Dyed filament yarn having clear hue

An aromatic polyester filament yarn dyed in a chromatic color and exhibiting a bright and clear shade, wherein

• (a) the filaments of the yarn are composed of an aromatic polyester polymer copolymerized with an aliphatic dicarboxylic acid component and/or an aliphatic diol component copolymerized in an initial or later polymerization of polyester components and have a glass transition temperature (Tg) of not higher than 65° C.,
• (b) uneven build-up of dye exists in the individual filaments in the longitudinal direction, whereby the difference in the brightness L* between deeply dyed portions and lightly dyed portions is at least 10 and the yarn includes at least 3 levels of uneven build-up of dye among the filaments,
• (c) the difference in the brightness L* of the yarn is up to 1 despite the presence of the uneven build-up of dye as set forth in (b),
• (d) the yarn has a chromaticity C* of at least 36 expressed in the L*a*b* color specification system when dyed with an aqueous dispersion of 1% of o.w.f. of a disperse dye based on C.I. Disperse Blue 56,
• (e) the yarn is flat,
• (f) very fine unevenness of the dye build-up comprising deeply dyed portions of a length of about 45 to 300 μm and lightly dyed portions of a length of 15 to 150 μm exist in the individual filaments in the longitudinal direction, and
• (g) the aromatic polyester filament yarn has been dyed at a temperature from 90° C. to 105° C. and, thereafter reduction cleaned in an alkaline bath having a pH from 9.0 to 13.5 at a temperature from 40 to 65° C.