Adhesive film for polarizing plate, polarizing plate comprising the same and optical display apparatus comprising the same
An adhesive film for polarizing plates, a polarizing plate including the same, and an optical display apparatus including the same are provided. An adhesive film for polarizing plates is formed of an adhesive composition including a (meth)acrylic copolymer, an isocyanate curing agent, a metal chelate curing agent, and an antistatic agent, and has a surface resistance difference ΔSR of 1.0 (log(Ω/□)) or less, as calculated by Equation 1 and, in Equation 1, SR1 is 10 (log(Ω/□)) or less.
1. An adhesive film for polarizing plates formed of an adhesive composition comprising a (meth)acrylic copolymer, an isocyanate curing agent, a metal chelate curing agent, and an antistatic agent,
the adhesive film having a surface resistance difference ΔSR of about 1.0 or less, as calculated by the following Equation 1:
Δ SR=SR 2− SR 1,
where SR1 is a common logarithm value (unit: log (Ω/□)) of initial surface resistance of the adhesive film, and
SR2 is a common logarithm value (unit: log (Ω/□)) of surface resistance of the adhesive film as measured after the adhesive film is left at 85° C. and 85% RH for 250 hours, and
in Equation 1, SR1 is about 10 (log (Ω/□)) or less,
wherein the (meth)acrylic copolymer comprises a (meth)acrylic copolymer of a monomer mixture comprising a (meth)acrylic monomer having a glass transition temperature (Tg) of about 0° C. or more in a homopolymer phase,
wherein the antistatic agent is present in an amount of about 5 parts by weight to about 30 parts by weight relative to 100 parts by weight of the (meth)acrylic copolymer,
wherein the adhesive film has an initial peel strength of about 1.5 N/25 mm to 5 N/25 mm at 25° C., and a peel strength difference of about 2.0 N/25 mm or less between the initial peel strength at 25° C. and a peel strength at 85° C. after the adhesive film is left at 85° C. for 5 min, and
wherein the peel strength of the adhesive film at 85° C. is at least about 1.0 N/25 mm.
2. The adhesive film for polarizing plates according to claim 1 , wherein the adhesive film has a surface resistance of about 1×10 8 Ω/□ to about 1×10 11 Ω/□, as measured after the adhesive film is left at 85° C. and 85% RH for 250 hours.
3. The adhesive film for polarizing plates according to claim 1 , wherein the peel strength difference is about 1.0 N/25 mm or more.
4. The adhesive film for polarizing plates according to claim 1 , wherein the adhesive film has a modulus of about 40 kPa or more at 85° C.
5. The adhesive film for polarizing plates according to claim 1 , wherein the adhesive composition has a gel fraction difference of about 5% or less between a gel fraction after aging for 4 days and a gel fraction after aging for 7 days, as calculated by the following Equation 2:
Gel fraction=( WC−WA )/( WB−WA )×100,
where WA is a weight of a wire mesh,
WB is a total weight of the wire mesh and a specimen wrapped by the wire mesh so as not to leak therefrom, in which the specimen having the adhesive film stacked on a release film is obtained by coating 1.0 g of the adhesive composition to a thickness of 15 μm on the release film, followed by aging the adhesive composition on the release film at 35° C. and 45% RH for 4 days or 7 days, and
WC is a total weight of the wire mesh and the adhesive film, in which the adhesive film wrapped by the wire mesh is completely dipped in a sample bottle containing 50 cc ethyl acetate, left for 1 day, and dried at 100° C. for 12 hours.
6. The adhesive film for polarizing plates according to claim 1 , wherein the (meth)acrylic copolymer is free from a carboxylic acid group.
7. The adhesive film for polarizing plates according to claim 1 , wherein the monomer mixture comprises the (meth)acrylic monomer having the glass transition temperature (Tg) of about 0° C. or more in the homopolymer phase, an alkyl group-containing (meth)acrylic monomer, and a crosslinking functional group-containing (meth)acrylic monomer.
8. The adhesive film for polarizing plates according to claim 7 , wherein the (meth)acrylic monomer having the glass transition temperature (Tg) of about 0° C. or more in the homopolymer phase comprises at least one selected from among methyl acrylate, methyl methacrylate, t-butyl acrylate, t-butyl methacrylate, isobornyl acrylate, isobornyl methacrylate, and acryloyl morpholine.
9. The adhesive film for polarizing plates according to claim 7 , wherein the monomer mixture comprises about 1 wt % to about 40 wt % of the (meth)acrylic monomer having the glass transition temperature (Tg) of about 0° C. or more in the homopolymer phase, about 40 wt % to about 95 wt % of the alkyl group-containing (meth)acrylic monomer, and about 0.01 wt % to about 20 wt % of the crosslinking functional group-containing (meth)acrylic monomer.
10. The adhesive film for polarizing plates according to claim 7 , wherein the monomer mixture comprises an aromatic group-containing (meth)acrylic monomer.
11. The adhesive film for polarizing plates according to claim 10 , wherein the aromatic group-containing (meth)acrylic monomer has a glass transition temperature of less than about 5° C. in a homopolymer phase and is present in an amount of about 1 wt % to about 35 wt % in the monomer mixture.
12. The adhesive film for polarizing plates according to claim 1 , wherein the isocyanate curing agent has an isocyanurate group.
13. The adhesive film for polarizing plates according to claim 1 , wherein the antistatic agent comprises at least one selected from among a surfactant, an ionic liquid, an alkali metal salt, a metal oxide, fine metal particles, a conductive polymer, carbon, and carbon nanotubes.
14. The adhesive film for polarizing plates according to claim 1 , wherein the adhesive film comprises about 0.01 parts by weight to about 5 parts by weight of the isocyanate curing agent, and about 0.01 parts by weight to about 5 parts by weight of the metal chelate curing agent.
15. A polarizing plate comprising: a polarizer and the adhesive film for polarizing plates according to claim 1 stacked on a surface of the polarizer.
16. An optical display apparatus comprising the polarizing plate according to claim 15 .