| 摘要 |
PURPOSE:To accelerate the production speed and at the same time manufacture a film excellent in flatness by a method wherein a cooling surface equipped with micro-crack structure having special shape is provided. CONSTITUTION:A cooling surface is shiftable as a drum-shaped body of rotation or a belt conveyor. A micro-crack formed on the cooling surface develops from the surface toward a depth. In the cross section of the crack 12, the groove width of an opening part 12A at the surface layer of the cooling surface is narrower and the groove width of an interior part 12B is wider than that of said opening part 12A. Accordingly, the above-mentioned micro-crack has a higher capacity to deliver caught-in air to its interior part layer as compared with that of conventional micro-crack. Though the micro-cracks are formed irregularly, the draft resistance measured by vacuum leakage method is preferably 20,000sec or less, more preferably 10,000sec or less and the range of the most preferable draft resistance is 10-1,000sec. |
