Polarizing plate for light emitting displays and light emitting display comprising the same
A polarizing plate for light emitting displays and a light emitting display including the same are provided. A polarizing plate includes: a polarizer; and a first liquid crystal retardation film, a first bonding layer, and a second liquid crystal retardation film sequentially stacked on a surface of the polarizer, and the first bonding layer has a glass transition temperature of about 70° C. to about 100° C. and is formed of a composition including at least one selected from among an alicyclic group-containing glycidyl ether and an aromatic group-containing glycidyl ether.
1. A polarizing plate for light emitting displays, comprising: a polarizer; and
a first liquid crystal retardation film, a first bonding layer, and a second liquid crystal retardation film sequentially stacked on a surface of the polarizer, each of the first liquid crystal retardation film and the second liquid crystal retardation film being formed of a liquid crystal compound,
wherein the first bonding layer is directly formed on each of the first liquid crystal retardation film and the second liquid crystal retardation film,
wherein the first bonding layer has a glass transition temperature of about 70° C. to about 100° C. and is formed of a composition comprising:
an epoxy compound comprising at least one selected from among an alicyclic group-containing glycidyl ether and an aromatic group-containing glycidyl ether, the alicyclic group-containing glycidyl ether consisting of at least one selected from among 1,4-cyclohexane dimethanol diglycidyl ether, bis(4-hydroxycyclohexyl)methane diglycidyl ether, and 2,2-bis(4-hydroxycyclohexyl)-pro pane diglycidyl ether, and the aromatic group-containing glycidyl ether is resorcinol diglycidyl ether, and
a (meth)acrylate compound comprising a (meth)acrylate containing at least one hydroxyl group,
wherein the at least one selected from among the alicyclic group-containing glycidyl ether and the aromatic group-containing glycidyl ether is present in about 20 wt % to 75 wt % in the composition for the first bonding layer in terms of solid content, provided that the at least one selected from among the alicyclic group-containing glycidyl ether and the aromatic group-containing glycidyl ether is present in an amount of at least 33 wt % based on a total amount of the epoxy compound,
wherein the (meth)acrylate containing at least one hydroxyl group is present in an amount of about 5 parts by weight to about 20 parts by weight relative to a total of 100 parts by weight of the epoxy compound and the (meth)acrylate compound, and
wherein a peel strength of the first bonding layer with respect to each of the first liquid crystal retardation film and the second liquid crystal retardation film before the polarizing plate is left at 25° C. for 72 hours is about 100 gf/25 mm or more, and a peel strength of the first bonding layer with respect to each of the first liquid crystal retardation film and the second liquid crystal retardation film after the polarizing plate is left at 25° C. for 72 hours is about 200 gf/25 mm or more.
2. The polarizing plate for light emitting displays according to claim 1 , wherein the polarizing plate has a polarization degree variation ΔPE 1 or ΔPE 2 of about 1% or less according to Equation 1 or 2:
Δ PE 1 =|P 1− P 2|, Equation 1
where P1 indicates an initial degree of polarization (unit: %) as measured on a specimen obtained by cutting the polarizing plate to a size of 3 cm×3 cm (length×width, MD of polarizer×TD of the polarizer), and P2 indicates a degree of polarization (unit: %), as measured on the specimen after leaving the specimen at a constant temperature of 85° C. for 500 hours; and
Δ PE 2 =|P 1− P 3|, Equation 2
where P3 indicates a degree of polarization (unit: %), as measured on the specimen after leaving the specimen under constant temperature and humidity conditions of 60° C. and 95% for 500 hours.
3. The polarizing plate for light emitting displays according to claim 1 , wherein the composition further comprises an aliphatic acyclic glycidyl ether.
4. The polarizing plate for light emitting displays according to claim 1 , wherein the composition is free from any alicyclic epoxy compound.
5. The polarizing plate for light emitting displays according to claim 1 , wherein the (meth)acrylate compound further comprises a (meth)acrylate containing an aromatic group.
6. The polarizing plate for light emitting displays according to claim 1 , wherein the composition further comprises a photo-cationic initiator and a photo-enhancer.
7. The polarizing plate for light emitting displays according to claim 1 , wherein the composition comprises:
about 20 parts by weight to about 95 parts by weight of the at least one selected from among the alicyclic group-containing glycidyl ether and the aromatic group-containing glycidyl ether;
about 5 parts by weight to about 80 parts by weight of the (meth)acrylate compound; and
about 0.5 parts by weight to about 10 parts by weight of a photo-cationic initiator and about 0.1 parts by weight to about 10 parts by weight of a photo-enhancer;
all relative to a total of 100 parts by weight of the (meth)acrylate compound and the at least one selected from among the alicyclic group-containing glycidyl ether and the aromatic group-containing glycidyl ether.
8. The polarizing plate for light emitting displays according to claim 1 , wherein the composition comprises:
about 20 parts by weight to about 94 parts by weight of the at least one selected from among the alicyclic group-containing glycidyl ether and the aromatic group-containing glycidyl ether;
about 1 part by weight to about 40 parts by weight of an aliphatic acyclic glycidyl ether;
about 5 parts by weight to about 75 parts by weight of the (meth)acrylate compound; and
about 0.5 parts by weight to about 10 parts by weight of a photo-cationic initiator and about 0.1 parts by weight to about 10 parts by weight of a photo-enhancer;
all relative to a total of 100 parts by weight of the at least one selected from among the alicyclic group-containing glycidyl ether and the aromatic group-containing glycidyl ether, the aliphatic acyclic glycidyl ether, and the (meth)acrylate compound.
9. The polarizing plate for light emitting displays according to claim 1 , wherein the liquid crystal compound of each of the first liquid crystal retardation film and the second liquid crystal retardation film is a (meth)acrylic liquid crystal compound containing an alicyclic group or a (meth)acrylic liquid crystal compound containing an aromatic group.
10. The polarizing plate for light emitting displays according to claim 1 , further comprising:
a second bonding layer between the polarizer and the first liquid crystal retardation film,
the second bonding layer having a different glass transition temperature than the first bonding layer.
11. The polarizing plate for light emitting displays according to claim 10 , wherein the second bonding layer is formed of a water-based bonding agent or a photocurable bonding agent.
12. The polarizing plate for light emitting displays according to claim 1 , further comprising:
a protective layer on another surface of the polarizer.
13. The polarizing plate for light emitting displays according to claim 12 , wherein the protective layer comprises at least one of a protective film or a protective coating layer.
14. A light emitting display comprising the polarizing plate for light emitting displays according to claim 1 .
15. The light emitting display according to claim 14 , wherein the light emitting display comprises a foldable light emitting display.