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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
  • B29C64/10—Processes of additive manufacturing
  • B29C64/106—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
  • B29C64/124—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified
  • B29C64/129—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified characterised by the energy source therefor, e.g. by global irradiation combined with a mask
  • B29C64/135—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified characterised by the energy source therefor, e.g. by global irradiation combined with a mask the energy source being concentrated, e.g. scanning lasers or focused light sources
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
  • B29C64/10—Processes of additive manufacturing
  • B29C64/106—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
  • B29C64/124—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y10/00—Processes of additive manufacturing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y70/00—Materials specially adapted for additive manufacturing
• • 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
  • G03F7/0037—Production of three-dimensional images
• • 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
• • 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
  • G03F7/038—Macromolecular compounds which are rendered insoluble or differentially wettable
  • G03F7/0388—Macromolecular compounds which are rendered insoluble or differentially wettable with ethylenic or acetylenic bands in the side chains of the photopolymer
• • 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
  • G03F7/075—Silicon-containing compounds
  • G03F7/0757—Macromolecular compounds containing Si-O, Si-C or Si-N bonds
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/22—Secondary treatment of printed circuits
  • H05K3/28—Applying non-metallic protective coatings
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/22—Secondary treatment of printed circuits
  • H05K3/28—Applying non-metallic protective coatings
  • H05K3/285—Permanent coating compositions
  • H05K3/287—Photosensitive compositions
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
  • H05K2203/14—Related to the order of processing steps
  • H05K2203/1476—Same or similar kind of process performed in phases, e.g. coarse patterning followed by fine patterning
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/0011—Working of insulating substrates or insulating layers
  • H05K3/0017—Etching of the substrate by chemical or physical means
  • H05K3/0023—Etching of the substrate by chemical or physical means by exposure and development of a photosensitive insulating layer
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K3/00—Apparatus or processes for manufacturing printed circuits
  • H05K3/46—Manufacturing multilayer circuits
  • H05K3/4644—Manufacturing multilayer circuits by building the multilayer layer by layer, i.e. build-up multilayer circuits
  • H05K3/4673—Application methods or materials of intermediate insulating layers not specially adapted to any one of the previous methods of adding a circuit layer
  • H05K3/4676—Single layer compositions
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31855—Of addition polymer from unsaturated monomers
  • Y10T428/31909—Next to second addition polymer from unsaturated monomers

Definitions

• the invention relates to photocurable compositions, more particularly to photocurable compositions for stereolithography.
• U.S. Pat. No. 5,002,854 to Fan et al. discloses a photohardenable composition for stereolithography containing filler particles that are core shell polymers.
• the core is a crosslinked multifunctional ethylenically unsaturated monomer; the shell is based on a monofunctional ethylenically unsaturated monomer.
• the particles are non-reactive and do not chemically bond to the polymer matrix formed on curing the composition.
• U.S. Pat. No. 5,461,088 to Wolf et al. discloses a stereolithography formulation containing a polysiloxane block copolymer that is added to the formulation as an oil or crystals.
• the block copolymer is not a core-shell polymer and contains no reactive epoxy groups or ethylenically unsaturated groups.
• U.S. Pat. No. 5,463,084 to Crivello et al. discloses a photocurable composition containing silicone oxetane monomers that are liquid.
• U.S. Pat. No. 5,639,413 to Crivello discloses a photocurable composition containing a cyclohexylepoxy siloxane monomer that is liquid.
• 3-D objects made by stereolithography are generally clear or slightly hazy, and tend to have rough surfaces.
• Opaque white objects with smooth surfaces are desirable as similar to plastic objects made by non-stereolithography processes.
• Smooth sidewalls are especially useful when using an object prepared from stereolithography as a model to prepare a mold.
• the invention provides a photocurable composition, including (a) a cationically curable monomer; (b) a radically curable monomer; (c) reactive particles comprising a crosslinked polysiloxane core and a shell of reactive groups on an outer surface of the core, wherein the reactive groups comprise epoxy groups, ethylenically unsaturated groups, or hydroxy groups; (d) a radical photoinitiator; and (e) a cationic photoinitiator.
• the invention also provides a method of making a 3-D object from such a composition by forming a first layer of the photocurable composition; exposing the first layer to actinic radiation sufficient to harden the first layer; forming a second layer of the photocurable composition above the hardened first layer; exposing the second layer to actinic radiation sufficient to harden the second layer; and repeating the previous two steps as needed to form a 3-D object.
• Stepolithography is a process that produces solid objects from computer-aided design (“CAD”) data.
• CAD data of an object is first generated and then is sliced into thin cross sections.
• a computer controls a laser beam that traces the pattern of a slice through a liquid plastic, solidifying a thin layer of the plastic corresponding to the slice.
• the solidified layer is recoated with liquid plastic and the laser beam traces another slice to harden another layer of plastic on top of the previous one.
• the process continues layer by layer to complete the part.
• a desired part may be built in a matter of hours. This process is described in U.S. Pat. No. 5,476,748 to Steinmann et al., U.S. Patent Publication No. 2001/0046642 to Johnson et al., and by Jacobs in “Rapid Prototyping & Manufacturing” (Society of Manufacturing Engineers, 1992), the entire contents of which documents are incorporated herein by reference.
• 3-D object means a three-dimensional object made from at least two layers of a cured resin composition.
• Polymerization is a chemical reaction linking monomers to form larger molecules.
• the resulting polymers have units that correspond to the monomers.
• a “monomer” is a compound that is capable of polymerizing with other monomers to form a polymer chain or matrix.
• the term “monomer” refers to compounds with one or more reactive groups and includes oligomers that are, e.g., dimers or trimers formed from two or three monomer units, respectively.
• Crosslinked means a polymer that contains bonds between atoms of two or more different polymer chains. The result is a matrix that develops rigidity because the polymer chains are bonded together and can not flow freely.
• Crosslinked polymers generally result from polymerizing monomers that have more than one reactive site, i.e., the monomers are polyfunctional.
• “Curing” means to polymerize a mixture including one or more monomers and one or more initiators. “Hardening” may be synonymous with curing and emphasizes that when polymerized, liquid monomer mixtures tend to become solid.
• Photocurable composition means a composition that may be cured or hardened by a polymerization reaction that is initiated by actinic radiation.
• Actinic radiation is light energy at a wavelength that allows a given chemical compound to absorb the light energy and form a reactive species.
• a laser beam or a flood lamp generates the actinic radiation.
• “Cationically curable” means a monomer that can polymerize by cationic polymerization, a mechanism that involves cations, i.e., chemical species that are positively charged.
• Radically curable means a monomer that can polymerize by radical polymerization, a mechanism that involves radicals, i.e., chemical species with an unpaired valence electron.
• Photoinitiator is a compound that absorbs actinic radiation to form a reactive species that initiates a chemical reaction such as polymerization.
• a “cationic photoinitiator” is a photoinitiator that generates cations when exposed to actinic radiation and thereby initiates cationic polymerization.
• a “radical photoinitiator” is a photoinitiator that generates radicals when exposed to actinic radiation and thereby initiates radical polymerization.
• (Meth)acrylate refers to an acrylate, methacrylate, or a combination thereof.
• Hybrid composition means a photocurable composition with at least one radically curable component and at least one cationically curable component.
• the photocurable composition preferably contains from 15 to 80% by weight of cationically curable monomer, more preferably from 50 to 75% by weight.
• the cationically curable monomer may include one or more epoxide compounds in which the epoxide groups form part of an alicyclic or heterocyclic ring system.
• the alicyclic epoxide preferably includes at least one alicyclic polyepoxide having at least two epoxy groups per molecule.
• the alicyclic polyepoxide is in a relatively pure form in terms of oligomer (e.g., dimer, trimer, etc.) content.
• the alicyclic polyepoxide has a monomer purity of over about 90%, more preferably over about 94%, even more preferably 98% or higher. Ideally, dimers or trimers or higher oligomers are substantially eliminated.
• the alicyclic polyepoxide has an epoxy equivalent weight from 80 and 330, more preferably from 90 and 300, even more preferably from 100 and 280.
• Examples of alicyclic polyepoxides include bis(2,3-epoxycyclopentyl) ether, 2,3-epoxycyclopentyl glycidyl ether, 1,2-bis(2,3-epoxycyclopentyloxy)ethane, bis(4-hydroxycyclohexyl)methane diglycidyl ether, 2,2-bis(4-hydroxycyclohexyl)propane diglycidyl ether, 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate, di(3,4-epoxycyclohexylmethyl) hexanedioate, di(3,4-epoxy-6-methylcyclohexylmethyl) hexanedioate, ethylenebis(3,4-epoxycyclopenty
• the photocurable composition preferably contains from 5 to 80% by weight, more preferably from 10 and 75% by weight, even more preferably from 15 to 70% by weight of alicyclic polyepoxide.
• the component (a) may include a monomer with at least one epoxycyclohexyl group that is bonded directly or indirectly to a group containing at least one silicon atom. These monomers may be linear, branched, or cyclic in structure. Examples are disclosed in U.S. Pat. No. 5,639,413, which is incorporated herein by reference.
• the photocurable composition preferably includes one or more cationically curable compounds that are polyglycidyl ethers, poly( ⁇ -methylglycidyl) ethers, polyglycidyl esters, poly( ⁇ -methylglycidyl) esters, poly(N-glycidyl) compounds, and poly(S-glycidyl) compounds.
• Cationically curable oxetanes are disclosed in U.S. Pat. No. 5,463,084, incorporated herein by reference.
• Polyglycidyl ethers can be obtained by reacting a compound having at least two free alcoholic hydroxyl groups and/or phenolic hydroxyl groups with a suitably substituted epichlorohydrin under alkaline conditions or in the presence of an acidic catalyst followed by alkali treatment.
• Ethers of this type may be derived, for example, from acyclic alcohols, such as ethylene glycol, diethylene glycol and higher poly(oxyethylene) glycols, propane-1,2-diol, or poly(oxypropylene) glycols, propane-1,3-diol, butane-1,4-diol, poly(oxytetramethylene) glycols, pentane-1,5-diol, hexane-1,6-diol, hexane-2,4,6-triol, glycerol, 1,1,1-trimethylolpropane, bistrimethylolpropane, pentaerythritol, sorbitol, and from polyepichlorohydrins.
• acyclic alcohols such as ethylene glycol, diethylene glycol and higher poly(oxyethylene) glycols, propane-1,2-diol, or poly(oxypropylene) glycols, propane-1,3-dio
• Suitable glycidyl ethers can also be obtained from cycloaliphatic alcohols such as 1,3- or 1,4-dihydroxycyclohexane, bis(4-hydroxycyclohexyl)methane, 2,2-bis(4-hydroxycyclohexyl)propane or 1,1-bis(hydroxymethyl)cyclohex-3-ene, or aromatic alcohols such as N,N-bis(2-hydroxyethyl)aniline or p,p′-bis(2-hydroxyethylamino)diphenylmethane.
• cycloaliphatic alcohols such as 1,3- or 1,4-dihydroxycyclohexane, bis(4-hydroxycyclohexyl)methane, 2,2-bis(4-hydroxycyclohexyl)propane or 1,1-bis(hydroxymethyl)cyclohex-3-ene
• aromatic alcohols such as N,N-bis(2-hydroxyethyl)aniline or p,p′-bis(2-hydroxye
• Examples of preferred polyglycidyl ethers include trimethylolpropane triglycidyl ether, triglycidyl ether of polypropoxylated glycerol, and diglycidyl ether of 1,4-cyclohexanedimethanol.
• Uvacure 1500, Uvacure 1501, Uvacure 1502 (1501 and 1502 have been discontinued by UCB), Uvacure 1530, Uvacure 1531, Uvacure 1532, Uvacure 1533, Uvacure 1534, Uvacure 1561, Uvacure 1562, all commercial products of UCB Radcure Corp., Smyrna, Ga.; UVR-6100, UVR-6105, UVR-6110, UVR-6128, UVR-6200, UVR-6216 of DOW Corp.; the Araldite GY series that is Bisphenol A epoxy liquid resins, the Araldite CT and GT series that is Bisphenol A epoxy solid resins, the Araldite GY and PY series that is Bisphenol F epoxy liquids, the cycloaliphatic epoxides Araldite CY 179 and PY 284, the Araldite DY and RD reactive diluents series, the Araldite ECN series of epoxy
• the cationically curable monomer may include compounds containing vinyl ether groups.
• Preferred examples are aliphatic polyalkoxy di(poly)vinylethers, polyalkylene di(poly)vinylethers, and hydroxy-functionalized mono(poly)vinylethers. More preferred vinylethers are those having aromatic or alicyclic moieties in their molecules.
• the vinylether component is from 0.5 to 20% by weight of the photocurable composition. More preferably the vinylether component is from 2 to 17% by weight. Even more preferably, the vinyl ether component is from 3 to 14% by weight.
• vinyl ethers include ethyl vinylether, n-propyl vinylether, isopropyl vinylether, n-butyl vinylether, isobutyl vinylether, octadecyl vinylether, cyclohexyl vinylether, butanediol divinylether, cyclohexanedimethanol divinylether, diethyleneglycol divinylether, triethyleneglycol divinylether, tert-butyl vinylether, tert-amyl vinylether, ethylhexyl vinylether, dodecyl vinylether, ethyleneglycol divinylether, ethyleneglycolbutyl vinylether, hexanediol divinylether, triethyleneglycol methylvinylether, tetraethyleneglycol divinylether, trimethylolpropane trivinylether, aminopropyl vinylether, diethylaminoethyl vinylether,
• Examples of commercial vinyl ethers include the Pluriol-E200 divinyl ether (PEG200-DVE), poly-THF290 divinylether (PTHF290-DVE) and polyethyleneglycol-520 methyl vinylether (MPEG500-VE) all of BASF Corp.
• PEG200-DVE Pluriol-E200 divinyl ether
• PTHF290-DVE poly-THF290 divinylether
• MPEG500-VE polyethyleneglycol-520 methyl vinylether
• hydroxy-functionalized mono(poly)vinylethers include polyalkyleneglycol monovinylethers, polyalkylene alcohol-terminated polyvinylethers, butanediol monovinylether, cyclohexanedimethanol monovinylether, ethyleneglycol monovinylether, hexanediol monovinylether, and diethyleneglycol monovinylether.
• Examples of commercial vinyl ethers include Vectomer 4010 (HBVE isophthalate), Vectomer 4020 (pentanedioic acid, bis[[4[(ethenyloxy)methyl]cyclohexyl]methyl] ester), Vectomer 4051 (CHMVE terephthalate), Vectomer 4060 (vinyl ether terminated aliphatic ester monomer: HBVE adipate), and Vectomer 5015 (tris(4-vinyloxybutyl)trimellitate), all of Morflex, Inc., Greensboro, N.C. Preferred vinyl ethers are Vectomer 4010 and Vectomer 5015.
• the photocurable composition of the invention may include mixtures of the cationically curable compounds described above.
• the radically curable monomer (b) of the invention is preferably ethylenically unsaturated. More preferably, the monomer is a (meth)acrylate.
• the monomer may include at least one poly(meth)acrylate, e.g., a di-, tri-, tetra- or pentafunctional monomeric or oligomeric aliphatic, cycloaliphatic, or aromatic (meth)acrylate.
• the poly(meth)acrylate preferably has a molecular weight of from 200 to 500.
• di(meth)acrylates include di(meth)acrylates of cycloaliphatic or aromatic diols such as 1,4-dihydroxymethylcyclohexane, 2,2-bis(4-hydroxy-cyclohexyl)propane, bis(4-hydroxycyclohexyl)methane, hydroquinone, 4,4′-dihydroxybiphenyl, Bisphenol A, Bisphenol F, bisphenol S, ethoxylated or propoxylated Bisphenol A, ethoxylated or propoxylated Bisphenol F, and ethoxylated or propoxylated bisphenol S.
• Di(meth)acrylates of this kind are known and some are commercially available, e.g., Ebecryl 3700 (UCB Chemicals).
• the di(meth)acrylate may be acyclic aliphatic, rather than cycloaliphatic or aromatic.
• the poly(meth)acrylate includes a tri(meth)acrylate or higher.
• Preferred compositions are those in which the free radically curable component contains a tri(meth)acrylate or a penta(meth)acrylate. Examples are the tri(meth)acrylates of hexane-2,4,6-triol, glycerol, 1,1,1-trimethylolpropane, ethoxylated or propoxylated glycerol, and ethoxylated or propoxylated 1,1,1trimethylolpropane.
• hydroxyl-containing tri(meth)acrylates obtained by reacting triepoxide compounds (e.g., the triglycidyl ethers of the triols listed above) with (meth)acrylic acid.
• triepoxide compounds e.g., the triglycidyl ethers of the triols listed above
• Other examples are pentaerythritol tetraacrylate, bistrimethylolpropane tetraacrylate, pentaerythritol monohydroxytri(meth)acrylate, or dipentaerythritol monohydroxypenta(meth)acrylate.
• the poly(meth)acrylate may include polyfunctional urethane (meth)acrylates.
• Urethane (meth)acrylates can be prepared by, e.g., reacting a hydroxyl-terminated polyurethane with acrylic acid or methacrylic acid, or by reacting an isocyanate-terminated prepolymer with hydroxyalkyl (meth)acrylates to give the urethane (meth)acrylate.
• Suitable aromatic tri(meth)acrylates are the reaction products of triglycidyl ethers of trihydric phenols and phenol or cresol novolaks containing three hydroxyl groups, with (meth)acrylic acid.
• SR® 368 is an example of an isocyanurate triacrylate, which is preferably included in the photocurable composition with a smaller amount of a monohydroxypentaacrylate such as SR® 399 to avoid producing tacky sidewalls in the 3-D object.
• acrylates include KAYARAD R-526, HDDA, NPGDA, TPGDA, MANDA, R-551, R-712, R-604, R-684, PET-30, GPO-303, TMPTA, THE-330, DPHA-2H, DPHA-2C, DPHA-21, D-310, D-330, DPCA-20, DPCA-30, DPCA-60, DPCA-120, DN-0075, DN-2475, T-1420, T-2020, T-2040, TPA-320, TPA-330, RP-1040, R-01 1, R-300, R-205 (Nippon Kayaku Co., Ltd.), Aronix M-210, M-220, M-233, M-240, M-215, M-305, M-309, M-310, M-315, M-325, M-400, M-6200, M-6400 (Toagosei Chemical Industry Co, Ltd.), Light acrylate BP-4EA, BP-4PA
• the radically curable monomer includes a compound having at least one terminal and/or at least one pendant (i.e., internal) unsaturated group and at least one terminal and/or at least one pendant hydroxyl group.
• the composition may contain more than one such compound.
• examples of such compounds include hydroxy mono(meth)acrylates, hydroxy poly(meth)acrylates, hydroxy monovinylethers, and hydroxy polyvinylethers.
• Commercially available examples include dipentyaerythritol pentaacrylate (SR® 399), pentaerythritol triacrylate (SR® 444), and bisphenol A diglycidyl ether diacrylate (Ebecryl 3700).
• the photocurable composition preferably contains up to 60%, more preferably from 5 to 20%, even more preferably from 9 to 15% of radically curable monomer(s).
• the photocurable composition contains up to 40% by weight, more preferably from 5 to 20% by weight, of a cycloaliphatic or aromatic di(meth)acrylate and up to 15% by weight, preferably up to 10% by weight of a poly(meth)acrylate with 3 or more (meth)acrylate groups.
• the ratio of diacrylate to poly(meth)acrylate with 3 or more (meth)acrylate groups may vary, but preferably the latter is no more than 50% of total (meth)acrylates.
• the photocurable composition may contain much smaller relative amounts of di(meth)acrylate, and may even contain exclusively poly(meth)acrylates with 3 or more (meth)acrylate groups as radically curable monomer (b) with no or substantially no di(meth)acrylate.
• the photocurable composition of the invention may include mixtures of the radically curable compounds described above.
• the reactive particles have a core containing a crosslinked polysiloxane and a shell containing reactive groups.
• the reactive particles may be made by the method disclosed in U.S. Pat. No. 4,853,434 to Block, incorporated in its entirety herein by reference.
• Block discloses reactive particles that are useful in producing fiber-reinforced plastics, structural adhesives, laminated plastics, and annealing lacquers.
• the core is a crosslinked polyorganosiloxane rubber that may include dialkylsiloxane repeating units, where “alkyl” is C1-C6 alkyl.
• the core preferably includes dimethylsiloxane repeating units.
• the reactive groups preferably include epoxy groups, ethylenically unsaturated groups, and/or hydroxy groups.
• the reactive groups may include oxirane, glycidyl, vinyl ester, vinyl ether, or acrylate groups, or combinations thereof.
• the reactive particles react with the polymer matrix that forms when the photocurable composition is polymerized by forming one or more chemical bonds to the polymer matrix via the reactive groups.
• the reactive groups react substantially completely on curing the photocurable composition.
• the amount of reactive particles in the photocurable composition may be varied as needed depending on the particular components (a) and (b) in a given photocurable composition. At high concentrations of reactive particles the photocurable composition may become too viscous and bubble formation may be a problem.
• the photocurable composition contains from 1 to 50% by weight of the reactive particles, more preferably from 5 to 15% by weight.
• the reactive particles preferably have an average particle diameter of 0.01 to 50 ⁇ m, more preferably 0.1 to 5 ⁇ m.
• Preferred reactive particles that are available commercially are Albidur EP 2240, Albidur VE 3320, and Albidur EP 5340 (Hanse Chemie, Germany).
• the reactive particles are added to the photocurable composition as a mixture of the reactive particles and a reactive liquid medium containing, e.g., epoxy or ethylenically unsaturated groups.
• the reactive organosiloxane particles are dispersed in bisphenol A glycidyl ether, in bisphenol A vinyl ester for Albidur VE 3320, and in cycloaliphatic epoxide for Albidur EP 5340.
• Radical photoinitiator (d) may be chosen from those commonly used to initiate radical photopolymerization.
• radical photoinitiators include benzoins, e.g., benzoin, benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin phenyl ether, and benzoin acetate; acetophenones, e.g., acetophenone, 2,2-dimethoxyacetophenone, and 1,1dichloroacetophenone; benzil ketals, e.g., benzil dimethylketal and benzil diethyl ketal; anthraquinones, e.g., 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 1-chloroanthraquinone and 2-amylanthraquinone
• the photocurable composition includes a 1-hydroxy phenyl ketone, more preferably 1-hydroxycyclohexyl phenyl ketone, e.g., Irgacure 184 (Ciba Specialty Chemicals).
• a 1-hydroxy phenyl ketone more preferably 1-hydroxycyclohexyl phenyl ketone, e.g., Irgacure 184 (Ciba Specialty Chemicals).
• the radical photoinitator is preferably present at from 0.1 to 10% by weight, more preferably from 0.3 to 8% by weight, most preferably from 0.4 to 7% by weight of the photocurable composition.
• Cationic photoinitiators may be chosen from those commonly used to initiate cationic photopolymerization. Examples include onium salts with anions of weak nucleophilicity, e.g., halonium salts, iodosyl salts, sulfonium salts, sulfoxonium salts, or diazonium salts. Metallocene salts are also suitable as photoinitiators. Onium salt and metallocene salt photoinitiators are described in U.S. Pat. No. 3,708,296; “UV-Curing, Science and Technology”, (Editor: S. P.
• Examples of commercial cationic photoinitiators include UVI-6974, UVI-6976, UVI-6970, UVI-6960, UVI-6990 (manufactured by DOW Corp.), CD-1010, CD-1011, CD-1012 (manufactured by Sartomer Corp.), Adekaoptomer SP-150, SP-151, SP-170, SP-171 (manufactured by Asahi Denka Kogyo Co., Ltd.), Irgacure 261 (Ciba Specialty Chemicals Corp.), CI-2481, CI-2624, CI-2639, CI-2064 (Nippon Soda Co, Ltd.), DTS-102, DTS-103, NAT-103, NDS-103, TPS-103, MDS-103, MPI-103, BBI-103 (Midori Chemical Co, Ltd.).
• the cationic photoinitiators can be used either individually or in combination of two or more.
• the cationic photoinitator is preferably present at from 0.05 to 12% by weight, more preferably from 0.1 to 11% by weight, most preferably from 0.15 to 10% by weight of the photocurable composition.
• the radical and cationic photoinitiators are preferably selected and their concentrations are preferably adjusted to achieve an absorption capacity such that the depth of cure at the normal laser rate is from about 0.1 to about 2.5 mm.
• the photocurable composition may contain a variety of other components.
• examples of such components include modifiers, tougheners, stabilizers, antifoaming agents, leveling agents, thickening agents, flame retardants, antioxidants, pigments, dyes, fillers, and combinations thereof.
• the photocurable composition may contain one or more polytetramethylene ether glycols (“poly THF”).
• the poly THF preferably has molecular weight from about 250 to 2500.
• the poly THF may be terminated with hydroxy, epoxy, or ethylenically unsaturated group(s).
• Polytetramethylene ether glycols are commercially available in the Polymeg® line (Penn Specialty Chemicals).
• the photocurable composition includes Polymeg® 1000 or Polymeg® 2000.
• the photocurable composition may also contain one or more diols such as 1,4-cyclohexanedimethanol (“CHDM”).
• CHDM 1,4-cyclohexanedimethanol
• the photocurable composition may also contain one or more stabilizers.
• Preferred stabilizers are hindered amines, e.g., benzyl dimethyl amine (“BDMA”).
• the actinic radiation is generally a beam of light that is controlled by a computer.
• the beam is a laser beam controlled by a mirror.
• any stereolithography machine may be used to carry out the inventive method.
• Stereolithography equipment is commercially available from various manufacturers. Table I lists commercial SL equipment available from 3D Systems, Inc. (Valencia, Calif.). TABLE I Stereolithography Machines Machine Wavelength (nm) SLA 250 325 SLA 2500 (Viper) 355 SLA 3500 355 SLA 500 351 SLA 5000 355 SLA 7000 355
• Green model is the 3-D object initially formed by the stereolithography process of layering and curing, where typically the layers are not completely cured. This permits successive layers to better adhere by bonding together when further cured.
• Postcuring is the process of reacting a green model to further cure the partially cured layers.
• a green model may be postcured by exposure to heat, actinic radiation, or both.
• Green strength is a general term for mechanical performance properties of a green model, including modulus, strain, strength, hardness, and layer-to-layer adhesion. For example, green strength may be reported by measuring flexural modulus (ASTM D 790). An object having low green strength may deform under its own weight, or may sag or collapse during curing.
• D p Pulsion depth
• Working curve of cure depth (mm) against the log of exposure (mJ/cm 2 ).
• Cur depth is the measured thickness of a layer formed by exposing the photocurable composition to a specified dose of energy from the laser.
• E c Crohn's Exposure
• Dispersed means a separate phase, e.g., of particles distributed by mixing in a photocurable composition.
• the general procedure used for preparing 3-D objects with SL equipment is as follows.
• the photocurable composition was placed in a 300-700 ml plastic container or in a vat designed for use with the stereolithography machines. The specific container depends on the size of the desired 3-D object.
• the photocurable composition was poured into the container within the machine at about 30° C.
• the surface of the composition, in its entirety or a predetermined pattern, was irradiated with a UV/VIS light source so that a layer of a desired thickness cured and solidified in the irradiated area.
• a new layer of the photocurable composition was formed on the solidified layer.
• the new layer was likewise irradiated over the entire surface or in a predetermined pattern.
• the newly solidified layer adhered to the underlying solidified layer. Repeating the layer formation step and the irradiation step produced a green model of multiple solidified layers.
• the green model was then rinsed in tripropylene glycol monomethyl ether (“TPM”).
• TPM tripropylene glycol monomethyl ether
• PCA postcure apparatus
• Stereolithography equipment typically allows for setting various operational parameters. Examples thereof appear in Tables II and III below. The parameters are well known to a person of skill in the art of stereolithography and may be adjusted as needed depending on various factors, including the specific photocurable composition and the geometry of the desired 3-D object.
• Layer Thickness is the thickness of each slice or layer of the 3-dimensional object that is to be built.
• “Hatch Overcure” is the depth beyond the layer thickness which is exposed during a given pass (hatch) of the laser.
• Fill Cure Depth is the absolute depth of curing for the fill vectors on a given pass of fill. Fills are tightly spaced vectors drawn on the regions of the part that form upfacing or downfacing surfaces.
• Preferred Blade Gap is a distance, given in percent of layer thickness, describing the preferred distance between the bottom of the recoater and last layer of the part at time of sweeping. TABLE II Parameter Value Layer thickness 0.004 inch Hatch Overcure 0.000 inch Hatch Spacing 0.004 inch Fill Cure Depth 0.010 inch Fill Spacing 0.004 inch Border Overcure 0.009 inch Preferred Blade Gap 0.004 inch D p 0.0063 inch E c 9.2 mJ/cm 2
• the following components were mixed at room temperature in a container to form a homogeneous photocurable composition.
• the composition was an opaque liquid with a viscosity of 195 CPS at 30° C. (Brookfield, RVT).
• a 3D Systems Viper Si2 (SLA 2500) machine was used to prepare 10 objects using the formulation of Example 1.
• the machine settings used are those in Table II.
• the objects were opaque white or off-white and had a glossy surface.
• An SLA 5000 machine was used to prepare 24 objects using the formulation of Example 1.
• the machine settings used are those in Table III.
• the objects were opaque white or off-white and had a glossy surface.

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