| 摘要 |
Provided are a developing unit alleviating fogging occurrence and an electrophotographic image forming apparatus providing images over long periods. The developing unit comprises at least toner (1), developing roller (2). (1) when a displacement amount when a load is applied at Y° C. and 9.8×10-5 N/sec to 2.94×10-4 N is X2(Y), a displacement amount when the toner is left to stand for 0.1 second is X3(Y), a displacement amount when the load is reduced at 9.8×10-5 N/sec to ON is X4(Y), and percentage of (X3(Y)-X4(Y)) to X3(Y) is Z(Y), 40@Z(25)@80 and 10@Z(50)@55 are satisfied; when a gradient from the origin to the maximum load in the load-displacement curve at 25° C. is R(25), 0.49×10-3@R(25)@1.70×10-3 is satisfied; the toner has glass transition temperature TgA (40° C.-60° C.) and maximum endothermic peak temperature P1 (70° C.-110° C.), 15° C.@(P1-TgA)@70° C. is satisfied. (2) developing roller comprises a surface layer containing a urethane resin having structure (a), and one or both structures (b)-(c). |
