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
  • G03F7/26—Processing photosensitive materials; Apparatus therefor
  • G03F7/38—Treatment before imagewise removal, e.g. prebaking
• • 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
• • 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
  • C08F16/00—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 an alcohol, ether, aldehydo, ketonic, acetal or ketal radical
  • C08F16/12—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 an alcohol, ether, aldehydo, ketonic, acetal or ketal radical by an ether radical
• • 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
  • C08F283/00—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G
  • C08F283/10—Macromolecular compounds obtained by polymerising monomers on to polymers provided for in subclass C08G on to polymers containing more than one epoxy radical per molecule
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/68—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the catalysts used
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G65/00—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule
  • C08G65/02—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring
  • C08G65/04—Macromolecular compounds obtained by reactions forming an ether link in the main chain of the macromolecule from cyclic ethers by opening of the heterocyclic ring from cyclic ethers only
  • C08G65/06—Cyclic ethers having no atoms other than carbon and hydrogen outside the ring
  • C08G65/16—Cyclic ethers having four or more ring atoms
  • C08G65/18—Oxetanes
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L29/00—Compositions of homopolymers or 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 an alcohol, ether, aldehydo, ketonic, acetal or ketal radical; Compositions of hydrolysed polymers of esters of unsaturated alcohols with saturated carboxylic acids; Compositions of derivatives of such polymers
  • C08L29/10—Homopolymers or copolymers of unsaturated ethers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L63/00—Compositions of epoxy resins; Compositions of derivatives of epoxy resins
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L71/00—Compositions of polyethers obtained by reactions forming an ether link in the main chain; Compositions of derivatives of such polymers
  • C08L71/02—Polyalkylene oxides
• • 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
  • G03F7/0045—Photosensitive materials with organic non-macromolecular light-sensitive compounds not otherwise provided for, e.g. dissolution inhibitors
• • 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
• • 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
  • G03F7/038—Macromolecular compounds which are rendered insoluble or differentially wettable

Definitions

• the present invention relates to liquid compositions for additive fabrication processes that are hybrid-curable in the UV or visible spectra.
• Additive fabrication processes for producing three dimensional objects are well known. Additive fabrication processes utilize computer-aided design (CAD) data of an object to build three- dimensional parts. These three-dimensional parts may be formed from liquid resins, powders, or other materials.
• CAD computer-aided design
• Stereolithography is a process for rapidly producing models, prototypes, patterns, and production parts in certain applications.
• SL uses CAD data of an object wherein the data is transformed into thin cross-sections of a three-dimensional object.
• the data is loaded into a computer which controls a laser that traces a pattern of a cross section through a liquid radiation curable resin composition contained in a vat, solidifying a thin layer of the resin corresponding to the cross section.
• the solidified layer is recoated with resin and the laser traces another cross section to harden another layer of resin on top of the previous layer.
• the process is repeated layer by layer until the three-dimensional object is completed.
• the three- dimensional object When initially formed, the three- dimensional object is, in general, not fully cured, and is called a "green model.” Although not required, the green model may be subjected to post-curing to enhance the mechanical properties of the finished part.
• An example of an SL process is described in, for example, U.S. Patent No.
• Lasers have traditionally served as the radiation source of choice in additive fabrication processes such as stereolithography.
• the use of gas lasers to cure liquid radiation curable resin compositions is well known.
• the delivery of laser energy in a stereolithography system can be Continuous Wave (CW) or Q-switched pulses.
• CW lasers provide continuous laser energy and can be used in a high speed scanning process.
• Historically, several types of lasers have been used in stereolithography, with peak spectral outputs ranging traditionally from 193 nm to 355 nm in wavelength, although other wavelength variants exist.
• the light emitted from lasers is
• Laser-based systems particularly those operating at a peak spectral output of at or near 355nm, are not without their drawbacks, however.
• the significant power output of such laser-based systems sometimes generates excessive heat at the point of irradiation which may be detrimental to the resin.
• the use of a laser at any wavelength requires scanning point-by-point on the resin surface, a process which can be particularly time-consuming when the cross-sectional pattern to be cured is large or complex.
• 355nm laser-based systems are expensive and are associated with high maintenance costs and energy consumption.
• DLP Digital Light Processing
• image projection systems are said to be cross-section independent, meaning the exposure time of a given layer does not change with increasing shape complexity of any given layer. This makes them particularly well-suited for parts created via additive fabrication with complex and detailed geometries.
• DLP and LCD are not alternative methods of producing light itself; rather they provide a way of processing the light emanating from existing light sources into a more desirable pattern. Thus, coupled input light sources are also still needed.
• the light input to an image projection system may be from any source, including traditional lamps or even lasers, more commonly the input light is collimated from one or more light emitting diodes (LEDs).
• LEDs light emitting diodes
• LEDs are semiconductor devices which utilize the phenomenon of electroluminescence to generate light. At present, LED light sources for additive fabrication systems currently emit light
• LEDs provide the advantage that they theoretically operate at close to peak efficiency for a longer duration than other light sources. Furthermore, they are typically more energy efficient and inexpensive to maintain, resulting in a lower initial and ongoing cost of ownership than versus laser-based optics systems.
• LED/DLP or (5) LED/LCD.
• Systems not utilizing DLP technology may also incorporate other collimating or focusing lenses/mirrors to selectively direct the light onto the liquid resin.
• UV/vis Such longer wavelengths (i.e. from 375nm to 500nm) are heretofore referred to as "UV/vis”.
• the irradiance at the resin surface imparted by the UV/vis optics on existing 365 nm or 405 nm DLP-based commercial additive fabrication systems can be as low as 0.1 W/cm or even 0.0002 W/cm 2 for some more economical desktop units.
• These relatively reduced radiation energies / intensities make it more difficult for photopolymerization reactions to occur in the radiation-curable resins via such UV/vis optics unless exposure times become prohibitively long. This in turn increases part build times significantly, such that the theoretical speed advantage of photomasking display systems is negated.
• fewer photoinitiating systems - in particular cationic photoinitiating systems - exist on the market for promoting photopolymerization at such longer UV/vis wavelengths.
• Radically-polymerizable resins are known to exist for systems employing UV/vis optics. Such resins generally consist of one or more (meth)acrylate compounds (or other free-radical polymerizable organic compounds) along with a free-radical photoinitiator for radical generation. U.S. Pat. No. 5,418,112 describes one such radical-curable system. Although radically- polymerizable resins will readily cure under even the relatively lower energy and lower intensity afforded by UV/vis optics, they are not suitable for all additive fabrication applications. First, (meth)acrylate based resins considered suitable for additive fabrication processes have traditionally produced cured parts with insufficient mechanical properties to be incorporated into many end-use applications.
• hybrid curable resin Another well-known type of resin suitable for use in additive fabrication systems is a "hybrid" curable resin, or one that comprises: (1) epoxies, oxetanes, or other types of cationically polymerizable compounds; (2) one or more cationic photoinitiators; (3) acrylate resins or other types of free radical polymerizable compounds; and (4) one or more free radical photoinitiators.
• hybrid curable systems are described in, for example, U.S. Pat. No. 5,434,196.
• Such resins have long-been known to result in cured parts produced via additive fabrication processes with superior mechanical properties relative to all-acrylate based resins.
• hybrid curable systems are superior to all-acrylate systems in that they suffer less from the differential shrinkage problems that have long-plagued all-acrylate systems.
• the first aspect of the invention is a liquid radiation UV/vis curable composition for additive fabrication comprising a cationically curable constituent which further contains a cycloaliphatic epoxy component that undergoes cationic polymerization; at least one free-radically curable constituent that undergoes free-radical polymerization; a cationic photoinitiator; and a free- radical photoinitiator; wherein after the liquid radiation UV/vis curable composition is exposed to UV/vis optics emitting radiation with a peak spectral output at 400nm and an irradiance at a surface of the liquid radiation UV/vis curable composition of at least 2mW/cm 2 for at least 10 seconds, the cycloaliphatic epoxy component achieves a T95 value of at less than or equal to about 70 seconds; and a plateau conversion of at least about 20%.
• a first aspect of the invention is a liquid UV/vis radiation curable composition for additive fabrication comprising a cationically curable constituent which undergoes a cationic polymerization, the cationically curable constituent further comprising a cycloaliphatic epoxy component and an oxetane component; a free-radically curable constituent that undergoes a free- radical polymerization; and a photoinitiating package further comprising a cationic photoinitiator; a vinyl ether diluent monomer; and a free-radical photoinitiator; wherein when the liquid UV/vis radiation curable composition is exposed to UV/vis optics emitting radiation with a peak spectral output at 400nm and an irradiance at a surface of the liquid UV/vis radiation curable composition of 2mW/cm 2 for 10 seconds, the cycloaliphatic epoxy component achieves the following: (i) a T95 value of at less than or equal to about 70 seconds, more preferably less
• the second aspect of the invention is a liquid radiation curable composition for additive fabrication comprising: (a) a cationically polymerizable component; (b) an iodonium salt cationic photoinitiator; (c) a photosensitizer for photosensitizing component (b); (d) a reductant for reducing component (b); (e) a free-radically polymerizable component; and optionally, (f) a free-radical photoinitiator; wherein the composition is curable by UV/vis optics imparting a dose of 20mJ/cm 2 and emitting radiation at a peak spectral intensity from about 375nm to about 500nm, more
• a second aspect of the invention is a liquid radiation curable composition for additive fabrication comprising: a cationically polymerizable component; an iodonium salt cationic photoinitiator; a photosensitizer for photosensitizing the iodonium salt cationic photoinitiator; a first reductant for reducing the iodonium salt cationic photoinitiator; a free-radically polymerizable component; optionally, a free-radical photoinitiator; and a second reductant for reducing the iodonium salt cationic photoinitiator possessing an electron-donating substituent attached to a vinyl group; wherein the composition is curable by UV/vis optics imparting a dose of 20mJ/cm 2 and emitting radiation at a peak spectral intensity from about 375nm to about 500nm, more preferably from about 380nm to about 450nm, more preferably from about 390 nm to about 425 nm, more
• a third aspect of the invention is a a liquid radiation curable composition for additive fabrication comprising from about 30 wt.% to about 80 wt.% of at least one cationically
• polymerizable component further comprising a cycloaliphatic epoxide and an oxetane; from about 1 wt.%) to about 8 wt.%) of a sulfonium salt cationic photoinitiator that possesses an absorbance of less than 0.01 at 400nm; from about 0.5 wt.% to about 3 wt.% of a compound according to the following formula (V) :
• R contains an aliphatic chain from C 1 -C 2 0; a free-radically polymerizable component; and a diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide free-radical photoinitiator; wherein the composition is curable by UV/vis optics imparting a dose of 20mJ/cm 2 and emitting radiation at a peak spectral intensity from about 375nm to about 500nm, more preferably from about 380nm to about 450nm, more preferably from about 390 nm to about 425 nm.
• a fourth aspect of the invention is a method of forming a three-dimensional article via an additive fabrication system utilizing UV/vis optics, the method comprising: (1) providing the liquid radiation curable composition for additive fabrication of any of the first, second, or third aspect of the invention; (2) establishing a first liquid layer of the liquid radiation curable resin; (3) exposing the first liquid layer imagewise to actinic radiation via a UV/vis optics configuration to form an imaged cross-section, thereby forming a first cured layer; (4) forming a new layer of liquid radiation curable resin in contact with the first cured layer; (5) exposing said new layer imagewise to actinic radiation to form an additional imaged cross-section; and (6) repeating steps (4) and (5) a sufficient number of times in order to build up a three-dimensional article; wherein the UV/vis optics emit radiation at a peak spectral intensity from about 375nm to about 500nm, more preferably from about 380nm to about 450nm, more preferably from about 3
• a fifth aspect of the invention is the three-dimensional part formed by the process according to the fourth aspect of the invention using the liquid radiation curable composition of any of the first, second, or third aspects of the invention.
• Figure 1 is a plot depicting the RT-FTIR (under a 365nm cure condition) of
• Figure 2 is a plot depicting the RT-FTIR (under a 365nm cure condition) of oxetane conversion of Plastcure ABS 3650.
• Figure 3 is a plot depicting the RT-FTIR (under a 400 nm cure condition) of cycloaliphatic epoxide conversion of a liquid hybrid radiation curable composition for additive fabrication employing a photoinitiating package that uses a photoinitiator claimed to be useful for 400 nm wavelengths.
• Figure 4 is a plot depicting the RT-FTIR (under a 400 nm cure condition) of oxetane conversion of a liquid hybrid radiation curable composition for additive fabrication employing a photoinitiating package that uses a photoinitiator claimed to be useful for 400 nm wavelengths.
• Figure 5 is a plot depicting the RT-FTIR (under a 365nm cure condition) of
• Figure 6 is a plot depicting the RT-FTIR (under a 365nm cure condition) of oxetane conversion of a liquid hybrid radiation curable composition for additive fabrication employing a photoinitiating package that has is designed to be suitable for additive fabrication machines operating with a peak spectral intensity at 365nm.
• Figures 7, 9, 11, and 13 are plots depicting the RT-FTIR (under a 400nm cure condition) of cycloaliphatic epoxide conversion of a liquid hybrid radiation curable composition for additive fabrication according to the present invention.
• Figures 8, 10, 12, and 14 are plots depicting the RT-FTIR (under a 400nm cure condition) of oxetane conversion of a liquid hybrid radiation curable composition for additive fabrication according to the present invention.
• UV/vis is defined as the region of the electromagnetic spectrum from 375 nanometers (nm) to 500 nanometers (nm).
• UV/vis optics is defined as any electrical, mechanical, or electro-mechanical system which generates and directs/displays actinic radiation that operates at a peak spectral intensity of between 375nm to 500nm.
• Specific non-limiting examples of UV/vis optics include lasers, LEDs, one or more LEDs coupled to a DLP display system, one or more LEDs which are coupled to a LCD display system, lasers coupled to a DLP display system, and lasers coupled to a LCD display system.
• a first embodiment of the invention is a liquid UV/vis radiation curable composition for additive fabrication comprising:
• a cationically curable constituent which undergoes a cationic polymerization, the cationically curable constituent further comprising a cycloaliphatic epoxy component and an oxetane component;
• a photoinitiating package further comprising
• liquid UV/vis radiation curable composition wherein when the liquid UV/vis radiation curable composition is exposed to UV/vis optics emitting radiation with a peak spectral output at 400nm and an irradiance at a surface of the liquid UV/vis radiation curable composition of 2mW/cm 2 for 10 seconds,
• the cycloaliphatic epoxy component achieves the following:
• T95 value of at less than or equal to about 70 seconds, more preferably less than or equal to about 55 seconds, more preferably less than or equal to about 53 seconds, more preferably less than or equal to about 50 seconds;
• T95 value of at less than or equal to about 50 seconds, more preferably less than about 42 seconds, more preferably less than about 34 seconds, more preferably less than about 23 seconds;
• the liquid radiation curable resins for additive fabrication of the invention comprise at least one cationically polymerizable component; that is a component which undergoes polymerization initiated by cations or in the presence of acid generators.
• the cationically polymerizable components may be monomers, oligomers, and/or polymers, and may contain aliphatic, aromatic, cycloaliphatic, arylaliphatic, heterocyclic moiety(ies), and any combination thereof.
• the cationically polymerizable component includes at least one cycloaliphatic compound.
• Suitable cyclic ether compounds can comprise cyclic ether groups as side groups or groups that form part of an alicyclic or heterocyclic ring system.
• the cationic polymerizable component is selected from the group consisting of cyclic ether compounds, cyclic acetal compounds, cyclic thioethers compounds, spiro-orthoester compounds, cyclic lactone compounds, and any combination thereof.
• Suitable cationically polymerizable components include cyclic ether compounds such as epoxy compounds and oxetanes, cyclic lactone compounds, cyclic acetal compounds, cyclic thioether compounds, and spiro-orthoester compounds. Specific examples of cationically
• 11 polymerizable components include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, brominated bisphenol A diglycidyl ether, brominated bisphenol F diglycidyl ether, brominated bisphenol S diglycidyl ether, epoxy novolac resins, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenol F diglycidyl ether, hydrogenated bisphenol S diglycidyl ether, 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexanecarboxylate, 2-(3,4- epoxycyclohexyl-5,5-spiro-3,4-epoxy)-cyclohexane-l,4-dioxane, bis(3,4- epoxycyclohexylmethyl)adipate, vinylcyclohexene oxide, 4-vinylepoxycyclohexane,
• the cationically polymerizable component may optionally also contain polyfunctional materials including dendritic polymers such as dendrimers, linear dendritic polymers, dendrigraft polymers, hyperbranched polymers, star branched polymers, and hypergraft polymers with epoxy or oxetane functional groups.
• dendritic polymers may contain one type of polymerizable functional group or different types of polymerizable functional groups, for example, epoxy and oxetane functions.
• composition of the present invention also comprises one or more mono or poly glycidylethers of aliphatic alcohols, aliphatic polyols, polyesterpolyols or
• polyetherpolyols examples include 1,4-butanedioldiglycidylether, glycidylethers of polyoxyethylene and polyoxypropylene glycols and triols of molecular weights from about 200 to about 10,000; glycidylethers of polytetramethylene glycol or poly(oxyethylene- oxybutylene) random or block copolymers.
• polymerizable component comprises a polyfunctional glycidylether that lacks a cyclohexane ring in the molecule.
• the cationically polymerizable component includes a neopentyl glycol diglycidyl ether.
• the cationically polymerizable component includes a 1,4 cyclohexanedimethanol diglycidyl ether.
• ErisysTM GE 22 ErisysTM products are available from Emerald Performance MaterialsTM
• HeloxyTM modifiers are available from Momentive Specialty Chemicals
• Grilonit® F713 examples of commercially available preferred monofunctional glycidylethers are HeloxyTM 71, HeloxyTM 505, HeloxyTM 7, HeloxyTM 8, and HeloxyTM 61.
• the epoxide is 3,4-epoxycyclohexylmethyl-3',4- epoxycyclohexanecarboxylate (available as CELLOXIDETM 202 IP from Daicel Chemical, or as CYRACURETM UVR-6105 from Dow Chemical), hydrogenated bisphenol A-epichlorohydrin based epoxy resin (available as EPONTM 1510 from Momentive), 1,4-cyclohexanedimethanol diglycidyl ether (available as HELOXYTM 107 from Momentive), a hydrogenated bisphenol A
• the cationic polymerizable component includes a
• cycloaliphatic epoxy for example, a cycloaliphatic epoxy with 2 or more than 2 epoxy groups according to the following formula I:
• R is a carbon atom, an ester-containing Ci-Cio aliphatic chain, or a Ci-Cio alkyl chain.
• the cationic polymerizable component includes an epoxy having an aromatic or aliphatic glycidyl ether group with 2 (difunctional) or more than 2 (polyfunctional) epoxy groups.
• the above-mentioned cationically polymerizable compounds can be used singly or in combination of two or more thereof.
• the cationic polymerizable component further comprises at least two different epoxy components.
• the cationic polymerizable component also comprises an oxetane component.
• the cationic polymerizable component includes an oxetane, for example, an oxetane containing 1, 2 or more than 2 oxetane groups.
• the oxetane employed is monofunctional, and additionally possesses a hydroxyl group. According to an embodiment, the oxetane possesses the following structure:
• the oxetane component is present in a suitable amount from about 5 to about 50 wt% of the resin composition. In another embodiment, the oxetane component is present in an amount from about 10 to about 25 wt% of the resin composition, and in yet another embodiment, the oxetane component is present in an amount from 20 to about 30 wt% of the resin composition.
• the liquid radiation curable resin for additive fabrication can therefore include suitable amounts of the cationic polymerizable component, for example, in certain embodiments, in an amount from about 10 to about 80% by weight of the resin composition, in further embodiments from about 20 to about 70 wt% of the resin composition, and in further embodiments from about 25 to about 65 wt% of the resin composition, in further preferred embodiments from about 30 to about 80 wt%, more preferably from about 50 to about 85 wt% of the resin composition
• the liquid radiation curable resin for additive fabrication of the invention comprises at least one free-radical polymerizable component, that is, a component which undergoes polymerization initiated by free radicals.
• the free-radical polymerizable components are monomers, oligomers, and/or polymers; they are monofunctional or polyfunctional materials, i.e., have 1, 2, 3, 4, 5, 6, 7, 8, 9, 10...20...30...40...50...100, or more functional groups that can polymerize by free radical initiation, may contain aliphatic, aromatic, cycloaliphatic, arylaliphatic, heterocyclic moiety(ies), or any combination thereof.
• polyfunctional materials include dendritic polymers such as dendrimers, linear dendritic polymers, dendrigraft polymers, hyperbranched polymers, star branched polymers, and hypergraft polymers; see, e.g., US 2009/0093564 Al.
• the dendritic polymers may contain one type of polymerizable functional group or different types of polymerizable functional groups, for example, acrylates and methacrylate functions.
• Examples of free-radical polymerizable components include acrylates and methacrylates such as isobornyl (meth)acrylate, bornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, 4-butylcyclohexyl (meth)acrylate, acryloyl morpholine, (meth)acrylic acid, 2- hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, isobutyl (
• poly functional free-radical polymerizable components include those with (meth)acryloyl groups such as trimethylolpropane tri(meth)acrylate, pentaerythritol (meth)acrylate, ethylene glycol di(meth)acrylate, bisphenol A diglycidyl ether di(meth)acrylate, dicyclopentadiene dimethanol di(meth)acrylate, [2-[l, l-dimethyl-2-[(l-oxoallyl)oxy]ethyl]-5-ethyl-l,3-dioxan-5- yljmethyl acrylate; 3,9-bis(l, l-dimethyl-2-hydroxyethyl)-2,4,8, 10-tetraoxaspiro[5.5]undecane di(meth)acrylate; dipentaerythritol monohydroxypenta(meth)acrylate, propoxylated
• tri(meth)acrylate pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)crylate, tricyclodecane diyl dimethyl di(meth)acrylate and alkoxylated versions (e.g., ethoxylated and/or propoxylated) of any of the preceding monomers, and also di(meth)acrylate of a diol which is an ethylene oxide or propylene oxide adduct to bisphenol A, di(meth)acrylate of a diol which is an ethylene oxide or propylene oxide adduct to hydrogenated bisphenol A, epoxy (meth)acrylate which is a (meth)acrylate adduct to bisphenol A of diglycidyl ether, diacrylate of polyoxy alkylated bisphenol A, and triethylene glycol divinyl ether, and adducts of hydroxy ethyl acrylate.
• the radically polymerizable component is a polyfunctional (meth)acrylate.
• the polyfunctional (meth)acrylates may include all methacryloyl groups, all acryloyl groups, or any combination of methacryloyl and acryloyl groups.
• the free-radical polymerizable component is selected from the group consisting of bisphenol A diglycidyl ether di(meth)acrylate, ethoxylated or propoxylated bisphenol A or bisphenol F di(meth)acrylate, dicyclopentadiene dimethanol di(meth)acrylate, [2-[l,l-dimethyl-2- [(1 -oxoallyl)oxy] ethyl] -5-ethyl- 1 , 3 -dioxan-5 -yl] methyl acrylate, dipentaerythritol
• the polyfunctional (meth)acrylate has more than 2 functional groups. According to another embodiment, the polyfunctional (meth)acrylate has more than 3 functional groups. In yet another embodiment, the polyfunctional (meth)acrylate has more than 4 functional groups.
• the radically polymerizable component consists exclusively of a single polyfunctional (meth)acrylate component.
• the exclusive radically polymerizable component is tetra-functional, in further embodiments, the exclusive radically polymerizable component is penta-functional, and in further embodiments, the exclusive radically polymerizable component is hexa-functional.
• the free-radical polymerizable component is contains an aromatic (meth)acrylate.
• Aromatic acrylates may be derived from, as non-limiting examples, bisphenol-A, bisphenol-S, or bisphenol-F.
• the aromatic selected from the group consisting of bisphenol A diglycidyl ether diacrylate, dicyclopentadiene dimethanol diacrylate, [2- [ 1 , 1 -dimethyl-2- [( 1 -oxoallyl)oxy]ethyl]-5 -ethyl- 1 , 3 -dioxan-5 -yl] methyl aery late, dipentaerythritol monohydroxypentaacrylate, propoxylated trimethylolpropane triacrylate, and propoxylated neopentyl glycol diacrylate, and any combination thereof.
• the aromatic (meth)acrylate is difunctional.
• the liquid radiation curable resins for additive fabrication of the invention include one or more of bisphenol A diglycidyl ether di(meth)acrylate,
• trimethylolpropane triacrylate and/or propoxylated neopentyl glycol diacrylate.
• the above-mentioned radically polymerizable compounds can be used singly or in combination of two or more thereof.
• the liquid radiation curable resin for additive fabrication can include any suitable amount of the free-radical polymerizable components, for example, in certain embodiments, in an amount up to about 50 wt% of the resin composition, in certain embodiments, from about 2 to about 40 wt% of the resin composition, in other embodiments from about 5 to about 30 wt%, and in further embodiments from about 10 to about 20 wt% of the resin composition, in yet further preferred embodiments from about 8 to about 50 wt%, more preferably from about 15 to about 25 wt% of the resin composition.
• the liquid radiation curable resin composition includes a cationic photoinitiator.
• the cationic photoinitiator initiates cationic ring-opening polymerization upon irradiation of light.
• any suitable iodonium-based cationic photoinitiator can be used, for example, those with cations selected from the group consisting of diaryl iodonium salts, triaryl iodonium salts, aromatic iodonium salts, and any combination thereof.
• the cation of the cationic photoinitiator is selected from the group consisting of aromatic diazonium salts, aromatic sulfonium salts, aromatic iodonium salts, metallocene based compounds, aromatic phosphonium salts, acylsulphonium salts, and any combination thereof.
• the cation is a polymeric sulfonium salt, such as in US5380923 or US5047568, or other aromatic heteroatom-containing cations and naphthyl- sulfonium salts such as in US7611817, US7230122, US2011/0039205, US2009/0182172,
• the cationic photoinitiator is selected from the group consisting of triarylsulfonium salts, diaryliodonium salts, and metallocene based compounds, and any combination thereof.
• Onium salts e.g., iodonium salts and sulfonium salts, and ferrocenium salts, have the advantage that they are generally more thermally stable.
• the cationic photoinitiator has an anion selected from the group consisting of BF 4 " , AsF 6 “ , SbF 6 “ , PF 6 “ , [B(CF 3 ) 4 ] “ , B(C 6 F 5 ) 4 “ , B[C 6 H 3 -3,5(CF 3 ) 2 ] 4 -,
• the cationic photoinitiator has a cation selected from the group consisting of aromatic sulfonium salts, aromatic iodonium salts, and metallocene based compounds with at least an anion selected from the group consisting of SbF 6 ⁇ , PF 6 ⁇ , B(C 6 F 5 ) ⁇ , [B(CF 3 ) ] " , tetrakis(3,5-difluoro-4-methoxyphenyl)borate, perfluoroalkylsulfonates, perfluoroalkylphosphates, tris[(perfluoroalkyl)sulfonyl]methides, and [(C 2 F 5 ) 3 PF 3 ] " .
• Examples of cationic photoinitiators suitable in other embodiments include 4-[4-(3- chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium hexafluoroantimonate, 4-[4-(3- chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium tetrakis(pentafluorophenyl)borate, 4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium tetrakis(3,5-difluoro-4- methyloxyphenyl)borate, 4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium tetrakis(2,3,5,6-tetrafluoro-4
• the cationic photoinitiator component includes, either alone or in a mixture: bis[4-diphenylsulfoniumphenyl]sulfide bishexafluoroantimonate;
• thiophenoxyphenyl sulfonium hexafluoroantimonate available as Chivacure 1176 from Chitec
• tris(4-(4-acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate Irgacure® PAG 290 from BASF
• tris(4-(4-acetylphenyl)thiophenyl)sulfonium tris[(trifluoromethyl)sulfonyl]methide Irgacure® GSID 26-1 from BASF
• the liquid radiation curable resin for additive fabrication comprises an aromatic triaryl sulfonium salt cationic photoinitiator.
• aromatic triaryl sulfonium salts Use of aromatic triaryl sulfonium salts in additive fabrication applications is known. Please see US 20120251841 to DSM IP Assets, B.V., U.S. Pat. No. 6,368,769, to Asahi Denki Kogyo, which discusses aromatic triaryl sulfonium salts with tetraryl borate anions, including tetrakis(pentafluorophenyl)borate, and
• Triarylsulfonium salts are disclosed in, for example, J Photopolymer Science & Tech (2000), 13(1), 117-118 and J Poly Science, Part A (2008), 46(11), 3820-29.
• Triarylsulfonium salts Ar 3 S + MXn ⁇ with complex metal halide anions such as BF 4 " , AsF 6 " , PF 6 “ , and SbF 6 " are disclosed in J Polymr Sci, Part A (1996), 34(16), 3231-3253.
• photoinitiator is tris(4-(4-acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate.
• Tris(4-(4-acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate is known commercially as IRGACURE® PAG-290, and is available from Ciba/BASF.
• the cationic photoinitiator is an aromatic triaryl sulfonium salt that possesses an anion represented by SbF 6 ⁇ , PF 6 ⁇ , BF 4 ⁇ , (CF 3 CF 2 )3PF 3 ⁇ , (CeF 5 ) B ⁇ ,
• Another cationic photoinitiator is an aromatic triaryl sulfonium cationic photoinitiator has an anion that is a flu oroalkyl- substituted fluorophosphate.
• aromatic triaryl sulfonium cationic photoinitiator having a fluoroalkyl- substituted fluorophosphate anion is the CPI-200 series (for example CPI-200K® or CPI-210S®) or 300 series, available from San-Apro Limited.
• cationic photoinitiators which are designed to be especially suitable for absorbing light and generating photoreactive species at UV/vis wavelengths. Incorporation of one or more of these cationic photoinitiators into a liquid radiation curable composition for UV/vis cure would be achieved through "direct" excitation of the photoinitiator.
• UV/vis-direct excitation cationic photoinitiators include: Irgacure 261, Irgacure PAG 103, and Irgacure PAG 121, each of which is available commercially from BASF, R-Gen ® 262 ( ⁇ 5 -2,4-cyclopentadien-l-yl)[(l,2,3,4,5,6-r
• compositions used in additive fabrication processes utilizing UV/vis optics Although not wishing to be bound by any theory, it is surmised that, since the free radical portion of the polymer network cures at a much higher rate, the free radical curing portion of the resin builds up viscosity and
• the liquid radiation curable resin composition can include any suitable amount of the cationic photoinitiator, for example, in certain embodiments, in an amount up to about 15% by weight of the resin composition, in certain embodiments, up to about 5% by weight of the resin composition, and in further embodiments from about 2% to about 10% by weight of the resin composition, and in other embodiments, from about 0.1% to about 5% by weight of the resin composition.
• the amount of cationic photoinitiator is from about 0.2 wt% to about 4 wt% of the total resin composition, and in other embodiments from about 0.5 wt% to about 3 wt%.
• the liquid radiation curable resin for additive fabrication of the present invention includes a free-radical photoinitiator.
• the liquid radiation curable resin composition includes a photoinitiating system contains at least one photoinitiator having a cationic initiating function, and at least one photoinitiator having a free radical initiating function. Additionally, the photoinitiating system can include a photoinitiator that
• the photoinitiator is a compound that chemically changes due to the action of light or the synergy between the action of light and the electronic excitation of a sensitizing dye to produce at least one of a radical, an acid, and a base.
• free radical photoinitiators are divided into those that form radicals by cleavage, known as “Norrish Type I” and those that form radicals by hydrogen abstraction, known as “Norrish type II".
• the Norrish type II photoinitiators require a hydrogen donor, which serves as the free radical source.
• the Norrrish type II photoinitiators are generally slower than Norrish type I photoinitiators which are based on the unimolecular formation of radicals.
• Norrish type II photoinitiators possess better optical absorption properties in the near-UV spectroscopic region.
• Photolysis of aromatic ketones such as benzophenone, thioxanthones, benzil, and quinones
• hydrogen donors such as alcohols, amines, or thiols
• the photopolymerization of vinyl monomers is usually initiated by the radicals produced from the hydrogen donor.
• the ketyl radicals are usually not reactive toward vinyl monomers because of the steric hindrance and the derealization of an unpaired electron.
• the liquid radiation curable resin for additive fabrication includes at least one free radical photoinitiator, e.g., those selected from the group consisting of benzoylphosphine oxides, aryl ketones, benzophenones, hydroxylated ketones, 1- hydroxyphenyl ketones, ketals, metallocenes, and any combination thereof.
• at least one free radical photoinitiator e.g., those selected from the group consisting of benzoylphosphine oxides, aryl ketones, benzophenones, hydroxylated ketones, 1- hydroxyphenyl ketones, ketals, metallocenes, and any combination thereof.
• the liquid radiation curable resin for additive fabrication includes at least one free-radical photoinitiator selected from the group consisting of 2,4,6-trimethylbenzoyl diphenylphosphine oxide and 2,4,6-trimethylbenzoyl phenyl, ethoxy phosphine oxide, bis(2,4,6- trimethylbenzoyl)-phenylphosphineoxide, 2-methyl-l-[4-(methylthio)phenyl]-2- morpholinopropanone-1, 2-benzyl-2-(dimethylamino)-l-[4-(4-morpholinyl) phenyl]- 1-butanone, 2- dimethylamino-2-(4-methyl-benzyl)-l-(4-morpholin-4-yl-phenyl)-butan-l-one, 4-benzoyl-4'-methyl diphenyl sulphide, 4,4'- bis(diethylamino) benzophenone, and 4,4
• Suitable free-radical photoinitiators absorbing in this area include: benzoylphosphine oxides, such as, for example, 2,4,6-trimethylbenzoyl
• the free-radical photoinitiator is an acylphosphine oxide photoinitiator.
• Acylphosphine oxide photoinitiators are disclosed for example in U.S. Pat. Nos. 4,324,744, 4,737,593, 5,942,290, 5,534,559, 6,020,528, 6,486,228, and 6,486,226.
• acylphosphine oxide photoinititors are bisacylphosphine oxides (BAPO) or monoacylphosphine oxides (MAPO).
• the bisacylphosphine oxide photoinitiators are of the formula II:
• R 50 is C 1 -C 12 alkyl, cyclohexyl or phenyl which is unsubstituted or is substituted by 1 to 4 halogen or Ci-C 8 alkyl
• R 51 and R 52 are each independently of the other Ci-C 8 alkyl or Ci- C 8 alkoxy
• R 53 is hydrogen or Ci-C 8 alkyl
• R 54 is hydrogen or methyl.
• R 50 is C 2 -C 10 alkyl, cyclohexyl or phenyl which is unsubstituted or is substituted by 1 to 4 C 1 -C 4 alkyl, CI or Br.
• R 50 is C 3 -C 8 alkyl, cyclohexyl or phenyl which is unsubstituted or is substituted in the 2-, 3-, 4- or 2,5-positions by Ci- C 4 alkyl.
• R 50 is C 4 -C 12 alkyl or cyclohexyl
• R 51 and R 52 are each independently of the other Ci-C 8 alkyl or Ci-C 8 alkoxy
• R 53 is hydrogen or Ci-C 8 alkyl.
• R 51 and R 52 are C 1 -C 4 alkyl or Ci-C 4 alkoxy and R 53 is hydrogen or C 1 -C 4 alkyl.
• R 51 and R 52 are methyl or methoxy and R 53 is hydrogen or methyl.
• R 51 , R 52 and R 53 are methyl.
• R 51 , R 52 and R 53 are methyl and R 54 is hydrogen.
• R50 is C 3 -C 8 alkyl.
• R51 and R52 are methoxy
• R 53 and R54 are hydrogen and R 50 is isooctyl.
• R 50 is isobutyl.
• R 50 is phenyl.
• the present bisacylphosphine oxide photoinitiator is for example bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (CAS# 162881-26-7) or is bis(2,4,6-trimethylbenzoyl)-(2,4-bis-pentyloxyphenyl)phosphine oxide.
• the monoacylphosphine oxide photoinitiators are of the formula III:
• Ri and R 2 independently of o l, phenyl which is unsubstituted or substituted from one to four times by halogen, Ci-C 8 alkyl and/or Ci-C 8 alkoxy, or are cyclohexyl or a group -COR 3 , or Ri is -OR 4 ;
• R 3 is phenyl which is unsubstituted or substituted from one to four times by Ci-C 8 alkyl, Ci-C 8 alkoxy, Ci-C 8 alkylthio and/or halogen;
• R 4 is Ci-C 8 alkyl, phenyl or benzyl.
• Ri is -OR 4 .
• R 2 is phenyl which is unsubstituted or substituted from one to four times by halogen, Ci-C 8 alkyl and/or Ci-C 8 alkoxy.
• R 3 is phenyl which is unsubstituted or substituted from one to four times by Ci- C 8 alkyl.
• the present monoacylphosphine oxide is 2,4,6- trimethylbenzoylethoxyphenylphosphine oxide or 2,4,6-trimethylbenzoyldiphenylphosphine oxide.
• the liquid radiation curable resin for additive fabrication can include any suitable amount of the free-radical photoinitiator as component (d), for example, in certain embodiments, in an amount up to about 10 wt% of the resin composition, in certain embodiments, from about 0.1 to
• one or more cationic and/or free-radical are cationic and/or free-radicals.
• photoinitiators are included in the resin composition with a diluent monomer.
• the cationic and free-radical photoinitiators are those discussed herein, and any suitable diluent may be used.
• Common liquid diluents for dispersing certain cationic photoinitiators include (poly)propylene glycol or (poly)propylene carbonate.
• vinyl ether as a diluent monomer or dispersing agent in combination with at least one cationic
• photoinitiator induces improved photopolymerization efficacy when subjected to cure under UV/vis optics conditions according to the present invention.
• the cationic photoinitiator is present in an amount from about 8 wt% to about 50 wt%, more preferably from about 30 wt% to about 45 wt%; the vinyl ether diluent monomer is present in an amount from about 25 wt% to about 90 wt%, more preferably from about 40 wt% to about 60 wt%; and the free- radical photoinitiator is present in amount from about 8 wt% to about 30 wt%, more preferably from about 10 wt% to about 25 wt%; wherein the cationic photoinitiator is at least partially dissolved in a solution with the vinyl ether diluent monomer in a ratio of from 0.1:1 to 1:1.
• a second aspect of the claimed invention is a liquid radiation curable composition for additive fabrication comprising:
• composition is curable by UV/vis optics imparting a dose of 20mJ/cm 2 and emitting radiation at a peak spectral intensity from about 375nm to about 500nm, more
• 25 preferably from about 380nm to about 450nm, more preferably from about 390 nm to about 425 nm, more preferably from about 395 nm to about 410 nm.
• the cationically polymerizable components, the free-radically polymerizable components, and the free-radical photoinitiators according to a first aspect of the invention are equally suitable for use in the second aspect of the claimed invention.
• the description of iodonium salt cationic photoinitiators above pertaining to the first aspect of the claimed invention is also equally suitable for use in the second aspect of the claimed invention.
• the iodonium salt cationic photoinitiator is a diphenyl iodonium salt.
• diphenyl iodonium salts photoinitiators are, for example, (4-methylphenyl)[4-(2-methylpropyl) phenyl]-, hexafluorophosphate, [4-(l-methylethyl)phenyl](4-methylphenyl)-,
• the liquid radiation curable resin composition may include a photosensitizer.
• photosensitizer is used to refer to any substance that either increases the rate of photoinitiated polymerization or shifts the wavelength at which polymerization occurs; see textbook by G. Odian, Principles of Polymerization, 3 Ed., 1991, page 222. Substances which operate by way of the latter definition, and are used in conjunction with photoinitiators that would otherwise not absorb light of a specific wavelength are said to operate by way of an "indirect excitation" mechanism with their associated photoinitiator. Applicants have harnessed this mechanism to formulate compositions of the current invention which are suitable for cure via UV/vis optics.
• a variety of compounds can be used as photo sensitizers, including heterocyclic and fused-ring aromatic hydrocarbons, organic dyes, and aromatic ketones. Examples of
• photo sensitizers include those selected from the group consisting of methanones, xanthenones, pyrenemethanols, anthracenes, pyrene, perylene, quinones, xanthones, thioxanthones, benzoyl esters, benzophenones, and any combination thereof.
• photosensitizers include those selected from the group consisting of [4-[(4-methylphenyl)thio]phenyl]phenyl- methanone, isopropyl-9H-thioxanthen-9-one, 1-pyrenemethanol, 9-(hydroxymethyl)anthracene,
• the novel mixtures may also contain various photoinitiators of different sensitivity to radiation of emission lines with different wavelengths to obtain a better utilization of a UV light source.
• the use of known photoinitiators of different sensitivity to radiation of emission lines is well known in the art of additive fabrication, and may be selected in accordance with radiation sources of, for example, 351, nm 355 nm, 365 nm, 385 nm, and 405nm.
• the photosensitizer is a fluorone, e.g., 5,7-diiodo-3-butoxy-6- fluorone, 5,7-diiodo-3-hydroxy-6-fluorone, 9-cyano-5,7-diiodo-3-hydroxy-6-fluorone, or a photosensitizer is
• photoinitiators When photo sensitizers are employed, other photoinitiators absorbing at shorter wavelengths can be used. Examples of such photoinitiators include: benzophenones, such as benzophenone, 4-methyl benzophenone, 2,4,6-trimethyl benzophenone, and
• 1-hydroxyphenyl ketones such as 1-hydroxycyclohexyl phenyl ketone, phenyl (l-hydroxyisopropyl)ketone, 2-hydroxy-l-[4-(2-hydroxyethoxy) phenyl] -2-methyl-
• cationic photoinitiators have low absorption at the preferred actinic wavelength.
• an additive fabrication application of interest utilizes UV/optics having a peak intensity at about 400 nm.
• Iodonium salts such as, for example, Rhodorsil 2074, available from Rhodia Silicones, Irgacure 250 Iodonium, (4-methylphenyl)[4-(2- methylpropyl)phenyl]-hexafluorophosphate(l-) available from Ciba, and UV9380c, available from GE Silicones, have insufficient direct absorption at the preferred wavelength and therefore require excessive concentration or require a sensitizer.
• triplet sensitizers such as thioxanthones and Michelers ketone are sometimes used to absorb the actinic energy and then transfer the energy to the iodonium initiator in an efficient manner.
• thioxanthones and Michelers ketones are prone to orange or red color formation, safety concerns, and, while they have significant actinic absorption out to 430 nm, they are not very effective at sensitizing the photoreaction at curing light wavelengths of about 400 nm.
• chloropropyl thioxanthone is a suitable sensitizer for iodonium initiators especially for use in stereolithography since it does not have significant light absorption above 500 nm and creates articles with less color.
• sensitizers with high extinction coefficients at 400 nm.
• benzophenone may, in some cases, act as a triplet sensitizer, but at laser wavelengths of, for example, a frequency tripled YAG laser (Coherent AVIA model #355-1800) operating at approximately 355 nm, the extinction coefficient is on the order of 108 liters/mole-cm.
• CPTX at the using the same laser at the same laser wavelength of approximately 400 nm has an extinction coefficient of almost X times that of benzophenone, 2585 liters/mole-cm. This suggests that CPTX may require l/X the concentration in a formulation to provide an equivalent light absorption effect. It is, therefore, preferred - although not required - for the sensitizer to have an extinction coefficient greater than 300 liters/mole-cm, or higher such as greater than 1000 liters/mole-cm, and preferably greater than 2000 liters/mole-cm at curing light wavelengths greater than 380 nm.
• CPTX may be used to improve the activity of the cationic photoinitiator
• the sensitizer used in combination with the above-mentioned cationic photoinitiators is not necessarily limited thereto.
• a variety of compounds can be used as photo sensitizers,
• sensitizers include compounds disclosed by J. V. Crivello in Advances in Polymer Science, 62, 1 (1984), and by J. V. Crivello & K. Dietliker, "Photoinitiators for Cationic
• the liquid radiation curable resin for additive fabrication can include any suitable amount of the other cationic photoinitiator or photosensitizer, for example, in certain embodiments, in an amount an amount from 0.1 to 10 wt% of the resin composition, in certain embodiments, from about 1 to about 8 wt% of the resin composition, and in further embodiments from about 2 to about 6 wt% of the resin composition. In an embodiment, the above ranges are particularly suitable for use with epoxy monomers. In another embodiment, the photosensitizer may be employed in an amount of from about 0.05% to about 2% by weight of the total composition to which it is incorporated.
• reductants are components that lose, or "donate”, one or
• Photoinitiated cationic polymerization of monomers plays a necessary role in hybrid cure additive fabrication applications. Because of the additives used in different applications, when targeting a specific spectral sensitivity, the wavelength flexibility of photoinitiation becomes a fundamental factor in determining the curing performance of specific formulations. Therefore, photoinitiating systems for cationic polymerization that are sensitive particularly to longer wavelengths, such as those emitted by modern UV/vis optics, are
• Suitable reductants for facilitating free radical promoted cationic polymerization generally include some of the aforementioned free-radical photoinitiators such as acylphosphine oxides, along with amines, benzoin and its derivatives, o-phataldehyde, polysilanes, and compounds having electron-donating substituents attached to a vinyl group such as vinyl ethers or vinyl halides, to name a few.
• free-radical photoinitiators such as acylphosphine oxides, along with amines, benzoin and its derivatives, o-phataldehyde, polysilanes, and compounds having electron-donating substituents attached to a vinyl group such as vinyl ethers or vinyl halides, to name a few.
• Amines are considered to be efficient hydrogen donors, and by virtue of chain transfer mechanisms will readily form free-radicals which will reduce a cationic photoinitiator with which they are associated. Therefore, in certain embodiments, they can act as suitable reductants.
• radicals formed by the irradiation of systems containing a xanthene dye and an aromatic amine can serve as reductants to a diphenyliodonium salt.
• dimanganese decacarbonyl-organic halide combination is an efficient reductant for cationic polymerization at UV/vis wavelengths when used in conjunction with onium salts.
• acylphosphine oxides are suitable reductants to contribute to the promotion the cationic polymerization of appropriate monomers at UV/vis wavelengths.
• Cationic polymerizations of tetrahydrofuran and butyl vinyl ether can be readily initiated upon irradiation in the presence of bisacylphosphine oxide and diphenyliodonium salt at UV/vis wavelengths. It is believed, without wishing to be bound by theory, that photoinitiated bisacylphosphine oxide readily abstracts hydrogen from appropriate donors (e.g.
• acylphosphine oxides and, more preferably substituted acylphosphine oxides, in combination with suitable onium salts, such as iodonium and pyridinium salts, have been found to be efficient and effective reductants for facilitating free cationic polymerization at UV/vis curing wavelengths.
• the proposed initiation mechanism seems to involve the photogeneration of phosphinoyl radicals and benzoyl radicals in the first step.
• the reductant for reducing the cationic photoinitiator is represented by the following formula IV:
• Ari is a substituted or unsubstituted aromatic group
• Ri is Ari, a C 2 -C 20 aliphatic chain, or a C 2 -C 20 alkyl chain
• R 2 is Ri or contains one or more substituted or unsubstituted acyl phenyl groups.
• the liquid radiation curable resin for additive fabrication can include any suitable amount of a reductant for reducing the cationic photoinitiator, for example, in certain embodiments, in an amount from 0.01 to 30 wt% in certain embodiments, in an amount an amount from 0.01 to 10 wt% of the resin composition in other preferred embodiments, in other certain embodiments, from about 1 to about 8 wt% of the resin composition, and in further embodiments from about 2 to about 6 wt% of the resin composition.
• the above ranges are particularly suitable for use with iodonium salt photoinitiators.
• the same reductant component may simultaneously serve as a free-radical photoinitiator and reductant, thereby simultaneously promoting both free-radical polymerization and cationic polymerization.
• the reductant may be employed in an amount of from about 0.05% to about 4% by weight of the total composition to which it is incorporated.
• Vinyl ethers can be created from a variety of starting materials such as ethers, esters or biscarbamates, or vinyl ether terminated (poly) urethane or carbonates. Some non-limiting examples of each are included below:
• Vinyl ether monomers from ethers include divinyl ether such as ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, isobutyl vinyl ether, butylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinylether, cyclohexanediol divinyl ether, bisphenol A alkylene oxide divinyl ether, and bisphenol F alkylene oxide divinyle ether; and polyfunctional vinyl ethers such as trimethylolethane trivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerol trivinyl ether, pentaery
• Vinyl ether monomers from esters or biscarbamate Specific examples of polyfunctional vinyl ethers such as divinyl adipate, divinyl terephthalate, divinyl cyclohexyl dicaroxylate.
• Vinyl ether terminated urethanes or carbonate Specific examples of polyfunctional vinylether, such as polyurethane or polycarbonate endcapped with hydorxy vinyl ether in which it
• hydroxyl group has at least a hydroxyl group and at least a vinyl ether group in intramolecular.
• the component possessing an electron-donating substituent attached to a vinyl group is one or more of the following: vinyl ether, vinyl ester, vinyl thioether, n- vinyl carbazole, n-vinyl pyrollidone, n-vinyl caprolactam, allyl ether, and vinyl carbonate.
• the component possessing an electron-donating substituent attached to a vinyl group is multifunctional.
• One or more of the aforementioned components possessing an electron-donating substituent attached to a vinyl group can be employed in compositions according to the present invention in any suitable amount, and may be chosen singly or in combination of one or more of the types enumerated herein.
• the component possessing an electron-donating substituent attached to a vinyl group is present in an amount, relative to the entire weight of the composition, of from about 1 wt.% to about 25 wt.%, more preferably from about 5 wt.% to about 20 wt.%), more preferably about 5 wt.% to about 12 wt.%.
• the component possessing an electron-donating substituent attached to a vinyl group is present in an amount from 1 wt.% to 15wt.%, more preferably from 1 wt.% to 10 wt%, more preferably from 3 wt.% to about 8 wt.%.
• Stabilizers are often added to the resin compositions in order to further prevent a viscosity build-up, for instance a viscosity build-up during usage in a solid imaging process.
• the liquid radiation curable resin composition for additive fabrication comprises from 0.1 wt% to 3% of a stabilizer.
• additives include organic and inorganic fillers, dyes, pigments, antioxidants, wetting agents, bubble breakers, chain transfer agents, leveling agents, defoamers, surfactants and the like. Such additives are known and can be generally employed as is desirable for a particular application, as will be appreciated by one of ordinary skill in the art.
• the liquid radiation curable resin composition for additive fabrication of the invention can further include one or more additives selected from the group consisting of bubble breakers, antioxidants, surfactants, acid scavengers, pigments, dyes, thickeners, flame retardants, silane coupling agents, ultraviolet absorbers, resin particles, core-shell particle impact modifiers, soluble polymers and block polymers.
• additives selected from the group consisting of bubble breakers, antioxidants, surfactants, acid scavengers, pigments, dyes, thickeners, flame retardants, silane coupling agents, ultraviolet absorbers, resin particles, core-shell particle impact modifiers, soluble polymers and block polymers.
• hydroxy-functional compounds to enhance the properties of the parts made from the resin compositions.
• any hydroxy group may be employed for the particular purpose.
• the hydroxyl-containing material preferably contains one or more primary or secondary aliphatic hydroxyl.
• the hydroxyl group may be internal in the molecule or terminal.
• Monomers, oligomers or polymers can be used.
• the hydroxyl equivalent weight i.e., the number average molecular weight divided by the number of hydroxyl groups, is preferably in the range of 31 to 5000.
• the resin composition preferably comprises, relative to the total weight of the resin composition, at most 10 wt % of one or more non-free radical polymerizable hydroxy- functional compounds, more preferably at most 5 wt %, and most preferably at most 2 wt %.
• compositions according to the present invention may become particularly optimized for curing via certain additive fabrication processes utilizing UV/vis optics if ratios of the various required components are controlled relative to each other.
• the weight ratio of the iodonium salt cationic photoinitiator to the photo sensitizer to the first reductant to the second reductant possessing an electron-donating substituent attached to a vinyl group is from about 2:2: 1 :2 to about 20: 1:5:25, more preferably about 10:1 :2: 12. If the amount of the iodonium salt cationic photoinitiator becomes too large, radiation absorbance becomes too significant, impeding the ability to cure to layers of a sufficient depth. If it becomes too low relative the other constituents, cationic cure is not initiated to required levels to
• the amount of the photosensitizer generally should not exceed that of the amount of the iodonium salt cationic photoinitiator, although it should be present in an amount sufficient to enable the indirect excitation of said cationic photoinitiator.
• the reductant also should generally not exceed that of the cationic photoinitiator which it reduces, but it similarly should be present in an amount sufficient to facilitate the free- radically promoted cationic polymerization.
• the component possessing an electron- donating substituent attached to a vinyl group can be present in the greatest amount by weight relative the aforementioned other constituents to sufficiently enable additional cationic
• the ratio of the iodonium salt cationic photoinitiator to the photosensitizer is from 1 :3 to 10:1. In an embodiment, the ratio of the iodonium salt cationic photoinitiator to the reductant is from 1:5 to 10:1.
• the third aspect of the claimed invention is a liquid radiation curable composition for additive fabrication comprising:
• component further comprising a cycloaliphatic epoxide and an oxetane
• R contains an aliphatic chain from C1-C20;
• composition is curable by UV/vis optics imparting a dose of 20mJ/cm 2 and emitting radiation at a peak spectral intensity from about 375nm to about 500nm, more preferably from about 380nm to about 450nm, more preferably from about 390 nm to about 425 nm.
• the cationic photoinitiator used in the formulation of a liquid radiation curable composition for additive fabrication wherein the composition is curable by UV/vis optics is a sulfonium salt.
• the description of sulfonium salt cationic photoinitiators above pertaining to the first aspect of the claimed invention is also equally suitable for use in the this third aspect of the claimed invention.
• the cationic photoinitiator is a triaryl sulfonium salt.
• the (triaryl)sulfonium salt cationic photoinitiator actually possesses an extremely low direct absorbance at UV/vis wavelengths.
• the (triaryl)sulfonium salt photoinitiator used possesses an absorbance at 400nm of less than 0.05, more preferably less than 0.01, more preferably less than 0.005, and most preferably less than 0.001.
• indirect excitation of cationic photoinitiators is a more preferable mechanism to initiate cationic polymerization of liquid radiation curable compositions for additive fabrication utilizing UV/vis optics than via direct excitation of those cationic photoinitiators possessing significant absorbance at 400nm.
• the sulfonium salt cationic photoinitiator is a triarylsulfonium salt with a cation according to the following structure:
• the triarylsulfonium salt further possesses an hexafluoroantimonate or an hexafluorophosphate counterion.
• the sulfonium salt cationic photoinitiator is present in the composition in any suitable amount from 0.01 wt% to 15 wt%, in another embodiment from 1 wt% to 8 wt%, in another embodiment from 2 wt% to 5wt%.
• the cationically polymerizable components and the free-radically polymerizable components according to a first and second aspect of the invention are equally suitable for use in the third aspect of the claimed invention as well.
• the liquid radiation curable composition for additive fabrication according to the third aspect of the invention also contains a free-radical photoinitiator.
• a free-radical photoinitiator includes a diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide.
• improved curing properties can be generated alongside a sulfonium salt cationic photoinitiator if the free radical photoinitiator component possesses less than 50% of a compound containing two or more carboxyl groups, preferably less than 33% of a compound containing two or more carboxyl groups, relative to the entire amount of free radical photoinitiator present in the composition.
• the liquid radiation curable composition for additive fabrication according to the third aspect of the invention also contains a photosensitizer.
• the photosensitizer may be chosen generally according to the description of photosensitizers according to the second aspect of the invention.
• the photosensitizer employed possesses a structure according to the following formul
• R contains an aliphatic chain from C1-C20;
• the photosensitizer employed is an anthracene-based photoinitiator.
• anthracene-based photoinitiator Commercially available of such photosensitizers include AnthracureTM UVS-1101 and UVS-1331, available from Kawasaki Chemical.
• the photosensitizer is present in any suitable amount from about 0.5 wt.% to about 10 wt.%, more preferably from 0.5 wt.% to 3 wt.%.
• the fourth aspect of the claimed invention is a method of forming a three-dimensional article via an additive fabrication system utilizing UV/vis optics, the method comprising:
• UV/vis optics emit radiation at a peak spectral intensity from about 375nm to about 500nm, more preferably from about 380nm to about 450nm, more preferably from about 390 nm to about 425 nm, more preferably from about 395 nm to about 410 nm.
• liquid radiation curable composition provided in the aspect of the invention as mentioned above must be suitable for cure via additive fabrication systems utilizing UV/vis optics. Such compositions are described in, inter alia, the first, second, and third aspects of the current invention.
• a layer may be of any suitable thickness and shape, and is dependent on the additive fabrication process utilized. For example, it may be selectively dispensed via jetting, or it may be added by dipping the previously cured layer into a vat of resin, producing a layer of substantially uniform thickness, as is typical with most stereolithography processes. It another non-limiting embodiment, it may alternatively be transferred via a foil, film or carrier in a predefined thickness via a cartridge or dispenser.
• exposing refers to irradiating with actinic radiation.
• inventive liquid radiation compositions for additive fabrications as described herein are particularly suitable for imparting hybrid cure via UV/vis optics.
• the UV/vis optics utilize one or more LEDs as a light source.
• the light source is a laser.
• the LED or laser light source is coupled to a DLP or LCD image projection system.
• the image projection systems includes an LCD display, the light source
• 39 may be configured to emit actinic radiation exclusively above 400nm, to minimize the detrimental effect UV wavelengths have upon LCD componentry.
• the fifth aspect of the claimed invention is the three-dimensional part formed by the fourth aspect of the invention using the liquid radiation curable composition of the first, second, or third aspects of the invention.
• FTIR Real Time Fourier Transform Infrared
• MCT mercury cadmium telluride
• ATR Attenuated Total Reflection
• UV/Vis light control a Digital Light Lab LED spot lamp (365nm, 395nm, and 400nm) and controller (AccuCure Photo Rheometer) were used. Calibrated continuous mode was selected. Light intensity and duration (light exposure time) were selected before measurement.
• a base resin for additive fabrication was prepared according to well-known methods in the art by combining an oxetane component, a cycloaliphatic epoxide component, a polyol component, a glycidyl ether epoxide component, and an acrylate component.
• Irgacure PAG 103 (used in Comparative Example 1) and Irgacure PAG 121 (used in Comparative Example 2) are available through BASF and are explicitly promoted as non-ionic cationic photoacid photoinitiators for cationic cure resins with significant absorbance at UV/vis spectra.
• CPI 400 (used in Comparative Example 3) is a cationic photoinitiator available through San Apro with a notable absorbance at 400nm. The three aforementioned cationic photoinitiators
• T 95 and plateau conversion for cycloaliphatic epoxy components is calculated as described in the test methodology section above.
• Comparative Example 4 employs a photoinitiating package which has been shown to be suitable for curing at 365 nm wavelengths is therefore useful to benchmark against the inventive examples performed in Table 3 using the same base resin.
• Table 1 is the base resin used for most of the formulas in tables 2, 3, and 4.
• Table 2 uses known commercial technology used in 365 nm curing applications to establish acceptable levels of performance using the RT-FTIR methodology described herein.
• Table 3 uses cationic photoinitiators which are known to absorb in the UV/vis spectra, and which would be expected to be suitable for inclusion in liquid hybrid radiation curable compositions for additive fabrication systems employing UV/vis optics by way of a direct excitation mechanism.
• cationic photoinitiators which are known to absorb in the UV/vis spectra, and which would be expected to be suitable for inclusion in liquid hybrid radiation curable compositions for additive fabrication systems employing UV/vis optics by way of a direct excitation mechanism.
• None of these options approach the cure performance of the 365 nm created benchmarks from Table 2.
• Three different photoinitiators were claimed by the supplier to be useful for curing at circa 405 nm wavelengths. All three were tested and only the CPI-400 showed any measurable cure activity.
• the data generated from this experiment was inputted into the curve fitting software as described in the test methodology section above, but the data was so statistically marginal in the test that the r 2 values never reached an acceptable level. Therefore although not statistically significant to evidence
• Table 4 represents the testing of the inventive concepts discussed herein as cured at 400 nm (at the intensities and time durations cited). As can be seen, all the examples achieve the results that are comparable or even better than the 365 nm acceptability criteria established in Table 2. A lower time to achieve 95% of the plateau T 95 is desirable whereas a higher degree of plateau conversion is desirable.
• wt. % means the amount by mass of a particular constituent relative to the entire liquid radiation curable composition for additive fabrication into which it is incorporated.

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