| Multilayer slide coating flow is an operation of simultaneously depositing more than one layer of liquid onto a fast-moving substrate. This high-precision-coating technique is the major workhorse of graphic arts, x-ray, and color photographic film manufacture. This thesis reports advances, both experimental and theoretical, in fundamental understanding of the physical mechanisms that underlie the technique.;A prototype of a three-layer slide coating die was designed, built, and used for coating experiments in both the university laboratory and an industrial pilot plant. Coating of two and three layers of glycerine-water solutions simultaneously onto a fine cylindrical metal roll at capillary numbers of the order of unity was visualized by techniques of hydrogen bubbles, dye injection and optical sectioning. One-, two-, and three-layer coating flows of glycerine-water and aqueous cellulosic polymer blend were further studied by the method of 'coating window' mapping.;A theory of steady, two-dimensional, multilayer viscous film flows was put forth, which employed Galerkin's method with finite element basis functions and incorporated a correlation of apparent dynamic contact angle developed from flow visualizations. Computed progressions of steady states with parameters being varied incrementally were converted into animation sequences. The steady flow model was validated by comparing computed predictions of streamlines and shapes of the free surfaces and liquid/liquid transition zones with visualized ones.;Linear stability theory was applied to examine effects of layer thicknesses and viscosities in a two-layer slide coating flow on barring-like and also ribbing-like flow instabilities. The feasibility of reducing peak response of final-coating-thickness by advanced, closed-loop feedback control was explored. An efficient method of predicting frequency response in coating flow by use of system natural frequencies and normal modes, i.e. via modal analysis, was put forth and its application was illustrated.;Three-dimensional flow aspects in infinite-cavity-slot die design were studied using the Galerkin/finite element method. Effects were examined of feed location, chamber shape, slot length, chamber-height-to-slot-height aspect ratio, liquid inertia, and secondary chamber on slot-exit outflow uniformity. The three-dimensional flow model was also used to validate simpler analysis of one-dimensional flow in chamber and two-dimensional flow in slot. |
