JP4946318B2 - Adhesive composition and substrate for flexible printed wiring board - Google Patents

Description

  The present invention relates to an adhesive composition and a substrate for a flexible printed wiring board, and in particular, an adhesive capable of forming an adhesive layer that exhibits excellent electrical properties such as low dielectric constant and low dielectric loss, and sufficient adhesive strength. The present invention relates to a composition and a substrate for a flexible printed wiring board using the composition.

  2. Description of the Related Art In recent years, as communication devices such as electronic devices and mobile phones have become lighter, thinner, and smaller, flexible circuit boards that are advantageous for circuit design have been used for many of these communication devices. This flexible circuit board has, for example, a structure in which an insulating film layer made of polyimide and a copper foil layer that is a circuit board are integrated through an adhesive layer. The circuit board can be produced by etching a copper foil.

  The adhesive composition that forms the adhesive layer has good compatibility with thermosetting resins such as epoxy resins, and is generally sufficiently hard and brittle with sufficient adhesive strength and toughness for the thermosetting resins. For the purpose of imparting acrylonitrile, those containing a copolymer containing acrylonitrile (for example, acrylonitrile-butadiene copolymer or carboxy-modified acrylonitrile-butadiene copolymer) are known (for example, Patent Documents 1 to 3). .

Japanese Patent Laid-Open No. 10-102025 JP 2002-235063 A JP 2003-165898 A

  However, when the acrylonitrile-containing copolymer contains a predetermined amount or more of acrylonitrile, the electrical characteristics of the formed adhesive layer, particularly low dielectric constant and low dielectric loss, are inferior. In the future, it is expected that the density of the flexible circuit will increase. In the density increase of the flexible circuit, not only the adhesive performance but also excellent electrical characteristics (low dielectric loss and low dielectric loss) are desired.

  The present invention has been made in view of such problems of the prior art, and the problem is that (A) (a-1) a single monomer having at least two ethylenically polymerizable unsaturated groups. A copolymer having a structural unit derived from a monomer and (a-2) a structural unit derived from a monomer having an alcoholic hydroxyl group, (B) a thermosetting resin, and (C) a curing agent. An object of the present invention is to provide an adhesive composition that retains sufficient adhesive performance and has excellent electrical characteristics in increasing the density of flexible circuits.

  As a result of intensive studies to achieve the above problems, the present inventors have found that the above problems can be achieved by including a specific copolymer, a thermosetting resin, and a curing agent. The present invention has been completed.

  That is, according to the present invention, the following adhesive composition and flexible printed wiring board substrate are provided.

[1] (A) (a-1) a structural unit derived from a monomer having at least two ethylenically polymerizable unsaturated groups and (a-2) a structural unit derived from a monomer having an alcoholic hydroxyl group And (a-3) a copolymer having a structural unit derived from acrylonitrile , (B) a thermosetting resin, and (C) a curing agent, and (a) the above-mentioned (a) contained in the copolymer -3) The adhesive composition whose ratio of the structural unit derived from acrylonitrile is 5 mol% or less with respect to 100 mol% of all the structural units which comprise the said (A) copolymer .

[2] The proportion of the structural unit (a-1) is 50 to 95 mol% with respect to 100 mol% of all structural units constituting the copolymer (A), and the structure (a-2) The adhesive composition according to [1], wherein the unit ratio is 5 to 50 mol% with respect to 100 mol% of all structural units constituting the copolymer (A).

[ 3 ] The adhesive composition according to [1] or [ 2 ], which contains an epoxy resin as the (B) thermosetting resin.

[ 4 ] The adhesive composition according to any one of [1] to [ 3 ], wherein the content of alkali metal ions contained in the copolymer (A) is 50 ppm or less.

[ 5 ] The insulating film layer, the circuit board, and the adhesive composition according to any one of [1] to [ 4 ] are formed between the insulating film layer and the circuit board. And a flexible printed wiring board substrate comprising: the insulating film layer; and an adhesive layer that bonds the circuit board.

  The adhesive composition of the present invention has an effect that an adhesive layer having excellent electrical characteristics (low dielectric loss and low dielectric loss) can be formed while maintaining sufficient adhesive performance.

  Further, the flexible printed wiring board substrate of the present invention has an effect of including an adhesive layer having excellent electrical characteristics (low dielectric loss and low dielectric loss) while maintaining sufficient adhesive performance.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below, but the present invention is not limited to the following embodiment, and is based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention. It should be understood that modifications and improvements as appropriate to the following embodiments also fall within the scope of the present invention.

[1] Adhesive composition:
The adhesive composition of the present invention comprises (A) (a-1) a structural unit derived from a monomer having at least two ethylenically polymerizable unsaturated groups and (a-2) a single monomer having an alcoholic hydroxyl group. A copolymer having a structural unit derived from the body (hereinafter sometimes referred to as “(A) copolymer”), (B) a thermosetting resin, and (C) a curing agent. . With such a configuration, it is possible to form an adhesive layer having excellent electrical characteristics (low dielectric loss / low dielectric loss) while maintaining sufficient adhesive performance. The details will be described below.

[1-1] (A) Copolymer:
The (A) copolymer contained in the adhesive composition of the present invention comprises (a-1) a structural unit derived from a monomer having at least two ethylenically polymerizable unsaturated groups (hereinafter referred to as “(a- 1) structural unit ”and (a-2) a structural unit derived from a monomer having an alcoholic hydroxyl group (hereinafter sometimes referred to as“ (a-2) structural unit ”). Is.

  The structural unit (a-1) is not particularly limited as long as it is derived from a monomer having at least two ethylenically polymerizable unsaturated groups. Examples of the monomer having at least two ethylenically unsaturated groups include a diene monomer, and examples of the diene monomer include 1,3-butadiene, dimethylbutadiene, Examples include chloroprene, 1,3-pentadiene, isoprene and the like.

  The proportion of the structural unit (a-1) is preferably 50 to 95 mol% with respect to 100 mol% of all structural units constituting the (A) copolymer. More preferably, it is 55-85 mol%, Most preferably, it is 60-85 mol%. (A-1) When the proportion of the structural units is in the above range, the resulting copolymer has rubber elasticity and sufficient adhesive strength is obtained. Moreover, there exists a possibility that adhesive force may fall that the ratio of the said (a-1) structural unit is less than 50 mol%. On the other hand, if the proportion of the (a-1) structural unit is more than 95 mol%, the compatibility with the thermosetting resin to be blended is lowered.

  (A-2) The structural unit is not particularly limited as long as it is derived from a monomer having an alcoholic hydroxyl group. As the monomer having an alcoholic hydroxyl group, (meth) acrylate having an alcoholic hydroxyl group is preferable. Examples of the monomer having an alcoholic hydroxyl group include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- Hydroxy-3-phenoxypropyl (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol di (meth) acrylate monostearate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, epoxy (meth) acrylates Etc. Epoxy (meth) acrylates can be obtained, for example, by reaction of bisphenol A diglycidyl ether, glycol diglycidyl ether, and the like with (meth) acrylic acid, hydroxyalkyl (meth) acrylate, and the like.

  The proportion of the structural unit (a-2) is preferably 5 to 50 mol% with respect to 100 mol% of all structural units constituting the (A) copolymer. More preferably, it is 15-45 mol%, Most preferably, it is 15-40 mol%. (A-2) When the proportion of the structural unit is within the above range, the obtained copolymer has good compatibility with the thermosetting resin to be blended, has toughness, and has sufficient adhesiveness. .

  The (A) copolymer contains other structural units (hereinafter may be referred to as “other structural units”) in addition to the (a-1) structural unit and (a-2) structural unit. It may be a thing. Other structural units include those derived from a monomer copolymerizable with a monomer having at least two ethylenically polymerizable unsaturated groups, a monomer having an alcoholic hydroxyl group, and the like. There is no limit. Moreover, it is preferable that the ratio of another structural unit is 5-30 mol% with respect to 100 mol% of all the structural units which comprise a (A) copolymer. More preferably, it is 5 to 25 mol%, and particularly preferably 1 to 15 mol%. However, when the other structural unit is a structural unit derived from acrylonitrile, the proportion of the other structural unit (structural unit derived from acrylonitrile) is 5 with respect to 100 mol% of the copolymer (A). It is preferable that it is below mol%. Most preferably, it does not contain a structural unit derived from acrylonitrile.

  Examples of other structural units include those derived from monomers such as a monomer having a carboxyl group and a monomer having an epoxy group.

  Monomers having a carboxyl group include unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, tetraconic acid, cinnamic acid, and non-polymerized phthalic acid, succinic acid, adipic acid, etc. A free carboxyl group-containing ester such as a monoester of a functional polyvalent carboxylic acid and a hydroxyl-containing unsaturated compound such as (meth) allyl alcohol and 2-hydroxyethyl (meth) acrylate, and salts thereof. .

  Examples of the monomer having an epoxy group include (meth) allyl glycidyl ether, glycidyl (meth) acrylate, and 3,4-oxycyclohexyl (meth) acrylate.

  The method for producing the (A) copolymer is not particularly limited, and for example, an emulsion polymerization method, a suspension polymerization method, or a solution polymerization method can be used. Among these, it is preferable to manufacture by an emulsion polymerization method.

  When manufacturing by emulsion polymerization, first, each monomer is emulsified in water using a surfactant. Then, radical polymerization initiators, such as a peroxide catalyst and a redox-type catalyst, and molecular weight regulators, such as a mercaptan-type compound and a terpene compound, are added as a polymerization initiator, and it superposes | polymerizes at 0-50 degreeC. Next, after reaching a predetermined polymerization conversion rate, a polymerization terminator is added to stop the polymerization reaction, such as N, N-diethylhydroxylamine. After termination of the polymerization reaction, a copolymer emulsion can be obtained by removing unreacted monomers in the polymerization system by steam distillation or the like. The obtained copolymer emulsion is added to an electrolyte aqueous solution having a predetermined concentration, and the (A) copolymer in the copolymer emulsion is coagulated (breaking the emulsion), then washed with water and dried. (A) A copolymer can be isolated.

  (A) As a coagulation method of the copolymer, in addition to salting out by adding the copolymer emulsion to the electrolyte aqueous solution having the predetermined concentration, when a nonionic surfactant is used as the surfactant, There is a method of heating to a cloud point or higher of the nonionic surfactant to solidify the copolymer (A). In addition, when a surfactant other than the nonionic surfactant is used, the nonionic surfactant is added after the polymerization, and the copolymer (A) may be solidified by heating above the cloud point. it can.

  The surfactant is not particularly limited, but for example, anions such as alkyl sulfate ester salts, polyoxyethylene alkyl ether sulfate ester salts, alkylbenzene sulfonate salts, alkyl diphenyl ether disulfonate salts, dipotassium alkenyl succinates, and sodium alkane sulfonates. Surfactants; cationic surfactants such as alkylamine salts and quaternary ammonium salts; polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene sorbitan fatty acid esters, fatty acid monoglycerides Nonionic surfactants and amphoteric surfactants such as, and reactive emulsifiers can be used. These surfactants can be used alone or in admixture of two or more.

  (A) A copolymer is normally 50-200 mass parts with respect to 100 mass parts of (B) thermosetting resins, Preferably it is mix | blended in the quantity of 70-150 mass parts. When the blending amount is within the above range, there is an advantage that the adhesiveness of the obtained adhesive layer is improved and peeling during long-term use is less likely to occur. Moreover, there exists an advantage that the compatibility of (A) copolymer and another component improves, and the heat resistance of the adhesive layer obtained improves.

  The (A) copolymer preferably has a glass transition temperature (Tg) of −90 to 0 ° C., more preferably −80 to −10 ° C., and particularly preferably −70 to −20 ° C. . (A) When the glass transition temperature (Tg) of a copolymer is less than -90 degreeC, there exists a possibility that the heat resistance of a copolymer may fall. On the other hand, if it exceeds 0 ° C., the rubber elasticity of the copolymer may be lost. In this specification, “glass transition temperature (Tg)” refers to a value measured by a differential scanning calorimeter. Specifically, after (A) the copolymer is heated and dried, analysis is performed using a differential scanning calorimeter (trade name “EXSTAR6000DSC”, manufactured by Seiko Instruments Inc.) at a temperature increase rate of 10 ° C./min. This is the value when

The (A) copolymer preferably has a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 40 to 90, more preferably 45 to 85, and particularly preferably 50 to 80. (A) If the Mooney viscosity of the copolymer is less than 40, the viscosity of the rubber is too low and the tackiness becomes strong, which may reduce the productivity. On the other hand, if it exceeds 90, workability may be reduced. In the present specification, when “Mooney viscosity” is used, preheating is performed using a Mooney tester (manufactured by Alpha Technology Co., Ltd., trade name “MOONEY MV 2000E”) according to JIS K6300, using an ML rotor. The value measured under the conditions of 1 minute, rotor operating time 4 minutes, temperature 100 ° C.

  In addition, it is preferable that the quantity of the alkali metal ion contained in (A) copolymer is 50 ppm or less. More preferably, it is 30 ppm or less, Most preferably, it is 20 ppm or less. If the alkali metal ion content is more than 50 ppm, insulation failure may occur. In addition, as an alkali metal ion, it is preferable that they are a sodium ion and a potassium ion. That is, the total amount of sodium ions and potassium ions is preferably 50 ppm or less.

  Further, in the adhesive composition of the present invention, the proportion of structural units derived from (a-3) acrylonitrile contained in (A) the copolymer is 100 mol% of all structural units constituting the copolymer (A). The content is preferably 5 mol% or less. More preferably, it is 3 mol% or less, More preferably, it is 2 mol% or less, Especially preferably, it is 1 mol% or less. In addition, the ratio of the structural unit derived from the most preferable acrylonitrile is 0 mol%, ie, the case where it is not contained at all.

  Here, the conventional adhesive composition contains a copolymer containing a structural unit derived from acrylonitrile in a predetermined amount or more from the viewpoint of compatibility with a thermosetting resin, particularly an epoxy resin, and acrylonitrile. Examples of the copolymer containing a structural unit derived from acrylonitrile-butadiene copolymer and carboxy-modified acrylonitrile-butadiene copolymer are used. For example, Patent Document 1 includes an acrylonitrile-butadiene copolymer as a copolymer containing a structural unit derived from acrylonitrile, and the acrylonitrile-butadiene copolymer has an acrylonitrile content of 10 to 50 mol%. We are disclosing things. However, the adhesive layer formed by the adhesive composition is not sufficient in terms of electrical characteristics (particularly, low dielectric loss and low dielectric loss), and still leaves room for improvement.

  On the other hand, in the adhesive composition of the present invention, the proportion of structural units derived from (a-3) acrylonitrile contained in (A) the copolymer is 100 mol% of all structural units constituting the copolymer (A). However, in such a case, a decrease (deterioration) in electrical characteristics (particularly, low dielectric loss and low dielectric loss) due to a structural unit derived from acrylonitrile is avoided. be able to. Moreover, even if the ratio of the said (a-3) structural unit is 5 mol% or less by containing (a-2) structural unit in (A) copolymer, it is favorable with an epoxy resin. Compatibility can be improved. Thus, the adhesive layer formed by the adhesive composition of the present invention maintains excellent compatibility with thermosetting resins, particularly epoxy resins, while having excellent electrical properties (particularly low dielectric and low dielectric properties). There is an advantage of exhibiting (dielectric loss).

[1-2] (B) Thermosetting resin:
The (B) thermosetting resin contained in the adhesive composition of the present invention is not particularly limited, and an epoxy resin, a phenol resin, or the like can be used. Among these, an epoxy resin is preferable. The epoxy resin preferably has a structure having at least two epoxy groups in the molecule. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, naphthol novolac type epoxy resin, biphenyl novolac type epoxy resin, phenol novolac type epoxy resin, cresol novolak type epoxy resin, etc. It is done. Among these, a bisphenol type epoxy resin is preferable. In addition, the said (B) thermosetting resin can be used individually or in combination of 2 or more types. In addition, a halogenated epoxy resin such as a brominated epoxy resin can be added to the epoxy resin for imparting flame retardancy.

[1-3] (C) Curing agent:
The (C) curing agent contained in the adhesive composition of the present invention is not particularly limited. For example, amines such as diaminodiphenylmethane, diaminodiphenyl sulfide, diaminodiphenylsulfone, diaminobenzophenone, polyamide resin, 2-alkyl- Imidazole derivatives such as 4-methylimidazole and 2-phenyl-4-alkylimidazole, acid anhydrides such as phthalic anhydride and trimellitic anhydride, phenol resins, polysulfide resins, polyvinylphenols, dicyandiamide, dibasic Examples include acid dihydrazide, organic boron, organic phosphine, guanidines and salts thereof. In addition, these can be used individually or in combination of 2 or more types. For the purpose of accelerating the curing reaction, a curing accelerator can be used in combination with the (C) curing agent. Here, in the present specification, the “curing agent” is a concept including one that forms a crosslinked structure by itself and one that does not form a crosslinked structure by itself but promotes a crosslinking reaction. The “curing accelerator” means an agent that increases the crosslinking reaction effect of the curing agent.

  (C) It is preferable that the compounding quantity of a hardening | curing agent is 0.1-20 mass parts with respect to 100 mass parts of (B) thermosetting resins, and it is still more preferable that it is 0.5-10 mass parts. . (C) If the blending amount of the curing agent is less than 0.1 parts by mass, curing may be insufficient. On the other hand, if it exceeds 20 parts by mass, the storage stability may be lowered.

[1-4] Other additives:
The adhesive composition of the present invention comprises, in addition to (A) a copolymer, (B) a thermosetting resin, and (C) a curing agent, as necessary, an organic solvent, an adhesion assistant, a leveling agent, and an inorganic filler. , Polymer additives, reactive diluents, wettability improvers, surfactants, plasticizers, antioxidants, antistatic agents, antifungal agents, humidity control agents, flame retardants and other additives These additives may be used in amounts that do not impair the effects of the present invention.

  The organic solvent can be added to improve the handleability of the adhesive composition or to adjust the viscosity and storage stability. Such an organic solvent is not particularly limited. For example, ethylene glycol monoalkyl ether acetates such as ethylene glycol monomethyl ether acetate and ethylene glycol monoethyl ether acetate; propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl Propylene glycol monoalkyl ethers such as ether and propylene glycol monobutyl ether; Propylene glycol dialkyl ethers such as propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol dipropyl ether and propylene glycol dibutyl ether; Propylene glycol monomethyl ether acetate and propylene glycol Monoethyl ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monoalkyl ether acetates such as propylene glycol monobutyl ether acetate;

  Cellosolves such as ethyl cellosolve and butylcellosolve; Carbitols such as butylcarbitol; Lactic acid esters such as methyl lactate, ethyl lactate, n-propyl lactate, isopropyl lactate; Ethyl acetate, n-propyl acetate, isopropyl acetate, n acetate Aliphatic carboxylic acid esters such as butyl, isobutyl acetate, n-amyl acetate, isoamyl acetate, isopropyl propionate, n-butyl propionate, isobutyl propionate; methyl 3-methoxypropionate, ethyl 3-methoxypropionate, Other esters such as methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, methyl pyruvate, ethyl pyruvate; aromatic hydrocarbons such as toluene, xylene; 2-butanone (methyl ethyl ketone), 2-heptanone, 3-hep Non-, ketones such as 4-heptanone and cyclohexanone; Amides such as N-dimethylformamide, N-methylacetamide, N, N-dimethylacetamide and N-methylpyrrolidone; Lactones such as γ-butyrolacun . Among these, aromatic hydrocarbons and ketones are preferable. These organic solvents can be used alone or in admixture of two or more.

[2] Preparation of adhesive composition-containing varnish:
The adhesive composition-containing varnish containing the adhesive composition of the present invention can be prepared, for example, as follows. First, (B) thermosetting resin and (A) copolymer are put into the organic solvent and completely dissolved using a stirrer. Then, the said adhesive composition containing varnish can be obtained by adding (C) hardening | curing agent, making it a uniform solution, and preparing solid content concentration to about 40 (35-45)%.

[3] Flexible printed wiring board substrate:
The flexible printed wiring board substrate of the present invention is formed by the insulating film layer, the circuit board, and the above-described adhesive composition of the present invention, and is disposed between the insulating film layer and the circuit board. And an adhesive layer for adhering the insulating film layer and the circuit board. Such a substrate for a flexible printed wiring board can be obtained by, for example, applying the above-described adhesive composition-containing varnish to an insulating film layer, placing a circuit board on the coating film, and drying it. it can. The circuit board can be formed of, for example, copper foil, aluminum foil, silver foil, gold foil, or the like.

  As a method for applying the adhesive composition-containing varnish to the insulating film layer, for example, a coating method such as a dipping method, a spray method, a bar coating method, a roll coating method, or a spin coating method can be used. Moreover, as an insulating film layer, a polyimide film, a polyester film, a polyethylene naphthalate film, a polyetherimide film etc. can be mentioned, for example.

  In addition, the said flexible printed wiring board board | substrate can also adhere | attach two or more, and can also be set as a multilayered flexible printed wiring board board | substrate.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified.

  (A-1) Copolymer to (A-5) Copolymer were synthesized by the following method and used in Examples and Comparative Examples.

(Synthesis Example 1)
[Synthesis of (A-1) Copolymer]
An aqueous solution in which 5 parts of sodium dodecylbenzenesulfonate was dissolved, and 40 parts (61.6 mol%) of butadiene and 60 parts (38.4 mol%) of 2-hydroxyethyl methacrylate as raw material monomers were placed in an autoclave. Subsequently, 0.2 parts of t-dodecyl mercaptan and a dox catalyst were charged into the autoclave as molecular weight regulators, and the temperature was adjusted to 10 ° C. Thereafter, 0.01 part of paramentane hydroxide was added as a polymerization initiator, and emulsion polymerization was carried out to a polymerization conversion rate of 75%. Next, N, N-diethylhydroxylamine was added as a reaction terminator to obtain a copolymer emulsion. Water vapor was blown into the obtained copolymer emulsion to remove unreacted raw material monomers (butadiene and 2-hydroxyethyl methacrylate). The solution from which the raw material monomer was removed was added to a 5% calcium chloride aqueous solution to precipitate a copolymer. The copolymer thus precipitated was washed with distilled water and dried with a blower dryer set at 80 ° C. to isolate the copolymer (A-1).

In addition, it was 70 when the Mooney viscosity (ML1 _{+ 4} (100 degreeC)) was measured about the (A-1) copolymer using the Mooney tester (made by Alpha Technology). Further, when the content of alkali metal ions contained in the copolymer (A-1) was analyzed using an atomic absorption photometer (manufactured by Hitachi High-Tech), Na: 20 ppm, K: 10 ppm (of alkali metal ions) Total content: 30 ppm). (A-1) The glass transition temperature (Tg) of the copolymer was −12 ° C. (A-1) The content ratio of (a-1) structural units is 65.0 mol% with respect to 100 mol% of all structural units of the copolymer, and (a-2) the content ratio of structural units is It was 35.0 mol%. In addition, the content rate of the structural unit derived from acrylonitrile is 0 mol%.

(Synthesis Example 2)
[(A-2) Synthesis of copolymer]
An aqueous solution in which 10 parts of polyoxyethylene alkyl ether was dissolved, 75 parts (89.8 mol%) of butadiene and 25 parts (10.2 mol%) of 2-hydroxybutyl methacrylate as raw material monomers, and 2 parts of terpinolene as a molecular weight regulator were used. Except for the above, a copolymer emulsion was obtained in the same manner as in Synthesis Example 1. Thereafter, steam was blown into the obtained copolymer emulsion to remove unreacted raw material monomers (butadiene and 2-hydroxybutyl methacrylate). The solution from which the raw material monomers had been removed was added to a 5% ammonium sulfate (cloud point depressant) aqueous solution, and the copolymer was precipitated by blowing water vapor further. Thereafter, the precipitated copolymer was washed with distilled water and dried with a blow dryer set at 80 ° C., thereby isolating the copolymer (A-2).

In addition, it was 65 when the Mooney viscosity (ML1 _{+ 4} (100 degreeC)) was measured about the (A-2) copolymer using the Mooney tester (made by Alpha Technology). Further, when the content of alkali metal ions contained in the copolymer (A-2) was analyzed using an atomic absorption photometer (manufactured by Hitachi High-Tech), Na: 15 ppm, K: 8 ppm (of alkali metal ions) Total content: 23 ppm). (A-2) The glass transition temperature (Tg) of the copolymer was -48 ° C. (A-2) The content ratio of (a-1) structural units is 90.0 mol% with respect to 100 mol% of all structural units of the copolymer, and (a-2) the content ratio of structural units is 10%. 0.0 mol%. In addition, the content rate of the structural unit derived from acrylonitrile is 0 mol%.

(Synthesis Example 3)
[Synthesis of (A-3) Copolymer]
The copolymer (A-3) was synthesized and isolated in the same manner as in Synthesis Example 2 except that 75 parts (74.6 mol%) of butadiene and 25 parts (25.4 mol%) of acrylonitrile were used as raw material monomers. .

(A-3) About the copolymer, when the Mooney viscosity (ML1 _{+ 4} (100 degreeC)) was measured using the Mooney tester (made by Alpha Technology), it was 72. Further, when the content of alkali metal ions contained in the copolymer (A-3) was analyzed using an atomic absorption photometer (manufactured by Hitachi High-Tech), Na: 17 ppm, K: 7 ppm (of alkali metal ions) Total content; 24 ppm). (A-3) The glass transition temperature (Tg) of the copolymer was -42 ° C. (A-3) The content ratio of (a-1) structural units is 75.5 mol% with respect to 100 mol% of all structural units of the copolymer, and (a-2) the content ratio of structural units is It was 0 mol%. In addition, the content rate of the structural unit derived from acrylonitrile is 24.5 mol%.

[Synthesis of (A-4) Copolymer]
An aqueous solution in which 10 parts of polyoxyethylene alkyl ether is dissolved, and as raw material monomers, butadiene 72 parts (86.1 mol%) and 2-hydroxybutyl methacrylate 25 parts (10.2 mol%), acrylonitrile 3 parts (3.7 mol%) molecular weight A copolymer emulsion was obtained in the same manner as in Synthesis Example 1 except that 2 parts of terpinolene was used as a regulator. Thereafter, steam was blown into the obtained copolymer emulsion to remove unreacted raw material monomers (butadiene and 2-hydroxybutyl methacrylate). The solution from which the raw material monomers had been removed was added to a 5% ammonium sulfate (cloud point depressant) aqueous solution, and the copolymer was precipitated by blowing water vapor further. Then, the copolymer (A-4) was isolated by washing with water with the distilled water and drying with the ventilation drying machine set to 80 degreeC.

About (A-4) copolymer, the Mooney viscosity (ML1 _{+ 4} (100 degreeC)) was measured using the Mooney tester (made by Alpha Technology), it was 70. Further, when the content of alkali metal ions contained in the copolymer (A-4) was analyzed using an atomic absorption photometer (manufactured by Hitachi High-Tech), Na: 16 ppm, K: 8 ppm (of alkali metal ions) Total content; 24 ppm). (A-4) The glass transition temperature (Tg) of the copolymer was -44 ° C. (A-4) The content ratio of (a-1) structural units is 76.5 mol% with respect to 100 mol% of all structural units of the copolymer, and (a-2) the content ratio of structural units is It was 10.0 mol%. In addition, the content rate of the structural unit derived from acrylonitrile is 3.5 mol%.

[Synthesis of (A-5) Copolymer]
An aqueous solution in which 10 parts of polyoxyethylene alkyl ether was dissolved, 30 parts (55.6 mol%) of butadiene and 70 parts (45.4 mol%) of 2-hydroxybutyl methacrylate as raw material monomers, and 2 parts of terpinolene as a molecular weight regulator were used. Except for the above, a copolymer emulsion was obtained in the same manner as in Synthesis Example 1. Thereafter, steam was blown into the obtained copolymer emulsion to remove unreacted raw material monomers (butadiene and 2-hydroxybutyl methacrylate). The solution from which the raw material monomers had been removed was added to a 5% ammonium sulfate (cloud point depressant) aqueous solution, and the copolymer was precipitated by blowing water vapor further. Then, the copolymer (A-5) was isolated by washing with water with the distilled water and drying with the ventilation drying machine set to 80 degreeC.

With respect to the copolymer (A-5), the Mooney viscosity (ML _{1 + 4} (100 ° C.)) was measured by using a Mooney tester (manufactured by Alpha Technology Co., Ltd.). Further, when the content of alkali metal ions contained in the copolymer (A-5) was analyzed using an atomic absorption photometer (manufactured by Hitachi High-Tech), Na: 15 ppm, K: 5 ppm (of alkali metal ions) Total content: 20 ppm). The glass transition temperature (Tg) of the (A-5) copolymer was −3 ° C. (A-5) The content ratio of (a-1) structural units is 56.5 mol% with respect to 100 mol% of all structural units of the copolymer, and (a-2) the content ratio of structural units is It was 43.5 mol%. In addition, the content rate of the structural unit derived from acrylonitrile is 0 mol%.

  In addition, (a-1) structural unit (a-1) structural unit, (a-2) structural unit, structural unit derived from acrylonitrile ((a-3) contained in (A-1) copolymer to (A-5) copolymer Table 1 shows the content (ratio) (mol%) of () structural unit).

Example 1
(A) 70 parts of (A-1) copolymer obtained in Synthesis Example 1 as a copolymer, (B) epoxy resin (trade name “Epicoat 828”, manufactured by Japan Epoxy Resin Co., Ltd., in the table, as a thermosetting resin 50 parts of “B-1”) and 50 parts of (B) epoxy resin (trade name “Epicoat 1001” manufactured by Japan Epoxy Resin Co., Ltd., indicated as “B-2” in the table) as a thermosetting resin, The solution was charged into 263 parts of methyl ethyl ketone (organic solvent) and completely dissolved with a stirrer “MAZERA Z” (manufactured by Tokyo Science Instruments Co., Ltd.). Thereafter, 5 parts of diaminodiphenylmethane (trade name “SumiCure M”, manufactured by Sumitomo Chemical Co., Ltd., indicated as “C-1” in the table) were added as a curing agent (C), and the mixture was made uniform with the agitator. Thus, an adhesive composition-containing varnish (adhesive composition) having a solid concentration of about 40% was obtained. The obtained adhesive composition-containing varnish was evaluated by the respective methods described below.

[Compatibility]
The said adhesive composition containing varnish was put into the transparent glass bottle, and the cloudiness of the solution and the presence or absence of the deposit were confirmed visually. The judgment was “good” when the solution was uniform, and “bad” when the solution became cloudy and precipitates were confirmed.

[Electrical characteristics]
The adhesive composition-containing varnish was applied to a SUS plate having a mirror-finished surface, and heated in a convection oven at 90 ° C. for 15 minutes. Then, it further heated at 170 degreeC for 1 hour, and formed the 20-micrometer-thick adhesive layer on the SUS board. An aluminum electrode was formed on the adhesive layer, and the dielectric constant and dielectric loss were measured with a dielectric constant / dielectric loss measuring machine (manufactured by Hewlett Packard: LCR meter HP4248) under the condition of a frequency of 1 MHz.

[Adhesiveness]
The adhesive composition-containing varnish was applied to a 1 mm thick copper plate and heated in a convection oven at 90 ° C. for 15 minutes. Then, it further heated at 170 degreeC for 1 hour, and formed the 20-micrometer-thick adhesive layer on the SUS board. After a polyimide film (Ube Industries, Upilex 75S) is layered on this adhesive layer, it is pressure-bonded under a condition of 130 ° C., 0.5 MPa, 1 minute using a press machine (manufactured by Kansai Roll). It was. Thereafter, the adhesive layer was cured by heating in a clean oven at 170 ° C. for 1 hour. A sample plate (copper plate-adhesive layer-polyimide film) thus obtained was formed on the polyimide film side with a 1 cm wide cut using a cutter, and a 90-degree peel test was performed. Specifically, 90 degree peel strength (kg / cm) was measured using an adhesion tester (manufactured by Yamamoto Metal Tester Co., Ltd.) in accordance with JIS C6481 (Test method for copper-clad laminate for printed wiring board). The measured peel strength was used as an index for determining adhesiveness.

  The evaluation results of the above evaluations in this example are that the compatibility is good, the electrical properties are dielectric constant 3.4, dielectric loss 0.03, and peel strength 1.1 (kg / cm). there were.

(Examples 2 to 4, Comparative Example 1)
An adhesive composition (adhesive composition-containing varnish) was obtained in the same manner as in Example 1 except that the formulation shown in Table 2 was used. Table 2 shows each evaluation result of the obtained adhesive composition.

  As shown in Table 2, if the adhesive compositions of Examples 1 to 4 were used, excellent electrical performance was maintained while maintaining sufficient adhesive performance as compared to the case where the adhesive composition of Comparative Example 1 was used. It is apparent that an adhesive layer having characteristics (low dielectric loss / low dielectric loss) can be formed.

  The adhesive composition of the present invention can form an adhesive layer having excellent electrical properties (low dielectric loss and low dielectric loss) while maintaining sufficient adhesive performance. Such an adhesive composition of the present invention In particular, the product can be suitably used as an adhesive layer for a flexible printed wiring board substrate of communication equipment such as electronic equipment and mobile phones.

Claims (5)

(A) (a-1) a structural unit derived from a monomer having at least two ethylenically polymerizable unsaturated groups, (a-2) a structural unit derived from a monomer having an alcoholic hydroxyl group, and (a -3) a copolymer containing a structural unit derived from acrylonitrile ,
(B) contains a thermosetting resin, and (C) a curing agent ,
The proportion of structural units derived from the (a-3) acrylonitrile contained in the (A) copolymer is 5 mol% with respect to 100 mol% of all structural units constituting the (A) copolymer. The adhesive composition which is the following . The proportion of the structural unit (a-1) is 50 to 95 mol% with respect to 100 mol% of all structural units constituting the (A) copolymer,
2. The adhesive composition according to claim 1, wherein a ratio of the (a-2) structural unit is 5 to 50 mol% with respect to 100 mol% of all structural units constituting the (A) copolymer. The adhesive composition according to claim 1 or 2 , comprising an epoxy resin as the (B) thermosetting resin. The adhesive composition according to any one of claims 1 to 3 , wherein the content of alkali metal ions contained in the copolymer (A) is 50 ppm or less. An insulating film layer;
A circuit board;
It forms with the adhesive composition as described in any one of Claims 1-4 , It arrange | positions between the said insulating film layer and the said circuit board, and adhere | attaches the said insulating film layer and the said circuit board A flexible printed wiring board substrate, comprising: