Patent ID: 8649093

Claim:
A polarizing fiber having an absorption axis in a longitudinal direction thereof; wherein a cross sectional form perpendicular to the longitudinal direction has a sea-island structure, the cross sectional form being made up in the longitudinal direction; a resin that constitutes a sea region of the sea-island structure comprises a dichroic dye; a resin that constitutes island regions of the sea-island structure is a transparent resin; the number of the island regions is 2 or more; and a long diameter of each of the island regions is from 0.1 to 8.0 μm, and wherein when the refractive index of the resin that constitutes the island regions in a direction perpendicular to the longitudinal direction is represented by n i1 and the refractive index of the resin that constitutes the sea region in the direction perpendicular to the longitudinal direction is represented by n s1 , the difference between the refractive indexes, Δn 1 =|n s1 −n i1 |, is 0.02 or less; and when the refractive index of the resin that constitutes the island regions in the longitudinal direction is represented by n i2 and the refractive index of the resin that constitutes the sea region in the longitudinal direction is represented by n s2 , the difference between the refractive indexes, Δn 2 =|n s2 −n i2 |, is 0.03 or more and 0.05 or less.