Apparatus for controlling color of polarizing film and method of controlling the same

1. An apparatus for controlling a color of a polarizing film that exhibits polarizing properties, by dyeing a substrate film with iodine and potassium through a continuous process and orienting the substrate film, wherein the apparatus comprises:

a dyeing bath configured to dye a polyvinyl alcohol film by dipping the polyvinyl alcohol film has been previously washed, the dyeing bath including an aqueous iodine solution and an aqueous potassium solution, an iodine densitometer, and a potassium densitometer to measure concentrations of iodine and potassium of the dyeing bath;

a complementary bath configured to dye the polyvinyl alcohol film in an aqueous potassium solution by dipping the complementary bath including a potassium densitometer to measure a concentration of potassium of the complementary bath;

a composition feeder to feed amounts of a composition to the dyeing bath and a composition to the complementary bath;

a device oven configured to dry the polyvinyl alcohol film which was previously dipped in the dyeing bath and the complementary bath, the device oven including a device oven thermometer to measure a temperature of the device oven;

a 4-stage oven configured to dry the polyvinyl alcohol film which was previously dried in the device oven, the 4-stage oven including a 4-stage oven thermometer to measure a temperature of the 4-stage oven; and

a central controller connected to the iodine and potassium densitometer of the dyeing bath and the potassium densitometer of the complementary bath, and configured to predict a color value of the polyvinyl alcohol film on the basis of input data measured through the iodine and potassium densitometers of the dyeing bath, the potassium densitometer of the complementary bath, and the thermometers of the device oven and the 4-stage oven, and

said central controller is configured to control temperatures of the device oven and the 4-stage oven and amounts of compositions fed to the dyeing bath and complementary bath,

wherein said central controller is configured to predict the color value of the polyvinyl alcohol film with a polyvinyl alcohol film color value prediction model based on partial least squares.

2. The apparatus according to claim 1 , wherein the device oven comprises two ovens.

3. The apparatus according to claim 1 , wherein the 4-stage oven comprises four ovens.

4. The apparatus according to claim 1 , wherein the composition fed to the dyeing bath comprises iodine and potassium.

5. The apparatus according to claim 1 , wherein the composition fed to the complementary bath comprises potassium.

6. The apparatus according to claim 1 ,

wherein the composition feeder adds the composition to the dyeing bath and the composition to the complementary bath, based on the color value of the polyvinyl alcohol film predicted by the central controller.

7. The apparatus according to claim 1 , wherein the polyvinyl alcohol film color value prediction model comprises a function regarding a potassium concentration of the complementary bath, iodine and potassium concentrations of the dyeing bath, a temperature of the device oven including two ovens, and a temperature of the 4-stage oven including four ovens.

8. The apparatus according to claim 7 , wherein the polyvinyl alcohol film color value prediction model (y) is represented by the following Equation 1:

y=ax 1 +bx 2 +cx 3 +dx 4 +ex 5 +fx 6 +gx 7 +hx 8+ ix 9+ h   (1)

wherein x 1 is a potassium concentration of a complementary bath, x 2 is an iodine concentration of the dyeing bath, x 3 is a potassium concentration of the dyeing bath, x 4 is a temperature of an inclined oven, x 5 is a temperature of a first stage oven, x 6 is a temperature of a second stage oven, x 7 is a temperature of a third stage oven, x 8 is a temperature of a first device oven, and x 9 is a temperature of a second device oven, a, b, c, d, e, f, g, h, and i are regression coefficients obtained through partial least squares, and h is a constant obtained through partial least squares.

9. The apparatus according to claim 1 , further comprising:

a washing bath to wash the polyvinyl alcohol (PVA) film as the substrate film with water; and

a drawing bath to draw the polyvinyl alcohol film dyed with iodine and potassium using a drawing roller and thereby orient the polyvinyl alcohol film after being dyed with iodine and potassium.

10. The apparatus according to claim 1 , further comprising:

a swelling bath to swell the polyvinyl alcohol film which has been previously washed; and

a cleaning bath to clean the polyvinyl alcohol film which has been previously dyed.