阅读说明：本技术 粘合剂组合物、粘合层及粘合膜 (Adhesive composition, adhesive layer and adhesive film ) 是由 纲岛启次 小松崎优纪 于 2020-08-13 设计创作，主要内容包括：本发明提供一种粘合剂组合物、粘合层及粘合膜,其目的在于在维持光学透明性的状态下进行高粘接力化并赋予耐久性。本发明的粘合剂组合物包含：丙烯酸聚合物(A)、交联剂(B)以及硅烷偶合剂(C),所述丙烯酸聚合物(A)包含：源自(甲基)丙烯酸酯单体(a1)的单元；源自具有氮原子的单体(a2)的单元；以及源自选自由具有酸基的单体(a3)及具有羟基的单体(a4)所组成的群组中的至少一种的单元,所述硅烷偶合剂(C)具有能够与所述丙烯酸聚合物(A)进行反应的基。(The invention provides an adhesive composition, an adhesive layer and an adhesive film, aiming at realizing high adhesion and durability in a state of maintaining optical transparency. The adhesive composition of the present invention comprises: an acrylic polymer (A), a crosslinking agent (B), and a silane coupling agent (C), the acrylic polymer (A) comprising: units derived from (meth) acrylate monomer (a 1); a unit derived from a monomer (a2) having a nitrogen atom; and a unit derived from at least one selected from the group consisting of a monomer (a3) having an acid group and a monomer (a4) having a hydroxyl group, the silane coupling agent (C) having a group capable of reacting with the acrylic polymer (a).)

1. An adhesive composition comprising an acrylic polymer A, a crosslinking agent B and a silane coupling agent C,

the acrylic polymer a comprises: units derived from (meth) acrylate monomer a 1; units derived from monomer a2 having a nitrogen atom; and a unit derived from at least one selected from the group consisting of a monomer a3 having an acid group and a monomer a4 having a hydroxyl group,

the silane coupling agent C has a group capable of reacting with the acrylic polymer A.

2. The adhesive composition according to claim 1, wherein the monomer a2 having a nitrogen atom is a (meth) acrylamide monomer.

3. The adhesive composition according to claim 1 or 2, wherein the content of the silane coupling agent C is 0.0005 parts by mass or more and 0.5 parts by mass or less with respect to 100 parts by mass of the acrylic polymer a.

4. The adhesive composition according to any one of claims 1 to 3, further comprising a solvent D.

5. An adhesive layer formed from the adhesive composition of any one of claims 1 to 4.

6. An adhesive film having the adhesive layer of claim 5.

Technical Field

The invention relates to an adhesive composition, an adhesive layer and an adhesive film.

Background

Adhesive sheets are used in various fields such as automobiles, buildings, and electronic devices. In particular, in recent years, the present invention is effectively used in various fields such as surface protection of a tablet (tablet) or a portable electronic device such as a smartphone, fixation of a member, and protection in a processing step of a member to be used. The pressure-sensitive adhesive sheet used in such electronic devices is further required to have high performance and high functionality in terms of the properties of the product. In particular, there is a demand for a clear image (display is not hindered) that does not peel off and has no defects even in various usage environments.

In addition, these mobile devices represented by smartphones are frequently transported and are likely to be dropped by mistake during use. When the glass is dropped, the surface glass may be broken and fragments of the glass may be scattered and damaged, which may cause damage. Therefore, a scattering prevention film for the purpose of preventing scattering of glass fragments may be attached.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent laid-open publication No. 2017-48328

[ patent document 2] Japanese patent application laid-open No. 2019-70148

[ patent document 3] Japanese patent laid-open publication No. 2019-70149

[ patent document 4] Japanese patent application laid-open No. 2019-70152

[ patent document 5] Japanese patent laid-open No. 2019-77881

[ patent document 6] Japanese patent laid-open No. 2019-77882

[ patent document 7] Japanese patent laid-open No. 2019-90040

Disclosure of Invention

[ problems to be solved by the invention ]

Since the scattering prevention film prevents scattering of fragments by being attached to the surface glass, a smartphone or the like is used in a state of being attached. Therefore, it is required to have high optical transparency (high transparency of the coating film) without peeling off (high adhesion) under various environments. Further, it is also required that the adhesive force is not reduced (durability) even when the film is stored in a severe high-temperature and high-humidity environment. The biggest theme is to take into account all of these requirements. However, it is not achieved to balance these required performances at a high level. The present invention has been made in view of the above circumstances, and an object thereof is to provide durability by increasing adhesion force while maintaining optical transparency.

[ means for solving problems ]

Adhesive composition of the invention: by using a specific monomer composition for the acrylic polymer, the cohesive force of the pressure-sensitive adhesive film can be increased while maintaining the optical transparency, and high transparency, high adhesion force, and durability can be achieved at the same time.

Specifically, the adhesive composition: comprising an acrylic polymer (A), a crosslinking agent (B) and a silane coupling agent (C), the acrylic polymer (A) comprising: units derived from (meth) acrylate monomer (a 1); a unit derived from a monomer (a2) having a nitrogen atom; and a unit derived from at least one selected from the group consisting of a monomer (a3) having an acid group and a monomer (a4) having a hydroxyl group, the silane coupling agent (C) having a group capable of reacting with the acrylic polymer (a).

[ Effect of the invention ]

By using the adhesive composition of the present invention, high adhesion can be achieved while maintaining optical transparency, and durability can be imparted.

Detailed Description

The adhesive composition of the present invention comprises an acrylic polymer (a) and a crosslinking agent (B).

The acrylic polymer (A) comprises: units derived from (meth) acrylate monomer (a 1); a unit derived from a monomer (a2) having a nitrogen atom; and a unit derived from at least one selected from the group consisting of a monomer (a3) having an acid group and a monomer (a4) having a hydroxyl group.

Examples of the (meth) acrylate monomer (a1) include: alkyl (meth) acrylates in which an alkyl group is ester-bonded, cyclic ether-containing (meth) acrylate monomers, alicyclic structure-containing (meth) acrylate monomers, aromatic ring-containing (meth) acrylate monomers, alkylene oxide structure-containing (meth) acrylate monomers, and the like.

Examples of the alkyl group in the alkyl (meth) acrylate include: a linear alkyl group such as a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, a lauryl group, and a stearyl group; branched alkyl groups such as isopropyl, isobutyl, tert-butyl, isopentyl, neopentyl, isohexyl, isoheptyl, isooctyl, 2-ethylhexyl, isononyl, isodecyl, and isostearyl. The number of carbon atoms of the alkyl group is preferably 1 or more, and preferably 20 or less, more preferably 15 or less, and further preferably 12 or less.

Examples of the alkyl (meth) acrylate include: methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, and the like.

Further, examples of the (meth) acrylate ester monomer (a1) include: cyclic ether-containing (meth) acrylate monomers such as glycidyl (meth) acrylate and tetrahydrofurfuryl (meth) acrylate; alicyclic structure-containing (meth) acrylate monomers such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate; aromatic ring-containing (meth) acrylate monomers such as phenoxyethyl (meth) acrylate and benzyl (meth) acrylate; and (meth) acrylate monomers containing an alkylene oxide structure, such as 2-methoxyethyl (meth) acrylate, methoxybutyl (meth) acrylate, and methoxypolyethylene glycol (meth) acrylate.

The alkyl (meth) acrylate preferably contains a low Tg monomer (a1-1) having a glass transition temperature (Tg) of a homopolymer of less than-15 ℃ and a high Tg monomer (a1-2) having a glass transition temperature (Tg) of a homopolymer of-15 ℃ or higher.

The low Tg monomer (a1-1) may have a glass transition temperature (Tg) of less than-15 ℃, preferably-20 ℃ or less, more preferably-25 ℃ or less, and the lower limit thereof may be, for example, -100 ℃ or more.

The content of the low Tg monomer (a1-1) in the alkyl (meth) acrylate is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 45% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

The glass transition temperature of the high Tg monomer (a1-2) is-15 ℃ or higher, preferably-10 ℃ or higher, more preferably-10 ℃ or higher, and the upper limit thereof may be 150 ℃ or lower and 100 ℃ or lower, for example.

The content of the high Tg monomer (a1-2) is preferably 15 parts by mass or more, more preferably 20 parts by mass or more, further preferably 25 parts by mass or more, and preferably 50 parts by mass or less, more preferably 45 parts by mass or less, further preferably 40 parts by mass or less, relative to 100 parts by mass of the low Tg monomer (a 1-1).

The unit derived from the high Tg monomer (a1-2) is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 25% by mass or more, and preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less in the acrylic polymer (a).

One or more (meth) acrylate monomers (a1) may be used, and alkyl acrylate and alicyclic structure-containing (meth) acrylate monomers are preferred in terms of providing flexibility and cohesive force in a well-balanced manner.

In the acrylic polymer (a), the content of the unit derived from the (meth) acrylate monomer (a1) is preferably 50% by mass or more, more preferably 70% by mass or more, and is preferably 97% by mass or less, more preferably 95% by mass or less.

The monomer (a2) having a nitrogen atom is a monomer having a nitrogen atom and a polymerizable double bond in the molecule, and is preferably a monomer having an amide bond and a polymerizable double bond in the molecule, and examples thereof include: lactam compounds having a vinyl group; (meth) acrylamide monomers; and (meth) acrylate compounds having a functional group containing a nitrogen atom (for example, an amino group, a 1-substituted amino group, a 2-substituted amino group, a nitrile group, or the like).

Examples of the lactam compound having a vinyl group include: n-vinylpyrrolidone, N-vinylcaprolactam, and the like.

The (meth) acrylamide monomer includes: a hydrogen atom or a hydrocarbon group (preferably an aliphatic hydrocarbon group; wherein-CH is contained in the hydrocarbon group) is bonded to the nitrogen atom of the (meth) acrylamide₂A compound which may be substituted with-CO-, and a hydrogen atom contained in the hydrocarbon group may be substituted with a hydroxyl group), and the like. In addition, when two or more groups (the hydrocarbon group) substitute for the nitrogen atom of the (meth) acrylamide, these groups may be bonded to each other to form a ring including the nitrogen atom.

The number of carbon atoms of the hydrocarbon group (preferably, aliphatic hydrocarbon group) substituted with a nitrogen atom contained in the amide bond is preferably 1 or more, and preferably 10 or less, and more preferably 6 or less.

One or two or more kinds of the (meth) acrylamide monomers may be used. The (meth) acrylamide monomer may be any of (meth) acrylamide, an N-1 substituted (meth) acrylamide compound, and an N, N-2 substituted (meth) acrylamide compound.

As the (meth) acrylamide compound, one or two or more kinds may be used, and examples thereof include: (meth) acrylamide; n-1 substituted (meth) acrylamide compounds such as N-isopropyl (meth) acrylamide, N- (1, 1-dimethyl-3-oxobutyl) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N- (2-hydroxymethyl) acrylamide, and N- (2-hydroxyethyl) acrylamide; n-2 substituted (meth) acrylamide compounds such as N- (meth) acryloylmorpholine, N- (meth) acryloylpiperidone, N- (meth) acryloylpiperidine, N- (meth) acryloylpyrrolidine, N- (meth) acryloyl-4-piperidone, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, N-diisopropyl (meth) acrylamide, N-methylenebis (meth) acrylamide, and N, N-dimethylaminopropyl (meth) acrylamide.

Among them, the (meth) acrylamide monomer preferably contains a monomer represented by the formula (1).

[ solution 1]

[ in the formula (1), R¹Represents a hydrogen atom or a methyl group; r²And R³Each independently represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and-CH contained in the hydrocarbon group₂-may be substituted by-CO-or-O-, the hydrogen atom contained in said hydrocarbon group may be substituted by a hydroxyl group, R²And R³May be bonded to each other to form a ring containing a nitrogen atom]。

As said R²And R³The hydrocarbon group represented by (a) may be one or two or more, and examples thereof include: a straight-chain or branched saturated aliphatic hydrocarbon group; straight-chain or branched unsaturated aliphatic hydrocarbon groups, and the like. Among them, a straight-chain or branched saturated aliphatic hydrocarbon group is preferable, and a branched saturated aliphatic hydrocarbon group is more preferable. Preferably R²And R³Is a hydrogen atom.

The (meth) acrylamide monomer also preferably contains R²And R³Both of which are the (meth) acrylamide monomers of the hydrocarbon group. In the presence of said compound containing R²And R³When both are the hydrocarbon group-containing (meth) acrylamide monomers, the content of the unit derived from the monomer is preferably 0.5% by mass or more, more preferably 1% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less in the acrylic polymer (a).

In the monomer (a2) having a nitrogen atom, the content of the unit derived from the acrylamide monomer is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more, with the upper limit being 100% by mass.

Examples of the (meth) acrylate compound having a functional group containing a nitrogen atom (for example, an amino group, a 1-substituted amino group, a 2-substituted amino group, a nitrile group, and the like) include: (meth) acrylonitrile, t-butylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, and the like.

In the acrylic polymer, the content of the unit derived from the nitrogen atom-containing monomer (a2) is preferably 0.5% by mass or more, more preferably 1% by mass or more, and preferably 20% by mass or less, more preferably 15% by mass or less.

The monomer (a3) having an acid group includes a monomer having an acid group and a polymerizable double bond, preferably a monomer having a carboxyl group and a monomer having a sulfo group, and preferably a monomer having a carboxyl group.

As the monomer having a carboxyl group, one or two or more kinds may be used, and examples thereof include: (meth) acrylic acid; carboxyalkyl (meth) acrylates such as carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, and β -carboxyethyl (meth) acrylate; unsaturated carboxylic acids such as itaconic acid, itaconic anhydride, maleic acid, maleic anhydride, fumaric acid, and crotonic acid.

In the monomer (a3) having an acid group, the content of the monomer having a carboxyl group is preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more, with the upper limit being 100% by mass.

In the acrylic polymer (a), the content of the unit derived from the monomer (a3) having an acid group is preferably 1% by mass or more, more preferably 2.5% by mass or more, and even more preferably 4% by mass or more, and is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 12% by mass or less.

Examples of the monomer (a4) having a hydroxyl group include monomers having a hydroxyl group and a polymerizable double bond. Examples of the monomer (a4) having a hydroxyl group include: hydroxyalkyl (meth) acrylates; hydroxyalkyl (meth) acrylamides; polyalkylene glycol (meth) acrylates and the like, preferably hydroxyalkyl (meth) acrylates.

As the monomer having a hydroxyl group (a4), there may be specifically mentioned: hydroxyalkyl (meth) acrylates having an alkyl (alkylene) group having 2 to 10 carbon atoms such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl (meth) acrylate; hydroxyalkyl (meth) acrylamides having an alkyl (alkylene) group having 2 to 8 carbon atoms such as 2-hydroxyethyl (meth) acrylamide, 4-hydroxyethyl (meth) acrylamide, 6-hydroxyhexyl (meth) acrylamide, and 8-hydroxyoctyl (meth) acrylamide; polyalkylene glycol (meth) acrylates such as polyethylene glycol (meth) acrylates, and the like.

The content of the unit derived from the hydroxyl group-containing monomer (a4) in the acrylic polymer (a) is preferably 0.01% by mass or more, more preferably 0.03% by mass or more, further preferably 0.05% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, further preferably 3% by mass or less.

The total of the units derived from the monomer (a3) having an acid group and the monomer (a4) having a hydroxyl group is preferably 2% by mass or more, more preferably 3% by mass or more, further preferably 5% by mass or more, and preferably 30% by mass or less, more preferably 22% by mass or less, further preferably 17% by mass or less in the acrylic polymer (a).

In the acrylic polymer (a), the total of units derived from the (meth) acrylate monomer (a1), the monomer having a nitrogen atom (a2), the monomer having an acid group (a3), and the monomer having a hydroxyl group (a4) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and the upper limit is 100% by mass in the acrylic polymer (a).

The acrylic polymer (a) may have units derived from monomers (ax) other than the (meth) acrylate monomer (a1), the monomer having a nitrogen atom (a2), the monomer having an acid group (a3), and the monomer having a hydroxyl group (a 4).

As the other monomers (ax), one or two or more kinds may be used, and examples thereof include: vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl versatate; vinyl ether monomers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, pentyl vinyl ether, and hexyl vinyl ether; aromatic vinyl monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, ethylvinylbenzene, α -methylstyrene, p-methoxystyrene, p-t-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and p-hydroxystyrene; isoprene, chloroprene, butadiene, ethylene, tetrafluoroethylene, vinylidene fluoride, and the like.

The content of the unit derived from another monomer (ax) in the acrylic polymer (a) is preferably 20% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less, and the lower limit is 0% by mass.

The weight average molecular weight of the acrylic polymer (a) is preferably 10 ten thousand or more, more preferably 20 ten thousand or more, further preferably 30 ten thousand or more, and preferably 200 ten thousand or less, more preferably 180 ten thousand or less, further preferably 150 ten thousand or less.

In the present specification, the number average molecular weight and the weight average molecular weight of the acrylic polymer (a) are converted values measured by Gel Permeation Chromatography (GPC) using polystyrene as a standard sample.

In the pressure-sensitive adhesive composition of the present invention, the content of the acrylic polymer (a) is preferably 15% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more, and preferably 100% by mass or less in nonvolatile components.

In the present specification, the nonvolatile component of the pressure-sensitive adhesive composition means a portion obtained by removing a solvent component which is optionally contained in the pressure-sensitive adhesive composition.

The acrylic polymer (a) can be produced by copolymerizing the (meth) acrylate monomer (a1), the monomer having a nitrogen atom (a2), the monomer having an acid group (a3), the monomer having a hydroxyl group (a4), and other monomers (ax) used as necessary in the presence of a polymerization initiator.

As the polymerization initiator, for example, one or two or more of thermal polymerization initiators can be used, and there can be mentioned: peroxide initiators such as benzoyl peroxide and lauroyl peroxide; azo initiators such as azobismethylbutyronitrile and azobisisobutylnitrile.

The adhesive composition of the present invention contains a crosslinking agent (B). As the crosslinking agent, one or two or more kinds may be used, and for example, there may be mentioned: isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, polyvalent metal salt crosslinking agents, metal chelate crosslinking agents, ketone-hydrazide crosslinking agents, oxazoline crosslinking agents, carbodiimide crosslinking agents, silane crosslinking agents, and the like.

Among them, isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, and carbodiimide crosslinking agents are preferable, isocyanate crosslinking agents, epoxy crosslinking agents, and carbodiimide crosslinking agents are more preferable, and epoxy crosslinking agents are particularly preferable.

The content of the epoxy crosslinking agent in the crosslinking agent (B) is preferably 30% by mass or more, more preferably 50% by mass or more, further preferably 80% by mass or more, further preferably 90% by mass or more, and preferably 100% by mass or less.

The content of the crosslinking agent (B) is preferably 0.01 part by mass or more, more preferably 0.05 part by mass or more, and even more preferably 0.1 part by mass or more, and is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 1 part by mass or less, relative to 100 parts by mass of the acrylic polymer (a).

The adhesive composition of the present invention contains a silane coupling agent (C). The silane coupling agent is a compound having a functional group and a reactive silicon group, and the silane coupling agent (C) in the present invention has a group capable of reacting with the acrylic polymer (a) and a reactive silicon group. The silane coupling agent (C) preferably has at least a group capable of reacting with an acid group when the acrylic polymer (a) contains a unit derived from the monomer (a3) having an acid group, and preferably has at least a group capable of reacting with a hydroxyl group when the acrylic polymer (a) contains a unit derived from the monomer (a4) having a hydroxyl group. In the case where the acrylic polymer (a) contains both a unit derived from the monomer (a3) having an acid group and a unit derived from the monomer (a4) having a hydroxyl group, two or more compounds each having a group capable of reacting with an acid group and a group capable of reacting with a hydroxyl group may be used in combination, or only a compound having a group capable of reacting with an acid group may be used.

Examples of the group capable of reacting with an acid group include: examples of the group capable of reacting with a hydroxyl group include an epoxy group and an amino group: isocyanate groups, isocyanurate groups, and the like.

As the reactive silicon group, there may be mentioned: trialkoxysilyl groups such as trimethoxysilyl group and triethoxysilyl group; examples of the methyldialkoxysilyl group include a methyldialkoxysilyl group such as a methyldimethoxysilyl group and a methyldiethoxysilyl group, and also include a group obtained by hydrolyzing a part or all of the trialkoxysilyl group and the methyldialkoxysilyl group.

Examples of the silane coupling agent (C) include: silane coupling agents having an epoxy group such as 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane and 3-glycidoxypropyltriethoxysilane; silane coupling agents having an isocyanate group such as 3-isocyanatopropylmethyldimethoxysilane, 3-isocyanatopropyltrimethoxysilane, 3-isocyanatopropylmethyldiethoxysilane and 3-isocyanatopropyltriethoxysilane; silane coupling agents having an amino group such as N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, and 3-aminopropyltriethoxysilane.

The content of the silane coupling agent (C) is preferably 0.0005 parts by mass or more, more preferably 0.001 parts by mass or more, and even more preferably 0.002 parts by mass or more, and is preferably 0.5 parts by mass or less, more preferably 0.1 parts by mass or less, and even more preferably 0.07 parts by mass or less, with respect to 100 parts by mass of the acrylic polymer (a).

The adhesive composition of the present invention preferably comprises a solvent (D). As the solvent (D), one or two or more kinds may be used, and for example, there may be mentioned: aromatic hydrocarbon solvents such as toluene and xylene; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone and methyl ethyl ketone; and aliphatic hydrocarbon solvents such as hexane. Among them, the ester solvent is preferably contained.

The content of the ester solvent in the solvent (D) is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 70% by mass or more, and preferably 100% by mass or less.

The content of the solvent (D) in the adhesive composition is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 50% by mass or more, and preferably 90% by mass or less, more preferably 70% by mass or less, and even more preferably 65% by mass or less.

In the pressure-sensitive adhesive composition of the present invention, in order to maintain low yellowing, the content of the adhesion-imparting resin is preferably reduced, and is preferably less than 10 parts by mass, more preferably 8 parts by mass or less, further preferably 3 parts by mass or less, further more preferably 1 part by mass or less, and preferably 0 part by mass, relative to 100 parts by mass of the acrylic polymer.

The adhesive composition of the present invention may also contain a base (ammonia or the like) or an acid for adjusting the pH; a foaming agent; a plasticizer; a softening agent; an antioxidant; fillers such as glass or plastic fibers, balloon beads, and metal powder; colorants such as pigment-dyes; a pH value adjusting agent; a film-forming auxiliary agent; leveling agent; a tackifier; a hydrophobizing agent; defoaming agents; an acid catalyst; acid generators, and the like as additives.

The adhesive layer can be formed by applying the adhesive composition to a support and drying it. The support may be any substrate such as a release sheet or an adhesive sheet.

As the coating method, a knife coater, a reverse coater, a die coater, a lip die coater, a slit die coater, a gravure coater, a curtain coater, or the like can be used.

The thickness of the adhesive layer is preferably 5 μm or more, more preferably 10 μm or more, further preferably 15 μm or more, and preferably 150 μm or less, more preferably 100 μm or less, further preferably 75 μm or less.

The adhesive film of the present invention (an adhesive sheet or an adhesive tape is also included in the technical scope of the adhesive film of the present invention) has the adhesive layer and the substrate. The substrate may be in any shape such as a film, a sheet, a tape, a plate, or a three-dimensional shape, and examples of the material of the substrate include plastics such as polyester resin, polypropylene resin, polyethylene resin, polyimide resin, vinyl chloride resin, and urethane resin; rubber; non-woven fabrics; a metal foil; paper and the like are preferable, and polyester resin is more preferable. The substrate may be a substrate having a smooth surface, or a substrate having irregularities on the surface, such as a fibrous substrate or a foam substrate.

The thickness of the base material is preferably 0.1 μm or more, and preferably 1,000 μm or less.

The adhesive film obtained from the adhesive composition of the present invention can be highly adhesive while maintaining optical transparency and can improve durability, and is useful as a protective film, particularly a protective film for preventing scattering.

[ examples ]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples, and it goes without saying that the present invention can be carried out by appropriately changing the examples within a range that can be adapted to the gist described above and described later, and these are included in the technical scope of the present invention.

[ Synthesis example 1]

< Synthesis of acrylic resin (A) >

200 parts by mass of n-butyl acrylate, 277 parts by mass of 2-ethylhexyl acrylate, 400 parts by mass of cyclohexyl acrylate, 50 parts by mass of diacetone acrylamide, 70 parts by mass of acrylic acid, 3 parts by mass of 4-hydroxybutyl acrylate and 1000 parts by mass of ethyl acetate were put into a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen gas inlet tube and a thermometer, and the temperature was raised to 70 ℃ while blowing nitrogen gas under stirring. After 1 hour, 10 parts by mass (5% by mass of solid content) of a2, 2' -azobis (2-methylbutyronitrile) solution obtained by dissolving in ethyl acetate in advance was added. Thereafter, the mixture was held at 70 ℃ for 8 hours under stirring, and then the contents were cooled and filtered through a 200-mesh wire gauze to obtain an acrylic resin (A1) having a nonvolatile content of 50 mass%, a viscosity of 100,000 mPas and a weight-average molecular weight of 90 ten thousand.

Synthesis examples 2 to 7 and comparative Synthesis example 1

Acrylic resins (a2) to (a7) and a comparative acrylic resin (a1') were obtained in the same manner as in synthesis example 1, except that the (meth) acrylate monomer (a1), the monomer having a nitrogen atom (a2), the monomer having an acid group (A3), and the monomer having a hydroxyl group (a4) were changed as shown in tables 1 to 3.

[ example 1]

With respect to 100 parts by mass of the acrylic resin (a1) obtained in synthesis example 1, 0.003 part by mass of 3-glycidoxypropyltrimethoxysilane and 0.1 part by mass of an epoxy-based crosslinking agent (fantasy (finetack) hardener EX-50; manufactured by Deisen (DIC) (inc.)) were mixed with stirring in such a manner as to become uniform, thereby obtaining an acrylic adhesive composition.

Examples 2 to 7 and comparative examples 1 to 5

An acrylic pressure-sensitive adhesive composition was obtained in the same manner as in example 1 except that 100 parts by mass of each of the acrylic resins (a2) to (a7) and (a1') obtained in synthesis examples 2 to 7, comparative synthesis example 1 and comparative acrylic resin (a1') were used instead of 100 parts by mass of the acrylic resin (a1) obtained in synthesis example 1, and the respective changes were made as shown in tables 1 to 3.

[ method of processing adhesive film ]

The acrylic pressure-sensitive adhesive composition obtained in the above example was applied to the surface of a polyethylene terephthalate film (release PET50) whose surface was subjected to release treatment and whose thickness was 50 μm so that the film thickness after drying the solvent was 25 μm, and the solvent was volatilized in a dryer at 80 ℃ for 3 minutes, followed by lamination of a PET50 μm film.

[ measuring method of adhesive Strength ]

The adhesive film produced by the above method was cut into a width of 25mm, and the thus-obtained article was used as a test piece. The adherend was a glass plate and was attached to the adherend by a 2kg roller × 2 reciprocations. After 1 hour of the attachment, 180 degree peel strength was measured at 23 ℃ and 50% RH to obtain adhesive strength.

[ method for measuring Wet-Heat resistant adhesive Strength ]

The adhesive film produced by the above method was cut into a width of 25mm, and the thus-obtained article was used as a test piece. The adherend was a glass plate and was attached to the adherend by a 2kg roller × 2 reciprocations. After 1 hour of attachment, the plate was left at 85 ℃ and 85% RH for 250 hours. Thereafter, the sheet was left to stand at 23 ℃ and 50% RH for 1 hour, and then the 180-degree peel strength was measured in the same manner as in the above method to obtain a wet heat resistant adhesive strength.

[ method for measuring holding force ]

The adhesive film produced by the above method was cut into a width of 25mm, and the thus-obtained article was used as a test piece. The stainless steel plate subjected to the mirror finish was attached to the stainless steel plate by 2 reciprocal movements with a 2kg roller having an adhesive area of 25mm × 25 mm. The test piece attached to the stainless steel plate was subjected to a load of 1kg in a direction (shear direction) of 0 ° with respect to the stainless steel plate in an environment of 70 ℃, and the time until the adhesive film slipped off from the adherend was measured, and the retention time was defined as the retention force. When the holding was performed even after 24 hours, the holding time was set to 24 hours or more, and the deviation width from the initial sticking position was measured and described together.

[ method for measuring yellow Change (b) ]

The adhesive film prepared by the above method was attached to a glass plate, and the thus-obtained article was used as a test piece. The test piece was measured for the degree of yellowing (b) according to Japanese Industrial Standard (JIS) K7105 using a light source C, a visual field of view of 2 degrees, and a "spectrocolorimeter" CM-5000d (Konica Minolta Sensing) (manufactured by Konica Minolta Sensing Co., Ltd.).

[ measurement methods of haze and light transmittance ]

The adhesive film prepared by the above method was attached to a glass plate, and the thus-obtained article was used as a test piece. The haze and the light transmittance were measured by a haze meter "NDH 5000" (manufactured by Nippon Denshoku industries Co., Ltd.) on the test piece according to JIS K7361-1.

[ measurement methods of yellowing (b), haze, and light transmittance after Wet Heat resistance test ]

The adhesive film prepared by the method was attached to a glass plate and left to stand at 85 ℃ x 85% RH for 250 hours and 500 hours. Thereafter, another piece of the release PET50 was peeled off, and the yellowing factor (b) was measured in accordance with JIS K7105 in the same manner as described above.

Examples 1 to 10 are examples of the present invention, and can provide durability by increasing the adhesion force while maintaining the optical transparency.

Comparative example 1 and comparative examples 3 to 5 are examples containing no silane coupling agent, and have poor adhesion after resistance to moist heat. Comparative example 2 is an example using a silane coupling agent that does not correspond to the silane coupling agent (C) of the present invention, and is inferior in optical transparency.