Label assembly, label printer and method for printing information on label sheet

The present invention relates to a label assembly, a label printer and a method for printing information on a label sheet. As shown in the pictures (1A) and (1B), the label assembly (1A) is provided with the following components: a release paper sheet (11) which is provided with two surfaces, and a plurality of label sheets (12A) which are respectively attached to the surface of the release paper sheet (11). Each label sheet (12A) comprises a printable area (E1). Through using a color which is different from the color of the release paper sheet (11) in the aspects of light transmission coefficient or reflectivity, from a printing starting reference position (14S) to a printing finishing reference position (14E), the other surface of the release paper sheet (11) is provided with printable area marks (13A). The printing starting reference position (14S) is corresponding with one end of the printable area (E1) of each label sheet (12A), and the printing finishing reference position (14E) is corresponding with th