Slit die, and method and device for producing base material with coating film

A slit die has a combined, opposing pair of lips. Between the lips, the die has a lip gap and a coating liquid discharge opening formed at the lower end of the lip gap. At least one of the lips is constituted of two blocks that are vertically layered over each other and relatively movable in the direction perpendicular to the length direction of the discharge opening. The slit die further has a block-engaging element for engaging the blocks together in such a way that relative positions of the blocks are adjustable, a block-fastening element for fastening the blocks together after their relative positions are adjusted, a positioning element attached to outer surfaces of the blocks, on the side opposite the discharge opening side, and defining the positions to which the blocks are relatively moved, and a fixing element for fixing the positioning element to the blocks.