A carbon film is coated over the surface of a spacer. The carbon film has the following three features when the binding state of carbon is analyzed by X-ray photoelectron spectroscopy: (a) an integral area of a region of 284.5 eV or below is 27% or less of an integral area attributed to carbon, (b) an integral area of a region of 286.0 eV-287.0 eV is 18% or less thereof, and (c) an integral area of a region of 287.0 eV or above is 9% or more thereof.