Inkjet inks for printed circuit boards

Abstract

1. A radiation curable composition comprising at least one polymerizable compound and an adhesion promoter, wherein the adhesion promoter is: - a polymerizable group selected from the group consisting of acrylates, methacrylates, acrylamides, methacrylamides, styrenes, maleimides, vinyl ethers and vinyl esters, and - adhesion-promoting groups containing at least one nitrogen-containing 5- or 6-membered heteroaromatic ring A composition comprising:

Description

[Technical field]

[0001] The present invention relates to radiation curable ink-jet inks for use in the manufacture of printed circuit boards. [Background technology]

[0002] Printed circuit board (PCB) production workflows are gradually transitioning from standard to digital workflows in order to reduce the amount of process steps and to reduce costs and environmental impact, especially for short run production.

[0003] Inkjet printing is the preferred digital manufacturing technique for various steps in the PCB manufacturing process, from etching resist on solder mask to legend printing. The preferred inkjet inks are UV curable inkjet inks.

[0004] In the different manufacturing processes of PCBs, the adhesion of inkjet inks to various substrates is of great importance. When radiation curable inkjet inks are used in the production of solder masks, the adhesion of the cured inkjet inks on several substrates needs to withstand the harsh conditions used during soldering (solder resistance) and ENIG plating (ENIG plating resistance). In particular, the ENIG plating process, where harsh and changing conditions (pH and temperature) are used, is very demanding with regard to the adhesion requirements of the inkjet ink.

[0005] As more mobile devices are used, the demand for flexible PCBs is increasing. Such flexible PCBs typically have thinner copper circuits. The solder mask must adhere well to the copper circuitry, and traditionally, in rigid PCBs, copper pre-treatments, e.g., microetching, are performed to improve adhesion between the circuitry and the solder mask. However, all of these pre-treatments remove copper, thus resulting in thinner copper circuits. As the copper circuitry of flexible PBC becomes thinner, such pretreatment is undesirable as it results in copper circuitry that is too thin.

[0006] As an alternative approach to improve adhesion between copper circuitry and solder mask, the provision of a primer or surface treatment solution has been proposed. US Patent No. 5,399, 636 (Shikoku Chemicals Corp.) discloses a surface treatment solution containing an azole silane compound. US Patent No. 5,399, 636 (Camtek) discloses a surface treatment with an intermediate layer, preferably a monolayer, of molecules that contain polar groups that physically bond to the substrate, e.g., copper, and groups that optimize the surface energy toward the formulation printed on the substrate. However, the provision of such a primer or surface treatment solution requires additional process steps, complicating the manufacturing process and increasing the manufacturing costs and its ecological impact.

[0007] Therefore, there is a need for a radiation curable solder mask inkjet ink that has excellent adhesion to untreated copper under the harsh conditions used during soldering and ENIG plating. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] European Patent Application Publication No. 3018137 [Patent Document 2] International Publication No. 2014 / 111942 Brochure Summary of the Invention

[0009] It is an object of the present invention to provide a radiation curable inkjet ink for use in a method for manufacturing flexible printed circuit boards (PCBs) involving an inkjet printing process, whereby a solder mask having improved solder and ENIG resistance is achieved.

[0010] The object of the present invention is achieved by a radiation curable inkjet ink as defined in claim 1.

[0011] Further objects of the present invention will become apparent from the following description. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] definition For example, the term "monofunctional" in a monofunctional polymerizable compound means that the polymerizable compound contains one polymerizable group.

[0013] For example, the term "difunctional" in a difunctional polymerizable compound means that the polymerizable compound contains two polymerizable groups.

[0014] For example, the term "multifunctional" in a multifunctional polymerizable compound means that the polymerizable compound contains three or more polymerizable groups.

[0015] The term "alkyl" refers to all possible variants for each number of carbon atoms in the alkyl group, namely, methyl, ethyl, in the case of three carbon atoms: n-propyl and isopropyl; in the case of four carbon atoms: n-butyl, isobutyl and tertiary butyl; in the case of five carbon atoms: n-pentyl, 1,1-dimethyl-propyl, 2,2-dimethylpropyl and 2-methyl-butyl, etc.

[0016] Unless otherwise specified, substituted or unsubstituted alkyl groups are preferably C1-C6-alkyl groups.

[0017] Unless otherwise specified, a substituted or unsubstituted alkenyl group is preferably a C2-C6-alkenyl group.

[0018] Unless otherwise specified, a substituted or unsubstituted alkynyl group is preferably a C2-C6 alkynyl group.

[0019] Unless otherwise specified, a substituted or unsubstituted alkaryl group is preferably a phenyl or naphthyl group containing one, two, three or more C1-C6-alkyl groups.

[0020] Unless otherwise specified, the substituted or unsubstituted aralkyl group is preferably a C7-C alkyl group, including a phenyl or naphthyl group. 20 -alkyl group.

[0021] Unless otherwise specified, the substituted or unsubstituted aryl groups are preferably phenyl or naphthyl groups.

[0022] Unless otherwise specified, a substituted or unsubstituted heteroaryl group is preferably a 5- or 6-membered ring substituted with 1, 2 or 3 oxygen, nitrogen, sulfur, selenium atoms, or combinations thereof.

[0023] For example, the term "substituted" in a substituted alkyl group means that the alkyl group may be substituted with atoms other than those normally present in such groups, i.e., carbon and hydrogen. For example, substituted alkyl groups may contain halogen atoms or thiol groups. Unsubstituted alkyl groups contain only carbon and hydrogen atoms.

[0024] Unless otherwise specified, the substituted alkyl, alkenyl, alkynyl, aralkyl, alkaryl, aryl and heteroaryl groups are preferably substituted with one or more moieties selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl and tert-butyl, esters, amides, ethers, thioethers, ketones, aldehydes, sulfoxides, sulfones, sulfonate esters, sulfonamides, -Cl, -Br, -I, -OH, -SH, -CN and -NO2.

[0025] Radiation curable composition The radiation curable composition according to the present invention comprises at least one polymerizable compound and an adhesion promoter as described below.

[0026] The radiation curable composition may further comprise other ingredients such as initiators, adhesion promoters, colorants, polymeric dispersants, polymerization inhibitors, flame retardants, or surfactants.

[0027] The radiation curable composition is preferably a radiation curable ink jet ink.

[0028] The radiation curable inkjet ink may be cured with any type of radiation, but is preferably cured with UV radiation, more preferably UV radiation from a UV LED. Thus, the radiation curable inkjet ink is preferably a UV curable inkjet ink.

[0029] For reliable industrial inkjet printing, the viscosity of the radiation curable inkjet inks is all below 1000s -1 At a shear rate of 100°C, the viscosity is preferably 20 mPa.s or less at 45°C, more preferably 1 to 18 mPa.s at 45°C, and most preferably 4 to 14 mPa.s at 45°C.

[0030] The spray temperature is preferably 10 to 70°C, more preferably 20 to 55°C, and most preferably 25 to 50°C.

[0031] For good image quality and adhesion, the surface tension of the radiation curable inkjet ink is preferably in the range of 18 to 70 mN / m at 25°C, more preferably in the range of 20 to 40 mN / m at 25°C.

[0032] Adhesion promoter The radiation curable inkjet ink comprises an adhesion promoter comprising: - a polymerizable group selected from acrylates, methacrylates, acrylamides, methacrylamides, styrenes, maleimides, vinyl ethers and vinyl esters, and - an adhesion-promoting group which comprises at least one nitrogen-containing 5- or 6-membered heteroaromatic ring.

[0033] The nitrogen of a nitrogen-containing 5- or 6-membered heteroaromatic ring is preferably not covalently bonded to a hydrogen.

[0034] The nitrogen-containing 5- or 6-membered heteroaromatic ring is preferably selected from N-alkylated imidazole, N-alkylated benzimidazole, pyridine, quinoline and isoquinoline, more preferably selected from pyridine and N-alkylated imidazole. Most preferably, the nitrogen-containing 5- or 6-membered heteroaromatic ring is N-alkylated imidazole.

[0035] The nitrogen-containing five- or six-membered heteroaromatic ring preferably has a pKa of the conjugate acid of at least 3.5, more preferably at least 4.5.

[0036] The ethylenically unsaturated bond is preferably selected from the group consisting of acrylates, methacrylates, acrylamides and methacrylamides, more preferably from the group consisting of acrylates and methacrylates. The ethylenically unsaturated bond is most preferably an acrylate.

[0037] The adhesion promoter preferably contains at least two nitrogen-containing five- or six-membered heteroaromatic rings.

[0038] In a preferred embodiment, the adhesion promoter is an oligomeric adhesion promoter.

[0039] In a more preferred embodiment, the adhesion promoter is an oligomeric adhesion promoter according to Formula I. [ka] (In the formula, R1 is selected from the group consisting of hydrogen and a methyl group; X is selected from the group consisting of an oxygen atom, a sulfur atom, and NR2; L1 represents a divalent linking group containing 15 or fewer carbon atoms; L2 represents a divalent linking group containing 8 or fewer carbon atoms; R2 represents a group selected from the group consisting of hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted alkaryl groups, substituted or unsubstituted aralkyl groups, and substituted or unsubstituted aryl or heteroaryl groups; A represents a nitrogen-containing 5- or 6-membered heteroaromatic ring; L2 preferably represents a substituted or unsubstituted alkylene group, more preferably an unsubstituted alkylene group, and most preferably a C1 to C6 unsubstituted alkylene group. X preferably represents an oxygen atom or NR2, more preferably an oxygen atom; R1 preferably represents hydrogen.

[0040] In another preferred embodiment, the adhesion promoter is an adhesion promoter according to Formula II. [ka] (In the formula, R3 is selected from the group consisting of hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted alkaryl groups, substituted or unsubstituted aralkyl groups, and substituted or unsubstituted aryl or heteroaryl groups; R4 and R5 are independently selected from the group consisting of hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted alkaryl groups, substituted or unsubstituted aralkyl groups, and substituted or unsubstituted aryl or heteroaryl groups; R4 and R5 may represent the atoms necessary to form a 5- to 8-membered ring; R6 and R7 are independently selected from the group consisting of hydrogen and a methyl group; Y is selected from the group consisting of an oxygen atom, a sulfur atom, and NR8; R8 is selected from the group consisting of hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted alkaryl groups, substituted or unsubstituted aralkyl groups, and substituted or unsubstituted aryl or heteroaryl groups; L3 represents an n+m valent linking group, provided that n+m is 6 or less; n and m each independently represent an integer of 1 to 5; Y preferably represents an oxygen atom, R4 and R5 are preferably selected from the group consisting of hydrogen and substituted or unsubstituted alkyl groups, more preferably hydrogen; R6, R7 and R8 preferably represent hydrogen, R3 is preferably selected from the group consisting of hydrogen and substituted or unsubstituted alkyl groups, more preferably hydrogen and C1-C6 alkyl groups.

[0041] Exemplary adhesion promoters according to the present invention are shown in Table 1 below. [Table 1-1]

[0042] [Table 1-2]

[0043] The amount of the above mentioned adhesion promoters is preferably 0.1 to 10% by weight, more preferably 0.25 to 5% by weight, and most preferably 0.5 to 2.5% by weight, based on the total weight of the radiation curable composition.

[0044] The radiation curable composition may further comprise an adhesion promoter, such as, for example, acrylic acid or other acid-containing acrylates. Such further adhesion promoters are preferably selected from the monofunctional alkoxysilane compounds and the di- or polyfunctional alkoxysilane compounds described below.

[0045] Further adhesion promoters The radiation curable composition may comprise a further adhesion promoter, preferably selected from the monofunctional alkoxysilane compounds and the di- or polyfunctional alkoxysilane compounds described below.

[0046] Monofunctional alkoxysilane compounds The radiation curable inkjet ink preferably comprises a monofunctional alkoxysilane functionalized with a cyclic ether group selected from the group consisting of epoxides and oxetanes. The cyclic ether is preferably an epoxide.

[0047] Monofunctional alkoxysilanes contain at least one alkoxy group, more preferably at least two alkoxy groups, and most preferably three alkoxy groups.

[0048] The alkoxy group is preferably a C1 to C4 alkoxy group, more preferably a methoxy, ethoxy or isopropoxy group, most preferably a methoxy or ethoxy group.

[0049] Representative examples of monofunctional alkylsilanes functionalized with a cyclic ether group selected from the group consisting of epoxides and oxetanes are shown in Table 2. [Table 2-1]

[0050] [Table 2-2]

[0051] The amount of monofunctional alkoxysilane is preferably 0.1 to 10% by weight, more preferably 0.5 to 7.5% by weight, and most preferably 1 to 5% by weight, based on the total weight of all inkjet inks.

[0052] Di- or polyfunctional alkoxysilane compounds The radiation curable composition preferably comprises a di- or polyfunctional alkoxysilane compound.

[0053] The di- or polyfunctional alkoxysilane preferably has at least two alkoxysilane moieties according to formula III. [ka] (In the formula, L represents a divalent linking group selected from the group consisting of a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkenylene group, a substituted or unsubstituted alkynylene group, and a substituted or unsubstituted arylene group; R represents a group selected from the group consisting of substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted alkaryl groups, substituted or unsubstituted aralkyl groups, and substituted or unsubstituted aryl or heteroaryl groups; L preferably represents a substituted or unsubstituted alkylene group, more preferably an unsubstituted alkylene group, and most preferably a propylene group. R preferably represents a substituted or unsubstituted alkyl group, more preferably an unsubstituted alkyl group, most preferably a C1 to C6 alkyl group, and particularly preferably a methyl or ethyl group.

[0054] Representative examples of di- or polyfunctional alkylsilanes are shown in Table 3. [Table 3-1]

[0055] [Table 3-2]

[0056] Particularly preferably, the di- or polyfunctional alkylsilane is a poly(urethane silane) hybrid crosslinker as disclosed in European Coating Journal, 2014 (7 / 8), 21-25).

[0057] Such compounds are commercially available from Evonik as their VESTANAT® EP-MF product line.

[0058] The amount of di- or polyfunctional alkoxysilane is preferably 0.1 to 10% by weight, more preferably 0.5 to 7.5% by weight, and most preferably 1 to 5% by weight, based on the total weight of all inkjet inks.

[0059] The radiation curable composition may further comprise an adhesion promoter such as acrylic acid or other carboxylate-containing acrylates.

[0060] The total amount of adhesion promoters is preferably 0.1 to 20% by weight, more preferably 0.5 to 15% by weight, and most preferably 1 to 10% by weight, based on the total weight of all inkjet inks.

[0061] Too little may result in insufficient adhesion of the inkjet ink, too much may increase the ink viscosity and the shelf life of the ink may become more critical.

[0062] Photoinitiators The radiation curable inkjet ink preferably includes a photoinitiator, preferably a free radical photoinitiator.

[0063] Free radical photoinitiators are chemical compounds that initiate the polymerization of monomers and oligomers by the formation of free radicals when exposed to actinic radiation. Norrish type I initiators are initiators that cleave after excitation to immediately generate the initiating radical. Norrish type II initiators are photoinitiators that are activated by actinic radiation to form free radicals by hydrogen abstraction from a second compound that becomes the actual initiating free radical. This second compound is called a polymerization synergist or coinitiator. Both type I and type II photoinitiators can be used alone or in combination in the present invention.

[0064] Suitable photoinitiators are disclosed in CRIVELLO, JV, et al. Photoinitiators for Free Radical, Cationic and Anionic Photopolymerization. 2nd edition. Edited by BRADLEY, G.. London, UK: John Wiley and Sons Ltd, 1998. p. 276-293.

[0065] Specific examples of free radical photoinitiators may include, but are not limited to, the following compounds or combinations thereof: benzophenone and substituted benzophenones; 1-hydroxycyclohexyl phenyl ketone; thioxanthones such as isopropylthioxanthone; 2-hydroxy-2-methyl-1-phenylpropan-1-one; 2-benzyl-2-dimethylamino-(4-morpholinophenyl)butan-1-one; benzyl dimethyl ketal; 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one; 2,2-dimethoxy-1,2-diphenylethan-1-one or 5,7-diiodo-3-butoxy-6-fluorone.

[0066] The preferred photoinitiator is an acylphosphine oxide compound. The acylphosphine oxide compound may be selected from the group consisting of mono-acylphosphine oxide and di-acylphosphine oxide. The preferred acylphosphine oxide photoinitiator is diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate (TPO-L), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide) (BAPO), bis(2,6-dimethyl-benzoyl)-2,4,4-trimethylpentylphosphine oxide and 2,4,6-trimethoxybenzoyl-diphenylphosphine oxide.

[0067] Other preferred photoinitiators are α-hydroxy-ketone Type I photoinitiators such as, for example, oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl-phenyl]propanone], available as Esacure® KIP IT from IGM resins.

[0068] Preferred amounts of photoinitiator are from 0.2 to 20 wt.%, more preferably from 0.5 to 10 wt.%, most preferably from 1 to 8 wt.%, and especially preferably from 1.5 to 6 wt.%, all based on the total weight of the radiation curable inkjet ink.

[0069] To further enhance photosensitivity, the radiation curable inkjet ink may further comprise a coinitiator. Suitable examples of coinitiators can be divided into three groups: (1) Tertiary aliphatic amines such as methyldiethanolamine, dimethylethanolamine, triethanolamine, triethylamine, and methylmorpholine; (2) Aromatic amines such as amyl paradimethyl-aminobenzoate, 2-n-butoxyethyl-4-(dimethylamino)benzoate, 2-(dimethylamino)-ethyl benzoate, ethyl-4-(dimethyl-amino)benzoate, and 2-ethylhexyl-4-(dimethylamino)benzoate; and (3) (meth)acrylated amines such as dialkylaminoalkyl(meth)acrylates (e.g., diethyl-aminoethyl acrylate) or N-morpholinoalkyl-(meth)acrylates (e.g., N-morpholinoethyl-acrylate).

[0070] Preferred coinitiators are aminobenzoates.

[0071] A preferred small molecule aminobenzoate is Genocure® EPD from RAHN.

[0072] Particularly preferably, the aminobenzoate coinitiator is selected from the group consisting of polymerizable, oligomeric and polymeric aminobenzoate coinitiators.

[0073] Polymerizable coinitiators are disclosed in EP 2033949 (Agfa Graphics NV).

[0074] In a more preferred embodiment, the aminobenzoate coinitiator is an oligomeric aminobenzoate derivative.

[0075] Particularly preferably, the aminobenzoate is a polyether derivative of aminobenzoate, where the polyether is selected from the group consisting of poly(ethylene oxide), poly(propylene oxide), copolymers thereof, and poly(tetrahydrofuran), ethoxylated or propoxylated neopentyl glycol, ethoxylated or propoxylated trimethylpropane, and ethoxylated or propoxylated pentaerythritol.

[0076] Preferred oligomeric aminobenzoates are disclosed in WO 1996 / 33157 (Lambson Fine Chemicals Ltd.) and WO 2011 / 030089 (Sun Chemicals BV).Typical examples of polyethylene glycol bis-p-dimethylaminobenzoates are OMNIPOL ASA, available from IGM Resins, and Speedcure 7040, available from Lambson Fine Chemicals.

[0077] Other oligomeric or polymeric coinitiators are, for example, ESACURE A198 from IGM, a multifunctional amine, and SARTOMER® CN3755 from ARKEMA, an acrylated amine coinitiator.

[0078] polymerizable compound The radiation curable composition comprises at least one polymerizable compound.

[0079] The polymerizable compound is preferably a free-radically polymerizable compound.

[0080] The free radically polymerizable compound may be a monomer, an oligomer and / or a prepolymer. The monomer is also called a diluent.

[0081] These monomers, oligomers and / or prepolymers may have different degrees of functionality, i.e., different amounts of free-radically polymerizable groups.

[0082] Mixtures including combinations of mono-, di-, tri- and higher functional monomers, oligomers and / or prepolymers may be used. The viscosity of the radiation curable inkjet ink may be adjusted by varying the ratio of monomers and oligomers.

[0083] In a preferred embodiment, the monomer, oligomer or polymer comprises at least one acrylate group as the polymerizable group.

[0084] Preferred monomers and oligomers are those listed in EP 1 911 814 A1, paragraphs

[0106] to

[0115] .

[0085] In a preferred embodiment, the radiation curable inkjet ink comprises a monomer comprising a vinyl ether group and an acrylate or methacrylate group. Such monomers are disclosed in European Patent It is disclosed in Published Application No. 2848659, paragraphs

[0099] to

[0104] . A particularly preferred monomer containing a vinyl ether group and an acrylate group is 2-(2-vinyloxyethoxy)ethyl acrylate.

[0086] The polymerizable compound is preferably selected from the group consisting of acryloylmorpholine, cyclic trimethylpropane formol acrylate, isobornyl acrylate, lauryl acrylate, dipropylene glycol diacrylate, trimethylolpropane triacrylate, 2-(vinylethoxy)ethyl acrylate and urethane acrylate.

[0087] Phenolic Compounds The radiation curable inkjet ink preferably comprises a phenolic compound, more preferably a phenolic compound as disclosed in WO 2018 / 087056 (Agfa Gevaert, Electra The phenolic compounds include those containing at least two phenolic groups, as disclosed in paragraphs

[0053] to

[0068] of the International Publication WO 2005 / 023363 A1, which are incorporated herein by reference.

[0088] The amount of the phenol compound is preferably 0.5 to 20% by weight, more preferably 1 to 15% by weight, and most preferably 2.5 to 10% by weight, based on the total weight of the inkjet ink.

[0089] Coloring agent The radiation curable inkjet ink may be a substantially colorless inkjet ink or may include at least one colorant. For example, if the inkjet ink is used as an etch resist, the colorant allows the manufacturer of the conductive pattern to clearly see the temporary mask and allow visual inspection of the quality. If the inkjet ink is used to apply a solder mask, the inkjet ink typically includes a colorant. The preferred color for the solder mask is green, although other colors such as black or red may be used.

[0090] The colorant may be a pigment or a dye.

[0091] The color pigments may be selected from those disclosed by HERBST, Willy, et al. Industrial Organic Pigments, Production, Properties, Applications. 3rd edition. Wiley - VCH, 2004. ISBN 3527305769. Suitable pigments are disclosed in paragraphs

[0128] to

[0138] of WO 2008 / 074548.

[0092] The pigment particles in inkjet inks must be small enough to permit free flow of the ink through the inkjet printing device, especially the ejecting nozzles. It is also desirable to use small particles for maximum color strength and to slow settling. Most preferably, the average pigment particle size is 150 nm or less. The average particle size of the pigment particles is determined by Brookhaven Instruments Particle It is preferable to measure using a Sizer BI90plus.

[0093] Generally, dyes exhibit higher photobleaching than pigments, but do not cause jettability problems. Anthraquinone dyes have been found to exhibit only slight photobleaching under normal UV curing conditions used in UV curable inkjet printing. In a preferred embodiment, the colorant in the radiation curable inkjet ink is an anthraquinone dye, such as Macrolex™ Blue 3R (CASRN 325781-98-4) from LANXESS.

[0094] Other preferred dyes include crystal violet and copper phthalocyanine dyes.

[0095] In a preferred embodiment, the colorant is present in an amount of from 0.5 to 6.0% by weight, more preferably from 1.0 to 2.5% by weight, based on the total weight of the radiation curable inkjet ink.

[0096] Polymer Dispersants When the colorant in the radiation curable ink jet is a pigment, it is preferred that the radiation curable ink jet includes a dispersant, more preferably a polymeric dispersant, for dispersing the pigment.

[0097] Suitable polymeric dispersants are copolymers of two monomers, but may contain three, four, five or even more monomers. The properties of the polymeric dispersant depend on both the nature of the monomers and their distribution in the polymer. The copolymeric dispersant preferably has the following polymer composition: Statistically polymerized monomers (e.g. monomers A and B polymerized ABBAABAB); Alternating monomers (e.g. monomers A and B polymerized ABABABAB); Gradient (tapered) polymerized monomers (e.g., monomers A and B polymerized to AAABAABBABBBB); Block copolymers (e.g., monomers A and B polymerized to AAAAABBBBBB), where the block length of each of the blocks (2, 3, 4, 5 or even more) is important for the dispersing ability of the polymeric dispersant; Graft copolymers (graft copolymers consist of a polymer backbone with polymer side chains attached to the backbone); and Mixed forms of these polymers, e.g. block gradient copolymers.

[0098] Suitable polymeric dispersants are listed in the "Dispersants" section of EP 1 911 814 A, more specifically in paragraphs

[0064] to

[0070] and

[0074] to

[0077] .

[0099] Commercially available examples of polymeric dispersants are: DISPERBYK™ dispersants available from BYK CHEMIE GMBH; · SOLSPERSE™ dispersants available from NOVEON; · TEGO™ DISPERS™ dispersants from EVONIK; · EDAPLAN(TM) dispersants from MUENZING CHEMIE; · ETHACRYL™ dispersants from LYONDELL; · GANEX™ dispersants from ISP; · DISPEX™ and EFKA™ dispersants from CIBA SPECIALTY CHEMICALS INC; DISPONER™ dispersants from DEUCHEM; and · JONCRYL(TM) dispersants from JOHNSON POLYMER.

[0100] Polymerization Inhibitors The radiation curable inkjet ink may include at least one inhibitor to improve the thermal stability of the ink.

[0101] Suitable polymerization inhibitors include phenol-type antioxidants, hindered amine light stabilizers, fluorescent antioxidants, hydroquinone monomethacrylates commonly used for (meth)acrylate monomers, and the like. These include diphenyl ethers, and hydroquinone; t-butyl-catechol, pyrogallol, and 2,6-di-tert.butyl-4-methylphenol (=BHT) may also be used.

[0102] Suitable commercially available inhibitors are, for example, Sumilizer™ GA-80, Sumilizer™ GM and Sumilizer™ GS manufactured by Sumitomo Chemical Co. Ltd.; Genorad™ 16, Genorad™ 18 and Genorad™ 20 from Rahn AG; Irgastab™ UV10 and Irgastab™ UV22, Tinuvin™ 460 and CGS20 from Ciba Specialty Chemicals; Floorstab™ UV family (UV-1, UV-2, UV-5 and UV-8) from Kromachem Ltd, Additol™ S family (S100, S110, S120 and S130) from Cytec Surface Specialties.

[0103] Adding an excessive amount of these polymerization inhibitors may slow down the curing speed, so it is preferable to determine the amount that will prevent polymerization prior to blending. The amount of polymerization inhibitor is preferably less than 5% by weight, and more preferably less than 3% by weight, of the total radiation-curable inkjet ink.

[0104] Surfactants The radiation curable inkjet ink may include at least one surfactant.

[0105] The surfactants may be anionic, cationic, nonionic, or zwitterionic and are typically added in a total amount of less than 1 wt %, based on the total weight of the radiation curable inkjet ink.

[0106] Suitable surfactants include fluorinated surfactants, fatty acid salts, ester salts of higher alcohols, alkylbenzenesulfonates, sulfosuccinates, and phosphates of higher alcohols (e.g., sodium dodecylbenzenesulfonate and sodium dioctyl sulfosuccinate), ethylene oxide adducts of higher alcohols, ethylene oxide adducts of alkylphenols, ethylene oxide adducts of polyhydric alcohol fatty acid esters, and acetylene glycol and ethylene oxide adducts thereof (e.g., polyoxyethylene nonylphenyl ether, and SURFYNOL™ 104, 104H, 440, 465, and TG available from AIR PRODUCTS & CHEMICALS INC).

[0107] Preferred surfactants are selected from fluorosurfactants (such as fluorinated hydrocarbons) and silicone surfactants.Silicone surfactants are preferably siloxanes, and can be alkoxylated, polyether modified, polyether modified hydroxy functional, amine modified, epoxy modified, and other modified, or combinations thereof.Preferred siloxanes are polymers, such as polydimethylsiloxane.

[0108] Preferred commercially available silicone surfactants include BYK™ 333 and BYK™ UV 3510 from BYK Chemie.

[0109] In a preferred embodiment, the surfactant is a polymerizable compound.

[0110] Preferred polymerizable silicone surfactants include (meth)acrylated silicone surfactants. Most preferably, the (meth)acrylated silicone surfactant is an acrylated silicone surfactant, since acrylates are more reactive than methacrylates.

[0111] In a preferred embodiment, the (meth)acrylated silicone surfactant is a polyether-modified (meth)acrylated polydimethylsiloxane or a polyester-modified (meth)acrylated polydimethylsiloxane.

[0112] Preferably, the surfactant is present in the radiation curable inkjet ink in an amount of 0 to 3 wt %, based on the total weight of the radiation curable inkjet ink.

[0113] Flame retardants The radiation curable inkjet ink preferably includes a flame retardant.

[0114] Preferred flame retardants are inorganic flame retardants such as alumina trihydrate and boehmite, and organic phosphor compounds such as organic phosphates (e.g., triphenyl phosphate (TPP), resorcinol bis(diphenyl phosphate) (RDP), bisphenol A diphenyl phosphate (BADP), and tricresyl phosphate (TCP)); organic phosphonates (e.g., dimethyl methyl phosphonate (DMMP)); and organic phosphinates (e.g., aluminum dimethyl phosphinate).

[0115] Other suitable organic phosphor compounds are disclosed in US Pat. No. 8,273,805 (JNC Corporation) and European Patent Application Publication No. 3,498,788 (Agfa Gevaert).

[0116] Preparation of inkjet inks The preparation of pigmented radiation curable inkjet inks is well known to those skilled in the art. A preferred method of preparation is disclosed in WO 2011 / 069943, paragraphs

[0076] to

[0085] .

[0117] Printed circuit board manufacturing method A method for manufacturing a printed circuit board (PCB) according to the present invention comprises at least one inkjet printing step in which a radiation curable inkjet ink as described above is jetted and cured onto a substrate.

[0118] According to a preferred embodiment, the method for manufacturing a PCB includes an inkjet printing process in which a solder mask is provided.

[0119] Solder masks are typically applied by jetting and curing a radiation curable ink-jet ink onto a dielectric substrate containing a conductive pattern.

[0120] A heat treatment is preferably applied to the jetted and cured radiation curable inkjet ink. The heat treatment is preferably carried out at a temperature of 80° C. to 250° C. The temperature is preferably at least 100° C., more preferably at least 120° C. To prevent carbonization of the solder mask, the temperature is preferably at most 200° C., more preferably at most 160° C.

[0121] The heat treatment is typically carried out for 15 to 90 minutes.

[0122] The purpose of the heat treatment is to further increase the degree of polymerization of the solder mask.

[0123] The substrate is typically a dielectric substrate having a conductive circuit thereon.

[0124] The dielectric substrate of an electronic device can be any non-conductive material. Examples include paper / resin composite or resin / fiberglass composite, ceramic substrate, polyester or polyimide. For flexible PCBs, the dielectric substrate is preferably a polyimide-based substrate.

[0125] The conductive circuitry is typically made from any metal or alloy conventionally used to prepare electronic devices, such as gold, silver, palladium, nickel / gold, nickel, tin, tin / lead, aluminum, tin / aluminum and copper, etc. The conductive circuitry is preferably made from copper, more preferably virgin copper.

[0126] The radiation curable inkjet ink may be cured by exposing the ink to actinic radiation, such as electron beam or ultraviolet (UV) radiation. Preferably, the radiation curable inkjet ink is cured by UV radiation, more preferably using UV LED curing.

[0127] A method for manufacturing a PCB may include two, three or more inkjet printing steps. For example, a method may include two inkjet printing steps, where in one inkjet printing step an etch resist is applied onto a metal surface and in another inkjet printing step a solder mask is applied onto a dielectric substrate containing conductive circuits.

[0128] A third inkjet printing step may be used for legend printing.

[0129] Inkjet Printing Device The radiation curable inkjet ink may be jetted by one or more printheads, which eject droplets in a controlled manner through nozzles onto a substrate that is moving relative to the printheads.

[0130] The preferred print head for the inkjet printing system is a piezoelectric head. Piezoelectric inkjet printing is based on the movement of a piezoelectric ceramic transducer when a voltage is applied. The application of a voltage causes the shape of the piezoelectric ceramic transducer in the printhead to change, creating a void that is then filled with ink. When the voltage is removed again, the ceramic expands to its original shape and ink droplets are ejected from the printhead. However, the inkjet printing method according to the present invention is not limited to piezoelectric inkjet printing. Other inkjet printheads can be used, including various types such as continuous type.

[0131] An inkjet printhead typically scans back and forth in a transverse direction across a moving ink-receptive surface (substrate). Often the inkjet printhead does not print on the return. Bidirectional printing is preferred to obtain high areal throughput. Another preferred method of printing is by a "single pass printing process", which can be done by using a page-width inkjet printhead or multiple staggered inkjet printheads that span the entire width of the ink-receptive surface. In a single pass printing process, the inkjet printhead typically remains stationary and the ink-receptive surface is transported under the inkjet printhead.

[0132] curing equipment The radiation curable inkjet ink can be cured by exposing the ink to actinic radiation, such as electron beam or ultraviolet radiation. Preferably, the radiation curable inkjet ink is cured by ultraviolet radiation, more preferably using UV LED curing.

[0133] In inkjet printing, the curing means may be placed in combination with the print head of the inkjet printer and move along with the inkjet printer, so that the curable liquid is exposed to the curing radiation immediately after being jetted.

[0134] In such configurations, except for UV LEDs, it can be difficult to provide a small enough radiation source that is connected to and moves with the print head. Therefore, one may use a stationary fixed radiation source, e.g., a curing UV light source, connected to the radiation source by a flexible radiation conducting means such as a fiber optic bundle or an internally reflective flexible tube.

[0135] Alternatively, actinic radiation may be supplied to the radiation head from a fixed source by an arrangement of mirrors including a mirror on the radiation head.

[0136] The radiation source may also be an elongated radiation source that extends across the substrate to be cured, which may be adjacent to the traverse path of the print head so that successive rows of the image formed by the print head pass beneath the radiation source in a stepwise or continuous manner.

[0137] Any ultraviolet light source, such as high or low pressure mercury lamp, cold cathode fluorescent lamp, black light, ultraviolet LED, ultraviolet laser and flashlight, may be used as the radiation source, so long as a portion of the emitted light can be absorbed by the photoinitiator or photoinitiator system. Among these, preferred ultraviolet light sources are those that exhibit a relatively long wavelength UV contribution with a dominant wavelength of 300-400 nm. Specifically, UV-A light sources are preferred because they reduce light scattering, resulting in more efficient internal curing.

[0138] UV radiation is generally classified as UV-A, UV-B, and UV-C as follows: UV-A: 400nm~320nm UV-B: 320nm~290nm · UV-C: 290nm~100nm.

[0139] In a preferred embodiment, the radiation curable inkjet ink is cured by UV LEDs. The inkjet printing apparatus preferably includes one or more UV LEDs having a wavelength greater than 360 nm, preferably greater than 380 nm, and most preferably a UV LED having a wavelength of about 395 nm.

[0140] Furthermore, it is possible to cure the ink image using two light sources of different wavelengths or irradiance, either sequentially or simultaneously. For example, the first UV source can be selected to be rich in UV-C, especially in the range of 260 nm to 200 nm. The second UV source can then be a different lamp, for example a gallium doped lamp, rich in UV-A, or high in both UV-A and UV-B. The use of two UV sources has been found to have the advantages of, for example, rapid curing speed, and high degree of cure.

[0141] To facilitate curing, inkjet printing apparatus often include one or more oxygen depletion units that deploy a blanket of nitrogen or other relatively inert gas (e.g., CO2) with adjustable position and adjustable inert gas concentration to reduce the oxygen concentration in the curing environment. Residual oxygen levels are typically maintained as low as 200 ppm, but typically range from 200 ppm to 1200 ppm. EXAMPLES

[0142] material All materials used in the following examples were purchased from Aldrich Chemical Industries, Ltd. unless otherwise stated. It was readily available from standard sources such as EMICAL Co (Belgium) and ACROS (Belgium). The water used was deionized water.

[0143] DISP-1 is a concentrated black pigment dispersion having a composition according to Table 4 and was prepared as follows: [Table 4]

[0144] Concentrated black pigment dispersion DISP-1 was prepared by dissolving 31.9 g of Special Black 550, 14.6 g of Sunfast Blue in 235 g VEEA as the liquid medium. 15 4, 2.8 g of the inhibitor INHIB and 65.6 g of PRESOL were made by mixing for 30 minutes in a vessel equipped with a DISPERLUX™ disperser (from DISPERLUX SARL, Luxembourg). This mixture was then milled in a DYNO™-MILL RL from WAB Willy A. Bachofen (Switzerland) using 0.40 mm yttrium-stabilized zirconium oxide beads. The bead mill was filled 42% with grinding beads and operated for 188 minutes in recirculation mode by using a tip speed of 11.8 m / s. The milling chamber was water-cooled during the operation. The average particle size was 116 nm.

[0145] VEEA is 2-(2-vinylethoxy)ethyl acrylate available from NIPPON SHOKUBAI.

[0146] PRESOL was prepared by dissolving 429 g of EFKA7701 in 633 g of VEEA followed by the addition of 10.7 g of INHIB.

[0147] EFKA 7701 is a polymeric dispersant supplied by BASF.

[0148] INHIB is a mixture forming a polymerization inhibitor having a composition according to Table 5. [Table 5]

[0149] Cupferron™ AL is aluminum N-nitrosophenylhydroxylamine from WAKO CHEMICALS LTD.

[0150] DPGDA is a gypsum carbide copolymer available from ARKEMA as Sartomer SR508. It is propylene diacrylate.

[0151] ACMO is acryloylmorpholine available from RAHN.

[0152] EDIOXMA is a mixture of trimethylol formal acrylate and trimethylol propane triacrylate commercially available as Photomer 4141, supplied by IGM Resins.

[0153] ISOPA is 3,3,5-trimethylcyclohexyl acrylate commercially available as Sartomer CD420, supplied by Arkema.

[0154] NK ESTER is 2-(acryloyloxy)ethyl succinate supplied by KOWA Europe GMBH.

[0155] MONOSIL-1 is 3-glycidoxypropyltrimethoxysilane available as Silane Z-6040 from DOW CORNING.

[0156] MULTISIL-9 is a difunctional alkoxysilane available from EVONIK as Vestanat® EP-MF-204.

[0157] BAPO is a bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide photoinitiator available as Irgacure™ 819 from BASF.

[0158] ITX is Speedcure™ ITX, a mixture of isopropylthioxanthone isomers, from LAMBSON SPECIALTY CHEMICALS.

[0159] TPO is 2,4,6-trimethylbenzoyldiphenylphosphine oxide, commercially available as Genocure TPO, supplied by Rahn AG.

[0160] Omnipol ASA is a 4-dimethyl-benzoic acid ester of low molecular weight poly(ethylene glycol) supplied by IGM Resins.

[0161] Ebecryl 1360 is a polysiloxane hexaacrylate slip agent from ALLNEX.

[0162] FR01 is a flame retardant commercially available from ADEKA PALMAROL under the trade name ADK Stab FP600.

[0163] method Inkjet ink adhesion Adhesion is measured by BRAIVE in accordance with ISO2409:1992 Paints and varnishes cross-cut test (International Standard 1992-08-15). A Braive No. 1536 cross-cut tester from INSTRUMENTS was used in conjunction with Tesatape™ 4104 PVC tape with 1 mm spacing between cuts.

[0164] The evaluation was performed according to the criteria shown in Table 6, and both the adhesion at the cross cut and the adhesion outside the cross cut were evaluated. [Table 6]

[0165] Solder Resistance The solder resistance of the inkjet ink was verified using the SPL600240 Digital Dynamic Solder, available from L&M PRODUCTS, filled with "K" grade 63:37 tin / lead solder, available from SOLDER CONNECTION. The solder temperature was set to 290°C.

[0166] Solder flux SC7560A from SOLDER CONNECTION was applied to the surface of the sample using a Q-tip (i.e., inkjet coating on the copper surface as described in Adhesion) and the surface was cleaned. The solder flux was allowed to dry by placing the sample over a solder pot for 10 minutes.

[0167] After placing the sample in the solder pot, a solder wave was formed for 10 seconds, which was repeated a total of three times, after which the sample was allowed to cool for at least 10 minutes.

[0168] The adhesion of the inkjet ink was then evaluated as described above.

[0169] ENIG Resistant First, the substrate was immersed in a bath of acidic cleaner (Umicore cleaner 865) for 4 minutes at 40° C. The substrate was then removed and immersed in a rinse bath of deionized water (DW) for 90 seconds at room temperature (RT).

[0170] Second, the substrate was immersed in a microetching bath containing 8.5 wt% Na2S2O8 and ±3.2 wt% H2S04 (98%) in water for 100 s at a temperature between 26 and 33 °C. The substrate was then removed and immersed in a rinse bath of DW at RT for 90 s.

[0171] Third, the substrate was immersed in a palladium activator bath (Accemulta MKN 4) for 90 seconds at a temperature of approximately 30° C. The substrate was then removed and immersed in a rinse bath of DW at RT for 90 seconds.

[0172] The substrate was then immersed in a nickel bath (Nimuden NPR 4) for 35 minutes at a temperature of approximately 85° C. The substrate was then removed and immersed in a rinse bath of DW at RT for 90 seconds.

[0173] Finally, the substrate was immersed in a gold bath (Gobright TAM 55) for 12 minutes at a temperature of approximately 80° C. The substrate was then removed and immersed in a rinse bath of DW at RT for 90 seconds.

[0174] The adhesion of the inkjet ink was then evaluated as described above. EXAMPLES

[0175] This example illustrates the synthesis of an adhesion promoter according to the present invention.

[0176] Synthesis of ADH-01 [ka]

[0177] 14.4 g (0.15 mol) 2-ethyl-imidazole was added to 44.4 g ((0.15 mol) trimethylolpropane triacrylate) and the mixture was heated to 70° C. for 4 hours. The mixture was allowed to cool to room temperature and ADH-1 was used as an adhesion promoter without further purification. ADH-1 was analyzed using LC-MS. The main components of the mixture are listed in Table 7 below. [Table 7]

[0178] Synthesis of ADH-2 [ka]

[0179] 40 g (0.36 mol) 3-hydroxymethyl-pyridine was dissolved in 600 ml methyl tert.butyl ether. 101 ml (73 g, 0.72 mol) triethylamine was added. The mixture was cooled to -4°C. 34 ml (45 g, 0.36 mol) 3- Chloro-proionyl chloride was added dropwise over 45 minutes while keeping the temperature below 5°C. The reaction was allowed to continue at room temperature for 72 hours. The reaction mixture was extracted twice with 500 ml water and 300 ml water. The pooled water fractions were extracted with 300 ml methyl tert.butyl ether. The methyl tert.butyl ether fractions were pooled, dried over MgSO4 and evaporated under reduced pressure.

[0180] The crude ADH-2 was purified by preparative column chromatography on a Graceresolv RS80 column using a gradient elution from hexane / methylene chloride 50 / 50 to hexane / ethyl acetate 50 / 50.

[0181] 11.2 g of ADH-2 was isolated (TLC Silica gel 60F supplied by Merck 254 TLC analysis above, eluent: hexane / ethyl acetate 50 / 50, R f :0.45)

[0182] Synthesis of ADH-3 [ka]

[0183] 39 g (0.32 mol) 2-(aminoethyl)pyridine was dissolved in 350 ml tetrahydrofuran. 0.35 g BHT was added as a stabilizer and the mixture was cooled to -5°C. 51.1 g (0.33 mol) 2-isocyanatoethyl methacrylate was added while maintaining the temperature below 0°C. The reaction was allowed to continue for 30 minutes at 0°C and then for 30 minutes at room temperature. The solvent was removed under reduced pressure. The residue was treated with ethyl acetate and then with hexane.

[0184] Crude ADH-3 was isolated and purified by preparative column chromatography on a Prochrom LC80 column using Kromasil Si60A 10 μm as stationary phase and methylene chloride / ethanol 85 / 15 as eluent.

[0185] 57.5 g (yield: 65%) of ADH-3 was isolated (TLC Silica gel 60F supplied by Merck). 254 TLC analysis at: eluent methylene chloride / ethanol 85 / 15:R f =0.51).

[0186] Synthesis of ADH-4 [ka]

[0187] 39 g (0.32 mol) 2-(2-hydroxymethyl)pyridine was dissolved in 350 ml ethyl acetate. 0.35 g BHT and 0.25 g dibutyltin dilaurate were added and the mixture was cooled to -5° C. 51.6 g (0.33 mol) 2-isocyanatoethyl methacrylate was added while maintaining the temperature at -5° C. The reaction was allowed to continue for 16 hours at room temperature.

[0188] The solvent was removed under reduced pressure and the residue was treated with ethyl acetate. The mixture was concentrated to 100 ml and ADH-4 was allowed to slowly crystallize.

[0189] The crystallized ADH-4 was isolated, treated with ethyl acetate, isolated and dried. 83 g (yield: 93%) of ADH-4 was isolated.

[0190] Synthesis of ADH-5 [ka]

[0191] 7.15 g (30 mmol) of neopentyl glycol diacrylate was dissolved in 30 ml of ethyl acetate. 0.11 g of BHT was added as a stabilizer. 3.08 g (24 mmol) of 1-(3-aminopropyl)-imidazol was added over 15 minutes. The reaction mixture was heated to reflux and the reaction was allowed to continue under reflux for 16 hours.

[0192] The mixture was allowed to cool to room temperature and the solvent was removed under reduced pressure.

[0193] 9.48 g (yield: 93%) of ADH-5 was isolated as a viscous oil and used without further purification. EXAMPLES

[0194] This example demonstrates the improved adhesion of cured inkjet inks according to the present invention to untreated copper and the improved solder and ENIG resistance of such cured inkjet inks. Preparation of Comparative Ink COMP-1 and Inks INV-1 to INV-5 of the Present Invention

[0195] Comparative radiation curable inkjet ink COMP-1 and inventive radiation curable inkjet inks INV-1 to INV-5 were prepared according to Table 8. All weight percentages (wt %) are based on the total weight of the radiation curable inkjet ink.

[0196] [Table 8]

[0197] Comparative sample COMP-01 and inventive samples INV-1 to INV-06 were obtained by jetting the ink using a Microcraft MJP 2013 K1 (resolution 720x1440 dpi, 3 multiple passes at 45°C jetting temperature, 50% pincure after each pass using an LED 395nm 8W lamp) to obtain a solder mask layer with a final thickness of + / - 22μm. After printing, the samples were baked in an oven at 150°C for 1 hour.

[0198] The cured ink was tested for adhesion to untreated copper and solder and ENIG resistance as described above, and the results are shown in Table 9.

[0199] [Table 9]

[0200] From the results in Table 9, it can be seen that the adhesion promoter containing at least one ethylenically unsaturated bond and one nitrogen-containing 5- or 6-membered heteroaromatic ring is effective in improving the solderability of the inkjet ink to untreated copper. It is clear that the mask performance is significantly improved.

Claims

1. 1. A radiation curable composition comprising at least one polymerizable compound and an adhesion promoter, the adhesion promoter comprising: - a polymerizable group selected from acrylate or methacrylate, and - adhesion-promoting groups containing at least one nitrogen-containing 5- or 6-membered heteroaromatic ring Including, the nitrogen-containing 5- or 6-membered heteroaromatic ring is an N-alkylated benzimidazole; and the nitrogen-containing 5- or 6-membered heteroaromatic ring has a pKa of the conjugate acid of at least 3.5; The adhesion promoter is represented by Formula II 【Chemistry 2】 (In the formula, R 3 is selected from the group consisting of hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted alkaryl groups, substituted or unsubstituted aralkyl groups, and substituted or unsubstituted aryl or heteroaryl groups; R 4 and R 5 are independently selected from the group consisting of hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted alkaryl groups, substituted or unsubstituted aralkyl groups, and substituted or unsubstituted aryl or heteroaryl groups; R 4 and R 5 may together represent the atoms necessary to form a 5- to 8-membered ring; R 6 and R 7 is independently selected from the group consisting of hydrogen and a methyl group; Y is an oxygen atom, a sulfur atom, or NR 8 Selected from: R 8 is selected from the group consisting of hydrogen, substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted alkaryl groups, substituted or unsubstituted aralkyl groups, and substituted or unsubstituted aryl or heteroaryl groups; L 3 represents an n+m valent linking group, with the proviso that n+m is 6 or less; n and m independently represent an integer of 1 to 5. having a chemical structure according to the invention The polymerizable compound is selected from the group consisting of acryloylmorpholine, cyclic trimethylolpropane formal acrylate, isobornyl acrylate, lauryl acrylate, dipropylene glycol diacrylate, trimethylolpropane triacrylate, 2-(vinylethoxy)ethyl acrylate, urethane acrylate, 3,3,5-trimethylcyclohexyl acrylate, and 2-(acryloyloxy)ethyl succinate. Radiation curable composition.

2. 10. The radiation curable composition of claim 1, further comprising a silane compound selected from di- or multi-functional alkoxysilanes, and monofunctional alkoxysilanes functionalized with a group selected from the group consisting of epoxides and oxetanes.

3. The di- or polyfunctional alkoxysilane is represented by the formula III 【Chemistry 3】 (In the formula, L represents a divalent linking group selected from the group consisting of a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkenylene group, a substituted or unsubstituted alkynylene group, and a substituted or unsubstituted arylene group; R represents a group selected from the group consisting of substituted or unsubstituted alkyl groups, substituted or unsubstituted alkenyl groups, substituted or unsubstituted alkynyl groups, substituted or unsubstituted alkaryl groups, substituted or unsubstituted aralkyl groups, and substituted or unsubstituted aryl or heteroaryl groups. The radiation curable composition of claim 2 comprising at least two alkoxysilane moieties according to

4. The radiation curable composition of claim 1 which is an ink-jet ink.

5. 13. A method for manufacturing a printed circuit board (PCB) comprising an inkjet printing process, in which a radiation curable composition as defined in claim 1 is sprayed onto a substrate and cured.

6. The method of claim 5 , wherein curing is performed using LED UV radiation.

7. The method of claim 5 , wherein the inkjet printing process comprises solder mask printing.

8. The method of claim 5, also comprising a heating step.

9. The method of claim 5 , wherein the substrate is a dielectric substrate provided with conductive circuits.

10. The method of claim 9 , wherein the dielectric substrate is a polyimide-based substrate.

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