U.S. patent application number 13/515629 was filed with the patent office on 2012-10-11 for led curable liquid resin compositions for additive fabrication.
This patent application is currently assigned to DSM IP ASSETS, B.V.. Invention is credited to Timothy Bishop, Ken Dake, Jigeng Xu.
Application Number | 20120259031 13/515629 |
Document ID | / |
Family ID | 43532791 |
Filed Date | 2012-10-11 |
United States Patent
Application |
20120259031 |
Kind Code |
A1 |
Dake; Ken ; et al. |
October 11, 2012 |
LED CURABLE LIQUID RESIN COMPOSITIONS FOR ADDITIVE FABRICATION
Abstract
Disclosed is a photocurable resin composition for additive
fabrication comprising a polymerizable component that is
polymerizable by free-radical polymerization, cat ionic
polymerization, or both free-radical polymerization and cationic
polymerization, and a photoinitiating system capable of initiating
the free-radical polymerization, cationic polymerization, or both
free-radical polymerization and cationic polymerization. The
photocurable resin composition is a liquid at about 25.degree. C.,
and is capable of curing to provide a solid upon irradiation with
light emitted from a light emitting diode (LED), wherein the light
has a wavelength of from about 100 nm to about 900 nm. Also
disclosed is a three-dimensional article prepared from the
photocurable resin composition for additive fabrication, and a
process for preparing three-dimensional articles by additive
fabrication.
Inventors: |
Dake; Ken; (South Elgin,
IL) ; Xu; Jigeng; (South Elgin, IL) ; Bishop;
Timothy; (Algonquin, IL) |
Assignee: |
DSM IP ASSETS, B.V.
HEERLEN
NL
|
Family ID: |
43532791 |
Appl. No.: |
13/515629 |
Filed: |
December 16, 2010 |
PCT Filed: |
December 16, 2010 |
PCT NO: |
PCT/US10/60677 |
371 Date: |
June 13, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61287620 |
Dec 17, 2009 |
|
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|
Current U.S.
Class: |
522/11 ; 264/401;
522/101; 522/168; 522/27; 522/29; 522/33; 522/55; 522/66 |
Current CPC
Class: |
G03F 7/029 20130101;
G03F 7/0045 20130101; G03F 7/027 20130101; B29C 2033/0005 20130101;
B33Y 10/00 20141201; B33Y 70/00 20141201; B29C 2035/0827 20130101;
G03F 7/038 20130101; G03F 7/0037 20130101; Y10T 428/31515 20150401;
B29C 64/135 20170801 |
Class at
Publication: |
522/11 ; 264/401;
522/27; 522/29; 522/33; 522/55; 522/66; 522/101; 522/168 |
International
Class: |
C08F 2/50 20060101
C08F002/50; C08J 3/28 20060101 C08J003/28; C08G 65/18 20060101
C08G065/18; B29C 35/08 20060101 B29C035/08 |
Claims
1. A photocurable resin composition for additive fabrication
comprising a polymerizable component that is polymerizable by
free-radical polymerization, cationic polymerization, or both
free-radical polymerization and cationic polymerization, and a
photoinitiating system capable of initiating the free-radical
polymerization, cationic polymerization, or both free-radical
polymerization and cationic polymerization; wherein the
photocurable resin composition is a liquid at about 25.degree. C.,
and is capable of curing to provide a solid upon irradiation with
light emitted from a light emitting diode (LED), wherein the light
has a wavelength of from about 100 nm to about 900 nm, preferably
from 200 nm to about 600 nm, more preferably from about 280 nm to
about 500 nm, more preferably from about 300 nm to about 475 nm,
more preferably from about 340 nm to about 415 nm, preferably
having a peak at about 365 nm, and wherein the liquid photocurable
resin composition has a Critical Exposure (Ec) and a Depth of
Penetration (Dp) as measured on a layer of the photocurable resin
composition as the composition is curing, wherein Ec is from about
0.01 seconds to about 6.0 seconds and Dp is 1/4 to 4 times,
preferably from 1/3 to 3 times, the thickness of the layer.
2. The photocurable resin composition for additive fabrication of
claim 1, wherein the Dp is from about 1 to about 8 mils, preferably
from about 1 to about 7 mils, more preferably from about 2 to about
7 mils.
3. The photocurable resin composition for additive fabrication of
claim 1, wherein the photocurable resin composition as it is curing
with a light intensity of 50 mW/cm.sup.2 for 1.0 second has a
storage shear modulus (G') value of greater than about
1.0.times.10.sup.5 Pa, preferably from about 1.0.times.10.sup.5 Pa
to about 1.0.times.10.sup.7 Pa, more preferably from about
5.0.times.10.sup.6 Pa to about 1.0.times.10.sup.7 Pa when it is
measured at 3.9 seconds from the start of light exposure on a Real
Time-Dynamic Mechanical Analyzer (RT-DMA) with an 8 mm plate at a
sample gap of 0.10 mm.
4. The photocurable resin composition for additive fabrication of
claim 1, wherein the photocurable resin composition for additive
fabrication comprises at least one free-radical photoinitiator,
preferably selected from the group consisting of benzoylphosphine
oxides, aryl ketones, benzophenones, hydroxylated ketones,
1-hydroxyphenyl ketones, ketals, metallocenes, and any combination
thereof, more preferably selected from the group consisting of
2,4,6-trimethylbenzoyl diphenylphosphine oxide and
2,4,6-trimethylbenzoyl phenyl, ethoxy phosphine oxide,
bis(2,4,6-tnmethylbenzoyl)-phenylphosphineoxide,
2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-I,
2-benzyl-2-(dimethylamino)-I-[4-(4-morpholinyl)phenyl]-1-butanone,
2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-I-o-
ne, 4-benzoyl-4'-methyl diphenyl sulphide,
4,4'-bis(diethylamino)benzophenone, and
4,4'-bis(N,N'-dimethylamino) benzophenone (Michler's ketone),
benzophenone, 4-methyl benzophenone, 2,4,6-trimethyl benzophenone,
dimethoxybenzophenone, 1-hydroxycyclohexyl phenyl ketone, phenyl
(1-hydroxyisopropyl)ketone,
2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone,
4-isopropylphenyl(1-hydroxyisopropyl)ketone,
oligo-[2-hydroxy-2-methyl-I-[4-(I-methylvinyl)phenyl]propanone],
camphorquinone, 4,4'-bis(diethylamino)benzophenone, benzil dimethyl
ketal, bis(eta 5-2-4-cyclopentadien-I-yl)
bis[2,6-difluoro-3-(IH-pyrrol-I-yl)phenyl]titanium, and any
combination thereof.
5. The photocurable resin composition for additive fabrication of
claim 1, wherein the photoinitiating system is a photoinitiator
having both cationic initiating function and free radical
initiating function.
6. The photocurable resin composition for additive fabrication of
claim 1 wherein the photocurable resin composition for additive
fabrication comprises at least one cationic photoinitiator,
preferably 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, sulfonium antimonate
salts, ferrocenes, di(cyclopentadienyliron)arene salt compounds,
and pyridinium salts, and any combination thereof, more preferably
selected from the group consisting of aromatic diazonium salts,
aromatic sulfonium salts, aromatic iodonium salts, metallocene
based compounds, aromatic phosphonium salts and silanol aluminium
complexes, more preferably selected from the group consisting of
aromatic sulfonium salts, aromatic iodonium salts, and metallocene
based compounds, even more preferably selected from the group
consisting of triarylsulfonium salts, diaryliodonium salts, and
metallocene based compounds.
7. The photocurable resin composition for additive fabrication of
claim 1, wherein the cationic photoinitiator is at least one with
an anion selected from the group consisting of BF.sub.4.sup.-,
AsF.sub.6.sup.-, SbF.sub.6.sup.-, PF.sub.6.sup.-,
B(C.sub.6F.sub.6).sub.4.sup.-, perfluoroalkylsulfonates,
perfluoroalkylphosphates, and carborane anions.
8. The photocurable resin composition for additive fabrication of
claim 1 wherein the cationic photoinitiator is at least one 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.sub.6.sup.-, PF.sub.6.sup.-, B(C.sub.6F.sub.5).sub.4.sup.-,
perfluoroalkylsulfonates, perfluoroalkylphosphates, and
(CH.sub.6B.sub.11Cl.sub.6).sup.-.
9. The photocurable resin composition for additive fabrication of
claim 1, wherein the cationic photoinitiator is an aromatic
sulfonium salt based cationic photoinitiator selected from the
group consisting of 4-(4-benzoylphenylthio)phenyldiphenylsulfonium
hexafluoroantimonate,
4-(4-benzoylphenylthio)phenylbis(4-hydroxyethyloxyphenyl)sulfonium
hexafluoroantimonate,
4-(4-benzoylphenylthio)phenylbis(4-fluorophenyl)sulfonium
hexafluoroantimonate,
4-(4-benzoylphenylthio)phenylbis(4-chlorophenyl)sulfonium
hexafluoroantimonate,
4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium
hexafluoroantimonate,
4-(4-benzoylphenylthio)phenylbis(4-methylphenyl)sulfonium
hexafluoroantimonate,
4-(4-benzoylphenylthio)phenylbis(4-hydroxyethylphenyl)sulfonium
hexafluoroantimonate,
4-[4-(4-hydroxyethyloxybenzoyl)phenylthio]phenylbis(4-fluoro
phenyl)sulfonium hexafluoroantimonate,
4-[4-(4-hydroxyethyloxybenzoyl)phenylthio]phenyldiphenylsulfonium
hexafluoroantimonate,
4-[4-(4-hydroxyethyloxybenzoyl)phenylthio]phenylbis(4-hydroxyethyloxyphen-
yl)sulfonium hexafluoroantimonate,
4-(4-benzoylphenylthio)phenylbis(4-methoxyethoxyphenyl)sulfonium
hexafluoroantimonate,
4-[4-(3-methoxybenzoyl)phenylthio]phenyldiphenylsulfonium
hexafluoroantimonate,
4-[4-(3-methoxycarbonylbenzoyl)phenylthio]phenyldiphenylsulfonium
hexafluoroantimonate,
4-[4-(2-hydroxymethylbenzoyl)phenylthio]phenyldiphenylsulfonium
hexafluoroantimonate,
4-[4-(4-methylbenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium
hexafluoroantimonate,
4-[4-(4-)phenylthio]phenylbis(4-fluorophenyl)sulfonium
hexafluoroantimonate,
4-[4-(4-fluorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium
hexafluoroantimonate,
4-[4-(2-methoxycarbonylbenzoyl)phenylthio]phenylbis(4-fluoro
phenyl)sulfonium hexafluoroantimonate,
bis[4-(diphenylsulfonio)phenyl]sulfide bishexafluorophosphate,
bis[4-(diphenylsulfonio)phenyl]sulfide bistetrafluoroborate,
bis[4-(diphenylsulfonio)phenyl]sulfide
tetrakis(pentafluorophenyl)borate,
diphenyl-4-(phenylthio)phenylsulfonium hexafluorophosphate,
diphenyl-4-(phenylthio)phenylsulfonium tetrafluoroborate,
diphenyl-4-(phenylthio)phenylsulfonium
tetrakis(pentafluorophenyl)borate, triphenylsulfonium
hexafluorophosphate, triphenylsulfonium hexafluoroantimonate,
triphenylsulfonium tetrafluoroborate, triphenylsulfonium
tetrakis(pentafluorophenyl)borate,
bis[4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide
bishexafluorophosphate,
bis[4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide
bistetrafluoroborate, and
bis[4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide
tetrakis(pentafluorophenyl)borate.
10. The photocurable resin composition for additive fabrication of
claim 1 wherein the cationic photoinitiator is an aromatic iodonium
salt based cationic photoinitiator selected from the group
consisting of diphenyliodonium hexafluorophosphate,
diphenyliodonium hexafluoroantimonate, diphenyliodonium
tetrafluoroborate, diphenyliodonium
tetrakis(pentafluorophenyl)borate, bis(dodecylphenyl)iodonium
hexafluorophosphate, bis(dodecylphenyl)iodonium
hexafluoroantimonate, bis(dodecylphenyl)iodonium tetrafluoroborate,
bis(dodecylphenyl)iodonium tetrakis(pentafluorophenyl)borate,
4-methylphenyl-4-(1-methylethyl)phenyliodonium hexafluorophosphate,
4-methylphenyl-4-(1-methylethyl)phenyliodonium
hexafluoroantimonate,
4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrafluoroborate,
and 4-methylphenyl-4-(1-methylethyl)phenyliodonium
tetrakis(pentafluorophenyl)borate.
11. The photocurable resin composition for additive fabrication of
claim 1, wherein the cationic photoinitiator is selected from the
group consisting of tetrakis(pentafluorophenyl)borate or
hexafluoroantimonate salt of
4-(4-benzoylphenylthio)phenyldiphenylsulfonium,
4-(4-benzoylphenylthio)phenylbis(4-hydroxyethyloxyphenyl)sulfonium,
4-(4-benzoylphenylthio)phenylbis(4-fluorophenyl)sulfonium,
4-(4-benzoylphenylthio)phenylbis(4-chlorophenyl)sulfonium,
4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium,
4-[4-(2-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium,
(4-thiophenoxyphenyl)diphenylsulfonium,
S,S,S',S'-tetraphenylthiobis(4,1-pheny lene)disulfonium,
triphenylsulfonium, (chlorophenyl)diphenylsulfonium,
chloro[S-(phenyl)thianthrenium], S-(phenyl)thianthrenium,
diphenyl-4-(4'-thiophenoxy)thiophenoxyphenylsulfonium,
phenyldi(4-thiophenoxyphenyl)sulfonium,
S-(4-thiophenoxyphenyl)thianthrenium, and
(thiodi-4,1-phenylene)bis[bis[4-(2-hydroxyethoxy)phenyl]sulfonium,
tris(4-(4-acetylphenyl)thiophenyl)sulfonium,
bis(4-dodecylphenyl)iodonium,
[4-[(2-hydroxytetradecyl)oxy]phenyl]phenyliodonium,
(4-methylphenyl)[4-[[2-[[[[3-(trifluoromethyl)phenyl]amino]carbonyl]oxy]t-
etradecyl]oxy]phenyl]iodonium, bis(4-dodecylphenyl)iodonium,
[4-(1-methylethyl)phenyl](4-methylphenyl)iodonium, and any
combination thereof.
12. The photocurable resin composition for additive fabrication of
claim 1, wherein the cationic photoiniator is a sulfonium borate
photoinitiator, more preferably a triarylsulfonium borate, more
preferably tris(4-(4-acetylphenyl)thiophenyl)sulfonium
tetrakis(pentafluorophenyl)borate or
4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium
tetrakis(pentafluorophenyl)borate.
13. The photocurable resin composition for additive fabrication of
claim 1, wherein the polymerizable component is polymerizable by
both free-radical polymerization and cationic polymerization.
14. The photocurable resin composition for additive fabrication of
claim 1, wherein the polymerizable component is a vinyloxy
compound, preferably selected from the group consisting of
bis(4-vinyloxybutyl)isophthalate,
tris(4-vinyloxybutyl)trimellitate, and combinations thereof.
15. The photocurable resin composition for additive fabrication of
claim 1, which further includes a photosensitizer, preferably
selected from the group consisting of methanones, xanthenones,
pyrenemethanols, anthracenes, quinones, xanthones, thioxanthones,
benzoyl esters, benzophenones, and any combination thereof, more
preferably 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, anthracene,
anthraquinones, 2-methylanthraquinone, 2-ethylanthraquinone,
2-tertbutylanthraquinone, 1-chloroanthraquinone,
2-amylanthraquinone, thioxanthones and xanthones, isopropyl
thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone,
1-chloro-4-propoxythioxanthone, methyl benzoyl formate,
methyl-2-benzoyl benzoate, 4-benzoyl-4'-methyl diphenyl sulphide,
4,4'-bis(diethylamino)benzophenone, and any combination
thereof.
16. The photocurable resin composition for additive fabrication of
claim 15, wherein the photosensitizer is a fluorone, preferably
selected from the group consisting of
5,7-diiodo-3-butoxy-6-fluorone, 5,7-diiodo-3-hydroxy-6-fluorone,
9-cyano-5,7-diiodo-3-hydroxy-6-fluorone, ##STR00007## and any
combination thereof.
17. The photocurable resin composition for additive fabrication of
claim 1, which further includes a chain transfer agent, preferably
a chain transfer agent for a cationic polymerizable component which
is preferably a hydroxyl-containing compound, more preferably a
compound containing 2 or more than 2 hydroxyl-groups, preferably
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, or hyperbranched polyols, more
preferably a polyether polyol comprising an alkoxy ether group of
the formula [(CH.sub.2).sub.nO].sub.m, wherein n can be 1 to 6 and
m can be 1 to 100, or polytetrahydrofuran.
18. The photocurable resin composition for additive fabrication of
claim 1, which further includes one or more additives selected from
the group consisting of bubble breakers, antioxidants, surfactants,
acid scavengers, pigments, dyes, thickneners, flame retardants,
silane coupling agents, ultraviolet absorbers, resin particles,
core-shell particle impact modifiers, soluble polymers and block
polymers.
19. The photocurable resin composition for additive fabrication of
claim 1, wherein the ratio by weight of cationic photoinitiator to
free-radical photoinitiator is less than about 4.0, preferably from
about 0.1 to about 4.0, preferably from about 0.1 to about 2.0,
more preferably from about 0.1 to about 1.5, more preferably from
about 0.2 to about 1.0.
20. The photocurable resin composition for additive fabrication of
claim 1, wherein the photocurable resin composition is free or
substantially free of antimony-containing initiator.
21. The photocurable resin composition for additive fabrication of
claim 1, wherein the ratio by weight of cationic polymerizable
component to free-radical polymerizable component is less than
about 7.0, preferably from about 0.5 to about 6.5, more preferably
from about 1.0 to about 6.5, more preferably from about 0.5 to
about 2.0, more preferably from about 1.0 to about 1.5.
22. The photocurable resin composition for additive fabrication of
claim 1, wherein at least about 30 wt %, preferably 40 wt %, of the
ingredients in the photocurable resin for additive fabrication are
bio-based, rather than petroleum based.
23. A three-dimensional article comprising a cured photocurable
resin, wherein the cured photocurable resin is obtained by curing
the photocurable resin composition for additive fabrication of
claim 1 by irradiating it with light emitted from a light emitting
diode (LED) light having a wavelength from about 100 nm to about
900 nm, preferably from 200 nm to about 600 nm, more preferably
from about 280 nm to about 500 nm, more preferably from about 300
nm to about 475 nm, preferably having a peak at about 365 nm.
24. A process for making a three-dimensional object comprising the
steps of forming and selectively curing a layer of the photocurable
resin composition for additive fabrication of claim 1 by
irradiation with light from a light emitting diode (LED) having a
wavelength from about 100 nm to about 900 nm, preferably from 200
nm to about 600 run, more preferably from about 280 nm to about 500
nm, more preferably from about 300 nm to about 475 nm, preferably
having a peak at about 365 nm, and repeating the steps of forming
and selectively curing a layer of the photocurable resin
composition a plurality of times to obtain a three-dimensional
object.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to photocurable resin
compositions used in additive fabrication applications.
BACKGROUND OF THE INVENTION
[0002] 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.
[0003] 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. When
initially formed, 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. Pat. No.
4,575,330.
[0004] There are several types of lasers used in stereolithography,
ranging from 193 nm to 355 nm in wavelength. The use of bulky and
expensive gas lasers to cure liquid radiation curable resins is
well known. The delivery of laser energy in a stereolithography
system can be Continuous Wave (CW) or Q-switched pulses. CW lasers
provide continuous laser energy and can be used in a high speed
scanning process. However, their output power is limited which
reduces the amount of curing that occurs during object creation. As
a result the finished object will need additional post process
curing. In addition, excess heat could be generated at the point of
irradiation which may be detrimental to the resin. Further, the use
of a laser requires scanning point by point on the resin which can
be time-consuming.
[0005] Light emitting diodes (LEDs) are semiconductor devices which
utilize the phenomenon of electroluminescence to generate light.
LEDs consist of a semiconducting material doped with impurities to
create a p-n junction capable of emitting light as positive holes
join with negative electrons when voltage is applied. The
wavelength of emitted light is determined by the materials used in
the active region of the semiconductor. Typical materials used in
semiconductors of LEDs include, for example, elements from Groups
13 (III) and 15 (V) of the periodic table. These semiconductors are
referred to as III-V semiconductors and include, for example, GaAs,
GaP, GaAsP, AlGaAs, InGaAsP, AlGaInP, and InGaN semiconductors.
Other examples of semiconductors used in LEDs include compounds
from Group 14 (IV-IV semiconductor) and Group 12-16 (II-V1). The
choice of materials is based on multiple factors including desired
wavelength of emission, performance parameters, and cost.
[0006] Early LEDs used gallium arsenide (GaAs) to emit infrared
(IR) radiation and low intensity red light. Advances in materials
science have led to the development of LEDs capable of emitting
light with higher intensity and shorter wavelengths, including
other colors of visible light and UV light. It is possible to
create LEDs that emit light across a wide wavelength spectrum, for
example, from a low of about 100 nm to a high of about 900 nm.
Typically, LED UV light sources currently emit light at wavelengths
between 300 and 475 nm, with 365 nm, 390 nm, and 395 nm being
common peak spectral outputs. See textbook,"Light-Emitting Diodes"
by E. Fred Schubert, 2'' Edition, .COPYRGT. E. Fred Schubert 2006,
published by Cambridge University Press.
[0007] Several manufacturers offer LED lamps for commercial curing
applications. For example, Phoseon Technology, Summit UV, Honle UV
America, Inc., IST Metz GmbH, Jenton International Ltd., Lumos
Solutions Ltd., Solid UV Inc., Seoul Optodevice Co., Ltd.,
Spectronics Corporation, Luminus Devices Inc., and Clearstone
Technologies, are some of the manufacturers offering LED lamps for
curing ink-jet printing compositions, PVC floor coating
compositions, metal coating compositions, plastic coating
composition, and adhesive compositions.
[0008] LED curing devices are used in dental work. An example of
such a device is the ELIPAR.TM. FreeLight 2 LED curing light from
3M ESPE. This device emits light in the visible region with a peak
irradiance at 460 nm. LED equipment is also being tested for use in
the ink-jet printing, including, for example, by IST Metz.
[0009] Although LED lamps are available, photocurable compositions
suitable for additive fabrication and curable by the use of LED
light are not well known commercially. For example, U.S. Pat. No.
7,211,368 reportedly discloses a liquid stereolithography resin
comprising a first urethane acrylate oligomer, a first acrylate
monomer, a polymerization modifier, a second urethane acrylate
oligomer different from the first urethane acrylate oligomer, and a
stabilizer. The first urethane acrylate oligomer is an aliphatic
polyester urethane diacrylate oligomer, the first acrylate monomer
is ethoxylated (3) trimethylolpropane acrylate, and the
polymerization modifier is selected from the group consisting of
isobornyl acrylate, ethoxylated (5) pentaerythritol tetraacrylate,
an aliphatic urethane acrylate, tris-(2-hydroxyethyl)isocyanurate
triacrylate, and mixtures thereof. The resin includes 5-35 weight %
of an aliphatic polyester urethane diacrylate oligomer and 0.5-25
weight % ethoxylated (3) trimethylolpropane acrylate, wherein the
resin includes 15-45 weight % ethoxylated (5) pentaerythritol
tetraacrylate. However, the '368 patent indicates that a laser is
used to cure the resin. Further, the '368 patent fails to disclose
the use of an acid generating photoinitiator, such as a cationic
photoinitiator.
[0010] More recently, some attention has been given to the use of
LEDs in additive fabrication processes. U.S. Pat. No. 6,927,018 and
U.S. Patent Application Publication No. 2005/0227186 purportedly
provide a method, article of manufacture and system for fabricating
an article using photo-activatable building material. The method
according to the '018 patent and the '186 publication includes the
steps of applying a layer of the photo-activatable building
material to a preselected surface, scanning the layer using a
plurality of light-emitting centers to photo-activate the layer of
photo-activatable building material in accordance with a
predetermined photo-initiation process to obtain polymerization of
the building material. Scanning is accomplished at a predetermined
distance using a predetermined light intensity, and repeating the
steps of applying the layer. Each layer is applied to an
immediately previous layer, and the layer is scanned with the
plurality of light-emitting centers to polymerize the building
material until the article is fabricated. While the '018 patent and
the '186 publication mention UV LEDs and laser diodes as suitable
light-emitting centers, they fail to disclose detailed information
on photo-activatable building material suitable for LED cure.
[0011] U.S. Pat. No. 7,270,528 purportedly discloses a flash curing
system for solid freeform fabrication which generates a plurality
of radiation emitting pulses that forms a planar flash. The planar
flash initiates curing of a curable material dispensed by a solid
freeform fabrication apparatus. The '528 patent, while mentioning
UV light-emitting diodes (LED) lamps in the specification, sets
forth examples where a flash lamp is used to cure the resin
composition. The resin composition illustrated in the '528 patent
does contain a cationically curable monomer or a cationic
photoinitiator.
[0012] U.S. Patent Application Publication No. 2008/0231731 or
2008/0169589 or European Patent Application No. EP 1950032
purportedly discloses a solid imaging apparatus that includes a
replaceable cartridge containing a source of build material and an
extendable and retractable flexible transport film for transporting
the build material layer-by-layer from the cartridge to the surface
of a build in an image plane. If desired, the apparatus can produce
a fully reacted build. A high intensity UV source is said to cure
the build between layers. The above publications state that the
solid imaging radiation that is used to cure the build material can
be "any actinic radiation which causes a photocurable liquid to
react to produce a solid, whether a visible or UV source or other
source,"
[0013] International Patent Publication No. WO 2008/118263 is
directed to a system for building a three-dimensional object based
on build data representing the three-dimensional object, wherein
the system includes an extrusion head that deposits a
radiation-curable material in consecutive layers at a high
deposition rate. The radiation-curable material of each of the
consecutive layers is cooled to a self-supporting state. The system
is said to include a radiation source that selectively exposes
portions of the consecutive layers to radiation at a high
resolution in accordance with the build data. It is stated that the
exposure head includes a linear array of high resolution, UV
light-emitting diodes (LEDs). P71-1464 CUREBAR.TM. and P150-3072
PRINTHEAD.TM. are described as examples of suitable UV-radiation
sources for the exposure head. The '263 publication fails to
describe exemplary photocurable formulations suitable for curing by
LED light in an additive fabrication process.
[0014] International Patent Publication No. WO 2005/103121,
entitled "Method for photocuring of Resin Compositions", assigned
to DSM IP Assets B.V., describes and claims Methods for Light
Emitting Diode (LED) curing of a curable resin composition
containing a photoinitiating system, characterized in that the
highest wavelength at which absorption maximum of the
photoinitiating system occurs (.lamda..sub.Max PIS) is at least 20
nm below, and at most 100 nm below, the wavelength at which the
emission maximum of the LED occurs (.lamda..sub.LED). The invention
in this PCT patent application relates to the use of LED curing in
structural applications, in particular in applications for the
lining or relining of objects, and to objects containing a cured
resin composition obtained by LED curing. This invention provides a
simple, environmentally safe and readily controllable method for
(re)lining pipes, tanks and vessels, especially for such pipes and
equipment having a large diameter, in particular more than 15 cm.
The specification does not describe LED radiation curable
photocurable resins.
[0015] U.S. Patent Application Publication No. 2007/0205528
reportedly discloses an optical molding process wherein the
radiation source used is a non-coherent source of radiation. The
'528 publication indicates that the photocurable compositions are
formulated so as to enable the production of three-dimensional
articles having better performance when irradiated with
conventional (non-coherent) UV rather than with Laser UV, and
states that the photocurable compositions disclosed are more
appropriate for UV non-coherent irradiation than for Laser UV.
While the '528 publication mentions that "the exposure system uses
irradiation from non-coherent light sources, e.g., a xenon fusion
lamp, or light emitting diode bars," the exemplified exposure was
reportedly carried out according to the method of WO 00/21735,
which is said to describe an apparatus and a method wherein the
photosensitive material is exposed to a light source illuminating a
cross-section of a material by at least two modulator arrangements
of individually controllable light modulators.
[0016] U.S. Patent Application Publication No. 2009/0267269A or WO
2009/132245 reportedly discloses a continuous-wave (CW) ultraviolet
(UV) curing system for solid freeform fabrication (SFF), wherein
the curing system is configured to provide an exposure of UV
radiation for one or more layers of UV-curable material. It is
reported that one or more UV exposures may initiate curing of a
curable material in the layer dispensed by a solid freeform
fabrication apparatus. According to the '269 or '245 publication,
one approach to provide the single or multiple UV exposures is the
use of one or more UV LEDs, which generate UV radiation without
generating any substantial amounts of infrared (IR) radiation at
the same time.
[0017] The foregoing shows that there is an unmet need to provide
photocurable resin compositions for additive fabrication which are
capable of curing by irradiation by LED light.
BRIEF SUMMARY OF THE INVENTION
[0018] The invention provides a photocurable resin composition for
additive fabrication comprising a polymerizable component that is
polymerizable by free-radical polymerization, by cationic
polymerization, or by both free-radical polymerization and cationic
polymerization, and a photoinitiating system capable of initiating
the free-radical polymerization, cationic polymerization, or both
free-radical polymerization and cationic polymerization. The
invention also provides a three-dimensional article comprising a
cured resin composition which is obtained by curing the
photocurable resin composition for additive fabrication, and a
method of curing the photocurable resin composition for additive
fabrication.
[0019] In an embodiment, wherein the ratio by weight of cationic
photoinitiator to free-radical photoinitiator is less than about
4.0.
[0020] In another embodiment, the ratio by weight of cationic
polymerizable component to free-radical polymerizable component is
less than about 7.0.
[0021] In another embodiment, greater than at least 30 wt % of the
ingredients in the photocurable resin composition for additive
fabrication are bio-based, rather than petroleum based.
[0022] In an aspect, the invention provides a photocurable resin
composition for additive fabrication comprising a polymerizable
component that is polymerizable by free-radical polymerization, by
cationic polymerization, or by both free-radical polymerization and
cationic polymerization, and a photoinitiating system capable of
initiating the free-radical polymerization, cationic
polymerization, or both free-radical polymerization and cationic
polymerization; wherein the photocurable resin composition for
additive fabrication is a liquid at about 25.degree. C., and is
capable of curing to provide a solid upon irradiation with light
emitted from a light emitting diode (LED), wherein the light has a
wavelength of from about 100 nm to about 900 nm; and wherein the
liquid photocurable resin composition for additive fabrication has
a Critical Exposure (Ec) and a Depth of Penetration (Dp) as
measured on a layer of the resin composition for additive
fabrication as the composition is curing upon exposure to LED
light, wherein Ec is less than about 6.0 seconds and Dp is 1/4 to 4
times the thickness of the layer.
[0023] In another aspect, the invention provides a
three-dimensional article comprising a cured photocurable resin,
wherein the cured photocurable resin is obtained by curing a
photocurable resin composition for additive fabrication by
irradiating it with light emitted from a light emitting diode (LED)
light having a wavelength from about 100 nm to about 900 nm; the
photocurable resin composition for additive fabrication comprising:
a polymerizable component that is polymerizable by free-radical
polymerization, cationic polymerization, or both free-radical
polymerization and cationic polymerization, and a photoinitiating
system capable of initiating the free-radical polymerization,
cationic polymerization, or both free-radical polymerization and
cationic polymerization; wherein the photocurable resin composition
is a liquid at about 25.degree. C., and is capable of curing to
provide a solid upon irradiation with light emitted from a light
emitting diode (LED), wherein the light has a wavelength of from
about 100 nm to about 900 nm, and wherein the liquid photocurable
resin composition has a Critical Exposure (Ec) and a Depth of
Penetration (Dp) as measured on a layer of the photocurable resin
composition as the composition is curing, wherein Ec is from about
0.01 seconds to about 6.0 seconds and Dp is 1/4 to 4 times the
thickness of the layer.
[0024] In a further aspect, the invention provides a process for
making a three-dimensional article comprising the steps of: forming
and selectively curing a layer of a photocurable resin composition
by irradiation with a light emitting diode (LED) light having a
wavelength from about 100 nm to about 900 nm, the photocurable
resin composition comprising: a polymerizable component that is
polymerizable by free-radical polymerization, cationic
polymerization, or both free-radical polymerization and cationic
polymerization, and a photoinitiating system capable of initiating
the free-radical polymerization, cationic polymerization, or both
free-radical polymerization and cationic polymerization; wherein
the photocurable resin composition is a liquid at about 25.degree.
C., and is capable of curing to provide a solid upon exposure to a
light emitting diode (LED) light having a wavelength of from about
100 nm to about 900 nm, and wherein the liquid photocurable resin
composition has a Critical Exposure (Ec) and a Depth of Penetration
(Dp) as measured on a layer of the photocurable resin composition
as the composition is curing, wherein Ec is from about 0.01 seconds
to about 6.0 seconds and Dp is 1/4 to 4 times the thickness of the
layer; and repeating the steps of forming and selectively curing a
layer of the photocurable resin composition a plurality of times to
obtain the three-dimensional article.
DETAILED DESCRIPTION OF THE INVENTION
[0025] The present invention provides a LED photocurable resin
composition for additive fabrication comprising a polymerizable
component that is polymerizable by at least one of a free-radically
initiated polymerization and a cationically initiated
polymerization, and a photoinitiating system capable of initiating
the polymerization of a free-radically polymerizable component
and/or the cationically polymerizable component. The photocurable
resin composition for additive fabrication of the invention is
characterized by one or more advantages, for example, rapid cure
and improved mechanical properties of the resulting cured resin and
the three-dimensional article.
[0026] In accordance with an embodiment, the photocurable resin
composition is a liquid at about 25.degree. C., and is capable of
curing to provide a solid upon irradiation with light emitted from
a light emitting diode (LED), wherein the light has a wavelength of
from about 100 nm to about 900 nm.
[0027] The wavelength of the light can be in the UV or visible
region or higher into the infrared region. In the UV range, UVA,
UVB, and UVC are possible, which are characterized by the
wavelength of from about 320 to about 400 nm, from about 280 to
about 320 nm, and from about 100 to about 280 nm, respectively.
[0028] The photocurable resin composition for additive fabrication
is highly photosensitive. For example, it has a Critical Exposure
(Ec) and a Depth of Penetration (Dp) as measured on a layer of the
photocurable resin composition as the composition is curing,
wherein Ec is from about 0.01 seconds to about 6.0 seconds and Dp
is about 1/4 to about 4 times the thickness of the layer. In an
embodiment, the wavelength of the LED light is 365 nm.
[0029] In embodiments, Ec is about 0.01 seconds to about 1, 2, 3,
4, 5, or 6 seconds. In embodiments, Dp is about 1/4 to about 2
times the thickness of the layer. In an embodiment, Ec is from
about 0.01 seconds to about 2.0 seconds.
[0030] The photosensitivity of the liquid formulations was
determined by using a technique similar to the so-called
WINDOWPANES.TM. technique, a technique known to those skilled in
the art of stereolithography. In this technique, single-layer test
specimens are produced by using different amounts of exposure
energies to cure the liquid formulation to solid, and the solid
resin layer thicknesses obtained are measured. The resulting layer
thickness is plotted on a graph against the natural logarithm of
the irradiation energy used to provide a "working curve." The slope
of this curve is termed Dp (given in mm or mils). The energy value
at which the curve passes through the x-axis is termed Ec (and is
the energy at which gelling of the material just takes place; P.
Jacobs, Rapid Prototyping and Manufacturing, Soc. of Manufacturing
Engineers, 1992, p. 270 ff.). Alternatively, the exposure time (in
seconds) rather than the exposure energy (in mW/cm.sup.2) is used
for calculating the Ec values when the intensity of the irradiation
light is constant, as in the case of using LED light as the light
curing sources.
[0031] In a particular embodiment, Dp is from about 1 to about 8
mils, more particularly from about 1 to about 7 mils, and in
embodiments, from about 1 mil to about 7 mils or from about 2 to
about 5 mils, even more particularly from about 2 mils to about 4
mils.
[0032] Embodiments of the invention include photocurable resin
compositions which display advantageous mechanical properties such
as storage modulus as it is curing. For example, the photocurable
resin composition, as it is curing has a storage shear modulus (G')
value greater than 1.0.times.10.sup.5 Pa, e.g., from about
5.0.times.10.sup.5 Pa to about 1.0.times.10.sup.6 Pa or to about
1.0.times.10.sup.7 Pa, when measured on a Real Time-Dynamic
Mechanical Analyzer (RT-DMA) with an 8 mm plate and a sample gap of
0.10 mm at 3.9 seconds from the beginning of light exposure of
44-50 mW/cm.sup.2 light intensity for 1.0 second. In some
embodiments, the G' value is from about 6.0.times.10.sup.5 Pa to
about 9.0.times.10.sup.5 Pa, and in some other embodiments, the G'
value is from about 7.0.times.10.sup.5 Pato about
8.0.times.10.sup.5 Pa.
[0033] In accordance with an embodiment, the photocurable resin
composition for additive fabrication includes at least one
free-radical polymerizable component and at least one cationic
polymerizable component.
[0034] In accordance with an embodiment of the invention, the
photocurable resin composition for additive fabrication of the
invention comprises at least one free-radical polymerizable
component, that is, a component which undergoes polymerization
initiated by free radicals. The free-radical polymerizable
components are monomers, oligomers, and/or polymers; they are
monofunctional or polyfunctional materials, i.e., have 1, 2, 3, 4,
5, 6, 7, 8, 9, 10, 20, 30, 40, 50, 100, or more functional groups
that can polymerize by free radical initiation, may contain
aliphatic, aromatic, cycloaliphatic, arylaliphatic, heterocyclic
moiety(ies), or any combination thereof. Examples of 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 A1. The dendritic polymers may contain one type of
polymerizable functional group or different types of polymerizable
functional groups, for example, acrylates and methacrylate
functions.
[0035] Examples of free-radical polymerizable components include
acrylates and methacrylates such as isobornyl (meth)acrylate,
bornyl (meth)acrylate, tricyclodecanyl (meth)acrylate,
dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate,
cyclohexyl (meth)acrylate, benzyl (meth)acrylate, 4-butylcyclohexyl
(meth)acrylate, acryloyl morpholine, (meth)acrylic acid,
2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,
2-hydroxybutyl (meth)acrylate, methyl (meth)acrylate, ethyl
(meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate,
butyl (meth)acrylate, amyl (meth)acrylate, isobutyl (meth)acrylate,
t-butyl (meth)acrylate, pentyl (meth)acrylate, caprolactone
acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl
(meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate,
2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl
(meth)acrylate, isodecyl (meth)acrylate, tridecyl (meth)acrylate,
undecyl (meth)acrylate, lauryl (meth)acrylate, stearyl
(meth)acrylate, isostearyl (meth)acrylate, tetrahydrofurfuryl
(meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol
(meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate,
polyethylene glycol mono(meth)acrylate, polypropylene glycol
mono(meth)acrylate, methoxyethylene glycol (meth)acrylate,
ethoxyethyl (meth)acrylate, methoxypolyethylene glycol
(meth)acrylate, methoxypolypropylene glycol (meth)acrylate,
diacetone (meth)acrylamide, beta-carboxyethyl (meth)acrylate,
phthalic acid (meth)acrylate, dimethylaminoethyl (meth)acrylate,
diethylaminoethyl (meth)acrylate, butylcarbamylethyl
(meth)acrylate, n-isopropyl (meth)acrylamide fluorinated
(meth)acrylate, 7-amino-3,7-dimethyloctyl (meth)acrylate.
[0036] Examples of 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-[1,1-dimethyl-2-[(1-oxoallyl)oxy]ethyl]-5-ethyl-1,3-dioxan-5-yl]methyl
acrylate;
3,9-bis(1,1-dimethyl-2-hydroxyethyl)-2,4,8,10-tetraoxaspiro[5.5-
]undecane di(meth)acrylate; dipentaerythritol
monohydroxypenta(meth)acrylate, propoxylated trimethylolpropane
tri(meth)acrylate, propoxylated neopentyl glycol di(meth)acrylate,
tetraethylene glycol di(meth)acrylate, polyethylene glycol
di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol
di(meth)acrylate, neopentyl glycol di(meth)acrylate, polybutanediol
di(meth)acrylate, tripropyleneglycol di(meth)acrylate, glycerol
tri(meth)acrylate, phosphoric acid mono- and di(meth)acrylates,
C.sub.7-C.sub.20 alkyl di(meth)acrylates,
tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate,
tris(2-hydroxyethyl)isocyanurate di(meth)acrylate, pentaerythritol
tri(meth)acrylate, pentaerythritol tetra(meth)acrylate,
dipentaerythritol hexa(meth)crylate, tricyclodecane diyl dimethyl
di(meth)acrylate and alkoxylated versions (e.g., ethoxylated and/or
propoxylated) of any of the preceding monomers, and also
di(meth)acrylate of a diol which is an ethylene oxide or propylene
oxide adduct to bisphenol A, di(meth)acrylate of a diol which is an
ethylene oxide or propylene oxide adduct to hydrogenated bisphenol
A, epoxy (meth)acrylate which is a (meth)acrylate adduct to
bisphenol A of diglycidyl ether, diacrylate of polyoxyalkylated
bisphenol A, and triethylene glycol divinyl ether, and adducts of
hydroxyethyl acrylate.
[0037] In accordance with an embodiment, the polyfunctional
(meth)acrylates of the polyfunctional component may include all
methacryloyl groups, all acryloyl groups, or any combination of
methacryloyl and acryloyl groups. In an embodiment, 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-[1,1-dimethyl-2-[(1-oxoallyl)oxy]ethyl]-5-ethyl-1,3-dioxan-5-yl]methyl
acrylate, dipentaerythritol monohydroxypenta(meth)acrylate,
dipentaerythritol hexa(meth)crylate, propoxylated
trimethylolpropane tri(meth)acrylate, and propoxylated neopentyl
glycol di(meth)acrylate, and any combination thereof.
[0038] In another embodiment, the free-radical polymerizable
component is selected from the group consisting of bisphenol A
diglycidyl ether diacrylate, dicyclopentadiene dimethanol
diacrylate,
[2-[1,1-dimethyl-2-[(1-oxoallyl)oxy]ethyl]-5-ethyl-1,3-dioxan-5-yl]methyl
acrylate, dipentaerythritol monohydroxypentaacrylate, propoxylated
trimethylolpropane triacrylate, and propoxylated neopentyl glycol
diacrylate, and any combination thereof.
[0039] In specific embodiments, the photocurable resin compositions
for additive fabrication 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.
[0040] The photocurable resin composition for additive fabrication
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.
[0041] In accordance with an embodiment, the photocurable resin
compositions for additive fabrication of the invention comprise at
least one cationically polymerizable component, that is, a
component which undergoes polymerization initiated by cations or in
the presence of acid generators. The cationically polymerizable
components may be monomers, oligomers, and/or polymers, and may
contain aliphatic, aromatic, cycloaliphatic, arylaliphatic,
heterocyclic moiety(ies), and any combination thereof. Suitable
cyclic ether compounds can comprise cyclic ether groups as side
groups or groups that form part of an alicyclic or heterocyclic
ring system.
[0042] 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.
[0043] 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.
Specific examples of 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-vinylepoxycyclohexane, vinylcyclohexene dioxide, limonene oxide,
limonene dioxide, bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate,
3,4-epoxy-6-methylcyclohexyl-3',4'-epoxy-6'-methylcyclohexanecarboxylate,
.epsilon.-caprolactone-modified
3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylates,
trimethylcaprolactone-modified
3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexane carboxylates,
.beta.-methyl-.delta.-valerolactone-modified
3,4-epoxycyclohexcylmethyl-3',4'-epoxycyclohexane carboxylates,
methylenebis(3,4-epoxycyclohexane), bicyclohexyl-3,3'-epoxide,
bis(3,4-epoxycyclohexyl) with a linkage of --O--, --S--, --SO--,
--SO.sub.2--, --C(CH.sub.3).sub.2--, --C(CBr.sub.3).sub.2--,
--C(CF.sub.3).sub.2--, --C(CCl.sub.3).sub.2--, or
--CH(C.sub.6H.sub.5)--, dicyclopentadiene diepoxide,
di(3,4-epoxycyclohexylmethyl)ether of ethylene glycol,
ethylenebis(3,4-epoxycyclohexanecarboxylate),
epoxyhexahydrodioctylphthalate, epoxyhexahydro-di-2-ethylhexyl
phthalate, 1,4-butanediol diglycidyl ether, 1,6-hexanediol
diglycidyl ether, neopentylglycol diglycidyl ether, glycerol
triglycidyl ether, trimethylolpropane triglycidyl ether,
polyethylene glycol diglycidyl ether, polypropylene glycol
diglycidyl ether, polyglycidyl ethers of polyether polyol obtained
by the addition of one or more alkylene oxides to aliphatic
polyhydric alcohols such as ethylene glycol, propylene glycol, and
glycerol, diglycidyl esters of aliphatic long-chain dibasic acids,
monoglycidyl ethers of aliphatic higher alcohols, monoglycidyl
ethers of phenol, cresol, butyl phenol, or polyether alcohols
obtained by the addition of alkylene oxide to these compounds,
glycidyl esters of higher fatty acids, epoxidated soybean oil,
epoxybutylstearic acid, epoxyoctylstearic acid, epoxidated linseed
oil, epoxidated polybutadiene,
1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene,
3-ethyl-3-hydroxymethyloxetane,
3-ethyl-3-(3-hydroxypropyl)oxymethyloxetane,
3-ethyl-3-(4-hydroxybutyl)oxymethyloxetane,
3-ethyl-3-(5-hydroxypentyl)oxymethyloxetane,
3-ethyl-3-phenoxymethyloxetane,
bis((1-ethyl(3-oxetanyl))methyl)ether,
3-ethyl-3-((2-ethylhexyloxy)methyl)oxetane,
3-ethyl-((triethoxysilylpropoxymethyl)oxetane,
3-(meth)-allyloxymethyl-3-ethyloxetane,
(3-ethyl-3-oxetanylmethoxy)methylbenzene,
4-fluoro-[1-(3-ethyl-3-oxetanylmethoxy)methyl]benzene,
4-methoxy-[1-(3-ethyl-3-oxetanylmethoxy)methyd-benzene,
[1-(3-ethyl-3-oxetanylmethoxy)ethyl]phenyl ether,
isobutoxymethyl(3-ethyl-3-oxetanylmethyl)ether,
2-ethylhexyl(3-ethyl-3-oxetanylmethyl)ether, ethyldiethylene
glycol(3-ethyl-3-oxetanylmethyl)ether, dicyclopentadiene
(3-ethyl-3-oxetanylmethyl)ether,
dicyclopentenyloxyethyl(3-ethyl-3-oxetanylmethyl)ether,
dicyclopentenyl(3-ethyl-3-oxetanylmethyl)ether,
tetrahydrofurfuyl(3-ethyl-3-oxetanylmethyl)ether,
2-hydroxyethyl(3-ethyl-3-oxetanylmethyl)ether,
2-hydroxypropyl(3-ethyl-3-oxetanylmethyl)ether, and any combination
thereof. Examples of polyfunctional materials that are cationically
polymerizable include dendritic polymers such as dendrimers, linear
dendritic polymers, dendrigraft polymers, hyperbranched polymers,
star branched polymers, and hypergraft polymers with epoxy or
oxetane functional groups. The dendritic polymers may contain one
type of polymerizable functional group or different types of
polymerizable functional groups, for example, epoxy and oxetane
functions.
[0044] In embodiments of the invention, the cationic polymerizable
component is at least one selected from the group consisting of a
cycloaliphatic epoxy and an oxetane. In a specific embodiment, the
cationic polymerizable component is an oxetane, for example, an
oxetane containing 2 or more than 2 oxetane groups. In another
specific embodiment, the cationic polymerizable component is a
cycloaliphatic epoxy, for example, a cycloaliphatic epoxy with 2 or
more than 2 epoxy groups.
[0045] In an embodiment, the epoxide is
3,4-epoxycyclohexylmethyl-3',4-epoxycyclohexanecarboxylate
(available as CELLOXIDE.TM. 2021 P from Daicel Chemical, or as
CYRACURE.TM. UVR-6105 from Dow Chemical), hydrogenated bisphenol
A-epichlorohydrin based epoxy resin (available as EPONEX.TM. 1510
from Hexion), 1,4-cyclohexanedimethanol diglycidyl ether (available
as HELOXY.TM. 107 from Hexion), a mixture of dicyclohexyl diepoxide
and nanosilica (available as NANOPDX.TM.), and any combination
thereof.
[0046] The above-mentioned cationically polymerizable compounds can
be used singly or in combination of two or more thereof.
[0047] The photocurable resin composition for additive fabrication
can include any suitable amount of the cationic polymerizable
component, for example, in certain embodiments, in an amount up to
about 95% by weight of the composition, and in certain embodiments,
up to about 50% by weight of the composition. In further
embodiments the amount of the cationic polymerizable component is
from about 5% to about 70% by weight of the composition. In further
embodiments from about 5% to about 25% by weight of the
composition
[0048] In accordance with an embodiment, the polymerizable
component of the photocurable resin composition for additive
fabrication 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. Other
examples of such a polymerizable component include those that
contain an acrylate and an epoxy group, or an acrylate and an
oxetane group, on a same molecule.
[0049] In embodiments, the photocurable resin composition for
additive fabrication 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 function 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.
[0050] Typically, free radical photoinitiators are divided into
those that form radicals by cleavage, known as "Norrish Type I" and
those that form radicals by hydrogen abstraction, known as "Norrish
type II". The Norrish type II photoinitiators require a hydrogen
donor, which serves as the free radical source. As the initiation
is based on a bimolecular reaction, the Norrish type II
photoinitiators are generally slower than Norrish type I
photoinitiators which are based on the unimolecular formation of
radicals. On the other hand, 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, in the presence
of hydrogen donors, such as alcohols, amines, or thiols leads to
the formation of a radical produced from the carbonyl compound
(ketyl-type radical) and another radical derived from the hydrogen
donor. 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 delocalization of an
unpaired electron.
[0051] To successfully formulate a photocurable resin composition
for additive fabrication, it is necessary to review the wavelength
sensitivity of the photoinitiator(s) present in the composition to
determine if they will be activated by the LED light chosen to
provide the curing light.
[0052] In accordance with an embodiment, the photocurable resin
composition for additive fabrication includes at least one free
radical photoinitiator, e.g., those selected from the group
consisting of benzoylphosphine oxides, aryl ketones, benzophenones,
hydroxylated ketones, 1-hydroxyphenyl ketones, ketals,
metallocenes, and any combination thereof.
[0053] In an embodiment, the photocurable resin composition for
additive fabrication includes at least one free-radical
photoinitiator selected from the group consisting of
2,4,6-trimethylbenzoyl diphenylphosphine oxide and
2,4,6-trimethylbenzoyl phenyl, ethoxy phosphine oxide,
bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide,
2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1,2-benzyl-2-(dim-
ethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone,
2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-o-
ne, 4-benzoyl-4'-methyl diphenyl sulphide, 4,4'-bis(diethylamino)
benzophenone, and 4,4'-bis(N,N'-dimethylamino)benzophenone
(Michler's ketone), benzophenone, 4-methyl benzophenone,
2,4,6-trimethyl benzophenone, dimethoxybenzophenone,
1-hydroxycyclohexyl phenyl ketone, phenyl
(1-hydroxyisopropyl)ketone,
2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone,
4-isopropylphenyl(1-hydroxyisopropyl)ketone,
oligo-[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone],
camphorquinone, 4,4'-bis(diethylamino)benzophenone, benzyl dimethyl
ketal, bis(eta 5-2-4-cyclopentadien-1-yl)
bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titanium, and any
combination thereof.
[0054] For LED light sources emitting in the 300-475 nm wavelength
range, especially those emitting at 365 nm, 390 nm, or 395 nm,
examples of 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-1-[4-(methylthio)phenyl]-2-morpholinopropanone-1 (Irgacure
907 from Ciba),
2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone
(Irgacure 369 from Ciba),
2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-o-
ne (Irgacure 379 from Ciba), 4-benzoyl-4'-methyl diphenyl sulphide
(Chivacure BMS from Chitec), 4,4'-bis(diethylamino) benzophenone
(Chivacure EMK from Chitec), and
4,4'-bis(N,N'-dimethylamino)benzophenone (Michler's ketone). Also
suitable are mixtures thereof.
[0055] Additionally, photosensitizers are useful in conjunction
with photoinitiators in effecting cure with LED light sources
emitting in this wavelength range. Examples of 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
1-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 from Chitec),
4,4'-bis(diethylamino)benzophenone (Chivacure EMK from Chitec).
[0056] It is possible for LED UV light sources to be designed to
emit light at shorter wavelengths. In embodiments, a
photosensitizer is used when curing with LED light sources emitting
at wavelengths from between about 100 and about 300 nm. When
photosensitizers, such as those previously listed are present in
the formulation, other photoinitiators absorbing at shorter
wavelengths can be used. Examples of such photoinitiators include:
benzophenones, such as benzophenone, 4-methyl benzophenone,
2,4,6-trimethyl benzophenone, and dimethoxybenzophenone, and,
1-hydroxyphenyl ketones, such as 1-hydroxycyclohexyl phenyl ketone,
phenyl (1-hydroxyisopropyl)ketone,
2-hydroxy-1-[4-(2-hroxyethoxy)phenyl]-2-methyl-1-propanone, and
4-isopropylphenyl(1-hydroxyisopropyl)ketone, benzil dimethyl ketal,
and oligo-[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone]
(Esacure KIP 150 from Lambeth).
[0057] LED light sources can also be designed to emit visible
light. For LED light sources emitting light at wavelengths from
about 475 nm to about 900 nm, examples of suitable free radical
photoinitiators include: camphorquinone,
4,4'-bis(diethylamino)benzophenone (Chivacure EMK from Chitec),
4,4'-bis(N,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-1-yl)
bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titanium (Irgacure 784
from Ciba), and the visible light photoinitiators from Spectra
Group Limited, Inc. such as H-Nu 470, H-Nu-535, H-Nu-635,
H-Nu-Blue-640, and H-Nu-Blue-660. It is often desirable to employ a
photosensitizer with a photoinitiator for LED light sources
emitting between 475 nm and 900 nm.
[0058] In one embodiment of the instant claimed invention, the
light emitted by the LED is UVA radiation, which is radiation with
a wavelength between about 320 and about 400 nm. In one embodiment
of the instant claimed invention, the light emitted by the LED is
UVB radiation, which is radiation with a wavelength between about
280 and about 320 nm. In one embodiment of the instant claimed
invention, the light emitted by the LED is UVC radiation, which is
radiation with a wavelength between about 100 and about 280 nm.
[0059] The photocurable resin composition for additive fabrication
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.
[0060] In accordance with an embodiment, the photocurable resin
composition for additive fabrication includes a photoinitiating
system that is a photoinitiator having both cationic initiating
function and free radical initiating function.
[0061] In accordance with an embodiment, the photocurable resin
composition for additive fabrication includes a cationic
photoinitiator. The cationic photoinitiator generates photoacids
upon irradiation of light. They generate Bronsted or Lewis acids
upon irradiation. Any suitable cationic photoinitiator can be used,
for example, those 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, sulfonium antimonate
salts, ferrocenes, di(cyclopentadienyliron)arene salt compounds,
and pyridinium salts, and any combination thereof. Onium salts,
e.g., iodonium salts, sulfonium salts and ferrocenes, have the
advantage that they are thermally stable. Thus, any residual
photoinitiator does not continue to cure after the removal of the
irradiating light. Cationic photoinitiators offer the advantage
that they are not sensitive to oxygen present in the
atmosphere.
[0062] The photocurable resin composition for additive fabrication
of the invention includes at least one cationic photoinitiator,
wherein 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 silanol aluminium complexes, and any
combination thereof. In an embodiment, the cationic photoinitiator
is selected from the group consisting of aromatic sulfonium salts,
aromatic iodonium salts, and metallocene based compounds, and any
combination thereof. In another embodiment, the cationic
photoinitiator is selected from the group consisting of
triarylsulfonium salts, diaryliodonium salts, and metallocene based
compounds, and any combination thereof.
[0063] In a particular embodiment, the cationic photoinitiator has
an anion selected from the group consisting of BF.sub.4.sup.-,
AsF.sub.6.sup.-, SbF.sub.6.sup.-, PF.sub.6.sup.-,
B(C.sub.6F.sub.5).sub.4.sup.-, perfluoroalkylsulfonates,
perfluoroalkylphosphates, and carborane anions.
[0064] In an embodiment, 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.sub.6.sup.-, PF.sub.6.sup.-, B(C.sub.6F.sub.5).sub.4.sup.-,
perfluoroalkylsulfonates, perfluoroalkylphosphates, and
(CH.sub.6B.sub.11Cl.sub.6).sup.-.
[0065] In a particular embodiment, the cationic photoinitiator is
an aromatic sulfonium salt based cationic photoinitiator selected
from the group consisting of
4-(4-benzoylphenylthio)phenyldiphenylsulfonium
hexafluoroantimonate,
4-(4-benzoylphenylthio)phenylbis(4-hydroxyethyloxyphenyl)sulfonium
hexafluoroantimonate,
4-(4-benzoylphenylthio)phenylbis(4-fluorophenyl)sulfonium
hexafluoroantimonate,
4-(4-benzoylphenylthio)phenylbis(4-chlorophenyl)sulfonium
hexafluoroantimonate,
4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium
hexafluoroantimonate,
4-(4-benzoylphenylthio)phenylbis(4-methylphenyl)sulfonium
hexafluoroantimonate,
4-(4-benzoylphenylthio)phenylbis(4-hydroxyethylphenyl)sulfonium
hexafluoroantimonate,
4-[4-(4-hydroxyethyloxybenzoyl)phenylthio]phenylbis(4-fluoro
phenyl)sulfonium hexafluoroantimonate,
4-[4-(4-hydroxyethyloxybenzoyl)phenylthio]phenyldiphenylsulfonium
hexafluoroantimonate,
4-[4-(4-hydroxyethyloxybenzoyl)phenylthio]phenylbis(4-hydroxyethyloxyphen-
yl)sulfonium hexafluoroantimonate,
4-(4-benzoylphenylthio)phenylbis(4-methoxyethoxyphenyl)sulfonium
hexafluoroantimonate,
4-[4-(3-methoxybenzoyl)phenylthio]phenyldiphenylsulfonium
hexafluoroantimonate,
4-[4-(3-methoxycarbonylbenzoyl)phenylthio]phenyldiphenylsulfonium
hexafluoroantimonate,
4-[4-(2-hydroxymethylbenzoyl)phenylthio]phenyldiphenylsulfonium
hexafluoroantimonate,
4-[4-(4-methylbenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium
hexafluoroantimonate, 4-[4-(4-)
phenylthio]phenylbis(4-fluorophenyl)sulfonium hexafluoroantimonate,
4-[4-(4-fluorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium
hexafluoroantimonate,
4-[4-(2-methoxycarbonylbenzoyl)phenylthio]phenylbis(4-fluoro
phenyl)sulfonium hexafluoroantimonate,
bis[4-(diphenylsulfonio)phenyl]sulfide bishexafluorophosphate,
bis[4-(diphenylsulfonio)phenyl]sulfide bistetrafluoroborate,
bis[4-(diphenylsulfonio)phenyl]sulfide
tetrakis(pentafluorophenyl)borate,
diphenyl-4-(phenylthio)phenylsulfonium hexafluorophosphate,
diphenyl-4-(phenylthio)phenylsulfonium tetrafluoroborate,
diphenyl-4-(phenylthio)phenylsulfonium
tetrakis(pentafluorophenyl)borate, triphenylsulfonium
hexafluorophosphate, triphenylsulfonium hexafluoroantimonate,
triphenylsulfonium tetrafluoroborate, triphenylsulfonium
tetrakis(pentafluorophenyl)borate,
bis[4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide
bishexafluorophosphate,
bis[4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide
bistetrafluoroborate, and
bis[4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl]sulfide
tetrakis(pentafluorophenyl)borate, and any combination thereof.
[0066] In another embodiment, the cationic photoinitiator is an
aromatic iodonium salt based cationic photoinitiator selected from
the group consisting of diphenyliodonium hexafluorophosphate,
diphenyliodonium hexafluoroantimonate, diphenyliodonium
tetrafluoroborate, diphenyliodonium
tetrakis(pentafluorophenyl)borate, bis(dodecylphenyl)iodonium
hexafluorophosphate, bis(dodecylphenyl)iodonium
hexafluoroantimonate, bis(dodecylphenyl)iodonium tetrafluoroborate,
bis(dodecylphenyl)iodonium tetrakis(pentafluorophenyl)borate,
4-methylphenyl-4-(1-methylethyl)phenyliodonium hexafluorophosphate,
4-methylphenyl-4-(1-methylethyl)phenyliodonium
hexafluoroantimonate,
4-methylphenyl-4-(1-methylethyl)phenyliodonium tetrafluoroborate,
and 4-methylphenyl-4-(1-methylethyl)phenyliodonium
tetrakis(pentafluorophenyl)borate, and any combination thereof.
[0067] In certain embodiments, the cationic photoinitiator is
selected from the group consisting of
tetrakis(pentafluorophenyl)borate or hexafluoroantimonate salt of
4-(4-benzoylphenylthio)phenyldiphenylsulfonium,
4-(4-benzoylphenylthio)phenylbis(4-hydroxyethyloxyphenyl)sulfonium,
4-(4-benzoylphenylthio)phenylbis(4-fluorophenyl)sulfonium,
4-(4-benzoylphenylthio)phenylbis(4-chlorophenyl)sulfonium,
4-[4-(3-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium,
4-[4-(2-chlorobenzoyl)phenylthio]phenylbis(4-fluorophenyl)sulfonium,
(4-thiophenoxyphenyl)diphenylsulfonium,
S,S,S',S'-tetraphenylthiobis(4,1-phenylene)disulfonium,
triphenylsulfonium, (chlorophenyl)diphenylsulfonium,
chloro[S-(phenyl)thianthrenium], S-(phenyl)thianthrenium,
diphenyl-4-(4'-thiophenoxy)thiophenoxyphenylsulfonium,
phenyldi(4-thiophenoxyphenyl)sulfonium,
S-(4-thiophenoxyphenyl)thianthrenium, and
(thiodi-4,1-phenylene)bis[bis[4-(2-hydroxyethoxy)phenyl]sulfonium,
tris(4-(4-acetylphenyl)thiophenyl)sulfonium,
bis(4-dodecylphenyl)iodonium,
[4-[(2-hydroxytetradecyl)oxy]phenyl]phenyliodonium,
(4-methylphenyl)[4-[[2-[[[[3-(trifluoromethyl)phenyl]amino]carbonyl]oxy]t-
etradecyl]oxy]phenyl]iodonium, bis(4-dodecylphenyl)iodonium,
[4-(1-methylethyl)phenyl](4-methylphenyl)iodonium, and any
combination thereof.
[0068] In an illustrative embodiment, the photocurable resin
composition for additive fabrication includes a cationic
photoinitiator selected from the group consisting of
triarylsulfonium SbF.sub.6.sup.-, triarylsulfonium borate,
tris(4-(4-acetylphenyl)thiophenyl)sulfonium
tetrakis(pentafluorophenyl)borate, diaryliodonium borate, iodonium
[4-(1-methylethyl)phenyl](4-methylphenyl)-tetrakis(pentafluorophenyl)bora-
te, and any combination thereof. A normucleophilic anion serves as
the counterion. Examples of such anions include BF.sub.4.sup.-,
AsF.sub.6.sup.-, SbF.sub.6.sup.-, PF.sub.6.sup.-,
B(C.sub.6F.sub.5).sub.4.sup.-, perfluoroalkylsulfonates,
perfluoroalkylphosphates, and carborane anions such as
(CH.sub.6B.sub.11Cl.sub.6).sup.-.
[0069] 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
tetrakis(pentafluorophenyl)borate, and
tris(4-(4-acetylphenyl)thiophenyl)sulfonium
tetrakis(pentafluorophenyl)borate (GSID4480-1 also known as
IRGACURE.RTM. PAG 290) from Ciba used in some of the example
compositions.
[0070] In some embodiments it is desirable for the photocurable
resin composition for additive fabrication to include a
photosensitizer. The term "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.sup.rd Ed., 1991, page 222. Examples of 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. Particular examples of
photosensitizers include those selected from the group consisting
of [4-[(4-methylphenyl)thio]phenyl]phenyl.sup.-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-ethylanthraquinone,
2-tertbutylanthraquinone, 1-chloroanthraquinone,
2-amylanthraquinone, thioxanthones and xanthones, isopropyl
thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone,
1-chloro-4-propoxythioxanthone, methyl benzoyl formate,
methyl-2-benzoyl benzoate, 4-benzoyl-4'-methyl diphenyl sulphide,
4,4'-bis(diethylamino) benzophenone, and any combination
thereof.
[0071] Additionally, photosensitizers are useful in combination
with photoinitiators in effecting cure with LED light sources
emitting in the wavelength range of 300-475 nm. Examples of
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
1-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 from Chitec),
4,4'-bis(diethylamino)benzophenone (Chivacure EMK from Chitec).
[0072] In an embodiment, 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
##STR00001##
and any combination thereof.
[0073] The photocurable resin composition for additive fabrication
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.
[0074] When photosensitizers are employed, other photoinitiators
absorbing at shorter wavelengths can be used. Examples of such
photoinitiators include: benzophenones, such as benzophenone,
4-methyl benzophenone, 2,4,6-trimethyl benzophenone, and
dimethoxybenzophenone, and 1-hydroxyphenyl ketones, such as
1-hydroxycyclohexyl phenyl ketone, phenyl
(1-hydroxyisopropyl)ketone,
2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, and
4-isopropylphenyl(1-hydroxyisopropyl)ketone, benzil dimethyl ketal,
and oligo-[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone]
(Esacure KIP 150 from Lamberti). These photoinitiators when used in
combination with a photosensitizer are suitable for use with LED
light sources emitting at wavelengths from about 100 nm to about
300 nm.
[0075] LED light sources that emit visible light are also known.
For LED light sources emitting light at wavelengths greater than
about 400 nm, e.g., from about 475 nm to about 900 nm, examples of
suitable photoinitiators include: camphorquinone,
4,4'-bis(diethylamino) benzophenone (Chivacure EMK from Chitec),
4,4'-bis(N,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-1-yl)bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titan-
ium (Irgacure 784 from Ciba), and the visible light photoinitiators
from Spectra Group Limited, Inc. such as H-Nu 470, H-Nu-535,
H-Nu-635, H-Nu-Blue-640, and H-Nu-Blue-660.
[0076] 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, .alpha.-hydroxyalkylphenones,
4-benzoyl-4'-methyldiphenyl sulfide, acridine orange, and
benzoflavin.
[0077] There are a large number of known and technically proven
cationic photoinitiators that are suitable. They include, for
example, 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 94915,
which are both hereby incorporated in their entirety by
reference.
[0078] A survey of other current onium salt initiators and/or
metallocene salts can be found in "UV Curing, Science and
Technology", (Editor S. P. Pappas, Technology Marketing Corp., 642
Westover Road, Stamford, Conn., U.S.A.) or "Chemistry &
Technology of UV & EB Formulation for Coatings, Inks &
Paints", Vol. 3 (edited by P. K. T. Oldring).
[0079] Suitable ferrocene type cationic photoinitiators include,
for example, di(cyclopentadienyliron)arene salt compounds of
formula (I) as disclosed in Chinese Patent No. CN 101190931:
##STR00002##
wherein anion MXn is selected from BF4, PF6, SbF6, AsF6,
(C6F5).sub.4B, C104, CF3SO3, FSO3, CH3SO3, C4F9SO3, and Ar is a
fused ring or polycyclic arene.
[0080] Other illustrative ferrocene type cationic photoinitiators
include, for example, (.eta.6-Carbazole)(.eta.5-cyclopenta-dienyl)
iron hexafluorophosphate salts, specifically
[cyclopentadiene-Fe--N-butylcarbazole]hexafluoro-phosphate (C4-CFS
PF6) and [cyclopentadiene-Fe--N-octyl-carbazole]hexafluorophosphate
(C8-CFS PF6), bearing C4 and C8 alkyl chains, respectively, on the
nitrogen atom (see Polymer Eng. & Science (2009), 49(3),
613-618); ferrocenium dication salts, e.g., biphenyl
bis[(.pi.-cyclopentadienyl)iron]hexafluorophosphate
([bis(Cp-Fe)-biphenyl](PF6).sub.2) and straight
cyclopentadien-iron-biphenyl hexafluorophosphate
([Cp-Fe-biphenyl]+PF6-) as disclosed in Chinese J. Chem. Engnrng
(2008), 16(5), 819-822 and Polymer Bulltn (2005), 53(5-6), 323-331;
cyclopentadienyl-Fe-carbazole hexafluorophosphate
([Cp-Fe-carbazole]+PF6-), cyclopentadienyl-Fe--N-ethylcarbazole
hexafluorophosphate ([Cp-Fe-n-ethylcarbazole]+PF6-) and
cyclopentadienyl-Fe-aminonaphthalene hexafluorophosphate
([Cp-Fe-aminonaphthalene]+PF6-) as disclosed in J Photochem. &
Photobiology, A: Chemistry (2007), 187(2-3), 389-394 and Polymer
Intnl (2005), 54(9), 1251-1255; 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.
of Chem Engnrng (2006), 14(6), 806-809; 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(.eta.6-tol)]BF4, as disclosed in
Ganguang Kexue Yu Guang Huaxue (2002), 20(3), 177-184, Ferrocenium
salts (.eta.6-.alpha.-naphthoxybenzene)
(.eta.5-cyclopentadienyl)iron hexafluorophosphate (NOFC-1) and
(.eta.6-.beta.-naphthoxybenzene)(.eta.5-cyclopentadienyl)iron
hexafluorophosphate (NOFC-2), as disclosed in Int. J. of
Photoenergy (2009), Article ID 981065; (.eta.6-Diphenyl-methane)
(.eta.5-cyclopentadienyl) iron hexafluorophosphate and
(.eta.6-benzophenone) (.eta.5-cyclopenta-dienyl)iron
hexafluorophosphate, as disclosed in Progress in Organic Coatings
(2009), 65(2), 251-256; [CpFe(.eta.6-isopropyl-benzene)]PF6, as
disclosed in Chem Comm (1999), (17), 1631-1632; and any combination
thereof.
[0081] 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. Pat. Nos. 5,639,413; 5,705,116;
5,494,618; 6,593,388; and Chemistry of Materials (2002), 14(11),
4858-4866; aromatic sulfonium or iodonium salts as disclosed in
U.S. Patent Application No. 2008/0292993; diaryl-, triaryl-, or
dialkylphenacylsulfonium salts, as disclosed in US2008260960 and J.
Poly Sci, Part A (2005), 43(21), 5217; diphenyl-iodonium
hexafluorophosphate (Ph2I+PF6-), as disclosed in Macromolecules
(2008), 41(10), 3468-3471; onium salts using onium salts using less
toxic anions to replace, e.g., SbF6-. Mentioned are anions:
B(C6F5)4-, Ga(C6F5)4- and perfluoroalkyl fluorophosphate,
PFnRf(6-n)-, as disclosed in Nettowaku Porima (2007), 28(3),
101-108; Photoactive allyl ammonium salt (BPEA) containing
benzophenone moiety in the structure, as disclosed in Eur Polymer J
(2002), 38(9), 1845-1850; 1-(4-Hydroxy-3-methylphenyl)
tetrahydrothiophenium hexafluoroantimonate, as disclosed in Polymer
(1997), 38(7), 1719-1723; and any combination thereof.
[0082] Illustrative iodonium type cationic photoinitiators include,
for example, diaryliodonium salts having counterions like
hexafluorophosphate and the like, such as, for example,
(4-n-pentadecyloxy-phenyl)phenyliodonium hexafluoroantimonate, as
disclosed in US2006041032; diphenyliodonium hexafluorophosphate, as
disclosed in U.S. Pat. No. 4,394,403 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. & Methods in Physics Res, B (2007), 264(2),
318-322; 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.
[0083] Illustrative sulfonium type cationic photoinitiators
include, for example, UVI 6992 (sulfonium salt) as disclosed in
Japanese patent JP2007126612; compounds of the formula:
##STR00003##
where R1-2=F; R3=isopropyl; R4=H; X=PF6, as disclosed in Japanese
patent JP10101718; thioxanthone-based sulfonium salts, e.g., of the
formula:
##STR00004##
as disclosed in U.S. Pat. No. 6,054,501; (Acyloxyphenyl)sulfonium
salts of the type R.sub.3-xS+R.sub.3x A-, where A- is a
non-nucleophilic anion such as AsF.sub.6--, and R.sub.3 may be the
phenyl group shown below:
##STR00005##
as disclosed in U.S. Pat. Nos. 5,159,088;
9,10-dithiophenoxyanthracene alkyldiarylsulfonium salts, e.g.,
ethylphenyl(9-thiophenoxy-anthracenyl-10) sulfonium
hexafluoroantimonate, and the like, as disclosed in U.S. Pat. No.
4,760,013; etc.; triphenylsulfonium hexafluorophosphate salt, as
disclosed in U.S. Pat. No. 4,245,029;
S,S-dimethyl-S-(3,5-dimethyl-2-hydroxyphenyl)sulfonium salts, as
disclosed in J Poly Sci, Part A (2003), 41(16), 2570-2587;
Anthracene-bound sulfonium salts, as disclosed in J Photochem &
Photobiology, A: Chemistry (2003), 159(2), 161-171;
triarylsulfonium salts, as disclosed in J Photopolymer Science
& Tech (2000), 13(1), 117-118 and J Poly Science, Part A
(2008), 46(11), 3820-29; S-aryl-S,S-cycloalkylsulfonium salts, as
disclosed in J Macromol Sci, Part A (2006), 43(9), 1339-1353;
dialkylphenacylsulfonium salts, as disclosed in UV & EB Tech
Expo & Conf, May 2-5, 2004, 55-69 and ACS Symp Ser (2003), 847,
219-230; Dialkyl(4-hydroxyphenyl)sulfonium salts, and their
isomeric dialkyl(2-hydroxyphenyl)sulfonium salts, as disclosed in
ACS 224th Natnl Meeting, Aug. 18-22, 2002, POLY-726;
Dodecyl(4-hydroxy-3,5-dimethylphenyl)methylsulfonium
hexafluorophosphate and similar alkyl analogs other than dodecyl.
Tetrahydro-1-(4-hydroxy-3,5-dimethylphenyl)thiophenium
hexafluorophosphate and
tetrahydro-1-(2-hydroxy-3,5-dimethylphenyl)thiophenium
hexafluorophosphate, as disclosed in ACS Polymer Preprints (2002),
43(2), 918-919; photoinitiators with the general structure
Ar'S+CH3(C12H25)SbF6-, where Ar' is phenacyl (I), 2-indanonyl (II),
4-methoxyphenacyl (III), 2-naphthoylmethyl (IV), 1-anthroylmethyl
(V), or 1-pyrenoylmethyl (VI), as disclosed in J Polymr Sci, Part A
(2000), 38(9), 1433-1442; Triarylsulfonium salts Ar3S+MXn- with
complex metal halide anions such as BF4-, AsF6-, PF6-, and SbF6-,
as disclosed in J Polymr Sci, Part A (1996), 34(16), 3231-3253;
Dialkylphenacylsulfonium and dialkyl(4-hydroxyphenyl)sulfonium
salts, as disclosed in Macromolecules (1981), 14(5), 1141-1147;
Triarylsulfonium salts R2R1S+MFn- (R, R1=Ph or substituted phenyl;
M=B, As, P; n=4 or 6) and the sulfonium salt of formula (I):
##STR00006##
as disclosed in J. Polymr. Sci, Polymr Chem Edition (1979), 17(4),
977-99; aromatic sulfonium salts with, e.g., PF6- anion, e.g., UVI
6970, as disclosed in JP 2000239648; and any combination
thereof.
[0084] 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(11), 2428-31;
N,N'-diethoxy-4,4'-azobis(pyridinium)hexafluorophosphate (DEAP), as
disclosed in Macromolecular Rapid Comm (2008), 29(11), 892-896; and
any combination thereof.
[0085] Other 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
hexafluoro-antimonate (IA) with tolylcumyl-iodonium
tetrakis(pentafluoro-phenyl)borate (IB), and
cumenecyclopentadienyliron(II) hexafluorophosphate with IA and IB,
as disclosed in Designed Monomers and Polymers (2007), 10(4),
327-345; Diazonium salts, e.g., 4-(hexyloxy)-substituted diazonium
salts with complex anions, as disclosed in ACS Symp Series (2003),
847, 202-212; 5-Arylthianthrenium salts, as disclosed in J Poly
Sci, Part A (2002), 40(20), 3465-3480; and any combination
thereof.
[0086] Other suitable cationic photoinitiators include, for
example, triarylsulfonium salts such as triarylsulfonium borates
modified for absorbing long wavelength UV. Illustrative examples of
such 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; U.S. Pat. No. 6,368,769
WO2009047105; WO2009047151; WO2009047152; US 20090208872; and U.S.
Pat. No. 7,611,817.
[0087] 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)sulfon-
ium hexafluoroantimonate (as SP-172) and SP-300 (both available
from Adeka).
[0088] The photocurable resin composition for additive fabrication
can include any suitable amount of the cationic photoinitiator, for
example, in certain embodiments, in 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. In a further
embodiment from about 0.4 wt % to about 6.5 wt % of the
composition. In an embodiment, the above ranges are particularly
suitable for use with epoxy monomers.
[0089] In accordance with an embodiment, the photocurable resin
composition for additive fabrication 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. In an embodiment, 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. In accordance with an embodiment, chain
transfer to a different monomer is a preferred mechanism. In
embodiments, chain transfer tends to produce branched molecules or
crosslinked molecules. Thus, chain transfer offers a way of
controlling the molecular weight distribution, crosslink density,
thermal properties, and/or mechanical properties of the cured resin
composition.
[0090] Any suitable chain transfer agent can be employed. For
example, 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. In an embodiment, 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.sub.2).sub.nO].sub.m,
wherein n can be 1 to 6 and m can be 1 to 100.
[0091] A particular example of a chain transfer agent is
polytetrahydrofuran such as TERATHANE.TM..
[0092] The photocurable resin composition for additive fabrication
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.
[0093] The photocurable resin composition for additive fabrication
of the invention can further include one or more additives selected
from the group consisting of bubble breakers, antioxidants,
surfactants, acid scavengers, pigments, dyes, thickneners, 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 about 8 nanometers to about 50
microns.
[0094] 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. Preferred 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. Most preferred examples of 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. Other possible
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.
[0095] In accordance with an embodiment of the invention, the
photocurable resin composition for additive fabrication 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.sub.g),
and/or mechanical properties (e.g., tensile strength, storage
modulus, loss modulus) of the photocurable resin composition for
additive fabrication or of the cured article.
[0096] Accordingly, in an embodiment, the ratio by weight of
cationic photoinitiator to free-radical photoinitiator (CPI/RPI) 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.
[0097] In accordance with an embodiment, the photocurable resin
composition for additive fabrication 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.
[0098] In accordance with an embodiment, the photocurable resin
composition for additive fabrication is free or substantially free
of antimony-containing initiator (less than 1.5% by weight).
[0099] The present invention further provides a three-dimensional
article comprising a cured photocurable resin composition for
additive fabrication, wherein the cured photocurable resin
composition for additive fabrication is obtained by curing a
photocurable resin composition for additive fabrication by
irradiating it with light emitted from a light emitting diode (LED)
light having a wavelength from about 100 nm to about 900 nm.
[0100] The present invention further provides a process for making
a three-dimensional article comprising the steps of forming and
selectively curing a layer of a photocurable resin composition for
additive fabrication by irradiation with a light emitting diode
(LED) light having a wavelength from about 100 nm to about 900 nm,
the photocurable resin composition and repeating the steps of
forming and selectively curing a layer of the photocurable resin
composition a plurality of times to obtain the three-dimensional
article.
[0101] As used herein, the term "renewable resource material" is
defined as a starting material that is not derived from petroleum
but as a starting material derived from a plant including the
fruits, nuts and/or seeds of plants. These plant derived materials
are environmentally friendly and biologically based materials.
Thus, these starting materials are also frequently called
"bio-based" materials or "natural oil" materials.
[0102] Further to the understood definition of "bio-based,"
according to the FRSIA(Farm Security and Rural Investment Act),
"biobased products" are products determined by the U.S. Secretary
of Agriculture to be "commercial or industrial goods (other than
food or feed) composed in whole or in significant part of
biological products, forestry materials, or renewable domestic
agricultural materials, including plant, animal or marine
materials.
[0103] Biobased content may be determined by testing to ASTM Method
D6866-10, STANDARD TEST METHODS FOR DETERMINING THE BIOBASED
CONTENT OF SOLID, LIQUID, AND GASEOUS SAMPLES USING RADIOCARBON
ANALYSIS. This method, similar to radiocarbon dating, compares how
much of a decaying carbon isotope remains in a sample to how much
would be in the same sample if it were made of entirely recently
grown materials. The percentage is called the product's biobased
content.
[0104] Persons of ordinary skill in the art of photocurable resin
compositions for additive fabrication are aware of how to select
ingredients and understand whether the ingredient is bio-based or
petroleum based. What is different now is the sheer abundance of
bio-based raw materials suitable for use in photocurable resin
compositions for additive fabrication. For example, bio-based raw
materials can be found in polyols and other ingredients.
[0105] In embodiments of the invention, the photocurable resin
compositions for additive fabrication comprise at least 30 wt % of
bio-based ingredients, rather than petroleum based ingredients. In
other embodiments, the photocurable resin compositions for additive
fabrication comprise at least 40 wt % of bio-based ingredients,
rather than petroleum based ingredients.
[0106] The following examples further illustrate the invention but,
of course, should not be construed as in any way limiting its
scope.
Examples 1-56
[0107] These examples illustrate embodiments of the photocurable
resin compositions for additive fabrication. Tables 1A-1D describe
the various components of the photocurable resin compositions for
additive fabrication illustrated in Tables 2-7.
TABLE-US-00001 TABLE 1A Trade Name CAS RN Function in Formula
Chemical Descriptor Supplier 1-pyrenemethanol 24463-15-8
Photosensitizing agent 1-pyrenemethanol Sigma Aldrich
9-anthracenemethanol 1468-95-7 Photosensitizing agent
9-(Hydroxymethyl)anthracene Sigma Aldrich NK Ester A-DOG 87320-05-6
Free radical polymerizable
[2-[1,1-dimethyl-2-[(1-oxoallyl)oxy]ethyl]-5-ethyl- Kowa monomer or
oligomer 1,3-dioxan-5-yl]methyl acrylate Anthracene 120-12-7
Photosensitizing agent Anthracene Sigma Aldrich Anthracure UVS 1101
68818-86-0 Photosensitizing agent 9,10-Diethoxy-anthracene, Kawaski
Kasei BYK A 501 proprietary mixture Bubble breaker Naphtha/methoxy
propanol acetate BYK-Chemie CD 406 67905-41-3 Free radical
polymerizable 1,4-Cyclohexanedimethanol diacrylate Sartomer monomer
or oligomer CD 536 87320-05-6 Free radical polymerizable
2-Propenoic acid, [2-[1,1-dimethyl-2-[(1-oxo-2- Sartomer monomer or
oligomer propenyl)oxy]ethyl]-5-ethyl-1,3-dioxan-5-yl]methyl ester
Celloxide 2021P 25085-98-7; 2386- Cationic polymerizable
(3',4'-Epoxycyclohexylmethyl) 3,4- Daicel Chemical 87-0 monomer or
oligomer epoxycyclohexanecarboxylate Chivacure 1176 159120-95-3
Photoacid generator A mixture of: bis[4- Chitec (mixture)
diphenylsulfoniumphenyl]sulfide bishexafluoroantimonate;
thiophenoxyphenylsulfonium hexafluoroantimonate and propylene
carbonate. CHDM 105-08-8 Chain transfer agent for
1,4-Cyclohexanedimethanol Eastman cationic monomers Chemical
Chivacure BMS 83846-85-9 Photosensitizing agent
[4-[(4-methylphenyl)thio]phenyl]phenyl-methanone Chitec Chivacure
ITX 75081-21-9 Photosensitizing agent
Isopropyl-9H-thioxanthen-9-one Chitec
TABLE-US-00002 TABLE 1B Trade Name CAS RN Function in Formula
Chemical Descriptor Supplier COPIKEM 14 ORANGE 67697-75-0 Color
change dye 3-[N,N-bis(4-octylphenyl)amino]-3-(4- Hilton Davis
dimethylaminophenyl)phthalide Darocur 1173 7473-98-5 Free radical
generator 1-Hydroxy-1-methylethyl phenyl ketone Ciba EBECRYL 3700
4687-94-9 Free radical Bisphenol A diglycidyl ether diacrylate
Cytec polymerizable monomer or oligomer EPONOX 1510 30583-72-
Cationic polymerizable Hydrogenated bisphenol A-epichlorohydrin
based Hexion 3/13410-58-7 monomer or oligomer epoxy resin GRILONIT
F713 26951-52-0 Cationic polymerizable Poly(oxy-1,4-butanediyl),
a-(oxiranylmethyl)-w- EMS monomer or oligomer (oxiranylmethoxy)-
Irgacure PAG 290 Not known Photoacid generator
tris(4-(4-acetylphenyl)thiophenyl)sulfonium Ciba/BASF (GSID 4480-1)
tetrakis(pentafluorophenyl)borate Heloxy 107 14228-73-0 Cationic
polymerizable 1,4-Cyclohexanedimethanol diglycidyl ether Hexion
monomer or oligomer Intermediate DG-0049 proprietary Pigment
dispersion for Pigment dispersion for color effects Desotech
mixture color effects Irgacure 184 947-19-3 Free radical generator
1-Hydroxy-1-cyclohexyl phenyl ketone Ciba IRGANOX 1035 41484-35-9
Antioxidant Benzenepropanoic acid, 3,5-bis(1,1- Ciba
dimethylethyl)-4-hydroxy-, thiodi-2,1-ethanediyl ester Kayarad R
684 42594-17-2 Free radical Dicyclopentadienedimethanol diacrylate
Nippon polymerizable monomer Kayaku or oligomer
TABLE-US-00003 TABLE 1C Trade Name CAS RN Function in Formula
Chemical Descriptor Supplier Longnox 10 6683-19-8 Antioxidant
Pentaerythritol tetrakis[(3,5-di-tert-butyl-4- Longchem
hydroxyphenyl)propionate] C&S Int. Orange Pigment proprietary
Pigment dispersion for Desotech mixture color effects OXT-101
3047-32-3 Cationic polymerizable 3-Ethyl-3-oxetanemethanol Toagosei
monomer or oligomer OXT-121 142627-97-2 Cationic polymerizable
1,4-Bis[(3-ethyl-3- Toagosei monomer or oligomer
oxetanylmethoxy)methyl]benzene OXT-221 18934-00-4 Cationic
polymerizable 3,3'-[Oxybis(methylene)]bis[3-ethyl-oxetane Toagosei
monomer or oligomer Polyvinyl pyrrolidone 9003-39-8 Acid scavenger
Poly[N-vinylpyrrolidinone]; PVP Sigma Aldrich Red Pigment
proprietary Pigment dispersion for Desotech mixture color effects
Rhodorsil 2074 178233-72-2 Photoacid generator Iodonium,
[4-(1-methylethyl)phenyl](4- Rhodia methylphenyl)-,
tetrakis(pentafluorophenyl)borate Rubidium carbonate 584-09-8 Acid
scavenger Dirubidium carbonate; Rb2CO3 Sigma Aldrich Silwet L 7600
mixture Leveling agent Polyalkyleneoxide modified
polydimethylsiloxane Momentive SR 399 60506-81-2 Free radical
Dipentaerythritol monohydroxypentaacrylate Sartomer polymerizable
monomer or oligomer SR 492 53879-54-2 Free radical Propoxylated
trimethylolpropane triacrylate Sartomer polymerizable monomer or
oligomer
TABLE-US-00004 TABLE 1D Trade Name CAS RN Function in Formula
Chemical Descriptor Supplier SR 9003 84170-74-1 Free radical
Propoxylated neopentyl glycol diacrylate Sartomer polymerizable
monomer or oligomer TERATHANE 1000 25190-06-1 Chain transfer agent
for Poly(tetramethylene ether) glycol Invista cationic monomers
VEctomer .RTM. VE 4010 130066-57-8 Cationic polymerizable
Bis(4-vinyloxybutyl) isophthalate Vertellus monomer or oligomer
VEctomer .RTM. VE 5015 196109-17-8 Cationic polymerizable
Tris[4-(vinyloxy)butyl] trimellitate Vertellus monomer or
oligomer
TABLE-US-00005 TABLE 2 Composition Example 1 Example 2 Example 3
Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Name
Part Part Part Part Part Part Part Part Part EBECRYL-3700 25.000
19.659 19.659 19.659 19.659 25.000 25.000 25.000 24.611 CD 406
7.000 7.000 7.000 7.000 Kayarad R 684 6.891 Kowa A-DOG SR492
VEctomer .RTM. VE 5015 VEctomer .RTM. VE 4010 Celloxide 2021P
36.000 54.040 54.04 54.04 54.04 43.910 41.620 39.215 42.034 OXT-101
8.603 8.603 8.603 8.603 OXT-221 OXT-121 TERATHANE-1000 25.000
10.463 10.463 10.463 10.463 17.085 19.375 21.780 19.568 Chivacure
1176 GSID4480-1 CPI 4.000 Rhodorsil 2074 0.750 1 1.5 2 2.000 2.000
2.000 1.969 Irgacure 184 3.000 4.259 4.005 3.5025 3 3.000 3.000
3.000 2.953 Darocur 1173 Chivacure BMS 2.000 2 2 2 2.000 2.000
2.000 1.969 Chivacure ITX 1-pyrenemethanol 9-anthracenemethanol
Anthracure UVS 1101 Longnox 10 0.001 0.005 0.0075 0.01 PVP 0.005
0.005 0.005 0.005 0.005 0.005 0.005 0.005 Rubidium carbonate Silwet
L 7600 0.200 0.2 0.2 0.2 BYK A 501 0.020 0.02 0.02 0.02 Total
100.000 100.000 100.000 100.000 100.000 100.000 100.000 100.000
100.000
TABLE-US-00006 TABLE 3 Example Example Example Example Example
Example Example Example Example Composition 10 11 12 13 14 15 16 17
18 Name Part Part Part Part Part Part Part Part Part EBECRYL-3700
25.000 25.000 25.000 32.000 CD 406 7.000 7.000 7.000 Kayarad R 684
32.000 16.000 32.000 16.000 Kowa A-DOG 16.000 32.000 0.000 16.000
SR492 VEctomer .RTM. VE 5015 VEctomer .RTM. VE 4010 Celloxide 2021P
42.698 46.920 49.570 46.920 46.920 41.055 41.055 41.055 41.055
OXT-101 6.212 6.212 6.212 6.212 OXT-221 OXT-121 TERATHANE-1000
19.877 14.075 11.425 14.075 14.075 10.948 10.948 10.948 10.948
Chivacure 1176 GSID4480-1 CPI Rhodorsil 2074 2.000 2.000 2.000
2.000 2.000 1.553 1.553 1.553 1.553 Irgacure 184 3.000 3.000 3.000
3.000 3.000 6.213 6.213 6.213 6.213 Darocur 1173 Chivacure BMS
2.000 2.000 2.000 2.000 1.553 1.553 1.553 1.553 Chivacure ITX 0.420
1-pyrenemethanol 9-anthracenemethanol Anthracure UVS 1101 Longnox
10 0.116 0.116 0.116 0.116 PVP 0.005 0.005 0.005 0.005 0.005 0.008
0.008 0.008 0.008 Rubidium carbonate Silwet L 7600 0.311 0.311
0.311 0.311 BYK A 501 0.031 0.031 0.031 0.031 Total 100.000 100.000
100.000 100.000 100.000 100.000 100.000 100.000 100.000
TABLE-US-00007 TABLE 4 Example Example Example Example Example
Example Example Example Example Composition 19 20 21 22 23 24 25 26
27 Name Part Part Part Part Part Part Part Part Part EBECRYL-3700
CD 406 Kayarad R 684 29.009 29.009 48.102 Kowa A-DOG 28.510 SR492
VEctomer .RTM. VE 5015 38.000 VEctomer .RTM. VE 4010 35.726 24.208
52.780 Celloxide 2021P 33.018 33.018 25.045 16.970 89.280 48.780
40.000 37.000 28.330 OXT-101 3.995 3.995 3.995 3.995 3.995 3.995
3.995 3.995 3.995 OXT-221 27.752 27.752 41.000 24.200 OXT-121
50.530 TERATHANE-1000 Chivacure 1176 GSID4480-1 CPI Rhodorsil 2074
1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 Irgacure 184
4.000 4.000 4.000 4.000 4.000 4.000 4.000 Darocur 1173 4.000 4.000
Chivacure BMS 1.000 1.500 1.000 1.500 1.500 1.000 1.000 Chivacure
ITX 0.250 0.250 1-pyrenemethanol 9-anthracenemethanol Anthracure
UVS 1101 Longnox 10 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005
0.005 PVP Rubidium carbonate Silwet L 7600 0.200 0.200 0.200 0.200
0.200 0.200 0.200 0.200 0.200 BYK A 501 0.020 0.020 0.020 0.020
0.020 0.020 0.020 0.020 0.020 Total 100.000 100.000 100.000 100.000
100.000 100.000 100.000 100.000 100.000
TABLE-US-00008 TABLE 5 Example Example Example Example Example
Example Example Example Example Composition 28 29 30 31 32 33 34 35
36 Name Part Part Part Part Part Part Part Part Part EBECRYL-3700
17.343 24.936 24.924 17.536 17.237 24.449 CD 406 6.982 6.979 6.846
Kayarad R 684 32.796 56.22 Kowa A-DOG 32.796 SR492 23.424 23.424
VEctomer .RTM. VE 5015 VEctomer .RTM. VE 4010 Celloxide 2021P
26.432 26.432 26.432 53.283 35.01 34.993 53.878 52.959 34.326
OXT-101 3.999 3.999 3.999 8.483 8.577 8.431 OXT-221 OXT-121
TERATHANE-1000 7.049 7.049 7.049 10.317 24.936 24.924 10.432 10.254
24.449 Chivacure 1176 4.023 3.391 3.39 4.068 3.998 3.325 GSID4480-1
CPI 2 2.2 Rhodorsil 2074 1 1 1 Irgacure 184 4 4 4 4.93 4.489 4.486
4.985 4.9 4.401 Chivacure BMS 1 1 1 1-pyrenemethanol 1.4
9-anthracenemethanol 0.25 Anthracure UVS 1101 0.3 0.3 Longnox 10
0.075 0.075 0.075 PVP 0.005 0.005 0.005 0.005 0.005 0.005 Rubidium
carbonate 0.005 0.005 0.005 Silwet L 7600 0.2 0.2 0.2 0.197 0.199
0.196 BYK A 501 0.02 0.02 0.02 0.02 0.02 0.02 Total 100 100 100 100
100 100 100 100 100
TABLE-US-00009 TABLE 6 Example Example Example Example Example
Example Example Example Example Example Composition 37 38 39 40 41
42 43 44 45 46 Component Part Part Part Part Part Part Part Part
Part Part Ebecryl 3700 25.000 16.000 SR 399 6.353 7.000 6.353 8.198
8.216 Sartomer 9003 4.099 4.108 CD 406 7.000 Kayarad R 684 16.000
32.000 25.647 25.647 Kowa A-DOG 16.000 32.000 16.000 25.000 Epon
1510 43.990 43.990 43.990 43.990 43.990 43.990 43.990 63.003 63.142
Heloxy 107 43.990 OXT-101 16.000 16.000 16.000 16.000 16.000 16.000
16.000 16.000 16.957 16.994 Chivacure 1176 Rhodorsil PI 2074 2.000
2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.000 2.004
1-Pyrenemethanol 9-Anthracene- methanol Anthracure UVS 1101
Anthracene Irgacure 184 4.000 4.000 4.000 4.000 4.000 4.000 4.000
4.000 2.799 2.806 Darocur 1173 Chivacure BMS 2.000 2.000 2.000
2.000 2.000 2.000 2.000 2.000 2.000 2.004 Longnox 10 0.010 0.010
0.010 0.010 0.010 0.010 0.010 0.010 0.500 0.501 Polyvinyl 0.005
0.005 pyrrolidone Silwet L7600 0.200 0.200 BYK A501 0.020 0.020
Intermediate 0.220 DG-0049 Total 100.000 100.000 100.000 100.000
100.000 100.000 100.000 100.000 100.000 100.000
TABLE-US-00010 TABLE 7 Example Example Example Example Example
Example Example Example Example Example Composition 47 48 49 50 51
52 53 54 55 56 Component Part Part Part Part Part Part Part Part
Part Part Ebecryl 3700 SR 399 8.292 8.292 8.292 8.292 8.292 7.822
7.905 7.909 7.909 8.014 Sartomer 9003 4.147 4.147 4.147 4.147 4.147
3.911 3.953 3.955 3.955 4.007 CD 406 Kayarad R 684 Kowa A-DOG Epon
1510 64.051 64.051 64.051 64.051 64.051 60.420 61.064 61.094 61.094
62.266 Heloxy 107 OXT-101 17.191 17.191 17.191 17.191 17.191 16.217
16.389 16.398 16.398 16.555 Chivacure 1176 4.831 4.883 4.885 4.885
1.547 Rhodorsil PI 2074 1.545 2.045 2.045 1.045 1.045 0.516
1-Pyrenemethanol 1.400 9-Anthracene- 0.350 0.350 methanol
Anthracure 0.300 UVS 1101 Anthracene 0.300 Irgacure 184 1.75 0.5 2
1.5 3 3.747 3.787 3.789 3.789 1.200 Darocur 1173 4.000 Chivacure
BMS 1.273 2.023 0.523 2.023 0.523 Longnox 10 1.307 1.307 1.307
1.307 1.307 1.233 1.246 1.246 1.246 1.255 Polyvinyl 0.005 0.005
0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.005 pyrrolidone Silwet
L7600 0.209 0.209 0.209 0.209 0.209 0.197 0.199 0.199 0.199 0.201
BYK A501 0.021 0.021 0.021 0.021 0.021 0.020 0.020 0.020 0.020
0.020 Intermediate 0.209 0.209 0.209 0.209 0.209 0.197 0.199 0.199
0.199 0.063 DG-0049 Total 100.000 100.000 100.000 100.000 100.000
100.000 100.000 100.000 100.000 100.000
Example 57
[0108] This Example illustrates some of the properties of the
photocurable resin composition for additive fabrication embodiments
set forth in Examples 1-56. Tables 8-26 set forth the Dp, Ec, and
E3-E5 values and Table 27 sets forth the CPI/RPI and CPC/RPC
values.
[0109] The photosensitivity of the compositions are evaluated by
measuring Critical Energy (Ec) values, Depth of Penetration (Dp)
values, and Storage Shear Modulus (G') upon exposure to curing
light. The Ec and Dp values are measured using a photo cure speed
test using LED light (365 nm). The G' values were measured using a
StressTech Rheometer manufactured by Reologicia Instruments AB,
Sweden. Each of the methods are summarized below.
[0110] The photo cure speed test using 365 nm LED light is used to
measure values for Ec and Dp. A single UV LED "bare bulb" (Model
No. NCSUO33A; Nichia Corporation, Japan) having a peak wavelength
of 365 nm is used as the LED light source in a light curing
apparatus, wherein the single LED light is bottom-mounted on a flat
surface inside a 30.degree. C. chamber and positioned in an
upward-looking arrangement and pointing vertically. The LED light
is powered by a 3.30 V/0.050 A DC output from a Programmable Power
Supply (Model No. PSS-3203; GW Instek).
[0111] A 10-mil sheet of polyester film (Melinex #515, Polybase
Mylar D, 0.010 gauge) is placed at a distance of 12 mm above from
the bottom of the LED light bulb. A drop of the liquid resin is
placed on the polyester film over the center of the LED light. The
resin is exposed to the LED light through the polyester film for a
specific time interval. The process is repeated with fresh resin
for 2, 4, 6, 8, 10 second exposure times or up to 12, 16, or 20
seconds for slow curing resin formulations.
[0112] After exposure to the LED light, the sample is allowed to
age inside the 30.degree. C. chamber for at least 15 minutes, after
which time any uncured resin is removed from the exposed areas by
blotting with a Kimwipe EX-L (Kimberly Clark). A thickness
measurement is then taken on the center of the exposed area using
an ABSOLUTE Digimatic Indicator (Model ID-C112CE, Mitutoyo
Corporation, Japan). The measured thickness of each sample is
plotted as a function of the natural logarithm of the exposure
time. The depth of penetration (Dp; mil) of the resin composition
is the slope of the least squares fit line. The Ec (sec) is the
X-axis crossing point (Y=0) of the line. The E.sub.3, E.sub.4, or
E.sub.5 is, respectively, the time (in seconds) required to produce
a layer having a thickness of 3, 4, or 5 mils, respectively.
[0113] Alternatively, when the intensity of the incident light
(mW/cm.sup.2) from the light source on the resin surface is known,
the exposure energy (mJ/cm.sup.2) rather than the exposure time (in
seconds) is used for calculating the Dp and Ec values.
[0114] The tensile properties (tensile strength, percent elongation
at break, and modulus) of cured samples of the photocurable resin
compositions for additive fabrication are tested on films, where
applicable, using a universal testing instrument, Instron Model
4201 equipped with a suitable personal computer and Instron
software to yield values of tensile strength, percent elongation at
break, and elastic modulus. The tensile test is performed on the
Instron with a crosshead speed of 1.00 inch/min and a crosshead jaw
separation of 2.00 inches in a 50% relative humidity room at room
temperature. Samples are prepared for testing by curing the liquid
resin composition applied on Mylar (0.01 gauge) with a 5 mil square
draw bar, and cured on an unfiltered Fusion D bulb (600W) in
nitrogen with an exposure of 300 mJ/cm.sup.2. The cured film
samples were cut within 1 hour of cure to have 0.5.times.4'' strips
and conditioned in a 50% relative humidity room at RT for 24 hours
before the tensile test was performed. Tensile test data was not
performed for Examples 1-5, 13-27, 31-36, and 45-56.
[0115] Real Time Dynamic Mechanical Analysis (RT-DMA)
[0116] Real Time Dynamic Mechanical Analysis (RT-DMA), including
the storage shear modulus (G'), is carried out under ambient lab
conditions (20-23.degree. C. and 25-35% RH), on compositions
undergoing curing using a StressTech Rheometer (Reologicia
Instruments AB, Sweden) with an 8 mm plate, a gap of 0.1 mm or 0.05
mm, as specified in the Tables 15-23, and modified to include a
mercury lamp light source (OMNICURE Series 2000 available from
EXFO), fitted with a 365 nm interference filter (also available
from EXFO) placed in the light path and a liquid-filled light guide
for conveying light from the source to the rheometer. The 365 nm
interference filter produces the spectral output shown in FIG. 1.
The samples are evaluated under the following parameters: 10 s of
equilibrium time; frequency of 10 Hz; 44-50 mW/cm2 light intensity
(as specified in the Tables 15-23) by the IL 1400 radiometer with
XRL140B detector (International Light, Newburyport, Mass.); 1.0 s
exposure that starts at 2.1 seconds from the beginning of data
collection; FFT smoothing of curves; G' taken at 2.5, 2.7, 3, 4,
and 6 s from the beginning of data collection by using the
accompanying software for data analysis.
[0117] FIG. 2 shows a schematic of the RT-DMA apparatus. The
photocurable resin composition (1) is placed on a plane (2). The
amount of liquid resin used should be approximately the amount
indicated in the figure. The plane is a quartz plate that is sold
with the StressTech Rheometer. The 8 mm plate (3) is positioned
with a 0.1 mm gap (4) between the plate and the plane. The gap is
set via the software accompanying the StressTech Rheometer. Light
(5) is provided though the plane (2). Please see the publication
"Dynamic Mechanical Analysis of UV-Curable Coatings While Curing"
by Robert W. Johnson available at
http://reologicainstruments.com/PDF%20files/BobJohnsonUVpaper.pdf,
and hereby incorporated by reference in its entirety, for more
information on RT-DMA. G' data was not measured for Examples
45-56.
TABLE-US-00011 TABLE 8 Example 1 Example 2 Example 3 Example 4
Example 5 Example 6 Example 7 Example 8 Example 9 Dp (mil) 3.53
2.72 2.73 2.62 2.78 2.79 2.95 2.91 2.78 Ec (s) 1.13 1.27 0.94 0.81
0.97 0.77 0.70 0.71 1.00 E3 (s) 2.64 3.81 2.83 2.53 2.85 2.27 1.93
2.00 2.95 E4 (s) 3.50 5.50 4.08 3.71 4.09 3.25 2.71 2.82 4.24 E5
(s) 4.65 7.95 5.88 5.43 5.85 4.65 3.80 3.98 6.07
TABLE-US-00012 TABLE 9 Example Example Example Example Example
Example Example Example Example 10 11 12 13 14 15 16 17 18 Dp (mil)
1.85 2.60 2.66 3.37 3.40 3.99 3.39 3.75 3.50 Ec (s) 0.36 0.75 0.80
0.84 0.77 0.82 0.72 0.75 0.68 E3 (s) 1.79 2.38 2.48 2.04 1.87 1.74
1.75 1.67 1.60 E4 (s) 3.08 3.50 3.61 2.75 2.51 2.23 2.34 2.18 2.13
E5 (s) 5.28 5.15 5.26 3.70 3.36 2.87 3.15 2.85 2.83
TABLE-US-00013 TABLE 10 Example Example Example Example Example
Example Example Example Example 19 20 21 22 23 24 25 26 27 Dp (mil)
5.79 4.59 7.12 4.96 3.32 6.70 4.19 5.90 4.40 Ec (s) 0.92 0.69 0.80
0.82 1.33 0.91 0.69 1.18 1.23 E3 (s) 1.55 1.34 1.22 1.50 3.27 1.43
1.41 1.97 2.44 E4 (s) 1.84 1.66 1.40 1.84 4.42 1.66 1.79 2.33 3.07
E5 (s) 2.18 2.06 1.61 2.25 5.98 1.93 2.27 2.76 3.85
TABLE-US-00014 TABLE 11 Example Example Example Example Example
Example Example Example Example 28 29 30 31 32 33 34 35 36 Dp (mil)
5.98 6.84 6.47 1.95 1.63 2.23 2.33 5.69 5.42 Ec (s) 1.06 1.36 1.30
0.63 1.69 0.98 1.04 1.15 1.22 E3 (s) 1.75 2.10 2.06 2.92 10.66 3.78
3.77 1.96 2.13 E4 (s) 2.07 2.43 2.41 4.88 19.71 5.92 5.79 2.33 2.56
E5 (s) 2.45 2.82 2.81 8.14 36.43 9.27 8.89 2.78 3.08
TABLE-US-00015 TABLE 12 Exam- Exam- Exam- Exam- Exam- Exam- ple 37
ple 38 ple 39 ple 40 ple 41 ple 42 Dp (mil) 2.44 3.64 3.38 3.87
2.88 3.60 Ec (s) 0.62 0.77 0.73 0.74 0.76 0.75 E3 (s) 2.11 1.76
1.78 1.61 2.16 1.72 E4 (s) 3.17 2.31 2.39 2.09 3.05 2.28 E5 (s)
4.78 3.04 3.22 2.70 4.32 3.01
TABLE-US-00016 TABLE 13 Example 43 Example 44 Example 45 Example 46
Example 47 Example 48 Example 49 Example 50 Dp (mil) 4.05 3.38 2.83
2.89 4.15 3.01 9.04 2.80 Ec (s) 0.77 0.59 0.88 0.91 1.39 1.19 2.00
1.19 E3 (s) 1.62 1.44 2.53 2.57 2.86 3.24 2.79 3.47 E4 (s) 2.08
1.94 3.59 3.63 3.63 4.52 3.12 4.96 E5 (s) 2.66 2.61 5.12 5.13 4.62
6.30 3.48 7.08
TABLE-US-00017 TABLE 14 Exam- Exam- Exam- Exam- Exam- Exam- ple 51
ple 52 ple 53 ple 54 ple 55 ple 56 Dp (mil) 7.62 3.09 2.38 2.47
3.32 2.86 Ec (s) 1.69 2.36 4.34 1.81 5.31 5.57 E3 (s) 2.51 6.22
15.31 6.09 13.12 15.92 E4 (s) 2.86 8.59 23.31 9.12 17.74 22.59 E5
(s) 3.26 11.87 35.48 13.67 23.97 32.04
TABLE-US-00018 TABLE 15 Time (sec) Storage shear modulus (G'; Pa)
Seconds 50 mW/cm.sup.2/1 sec exposure; 0.10 mm gap after light on
Example 1 Example 2 Example 3 Example 4 Example 5 0.4 1.27E+03
1.43E+03 1.58E+03 7.70E+02 1.23E+03 0.6 5.51E+03 1.23E+03 4.40E+03
1.33E+03 2.87E+03 0.9 1.19E+05 1.79E+04 6.75E+04 3.81E+04 5.74E+04
1.9 6.27E+05 1.21E+05 2.25E+05 2.25E+05 2.26E+05 3.9 1.03E+06
1.74E+05 3.46E+05 3.74E+05 3.91E+05
TABLE-US-00019 TABLE 16 Time (sec) Seconds Storage shear modulus
(G'; Pa) after 44 mW/cm.sup.2/1 sec exposure; 0.05 mm gap light on
Example 6 Example 7 Example 8 Example 9 Example 10 0.4 3.10E+02
3.10E+02 1.99E+05 3.10E+02 2.45E+04 0.6 1.98E+04 1.61E+04 5.43E+05
1.61E+04 2.14E+05 0.9 2.23E+05 2.23E+05 1.34E+06 2.23E+05 8.33E+05
1.9 9.38E+05 9.38E+05 2.41E+06 9.38E+05 1.65E+06 3.9 1.47E+06
1.46E+06 4.16E+06 1.48E+06 2.74E+06
TABLE-US-00020 TABLE 17 Time (sec) Storage shear modulus (G'; Pa)
Seconds after 44 mW/cm.sup.2/1 sec exposure; 0.10 mm gap light on
Example 11 Example 12 Example 13 Example 14 0.4 7.67E+02 8.70E+02
2.74E+03 7.87E+02 0.6 5.27E+02 1.02E+03 7.15E+03 5.83E+03 0.9
3.08E+04 2.66E+04 8.01E+04 1.34E+05 1.9 2.48E+05 2.18E+05 3.86E+05
7.53E+05 3.9 3.57E+05 3.05E+05 6.58E+05 1.41E+06
TABLE-US-00021 TABLE 18 Time (sec) Storage shear modulus (G'; Pa)
Seconds after 44 mW/cm.sup.2/1 sec exposure; 0.10 mm gap light on
Example 15 Example 16 Example 17 Example 18 0.4 1.82E+03 1.03E+03
2.87E+03 8.24E+03 0.6 7.70E+04 2.13E+04 3.17E+04 7.29E+04 0.9
5.61E+05 2.48E+05 2.57E+05 3.71E+05 1.9 2.40E+06 7.92E+05 1.02E+06
1.30E+06 3.9 3.90E+06 1.17E+06 1.59E+06 2.04E+06
TABLE-US-00022 TABLE 19 Storage shear modulus (G'; Pa) 47
mW/cm.sup.2/1 sec exposure; 0.10 mm gap Example 19 Example 20
Example 21 Example 22 Example 23 2.53E+03 1.59E+04 8.35E+04
3.97E+04 1.66E+03 2.14E+04 1.03E+04 4.30E+05 3.19E+05 1.66E+03
1.87E+05 8.46E+04 1.10E+06 1.36E+06 1.66E+03 6.75E+05 2.71E+05
2.55E+06 3.93E+06 1.66E+03 1.05E+06 4.23E+05 2.96E+06 5.41E+06
1.66E+03
TABLE-US-00023 TABLE 20 Time (sec) Seconds after Storage shear
modulus (G'; Pa) 47 mW/cm.sup.2/1 sec exposure; 0.10 mm gap light
on Example 24 Example 25 Example 26 Example 27 Example 28 Example
29 Example 30 0.4 1.47E+03 1.75E+03 1.14E+03 1.82E+03 2.11E+04
7.20E+04 1.90E+04 0.6 1.65E+03 1.36E+03 1.14E+03 1.82E+03 4.09E+05
6.20E+05 3.57E+05 0.9 1.22E+03 1.27E+03 1.14E+03 1.82E+03 2.48E+06
2.96E+06 1.85E+06 1.9 1.78E+03 1.27E+03 1.14E+03 1.82E+03 5.58E+06
9.45E+06 6.37E+06 3.9 5.61E+04 1.80E+04 1.14E+03 1.82E+03 1.08E+07
1.27E+07 9.31E+06
TABLE-US-00024 TABLE 21 Time (sec) Seconds after Storage shear
modulus (G'; Pa) 50 mW/cm.sup.2/1 sec exposure; 0.10 mm gap light
on Example 31 Example 32 Example 33 Example 34 Example 35 Example
36 0.4 1.52E+03 1.31E+03 1.17E+03 1.22E+03 1.15E+03 3.06E+03 0.6
9.97E+02 1.14E+03 1.26E+03 1.24E+03 1.07E+04 7.69E+04 0.9 1.21E+03
9.07E+02 4.95E+03 1.78E+03 9.93E+04 4.56E+05 1.9 1.75E+03 1.49E+03
7.42E+04 2.42E+04 2.77E+05 1.58E+06 3.9 3.82E+03 1.75E+03 1.09E+05
3.29E+04 4.59E+05 2.54E+06
TABLE-US-00025 TABLE 22 Time (sec) Seconds Storage shear modulus
(G'; Pa) 44 mW/cm.sup.2/1 sec exposure; 0.05 mm gap after light on
Example 37 Example 38 Example 39 Example 40 Example 41 Example 42
Example 43 Example 44 0.4 8.67E+03 1.89E+05 7.71E+04 1.00E+05
4.46E+04 3.12E+05 8.28E+05 6.64E+05 0.6 1.12E+05 5.94E+05 4.52E+05
5.02E+05 2.50E+05 8.90E+05 1.11E+06 2.29E+06 0.9 4.62E+05 1.40E+06
1.46E+06 1.56E+06 9.16E+05 1.71E+06 1.97E+06 3.56E+06 1.9 1.10E+06
2.94E+06 2.73E+06 2.86E+06 1.64E+06 2.66E+06 3.30E+06 5.30E+06 3.9
1.63E+06 4.36E+06 4.56E+06 4.37E+06 2.66E+06 4.90E+06 4.86E+06
5.15E+06
TABLE-US-00026 TABLE 23 Time (sec) Seconds after Storage shear
modulus (G'; Pa) 44 mW/cm.sup.2/1 sec exposure; 0.10 mm gap light
on Example 37 Example 38 Example 39 Example 40 Example 41 Example
42 Example 43 Example 44 0.4 1.14E+03 5.17E+03 1.14E+03 6.31E+03
9.45E+02 2.57E+04 6.07E+03 2.75E+04 0.6 1.16E+03 2.77E+04 1.16E+03
2.32E+04 2.85E+03 1.25E+05 5.31E+04 3.05E+05 0.9 1.82E+04 2.22E+05
1.82E+04 2.44E+05 6.57E+04 6.39E+05 5.11E+05 1.19E+06 1.9 1.87E+05
8.47E+05 1.87E+05 1.12E+06 3.89E+05 2.20E+06 2.11E+06 3.17E+06 3.9
2.74E+05 1.26E+06 2.76E+05 1.79E+06 6.83E+05 3.19E+06 3.00E+06
4.21E+06
TABLE-US-00027 TABLE 24 Tensile test on thin cured strips (24 h
after cure) Example 6 Example 7 Example 8 Example 9 Example 10
Example 11 Example 12 Elastic Modulus (MPa) 1403 1023 666 537 1030
2262 1892 Elongation at Break (%) 5.8 10.9 19.5 14.6 7.9 2.9 2.2
Tensile Strength (MPa) 44.2 32.4 26.5 17.8 35.7 51.9 35.8
TABLE-US-00028 TABLE 25 Tensile test on thin cured strips (24 h
after cure) Example 28 Example 29 Example 30 Elastic Modulus (MPa)
1674 1968 1590 Elongation at Break (%) 4.9 3.3 2.1 Tensile Strength
(MPa) 50.6 49.9 29.6
TABLE-US-00029 TABLE 26 Tensile test on thin cured strips (24 hrs
after cure) Example Example Example Example Example Example Example
Example 37 38 39 40 41 42 43 44 Elastic Modulus (MPa) 1811 1685
1844 1692 1769 1681 1786 394 Elongation at Break (%) 2.5 1.5 1.9
1.1 2.5 1.6 0.9 14.4 Tensile Strength (MPa) 39.1 22.1 28.7 18.1
38.4 24.5 14.2 19.0
TABLE-US-00030 TABLE 27 Example No. CPI/RPI CPC/RPC 1 1.33 1.13 2
0.18 3.19 3 0.25 3.19 4 0.43 3.19 5 0.67 3.19 6 0.67 1.37 7 0.67
1.30 8 0.67 1.23 9 0.67 1.33 10 0.67 1.33 11 0.67 1.47 12 0.67 1.55
13 0.67 1.47 14 0.67 1.47 15 0.25 1.48 16 0.25 1.48 17 0.25 1.48 18
0.25 1.48 19 0.25 2.23 20 0.25 2.27 21 0.25 2.23 22 0.25 0.94 23
0.25 N/A 24 0.25 N/A 25 0.25 N/A 26 0.25 N/A 27 0.25 N/A 28 0.25
0.54 29 0.25 0.54 30 0.25 0.54 31 0.82 3.56 32 0.76 1.10 33 0.76
1.10 34 0.82 3.56 35 1.22 3.56 36 1.26 1.10 37 0.50 1.87 38 0.50
1.87 39 0.50 1.87 40 0.50 1.87 41 0.50 1.87 42 0.50 1.87 43 0.50
1.87 44 0.50 1.87 45 0.71 6.50 46 0.71 6.50 47 0.88 6.53 48 4.09
6.53 49 1.02 6.53 50 0.70 6.53 51 0.35 6.53 52 1.29 6.53 53 1.29
6.53 54 1.29 6.53 55 1.29 6.53 56 0.40 6.56
Comparative Example 1
[0118] This comparative example illustrates the results obtained
when curing a typical laser curable resin with LED light. A solid
state laser emitting at 354.7 nm is used, with 1 mil scan spacing,
65 mW/cm.sup.2 power, and 58 kHz frequency, for obtaining the Ec
and Dp values from the "working curve" by using WINDOWPANES.TM.
technique. The LED is a single UV LED "bare bulb" (Model No.
NCSUO33A; Nichia Corporation, Japan) having a peak wavelength of
365 nm and is used as the LED light source in a light curing
apparatus, wherein the single LED light is bottom-mounted on a flat
surface inside a 30.degree. C. chamber and positioned in an
upward-looking arrangement and pointing vertically. The LED light
is powered by a 3.30 V/0.050 A DC output from a Programmable Power
Supply (Model No. PSS-3203; GW Instek).
[0119] The composition of Comparative Example 1 is shown in Table
28. Ec and Dp data, as determined using the previously mentioned
methods, when cured with both laser light and LED light is shown in
Table 29.
TABLE-US-00031 TABLE 28 Comparative Example 1 Component wt %
Ebecryl 3700 20 Celloxy 2021P 70.78 Chivacure 1176 5 Irgacure 184 4
Silwet 7600 0.2 BYK A501 0.02 Total 100
TABLE-US-00032 TABLE 29 Laser Light LED Light Ec 6.89 mJ/cm.sup.2
0.45 seconds Dp 4.10 mils 19.05 mils
[0120] All references, including publications, patent applications,
and patents, cited herein are hereby incorporated by reference to
the same extent as if each reference were individually and
specifically indicated to be incorporated by reference and were set
forth in its entirety herein.
[0121] The use of the terms "a" and "an" and "the" and similar
referents in the context of describing the invention (especially in
the context of the following claims) are to be construed to cover
both the singular and the plural, unless otherwise indicated herein
or clearly contradicted by context. The terms "comprising,"
"having," "including," and "containing" are to be construed as
open-ended terms (i.e., meaning "including, but not limited to,")
unless otherwise noted. Recitation of ranges of values herein are
merely intended to serve as a shorthand method of referring
individually to each separate value falling within the range,
unless otherwise indicated herein, and each separate value is
incorporated into the specification as if it were individually
recited herein. All methods described herein can be performed in
any suitable order unless otherwise indicated herein or otherwise
clearly contradicted by context. The use of any and all examples,
or exemplary language (e.g., "such as") provided herein, is
intended merely to better illuminate the invention and does not
pose a limitation on the scope of the invention unless otherwise
claimed. No language in the specification should be construed as
indicating any non-claimed element as essential to the practice of
the invention.
[0122] Preferred embodiments of this invention are described
herein, including the best mode known to the inventors for carrying
out the invention. Variations of those preferred embodiments may
become apparent to those of ordinary skill in the art upon reading
the foregoing description. The inventors expect skilled artisans to
employ such variations as appropriate, and the inventors intend for
the invention to be practiced otherwise than as specifically
described herein. Accordingly, this invention includes all
modifications and equivalents of the subject matter recited in the
claims appended hereto as permitted by applicable law. Moreover,
any combination of the above-described elements in all possible
variations thereof is encompassed by the invention unless otherwise
indicated herein or otherwise clearly contradicted by context.
* * * * *
References