Toothbrush

Abstract

The invention provides a toothbrush which is provided with a handle body formed by hard resin and a brush part formed by soft resin. The handle body has a neck portion and a fitting portion. The brush section has a brush base section and a monofilament. The brush base portion has a fitting hole. The monofilaments protrude from the brush base portion toward the front surface side. The neck part has a first neck part and a second neck part which is closer to the rear end side than the first neck part. And the length of the distance between the first neck part and the second neck part is equal to the length of the embedding part. The thickness of the neck portion is the thinnest at the first neck portion, and is constant or gradually thickened from the first neck portion toward the rear end side. If the thickness of the first neck portion is T1, the thickness of the second neck portion is T2, and the maximum thickness of the fitting portion is Tm, the relationships of 3.0 mm < = T1 < = 4.5 mm, 1.5 mm < = Tm < = 2.5 mm, and (T2-T1) / Tm < = 0.6 are satisfied.

Description

Technical Field

[0001] The present invention relates to a toothbrush. This application claims priority based on Japanese Patent Application No. 2022-205743 filed in Japan on December 22, 2022, the content of which is incorporated herein by reference. Background Art

[0002] There has been proposed an integrally molded toothbrush that is manufactured only by an injection molding machine (for example, Patent Document 1). Since the integrally molded toothbrush forms the monofilaments and the head base portion integrally, there is no need to order materials for the monofilaments and a tufting machine, and the manufacturing cost can be reduced compared to a tufted toothbrush.

[0003] There has been proposed an integrally molded toothbrush that separately forms a brush part having monofilaments and insertion holes, and a handle body having an insertion part provided at one end, and the insertion part is fitted into the insertion hole to form (for example, Patent Document 2). In the toothbrush described in Patent Document 2, since the brush part can be replaced, it is expected to save resources by, for example, only discarding the brush part and being able to reuse the handle body. Prior Art Documents Patent Documents

[0004] Patent Document 1: Japanese Utility Model Publication No. 61-207233 Patent Document 2: Chinese Patent Application Publication No. 107041792 Specification Technical Problems to be Solved by the Invention

[0005] From the viewpoint of the in-mouth operability of the toothbrush, particularly the operability for molars, it is desired to thin the head of the toothbrush. When pursuing the thinning of the head in the above-mentioned conventional toothbrushes, the insertion part of the handle body formed of a hard resin is covered by the brush part formed of a soft resin. Therefore, it is difficult to increase the thickness of the insertion part, and thus it is difficult to improve the rigidity of the head. Therefore, when using the toothbrush, the flexure of the head tends to become large, resulting in a problem of reduced operability of the toothbrush. Summary of the Invention

[0006] The present invention has been completed in consideration of the above points, and one of the purposes is to provide a toothbrush that can achieve thinning of the brush head and suppress an increase in flexure of the brush head even when using a brush part formed of a soft resin. Technical Means for Solving the Technical Problems

[0007] The present invention includes the following configurations. [1] A toothbrush comprising: a handle body formed of a hard resin and extending in the longitudinal axis direction, and The brush part, which is formed of a soft resin, is provided on one side in the major axis direction of the handle body; The handle body has: a neck portion that extends in the major axis direction, and a fitting portion that is disposed on one side in the major axis direction with respect to the neck portion and protrudes toward one side in the major axis direction; The brush part has: a brush base portion, and a plurality of monofilaments that are integrally formed with the brush base portion; The brush base portion has a fitting hole into which the fitting portion is inserted and fitted, and the plurality of monofilaments respectively protrude from the brush base portion toward the thickness direction that intersects the major axis direction; The neck portion has: a first neck portion; and a second neck portion that is located on the other side in the major axis direction with respect to the first neck portion; The length of the distance between the first neck portion and the second neck portion is equal to the dimension in the major axis direction of the fitting portion. The dimension in the thickness direction of the neck portion is the smallest at the first neck portion and is constant or gradually increases toward the other side in the major axis direction. When the dimension in the thickness direction of the first neck portion is set as T1, the dimension in the thickness direction of the second neck portion is set as T2, and the maximum dimension in the thickness direction of the fitting portion is set as Tm, the relationship 3.0 mm ≤ T1 ≤ 4.5 mm, 1.5 mm ≤ Tm ≤ 2.5 mm, and (T2 - T1) / Tm ≤ 0.6 is satisfied. [2] For the toothbrush according to [1], the neck portion has a third neck portion that is located on the other side in the major axis direction with respect to the first neck portion, in the major axis direction, the length of the distance between the first neck portion and the third neck portion is equal to twice the length of the dimension in the major axis direction of the fitting portion. When the dimension in the thickness direction of the first neck portion is set as T1, the dimension in the thickness direction of the third neck portion is set as T3, and the maximum dimension in the thickness direction of the fitting portion is set as Tm, the relationship (T3 - T1) / Tm ≤ 1.5 is satisfied. [3] For the toothbrush according to [1] or [2], when the dimension in the thickness direction of the first neck portion is set as T1 and the maximum dimension in the thickness direction of the fitting portion is set as Tm, the relationship T1 ≤ 2.5 × Tm is satisfied. [4] In the toothbrush according to any one of [1] to [3], when the dimension in the thickness direction of the first neck is set as T1 and the maximum dimension in the thickness direction of the brush base portion is set as Tb, the relationship T1 < Tb is satisfied. [5] In the toothbrush according to any one of [1] to [4], the neck has a fourth neck, which is located on the other side of the first neck in the long axis direction. The length of the dimension in the thickness direction of the fourth neck is equal to the maximum dimension in the thickness direction of the brush base portion. The distance between the end on the other side of the long axis direction of the fitting portion and the fourth neck is longer than the dimension in the long axis direction of the brush portion. [6] In the toothbrush according to any one of [1] to [5], the handle body has a connecting portion connecting the neck and the fitting portion. When the dimension in the thickness direction of the first neck is set as T1 and the maximum dimension in the thickness direction of the connecting portion is set as Tk, the relationship T1 < Tk is satisfied. [7] In the toothbrush according to [6], it includes a brush head portion composed of the connecting portion, the fitting portion, and the brush portion. The ratio of the dimension in the long axis direction of the neck to the distance between the end on one side of the long axis direction of the brush head portion and the end on the other side of the long axis direction of the neck is 60% or more, and the ratio of the dimension in the long axis direction of the fitting portion to the dimension in the long axis direction of the brush portion is 80% or more. [8] In the toothbrush according to [7], in the width direction orthogonal to both the long axis direction and the thickness direction, the dimension in the width direction of the first neck is smaller than the maximum dimension in the width direction of the fitting portion. The neck has a fifth neck, which is located on the other side of the first neck in the long axis direction. The dimension in the width direction of the fifth neck is equal to the maximum dimension in the width direction of the fitting portion. The length of the distance between the first neck and the fifth neck is equal to or greater than the dimension in the long axis direction of the brush head portion. Effects of the Invention

[0008] In the present invention, it is possible to provide a toothbrush that can achieve thinning of the head and suppress an increase in deflection of the brush head even when using a brush portion formed of a soft resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a front view showing the toothbrush of the embodiment. Figure 2 It is a side view showing the toothbrush of the embodiment. Figure 3 This is the front view of the handle body showing the embodiment. Figure 4 This is the side view of the handle body showing the embodiment. Figure 5 This is the front view of the brush part showing the embodiment. Figure 6 This is the cross-sectional view of the brush part showing the embodiment, and it is Figure 5 the cross-sectional view A-A in Figure 7 This is a view showing a part of the toothbrush of the embodiment. Detailed Embodiment

[0010] Hereinafter, an example of the toothbrush of the present invention will be shown and described based on the accompanying drawings. In addition, the dimensions of the figures illustrated in the following description are examples, and the present invention is not necessarily limited thereto, and can be implemented with appropriate changes within the scope of not changing its main idea.

[0011] In each of the accompanying drawings, an XYZ coordinate system is shown as a three-dimensional orthogonal coordinate system. In the XYZ coordinate system, the X-axis direction is the major axis direction. The major axis direction is the direction in which the toothbrush extends. The +X side is the front end side of the toothbrush, and the -X side is the rear end side of the toothbrush. In the following description, the front end side of the toothbrush will be simply referred to as the "front end side" or "one side in the major axis direction", and the rear end side of the toothbrush will be simply referred to as the "rear end side" or "the other side in the major axis direction". The Y-axis direction is the direction orthogonal to the major axis direction and is the width direction of the toothbrush. The +Y side is one side in the width direction of the toothbrush, and the -Y side is the other side in the width direction of the toothbrush. The Z-axis direction is the direction that intersects the X-axis direction and is orthogonal to the Y-axis direction, and is the thickness direction of the toothbrush. In the present embodiment, the Z-axis direction is orthogonal to both the X-axis direction and the Y-axis direction. The +Z side is the front side of the toothbrush, and the -Z side is the back side of the toothbrush. In the following description, the front side of the toothbrush will be simply referred to as the "front side", and the back side of the toothbrush will be simply referred to as the "back side".

[0012] In the following description, the dimension in the major axis direction of a component may sometimes be simply referred to as the "length". In addition, the dimension in the width direction of a component may sometimes be simply referred to as the "width", and the dimension in the thickness direction of a component may sometimes be simply referred to as the "thickness". In addition, the situation of observing an object from the front side may sometimes be referred to as the "front view", and the shape of an object observed from the front side may sometimes be referred to as the "front view shape". In addition, the situation of observing an object from the width direction may sometimes be referred to as the "side view", and the shape of an object observed from the width direction may sometimes be referred to as the "side view shape".

[0013] Figure 1 This is the front view of the toothbrush 1 of the present embodiment.Figure 2 is a side view showing the toothbrush 1 of the present embodiment. As Figure 1 shown, the toothbrush 1 includes a handle body 10 and a brush part 20. The handle body 10 and the brush part 20 are separate components. The handle body 10 and the brush part 20 are each made of resin. The handle body 10 is rod-shaped and extends in the long axis direction. The brush part 20 is provided on the front end side of the handle body 10, that is, on one side (+X side) in the long axis direction. In the present embodiment, the brush part 20 is detachably attached to the handle body 10. In addition, the brush part 20 may also be formed by insert molding with the handle body 10 as an insert part, and in this case, the brush part 20 and the handle body 10 may also be integrated.

[0014] Figure 3 is a front view showing the handle body 10 of the present embodiment. Figure 4 is a side view showing the handle body 10 of the present embodiment. The handle body 10 has: a rod-shaped handle main body part 11 extending in the long axis direction, and a fitting part 15 protruding from the front end side end of the handle main body part 11 toward the front end side, that is, one side (+X side) in the long axis direction. In the toothbrush 1 of the present embodiment, the brush part 20 is attached to the handle body 10 by fitting the fitting part 15 into a fitting hole 27 of the brush part 20 described later. In addition, the length of the handle body 10 can be, for example, 100 mm or more and 200 mm or less.

[0015] In the present embodiment, the handle body 10 is formed of a hard resin. As an example of the hard resin forming the handle body 10, resins having a flexural modulus (JIS K7171) of 1500 MPa or more and 3000 MPa or less can be exemplified. Specifically, for example, polypropylene resin (PP), polybutylene terephthalate resin (PBT), polyoxymethylene resin (POM), polyester resin (PCTA), polyethylene terephthalate copolymer (PETG), high-density polyethylene (HDPE) can be exemplified. Among them, polypropylene resin, which is a general-purpose resin, is preferred in terms of cost, and polybutylene terephthalate resin and polyoxymethylene resin are preferred in terms of strength.

[0016] As Figure 3 shown, the front view shape of the handle main body part 11 of the present embodiment is such that the width gradually narrows from the front end side toward the rear end side and reaches the first boundary part 13a, and when it reaches the first boundary part 13a, the width gradually widens. Then, it changes in such a way that the width widens after gradually narrowing, and then narrows. The front view shape of the rear end part of the handle main body part 11 is substantially semicircular. In addition, in the case where the front view shape of the handle main body part 11 gradually narrows from the front end side toward the rear end side, then extends in the long axis direction with the same width, and then the width gradually widens, the front end side end of the part extending in the long axis direction with the same width is set as the first boundary part 13a.

[0017] AsFigure 4 As shown, the side view shape of the handle main body 11 of the present embodiment changes in the following manner: from the front end side towards the rear end side, the thickness gradually thins, then has a constant thickness or the thickness gradually increases until reaching the second boundary portion 13b. When reaching the second boundary portion 13b, the thickness gradually thins, then extends with a substantially constant thickness, and then the thickness thins. The side view shape of the rear end portion of the handle main body 11 is a substantially semi-circular shape. In addition, in the case where the side view shape of the handle main body 11 from the front end side towards the rear end side, after the thickness gradually thins, it has a constant thickness or the thickness gradually increases, then extends in the long axis direction with the same thickness, then after the thickness gradually thins, it extends with a substantially constant thickness, and then the thickness thins, the end portion on the front end side of the portion extending in the long axis direction with the same thickness is set as the second boundary portion 13b.

[0018] In addition, in the present invention, the shape of the handle main body 11 is not limited to the shape of the present embodiment, and can be appropriately set in consideration of strength, operability, designability, etc. The size of the handle main body 11 is not particularly limited and can be appropriately set. The handle main body 11 has a grip portion 12, a neck portion 13, and a connecting portion 14.

[0019] The grip portion 12 is the portion of the handle main body 11 on the rear end side of the second boundary portion 13b. In the present embodiment, the length of the grip portion 12 is greater than the sum of the lengths of the neck portion 13 and the connecting portion 14. As Figure 3 shown, a finger contact portion 17 is provided on the front end side portion of the surface of the grip portion 12 facing the front side. The finger contact portion 17 is formed of a soft resin. As the soft resin forming the finger contact portion 17, various elastomers such as polyurethane-based and styrene-based can be used. When the user uses the toothbrush 1, by holding the grip portion 12 and bringing the fingers into contact with the finger contact portion 17, the gripability of the toothbrush 1 can be improved.

[0020] The neck portion 13 is the portion of the handle main body 11 between the first boundary portion 13a and the second boundary portion 13b. The neck portion 13 is a rod-shaped portion extending in the long axis direction. The shape and the like of the neck portion 13 will be described in detail below.

[0021] The connecting portion 14 is the portion of the handle main body 11 on the front end side of the first boundary portion 13a. The connecting portion 14 connects the neck portion 13 and the fitting portion 15. The width of the connecting portion 14 is the widest at the end portion on the front end side and gradually narrows towards the rear end side, and is the narrowest at the end portion on the rear end side. As Figure 4 shown, the thickness of the connecting portion 14 advances with a substantially same thickness from the front end side towards the rear end side. In the present embodiment, strictly speaking, the thickness of the connecting portion 14 is the thickest at the end portion on the front end side, gradually thins towards the rear end side, and is the thinnest at the end portion on the rear end side. As Figure 3 and Figure 4As shown, the connecting portion 14 has a first opposing surface 14a. The first opposing surface 14a is the surface facing the front end side among the outer side surfaces of the connecting portion 14.

[0022] As Figure 2 shown, in a state where the brush portion 20 is attached to the handle body 10, the fitting portion 15 is located inside the brush portion 20. As Figure 3 and Figure 4 shown, the fitting portion 15 protrudes from the first opposing surface 14a of the connecting portion 14 toward the front end side. The fitting portion 15 is arranged on the front end side, that is, on one side (+X side) in the long axis direction, compared with the neck portion 13. In addition, in the following description, the root of the fitting portion 15 refers to the end portion on the rear end side of the fitting portion 15, which is the portion connected to the connecting portion 14.

[0023] As Figure 3 shown, a pair of recessed portions 15a, 15b are provided in the fitting portion 15. One recessed portion 15a recesses from the surface of the fitting portion 15 facing one side (+Y side) in the width direction toward the other side (-Y side) in the width direction. The other recessed portion 15b recesses from the surface of the fitting portion 15 facing the other side in the width direction toward one side in the width direction. Each of the pair of recessed portions 15a, 15b is substantially semicircular in a front view.

[0024] Figure 5 is a front view showing the brush portion 20 of the present embodiment. Figure 6 is a sectional view showing the brush portion 20 of the present embodiment, and is Figure 5 the sectional view taken along line A-A in The brush portion 20 is formed of a soft resin. As Figure 5 and Figure 6 shown, the brush portion 20 has a brush base portion 21 and a plurality of filaments 28 integrally formed with the brush base portion 21.

[0025] As Figure 5 shown, the front view shape of the brush base portion 21 of the present embodiment changes curvilinearly in such a manner that the width gradually becomes wider from the front end side toward the rear end side. The front view shape of the front end portion of the brush base portion 21 is substantially semicircular. As Figure 6 shown, the side view shape of the brush base portion 21 of the present embodiment changes in such a manner that the thickness gradually becomes thicker from the front end side toward the rear end side. More specifically, the surface of the brush base portion 21 facing the back side (-Z side) is located on the back side from the front end side toward the rear end side. The surface of the brush base portion 21 facing the front side, that is, the upper surface 21a, is a plane extending in a direction orthogonal to the thickness direction.

[0026] The surface of the outer side of the brush base portion 21 facing the rear end side is the second opposing surface 21b. Although not shown, the second opposing surface 21b is substantially rectangular when viewed along the long axis direction. As Figure 1As shown, in a state where the brush part 20 is attached to the handle body 10, the second opposing surface 21b opposes the first opposing surface 14a of the handle body 10 in the major axis direction. In the present embodiment, the second opposing surface 21b contacts the first opposing surface 14a in the major axis direction.

[0027] As Figure 6 shown, the brush base part 21 has a fitting hole 27 recessed from the second opposing surface 21b toward the front end side. As Figure 2 shown, the fitting part 15 is inserted into and fitted to the fitting hole 27. Thus, the brush part 20 is detachably attached to the handle body 10. As Figure 6 shown, the surface of the inner side of the fitting hole 27 facing the back side (-Z side) is a plane extending in a direction orthogonal to the thickness direction. The surface of the inner side of the fitting hole 27 facing the front side (+Z side) is located on the back side from the front end side toward the rear end side.

[0028] As Figure 5 shown, when viewed in the thickness direction, a pair of protrusion parts 27a, 27b are provided in the fitting hole 27. One protrusion part 27a protrudes from the surface of the fitting hole 27 facing the other side (-Y side) in the width direction toward the other side in the width direction. The other protrusion part 27b protrudes from the surface of the fitting hole 27 facing one side (+Y side) in the width direction toward one side in the width direction. When viewed in the thickness direction, each of the pair of protrusion parts 27a, 27b is substantially semicircular. When the fitting part 15 is inserted into the fitting hole 27, the pair of protrusion parts 27a, 27b are respectively fitted to the pair of recessed parts 15a, 15b.

[0029] As Figure 6 shown, the plurality of monofilaments 28 each protrude from the upper surface 21a of the brush base part 21 toward the front side, that is, one side (+Z side) in the thickness direction. As Figure 5 and Figure 6 shown, the part on the back side (-Z side) of each monofilament 28 is a substantially triangular prism shape in which the cross-section orthogonal to the thickness direction is substantially triangular, and the part on the front side of each monofilament 28 is a triangular pyramid shape that tapers toward the front side. As Figure 5 shown, the plurality of columns formed by the plurality of monofilaments 28 arranged along the width direction are arranged on the upper surface 21a at intervals in the major axis direction. In addition, the shape of the monofilament 28 is not limited to the present embodiment. For example, the shape of the cross-section orthogonal to the thickness direction may also be a polygonal shape such as a quadrilateral, a circular shape, a semicircular shape, a star shape, and a spatula shape. Further, the monofilament 28 may also be a columnar shape protruding from the brush base part 21 toward the front side, or may be a tapered shape that tapers as it goes from the brush base part 21 toward the front side.

[0030] As the soft resin constituting the brush part 20, various elastomers can be used, but polyurethane is preferred. Compared with other elastomers such as styrene-based and polyester-based elastomers, polyurethane has a higher tensile strength. Therefore, even when made very thin, mechanical strength can be ensured. Thus, breakage during the fitting of the fitting part 15 and the fitting hole 27 and during the use of the toothbrush 1 can be suppressed.

[0031] In addition, compared with the above-mentioned other elastomers, polyurethane has a wider range of selectable hardnesses, and the resin hardness considering its usability (for example, the buckling of the tip of the brush-formed body) can be selected according to the thickness of the brush part 20. As the hardness of polyurethane, a Shore hardness of A90 or more and A100 or less, or a Shore hardness of D40 or more and D70 or less is preferred. When the hardness of polyurethane is softer than Shore A90, it is likely to deform when formed with a thin wall, so the fitting becomes weak, and the brush part 20 is likely to fall off during the use of the toothbrush 1. When the hardness of polyurethane is harder than Shore D70, pain may occur when the tip contacts the oral tissue when the back surface of the brush base part 21 is inclined. By setting the hardness of polyurethane to be Shore A90 or more and D70 or less, it is possible to suppress the brush part 20 from falling off during the use of the toothbrush 1 and to suppress pain from occurring when the tip of the brush base part 21 contacts.

[0032] In polyurethane, any one of saturated / unsaturated hydrocarbons with 10 or more carbon atoms, higher alcohols, fatty acid amides, fatty acid esters, low molecular weight polyethylene, polyethylene glycol (PEG), fatty acid metal salts, long chain fatty acids, fatty acid glycerols, and silicones in the range of 0.01 wt% (mass%) or more and 1.0 wt% (mass%) or less is compounded, and functions as a lubricant and a mold release agent. In addition, as polyurethane, ether-based polyurethane is preferably used from the viewpoints of ensuring water resistance and antibacterial properties.

[0033] As Figure 1 and Figure 2 shown, the toothbrush 1 of the present embodiment includes a brush head 5. In the present embodiment, the brush head 5 is composed of a connecting part 14, a fitting part 15, and a brush part 20. The brush head 5 is the part of the toothbrush 1 on the front end side with respect to the neck part 13. In addition, the brush head 5 is the part of the toothbrush 1 on the front end side with respect to the first boundary part 13a. During the use of the toothbrush 1, the brush head 5 is the part located in the oral cavity and cleaning the oral cavity.

[0034] The maximum width of the brush head 5 is preferably 11 mm or less. By making the maximum width of the brush head 5 11 mm or less, the operability of the brush head 5 in the oral cavity can be improved, and thus the cleaning property in the oral cavity can be improved.

[0035] Figure 7 is a view showing a part of the toothbrush 1 of the present embodiment. More specifically, Figure 7The side view of (a) shows a part of the toothbrush 1 of the present embodiment. Figure 7 The side view of (b) shows a part of the handle body 10 of the present embodiment. Figure 7 The front view of (c) shows a part of the handle body 10 of the present embodiment.

[0036] Next, the shape of the neck 13 of the present embodiment will be described in detail. As described above, the neck 13 is the part between the first boundary portion 13a and the second boundary portion 13b in the handle body 10. As Figure 7 As shown in (c), the width of the neck 13 of the present embodiment gradually widens from the first boundary portion 13a toward the second boundary portion 13b. That is, the width of the neck 13 is the narrowest at the first boundary portion 13a and the widest at the second boundary portion 13b. As Figure 7 As shown in (b), the thickness of the neck 13 of the present embodiment thins from the first boundary portion 13a toward the second boundary portion 13b, and then extends toward the rear end side with a constant thickness or gradually thickens. The thickness of the neck 13 is the thinnest at a position slightly closer to the rear end side than the first boundary portion 13a and the thickest at the second boundary portion 13b. In addition, in the present embodiment, the boundary between the neck 13 and the grip portion 12 is the second boundary portion 13b. However, when the second boundary portion 13b is not clear, the boundary between the neck 13 and the grip portion 12 may also be the position of the front end side end portion of the finger contact portion 17, or may be the position of the rear end side of 42.2% of the total length of the handle body 10 from the front end side end portion of the handle body 10. In the following description, the boundary between the neck 13 and the grip portion 12 is the second boundary portion 13b. In this case, the position of the rear end side end portion of the neck 13 is the second boundary portion 13b.

[0037] As Figure 7 As shown in (a), the neck 13 has a first neck P1, a second neck P2, a third neck P3, a fourth neck P4, and a fifth neck P5. The first neck P1, the second neck P2, the third neck P3, the fourth neck P4, and the fifth neck P5 are each a part of the neck 13. Each neck may be arranged at mutually different positions or may be arranged at mutually the same positions.

[0038] The first neck portion P1 is the thinnest part of the neck 13. That is, the thickness of the neck 13, i.e., the dimension in the thickness direction, is the smallest at the first neck portion P1. As described above, the thickness of the neck 13 of the present embodiment thins from the first boundary portion 13a toward the second boundary portion 13b, and then becomes constant or gradually thickens. Therefore, the dimension in the thickness direction of the neck 13 becomes constant or gradually increases from the first neck portion P1 toward the rear end side, i.e., the other side in the long axis direction (-X side). In the present embodiment, the first neck portion P1 is disposed at a position slightly closer to the rear end side than the first boundary portion 13a. Further, in the neck 13, when the thinnest part of the neck 13 extends in the long axis direction with the same thickness, the end portion on the front end side of the thinnest part of the neck 13 is defined as the first neck portion P1.

[0039] According to the present embodiment, the thickness T1 of the first neck portion P1 is 3.0 mm or more and 4.5 mm or less. When the thickness T1 of the first neck portion P1 is thinner than 3.0 mm, the rigidity of the first neck portion P1 becomes too small, so that when the toothbrush 1 is used, stress is likely to concentrate on the first neck portion P1. As a result, the first neck portion P1 is likely to be locally deflected, and thus the usability of the toothbrush 1 is reduced. When the thickness T1 of the first neck portion P1 is thicker than 4.5 mm, the thickness of the portion of the neck 13 close to the brush head portion 5 becomes too thick, so that the operability of the brush head portion 5 in the oral cavity is reduced, and the usability of the toothbrush 1 is reduced. In the present embodiment, by setting the thickness T1 of the first neck portion P1 to be 3.0 mm or more and 4.5 mm or less, it is possible to suppress local deflection of the first neck portion P1 and to make the thickness of the portion of the neck 13 close to the brush head portion 5 thinner, so that a reduction in the usability of the toothbrush 1 can be suppressed.

[0040] The second neck portion P2 is located on the rear end side with respect to the first neck portion P1, i.e., the other side in the long axis direction (-X side). The length of the distance between the first neck portion P1 and the second neck portion P2 is equal to the length Lm of the fitting portion 15, i.e., the dimension in the long axis direction.

[0041] According to the present embodiment, Figure 7 the maximum thickness Tm of the fitting portion 15 shown in (b) thereof, i.e., the maximum dimension in the thickness direction, is 1.5 mm or more and 2.5 mm or less. When the maximum thickness Tm of the fitting portion 15 is thinner than 1.5 mm, the rigidity of the fitting portion 15 becomes too small, so that when the toothbrush 1 is used, the deflection in the thickness direction of the fitting portion 15 is likely to increase. When the maximum thickness Tm of the fitting portion 15 is thicker than 2.5 mm, it is difficult to make the thickness of the brush head portion 5 thinner, and it is difficult to achieve thinning of the brush head portion 5. In the present embodiment, by setting the maximum thickness Tm of the fitting portion 15 to be 1.5 mm or more and 2.5 mm or less, it is possible to suppress an increase in the deflection in the thickness direction of the fitting portion 15 and to achieve thinning of the brush head portion 5. Therefore, the operability of the brush head portion 5 in the oral cavity can be improved.

[0042] According to the present embodiment, the neck portion 13 has: a first neck portion P1, and a second neck portion P2 located on the rear end side, that is, on the other side (-X side) in the long axis direction, with respect to the first neck portion P1. The length of the distance between the first neck portion P1 and the second neck portion P2 is equal to the length Lm of the fitting portion 15. The thickness of the neck portion 13 is the thinnest at the first neck portion P1. The thickness T1 of the first neck portion P1, the thickness T2 of the second neck portion P2, and the maximum thickness Tm of the fitting portion 15 satisfy the relationship of 3.0 mm ≤ T1 ≤ 4.5 mm, 1.5 mm ≤ Tm ≤ 2.5 mm, and (T2 - T1) / Tm ≤ 0.6. In the following description, (T2 - T1) / Tm is sometimes referred to as the first ratio. Since the maximum thickness Tm of the fitting portion 15 is 2.5 mm or less, as described above, thinning of the brush head portion 5 can be achieved. In addition, since the thickness T1 of the first neck portion P1 is 4.5 mm or less, the minimum thickness of the neck portion 13 can be made thinner. And since the first ratio is 0.6 or less, the difference between the thickness T2 of the second neck portion P2 and the thickness T1 of the first neck portion can be reduced. The second neck portion P2 is located at a position on the rear end side by the length Lm of the fitting portion 15 from the first neck portion P1. Thereby, it is possible to suppress the rigidity in the thickness direction of the portion between the first neck portion P1 and the second neck portion P2 in the neck portion 13 from becoming excessively large with respect to the rigidity in the thickness direction of the brush head portion 5. Therefore, when the toothbrush 1 is used and a force is applied to the brush head portion 5 in the thickness direction, the portion between the first neck portion P1 and the second neck portion P2 in the neck portion 13 is greatly deflected in the thickness direction, and the force applied to the brush head portion 5 can be absorbed by this deflection. Thereby, the stress applied to the root of the fitting portion 15 of the brush head portion 5 can be reduced, and thus an increase in the deflection in the thickness direction of the fitting portion 15 can be suppressed. Therefore, the deflection of the brush head portion 5 in the thickness direction can be suppressed. Therefore, even in the case where the brush portion 20 is formed of a soft resin, thinning of the brush head portion 5 can be achieved and an increase in the deflection of the brush head portion 5 can be suppressed. Therefore, the operability of the toothbrush 1 can be improved. In addition, in the toothbrush 1 of the present embodiment, the above-described effects are significantly exhibited when the maximum width of the brush head portion 5, where deflection in the thickness direction of the brush head portion 5 is likely to occur, is 11 mm or less.

[0043] In addition, according to the present embodiment, as described above, when the toothbrush 1 is used, the increase in the flexure of the fitting portion 15 can be suppressed, and thus the generation of a gap between the first opposing surface 14a of the handle body 10 and the second opposing surface 21b of the brush portion 20 can be suppressed. Therefore, the displacement of the brush portion 20 relative to the handle body 10 in the long axis direction can be suppressed, and thus the user can brush the intended site. Therefore, the followability of the brush portion 20 with respect to the movement of the user's hand can be improved. In addition, the entry of toothpaste and saliva between the first opposing surface 14a and the second opposing surface 21b can be suppressed, and thus the deterioration of the hygiene of the toothbrush 1 can be suppressed.

[0044] Furthermore, the first ratio is more preferably 0.4 or less. When the first ratio is 0.4 or less, the increase in the flexure of the brush head 5 can be more appropriately suppressed. Therefore, the operability of the toothbrush 1 can be further improved, the followability of the brush portion 20 can be further improved, and the deterioration of the hygiene of the toothbrush 1 can be more appropriately suppressed.

[0045] Preferably Figure 7 As shown in (a), the longer the length Lb of the brush portion 20 is, the longer the length Lm of the fitting portion 15 that supports the brush portion 20 in the thickness direction is. However, in this case, the stress applied to the root of the fitting portion 15 tends to increase. On the other hand, in the present embodiment, the position of the second neck portion P2 in the long axis direction is the position that is distanced from the first neck portion P1 by the length Lm of the fitting portion 15 toward the rear end side. Therefore, the longer the length Lm of the fitting portion 15 is, the longer the distance between the first neck portion P1 and the second neck portion P2 can be. Conversely, the shorter the length Lm of the fitting portion 15 is, the shorter the distance between the first neck portion P1 and the second neck portion P2 can be. Thereby, the rigidity in the thickness direction of the portion between the first neck portion P1 and the second neck portion P2 in the neck portion 13 can be appropriately adjusted according to the length Lm of the fitting portion 15. Therefore, the force applied to the brush head 5 can be appropriately absorbed by the flexure of the portion between the first neck portion P1 and the second neck portion P2 in the neck portion 13, and thus the increase in the stress applied to the root of the fitting portion 15 can be suppressed. Therefore, even when the brush portion 20 is formed of a soft resin, the thinning of the brush head 5 can be achieved, and the increase in the flexure of the brush head 5 can be suppressed, and thus the operability of the toothbrush 1 can be improved.

[0046] In addition, in the present embodiment, as described above, the thickness of the brush head 5 can be thinned, and the thickness of the portion of the neck portion 13 close to the brush head 5, that is, the first neck portion P1, can be thinned. Therefore, the operability of the toothbrush 1 in the oral cavity can be improved.

[0047] In addition, if the first ratio is greater than 0.6, the flexure of the neck portion 13 becomes too small, and thus the flexure of the brush head 5 increases, and the operability of the toothbrush 1 tends to deteriorate. Preferably, the length Lm of the fitting portion 15 is 20 mm or less. Thereby, an increase in the deflection in the thickness direction of the fitting portion 15 can be suppressed, and thus the operability of the toothbrush 1 can be improved. Preferably, the thickness T2 of the second neck portion P2 is 5 mm or less. Thereby, an excessive increase in the rigidity of the portion between the first neck portion P1 and the second neck portion P2 in the neck portion 13 can be suppressed, and thus an increase in the deflection in the thickness direction of the brush head portion 5 can be suppressed. Therefore, the operability of the toothbrush 1 can be improved. Moreover, preferably, the width of the second neck portion P2 is 5 mm or less. Thereby, an increase in the rigidity of the portion between the first neck portion P1 and the second neck portion P2 can be suppressed, and thus an increase in the deflection in the thickness direction of the brush head portion 5 can be suppressed. Therefore, the operability of the toothbrush 1 can be improved.

[0048] As Figure 7 shown in (a) of [], the third neck portion P3 is located on the rear end side with respect to the first neck portion P1, that is, on the other side (-X side) in the major axis direction. In the major axis direction, the length of the distance between the first neck portion P1 and the third neck portion P3 is equal to twice the length of the length Lm of the fitting portion 15, that is, the dimension in the major axis direction. The length of the distance between the second neck portion P2 and the third neck portion P3 is equal to the length Lm of the fitting portion 15.

[0049] According to the present embodiment, the neck portion 13 has the third neck portion P3. If the thickness of the first neck portion P1 is T1, the thickness of the third neck portion P3 is T3, and the maximum thickness of the fitting portion 15 is Tm, then the relationship of (T3 - T1) / Tm ≤ 1.5 is satisfied. Thereby, the difference between the thickness T3 of the third neck portion P3 and the thickness T1 of the first neck portion P1 can be reduced, and the third neck portion P3 is located at a position 2 times the length Lm of the fitting portion 15 closer to the rear end side from the first neck portion P1. Thereby, an excessive increase in the rigidity in the thickness direction of the portion between the first neck portion P1 and the third neck portion P3 in the neck portion 13 with respect to the rigidity in the thickness direction of the brush head portion 5 can be suppressed. Therefore, when using the toothbrush 1, the force applied to the brush head portion 5 can be more appropriately absorbed by the deflection of the portion between the first neck portion P1 and the third neck portion P3 in the neck portion 13. Thereby, the stress applied to the root of the fitting portion 15 can be further reduced, and thus an excessive increase in the deflection in the thickness direction of the fitting portion 15 can be more appropriately suppressed. Therefore, even when the brush portion 20 is formed of a soft resin, thinning of the brush head portion 5 can be achieved, and an increase in the deflection of the brush head portion 5 can be more appropriately suppressed. Therefore, the operability of the toothbrush 1 can be further improved, the followability of the brush portion 20 can be further improved, and a decrease in the hygiene of the toothbrush 1 can be more appropriately suppressed. In addition, in the following description, (T3 - T1) / Tm may sometimes be referred to as the second ratio.

[0050] In addition, the second ratio is more preferably 1.3 or less. When the second ratio is 1.3 or less, it is possible to more appropriately suppress the rigidity in the thickness direction of the portion between the first neck P1 and the third neck P3 in the neck 13 from becoming excessive. Therefore, the force applied to the brush head 5 can be further absorbed by the flexure in the thickness direction of the neck 13. As a result, the increase in the flexure of the brush head 5 can be more appropriately suppressed, and thus the operability of the toothbrush 1 can be further improved.

[0051] If the second ratio is greater than 1.5, the flexure of the neck 13 becomes too small, so the flexure of the brush head 5 increases, and the operability of the toothbrush 1 is likely to decrease. The thickness T3 of the third neck P3 is preferably 8 mm or less, and more preferably 7 mm or less. Thereby, it is possible to suppress the rigidity of the portion between the first neck P1 and the third neck P3 in the neck 13 from becoming excessive. Therefore, the force applied to the brush head 5 can be further absorbed by the flexure of the neck 13. As a result, the increase in the flexure of the brush head 5 can be more appropriately suppressed, and thus the operability of the toothbrush 1 can be further improved.

[0052] According to the present embodiment, if the thickness of the first neck P1 is set as T1 and the maximum thickness of the fitting portion 15 is set as Tm, the relationship of T1 ≤ 2.5 × Tm is satisfied. Therefore, it is possible to suppress the maximum thickness Tm of the fitting portion 15 from becoming too thin relative to the thickness of the neck 13, and thus it is possible to suppress the rigidity in the thickness direction of the fitting portion 15 from becoming too small. Therefore, it is possible to suppress the increase in the flexure in the thickness direction of the brush head 5, and thus the operability of the toothbrush 1 can be more appropriately improved, and the followability of the brush portion 20 can be further improved, and the decrease in the hygiene of the toothbrush 1 can be more appropriately suppressed.

[0053] In addition, it is preferable that the thickness T1 of the first neck P1 and the maximum thickness Tm of the fitting portion 15 satisfy the relationship of T1 ≤ 2.0 × Tm. Thereby, the increase in the flexure in the thickness direction of the brush head 5 can be more appropriately suppressed, and thus the operability of the toothbrush 1 can be more appropriately improved.

[0054] According to the present embodiment, if the thickness of the first neck P1 is set as T1 and the maximum thickness of the brush base portion 21, that is, the maximum dimension in the thickness direction, is set as Tb, the relationship of T1 < Tb is satisfied. Therefore, it is possible to suppress the thickness of the neck 13 from becoming too thick, and thus it is possible to suppress the rigidity in the thickness direction of the neck 13 from becoming too high relative to the rigidity in the thickness direction of the brush head 5. Therefore, the increase in the flexure in the thickness direction of the brush head 5 can be more appropriately suppressed, and thus the operability of the toothbrush 1 can be more appropriately improved.

[0055] In addition, it is preferable that the maximum thickness Tb of the brush base portion 21 is 3.5 mm or more and 4.5 mm or less. When the maximum thickness Tb of the brush base portion 21 is less than 3.5 mm, the rigidity in the thickness direction of the brush base portion 21 becomes too small. Therefore, when the toothbrush 1 is used, the deflection in the thickness direction of the brush portion 20 is likely to increase. When the maximum thickness Tb of the brush base portion 21 is greater than 4.5 mm, it is difficult to make the brush head portion 5 thinner. In the present embodiment, by setting the maximum thickness Tb of the brush base portion 21 to be 3.5 mm or more and 4.5 mm or less, it is possible to suppress an increase in the deflection in the thickness direction of the brush portion 20 and to make the brush head portion 5 thinner. Therefore, the operability of the toothbrush 1 can be improved.

[0056] As Figure 7 shown in (a) of, the fourth neck portion P4 is located on the rear end side, that is, on the other side (-X side) in the long axis direction, as compared with the first neck portion P1. In the present embodiment, in the long axis direction, the fourth neck portion P4 is located between the second neck portion P2 and the third neck portion P3. The position of the fourth neck portion P4 is not limited thereto, and it may be located on the front end side as compared with the second neck portion P2, or may be located on the rear end side as compared with the third neck portion P3.

[0057] According to the present embodiment, the thickness T4 of the fourth neck portion P4, that is, the dimension in the thickness direction, is the same as the maximum thickness Tb of the brush base portion 21. In the long axis direction, the distance L3 between the end portion on the rear end side of the fitting portion 15 and the fourth neck portion P4 is longer than the length Lb of the brush portion 20. Thus, in the neck portion 13, it is possible to lengthen the length of the portion that is thinner than the maximum thickness Tb of the thin brush base portion 21. Therefore, it is possible to suppress the rigidity in the thickness direction of the neck portion 13 from becoming too large. Therefore, when the toothbrush 1 is used, the force applied to the brush head portion 5 can be more appropriately absorbed by the deflection of the neck portion 13. Therefore, it is possible to more appropriately reduce the stress applied to the root portion of the fitting portion 15. Therefore, it is possible to more appropriately suppress an increase in the deflection in the thickness direction of the brush head portion 5. Therefore, the operability of the toothbrush 1 can be more appropriately improved.

[0058] In addition, it is preferable that the distance L3 between the end portion on the rear end side of the fitting portion 15 and the fourth neck portion P4 is 20 mm or more. When the distance L3 between the end portion on the rear end side of the fitting portion 15 and the fourth neck portion P4 is less than 20 mm, the portion on the front end side of the neck portion 13, that is, the portion of the neck portion 13 close to the fitting portion 15 is likely to flex in the thickness direction. Therefore, it is difficult to reduce the stress applied to the root portion of the fitting portion 15. By setting the distance L3 between the end portion on the rear end side of the fitting portion 15 and the fourth neck portion P4 to 20 mm or more, the portion of the neck portion 13 from the fitting portion 15 to the portion farther from it on the rear end side is likely to flex in the thickness direction. Therefore, the stress applied to the root portion of the fitting portion 15 can be further reduced. Therefore, the increase in the flexure of the brush head portion 5 in the thickness direction can be more appropriately suppressed, and thus the operability of the toothbrush 1 can be more appropriately improved.

[0059] In addition, it is preferable that the ratio of the distance L3 between the end portion on the rear end side of the fitting portion 15 and the fourth neck portion P4 to the distance L1 between the end portion on the rear end side of the fitting portion 15 and the end portion on the rear end side of the neck portion 13 is 40% or more. Thereby, the length of the portion of the neck portion 13 that is thinner than the maximum thickness Tb of the brush base portion 21 can be more appropriately lengthened. Therefore, during the use of the toothbrush 1, the length of the portion of the neck portion 13 that flexes in the thickness direction can be lengthened, and thus the stress applied to the root portion of the fitting portion 15 can be further reduced. Therefore, the increase in the flexure of the brush head portion 5 in the thickness direction can be more appropriately suppressed, and thus the operability of the toothbrush 1 can be more appropriately improved.

[0060] In addition, it is preferable that the ratio of the distance L4 between the end portion on the rear end side of the fitting portion 15 and the first neck portion P1 to the distance L1 between the end portion on the rear end side of the fitting portion 15 and the end portion on the rear end side of the neck portion 13 is 10% or more and 60% or less. More preferably, the ratio of the distance L4 between the end portion on the rear end side of the fitting portion 15 and the first neck portion P1 to the distance L1 between the end portion on the rear end side of the fitting portion 15 and the end portion on the rear end side of the neck portion 13 is 10% or more and 30% or less. Thereby, the first neck portion P1 can be arranged close to the end portion on the rear end side of the fitting portion 15. Therefore, during the use of the toothbrush 1, the portion of the neck portion 13 close to the fitting portion 15 flexes in the thickness direction, and thus the stress applied to the root portion of the fitting portion 15 can be further reduced. Therefore, the increase in the flexure of the brush head portion 5 in the thickness direction can be more appropriately suppressed, and thus the operability of the toothbrush 1 can be more appropriately improved.

[0061] As described above, the thickness of the connecting portion 14 is the thickest at the end portion on the front end side, gradually thins toward the rear end side, and is the thinnest at the end portion on the rear end side. Therefore, as shown in (b) of Figure 7 The connecting portion 14 has the maximum thickness Tk of the connecting portion 14, that is, the maximum dimension in the thickness direction, at the end portion on the front end side of the connecting portion 14.

[0062] According to this embodiment, if the thickness of the first neck P1 is set as T1 and the maximum thickness of the connecting portion 14 is set as Tk, the relationship of T1 < Tk is satisfied. Therefore, it is possible to suppress the thickness of the neck 13 from becoming too thick relative to the connecting portion 14 that constitutes the brush head 5, and thus it is possible to suppress the rigidity in the thickness direction of the neck 13 from becoming too high relative to the rigidity in the thickness direction of the brush head 5. Therefore, it is possible to suppress an increase in the deflection in the thickness direction of the brush head 5, and thus it is possible to more appropriately improve the operability of the toothbrush 1.

[0063] According to this embodiment, the ratio of the length Ln of the neck 13 to the distance L5 between the end portion on the front end side of the brush head 5, that is, one side in the major axis direction (+X side), and the end portion on the rear end side of the neck 13, that is, the other side in the major axis direction (-X side), is 60% or more. Generally, from the viewpoint of the usability of the toothbrush 1, the distance L5 from the front end of the brush head 5 to the rear end of the neck 13 is limited within a predetermined range. In contrast, in this embodiment, it is possible to relatively increase the length Ln of the neck 13 with respect to the length Lh of the brush head 5. Therefore, when using the toothbrush 1, it is easy to increase the deflection in the thickness direction of the neck 13, and thus it is easy to absorb the force applied to the brush head 5 through this deflection. Therefore, it is possible to more appropriately suppress an increase in the deflection in the thickness direction of the brush head 5, and thus it is possible to more appropriately improve the operability of the toothbrush 1.

[0064] In addition, when the ratio of the length Ln of the neck 13 to the distance L5 between the end portion on the front end side of the brush head 5 and the end portion on the rear end side of the neck 13 is less than 60%, the length Ln of the neck 13 becomes relatively too short with respect to the length Lb of the brush head 5. Therefore, when using the toothbrush 1, the deflection of the neck 13 is likely to become small. Therefore, the deflection of the brush head 5 is likely to increase.

[0065] According to this embodiment, the ratio of the length Lm of the fitting portion 15 to the length Lb of the brush portion 20 is 80% or more. Therefore, it is possible to increase the contact area between the inner surface of the fitting hole 27 of the brush portion 20 and the outer surface of the fitting portion 15, and thus it is possible to increase the frictional force between the brush portion 20 and the fitting portion 15. Thereby, it is possible to suppress the brush portion 20 from moving in the major axis direction with respect to the handle body 10, and thus it is possible to further improve the followability of the brush portion 20 and to more appropriately suppress a decrease in the hygiene of the toothbrush 1.

[0066] In addition, when the brush part 20 is formed by insert molding with the handle body 10 as an insert part, the joint area between the inner side surface of the fitting hole 27 of the brush part 20 and the outer side surface of the fitting part 15 can be enlarged. Therefore, the joint force between the brush part 20 and the fitting part 15 can be increased. Thus, as described above, the movement of the brush part 20 relative to the handle body 10 in the long axis direction can be suppressed. Therefore, the followability of the brush part 20 can be further improved, and the reduction of the hygiene of the toothbrush 1 can be more appropriately suppressed.

[0067] As Figure 7 As shown in (c) of [reference], the fifth neck P5 is located on the rear end side, that is, the other side in the long axis direction (-X side), compared to the first neck P1. In the present embodiment, in the long axis direction, the fifth neck P5 is located between the third neck P3 and the second boundary part 13b. The position of the fifth neck P5 is not limited to this, and it may also be located on the front end side compared to the third neck P3.

[0068] According to the present embodiment, the width W1 of the first neck P1, that is, the dimension in the width direction, is smaller than the maximum width Wm of the fitting part 15, that is, the maximum dimension in the width direction. The dimension of the width W5 of the fifth neck P5 is equal to the maximum width Wm of the fitting part 15. The length of the distance L2 between the first neck P1 and the fifth neck P5 in the long axis direction is equal to or greater than the length Lh of the brush head 5. Therefore, the width between the first neck P1 and the fifth neck P5 in the neck 13 can be made narrower than the maximum width Wm of the fitting part 15. Therefore, compared to the rigidity in the width direction of the fitting part 15, the rigidity in the width direction of the part between the first neck P1 and the fifth neck P5 in the neck 13 can be reduced. Therefore, when the toothbrush 1 is in use, if a force is applied to the brush head 5 in the width direction, the part between the first neck P1 and the fifth neck P5 in the neck 13 will be greatly deflected in the width direction, and the force applied to the brush head 5 in the width direction can be absorbed by this deflection. Thereby, the stress applied to the root of the fitting part 15 can be reduced, and thus the increase in the deflection of the fitting part 15 in the width direction can be suppressed. Thereby, the increase in the deflection of the brush head 5 in the width direction can be suppressed, and thus the operability of the toothbrush 1 can be improved. In addition, the movement of the brush part 20 relative to the handle body 10 in the long axis direction can be suppressed. Therefore, the followability of the brush part 20 can be further improved, and the reduction of the hygiene of the toothbrush 1 can be more appropriately suppressed.

[0069] As described above, in the toothbrush 1 of the present embodiment, when the brush part 20 formed of a soft resin is used, the thinning of the brush head 5 can be achieved, and the increase in the deflection of the brush head 5 can be suppressed.

[0070] [Embodiment] Hereinafter, embodiments will be shown and the present invention will be described in detail. However, the present invention is not limited to the following embodiments and can be implemented with appropriate modifications without departing from the gist thereof.

[0071] (Examples 1 to 8, Comparative Example 1) According to the specifications shown in [Table 1], the thickness of the above-mentioned first neck (the minimum thickness of the neck): T1, the maximum thickness of the fitting part: Tm, the length of the fitting part: Lm, the thickness of the second neck: T2, the first ratio: (T2 - T1) / Tm, the thickness of the third neck: T3, the second ratio: (T3 - T1) / Tm, the ratio of the thickness of the first neck to the maximum thickness of the fitting part: T1 / Tm, the maximum thickness of the brush base part: Tb, and the ratio of the maximum thickness of the brush base part to the thickness of the first neck: Tb / T1. Toothbrushes with at least one different parameter were used as samples for Examples 1 to 8 and Comparative Example 1.

[0072] The length Lh of the brush head of each sample was 21 mm. The maximum width of the brush head of each sample was 11 mm. The maximum width Wm of the fitting part of each sample was 8 mm. The hard resin constituting the handle body of each sample was polyoxymethylene resin (POM). The soft resin constituting the brush part of each sample was polyurethane resin (PU). The minimum width of the neck of each sample was 4.5 mm. The length Ln of the neck of each sample was 48.5 mm. The length of the connecting part of each sample was 7.5 mm. The arrangement of the filaments of each sample was Figure 5 the arrangement shown. The number of filaments of each sample was 149. The hair height of the filaments of each sample was 10.0 mm. The shape of the cross-section orthogonal to the thickness direction at the root of the filaments of each sample was a triangular shape with a base size of 0.90 mm and a height of 0.70 mm. The side view shape of the filaments of each sample was Figure 6 the shape shown.

[0073] [Evaluation Method] For each sample of Examples 1 to 8 and Comparative Example 1, an evaluation was made according to the feeling that there was no deformation of the brush head during the cleaning of the molars and the brush head followed the movement of the hand well for grinding.

[0074] (1) Evaluation method for the feeling that there is no deformation of the brush head during the cleaning of the molars and the brush head follows the movement of the hand well for grinding The toothbrushes of Examples 1 to 8 and Comparative Example 1 were evaluated according to the following criteria. 5 points: Can be felt very strongly 4 points: Can be felt slightly 3 points: Neither 2 points: Can hardly be felt 1 point: Can't be felt at all Moreover, the average value of the evaluation scores of the 10-expert panel is calculated, and the evaluation is carried out in the following five stages. ☆(star mark): 4.5 points or more ◎(double circle mark): 4.0 points or more and less than 4.5 points ○(circle mark): 3.5 points or more and less than 4.0 points △(triangle mark): 3.0 points or more and less than 3.5 points ×(cross mark): less than 3.0 points. In addition, in the evaluation columns of Examples 1 to 8 and Comparative Example 1 in Table 1, the average value of the evaluation scores of the 10-expert panel and the above five-stage evaluation are recorded in parentheses together.

[0075] [Table 1]

[0076] As shown in [Table 1], for Examples 1 to 8 where the first ratio (T2 - T1) / Tm is 0.6 or less, the average value of the evaluation scores of the 10-expert panel is 3.0 points or more, and for the cleaning of the molars, there is no deformation of the brush head, and the brush head follows the movement of the hand well and has a good feeling of grinding, resulting in good results.

[0077] In contrast, for Comparative Example 1 where the first ratio (T2 - T1) / Tm is greater than 0.6, the average value of the evaluation scores of the 10-expert panel is less than 3.0 points, and for the cleaning of the molars, there is no deformation of the brush head, and the brush head follows the movement of the hand well and has a good feeling of grinding, but good results are not obtained. As described above, if the first ratio (T2 - T1) / Tm is greater than 0.6, then during the cleaning of the molars, sufficient flexion of the neck is not obtained, so stress is concentrated at the root of the fitting part. As a result, the flexion in the thickness direction of the fitting part increases, so the deformation of the brush head becomes larger, and the brush head is difficult to follow the movement of the hand, so the grinding performance of the molars is reduced.

[0078] Comparing with the structure of Example 1, in Example 2 where the first ratio (T2 - T1) / Tm is less than 0.4, the evaluation in the five-stage evaluation is the same as that of Example 1, but a better result than Example 1 is obtained in the average value of the evaluation scores of the 10-expert panel. This is because, in Example 2, compared with Example 1, the flexion in the thickness direction from the first neck to the second neck can be increased, so the flexion in the thickness direction of the brush head can be more appropriately suppressed.

[0079] When compared with the structure of Example 2, in Example 3 where the second ratio (T3 - T1) / Tm is less than 1.5, better results than those of Example 2 are obtained. This is because, in Example 3, the deflection in the thickness direction from the first neck to the third neck can be increased compared with Example 2, and thus the deflection in the thickness direction of the brush head can be more appropriately suppressed. Also, when compared with the structure of Example 3, in Example 4 where the second ratio (T3 - T1) / Tm is less than 1.3, better results than those of Example 3 are obtained for the same reason.

[0080] When compared with the structure of Example 4, in Example 5 where the ratio T1 / Tm of the thickness of the first neck to the maximum thickness of the fitting portion is 2.5 or less, better results than those of Example 4 are obtained. This is because, in Example 5, the maximum thickness of the fitting portion can be prevented from becoming too thin compared with Example 4, and thus the deflection of the brush head can be more appropriately reduced. Also, when compared with the structure of Example 5, for Example 6 where the ratio T1 / Tm of the thickness of the first neck to the maximum thickness of the fitting portion is 2.0 or less, better results than those of Example 5 are obtained for the same reason.

[0081] When compared with the structure of Example 6, in Example 7 where the ratio Tb / T1 of the maximum thickness of the brush base portion to the thickness of the first neck is greater than 1.0, better results than those of Example 6 are obtained. This is because, in Example 7, compared with Example 6, the thickness of the neck can be prevented from becoming too thick relative to the maximum thickness of the brush base portion, and thus the deflection in the thickness direction of the neck can be further increased. Thereby, the deflection of the brush head can be more appropriately reduced.

[0082] When compared with the structure of Example 7, in Example 8 where the second ratio (T3 - T1) / Tm is 1.0 or less, the ratio T1 / Tm of the thickness of the first neck to the maximum thickness of the fitting portion is less than 2.0, and the ratio Tb / T1 of the maximum thickness of the brush base portion to the thickness of the first neck is greater than 1.1, better results than those of Example 7 are obtained.

[0083] As described above, the preferred embodiments of the present invention have been described, but the present invention is of course not limited to this example. The shapes, combinations, etc. of the respective components shown in the above examples are just examples, and various changes can be made based on design requirements and the like without departing from the gist of the present invention.

[0084] The structures of the fitting portion and the fitting hole are not limited to the structures of the present embodiment. For example, the fitting portion may have a protruding portion protruding in the width direction, and the fitting hole may have a recessed portion recessed in the width direction and fitting with the protruding portion.

[0085] In addition, in the present embodiment, a structure in which the handle body is formed of a hard resin is illustrated, but the structure is not limited thereto. For example, a structure in which a part of the handle body such as the handle portion is covered with a soft resin may also be used. In the case of this structure, the decorativeness and the grip of the toothbrush can be improved. Industrial applicability

[0086] When the toothbrush of the present invention uses a bristle part formed of a soft resin, it is possible to reduce the thickness of the brush head, and it is possible to suppress defective molding in a brush molding body that can suppress an increase in the deflection of the brush head. Therefore, it can be suitably used as a toothbrush of a thin brush head type. Symbol description

[0087] 1 Toothbrush 5 Brush head 10 Handle body 13 Neck 14 Connecting part 15 Fitting part 20 Bristle part 21 Brush base part 27 Fitting hole 28 Monofilament Lm Length of the fitting part (dimension in the major axis direction of the fitting part) P1 First neck P2 Second neck P3 Third neck P4 Fourth neck P5 Fifth neck T1 Thickness of the first neck (dimension in the thickness direction of the first neck) T2 Thickness of the second neck (dimension in the thickness direction of the second neck) T3 Thickness of the third neck (dimension in the thickness direction of the third neck) Tk Maximum thickness of the connecting part (maximum dimension in the thickness direction of the connecting part) Tm Maximum thickness of the fitting part (maximum dimension in the thickness direction of the fitting part)

Claims

1. A toothbrush, wherein, Comprising: a handle body formed of a hard resin and extending in the long axis direction, and a brush part formed of a soft resin and provided on one side of the handle body in the long axis direction; the handle body has: a neck extending in the long axis direction, and a fitting part that is arranged on one side of the neck in the long axis direction and protrudes toward one side of the long axis direction; the brush part has: a brush base part, and a plurality of monofilaments integrally formed with the brush base part; the brush base part has a fitting hole into which the fitting part is inserted and fitted, the plurality of monofilaments respectively protrude from the brush base part toward the thickness direction intersecting the long axis direction, the neck has: a first neck, and a second neck that is located on the other side of the long axis direction compared to the first neck; the length of the distance between the first neck and the second neck is equal to the dimension of the fitting part in the long axis direction, the dimension of the neck in the thickness direction is the smallest at the first neck and is constant or gradually increases from the first neck toward the other side of the long axis direction, when the dimension of the first neck in the thickness direction is set as T1, the dimension of the second neck in the thickness direction is set as T2, and the maximum dimension of the fitting part in the thickness direction is set as Tm, the relationship of 3.0 mm ≤ T1 ≤ 4.5 mm, 1.5 mm ≤ Tm ≤ 2.5 mm, and (T2 - T1) / Tm ≤ 0.6 is satisfied.

2. The toothbrush according to claim 1, wherein the neck has a third neck that is located on the other side of the long axis direction compared to the first neck, in the long axis direction, the length of the distance between the first neck and the third neck is equal to twice the dimension of the fitting part in the long axis direction, when the dimension of the first neck in the thickness direction is set as T1, the dimension of the third neck in the thickness direction is set as T3, and the maximum dimension of the fitting part in the thickness direction is set as Tm, the relationship of (T3 - T1) / Tm ≤ 1.5 is satisfied.

3. The toothbrush according to claim 1 or 2, wherein when the dimension of the first neck in the thickness direction is set as T1 and the maximum dimension of the fitting part in the thickness direction is set as Tm, the relationship of T1 ≤ 2.5 × Tm is satisfied.

4. The toothbrush according to claim 1 or 2, wherein when the dimension of the first neck in the thickness direction is set as T1 and the maximum dimension of the brush base part in the thickness direction is set as Tb, the relationship of T1 < Tb is satisfied.

5. The toothbrush according to claim 1 or 2, wherein the neck has a fourth neck that is located on the other side of the long axis direction compared to the first neck, the length of the dimension of the fourth neck in the thickness direction is equal to the maximum dimension of the brush base part in the thickness direction, the distance between the end on the other side of the long axis direction of the fitting part and the fourth neck is longer than the dimension of the brush part in the long axis direction.

6. The toothbrush according to claim 1 or 2, wherein, the handle body has a connecting portion connecting the neck portion and the fitting portion, when the dimension in the thickness direction of the first neck portion is set as T1 and the maximum dimension in the thickness direction of the connecting portion is set as Tk, the relationship of T1 < Tk is satisfied.

7. The toothbrush according to claim 6, wherein, it includes a brush head portion composed of the connecting portion, the fitting portion, and the brush portion, the ratio of the dimension in the long axis direction of the neck portion to the distance between one end in the long axis direction of the brush head portion and the other end in the long axis direction of the neck portion is 60% or more, the ratio of the dimension in the long axis direction of the fitting portion to the dimension in the long axis direction of the brush portion is 80% or more.

8. The toothbrush according to claim 7, wherein, in the width direction orthogonal to both the long axis direction and the thickness direction, the dimension in the width direction of the first neck portion is smaller than the maximum dimension in the width direction of the fitting portion, the neck portion has a fifth neck portion, and this fifth neck portion is located on the other side in the long axis direction compared to the first neck portion, the dimension in the width direction of the fifth neck portion is equal to the maximum dimension in the width direction of the fitting portion, the length of the distance between the first neck portion and the fifth neck portion is equal to or greater than the dimension in the long axis direction of the brush head portion.

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