JP5301779B2 - Adhesive composition and adhesive sheet - Google Patents

Description

The present invention is a resin composition for pressure-sensitive adhesives, which is mainly composed of an acrylic polymer obtained by copolymerizing a (meth) acrylic acid alkyl ester as a main component, and has less outgassing. The present invention relates to a pressure-sensitive adhesive composition and a pressure-sensitive adhesive sheet using a resin composition , which are excellent in pressure-sensitive adhesive properties such as strength and corrosion resistance.

  Conventionally, pressure-sensitive adhesive compositions have been frequently used in various fields. In the above-mentioned pressure-sensitive adhesive composition, those that exhibit strong adhesiveness are usually provided with an adhesive force by introducing a large amount of acid, but a type that does not use an acid due to problems such as corrosion of the adhesive object (acid-free) ) Is also demanded. In particular, for electronic component applications, there is a demand for a pressure-sensitive adhesive composition that does not cause generation of gas that causes malfunction and corrodes an electronic member and causes appearance defects.

The information label used for bonding to the electronic member, particularly the precision electronic member, and the adhesive and adhesive sheet for fixing the electronic member are premised on not generating foreign matters such as dust. Low boiling volatile components and residual solvent-derived gas (outgas) contained in the sheet are also a kind of foreign matter, and these cause malfunction of the electronic member. That is, since the inside of an electronic device provided with a precise electronic member is in a high temperature and high humidity atmosphere when used, it is necessary to suppress the amount of gas generated in such an atmospheric state. As a method for reducing the amount of such outgas generation, a method of using an acrylic polymer containing no acid group as an adhesive has been proposed (see Patent Document 1).
JP 2003-268335 A

  However, in the pressure-sensitive adhesive using an acrylic polymer into which a functional group other than an acid group such as a hydroxyl group is introduced as in Patent Document 1, a low outgas type pressure-sensitive adhesive sheet is obtained, but no acid group is introduced. Therefore, the adhesive strength was insufficient.

The present invention has been made in view of such circumstances. In addition to the fact that the generation amount of gas that causes malfunction of the electronic member, particularly the generation amount of gas in a high-temperature and high-humidity atmosphere is small, the precision electronic member without causing corrosion poor appearance and adhesive properties, especially a resin composition excellent in adhesiveness and tackiness to metal, in particular pressure-sensitive adhesive composition using an adhesive resin composition as well as providing the pressure-sensitive adhesive sheet For that purpose.

In order to achieve the above object, the present invention provides an ethylenically unsaturated monomer having two or more nitrogen atom-containing heterocyclic structures that do not open a ring as a copolymerizable monomer component constituting an acrylic copolymer. We found it important to use.
That is, the present invention is an adhesive composition that does not contain an acid group-containing unsaturated monomer as a copolymerization component, and is mainly composed of a copolymer comprising the following components (A) to (C): A copolymer in which the structural unit derived from the component (C) in the copolymer is 5 to 30% by weight of the copolymer composed of the components (A) to (C) , and a crosslinking agent. The pressure-sensitive adhesive composition is the first gist.
(A) Alkyl ester of (meth) acrylic acid.
(B) Functional group-containing unsaturated monomers (excluding acid group-containing unsaturated monomers).
(C) An ethylenically unsaturated monomer having two or more nitrogen atom-containing heterocyclic structures that are not ring-opened.

Moreover, this invention makes a 2nd summary the adhesive sheet by which an adhesive layer is formed in the base-material surface using the said adhesive composition.

  That is, the present inventors have intensively studied to obtain a resin composition that suppresses the amount of gas generated in a high-temperature and high-humidity atmosphere, does not cause appearance defects due to corrosion, and has excellent adhesion to metal. Piled up. And first, as a result of repeated research to investigate the cause of gas generation, acrylic acid, which is a monomer having a crosslinkable functional group of an acrylic pressure-sensitive adhesive, is the cause of increasing corrosion and outgassing of metal members I got the knowledge that it has become. And based on this knowledge, as a result of further research, a copolymer having a specific proportion of structural units derived from each of the specific monomers substantially without using acrylic acid and Then, since it does not contain an acid group, it is possible to reduce the amount of gas generated, corrosion of metals such as electronic members is suppressed, and excellent metal adhesion and good tack force can be obtained, The present invention has been reached.

Thus, the present invention, the (A) ~ (C) with Ingredient, structural units derived to the component (C) is a resin composition mainly composed of a copolymer comprising a certain percentage . For this reason, it has excellent adhesive properties such as metal adhesion and tack force, and also suppresses gas generation, especially in high-temperature and high-humidity atmospheres, and prevents the appearance of adherends from being damaged due to corrosion. Is done. Therefore, when the pressure-sensitive adhesive composition containing the above-mentioned resin composition and containing a crosslinking agent is used as a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is formed on a base material, operation failure or adhesion caused by the generated gas. Since the appearance defect due to body corrosion is prevented, it is suitably used for electronic member applications.

  When the ethylenically unsaturated monomer having two or more nitrogen atom-containing heterocyclic structures that are not ring-opened, which is the component (C), is an ethylenically unsaturated group-containing imidazole compound, the amount of the metal is further increased. Adhesive properties such as adhesion and tack force, and an effect of improving corrosion resistance can be obtained.

  Further, when the functional group-containing unsaturated monomer as the component (B) is an unsaturated monomer having at least one of a hydroxyl group and an amide group, the resin composition is excellent in copolymerizability and excellent in physical properties. Is obtained.

The resin composition according to the present invention comprises a (meth) acrylic acid alkyl ester (component A), a functional group-containing unsaturated monomer (component B), and two or more nitrogen atom-containing heterocyclic structures that do not open a ring. It is copolymerized by using an ethylenically unsaturated monomer (C component) and an unsaturated monomer (D component) other than the B component copolymerizable with the A to C components as necessary. A copolymer is the main component.

  In the present invention, the “main component” means that the copolymer component occupies 50% by weight or more of the entire pressure-sensitive adhesive resin composition. And in this invention, the structural unit derived | led-out from each component of said A-D component means the structural unit provided with the basic structure of each component of said A-D component in a copolymer. In the present invention, (meth) acrylic acid is acrylic acid or methacrylic acid, (meth) acryl is acrylic or methacrylic, (meth) acryloyl is acryloyl or methacryloyl, and (meth) acrylate is acrylate or Each means methacrylate.

  Although it does not specifically limit as said (meth) acrylic-acid alkylester (A component), Usually, it is preferable that it is a (meth) acrylic-acid alkylester which has a C1-C18 alkyl group, for example, (meth) Methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth ) Octyl acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, ( (Meth) acrylic acid lauryl, (meth) acrylic acid stearyl, (meth) acrylic acid Njiru, (meth) (meth) acrylic acid esters such as isobornyl acrylate and the like. These may be used alone or in combination of two or more. Especially, it is preferable to use the (meth) acrylic-acid alkylester which has C4-C8 alkyl groups, such as butyl acrylate and acrylate 2-ethylhexyl, from a viewpoint of copolymerizability and versatility.

  In general, the structural unit derived from the component A is preferably set to 50 to 94.9% by weight of the copolymer composed of the components A to D when the components A to C and the component D are included. More preferably, it is 68-94.5 weight%. That is, if the structural unit derived from the component A is too small, the versatility tends to be inferior, and if it is too large, the content of other copolymer components, particularly the functional group-containing unsaturated monomer, is insufficient, This is because there is a tendency to have insufficient cohesive strength. In addition, the ratio with respect to the whole copolymer which consists of A-C component or A-D component of the structural unit derived | led-out from said A component is the compounding ratio of A component in the whole copolymerizable monomer component at the time of copolymer preparation. It is equivalent. Hereinafter, the same applies to the components B to D.

  The functional group-containing unsaturated monomer (component B) is not particularly limited as long as it is a monomer that usually has one functional group capable of reacting with a crosslinking agent. For example, (meth) acrylic acid 2-hydroxyethyl, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, polycaprolactone modified products of 2-hydroxyethyl (meth) acrylate, etc. Hydroxyl group-containing monomer; epoxy group-containing monomer such as glycidyl (meth) acrylate and alicyclic epoxy group-containing monomer; (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide N, N-dibutyl (meth) acrylamide, N-methylolacrylamide, N-methoxy Amide group-containing monomers such as til acrylamide, N- (n-butoxymethyl) acrylamide, dimethylaminopropyl acrylamide and t-butyl acrylamide; dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl ( Examples thereof include amino group-containing monomers such as (meth) acrylamide; isocyanate group-containing monomers such as 2- (meth) acryloyloxyethyl isocyanate and (meth) acryloyl isocyanate. These may be used alone or in combination of two or more. Especially, from the point of copolymerizability, versatility, etc. containing a hydroxyl group having a C2-C4 hydroxyalkyl group such as 2-hydroxyethyl (meth) acrylate and 4-hydroxylbutyl (meth) acrylate ( Amide group-containing monomers such as (meth) acrylate and (meth) acrylamide are preferably used.

  The structural unit derived from the component B is preferably set to 0.1 to 10% by weight of the copolymer composed of the components A to C or the components A to D. More preferably, it is 0.5 to 7% by weight. That is, when the structural unit derived from the component B is too small, the pressure-sensitive adhesive composition tends to have insufficient cohesive force, and when it is excessive, the cohesive force becomes excessively high and good adhesive properties are obtained. This is because it tends to be difficult. In addition, the ratio of the structural unit derived from the B component to the entire copolymer is based on the blending ratio of the B component in the entire copolymerizable monomer component at the time of preparing the copolymer.

  As said ethylenically unsaturated monomer (C component) which has a 2 or more nitrogen atom containing heterocyclic structure which is not ring-opened, the 5- to 8-membered ring structure which has 2-3 nitrogen atoms normally is 1-3. This is an ethylenically unsaturated monomer having a number of monomers and maintaining a heterocyclic structure even after formation of a copolymer. Specific examples of these monomers include N-vinylimidazole, N- (meth) acryloylpyrazole, N- (meth) acryloylpyrazoline, N-allylimidazole and the like. These may be used alone or in combination of two or more. Of these, ethylenically unsaturated monomers having a five-membered heterocyclic structure having two nitrogen atoms are preferred from the viewpoints of metal adhesion, tack, corrosion resistance, and modification of adhesive properties. -Ethylenically unsaturated group-containing imidazole compounds such as vinylimidazole and N-allylimidazole are preferably used.

  The structural unit derived from the C component needs to be set to 5 to 30% by weight of the copolymer composed of the A to C components or the A to D components. More preferably, it is 5 to 20% by weight. That is, if the structural unit derived from the component C is less than 5% by weight, there is little contribution to metal adhesion, and sufficient adhesive properties cannot be obtained. If it exceeds 30% by weight, a thickening phenomenon occurs during the polymerization reaction in resin preparation. This is because it is difficult to obtain a copolymer. In addition, the ratio of the structural unit derived from the C component to the entire copolymer is based on the mixing ratio of the C component in the entire copolymer monomer component at the time of preparing the copolymer.

  Examples of the unsaturated monomer (D component) other than the B component copolymerizable with the A to C components include ethylenically unsaturated monomers such as styrene, vinyl acetate and (meth) acrylonitrile. These may be used alone or in combination of two or more.

  The structural unit derived from the component D is preferably set to 0 to 10% by weight of the copolymer composed of the components A to D. More preferably, it is 5% by weight or less. That is, if there are too many structural units derived from the component D, the pressure-sensitive adhesive may become too hard, and it is difficult to obtain good pressure-sensitive adhesive properties. In addition, the ratio with respect to the whole copolymer which consists of an A-D component of the structural unit derived | led-out from the said D component is based on the mixture ratio of D component in the whole copolymer monomer component at the time of copolymer preparation.

In the resin composition according to the present invention, the main component (meth) acrylic copolymer is prepared by blending the above-mentioned components A to C or components A to D at a predetermined ratio and copolymerizing them according to various polymerization methods. can do. The polymerization method is not particularly limited and includes conventionally known methods such as solution polymerization method, bulk polymerization method, emulsion polymerization method, suspension polymerization method and the like. For example, the components A to C or components A to D are dissolved in a polymerization solvent in a predetermined ratio, and a polymerization initiator is added thereto, and the temperature is raised to 70 to 85 ° C. while stirring to perform a polymerization reaction. Furthermore, a (meth) acrylic copolymer can be prepared by adding a polymerization initiator to this and advancing the polymerization reaction.

  The acrylic copolymer obtained in the present invention is produced by a method well known to those skilled in the art such as radical polymerization of the above-mentioned components A to C or components A to D in an organic solvent at a predetermined ratio.

  As the polymerization initiator, various conventionally known polymerization initiators can be used. For example, azo initiators such as azobisisobutyronitrile and 4,4′-azobis (4-cyanovaleric acid), benzoyl Examples thereof include peroxide radical polymerization initiators such as peroxide and lauroyl peroxide. These may be used alone or in combination of two or more. The polymerization solvent is not particularly limited, and examples thereof include aromatic hydrocarbons such as toluene and xylene; esters such as methyl acetate, ethyl acetate, and butyl acetate; n-propyl alcohol, isopropyl alcohol, and the like. Aliphatic alcohols; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone can be used, which can be appropriately selected according to the monomer used. These solvents may be used alone or in combination.

The resin composition according to the present invention mainly composed of this manner have been fabricated (meth) acrylic copolymer is very useful as an adhesive resin composition, in the resin composition, cross-linking A pressure-sensitive adhesive composition is obtained by blending the agent. In addition, as a crosslinking method, from the viewpoint of reproducibility, product stability, and versatility, there is usually a method in which a crosslinking agent is added to the crosslinking resin composition (adhesive resin composition) to cause a crosslinking reaction. it may be subjected to electron beam irradiation or heat treatment.

  Then, the pressure-sensitive adhesive composition is subjected to a crosslinking treatment under predetermined conditions.

  Examples of the cross-linking treatment method include cross-linking by electron beam irradiation, cross-linking by heating, etc. Among them, from the viewpoint of reproducibility, product stability, and versatility, heat cross-linking treatment using a cross-linking agent is preferable. Used.

  The cross-linking agent is not particularly limited. For example, epoxy-based, metal salt, metal aldehyde, aldehyde-based compound, non-amino resin-based amino compound, urea-based, isocyanate-based, metal chelate-based, melamine-based, aziridine Examples thereof include cross-linking agents used in ordinary pressure-sensitive adhesives. Especially, tolylene diisocyanate-3 functional alcohol adduct, isophorone diisocyanate-3 functional alcohol adduct, hexamethylene diisocyanate-3 functional alcohol adduct, tolylene diisocyanate trimer, isophorone diisocyanate trimer, hexamethylene Isocyanate-based crosslinking agents such as diisocyanate trimers and burette-type hexamethylene diisocyanate trimers are preferably used from the viewpoint of versatility and stability of physical properties. These may be used alone or in combination of two or more.

  The amount of the crosslinking agent used is not particularly limited, but is preferably set to 0.01 to 15 parts, particularly preferably 100 parts by weight (hereinafter abbreviated as “parts”) for the resin composition for pressure-sensitive adhesives. Is 0.1 to 5 parts. When the amount of the crosslinking agent used is too small, the pressure-sensitive adhesive tends to be insufficiently aggregated. Conversely, when the amount of the crosslinking agent used is too large, the pot life is deteriorated, that is, a gelation phenomenon tends to occur. Because it is seen.

  Furthermore, the pressure-sensitive adhesive composition of the present invention includes, if necessary, rosin resins such as coumarone-indene resin, rosin ester, hydrogenated rosin, polymerized rosin, disproportionated rosin, terpene resin, terpene-phenol. Range in which various conventionally known additives such as various tackifiers such as resin and petroleum resin, antistatic agent, colorant, filler, diluent, anti-aging agent and ultraviolet absorber are not impaired the effect of the present invention It can mix | blend suitably within. These additives are used alone or in combination of two or more. What is necessary is just to set these addition amounts timely so that the desired physical property may be obtained.

  In the said adhesive composition, it is preferable that the final gel fraction is 10% or more by bridge | crosslinking. That is, when the gel fraction is too small, the cohesive force is insufficient, and there is a tendency that the practical physical properties as an adhesive are poor. Normally, the upper limit of the gel fraction is 100%, but a preferable upper limit is 96%.

  The gel fraction is a measure for crosslinking and is calculated by the following method. That is, the dried pressure-sensitive adhesive (cross-linked product cross-linked by the combined use of an acrylic copolymer and a cross-linking agent) is wrapped with a 200-mesh SUS wire mesh, immersed in toluene at 23 ° C. for 24 hours, and remains in this wire mesh. The weight percentage of the insoluble cross-linked product thus obtained is defined as the gel fraction (%).

  A pressure-sensitive adhesive sheet can be produced by forming a pressure-sensitive adhesive layer using the pressure-sensitive adhesive composition. That is, the pressure-sensitive adhesive sheet can be produced, for example, as follows. First, the pressure-sensitive adhesive composition is applied to the surface of the base material so as to have a predetermined thickness, and heat-dried to form a pressure-sensitive adhesive layer. Next, a pressure-sensitive adhesive sheet can be produced by attaching a release sheet to the pressure-sensitive adhesive layer surface as necessary. In use, the release sheet is released from the pressure-sensitive adhesive layer and used. In this way, a pressure-sensitive adhesive sheet is obtained in which a pressure-sensitive adhesive layer is formed on the base material surface, and a release sheet is provided on the pressure-sensitive adhesive layer surface as necessary.

  Although it does not specifically limit as said base material, For example, polyester-type resin, such as metal foil, such as aluminum, copper, and iron; polyethylene naphthalate, a polyethylene terephthalate, a polybutylene terephthalate, a polyethylene terephthalate / isophthalate copolymer Polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; Polyfluorinated ethylene resins such as polyvinyl fluoride, polyvinylidene fluoride, and polyfluorinated ethylene; Polyamides such as nylon 6, nylon 6, 6; Polyvinyl chloride, polyvinyl chloride / Vinyl acetate copolymers, ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, vinyl polymers such as polyvinyl alcohol and vinylon; cellulose resins such as cellulose triacetate and cellophane; polymeta Acrylic resins such as methyl laurate, polyethyl methacrylate, polyethyl acrylate, and polybutyl acrylate; synthetic resin films or sheets such as polystyrene, polycarbonate, polyarylate, polyimide, paper such as fine paper, glassine paper, glass Examples thereof include a single layer or a multi-layer selected from fiber, natural fiber, synthetic fiber and the like.

  Furthermore, the release sheet is not particularly limited, and for example, a release resin-molded sheet such as a synthetic resin sheet, paper, cloth, or nonwoven fabric exemplified for the base material can be used.

  Moreover, as said heat drying conditions, what is necessary is just to be able to dry an adhesive composition, For example, the conditions for about 1 to 5 minutes at 70-150 degreeC are mention | raise | lifted.

  Thus, the thickness of the adhesive sheet obtained is not specifically limited, It sets suitably according to a use, For example, it is preferable to set to the range of 30-300 micrometers. Moreover, it is preferable to set the thickness of a base material in the range of 15-75 micrometers, and also it is preferable to set the thickness of an adhesive layer in the range of 5-200 micrometers.

  In using the pressure-sensitive adhesive sheet of the present invention, the type of adherend is not particularly limited. For example, metal foil of aluminum, copper, iron; polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, polyethylene terephthalate / isophthalate Polyester resins such as copolymers; Polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; Polyfluorinated ethylene resins such as polyvinyl fluoride, polyvinylidene fluoride, and polyfluorinated ethylene; Polyamides such as nylon 6, nylon 6,6, and the like A vinyl polymer such as polyvinyl chloride, polyvinyl chloride / vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyvinyl alcohol, vinylon; cellulose triacetate, cellophane, etc. Cellulose-based resins; polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, acrylic resins such as polybutyl acrylate; polystyrene, polycarbonate, polyarylate, synthetic resin films such as polyimide, sheet or plate and the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

[Example 1]
"Preparation of acrylic copolymer solution"
93.0 parts of butyl acrylate, 2.0 parts of 2-hydroxyethyl acrylate, and 5.0 parts of N-vinylimidazole are reacted with 0.1 part of azobisisobutyronitrile and 140 parts of ethyl acetate as a polymerization initiator. In a vessel, the temperature is raised to 80 ° C. with stirring, and the polymerization reaction is carried out. Further, a polymerization catalyst solution in which 0.1 part of azobisisobutyronitrile is dissolved in 30 parts of ethyl acetate is added over 7 hours. And polymerized. After completion of the reaction, a diluent solvent (ethyl acetate) was added to prepare a 40% by weight solution of an acrylic copolymer.

"Production of adhesive sheet"
As the substrate, a polyethylene terephthalate (PET) film having a thickness of 25 μm (Plumac Corporation, Lumirror T-25) was used. On the other hand, a 25 μm-thick polyethylene terephthalate (PET) film (manufactured by Panac, SEPA100) was used as the release sheet. Moreover, as an adhesive, the adhesive composition which added 1.2 weight% isocyanate type crosslinking agent (The Nippon Polyurethane company make, Coronate L55E) with respect to the resin solid content of the said acrylic copolymer solution was produced. .

  And the said adhesive composition was apply | coated to the single side | surface of the said base material using an applicator so that the thickness after drying might be 25 micrometers, and it heat-dried at 100 degreeC for 2 minutes, and formed the adhesive layer. Subsequently, the adhesive sheet was produced by bonding the release sheet to the surface of the adhesive layer.

[Examples 2 to 4, Comparative Examples 1 to 4]
While using each component shown in Table 1 to Table 2 below, the blending amount was changed to the ratio shown in Table 1 to Table 2 below. Other than that was carried out similarly to Example 1, and produced the 40 weight% solution of the acryl-type copolymer.

  Further, a pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 using the acrylic copolymer solution.

[Examples 5 and 6]
"Preparation of acrylic copolymer solution"
While using each component shown in Table 1 to Table 2 below, the blending amount was changed to the ratio shown in Table 1 to Table 2 below. Other than that was carried out similarly to Example 1, and produced the 40 weight% solution of the acryl-type copolymer.

"Production of adhesive sheet"
As the base material and release sheet, the same materials as in Example 1 were used. Moreover, as an adhesive, the adhesive composition which added 1.0 weight% isocyanate type crosslinking agent (Nippon Polyurethane Co., Ltd. coronate HX) with respect to the resin solid content of the said acrylic copolymer solution was produced. . And the adhesive sheet was produced like the said Example 1. FIG.

  Using the acrylic copolymer solutions and pressure-sensitive adhesive sheets of Examples and Comparative Examples thus obtained, the characteristics were evaluated according to the following methods. The results are also shown in Tables 1 and 2 below.

(1) Characteristics after 40 ° C. × 3 Days After the adhesive sheet was cured at 40 ° C. for 3 days, the adhesive force and gel fraction were measured as follows.

〔Adhesive force〕
Each pressure-sensitive adhesive sheet was cut to prepare a test piece having a size of 25 mm × 120 mm, and this test piece was pressure-bonded by a method in which a 2 kg roller was reciprocated once as a adherend on a stainless steel plate. After standing for 24 hours, the peel rate was 180 ° (adhesive strength) at a peel rate of 0.3 m / min in an atmosphere of 23 ° C. × 50% RH.

[Gel fraction]
The dried pressure-sensitive adhesive (cross-linked product cross-linked by the combined use of an acrylic copolymer and a cross-linking agent) is wrapped with a 200-mesh SUS wire mesh, immersed in toluene at 23 ° C. for 24 hours, and remains undissolved in the wire mesh. The weight percentage of the cross-linked product is defined as the gel fraction (%).

(2) Characteristics after 40 ° C. × 3 days and further after 70 ° C. × 3 days The above adhesive sheet was cured at 40 ° C. for 3 days, and further cured at 70 ° C. for 3 days. The rate and adhesive strength were measured.

[Finger tuck evaluation]
Each pressure-sensitive adhesive sheet was cut to prepare a test piece having a size of 10 cm × 10 cm. The index finger was pressed against the test piece, and the tack force was evaluated by tactile sensation.
○: Tack feeling is strong △: Tack feeling is weak ×: Tack feeling is almost absent

(Metal corrosion resistance)
Each pressure-sensitive adhesive sheet was cut to prepare a test piece having a size of 25 mm × 100 mm, and this test piece was attached as an adherend to a test copper plate manufactured by Nippon Test Panel. And it was allowed to stand for 7 days under the condition of temperature 60 ° C. × humidity 90% RH with a constant temperature and humidity machine manufactured by Kato Co., Ltd., and the corrosion condition of the copper plate was visually observed and evaluated according to the following criteria.
○: No corrosion or discoloration is observed on the copper plate surface.
Δ: Some discoloration is observed on the surface of the copper plate.
X: Severe corrosion and discoloration are seen on the copper plate surface.

  From the above results, the Example products showed high adhesive strength and tack strength, and good results were obtained with no corrosion or discoloration on the copper plate surface with respect to metal corrosion resistance. Further, in the example products, it was found that there was little change in the gel fraction after aging at 40 ° C. × 3 days to 70 ° C. × 3 days, and the crosslinking was completed quickly. In addition to having good adhesive properties, it also has the effect that the curing time until the adhesive properties are obtained is short.

  In contrast, the comparative example 1 product made of butyl acrylate, vinyl acetate and acrylic acid gave satisfactory values for adhesive strength, but severe corrosion on the copper plate surface for metal corrosion resistance. The discoloration was seen and evaluation was bad. In Comparative Example 2 in which the amount of N-vinylimidazole used was less than a specific range, good results were obtained with respect to metal corrosion resistance, but the adhesive strength and tack strength were insufficient. -The comparative example 3 product in which the usage-amount of vinyl imidazole exceeds a specific range became difficult to produce an acrylic copolymer, and could not be evaluated. Furthermore, although the four comparative examples using acryloylmorpholine having one nitrogen atom have good adhesive strength and metal corrosiveness, the glass transition temperature becomes too high, so that the tackiness is not obtained. It was insufficient as an adhesive.

The resin composition according to the present invention is used, for example, as a peelable (including re-peelable) pressure-sensitive adhesive material. The pressure-sensitive adhesive sheet formed by forming a pressure-sensitive adhesive layer on the substrate surface using the pressure-sensitive adhesive composition formed using the resin composition is useful for a sticker label, a fixing sheet for electronic members, and the like.

Claims (2)

A pressure-sensitive adhesive composition containing as a main component a copolymer comprising the following components (A) to (C) without containing an acid group-containing unsaturated monomer as a copolymer component, A pressure-sensitive adhesive composition comprising a copolymer in which the structural unit derived from the component (C) is 5 to 30% by weight of the copolymer composed of the components (A) to (C) , and a crosslinking agent .
(A) Alkyl ester of (meth) acrylic acid.
(B) Functional group-containing unsaturated monomers (excluding acid group-containing unsaturated monomers).
(C) An ethylenically unsaturated monomer having two or more nitrogen atom-containing heterocyclic structures that are not ring-opened. The adhesive sheet by which an adhesive layer is formed in the base-material surface using the adhesive composition of Claim 1 .