Patent ID: 7070834

Claim:
A production method of a porous medium comprising a non-water-absorptive support and a porous layer provided on the support, the method comprising: applying Water-based Composition A comprising inorganic microparticles of an average primary particle diameter of less than or equal to 30 nm, a hydrophilic binder and water onto the support to form a layer, drying the layer to form the porous layer, and applying Water-based Composition B onto the dried porous layer, wherein the Water-based Composition A further comprises a compound represented by formula (1) having a molecular weight of less than or equal to 200, wherein R 1 , R 2 and R 3 each represent a hydrogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, an aryl group, an acyl group, a heteroaryl group, a heterocyclic group, —NR 4 R 5 , or —OR 6 ; R 4 , R 5 and R 6 each represent a hydrogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, an aryl group, an acyl group, a heteroaryl group, a heterocyclic group, an amino group or a cyano group further, R 1 and R 2 , R 1 and R 3 , and R 1 and R 4 may be joined together to form a ring; and X represents an oxygen atom or NH, wherein the Water-based Composition B comprises a component which forms coagulants in the Water-based Composition A or increases viscosity of Water-based Composition A, when the component is added in the Water-based Composition A, and the Water-based Composition A does not comprise a component which forms coagulants in the Water-based Composition A or increases viscosity of Water-based Composition A, when the component is added in the Water-based Composition A.