Elliptically polarizing plate and organic light-emitting device
An elliptically polarizing plate and an organic light-emitting device. The elliptically polarizing plate has superior visibility and excellent reflection characteristics and color characteristics on the side as well as the front, and an organic light-emitting device comprising the same.
1. An elliptically polarizing plate comprising sequentially, a linear polarizer, a first retardation film, a second retardation film, a third retardation film and a fourth retardation film,
wherein the first retardation film is a +B plate or a −A plate having an Nz value of less than 1 in Equation 1:
Nz =( nx−nz )/( nx−ny ). [Equation 1]
wherein the second retardation film is a −B plate having an Nz value of more than 1 in Equation 1, or a −C plate satisfying Expression 1:
nx=ny>nz [Expression 1]
wherein the third retardation film has an Nz value of 0.8 to 1.2 in Equation 1, and wherein an in-plane slow axis of the third retardation film forms an angle of 43 degrees to 47 degrees with an absorption axis of the linear polarizer; and
wherein the fourth retardation film is a +B plate having an Nz value of −4.0 or less in Equation 1, or a +C plate satisfying Expression 2:
nx=ny<nz [Expression 2]
wherein a sum of a thickness direction retardation value of the first retardation film and a thickness direction retardation value of the second retardation film is in a range of −40 nm to 70 nm and the thickness direction retardation (Rth) is defined by Equation 2:
Rth =( nz−ny )× d [Equation 2]
wherein, nx, ny and nz are refractive indexes of the first to fourth retardation films in x-axis, y-axis and z-axis directions, respectively, and
wherein the x-axis is a direction parallel to an in-plane slow axis of the first to fourth retardation films, the y-axis is a direction parallel to an in-plane fast axis of the first to fourth retardation films, the z-axis is a thickness direction of the first to fourth retardation films, and d is a thickness of the first to fourth retardation films.
2. The elliptically polarizing plate according to claim 1 , wherein the Nz value of the first retardation film is from −6 to 0.5.
3. The elliptically polarizing plate according to claim 1 , wherein the first retardation film has an in-plane retardation value of 0 nm to 180 nm for light having a wavelength of 550 nm.
4. The elliptically polarizing plate according to claim 1 , wherein the thickness direction retardation value of the first retardation film is 0 nm to 220 nm.
5. The elliptically polarizing plate according to claim 1 , wherein the in-plane slow axis of the first retardation film is parallel to the absorption axis of the linear polarizer.
6. The elliptically polarizing plate according to claim 1 , wherein the first retardation film has an R(450)/R (550) value of 0.6 to 1.3, wherein R(λ) is an in-plane retardation value of the first retardation film for light having a wavelength of λnm.
7. The elliptically polarizing plate according to claim 1 , wherein the second retardation film is a −B plate having an Nz value of 3.1 or more.
8. The elliptically polarizing plate according to claim 1 , wherein the second retardation film is a −B plate having an in-plane retardation value of 0.5 nm to 55 nm for light having a wavelength of 550 nm.
9. The elliptically polarizing plate according to claim 1 , wherein the second retardation film is a −B plate and wherein the thickness direction retardation value of the second retardation film is from −160 nm to −5 nm.
10. The elliptically polarizing plate according to claim 1 , wherein the second retardation film is a −B plate, and wherein the in-plane slow axis of the second retardation film is perpendicular or parallel to the absorption axis of the linear polarizer.
11. The elliptically polarizing plate according to claim 1 , wherein the second retardation film is a −C plate and wherein the thickness direction retardation value of the second retardation film is from −220 nm to 0 nm.
12. The elliptically polarizing plate according to claim 1 , wherein the second retardation film has an R(450)/R (550) value of 0.6 to 1.3 or Rth (450)/Rth (550) value of 0.6 to 1.3, wherein R(λ) is an in-plane retardation value of the second retardation film for light having a wavelength of 2 nm, and Rth(λ) is the thickness direction retardation value of the second retardation film for light having a wavelength of λnm.
13. The elliptically polarizing plate according to claim 1 , wherein the third retardation film has an in-plane retardation value of 130 nm to 150 nm for light having a wavelength of 550 nm.
14. The elliptically polarizing plate according to claim 1 , wherein the third retardation film has an R(450)/R (550) value of 0.6 to 1.0, wherein R(λ) is an in-plane retardation value of the third retardation film for light having a wavelength of λnm.
15. The elliptically polarizing plate according to claim 1 , wherein the thickness direction retardation value of the fourth retardation film is from 0 nm to 300 nm.
16. The elliptically polarizing plate according to claim 1 , wherein the fourth retardation film has an Rth(450)/Rth (550) value of 0.6 to 1.3, wherein Rth (λ) is the thickness direction retardation value of the fourth retardation film for light having a wavelength of λnm.
17. An organic light-emitting device comprising the elliptically polarizing plate of claim 1 and an organic light-emitting display panel.
18. The organic light-emitting device according to claim 17 , wherein the fourth retardation film of the elliptically polarizing plate is disposed adjacent to the organic light-emitting display panel.