Polyacrylonitrile-based artificial hair, head ornament product including the same, and method for producing same

A polyacrylonitrile-based artificial hair comprising:

• a broad bean-shaped transverse cross section having an outer peripheral shape that includes:
• an upper peripheral portion with a recessed portion having a curved shape at a center of the upper peripheral portion, and
• a lower peripheral portion curved in an arc,
• wherein in the broad bean-shaped transverse cross section, a ratio Lf/Sf of a longest diameter Lf to a shortest diameter Sf is 1.20 or more,
• in the broad bean-shaped transverse cross section, a ratio a/b of a smallest cross-sectional thickness a of the recessed portion to a largest cross-sectional thickness b of protrusions on both sides of the recessed portion is 0.51 to 0.91, a major axis of the broad bean-shaped transverse cross section is located above a bottom of the recessed portion,
• the major axis is a longest line segment among line segments connecting any two points on an outer periphery of the transverse cross section,
• the longest diameter Lf indicates a length of the major axis,
• the shortest diameter Sf indicates a direct distance between two parallel lines that are parallel to the major axis, wherein the two parallel lines sandwich the broad bean-shaped transverse cross section,
• the smallest cross-sectional thickness a of the recessed portion indicates a smallest thickness of a portion directly below the bottom of the recessed portion in the broad bean-shaped transverse cross section, and
• the largest cross-sectional thickness b of the protrusions indicates a largest thickness of portions above the bottom of the recessed portion and in the protrusions of the broad bean-shaped transverse cross section.