| 摘要 |
PURPOSE:To enhance preservability and recording density by containing a carboxy modified polyvinyl acetoacetal resin and/or a carboxy modified acetoacetal/butyl acetal mixed polyvinyl acetal resin. CONSTITUTION:The content of the carboxyl group contained in a carboxy modified polyvinyl acetoacetal resin (A) and/or a carboxy modified acetoacetal/ butyl acetal mixed polyvinyl acetal resin is shown as the wt. percentage of the carboxyl group in the acetal resin or (B) and as the value of the carboxyl group in the mixture of the acetal resins (A), (B). The content of the carboxyl group in the acetal resin (A) and/or (B) is usually 0.5-9wt.%, pref., 0.57wt.%, further pref., 2-5wt.% and, when the content is below 0.5wt.%, sufficient preservability and recording density are not obtained and, even when the content exceeds 9 wt.%, preservability and recording density are not enhanced to a large extent. |
