Method and apparatus for drying coating film and method for producing optical film

The present invention provides a method for drying a coating film comprising drying a coating film of an organic solvent-containing coating liquid applied to a running band-shaped flexible substrate, the drying method comprising the steps of: providing a heater at a position opposed to the band-shaped flexible substrate at a running position immediately after coating; and heating the band-shaped flexible substrate by the heater; wherein when TW( ° C.) denotes the surface temperature of the band-shaped flexible substrate; TH( ° C.) denotes the surface temperature of the heater; lambda(W/m.K) denotes the heat-transfer coefficient of air; d(m) denotes the distance between the heater and the band-shaped flexible substrate (web); eta denotes the efficiency of heat transfer; and sigma denotes the Stefan-Boltzmann constant (5.670x10-8 W/m2K4), the ratio of radiant heat transfer represented by QR/(QR+QC) is 0.25 or more and 0.6 or less, wherein QC and QR are represented by the following equations, respectively: QC=lambda/d.(TH-TW) where QC denotes heat transfer by air, and QR=eta{(TH+273)4-(TW+273)4} where QR denotes heat transfer by radiant.