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Abstract

The present invention aims to provide printability improving agents and surface-treating agents capable of improving offset printability of papers, especially newsprint papers to be printed with offset inks as well as papers, especially newsprint papers that can be successfully printed with offset inks. According to a first aspect of the present invention, a printability improving agent comprising a cationic copolymer consisting of one or more hydrophobic monomer unit(s) selected from a specific group and a quaternary ammonium salt-containing monomer unit or a surface-treating agent comprising the printability improving agent and a water-soluble polymer material selected from a specific group is applied on the surface of a base paper, especially a newsprint base paper. According to a second aspect of the present invention, a hydrophobic monomer unit selected from a specific group and a quaternary ammonium salt-containing monomer unit is polymerized to give a cationic copolymer, which is then further polymerized with a hydrophobic monomer to give a copolymer. Alternatively, a hydrophobic monomer unit selected from a specific group and a quaternary ammonium salt-containing monomer unit is polymerized to give a cationic copolymer, which is further polymerized with a hydrophobic monomer in the presence of a surfactant to give a copolymer. A printability improving agent comprising the copolymer or a surface-treating agent comprising the printability improving agent and a water-soluble polymer material selected from a specific group is applied on the surface of a base paper, especially a newsprint base paper.

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First Claim