TW201816040A - Adhesive composition and adhesive sheet - Google Patents

Abstract

Disclosed are: an adhesive composition comprising an acrylic copolymer (A) having an acid value of 30 mgKOH/g or more and a weight-average molecular weight of 500,000 or more, a thermosetting resin (B) capable of reacting with an amine-based curing agent and an amine-based curing agent (C); and an adhesive sheet prepared by using the same. The adhesive composition is improved in the property of preventing the protrusion of adhesive when it is heated, pressed and cured, while keeping excellent adhesiveness and flexibility after curing.

Description

 Substance composition and follow-up film  

The present invention relates to an acrylic resin composition which maintains the excellent adhesiveness and the flexibility after curing, and which improves the paste overflow resistance during heat press curing, and a resin sheet using the same.

A flexible printed circuit (FPC) is incorporated in a portable electronic device such as a smart phone or a wearable terminal, and the FPCs are generally joined by a bonding material such as an adhesive. In recent years, with the miniaturization and thinning of these electronic devices, the joint area of the FPC is also narrowed, and the necessity of preventing the occurrence of bleeding or the overflow of the paste during curing of the adhesive is increased. Further, in an electronic device that is miniaturized and thinned, the FPC is bent to a sharper angle, so that flexibility is required for the adhesive after curing. This is because if the flexibility is lacking, the joint portion may be cracked or broken.

For example, Patent Document 1 discloses an adhesive for electronic parts for the purpose of preventing occurrence of bleeding. The adhesive contains a curable compound such as an epoxy resin, a curing agent, inorganic fine particles, and a polyether modified siloxane. In addition, it is described that the cause of the phenomenon of bleeding is attributed to the fact that the liquid component contained in the adhesive for electronic components and the inorganic fine particles formulated to impart the coating property to impart the shakeability are low, and the polyether is modified by adding polyether. The phthalocyanine prevents the separation of the liquid component from the inorganic granules and prevents the occurrence of bleed.

Patent Document 2 discloses a resin composition for the purpose of preventing the resin composition from overflowing from the edge of the circuit member. The resin composition contains, as an essential component, a thermosetting resin such as an epoxy resin, a compound having flux activity, and a core-shell particle having a core layer containing a rubber-based component and an outer shell layer containing an acrylic component, and An inorganic filler is contained as an optional component. Further, it is described that the core-shell particles can prevent voids from occurring between the circuit member and the resin composition and in the resin composition, and can prevent the resin composition from overflowing from the edge of the circuit member.

Patent Document 3 discloses a thermosetting adhesive composition or a thermosetting tape or sheet which can be used for a flexible printed circuit board. It is described that the thermosetting adhesive composition has an acrylic polymer as an elastomer component, and further contains a phenol resin and a hexamethylenetetramine which is a crosslinking agent of a phenol resin, thereby achieving both storage stability before hardening. And adhesion or heat resistance after hardening.

However, since the adhesive composition of Patent Documents 1 and 2 contains an epoxy resin as a main component, the flexibility after curing is inferior, and for example, it is not suitable for the subsequent use of a member bent at an acute angle such as FPC. Further, since the adhesive composition of Patent Documents 1 and 2 contains a filler, if the content of the filler is large, the adhesion is lowered. Further, the inclusion of a filler is also inferior in terms of dispersibility, workability, and coatability.

On the other hand, in Patent Document 3, an acrylic polymer is used instead of an epoxy resin as an elastomer component, and a filler is not used. However, no research has been conducted on the problem of paste overflow during heat and pressure hardening. Further, in Patent Document 3, when the content of the carboxyl group-containing monomer in the monomer component constituting the acrylic polymer is more than 7% by mass, flexibility is lacking, and in the examples, only the carboxyl group-containing monomer is used. The acrylic polymer is contained in an amount of 1 or 2% by mass.

However, in an electronic device, there is a case where an erroneous action or material destruction of a component occurs due to an adverse effect of static electricity or electromagnetic waves. In order to prevent such an adverse effect, there is a method of using a conductive tape as a tape for fixing a member such as a component inside the machine. Specifically, an adhesive tape in which an adhesive layer is added with conductive particles is known.

For example, Patent Document 4 describes that a resin-like conductive filler and a specific non-conductive filler having an average particle diameter are blended in a thermosetting adhesive composition to suppress resin overflow. However, if the adhesive sheet comprising the thermosetting adhesive composition of Patent Document 4 is used for the portable electronic device which has been miniaturized and thinned as described above, it may not be affected by the non-conductive filler. Get sufficient conductivity. Further, it is not preferable in terms of dispersibility, workability, and coatability in addition to the conductive filler and the non-conductive filler.

 [Previous Technical Literature]    [Patent Literature]  

Patent Document 1: Japanese Patent Laid-Open Publication No. 2011-195735

Patent Document 2: Japanese Patent Laid-Open Publication No. 2015-030745

Patent Document 3: Japanese Patent Laid-Open Publication No. 2010-065078

Patent Document 4: Japanese Patent Laid-Open No. 2016-102204

An object of the present invention is to provide an acrylic resin composition which maintains the excellent adhesiveness and the flexibility after curing, and which improves the paste overflow resistance during heat press curing, and a back sheet using the same.

In order to achieve the above object, the present inventors have conducted an effort to find an acrylic copolymer (A), a thermosetting resin (B), and an amine hardener (C) having a specific acid value and a weight average molecular weight. Very effective, thus completing the present invention.

In other words, the present invention is an adhesive composition containing an acrylic copolymer (A) having an acid value of 30 mgKOH/g or more and a weight average molecular weight of 500,000 or more, and a thermosetting property capable of undergoing a hardening reaction with an amine curing agent. Resin (B) and an amine hardener (C).

Further, the present invention is a back sheet formed of the above-described adhesive composition.

The adhesive composition of the present invention and the adhesive sheet using the same are excellent in paste-resistant overflow resistance. Moreover, excellent adhesion and softness after hardening are also maintained. For example, it is not always necessary to use a large amount of a filler as in the prior art to improve the paste overflow resistance, so that it is possible to maintain excellent properties without changing the paste overflow property.

Further, in the case where the adhesive composition of the present invention contains conductive particles, it is not always necessary to use a non-conductive filler in addition to the conductive filler as in the thermosetting property of the patent document 4 to improve the paste overflow resistance. Therefore, it is also possible to maintain excellent conductivity (as a result of the antistatic property or electromagnetic wave shielding property) and to improve the paste overflow resistance.

In general, the amount of overflow of the paste when the adhesive sheet is subjected to heat and pressure hardening is not necessarily proportional to the softness after hardening. Since the molecular structure of the components in the composition is different before and after the hardening, the composition having a lower thermal fluidity before the hardening is required, and the softness after hardening is higher. In the present invention, a composition can be provided which has a relatively low thermal fluidity before and during hardening and a small amount of paste overflow, but maintains excellent adhesion and has sufficient flexibility after hardening. This effect is considered to be an interaction of a relatively large amount of a free acid, a thermosetting resin (B), and an amine hardener (C) in an acrylic copolymer (A) having a moderate weight average molecular weight. caused.

For example, there are irregularities on the surface of a conventional FPC, but in recent years, FPC having a flat surface has also been made into a product. Conventionally, when the adhesive composition is applied to the surface of the FPC, the adhesive composition is infiltrated into the uneven structure of the surface of the FPC, but in the case of a flat FPC, the infiltrated portion overflows during the press-fitting. The tendency. On the other hand, the adhesive sheet of the present invention has a relatively low thermal fluidity before and during hardening, but has sufficient flexibility after curing, and is therefore particularly useful for the purpose of joining such flat FPCs to each other.

Further, the adhesive composition of the present invention and the use of the adhesive sheet having the characteristics of relatively small dimensional change caused by heat are also required for miniaturization and high density of electronic components to be mounted on an electronic device. It is especially useful for bonding applications.

1‧‧‧Next film

2‧‧‧Release paper

3‧‧‧FPC

4‧‧‧ test strips

5‧‧‧ glass plate

Fig. 1 (A) to (D) are schematic cross-sectional views showing an example of a method of using the substrate-free underlayer of the present invention.

2(A) to (C) are schematic views for explaining the evaluation method of the amount of paste overflow in the examples.

 <Binder composition>  

The adhesive composition of the present invention contains a composition of an acrylic copolymer (A), a thermosetting resin (B) which can be cured by an amine curing agent, and an amine curing agent (C).

The acrylic copolymer (A) used in the present invention has an acid value of 30 mgKOH/g or more, preferably 30 to 150 mgKOH/g, more preferably 30 to 120 mgKOH/g. When the acid value of the acrylic copolymer (A) is too low, properties such as paste overflow resistance and heat resistance are lowered. The acid value is the amount (mg) of KOH required to neutralize 1 g of the nonvolatile component of the acrylic copolymer (A).

The weight average molecular weight (Mw) of the acrylic copolymer (A) is 500,000 or more, preferably 550,000 to 1.7 million, more preferably 60 to 1.4 million. When the Mw of the acrylic copolymer (A) is too low, properties such as paste overflow resistance and heat resistance are lowered. The weight average molecular weight is a value measured by a Gel Permeation Chromatography (GPC) method.

The theoretical Tg of the acrylic copolymer (A) is preferably 150 ° C or lower, more preferably -100 to 100 ° C. The theoretical Tg is a value calculated by the formula of FOX.

The acrylic copolymer (A) is a copolymer comprising a monomer unit derived from a (meth)acrylic monomer as a main component. In addition, the specific type and content of each monomer unit are not particularly limited as long as it includes a monomer unit having an acid group for making the acid value of the acrylic copolymer (A) 30 mgKOH/g or more. However, the acrylic copolymer (A) used in the present invention preferably contains a monomer unit derived from an alkyl (meth)acrylate (A1) having an alkyl group having 1 to 14 carbon atoms, and a source thereof. From the monomer unit of the carboxyl group-containing monomer (A2).

Specific examples of the alkyl (meth)acrylate (A1) having an alkyl group having 1 to 14 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, and (methyl). Propyl acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, Isodecyl (meth)acrylate, lauryl (meth)acrylate. Among them, preferred is butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate. The content of the alkyl (meth)acrylate (A1) is preferably from 85 to 95% by mass, more preferably from 88 to 92% by mass, based on 100% by mass of the monomer unit constituting the acrylic copolymer (A).

Specific examples of the carboxyl group-containing monomer (A2) include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid, and 2-carboxy-1-butene. 2-carboxy-1-pentene, 2-carboxy-1-hexene, 2-carboxy-1-heptene. Among them, acrylic acid, methacrylic acid, and especially acrylic acid are preferable. The content of the carboxyl group-containing monomer (A2) is preferably 5% by mass or more, more preferably 6% by mass or more, and even more preferably 7% by mass or more based on 100% by mass of the monomer unit constituting the acryl-based copolymer (A). The best is 8 mass% or more. Further, the upper limit of the content is not particularly limited, but is preferably 15% by mass or less, and more preferably 12% by mass or less.

The acrylic copolymer (A) may contain a monomer unit derived from a monomer other than the components (A1) and (A2) within a range not impairing the effects of the present invention. Specific examples of the monomer other than the components (A1) and (A2) include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and (meth)acrylic acid 4- a hydroxyl group-containing monomer such as hydroxybutyl ester; and vinyl acetate. In the case of containing a hydroxyl group-containing monomer, the content thereof is preferably from 0.01 to 0.5% by mass, more preferably from 0.05 to 0.15% by mass, based on 100% by mass of the monomer unit constituting the acrylic copolymer (A). In the case of containing vinyl acetate, the content thereof is preferably from 1 to 5% by mass, and more preferably from 2 to 4% by mass, based on 100% by mass of the monomer unit constituting the acrylic copolymer (A).

The polymerization method for producing the acrylic copolymer (A) is not particularly limited, and from the viewpoint of easy polymer design, radical solution polymerization is preferred.

The thermosetting resin (B) used in the present invention is not particularly limited as long as it is a thermosetting resin which can undergo a curing reaction with the amine curing agent (C). By curing the thermosetting resin (B) and the amine curing agent (C) to form a crosslinked structure, properties such as adhesion and heat resistance are improved. Examples of the thermosetting resin (B) include a phenol resin, an epoxy resin, a urea resin, a cyanate resin, a maleimide resin, and an acetal resin. Among them, in terms of heat resistance or adhesion, a phenol resin or an epoxy resin is preferred, and a phenol resin is preferred.

Specific examples of the phenol resin include a phenol novolak resin, a cresol novolak resin, a third butyl phenol novolak resin, a phenol aralkyl resin, a dicyclopentadiene cresol novolak resin, and a dicyclopentanyl group. Diene phenol novolak resin, benzene dimethyl modified phenol novolak resin, naphthol novolac resin, trisphenol novolac resin, tetraphenol novolac resin, bisphenol A novolac resin, poly p-vinylphenol resin, Resorcinol type phenol resin, polyhydroxy styrene such as polyparaxyl styrene. Among them, a phenol novolak resin is preferred in terms of the bonding strength when the FPCs are brought together. Two or more kinds of phenol resins may also be used in combination.

By using the thermosetting resin (B) as a curing component, properties such as adhesion, heat resistance, and paste overflow resistance are improved. The content of the thermosetting resin (B) is preferably 20 to 60 parts by mass, more preferably 30 to 50 parts by mass, per 100 parts by mass of the acrylic copolymer (A).

The amine-based curing agent (C) used in the present invention is a component which reacts with a carboxyl group in the thermosetting resin (B) and the acrylic copolymer (A) to form a crosslinked structure. Specific examples thereof include a chain aliphatic amine (for example, di-ethyltriamine, tri-ethyltetramine, hexamethylenediamine, N,N-dimethylpropylamine, dimethylbenzyl). Amine, 2-(dimethylamino)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, m-xylylenediamine, etc.), a cyclic aliphatic amine (for example, N-amino group B) Kipi , bis(3-methyl-4-aminocyclohexyl)methane, bis(4-aminocyclohexyl)methane, blue diamine, isophorone diamine, 1,3-bis(aminomethyl) Cyclohexane, etc.), heterocyclic amines (for example, hexamethylenetetramine, piperazine N,N-dimethylperazine , tri-ethyl diamine, melamine, melamine, etc.), aromatic amines (for example, m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diamine Diphenyl hydrazine, etc.). Two or more kinds of amine-based curing agents (C) may also be used in combination. Among them, hexamethylenetetramine is preferred in terms of reliability and the like.

By using the amine-based curing agent (C), properties such as flexibility and paste overflow resistance are improved as compared with other curing agents. The content of the amine-based curing agent (C) is preferably less than 1 part by mass, more preferably 0.1 to 0.8 part by mass, per 100 parts by mass of the total of the acrylic copolymer (A) and the thermosetting resin (B).

The adhesive composition of the present invention preferably further contains a thermally conductive filler or a conductive filler, and more preferably contains conductive particles (D). Further, the conductive particles (D) preferably contain metal particles. Specific examples of the conductive particles (D) include metal particles containing a metal such as nickel, copper, chromium, gold, silver, or an alloy or a modified product thereof, and a surface of a core particle containing a metal or an alloy thereof or a modified substance. Metal particles, carbon particles, and graphite particles formed by plating different kinds of metals or alloys or modified materials thereof. Further, conductive particles obtained by coating a metal on the surface of the resin may also be used. Two or more kinds of conductive particles (D) may also be used in combination. Among them, metal particles are preferable, and nickel particles, copper particles, and metal particles obtained by plating silver on the surface of the core particles containing metal are more preferable. The shape of the conductive particles (D) is not particularly limited, and conductive particles (D) having a known shape such as a long line shape, a spike shape, a chip shape, or a spherical shape can be used. Among them, in terms of the fact that the contact points of the conductive particles tend to increase and the resistance value is stabilized, it is preferably a long line shape, a spike shape, or a chip shape. The size (average diameter) of the conductive particles is preferably from 0.1 to 100 μm.

By using the conductive particles (D), the conductivity of the adhesive composition is improved, whereby the electrification of the static electricity can be suppressed and the electromagnetic waves can be shielded. The content of the conductive particles (D) is preferably 0.01 to 100 parts by mass, more preferably 5 to 80 parts by mass, based on 100 parts by mass of the total of the acrylic copolymer (A) and the thermosetting resin (B). Good for 20~50 parts by mass.

The adhesive composition of the present invention may further contain other additives as needed. For example, it may also contain an anti-aging agent, a filler, a coloring agent (pigment or dye, etc.), an ultraviolet absorber, an antioxidant, an adhesion-imparting agent, a plasticizer, a softener, a surfactant, an antistatic agent, a thermal conductive agent, and an anti-aging agent. Additives such as heat shrinking agents and flame retardants.

The adhesive composition of the present invention is excellent in flexibility after heat curing. For example, the Young's modulus according to JIS K 6251 after thermal hardening measured by the following method is preferably 50.0 MPa or less, more preferably 20.0 MPa or less, still more preferably 10.0 MPa or less, and most preferably 5.0 MPa or less. Further, the elongation according to JIS K 6251 after thermal curing measured by the following method is preferably 100% or more, more preferably 200% or more, and still more preferably 300% or more. Further, the tensile strength according to JIS K 6251 after thermal curing is preferably 0.1 MPa or more, more preferably 0.2 MPa or more, and still more preferably 0.3 MPa or more.

 (Young's modulus, elongation and tensile strength)  

The adhesive composition was formed into a sheet having a thickness of 25 μm, and was superposed on 8 sheets, and hardened at 180 ° C for 2 hours to obtain a test piece having a thickness of 200 μm, a longitudinal direction of 50 mm, and a lateral direction of 10 mm. For the test piece, according to JIS K 6251 The elongation and the tensile strength were measured under the conditions of a tensile speed of 300 mm/min and a cross between the chucks, and the Young's modulus was calculated from the values of the elongation and the tensile strength.

The adhesive composition of the present invention is excellent in paste repellency at the time of heat and pressure hardening. Specifically, the amount of paste overflow measured by the following method is 60 mm or less, preferably 50 mm or less, more preferably 45 mm or less.

 (paste overflow)  

The adhesive composition was formed into a sheet having a thickness of 25 μm, and was superposed on four sheets to obtain a test piece having a thickness of 100 μm, a longitudinal direction of 10 mm, and a lateral direction of 10 mm, and the test piece was sandwiched between glass sheets at a temperature of 150. °C, a pressure of 1.0 MPa, heating and pressurizing for 60 minutes, followed by totaling the length of the longitudinal direction (X mm) of the test piece in the overflow state and the length of the lateral direction (Y mm) as a paste overflow amount .

 <Next piece>  

The adhesive sheet of the present invention is a back sheet formed of the above-described adhesive composition. The adhesive sheet may be a sheet containing a separate body of the adhesive composition (the adhesive sheet having no base type), or may be an adhesive sheet in which an adhesive layer containing an adhesive composition is formed on one or both sides of the substrate. .

The baseless type back sheet can be formed, for example, by applying an adhesive composition to a support such as release paper, followed by drying. On the other hand, in the case of a substrate having a substrate, the adhesive composition can be applied to the substrate, followed by drying to form an adhesive layer, or on a support such as a release paper. An adhesive layer is formed, and the adhesive layer is bonded to one side or both sides of the substrate. The adhesive layer of the baseless type back sheet and the back sheet having the substrate may be a single layer, or may be a laminate including a plurality of layers.

The coating method of the subsequent composition is not particularly limited, and any known method can be used. Specific examples thereof include coating using a roll coater, a die coater, a lip coater, a dip roll coater, a bar coater, a knife coater, and a spray roll coater.

Fig. 1 is a schematic cross-sectional view showing an example of a method of using a substrate-free back sheet of the present invention. First, as shown in FIG. 1(A), the back sheet 1 formed on the release paper 2 is prepared. Then, as shown in Fig. 1(B), the back sheet 1 was laminated on the FPC 3, and pressed at a temperature of 100 ° C for 10 seconds from the release paper 2 side to perform pre-fixing. Thereafter, as shown in FIG. 1(C), the release paper 2 is peeled off. Then, as shown in Fig. 1(D), another FPC 3 is laminated on the back sheet 1, and is pressed at a temperature of 150 to 180 ° C for 30 to 60 minutes to be officially fixed.

The thickness of the sheet is not particularly limited, and is preferably 2 to 100 μm, more preferably 3 to 100 μm, still more preferably 4 to 50 μm, and most preferably 5 to 40 μm in terms of adhesion or workability. Further, in the case of the back sheet having the substrate, the thickness of the substrate is not particularly limited, and therefore the thickness of the entire back sheet having the substrate is not particularly limited. However, the thickness of the adhesive layer of such a sheet is preferably from 2 to 100 μm, more preferably from 3 to 100 μm, still more preferably from 4 to 50 μm, most preferably from 5 to 40 μm.

In the case where the adhesive sheet of the present invention has a substrate, the substrate is not particularly limited, and any known substrate may be used. Specific examples thereof include a fibrous base material such as paper, cloth, nonwoven fabric, and mesh, an olefin resin, a polyester resin, a polyvinyl chloride resin, a vinyl acetate resin, and a polyamide resin. a resin film such as a polyimide ether resin, a polyether ether ketone (PEEK, a polyetheretherketone) or a polyphenylene sulfide (PPS), a resin sheet, a rubber sheet, a foam sheet, a metal foil, a metal plate, or the like The laminate (especially a laminate of a resin substrate and a substrate other than a resin or a laminate of resin substrates). The substrate may be either a single layer or a plurality of layers. It is also possible to perform various processes such as back surface treatment, antistatic treatment, and primer treatment on the surface of the base material on which the adhesive layer is provided.

The backsheet of the present invention can also be protected with release paper or other film. The release paper or other film is not particularly limited, and a known one may be used as needed.

In the case where the adhesive sheet of the present invention has a substrate, a conductive substrate can be used as the substrate to form a conductive adhesive sheet. For example, a conductive adhesive layer is obtained by forming a conductive adhesive layer on one surface or both surfaces of a conductive substrate by using the adhesive composition of the present invention containing the conductive particles (D). The conductive substrate helps to suppress the effect of electrostatic charging or the effect of shielding electromagnetic waves. For example, with the miniaturization and thinning of products in recent years, the use of tapes for sharp corners has increased, and the use of tapes having a highly conductive conductive substrate (metal foil, etc.) is also required at acute angles. Not used as a problem. On the other hand, since the adhesive layer formed of the adhesive composition of the present invention is excellent in various properties such as adhesion and flexibility after curing, even if a conductive substrate having a strong plasticity is used, it can be satisfactorily Used for sharp corners.

The conductive substrate is preferably a metal substrate, more preferably a metal foil. Specific examples of the metal include aluminum, copper, nickel, stainless steel, iron, chromium, and titanium. Among them, copper and aluminum are preferred, and copper is preferred. The thickness of the conductive substrate is preferably from 1 to 50 μm, more preferably from 5 to 35 μm, still more preferably from 6 to 20 μm.

The thickness of the adhesive layer of the conductive adhesive sheet is preferably from 1 to 100 μm, more preferably from 3 to 50 μm, still more preferably from 5 to 30 μm, most preferably from 7 to 20 μm. The subsequent layer may be formed only on one side of the conductive substrate, but is preferably formed on both sides to form a double-sided tape.

 [Examples]  

Hereinafter, the present invention will be described in further detail by way of examples and comparative examples. In the following description, "parts" means parts by mass, and "%" means % by mass.

 <Production Examples 1 to 4 and C1 to C2 (Preparation of Acrylic Copolymer (A))>  

The component (A1), the component (A2) and other components, and ethyl acetate shown in Table 1 were added to a reaction apparatus equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas introduction tube, and the mixture was transferred as a chain. The n-dodecyl mercaptan and 0.1 part of lauryl peroxide as a peroxide-based radical polymerization initiator. Nitrogen gas was sealed in the reaction apparatus, and while stirring, a polymerization reaction was carried out at 68 ° C for 3 hours under a nitrogen gas stream, and then polymerization was carried out at 78 ° C for 3 hours. Then, it was cooled to room temperature, and ethyl acetate was added. Thereby, the acrylic copolymer (A) having a solid concentration of 30% was obtained.

The acid value, theoretical Tg, and weight average molecular weight (Mw) of each acrylic copolymer are shown in Table 1. The acid value is the amount (mg) of KOH required to neutralize 1 g of the nonvolatile component of the copolymer. The theoretical Tg is a value calculated by the formula of FOX. The weight average molecular weight (Mw) is a value obtained by measuring the molecular weight in terms of standard polystyrene of the acrylic copolymer by the GPC method under the following measuring apparatus and conditions.

‧Device: LC-2000 Series (manufactured by JASCO Corporation)

‧Tube: 2 Shodex (registered trademark) KF-806MX and 1 Shodex (registered trademark) KF-802X manufactured by Showa Denko

‧ Eluent: Tetrahydrofuran (THF, Tetrahydrofuran)

‧Flow rate: 1.0mL/min

‧column temperature: 40 ° C

‧Injection amount: 100μL

‧Detector: Refractometer (RI, Refractive Index)

‧ Measurement sample: The acrylic copolymer was dissolved in THF to prepare a solution having a concentration of the acrylic copolymer of 0.5% by mass, and the mixture was removed by filtration using a filter.

Abbreviations in the tables indicate the following compounds.

"2-EHA": 2-ethylhexyl acrylate

"BA": n-butyl acrylate

"MA": Methyl acrylate

"EA": ethyl acrylate

"AA": Acrylic

"4-HBA": 4-hydroxybutyl acrylate

"Vac": vinyl acetate

"ACMO": Acetylene Porphyrin

 <Examples 1 to 4 and Comparative Examples 1 to 5 (Preparation of an adhesive composition and production of an adhesive sheet)>  

As shown in Tables 2 and 3, 100 parts of the solid content of the acrylic copolymer obtained as the acrylic copolymer (A) in Production Examples 1 to 4 and C1 to C2 was added as a thermosetting resin (B). A novolak phenol resin (manufactured by Arakawa Chemical Co., Ltd., trade name: Tamanol (registered trademark) 759) and hexamethylenetetramine as an amine-based hardener (C) (manufactured by Ouchi Shinko Chemical Co., Ltd., trade name Nocceler (registered trademark) H) and mixing to obtain an adhesive composition.

This adhesive composition was applied onto the fluorenone-treated release paper so that the thickness after drying became 25 μm. Then, the solvent was removed and dried at 100 ° C to obtain a baseless type of back sheet on the release paper.

 <evaluation test>  

The succeeding sheets obtained in Examples 1 to 4 and Comparative Examples 1 to 5 were evaluated by the following methods. The results are shown in Tables 2 and 3.

 (paste overflow)  

Four sheets of a thickness of 25 μm were stacked and cut, and a test piece 4 having a thickness of 100 μm, a longitudinal direction of 10 mm, and a lateral direction of 10 mm was obtained. As shown in Fig. 2(A), the test piece 4 was sandwiched between the glass plates 5, and heated and pressurized at a temperature of 150 ° C and a pressure of 1.0 MPa for 60 minutes to proceed. The test piece 4 shown in Fig. 2(B) is in a state of overflowing from the original state as shown in Fig. (C) by the heating and pressurization. The maximum length (X mm) of the test piece 4 in the overflow state and the maximum length (Y mm) of the lateral direction were totaled as the paste overflow amount.

 (Young's modulus, elongation and tensile strength)  

The laminate having a thickness of 25 μm was overlaid with 8 sheets, hardened at 180 ° C for 2 hours, and cut, to obtain a test piece having a thickness of 200 μm, a longitudinal direction of 50 mm, and a lateral direction of 10 mm. Then, using a tensile tester, elongation and tensile strength were measured in accordance with JIS K 6251 at a tensile speed of 300 mm/min and a cross between the chucks, and Young's value was calculated from the values of the elongation and the tensile strength. Modulus.

 (and then force)  

The 25 μm thick backsheet was bonded to a 25 μm thick polyimide film by a laminator set at 100 °C. Then, the test piece was obtained by hardening at 1.25 MPa, 180 ° C for 2 hours, followed by SUS 304 plate. Using a tensile tester, a 180° peel test was performed under normal temperature (23° C., 50% RH) and a tensile speed of 300 mm/min in accordance with JIS Z 0237, and the peel adhesion (N/20 mm) was measured.

 <evaluation>  

As is clear from Table 2, in the case of the heat-pressure-hardening of the succeeding films of Examples 1 to 4, the amount of paste overflow was small, and the paste-resistant property was excellent. Further, it can be understood from the measurement results of the Young's modulus, the tensile strength, and the elongation that the cured sheet has sufficient flexibility. Further, it can be understood from the measurement results of the adhesion force that the heat resistance and the adhesion are also sufficient.

As is clear from Table 3, since the weight average molecular weight (Mw) of the acrylic copolymer (A) was low in the adhesive sheet of Comparative Example 1, the paste overflow amount exceeded 60 mm, and the paste overflow resistance was inferior. In the adhesive sheets of Comparative Examples 2 and 3, since the acid value of the acrylic copolymer (A) was low, the paste overflow resistance was inferior, and the elongation (%) and the adhesion were also inferior.

In Comparative Examples 4 and 5, an example in which a back sheet was produced in the same manner as in Examples 1 and 3 except that the thermosetting resin (B) was not used was used. As can be seen from Table 3, the adhesive films of Comparative Examples 4 and 5 were significantly inferior to those of Examples 1 and 3.

 <Examples 5 to 9 (Preparation of an adhesive composition and production of a sheet)>  

An adhesive composition was prepared in the same manner as in Example 1 except that the metal particles (D1) to (D3) as the conductive particles (D) were added and mixed in an amount (parts) shown in Table 4, and a substrate-free composition was obtained. The type of film.

"D1": nickel-based conductive particles (manufactured by Vale, trade name Nickel powder-Type 255, long-line shape, average particle diameter 2.2 to 2.8 μm)

"D2": nickel-based conductive particles (manufactured by NOVAMET Co., Ltd., trade name HCA-1, flaky)

"D3": copper (core)-silver (plating)-based conductive particles (manufactured by TOYO ALUMINIUM Co., Ltd., trade name: TFM-C05F, spherical, average particle size: 6 μm)

 <evaluation test>  

The succeeding sheets obtained in Examples 5 to 9 were evaluated by the above methods. Further, the resistance value was also measured by the following method. The results are shown in Table 4.

 (resistance)  

The 25 mm × 25 mm slab was cut into a brass (gold plated) electrode, and a voltage of 3.5 N was applied from the upper portion of the electrode to adjust the voltage by a current of 0.1 A, and R ( The resistance value (C2) is calculated by the equation of resistance value = V (voltage) / I (current).

As is clear from Table 4, since the electrode sheets of Examples 5 to 9 contain the conductive particles (D), the electric resistance value is low, the electric conductivity is excellent, and the paste overflow resistance is further superior to that of the first embodiment. Further, although the conductive particles (D) are contained, sufficient adhesion and sufficient flexibility after curing are maintained.

 (industrial availability)  

The adhesive composition of the present invention and the adhesive sheet using the same maintain excellent adhesiveness and flexibility after curing, and the paste-resistant property at the time of heat-pressure hardening is improved. Therefore, it can be used in all applications in the field where such characteristics are required. For example, it can be used in portable electronic devices such as smart phones, tablets, car navigation systems, cameras, audio-visual machines, game machines, and information machines. Specifically, it is very useful, for example, in the use of joining FPCs in an electronic device to each other.

Claims (12)

 An adhesive composition comprising an acrylic copolymer (A) having an acid value of 30 mgKOH/g or more and a weight average molecular weight of 500,000 or more, a thermosetting resin (B) capable of undergoing a curing reaction with an amine curing agent, and And an amine hardener (C).    The acrylic resin composition of claim 1, wherein the acrylic copolymer (A) comprises a monomer unit (A1) derived from an alkyl (meth)acrylate having an alkyl group having 1 to 14 carbon atoms.    The adhesive composition of claim 1, wherein the acrylic copolymer (A) comprises a monomer unit (A2) derived from a carboxyl group-containing monomer, and the content of the monomer unit is 5% by mass or more.    The composition of the thermosetting resin (B) is 20 to 60 parts by mass based on 100 parts by mass of the acrylic copolymer (A).    The content of the amine-based curing agent (C) is less than 1 part by mass based on 100 parts by mass of the total of the acrylic copolymer (A) and the thermosetting resin (B).    The adhesive composition of claim 1, which further contains conductive particles (D).    The adhesive composition of claim 6, wherein the conductive particles (D) comprise metal particles.    The content of the conductive particles (D) is 0.01 to 100 parts by mass based on 100 parts by mass of the total of the acrylic copolymer (A) and the thermosetting resin (B).    The adhesive composition according to claim 1, wherein the Young's modulus measured by the following method is 50.0 MPa or less, and the elongation is 100% or more, (Young's modulus and elongation), and the adhesive composition is formed. In the form of a sheet having a thickness of 25 μm, 8 sheets were overlapped and hardened at 180° C. for 2 hours to obtain a test piece having a thickness of 200 μm, a longitudinal direction of 50 mm, and a lateral direction of 10 mm, and the test piece was subjected to a tensile speed of 300 mm/min according to JIS K 6251. The elongation and tensile strength were measured under conditions of 10 mm between the chucks, and the Young's modulus was calculated from the values of the elongation and the tensile strength.    The adhesive composition according to claim 1, wherein the paste overflow amount measured by the following method is 60 mm or less, and the paste composition is formed into a sheet having a thickness of 25 μm, and is superposed thereon. A test piece having a thickness of 100 μm, a longitudinal direction of 10 mm, and a lateral direction of 10 mm was obtained, and the test piece was sandwiched between glass plates, and heated and pressurized at a temperature of 150 ° C and a pressure of 1.0 MPa for 60 minutes, followed by overflow. The longitudinal length (X mm) of the test piece is combined with the maximum value of the lateral length (Y mm) as the paste overflow amount.    An adhesive sheet formed from the adhesive composition of claim 1.    The thickness of the film of claim 11 is 2 to 100 μm.