Abstract: A toner includes toner particle containing at least a strontium titanate particle on the surface of the toner particle, and the toner is a water-washed toner from which strontium titanate particle desorbable by water washing are removed by water washing. The water-washed toner contains the strontium titanate particle having a number average particle diameter of primary particle (D1) of 10 nm or more and 150 nm or less, and when the distribution of an Sr element in the water-washed toner in the depth direction is determined, (i) the Sr element abundance on the outermost surface x satisfying 0.00<x?0.80, and (ii) the difference between x and xp “xp?x” satisfying 0.00<xp?x?0.95, where xp is the maximum peak value (atomic %) of the Sr element abundance in the region from the outermost surface to 50 nm.

Abstract: An image forming apparatus in which occurrence of an image failure in association with contamination caused by an external additive, such as silica, adhering to a charging unit is suppressed. The image forming apparatus is configured to charge an image bearing member through use of the charging unit, and uses toner having, on a surface thereof, strontium titanate particles and silica particles having predetermined physical properties.

Abstract: An image forming apparatus includes a photosensitive member, a charging roller, an image forming portion. The charging roller includes an electroconductive rubber layer and is 20 ?m or more and 35 ?m or less in ten point average roughness of a surface thereof and 130 ?m or more and 250 ?m or less in average interval of surface unevenness.

Abstract: An image forming apparatus includes a photosensitive member and a charge roller. The photosensitive member comprises a base body, and a photosensitive layer which is a monolayer formed on the base body and comprises a charge generating agent, a charge transport agent and a binder resin. The charge roller configured to contact the photosensitive member and charge the photosensitive member by application of only a DC voltage. The charge roller comprises a conductive rubber layer, and a ten-point average roughness of a surface of the charge roller is 0.9 ?m or more and 8.5 ?m or less.

Abstract: A toner includes toner particle containing at least a strontium titanate particle on the surface of the toner particle, and the toner is a water-washed toner from which strontium titanate particle desorbable by water washing are removed by water washing. The water-washed toner contains the strontium titanate particle having a number average particle diameter of primary particle (D1) of 10 nm or more and 150 nm or less, and when the distribution of an Sr element in the water-washed toner in the depth direction is determined, (i) the Sr element abundance on the outermost surface x satisfying 0.00<x?0.80, and (ii) the difference between x and xp “xp?x” satisfying 0.00<xp?x?0.95, where xp is the maximum peak value (atomic %) of the Sr element abundance in the region from the outermost surface to 50 nm.

Abstract: An image forming apparatus in which occurrence of an image failure in association with contamination caused by an external additive, such as silica, adhering to a charging unit is suppressed. The image forming apparatus is configured to charge an image bearing member through use of the charging unit, and uses toner having, on a surface thereof, strontium titanate particles and silica particles having predetermined physical properties.