Method of manufacturing porous film and porous film

Abstract

A porous film having favorable characteristics is manufactured. A method of manufacturing the porous film of the present invention includes: (a) a step of modifying a first filler to be hydrophobic by mixture of the first filler and an additive; (b) a step of forming a coating liquid by mixture of the hydrophobic first filler, a second filler and solvent; and (c) a step of forming a coating film (CF) by application of the coating liquid onto a surface of a porous base substance (S). In the step (a), the first filler is a cellulose, and a hydrophilic group of the cellulose is substituted with a hydrophobic group by a reaction between the cellulose and the additive. When the coating film is formed on the surface of the porous base substance as described above, mechanical strength and heat resistance of the porous film (separator) can be improved. For example, thermal deformation of the porous film (separator) can be equal to or lower than 5%.

Dependencies are inferred from the claim text.