JP2008081678A - Adhesive composition and substrate for flexible printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive composition capable of forming an adhesive layer having excellent electrical characteristics such as low dielectric constant and low dielectric loss while having sufficient adhesive strength and heat resistance. <P>SOLUTION: The adhesive composition comprises (A) a copolymer, (B) a thermosetting resin and (C) a curing agent. (A) The copolymer includes (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 hydroxy group and (a-3) a structural unit derived from at least one kind selected from the group consisting of styrene, a styrene derivative, (meth)acrylic acid and an acrylic or a methacrylic acid derivative. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an adhesive composition and a substrate for a flexible printed wiring board, and in particular, forms an adhesive layer having an excellent electrical property such as low dielectric constant and low dielectric loss while having sufficient adhesive strength and heat resistance. The present invention relates to a possible adhesive composition and a substrate for a flexible printed wiring board using the same.

  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 gives sufficient adhesive strength and toughness to resins that are generally hard and brittle. For this purpose, 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 flexible circuits will increase, and in the case of increasing the density of flexible circuits, the adhesive layer will not only have adhesive performance, but also excellent electrical characteristics (low dielectric and low dielectric loss), and flexible circuits. It is anxious to have resistance (heat resistance) to the generated heat.

  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 structural unit derived from a monomer, (a-2) a structural unit derived from a monomer having an alcoholic hydroxyl group, and (a-3) styrene, a styrene derivative, (meth) acrylic acid, and a (meth) acrylic acid derivative. It is providing the adhesive composition containing the copolymer containing the structural unit derived from at least 1 type selected from the group which consists of, (B) thermosetting resin, and (C) hardening | curing agent.

  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 comprising styrene, a styrene derivative, (meth) acrylic acid, and a structural unit derived from at least one selected from the group consisting of (meth) acrylic acid derivatives, (B) thermosetting Adhesive composition containing an adhesive resin and (C) a curing agent.

[2] The proportion of the structural unit (a-1) is 50 to 90 mol% with respect to 100 mol% of all structural units constituting the copolymer (A), and the structure (a-2) The proportion of units is 5 to 45 mol% with respect to 100 mol% of all structural units constituting the copolymer (A), and the proportion of the structural unit (a-3) is the same as that of the copolymer (A). The adhesive composition according to [1], which is 1 to 25 mol% with respect to 100 mol% of all structural units constituting the polymer.

[3] The proportion of structural units derived from (a-3) acrylonitrile contained in the (A) copolymer is 5 with respect to 100 mol% of all structural units constituting the (A) copolymer. The adhesive composition according to the above [1] or [2], which is not more than mol%.

[4] The adhesive composition according to any one of [1] to [3], which contains an epoxy resin as the (B) thermosetting resin.

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

[6] The insulating film layer, the circuit board, and the adhesive composition according to any one of [1] to [5] are formed and disposed 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 it can form an adhesive layer excellent in electrical characteristics such as low dielectric constant and low dielectric loss while having sufficient adhesive strength and heat resistance. is there.

  In addition, the substrate for a flexible printed wiring board of the present invention has an effect that it has an adhesive layer having excellent electrical properties such as low dielectric constant and low dielectric loss while having sufficient adhesive strength and heat resistance. is there.

  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 comprising a structural unit derived from a body and a structural unit derived from at least one selected from the group consisting of (a-3) styrene, a styrene derivative, (meth) acrylic acid, and a (meth) acrylic acid derivative (Hereinafter 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 a sufficient adhesive force and heat resistance and excellent electrical characteristics such as low dielectric constant and low dielectric loss. Hereinafter, structural units derived from styrene and styrene derivatives may be referred to as “(a-3-1) structural units”, and structural units derived from (meth) acrylic acid and (meth) acrylic acid derivatives are “ (A-3-2) Structural unit ". 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) a 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 ”) and (a -3) A structural unit derived from at least one selected from the group consisting of styrene, a styrene derivative, (meth) acrylic acid, and a (meth) acrylic acid derivative (hereinafter referred to as “(a-3) structural unit”). A).

  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 90 mol% with respect to 100 mol% of all structural units constituting the (A) copolymer. More preferably, it is 55-90 mol%, Most preferably, it is 60-85 mol%. (A-1) When the proportion of the structural units is within 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 may be 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 45 mol% with respect to 100 mol% of all structural units constituting the (A) copolymer. More preferably, it is 7-30 mol%, Most preferably, it is 10-20 mol%. (A-2) When the proportion of the structural unit is within the above range, the obtained polymer has good compatibility with the thermosetting resin to be blended, has toughness, and has sufficient adhesiveness.

  (A-3) Examples of styrene and styrene derivatives that may be used for constituting a structural unit include aromatics such as α-methylstyrene, o-methoxystyrene, p-hydroxystyrene, and p-isopropenylphenol. A vinyl compound is mentioned. Examples of (a-3) (meth) acrylic acid and (meth) acrylic acid derivatives that may be used for constituting the structural unit include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, Examples include propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, lauryl (meth) acrylate, polyethylene glycol (meth) acrylate, and polypropylene glycol (meth) acrylate. In addition, since (a-3) structural units are “structural units derived from at least one selected from the group consisting of styrene, styrene derivatives, (meth) acrylic acid, and (meth) acrylic acid derivatives”. Can be used alone or in combination of two or more.

  The proportion of the structural unit (a-3) is preferably 1 to 25 mol% with respect to 100 mol% of all structural units constituting the (A) copolymer. More preferably, it is 1-20 mol%, Most preferably, it is 1-18 mol%. (A-3) When the proportion of the structural unit is within the above range, the heat resistance of the cured product obtained from the adhesive composition is good.

  In addition, the (A) copolymer includes other structural units (hereinafter referred to as “other structural units”) in addition to the (a-1) structural unit, (a-2) structural unit, and (a-3) structural unit. May be included). Other structural units include monomers having at least two ethylenically polymerizable unsaturated groups, monomers having alcoholic hydroxyl groups, styrene, styrene derivatives, (meth) acrylic acid, and (meth) acrylic. There is no particular limitation as long as it is derived from a monomer copolymerizable with at least one selected from the group consisting of acid derivatives. Moreover, it is preferable that the ratio of another structural unit is 1-20 mol% with respect to 100 mol% of all the structural units which comprise a (A) copolymer. More preferably, it is 1-15 mol%, Most preferably, it is 1-10 mol%. However, when the other structural unit is a structural unit derived from (a-4) acrylonitrile, the ratio of the other structural unit ((a-4) structural unit derived from acrylonitrile) is the same as that in (A). It is necessary to be 5 mol% or less with respect to 100 mol% of the polymer. Most preferably, (a-4) no structural unit derived from acrylonitrile is contained.

  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, and examples thereof include 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, (A) the copolymer was heated and dried to prepare a dry film having a thickness of 50 μm / width of 3 mm, and the film was raised using a differential scanning calorimeter (trade name “EXSTAR6000DSC” manufactured by Seiko Instruments Inc.). It is a value when analyzed at a temperature rate of 10 ° C./min.

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.

  Furthermore, in the adhesive composition of the present invention, the proportion of structural units derived from (a-4) 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 (a-4) acrylonitrile is 0 mol%, that is, 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-4) acrylonitrile contained in (A) the copolymer is 100 mol% of all structural units constituting the copolymer (A). In such a case, (a-4) a decrease in electrical characteristics (particularly, low dielectric loss / low dielectric loss) due to the structural unit derived from acrylonitrile ( (Deterioration) can be avoided. 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).

  Moreover, since the said (A) copolymer contains the (a-3) structural unit, the adhesive bond layer formed by the adhesive composition of this invention has the advantage that it has sufficient heat resistance. . That is, when it contains a structural unit derived from styrene and a styrene derivative, it acts to increase the Tg of the copolymer and thus exhibits heat resistance. Moreover, when it contains the structural unit derived from (meth) acrylic acid and a (meth) acrylic acid derivative, a crosslinking density increases by reacting with (B) thermosetting resin, and heat resistance is exhibited. (B) The reaction with the thermosetting resin specifically exhibits heat resistance because the crosslinking density is increased by the reaction of the carboxyl group and the epoxy group to form a crosslinked structure (the Tg of the cured product is To rise.

  The (A) copolymer contains a structural unit derived from the styrene and the styrene derivative, thereby achieving a high Tg of the copolymer and exhibiting more excellent electrical characteristics. .

[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, diaminodiphenylsulfide, 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, phenolic 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) There exists a possibility that it may become inadequate hardening that the compounding quantity of a hardening | curing agent is less than 0.1 mass part. 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 butyl cellosolve; Carbitols such as butyl carbitol; 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.

  The (A-1) copolymer to the (A-6) copolymer were synthesized by the following method and used in the 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 as raw material monomers, 55 parts (74.4 mol%) of butadiene, 25 parts (11.6 mol%) of 2-hydroxybutyl methacrylate, and 20 parts (14.0 mol%) of styrene In an autoclave. Subsequently, 0.2 parts of t-dodecyl mercaptan and a redox catalyst were charged in 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, 2-hydroxybutyl methacrylate, and styrene). 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 60 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: 22 ppm, K: 12 ppm (of alkali metal ions) Total content: 34 ppm). (A-1) The glass transition temperature (Tg) of the copolymer was -23 ° C. (A-1) The content ratio of (a-1) structural units is 73.5 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 12.0 mol%, and the content rate of the (a-3) structural unit ((a-3-2) structural unit) was 14.5 mol%. In addition, the content rate of the structural unit derived from (a-4) acrylonitrile is 0 mol%.

(Synthesis Example 2)
[(A-2) Synthesis of copolymer]
An aqueous solution in which 10 parts of polyoxyethylene alkyl ether is dissolved, as raw material monomers, butadiene 75 parts (87.4 mol%), 2-hydroxyethyl methacrylate 23 parts (11.1 mol%), and methacrylic acid 2 parts (1.5 mol%) Then, a copolymer emulsion was obtained in the same manner as in Synthesis Example 1 except that 2 parts of terpinolene was used as a molecular weight regulator. Thereafter, steam was blown into the obtained copolymer emulsion to remove unreacted raw material monomers (butadiene, 2-hydroxyethyl methacrylate, and methacrylic acid). 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 90 ° C. to isolate the copolymer (A-2).

In addition, it was 72 when the Mooney viscosity (ML1 _{+ 4} (100 degreeC)) was measured about the (A-2) copolymer using the Mooney tester (made by an alpha technology company). 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: 11 ppm, K: 7 ppm (of alkali metal ions) Total content: 18 ppm). (A-2) The glass transition temperature (Tg) of the copolymer was -47 ° C. (A-2) The content ratio of (a-1) structural units is 87.4 mol% with respect to 100 mol% of all structural units of the copolymer, and (a-2) the content ratio of structural units is The content ratio of (a-3) structural unit ((a-3-2) structural unit) was 1.8 mol%. In addition, the content rate of the structural unit derived from (a-4) acrylonitrile is 0 mol%.

(Synthesis Example 3)
[Synthesis of (A-3) Copolymer]
As raw material monomers, butadiene 50 parts (70.2 mol%), 2-hydroxybutyl methacrylate 30 parts (14.4 mol%), styrene 15 parts (10.9 mol%), and methacrylic acid 5 parts (4.4 mol%), A copolymer emulsion was obtained in the same manner as in Synthesis Example 2 except that 2 parts of terpinolene was used as a molecular weight regulator. Thereafter, steam was blown into the obtained copolymer emulsion to remove unreacted raw material monomers (butadiene, 2-hydroxybutyl methacrylate, styrene, and methacrylic acid). 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 90 ° C., thereby isolating the copolymer (A-3).

In addition, it was 75 when the Mooney viscosity (ML1 _{+ 4} (100 degreeC)) was measured about the (A-3) copolymer using the Mooney tester (made by Alpha Technology). 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: 12 ppm, K: 4 ppm (of alkali metal ions) Total content: 16 ppm). (A-3) The glass transition temperature (Tg) of the copolymer was -14 ° C. (A-3) The content ratio of (a-1) structural units is 70.0 mol% with respect to 100 mol% of all structural units of the copolymer, and (a-2) the content ratio of structural units is 14.2 mol%, (a-3-1) structural unit content was 10.2 mol%, and (a-3-2) structural unit content was 5.6 mol%. . In addition, the content rate of the structural unit derived from (a-4) acrylonitrile is 0 mol%.

(Synthesis Example 4)
[Synthesis of (A-4) Copolymer]
In the same manner as in Synthesis Example 1, except that 65 parts (67.2 mol%) of butadiene, 25 parts (26.3 mol%) of acrylonitrile, and 10 parts (6.5 mol%) of methacrylic acid were used as raw material monomers, A-4) A copolymer was synthesized and isolated.

In addition, it was 72 when the Mooney viscosity (ML1 _{+ 4} (100 degreeC)) was measured about the (A-4) copolymer using the Mooney tester (made by Alpha Technology). 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: 20 ppm, K: 10 ppm (of alkali metal ions) Total content: 30 ppm). (A-4) The glass transition temperature (Tg) of the copolymer was −25 ° C. (A-4) The content ratio of (a-1) structural units is 67.0 mol% with respect to 100 mol% of all structural units of the copolymer, and (a-2) the content ratio of structural units is The content ratio of (a-3) structural unit ((a-3-2) structural unit) was 6.8 mol%. In addition, the content rate of the structural unit derived from (a-4) acrylonitrile is 26.2 mol%.

(Synthesis Example 5)
[Synthesis of (A-5) Copolymer]
A copolymer (A-5) was synthesized and synthesized in the same manner as in Synthesis Example 2, except that 75 parts of butadiene (74.6 mol%) and 25 parts of acrylonitrile (25.4 mol%) were used as raw material monomers. Released.

In addition, it was 72 when the Mooney viscosity (ML1 _{+ 4} (100 degreeC)) was measured about the (A-5) copolymer using the Mooney tester (made by Alpha Technology). 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: 17 ppm, K: 7 ppm (of alkali metal ions) Total content; 24 ppm). The glass transition temperature (Tg) of the (A-5) copolymer was -42 ° C. (A-5) The content ratio of (a-1) structural units is 74.2 mol% with respect to 100 mol% of all structural units of the copolymer, and (a-2) the content ratio of structural units is The content ratio of (a-3) structural unit was 0 mol%. In addition, the content rate of the structural unit derived from (a-4) acrylonitrile is 25.8 mol%.

(Synthesis Example 6)
[Synthesis of (A-6) Copolymer]
An aqueous solution in which 10 parts of polyoxyethylene alkyl ether is dissolved, and as raw material monomers, 70 parts of butadiene (84.5 mol%), 25 parts of 2-hydroxybutyl methacrylate (10.3 mol%), and 2 parts of methacrylic acid (1.5 mol%) A copolymer emulsion was obtained in the same manner as in Synthesis Example 1, except that 3 parts of acrylonitrile (3.7 mol%) and 2 parts of terpinolene were used as a molecular weight 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-6) was isolated by washing the precipitated copolymer with distilled water and drying it with an air dryer set at 80 ° C.

In addition, it was 70 when the Mooney viscosity (ML1 _{+ 4} (100 degreeC)) was measured about the (A-6) copolymer using the Mooney tester (made by Alpha Technology). Further, when the content of alkali metal ions contained in the copolymer (A-6) was analyzed using an atomic absorption photometer (manufactured by Hitachi High-Tech), Na: 14 ppm, K: 4 ppm (of alkali metal ions) Total content: 18 ppm). The glass transition temperature (Tg) of the (A-6) copolymer was -41 ° C. (A-6) The content ratio of (a-1) structural units is 85.0 mol% with respect to 100 mol% of all structural units of the copolymer, and (a-2) the content ratio of structural units is The content ratio of (a-3) structural unit ((a-3-2) structural unit) was 1.5 mol%. In addition, the content rate of the structural unit derived from (a-4) acrylonitrile is 3.3 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 toluene (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.

[Glass-transition temperature]
Viscoelasticity measurement was performed using TMA / SS6100 (manufactured by Seiko Instruments Inc.), and the glass transition temperature (Tg) of the cured product was determined from the behavior of tan δ. The test conditions were a test piece thickness of 50 μm / width of 3 mm, and a heating rate of 5 ° C./min.

  The evaluation results of the above evaluations in this example are that the compatibility is good, the dielectric constant is 3.3, the dielectric loss is 0.02, and the peel strength is 1.2 (kg / cm) as electrical characteristics. The glass transition temperature (Tg) was 140.

(Examples 2 to 4, Comparative Examples 1 and 2)
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, when the adhesive compositions of Examples 1 to 4 are used, they have sufficient adhesive strength and heat resistance as compared with the case where the adhesive compositions of Comparative Examples 1 and 2 are used. However, it is apparent that an adhesive layer having excellent electrical characteristics such as low dielectric constant and low dielectric loss can be formed.

  The adhesive composition of the present invention can form an adhesive layer excellent in electrical characteristics such as low dielectric constant and low dielectric loss while having sufficient adhesive strength and heat resistance. In particular, the adhesive composition can be suitably used as an adhesive layer for a flexible printed wiring board substrate of a communication device such as an electronic device or a mobile phone.

Claims (6)

(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 comprising styrene, a styrene derivative, (meth) acrylic acid, and a structural unit derived from at least one selected from the group consisting of (meth) acrylic acid derivatives,
(B) An adhesive composition containing a thermosetting resin and (C) a curing agent. The proportion of the structural unit (a-1) is 50 to 90 mol% with respect to 100 mol% of all structural units constituting the copolymer (A),
The proportion of the structural unit (a-2) is 5 to 45 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-3) structural unit is 1 to 25 mol% with respect to 100 mol% of all structural units constituting the (A) copolymer.   The proportion of structural units derived from (a-3) acrylonitrile contained in the (A) copolymer is 5 mol% or less with respect to 100 mol% of all structural units constituting the (A) copolymer. The adhesive composition according to claim 1 or 2.   The adhesive composition according to any one of claims 1 to 3, comprising an epoxy resin as the (B) thermosetting resin.   The adhesive composition according to any one of claims 1 to 4, 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 is formed with the adhesive composition according to any one of claims 1 to 5, and is disposed between the insulating film layer and the circuit board to bond the insulating film layer and the circuit board. A flexible printed wiring board substrate, comprising: an adhesive layer to be printed.