Liquid-crystal polyester and liquid-crystal polyester film

A liquid crystal polyester comprising a structural unit derived from 6-hydroxy-2-naphthoic acid, wherein

• in thermal extraction GC-MS analysis of the liquid crystal polyester under the following measuring conditions, the relative content of an impurity component determined from the GC peak area in the total ion chromatogram using methyl 6-hydroxy-2-naphthoate as a standard sample is 50 ppm or less based on the mass of the liquid crystal polyester, and
• the impurity component has main peaks at m/z=228, 186, 171, and 143 in the MS spectrum chart and a retention time detected in the range of 11.5 to 12.5 min in the total ion chromatogram:
• (Measuring conditions of thermal extraction GC-MS)
• Thermal extraction temperature:
• 300° C. for 15 min;
• ITF temperature:
• 320° C.;
• Column:
• 0.25 mm diameter×30 m (stationary phase:
• 5% diphenyl dimethyl polysiloxane, film thickness:
• 0.25 μm);
• Inlet temperature:
• 320° C.;
• Split ratio:
• 100:1;
• Oven temperature:
• 50° C. (1 min), 20° C./min, then 350° C. (5 min);
• Carrier gas:
• Helium at 103.3 mL/min;
• Electron ionization energy:
• 1435 eV;
• Measuring mass range:
• m/z 35 to 600;
• MS interface temperature:
• 350° C.;
• and
• Solvent waiting time:
• 4 min.