Method for forming a coating on a substrate
First Claim
1. A method for coating a moving web with a coating liquid comprising:
- conducting a moving web over a backing support means;
urging a first portion of at least one stationary smoothing film toward at least a portion of said backing support means by means of pliant pressure generating means, to thereby form a high-hydrodynamic-pressure and a static force coating zone of a length which is coincident with said first portion;
metering a coating liquid onto the web adjacent the confluence of the smoothing film and the web;
providing a second portion of said stationary film which trails said first portion in the direction in which said web is moving, which second portion of said smoothing film is not urged against said web and the coating liquid carried thereby;
adjusting the position of said pliant pressure generating means, relative said backing support means, to thereby control the length of said coating zone; and
adjusting said static force which exists within said controlled-length coating zone in a manner which does not affect the length of said coating zone;
thereby providing a coating nip having a length which is a function of said position adjustment, and having a static force which is a function of said force adjustment, such that the coating liquid is subjected to said static force, in the environment of the moving web and the first portion of the stationary film, for at least a critical time duration which insures uniform coating to the length of the web.
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Accused Products
Abstract
Method and apparatus for coating a moving web and for independently controlling the coating'"'"'s width, thickness and uniformity of thickness along the length of the web. A back-up roller supports the moving web on a portion of the roller'"'"'s periphery. A stationary and pliant smoothing film is positioned adjacent the exposed surface of the web which is supported by the back-up roller. A coating liquid is metered to the confluence of the web and the smoothing film, the metering rate being selected to produce a desired coating width. A pliant pressure generating means, in the form of a membrane or a force web, holds a length of the smoothing film against the moving web with a static force whose magnitude is selected in accordance with a desired coating thickness. The relative position of the back-up roller and the pressure generating means determines the length of coincidence of the moving web, the coating liquid, and stationary smoothing film. This length is selected, by virtue of selecting a relative position, to apply high hydrodynamic pressure to the coating liquid for at least a critical time interval, such that slight variation of this time interval does not produce appreciable variation in coating thickness along the length of the web, and lineal uniformity of coating thickness is thus achieved.
53 Citations
6 Claims
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1. A method for coating a moving web with a coating liquid comprising:
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conducting a moving web over a backing support means; urging a first portion of at least one stationary smoothing film toward at least a portion of said backing support means by means of pliant pressure generating means, to thereby form a high-hydrodynamic-pressure and a static force coating zone of a length which is coincident with said first portion; metering a coating liquid onto the web adjacent the confluence of the smoothing film and the web; providing a second portion of said stationary film which trails said first portion in the direction in which said web is moving, which second portion of said smoothing film is not urged against said web and the coating liquid carried thereby; adjusting the position of said pliant pressure generating means, relative said backing support means, to thereby control the length of said coating zone; and adjusting said static force which exists within said controlled-length coating zone in a manner which does not affect the length of said coating zone; thereby providing a coating nip having a length which is a function of said position adjustment, and having a static force which is a function of said force adjustment, such that the coating liquid is subjected to said static force, in the environment of the moving web and the first portion of the stationary film, for at least a critical time duration which insures uniform coating to the length of the web. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification