| 摘要 |
PURPOSE:To provide a direct drawing type planographic plate material free of possibilities of smearing, blurring, missing of printed characters, exfoliation of images at the time of printing or the like, by providing a surface layer comprising as main constituent a hydrophilic colloid comprising a silica-alumina colloidal inorganic pigment and a binder and a cross-linking agent for making the colloid water-insoluble on a base. CONSTITUTION:A surface layer comprising as main constituents a hydrophilic colloid comprising a silica-alumina inorganic pigment obtained by absorbing a basic alumina sol onto colloidal silica having a particle diameter of 7-50mum and a binder and a cross-linking agent for making the colloid water-insoluble is provided on a base. The colloidal silica must have a primary particle diameter of 7-50mum. If the particle diameter is above the range, water absorption is lowered, and smearing is liable to occur at the time of printing. If The particle diameter is below the range, water absorption is increased, and images are blurred. The produce a direct drawing type planographic plate material, a mixture of appropriate amounts of the silica-alumina colloidal inorganic pigment, inorganic pigment, the binder and the cross-linking agent is dissolved or dispersed in water, the resultant material is applied to the base, and is dried. |
