Patent ID: 7767298

Claim:
An electrically conductive composite fiber comprising an electrically conductive layer formed of a polyester-based polymer (A) having a melting point of 200° C. or higher and comprising from 23 to 33% by weight of electrically conductive carbon black, and a protective layer formed of a polyester-based polymer (B) having a melting point of 210° C. or higher, wherein the electrically conductive composite fiber satisfies the following formulas (I) to (III): 0≦|φ1−φ2|≦1.1 (I) 1.8≦DT≦4.5 (II) 50≦DE≦90 (III), wherein φ1 means an SP value [(cal/cm 3 ) 1/2 ] of the polyester-based polymer (A), φ2 means an SP value [cal/cm 3 ) 1/2 ] of the polyester-based polymer (B), DT means the fiber strength (cN/dtex), and DE means the elongation at break (%).