JP2018115297A - Inkjet curable composition, cured product, and printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet curable composition wherein, when a coating for solder resist or symbol marking is formed by inkjet printing and then cured, its surface curability is excellent, and the adhesion is also excellent.SOLUTION: An inkjet curable composition has (A) a photopolymerizable monofunctional monomer having a cyclic skeleton, (B) a photopolymerizable bifunctional monomer with a viscosity at 25°C of 100 mPa s or less, (C) a photopolymerizable polyfunctional monomer having three or more functional groups with a viscosity at 25°C of 500 mPa s or less, and (D) a photopolymerization initiator.SELECTED DRAWING: None

Description

  The present invention relates to an inkjet curable composition suitable for forming, for example, a solder resist or symbol marking of a printed wiring board by an inkjet printing method, a cured product using the same, and a printed wiring board.

The ink jet printing method is a method in which a droplet of a photocurable composition is ejected onto a substrate using an ink jet printer and then irradiated with an active energy ray such as UV to be immediately cured. The inkjet printing method can draw a specified printing pattern directly from digital data, can reduce the amount of ink used, and does not require a screen printing plate, enabling more efficient production than conventional methods. It is. Moreover, since the inkjet printing method is non-contact printing, it can be easily printed on a substrate with unevenness or a substrate having flexibility, and application to a printed wiring board material is expected.
For example, among the printed wiring board materials, the solder resist formed as the outermost protective film can be produced by applying the inkjet printing method, eliminating the need for the exposure and development process in the conventional alkali development type screen printing method. The film is formed by an environmentally friendly method that facilitates line management.
The ink for ink jet printing needs to have a low viscosity compared with the ink for conventional screen printing so that it can be discharged with an ink jet printer, for example, the viscosity at the time of application | coating needs to be 50 mP * s or less. Therefore, there is an ink jet resist composition in which the viscosity of the monomer component is adjusted (Patent Document 1).

Japanese Patent No. 4456833

  Since the conventional curable composition for inkjet is an ink adapted to low viscosity, the dissolution and diffusion of oxygen were fast. In addition, since the ink jet printing method ejects ink as fine droplets, the droplets at the time of ejection have a large specific surface area and oxygen is more easily dissolved. For these reasons, when UV curing after ink jet printing, the ink is susceptible to so-called oxygen inhibition, in which curing is inhibited by oxygen in the air, and thus the cured coating film is likely to have a reduced surface curability. In addition, since the ink contains a large amount of a low-viscosity diluent in order to reduce the viscosity, various properties such as adhesion to the base were liable to deteriorate. Since solder resist and symbol marking for printed wiring boards are particularly important for base adhesion, it has been desired to form a solder resist or symbol marking with high base adhesion using an ink jet printing method.

  The present invention effectively solves the above-mentioned problems, and has a good surface curability when a coating film is formed and cured by an ink jet printing method, and has a good adhesion and a curable composition for ink jet. It is an object to provide a product, a cured product using the product, and a printed wiring board.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a specific type of photopolymerizable monofunctional monomer, a photopolymerizable bifunctional monomer having a specific viscosity or lower, and a trifunctional or higher light having a specific viscosity or lower It discovered that the composition which combined the polymerizable polyfunctional monomer can obtain favorable surface curability and adhesiveness, and obtained the curable composition for inkjet of this invention from there.

  The curable composition for inkjet of the present invention includes (A) a photopolymerizable monofunctional monomer having a cyclic skeleton, (B) a photopolymerizable bifunctional monomer having a viscosity at 25 ° C. of 100 mPa · s or less, and (C). It includes a photopolymerizable polyfunctional monomer having a viscosity at 25 ° C. of 500 mPa · s or less and having a functionality of 3 or more, and (D) a photopolymerization initiator.

The curable composition for inkjet according to the present invention includes (A) a monofunctional monomer having a cyclic hydrocarbon skeleton and a monofunctional monomer having a heterocyclic skeleton as the photopolymerizable monofunctional monomer having the cyclic skeleton (A). It is preferable that two or more monofunctional monomers having the heterocyclic skeleton are included.
Moreover, it is preferable that the said curable composition for inkjet of this invention contains the compound which has a triazine ring further.

  The cured product of the present invention is a cured product of the above-described inkjet curable composition.

  The printed wiring board of this invention has said hardened | cured material.

  The curable composition for inkjet of the present invention is excellent in inkjet printability, and can achieve both good surface curability and good adhesion of a coating film by an inkjet printing method. Further, by irradiating the curable composition for inkjet of the present invention with light, a cured product excellent in various properties such as pencil hardness and plating resistance in addition to surface curability and adhesion can be obtained. Furthermore, the curable composition for inkjet of the present invention is formed on a substrate of a printed wiring board and can be provided as the cured product by light irradiation.

The curable composition for inkjet of the present invention includes (A) a photopolymerizable monofunctional monomer having a cyclic skeleton, (B) a photopolymerizable bifunctional monomer having a viscosity at 25 ° C. of 100 mPa · s or less, and (C). It has a viscosity at 25 ° C. of 500 mPa · s or less and contains a photopolymerizable polyfunctional monomer having 3 or more functional groups and (D) a photopolymerization initiator.
In the present specification, the curable composition for inkjet means a composition for use in a method of printing characters and patterns in a non-contact manner by discharging the curable composition onto a substrate, for example, A composition for printing characters and patterns on a substrate by a printing method using a jet dispenser as well as a printing method such as a piezo method, a thermal method or an electrostatic method is also included.

[(A) Photopolymerizable monofunctional monomer having a cyclic skeleton]
The curable composition for inkjet of the present invention includes a photopolymerizable monofunctional monomer having a cyclic skeleton. The photopolymerizable monofunctional monomer having a cyclic skeleton reduces the viscosity of the curable composition for inkjet of the present invention as a diluent. In addition, the coating film hardness, particularly the pencil hardness, is improved while maintaining the adhesion of the cured product of the curable composition for inkjet of the present invention. The photopolymerizable monofunctional monomer having a cyclic skeleton can improve adhesion and surface curability as compared with a photopolymerizable monofunctional monomer having no cyclic skeleton, such as butyl acrylate. Therefore, by including a photopolymerizable monofunctional monomer having a cyclic skeleton, adhesion and surface curability superior to conventional ones can be obtained.

  Examples of the photopolymerizable monofunctional monomer having a cyclic skeleton include isobonyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, glycidyl (meth) acrylate, γ-butyrolactone (meth) acrylate, γ-butyrolactone (meth) acrylate, and the like. Examples include (meth) acrylates and (meth) acryloyl such as acryloylmorpholine. In the present specification, “(meth) acrylate” is a generic term for acrylate and methacrylate, and “(meth) acryloyl” is a generic term for acryloyl and methacryloyl.

(A) The photopolymerizable monofunctional monomer having a cyclic skeleton includes a monofunctional monomer having a cyclic hydrocarbon skeleton such as isobornyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, glycidyl (meth) acrylate, and γ-butyrolactone. It is preferable to use in combination with a monofunctional monomer having a heterocyclic skeleton such as (meth) acrylate or (meth) acryloylmorpholine. By including a monofunctional monomer having a cyclic hydrocarbon skeleton, excellent adhesion can be obtained. A monofunctional monomer having a heterocyclic skeleton is less susceptible to oxygen inhibition than a monofunctional monomer having a cyclic hydrocarbon skeleton, and therefore excellent surface curability can be obtained by including the monofunctional monomer having the heterocyclic skeleton. . Therefore, by using a monofunctional monomer having a cyclic hydrocarbon skeleton and a monofunctional monomer having a heterocyclic skeleton in combination, excellent adhesion and excellent surface curability can be achieved at a higher level.
In this case, the monofunctional monomer having a heterocyclic skeleton can be used in combination of two or more types to further improve the adhesion and excellent surface curability according to the characteristics of each monofunctional monomer. It is preferable because both levels can be achieved.

(A) As for the compounding quantity of the photopolymerizable monofunctional monomer which has cyclic skeleton, 10-80 mass parts is preferable in 100 mass parts of curable compositions of this invention. By including 10 parts by mass or more, adhesion and surface curability are improved. Moreover, by including in 80 mass parts or less, the fall of the crosslinking density in hardened | cured material can be prevented, and a coating-film characteristic becomes favorable.
Moreover, when it contains the monofunctional monomer which has cyclic hydrocarbon skeleton, and the monofunctional monomer which has heterocyclic skeleton, the monofunctional monomer which has heterocyclic skeleton with respect to 100 mass parts of monofunctional monomers which have cyclic hydrocarbon skeleton The blending ratio is preferably 12.5 to 600 parts by mass.
Since the curable composition of this invention is used for the inkjet method, it is preferable that it is sufficiently low viscosity, for example, 50 mPa * s or less at 50 degreeC. In the present specification, the viscosity is a value measured according to JIS K2283.

[(B) Photopolymerizable bifunctional monomer having a viscosity at 25 ° C. of 100 mPa · s or less]
The curable composition for inkjet according to the present invention contains a photopolymerizable bifunctional monomer having a viscosity at 25 ° C. of 100 mPa · s or less. Since the photopolymerizable bifunctional monomer is less reactive than the trifunctional or higher polyfunctional monomer described later, the photopolymerizable bifunctional monomer is used in combination with the monofunctional monomer as a diluent for the trifunctional or higher polyfunctional monomer. The viscosity of the curable composition is lowered and the surface curability is improved because the reactivity is higher than that of the monofunctional monomer. However, when the viscosity of the photopolymerizable bifunctional monomer is high, the viscosity of the curable composition for inkjet is increased. By setting the viscosity at 25 ° C. of the photopolymerizable bifunctional monomer to 100 mPa · s or less, the handleability as a diluent of the bifunctional (meth) acrylate compound is improved, and each component can be mixed uniformly. As a result, it can be expected that the entire surface of the coating film adheres uniformly to the substrate. The viscosity at 25 ° C. of the photopolymerizable bifunctional monomer is preferably 1 to 100 mPa · s, and particularly preferably 3 to 30 mPa · s.

Examples of the photopolymerizable bifunctional monomer having a viscosity at 25 ° C. of 100 mPa · s or less include 2-hydroxy-3-acryloyloxypropyl (meth) acrylate, hydroxypivalylhydroxypivalate di (meth) acrylate, 1,3 -Butylene glycol di (meth) acrylate), 2, methyl-1,3-butylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, 3, methyl-1,5-pentanediol di (meth) acrylate, ethoxylated 1,6-hexanediol di ( (Meth) acrylate, neopentyl glycol di (meth) acryl Propoxylated neopentyl glycol di (meth) acrylate, polyethylene glycol # 200 di (meth) acrylate, polyethylene glycol # 400 di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) Acrylate, polypropylene glycol # 400 di (meth) acrylate, polypropylene glycol (# 700) di (meth) acrylate, 1,10-decanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1, 9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, glycerin di (meth) acrylate, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate Triethylene glycol di (meth) acrylate, polyethylene glycol # 200 di (meth) acrylate, polyethylene glycol # 400 di (meth) acrylate, polyethylene glycol # 600 di (meth) acrylate, polyethylene glycol # 1000 di (meth) acrylate, ethoxy Polypropylene glycol # 700 di (meth) acrylate, polypropylene glycol # 400 di (meth) acrylate, and the like. These 1 type (s) or 2 or more types can be used.
(B) As for the compounding quantity of the photopolymerizable bifunctional monomer whose viscosity in 25 degreeC is 100 mPa * s or less, 10-80 mass parts is preferable in 100 mass parts of curable compositions of this invention. By containing it in 10 parts by mass or more, the curable composition can have a sufficiently low viscosity, for example, 50 mPa · s or less at 50 ° C. By including it at 80 parts by mass or less, adhesion and surface curability are improved.

[(C) Trifunctional or higher photopolymerizable polyfunctional monomer having a viscosity at 25 ° C. of 500 mPa · s or less]
The inkjet curable composition of the present invention has a viscosity at 25 ° C. of 500 mPa · s or less and contains a photopolymerizable polyfunctional monomer having three or more functions. A trifunctional or higher functional photopolymerizable polyfunctional monomer is highly reactive and improves surface curability. However, when the viscosity of the photopolymerizable polyfunctional monomer having three or more functions is high, the viscosity of the curable composition for inkjet is increased. By setting the viscosity at 25 ° C. of the photopolymerizable polyfunctional monomer of 3 or more functions to 500 mPa · s or less, in combination with the photopolymerizable monofunctional monomer and the photopolymerizable bifunctional monomer of other components, It can be easily discharged. The viscosity at 25 ° C. of the tri- or higher functional photopolymerizable polyfunctional monomer is, for example, 10 to 500 mPa · s, and preferably 30 to 100 mPa · s.

A trifunctional or higher functional photopolymerizable polyfunctional monomer having a viscosity at 25 ° C. of 500 mPa · s or less is, for example, as a trifunctional photopolymerizable polyfunctional monomer,
Ethoxylated trimethylolpropane triacrylate (TMP3EOTA, TMP9EOTA),
Propoxylated trimethylolpropane triacrylate (TMP3POTA),
Modified trimethylolpropane triacrylate and alkylene oxide such as propoxylated glyceryl triacrylate (G3POTA, G3.5POTA);
Trimethylolpropane trimethacrylate and alkylene oxide modified products such as ethoxylated trimethylolpropane trimethacrylate (TMP3EOTMA, TMP9EOTMA);
Pentaerythritol tri (meth) acrylate;
As tetrafunctional photopolymerizable polyfunctional monomer, pentaerythritol tetra (meth) acrylate, ethoxylated pentaerythritol tetra (meth) acrylate (EO35mol)
And one or more of these can be used.
(C) The blending amount of the photopolymerizable polyfunctional monomer having a viscosity at 25 ° C. of 500 mPa · s or less and having 3 or more functional groups is preferably 20 to 50 parts by mass in 100 parts by mass of the curable composition of the present invention. By including it at 20 parts by mass or more, the surface curability of the curable composition becomes sufficiently high, and by including it at 50 parts by mass or less, the viscosity becomes good.

[(D) Photopolymerization initiator]
The curable composition for inkjet of the present invention contains a photopolymerization initiator.

Specific examples of the photopolymerization initiator include benzoin and benzoin alkyl ethers such as benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin isopropyl ether; acetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2 -Acetophenones such as diethoxy-2-phenylacetophenone and 1,1-dichloroacetophenone; 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2-benzyl-2-dimethyl Amino-1- (4-morpholinophenyl) -butan-1-one, 2- (dimethylamino) -2-[(4-methylphenyl) methyl] -1- [4- (4-morpholinyl) phenyl] -1 -Amino acids such as butanone and N, N-dimethylaminoacetophenone Acetophenones; anthraquinones such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 1-chloroanthraquinone; 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2, Thioxanthones such as 4-diisopropylthioxanthone; Ketals such as acetophenone dimethyl ketal and benzyl dimethyl ketal; 2,4,5-triarylimidazole dimer; Riboflavin tetrabutyrate; 2-mercaptobenzimidazole, 2-mercaptobenzoxazole Thiol compounds such as 2-mercaptobenzothiazole; 2,4,6-tris-s-triazine, 2,2,2-tribromoethanol, tribromomethylphenylsulfone, etc. Machine halogen compounds; benzophenone, 4,4'-benzophenone or xanthone such as bisdiethylaminobenzophenone; 2,4,6-trimethylbenzoyl phosphine oxide such as diphenylphosphine oxide, and the like.
One kind of the photopolymerization initiator may be used, or two or more kinds thereof may be used in combination.
(D) As for the mixture ratio of a photoinitiator, the range of 1-15 mass parts is preferable in 100 mass parts of curable compositions.

The inkjet curable composition of the present invention may contain a compound having a triazine ring. Examples of the compound having a triazine ring include known and commonly used compounds, such as guanamine, acetoguanamine, benzoguanamine, and melamine. The compounds having a triazine ring can be used alone or as a mixture of two or more. By blending a compound having a triazine ring, the coating film of the curable composition is given hardness, pencil hardness is improved, and a balance with adhesion is obtained.
Among them, from the viewpoint of improving pencil hardness, a compound having a triazine ring having at least one of an amino group and an unsaturated double bond is preferable. Specific examples of such a compound having a triazine ring include guanamine, acetoguanamine. , Benzoguanamine, melamine, 2,4-diamino-6-vinyl-S-triazine (VT manufactured by Shikoku Chemicals), 2,4-diamino-6-methacryloyloxyethyl-S-triazine (MAVT manufactured by Shikoku Chemicals), 2 , 4-diamino-6-vinyl-S-triazine isocyanuric acid adduct (VT-OK manufactured by Shikoku Chemicals) and the like. In particular, the adhesion is further improved by containing melamine.
The compounding ratio of the compound having a triazine ring is preferably in the range of 1 to 10 parts by mass in 100 parts by mass of the curable composition.

[Colorant]
The ink-jet curable composition of the present invention contains a known and commonly used colorant such as phthalocyanine blue, phthalocyanine green, iodine green, disazo yellow, crystal violet, titanium oxide, carbon black, naphthalene black and the like. Can be included.
Such colorants may be used alone or in admixture of two or more, and the blending amount is 0.1 to 30 parts by weight with respect to 100 parts by weight of the nonvolatile content of the curable composition for inkjet. Yes, preferably 0.5 to 2 parts by mass. Visibility improves that the compounding quantity of a coloring material is 0.1 mass part or more, and the photocurability of a coating-film lower part improves that it is 30 mass parts or less.

  When a white pigment is included as a colorant, titanium oxide, zinc oxide, magnesium oxide, zirconium oxide, aluminum oxide, barium sulfate, silica, talc, mica, aluminum hydroxide, calcium silicate, aluminum silicate, hollow resin particles, sulfide A known white pigment such as zinc can be used. Among these, titanium oxide is preferable because of its high colorability and reflectance. These white pigments may be used alone or in combination of two or more. The titanium oxide may be a rutile type titanium oxide or an anatase type titanium oxide, but it is preferable to use a rutile type titanium from the viewpoint of colorability, concealability and stability. Anatase-type titanium oxide, which is the same titanium oxide, has higher whiteness compared to rutile-type titanium oxide and is often used as a white pigment. The emitted light may cause discoloration of the resin in the insulating resin composition. In contrast, rutile-type titanium oxide is slightly inferior to anatase-type in whiteness, but has almost no photoactivity, so that the resin is deteriorated by light due to the photoactivity of titanium oxide (yellowing). Is remarkably suppressed and is stable against heat. For this reason, when it is used as a white pigment in the insulating layer of the printed wiring board on which the LED is mounted, a high reflectance can be maintained over a long period of time.

  A well-known thing can be used as a rutile type titanium oxide. There are two types of production methods for rutile titanium oxide, a sulfuric acid method and a chlorine method. In the present invention, those produced by any of the production methods can be suitably used. Here, the sulfuric acid method uses ilmenite ore or titanium slag as a raw material, dissolves this in concentrated sulfuric acid, separates iron as iron sulfate, and hydrolyzes the solution to obtain a hydroxide precipitate. A production method in which rutile titanium oxide is taken out by baking at a high temperature. On the other hand, the chlorine method uses synthetic rutile or natural rutile as a raw material, reacts with chlorine gas and carbon at a high temperature of about 1000 ° C to synthesize titanium tetrachloride, and oxidizes this to extract rutile titanium oxide. Say. Among them, rutile-type titanium oxide produced by the chlorine method is particularly effective in suppressing the deterioration (yellowing) of the resin due to heat, and is more preferably used in the present invention.

The blending amount of the white colorant has a large influence on the absorbance, and is preferably 5 to 50 parts by mass, more preferably 10 to 30 parts by mass, and particularly preferably 20 to 30 parts by mass in 100 parts by mass of the curable composition. . If a white pigment is 5 mass parts or more, the reflectance of a composition will become enough. 50
If it is below mass parts, an excessive increase in the viscosity of the composition and a decrease in printability can be suppressed.

  When a black colorant is included as the colorant, carbon, aniline black, iron oxide, or the like can be used. The compounding amount of the black pigment has a large influence on the absorbance, and is preferably 5 to 50 parts by mass, more preferably 10 to 30 parts by mass, and particularly preferably 20 to 30 parts by mass in 100 parts by mass of the curable composition.

The ink-jet curable composition of the present invention may contain a wetting and dispersing agent. As the wetting and dispersing agent, those having an effect of assisting the dispersion of the pigment can be generally used. Examples of such a wetting and dispersing agent include compounds having a polar group such as a carboxyl group, a hydroxyl group, and an acid ester, polymer compounds such as acid-containing compounds such as phosphate esters, copolymers containing an acid group, and hydroxyl group-containing compounds. Polycarboxylic acid esters, polysiloxanes, salts of long-chain polyaminoamides and acid esters, and the like can be used.
Among these wetting and dispersing agents, those having an acid value are preferable because they are more effective for dispersing inorganic pigments such as titanium oxide.
Specific examples of the wetting and dispersing agent having an acid value include Anti-Terra-U, Anti-Terra-U100, Anti-Terra-204, Anti-Terra-205, Disperbyk-101, Disperbyk-102, Disperbyk-106, Disperbyk. -110, Disperbyk-111, Disperbyk-130, Disperbyk-140, Disperbyk-142, Disperbyk-145, Disperbyk-170, Disperbyk-171, Disperbyk-174, Disperbyk-180, Disperkk180, Disperk20 , Disperbyk-2096, BYK-P104, BYK P104S, BYK-P105, BYK-9076, BYK-220S (manufactured by both by BYK Chemie), and the like.
The acid value of the wet dispersant having these acid values is preferably 10 to 300 mgKOH / g.
The amount of the wet dispersant is preferably 5 to 75 parts by mass with respect to 100 parts by mass of the colorant.

  The curable composition for inkjet of the present invention can contain a surface tension adjusting agent. The compounding amount of the surface tension modifier is preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the composition.

  In addition to the above components, the curable composition for inkjet of the present invention includes a surfactant, a matting agent, a polyester resin for adjusting the film properties, a polyurethane resin, a vinyl resin, an acrylic resin, as necessary. At least one kind of antifoaming agent and leveling agent such as resin, rubber-based resin, wax, silicone-based, fluorine-based, and polymer-based, adhesion-imparting agent such as imidazole-based, thiazole-based, triazole-based, and silane coupling agent The known and conventional additives such as can be blended.

  Since the curable composition having the above components is applied to an inkjet method, the viscosity of the curable composition at 50 ° C. is preferably 5 to 50 mPa · s, and preferably 5 to 20 mPa · s. More preferred. As a result, smooth printing can be performed without applying an unnecessary load to the inkjet printer.

  The viscosity of a curable composition means the viscosity measured at normal temperature (25 degreeC) or 50 degreeC according to JISK2283. If the viscosity at room temperature is 150 mPa · s or less, or the viscosity at 50 ° C. is 5 to 50 mPa · s, good printing by the ink jet printing method is possible.

Moreover, it is preferable that the largest particle size of the particle | grains contained in a curable composition is 0.1-5 micrometers or less, and it is more preferable that it is 0.1-1 micrometer. If the maximum particle size is 0.1 μm or more, the cohesive force of the particles will not be too high, and if it is 5 μm or less, the possibility of problems such as nozzle clogging during ink jet printing is reduced, which is preferable. .
The maximum particle size of the particles contained in the composition can be measured with a particle size distribution meter, and the D100 value is taken as the maximum particle size.

<Hardened product>
The curable composition of the present invention can form a cured product by light irradiation with a light source for light irradiation after coating on a substrate by an ink jet method.

Light irradiation is performed by irradiation with ultraviolet rays or active energy rays, but ultraviolet rays are preferred. As a light source for light irradiation, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a xenon lamp, a metal halide lamp, an LED (light emitting diode) UV lamp, or the like is suitable. Examples of the wavelength of the light source include 365 nm, 385 nm, 395 nm, and 405 nm, but better surface curability can be expected by using a short wavelength light source.
In addition, electron beams, α rays, β rays, γ rays, X rays, neutron rays, and the like can also be used.

  Further, if necessary, it is cured by heating after light irradiation. Here, the heating temperature is, for example, 80 to 200 ° C. By setting this heating temperature range, it can be sufficiently cured. The heating time is, for example, 10 to 100 minutes.

<Printed wiring board>
A printed wiring board has the hardened | cured material of the curable composition for inkjet, and specifically has a hardened | cured material which consists of a curable composition on the base material which has a circuit pattern. The printed wiring board can be manufactured by the following method.

  First, the curable composition is adjusted to a viscosity suitable for the coating method with an organic solvent as necessary, and is applied on a circuit-formed substrate by an inkjet method to form a cured product having a pattern. Here, when a curable composition contains a photobase generator, it is preferable to heat hardened | cured material after the light irradiation for hardening. The heating temperature is, for example, 80 to 200 ° C.

When the curable composition of the present invention is applied as an ink for an ink jet system by the above composition, it can be printed on a flexible wiring board in a roll-to-roll system. In addition, the curable composition of the present invention is excellent in surface curability and adhesion to a printed wiring board including, for example, a plastic base material mainly composed of polyimide and the like, and a conductor circuit provided thereon, Moreover, it is possible to form a cured pattern coating film having excellent characteristics such as solder heat resistance, chemical resistance, solvent resistance, pencil hardness, and electroless gold plating resistance.
Although the curable composition is suitable as a material for forming a cured product of a printed wiring board, it is particularly suitable as a material for forming a permanent film of a printed wiring board. Among them, a solder resist, a symbol marking formed on the solder resist, etc. It is suitable as a material for forming a permanent insulating film.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated concretely, this invention is not limited only to these Examples. In the following description, “part” means part by mass unless otherwise specified.

  A monofunctional monomer, a bifunctional monomer, a trifunctional or higher polyfunctional monomer, a photopolymerization initiator, and an additive shown in Table 1 were prepared.

  Each component in Table 1 was appropriately mixed with a stirrer using appropriate components to prepare a curable composition for inkjet. Table 2 shows the components and blending amounts of Examples 1 to 8 and Comparative Examples 1 to 6.

  Using the ink-jet curable compositions of Examples 1 to 8 and Comparative Examples 1 to 6 shown in Table 2, the substrate was drawn on an ink-jet printer under the following conditions, and then UV-cured to prepare a test substrate. . In addition, the copper clad laminated board for printed wiring boards (FR-4, 150 mm x 95 mm x 1.6 mm) was used as a base material.

<Drawing conditions by inkjet printer>
・ Film thickness: 20μm
・ Equipment: Piezo type inkjet printer (using Fujifilm Global Graphic Systems' material printer DMP-2831 (head temperature 50 ° C.))
<UV curing conditions>
Exposure amount: 1000 mJ / cm ²
・ Wavelength: 385nm

The ink jet ejection properties during ink jet printing, the UV curability of the coating film, the adhesion, the coating film hardness, and the electroless Ni / Au plating resistance were examined. Each evaluation standard is as follows.
(1) Inkjet printability (ejectability)
Droplet can be ejected straight and stably: 〇 Droplet cannot be ejected stably: ×
When the injection was not stable and could not be applied, the subsequent evaluation was not performed.

(2) Surface curability (UV curability)
The surface of the cured product was touched with a finger to evaluate tack (stickiness).
Without tack: ◎
There is tack, but does not transcribe: ○
There is tack, but some transfer is seen: △
Liquid component remains: ×

(3) Adhesiveness A cross-cut tape peel test based on JIS K 5400: 1990 was carried out on the cured coating film and evaluated.
No peeling: Yes Some peeling: △
With peeling: ×

(4) Pencil hardness (coating film hardness)
Measured according to JIS K 5400.

(5) Resistance to electroless Ni / Au plating Using a commercially available electroless Ni / Au plating bath, electroless nickel gold plating was performed under the conditions of Ni: 0.5 μm, Au: 0.3 μm. The surface state was observed, and whitening was determined according to the following evaluation criteria.
No whitening / blowing: 〇 Slight surface whitening: △
Surface whitening and swelling: ×
Moreover, the adhesiveness of the cured coating film after electroless Ni / Au plating was subjected to a cross-cut tape peel ring test based on JIS K 5400: 1990, and the adhesion was evaluated according to the following criteria.
No peeling: Yes Some peeling: △
With peeling: ×

The evaluation results of Examples 1 to 8 and Comparative Examples 1 to 6 are also shown in Table 2.
As can be seen from Table 2, Examples 1 to 8 using the composition of the present invention were excellent in ink jet printability, surface curability, adhesion, pencil hardness, and electroless Ni / Au plating resistance. In particular, Examples 2 to 3 including a monofunctional monomer having a cyclic hydrocarbon skeleton and a monofunctional monomer having a heterocyclic skeleton, and containing two types of monofunctional monomers having the heterocyclic skeleton have high pencil hardness. Excellent surface curability was obtained. In particular, Example 3 containing melamine had higher pencil hardness and excellent surface curability.

On the other hand, the comparative example 1 which does not contain the monofunctional monomer which has cyclic hydrocarbon frame | skeleton and contains butyl acrylate was inferior in surface curability, plating tolerance, etc.
Further, Comparative Example 2 which does not include a photopolymerizable bifunctional monomer having a viscosity at 25 ° C. of 100 mPa · s or less has a large amount of the trifunctional monomer and cannot perform ink jet printing.
Further, Comparative Example 3 which does not contain a photopolymerizable bifunctional monomer having a viscosity at 25 ° C. of 100 mPa · s or less has a large amount of monofunctional monomer, and is inferior in surface curability, pencil hardness and the like.
In addition, tricyclodecane dimethanol diacrylate which does not contain a photopolymerizable bifunctional monomer having a viscosity at 25 ° C. of 100 mPa · s or less and is a photopolymerizable bifunctional monomer having a viscosity at 25 ° C. exceeding 100 mPa · s is used instead. Including Comparative Example 4, inkjet printing was not possible.
Further, Comparative Example 5, which does not include a trifunctional or higher functional photopolymerizable polyfunctional monomer having a viscosity at 25 ° C. of 500 mPa · s or less, has a large amount of monofunctional monomer, and has surface curability as compared with Comparative Example 3. The plating resistance was inferior.
Further, it does not include a tri- or higher functional photopolymerizable polyfunctional monomer having a viscosity at 25 ° C. of 500 mPa · s or less. Instead, it is a tri- or higher functional photopolymerizable polyfunctional monomer having a viscosity at 25 ° C. exceeding 500 mPa · s. In Comparative Example 6 containing certain tris (2-hydroxyethyl) isocyanurate triacrylate, inkjet printing was not possible.

(Examples 9 to 11)
Examples 9 to 11 are the same as Example 8 except that each composition was cured with a different light source to prepare a test substrate as shown in Table 3.
As can be seen from Table 3, Examples 9 to 11 using the composition of the present invention were excellent in inkjet printability, surface curability, adhesion, pencil hardness, and electroless Ni / Au plating resistance. In particular, in Example 9 using a light emitting diode (LED) having a wavelength of 365 nm as a light source, the surface curability was good.

  Each component in Table 1 was appropriately mixed with a stirrer using appropriate components to prepare a curable composition for inkjet. Table 2 shows the components and blending amounts of Example 1, Reference Examples 1 to 7, and Comparative Examples 1 to 6.

  Using the ink-jet curable compositions of Example 1, Reference Examples 1 to 7 and Comparative Examples 1 to 6 shown in Table 2, the test substrate was drawn on an ink-jet printer under the following conditions and then UV-cured. Made the material. In addition, the copper clad laminated board for printed wiring boards (FR-4, 150 mm x 95 mm x 1.6 mm) was used as a base material.

The evaluation results of Example 1, Reference Examples 1 to 7, and Comparative Examples 1 to 6 are also shown in Table 2.
As can be seen from Table 2, Example 1 and Reference Examples 1 to 7 using the composition of the present invention are excellent in ink jet printability, surface curability, adhesion, pencil hardness, and electroless Ni / Au plating resistance. It was. Among them, Reference Example 2 and Example 1, which contain a monofunctional monomer having a cyclic hydrocarbon skeleton and a monofunctional monomer having a heterocyclic skeleton, and containing two kinds of monofunctional monomers having the heterocyclic skeleton, have a pencil hardness. And high surface curability was obtained. In particular, Example 1 containing melamine had higher pencil hardness and excellent surface curability.

(Reference Examples 8 to 10)
Reference Examples 8 to 10 are the same as Reference Example 7 except that each composition was cured with a different light source to prepare a test substrate as shown in Table 3.
As can be seen from Table 3, Reference Examples 8 to 10 using the composition of the present invention were excellent in ink jet printability, surface curability, adhesion, pencil hardness, and electroless Ni / Au plating resistance. In particular, in Reference Example 8 using a light emitting diode (LED) having a wavelength of 365 nm as a light source, the surface curability was good.

Claims (6)

  (A) a photopolymerizable monofunctional monomer having a cyclic skeleton, (B) a photopolymerizable bifunctional monomer having a viscosity at 25 ° C. of 100 mPa · s or less, and (C) a viscosity at 25 ° C. of 500 mPa · s or less. A curable composition for inkjet, comprising a photopolymerizable polyfunctional monomer having three or more functions and (D) a photopolymerization initiator.   The curable composition for inkjet according to claim 1, comprising (A) a monofunctional monomer having a cyclic hydrocarbon skeleton and a monofunctional monomer having a heterocyclic skeleton as the photopolymerizable monofunctional monomer having a cyclic skeleton.   The curable composition for inkjet according to claim 2, comprising two or more monofunctional monomers having the heterocyclic skeleton.   Furthermore, the curable composition for inkjet as described in any one of Claims 1-3 containing the compound which has a triazine ring.   Hardened | cured material of the curable composition for inkjet as described in any one of Claims 1-4.   A printed wiring board having a cured product of the curable composition for inkjet according to claim 5.