Developer material, developer material cartridge, image forming device, and image forming apparatus

An image forming device, comprising:

• a developer material including
• pulverized base particles containing at least a binder resin and a colorant therein and having a mean volume particle diameter in the range of 3.9-6.1 μm, and
• an external additive including particles having a mean particle diameter in the range of 30-110 nm, said external additive being present in an amount in the range of 1.0-3.0 weight parts based on 100 weight parts of the base particles, the external additive covering a surface of the base particles;
• a latent image bearing body;
• a charging member that charges a surface of said latent image bearing body;
• a developer material bearing body that supplies the developer material to a latent image formed on said the latent image bearing body to form a visible image;
• a resilient member in contact with said latent image bearing body, said resilient member being disposed upstream of said charging member and downstream of said developer material bearing body, the resilient member applying a line pressure in the range of 0.8-2.4 gf/mm on said latent image bearing body.

An image forming apparatus, comprising:

• a developer material including
• pulverized base particles containing at least a binder resin and a colorant therein and having a mean volume particle diameter in the range of 3.9-6.1 μm, and
• an external additive including particles having a mean particle diameter in the range of 30-110 nm, said external additive being present in an amount in the range of 1.0-3.0 weight parts based on 100 weight parts of the base particles, the external additive covering a surface of the base particles;
• a latent image bearing body;
• a charging member that charges a surface of said latent image bearing body;
• a developer material bearing body that supplies the developer material to a latent image formed on said the latent image bearing body to develop the latent image into a visible image;
• and
• a resilient member in contact with said latent image bearing body, said resilient member being disposed upstream of said charging member and downstream of said developer material bearing body and transferring the visible image on a print medium, the resilient member applying a line pressure in the range of 0.8-2.4 gf/mm on said latent image bearing body.