JP5325582B2 - Adhesive composition, adhesive sheet and adhesive laminate - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive composition that has a high adhesive strength to adherends such as metals, has a short seasoning (curing) period, and has a very low corrosiveness to metal, and the pressure-sensitive adhesive composition The present invention relates to an adhesive sheet having an adhesive layer formed from a product, and an adhesive laminate.

  In recent years, in the field of precision electronic components such as hard disks and circuit boards, various types and small lots have progressed. For production management, for example, bar code printed adhesive labels (information labels) are attached to each member. Or, a double-sided pressure-sensitive adhesive sheet is often used for bonding, or a pressure-sensitive adhesive sheet is often used for electrical insulation.

  Conventionally, in such a pressure-sensitive adhesive sheet or pressure-sensitive adhesive label, a pressure-sensitive adhesive composition containing an acrylic polymer having a carboxyl group and a crosslinking agent having a functional group capable of reacting with the carboxyl group (such as an isocyanate-based crosslinking agent) is used as the pressure-sensitive adhesive. An acrylic pressure-sensitive adhesive obtained by crosslinking by heating is generally used.

  However, although the acrylic pressure-sensitive adhesive has excellent adhesion to metal, it has a carboxyl group that is an acid, so that it may not be used for an adhesive label that corrodes metal and is attached to a metal precision electronic member. It was.

  In order to solve this problem, for example, Patent Document 1 discloses an acrylic copolymer composed of (meth) acrylic acid alkyl ester, vinyl acetate, and an acrylic monomer having a hydroxyl group or an amino group as a crosslinking origin, and isocyanate. A pressure-sensitive adhesive sheet obtained by using a system cross-linking agent has been proposed.

However, the seasoning (curing) period in the reaction system of this pressure-sensitive adhesive sheet is usually as long as about 1 to 2 weeks at room temperature, and there is a problem that a storage place must be secured. Moreover, the adhesive force with respect to the metal of the obtained adhesive sheet was also a problem.
Japanese Patent Laid-Open No. 2005-154531

  The present invention has been made in view of the state of the prior art, and has a pressure-sensitive adhesive layer that has high adhesion to an adherend such as metal, has a short seasoning period, and has extremely low corrosiveness to metal. It is an object to provide a pressure-sensitive adhesive composition, a pressure-sensitive adhesive sheet formed from the pressure-sensitive adhesive composition, and a pressure-sensitive adhesive laminate.

  As a result of intensive studies to solve the above problems, the present inventors have found that the monomer composition contains an N-vinyl cyclic lactam monomer and an acrylic monomer and does not contain a monomer having a carboxyl group. When an adhesive copolymer containing an acrylic copolymer obtained by polymerizing a product and a diisocyanate compound as a crosslinking agent is used, it has a high adhesive force to an adherend such as a metal and has a seasoning period. The present inventors have found that a pressure-sensitive adhesive composition that is short and has extremely low corrosiveness to metals can be obtained, and the present invention has been completed by generalizing this knowledge.

Thus, according to the first aspect of the present invention, the following pressure-sensitive adhesive compositions (1) to (5) are provided.
(1) An acrylic copolymer obtained by polymerizing a monomer composition containing an N-vinyl cyclic lactam monomer and an acrylic monomer and not containing a monomer having a carboxyl group, and a polyisocyanate compound A pressure-sensitive adhesive composition comprising:
(2) The pressure-sensitive adhesive composition according to (1), wherein a blending ratio of the N-vinyl cyclic lactam monomer is 5 to 35 mol% with respect to the entire monomer composition.
(3) The pressure-sensitive adhesive composition according to (1) or (2), wherein the N-vinyl cyclic lactam monomer is N-vinyl-2-pyrrolidone.

(4) In any one of (1) to (3), the number of isocyanate groups in the polyisocyanate compound is 0.3 to 5 equivalents relative to the number of cyclic lactams contained in the acrylic copolymer. The pressure-sensitive adhesive composition described.
(5) The pressure-sensitive adhesive composition according to any one of (1) to (4), wherein the polyisocyanate compound is an aromatic polyisocyanate compound.

According to the second aspect of the present invention, the following pressure-sensitive adhesive sheet (6) is provided.
(6) A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition according to any one of (1) to (5).
According to the third aspect of the present invention, there is provided the following adhesive laminate (7).
(7) A pressure-sensitive adhesive laminate obtained by attaching the pressure-sensitive adhesive sheet according to (6) to a metal adherend.

  According to the pressure-sensitive adhesive composition of the present invention, the pressure-sensitive adhesive has high adhesion to metals, has a significantly shorter seasoning period than conventional ones, and does not contain a carboxyl group that is an acid and therefore does not corrode metals. A layer can be formed.

The pressure-sensitive adhesive sheet of the present invention can be preferably used as an information label for production management, a pressure-sensitive adhesive sheet for electrical insulation, and member fixing in the field of precision electronic members such as metal hard disks and circuit boards.
The pressure-sensitive adhesive laminate of the present invention is excellent in adhesiveness between the pressure-sensitive adhesive sheet and the adherend metal, and the metal does not corrode.

Hereinafter, the present invention will be described in detail by dividing it into 1) an adhesive composition, 2) an adhesive sheet, and 3) an adhesive laminate.
1) Adhesive composition The adhesive composition of the present invention is obtained by polymerizing a monomer composition containing an N-vinyl cyclic lactam monomer and an acrylic monomer and not containing a monomer having a carboxyl group. It contains an acrylic copolymer obtained and a polyisocyanate compound.

  The acrylic copolymer used in the present invention contains (i) an N-vinyl cyclic lactam monomer and (ii) an acrylic monomer, and (iii) does not contain a monomer having a carboxyl group. It is obtained by polymerizing the characteristic monomer composition.

(I) The N-vinyl cyclic lactam monomer is a compound having a cyclic lactam structure in which a vinyl group is bonded to a nitrogen atom constituting the lactam structure.
Examples of the cyclic lactam structure include a β-lactam structure, a γ-lactam structure, a δ-lactam structure, and an ε-lactam structure, and a γ-lactam structure and a δ-lactam structure are preferable.

Specific examples of the N-vinyl cyclic lactam monomer include N-vinyl pyrrolidone, N-vinyl valerolactam (N-vinyl-2-piperidone), N-vinyl caprolactam and the like.
Among these, N-vinyl-2-pyrrolidone is particularly preferable from the viewpoint of better expressing the desired effect of the present invention.
N-vinyl cyclic lactam monomers can be used singly or in combination of two or more.

  The blending ratio of the N-vinyl cyclic lactam monomer is preferably 5 to 35 mol% with respect to the entire monomer composition. When the ratio is less than 5 mol%, sufficient cohesive force may not be obtained, and when it exceeds 35 mol%, the composition of the obtained copolymer may be nonuniform.

(Ii) Examples of acrylic monomers include (meth) acrylic acid esters having no carboxyl group in the molecule.
Specific examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, (meth) acrylic acid. Isobutyl, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) acrylic acid Ester moieties such as 2-ethylhexyl, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate (Meth) acrylic acid alkyl ester having 1 to 20 carbon atoms in the alkyl group. Here, “(meth) acryl” represents “acryl” or “methacryl”.
These acrylic monomers can be used alone or in combination of two or more.

(Iii) The monomer composition does not include a monomer having a carboxyl group. Thereby, the adhesive composition with low corrosiveness with respect to a metal can be obtained.

  If desired, the monomer composition may contain another monomer that is copolymerizable with the N-vinyl cyclic lactam monomer or acrylic monomer and does not have a carboxyl group as a copolymerization component. May be.

  Other monomers include vinyl esters such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene, and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; styrene, α-methylstyrene, and the like. Styrene monomers; Diene monomers such as butadiene, isoprene and chloroprene; Nitrile monomers such as acrylonitrile and methacrylonitrile;

  The monomers in these monomer compositions may contain groups having active hydrogen such as hydroxyl groups and amino groups. When a monomer containing a group having active hydrogen is used, the cohesive force of the resulting pressure-sensitive adhesive composition may become stronger. However, in the present invention, a pressure-sensitive adhesive composition having a sufficient cohesive force can be obtained without using such a monomer.

  The method for polymerizing the monomer composition comprising the N-vinyl cyclic lactam monomer, the acrylic monomer, and, if desired, another monomer is not particularly limited, and a conventionally known method can be employed. Among these, a method of radical polymerization of a monomer composition in a solvent using a radical polymerization initiator is simple and preferable.

  Examples of the radical polymerization initiator used include azobisisobutyronitrile (AIBN), 2,2′-azobis (2-aminodipropane) dihydrochloride, 4,4′-azobis (4-cyanovaleric acid), and the like. And azo initiators; peroxide radical polymerization initiators such as benzoyl peroxide; and the like.

  The use amount of the radical polymerization initiator is preferably in the range of 0.01 to 5 parts by mass, particularly preferably in the range of 0.1 to 1 part by mass with respect to 100 parts by mass of the monomer composition.

The solvent to be used is not particularly limited as long as it is inert to the monomer composition. For example, ester solvents such as ethyl acetate; ketone solvents such as acetone; ether solvents such as diethyl ether; toluene, Examples include aromatic hydrocarbon solvents such as xylene. Among these, ester solvents such as ethyl acetate are preferable because the reaction proceeds smoothly.
Although the usage-amount of a solvent is not restrict | limited in particular, Usually, it is 10-70 mass% of the whole reaction mixture.

  In addition, there is no restriction | limiting in particular about the form of copolymerization of an acrylic copolymer, Any of random copolymerization, block copolymerization, and graft copolymerization may be sufficient.

The molecular weight of the resulting acrylic copolymer is preferably 200,000 or more in terms of mass average molecular weight, and more preferably in the range of 300,000 to 2,000,000. If the mass average molecular weight is less than 200,000, the heat resistance is inferior, and the adhesive force to the adherend may be insufficient.
The mass average molecular weight is a value in terms of polystyrene measured by gel permeation chromatography (GPC) method.

  The pressure-sensitive adhesive composition of the present invention contains a polyisocyanate compound as a crosslinking agent in addition to the acrylic copolymer.

  As the polyisocyanate compound, aromatic polyisocyanate compounds, aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, and the like can be used.

  Examples of the aromatic polyisocyanate compound include 4,4′-diphenylmethane diisocyanate, tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), tolidine diisocyanate, naphthalene-1,5-diisocyanate, tetramethylene xylylene diisocyanate, poly Methylene polyphenyl polyisocyanate; and derivatives thereof. Examples of these derivatives include modified products such as isocyanurate, biuret and uretdione.

  Examples of the aliphatic polyisocyanate include tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate (HMDI), heptamethylene diisocyanate, octamethylene diisocyanate, decamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3 -Methyl-1,5-pentane diisocyanate and derivatives thereof.

Examples of the alicyclic polyisocyanate compound include 3,3,5-trimethyl-1-isocyanato-5-isocyanatomethylcyclohexane, 1,6-bisisocyanatomethylcyclohexane, bis (4,4′isocyanatocyclohexyl). ) Methane, and derivatives thereof.
These polyisocyanate compounds can be used alone or in combination of two or more.

  Among these, an aromatic polyisocyanate compound is preferable and a tolylene diisocyanate compound is more preferable from the viewpoint of better expressing the desired effect of the present invention.

  It is preferable that the number of isocyanate groups in the polyisocyanate compound to be used is 0.3 to 5 equivalents with respect to the number of cyclic lactams contained in the acrylic copolymer. When the amount is less than 0.3 equivalent, sufficient cohesive force may not be obtained, and when the amount exceeds 5 equivalents, the adhesive strength may be reduced.

  The method for preparing the pressure-sensitive adhesive composition of the present invention is not particularly limited. For example, a method for dissolving or dispersing the acrylic copolymer and the polyisocyanate compound in a solvent, a solvent for the acrylic copolymer. Examples thereof include a method of mixing a solution with a polyisocyanate compound or a solvent solution thereof.

  Examples of the solvent used for the preparation include the same solvents as exemplified as the solvent used when the acrylic copolymer is produced. In addition, the reaction mixture obtained when the acrylic copolymer is synthesized can be used as it is as the acrylic copolymer.

  The pressure-sensitive adhesive composition of the present invention is conventionally used for other pressure-sensitive adhesives, tackifying resins such as urethane resins and polyester resins, and conventional acrylic pressure-sensitive adhesives as long as they do not depart from the purpose of the present invention. Various additive components may be included.

  As will be described later, the pressure-sensitive adhesive composition of the present invention forms a pressure-sensitive adhesive layer that has high adhesion to adherends such as metals, has a short seasoning period, and has extremely low corrosiveness to metals. can do.

2) Adhesive sheet The adhesive sheet of this invention has the adhesive layer formed from the adhesive composition of this invention.
The pressure-sensitive adhesive sheet of the present invention is not particularly limited as long as it has a pressure-sensitive adhesive layer, and even if it is composed of only a pressure-sensitive adhesive layer, a laminate of the pressure-sensitive adhesive layer and other layers. It may be.

  Specific examples of the pressure-sensitive adhesive sheet made of a laminate include (i) a base sheet-adhesive sheet made of a pressure-sensitive adhesive layer, (ii) a release sheet-pressure-sensitive adhesive layer, and (iii) a base sheet-adhesive. Pressure sensitive adhesive layer-release sheet, (iv) pressure sensitive adhesive layer-base sheet-pressure sensitive adhesive sheet, (v) release sheet-pressure sensitive adhesive layer-release sheet, etc. Can be mentioned.

The base sheet has a barcode, lot number. Such information may be printed.
There is no restriction | limiting in particular as said base material sheet, For example, the film which consists of polyester, such as polyolefin, such as polyethylene and a polypropylene, polyethylene terephthalate (PET); The film on which metal vapor deposition was given; Synthetic paper, fine paper, impregnated paper Paper such as aluminum foil, copper foil, iron foil, and the like; sheets made of a porous material such as nonwoven fabric; and the like.

  There is no restriction | limiting in particular in the thickness of these base material sheets, Usually, it is 3-250 micrometers, and 10-200 micrometers is preferable from a viewpoint of handleability.

  The release sheet has a role of protecting the surface of the pressure-sensitive adhesive layer. When the pressure-sensitive adhesive sheet is attached to the adherend, the release sheet is peeled off from the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer surface is attached to the adherend. Affixed.

  There is no restriction | limiting in particular as a release sheet to be used, For example, films made of various resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyarylate, polyethylene, polypropylene; paper such as glassine paper, fine paper, clay coat paper; Examples include paper laminated with a resin film such as polyethylene and polypropylene; paper subjected to a sealing treatment with cellulose, starch, polyvinyl alcohol, acrylic-styrene resin, and the like.

The surface of the release sheet that contacts the pressure-sensitive adhesive layer is preferably subjected to a release treatment.
The method of release treatment of the release sheet is not particularly limited, and examples thereof include a conventionally known method using a release agent such as an olefin resin, a long-chain alkyl release agent, a fluorine release agent, and a silicone release agent. It is done.

  The method for producing the adhesive sheet is not particularly limited. For example, the pressure-sensitive adhesive sheet of (iii) is: (a) a pressure-sensitive adhesive layer is formed by coating the pressure-sensitive adhesive composition on at least one surface of a base sheet, and a release sheet is formed on the surface of the formed pressure-sensitive adhesive layer (B) coating the pressure-sensitive adhesive composition on the release-treated surface of the release sheet to form a pressure-sensitive adhesive layer, and then using the resulting pressure-sensitive adhesive layer as a base material And a method of transferring to a sheet.

  The method for applying the pressure-sensitive adhesive composition of the present invention to the base sheet or the release sheet is not particularly limited. For example, a roll knife coater, a die coater, a roll coater, a bar coater, a gravure roll coater, a reverse roll coater, etc. And a method using a known coating apparatus.

  After coating the pressure-sensitive adhesive composition, the solvent and low-boiling components are removed by drying. In this case, in order to prevent the solvent and low boiling point components from remaining, it is desirable to heat dry at a temperature of 80 to 150 ° C. for 30 seconds to 5 minutes.

  Although the thickness (dry film thickness) of the obtained adhesive layer is not specifically limited, Usually, 3-100 micrometers, Preferably it is 5-75 micrometers, More preferably, it is 10-50 micrometers.

  Although the thickness of the adhesive sheet of this invention is not specifically limited, Usually, 5-300 micrometers, Preferably it is 8-200 micrometers.

  The pressure-sensitive adhesive sheet of the present invention has an excellent pressure-sensitive adhesive force, and is particularly excellent in the pressure-sensitive adhesive force to metal. It can be confirmed that the pressure-sensitive adhesive sheet of the present invention is excellent in adhesive strength, for example, by measuring the adhesive strength according to JIS Z0237.

  The pressure-sensitive adhesive sheet of the present invention has a shorter seasoning period than conventional ones. Therefore, it is not necessary to secure a storage place for the seasoning period as in the prior art.

  The short seasoning period indicates that, for example, after preparing the pressure-sensitive adhesive sheet and placing it at room temperature (10 to 25 ° C.) for 1 to 3 days, when the gel fraction of the pressure-sensitive adhesive layer is measured, it already shows a sufficiently high value. This can be confirmed. That is, it can be seen that in the pressure-sensitive adhesive layer, the crosslinking reaction with the polyisocyanate compound has already proceeded sufficiently after 1 to 3 days. Moreover, since the value measured 1-3 days after preparing the said adhesive sheet is equivalent to the value measured 14 days later, it can confirm.

  The pressure-sensitive adhesive sheet of the present invention has extremely low corrosiveness to metals. This can be confirmed, for example, by sticking a pressure-sensitive adhesive sheet to a copper plate and leaving it at high temperature and high humidity, then peeling off the pressure-sensitive adhesive sheet, and visually observing the surface of the copper plate after peeling, and there is no change. it can.

  Since the pressure-sensitive adhesive sheet of the present invention has the characteristics as described above, it can be used for various purposes such as for information labels, for fixing, for insulating, etc. on adherends made of metal or the like.

3) Pressure-sensitive adhesive laminate The pressure-sensitive adhesive laminate of the present invention is formed by attaching the pressure-sensitive adhesive sheet of the present invention to a metal adherend.
As the metal adherend, a precision electronic member is particularly preferable. Examples of the precision electronic member include a hard disk device; a semiconductor component such as an additional memory or an IC card; a semiconductor manufacturing device; a relay switch; a circuit board;

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the examples.
[Example 1]
Monomer consisting of 90 mol% 2-ethylhexyl acrylate (2EHA) and 10 mol% N-vinyl-2-pyrrolidone (VP) in a reactor equipped with a thermometer, stirrer, reflux condenser and nitrogen gas inlet tube 292 g of the composition and 450 ml of ethyl acetate as a solvent were added, 0.30 g of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and solution polymerization was performed at 60 ° C. for 16 hours in a nitrogen gas atmosphere. A solution containing a copolymer was obtained. The solid content of this solution was 40% by mass. Moreover, the mass average molecular weight of the obtained acrylic copolymer was 680,000.

  To the solution containing the acrylic copolymer obtained above, a tolylene diisocyanate (TDI) polyisocyanate compound (manufactured by Toyo Ink Manufacturing Co., Ltd., trade name “Olivein BHS8515”, solid content 37.5% by mass, below) The same) was blended in an amount such that the solid content of the TDI polyisocyanate compound was 10 parts by mass with respect to 100 parts by mass of the solid content of the acrylic copolymer to prepare an adhesive composition 1.

On one side of a 50 μm-thick polyethylene terephthalate (PET) film (trade name “PET50T-60 Toray” manufactured by Toray Industries, Inc.) as a base sheet, the thickness after drying is 30 μm. Then, coating was performed with a roll knife coater, and the obtained coating film was dried at 90 ° C. for 3 minutes to form an adhesive layer.
Next, a release sheet (trade name “SP-PET381038”, manufactured by Lintec Corporation) was laminated on the formed pressure-sensitive adhesive layer to prepare a pressure-sensitive adhesive sheet 1.

[Example 2]
As shown in Table 1 below, xylylene diisocyanate (XDI) polyisocyanate compound (manufactured by Soken Chemical Co., Ltd., trade name “TD-75) was used in place of the TDI polyisocyanate compound. Thus, an adhesive composition 2 and an adhesive sheet 2 were produced.

Example 3
As shown in Table 1 below, except that 9.7 parts by mass of hexamethylene diisocyanate (HMDI) polyisocyanate compound (manufactured by Nippon Polyurethane Co., Ltd., trade name “Coronate HL”) is used instead of the TDI polyisocyanate compound, In the same manner as in Example 1, a pressure-sensitive adhesive composition 3 and a pressure-sensitive adhesive sheet 3 were produced.

Example 4
As shown in Table 1 below, the pressure-sensitive adhesive composition 4 and the pressure-sensitive adhesive sheet 4 were prepared in the same manner as in Example 1 except that the amount of the TDI-based polyisocyanate compound was changed from 10 parts by mass to 5.1 parts by mass. Produced.

Example 5
As shown in Table 1 below, a pressure-sensitive adhesive composition 5 and a pressure-sensitive adhesive sheet 5 were prepared in the same manner as in Example 1 except that the blending amount of the TDI-based polyisocyanate compound was changed from 10 parts by mass to 40 parts by mass. .

[Comparative Example 1]
As shown in Table 1 below, instead of N-vinyl-2-pyrrolidone (VP), acrylic acid (AAc) was used, and the amount of TDI polyisocyanate compound was changed to 5.8 parts by mass. In the same manner as in Example 1, a pressure-sensitive adhesive composition 6 and a pressure-sensitive adhesive sheet 6 were produced.

[Comparative Example 2]
As shown in Table 1 below, instead of N-vinyl-2-pyrrolidone (VP), 2-hydroxyethyl acrylate (HEA) was used, and the compounding amount of the TDI polyisocyanate compound was 7.7 parts by mass. A pressure-sensitive adhesive composition 7 and a pressure-sensitive adhesive sheet 7 were produced in the same manner as in Example 1 except for changing.

[Comparative Example 3]
As shown in Table 1 below, a pressure-sensitive adhesive composition 8 and a pressure-sensitive adhesive sheet 8 were produced in the same manner as in Example 1 except that no TDI polyisocyanate compound was used.

[Comparative Example 4]
As shown in Table 1 below, in place of 10 parts by mass of the TDI-based polyisocyanate compound, a polyfunctional metal chelate compound (manufactured by Soken Chemical Co., Ltd., trade name “M-5A”) was used except that 2.5 parts by mass was used. In the same manner as in Example 1, a pressure-sensitive adhesive composition 9 and a pressure-sensitive adhesive sheet 9 were produced.

[Comparative Example 5]
As shown in Table 1 below, Examples were used except that 2.1 parts by mass of a polyfunctional epoxy compound (manufactured by Soken Chemical Co., Ltd., trade name “E-AX”) was used instead of 10 parts by mass of the TDI polyisocyanate compound. In the same manner as in Example 1, an adhesive composition 10 and an adhesive sheet 10 were produced.

[Comparative Example 6]
As shown in Table 1 below, Examples are used except that 3.5 parts by mass of a polyfunctional aziridine compound (trade name “BXX-5134” manufactured by Toyo Ink Co., Ltd.) is used instead of 10 parts by mass of the TDI-based polyisocyanate compound. In the same manner as in Example 1, an adhesive composition 11 and an adhesive sheet 11 were produced.

  The following measurements and evaluation tests were performed on the pressure-sensitive adhesive compositions 1 to 11 and the pressure-sensitive adhesive sheets 1 to 11 obtained in Examples 1 to 5 and Comparative Examples 1 to 6.

<Measurement of gel fraction>
The pressure-sensitive adhesive compositions 1 to 11 used in Examples 1 to 5 and Comparative Examples 1 to 6 were respectively coated on a release sheet (trade name “SP-PET381038” manufactured by Lintec Corporation), and 90 ° C. × After heat-drying under conditions of 3 minutes, the pressure-sensitive adhesive sheet obtained by sticking another release sheet to the pressure-sensitive adhesive surface was left at room temperature for 1, 3, 7 and 14 days, respectively.
After leaving for each period, for each adhesive sheet, the adhesive layer (100 mm × 100 mm, mass Ag) is peeled off from the release sheet and wrapped in a 120 mm × 120 mm nylon mesh (# 200), which is a Soxhlet extractor And extracted for 16 hours under reflux of ethyl acetate.
After the extraction treatment, the pressure-sensitive adhesive remaining in the nylon mesh is dried at 100 ° C. for 2 hours, and after conditioning in an atmosphere of 23 ° C. and 50% RH for 3 hours or more, the mass of the pressure-sensitive adhesive is measured (Bg). The gel fraction was calculated by the following formula. The results are shown in Table 2 below.

<Measurement of adhesive strength>
Each of the pressure-sensitive adhesive sheets 1 to 11 was cured at room temperature for 7 days, cut into a width of 25 mm and a length of 250 mm to obtain a test piece. In accordance with JIS Z0237, one end of the adhesive layer surface of the test piece is attached to one end of the test plate (SUS plate) so that the pasting area is 25 mm wide × about 90 mm long, and is reciprocated once with a 2 kg roller. And crimped. Twenty-four hours after pressure bonding, the adhesive strength (N / 25 mm) was measured when the test piece was peeled at a peeling angle of 180 degrees and a peeling speed of 300 mm / min. The measurement results are shown in Table 2 below.

<Measurement of holding power>
Each of the adhesive sheets 1 to 11 was cured at room temperature for 7 days, cut into a width of 25 mm × a length of 750 mm, and used as a test piece. In accordance with JIS Z 0237, one end of the adhesive layer surface of the test piece is pasted to one end of the test plate (SUS plate) so that the pasting area is 25 mm wide × 25 mm long, and is reciprocated 5 times with a 2 kg roller. And crimped. Fifteen minutes after the pressure bonding, it was set in a creep tester and left at 40 ° C. for 15 minutes. A load of 9.807 N was applied vertically downward to this product, and the time until the product was dropped was determined and used as the holding force (seconds). The measurement results are shown in Table 2 below. The test was performed up to 70000 seconds.

<Evaluation of copper plate corrosion>
Each of the pressure-sensitive adhesive sheets 1 to 11 was cured at room temperature for 7 days, a test piece cut to a size of 25 mm × 50 mm was attached to a copper plate, and then allowed to stand at 60 ° C. and 95% RH for 7 days. Then, the test piece was peeled off from the copper plate, and the change of the copper plate surface after peeling was observed visually.
Evaluation was made with ○ indicating that there was no change in appearance and × indicating that there was change in appearance. The evaluation results are shown in Table 2 below.

From Table 2, the gel fraction of the pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets 1 to 5 of Examples 1 to 5 was sufficiently high even after 1 day, and was almost the same as the measured value after 14 days after 3 days. From this result, the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheets 1 to 5 has a seasoning period of approximately 1 to 3 days. In other words, the crosslinking reaction with the polyisocyanate compound has already progressed after 1 to 3 days, and sufficient agglomeration has occurred. It can be seen that it has power.
Moreover, the adhesive sheets 1-5 were excellent in adhesive force and holding power, and did not corrode a copper plate.

On the other hand, in the pressure-sensitive adhesive sheet 6 of Comparative Example 1, a change in the appearance of the copper plate surface was observed, and it is assumed that the copper plate was corroded. The adhesive sheet 7 of Comparative Example 2 was inferior in adhesive strength.
In Comparative Examples 1 and 2, it is considered that the gel fraction of the pressure-sensitive adhesive layer is not sufficient even after 3 days from the preparation of the pressure-sensitive adhesive sheet, and the unreacted polyisocyanate compound remains. It can be seen that the seasoning period is longer than 3 days and shorter than 7 days.

  The pressure-sensitive adhesive sheets 8 to 11 of Comparative Examples 3 to 6 that did not use the polyisocyanate compound were inferior in holding power and pressure-sensitive adhesive strength to the pressure-sensitive adhesive sheets 1 to 5 of Examples 1 to 5.

Claims (7)

An acrylic copolymer obtained by polymerizing a monomer composition containing an N-vinyl cyclic lactam monomer and an acrylic monomer and not containing a monomer having a group containing active hydrogen , and polyisocyanate A pressure-sensitive adhesive composition comprising a compound.

  The pressure-sensitive adhesive composition according to claim 1, wherein the blending ratio of the N-vinyl cyclic lactam monomer is 5 to 35 mol% with respect to the whole monomer composition.   The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the N-vinyl cyclic lactam monomer is N-vinyl-2-pyrrolidone.   The pressure-sensitive adhesive composition according to any one of claims 1 to 3, wherein the number of isocyanate groups in the polyisocyanate compound is 0.3 to 5 equivalents relative to the number of cyclic lactams contained in the acrylic copolymer. object.   The pressure-sensitive adhesive composition according to claim 1, wherein the polyisocyanate compound is an aromatic polyisocyanate compound.   The adhesive sheet which has an adhesive layer formed from the adhesive composition in any one of Claims 1-5.   A pressure-sensitive adhesive laminate obtained by attaching the pressure-sensitive adhesive sheet according to claim 6 to a metal adherend.