WO1997021737A1 - Photoinitiator composition containing a borate salt and a hypervalent atom-containing salt - Google Patents

Photoinitiator composition containing a borate salt and a hypervalent atom-containing salt

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Publication number
WO1997021737A1
WO1997021737A1 PCT/US1996/019806 US9619806W WO9721737A1 WO 1997021737 A1 WO1997021737 A1 WO 1997021737A1 US 9619806 W US9619806 W US 9619806W WO 9721737 A1 WO9721737 A1 WO 9721737A1
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WO
WIPO (PCT)
Prior art keywords
salt
composition
group
substituted
borate
Prior art date
Application number
PCT/US1996/019806
Other languages
French (fr)
Inventor
Ananda M. Sarker
Salah A. Hassoon
Alexander Y. Polykarpov
Anita M. Deraaf
Thomas L. Marino
Douglas C. Neckers
Original Assignee
Spectra Group Limited, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Spectra Group Limited, Inc. filed Critical Spectra Group Limited, Inc.
Priority to AU15654/97A priority Critical patent/AU1565497A/en
Publication of WO1997021737A1 publication Critical patent/WO1997021737A1/en

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/004—Photosensitive materials
    • G03F7/027—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds
    • G03F7/028—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds with photosensitivity-increasing substances, e.g. photoinitiators
    • G03F7/029—Inorganic compounds; Onium compounds; Organic compounds having hetero atoms other than oxygen, nitrogen or sulfur
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
    • B01J31/0234—Nitrogen-, phosphorus-, arsenic- or antimony-containing compounds
    • B01J31/0235—Nitrogen containing compounds
    • B01J31/0239—Quaternary ammonium compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
    • B01J31/0234—Nitrogen-, phosphorus-, arsenic- or antimony-containing compounds
    • B01J31/0255—Phosphorus containing compounds
    • B01J31/0267—Phosphines or phosphonium compounds, i.e. phosphorus bonded to at least one carbon atom, including e.g. sp2-hybridised phosphorus compounds such as phosphabenzene, the other atoms bonded to phosphorus being either carbon or hydrogen
    • B01J31/0268—Phosphonium compounds, i.e. phosphine with an additional hydrogen or carbon atom bonded to phosphorous so as to result in a formal positive charge on phosphorous
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
    • B01J31/12—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing organo-metallic compounds or metal hydrides
    • B01J31/14—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing organo-metallic compounds or metal hydrides of aluminium or boron
    • B01J31/146—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing organo-metallic compounds or metal hydrides of aluminium or boron of boron

Definitions

  • the present invention relates to photoinitiator compositions. More particularly, the invention relates to a borate salt and a salt containing a hypervalent heteroatom (e.g. , an onium salt) which in combination form an effective redox pair capable of efficiently initiating free radical polymerization
  • the invention also relates to a photohardenable composition containing the aforesaid photoinitiator system and more particularly to an anaerobic composition containing the same.
  • the present invention provides a photoreactive or otherwise activated initiator composition containing a borate salt and a hypervalent heteroatom-containing salt such as an onium salt which form a redox pair such that upon exposure to actinic radiation, electron transfer occurs accompanied by the generation of free radicals capable of hardening an organic monomer or polymer by polymerization or crosslmkmg even m the absence of a sensitizer.
  • a photoreactive or otherwise activated initiator composition containing a borate salt and a hypervalent heteroatom-containing salt such as an onium salt which form a redox pair such that upon exposure to actinic radiation, electron transfer occurs accompanied by the generation of free radicals capable of hardening an organic monomer or polymer by polymerization or crosslmkmg even m the absence of a sensitizer.
  • the borate salt/hypervalent heteroatom-containmg salt system behaves as a donor/acceptor pair m which an electron is transferred from the borate donor compound to the hypervalent heteroatom-containing acceptor compound, causing both compounds to release radicals which are capable of polymerizing or curing an organic monomer or polymer containing ethylemc unsaturation.
  • a donor/acceptor pair m which an electron is transferred from the borate donor compound to the hypervalent heteroatom-containing acceptor compound, causing both compounds to release radicals which are capable of polymerizing or curing an organic monomer or polymer containing ethylemc unsaturation.
  • a principal object of the present invention is to provide a photoinitiator system which contains a hypervalent heteroatom-containmg salt such as an onium salt in combination with a borate salt wherein the borate salt and the hypervalent heteroatom-containmg salt form a redox pair.
  • a hypervalent heteroatom-containmg salt such as an onium salt in combination with a borate salt wherein the borate salt and the hypervalent heteroatom-containmg salt form a redox pair.
  • a further object of the present invention is to provide a photosensitive composition containing a photohardenable compound which is an ethylenically unsaturated organic monomer or polymer, and the aforementioned photoinitiator system.
  • Still another object of the invention is to provide a hardenable composition which can be triggered by any other recognized method of removing polymerization inhibitors, e.g, increasing the external pressure or heat.
  • a photoinitiator system containing a reactive hypervalent heteroatom-containmg salt m combination with a tetraorganoborate salt wherein the hypervalent heteroatom-containmg salt and the borate salt form a redox pair.
  • the present invention also provides an initiator composition comprising a sensitizer, a hypervalent heteroatom- containmg salt and a borate salt.
  • the hypervalent heteroatom-containmg salt and the borate salt are capable of reacting their ground state.
  • compositions of the invention are anaerobically polymerizable. In the presence of oxygen, the compositions give no apparent polymerization. Once oxygen has been exhausted (i.e., an anaerobic state) through reaction with the free radicals, the borate salt and the hypervalent heteroatom-containmg salt reaction generates radicals which are capable of polymerizing the composition.
  • a radical inhibitor such as oxygen, a substituted phenol, or any of the many other compounds known in the art as free radical stabilizers.
  • compositions of the present invention are distinguishable from those of Farid, U.S. Patent 4,859,572, in that the borate salt and hypervalent heteroatom-containmg salt which, preferably, is an onium salt, form a redox pair which is capable of reacting in its ground state
  • the sensitizer must be selected so that it s more cathodic than the electron acceptor and/or more anodic than the electron donor m order for the electron transfers to occur and for radicals to be generated. This is not a requirement m the present invention because the borate donor and hypervalent heteroatom-containmg salt acceptor are capable of reacting with each other m the compositions in the ground state and no sensitizer is required.
  • the borate salt alone nor the hypervalent heteroatom-containmg salt alone absorb light in the visible region
  • preliminary studies suggest that when combined, they may form a charge transfer complex that absorbs m the visible region.
  • the ion pair may function as an absorber.
  • Electron transfer and radical formation leading to polymer formation is not controlled only by the redox potentials of the sensitizer. Rather polymerization is moderated by the presence of an inhibitor, like oxygen; the sensitizer composition freely reacts in the absence of the inhibitor as is required in an anaerobic state.
  • the present invention provides a photosensitive composition containing a photohardenable compound which is an organic monomer or polymer having ethylemc unsaturation, and the aforementioned photoinitiator compositions.
  • a combination of a borate salt and a reactive hypervalent heteroatom-containing salt e.g., an onium salt are useful as a photoinitiator system.
  • the borate salt is represented by the formula (I) :
  • R 1 , R , R 3 and R 4 are independently selected from the group consisting of substituted and unsubstituted alkyl, substituted and unsubstituted aryl, substituted and unsubstituted alkenyl, substituted and unsubstituted alkynyl, substituted and unsubstituted alicyclic, substituted and unsubstituted heterocyclic groups, and a cyclic group wherein at least two of said R 1 , R z , R 3 and R 4 may combine the form said cyclic group, with the proviso that at least one of R 1 , R 2 , R 3 and R 4 is an alkyl group, and wherein Z ⁇ is a cationic species capable of forming a reactive salt with an anionic borate species .
  • An alkyl group represented by R 1 to R 4 includes a straight, branched or cyclic alkyl group and preferably has 1 to 18 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a stearyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, etc .
  • a substituent such as a halogen atom, e.g., a chlorine atom, a bromine atom, etc.
  • an aryl group preferably, a phenyl group
  • An aryl group represented by R 1 to R 4 includes an aryl group having 1 to 3 rings, such as a phenyl group, a naphthyl group, etc., and a substituted aryl group represented by R 1 to R 4 includes an aryl group described above having the same substituent as that for the alkyl group or an alkyl group having 1 to 14 carbon atoms.
  • An alkenyl group represented by R 1 to R 4 includes a straight, branched or cyclic alkenyl group having 2 to 18 carbon atoms and a substituent for the alkenyl group includes the same substituent as that for the alkyl group.
  • An alkynyl group represented by R 1 to R 4 includes a straight or branched alkynyl group having 2 to 18 carbon atoms, and a substituent for the alkynyl group includes the same substituent as that for the alkyl group.
  • a heterocyclic group represented by R 1 to R 4 includes a 5 or more-membered ring, preferably 5 to 7-membered ring containing at least one atom selected from the group consisting of N, S and 0, and the heterocyclic ring may contain a condensed ring.
  • the substituent for the heterocyclic group includes the same substituent as that for the aryl group.
  • the anionic species of the borate is a t ⁇ arylalkylborate such as triphenyl (n-butyl) borate, t ⁇ phenyl (sec-butyl) borate, etc.
  • the cationic species of the borate is an alkali metal such as Li ⁇ or a quaternary ammonium, phosphonium, sulf onium or lodonium cation.
  • Z ⁇ is a quaternary ammonium cation, it is typically a tetraalkyl ammonium cation where the alkyl substituent contains about 1 to 10 carbons such as methyl, ethyl, butyl, hexyl octyl, etc.; a choline substituent such as acetylcholme, butylcholine, etc. ; trimethylcetylammonium; cetylpyridimum, benzethomum; and the like.
  • the borate salt is a butyrylcholine triarylalkylborate, acetylchol e triarylalkylborate or tetrahexylammonium triarylalkylborate .
  • the hypervalent heteroatom- containmg salt/borate salt photoinitiator system is an acceptor/donor system m which an electron is transferred from the borate salt to the hypervalent heteroatom-containmg salt causing both components to immediately decompose.
  • the decomposition products presumably, include an alkyl radical such as n-butyl radical and at least one phenyl radical, both of which are capable of initiating acrylate curing or polymerization although the alkyl radical is apparently much more reactive.
  • the hypervalent heteroatom-containmg salt must be a strong enough oxidant to oxidize the borate salt.
  • the hypervalent heteroatom-containmg salt may be an lodonium salt, a sulfonium salt, an oxonium salt, a sulfoxonium salt, a carbamoylsulfoxonium salt, a pyrylium salt, a thiapyrylium salt, a diazonium salt, a ferrocenium salt, and the like.
  • the hypervalent heteroatom-containmg salt is an onium salt.
  • the onium salt useful in the present invention includes but is not limited to those onium salts disclosed in U.S. Patent No.
  • onium salts examples include diaryliodonium hexafluorophosphates, diaryliodonium arsenates and diaryliodonium antimonates.
  • useful onium salts include diaryl lodonium salts such as diphenyliodonium hexafluorophosphate and 4 -( (2-hydroxy) tetradecyloxyphenyl) phenyl lodonium hexafluoroantimonate (CD 1012) .
  • the onium salt is a lodonium salt, it can be represented by the formula (III) :
  • R r is a monovalent aromatic organic radical
  • R 6 is a divalent organic radical
  • M is a metal or a metalloid
  • Q is a halogen, alkyl, aryl, alkylaryl, or equivalent radical
  • a and b are whole numbers equal to 0, 1 or 2
  • c is equal to d-e
  • e is equal to the valence of M and is an integer equal to 2 to 7 inclusive
  • d is greater than e and is an integer having a value up to 8
  • Radicals included by R 5 can be the same or different aromatic, carbocyrlic or heterocyclic radicals having from 6 to 20 carbon atom; , which can be substituted on the ring with from 1 to 4 monovalent radicals selected from C ⁇ 18) alkoxy, C (1 18) alkyl, nitro, chloro, etc.
  • R 5 is more particularly phenyl, chlorophenyl, nitrophenyl, methoxyphenyl, pyridyl, etc.
  • Radicals included by R 6 are divalent radicals such as
  • Metal or metalloids included by M or formula (III) are transition metals such as Sb, Fe, Sn, Bi, Al, Ga, In, Ti, Zr, Sc, V, Cr, Mn, Cs, rare earth elements such as the lanthanides, for example, Cd, Pr, Nd, etc., actinides, such as Th, Pa, U, Np, etc. and metalloids such as B, P, As, etc.
  • Transition metals included by MQ d "(d ⁇ e) are, for example, BF 4 , PF 6 , AsF 6 , SbF 6 , FeCl 4 ⁇ SnCl 6 ", SbCl 6 , BiCl 3 ⁇ etc.
  • Halonium salts (especially iodonium salts) included by formula III are, for example,
  • halonium salts of formula III can be made by the procedures described by 0.
  • Other aryliodonium salts include the polymeric iodonium salts which are described in U.S. Patent No. 4,780,511 to Crivello and are hereby incorporated herein by reference.
  • ArN2 + where Ar is as defined above may be employed m the present invention.
  • Onium salts found to be particularly useful m the photoinitiator system of the invention are iodonium salts whicn include (4-octyloxyphenyl) phenyliodonium (OPPI) , b ⁇ s(4- dodecyl-phenyl) iodonium hexafluoroantimonate (DDPI) , diphenyliodonium hexafluoroantimonate (DPI) , 4-( (2-hydroxy) tetradecyloxyphenyl) phenyl iodonium hexafluoroantimonate (CD 1012) and diphenyliodonium hexafluorophosph ate (DPIP) .
  • OPPI (4-octyloxyphenyl) phenyliodonium
  • DDPI diphenyliodonium hexafluoroantimonate
  • DPI diphenyliodonium hexa
  • the present invention also provides a photosensitive composition containing a photohardenable compound and the aforementioned photoinitiator composition.
  • the photohardenable compound is characterized as being an organic monomer or polymer containing ethylemc unsaturation sites .
  • the aforementioned photohardenable compound may be a monomer, an oligomer such as a dimer or trimer, or a mixture thereof:
  • Suitable monomers and the copolymer thereof include esters of unsaturated carboxylic acids and aliphatic polyhyd ⁇ c alcohol compounds, and amides of unsaturated carboxylic acids and aliphatic polyhydric am e compounds .
  • monomers of the esters of aliphatic polyhydric alcohol compounds and unsaturated carboxylic acids include an acrylic acid ester, such as ethylene glycol diacrylate, triethylene glycol diacrylate, 1, 3-butanediol diacrylate, tetramethylene glycol diacrylate, propylene glycol diacrylate, neopentyl glycol diacrylate, t ⁇ methylolpropane triacrylate, trimethylolpropane tri (acryloyloxypropyl) ether, trimethylolethane triacrylate, hexanediol diacrylate, 1, 4-cyclohexanediol diacrylate, tetraethylene glycol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaeryth ⁇ tol diacrylate, dipentaerythritol triacrylate, dipentaeryth ⁇ to
  • Specific examples also include monomers of methacrylic acid esters such as tetramethylene glycol dimethacrylate, triethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, ethylene glycol dimethacrylate, 1, 3-butanediol dimethacrylate, hexanediol dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol dimethacrylate, dipentaerythritol hexamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate, bis- [p- (3-methacryloxy-2- hydroxypropoxy)phenyl] dimethylmethane,
  • Specific examples further include monomers of ltacomc acid esters such as ethylene glycol dntaconate, propylene glycol dntaconate, 1, 3-butanediol dntaconate, 1,4 butanediol dntaconate, tetramethylene glycol dntaconate, pentaerythritol dntaconate, sorbitol tetraitaconate, etc.
  • monomers of ltacomc acid esters such as ethylene glycol dntaconate, propylene glycol dntaconate, 1, 3-butanediol dntaconate, 1,4 butanediol dntaconate, tetramethylene glycol dntaconate, pentaerythritol dntaconate, sorbitol tetraitaconate, etc.
  • crotonic acid esters such as ethylene glycol dicrotonate, tetramethylene glycol dicrotonate, pentaerythritol dicrotonate, and sorbitol tetradicrotonate.
  • isocrotonic acid esters such as ethylene glycol diisocrotonate, pentaerythritol diisocrotonate, sorbitol tetraisocrotonate, etc .
  • maleic acid esters are ethylene glycol dimaleate, triethylene glycol dimaleate, pentaerythritol dimaleate, sorbitol tetramaleate, etc.
  • Suitable specific monomers of the amides of an aliphatic polyhydric amine compound and an unsaturated carboxyolic acids include methylene-bis-acrylamide, methylene- bis-methacrylamide, 1, 6-hexamethylene-bis-acrylamide, 1,6- hexamethylene-bis-methacrylamide, diethylenetriamine-tris- acrylamide, xylylene-bis-acrylamide, and xylylene-bis- methacryamide .
  • polymerizable compounds having an ethylenically unsaturated bond are vinylurethane compounds having two or more polymerizable vinyl groups in one molecule obtained by adding a vinyl monomer having a hydroxy group to a polyisocynate compound having two or more isocyanate groups in one molecule.
  • polyfunctional acrylates and methacrylates such as urethane acrylates, polyester acrylates, and epoxy acrylates which may be obtained by reacting epoxy resins and (meth) acrylic acid.
  • urethane acrylates such as urethane acrylates, polyester acrylates, and epoxy acrylates which may be obtained by reacting epoxy resins and (meth) acrylic acid.
  • Good photohardenable results have been obtained using a mixture of resins containing about 70% polyurethane acrylate, about 20% tripropyleneglycmediacrylate (TPGDA) and about 10% ethoxyethoxyethylacrylate (EOEOEA) .
  • TPGDA tripropyleneglycmediacrylate
  • EEOEA ethoxyethoxyethylacrylate
  • the amount of borate found to be effective is about 0.05 to 2.5% by weight, and the amount of onium salt is about 0.1 to 2.5% by weight based on the total weight of the photosensitive composition.
  • the hypervalent heteroatom-containmg salt is a strong enough oxidizing agent to oxidize the reducing agent under ground state conditions.
  • the system does not undergo spontaneous reaction due to the presence of oxygen or other inhibitors m the composition
  • the hypervalent heteroatom-containmg salt absorbs sufficient radiation, even with relatively long wavelength sources, to generate radical chains which effectively remove the inhibitor.
  • oxygen alone may stabilize the composition, an inhibitor which quenches free radicals is generally added.
  • Typical examples of such inhibitors include aromatic phenols such as butylated hydroxytoluene (BHT) , 2 , 6-d ⁇ -tert-butyl catechol, hydroqumone , and other radical inhibitors known in the art.
  • the effectiveness of the photoinitiator composition may be enhanced by the incorporation of a sensitizer into the composition.
  • the sensitizer Upon exposing the composition to actinic radiation, the sensitizer is activated to an excited state whereupon it generates radicals which react with the inhibitors to exhaust them such that the borate and the onium salt can react spontaneously.
  • Examples of effective sensitizers useful the present invention are dyes such as coumarm dyes, merocyanme dyes, merostyryl dyes, oxonol dyes, methme, polymethme, tnarylmethane, mdolme, thiazme, xanthene, oxaz e, acridme, hemioxonol dyes, keto dyes such as fluorones and xanthones; e.g., 2-methyl- , 10-phenanthrenequmones; 2,4-3- d ⁇ odo-6-butoxy-3-fluorone (DIBF) ; 2 , 4, 5, 7-tetra ⁇ odohydroxy- fluorone (TIHF) ; 2 , 4 , 5 , 7-tetra ⁇ odo-9-cyanohydroxy-3-fluorone (TIHCF) isopropylthioxanthone (ITX) ; rose bengal;
  • Preferred sensitizers include 2 , 4-dnodo-6-butoxyfluorone (DIBF) ; 2 , 4 , 5, 7-tetra ⁇ odo-3- hydroxyfluorone (TIHF) ; 2 , 4 , 5, 7-tetra ⁇ odo-9-cyanohydroxy-3- fluorone (TIHCF) , isopropylthioxanthone (ITX) ; rose bengal; - eos , erythrosm, methylene blue and other compunds as disclosed m U.S. Pat. No. 5,451,343, the contents of which are incorporated herein by reference.
  • DIBF 4-dnodo-6-butoxyfluorone
  • TIHF 7-tetra ⁇ odo-3- hydroxyfluorone
  • TIHCF isopropylthioxanthone
  • IX isopropylthioxanthone
  • rose bengal - eos , erythros
  • the dye sensitizer may be used a concentration of about 0.01 to 0.5% by weight of the composition.
  • the amines most useful in carrying out the invention are alkylammes and most preferably N,N-di-alkylammes such as N,N-dialkylamlme.
  • N,N-d ⁇ alkylan ⁇ lmes useful m this invention include dialkyla lmes substituted at one or more of the ortho, eta- , or para- position by the following groups: methyl, ethyl, isopropyl, t-butyl, 3 , 4-tetramethylene, phenyl, trifluoromethyl, acetyl, ethoxycarbonyl, carboxy, carboxylate, cyano, t ⁇ methylsilylmethyl, trimethylsilyl , triethylsilyl, tnmethylgermanyl, triethylgermanyl, trimethylstannyl , triethylstannyl, n-butoxy, n-pentyloxy, phenoxy, hydroxy, acety
  • N,N-dialkylamlmes useful in the present invention are 4-cyano-N,N- dimethylanilme, 4-acetyl-N,N-dimethylanilme, 4-bromo-N,N- dimethylanilme, ethyl 4- (N,N-dimethylammo) benzoate, 3- chloro-N, -dimethylaniline, 4-chloro-N, N-dimethylanilme, 3- ethoxy-N,N-dimethylaniline, 4-fluoro-N,N-dimethylanilme, 4- methyl N,N-dimethylanilme, 4-ethoxy-N,N-d ⁇ methylan ⁇ lme, N,N- dimethylamlme, 3-hydroxy-N,N-d ⁇ methylan ⁇ lme,N,N,N ,N - tetramethyl-1 , 4-dia line, 4-acetam ⁇ do-N,N-dimethylamline, etc.
  • N,N-d ⁇ alkylamlmes which are substituted with an alkyl group m the ortho-position such as 2 , 6-d ⁇ sopropyl-N,N- dimethylamlme (DIDMA) , 2 , 6-d ⁇ ethyl-N,N-dimethylanilme, N,N, 2 , 4 , 6-pentamethylamlme (PMA) and 2 , 6-d ⁇ ethyl-4-octyl- N,N-dimethylamlme are preferred.
  • DIDMA 6-d ⁇ sopropyl-N,N- dimethylamlme
  • PMA 6-pentamethylamlme
  • 2-A 6-d ⁇ ethyl-4-octyl- N,N-dimethylamlme
  • amines include n-phenylglycine (NPG) , triethylamine tetraalkylethylenediammes such as tetramethyl- and tetraethyl-ethylenediamme, tetramethyl- and tetraethyl- diethylenetriamme, triethanolam e, etc.
  • NPG n-phenylglycine
  • triethylamine tetraalkylethylenediammes such as tetramethyl- and tetraethyl-ethylenediamme, tetramethyl- and tetraethyl- diethylenetriamme, triethanolam e, etc.
  • the alkylammes are preferably used in concentrations of about 0.1 to 5% by weight of the composition.
  • the photoinitiator system and the photohardenable composition described above are useful in a variety of end use applications such as coatings for metal, wood, electronic parts, etc., paints, inks, photobleachable dyes; medical applications, color change indicators.
  • One such use of the aforementioned photomitiators is m combination with a pH sensitive sensitizer which not only contributes to the curing of the composition, but it also can change in response to changes pH, thereby allowing the photoinitiator system to also function as a micro-sensor in the fabrication of fiber optic light sensors such as described in PCT application No. WO 94/06040, the contents of which are hereby incorporated by reference .
  • a sample designation of concentration of components as 0:7:10:0 means that the sample contains no dye, 7 mmolar onium salt, 10 mmolar borate salt and no amine.
  • Specific onium salts include (4-octyloxyphenyl) phenyliodonium hexafluoroantimonate (OPPI) , bis (4-dodecylphenyl iodonium hexafluorantimonate (DDPI) , diphenyliodonium hexafluoroantimonate (DPI) , diphenyliodomum hexafluorophosph ate (DPIP) and t ⁇ phenyl sulfo um hexafluoroantimonate.
  • OPPI (4-octyloxyphenyl) phenyliodonium hexafluoroantimonate
  • DDPI bis (4-dodecylphenyl iodonium hex
  • the borates include a series based around triphenyl n-butyl quaternary ammonium salts. Control experiments with either onium or borate alone did not result in cure. It has also been observed that other additives such as dye sensitizers and amines significantly improve cure speed.
  • FTIR data is shown in Table 1 (Visible Light Cure Without Sensitizer) for an polyester acrylate.
  • a 0:7:10:0 sample (E) shows little cure after 20 second exposure to a visible light source (tungsten halogen dental lamp) supporting the oxygen inhibition observation. Thereafter polymer quickly forms reaching 84% double bond conversion after 80 seconds.
  • small beads of acrylate are placed on a glass slide and exposed to a tungsten halogen light source (an overhead projector) noting initial cure times indicated by when the sample begins to fume. Fuming is a result of the forming polymer's exotherm and can be qualitatively related to speed of cure and final polymer hardness.
  • the 0:7:20:0 sample (19) exhibited a 14 second fume time, essentially identical to the 0:7:10:0 sample.
  • improved cure was achieved.
  • having a greater concentration of the acceptor provides a better opportunity for the borate to react which generates a higher quantum yield of n-butyl radicals and is thus a more efficient system.
  • the fume time is substantially reduced from 15 to 7 seconds. This is basically equal to the 0:14:20:0 sample indicating that only half the borate is needed at the higher ratio of onium.
  • fume time is longer at 11 seconds but still shorter than 15 seconds for the 0:7:10:0 sample (17) .
  • Reducing the onium to 0:7:5:0 (22) illustrates the importance of a high onium ratio since fume times for this sample is long at 25 seconds.
  • Table 2 Formulated acrylate resin without sensitizers cured with various light sources and different s eeds.
  • ⁇ Lucirine 2,4,6 - tri-met ylbenzoyldiphenyl-phosphine oxide
  • the IDIHI- ' J used is 0.05%.
  • the indicated ratios are molar ratios.
  • Samples are aired between salt plates with a 75 W dental lamp at 1 inch distance.
  • the curing time is an accumulative time.
  • Irgacure 907 l-methyl-l-[4-(rnethylthio)phenyl_- 2-morpholinopropa ⁇ one-l (UV photoinitiator)

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Abstract

A photoinitiator system consisting essentially of a reactive hypervalent atom-containing salt and a borate salt, the borate salt being represented by formula (I) wherein R1, R2, R3, and R4 are independently selected from the group consisting of substituted and unsubstituted alkyl, substituted and unsubstituted aryl, substituted and unsubstituted alkenyl, substituted and unsubstituted alkynyl, substituted and unsubstituted alicyclic, substituted and unsubstituted heterocyclic groups, and a cyclic group wherein at least two of R1, R2, R3, and R4 may combine to form a cyclic group, with the proviso that at least one of R1, R2, R3, and R4 is an alkyl group, and wherein Z+ is a quaternary ammonium cation or an alkali metal cation wherein the onium salt is a sufficient strong oxidant to oxidize the borate salt; and a photosensitive composition containing the photoinitiator system are disclosed.

Description

PHOTOINITIATOR COMPOSITION CONTAINING A BORATE SALT AND A HYPERVALENT ATOM-CONTAINING SALT
Background of the Invention
The present invention relates to photoinitiator compositions. More particularly, the invention relates to a borate salt and a salt containing a hypervalent heteroatom (e.g. , an onium salt) which in combination form an effective redox pair capable of efficiently initiating free radical polymerization The invention also relates to a photohardenable composition containing the aforesaid photoinitiator system and more particularly to an anaerobic composition containing the same.
Summary of the Invention
The present invention provides a photoreactive or otherwise activated initiator composition containing a borate salt and a hypervalent heteroatom-containing salt such as an onium salt which form a redox pair such that upon exposure to actinic radiation, electron transfer occurs accompanied by the generation of free radicals capable of hardening an organic monomer or polymer by polymerization or crosslmkmg even m the absence of a sensitizer. In accordance with the invention, the borate salt/hypervalent heteroatom-containmg salt system behaves as a donor/acceptor pair m which an electron is transferred from the borate donor compound to the hypervalent heteroatom-containing acceptor compound, causing both compounds to release radicals which are capable of polymerizing or curing an organic monomer or polymer containing ethylemc unsaturation. Of course, it is recognized that many processes can activate this polymerizable composition. These include exposure to actinic radiation, and the application of pressure or heat, etc., wherein polymerization inhibitors might be removed A principal object of the present invention is to provide a photoinitiator system which contains a hypervalent heteroatom-containmg salt such as an onium salt in combination with a borate salt wherein the borate salt and the hypervalent heteroatom-containmg salt form a redox pair.
A further object of the present invention is to provide a photosensitive composition containing a photohardenable compound which is an ethylenically unsaturated organic monomer or polymer, and the aforementioned photoinitiator system.
Still another object of the invention is to provide a hardenable composition which can be triggered by any other recognized method of removing polymerization inhibitors, e.g, increasing the external pressure or heat.
These and other objects are accomplished in accordance with the present invention which, in one embodiment, provides: a photoinitiator system containing a reactive hypervalent heteroatom-containmg salt m combination with a tetraorganoborate salt wherein the hypervalent heteroatom-containmg salt and the borate salt form a redox pair. The present invention also provides an initiator composition comprising a sensitizer, a hypervalent heteroatom- containmg salt and a borate salt. The hypervalent heteroatom-containmg salt and the borate salt are capable of reacting their ground state. However, polymerization is prevented by a radical inhibitor, such as oxygen, a substituted phenol, or any of the many other compounds known in the art as free radical stabilizers. Upon exposure, the systems function to react with oxygen or added inhibitor. Upon the loss of the inhibitor, the borate and hypervalent heteroatom-containmg salts react to generate radicals which polymerize the composition. Thus, the compositions of the invention are anaerobically polymerizable. In the presence of oxygen, the compositions give no apparent polymerization. Once oxygen has been exhausted (i.e., an anaerobic state) through reaction with the free radicals, the borate salt and the hypervalent heteroatom-containmg salt reaction generates radicals which are capable of polymerizing the composition.
The compositions of the present invention are distinguishable from those of Farid, U.S. Patent 4,859,572, in that the borate salt and hypervalent heteroatom-containmg salt which, preferably, is an onium salt, form a redox pair which is capable of reacting in its ground state In accordance with the teachings of Farid, the sensitizer must be selected so that it s more cathodic than the electron acceptor and/or more anodic than the electron donor m order for the electron transfers to occur and for radicals to be generated. This is not a requirement m the present invention because the borate donor and hypervalent heteroatom-containmg salt acceptor are capable of reacting with each other m the compositions in the ground state and no sensitizer is required. While neither the borate salt alone nor the hypervalent heteroatom-containmg salt alone (e.g., an onium salt) absorb light in the visible region, preliminary studies suggest that when combined, they may form a charge transfer complex that absorbs m the visible region. Hence, the ion pair may function as an absorber. Electron transfer and radical formation leading to polymer formation is not controlled only by the redox potentials of the sensitizer. Rather polymerization is moderated by the presence of an inhibitor, like oxygen; the sensitizer composition freely reacts in the absence of the inhibitor as is required in an anaerobic state.
In addition to the photoinitiator compositions, the present invention provides a photosensitive composition containing a photohardenable compound which is an organic monomer or polymer having ethylemc unsaturation, and the aforementioned photoinitiator compositions. Detailed Description of the Invention
In accordance with one embodiment of the present invention, a combination of a borate salt and a reactive hypervalent heteroatom-containing salt, e.g., an onium salt are useful as a photoinitiator system. The borate salt is represented by the formula (I) :
R» Rl
R* K*
( i :
wherein R1, R , R3 and R4 are independently selected from the group consisting of substituted and unsubstituted alkyl, substituted and unsubstituted aryl, substituted and unsubstituted alkenyl, substituted and unsubstituted alkynyl, substituted and unsubstituted alicyclic, substituted and unsubstituted heterocyclic groups, and a cyclic group wherein at least two of said R1, Rz, R3 and R4 may combine the form said cyclic group, with the proviso that at least one of R1, R2, R3 and R4 is an alkyl group, and wherein Zθ is a cationic species capable of forming a reactive salt with an anionic borate species .
An alkyl group represented by R1 to R4 includes a straight, branched or cyclic alkyl group and preferably has 1 to 18 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a stearyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, etc .
A substituted alkyl group represented by R1 to R4 includes an alkyl group described above having a substituent, such as a halogen atom, e.g., a chlorine atom, a bromine atom, etc. ; an aryl group, preferably, a phenyl group; a -N=RSR6 group, wherein R5 and R6 each represents a hydrogen atom, an alkyl group having 1 to 14 carbon atoms or an aryl group; a - COOR7 group, wherein R7 represents an alkyl group having 1 to 14 carbon atoms or aryl group; a -OCOR8 group or a -OR8 group, wherein R8 represents an alkyl group having 1 to 14 carbon atoms or an aryl group.
An aryl group represented by R1 to R4 includes an aryl group having 1 to 3 rings, such as a phenyl group, a naphthyl group, etc., and a substituted aryl group represented by R1 to R4 includes an aryl group described above having the same substituent as that for the alkyl group or an alkyl group having 1 to 14 carbon atoms.
An alkenyl group represented by R1 to R4 includes a straight, branched or cyclic alkenyl group having 2 to 18 carbon atoms and a substituent for the alkenyl group includes the same substituent as that for the alkyl group.
An alkynyl group represented by R1 to R4 includes a straight or branched alkynyl group having 2 to 18 carbon atoms, and a substituent for the alkynyl group includes the same substituent as that for the alkyl group.
A heterocyclic group represented by R1 to R4 includes a 5 or more-membered ring, preferably 5 to 7-membered ring containing at least one atom selected from the group consisting of N, S and 0, and the heterocyclic ring may contain a condensed ring. The substituent for the heterocyclic group includes the same substituent as that for the aryl group. Preferably, the anionic species of the borate is a tπarylalkylborate such as triphenyl (n-butyl) borate, tπphenyl (sec-butyl) borate, etc.
Preferably, the cationic species of the borate is an alkali metal such as Li© or a quaternary ammonium, phosphonium, sulf onium or lodonium cation. When Zθ is a quaternary ammonium cation, it is typically a tetraalkyl ammonium cation where the alkyl substituent contains about 1 to 10 carbons such as methyl, ethyl, butyl, hexyl octyl, etc.; a choline substituent such as acetylcholme, butylcholine, etc. ; trimethylcetylammonium; cetylpyridimum, benzethomum; and the like. In a preferred aspect of the invention the borate salt is a butyrylcholine triarylalkylborate, acetylchol e triarylalkylborate or tetrahexylammonium triarylalkylborate .
Examples of useful borate salts are illustrated by the following compounds 1-21:
1. Ar.B°(nC4H9)Nβ(C2H5)4
2. Ar3Bθ(nC4H9)N°(CH3)4
3. (P-CH30-C6H4) 3BΘ (nC4H9) N® (nC4H9) 4
4. Ar, (nC4H9)BθNθ(nC4H9)4
5. Ar3B°(nC4H9) ιβ
6. Ar3Bθ(nC4H9)N*(C6H13)4
7. Ar3Bθ-Bu (CH3) 3Nβ (CH2) 2C02 (CH2) 2CH3
8. Ar 3BΘ - Bu ( CH3 ) 3N® ( CH2 ) 2OCO ( CH2 ) 2CH3
9. Ar3B°sec-Bu (CH3) 3NΘ (CH2) 2C02 (CH2) 2CH3
10. Ar3Bθ-sec-BuNφ(CGH13)4
11. Ar3Bθ-BuN*(C8H17)4
12. Ar3Bθ-BuN®(CH3)4 13. ArBθ- (n-Bu)3Nφ(CH3)4
14. Ar3Bθ-Bu(CH3)3 "CH2CH2OH
15. ArBθ- (Et)3Nφ(CH3)4
16. Ar2B (n-Bu)2Nφ(CH3)4
17. Ar3BθBuPβ(C4H9)4
18. Ar4BθNφ(C4H9)4
19. Ar3BθBuN®(C4H9)4
20. ArBθMe,N*Me
21. (nBu) 4BθNφMe4
As mentioned above, the hypervalent heteroatom- containmg salt/borate salt photoinitiator system is an acceptor/donor system m which an electron is transferred from the borate salt to the hypervalent heteroatom-containmg salt causing both components to immediately decompose. The decomposition products, presumably, include an alkyl radical such as n-butyl radical and at least one phenyl radical, both of which are capable of initiating acrylate curing or polymerization although the alkyl radical is apparently much more reactive.
The hypervalent heteroatom-containmg salt must be a strong enough oxidant to oxidize the borate salt. The hypervalent heteroatom-containmg salt may be an lodonium salt, a sulfonium salt, an oxonium salt, a sulfoxonium salt, a carbamoylsulfoxonium salt, a pyrylium salt, a thiapyrylium salt, a diazonium salt, a ferrocenium salt, and the like. Preferably, the hypervalent heteroatom-containmg salt is an onium salt. The onium salt useful in the present invention includes but is not limited to those onium salts disclosed in U.S. Patent No. 4,777,530 to Gottschalk et al . , the contents of which are incorporated herein by reference to the extent of the disclosure of such onium salts. Examples of useful onium salts include diaryliodonium hexafluorophosphates, diaryliodonium arsenates and diaryliodonium antimonates. Representative examples of such onium salts include diaryl lodonium salts such as diphenyliodonium hexafluorophosphate and 4 -( (2-hydroxy) tetradecyloxyphenyl) phenyl lodonium hexafluoroantimonate (CD 1012) .
When the onium salt is a lodonium salt, it can be represented by the formula (III) :
- -<.dα--ee))
(R5 aR6bi]+c IMQ J : nι
where Rr is a monovalent aromatic organic radical, R6 is a divalent organic radical, M is a metal or a metalloid and Q is a halogen, alkyl, aryl, alkylaryl, or equivalent radical, a and b are whole numbers equal to 0, 1 or 2, c is equal to d-e, e is equal to the valence of M and is an integer equal to 2 to 7 inclusive; and d is greater than e and is an integer having a value up to 8
Radicals included by R5 can be the same or different aromatic, carbocyrlic or heterocyclic radicals having from 6 to 20 carbon atom; , which can be substituted on the ring with from 1 to 4 monovalent radicals selected from Cα 18) alkoxy, C(1 18) alkyl, nitro, chloro, etc. R5 is more particularly phenyl, chlorophenyl, nitrophenyl, methoxyphenyl, pyridyl, etc. Radicals included by R6 are divalent radicals such as
^ O ~_iQ) etc. Metal or metalloids included by M or formula (III) are transition metals such as Sb, Fe, Sn, Bi, Al, Ga, In, Ti, Zr, Sc, V, Cr, Mn, Cs, rare earth elements such as the lanthanides, for example, Cd, Pr, Nd, etc., actinides, such as Th, Pa, U, Np, etc. and metalloids such as B, P, As, etc. Complex anions included by MQd "(d~e) are, for example, BF4 , PF6 , AsF6 , SbF6 , FeCl4\ SnCl6", SbCl6 , BiCl3\ etc.
Halonium salts (especially iodonium salts) included by formula III are, for example,
Figure imgf000011_0001
The halonium salts of formula III can be made by the procedures described by 0. A. Ptitsyna, M.E. Pudecova, et al . , Dokl, Adad Nauk, SSSR, 163, 383 (1965) ; Dokl , Chem., 163, 671 (1965) . F. Marshall Beringer, M. Drexler, E. M. Gindler, J. Am. Chem. Soc . , 75, 2705 (1953) . J. Collette, D. McGreer, R. Crawford, et al . , J. Am. Chem. Soc. 78, 3819 (1956) . Other aryliodonium salts include the polymeric iodonium salts which are described in U.S. Patent No. 4,780,511 to Crivello and are hereby incorporated herein by reference.
Particularly preferred iodonium salts of formula (III) include salts having the following structures: CnH2n+1 C6H4I C6H5) , (CnH2ntlC6H4)2 I\ (CnH2n+1OC6H4) I+ (C6H5) and (CnH2nτlOC6H4)2I+ where n=8 to 12.
In addition, ferrocenium salts of formula:
Figure imgf000012_0001
and diazonium salts of formula:
ArN2+ where Ar is as defined above may be employed m the present invention.
Onium salts found to be particularly useful m the photoinitiator system of the invention are iodonium salts whicn include (4-octyloxyphenyl) phenyliodonium (OPPI) , bιs(4- dodecyl-phenyl) iodonium hexafluoroantimonate (DDPI) , diphenyliodonium hexafluoroantimonate (DPI) , 4-( (2-hydroxy) tetradecyloxyphenyl) phenyl iodonium hexafluoroantimonate (CD 1012) and diphenyliodonium hexafluorophosph ate (DPIP) .
The present invention also provides a photosensitive composition containing a photohardenable compound and the aforementioned photoinitiator composition. The photohardenable compound is characterized as being an organic monomer or polymer containing ethylemc unsaturation sites . The aforementioned photohardenable compound may be a monomer, an oligomer such as a dimer or trimer, or a mixture thereof:
Examples of suitable monomers and the copolymer thereof include esters of unsaturated carboxylic acids and aliphatic polyhydπc alcohol compounds, and amides of unsaturated carboxylic acids and aliphatic polyhydric am e compounds .
Specific examples of monomers of the esters of aliphatic polyhydric alcohol compounds and unsaturated carboxylic acids include an acrylic acid ester, such as ethylene glycol diacrylate, triethylene glycol diacrylate, 1, 3-butanediol diacrylate, tetramethylene glycol diacrylate, propylene glycol diacrylate, neopentyl glycol diacrylate, tπmethylolpropane triacrylate, trimethylolpropane tri (acryloyloxypropyl) ether, trimethylolethane triacrylate, hexanediol diacrylate, 1, 4-cyclohexanediol diacrylate, tetraethylene glycol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythπtol diacrylate, dipentaerythritol triacrylate, dipentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, sorbitol triacrylate, sorbitol tetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate, tri (acryloyloxyethyl) isocyanurate, polyester acrylate oligo er, etc.
Specific examples also include monomers of methacrylic acid esters such as tetramethylene glycol dimethacrylate, triethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, ethylene glycol dimethacrylate, 1, 3-butanediol dimethacrylate, hexanediol dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol dimethacrylate, dipentaerythritol hexamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate, bis- [p- (3-methacryloxy-2- hydroxypropoxy)phenyl] dimethylmethane, bis [p- (acryloxyethoxy)phenyl] dimethylmethane, etc.
Specific examples further include monomers of ltacomc acid esters such as ethylene glycol dntaconate, propylene glycol dntaconate, 1, 3-butanediol dntaconate, 1,4 butanediol dntaconate, tetramethylene glycol dntaconate, pentaerythritol dntaconate, sorbitol tetraitaconate, etc. Also, specific examples include monomers of crotonic acid esters such as ethylene glycol dicrotonate, tetramethylene glycol dicrotonate, pentaerythritol dicrotonate, and sorbitol tetradicrotonate.
Specific examples include monomers of isocrotonic acid esters such as ethylene glycol diisocrotonate, pentaerythritol diisocrotonate, sorbitol tetraisocrotonate, etc .
In addition, specific examples include monomers of maleic acid esters are ethylene glycol dimaleate, triethylene glycol dimaleate, pentaerythritol dimaleate, sorbitol tetramaleate, etc.
Mixtures of the aforesaid ester monomers can be also used.
Suitable specific monomers of the amides of an aliphatic polyhydric amine compound and an unsaturated carboxyolic acids include methylene-bis-acrylamide, methylene- bis-methacrylamide, 1, 6-hexamethylene-bis-acrylamide, 1,6- hexamethylene-bis-methacrylamide, diethylenetriamine-tris- acrylamide, xylylene-bis-acrylamide, and xylylene-bis- methacryamide .
Other examples of polymerizable compounds having an ethylenically unsaturated bond are vinylurethane compounds having two or more polymerizable vinyl groups in one molecule obtained by adding a vinyl monomer having a hydroxy group to a polyisocynate compound having two or more isocyanate groups in one molecule.
Also, still other examples thereof include polyfunctional acrylates and methacrylates, such as urethane acrylates, polyester acrylates, and epoxy acrylates which may be obtained by reacting epoxy resins and (meth) acrylic acid. Good photohardenable results have been obtained using a mixture of resins containing about 70% polyurethane acrylate, about 20% tripropyleneglycmediacrylate (TPGDA) and about 10% ethoxyethoxyethylacrylate (EOEOEA) .
The amount of borate found to be effective is about 0.05 to 2.5% by weight, and the amount of onium salt is about 0.1 to 2.5% by weight based on the total weight of the photosensitive composition.
In accordance with the invention, the hypervalent heteroatom-containmg salt is a strong enough oxidizing agent to oxidize the reducing agent under ground state conditions. However, the system does not undergo spontaneous reaction due to the presence of oxygen or other inhibitors m the composition In the absence of a sensitizer, upon exposure, it is believed that the hypervalent heteroatom-containmg salt absorbs sufficient radiation, even with relatively long wavelength sources, to generate radical chains which effectively remove the inhibitor. Where oxygen alone may stabilize the composition, an inhibitor which quenches free radicals is generally added. Typical examples of such inhibitors include aromatic phenols such as butylated hydroxytoluene (BHT) , 2 , 6-dι-tert-butyl catechol, hydroqumone , and other radical inhibitors known in the art.
In another aspect of the invention, the effectiveness of the photoinitiator composition may be enhanced by the incorporation of a sensitizer into the composition. Upon exposing the composition to actinic radiation, the sensitizer is activated to an excited state whereupon it generates radicals which react with the inhibitors to exhaust them such that the borate and the onium salt can react spontaneously.
Examples of effective sensitizers useful the present invention are dyes such as coumarm dyes, merocyanme dyes, merostyryl dyes, oxonol dyes, methme, polymethme, tnarylmethane, mdolme, thiazme, xanthene, oxaz e, acridme, hemioxonol dyes, keto dyes such as fluorones and xanthones; e.g., 2-methyl- , 10-phenanthrenequmones; 2,4-3- dιιodo-6-butoxy-3-fluorone (DIBF) ; 2 , 4, 5, 7-tetraιodohydroxy- fluorone (TIHF) ; 2 , 4 , 5 , 7-tetraιodo-9-cyanohydroxy-3-fluorone (TIHCF) isopropylthioxanthone (ITX) ; rose bengal; etc. as disclosed m U.S. Pat. No. 4,859,572 to Farid et al . and U.S. Pat. No. 5,055,372 to Shanklm et al . , the contents of which are incorporated herein by reference to the extent of the disclosure of such sensitizers. Preferred sensitizers include 2 , 4-dnodo-6-butoxyfluorone (DIBF) ; 2 , 4 , 5, 7-tetraιodo-3- hydroxyfluorone (TIHF) ; 2 , 4 , 5, 7-tetraιodo-9-cyanohydroxy-3- fluorone (TIHCF) , isopropylthioxanthone (ITX) ; rose bengal; - eos , erythrosm, methylene blue and other compunds as disclosed m U.S. Pat. No. 5,451,343, the contents of which are incorporated herein by reference.
The dye sensitizer may be used a concentration of about 0.01 to 0.5% by weight of the composition.
In addition to the dye sensitizer, other additives such as amines may be used to significantly improve cure speed Although the use of an amme in addition to the dye sensitizer does not always appear to assist initial cure or final cure of the photohardenable compound, it substantially improves the final color of the composition making the composition almost colorless compared to samples without amine which retain some color.
The amines most useful in carrying out the invention are alkylammes and most preferably N,N-di-alkylammes such as N,N-dialkylamlme. Examples of N,N-dιalkylanιlmes useful m this invention include dialkyla lmes substituted at one or more of the ortho, eta- , or para- position by the following groups: methyl, ethyl, isopropyl, t-butyl, 3 , 4-tetramethylene, phenyl, trifluoromethyl, acetyl, ethoxycarbonyl, carboxy, carboxylate, cyano, tπmethylsilylmethyl, trimethylsilyl , triethylsilyl, tnmethylgermanyl, triethylgermanyl, trimethylstannyl , triethylstannyl, n-butoxy, n-pentyloxy, phenoxy, hydroxy, acetyloxy, methylthio, ethylthio, isopropylthio, thio- (mercapto-) , acetylthio, fluoro, chloro, bromo and lodo.
Representative examples of N,N-dialkylamlmes useful in the present invention are 4-cyano-N,N- dimethylanilme, 4-acetyl-N,N-dimethylanilme, 4-bromo-N,N- dimethylanilme, ethyl 4- (N,N-dimethylammo) benzoate, 3- chloro-N, -dimethylaniline, 4-chloro-N, N-dimethylanilme, 3- ethoxy-N,N-dimethylaniline, 4-fluoro-N,N-dimethylanilme, 4- methyl N,N-dimethylanilme, 4-ethoxy-N,N-dιmethylanιlme, N,N- dimethylamlme, 3-hydroxy-N,N-dιmethylanιlme,N,N,N ,N - tetramethyl-1 , 4-dia line, 4-acetamιdo-N,N-dimethylamline, etc. N,N-dιalkylamlmes which are substituted with an alkyl group m the ortho-position such as 2 , 6-dιιsopropyl-N,N- dimethylamlme (DIDMA) , 2 , 6-dιethyl-N,N-dimethylanilme, N,N, 2 , 4 , 6-pentamethylamlme (PMA) and 2 , 6-dιethyl-4-octyl- N,N-dimethylamlme are preferred.
Other useful amines include n-phenylglycine (NPG) , triethylamine tetraalkylethylenediammes such as tetramethyl- and tetraethyl-ethylenediamme, tetramethyl- and tetraethyl- diethylenetriamme, triethanolam e, etc.
The alkylammes are preferably used in concentrations of about 0.1 to 5% by weight of the composition.
The photoinitiator system and the photohardenable composition described above are useful in a variety of end use applications such as coatings for metal, wood, electronic parts, etc., paints, inks, photobleachable dyes; medical applications, color change indicators. One such use of the aforementioned photomitiators is m combination with a pH sensitive sensitizer which not only contributes to the curing of the composition, but it also can change in response to changes pH, thereby allowing the photoinitiator system to also function as a micro-sensor in the fabrication of fiber optic light sensors such as described in PCT application No. WO 94/06040, the contents of which are hereby incorporated by reference .
A series of tests were performed to demonstrate the effectiveness of borate salt/onium salt formulations in typical acrylate solutions. For purposes of clarification, the concentration of the components m each of the test samples is expressed m terms of molar concentration of the components in the following order:
DYE. ONIUM: BORATE: AMINE
For example, a sample designation of concentration of components as 0:7:10:0 means that the sample contains no dye, 7 mmolar onium salt, 10 mmolar borate salt and no amine. Specific onium salts include (4-octyloxyphenyl) phenyliodonium hexafluoroantimonate (OPPI) , bis (4-dodecylphenyl iodonium hexafluorantimonate (DDPI) , diphenyliodonium hexafluoroantimonate (DPI) , diphenyliodomum hexafluorophosph ate (DPIP) and tπphenyl sulfo um hexafluoroantimonate. The borates include a series based around triphenyl n-butyl quaternary ammonium salts. Control experiments with either onium or borate alone did not result in cure. It has also been observed that other additives such as dye sensitizers and amines significantly improve cure speed.
FTIR data is shown in Table 1 (Visible Light Cure Without Sensitizer) for an polyester acrylate. A 0:7:10:0 sample (E) , shows little cure after 20 second exposure to a visible light source (tungsten halogen dental lamp) supporting the oxygen inhibition observation. Thereafter polymer quickly forms reaching 84% double bond conversion after 80 seconds. In another study described in Table 2, small beads of acrylate are placed on a glass slide and exposed to a tungsten halogen light source (an overhead projector) noting initial cure times indicated by when the sample begins to fume. Fuming is a result of the forming polymer's exotherm and can be qualitatively related to speed of cure and final polymer hardness. For the 0:7:10:0 sample (17) fuming initiates after 15 seconds and the polymer formed is hard and slightly bendable . This data clearly shows that hard polymer can be obtained with high double bond conversion by combining an onium and a borate and curing with visible light. Exposure of the same sample to a Fusion "Q" bulb which emits high intensity UV and visible light also initiates cure.
The concentration of onium and borate and their ratio is important to optimizing cure response as are other factors discussed later. In Table 1 a 0:14:20:0 formulation (A) exhibits substantially faster cure and achieves a higher degree of cure than the 0:7:10:0 sample (E) . This is not too surprising since the concentration of onium/borate m sample (A) is double over that of sample (E) . However, the results in sample (A) are still impressive : after 5 seconds exposure double bond conversion is 23% whereas after 80 seconds it's 93%. Fume time in sample (A) is also significantly shorter at 6 seconds than for sample (E) (15 seconds) as noted m Table 2. The 0:7:20:0 sample (19) exhibited a 14 second fume time, essentially identical to the 0:7:10:0 sample. However, by increasing the onium relative to the borate, improved cure was achieved. Apparently having a greater concentration of the acceptor provides a better opportunity for the borate to react which generates a higher quantum yield of n-butyl radicals and is thus a more efficient system. For example, by doubling the ratio of onium to borate from 0:7:10:0 to 0:14:10:0, the fume time is substantially reduced from 15 to 7 seconds. This is basically equal to the 0:14:20:0 sample indicating that only half the borate is needed at the higher ratio of onium. by reducing the borate further to 0:14:5:0 (13) fume time is longer at 11 seconds but still shorter than 15 seconds for the 0:7:10:0 sample (17) . Reducing the onium to 0:7:5:0 (22) illustrates the importance of a high onium ratio since fume times for this sample is long at 25 seconds.
The selection of the type of onium and borate also influences cure. Using DDPI instead of OPPI (Table 1) improves cure as seen in sample C: after 5 and 20 seconds exposure double bond conversion is 7% and 52%, respectively, compared to 0% and 7% for the OPPI case (E) . The reason for this improvement is unclear but could involve absorbance differences between the onium salts (DDPI is a red solution) As mentioned earlier, most borates alone do not induce cure with either visible or UV light. DIDMA by itself does not induce cure with visible light although some polymer is formed with UV since DIDMA decomposition radicals are produced. Borate plus amine, however, does cause some very soft polymer to form under visible light (FTIR after 80 seconds exposure is 48% conversion) . This result is not fully understood although a small source of radicals is apparently generated to cause some cure .
Additional investigations were made to determine whether the presence of an amine would improve onium/borate cure results. The reasoning is that when an electron is transferred from the borate to the onium, decomposition products include phenyl radicals which are relatively poor initiators. By incorporating an amine, the phenyl radical can abstract a hydrogen atom from the amine forming the amine radical which is a very facile initiator. Another contribution of the amme is likely as an autooxidizer which would scavenge oxygen and enhance cure rates . The amme case is supported by samples B and D in Tale 1. By adding a 1:1 or a 2:1 molar ratio of an amme to the borate the induction period is reduced and cure starts earlier For example, at 20 seconds light exposure, the double bond conversation is 7%, 54% and 71%, respectively, for samples E, D and B containing 0, 10 (NPG) and 20 (DIDMA) millimolar ratios of amine. Fume times as detailed in Table 2 (samples 17, 11 and 2) are also shortened when higher amounts of amine are used: 0,10 and 20 molar ratios of DIDMA results 15, 11 and 5 seconds, respectively, before fuming occurs. Adding amine to other optimized ratios such as 0:14:10:0 (sample 5 versus sample (C) and 0:14:5:0 (sample 13 versus sample 10) shows a modest improvement in what are already short fume times.
Adding UV and visible light sensitizers to onium/borate formulations significantly improves cure, particularly speed of cure. In Table 3 sample E, 1:7:10:0, contains 0.05 w . % DIBF and exhibits 80% double bond conversion after only 5 seconds exposure compared to 7% without DIBF (Table 1, sample 6) which is a marked improvement. Fume times for samples containing a sensitizer is instantaneous, which tracks the FTIR data. Reducing DIBF to 0.01 wt% (Table 3, sample L) provides 68% double bond conversion after 5 seconds and 85% after 60 seconds, identical to the 0.05 wt% sample (Table 3, sample M) . Adding amine to DIBF containing samples does not appear to assist initial cure or final cure salts (Table 3, samples D,F) unlike samples without sensitizer where amine did show improvement. However, the presence of the amme substantially improves final color making the sample almost colorless compared to samples without amme which retain some color. In addition, tests performed with the "Q" or mercury arc bulb indicates that amine provides harder polymer and again better color. Samples using thioxanthone (ITX) , rose bengal or TIHF as the sensitizer also exhibits significant cure when combined with onium/borate as shown m Table 3.
Lowering the OPPI ratio (1:2:10:0, sample J, Table 3) only modestly affects 5 second conversion results - 75% vs 80% - and final cure is essentially the same. However, final color is much improved with lower OPPI concentrations. Lowering both the OPPI and DIBF as shown in sample N reduces 5 second cure to 42% although final cure is again comparable. Other variations of the components are shown in Table 3. Table 5 shows some data for UV exposure of these systems.
Table 1
Figure imgf000022_0001
Table 2 Formulated acrylate resin without sensitizers cured with various light sources and different s eeds.
Figure imgf000023_0001
• 0 5% Sulfonium + 0.5 % BORATE VI (0:7:10.0) starts only fuming after 35 sec and is not cured at 30 sec whereas 0 3
% DPI+SbF6" 0 5 % BORATE VI (0.7:10.0) starts fuming after 15 sec and 0.35% DPI+FFβ"' 0 5 % BORATE VI (0.7:10.0) starts fuming after less than 15 sec and gives good cure, better than the SbF6 and comparable with the OPPI
•• The 1.7:0:10 (NPG) gives very good cure, much better than the 1:10 .0:10 (DIDMA) but the glassy feeling that we got with the borate is also not reached with the NPG A sample to make up is the 1:0.10.21 (NPG) and see how it compares. Table 3 Double bond conversion of an acrylale resin measured wilh Fourier Traπformalion Infrared
ω c
09
H C -I I m ro o I x m m
H c ro en
Figure imgf000024_0001
** 13 sec cure instead of 10 sec
^Lucirine = 2,4,6 - tri-met ylbenzoyldiphenyl-phosphine oxide
C 09 CO
H
I ro o rn I in x m m
H
3 c r- ro en
Figure imgf000025_0001
The IDIHI-'J used is 0.05%. The indicated ratios are molar ratios.
Samples are aired between salt plates with a 75 W dental lamp at 1 inch distance. The curing time is an accumulative time.
*** The formulation 1:10:0:0 gives Ihe same data as 1:2:0:0.
Tabl e <? Formulated acrylate resin with sensitizers cured with various light sources and different speeds.
Figure imgf000026_0001
t ere is no indication in brackets behind tne ratio then it means that the system DIDF OPPI UORATE VI DIDMΛ
* All the samples are cured as small drops, buttons
Figure imgf000027_0001
"Irgacure 907 = l-methyl-l-[4-(rnethylthio)phenyl_- 2-morpholinopropaπone-l (UV photoinitiator)
Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.
What is claimed is:

Claims

1. A photoinitiator composition comprising a reactive hypervalent heteroatom-containing salt and a borate salt, said borate salt being represented by the formula (I):
Figure imgf000029_0001
wherein R1, R2, R3, and R4 are independently selected from the group consisting of substituted and unsubstituted alkyl, substituted and unsubstituted aryl, substituted and
unsubstituted alkenyl, substituted and unsubstituted alkynyl, substituted and unsubstituted alicylic, substituted and
unsubstituted heterocyclic groups, and a cyclic group wherein at least two of said R1, R2, R3, and R4 may combine to form said cyclic group, with the provision that at least one of R1, R- , R3, and R4 is an alkyl group, and wherein Z+ is a quaternary ammonium, phosphonium, sulfonium or halonium cation or an alkali metal cation, with the proviso that wherein the
hypervalent heteroatom-containing salt is a sufficiently strong oxidant to oxidize the borate salt.
2. The photoinitiator composition of claim 1, wherein said borate salt is a triarylalkylborate salt, aryltrialyl borate salt or a diaryldialkylborate salt.
3. The photoinitiator composition of claim 2, wherein said borate salt is triphenyl-n-butylborate.
4. The photoinitiator composition of claim 1, wherein Z+ is a quaternary ammonium or phosphonium cation.
5. The photoinitiator composition of claim 4, wherein said Z⊕ is a quaternary ammonium cation selected from the group consisting of acetylcholine, butyrylcholine,
trimethylcetylammonium, cetylpyridinium, benzethonium, and tetraalkylammonium, wherein said alkyl groups contain about 1- 10 carbon atoms.
6. The photoinitiator composition of claim 1, wherein said hypervalent heteroatom-containing salt is a halonium, sulfonium, pyrylium, oxonium, sulfoxonium,
carbamoylsulfoxonium, thiapyrylium, diazonium, or ferrocenium salt.
7. The photoinitiator composition of claim 6 wherein said hypervalent heteroatom-containing salt is an onium salt selected from the group consisting of bis {dodecylphenyl)-iodonium hexafluoroantimonate, (4-octyloxyphenyl)-phenyl iodonium hexafluoroantimonate, 4-((2-hydroxy)
tetradecyloxyphenyl) phenyliodonium hexafluoroantimonate (CD 1012), diphenyl iodonium hexafluorophosphinate, diphenyl lodonium hexafluoroantimonate and triphenylsulfonium
hexaf luoroantimonate.
8. The photoinitiator composition of claim 1 wherein said photoinitiator system further includes an alkylamine.
9. The photoinitiator composition of claim 8, wherein said alkylamine is an N, N-dialkylaniline.
10. The photoinitiator composition of claim 9, wherein said N, N-dialkylamine is selected from the group consisting of 2,6-diisopropyl-N,N-dimethylaniline, 2,6-diethyl-N,N-dimethylaniline, N,N,2,4,6-pentamethylaniline and p-tert-butyl-N,N-dimethylaniline.
11. A photohardenable composition comprising a
photohardenable compound and a photoinitiator composition including a hypervalent heteroatom-containing salt and a borate salt, said borate salt being represented by the formula
(I) :
Figure imgf000030_0001
wherein R1 , R2, R3, and R4 are independently selected from the group consisting of substituted and unsubstituted alkyl, substituted and unsubstituted aryl, substituted and
unsubstituted alkenyl, substituted and unsubstituted alkynyl, substituted and unsubstituted aclicyclic, substituted and unsubstituted heterocyclic groups, and a cyclic group wherein at least two of said R1, R2, R3, and R4 may combine to form said cyclic group, with the proviso that at least one of R1, R2 , R3 and R4 is an alkyl group, and Z+ is a quaternary ammonium, phosphonium, sulfonium or halonium cation or an alkali metal cation, with the proviso that the hypervalent heteroatom-containing salt is a sufficiently strong oxidant to oxidize said borate salt.
12. The photohardenable composition of claim 11, wherein said photohardenable compound is an acrylate monomer, a methacrylate monomer or a mixture thereof.
13. The photohardenable composition of claim 11, wherein said borate salt is a triarylalkylborate salt or a diaryl - dialkylborate salt.
14. The photohardenable composition of claim 13, wherein said borate salt is triphenyl-n-butylborate.
15. The photohardenable composition of claim 11, wherein Z+ is a quaternary ammonium or phosphonium cation.
16. The photohardenable composition of claim 15, wherein Z+ is a quaternary ammonium cation selected from the group consisting of acetylcholine, butyrylcholine,
trimethylcetylammonium, cetylpyridinium, benzethomum, and tetraalkylammonium, wherein said alkyl groups contain about 1- 10 carbon atoms.
17. The photohardenable composition of claim 11, wherein said hypervalent heteroatom-containing salt is a halonium, sulfonium, pyrylium, oxonium, sulfoxonium,
carbamylsulfoxonium, thiapyrylium, diazonium, or ferrocenium salt.
18. The photohardenable composition of claim 17 wherein said hypervalent heteroatom-containing salt is an onium salt selected from the group consisting of bis (dodecylphenyl)-lodonium hexafluoroantimonate, (4-octyloxphenyl)-phenyl iodonium hexafluoroantimonate, 4-((2-hydroxy)tetradecyloxyphenyl) phenyl iodonium
hexafluoroantimonate (CD 1012) diphenyl iodonium
hexafluorophosphinate, diphenyl iodonium hexafluoroantimonate and triphenyl sulfonium hexafluoroantimonate.
19. The photohardenable composition of claim 11 wherein said photoinitiator system further includes an alkylamine.
20. The photohardenable composition of claim 19, wherein said alkylamine is an N, N-dialkylaniline.
21. The photohardenable composition of claim 20, wherein said N, N-dialkylaniline is selected from the group consisting of 2,6-diisopropyl-N, N-dimethylaniline, 2,6-diethyl-N, N-dimethylaniline, N,N,2,4,6-pentamethylaniline and p-tert-butyl-N,N-dimethylaniline.
22. The photoinitiator composition of claim 1 wherein said composition additionally includes a sensitizer.
23. The photoinitiator composition of claim 22, wherein said sensitizer is a dye selected from the group consisting of 2,4-diiodo-6-butoxy-3-fluorone, 2,4,5,7-tetraiodo-3- hydroxyfluorone, 2,4,5,7-tetraiodo-9-cyanohydroxy-3-fluorone, isopropylthioxanthone and rose bengal.
24. The photoinitiator composition of claim 22, wherein the excited state of said sensitizer is a triplet state.
25. The photohardenable composition of claim 11 wherein said composition additionally includes a sensitizer.
26. The photohardenable composition of claim 25, wherein said sensitizer is a dye selected from the group consisting of 2,4-diiodo-6-butyoxy-3-fluorone, 2,4,5, 7-tetraiodo-3-hydroxyfluorone, 2,4,5,7-tetraiodo-9-cyanohydroxy-3-fluorone, isopropylthioxanthone and rose bengal.
27. The photohardenable composition of claim 24, wherein the excited state of said sensitizer is a triplet state.
PCT/US1996/019806 1995-12-14 1996-12-05 Photoinitiator composition containing a borate salt and a hypervalent atom-containing salt WO1997021737A1 (en)

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CN113429210A (en) * 2021-07-16 2021-09-24 嘉兴饶稷科技有限公司 Silicon carbide ceramic slurry with high photosensitive activity and preparation method thereof

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