A process for protecting a surface of a metal layer or a metal oxide layer including providing a protective film containing a base material and a pressure-sensitive adhesive layer formed thereon, wherein the surface of the pressure-sensitive adhesive layer has a contact angle with methylene iodide as measured just after contact, θ1, of 70° or smaller and a change in contact angle with methylene iodide through 30-second standing, Δθ, of 8% or less.