Classifications

• • 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
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
  • B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
• • 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
  • 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
  • G03F7/09—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers
  • G03F7/105—Photosensitive materials characterised by structural details, e.g. supports, auxiliary layers having substances, e.g. indicators, for forming visible 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
  • G03F7/16—Coating processes; Apparatus therefor
  • G03F7/168—Finishing the coated layer, e.g. drying, baking, soaking
• • 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
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
  • B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
  • B29C2035/0833—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation using actinic light
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
  • B29K2995/0018—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds having particular optical properties, e.g. fluorescent or phosphorescent
  • B29K2995/002—Coloured
  • B29K2995/0021—Multi-coloured

Definitions

• Additive fabrication processes for producing three dimensional articles are known in the field.
• Additive fabrication processes utilize computer-aided design (CAD) data of an object to build three-dimensional parts layer-by-layer. These three-dimensional parts may be formed from liquid resins, powders, or other materials.
• CAD computer-aided design
• a non-limiting example of an additive fabrication process is stereolithography
• SL Stereolithography is a well-known 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 beam that traces the 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 beam 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 is, in general, not fully cured and therefore may be subjected to post-curing, if required.
• An example of an SL process is described in U.S. Patent No. 4,575,330.
• liquid radiation curable resin used in stereolithography and other additive fabrication processes for forming three-dimensional objects can be solidified by light energy.
• liquid radiation curable resins are cured by ultra-violet (UV) light.
• UV light is typically produced by lasers (as in stereolithography), lamps, or light emitting diodes (LEDs).
• lasers as in stereolithography
• LEDs light emitting diodes
• the delivery of energy by a laser 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.
• the final color and/or clarity of the cured three dimensional part is not substantially different from that of the resin from which it was formed. However with others, it is typical that the final color and/or clarity develops in the three dimensional article as it is cured.
• Some known resins may be clear in liquid forms and form opaque three-dimensional articles upon cure.
• Other known resins may be colorless in liquid form and capable of curing into colored three-dimensional articles.
• some resins appear as a first color in liquid form and turn a second color upon cure.
• color is defined as follows:
• color is the visual perceptual property corresponding in humans to the categories called red, yellow, green, etc. Color derives from the spectrum of light (distribution of light energy versus wavelength) interacting in the eye with the spectral sensitivities of the light receptors. Color categories and physical specifications of color are also associated with objects, materials, light sources, etc., based on their physical properties such as light absorption, reflection, or emission spectra. Typically, only features of the composition of light that are detectable by humans are included, thereby objectively relating the psychological phenomenon of color to its physical specification.
• Color and transparency are two distinct principles. For instance, something may visually appear perfectly clear and still colored. For instance, certain colored glass is entirely transparent to the eye and possesses a color. Similarly, something may be colorless and also clear or opaque. Colorless is defined as lacking all color. For instance, pure liquid water is clear and colorless. An article that is visually perceived as perfectly clear and as a color, for instance, blue, is reflecting the blue color while allowing all other wavelengths of light to pass through. When a viewer perceives white, the article will appear less transparent because all colors are being reflected back at the viewer and thus not passing through the article.
• U.S. Patent No. 5,677, 107 discloses a method for preparing and selectively coloring a three-dimensional article by adding or removing color.
• the coloring agent is photoresponsive and the method claimed is dependent on using a photoresponsive coloring agent.
• U.S. Patent No. 5,942,554 discloses a method of effecting color change in polymeric bodies of either thermal curable or photocurable resins.
• the color-changing compound is sensitive to acid produced during polymerization of the resin.
• the acid is produced from the initiating species which are activated by either light or temperature. The color change occurs when the coloring agent is exposed to the acid.
• U.S. Patent No. 6,664,024 discloses a photocurable resin composition for forming three-dimensional objects that can be selectively colored that utilizes a photoactivated coloring compound.
• U.S. Published Patent Application No. 2004/0076909 discloses a liquid resin composition for use in forming three-dimensional objects which comprises particles dispersed in the composition which are micro-capsules containing a photosensitive color changing composition.
• Dp depth of penetration
• Colorless or transparent resins typically possess a lower depth of penetration (Dp) than do equivalent colorless or transparent resins.
• Depth of penetration is a measure of how deep visible light or any actinic radiation can penetrate into a material. It is defined as the depth at which the intensity of the radiation inside the material falls to 1/e (or approximately 37%) of its original value at or just beneath the surface. If the Dp of the material becomes too low, the light cannot penetrate a layer of material deep enough to form a sufficiently cured layer. This disruption in the necessary photopolymerization process is especially apparent in opaque or deeply colored resins (such as black or dark blue), which necessarily possess a lower Dp.
• Black or nearly black resins have existed in additive fabrication applications operating via photopolymerization, such as stereolithography. However they have been notoriously difficult to operate in such additive fabrication applications for a variety of reasons. First, because of their inherent dark color and/or opacity, their associated Dp is less than that for ideal suitability in additive fabrication via photopolymerization. Even those with relatively less black color, their opacity and/or color necessitate an increased energy dose to undergo polymerization than do similarly-formulated clear, colorless resins.
• black resins for additive fabrication processes have been successfully used because of an additional difficulty associated with their use via photopolymerization.
• Such resins contain black or darkly colored pigments or dyes which inherently have a tendency to absorb most or all incoming light, such as the incoming light from a source of actinic radiation used to cure the resin in additive fabrication processes. This absorption reduces the amount of light available for the photoinitiators, thereby limiting the number of cationic and/or free-radical species generated, often to a level unacceptable for the required polymerization process.
• resins which use a latent coloring component to impart a dark or black color to the resin after curing do not allow for further color changes and are not reversible. Additionally, the color effect is not always imparted uniformly or with a desired color intensity.
• the first aspect of the instant claimed invention is a method of forming a three-dimensional article via additive fabrication comprising: (1) inducing an increase in a depth of penetration (Dp) of a radiation curable resin, thereby forming a radiation curable resin having an increased Dp; (2) establishing a layer of the radiation curable resin having the increased Dp; (3) exposing the layer imagewise to actinic radiation to form an imaged cross-section, thereby forming a cured layer; (4) forming a new layer of radiation curable resin having the increased Dp in contact with the cured layer; (5) exposing said new layer imagewise to actinic radiation to form an additional cured layer; and (6) repeating steps (4) and (5) a sufficient number of times in order to build up a three-dimensional article.
• Dp depth of penetration
• the second aspect of the instant claimed invention is a method of forming via additive fabrication a three-dimensional article capable of changing color comprising: (1) heating a liquid radiation curable resin, thereby forming a liquid radiation curable resin having an increased depth of penetration (Dp); (2) establishing a first liquid layer of the liquid radiation curable resin having the increased Dp; (3) exposing the first liquid layer imagewise to actinic radiation to form an imaged cross-section, thereby forming a first cured layer; (4) forming a new layer of liquid radiation curable resin having the increased Dp in contact with the first cured layer; (5) exposing said new layer imagewise to actinic radiation to form an additional cured layer; and (6) repeating steps (4) and (5) a sufficient number of times in order to build up a three-dimensional article; wherein the liquid radiation curable resin further comprises at least one thermochromic component having an activation temperature and a terminal activation temperature, such that the thermochromic component changes from a colored state to a partially colored state at the activation temperature,
• the third aspect of the instant claimed invention is a method of forming via additive fabrication a three-dimensional article capable of color or opacity change comprising: (1) inducing an at least temporary change in a depth of penetration (Dp) of a liquid radiation curable resin, thereby forming a liquid radiation curable resin having an at least temporarily modified Dp, wherein the temporary change in the Dp is occasioned by subjecting the liquid radiation curable resin to an alteration in an environmental condition selected from the group consisting of heat, light, pH, magnetism, pressure, and electric current; (2) establishing a first liquid layer of the liquid radiation curable resin having the at least temporarily modified Dp; (3) exposing the first liquid layer imagewise to actinic radiation to form an imaged cross-section, thereby forming a first cured layer; (4) forming a new layer of liquid radiation curable resin having the at least temporarily modified Dp in contact with the first cured layer; (5) exposing said new layer imagewise to actinic radiation to form an additional imaged cross-section; and
• the fourth aspect of the instant claimed invention is a three-dimensional object formed by the method of the first, second, or third aspect of the instant claimed invention.
• a visual effect initiator is defined as a component capable of incorporation into a liquid radiation curable resin that can be used to form three-dimensional objects and that is capable of imparting a change in the color or opacity of the liquid radiation curable resin, as well as the cured three-dimensional article made therefrom, in response to an alteration of an environmental condition.
• Such conditions include, as non-limiting examples, a change in temperature, light, pH, magnetism, pressure, and electric current.
• the activation point of a visual effect initiator is defined as the point along the range of a specific environmental condition at which the visual effect initiator begins to exhibit a color and/or opacity change.
• a visual effect initiator which is responsive to changes in pH might start to transform from transparent to an increased amount of opacity if the alkalinity of the solution in which it is immersed is increased to 8.0.
• a visual effect initiator which is responsive to changes in electric current might begin to transform from a red color towards a state of reduced red color if an electric current of above 10 milliamperes were imparted to the visual effect initiator.
• the terminal activation point of a visual effect initiator is defined as the point along the range of a specific environmental condition at which the visual effect initiator completes a color and/or opacity change.
• a visual effect initiator which is responsive to changes in pH might reach a completely opaque state (that is, approximately allowing 0% light transmission therethrough) if the alkalinity of the solution in which it is immersed is increased to 10.0. Further increases in the pH beyond this point would not yield further changes to the visual state of the resin into which the visual effect initiator were immersed.
• a visual effect initiator which is responsive to changes in electric current might reach a completely colorless state if the electric current of 15 milliamperes were imparted to the visual effect initiator. Further increases in the current would not yield additional changes to the visual state of the resin into which the visual effect initiator were immersed.
• a colored state is defined herein as a visual state in which a certain amount of color is exhibited by a visual effect initiator.
• a partially colorless state is defined as a visual state in which a visual effect initiator exhibits a measurably lower amount of color than it does in a colored state. That is, it absorbs a measurably lower amount of visible light in the region between approximately 390 nm and 780 nm.
• the terms colored state and partially colored state are relative, and may be different for different objects. However, in all such cases, for a given object, the amount of color exhibited during the partially colorless state is necessarily lower than it is in the colored state.
• a substantially colorless state is defined as a state in which the object (component, resin, or three-dimensional article) shows an absorbance of visible light in the region between approximately 390 nm and 780 nm of less than 0.2, measured on a sample having a thickness of 1 cm, when absorbance is measured on a UV-VIS spectrophotometer in accordance with ASTM El 164-94. Further methods of measuring color are discussed in US 20030149124, assigned to the Applicant, which is hereby incorporated by reference.
• thermochromic components constitute a non-limiting subset of such visual effect initiators.
• a thermochromic component is defined herein as a component capable of incorporation in a liquid radiation curable resin that changes the amount of color and/or opacity exhibited in response to a change in temperature.
• Thermochromic components have the ability to impart a change in the amount of color and/or opacity exhibited in the liquid radiation curable resin into which they are immersed, and similarly are capable of imparting a change in the amount of color and/or opacity exhibited in the three-dimensional part cured therefrom.
• the activation temperature of a thermochromic is defined as the temperature at which it begins to exhibit a color and/or opacity change.
• a thermochromic component which is capable of color change from black to colorless might appear black at temperatures of below 31 degrees Celsius. At this hypothetical activation temperature of 31 degrees Celsius, such a thermochromic component would begin to exhibit a color change from black to colorless.
• the terminal activation temperature of a thermochromic component is the temperature at which the color and/or opacity change is completed. Further changes in temperature beyond the terminal activation temperature in a direction away from the activation temperature will yield no further changes to the visual state of the thermochromic component.
• a thermochromic component which is capable of color change from black to colorless might appear black at temperatures of below 31 degrees Celsius. At its hypothetical activation temperature of 31 degrees Celsius, such a thermochromic component would begin to exhibit a color change from black to colorless. As the temperature is increased, the component would exhibit gradually decreasing amounts of black color. Finally, at a hypothetical terminal activation temperature of 35 degrees Celsius, such a thermochromic component would appear completely colorless.
• the locking temperature of a thermochromic component is the temperature at which any change in color and/or opacity will be permanent or semi-permanent. Permanent color and/or opacity change is irreversible. Semi-permanent color and/or opacity change is reversible under certain circumstances; i.e. to reverse the color change, the thermochromic component might have to be cooled to significantly below room temperature. Non- permanent color and/or opacity change is any change that occurs that is not permanent or semi-permanent. Non-permanent color and/or opacity change is reversible. Thermochromic components lacking a locking temperature are non-permanent and can impart reversible color and/or opacity changes into the liquid radiation curable resin into which they are immersed, along with the three-dimensional part cured therefrom.
• a thermally sensitive transparency modifier is a component capable of incorporation into a liquid radiation curable resin that has the ability to change the transparency of a liquid radiation curable resin or a three dimensional article made therefrom due to a change in temperature. The transparency is typically changed by modifying the light scattering properties of the selectively cured section of the three-dimensional article produced from a liquid radiation curable resin.
• a thermochromic component can also be a thermally sensitive transparency modifier and a thermally sensitive transparency modifier can also be a thermochromic component. In fact, even a component that is substantially thermochromic will often also affect the visual transparency of the three-dimensional article in some small way.
• a thermally sensitive visual effect initiator may be a thermochromic component, a thermally sensitive transparency modifier, or both.
• an object that is violet reflects light through a medium which is a vacuum of a wavelength of from 390 nm to 455 nm.
• blue is defined as from greater than 455 nm to 492 nm
• green is defined as from greater than 492 nm to 577 nm
• yellow is defined as from greater than 577 nm to 597 nm
• orange is defined as from greater than 597 nm to 622 nm
• red is defined as from greater than 622 nm to 780 nm.
• An object that is white reflects all visible light.
• a microcapsule is a particle of less than
• the heat of polymerization of the resin is the heat given off by the exothermic reaction of polymerization. Intensity is defined as the time-averaged power per unit area. Dose is the total power per unit area.
• the first aspect of the instant claimed invention is a method of forming a three-dimensional article via additive fabrication comprising: inducing an increase in a depth of penetration (Dp) of a radiation curable resin, thereby forming a radiation curable resin having an increased Dp; establishing a layer of the radiation curable resin having the increased Dp; exposing the layer imagewise to actinic radiation to form an imaged cross- section, thereby forming a cured layer; forming a new layer of radiation curable resin having the increased Dp in contact with the cured layer; exposing said new layer imagewise to actinic radiation to form an additional cured layer; and repeating the forming and exposing steps a sufficient number of times in order to build up a three-dimensional article.
• Dp depth of penetration
• 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.
• a resin which could form three-dimensional articles which gradually and reversibly changed in response to changing temperatures would be useful to determine at what points or locations a part cured by way of additive fabrication was heating up (perhaps due to increased friction), potentially indicating design flaws. Further, such "smart-parts" could provide such feedback without the need for expensive monitoring equipment, such as thermal imaging cameras. This would decrease cost and increase effectiveness of thermal testing currently performed in the automotive, aerospace, and nautical industries.
• this may be performed by increasing the intensity of the actinic radiation source, increasing the duration of time during which any given portion of the liquid radiation curable resin is exposed to such actinic radiation, by adjusting the focal parameters of the light source, or by altering the part's programmed layer thickness.
• the Dp of a given resin need not be static or immutable.
• a liquid radiation curable resin for additive fabrication By inducing certain changes in various environmental conditions to a liquid radiation curable resin for additive fabrication, inventors have discovered that it is possible, if at least temporarily, to alter that resin's Dp.
• resins with dynamic Dp values possess a visual effect initiator having an activation point.
• the visual effect initiator also possesses a terminal activation point.
• the visual effect initiator is a thermochromic component having an activation temperature.
• the thermochromic component also has a terminal activation temperature.
• the current would then be removed upon completion of the layer or part build, such that the desired aesthetic effects (in this case, a certain degree of opacity) could be restored and appreciated.
• This method would ensure that the liquid radiation curable resin could be modified to achieve maximum suitability for use in an additive fabrication process, without sacrificing the desired aesthetic qualities in a three-dimensional part cured therefrom.
• the method of forming a three-dimensional article via additive fabrication would incorporate liquid radiation curable resin possessing a thermochromic component having an activation temperature and a terminal activation temperature.
• the thermochromic component is black below its activation temperature, and gradually transitions from black to clear from between the activation temperature to the terminal activation temperature, and becomes substantially colorless at and above the terminal activation temperature.
• the thermochromic component would therefore necessarily impart a change in the resin's color, opacity, or both. This, in turn, would provide a concomitant increase in the resin's depth of penetration (Dp). It naturally follows from the foregoing that the Dp would increase inversely with the intensity of the black color exhibited in the resin.
• the temperature of the vat in which the liquid radiation curable resin for additive fabrication were stored could be controlled as an alternative means to control the Dp of the resin.
• the vat into which the resin were inserted one could adjust the energy- efficiency, accuracy, and speed with which the three-dimensional parts might be built, all without modifying cure dose, scan speed, focal parameters, or programmed layer thickness.
• thermochromic component transitions from a colored state of red, orange, yellow, green, blue, indigo, violet, or white, to a partially colorless state at its activation temperature, and to a substantially colorless state at its terminal activation temperature.
• thermochromic component transitions from an opaque state to a partially transparent state at its activation temperature, and to a substantially transparent state at its terminal activation temperature.
• thermochromic component transitions from a colored state of red, orange, yellow, green, blue, indigo, violet, white, or black, to a second colored state at its activation temperature, and to a third colored state at its terminal activation temperature.
• the second colored state is a starting point in a transition towards another color or the same color of somewhat different intensity.
• the third colored state is a finishing point in the transition towards another color or the same color of somewhat different intensity.
• a three-dimensional part has been formed from a liquid radiation curable resin via an additive fabrication according to the first aspect of the invention, it may be desirable to restore its appearance to the pre-Dp-increased visual state. Consistent with an embodiment of the method of the first aspect of the invention, this might be performed by reversing the change in the environmental condition upon the three-dimensional cured part that was originally imposed upon the liquid radiation curable resin during the part build. More specifically, a further (and opposite) change to the environmental condition would have to be imposed such that that condition were brought to below the activation point of the included visual effect initiator. This might be effectuated by, for example, an elimination of the magnetic force, pressure, or electric current originally applied to a liquid radiation curable resin.
• the liquid radiation curable composition for additive fabrication comprises a visual effect initiator which is a thermochromic component, and which exists as black at temperatures up to its activation temperature of about 20 degrees Celsius, more preferably about 30 degrees Celsius, more preferably 31 degrees Celsius.
• the thermochromic component will begin to fade gradually from partially colorless to substantially colorless when the terminal activation temperature has been reached at 41 degrees Celsius, more preferably 40 degrees Celsius, more preferably 35 degrees Celsius. Increases in temperature beyond its terminal activation point would not yield additional changes to the visual appearance.
• a three-dimensional article had been created, it would be possible to restore the original black appearance by cooling the article to a point back below the activation temperature. What had started as a black resin, and became an at least partially colorless resin (with an increased Dp) during a part build in order to improve suitability for use in an additive fabrication process, again appears black, consistent with the original aesthetic design choice.
• the activation temperature of the thermochromic component is from -15 degrees Celsius to about 75 degrees Celsius, more preferably from about 20 degrees Celsius to about 65 degrees Celsius, more preferably from about 30 degrees Celsius to about 43 degrees Celsius, more preferably from about 31 degrees Celsius to about 35 degrees Celsius.
• the difference between the activation temperature and the terminal activation temperature is from about 0 to about 50 degrees Celsius, more preferably from about 1 to about 25 degrees Celsius, more preferably from about 2 to about 10 degrees Celsius.
• the visual effect initiator is non-permanent and reversible.
• the visual effect initiator is a thermochromic component that does not possess a locking temperature; that is, the changes in color or opacity are always reversible, regardless the amount of heat applied or removed.
• the visual effect initiator is reversible or the thermochromic component does not possess a locking temperature, it is possible to repeatedly apply and remove heat to above and below the activation point to produce a desired, non-permanent visual effect.
• the visual effects caused by certain visual effect initiators according to the present invention continue to be able to be imparted to the three-dimensional article even after the additive fabrication process has completed.
• thermochromic component may be employed in prototyping applications for the automotive, aerospace, or nautical industries. Engineers might fashion a three-dimensional article from such resin, and then apply it to test mechanical devices.
• the reversible and changeable nature of the resin would indicate relative locations of higher and lower temperature during operation, perhaps due to friction or proximity to heat generating componentry. Flaws or weaknesses in a particular design could quickly be identified in realtime, and all without the need for expensive thermal imaging equipment.
• resins could be incorporated into the fabrication of end-use components, and would provide an intrinsic indicator that a component is perhaps overheating or needs to be replaced.
• Resins incorporating visual effect initiators are also advantageous in that they can be used with a hybrid curing system.
• a hybrid curing system is a curing system consisting of free-radical and cationic photoinitiators along with free-radical and cationic polymerizable components.
• a non-hybrid system is subject to irradiation in order to form a three-dimensional article, the formed three-dimensional article possesses undesirable physical properties.
• Hybrid systems allow for three-dimensional articles that possess excellent mechanical properties.
• the origin of the change in visual state due to the presence of a visual effect initiator can occur from changes in light absorption, light reflection, and/or light scattering with temperature.
• Visual effect initiators can be present in various types of compounds, and may contain microcapsules which shield a change in a pigment or dye until an activation point has been reached.
• the visual effect initiator is a thermochromic component.
• the thermochromic component contains a microcapsule that further includes a heat-sensitive component or components, such as pigments or dyes.
• the component contained in the microcapsule is a leuco dye, which possesses two forms, one of which is colorless above the activation temperature or terminal activation temperature.
• thermochromism in polymers can be found in Thermochromic Phenomena in Polymers, ⁇ 2008 Arno Seeboth and Detlef L5tzsch. Additional information concerning thermochromic compounds can be found in Organic Photochromic and Thermochromic Compounds, Volume 2, ⁇ 1999 John C. Crano and Robert J. Guglielmetti.
• thermochromic components can be found in US Patent Nos.
• thermochromic compounds can be found in, for instance, Japanese patent publications 2005-220201, 2007- 332232, 2003-313453, 2001-242249, 10-152638, 03-076783, 03-076786, and 1522236.
• Examples of a commercially available thermochromic component are the YT-, OT-, MT-, RT-, GT-, ST-, BT-, VT-, and LT- series thermochromic pigments sold through Kelly Chemical Corporation, in Taipei, Taiwan.
• thermochromic pigments sold through Kelly possess a particle size distribution of from 1 to 6 micrometers, and possess approximately 50 to 80% by weight of methyl stearate, from approximately 1 to 5% by weight of a melamine formaldehyde resin, from approximately 5 to 15% by weight of pH control additives, and from approximately 2 to 10% by weight of a color agent.
• the visual effect initiator is halochromic.
• Halochromic components change color based pH. Alone, such components are not effective with a hybrid curing system unless they can be appropriately contained and shielded from the acid present during cationic polymerization. If the halochromic components are not appropriately contained, for instance in an acid-impermeable microcapsule, the acid created from the cationic photoinitiating system will react with the halochromic components and cause the halochromic components to prematurely change color.
• a non-hybrid curing system is used.
• a hybrid curing system is used.
• thermochromic component does not undergo any significant visual color or transparency change in response to the acid produced during the polymerization of the liquid radiation curable resin.
• the visual effect initiator comprises an acid- impermeable microcapsule. In another embodiment the visual effect initiator comprises a microcapsule that is substantially impermeable to acid.
• the visual effect initiator component is a thermochromic component which also comprises a halochromic component contained within an acid- impermeable, or substantially acid-impermeable microcapsule.
• a thermochromic component is activated upon heating to separate a pH control agent from a halochromic dye.
• the microcapsules exhibit no color, wherein upon cooling, they exhibit the specified color, for example red, orange, yellow, green, blue, indigo, violet, white, or black. In such a configuration, the color change is reversible and non-permanent.
• the visual effect initiators of the present invention can be incorporated into a liquid radiation curable resin without any substantial reduction in the mechanical properties of the resin.
• the visual effect initiator is incorporated into a liquid radiation curable resin by mixing the visual effect initiator into the liquid radiation curable resin.
• the visual effect initiator is incorporated into a liquid radiation curable resin by mixing the liquid radiation curable resin into the visual effect initiator.
• the visual effect initiator is incorporated into the liquid radiation curable resin along with the solvent which contains the visual effect initiator and, in another embodiment, without the solvent.
• the visual effect initiator may be incorporated into the liquid radiation curable resin in any suitable amount, and may be chosen singly or in combination of one or more of the types enumerated herein.
• the amount of the visual effect initiator is present in an amount from about 0.005 wt% to about 10 wt%.
• the amount of visual effect initiator is present in an amount from about 0.005 wt% to about 5 wt%.
• the amount of visual effect initiator is present in an amount from about 0.005 wt% to about 2 wt%.
• the amount of visual effect initiator is present in an amount from about 0.005 wt% to about 1 wt%.
• the amount of visual effect initiator is present in an amount from about 0.01 wt% to about 1 wt%. In another embodiment, the amount of visual effect initiator is present in an amount from about 0.05 wt% to about 5 wt%. In another embodiment, the amount of visual effect initiator is present in an amount from about 0.5 wt% to about 1 wt%.
• the amount of the thermochromic component is present in an amount from about 0.005 wt% to about 10 wt%. In another embodiment, the amount of thermochromic component is present in an amount from about 0.005 wt% to about 5 wt%. In another embodiment, the amount of thermochromic component is present in an amount from about 0.005 wt% to about 2 wt%. In another embodiment, the amount of thermochromic component is present in an amount from about 0.005 wt% to about 1 wt%. In another embodiment, the amount of thermochromic component is present in an amount from about 0.01 wt% to about 1 wt%.
• thermochromic component is present in an amount from about 0.05 wt% to about 5 wt%. In another embodiment, the amount of thermochromic component is present in an amount from about 0.5 wt% to about 1 wt%. [0068] In an embodiment, the visual effect initiator is incorporated into Somos®
• Somos® WaterClear® Ultra 10122 liquid radiation curable resin.
• the visual effect initiator is incorporated into Somos® Watershed® XC 1 1122 liquid radiation curable resin.
• Somos® WaterClear® Ultra 10122 and Somos® Watershed® XC 1 1122 are liquid radiation curable resins manufactured by DSM Desotech, Inc. Both Somos® WaterClear® Ultra 10122 and Somos® Watershed® XC 1 1 122 are substantially colorless and transparent after full cure.
• Somos® WaterClear® Ultra 10122 comprises between 45-70 wt% of epoxies, 10-25 wt% of acrylates, 5-15 wt% of oxetane, 5-15 wt% of polyol, 1-15 wt% of photoinitiators, and 0-10 wt% of additives.
• Somos® Watershed® XC 11 122 comprises between 45-70 wt% of epoxies, 5-20 wt% of acrylate, 10-25 wt% of oxetane, 1-15 wt% of photoinitiators, and 0-10 wt% of additives.
• the visual effect initiator is incorporated into a filled resin, such as Somos® PerFORMTM, NanoTool® HP, or NanoTool®.
• a filled resin such as Somos® PerFORMTM, NanoTool® HP, or NanoTool®.
• Such filled resins are typically milky white and at least partially opaque.
• such filled liquid radiation curable resins for additive fabrication include suitable amounts of a cationically polymerizable component, a free-radical polymerizable component, a cationic photoinitiator, a free-radical photoinitiator, and a filler component.
• the filler component can include any suitable amount of inorganic filler or combination of inorganic fillers, for example, in an amount up to about 80 wt% of the resin composition, in certain embodiments from about 30 to about 80 wt% of the resin composition, and in further embodiments from about 50 to about 70 wt% of the resin composition. If the amount of the filler is too small, the water and heat resistant properties, durability, and structural rigidity of the molds made of the prepared resin composition do not increase sufficiently. On the other hand, if the amount of the filler component is too large, various problems might emerge. First, the fluidity of the prepared resin composition becomes too low, rendering it difficult or even un-workable in additive fabrication processes. Further, the ability to adjust the Dp of the resin to suitable levels is compromised by the excessive presence of light scattering and/or absorbing particles. This can also affect the time needed for radiation curing of the resin composition, causing the processing time to increase substantially.
• thermochromic components are additives for additive fabrication.
• desirable mechanical properties such as a high modulus and stiffness.
• thermochromic components such as thermochromic components
• the friction generated by wind traversing over select surfaces would be evidenced by the portions along a three-dimensional article in which the thermochromic component is heated above its activation temperature or terminal activation temperature, allowing engineers to assess in real time areas of relative higher loading.
• the liquid radiation curable resin comprises at least one visual effect initiator which is a transparency modifier.
• a transparency modifier may also be a thermochromic component, or it may be activated by response to other changes in other environmental conditions, such as light, pressure, magnetism, pH, or electric current.
• the transparency modifier may operate by modifying how light passes through the three- dimensional article. This light scattering effect causes the article to become opaque or substantially opaque in certain sections. If the three-dimensional article is clear and colorless in sections where the transparency modifier is not activated, the article may appear to be white in sections where the transparency has been modified. This is because the modification to the transparency causes light to reflect back at the viewer, thus producing the white color.
• the amount of transparency modifier is present in an amount from about 0.005 wt% to about 5 wt%. In another embodiment, the amount of transparency modifier is present in an amount from about 0.005 wt% to about 3 wt%. In another embodiment, the amount of transparency modifier is present in an amount from about 0.005 wt% to about 2 wt%. In another embodiment, the amount of transparency modifier is present in an amount from about 0.005 wt% to about 1 wt%. In another embodiment, the amount of transparency modifier is present in an amount from about 0.01 wt% to about 5 wt%. In another embodiment, the amount of transparency modifier is present in an amount from about 0.05 wt% to about 5 wt%. In another embodiment, the amount of transparency modifier is present in an amount from about 0.01 wt% to about 2 wt%.
• the transparency modifier is incorporated into a substantially clear liquid radiation curable resin.
• the transparency modifier is incorporated into a substantially clear and colorless liquid radiation curable resin.
• more than one visual effect initiator is incorporated into the liquid radiation curable resin composition. In one embodiment, each of the more than one visual effect initiators has the same activation and/or locking temperature.
• the liquid radiation curable resin comprises a visual effect initiator, a free radical polymerizable component, and a photoinitiating system capable of initiating free radical polymerization.
• the liquid radiation curable resin comprises a visual effect initiator, a cationic polymerizable component, and a photoinitiating system capable of initiating cationic polymerization.
• the liquid radiation curable resin comprises a visual effect initiator, a free radical polymerizable component, a photoinitiating system capable of initiating free radical polymerization, a cationic polymerizable component, and a photoinitiating system capable of initiating cationic polymerization.
• the liquid radiation curable resin of the invention may comprise 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 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 -hydroxy ethyl (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, isobuty
• polyfunctional 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-yl]methyl 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 trimethylolpropane tri(meth)acryl
• the polyfunctional (meth)acrylates of the polyfunctional component 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-[(l- oxoallyl)oxy]ethyl]-5-ethyl-l,3-dioxan-5-yl]methyl acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)crylate, propoxylated trimethylolpropane
• the free-radical polymerizable component is selected from the group consisting of bisphenol A diglycidyl ether diacrylate, dicyclopentadiene dimethanol diacrylate, [2-[l, l-dimethyl-2-[(l-oxoallyl)oxy]ethyl]-5-ethyl-l,3-dioxan-5- yljmethyl acrylate, dipentaerythritol monohydroxypentaacrylate, propoxylated trimethylolpropane triacrylate, and propoxylated neopentyl glycol diacrylate, and any combination thereof.
• the liquid radiation curable resin compositions of the invention include one or more of bisphenol A diglycidyl ether di(meth)acrylate, dicyclopentadiene dimethanol di(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, and/or propoxylated neopentyl glycol di(meth)acrylate, and more specifically one or more of bisphenol A diglycidyl ether diacrylate, dicyclopentadiene dimethanol diacrylate, dipentaerythritol monohydroxypentaacrylate, propoxylated trimethylolpropane triacrylate, and/or propoxylated neopentyl glycol diacrylate.
• the liquid radiation curable resin composition can include any suitable amount of the free-radical polymerizable component, for example, in certain embodiments, in an amount up to about 95% by weight of the composition, in certain embodiments, up to about 50% by weight of the composition, and in further embodiments from about 5% to about 25% by weight of the composition.
• the liquid radiation curable resin composition of the present invention includes a photoinitiating system.
• the photoinitiating system can be a free- radical photoinitiator or a cationic photoinitiator or a photoinitiator that contains both free- radical initiating function and cationic initiating functions on the same molecule.
• 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 ⁇ ".
• the Norrish type II photoinitiators require a hydrogen donor, which serves as the free radical source.
• the Norrish 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 composition 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 composition 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, Ws(2,4,6-trimethylbenzoyl)-phenylphosphineoxide, 2-methyl-l-[4- (methylthio)phenyl]-2-morpholinopropanone-l, 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,
• suitable free-radical photoinitiators absorbing in this area include: benzoylphosphine oxides, such as, for example, 2,4,6-trimethylbenzoyl diphenylphosphine oxide (Lucirin TPO from BASF) and 2,4,6- trimethylbenzoyl phenyl, ethoxy phosphine oxide (Lucirin TPO-L from BASF), bis(2,4,6- trimethylbenzoyl)-phenylphosphineoxide (Irgacure 819 or BAPO from Ciba), 2-methyl-l-[4- (methylthio)phenyl]-2-morpholinopropanone-l (Irgacure 907 from Ciba), 2-benzyl-2- (dimethylamino)-l-[4-(4-morpholin
• photosensitizers are useful in conjunction with photoinitiators in effecting cure with light sources emitting in this wavelength range.
• suitable photosensitizers include: anthraquinones, such as 2-methylanthraquinone, 2- ethylanthraquinone, 2-tertbutylanthraquinone, 1-chloroanthraquinone, and 2- amylanthraquinone, thioxanthones and xanthones, such as isopropyl thioxanthone, 2- chlorothioxanthone, 2,4-diethylthioxanthone, and l-chloro-4-propoxythioxanthone, methyl benzoyl formate (Darocur MBF from Ciba), methyl-2-benzoyl benzoate (Chivacure OMB from Chitec), 4-benzoyl-4'-methyl diphenyl sulphide (Chivacure BMS
• UV light sources it is possible for UV light sources to be designed to emit light at shorter wavelengths.
• a photosensitizer with a photoinitiator.
• photosensitizers such as those previously listed are present in the formulation, other photoinitiators absorbing at shorter wavelengths can be used.
• photoinitiators include: benzophenones, such as benzophenone, 4-methyl benzophenone, 2,4,6-trimethyl benzophenone, and dimethoxybenzophenone, and , 1-hydroxyphenyl ketones, such as 1-hydroxycyclohexyl phenyl ketone, phenyl (l-hydroxyisopropyl)ketone, 2 -hydroxy - l-[4-(2-hroxyethoxy) phenyl]-2-methyl-l-propanone, and 4-isopropylphenyl(l- hydroxyisopropyl)ketone, benzil dimethyl ketal, and oligo-[2-hydroxy-2-methyl-l-[4-(l- methylvinyl)phenyl] propanone] (Esacure KIP 150 from Lamberti).
• benzophenones such as benzophenone, 4-methyl benzophenone, 2,4,6-trimethyl benzophenone, and dimethoxybenzophenone
• Light sources can also be designed to emit visible light.
• suitable free radical photoinitiators include: camphorquinone, 4,4'- bis(diethylamino) benzophenone (Chivacure EMK from Chitec), 4,4'-bis( ,N'-dimethylamino) benzophenone (Michler's ketone), bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (Irgacure 819 or BAPO from Ciba), metallocenes such as bis (eta 5-2-4-cyclopentadien-l-yl) bis [2,6-difluoro-3-(lH- pyrrol-l-yl) phenyl] titanium (Irgacure 784 from Ciba), and the visible light photo initiators from Spectra Group Limited, Inc. such as H-Nu 470, H-
• the liquid radiation curable resin composition can include any suitable amount of the free-radical photoinitiator, for example, in certain embodiments, in an amount up to about 15% by weight of the composition, in certain embodiments, up to about 10% by weight of the composition, and in further embodiments from about 1% to about 5% by weight of the composition.
• the amount of free-radical photoinitiator is present in an amount of from about 1 wt% to about 8 wt% of the total composition, more preferably from about 1 wt% to about 6 wt% of the total composition.
• liquid radiation curable resin compositions 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.
• 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 vinyl ether compounds, and any combination thereof.
• Examples of cationically polymerizable components include cyclic ether compounds such as epoxy compounds and oxetanes, cyclic lactone compounds, cyclic acetal compounds, cyclic thioether compounds, spiro orthoester compounds, and vinylether compounds.
• cationically 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- 1 ,4-dioxane, bis(3 ,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene oxide, 4-vinylepoxycyclo
• dendritic polymers may contain one type of polymerizable functional group or different types of polymerizable functional groups, for example, epoxy and oxetane functions.
• the cationic polymerizable component is at least one selected from the group consisting of a cycloaliphatic epoxy and an oxetane.
• the cationic polymerizable component is an oxetane, for example, an oxetane containing 2 or more than 2 oxetane groups.
• the cationic polymerizable component is a cycloaliphatic epoxy, for example, a cycloaliphatic epoxy with 2 or more than 2 epoxy groups.
• 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 EPONEXTM 1510 from Hexion), 1,4- cyclohexanedimethanol diglycidyl ether (available as HELOXYTM 107 from Hexion), a mixture of dicyclohexyl diepoxide and nanosilica (available as NANOPOXTM), and any combination thereof.
• CELLOXIDETM 202 IP from Daicel Chemical, or as CYRACURETM UVR-6105 from Dow Chemical
• EPONEXTM 1510 from Hexion
• 1,4- cyclohexanedimethanol diglycidyl ether available as HELOXYTM 107 from Hexion
• the liquid radiation curable resin composition can include any suitable amount of the cationic polymerizable component, for example, in certain embodiments, in an amount an amount up to about 95% by weight of the composition, in certain embodiments, up to about 50% by weight of the composition, and in further embodiments from about 5% to about 25% by weight of the composition. In other embodiments the amount of cationically polymerizable components if from about 10 wt% to about 80 wt% of the total composition.
• the polymerizable component of the liquid radiation curable resin composition is polymerizable by both free-radical polymerization and cationic polymerization.
• An example of such a polymerizable component is a vinyloxy compound, for example, one selected from the group consisting of bis(4- vinyloxybutyl)isophthalate, tris(4-vinyloxybutyl) trimellitate, and combinations thereof.
• the liquid radiation curable resin composition includes a photoinitiating system that is a photoinitiator having both cationic initiating function and free radical initiating function.
• the liquid radiation curable resin composition includes a cationic photoinitiator. The cationic photoinitiator generates photoacids upon irradiation of light. They generate Bronsted or Lewis acids upon irradiation.
• the cationic photoinitiator triaryl sulfonium tetrakis(pentafluorophenyl) borate is available from Bayer/Ciba. Triaryl sulfonium tetrakis(pentafluorophenyl) borate can be used either as the only cationic photoinitiator present in the photocurable composition or in combination with other cationic photoinitiators. In an embodiment, triaryl sulfonium tetrakis(pentafluorophenyl) borate is used in combination with sulfonium antimonate type photoinitiators.
• the liquid radiation curable resin composition includes a cationic photoinitiator.
• the cationic photoinitiator initiates cationic ring-opening polymerization upon irradiation of light.
• any suitable cationic photoinitiator can be used, for example, those with cations selected from the group consisting of onium salts, halonium salts, iodosyl salts, selenium salts, sulfonium salts, sulfoxonium salts, diazonium salts, metallocene salts, isoquinolinium salts, phosphonium salts, arsonium salts, tropylium salts, dialkylphenacylsulfonium salts, thiopyrilium salts, diaryl iodonium salts, triaryl sulfonium salts, ferrocenes, di(cyclopentadienyliron)arene salt compounds, and pyridinium 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, 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 US761 1817, US7230122, US201 1/0039205, US2009/0182172, US7678528, EP2308865, WO2010046240, or EP2218715.
• 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 -, B(C 6 H 4 CF 3 ) 4 , B(C 6 H 3 F 2 V, B[C 6 F 4 -4(CF 3 )] 4 -, Ga(C 6 F 5 f, [(C 6 F 5 ) 3 B-C 3 H 3 N 2 - B(C 6 F 5 ) 3 ] " , [(C 6 F5) 3 B-NH 2 -B(C 6 F5) 3 ] " , tetrakis(3,5-difluoro-4-alkyloxyphenyl)borate, tetrakis(2,3,5,6-tetrafluoro-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(C6F5) 4 ⁇ , [B(CF3) 4 ] " , 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 useful for curing at 300-475 nm, particularly at 365 nm UV light, without a sensitizer include 4-[4-(3- chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium hexafluoroantimonate, 4-[4- (3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium
• Preferred cationic photoinitiators include, either alone or in a mixture: bis[4- diphenylsulfoniumphenyl] sulfide bishexafluoroantimonate; thiophenoxyphenylsulfonium 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), and tris(4-(4- acetylphenyl)thiophenyl)sulfonium hexafluoro
• 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 10% by weight of the composition, in certain embodiments, up to about 5% by weight of the composition, and in further embodiments from about 0.1% to about 5% by weight of the composition.
• the amount of cationic photoinitiator is from about 0.2 wt% to about 4 wt% of the total composition, and in other embodiments from about 0.5 wt% to about 3 wt%.
• the above ranges are particularly suitable for use with epoxy monomers.
• the liquid radiation curable resin composition it is desirable for the liquid radiation curable resin composition to 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 rd Ed., 1991, page 222.
• photosensitizers 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, 9, 10- diethoxyanthracene, 9, 10-dimethoxyanthracene, 9, 10-dipropoxyanthracene, 9, 10- dibutyloxyanthracene, 9-anthracenemethanol acetate, 2-ethyl-9, 10-dimethoxyanthracene, 2- methyl-9, 10-dimethoxyanthracene, 2-t-butyl-9, 10-dimethoxyanthracene, 2-ethyl-9, 10- diethoxyanthracene and 2-methyl-9, 10-diethoxyanthracene, anthracene, anthraquinones, 2- methylanthraquinone, 2-ethylan
• photosensitizers are useful in combination with photoinitiators in effecting cure with light sources emitting in the wavelength range of 300-475 nm.
• suitable photosensitizers include: anthraquinones, such as 2-methylanthraquinone, 2- ethylanthraquinone, 2-tertbutylanthraquinone, 1-chloroanthraquinone, and 2- amylanthraquinone, thioxanthones and xanthones, such as isopropyl thioxanthone, 2- chlorothioxanthone, 2,4-diethylthioxanthone, and l-chloro-4-propoxythioxanthone, methyl benzoyl formate (Darocur MBF from Ciba), methyl-2-benzoyl benzoate (Chivacure OMB from Chitec), 4-benzoyl-4'-methyl diphenyl sulphide
• 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
• the liquid radiation curable resin composition can include any suitable amount of the photosensitizer, for example, in certain embodiments, in an amount up to about 10% by weight of the composition, in certain embodiments, up to about 5% by weight of the composition, and in further embodiments from about 0.05% to about 2% by weight of the composition.
• photoinitiators absorbing at shorter wavelengths
• photoinitiators include: benzophenones, such as benzophenone, 4-methyl benzophenone, 2,4,6-trimethyl benzophenone, and dimethoxybenzophenone, and 1-hydroxyphenyl ketones, such as 1-hydroxycyclohexyl phenyl ketone, phenyl (l-hydroxyisopropyl)ketone, 2-hydroxy-l-[4-(2-hydroxyethoxy) phenyl]-2- methyl- 1 -propanone, and 4-isopropylphenyl(l-hydroxyisopropyl)ketone, benzil dimethyl ketal, and oligo-[2-hydroxy-2-methyl-l-[4-(l-methylvinyl)phenyl] propanone] (Esacure KIP 150 from Lamberti).
• benzophenones such as benzophenone, 4-methyl benzophenone, 2,4,6-trimethyl benzophenone, and dimethoxybenzoph
• Light sources that emit visible light are also known.
• suitable photoinitiators include: camphorquinone, 4,4'- te(diethylamino) benzophenone (Chivacure EMK from Chitec), 4,4'-/ra(N,N'-dimethylamino) benzophenone (Michler's ketone), /ro(2,4,6-trimethylbenzoyl)-phenylphosphineoxide (Irgacure 819 or BAPO from Ciba), metallocenes such as bis(eta 5-2-4-cyclopentadien-l-yl) fo ' s[2,6-difluoro- 3-(lH-pyrrol-l-yl) phenyl] titanium (Irgacure 784 from Ciba), and the visible light
• a photosensitizer or co-initiator may be used to improve the activity of the cationic photoinitiator. It is for either increasing the rate of photoinitiated polymerization or shifting the wavelength at which polymerization occurs.
• the sensitizer used in combination with the above-mentioned cationic photoinitiator is not particularly limited.
• a variety of compounds can be used as photosensitizers, including heterocyclic and fused-ring aromatic hydrocarbons, organic dyes, and aromatic ketones. Examples of 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 Polymerization” in Chemistry & technology of UV & EB formulation for coatings, inks & paints. Volume III, Photoinitiators for free radical and cationic polymerization, by K. Dietliker; [Ed. by P.K.T. Oldring], SITA Technology Ltd, London, 1991.
• Specific examples include polyaromatic hydrocarbons and their derivatives such as anthracene, pyrene, perylene and their derivatives, thioxanthones, a- hydroxyalkylphenones, 4-benzoyl-4'-methyldiphenyl sulfide, acridine orange, and benzo flavin.
• cationic photoinitiators include, for example, onium salts with anions of weak nucleophilicity.
• onium salts with anions of weak nucleophilicity examples are halonium salts, iodosyl salts or sulfonium salts, such as are described in published European patent application EP 153904 and WO 98/28663, sulfoxonium salts, such as described, for example, in published European patent applications EP 35969, 44274, 54509, and 164314, or diazonium salts, such as described, for example, in U.S. Pat. Nos. 3,708,296 and 5,002,856. All eight of these disclosures are hereby incorporated in their entirety by reference.
• Other cationic photoinitiators are metallocene salts, such as described, for example, in published European applications EP 94914 and
• Suitable ferrocene type cationic photoinitiators include, for example, di(cyclopentadienyliron)arene salt compounds of formula (I) as disclosed in Chinese Patent
• anion MXn is selected from BF4, PF6, SbF6, AsF6, (C6F5)4B, C104, CF3S03, FS03, CH3S03, C4F9S03, and Ar is a fused ring or polycyclic arene.
• ferrocene type cationic photoinitiators include, for example,(i ⁇
• ferrocenium dication salts e.g., biphenyl bis[( -cyclopentadienyl) iron] hexafluorophosphate ([bis(Cp-Fe)-biphenyl] (PF6)2) and straight cyclopentadien-iron- biphenyl hexafluorophosphate ([Cp-Fe-biphenyl]+PF6-) as disclosed in Chinese J. Chem.
• alkoxy-substituted ferrocenium salts for example, [cyclopendadien-Fe-anisole]PF6, [cyclopendadien-Fe- anisole]BF4, [cyclopendadien-Fe-diphenylether]PF6, [cyclo-pendadien-Fe- diphenylether]BF4, and [cyclopendadien-Fe-diethoxy-benzene]PF6, as disclosed in Chinese J.
• cyclopentadiene-iron-arene tetrafluoroborates for example, cyclopentadiene-iron-naphthalene tetrafluoroborate ([Cp-Fe-Naph] BF4) salt, as disclosed in Imaging Science J (2003), 51(4), 247-253; ferrocenyl tetrafluoroborate ([Cp-Fe- CP]BF4), as disclosed in Ganguang Kexue Yu Guang Huaxue (2003), 21(1), 46-52; [CpFe ⁇
• Suitable onium type cationic photoinitiators include, for example, iodonium and sulfonium salts, as disclosed in Japanese Patent JP 2006151852.
• Other illustrative onium type photoinitiators include, for example, onium salts such as, diaryliodonium salts, triarylsulfonium salts, aryl-diazonium salts, ferrocenium salts, diarylsulfoxonium salts, diaryl-iodoxonium salts, triaryl-sulfoxonium salts, dialkylphenacyl-sulfonium salts, dialkylhydroxy-phenylsulfonium salts, phenacyl-triarylphosphonium salts, and phenacyl salts of heterocyclic nitrogen-containing compounds, as disclosed in U.S.
• BPEA Photoactive allyl ammonium salt
• Illustrative iodonium type cationic photoinitiators include, for example, diaryliodonium salts having counterions like hexafluoro-phosphate and the like, such as, for example, (4-n-pentadecyloxy-phenyl)phenyliodonium hexa-fluoroantimonate, as disclosed in US2006041032; diphenyliodonium hexafluorophosphate, as disclosed in US4394403 and Macromolecules (2008), 41(2), 295-297; diphenyliodonium ions as disclosed in Polymer (1993), 34(2), 426-8; Diphenyliodonium salt with boron tetrafluoride (Ph2I+ BF4-), as disclosed in Yingyong Huaxue (1990), 7(3), 54-56; SR-1012, a diaryldiodonium salt, as disclosed in Nuclear Inst.
• diaryliodonium salts e.g., 4,4'-di-tert-butyldiphenyl-iodonium hexafluoroarsenate, as disclosed in J Polymr Sci, Polymr Chem Edition (1978), 16(10), 2441-2451;
• Diaryliodonium salts containing complex metal halide anions such as diphenyliodonium fluoroborate, as disclosed in J Polymr Sci, Poly Sympos (1976), 56, 383-95; and any combination thereof.
• Illustrative sulfonium type cationic photoinitiators include, for example, UVI
• Rl-2 F
• R3 isopropyl
• R4 H
• X PF6, as disclosed in Japanese patent JP10101718
• thioxanthone-based sulfonium salts e.g., of the formula:
• Suitable pyridinium type cationic photoinitiators include, for example, N- ethoxy 2-methylpyridinium hexafluorophosphate (EMP+ PF6-), as disclosed in Turkish J of Chemistry (1993), 17(1), 44-49; Charge-transfer complexes of pyridinium salts and aromatic electron donors (hexamethyl-benzene and 1 ,2,4-trimethyoxy -benzene), as disclosed in Polymer (1994), 35(1 1), 2428-31 ; N,N'-diethoxy-4,4'-azobis(pyridinium) hexafluorophosphate (DEAP), as disclosed in Macromolecular Rapid Comm (2008), 29(1 1), 892-896; and any combination thereof.
• EMP+ PF6- N- ethoxy 2-methylpyridinium hexafluorophosphate
• EMP+ PF6- Charge-transfer complexes of pyridinium salts and aromatic electron donors (
• Suitable cationic photoinitiators include, for example, Acylgermane based photoinitiator in the presence of onium salts, e.g., benzoyltrimethylgermane (BTG) and onium salts, such as diphenyl-iodonium hexafluorophosphate (Ph2I+PF6-) or N-ethoxy-2- methyl-pyridinium hexafluorophosphate (EMP+PF6-), as disclosed in Macromolecules (2008), 41(18), 6714-6718; Di-Ph diselenide (DPDS), as disclosed in Macromolecular Symposia (2006), 240, 186-193; N-phenacyl-N,N-dimethyl-anilinium hexafluoroantimonate (PDA+SbF6-), as disclosed in Macromol Rapid Comm (2002), 23(9), 567-570; Synergistic blends of: diaryliodonium hexa
• Suitable cationic photoinitiators include, for example, triarylsulfonium salts such as triarylsulfonium borates modified for absorbing long wavelength UV.
• modified borates include, for example, SP-300 available from Denka, tris(4-(4-acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate (GSID4480-1 or Irgacure PAG-290) available from Ciba/BASF, and those photoinitiators disclosed in WO1999028295; WO2004029037; WO2009057600; US6368769 WO2009047105; WO2009047151; WO2009047152; US 20090208872; and US 7611817.
• Preferred cationic photoinitiators include a mixture of: bis [4- diphenylsulfoniumphenyl] sulfide bishexafluoroantimonate; thiophenoxyphenylsulfonium hexafluoroantimonate (available as Chivacure 1176 from Chitec); tris(4-(4- acetylphenyl)thiophenyl)sulfonium tetrakis(pentafluorophenyl)borate (GSID4480-1 from Ciba/BASF), iodonium, [4-( 1 -methylethyl)phenyl](4-methylphenyl)-, tetrakis(pentafluorophenyl)borate (available as Rhodorsil 2074 from Rhodia), 4-[4-(2- chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium hex
• the liquid radiation curable resin composition can include any suitable amount of the cationic photoinitiator, for example, in certain embodiments, in an amount an amount up to about 50% by weight of the composition, in certain embodiments, up to about 20% by weight of the composition, and in further embodiments from about 1% to about 10% by weight of the composition.
• the amount of cationic photoinitiator is from about 0.25 wt% to about 8 wt% of the total composition, more preferably from about 1 wt% to about 6 wt%. In an embodiment, the above ranges are particularly suitable for use with epoxy monomers.
• the liquid radiation curable resin composition can further include a chain transfer agent, particularly a chain transfer agent for a cationic monomer.
• the chain transfer agent has a functional group containing active hydrogen. Examples of the active hydrogen-containing functional group include an amino group, an amide group, a hydroxyl group, a sulfo group, and a thiol group.
• the chain transfer agent terminates the propagation of one type of polymerization, i.e., either cationic polymerization or free-radical polymerization and initiates a different type of polymerization, i.e., either free-radical polymerization or cationic polymerization.
• chain transfer to a different monomer is a preferred mechanism.
• chain transfer tends to produce branched molecules or crosslinked molecules.
• chain transfer offers a way of controlling the molecular weight distribution, crosslink density, thermal properties, and/or mechanical properties of the cured resin composition.
• the chain transfer agent for a cationic polymerizable component is a hydroxyl-containing compound, such as a compound containing 2 or more than 2 hydroxyl-groups.
• the chain transfer agent is selected from the group consisting of a polyether polyol, polyester polyol, polycarbonate polyol, ethoxylated or propoxylated aliphatic or aromatic compounds having hydroxyl groups, dendritic polyols, hyperbranched polyols.
• An example of a polyether polyol is a polyether polyol comprising an alkoxy ether group of the formula [(CH 2 )nO] m , wherein n can be 1 to 6 and m can be 1 to 100.
• a particular example of a chain transfer agent is polytetrahydrofuran such as TERATHANETM.
• the liquid radiation curable resin composition can include any suitable amount of the chain transfer agent, for example, in certain embodiments, in an amount up to about 50% by weight of the composition, in certain embodiments, up to about 30% by weight of the composition, and in certain other embodiments from about 10% to about 20% by weight of the composition.
• the liquid radiation curable resin composition 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, organic, inorganic, or organic-inorganic hybrid fillers of sizes ranging from 8 nanometers to about 50 microns.
• 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, organic, inorganic, or organic-inorganic hybrid fillers of sizes ranging from 8 nanometers to about 50 microns.
• Stabilizers are often added to the compositions in order to prevent a viscosity build-up, for instance a viscosity build-up during usage in a solid imaging process.
• stabilizers include those described in U.S. Pat. No. 5,665,792, the entire disclosure of which is hereby incorporated by reference.
• Such stabilizers are usually hydrocarbon carboxylic acid salts of group IA and IIA metals.
• these salts are sodium bicarbonate, potassium bicarbonate, and rubidium carbonate.
• Rubidium carbonate is preferred for formulations of this invention with recommended amounts varying between 0.0015 to 0.005% by weight of composition.
• Alternative stabilizers include polyvinylpyrrolidones and polyacrylonitriles.
• additives include dyes, pigments, fillers (e.g. silica particles— preferably cylindrical or spherical silica particles—, talc, glass powder, alumina, alumina hydrate, magnesium oxide, magnesium hydroxide, barium sulfate, calcium sulfate, calcium carbonate, magnesium carbonate, silicate mineral, diatomaceous earth, silica sand, silica powder, titanium oxide, aluminum powder, bronze powder, zinc powder, copper powder, lead powder, gold powder, silver dust, glass fiber, titanic acid potassium whisker, carbon whisker, sapphire whisker, beryllia whisker, boron carbide whisker, silicon carbide whisker, silicon nitride whisker, glass beads, hollow glass beads, metaloxides and potassium titanate whisker), antioxidants, wetting agents, photosensitizers for the free-radical photoinitiator, chain transfer agents, leveling agents, defoamers, surfactants and the like.
• fillers e.g.
• the liquid radiation curable resin composition contains the polymerizable components such that the desired photosensitivity is obtained by choosing an appropriate ratio of the initiators and/or polymerizable components.
• the ratio of the components and of the initiators affect the photosensitivity, speed of curing, degree of curing, crosslink density, thermal properties (e.g., T g ), and/or mechanical properties (e.g., tensile strength, storage modulus, loss modulus) of the liquid radiation curable resin composition or of the cured article.
• the ratio by weight of cationic photoinitiator to free-radical photoinitiator is less than about 4.0, preferably from about 0.1 to about 2.0, and more preferably from about 0.2 to about 1.0.
• the liquid radiation curable resin composition has a ratio by weight of cationic polymerizable component to free-radical polymerizable component (CPC/RPC) is less than about 7.0, or less than about 5.0, e.g., from about 0.5 to about 2.0, and more preferably from about 1.0 to about 1.5.
• CPC/RPC ratio by weight of cationic polymerizable component to free-radical polymerizable component
• the second aspect of the instant claimed invention is a method of forming via additive fabrication a three-dimensional article capable of changing color comprising: (1) heating a liquid radiation curable resin, thereby forming a liquid radiation curable resin having an increased depth of penetration (Dp); (2) establishing a first liquid layer of the liquid radiation curable resin having the increased Dp; (3) exposing the first liquid layer imagewise to actinic radiation to form an imaged cross-section, thereby forming a first cured layer; (4) forming a new layer of liquid radiation curable resin having the increased Dp in contact with the first cured layer; (5) exposing said new layer imagewise to actinic radiation to form an additional cured layer; and (6) repeating steps (4) and (5) a sufficient number of times in order to build up a three-dimensional article; wherein the liquid radiation curable resin further comprises at least one thermochromic component having an activation temperature and a terminal activation temperature, such that the thermochromic component changes from a colored state to a partially colored state at the activation temperature,
• thermochromic component possessing an activation temperature and a terminal activation temperature
• the liquid radiation curable resin comprises both a thermochromic component and at least one non-thermochromic pigment or dye.
• the non-thermochromic pigment or dye is not visually responsive to changes in environmental conditions, such as temperature. Thus it is not a visual effect initiator.
• Such a component is added to establish a "baseline" color and/or opacity, or one which will remain even if the additional effects to the visual state or color imparted by the thermochromic component are removed.
• the liquid radiation curable resin includes a thermochromic which possesses a color below its activation temperature, and gradually transitions to a colorless state from an increase in temperature from the activation temperature to the terminal activation temperature.
• a thermochromic which possesses a color below its activation temperature, and gradually transitions to a colorless state from an increase in temperature from the activation temperature to the terminal activation temperature.
• thermochromic component appears blue below its activation temperature, and transitions to at least partially colorless at the activation temperature, and whereupon reaching the terminal activation point, it becomes substantially colorless.
• the non-thermochromic pigment or dye appears immutably yellow.
• the resulting liquid radiation curable resin for additive fabrication into which the thermochromic component and the non-thermochromic pigment or dye were incorporated would appear green. If the resin were heated to the activation temperature, the thermochromic component would begin fading to clear, whereupon the resulting mixture would appear increasingly greenish-yellow as the resin were further heated. Then, upon heating the resin to the terminal activation point of the thermochromic component, the resin would appear yellow, as the only contribution to color would be provided by the yellow non- thermochromic pigment.
• thermochromic component and non-thermochromic pigment or dye would each be a different primary color (red, blue, or yellow), whereupon the thermochromic component would transition to substantially colorless at above its terminal activation temperature.
• the resin would appear a secondary color (purple, orange, or green) below the activation temperature, then would gradually transition to the primary color of the non-thermochromic component from above the activation temperature to the terminal activation temperature of the thermochromic component.
• thermochromic component and non-thermochromic pigment or dye are the same color below the activation temperature. In another embodiment, they are the same color at and above the terminal activation temperature. In an embodiment, the thermochromic component changes from one color to another color at its activation temperature. In another embodiment, the thermochromic component changes from one color to another color at its terminal activation temperature. In an embodiment, the thermochromic component changes from one color to at least partially colorless at its activation temperature. In another embodiment, the thermochromic component changes to a substantially colorless state at its terminal activation temperature.
• thermochromic components having different activation temperatures, to impart in the liquid radiation curable resin, or the three-dimensional article cured therefrom, a multitude of color changing states (brought about by a concomitant number of different activation temperatures), such that a variety of colors could be experienced.
• thermochromic components transitioned to at least partially clear and/or colorless at their activation temperature
• the Dp would also be increased, if only slightly.
• the variable amount of heat applied could be used as a method to fine-tune the Dp of the associated resin in such a situation, as it would increase stepwise along each successively higher activation temperature.
• the third aspect of the instant claimed invention is a method of forming via additive fabrication a three-dimensional article capable of color or opacity change comprising: (1) inducing an at least temporary change in a depth of penetration (Dp) of a liquid radiation curable resin, thereby forming a liquid radiation curable resin having an at least temporarily modified Dp, wherein the temporary change in the Dp is occasioned by subjecting the liquid radiation curable resin to an alteration in an environmental condition selected from the group consisting of heat, light, pH, magnetism, pressure, and electric current; (2) establishing a first liquid layer of the liquid radiation curable resin having the at least temporarily modified Dp; (3) exposing the first liquid layer imagewise to actinic radiation to form an imaged cross-section, thereby forming a first cured layer; (4) forming a new layer of liquid radiation curable resin having the at least temporarily modified Dp in contact with the first cured layer; (5) exposing said new layer imagewise to actinic radiation to form an additional imaged cross-section; and
• the change in the Dp of the liquid radiation curable resin for additive fabrication is modified by either increasing or decreasing it in response to a change in an environmental condition.
• an alteration might be occasioned by adjusting various environmental conditions such as, for example, the ambient temperature, light, pH, magnetism, pressure, or electric current.
• two or more visual effect initiators are incorporated into the liquid radiation curable resin.
• more than one visual effect initiator can be incorporated into the liquid radiation curable resin wherein the more than one visual effect initiators all have the same activation point in order to obtain unique combinations of color and/or transparency.
• the visual effect initiators possess different activation points, such that multiple visual states are possible, as an alteration to an environmental condition occurs across the various activation points.
• the visual effect initiator which imparts a change to the visual state of the liquid radiation curable resin similarly is capable of imparting the same change to the visual state of the three-dimensional article cured therefrom.
• the liquid radiation curable resin is capable of undergoing changes in a visual state at the activation point of its associated visual effect initiator in response to the same change in the environmental condition, such as heat, light, pH, pressure, magnetism, or electric current, even after curing, and whereupon the part build has been completed.
• the light source used to provide actinic radiation to cure the liquid radiation curable resin is a laser such as a He-Cd laser or an Argon ion laser. Such lasers are common on commercially available stereolithography machines and known in the art.
• the light source is a light-emitting diode (LED).
• the light source is a lamp.
• the light is delivered to the liquid radiation curable resin using an image produced from a DMD (digital micromirror device) chip or LCD display. At least two intensities can be created by a single light source or by multiple light sources.
• a single light source is used.
• a second light source is used in combination with the first light source to increase the light intensity delivered to certain areas of the radiation curable resin.
• the fourth aspect of the instant claimed invention is a three-dimensional object formed by the method of the first, second, or third aspect of the instant claimed invention.

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