Curable adhesive compositions
Curable adhesive compositions comprising a urethane pre-polymer are provided that exhibit a high refractive index.
1. A curable adhesive composition, comprising:
about 5 wt % to about 30 wt % of a urethane pre-polymer comprising (i) an isocyanate and (ii) an allylic phenol comprising a bisphenol A component;
about 20 wt % to about 60 wt % of at least one acrylate;
about 15 wt % to about 60 wt % of at least one vinyl resin; and
a photoinitiator;
wherein the adhesive composition has a refractive index, after curing, of greater than 1.60 at a wavelength of 589.3 nm and 25° C., and the viscosity of the adhesive increases by less than 100% over about 8 hours.
2. The composition of claim 1 , wherein the viscosity of the adhesive increases by less than 100% over about 24 hours.
3. The composition of claim 1 , wherein the isocyanate is m-xylene diisocyanate.
4. The composition of claim 1 , wherein the allylic phenol is diallylether bisphenol A or ortho-diallyl bisphenol A.
5. The composition of claim 1 , wherein the urethane pre-polymer comprises xylene diisocyanate and ortho-diallyl bisphenol A.
6. The composition of claim 1 , wherein the adhesive composition, after curing, has a refractive index of about 1.60 to about 1.74.
7. The composition of claim 1 , wherein the adhesive composition comprises:
about 0.01 wt % to about 5 wt % of at least one photoinitiator.
8. The composition of claim 1 , further comprising a stabilizer.
9. The composition of claim 8 , wherein the stabilizer is a nitrosamine.
10. The composition of claim 1 , further comprising a thiol component.
11. The composition of claim 10 , wherein the thiol component is 1,2-bis(2-mercapto ethylthio)-3-mercapto propane or trimethylolpropane tris(3-mercaptopropionate).
12. The composition of claim 1 , wherein the adhesive composition comprises about 20 wt % to about 25 wt % of at least one vinyl resin.
13. The composition of claim 1 , further comprising at least one naphthalene component.
14. The composition of claim 13 , wherein the naphthalene component is 1-bromo naphthalene.
15. The composition of claim 1 , wherein the adhesive composition is curable by ultraviolet radiation.