Method for applying a coating liquid to a web

A method for applying a coating liquid onto a web, comprising the steps of:

• selecting a coating liquid;
• forming a liquid reservoir and a slot with an outlet portion in accordance with the formula:
• ##EQU11## wherein D is the internal diameter of the liquid reservoir, d is the internal width of the slot, L.sub.1 is the internal depth of the slot from the reservoir to the outlet portion at a liquid supply location of the reservoir, L.sub.2 is the internal depth of the slot from the reservoir to the outlet portion at a liquid drain location of the reservoir, W is the internal length of the outlet portion, .eta..sub.p is the viscosity of the liquid while flowing through the reservoir, .eta..sub.s is the viscosity of the liquid while flowing through the slot, Q.sub.1 is the quantity of the liquid supplied to the reservoir at the liquid supply location, and Q.sub.2 is the quantity of the liquid drained from the reservoir at the liquid drain location;
• supplying the quantity Q.sub.1 of the liquid to the reservoir;
• draining the quantity Q.sub.2 of the liquid from the reservoir, the quantity Q.sub.2 being less than the quantity Q.sub.1 ;
• feeding the remaining quantity of the liquid through the slot to the outlet portion;
• and
• continuously moving a surface of the web along the outlet portion of the slot while discharging the remaining quantity of the liquid from the outlet portion of the slot onto the surface of the web, so as to form a film of the liquid on the surface.