Adhesive sheet and method for manufacturing same

Abstract

To provide a pressure sensitive adhesive sheet having a pressure sensitive adhesive layer which can be reattached immediately after being attached, exhibits sufficient adhesion after being aged, and is excellent in heat resistance and hydrolysis resistance.SOLUTION: A pressure sensitive adhesive sheet 10 is provided, comprising a base material 4, and a pressure sensitive adhesive layer 2 provided on the base material 4. The pressure sensitive adhesive layer 2 contains a polyurethane resin (A) and an isocyanate-based crosslinking agent (B), the polyurethane resin (A) has a structural unit derived from polycarbonate polyol (a) and has a hydroxyl value of 1-20 mgKOH / g, the isocyanate-based crosslinking agent (B) is tri- or higher functional aliphatic polyisocyanate, in the pressure sensitive adhesive layer 2, a value of a ratio NCO / OH of the content of the isocyanate-based crosslinking agent (B) to the content of the polyurethane resin (A) is 0.8 to 3.0 by a molar ratio of the isocyanate group (NCO) in the isocyanate-based crosslinking agent (B) to a hydroxyl group (OH) in the polyurethane resin (A).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet and a method for producing the same. [Background technology]

[0002] Conventionally, polyurethane-based pressure-sensitive adhesives have been used from the viewpoints of adhesive stability at low temperatures, adhesiveness at room temperature, flexibility, processability, removability, low adhesive residue, ease of various molecular designs, and the like.

[0003] For example, a pressure-sensitive adhesive containing a polyurethane polyol obtained by reacting a polyester polyol and a polyether polyol with a polyisocyanate compound, which has good adhesion to an adherend and good wettability, and a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer formed with this pressure-sensitive adhesive have been proposed (Patent Document 1). Also, a pressure-sensitive adhesive composition containing a urethane resin obtained using a polyol containing a polycarbonate polyol and a polyisocyanate crosslinking agent in a ratio of NCO / OH = 0.1 to 0.5 has been described (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5707715 [Patent Document 2] Patent No. 6874356 Summary of the Invention [Problem to be solved by the invention]

[0005] The adhesive tape proposed in Patent Document 1 had fairly good adhesion to the substrate. However, because the adhesion immediately after application (initial adhesion) was high, it was difficult to reapply. For this reason, when using the adhesive tape proposed in Patent Document 1 as, for example, a decorative film for interior and exterior parts of a vehicle, care had to be taken to avoid failure in application. Furthermore, the heat resistance and hydrolysis resistance of the adhesive layer of this adhesive tape were not particularly good, leaving room for further improvement.

[0006] Furthermore, the pressure-sensitive adhesive composition proposed in Patent Document 2 has an excessive amount of hydroxyl groups, which results in an excessively high initial adhesive strength, making it difficult to reposition the adhesive.

[0007] The present invention has been made in consideration of the problems of the prior art, and an object of the present invention is to provide a pressure-sensitive adhesive sheet having an adhesive layer with excellent heat resistance and hydrolysis resistance that can be repositioned immediately after application and that shows sufficient adhesion after aging. Another object of the present invention is to provide a method for producing this pressure-sensitive adhesive sheet. [Means for solving the problem]

[0008] That is, according to the present invention, the following pressure-sensitive adhesive sheet is provided. [1] A pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer provided on the substrate, wherein the pressure-sensitive adhesive layer contains a polyurethane resin (A) and an isocyanate-based crosslinking agent (B), the polyurethane resin (A) has structural units derived from a polycarbonate polyol (a) and has a hydroxyl value of 1 to 20 mgKOH / g, the isocyanate-based crosslinking agent (B) is an aliphatic polyisocyanate having three or more functionalities, and the ratio of the content of the isocyanate-based crosslinking agent (B) to the content of the polyurethane resin (A) in the pressure-sensitive adhesive layer is NCO / OH, which is the molar ratio of the isocyanate groups (NCO) in the isocyanate-based crosslinking agent (B) to the hydroxyl groups (OH) in the polyurethane resin (A), such that NCO / OH=0.8 to 3.0. [2] The pressure-sensitive adhesive sheet according to [1], wherein the ratio of the peel strength Y (N / 20 mm) after 24 hours at 25°C to the initial peel strength X (N / 20 mm) of the pressure-sensitive adhesive layer is Y / X≧3.0. [3] The pressure-sensitive adhesive sheet according to [1] or [2], wherein the isocyanate-based crosslinking agent (B) has hexamethylene diisocyanate as a constituent unit. [4] The pressure-sensitive adhesive sheet according to any one of [1] to [3], wherein the weight-average molecular weight of the polyurethane resin (A) is 10,000 to 100,000. [5] The adhesive sheet according to any one of [1] to [4], wherein the thickness of the adhesive layer is 10 to 50 μm. [6] The pressure-sensitive adhesive sheet according to any one of [1] to [5], further comprising a peelable separate film, wherein the substrate, the pressure-sensitive adhesive layer, and the separate film are laminated in this order. [7] The pressure-sensitive adhesive sheet according to any one of [1] to [5], further comprising a surface layer, wherein the surface layer, the substrate, and the pressure-sensitive adhesive layer are laminated in this order, and the substrate is a resin layer having a design. [8] The pressure-sensitive adhesive sheet according to any one of [1] to [5], further comprising a surface layer and a design layer, wherein the surface layer, the design layer, the substrate, and the pressure-sensitive adhesive layer are laminated in this order.

[0009] Furthermore, according to the present invention, there is provided the following method for producing a pressure-sensitive adhesive sheet. [9] A method for producing a pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer provided on the substrate, the method comprising the steps of: applying a pressure-sensitive adhesive composition to the substrate to form a coating layer; and aging the coating layer at 40°C or higher for 24 hours or more to form a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive composition contains a polyurethane resin (A) and an isocyanate-based crosslinking agent (B), the polyurethane resin (A) has structural units derived from polycarbonate polyol (a) and has a hydroxyl value of 1 to 20 mgKOH / g, the isocyanate-based crosslinking agent (B) is an aliphatic polyisocyanate having three or more functionalities, and the ratio of the content of the isocyanate-based crosslinking agent (B) to the content of the polyurethane resin (A) in the pressure-sensitive adhesive composition is NCO / OH=0.8 to 3.0, which is the molar ratio of the isocyanate groups (NCO) in the isocyanate-based crosslinking agent (B) to the hydroxyl groups (OH) in the polyurethane resin (A). [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer that is repositionable immediately after application, exhibits sufficient adhesion after aging, and has excellent heat resistance and hydrolysis resistance. Furthermore, according to the present invention, it is possible to provide a method for producing this pressure-sensitive adhesive sheet. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view schematically illustrating one embodiment of a pressure-sensitive adhesive sheet of the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing another embodiment of the pressure-sensitive adhesive sheet of the present invention. [Figure 3] FIG. 2 is a cross-sectional view schematically showing another embodiment of the pressure-sensitive adhesive sheet of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] <Adhesive sheet>

[0023] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. One embodiment of the pressure-sensitive adhesive sheet of the present invention includes a substrate and a pressure-sensitive adhesive layer provided on the substrate. The pressure-sensitive adhesive layer contains a polyurethane resin (A) and an isocyanate-based crosslinking agent (B). The polyurethane resin (A) has structural units derived from a polycarbonate polyol (a) and has a hydroxyl value of 1 to 20 mgKOH / g. The isocyanate-based crosslinking agent (B) is an aliphatic polyisocyanate having three or more functionalities. In the pressure-sensitive adhesive layer, the ratio of the content of the isocyanate-based crosslinking agent (B) to the content of the polyurethane resin (A) is NCO / OH, which is the molar ratio of the isocyanate groups (NCO) in the isocyanate-based crosslinking agent (B) to the hydroxyl groups (OH) in the polyurethane resin (A), such that NCO / OH = 0.8 to 3.0.

[0024] Hereinafter, the pressure-sensitive adhesive sheet of the present invention will be described in detail.

[0013] (Polyurethane resin (A)) The polyurethane resin (A) contained in the adhesive layer is a resin component having structural units derived from polycarbonate polyol (a). The polycarbonate polyol (a) is a polycarbonate having two or more hydroxyl groups (OH) per molecule. The polyurethane resin (A) can be obtained, for example, by reacting the polycarbonate polyol (a) with a polyisocyanate component (b) to form a urethane bond. The polyisocyanate component (b) is a compound having two or more isocyanate groups (NCO) per molecule.

[0014] The polyurethane resin (A) typically has a hydroxyl group in its molecular structure that can react with the isocyanate-based crosslinking agent (B). The hydroxyl value of the polyurethane resin (A) is 1 to 20 mgKOH / g, preferably 3 to 17 mgKOH / g, and more preferably 5 to 15 mgKOH / g. By using a polyurethane resin (A) having a hydroxyl group, it is possible to form an adhesive layer with excellent heat resistance and hydrolysis resistance by reacting it with an isocyanate-based crosslinking agent (B) having an isocyanate group. If the hydroxyl value of the polyurethane resin (A) is too low, it will not be able to sufficiently react with the isocyanate group of the isocyanate-based crosslinking agent (B), resulting in excessively high initial adhesive strength, making repositioning difficult, and making it difficult to improve heat resistance and hydrolysis resistance. On the other hand, if the hydroxyl value of the polyurethane resin (A) is too high, a large amount of the isocyanate-based crosslinking agent (B) must be added, resulting in an adhesive layer that is too hard and has insufficient adhesive properties.

[0015] The polycarbonate polyol (a) is a component that has excellent hydrolysis resistance and heat resistance. Therefore, by using the polyurethane resin (A) having structural units derived from the polycarbonate polyol (a), it is possible to form an adhesive layer that has excellent heat resistance and hydrolysis resistance.

[0016] Examples of the polycarbonate polyol (a) include polytetramethylene carbonate diol, polypentamethylene carbonate diol, polyneopentyl carbonate diol, polyhexamethylene carbonate diol, poly(1,4-cyclohexanedimethylene carbonate) diol, polydecamethylene carbonate diol, polycyclohexanedimethanol / hexanediol copolymer carbonate diol, and random / block copolymers thereof. Among these, crystalline polycarbonate polyols such as polyhexamethylene carbonate are preferred from the standpoints of cost and availability.

[0017] The number average molecular weight (Mn) of the polycarbonate polyol (a) is preferably 500 to 6,000, more preferably 700 to 3,000, and particularly preferably 800 to 2,000. If the number average molecular weight (Mn) of the polycarbonate polyol (a) is too large, the cohesive force of the urethane bond may not be easily expressed, and the mechanical properties of the adhesive layer may be slightly reduced. Furthermore, if the number average molecular weight (Mn) of the crystalline polycarbonate polyol (a) is too large, the adhesive layer formed may be prone to whitening. Therefore, when polycarbonate polyol (a) is used alone as the polyol component, the number average molecular weight (Mn) of the polycarbonate polyol (a) is preferably 3,000 or less. The number average molecular weight (Mn) of the polycarbonate polyol (a) is a value measured by terminal functional group quantification method.

[0018] As the polyol component constituting the polyurethane resin (A), a short-chain diol can be used together with the polycarbonate polyol (a) as needed. The short-chain diol is a component that functions as a chain extender. Examples of short-chain diols include aliphatic glycols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,6-hexamethylene glycol, and neopentyl glycol, and their low molar alkylene oxide adducts (number average molecular weight of less than 500 as measured by terminal functional group quantitative analysis); alicyclic glycols such as 1,4-bishydroxymethylcyclohexane and 2-methyl-1,1-cyclohexanedimethanol, and their low molar alkylene oxide adducts (number average molecular weight of less than 500); aromatic glycols such as xylylene glycol, and their low molar alkylene oxide adducts (number average molecular weight of less than 500); bisphenols such as bisphenol A, thiobisphenol, and sulfonebisphenol, and their low molar alkylene oxide adducts (number average molecular weight of less than 500); and the like.

[0019] Furthermore, as the polyol component constituting the polyurethane resin (A), a polyhydric alcohol compound can be used together with the polycarbonate polyol (a), if necessary. Examples of the polyhydric alcohol compound include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, tris-(2-hydroxyethyl)isocyanurate, 1,1,1-trimethylolethane, and 1,1,1-trimethylolpropane.

[0020] The polyisocyanate component (b) may be a conventionally known polyisocyanate component used in the production of polyurethane resins. Examples of the polyisocyanate component (b) include toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, 4-methoxy-1,3-phenylene diisocyanate, 4-isopropyl-1,3-phenylene diisocyanate, 4-chloro-1,3-phenylene diisocyanate, 4-butoxy-1,3-phenylene diisocyanate, 2,4-diisocyanate diphenyl ether, 4,4'-methylenebis(phenylene isocyanate) (MDI), crude MDI, polymeric MDI, jurylene diisocyanate, xylylene diisocyanate (XDI), 1,5-naphthalene diisocyanate, benzidine diisocyanate, and o-nitrobenzidine diisocyanate. Examples of the diisocyanate include aromatic diisocyanates such as methylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 1,10-decamethylene diisocyanate; alicyclic diisocyanates such as 1,4-cyclohexylene diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,5-tetrahydronaphthalene diisocyanate, isophorone diisocyanate, and hydrogenated XDI; and polyurethane prepolymers obtained by reacting these diisocyanates with low-molecular-weight polyols so that the terminals are isocyanate groups.

[0021] Among these polyisocyanate components (b), aliphatic or alicyclic diisocyanates are preferred because they can form an adhesive layer with superior light resistance, and isophorone diisocyanate is particularly preferred because it can form an adhesive layer with superior adhesion and solution stability.

[0022] (Method for producing polyurethane resin (A)) The polyurethane resin (A) can be produced by a conventional method for producing polyurethane resins. For example, the polyurethane resin (A) can be obtained by reacting a polycarbonate polyol (a), a polyisocyanate component (b), and optional reactive components such as a short-chain diol in the presence or absence of an organic solvent that does not contain active hydrogen in the molecule. The reaction ratio of the polycarbonate polyol (a) to the polyisocyanate component (b) is preferably NCO / OH=0.80 to 0.99, more preferably NCO / OH=0.90 to 0.97, where NCO / OH is the molar ratio of the isocyanate groups (NCO) in the polyisocyanate component (b) to the hydroxyl groups (OH) in the polycarbonate polyol (a). The reaction can be carried out by a one-shot method or a multi-stage method. The reaction temperature is usually 20 to 150°C, preferably 60 to 110°C. By adding an isocyanate-based crosslinking agent (B) described below in an amount equivalent to 1 to 2 times the NCO equivalent of the hydroxyl groups of the polyurethane resin (A) obtained at the above molar ratio (NCO(b) / OH(a)), it is possible to achieve adhesive performance equivalent to that achieved when a polyester polyol or a polyether polyol is used, even when a polycarbonate polyol (a) is used.

[0023] The weight average molecular weight (Mw) of the polyurethane resin (A) is preferably 10,000 to 100,000, and more preferably 10,000 to 50,000. By setting the weight average molecular weight (Mw) of the polyurethane resin (A) within the above range, the polyurethane resin (A) can more effectively exhibit its properties such as flexibility, adhesiveness, and heat resistance. The weight average molecular weight (Mw) of the polyurethane resin (A) is a value measured by gel permeation chromatography (GPC). The weight average molecular weight (Mw) of the polyurethane resin (A) can be measured using the following apparatus and conditions. (1) Equipment: Product name "HLC-8020" (manufactured by Tosoh Corporation) (2) Column: Product name "TSKgel G2000HXL", "G3000HXL", "G4000GXL" (manufactured by Tosoh Corporation) (3) Solvent: THF (4)Flow rate: 1.0ml / min (5) Sample concentration: 2 g / L (6) Injection volume: 100μL (7) Temperature: 40℃ (8) Detector: Model number "RI-8020" (manufactured by Tosoh Corporation) (9) Standard material: TSK standard polystyrene (manufactured by Tosoh Corporation)

[0024] A catalyst can be used, if necessary, when reacting the polycarbonate polyol (a) with the polyisocyanate component (b). Examples of catalysts include salts of metals with organic or inorganic acids, such as dibutyltin laurate, dioctyltin laurate, stannous octoate, zinc octoate, and tetra-n-butyl titanate; organometallic derivatives; organic amines, such as triethylamine; and diazabicycloundecene catalysts. Using an excess of catalyst can easily induce decomposition reactions that decompose substances other than the polyurethane resin (A). As a result, the heat resistance at high temperatures and long-term heat resistance of the resulting adhesive layer containing the polyurethane resin (A) may be reduced. Therefore, it is preferable to appropriately control the amount of catalyst used.

[0025] The polycarbonate polyol (a) and the polyisocyanate component (b) may be reacted without using a solvent or in the presence of an organic solvent, which may be inactive to isocyanate groups or less active than the reactive components to isocyanate groups. Examples of organic solvents include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aromatic hydrocarbon solvents such as toluene, xylene, Swazol (trade name, manufactured by Cosmo Oil Co., Ltd.), and Solvesso (trade name, manufactured by Exxon Chemical Co., Ltd.); aliphatic hydrocarbon solvents such as n-hexane; alcohol-based solvents such as methanol, ethanol, and isopropyl alcohol; ether-based solvents such as dioxane and tetrahydrofuran; ester-based solvents such as ethyl acetate, butyl acetate, and isobutyl acetate; glycol ether ester-based solvents such as ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, 3-methyl-3-methoxybutyl acetate, and ethyl-3-ethoxypropionate; amide-based solvents such as dimethylformamide and dimethylacetamide; lactam-based solvents such as N-methyl-2-pyrrolidone; carbonate-based solvents such as dimethyl carbonate and diethyl carbonate; etc. Among these, toluene and methyl ethyl ketone are preferred from the viewpoints of the solubility of the polyurethane resin (A) and the drying properties of the adhesive.

[0026] (Isocyanate-based crosslinking agent (B)) The isocyanate crosslinking agent (B) is a trifunctional or higher aliphatic polyisocyanate. That is, the isocyanate crosslinking agent (B) is a compound having three or more isocyanate groups (NCO) per molecule. The ratio of the content of the isocyanate crosslinking agent (B) to the content of the polyurethane resin (A) in the adhesive layer is the molar ratio of the isocyanate groups (NCO) in the isocyanate crosslinking agent (B) to the hydroxyl groups (OH) in the polyurethane resin (A), NCO / OH = 0.8 to 3.0, preferably NCO / OH = 1.0 to 2.0, and more preferably NCO / OH = 1.2 to 1.8. If the NCO / OH value is less than 0.8, the amount of remaining hydroxyl groups will be excessive. On the other hand, if the NCO / OH value is more than 3.0, the amount of remaining isocyanate groups will be excessive. In either case, crosslinking becomes insufficient, the initial adhesive strength becomes excessively high, re-adhesion becomes difficult, and the heat resistance and hydrolysis resistance of the adhesive layer become insufficient.

[0027] In the adhesive layer, the amount of the isocyanate-based crosslinking agent (B) relative to 100 parts by mass of the polyurethane resin (A) is preferably 2 to 50 parts by mass, more preferably 3 to 20 parts by mass. If the amount of the isocyanate-based crosslinking agent (B) is too small, the heat resistance and hydrolysis resistance of the adhesive layer may be somewhat insufficient. On the other hand, if the amount of the isocyanate-based crosslinking agent (B) is too large, the adhesive layer may become hard and brittle, and the peel strength may decrease, resulting in somewhat insufficient performance as an adhesive.

[0028] As the isocyanate-based crosslinking agent (B), a conventionally known isocyanate-based crosslinking agent such as an isocyanurate, biuret, adduct, or polymeric form of an aliphatic diisocyanate compound can be used. Examples of the isocyanate-based crosslinking agent (B) include blocked polyisocyanates such as polyfunctional aliphatic isocyanates, fatty acid-modified polyfunctional aliphatic isocyanates, and blocked polyfunctional aliphatic isocyanates, and trifunctional or higher aliphatic polyisocyanates such as polyisocyanate prepolymers.

[0029] As the isocyanate-based crosslinking agent (B), a modified product of hexamethylene diisocyanate (HDI) or a modified product of isophorone diisocyanate (IPDI) is preferred, and a modified product of hexamethylene diisocyanate is more preferred. By using a modified product of hexamethylene diisocyanate, i.e., an isocyanate-based crosslinking agent (B) having hexamethylene diisocyanate as a structural unit, an adhesive layer with improved adhesiveness can be formed. When an aromatic polyisocyanate such as diphenylmethane diisocyanate or tolylene diisocyanate is used, the adhesive layer formed becomes hard and brittle, and the peel strength decreases. It is also preferable to use, together with the isocyanate-based crosslinking agent (B), a polyisocyanate polymer, an adduct with other compounds, or a urethane prepolymer obtained by reacting a low-molecular-weight polyol or polyamine to form a terminal isocyanate.

[0030] (additives) The adhesive layer may contain various additives as needed, such as weather resistance improvers, abrasion resistance improvers, polymerization inhibitors, crosslinking agents, infrared absorbers, antistatic agents, adhesion improvers, leveling agents, thixotropy-imparting agents, coupling agents, plasticizers, antifoaming agents, fillers, solvents, and colorants.

[0031] (adhesive sheet) Fig. 1 is a cross-sectional view schematically showing one embodiment of the pressure-sensitive adhesive sheet of the present invention. The pressure-sensitive adhesive sheet 10 of the embodiment shown in Fig. 1 comprises a substrate 4 and a pressure-sensitive adhesive layer 2 provided on the substrate 4. The pressure-sensitive adhesive sheet 10 also comprises a peelable separate film 6, with the substrate 4, pressure-sensitive adhesive layer 4, and separate film 6 laminated in this order. The pressure-sensitive adhesive sheet 10 of this embodiment is useful, for example, as a paint protection film (PPF) or an optical film for protecting personal computer displays and smartphone screens.

[0032] Fig. 2 is a cross-sectional view schematically showing another embodiment of the pressure-sensitive adhesive sheet of the present invention. Pressure-sensitive adhesive sheet 20 of the embodiment shown in Fig. 2 comprises a substrate 4 and a pressure-sensitive adhesive layer 2 provided on the substrate 4. Pressure-sensitive adhesive sheet 20 further comprises a skin layer 5 and may further comprise a design layer 8 as needed, with the skin layer 5, design layer 8, substrate 4, and pressure-sensitive adhesive layer 2 laminated in this order. A separate film 6 is provided on the pressure-sensitive adhesive layer 2.

[0033] Fig. 3 is a cross-sectional view schematically showing another embodiment of the pressure-sensitive adhesive sheet of the present invention. Pressure-sensitive adhesive sheet 30 of the embodiment shown in Fig. 3 comprises a resin layer 13 having a design, and an adhesive layer 2 provided on the resin layer 13 having a design. This resin layer 13 having a design functions as a substrate supporting the adhesive layer 2. Pressure-sensitive adhesive sheet 30 also comprises a skin layer 5, in which the skin layer 5, the resin layer 13 having a design (substrate), and the adhesive layer 2 are laminated in this order. A separate film 6 is provided on the adhesive layer 2. A guard film 15 is provided on the back surface of the skin layer 5. Pressure-sensitive adhesive sheet 20 shown in Fig. 2 and pressure-sensitive adhesive sheet 30 shown in Fig. 3 are useful as sheets (films) for imparting scratch resistance and design to, for example, housings and displays for home appliances such as personal computers, and interior and exterior parts of vehicles.

[0034] [Base material] The substrate is a member used to support the adhesive layer. Typically, a sheet or film made of a thermoplastic resin is used as the substrate. Examples of thermoplastic resins include polyethylene terephthalate (PET), polycarbonate, ABS resin, urethane resin, polyolefin resin, acrylic resin, and alloy resin. The thickness of the substrate may be appropriately set depending on the intended use of the adhesive sheet. The thickness of the substrate may be, for example, 20 to 3000 μm, and preferably 50 to 2000 μm. As shown in FIG. 3, a resin layer 13 having a design may be used as the substrate.

[0035] [Adhesive layer] The adhesive layer is formed by applying an adhesive composition containing the polyurethane resin (A) and the isocyanate-based crosslinking agent (B) to form a coating layer, followed by drying and aging the coating layer. The dry thickness of the adhesive layer is usually 1 to 50 μm, and preferably 3 to 40 μm.

[0036] [Separate film] The separate film is a film (layer) whose main purpose is to protect the adhesive layer. For example, a film made of a thermoplastic resin is used as the separate film. The thickness and material of the separate film are not particularly limited. Specifically, a PET film with a thickness of about 50 to 100 μm is suitable as the separate film.

[0037] [Design layer] Materials constituting the design layer include thermoplastic resins; curable resins such as thermosetting resins and UV-curable resins; and the like. Thermoplastic resins include acrylic resins, acrylic-modified polyolefin resins, chlorinated polyolefin resins, acid-modified polyolefin resins, vinyl chloride-vinyl acetate copolymers, thermoplastic urethane resins, thermoplastic polyester resins, polyamide resins, and rubber-based resins. Curable resins include urethane resins, acrylic resins, and epoxy resins. Design layers can be formed by adding colorants and extender pigments such as silica, organic beads, pigments, and dyes to these resins. Colorants include inorganic pigments such as carbon black, iron black, titanium white, antimony white, yellow lead, titanium yellow, red iron oxide, cadmium red, ultramarine blue, and cobalt blue; organic pigments and dyes such as quinacridone red, isoindolinone yellow, and phthalocyanine blue; metallic pigments consisting of scaly flakes of aluminum, brass, etc.; and pearlescent pigments consisting of scaly flakes of titanium dioxide-coated mica and basic lead carbonate, etc. Alternatively, the design layer may be a thin metal film formed by vapor deposition, sputtering, foil transfer, or the like using a metal such as aluminum, chromium, gold, silver, or copper.

[0038] The thickness of the design layer is usually 2 to 500 μm, preferably 5 to 300 μm. When the design layer is a thin metal film formed by vapor deposition or the like, the thickness of the design layer (thin metal film) is usually 0.001 to 1 μm, preferably 0.005 to 0.5 μm.

[0039] [Epidermal layer] The surface layer is a layer having scratch resistance. Materials that can be used to form the surface layer include thermoplastic resins, thermosetting resins, and ultraviolet-curing resins. Examples of thermoplastic resins include acrylic resins, thermoplastic urethane resins, thermoplastic polyester resins, and polyamide resins. Examples of thermosetting resins and ultraviolet-curing resins include urethane resins, acrylic resins, and epoxy resins. Of these, thermosetting resins and ultraviolet-curing resins are preferred because they have particularly excellent scratch resistance. The thickness of the surface layer may be appropriately set depending on the intended use of the pressure-sensitive adhesive sheet, etc. The thickness of the surface layer may be, for example, 2 to 200 μm, preferably 5 to 100 μm.

[0040] [Guard film] The guard film is usually a resin film (sheet) made of a thermoplastic resin. Examples of thermoplastic resins include polyethylene terephthalate (PET), polycarbonate, ABS resin, urethane resin, polyolefin resin, acrylic resin, and alloy resin. The thickness of the guard film may be appropriately set depending on the intended use of the pressure-sensitive adhesive sheet. The thickness of the guard film may be, for example, 3 to 500 μm, and preferably 10 to 300 μm.

[0041] <Method of manufacturing adhesive sheet> The pressure-sensitive adhesive sheet of the present invention can be produced according to the method described below. Specifically, one embodiment of the pressure-sensitive adhesive sheet production method of the present invention is a method for producing a pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer provided on the substrate, and includes the steps of applying a pressure-sensitive adhesive composition to the substrate to form a coating layer (step (1)) and aging the coating layer at 40°C or higher for 24 hours or more to form a pressure-sensitive adhesive layer (step (2)). The pressure-sensitive adhesive composition contains the aforementioned polyurethane resin (A) and isocyanate-based crosslinking agent (B). The ratio of the content of the isocyanate-based crosslinking agent (B) to the content of the polyurethane resin (A) in the pressure-sensitive adhesive composition is NCO / OH, which is the molar ratio of the isocyanate groups (NCO) in the isocyanate-based crosslinking agent (B) to the hydroxyl groups (OH) in the polyurethane resin (A), of 0.8 to 3.0.

[0042] In step (1), a pressure-sensitive adhesive composition is applied to a substrate to form a coating layer. The pressure-sensitive adhesive composition can be obtained by mixing the aforementioned polyurethane resin (A) and isocyanate crosslinking agent (B) in a predetermined ratio. The thickness of the coating layer formed may be such that the pressure-sensitive adhesive layer formed in step (2) has a predetermined thickness (e.g., 10 to 50 μm). Methods for applying the pressure-sensitive adhesive composition to a substrate include conventional printing methods such as gravure coating, gravure reverse coating, gravure offset coating, spinner coating, roll coating, reverse roll coating, kiss coating, wheel coating, dip coating, solid coating by silk screen, wire bar coating, flow coating, comma coating, and spray coating.

[0043] In step (2), the coating layer formed in step (1) is aged. This forms an adhesive layer on the substrate, thereby obtaining the desired adhesive sheet. If necessary, a separate film may be attached to the formed adhesive layer. The temperature for aging the coating layer is 40°C or higher, preferably 40 to 60°C. The time for aging the coating layer is 24 hours or longer, preferably 24 to 72 hours. The coating layer may be dried before aging. The temperature for drying the coating layer is preferably 60 to 100°C, more preferably 70 to 90°C.

[0044] When manufacturing a PSA sheet having a skin layer, for example, a resin composition for forming a skin layer (hereinafter also referred to as "skin layer coating") is applied to a guard film, a substrate, and a design layer to form a coating layer. The formed coating layer is then dried to form a skin layer on the surface of the guard film or the like. Examples of methods for applying the skin layer coating to the surface of the guard film or the like include conventional printing methods such as gravure coating, gravure reverse coating, gravure offset coating, spinner coating, roll coating, reverse roll coating, kiss coating, wheel coating, dip coating, solid coating by silk screen, wire bar coating, flow coating, comma coating, and spray coating.

[0045] The drying temperature for the coating layer is typically 60 to 100°C, preferably 70 to 90°C. To complete the thermosetting reaction, the coating may be aged after drying, if necessary. The aging conditions are typically 30 to 60°C for about 1 to 3 days. If necessary, the dried coating layer may be irradiated with ultraviolet light. UV irradiation may be carried out when a surface layer or adhesive layer is formed on the surface of a guard film or the like, or after the surface layer or adhesive layer is formed. Furthermore, the surface of a coating layer formed by applying a coating material for a surface layer may be decorated by an inkjet method. For example, UV-curable inkjet ink can be used for the decoration.

[0046] When manufacturing a pressure-sensitive adhesive sheet having a design layer, for example, a resin composition for forming the design layer is applied to a substrate or a surface layer to form a coating layer. The formed coating layer is then dried to form a design layer on the surface of the substrate or the like. The substrate sheet may be surface-modified by a primer treatment, a corona discharge treatment, or the like. Methods for applying the resin composition for forming the design layer to the surface of the substrate or the like include conventional printing methods such as gravure coating, gravure reverse coating, gravure offset coating, spinner coating, roll coating, reverse roll coating, kiss coating, wheel coating, dip coating, solid coating by silk screen, wire bar coating, flow coating, comma coating, and spray coating.

[0047] The drying temperature of the coating layer is usually 60 to 100° C., preferably 70 to 90° C. The design layer can also be formed by an inkjet method. When forming the design layer by the inkjet method, it is preferable to use a UV-curable inkjet ink.

[0048] A design layer previously formed on a transfer sheet may be transferred to the surface of a substrate or the like. A primer layer may be provided between the design layer and the substrate or the like to improve adhesion between the two layers. Furthermore, to improve the design of the design layer, a metal thin film or the like may be formed, or the design layer may be laminated to form a multi-layered design layer. The metal thin film can be formed by vacuum deposition, sputtering, foil transfer, or other methods using metals such as aluminum, chromium, gold, silver, and copper. Furthermore, after forming the design layer on the substrate, the aforementioned surface layer paint may be applied to the formed design layer to form a coating layer, and the formed coating layer may be dried to form the surface layer. [Example]

[0049] The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" and "%" are by mass unless otherwise specified.

[0050] <Production of Polyurethane Resin (A)> (Polyurethane Resin A1) A reaction vessel equipped with a stirrer, reflux condenser, thermometer, nitrogen inlet, and manhole was prepared. While the inside of the reaction vessel was purged with nitrogen, 200.0 g of polyhexamethylene carbonate diol having hydroxyl groups at both ends (trade name "Duranol T6001", manufactured by Asahi Kasei Chemicals, Mn 1,000) and 20.0 g of 1,3-butylene glycol were charged. Next, 103.0 g of methyl ethyl ketone (MEK) was charged and stirred. After the system became homogeneous, 89.0 g of isophorone diisocyanate (IPDI) was charged at a temperature of 50°C and reacted at 80°C to obtain a reaction solution. The viscosity of the reaction solution was adjusted by dilution with MEK, and the viscosity of the reaction solution at 2,270 cm originating from free isocyanate groups was measured by infrared absorption spectroscopy. -1 The reaction was continued until the absorption of HCl disappeared, yielding a resin solution AA1 containing polyurethane resin A1. The solids content of the resulting resin solution AA1 was 30%. The hydroxyl value of polyurethane resin A1 was 7.7 mg KOH / g, and Mw was 24,000.

[0051] (Polyurethane Resin A2) While the inside of the reaction vessel was purged with nitrogen, 200.0 g of polydecamethylene carbonate diol (Mn 1,000) having hydroxyl groups at both ends and 20.0 g of 1,3-butylene glycol were charged. Next, 103.0 g of MEK was charged and stirred. After the system became homogeneous, 89.0 g of IPDI was charged at a temperature of 50°C and the reaction was carried out at 80°C to obtain a reaction solution. The viscosity of the reaction solution was adjusted by dilution with MEK, and the peak of 2,270 cm originating from free isocyanate groups was measured by infrared absorption spectroscopy. -1 The reaction was allowed to proceed until the absorption of HCl disappeared, yielding a resin solution AA2 containing a polyurethane resin A2. The solids content of the resulting resin solution AA2 was 30%. The hydroxyl value of the polyurethane resin A2 was 7.7 mg KOH / g, and the Mw was 26,000.

[0052] (Polyurethane Resin A3) While the inside of the reaction vessel was purged with nitrogen, 200.0 g of polycyclohexanedimethanol / hexanediol copolymer carbonate diol having hydroxyl groups at both ends (trade name "ETERNACOLLUM-90 (1 / 3)", manufactured by Ube Industries, Ltd., Mn 1,000) and 20.0 g of 1,3-butylene glycol were charged. Next, 103.0 g of MEK was charged and stirred. After the system became homogeneous, 89.0 g of IPDI was charged at a temperature of 50°C and reacted at 80°C to obtain a reaction liquid. The viscosity of the reaction liquid was adjusted by dilution with MEK, and the viscosity of the reaction liquid at 2,270 cm originating from free isocyanate groups as measured by infrared absorption spectroscopy was measured. -1 The reaction was allowed to proceed until the absorption of HCl disappeared, yielding a resin solution AA3 containing polyurethane resin A3. The solids content of the resulting resin solution AA3 was 30%. The hydroxyl value of polyurethane resin A3 was 7.7 mg KOH / g, and Mw was 25,000.

[0053] (Polyurethane resin A4) While the inside of the reaction vessel was purged with nitrogen, 200.0 g of polyhexamethylene carbonate diol having hydroxyl groups at both ends (trade name "Duranol T6001", manufactured by Asahi Kasei Chemicals Corporation, Mn 1,000) and 20.0 g of 1,3-butylene glycol were charged. Next, 101.5 g of MEK was charged and stirred. After the system became homogeneous, 84.4 g of IPDI was charged at a temperature of 50°C and reacted at 80°C to obtain a reaction liquid. The viscosity of the reaction liquid was adjusted by dilution with MEK, and the viscosity of the reaction liquid at 2,270 cm originating from free isocyanate groups was measured by infrared absorption spectroscopy. -1 The reaction was allowed to proceed until the absorption of HCl disappeared, yielding a resin solution AA4 containing polyurethane resin A4. The solids content of the resulting resin solution AA4 was 30%. The hydroxyl value of polyurethane resin A4 was 15.6 mg KOH / g, and Mw was 12,000.

[0054] (Polyurethane Resin A5) While the inside of the reaction vessel was purged with nitrogen, 200.0 g of polyhexamethylene carbonate diol having hydroxyl groups at both ends (trade name "Duranol T6001", manufactured by Asahi Kasei Chemicals Corporation, Mn 1,000) and 20.0 g of 1,3-butylene glycol were charged. Next, 96.6 g of MEK was charged and stirred. After the system became homogeneous, 69.8 g of tolylene diisocyanate (TDI) was charged at a temperature of 50°C and reacted at 80°C to obtain a reaction liquid. The viscosity of the reaction liquid was adjusted by dilution with MEK, and the viscosity of the reaction liquid at 2,270 cm originating from free isocyanate groups was measured by infrared absorption spectroscopy. -1 The reaction was allowed to proceed until the absorption of α-methyl-2-propanol disappeared, yielding a resin solution AA5 containing polyurethane resin A5. The solids content of the resulting resin solution AA5 was 30%. The hydroxyl value of polyurethane resin A5 was 8.2 mg KOH / g, and Mw was 22,000.

[0055] (Polyurethane Resin A6) While the inside of the reaction vessel was purged with nitrogen, 200.0 g of polytetramethylene ether glycol having hydroxyl groups at both ends (trade name "PTMG1000", manufactured by Mitsubishi Chemical Corporation, Mn1,000) and 20.0 g of 1,3-butylene glycol were charged. Next, 103.0 g of MEK was charged and stirred. After the system became homogeneous, 89.0 g of IPDI was charged at a temperature of 50°C and reacted at 80°C to obtain a reaction solution. The viscosity of the reaction solution was adjusted by dilution with MEK, and a peak at 2,270 cm originating from free isocyanate groups was measured by infrared absorption spectroscopy. -1 The reaction was allowed to proceed until the absorption of α-methyl-2-propanol disappeared, yielding a resin solution AA6 containing polyurethane resin A6. The resulting resin solution AA6 had a solids content of 30%. The hydroxyl value of polyurethane resin A6 was 7.7 mg KOH / g, and Mw was 28,000.

[0056] (Polyurethane Resin A7) While the inside of the reaction vessel was purged with nitrogen, 200.0 g of polycaprolactone diol having hydroxyl groups at both ends (trade name "Placcel 210", manufactured by Daicel Corporation, Mn 1,000) and 20.0 g of 1,3-butylene glycol were charged. Next, 103.0 g of MEK was charged and stirred. After the system became homogeneous, 89.0 g of IPDI was charged at a temperature of 50°C and reacted at 80°C to obtain a reaction solution. The viscosity of the reaction solution was adjusted by dilution with MEK, and the viscosity of the reaction solution at 2,270 cm originating from free isocyanate groups was measured by infrared absorption spectroscopy. -1 The reaction was allowed to proceed until the absorption of α-methyl-2-propanol disappeared, yielding a resin solution AA7 containing polyurethane resin A7. The solids content of the resulting resin solution AA7 was 30%. The hydroxyl value of polyurethane resin A7 was 7.7 mg KOH / g, and Mw was 23,000.

[0057] (Polyurethane Resin A8) While the inside of the reaction vessel was purged with nitrogen, 200.0 g of polyhexamethylene carbonate diol having hydroxyl groups at both ends (trade name "Duranol T6001", manufactured by Asahi Kasei Chemicals Corporation, Mn 1,000) and 20.0 g of 1,3-butylene glycol were charged. Next, 98.3 g of MEK was charged and stirred. After the system became homogeneous, 75.0 g of IPDI was charged at a temperature of 50°C and reacted at 80°C to obtain a reaction liquid. The viscosity of the reaction liquid was adjusted by dilution with MEK, and the viscosity of the reaction liquid at 2,270 cm originating from free isocyanate groups as measured by infrared absorption spectroscopy was 0.01 g. -1 The reaction was allowed to proceed until the absorption of HCl disappeared, yielding a resin solution AA8 containing polyurethane resin A8. The solids content of the resulting resin solution AA8 was 30%. The hydroxyl value of polyurethane resin A8 was 32.1 mg KOH / g, and Mw was 5,600.

[0058] (Polyurethane Resin A9) While the inside of the reaction vessel was purged with nitrogen, 200.0 g of polyhexamethylene carbonate diol having hydroxyl groups at both ends (trade name "Duranol T6001", manufactured by Asahi Kasei Chemicals Corporation, Mn 1,000) and 20.0 g of 1,3-butylene glycol were charged. Next, 104.5 g of MEK was charged and stirred. After the system became homogeneous, 93.5 g of IPDI was charged at a temperature of 50°C and reacted at 80°C to obtain a reaction liquid. The viscosity of the reaction liquid was adjusted by dilution with MEK, and the viscosity of the reaction liquid at 2,270 cm originating from free isocyanate groups was measured by infrared absorption spectroscopy. -1 The reaction was allowed to proceed until the absorption of HCl disappeared, yielding a resin solution AA9 containing polyurethane resin A9. The solids content of the resulting resin solution AA9 was 30%. The hydroxyl value of polyurethane resin A9 was 0.3 mg KOH / g, and Mw was 113,000.

[0059] <Production of adhesive sheets (1)> (Examples 1 to 13, Comparative Examples 1 to 10) The following isocyanate-based crosslinking agents B1 to B3 were prepared. Isocyanate-based crosslinking agent B1: HDI TMP adduct, product name "D-160N", manufactured by Mitsui Chemicals, Inc., solid content 75%, NCO% 12.6% Isocyanate crosslinking agent B2: Isocyanurate of HDI, product name "D-170N", manufactured by Mitsui Chemicals, Inc., solids content 100%, NCO% 20.7% Isocyanate-based crosslinking agent B3: TDI TMP adduct, product name "D-101E", manufactured by Mitsui Chemicals, Inc., solid content 75%, NCO% 13.3%

[0060] The types and amounts (unit: parts) of polyurethane resin (A) and isocyanate-based crosslinking agent (B) shown in Tables 1-1 to 1-3 were mixed to obtain pressure-sensitive adhesive compositions. The molar ratio (NCO / OH (mol / mol)) of the isocyanate groups (NCO) in the isocyanate-based crosslinking agent (B) to the hydroxyl groups (OH) in the polyurethane resin (A) is shown in Tables 1-1 to 1-3. The resulting pressure-sensitive adhesive composition was diluted with MEK to prepare a coating solution with a solids content of 25%. The prepared coating solution was applied to the entire surface of one side of a substrate: a PET film (trade name "Lumirror," manufactured by Panac Corporation, thickness: 50 μm) or an acrylonitrile-butadiene-styrene copolymer (ABS) sheet (trade name "ToughAce® EAR802," manufactured by Sumitomo Bakelite Co., Ltd., thickness: 1 mm). After drying at 100°C for 1 minute, the coating was left in a 50°C oven for 48 hours to allow the curing reaction to proceed. This resulted in a pressure-sensitive adhesive sheet having a 30 μm thick adhesive layer. The resulting pressure-sensitive adhesive sheet was then cut into a width of 20 mm to prepare a pressure-sensitive adhesive tape for evaluation.

[0061] <Evaluation of adhesive sheets (1)> (Initial peel strength) The types of adhesive-receiving member and adhesive tape shown in Tables 1-1 to 1-3 were laminated so that the adhesive layer of the adhesive tape was in contact with the surface of the adhesive-receiving member, and then adhered using a roller. Then, using an autograph (product name "Autograph AGS-J500N", manufactured by Shimadzu Corporation), the adhesive tape was peeled 180° from the adhesive-receiving member at a pulling speed of 300 mm / min, and the peel strength (initial peel strength X (N / 20 mm)) was measured. The results are shown in Tables 1-1 to 1-3. If the initial peel strength X is low, the tape can be peeled and re-applied. If the initial peel strength X is greater than 10 N / 20 mm, it becomes difficult to peel and re-apply. From the above, the initial peel strength X is preferably 10 N / 20 mm or less, and more preferably 5 N / 20 mm or less.

[0062] (peel strength after 24 hours) The types of adhesive-receiving member and adhesive tape shown in Tables 1 to 1-3 were laminated so that the adhesive layer of the adhesive tape was in contact with the surface of the adhesive-receiving member, and then adhered using a roller. After leaving the sample at room temperature (25°C) for 24 hours, the adhesive tape was peeled 180° from the adhesive-receiving member at a pulling rate of 300 mm / min using an autograph (product name "Autograph AGS-J500N", manufactured by Shimadzu Corporation) to measure the peel strength (peel strength Y (N / 20 mm) after 24 hours). The results are shown in Tables 1-1 to 1-3. The peel strength Y after 24 hours is preferably 10 N / 20 mm or more, and more preferably 14 N / 20 mm or more.

[0063] Furthermore, the ratio (Y / X) of the peel strength Y (N / 20 mm) after 24 hours to the initial peel strength X (N / 20 mm) was calculated. The results are shown in Tables 1-1 to 1-3. The Y / X value is preferably 3.0 or greater. If the Y / X value is less than 3.0, initial re-adhesion is difficult or adhesion (stickiness) is insufficient over a long period of time.

[0064] (Peel strength after heat resistance test) The types of adhesive tape and adhesive member shown in Tables 1-1 to 1-3 were laminated so that the adhesive layer of the adhesive tape was in contact with the surface of the adhesive member, and the laminate was adhered using a roller. The laminate was then left at room temperature (25°C) for 24 hours. A heat resistance test was then conducted at 120°C for 400 hours. Next, an autograph (product name "Autograph AGS-J500N", manufactured by Shimadzu Corporation) was used to measure the peel strength (peel strength after heat resistance test (N / 20 mm)) by peeling the adhesive tape 180° from the adhesive member at a pulling rate of 300 mm / min. The results are shown in Tables 1-1 to 1-3. The peel strength after the heat resistance test is preferably 5 N or more, and more preferably 10 N or more.

[0065] (Peel strength after hydrolysis resistance test) The types of adhesive tape and adhesive substrate shown in Tables 1-1 to 1-3 were laminated so that the adhesive layer of the adhesive tape was in contact with the surface of the adhesive substrate, and the substrate was adhered using a roller. The substrate was then left at room temperature (25°C) for 24 hours. A jungle test (hydrolysis resistance test) was then performed, in which the substrate was held at a temperature of 70°C and a relative humidity of 95% for 8 weeks. Next, an autograph (product name "Autograph AGS-J500N", manufactured by Shimadzu Corporation) was used to peel the adhesive tape from the adhesive substrate at a 180° angle at a pulling rate of 300 mm / min, and the peel strength (peel strength after hydrolysis resistance test (N / 20 mm)) was measured. The results are shown in Tables 1-1 to 1-3. The peel strength after the hydrolysis resistance test is preferably 5 N or more, and more preferably 10 N or more.

[0066] TIFF0007725432000001.tif177170

[0067] TIFF0007725432000002.tif165170

[0068] TIFF0007725432000003.tif178170

[0069] <Production of polyurethane resin for skin layer> A reaction vessel equipped with a stirrer, reflux condenser, thermometer, air inlet, and manhole was prepared. While the inside of the reaction vessel was purged with air, 400.0 g of polyhexamethylene carbonate diol (trade name "Placcel CD220", manufactured by Daicel Chemical Industries, Ltd., hydroxyl value 56.1 mg KOH / g), 80.0 g of 1,4-butanediol, and 160.0 g of a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (hydroxyl value 102.9 mg KOH / g) were charged. Next, 226 g of MEK was charged and stirred. After the system became homogeneous, 103.8 g of HDI and 161.9 g of 4,4'-methylenebis-cyclohexyl diisocyanate were charged at a temperature of 50°C, and the reaction was carried out at 80°C using a catalyst (dibutyltin laurate). The viscosity of the reaction solution was adjusted by diluting with a solvent, and the 2,270 cm peak due to the free isocyanate group was measured by infrared absorption spectroscopy. -1 The reaction was continued until the absorption of methyl ketone disappeared. Cyclohexanone was added until the mass ratio of MEK to cyclohexanone reached 1:1, yielding a resin solution containing polyurethane resin. The viscosity of the resulting resin solution at 20°C was 500 dPa·s, and the solids content was 45%. The double bond equivalent of the polyurethane resin was 588 g / eq., and the Mw was 46,000. Furthermore, the proportion of structural units derived from polycarbonate polyol in the polyurethane resin was approximately 44%.

[0070] <Preparation of the surface layer paint> 1,100 g of a resin solution containing polyurethane resin for the surface layer was mixed with 2.25 g of a photopolymerization initiator (product name "Irgacure 184" manufactured by BASF). 2.25 g of non-yellowing polyisocyanate (product name "Duranate TPA-100" manufactured by Asahi Kasei Corporation, 100% solids, 23.1% isocyanate), MEK, and cyclohexanone (MEK:cyclohexanone = 1:1 (mass ratio)) were then added to obtain a surface layer coating with a solids content of 30%.

[0071] <Preparation of paint for design layer> 100 parts of Resin Solution AA1, 16 parts of carbon black, and 214 parts of MEK were mixed, and then glass beads were added and dispersed using a paint shaker to obtain a dispersion. 100 parts of the resulting dispersion were mixed with 360 parts of Resin Solution AA1, 400 parts of MEK, and 20 parts of a polyisocyanate crosslinker (trade name "Coronate HX" manufactured by Nippon Polyurethane Co., Ltd.), and the mixture was stirred until homogeneous to obtain a black paint for the design layer.

[0072] <Adhesive sheet manufacturing (2)> (Examples 14 to 16) A 200 μm thick amorphous PET film (trade name "Novaclear", manufactured by Mitsubishi Chemical Corporation) was prepared as a guard film. The surface of the guard film was coated with a coating material for the surface skin layer using a bar coater, and then dried at 90°C for 2 minutes to form a coating layer with a thickness of 15 μm. An ultraviolet irradiator (trade name "UniCure UVC-02512S1AA01", manufactured by Ushio Inc.) was used to irradiate the film with an integrated light dose of 2,000 mJ / cm. 2 The coating layer was irradiated with UV light so that it hardened and formed a skin layer. The surface of the formed skin layer was coated with the paint for the design layer using a bar coater, and then dried at 90°C for 2 minutes to form a 20 μm-thick substrate (a resin layer with a design applied).

[0073] Separately, a pressure-sensitive adhesive composition was obtained by mixing the polyurethane resin (A) and isocyanate-based crosslinking agent (B) in the types and amounts (unit: parts) shown in Table 2-1. The obtained pressure-sensitive adhesive composition was diluted with MEK to prepare a coating liquid with a solids content of 25%. The prepared coating liquid was applied to the surface of the substrate (designed resin layer) using a bar coater. After drying at 100°C for 1 minute, a separate film (80 μm thick PET film) was attached. Next, the mixture was aged at 45°C for 24 hours to obtain a pressure-sensitive adhesive sheet with a 20 μm thick adhesive layer.

[0074] Examples 17 to 22 The surface of the substrate shown in Table 2-1 was coated with the surface layer paint using a bar coater, and then dried at 90°C for 2 minutes to form a coating layer with a thickness of 15 μm. An ultraviolet irradiator (trade name "UniCure UVC-02512S1AA01", manufactured by Ushio Inc.) was used to irradiate the surface with an integrated light dose of 2,000 mJ / cm. 2 The coating layer was irradiated with UV light so that the coating layer was cured to form a surface layer.

[0075] Separately, a pressure-sensitive adhesive composition was obtained by mixing the polyurethane resin (A) and the isocyanate-based crosslinking agent (B) in the types and amounts (unit: parts) shown in Tables 2-1 and 2-2. The obtained pressure-sensitive adhesive composition was diluted with MEK to prepare a coating liquid with a solids content of 25%. The prepared coating liquid was applied to the back surface of the substrate (the surface opposite to the surface on which the skin layer was formed) using a bar coater. After drying at 80°C for 2 minutes, a separate film (a PET film with a thickness of 80 μm) was attached. Next, the mixture was aged at 45°C for 24 hours to obtain a pressure-sensitive adhesive sheet with a 20 μm-thick adhesive layer.

[0076] (Examples 23 to 28, Comparative Examples 11 to 13) Resin solution AA1 was applied to the surface of the substrates shown in Tables 2-2 and 2-3 using a bar coater, and then dried at 90°C for 2 minutes to form a primer layer with a thickness of 5 μm. A design layer paint was applied to the surface of the primer layer with a bar coater, and then dried at 90°C for 2 minutes to form a design layer with a thickness of 20 μm. A skin layer paint was applied to the surface of the design layer with a bar coater, and then dried at 90°C for 2 minutes to form a coating layer with a thickness of 15 μm. An ultraviolet irradiator (trade name "UniCure UVC-02512S1AA01", manufactured by Ushio Inc.) was used to apply the coating with an accumulated light dose of 2,000 mJ / cm. 2 The coating layer was irradiated with UV light so that the coating layer was cured to form a surface layer.

[0077] Separately, a pressure-sensitive adhesive composition was obtained by mixing the polyurethane resin (A) and isocyanate-based crosslinking agent (B) in the types and amounts (units: parts) shown in Tables 2-2 and 2-3. The obtained pressure-sensitive adhesive composition was diluted with MEK to prepare a coating liquid with a solids content of 25%. The prepared coating liquid was applied to the back surface of the substrate (the surface opposite to the surface on which the primer layer, design layer, and skin layer were formed) using a bar coater. After drying at 80°C for 2 minutes, a separate film (a PET film with a thickness of 80 μm) was attached. Next, the mixture was aged at 45°C for 24 hours to obtain a pressure-sensitive adhesive sheet with a 20 μm-thick adhesive layer.

[0078] <Evaluation of adhesive sheets (2)> (Heat resistance) The types of adhesive-receiving materials and adhesive sheets shown in Tables 2-1 to 2-3 were laminated so that the adhesive layer of the adhesive sheet was in contact with the surface of the adhesive-receiving material, and after being adhered using a roller, were left at room temperature (25°C) for 24 hours. A heat resistance test was then conducted by holding the material at 120°C for 400 hours. The appearance of the adhesive layer after the test was observed, and the heat resistance of the adhesive layer was evaluated according to the evaluation criteria shown below. The results are shown in Tables 2-1 to 2-3. ◯: No peeling, yellowing, whitening, cracking, cracking, or wrinkling occurred in the adhesive. ×: The adhesive peeled off, yellowed, whitened, cracked, cracked, wrinkled, or the like.

[0079] (Hydrolysis resistance) The types of adhesive-receiving materials and adhesive sheets shown in Tables 2-1 to 2-3 were laminated so that the adhesive layer of the adhesive sheet was in contact with the surface of the adhesive-receiving material, and then adhered using a roller.Then, the materials were left at room temperature (25°C) for 24 hours.A jungle test (hydrolysis resistance test) was then conducted, in which the materials were kept at a temperature of 70°C and a relative humidity of 95% for 8 weeks.The appearance of the adhesive layer after the test was observed, and the hydrolysis resistance of the adhesive layer was evaluated according to the evaluation criteria shown below.The results are shown in Tables 2-1 to 2-3. ◯: No peeling, yellowing, whitening, cracking, cracking, wrinkling, etc. occurred in the adhesive. ×: The adhesive peeled off, yellowed, whitened, cracked, cracked, wrinkled, or the like.

[0080] (Lightfastness) The types of adhesive-receiving materials and adhesive sheets shown in Tables 2-1 to 2-3 were laminated so that the adhesive layer of the adhesive sheet was in contact with the surface of the adhesive-receiving material, and after being adhered using a roller, were left at room temperature (25°C) for 24 hours. After that, an accelerated test was carried out using a xenon weatherometer according to the following conditions in accordance with JASO M346-1993. ·Irradiance: 48~162W / m 2 ·Wavelength: 300~400nm Black panel temperature: 89±3℃ Irradiation time: 8 weeks ·Heat amount: 2,000kJ

[0081] After the test, the appearance of the adhesive layer was observed, and the light resistance of the adhesive layer was evaluated according to the following evaluation criteria. The results are shown in Tables 2-1 to 2-3. ◯: No peeling, yellowing, whitening, cracking, cracking, wrinkling, etc. occurred in the adhesive. ×: The adhesive peeled off, yellowed, whitened, cracked, cracked, wrinkled, or the like.

[0082] TIFF0007725432000004.tif182170

[0083] TIFF0007725432000005.tif177170

[0084] TIFF0007725432000006.tif173170 [Industrial Applicability]

[0085] The pressure-sensitive adhesive sheet of the present invention is suitable as a material for producing, for example, interior or exterior materials for vehicles such as automobiles; housings for home appliances such as televisions, personal computers, and mobile phones; surfaces of displays; interior materials for buildings such as walls, floors, and ceilings; containers, etc. [Explanation of symbols]

[0086] 2: Adhesive layer 4: Base material 5: Epidermal layer 6: Separate film 8: Design layer 10, 20, 30: Adhesive sheet 13: Designed resin layer 15: Guard film

Claims

1. A pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer provided on the substrate, the adhesive layer contains a polyurethane resin (A) and an isocyanate-based crosslinking agent (B), the polyurethane resin (A) has a structural unit derived from a polycarbonate polyol (a) and has a hydroxyl value of 1 to 20 mgKOH / g, the isocyanate-based crosslinking agent (B) is a tri- or higher functional aliphatic polyisocyanate, In the pressure-sensitive adhesive sheet, the ratio of the content of the isocyanate crosslinking agent (B) to the content of the polyurethane resin (A) in the pressure-sensitive adhesive layer is NCO / OH=0.8 to 3.0, in terms of the molar ratio of isocyanate groups (NCO) in the isocyanate crosslinking agent (B) to hydroxyl groups (OH) in the polyurethane resin (A).

2. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the ratio of the peel strength Y (N / 20 mm) after 24 hours at 25°C to the initial peel strength X (N / 20 mm) of the pressure-sensitive adhesive layer is Y / X≧3.

0.

3. The pressure-sensitive adhesive sheet according to claim 1, wherein the isocyanate-based crosslinking agent (B) has hexamethylene diisocyanate as a constituent unit.

4. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the weight average molecular weight of the polyurethane resin (A) is 10,000 to 100,000.

5. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer has a thickness of 10 to 50 μm.

6. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, further comprising a peelable separate film, wherein the substrate, the pressure-sensitive adhesive layer, and the separate film are laminated in this order.

7. The adhesive tape further includes a skin layer, and the skin layer, the base material, and the adhesive layer are laminated in this order, The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the substrate is a resin layer having a design.

8. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, further comprising a surface layer and a design layer, wherein the surface layer, the design layer, the substrate, and the pressure-sensitive adhesive layer are laminated in this order.

9. A method for producing a pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer provided on the substrate, the method comprising: a step of applying a pressure-sensitive adhesive composition onto the substrate to form a coating layer; and a step of aging the coating layer at 40°C or higher for 24 hours or more to form an adhesive layer, the pressure-sensitive adhesive composition contains a polyurethane resin (A) and an isocyanate-based crosslinking agent (B), the polyurethane resin (A) has a structural unit derived from a polycarbonate polyol (a) and has a hydroxyl value of 1 to 20 mgKOH / g, the isocyanate-based crosslinking agent (B) is a tri- or higher functional aliphatic polyisocyanate, A method for producing a pressure-sensitive adhesive sheet, wherein the ratio of the content of the isocyanate crosslinking agent (B) to the content of the polyurethane resin (A) in the pressure-sensitive adhesive composition is NCO / OH=0.8 to 3.0, in terms of the molar ratio of isocyanate groups (NCO) in the isocyanate crosslinking agent (B) to hydroxyl groups (OH) in the polyurethane resin (A).

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