Back to results
US 8,012,571 B2Granted
Optical film comprising birefringent naphthalate copolyester having branched or cyclic C4-C10 alkyl units
Assignee3M Innovative Properties Company
InventorsYufeng Liu, David T. Yust, Stephen A. Johnson, Kristopher J. Derks
Life of this patent
Estimating the term…
Abstract
The present invention relates to multilayer optical films and birefringent copolyester films. The birefringent copolyester optical layer or birefringent copolyester film comprises a major amount of naphthalate units, ethylene units, and a minor amount of branched or cyclic C4 to C10 alkyl units. Also described are certain copolyester polymeric materials further comprising subunits of a phthalate ionomer such as dimethyl sulfosodium isophthtalate ionomer.
Claims21
A multilayer optical film comprising:
- at least one first birefringent optical layer having an out-of-plane birefringence of at least 0.10 at 632.8 nm after the multilayer film is formed comprising a copolyester, wherein the copolyester comprises
- 40 to 50 mol % naphthalate units,
- 35 to 49 mol % ethylene units, and
- 1 to 8 mol % of branched or cyclic C4-C10 alkyl units;
- and
- at least one second optical layer having a lower birefringence than the first optical layer.
3 more elements
Dependencies are inferred from the claim text.