Etch-resistant inkjet ink

Abstract

An etch-resistant inkjet ink comprising: - one or more photoinitiators, wherein at least one photoinitiator is a thioxanthone compound; - one or more acrylamides according to formula (I), wherein R represents H or CH3; R1 and R2 independently represent optional substituted alkyl groups; R1 and R2 may represent necessary atoms for forming a 5- or 6-membered ring; - one or more polymerizable compounds according to formula (II), wherein X = O, S or NH; R = H or CH3; L is an optional substituted one to five-atom divalent linker; n is 0 or 1; and A is an optional substituted aromatic group; - one or more polyfunctional (meth)acrylates.

Description

Technical Field

[0001] This invention relates to an etch-resistant inkjet ink, particularly for use in the manufacture of printed circuit boards (PCBs). Background Technology

[0002] The manufacture of printed circuit boards (PCBs) has traditionally involved a complex process with multiple photolithography and etching steps, resulting in significant waste. There is growing interest in digitalizing PCB manufacturing workflows to reduce process steps, production costs, and waste.

[0003] Inkjet printing is the preferred digital manufacturing technology for several PCB production steps, such as applying resist and soldering masks or printing patterns.

[0004] In PCB manufacturing, etch-resistant inkjet ink is used to form copper circuits. The etch-resistant inkjet ink is applied to a copper laminate (i.e., copper-clad laminate) to form a mask. The copper is then removed from the areas of the copper-clad laminate where the mask is not present, and the mask is subsequently removed in a so-called stripping step.

[0005] EP-A 2809735 (AGFA-GEVAERT NV) discloses an etch-resistant inkjet ink and a method for manufacturing a PCB using the inkjet ink.

[0006] EP-A 3201277 (AGFA-GEVAERT NV) and EP-A 32011278 (AGFA-GEVAERT NV) disclose digital manufacturing methods for metal articles and embossed elements for decorative surfaces, respectively. Both methods use etch-resistant inkjet inks, such as those disclosed in EP-A 2915856 (AGFA-GEVAERT NV) or EP-A 3000853 (AGFA-GEVAERT NV).

[0007] Other anti-etch inkjet inks are disclosed in JP-A 2016 / 102138 and JP-A 2016 / 191010 (both from GOOCHEMICAL CO LTD).

[0008] Printed circuit boards (PCBs) come in many types, one of which is the high-current PCB, also known as a thick copper PCB. These units offer several useful characteristics for applications with high current and variable temperatures. Thick copper PCBs can withstand higher temperatures for longer periods, handle higher current values, and provide stronger connections.

[0009] These high-current PCBs are typically used in devices or equipment that require a large amount of power, such as electric vehicles or solar converters.

[0010] These PCBs are uniquely designed with thicker, heavier copper layers, which contribute to their durability. The typical thickness of the copper layer is 300 to 800 µm.

[0011] Suitable etch-resistant inkjet inks must withstand etching conditions while being completely removed during the stripping process.

[0012] Thicker copper layers in high-current PCBs require longer etching times. It has been observed that existing etch-resistant inkjet inks cannot withstand such long etching times. Furthermore, improving the adhesion of etch-resistant inkjet inks to copper to withstand longer etching times often results in poorer peeling behavior, i.e., incomplete removal during the peeling step.

[0013] Therefore, there is a need for an etch-resistant inkjet ink that can achieve optimal results in the manufacture of high-current PCBs. Summary of the Invention

[0014] One object of the present invention is to provide an etch-resistant inkjet ink for manufacturing high-current PCBs.

[0015] This objective of the present invention is achieved by the inkjet ink according to claim 1.

[0016] Another object of the present invention is to provide a digital manufacturing method for high-current PCBs. This object of the present invention is achieved by the manufacturing method according to claim 13.

[0017] Other objects of the invention will become apparent from the following description. Detailed Implementation

[0018] definition The term "monofunctional," for example in monofunctional polymerizable compounds, means that the polymerizable compound contains a single polymerizable group.

[0019] The term "difunctional," for example in a difunctional polymerizable compound, means that the polymerizable compound contains two polymerizable groups.

[0020] The term "multifunctional," for example in multifunctional polymerizable compounds, means that the polymerizable compound contains more than two polymerizable groups.

[0021] The term "alkyl" refers to all possible variations of each number of carbon atoms in an alkyl group, namely: methyl; ethyl; for three carbon atoms: n-propyl and isopropyl; for four carbon atoms: n-butyl, isobutyl, and tert-butyl; for five carbon atoms: n-pentyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl, and 2-methylbutyl, etc.

[0022] Unless otherwise stated, the substituted or unsubstituted alkyl groups are preferably C1 to C6-alkyl groups.

[0023] Unless otherwise stated, the substituted or unsubstituted alkenyl groups are preferably C2 to C6-alkenyl groups.

[0024] Unless otherwise stated, the substituted or unsubstituted alkynyl group is preferably a C2 to C6 alkynyl group.

[0025] Unless otherwise stated, the substituted or unsubstituted alkylaryl group is preferably a phenyl or naphthyl group comprising one, two, three or more C1 to C6-alkyl groups.

[0026] Unless otherwise specified, the substituted or unsubstituted aralkyl group is preferably a C7 to C8 group containing a phenyl or naphthyl group. 20 -alkyl group.

[0027] Unless otherwise stated, the substituted or unsubstituted aryl group is preferably a phenyl group or a naphthyl group.

[0028] Unless otherwise stated, the substituted or unsubstituted heteroaryl group is preferably a five- or six-membered ring substituted with one, two or three oxygen atoms, nitrogen atoms, sulfur atoms, selenium atoms or combinations thereof.

[0029] In the context of substituted alkyl groups, the term "substituted" means that the alkyl group can be replaced by atoms other than those normally present in such groups (i.e., carbon and hydrogen). For example, a substituted alkyl group can contain halogen atoms or thiol groups. An unsubstituted alkyl group contains only carbon and hydrogen atoms.

[0030] Unless otherwise stated, the substituted alkyl group, substituted alkenyl group, substituted alkynyl group, substituted aralkyl group, substituted alkylaryl group, substituted aryl group and substituted heteroaryl group are preferably substituted by one or more substituents selected from the following: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl and tert-butyl, ester, amide, ether, thioether, ketone, aldehyde, sulfoxide, sulfone, sulfonate, sulfonamide, -Cl, -Br, -I, -OH, -SH, -CN and -NO2.

[0031] Anti-etching inkjet ink The anti-etching inkjet ink according to the present invention comprises: - One or more photoinitiators, wherein at least one photoinitiator is a thioxanthone compound. - One or more (meth)acrylamides according to formula I, in R = H or CH3; R1 and R2 represent the alkyl groups that are optionally substituted, independently of each other; R1 and R2 can represent the necessary atoms for forming a 5- or 6-membered ring; - One or more polymerizable compounds according to Formula II, and in X = O, S, or NH, with O being preferred; R = H or CH3, preferably H; L is a divalent linker for a randomly substituted one to five atomic groups; n is 0 or 1, and A is an optional aromatic group to be substituted, preferably a phenyl group. - One or more polyfunctional (meth)acrylates.

[0032] According to a preferred embodiment, the etch-resistant inkjet ink also contains one or more (meth)acrylates containing acid groups.

[0033] (meth)acrylamide according to formula I The etch-resistant inkjet ink according to the present invention comprises one or more (meth)acrylamides according to Formula I. in R is H or CH3, with H being preferred. R1 and R2 independently represent H, an alkyl group that is optionally substituted, or the necessary atom to form a 5- or 6-membered ring.

[0034] The alkyl group is preferably a C1-C6 alkyl group, more preferably a C1-C3 alkyl group. Highly preferred alkyl groups are selected from methyl, ethyl, propyl, butyl, isopropyl, isobutyl and tert-butyl.

[0035] Preferred (meth)acrylamides according to Formula I are listed in Table 1, but are not limited thereto.

[0036] Table 1 Etching-resistant inkjet inks may contain two or more (meth)acrylamides according to Formula I.

[0037] The total amount of (meth)acrylamide according to Formula I is preferably 5 to 75% by weight, more preferably 10 to 60% by weight, and most preferably 15 to 45% by weight, all relative to the total weight of the inkjet ink.

[0038] In a preferred embodiment of the etch-resistant inkjet ink, at least one acrylamide is a cyclic acrylamide. A preferred cyclic acrylamide is acrylomorpholine.

[0039] In a preferred embodiment of the etch-resistant inkjet ink, the acrylamide is selected from acrylomorpholine and diethylacrylamide.

[0040] According to Formula II polymerizable compounds The etch-resistant inkjet ink according to the present invention comprises one or more polymerizable compounds according to Formula II. in X = O, S, or NH, with O being preferred; R = H or CH3, preferably H; L is a divalent linker for a randomly substituted one to five atomic groups; n is 0 or 1, and A is an optional substituted aromatic group, preferably a phenyl group.

[0041] Preferred compounds according to formula II are listed in Table 2, but are not limited thereto.

[0042] Table 2 Etching-resistant inkjet inks may contain two or more polymerizable compounds according to Formula II.

[0043] The total amount of the polymerizable compound according to Formula II is preferably 2.5 to 50% by weight, more preferably 5 to 40% by weight, and most preferably 10 to 30% by weight, all relative to the total weight of the inkjet ink.

[0044] In a preferred embodiment of the etch-resistant inkjet ink, the polymerizable compound according to Formula II is 2-phenoxyethyl acrylate (PEA).

[0045] Multifunctional (meth)acrylates The etch-resistant inkjet ink according to the present invention comprises one or more polyfunctional (meth)acrylates, preferably one or more polyfunctional acrylates. The polyfunctional (meth)acrylates mentioned herein are polymerizable compounds containing two or more (meth)acrylate groups.

[0046] Single polyfunctional acrylates or mixtures of polyfunctional acrylates may be used.

[0047] The total amount of polyfunctional (meth)acrylate is preferably 1 to 50% by weight, more preferably 2.5 to 25% by weight, and most preferably 5 to 15% by weight, all relative to the total weight of the inkjet ink.

[0048] In a preferred embodiment, the multifunctional acrylate is selected from dipropylene glycol diacrylate, neopentyl glycol diacrylate, neopentyl glycol (2x propoxylated) diacrylate, pentaerythritol tetraacrylate, 1,6-hexanediol diacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, tripropylene glycol diacrylate, di(trimethylolpropane) tetraacrylate, ethoxylated pentaerythritol tetraacrylate, and polyethylene glycol diacrylate.

[0049] In a highly preferred embodiment of the etch-resistant inkjet ink, the multifunctional acrylate includes tripropylene glycol diacrylate.

[0050] (Meth)acrylates containing acid groups Etching-resistant inkjet inks preferably contain one or more (meth)acrylates containing carboxylic acid groups, phosphate groups or phosphonic acid groups.

[0051] It has been observed that the presence of (meth)acrylates containing carboxylic acid groups, phosphate groups, or phosphonic acid groups results in improved adhesion of etch-resistant inkjet inks cured during the etching step to copper.

[0052] Suitable examples of monofunctional (meth)acrylates containing carboxylic acid groups include compounds represented by formula III. in R represents H or CH3, preferably H; and Z represents a divalent organic group.

[0053] The preferred divalent organic groups Z are those according to formula IV. -CH2-CH2-O-CO-Z´-(COOH) m Formula IV Where Z' represents a substituted or unsubstituted phenyl ring and m represents an integer from 1 to 3.

[0054] Preferred examples of (meth)acrylates containing carboxylic acid groups are disclosed in Table 3, but are not limited thereto.

[0055] Table 3 Inkjet inks may contain two or more different (meth)acrylates, which contain carboxylic acid groups, phosphate groups or phosphonic acid groups.

[0056] The total amount of (meth)acrylate containing carboxylic acid groups, phosphate groups or phosphonic acid groups is preferably 0.5 to 25% by weight, more preferably 2.5 to 15% by weight, and most preferably 5 to 10% by weight, all relative to the total weight of the inkjet ink.

[0057] Preferred carboxylic acid-containing (meth)acrylates are 2-acryloyloxyethyl phthalate and carboxyethyl acrylate.

[0058] Preferred examples of (meth)acrylates containing phosphate or phosphonic acid groups include 2-(methacryloyloxy)ethyl phosphate, 2-hydroxyethyl methacrylate phosphate, and bis[2-(methacryloyloxy)ethyl)] phosphate.

[0059] Preferred examples of (meth)acrylates containing phosphate groups are compounds according to formula P-1 or P-2. Where R' represents C n H 2n+1 , where n represents an integer between 6 and 18.

[0060] Preferred examples of (meth)acrylates containing phosphate groups are disclosed in Table 4, but are not limited thereto.

[0061] Table 4 In a particularly preferred embodiment of the etch-resistant inkjet ink, the (meth)acrylate containing a carboxylic acid group, a phosphate group, or a phosphonic acid group is selected from 2-carboxyethyl acrylate, 2-acryloyl ethyl succinate, 2-acryloyloxyethyl phthalate, and 2-hydroxyethyl methacrylate phosphate, more preferably selected from 2-carboxyethyl acrylate and 2-acryloyloxyethyl phthalate.

[0062] Other polymerizable compounds Other polymerizable compounds, besides those disclosed above, may preferably be present in the etch-resistant inkjet ink in an amount of 0 to 20% by weight, more preferably up to 15% by weight, and most preferably up to 10% by weight, all weight percentages (wt%) based on the total weight of the polymerizable composition.

[0063] Other polymerizable compounds are preferably composed of one or more monomers, oligomers, and / or prepolymers. These monomers, oligomers, and / or prepolymers may have different functionalities. Mixtures including combinations of monofunctional, difunctional, trifunctional, and higher functional monomers, oligomers, and / or prepolymers may be used.

[0064] Other particularly preferred monomers and oligomers are those listed in

[0106] to

[0115] of EP-A 1911814 (AGFA).

[0065] According to a preferred embodiment of the inkjet ink, the other polymerizable compound is hydroxyphenyl methacrylate.

[0066] Photoinitiator The anti-etching inkjet ink according to the present invention contains one or more photoinitiators, preferably free radical photoinitiators, wherein at least one photoinitiator is a thioxanone compound.

[0067] The presence of thioxanone compounds as photoinitiators has been observed to improve the curing properties (UV sensitivity) of etch-resistant inkjet inks.

[0068] Preferred thioxanone compounds are listed in Table 5 below, but are not limited thereto.

[0069] Table 5 In a particularly preferred embodiment of the etch-resistant inkjet ink, the thioxanone compound is Darocur. TM ITX is a mixture of isomers of 2- and 4-isopropyl-thioxanthone (THIOX-04 and THIOX-05). Thioxanthone photoinitiators such as Darocur have been observed in inkjet inks according to the present invention. TM The presence of ITX promotes the curing of the top of the printed layer, which results in a layer with lower tack.

[0070] The amount of such thioxanthone photoinitiator is preferably 0.5 to 20% by weight, more preferably 1 to 10% by weight, and most preferably 2 to 6% by weight, all relative to the total weight of the inkjet ink.

[0071] In addition to thioxanthone compounds, inkjet inks may also contain one or more other photoinitiators.

[0072] Suitable photoinitiators are disclosed in CRIVELLO, JV et al., Photoinitiators for FreeRadical, Cationic and Anionic Photopolymerization. 2nd ed. BRADLEY, G., London, UK: JohnWiley and Sons Ltd, 1998. pp. 276-293.

[0073] The inkjet ink according to the present invention preferably contains an acylphosphine oxide photoinitiator. The acylphosphine oxide compound may be selected from monoacylphosphine oxide and diacylphosphine oxide.

[0074] Preferred acylphosphine oxide photoinitiators are selected from diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), ethyl phenyl(2,4,6-trimethylbenzoyl)phosphine sulfate (TPO-L), phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), bis(2,6-dimethyl-benzoyl)-(2,4,4-trimethyl-pentyl)phosphine oxide, and 2,4,6-trimethoxy-benzoyl-diphenylphosphine oxide. Particularly preferred acylphosphine oxide photoinitiators are selected from BAPO, TPO, and TPO-L.

[0075] The amount of such acylphosphine oxide photoinitiator is preferably 0.5 to 20% by weight, more preferably 1 to 10% by weight, and most preferably 2 to 6% by weight, all relative to the total weight of the inkjet ink.

[0076] A preferred embodiment of the inkjet ink comprises both a thioxanthone-type photoinitiator and an acylphosphine oxide-type photoinitiator. A highly preferred embodiment comprises ITX and BAPO, or ITX, BAPO, and TPO-L.

[0077] Other preferred photoinitiators are α-hydroxy ketone type I photoinitiators, such as oligomeric [2-hydroxy-2-methyl-1-[4-(1-methylvinylphenyl]propanone], which can be obtained from IGM resins with Esacure® KIP IT.

[0078] To further enhance photosensitivity, curable inkjet compositions may also contain co-initiators. Suitable examples of co-initiators can be categorized into three types: (1) Tertiary aliphatic amines, such as methyldiethanolamine, dimethylethanolamine, triethanolamine, triethylamine and N-methylmorpholine; (2) Aromatic amines, such as pentyl-p-dimethylaminobenzoate, 2-n-butoxyethyl-4-(dimethylamino)benzoate, 2-(dimethylamino)-ethylbenzoate, ethyl-4-(dimethylamino)benzoate and 2-ethylhexyl-4-(dimethylamino)benzoate; and (3) (meth)acrylated amines, such as dialkylaminoalkyl (meth)acrylates (e.g., diethylaminoethyl acrylate) or N-morpholinoalkyl-(meth)acrylates (e.g., N-morpholinoethyl acrylate).

[0079] The preferred co-initiator is an aminobenzoate.

[0080] A preferred low molecular weight aminobenzoate is Genocure® EPD from RAHN.

[0081] The particularly preferred aminobenzoate co-initiators are selected from polymerizable, oligomeric, and polymerizable aminobenzoate co-initiators.

[0082] The polymerizable co-initiator is disclosed in EP-A 2033949 (AGFA NV).

[0083] In a more preferred embodiment, the aminobenzoate co-initiator is an oligomeric aminobenzoate derivative.

[0084] Particularly preferred aminobenzoic acid esters are polyether derivatives of aminobenzoic acid esters, wherein the polyether is selected from 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.

[0085] Preferred oligomeric amino benzoates are disclosed in WO1996 / 33157 (LAMBSON FINE CHEMICAL STLtd.) and WO2011 / 030089 (SUN CHEMICALS BV). Typical examples of polyethylene glycol bis(p-dimethylamino)benzoates are OMNIPOL ASA, commercially available from IGM Resins, and Speedcure 7040, commercially available from Lambson Fine Chemicals.

[0086] Other oligomerizing or polymerizing co-initiators include, for example, ESACURE A 198 (a multifunctional amine from IGM) and SARTOMER® CN3755 (an acrylated amine co-initiator from ARKEMA).

[0087] The amount of co-initiator is preferably 0.5 to 15% by weight, more preferably 1 to 10% by weight, and most preferably 2.5 to 7.5% by weight, all relative to the total weight of the inkjet ink.

[0088] Colorant Etching-resistant inkjet printers can be substantially colorless inkjet inks, but preferably they contain at least one colorant. The colorant will make the temporary mask clearly visible to the manufacturer of, for example, conductive patterns, thus allowing for visual inspection of quality.

[0089] The colorant in inkjet ink can be a pigment or dye, but dyes that are not bleached by the UV curing step are preferred.

[0090] Pigments can be black, white, cyan, magenta, yellow, red, orange, purple, blue, green, brown, or mixtures thereof. Colored pigments can be selected from those disclosed in HERBST, Willy et al., Industrial Organic Pigments, Production, Properties, Applications. 3rd ed. Wiley-VCH, 2004. ISBN 3527305769.

[0091] Suitable pigments are disclosed in paragraphs

[0128] to

[0138] of WO2008 / 074548 (AGFA NV).

[0092] The pigment particles in inkjet inks should be small enough to allow the ink to flow freely through the inkjet printing apparatus, especially at the jet nozzles. Small particles are also desirable for achieving maximum color intensity and slowing settling. Most preferably, the average pigment particle size is no greater than 150 nm. The average particle size is preferably determined using a Brookhaven Instruments Particle Sizer BI90plus based on the principle of dynamic light scattering.

[0093] Typically, dyes exhibit higher light fading than pigments, but this does not cause problems with jetting performance. Anthraquinone dyes were found to exhibit only slight light fading under normal UV curing conditions used in inkjet printing processes.

[0094] In a preferred embodiment, the colorant in the etch-resistant inkjet ink is an anthraquinone dye, such as Macrolex from LANXESS. TM Blue 3R (CASRN 325781-98-4).

[0095] Other preferred dyes include crystal violet and copper phthalocyanine dyes.

[0096] The amount of colorant is preferably 0.25 to 5.0% by weight, more preferably 0.5 to 2.5% by weight, both based on the total weight of the inkjet ink.

[0097] Polymer dispersants If the colorant in the etch-resistant inkjet ink is a pigment, then the inkjet ink preferably contains a dispersant, more preferably a polymeric dispersant, to disperse the pigment.

[0098] Suitable polymeric dispersants are copolymers of two monomers, but they can contain three, four, five, or even more monomers. The properties of polymeric dispersants depend on the properties of the monomers and their distribution in the polymer. Copolymeric dispersants preferably have the following polymer composition: - Statistical polymerization of monomers (e.g., monomers A and B polymerize into ABBAABAB); - Alternating polymerization of monomers (e.g., monomers A and B polymerize to form ABABABAB); - Gradient (gradual) polymerization of monomers (e.g., monomers A and B polymerize into AAABAABBABBBB); - Block copolymers (e.g., monomers A and B polymerized into AAAAABBBBBB), where the block length of each block (2, 3, 4, 5 or even more) is important for the dispersing ability of polymeric dispersants; - Graft copolymers (graft copolymers consist of a polymer backbone and polymer side chains attached to the backbone); and - These polymers can be in mixed forms, such as block gradient copolymers.

[0099] Suitable polymeric dispersants are listed in the “Dispersants” section of EP-A 1911814 (AGFA NV), and more specifically in

[0064] to

[0070] and

[0074] to

[0077] .

[0100] Polymer inhibitors Etching-resistant inkjet inks may contain at least one inhibitor to improve the thermal stability of the ink.

[0101] Suitable polymerization inhibitors include phenolic antioxidants, hindered amine light stabilizers, phosphorus-based antioxidants, hydroquinone monomethyl ether commonly used in (meth)acrylate monomers, and hydroquinone. Tert-butylcatechol, pyrogallol, 2,6-di-tert-butyl-4-methylphenol (BHT), and phenothiazines can also be used.

[0102] The inhibitor is preferably a polymerizable inhibitor.

[0103] Since excessive addition of these polymerization inhibitors may reduce the curing rate, it is preferable to determine the amount that can prevent polymerization before blending. The amount of polymerization inhibitor is preferably less than 5% by weight, more preferably less than 3% by weight, relative to the total weight of the inkjet ink.

[0104] surfactants Etching-resistant inkjet inks may contain at least one surfactant, but preferably no surfactant.

[0105] Surfactants can be anionic, cationic, nonionic, or amphoteric, and are typically added in a total amount of less than 1% by weight 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, alkylbenzene sulfonates, sulfosuccinate salts and phosphate salts of higher alcohols (e.g., sodium dodecylbenzene sulfonate and sodium dioctyl sulfosuccinate), ethylene oxide adducts of higher alcohols, ethylene oxide adducts of alkylphenols, ethylene oxide adducts of polyol fatty acid esters, and acetylene glycol and its ethylene oxide adducts.

[0107] Preferred surfactants are selected from fluorinated surfactants (such as fluorinated hydrocarbons) and organosilicon surfactants. Organosilicon surfactants are preferably siloxanes and may be alkoxylated, polyether-modified, polyether-modified hydroxyl-functionalized, amine-modified, epoxy-modified, and other modified or combinations thereof. Preferred siloxanes are polymerized, such as polydimethylsiloxane.

[0108] Preferred commercially available silicone surfactants include BYK from BYK Chemie. TM 333 and BYK TM UV3510 and Tego® glide from Evonik Industries.

[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 because 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] The amount of surfactant is preferably 0 to 3% by weight, more preferably 0.01 to 1% by weight, all based on the total weight of the radiation-curable inkjet ink.

[0113] Flame retardant Etching-resistant inkjet inks may contain flame retardants.

[0114] Preferred flame retardants are inorganic flame retardants, such as alumina trihydrate and boehmite; organophosphorus compounds, such as organophosphates (e.g., triphenyl phosphate (TPP), resorcinol bis(diphenyl phosphate) (RDP), bisphenol A diphenyl phosphate (BADP), and tricresyl phosphate (TCP)); organophosphonates (e.g., dimethyl methylphosphonate (DMMP)); and organophosphines (e.g., aluminum dimethylphosphines).

[0115] Other preferred organophosphorus compounds are disclosed in US8273805.

[0116] Preparation of inkjet ink The preparation of radiation-curable inkjet inks with added pigments is well known to those skilled in the art. Preferred preparation methods are disclosed in paragraphs

[0076] to

[0085] of WO2011 / 069943 (AGFA NV).

[0117] Chemical milling method The chemical milling method according to the present invention uses the inkjet ink described above as an etch-resistant inkjet ink.

[0118] Chemical milling, also known as industrial etching, is a subtractive manufacturing process that uses a temperature-controlled bath of etching chemicals to remove material to create an object with a desired shape.

[0119] Chemical milling methods can be used to manufacture decorative or precision components. Such methods are disclosed, for example, in EP-A3201277 (AGFA-GEVAERT NV).

[0120] In another embodiment, a chemical milling method is used to manufacture decorative etched glass plates. Such methods are disclosed, for example, in WO2013 / 189762 (AGC) and EP-A 3210946 (AGFA-GEVAERT NV).

[0121] The chemical milling method according to the present invention includes the following steps: a) Forming a protected area on a metal or glass surface by spraying and curing an anti-etching inkjet ink as described above. b) Removing metal or glass from unprotected areas of a metal or glass surface by etching, and c) Remove at least partially the cured inkjet ink from the protected area of ​​the metal or glass surface.

[0122] Methods for manufacturing printed circuit boards (PCBs) The method for manufacturing a PCB according to the present invention uses inkjet inks described above as etch-resistant inkjet inks.

[0123] The method includes the following steps: a) A protected area is formed on a metal surface by spraying and curing an anti-etching inkjet ink as described above. b) Remove metal from unprotected areas of the metal surface by etching, and c) Remove at least partially the cured inkjet ink from the protected area of ​​the metal surface.

[0124] In PCB manufacturing, metal foils or sheets are used to form conductive circuits. The metal sheets can be attached to the substrate.

[0125] There are no restrictions on the properties of the metal surface. The metal surface is preferably composed of copper, aluminum, nickel, iron, tin, titanium, or zinc, but it can also be an alloy containing these metals. In a preferred embodiment, the metal surface is made of copper. Copper has high electrical conductivity and is a relatively inexpensive metal, making it ideal for manufacturing printed circuit boards.

[0126] Metal sheets used for standard PCBs typically have a thickness of 35 to 105 µm. Metal sheets used for high-current PCBs typically have a thickness of more than 150 µm, preferably 300 to 800 µm.

[0127] Metal sheets or foils are typically attached to a substrate.

[0128] There are no practical restrictions on the type of substrate, as long as it is non-conductive. The substrate can be made of ceramic, glass, or plastic, or even a second (cheaper) metal plate. The metal can also be an alloy.

[0129] A substrate is a dielectric material, most commonly composed of epoxy resin and fiberglass braided fabric (and sometimes, non-woven fabric). The chosen substrate material will determine the mechanical, thermal, and chemical properties of the circuit board.

[0130] The most widely used substrate in PCB manufacturing is FR-4. It consists of a glass-reinforced epoxy resin laminate. Epoxy resin is fire-retardant, water-resistant, and non-hygroscopic.

[0131] Ceramic substrates are also used, especially for better thermal performance. Polyimide substrates are commonly used for flexible PCBs.

[0132] For thick copper PCBs, the range of substrates can range from standard FR-4 with an operating temperature of 130°C to more advanced materials with extremely high glass transition temperatures (Tg).

[0133] Cleaning the metal surface is preferable before printing resist inkjet inks. This is especially important when the metal surface is handled by hand (and without gloves). Cleaning removes dust particles and grease, which can interfere with the adhesion of inkjet inks to the metal surface. In PCBs, copper surfaces are often cleaned by micro-etching. The oxide layer of copper is removed and roughness is introduced to improve adhesion.

[0134] Etching steps A resist is provided on the metal or glass surface by applying and curing an etch-resistant inkjet ink as described above to form a cured image on the metal or glass surface. The metal or glass surface that was never covered by the cured image is then removed by etching.

[0135] In PCB manufacturing, depending on the etchant used, two wet etching methods are typically employed: acid etching or alkaline etching. In the PCB manufacturing according to the present invention, acid etching is preferred.

[0136] The etchant used for acid etching is preferably an aqueous solution with a pH less than 3, more preferably less than 2. The acid etchant preferably includes at least one acid selected from nitric acid, picric acid, hydrochloric acid, hydrofluoric acid, and sulfuric acid.

[0137] The etchant used for alkaline etching is preferably an aqueous solution with a pH of 8 to 10, and more preferably not exceeding 9. The alkaline etchant preferably includes at least one alkali selected from ammonia or ammonium hydroxide, potassium hydroxide, and sodium hydroxide.

[0138] The etchant preferably contains metal salts such as copper dichloride, copper sulfate, potassium ferricyanide, and ferric chloride, with copper dichloride being the most preferred.

[0139] For PCB manufacturing, etching time depends on the amount of copper that needs to be removed. When producing high-current PCBs, the etching time will typically be longer than that for manufacturing standard PCBs.

[0140] The etching time for standard PCBs is typically 1 to 15 minutes, while for high-current PCBs, the etching time is typically 30 to 45 minutes.

[0141] Etching is preferably performed at a temperature of 30 to 50°C.

[0142] For chemical milling or etching of glass, different etchants and etching conditions can be used, as described in EP-A3201277 (AGFA-GEVAERT NV) and EP-A 3210946 (AGFA GEVAERT NV), respectively.

[0143] It is preferable to rinse with water after etching to remove any residual etchant.

[0144] Peeling steps After etching, the cured etch-resistant inkjet ink must be at least partially removed from the metal or glass surface so that, for example, an electrical or electronic device can contact the remaining metal surface (conductive pattern), or to make decorative features of the etched metal plate fully visible. For example, electronic components such as transistors must be able to make electrical contact with conductive (copper) patterns on a printed circuit board. In a preferred embodiment, the cured etch-resistant inkjet ink is completely removed from the metal surface.

[0145] In a preferred embodiment, the cured etch-resistant inkjet ink is removed from the protected area using an alkaline stripping bath. Such an alkaline stripping bath is preferably an aqueous solution, more preferably an aqueous sodium hydroxide solution with a pH > 10. The stripping step is preferably carried out at a temperature between 30 and 50°C.

[0146] Inkjet printing equipment The etch-resistant inkjet ink according to the invention can be sprayed by spraying small droplets onto one or more printheads on a substrate in a controlled manner through nozzles, the substrate being moved relative to the printheads.

[0147] A piezoelectric printhead is the preferred printhead for an inkjet printing system. Piezoelectric inkjet printing is based on the movement of a piezoelectric ceramic transducer when a voltage is applied to it. The application of voltage alters the shape of the piezoelectric ceramic transducer in the printhead, creating a void that is subsequently filled with ink. When the voltage is removed, the ceramic expands back to its original shape, ejecting ink droplets from the printhead. However, the inkjet printing method according to the invention is not limited to piezoelectric inkjet printing. Other inkjet printheads can be used, including various types such as continuous inkjet printheads.

[0148] Inkjet printheads typically scan laterally back and forth across the moving surface of the ink-receiving object. Typically, the printhead does not print on the return stroke. For high area throughput, bidirectional printing is preferred. Another preferred printing method is a "single-pass" printing process, which can be performed using a page-width inkjet printhead or by using multiple staggered inkjet printheads covering the entire width of the ink-receiving surface. In a single-pass printing process, the printhead is typically kept stationary while the ink-receiving surface is conveyed beneath the printhead.

[0149] Curing device Etching-resistant inkjet inks can be cured by exposing them to photochemical radiation, such as electron beams or ultraviolet radiation. Preferably, the inkjet ink is cured by ultraviolet radiation, and more preferably by UV LED curing.

[0150] In inkjet printing, the curing method can be combined with the printhead of the inkjet printer and travel with the printhead, so that the curable liquid is quickly exposed to curing radiation after being sprayed.

[0151] In such an arrangement, it may be difficult to provide a sufficiently small radiation source, other than a UV LED, that is connected to the printhead and travels with it. Therefore, a statically fixed radiation source, such as a curing UV light source, can be used, which is connected to the radiation source by means of a flexible radiation conduction device such as a fiber bundle or an internal reflective flexible tube.

[0152] Alternatively, photochemical radiation can be supplied to the radiator from a fixed source by arranging mirrors, including mirrors, on the radiator.

[0153] The radiation source can also be an elongated radiation source that extends laterally across the substrate to be cured. It can be adjacent to the lateral path of the printhead, so that subsequent rows of images formed by the printhead can pass under the radiation source in a step-by-step or continuous manner.

[0154] Any ultraviolet light source, as long as a portion of the emitted light can be absorbed by a photoinitiator or photoinitiator system, can be used as a radiation source, such as high-pressure or low-pressure mercury lamps, cold cathode tubes, black lights, ultraviolet LEDs, ultraviolet lasers, and flash lamps. Among these, sources exhibiting a relatively long wavelength UV contribution with a dominant wavelength of 300-400 nm are preferred. Specifically, UV-A light sources are preferred because the reduced light scattering from this source leads to more efficient internal curing.

[0155] UV radiation is typically classified as UV-A, UV-B, and UV-C as follows: • UV-A: 400 nm to 320 nm • UV-B: 320 nm to 290 nm • UV-C: 290 nm to 100 nm.

[0156] In a preferred embodiment, the etch-resistant inkjet ink is cured by a UV LED. The inkjet printing apparatus preferably includes one or more UV LEDs with a wavelength preferably greater than 360 nm, more preferably one or more UV LEDs with a wavelength greater than 380 nm, and most preferably a UV LED with a wavelength of about 395 nm.

[0157] Furthermore, two light sources with different wavelengths or illuminances can be used continuously or simultaneously to cure ink images. For example, the first UV source can be selected to be rich in UV-C, particularly in the 260 nm–200 nm range. Then, the second UV source can be rich in UV-A, such as a gallium-doped lamp, or different lamps with high levels of both UV-A and UV-B. Using two UV sources has been found to have advantages such as faster curing speed and higher curing degree.

[0158] To facilitate curing, inkjet printing apparatuses typically include one or more oxygen-deficient units. These units contain a cover layer of nitrogen or other relatively inert gases (e.g., CO2) with adjustable position and concentration to reduce the oxygen concentration in the curing environment. Residual oxygen levels are typically kept as low as 200 ppm, but are generally in the range of 200 ppm to 1200 ppm. Example

[0159] Material Unless otherwise stated, all materials used in the following examples are readily available from standard sources such as ALDRICH CHEMICAL Co. (Belgium) and ACROS (Belgium). The water used was deionized water.

[0160] SR606A is available from ARKEMA as a Sartomer TM Neopentyl glycol hydroxytrimethyl acetate diacrylate obtained from SR606A.

[0161] AA-4 is diethylacrylamide from KJ Chemicals Corporation.

[0162] AA-5 is an acrylamide morpholine derived from RAHN.

[0163] ITX is available from BASF via Darocur TM A mixture of 2- and 4-isopropylthioxanthone isomers obtained by ITX.

[0164] TPO is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, a compound that can be obtained from BASF using Darocur. TM TPO-derived photoinitiators.

[0165] TPO-L is ethyl phenyl (2,4,6-trimethylbenzoyl)phosphinic acid, which is commercially available from ARKEMA as SpeedCure TPO-L.

[0166] EPD is available from RAHN via Genocure TM Ethyl 4-dimethylaminobenzoate obtained by EPD.

[0167] MC-4 is phthalic acid (2-acryloyloxyethyl ester) from ARKEMA.

[0168] MC-5 is 2-carboxyethyl acrylate from ALDRICH.

[0169] INHIB is a mixture that forms a polymerization inhibitor and has a composition according to Table 6.

[0170] Table 6 Cupferron TM AL is aluminum N-nitrosophenylhydroxylamine from WAKO CHEMICALS LTD.

[0171] Dye-1 is available from LANXESS using Macrolex. TM Blue 3R yields a blue anthraquinone dye.

[0172] TEGO 410 is a polyether siloxane surfactant that is commercially available from EVONIK under the TEGO® Glide brand.

[0173] The CuCl2 etching solution is a solution of 34.9 g of copper chloride (2) hydrate in 80 g of distilled water and 17 g of HCl (37%).

[0174] II-1 is an N-phenylacrylamide derived from Chemosyntha BV.

[0175] II-2 is an N-benzylacrylamide derived from Chemosyntha BV.

[0176] II-3 is N-benzylmethylacrylamide prepared according to Abel et al. (Macromolecules (Washington, D.C., USA), 49(2), 465-474(2016)).

[0177] II-4 is N-(2-phenylethyl)acrylamide prepared as disclosed in WO2010086211 (Agfa Graphics NV).

[0178] II-6 is N-(4-phenylbutyl)acrylamide prepared as described below.

[0179] 3-Chloro-N-(4-phenylbutyl)propionamide 14.29 g (0.1 mol) of 4-phenylbutylamine was dissolved in 150 mL of ethyl acetate. A solution of 9 g (0.107 mol) of sodium bicarbonate in 180 mL of water was added, and the mixture was cooled to 0 °C. A solution of 13.96 g (0.11 mol) of 3-chloropropionyl chloride in 30 mL of ethyl acetate was added, while stirring vigorously and maintaining the temperature at 0 °C. The reaction was allowed to continue for one hour. The ethyl acetate fraction was separated, dried over MgSO4, and evaporated under reduced pressure. 23.5 g (y: 98%) of crude 3-chloro-N-(4-phenylbutyl)propionamide was obtained and used directly in step two without intermediate purification.

[0180] N-(4-Phenylated Butyl)acrylamide 23 g (0.096 mol) of 3-chloro-N-(4-phenylbutyl)acrylamide was dissolved in 130 mL of ethyl acetate. 21.9 g (0.144 mol) of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) was added, and the reaction was continued at room temperature for two hours, followed by a further reaction at 50 °C for 90 minutes. The reaction mixture was cooled to room temperature, and the precipitated salt was removed by filtration. The solvent was removed under reduced pressure, and the crude N-(4-phenylbutyl)acrylamide was purified by preparative column chromatography on a Merck-supplied SVP D40 rapid column (eluent: dichloromethane). 13.3 g (y: 68%) of N-(4-phenylbutyl)acrylamide was isolated (on a Merck-supplied TLC silica gel column at 60°F). 254 TLC analysis was performed on the plate using dichloromethane / methanol 98 / 2 as the eluent. f :0.3).

[0181] II-7 is 2-phenoxyethyl methacrylate from Arkema.

[0182] II-8 is 2-phenoxyethyl acrylate from IGM Resins.

[0183] II-9 is benzyl acrylate from ABCR GmbH & Co.

[0184] II-10 is benzyl methacrylate from Sigma-Aldrich NV.

[0185] II-11 is 2-phenylthioethyl acrylate from Bimax Chemicals Ltd.

[0186] II-12 is 2-hydroxy-3-phenoxypropyl acrylate and is commercially available from Sartamomer CN131B.

[0187] method Pre-processed substrate In this embodiment, a Cu-clad laminate (EM-825(I) CAF Resistant 0.152mm) available from CCI EUROLAM was used as the substrate. This substrate was tested at 25°C using MECBrite available from MEC Europe. TM Pre-treat with CA-95MH acid pretreatment solution for 20 seconds.

[0188] Printing and curing Examples 1 to 3 were printed on the aforementioned substrate using a MicroCraft CPS2013 printer (4 passes, 1440x1440 dpi) equipped with a KM1024i SHE printhead from Konica Minolta at temperatures ranging from 40 to 55°C. The temperature was adjusted to 45°C. The printing speed was 20 inches per second; UV curing was performed using 12 W LEDs (395 nm) at 100% total LED power in all print passes, with two additional UV curing passes (100% LED power) at the end of the printing process.

[0189] Example 4 was printed on the aforementioned substrate using a MicroCraft CPS2013 printer (4 passes, 1440x1440 dpi) equipped with a KM1024i SHE printhead from Konica Minolta, at temperatures ranging from 40 to 55°C. The temperature was adjusted to 45°C. The printing speed was 20 inches per second; UV curing was performed using 12 W LEDs (395 nm), with 100% of the total LED power used in all print passes. No additional UV curing passes were applied at the end of the printing process.

[0190] Etching In the Rotaspray (model RS-1210 from Mega Electronics), etching was performed at 50°C for 15 minutes using a CuCl2 etching solution.

[0191] peeling In Examples 1 to 3, a 5% by weight NaOH solution was used in Rotaspray for 4 minutes at 50°C to perform peeling.

[0192] In Example 4, a 5% by weight NaOH solution was used to perform peeling at 50°C for different peeling times.

[0193] Etching resistance Evaluate etching resistance after etching. Rinse the etched copper plate with water and visually inspect it. Use the following evaluation methods: 0 = No peeling of cured ink 1 = A small amount of cured ink has peeled off (approximately 25%). 2 = A large amount of cured ink has peeled off (approximately 50%). 3 = Almost all of the cured ink has peeled off (75-100%). For PCB manufacturing, an etch resistance of less than 2 is preferred.

[0194] peelability In Examples 1 to 3, peelability was visually evaluated 4 minutes after the peeling process. The following evaluation method was used: 0 = All (100%) UV-cured ink was peeled off from the copper plate. 1 = A large amount (50-75%) of UV-cured ink was peeled off from the copper plate. 2 = A small amount (approximately 25%) of UV-cured ink was peeled off from the copper plate. 3 = Almost no UV-cured ink peeled off from the copper plate For PCB manufacturing, a peelability of less than 2 is preferred.

[0195] In Example 4, the peelability was visually evaluated using the following assessment criteria: 0.5 = All UV-cured ink is removed within 20 seconds. 1.0 = All UV-cured ink is removed within 40 seconds. 1.5 = All UV-cured ink is removed within 60 seconds. 3.0 = All UV-cured inks are removed within 120 seconds. For PCB manufacturing, a peelability of less than 3 is preferred.

[0196] UV sensitivity UV (LED) sensitivity was evaluated on a 10 µm inkjet ink coating on a PET substrate. Curing was performed using a single pass of 200% LED at 20 m / min. The following evaluation was conducted after UV exposure of the sample and rubbing with a cotton swab under moderate pressure: 0 = No visible scratches; 0.5 = Scratches are visible only on the ink coating; no scratches are visible on the uncoated substrate. 1.0 = Scratches are visible on both the ink-coated and uncoated substrates.

[0197] For PCB manufacturing, UV sensitivity is preferably less than 1.

[0198] Viscosity Using the "Robotic Viscometer TypeVISCObot" from CAMBRIDGE APPLIED SYSTEMS, at 45°C and 1000 s -1 The viscosity of the ink was measured at a certain shear rate.

[0199] For industrial inkjet printing, at 45°C and 1000 s -1 The viscosity at the shear rate is preferably between 5.0 and 15 mPa·s. More preferably, at 45°C and 1000 s⁻¹, the viscosity is...-1 The viscosity at the shear rate is less than 15 mPa·s.

[0200] Example 1 Comparative inkjet ink COMP-1 and the inkjet ink INV-2 of the present invention were prepared according to Table 7. Weight percentages (wt%) are based on the total weight of the radiation-curable compositions.

[0201] Table 7 Ingredients (weight %) COMP-1 INV-1 AA-5 37.5 32.05 II-8 - 10 SR606A 42.55 38 MC-5 3 3 MC-4 4 4 INHIB 1 1 ITX 4 4 EPD 4 4 TPO 2.95 2.95 Dye-1 1 1 Then, as described above, the inkjet inks COMP-1 and INV-1 are printed and cured. Table 8 shows the etch resistance and peelability evaluated as described above. Table 8 COMP-1 INV-1 Etching resistance 2 0 peelability 1 0 As can be clearly seen from Table 8, compared with inkjet inks that do not contain polymerizable compounds according to Formula II, the ink of the present invention INV-1 containing such compounds has improved etch resistance while maintaining sufficient peelability.

[0202] Example 2 Prepare the inkjet inks INV-2 to INV-7 of the present invention according to Table 9.

[0203] All weight percentages (%) are based on the total weight of the radiation-curable composition.

[0204] Table 9 Ingredients (weight %) INV-2 INV-3 INV-4 INV-5 INV-6 INV-7 AA-5 37.05 27.05 22.05 35.05 36.05 39.05 II-8 5 15 20 10 10 10 SR606A 38 38 38 38 38 38 MC-5 3 3 3 x 3 x MC-4 4 4 4 4 x x INHIB 1 1 1 1 1 1 ITX 4 4 4 4 4 4 EPD 4 4 4 4 4 4 TPO 2.95 2.95 2.95 2.95 2.95 2.95 Dye-1 1 1 1 1 1 1 Then, inkjet inks INV-2 to INV-7 are printed and cured as described above. Table 10 shows the etch resistance and peelability evaluated as described above.

[0205] Table 10 INV-2 INV-3 INV-4 INV-5 INV-6 INV-7 Etching resistance 1 0 0 1 1 1.5 peelability 1 0 0 1 0 0 As can be clearly seen from Table 10, all inks of the present invention containing such compound II exhibit improved etch resistance compared to inkjet inks (COMP-01) that do not contain the polymerizable compound according to Formula II, while maintaining sufficient peelability. It is also clear that etch resistance improves as the amount of the polymerizable compound according to Formula II increases.

[0206] Table 10 also clearly shows that monofunctional acrylates MC-4 and MC-5, which contain carboxyl groups, have an impact on etch resistance (INV-5 and INV-6). However, even in the absence of such acrylates (INV-7), etch resistance remains sufficient when the ink contains polymerizable compounds according to Formula II.

[0207] Example 3 The inkjet inks INV-8 to INV-17 of the present invention were prepared according to Table 11. Weight percentages (wt%) are based on the total weight of the radiation-curable composition.

[0208] Table 11 Ingredients (weight %) INV-8 INV-9 INV-10 INV-11 INV-12 INV-13 INV-14 INV-15 INV-16 INV-17 AA-5 32 32 32 32 32 32 32 32 32 32 II-9 10 - - - - - - - - - II-10 - 10 - - - - - - - - II-3 - - 10 - - - - - - - II-11 - - - 10 - - - - - - II-12 - - - - 10 - - - - - II-1 - - - - - 10 - - - - II-2 - - - - - - 10 - - - II-4 - - - - - - - 10 - - II-6 - - - - - - - - 10 - II-7 - - - - - - - - - 10 SR606A 38 38 38 38 38 38 38 38 38 38 MC-5 3 3 3 3 3 3 3 3 3 3 MC-4 4 4 4 4 4 4 4 4 4 4 INHIB 1 1 1 1 1 1 1 1 1 1 ITX 4 4 4 4 4 4 4 4 4 4 EPD 4 4 4 4 4 4 4 4 4 4 TPO 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 Dye-1 1 1 1 1 1 1 1 1 1 1 Then, inkjet inks INV-8 to INV-17 are printed and cured as described above. Table 12 shows the etch resistance and peelability evaluated as described above.

[0209] Table 12 INV-8 INV-9 INV-10 INV-11 INV-12 INV-13 INV-14 INV-15 INV-16 INV-17 Etching resistance 0 0 0 0 0 0 0 0 0 0 peelability 1 0 0 1 1 0 0 0 0 1 As can be clearly seen from Table 12, all inks INV-8 to INV-17 containing polymerizable compounds according to Formula II have improved etch resistance and sufficient peelability.

[0210] Example 4 Comparative inkjet inks COMP-2 to COMP-4 and the inkjet inks INV-18 to INV-24 of the present invention were prepared according to Table 13. Weight percentages (wt%) are based on the total weight of the radiation-curable compositions.

[0211] Table 13 Ingredients (weight %) INV-18 COMP-2 INV-19 INV-20 INV-21 AA-4 15 15 15 - 7.5 AA-5 12.5 16.5 14.5 12.5 12.5 II-8 30.8 30.8 30.8 30.8 30.8 SR606A 8.5 8.5 8.5 23.5 16 MC-5 16 16 16 16 16 MC-4 4 4 4 4 4 INHIB 1 1 1 1 1 BAPO 4.7 4.7 4.7 4.7 4.7 ITX 4 - 2 4 4 TPO-L 2.5 2.5 2.5 2.5 2.5 Dye-1 1 1 1 1 1 TEGO 410 0.02 0.02 0.02 0.02 0.02 Ingredients (weight %) INV-22 INV-23 COMP-3 COMP-4 INV-24 AA-4 15 15 - 15 15 AA-5 - 6 - 21 17 II-8 30.78 30.78 30.78 30.78 30.78 SR606A 21 15 36 - 4 MC-5 16 16 16 16 16 MC-4 4 4 4 4 4 INHIB 1 1 1 1 1 BAPO 4.7 4.7 4.7 4.7 4.7 ITX 4 4 4 4 4 TPO-L 2.5 2.5 2.5 2.5 2.5 Dye-1 1 1 1 1 1 TEGO 410 0.02 0.02 0.02 0.02 0.02 The inkjet ink was then printed and cured as described above. Table 14 shows the etch resistance, peelability, and curing efficiency evaluated as described above.

[0212] Table 14 INV-18 COMP-2 INV-19 INV-20 INV-21 Etching resistance 0 0 0 1 1 peelability 0.5 0.5 0.5 1 0.5 UV sensitivity 0 1 0.5 0.5 0.5 INV-22 INV-23 COMP-3 COMP-4 INV-24 Etching resistance 1.5 1.5 1.5 2 1 peelability 0.5 1 1.5 1.5 1.5 UV sensitivity 0.5 0.5 1 0.5 0.5 The results in Table 14 clearly show that: Inkjet inks without thioxanthone photoinitiators have insufficient UV sensitivity (COMP-2). The amount of thioxanthone photoinitiator affects UV sensitivity (INV-18; INV-19).

[0213] Inkjet inks that do not contain acrylamide according to Formula 1 have insufficient UV sensitivity (COMP-3). The amount of acrylamide affects UV sensitivity, etch resistance, and / or peelability (INV-20 to INV-23).

[0214] Inkjet inks without polyfunctional (meth)acrylates have insufficient etch resistance and peelability (COMP-4). The amount of polyfunctional (meth)acrylates affects etch resistance and peelability (INV-24).

Claims

1. An etch-resistant inkjet ink, the etch-resistant inkjet ink comprising: - One or more photoinitiators, wherein at least one photoinitiator is a thioxanthone compound. - One or more acrylamides according to formula I, in R represents H or CH3; R1 and R2 represent the alkyl groups that are optionally substituted, independently of each other; R1 and R2 can represent the necessary atoms for forming a 5- or 6-membered ring; - One or more polymerizable compounds according to Formula II, and in X = O, S, or NH. R = H or CH3, L is a divalent linker for a randomly substituted one to five atomic groups; n is 0 or 1; and A is an optional substituted aromatic group; - One or more polyfunctional (meth)acrylates.

2. The anti-etching inkjet ink according to claim 1, wherein at least one photoinitiator is an acylphosphine oxide compound.

3. The etch-resistant inkjet ink according to claim 1 or 2, wherein the amount of the thioxanone compound is 1 to 10 by weight relative to the total weight of the inkjet ink.

4. The etch-resistant inkjet ink according to any one of the preceding claims, wherein the amount of the acylphosphine oxide compound is 1 to 10 by weight relative to the total weight of the inkjet ink.

5. The etch-resistant inkjet ink according to any one of the preceding claims, wherein the compound according to Formula I is selected from 4-acryloylmorpholine (ACMO) and diethylacrylamide.

6. The etch-resistant inkjet ink according to any one of the preceding claims, wherein the total amount of the compound according to Formula I is 25 to 60 by weight relative to the total weight of the inkjet ink.

7. The etch-resistant inkjet ink according to any one of the preceding claims, wherein the compound according to formula II is phenoxyethyl acrylate (PEA).

8. The etch-resistant inkjet ink according to any one of the preceding claims, wherein the total amount of the compound according to formula II is 2.5 to 25% by weight.

9. The etch-resistant inkjet ink according to any one of the preceding claims, wherein the etch-resistant inkjet ink further comprises one or more (meth)acrylates containing acid groups.

10. The etch-resistant inkjet ink of claim 9, wherein the amount of the acid-containing (meth)acrylate is 2.5 to 25% by weight relative to the total weight of the inkjet ink.

11. The etch-resistant inkjet ink according to any one of the preceding claims, wherein the total amount of the polyfunctional (meth)acrylate is 2.5 to 25% by weight.

12. A method for inkjet printing, the method comprising the steps of: a) Forming a protected area on a metal or glass surface by spraying and curing the anti-etching inkjet ink according to any one of claims 1 to 11; b) Remove the metal or glass from the unprotected area of ​​the metal or glass surface by etching, and c) Remove at least partially the cured inkjet ink from the protected area of ​​the metal or glass surface.

13. The inkjet printing method according to claim 12 is used to manufacture a printed circuit board (PCB).

14. The inkjet printing method according to claim 13, wherein the PCB is a high-current PCB.

15. Use of the etch-resistant inkjet ink according to any one of claims 1 to 11 in the manufacture of PCBs.

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