PURPOSE: To obtain a protective adhesive film which enables easy removal of the air present between the film stuck to a sign board and the board and hence does not impair the appearance of the board by forming an adhesive layer contg. a microspherical self-adhesive.

CONSTITUTION: An adhesive layer comprising a microspherical self-adhesive alone or together with a binder is formed on one side of a transparent substrate film. The self-adhesive is pref. an acrylic, has pref. a particle size of 5-50μm and is produced by, e.g. polymerizing monomers in soln., dispersing the resultant copolymer in water to provide an aq. suspension, and removing water and the solvent with a centrifugal separator. As the binder is used a self-adhesive or a synthetic resin binder.