Patent ID: 6472021
Filing Date: 2002-10-29
Classification: B05D,G03C,Y10S

Abstract:
A method of curtain coating which avoids coating defects due to recirculation, the curtain, being formed from at least one layer of coating solution, having a composite density &rgr; (kgmâˆ’3) and a total volumetric flow rate per unit curtain width Q (m2sâˆ’1), the curtain being allowed to free fall a distance h (m), at a velocity U (msâˆ’1), onto a continuously moving substrate having a velocity S (msâˆ’1) with an application angle of &thgr; between the horizontal and tangent to the substrate at the point of impingement, the dynamic surface tension at the rear of the falling curtain being &sgr; (mNmâˆ’1), the aforementioned variable parameters being controlled so as to satisfy the following inequality;We<7.82.(Ca)0.39 where We=Ï &it;â€ƒ&it;QU&it;â€ƒ&it;cos&it;â€ƒ&it;Î¸Ïƒ-Î±&it;â€ƒ&it;Fx&it;â€ƒ&it;andCa=Î·&af;(S+U&it;â€ƒ&it;sin&it;â€ƒ&it;Î¸)Ïƒ-Î±&it;â€ƒ&it;Fx,&eegr;= the viscosity of the coating solution and Fx is the horizontal component of an electric force applied at the coating point,recirculation being avoided if the above inequality is satisfied.