Seat backs for vehicular seats

摘要

A seat back for a vehicular seat has a plate member for supporting a back of a pad and an elastic support mechanism for holding the plate member for moving the plate member in a forward and backward direction. The plate member includes a thoracic vertebra avoiding portion having at least one of a hole and a recessed portion recessed in a direction away from the thoracic vertebrae of a user, so as to avoid a pushing force to the thoracic vertebrae. In addition the thoracic vertebra avoiding portion is vertically elongated at a substantially widthwise center position of the plate member and has a width of 40 to 100 mm.