US 11,746,445 B2
Carbon fiber bundle, prepreg, and fiber-reinforced composite material
Shuhei Yoshida, Osaka (JP); Hidekazu Yoshikawa, Osaka (JP); Yosuke Nakamura, Osaka (JP); Hironori Kawamoto, Osaka (JP); Takaya Suzuki, Osaka (JP); and Toru Kaneko, Osaka (JP)
Assigned to TEIJIN LIMITED, Osaka (JP); and Teijin Carbon Europe GmbH, Wuppertal (DE)
Filed by Teijin Limited, Osaka (JP); and Teijin Carbon Europe GmbH, Wuppertal (DE)
Filed on Sep. 13, 2022, as Appl. No. 17/943,658.
Application 17/943,658 is a division of application No. 16/768,370, previously published as PCT/JP2018/043220, filed on Nov. 22, 2018.
Claims priority of application No. 2017-231749 (JP), filed on Dec. 1, 2017; and application No. 2018-207301 (JP), filed on Nov. 2, 2018.
Prior Publication US 2023/0017814 A1, Jan. 19, 2023
Int. Cl. D01F 9/22 (2006.01); C08J 5/24 (2006.01)
CPC D01F 9/22 (2013.01) [C08J 5/248 (2021.05); C08J 2300/22 (2013.01); C08J 2300/24 (2013.01)] 7 Claims
 
1. A carbon fiber which simultaneously satisfies the following formulae (1), (2), (A), and (B):
Lc/d≤2.9  (1)
TS×d×Lc>6.0×105  (2)
75≤X-ray crystal orientation degree (%)≤81.9  (A)
1.72≤specific gravity (g/cm3)≤1.76  (B)
wherein:
Lc is an X-ray crystallite size (Å),
d is a filament diameter (μm), and
TS is a strand tensile strength (MPa),
and which satisfies:
the strand tensile strength of the carbon fiber is 4,700 MPa or more, and
the X-ray crystallite size of the carbon fiber is 19 to 21 Å.