Patent Abstract:
The present coating system ( 100 ) provides a multilayer coating apparatus for coating an object ( 112 ). The multilayer coating apparatus includes a slide hopper ( 116, 140 ). The slide hopper includes a main body ( 116, 140 ), the main body essentially including a plurality of separate cavities ( 118, 120, 122 ) for receiving coating materials, a plurality of separate slots ( 124, 126, 128 ) in communication with the corresponding cavities, and a plurality of separate projection portions ( 130, 132, 134 ) formed on the slide hopper, the projection portions each having a substantially sloping slide surface ( 131, 133, 135 ) configured for allowing the particular coating material exiting from the slot to directly flow onto the object.

Full Description:
BACKGROUND OF THE INVENTION  
   1. Field of the Invention 
   The present invention relates to multi-layer coating apparatuses and, particularly, to a multilayer coating apparatus for delivering coating materials to a surface of an object. 
   2. Discussion of the Related Art 
   A coating apparatus is for applying a coating material onto a surface of an object. The coating apparatus is usually required to be capable of controlling a flux or other coating material flowing to the surface, a flow velocity, a relative moving velocity between the surface of the object and the coating apparatus, and a distance between the object and the coating apparatus, in order to control a thickness of the coating material formed on the object and to distribute the coating material evenly on the surface of the object. In general, in many circumstances, a plurality of layers of the various coating materials is required to be coated/formed on an object. For example, a photosensitive composite film stack usually includes nine or more layers of materials. Thus, a multilayer coating apparatus that is capable of simultaneously coating a plurality of layers of materials is demanded. 
   In order to improve the coating quality, many modifications have been made to the coating apparatus. For example, an unfluctuating rolling edge has been proposed to sustain a flux of the liquid flowing on the slide surface, and/or an inhaled air removal device has been devised for eliminating an excess of inhaled air brought into the coating area by the moving object. 
   Slide hoppers are often employed in such multilayer coating apparatuses for supplying and guiding the coating materials to flow onto a surface of an object. A conventional slide-hopper-type, multilayer coating apparatus having a slide/extrusion hopper is adapted for dispensing a liquid composition onto a moving object. Such coating apparatuses generally can be categorized into a slide-rolling-edge type and a slide-curtain type. 
   China Patent Application No. 01100242.5 discloses a slide rolling edge type, multilayer coating apparatus and a slide curtain type, multilayer coating apparatus. In accordance with that application and referring to  FIG. 3 , the slide rolling edge type, multilayer coating apparatus  10  is illustrated. The slide rolling edge type, multilayer coating apparatus  10  includes a slide hopper  16  and a roller spindle  34 . An object  12  to be coated is wound on the outer circumference of the roller spindle  34  and is driven to jointly rotate with the roller spindle  34 . Coating materials  14 A,  14 B and  14 C are forced to flow from corresponding material containers (not shown) to corresponding cavities  18 ,  20  and  22  by corresponding pumps (not shown). The coating materials  14 A,  14 B and  14 C extend breadthwise to a predetermined width. The coating materials  14 A,  14 B and  14 C are extruded through corresponding slots  24 ,  26  and  28 . The coating materials  14 A,  14 B and  14 C are then combined into a multilayer composite coating material  14  on a slide surface  30 . The multilayer composite coating material  14  flows down along a projection portion  32  of the slide surface  30 , forming a rolling coating material edge  36  bounded by the projection portion  32  and the moving object  12 . Herein, an inhaled air removal device  38  is employed to remove the air brought/carried by the moving object  12  and to thereby stably sustain the rolling edge  36 . Therefore, a multilayer coating film A is formed on the moving object  12 . 
     FIG. 4  illustrates a slide curtain type coating apparatus  10 ′, as per the above-referenced application. The slide curtain type coating apparatus  10 ′ is similar to the slide rolling edge type, multilayer coating apparatus  10 , as illustrated in  FIG. 3 . However, in the case of the slide curtain type coating apparatus  10 ′, the projection portion  32  of the slide surface is located farther away from the object  12  to be coated, when considered relative to the projection portion  32  of the slide rolling edge type coating device  10 . The multilayer composite coating material  14  falls in the form of a curtain from the projection portion  32  of the slide surface  30  to the object  12 . The multilayer composite coating material  14  is then extended to form a multilayer coating film A. A pair of guiding means  44  is disposed for guiding the falling multilayer composite coating material  14 . An inhaled air removal device  46  is disposed and configured for removing the air brought/carried by the moving object  12  and for thereby promoting the formation of an even coating on the object  12 . 
   The foregoing moving objects  12  to be coated may, for example, be ordinary papers, plastic films, resin half-tone papers or a composite papers, or potentially a flexible electronic substrate material. The coating materials  14 A,  14 B and  14 C generally comprise emulsion, surface-active agents, and/or viscosity enhancing agents, as well as, of course, the primary coating material(s). 
   However, the aforementioned multilayer composite material  14  is formed on the slide surface  30  of the slide hopper  16  prior to being coated onto the object  12 . Therefore, mutual diffusion between the coating materials  14 A,  14 B and  14 C can inevitably occur. This mutual diffusion may adversely impair the coating quality. 
   Accordingly, a multilayer coating apparatus and a related method are needed in the art which can avoid the potential mutual diffusion of coating materials prior to their being coated on the object. 
   SUMMARY 
   The present invention provides a multilayer coating apparatus for coating an object. The multilayer coating apparatus includes a slide hopper. The slide hopper has a main body, the main body essentially including a plurality of separate cavities for receiving coating materials, a plurality of separate slots in communication with the corresponding cavities, and a plurality of separate projection portions formed on the slide hopper. The projection portions each have a substantially sloping slide surface configured for allowing the coating material exiting from the slot to directly flow onto the object. 
   Compared with the conventional technologies, the multilayer coating apparatus according to the present invention delivers coating materials to the surface to be coated via a plurality of independent slide surfaces. Since these slide surfaces are independent of each other, diffusion between coating materials before they reach to the surface to be coated can mostly be avoided, thus improving coating quality. 
   Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS  
     Many aspects of the present coating system and the method of its use can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, the emphasis instead being placed upon clearly illustrating the principles of the present coating system and its use. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
       FIG. 1  is a schematic cross-sectional view of a slide rolling edge type, multilayer coating apparatus according to a preferred embodiment of the present coating system; 
       FIG. 2  is a schematic cross-sectional view of a multilayer coating apparatus according to another preferred embodiment of the present coating system; 
       FIG. 3  is a schematic cross-sectional view of a conventional multilayer coating apparatus; and 
       FIG. 4  is a schematic cross-sectional view of another conventional multilayer coating apparatus. 
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate at least one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
   Referring now to  FIG. 1 , a multilayer coating apparatus  100  according to a preferred embodiment of the present coating system is shown. The multilayer coating apparatus  100  includes a slide hopper  116  and a roller spindle  110 . An object  112  to be coated is wound on the outer circumference of the roller spindle  34  and is driven to move jointly with the roller spindle  110 . The slide hopper  116  has a main body  117  that generally includes a plurality of cavities  118 ,  120  and  122  and has a plurality of slots  124 ,  126  and  128  defined therein. The cavities  118 ,  120  and  122  are respectively configured for accommodating coating materials  114 A,  114 B and  114 C. 
   The slide hopper  116  further comprises a plurality of flat projection portions  130 ,  132  and  134  located on the top thereof, respectively corresponding to and communicating with the slots  124 ,  126  and  128 . The flat projection portions  130 ,  132  and  134  correspondingly have associated sloping slide surfaces  131 ,  133  and  135 . The plurality of slots  124 ,  126  and  128  are, respectively, in fluid communication with the corresponding cavities  118 ,  120 ,  122 . The coating materials  114 A,  114 B and  114 C can be forced to flow into the cavities  118 ,  120  and  122  from corresponding containers (not shown) by flux controlling pumps (not shown). Widths of the slots  124 ,  126  and  128  are advantageously equal (or at least approximately so, depending on the degree of precision required) to the width of the surface to be coated (or as the case may be, to the width of the portion of the surface desired to be coated). 
   The object  112  wound on the roller spindle  110  is driven to move jointly therewith. The ends of the flat projection portions  130 ,  132  and  134  are preferably disposed as close as possible to the surface of the object  112  to facilitate the formation of a uniform and even coating on the object  12 . Upon being respectively extruded from the slots  124 ,  126  and  128 , the coating materials  114 A,  114 B and  114 C, under a gravitational force acting thereon, flow along the corresponding slide plane surfaces  131 ,  133  and  135  to the lower ends of the projection portions  130 ,  132  and  134 . Thus, the coating materials flow separately prior to be coated on the object  112 . Therefore, mutual diffusion between the coating materials, prior to reaching the object to be coated, is effectively eliminated. 
     FIG. 2  shows a multilayer coating apparatus  100 ′ for coating an object  112  according to another preferred embodiment of the present coating system. The multilayer coating apparatus  100 ′ includes a slide hopper  140  and a roller spindle  110 . An object  112  is wound on the outer circumference of the roller spindle  34  and is driven to move jointly with the roller spindle  110 . The slide hopper  140  has a main body  142  that generally includes a plurality of cavities  118 ,  120  and  122  and has a plurality of slots  124 ,  126  and  128  defined therein. The slots  124 ,  126  and  128  are respectively in fluid communication with the cavities  118 ,  120 ,  122 . The plurality of cavities  118 ,  120  and  122  are respectively configured for accommodating coating materials  114 A,  114 B and  114 C. 
   The slide hopper  140  further comprises a plurality of curved projection portions  170 ,  172  and  174  located on the top of the slide hopper  140 . These curved projection portions  170 ,  172  and  174  respectively correspond to and fluidly communicate with the slots  124 ,  126  and  128 . The curved projection portions  170 ,  172  and  174  each have sloping curved slide surfaces  171 ,  173  and  175  for guiding coating materials  114 A,  114 B and  114 C to flow toward the object  112 . 
   The coating materials  114 A,  114 B and  114 C are forced to flow from corresponding containers (not shown) to the cavities  118 ,  120  and  122  by means of flux controlling pumps (not shown). Widths of the slots  124 ,  126  and  128  are substantially equal to a width of the to-be-coated surface of the object  112  (or to the width of portion thereof to be coated, as the case may be). Guiding means  180 ,  182  and  184  are additionally provided and are configured to allow the coating materials  114 A,  114 B and  114 C to smoothly flow from the projection bent slide edges  170 ,  172  and  174  onto the surface of the object  112 . The object  112  is wound on and driven by a roller  110 . 
   Upon being extruded from the slots  124 ,  126  and  128 , the coating materials  114 A,  114 B and  114 C, under the gravitational force acting thereon, flow along the corresponding slide curving surfaces  171 ,  173  and  175  to corresponding lower ends of the bent slide edges  170 ,  172  and  174 . Thereafter, the coating materials  114 A,  114 B and  114 C, being guided by the guiding means  180 ,  182 , and  184 , fall down to the surface of the object to be coated  112 . Thus, the coating materials flow separately prior to being coated on the object  112 . Therefore, mutual diffusion, prior to reaching the object to be coated, is effectively avoided. 
   According to another aspect of the foregoing embodiments, the slide hoppers  116  and  140  can advantageously be made of any of various ceramic materials or ceramic-based composites, including oxide ceramics, such as Al x O y , Zr x O y , Mg 2 SiO 4 , and ZrSiO x ; nitride ceramics such as Si x N y , Ti x N y , Al x N y , and B x N y ; and carbide ceramics such as Si x C y , Ti x C y , W x C y , and Cr x C y ; and composites composed substantially of at least one of such materials. In addition, an inhaled air removal device, such as those illustrated in  FIGS. 3 and 4 , may also be employed with the present embodiments of the coating system in order to remove the air brought/carried by the object  112 . 
   It is to be further understood that the above-described embodiments illustrate the scope of the invention but do not restrict the scope of the invention. Variations may be made to the embodiments without departing from the spirit or scope of the invention as claimed herein.

Technology Classification (CPC): 1