Adhesive composition for polarizing plate and polarizing plate and optical member including adhesive layer formed using the same
A polarizing plate and an optical member, the polarizing plate including an adhesive layer, the adhesive layer being prepared from an adhesive composition including a (meth)acrylic copolymer, a crosslinking agent, and a tackifier, the tackifier including an acrylic modified petroleum resin represented by Formula 1: R′—CO—O—R [Formula 1] wherein R′ is a petroleum resin and R is a C 1 -C 20 alkyl group or a C 6 -C 50 aryl group.
1. A polarizing plate comprising an adhesive layer, the adhesive layer being prepared from an adhesive composition including:
a (meth)acrylic copolymer,
a crosslinking agent, and
a tackifier, the tackifier including a petroleum resin represented by Formula 1:
R′—CO—O—R [Formula 1]
wherein R′ is a petroleum resin and R is a C 1 -C 20 alkyl group or a C 6 -C 50 aryl group.
2. The polarizing plate as claimed in claim 1 , wherein the petroleum resin has a structure represented by Formula 2:
wherein R is a C 1 -C 20 alkyl group or a C 6 -C 50 aryl group, R 1 to R 23 are each independently hydrogen or a C 1 -C 5 alkyl group, n is an integer from 0 to about 5, and m is an integer from 0 to about 10.
3. The polarizing plate as claimed in claim 2 , wherein each of R 1 to R 23 in Formula 2 is hydrogen and n is 0.
4. The polarizing plate as claimed in claim 1 , wherein the petroleum resin has a softening point of about 50° C. to about 150° C.
5. The polarizing plate as claimed in claim 1 , wherein the petroleum resin is present in the adhesive composition in an amount of about 0.1 to about 10 parts by weight, based on 100 parts by weight of the (meth)acrylic copolymer.
6. The polarizing plate as claimed in claim 1 , wherein the (meth)acrylic copolymer is a copolymer of a monomer mixture including a (meth)acrylic monomer having a hydroxyl group.
7. The polarizing plate as claimed in claim 1 , wherein the (meth)acrylic copolymer is a copolymer of a monomer mixture including a vinyl monomer having a hydroxyl group and a vinyl monomer having a carboxylic acid group.
8. The polarizing plate as claimed in claim 7 , wherein the monomer mixture includes:
at least about 0.5 wt % of the vinyl monomer having a hydroxyl group, and
at least about 0.1 wt % of the vinyl monomer having a carboxylic acid group.
9. The polarizing plate as claimed in claim 1 , wherein:
the (meth)acrylic copolymer is a copolymer of a vinyl monomer having a hydroxyl group, a vinyl monomer having a carboxylic acid group, a vinyl monomer having an alkyl group, and a vinyl monomer having an aromatic group, and
at least one of the vinyl monomer having a hydroxyl group, the vinyl monomer having a carboxylic acid group, the vinyl monomer having an alkyl group, and the vinyl monomer having an aromatic group is a (meth)acrylic monomer.
10. The polarizing plate as claimed in claim 1 , wherein the crosslinking agent is a mixture of an isocyanate crosslinking agent and an epoxy crosslinking agent.
11. The polarizing plate as claimed in claim 1 , wherein the composition further includes a crosslinking accelerator, a silane coupling agent, or a mixture thereof.
12. The polarizing plate as claimed in claim 11 , wherein the composition includes the crosslinking accelerator, the crosslinking accelerator being selected from the group of metal compounds, metals, and mixtures thereof.
13. The polarizing plate as claimed in claim 11 , wherein the composition includes the crosslinking accelerator, the crosslinking accelerator being present in an amount of about 0.001 to about 1 part by weight, based on 100 parts by weight of the (meth)acrylic copolymer.
14. An optical member comprising an adhesive layer, the adhesive layer including a tackifier, wherein the tackifier includes a petroleum resin having softening point of about 50° C. to about 150° C., and
wherein the optical member has a brightness difference of not greater than about 1%, as determined by Equation 1:
Δ L =[( a+b+d+e )/4 ]−c [Equation 1]
wherein a, b, d and e represent brightness values measured at central points of sides of a panel including the optical member, and c represents a brightness value of a center of the panel including the optical member.
15. The optical member as claimed in claim 14 , wherein the petroleum resin has a structure represented by Formula 2:
wherein R is a C 1 -C 20 alkyl group or a C 6 -C 50 aryl group, R 1 to R 23 are each independently hydrogen or a C 1 -C 5 alkyl group, n is an integer from 0 to about 5, and m is an integer from 0 to about 10.
16. The optical member as claimed in claim 15 , wherein each of R 1 to R 23 in Formula 2 is hydrogen and n is 0.