Patent ID: 6703176
Filing Date: 2004-03-09
Classification: G03G

Abstract:
A toner comprising:at least a binding resin and a coloring agent, wherein said toner has the following characteristics (i) to (iv): (i) its weight mean particle size is 5 &mgr;m to 12 &mgr;m; (ii) not less than 90%, (in terms of cumulative value based on the number of particles of particles of not less than 3 &mgr;m has a circularity â€œaâ€  of not less than 0.900 given by the following equation (1): Circularity a=Lo/Lâ€ƒâ€ƒ(1) where, Lo denotes a periphery length of a circle having the same projected area as a particle image and L denotes a periphery length of the particle image;(iii) a relationship between a cut ratio Z and a weight mean size X of said toner fulfills the following equation (2): Cut ratio Z&lE;5.3Ã—Xâ€ƒâ€ƒ(2) where the cut ratio Z is a value calculated with the following equation (3):Z=(1âˆ’B/A)Ã—100â€ƒâ€ƒ(3) wherein A in a particle density (the number of particles/&mgr;l) is of all measured particles measured with a flow type particle image analyzer and B is a particle density (the number of particles/&mgr;l) of measured particles having a circular equivalent size of not less than 3 &mgr;m; and(iv) a relationship between a cumulative value based on the number of particles Y of particles having a circularity of not less than 0.950 and a weight mean size X fulfills the following equation (4): Y&gE;exp 5.51Ã—Xâˆ’0.645â€ƒâ€ƒ(4) where the weight mean size X is 5 to 12 &mgr;m, and the number of the particles Y is 63.01% to 80.42%;the toner has 5 to 35% by number of particles with a particle size of less than 4.00 &mgr;m and of 0 to 20% by volume of particles with particle size of not less than 10.08 &mgr;m; and the toner has been produced by (a) melt-kneading a mixture containing at least a binding resin having a glass transition temperature (Tg) of 45 to 75Â° C. and a coloring agent to obtain a kneaded product, (b) cooling the obtained kneaded product and thereafter roughly pulverizing the cooled product with grinding means to obtain a roughly pulverized product, (c) introducing a powder raw material of the resulting pulverized product into a first metering feeder and introducing a predetermined quantity of powder raw material from the first metering feeder into a mechanical mill, wherein said mechanical mill has been provided at least with a rotor mounted on a center rotary shaft, a stator disposed around the rotor with a constant distance from surfaces of said rotor being maintained, a powder introducing orifice for introducing a powder raw material and a powder discharging orifice for discharging ground powder and has been so configured than an annular space formed by maintaining the distance in an airtight state, (d) finely pulverizing the powder raw material to obtain a finely pulverized product by rotating said rotor of said mechanical mill at high speed to obtain a finely pulverized product; and (e) classifying the finely pulverized product to obtain the toner.