Patent ID: 8874007

Claim:
A developing unit, comprising at least: a toner of ( 1 ); a developing roller of ( 2 ); and a toner regulating member for controlling a toner amount on a surface of the developing roller: ( 1 ) a toner, comprising: toner particles each containing at least a binder resin, a coloring agent, and a wax component; and an inorganic fine powder, wherein: when a displacement amount (μm) obtained when a load is applied to one particle of the toner at a temperature of Y° C. and at a loading rate of 9.8×10 −5 N/sec, and the load is reached at a maximum load of 2.94×10 −4 N, is defined as a displacement amount X 2(Y) , a displacement amount (μm) obtained when, after the load has reached the maximum load, the particle is left to stand under the maximum load for 0.1 second, is defined as a maximum displacement amount X 3(Y) , a displacement amount (μm) obtained when, after the standing for 0.1 second, the load is reduced at an unloading rate of 9.8×10 −5 N/sec, and then the load is reached at 0 N, is defined as a displacement amount X 4(Y) , a difference between the maximum displacement amount X 3(Y) and the displacement amount X 4(Y) , is defined as an elastic displacement amount (X 3(Y) −X 4(Y) ), and a percentage of the elastic displacement amount (X 3(Y) −X 4(Y) ) to the maximum displacement amount X 3(Y) , {(X 3(Y) −X 4(Y) )/X 3(Y) }×100, is defined as Z(Y) (%), Z(25), Z(Y) at the temperature Y is 25° C., satisfies a relationship of 40≦Z(25)≦80, and Z(50), Z(Y) at the temperature Y is 50° C., satisfies a relationship of 10≦Z(50)≦55; in a load-displacement curve of which a displacement amount of the toner versus the load thereon at a temperature of 25° C. is plotted, when a gradient of the load-displacement curve from an origin to a point at which the load reaches the maximum load, is defined as R(25) (N/μm), 2.94×10 −4 /displacement amount X 2(25) , R(25) satisfies a relationship of 0.49×10 −3 ≦R(25)≦1.70×10 −3 ; having a glass transition temperature (TgA) of 40° C. or more and 60° C. or less, and a peak temperature (P1) of a maximum endothermic peak of 70° C. or more and 110° C. or less; and satisfying a relationship of 15° C.≦(P1−TgA)≦70° C.; and ( 2 ) a developing roller, comprising: a mandrel; an elastic layer formed on a periphery of the mandrel; and a surface layer containing a urethane resin, the surface layer coating a peripheral surface of the elastic layer, wherein the urethane resin has, between two adjacent urethane bonds, a structure represented by the following structural formula (a), and one or both of structures selected from a structure represented by the following structural formula (b) and a structure represented by the following structural formula (c)