Plastic film

1. A plastic film, comprising:

a support substrate; and

a coating layer which is formed on one side of the support substrate, the coating layer comprising a crosslinked copolymer of tri- to hexafunctional acrylate-based monomers, a thermosetting resin, and inorganic fine particles,

wherein the thermosetting resin is a thermoset of a prepolymer composition comprising a polyester-based polyurethane oligomer, a polyol, and a polyisocyanate; the polyol is selected from the group consisting of polyethylene glycol polyol, polycaprolactone polyol, polyester polyol, polyether polyol, polyacryl polyol, polycarbonate polyol, and a combination thereof; and

wherein the plastic film exhibits a pencil hardness of 6H or more at a load of 1 kg.

2. The plastic film of claim 1 , wherein the thermosetting prepolymer composition contains the polyester-based polyurethane oligomer in an amount of 10 to 40 wt %, the polyol in an amount of 5 to 30 wt %, and the polyisocyanate in an amount of 50 to 80 wt %, based on the total weight thereof.

3. The plastic film of claim 1 , wherein the polyester-based polyurethane oligomer has a number average molecular weight of 1,000 to 100,000 g/mol.

4. The plastic film of claim 1 , wherein the polyisocyanate is polymerized from at least one selected from the group 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,4-cyclohexyl diisocyanate, isophorone diisocyanate, α,α-xylylene diisocyanate, 4,4′-dimethylmethane diisocyanate, 1,3-phenylene diisocyanate and toluene diisocyanate, a dimer thereof, and a trimer thereof.

5. The plastic film of claim 1 , wherein the crosslinked copolymer of tri- to hexafunctional acrylate-based monomers and the thermosetting resin are used at a weight ratio of from approximately 1:0.01 to 1:3.

6. The plastic film of claim 1 , wherein the thermosetting prepolymer composition further comprises at least one catalyst selected from the group consisting of dibutyltindilaurate (DBTDL), zinc octoate, iron acetyl acetonate, N,N-dimethyl ethanolamine, and triethylene diamine.

7. The plastic film of claim 1 , wherein the tri- to hexafunctional acrylate-based monomers include at least one selected from the group consisting of trimethylolpropane triacrylate (TMPTA), trimethylolpropane ethoxy triacrylate (TMPEOTA), glycerin propoxylated triacrylate (GPTA), pentaerythritol tetraacrylate (PETA), and dipentaerythritol hexaacrylate (DPHA).

8. The plastic film of claim 1 , wherein the inorganic fine particles have a diameter of 100 nm or less.

9. The plastic film of claim 1 , wherein the inorganic fine particles comprise at least one selected from the group consisting of silica nanoparticles, aluminum oxide fine particles, titanium oxide fine particles, and zinc oxide fine particles.

10. The plastic film of claim 1 , wherein the coating layer comprises the crosslinked copolymer of tri- to hexafunctional acrylate-based monomers in an amount of 40 to 80 parts by weight, the thermosetting resin in an amount of 5 to 50 parts by weight, and the inorganic fine particles in an amount of 5 to 40 parts by weight, based on 100 parts by weight thereof.

11. The plastic film of claim 1 , wherein the coating layer is formed on both sides of the support substrate.

12. The plastic film of claim 1 , wherein the coating layer has an interpenetrating polymer network (IPN) structure.

13. The plastic film of claim 12 , wherein the coating layer contains an IPN structure comprising both a first crosslinked structure induced by photocuring the tri- to hexafunctional acrylate-based monomers and a second crosslinked structure induced by thermosetting the thermosetting prepolymer composition.

14. The plastic film of claim 1 , exhibiting no cracks after a steel bead weighing 22 g is freely dropped from a height of 40 cm thereto.

15. The plastic film of claim 1 , allowing two or less scratches to be produced thereon when being tested by double rubbing 400 times with a steel wool #0000 under a load of 500 g.