Conductive coating, method for preparing a coating, roller, and method for manufacturing a roller and using a coating
A conductive coating is described, suitable for coating a developer, charge or transfer roller in a developing apparatus to give a charge providing layer. The coating comprises a conductive polymer in a matrix. A roller is also described, suitable for a developing apparatus comprising, from the center to the periphery, a conductive mandrel, a conductive elastic base layer and a charge providing layer.
1. A conductive coating suitable for coating a developer, charge or transfer roller in a developing apparatus to form a charge providing layer, said coating comprising
a conductive polymer in a matrix, said matrix comprising a methacrylic acid-acrylic ester copolymer and a polyurethane dispersion, wherein the methacrylic acid-acrylic ester copolymer and the polyurethane dispersion:
are present in a ratio of 1:30 to 1:100 and
show micro phase separation.
2. The conductive coating according to claim 1 , wherein the methacrylic acid-acrylic ester copolymer is a thickening agent.
3. The conductive coating according to claim 1 , wherein the coating further comprises additives.
4. The conductive coating according to claim 3 , wherein the additives are selected from the group consisting of one or more of a base, a leveling agent, a wetting agent, a surfactant, an antioxidant, a viscosity reducing agent, a thickening agent and a stabilizer.
5. A method for preparing the conductive coating according to claim 1 , comprising the step of mixing an aqueous solution of a conductive polymer, an aqueous dispersion of an methacrylic acid-acrylic ester copolymer and an aqueous polyurethane dispersion.
6. A roller suitable for a developing apparatus comprising, from centre to periphery, a conductive mandrel, a conductive elastic base layer and a charge providing layer, wherein the charge providing layer is obtained by drying the conductive coating according to claim 1 .
7. The roller according to claim 6 , wherein the base layer is made of a rubber chosen from the group consisting of silicone rubber, ethylene-propylene-diene copolymer rubber (EPDM), urethane rubber, and nitrile-butadiene rubber (NBR).
8. The roller according to claim 6 , wherein the charge providing layer has a surface roughness (SRa) of 0.1 μm<Sra<3 μm, measured according to ISO 4287:1997.
9. The roller according to claim 6 , wherein the ratio between surface roughness of the charge providing layer in an axial direction (SR ax ) measured according to ISO 4287:1997 and surface roughness of the charge providing layer in a radial direction (SR rad ) measured according to ISO 4287:1997 of the roller is 0.5<SR ax /SRr rad <2.
10. The roller according to claim 9 , wherein the ratio between surface roughness of the charge providing layer in an axial direction (SR ax ) measured according to ISO 4287:1997 and surface roughness of the charge providing layer in a radial direction (SR rad ) measured according to ISO 4287:1997 of the roller is 0.75<Sra ax /SRa rad <1.25.
11. The roller according to claim 10 , wherein the ratio between surface roughness of the charge providing layer in an axial direction (SR ax ) measured according to ISO 4287:1997 and surface roughness of the charge providing layer in a radial direction (SR rad ) measured according to ISO 4287:1997 of the roller is 0.9<SRa ax /SRa rad <1.1.
12. A method for manufacturing a roller comprising, from centre to the periphery, a conductive mandrel, a conductive elastic base layer and a charge providing layer, the method comprising the steps of
applying the coating of claim 1 on the base layer and
drying the coating of claim 1 , to form the charge providing layer.
13. The method according to claim 12 , wherein the coating is applied after roughening of the outer surface of the base layer.
14. The method according to claim 13 , wherein the coating is applied by blasting.
15. The method according to claim 12 , wherein the coating is dried at a temperature below 60° C., preferably at a temperature of 40° C. or below in order to control the surface roughness of the resulting charge providing layer.
16. The method according to claim 12 , wherein the coating is applied by dipping, spraying or rolling.
17. A method of using the coating according to claim 1 , the method comprising obtaining a micro phase separated charge providing layer on a roller in a developing apparatus.
18. The method according to claim 17 wherein the roller is a charge roller, developer roller or transfer roller, preferably a developer roller.
19. A roller suitable for a developing apparatus comprising, from centre to periphery, a conductive mandrel, a conductive elastic base layer and a charge providing layer, wherein the roller has a surface roughness of at least 1.3 μm measured according to ISO 4287:1997 and a resistance of at least 3.8*10^5 ohm.
20. The conductive coating according to claim 1 , wherein the methacrylic acid-acrylic ester copolymer and the polyurethane dispersion are present in a ratio of 1:40 to 1:80.
21. The conductive coating according to claim 1 , wherein the methacrylic acid-acrylic ester copolymer and the polyurethane dispersion are present in a ratio of 1:50 to 1:60.