Abstract: This is an invention of a thermal development device that controls wrinkles generated due to thermal deformation of a photosensitive member while it thermally develops images. This device heats uniformly and is a thermal development device that prevents deterioration of image quality due to unevenness in concentration that is caused by wrinkles. On the surface of a thermal development device (40) heating cylinder (41, 241, 341, 441) are: periodic circular-arc-shaped peaks and valleys, projection-type peaks and valleys on both ends of the heating cylinder, a crown-shaped curvature, and a linear projection that is formed in the shape of a spiral. In addition, a nip roller (50) that engages the photosensitive member at the heating cylinder (541) in the region of an initial heating position is provided. Further, for the nip roller, the heating cylinder (541) release and engaged conditions can be selected.

Abstract: In an image formation apparatus utilizing a photosensitive heat developable member, an image formation apparatus has a specific process control characteristic extending from heat development to pressure transfer, so as to obtain stable image formation regardless of the environmental temperature or conditions of use for the device. Therefore, it is effective to detect temperature and humidity from heat development to pressure transfer, control the temperature of heat development, and heating time, or maintain a uniform temperature for the photosensitive member until pressure transfer occurs after heat development, and in particular, to cool the photosensitive member below a predetermined temperature. The method of cooling is carried out so as to 1) cool below the temperature of the pressure transfer plus 50.degree. C., and 2) start to cool within 10 seconds after the completion of heat development.