Patent ID: 6517909
Filing Date: 2003-02-11
Classification: B05D,G03C

Abstract:
A method for curtain coating a liquid composition onto a moving web at a coating point where the moving web is supported on a backing roller, the method comprising the steps of:(a) partially wrapping the moving web around the backing roller, the backing roller including a relief patterned area on the surface thereof, the relief patterned area including relieved features and non-relieved features, the relief patterned area being at least 30% of the width of the moving web, the relief patterned area being circumferential of the backing roller, the relieved features and the non-relieved features creating an electrostatic force difference exerted on the liquid composition at the coating point when an electrostatic field is applied thereto; (b) specifying a predetermined acceptable level of coating thickness non-uniformity, the level of coating thickness non-uniformity increasing with an increase in electrostatic force difference and decreasing with an increase in web speed; (c) Drying a web speed; (d) varying the electrostatic force difference exerted on the liquid composition at the coating point, the electrostatic force difference determined by the relief patterned area, a capacitance of the moving web per unit area, and an electrostatic charge coating assist level, to determine a maximum electrostatic force difference for the specified web speed that achieves the predetermined acceptable level of coating thickness non-uniformity, (e) displaying the liquid composition from a curtain coating apparatus with a curtain height greater than or equal to 5 centimeters onto the moving web at the coating point; (f) moving the web at the specified web speed; and (g) generating an operating electrostatic force difference at the coating point that is not greater than the maximum electrostatic force difference for the specified web speed.