Method for avoiding re-circulation defects in curtain coating
AssigneeEastman Kodak Company
InventorChristopher L. Bower
Life of this patent
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Abstract
A method of curtain coating, the curtain being formed from at least one layer of coating solution having a composite density ρ (kgm−3) and a total volumetric flow rate per unit curtain width Q (m2s−1), the curtain being allowed to free fall a distance h (m), at a velocity U (ms−1), onto a continuously moving substrate having a velocity S (ms−1) with an application angle of θ 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 σ (mNm−1), the aforementioned variable parameters being controlled so as to prevent recirculation.
Claims5
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 ρ (kgm−3) and a total volumetric flow rate per unit curtain width Q (m2s−1), the curtain being allowed to free fall a distance h (m), at a velocity U (ms−1), onto a continuously moving substrate having a velocity S (ms−1) with an application angle of θ 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 σ (mNm−1), the aforementioned variable parameters being controlled so as to satisfy the following inequality;
- We<7.82.(Ca)0.39
- where We = ρ QU cos θ σ - α F x and Ca = η ( S + U sin θ ) σ - α F x ,
- η= 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.
Dependencies are inferred from the claim text.