JP2008266531A - Halogen-free epoxy resin composition, cover-lay film, bonding sheet, prepreg and laminated sheet for printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a halogen-free epoxy resin composition having improved physical properties such as adhesive strength to a substrate, electrical insulating properties, flexibility, flame retardance, solder heat resistance and appearance as compared with those of the conventional resin composition. <P>SOLUTION: The halogen-free epoxy resin composition is provided. The composition is obtained by compounding each of the components of (A) a novolak type epoxy resin having a phenol skeleton and a biphenyl skeleton without containing a halogen, (B) a diaminodiphenyl sulfone, (C) an acrylonitrile-butadiene rubber containing carboxy groups, (D) a curing accelerator containing at least one of organic phosphines and a phosphonium salt, (E) a phosphorus-based flame retardant, (F) a filler containing at least aluminum hydroxide and (G) a phenolic antioxidant as essential components. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a halogen-free epoxy resin composition that can be particularly suitably used as an adhesive for flexible printed wiring boards, and a coverlay film, a bonding sheet, a prepreg, and a laminated board for printed wiring boards that are produced using the same. It is about.

  In recent years, the use of flexible printed wiring boards that can be three-dimensionally mounted has been expanded in response to demands for weight reduction and higher density accompanying downsizing of electronic devices. The layer structure of the flexible printed wiring board is basically a metal foil layer / adhesive layer / film layer, and a coverlay film (adhesive layer / film layer) on the circuit (metal foil layer) for the purpose of protecting the prepared circuit. ). There are many adhesives for flexible printed wiring boards, such as adhesion strength to each substrate, electrical insulation, and flexibility, as well as flame resistance, solder heat resistance, circuit fillability, dimensional stability, and work stability. The physical properties are required.

  In particular, adhesives for flexible printed circuit boards require moderate flexibility, and epoxy resins containing high molecular weight elastomer components, especially acrylonitrile butadiene rubber, have been used for the purpose of developing flexibility. .

  However, the elastomer component contains a carbon-carbon double bond that is easily oxidized, and is oxidized by oxygen in the air during varnish preparation or heating and pressurization, and the elastomer component is likely to deteriorate. It is known that when molecules are cut by oxygen or heat, not only is the flexibility lowered due to the alteration of the elastomer component, but generally the adhesion strength and electrical insulation properties are also significantly reduced.

  Moreover, in order to obtain sufficient flexibility, the higher the molecular weight of the elastomer component, the better. However, as the molecular weight increases, the compatibility with the solvent and the epoxy resin tends to decrease. As means for solving this problem, means for improving the compatibility by introducing a carboxyl group into the elastomer component has been proposed.

  However, since the carboxyl group itself is acidic, if the curing reaction is insufficient and the functional group remains in the system, there is a concern that the electrical insulation property may be further lowered.

In addition, an adhesive composition containing a thermosetting resin, acrylonitrile butadiene rubber, and an antioxidant as essential components is also provided (see, for example, Patent Document 1), but adhesion strength to a substrate, electrical insulation, There is still room for improvement in physical properties such as flexibility, flame retardancy, solder heat resistance, and appearance.
Japanese Patent Laid-Open No. 7-30250

  The present invention has been made in view of the above points, and physical properties such as adhesion strength to a substrate, electrical insulation, flexibility, flame retardancy, solder heat resistance, and appearance are improved as compared with conventional ones. Another object of the present invention is to provide a halogen-free epoxy resin composition, a coverlay film, a bonding sheet, a prepreg, and a laminate for a printed wiring board.

The halogen-free epoxy resin composition according to claim 1 of the present invention is
(A) a novolac type epoxy resin containing no phenol and having a phenol skeleton and a biphenyl skeleton,
(B) diaminodiphenyl sulfone,
(C) an acrylonitrile-butadiene rubber containing a carboxyl group,
(D) a curing accelerator containing at least one of organic phosphines and phosphonium salts,
(E) phosphorus flame retardant,
(F) a filler containing at least aluminum hydroxide,
(G) The phenolic antioxidants (A) to (G) are blended as essential components.

  The invention according to claim 2 is characterized in that, in claim 1, as the component (G), in addition to the phenolic antioxidant, a thioether antioxidant is used in combination.

  The invention according to claim 3 is characterized in that, in claim 1, as component (G), in addition to a phenolic antioxidant, a phosphorus antioxidant is used in combination.

  The invention according to claim 4 is characterized in that, in claim 1 or 2, the phenolic antioxidant is a tetraester hindered phenol represented by the following structural formula 1.

  A coverlay film according to claim 5 of the present invention is characterized in that the halogen-free epoxy resin composition according to any one of claims 1 to 4 is applied to at least one surface of the film. is there.

  A bonding sheet according to claim 6 of the present invention is characterized in that the halogen-free epoxy resin composition according to any one of claims 1 to 4 is applied to at least one surface of a film. .

  A prepreg according to claim 7 of the present invention is obtained by impregnating a woven fabric or a nonwoven fabric with the halogen-free epoxy resin composition according to any one of claims 1 to 4. .

  A laminated board for a printed wiring board according to an eighth aspect of the present invention is characterized in that a metal foil is laminated on one side or both sides of the prepreg according to the seventh aspect.

  According to the halogen-free epoxy resin composition according to claim 1 of the present invention, in the system in which the components (A) to (F) coexist, a phenolic antioxidant excellent in radical scavenging ability is used as the component (G). By this, the component (C) that is an elastomer component can be prevented from oxidative degradation or thermal degradation when the varnish is prepared or heated and pressurized, and adhesion strength to the substrate, electrical insulation, flexibility, It is possible to improve physical properties such as flame retardancy, solder heat resistance and appearance as compared with conventional ones.

  According to the invention of claim 2, the phenolic antioxidant excellent in radical scavenging ability and the thioether antioxidant excellent in peroxide resolution coexist, whereby the phenolic antioxidant is used alone. Compared with the case of using, long-term stability of various physical properties can be obtained.

  According to the invention of claim 3, the phenolic antioxidant excellent in radical scavenging ability and the phosphorus antioxidant superior in peroxide resolution coexist, whereby the phenolic antioxidant is used alone. Compared with the case of using, long-term stability of various physical properties can be obtained.

  According to the invention which concerns on Claim 4, electrical insulation can be maintained over a long term.

  According to the coverlay film of claim 5 of the present invention, physical properties such as adhesion strength to a substrate, electrical insulation, flexibility, flame retardancy, solder heat resistance, and appearance are improved as compared with the conventional one. It is something that can be done.

  According to the bonding sheet according to claim 6 of the present invention, physical properties such as adhesion strength to a substrate, electrical insulation, flexibility, flame retardancy, solder heat resistance and appearance are improved as compared with the conventional one. It is something that can be done.

  According to the prepreg according to claim 7 of the present invention, physical properties such as adhesion strength to a substrate, electrical insulation, flexibility, flame retardancy, solder heat resistance, and appearance can be improved as compared with conventional ones. It can be done.

  According to the laminated board for a printed wiring board according to claim 8 of the present invention, physical properties such as adhesion strength to the substrate, electrical insulation, flexibility, flame retardancy, solder heat resistance, and appearance are compared with those of the conventional one. Can be improved.

  Embodiments of the present invention will be described below.

  In the present invention, examples of the novolak type epoxy resin which does not contain a halogen and has a phenol skeleton and a biphenyl skeleton used as the component (A) include those represented by the following structural formula 2.

  In Structural Formula 2, n is preferably an integer of 1 to 10, and the average molecular weight is preferably 700 to 1500, and the weight average molecular weight is preferably 1000 to 3000.

  In the present invention, the epoxy resin of the component (A) is an essential component as the epoxy resin, but other epoxy resins may be used in addition to the epoxy resin (A). The epoxy resin used in combination is not particularly limited as long as it does not contain halogen and has two or more epoxy groups in one molecule. For example, an epoxy resin that is a glycidyl etherified product of a polyphenol compound , Epoxy resins that are glycidyl etherified products of various novolak resins, alicyclic epoxy resins, heterocyclic epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, epoxy resins that are glycidylated halogenated phenols, etc. It is done.

  Examples of epoxy resins that are glycidyl etherified products of polyphenol compounds include bisphenol A, bisphenol F, bisphenol S, 4,4′-biphenylphenol, tetramethylbisphenol A, dimethylbisphenol A, tetramethylbisphenol F, dimethylbisphenol F, tetra Methyl bisphenol S, dimethyl bisphenol S, tetramethyl-4,4′-biphenol, dimethyl-4,4′-biphenylphenol, 1- (4-hydroxyphenyl) -2- [4- (1,1-bis- ( 4-hydroxyphenyl) ethyl) phenyl] propane, 2,2′-methylene-bis (4-methyl-6-tert-butylphenol), 4,4′-butylidene-bis (3-methyl-6-tert-butylphenol) , Trishydroxyphenylmethane, resorcinol, hydroquinone, pyrogallol, phenols having a diisopropylidene skeleton, phenols having a fluorene skeleton such as 1,1-di-4-hydroxyphenylfluorene, glycidyl of a polyphenol compound such as phenolized polybutadiene An epoxy resin which is an etherified product is exemplified.

  Examples of epoxy resins that are glycidyl etherified products of various novolak resins include novolaks made from various phenols such as phenol, cresols, ethylphenols, butylphenols, octylphenols, bisphenol A, bisphenol F, bisphenol S, and naphthols. Examples thereof include glycidyl etherified products of various novolak resins such as resins, xylylene skeleton-containing phenol novolak resins, dicyclopentadiene skeleton-containing phenol novolak resins, biphenyl skeleton-containing phenol novolak resins, fluorene skeleton-containing phenol novolak resins, and furan skeleton-containing phenol novolak resins. .

  Examples of the alicyclic epoxy resin include alicyclic epoxy resins having an aliphatic skeleton such as cyclohexane, and examples of the aliphatic epoxy resin include 1,4-butanediol, 1,6-hexanediol, and polyethylene. Examples thereof include glycidyl ethers of polyhydric alcohols such as glycol and pentaerythritol.

  Examples of the heterocyclic epoxy resin include heterocyclic epoxy resins having a heterocyclic ring such as an isocyanuric ring and a hydantoin ring, and examples of the glycidyl ester epoxy resin include carboxylic acids such as hexahydrophthalic acid diglycidyl ester. Examples of the glycidylamine epoxy resin include epoxy resins obtained by glycidylating amines such as aniline and toluidine.

  When the epoxy resin of component (A) is used in combination with another epoxy resin, the ratio of the two is not particularly limited, but the epoxy resin of component (A) is 50% by weight or more in the total amount of the epoxy resin. It is preferable. It becomes possible to reduce an unreacted carboxyl group by mix | blending 50 weight% or more of the epoxy resin of (A) component with high reactivity with a carboxyl group.

  Examples of the diaminodiphenyl sulfone used as the curing agent for the component (B) in the present invention include 3,3′-diaminodiphenyl sulfone and 4,4′-diaminodiphenyl sulfone. 3,3′-diaminodiphenyl sulfone is preferable from the viewpoint of reliability and electrical insulation reliability.

  In the epoxy resin composition of the present invention, the blending ratio of the epoxy resin containing at least the epoxy resin (A) and the component (B) of the curing agent is not particularly limited, but 1 mol of epoxy groups possessed by the epoxy resin On the other hand, it is preferable to set the number of moles of NH groups of diaminodiphenylsulfone to be in the range of 0.75 to 1.25 moles.

  In the present invention, as the elastomer of component (C), acrylonitrile-butadiene rubber containing a carboxyl group is used from the viewpoint of compatibility with solvents and epoxy resins and flex resistance required for applications such as flexible printed wiring boards. Use.

  As specific examples of acrylonitrile-butadiene rubber containing a carboxyl group, “PNR-1HC” manufactured by JSR Corporation, “Nipol 1072J”, “Nipol DN631”, “Nipol Corporation” manufactured by Nippon Zeon Co., Ltd. "FN3703", "Hiker" and "CTBN" manufactured by BF Goodrich. Although not particularly limited to these, those having as little ionic impurities as possible are more preferable from the viewpoint of electrical insulation reliability.

  As the component (C), in addition to acrylonitrile / butadiene rubber, for example, butadiene rubber, epoxy-modified butadiene rubber, isoprene rubber, phenoxy resin, polyamideimide resin, polyester resin and the like may be used in combination.

  (C) The compounding quantity of a component has the preferable range of 10-75 weight part with respect to 100 weight part in total of the epoxy resin and hardening | curing agent (B) which contain an epoxy resin (A) at least. This blending ratio was confirmed by experiments, and if the blending amount of component (C) is less than 10 parts by weight, the flexibility is insufficient and the flexibility and flexibility required for FPC applications are satisfied. And the adhesion strength is insufficient. Moreover, when the compounding quantity of (C) component exceeds 75 weight part, ensuring of the required flame retardance will become difficult.

  In the present invention, as the curing accelerator of the component (D), organic phosphines or phosphonium salts are mentioned as essential components. One of these may be used alone, or both may be used in combination.

  Examples of organic phosphines include triphenylphosphine, tri-o-toluylphosphine, tri-m-toluylphosphine, tri-p-toluylphosphine, tri-2,4-xylylphosphine, and tri-2,5-xylyl. Phosphine, tri-3,5-xylylphosphine, tribenzylphosphine, tris (p-methoxyphenyl) phosphine, tris (p-tert-butoxyphenyl) phosphine, diphenylcyclohexylphosphine, tricyclohexylphosphine, tributylphosphine, tri-tert -Butylphosphine, tri-n-octylphosphine, diphenylphosphinostyrene and the like.

  Examples of phosphonium salts include tetrabutylphosphonium hydroxide, tetrabutylphosphonium acetate, tetrabutylphosphonium hydrogen difluoride, tetrabutylphosphonium dihydrofluoride, tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetra-p-triborate, benzyl Triphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetrafluoroborate, p-tolyltriphenylphosphonium tetra-p-tolylborate, triphenylphosphinetriphenylborane, 1,2-bis (diphenylphosphino) ethane, 1,3- Bis (diphenylphosphino) propane, 1,4-bis (diphenylphosphino) butane, 1,5-bis Such diphenylphosphino) pentane, and the like. The curing accelerator used in the present invention is not particularly limited as long as it is an organic phosphine or phosphonium salt that promotes the reaction between an epoxy group and a carboxyl group.

  The blending amount of the curing accelerator (D) is preferably in the range of 0.05 to 1 part by weight with respect to a total of 100 parts by weight of the epoxy resin containing at least the epoxy resin (A) and the curing agent (B). This blending ratio has been confirmed by experiments, and the blending amount varies depending on the type of epoxy resin and curing accelerator (D) used, but the blending amount of the curing accelerator (D) is less than 0.05 parts by weight. When it is, reaction of the epoxy group of an epoxy resin and the carboxyl group contained in an elastomer will become slow, and there exists a possibility that insulation reliability may fall. Moreover, when the compounding quantity of a hardening accelerator (D) exceeds 1 weight part, since the remarkable viscosity raise of a varnish is caused, it is unpreferable practically.

  Examples of the phosphoric flame retardant of component (E) added to impart flame retardancy include aromatic phosphoric esters, or their condensation types, phosphazenes, 9,10-dihydro-9-oxa-10. -A compound group including phosphaphenanthrene-10-oxide in its structure is included, and these phosphorus-based flame retardants tend to decrease in Tg and adhesion strength with an increase in the amount of addition thereof. Or what does not melt | dissolve in a resin composition as much as possible is preferable. That is, the solubility in 100 g of methyl ethyl ketone or toluene at room temperature (25 ° C.) is preferably 1 g or less. The lower the solubility, the better. Therefore, it is ideal that the solubility is zero. Furthermore, from the viewpoint of electrical insulation reliability and adhesion, a phosphoric ester amide compound having the structure of the following structural formula 3 that is excellent in hydrolysis resistance is desirable.

(In Structural Formula 3, R is a group containing an amide group)
The blending amount of the flame retardant (E) is preferably in the range of 3 to 70 parts by weight with respect to 100 parts by weight in total of the epoxy resin containing at least the epoxy resin (A) and the curing agent (B). This blending ratio has been confirmed by experiments. When the blending amount of the flame retardant (E) is less than 3 parts by weight, a sufficient flame retardant effect cannot be obtained, and the blending of the flame retardant (E) is not possible. When the amount exceeds 70 parts by weight, the Tg and adhesion strength are remarkably lowered, which is unsuitable for practical use.

  In the present invention, the filler of the component (F) is one in which aluminum hydroxide is essential, but other than aluminum hydroxide is not particularly limited. For example, magnesium hydroxide, magnesium hydroxide type In addition to inorganic fillers such as composite metal hydroxides, zinc borate, boron nitride, silicon nitride, barium sulfate, talc, clay, mica, silica, hydrotalcite, and organic fillers that are insoluble in organic solvents Good. Aluminum hydroxide may be used alone, or two or more kinds other than aluminum hydroxide may be used in combination.

  The blending amount of the filler (F) containing at least aluminum hydroxide is preferably in the range of 20 to 175 parts by weight with respect to a total of 100 parts by weight of the epoxy resin containing at least the epoxy resin (A) and the curing agent (B). This blending ratio has been confirmed by experiments, and if the blending amount of the filler (F) is less than 20 parts by weight, sufficient effects for reducing the linear expansion coefficient and imparting flame retardancy due to the addition of the filler can be obtained. When it is difficult to obtain and exceeds 175 parts by weight, the adhesion strength and bendability are lowered, making it unsuitable for practical use.

  In the present invention, as the antioxidant of the component (G), a phenolic antioxidant excellent in radical scavenging ability is used. Such phenolic antioxidants include 2,6-di-tert-butyl-p-cresol, 4,4′-butylidenebis- (6-tert-butyl-3-methylphenol), 2,2,2 '-Methylenebis- (4-methyl-6-tert-butylphenol), 2,2'-methylenebis- (4-ethyl-6-tert-butylphenol), 2,6-di-tert-butyl-4-ethylphenol, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, n-octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, tetrakis [Methylene-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] methane (shown by structural formula 1 Toraester type hindered phenol), triethylene glycol bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate], tris (3,5-di-tert-butyl-4-hydroxybenzyl) ) Isocyanurate. Among these phenolic antioxidants, the tetraester type hindered phenol represented by the above structural formula 1 is particularly effective because of its high radical scavenging ability in a system in which the components (A) to (F) coexist. Therefore, it is preferable.

  Further, as the component (G), it is preferable to use a thioether antioxidant together with a phenol antioxidant. Thioether antioxidants are excellent in peroxide resolution. Specific examples include ditridecyl thiodipropionate, dimyristyl thiodipropionate, distearyl thiodipropionate, and dilauryl thiodipropionate. Is mentioned. In particular, ditridecylthiodipropionate has a large synergistic effect when used in combination with a phenolic antioxidant, and long-term thermal stability can be imparted by using this in combination.

  Moreover, it is preferable to use together with a phosphorus antioxidant other than a phenolic antioxidant as (G) component. Phosphorous antioxidants are also excellent in peroxide resolution. Specific examples include distearyl pentaerythritol diphosphite, bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite, tris ( 2,4-di-tert-butylphenyl) phosphite, cyclic neopentanetetraylbis (2,6-di-tert-butyl-4-methylphenyl) phosphite, tris (nonylphenoxy) phosphite, 4 , 4'-isopropylidenediphenol-alkyl (C12-15) phosphite, 2-ethylhexyl-diphenyl phosphite, and the like. The synergistic effect, especially when used in combination with phenolic antioxidants, is distearyl pentaerythritol diphosphite, which also inactivates curing accelerators, flame retardants, and ionic impurities in the composition. Excellent electrical insulation can be maintained for a long time.

  The blending amount of the antioxidant of the component (G) is in the range of 0.1 to 10.0 parts by weight with respect to a total of 100 parts by weight of the epoxy resin containing at least the epoxy resin (A) and the curing agent (B). preferable. This blending ratio has been confirmed by experiments, but the blending amount varies depending on the type of epoxy resin and curing accelerator used. When the blending amount of the component (G) is less than 0.1 part by weight, the effect of preventing the deterioration of the elastomer component which is the component (C) is small, and the possibility that the electrical insulation property is lowered is increased. Moreover, when the compounding quantity of (G) component exceeds 10.0 weight part, not only adhesive strength falls, but the dispersion | distribution in a varnish becomes difficult and there exists a possibility that it may become an external appearance defect after coating.

  The halogen-free epoxy resin composition according to the present invention is prepared by blending the components (A) to (G). In addition, other additives may be added to the halogen-free epoxy resin composition as necessary. For example, an antifoaming agent, a leveling agent, a dispersing agent, a coupling agent, an ultraviolet absorber and the like can be mentioned, but the invention is not particularly limited thereto. The composition to which various additives are added can obtain the required physical properties without problems in appearance when applied onto a film using a comma coater or a die coater.

  The halogen-free epoxy resin composition can be prepared by carrying out dispersion and pulverization for a predetermined time under a predetermined condition using a media mill such as a bead mill. At this time, the blending procedure of each component is not limited and can be changed as necessary, and the above additives may be added as appropriate.

  In addition to the bead mill, a media mill, a grain mill, a basket mill, a ball mill, or the like can be used as the media mill in the dispersion / pulverization step, and a roll kneading dispersion method can also be used. Although pulverization by a dry method such as a jet mill is possible, using the wet method as described above, the resin varnish can be prepared and the filler containing aluminum hydroxide can be dispersed in the resin composition at the same time. It is more preferable because the process can be simplified.

  Thus, the halogen-free epoxy resin composition according to the present invention comprises (A) a novolak type epoxy resin that does not contain halogen and has a phenol skeleton and a biphenyl skeleton, (B) diaminodiphenylsulfone, and (C) a carboxyl group. Acrylonitrile-butadiene rubber contained, (D) a curing accelerator containing at least one of organic phosphines and phosphonium salts, (E) a phosphorus flame retardant, (F) a filler containing at least aluminum hydroxide, (G ) By blending the components (A) to (G) of the phenolic antioxidant as essential components, not only the adhesion strength to the substrate, flexibility, flame retardancy, dimensional stability, and work stability In addition, electrical insulation can be maintained over a long period of time.

  By the way, when using an amine compound as a hardening | curing agent of an epoxy resin, imidazoles are normally used for the hardening accelerator. However, imidazole curing accelerators promote all reactions such as epoxy groups and amino groups, epoxy groups and carboxyl groups, and self-polymerized epoxy groups and epoxy groups, so that carboxyl groups that adversely affect electrical insulation are not present. The probability of remaining increases. Since the carboxyl group of the elastomer component which is the component (C) is a functional group necessary from the viewpoint of compatibility with the solvent and the epoxy resin, in order not to lower the electrical insulation properties such as volume resistivity, the epoxy group and the carboxyl group The key point is how efficiently the carboxyl group is reacted and the carboxyl group is consumed efficiently.

  On the other hand, the amino group of diaminodiphenyl sulfone as component (B) has a high reaction activity in itself, and the reaction between the epoxy group and the amino group proceeds at a level that does not cause any problem even in the absence of a curing accelerator. To do. Therefore, in the system in which the components (A) to (G) coexist, the organic phosphines and phosphonium salts as the component (D) can selectively promote the reaction between the epoxy group and the carboxyl group, and the electric insulation. Carboxyl groups that adversely affect the properties can be efficiently consumed.

  Regarding the required flame retardancy, the novolak type epoxy resin which does not contain halogen and has a phenol skeleton and a biphenyl skeleton, which is a component (A), is derived from a high carbonization rate and is excellent in flame retardancy. As a component that compensates for the lack of flame retardancy, a phosphorus-based flame retardant as component (E) and a filler containing at least aluminum hydroxide as component (F) are blended.

  In order to control the reactivity for the above reasons and to obtain the required adhesion strength, flexibility, electrical insulation, flame retardancy, etc., a combination of components (A) to (F) is essential. In order to ensure higher reliability, it is necessary to effectively prevent oxidative degradation and thermal degradation of the elastomer component (C), and therefore a phenolic antioxidant is added as component (G). It is. In the process where the elastomer component deteriorates due to oxygen and heat, radicals are mainly generated, but these radicals are efficiently captured by phenolic antioxidants, and thioether antioxidants and phosphorus antioxidants Since the peroxide, which is a radical source, is decomposed, it is possible to prevent a decrease in electrical insulation and to significantly improve other physical properties.

  Next, a cover lay film and a bonding sheet can be manufactured using the halogen-free epoxy resin composition according to the present invention obtained as described above. These coverlay films and bonding sheets are formed with a structure in which a halogen-free epoxy resin composition is applied as an adhesive layer on at least one surface of a film-like substrate such as an electrical insulating film or a release material film. . Specifically, a film base cover lay having a three-layer structure of an electrical insulating film / adhesive layer / release material, a three-layer structure of a release material / adhesive layer / release material, or a release material / adhesive There are dry film type coverlays and bonding sheets consisting of a two-layer structure of layers, but in addition to these, by forming in the configuration of an electrically insulating film / adhesive layer / metal foil, as a single-sided flexible printed wiring board, Or it can also be used also as a double-sided flexible printed wiring board by forming in the structure of metal foil / adhesive layer / electrical insulating film / adhesive layer / metal foil.

  Examples of the electrical insulating film include polyimide film, PET (polyethylene terephthalate) film, polyester film, polyparabanic acid film, polyether ether ketone film, polyphenylene sulfide film, aramid film, polycarbonate film, polyarylate film, and the like. The thickness is preferably in the range of 3 to 200 μm, but an appropriate thickness may be used as necessary. It may also be a laminate of a plurality of films selected from these, and may be subjected to surface treatment such as hydrolysis treatment, corona discharge treatment, flame treatment, plasma treatment, ion bombardment treatment, and easy adhesion coating treatment as necessary. Good.

  Further, the release material is not particularly limited as long as it can be removed without impairing the form of the coverlay film, its adhesive layer, and bonding sheet, but a polyolefin film, a polyester film, a TPX film, and these films. And a film in which a release agent layer is provided, and paper obtained by laminating these films on a paper substrate.

  Examples of the metal foil include electrolytic copper foil, rolled copper foil, aluminum foil, tungsten foil, and iron foil. Generally, from the viewpoint of workability, flexibility, electrical conductivity, etc. Copper foil and rolled copper foil are used.

  In producing the film base coverlay, first, a varnish of a halogen-free epoxy resin composition is applied to an electrically insulating film using a comma coater, a die coater or the like. This is passed through an in-line drier and heated to remove the solvent contained in the varnish to form an adhesive layer. Next, the release material is applied to the adhesive surface of the electrically insulating film with adhesive. A film base coverlay can be obtained by pressure-bonding the film with a hot roll or the like. Moreover, it can replace with the mold release material film in this case, and can also obtain a flexible printed wiring board by hardening an adhesive bond layer by a heating process, after crimping metal foil.

  In producing the above-described dry film type coverlay or bonding sheet, first, a varnish of a halogen-free epoxy resin composition is applied to a release material film using a comma coater, a die coater or the like. This is passed through an in-line dryer and heated to remove the solvent contained in the varnish to form an adhesive layer. Then, if necessary, further to the adhesive surface of the release material film with adhesive, A dry film type coverlay or a bonding sheet can be obtained by pressure-bonding the release material film with a hot roll or the like.

  Moreover, a prepreg can be manufactured using the halogen-free epoxy resin composition according to the present invention obtained as described above. A prepreg is obtained by impregnating a varnish of a halogen-free epoxy resin composition into a base material such as a woven fabric or a non-woven fabric, passing it through an in-line drier and drying it by heating to remove the solvent contained in the varnish. It is what Although it does not specifically limit as this base material, A glass woven fabric and a glass nonwoven fabric are used suitably from a heat resistant and workable viewpoint.

  One or a plurality of the prepregs thus obtained are laminated, and a laminated sheet for a printed wiring board is manufactured by laminating a metal foil on one side or both sides of the laminate, followed by heat molding. Can do.

  Next, the present invention will be specifically described with reference to examples. Needless to say, the present invention is not limited to these examples. In addition, about the numerical value which shows the compounding quantity described in an Example and a comparative example, unless it specifically limits, it is a basis of weight. In addition, since the present invention relates to a resin composition excellent in flexibility as well as adhesiveness and electrical insulation reliability, the evaluation of adhesive resin compositions described in Examples and Comparative Examples is a film. This was done using a base coverlay.

(Examples 1-8 and Comparative Examples 1-6)
According to the composition shown in Table 1, (A) epoxy resin, (C) elastomer, (E) phosphorus flame retardant, (F) filler, and (G) antioxidant in an organic solvent composed of methyl ethyl ketone and toluene. An adhesive composition was prepared by mixing. Further, the adhesive composition was dispersed and pulverized simultaneously using a bead mill. Then, the uniform varnish of the adhesive composition was prepared by adding (B) curing agent and (D) curing accelerator and stirring.

In addition, each component shown in Table 1 and Table 2 is as follows.
NC3000: Novolac type epoxy resin (A) containing no phenol and having a phenol skeleton and a biphenyl skeleton (“NC3000” manufactured by Nippon Kayaku Co., Ltd.)
・ Epicoat 1001; bisphenol A type epoxy resin (“Epicoat 1001” manufactured by Japan Epoxy Resin Co., Ltd.)
3,3′-DDS; 3,3′-diaminodiphenylsulfone, PNR-1HC; carboxyl group-containing acrylonitrile-butadiene rubber (“PNR-1HC” manufactured by JSR Corporation)
· TPP; triphenylphosphine · SP703H; phosphoric ester amide ("SP703H" manufactured by Shikoku Chemicals Co., Ltd.)
CL303M; aluminum hydroxide (“CL303M” manufactured by Sumitomo Chemical Co., Ltd.)
AO-60; tetraester type hindered phenol represented by Structural Formula 1 (“AO-60” manufactured by ADEKA Corporation)
AO-50; monoester type hindered phenol ("AO-50" manufactured by ADEKA Corporation)
AO-503; thioether antioxidant (ditridecylthiodipropionate, “AO-503” manufactured by ADEKA Corporation)
PEP-8: Phosphorous antioxidant (distearyl pentaerythritol diphosphite, “PEP-8” manufactured by ADEKA Corporation)
Using the comma coater and the in-line dryer connected to the varnish of the epoxy resin composition obtained in Examples 1-8 and Comparative Examples 1-6 as described above, a polyimide film having a thickness of 12.5 μm A film base coverlay was produced by coating and drying on one side of the film and forming an adhesive layer having a thickness of 12.5 μm after drying.

The film base coverlay thus obtained was evaluated for adhesion strength, flexibility, solder heat resistance, flame retardancy, migration (electrical insulation), and appearance after molding. The preparation conditions and evaluation conditions of the samples used for each of these evaluations are shown below, and the evaluation results are shown in Tables 1 and 2.
(1) Adhesion strength was obtained by laminating the adhesive layer surface of the film base coverlay on the glossy surface of a rolled copper foil having a thickness of 35 μm, and heating and pressing at 180 ° C. for 1 hour to produce a sample. The peel strength when peeled off in the 90 ° direction was evaluated.
(2) Flexibility was tested by the MIT method, the measurement conditions were set to R = 0.38 mm, and the load was 500 g, and evaluated by the number of bending until the circuit could not be conducted.
(3) For solder heat resistance, a sample was prepared by laminating the adhesive layer surface of the film base coverlay on the glossy surface of a rolled copper foil with a thickness of 35 μm, and heating and pressure molding at 180 ° C. for 1 hour. The appearance after immersion for 10 seconds in a solder bath heated to 320 ° C. was evaluated. Judgment criteria are as follows.
“○”: No bulge.
“Δ”: Those with minute blisters of less than φ2 mm.
“×”: There is a blister of φ2 mm or more.
(4) Flame retardancy is achieved by preparing a sample by laminating a 12.5 μm polyimide film on the adhesive layer surface of the film base coverlay, and heating and pressure molding at 180 ° C. for 1 hour. UL standard 94V-0 grade It was evaluated by whether it can be achieved.
(5) For migration, a sample is prepared by laminating the adhesive layer surface of the film base coverlay to a test piece provided with a comb-shaped electrode on a single-sided flexible printed wiring board, and heating and pressure molding at 180 ° C. for 1 hour, This was tested by applying a voltage of 10 V for 250 hours in an environment of 85 ° C./85% RH, and the degree of migration after this test was visually evaluated. Judgment criteria are as follows.
“◯”: No discoloration and no dendrite.
“Δ”: No short circuit in less than 250 hours, but slightly discolored or dendrite was generated.
“X”: A short circuit, discoloration, or dendrite was generated in less than 250 hours.
(6) The appearance after molding was prepared by pasting the adhesive layer surface of the film base coverlay on the glossy surface of a rolled copper foil having a thickness of 35 μm, and heating and pressing at 180 ° C. for 1 hour. The appearance of the sample was visually evaluated. Judgment criteria are as follows.
“O”: No irregularities on the surface.
“△”: The surface is slightly uneven.
"X": The surface has unevenness due to aggregation.

  However, with respect to adhesion strength, flexibility, and migration, both the initial sample and the sample after the accelerated test stored for 6 days in a 40 ° C. environment were evaluated. Storage at 40 ° C. for 6 days corresponds to a state in which 6 months have passed in normal refrigerated storage (5 ° C.).

  As can be seen in Tables 1 and 2, no significant differences were confirmed in both the examples and comparative examples regarding solder heat resistance, flame retardancy, and appearance after molding. Regarding other physical properties, in both the initial and post-acceleration samples, Examples 1 to 8 have higher peel strength and flexibility, better migration resistance, adhesion and flexibility than Comparative Examples 1 to 6. The physical properties required for the adhesive for flexible printed wiring boards, such as properties and electrical insulation, could be obtained satisfactorily.

  In addition, Examples 5 to 8 in which a plurality of antioxidants are used in combination maintain the initial physical properties even after the accelerated test for storage at 40 ° C. for 6 days, which makes it possible to extend the pot life. It was.

Claims (8)

(A) a novolac type epoxy resin containing no phenol and having a phenol skeleton and a biphenyl skeleton,
(B) diaminodiphenyl sulfone,
(C) an acrylonitrile-butadiene rubber containing a carboxyl group,
(D) a curing accelerator containing at least one of organic phosphines and phosphonium salts,
(E) phosphorus flame retardant,
(F) a filler containing at least aluminum hydroxide,
(G) A halogen-free epoxy resin composition comprising the components (A) to (G) of the phenolic antioxidant as essential components.   The halogen-free epoxy resin composition according to claim 1, wherein, as the component (G), in addition to a phenolic antioxidant, a thioether antioxidant is used in combination.   The halogen-free epoxy resin composition according to claim 1, wherein the component (G) comprises a phenolic antioxidant as well as a phosphorus antioxidant. The halogen-free epoxy resin composition according to any one of claims 1 to 3, wherein the phenolic antioxidant is a tetraester type hindered phenol represented by the following structural formula 1.

  A coverlay film comprising the halogen-free epoxy resin composition according to any one of claims 1 to 4 applied to at least one surface of a film.   A bonding sheet obtained by applying the halogen-free epoxy resin composition according to any one of claims 1 to 4 to at least one surface of a film.   A prepreg obtained by impregnating a woven fabric or a nonwoven fabric with the halogen-free epoxy resin composition according to any one of claims 1 to 4.   A laminate for a printed wiring board, comprising a metal foil laminated on one or both sides of the prepreg according to claim 7.