Adhesive sheet and laminate using same

Abstract

To provide an adhesive sheet capable of maintaining excellent durability even when used for a long time in an extremely high temperature or humid heat environment, and to provide a laminate using the same. An adhesive sheet according to an embodiment is for bonding a transparent member used in a display device and a functional substrate, wherein the adhesive sheet contains an acrylic copolymer, and the loss tangent at 105°C is 0.280-0.310 at 1 Hz.

Description

Pressure-sensitive adhesive sheet and laminate using the same

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

[0002] Automotive equipment includes in-vehicle displays for car navigation systems, display audio systems, rear seat entertainment systems, and the like. The use of display devices for operating these display devices, particularly touch panel display devices, is expanding. Shatterproof films are used on the outermost surfaces of the display screens of such display devices to prevent injury to passengers due to breakage of the display screen cover glass or glass substrate in the event of an accident or other incident.

[0003] Furthermore, for display devices that are primarily used outdoors, such as smartphones, an anti-reflection film that prevents reflection of external light and maintains the visibility of the display on the display device is attached to the outermost surface of the display device.

[0004] The above-mentioned film is attached to a display screen or the like via an adhesive sheet. When such a film is used for a long period of time in a high-temperature, high-humidity environment, for example, inside a car, the adhesive sheet deteriorates, making it difficult to maintain the durability of the adhesive sheet. For example, there have been problems such as the generation of bubbles due to foreign matter between the adhesive sheet and the display screen, or peeling of the film due to a decrease in the adhesiveness of the adhesive sheet.

[0005] To solve such problems, for example, Patent Document 1 discloses a shatterproof adhesive sheet having a shatterproof film with an adhesive layer, which has high durability even in a humid and hot environment.

[0006] Japanese Patent Application Laid-Open No. 2020-070313

[0007] However, in recent years, the quality requirements for these films have been increasing day by day, and even the technology of Patent Document 1 could not cope with harsh environments such as "humid heat test: 90°C, 95% RH" and "high temperature test: 105°C."

[0008] Therefore, an object of the present invention is to provide a pressure-sensitive adhesive sheet that can maintain excellent durability even when used for a long period of time in a severe high-temperature or humid-hot environment, and a laminate using the same.

[0009] The present inventors have conducted extensive research and found that the above-mentioned problems can be solved by using a pressure-sensitive adhesive sheet with a specific composition, and have thus completed the present invention.

[0010] One aspect of the present invention is a pressure-sensitive adhesive sheet for bonding a transparent member used in a display device to a functional substrate, the pressure-sensitive adhesive sheet containing an acrylic copolymer and having a loss tangent at 1 Hz and 105°C of 0.280 to 0.310.

[0011] In the pressure-sensitive adhesive sheet of the above aspect, it is preferable that the acrylic copolymer comprises a copolymer of a monomer mixture (a) containing methyl (meth)acrylate, a (meth)acrylic acid ester other than methyl (meth)acrylate, and a carboxyl group-containing monomer copolymerizable with the methyl (meth)acrylate and the (meth)acrylic acid ester other than methyl (meth)acrylate, and a copolymer of a monomer mixture (b) containing methyl methacrylate and a tertiary amine-containing methacrylic acid.

[0012] In the pressure-sensitive adhesive sheet of the above embodiment, it is preferred that the (meth)acrylic acid ester other than methyl (meth)acrylate is butyl (meth)acrylate, and the carboxyl group-containing monomer is (meth)acrylic acid.

[0013] In the pressure-sensitive adhesive sheet of the above embodiment, the copolymer of the monomer mixture (a) preferably has an acid value of 40 to 90 mgKOH / g.

[0014] Another aspect of the present invention is a laminate, which is a laminate in which a transparent member used in a display device and a functional substrate are bonded together via the pressure-sensitive adhesive sheet of the above aspect.

[0015] In the laminate of the above aspect, the functional substrate is preferably an anti-reflection film.

[0016] In the laminate of the above embodiment, edge peeling after 72 hours in an environment of 90° C. and 95% RH is preferably less than 1 mm.

[0017] In the laminate of the above aspect, the water vapor transmission rate of the anti-reflection film is 1.5 g / (m ２ ・1 day) or less is preferable.

[0018] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that can maintain excellent durability even when used for a long period of time under severe high-temperature or humid-hot environments, and a laminate using the same.

[0019] Fig. 1 is a schematic cross-sectional view of a laminate obtained by laminating a transparent member and a functional substrate using the pressure-sensitive adhesive sheet according to the present embodiment. Fig. 2 is a schematic cross-sectional view of an anti-reflection film used in the functional substrate as one embodiment of the laminate according to the present embodiment.

[0020] Hereinafter, embodiments of the present disclosure will be described in detail. In this specification, the expression "a to b" in the description of a numerical range means a to b, unless otherwise specified.

[0021] Hereinafter, "(meth)acrylic" is meant to encompass both "acrylic" and "methacrylic", and "(meth)acrylate" is meant to encompass both "acrylate" and "methacrylate".

[0022] In this specification, one of the objects to which the pressure-sensitive adhesive sheet according to the present embodiment is attached (for example, the display screen of a display device such as a car navigation system or a smartphone, or a transparent protective member such as an acrylic plate or glass laminated on the display screen via an air layer) is referred to as a "transparent member." Furthermore, the other object to which the pressure-sensitive adhesive sheet according to the present embodiment is attached (for example, a substrate having functionality such as a shatterproof film or an anti-reflection film) is referred to as a "functional substrate."

[0023] The pressure-sensitive adhesive sheet according to this embodiment, the method for producing the pressure-sensitive adhesive sheet, the physical properties of the pressure-sensitive adhesive sheet, the configuration of a laminate using the pressure-sensitive adhesive sheet, each component of the laminate, and the method for producing the laminate will be described below.

[0024] 1. Pressure-sensitive adhesive sheet The pressure-sensitive adhesive sheet of this embodiment is a pressure-sensitive adhesive sheet for bonding a transparent member used in a display device such as a car navigation system to a functional member such as an anti-reflection film. The pressure-sensitive adhesive sheet contains an acrylic copolymer.

[0025] The acrylic copolymer preferably comprises an acrylic copolymer (A) described below and an acrylic copolymer (B) described below.

[0026] 1-1. Acrylic Copolymer (A) The acrylic copolymer (A) is obtained by copolymerizing the monomer mixture (a).

[0027] <<Monomer Mixture (a)>> The monomer mixture (a) contains methyl (meth)acrylate, a (meth)acrylic acid ester other than methyl (meth)acrylate, and a carboxyl group-containing monomer copolymerizable with methyl (meth)acrylate and a (meth)acrylic acid ester other than methyl (meth)acrylate.

[0028] By using methyl (meth)acrylate as an essential component of the monomer mixture (a), the resulting acrylic copolymer (A) has excellent compatibility with the acrylic copolymer (B) described below and exhibits excellent transparency.

[0029] As the (meth)acrylic acid ester other than methyl (meth)acrylate, alkyl (meth)acrylate and alkoxyalkyl (meth)acrylate can be used.

[0030] Examples of (meth)acrylic acid alkyl esters include butyl (meth)acrylate, isobutyl (meth)acrylate, ethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc. Examples of (meth)acrylic acid alkoxyalkyl esters include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-(n-propoxy)ethyl (meth)acrylate, 2-(n-butoxy)ethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 2-(n-propoxy)propyl acrylate, 2-(n-butoxy)propyl (meth)acrylate, etc., and two or more of these may be used in combination.

[0031] Examples of carboxyl group-containing monomers copolymerizable with methyl (meth)acrylate and (meth)acrylic acid esters other than methyl (meth)acrylate include (meth)acrylic acid, β-carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, crotonic acid, maleic acid, and fumaric acid, and two or more of these may be used in combination.

[0032] The monomer mixture (a) may further contain a hydroxyl group-containing monomer, which allows the crosslinking reaction to proceed sufficiently and provides high adhesive strength.

[0033] Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and 4-hydroxymethylcyclohexyl (meth)acrylate, and two or more of these may be used in combination.

[0034] <Monomer Content> The content of methyl (meth)acrylate in the monomer mixture (a) is preferably 10 to 40% by mass, more preferably 15 to 30% by mass. When the content of methyl (meth)acrylate is within the above range, the compatibility of the resulting acrylic copolymer (A) with the acrylic copolymer (B) described below is further improved, and the transparency of the pressure-sensitive adhesive sheet is further improved. In addition, the hardness of the acrylic copolymer (A) becomes appropriate, and the peel strength of the pressure-sensitive adhesive sheet can be further improved.

[0035] Furthermore, from the viewpoint of the adhesive strength of the resulting pressure-sensitive adhesive sheet, the content of the (meth)acrylic acid ester other than methyl (meth)acrylate in the monomer mixture (a) is preferably 60 to 80 mass %, and the content of the carboxyl group-containing monomer is preferably 0.5 to 10 mass %.

[0036] <<Weight Average Molecular Weight>> The weight average molecular weight (Mw) of the acrylic copolymer (A) is preferably 300,000 to 1,500,000, and more preferably 400,000 to 1,200,000. When the weight average molecular weight is within this range, the pressure-sensitive adhesive sheet has good hardness, heat resistance, and heat and humidity resistance. This makes it possible to obtain a pressure-sensitive adhesive sheet that is resistant to lifting and peeling. Furthermore, since the cohesive strength of the acrylic copolymer is maintained, pressure-sensitive adhesive sheets formed from pressure-sensitive adhesive compositions containing the acrylic copolymer (A) are prevented from undergoing internal cohesive failure. This prevents the coalescence of microbubbles in the cohesive failure region, thereby preventing bubble growth and preventing a decrease in the transparency and visibility of the pressure-sensitive adhesive sheet even under high temperature and high humidity conditions. Furthermore, the acrylic copolymer is easily produced.

[0037] The weight-average molecular weight of the acrylic copolymer (A) is a value measured by the following measurement method and conditions. Specific measurement methods and conditions are described below. (Measurement Method) (1) A solution of a (meth)acrylic polymer is applied to a release film and dried at 100°C for 2 minutes to obtain a film-like (meth)acrylic polymer. (2) A sample solution having a solids concentration of 0.2% by mass is obtained using the film-like (meth)acrylic polymer obtained in (1) above and tetrahydrofuran. (3) The weight-average molecular weight (Mw) of the (meth)acrylic polymer is measured using gel permeation chromatography (GPC) under the following conditions, expressed as a standard polystyrene equivalent value. (Conditions) Measuring device: High-speed GPC (Model: HLC-8220 GPC, manufactured by Tosoh Corporation) Detector: Differential refractometer (RI) (built into HLC-8220, manufactured by Tosoh Corporation) Column: Four TSK-GEL GMHXL (manufactured by Tosoh Corporation) connected in series Column temperature: 40°C Eluent: Tetrahydrofuran Sample concentration: 0.2% by mass Injection volume: 100 μL Flow rate: 0.6 mL / min

[0038] <<Glass Transition Temperature>> The acrylic copolymer (A) preferably has a glass transition temperature of −60 to −10° C., more preferably −50 to −18° C. When the glass transition temperature is within the above range, the cohesive strength of a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition containing the acrylic copolymer (A) is sufficient, making it possible to suppress internal cohesive failure and maintain adhesive strength.

[0039] The glass transition temperature of the acrylic copolymer (A) is a value expressed as absolute temperature (K) calculated from the following formula (1), which is converted into Celsius temperature (°C) using the following formula (2):

[0040] Tg in formula (1) is the glass transition temperature of the acrylic copolymer (A) expressed in absolute temperature (K), Tg １ , Tg ２ , ..., Tg (ｋ－１) , Tg ｋ (Hereinafter, Tg ｋ The glass transition temperature (m) is expressed as the absolute temperature (K) when each monomer constituting the acrylic copolymer (A) is made into a homopolymer. １ , m ２ , ..., m (ｋ－１) , m ｋ is the molar fraction of each monomer constituting the acrylic copolymer (A).

[0041]

[0042] The glass transition temperature (Tg ｋ The heat capacity is measured using a differential scanning calorimeter (DSC, model number: EXSTAR6000, manufactured by Seiko Instruments Inc.) in a nitrogen gas flow using 10 mg of a measurement sample at a heating rate of 10°C / min, and the heat capacity is the value at the inflection point of the obtained DSC curve.

[0043] <<Acid Value>> The acrylic copolymer (A) preferably has an acid value of 40 to 90 mgKOH / g, more preferably 45 to 80 mgKOH / g. When the acid value is within this range, the cohesive strength of a pressure-sensitive adhesive sheet formed from a pressure-sensitive adhesive composition containing the acrylic copolymer (A) is sufficient, and foaming can be suppressed during durability testing of the pressure-sensitive adhesive sheet. This also facilitates the production of the pressure-sensitive adhesive sheet.

[0044] The acid value of the acrylic copolymer (A) can be calculated by the following formula: In the following formula, 56.1 is the molecular weight of KOH.

[0045] E in formula (3) １ E represents the content (mass%) of the monomer having a carboxyl group in all the monomers used in the acrylic copolymer. ２ indicates the molecular weight of the monomer having a carboxyl group used in the acrylic copolymer. ３ indicates the number of carboxyl groups contained in one molecule of the carboxyl group-containing monomer.

[0046] <<Content>> The content of the acrylic copolymer (A) is preferably from 65 to 95 parts by mass, and more preferably from 75 to 85 parts by mass, per 100 parts by mass of the total acrylic copolymer.

[0047] 1-2. Acrylic Copolymer (B) The acrylic copolymer (B) is obtained by copolymerizing the monomer mixture (b). The acrylic copolymer (B) will be described below.

[0048] <<Monomer Mixture (b)>> The monomer mixture (b) contains methyl methacrylate and tertiary amine-containing methacrylic acid.

[0049] Examples of the tertiary amine-containing methacrylic acid include dimethylaminoethyl methacrylate and dimethylaminopropyl methacrylate, and two or more of these may be used in combination.

[0050] <Monomer Content> The content of methyl methacrylate in the monomer mixture (b) is preferably 90 to 99% by mass. Furthermore, the content of tertiary amine-containing methacrylic acid in the monomer mixture (b) is preferably 1 to 10% by mass. When the content of tertiary amine-containing methacrylic acid is within the above range, the cohesive strength of the PSA sheet formed from the PSA composition containing the acrylic copolymer (B) is sufficient, and cohesive failure can be suppressed. Furthermore, compatibility with the acrylic copolymer (A) is improved.

[0051] <<Weight Average Molecular Weight>> The weight average molecular weight (Mw) of the acrylic copolymer (B) is preferably 5,000 to 50,000, and more preferably 10,000 to 30,000. When the weight average molecular weight is within this range, the pressure-sensitive adhesive sheet has good hardness, heat resistance, and heat and humidity resistance. This makes it possible to obtain a pressure-sensitive adhesive sheet that is less likely to lift or peel. The method for measuring the weight average molecular weight is the same as the method described above for the acrylic copolymer (A).

[0052] <<Glass Transition Temperature>> The glass transition temperature of the acrylic copolymer (B) is preferably 100°C or higher. By setting the glass transition temperature within the above range, the heat resistance of the pressure-sensitive adhesive sheet can be fully exhibited. The glass transition temperature of the acrylic copolymer (B) can be measured using the above formulas (1) and (2), as in the case of the acrylic copolymer (A).

[0053] That is, the glass transition temperature of the acrylic copolymer (B) is a value calculated by the above formula (1) and expressed as absolute temperature (K), converted into Celsius temperature (°C) by the above formula (2).

[0054] Here, Tg in the above formula (1) is the glass transition temperature of the acrylic copolymer (B) expressed in absolute temperature (K), Tg １ , Tg ２ , ..., Tg (ｋ－１) , Tg ｋ (Hereinafter, Tg ｋ The glass transition temperature, m, is expressed as absolute temperature (K) when each monomer constituting the acrylic copolymer (B) is made into a homopolymer. １ , m ２, ..., m (ｋ－１) , m ｋ is the molar fraction of each monomer constituting the acrylic copolymer (B).

[0055] <<Content>> The content of the acrylic copolymer (B) is preferably 10 to 35 parts by mass, and more preferably 15 to 25 parts by mass, per 100 parts by mass of the total acrylic copolymer. Furthermore, the content is preferably 10 to 50 parts by mass, and more preferably 20 to 30 parts by mass, per 100 parts by mass of the acrylic copolymer (A). When the content of the acrylic copolymer (B) is within this range, a pressure-sensitive adhesive sheet with excellent durability can be formed.

[0056] 2. Method for Producing Pressure-Sensitive Adhesive Sheet The pressure-sensitive adhesive sheet of the present embodiment can be produced by a known method and is not particularly limited. An example of the method for producing a pressure-sensitive adhesive sheet will be described below.

[0057] The method for producing a pressure-sensitive adhesive sheet includes a preparation step of preparing an acrylic copolymer solution, a pressure-sensitive adhesive composition preparation step of adding a crosslinking agent and the like to the acrylic copolymer solution and mixing and stirring the mixture to prepare a pressure-sensitive adhesive composition, a coating film formation step of applying the pressure-sensitive adhesive composition to a sheet and drying it to form a coating film of the pressure-sensitive adhesive composition (pressure-sensitive adhesive composition layer), and a curing step of curing the pressure-sensitive adhesive composition layer.

[0058] In the preparation step, an acrylic copolymer solution is prepared. The method for producing the acrylic copolymer solution is not particularly limited, and the solution can be produced by a conventionally known polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization, or suspension polymerization using a polymerization initiator such as benzoyl peroxide or azobisisobutyronitrile.

[0059] In preparing the acrylic copolymer solution of this embodiment, it is preferable to use solution polymerization because the treatment process is relatively simple and can be completed in a short time. Hereinafter, a method for producing the acrylic copolymer solution by solution polymerization will be described.

[0060] The acrylic copolymer solution of the present embodiment is produced from a predetermined organic solvent, a polymerization initiator, materials for the monomer mixture (a), materials for the monomer mixture (b), and a chain transfer agent used as needed.

[0061] A polymerization vessel is charged with a predetermined organic solvent, a monomer mixture, a polymerization initiator, and an optional chain transfer agent, and the mixture is heated and reacted for about 1 to 10 hours under stirring in a nitrogen stream. In this case, at least a portion of the organic solvent, the monomer mixture, the polymerization initiator, and / or the chain transfer agent may be added sequentially. The heating temperature is not particularly limited and can be set appropriately depending on the molecular weight of the target acrylic copolymer, but is preferably 50 to 70°C.

[0062] Each component constituting the acrylic copolymer solution will be described below. The materials for the monomer mixture (a) and the monomer mixture (b) are the same as those described above, and therefore will not be described here.

[0063] <Organic Solvent> Examples of organic solvents used in the polymerization reaction include aromatic hydrocarbon compounds, aliphatic or alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, and alcohol compounds.

[0064] More specifically, examples of the hydrocarbon compounds include aromatic hydrocarbon compounds such as toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha; aliphatic or alicyclic hydrocarbon compounds such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, and turpentine; ester compounds such as ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, and methyl benzoate; acetone, methyl ethyl ketone, methyl-i-butyl acetate, and the like. Examples of the alcohol compound include ketones, ketone compounds typified by isophorone, cyclohexanone, and methylcyclohexanone; glycol ether compounds typified by ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; and alcohol compounds typified by methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, and t-butyl alcohol.

[0065] In the polymerization reaction, these organic solvents may be used alone or in combination of two or more.

[0066] In producing the acrylic copolymer solution, it is preferable to use an organic solvent that is unlikely to cause chain transfer during the polymerization reaction, such as an aromatic hydrocarbon compound, an ester compound, a ketone compound, or an alcohol compound. In particular, from the viewpoints of the solubility of the acrylic copolymer, ease of the polymerization reaction, etc., it is preferable to use toluene, ethyl acetate, methyl ethyl ketone, t-butyl alcohol, etc.

[0067] <Polymerization Initiator> Examples of the polymerization initiator include organic peroxides and azo compounds that are commonly used in solution polymerization. Examples of organic peroxides include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-amylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane, and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane.

[0068] Examples of azo compounds include 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2,4-dimethylvaleronitrile) (ABVN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), and 2,2'-azobis(isobutyrate) dimethyl.

[0069] In the polymerization reaction, these polymerization initiators may be used alone or in combination of two or more.

[0070] The amount of the polymerization initiator to be added is not particularly limited and is appropriately determined depending on the molecular weight of the desired acrylic copolymer.

[0071] <Chain Transfer Agent> In producing the acrylic copolymer solution, a chain transfer agent may be used as needed within a range that does not impair the objects and effects of the present invention. Examples of the chain transfer agent include cyanoacetic acid, alkyl ester compounds of cyanoacetic acid having 1 to 8 carbon atoms, bromoacetic acid, alkyl ester compounds of bromoacetic acid having 1 to 8 carbon atoms, aromatic compounds represented by α-methylstyrene, anthracene, phenanthrene, fluorene, and 9-phenylfluorene, aromatic nitro compounds represented by p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, and p-nitrotoluene, benzoquinone and benzoquinone derivatives represented by 2,3,5,6-tetramethyl-p-benzoquinone, borane derivatives represented by tributylborane, carbon tetrabromide, tetrabromide, tetrachloromethane, benzoquinone derivatives represented by benzoquinone ... Examples of the halogenated hydrocarbon compounds include carbon chloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, and 3-chloro-1-propene; aldehyde compounds include chloral and furaldehyde; alkyl mercaptan compounds having 1 to 18 carbon atoms; aromatic mercaptan compounds include thiophenol and toluene mercaptan; mercaptoacetic acid; alkyl ester compounds of mercaptoacetic acid having 1 to 10 carbon atoms; hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms; and terpene compounds include vinene and terpinolene.

[0072] When a chain transfer agent is used in producing the acrylic copolymer solution, the amount of the chain transfer agent to be added is not particularly limited and is appropriately set depending on the molecular weight of the target acrylic copolymer.

[0073] 2-2. Pressure-sensitive adhesive composition preparation step The pressure-sensitive adhesive composition of the present embodiment is prepared by adding a crosslinking agent to the above-described acrylic copolymer solution, and mixing and stirring the mixture. In addition to the acrylic copolymer solution and the crosslinking agent, the pressure-sensitive adhesive composition may contain other components as necessary.

[0074] The pressure-sensitive adhesive composition of the present embodiment contains the organic solvent used in producing the acrylic copolymer solution in the preparation step described above, but may also be diluted with a further appropriate solvent to have a viscosity suitable for forming a pressure-sensitive adhesive composition layer.

[0075] Each component of the pressure-sensitive adhesive composition will be described below. The acrylic copolymer solution is the same as described above, so a description thereof will be omitted here.

[0076] <Crosslinking Agent> The type of crosslinking agent is not particularly limited, and examples thereof include polyisocyanate compounds, epoxy compounds, metal chelate compounds, etc. Furthermore, only one type of crosslinking agent may be contained, or two or more types may be contained.

[0077] Here, the term "polyisocyanate compound" refers to a compound having two or more isocyanate groups in the molecule, and the term "epoxy compound" refers to a compound having at least one epoxy group in the molecule.

[0078] Examples of the polyisocyanate compound include aromatic polyisocyanate compounds such as xylylene diisocyanate (XDI), diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate (TDI), and aliphatic or alicyclic polyisocyanate compounds such as hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate (PDI), isophorone diisocyanate, and hydrogenated products of aromatic polyisocyanate compounds.

[0079] Further, examples of the polyisocyanate compound include dimers of the above polyisocyanate compounds, trimers of the above polyisocyanate compounds, pentamers of the above polyisocyanate compounds, adducts of the above polyisocyanate compounds with polyol compounds (e.g., trimethylolpropane), and biuret compounds of the above polyisocyanate compounds.

[0080] Among the above, from the viewpoint of pot life, for example, tolylene diisocyanate (TDI) is preferred, and an adduct of tolylene diisocyanate (TDI) and trimethylolpropane is more preferred.

[0081] Commercially available products can be used as the polyisocyanate compound. Examples of commercially available polyisocyanate compounds include "Coronate (registered trademark) HX," "Coronate (registered trademark) HL-S," "Coronate (registered trademark) L," "Coronate (registered trademark) L-45E," "Coronate (registered trademark) 2031," "Coronate (registered trademark) 2037," "Coronate (registered trademark) 2234," "Coronate (registered trademark) 2785," "Aquanate (registered trademark) 200," and "Aquanate (registered trademark) 210" (all manufactured by Tosoh Corporation), "Sumidur (registered trademark) N3300," "Desmodur (registered trademark) N3400," and "Sumidur (registered trademark) N-75" (all manufactured by Sumika Covestro Urethane Co., Ltd.), "Duranate (registered trademark) E-405-80T", "Duranate (registered trademark) AE700-100", "Duranate (registered trademark) 24A-100", and "Duranate (registered trademark) TSE-100" (all manufactured by Asahi Kasei Corporation), as well as "Takenate (registered trademark) D-110N", "Takenate (registered trademark) D-120N", "Takenate (registered trademark) M-631N", "MT-Olestar (registered trademark) NP1200", and "Stabio (registered trademark) XD-340N" (all manufactured by Mitsui Chemicals, Inc.).

[0082] Examples of epoxy compounds include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, and diglycerol polyglycidyl ether. diglycidyl ether, polyglycerol polyglycidyl ether, resorcinol diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris(glycidyl)isocyanurate, tris(glycidoxyethyl)isocyanurate, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidyl-1,3-benzenedi(methanamine).

[0083] Commercially available epoxy compounds can be used, including "TETRAD (registered trademark)-X" and "TETRAD (registered trademark)-C" (both manufactured by Mitsubishi Gas Chemical Company, Inc.).

[0084] Examples of metal chelate compounds include aluminum chelate compounds typified by aluminum monoacetylacetonate bis(ethylacetoacetate), aluminum tris(ethylacetoacetate), and aluminum tris(acetylacetonate), titanium chelate compounds, zirconium chelate compounds, and cobalt chelate compounds.

[0085] Commercially available metal chelate compounds can be used, including "Alumichelate A," "Alumichelate D," and "ALCH-TR" (all manufactured by Kawaken Fine Chemicals Co., Ltd.).

[0086] Among the above, the crosslinking agent preferably contains at least one of a polyisocyanate compound and an epoxy compound, more preferably an epoxy compound, and even more preferably a tetrafunctional epoxy compound, from the viewpoint of being able to form a pressure-sensitive adhesive sheet that has a better balance of reworkability and resistance to peeling from the application surface when an impact is applied.

[0087] The amount of crosslinking agent in the pressure-sensitive adhesive composition of this embodiment is preferably 0.01 to 10 parts by mass, and more preferably 0.01 to 1 part by mass, per 100 parts by mass of the acrylic copolymer solution. By adjusting the amount of crosslinking agent to fall within the above range, the pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition has sufficient cohesive strength, making it possible to suppress internal cohesive failure. Furthermore, the hardness of the pressure-sensitive adhesive sheet can be adjusted appropriately.

[0088] <Other Components> The pressure-sensitive adhesive composition of the present embodiment may contain, in addition to the acrylic copolymer solution and crosslinking agent, other components as necessary, such as a leveling agent, a crosslinking aid, a plasticizer, a softener, a filler, an antistatic agent, an antioxidant, an ultraviolet absorber, an antioxidant, a preservative, an antifungal agent, a plasticizer, an antifoaming agent, a wettability adjuster, a light stabilizer, a surfactant, etc.

[0089] 2-3. Coating Film Formation Step Subsequently, the pressure-sensitive adhesive composition can be applied to a release film such as a PET film using a coating machine such as a roll coater, reverse coater, comma coater, lip coater, die coater, etc., followed by drying, to form a coating film of the pressure-sensitive adhesive composition (pressure-sensitive adhesive composition layer). When the pressure-sensitive adhesive composition layer is cured in the curing step described below, it becomes a pressure-sensitive adhesive sheet.

[0090] The thickness of the pressure-sensitive adhesive composition layer is preferably 1 to 50 μm, more preferably 5 to 40 μm, and even more preferably 10 to 30 μm. By setting the thickness of the pressure-sensitive adhesive composition layer within the above range, the pressure-sensitive adhesive sheet can have sufficient adhesive strength. This is also appropriate from the viewpoint of production costs.

[0091] In order to protect the surface of the pressure-sensitive adhesive composition layer, a release film may be provided on the coating surface of the pressure-sensitive adhesive composition after coating and drying.

[0092] The release film according to the present embodiment is not particularly limited as long as it does not impair the effects of the present invention, and examples thereof include polyesters such as polyethylene terephthalate and polyethylene naphthalate; polycycloolefins, polyacetates, polyethersulfones, polycarbonates, polyamides, polyimides, (meth)acrylic polymers, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylates, and polyphenylene sulfide.

[0093] The thickness of the release film is preferably 1 to 150 μm.

[0094] 2-4. Curing Step The curing step is a step in which the pressure-sensitive adhesive composition layer of the present embodiment is subjected to a treatment such as leaving it to stand under a specific temperature and humidity environment (for example, normal temperature and humidity) (referred to as curing in the present embodiment), thereby causing curing in the pressure-sensitive adhesive composition layer and forming the pressure-sensitive adhesive sheet of the present embodiment. Note that in this step, the degree of curing is not limited, and may be partial curing or complete curing.

[0095] 3. Physical Properties of the Pressure-Sensitive Adhesive Sheet 3-1. Loss Tangent The loss tangent (tan δ) of the pressure-sensitive adhesive sheet of this embodiment at 1 Hz and 105° C. is 0.280 to 0.310, and preferably 0.285 to 0.305.

[0096] The loss tangent is one of the parameters that indicates stress relaxation behavior (delay in deformation when force is applied), and a small loss tangent value indicates that the adhesive sheet has small stress relaxation, i.e., has hard properties, while a large loss tangent value indicates that the adhesive sheet has large stress relaxation, i.e., has soft properties.

[0097] When the loss tangent of the adhesive sheet at 1 Hz and 105°C is within this range, the hardness and softness of the adhesive sheet are optimized, so that when two objects are attached via the adhesive sheet, foaming and peeling between the objects can be suppressed even when exposed to a harsh high-temperature test, for example, an environment of 105°C for 1000 hours.

[0098] Furthermore, even when subjected to a severe humidity and heat test, for example, under an environment of 90°C and 95% RH for 72 hours, edge peeling between each adherend and the PSA sheet can be suppressed, i.e., peeling after 72 hours under an environment of 90°C and 95% RH can be reduced to less than 1.0 mm.

[0099] Edge peeling refers to peeling that occurs at the edge of an object to be adhered due to a difference in elongation of each object in a humid and hot environment.

[0100] The method for measuring the loss tangent will be described. First, the thickness of the pressure-sensitive adhesive sheet is adjusted to 1 mm, and then the pressure-sensitive adhesive sheet is punched out with a circular mold having a diameter of 8 mm to obtain a test piece. Next, the loss modulus of the test piece is measured at 105°C in a shear mode at a frequency of 1 Hz using a dynamic viscoelasticity measuring device (manufactured by Thermo Fisher Scientific, HAAKE MARS) with an 8 mm parallel plate, thereby measuring the loss tangent.

[0101] 4. Laminate 4-1. Configuration of Laminate Fig. 1 is a schematic cross-sectional view showing an example of the configuration of the laminate of this embodiment. As shown in Fig. 1, the laminate 100 has a configuration in which a transparent member 10 and a functional substrate 30 are bonded together with an adhesive sheet 20 (transparent member 10 / adhesive sheet 20 / functional substrate 30). The configuration of the laminate of this embodiment is not limited to this.

[0102] More specifically, the pressure-sensitive adhesive sheet of the present embodiment can be used to bond a transparent member, such as a display screen of an in-vehicle display such as a car navigation system, display audio, or rear seat entertainment device, or a display device including a smartphone, or a transparent protective member such as an acrylic plate or glass laminated on the display screen via an air layer, to a functional substrate such as a shatterproof film or an anti-reflection film, etc. In particular, when the functional substrate is an anti-reflection film, the effects of the present invention can be fully exhibited.

[0103] 4-2. Components of the Laminate and Method for Producing the Laminate <<Functional Substrate>> <Aspect 1: Antireflection Film>> Fig. 2 is a cross-sectional schematic diagram showing an example of an antireflection film 30 used as the functional substrate of this embodiment. An example in which the functional substrate is an antireflection film 30 will be described below. The functional substrate is not limited to this as long as the effects of the present invention are achieved.

[0104] 2, the antireflection film 30 of this embodiment includes a transparent substrate film 31 and a hard coat layer 32, a first primer layer 33, a second primer layer 34, and an antireflection layer 35 laminated in this order on the transparent substrate film 31. Furthermore, an antifouling layer 36 is laminated on the antireflection layer 35 as an optional layer.

[0105] (Transparent Substrate Film) The transparent substrate film 31 is not limited to any particular material as long as it achieves the effects of the present invention. Generally, cellulose acetate resins such as triacetyl cellulose, polyethylene terephthalate resins, and the like can be used. Furthermore, when using these, the degree of acetylation does not matter. The thickness of the transparent substrate film 31 can be appropriately selected depending on the intended use, and is preferably 25 to 300 μm. The transparent substrate film 31 may also contain additives such as plasticizers, ultraviolet absorbers, and anti-degradants.

[0106] (Hard Coat Layer) A hard coat layer 32 is preferably provided on the transparent substrate film 31 to ensure sufficient mechanical strength of the anti-reflection layer 35. The hard coat layer 32 may be made of an ionizing radiation or UV-curable resin or a thermosetting resin. UV-curable acrylic resins such as acrylic esters, acrylamides, methacrylic esters, and methacrylamides are ideal, as well as organosilicon resins and polysiloxane resins. A polymerization initiator may be added to these materials to improve curing properties. The thickness of the hard coat layer 32 is preferably 0.5 μm or greater, and more preferably 3 to 20 μm. The hard coat layer 32 may also be subjected to an anti-glare treatment by dispersing transparent fine particles with an average particle size of less than 3 μm.

[0107] After the hard coat layer 32 is provided on the transparent substrate film 31, it is preferable that the transparent substrate film 31 be subjected to an alkaline saponification treatment. In particular, for cellulose acetate resin substrates, an alkaline saponification treatment is preferable, in which ester groups are hydrolyzed to give hydroxyl groups. Since the saponification treatment is performed in a liquid, it has high erosion and penetration properties, and improves adhesion with subsequent layers.

[0108] After the saponification treatment, the hard coat layer 32 may be further subjected to a surface treatment. Examples of the surface treatment method include corona discharge treatment, electron beam treatment, flame treatment, glow discharge treatment, and atmospheric pressure plasma treatment.

[0109] (Primer Layer) Next, a first primer layer 33 and a second primer layer 34 are formed in this order on the hard coat layer 32. Examples of materials for the primer layer include metals such as silicon, nickel, chromium, tin, gold, silver, platinum, zinc, titanium, tungsten, zirconium, and palladium, alloys of two or more of these metals, and metal compounds such as oxides, fluorides, sulfides, and nitrides of these metals, which may also be mixtures. In this case, it is preferable that the first primer layer 33 and the second primer layer 34 be formed as films with different compositions.

[0110] The first primer layer 33 is a layer that forms a micro-irregular surface to form an irregular growth direction for subsequent layers. It is sufficient for a trace amount of particles to be attached to the substrate surface, and the film may be particulate or island-shaped. Its thickness is preferably 5 nm or less, more preferably 2 nm or less. Furthermore, to form subsequent films irregularly, a thin film may be formed in a zigzag or wavy structure, but it is necessary to select a film thickness and material that does not affect transparency. Examples of film formation conditions for such layers include a sputtering method with an extremely short film formation time, such as irradiation for a few seconds, depending on the device conditions.

[0111] The first primer layer 33 is preferably formed from alumina, silica, niobium oxide, titanium oxide, or the like.

[0112] The second primer layer 34 is used to improve adhesion. Its thickness may be such that it does not impair the transparency of the substrate, and is preferably 1 to 10 nm, and is preferably thicker than the first primer layer 33.

[0113] The second primer layer 34 may be made of a material having one extra bond such as SiO, or may be made of a commercially available silane coupling agent.

[0114] These primer layers are preferably formed by dry coating methods such as sputtering, reactive sputtering, vapor deposition, ion plating, and chemical vapor deposition (CVD), with sputtering being particularly preferred.

[0115] (Antireflection Layer) Examples of the antireflection layer 35 include a layer made of a low-refractive-index transparent thin film layer having a refractive index of less than 1.6 for light at a wavelength of 550 nm and an extinction coefficient of 0.5 or less for light at a wavelength of 550 nm, a layer made of a plurality of optical thin films having different refractive indices, such as a high-refractive-index transparent thin film layer having a refractive index of 1.9 or more for light at a wavelength of 550 nm, a low-refractive-index transparent thin film layer having a refractive index of less than 1.6, or a medium-refractive-index transparent thin film layer having a refractive index of 1.6 to 1.9. For example, an example of an alternate layer made of high-refractive-index transparent thin film layers and low-refractive-index transparent thin film layers is a layer made of a high-refractive-index transparent thin film layer, a low-refractive-index transparent thin film layer, a high-refractive-index transparent thin film layer, and a low-refractive-index transparent thin film layer, in that order from the substrate side.

[0116] Examples of materials for the high-refractive-index transparent thin film layer include metals such as indium, tin, titanium, silicon, zinc, zirconium, niobium, magnesium, bismuth, cerium, tantalum, aluminum, germanium, potassium, antimony, neodymium, lanthanum, thorium, and hafnium, as well as alloys of two or more of these metals, and oxides, fluorides, sulfides, and nitrides thereof. Specific examples include, but are not limited to, titanium oxide, niobium oxide, zirconium oxide, tantalum oxide, zinc oxide, indium oxide, and cerium oxide. Furthermore, when multiple layers are stacked, it is not necessary to select the same material; materials may be selected appropriately depending on the purpose.

[0117] Examples of materials for the low refractive index transparent thin film layer include, but are not limited to, silicon oxide, titanium nitride, magnesium fluoride, barium fluoride, calcium fluoride, hafnium fluoride, lanthanum fluoride, etc. Furthermore, when multiple layers are stacked, it is not necessary to select the same material, and an appropriate material may be selected depending on the purpose.

[0118] Examples of the medium refractive index transparent thin film layer include aluminum oxide and cerium fluoride.

[0119] The antireflection layer 35 made of these optical thin film layers can be formed by dry coating methods such as sputtering, reactive sputtering, vapor deposition, ion plating, and chemical vapor deposition (CVD). Sputtering is preferred because it allows for the formation of thin films with excellent visibility due to high film thickness uniformity and fewer defects such as pinholes, and because it allows for the formation of dense films, it allows for the formation of thin films with excellent mechanical properties such as scratch resistance. Among these methods, dual magnetron sputtering (DMS), which deposits films by applying a voltage in the medium frequency range, is optimal because it allows for high productivity due to its higher film formation rate and high discharge stability.

[0120] (Anti-fouling layer) If necessary, an anti-fouling layer 36 may be provided on the anti-reflection layer 35 as the outermost layer. The anti-fouling layer 36 is a layer obtained from a fluorine-containing silicon compound having two or more silicon atoms bonded to a reactive functional group. Here, the reactive functional group refers to a group that can react with and bond to the uppermost layer of the anti-reflection layer. The anti-fouling layer 36 is also a layer formed by reacting reactive functional groups of fluorine-containing silicon compounds with each other. This makes the surface less susceptible to staining, and even if stains do occur, it can improve wiping performance.

[0121] <Aspect 2: Antireflection film treated by dry coating method> The functional substrate 30, which is a constituent member of the laminate 100, may be an antireflection film treated by dry coating method. In conventional techniques, an antireflection film treated by dry coating method has a reduced water vapor permeability, and therefore has a problem in that water vapor from the antireflection film is likely to be trapped inside the laminate when placed in a harsh environment such as the above-mentioned harsh high-temperature test or harsh moist heat test environment.

[0122] In contrast, the adhesive sheet of this embodiment can withstand the above-mentioned high temperature test or harsh humid heat test environment, and therefore can suppress foaming and peeling of the laminate and edge peeling even when an anti-reflective film treated by a dry coating method is used as the functional substrate.

[0123] More specifically, in the laminate 100 of this embodiment, the water vapor permeability of the anti-reflection film treated by the dry coating method is, for example, 1.5 g / (m ２ Even if the heating time is less than 1 day, foaming and peeling of the laminate and edge peeling can be suppressed.

[0124] (Water Vapor Transmission Rate) The water vapor transmission rate of the antireflection film was measured by setting a 100 mm x 100 mm piece of the antireflection film in a water vapor transmission rate measuring device (product name: PERMATRAN-W3 / 34, manufactured by MOCON Corporation) and continuously measuring the water vapor transmission rate 24 hours later under conditions of 40°C and a relative humidity of 90% using an infrared sensor method in accordance with JIS 7129 (ISO 15106-2).

[0125] Next, the present invention will be explained in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples in any way.

[0126] <Preparation of Acrylic Copolymer (A) Solutions: A-1 to A-8> 100 parts by mass of the materials for the monomer mixture (a) {butyl (meth)acrylate (BA), methyl (meth)acrylate (MA), and (meth)acrylic acid (AA)} blended in the proportions shown in Table 1 below, and 140 parts by mass of ethyl acetate were charged into a flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet tube. Nitrogen was introduced through the nitrogen inlet tube to create a nitrogen atmosphere inside the flask, and then 0.2 parts by mass of AIBN was added. A polymerization reaction was carried out for 10 hours while heating the flask to 67°C, yielding acrylic copolymer (A) solutions A-1 to A-8. The glass transition temperatures, weight average molecular weights (Mw), and acid values ​​of the acrylic polymers (A) A-1 to A-8 obtained by removing the solvent from the resulting acrylic polymer (A) solutions A-1 to A-8 were measured using the methods described above. The evaluation results are shown in Table 1 below.

[0127]

[0128] <Production of Acrylic Copolymer (B) Solution: B-1> 98 parts by mass of methyl methacrylate, 2 parts by mass of dimethylaminoethyl methacrylate, and 100 parts by mass of toluene were charged into a flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet tube. Nitrogen was introduced through the nitrogen inlet tube to create a nitrogen atmosphere inside the flask, and then 2 parts by mass of AIBN was added. A polymerization reaction was carried out for 8 hours while heating the flask to 90°C, thereby obtaining acrylic polymer (B) solution B-1.

[0129] <Preparation of Pressure-Sensitive Adhesive Compositions> Pressure-sensitive adhesive compositions for each of the Examples and Comparative Examples were prepared by mixing and stirring an acrylic copolymer (A) solution, an acrylic copolymer (B) solution, and a crosslinking agent (a polyfunctional epoxy resin, manufactured by Mitsubishi Gas Chemical Company, Inc., TETRAD-X) in the blending ratios shown in Table 2. The blending amounts in Table 2 indicate parts by mass of the solid content excluding the solvent.

[0130] <Preparation of double-sided release film-attached pressure-sensitive adhesive sheets (for evaluating loss tangent)> Each of the prepared pressure-sensitive adhesive compositions was coated onto a 38 μm-thick PET film, release film P, so that the film thickness after drying would be 25 μm, and then dried to form a coating of the pressure-sensitive adhesive composition with a release film (pressure-sensitive adhesive composition layer). Subsequently, release film Q, which has a lighter release strength than release film P, was attached to the surface of the pressure-sensitive adhesive composition layer with a release film. This was then aged for 1 week in an environment at a temperature of 23°C and a humidity of 55%, to obtain pressure-sensitive adhesive sheets with double-sided release films (for evaluating loss tangent) for each Example and Comparative Example.

[0131] (Measurement of loss tangent (tanδ)) Using only the adhesive sheets of the double-sided release film-attached adhesive sheets (for loss tangent evaluation) obtained in each Example and Comparative Example, a plurality of identical adhesive sheets were laminated so that each adhesive sheet had a thickness of 1 mm, and then punched out with a circular mold with a diameter of 8 mm to obtain test pieces for each Example and Comparative Example. Subsequently, the loss modulus of each prepared test piece was measured at 105 ° C. in shear mode at a frequency of 1 Hz using a dynamic viscoelasticity measuring device (manufactured by Thermo Fisher Scientific, HAAKE MARS) with an 8 mm parallel plate, to obtain the loss tangent. The loss tangent of each adhesive sheet is shown in Table 2 below.

[0132] <Preparation of release film and adhesive sheet with functional member (for durability test)> Each of the prepared adhesive compositions was applied to a release film P, which was a PET film with a thickness of 38 μm, so that the film thickness after drying would be 25 μm, and then dried to form an adhesive composition layer with a release film. Subsequently, a functional substrate A (water vapor permeability: 0.5 g / (m)) was applied to the surface of each prepared adhesive composition layer with a release film. ２ 1 day) was attached.

[0133] In addition, instead of the functional substrate A, a functional substrate B (water vapor permeability: 1.0 g / (m ２ The same procedure as above was carried out except that the same 1-day (1 day) was used.

[0134] This was left to cure for 1 week in an environment of 23°C temperature and 55% humidity to obtain a pressure-sensitive adhesive sheet (for durability test) with a release film and functional substrate A / B of each Example and Comparative Example.

[0135] As the functional substrates A and B, antireflection films were used, each of which was produced by laminating an antireflection layer on a triacetyl cellulose film having a thickness of 60 μm by a sputtering process.

[0136] (Durability test) The release film P was peeled off from the obtained release film and functional substrate A / B-attached adhesive sheet (for durability test) of each Example and Comparative Example, and the adhesive sheet surface was attached to a 1.8 mm glass plate (soda glass) using a desktop laminator to prepare a measurement sample (laminate) of each Example and Comparative Example. Using each measurement sample prepared, the presence or absence of foaming / peeling and edge peeling were evaluated under the following conditions. The evaluation results are shown in Table 2 below.

[0137] (Presence or absence of foaming / peeling) Each measurement sample was placed in a thermostatic chamber at 105°C and left for 1000 hours. Thereafter, the presence or absence of foaming / peeling was visually observed. Evaluation criteria: A: No foaming / peeling; C: Foaming or peeling;

[0138] (Edge peeling) Each measurement sample was placed in a constant temperature and humidity chamber at 90°C and 95% RH and left for 72 hours. After that, edge peeling that occurred on the measurement sample was visually observed and its width was measured. Evaluation criteria A: Edge peeling width is less than 0.7 mm B: Edge peeling width is 0.7 mm or more but less than 1.0 mm C: Edge peeling width is 1.0 mm or more

[0139]

[0140] The pressure-sensitive adhesive sheet of the present invention can maintain excellent durability even when used for long periods of time under harsh high-temperature or humid-hot environments, and can therefore be suitably used as a pressure-sensitive adhesive sheet for attaching functional films such as shatterproof films and anti-reflection films used on the display screens of in-vehicle display devices. CROSS-REFERENCE TO RELATED APPLICATIONS

[0141] This application claims priority based on Japanese Patent Application No. 2024-20309, filed with the Japan Patent Office on February 14, 2024, the entire disclosure of which is incorporated herein by reference in its entirety.

[0142] 100 Laminate 10 Transparent member 20 Pressure-sensitive adhesive sheet 30 Functional substrate (anti-reflection film)

Claims

1. An adhesive sheet for bonding a transparent member used in a display device to a functional substrate, the adhesive sheet containing an acrylic copolymer and having a loss tangent at 1 Hz and 105°C of 0.280 to 0.

310.

2. The pressure-sensitive adhesive sheet according to claim 1, wherein the acrylic copolymer comprises: a copolymer of a monomer mixture (a) containing methyl (meth)acrylate, a (meth)acrylic acid ester other than methyl (meth)acrylate, and a carboxyl group-containing monomer copolymerizable with said methyl (meth)acrylate and said (meth)acrylic acid ester other than methyl (meth)acrylate; and a copolymer of a monomer mixture (b) containing methyl methacrylate and a tertiary amine-containing methacrylic acid.

3. The pressure-sensitive adhesive sheet according to claim 2, wherein the (meth)acrylic acid ester other than methyl (meth)acrylate is butyl (meth)acrylate, and the carboxyl group-containing monomer is (meth)acrylic acid.

4. The pressure-sensitive adhesive sheet according to claim 2 or 3, wherein the copolymer of said monomer mixture (a) has an acid value of 40 to 90 mg KOH / g.

5. A laminate obtained by bonding a transparent member used in a display device and a functional substrate via the adhesive sheet according to any one of claims 1 to 3.

6. The laminate according to claim 5, wherein the functional substrate is an anti-reflection film.

7. The laminate according to claim 6, which exhibits edge peeling of less than 1 mm after 72 hours in an environment of 90°C and 95% RH.

8. The water vapor permeability of the anti-reflection film is 1.5 g / (m ２ The laminate according to claim 6, wherein the tensile strength is 100% or less per day.

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