| 摘要 |
1,072,951. Web coating apparatus. GEVAERT PHOTO-PRODUCTEN N.V. March 23, 1964, No. 12211/64. Heading D1L. A method of coating a liquid composition on to one side of a web comprises advancing the web and causing the liquid to flow as a continuous film on to the web from a slot like orifice located adjacent the web surface, the flow being achieved or assisted by maintaining an electrostatic field between the liquid composition supplied to the orifice and an electrically conductive member or part which is close to or in contact with the other side of the web. The apparatus shown in Fig. 1 comprises a backing roller 13 to which web 11 is fed, coating head 17 communicating with tray 18 for coating composition and electrical supply 14. Roller 13 is insulated by journalling its shaft in insulated bearings and means are provided for connecting said shaft to the potential source 14. The potential difference between the backing roller and the emulsion supply creates an electrostatic field which traverses the web and the air gap between the web and the coating head and establishes an emulsion meniscus between the web and the coating head. The backing roller may be slightly less in width than the web so that no or considerably less emulsion is applied to the margins of the web. If the web to be coated is of non-insulating material the backing roller comprises a metal core having a thin insulating surface layer. Instead of backing roller 13, two horizontally spaced rollers located along the web path, one on either side of the coating orifice together with a backing strip located between the rollers, may be provided (Fig. 3, not shown). A device for "double coating" includes a coating head (24) to which there are connected two supplies (21), (22) with a wall (29) therebetween. The outlet orifices (25), (26) are formed between said wall (29) and two adjustable members (27, 28) and a thermostatically controlled heating element (20) may be incorporated in the coating head. |
