Patent ID: 7449275

Claim:
A process for preparing a toner comprising the steps of: (I) melt-kneading a raw material mixture containing a resin binder and a colorant; (II) cooling the melt-kneaded mixture obtained in the step (I) and pulverizing the cooled mixture to give a pulverized product having a volume-median particle size (D 50 v) of from 10 to 1000 μm; (III) pulverizing the pulverized product obtained in the step (II) in the presence of from one to m external additives having an average particle size of from 8 to 50 nm; and (IV) classifying the pulverized product obtained in the step (III), wherein the resulting toner has a volume-median particle size (D 50 v) of from 3.5 to 8 μm, and the total amount of m of external additive(s) in the step (III) satisfies the formula (a): 10 ≤ P ≤ 180 ⁢ ⁢ wherein ⁢ ⁢ P = ∑ n = 1 m ⁢ ⁢ Dt · ρ ⁢ ⁢ t 4 · dn · ρ ⁢ ⁢ n × Cn × 100 × 1 2 ( a ) wherein Dt is a volume-median particle size of a desired toner (D 50 v, μm); dn is an average particle size (μm) of an external additive n; ρt is a true density of mother toner particles; ρn is a true density of an external additive n; Cn is a weight ratio of an external additive n to the pulverized product obtained in the step (II); and m is an integer of 1 or more, and wherein the resulting toner has a standard deviation of a volume base particle size distribution of ¼ of the toner D 50 v or less, and contains particles having particle sizes of (1.4× the toner D 50 v) μm or more in an amount of 5% by volume or less, and particles having particle sizes of (0.6× the toner number-median particle size (D 50 p)) μm or less in an amount of 5% by number or less.