Disclosed is a fixing roller which comprises a core 16 , a porous material layer 22 disposed in surrounding relation to an outer peripheral surface of the core 16 , and a thin-walled metal sleeve 26 covering an outer peripheral surface of the porous material layer 22 . The porous material layer 22 comprises a closed cell-type silicone elastomer. The present invention provides a fixing roller capable of ensuring enhanced durability and maintaining a usable state over long periods under the condition of being actually driven and rotated.
1. A fixing roller comprising:
a core;
a porous material layer with a plurality of cells comprising a closed cell-type silicone elastomer prepared using an emulsion composition, said porous material layer being disposed in surrounding relation to an outer peripheral surface of said core; and
a thin-walled metal sleeve covering an outer peripheral surface of said porous material layer,
wherein each of the cells accounting for 50% or more of the total cell number satisfies the following formula:
0≦( m−n )/ m≦ 0.5,
wherein m represents a maximum diameter of the cell, and n represents a minimum diameter of the cell.
2. The fixing roller as defined in claim 1 , wherein said silicone elastomer forming said porous material layer having a plurality of cells with a closed cell ratio of 60% or more, wherein ones of the cells accounting for 50% or more of a total cell number individually have a diameter of 50 μm or less.
3. The fixing roller as defined in claim 2 , wherein said silicone elastomer has a closed-cell ratio of 80% or more.
4. The fixing roller as defined in claim 2 , wherein each of said cells has a diameter ranging from 0.1 μm to 70 μm.
5. The fixing roller as defined in claim 1 , wherein each of the cells accounting for 50% or more of the total cell number satisfies the following formula:
0≦( m−n )/ n≦ 0.5,
wherein m represents a maximum diameter of the cell, and n represents a minimum diameter of the cell.
6. The fixing roller as defined in claim 5 , wherein said silicone elastomer has an average cell diameter of 30 μm or less.
7. The fixing roller as defined in claim 1 , wherein said porous material layer is prepared using a water-in-oil emulsion composition which contains a liquid silicone rubber material curable to form a silicone elastomer, a silicone oil material having a surface-active function, and water.
8. The fixing roller as defined in claim 1 , which includes a release layer formed around an outer peripheral surface of said thin-walled metal sleeve.
9. The fixing roller as defined in claim 8 , which includes an elastic layer interposed between said release layer and said thin-walled metal sleeve.
10. The fixing roller as defined in claim 1 , which includes an elastic layer formed on an outer peripheral surface of said thin-walled metal sleeve.
11. The fixing roller as defined in claim 10 , which includes a release layer formed on an outer peripheral surface of said elastic layer.
12. The fixing roller as defined in claim 11 , wherein said release layer is made of fluororesin.
13. The fixing roller as defined in claim 12 , wherein said fluororesin is coated on an outer peripheral surface of said elastic layer.
14. The fixing roller as defined in claim 12 , wherein said fluororesin is formed in a tube shape, and cover over an outer peripheral surface of said elastic layer.
15. The fixing roller as defined in claim 11 , wherein said release layer is made of fluororesin.
16. The fixing roller as defined in claim 15 , wherein said fluororesin is coated on an outer peripheral surface of said elastic layer.
17. The fixing roller as defined in claim 15 , wherein said fluororesin is formed in a tube shape, and cover over an outer peripheral surface of said elastic layer.