Abstract: A recording sheet is provided by forming, on at least one side of a substrate sheet, an ink absorbing layer comprising a cationic polymer having at least crosslinking groups. The ink absorbing layer may comprise (1) a cationic polymer containing a crosslinking monomer (e.g. a monomer having a hydrolyzable condensing group such as alkoxysilyl) as a comonomer unit, (2) a cationic polymer containing a crosslinking monomer and a hydrophilic monomer (e.g. a monomer having a polyoxyalkylene unit) as comonomer units, or (3) the above cationic polymers (1) and (2), and a hydrophilic polymer. The cationic polymer and the hydrophilic polymer may have interacting reactive groups. This recording sheet is useful for the improvement of the water resistance and ink absorption in an ink jet recording sheet.

Abstract: A recording sheet is provided by forming, on at least one side of a substrate sheet, an ink absorbing layer comprising a cationic polymer having at least crosslinking groups. The ink absorbing layer may comprise (1) a cationic polymer containing a crosslinking monomer (e.g. a monomer having a hydrolyzable condensing group such as alkoxysilyl) as a comonomer unit, (2) a cationic polymer containing a crosslinking monomer and a hydrophilic monomer (e.g. a monomer having a polyoxyalkylene unit) as comonomer units, or (3) the above cationic polymers (1) and (2), and a hydrophilic polymer. The cationic polymer and the hydrophilic polymer may have interacting reactive groups. This recording sheet is useful for the improvement of the water resistance and ink absorption in an ink jet recording sheet.

Abstract: Porous membranes having a micro phase separation structure and showing a light transmittance at the wavelength of 400 nm of not less than 30% are obtained by the dry phase conversion method comprising drying a coating layer of a dope containing a polymer, a good solvent for the polymer and a poor solvent for the polymer which solvent has a higher boiling point than the good solvent. The polymer includes cellulose derivatives, vinyl-series polymers such as acrylonitrile-series polymers and (meth)acrylic acid ester-series polymers, polysulfone-series polymers, and the like. The porous polymer membranes have a porosity of 10 to 60%, a mean pore size of about 0.002 to 0.35 &mgr;m and a maximum pore size of not greater than 0.4 &mgr;m. These porous membranes shows not only excellent transparency but also high productivity.