Electrostatic charge image developing toner, electrostatic charge image developer, toner cartridge, process cartridge, image forming apparatus, and image forming method

1. An electrostatic charge image developing toner comprising:

toner particles; and

an external additive having an average particle diameter of from about 70 nm to about 420 nm, an average circularity of equal to or less than about 0.9, and a standard deviation of the circularity of greater than 0.2,

wherein the circularity of the external additive is calculated by the following expression:

circularity=[2×( A π) 1/2 ]/PM

where, in the expression, A is a projection area of an external additive particle, and PM is the perimeter of the external additive particle.

2. The electrostatic charge image developing toner according to claim 1 , wherein the average circularity of the external additive is equal to or more than about 0.5.

3. The electrostatic charge image developing toner according to claim 1 , wherein the external additive is a sol-gel silica.

4. The electrostatic charge image developing toner according to claim 1 , wherein the external additive is a sol-gel silica treated with an organic silicon compound as a hydrophobizing agent.

5. An electrostatic charge image developer comprising the electrostatic charge image developing toner according to claim 1 .

6. An electrostatic charge image developer comprising the electrostatic charge image developing toner according to claim 2 .

7. A toner cartridge containing the electrostatic charge image developing toner according to claim 1 and being detachable from an image forming apparatus.

8. A process cartridge comprising a developing unit that contains the electrostatic charge image developer according to claim 5 and that develops an electrostatic charge image formed on the surface of an image holding member with the electrostatic charge image developer to form a toner image and being detachable from an image forming apparatus.

9. An image forming apparatus comprising:

an image holding member;

a charging unit that charges the surface of the image holding member;

an electrostatic charge image forming unit that forms an electrostatic charge image on the surface of the image holding member;

a developing unit that contains the electrostatic charge image developer according to claim 5 and that develops the electrostatic charge image with the electrostatic charge image developer to form a toner image;

a transfer unit that transfers the toner image to a recording medium;

a cleaning unit that has a cleaning blade cleaning the surface of the image holding member; and

a fixing unit that fixes the toner image onto the recording medium.

10. An image forming method comprising:

charging the surface of an image holding member;

forming an electrostatic charge image on the surface of the image holding member;

developing the electrostatic charge image with the electrostatic charge image developer according to claim 5 to form a toner image;

transferring the toner image to a recording medium;

cleaning the surface of the image holding member by the use of a cleaning blade; and

fixing the toner image onto the recording medium.