Electrostatic image developer, process cartridge, image forming apparatus, and image forming method

1. An electrostatic image developer comprising:

a toner containing toner particles;

a carrier; and

an external additive containing titanium dioxide particles of two types having different refractive indexes, fatty acid metal salt particles, and an abrasive,

wherein the titanium dioxide particles of two types having different refractive indexes include titanium dioxide particles (A) adhered to the toner particles and titanium dioxide particles (B) adhered to the carrier;

a content of the titanium dioxide particles (A) is 0.1% by mass or more and 50% by mass or less relative to a content of the titanium dioxide particles (B),

a refractive index of the titanium dioxide particles (A) is 2.0 or more and less than 2.4;

a refractive index of the titanium dioxide particles (B) is 2.4 or more and 2.8 or less; and

the titanium dioxide particles (A) are obtained by treating titanium dioxide particles with one or more hydrophobilization treatment agents selected from the group consisting of a silane coupling agent, silicone oil, a titanate-based coupling agent, and an aluminum-based coupling agent.

2. The electrostatic image developer according to claim 1 ,

wherein the fatty acid metal salt particles are fatty acid zinc particles; and

the abrasive is composed of titanic acid metal salt particles.

3. The electrostatic image developer according to claim 2 ,

wherein the fatty acid metal salt particles are zinc stearate particles; and

the abrasive is composed of strontium titanate particles.

4. The electrostatic image developer according to claim 1 ,

wherein a content of the fatty acid metal salt particles is 1% by mass or more and 10% by mass or less relative to a content of the titanium dioxide particles (A).

5. The electrostatic image developer according to claim 1 ,

wherein a content of the fatty acid metal salt particles is 2% by mass or more and 9% by mass or less relative to a content of the titanium dioxide particles (A).

6. The electrostatic image developer according to claim 1 ,

wherein a content of the fatty acid metal salt particles is 3% by mass or more and 8% by mass or less relative to a content of the titanium dioxide particles (A).

7. The electrostatic image developer according to claim 2 ,

wherein a content of the fatty acid metal salt particles is 1% by mass or more and 10% by mass or less relative to a content of the titanium dioxide particles (A).

8. The electrostatic image developer according to claim 3 ,

wherein a content of the fatty acid metal salt particles is 1% by mass or more and 10% by mass or less relative to a content of the titanium dioxide particles (A).

9. The electrostatic image developer according to claim 1 ,

wherein a content of the abrasive is 1% by mass or more and 10% by mass or less relative to a content of the titanium dioxide particles (A).

10. An electrostatic image developer comprising:

a toner containing toner particles;

a carrier; and

an external additive containing titanium dioxide particles of two types having different crystallite diameters, fatty acid metal salt particles, and an abrasive,

wherein the titanium dioxide particles of two types having different crystallite diameters include titanium dioxide particles (A) adhered to the toner particles and titanium dioxide particles (B) adhered to the carrier;

wherein the titanium dioxide particles of two types having different refractive indexes include titanium dioxide particles (A) adhered to the toner particles and titanium dioxide particles (B) adhered to the carrier;

a refractive index of the titanium dioxide particles (A) is lower than a refractive index of the titanium dioxide particles (B);

a content of the titanium dioxide particles (A) is 0.1% by mass or more and 50% by mass or less relative to a content of the titanium dioxide particles (B);

a crystallite diameter of the titanium dioxide particles (A) is 12 nm to 16 nm;

a crystallite diameter of the titanium dioxide particles (B) is 40 to 44 nm; and

the titanium dioxide particles (A) are obtained by treating titanium dioxide particles with one or more hydrophobilization treatment agents selected from the group consisting of a silane coupling agent, silicone oil, a titanate-based coupling agent, and an aluminum-based coupling agent.

11. A process cartridge detachable from an image forming apparatus, comprising:

a developing unit that contains the electrostatic image developer according to claim 1 and that develops, as a toner image with the electrostatic image developer, an electrostatic image formed on a surface of an image holding member.

12. An image forming apparatus comprising:

an image holding member;

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

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

a developing unit that contains the electrostatic image developer according to claim 1 and that develops, as a toner image with the electrostatic image developer, the electrostatic image formed on the surface of an image holding member;

a transfer unit that transfers the toner image formed on the surface of the image holding member to a surface of a recording medium; and

a fixing unit that fixes the toner image transferred to the surface of the recording medium.

13. An image forming method comprising:

charging a surface of an image holding member;

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

developing, as a toner image with the electrostatic image developer according to claim 1 , the electrostatic image formed on the surface of an image holding member;

transferring the toner image formed on the surface of the image holding member to a surface of a recording medium; and

fixing the toner image transferred to the surface of the recording medium.