| 摘要 |
PROBLEM TO BE SOLVED: To improve an image reproducibility by specifying a reflectivity of an illuminated light having the same wavelength as that of a laser beam of a base of a direct lithography type lithographic printing plate master. SOLUTION: In the case of transmitting an illuminated laser beam through a thermosensitive layer, an adverse influence of a reproduction fault or the like of fine halftone dots according to removal or drop of the layer by an excess supply energy from below the layer and a halation from below is affected to the layer. Thus, a reflectivity of a base is set to less than 50%, or particularly it is best to set it to less than 10%. If the reflectivity of the base is higher than 50%, the layer is affected from below by a laser beam reflected on the base through the layer. As a method for providing a scattering means for realizing the less than 50% of the reflectivity, there is a method for roughing treating such as anodizing, alkali treating, graining treatment or the like of the base. Meanwhile, as a method for providing a means for transmitting and absorbing a laser beam, there is a method for forming the base itself as a material for transmitting or absorbing the laser beam. |
