Adhesive sheet

Abstract

To provide a pressure-sensitive adhesive sheet having excellent anchoring properties between an adhesion-facilitating layer and a pressure-sensitive adhesive layer and also having excellent preservation properties.SOLUTION: A pressure-sensitive adhesive sheet 1 includes a plastic substrate 2, an adhesion-facilitating layer 3, and a pressure-sensitive adhesive layer 4 in this order toward one side in a thickness direction. The adhesion-facilitating layer 3 includes an adhesive composition containing a polyester component and an oxazoline component. The pressure-sensitive adhesive layer 4 contains a water-dispersible polymer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an adhesive sheet.

Background Art

[0002] Conventionally, in various technical fields, an adhesive sheet including a base material and an adhesive layer has been used. Such an adhesive layer is formed by applying an adhesive composition to a base material. From the viewpoint of reducing the environmental load, as the adhesive composition, a water-dispersion type adhesive composition (emulsion) that does not contain an organic solvent is known to be used.

[0003] On the other hand, when such a water-dispersion type adhesive composition is applied to a plastic base material, the adhesion between the water-dispersion type adhesive composition and the plastic base material is insufficient, which may cause peeling.

[0004] Therefore, improving the adhesion between the water-dispersion type adhesive composition and the plastic base material has been studied.

[0005] Specifically, an adhesive sheet including a plastic film base material, an undercoat layer formed from an aqueous undercoat agent containing an oxazoline group-containing acrylic aqueous emulsion, and an adhesive layer formed from a water-dispersion type adhesive composition in this order has been proposed (see, for example, Example 1 of Patent Document 1). In Patent Document 1, by interposing an undercoat layer between the plastic film base material and the adhesive layer, the anchoring property of the water-dispersion type adhesive composition to the plastic film base material is improved.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] On the one hand, since the undercoat layer of Patent Document 1 is formed from an oxazoline group-containing acrylic aqueous emulsion, there is a problem that discoloration occurs during long-term storage and the appearance deteriorates.

[0008] The present invention provides a pressure-sensitive adhesive sheet that is excellent in anchoring properties between the easy-adhesion layer and the pressure-sensitive adhesive layer and is excellent in storage stability.

Means for Solving the Problems

[0009] The present invention [1] includes a plastic substrate, an easy-adhesion layer, and a pressure-sensitive adhesive layer in this order toward one side in the thickness direction, the easy-adhesion layer includes an adhesive composition containing a polyester component and an oxazoline component, and the pressure-sensitive adhesive layer includes a water-dispersible polymer, and is a pressure-sensitive adhesive sheet.

[0010] The present invention [2] includes the pressure-sensitive adhesive sheet according to [1] above, wherein the thickness of the pressure-sensitive adhesive layer is 1 μm or more and 20 μm or less.

[0011] The present invention [3] includes the pressure-sensitive adhesive sheet according to [1] or [2] above, wherein the pressure-sensitive adhesive layer includes a leveling agent.

[0012] The present invention [4] includes the pressure-sensitive adhesive sheet according to any one of [1] to [3] above, wherein in the adhesive composition, the intensity ratio of the peak intensity derived from the oxazoline component to the peak intensity derived from the polyester component measured by TOF-SIMS is 2 or more and 50 or less.

[0013] The present invention [5] includes the pressure-sensitive adhesive sheet according to any one of [1] to [4] above, wherein the thickness of the easy-adhesion layer is 50 nm or less.

[0014] The present invention [6] includes the pressure-sensitive adhesive sheet according to any one of [1] to [5] above, further including the easy-adhesion layer and the pressure-sensitive adhesive layer in this order toward the other side in the thickness direction of the plastic substrate.

Effects of the Invention

[0015] In the pressure-sensitive adhesive sheet of the present invention, an easy-adhesion layer is provided between the plastic substrate and the pressure-sensitive adhesive layer. Further, the easy-adhesion layer contains an adhesive composition containing a polyester component and an oxazoline component. Therefore, the anchoring property between the easy-adhesion layer and the pressure-sensitive adhesive layer is excellent, and the storage stability is excellent.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0017] With reference to FIG. 1, an embodiment of the pressure-sensitive adhesive sheet of the present invention will be described.

[0018] <Pressure-sensitive adhesive sheet> The pressure-sensitive adhesive sheet 1 has a film shape (including a sheet shape) having a predetermined thickness. The pressure-sensitive adhesive sheet 1 extends in a plane direction orthogonal to the thickness direction. The pressure-sensitive adhesive sheet 1 has a flat upper surface and a flat lower surface.

[0019] The pressure-sensitive adhesive sheet 1 includes a plastic substrate 2, an easy-adhesion layer 3, and a pressure-sensitive adhesive layer 4 in this order toward one side in the thickness direction. Specifically, the pressure-sensitive adhesive sheet 1 includes a plastic substrate 2, an easy-adhesion layer 3 disposed directly on the upper surface (one surface in the thickness direction) of the plastic substrate 2, and a pressure-sensitive adhesive layer 4 disposed directly on the upper surface (one surface in the thickness direction) of the easy-adhesion layer 3.

[0020] The thickness of the adhesive sheet 1 is, for example, 500 μm or less, preferably 400 μm or less, more preferably 300 μm or less, still more preferably 200 μm or less, and, for example, 10 μm or more, more preferably 30 μm or more, still more preferably 50 μm or more.

[0021] <Plastic substrate> The plastic substrate 2 is a substrate for ensuring the mechanical strength of the adhesive sheet 1.

[0022] The plastic substrate 2 has a film shape. The plastic substrate 2 preferably has flexibility. The plastic substrate 2 is disposed on the entire lower surface of the easy-adhesion layer 3 so as to be in contact with the lower surface of the easy-adhesion layer 3.

[0023] Examples of the plastic substrate 2 include a polyester sheet (polyethylene terephthalate (PET) sheet), a polyolefin sheet (for example, a polyethylene sheet, a polypropylene sheet), a polyvinyl chloride sheet, a polyimide sheet, and a polyamide sheet (nylon sheet), and preferably, a polyethylene terephthalate (PET) sheet.

[0024] The plastic substrate 2 preferably has transparency. The total light transmittance (JIS K 7375-2008) of the plastic substrate 2 is, for example, 80% or more, preferably 85% or more.

[0025] The thickness of the plastic substrate 2 is, for example, 1 μm or more, and, for example, 100 μm or less.

[0026] <Easy-adhesion layer> The easy-adhesion layer 3 is a layer for imparting an anchoring property (the anchoring property between the easy-adhesion layer 3 and the adhesive layer 4, the same applies hereinafter) to the adhesive sheet 1.

[0027] The easy-adhesion layer 3 has a film shape. The easy-adhesion layer 3 is disposed on the entire lower surface of the adhesive layer 4 so as to be in contact with the lower surface of the adhesive layer 4.

[0028] The easy - adhesion layer 3 is formed from an easy - adhesion composition.

[0029] [Easy - adhesion composition] The easy - adhesion composition contains an adhesive composition. That is, the easy - adhesion layer 3 contains an adhesive composition.

[0030] The adhesive composition contains an oxazoline - group - containing polyester polymer. The oxazoline - group - containing polyester polymer contains a polyester component and an oxazoline component. That is, the adhesive composition contains a polyester component and an oxazoline component.

[0031] In the oxazoline - group - containing polyester polymer, the polyester component is a polymer in which ester bonds formed by dehydration condensation of a polyvalent carboxylic acid and a polyol link them.

[0032] Examples of the polyvalent carboxylic acid include phthalic acid (terephthalic acid, isophthalic acid), naphthalenedicarboxylic acid, and preferably phthalic acid. That is, preferably, the oxazoline - group - containing polyester polymer contains a structural unit derived from phthalic acid. Examples of the polyol include aliphatic glycols having 2 to 8 carbon atoms.

[0033] In the oxazoline - group - containing polyester polymer, the oxazoline component is a unit containing an oxazoline group. That is, the oxazoline - group - containing polyester polymer is an oxazoline - modified polyester.

[0034] The oxazoline - group - containing polyester polymer is obtained by the reaction of a polyester component and an oxazoline component. Specifically, it is obtained by the reaction of a water - soluble copolymerized polyester (polyester component) described in JP - A - 06 - 293838 and an oxazoline - based reactive polymer (oxazoline component).

[0035] Further, the blending ratio of the oxazoline component is appropriately adjusted so that the intensity ratio of the peak intensity derived from the oxazoline component to the peak intensity derived from the polyester component measured by TOF-SIMS described later is within a predetermined range.

[0036] In such an oxazoline group-containing polyester polymer, the intensity ratio of the peak intensity derived from the oxazoline component to the peak intensity derived from the polyester component measured by TOF-SIMS (peak intensity derived from the oxazoline component / peak intensity derived from the polyester component) is, from the viewpoint of improving the anchoring property, for example, 1 or more, preferably 2 or more, more preferably 5 or more, still more preferably 10 or more, and also from the viewpoint of improving the anchoring property, for example, 50 or less, preferably 30 or less, more preferably 20 or less, still more preferably 15 or less.

[0037] In TOF-SIMS, when the oxazoline group-containing polyester polymer contains a structural unit derived from phthalic acid, the fragment ion of the polyester component is C7H4O as shown in the following general formula (1). + It is.

Chemical formula

[0038] Further, the fragment ion of the oxazoline component is C6H as shown in the following general formula (2). 10 NO + It is.

Chemical formula

[0039] The method for measuring the above intensity ratio will be described in detail in the examples described later.

[0040] And, although it will be described in detail later, the easy-adhesion layer 3 is formed by applying an easy-adhesion composition to one surface in the thickness direction of the plastic substrate 2, heating if necessary, and drying.

[0041] The water contact angle of the easy - adhering layer is, for example, 60° or more, and, for example, 75° or less, preferably 71° or less, more preferably 68° or less, still more preferably 65° or less.

[0042] The method for measuring the water contact angle will be described in detail in the examples described later.

[0043] The thickness of the easy - adhering layer 3 is, for example, 50 nm or less, more preferably 45 nm or less, and, for example, 1 nm or more, preferably 10 nm or more.

[0044] If the thickness of the easy - adhering layer 3 is equal to or less than the above upper limit, for example, when this adhesive sheet 1 is used in the manufacture of electronic devices, the thinning of the electronic devices can be achieved.

[0045] <Adhesive layer 4> The adhesive layer 4 is a layer for adhering the adhesive sheet 1 to an arbitrary adherend.

[0046] The adhesive layer 4 is formed from a water - dispersed adhesive composition.

[0047] [Water - dispersed adhesive composition] The water - dispersed adhesive composition contains a water - dispersed polymer and water. That is, the adhesive layer 4 contains a water - dispersed polymer.

[0048] (Water - dispersed polymer) Examples of the water - dispersed polymer include a water - dispersed acrylic polymer, a water - dispersed urethane polymer, a water - dispersed polyaniline - based polymer, and a water - dispersed polyester - based polymer. Preferably, a water - dispersed acrylic polymer is mentioned.

[0049] The water - dispersed acrylic polymer is a polymer of monomer components.

[0050] The monomer component contains (meth)acrylic acid alkyl ester as a main component. Here, (meth)acrylic acid is defined as acrylic acid and / or methacrylic acid.

[0051] Examples of the (meth)acrylic acid alkyl ester include (meth)acrylic acid alkyl esters having a linear or branched alkyl group with 1 to 20 carbon atoms. Such (meth)acrylic acid alkyl esters include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, isotridecyl (meth)acrylate, tetradecyl (meth)acrylate, isotetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. The (meth)acrylic acid alkyl ester is preferably an acrylic acid alkyl ester having an alkyl group with 1 to 12 carbon atoms, more preferably methyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate.

[0052] (Meth)acrylic acid alkyl esters can be used alone or in combination of two or more. Preferably, they are used in combination with methyl acrylate and an acrylic acid alkyl ester having an alkyl group with 2 to 8 carbon atoms. More preferably, they are used in combination of methyl acrylate and 2-ethylhexyl acrylate, and in combination of butyl acrylate and 2-ethylhexyl acrylate. Even more preferably, the combination of methyl acrylate and 2-ethylhexyl acrylate is mentioned.

[0053] The proportion of the (meth)acrylic acid alkyl ester is, for example, 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, particularly preferably 97% by mass or more, for example, 99.5% by mass or less, preferably 99% by mass or less, based on the monomer component.

[0054] Also, the monomer component preferably contains a vinyl monomer containing a carboxy group. If the monomer component contains a vinyl monomer containing a carboxy group, the oxazoline group derived from the oxazoline component of the adhesive composition contained in the easy-adhesion layer 3 reacts with the carboxy group derived from the above-mentioned vinyl monomer containing a carboxy group, and the adhesion (anchoring property) between the easy-adhesion layer 3 and the pressure-sensitive adhesive layer 4 can be improved.

[0055] Examples of the vinyl monomer containing a carboxy group include acrylic acid, methacrylic acid, 2-carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Preferably, acrylic acid and / or methacrylic acid are mentioned.

[0056] The proportion of the vinyl monomer containing a carboxy group is, for example, 0.1% by mass or more, preferably 1.0% by mass or more, more preferably 1.5% by mass or more, based on the monomer component. The proportion of the vinyl monomer containing a functional group in the monomer component is, for example, 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less.

[0057] The carboxy group-containing vinyl monomer can be used alone or in combination of two or more.

[0058] Further, the monomer component may contain one or more functional group-containing vinyl monomers copolymerizable with an (alkyl) acrylate and a carboxy group-containing vinyl monomer. The functional group-containing vinyl monomer is useful for modifying the acrylic polymer, such as securing the cohesive force of the acrylic polymer and introducing crosslinking points into the acrylic polymer.

[0059] Examples of the functional group-containing vinyl monomer (excluding the carboxy group-containing vinyl monomer) include an acid anhydride vinyl monomer, a hydroxyl group-containing vinyl monomer, a sulfo group-containing vinyl monomer, a phosphate group-containing vinyl monomer, a cyano group-containing vinyl monomer, and a glycidyl group-containing vinyl monomer.

[0060] Examples of the acid anhydride vinyl monomer include maleic anhydride and itaconic anhydride.

[0061] Examples of the hydroxyl group-containing vinyl monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (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)methyl (meth)acrylate.

[0062] Examples of the sulfo group-containing vinyl monomer include styrene sulfonic acid, allyl sulfonic acid, sodium vinyl sulfonate, 2-(meth)acrylamide-2-methylpropane sulfonic acid, (meth)acrylamide propane sulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxy naphthalene sulfonic acid.

[0063] Examples of the phosphate group-containing vinyl monomer include 2-hydroxyethyl acryloyl phosphate.

[0064] Examples of the cyano group-containing vinyl monomer include acrylonitrile and methacrylonitrile.

[0065] Examples of the glycidyl group-containing vinyl monomer include glycidyl (meth)acrylate and 2-ethylglycidyl (meth)acrylate.

[0066] The proportion of the functional group-containing vinyl monomer is, for example, 0% by mass or more, preferably 1.0% by mass or more, more preferably 5% by mass or more, and, for example, 20% by mass or less, preferably 10% by mass or less with respect to the monomer component.

[0067] The functional group-containing vinyl monomer can be used alone or in combination of two or more.

[0068] And the water-dispersible acrylic polymer is obtained, for example, by emulsion polymerization of the above monomer component. In the emulsion polymerization, for example, first, a mixture containing the monomer component, an emulsifier, and water is stirred to prepare a monomer emulsion. Next, a polymerization initiator is added to the monomer emulsion to start a polymerization reaction. A chain transfer agent may be used in this polymerization reaction to adjust the molecular weight of the acrylic polymer. The polymerization method may be dropwise polymerization or bulk polymerization. The polymerization time is, for example, 0.5 hours or more and, for example, 10 hours or less. The polymerization temperature is, for example, 50°C or more and, for example, 80°C or less.

[0069] Examples of the emulsifier include anionic emulsifiers, nonionic emulsifiers, and radical polymerizable emulsifiers (reactive emulsifiers).

[0070] Examples of anionic emulsifiers include sodium polyoxyethylene lauryl sulfate, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, and sodium polyoxyethylene alkyl sulfosuccinate. Preferably, sodium polyoxyethylene alkyl ether sulfate is used.

[0071] Examples of nonionic emulsifiers include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene polyoxypropylene block polymer.

[0072] Examples of radical polymerizable emulsifiers (reactive emulsifiers) include emulsifiers in which radical polymerizable functional groups such as vinyl group, propenyl group, isopropenyl group, vinyl ether group, and allyl ether group are introduced into the above anionic emulsifiers and the above nonionic emulsifiers. Specifically, ammonium-α-sulfonato-ω-1-(allyloxymethyl) alkyloxypolyoxyethylene can be mentioned. When a reactive emulsifier is used, the acrylic polymer, which is a water-dispersed polymer obtained by emulsion polymerization, contains monomer units derived from the reactive emulsifier.

[0073] The blending ratio of the emulsifier is, for example, 0.2 parts by mass or more and, for example, 10 parts by mass or less with respect to 100 parts by mass of the monomer component.

[0074] The emulsifier can be used alone or in combination of two or more.

[0075] Examples of the polymerization initiator include azo-based polymerization initiators and peroxide-based polymerization initiators.

[0076] Examples of azo polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis{2-[N-(2-carboxyethyl)amidinopropane]} n hydrate, and 2,2'-azobis(N,N'-dimethyleneisobutylamidine).

[0077] Examples of peroxide polymerization initiators include benzoyl peroxide, t-butyl hydroperoxide, and hydrogen peroxide.

[0078] Preferably, the polymerization initiator is an azo polymerization initiator, and more preferably, 2,2'-azobis{2-[N-(2-carboxyethyl)amidinopropane]} n hydrate.

[0079] The compounding ratio of the polymerization initiator is, for example, 0.01 parts by mass or more and, for example, 2 parts by mass or less with respect to 100 parts by mass of the monomer component.

[0080] The polymerization initiator can be used alone or in combination of two or more.

[0081] Examples of chain transfer agents include glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, t-lauryl mercaptan, t-dodecyl mercaptan, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. Preferably, t-dodecyl mercaptan is mentioned.

[0082] The compounding ratio of the chain transfer agent is, for example, 0.001 parts by mass or more and, for example, 0.5 parts by mass or less with respect to 100 parts by mass of the monomer component.

[0083] The chain transfer agent can be used alone or in combination of two or more.

[0084] And through such emulsion polymerization, the water-dispersible acrylic polymer is prepared as an aqueous dispersion, specifically, an aqueous dispersion (emulsion) in which the water-dispersible acrylic polymer is dispersed in water. That is, the aqueous dispersion is also a water-dispersible pressure-sensitive adhesive composition containing the water-dispersible polymer and water.

[0085] And the weight average molecular weight (Mw) of the obtained water-dispersible acrylic polymer is, for example, 100,000 or more, preferably 300,000 or more, and, for example, 5,000,000 or less, preferably 3,000,000 or less. The weight average molecular weight of the acrylic polymer is measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene conversion.

[0086] (Leveling agent) The water-dispersible pressure-sensitive adhesive composition preferably contains a leveling agent. That is, the pressure-sensitive adhesive layer 4 preferably contains a leveling agent. If the water-dispersible pressure-sensitive adhesive composition contains a leveling agent, the wettability of the water-dispersible pressure-sensitive adhesive composition with respect to the plastic substrate 2 (easy-adhesion layer 3) can be improved. And by improving the wettability, a thin pressure-sensitive adhesive layer 4 (for example, having a thickness of 20 μm or less) can be formed.

[0087] Examples of the leveling agent include "Surfynol 420" (an acetylene glycol ethylene oxide-based surfactant, manufactured by Nissin Chemical Industry Co., Ltd.), "Pelecos OT-P" (sodium dialkyl sulfosuccinate, manufactured by Kao Corporation), "Neocol P" (sodium dialkyl sulfosuccinate, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), "Neocol SW-C" (sodium dialkyl sulfosuccinate, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), "Nopco Wet 50" (a sulfonic acid-based anionic surfactant, manufactured by San Nopco Limited), "SN Wet 126" (a modified silicone / special polyether-based surfactant, manufactured by San Nopco Limited), "SN Wet FST2" (a nonionic wetting agent of polyoxyalkylene amine, manufactured by San Nopco Limited), "SN Wet S" (a nonionic wetting agent of polyoxyalkylene amine ether, manufactured by San Nopco Limited), and "SN Wet 125" (a modified silicone-based surfactant, manufactured by San Nopco Limited).

[0088] Preferably, the leveling agent includes sodium dialkyl sulfosuccinate. If the leveling agent contains sodium dialkyl sulfosuccinate, the wettability of the water-dispersible pressure-sensitive adhesive composition with respect to the plastic substrate 2 (the easy-adhesion layer 3) can be further improved.

[0089] In addition, the number of carbon atoms of sodium dialkyl sulfosuccinate is, for example, 4 or more, preferably 6 or more, more preferably 8 or more, and, for example, 20 or less, preferably 12 or less, more preferably 10 or less.

[0090] The content of the leveling agent is, for example, 0.5 part by mass or more, preferably 1 part by mass or more, and, for example, less than 5 parts by mass, preferably 3 parts by mass or less, more preferably 2.5 parts by mass or less with respect to 100 parts by mass of the water-dispersible polymer.

[0091] The leveling agent can be used alone or in combination of two or more.

[0092] (Thickener) The water-dispersible pressure-sensitive adhesive composition may also contain a thickener. That is, the pressure-sensitive adhesive layer 4 may also contain a thickener. If the water-dispersible pressure-sensitive adhesive composition contains a thickener, the fluidity of the water-dispersible pressure-sensitive adhesive composition can be reduced to suppress repellency.

[0093] Examples of the thickener include polyacrylic acid-based thickeners (e.g., polyacrylic acid), carboxylic acid-based copolymers, urethane thickeners, and polyvinyl alcohol-based thickeners. Preferably, polyacrylic acid-based thickeners are mentioned. Commercially available products can also be used as the thickener. Specifically, "Aron A-10H" (polyacrylic acid, manufactured by Toagosei Co., Ltd.) can be mentioned.

[0094] The weight-average molecular weight of the thickener measured by GPC is, for example, 50,000 or more, preferably 100,000 or more, more preferably 150,000 or more, and, for example, 300,000 or less, preferably 250,000 or less.

[0095] The content of the thickener is, for example, 1 part by mass or more, preferably 2 parts by mass or more, and, for example, less than 8 parts by mass, preferably 6 parts by mass or less, more preferably 4 parts by mass or less with respect to 100 parts by mass of the water-dispersible polymer.

[0096] In addition, the content of the thickener is, for example, 50 parts by mass or more, preferably 100 parts by mass or more, more preferably 130 parts by mass or more, and, for example, 500 parts by mass or less, preferably 300 parts by mass or less, more preferably 200 parts by mass or less with respect to 100 parts by mass of the leveling agent.

[0097] The thickener can be used alone or in combination of two or more.

[0098] (Other components) The water-dispersible pressure-sensitive adhesive composition may also contain other components. That is, the pressure-sensitive adhesive layer 4 may also contain other components. Examples of other components include tackifiers, silane coupling agents, crosslinking agents, fillers, antioxidants, surfactants, release aids, and antistatic agents.

[0099] Examples of the tackifier include various tackifier resins such as rosin-based resins, rosin derivative resins, petroleum-based resins, terpene-based resins, phenolic resins, and ketone-based resins.

[0100] The content of the tackifier is, for example, 5 parts by mass or more and, for example, 40 parts by mass or less with respect to 100 parts by mass of the water-dispersed polymer.

[0101] Other components can be used alone or in combination of two or more.

[0102] (Organic solvent) The water-dispersed adhesive composition does not contain an organic solvent. Therefore, the environmental load can be reduced.

[0103] (Preparation of water-dispersed adhesive composition)

[0104] The water-dispersed adhesive composition can be prepared, for example, by adding each component (a leveling agent optionally blended, a thickener optionally blended, and other components optionally blended) to an emulsion polymerization liquid of a water-dispersed polymer (the emulsion polymerization liquid contains a water-dispersed polymer and water). Further, the water content of the water-dispersed adhesive composition is increased or decreased to adjust the solid content concentration.

[0105] The solid content concentration of the water-dispersed adhesive composition is, for example, 10% by mass or more, preferably 20% by mass or more, and, for example, 60% by mass or less, preferably 40% by mass or less.

[0106] And, as will be described in detail later, the adhesive layer 4 can be disposed by applying the water-dispersed adhesive composition to a release film to form the adhesive layer 4 and transferring this to one side in the thickness direction of the easy-adhesion layer 3.

[0107] The thickness of the adhesive layer 4 is, from the viewpoint of improving the anchoring property, for example, 1 μm or more, preferably 3 μm or more, and, for example, 30 μm or less. When this adhesive sheet 1 is used in the manufacture of electronic devices, from the viewpoint of making the electronic devices thinner, it is preferably 20 μm or less, more preferably 15 μm or less.

[0108] <Method for manufacturing an adhesive sheet> With reference to FIGS. 2A to 2C, an embodiment of the method for manufacturing an adhesive sheet will be described.

[0109] The method for manufacturing an adhesive sheet includes a first step of preparing a plastic substrate 2, a second step of disposing (forming) an easy-adhesion layer 3 on one surface in the thickness direction of the plastic substrate 2, and a third step of disposing (forming) an adhesive layer 4 on one surface in the thickness direction of the easy-adhesion layer 3.

[0110] [First step] In the first step, as shown in FIG. 2A, a plastic substrate 2 is prepared.

[0111] [Second step] In the second step, as shown in FIG. 2B, an easy-adhesion layer 3 is disposed (formed) on one surface in the thickness direction of the plastic substrate 2.

[0112] To dispose (form) the easy-adhesion layer 3 on one surface in the thickness direction of the plastic substrate 2, an easy-adhesion composition is applied to one surface in the thickness direction of the plastic substrate 2, heated if necessary, and dried.

[0113] The heating temperature is, for example, 30°C or more, preferably 60°C or more, and, for example, 150°C or less. Also, the heating time is, for example, 0.5 minutes or more and, for example, 60 minutes or less.

[0114] Thereby, the easy-adhesion layer 3 is disposed (formed) on one surface in the thickness direction of the plastic substrate 2.

[0115] [Third step] In the third step, as shown in FIG. 2C, an adhesive layer 4 is disposed (formed) on one surface in the thickness direction of the easy-adhesion layer 3.

[0116] In order to dispose (form) the pressure-sensitive adhesive layer 4 on one surface in the thickness direction of the easy-adhesion layer 3, first, the pressure-sensitive adhesive layer 4 is prepared.

[0117] In order to prepare the pressure-sensitive adhesive layer 4, a water-dispersible pressure-sensitive adhesive composition is applied on one surface in the thickness direction of a release film (not shown), heated if necessary, and dried. Thereby, the pressure-sensitive adhesive layer 4 is prepared.

[0118] Then, by transferring this pressure-sensitive adhesive layer 4 to one surface in the thickness direction of the easy-adhesion layer 3, the pressure-sensitive adhesive layer 4 is disposed (formed) on one surface in the thickness direction of the easy-adhesion layer 3.

[0119] As described above, the adhesive sheet 1 is manufactured.

[0120] <Function and Effect> In the adhesive sheet 1, an easy-adhesion layer 3 is provided between the plastic base material 2 and the pressure-sensitive adhesive layer 4. Further, the easy-adhesion layer 3 contains an adhesive composition containing a polyester component and an oxazoline component. Therefore, the anchoring property between the easy-adhesion layer 3 and the pressure-sensitive adhesive layer 4 is excellent.

[0121] Specifically, as described above, if the pressure-sensitive adhesive layer 4 has a functional group capable of reacting with an oxazoline group (for example, a carboxy group derived from the above carboxy group-containing vinyl monomer), by reacting with the oxazoline group derived from the oxazoline component of the adhesive composition contained in the easy-adhesion layer 3, the adhesion (anchoring property) between the easy-adhesion layer 3 and the pressure-sensitive adhesive layer 4 can be further improved.

[0122] In addition, the pressure-sensitive adhesive sheet 1 has excellent storage stability. As for what is meant by excellent storage stability, although it will be described in detail in the examples described later, it means that discoloration can be suppressed when the easy-adhesion layer 3 is stored in a predetermined environment. In the pressure-sensitive adhesive sheet 1, the easy-adhesion layer 3 contains an adhesive composition containing a polyester component and an oxazoline component, and does not contain a radical initiator during the polymerization process. Therefore, it does not cause coloring due to the remaining initiator over time. Thus, it has excellent storage stability. On the other hand, when the easy-adhesion layer 3 contains the acrylic adhesive of Patent Document 1, a radical initiator needs to be added to prepare the acrylic resin. From the viewpoint of generating coloring due to the remaining radical initiator, the storage stability decreases.

[0123] In addition, since the acrylic adhesive has fewer polar components and lower polarity compared with the polyester component, the interaction with the adhesive layer 4 becomes lower. On the other hand, the adhesive composition containing the polyester component contains many polar groups, so the polarity becomes higher, and the interaction with the adhesive layer 4 is likely to occur. As a result, the adhesion to the adhesive layer 4 is likely to increase.

[0124] Moreover, the water-dispersion type adhesive composition forming the adhesive layer 4 does not contain an organic solvent. Therefore, the environmental load can be reduced.

[0125] Such a pressure-sensitive adhesive sheet 1 has excellent anchoring property and storage stability and can reduce the environmental load, so it can be suitably used for various electronic devices.

[0126] <Modification Example> In the modification example, for the members and steps similar to those in one embodiment, the same reference numerals are given, and the detailed description thereof is omitted. In addition, the modification example can achieve the same effects as those in one embodiment unless otherwise specified. Furthermore, one embodiment and the modification example can be combined as appropriate.

[0127] In the above-described third step, the adhesive layer 4 is disposed (formed) on the release film, and the adhesive layer 4 is transferred to one side in the thickness direction of the easy-adhesion layer 3, so that the adhesive layer 4 is disposed (formed) on one side in the thickness direction of the easy-adhesion layer 3.

[0128] On the other hand, on one side in the thickness direction of the easy - adhesion layer 3, by applying the water - dispersible pressure - sensitive adhesive composition, heating if necessary, and drying, without performing the above - mentioned transfer, the pressure - sensitive adhesive layer 4 can be disposed (formed) on one side in the thickness direction of the easy - adhesion layer 3.

[0129] On one side in the thickness direction of the pressure - sensitive adhesive layer 4, a release film can be disposed from the viewpoint of protecting the pressure - sensitive adhesive layer 4.

[0130] Also, the easy - adhesion layer 3 and the pressure - sensitive adhesive layer 4 can be provided in order toward the other side in the thickness direction of the plastic substrate 2. Specifically, by disposing the easy - adhesion layer 3 and the pressure - sensitive adhesive layer 4 in order on the other side in the thickness direction of the plastic substrate 2, an adhesive sheet 1 (double - sided adhesive sheet) provided with the pressure - sensitive adhesive layer 4, the easy - adhesion layer 3, the plastic substrate 2, the easy - adhesion layer 3, and the pressure - sensitive adhesive layer 4 in order toward one side in the thickness direction can be formed.

Examples

[0131] Examples and comparative examples are shown below to explain the present invention more specifically. Note that the present invention is not limited to any examples and comparative examples. Also, specific numerical values such as the blending ratio (content ratio), physical property values, parameters, etc. used in the following description can be replaced with the upper limit values (numerical values defined as "below", "less than") or lower limit values (numerical values defined as "above", "exceeding") of the corresponding blending ratio (content ratio), physical property values, parameters, etc. described in the above - mentioned "Mode for Carrying Out the Invention".

[0132] <Details of Each Component> The details of each component are as follows. Aqualon KH1025: Ammonium - α - sulfonato - ω - 1 - (allyloxymethyl) alkyloxy polyoxyethylene, manufactured by Dai - Ichi Kogyo Seiyaku Co., Ltd. Latemul E - 118B: Sodium polyoxyethylene alkyl ether sulfate, manufactured by Kao Corporation "VA-057": 2,2'-azobis{2-[N-(2-carboxyethyl)amidinopropane]} n-hydrate, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd. KBM-503: 3-methacryloxypropyltrimethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd. Pelec OT-P: Sodium dialkylsulfosuccinate (8 carbon atoms), leveling agent, manufactured by Kao Corporation Aron A-10H: Polyacrylic acid, weight average molecular weight 200,000, manufactured by Toagosei Co., Ltd. Super Ester E-865NT: Polymerized rosin ester, manufactured by Arakawa Chemical Industries, Ltd. Tamanol E-200NT: Terpene resin, manufactured by Arakawa Chemical Industries, Ltd. Adhesive Composition A: An adhesive composition containing a polyester polymer containing an oxazoline group, the intensity ratio of the peak intensity derived from the oxazoline component to the peak intensity derived from the polyester component measured by TOF-SIMS is 11 Adhesive Composition B: An adhesive composition containing a polyester polymer containing an oxazoline group, the intensity ratio of the peak intensity derived from the oxazoline component to the peak intensity derived from the polyester component measured by TOF-SIMS is 16 Adhesive Composition C: An adhesive composition containing a polyester polymer containing an oxazoline group, the intensity ratio of the peak intensity derived from the oxazoline component to the peak intensity derived from the polyester component measured by TOF-SIMS is 1.4 Adhesive Composition D: An adhesive composition containing a polyester polymer containing an oxazoline group, the intensity ratio of the peak intensity derived from the oxazoline component to the peak intensity derived from the polyester component measured by TOF-SIMS is 32 Adhesive Composition E: An adhesive composition containing a polyester polymer not containing an oxazoline group, the intensity ratio of the peak intensity derived from the oxazoline component to the peak intensity derived from the polyester component measured by TOF-SIMS is 0 Epocros WS-700: An aqueous solution containing an acrylic polymer containing an oxazoline group, manufactured by Nippon Shokubai Co., Ltd.

[0133] <Synthesis of water-dispersed polymer> Synthesis Example 1 To a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 0.07 part by mass of Aqualon KH-1025 (emulsifier) and 61.1 parts by mass of distilled water were added, and nitrogen substitution was carried out at room temperature (25 °C) for 1 hour while stirring. Then, 0.1 part by mass of VA-057 (polymerization initiator) was further added, and the temperature was raised to 60 °C. Further, a mixture of 85 parts by mass of 2-ethylhexyl acrylate (2EHA), 13 parts by mass of methyl acrylate (MA), 1.25 parts by mass of acrylic acid (AA), 0.75 part by mass of methacrylic acid (MAA), 0.025 part by mass of t-dodecanethiol (chain transfer agent), 0.02 part by mass of KBM-503 (crosslinking agent), and 1.93 parts by mass of Aqualon KH-1025 (emulsifier) emulsified with 28 parts by mass of distilled water was polymerized by dropping it at 60 °C over 4 hours. Then, it was cooled to room temperature, and the pH was adjusted to 6 using 10% aqueous ammonia as a pH adjuster. Thereby, a water-dispersible acrylic polymer was synthesized.

[0134] Synthesis Example 2 To a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 40 parts by mass of distilled water were added, and nitrogen substitution was carried out at room temperature (25 °C) for 1 hour while stirring. Then, 0.1 part by mass of VA-057 (polymerization initiator) was further added, and the temperature was raised to 60 °C. Further, a mixture of 86.58 parts by mass of butyl acrylate (BA), 9.62 parts by mass of 2-ethylhexyl acrylate (2EHA), 3.77 parts by mass of acrylic acid (AA), 0.055 part by mass of n-dodecanethiol (chain transfer agent), 0.07 part by mass of KBM-503 (crosslinking agent), and 2 parts by mass of Latemul E-118B (emulsifier) emulsified with 29.3 parts by mass of distilled water was polymerized by dropping it at 60 °C over 4 hours. Then, it was cooled to room temperature, and the pH was adjusted to 6 using 10% aqueous ammonia as a pH adjuster. Thereby, a water-dispersible acrylic polymer was synthesized.

[0135] <Preparation of Water-Dispersible Adhesive Composition> Preparation Example 1 To 100 parts by mass of the solid content of the water-dispersible acrylic polymer of Synthesis Example 1, 30 parts by mass of Super Ester E-865NT (tackifier), 3 parts by mass of Aron A-10H (thickener), and 2 parts by mass of Perpex OT-P (leveling agent) were added, and diluted and neutralized with distilled water and 10% aqueous ammonia to prepare a water-dispersible pressure-sensitive adhesive composition (solid content concentration: 25% by mass).

[0136] Preparation Example 2 To 100 parts of the solid content of the water-dispersible acrylic polymer of Synthesis Example 2, 30 parts by mass of Tamanol E-200NT (tackifier), 3 parts by mass of Aron A-10H (thickener), and 2 parts by mass of Perpex OT-P (leveling agent) were added, and diluted and neutralized with distilled water and 10% aqueous ammonia to prepare a water-dispersible pressure-sensitive adhesive composition (solid content concentration: 25% by mass).

[0137] <Manufacture of Adhesive Sheet> Example 1 [First Step] As a plastic substrate, a polyethylene terephthalate (PET) sheet was prepared.

[0138] [Second Step] On one surface in the thickness direction of the polyethylene terephthalate (PET) sheet, Adhesive Composition A was applied and dried to dispose an easy-adhesion layer.

[0139] [Third Step] On the surface of a release film (SCA1 treatment (silicone-based release treatment) manufactured by Fuji Photo Film Co., Ltd.), the water-dispersible pressure-sensitive adhesive composition of Preparation Example 1 was applied and dried to form (dispose) a pressure-sensitive adhesive layer. Next, this pressure-sensitive adhesive layer was transferred onto one surface in the thickness direction of the easy-adhesion layer. Thereby, an adhesive sheet was manufactured.

[0140] Examples 2 to 7, and Comparative Examples 1 to 3 In the same manner as in Example 1, an adhesive sheet was manufactured. However, the formulation was changed according to Table 1. In Comparative Example 2, the second step was carried out as follows.

[0141] [Second Step] On one side in the thickness direction of a 50-μm-thick PET film (manufactured by Toray Industries, Inc., trade name "Lumirror S10") (plastic substrate) that has been subjected to corona discharge treatment on both sides, Epocros WS-700 was applied and dried at 130°C for 1 minute to form (arrange) an easy-adhesion layer.

[0142] <Evaluation> [Water contact angle] The water contact angle was measured for the easy-adhesion layer of each example and each comparative example. Specifically, using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., trade name "CX-A type"), 2 μL of pure water was dropped onto the surface of the easy-adhesion layer in an environment of 23°C / 50%RH, and the contact angle of the droplet was measured 5 seconds after dropping. The results are shown in Table 1.

[0143] [Intensity ratio of the peak intensity derived from the oxazoline component to the peak intensity derived from the polyester component measured by TOF-SIMS] For each adhesive composition and the acrylic adhesive (Epocros WS-700), the peak intensity derived from the polyester component and the peak intensity derived from the oxazoline component were measured by TOF-SIMS based on the following measurement conditions. Specifically, C7N4O + (m / z 104) was used as the fragment ion of the polyester component, and C6H 10 NO + (m / z 112) was used as the fragment ion of the oxazoline component.

[0144] From the obtained peak intensities, the intensity ratio of the peak intensity derived from the oxazoline component to the peak intensity derived from the polyester component was calculated. The results are shown in Table 1. Since the acrylic adhesive does not contain a polyester component, the above intensity ratio could not be measured. (Measurement conditions) Device: ION-TOF, TOF-SIMS 5 Irradiated primary ion: Bis 2+ Primary ion acceleration voltage: 25 kV Measurement area: 300 μm square (a neutralizer gun for charge correction was used for measurement)

[0145] [Anchoring property] The pressure-sensitive adhesive sheets of each example and each comparative example were cut into pieces with a width of 20 mm and a length of 100 m to obtain samples. Then, the plastic substrate and the applicator plate in this sample were attached using a double-sided tape. Next, cuts were made at 10 mm intervals only in the adhesive layer so as to be perpendicular to the longitudinal direction.

[0146] Next, single-sided tape No. 315 (manufactured by Nitto Denko Corporation) was bonded to the adhesive surface, and it was pressure-bonded once back and forth with a 2 kg roller and cured at room temperature for 30 minutes. Then, the single-sided tape No. 315 was peeled off, and the peel strength (unit: N / 20 mm) between the easy-adhesion layer and the adhesive layer was measured. The results are shown in Table 1.

[0147] Also, the anchoring property was evaluated based on the following criteria. The results are shown in Table 1. (Criteria) 〇: The peel strength was 15 or more. △: The peel strength was 13 or more and less than 15. ×: The peel strength was less than 13.

[0148] [Blocking resistance] Two easy-adhesion layers (films each comprising a plastic substrate and an easy-adhesion layer) of each example and each comparative example were prepared, and their easy-adhesion layers were bonded to each other and pressure-bonded at 80 °C and 0.4 MPa for 30 minutes. Then, this was peeled off. The blocking resistance was evaluated based on the following criteria. The results are shown in Table 1. (Criteria) ◎: It was easily peeled off. 〇: It was peeled off. △: It was difficult to peel off. ×: It was not peeled off.

[0149] [Appearance] The easy-adhesion layer of each example and each comparative example (a film comprising a plastic substrate after the second step and the easy-adhesion layer) was stored in an 80°C / 90% environment for one week, and then 10 films were laminated and visually inspected. The appearance was evaluated based on the following criteria. The results are shown in Table 1. 〇: No change in color or taste was observed. ×: A change in color or taste was observed.

[0150]

Table 1

Explanation of symbols

[0151] 1 Adhesive sheet 2 Plastic substrate 3 Easy-adhesion layer 4 Adhesive layer

Claims

**Claim 1** A pressure-sensitive adhesive sheet comprising a plastic substrate, an easy-adhesion layer, and a pressure-sensitive adhesive layer, sequentially provided in this order toward one side in the thickness direction; wherein the easy-adhesion layer contains an adhesive composition containing a polyester component and an oxazoline component; and the pressure-sensitive adhesive layer contains a water-dispersible polymer. **Claim 2** The pressure-sensitive adhesive sheet according to claim 1, wherein the thickness of the pressure-sensitive adhesive layer is 1 μm or more and 20 μm or less. **Claim 3** The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive layer contains a leveling agent. **Claim 4** The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein, in the adhesive composition, the intensity ratio of the peak intensity derived from the oxazoline component to the peak intensity derived from the polyester component measured by TOF-SIMS is 2 or more and 50 or less. **Claim 5** The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the thickness of the easy-adhesion layer is 50 nm or less. **Claim 6** The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, further comprising the easy-adhesion layer and the pressure-sensitive adhesive layer, sequentially provided in this order toward the other side in the thickness direction of the plastic substrate.

Images