Charging roller, process cartridge, image forming apparatus, and image forming method

A charging roller comprising:

• a conductive shaft;
• an elastic body layer formed on an outer periphery of the conductive shaft;
• and
• a surface layer formed on an outer periphery of the elastic body layer, wherein
• the surface layer contains a binder resin and conductive particles,
• the binder resin contains only a thermoplastic resin,
• the conductive particles contain first conductive particles and second conductive particles,
• the first conductive particles are carbon black particles,
• a particle size distribution of the conductive particles has at least one peak within a range of not less than 0.01 μm but not more than 1 μm, and
• a water contact angle of the thermoplastic resin and a ratio of a surface area of the first conductive particles with respect to a surface area of the entire conductive particles satisfy expressions (1) to (3):
• 4
• ⁢
• 0
• ≤
• y
• <
• 180
• (
• 1
• )
• y
• ≤
• (
• 800
• /
• 13
• )
• ⁢
• x
• +
• (
• 408
• /
• 13
• )
• (
• 2
• )
• y
• ≤
• -
• 4
• ⁢
• 0
• ⁢
• 0
• ⁢
• x
• +
• 3
• ⁢
• 440
• (
• 3
• )
• (where, y denotes the water contact angle of the thermoplastic resin, and x denotes the ratio of the surface area of the first conductive particles to the surface area of the entire conductive particles, in the expressions (1) to (3)).