A liquid carrying container which is removably mounted to a body of an image forming device is disclosed. Less than ninety percent of the mould cavity is filled with the molten plastics material when the packing piston starts its working stroke and the packing piston starts its working stroke while molten plastics material is still being fed from the metering cavity. Thereby, the optical image detector solves a noise and an after-image of the optical image generated owing to lack of the quantity of light of the light source, so that it is possible to accurately obtain an image of the subject and to provide a power saving effect.