Abstract:
A microporous polypropylene film exhibiting enhanced film forming properties in β-crystal technique; a microporous polypropylene film of markedly lowered specific gravity; a microporous polypropylene film of highly enhanced permeability; and a process for producing these microporous polypropylene films. There is provided a microporous polypropylene film comprising a polypropylene whose Trouton's ratio is specified. Further, there is provided a microporous polypropylene film comprising a polypropylene whose main chain skeleton contains long-chain branching. Still further, there is provided a microporous polypropylene film comprising a polypropylene whose formula of relationship between melt tension and melt flow rate is specified. Still further, there is provided a microporous polypropylene film comprising a polypropylene whose profile of film in-plane intensity distribution in azimuthal angle direction of (-113) face as identified by X-ray diffractometry is specified.
Abstract:
A biaxially oriented white polypropylene film for thermal transfer recording (first form), comprised of a polypropylene resin of 30% or higher β-crystal ratio and 140 to 172°C melting temperature, characterized in that the biaxially oriented white polypropylene film has substantially non-nucleated voids, a void ratio of 30 to 80%, a sum of strengths (F2 values) at 2% elongation in the longitudinal direction and the width direction of the film of 10 to 70 MPa and a surface gloss of 10 to 145%.