and comparative examples were cut to a size of 25 mm wide x 100 mm long. The release film was peeled off the cut test adhesive sheets, and the exposed adhesive layer was attached to the following two types of substrates under a 25°C, 50% RH atmosphere. During attachment, a 2 kg roller was passed back and forth once to press the adhesive sheet onto the substrate. After that, the samples were left for 24 hours under a 23°C, 50% RH environment and used as samples for adhesion strength measurement. Next, as a heat resistance test, the test laminate was left at 80°C for 500 hours, then cooled in a 25°C, 50%RH atmosphere, and the formation of bubbles and lifting or peeling of the test laminate were visually evaluated under the following conditions. Furthermore, as an evaluation of moisture heat resistance, the above test laminate was left at 60°C, 95%RH atmosphere for 500 hours, then cooled in a 25°C, 50%RH atmosphere, and the formation of bubbles and lifting or peeling of the adhesive sheet were visually evaluated under the following conditions. Heat resistance and moisture heat resistance were evaluated based on the following three-stage evaluation criteria. [Evaluation Criteria] ◎: No bubbles, lifting, or peeling were observed at all, and there are absolutely no practical problems. ○: While fewer than 5 instances of air bubbles, lifting, or peeling were observed in total, this does not pose a practical problem. ×: Air bubbles, lifting, and peeling were observed in a total of 5 or more locations, which poses a practical problem.

[0075] <Adherend> • Stainless steel (SUS) plate (SUS304, 360 grit polished) • Polypropylene (PP) sheet (manufactured by Yuko Shoji Co., Ltd., product name "PP(PP-N-BN) )」, thickness: 2mm)

[0076] [Table 1]

[0077] The results in Table 1 show that the adhesives of Examples 1 to 10 exhibited excellent coatability, and furthermore, the adhesive sheets using these adhesives demonstrated good heat resistance and moisture-heat resistance in addition to adhesive strength. This indicates that articles using the adhesives and adhesive sheets of the present invention have excellent coatability, adhesive strength, heat resistance, and moisture-heat resistance. On the other hand, the adhesives and adhesive sheets of Comparative Examples 1 to 4 were unable to satisfy all of the above characteristics.

Claims

1. A hot melt adhesive comprising a thermoplastic resin (A), a tackifying resin (B), a plasticizer (C), and a photopolymerization initiator (D), characterized in that the adhesive layer, which is a photocured product of the hot melt adhesive, has a holding power of 72,000 seconds or more in accordance with JIS Z0237:2009.

2. The hot melt adhesive according to claim 1, characterized in that it contains 100 to 250 parts by mass of the tackifying resin (B) per 100 parts by mass of the thermoplastic resin (A).

3. The hot melt adhesive according to claim 1, characterized in that the thermoplastic resin (A) is a diene-styrene thermoplastic resin.

4. The hot melt adhesive according to claim 1, characterized in that its melt viscosity at 150°C is 2,000 to 15,000 mPa·s.

5. An adhesive sheet comprising an adhesive layer which is a photocured product of the hot melt adhesive described in any one of claims 1 to 4.

6. An article to which the adhesive sheet described in claim 5 is attached.

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