Transfer belt and image forming device

A transfer belt comprising:

• at least an elastic layer,
• wherein the transfer belt is used to transfer a toner image onto a recording medium, the toner image being carried on a first main surface which is one of a pair of main exposed surfaces including the first main surface and a second main surface being positioned to face each other,
• when, using a lower block including a curved convex surface having a width of 20 [mm] and a curvature radius of 20 [mm] as an upper surface and a hole section having a diameter of 1.25 [mm] formed at an apex of the curved convex surface and an upper block including a curved concave surface having a width of 20 [mm] and a curvature radius of 20.3 [mm] as a lower surface, the transfer belt is placed on the upper surface of the lower block so that the first main surface faces the upper surface of the lower block, a part of the transfer belt is interposed between the curved convex surface and the curved concave surface by moving down the upper block toward the lower block, and a pressed region which is the part of the transfer belt reaches a pressing force of 200 [kPa] at a pressing speed of 4 [kPa/ms] and then is constantly pressed by a pressing force of 200 [kPa],
• if a maximum value of displacement of a measurement region which is a portion of the first main surface corresponding to the hole section is indicated by “a” [μm], and a period of time from a point in time at which pressing against the pressed region starts to a point in time at which the maximum value of the displacement of the measurement region is observed is indicated by t1 [s],
• k1 [μm/s] calculated by a/t1 using “a” and “k1” satisfies a condition of 60≦k1≦320.