Polarizing plate and optical display device comprising same
A polarizing plate and an optical display comprising the same are disclosed. The polarizing plate includes: a polarizer and a first protective layer stacked on one surface of the polarizer via a bonding layer, wherein the bonding layer is formed of a bonding layer composition including an epoxy compound and a photocationic initiator, and the polarizing plate has a chrominance variation ΔE of 5.2 or less, as calculated by Equation 1.
1. A polarizing plate comprising:
a polarizer; and
a first protective layer stacked on a first surface of the polarizer via a first bonding layer,
wherein the first bonding layer has a pH of 1 to 3 and is formed of a bonding layer composition comprising an epoxy compound and a photocationic initiator, and the polarizing plate has a chrominance variation ΔE of 5.2 or less, as calculated by Equation 1:
Δ E =[(Δ L ) 2 +(Δ a *) 2 +(Δ b *) 2 ] 1/2 , <Equation 1>
where ΔL is L 2 −L 1 ; Δa* is (a*) 2 −(a*) 1 ; and Δb* is (b*) 2 −(b*) 1 , in which L 1 is an L value of the polarizing plate before the polarizing plate is left at 95° C. or 60° C. and 95% RH for 500 hours; L 2 is an L value of the polarizing plate after the polarizing plate is left at 95° C. or 60° C. and 95% RH for 500 hours; (a*) 1 is an a* value of the polarizing plate before the polarizing plate is left at 95° C. or 60° C. and 95% RH for 500 hours; (a*) 2 is an a* value of the polarizing plate after the polarizing plate is left at 95° C. or 60° C. and 95% RH for 500 hours; (b*) 1 is a b* value of the polarizing plate before the polarizing plate is left at 95° C. or 60° C. and 95% RH for 500 hours; and (b*) 2 is a b* value of the polarizing plate after the polarizing plate is left at 95° C. or 60° C. and 95% RH for 500 hours, and
wherein the polarizing plate has a light transmittance variation ratio of 1.5% or less, as calculated by Equation 4:
Light transmittance variation ratio=| T 2 −T 1 |/T 1 ×100, <Equation 4>
where T 1 is a light transmittance of the polarizing plate measured at a wavelength of 380 nm to 780 nm before the polarizing plate is left at 95° C. or 60° C. and 95% RH for 500 hours, and T 2 is a light transmittance of the polarizing plate measured at a wavelength of 380 nm to 780 nm after the polarizing plate is left at 95° C. or 60° C. and 95% RH for 500 hours.
2. The polarizing plate according to claim 1 , wherein the bonding layer composition is a non-(meth)acrylate composition.
3. The polarizing plate according to claim 1 , wherein the epoxy compound comprises a mixture of an aromatic epoxy compound and an acyclic aliphatic epoxy compound.
4. The polarizing plate according to claim 1 , wherein the bonding layer composition further comprises an oxetane compound.
5. The polarizing plate according to claim 1 , wherein the bonding layer composition comprises 30 wt % to 70 wt % of an aromatic epoxy compound, 10 wt % to 50 wt % of an acyclic aliphatic epoxy compound, 10 wt % to 40 wt % of an oxetane compound, and 1 wt % to 10 wt % of a photocationic initiator in terms of solid content.
6. The polarizing plate according to claim 1 , wherein the bonding layer composition further comprises a photosensitizer.
7. The polarizing plate according to claim 1 , wherein the polarizer is free from zinc.
8. The polarizing plate according to claim 1 , wherein the polarizer contains zinc.
9. The polarizing plate according to claim 1 , further comprising: a second protective layer formed on a second surface of the polarizer.
10. The polarizing plate according to claim 9 , wherein the first protective layer has a moisture permeation of 500 g/m 2 ·24 hr or more and the second protective layer has a moisture permeation of 100 g/m 2 ·24 hr or less.
11. The polarizing plate according to claim 9 , wherein the second protective layer is formed on the second surface of the polarizer via a second bonding layer.
12. The polarizing plate according to claim 11 , wherein the second bonding layer is formed of the bonding layer composition.
13. An optical display device comprising the polarizing plate according to claim 1 .
14. A polarizing plate comprising:
a polarizer; and
a first protective layer stacked on a first surface of the polarizer via a first bonding layer,
wherein the first bonding layer is formed of a bonding layer composition comprising an epoxy compound and a photocationic initiator, and the polarizing plate has a chrominance variation ΔE of 5.2 or less, as calculated by Equation 1:
Δ E =[(Δ L ) 2 +(Δ a *) 2 +(Δ b *) 2 ] 1/2 , <Equation 1>
where ΔL is L 2 -L 1 , Δa* is (a*) 2 −(a*) 1 ; and Δb* is (b*) 2 −(b*) 1 , in which L 1 is an L value of the polarizing plate before the polarizing plate is left at 95° C. or 60° C. and 95% RH for 500 hours; L 2 is an L value of the polarizing plate after the polarizing plate is left at 95° C. or 60° C. and 95% RH for 500 hours; (a*) 1 is an a* value of the polarizing plate before the polarizing plate is left at 95° C. or 60° C. and 95% RH for 500 hours; (a*) 2 is an a* value of the polarizing plate after the polarizing plate is left at 95° C. or 60° C. and 95% RH for 500 hours; (b*) 1 is a b* value of the polarizing plate before the polarizing plate is left at 95° C. or 60° C. and 95% RH for 500 hours; and (b*) 2 is a b* value of the polarizing plate after the polarizing plate is left at 95° C. or 60° C. and 95% RH for 500 hours, and
wherein the first bonding layer has a pH of 1 to 3 and a storage modulus ratio of 0.25 to 0.60, as calculated by Equation 2:
Storage modulus ratio= G 150/( G 100 +G 150), <Equation 2>
where G100 is a storage modulus (unit: MPa) of the first bonding layer at 100° C. and G150 is a storage modulus (unit: MPa) of the first bonding layer at 150° C.