PROBLEM TO BE SOLVED: To provide: a curable resin composition which can be preferably used for manufacturing devices such as LCD and CMOS image sensor, and which makes possible to meet performances generally required as a protection film, such as having transparency and solvent resistance, and to form a protection film low in sublimability at a lower temperature; a protection film formed from such a composition; and a method for forming such a protection film.SOLUTION: A curable resin composition according to the present invention comprises: a polymer (A) having at least one selected from a group consisting of a radical-polymerizable group, a cation polymerizable group and a hydrolyzed silyl group; and an acid-generating agent (B). In the curable resin composition, the oxygen-generating agent (B) is a sulfonium salt expressed by the following general formula (1). The curable resin composition is used for an application of forming a protection film for a liquid crystal display device or a protection film for a
