Porous ceramic filter and process of producing the same

Claim 1

A process of producing a porous ceramic filter consisting of a planar porous support formed of a ceramic material, and a filtering layer formed on an upper surface of said porous ceramic support, comprising the steps of: preparing a suspension containing a ceramic powder of a particle size distribution; holding said planar porous support such that said upper surface extends substantially horizontally, and holding said upper surface of said porous support in contact with said suspension while maintaining said suspension in a stationary state, so that particles of said ceramic powder are sedimented by gravity and thereby deposited on said upper surface of said porous support, in the order of size of said particles, whereby an unfired layer for said filtering layer is formed of the deposited particles of said ceramic powder on said upper surface of said porous ceramic support, said particle size distribution of said ceramic powder being determined such that the particle size of said unfired layer for said filtering layer decreases substantially continuously in a direction from a bottom toward an exposed surface of said unfired layer, from a maximum at said bottom to a minimum on said exposed surface; removing aqueous components from said porous ceramic support and said unfired layer of the deposited particles, and firing said porous ceramic support and said unfired layer, into the porous ceramic layer.