To provide a method for producing an optical sheet capable of reducing a warp amount within a range to prevent the occurrence of image disturbance in a liquid crystal display device even if a warp tendency changes after installation to the liquid crystal display device.
A resin material is supplied to a die 8 after casting the resin material into a hopper 7 and heating and melting (softening) the resin material in a cylinder 6. Then, the resin material is extruded from the die 8 as an optical sheet 3 to be cooled down while being extended and molded with cooling rolls 9-11. In this process, temperatures of the peripheral surfaces 12-14 of the respective cooling rolls 9-11 are regulated so that a temperature T1 of the surface 31 of the optical sheet 3 passed through a cooling roll group 4 to be cooled down becomes close to a glass transition temperature Tg of the resin material in a detectable range of a temperature sensor 5. In this way, when the temperature T1 of the surface 31 of the optical sheet 3 reaches a temperature around the Tg, regulation is carried out so that a surface temperature difference (a difference obtained by subtracting the temperature T1 of the surface 31 from the temperature T2 of the back surface 32) of the optical sheet 3 falls in the range of 2.5-4.0°C.
SAKAMOTO TAKASHI
| JP2002120249A | 2002-04-23 |
| WO2006054520A1 | 2006-05-26 |
Mio Kawasaki
Kyoumura Junji