Optical film laminates
Optical film laminates of birefringent polyester films and adhesive are disclosed. The laminates have a thickness of at least 10 mils (0.25 mm). The laminates of the invention are useful in displays having a diagonal of 37 in (94 cm) or greater.
1. An optical film laminate comprising:
a first birefringent polyester base film having a structured surface disposed on a first surface of the first polyester base film;
a second birefringent polyester base film; and
an adhesive having a Tg of 0° C. or greater between the first and second birefringent polyester base films, wherein the adhesive bonds a surface of the second birefringent polyester base film to a second surface of the first polyester base film, wherein the thickness of the bonded first and second base films is 10 mils (0.25 mm) or greater, wherein the first and second base films have out-of-plane birefringence greater than 0.05.
2. The optical film laminate of claim 1 wherein the thickness of one of the first or second base films is at least 5 mils (0.13 mm).
3. The optical film laminate of claim 1 wherein the thickness of each of the first and second base films is at least 5 mils (0.13 mm).
4. The optical film laminate of claim 1 wherein the structured surface comprises prisms.
5. The optical film laminate of claim 1 wherein the structured surface comprises elongated prisms.
6. The optical film laminate of claim 1 wherein the first and second base films comprise a polyester selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, poly(ether esters), polyethylene terephthalate modified by at least one diacid, polyethylene terephthalate modified by at least one diol, modified by at least one diol and one diacid, polyethylene naphthalate modified by at least one diacid, polyethylene naphthalate modified by at least one diol, polyethylene naphthalate modified by at least one diacid and one diol, and copolymers or blends there of.
7. The optical film laminate of claim 1 wherein the adhesive is two adhesive layers.
8. The optical film laminate of claim 1 wherein the surfaces of the first and second base films in contact with the adhesive are surface treated.
9. The optical film laminate of claim 1 wherein the first and second base films have a shrinkage difference of less than 1% in either MD or TD, as tested at 150° C. for 15 minutes.
10. An optical display comprising:
a light source;
an LCD panel; and
an optical film laminate according to claim 1 between the light source and the LCD panel.
11. The optical display of claim 10 further comprising a protective sheet on a viewing surface of the LCD panel.
12. The optical display of claim 11 wherein the viewing surface has at least a 94 cm diagonal.
13. The optical display of claim 10 wherein the optical film laminate is adjacent the light source.
14. The optical film laminate of claim 1 wherein the optical film laminate has a gain greater than or equal to about 1.62.
15. The optical film laminate of claim 1 wherein the optical film laminate has an average stiffness of greater than about 20 N/mm.
16. The optical film laminate of claim 1 wherein the adhesive is a UV curable acrylate adhesive or a sulfonated polyester adhesive.