Cellulose acetate films mfr. - suitable as high-quality bases for photographic films

摘要

A film of cellulose acetate (CA) is prepd. by dropping on to a support surface, from a first drop-funnel, a soln. of CA in an amt. corresp. to 10-90% of the predetermined thickness of the final film to form the first layer and then, before sepn. of the film from the support at a predetermined position, dropping a second soln. of CA corresp. to the remaining thickness of finished film on to the surface of the first layer. The second drop-funnel is positioned 30-60% along the distance between the first drop-funnel and the predetermined sepn. point. The film is removed from the support while it still contains up to 80% (by wt. of CA) of solvent and then dried conventionally. Films prepd. in this way are used particularly as high-quality planar bases for photographic films. The method enables CA films to be prepd. much more quickly than before. In earlier methods using only one drop-funnel, the film could not be removed from the support until fully dried, previous methods using two funnels had led to foam prodn. and retention of undried portions in the layer, thus impairing the flatness and transparency of the film. The present method overcomes these problems.