JP2012025917A - Halogen-free epoxy resin composition, coverlay film, bonding sheet, prepreg and laminate for printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a halogen-free epoxy resin composition assuring required flame retardancy without using a halogen and having sufficient adhesiveness, electric insulation reliability and bending property required for a use for a flexible printed wiring board and the like.SOLUTION: The halogen-free epoxy resin composition is prepared by compounding components of (A) an epoxy resin having no halogen, (B) a curing agent, (C) an elastomer, (D) a curing accelerator, (E) a flame retardant and (F) a filler. The component (A) contains a novolac epoxy resin having a phenol skeleton and a biphenyl skeleton. The component (B) contains a dicyandiamide. The component (C) contains at least one in acrylonitrile butadiene rubber having a carboxyl group and acryl rubber having a carboxyl group. The component (D) contains at least one in organic phosphines and phosphonium salt. The component (E) contains a phosphorus-based flame retardant. The component (F) contains aluminum hydroxide.

Description

  The present invention relates to a halogen-free epoxy resin composition containing no halogen such as a halogen-based flame retardant, and a coverlay film, a bonding sheet, a prepreg, and a laminate for a printed wiring board manufactured using the halogen-free epoxy resin composition It is about.

  Flame retardant epoxy resins are used in various electrical insulating materials because of their self-extinguishing properties and good mechanical and electrical properties. As such a flame retardant epoxy resin, a derivative centered on tetrabromobisphenol A, that is, a brominated epoxy resin has been widely used (see, for example, Patent Document 1). In the molded product, the bromine is easily decomposed when heated. Especially, aromatic bromine compounds not only generate corrosive bromine and hydrogen bromide by thermal decomposition, but also highly toxic polybromodibenzofuran depending on the combustion conditions. Or polybrom dibenzodioxin, which may cause adverse effects on the human body. Further, when a bromine-containing compound is added, bromine is easily decomposed when the molded product is heated, so that it is difficult to maintain heat resistance for a long period of time.

  For these reasons, there is a demand for a halogen-free epoxy resin composition that can achieve the flame retardancy required without using a bromine-containing compound and that is excellent in mechanical and electrical properties.

  In recent years, therefore, many halogen-free methods for obtaining flame retardancy have been adopted by using phosphorus-containing compounds typified by phosphate esters or those containing metal hydrates added to or combined with these as flame retardants. ing. However, phosphoric acid ester compounds generally have high hygroscopicity, and hydrolysis reaction proceeds under humidified conditions, which may cause a decrease in electrical insulation. As used as a plasticizer, the glass transition temperature (Tg) and adhesion strength decrease as the amount added increases, so the amount used is naturally limited. For metal hydrates used in combination with phosphate esters, the flame retardant effect depends on the amount added, but as the amount added increases, the elastic modulus of the resin matrix increases, so that sufficient flame retardancy is achieved. If the amount of addition is increased to a level that can ensure sufficient resistance, not only the flexibility required for applications such as a flexible printed wiring board cannot be sufficiently satisfied, but also the adhesion strength decreases.

  For the purpose of expressing this flexibility, an epoxy resin composition containing a high molecular weight elastomer has been proposed. In order to obtain sufficient flexibility by blending the elastomer, the larger the molecular weight of the elastomer, the better. However, the solvent solubility and the compatibility with the resin matrix tend to decrease as the molecular weight increases. Therefore, proposals to improve the solvent solubility and compatibility with the resin matrix using an elastomer containing a carboxyl group have been made widely, but since the carboxyl group itself is acidic, it remains in the system. Electrical insulation reliability tends to decrease, and both physical properties of solvent solubility and resin matrix compatibility and electrical insulation reliability are in a trade-off relationship.

JP-A-5-51433

  The present invention has been made in view of the above points, and is required for applications such as adhesion, electrical insulation reliability, flexible printed wiring boards, and the like, ensuring flame retardancy required without using halogen. It is an object of the present invention to provide a halogen-free epoxy resin composition, a cover lay film, a bonding sheet, a prepreg, and a laminate for a printed wiring board that satisfy flexibility.

  The halogen-free epoxy resin composition according to the present invention contains (A) an epoxy resin, (B) a curing agent, (C) an elastomer, (D) a curing accelerator, (E) a flame retardant, and (F) filled without halogen. In the halogen-free epoxy resin composition prepared by blending each component of the material, the component (A) includes a novolac type epoxy resin having a phenol skeleton and a biphenyl skeleton, and the component (B) includes dicyandiamide. The component (C) includes at least one of an acrylonitrile butadiene rubber containing a carboxyl group and an acrylic rubber containing a carboxyl group, and the component (D) is at least one of an organic phosphine and a phosphonium salt. The component (E) contains a phosphorus-based flame retardant, and the component (F) is aluminum hydroxide. Is characterized in that comprises a.

  In the halogen-free epoxy resin composition, the component (C) is 10 to 75 parts by mass and the component (D) is 0.05 to 1 part by mass with respect to 100 parts by mass in total of the components (A) and (B). Part, the (E) component is preferably 3 to 70 parts by mass, and the (F) component is preferably 20 to 175 parts by mass.

  In the halogen-free epoxy resin composition, the phosphorus-based flame retardant contained in the component (E) is preferably an alkyl phosphinic acid represented by the following structural formula (1).

  In the halogen-free epoxy resin composition, the aluminum hydroxide contained in the component (F) has an average particle diameter before dispersion in the halogen-free epoxy resin composition of 2 μm or more, and the halogen-free epoxy resin composition In the halogen-free epoxy resin composition, the average particle size is preferably adjusted to 2 to 4 μm by the pulverizing action when dispersed in a product.

  The coverlay film according to the present invention is characterized in that the halogen-free epoxy resin composition is applied to at least one surface of the film.

  The bonding sheet according to the present invention is characterized in that the halogen-free epoxy resin composition is applied to at least one surface of a film.

  The prepreg according to the present invention is characterized in that the halogen-free epoxy resin composition is impregnated in a woven fabric or a non-woven fabric.

  The laminated board for printed wiring boards according to the present invention is characterized in that a metal foil is laminated on one side or both sides of the prepreg.

  According to the present invention, the flame retardancy required without using halogen is ensured, and the flexibility required for applications such as adhesion, electrical insulation reliability, and flexible printed wiring board is satisfied.

  Embodiments of the present invention will be described below.

  The halogen-free epoxy resin composition according to the present invention comprises (A) an epoxy resin, (B) a curing agent, (C) an elastomer, (D) a curing accelerator, (E) a flame retardant, and (F) a filler. Is prepared. However, the components (A) to (F) do not contain halogen. Hereinafter, each component will be described in order.

  First, the epoxy resin as the component (A) includes a novolac type epoxy resin having a phenol skeleton and a biphenyl skeleton. As such an epoxy resin, one represented by the following structural formula (2) should be used. Can do.

  In the structural formula (2), n is preferably an integer of 1 to 10, the number average molecular weight is preferably 700 to 1500, and the weight average molecular weight is preferably 1000 to 3000.

  In the present invention, as the epoxy resin as the component (A), other epoxy resins may be used in combination with the novolak type epoxy resin having a phenol skeleton and a biphenyl skeleton. The other epoxy resin 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, alicyclic epoxy resins, aliphatic epoxy resins, heterocyclic epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins and the like that are glycidyl etherified products of various novolak resins can be used.

  Examples of the epoxy resin that is a glycidyl etherified product of a polyphenol compound include bisphenol A, bisphenol F, bisphenol S, 4,4′-biphenylphenol, tetramethylbisphenol A, dimethylbisphenol A, tetramethylbisphenol F, dimethylbisphenol F, Tetramethylbisphenol S, dimethylbisphenol 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-butyl) Fenault ), Trishydroxyphenylmethane, resorcinol, hydroquinone, pyrogallol, phenols having a diisopropylidene skeleton, phenols having a fluorene skeleton such as 1,1-di-4-hydroxyphenylfluorene, and polyphenol compounds such as phenolized polybutadiene An epoxy resin or the like that is a glycidyl etherified product can be used.

  Examples of epoxy resins that are glycidyl etherified products of various novolak resins include, for example, various phenols such as phenol, cresols, ethylphenols, butylphenols, octylphenols, bisphenol A, bisphenol F, bisphenol S, and naphthols. Glycidyl etherification products of various novolak resins such as novolak resin, xylylene skeleton-containing phenol novolak resin, dicyclopentadiene skeleton-containing phenol novolak resin, biphenyl skeleton-containing phenol novolak resin, fluorene skeleton-containing phenol novolak resin, etc. Can be used.

  As the alicyclic epoxy resin, for example, an alicyclic epoxy resin having an aliphatic skeleton such as cyclohexane can be used, and as the aliphatic epoxy resin, for example, 1,4-butanediol, 1,6 -Glycidyl ethers of polyhydric alcohols such as hexanediol, polyethylene glycol and pentaerythritol can be used.

  As the heterocyclic epoxy resin, for example, a heterocyclic epoxy resin having a heterocyclic ring such as an isocyanuric ring or a hydantoin ring can be used. As the glycidyl ester-based epoxy resin, for example, hexahydrophthalic acid diglycidyl ester is used. An epoxy resin composed of carboxylic acids such as glycidylamine can be used, and as the glycidylamine epoxy resin, for example, an epoxy resin obtained by glycidylation of amines such as aniline and toluidine can be used.

  (A) As a component, when using a novolak type epoxy resin having a phenol skeleton and a biphenyl skeleton in combination with another epoxy resin, the ratio of the two is not particularly limited, but with respect to the total amount of the component (A), The content of the novolac type epoxy resin having a phenol skeleton and a biphenyl skeleton is preferably 50% by mass or more.

  Next, the curing agent as component (B) contains dicyandiamide, but other curing agents may be used in combination. The other curing agent is not particularly limited as long as it does not contain a halogen. For example, diaminodiphenylsulfone such as 3,3′-diaminodiphenylsulfone or 4,4′-diaminodiphenylsulfone is used. Can be used. In particular, 3,3'-diaminodiphenyl sulfone is preferable from the viewpoint of adhesion and electrical insulation reliability.

  In the present invention, the blending ratio of the epoxy resin as the component (A) and the dicyandiamide as the component (B) is not particularly limited, but dicyandiamide with respect to 1 mol of the epoxy group contained in the epoxy resin. It is preferable to set so that the number of moles of NH groups is 0.75 to 1.25 moles.

  Next, the elastomer as component (C) contains acrylonitrile butadiene rubber and carboxyl groups containing carboxyl groups from the viewpoint of compatibility with epoxy resins and flexibility required in applications such as flexible printed wiring boards. It contains at least one of the acrylic rubbers contained.

  As specific examples of the acrylonitrile butadiene rubber containing a carboxyl group, “PNR-1H” manufactured by JSR Corporation, “Nipol 1072J”, “Nipol DN631” and “Nipol FN3703” manufactured by Nippon Zeon Co., Ltd. "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.

  Moreover, the acrylic rubber containing a carboxyl group is an acrylic rubber containing at least one carboxyl group in at least one molecule, and mainly comprises an acrylic acid alkyl ester (including a methacrylic acid ester, the same shall apply hereinafter), It is a copolymer containing a vinyl monomer containing a carboxyl group and, if necessary, acrylonitrile, styrene, ethylene or the like. Examples of the alkyl acrylate ester include, for example, ethyl acrylate (including ethyl methacrylate; the same shall apply hereinafter), propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, undecyl acrylate, Monomers containing epoxy groups such as monomers such as lauryl acrylate, monomers having a hydroxyl group such as 2-hydroxyethyl acrylate, 2-hydroxylpropyl acrylate and allyl alcohol, and epichlorohydrin-modified products such as glycidyl acrylate Etc. can be used. From these, one type or two or more types can be selected and used. As the vinyl monomer containing a carboxyl group, for example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, maleic anhydride and the like can be used, but are not limited thereto, The polymerization method is not particularly limited, but is preferably one having as few ionic impurities as possible from the viewpoint of electrical insulation reliability.

  In the present invention, the elastomer as component (C) may be used in combination with other elastomers in addition to acrylonitrile butadiene rubber containing carboxyl groups and acrylic rubber containing carboxyl groups. Other elastomers are not particularly limited as long as they do not contain halogen. For example, butadiene rubber, epoxy-modified butadiene rubber, isoprene rubber, phenoxy resin, polyamideimide resin, polyester resin, etc. may be used. it can.

  Here, it is preferable that the compounding quantity of (C) component is 10-75 mass parts with respect to a total of 100 mass parts of (A) and (B) component. When the blending amount of the component (C) is less than 10 parts by mass, the flexibility is insufficient, and the flexibility and flexibility required in applications such as flexible printed wiring boards may not be satisfied. Adhesion strength may also be insufficient. On the contrary, when the blending amount of the component (C) exceeds 75 parts by mass, it may be difficult to ensure the required flame retardancy.

  Next, the curing accelerator as component (D) contains at least one of organic phosphines and phosphonium salts.

  Here, as organic phosphines, for example, triphenylphosphine, tri-o-toluylphosphine, tri-m-toluylphosphine, tri-p-toluylphosphine, tri-2,4-xylylphosphine, tri-2, 5-xylylphosphine, 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 can be used.

  Examples of the phosphonium salt include tetrabutylphosphonium hydroxide, tetrabutylphosphonium acetate, tetrabutylphosphonium hydrogen difluoride, tetrabutylphosphonium dihydrogen trifluoride, tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetra- p-triborate, benzyltriphenylphosphonium tetraphenylborate, tetraphenylphosphonium tetrafluoroborate, p-tolyltriphenylphosphonium tetra-p-tolylborate, triphenylphosphinetriphenylborane, 1,2-bis (diphenylphosphino) ethane 1,3-bis (diphenylphosphino) propane, 1,4-bis (diphenylphosphino) buta It can be used 1,5-bis (diphenylphosphino) pentane.

  The organic phosphines and phosphonium salts are not limited to those described above, and two or more types may be used in combination.

  Moreover, it is preferable that the compounding quantity of (D) component is 0.05-1 mass part with respect to a total of 100 mass parts of (A) and (B) component. When the blending amount of the component (D) is less than 0.05 parts by mass, the reaction between the epoxy group of the epoxy resin and the carboxyl group contained in the elastomer is delayed, and the electrical insulation reliability may be reduced. On the contrary, when the blending amount of the component (D) exceeds 1 part by mass, there is a risk of causing a significant increase in viscosity when the halogen-free epoxy resin composition is used as a varnish.

  Next, the flame retardant as the component (E) contains a phosphorus flame retardant, and as such a phosphorus flame retardant, from the viewpoint of electrical insulation reliability and adhesion, the structural formula (1) It is preferable to use the alkylphosphinic acid represented. Moreover, this alkylphosphinic acid is excellent in hydrolysis resistance.

  In this invention, as a flame retardant which is (E) component, you may use together another flame retardant other than the alkyl phosphinic acid represented by the said Structural formula (1). Other flame retardants are not particularly limited as long as they do not contain halogen. For example, aromatic phosphoric acid esters or condensed types thereof, phosphazenes, 9,10-dihydro-9-oxa A compound group containing -10-phosphaphenanthrene-10-oxide in its structure can be used. These phosphorus-based flame retardants have a tendency to decrease in glass transition temperature (Tg) and adhesion strength as their blending amount increases, so that they do not dissolve in varnish-like halogen-free epoxy resin compositions as much as possible. Is preferred. That is, the solubility in 100 g of methyl ethyl ketone and 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. In addition, as a flame retardant other than the phosphorus-based flame retardant, a silicone compound, a hindered amine, or the like may be used in combination.

  Here, it is preferable that the compounding quantity of (E) component is 3-70 mass parts with respect to a total of 100 mass parts of (A) and (B) component. When the blending amount of the component (E) is less than 3 parts by mass, a sufficient flame retardant effect may not be obtained. On the contrary, when the compounding amount of the component (E) exceeds 70 parts by mass, the glass transition temperature (Tg) and adhesion strength of the cured product of the halogen-free epoxy resin composition may be remarkably reduced.

  Next, although the filler which is (F) component contains aluminum hydroxide, you may use other fillers together besides this. Other fillers are not particularly limited as long as they do not contain halogen. For example, magnesium hydroxide, magnesium hydroxide-based composite metal hydroxide, zinc borate, boron nitride, silicon nitride, In addition to inorganic fillers such as barium sulfate, talc, clay, mica, silica, and hydrotalcite, organic fillers that are insoluble in organic solvents can be used.

Here, about the aluminum hydroxide contained in (F) component, it is preferable that the average particle diameter before disperse | distributing to a halogen-free epoxy resin composition is 2 micrometers or more (an upper limit is 30 micrometers). The reason for this is as follows. That is, when producing aluminum hydroxide, Na ₂ O is by-produced in the process, and this Na ₂ O adheres directly to the surface of the aluminum hydroxide particles. Usually, Na ₂ O is removed by washing aluminum hydroxide. However, since aluminum hydroxide having an average particle size of less than 2 μm has a large specific surface area, Na ₂ O is a particle of aluminum hydroxide even after washing. Often remains on the surface. Therefore, this Na ₂ O may reduce the heat resistance and electrical insulation reliability of the cured product of the halogen-free epoxy resin composition. Therefore, the average particle diameter of aluminum hydroxide before being dispersed in the halogen-free epoxy resin composition is preferably 2 μm or more. In addition, in this invention, an average particle diameter shows D50 value measured using a laser diffraction type particle size distribution measuring apparatus.

  In preparing the halogen-free epoxy resin composition, the components (A) to (F) are blended and dispersed. At this time, the aluminum hydroxide particles contained in the component (F) have a pulverizing action. Therefore, the average particle size after dispersion is smaller than the average particle size before dispersion. And finally, it is preferable that the average particle diameter of aluminum hydroxide is adjusted to 2 to 4 μm in the halogen-free epoxy resin composition. If the average particle size is less than 2 μm, sufficient adhesion strength may not be obtained. On the contrary, when the average particle size exceeds 4 μm, the surface of the cured product of the halogen-free epoxy resin composition is uneven due to the excessively large particle size of aluminum hydroxide, or the distance between circuits / circuits is narrow There is a risk that the probability of occurrence of insulation failure increases and the electrical insulation reliability decreases.

  Moreover, it is preferable that the compounding quantity of (F) component is 20-175 mass parts with respect to a total of 100 mass parts of (A) and (B) component. When the blending amount of the component (F) is less than 20 parts by mass, it may be difficult to obtain a sufficient effect for reducing the linear expansion coefficient and imparting flame retardancy by adding a filler. On the other hand, when the blending amount of the component (F) exceeds 175 parts by mass, the adhesion strength and the flexibility are lowered, which may be unsuitable for practical use.

  (F) As a component, when using aluminum hydroxide and another filler together, the ratio of both is not particularly limited, but aluminum hydroxide is 25% by mass or more based on the total amount of component (F). It is preferable that

  The halogen-free epoxy resin composition according to the present invention is prepared by blending the components (A) to (F), but other additives may be blended as necessary. As other additives, for example, an antifoaming agent, a leveling agent, a dispersing agent, a coupling agent, an antioxidant, an ultraviolet absorber, and the like can be used, but not particularly limited thereto.

  In preparing the halogen-free epoxy resin composition, first, the epoxy resin as the component (A), the curing agent as the component (B), the elastomer as the component (C), and the curing accelerator as the component (D) (E) The flame retardant which is a component is melt | dissolved in an organic solvent, and is mix | blended. Furthermore, when the filler which is (F) component is added and mix | blended with this resin solution, and it disperse | distributes and grind | pulverizes using media mills, such as a bead mill, a halogen-free epoxy resin composition can be obtained as a varnish. In addition, the flame retardant which is (E) component does not necessarily need to melt | dissolve in the organic solvent. Further, the blending procedure of each component does not need to be in the above order, and can be changed as necessary, and other additives may be added as appropriate.

  The conditions for dispersion / pulverization using a media mill can be set as follows. For example, when using a bead mill, first, varnish is prepared by changing various conditions such as bead composition, bead diameter, bead filling rate, rotation speed, discharge amount, circulation number, temperature, time, and the like. Next, about these varnishes, the average particle diameter of aluminum hydroxide can be measured using a laser diffraction type particle size distribution measuring device, and the conditions for dispersion and grinding can be optimized and set based on the measurement results. However, since there is an optimum value unique to each device, it is not limited to a specific condition. The dispersion / pulverization may be performed using a bead mill, a grain mill, a basket mill, a ball mill, or the like as a media mill, and may also be performed using a roll kneading dispersion method or the like. Grinding by a dry method such as a jet mill is possible, but if the above wet method is used, the preparation of the varnish and the dispersion of the filler containing aluminum hydroxide can be performed simultaneously, and the process can be simplified. Therefore, the wet method is more preferable.

  A coverlay film and a bonding sheet can be produced using the halogen-free epoxy resin composition obtained as described above. That is, a coverlay film and a bonding sheet can be manufactured by applying a halogen-free epoxy resin composition to at least one surface of a film such as an electrical insulating film or a release film to form an adhesive layer. Specific examples include a film-based coverlay film having a three-layer structure of an electrical insulating film / adhesive layer / release film, a three-layer structure of release film / adhesive layer / release film, or a mold release. Examples thereof include a dry film type coverlay film and a bonding sheet having a two-layer structure of film / adhesive layer. Also, by laminating like electrical insulating film / adhesive layer / metal foil, laminating like single side flexible printed wiring board or metal foil / adhesive layer / electrical insulating film / adhesive layer / metal foil By doing so, a double-sided flexible printed wiring board etc. can also be manufactured.

  Here, as the electrical insulating film, for example, polyimide film, polyethylene terephthalate (PET) film, polyester film, polyparabanic acid film, polyether ether ketone film, polyphenylene sulfide film, aramid film, polycarbonate film, polyarylate film, etc. Can be used. The thickness of the electrically insulating film is preferably 3 to 200 μm, but an appropriate thickness may be used as necessary. Moreover, it may be a laminate of a plurality of films selected from these, and may be subjected to surface treatment such as hydrolysis, corona discharge, low temperature plasma, physical roughening, and easy adhesion coating treatment as necessary. Good.

  In addition, as the release film, for example, a polyolefin film, a polyester film, a TPX film, a film in which a release agent layer is provided on these films, or a paper in which these films are laminated on a paper base material may be used. it can.

  In addition, as the metal foil, for example, electrolytic copper foil, rolled copper foil, aluminum foil, tungsten foil, iron foil, etc. can be used, but generally from the viewpoint of workability, flexibility, electrical conductivity, etc. It is preferable to use electrolytic copper foil, rolled copper foil or the like.

  In producing the above film-based coverlay film, 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. Next, 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 surface of the adhesive layer of the electrically insulating film with the adhesive layer On the other hand, a film-based coverlay film can be obtained by pressure-bonding the release film with a hot roll or the like. At this time, it is also possible to obtain a flexible printed wiring board by using a metal foil instead of the release film and curing the adhesive layer by a heating process after pressure bonding the metal foil.

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

  Moreover, a prepreg can be manufactured using the halogen-free epoxy resin composition obtained as mentioned 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, and heating and drying the varnish through an in-line dryer to remove the solvent contained in the varnish. Is. Although it does not specifically limit as this base material, From a heat resistant and workable viewpoint, it is preferable to use a glass woven fabric, a glass nonwoven fabric, etc.

  Next, after laminating a metal foil on one side or both sides of the prepreg obtained as described above, a laminate for a printed wiring board can be produced by heating and pressing. In addition, the prepreg laminated | stacked with metal foil can use what laminated | stacked not only 1 sheet but multiple sheets.

  Hereinafter, the present invention will be specifically described by way of examples.

(Examples 1-5 and Comparative Examples 1-6)
According to the blending composition (parts by mass) described in Table 1 below, for Examples 1 to 5 and Comparative Example 1, (A) epoxy resin, (B) curing agent, (C) elastomer, and (E) flame retardant were methyl ethyl ketone. And it melt | dissolved in the organic solvent (volume ratio is 50:50) which consists of propylene glycol monomethyl ether, and obtained the resin solution. On the other hand, about Comparative Examples 2-6, it melt | dissolved in the organic solvent which consists of methyl ethyl ketone, and obtained the resin solution. However, about Examples 2-5, the phosphinic acid aluminum which is (E) component was insoluble in the organic solvent, and it became the state which does not melt | dissolve completely. Then, aluminum hydroxide as component (F) described in Table 1 below is added to each resin solution, and dispersed using a bead mill so that the average particle size after dispersion and pulverization becomes the value described in Table 1 below. And crushing were performed simultaneously. Then, the uniform varnish of the halogen free epoxy resin composition was obtained by further adding and stirring the (D) hardening accelerator of following Table 1, and stirring. The aluminum hydroxide in this halogen-free epoxy resin composition shows the average particle diameter before being dispersed and pulverized and the average particle diameter after being dispersed and pulverized are shown in Table 1 below.

  In addition, each component shown in the following Table 1 does not contain any halogen, and is specifically as follows.

(A) Epoxy resin NC3000: Novolac-type epoxy resin (A) having a phenol skeleton and a biphenyl skeleton (“NC3000” manufactured by Nippon Kayaku Co., Ltd.)
N740; phenol novolac type epoxy resin (“N740” manufactured by Dainippon Ink and Chemicals, Inc.)
・ Epicoat 1001; bisphenol A type epoxy resin (“Epicoat 1001” manufactured by Japan Epoxy Resin Co., Ltd.)
(B) Curing agent • DICY; dicyandiamide • 4,4′-DDS; 4,4′-diaminodiphenylsulfone • 3,3′-DDS; 3,3′-diaminodiphenylsulfone • C-200S; 3,3 ′ , 5,5′-Tetramethyl-4,4′-diaminodiphenylmethane (“C-200S” manufactured by Nippon Kayaku Co., Ltd.)
-PSM-4261; phenol novolac resin ("PSM-4261" manufactured by Gunei Chemical Industry Co., Ltd.)
(C) Elastomer • Nipol 1072; carboxyl group-containing nitrile butadiene rubber (“Nipol 1072” manufactured by Nippon Zeon Co., Ltd.)
-Baymac G; carboxyl group-containing ethylene-methyl acrylate copolymer (Mitsui-DuPont Polychemical Co., Ltd. "Baymac G")
・ Nipol AR12: Carboxyl group-containing acrylic rubber (“Nipol AR12” manufactured by Nippon Zeon Co., Ltd.)
(D) Curing accelerator-TPP; Triphenylphosphine-TMTP; Tri-m-toluylphosphine-TPP-S; Triphenylphosphine triphenylborane-2E4MZ; 2-ethyl-4-imidazole (Shikoku Chemical Industries, Ltd.) “2E4MZ”)
(E) Flame retardant FP-100; Phosphazene ("FP-100" manufactured by Fushimi Pharmaceutical Co., Ltd.)
· "OP935"; the structural formula (1) alkyl phosphinic acid represented by (Clariant "OP935", aluminum phosphinates, _{R 1} and _{R 2} is an alkyl group having 1 to 6 carbon atoms)
(F) Filler ・ Heidilite H-32; aluminum hydroxide (“Heidilite H-32” manufactured by Showa Denko KK, average particle size 8 μm)
CE-300A; aluminum hydroxide (“CE-300A” manufactured by Sumitomo Chemical Co., Ltd., average particle size: 7 μm)
-CL303; aluminum hydroxide ("CL303" manufactured by Sumitomo Chemical Co., Ltd., average particle size 4 m)
・ Hijilite H-43M; aluminum hydroxide (“Hijilite H-43M” manufactured by Showa Denko KK, average particle size of 0.75 μm)
Next, the varnishes of the halogen-free epoxy resin compositions of Examples 1 to 5 and Comparative Examples 1 to 6 were used on one side of a polyimide film having a thickness of 12.5 μm using a comma coater and an inline dryer connected thereto. A film-based coverlay film was produced by applying and drying to form an adhesive layer having a thickness of 12.5 μm after drying.

  The film-based coverlay film thus obtained was evaluated for adhesion strength, flexibility, solder heat resistance, flame resistance, migration, 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 Table 1 below.

  (1) Adhesion strength was obtained by attaching a coverlay film adhesive layer to a 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 an adhesive layer of a coverlay film on a 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 was evaluated after being immersed in a solder bath heated to ° C. for 10 seconds. And what was not changed in the appearance before and after immersion was judged as “OK”, and those other than this were judged as “NG”.

  (4) For flame retardancy, a 25 μm thick polyimide film is bonded to the adhesive layer of the coverlay film, and a sample is prepared by heating and pressing at 180 ° C. for 1 hour, and the UL standard 94V-0 grade is used. Evaluation was based on whether or not it could be achieved.

  (5) In migration, a comb-shaped electrode is provided on a single-sided flexible printed wiring board, an adhesive layer of a coverlay film is bonded to this surface, and a sample is prepared by heating and pressing at 180 ° C. for 1 hour. After applying a voltage of 10 V for 250 hours in an environment of 85 ° C./85% RH, the degree of migration was visually evaluated. Then, “◯” indicates that no migration is observed, “Δ” indicates that the migration degree is small, and “x” indicates that the migration degree is large.

  (6) Appearance after molding was as follows. The cover layer film adhesive layer was bonded to the glossy surface of a rolled copper foil having a thickness of 35 μm, and the sample was prepared by heating and pressing at 180 ° C. for 1 hour. The appearance was evaluated visually. Then, a case where no abnormality was observed was determined as “◯”, and a case where abnormality was observed was determined as “×”.

  As is clear from Table 1 above, each example has high peel strength and good adhesion, and has high flexibility and satisfies the flexibility required for applications such as flexible printed wiring boards. In addition, it was confirmed that the material had good migration resistance, satisfied electrical insulation, and had high flame resistance. And since the thing of each Example does not contain halogens, such as a halogenated flame retardant, it is useful as a material with little toxic gas and smoke generation.

Claims (8)

  Halogen prepared by blending each component of (A) epoxy resin not containing halogen, (B) curing agent, (C) elastomer, (D) curing accelerator, (E) flame retardant and (F) filler. In the free epoxy resin composition, the component (A) includes a novolak epoxy resin having a phenol skeleton and a biphenyl skeleton, the component (B) includes dicyandiamide, and the component (C) includes a carboxyl group. Including at least one of acrylonitrile butadiene rubber and carboxyl group-containing acrylic rubber, wherein the component (D) includes at least one of organic phosphines and phosphonium salts, and the component (E) is a phosphorus-based compound. A halogen-free epoxy resin containing a flame retardant, wherein the component (F) contains aluminum hydroxide Composition.   10 to 75 parts by mass of the (C) component, 0.05 to 1 part by mass of the (D) component, and 3 of the (E) component with respect to a total of 100 parts by mass of the (A) and (B) components. The halogen-free epoxy resin composition according to claim 1, wherein the component (F) is 20 to 175 parts by mass. The halogen-free epoxy resin composition according to claim 1 or 2, wherein the phosphorus-based flame retardant contained in the component (E) is an alkylphosphinic acid represented by the following structural formula (1).

  The aluminum hydroxide contained in the component (F) has an average particle size of 2 μm or more before dispersion in the halogen-free epoxy resin composition, and is pulverized when dispersed in the halogen-free epoxy resin composition. 4. The halogen-free epoxy resin composition according to claim 1, wherein an average particle size is adjusted to 2 to 4 μm in the halogen-free epoxy resin composition. 5.   A coverlay film, wherein 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.   A bonding sheet, wherein 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, wherein the halogen-free epoxy resin composition according to any one of claims 1 to 4 is impregnated in a woven fabric or a non-woven fabric.   A laminate for a printed wiring board, wherein a metal foil is laminated on one side or both sides of the prepreg according to claim 7.