Fixing belt, fixing device, and image forming apparatus

1. A fixing belt comprising:

an annular resin base layer having a water absorption rate of 3% or less;

a metal layer provided on an outer peripheral surface of the resin base layer; and

an elastic layer provided on an outer peripheral surface of the metal layer,

wherein the annular resin base layer is obtained by:

forming an annular resin base film, and

immersing the annular resin base film in an aqueous sodium hydroxide solution,

wherein the water absorption rate is determined by:

immersing a sample of the base layer in the boiling water for 1 hour to obtain a water-absorbed sample, and then measuring a mass W 1 the water-absorbed sample;

drying the water-absorbed sample at 120° C. for 2 hours to obtain a dried sample, and then measuring a mass W 2 of the dried sample; and

calculating the water absorption rate by the following formula:

Water absorption rate (% by mass)=( W 1− W 2)/ W 2×100.

2. The fixing belt according to claim 1 , wherein a water absorption rate of the resin base layer is 2.5% or less.

3. The fixing belt according to claim 2 , wherein the water absorption rate of the resin base layer is 0.5% or more and 2.3% or less.

4. The fixing belt according to claim 1 , wherein the resin base layer is a base layer containing an aromatic polyimide resin.

5. The fixing belt according to claim 4 , wherein the aromatic polyimide resin is a polyimide resin having a structural unit represented by general formula (PI1) below,

(in the general formula, R P1 represents a phenyl group or a biphenyl group, and R P2 represents a divalent organic group).

6. The fixing belt according to claim 1 , wherein a thickness of the resin base layer is 20 μm or more and 200 μm or less.

7. The fixing belt according to claim 6 , wherein the thickness of the resin base layer is 30 μm or more and 150 μm or less.

8. The fixing belt according to claim 7 , wherein the thickness of the resin base layer is 40 μm or more and 130 μm or less.

9. The fixing belt according to claim 1 , wherein the metal layer has an underlaying metal layer provided on the outer peripheral surface of the resin base layer, a metal heat-generating layer provided on the outer peripheral surface of the underlaying metal layer, and a metal protection layer provided on the outer peripheral surface of the metal heat-generating layer.

10. A fixing device comprising:

the fixing belt according to claim 1 ;

a pressure member that presses an outer peripheral surface of the fixing belt; and

an electromagnetic induction device that allows at least a portion of the metal layer of the fixing belt to generate heat by electromagnetic induction,

wherein a recording medium with an unfixed toner image formed on a surface thereof is held between the fixing belt and the pressure member, thereby fixing the toner image to the recording medium.

11. The fixing device according to claim 10 , wherein a heating rate of the surface of the fixing belt by the electromagnetic induction device is 40° C./sec or more from 25° C. to 120° C.

12. The fixing device according to claim 11 , wherein the heating rate is 50° C./sec or more and 60° C./sec or less.

13. An image forming apparatus comprising:

an image holding member;

a charging device that charges a surface of the image holding member;

an electrostatic latent image forming device that forms an electrostatic latent image on the charged surface of the image holding member;

a developing device that develops the electrostatic latent image formed on the surface of the image holding member with a toner to form a toner image;

a transfer device that transfers the toner image formed on the surface of the image holding member to a recording medium; and

the fixing device according to claim 10 that fixes the toner image to the recording medium.