JP2009290166A - Coverlay film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flame-resistant coverlay film allowing thermocompression bonding at a low temperature below 250°C, and using a non-halogen and non-phosphorous adhesive resin composition with excellent flame retardancy, solder heat resistance after moisture absorption, workability and the like. <P>SOLUTION: In this coverlay film with an adhesive layer formed on a surface of a polyimide film, an adhesive resin composition constituting the adhesive layer contains, as essential constituents: (A) a polyimide resin having a siloxane unit; (B) an aromatic group-substituted naphthol type epoxy resin of a structure obtained by epoxidizing a naphthol resin having a structure whose aromatic group is substituted by a naphthalene ring; and (C) citrate ester. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coverlay film used for a flexible printed wiring board.

  As a printed wiring board, conventionally, a base material made of paper-phenolic resin, glass fiber-epoxy resin, or a base material such as a polyimide film or a polyethylene terephthalate film and a metal foil are used.

  Further, in recent years, printed wiring boards used in the fields of electrical / electronic equipment and precision equipment have a reduced wiring occupation area, and thus the demand for multilayer printed circuit boards has been increasing. Various adhesives or adhesive films are used in the process of producing a multilayer printed wiring board by laminating printed wiring boards or compounding different kinds of circuit materials.

  As such an adhesive, a prepreg adhesive in which a woven fabric such as glass fiber is impregnated with an epoxy or bismaleimide resin is known. However, these have problems such as insufficient flexibility and poor dimensional stability. Conventionally, adhesives such as acrylonitrile butadiene rubber / phenol resin, phenol resin / butyral resin, acrylonitrile butadiene rubber / epoxy resin have been proposed (for example, JP-A-4-29393 and JP-A-4-36366). JP-A-4-41581). However, these adhesives do not have sufficient chemical resistance and heat resistance, have large thermal degradation, insufficient heat resistance to moisture-absorbing solder, and workability such as generation of smear during drilling to form through holes. The point was not enough.

  In addition, a polyimide adhesive having excellent heat resistance has been proposed (see, for example, US Pat. No. 4,543,295). However, such polyimides have difficulties in practicality because they require a thermocompression bonding temperature of 250 ° C. or higher in order to bond substrates such as copper or polyimide film and obtain satisfactory adhesive strength. It was.

  Patent Document 1 discloses an adhesive using polyimide made of diaminopolysiloxane and aromatic tetracarboxylic acid as raw materials for thermocompression bonding at a low temperature. However, such a polyimide alone has a drawback in that the adhesive strength is not sufficient and the reliability is poor.

  As a polyimide adhesive having excellent adhesive strength, for example, Patent Document 2 discloses a film adhesive made of polyamideimide and an epoxy resin as an adhesive for manufacturing a flexible printed circuit board (FPC). However, when such a film is used for bonding uneven surfaces on which circuits are formed, such as the production of multilayer printed wiring boards, the filling of the circuit surfaces is not sufficient, and sufficient heat resistance to the solder bath is obtained. I can't.

  For this reason, adhesives for multilayer printed circuit boards and adhesives for coverlay films can be pressed at low temperatures of 250 ° C or lower, and adhesive strength, chemical resistance, heat resistance, hygroscopic solder heat resistance, and dimensional stability during wiring processing Materials with excellent properties and the like have been demanded. Moreover, the material excellent in the flame retardance from the point of ensuring fire safety has been calculated | required.

  In the conventional adhesive film, a resin or additive containing a halogen such as bromine has been used to impart flame retardancy. Halogen has been widely used for the purpose of imparting flame retardancy, cost performance, and resistance to plastic deterioration. However, there is a concern that the halogen contained therein may cause harmful substances such as dioxin during combustion, and it is strongly desired to eliminate the halogen from the material.

  Various non-halogen materials have been developed as flame retardant materials that replace halogen. Among them, the most common method is the use of a resin containing phosphorus or the addition of an organic phosphorus compound. Examples of such a material containing a phosphorus compound include JP-A No. 2004-231792, JP-A No. 2005-15761, JP-A No. 2005-171044, and JP-A No. 2005-60489. However, there are concerns that phosphorus compounds may cause soil and water pollution, and safety is not sufficient, and in the future, phosphorus compounds need to be excluded from materials, Adhesive film is no exception.

  From these points, non-halogen and non-phosphorus flame retardant adhesive films are desired. An example of such an adhesive film is Patent Document 3. However, such an adhesive film has a problem that the migration resistance is lowered by the inclusion of a metal hydroxide or the like.

  By the way, Patent Document 4 discloses a heat-resistant adhesive film for printed circuit boards made of a polyimide having a silicon unit and an epoxy resin. However, the epoxy resin used here is a general epoxy resin derived from bisphenol A or a phenol resin, and the type of polyimide and the combination with the epoxy resin are also general, and the flame retardant Consideration was not enough. Patent Document 5 discloses an acenaphthylene-modified phenolic resin and an epoxy resin obtained by epoxidizing it. However, there is no disclosure about using such acenaphthylene-modified phenolic resin or epoxy resin as an adhesive in combination with polyimide.

JP-A-4-23879 Japanese Patent Laid-Open No. 52-91082 JP 2004-146286 A JP 2001-203467 A International Publication WO2003 / 104295 Pamphlet

  The object of the present invention is to provide a flame-retardant material using a non-halogen / non-phosphorus adhesive resin composition that can be pressed at a low temperature of 250 ° C. or lower and is excellent in heat resistance, hygroscopic solder heat resistance, workability, etc. It is to provide a coverlay film.

  As a result of intensive studies to achieve the above object, the present inventors have completed the present invention by using a specific component in a mixed resin of a specific polyimide resin and an epoxy resin.

That is, the present invention is a cover lay film formed from a polyimide film and an adhesive resin composition, and the adhesive resin composition includes the following components (A) to (C)
(A) a polyimide resin having a siloxane unit,
(B) an aromatic group-substituted naphthol type epoxy resin having a structure obtained by epoxidizing a naphthol resin having a structure in which an aromatic ring-containing group is substituted with a naphthalene ring, and (C) represented by the following general formula (1) Citrate ester,
Is a cover lay film characterized by containing.

一般式（１）において、Xは水酸基又はアセチル基を示し、Rは炭素数１〜６のアルキル基を示す。

In General formula (1), X shows a hydroxyl group or an acetyl group, R shows a C1-C6 alkyl group.

  Moreover, (A) component has the repeating unit represented by the following general formula (2) and (3), and the composition ratio of the repeating unit represented by general formula (2) and (3) is (2). / (3) = The range of 50/50 to 10/90 (molar ratio) makes the physical properties of the coverlay film favorable.

一般式（２）において、Ar₁は４価の芳香族基を示し、R₁及びR₂は２価の炭化水素基を示し、R₃及びR₄は炭素数１〜６の１価の炭化水素基を示し、mは１以上の整数であり、mの数平均値は１〜２０の範囲にある。一般式（３）において、Ar₁は４価の芳香族基を示し、Ar₂は２価の芳香族基を示す。

In the general formula (2), Ar ₁ represents a tetravalent aromatic group, R ₁ and R ₂ represent a divalent hydrocarbon group, and R ₃ and R ₄ represent a monovalent carbon having 1 to 6 carbon atoms. A hydrogen group is shown, m is an integer of 1 or more, and the number average value of m is in the range of 1-20. In the general formula (3), Ar ₁ represents a tetravalent aromatic group, and Ar ₂ represents a divalent aromatic group.

  The adhesive resin composition comprises (C) component 1 to 45 parts by weight with respect to 100 parts by weight of resin component (A) 65 to 98% by weight and (B) component 2 to 35% by weight. It becomes the physical property of a coverlay film by becoming further or containing 1-15 weight part of epoxy resin hardening | curing agents with respect to a total of 100 weight part of (A) component and (B) component.

Further, instead of with the epoxy resin curing agent or the epoxy resin curing agent, 1 to 20 mol% of Ar ₂ in the general formula (3) is a repeating unit of the polyimide resin containing the siloxane unit represented by the following general formula (4 The physical properties of the coverlay film can be improved by being a divalent aromatic group having a functional group reactive with the epoxy group represented by (2).

ここで、式中、Ar₃は３価又は４価の芳香族基を示し、Yは水酸基、アミノ基、カルボキシル基又はメルカプト基を示し、kは１又は２を示す。

Here, in the formula, Ar ₃ represents a trivalent or tetravalent aromatic group, Y represents a hydroxyl group, an amino group, a carboxyl group, or a mercapto group, and k represents 1 or 2.

  The component (B) is preferably an aromatic group-substituted naphthol type epoxy resin having a structure represented by the following general formula (5) or (6).

但し、Gはグリシジル基を示し、Rは芳香族環含有基又は水素を示し、Xはアルキレン基又は-Z-Ar₄-Z-で表されるアラルキレン基を示し、ｐは０以上の整数であり、pの数平均値は０〜１５の範囲にあり、qは１又は２を示し、そしてR中に芳香族環含有基が占める割合は１０モル％以上である。また、Zはアルキレン基を示し、Ar₄は２価の芳香族基を示す。

Wherein G represents a glycidyl group, R represents an aromatic ring-containing group or hydrogen, X represents an alkylene group or an aralkylene group represented by —Z—Ar ₄ —Z—, and p is an integer of 0 or more. The number average value of p is in the range of 0 to 15, q is 1 or 2, and the ratio of the aromatic ring-containing group in R is 10 mol% or more. Z represents an alkylene group, and Ar ₄ represents a divalent aromatic group.

但し、Gはグリシジル基を示し、R₅、R₆及びR₇は水素原子又は炭素数１〜６のアルキル基を示し、Rは下記一般式（a）で示されるアセナフテニル基、下記一般式（b）で示されるインダニル基又は下記一般式（c）で示されるα−メチルベンジル基から選ばれる芳香族環含有基あるいは水素を示すが、R中に芳香族環含有基が占める割合は１０モル％以上であり、ｐは０以上の整数であり、pの数平均値は０〜１５の範囲にあり、qは１又は２を示す。

However, G is a glycidyl group, R _5, R ₆ and R ₇ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, acenaphthenyl group R is represented by the following general formula (a), the following general formula ( An aromatic ring-containing group or hydrogen selected from the indanyl group shown by b) or the α-methylbenzyl group shown by the following general formula (c) is shown, but the proportion of the aromatic ring-containing group in R is 10 mol. %, P is an integer of 0 or more, the number average value of p is in the range of 0 to 15, and q is 1 or 2.

  The coverlay film of the present invention can be thermocompression bonded at a lower temperature than conventional polyimide adhesives without impairing the heat resistance and electrical properties inherent to polyimide. Excellent flame retardancy even without halogen and phosphorus elements. Therefore, at the time of incineration disposal, it is possible to reduce the risk of generation of harmful substances such as dioxin and soil / water pollution.

  Hereinafter, the coverlay film of the present invention will be described in detail. The coverlay film of the present invention has an adhesive layer on the surface of a polyimide film. The adhesive layer is formed of an adhesive resin composition. First, each component of the adhesive resin composition will be described.

  The adhesive resin composition forming the cover lay film of the present invention contains the above components (A) to (C) as essential components. The component (A) is a polyimide resin having a siloxane unit, the component (B) is an aromatic group-substituted naphthol type epoxy resin, and the component (C) is a citrate ester. Moreover, it is desirable that this adhesive resin composition does not substantially contain a halogen element and a phosphorus element. Here, “substantially free of halogen element and phosphorus element” means that the halogen element or phosphorus compound does not contain 900 wtppm or more of halogen or phosphorus and the halogen compound or phosphorus compound.

  The polyimide resin having a siloxane unit as the component (A) (hereinafter referred to as siloxane-containing polyimide resin) is not particularly limited as long as it has a siloxane skeleton in the molecular structure. For example, the general formula (2) and ( What has a repeating unit represented by 3) is mentioned. Preferably, the constitutional ratio of the repeating units represented by the general formulas (2) and (3) is in the range of (2) / (3) = 50/50 to 10/90 (molar ratio), preferably 50/50. It is good to be in the range of ~ 20/80.

As the siloxane-containing polyimide resin, it is desirable to use a solvent-soluble polyimide resin having good film moldability. Furthermore, if a functional group capable of reacting with an epoxy group is contained in the polyimide resin, the epoxy resin curing agent can be dispensed with or in a small amount. In order to have a functional group capable of reacting with an epoxy group in the polyimide resin, 1 to 20 mol%, preferably 2 to 10 mol%, of Ar ₂ in the general formula (3) is the above general formula (4). There is a method of using a raw material aromatic diamine so that a polyimide resin having an aromatic group represented by

The siloxane-containing polyimide resin is usually obtained by reacting diaminosiloxane and aromatic diamine with tetracarboxylic dianhydride. Since Ar ₁ in the above general formulas (2) and (3) can be said to be a residue of tetracarboxylic dianhydride, Ar ₁ is understood from the description of tetracarboxylic dianhydride. Moreover, since the siloxane unit in General formula (2) can be called the residue of a diaminosiloxane, a siloxane unit is understood from diaminosiloxane description. Furthermore, since Ar ₂ in the general formula (2) can be said to be a residue of an aromatic diamine, Ar ₂ is understood from the explanation of the aromatic diamine.

  As specific examples of tetracarboxylic dianhydride, preferably 3,3 ′, 4,4′-diphenyl ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, And one or more tetracarboxylic dianhydrides selected from 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride and 2,2 ′, 2,3′-benzophenone tetracarboxylic dianhydride. It is done. Also, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,3,3 ′, 4′-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 1,4,5 , 8-Naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 3,3,6,7 Other tetracarboxylic acids such as anthracene tetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, 4,4 ′-(hexafluoroisopyridene) phthalic dianhydride Although an anhydride is also mentioned, when using these other tetracarboxylic dianhydrides, it is good to use together with 1 or more types of the tetracarboxylic dianhydride mentioned as said preferable. When other tetracarboxylic dianhydrides are used in combination, the range of 5 to 50 mol% is preferable.

で表されるジアミノシロキサンが用いられる。一般式（７）において、R₁〜R₄は一般式（２）のそれらと同じ意味を有する。 As diaminosiloxane, the following general formula (7)

The diaminosiloxane represented by these is used. In the general formula (7), R _{1 to} R ₄ have the same meaning as those in the general formula (2).

R ₁ and R _{2 each} represent a divalent hydrocarbon group, preferably an alkylene group having 1 to 6 carbon atoms or a phenylene group. R ₃ and R ₄ represent a hydrocarbon group having 1 to 6 carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms or a phenyl group. These may be the same or different.

  m is an integer of 1 or more, and the number average value of m is in the range of 1 to 20, but the number average value is preferably in the range of 2 to 14. If it is less than this range, the filling property as an adhesive resin composition is lowered, and if it is more, the adhesive property is lowered, which is not preferable. The same applies to the siloxane unit in the general formula (2).

  By using diaminosiloxane as a siloxane-containing polyimide resin, the coverlay film of the present invention can be given fluidity at the time of thermocompression bonding, and the filling property on the printed wiring board circuit can be improved.

Preferable specific examples of diaminosiloxane include diaminosiloxanes represented by the following formula.

More preferable specific examples of the diaminosiloxane include phenyl group-substituted diaminosiloxanes represented by the following formula. Here, j and n in the following formula are the total number of j and n being an integer of 1 or more, and the number average value is in the range of 1 to 20, preferably in the range of 2 to 14.

In the general formula (3), specific examples of the aromatic diamine that gives Ar ₂ include m-phenylenediamine, p-phenylenediamine, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, and benzidine. 4,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 4,4′-diamino -P-terphenyl and the like are mentioned, but 2,2-bis (3-aminophenoxyphenyl) propane, 2,2-bis (4-aminophenoxyphenyl) propane, 3 for the purpose of improving the solubility in organic solvents. , 3-bis (3-aminophenoxyphenyl) sulfone, 4,4-bis (3-amino Phenoxyphenyl) sulfone, 3,3-bis (4-aminophenoxyphenyl) sulfone, 4,4-bis (4-aminophenoxyphenyl) sulfone, 2,2-bis (3-aminophenoxyphenyl) hexafluoropropane, 2, , 2-bis (4-aminophenoxyphenyl) hexafluoropropane, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 4,4- (p-phenylenediene) It is preferable to use one or more diamines having three or more aromatic rings such as isopropylidene) bisaniline and 4,4- (m-phenylenediisopropylidene) bisaniline. Aromatic diamines that give Ar ₂ do not have siloxane units or silicon units.

It is also advantageous to use a reactive aromatic diamine represented by the following general formula (8) having a functional group reactive with an epoxy resin as a part of the aromatic diamine.

In the general formula (8), Ar ₃ , Y and k have the same meanings as those in the general formula (4). Such reactive aromatic diamines include 2,5-diaminophenol, 3,5-diaminophenol, 4,4 ′-(3,3′-dihydroxy) diaminobiphenyl, 4,4 ′-(2,2 '-Dihydroxy) diaminobiphenyl, 2,2'-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 3,3', 4,4'-biphenyltetraamine, 3,3 ', 4,4' -Tetraaminodiphenyl ether, 4,4 '-(3,3'-dicarboxy) diphenylamine, 3,3'-dicarboxy-4,4'-diaminodiphenyl ether, and the like are particularly preferable. At least one of (3,3′-dihydroxy) diphenylamine and 4,4 ′-(2,2′-dihydroxy) diphenylamine. By using the reactive aromatic diamine, it reacts with the epoxy resin at the time of thermocompression bonding to form a crosslinked structure, so that the adhesive strength and chemical resistance of the adhesive film of the present invention can be further improved. The reactive aromatic diamine is preferably used in the range of 1 to 20 mol%, more preferably in the range of 2 to 10 mol% of the total aromatic diamine.

  The siloxane-containing polyimide resin is represented by the above general formulas (2) and (3) by reacting the above diaminosiloxane and aromatic diamine with tetracarboxylic dianhydride in a solvent to form a precursor resin, followed by heat ring closure. A polyimide resin having a repeating unit can be produced.

  As the component (B), an aromatic group-substituted naphthol type epoxy resin is used. The contribution of the aromatic substituted naphthalene skeleton generated by reaction with an aromatic compound having an ethylenically unsaturated bond (hereinafter referred to as an ethylenic aromatic compound) improves the heat resistance of the coverlay film of the present invention.

  An aromatic group-substituted naphthol type epoxy resin is an aromatic having a structure in which an aromatic ring-containing group is substituted on a naphthalene ring (naphthol ring) by reacting a naphthol resin, preferably a naphthol novolak resin, with an ethylenic aromatic compound. It has a structure obtained by obtaining a group-substituted naphthol resin and then epoxidizing the hydroxyl group of the naphthol resin with epichlorohydrin to form an OG group (glycidyl ether group). However, the production method of the aromatic group-substituted naphthol type epoxy resin is not limited to the above method.

Preferred examples of the aromatic group-substituted naphthol type epoxy resin include an epoxy resin represented by the above general formula (5). In the general formula (5), G represents a glycidyl group, R represents an aromatic ring-containing group (hereinafter referred to as an aromatic group) or hydrogen, and X is represented by an alkylene group or —Z—Ar ₄ —Z—. P is an integer of 0 or more, the number average value of p is in the range of 0 to 15, q is 1 or 2, and the proportion of aromatic groups in R is 10 mol. % Or more. Z represents an alkylene group, and Ar ₄ represents a divalent aromatic group. X and Z are alkylene groups, preferably an alkylene group having 1 to 3 carbon atoms, and more preferably a methylene group. When R is an aromatic group, the aromatic group is preferably a 1-3 ring aromatic hydrocarbon group having 7 to 15 carbon atoms.

X is derived from a cross-linking agent that reacts with naphthol when producing naphthol resin. When the cross-linking agent is formalin, a methylene group is provided, and when it is RO-H ₂ C-Ph-CH ₂ -OR (R is H or alkyl, Ph is phenylene), -H ₂ C-Ph-CH ₂ The aralkyl group represented by-is given. Ar ₄ represents a divalent aromatic group, preferably a phenylene group or a biphenylene group. Further, at least 10 mol%, preferably 20 mol% or more, more preferably 30 mol% or more of all naphthalene nuclei are substituted with aromatic groups. If this substitution rate is low, sufficient flame retardancy cannot be obtained. Since the epoxy resin is a mixture, the epoxy resin as a whole needs only to have 10 moles or more of aromatic groups per 100 moles of all naphthalene nuclei. However, 80 mol% or more may be substituted with an aromatic group, but since the effect is saturated, 20 to 80 mol%, preferably 30 to 70 mol% is preferable. Moreover, p is an integer greater than or equal to 0, the number average value of p exists in the range of 0-15, Preferably it is the range of 0-5 as an average value, More preferably, it exists in the range of 0.1-3. q represents 1 or 2, but is preferably 1.

Moreover, as an aromatic group substituted naphthol type | mold epoxy resin, the epoxy resin represented by the said General formula (6) is illustrated preferably. Here, G is a glycidyl group, R _5, R ₆ and R ₇ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. R represents an aromatic group or hydrogen, preferably selected from the acenaphthenyl group represented by the above formula (a), the indanyl group represented by the formula (b), or the α-methylbenzyl group represented by the formula (c). The ratio of the aromatic group in R is preferably 10 mol% or more, preferably 20 mol or more, more preferably 30 mol or more, and p is an integer of 0 or more. , P is in the range of 0 to 15, and q is 1 or 2. In addition, it can be understood that the symbol corresponding to the general formula (5) has a similar meaning.

  An example of a method for producing the aromatic group-substituted naphthol type epoxy resin as the component (B) will be described. Although not particularly limited, an ethylenic aromatic compound can be added to a naphthalene ring of a naphthol resin because it can use a Friedel-Crafts reaction. The naphthol resin having an aromatic group-substituted naphthalene skeleton thus obtained can be converted to an epoxy resin by reacting epichlorohydrin using a known method. The naphthol resin used here may be a naphthol novolak resin or a naphthol aralkyl resin, but a naphthol aralkyl resin is preferred from the viewpoint of moisture resistance and impact resistance. Such an aromatic group-substituted naphthol type epoxy resin can be produced, for example, by the method disclosed in Patent Document 5.

  The aromatic group-substituted naphthol type epoxy resin has an average of 0.1 or more, preferably 0.2 or more, and more preferably 0.3 or more ethylene for one naphthalene nucleus having a naphthol structure. An epoxy resin containing a compound to which an aromatic compound is added is preferable, and an aromatic group-unsubstituted naphthalene nucleus may be included. When the naphthol resin is a naphthol aralkyl resin, when it reacts with an ethylenic aromatic compound, the ethylenic aromatic compound not only reacts with the naphthalene nucleus, but also partially substitutes with a benzene ring constituting the aralkyl. It is possible, but it does not matter.

More specifically, an aromatic group-substituted naphthol type epoxy resin represented by the following general formula (9) is preferably exemplified. Here, G represents a glycidyl group, and R represents an aromatic group or hydrogen, but is preferably an acenaphthenyl group represented by the formula (a), an indanyl group represented by the formula (b), or a formula (c). An aromatic group selected from an α-methylbenzyl group or hydrogen is preferable, and the proportion of the aromatic group in R is 10 mol% or more, preferably 20 mol or more, more preferably 30 mol or more, p Is an integer of 0 or more, and the number average value of p is in the range of 0-15. It can be understood that the symbols corresponding to the general formula (6) have the same meaning.

  The citrate ester of the component (C) is represented by the above general formula (1). By blending such a citrate ester, the low temperature pressure-bonding property and heat resistance can be obtained without deteriorating the original properties of the polyimide resin. And circuit fillability can be improved. Moreover, the curvature as a coverlay film can be suppressed and a flame retardance can be provided further. In the general formula (1), R represents an alkyl group having 1 to 6 carbon atoms, but three Rs may be the same or different. X represents a hydroxyl group or an acetyl group.

  Specific examples of such citric acid esters include, for example, citric acid trimethyl ester, citric acid triethyl ester, citric acid tri-n-propyl ester, citric acid tributyl ester, citric acid tri-n-pentyl ester, acetyl triethyl citrate And acetyl tributyl citrate. Of these, tributyl citrate is particularly preferable because of the great effect of the present invention. These citrate esters may be used alone or in combination of two or more.

  Component (A) and component (B) are preferably blended in the range of 65 to 98% by weight of component (A) and 2 to 35% by weight of component (B), more preferably 70 to 90% by weight of component (A). (B) The range of 10-30 weight% of a component is good. Moreover, since the component (A) and the component (B) are resin components, they are also referred to as resin components. The resin component may contain a resin other than the component (A) and the component (B), but the component (A) and the component (B) preferably occupy 80% by weight or more of the resin component. Moreover, it is preferable to mix | blend 1-45 weight part of (C) component with respect to the sum total of (A) component and (B) component, or 100 weight part of mixed resin. A more preferable amount of component (C) is in the range of 10 to 40 parts by weight. By mix | blending in this range, low-temperature press-bonding property, heat resistance, and circuit filling property can further be improved, without reducing the original characteristic of a polyimide resin. When the blending amount of the component (C) is less than 1 part by weight, the effect of improving the low temperature pressure-bonding property and the circuit filling property is small.

  Moreover, an epoxy resin hardening | curing agent can also be mix | blended with an adhesive resin composition as needed other than the said component as an essential component. Further, this epoxy resin curing agent is desirable because it substantially does not contain a halogen element and a phosphorus element so that the effects of the present invention can be easily exerted. The blending ratio of the epoxy resin curing agent is preferably 1 to 15% by weight, more preferably 5 to 10% by weight with respect to 100 parts by weight of the mixed resin of the component (A) and the component (B) or the total thereof. is there. From another viewpoint, the range of 20 to 70% by weight of the epoxy resin is preferable. The use of the epoxy resin curing agent is effective when a siloxane-containing polyimide resin that does not have the functional group represented by the general formula (4) in the molecule is used.

  Specific examples of the epoxy resin curing agent include phenol novolak, 0-cresol novolak, phenol such as phenol resol, naphthols, amines such as diethylenetriamines, acid anhydrides such as pyromellitic anhydride and phthalic anhydride, and the like. Can be mentioned.

  Furthermore, in addition to the above components, conventionally known curing accelerators, coupling agents, fillers, pigments, and the like may be appropriately blended in the adhesive resin composition as necessary. Moreover, other polyimide resins or other epoxy resins other than those described above can be blended in a small amount within a range that does not impair the effects of the present invention. Note that these components are desirable because they are substantially free of halogen elements and phosphorus elements so that the effects of the present invention can be easily achieved.

  The coverlay film of this invention is obtained by providing the adhesive bond layer which consists of said adhesive resin composition on the surface of a polyimide film. As a method of forming the cover lay film of the present invention, a conventional method can be used. As an example of a suitable forming method, the components of the above adhesive resin composition are dissolved in a solvent, and the obtained resin composition solution is applied onto a polyimide film by a conventionally known method and dried. There is a method of making a coverlay film of the invention. After coating the polyimide film with a thickness of 2 to 200 μm, preferably 5 to 100 μm, more preferably 10 to 50 μm, 50 to 140 ° C., preferably 80 to 140 ° C., more preferably 100 to 140 ° C. By performing drying, a coverlay film can be obtained. The thickness of the polyimide film may be an appropriate thickness as required, but is preferably 3 to 50 μm, more preferably 5 to 30 μm.

  Representative examples of the solvent used in the formation step include N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-diethylacetamide, Amide solvents such as N, N-dimethylmethoxyacetamide, dimethyl sulfoxide and N-methyl-2-pyrrolidone, tetrahydrofuran, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, dioxane, γ-butyrolactone, xylenol, phenol, methyl cellosolve, ethyl cellosolve, methyl Examples include cellosolve acetate, ethyl cellosolve acetate, ethers such as toluene, xylene, and methyl ethyl ketone, esters, and alcohol solvents. Also, the solvent used in the production of the polyimide resin may be used as it is.

As a preferred method of using the coverlay film of the present invention, the coverlay film of the present invention is coated on the circuit board on which the conductor circuit is formed so that a desired portion of the conductor circuit is coated, and then the pressure is applied. An insulating coating can be formed by thermocompression bonding under conditions of 1 to 100 kg / cm ² and a temperature of 20 to 250 ° C.

  EXAMPLES Hereinafter, although an Example demonstrates this invention based on an Example, this invention is not limited at all by these Examples. In the examples of the present invention, unless otherwise specified, various measurements and evaluations are as follows.

[Evaluation of solder heat resistance]
Solder heat resistance was evaluated by placing the adhesive side of a test piece with a width of 10 mm and a length of 100 mm on a glossy surface of copper foil (thickness of 35 μm), and heating at 180 ° C. for 60 minutes at 40 kg / cm ^2. A crimped product was used. This test piece with copper foil was allowed to stand for 24 hours at 25 ° C. and 50% relative humidity, and then immersed in a solder bath set at each evaluation temperature for 60 seconds, and the adhesion state was observed, foamed, blistered, peeled, etc. Checked for defects. In addition, "300 degreeC" in a table | surface means that a malfunction is not recognized when evaluated in a 300 degreeC solder bath.

[Measurement of adhesive strength]
Adhesive strength is 10 mm wide and 100 mm long using a tensile tester (Toyo Seiki Co., Ltd., Strograph-M1), and the adhesive surface of the test piece is a glossy surface of copper foil (35 μm thickness) or polyimide film ( It is placed on Kaneka Co., Ltd. (apical NPI), thermocompression bonded under conditions of 180 ° C, 60 minutes, 40 kg / cm ² , and then the strength at the time of peeling at a speed of 50 mm / min in the 180 ° direction is the adhesive strength. And In addition, the adhesive strength 1 is the adhesive strength with respect to copper foil, and the adhesive strength 2 is the adhesive strength with respect to a polyimide film.

[Evaluation of folding resistance]
Folding resistance is placed on a copper clad laminate that has been processed into a conductor width of 0.13 mm to 0.91 mm and a space between conductors of 0.18 mm to 0.20 mm, and is 180 ° C., 60 minutes, 40 kg / cm ^2. What was thermocompression-bonded under these conditions was used. An IPC bending test was conducted with a curvature radius of 1.25 mm, a bending speed of 1,500 rpm, a stroke of 20 mm, and a cover lay attached to the outside. Judgment is made by measuring the number of bendings until the resistance value is increased by 5%. It was judged as “possible”.

[Evaluation of flame resistance]
The flame resistance was evaluated at a level indicating the degree of flame retardancy by a combustion test based on UL-94, and the flame resistance was judged at two levels of “VTM-0” and “no flame resistance”. “VTM-0” means flame resistance.

[Measurement of glass transition temperature (Tg)]
The glass transition temperature was measured using a thermomechanical analyzer (Bruker, 4000SA) with a test piece having a width of 2 mm and a length of 30 mm at a distance between chucks of 15 mm, a load of 2 g, and a heating rate of 5 ° C./min. Measure the amount of thermal expansion of the fragrance of the length of the test piece, and let the inflection point be Tg.

The abbreviations used in the examples represent the following compounds.
ODPA: 3,3 ', 4,4'-diphenyl ether tetracarboxylic dianhydride
DSDA: 3,3 ', 4,4'-diphenylsulfonetetracarboxylic dianhydride
BAPP: 2,2-bis (4-aminophenoxyphenyl) propane
HAB: 4,4 ′-(3,3′-dihydroxy) diaminobiphenyl resin A: naphthol type epoxy resin of synthesis example 7 (acenaphthenyl group substitution type)
Resin B: Naphthol type epoxy resin of Synthesis Example 9 (indenyl group substitution type)
Resin C: Naphthol-type epoxy resin of Synthesis Example 11 (styryl group-substituted type)
TBC: Tributyl citrate
ATBC: Acetyltributyl citrate
DOP: Di-2-ethylhexyl phthalate
PPA: Polypropylene-Adipate
DOS: Di-2-ethylhexyl sebacate
PSX-A and PSX-B: diaminosiloxane represented by the following formula (10) (however, the number average value of m is in the range of 1-20, the weight average molecular weight of PSX-A is 740, the weight of PSX-B) The average molecular weight is 1240.)
PSX-Ph: diaminosiloxane represented by the following formula (11) (however, the number average value of the total number of j and n is in the range of 2 to 20, j and n are both 1 or more, and the weight average molecular weight is 1320.)
NA resin: 1-naphthol aralkyl resin represented by the following formula (12) (SN-485 manufactured by Nippon Steel Chemical Co., Ltd., weight average molecular weight is 485)

Synthesis example 1
A 1000 ml separable flask was charged with 34.12 g of ODPA (0.11 mol), 200 g of N-methyl-2-pyrrolidone and 200 g of xylene and mixed well at room temperature. .64 g of PSX-A (0.036 mol) was added dropwise and the reaction solution was ice-cooled with stirring to give 28.74 g of BAPP (0.07 mol) and 0.86 g of HAB (0.004 mol). And stirred at room temperature for 2 hours to obtain a polyamic acid solution. This polyamic acid solution was heated to 190 ° C., heated and stirred for 20 hours to obtain a polyimide solution a having a logarithmic viscosity of 0.94 dl / g.

Synthesis Examples 2-5
Except for the raw material compositions shown in Table 1, polyimide solutions b to e were prepared in the same manner as in Example 1.

Synthesis Example 6
In a 500 ml separable flask, 180 g of NA resin and 20 g of acenaphthylene were used and stirred at 100 ° C. for 1 hour to carry out addition reaction to obtain 200 g of acenaphthylene-modified naphthol aralkyl resin. The softening point of the obtained acenaphthenyl group-substituted naphthol aralkyl resin was 54 ° C. as a result of measurement according to JIS K 2548, and the hydroxyl group equivalent (OH equivalent) was 236. Further, the addition reaction rate of acenaphthylene by GPC was 99%, and the substitution rate of acenaphthenyl group (number of moles of acenaphthylene added per mole of naphthalene ring) was 0.4.

Synthesis example 7
Next, 100 g of the acenaphthenyl group-substituted naphthol aralkyl resin thus obtained is dissolved in 400 g of epichlorohydrin, and 40 g of 50% aqueous sodium hydroxide solution is added over 4 hours at 60 ° C. under a reduced pressure of 100 mmHg. Reacted for hours. During this reaction, the produced water was removed out of the system by azeotropy with epichlorohydrin.
After completion of the reaction, after completion of the reaction, excess epichlorohydrin was distilled off under reduced pressure. 450 g of methyl isobutyl ketone was added to the residue to dissolve the epoxy resin, followed by filtration under reduced pressure, and the epoxy resin was recovered from the filtrate. Thereafter, 20 g of a 20% aqueous sodium hydroxide solution was added, and the mixture was reacted at 80 ° C. for 2 hours. Subsequently, filtration and washing with water were performed, and methyl isobutyl ketone was distilled off under reduced pressure to obtain 120 g of a brown acenaphthenyl group-substituted naphthol type epoxy resin (resin A). The obtained resin A had a softening point of 48 ° C. and an epoxy equivalent of 308.

Synthesis example 8
In a 500 ml separable flask, 180 g of NA resin and 39 g of indene were used and stirred at 100 ° C. for 1 hour to carry out an addition reaction to obtain 218 g of naphthol aralkyl resin substituted with indanyl group. The softening point of the obtained indanyl group-substituted naphthol aralkyl resin was 107 ° C. as a result of measurement according to JIS K 2548, and the hydroxyl group equivalent (OH equivalent) was 261. The addition reaction rate of indene by GPC was 99%, and the indanyl group substitution rate was 0.4.

Synthesis Example 9
Next, 100 g of the indanyl group-substituted naphthol aralkyl resin thus obtained was dissolved in 285 g of epichlorohydrin, and 35 g of a 50% aqueous sodium hydroxide solution was added over 4 hours at 60 ° C. under a reduced pressure of 100 mmHg. Reacted for hours. During this reaction, the produced water was removed out of the system by azeotropy with epichlorohydrin.
After completion of the reaction, after completion of the reaction, excess epichlorohydrin was distilled off under reduced pressure, 285 g of methyl isobutyl ketone was added to the residue to dissolve the epoxy resin, and sodium chloride was removed by washing with water. Thereafter, 20 g of a 20% aqueous sodium hydroxide solution was added, and the mixture was reacted at 80 ° C. for 2 hours. Subsequently, filtration and washing were performed, and methyl isobutyl ketone was distilled off under reduced pressure to obtain 110 g of a brown indanyl group-substituted naphthol type epoxy resin (resin B). The obtained resin B had a softening point of 95 ° C. and an epoxy equivalent of 320.

Synthesis Example 10
In a 500 ml separable flask, 180 g of NA resin and 35 g of styrene were used and stirred at 140 ° C. for 1 hour to carry out addition reaction to obtain 213 g of naphthol aralkyl resin substituted with α-methylbenzyl group. The softening point of the obtained α-methylbenzyl group-substituted naphthol aralkyl resin was 88 ° C. as a result of measurement according to JIS K 2548, and the hydroxyl group equivalent (OH equivalent) was 258. The addition reaction rate of styrene by GPC was 99%, and the α-methylbenzyl group substitution rate was 0.4.

Synthesis Example 11
Next, 100 g of the α-methylbenzyl group-substituted naphthol aralkyl resin thus obtained was dissolved in 290 g of epichlorohydrin, and 60 g of 50% aqueous sodium hydroxide solution was added over 4 hours under a reduced pressure of 100 mmHg. The reaction was carried out at 5 ° C for 5 hours. During this reaction, the produced water was removed out of the system by azeotropy with epichlorohydrin.
After completion of the reaction, excess epichlorohydrin was distilled off under reduced pressure, 285 g of methyl isobutyl ketone was added to the residue to dissolve the epoxy resin, and sodium chloride was removed by washing with water. Thereafter, 20 g of a 20% aqueous sodium hydroxide solution was added, and the mixture was reacted at 80 ° C. for 2 hours. Subsequently, filtration and washing with water were performed, and methyl isobutyl ketone was distilled off under reduced pressure to obtain 109 g of a brown α-methylbenzyl group-substituted naphthol type epoxy resin (resin C). The obtained resin C had a softening point of 75 ° C. and an epoxy equivalent of 317.

Example 1
30 parts by weight of the resin A obtained in Synthesis Example 7 was mixed with 70 parts by weight of the solid content of the polyimide solution a obtained in Synthesis Example 1. Furthermore, 30 parts by weight of TBC was mixed with 100 parts by weight of a mixed resin of a polyimide resin having an siloxane unit and an epoxy resin, and stirred at room temperature for 2 hours to prepare an adhesive resin (resin composition) solution.

  This resin solution is applied to one side of a polyimide film (product name: Apical NPI, manufactured by Kaneka Corporation) of length x width x thickness = 200 mm x 300 mm x 25 μm, dried at 135 ° C. for 5 minutes, and bonded. A cover lay film having an agent layer thickness of 25 μm was obtained. The glass transition temperature of this film was 140 ° C. The adhesive strength 1 and adhesive strength 2 of this film were 1.0 kN / m and 0.8 kN / m, respectively. Also, the solder heat resistance was good, with no defects such as blistering and peeling being observed. The results are shown in Tables 2 and 3.

Examples 2-10
A polyimide solution was prepared in the same manner as in Example 1 with the composition shown in Table 1, a resin composition was prepared with the composition shown in Table 2, and a film was formed. Tables 2 and 3 show the results of measuring the various characteristics. When an epoxy resin curing agent was used, naphthol resin (manufactured by Toto Kasei Co., Ltd., ESN-485) was used as the epoxy resin curing agent.

Comparative Example 1
In Example 1, a film was prepared in the same manner as in Example 1 except that TBC was not used. This film curled and was difficult to use. The results of measuring various properties of the film are shown in Tables 2 and 3.

Comparative Example 2
A film was prepared in the same manner as in Example 1 except that TBC was not used in Example 2. This film curled and was difficult to use. The results of measuring various properties of the film are shown in Tables 2 and 3.

Comparative Example 3
A film was prepared in the same manner as in Example 1 except that TBC was not used in Example 3. This film curled and was difficult to use. The results of measuring various properties of the film are shown in Tables 2 and 3.

Comparative Examples 4-6
A polyimide solution was prepared with the composition shown in Table 1 in the same manner as in the Examples, a resin composition was prepared with the composition shown in Table 2, and a film was formed. The results of measuring various properties of the film are shown in Tables 2 and 3.

Claims (7)

In the cover lay film in which the adhesive layer is provided on the surface of the polyimide film, the adhesive resin composition constituting the adhesive layer includes the following components (A) to (C):
(A) a polyimide resin having a siloxane unit,
(B) an aromatic group-substituted naphthol type epoxy resin having a structure obtained by epoxidizing a naphthol resin having a structure in which an aromatic ring-containing group is substituted with a naphthalene ring, and (C) represented by the following general formula (1) Citrate ester,
A cover lay film characterized by containing an essential component.

(In the formula, X represents a hydroxyl group or an acetyl group, and R represents an alkyl group having 1 to 6 carbon atoms.) The component (A) has repeating units represented by the following general formulas (2) and (3), and the composition ratio of the repeating units represented by the general formulas (2) and (3) is (2) / ( The coverlay film according to claim 1, wherein 3) = 50/50 to 10/90 (molar ratio).

(In General Formula (2), Ar ₁ represents a tetravalent aromatic group, R ₁ and R ₂ represent a divalent hydrocarbon group, and R ₃ and R ₄ represent a monovalent monovalent group having 1 to 6 carbon atoms. Represents a hydrocarbon group, m is an integer of 1 or more, and the number average value of m is in the range of 1 to 20. In the general formula (3), Ar ₁ represents a tetravalent aromatic group, Ar ₂ Represents a divalent aromatic group.)   The adhesive resin composition is obtained by blending 1 to 45 parts by weight of component (C) with respect to 100 parts by weight of resin component consisting of 65 to 98% by weight of component (A) and 2 to 35% by weight of component (B). The coverlay film according to claim 1 or 2, characterized in that   The adhesive resin composition further contains 1 to 15 parts by weight of an epoxy resin curing agent with respect to a total of 100 parts by weight of the component (A) and the component (B). The coverlay film as described. 1 to 20 mol% of Ar ₂ in the general formula (3) is a divalent aromatic group having a functional group reactive with an epoxy group represented by the following general formula (4) Item 5. A coverlay film according to any one of Items 2 to 4.

(In the formula, Ar ₃ represents a trivalent or tetravalent aromatic group, Y represents a hydroxyl group, an amino group, a carboxyl group, or a mercapto group, and k represents 1 or 2.) The coverlay film according to any one of claims 1 to 5, wherein the component (B) is an aromatic group-substituted naphthol type epoxy resin having a structure represented by the following general formula (5).

(In the formula, G represents a glycidyl group, R represents an aromatic ring-containing group or hydrogen, X represents an alkylene group or an aralkylene group represented by -Z-Ar ₄ -Z-, and p is 0 or more. It is an integer, the number average value of p is in the range of 0 to 15, q is 1 or 2, and the proportion of the aromatic ring-containing group in R is 10 mol% or more, and Z is Represents an alkylene group, and Ar ₄ represents a divalent aromatic group.) The coverlay film according to claim 6, wherein the component (B) is an aromatic group-substituted naphthol type epoxy resin having a structure represented by the following general formula (6).

(In the formula, G represents a glycidyl group, R ₅ , R ₆ and R ₇ represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, R represents an acenaphthenyl group represented by the following general formula (a), An aromatic ring-containing group or hydrogen selected from an indanyl group represented by the formula (b) or an α-methylbenzyl group represented by the following general formula (c) is represented, but the proportion of the aromatic ring-containing group in R is 10 mol% or more, p is an integer of 0 or more, the number average value of p is in the range of 0 to 15, and q is 1 or 2.)