Patent ID: 7000375

Claim:
A polyester false-twist textured yarn comprising a false-twist textured yarn, of a multifilament yarn, comprising a polyester resin, wherein cross-sectional profiles of a plurality of individual filaments, from which the false-twist textured multifilament yarn is constituted, satisfy all of the requirements (1) to (3) shown below: (1) the cross-sectional profiles of the plurality of individual filaments each have 3 to 6 convexities and 3 to 6 concavities formed between the convexities, and the average number of the concavities having a ratio (H/W) of a largest depth (H) of the individual concavities to a largest opening width of the individual concavities of 0.3 or more is in the range of from 50 to 80% of the total number of the concavities; (2) an average flatness factor of the cross-sectional profiles of the plurality of individual filaments represented by ratios (L 1 /L 2 ) of largest lengths (L 1 ) of the cross-sectional profiles of the plurality of individual filaments to largest widths (L 2 ) at right angles to the direction of the largest lengths (L 1 ) is in the range from 1.5 to 3.5; and (3) a standard deviation of the flatness factors of the plurality of individual filaments is in the range of from 0.3 to 1.0.