Monochromatic actinic radiation curable coatings for optical fiber
Described herein is a method for coating optical fiber where the coating has been cured by application of a source of monochromatic actinic radiation, such as a light emitting diode, wherein the coating contains a urethane(meth)acrylate oligomer; a (meth)acrylate diluent monomer; a diluent monomer having an electron donating group adjacent to the vinyl group, such as a vinyl ether monomer; and a photoinitiator. Also described are compositions which are capable of undergoing photopolymerization when coated on an optical fiber and when irradiated by a light emitting diode (LED) with improved surface cure and reduced yellowing. Also described are the coated optical fibers produced by such processes and compositions.
1. A liquid radiation curable composition for coating an optical fiber comprising:
(a) a component possessing an electron-donating substituent attached to a vinyl group, which is present in an amount from about 0.5 wt. % to about 20 wt. %, relative the total weight of the liquid radiation curable composition;
(b) a (meth)acrylate oligomer;
(c) a (meth)acrylate diluent monomer; and
(d) a free-radical photoinitiator component;
wherein component (a) comprises a multifunctional vinyl ether monomer; and
wherein the composition is configured to attain
a top surface percent reacted acrylate unsaturation (% RAU) of at least about 71% according to an LED DSC method, when said composition is cured by a source of monochromatic actinic radiation with a peak spectral output from about 355 nm to about 420 nm.
2. The liquid radiation curable composition for coating an optical fiber of claim 1 , wherein the electron-donating substituent does not contain a nitrogen atom.
3. The liquid radiation curable composition for coating an optical fiber of claim 2 , wherein the (meth)acrylate diluent monomer comprises N-substituted (meth)acrylamide, vinyl acetate, styrene, alkylstyrene, halostyrene, N-vinylpyrrolidone, N-vinyl caprolactam, vinyl chloride or vinylidene chloride.
4. The liquid radiation curable composition for coating an optical fiber of claim 2 , wherein the component possessing an electron-donating substituent attached to a vinyl group consists of multifunctional vinyl ether monomers.
5. The liquid radiation curable composition for coating an optical fiber of claim 4 , wherein the vinyl ether monomer is alkoxylated.
6. The liquid radiation curable composition for coating an optical fiber of claim 5 , wherein the vinyl ether monomer is present in an amount, relative to the entire weight of the composition, of from about 0.5 wt. % to about 15 wt. %, and contains a backbone selected from the group consisting of an ethylene oxide, propylene oxide or butylene oxide.
7. The liquid radiation curable composition for coating an optical fiber of claim 2 , wherein the free-radical photoinitiator component (d) has an average of not more than 12 conjugated double-bonds in any single molecule.
8. The liquid radiation curable composition for coating an optical fiber of claim 7 , wherein the additive package further comprises a dye, colorant, or pigment.
9. The liquid radiation curable composition for coating an optical fiber of claim 8 , wherein, relative to the entire weight of the composition,
the (meth)acrylate oligomer is present in an amount from 10 wt % to 90 wt %;
the (meth)acrylate diluent monomer is present in an amount from 10 wt % to 90 wt %;
the free-radical photoinitiator component is present in an amount from 0.1 wt % to 10 wt %;
and the dye, colorant, or pigment is present in an amount from 0 wt % to 10 wt % by dry weight.
10. The liquid radiation curable composition for coating an optical fiber of claim 9 , wherein the a free-radical photoinitiator component (d) consists of a mono acyl phosphine oxide.
11. The liquid radiation curable composition for coating an optical fiber of claim 9 , wherein the (meth)acrylate diluent monomer component (c) comprises ethylene glycol diacrylate, propylene glycol diacrylate, neopentyl glycol diacrylate, hexamethylene glycol diacrylate, bisphenol A diacrylate, 4,4′-bis(2-acryloyloxyethoxy)diphenylpropane, trimethylolpropane triacrylate, pentaerythritol triacrylate and tetraacrylate, vinyl acrylate, divinyl benzene, divinyl succinate, diallyl phthalate, triallyl phosphate, triallyl isocyanurate or tris(2-acryloylethyl)isocyanurate.
12. The liquid radiation curable composition for coating an optical fiber of claim 11 , wherein the (meth)acrylate oligomer component (b) comprises a urethane acrylate oligomer comprising a backbone derived from a polyol which has been reacted with a diisocyanate and a hydoxyalkylacrylate.
13. The liquid radiation curable composition for coating an optical fiber of claim 1 , wherein the source of monochromatic actinic radiation is one or more light emitting diodes (LEDs).
14. The liquid radiation curable composition for coating an optical fiber of claim 1 , further comprising an additive package comprising:
from about 0 wt. % to about 2 wt. % of isopropylthioxanthone; and
from about 0 wt. % to about 3 wt. % of pentaerythritol tetra-3-mercaptopropionate.
15. The liquid radiation curable composition for coating an optical fiber of claim 1 , wherein the composition is configured to attain a yellowness index of less than 30 within 45 minutes after curing.
16. The liquid radiation curable composition for coating an optical fiber of claim 15 , wherein the composition is configured to attain a yellowness index of less than 20 within 45 minutes after curing.
17. The liquid radiation curable composition for coating an optical fiber of claim 16 , wherein the composition is configured to attain a top surface percent reacted acrylate unsaturation (% RAU) of at least about 75%.
18. The liquid radiation curable composition for coating an optical fiber of claim 16 , wherein the composition is configured to attain a top surface percent reacted acrylate unsaturation (% RAU) of at least about 80%.
19. The liquid radiation curable composition for coating an optical fiber of claim 16 , wherein the composition is configured to attain a top surface percent reacted acrylate unsaturation (% RAU) from 75% to 85%.
20. The liquid radiation curable composition for coating an optical fiber of claim 15 , wherein the composition is configured to attain a yellowness index of less than 12 within 45 minutes after curing.