Optical film
An optical film, a circular polarizing plate, and a display device are provided. The optical film may exhibit a desired phase retardation property in a wide wavelength range even when it is relatively thin. The optical film may exhibit the ¼ wavelength phase retardation property. The optical film may be manufactured by a simple process. The optical film may be used in LCDs such as a reflective LCD, or OLEDs.
1. An optical film of which R(650)/R(550) is larger than R(450)/R(550), comprising:
an optically anisotropic polymeric layer which has an absolute value of a difference between R(450)/R(550) and R(650)/R(550) of 5 or less; and
a liquid crystal layer which has R(450)/R(550) that is larger than R(650)/R(550) and of which an optical axis forms an angle of 61.5 degrees with the optical axis of the polymeric layer, on the polymeric layer.
2. The optical film of claim 1 , wherein the optical film has the ¼ wavelength retardation property.
3. The optical film of claim 1 , wherein the optical film has the in-plane phase retardation with respect to light having the wavelength of 550 nm in the range from 110 nm to 220 nm.
4. The optical film of claim 3 , wherein the R(450)/R(550) of the optical film is 0.81 to 0.99, and the R(650)/R(550) is 1.01 to 1.19.
5. The optical film of claim 1 , wherein the polymeric layer has the in-plane phase retardation with respect to light having the wavelength of 550 nm in the range from 200 to 290 nm.
6. The optical film of claim 5 , wherein the polymeric layer has the R(450)/R(550) in the range from 0.95 to 1.05, and the R(650)/R(550) in the range from 0.95 to 1.05.
7. The optical film of claim 1 , wherein the polymeric layer comprises a polyolefin film, a cycloolefin polymer film, a polyvinylchloride film, a polyacrylonitrile film, a polysulfone film, a polyacrylate film, a polyvinylalcohol film or a cellulose ester polymer film, or a copolymer film of at least two monomers selected from monomers forming the above polymer.
8. The optical film of claim 1 , wherein the optical axis of the polymeric layer forms an angle of 45 or 67.5 degrees with a lengthwise direction or a breadthwise direction of the polymeric layer, or forms an angle falling with the range from 45 to 67.5 degrees with the lengthwise direction or the breadthwise direction of the polymeric layer.
9. The optical film of claim 1 , wherein the liquid crystal layer has the in-plane phase retardation with respect to light having the wavelength of 550 nm of 95 to 145 nm.
10. The optical film of claim 9 , wherein the liquid crystal layer has the R(450)/R(550) in the range from 1.01 to 1.19, and the R(650)/R(550) in the range from 0.81 to 0.99.
11. The optical film of claim 1 , wherein a difference between the refractive index of the liquid crystal layer in the in-plane slow axis direction and the refractive index of the liquid crystal layer in the in-plane fast axis direction may be from 0.05 to 0.2, and wherein the liquid crystal layer has the thickness from 0.5 to 2.0 μm.
12. A circular polarizing plate, comprising:
a linear polarizer; and
the optical film of claim 1 on one surface of the linear polarizer.
13. The circular polarizing plate of claim 12 , wherein the light absorption axis of the linear polarizer forms an angle of 45 or 67.5 degrees or forms an angle falling within the range from 45 to 67.5 degrees with the optical axis of the polymeric layer of the optical film.
14. The circular polarizing plate of claim 12 , further comprising:
an adhesive layer that attaches the linear polarizer and the optical film and has a glass transition temperature of 36° C. or more.
15. A display device comprising the circular polarizing plate of claim 12 .
16. The display device of claim 15 , which is a reflective liquid crystal display, a transflective liquid crystal display or an organic light emitting device.
17. An optical film of which R(650)/R(550) is larger than R(450)/R(550), comprising:
an optically anisotropic polymeric layer which has an absolute value of a difference between R(450)/R(550) and R(650)/R(550) of 5 or less; and
a liquid crystal layer which has R(450)/R(550) that is larger than R(650)/R(550) and of which an optical axis is formed to be perpendicular to an optical axis of the polymeric layer, on the polymeric layer.
18. The optical film of claim 17 , wherein the optical film has the ¼ wavelength retardation property.
19. The optical film of claim 17 , wherein the optical film has the in-plane phase retardation with respect to light having the wavelength of 550 nm in the range from 110 nm to 220 nm.
20. The optical film of claim 17 , wherein the R(450)/R(550) of the optical film is 0.81 to 0.99, and the R(650)/R(550) is 1.01 to 1.19.
21. The optical film of claim 17 , wherein the polymeric layer has the in-plane phase retardation with respect to light having the wavelength of 550 nm in the range from 200 to 290 nm.
22. The optical film of claim 17 , wherein the polymeric layer has the R(450)/R(550) in the range from 0.95 to 1.05, and the R(650)/R(550) in the range from 0.95 to 1.05.
23. The optical film of claim 17 , wherein the polymeric layer comprises a polyolefin film, a cycloolefin polymer film, a polyvinylchloride film, a polyacrylonitrile film, a polysulfone film, a polyacrylate film, a polyvinylalcohol film or a cellulose ester polymer film, or a copolymer film of at least two monomers selected from monomers forming the above polymer.
24. The optical film of claim 17 , wherein the optical axis of the polymeric layer forms an angle of 45 or 67.5 degrees with a lengthwise direction or a breadthwise direction of the polymeric layer, or forms an angle falling with the range from 45 to 67.5 degrees with the lengthwise direction or the breadthwise direction of the polymeric layer.
25. The optical film of claim 17 , wherein the liquid crystal layer has the R(450)/R(550) in the range from 1.01 to 1.19, and the R(650)/R(550) in the range from 0.81 to 0.99.
26. The optical film of claim 17 , wherein a difference between the refractive index of the liquid crystal layer in the in-plane slow axis direction and the refractive index of the liquid crystal layer in the in-plane fast axis direction may be from 0.05 to 0.2, and wherein the liquid crystal layer has the thickness from 0.5 to 2.0 μm.
27. A circular polarizing plate, comprising:
a linear polarizer; and
the optical film of claim 17 on one surface of the linear polarizer.
28. The circular polarizing plate of claim 27 , wherein the light absorption axis of the linear polarizer forms an angle of 45 or 67.5 degrees or forms an angle falling within the range from 45 to 67.5 degrees with the optical axis of the polymeric layer of the optical film.
29. The circular polarizing plate of claim 27 , further comprising:
an adhesive layer that attaches the linear polarizer and the optical film and has a glass transition temperature of 36° C. or more.
30. A display device comprising the circular polarizing plate of claim 27 .
31. The display device of claim 30 , which is a reflective liquid crystal display, a transflective liquid crystal display or an organic light emitting device.
32. The optical film of claim 17 , wherein the liquid crystal layer has the in-plane phase retardation with respect to light having the wavelength of 550 nm of 95 to 145 nm.