JPWO2020080352A1 - Resin composition, hardened film, printed wiring board with hardened film and its manufacturing method - Google Patents

Abstract

The resin composition contains (a) a binder resin, (b) a thermosetting resin, and (c) a flame retardant. (A) The binder resin is a polymer having a urethane bond in the molecule, and may further have a carboxy group and / or a photopolymerizable functional group. (C) The flame retardant is an organic phosphorus compound represented by the following general formula. In the formula, R ² and R ⁵ are independently a phenyl group which may have a substituent, a naphthyl group which may have a substituent, or an anthryl group which may have a substituent; R ¹ , R ³ , R ⁴ and R ⁶ each independently have a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group which may have a substituent, and a naphthyl group which may have a substituent. , Or an anthryl group which may have a substituent.

Description

The present invention relates to a resin composition, a cured film obtained by curing the resin composition, and a printed wiring board provided with the cured film.

An insulating cured film is formed on the circuit of the printed wiring board using an insulating thermosetting resin or an ultraviolet curable resin in order to maintain insulation reliability. Flame retardants may be required for the insulating cured film, and a non-halogen flame retardant is used from the viewpoint of environmental load (Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-21243

In order to give the insulating cured film on the printed wiring board sufficient flame retardancy, it is necessary to add a large amount of flame retardant, which may cause a decrease in the strength and heat resistance of the cured film. In addition, there is a concern that bleed-out may occur when a liquid flame retardant is used, and when a flame retardant such as a metal phosphinic acid salt or aluminum hydroxide is used, the flame retardant is eluted or desorbed by alkaline development or chemical treatment after curing. May be done. Furthermore, if a large amount of flame retardant is added to enhance the flame retardancy, the flexibility of the cured film may decrease.

An object of the present invention is to provide a cured film having excellent flame retardancy, less likely to cause problems such as bleed-out, and having excellent flexibility, and a resin composition used for forming the cured film.

The resin composition of the present invention contains (a) a binder resin, (b) a thermosetting resin, and (c) a flame retardant. (A) The binder resin is a polymer having a urethane bond in the molecule, and may further have a carboxy group and / or a photopolymerizable functional group. The acid value of the binder resin may be 5 to 200 mgKOH / g. (B) The thermosetting resin is, for example, a polyfunctional epoxy resin.

(C) The flame retardant is an organophosphorus compound (spirocyclic diphosphonate compound) represented by the following general formula.

In the formula, R ² and R ⁵ are independently a phenyl group which may have a substituent, a naphthyl group which may have a substituent, or an anthryl group which may have a substituent. R ¹ , R ³ , R ⁴ and R ⁶ each independently have a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group which may have a substituent, and a naphthyl group which may have a substituent. , Or an anthryl group which may have a substituent.

In addition to the above components (a), (b) and (c), the resin composition comprises (d) a compound having an ethylenically unsaturated group (photocurable compound), (e) a photopolymerization initiator, and the like. (F) It may contain a colorant or the like. The content of the component (c) in the resin composition may be about 10 to 30 parts by weight with respect to 100 parts by weight of the total solid content.

A coating film (insulating film) is formed by applying the above resin composition on a substrate and drying the solvent if necessary. A cured film is obtained by photocuring and / or thermosetting this insulating film. For example, the above resin composition is applied to the surface of a printed wiring board to form a coating film, and at least a part of the surface of the coating film is irradiated with active light to perform photocuring, and if necessary, alkali. A printed wiring board with a cured film can be formed by heating the coating film after photo-curing and performing thermosetting after the development by the above. The printed wiring board may be a flexible printed wiring board using a flexible film base material such as a polyimide film.

The cured film formed from the above resin composition has excellent flame retardancy, is less likely to cause problems such as bleeding out of the flame retardant, and is also excellent in flexibility.

The resin composition of the present invention contains (a) a binder resin, (b) a thermosetting resin, and (c) an organic phosphorus-based compound. Since it has a thermosetting resin, the resin composition has thermosetting property. (A) The binder resin may be one having reactivity with the thermosetting resin.

(A) The binder resin may have a photocurable functional group such as an ethylenically unsaturated group. Since the resin composition contains a binder resin having photocurability, the resin composition has photocurability (photosensitivity) in addition to thermosetting property. The resin composition may further contain (d) a compound having an ethylenically unsaturated group (photocurable compound). The resin composition may further contain (e) a photopolymerization initiator.

The resin composition may further contain (f) a colorant. By containing the colorant, the insulating film obtained from the resin composition can be arbitrarily colored.

<(A) Binder resin>
The binder resin is a polymer that is soluble in an organic solvent and has a weight average molecular weight of 1,000 or more and 1,000,000 or less in terms of polyethylene glycol. The weight average molecular weight of the binder resin is more preferably 2,000 to 200,000, further preferably 3,000 to 100,000, and particularly preferably 4,000 to 50,000. When the weight average molecular weight of the binder resin is within the above range, a cured film having excellent heat resistance and flexibility can be easily obtained.

The binder resin is a urethane-based polymer having at least one urethane bond in the molecule. By using a urethane-based polymer as the binder resin and (c) an organic phosphorus-based compound described later as the flame retardant, excellent flame retardancy can be imparted without reducing the flexibility of the insulating cured film. Urethane-based polymers are obtained, for example, by reacting diols with diisocyanates.

The diisocyanate compound may be either an alicyclic diisocyanate compound or an aliphatic diisocyanate compound. The diisocyanate compound may be a reaction product of a compound having two or more functional groups capable of reacting with an isocyanate group, and may be, for example, a urethane compound having an isocyanate group at the terminal.

The diisocyanate compound may be any of aromatic isocyanate, alicyclic isocyanate, aliphatic isocyanate and alicyclic diisocyanate. The diisocyanate compound may be a reaction product of a compound having two or more functional groups capable of reacting with the isocyanate group of the diisocyanate compound, and may be, for example, a urethane compound having an isocyanate group at the terminal. Above all, when an alicyclic diisocyanate or an aliphatic diisocyanate is used, the resin composition tends to have excellent photosensitivity. Examples of the alicyclic diisocyanate include hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and norbornene diisocyanate. Examples of the aliphatic diisocyanate include hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate.

Examples of the diol include ethylene glycol, diethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 1, 6-Hexanediol, 1,8-octanediol, 2-methyl1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol Alkylene diols such as: polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyalkylene diols such as random copolymers of tetramethylene glycol and neopentyl glycol; obtained by reacting polyhydric alcohol with polybasic acid. Polypolydiol; Polycarbonate diol having a carbonate skeleton; Polycaprolactone diol obtained by ring-opening addition reaction of lactones such as γ-butyl lactone, ε-caprolactone, δ-valerolactone; ethylene oxide adduct of bisphenol A and bisphenol A , A propylene oxide adduct of bisphenol A, hydrogenated bisphenol A, an ethylene oxide adduct of hydrogenated bisphenol A, a propylene oxide adduct of hydrogenated bisphenol A, and the like. Two or more kinds of diols may be used in combination. Among the above, when long-chain diols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polyoxyalkylene diol, polyester diol, polycarbonate diol, and polycaprolactone diol are used, the elasticity of the cured film is lowered and the film is flexible. Tends to improve.

The binder resin may have a carboxy group in the molecule. By having a carboxy group, the binder resin reacts with the component (b) described later, so that the heat resistance and chemical resistance of the cured film tend to be improved. Further, when used as a photosensitive resin composition, since the binder resin has a carboxy group, the solubility in an alkaline developer is improved, so that a fine pattern can be formed in a short time of development. The acid value of the binder resin is preferably 5 to 200 mgKOH / g, more preferably 15 to 100 mgKOH / g. When the binder resin has an appropriate acid value, a crosslinked structure with the component (b) is densely formed, so that the heat resistance, insulation reliability and chemical resistance of the cured film can be improved.

A polymer having a carboxy group in the molecule can be obtained, for example, by using a compound having two hydroxyl groups and one carboxy group in the molecule as a diol component for forming a urethane-based polymer. Examples of the diol compound containing two hydroxyl groups and one carboxy group include 2,2-bis (hydroxymethyl) propionic acid, 2,2-bis (2-hydroxyethyl) propionic acid, and 2,2-bis (3-). Hydroxymepropyl) propionic acid, 2,3-dihydroxy-2-methylpropionic acid, 2,2-bis (hydroxymethyl) butanoic acid, 2,2-bis (2-hydroxyethyl) butanoic acid, 2,2-bis Alibo diols such as (3-hydroxypropyl) butanoic acid, 2,3-dihydroxybutanoic acid, 2,4-dihydroxy-3,3-dimethylbutanoic acid, and 2,3-dihydroxyhexadecanoic acid; 2,3- Fragrant diols such as dihydroxybenzoic acid, 2,4-dihydroxybenzoic acid, 2,5-dihydroxybenzoic acid, 2,6-dihydroxybenzoic acid, 3,4-dihydroxybenzoic acid, and 3,5-dihydroxybenzoic acid Can be mentioned.

The binder resin may have an ethylenically unsaturated group in the molecule. Ethylene unsaturated groups include vinyl groups and (meth) acryloyl groups. In the present specification, "(meth) acrylic" means acrylic or methacryl, and "(meth) acryloyl" means acryloyl or methacryloyl.

If the binder resin has a photocurable functional group such as a (meth) acryloyl group, a photocurable film can be formed from the resin composition. Further, when the resin composition contains the component (d) described later, the binder resin having a photocurable functional group also reacts with the component (d), so that the crosslink density of the photocurable film is increased, and heat resistance and heat resistance are increased. Chemical resistance tends to improve. By increasing the photocrosslinking density, the elution of the flame retardant into the developer or the like tends to be suppressed.

Polymers having a (meth) acryloyl group in the molecule include, for example, a compound containing a hydroxyl group and at least one (meth) acryloyl group in the molecule in addition to a diol component and a diisocyanate component for forming a urethane-based polymer. / Or obtained by using a compound containing an isocyanate group and at least one (meth) acryloyl group in the molecule.

Examples of compounds having a hydroxyl group and a (meth) acryloyl group in the molecule include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 2-hydroxy-3-phenoxy. Propyl (meth) acrylate, 2-hydroxy-1-acryloxy-3-methacryloxypropane, o-phenylphenol glycidyl ether (meth) acrylate, polyethylene glycol mono (meth) acrylate, pentaerythritol tri (meth) acrylate, tris (2) -Hydroxyethyl) isocyanurate di (meth) acrylate, 1,4-cyclohexanedimethanol mono (meth) acrylate, 4-hydroxyphenyl (meth) acrylate, 2- (4-hydroxyphenyl) ethyl (meth) acrylate, N- Examples thereof include methylol acrylamide and 3,5-dimethyl-4-hydroxybenzyl acrylamide. Examples of the compound having an isocyanate group and a (meth) acryloyl group in the molecule include 2- (meth) acryloyloxyethyl isocyanate, 1,1- (bisacryloyloxymethyl) ethyl isocyanate, and 2- (2-methacryloyloxyethyloxy). Ethyl isocyanate and the like can be mentioned.

The binder resin may have two or more photocurable functional groups in one molecule. For example, in the polymerization of urethane polymer, in addition to diol and diisocyanate, a compound having one hydroxyl group and one (meth) acryloyl group in one molecule is used, and if the ratio is increased, both ends of the polymer chain ( A urethane di (meth) acrylate having a meta) acryloyl group can be obtained.

From the viewpoint of improving the adhesion between the cured film formed from the resin composition and the substrate material such as the polyimide film, the content of the component (a) in the resin composition is 10 with respect to 100 parts by weight of the total solid content. ~ 80 parts by weight is preferable, 20 to 70 parts by weight is more preferable, and 30 to 60 parts by weight is further preferable.

<(B) Thermosetting resin>
A thermosetting resin is a compound having at least one thermosetting functional group in the molecule. Examples of the thermosetting resin include epoxy resin, oxetane resin, isocyanate resin, blocked isocyanate resin, bismaleimide resin, bisallyl nadiimide resin, polyester resin (for example, unsaturated polyester resin), diallyl phthalate resin, silicon resin, and vinyl ester. Resin, melamine resin, polybismaleimide triazine resin (BT resin), cyanate resin (for example, cyanate ester resin, etc.), urea resin, guanamine resin, sulfoamide resin, aniline resin, polyurea resin, thiourethane resin, polyazomethine resin, episulfide resin. , En-thiol resin, benzoxazine resin and the like. A polyfunctional epoxy resin having two or more epoxy groups in one molecule is preferable because it can impart heat resistance to the cured film and also impart adhesiveness to a conductor such as a metal foil or a circuit board.

Examples of the polyfunctional epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, biphenyl type epoxy resin, phenoxy type epoxy resin, naphthalene type epoxy resin, and phenol novolac. Examples thereof include a type epoxy resin, a cresol novolac type epoxy resin, a trisphenol methane type epoxy resin, a dicyclopentadiene type epoxy resin, and an amine type epoxy resin. The epoxy resin may be a modified epoxy resin such as urethane, rubber, chelate, or dimer acid. As the component (b), a commercially available epoxy resin may be used as it is.

From the viewpoint of heat resistance and chemical resistance of the cured film, the epoxy equivalent of the epoxy resin (mass (g) of the compound containing 1 equivalent of the epoxy group) is preferably 2000 or less, and more preferably 1500 or less. The weight average molecular weight of the epoxy resin is preferably about 150 to 2000, more preferably about 200 to 1500.

From the viewpoint of improving the heat resistance and chemical resistance of the cured film formed from the resin composition, the content of the component (b) in the resin composition is 1 to 70 parts by weight with respect to 100 parts by weight of the total solid content. Is preferable, 5 to 50 parts by weight is more preferable, and 10 to 20 parts by weight is further preferable.

The resin composition may contain a curing agent and / or a curing accelerator for the thermosetting resin. Examples of the curing agent include phenolic resins such as phenol novolac resin, cresol novolac resin, and naphthalene-type phenol resin, amino resins, urea resins, melamine, and dicyandiamide. Examples of the curing accelerator include phosphine compounds such as triphenylphosphine; amine compounds such as tertiary amines, trimethanolamine, triethanolamine and tetraethanolamine; 1,8-diazabicyclo [5,4,0]. ] -7-Undecenium Tetraphenylborate and other borate compounds; imidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 1-benzyl-2-methyl Imidazoles such as imidazole, 2-heptadecylimidazole, 2-isopropylimidazole, 2,4-dimethylimidazole, 2-phenyl-4-methylimidazole; 2-methylimidazoline, 2-ethylimidazoline, 2-isopropylimidazoline, 2- Imidazolines such as phenylimidazolin, 2-undecylimidazolin, 2,4-dimethylimidazolin, 2-phenyl-4-methylimidazolin; 2,4-diamino-6- [2'-methylimidazolyl- (1')]- Ethyl-s-triazine, 2,4-diamino-6- [2'-undecylimidazolyl- (1')]-ethyl-s-triazine, 2,4-diamino-6 [2'-ethyl-4'- Examples thereof include azine-based imidazoles such as methylimidazolyl- (1')]-ethyl-s-triazine.

<(C) Flame retardant>
The resin composition contains an organic phosphorus compound (spirocyclic diphosphonate compound) represented by the following general formula as a flame retardant.

In the formula, R ² and R ⁵ are independently a phenyl group which may have a substituent, a naphthyl group which may have a substituent, or an anthryl group which may have a substituent. R ¹ , R ³ , R ⁴ and R ⁶ each independently have a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group which may have a substituent, and a naphthyl group which may have a substituent. , Or an anthryl group which may have a substituent.

The above-mentioned organophosphorus compound can be produced, for example, by the method described in JP-A-2004-35480.

By using a urethane polymer as the binder resin and a spiro ring diphosphonate compound as the flame retardant, an insulating film exhibiting excellent flame retardancy can be obtained by adding a small amount of the flame retardant. Since the amount of the flame retardant added is small, it is possible to suppress the decrease in heat resistance and film strength due to the addition of the flame retardant. It is considered that the thermal decomposition behavior of the polymer and the flame retardant is matched as a factor for improving the flame retardancy by the combination of the binder resin and the flame retardant. For example, since free radicals generated by thermal decomposition of a polymer are trapped by a flame retardant, it is considered that the ability to stop the chain reaction at the initial stage of combustion is one factor contributing to the improvement of flame retardancy.

When the resin composition is used as a photosensitive resin composition, by using a spirocyclic diphosphonate compound as a flame retardant, the flame retardancy and adhesion of the photocurable film are unlikely to change before and after alkaline development, and the flame retardant. Bleedout is unlikely to occur. The reason why the characteristic change before and after alkaline development is small is that the flame retardant is an organic phosphorus compound, so it has high compatibility with the binder resin, and the flame retardant is solid at room temperature and elutes into the alkaline developer. Difficult things can be mentioned.

In general, a cured film containing a flame retardant tends to have lower flexibility and inferior bending resistance as the content of the flame retardant increases. In the combination of the spiro ring diphosphonate flame retardant, the flexibility is unlikely to decrease even if the flame retardant is added. Therefore, the resin composition of the present invention can also be suitably used for forming an insulating protective film for a flexible printed wiring board for a foldable device.

The content of the component (c) in the resin composition is preferably 1 to 50 parts by weight, more preferably 5 to 40 parts by weight, still more preferably 10 to 30 parts by weight, based on 100 parts by weight of the total solid content. The above-mentioned spiro ring diphosphonate-based compound tends to exhibit a flame-retardant effect even in a small amount as compared with an inorganic phosphorus-based compound. Therefore, the content of the component (c) in the resin composition may be 20 parts by weight or less or 15 parts by weight or less. The amount of phosphorus atoms contained in the total solid content of the resin composition is preferably 0.5 to 10% by weight, more preferably 1 to 7% by weight, still more preferably 1.5 to 5% by weight. The phosphorus atom content may be 4% by weight or less or 3% by weight or less.

<(D) Photocurable compound>
The resin composition may contain a photocurable compound. By including the photocurable compound, the resin composition is photosensitive. (A) When the binder resin has a photocurable functional group, the photocurable compound also reacts with the component (a), so that the crosslink density of the photocurable film is increased, and the heat resistance and chemical resistance tend to be improved. be.

The photocurable compound has at least one photocurable functional group. As the photocurable functional group, an ethylenically unsaturated group is preferable. Ethylene unsaturated groups include (meth) acryloyl groups and vinyl groups. The component (d) preferably has two or more photocurable functional groups in one molecule.

From the viewpoint of increasing the crosslink density of the photocurable film, as the component (d), a component having a lower molecular weight than the component (a) is used. The weight average molecular weight of the component (d) is preferably 2000 or less, more preferably 1500 or less, and even more preferably less than 1000. The functional group equivalent (1 equivalent of the mass (g) of the compound containing an ethylenically unsaturated group) of the component (d) is preferably 1000 or less, more preferably 750 or less, still more preferably 500 or less.

Examples of the polyfunctional (meth) acrylate having two or more (meth) acryloyl groups in one molecule include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene. Glycoldi (meth) acrylate, polyethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, 2-hydroxy-1- (meth) Acryloxy-3- (meth) acryloxipropane, 1,4-butanediol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol Di (meth) acrylate, pentaerythritol di (meth) acrylate, tricyclodecanedimethanol di (meth) acrylate, 2,4-diethyl-1,5-pentanediol di (meth) acrylate, 2-hydroxy-1,3 -Di (meth) acryloxipropane, 3-methyl-1,5-pentanediol di (meth) acrylate, 2,4-diethyl-1,5-pentanediol di (meth) acrylate, 1,4-cyclohexanedimethanol Di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 4,4'-isopropyridene diphenol di (meth) acrylate, 2,2-bis [4-((meth) acryloxyethoxy) phenyl ] Propane, 2,2-bis [4-((meth) acryloxy diethoxy) phenyl] propane, 2,2-bis [4-((meth) acryloxy polyethoxy) phenyl] propane, 2,2-hydrogenated bis [4-((Meta) Acryloxy Polyethoxy) Phenyl] Propane, 2,2-Bis [4-((Meta) Acryloxy Polypropoxy) Phenyl] Propane, Bisphenol F EO Modified (n = 2-50) Di (Meta) ) Acrylate, bifunctional (meth) acrylate such as bisphenol A EO modified (n = 2 to 50) di (meth) acrylate, bisphenol S EO modified (n = 2 to 50) di (meth) acrylate; (Meta) acrylate, pentaerythritol tri (meth) acrylate, ethoxylated totimethylol propantri (meth) acrylate, pro Trifunctional (meth) acrylates such as poxylated totimethylol propantri (meth) acrylates, tri-isocyanurates (ethane (meth) acrylates), 1,3,5-tri (meth) acryloylhexahydro-s-triazines; tetramethylols. Methantetra (meth) acrylate, pentathritol tetra (meth) acrylate, ethoxylated pentathritol tetra (meth) acrylate, propoxylated pentathritol tetra (meth) acrylate, ditrimethylolpropanetetra (meth) acrylate, dipentaerythritol Examples thereof include tetrafunctional or higher functional (meth) acrylates such as hexa (meth) acrylate and dipentaerythritol poly (meth) acrylate. Among the above, bisphenol A EO-modified (n = 2 to 50) di (meth) acrylate is preferable because the solubility of the photosensitive resin composition in an aqueous developer such as an alkaline aqueous solution is improved and the development time can be shortened. ..

When the resin composition contains the component (d), the content thereof is preferably 1 to 50 parts by weight, more preferably 5 to 40 parts by weight, and 10 to 10 parts by weight, based on 100 parts by weight of the total solid content of the resin composition. 30 parts by weight is more preferable.

<(F) Photopolymerization initiator>
When the component (a) has a photopolymerizable functional group and / or when the resin composition contains the component (d), the resin composition preferably contains (e) a photopolymerization initiator. The photopolymerization initiator is a compound that absorbs and activates light energy such as UV (ultraviolet light) to initiate and promote the reaction of radically polymerizable groups. When the resin composition contains a photopolymerization initiator, the resin composition can be used as a photosensitive resin composition.

Examples of photoradical polymerization initiators are self-cleaving photoradical polymerization initiators such as benzoin compounds, acetophenones, aminoketones, oxime esters, acylphosphine oxide compounds, azo compounds; and benzophenones, benzoins. Hydrogen abstraction type photoradicals such as ethers, benzyl ketals, dibenzosverones, anthraquinones, xanthones, thioxanthones, halogenoacetophenones, dialkoxyacetophenones, hydroxyacetophenones, halogenobis imidazoles, and halogenotriazines. A polymerization initiator can be mentioned.

The content of the component (e) in the resin composition may be appropriately set. From the viewpoint of enhancing the photosensitivity and preventing overexposure, the content of the component (e) is preferably 0.1 to 10 parts by weight, preferably 0, based on 100 parts by weight of the total of the components (a) and (d). .3 to 5 parts by weight is more preferable, and 0.5 to 3 parts by weight is further preferable.

<(F) Colorant>
When the resin composition contains (f) a colorant, the insulating film formed by the resin composition can be arbitrarily colored. The colorant is either a dye or a pigment. Examples of the colorant include a blue colorant, a red colorant, a yellow colorant, an orange colorant, a purple colorant and the like. By combining a plurality of colorants, insulating films of various colors can be formed. For example, by combining a blue pigment, an orange pigment, and a purple pigment, a black colorant can be obtained as a black colorant.

Examples of the blue colorant include phthalocyanine-based, anthraquinone-based, and dioxazine-based pigments such as C.I. I. Pigment Blue 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 60; Dye-based Solvent Blue 35, 63, 68, 70, 83, 87, 94, 97, 122, 136, 67, 70 can be mentioned. In addition to the above, metal-substituted or unsubstituted phthalocyanine compounds can also be used as the blue colorant.

Examples of the orange colorant include C.I. I. Pigment Orange 5, 13, 14, 16, 17, 24, 34, 36, 38, 40, 43, 46, 49, 51, 55, 59, 61, 63, 64, 71, 73.

Examples of the purple colorant include C.I. I. Pigment Violet 19, 23, 29, 30, 32, 36, 37, 38, 39, 40, 50; Solvent Violet 13, 36.

The content of the component (f) may be appropriately set according to the type of the colorant and the color of the insulating film. For example, about 1 to 10 parts by weight with respect to 100 parts by weight of the total solid content of the resin composition. It may be about 2 to 7 parts by weight or about 3 to 5 parts by weight.

<Other ingredients>
The resin composition may contain a solvent in addition to the above-mentioned components (a) to (f). The solvent is not particularly limited as long as it can dissolve a resin component such as a binder polymer, and sulfoxides, formamides, acetamides, pyrrolidones, acetates, ethers, hexamethylphosphoramides, γ-butyrolactone and the like. The polar organic solvent of is preferably used. These polar organic solvents can also be used in combination with aromatic hydrocarbons such as xylene and toluene.

The resin composition may contain various additives such as a defoaming agent, a leveling agent, an adhesion imparting agent, a stabilizer, and a filler, if necessary. Examples of the defoaming agent and the leveling agent include acrylic compounds, vinyl compounds, and silicone compounds.

<Preparation of resin composition>
A resin composition is prepared by mixing each of the above components. Each of the above components may be subjected to operations such as pulverization / dispersion and defoaming, if necessary, before and / or after mixing. The pulverization / dispersion may be carried out using, for example, a kneading device such as a bead mill, a ball mill, or a three-roll.

<Formation of insulating film>
An insulating film can be formed by applying the resin composition (solution) on the substrate and drying the solvent if necessary. As the substrate, for example, a printed wiring board is used. Insulation reliability is enhanced by forming an insulating film on the metal wiring of the printed wiring board. The printed wiring board may be a flexible printed wiring board using a flexible substrate such as a polyimide film.

The resin composition may be applied onto the substrate by screen printing, curtain roll, reverse roll, spray coating, rotary coating using a spinner, or the like. The thickness of the coating film may be adjusted so that the thickness after drying is about 5 to 100 μm, preferably 10 to 100 μm. When drying by heating, the drying temperature is preferably 120 ° C. or lower, more preferably 40 to 100 ° C. from the viewpoint of suppressing the thermosetting reaction.

The dried coating film may be used as it is as an insulating film. From the viewpoint of enhancing the heat resistance and chemical resistance of the insulating film, it is preferably cured by thermosetting and / or photocuring. When forming a thermosetting film, the component (b) may be cured by heat treatment of the coating film. When the component (a) has a carboxy group, the crosslink density is increased by the reaction between the component (a) and the component (b). From the viewpoint of sufficiently advancing thermosetting and suppressing oxidation of metal wiring due to heat, the curing temperature (maximum temperature at the time of thermosetting) is preferably 100 to 250 ° C or lower, more preferably 120 to 200 ° C, and 130. ~ 180 ° C. is more preferable.

When forming a photocurable film, the coating film may be exposed. At the time of exposure, a negative photomask is placed on the coating film and irradiated with active rays such as ultraviolet rays, visible rays, and electron beams to selectively cure the exposed portion. Next, by carrying out development by showering, paddle, dipping or the like, the unexposed portion is melted, so that a pattern cured film is formed.

An alkaline aqueous solution is generally used as the developing solution. When the component (a) has a carboxy group and a photocurable functional group, the component (a) has alkali solubility in the unexposed coating film, and the component (a) is photocured in the coating film after exposure. Therefore, it does not have alkali solubility. Therefore, if a photomask is placed, exposure is performed, and development is performed using an alkaline developer, the unexposed portion dissolves in the developer, so that a pattern-cured film is formed. As described above, since the spiro ring diphosphonate flame retardant of the component (c) is difficult to elute in an alkaline developer, the properties such as flame retardancy and adhesion of the cured film can be maintained even after alkaline development. ..

Examples of the alkaline compound in the developing solution include alkali metals, alkaline earth metals, ammonium ions, hydroxides, carbonates, hydrogen carbonates, amine compounds and the like. Specific examples of the alkaline compound include sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, ammonium hydrogencarbonate, tetramethylammonium hydroxide, and tetraethylammonium hydroxy. Do, tetrapropylammonium hydroxide, tetraisopropylammonium hydroxide, N-methyldiethanolamine, N-ethyldiethanolamine, N, N-dimethylethanolamine, triethanolamine, triisopropanolamine, triisopropylamine and the like can be mentioned.

The developer may contain an organic solvent that is miscible with water, such as metall, etanol, n-propanol, isopropanol, and N-methyl-2-pyrrolidone. The alkali concentration of the developer is generally 0.01 to 20% by weight, preferably 0.02 to 10% by weight, and the temperature of the developer is generally 0 to 80 ° C, preferably 10 to 60 ° C. The pattern cured film (relief pattern) after development is preferably rinsed with a rinsing solution such as water or an acidic aqueous solution.

The insulating film may be further heat-cured by heating after photo-curing. The coating film after photocuring has thermosetting property because the thermosetting functional group such as the epoxy group of the component (b) remains unreacted. Since the carboxy group of the component (a) reacts with the epoxy group of the component (b) by heating, a crosslinked network of the binder resin and the thermosetting resin is formed, and the heat resistance of the cured film is improved. As described above, the curing temperature is preferably 100 to 250 ° C., more preferably 120 to 200 ° C., and preferably 130 to 180 ° C. from the viewpoint of sufficiently advancing the thermosetting and suppressing the oxidation of the metal wiring due to heat. More preferred.

The cured film obtained from the resin composition has excellent heat resistance and flame retardancy, and is therefore suitably used as a surface protective material for printed circuit boards. Further, since the cured film is excellent in flexibility, it is also suitably used as a cured film of a flexible printed circuit board provided with metal wiring on a flexible film such as a polyimide film.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

[Synthesis example]
In the following synthesis example, a polymer having a carboxy group in the molecule was polymerized. The properties of the polymers obtained in Synthesis Examples 1 and 2 were evaluated by the following methods.

<Solid content concentration>
The measurement was performed according to JIS K 5601-1-2. The drying conditions were 170 ° C. × 1 hour.

<Weight average molecular weight>
The measurement was performed by gel permeation chromatography (GPC) under the following conditions.
Equipment used: Tosoh HLC-8220 GPC equivalent Column: Tosoh TSK gel Super AWM-H (6.0mm ID x 15cm) x 2 Guard columns: Tosoh TSK guard column Super AW-H
Eluent: 30mM LiBr + 20mM H ₃ PO ₄ in DMF
Flow velocity: 0.6 mL / min
Column temperature: 40 ° C
Detection conditions: RI: Polarity (+), Response (0.5 sec)
Sample concentration: Approximately 5 mg / mL
Molecular weight standard product: PEG (polyethylene glycol)

<Acid value>
The measurement was performed according to JIS K 5601-2-1.

(Synthesis Example 1)
In a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a nitrogen introduction tube, 40.00 g of 1,2-bis (2-methoxyethoxy) ethane (methyltriglime) and 20.62 g of norbornene diisocyanate as a solvent for polymerization ( 0.100 mol) was charged and heated to 80 ° C. with stirring under a nitrogen stream to dissolve it. In this solution, polycarbonate diol (manufactured by Asahi Kasei Co., Ltd., trade name: PCDL T5652, weight average molecular weight 2000): 50.00 g (0.025 mol), 2,2-bis (hydroxymethyl) butanoic acid: 3.70 g ( 0.025 mol) and 2-hydroxyethyl methacrylate: 13.02 g (0.100 mol) dissolved in methyl triglime: 40.00 g were added over 1 hour. This solution was heated and stirred at 80 ° C. for 5 hours to obtain a solution of a urethane polymer (a1) containing a carboxy group in the molecule and having a methacryloyl group at the terminal. The solid content concentration of the solution was 52%, the weight average molecular weight of the polymer was 8,600, and the acid value was 18 mgKOH / g.

(Synthesis Example 2)
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a nitrogen introduction tube was charged with 100.0 g of methyl triglime as a solvent for polymerization, and the temperature was raised to 80 ° C. while stirring under a nitrogen stream. To this, 12.0 g (0.14 mol) of methacrylic acid, 28.0 g (0.16 mol) of benzyl methacrylate and 60.0 g (0.42 mol) of butyl methacrylate, which were premixed at room temperature, were added. And 0.5 g of azobisisobutyronitrile as a radical polymerization initiator was added dropwise from a dropping funnel over 3 hours while keeping the temperature at 80 ° C. After completion of the dropping, the reaction solution was heated to 90 ° C. while stirring, and the reaction solution was stirred for another 2 hours while maintaining the temperature at 90 ° C. to obtain a solution of an acrylic polymer (a2) containing a carboxy group in the molecule. Got The solid content concentration of the solution was 50%, the weight average molecular weight of the polymer was 48,000, and the acid value was 78 mgKOH / g.

[Preparation of resin composition]
The compositions having the formulations shown in Table 1 (unit: parts by weight) were dissolved in methyl triglime, stirred by a stirrer, and then dispersed by a three-roll mill. Then, defoaming was performed with a defoaming device to prepare a uniform solution. The amount of methyl triglime as a solvent (the total amount of the solvent including the solvent contained in the polymer solution of the above synthesis example) was 30 parts by weight. In addition to the components shown in Table 1, each resin composition contains 1.0 part by weight of a photopolymerization initiator (etanone, 1- [9-ethyl-6- (2-methylbenzoyl) -9H-carbazole-3). -Il]-, 1- (o-acetyloxime; "Irgacure OXE02" manufactured by BASF) and 0.1 parts by weight of a butadiene defoamer ("Floren AC-2000" manufactured by Kyoeisha Chemical Co., Ltd.) were added.

[Formation and evaluation of cured film]
<Formation of cured film on polyimide film>
The resin composition was applied onto a polyimide film having a thickness of 25 μm (“Apical 25 NPI” manufactured by Kaneka Corporation) by screen printing so that the final dry thickness was 20 μm, dried at 80 ° C. for 20 minutes, and then 100 mJ / cm ² . The film was exposed by irradiating the integrated exposure amount of ultraviolet rays. Then, a 1.0 wt% sodium carbonate aqueous solution at 30 ° C. was sprayed at a discharge pressure of ^{1.0 kgf / mm 2 for 60 seconds for development.} After development, it was thoroughly washed with pure water and then heated in an oven at 140 ° C. for 60 minutes to form a cured film (after development) on the polyimide film.

In the same manner as above, the resin composition is applied onto the polyimide film, dried and exposed, and then heated in an oven at 140 ° C. for 60 minutes without development to form a cured film (development) on the polyimide film. Previous) was formed.

<Flame retardant>
Using a polyimide film on which a cured film (before and after development) was formed as a sample, a flame retardancy test was conducted as follows according to the flame retardancy UL94 standard.
A polyimide film with a cured film is cut into a width of 50 mm and a length of 200 mm, a marked line is placed in the central part (125 mm portion) in the length direction, and the film is rolled into a cylinder so that the cured film side is on the outside. A tape was attached to the upper overlapping portion (75 mm in the length direction) and the upper portion so that there was no gap, and a cylinder for flame retardancy test was prepared.

Clamp the top of the sample to fix it vertically, bring the burner flame close to the bottom of the sample for 3 seconds, ignite it, move the burner flame away after 3 seconds, and measure how many seconds the sample flame or combustion disappears. bottom. This test was repeated twice for each sample, and the flame and combustion stopped within 10 seconds after the burner flame was moved away from the sample, and the flame self-extinguished without reaching the marked line is OK, 2 Those that did not extinguish the fire within 10 seconds in any one of the times, or those in which the flame rose to the marked line and burned were regarded as NG. Five samples were tested and evaluated according to the following criteria.
A: All 5 were OK B: 1 to 4 out of 5 were OK C: All 5 were NG

<Adhesion>
Using the polyimide film on which the cured film (before and after development) was formed as a sample, the adhesion of the cured film was evaluated according to the grid tape method of JIS K5400. The tape peeling test was repeated 5 times for one sample, and the evaluation was performed according to the following criteria from the residual area ratio (residual film ratio) of the cured film in the sample after the test.
A: No peeling was observed (remaining area ratio 100%)
B: Peeling was observed, but the residual area ratio was 95% or more C: Residual area ratio was 80% or more and less than 95 D: Residual area ratio was less than 80%

The polyimide film on which the cured film (after development) was formed was cut into a size of 5 mm × 100 mm, bent 180 ° so that the cured film was on the outside, and a load of 100 g was placed on the bent portion for 3 seconds. After removing the load, the bent portion was observed with an optical microscope to evaluate the presence or absence of cracks. This work was carried out until the cured film cracked, and evaluated according to the following criteria.
A: No cracks occurred even after 10 bends B: Cracks occurred after 2 or more and 9 or less bends C: Cracks occurred after 1 bend

<Tackiness>
In the same manner as described above, the resin composition was applied onto the polyimide film and dried at 80 ° C. for 20 minutes to prepare a polyimide film on which a coating film (B stage film) was formed. The two films were overlapped so that the coating films were in contact with each other, and the state when the two films were peeled off was observed and evaluated according to the following criteria.
A: No sticking between the coating films and no sticking marks left on the coating film B: Marks left after the coating films were stuck and peeled off, or the coating films were completely stuck to each other What could not be peeled off

<Bleed out>
A copper foil of a flexible copper-clad laminate in which a polyimide film with a thickness of 25 μm (“Apical 25 NPI” manufactured by Kaneka) and an electrolytic copper foil with a thickness of 12 μm are laminated with a polyimide adhesive is formed into a comb shape with a line width / space width = 100 μm / 100 μm. The pattern was etched and immersed in a 10% by volume sulfuric acid aqueous solution for 1 minute to surface-treat the copper foil, and then washed with pure water to prepare a flexible printed wiring board. A fat composition is applied to the wiring forming surface of this flexible printed wiring board by screen printing so that the final dry thickness is 20 μm, and the cured film is dried, exposed, developed, washed and heated in the same manner as described above. A flexible printed wiring board with was obtained. The wiring terminal of this sample was connected to a power source, a DC current of 100 V was applied for 1000 hours in an environmental tester at 85 ° C. and 85% RH, and then the sample was visually observed and evaluated according to the following criteria.
A: No abnormality such as swelling or exudation on the surface of the test piece and copper wiring B: Abnormality such as swelling or exudation on the surface of the test piece and / or copper wiring

[Evaluation results]
The composition of the resin compositions of Examples and Comparative Examples (formulation and P atom content with respect to the total solid content) and the evaluation results are listed in Table 1. The shaded items in Table 1 have not been evaluated. Details of each component are as shown below.

<1> Mitsubishi Chemical "jER828US"; bisphenol A type epoxy resin (average molecular weight 370, epoxy equivalent 190)
<2> Hitachi Kasei "Funkril FA-321M"; EO-modified bisphenol A dimethacrylate (average molecular weight 804)
<3> Teijin "Fireguard FCX-210"; Spirocyclic diphosphonate flame retardant <4> Clariant "Exolit OP-935"; Phosphate metal salt flame retardant <5> Otsuka Chemical "SPB-100L" Phosphazen flame retardant <6> Navaltec "APYRAL AOH60"; Aluminum hydroxide flame retardant <7> Oyagi Chemical Industry "CR-733S"; Phosphate ester flame retardant <8> Blue pigment below, orange Black pigment in which pigment and purple pigment are mixed at a weight ratio of 1: 1: 1. Blue pigment: Made by BASF Pigment Blue 15: 4
Orange Pigment: Clariant Pigment Orange 43
Purple Pigment: Clariant Pigment Violet 19

In Reference Example 1 and Reference Example 2 to which no flame retardant was added, the breakage resistance was good, but the flame retardancy was insufficient. No improvement in flame retardancy was observed in Comparative Example 4 using a phosphazene-based flame retardant, Comparative Example 5 using an aluminum hydroxide-based flame retardant, and Comparative Example 6 using a phosphoric acid ester-based flame retardant. Further, in Comparative Example 4 and Comparative Example 6 in which the liquid flame retardant was used, the tackiness was deteriorated.

In Comparative Examples 1 to 3 using the metal salt-based phosphinic acid flame retardant, the flame retardant is inferior when the amount of the flame retardant used is small, and the breakage resistance tends to decrease when the amount of the flame retardant added is increased. Was seen. Further, in these comparative examples, flame retardancy and adhesion tended to decrease after alkaline development. This is considered to be due to the elution and desorption of the flame retardant due to alkaline development.

Examples 1 and 2 using the spiro ring diphosphonate flame retardant were excellent in flame retardancy. Further, from the comparison between Example 1 and Comparative Examples 1 to 6, it can be seen that the flame retardant of the spiro ring diphosphonate-based flame retardant is improved by adding a small amount. It is considered that this is because the radical trap mechanism of the flame retardant acted effectively on the free radicals generated at the start of combustion.

In Examples 1 and 2, the cured film showed high adhesion, and the adhesion and heat resistance did not decrease even after alkaline development. Further, in Examples 1 and 2, the same good break resistance as in Reference Example 1 containing no flame retardant was exhibited, and the break resistance did not decrease due to the addition of the flame retardant.

In Comparative Examples 7 and 8 in which an acrylic polymer was used as the binder resin and a spiro ring diphosphonate flame retardant was added, the flame retardancy, adhesion, and tackiness were good as in Examples 1 and 2. However, in Comparative Examples 7 and 8, the breakage resistance decreased as the amount of the flame retardant added increased.

From the above results, when a spiro ring diphosphonate flame retardant is added to a resin composition containing a urethane binder, it is specifically cured with excellent flame retardancy and adhesion, and also with excellent flexibility. It can be seen that a film can be formed.

Claims (14)

A curable resin composition containing (a) a binder resin, (b) a thermosetting resin, and (c) a flame retardant.
The binder resin (a) is a polymer having a urethane bond in the molecule.
The resin composition in which the flame retardant (c) is an organic phosphorus compound represented by the following general formula:

In the formula, R ² and R ⁵ are independently a phenyl group which may have a substituent, a naphthyl group which may have a substituent, or an anthryl group which may have a substituent; R ¹ , R ³ , R ⁴ and R ⁶ each independently have a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group which may have a substituent, and a naphthyl group which may have a substituent. , Or an anthryl group which may have a substituent. The resin composition according to claim 1, wherein the binder resin (a) has a carboxy group in the molecule. The resin composition according to claim 2, wherein the acid value of the binder resin (a) is 5 to 200 mgKOH / g. The resin composition according to any one of claims 1 to 3, wherein the binder resin (a) has an ethylenically unsaturated group in the molecule. The resin composition according to any one of claims 1 to 4, further comprising (d) a compound having an ethylenically unsaturated group. The resin composition according to claim 4 or 5, further comprising (e) a photopolymerization initiator. The resin composition according to any one of claims 1 to 6, further comprising (f) a colorant. The resin composition according to any one of claims 1 to 7, wherein the thermosetting resin (b) is a polyfunctional epoxy resin. The resin composition according to any one of claims 1 to 8, wherein the content of the flame retardant (c) with respect to 100 parts by weight of the total solid content is 10 to 30 parts by weight. A cured film made of a cured product of the resin composition according to any one of claims 1 to 9. A printed wiring board with a cured film provided with the cured film according to claim 10 on the printed wiring board. The printed wiring board with a cured film according to claim 11, wherein the printed wiring board has flexibility. The resin composition according to any one of claims 1 to 9 is applied to a metal wiring forming surface of a printed wiring board to form a coating film.
A method for manufacturing a printed wiring board with a cured film, which is cured by heating and / or exposing the coating film. The resin composition according to any one of claims 1 to 9 is applied to a metal wiring forming surface of a printed wiring board to form a coating film.
At least a part of the surface of the coating film is irradiated with active light to cure the light.
A patterned cured film is formed by developing with an alkali and dissolving and removing the uncured coating film.
A method for manufacturing a printed wiring board with a cured film.