Image formation method
A toner includes a polyol-based resin having multiple hydroxyl groups in a molecular chain thereof in which a ratio of epoxy group to hydroxyl group is from 0.990 to 1.010. A stirring and transfer device satisfies 1000000≦α×β×γ≦16000000, wherein α represents a number of rotation per minute, β (mm) represents a pitch and γ (mm) represents a transfer path length of the stirring and transfer device. A temperature Tin (° C.) in a development device during stirring and transfer of a two component developing agent satisfies 3020 C.<Tin<60° C., and the toner satisfies Y≦−0.5X+45, 5≦X<40, 5≦Y≦35, wherein X (%) represents a degree of agglomeration of a mother toner particle and Y (%) represents a degree of agglomeration of the toner which has been preserved at 55° C. for 24 hours.
1. An image formation method comprising:
charging an image bearing member;
irradiating a surface of the image bearing member to form a latent electrostatic image thereon;
developing the latent electrostatic image with a two component developing agent comprising a carrier and a toner comprising a mother toner particle and an external additive by a development device comprising a rotating stirring and transfer device configured to transfer and stir the developing agent;
transferring the developed image to a transfer medium; and
fixing the developed image on the transfer medium,
wherein the toner comprises a polyol-based resin as a binder resin, the polyol based resin having multiple hydroxyl groups in a molecular chain thereof in which a ratio (EX/OH) of epoxy group (EX) to hydroxyl group (OH) is from 0.990 to 1.010, the stirring and transfer device satisfies the following relationship (I):
1.0×10 6 ≦α×β×γ≦16.0×10 6
wherein α represents a number of rotation per minute, β (mm) represents a pitch and γ (mm) represents a transfer path length of the stirring and transfer device,
a temperature Tin (° C.) in the development device during stirring and transfer of the two component developing agent satisfies the following relationship (II):
30° C.<Tin<60° C.,
and the toner satisfies the following relationships (III):
Y ≦−0.5 X +45, 5≦ X ≦40, 5 ≦Y ≦35,
wherein X (%) represents a degree of agglomeration of the mother toner particle and Y (%) represents a degree of agglomeration of the toner which has been preserved at 55° C. for 24 hours.
2. The image formation method according to claim 1 , wherein the external additive comprises an inorganic particulate and an attachment ratio of the inorganic particulate to a surface of the mother toner particle satisfies the following relationship (IV):
65%≦( M 1 /M 0 )≦95%,
wherein M 1 represents an amount of the inorganic particulate attached to the mother toner particle after one minute ultrasonic treatment under a condition of a resonance frequency of 25 KHz for a surface active agent aqueous solution in which the toner is dissolved, and M 0 represents an amount of the inorganic particulate attached to the mother toner particle before the ultrasonic treatment.
3. The image formation method according to claim 1 , wherein the mother toner particle has an average circularity of from 0.910 to 0.970.