Surface Pigment Volume Concentration changes with pigment loading for particulate magnetic tape

The Surface Magnetic Pigment Concentration (SPVC) is measured by XPS analysis to a depth of 50A° and compared to the calculated bulk Pigment Volume Concentration (PVC) of particulate magnetic tape. To obtain the required resolution, a modified Van Cittert Algorithm is used to deconvolute the initial X-ray photoelectron spectra. The SPVC is obtained from the intensity of the O1Sratio of the metal oxide to polymer oxygen, as well as from the ratio of intensity of the metal core electron peak to the polymeric C1Speak. The two magnetic pigments studied are acicular ferro magnetic CrO2and acicular ferri magnetic ΓFe2O3in a polyester-urethane binder. All particulate tape surfaces analyzed were calendered.