Toner for developing electrostatic image, process for producing the same, developer for developing electrostatic image and process for forming image

1. A toner for developing an electrostatic image, comprising a colorant, a binder resin and a polyolefin resin, the polyolefin resin having a polar group and having a glass transition point of 20° C. or less and a weight average molecular weight of 10,000 or more.

2. The toner for developing an electrostatic image as claimed in claim 1 , wherein the polyolefin resin is a copolymer.

3. The toner for developing an electrostatic image as claimed in claim 2 , wherein the polyolefin resin has a copolymenzation ratio of a monomer having a polar group to a polyolefin monomer of from 5/95 to 50/50.

4. The toner for developing an electrostatic image as claimed in claim 1 , wherein toner particles of the toner have a shape factor (SF1) of from 100 to 140.

5. The toner for developing an electrostatic image as claimed in claim 1 , wherein the toner has a volume particle size distribution index GSDv of 1.30 or less.

6. The toner for developing an electrostatic image as claimed in claim 1 , wherein the toner has a surface property index, which is defined by the following equation, of 2.0 or less in a state where no external additive is added:

(surface property index)=(measured value of specific surface area)/(calculated value of specific surface area) (calculated value of specific surface area)=6Σ( n×R 2 )/(ρ×Σ( n×R 3 ))

wherein n represents the number of particles in a channel of a Coulter counter, R represents the channel particle diameter of the Coulter counter, and ρ represents the density of the toner, with a number of channels of 16 and a size of division of 0.1 interval in log scale.

7. The toner for developing an electrostatic image as claimed in claim 1 , wherein a content of the polyolefin resin is in a range of from 0.5 to 30%.

8. The toner for developing an electrostatic image as claimed in claim 1 , wherein the polyolefin resin is an ethylene-vinyl acetate copolymer or an ethylene-acrylic acid copolymer.

9. The toner for developing an electrostatic image as claimed in claim 1 , wherein toner particles of the toner are produced by a process comprising the steps of:

aggregating particles in a dispersion containing the particles dispersed therein, the particles containing resin particles containing the polyolefin resin; and coalescing the aggregated particles by heating.

10. The toner for developing an electrostatic image as claimed in claim 1 , wherein toner particles of the toner is produced by a process comprising the steps of:

aggregating resin particles and releasing agent particles to generate aggregated particles, the resin particles containing fine particles having a median particle diameter of 1 μm or less comprising a polyolefin resin having a polar group, a glass transition point of 20° C. or less and a weight average molecular weight of 10,000 or more; covering the aggregated particles with a resin to form capsulated aggregated particles, the resin being different from the polyolefin resin and the releasing agent; and coalescing the capsulated aggregated particles by heating.

11. A developer for developing an electrostatic image, comprising a toner and a carrier, wherein the toner is the toner for deycloping an electrostatic image as claimed in claim 1 .

12. The developer for developing an electrostatic image as claimed in claim 11 , wherein, the carrier has a resin coating layer.

13. A process for producing an image comprising the steps of: forming an electrostatic latent image on an electrostatic latent image holding member; developing the electrostatic latent image with a developer; transferring a toner image thus formed to a transfer body; and fixing the toner image on the transfer body, the toner for forming the toner image comprising a polyolefin resin, a colorant, and a binder resin, the polyolefin resin having a polar group, a glass transition point of 20° C. or less and a weight average molecular weight of 10,000 or more.

14. The process for producing an image as claimed in claim 13 , further comprising: recovering the toner left untransferred from the electrostatic latent image holding member and putting the recovered toner in a developing device after the transferring step.

15. The process for producing an image as claimed in claim 13 , wherein the transferring step uses an intermediate transfer material.

16. The toner for developing an electrostatic image as claimed in claim 1 , wherein the polyolefm resin is different from the binder resin.