| 摘要 |
PURPOSE: To improve flatness and, further, improve copy machine passing prop erty by a method wherein a biaxially oriented film is constituted of a styrene polymer having syndiotactic structure, satisfying a specified formula, and pro vided with a specified thickness. CONSTITUTION: A biaxially oriented film is constituted of a polystyrene polymer, having syndioactic structure and satisfying the formula of [Amax/90( deg.)]×[HSmax/R]<=0.007, and is provided with the thickness of 25μm. In the case of a sheet type sample, squares, having one side of 100mm long, are cut out of four apexes of a rectangular specimen and the direction of orientation of particles are obtained while the maximum value among the angles of directions of orientations of other three points when the direction of orientation of particles at a measured point at first is specified as 0 deg.. Hsmax is the maximum dimensional changing rate upon the dry heat treatment for 30min. at 150 deg.C while contraction is specified so as to be positive. R is equal to Dmm/100 mm and the maximum value is 1 (one). D means a distance between a point, whereat the direction of orientation of particles is measured at first, and a point, whereat Amax is shown, and here D is a distance between the intersecting points of diagonals of squares, employed for the measurement. |
