Patent ID: 7897312

Claim:
A photoreceptor for electrophotography, comprising: an under coat layer having a thickness of 6 to 15 μm, the undercoat layer containing a binder resin and particles of surface treated titanium oxide containing niobium element; and a charge generation layer and a charge transport layer provided on a substrate, and a thickness of the charge transport layer being 5-15 μm; wherein the under coat layer has a gradient of a straight line represented by α, α being not more than 0.8, wherein α is linearly approximated by the following formula (a): φ UCL =α·φ M +β (a) (α,β:constant), wherein φ UCL represents a work function of the under coat layer and φ M represents a work function of a conductive electrode material, both work functions obtained by measuring a contact potential difference of conductive electrode materials.