Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2/00—Processes of polymerisation
  • C08F2/46—Polymerisation initiated by wave energy or particle radiation
  • C08F2/48—Polymerisation initiated by wave energy or particle radiation by ultraviolet or visible light
  • C08F2/50—Polymerisation initiated by wave energy or particle radiation by ultraviolet or visible light with sensitising agents
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2/00—Processes of polymerisation
  • C08F2/46—Polymerisation initiated by wave energy or particle radiation
  • C08F2/48—Polymerisation initiated by wave energy or particle radiation by ultraviolet or visible light
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F22/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals each having only one carbon-to-carbon double bond, and at least one being terminated by a carboxyl radical and containing at least one other carboxyl radical in the molecule; Salts, anhydrides, esters, amides, imides or nitriles thereof
  • C08F22/10—Esters
  • C08F22/12—Esters of phenols or saturated alcohols
  • C08F22/18—Esters containing halogen
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J151/00—Adhesives based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers
  • C09J151/08—Adhesives based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers grafted on to macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
• • 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
• • 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
• • 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
  • G03F7/031—Organic compounds not covered by group G03F7/029
• • 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
  • G03F7/032—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds with binders
  • G03F7/033—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds with binders the binders being polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds, e.g. vinyl polymers

Definitions

• This invention relates generally to photopolymerizable compositions and more particularly to photopolymerizable compositions which include maleimide compounds as a component and methods of using the same.
• Ethylenically unsaturated compounds can be polymerized by exposure to radiation, typically ultraviolet light, in the presence of a photoinitiating system.
• the photoinitiating system includes (1) a compound capable of initiating polymerization of the ethylenically unsaturated compound upon exposure to radiation (a "photoinitiator") and optionally (2) a coinitiator or synergist, that is, a molecule which serves as a hydrogen atom donor.
• the coinitiators or synergists are typically alcohols, tertiary amines, amides, or ethers which have labile hydrogens attached to a carbon adjacent to a heteroatom.
• Currently commercially available photoinitiators include benzophenones and derivatives thereof, such as thioxanthone derivatives.
• N-aliphatic and ortho-substituted (i.e. "twisted") N-aromatic maleimides have been investigated as comonomer- photoinitiators of UV-curable acrylic systems. These maleimides have been observed to require the presence of a hydrogen atom-donor synergist (such as an amine, ether, thiol, or the like) to obtain reasonable rates of initiation and polymerization.
• a hydrogen atom-donor synergist such as an amine, ether, thiol, or the like
• compositions of the invention include at least one radiation curable compound.
• the compositions preferably include ethylenically unsaturated compounds, and in particular, acrylate derivatives.
• compositions further include at least one maleimide which is capable of initiating the photopolymerization of a radiation curable compound.
• the maleimide can be an alkyl maleimide, functionalized aliphatic maleimide, aromatic maleimide, maleimide, maleic anhydride, or mixtures thereof.
• the maleimide component can be substantially completely consumed during initiation and photopolymerization (incorporated into the polymer structure).
• composition further includes additional photoactive compounds as sensitizers.
• the composition includes at least one benzophenone compound which is capable of initiating polymerization of the ethylenically unsaturated compound upon exposure to radiation.
• benzophenone compound which is capable of initiating polymerization of the ethylenically unsaturated compound upon exposure to radiation.
• benzophenone compound includes benzophenone and derivatives thereof, including thioxanthone and derivatives of thioxanthone.
• the composition optionally includes at least one coinitiator or synergist as a hydrogen atom donor or an electron donor.
• the hydrogen atom donor can be present as a separate compound or can be included as a molecular component of the photopolymerizable compound.
• the present invention also provides methods for radiation curing of photopolymerizable compositions of the invention.
• FIG. 1 is a graph illustrating photo-differential scanning calorimetry (DSC) exotherm rates for the photopolymerization of 1,6-hexanediol diacrylate (HDD A) with photoinitiator packages of 3% benzophenone (BZPN)/1% methyl diethanol amine (NMDEA) and 0.31% N-methyl maleimide (MMI)/1% NMDEA;
• Figure 2 is a graph illustrating photo-DSC exotherm rates for the photopolymerization of polyethylene glycol diacrylate (PEG 400 DA) with photoinitiator packages of 3% BZPN/1% NMDEA and 0.31% MMI/1% NMDEA;
• Figure 3 is a graph illustrating photo-DSC exotherm rates for the photopolymerization of HDD A with photoinitiator packages of 3% BZPN/1% NMDEA, 0.31% MMI/1% NMDEA, and 3% BZPN/0.31% MMI/1% NMDEA;
• Figure 4 is a graph illustrating photo-DSC exotherm rates for the photopolymerization of HDD A with photoinitiator packages of 3% BZPN/0.31% n- phenyl maleimide (N-PHMI)/1% NMDEA, 3% BZPN/0.31% N-hexyl maleimide (N- HMI)/1% NMDEA, 3% BZPN/0.31% N-cyclohexyl maleimide (N-CHMI)/1% NMDEA, 3% BZPN/0.31% maleic anhydride/1% NMDEA, and 3% BZPN/3% Irgacure 651 ( ⁇ , ⁇ -dimethoxy deoxybenzoin (BDK)
• Figure 5 is a graph illustrating photo-DSC exotherm rates for the photopolymerization of HDD A with photoinitiator packages of 3% BZPN/0.31% maleimide (MI)/1% NMDEA, 3% BZPN/0.31% N-2-n-tert-butyl-phenyl maleimide/1% NMDEA, 3% BZPN/0.31% DEFMR (diethylfumarate)/l% NMDEA, 3% BZPN/0.31% HMI/1% NMDEA, and 3% BZPN/0.31% maleic anhydride/1% NMDEA.
• Maleimides useful in the compositions of the invention include maleimides of the formula
• each Ri and R 2 is independently selected from the group consisting of hydrogen, Cl to CIO alkyl, cycloalkyl, aryl, alkoxy, and halogen, or R_ and R 2 together form a fused saturated or unsaturated five or six membered cyclic hydrocarbon or heterocyclic ring system containing one or two O, N or S atoms, optionally substituted with alkyl, aryl, halogen, arylalkyl, alkylaryl, cycloalkyl, alkoxy, heteroatoms, silicon, and the like.
• Such compounds are commercially available and/or can be prepared using commercially available starting materials using techniques known in the art.
• Alkyl maleimides useful in the invention include compounds having at least one maleimide functional group substituted with a linear, branched or cyclic Cl- C10 alkyl radical at the nitrogen atom.
• Exemplary alkyl maleimide compounds can have the formula below:
• each Ri and R is independently selected from the group consisting of hydrogen, Cl to CIO alkyl, cycloalkyl, aryl, alkoxy, and halogen, or Rj and R 2 together form a fused saturated or unsaturated five or six membered cyclic hydrocarbon or heterocyclic ring system containing one or two O, N or S atoms, optionally substituted with alkyl, aryl, halogen, arylalkyl, alkylaryl, cycloalkyl, alkoxy, heteroatoms, silicon, and the like; and
• R is straight chain, branched or cyclic C1-C10 alkyl, optionally substituted with one or more C1-C4 alkyl, and preferably is C1-C4 alkyl or C6 cycloalkyl.
• alkyl maleimides include without limitation methyl maleimide, hexyl maleimide, cyclohexyl maleimide, and the like. Such compounds are known in the art and can be prepared using techniques known in the art. See, for example, Z.Y. Wang, Synthetic Comm. 20(11) 1607-1610 (1990); P.O. Tawney et al., J. Org. Chem. 26, 15 (1961); and U.S. Patent No. 2,542,145.
• Aliphatic maleimide compounds useful in the invention include compounds having at least one maleimide unit substituted with a functionalized aliphatic substituent at the nitrogen atom.
• the aliphatic substituent preferably is a linear or branched Cl to CIO alkyl, and more preferably methyl or ethyl.
• the alkyl is optionally substituted with Cl to C4 alkyl, Cl to C4 alkoxy, halogen, and the like as described below.
• Aliphatic maleimides useful in the invention can be monofunctional (have one maleimide functional group), or can be di- or multi-functional (have two or more maleimide functional groups).
• two or more aliphatic maleimide units can be connected or coupled via a spacer group(s), such as, but not limited to, linear or branched Cl to CIO alkyl, C3 to C6 cycloalkyl optionally substituted with
• Cl to C4 alkyl Cl to CIO oxyalkyl, which can include one or more oxygen atoms,
• maleimide compounds useful in the invention include maleimide units connected to polymeric or oligomeric compounds (typically having a molecular weight of at least about 1000).
• unsaturated polyester resins with varying percent maleimide functionality incorporated therein as known in the art can be used.
• Exemplary aliphatic maleimide compounds can have the formula below:
• each R ⁇ and R 2 is independently selected from the group consisting of hydrogen, Cl to CIO alkyl, cycloalkyl, aryl, alkoxy, and halogen, or R ⁇ and R 2 together form a fused saturated or unsaturated five or six membered cyclic hydrocarbon or heterocyclic ring system containing one or two O, N or S atoms, optionally substituted with alkyl, aryl, halogen, arylalkyl, alkylaryl, cycloalkyl, alkoxy, heteroatoms, silicon, and the like;
• R 4 is linear or branched Cl to CIO alkyl, heteroatom, or silicon - SiH 2 -;
• FG is a functional group selected from the group consisting of -OR 3 , -SR 3 , -SiH 2 R 3 ,-OC(O)N(R 3 ) 2 , -
• OC(O)OR 3 -CN, halogen, -CH 2 N-aryl-FG ⁇ -CH 2 N-aryl-R 3 -FG ⁇ sulfonic acid, quaternary ammonium, and salts thereof, in which each R 3 is selected from the group consisting of hydrogen, alkyl, aryl, cycloalkyl, arylalkyl, and alkylaryl, and in which FG' is selected from the group consisting of -OR 3 , -SR 3 , -SiH 2 R 3 , -OC(O)N(R 3 ) 2 , -
• FG is selected from the group consisting of hydrogen, alkyl, aryl, cycloalkyl, alkylaryl, arylalkyl, alkyl-FG", and aryl-FG", wherein FG" is the same as FG' as defined in (cl) above, or
• (c3) FG is a functional group as defined in (cl) in combination with a spacer group linking said maleimide unit with at least one other maleimide unit to form a di- or multifunctional maleimide compound.
• exemplary spacer groups include without limitation linear or branched Cl to CIO alkyl, C3 to C6 cycloalkyl, optionally substituted with lower Cl to C4 alkyl, Cl to CIO oxyalkyl, which can include one or more oxygen atoms, such as that derived from ethylene glycol, carbonate, and the like.
• Aliphatic maleimides useful in the invention are described, for example, in pending U.S. application Serial No.
• aliphatic maleimides useful in the invention include, but are not limited to: hydroxy methylmaleimide (HMMI)
• IPBUBEMI isophorone bisurethane bisethylmaleimide
• BPMI bispropyl maleimide
• aliphatic maleimides which include at least one maleimide unit as described above can be prepared using techniques known in the art. See, for example, Z.Y. Wang, Synthetic Comm. 20(11) 1607-1610 (1990); P.O. Tawney et al., J. Org. Chem. 26, 15 (1961); and U.S. Patent No. 2,542,145.
• Aromatic maleimides useful in invention include compounds according to formula below:
• each of R 5 , Re, R 7 , R 8 , and R 9 is independently selected from the group consisting of H, CX 3 , COOR 12 , COR 12 , OR 12 , CN, SR 12 , N(R 12 ) 2 , R 13 , X, and MI;
• Rio and R ⁇ each is independently selected from the group consisting of H, Cl to CIO alkyl, preferably C1-C4 alkyl, more preferably CH 3 , cycloalkyl, aryl, alkoxy, and halogen, preferably chloride, or Rj and R 2 together form a fused saturated or unsaturated five or six membered cyclic hydrocarbon or hetero cyclic ring system containing one or two O, N or S atoms, optionally substituted with alkyl, aryl, halogen, arylalkyl, alkylaryl, cycloalkyl, alkoxy, heteroatoms, silicon, and the like;
• X is halide, preferably F, Cl, Br, or I;
• R 12 is selected from the group consisting of H, lower alkyl, cycloalkyl, and aryl;
• R 13 is selected from the group consisting of lower alkyl, cycloalkyl, and aryl, or Rj 3 is a spacer group connecting at least two compounds of the above formula to form a di- or multi-functional maleimide;
• R 10 and R ⁇ are as defined above.
• two or more aromatic maleimide units can be connected or coupled via a spacer group(s), such as, but not limited to, linear or branched Cl to CIO alkyl, C3 to C6 cycloalkyl optionally substituted with Cl to C4 alkyl, Cl to CIO oxyalkyl, which can include one or more oxygen atoms, such as that derived from ethylene glycol, carbonate, aryl, alkylaryl, arylalkyl, and the like.
• the spacer group can be , for example:
• Y and Z are each independently selected from C2 to CIO alkylene, m is an integer from 1 to 10, and n is an integer from 1 to 10;
• Exemplary aromatic maleimides useful in the invention include, but are not limited to: phenyl maleimide (PMI)
• N-(2-t-butylphenyl)maleimide NtBPMI
• aromatic maleimides can be prepared using techniques known in the art, with slight modifications as noted herein.
• the compounds for example, can be synthesized using a two step method, which begins with the reaction of a suitably substituted aromatic amine with maleic anhydride (or a substituted maleic anhydride, such as citraconic anhydride) in a polar solvent, such as diethylether, to produce the amic acid in near quantitative yields.
• the amic acid is then recovered from the solvent and residual solvent and water can be removed from the recovered product.
• the second step is acid catalyzed ring closure to form the imide.
• This reaction is performed by dissolving the amic acid in a suitable solvent, such as an organic hydrocarbon solvent such as toluene, optionally with a small amount of cosolvent, such as dimethylsulfoxide (DMSO), adding a catalytic amount of concentrated sulfuric acid, heating the mixture, preferably to reflux, and removing water through the water/solvent azeotrope. Excess solvent can then be removed, and
• a suitable solvent such as an organic hydrocarbon solvent such as toluene
• cosolvent such as dimethylsulfoxide (DMSO)
• Aromatic maleimides useful in the invention are described, for example, in pending provisional application Serial No. 60/047,729, filed May 27, 1997, titled “Aromatic Maleimides,” and it s corresponding published international application PCT Publication No. WO 98/54134, the entire disclosure of each of which is hereby incorporated by reference.
• alkyl refers to linear or branched Cl to CIO alkyl, such as but not limited to methyl, ethyl, propyl, butyl, isopropyl, and the like, optionally substituted with halogen, aryl, arylalkyl, alkylaryl, cycloalkyl, alkoxy, heteroatoms, silicon, and the like.
• alkoxy refers to linear or branched Cl to CIO alkoxy.
• cycloalkyl refers to C3 to C6 cycloalkyl, such as but not limited to cyclopentyl and cyclohexyl, also optionally substituted with halogen, aryl, alkyl, arylalkyl, alkylaryl, alkoxy, heteroatoms, silicon and the like.
• aryl refers to C3 to CIO cyclic aromatic groups such as but not limited to phenyl, naphthyl, and the like, optionally substituted with halogen, alkyl, arylalkyl, alkylaryl, cycloalkyl, alkoxy, heteroatoms, silicon, and the like.
• heteroatom refers to oxygen, sulfur, and nitrogen.
• the photopolymerizable compositions include at least one maleimide as defined above as a component thereof, for example, as a photoinitiator, a comonomer, and the like.
• a photoinitiator for example, as a photoinitiator, a comonomer, and the like.
• the term photopolymerizable composition refers to compositions which harden or cure upon exposure to radiation.
• compositions of the invention include ethylenically unsaturated compounds, including monomers and oligomers derived from acrylic and methacrylic acid, optionally dispersed or dissolved in a suitable solvent that is copolymerizable therewith, and mixtures thereof, which are photopolymerizable when exposed to a source of radiation (ultraviolet or UV radiation, or radiation outside the UV spectrum), particularly free radical polymerizable systems.
• a source of radiation ultraviolet or UV radiation, or radiation outside the UV spectrum
• the photopolymerizable compounds can be monofunctional, or can include two or more polymerizable ethylenically unsaturated groupings per molecule.
• photopolymerizable compounds or precursors include, but are not limited to, reactive vinyl monomers, including acrylic monomers, such as acrylic and methacrylic acids, and their amides, esters, salts and corresponding nitriles.
• Suitable vinyl monomers include, but are not limited to, methyl acrylate, ethyl acrylate, n- or tert-butylacrylate, isooctyl acrylate, methyl methacrylate, ethylmethacrylate, 2-ethylhexyl methacrylate, butylacrylate, isobutyl methacrylate, the corresponding hydroxy acrylates, i.e., hydroxy ethylacrylate, hydroxy propylacrylate, hydroxy ethylhexyl methacrylate, glycol acrylates, i.e., ethylene glycol dimethacrylate, hexamethylene glycol dimethacrylate, the allyl acrylates, i.e., allyl methacrylate, diallyl methacrylate, the epoxy acrylates, i.e., glycidyl methacrylate, and the aminoplast acrylates, i.e., melamine
• vinyl acetate, vinyl and vinylidene halides and amides i.e., methacrylamide, acrylamide, diacetone acrylamide, vinyl and vinylidene esters, vinyl and vinylidene ethers, vinyl and vinylidene ketones, butadiene, vinyl aromatics, i.e., styrene, alkyl styrenes, halostyrenes, alkoxystyrenes, divinyl benzenes, vinyl toluene, and the like are also included.
• Prepolymers include acrylated epoxides, polyesters and polyurethanes, and are typically combined with a suitable monomer for viscosity control.
• the photopolymerizable compounds may be polymerized to form homopolymers or copolymerized with various other monomers.
• the photopolymerizable compound can be present in the compositions of the invention in amounts from about 0 to about 99.8, preferably about 80 to about 99.8, percent by weight, based on the total weight of the composition.
• the maleimides can be used singly or as mixtures thereof, and are useful as photopolymerization initiators.
• the maleimide compounds can be present in the photopolymerizable composition in an amount sufficient to initiate polymerization thereof upon exposure to radiation.
• the composition can include about 0.01 to about 100, preferably about 0.01 to about 20, more preferably about 0.01 to about 10, percent by weight maleimide compound, based on the total weight of the photopolymerizable compounds.
• the inventors have found that only relatively low concentrations of the maleimide are required for desirable results.
• the maleimide can be present in amounts of about 0.01 mole percent to about 2 mole percent, and even less than about 0.1 mole percent.
• the benzophenone compound can be benzophenone or any derivative thereof, including thioxanthone and derivatives thereof, and mixtures of such compounds, having photoactive activity.
• Such compounds are known in the art and include compounds of the following structure:
• R 15 is selected from the group consisting of hydrogen, alkyl, aryl, cycloalkyl, arylalkyl, and alkylaryl;
• R 16 is one or more saturated or unsaturated five or six membered hydrocarbon or heterocyclic ring system, optionally substituted with one or more alkyl, cycloalkyl, or halogen;
• R 17 is selected from the group consisting of alkyl, aryl, cycloalkyl, arylalkyl, and alkylaryl.
• polymerizable moiety refers to ethylenically unsaturated moieties known in the art which are capable of reaction with another compound (for example, by a free radical mechanism), such as but not limited to, acrylate and methacrylate moieties.
• Another exemplary polymerizable entity is a maleimide moiety as described above.
• oligomeric and polymeric moieties refer to a moiety including two or more monomer units (dimer, trimer, etc.), typically having a molecular weight of at least about 500, and higher.
• the benzophenone compound can be an oligomer or polymer having one or more benzophenone functionalities incorporated therein (along the backbone and/or side chain).
• Exemplary oligomeric and polymeric moieties include but are not limited to a C2-C20 alkylene or polyalkylene polyol, wherein hydroxy groups of the polyol moiety are optionally alkylated, and preferably an alkylene or polyalkylene polyol derived from ethylene glycol.
• Other suitable oligomer or polymer moieties include C2-C20 alkylene or polyalkylene moieties end capped with trihaloalkyl, and optionally substituted with one or more halogen atoms along the chain, preferably fluorine.
• Other exemplary oligomeric or polymer moieties include C2-C20 alkylene or polyalkylene moieties including carbonate groups and end capped with lower alkyl.
• Other exemplary oligomeric or polymeric moieties include polyether ketones and poly acrylate and polymethacrylate based compounds. Such oligomeric and polymeric benzophenones are known in the art and are commercially available.
• Exemplary benzophenone compounds useful in the invention include without limitation benzophenone, thioxanthone, isopropylthioxanthone, chlorothioxanthone, methyl o-benzoylbenzoate, 4-morpholinobenzophenone, 4,4'- diphenoxybenzophenone, l-methyl-2-(2-ethylhexyloxy)thioxanthone, 4,4'-di-(4- isopropylphenoxy)benzophenone, acrylic acid 4-benzoylphenyl ester, 4,4'- diphenylbenzophenone, 4-phenylbenzophenone, and the like, as well as mixtures thereof.
• benzophenone compounds are in known in the art and are commercially available or can be produced using commercially available starting materials.
• the benzophenone photoinitiator can be present in an amount ranging from about 0.001 to about 5 percent by weight, based on the total weight of the composition.
• the sensitizer package also includes at least one coinitiator or synergist, that is, a molecule which serves as a hydrogen atom donor or an electron donor.
• Coinitiators or synergists are known in the art, and are typically alcohols, tertiary amines or ethers which have available hydrogens attached to a carbon adjacent to a heteroatom.
• the hydrogen atom donor can be present as a separate compound or can be included as a molecular component of the photopolymerizable
• -21- compound for example, polyethylene glycol diacrylate.
• coinitiators when a separate component are typically present in an amount between about 0.1 and about 5 percent by weight based on the total weight of the composition.
• the hydrogen atom donor component can be up to about 85 weight percent, and higher, of the photopolymerizable compound.
• Suitable compounds include, but are not limited to, triethanolamine, methyl-diethanolamine, ethyldiethanolamine and esters of dimethylamino benzoic acid. Other known coinitiators or accelerators can also be used.
• the photopolymerizable compositions of the invention may also contain other conventional agents, such as polymerization inhibitors, fillers, ultraviolet absorbers, organic peroxides, dyes, pigments, and the like.
• the photopolymerizable compositions can be applied or deposited on a surface of a substrate using conventional techniques and apparatus.
• the composition can be applied as a substantially continuous film. Alternatively, the composition can be applied in a discontinuous pattern.
• the thickness of the deposited composition can vary, depending upon the desired thickness of the resultant cured product.
• the substrate is coated with the uncured photopolymerizable composition and passed under a commercially available UV or excimer lamp on a conveyer moving at predetermined speeds.
• the substrate to be coated can be, for example, metal, wood, mineral, glass, paper, plastic, fabric, ceramic, and the like.
• the active energy beams used in accordance with the present invention may be visible light or ultraviolet light or may contain in their spectra both visible and ultraviolet light.
• the polymerization may be activated by irradiating the composition with ultraviolet light using any of the techniques known in the art for providing ultraviolet radiation, i.e., in the range of 200 nm and 450 nm ultraviolet radiation, and especially with the 308 nm emission from xenon chloride exciter lamps, commercially available from Fusion Systems, or by irradiating the composition with radiation outside of the ultraviolet spectrum.
• the radiation may be natural or artificial, monochromatic or polychromatic, incoherent or coherent and should be sufficiently intense to activate the photoinitiators of the invention and thus the polymerization.
• Conventional radiation sources include fluorescent lamps, excimer lamps, mercury, metal additive and arc lamps.
• Coherent light sources include pulsed nitrogen, xenon,
• compositions are useful in any of the types of applications known in the art for photopolymerizations, including as a binder for solids to yield a cured product in the nature of a paint, varnish, enamel, lacquer, stain or ink.
• the compositions can also be useful in the production of photopolymerizable surface coatings in printing processes, such as lithographic printing, screen printing, and the like.
• the compositions can also be useful in applications in which the compositions are applied to articles which are to be exposed to the environment, such as signage.
• Radiation cured coatings produced using conventional photoinitiators typically degrade over time (as evidenced by yellowing, increasing brittleness, and the like), which degradation is exacerbated by direct exposure to sunlight.
• radiation cured coatings prepared using the maleimide compounds can exhibit minimal degradation over time, even when exposed to direct sunlight.
• the maleimides can also be water soluble.
• HEMI 25.65 g, 0.182 moles
• pyridine 14.38 g, 0.182 moles
• Triethylene glycol bischloroformate (25.0 g, 0.091 moles) was added dropwise and stirred for 90 minutes.
• the pyridine salt was filtered off and the solution was combined with 200 mL of a IN HC1 solution.
• the product was extracted with methylene chloride and washed with a IN HC1 solution followed by water and then dried over magnesium sulfate.
• the red solution was diluted to a volume of 150 mL and purified by column chromatography (2.5 cm x 21 cm) using silica gel as the packing and methylene chloride as the mobile phase yielding white crystals, m.p. 65°C (26.75 g, 60.76%).
• the maleamic acid is characterized by a broad peak due to the acid proton near 13-14 ppm, a peak due to the amide proton near 10 ppm, and two doublets due to the ene protons near 6.4 ppm in the proton spectra.
• the maleamic acid is also characterized by two peaks near 165 ppm due to the two carbonyls in the carbon spectrum.
• the maleimide is characterized by the absence of the acid and amide proton peaks, and the single ene proton peak shifted to near 7.6 ppm in the proton spectrum. In the carbon spectrum the maleimide shows a single carbonyl peak near 170 ppm.
• the melting point of N-(2-CF 3 -phenyl)maleimide is measured using
• N-(2-t-butylphenyl)maleimide is also prepared as described in Example 12, except substituting 2-trifluoromethyl aniline with 2-tert-butyl aniline.
• the melting point of N-(2-t-butylphenyl)maleimide is measured using DSC at a heating rate of 20°C/min and is found to be 99.64C (endotherm peak maxima). Heat of fusion is also calculated to be 94.02 J/g.
• FIG. 17 is a graph illustrating photo-DSC exotherm rate results for the photopolymerization of a typical UV curable monomer (HDDA is 1 ,6-hexanediol diacrylate) with photoinitiator packages of benzophenone (BZPN)/1% methyl diethanol amine (NMDEA) and N-methyl maleimide (MMI)/1% NMDEA.
• BZPN benzophenone
• NMDEA methyl diethanol amine
• MMI N-methyl maleimide
• Figure 3 gives photo-DSC exotherm results in nitrogen saturated systems that incorporate three components (benzophenone sensitizer, methyl maleimide, and NMDEA) as the photoinitiator package for the polymerization of HDDA.
• the exotherm rate maximum increased dramatically when both methyl maleimide and benzophenone are present as compared to the exotherm rates for
• Figures 4 and 5 indicate that N-alkyl maleimides of widely varying structures (methyl maleimide MMI, hexyl maleimide HMI, and cyclohexyl maleimide CHMI) as well as both ortho-substituted (i.e., twisted) (tert-butyl maleimide NtBMI) N-aryl maleimides and simple substituted or unsubstituted (i.e., planar) (phenyl maleimide N-PMI) N-aryl maleimides (heretofore found to be ineffective upon direct excitation), can be sensitized to have much greater initiation efficiencies than benzophenone/NMDEA systems.
• thioxanthones available from First Chemical Corporation
• IX isopropyl thioxanthone
• LTX having the formula
• formulations with various photoinitiators were prepared containing HDDA and NMDEA, with and without MMI. These formulations were then tested by photo-differential scanning calorimetry (photo-DSC), using a Xenon- doped mercury lamp at 25 °C using (1) a 313 nm band pass filter, (2) a 365 nm band pass filter, and (3) the full arc of the lamp at different intensities.
• photo-DSC photo-differential scanning calorimetry
• sensitized maleimide/ITX/amine initiating system a typical conventional alpha-cleavage type photoinitiator.
• a short set of experiments was performed using one of the sensitized maleimide containing formulations from above and an HDDA formulation which contained 2,2-dimethoxy-2-phenylacetophenone (known commercially as BDK and
• N-methylmaleimide is used at low concentrations in conjunction with benzophenone, ITX, LTX, and XPI-115.
• Enhanced conversions are also noted when MMI is used in conjunction with XPI-113 and XPI-133.
• N-aromatic maleimides including N-phenylmaleimide, N-(2- trifluoromethylphenyl)maleimide, N-(2-t-butyl phenyl) maleimide. and ⁇ -methyl-N-(2- trifluoromethyl phenyl)maleimide.
• sensitized maleimide-containing acrylic formulations were observed to have higher rates of cure and higher relative conversions in air than the same formulations without the maleimide in nitrogen.

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