Abstract In a method of coating a support with a liquid coating composition in which the coating composition is applied by impingement of a free-falling curtain of coating composition onto the surface of the moving support, formation of edge beads along the edges of the coating which are of greater thickness than the remainder of the coating is effectively avoided by use of laterally adjustable edge guides which are initially positioned so as to establish a stable free-falling curtain and then moved laterally to a position in which they are slightly further apart, whereby the coating assumes a uniform thickness. The method of this invention is useful in both single-layer and multiple-layer curtain coating and are especially advantageous in the manufacture of photographic film and photographic paper in view of the need for precisely uniform thickness over the entire coated area.
In a curtain-coating method in which a support to be coated with a liquid coating composition is moved along a path through a coating zone and a free-falling curtain of said coating composition which extends transversely of said path is formed within said coating zone, between a pair of vertically positioned edge guides equipped with flexible extensions which bear on the moving support adjacent to the edges of said free-falling curtain, and is directed to impinge on the face of said moving support to deposit a coating thereon; the improvement comprising initially establishing a stable free-falling curtain with said edge guides positioned apart a predetermined distance whereby the coating formed has an edge bead adjacent each edge guide which is of greater thickness than the remainder of the coating and thus contains excess coating composition, then moving each of said edge guides away from the other by a distance substantially equal to the cross-sectional area of the excess coating composition in the adjacent bead divided by the thickness of the coating and securing said edge guides in the resulting position, whereby the coating formed thereafter is of substantially the same thickness at its edges as it is intermediate said edges.
Claim 2
Dependent Claim
36 words
A method as described in claim 2 wherein said edge guides are first moved apart a greater distance than that defined in claim 2 and are then moved together to the position defined in claim 2.
Claim 3
Dependent Claim
23 words
A method as described in claim 2 wherein said curtain is comprised of a plurality of distinct juxtaposed layers of liquid coating compositions.
Claim 4
Dependent Claim
22 words
A method as described in claim 4 wherein said coating compositions are photographic coating compositions and the support is photographic film base.
Claim 5
Dependent Claim
21 words
A method as described in claim 4 wherein said coating compositions are photographic coating compositions and the support is photographic paper.