Seat pad

1. A seat pad which includes a placement surface and side surfaces, the side surfaces extending in a direction orthogonal to a first lateral direction, the placement surface extending along the first lateral direction, and the first lateral direction being a left-right direction of an automobile;

wherein a lateral slit portion, which opens at the side surfaces and extends from the side surfaces toward a center of the seat pad in the first lateral direction, is formed;

wherein at least a portion of the lateral slit portion gradually becomes larger in a thickness direction, which is orthogonal to the placement surface, toward the center of the seat pad in the first lateral direction from the side surfaces; and

wherein a vertical slit portion, which extends from the lateral slit portion toward the placement surface side along the thickness direction, is provided on an end portion of the lateral slit portion in a second lateral direction, which is orthogonal to the first lateral direction along the placement surface.

2. The seat pad according to claim 1 ,

wherein the lateral slit portion gradually becomes larger in the thickness direction toward the center of the seat pad in the first lateral direction over the entire length of the lateral slit portion in the first lateral direction.

3. The seat pad according to claim 2 ,

wherein the lateral slit portion is curved so as to protrude in the thickness direction.

4. The seat pad according to claim 3 ,

wherein an uneven portion continuous in a regulation direction along the placement surface is formed on each of a first inner surface positioned on a placement surface side of inner surfaces defining the lateral slit portion along the thickness direction and a second inner surface positioned on a side opposite to the placement surface side of inner surfaces defining the lateral slit portion along the thickness direction, and

wherein a recessed portion and a protrusion portion in a first uneven portion, which is the uneven portion formed on the first inner surface, face a protrusion portion and a recessed portion respectively in the thickness direction in a second uneven portion, which is the uneven portion formed on the second inner surface.

5. The seat pad according to claim 3 ,

wherein the lateral slit portion is gradually lengthened in the first lateral direction toward a center of the seat pad in the second lateral direction over the entire length of the lateral slit portion in the second lateral direction.

6. The seat pad according to claim 2 ,

wherein an uneven portion continuous in a regulation direction along the placement surface is formed on each of a first inner surface positioned on a placement surface side of inner surfaces defining the lateral slit portion along the thickness direction and a second inner surface positioned on a side opposite to the placement surface side of inner surfaces defining the lateral slit portion along the thickness direction, and

wherein a recessed portion and a protrusion portion in a first uneven portion, which is the uneven portion formed on the first inner surface, face a protrusion portion and a recessed portion respectively in the thickness direction in a second uneven portion, which is the uneven portion formed on the second inner surface.

7. The seat pad according to claim 2 ,

wherein the lateral slit portion is gradually lengthened in the first lateral direction toward a center of the seat pad in the second lateral direction over the entire length of the lateral slit portion in the second lateral direction.

8. The seat pad according to claim 1 ,

wherein the lateral slit portion is curved so as to protrude in the thickness direction.

9. The seat pad according to claim 8 ,

wherein an uneven portion continuous in a regulation direction along the placement surface is formed on each of a first inner surface positioned on a placement surface side of inner surfaces defining the lateral slit portion along the thickness direction and a second inner surface positioned on a side opposite to the placement surface side of inner surfaces defining the lateral slit portion along the thickness direction, and

wherein a recessed portion and a protrusion portion in a first uneven portion, which is the uneven portion formed on the first inner surface, face a protrusion portion and a recessed portion respectively in the thickness direction in a second uneven portion, which is the uneven portion formed on the second inner surface.

10. The seat pad according to claim 8 ,

wherein the lateral slit portion is gradually lengthened in the first lateral direction toward a center of the seat pad in the second lateral direction over the entire length of the lateral slit portion in the second lateral direction.

11. The seat pad according to claim 1 ,

wherein an uneven portion continuous in a regulation direction along the placement surface is formed on each of a first inner surface positioned on a placement surface side of inner surfaces defining the lateral slit portion along the thickness direction and a second inner surface positioned on a side opposite to the placement surface side of inner surfaces defining the lateral slit portion along the thickness direction, and

wherein a recessed portion and a protrusion portion in a first uneven portion, which is the uneven portion formed on the first inner surface, face a protrusion portion and a recessed portion respectively in the thickness direction in a second uneven portion, which is the uneven portion formed on the second inner surface.

12. The seat pad according to claim 11 ,

wherein the lateral slit portion is gradually lengthened in the first lateral direction toward a center of the seat pad in the second lateral direction over the entire length of the lateral slit portion in the second lateral direction.