A phase change memory device having a multi-level and a method of driving the same are presented. The portion has a first part and a second part which is resiliently biased away from the first part. An erased cell in the present invention is a cell in the \u201coff\u201d state. The bottom plate has a surface facing the light guide plate and defining a curved surface and the curved surface comprises a curved reflection surface formed thereon. The browsing terminal includes: a receiving part for receiving contents data; a volatile memory for storing the received contents data; a display device with a memory function, which displays the contents data stored in the volatile memory; and a secondary battery for supplying power to the volatile memory and the display device. % and at least one polymer dispersant B, based on cationised dialkylaminoalkyl acrylamides with an average molecular weight of between 75,000 and 350,000 gmol.