Abstract: A seat back for a vehicular seat has a plate member for supporting a back of a pad and an elastic support mechanism for elastically holding the plate member for moving the plate member in a forward and backward direction with respect to a seat back frame. The plate member includes a first plate portion, a second plate portion positioned on the lower side of the first plate portion, and a third plate portion positioned on the lower side of the second plate portion. The first and third plate portions are more narrow than the second plate portion. The elastic support mechanism includes a rod-shaped elastic bridge member extending horizontally over the seat back frame on the back of the second plate portion. In addition, the elastic bridge member includes a bent portion at the center position as bent along the second plate portion toward the first plate portion.

Abstract: 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.

Abstract: 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.

Abstract: A seat back for a vehicular seat has a plate member for supporting a back of a pad and an elastic support mechanism for elastically holding the plate member for moving the plate member in a forward and backward with respect to a seat back frame. The plate member includes a first plate portion, a second plate portion positioned on the lower side of the first plate portion, and a third plate portion positioned on the lower side of the second plate portion. The first and third plate portions are more narrow than the second plate portion. The elastic support mechanism includes a rod-shaped elastic bridge member extending horizontally over the seat back frame on the back of the second plate portion. In addition, the elastic bridge member includes a bent portion at the center position as bent along the second plate portion toward the first plate portion.