Yellow electrostatic developing toner, developer for electrostatic development, production method of electrostatic developing toner, image forming method and image forming apparatus

1. A yellow toner comprising:

binder resin particles that do not contain a coloring agent or a release agent and have a shape factor SF1 of about 110 or less, the number of the binder resin particles being about 50 or less per 5,000 electrostatic developing toner particles;

inorganic particles that are silicon oxide particles that have a median diameter of 5 nm to 55 nm and are present in an amount of 0.01 mass % to 0.4 mass % based on the mass of the yellow toner; and

a yellow coloring agent that has an azo group.

2. The yellow toner as claimed in claim 1 , wherein

the yellow coloring agent is a monoazo-based yellow pigment.

3. The yellow toner as claimed in claim 2 , wherein

the monoazo-based yellow pigment is C.I. Pigment Yellow 74.

4. The yellow toner as claimed in claim 1 , wherein

the inorganic particles are silica.

5. The yellow toner as claimed in claim 1 , further comprising:

a release agent.

6. The yellow toner as claimed in claim 5 , wherein

the release agent has a weight average molecular weight of about 500 to about 5,000.

7. The yellow toner as claimed in claim 5 , wherein

the release agent has a melting temperature of about 60° C. to about 100° C.

8. The yellow toner as claimed in claim 1 , wherein

the binder resin particles are a styrene-acrylic resin.

9. The yellow toner as claimed in claim 1 , which has a volume average particle diameter of about 3 μm to about 10 μm.

10. A developer for electrostatic development, comprising:

the yellow toner claimed in claim 1 ; and

a carrier.

11. The developer for electrostatic development as claimed in claim 10 , wherein

the carrier is resin-coated.

12. The developer for electrostatic development as claimed in claim 10 , wherein

the carrier is coated with a resin obtained by polymerizing a monomer containing methyl methacrylate as a constituent component.

13. A production method of the yellow toner of claim 1 , comprising:

adding an aggregating agent to a coloring agent, which contains a monoazo-based pigment, and an inorganic particle to prepare a liquid dispersion having aggregated and dispersed therein the coloring agent and the inorganic particle;

mixing the liquid dispersion having aggregated and dispersed therein the coloring agent and the inorganic particle, a binder resin particle liquid dispersion having dispersed therein a binder resin particle, and a release agent liquid dispersion having dispersed therein a release agent, thereby causing aggregation into a particle that contains the release agent, the binder resin particle, the coloring agent and the inorganic particle and has a toner particle diameter; and

fusing the obtained particle by heating at a temperature not lower than a glass transition temperature of the binder resin particle, thereby forming a toner particle.

14. An image forming method comprising:

electrostatically charging a photoreceptor;

exposing the electrostatically charged photoreceptor to form a latent image on the photoreceptor;

developing the latent image to form a developed image;

transferring the developed image onto a transfer-receiving material; and

fixing a toner on a fixing substrate by heating,

wherein

the toner is the yellow toner claimed in claim 1 .

15. An image forming apparatus comprising:

a latent image forming unit that forms a latent image on a latent image holding member;

a developing unit that develops the latent image by using a developer for electrostatic development;

a transfer unit that transfers the developed toner image onto a transfer-receiving material; and

a fixing unit that fixes the toner image on the transfer-receiving material by heating,

wherein

the developer for electrostatic development is the developer for electrostatic development claimed in claim 10 .