JP2011094022A - Adhesive composition and adhesive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive composition for providing an adhesive sheet having improved adhesive performance without using a carboxy group-containing monomer and an adhesive sheet for sticking to a metal surface using the composition. <P>SOLUTION: The water dispersion type adhesive composition comprises an acrylic copolymer as a base polymer. The copolymer is a copolymerization reaction product of a monomer mixture having a composition comprising a prescribed amount of a 1-12C alkyl group-containing alkyl(meth) acrylate, a prescribed amount of an N-vinyl cyclic amide and/or (meth)acrylamide which may contain an N-alkyl group and a prescribed amount of a 2-4C N-hydroxyalkyl group-containing N-hydroxyalkyl(meth)acrylamide and substantially not containing a carboxy group-containing monomer. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a pressure-sensitive adhesive (also referred to as pressure-sensitive adhesive; the same shall apply hereinafter) agent composition and a pressure-sensitive adhesive sheet, and more specifically, a pressure-sensitive adhesive sheet suitable for various uses such as a direct application to a metal surface and the pressure-sensitive adhesive sheet. It is related with the adhesive composition.

  In recent years, pressure-sensitive adhesive sheets have been used in various aspects such as fixing (joining), conveying, protecting, and decorating articles. A typical example of such a pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition (acrylic pressure-sensitive adhesive composition) having an acrylic copolymer as a base polymer. As such an acrylic copolymer, one having a copolymer composition mainly containing alkyl (meth) acrylate (main component) and further containing a carboxyl group-containing monomer such as acrylic acid is used for the purpose of improving adhesive performance. It is done. In consideration of environmental sanitation, the pressure-sensitive adhesive composition containing such an acrylic copolymer is preferably in the form of an aqueous dispersion. Patent documents 1-3 are mentioned as a prior art literature about a water-dispersion type acrylic pressure-sensitive adhesive composition.

JP 2001-131511 A JP-A-5-271634 JP-A-5-105856

  By the way, the pressure-sensitive adhesive sheet used in connection with an article having a part made of a material susceptible to acid (for example, an article having a metal surface such as an electronic component) includes a carboxyl group-containing monomer as described above. When the copolymer composition is used, the carboxyl group in the acrylic copolymer can be a factor that adversely affects the material (for example, corrodes the metal surface). Therefore, the pressure-sensitive adhesive layer provided in the pressure-sensitive adhesive sheet for such applications (especially those directly attached to a metal surface) is based on an acrylic copolymer having a copolymer composition substantially free of carboxyl group-containing monomers. It is desirable to form from the adhesive composition made into a polymer.

  However, a pressure-sensitive adhesive sheet formed using a pressure-sensitive adhesive composition based on an acrylic copolymer that does not use a carboxyl group-containing monomer tends to have insufficient adhesive performance. Therefore, the desired cohesive force (holding force; for example, durability against load in the shear direction (peeling resistance)) was exhibited without using a carboxyl group-containing monomer, and the repulsion resistance (curved surface adhesion) was further enhanced. It would be useful if a water-dispersed pressure-sensitive adhesive composition capable of forming a pressure-sensitive adhesive sheet (hereinafter sometimes referred to as an aqueous emulsion pressure-sensitive adhesive or simply an emulsion pressure-sensitive adhesive) is provided.

  The present invention is a water-dispersed acrylic pressure-sensitive adhesive composition (acrylic emulsion pressure-sensitive adhesive) that can form a pressure-sensitive adhesive sheet with good pressure-sensitive adhesive performance (particularly repulsion resistance and cohesive strength) without substantially using a carboxyl group-containing monomer. It is an object to provide an agent. Another object of the present invention is to provide a pressure-sensitive adhesive sheet for sticking a metal surface using the pressure-sensitive adhesive composition.

According to the present invention, there is provided a water-dispersed pressure-sensitive adhesive composition comprising an acrylic copolymer as a base polymer (a main component in a polymer component). The acrylic copolymer is a copolymerization reaction product of a monomer mixture (also referred to as a monomer component or a starting monomer) that satisfies any of the following conditions (A) to (D).
(A) As the monomer m1, the following formula (I):
CH ₂ = C (R ¹ ) COOR ² (I)
(In Formula (I), R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1 to 12 carbon atoms.); One or more alkyl (meth) acrylates represented by: And 35 to 97.5% by mass of the total monomer component (total amount of all monomers contained in the monomer mixture).
(B) As monomer m2, 2-40 mass% of all the monomer components is contained 1 type or 2 types or more selected from N-vinyl cyclic amide and (meth) acrylamide which may have an N-alkyl group.
(C) As the monomer m3, the following formula (II):
^{_{CH 2 = C (R 3)}} CONHR 4 (II)
(In the formula (II), R ³ is a hydrogen atom or a methyl group, and R ⁴ is a hydroxyalkyl group having 2 to ⁴ carbon atoms); It contains 0.1 to 25% by weight of the total monomer components of (meth) acrylamide.
(D) A monomer having a carboxyl group is substantially not contained.

  Since this pressure-sensitive adhesive composition is based on an acrylic copolymer having a copolymer composition that does not substantially contain a monomer having a carboxyl group (carboxyl group-containing monomer), a pressure-sensitive adhesive formed using the composition. Even when the agent layer is directly attached to a surface made of an acid-sensitive material such as a metal surface, the phenomenon that the carboxyl group corrodes the metal surface can be prevented. Further, as the acrylic copolymer as the base polymer, a carboxyl group-containing monomer is substantially used by using a copolymerization reaction product of a monomer mixture containing a predetermined amount of the monomers m2 and m3 while containing the monomer m1 as a main component. Even without this, a pressure-sensitive adhesive layer having high cohesive force and improved repulsion resistance (as a result, a pressure-sensitive adhesive sheet provided with the pressure-sensitive adhesive layer; the same shall apply hereinafter) can be formed. This pressure-sensitive adhesive layer can exhibit good pressure-sensitive adhesive performance (such as adhesive strength) on various resin surfaces such as ABS (acrylonitrile-butadiene-styrene) resin and acrylic resin. Therefore, according to such a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet suitable for various uses such as a purpose of directly sticking to a metal surface, a purpose of joining a metal part and a resin part, and the like can be formed.

（式（III）中、Ｒ^５は二価の有機基である。）；で表されるＮ−ビニル環状アミドから選択される一種または二種以上である。かかるＮ−ビニル環状アミドの一好適例として、Ｎ−ビニル−２−ピロリドンが挙げられる。
また、モノマーｍ３の好適例としては、Ｎ−（２−ヒドロキシエチル）（メタ）アクリルアミドが挙げられる。なかでもＮ−（２−ヒドロキシエチル）アクリルアミドの使用が好ましい。 In a preferred embodiment of the pressure-sensitive adhesive composition disclosed herein, the monomer m2 is represented by the following formula (III):

(In formula (III), R ⁵ is a divalent organic group.) One or more selected from N-vinyl cyclic amides represented by: A preferred example of such an N-vinyl cyclic amide is N-vinyl-2-pyrrolidone.
Moreover, N- (2-hydroxyethyl) (meth) acrylamide is mentioned as a suitable example of the monomer m3. Of these, the use of N- (2-hydroxyethyl) acrylamide is preferred.

  In a preferred embodiment of the pressure-sensitive adhesive composition disclosed herein, the starting monomer mixture of the acrylic copolymer further contains a silanol group-forming monomer as an optional component in addition to the monomers m1, m2, and m3. The blending amount of the silanol group-forming monomer may be 1 part by mass or less with respect to 100 parts by mass in total of the monomers m1, m2, and m3. The pressure-sensitive adhesive composition having such an acrylic copolymer as a base polymer can form a higher-performance pressure-sensitive adhesive layer. The silanol group-forming monomer has at least one functional group (silanol group-forming functional group) capable of forming a silanol group (Si—OH) in one molecule (preferably two or more, for example, two or three. ) Having a polymerizable compound. Preferable examples of the silanol group-forming functional group include a functional group (such as an alkoxysilyl group) that forms a silanol group by hydrolysis. For example, a silanol group-forming monomer (alkoxysilyl group-containing monomer) having one or two or more alkoxysilyl groups having 1 to 4 carbon atoms in one molecule is preferable.

  In another preferred embodiment, the total amount of the monomers m1, m2, and m3 is about 90% by mass or more of the total monomer components. According to the pressure-sensitive adhesive composition containing an acrylic copolymer, which is a copolymerization reaction product of a monomer mixture having such a composition, as a base polymer, a pressure-sensitive adhesive layer with better quality stability can be formed.

  As described above, the pressure-sensitive adhesive composition disclosed herein includes a copolymerization reaction product of a monomer mixture substantially free of a carboxyl group-containing monomer as a base polymer. It is suitable as a pressure-sensitive adhesive composition used for forming a sheet.

  The pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition disclosed herein can have good cohesive strength and repulsion resistance. In addition, it can exhibit good adhesive performance (adhesive strength etc.) on various resin surfaces such as ABS (acrylonitrile-butadiene-styrene) resin and acrylic resin. Therefore, as another aspect, according to the present invention, a pressure-sensitive adhesive sheet including a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition disclosed herein is provided.

  As still another aspect, according to the present invention, there is provided a pressure-sensitive adhesive sheet for sticking a metal surface, which includes a pressure-sensitive adhesive layer formed using any pressure-sensitive adhesive composition disclosed herein. Such a pressure-sensitive adhesive sheet may be one that does not corrode the metal surface even when attached directly to the metal surface. In addition, the pressure-sensitive adhesive sheet can exhibit good adhesion to the metal surface and can be excellent in cohesive strength and repulsion resistance.

It is sectional drawing which shows typically the example of 1 structure of the adhesive sheet which concerns on this invention. It is sectional drawing which shows typically another structural example of the adhesive sheet which concerns on this invention. It is sectional drawing which shows typically another structural example of the adhesive sheet which concerns on this invention. It is sectional drawing which shows typically another structural example of the adhesive sheet which concerns on this invention. It is sectional drawing which shows typically another structural example of the adhesive sheet which concerns on this invention. It is sectional drawing which shows typically another structural example of the adhesive sheet which concerns on this invention.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

The pressure-sensitive adhesive composition disclosed herein is based on an acrylic copolymer obtained by polymerizing a predetermined monomer mixture (starting monomer) (at least partially polymerized, typically almost completely polymerized). . The monomer mixture contains at least monomers m1, m2, and m3 as essential components.
The monomer m1 is a component constituting the main monomer (main component) of the monomer mixture, and is composed of an alkyl (meth) acrylate represented by the following formula (I), that is, a (meth) acrylic ester of an alkyl alcohol. Here, “(meth) acrylic acid” includes acrylic acid and methacrylic acid. The monomer m1 is the main monomer when the amount of the monomer m1 occupying in all monomer components (when two or more alkyl (meth) acrylates represented by the formula (I) are included, the total amount thereof) is 50. It means that it is at least mass%.

The monomer m1 may be one or more selected from alkyl (meth) acrylates represented by the following formula (I).
CH ₂ = C (R ¹ ) COOR ² (I)
Here, R ¹ in the formula (I) is a hydrogen atom or a methyl group. Moreover, R < ² > in Formula (I) is a C1-C12 alkyl group. The alkyl group may be linear or branched. Specific examples of the alkyl (meth) acrylate represented by the formula (I) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) ) Acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (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, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate And the like. Of these, alkyl (meth) acrylates in which R ² is an alkyl group having 2 to 10 carbon atoms (hereinafter, such a carbon number range may be represented as “C _2-10 ”) are preferable.

In one preferred embodiment, about 70% by mass or more (more preferably about 90% by mass or more) of the total amount of the monomer m1 is such that R ² in the above formula (1) is C _2-10 (more preferably C _4-8 ) Alkyl (meth) acrylate. Substantially all of the monomer m1 may be C _2-10 alkyl (more preferably C _4-8 alkyl) (meth) acrylate. The monomer mixture may have, for example, a composition containing butyl acrylate (BA) alone, a composition containing 2-ethylhexyl acrylate (2EHA) alone, a composition containing two kinds of BA and 2EHA, and the like as monomer m1.

  The content of the monomer m1 can be about 35 to 97.5% by mass (preferably about 50 to 95% by mass) of the total monomer components. In the pressure-sensitive adhesive composition in which the content of the monomer m1 is too smaller than the above range, the pressure-sensitive adhesive performance (adhesiveness, tack, etc.) of the pressure-sensitive adhesive layer formed from the composition tends to be insufficient. On the other hand, if the content of the monomer m1 is more than the above range, the amount of other monomers (monomer m2, m3, etc.) that can be included in the monomer mixture decreases, and it is difficult to achieve both cohesion and repulsion resistance. It tends to be. The content of the monomer m1 may be about 60 to 95% by mass (for example, about 80 to 90% by mass) of all monomer components. The composition of the starting monomer typically corresponds generally to the copolymerization ratio of an acrylic copolymer obtained by polymerizing the starting monomer.

  The monomer mixture further includes a monomer m2 in addition to the monomer m1 as the main monomer. This monomer m2 may be one or more selected from N-vinyl cyclic amide and (meth) acrylamide which may have an N-alkyl group.

  Examples of the N-vinyl cyclic amide include N-vinyl-2-pyrrolidone, N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazine. Examples include 2-one and N-vinyl-3,5-morpholinedione.

  Examples of the (meth) acrylamide that may have the N-alkyl group include (meth) acrylamide; N-alkyl (meth) acrylamide such as N-ethyl (meth) acrylamide and Nn-butyl (meth) acrylamide; N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, N, N-diisopropyl (meth) acrylamide, N, N-di (n-butyl) N, N-dialkyl (meth) acrylamides such as (meth) acrylamide and N, N-di (t-butyl) (meth) acrylamide; and cyclic (meta) such as N- (meth) acryloylmorpholine and N-acryloylpyrrolidine ) Acrylamide; (Meth) acrylamide (for example, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth)) having one or two N-alkyl groups having 1 to 4 carbon atoms (more preferably 1 or 2) The use of acrylamide) is preferred.

（式（III）中、Ｒ^５は二価の有機基である。）で表されるＮ−ビニル環状アミドの使用が好ましい。特に好ましいＮ−ビニル環状アミドとして、Ｎ−ビニル−２−ピロリドンが例示される。 As the monomer m2, the following formula (III):

(In formula (III), R ⁵ is a divalent organic group.) Use of an N-vinyl cyclic amide represented by formula (III) is preferred. A particularly preferred N-vinyl cyclic amide is exemplified by N-vinyl-2-pyrrolidone.

  The content of the monomer m2 can be about 2 to 40% by mass of the total monomer components. The content of the monomer m2 is preferably about 5 to 30% by mass (more preferably about 10 to 20% by mass). If the content of the monomer m2 is too small, the cohesive force tends to be insufficient. If the content of the monomer m2 is too large, it may be difficult to achieve well-balanced adhesive performance (adhesive strength, repulsion resistance, cohesive strength, etc.).

The monomer mixture further includes a monomer m3 in addition to the monomers m1 and m2. The monomer m3 may be one or more selected from N-hydroxyalkyl (meth) acrylamides represented by the following formula (II).
^{_{CH 2 = C (R 3)}} CONHR 4 (II)
Here, R ³ in the formula (II) is a hydrogen atom or a methyl group. Further, ^{R 4} in formula (II) is a hydroxyalkyl group having 2 to 4 carbon atoms. The alkyl group in the hydroxyalkyl group may be linear or branched. Specific examples of N-hydroxyalkyl (meth) acrylamide represented by the formula (II) include N- (2-hydroxyethyl) acrylamide, N- (2-hydroxyethyl) methacrylamide, N- (2-hydroxypropyl). ) Acrylamide, N- (2-hydroxypropyl) methacrylamide, N- (1-hydroxypropyl) acrylamide, N- (1-hydroxypropyl) methacrylamide, N- (3-hydroxypropyl) acrylamide, N- (3- Hydroxypropyl) methacrylamide, N- (2-hydroxybutyl) acrylamide, N- (2-hydroxybutyl) methacrylamide, N- (3-hydroxybutyl) acrylamide, N- (3-hydroxybutyl) methacrylamide, N- (4-Hydroxybutyl) acryl Amide, N-(4-hydroxybutyl) methacrylamide, and the like. Since a pressure-sensitive adhesive layer having a good balance between hydrophilicity and hydrophobicity and an excellent balance of adhesive properties can be formed, N- (2-hydroxyethyl) acrylamide and N- (2- Hydroxyethyl) methacrylamide. In particular, the use of N- (2-hydroxyethyl) acrylamide (HEAA) is preferred. For example, it is preferable that 50% by mass or more (more preferably 70% by mass or more, typically substantially all) of the monomer m3 is HEAA.

  The monomer m3 can function as a component that contributes to improving the cohesiveness of the pressure-sensitive adhesive by the interaction between the molecules of the monomer m3. The monomer m3 content may be approximately 0.1 to 25% by weight of the total monomer components. If the content of the monomer m3 is too smaller than the above range, the pressure-sensitive adhesive layer obtained tends to have insufficient adhesive performance (adhesiveness at high temperature, durability against peeling in the presence of constant stress (cohesive force), etc.). is there. On the other hand, if the content of the monomer m3 is too much larger than the above range, the tackiness and adhesiveness at low temperatures tend to be lowered.

  In a preferred embodiment of the pressure-sensitive adhesive composition disclosed herein, the content of the monomer m3 is about 0.5% by mass or more (typically 0.5 to 20% by mass) of the total monomer components, and more preferably Is about 1% by mass or more (typically about 1 to 15% by mass, for example, about 1 to 10% by mass).

  The total content of the monomers m1, m2, and m3 can be, for example, approximately 70% by mass or more of the total monomer components. The total content is preferably about 90% by mass or more (more preferably about 95% by mass or more) of all monomer components. According to such a pressure-sensitive adhesive composition, an effect that a pressure-sensitive adhesive sheet having good cohesive strength and repulsion resistance can be formed is obtained.

  The total content of the monomers m2 and m3 is preferably about 5.5 to 60% by mass (more preferably 10.5 to 45% by mass) of all monomer components. Thereby, the dispersion stability (emulsion particle stability) of the aqueous dispersion containing the monomer mixture can be enhanced. Therefore, according to the monomer mixture of this embodiment, an acrylic copolymer having desired characteristics (for example, a gel fraction described later) can be suitably prepared by emulsion polymerization.

  In the technique disclosed herein, the monomer mixture is substantially free of carboxyl group-containing monomers. Here, the “carboxyl group-containing monomer” refers to a vinyl monomer (ethylenically unsaturated monomer) having at least one carboxyl group (which may be in the form of an anhydride) in one molecule. Specific examples of such a carboxyl group-containing monomer include ethylenically unsaturated monocarboxylic acids such as (meth) acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid and citraconic acid; maleic anhydride, An anhydride of ethylenically unsaturated dicarboxylic acid such as itaconic anhydride; and the like. In addition, the monomer mixture “substantially does not contain a carboxyl group-containing monomer” means that the monomer mixture does not contain any carboxyl group-containing monomer, or the content thereof is 0.1% by mass or less of the total monomer components. That means.

  It is preferable that the monomer mixture does not substantially contain a carboxyl group-containing monomer but also does not substantially contain a monomer containing an acidic group (sulfonic acid group, phosphoric acid group, etc.) other than the carboxyl group. That is, it does not contain any carboxyl group-containing monomer or other acidic group-containing monomer (which means that it includes a carboxyl group-containing monomer and another acidic group-containing monomer), or the total amount thereof is 0. It is preferable that it is 1 mass% or less. Such a pressure-sensitive adhesive composition is a pressure-sensitive adhesive layer in which an event of corroding the metal surface when it is directly attached to a metal surface is more highly suppressed (that is, the corrosiveness to the metal surface is more highly suppressed). Can be formed.

  In addition to the monomers m1, m2, and m3, the monomer mixture may contain one or more monomers copolymerizable with at least one of these monomers as an optional component. The copolymerizable monomer as an optional component can be, for example, a monomer copolymerizable with alkyl (meth) acrylate as the monomer m1 (except for monomers corresponding to the monomers m1, m2, and m3). Such optional components can be used for the purpose of more appropriately controlling various properties of the pressure-sensitive adhesive, the structure of the acrylic copolymer (for example, mass average molecular weight, gel fraction), and the like.

  As the copolymerizable monomer, for example, a silanol group-forming monomer can be used. The silanol group-forming monomer is a monomer having at least one functional group capable of introducing a crosslinked structure by a silanol group condensation reaction (silanol condensation) into the pressure-sensitive adhesive (pressure-sensitive adhesive layer) formed from the pressure-sensitive adhesive composition. possible. This silanol group-forming monomer can also be grasped as a crosslinking agent (coupling agent). As a suitable example of the above-mentioned silanol group-forming monomer, a silanol group-forming monomer (alkoxysilyl group-containing monomer) having at least one (preferably two or more, for example, two or three) alkoxysilyl groups in one molecule. ). From the viewpoint of copolymerization with an alkyl (meth) acrylate, an acryloyl group and a methacryloyl group in one molecule (hereinafter, the acryloyl group and the methacryloyl group may be collectively referred to as “(meth) acryloyl group”). Silanol group-forming monomers having one or more ethylenically unsaturated groups such as vinyl groups are preferred, and among them, (meth) acryloyl group and alkoxysilyl group (for example, one (meth) acryloyl group) in one molecule And a silanol group-forming monomer having 2 or 3 alkoxysilyl groups).

  Specific examples of such a silanol group-forming monomer include 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltriethoxysilane, 3- Examples include methacryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-acryloxypropylmethyldiethoxysilane. Further, as other silanol group-forming monomers, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyl Examples include triethoxysilane, 10-methacryloxydecyltrimethoxysilane, 10-acryloxydecyltrimethoxysilane, 10-methacryloxydecyltriethoxysilane, 10-acryloxydecyltriethoxysilane, and the like. A particularly preferred silanol group-forming monomer is exemplified by 3-methacryloxypropyltrimethoxysilane.

  Other examples of the copolymerizable monomer include monomers (excluding compounds corresponding to the monomers m2 and m3) containing nitrogen (N) as a constituent atom. Examples of such N-atom-containing monomers include amino group-containing monomers such as aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate; N Monomers having a maleimide skeleton such as cyclohexylmaleimide and N-phenylmaleimide; N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-2-ethylhexylitaconimide, N-laurylitaconimide, N -Itaconic imide monomers such as cyclohexyl leuconconimide; and the like.

Still other examples include monomers having an epoxy group, such as glycidyl (meth) acrylate and allyl glycidyl ether; methoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, methoxyethylene glycol (meth) acrylate, (meth ) Monomers having an alkoxy group such as methoxypolypropylene glycol acrylate; Monomers having a cyano group such as acrylonitrile and methacrylonitrile; Styrene monomers such as styrene and α-methylstyrene; Ethylene, propylene, isoprene, butadiene and isobutylene Α-olefins such as 2-methacryloxyethyl isocyanate and other monomers having isocyanate groups; vinyl ester monomers such as vinyl acetate and vinyl propionate; vinyl ethers Vinyl ether monomers such as tetrahydrofurfuryl (meth) acrylate, (meth) acrylic acid esters having a heterocyclic ring, monomers having halogen atoms such as fluorine (meth) acrylate, siloxanes such as silicone (meth) acrylate, etc. Monomer having a bond; alkyl (meth) acrylate in which R ² in formula (I) is an alkyl group having 21 or more carbon atoms; cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, bornyl (meth) acrylate, isobornyl (meth) ) (Meth) acrylates having an alicyclic hydrocarbon group such as acrylate; phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxydiethyleneglycol (meth) acrylate (Meth) acrylate having an aromatic hydrocarbon group, such as

  Examples of the copolymerizable monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, Polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, Dipentaerythritol hexa (meth) acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, divinylben Emissions, butyl di (meth) acrylate, may be used polyfunctional monomers such as hexyl di (meth) acrylate.

Other examples of the copolymerizable monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4- Hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, [4- (hydroxymethyl) cyclohexyl] hydroxyalkyl (meth) acrylates such as methyl acrylate; R ⁴ in the formula (II) is the number 1 or 5 or more hydroxyalkyl group having a carbon N- hydroxyalkyl (meth) acrylamide; Binirua Call, alkenyl alcohols such as allyl alcohol; etc., include monomers having a hydroxyl group.

  In addition, when using the monomer which has a hydroxyl group as said copolymerizable monomer, from a viewpoint that the effect by use of the monomer m3 can be exhibited more appropriately, it is necessary to use this hydroxyl group-containing monomer in a smaller amount than the monomer m3. preferable. In other words, the amount of the hydroxyl group-containing monomer contained in the monomer mixture exceeds 50% by mass (typically 60% by mass or more, more preferably 75% by mass or more, for example, 90% by mass or more). It is preferable that it is m3. Alternatively, the hydroxyl group-containing monomer contained in the monomer mixture may be substantially only the monomer m3.

  In a preferred embodiment of the pressure-sensitive adhesive composition disclosed herein, at least a silanol group-forming monomer is used as the copolymerizable monomer as an optional component. The amount of the silanol group-forming monomer used (when two or more silanol group-forming monomers are used, the total amount thereof) is about 1 part by mass or less with respect to a total of 100 parts by mass of the monomers m1, m2, and m3. It can be. The amount of the silanol group-forming monomer added is 0.005 to 0.5 parts by mass (preferably about 0.01 to 0.1 parts by mass, for example, about 0.01 to 0.05 parts by mass). preferable.

  The method for polymerizing the monomer mixture is not particularly limited, and conventionally known general polymerization methods (emulsion polymerization, solution polymerization, etc.) can be employed. It is preferable to employ emulsion polymerization because an acrylic copolymer, which is a copolymerization reaction product of the monomer mixture, is obtained in the form of an emulsion and the preparation of a water-dispersed pressure-sensitive adhesive composition is easy. When the monomer mixture is polymerized by a method other than emulsion polymerization (solution polymerization method, etc.), after the appropriate post-treatment step (step of removing the used organic solvent, etc.), the obtained acrylic copolymer is used. A water-dispersed pressure-sensitive adhesive composition can be prepared by dispersing in water using an appropriate emulsifier together with other pressure-sensitive adhesive components (additives and the like).

  The aspect of the emulsion polymerization is not particularly limited. For example, various known monomer supply methods, polymerization conditions (polymerization temperature, polymerization time, polymerization pressure, etc.), materials used ( Polymerization initiators, surfactants, etc.) can be employed as appropriate. For example, as a monomer supply method, any of a batch charging method, a continuous supply (dropping) method, a divided supply (dropping) method, etc., for supplying the entire monomer mixture to the polymerization vessel at a time can be employed. A part or all of the monomer mixture may be preliminarily mixed with water and emulsified, and the emulsion may be supplied into the reaction vessel.

Examples of the polymerization initiator include, but are not limited to, an azo initiator, a peroxide initiator, a substituted ethane initiator, a redox initiator in which a peroxide and a reducing agent are combined, and the like.
As the azo initiator, 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-Methylpropionamidine) disulfate, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] Examples thereof include dihydrochloride and 2,2′-azobis (N, N′-dimethyleneisobutylamidine) dihydrochloride.
Examples of the peroxide initiator include persulfates such as potassium persulfate and ammonium persulfate; benzoyl peroxide, t-butyl hydroperoxide, hydrogen peroxide, and the like.
Examples of substituted ethane-based initiators include phenyl-substituted ethane.
Examples of the redox initiator include a combination of persulfate and sodium bisulfite, a combination of peroxide and sodium ascorbate, and the like.

Although the usage-amount of a polymerization initiator can be suitably selected according to the kind of this initiator, the kind of monomer (composition of a monomer mixture), etc., it is 0.005 normally with respect to 100 mass parts of all monomer components normally. It is appropriate to select from a range of about 1 part by mass.
As a method for supplying the polymerization initiator, substantially the entire amount of the polymerization initiator to be used is put in a reaction vessel before starting the supply of the monomer mixture (typically, an aqueous solution of the polymerization initiator is placed in the reaction vessel). Any of a batch preparation method, a continuous supply method, a divided supply method, and the like can be adopted. From the viewpoint of ease of polymerization operation, ease of process control, etc., for example, a batch charging method can be preferably employed.
The polymerization temperature can be, for example, about 20 to 100 ° C. (typically 40 to 80 ° C.).

  As the emulsifier (surfactant), an anionic emulsifier, a nonionic emulsifier, and the like can be used. Anionic emulsifiers include polyoxyethylene alkyl ether sodium sulfate, polyoxyethylene alkyl phenyl ether ammonium sulfate, polyoxyethylene alkyl phenyl ether sodium sulfate, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, polyoxyethylene alkyl sulfosuccinic acid Sodium and the like are exemplified. Examples of the nonionic emulsifier include polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene polyoxypropylene block polymer, and the like. In addition, radical polymerization with a structure in which a radical polymerizable group (vinyl group, propenyl group, isopropenyl group, vinyl ether group (vinyloxy group), allyl ether group (allyloxy group), etc.) is introduced into these anionic or nonionic emulsifiers. A reactive emulsifier (reactive emulsifier) may be used. Such emulsifiers can be used alone or in combination of two or more. The amount of the emulsifier used (based on solid content) can be, for example, about 0.2 to 10 parts by mass (preferably about 0.5 to 5 parts by mass) with respect to 100 parts by mass of all monomer components.

For the above polymerization, conventionally known various chain transfer agents (which can also be grasped as molecular weight regulators or polymerization degree regulators) can be used as necessary. The chain transfer agent is selected from mercaptans such as dodecyl mercaptan (dodecanethiol), glycidyl mercaptan, 2-mercaptoethanol, mercaptoacetic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. Can be one or more. Of these, use of dodecanethiol is preferable. The amount of chain transfer agent used can be, for example, about 0.001 to 0.5 parts by mass with respect to 100 parts by mass of all monomer components. The amount used may be about 0.02 to 0.05 parts by mass. For example, an acrylic having a good result (a desired mass average molecular weight (for example, about 1 × 10 ⁵ to 2 × 10 ⁶ )) by setting the amount of the chain transfer agent used to about 0.025 to 0.035 parts by mass. Based copolymers) can be realized.

  In the double-sided pressure-sensitive adhesive sheet disclosed herein, a water-dispersed pressure-sensitive adhesive composition used for forming a pressure-sensitive adhesive layer may include a cross-linking agent (typically in the field of water-based pressure-sensitive adhesive compositions), if necessary. , An active ingredient is a crosslinkable compound having two or more crosslinkable functional groups capable of reacting with a functional group contained in the acrylic copolymer in one molecule. Good. For example, a carbodiimide crosslinking agent, a hydrazine crosslinking agent, an epoxy crosslinking agent, an isocyanate crosslinking agent, an oxazoline crosslinking agent, an aziridine crosslinking agent, a metal chelate crosslinking agent, a silane coupling agent, and the like can be used. The crosslinking agent may be water-soluble or oil-soluble. Or the adhesive composition of the composition in which this crosslinking agent is not mix | blended may be sufficient. For example, when a silanol group-forming monomer is used as the optional copolymerizable monomer, the silanol group-forming monomer can also function as a silane-based crosslinking agent. Can be adopted.

  In a preferred embodiment of the pressure-sensitive adhesive composition disclosed herein, the composition contains a tackifier. As the tackifier, for example, one or two or more selected from various tackifier resins such as rosin resins, rosin derivative resins, petroleum resins, terpene resins, phenol resins, and ketone resins are used. be able to.

Examples of the rosin resin include, in addition to rosins such as gum rosin, wood rosin and tall oil rosin, stabilized rosin (for example, stabilized rosin obtained by disproportionating or hydrogenating the rosin), and polymerized rosin (for example, the above-mentioned rosin resin). Rosin multimers, typically dimers), modified rosins (eg, unsaturated acid-modified rosin modified with an unsaturated acid such as maleic acid, fumaric acid, (meth) acrylic acid, etc.), etc. .
Examples of the rosin derivative resin include esterified products, phenol-modified products and esterified products of the rosin resin.
Examples of the petroleum resin include aliphatic petroleum resins, aromatic petroleum resins, copolymer petroleum resins, alicyclic petroleum resins, and hydrides thereof.
Examples of the terpene resins include α-pinene resins, β-pinene resins, aromatic modified terpene resins, and terpene phenol resins.
Examples of the ketone resins include ketone resins obtained by condensation of ketones (for example, aliphatic ketones such as methyl ethyl ketone, methyl isobutyl ketone, and acetophenone; alicyclic ketones such as cyclohexanone and methylcyclohexanone) and formaldehyde. Is done.

Examples of commercially available tackifiers that can be preferably used include trade names “Superester E-865”, “Superester E-865NT”, “Superester E-650”, and “Superester E” manufactured by Arakawa Chemical Industries, Ltd. -786-60 "," Tamanol E-100 "," Tamanol E-200 "," Tamanol 803L "," Pencel D-160 "," Pencel KK "; trade names" YS Polystar S "manufactured by Yashara Chemical Co., Ltd. “YS Polystar T”, “Mighty Ace G”; and the like are exemplified, but not limited thereto. From the viewpoint of enhancing the cohesiveness in a high temperature environment, for example, a tackifier having a softening point of about 140 ° C. or higher (typically 140 to 180 ° C.) can be preferably used. By using a tackifier having a softening point of about 160 ° C. or higher (typically 160 to 180 ° C.), a pressure-sensitive adhesive composition that provides a higher-performance pressure-sensitive adhesive layer can be provided. For example, it is possible to provide a pressure-sensitive adhesive composition in which cohesiveness and other properties (such as adhesive strength and repulsion resistance) in a relatively high temperature (for example, 40 ° C.) environment are well balanced at a higher level. Such tackifiers may be used alone or in combination of two or more.
Such a tackifier is typically used by being added to an emulsion of an acrylic copolymer. The addition mode of the tackifier is not particularly limited. Usually, it is appropriate to add the tackifier in the form of an aqueous dispersion (tackifier emulsion) in which the tackifier is dispersed in water.

The compounding amount of the tackifier can be, for example, about 50 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer in terms of nonvolatile content (solid content). Usually, it is appropriate that the amount is about 40 parts by mass or less. The lower limit of the tackifier content is not particularly limited, but usually good results can be obtained by setting it to about 1 part by mass or more with respect to 100 parts by mass of the polymer component.
In a preferred embodiment of the pressure-sensitive adhesive composition disclosed herein, the compounding amount of the tackifier is about 5 to 40 parts by mass (typically, based on solid content with respect to 100 parts by mass of the acrylic copolymer). About 5 to 30 parts by mass, for example, about 15 to 30 parts by mass).
According to such a pressure-sensitive adhesive composition, in a pressure-sensitive adhesive that has been crosslinked so as to have a gel fraction Gb of a preferable pressure-sensitive adhesive described later or a pressure-sensitive adhesive sheet including the pressure-sensitive adhesive, a plurality of adhesive properties, repulsion resistance, and high-temperature aggregation properties can be obtained. The characteristics can be realized in a balanced manner at a higher level.

  The pressure-sensitive adhesive layer provided in the pressure-sensitive adhesive sheet disclosed herein preferably has a gel fraction Gb of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, for example, about 15 to 90%. The monomer composition (for example, the amount of the monomer m3 used), the molecular weight of the acrylic copolymer, and the pressure-sensitive adhesive layer so that a pressure-sensitive adhesive having such a gel fraction (a pressure-sensitive adhesive after crosslinking in a composition containing a crosslinking agent) is formed. The conditions such as the formation conditions, the type and amount of the crosslinking agent, etc. may be set appropriately. If the gel fraction of the pressure-sensitive adhesive is too low, the cohesive force and repulsion resistance tend to be insufficient. On the other hand, if the gel fraction is too high, the adhesive strength and tack may be easily lowered. With a pressure-sensitive adhesive having a gel fraction in the range of about 20 to 85% (for example, about 25 to 80%), better adhesive performance can be realized. Here, as the “gel fraction Gb (%) of the pressure-sensitive adhesive”, a value measured by the following method is adopted.

[Method for measuring gel fraction (Gb) of adhesive]
The pressure-sensitive adhesive sample (mass W ₁ ) is wrapped in a purse-like shape with a porous polytetrafluoroethylene membrane (mass W ₂ ) having an average pore diameter of 0.2 μm, and the mouth is bound with an octopus thread (mass W ₃ ). This sample-containing purse is soaked in 50 mL of ethyl acetate and left at room temperature (typically 23 ° C.) for 7 days to elute only the sol component in the pressure-sensitive adhesive sample out of the porous membrane. Next, after removing the sample-containing purse and wiping off the ethyl acetate adhering to the outer surface, the sample-containing purse is dried in a dryer at 130 ° C. for 2 hours, and the mass (W ₄ ) of the sample-containing purse is measured. The gel fraction of the pressure-sensitive adhesive can be obtained by substituting each value into the following formula.
Gb (mass%) = [(W ₄ −W ₂ −W ₃ ) / W ₁ ] × 100%

  As the porous polytetrafluoroethylene (PTFE) membrane, a trade name “Nitoflon (registered trademark) NTF1122” available from Nitto Denko Corporation (average pore diameter 0.2 μm, porosity 75%, thickness 85 μm) Or it is desirable to cut the equivalent to about 100 mm × 100 mm. Further, as the octopus yarn, one having a thickness of about 1.5 mm and a length of about 100 mm can be preferably used.

In the pressure-sensitive adhesive composition disclosed herein, a polymer other than the acrylic copolymer can be appropriately blended for the purpose of viscosity adjustment (typically thickening). As such a viscosity adjusting polymer, a polymer having a rubber or elastomer property is preferable. For example, ethylene-vinyl acetate copolymer, acrylic rubber, natural rubber (NR), isoprene rubber (IR), styrene butadiene rubber (SBR), Chloroprene rubber (CR), butyl rubber (IIR), ethylene propylene rubber (EPM, EPDM), polyisobutylene, styrene-ethylene-butylene-styrene copolymer (SEBS), acrylonitrile-butadiene copolymer (NBR), styrene-butadiene -A styrene block copolymer (SBS), a styrene-isoprene-styrene block copolymer (SIS), a polyvinyl alkyl ether (for example, polyvinyl isobutyl ether) etc. can be illustrated. Among these, one kind may be used alone, or two or more kinds may be used in combination.
Such a polymer component can be used, for example, in the form of an emulsion in which the polymer component is dispersed in water and blended with the aqueous emulsion of the acrylic polymer. The content (mixing ratio) of the polymer component is usually about 50 parts by mass or less (for example, about 5 to 50 parts by mass) with respect to 100 parts by mass of the acrylic polymer, based on the nonvolatile content (solid content). Is appropriate. The blending ratio of the polymer component may be 5 parts by mass or less, and may be a pressure-sensitive adhesive composition having a composition that does not substantially contain the polymer component.

  The pressure-sensitive adhesive composition disclosed herein may contain an acid or a base (such as aqueous ammonia) used for the purpose of adjusting pH. Other optional components that can be contained in the composition include aqueous adhesives such as viscosity modifiers, leveling agents, plasticizers, fillers, colorants (pigments, dyes, etc.), stabilizers, preservatives, anti-aging agents, etc. Examples of various additives common in the field of agent compositions are exemplified. As such additives, conventionally known additives can be used in a conventional manner, and do not particularly characterize the present invention.

  The adhesive sheet for metal surface sticking which concerns on this invention is equipped with the adhesive layer formed using one of the adhesive compositions disclosed here. It may be a pressure-sensitive adhesive sheet with a base material in a form in which such a pressure-sensitive adhesive layer is fixedly provided on one or both sides of the sheet-like base material (support) (without intention to separate the pressure-sensitive adhesive layer from the base material), Or the base material-less adhesive sheet of the form which provided this adhesive layer on the support body which has peelability like a release liner (release paper, the resin sheet which gave the peeling process to the surface, etc.) may be sufficient. The concept of the pressure-sensitive adhesive sheet herein may include what are called pressure-sensitive adhesive tapes, pressure-sensitive adhesive labels, pressure-sensitive adhesive films and the like. In addition, the said adhesive layer is not limited to what was formed continuously, For example, the adhesive layer formed in regular or random patterns, such as a dot shape and stripe shape, may be sufficient.

  The pressure-sensitive adhesive sheet disclosed herein has a floating distance (mm) from the acrylic plate and the ABS plate in the repulsion resistance evaluation test described in the examples. 3 mm or less). A pressure-sensitive adhesive sheet having such characteristics is preferable because it has excellent adhesion (curved surface adhesion) to a surface having a step or a curve.

The pressure-sensitive adhesive sheet disclosed herein may have, for example, a cross-sectional structure schematically shown in FIGS. Among these, FIG. 1, FIG. 2 is a structural example of the adhesive sheet with a base material of a double-sided adhesive type. The pressure-sensitive adhesive sheet 11 shown in FIG. 1 is provided with a pressure-sensitive adhesive layer 2 on both surfaces of a substrate 1, and these pressure-sensitive adhesive layers 2 are each protected by a release liner 3 having at least a pressure-sensitive adhesive layer side. It has a configuration. The pressure-sensitive adhesive sheet 12 shown in FIG. 2 has a structure in which a pressure-sensitive adhesive layer 2 is provided on both surfaces of a base material 1 and one of the pressure-sensitive adhesive layers is protected by a release liner 3 having both surfaces as release surfaces. Have. This type of pressure-sensitive adhesive sheet 12 has a configuration in which the pressure-sensitive adhesive sheet 12 is wound to bring the other pressure-sensitive adhesive layer into contact with the back surface of the release liner 3, and the other pressure-sensitive adhesive layer is also protected by the release liner 3. It can be.
3 and 4 are configuration examples of the substrate-less pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet 13 shown in FIG. 3 has a configuration in which both surfaces of the base material-less pressure-sensitive adhesive layer 2 are respectively protected by a release liner 3 having at least a pressure-sensitive adhesive layer side. The pressure-sensitive adhesive sheet 14 shown in FIG. 4 has a configuration in which one surface of the base material-less pressure-sensitive adhesive layer 2 is protected by a release liner 3 whose both surfaces are release surfaces, and when this is wound, the pressure-sensitive adhesive layer 2 The other surface is in contact with the release liner 3 so that the other surface is also protected by the release liner 3.
5 and 6 are configuration examples of a single-sided adhesive type adhesive sheet with a substrate. The pressure-sensitive adhesive sheet 15 shown in FIG. 5 is provided with a pressure-sensitive adhesive layer 2 on one side of a substrate 1, and the release liner is such that the surface (adhesive surface) of the pressure-sensitive adhesive layer 2 is at least the pressure-sensitive adhesive layer side. 3 is protected. The adhesive sheet 16 shown in FIG. 6 has a configuration in which the adhesive layer 2 is provided on one surface of the substrate 1. The other surface of the substrate 1 is a release surface, and when the pressure-sensitive adhesive sheet 16 is wound, the pressure-sensitive adhesive layer 2 comes into contact with the other surface, and the surface (adhesive surface) of the pressure-sensitive adhesive layer is the other surface of the substrate 1. It can be configured to be protected by the surface.

  Examples of the base material constituting the pressure-sensitive adhesive sheet include plastic films such as polypropylene film, ethylene-propylene copolymer film, polyester film, and polyvinyl chloride film; foam base materials such as polyurethane foam and polyethylene foam; Paper, crepe paper, Japanese paper, etc .; cotton cloth, soft cloth, etc .; polyester nonwoven fabric, vinylon nonwoven fabric, etc .; aluminum foil, copper foil, etc. metal foil; etc. Can be used. As the plastic film, any of an unstretched film and a stretched (uniaxially stretched or biaxially stretched) film can be used. Moreover, surface treatment, such as application | coating of a primer and corona discharge treatment, may be given to the surface in which an adhesive layer is provided among base materials. The thickness of the substrate can be appropriately selected according to the purpose, but is generally about 10 μm to 500 μm (typically 10 μm to 200 μm).

  The pressure-sensitive adhesive layer is formed, for example, by applying (typically applying) any pressure-sensitive adhesive composition disclosed herein to a support (base material or release liner) and drying the composition. Can be done. Such a pressure-sensitive adhesive layer forming method requires an acrylic copolymer obtained by polymerizing a monomer mixture at least partially (preferably almost completely) by an appropriate polymerization method (typically thermal polymerization method) in advance. The pressure-sensitive adhesive composition can be preferably applied to a pressure-sensitive adhesive composition in a form in which a crosslinking agent, an additive, and the like used in accordance with are dispersed in an aqueous solvent (water and a mixed solvent containing water as a main component, typically water). In the case of a pressure-sensitive adhesive composition containing a cross-linking agent, an appropriate cross-linking treatment may be performed simultaneously or separately as necessary in addition to the drying.

  Application of the pressure-sensitive adhesive composition can be performed by using a conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, or a spray coater. From the viewpoint of promoting the crosslinking reaction and improving the production efficiency, the pressure-sensitive adhesive composition is preferably dried under heating. Although depending on the type of support to which the composition is applied, for example, a drying temperature of about 40 to 150 ° C. can be employed. In the case of a pressure-sensitive adhesive sheet with a base material, the pressure-sensitive adhesive composition may be directly applied to the base material to form a pressure-sensitive adhesive layer, and a pre-formed pressure-sensitive adhesive layer is laminated on the base material (transfer). May be.

  The thickness of the pressure-sensitive adhesive layer is not particularly limited, but usually, for example, good pressure-sensitive adhesive performance (for example, adhesive strength) can be realized by setting it to about 10 μm or more (preferably about 20 μm or more, more preferably about 30 μm or more). In general, it is appropriate to set the thickness to about 400 μm or less (typically about 200 μm or less, for example, about 100 μm or less).

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples. In the following description, “parts” and “%” are based on mass unless otherwise specified.

<Example 1>
86 g of butyl acrylate (BA), 201 g of 2-ethylhexyl acrylate (2EHA), 43 g of N-vinyl-2-pyrrolidone (NVP), 4 g of N- (2-hydroxyethyl) acrylamide (HEAA), and 3-methacryloxypropyltrimethoxy An oil layer composed of 0.1 g of silane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “KBM-503”; silane coupling agent) is added to an aqueous emulsifier solution (trade name “Ramtel E118B”, manufactured by Kao Corporation); A monomer emulsion was prepared by mixing with 26 g of an aqueous solution of sodium oxyethylene alkyl ether sodium sulfate) and 119 g of distilled water.

  In a reaction vessel equipped with a cooling tube, a nitrogen introducing tube, a thermometer, a dropping tube and a stirrer, 120 g of ion exchange water and 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydride 0.34 g of a rate (trade name “VA-057” manufactured by Wako Pharmaceutical Co., Ltd.) was added, and the mixture was purged with nitrogen at 60 ° C. for 1 hour while stirring. The monomer emulsion was gradually added dropwise over 3 hours while maintaining this at 60 ° C. After completion of dropping, the mixture was further stirred at 60 ° C. for 4 hours to obtain an aqueous dispersion of an acrylic copolymer (emulsion adhesive).

  This emulsion adhesive was applied to the first release liner (polyethylene terephthalate (PET) film (product name “MRF38”, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) having a thickness of 38 μm, the coated surface being peeled with silicone)). And dried at 130 ° C. for 3 minutes to form a pressure-sensitive adhesive layer having a thickness of 60 μm. On this pressure-sensitive adhesive layer, a second release liner (Mitsubishi Chemical Polyester Co., Ltd., trade name “MRN38”) was laminated so that the peeled surface was in contact with the pressure-sensitive adhesive layer, and the temperature was further increased to 50 ° C. The substrate-less double-sided PSA sheet was obtained by holding for 2 days (48 hours).

<Example 2>
For the emulsion adhesive of Example 1, rosin-based tackifier resin (trade name “Superester E-865”, manufactured by Arakawa Chemical Industries, Ltd.) is added to 100 parts of the acrylic copolymer contained in the emulsion. 20 parts in terms of conversion was added. Others were the same as in Example 1, and a double-sided pressure-sensitive adhesive sheet without substrate was obtained.

<Example 3>
An oil layer consisting of 275 g of 2EHA, 58 g of NVP, and 0.1 g of lauryl mercaptan (chain transfer agent), 26 g of an emulsifier aqueous solution (same as in Example 1), 0.1 g of the above-mentioned trade name “KBM-503”, and 119 g of distilled water To prepare a monomer emulsion. A substrate-less double-sided pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that this monomer emulsion was used.

<Example 4>
To the emulsion adhesive obtained in Example 3, 20 parts of the above-mentioned trade name “Superester E-865” in terms of solid content was added to 100 parts of the acrylic copolymer contained in the emulsion. Others were the same as in Example 3, and a double-sided pressure-sensitive adhesive sheet without substrate was obtained.

<Example 5>
An oil layer composed of 318 g of butyl acrylate (BA) and 0.1 g of lauryl mercaptan (chain transfer agent) was mixed with 26 g of an emulsifier aqueous solution (same as in Example 1), 15 g of acrylic acid (AA), 0.1 g of the above-mentioned trade name “KBM-503”. And a water layer composed of 119 g of distilled water to prepare a monomer emulsion. A substrate-less double-sided pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that this monomer emulsion was used.

<Example 6>
To the emulsion adhesive obtained in Example 5, 20 parts of the above-mentioned trade name “Superester E-865” in terms of solid content was added to 100 parts of the acrylic copolymer contained in the emulsion. Others were the same as in Example 5, and a double-sided pressure-sensitive adhesive sheet without a substrate was obtained.

  Table 1 shows the monomer mixture composition of the emulsion adhesives of Examples 1 to 6 and the amount of tackifier used. Table 2 shows the results of the following evaluations performed on the pressure-sensitive adhesive sheets of Examples 1 to 6.

[Gel fraction of adhesive layer]
About each adhesive sheet, the gel fraction of the adhesive layer was measured according to the above-mentioned method. As a sample for measuring the gel fraction, one obtained by cutting each adhesive sheet into an area equivalent to 17 cm ² and removing both release liners was used.

[Metal surface corrosion]
A 50 μm-thick PET film (without a release treatment) was bonded to the first adhesive surface exposed by removing the first release liner from each adhesive sheet. Next, the second adhesive surface exposed by removing the second release liner was bonded to a copper foil having a thickness of 35 μm to prepare a sample. After storing this sample in an environment of 60 ° C. and RH (relative humidity) 95% for 4 days, the state of the copper foil surface (the degree of discoloration compared to the color before storing in the above environment) was changed. The metal surface corrosivity was evaluated in the following two stages by visual inspection.
Low: No significant discoloration was observed.
High: Significant discoloration was observed.

[Adhesive force]
[Against acrylic]
A 50 μm-thick PET film (without release treatment) was bonded to the first adhesive surface exposed by removing the first release liner of each adhesive sheet. This was cut into a strip with a width of 20 mm, and the second adhesive surface exposed by removing the second release liner was cleaned on the surface with isopropanol (made by Mitsubishi Rayon Co., Ltd., trade name “Acrylite Plate 001”). ]) A sample that was bonded to (adhered body) and pressure-bonded by reciprocating a 2 kg roller was used as a sample. After holding this sample in an environment of 23 ° C. and RH 50% for 30 minutes, using a tensile tester, in accordance with JIS Z 0237, in an environment of 23 ° C. and RH 50%, at a tensile speed of 300 mm / min. Then, the 180 ° peeling adhesive strength with respect to the acrylic plate was measured as an initial value of the acrylic adhesive strength (N / 20 mm).
A sample prepared in the same manner was held in an environment of 40 ° C. and RH 50% for 2 days, then in an environment of 23 ° C. and RH 50% for 30 minutes, and then peeled and adhered to the acrylic plate by 180 ° in the same manner as described above. The force was measured as a normal value for the acrylic adhesive strength (N / 20 mm).
[Against ABS]
The initial stage of ABS adhesive strength (N / 20mm) was the same as the measurement of acrylic adhesive strength except that an ABS plate (made by Shin-Kobe Electric Machinery Co., Ltd., trade name “Kobe Poly Sheet ABS plate”) was used instead of the acrylic plate. Values and normal values were measured.

[Repulsion resistance]
[Against acrylic]
Each adhesive sheet was cut to a size of 10 mm x 90 mm, and an aluminum plate (thickness 0.5 mm) cut to the same size was bonded to the exposed first adhesive surface by peeling off the first release liner. Was made. After holding this test piece in an environment of 23 ° C. and RH 50% for one day, it is wound around a 67 mm diameter round bar (the aluminum piece side is the inside) and pressed for about 10 seconds to bend into a 150 mm diameter arc. It was. The second adhesive surface exposed by peeling off the second release liner from the test piece was pressure-bonded to an acrylic plate (adhered body) whose surface was washed with isopropanol so as not to float using a laminator. After maintaining this in an environment of 23 ° C. and RH 50% for 24 hours, the distance (mm) at which each end of the test piece lifted from the surface of the acrylic plate was measured. The values in Table 2 represent the total values at both ends.
[Against ABS]
The distance (mm) at which the end of the test piece was lifted from the surface of the ABS plate in the same manner as the repulsion resistance measurement for the acrylic plate, except that an ABS plate whose surface was washed with isopropanol was used instead of the acrylic plate. Was measured.

[40 ° C holding power]
A PET film having a thickness of 50 μm was bonded to the first adhesive surface exposed by removing the first release liner from each adhesive sheet. This was cut into 10 mm × 100 mm to prepare a test piece. The second adhesive surface exposed by peeling off the second release liner from the above test piece was attached to a bakelite plate (adhered body) whose surface was washed with toluene with an adhesive area of 10 mm × 20 mm, and a 2 kg roller. Was reciprocated once and crimped. After holding this at 40 ° C. for 30 minutes, the bakelite plate was suspended, and a load of 500 g was applied to the free end of the test piece. According to JIS Z 0237, the test piece was left in an environment of 40 ° C. for 2 hours in a state where the load was applied, and the displacement distance (mm) of the test piece from the initial attachment position after 2 hours was measured. In Table 2, “falling” indicates that the test piece dropped before 2 hours passed.

  As shown in Tables 1 and 2, the pressure-sensitive adhesive sheets according to Examples 5 and 6 using a carboxyl group-containing monomer (acrylic acid) all showed high metal surface corrosivity. On the other hand, among the pressure-sensitive adhesive sheets of Examples 1 to 4 that did not use the carboxyl group-containing monomer, the pressure-sensitive adhesive sheet of Example 3 using a monomer mixture not containing the monomer m3 was agglomerated although the metal surface corrosivity was remarkably suppressed. Both the force (40 ° C. holding force) and the repulsion resistance were significantly reduced. In the pressure-sensitive adhesive sheet of Example 4 in which the tackifier resin was added to the pressure-sensitive adhesive layer of Example 3, the repulsion resistance was remarkably improved, but the cohesive force remained insufficient. In contrast, the pressure-sensitive adhesive sheets of Examples 1 and 2 that do not use a carboxyl group-containing monomer and use a monomer mixture that includes both the monomer m2 and the monomer m3 in addition to the monomer m1 have metal surface corrosivity. First, both the acrylic plate and the ABS plate exhibited a sufficient adhesive force in both the initial state and the normal state, and exhibited a high cohesive force (holding force). In particular, when compared with the pressure-sensitive adhesive sheet of Example 3, the repulsion resistance was remarkably improved. Thus, according to the pressure-sensitive adhesive sheets of Examples 1 and 2 (particularly the pressure-sensitive adhesive sheet of Example 1), in addition to the low corrosiveness to the metal surface, the pressure-sensitive adhesive sheets of Examples 5 and 6 are all adhesive force, cohesive force and repulsion resistance. Excellent adhesion performance of approximately the same or higher was realized at the same time. That is, according to the pressure-sensitive adhesive sheets of Examples 1 and 2 to which the present invention is applied, while maintaining various other pressure-sensitive adhesive performances (here, pressure-sensitive adhesive force, cohesive strength and repulsion resistance) at a high level, the corrosiveness to the metal surface is maintained. It could be significantly reduced.

  As mentioned above, although the specific example of this invention was demonstrated in detail, these are only illustrations and do not limit a claim. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

1: Base material 2: Adhesive layer 3: Release liner 11, 12, 13, 14, 15, 16: Adhesive sheet

Claims (8)

A water-dispersed pressure-sensitive adhesive composition having an acrylic copolymer as a base polymer,
The acrylic copolymer is
The following conditions:
As the monomer m1, the following formula (I):
CH ₂ = C (R ¹ ) COOR ² (I)
(In Formula (I), R ¹ is a hydrogen atom or a methyl group, and R ² is an alkyl group having 1 to 12 carbon atoms.); One or more alkyl (meth) acrylates represented by: Containing 35-97.5% by weight of the total monomer components;
2 to 40% by mass of the total monomer components including one or more selected from the group consisting of N-vinyl cyclic amide and (meth) acrylamide which may have an N-alkyl group as the monomer m2;
As the monomer m3, the following formula (II):
^{_{CH 2 = C (R 3)}} CONHR 4 (II)
(In the formula (II), R ³ is a hydrogen atom or a methyl group, and R ⁴ is a hydroxyalkyl group having 2 to ⁴ carbon atoms); Containing 0.1 to 25% by weight of total monomer components; and
Substantially free of monomers having carboxyl groups;
A water-dispersed pressure-sensitive adhesive composition, which is a copolymerization reaction product of a monomer mixture satisfying any of the above.   The water-dispersed pressure-sensitive adhesive composition according to claim 1, wherein the monomer mixture contains a silanol group-forming monomer in a proportion of 1 part by mass or less with respect to a total of 100 parts by mass of the monomers m1, m2, and m3. The monomer m2 is represented by the following formula (III):

(Wherein, R ⁵ is a divalent organic group); or a water-dispersed pressure-sensitive adhesive composition according to claim 1 or 2, which is one or more N-vinyl cyclic amides represented by: .   The water-dispersed pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the monomer m3 is N- (2-hydroxyethyl) (meth) acrylamide.   The composition according to any one of claims 1 to 4, wherein a total content of the monomers m1, m2, and m3 is 90% by mass or more of all monomer components.   The composition as described in any one of Claim 1 to 5 used for the adhesive sheet for affixing directly on a metal surface.   An adhesive sheet provided with the adhesive layer formed using the composition as described in any one of Claims 1-5.   A pressure-sensitive adhesive sheet for sticking a metal surface, comprising a pressure-sensitive adhesive layer formed using the composition according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive layer is directly attached to a metal surface.

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