阅读说明：本技术 用于制造印刷电路板的喷墨油墨 (Inkjet inks for the manufacture of printed circuit boards ) 是由 J·罗库费尔 R·托夫斯 于 2019-02-28 设计创作，主要内容包括：包含根据式I的粘合促进剂的可辐射固化的喷墨油墨,其中X选自O和NR<Sub>3</Sub>,L表示包含1至20个碳原子的二价连接基团,R<Sub>1</Sub>选自氢、取代或未取代的烷基和取代或未取代的芳基,R<Sub>2</Sub>选自取代或未取代的烷基、取代或未取代的烯基、取代或未取代的炔基、取代或未取代的烷芳基、取代或未取代的芳烷基和取代或未取代的(杂)芳基,R<Sub>3</Sub>选自氢、取代或未取代的烷基、取代或未取代的烯基、取代或未取代的炔基、取代或未取代的烷芳基、取代或未取代的芳烷基和取代或未取代的(杂)芳基,R<Sub>2</Sub>和L可表示形成5至8元环所必需的原子。<Image he="97" wi="155" file="538769DEST_PATH_IMAGE001.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(Radiation curable inkjet ink comprising an adhesion promoter according to formula I wherein X is selected from O and NR 3 L represents a divalent linking group comprising from 1 to 20 carbon atoms, R 1 Selected from the group consisting of hydrogen, substituted or unsubstituted alkyl and substituted or unsubstituted aryl, R 2 Selected from the group consisting of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkylaryl, substituted or unsubstituted arylalkyl and substituted or unsubstituted (hetero) aryl, R 3 Selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, andsubstituted or unsubstituted (hetero) aryl, R 2 And L may represent the atoms necessary to form a 5 to 8 membered ring.)

1. A radiation curable inkjet ink comprising an adhesion promoter according to formula I,

wherein

X is selected from O and NR₃，

L represents a divalent linking group comprising 1 to 20 carbon atoms,

R₁selected from the group consisting of hydrogen, substituted or unsubstituted alkyl groups and substituted or unsubstituted aryl groups,

R₂selected from the group consisting of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, and substituted or unsubstituted (hetero) aryl,

R₃selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, and substituted or unsubstituted (hetero) aryl,

R₂and L may represent the atoms necessary to form a 5 to 8 membered ring.

2. The radiation curable inkjet ink according to claim 1 wherein X represents oxygen.

3. The radiation curable inkjet ink according to claim 1 or 2, wherein R₁Is hydrogenOr a methyl group.

4. The radiation curable inkjet ink according to any one of the preceding claims, wherein R₂Comprising at least one polymerizable group selected from the group consisting of acrylates, methacrylates, acrylamides, and methacrylamides.

5. The radiation curable inkjet ink according to any one of the preceding claims, wherein the amount of adhesion promoter is between 0.5 and 15 wt% relative to the total weight of the radiation curable inkjet ink.

6. The radiation curable inkjet ink according to any one of the preceding claims comprising a polymerizable compound having a pKa of at least 2.5.

7. The radiation curable inkjet ink according to claim 6, wherein the polymerizable compound is a phenolic monomer.

8. The radiation curable inkjet ink according to claim 7, wherein the phenolic monomer is selected from the group consisting of phenolic acrylates, phenolic methacrylates, phenolic acrylamides and phenolic methacrylamides.

9. A method of manufacturing a Printed Circuit Board (PCB), wherein an inkjet printing step is used, characterized in that in the inkjet printing step a radiation curable inkjet ink as defined in any one of claims 1 to 8 is jetted and cured on a substrate.

10. The method of claim 9, wherein curing is performed using UV radiation.

11. A method according to claim 9 or 10, wherein in the inkjet printing step a solder resist layer is provided on a dielectric substrate comprising a conductive pattern.

12. The method of claim 11, further comprising a heating step.

13. A method according to claim 9 or 10, wherein a resist is provided on the metal surface in the inkjet printing step.

14. The method of claim 13, wherein the metal surface is a copper surface.

15. The method according to claim 13 or 14, wherein a radiation curable inkjet ink as defined in any one of claims 6 to 8 is used.

Technical Field

The present invention relates to radiation curable inkjet inks that can be used to manufacture PCBs, for example as resist inkjet inks, and to methods of manufacturing such PCBs.

Background

The manufacturing workflow of Printed Circuit Boards (PCBs) is gradually shifting from standard workflow to digital workflow to reduce the amount of process steps and to reduce the cost and environmental impact of PCBs manufacturing, especially for small volume manufacturing. Ink jet is one of the preferred digital fabrication techniques in the different steps of the PCB manufacturing process, from resist on solder mask to letterpress (legend printing). Thus, a preferred inkjet ink is a UV curable inkjet ink.

Bonding is critical in the various manufacturing steps. Adhesion promoters are often required in order to maximize adhesion performance.

Several classes of adhesion promoters have been disclosed in the prior art, most of which have acidic properties.

WO2004/026977(Avecia) discloses a non-aqueous resist inkjet ink comprising 1 to 30 wt% of an acrylate functional monomer containing one or more acidic groups, the monomer acting as an adhesion promoter and a dissolution promoter during stripping.

WO2004/106437(Avecia) discloses a resist inkjet ink which preferably comprises a (meth) acrylate acidic adhesion promoter, such as (meth) acrylated carboxylic acids, (meth) acrylated phosphate esters and (meth) acrylated sulphonic acids.

However, in low viscosity inkjet inks, acid adhesion promoters are often the root cause of instability, which causes undesirable viscosity increases or colloidal instability in pigmented systems. Thus, there is a need for non-acidic adhesion promoters that combine excellent adhesion properties with high stability in low viscosity radiation curable formulations such as inkjet inks.

Disulfide-based adhesion promoters have been shown to have excellent bonding properties to precious metals in high viscosity UV curable compositions for Dental applications, as described, for example, in Ikemura et al, Dental Materials Journal, 30(4), 493-500 and 30(6), 827-836 (2011); EP-A2036532 (Kabushiki Kaisha Shofu); Tanaka et al, Dental Materials Journal, 26(4), 514-518 (2007); DE102005002750(Ernst Muehlbauer GmbH & Co); and WO2002/025282 (Motorola).

Therefore, there is a need for alternative adhesion promoters for radiation curable inkjet inks for PCB manufacturing processes.

Disclosure of Invention

It is an object of the present invention to provide a radiation curable inkjet ink for use in a process for manufacturing PCBs, which is characterized by good adhesion while maintaining excellent jetting, stability and release properties.

The object of the present invention has been achieved by the radiation curable inkjet ink as defined in claim 1 and the method of manufacturing a PCB as defined in claim 9.

It has been found that radiation curable compositions comprising disulfide based adhesion promoters according to formula I exhibit excellent adhesion during etching of copper while maintaining excellent stability and jetting properties.

Other objects of the present invention will become apparent from the following detailed description.

Detailed Description

Definition of

The term "monofunctional", for example in monofunctional polymerizable compounds, means that the polymerizable compound comprises one polymerizable group.

The term "difunctional", for example in difunctional polymerizable compounds, means that the polymerizable compound comprises two polymerizable groups.

The term "multifunctional", for example in a multifunctional polymerizable compound, means that the polymerizable compound comprises more than two polymerizable groups.

The term "alkyl" refers to all possible variations for each number of carbon atoms in the alkyl group, i.e., methyl; an ethyl group; for 3 carbon atoms: n-propyl and isopropyl; for 4 carbon atoms: n-butyl, isobutyl, and tert-butyl; for 5 carbon atoms: n-pentyl, 1-dimethyl-propyl, 2-dimethylpropyl, and 2-methyl-butyl, and the like.

Unless otherwise specified, substituted or unsubstituted alkyl is preferably C₁To C₆An alkyl group.

Unless otherwise specified, substituted or unsubstituted alkenyl is preferably C₂To C₆An alkenyl group.

Unless otherwise specified, substituted or unsubstituted alkynyl is preferably C₂To C₆Alkynyl.

Unless otherwise specified, a substituted or unsubstituted aralkyl group preferably contains one, two, three or more C₁To C₆Alkyl phenyl or naphthyl.

Unless otherwise specified, a substituted or unsubstituted alkaryl group is preferably a C comprising a phenyl or naphthyl group₇To C₂₀An alkyl group.

Unless otherwise specified, substituted or unsubstituted aryl is preferably phenyl or naphthyl.

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

In e.g. substituted alkyl, the term "substituted" means that the alkyl group may be substituted with atoms other than those typically present in such groups, i.e. carbon and hydrogen. For example, a substituted alkyl group may include a halogen atom or a thiol group. Unsubstituted alkyl groups contain only carbon and hydrogen atoms.

Unless otherwise specified, substituted alkyl, substituted alkenyl, substituted alkynyl, substituted aralkyl, substituted alkaryl, substituted aryl and substituted heteroaryl groups are preferredOptionally substituted with one or more members selected from: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl and tert-butyl, esters, amides, ethers, thioethers, ketones, aldehydes, sulfoxides, sulfones, sulfonates, sulfonamides, -Cl, -Br, -I, -OH, -SH, -CN and-NO₂。

Radiation curable inkjet inks

The radiation curable inkjet ink of the present invention includes an adhesion promoter as described below.

The radiation curable inkjet ink preferably further comprises a polymerizable compound having a pKa of at least 2.5.

The radiation curable inkjet ink can be cured by any type of radiation, for example by electron beam radiation, but is preferably cured by UV radiation, more preferably by UV radiation from UV LEDs. Thus, the radiation curable inkjet ink is preferably a UV curable inkjet ink.

For reliable industrial inkjet printing, the viscosity of the radiation curable inkjet ink is preferably no more than 20mpa.s at 45 ℃, more preferably between 1 and 18mpa.s at 45 ℃, and most preferably between 4 and 14mpa.s at 45 ℃.

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

The radiation curable inkjet ink may further comprise other polymerizable compounds, colorants, polymeric dispersants, photoinitiators or photoinitiating systems, polymerization inhibitors, flame retardants, or surfactants.

Adhesion promoter

The adhesion promoter has a chemical structure according to formula I,

wherein

X is selected from O and NR₃，

L represents a divalent linking group comprising 1 to 20 carbon atoms,

R₁selected from the group consisting of hydrogen, substituted or unsubstituted alkyl groups and substituted or unsubstituted aryl groups,

R₂selected from the group consisting of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, and substituted or unsubstituted (hetero) aryl,

R₃selected from the group consisting of hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted alkaryl, substituted or unsubstituted aralkyl, and substituted or unsubstituted (hetero) aryl,

R₂and L may represent the atoms necessary to form a 5 to 8 membered ring.

In a preferred embodiment, X represents oxygen.

In a further preferred embodiment, R₁Selected from hydrogen and methyl, particularly preferably hydrogen.

In another preferred embodiment, R₂Comprising at least one polymerizable group selected from the group consisting of acrylates, methacrylates, acrylamides and methacrylamides, more preferably acrylates and methacrylates, most preferably acrylates.

In an even more preferred embodiment, the adhesion promoter is an adhesion promoter according to formula II,

wherein

X is as defined above, and X is as defined above,

R₃selected from the group consisting of hydrogen and methyl,

L₁represents an aliphatic linking group comprising 2 to 12 carbon atoms.

In a particularly preferred embodiment, X (in formulae I and II) represents an oxygen atom and R represents₃Represents hydrogen.

In the most preferred embodiment, L₁Represents a substituted or unsubstituted alkylene group containing 2 to 6 carbon atoms, morePreference is given to ethylene, propylene, butylene, pentylene and hexylene.

Without being limited thereto, examples of disulfide adhesion promoters according to the present invention are given in table 1.

TABLE 1

The amount of adhesion promoter in the radiation curable inkjet ink is preferably between 0.1 and 20 wt. -%, more preferably between 0.5 and 15 wt. -%, most preferably between 1 and 10 wt. -%, relative to the total weight of the inkjet ink.

When the equivalent is too low, the adhesion of the inkjet ink to the metal surface may be insufficient, and when the equivalent is too high, the ink viscosity may increase, and the shelf life may become more critical.

Other polymerizable Compounds

In addition to the above adhesion promoters, the radiation curable inkjet ink preferably comprises other polymerizable compounds.

The other polymerizable compounds may be monomers, oligomers, and/or prepolymers. These monomers, oligomers and/or prepolymers may have different functionalities. Mixtures comprising combinations of mono-, di-, tri-, and higher functionality monomers, oligomers, and/or prepolymers may be used. By varying the ratio between the monomers and oligomers, the viscosity of the radiation curable inkjet ink can be adjusted.

Particularly preferred monomers and oligomers are those listed in EP-A1911814 (Agfa NV) [0106] to [0115 ].

Other preferred monomers and oligomers are those disclosed in EP-As 2809735, 2725075, 2915856, 3000853 and 3119170 (all from Agfa Gevaert NV).

The radiation curable inkjet ink preferably comprises a polymerizable compound having a pKa of at least 2.5, preferably at least 4, more preferably at least 5, most preferably at least 7.

The polymerizable compound having a pKa of at least 2.5 is preferably a phenolic monomer.

The phenolic compound is preferably selected from the group consisting of phenolic acrylates, phenolic methacrylates, phenolic acrylamides and phenolic methacrylamides, more preferably acrylates and methacrylates.

Without being limited thereto, typical phenolic monomers are given in table 2.

TABLE 2

In another preferred embodiment, the radiation curable composition comprises a monomer according to formula III,

wherein

A₁And A₂Is independently selected from the group consisting of acrylates, methacrylates, acrylamides and methacrylamides, and

L₂and L₃Represents a divalent linking group comprising 2 to 10 carbon atoms.

Preferably A₁And A₂Independently selected from acrylates and methacrylates, with acrylates being particularly preferred.

Specific examples of monomers according to formula III are disclosed in paragraph [0056] of EP-A2703180 (Agfa-Gevaert N.V.).

Coloring agent

The radiation curable inkjet may be a substantially colourless inkjet ink, but preferably the radiation curable inkjet comprises at least one colorant. The colorant makes the temporary resist layer clearly visible to the manufacturer of the conductive pattern, allowing visual inspection of the quality.

The colorant may be a pigment or a dye, but is preferably a dye that is not bleached by the UV curing step during the inkjet printing process of the radiation curable inkjet. The pigment can be black, white, cyan, magenta, yellow, red, orange, violet, blue, green, brown, mixtures thereof, and the like. The color pigments may be selected from those disclosed in HERBST, Willy et al, Industrial organic pigments, Production, Properties, applications, 3 rd edition Wiley-VCH, 2004. ISBN 3527305769.

Suitable pigments are disclosed in paragraphs [0128] to [0138] of WO 2008/074548.

The pigment particles in the inkjet ink should be small enough to allow the ink to flow freely through the inkjet printing device, particularly at the jet nozzle. It is also desirable to use small particles to obtain maximum color intensity and slow sedimentation. Most preferably, the average pigment particle size is no greater than 150 nm. The average particle size of the pigment particles is preferably determined on the basis of the dynamic light scattering principle using a Brookhaven Instrument Sizer BI90 plus.

Dyes generally exhibit higher photobleaching than pigments, but do not cause jettability problems. It has been found that anthraquinone dyes exhibit only slight photobleaching under the 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 from LANXESS^TMBlue 3R(CASRN 325781-98-4)。

Other preferred dyes include crystal violet and copper phthalocyanine dyes.

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

Polymeric dispersants

If the colorant in the radiation curable inkjet is a pigment, the radiation curable inkjet ink preferably comprises a dispersant, more preferably a polymeric dispersant, for dispersing the pigment.

Suitable polymeric dispersants are copolymers of two monomers, but they may comprise three, four, five or even more monomers. The nature of the polymeric dispersant depends both on the nature of the monomers and on their distribution in the polymer. The copolymer dispersant preferably has the following polymer composition:

statistically polymerized monomers (e.g., monomers a and B polymerized to ABBAABAB);

alternating polymerized monomers (e.g., monomers a and B polymerized to ABABABAB);

gradient (tapered) polymerized monomers (e.g., monomers a and B polymerized to aaabaababbabbb);

block copolymers (e.g., monomers a and B polymerized to AAAAABBBBBB), where the block length of each block (2, 3, 4, 5 or even greater) is important to the dispersability of the polymeric dispersant;

a graft copolymer (the graft copolymer is comprised of a polymeric backbone with polymeric side chains attached to the backbone); and

mixed forms of these polymers, such as block gradient copolymers.

Suitable polymeric dispersants are listed in EP-A1911814 in the section on "Dispersant", more particularly [0064] to [0070] and [0074] to [0077 ].

Commercial examples of polymeric dispersants are as follows:

• DISPERBYK^TMa dispersant from BYK CHEMIE GMBH;

•SOLSPERSE^TMa dispersant from NOVEON;

TEGO from EVONIK^TMDISPERS^TMA dispersant;

EDAPAN from M Ü NZING CHEMIE^TMA dispersant;

ETHACRYL from LYONDELL^TMA dispersant;

GANEX from ISP^TMA dispersant;

DISPEX from CIBA SPECIALTY CHEMICALS INC^TMAnd EFKA^TMA dispersant;

DISPONER from DEUCHEM^TMA dispersant; and

JONCRYL from JOHNSON polymerr^TMA dispersant.

Photoinitiator and photoinitiation system

The radiation curable inkjet ink preferably comprises at least one photoinitiator, but may comprise a photoinitiating system comprising a plurality of photoinitiators and/or co-initiators.

The photoinitiator in the radiation curable inkjet is preferably a free radical initiator, more specifically a Norrish type I initiator or a Norrish type II initiator. Free radical photoinitiators are compounds that initiate the polymerization of monomers and oligomers by forming free radicals upon exposure to actinic radiation. Norrish type I initiators are initiators which cleave immediately upon excitation to give an initiating free radical. Norrish type II initiators are photoinitiators that are activated by actinic radiation and form free radicals by abstracting a hydrogen from a second compound (which becomes the actual initiating free radical). This second compound is referred to as a polymerization synergist or co-initiator. Both type I and type II photoinitiators may be used in the present invention, either alone or in combination.

Suitable Photoinitiators are disclosed in CRIVELLO, j.v. et al, photonitiators for free radioactive and Anionic Photopolymerization, 2 nd edition, edited by BRADLEY, g., london, uk: john Wiley and Sons Ltd, 1998, pp 287-294.

Specific examples of photoinitiators may include, but are not limited to, the following compounds or combinations thereof: benzophenone and substituted benzophenones, 1-hydroxycyclohexyl phenyl ketone, thioxanthone (e.g. isopropylthioxanthone), 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-benzyl-2-dimethylamino- (4-morpholinophenyl) butan-1-one, benzyl dimethyl ketal, bis (2, 6-dimethylbenzoyl) -2,4, 4-trimethylpentylphosphine oxide, 2,4, 6-trimethylbenzoyldiphenylphosphine oxide, 2,4, 6-trimethoxybenzoyldiphenylphosphine oxide, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinopropan-1-one, 2-dimethoxy-1, 2-diphenylethan-1-one or 5, 7-diiodo-3-butoxy-6-fluorone.

Suitable commercially available photoinitiators include Irgacure^TM184、Irgacure^TM500、Irgacure^TM369、Irgacure^TM1700、Irgacure^TM651、Irgacure^TM819、Irgacure^TM1000、Irgacure^TM1300、Irgacure^TM1870、Darocur^TM1173、Darocur^TM2959、Darocur^TM4265 and Darocur^TMITX (from CIBA SPECIALTY CHEMICALS), Lucerin^TMTPO (from BASF AG), Esacure^TMKT046、Esacure^TMKIP150、Esacure^TMKT37 and Esacure^TMEDB (from LAMBERTI), H-Nu^TM470 and H-Nu^TM470X (from SPECTRA GROUP Ltd.).

The photoinitiator may be a so-called diffusion hindered photoinitiator. Diffusion hindered photoinitiators are photoinitiators that exhibit much lower mobility in the cured ink layer than monofunctional photoinitiators such as benzophenone. Several methods can be used to reduce the mobility of the photoinitiator. One approach is to increase the molecular weight of the photoinitiator in order to reduce the diffusion rate, e.g. polymerizing the photoinitiator. Another approach is to increase its reactivity in order to build it into the polymerization network, such as multifunctional photoinitiators (having 2, 3 or more photoinitiating groups) and polymerizable photoinitiators.

The diffusion hindered photoinitiator for radiation curable inkjet is preferably selected from non-polymeric multifunctional photoinitiators, oligomeric or polymeric photoinitiators and polymerizable photoinitiators. Most preferably, the diffusion hindered photoinitiator is a polymerizable initiator or a polymeric photoinitiator.

One preferred diffusion hindered photoinitiator contains one or more photoinitiating functional groups derived from a Norrish type I photoinitiator selected from the group consisting of benzoin ethers, benzil ketals, α -dialkoxyacetophenones, α -hydroxyalkylphenones, α -aminoalkylphenones, acylphosphine oxides, acylphosphine sulfides, α -haloketones, α -halosulfones, and phenylglyoxylates.

One preferred diffusion hindered photoinitiator contains one or more photoinitiating functional groups derived from a Norrish type II initiator selected from the group consisting of benzophenones, thioxanthones, 1, 2-diketones and anthraquinones.

Suitable diffusion-hindered photoinitiators are also those disclosed in EP-A2065362 in paragraphs [0074] and [0075] for bifunctional and polyfunctional photoinitiators, in paragraphs [0077] to [0080] for polymeric photoinitiators and in paragraphs [0081] to [0083] for polymerizable photoinitiators.

Preferred amounts of photoinitiator are from 0.1 to 20 wt%, more preferably from 2 to 15 wt%, and most preferably from 3 to 10 wt% of the total weight of the radiation curable inkjet.

To further improve the photosensitivity, the radiation curable inkjet may additionally comprise a co-initiator. Suitable examples of coinitiators can be divided into three classes: 1) aliphatic tertiary amines such as methyldiethanolamine, dimethylethanolamine, triethanolamine, triethylamine and N-methylmorpholine; (2) aromatic amines such as amyl p-dimethylaminobenzoate, 2-n-butoxyethyl 4- (dimethylamino) benzoate, 2- (dimethylamino) ethyl benzoate, 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). Preferred coinitiators are aminobenzoates.

When one or more co-initiators are included in a radiation curable inkjet ink, it is preferred for safety reasons that these co-initiators are diffusion hindered.

The diffusion hindered coinitiator is preferably selected from the group consisting of non-polymeric di-or multifunctional coinitiators, oligomeric or polymeric coinitiators and polymerizable coinitiators. More preferably, the diffusion hindered co-initiator is selected from the group consisting of polymeric co-initiators and polymerizable co-initiators. Most preferably the diffusion hindered co-initiator is a polymerizable co-initiator having at least one (meth) acrylate group, more preferably at least one acrylate group.

The radiation curable inkjet ink preferably includes a polymerizable or polymeric tertiary amine co-initiator.

Preferred diffusion hindered coinitiators are the polymerizable coinitiators disclosed in EP-A2053101, paragraphs [0088] and [0097 ].

The radiation curable inkjet ink preferably comprises from 0.1 to 20 wt% of the (diffusion hindered) co-initiator, more preferably from 0.5 to 15 wt%, most preferably from 1 to 10 wt% of the total weight of the radiation curable inkjet ink.

Polymerization inhibitor

The radiation curable inkjet ink may comprise at least one inhibitor for improving the thermal stability of the ink.

Suitable polymerization inhibitors include phenolic antioxidants, hindered amine light stabilizers, fluorescent type antioxidants, hydroquinone monomethyl ether, and hydroquinone, which are commonly used in (meth) acrylate monomers. Tert-butylcatechol, pyrogallol, 2, 6-di-tert-butyl-4-methylphenol (= BHT) may also be used.

Suitable commercially available inhibitors are, for example, Sumilizer^TMGA-80、Sumilizer^TMGM and Sumilizer^TMGS, produced by Sumitomo Chemical co. ltd.; genorad^TM16、Genorad^TM18 and Genorad^TM20, available from RahnAG; irgastab^TMUV10 and Irgastab^TMUV22、Tinuvin^TM460 and CGS20, available from Ciba specialty chemicals; floorstab^TMUV series (UV-1, UV-2, UV-5 and UV-8) available from Kromachem Ltd; additol^TMSeries S (S100, S110, S120 and S130) available from Cytec Surface Specialties.

The inhibitor is preferably a polymerizable inhibitor.

Since excessive addition of these polymerization inhibitors can reduce the curing speed, it is preferable to determine the amount capable of preventing polymerization before blending. The amount of polymerization inhibitor is preferably less than 5 wt%, more preferably less than 3 wt% of the total radiation curable inkjet ink.

Surface active agent

The radiation curable inkjet may comprise at least one surfactant, but preferably no surfactant is present. If no surfactant is present, the radiation curable inkjet ink does not spread well on the metal sheet, allowing for the creation of thin wires.

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

Suitable surfactants include fluorinated surfactants, fatty acid salts, ester salts of higher alcohols, alkylbenzene sulfonate salts, sulfosuccinate ester salts and phosphate ester salts of higher alcohols (e.g., sodium dodecylbenzenesulfonate and dioctyl sodium sulfosuccinate), ethylene oxide adducts of higher alcohols, ethylene oxide adducts of alkylphenols, ethylene oxide adducts of fatty acid polyol esters, and ethylene oxide adducts of acetylene glycol and ethylene oxide adducts thereof (e.g., polyoxyethylene nonylphenyl ether and SURFYNOL @^TM104. 104H, 440, 465 and TG from AIR PRODUCTS&CHEMICALS INC.)。

Preferred surfactants are selected from the group consisting of fluorosurfactants (such as fluorohydrocarbons) and silicone surfactants. The silicone surfactant is preferably a siloxane and may be alkoxylated, polyether modified hydroxy functional, amine modified, epoxy modified and other modifications or combinations thereof. Preferred silicones are polymeric, such as polydimethylsiloxane.

Preferred commercial silicone surfactants include BYK from BYK Chemie^TM333, and BYK^TMUV3510。

In a preferred embodiment, the surfactant is a polymerizable compound.

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.

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

The surfactant is preferably 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.

Preparation of inkjet inks

The preparation of pigmented radiation curable inkjet inks is well known to the skilled person. Preferred preparation processes are disclosed in paragraphs [0076] to [0085] of WO 2011/069943.

Method for manufacturing printed circuit board

The method of manufacturing a Printed Circuit Board (PCB) according to the present invention comprises at least one inkjet printing step, characterized in that in the inkjet printing step, a radiation curable inkjet ink containing the following adhesion promoter is used.

According to a preferred embodiment, the method of manufacturing a PCB comprises an inkjet printing step, wherein a resist is provided on a metal surface, preferably on a copper surface.

A resist is provided on the metal surface by jetting and curing a radiation curable inkjet ink on the metal surface, thereby forming protected areas of the metal surface. The metal is then removed from the unprotected areas of the metal surface by etching. After etching, at least part of the resist is removed from the protected area of the metal surface.

The inkjet printing step in which the resist is provided preferably comprises a radiation curable inkjet ink comprising an adhesion promoter as described below and a polymerizable compound having a pKa of at least 2.5.

The metal surface is preferably a metal foil or sheet attached to the substrate.

There is no practical limitation on the type of substrate bonded to the metal sheet as long as it is non-conductive. The substrate may be made of ceramic, glass or plastic, such as polyimide.

The metal sheet typically has a thickness between 9 and 105 μm.

There is no limitation on the nature of the metal surface. The metal surface is preferably made of copper, aluminum, nickel, iron, tin, titanium or zinc, but may also be an alloy comprising these metals. In a very preferred embodiment, the metal surface is made of copper. Copper has a high electrical conductivity and is a relatively inexpensive metal, which makes it very suitable for the manufacture of printed circuit boards.

The method can also be used to manufacture decorative etched metal sheets.

The metal surface used may be selected from the metals described above for the embodiment in which the conductive pattern is prepared. In this case, a solid metal plate is preferably used. However, metal foils attached to the substrate may also be used. There is no practical limitation on the type of substrate bonded to the metal foil. The substrate may be made of ceramic, glass or plastic or even a second (cheaper) metal plate. The metal may also be an alloy.

Such decorative metal sheets may be used for purposes other than purely decorative, for example to provide information. For example, it is also contemplated to consider aluminum nameplates as decorative metal plates, including decorative elements, in which a resist radiation curable inkjet ink is printed as a message, such as the name of a person or company, and then removed to produce a gloss glitter name over the pad etched background. Etching causes changes in the optical properties of the metal surface, such as changes in gloss. After removal of the cured radiation curable inkjet ink from the metal surface, an aesthetic effect is created between the etched and unetched metal surfaces.

In a preferred embodiment of the inkjet printing method, the metal surface is cleaned prior to printing the radiation curable inkjet ink. This is particularly desirable when manipulating metal surfaces by hand and without gloves. Cleaning removes dust particles and grease that can interfere with the adhesion of the radiation curable inkjet ink to metal surfaces. In PCBs, copper is typically cleaned by microetching. The oxide layer of copper is removed and roughness is introduced to improve adhesion.

The ink jet process can also be used to manufacture decorative etched glass sheets. Such a method is disclosed in, for example, WO2013/189762 (AGC).

According to another preferred embodiment, the method of manufacturing a PCB comprises an inkjet printing step wherein a solder resist layer is provided.

The solder mask is provided by spraying and curing a radiation curable inkjet ink, typically on a dielectric substrate containing a conductive pattern.

The heat treatment is preferably applied to the inkjet and cured radiation curable inkjet ink. The heat treatment is preferably carried out at a temperature between 80 ℃ and 250 ℃. The temperature is preferably not less than 100 ℃ and more preferably not less than 120 ℃. In order to prevent the solder resist from being scorched, the temperature is preferably not more than 200 ℃, more preferably not more than 160 ℃.

The heat treatment is generally carried out for a time between 15 and 90 minutes.

The purpose of the heat treatment is to further increase the degree of polymerization of the solder resist layer.

This further polymerization during heat treatment can be accelerated by adding to the solder resist inkjet ink a free radical initiator, a blocked thermal acid generator, a blocked acid catalyst and/or a thermosetting compound that promotes thermal curing of the polymer, such as peroxides, azo compounds, anhydrides and phenols.

The dielectric substrate of the electronic device can be any non-conductive material. The substrate is typically a paper/resin composite or a resin/fiberglass composite, a ceramic substrate, polyester or polyimide.

The conductive pattern is generally made of any metal or alloy conventionally used in the manufacture of electronic devices, such as gold, silver, palladium, nickel/gold, nickel, tin/lead, aluminum, tin/aluminum, and copper. The conductive pattern is preferably made of copper.

In both embodiments, the radiation curable solder resist inkjet ink can 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 LEDs.

The method of manufacturing a PCB may comprise two, three or more inkjet printing steps. For example, the method may comprise two inkjet printing steps, wherein in one inkjet printing step a resist is provided on the metal surface, and wherein in another inkjet printing step a solder mask is provided on the dielectric substrate comprising the conductive pattern.

The third ink jet printing step may be used for text printing.

Etching of

Etching of the metal surface, as in step b) of the inkjet printing method, is carried out by using an etchant. The etchant is preferably an aqueous solution with a pH <3 or where 8< pH < 10.

In a preferred embodiment, the etchant is an acidic aqueous solution having a pH of less than 2. The acidic etchant preferably includes at least one acid selected from the group consisting of nitric acid, picric acid, hydrochloric acid, hydrofluoric acid, and sulfuric acid.

Preferred etchants known in the art include Kalling's N ° 2, ASTM N ° 30, Kellers Etch, Klemm's reagent, Kroll's reagent, Marble's reagent, Murakami's reagent, Picral and Vilella's reagent.

In another preferred embodiment, the etchant is an aqueous alkaline solution having a pH of no greater than 9. The alkaline etchant preferably comprises at least one alkali selected from the group consisting of ammonia or ammonium hydroxide, potassium hydroxide and sodium hydroxide.

The etchant may also contain metal salts such as copper dichloride, copper sulfate, potassium ferricyanide, and ferric chloride.

Etching of the metal surface in PCB applications is preferably performed in a time range of a few seconds to a few minutes, more preferably 5 to 200 seconds. The etching is preferably carried out at a temperature between 35 and 60 ℃.

In other applications, for example in the manufacture of decorative metal plates, the etching time of the metal surface may be much longer, depending on the type and amount of metal that has to be removed during the etching step. The etching time may be greater than 15, 30 or even 60 minutes.

In the method in which the glass surface is etched, the etching solution is preferably an aqueous solution of hydrofluoric acid. Typically, the pH of the etching solution is between 0 and 5.

It is preferred to rinse with water after etching to remove any residual etchant.

Peeling off

After etching, the cured radiation curable inkjet ink must be at least partially removed from the metal surface so that, for example, an electrical or electronic device can be brought into contact with the remaining metal surface (conductive pattern) or the decorative features of the etched metal plate become 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 radiation curable inkjet ink is completely removed from the metal surface.

In a preferred embodiment, the cured radiation curable inkjet ink is removed from the protected areas in step c) by an alkaline stripping bath. Such alkaline stripping baths are typically aqueous solutions with a pH > 10.

In another embodiment, the cured radiation curable inkjet ink is removed from the protected areas in step c) by dry lamination. This "dry stripping" technique is currently unknown in the art of manufacturing printed circuit boards, and introduces some ecological and economic advantages in the manufacturing process. Dry stripping not only eliminates the need for a caustic alkaline stripping bath and its inherent liquid waste, but also allows for higher throughput. Dry peeling can be achieved, for example, by using an adhesive foil and roll-to-roll laminator-laminator. The cured radiation curable inkjet ink is removed from the metal surface by first laminating the adhesive foil with its adhesive side onto the cured radiation curable inkjet ink present on the metal surface followed by delamination. Delamination can be achieved in seconds by a roll-to-roll laminator-laminator machine, whereas alkaline stripping can take several minutes.

Ink jet printing apparatus

Radiation curable inkjet inks can be jetted by one or more print heads that eject small droplets through nozzles onto a substrate in a controlled manner, the substrate moving relative to the one or more print heads.

A preferred print head for use in an inkjet printing system is a piezoelectric head. Piezoelectric inkjet printing is based on the movement of a piezoelectric ceramic sensor when a voltage is applied thereto. Application of a voltage changes the shape of the piezo ceramic sensors in the print head, creating a void, which is then filled with ink. When the voltage is removed again, the ceramic expands to its original shape, ejecting a drop of ink from the print head. However, the inkjet printing method according to the present invention is not limited to piezoelectric inkjet printing. Other inkjet print heads may be used and include various types, such as a continuous type.

Inkjet print heads typically scan back and forth laterally across the surface of a moving ink-receiver. The ink jet print head typically does not print on the return path. In order to obtain high area throughput (area throughput), bidirectional printing is preferred. Another preferred printing method is the "single pass printing method", which can be performed by using a page wide inkjet print head or a plurality of staggered inkjet print heads covering the entire width of the metal sheet surface. In a single pass printing process, the inkjet print head is typically held stationary while the metal sheet surface is conveyed under the inkjet print head.

Curing device

Radiation curable inkjet inks can be cured by exposing them to actinic radiation such as electron beam or ultraviolet radiation. Preferably the radiation curable inkjet ink is cured by ultraviolet radiation, more preferably curing using a uv led.

In inkjet printing, a curing device may be arranged in combination with the print head of the inkjet printer, the curing device travelling with the print head such that the curable liquid is exposed to curing radiation shortly after jetting.

In such an arrangement, it may be difficult to provide a sufficiently small radiation source connected to and travelling with the print head, in addition to the UV LEDs. Thus, a stationary radiation source, for example a curing UV light source, may be used, connected to the radiation source by a flexible radiation conducting device, such as a fiber optic bundle or an internally reflective flexible tube.

Alternatively, actinic radiation may be supplied to the radiation head from a self-contained source through a mirror arrangement that includes a mirror on the radiation head.

The radiation source may also be an elongate radiation source extending transversely across the substrate to be cured. Which may be adjacent to the transverse path of the print head so that subsequent lines of the image formed by the print head pass under the radiation source in steps or continuously.

Any source of ultraviolet light (provided that a portion of the emitted light is absorbed by the photoinitiator or photoinitiator system) may be used as the radiation source, such as high or low pressure mercury lamps, cold cathode tubes, black light, ultraviolet LEDs, ultraviolet lasers, and flash lamps. Of these, preferred sources are those that exhibit a relatively long wavelength UV contribution with a dominant wavelength of 300 to 400 nm. In particular, UV-a light sources are preferred because they have reduced light scattering leading to more efficient internal curing.

UV radiation is generally classified as UV-A, UV-B and UV-C as follows:

UV-A: 400nm to 320nm

UV-B: 320nm to 290nm

UV-C: 290nm to 100 nm.

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

In addition, two light sources of different wavelengths or brightness may be used sequentially or simultaneously to cure the ink image. For example, the first UV source may be selected to be rich in UV-C, in particular in the range of 260nm to 200 nm. The second UV source may then be rich in UV-a, such as a gallium doped lamp, or a different lamp where both UV-a and UV-B are strong. The use of two UV sources has been found to be advantageous, such as a fast curing speed and a high degree of curing.

To facilitate curing, inkjet printing devices often include one or more oxygen-deficient units. These oxygen-depleted units are configured with nitrogen or other relatively inert gases (e.g., CO)₂) Has an adjustable position and an adjustable inert gas concentration to reduce the oxygen concentration in the curing environment. Residual oxygen levels are typically kept as low as 200 ppm, but are typically in the range of 200 ppm to 1200 ppm.