Polarizer protective film, polarizing plate and method for preparing polarizing plate

1. A polarizer protective film comprising a binder resin layer in which a poly(C 2-4 alkylene glycol)-modified polyfunctional urethane (meth)acrylate-based polymer and a bifunctional or higher polyfunctional (meth)acrylate-based compound form a cross-linked bond,

wherein the weight ratio of the bifunctional or higher polyfunctional (meth)acrylate-based compound to the poly(C 2-4 alkylene glycol)-modified polyfunctional urethane (meth)acrylate-based polymer is from 1.1 to 1.20, and

wherein the poly(C 2-4 alkylene glycol)-modified polyfunctional urethane (meth)acrylate-based polymer has a trifunctional or higher functional urethane bond and is bound to each poly(C 2-4 alkylene glycol)-modified (meth)acrylate-based compound via the urethane bond, and at least two poly(C 2-4 alkylene glycol)-modified (meth)acrylate-based compounds bound to each urethane bond comprises poly(C 2-4 alkylene glycol) repeating units whose numbers of repetitions are different from each other.

2. The polarizer protective film of claim 1 , wherein the difference of the number-average molecular weight between at least two poly(C 2-4 alkylene glycol)-modified (meth)acrylate-based compounds bound to the urethane bond is 100 to 500.

3. The polarizer protective film of claim 1 , wherein the poly(C 2-4 alkylene glycol)-modified polyfunctional urethane (meth)acrylate-based polymer comprises at least one selected from the group consisting of a polyethylene glycol-modified polyfunctional urethane (meth)acrylate-based polymer and a polypropylene glycol-modified polyfunctional urethane (meth)acrylate-based polymer.

4. The polarizer protective film of claim 1 , wherein the poly(C 2-4 alkylene glycol)-modified polyfunctional urethane (meth)acrylate-based polymer is a reactant between a trifunctional or higher functional polyvalent isocyanate-based compound; and at least two poly(C 2-4 alkylene glycol)- modified (meth)acrylate-based compounds including poly (C 2-4 alkylene glycol) repeating units whose numbers of repetitions are different from each other.

5. The polarizer protective film of claim 4 , wherein the polyvalent isocyanate-based compound is selected from the group consisting of an oligomer of a diisocyanate compound, a polymer of a diisocyanate compound, a cyclic polymer of a diisocyanate compound, hexamethylene diisocyanate isocyanurate, isophorone diisocyanate isocyanurate, toluene 2,6-diisocyanate isocyanurate, a triisocyanate compound and an isomer thereof.

6. The polarizer protective film of claim 4 , wherein each of the at least two poly (C 2-4 alkylene glycol)-modified (meth)acrylate-based compounds including poly (C 2-4 alkylene glycol) repeating units whose numbers of repetitions are different from each other has a number-average molecular weight of 200 to 1000.

7. The polarizer protective film of claim 1 , wherein the binder resin layer further includes a polycarbonate-modified bifunctional urethane (meth)acrylate-based polymer.

8. The polarizer protective film of claim 7 , wherein the polycarbonate-modified bifunctional urethane (meth)acrylate-based polymer has a bifunctional or higher functional urethane bond and is bound to each polycarbonate-modified (meth)acrylate-based compound via the urethane bond.

9. The polarizer protective film of claim 1 , wherein the bifunctional or higher polyfunctional (meth)acrylate-based compound includes at least one selected from the group consisting of polyfunctional urethane acrylate, 9-ethylene glycol diacrylate (9-EGDA), bisphenol A epoxy acrylate, polyether triacrylate, pentaerythritol tri/tetraacrylate(PETA), dipentaerythritol hexa-acrylate DPHA), trimethylolpropane triacrylate (TMPTA) and hexamethylene diacrylate (HDDA).

10. The polarizer protective film of claim 1 , wherein the weight ratio of the bifunctional or higher polyfunctional (meth)acrylate-based compound relative to the poly (C 2-4 alkylene glycol)-modified polyfunctional urethane (meth)acrylate-based polymer is from 1.5 to 1.15.

11. A polarizing plate comprising a polarizer and the polarizer protective film of claim 1 .

12. The polarizing plate of claim 11 , further comprising an adhesive layer positioned between the polarizer and the protective film.

13. The polarizing plate of claim 11 , further comprising a second polarizer protective film formed on one side of the polarizer.

14. The polarizing plate of claim 11 , wherein the thickness of the polarizer protective film is 1 μm to 100 μm, and the thickness of the polarizer is 5 μm to 300 μm.

15. A method for preparing a polarizing plate, comprising forming a polarizer protective film by photocuring a coating composition including a poly (C 2-4 alkylene glycol)-modified polyfunctional urethane (meth)acrylate-based polymer; a bifunctional or higher polyfunctional (meth)acrylate-based compound; and a photo-initiator; and laminating and adhering the polarizer protective film to one surface of a polarizer,

wherein the weight ratio of the bifunctional or higher polyfunctional (meth)acrylate-based compound to the poly (C 2-4 alkylene glycol)-modified polyfunctional urethane (meth)acrylate-based polymer is from 1.1 to 1.20, and

wherein the poly(C 2-4 alkylene glycol)-modified polyfunctional urethane (meth)acrylate-based polymer has a trifunctional or higher functional urethane bond and is bound to each poly(C 2-4 alkylene glycol)-modified (meth)acrylate-based compound via the urethane bond, and at least two poly(C 2-4 alkylene glycol)-modified (meth)acrylate-based compounds bound to each urethane bond comprises poly(C 2-4 alkylene glycol) repeating units whose numbers of repetitions are different from each other.

16. The method for preparing a polarizing plate of claim 15 , wherein the coating composition further includes an organic solvent; or at least one additive selected from the group consisting of an inorganic nanoparticle, a surfactant, a leveling agent and a dispersion stabilizer.