JP2012097195A - Flame-retardant adhesive composition and adhesive sheet and coverlay film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition not containing halogen, having high glass transition temperature and excellent processability, flexibility, electric insulation (migration resistance), adhesion, soldering heat resistance, and flame retardancy, and capable of providing a cured product that is suitably used for a flexible printed circuit board especially, and an adhesive sheet and a coverlay film using the same.SOLUTION: The flame-retardant adhesive composition not including halogen is provided, which contains (A) a trifunctional epoxy resin not including halogen, (B) a phenoxy resin having a weight-average molecular weight of 10,000-100,000 and a glass transition temperature of 70°C or more, (C) a curing agent, (D) a phosphazene compound, and (E) a thermoplastic resin. The adhesive sheet and the coverlay film using the same are also provided.

Description

  The present invention has a high glass transition temperature, excellent workability, flexibility, electrical insulation (migration resistance), adhesion, solder heat resistance, and flame resistance, and is particularly suitable for flexible printed circuit boards. The present invention relates to a flame-retardant adhesive composition containing no halogen that can give a usable cured product, and an adhesive sheet and a coverlay film using the same.

  In recent years, the development of the electronics field has been remarkable, and in particular, electronic devices for communication and consumer use such as personal computers, mobile phones, digital cameras, game machines, and hard disk drives have become smaller, thinner, lighter, and higher in circuit density. These demands on performance are becoming increasingly sophisticated. In response to such demands, a flexible printed circuit board (hereinafter referred to as “FPC”) is flexible and withstands repeated bending, so that three-dimensional high-density mounting is possible in a narrow space. In addition, the application is expanding as a composite part to which wiring to an electronic device, a cable, a connector function and the like are given.

  The FPC is a circuit in which a circuit is produced on an FPC substrate by a conventional method, and a coverlay film is bonded in such a manner as to protect the circuit depending on the purpose of use. As described above, with the downsizing, thinning, lightening, and high density of circuits of electronic devices, the demand for multilayer FPCs in which four or more FPCs are stacked is increasing. In this multilayer FPC, a multilayer structure is obtained by laminating two or more single-sided copper foils or double-sided copper foil FPCs using an adhesive sheet. Properties required for these FPCs include adhesion durability, solder heat resistance, flexibility, folding resistance, electrical insulation (migration resistance), flame retardancy, and the like.

  The adhesive sheet used for FPC is a sheet provided with a semi-cured adhesive layer on one side of a release substrate. The adhesive sheet is used as an adhesive material for manufacturing a multilayer FPC by bonding a plurality of FPCs produced by pressure-bonding a coverlay film, or for bonding an FPC and a reinforcing plate. Furthermore, the use as an insulating material for copper wiring, which has conventionally used coverlay films, and the use as an interlayer insulating material for bonding the copper wiring surfaces of a pair of FPCs are also being studied. Properties required for the adhesive sheet include high glass transition temperature, adhesiveness, solder heat resistance, flexibility, electrical insulation (migration resistance), flame retardancy, storage stability, workability, handling properties, and the like. .

  A coverlay film used for FPC is formed by applying a semi-cured adhesive to at least one surface of an electrically insulating base film, and usually a protective release sheet is provided on the adhesive coating layer. It is pasted together. The release sheet is used for the purpose of protecting the circuit of FPC, improving flexibility, and the like by attaching an exposed adhesive layer that is peeled off during use. Properties required for the coverlay film include high glass transition temperature, adhesion, solder heat resistance, flexibility, electrical insulation (migration resistance), flame retardancy, storage stability, workability, handling properties, etc. It is done.

  In recent years, the environment in which an FPC is placed has become increasingly severe as electronic devices become more sophisticated. In particular, the opportunity to repeatedly bend FPC at high temperatures and the opportunity to mount parts by wire bonding are increasing. With this increase, the glass transition temperature and the adhesive used for FPC have increased. High storage elastic modulus and excellent flexibility at high temperatures are becoming necessary. Furthermore, with the background of environmental issues, there is a tendency to prohibit the use of halogen compounds for components mounted on electronic equipment, and it is difficult to use bromine compounds that have been used to make FPCs flame-retardant in the past. It has become to.

  Therefore, regarding FPC substrates, materials using an adhesive with a high glass transition temperature, materials with a two-layer structure in which a metal foil and a heat-resistant resin are bonded without using an adhesive, etc. have been proposed. A technique has been adopted in which a phosphorus-based flame retardant is added as a flame retardant to an adhesive instead of a bromine compound, and the flame retardant is made without using a halogen. On the other hand, for adhesive sheets and coverlay films, from the viewpoint of processability and storage stability, an adhesive having a high glass transition temperature is used, and a flame retardant without using halogen with a phosphorus flame retardant. It has been proposed.

  Specific examples thereof include, for example, an adhesive composition comprising a thermoplastic resin, a phosphorus-containing phenoxy resin, a phosphorus-containing epoxy resin, and a curing agent (Japanese Patent Laid-Open No. 2003-176470: Patent Document 1), an epoxy resin, a curing agent, A resin composition comprising a phenoxy resin, a rubber component and a curing accelerator (Japanese Patent Laid-Open No. 2003-286391: Patent Document 2), a resin composition comprising a phenoxy resin, an epoxy resin and a curing agent (Japanese Patent Laid-Open No. 11-279260: Patent Document 3), adhesive composition comprising acrylic rubber, phenoxy resin and curing agent (Japanese Patent Application Laid-Open No. 2004-136663: Patent Document 4), phosphorus-containing phenoxy resin, epoxy resin, carboxyl group-containing butadiene rubber, curing agent, Adhesive composition comprising a curing accelerator, a metal hydroxide and an inorganic filler (JP 2003-292927 A) Publication: Patent Document 5), an adhesive composition comprising an epoxy resin, a polyfunctional aralkylphenol, a curing accelerator, an elastomer such as a carboxyl group-containing acrylonitrile butadiene rubber, a phosphazene compound and an inorganic filler (Japanese Patent Laid-Open No. 2004-077548) Patent document 6) etc. are proposed.

  However, in any adhesive composition, the cured product has a high glass transition temperature, excellent workability, flexibility, electrical insulation (migration resistance), adhesion and heat resistance, and does not contain halogen. It was not excellent in flame retardancy.

JP 2003-176470 A JP 2003-286391 A JP 11-279260 A JP 2004136663 A JP 2003-292927 A Japanese Patent Application Laid-Open No. 2004-075748

  The present invention was made in view of the above circumstances, has a high glass transition temperature, excellent workability, flexibility, electrical insulation (migration resistance), adhesiveness, solder heat resistance, and flame retardancy, It aims at providing the flame-retardant adhesive composition which does not contain the halogen which can give the hardened | cured material which can be used suitably especially for a flexible printed circuit board, and an adhesive sheet and coverlay film using the same.

  As a result of intensive studies to achieve the above object, the present inventors have found that (A) a trifunctional epoxy resin containing no halogen represented by the general formula (1) described later: 20 to 80 parts by mass, (B) Phenoxy resin having a weight average molecular weight of 10,000 to 100,000 and a glass transition temperature of 70 ° C. or higher: (C) Curing agent: (A) and (A) B) 0.1 to 50 parts by mass with respect to 100 parts by mass of the total component, (D) phosphazene compound: 5 to 120 parts by mass with respect to 100 parts by mass of the total of components (A) and (B), (E) Thermoplastic resin: A flame-retardant adhesive composition containing no halogen and containing 0.1 to 80 parts by mass with respect to a total of 100 parts by mass of components (A) and (B) has a high glass transition temperature. Excellent workability, flexibility, electrical insulation (My resistance ), Adhesiveness, solder heat resistance, and flame retardancy, and provides a cured product that can be suitably used especially for flexible printed circuit boards, so it is useful for adhesive sheets and coverlay films using the same. As a result, the present invention has been made.

（式（１）中、Ｒ₁は水素原子又は炭素原子数１〜６のアルキル基であり、それぞれ同一でも異なってもよく、ｍは０又は１を表す。Ｘは式（２），（３），（４）のいずれか一つを表し、式（２），（３），（４）中、Ｒ₂は水素原子又は炭素原子数１〜６のアルキル基であり、それぞれ同一でも異なってもよい。）
（Ｂ）重量平均分子量が１０，０００〜１００，０００であり、ガラス転移温度が７０℃以上のフェノキシ樹脂：（Ａ）成分と合わせて１００質量部となる量、
（Ｃ）硬化剤：（Ａ）及び（Ｂ）成分の合計１００質量部に対して０．１〜５０質量部、
（Ｄ）ホスファゼン化合物：（Ａ）及び（Ｂ）成分の合計１００質量部に対して５〜１２０質量部、
（Ｅ）熱可塑性樹脂：（Ａ）及び（Ｂ）成分の合計１００質量部に対して０．１〜８０質量部
を含有してなるハロゲンを含まない難燃性接着剤組成物。
請求項２：
フェノキシ樹脂が分子鎖両末端にエポキシ基を有するものである請求項１に記載の難燃性接着剤組成物。
請求項３：
熱可塑性樹脂が常温下でゴム弾性を有さないものである請求項１又は２に記載の難燃性接着剤組成物。
請求項４：
接着剤組成物中のリン含有率が１．８〜６．０質量％以上である請求項１〜３のいずれか１項に記載の難燃性接着剤組成物。
請求項５：
硬化後のガラス転移温度が１００℃以上である請求項１〜４のいずれか１項に記載の難燃性接着剤組成物。
請求項６：
硬化後の８５℃における貯蔵弾性率が１ＧＰａ以上である請求項１〜５のいずれか１項に記載の難燃性接着剤組成物。
請求項７：
片面銅箔若しくは両面銅箔フレキシブル印刷回路基板相互の接着用である請求項１〜６のいずれか１項に記載の難燃性接着剤組成物。
請求項８：
カバーレイフイルム作製用である請求項１〜６のいずれか１項に記載の難燃性接着剤組成物。
請求項９：
離型基材層と、該離型基材層上に設けられた請求項１〜６のいずれか１項に記載の接着剤組成物からなる接着剤層とを有する接着シート。
請求項１０：
電気絶縁性フィルムと、該電気絶縁性フィルム上に設けられた請求項１〜６のいずれか１項に記載の接着剤組成物からなる接着剤層とを有するカバーレイフィルム。
請求項１１：
電気絶縁性フィルムがポリイミドフィルムである請求項１０に記載のカバーレイフィルム。
請求項１２：
接着剤層上に設けられた離型基材層を更に有する請求項９、１０又は１１に記載の接着シート又はカバーレイフィルム。 Accordingly, the present invention provides the following flame retardant adhesive composition, and an adhesive sheet and coverlay film using the same.
Claim 1:
(A) Trifunctional epoxy resin not containing halogen represented by the following general formula (1): 20 to 80 parts by mass,

(In the formula (1), R ₁ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, which may be the same or different, and m represents 0 or 1. X represents the formula (2), (3 ), (4), and in formulas (2), (3), (4), R ₂ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, which may be the same or different. May be good.)
(B) a phenoxy resin having a weight average molecular weight of 10,000 to 100,000 and a glass transition temperature of 70 ° C. or higher: an amount of 100 parts by mass in combination with the component (A),
(C) Curing agent: 0.1 to 50 parts by mass with respect to 100 parts by mass in total of components (A) and (B),
(D) Phosphazene compound: 5 to 120 parts by mass with respect to 100 parts by mass in total of components (A) and (B),
(E) Thermoplastic resin: A flame-retardant adhesive composition containing no halogen and containing 0.1 to 80 parts by mass with respect to 100 parts by mass as a total of components (A) and (B).
Claim 2:
The flame retardant adhesive composition according to claim 1, wherein the phenoxy resin has an epoxy group at both ends of the molecular chain.
Claim 3:
The flame retardant adhesive composition according to claim 1 or 2, wherein the thermoplastic resin does not have rubber elasticity at room temperature.
Claim 4:
The flame-retardant adhesive composition according to any one of claims 1 to 3, wherein the phosphorus content in the adhesive composition is 1.8 to 6.0 mass% or more.
Claim 5:
The flame retardant adhesive composition according to any one of claims 1 to 4, wherein the glass transition temperature after curing is 100 ° C or higher.
Claim 6:
The flame retardant adhesive composition according to any one of claims 1 to 5, wherein the storage elastic modulus at 85 ° C after curing is 1 GPa or more.
Claim 7:
The flame-retardant adhesive composition according to any one of claims 1 to 6, wherein the flame-retardant adhesive composition is used for adhesion between single-sided copper foil or double-sided copper foil flexible printed circuit boards.
Claim 8:
The flame-retardant adhesive composition according to any one of claims 1 to 6, which is used for producing a cover lay film.
Claim 9:
The adhesive sheet which has a mold release base material layer and the adhesive bond layer which consists of an adhesive composition of any one of Claims 1-6 provided on this mold release base material layer.
Claim 10:
The coverlay film which has an electrically insulating film and the adhesive bond layer which consists of an adhesive composition of any one of Claims 1-6 provided on this electrically insulating film.
Claim 11:
The coverlay film according to claim 10, wherein the electrically insulating film is a polyimide film.
Claim 12:
The adhesive sheet or coverlay film according to claim 9, 10 or 11, further comprising a release substrate layer provided on the adhesive layer.

  According to the present invention, the glass transition temperature is high, and it has excellent workability, flexibility, electrical insulation (migration resistance), adhesiveness, solder heat resistance, and flame retardancy, especially for flexible printed circuit boards. It is possible to provide a halogen-free adhesive composition capable of giving a suitably usable cured product, and an adhesive sheet and coverlay film using the same.

(A) is a top view of the circuit formed in the longitudinal direction of the board | substrate for single-sided flexible printed wirings, (B) is an enlarged view of A part of (A) figure.

Hereinafter, the present invention will be described in detail.
<Flame-retardant adhesive composition>
The adhesive composition of the present invention is thermosetting and is used, for example, in the production of adhesive sheets and coverlay films. The adhesive composition of the present invention contains the above components (A) to (E), and may contain optional components such as a solvent, if necessary. When contains a solvent, the solvent is not included in the organic resin component.
Hereinafter, the components (A) to (E) will be described in detail.
The weight average molecular weight of each component in the present invention is a polystyrene equivalent value by GPC using tetrahydrofuran as a solvent.

（式（１）中、Ｒ₁は水素原子又は炭素原子数１〜６のアルキル基であり、それぞれ同一でも異なってもよく、ｍは０又は１を表す。Ｘは式（２），（３），（４）のいずれか一つを表し、式（２），（３），（４）中、Ｒ₂は水素原子又は炭素原子数１〜６のアルキル基であり、それぞれ同一でも異なってもよい。）
このようなエポキシ樹脂は、通常、重量平均分子量が１０，０００未満が好ましく、
また、分子骨格内にリン原子、硫黄原子、窒素原子等を含んでいてもよい。また、重量平均分子量の下限値は特に限定されないが、通常、５００以上が好ましい。 [Component (A)]
The epoxy resin as the component (A) is represented by the following general formula (1) and does not contain a halogen atom in the molecule, and is a trisphenol triglycidyl ether type having three epoxy groups in one molecule. It is an epoxy resin.

(In the formula (1), R ₁ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, which may be the same or different, and m represents 0 or 1. X represents the formula (2), (3 ), (4), and in formulas (2), (3), (4), R ₂ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, which may be the same or different. May be good.)
Such an epoxy resin usually has a weight average molecular weight of preferably less than 10,000,
Further, the molecular skeleton may contain a phosphorus atom, a sulfur atom, a nitrogen atom or the like. Moreover, the lower limit of the weight average molecular weight is not particularly limited, but is usually preferably 500 or more.

  As such an epoxy resin, for example, 2- [4- (2,3-epoxypropoxy) phenyl] -2- [4- [1,1-bis [4-([2,3-epoxypropoxy] phenyl] )] Ethyl] phenyl] propane and the like.

The (A) component epoxy resin is effective in improving the glass transition temperature, storage elastic modulus, flexibility and solder heat resistance of the cured product of the adhesive composition, and is also excellent in flexibility. In particular, the epoxy resin of component (A) is highly effective in improving the glass transition temperature of the cured product, and the epoxy resin of component (A) is 20 to 80 parts by weight, more preferably 30 to 80 parts by weight in the adhesive composition. Parts, particularly preferably 40 to 80 parts by mass, by mixing a general bifunctional epoxy resin such as a bisphenol A type epoxy resin or a general polyfunctional epoxy resin such as a cresol novolac type epoxy resin in the same manner Even if compared with (1), the hardened | cured material of the adhesive composition which mix | blended the epoxy resin of (A) component shows very high glass transition temperature.
In addition, the epoxy resin of (A) component may be used individually by 1 type, or may use 2 or more types together.

[(B) component]
The phenoxy resin as the component (B) has a weight average molecular weight of 10,000 to 100,000 and a glass transition temperature of 70 ° C. or higher.
Such a phenoxy resin preferably further has an epoxy group at both ends of the molecular chain, and when it does not have an epoxy group at both ends of the molecular chain, the solvent resistance of the cured product, the solder heat resistance, particularly when moisture is absorbed. The solder heat resistance may decrease.

  A weight average molecular weight becomes like this. Preferably it is 20,000-100,000, More preferably, it is 30,000-80,000. When the molecular weight is less than 10,000, the cured product may be inferior in heat resistance and flexibility, and in the case of exceeding 100,000, the cured product may be inferior in stability. When a solvent is used, the solubility of this component in the solvent may decrease.

  The glass transition temperature is preferably 70 to 200 ° C, more preferably 90 to 160 ° C. When the glass transition point is less than 70 ° C., the glass transition temperature and the storage elastic modulus of the cured product may be lowered, and the flexibility under high temperature conditions may be further lowered. When it exceeds 200 degreeC, the peeling strength of this hardened | cured material may be inferior.

  Examples of the component (B) phenoxy resin include bisphenol A type phenoxy resin, bisphenol F type phenoxy resin, copolymerized phenoxy resin of bisphenol A type and bisphenol F type, biphenyl type phenoxy resin, bisphenol S type phenoxy resin, and biphenyl. Copolymer phenoxy resin of phenphenol resin and bisphenol S type phenoxy resin, etc. Among them, bisphenol A type phenoxy resin, bisphenol A type and bisphenol F type copolymer phenoxy resin, biphenyl type phenoxy Examples thereof include bisphenol S-type phenoxy resins, and particularly preferable examples include bisphenol A-type phenoxy resins and copolymerized phenoxy resins of bisphenol A-type and bisphenol F-type.

(B) Although the compounding quantity of the phenoxy resin of a component is determined in consideration of the hardening state of an adhesive composition, the balance of the characteristic of hardened | cured material, etc., it is 100 mass together with 20-80 mass parts of (A) component. This is the amount to be part. When this blending amount satisfies such a range, the cured product has better adhesiveness, solder heat resistance, glass transition temperature, and workability.
In addition, the phenoxy resin of (B) component may be used individually by 1 type, or may use 2 or more types together.

[Component (C)]
(C) The hardening | curing agent which is a component may be a well-known thing used as a hardening | curing agent of an epoxy resin. Examples of the curing agent include aliphatic amine curing agents such as diethylenetriamine, tetraethylenetetramine, and tetraethylenepentamine; alicyclic amine curing agents such as isophoronediamine; diaminodiphenylmethane, diaminodiphenylsulfone, and phenylenediamine. Aromatic amine curing agent; phenolic resin such as resol type, novolac type; acid anhydride curing agent such as phthalic anhydride, pyromellitic anhydride, trimellitic anhydride, hexahydrophthalic anhydride, 4-methylhexahydrophthalic anhydride 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazo Imidazole compounds such as 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole; triphenylphosphine, tributylphosphine, tris (p-methylphenyl) phosphine, tris (p-methoxyphenyl) ) Organophosphines such as phosphine, tris (p-ethoxyphenyl) phosphine, triphenylphosphine / triphenylborate, tetraphenylphosphine / tetraphenylborate; dicyandiamide; boron trifluoride amine complex salt, tin borofluoride, zinc borofluoride And octylates such as tin octylate and zinc octylate. Among these, aliphatic amine-based curing agents, aromatic amine-based curing agents, and acid anhydride-based curing agents are preferable. , Imidazole compounds, Boron fluoride, Dicia Diamide, octylate and the like, particularly preferably an aromatic amine curing agent, acid anhydride curing agent, imidazole compounds include 硼弗 product.

The blending amount of the curing agent of component (C) is determined in consideration of the epoxy equivalent of component (A), the cured state of the adhesive composition, the balance of the properties of the cured product, and the like (A) and (B). It is 0.1-50 mass parts normally with respect to a total of 100 mass parts of a component, Preferably it is 0.5-40 mass parts, More preferably, it is 1-30 mass parts. When this blending amount satisfies such a range, the adhesiveness, solder heat resistance, solvent resistance, glass transition temperature, and electrical insulation of the cured product become better.
In addition, the hardening | curing agent of (C) component may be used individually by 1 type, or may use 2 or more types together.

（式中、Ｒは一価の有機基又はアミノ基等である。）
で表される構造を意味する。 [Component (D)]
The phosphazene compound as component (D) acts as a component imparting flame retardancy because it contains a phosphorus atom and a nitrogen atom in the molecule. Such a phosphazene compound is not particularly limited as long as it does not contain a halogen atom and has a phosphazene structure in the molecule. Here, the phosphazene structure is the following formula:

(In the formula, R is a monovalent organic group or an amino group.)
Means a structure represented by

（式中、Ｙは同一又は異種のハロゲン原子を含まない一価の有機基又はアミノ基であり、ｎは３〜１０の整数である。）
で示されるものであり、その融点は、好ましくは８０℃以上であり、より好ましくは９０〜１５０℃であり、特に好ましくは１００〜１５０℃である。
式中、ｎは好ましくは３〜９、より好ましくは３〜６の整数であり、Ｙで表されるハロゲン原子を含まない有機基又はアミノ基としては、例えば、炭素数１〜６のアルコキシ基、フェノキシ基、アミノ基、アリル基等が挙げられる。 As such a phosphazene compound, for example, cyclophosphazene oligomer is preferable from the viewpoint of heat resistance, moisture resistance, flame retardancy and chemical resistance. This cyclophosphazene oligomer has the following general formula (5)

(In the formula, Y is a monovalent organic group or amino group not containing the same or different halogen atoms, and n is an integer of 3 to 10.)
The melting point thereof is preferably 80 ° C. or higher, more preferably 90 to 150 ° C., and particularly preferably 100 to 150 ° C.
In the formula, n is preferably an integer of 3 to 9, more preferably 3 to 6, and the organic group or amino group not containing a halogen atom represented by Y is, for example, an alkoxy group having 1 to 6 carbon atoms. , Phenoxy group, amino group, allyl group and the like.

(D) Although the compounding quantity of the phosphazene compound of a component is determined in consideration of the hardening state of an adhesive composition, the balance of the characteristic of hardened | cured material, etc., with respect to a total of 100 mass parts of (A) and (B) component. The amount is usually 5 to 120 parts by mass, preferably 20 to 100 parts by mass, and more preferably 30 to 80 parts by mass. When this blending amount satisfies this range, the cured product has better flame retardancy, adhesion, solder heat resistance, and electrical insulation.
In addition, the phosphazene compound of (D) component may be used individually by 1 type, or may use 2 or more types together.

[(E) component]
The thermoplastic resin as component (E) is a high molecular weight thermoplastic resin that does not have rubber elasticity at room temperature (25 ° C.).
Specifically, it is a high molecular weight thermoplastic resin having an ester group, urethane group, ether group, or amide group skeleton in the molecule, and examples thereof include polyester urethane and polyether ester amide. These thermoplastic resins are cut at a temperature of 18 to 29 ° C. when stretched to 3 times the original length, or stretched to 2 times the original length, and the original length within 5 minutes. It does not return to 1.5 times or less, that is, it does not have rubber elasticity. By using such a high molecular weight thermoplastic resin that does not have rubber elasticity, the resulting adhesive composition has excellent processability without lowering the glass transition temperature.

  The thermoplastic resin as the component (E) may contain a reactive functional group such as a carboxyl group, an amino group, or a hydroxyl group in the molecule. When these reactive functional groups are contained, when the resulting adhesive composition is applied to a coverlay film, the adhesive composition flows in an appropriate manner when laminated and integrated by hot pressing. It is effective because it expresses sex. Furthermore, the thermoplastic resin as the component (E) may contain a phosphorus atom, a sulfur atom, a nitrogen atom, or the like. Containing these atoms is effective in improving flame retardancy and adhesion.

  Examples of commercially available thermoplastic resins that are component (E) include, for example, “Byron” series (manufactured by Toyobo, carboxyl-containing polyester resin), “TPAE” series (manufactured by Fuji Kasei, polyether ester amide). Etc.

(E) Although the compounding quantity of the thermoplastic resin of a component is decided in consideration of the hardening state of an adhesive composition, the balance of the characteristic of hardened | cured material, etc., it is 100 mass parts in total of (A) and (B) component. On the other hand, it is 0.1-80 mass parts normally, Preferably it is 0.5-60 mass parts, More preferably, it is 1-40 mass parts. When this blending amount satisfies such a range, the glass transition temperature, workability, adhesiveness, and solder heat resistance of the cured product become better.
In addition, the thermoplastic resin of (E) component may be used individually by 1 type, or may use 2 or more types together.

[Other optional ingredients]
In addition to the above components (A) to (E), if necessary, the adhesive composition of the present invention, and the adhesive sheet and coverlay film using the solvent, flame retardant, You may add arbitrary components, such as a coupling agent, antioxidant, an ion adsorption agent, and an inorganic filler.

In particular, the solvent used in the adhesive composition of the present invention includes methyl ethyl ketone (MEK), toluene, methanol, ethanol, isopropanol, acetone, N, N-dimethylformamide, cyclohexanone, N-methyl 2-pyrrolidone, dioxolane and the like. Preferably, MEK, toluene, N, N-dimethylformamide, and cyclohexanone are mentioned.
In addition, these solvents may be used individually by 1 type, or may use 2 or more types together.

  Here, the solid component density | concentration of a thermosetting adhesive solution should just be 20-50 mass%, More preferably, it is 25-40 mass%. If the solid content concentration is less than 20% by mass, there is a high possibility of unevenness in thickness when the adhesive is applied, and if it exceeds 50% by mass, the viscosity of the adhesive is high, resulting in poor coating properties.

  Moreover, it is desirable to add an inorganic filler to the adhesive composition of the present invention. The inorganic filler is a component blended for the purpose of assisting the flame retardancy of the cured product, improving the stability of the peeled state (cohesive peeling of the adhesive), stabilizing the moisture absorption resistance, and the like.

  Such an inorganic filler is not particularly limited as long as it is conventionally used for a coverlay film or an adhesive sheet. For example, metal hydroxides such as aluminum hydroxide and magnesium hydroxide; aluminum oxide, oxidation Metal oxides such as silicon and molybdenum oxide; boric acid compounds such as zinc borate and magnesium borate and the like, preferably metal hydroxides such as aluminum hydroxide and magnesium hydroxide, and zinc borate and boron Examples thereof include boric acid compounds such as magnesium acid, more preferably, aluminum hydroxide, magnesium hydroxide and zinc borate. Further, in order to improve the adhesion and water resistance of these inorganic fillers to the resin matrix and to improve the heat resistance, moisture absorption resistance, etc. of the cured product, the surface of the inorganic filler is a silane coupling agent. It is preferable that the surface is hydrophobized with a titanate coupling agent or the like.

The blending amount of the inorganic filler is usually an amount of 0 to 15 parts by mass, particularly 1 to 15 parts by mass, more preferably 1 to 15 parts by mass with respect to 100 parts by mass in total of the components (A) to (E). The amount is 10 parts by mass. When this blending amount satisfies such a range, the cured product has better adhesiveness, heat resistant adhesiveness, solder heat resistance, and moisture absorption resistance. In particular, when the blending amount exceeds 15 parts by mass, the glass transition temperature, flexibility and adhesiveness of the cured product may be lowered.
In addition, an inorganic filler may be used individually by 1 type, or may use 2 or more types together.

  In the case of mixing the above components, the order is not particularly limited, but can be determined by appropriately considering the solubility of the added components and the viscosity of the resulting adhesive solution. A pot mill, a ball mill, a homogenizer, a super mill, etc. can be used for mixing.

[Phosphorus content in flame retardant adhesive composition]
In the present invention, it is necessary that the content of the phosphorus element in the total adhesive composition with respect to the organic group resin component is 1.8 to 6.0% by mass, and more preferably 2.0 to 5.0% by mass. %, Particularly preferably 2.0 to 3.5% by mass. If this proportion is less than 1.8% by weight, it is difficult to satisfy the flame retardancy of the resulting adhesive composition, and if it exceeds 6.0% by weight, the phosphazene of component (D) in the adhesive composition The ratio of the compound or the like increases, and the adhesiveness, solder heat resistance, flexibility, solvent resistance, electrical insulation (migration), etc. of the adhesive composition decrease.

[Glass transition temperature and storage modulus after curing of flame retardant adhesive composition]
The adhesive composition of the present invention (including the case of the adhesive composition solution) is obtained by heat-treating the composition at 40 to 200 ° C, preferably 80 to 180 ° C, more preferably 120 to 180 ° C. Can be cured.
The glass transition temperature and the storage elastic modulus of the cured product of the adhesive composition thus obtained can be measured by a known dynamic viscoelasticity measurement method.

  100 degreeC or more is preferable, as for the glass transition temperature of the adhesive composition after hardening, 100-180 degreeC is more preferable, and 120-160 degreeC is especially preferable. When the glass transition temperature is in such a range, the cured product has better flexibility and solder heat resistance. In order to make the glass transition temperature within the above range, a method such as blending 20 to 80 parts by mass of the epoxy resin of component (A) in the adhesive composition can be mentioned.

  Further, the storage elastic modulus at 85 ° C. after curing is preferably 1.0 GPa or more, more preferably 1.2 to 5.0 GPa, and particularly preferably 1.5 to 4.0 GPa. If the storage elastic modulus at 85 ° C satisfies this range, the cured product will have better flexibility (especially flexibility at a high temperature around 85 ° C) and solder heat resistance, such as hard disk drives at high temperatures. It can be suitably used as an adhesive composition for an FPC coverlay film that is repeatedly bent. In addition, in order to make a storage elastic modulus into the said range, methods, such as mix | blending 20-80 mass parts of epoxy resin of (A) component in an adhesive composition, are mentioned.

  Furthermore, the storage elastic modulus at 25 ° C. after curing is preferably 2.0 GPa or more, more preferably 2.5 to 6.0 GPa, and particularly preferably 3.0 to 5.0 GPa. If the storage elastic modulus at 25 ° C. is satisfied, the cured product will have better flexibility (particularly, flexibility at room temperature around 25 ° C.) and solder heat resistance. It can be suitably used as an adhesive composition for an FPC coverlay film that is repeatedly bent. In addition, in order to make a storage elastic modulus into the said range, methods, such as mix | blending 20-80 mass parts of epoxy resin of (A) component in an adhesive composition, are mentioned.

<Adhesive sheet>
〔Constitution〕
The adhesive sheet which has the adhesive bond layer which consists of an adhesive composition of this invention has a mold release base material and this adhesive layer provided on this mold release base material. Specifically, for example, a two-layer structure having a release substrate and an adhesive layer, or a three-layer structure having an adhesive layer and a release substrate provided on both sides of the adhesive layer, etc. Can be mentioned. Any one of a two-layer structure and a three-layer structure may be appropriately selected according to a processing method at the time of manufacturing an FPC. This adhesive sheet is particularly preferably used for bonding between single-sided copper foils or double-sided copper foil flexible printed circuit boards.

  As the thickness of the adhesive layer, an arbitrary thickness can be selected depending on the purpose of use, but it is preferably 10 to 50 μm, more preferably 15 to 35 μm, and particularly preferably 15 to 25 μm in a dry state.

  The release substrate is not particularly limited as long as it is a film-like material that can be peeled off from the adhesive layer without impairing the form of the adhesive layer, if necessary. As such a release substrate, for example, a polyethylene (PE) film, a polypropylene (PP) film, a polymethylpentene (TPX) film, a PE film with a silicone release substrate, a PP film with a silicone release substrate, etc. Release papers such as PE resin-coated paper, PP resin-coated paper, and TPX resin-coated paper. The thickness of the release substrate may be appropriately selected as necessary. For example, when the release substrate is a release film, the thickness of the substrate is preferably 13 to 75 μm, When the release substrate is release paper, the thickness of the substrate is preferably 50 to 200 μm.

〔Production method〕
Next, the case where the organic solvent which is preferable embodiment is used is demonstrated as an example about the manufacturing method of the adhesive sheet of this invention.
First, an adhesive composition solution containing an organic solvent prepared in advance is applied to one side of a release substrate using a reverse roll coater, a comma coater, or the like. The release substrate coated with this adhesive composition solution is passed through an in-line dryer and heat-treated at 40 to 160 ° C. for 2 to 20 minutes to remove the organic solvent in the adhesive composition solution. The composition is made into a semi-cured state to form an adhesive sheet having a two-layer structure. Furthermore, another release base material is pressure-bonded to the application surface of the adhesive composition of the adhesive sheet by a heating roll under the conditions of a linear pressure of 0.2 to 20 kg / cm and a temperature of 40 to 120 ° C. Adhesive sheet. The release substrate is peeled off during use.
The “semi-cured state” means a state in which the curing reaction proceeds in a part of the composition in a dried state.

<Coverlay film>
〔Constitution〕
The coverlay film having an adhesive layer made of the adhesive composition of the present invention has an electrically insulating film and the adhesive layer provided on the electrically insulating film. Specifically, for example, a three-layer structure having an electrically insulating film, an adhesive layer, and a release substrate provided on the adhesive layer can be given. As the thickness of the adhesive layer, an arbitrary thickness can be selected depending on the purpose of use, but it is preferably 10 to 50 μm, more preferably 15 to 35 μm, and particularly preferably 15 to 25 μm in a dry state.

  Examples of electrical insulating films include polyimide film, polyethylene terephthalate (PET) film, polyester film, polyparabanic acid film, polyether ether ketone film, polyphenylene sulfide film, aramid film; glass fiber, aramid fiber, polyester fiber, etc. And impregnated with epoxy resin, polyester resin, diallyl phthalate resin as a matrix, and film or sheet and bonded with copper foil, etc., heat resistance, dimensional stability, machine From the viewpoint of properties (elastic modulus, elongation, etc.), a polyimide film, a polyparabanic acid film, and a polyphenylene sulfide film are preferable, and a polyimide film is particularly preferable.

The thickness of this electrically insulating film may be selected depending on the purpose of use, but is preferably 5 to 75 μm, more preferably 10 to 50 μm, and particularly preferably 12.5 to 25 μm. In addition, in order to improve adhesion to the adhesive layer, clean the film surface, improve dimensional stability, etc., surface treatment such as low-temperature plasma treatment, corona discharge treatment, sandblast treatment, etc. is performed on one or both sides of the film. May be.
The release substrate is as described in the section of the adhesive sheet.

〔Production method〕
Next, the case where the organic solvent which is preferable embodiment is used is demonstrated as an example about the manufacturing method of the coverlay film of this invention.
First, an adhesive composition solution containing an organic solvent prepared in advance is applied to one side of an electrically insulating film using a reverse roll coater, a comma coater, or the like. The film coated with the adhesive composition solution is passed through an in-line dryer and heat-treated at 40 to 160 ° C. for 2 to 20 minutes to remove the organic solvent in the adhesive composition solution. Semi-cured state. Next, the coated surface of the adhesive composition of the film and the release substrate are pressure-bonded with a heating roll under the conditions of a linear pressure of 0.2 to 20 kg / cm and a temperature of 40 to 120 ° C. to obtain a coverlay film. . The release substrate is peeled off during use.

  The adhesive sheet and coverlay film of the present invention thus obtained can be used for producing FPC according to a conventional method. In the FPC manufacturing process, the semi-cured adhesive composition layer may be completely cured each time one or both of the adhesive sheet and the coverlay film are bonded together, or the final FPC configuration is assembled. May be completely cured. The adhesive composition layer in the adhesive sheet and coverlay film of the present invention is completely cured by heating at 140 to 180 ° C. for 40 to 120 minutes under a pressure of 1 to 5 MPa, for example. Can do.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not limited to a following example. The following were used for the components (A) to (E) and other components used in Examples and Comparative Examples.
<Ingredients of flame retardant adhesive composition>

(A) Trifunctional epoxy resin not containing halogen represented by the above formula (1) [a-1] 2- [4- (2,3-epoxypropoxy) phenyl] -2- represented by the following formula (6) [4- [1,1-bis [4-([2,3-epoxypropoxy] phenyl)] ethyl] phenyl] propane (weight average molecular weight: about 600, 3 epoxy groups in one molecule)

(B) Phenoxy resin / [b-1] bisphenol A type phenoxy resin having a weight average molecular weight of 10,000 to 100,000 and a glass transition temperature of 70 ° C. or higher (weight average molecular weight: about 53,000, glass transition (Temperature: approx. 95 ° C, with epoxy groups at both ends of the molecular chain)
[B-2] Copolymerized phenoxy resin of bisphenol A type and bisphenol F type (copolymerization ratio: bisphenol A type / bisphenol F type = 50/50 (weight ratio), weight average molecular weight: about 60,000, glass transition (Temperature: approx. 80 ° C, with epoxy groups at both ends of the molecular chain)

(C) Curing agent: [c-1] 4,4′-diaminodiphenylsulfone, [c-2] 4-methylhexahydrophthalic anhydride, [c-3] 1-cyanoethyl-2-ethyl-4-methyl 45% by mass aqueous solution of imidazole / [c-4] tin borofluoride

・［ｄ−２］下記式（８）に示すシクロホスファゼン化合物（ｎ＝３〜６の混合物、燐含有率：約１２％）

(D) Phosphazene compound. [D-1] Cyclophosphazene compound represented by the following formula (7) (mixture of n = 3 to 6, phosphorus content: about 13%)

[D-2] Cyclophosphazene compound represented by the following formula (8) (mixture of n = 3 to 6, phosphorus content: about 12%)

(E) Thermoplastic resin [e-1] Byron UR3575 (trade name) (Toyobo, carboxyl group-containing phosphorus-containing urethane-modified polyester resin, phosphorus content: about 2.5%)
[E-2] TPAE-826-5A (trade name) (manufactured by Fuji Kasei, amino group-containing polyetheresteramide resin)

・［ｆ−３］下記式（１０）に示すクレゾールノボラック型エポキシ樹脂（ｎ＝５〜７の混合物、重量平均分子量：約１，７００、一分子中のエポキシ基：７〜９個）

・［ｆ−４］ニポール１０７２Ｂ（商品名）（日本ゼオン製、カルボキシル基含有アクリロニトリルブタジエンゴム、ガラス転移温度：０℃以下） Other components-[f-1] bisphenol A type epoxy resin (weight average molecular weight: about 300, two epoxy groups in one molecule)
[F-2] Glycidylamine type epoxy resin represented by the following formula (9) (weight average molecular weight: about 500, epoxy groups in one molecule: 4)

[F-3] Cresol novolac type epoxy resin represented by the following formula (10) (mixture of n = 5 to 7, weight average molecular weight: about 1,700, 7 to 9 epoxy groups in one molecule)

[F-4] Nipol 1072B (trade name) (manufactured by Nippon Zeon, carboxyl group-containing acrylonitrile butadiene rubber, glass transition temperature: 0 ° C. or less)

<Materials used>
・ Kapton 100H (trade name) (Toray DuPont, polyimide film, thickness: 25 μm)
-Apical NPI (trade name) (manufactured by Kaneka, polyimide film, thickness: 12.5 μm)
・ Y7TF (trade name) (manufactured by Lintec, release paper, thickness: approx. 130 μm)
・ PET38X (trade name) (Made by Lintec, release film, thickness: approx. 38 μm)
・ HTE (trade name) (Mitsui Metals, electrolytic copper foil, thickness: 18 μm and 35 μm)
RAS22S47 (trade name) (manufactured by Shin-Etsu Chemical Co., Ltd., single-sided three-layer flexible printed wiring board, Kapton 50H / adhesive layer thickness: 13 μm / rolled copper foil 18 μm)
・ KN16SR18A (trade name) (manufactured by Shin-Etsu Chemical Co., Ltd., single-sided double-layer flexible printed wiring board, apical NPI / rolled copper foil 18 μm)

<Examples 1-5, Comparative Examples 1-8>
Each component of the adhesive composition was mixed at a blending ratio (parts by mass) shown in Tables 1 and 2 to prepare a mixture. This mixture was dissolved in a mixed solvent of MEK / toluene (MEK: toluene = 80: 20 (mass ratio)) and sufficiently stirred using a ball mill so that the total concentration of solid components was 38% by mass. An adhesive composition solution was prepared.

  Next, this adhesive composition solution was applied on a release film (trade name: PET38X) using a reverse roll coater so that the thickness of the adhesive layer after drying was 25 μm. Thereafter, MEK and toluene were removed under heating and drying conditions at 140 ° C. for 10 minutes to make the adhesive composition semi-cured. A release paper (product name: Y7TF) is pressure-bonded to the adhesive surface of the film with the semi-cured adhesive composition using a roll laminator at a temperature of 70 ° C. and a linear pressure of 2 kg / cm. A sheet was produced.

  Moreover, the coverlay film was produced by the process similar to preparation of an adhesive sheet except having changed the release film into the polyimide film (Brand name: Kapton 100H, thickness: 25 micrometers).

About these adhesive sheets and coverlay films, physical properties were evaluated and measured according to the following evaluation and measurement methods. The results are shown in Tables 1 and 2. The adhesive sheet and the release substrate of the coverlay film were peeled off and used for sample preparation.
<Evaluation and measurement method>

(Configuration of evaluation sample)
The following samples 1 to 3 were subjected to thermocompression bonding under press processing conditions of 160 ° C., 5.0 MPa, and used as evaluation samples for peel strength, solder heat resistance, glass transition temperature, and storage modulus.
-Sample 1: Two surfaces of adhesive sheet covered with two RAS22S47 film surfaces-Sample 2: Adhesive layer of coverlay film and glossy surface of HTE foil (35 μm)-Sample 3: Adhesion The sheet is coated on both sides with a glossy surface of two HTE foils (35 μm)

(Physical property evaluation / measurement method)
1. Peel strength (according to JIS C6471)
Peel strength A: Sample 1 was cut to a width of 10 mm to prepare test piece 1, and RAS22S47 was continuously 50 mm at a speed of 50 mm / min in the direction of 90 degrees under the condition of 25 ° C. The minimum value of the load at the time of peeling was measured and taken as the peel strength.
Peel strength B: Sample 2 was cut to a width of 10 mm to prepare test piece 2, and for this test piece 2, the HTE foil was continuously applied at a speed of 50 mm / min in the direction of 90 degrees under the condition of 25 ° C. The minimum value of the load when peeling 50 mm was measured and taken as the peel strength.

2. Solder heat resistance (according to JIS C6471)
Normal solder heat resistance: Sample 2 was cut into a 25 mm square to prepare test piece 3, which was dried at 80 ° C. for 10 minutes and then floated on a solder bath for 30 seconds. Then, the external appearance of this test piece 3 was confirmed visually, and the presence or absence of a swelling, peeling, etc. was investigated. This operation was repeated while changing the temperature of the solder bath, and the maximum temperature at which the sample did not swell or peel off was measured.
Moisture-absorbing solder heat resistance: Sample 2 was cut into a 25 mm square to prepare test piece 4, which was left to stand at 40 ° C. and 90% RH for 1 hour, and then floated on a solder bath for 30 seconds. Thereafter, the maximum temperature was measured in the same manner as in the normal solder heat resistance section.

3. Glass transition temperature (Tg) and storage elastic modulus at 85 ° C. Sample 3 was heat treated at 150 ° C. for 4 hours, then the HTE foil was removed with ferric chloride aqueous solution to produce an adhesive sheet, and this adhesive sheet was cut. Thus, a test piece 5 (10 mm × 50 mm) was produced. Using the test piece 5, the Tg and storage elastic modulus of the adhesive were measured with a viscoelasticity measuring device (trade name: RSAIII, manufactured by Rheometric Co., Ltd.) with the temperature rising condition set to 5 ° C./min. Tg was a tan δ peak (maximum value), and the storage elastic modulus was a value at 85 ° C.

4). Migration resistance A press sample was prepared by laminating the treated surface of HTE foil (18 μm) and the adhesive composition layer of the coverlay film using a press device (temperature: 160 ° C., pressure: 3 MPa, time: 60 minutes). Produced. The copper foil of the press sample was etched, and a comb circuit having a pitch of 100 μm (line width / space width = 50 μm / 50 μm) made of a pair of comb electrodes was produced. Adhesive composition layer of another coverlay film was bonded to the surface on which this comb-shaped circuit was produced with a press device (temperature: 160 ° C., pressure: 3 MPa, time: 60 minutes), and migration resistance measurement was performed. A sample was prepared.
Under conditions of a temperature of 85 ° C. and a relative humidity of 85%, a DC voltage of 50 V was applied to each end of the two comb-shaped electrodes of this measurement sample using a migration tester (product name: MIG-87). Was applied to evaluate the migration resistance. When a short circuit (reduction in resistance value) occurs between the conductors within 1,000 hours after voltage application, or when dendrite growth is observed after 1,000 hours, it is evaluated as “bad” and indicated by × The case where the resistance value was maintained after 1,000 hours had passed and no dendrite was produced was evaluated as “good” and indicated by ◯.

5. Flexibility under the condition of a measurement temperature of 85 ° C. A pattern in which the circuit of 150 μm pitch (conductor 75 μm, line spacing 75 μm) shown in FIG. 1 is reciprocated 6 times in the longitudinal direction (MD: Machine Direction) of KN16SR18A was produced. The cover lay film was press-bonded to this at 160 ° C. and 5.0 MPa for 60 minutes, and further subjected to heat treatment at 150 ° C. for 4 hours to obtain a sample for measuring flexibility. For this sample, using a high-speed bending tester (trade name: SEK-31C4S, manufactured by Shin-Etsu Engineering Co., Ltd.), the measurement direction was measured under the conditions of a bending radius of 1.5 mm, a bending speed of 600 rpm, a stroke of 30 mm, and a measurement temperature of 85 ° C. As the inside of the cover lay, the number of bendings until the electrical resistance increased by 20% from the initial value was counted. A case where the number of bendings was less than 5 million was evaluated as “bad” and indicated by ×, and a case where the number of bendings was 5 million or more was evaluated as “good” and indicated by ○.

6). Flame retardance In accordance with UL94VTM-0 flame retardancy standard, the flame retardancy of the coverlay film was measured. A case where flame retardancy satisfying the UL94VTM-0 standard was evaluated as “good” and indicated by ◯, and a case where the sample did not satisfy the UL94VTM-0 standard was evaluated as “defective” and indicated by ×.

7). Workability The coverlay film was bent and opened in the direction of 180 degrees, and the adhesive layer was confirmed visually for breakage and chipping. When the adhesive layer is not broken or chipped, the processability is evaluated as good and indicated as ◯, and when the adhesive layer is broken or chipped, the processability is evaluated as poor. X.

<Evaluation results>
The compositions prepared in Examples 1 to 5 satisfy the requirements of the present invention and have a high glass transition temperature, excellent workability, flexibility and electrical insulation (migration resistance) while being halogen-free. Property), adhesiveness, solder heat resistance, and flame retardancy.
On the other hand, the compositions prepared in Comparative Examples 1 to 8 do not satisfy the requirements of the present invention, and include glass transition temperature, processability, flexibility, electrical insulation (migration resistance), adhesion, solder heat resistance. And at least one characteristic of flame retardancy was inferior to those prepared in the examples.

  According to the present invention, while being halogen-free, it has a high glass transition temperature, excellent workability, flexibility, electrical insulation (migration resistance), adhesion, solder heat resistance, and flame retardancy, In particular, since an adhesive composition that can provide a cured product that can be suitably used for a flexible printed circuit board, and an adhesive sheet and coverlay film using the same can be obtained, its industrial utility value is high.

1 Circuit formed in the longitudinal direction of a single-sided flexible printed wiring board 2 Copper foil

Claims (12)

(A) Trifunctional epoxy resin not containing halogen represented by the following general formula (1): 20 to 80 parts by mass,

(In the formula (1), R ₁ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, which may be the same or different, and m represents 0 or 1. X represents the formula (2), (3 ), (4), and in formulas (2), (3), (4), R ₂ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, which may be the same or different. May be good.)
(B) a phenoxy resin having a weight average molecular weight of 10,000 to 100,000 and a glass transition temperature of 70 ° C. or higher: an amount of 100 parts by mass in combination with the component (A),
(C) Curing agent: 0.1 to 50 parts by mass with respect to 100 parts by mass in total of components (A) and (B),
(D) Phosphazene compound: 5 to 120 parts by mass with respect to 100 parts by mass in total of components (A) and (B),
(E) Thermoplastic resin: A flame-retardant adhesive composition containing no halogen and containing 0.1 to 80 parts by mass with respect to 100 parts by mass as a total of components (A) and (B).   The flame retardant adhesive composition according to claim 1, wherein the phenoxy resin has an epoxy group at both ends of the molecular chain.   The flame retardant adhesive composition according to claim 1 or 2, wherein the thermoplastic resin does not have rubber elasticity at room temperature.   The flame-retardant adhesive composition according to any one of claims 1 to 3, wherein the phosphorus content in the adhesive composition is 1.8 to 6.0 mass% or more.   The flame retardant adhesive composition according to any one of claims 1 to 4, wherein the glass transition temperature after curing is 100 ° C or higher.   The flame retardant adhesive composition according to any one of claims 1 to 5, wherein the storage elastic modulus at 85 ° C after curing is 1 GPa or more.   The flame-retardant adhesive composition according to any one of claims 1 to 6, wherein the flame-retardant adhesive composition is used for bonding a single-sided copper foil or a double-sided copper foil flexible printed circuit board to each other.   The flame-retardant adhesive composition according to any one of claims 1 to 6, which is used for producing a cover lay film.   The adhesive sheet which has a mold release base material layer and the adhesive bond layer which consists of an adhesive composition of any one of Claims 1-6 provided on this mold release base material layer.   The coverlay film which has an electrically insulating film and the adhesive bond layer which consists of an adhesive composition of any one of Claims 1-6 provided on this electrically insulating film.   The coverlay film according to claim 10, wherein the electrically insulating film is a polyimide film.   The adhesive sheet or coverlay film according to claim 9, 10 or 11, further comprising a release substrate layer provided on the adhesive layer.

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