Toner for electrostatic image development, toner cartridge, process cartridge and image forming apparatus

Abstract

The invention provides a toner for electrostatic image development, containing a toner particle and external additive particles adhered to the surface of the toner particle, each of the external additive particles being constituted of plural irreversibly coalesced primary particles.

What is claimed is: 
     
       1. A toner for electrostatic image development, comprising a toner particle and external additive particles adhered to the surface of the toner particle, each of the external additive particles being constituted of a plurality of irreversibly coalesced primary particles, and the shape factor SF2 of the external additive particles, represented by the following formula (1), being in the range from 110 128 to 160:
   [(particle perimeter) 2 /(particle projected area×4×π)]×100   (1),
 
 
       
        
       
       wherein the number-average particle diameter D1 of the primary particles constituting the external additive particle and the number-average long axis diameter D2 of the external additive particle satisfies the relationship represented by the following formula (2):
   1.5≦D2/D1≦15   (2).
 
 
     
     
       2. The toner for electrostatic image development of  claim 1 , wherein the amount of the external additive particles adhered to the surface of the toner particle is from 5 to 300 in terms of number-average number of the particles adhered to one toner particle. 
     
     
       3. The toner for electrostatic image development of  claim 1 , wherein the number-average particle diameter D1 of the primary particles constituting the external additive particles and the number-average long axis diameter D2 of the external additive particles satisfy the relationship represented by the following formula (2):
   1.5≦D2/D1≦15   (2).
   
       
        
       
     
     
       4. The toner for electrostatic image development of  claim 1 , wherein the number-average long axis diameter of the external additive particles is from 0.06 μm to 1 μm. 
     
     
       5. The toner for electrostatic image development of  claim 1 , wherein the number-average long axis diameter of the primary particles is from 0.02 μm to 0.50 μm. 
     
     
       6. The toner for electrostatic image development of  claim 1 , wherein each of the external additive particle is obtained by coalescing from 2 to 300 primary particles on a projected area. 
     
     
       7. The toner for electrostatic image development of  claim 1 , wherein the glass transition temperature of the toner particle is from 35° C. to 70° C. 
     
     
       8. A toner cartridge that is attachable to and detachable from an image forming apparatus provided with a development unit, and accommodates the toner for electrostatic image development of  claim 1  to be supplied to the development unit. 
     
     
       9. The toner for electrostatic image development of  claim 1 , wherein the irreversibly coalesced primary particles are organic particles, or inorganic particles that are adhered to one another with a binder resin. 
     
     
       10. A method of forming an image, the method comprising:
 forming an electrostatic latent image on the surface of a latent image holding member; 
 developing the electrostatic latent image with a developer comprising the toner for electrostatic image development of  claim 1 , thereby forming a toner image; 
 transferring the toner image formed on the latent image holding member to the surface of a recording medium; and 
 fixing the toner image on the surface of the recording medium, wherein 
 the external additive particles included in the toner for electrostatic image development are constituted of a plurality of irreversibly coalesced organic primary particles. 
 
     
     
       11. A method of forming an image, the method comprising:
 forming an electrostatic latent image on the surface of a latent image holding member; 
 developing the electrostatic latent image with a developer comprising the toner for electrostatic image development of  claim 1 , thereby forming a toner image; 
 transferring the toner image formed on the latent image holding member to the surface of a recording medium; and 
 fixing the toner image on the surface of the recording medium, wherein 
 the external additive particles included in the toner for electrostatic image development are constituted of a plurality of irreversibly coalesced inorganic primary particles that are adhered to one another with a binder resin. 
 
     
     
       12. A method for producing the toner for electrostatic image development of  claim 1 , the method comprising:
 producing external additive particles, each of the external additive particles being produced by irreversibly coalescing a plurality of organic primary particles, and the shape factor SF2 of the external additive particles, represented by the following formula (1), being in the range from 110 128 to 160; and 
 mixing the external additive particles with toner particles so that the external additive particles adhere to the surface of each of the toner particles:
   [(particle perimeter) 2 /(particle projected area×4×π)]×100   (1).
 
 
 
     
     
       13. A method for producing the toner for electrostatic image development of  claim 1 , wherein the primary particles are inorganic primary particles, the method comprising:
 producing external additive particles, each of the external additive particles being produced by irreversibly coalescing a plurality of the inorganic primary particles by adhering the plurality of inorganic primary particles to one another with a binder resin, and the shape factor SF2 of the external additive particles, represented by the following formula (1), being in the range from 110 128 to 160; and 
 mixing the external additive particles with toner particles so that the external additive particles adhere to the surface of each of the toner particles:
   [(particle perimeter) 2 /(particle projected area×4×π)]×100   (1).
 
 
 
     
     
       14. A toner for electrostatic image development, comprising a toner particle and external additive particles adhered to the surface of the surface of the toner particle, each of the external additive particles being constituted of a plurality of irreversibly coalesced organic primary particles or a plurality of irreversibly coalesced inorganic primary particles that are adhered to one another with a binder resin. 
     
     
       15. The toner for electrostatic image development of claim 1, further comprising additional external additive particles adhered to the surface of the toner particle other than the external additive particles constituted of a plurality of irreversibly coalesced primary particles. 
     
     
       16. The toner for electrostatic image development of claim 1, further comprising re-dispersed primary particles adhered to the surface of the toner particle. 
     
     
       17. The toner for electrostatic image development of claim 1, further comprising up to 18% particles constituted of reversibly coalesced primary particles adhered to the surface of the toner particle based on a total number of particles constituted of coalesced primary particles adhered to the surface of the toner particle. 
     
     
       18. A toner for electrostatic image development, wherein the toner is formed by:
 producing external additive particles by irreversibly coalescing a plurality of primary particles, the shape factor SF2 of the external additive particles, represented by the following formula (1), being in the range of from 128 to 160; and   mixing the external additive particles with toner particles so that the external additive particles adhere to the surface of each of the toner particles:
   [(particle perimeter) 2 /(particle projected area×4×π)]×100   (1),
 
   wherein the number-average particle diameter D1 of the primary particles constituting the external additive particle and the number-average long axis diameter D2 of the external additive particle satisfies the relationship represented by the following formula (2):
   1.5≦D2/D1≦15   (2).
 
   
     
     
       19. The toner for electrostatic image development of claim 18, wherein the primary particles are inorganic primary particles and are coalesced by adhering the plurality of inorganic primary particles to one another with a binder resin. 
     
     
       20. The toner for electrostatic image development of claim 18, wherein the primary particles are organic primary particles and are coalesced by heating to melt surfaces of the primary particles. 
     
     
       21. The toner for electrostatic image development of claim 1, wherein the individual primary particles have a shape factor SF1 in a range of from 100 to 130, the shape factor SF1 being represented by the following formula (3):
   SF1=((ML 2 /A)×(π/4))×100   (3)
   where ML represents an absolute maximum length of the primary particles and A represents the projected area of the primary particles.   
     
     
       22. A toner for electrostatic image development, the toner comprising a toner particle and 5 to 300 external additive particles adhered to the surface of the toner particle that comprise a plurality of irreversibly coalesced primary particles and have a shape factor SF2 in a range of from 128 to 160, the shape factor SF2 being represented by the following formula (1):
   ((particle perimeter) 2 /(particle projected area×4×π))×100   (1),
   
       wherein the number-average particle diameter D1 of the primary particles constituting the external additive particle and the number-average long axis diameter D2 of the external additive particle satisfies the relationship represented by the following formula (2):
   1.5≦D2/D1≦15   (2).
 
 
       
        
       
     
     
       23. The toner for electrostatic image development of claim 22, wherein the number-average long axis diameter of the external additive particle is from 0.06 μm to 1 μm. 
     
     
       24. The toner for electrostatic image development of claim 22, wherein the number-average long axis diameter of the external additive particle is from 0.02 μm to 0.50 μm. 
     
     
       25. The toner for electrostatic image development of claim 22, wherein the external additive particle is obtained by coalescing from 2 to 300 primary particles on a projected area. 
     
     
       26. The toner for electrostatic image development of claim 22, wherein the glass transition temperature of the toner particle is from 35° C. to 70° C. 
     
     
       27. A toner cartridge that is attachable to and detachable from an image forming apparatus provided with a development unit, and contains the toner for electrostatic image development of claim 22. 
     
     
       28. The toner for electrostatic image development of claim 22, wherein the irreversibly coalesced primary particles are organic particles, or are inorganic particles that are adhered to one another with a binder resin. 
     
     
       29. A method of forming an image, the method comprising:
 forming an electrostatic latent image on the surface of a latent image holding member;   developing the electrostatic latent image with a developer comprising the toner for electrostatic image development of claim 22, thereby forming a toner image;   transferring the toner image formed on the latent image holding member to the surface of a recording medium, and   fixing the toner image on the surface of the recording medium.   
     
     
       30. The method of claim 29, wherein the irreversibly coalesced primary particles are organic particles, or are inorganic particles that are adhered to one another with a binder resin. 
     
     
       31. A method for producing the toner for electrostatic image development of claim 22, the method comprising:
 producing external additive particles by irreversibly coalescing a plurality of primary particles, the shape factor SF2 of the external additive particles, represented by the following formula (1), being in the range of from 128 to 160; and   mixing the external additive particles with toner particles so that the external additive particles adhere to the surface of each of the toner particles:
   [(particle perimeter) 2 /(particle projected area×4×π)]×100   (1).
 
   
       
        
       
     
     
       32. The method of claim 31, wherein the primary particles are inorganic primary particles coalesced by adhering the plurality of inorganic primary particles to one another with a binder resin. 
     
     
       33. The method of claim 31, wherein the primary particles are organic primary particles. 
     
     
       34. The toner for electrostatic image development of claim 22, further comprising additional external additive particles adhered to the surface of the toner particle other than the external additive particles that comprise a plurality of irreversibly coalesced primary particles. 
     
     
       35. The toner for electrostatic image development of claim 22, further comprising re-dispersed primary particles adhered to the surface of the toner particle. 
     
     
       36. The toner for electrostatic image development of claim 22, further comprising up to 18% particles comprised of reversibly coalesced primary particles adhered to the surface of the toner particle based on a total number of particles comprised of coalesced primary particles adhered to the surface of the toner particle. 
     
     
       37. The toner for electrostatic image development of claim 22, wherein the individual primary particles have a shape factor SF1 in a range of from 100 to 130, the shape factor SF1 being represented by the following formula (3):
   SF1=((ML 2 /A)×(π/4))×100   (3)
   where ML represents the absolute maximum length of the primary particles and A represents the projected area of the primary particles.   
     
     
       38. The toner for electrostatic image development of claim 13, wherein the inorganic primary particles are selected from the group consisting of silica, titanium oxide and cerium oxide.