| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a film by increasing a production velocity while preventing generation of oblique unevenness. SOLUTION: A cast film 44 is formed by co-casting two or more dopes each composed of a solid component containing a polymer and a solvent on a casting drum 34 the surface of which is cooled. The cast film 44 has a surface layer 44a facing to air on the casting drum 34 and an inner layer 44d that is in contact with the surface layer 44a and the casting drum 34 and is composed of a base layer 44b and a support layer 44c. The solid content C1 of the surface layer dope 70a is in the range of not less than 18 wt.% to not more than 20 wt.%, and is smaller than the solid content C2 of the base layer dope 70b by not less than 2 wt.% to not more than 5 wt.%. The thickness of the surface layer 44a is not less than 2% to not more than 10% of the whole thickness of the cast film 44. By this, an effective levelling effect on the surface layer 44a is obtained and the oblique unevenness is prevented. The cast film 44 is peeled off from the casting drum 34 and is dried, and the obtained film shows an excellent optical property. COPYRIGHT: (C)2009,JPO&INPIT |
