Pressing roller and image heating device using the pressing roller
A pressing roller includes a metal core and an elastic layer containing a needle-like filler which has an average length of 0.05 mm or more and 1 mm or less and a thermal conductivity of 500 W/(mK) or more. In the elastic layer, pore portions are dispersed.
1. A pressing roller comprising:
a metal core; and
an elastic layer containing a filler which has an average length of 0.05 mm or more and 1 mm or less and a thermal conductivity of 500 W/(mK) or more,
wherein in said elastic layer containing the filler, pore portions are dispersed,
wherein the pore portions have an average diameter of 70 μm or less,
wherein said elastic layer contains the filler of 5% or more and 40% or less in volume ratio, and the pore portions are formed with a volume ratio of 1% or more and 10% or less,
wherein a volume ratio of the pore portions is not more than a volume ratio of the filler, and
wherein the total volume ratio of the filler and the pore portions is not less than 10% and not more than 45%.
2. A roller according to claim 1 , wherein the filler has an orientation degree of 20% or more.
3. A roller according to claim 1 , wherein the filler is a pitch based carbon fiber.
4. A roller according to claim 1 , wherein the pore portions are formed with at least one species of a resin balloon, a glass balloon, a silica balloon, a carbon balloon and Shirasu balloon.
5. An image heating device comprising:
a heating member configured to heat a recording material on which an image is carried;
a pressing roller including a metal core and an elastic layer containing a filler which has an average length of 0.05 mm or more and 1 mm or less and a thermal conductivity of 500 W/(mK) or more,
wherein said elastic layer forms, together with said heating member, a nip in which the recording material is to be nip-conveyed,
wherein in said elastic layer containing the filler, pore portions are dispersed,
wherein the pore portions have an average diameter of 70 μm or less,
wherein said elastic layer contains the filler of 5% or more and 40% or less in volume ratio, and the pore portions are formed with a volume ratio of 1% or more and 10% or less,
wherein a volume ratio of the pore portions is not more than a volume ratio of the filler, and
wherein the total volume ratio of the filler and the pore portions is not less than 10% and not more than 45%.
6. A device according to claim 5 , wherein the filler has an orientation degree of 20% or more.
7. A device according to claim 5 , wherein the filler is a pitch based carbon fiber.
8. A device according to claim 5 , wherein said heating member includes a cylindrical film and a heater.
9. A device according to claim 8 , wherein the heater is contacted to an inner surface of the film, and the nip is formed between said pressing roller and the film.
10. A device according to claim 5 , wherein the pore portions are formed with at least one species of a resin balloon, a glass balloon, a silica balloon, a carbon balloon and Shirasu balloon.