Polarizer
Provided are a polarizing plate and a display. The illustrative polarizing plate may exhibit desired characteristics in a wide range of wavelengths, and have excellent reflection and visibility at an inclined angle. For example, the polarizing plate may be used in a reflective or transflective liquid crystal display or an organic light emitting device.
1. A polarizing plate for minimizing reflection in an organic light emitting device, comprising:
a polarizer; and a retardation layer laminated on one side of the polarizer,
wherein a reflectivity measure on a side of the polarizer of the polarizing plate is 10% or less at an inclined angle of 50 degrees and the inclined angle is an angle between a normal line of a surface of a polarizing plate and an observation direction,
wherein the retardation layer comprises a negative biaxial retardation film,
wherein an angle between a slow axis of the negative biaxial retardation film and a light absorption axis of the polarizer is from 40 degrees to 50 degrees,
wherein the retardation layer further comprises a C plate and
wherein the thickness direction retardation (Rth) of the retardation layer according to the equation Rth=d×(Nz−Ny) is from 10 nm to 250 nm,
wherein, d is a thickness of the retardation layer, and Ny and Nz are refractive indexes in y and z axes of the retardation layer, respectively, wherein the y axis is a direction parallel to a fast axis of the retardation layer and z axis is a normal direction of a plane formed by the x and y axes, wherein the x axis is a direction parallel to a slow axis of the retardation layer.
2. The polarizing plate according to claim 1 , wherein the in-plane retardation of the negative biaxial retardation film is from 100 nm to 200 nm.
3. The polarizing plate according to claim 1 , wherein the negative biaxial retardation film satisfies
R (450)/ R (550)< R (650)/ R (550),
wherein the R(450) is an in-plane retardation of the retardation film with respect to light having a wavelength of 450 nm, R(550) is an in-plane retardation of the retardation film with respect to light having a wavelength of 550 nm, and the R(650) is an in-plane retardation of the retardation film with respect to light having a wavelength of 650 nm.
4. The polarizing plate according to claim 1 , wherein the retardation layer comprises the negative biaxial retardation film and the C plate and wherein the C plate is disposed closer to the polarizer than the negative biaxial retardation film.
5. The polarizing plate according to claim 4 , wherein the negative biaxial retardation film has a first Rth value according to the equation Rth=d×(Nz−Ny), the C plate having a second Rth value according to the same equation as above, and the sum of the first and second Rth values is from 10 nm to 250 nm:
wherein, d is a thickness of the negative biaxial retardation film or C plate, and Ny and Nz are refractive indexes in y and z axes of the negative biaxial retardation film or C plate, respectively, wherein the y axis is a direction parallel to a fast axis of the negative biaxial retardation film or C plate and z axis is a normal direction of a plane formed by the x and y axes, wherein the x axis is a direction parallel to a slow axis of the negative biaxial retardation film or C plate.
6. The polarizing plate according to claim 1 , wherein the retardation layer comprises the negative biaxial retardation film and the C plate and wherein the negative biaxial retardation film is disposed closer to the polarizer than the C plate.
7. The polarizing plate according to claim 6 , wherein the negative biaxial retardation film has a first Rth value according to the equation Rth=d×(Nz−Ny), the C plate having a second Rth value according to the same equation as above, and the sum of the first and second Rth values is from 10 nm to 250 nm:
wherein, d is a thickness of the negative biaxial retardation film or C plate, and Ny and Nz are refractive indexes in y and z axes of the negative biaxial retardation film or C plate, respectively, wherein the y axis is a direction parallel to a fast axis of the negative biaxial retardation film or C plate and z axis is a normal direction of a plane formed by the x and y axes, wherein the x axis is a direction parallel to a slow axis of the negative biaxial retardation film or C plate.
8. An organic light emitting device comprising the polarizing plate of claim 1 and an electrode layer, wherein the electrode layer is transparent or reflective and wherein the polarizing plate is disposed outside the electrode layer.