Doctor Blade

Abstract

Doctor blade (or tape casting) is one of the widely used techniques for producing thin films on large area surfaces. Tape casting is a relatively new process which was originally developed during the 1940’s as a method of forming thin sheets of piezoelectric materials and capacitors [1] and is now an accepted precision coating method. One patent, issued in 1952, focuses on the use of aqueous and non aqueous slurries applied to moving plaster batts by a doctor blading device [2]. In the doctor blading process, a well-mixed slurry consisting of a suspension of ceramic particles along with other additives (such as binders, dispersants or plasticizers) is placed on a substrate beyond the doctor blade. When a constant relative movement is established between the blade and the substrate, the slurry spreads on the substrate to form a thin sheet which results in a gel-layer upon drying. The doctor blading can operate at speed up to several meters per minute and it is suitable to coat substrate with a very wide range of wet film thicknesses ranging from 20 to several hundred microns.