Apparatus for producing microporous plastic film

An apparatus for producing a microporous plastic film comprising

• a horizontal pattern roll randomly having pluralities of high-hardness, fine particles having sharp edges on a rolling surface of a roll body;
• an anvil roll arranged opposite to said pattern roll;
• a conveying means for passing a plastic film through a gap between said pattern roll and said anvil roll;
• a stationary frame rotatably supporting either one of said pattern roll and said anvil roll;
• a pair of laterally arranged movable frames for rotatably supporting the other of said pattern roll and said anvil roll, said movable frames comprising vertical rails along which the other of said pattern roll and said anvil roll moves up and down;
• a pair of laterally arranged carriages, to each of which each of said movable frames is fixed;
• and
• a pair of rails extending in a running direction of said plastic film;
• said carriages comprising guide members engaging said rails, so that at least one of said carriages is independently movable back and forth along said rails in a running direction of the plastic film, to generate positional difference between a pair of said laterally arranged movable frames in a running direction of said plastic film, so that a center axis of said pattern roll and a center axis of said anvil roll are relatively inclined to each other;
• said apparatus further comprising a strain-removing roll brought into contact with a perforated plastic film, and a pair of driving means for changing the heights of bearings rotatably supporting both ends of said strain-removing roll, at a position downstream of a gap between said pattern roll and said anvil roll;
• and
• at least one of said driving means being operated to move at least one end of said strain-removing roll up and down, thereby vertically inclining said strain-removing roll relative to the center axis of said horizontal pattern roll, to absorb strain generated in said perforated plastic film by the inclination of the center axis of said anvil roll to the center axis of said pattern roll.