Microvoided light diffuser
View Patent ↗The invention relates to a light diffuser comprising a thermoplastic layer containing thermoplastic polymeric material and microvoids having a substantially circular cross-section in a plane perpendicular to the direction of light travel and having a diffuse light transmission efficiency of at least 65%.
1. A high transmission light diffuser comprising a thermoplastic layer containing thermoplastic polymeric material and microvoids having a substantially circular cross-section in a plane perpendicular to the direction of light travel, wherein the thickness of the voided layer and void size and loading are sufficient to provide a diffuser having a diffuse light transmission efficiency of at least 65% and a light transmission greater than 80%.
2. The light diffuser of claim 1 wherein the difference in refractive index between the thermoplastic polymeric material and the microvoids is greater than 0.2.
3. The light diffuser of claim 1 wherein said microvoids are formed by organic microspheres.
4. The light diffuser of claim 1 wherein said microvoids are substantially free of scattering inorganic particles.
5. The light diffuser of claim 1 wherein the microvoids contain cross-linked polymer beads.
6. The light diffuser of claim 1 wherein the microvoids contain a gas.
7. The diffuser of claim 1 where thickness uniformity across the light diffuser is less than 0.10 micrometers.
8. The light diffuser of claim 1 whereinthe elastic modulus of the light diffuser is greater than 500 MPa.
9. The light diffuser of claim 1 wherein the impact resistance of the light diffuser is greater than 0.6 GPa.
10. The light diffuser of claim 1 wherein said light transmission is greater than 87%.
11. The light diffuser of claim 1 wherein said microvoids have a major axis diameter to minor axis diameter ratio of less than 2.0.
12. The light diffuser of claim 1 wherein said microvoids have a major axis diameter to minor axis diameter ratio of between 1.6 and 1.0.
13. The light diffuser of claim 1 wherein said thermoplastic layer contains greater than 4 index of refraction changes greater than 0.20 parallel to the direction of light travel.
14. The light diffuser of claim 1 wherein said microvoids have a average volume of between 8 and 42 cubic micrometers over an area of 1 cm 2 .
15. The light diffuser of claim 1 wherein said microvoids have a average volume of between 12 and 18 cubic micrometers over an area of 1 cm 2 .
16. The light diffuser of claim 1 wherein the said light diffuser has a thickness less than 250 micrometers.
17. The light diffuser of claim 1 wherein the said light diffuser has a thickness between 12.5 and 50 micrometers.
18. The light diffuser of claim 1 wherein said thermoplastic layer comprises polyolefin polymer.
19. The light diffuser of claim 1 wherein said thermoplastic layer comprises polyester polymer.
20. The light diffuser of claim 5 wherein said cross linked polymer beads have a mean particle size less than 2.0 micrometers.
21. The light diffuser of claim 5 wherein said cross linked polymer beads have a mean particle size between 0.30 and 1.7 micrometers.