Patent ID: 7927521
Filing Date: 2011-04-19
Classification: B29C,B29K,B29L,C08J,G02B,Y10T

Abstract:
1. A method for producing a cellulose acylate film, comprising: a film formation section in which a molten resin that melt-extruded a molten cellulose acylate resin from an extruder is extruded from a die in a form of a sheet, and a film is formed by sandwiching the resin between a pair of rollers each having such surface properties that an arithmetic average roughness Ra is 100 nm or less to cool and solidify the resin; and a stretching section in which the film formed in the film formation section is stretched at least in one of a longitudinal direction and a transverse direction by a factor of 1 or more than 1 and 2.5 or less, wherein the cellulose acylate resin has a number average molecular weight of 20,000 to 80,000, and the substitution degrees of the acyl groups satisfy the relations 2.0≦A+B≦3.0, 0≦A≦2.0 and 1.5≦B≦2.9, where A represents the substitution degree of the acetyl group and B represents the total sum of the substitution degrees of the acyl groups each having 3 to 7 carbon atoms, and extrusion conditions of the extruder has the screw compression ratio set to 2.5 to 4.5, L/D set to 20 to 50 showing the ratio of the length (L) to the inside diameter (D) of the cylinder, and extrusion temperature set to 190 to 240° C.