radial direction from the external periphery side to the internal periphery side of the friction plate 20 and in the opposite direction from the internal periphery side to the external periphery side fig2 shows a second embodiment of the present invention and is a plan view showing the mode of punching plural friction material segments from the friction material tape and adhering the segments to the core plate as the basic configuration is similar to that in the first embodiment there will be explained the different points only the friction material segments 11 are adhered and fixed for example with an adhesive material to both top and rear faces of the core plate 12 or a face thereof in the second embodiment a groove 17 in the friction material segment 11 is not provided in advance on the friction material tape 16 but is formed by plastic working such as pressing at the punching of the friction material segment 11 from the friction material tape 16 consequently after the adhesion of the friction material segments 11 on the core plate 12 the oil grooves 14 and the second oil grooves 17 are positioned radially at a substantially constant pitch the grooves 17 also communicate with the annular groove 15 thus communicating also with the oil grooves 14 in the present embodiment four.