Electrophotographic toner, method for producing the same, electrophotographic developer, and image forming method
View Patent ↗An electrophotographic toner having a core-shell structure including a crystalline resin in its core region or a sea-island structure including a crystalline resin in its island region, wherein the toner has 1) a resistance of 5.0×10 12 Ω·cm or higher, 2) a dynamic viscosity coefficient of 3×10 3 Pa·s or higher at a temperature which is 50° C. higher than a melting point of the crystalline resin, and 3) a dynamic viscosity coefficient of 1×10 5 Pa·s or lower at a temperature which is 10° C. higher than the melting point of the crystalline resin.
1. An electrophotographic toner having a core-shell structure including a crystalline polyester in its core region or a sea-island structure including a crystalline polyester in its island region, wherein the crystalline polyester is exposed on less than 20% of a surface area of the toner, and the toner has 1) a resistance of 5.0×10 12 Ω·cm or higher, 2) a dynamic viscosity coefficient of 3×10 3 Pa·s or higher at a temperature which is 50° C. higher than a melting point of the crystalline polyester, and 3) a dynamic viscosity coefficient of 1×10 5 Pa·s or lower at a temperature which is 10° C. higher than the melting point of the crystalline polyester.
2. The toner according to claim 1 , wherein a proportion of the crystalline polyester is 30% by mass to 90% by mass.
3. The toner according to claim 1 , wherein the melting point of the crystalline polyester is 40° C. to 100° C.
4. The toner according to claim 1 , wherein a weight-average molecular weight of the crystalline polyester is 8,000 to 100,000.
5. The toner according to claim 1 , further comprising a releasing agent in an amount of 0.1% by mass to 20% by mass.
6. The toner according to claim 5 , wherein the releasing agent has a melting point of 40 to 150° C.
7. The toner according to claim 1 , further comprising silica particles.
8. The toner according to claim 7 , wherein the silica particles were subjected to a hydrophobicity-imparting treatment.
9. The toner according to claim 7 , wherein a volume-mean particle diameter of the silica particles is 1 nm to 1,000 nm.
10. The toner according to claim 1 , wherein a volume-mean particle diameter of the toner is 3 to 20 μm.
11. The toner according to claim 1 , wherein a volume-particle-diameter distribution of the toner is 1.35 or less.
12. A developer comprising a toner and a carrier, wherein the toner has a core-shell structure including a crystalline polyester in its core region or a sea-island structure including a crystalline polyester in its island region, the crystalline polyester is exposed on less than 20% of a surface area of the toner, and the toner has 1) a resistance of 5.0×10 12 Ω·cm or higher, 2) a dynamic viscosity coefficient of 3×10 3 Pa·s or higher at a temperature which is 50° C. higher than a melting point of the crystalline polyester, and 3) a dynamic viscosity coefficient of 1×10 5 Pa·s or lower at a temperature which is 10° C. higher than the melting point of the crystalline resin.
13. The developer according to claim 12 , wherein a proportion of the crystalline polyester in the toner is 30% by mass to 90% by mass.
14. The developer according to claim 12 , wherein a weight-average molecular weight of the crystalline polyester is 8,000 to 100,000.
15. The developer according to claim 12 , wherein the carrier is coated with a resin.
16. An image forming method comprising:
forming an electrostatic latent image on a photoreceptor;
developing the electrostatic latent image by using a developer comprising a toner and a carrier to form a toner image;
transferring the toner image onto a image receiving body; and
thermally fixing the toner image on the image receiving body,
wherein the toner has a core-shell structure including a crystalline polyester in its core region or a sea-island structure including a crystalline polyester in its island region, the crystalline polyester is exposed on less than 20% of a surface area of the toner, and the toner has 1) a resistance of 5.0×10 12 Ω·cm or higher, 2) a dynamic viscosity coefficient of 3×10 3 Pa·s or higher at a temperature which is 50° C. higher than a melting point of the crystalline polyester, and 3) a dynamic viscosity coefficient of 1×10 5 Pa·s or lower at a temperature which is 10° C. higher than the melting point of the crystalline polyester.
17. The method according to claim 16 , wherein the thermal fixing of the toner is conducted by an electrophotographic fixing device comprising a fixing member and the fixing member has a surface with a thermal conductivity of 1 W/mK or higher.
18. The method according to claim 16 , wherein a proportion of the crystalline polyester in the toner is 30% by mass to 90% by mass.
19. The method according to claim 16 , wherein a weight-average molecular weight of the crystalline polyester is 8,000 to 100,000.