Electrostatic latent image bearer, and image forming method, image forming apparatus and process cartridge using the electrostatic latent image bearer

• US 20070015074A1
• Filed: 07/14/2006
• Published: 01/18/2007
• Est. Priority Date: 07/14/2005
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Sugino, Akihiro, Takada, Takeshi, Ikegami, Takaai
• Granted Patent: US 7,531,278 B2
• Time in Patent Office: Days
• US Class Current: 430/59.600
• CPC Class Codes: G03G 5/14704 comprising inorganic material
• CPC Class Codes: G03G 5/14708 comprising organic material
• CPC Class Codes: G03G 5/14721 Polyolefins; Polystyrenes; Waxes
• CPC Class Codes: G03G 5/14734 Polymers comprising at least one carboxyl radical, e.g. polyacrylic acid, polycrotonic acid, polymaleic acid; Derivatives thereof, e.g. their esters, salts, anhydrides, nitriles, amides
• CPC Class Codes: G03G 5/1476 Other polycondensates comprising oxygen atoms in the main chain; Phenol resins
• CPC Class Codes: G03G 5/14769 Other polycondensates comprising nitrogen atoms with or without oxygen atoms in the main chain
• CPC Class Codes: G03G 5/14773 Polycondensates comprising silicon atoms in the main chain
• CPC Class Codes: G03G 5/14791 Macromolecular compounds characterised by their structure, e.g. block polymers, reticulated polymers, or by their chemical properties, e.g. by molecular weight or acidity

Abstract

An electrostatic latent image bearer, comprising a substrate; a photosensitive layer overlying the substrate; and a protective layer overlying the photosensitive layer, wherein the protective layer includes a binder resin comprising a polyol, a polyisocyanate and an organic silicon compound having a hydroxyl or a hydrolyzable group.

Claims

1. An electrostatic latent image bearer, comprising:

a substrate;

a photosensitive layer, located overlying the substrate; and

a protective layer, located overlying the photosensitive layer,

wherein the protective layer comprises a binder resin comprising at least one polyol, at least one polyisocyanate and at least one organic silicon compound having a hydroxyl and/or a hydrolyzable group.

2. The electrostatic latent image bearer of claim 1, wherein the organic silicon compound is a hardening siloxane resin.

3. The electrostatic latent image bearer of claim 1, wherein the binder resin comprises the organic silicon compound in an amount of from 1 to 50% by weight based on total weight.

4. The electrostatic latent image bearer of claim 1, wherein the binder resin comprises plural polyols, and wherein at least one of the polyols has an OH equivalent (molecular weight/the number of hydroxyl groups) not less than 30 and less than 150.

5. The electrostatic latent image bearer of claim 4, wherein the binder resin comprises the polyol(s) having an OH equivalent (molecular weight/the number of hydroxyl groups) not less than 30 and less than 150 in an amount of from 10 to 90% by weight based on total weight of the polyols.

6. The electrostatic latent image bearer of claim 4, wherein at least one of the polyols has an OH equivalent not less than 150 and less than 1,500.

7. The electrostatic latent image bearer of claim 1, wherein the protective layer further comprises an electroconductive particulate material having the following formula:

M_xSb_yO_z

wherein M represents a metallic element; and

x, y and z represent molar ratios for respective elements.

8. The electrostatic latent image bearer of claim 7, wherein the protective layer comprises the electroconductive particulate material in an amount of from 1 to 65% by weight.

9. The electrostatic latent image bearer of claim 7, wherein the electroconductive particulate material is zinc antimonate.

10. The electrostatic latent image bearer of claim 7, wherein the electroconductive particulate material has a volume-average particle diameter of from 0.01 to 1 μ

m.

11. The electrostatic latent image bearer of claim 7, wherein the protective layer further comprises a particulate material selected from the group consisting of silica, alumina, titanium oxide and tin oxide.

12. The electrostatic latent image bearer of claim 11, wherein the protective layer comprises the electroconductive particulate material in an amount of from 10 to 100% by weight based on total weight of the electroconductive particulate material and the particulate material.

13. The electrostatic latent image bearer of claim 1, wherein the protective layer further comprises a charge transport material.

14. The electrostatic latent image bearer of claim 13, wherein the charge transport material has a functional group reactive with any one of the polyol, the polyisocyanate and the organic silicon compound.

15. The electrostatic latent image bearer of claim 14, wherein a weight ratio (D/R) of the charge transport material (D) to the binder resin (R) is from 1/10 to 15/10.

16. The electrostatic latent image bearer of claim 1, wherein the protective layer has a thickness of from 1 to 15 μ

m.

17. The electrostatic latent image bearer of claim 1, wherein the polyol, the polyisocyanate and the organic silicon compound having a hydroxyl or a hydrolyzable group are crosslinked.

18. An image forming apparatus, comprising:

the electrostatic latent image bearer according to claim 1;

a charger configured to charge the electrostatic latent image bearer;

an irradiator configured to irradiate the electrostatic latent image bearer to form an electrostatic latent image thereon;

an image developer configured to develop the electrostatic latent image with a toner to form a toner image thereon;

a transferer configured to transfer the toner image onto a recording medium; and

a fixer configured to fix the toner image thereon.

19. The image forming apparatus of claim 18, further comprising a cleaner configured to remove a toner remaining on the electrostatic latent image bearer.

20. The image forming apparatus of claim 18, wherein the charger charges the electrostatic latent image bearer with a DC voltage overlapped with an AC voltage while contacting or not contacting thereto.

21. The image forming apparatus of claim 18, wherein the charger is a charging roller charging the electrostatic latent image bearer with a gap therebetween and not contacting thereto while applied with a DC voltage overlapped with an AC voltage.

22. The image forming apparatus of claim 18, further comprising a lubricator configured to apply a lubricant on the surface of the electrostatic latent image bearer.

23. The image forming apparatus of claim 22, wherein the lubricant is a metallic soap.

24. The image forming apparatus of claim 23, wherein the metallic soap is a member selected from the group consisting of zinc stearate, aluminum stearate and calcium stearate.

25. The image forming apparatus of claim 18, wherein the toner comprises a binder resin, a colorant and a release agent.

26. The image forming apparatus of claim 18, wherein the apparatus comprises toner, and wherein the toner is prepared by a method comprising:

dissolving or dispersing toner constituents comprising a compound including a group having an active hydrogen and a polymer reactable therewith in an organic solvent to prepare a solution;

dispersing or emulsifying the solution in an aqueous medium to prepare a dispersion; and

removing the organic solvent from the dispersion.

27. The image forming apparatus of claim 18, wherein the toner has an average circularity of from 0.93 to 1.00.

28. The image forming apparatus of claim 19, wherein the toner has plural colors to form a color image when overlapped with each other.

29. The image forming apparatus of claim 18, wherein the electrostatic latent image bearer, the charger, the irradiator, the image developer, the transferer and the fixer are plural.

30. The image forming apparatus of claim 18, further comprising an intermediate transfer configured to transfer the toner image from the electrostatic latent image bearer to the transferer.

31. An image forming method, comprising:

charging the electrostatic latent image bearer according to claim 1;

irradiating the electrostatic latent image bearer to form an electrostatic latent image thereon;

developing the electrostatic latent image with a toner to form a toner image thereon;

transferring the toner image onto a recording medium; and

fixing the toner image thereon.

32. A process cartridge, comprising:

the electrostatic latent image bearer according to claim 1;

and

at least one of an irradiator, an image developer, a transferer and a cleaner.