Polarizing plate
Provided are a polarizing plate and a liquid crystal display device. The polarizing plate has lighter weight, a smaller thickness, and excellent physical properties such as durability, water resistance, workability, and light leakage preventing ability. In addition, the polarizing plate prevents curling of the polarizing plate or a polarizer in formation thereof, and has excellent thermal resistance or thermal shock resistance.
1. A polarizing plate, comprising:
a polarizer;
an active energy beam-curable adhesive layer; and
a pressure-sensitive adhesive layer having first and second surfaces, which are sequentially disposed,
wherein a difference in peel strength between the first and second surfaces with respect to alkali-free glass satisfies the following General Equation 1:
X 2 −X 1 >50 gf/25 mm [General Equation 1]
where X 1 is peel strength of the first surface with respect to alkali-free glass, and X 2 is peel strength of the second surface with respect to alkali-free glass.
2. The polarizing plate according to claim 1 , wherein the active energy beam-curable adhesive layer is directly attached to least one surface of the polarizer, and the first surface of the pressure-sensitive adhesive layer is directly attached to the adhesive layer.
3. The polarizing plate according to claim 1 , wherein the pressure-sensitive adhesive layer is a single-layered pressure-sensitive adhesive layer.
4. The polarizing plate according to claim 1 , wherein the polarizer is a polyvinylalcohol-based polarizer.
5. The polarizing plate according to claim 1 , wherein the peel strength of the first surface with respect to alkali-free glass is 5 to 100 gf/25 mm.
6. The polarizing plate according to claim 1 , wherein the peel strength of the second surface with respect to alkali-free glass is 100 to 1,000 gf/25 mm.
7. The polarizing plate according to claim 1 , wherein the pressure-sensitive adhesive layer has a tensile modulus gradient according to a thickness direction in a direction from the first surface to the second surface.
8. The polarizing plate according to claim 7 , wherein the pressure-sensitive adhesive layer has an average tensile modulus at 25° C. of 0.1 to 500 MPa.
9. The polarizing plate according to claim 1 , wherein the pressure-sensitive adhesive layer includes a crosslinked structure containing an acryl polymer crosslinked by a multifunctional crosslinking agent and a crosslinked structure containing a photopolymerizable compound.
10. The polarizing plate according to claim 9 , wherein the pressure-sensitive adhesive layer further includes a UV absorbent.
11. The polarizing plate according to claim 1 , wherein the active energy beam-curable adhesive layer includes an adhesive composition including an epoxy compound and/or an acryl-based monomer in a cured state.
12. The polarizing plate according to claim 11 , wherein the epoxy compound includes an alicyclic epoxy compound and/or a glycidyl ether-type epoxy compound.
13. The polarizing plate according to claim 11 , wherein the epoxy compound has a weight average molecular weight of 1,000 to 5,000.
14. The polarizing plate according to claim 11 , wherein the acryl-based monomer is a hydrophilic acryl-based monomer or a hydrophobic acryl-based monomer.
15. The polarizing plate according to claim 14 , wherein the hydrophilic acryl-based monomer has a hydroxyl group, a carboxyl group or an alkoxy group.
16. The polarizing plate according to claim 11 , wherein the adhesive composition further includes 1 to 40 parts by weight of a reactive oligomer.
17. The polarizing plate according to claim 11 , wherein the adhesive composition is a non-solvent type composition.
18. The polarizing plate according to claim 11 , wherein the adhesive composition has a viscosity at 25° C. of 5 to 1,000 cps.
19. The polarizing plate according to claim 1 , further comprising:
a protective film attached to a surface of the polarizer opposite to the surface to which the pressure-sensitive adhesive layer is attached.
20. The polarizing plate according to claim 19 , wherein the protective film is a cellulose film, a polyester film, a polycarbonate film, a polyethersulfone film, an acryl film or a polyolefin film.
21. The polarizing plate according to claim 1 , further comprising:
at least one layer selected from the group consisting of an anti-reflection layer, an anti-glare layer, a phase retardation plate, a wide viewing angle compensation film and a brightness enhancement layer.
22. A liquid crystal display device, comprising:
a liquid crystal panel; and
the polarizing plate according to claim 1 attached to one or both surfaces of the liquid crystal panel.
23. The device according to claim 22 , wherein the liquid crystal panel is attached to the second surface of the pressure-sensitive adhesive layer.
24. The device according to claim 22 , wherein the liquid crystal panel is a passive matrix-type panel, an active matrix-type panel, an in-plane switching panel or a vertically-aligned panel.