Polarizing plate and optical display including the same
A polarizing plate includes a polarizer, a bonding layer on an upper surface of the polarizer, a protective film on an upper surface of the bonding layer and having a moisture transmittance of about 30 g/m2·24 hr or less at 40° C. and 90 % relative humidity (RH), and a barrier layer on a lower surface of the polarizer and formed of a barrier layer composition including an alicyclic epoxy resin having a glass transition temperature of about 200° C. or more. The polarizing plate may have a light transmittance variation rate of 3% or less, as calculated by Equation 1: Light transmittance variation rate=| T 0− T 500|/ T 0×100 (1), where T 0 is an initial light transmittance and T 500 is a light transmittance after 500 hours as set forth herein.
1. A polarizing plate, comprising:
a polarizer;
a bonding layer on an upper surface of the polarizer;
a protective film on an upper surface of the bonding layer and having a moisture transmittance of about 30 g/m 2 ·24hr or less; and
a barrier layer on a lower surface of the polarizer and formed of a barrier layer composition including an alicyclic epoxy resin having a glass transition temperature of more than 200° C.,
wherein the polarizing plate has a light transmittance variation rate of 3 % or less, as calculated by Equation 1:
Light transmittance variation rate =| T 0 − T 500|/ T 0 ×100 (1),
where T 0 is an initial light transmittance of the polarizing plate at a wavelength of 400 nm to 700 nm and T 500 is a light transmittance of the polarizing plate at a wavelength of 400 nm to 700 nm after the polarizing plate is left at 85° C. and 85% RH for 500 hours and is then left at 25° C. for 1 hour,
wherein the polarizing plate has a thickness of about 115 μm or less,
wherein the polarizer is formed of a polyvinyl alcohol film, and the barrier layer is in direct contact with the polyvinyl alcohol film.
2. The polarizing plate as claimed in claim 1 , wherein the polarizing plate has a moisture content variation rate of about 10% or less, as calculated by Equation 3:
Moisture content variation rate=| W 500− W 0|/ W 0×100 (3),
where W 0 is an initial moisture content of the polarizing plate and W 500 is a moisture content of the polarizing plate after the polarizing plate is left at 85° C. and 85% RH for 500 hours.
3. The polarizing plate as claimed in claim 1 , wherein the protective film has an in-plane retardation (Re) of about 5,000 nm or more at a wavelength of 550 nm, as calculated by Equation 4:
Re = ( nx−ny )× d (4),
where nx and ny are indices of refraction of the protective film at a wavelength of 550 nm in x-axis and y-axis directions of the protective film, respectively, and d is a thickness of the protective film in units of nm.
4. The polarizing plate as claimed in claim 1 , wherein the protective film includes a film formed of a polyester resin.
5. The polarizing plate as claimed in claim 4 , wherein the polyester resin includes at least one selected from among polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene naphthalate.
6. The polarizing plate as claimed in claim 1 , wherein the protective film includes a film formed by stretching a film including a polyester resin at an elongation of 5 times to 8 times an initial length thereof in a transverse direction (TD).
7. The polarizing plate as claimed in claim 1 , wherein a machine direction (MD) of the polarizer is orthogonal to a transverse direction (TD) of the protective film.
8. The polarizing plate as claimed in claim 1 , wherein a ratio of a total thickness of the protective film and the bonding layer to a thickness of the barrier layer ranges from about 10:1 to about 50:1.
9. The polarizing plate as claimed in claim 1 , wherein the barrier layer has a thickness of about 2 μm to about 12 μm.
10. The polarizing plate as claimed in claim 1 , wherein the alicyclic epoxy resin is present in an amount of about 40 wt % to about 90 wt % in the barrier layer composition in terms of solid content.
11. The polarizing plate as claimed in claim 1 , wherein the barrier layer composition includes the alicyclic epoxy resin; a monofunctional (meth)acrylic compound, a bifunctional (meth)acrylic compound, or a mixture thereof; and an initiator.
12. The polarizing plate as claimed in claim 11 , wherein each of the monofunctional (meth)acrylic compound and the bifunctional (meth)acrylic compound includes at least one hydroxyl group.
13. The polarizing plate as claimed in claim 11 , wherein the barrier layer composition includes at least one of an epoxy monomer and a tri- or higher functional (meth)acrylic compound.
14. The polarizing plate as claimed in claim 13 , wherein the epoxy monomer includes a monofunctional epoxy monomer.
15. The polarizing plate as claimed in claim 1 , further comprising an adhesive layer on a lower surface of the barrier layer.
16. The polarizing plate as claimed in claim 15 , wherein the adhesive layer has a modulus of about 0.1 MPa or less at 23° C.
17. An optical display comprising the polarizing plate as claimed in claim 1 .
18. A polarizing plate, comprising:
a polarizer;
a bonding layer on an upper surface of the polarizer;
a protective film on an upper surface of the bonding layer and having a moisture transmittance of about 30 g/m2·24 hr or less; and
a barrier layer on a lower surface of the polarizer and formed of a barrier layer composition including an alicyclic epoxy resin having a glass transition temperature of about 200° C. or more, wherein the polarizing plate has a light transmittance variation rate of 3% or less, as calculated by Equation 1:
Light transmittance variation rate =| T 0− T 500|/ T 0×100 (1),
where T 0 is an initial light transmittance of the polarizing plate at a wavelength of 400 nm to 700 nm and T 500 is a light transmittance of the polarizing plate at a wavelength of 400 nm to 700 nm after the polarizing plate is left at 85° C. and 85% RH for 500 hours and is then left at 25° C. for 1 hour,
further comprising an adhesive layer on a lower surface of the barrier layer, wherein the adhesive layer has a modulus of about 0.1 MPa or less at 23° C.
19. The polarizing plate as claimed in claim 18 , wherein the alicyclic epoxy resin is present in an amount of about 40 wt % to about 90 wt % in the barrier layer composition in terms of solid content.
20. The polarizing plate as claimed in claim 18 , wherein the polarizing plate has a warpage of about 3 mm or less, wherein in measuring the warpage of the polarizing plate, the polarizing plate is cut to a size of 150 mm as measured in the MD of the polarizer×90 mm as measured in the TD of the polarizer to prepare a specimen, which in turn is attached to a 0.5 cm thick glass plate such that the adhesive layer of the polarizing plate contacted the glass plate, thereby preparing a specimen for the warpage measurement and warpage is measured after leaving the specimen at 85° C. for 24 hours.