To provide a friction member of a lock-up clutch used in a torque converter, divided into an outside diameter side friction member for performing slip control for making μ-ν characteristic a positive gradient to suppress occurrence of judder and an inside diameter side friction member having large coefficient of static friction and large torque capacity when engaging the clutch, and sticking them to a front cover side or a clutch piston side to improve performance of these friction members.

The drawing is a front view formed by viewing the outside diameter side friction member 71 and the inside diameter side friction member 72 from a friction face side. The outside diameter side friction member 71 is provided with a groove 74 in the circumferential direction to make oil pressure in the circumferential direction on a contact face equal, thereby improving the effect for suppressing occurrence of judder. The inside diameter side friction member 72 is provided with a groove 75 communicating with a lock-up release chamber at the radius to prevent formation of an oil film on a friction face when engaging the clutch, thereby increasing transmission torque.