| 摘要 |
PROBLEM TO BE SOLVED: To provide excellent heat resistance without staining a thermal head without stick even at the time of printing by the head of a high temperature, by manufacturing it out of a polypropylene having a specific value or more of isotactic degree as a raw material. SOLUTION: A biaxially oriented polypropylene film for a thermal transfer ribbon is obtained by extruding polypropylene resin melted at its melting point or higher and having isotactic degree of 97% or more from a T-die having a slit executed, cooling to solidify it by a cooling roll, then orienting a sheet four to six times in a lengthwise direction at predetermined temperature, then orienting it eight to twelve times in a width direction at predetermined temperature, and further heat treating it at specific temperature. Both the surfaces of the obtained film are corona discharged to improve adhesive properties of both an ink layer and a heat resist layer of its opposite surface at the time of becoming an ink ribbon. At this time, surface tensions of both the surfaces are made to become 32 dyn/cm or more. |
