JP4219592B2 - Curable adhesive composition, curable adhesive, and adhesive sheet using the same - Google Patents

Description

【００４６】
表１から明らかなように、実施例１の粘接着シートは、硬化前の粘弾性は優れた評価となり、また紫外光を照射して酸を発生させているため、比較的低温、短時間の加熱により、粘接着剤の硬化を完了させることができたため、硬化後の凝集性は優れた評価となった。また、酸を発生させた後は、加熱しなくとも常温（２３℃、６５％Ｒ.Ｈ．）で放置することにより硬化を完了させることができ、硬化後の凝集性は優れた評価となった。
【００４７】
実施例２の粘接着シートは、支持体が耐熱性を有さないものであったが、紫外光を照射することにより酸を発生し、常温（２３℃、６５％Ｒ．Ｈ．）にて一ヶ月放置することにより硬化を完了させることができたため、硬化後の凝集性は優れた評価となった。
【００４８】
比較例１の粘接着シートは、カチオン重合性化合物よりも熱可塑性ポリマーを多く配合しているため、硬化前の粘弾性は優れた評価となったが、硬化後の凝集性は低い評価となった。
【００４９】
比較例２の粘接着シートは、カチオン重合性化合物と熱可塑性ポリマーとを等量配合しているため、硬化前の粘弾性のうち粘着力については優れた評価となったが、糊残りと保持力については低い評価となった。また、硬化後の凝集性についても低い評価となった。
【００５０】
比較例３の粘接着シートは、熱可塑性ポリマーよりもカチオン重合性化合物を多く配合しているため、硬化後の凝集性は優れた評価となったが、硬化前の粘弾性は低い評価となった。
【００５１】
比較例４の粘接着シートは、硬化前の粘弾性は優れた評価であったが、ブレンステッド酸又はルイス酸を発生する光潜在性酸発生剤を添加していないため、１３０℃、２分間の加熱では、温度が低く、時間も短いため硬化を完了させることができず、硬化後の凝集性は低い評価となった。なお、比較例４の粘接着シートを１５０℃、２０分加熱したところ、硬化は完了し、硬化後の凝集性は優れたものとなったが、支持体が比較的耐熱性を有さないものであったため、支持体に若干の波うちが生じてしまった。
【００５２】
比較例５の粘接着シートは、比較例４と同様に、ブレンステッド酸又はルイス酸を発生する光潜在性酸発生剤を添加していないため、紫外光を照射し一ヶ月間放置しても硬化を促進させることはできず、凝集性の低い評価となった。また、支持体は耐熱性を有さないものであったため、１３０℃、２分間の加熱により支持体が変形し、使用に耐え得ないものとなり硬化後の凝集性の評価はできなかった。
【００５３】
以上のように、実施例の粘接着シートは、粘接着性組成物としてＮ−メチロール基を有する粘接着性化合物を配合しているため、硬化前は適度な粘弾性を有し、硬化後は優れた凝集性を有するものとなった。また、光の照射によってブレンステッド酸又はルイス酸を発生する光潜在性酸発生剤を添加しているため、低温、且つ短時間の加熱により粘接着性化合物の硬化を促進させることができ、比較的耐熱性を有さない支持体であっても支持体に波うちや変形などは生じず、使用可能となった。また、酸を発生させた後であれば、常温であっても粘接着性化合物の硬化を促進させることができたため、まったく耐熱性を有さない支持体であっても使用可能となった。
【００５４】
【発明の効果】
本発明によれば、硬化前は適度な粘弾性を有し、弱い圧力で圧着することができ、硬化後は高い凝集力により、優れた耐クリープ性や剥離性を有する粘接着剤組成物、粘接着剤、及びこれを用いた粘接着シートが得られる。
【図面の簡単な説明】
【図１】 保持力の評価装置の正面図
【図２】 保持力の評価装置の断面図
【符号の説明】
１・・・ステンレス板
２・・・粘接着シート
３・・・固定具
４・・・重り
５・・・アルミ板[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a curable adhesive composition, a curable adhesive, and an adhesive sheet having moderate viscoelasticity before curing and high cohesiveness after curing.
[0002]
[Prior art]
In general, the adhesive is in a liquid state, and is bonded to the adhesive substrate after being applied with a brush or a roller. After being joined, it is solidified by vaporization of a solvent or a high molecular weight reaction, and the adhesive substrate is firmly bonded. On the other hand, there is a limitation in handling such as high adhesive strength, complicated work to apply to the adhesive base material, relatively long reaction time, and fixing by some method until the adhesive solidifies. The pressure-sensitive adhesive may be liquid, but is generally supplied in a form applied to a film-like support. The form is basically a semi-solid viscoelastic body with a feeling of adsorption, it can be crimped to the adherend with a weak pressure, and the workability is good, but the disadvantage is that the cohesiveness is not as high as the adhesive. Have.
[0003]
In recent years, so-called “adhesives” have been proposed that compensate for the disadvantages of these adhesives and pressure-sensitive adhesives, have the convenience of pressure-sensitive adhesives when bonded, and solidify like adhesives in some way after bonding. . As such an adhesive, what consists of a thermoplastic polymer, a cationically polymerizable compound, a photocationic polymerization initiator etc. at least is provided.
[0004]
However, in order to maintain a viscoelastic body such as a pressure-sensitive adhesive as a shape before curing, such a visco-adhesive has to increase the addition ratio of the thermoplastic polymer, and after curing, the cohesive strength is increased. It will cause a decline. For example, when such an adhesive sheet using an adhesive is attached to an adherend and used as it is attached to the adherend after curing, the adhesive is little by little over time. A problem arises in that creep occurs in the layer and the adhesive sheet deviates from the adherend. In addition, when the adhesive sheet is peeled off from the adherend after curing, the adhesive will cause cohesive failure, so the adhesive sheet does not peel off from the adherend. There arises a problem that the adhesive remains on the adherend.
[0005]
[Problems to be solved by the invention]
Therefore, the present invention has an appropriate viscoelasticity before curing, can be pressure-bonded with a weak pressure, and has a high cohesive force after curing, an adhesive composition having excellent creep resistance and peelability, An object is to provide an adhesive and an adhesive sheet using the same.
[0006]
[Means for Solving the Problems]
That is, curable pressure-sensitive adhesive composition of the present invention contains a tacky adhesive compound having a N- methylol group, a photolatent acid generator generating Bronsted acid or Lewis acid.
[0007]
Moreover, the curable adhesive of this invention contains the said curable adhesive composition.
[0008]
The adhesive sheet of the present invention is an adhesive sheet in which an adhesive layer is provided on at least one surface of a support, and the adhesive layer is formed from the curable adhesive. It will be.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the curable adhesive composition, the curable adhesive, and the adhesive sheet of the present invention will be described in detail.
[0010]
The curable adhesive composition of the present invention comprises an adhesive compound having an N-methylol group and a photolatent acid generator that generates Bronsted acid or Lewis acid.
[0011]
The adhesive compound having an N-methylol group in the present invention is an adduct of amines and aldehydes, an adduct of amides and aldehydes, and all compounds obtained by etherifying these with alcohols. It points to. Examples include adducts of melamine formaldehyde, compounds containing monomers etherified with alcohols, copolymers of N-methylol (meth) acrylamide and monomers having an ethylenically unsaturated double bond, and the like. It is done.
[0012]
By using such an adhesive compound having an N-methylol group, a curable adhesive composition having an appropriate viscoelasticity before curing and an excellent cohesiveness after curing; can do. The weight average molecular weight of the copolymer is 1000 or more, preferably 10,000 or more, and more preferably 100,000 or more from the viewpoint of maintaining the shape as a viscoelastic body before curing.
[0013]
Next, the photolatent acid generator that generates Bronsted acid or Lewis acid in the present invention is a compound that generates an acid upon irradiation with light, and has the N-methylol group by generating an acid. Curing of the adhesive compound can be promoted. In particular, after generating the acid, when the curing of the adhesive compound having an N-methylol group is accelerated and completed by heating, the heating time can be shortened or the heating temperature can be lowered. Therefore, it can be used in an adhesive base material having relatively no heat resistance, and when used as an adhesive sheet described later, such a material can be used as a support. . Further, after the acid is generated, the curing can be accelerated and completed even at room temperature, so that it can be used for an adhesive base material having no heat resistance at all.
[0014]
Examples of such a photolatent acid generator include diphenyliodonium, ditolyliodonium, phenyl (p-anisyl) iodonium, bis (m-nitrophenyl) iodonium, bis (p-tert-butylphenyl) iodonium, bis (P-chlorophenyl) iodonium chloride such as iodonium, bromide, or iodonium salts such as borofluoride, hexafluorophosphate salt, hexafluoroarsenate salt, and triarylsulfonium salt, triarylphosphonium salt, iron arene complex Benzoin tosylate, pyrogallol trimesylate, o-nitrobenzyl tosylate, 2,5-dinitrobenzyl tosylate, N-tosylphthalimide, α-cyanobenzylidenetosylamine, p-nitroben Sulfonic acid esters such as lu-9,10-diethoxyanthracene-2-sulfonate, imide sulfonate, dialkyl-4-hydroxysulfonium salt, and silanol aluminum complex, but are not limited thereto, and Two or more types may be mixed and used.
[0015]
Here, such a photolatent acid generator is also used as a polymerization initiator of a cationic polymerizable compound such as a vinyl ether compound or an epoxy compound. In the present invention, the above-described N-methylol group is used. It is used for functioning as a catalyst in the self-condensation of an adhesive compound having an N-methylol group or a condensation reaction between an adhesive compound having an N-methylol group and other monomers described later.
[0016]
The content of such a photolatent acid generator is 0.01% by weight or more as a lower limit, preferably 0.1% by weight or more, and 10% by weight or less as an upper limit in the curable adhesive composition. Preferably it is 5 weight% or less. By setting it in such a range, a sufficient amount of acid is generated by light irradiation, and a curable adhesive composition having excellent cohesiveness after curing is obtained without containing excessive acid. be able to.
[0017]
In addition, the curable adhesive composition of the present invention may contain other monomer components, etc., depending on the use, and in particular, those that react with N-methylol groups such as polyol resins. This facilitates control of physical properties such as viscoelasticity. Examples of the polyol resin include those having a hydroxyl group or a carboxyl group in the side chain and / or terminal, such as an acrylic resin, a polyester resin, an epoxy resin, and an alkyd resin.
[0018]
By blending such a polyol resin, the polyol resin and the above-mentioned adhesive compound having an N-methylol group are copolymerized. Therefore, a conventional thermoplastic polymer is added to the viscoelasticity before curing. Compared with the case of maintaining the shape, the decrease in the cohesive force after curing can be reduced. In order to obtain a curable adhesive composition with more excellent cohesiveness, the content of the polyol resin may be 20% by weight or less, preferably 10% by weight or less in the curable adhesive composition. desirable.
[0019]
Next, the curable adhesive of the present invention contains the above curable adhesive composition, and if necessary, other resins, cross-linking agents, tackifiers, acid growth agents, dilutions Solvent, filler, colorant, matting agent, lubricant, antistatic agent, flame retardant, antibacterial agent, antifungal agent, ultraviolet absorber, light stabilizer, antioxidant, plasticizer, leveling agent, pigment dispersant, A flow regulator, an antifoaming agent, etc. can be mix | blended.
[0020]
Next, the pressure-sensitive adhesive sheet of the present invention is a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is provided on at least one surface of a support, and the pressure-sensitive adhesive layer is made of the above-described curable adhesive It is formed.
[0021]
Such an adhesive sheet is preferably paper or plastic film as a support, and the above-mentioned curable adhesive is required on the surface of the support. 1 μm to 70 μm, preferably in the range of 3 μm to 40 μm), and can be produced by bonding with a separator. The application means can be performed by a conventionally known method, for example, a bar coater, a blade coater, a spin coater, a roll coater, a gravure coater, a flow coater, spraying, screen printing or the like.
[0022]
The curable adhesive of the present invention as described above can be used for bonding substrates such as metals, plastics, paper, wood materials, inorganic materials, and combinations thereof. Moreover, the adhesive sheet | seat of this invention is applicable to the to-be-adhered body which uses the said base material as a material. Such a curable adhesive of the present invention is applied between a base material to be joined and cured, and the adhesive sheet of the present invention is applied to an adherend and cured. Can be implemented.
[0023]
The method of curing treatment varies depending on the application, etc., so it can not be said unconditionally, but after generating an acid by irradiation with light, an adhesive substrate coated with an adhesive or an adhesive sheet is adhesive Curing can be accelerated by applying heat suitable for the support or adherend of the sheet, and curing can be completed in a short time. Further, after the acid is generated, the curing can be completed by leaving it at room temperature without applying heat.
[0024]
In addition, as a method for generating an acid by irradiation with light, for example, ultraviolet rays in a wavelength region of 100 nm to 400 nm, preferably 200 nm to 400 nm, emitted from an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a metal halide lamp, etc. Or irradiation with an electron beam having a wavelength region of 100 nm or less emitted from a scanning or curtain type electron beam accelerator.
[0025]
The temperature of the curing process by heating varies depending on the type and content of the adhesive compound having an N-methylol group, a resin added as necessary, the thickness of the adhesive, the thermosetting time, etc. For example, it is about 20 minutes at 70 ° C. to 100 ° C., about 10 minutes at 100 ° C. to 130 ° C., and about 3 minutes at 130 ° C. or higher.
[0026]
The duration of curing by standing at room temperature also depends on the type and content of the adhesive compound having an N-methylol group, the resin added as necessary, the thickness of the adhesive, and the standing environment. For example, if the standing temperature is 23 ° C., it is about one month.
[0027]
As described above, according to the present invention, a curable adhesive composition that has moderate viscoelasticity before curing, can be pressure-bonded with a weak pressure, and has excellent cohesiveness after curing. A mold adhesive and an adhesive sheet using the same are obtained.
[0028]
【Example】
Hereinafter, the present invention will be described in more detail based on examples. In this example, “parts” and “%” are based on weight unless otherwise specified.
[0029]
[Example 1]
<Synthesis of an adhesive compound having an N-methylol group>
In a reaction vessel equipped with a stirrer, condenser, thermometer and nitrogen inlet tube, 6 parts of N-methylolacrylamide, 5 parts of 2-hydroxyethyl methacrylate, 3 parts of acrylic acid, 5 parts of ethyl acrylate, 61 parts of n-butyl acrylate, 10 parts of vinyl acetate, 10 parts of methyl acrylate, 30 parts of ethyl acetate, 30 parts of isopropyl alcohol, 0.05 part of α, α′-azobis (isobutyronitrile) were mixed and heated to 75 ° C. with stirring through nitrogen. . Thereafter, the reaction solution was kept at 75 ° C. and stirred for 8 hours to complete the reaction. To this, 70 parts of ethyl acetate and 70 parts of isopropyl alcohol were added to adjust the solid content to 33.3%, and an adhesive compound having an N-methylol group was synthesized.
[0030]
<Production of adhesive sheet>
The following curable adhesive is applied to one side of a 100 μm thick polyester film (Lumirror T60: Toray Industries, Inc.) using a bar coater, dried at 100 ° C. for 3 minutes, and then bonded to the separator. A sheet was produced. In addition, the thickness of the adhesive agent after drying was about 25 micrometers.
[0031]
<The curable adhesive of Example 1>
-79.3 parts of an adhesive compound having an N-methylol group-Photolatent acid generator (hexafluorophosphate arylsulfonium salt) 0.7 parts
<Cylite Cure UVI-6990: Union Carbide>
・ Ethyl acetate 10.0 parts ・ Toluene 10.0 parts
[Example 2]
The curable adhesive of Example 1 was applied to the separator of Example 1, dried at 100 ° C. for 3 minutes, and then bonded to an unstretched polypropylene film (CCU: Gunze) having a thickness of 80 μm. A landing sheet was prepared.
[0033]
[Comparative Example 1]
An adhesive sheet of Comparative Example 1 was produced in the same manner as in Example 1 except that the following curable adhesive was used instead of the curable adhesive of Example 1.
[0034]
<Curable adhesive of Comparative Example 1>
-Thermoplastic polymer (polyethyl acrylate) 80 parts (weight average molecular weight 1 million)
・ Cationically polymerizable compound (epoxy resin) 20 parts
<Epicoat 828: Japan Epoxy Resin>
・ Photocationic polymerization initiator (hexafluorophosphate arylsulfonium salt) 2 parts
<Cylite Cure UVI-6990: Union Carbide>
・ Methyl ethyl ketone 30 parts [0035]
[Comparative Example 2]
Comparative Example 1 was the same as Comparative Example 1 except that the curable adhesive of Comparative Example 1 was changed to 50 parts of the thermoplastic polymer, 50 parts of the cationic polymerizable compound, and 5 parts of the cationic photopolymerization initiator. 2 adhesive sheets were produced.
[0036]
[Comparative Example 3]
Comparative Example 1 was the same as Comparative Example 1 except that the curable adhesive of Comparative Example 1 was changed to 30 parts of the thermoplastic polymer, 70 parts of the cationic polymerizable compound, and 7 parts of the cationic photopolymerization initiator. 3 was produced.
[0037]
[Comparative Example 4]
A tacky adhesive sheet of Comparative Example 4 was prepared in the same manner as in Example 1 except that the photolatent acid generator was not added.
[0038]
[Comparative Example 5]
A tacky adhesive sheet of Comparative Example 5 was prepared in the same manner as Example 2 except that the curable tacky adhesive of Comparative Example 4 was used instead of the curable tacky adhesive of Example 2.
[0039]
About the adhesive sheet obtained in the Example and the comparative example, it evaluated about the viscoelasticity before hardening and the cohesion property after hardening as follows. The evaluation results are shown in Table 1.
[0040]
[Evaluation of viscoelasticity before curing]
About the viscoelasticity before hardening, the adhesive force and adhesive residue with respect to the stainless steel plate before hardening, and the retention strength before hardening were evaluated.
[0041]
For the evaluation of the adhesive strength to the stainless steel plate before curing and the evaluation of the adhesive residue, these adhesive sheets were cut into a size of width × length = 10 mm × 200 mm, and the adhesive layer of the adhesive sheet The entire surface was adhered and adhered to a stainless steel plate with a finger as an adherend, left in an environment of 23 ° C. and 65% RH for 24 hours, then peeled at a peeling speed of 300 mm / min and an angle of 180 ° for evaluation. . The evaluation of adhesive strength was “◯” when the adhesive strength was about 1000 g / 10 mm, and “X” when the adhesive strength was 700 g / 10 mm or less. Further, the evaluation of the adhesive residue was defined as “◯” when the adhesive layer did not leave any adhesive on the stainless steel plate, and “X” when the adhesive remained even a little.
[0042]
Evaluation of the holding force with respect to the stainless steel plate before hardening is demonstrated using FIG.1 and FIG.2. The surface of the adhesive layer 2 of the adhesive sheet 2 cut to a size of width × length = 10 mm × 110 mm is attached to the stainless steel plate 1 with a finger so that the contact area is 10 mm × 10 mm. After being left in an environment of 23 ° C. and 65% RH for 24 hours, a weight 4 of 1000 g was suspended using the fixture 3 in an environment of 80 ° C. and evaluated. In the evaluation, in order to prevent the adhesive sheet 2 from being stretched or broken due to the weight, an aluminum plate 5 is attached via an adhesive (not shown), and the adhesive sheet 2 is used together with a fixing tool. Fixed (FIG. 2). The evaluation was “◯” for those that did not fall for more than 1 hour and “x” for those that had fallen in less than 10 minutes.
[0043]
[Evaluation of cohesiveness after curing]
About the cohesion property after hardening, the retention strength with respect to the stainless steel plate after hardening was evaluated. Similar to the evaluation of the holding power before curing, the description will be made with reference to FIGS. The adhesive sheet 2 cut to the same size as the above evaluation was attached in the same manner as the above evaluation, and (b) Example 1, Comparative Example 4, Comparative Example 5, and (b) Example 1 shown below. After curing under the conditions of Example 2, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 5, a 2100 g weight 4 was hung using the fixture 3 in an 80 ° C. environment and evaluated. In the evaluation, the aluminum plate 5 was attached in the same manner as the above evaluation, and was fixed together with the adhesive sheet 2 with a fixture (FIG. 2). The evaluation was “◯” for those that did not fall for more than 24 hours, and “x” for those that had fallen in less than 10 minutes.
[0044]
(A) Ultraviolet light of 400 mJ / cm ² was irradiated from a metal halide lamp and heated at 130 ° C. for 2 minutes.
(B) Ultraviolet light was irradiated in the same manner as in (a) and left for one month in an environment of 23 ° C. and 65% RH.
[0045]
[Table 1]

[0046]
As can be seen from Table 1, the visco-adhesive sheet of Example 1 has an excellent evaluation of viscoelasticity before curing, and generates an acid by irradiating ultraviolet light. Since the curing of the adhesive could be completed by heating, the cohesiveness after curing was excellent. Further, after the acid is generated, curing can be completed by leaving it at room temperature (23 ° C., 65% RH) without heating, and the cohesiveness after curing is an excellent evaluation. It was.
[0047]
In the adhesive sheet of Example 2, the support did not have heat resistance, but an acid was generated by irradiating with ultraviolet light to normal temperature (23 ° C., 65% RH). Since the curing could be completed by leaving it to stand for one month, the cohesiveness after curing was an excellent evaluation.
[0048]
Since the adhesive sheet of Comparative Example 1 contains more thermoplastic polymer than the cationic polymerizable compound, the viscoelasticity before curing was excellent, but the cohesiveness after curing was low. became.
[0049]
Since the adhesive sheet of Comparative Example 2 contains an equal amount of a cationically polymerizable compound and a thermoplastic polymer, the adhesive strength of the viscoelasticity before curing was excellent. The holding power was low. Moreover, it became low evaluation also about the cohesion property after hardening.
[0050]
Since the adhesive sheet of Comparative Example 3 contains more cationic polymerizable compound than the thermoplastic polymer, the cohesiveness after curing was evaluated as excellent, but the viscoelasticity before curing was evaluated as low. became.
[0051]
The visco-adhesive sheet of Comparative Example 4 had excellent evaluation of viscoelasticity before curing, but no photolatent acid generator that generates Bronsted acid or Lewis acid was added. In the case of heating for a minute, the temperature was low and the time was short, so that the curing could not be completed, and the cohesiveness after curing was evaluated as low. In addition, when the adhesive sheet of Comparative Example 4 was heated at 150 ° C. for 20 minutes, the curing was completed and the cohesiveness after the curing was excellent, but the support was not relatively heat resistant. As a result, a slight wave was generated on the support.
[0052]
As in Comparative Example 4, the adhesive sheet of Comparative Example 5 was not added with a photolatent acid generator that generates Bronsted acid or Lewis acid, so it was irradiated with ultraviolet light and left for one month. However, the curing could not be promoted, and the evaluation was low in cohesion. Further, since the support had no heat resistance, the support was deformed by heating at 130 ° C. for 2 minutes, so that the support could not be used, and the aggregation after curing could not be evaluated.
[0053]
As mentioned above, since the adhesive sheet of an Example has mix | blended the adhesive compound which has N-methylol group as an adhesive composition, it has moderate viscoelasticity before hardening, After curing, it had excellent cohesiveness. Moreover, since a photolatent acid generator that generates Bronsted acid or Lewis acid by light irradiation is added, curing of the adhesive compound can be promoted by heating at a low temperature for a short time, Even a support that does not have a relatively high heat resistance can be used without any wave or deformation in the support. In addition, after generation of the acid, it was possible to promote the curing of the adhesive compound even at room temperature, so that even a support having no heat resistance can be used. .
[0054]
【The invention's effect】
According to the present invention, the adhesive composition has an appropriate viscoelasticity before curing, can be pressure-bonded with a weak pressure, and has excellent creep resistance and peelability due to high cohesion after curing. , An adhesive, and an adhesive sheet using the same are obtained.
[Brief description of the drawings]
FIG. 1 is a front view of a holding force evaluation device. FIG. 2 is a cross-sectional view of a holding force evaluation device.
DESCRIPTION OF SYMBOLS 1 ... Stainless steel plate 2 ... Adhesive sheet 3 ... Fixing tool 4 ... Weight 5 ... Aluminum plate

Claims (3)

And adhesive compounds having a N- methylol group, curable adhesive composition comprising a photolatent acid generator generating Bronsted acid or Lewis acid.   A curable adhesive comprising the curable adhesive composition according to claim 1.   An adhesive sheet provided with an adhesive layer on at least one surface of a support, wherein the adhesive layer is formed from the curable adhesive of claim 2. Adhesive sheet.

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