Liquid, hybrid UV/vis radiation curable resin compositions for additive fabrication

1. A liquid UV/vis radiation curable composition for additive fabrication comprising, relative to the weight of the entire composition:

from about 30 wt. % to about 80 wt. % of a cationically curable constituent which undergoes a cationic polymerization, the cationically curable constituent further optionally comprising a cycloaliphatic epoxy component and optionally also an oxetane component;

from about 8 wt. % to about 25 wt. % of a free-radically curable constituent that undergoes a free-radical polymerization; and

from about 3 wt. % to about 25 wt. % of a photoinitiating package further comprising an onium salt cationic photoinitiator;

a photosensitizer;

one or more reductants for reducing the onium salt cationic photoinitiator; and

optionally, a free-radical photoinitiator;

wherein the one or more reductants comprises a vinyl ether diluent monomer; and

wherein the photosensitizer is present in an amount from 0.05 wt. % to 5 wt. %.

2. The liquid UV/vis radiation curable composition of claim 1 , wherein the cationically curable constituent comprises the cycloaliphatic epoxy component and the oxetane component;

wherein a cycloaliphatic epoxide T 95 value of the composition is less than about 50 seconds, wherein the cycloaliphatic epoxide T 95 value is measured by Real Time Fourier Transform Infrared (FTIR) spectroscopy upon subjecting the composition to UV/vis optics emitting radiation with a peak spectral output at 400 nm and an irradiance at a surface of the composition of 2 mW/cm 2 for 10 seconds.

3. The liquid UV/vis radiation curable composition for additive fabrication of claim 2 , wherein a cycloaliphatic epoxide plateau conversion of the composition is greater than 43%; wherein the cycloaliphatic epoxide plateau conversion is measured by FTIR spectroscopy upon subjecting the composition to UV/vis optics emitting radiation with a peak spectral output at 400 nm and an irradiance at a surface of the composition of 2 mW/cm 2 for 10 seconds.

4. The liquid UV/vis radiation curable composition for additive fabrication of claim 2 , wherein an oxetane T 95 value of the composition is less than 23 seconds; wherein the oxetane T 95 value is measured by FTIR spectroscopy upon subjecting the composition to UV/vis optics emitting radiation with a peak spectral output at 400 nm and an irradiance at a surface of the composition of 2 mW/cm 2 for 10 seconds.

5. The liquid UV/vis radiation curable composition for additive fabrication of claim 4 , wherein an oxetane plateau conversion of the composition is greater than 59%; wherein the oxetane plateau conversion is measured by FTIR spectroscopy upon subjecting the composition to UV/vis optics emitting radiation with a peak spectral output at 400 nm and an irradiance at a surface of the composition of 2 mW/cm 2 for 10 seconds.

6. The liquid UV/vis radiation curable composition for additive fabrication of claim 1 , wherein, relative to the entire composition:

the cationically curable constituent is present in an amount from 50 wt. % to 75 wt. %; and

the free-radically curable constituent is present in an amount from 15 wt. % to 25 wt. %.

7. The liquid UV/vis radiation curable composition for additive fabrication of claim 1 , wherein, relative to the entire photoinitiating package:

the onium salt cationic photoinitiator is present in an amount from about 8 wt. % to about 50 wt. %;

the one or more reductants comprising the vinyl ether diluent monomer is present in an amount from about 25 wt. % to about 60 wt. %; and

wherein the onium salt 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.

8. The liquid UV/vis radiation curable composition for additive fabrication of claim 1 , wherein the one or more reductants comprise a free-radical photoinitiator which is configured to reduce the onium salt cationic photoinitiator upon forming a free-radical after dissociation upon being subjected to actinic radiation at UV/vis wavelengths.

9. The liquid UV/vis radiation curable composition for additive fabrication of claim 8 , wherein the onium salt cationic photoinitiator comprises a sulfonium salt or an iodonium salt.

10. The liquid UV/vis radiation curable composition for additive fabrication of claim 9 , wherein the onium salt cationic photoinitiator comprises (4-methylphenyl)[4-(2-methylpropyl) phenyl]-, hexafluorophosphate, [4-(1-methylethyl)phenyl](4-methylphenyl)-, tetrakis(pentafluorophenyl)borate(1-), (Bis(4-dodecylphenyl)iodonium hexaflurorantimonate), or (Bis(4-tert-butylphenyl)iodonium hexafluorophosphate).

11. The liquid UV/vis radiation curable composition for additive fabrication of claim 9 , wherein the photosensitizer comprises a thioxanthone.

12. The liquid UV/vis radiation curable composition for additive fabrication of claim 11 , wherein the thioxanthone is further selected from the group consisting of chloropropoxythioxanthones and isopropylthioxanthones.

13. The liquid UV/vis radiation curable composition for additive fabrication of claim 9 , wherein the one or more reductants for reducing the onium salt cationic photoinitiator further comprises a compound which is represented by the following formula (IV):

wherein Ar 1 , is a substituted or unsubstituted aromatic group, R 1 is Ar 1 or a C 2 -C 20 aliphatic chain, and R 2 is R 1 or contains one or more substituted or unsubstituted acyl phenyl groups.

14. The liquid UV/vis radiation curable composition for additive fabrication of claim 9 , wherein the free-radical photoinitiator comprises a hydroxycyclohexyl phenyl ketone.

15. The liquid UV/vis radiation curable composition for additive fabrication of claim 1 , wherein the vinyl ether contains more than one vinyl functional group.

16. The liquid UV/vis radiation curable composition for additive fabrication of claim 1 , wherein the cationically curable constituent comprises a glycidyl ether epoxy that is selected from the group consisting of bisphenol A-based glycidyl ether, a bisphenol S-based glycidyl ether, and a bisphenol F-based glycidyl ether.

17. The liquid UV/vis radiation curable composition for additive fabrication of claim 1 , wherein the photosensitizer comprises a compound according to the following formula (V):

wherein R contains an aliphatic chain from C 1 -C 20 .

18. A method of forming a three-dimensional article via an additive fabrication system utilizing UV/vis optics, the method comprising:

(1) providing the liquid UV/vis radiation curable composition for additive fabrication of claim 1 ;

(2) establishing a first liquid layer of the liquid UV/vis radiation curable composition for additive fabrication;

(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 375 nm to about 500 nm.

19. The method of forming a three-dimensional article via an additive fabrication system utilizing UV/vis optics of claim 18 , wherein the UV/vis optics configuration is selected from the group consisting of LED/DLP, laser/DLP, LED/LCD, and laser/LCD.

20. A three-dimensional part formed by the process of claim 19 .