| 摘要 |
PURPOSE:To reduce refractive index difference by drying a solvent-containing film in four continuous drying processes controlled in atmospheric temp. due to a tenter type dryer and a fifth drying process using a suspension or float type dryer. CONSTITUTION:First - fourth drying processes are performed by a tenter type dryer and a fifth drying process is performed by a suspension or float type dryer. The film apparent glass transition temps. Tg1-Tg5, atmospheric temps. Tc1-Tc5 and stagnation times tm1--tm5 in the first - fifth drying processes are set to Tg1<=Tc1<=Tg1+60, Tg2<=Tc2<=Tg2+60, Tg3<=Tc3<=Tg3+60, Tg4-70<=Tc4<=Tg4-20, Tg5-20<=Tc5<=Tg5+50, 1<=tm1<=5, 1<=tm2<=5, 0.5<=tm3<=2, 0.5<=tm4<=2.5 and 10<=tm5<=60. Both ends of a film are not grasped in the first drying process but grasped in the second drying process and, in the third drying process, after both ends of the film are cut off, the film is not grasped and the film is allowed to run without being grasped in the fourth drying process and the tension of the film in the longitudinal direction thereof is set to 0.5-2.5kg/cm<2> in the fifth drying process. |
