Positively chargeable toner, image forming method and image forming apparatus

An image forming method, comprising the steps of:

• forming an electrostatic latent image on an image-bearing member, and
• developing the electrostatic latent image with a monocomponent developer comprising a positively chargeable toner carried on and conveyed by a developer-carrying member;
• wherein the positively chargeable toner comprises a binder resin, an imidazole compound and a colorant;
• wherein
• the binder resin comprises at least one member selected from the group consisting of (i) a mixture of vinyl resin having a carboxyl group and a vinyl resin having a glycidyl group, (ii) a vinyl resin having both a carboxyl group and a glycidyl group, and (iii) a vinyl resin having a carboxyl group and a glycidyl group in a form reacted with each other, and
• the imidazole compound is a compound having an imidazole unit represented by formula (1) below:
• wherein R1, R3 and R4 independently denote hydrogen, an alkyl. group capable of having a substituent, an aryl group capable of having a substituent, an aralkyl group capable of having a substituent, an amino group capable of having a substituent, a heterocyclic ring capable of having a substitutent, or a halogen and R2 denotes hydrogen, an alkyl group capable of having a substituent, an aryl group capable of having a substituent, an aralkyl group capable of having a substituent, or a heterocyclic group capable of having a substituent with the proviso that two or more imidazole units can be combined with each other via two of the groups R1, R2, R3 and R4 and an intervening bonding group selected from the group consisting of phenylene group, propenylene group, vinylene group, alkenylene group and alkylene group each capable of having a substituent;
• and that R3 and R4 can be bonded to each other to form a saturated aliphatic ring, an unsaturated aliphatic ring, an aromatic ring or a heterocyclic ring.

An image forming apparatus, comprising:

• an image-bearing member,
• a latent image forming means for forming an electrostatic latent image on the image-bearing member, and
• a developing means comprising a developer-carrying member for carrying and conveying thereon a mono-component developer comprising a positively chargeable toner which comprises a binder resin, an imidazole compound and a colorant;
• wherein
• the binder resin comprises at least one member selected from the group consisting of (i) a mixture of vinyl resin having a carboxyl group and a vinyl resin having a glycidyl group, (ii) a vinyl resin having both a carboxyl group and a glycidyl group, and (iii) a vinyl resin having a carboxyl group and a glycidyl group in a form reacted with each other, and
• the imidazole compound is a compound having an imidazole unit represented by formula (1) below:
• wherein R1, R3 and R4 independently denote hydrogen, an alkyl group capable of having a substituent, an aryl group capable of having a substituent, an aralkyl group capable of having a substituent, an amino group capable of having a substituent;
• a heterocyclic ring capable of having a substituent, or a halogen;
• and R2 denotes hydrogen, an alkyl group capable of having a substituent, an aryl group capable of having a substituent, an aralkyl group capable of having a substituent, or a heterocyclic group capable of having a substituent, with the proviso that two or more imidazole units can be combined with each other via two of the groups R1, R2, R3 and R4 and an intervening bonding group selected from the group consisting of phenylene group, propenylene group, vinylene group, alkenylene group and alkylene group each capable of having a substituent;
• and that R3 and R4 can be bonded to each other to form a saturated aliphatic ring, an unsaturated aliphatic ring, an aromatic ring or a heterocyclic ring.