Method for manufacturing thin polarizer, thin polarizer manufactured using same, and polarizing plate
The present invention relates to a method for manufacturing a thin polarizer, the method comprising the steps of: forming an auxiliary support on both ends in the transverse direction (TD) of an unstretched polyvinyl alcohol-based film; and wet-stretching the polyvinyl alcohol-based film, which has the auxiliary support formed thereon, in the machine direction (MD) of the polyvinyl alcohol-based film, in such that the thickness of the polyvinyl alcohol-based film is 10 μm or less.
1. A method for manufacturing a thin polarizer, comprising the steps of:
forming an auxiliary support on both ends in transverse direction (TD) of an unstretched polyvinyl alcohol-based film; and
wet-stretching the polyvinyl alcohol-based film, which has the auxiliary support formed thereon, in a machine direction (MD) of the film in such that a thickness of the polyvinyl alcohol-based film is 10 μm or less,
wherein a ratio of a width of the auxiliary support to a width of the unstretched polyvinyl alcohol-based film is 0.06-0.25.
2. The method of claim 1 , wherein the auxiliary support is a polymer film comprising at least one selected from the group consisting of polyvinyl alcohol-based resin, low-density polyethylene resin, high-density polyethylene resin, high-density polyethylene/ethylene vinyl acetate copolymer resin, polypropylene resin, isophthalic acid-containing polyethylene terephthalate resin, water-soluble cellulose resin, and acrylic resin.
3. The method of claim 1 , wherein the auxiliary support is a polymer film having a glass transition temperature of 20° C. to 80° C.
4. The method of claim 1 , wherein the auxiliary support has a shrinkage rate of 3.0% or less after wet-stretching.
5. The method of claim 1 , wherein the auxiliary support is formed on at least one surface of upper and lower surfaces of both ends in the transverse direction (TD) of the unstretched polyvinyl alcohol-based film.
6. The method of claim 1 , wherein the step of forming the auxiliary support comprises a step of attaching a polymer film to both ends in the transverse direction (TD) of the unstretched polyvinyl alcohol-based film by an adhesive, followed by drying.
7. The method of claim 6 , wherein the adhesive is a water-based adhesive having a viscosity of 4 cP-50 cP.
8. The method of claim 1 , wherein the auxiliary support is formed by folding both ends in the transverse direction (TD) of the unstretched polyvinyl alcohol-based film, attaching the folded ends to the film by an adhesive, followed by drying.
9. The method of claim 1 , wherein the step of wet-stretching the polyvinyl alcohol-based film, which has the auxiliary support formed thereon, in a machine direction (MD) of the film, is performed by stretching the polyvinyl alcohol-based film 4-9 times at a temperature of 20° C. to 85° C.
10. The method of claim 1 , further comprising, after the step of wet-stretching the polyvinyl alcohol-based film, which has the auxiliary support formed thereon, in the machine direction (MD) of the film, a step of separating the auxiliary support from the polyvinyl alcohol-based film.