Patent ID: 7867567

Claim:
A coating method for discharging a coating solution from a slot tip end of a slot die, to which a lip land is closely disposed, to a web surface which continuously travels while being supported by a backup roller to form a bead between the slot tip end and the web, and coating the coating solution on the web surface while decompressing a web upstream side of the bead, comprising the steps of: setting P b so that a decompression degree P 0 −P b (kPa) at the web upstream side with respect to a web downstream side of the bead satisfies the following formula: P S1 <P 0 −P b ≦P S1 +0.2 where P S ⁢ 1 = 1.34 ⁢ ( μ ⁢ ⁢ v ⁢ / ⁢ σ 1 ) 2 / 3 ⁢ ( σ 1 ⁢ / ⁢ h ) - σ 4 ⁡ ( 1 + cos ⁢ θ ) d + 12 ⁢ μ ⁢ ⁢ vl 1 ⁢ { ( d ⁢ / ⁢ 2 ) - h } d 3 P 0 : pressure at the web downstream side of the bead P b : pressure at the web upstream side of the bead μ: viscosity of the coating solution (Pa·s) v: coating speed (m/min) σ 1 : surface tension of a downstream side bead (N/m) σ 4 : surface tension of an upstream side bead (N/m) h: wet film thickness of the coating solution coated on the web (m) d: a coating gap between the lip land and the web (m) l 1 : length in a web traveling direction of a downstream side lip land (m), and θ: a contact angle of the web and the bead; and performing coating while suppressing a stepped unevenness of the film thickness of the coating solution, wherein the viscosity of the coating solution (μ) is 0.005 Pa·s or lower, wherein the wet film thickness of the coating solution coated on the web (h) is 10 μm or less, and wherein a coating gap d of the lip land and the web is set so as to satisfy the following formula: d= (2 h/ 1.34)(μ v/σ 1 ) −2/3 ×α 0.25≦α<1.