Toothbrush

1. A toothbrush comprising:

a head portion provided on a tip end side in a long axis direction and having a bristle tufting surface;

a grip portion disposed on a rear end side from the head portion;

a neck portion disposed between the bristle tufting surface and the grip portion; and

an anisotropic deformation portion provided on a rear end side from the bristle tufting surface, in which a bending strength in a first direction orthogonal to the bristle tufting surface is smaller than a bending strength in a second direction orthogonal to the long axis direction and the first direction,

wherein the anisotropic deformation portion includes an elastic deformation portion that connects a first region on the tip end side of the anisotropic deformation portion and a second region on the rear end side of the anisotropic deformation portion and is elastically deformable in the first direction and the second direction,

any bending load when the head portion is displaced in the first direction with a reference displacement amount of 10 mm, 20 mm, or 30 mm in a state where the grip portion is supported is lower than a bending load when the head portion is displaced in the second direction with a reference displacement amount of 10 mm in a state where the grip portion is supported,

wherein the elastic deformation portion includes a first hard portion made of a hard resin and connecting the first region and the second region, and a soft portion made of a soft resin and covering a periphery of the hard portion,

wherein the anisotropic deformation portion includes a recessed portion that is open on at least one of a surface on one side and a surface on the other side in the first direction, and provided side by side with the elastic deformation portion in the second direction,

two of the elastic deformation portions are provided,

wherein the elastic deformation portions are provided on both sides in the second direction with the recessed portion interposed therebetween, and

wherein the first hard portion includes a first portion whose thickness in the first direction is thinner at the center side than at both ends in the long axis direction on one side and the other side of the first direction, respectively, and a second portion connecting the center sides of the first portion.

2. The toothbrush according to claim 1 , wherein a difference between the bending load when the head portion is displaced in the first direction with the reference displacement amount in a state where the grip portion is supported, and the bending load when the head portion is displaced in the second direction with the reference displacement amount is 5.0 N or more in all of the reference displacement amounts of 10 mm, 20 mm, and 30 mm in a state where the grip portion is supported.

3. The toothbrush according to claim 1 ,

wherein a ratio of the bending load when the head portion is displaced in the second direction with the reference displacement amount in a state where the grip portion is supported to the bending load when the head portion is displaced in the first direction with the reference displacement amount in a state where the grip portion is supported is 5.0 or more in all of the reference displacement amounts of 10 mm, 20 mm, and 30 mm.

4. The toothbrush according to claim 1 ,

wherein any difference between the bending load when the head portion is displaced in the first direction with the reference displacement amount of 10 mm or 20 mm in a state where the grip portion is supported, and the bending load when the head portion is displaced in the second direction with the reference displacement amount of 10 mm is 4.0 N or more in a state where the grip portion is supported.

5. The toothbrush according to claim 1 ,

wherein any ratio of the bending load when the head portion is displaced in the second direction with the reference displacement amount of 10 mm in a state where the grip portion is supported to the bending load when the head portion is displaced in the first direction with the reference displacement amount of 10 mm or 20 mm in a state where the grip portion is supported is 2.0 or more.

6. The toothbrush according to claim 1 ,

wherein the bending load when the head portion is displaced in the second direction with the reference displacement amount is 5.0 N or more in all of the reference displacement amounts of 10 mm, 20 mm, and 30 mm, and

the bending load when the head portion is displaced in the first direction with the reference displacement amount is 3.0 N or less in all of the reference displacement amounts of 10 mm, 20 mm, and 30 mm.

7. The toothbrush according to claim 1 ,

wherein the recessed portion includes a through-hole that penetrates the anisotropic deformation portion in the first direction.

8. The toothbrush according to claim 1 ,

wherein, in a cross section orthogonal to the long axis direction of the anisotropic deformation portion, an occupancy rate of a cross-sectional area of a space of the cavity or the recessed portion to a maximum cross-sectional area of the anisotropic deformation portion is 20% or more and 60% or less.

9. The toothbrush according to claim 1 , wherein the elastic deformation portion includes

a second hard portion is provided that is disposed in the cavity or the recessed portion, connects the first region and the second region, and is made of the hard resin, and

at least a portion of the second hard portion overlaps with the first hard portion in the second direction, and a bending strength of the second hard portion in the first direction is smaller than a bending strength of the second hard portion in the second direction.

10. The toothbrush according to claim 9 ,

wherein the second hard portion is disposed with a gap from the elastic deformation portion, and snaps and buckles when an external force exceeding a threshold value is applied to the head portion toward a back side which is a side opposite to the bristle tufting surface in the first direction.

11. The toothbrush according to claim 10 ,

wherein the second hard portion has a protrusion shape toward the back side when the external force in the first direction is equal to or less than the threshold value, and is reversed in a protrusion shape toward the bristle tufting surface side when the external force in the first direction exceeds the threshold value, and

an apex of the protrusion shape is located in the recessed portion both when the external force is equal to or less than the threshold value and when the external force exceeds the threshold value.

12. The toothbrush according to claim 10 ,

wherein the second hard portion has a protrusion shape toward the back side when the external force in the first direction is equal to or less than the threshold value, and is reversed in a protrusion shape toward the bristle tufting surface side when the external force in the first direction exceeds the threshold value, and

wherein the second hard portion includes a groove portion extending in the second direction on at least one of the bristle tufting surface side and the back side in a region including an apex of the protrusion shape.

13. The toothbrush according to claim 1 ,

wherein a length of the anisotropic deformation portion in the long axis direction is 15 mm or more and 30 mm or less.