Coating apparatus and method for applying coating solution on web

A method for applying a coating solution on a web, comprising:

• feeding said web continuously;
• and
• discharging said coating solution from a slot of a die, said discharged coating solution flowing on a slide surface of said die onto said web, with a bead formed between the slide surface and the web, a width of said coating solution being regulated by edge members which are provided in both sides on said slide surface, each said edge member having a regulation portion which is perpendicular to said slide surface and faces the other regulation portion,
• wherein a height Dg of said regulation portion satisfy a condition Db≦Dg≦Ds,
• Db being a minimum thickness of bead at vena contracta and Ds being an upper limit of a height of said regulation portion, which are represented as follows,
• Db=1.03×h1−1.50×he×U−1/3+12800×he2×U
• Ds(m)={3×η×q/(ρ×g×sin α)}1/3
• wherein
• h1 is a distance between said web and a lip of said die in m,
• he is a thickness of said coating layer formed on said web as the coating solution flows onto the web, in m,
• U is a feeding velocity of said web in m/s,
• η is an averaged viscosity of solution flowing on said slide surface at a shear rate in m·Pa·s,
• q is a total amount of said coating solution in a predetermined width in m3/(m·sec),
• ρ is an averaged density of said solution in kg/m3,
• g is an acceleration of gravity in m/sec2, and
• α is an angle of the slide surface with respect to horizontal, in °.