Production method of polarizing plate
The present application relates to a polymer film and a method for producing a polarizing plate. The present application can provide a polymer film satisfying optical and mechanical durability required in a polarizing plate effectively and capable of forming a polarizing plate without causing bending when applied to a display device, and a method for producing a polarizing plate to which the polymer film is applied. The present application can provide a polymer film capable of realizing the required optical and mechanical durability without causing bending even in a polarizing plate applied to a thin display device and/or a thin polarizing plate, and a method for producing a polarizing plate to which the polymer film is applied.
1. A method for producing a polarizing plate, comprising:
steaming a polyester polymer film by exposing the polymer film to steam while a temperature of the steam is in a range of 50° C. to 150° C. for 10 seconds to 1 hour,
water-treating the polymer film by immersing the polymer film in water having a temperature in a range of 10° C. to 30° C. for 5 to 1000 seconds,
heat-treating the polymer film,
wherein the polymer film before the heat treatment has a shrinkage force in a first direction in a range of 5.5N to 15N, wherein the polymer film after the heat treatment has a shrinkage force in the first direction in a range of 5N to 10N,
a ratio (S1/S2) of the shrinkage force (S1) of the polymer film after the heat treatment in the first direction to a shrinkage force (S2) in a second direction perpendicular to the first direction is 13 or more;
the heat treatment is performed at a temperature satisfying Equation 2 below:
( Tg− 60)° C.≤ T ≤( Tg+ 50)° C. [Equation 2]
the Tg is a glass transition temperature of the polymer film, the T is the heat treatment temperature and the unit of the glass transition temperature and the heat treatment temperature is ° C.;
attaching the heat-treated polymer film to a polarizing film having a light absorption axis formed in one direction, wherein the polymer film and the polarizing film are attached such that the first direction forms an angle in a range of 80 degrees to 100 degrees with the light absorption axis of the polarizing film, wherein a ratio (S Pro /S PVA ) of a shrinkage force (S PVA ) of the polarizing film in a direction parallel to the light absorption axis direction and the shrinkage force (S Pro ) of the polymer film in the first direction is in a range of 0.1 to 5.5; and
forming a pressure-sensitive adhesive layer on, a surface of a side opposite to a surface of the polarizing film on which the polymer film is attached and wherein thicknesses of the polarizing film, the polymer film and the, pressure-sensitive adhesive layer are adjusted so as to satisfy Equation 1 below:
0.01 to 26 N ·mm= a ×( S PVA ×( T 1 +b )+ S Pro ×( T 2 +b )) [Equation 1]
wherein, the T1 is a distance (unit: mm) from the lowermost portion of the pressure-sensitive adhesive layer to the center of the polarizing film, the T2 is a distance (unit: mm) from the lowermost portion of the pressure-sensitive adhesive layer to the center of the polymer film, the a is a number within a range of 0.5 to 2, and the b is a number within a range of 0.14 to 0.6.
2. The method for producing a polarizing plate according to claim 1 , wherein the shrinkage force (S2) of the polymer film before the heat treatment in the second direction is from 0.01N to 2N.
3. The method for producing a polarizing plate according to claim 1 , wherein a ratio (SB/SA) of the shrinkage force (SB) of the polymer film before the heat treatment in the first direction relative to a shrinkage force (SA) of the polymer film after the heat treatment in the first direction is more than 1.
4. The method for producing a polarizing plate according to claim 1 , wherein the heat treatment is performed for 10 to 1,000 seconds.
5. The method for producing a polarizing plate according to claim 1 , wherein the polymer film is attached to the polarizing film so that a ratio (SP/SV) of a shrinkage force (SP) of the polarizing plate in the light absorption axis direction to a shrinkage force (SV) of the polarizing plate in a direction perpendicular to the light absorption axis direction is in a range of 0.78 to 1.5.
6. The method for producing a polarizing plate according to claim 5 , wherein the polymer film is attached to the polarizing film so that a shrinkage force of the polarizing plate in a direction parallel to the light absorption axis of the polarizing film is in a range of 6.5N to 15N.
7. The method for producing a polarizing plate according to claim 5 , wherein the polymer film is attached to the polarizing film so that a shrinkage force of the polarizing plate in a direction perpendicular to the light absorption axis is in a range of 6.0N to 15N.
8. The method for producing a polarizing plate according to claim 1 , wherein a shrinkage force of the polarizing film in a direction parallel to the light absorption axis is in a range of 0.1 to 15N.
9. The method for producing a polarizing plate according to claim 1 , wherein an angle among angles formed by one side of the polarizing film and the light absorption axis of the polarizing film is from 0 to 10 degrees or from of 80 to 100 degrees.
10. The method for producing a polarizing plate according to claim 1 , wherein an angle among angles formed by one side of the polarizing film and the light absorption axis of the polarizing film is from 35 to 55 degrees or from 125 to 145 degrees.