Toothbrush

Abstract

In the present invention, a toothbrush comprises a handle body formed from a hard resin and a brush part formed from a soft resin. The brush part has a brush base section and filaments. Each of the filaments protrudes from the brush base section toward one side in the thickness direction. The handle body has a neck part, a connection part, and a fitting part. The connection part, the fitting part, and the brush base section form a head shaft part. A connection edge section is formed of one-side end in the long axis direction and one-side end in the width direction of the connection part. A neck edge section is formed of one-side end in the width direction of a portion having the smallest dimension in the width direction of the neck part. The maximum dimension in the thickness direction of the head shaft part is 3.0-4.5 mm. The minimum dimension in the width direction of the neck part is 3.0-4.5 mm. The angle formed between the central axis line and a first virtual line passing through both the connection edge section and the neck edge section is 17-28°.

Description

toothbrush

[0001] This application claims priority from Japanese Patent Application No. 2023-162902, filed on September 26, 2023, the contents of which are incorporated herein by reference.

[0002] One-piece molded toothbrushes with filaments made of soft resin have been proposed (see, for example, Patent Document 1). Because the filaments in these toothbrushes are flexible, they tend to provide a gentler feel than toothbrushes with bristles made of spun bristles.

[0003] International Publication No. 2019 / 055364

[0004] In the toothbrush described above, the brush portion is molded from a soft resin, so the volume of the hard resin constituting the head portion is smaller than in toothbrushes whose bristles are made of spun bristles. In the toothbrush described above, the width of the head portion and neck portion are generally widened to increase the rigidity of the head portion to neck portion, thereby suppressing deformation of the head portion. However, in such toothbrushes, if the deflection of the neck portion becomes too small, the brushing load is concentrated on the filament, which can cause the filament to deflect too much. In this case, the filament has difficulty penetrating between teeth, resulting in reduced interdental cleaning performance. Furthermore, if the rigidity of the neck portion is made too small, the neck portion deflects too much, reducing the maneuverability of the head portion in the oral cavity. This reduces the maneuverability of the toothbrush. Furthermore, during brushing, the movement of the filament tip (bristle tip) is difficult to coordinate with the movement of the user's hand, which affects interdental cleaning performance.

[0005] The present invention has been made in consideration of the above points, and one of its objects is to provide a toothbrush that can improve interdental cleaning performance while preventing a decrease in the operability of the toothbrush.

[0006] The present invention includes the following configurations: [1] A brush comprising: a handle body made of hard resin and extending in a longitudinal direction; and a brush section made of soft resin and disposed on one side of the handle body in the longitudinal direction, the brush section having a brush base and a plurality of filaments integrally molded with the brush base, each of the plurality of filaments protruding from the brush base toward one side in a thickness direction intersecting the longitudinal direction, the handle body having a neck section extending in the longitudinal direction, a connecting section protruding from the neck section to one side in the longitudinal direction, a fitting section protruding from the connecting section to one side in the longitudinal direction, a connecting edge section that is a part of the connecting section, and a neck edge section that is a part of the neck section, the connecting section, the fitting section, and and the brush base portion constitute a head shaft portion, the connecting edge portion is an end portion on one side in the longitudinal direction of the connecting portion and an end portion on one side in the width direction that intersects both the longitudinal direction and the thickness direction, the neck edge portion is an end portion on one side in the width direction of a part of the neck portion that has the smallest dimension in the width direction, the maximum dimension in the thickness direction of the head shaft is 3.0 mm or more and 4.5 mm or less, the minimum dimension in the width direction of the neck portion is 3.0 mm or more and 4.5 mm or less, and when viewed from the thickness direction, the angle formed by a first imaginary line that passes through both the connecting edge portion and the neck edge portion and a central axis that extends through the center of the handle body toward the longitudinal direction is 17° or more and 28° or less. [2] The toothbrush described in [1], wherein the brush base has a fitting hole into which the fitting portion is inserted and fitted, the handle body has a fitting edge portion, and the fitting edge portion is the other end of the fitting portion in the longitudinal direction and the end on one side in the width direction, and when viewed from the thickness direction, the angle formed by a second imaginary line passing through both the neck edge portion and the fitting edge portion and the central axis is 10° or more and 18° or less.[3] The neck portion has a first neck portion, a second neck portion, and a third neck portion, and the distance in the long axis direction between a connection tip portion, which is an end portion of the connection portion on one side in the long axis direction, and an end portion of the neck portion on the other side in the long axis direction is a first distance L1, the ratio of the distance between the connection tip portion and the first neck portion to the first distance in the long axis direction is 20%, the ratio of the distance between the connection tip portion and the second neck portion to the first distance in the long axis direction is 80%, and the ratio of the distance between the connection tip portion and the third neck portion to the first distance in the long axis direction is 100%, and the width direction dimension of the first neck portion is W1, the thickness direction dimension of the first neck portion is T1, the width direction dimension of the second neck portion is W2, the thickness direction dimension of the second neck portion is T2, the width direction dimension of the third neck portion is W3, and the thickness direction dimension of the third neck portion is T3, the total length is 130 mm. ４ ≦W1×T1 ３ ≦400mm ４ and 450 mm ４ ≦W2×T2 ３ ≦1200mm ４ And 2000mm ４ ≦W3×T3 ３ ≦5000mm ４[4] The toothbrush according to any one of [1] to [3], wherein each of the plurality of filaments has a first filament portion and a second filament portion, and when viewed in the width direction, the amount of reduction in the dimension of each of the plurality of filaments in the major axis direction per unit length in the thickness direction increases stepwise from the brush base portion toward one side in the thickness direction, the ratio of the distance between the end of the filament on one side in the thickness direction and the first filament portion to the dimension of the filament in the thickness direction is 15%, the second filament portion is a portion connected to the brush base, and the ratio of the area of ​​the cross section of the first filament portion perpendicular to the thickness direction to the area of ​​the cross section of the second filament portion perpendicular to the thickness direction is 20% or more and 30% or less. [5] A toothbrush as described in [4], wherein the ratio of the area of ​​the surface facing one side of the thickness direction of the brush base portion to the area of ​​the sum of the cross-sectional areas of the second filament portions of each of the multiple filaments perpendicular to the thickness direction is 25% or more and 35% or less. [6] The toothbrush of any one of [1] to [5], wherein when a pressure member is brought into contact with a plurality of filaments from one side in the thickness direction while the other end of the neck portion in the longitudinal direction is fixed, and the pressure member is moved to the other side in the thickness direction, the toothbrush satisfies the relationship RF1max-RF1min≦0.6 N / mm, where the reaction force that the pressure member receives from the plurality of filaments is defined as a first reaction force, the amount of fluctuation in the first reaction force when the position of the pressure member in the thickness direction changes by a first predetermined distance is defined as a first reaction force fluctuation rate, RF1max is defined as a first maximum value that is the maximum value of the first reaction force fluctuation rate within a range where the movement distance of the pressure member is 3.0 mm or less, RF1min is defined as a first minimum value that is the minimum value of the first reaction force fluctuation rate within a range where the movement distance of the pressure member is 3.0 mm or less, and RF1min is defined as the first predetermined distance. [7] The toothbrush described in [6], wherein the first average value RF1ave, which is the average value of the first reaction force fluctuation rate within a range in which the movement distance of the pressure member is 3.0 mm or less, is 0.5 N / mm or more and 1.0 N / mm or less.[8] When a pressure member is brought into contact with multiple filaments from one side in the thickness direction while supporting the brush base from the other side in the thickness direction, and the pressure member is moved to the other side in the thickness direction, the reaction force that the pressure member receives from the multiple filaments is defined as a second pressure, and RP is the second pressure fluctuation rate, which is the value obtained by dividing the amount of fluctuation in the second pressure when the position of the pressure member in the thickness direction changes by a second predetermined distance, and the second predetermined distance is defined as 0.1 mm, the second pressure fluctuation rate RP is 0.0 N / mm when the movement distance of the pressure member is within a range of 1.0 mm or less. ３ That's it, 10.0 x 10 －２ N / mm ３ The toothbrush according to any one of [1] to [7], which is as follows:

[0007] The present invention can provide a toothbrush that can improve interdental cleaning performance while preventing a decrease in toothbrush operability.

[0008] 6 is a front view of a toothbrush according to an embodiment; FIG. 7 is a side view of a toothbrush according to an embodiment; FIG. 8 is a front view of a handle body according to an embodiment; FIG. 9 is a side view of a handle body according to an embodiment; FIG. 10 is a front view of a brush unit according to an embodiment; FIG. 11 is a cross-sectional view of a brush unit according to an embodiment, taken along VI-VI in FIG. 5; FIG. 12 is a cross-sectional view of a portion of the brush unit according to an embodiment; FIG. 13 is a view of a portion of a toothbrush according to an embodiment; FIG. 14 is a front view of a portion of a toothbrush according to an embodiment; FIG. 15 is a side view of a first deflection test device; FIG. 16 is a view showing an example of a first reaction force according to an embodiment; FIG. 17 is a view showing a method for calculating a first reaction force variation rate according to an embodiment; FIG. 18 is a view showing an example of a first reaction force variation rate according to an embodiment; FIG. 19 is a side view of a second deflection test device; FIG. 19 is a view showing an example of a second pressure according to an embodiment; FIG. 19 is a view showing an example of a second pressure variation rate according to an embodiment; FIG. 19 is a view showing a first reaction force variation rate in a first deflection test; FIG. 19 is a view showing a second pressure variation rate in a second deflection test.

[0009] The toothbrush of the present invention will be described below with reference to the drawings, showing an example. Note that the dimensions of the drawings shown in the following description are merely examples, and the present invention is not necessarily limited to these. Appropriate changes can be made within the scope of the present invention.

[0010] In each drawing, an XYZ coordinate system is shown as a three-dimensional Cartesian coordinate system. In the XYZ coordinate system, the X-axis direction is the long axis direction. The long axis direction is the direction in which the toothbrush extends. The +X side is the tip side of the toothbrush, and the -X side is the rear end side of the toothbrush. In the following description, the tip side of the toothbrush will be simply referred to as the "tip side" or "one side in the long axis direction," and the rear end side of the toothbrush will be simply referred to as the "rear end side" or "other side in the long axis direction." The Z-axis direction is a direction that intersects with the X-axis direction and is the thickness direction of the toothbrush. In this embodiment, the Z-axis direction is perpendicular to the X-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" or "one side in the thickness direction," and the rear side of the toothbrush will be simply referred to as the "rear side" or "other side in the thickness direction." The Y-axis direction is the width direction of the toothbrush, and intersects both the X-axis direction and the Z-axis direction. In this embodiment, the Y-axis direction is perpendicular to both the X-axis direction and the Z-axis direction. The +Y side is one side of the width direction of the toothbrush, and the -Y side is the other side of the width direction of the toothbrush. In the following description, one side of the width direction of the toothbrush will be simply referred to as "one side of the width direction," and the other side of the width direction of the toothbrush will be simply referred to as "the other side of the width direction."

[0011] In the following description, the dimension of a member in the longitudinal direction may be simply referred to as "length." The dimension of a member in the width direction may be simply referred to as "width." The dimension of a member in the thickness direction may be simply referred to as "thickness." Viewing an object from the front side may be referred to as "front view," and the shape of an object viewed from the front side may be referred to as "front view shape." Viewing an object from the width direction may be referred to as "side view," and the shape of an object viewed from the width direction may be referred to as "side view shape."

[0012] FIG. 1 is a front view of the toothbrush 1 of this embodiment. FIG. 2 is a side view of the toothbrush 1 of this embodiment. As shown in FIG. 1, the toothbrush 1 includes a handle body 10 and a brush section 20. The handle body 10 and the brush section 20 are separate members. The handle body 10 and the brush section 20 are made of resin. The handle body 10 is rod-shaped and extends in the longitudinal direction. The brush section 20 is located on the tip side of the handle body 10, i.e., on one side (+X side) in the longitudinal direction.

[0013] Fig. 3 is a front view of the handle body 10 of this embodiment. Fig. 4 is a side view of the handle body 10 of this embodiment. As shown in Fig. 3, the handle body 10 has a rod-shaped handle main body 11 extending in the longitudinal direction, a fitting portion 15 that protrudes from the tip of the handle main body 11 toward the tip side, i.e., one side (+X side) in the longitudinal direction, and a fitting edge portion 15d. In the toothbrush 1 of this embodiment, the brush head 20 is attached to the handle body 10 by fitting the fitting portion 15 into a fitting hole 27 of the brush head 20, which will be described later. The length of the handle body 10 is, for example, 100 mm or more and 200 mm or less.

[0014] In this embodiment, the handle body 10 is formed of a hard resin. Examples of hard resins that form the handle body 10 include resins with a flexural modulus (JIS K7171) of 1500 MPa or more and 3000 MPa or less. Specific examples include polypropylene resin (PP), polybutylene terephthalate resin (PBT), polyacetal resin (POM), polyester resin (PCTA), polyethylene terephthalate copolymer (PETG), and high-density polyethylene (HDPE). Among these, polypropylene resin, which is a general-purpose resin, is preferred in terms of manufacturing costs, and polybutylene terephthalate resin and polyacetal resin are preferred in terms of strength.

[0015] As shown in FIG. 3 , the handle body 11 of this embodiment has a front view shape that gradually narrows from the tip end toward the rear end until it reaches the first boundary 13a. After reaching the first boundary 13a, the width gradually widens until it reaches the second boundary 13b. The width then gradually narrows, then widens, and then narrows again. The rear end of the handle body 11 has a substantially semicircular shape in front view. Note that, if the handle body 11 has a front view shape that gradually narrows from the tip end toward the rear end and then extends in the longitudinal direction at a constant width, the first boundary 13a is the tip of the portion that extends in the longitudinal direction at a constant width. The central axis J shown in FIG. 3 is a straight line extending through the center of the handle body 10 toward the longitudinal direction when viewed from the thickness direction. The front view shape of the handle body 11 is plane-symmetrical, with a plane that passes through the central axis J and extends in a direction perpendicular to the width direction as a plane of symmetry.

[0016] As shown in FIG. 4 , the handle body 11 of this embodiment has a side view that gradually decreases in thickness from the tip to the rear end, then curves to a first boundary 13a, gradually increasing in thickness, and then reaches a second boundary 13b. At the second boundary 13b, the handle body 11 continues to maintain a substantially constant thickness, then continues to decrease in thickness. The side view of the rear end of the handle body 11 is generally semicircular. More specifically, the second boundary 13b is a portion where a first upper edge 11a, whose front (+Z side) edge curves upward and downward as it extends from the tip to the rear end, joins with a second upper edge 11b, whose front edge curves downward as it extends from the tip to the rear end. Although not shown, the centers of curvature of the first upper edge 11a and the second upper edge 11b are both located above the handle body 11. The second boundary portion 13b is a portion of the handle body 11 where the apex of a convex shape that protrudes toward the front side is formed.

[0017] If the handle body 11 does not have a convex apex or if the convex apex is not visible, the second boundary 13b is the portion where the center of curvature of the edge on the front side (+Z side) of the handle body 11 changes. If the portion where the center of curvature of the edge on the front side of the handle body 11 changes cannot be identified, the second boundary 13b is the portion where the hard resin and the soft resin come into contact in the longitudinal direction. Furthermore, if the portion where the hard resin and the soft resin come into contact in the longitudinal direction cannot be identified, the second boundary 13b is the portion 73 mm rearward from the tip of the head portion 5 described below. In this embodiment, the tip of the head portion 5 is the tip of the brush portion 20.

[0018] In the present invention, the shape of the handle body 11 is not limited to the shape of this embodiment and can be set appropriately taking into consideration strength, operability, design, etc. The dimensions of the handle body 11 are not particularly limited and can be set appropriately. As shown in Figure 3, the handle body 11 has a grip portion 12, a neck portion 13, a connecting portion 14, a neck edge portion 13d, and a connecting edge portion 14d.

[0019] The grip portion 12 is a portion of the handle body 11 that is closer to the rear end than the second boundary portion 13b. The grip portion 12 is rod-shaped and extends in the longitudinal direction. As shown in FIGS. 1 and 2 , a finger rest 17 is provided on the outer surface of the grip portion 12. The finger rest 17 is made of a soft resin. Various elastomers, such as polyurethane-based and styrene-based elastomers, can be used as the soft resin for forming the finger rest 17. When using the toothbrush 1, the user can improve the grip of the toothbrush 1 by holding the grip portion 12 and placing their fingers on the finger rest 17.

[0020] As shown in Figure 3, the neck portion 13 is the portion of the handle body 11 between the first boundary portion 13a and the second boundary portion 13b. The neck portion 13 is rod-shaped and extends in the longitudinal direction. In this embodiment, the second boundary portion 13b is the boundary between the neck portion 13 and the grip portion 12. The shape of the neck portion 13 will be described in detail later.

[0021] The connecting portion 14 is a portion of the handle body 11 that is closer to the tip than the first boundary portion 13a. The first boundary portion 13a is the boundary between the connecting portion 14 and the neck portion 13. The connecting portion 14 protrudes from the neck portion 13 toward the tip, i.e., toward one side (+X side) in the longitudinal direction. The connecting portion 14 connects the neck portion 13 and the mating portion 15. The width of the connecting portion 14 is widest at the tip, gradually narrows toward the rear end, and is narrowest at the rear end. As shown in FIG. 4 , the thickness of the connecting portion 14 is thickest at the tip, gradually thins toward the rear end, and is thinnest at the rear end. The connecting portion 14 has a first opposing surface 14b. The first opposing surface 14b is the outer surface of the connecting portion 14 that faces the tip.

[0022] 3, the connection edge 14d is a part of the connection portion 14. The connection edge 14d is the tip of the connection portion 14, i.e., the end on one side (+X side) in the longitudinal direction and the end on one side (+Y side) in the width direction. In a front view, the connection edge 14d is the portion of the connection portion 14 that is located closest to one side in the width direction. The connection edge 14d is located on one side in the width direction of the first boundary portion 13a.

[0023] As shown in FIG. 2, when the brush unit 20 is attached to the handle body 10, the fitting portion 15 is located inside the brush unit 20. As shown in FIGS. 3 and 4, the fitting portion 15 protrudes distally from the first opposing surface 14b of the connecting portion 14. As shown in FIG. 3, the fitting portion 15 is provided with a pair of recesses 15a, 15b. One recess 15a is recessed from a surface facing one widthwise side (+Y side) of the fitting portion 15 toward the other widthwise side (-Y side). The other recess 15b is recessed from a surface facing the other widthwise side of the fitting portion 15 toward one widthwise side. Each of the pair of recesses 15a, 15b is substantially semicircular in front view.

[0024] The fitting edge 15d is the rear end of the fitting portion 15, i.e., the end on the other side (-X side) in the longitudinal direction and the end on one side (+Y side) in the width direction. The fitting edge 15d is located on one side in the width direction of the first boundary portion 13a. The fitting edge 15d is located on the other side in the width direction (-Y side) of the connecting edge 14d. Note that even in a configuration in which a through hole is present in the fitting portion 15, the fitting portion 15 still exists, and in this case, the hard resin portion covered with the soft resin is the fitting portion.

[0025] FIG. 5 is a front view showing the brush head 20 of this embodiment. FIG. 6 is a cross-sectional view showing the brush head 20 of this embodiment, taken along line VI-VI in FIG. 5 . FIG. 7 is a cross-sectional view showing a portion of the brush head 20 of this embodiment. The brush head 20 is formed of a soft resin. As shown in FIGS. 5 and 6 , the brush head 20 has a brush base 21 and a plurality of filaments 30 molded integrally with the brush base 21. In this embodiment, the brush head 20 is molded by insert molding using a handle body 10 made of a hard resin as an insert member. In other words, the toothbrush 1 of this embodiment is an integrally molded toothbrush in which the brush head 20 and the handle body 10 are molded integrally. The toothbrush 1 of this embodiment is an integrally molded toothbrush in which the filaments 30 are made of a soft resin.

[0026] As shown in Fig. 5, the shape of the brush base 21 in this embodiment when viewed from the front is curved so that its width gradually increases from the tip to the rear. The shape of the tip of the brush base 21 when viewed from the front is approximately semicircular. As shown in Fig. 6, the shape of the brush base 21 in this embodiment when viewed from the side is so that its thickness gradually increases from the tip to the rear. More specifically, the surface of the brush base 21 facing the rear (-Z side) is positioned closer to the rear as it moves from the tip to the rear. The upper surface 21a, which is the surface of the brush base 21 facing the front (+Z side), is a flat surface that extends in a direction perpendicular to the thickness direction.

[0027] The outer surface of the brush base 21 facing the rear end is the second opposing surface 21d. Although not shown, the second opposing surface 21d has a substantially rectangular shape when viewed in the longitudinal direction. As shown in Fig. 1, when the brush head 20 is attached to the handle body 10, the second opposing surface 21d faces the first opposing surface 14b of the handle body 10 in the longitudinal direction. In this embodiment, the second opposing surface 21d contacts the first opposing surface 14b in the longitudinal direction.

[0028] As shown in Fig. 6, the brush base 21 has a fitting hole 27 recessed from the second opposing surface 21d toward the tip end. As shown in Fig. 2, a fitting portion 15 is disposed inside the fitting hole 27. As shown in Fig. 6, the inner surface of the fitting hole 27 facing the rear side (-Z side) is a flat surface extending in a direction perpendicular to the thickness direction. The inner surface of the fitting hole 27 facing the front side (+Z side) is positioned closer to the rear side as it moves from the tip end to the rear end.

[0029] As shown in Fig. 5, the fitting hole 27 is provided with a pair of protrusions 27a, 27b. One of the protrusions 27a protrudes from the surface of the fitting hole 27 facing the other widthwise side (-Y side) toward the other widthwise side. The other protrusion 27b protrudes from the surface of the fitting hole 27 facing the other widthwise side (+Y side) toward the one widthwise side. When viewed in the thickness direction, each of the pair of protrusions 27a, 27b has a substantially semicircular shape. Each of the pair of protrusions 27a, 27b is fitted into each of the pair of recesses 15a, 15b.

[0030] As shown in FIG. 6 , each of the multiple filaments 30 protrudes from the upper surface 21 a of the brush base 21 toward the front side, i.e., toward one side in the thickness direction (+Z side). Each filament 30 is formed of a soft resin. As shown in FIG. 5 , multiple rows of multiple filaments 30 aligned along the width direction are arranged in the longitudinal direction on the upper surface 21 a. In the following description, the root of the filament 30 is the end of the filament 30 on the rear side, which is the portion connected to the brush base 21. The tip of the filament 30 is the end of the filament 30 on the front side. The shape and other details of the filament 30 will be described in detail later.

[0031] Although various elastomers can be used as the soft resin that constitutes the brush head 20, polyurethane is preferable. Compared to other elastomers such as styrene-based or polyester-based elastomers, polyurethane has a higher tensile strength, ensuring mechanical strength even when the brush head 20 is thin. This helps prevent breakage during use of the toothbrush 1.

[0032] Furthermore, compared to the other elastomers mentioned above, polyurethane has a wider range of hardness options, allowing for selection of resin hardness taking into account operability (e.g., bending of the tip of the brush part 20) depending on the thickness of the brush part 20. The hardness of polyurethane is preferably a Shore hardness of A90 or more and A100 or less, or a Shore hardness of D40 or more and D70 or less. If the polyurethane has a hardness softer than Shore 90A, it is prone to deformation when formed with a thin wall, weakening the fit and making the brush part 20 more likely to fall off during use of the toothbrush 1. If the polyurethane has a hardness harder than Shore 70D, and the back surface of the brush base part 21 is inclined, there is a risk of pain when the tip of the brush base part 21 comes into contact with the oral cavity. By setting the hardness of the polyurethane to Shore 90A or more and 70D or less, it is possible to prevent the brush part 20 from falling off when the toothbrush 1 is in use, and also to prevent pain when the tip of the brush base part 21 comes into contact with the oral cavity.

[0033] The polyurethane contains 0.01 wt% (mass%) or more and 1.0 wt% (mass%) or less of saturated / unsaturated hydrocarbons of C10 or more, 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 glycerin, and silicone, or a combination thereof, which function as a lubricant and mold release agent. Furthermore, from the viewpoint of ensuring water resistance and antibacterial properties, it is preferable to use ether-based polyurethane as the polyurethane.

[0034] 1 and 2 , the toothbrush 1 of this embodiment includes a head portion 5 and a head shaft portion 6. In this embodiment, the connecting portion 14, the fitting portion 15, and the brush portion 20 constitute the head portion 5. The head portion 5 is the portion of the toothbrush 1 that is closer to the tip than the first boundary portion 13a. When the toothbrush 1 is in use, the head portion 5 is located within the oral cavity and is the portion that cleans the oral cavity.

[0035] The maximum width of the head portion 5 is preferably 11 mm or less, which can improve the operability of the head portion 5 in the oral cavity, thereby improving the cleaning performance in the oral cavity.

[0036] In this embodiment, the connecting portion 14, the fitting portion 15, and the brush base portion 21 constitute the head shaft portion 6. The head shaft portion 6 is a part of the head portion 5. The head shaft portion 6 is the portion of the head portion 5 excluding the multiple filaments 30. The head shaft portion 6 is the portion of the handle body 10 that is closer to the tip than the first boundary portion 13a.

[0037] Fig. 8 is a diagram showing a portion of the toothbrush 1 of this embodiment. More specifically, Fig. 8(a) is a side view showing a portion of the toothbrush 1 of this embodiment. Fig. 8(b) is a side view showing a portion of the handle body 10 of this embodiment. Fig. 8(c) is a front view showing a portion of the handle body 10 of this embodiment. In this embodiment, the maximum thickness Th of the head shaft 6 shown in Fig. 8(b), i.e., the maximum dimension in the thickness direction of the head shaft 6, is 3.0 mm or more and 4.5 mm or less.

[0038] Next, the shape of the neck portion 13 of this embodiment will be described in detail. As described above, the neck portion 13 is the portion of the handle body 10 between the first boundary 13a and the second boundary 13b. As shown in FIG. 8(c), the width of the neck portion 13 of this embodiment gradually increases from the first boundary 13a to the second boundary 13b. The width of the neck portion 13 is narrowest at the first boundary 13a and widest at the second boundary 13b. As shown in FIG. 8(b), the thickness of the neck portion 13 of this embodiment extends from the first boundary 13a to the second boundary 13b at a constant thickness toward the rear end, then gradually increases in a linear manner, and then gradually increases in a curved manner toward the rear end. The thickness of the neck portion 13 is thinnest at the first boundary 13a and thickest at the second boundary 13b.

[0039] FIG. 9 is a front view showing a portion of the toothbrush 1 of this embodiment. As shown in FIG. 9 , the neck edge 13d is a part of the neck portion 13. The neck edge 13d is the end on one widthwise side (+Y side) of the first boundary 13a. As described above, the first boundary 13a is the narrowest part of the neck portion 13. Therefore, the neck edge 13d is the end on one widthwise side of the part of the neck portion 13 with the smallest widthwise dimension. In this embodiment, the width Wa of the first boundary 13a, i.e., the smallest widthwise dimension of the neck portion 13, is 3.0 mm or more and 4.5 mm or less. The first imaginary line V1 shown in FIG. 9 is a straight line passing through both the connecting edge 14d and the neck edge 13d when viewed from the thickness direction. In this embodiment, the first angle θ1, which is the angle between the first imaginary line V1 and the central axis J when viewed from the thickness direction, is 17° or more and 28° or less.

[0040] In an integrally molded toothbrush in which the filaments 30 are formed from a soft resin, if the rigidity of the head shaft 6 and neck portion 13 is too high, the head shaft 6 and neck portion 13 are less likely to flex when a brushing load in the thickness direction is applied to the brush head 20 during use of the toothbrush 1. Therefore, the flexing of the head shaft 6 and neck portion 13 makes it difficult for the brush head 20 to absorb the brushing load, and stress is concentrated on each filament 30. As a result, if the flexing of each filament 30 becomes too great during use of the toothbrush 1, it becomes difficult for each filament 30 to penetrate deep between teeth. This makes it difficult for each filament 30 to remove plaque between teeth, resulting in reduced interdental cleaning performance. Furthermore, if the rigidity of the head shaft 6 and neck portion 13 is too low, the flexing of the head shaft 6 and neck portion 13 becomes too great during use of the toothbrush 1. This reduces the maneuverability of the head head 5 within the oral cavity. This reduces the maneuverability of the toothbrush 1. Furthermore, the movement of the tips of the filaments 30 is difficult to coordinate with the movement of the user's hand, resulting in reduced interdental cleaning performance. In contrast, according to this embodiment, the maximum thickness Th of the head shaft 6, i.e., the maximum dimension in the thickness direction of the head shaft 6, is 3.0 mm or more and 4.5 mm or less. This prevents the head shaft 6 from becoming too rigid and also prevents the head shaft 6 from becoming too rigid. This allows the head shaft 6 to flex appropriately during use of the toothbrush 1, thereby preventing stress concentration on the filaments 30. Therefore, the portions of the toothbrush 1 extending from the filaments 30 to the head shaft 6 flex in coordination. This prevents the filaments 30 from flexing too much, thereby improving interdental cleaning performance. Furthermore, preventing the head shaft 6 from flexing too much prevents a decrease in operability of the toothbrush 1. Furthermore, the movement of the tips of the filaments 30 is easily coordinated with the movement of the user's hand, thereby more effectively improving interdental cleaning performance.

[0041] Furthermore, according to this embodiment, the width Wa of the first boundary 13a, i.e., the minimum widthwise dimension of the neck portion 13, is 3.0 mm or more and 4.5 mm or less. This prevents the neck portion 13 from becoming too rigid and also prevents the neck portion 13 from becoming too rigid. This allows the neck portion 13 to flex appropriately during use of the toothbrush 1, thereby preventing stress concentration on each filament 30. Therefore, the portions of the toothbrush 1 extending from each filament 30 to the neck portion 13 flex in unison. This prevents the filaments 30 from flexing too much, thereby more effectively improving interdental cleaning performance. Furthermore, this prevents the neck portion 13 from flexing too much. This more effectively prevents a decrease in operability of the toothbrush 1, and also more effectively improves interdental cleaning performance because the movement of the tip of each filament 30 is more easily coordinated with the movement of the user's hand.

[0042] Furthermore, according to this embodiment, the connection edge 14d is the tip side of the connection portion 14, i.e., the end on one side (+X side) in the longitudinal direction and the end on one side (+Y side) in the width direction, and the neck edge 13d is the end on one side in the width direction of the neck portion 13 where the width dimension is smallest. When viewed from the thickness direction, the first angle θ1 formed by the first imaginary line V1 passing through both the connection edge 14d and the neck edge 13d and the central axis J extending through the center of the handle body 10 in the longitudinal direction is 17° or more and 28° or less. If the first angle θ1 is less than 17°, the width of the neck portion 13 becomes too large relative to the width of the connection portion 14, resulting in excessive rigidity of the neck portion 13. As a result, when the toothbrush 1 is used, the neck portion 13 flexes too little, resulting in excessive flexure of each filament 30. This makes it difficult for each filament 30 to penetrate deep between teeth, thereby reducing interdental cleaning performance. Furthermore, if the first angle θ1 is greater than 28°, the width of the neck portion 13 becomes too small relative to the width of the connecting portion 14, resulting in too little rigidity of the neck portion 13. This results in excessive bending of the neck portion 13 and the connecting portion 14, reducing the maneuverability of the head portion 5 in the oral cavity and the maneuverability of the toothbrush 1. In contrast, according to the present embodiment, the first angle θ1 is greater than or equal to 17° and less than or equal to 28°, so that the neck portion 13 and the connecting portion 14 bend moderately and more uniformly in the longitudinal direction during use of the toothbrush 1. This more effectively prevents stress from concentrating on each filament 30 and more effectively prevents excessive bending of the neck portion 13 and the connecting portion 14. Therefore, since excessive bending of each filament 30 can be more effectively prevented, the interdental cleaning performance can be more effectively improved and the maneuverability of the toothbrush 1 can be more effectively prevented from decreasing. In this embodiment, the term "a member bends uniformly in the longitudinal direction" means that the member bends over the entire longitudinal direction, without bending locally in only a portion of the member in the longitudinal direction.

[0043] The first angle θ1 is preferably equal to or greater than 18° and equal to or less than 26°. This can more preferably improve the interdental cleaning performance and more preferably prevent a decrease in the operability of the toothbrush 1. Furthermore, the first angle θ1 is more preferably equal to or greater than 20° and equal to or less than 26°. This can more preferably improve the interdental cleaning performance and more preferably prevent a decrease in the operability of the toothbrush 1.

[0044] 8(c), the width Wb of the tip of the connecting portion 14 and the width Wa of the first boundary portion 13a, i.e., the minimum width of the neck portion 13, preferably satisfy the relationship 2.0≦Wb / Wa≦2.8. By satisfying this relationship, the rigidity of the neck portion 13 and the connecting portion 14 can be prevented from becoming too large or too small, allowing the neck portion 13 and the connecting portion 14 to bend more appropriately when the toothbrush 1 is in use. This can thereby more appropriately improve the interdental cleaning performance and more appropriately prevent a decrease in the operability of the toothbrush 1.

[0045] The width Wb of the tip of the connecting portion 14 is preferably 8 mm or more and 14 mm or less. This allows the connecting portion 14 to flex more appropriately when the toothbrush 1 is in use. This can more appropriately improve the interdental cleaning performance of the toothbrush 1 and more appropriately prevent a decrease in the operability of the toothbrush 1.

[0046] The length Lc of the connecting portion 14 shown in Figure 8(c) is preferably 5 mm or more and 10 mm or less. This allows the connecting portion 14 to bend more appropriately when the toothbrush 1 is in use. This can more appropriately improve the interdental cleaning performance of the toothbrush 1 and more appropriately prevent a decrease in the operability of the toothbrush 1.

[0047] The second imaginary line V2 shown in FIG. 3 is a straight line passing through both the neck edge 13d and the mating edge 15d when viewed from the thickness direction. The second angle θ2 between the second imaginary line V2 and the central axis J is greater than or equal to 10° and less than or equal to 18°. If the second angle θ2 is less than 10°, the head shaft 6 becomes too wide, resulting in excessive rigidity. As a result, the head shaft 6 is less flexible during use of the toothbrush 1, resulting in excessive bending of the filaments 30. This makes it difficult for the filaments 30 to penetrate deep between the teeth, resulting in poor interdental cleaning performance. Furthermore, if the second angle θ2 is greater than 18°, the head shaft 6 becomes too narrow, resulting in excessive rigidity. This excessive bending of the head shaft 6 reduces the maneuverability of the head 5 in the oral cavity and the maneuverability of the toothbrush 1. In contrast, according to the present embodiment, the second angle θ2 is equal to or greater than 10° and equal to or less than 18°, so that the head shaft 6 bends moderately and uniformly in the longitudinal direction when the toothbrush 1 is in use. This more effectively prevents the filaments 30 from bending too much, and more effectively prevents the head shaft 6 from bending too much. This more effectively prevents a decrease in the operability of the toothbrush 1, and more effectively improves the interdental cleaning performance because the movement of the tip of each filament 30 is more easily linked to the movement of the user's hand.

[0048] It is preferable that the second angle θ2 be equal to or greater than 11° and equal to or less than 16°. By setting the second angle θ2 within this range, it is possible to more effectively prevent the rigidity of the head shaft 6 from becoming too large or too small. This makes it possible to more effectively prevent the deflection of each filament 30 from becoming too large, and also makes it possible to more effectively prevent the deflection of the head shaft 6 from becoming too large. Therefore, it is possible to more effectively improve the interdental cleaning performance and more effectively prevent the operability of the toothbrush 1 from decreasing. Furthermore, it is more preferable that the second angle θ2 be equal to or greater than 12° and equal to or less than 16°. By setting the second angle θ2 within this range, it is possible to more effectively prevent the rigidity of the head shaft 6 from becoming too large. Therefore, it is possible to more effectively prevent the deflection of the head shaft 6 from becoming too small, and therefore makes it possible to more effectively prevent the deflection of each filament 30 from becoming too large. This makes it possible to more effectively improve the interdental cleaning performance.

[0049] 8(c), the width Wm of the rear end of the fitting portion 15 and the width Wa of the first boundary portion 13a, i.e., the minimum width of the neck portion 13, preferably satisfy the relationship 1.5≦Wm / Wa≦3.5. By satisfying this relationship, the rigidity of the head shaft 6 can be prevented from becoming too large or too small, so that the head shaft 6 bends more appropriately and more uniformly in the longitudinal direction during use of the toothbrush 1. This improves interdental cleaning performance and more effectively prevents a decrease in the operability of the toothbrush 1.

[0050] The width Wm of the rear end of the fitting portion 15 is preferably 6 mm or more and 12 mm or less. This allows the head shaft 6 to bend more appropriately and more uniformly in the longitudinal direction when the toothbrush 1 is in use. This can more appropriately improve the interdental cleaning performance and more appropriately prevent a decrease in the operability of the toothbrush 1.

[0051] As shown in FIG. 9 , the head portion 5 has a first head portion 5a and a head edge portion 5d. The first head portion 5a is the portion of the head portion 5 where the width of the head portion 5 is greatest. In this embodiment, the first head portion 5a is located between the center of the brush portion 20 in the longitudinal direction and the rear end of the brush portion 20. Note that, when the head portion 5 has a shape that extends in the longitudinal direction at its widest point, the rear end of the portion that extends in the longitudinal direction at its widest point is referred to as the first head portion 5a. The head edge portion 5d is an end portion on one side (+Y side) in the width direction of the first head portion 5a. In a front view, the head edge portion 5d is located on one side in the width direction of the first boundary portion 13a.

[0052] The third imaginary line V3 shown in Figure 9 is a straight line that passes through both the neck edge 13d and the head edge 5d when viewed from the thickness direction. The third angle θ3 between the third imaginary line V3 and the central axis J is preferably 15° or greater and 25° or less. Setting the third angle θ3 within this range effectively prevents the rigidity of the head shaft 6 from becoming too large or too small. This allows the head shaft 6 to bend more appropriately and more uniformly in the longitudinal direction during use of the toothbrush 1. This effectively improves interdental cleaning performance and effectively prevents a decrease in the operability of the toothbrush 1.

[0053] 9, the width Wh of the first head portion 5a (i.e., the maximum width of the head portion 5) and the width Wa of the first boundary portion 13a (i.e., the minimum width of the neck portion 13) preferably satisfy the relationship 2.5≦Wh / Wa≦4.5. By satisfying this relationship, the head shaft 6 bends more appropriately and more uniformly in the longitudinal direction during use of the toothbrush 1. This can more appropriately improve interdental cleaning performance and more appropriately prevent a decrease in the operability of the toothbrush 1.

[0054] The width Wh of the first head portion 5a, i.e., the maximum width of the head portion 5, is preferably 10 mm or more and 16 mm or less. This allows the head shaft 6 to bend more appropriately and more uniformly in the longitudinal direction when the toothbrush 1 is in use. This can more appropriately improve the interdental cleaning performance and more appropriately prevent a decrease in the operability of the toothbrush 1.

[0055] 8, the neck portion 13 has a first neck portion P1, a second neck portion P2, a third neck portion P3, a fourth neck portion P4, a fifth neck portion P5, a seventh neck portion P7, an eighth neck portion P8, a ninth neck portion P9, and a tenth neck portion P10. Each of the first neck portion P1, the second neck portion P2, the third neck portion P3, the fourth neck portion P4, the fifth neck portion P5, the seventh neck portion P7, the eighth neck portion P8, the ninth neck portion P9, and the tenth neck portion P10 is a part of the neck portion 13.

[0056] In the longitudinal direction, the first neck portion P1 is located between the first boundary portion 13a and the second boundary portion 13b. As shown in FIG. 8 , the first distance L1 is the distance in the longitudinal direction between the connection tip portion 14a, which is the tip of the connection portion 14, i.e., the end portion on one side (+X side) in the longitudinal direction, and the second boundary portion 13b, i.e., the end portion on the other side (-X side) in the longitudinal direction of the neck portion 13. In the longitudinal direction, the ratio of the distance L2 between the connection tip portion 14a and the first neck portion P1 to the first distance L1 is 20%. The first neck portion P1 is the portion on the tip side of the neck portion 13. The width W1 of the first neck portion P1 is wider than the width Wa of the first boundary portion.

[0057] In the longitudinal direction, the second neck portion P2 is located between the first neck portion P1 and the second boundary portion 13b. In the longitudinal direction, the ratio of the distance L3 between the connection tip portion 14a and the second neck portion P2 to the first distance L1 is 80%. The second neck portion P2 is the rear end portion of the neck portion 13. The width W2 of the second neck portion P2 is wider than the width W1 of the first neck portion P1. The thickness T2 of the second neck portion P2 is thicker than the thickness T1 of the first neck portion P1.

[0058] In the longitudinal direction, the third neck portion P3 is located closer to the rear end than the second neck portion P2. In this embodiment, the third neck portion P3 is the second boundary portion 13b. That is, the third neck portion P3 is the rear end of the neck portion 13. In the longitudinal direction, the ratio of the distance L4 between the connection tip portion 14a and the third neck portion P3 to the first distance L1 is 100%. The width W3 of the third neck portion P3 is wider than the width W2 of the second neck portion P2. The thickness T3 of the third neck portion P3 is thicker than the thickness T2 of the second neck portion P2.

[0059] According to this embodiment, the width W1 and thickness T1 of the first neck portion P1 are 130 mm. ４ ≦W1×T1 ３ ≦400mm ４ The width W2 of the second neck portion P2 and the thickness T2 of the second neck portion P2 are 450 mm. ４ ≦W2×T2 ３ ≦1200mm ４ The width W3 and thickness T3 of the third neck portion P3 are 2000 mm. ４ ≦W3×T3 ３ ≦5000mm ４ The relationship W1×T1 is satisfied. ３ is 130 mm ４ If the width W2 is smaller than the width T2, the rigidity of the tip end portion of the neck portion 13, including the first neck portion P1, becomes too low, causing the tip end portion of the neck portion 13 to bend significantly locally when the toothbrush 1 is in use. This reduces the operability of the head portion 5 in the oral cavity. This also reduces the operability of the toothbrush 1. Furthermore, the movement of the tip end of each filament 30 is less likely to be synchronized with the movement of the user's hand, resulting in reduced interdental cleaning performance. ３ is 450 mm ４ If W3×T3 is smaller than this, the rigidity of the rear end portion of the neck portion 13, including the second neck portion P2, becomes too low, causing the rear end portion of the neck portion 13 to bend significantly locally when the toothbrush 1 is in use. This reduces the operability of the toothbrush 1 and the interdental cleaning performance. ３ is 2000 mm ４If the width W1 is smaller than W1×T1, the rigidity of the rear end of the neck portion 13 becomes too small, and the rear end of the neck portion 13 locally bends significantly when the toothbrush 1 is in use. This reduces the operability of the toothbrush 1 and the interdental cleaning performance. ３ is 400 mm ４ If W2×T2 is larger than this, the rigidity of the distal end portion of the neck portion 13, including the first neck portion P1, becomes too high. As a result, when the toothbrush 1 is in use, the distal end portion of the neck portion 13 becomes too small, and the bending of each filament 30 becomes too large. Therefore, the cleaning performance between teeth deteriorates. ３ is 1200 mm ４ If W3×T3 is larger than this, the rigidity of the rear end portion of the neck portion 13, including the second neck portion P2, becomes too high. As a result, when the toothbrush 1 is in use, the rear end portion of the neck portion 13 becomes too small, and the bending of each filament 30 becomes too large. Therefore, the cleaning performance between teeth deteriorates. ３ is 5000 mm ４ If the value is greater than 1 / 2, the stiffness of the rear end of the neck portion 13 becomes too great. As a result, when the toothbrush 1 is in use, the bending of the rear end of the neck portion 13 becomes too small, and the bending of each filament 30 becomes too great. Therefore, the cleaning performance between teeth deteriorates.

[0060] In contrast, in this embodiment, the above relationship is satisfied, and therefore, large localized bending of a portion of the neck portion 13 can be prevented when the toothbrush 1 is in use. As a result, when the toothbrush 1 is in use, the neck portion 13 bends more appropriately and more uniformly in the longitudinal direction, and the bending of each filament 30 can be prevented from becoming too large. In other words, the filaments 30 can bend in a coordinated manner from the rear end of the neck portion 13. Therefore, a decrease in operability of the toothbrush 1 can be more effectively prevented, and the movement of the tip of each filament 30 can be more effectively coordinated with the movement of the user's hand, thereby more effectively improving interdental cleaning performance.

[0061] The width W1 of the first neck portion P1 is preferably 3.5 mm or more and 4.5 mm or less, and the thickness T1 of the first neck portion P1 is preferably 3.5 mm or more and 4.5 mm or less. This allows the distal end portion of the neck portion 13 to bend more appropriately and more uniformly in the longitudinal direction during use of the toothbrush 1. This can more appropriately improve interdental cleaning performance and more appropriately prevent a decrease in the operability of the toothbrush 1.

[0062] The width W2 of the second neck portion P2 is preferably 4.5 mm or more and 5.5 mm or less, and the thickness T2 of the second neck portion P2 is preferably 4.5 mm or more and 5.5 mm or less. This allows the rear end portion of the neck portion 13 to bend more appropriately and more uniformly in the longitudinal direction during use of the toothbrush 1. This can more appropriately improve interdental cleaning performance and more appropriately prevent a decrease in the operability of the toothbrush 1.

[0063] The width W3 of the third neck portion P3 is preferably 6.0 mm or more and 10.0 mm or less, and the thickness T3 of the third neck portion P3 is preferably 6.0 mm or more and 10.0 mm or less. This allows the rear end of the neck portion 13 to bend more appropriately when the toothbrush 1 is in use. This can more appropriately improve the interdental cleaning performance and more appropriately prevent a decrease in the operability of the toothbrush 1.

[0064] In the longitudinal direction, the fourth neck portion P4 is located between the first neck portion P1 and the second neck portion P2. In the longitudinal direction, the ratio of the distance between the connection tip portion 14a and the fourth neck portion P4 to the first distance L1 is 40%. The fourth neck portion P4 is the distal portion of the neck portion 13. The width W4 of the fourth neck portion P4 is preferably 3.5 mm or more and 4.5 mm or less, and the thickness T4 of the fourth neck portion P4 is preferably 3.5 mm or more and 4.5 mm or less. This allows the distal portion of the neck portion 13 to flex more appropriately and more uniformly in the longitudinal direction during use of the toothbrush 1. This can more appropriately improve interdental cleaning performance and more appropriately prevent a decrease in operability of the toothbrush 1.

[0065] In the longitudinal direction, the fifth neck portion P5 is located between the fourth neck portion P4 and the second neck portion P2. In the longitudinal direction, the ratio of the distance between the connection tip portion 14a and the fifth neck portion P5 to the first distance L1 is 60%. The fifth neck portion P5 is the rear end portion of the neck portion 13. The width W5 of the fifth neck portion P5 is preferably 4.0 mm or more and 5.0 mm or less, and the thickness T5 of the fifth neck portion P5 is preferably 4.0 mm or more and 5.0 mm or less. This allows the rear end portion of the neck portion 13 to bend more appropriately and more uniformly in the longitudinal direction during use of the toothbrush 1. This can more appropriately improve interdental cleaning performance and more appropriately prevent a decrease in operability of the toothbrush 1.

[0066] The seventh neck portion P7 is located closer to the rear end than the first boundary portion 13a. The distance in the longitudinal direction between the first boundary portion 13a and the seventh neck portion P7 is the same as the length Lm of the fitting portion 15. The thickness T7 of the seventh neck portion P7 is preferably 5.0 mm or less. This prevents the neck portion 13 from becoming too rigid, allowing the neck portion 13 to bend appropriately when the toothbrush 1 is in use. This prevents the filaments 30 from bending too much, thereby more effectively improving interdental cleaning performance.

[0067] The thickness Ta of the first boundary portion 13a (which is the minimum thickness of the neck portion 13), the thickness T7 of the seventh neck portion P7, and the maximum thickness Tm of the fitting portion 15 preferably satisfy the relationship (T7 - Ta) / Tm ≦ 0.6. In the following description, (T7 - Ta) / Tm may be referred to as the "first ratio." When the first ratio is 0.6 or less, it is easy to reduce the difference between the thickness Ta of the first boundary portion 13a and the thickness T7 of the seventh neck portion P7. This prevents the thickness T7 of the seventh neck portion P7 from becoming too thick. This prevents the stiffness of the portion of the neck portion 13 between the first boundary portion 13a and the seventh neck portion P7 from becoming too large relative to the stiffness of the head shaft 6. Therefore, during use of the toothbrush 1, the head shaft 6 and the neck portion 13 flex more appropriately and more uniformly in the longitudinal direction. This improves interdental cleaning performance and prevents the toothbrush 1 from becoming less maneuverable.

[0068] The eighth neck portion P8 is located closer to the rear end than the seventh neck portion P7. The longitudinal distance between the first boundary portion 13a and the eighth neck portion P8 is twice the length Lm of the fitting portion 15. The thickness T8 of the eighth neck portion P8 is preferably 8.0 mm or less. This prevents the neck portion 13 from becoming too rigid, allowing the neck portion 13 to bend appropriately when the toothbrush 1 is in use. This prevents the filaments 30 from bending too much, thereby more effectively improving interdental cleaning performance.

[0069] The thickness Ta of the first boundary portion 13a, the thickness T8 of the eighth neck portion P8, and the maximum thickness Tm of the fitting portion 15 preferably satisfy the relationship (T8 - Ta) / Tm ≦ 1.5. In the following description, (T8 - Ta) / Tm may be referred to as the "second ratio." When the second ratio is 1.5 or less, it is easy to reduce the difference between the thickness Ta of the first boundary portion 13a and the thickness T8 of the eighth neck portion P8. This prevents the thickness T8 of the eighth neck portion P8 from becoming too thick. This prevents the stiffness of the portion of the neck portion 13 between the first boundary portion 13a and the eighth neck portion P8 from becoming too large relative to the stiffness of the head shaft 6. This allows the head shaft 6 and the neck portion 13 to bend more appropriately and more uniformly in the longitudinal direction. This improves interdental cleaning performance and prevents the toothbrush 1 from becoming less maneuverable.

[0070] It is preferable that the thickness Ta of the first boundary portion 13a and the maximum thickness Tm of the fitting portion 15 satisfy the relationship Ta≦2.5×Tm. By satisfying this relationship, the maximum thickness Tm of the fitting portion 15 can be prevented from becoming too thin relative to the thickness of the neck portion 13, and therefore the rigidity of the fitting portion 15 can be prevented from becoming too small. Therefore, when the toothbrush 1 is in use, the head shaft 6 can be prevented from bending too much, and the operability of the toothbrush 1 can be more suitably improved.

[0071] The ninth neck portion P9 is located between the seventh neck portion P7 and the eighth neck portion P8. The location of the ninth neck portion P9 is not limited thereto; it may be located closer to the tip of the seventh neck portion P7 or closer to the rear end of the eighth neck portion P8. The thickness T9 of the ninth neck portion P9 is the same as the maximum thickness Tb of the brush base portion 21. In the longitudinal direction, the distance L6 between the rear end of the fitting portion 15 and the ninth neck portion P9 is longer than the length Lb of the brush portion 20. This allows the length of the thinner portion of the neck portion 13 to be longer than the maximum thickness Tb of the brush base portion 21, thereby preventing the neck portion 13 from becoming too rigid. Therefore, when the toothbrush 1 is in use, the neck portion 13 flexes appropriately, preventing the filaments 30 from flexing too much. This further improves interdental cleaning performance.

[0072] The ratio of the longitudinal distance L7 between the connection tip 14a of the connection portion 14 and the first boundary 13a to the first distance L1 is preferably 10% or more and 50% or less, and more preferably 10% or more and 30% or less. This allows the first boundary 13a, which is the thinnest part of the neck portion 13, to be positioned close to the fitting portion 15. Therefore, when the toothbrush 1 is in use, the portion of the neck portion 13 closest to the fitting portion 15 flexes, thereby reducing the stress applied to the fitting portion 15. This effectively prevents the fitting portion 15 from flexing too much, thereby more effectively improving the operability of the toothbrush 1.

[0073] The ratio of the length Ln of the neck portion 13 to the distance L8 between the tip of the head portion 5 and the rear end of the neck portion 13 is preferably 60% or more. This allows the neck portion 13 to bend appropriately when the toothbrush 1 is in use. This can more appropriately improve the interdental cleaning performance and more appropriately prevent a decrease in the operability of the toothbrush 1.

[0074] The ratio of the length Lm of the fitting portion 15 to the length Lb of the brush portion 20 is preferably 80% or more. This increases 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, thereby increasing the frictional force between the brush portion 20 and the fitting portion 15. This prevents the brush portion 20 from moving in the longitudinal direction relative to the handle body 10 when the toothbrush 1 is in use, thereby more preferably preventing a decrease in the operability of the toothbrush 1.

[0075] In this embodiment, in which the brush part 20 is molded by insert molding using the handle body 10 as an insert member, the joining area between the inner surface of the fitting hole 27 of the brush part 20 and the outer surface of the fitting part 15 can be increased, thereby increasing the joining strength between the brush part 20 and the fitting part 15. Therefore, when the toothbrush 1 is in use, movement of the brush part 20 in the longitudinal direction relative to the handle body 10 can be prevented, and deterioration in the operability of the toothbrush 1 can be more effectively prevented.

[0076] The tenth neck portion P10 is located between the eighth neck portion P8 and the second boundary portion 13b. The location of the tenth neck portion P10 is not limited thereto; it may be located further distal than the eighth neck portion P8. The width W10 of the tenth neck portion P10 is the same as the width Wm of the rear end of the fitting portion 15. The distance L5 between the first boundary portion 13a and the tenth neck portion P10 is preferably equal to or greater than the length Lh of the head portion 5. This allows the width between the first boundary portion 13a and the tenth neck portion P10 of the neck portion 13 to be narrower than the width Wm of the rear end of the fitting portion 15, thereby preventing the rigidity of the portion of the neck portion 13 between the first boundary portion 13a and the tenth neck portion P10 from becoming too great compared to the rigidity of the fitting portion 15. Therefore, when the toothbrush 1 is in use, the head shaft 6 and the neck portion 13 flex more appropriately and more uniformly in the longitudinal direction. Therefore, the cleaning performance between teeth can be more suitably improved, and the deterioration of the operability of the toothbrush 1 can be more suitably prevented.

[0077] The ratio of the length Lh of the head portion 5 to the distance L8 from the tip of the head portion 5 to the rear end of the neck portion 13 is preferably 40% or less. This prevents the neck portion 13 from becoming too short, allowing the neck portion 13 to bend more appropriately when using the toothbrush 1. This prevents the head portion 5 from bending too much, improving the operability of the toothbrush 1.

[0078] The side view of the neck portion 13 preferably has a shape that extends linearly from the tip to the rear end. If the side view of the neck portion 13 has a curved shape, such as an S-shape, stress tends to concentrate on the curved portion during use of the toothbrush 1, causing the curved portion to bend significantly in a localized manner. In contrast, in this embodiment, the side view of the neck portion 13 has a shape that extends linearly from the tip to the rear end, which prevents stress from concentrating on a portion of the neck portion 13. This prevents localized, significant bending of a portion of the neck portion 13, thereby more suitably improving the operability of the toothbrush 1.

[0079] The difference between the width and thickness dimensions of the tip end portion of the neck portion 13 is preferably small. The ratio of the thickness dimension to the width dimension of the tip end portion of the neck portion 13 is preferably 75% or more and 130% or less. The cross-sectional shape of the tip end portion of the neck portion 13 perpendicular to the major axis direction is preferably a shape in which the difference between the width and thickness dimensions is small, such as a circular shape or a square shape. Note that the tip end portion of the neck portion 13 is a portion of the neck portion 13 where the distance from the first boundary portion 13a is, for example, 30% or less of the length Ln of the neck portion 13.

[0080] It is preferable that no holes penetrating the fitting portion 15 in the thickness direction are provided in the fitting portion 15. This prevents a decrease in the rigidity of the fitting portion 15, and therefore prevents the head portion 5 from bending too much when the toothbrush 1 is in use. This can more suitably improve the operability of the toothbrush 1.

[0081] Next, the shape of the filaments 30 in this embodiment will be described in detail. As described above, each of the multiple filaments 30 protrudes from the upper surface 21a of the brush base 21 toward the front side (+Z side). As shown in FIG. 5, the cross-sectional shape of each filament 30 perpendicular to the thickness direction is a generally equilateral triangle protruding toward the tip. As shown in FIG. 6, each filament 30 has a generally triangular pyramid shape that becomes thinner toward the front side. As shown in FIG. 7, when viewed in the width direction, each filament 30 has a shape in which the reduction in the dimension in the major axis direction per unit length in the thickness direction gradually increases as it moves from the brush base 21 toward the front side. Note that the shape of the filaments 30 is not limited to this embodiment. For example, the cross-sectional shape perpendicular to the thickness direction may be a polygonal shape such as a square, a circle, a semicircle, a star, or other shape. In the following description, a shape in which the reduction in the dimension in the major axis direction per unit length in the thickness direction gradually increases as it moves from the brush base 21 toward the front side as viewed in the width direction may be referred to as a stepwise tapered shape. Each filament 30 has a first filament portion 30a, a second filament portion 30b, a third filament portion 30c, a fourth filament portion 30d, a fifth filament portion 30e, a sixth filament portion 30f, a first portion 31, a second portion 32, and a third portion 33. The filament 30 is composed of the first portion 31, the second portion 32, and the third portion 33. The first portion 31, the second portion 32, and the third portion 33 are arranged in this order from the brush base 21 toward the front side. The filament 30 is distributed in the order of the first portion 31, the second portion 32, and the third portion 33 in accordance with a stepwise taper from the brush base 21 toward the front side.

[0082] The first filament portion 30a is located closer to the front (+Z side) than the center in the thickness direction of the filament 30. The first filament portion 30a is part of the second portion 32. In this embodiment, the ratio of the distance Lf1 between the tip of the filament 30, i.e., the end on one side in the thickness direction, and the first filament portion 30a to the dimension Lf of the filament 30 in the thickness direction is 15%. The first filament portion 30a is the portion on the tip side of the filament 30.

[0083] The second filament portion 30b is the base of the filament 30. The second filament portion 30b is the portion of the filament 30 that connects to the brush base portion 21. The second filament portion 30b is the end portion of the first portion 31 on the rear side.

[0084] The third filament portion 30c is located between the first filament portion 30a and the second filament portion 30b. The third filament portion 30c is the boundary between the first portion 31 and the second portion 32. The third filament portion 30c is the end portion on the front side (+Z side) of the first portion 31 and the end portion on the back side (-Z side) of the second portion 32. A dimension D3 in the major axis direction of the third filament portion 30c is smaller than a dimension D2 in the major axis direction of the second filament portion 30b.

[0085] The fourth filament portion 30d is located between the first filament portion 30a and the tip of the filament 30. The fourth filament portion 30d is the boundary between the second portion 32 and the third portion 33. The fourth filament portion 30d is the end portion on the front side (+Z side) of the second portion 32 and the end portion on the back side (-Z side) of the third portion 33. A dimension D4 in the major axis direction of the fourth filament portion 30d is smaller than a dimension D3 in the major axis direction of the third filament portion 30c.

[0086] The first portion 31 is a portion of the filament 30 on the rear side (-Z side). The first portion 31 protrudes from the upper surface 21a of the brush base 21 toward the front side (+Z side). The first portion 31 is a portion of the filament 30 between the second filament portion 30b and the third filament portion 30c. In this embodiment, when viewed in the width direction, the rear end edge of the first portion 31 is linear and extends substantially toward the front side. When viewed in the width direction, the tip end edge of the first portion 31 is linear and located closer to the rear end as it approaches the front side. When viewed in the width direction, the dimension of the first portion 31 in the major axis direction decreases toward the front side. When the length of the first portion 31 in the thickness direction is M1, the first reduction rate R1, which is the amount of reduction in the dimension of the first portion 31 in the major axis direction per unit length in the thickness direction, is (D2 - D3) / M1.

[0087] The second portion 32 protrudes from the first portion 31 toward the front side (+Z side). The second portion 32 is a portion of the filament 30 between the third filament portion 30c and the fourth filament portion 30d. In this embodiment, the thickness direction length M2 of the second portion 32 is longer than the thickness direction length M1 of the first portion 31. The thickness direction length M2 of the second portion 32 may be shorter than or the same as the thickness direction length M1 of the first portion 31. In this embodiment, when viewed in the width direction, the rear end side edge of the second portion 32 is linear and extends substantially toward the front side. When viewed in the width direction, the tip end side edge of the second portion 32 is linear and located closer to the rear end as it approaches the front side. When viewed in the width direction, the dimension of the second portion 32 in the major axis direction decreases as it approaches the front side. A second reduction rate R2, which is the amount of reduction in the dimension of the major axis direction of the second portion 32 per unit length in the thickness direction, is (D3 - D4) / M2. In this embodiment, the second decrease rate R2 is greater than the first decrease rate R1.

[0088] The third portion 33 is a portion of the filament 30 closer to the front side (+Z side) than the fourth filament portion 30d. In this embodiment, the thickness direction length M3 of the third portion 33 is shorter than the thickness direction length M2 of the second portion 32. In this embodiment, when viewed in the width direction, the rear end edge of the third portion 33 is linear and extends substantially toward the front side. When viewed in the width direction, the tip end edge of the third portion 33 is linear and located closer to the rear end as it approaches the front side. The longitudinal dimension Dt of the front side end of the third portion 33 is smaller than the longitudinal dimension D4 of the rear side (-Z side) end of the third portion 33. When viewed in the width direction, the major axis dimension of the third portion 33 decreases toward the front side. A third reduction rate R3, which is the amount of reduction in the major axis dimension of the third portion 33 per unit length in the thickness direction, is (D4 - Dt) / M3. In this embodiment, the third decrease rate R3 is greater than the second decrease rate R2.

[0089] If the longitudinal dimension of the filaments 30 is constant from the base to the tip, the rigidity of the filaments 30 tends to be large. As a result, the flexure of the filaments 30 becomes too small during use of the toothbrush 1. This makes it difficult for the filaments 30 to absorb the brushing load applied to the brush head 20, causing stress to concentrate in the neck portion 13, which tends to flex more. This reduces the maneuverability of the head portion 5 within the oral cavity. This reduces the maneuverability of the toothbrush 1. Furthermore, the movement of the tips of the filaments 30 is difficult to coordinate with the movement of the user's hand, resulting in reduced interdental cleaning performance. Furthermore, if the reduction in the longitudinal dimension per unit length in the thickness direction of the filaments 30 is constant from the base to the tip, stress tends to concentrate in the thickness-wise central portion of each filament 30 during use of the toothbrush 1. This tends to locally increase the flexure of each filament 30 in the thickness-wise central portion. This makes it difficult for the filaments 30 to penetrate deep between teeth, resulting in reduced interdental cleaning performance.

[0090] In contrast, according to the present embodiment, as described above, the second reduction rate R2 of the second portion 32 is greater than the first reduction rate R1 of the first portion 31, and the third reduction rate R3 of the third portion 33 is greater than the second reduction rate R2. Therefore, in this embodiment, as viewed in the width direction, the reduction in the longitudinal dimension of each of the multiple filaments 30 per unit length in the thickness direction gradually increases from the brush base 21 toward the front side, i.e., toward one side (+Z side) in the thickness direction. Therefore, compared to when the longitudinal dimension of each filament 30 is the same from its base to its tip, excessive rigidity of each filament 30 can be suppressed, thereby suppressing excessive deflection of the neck portion 13. Furthermore, compared to when the reduction in the longitudinal dimension per unit length in the thickness direction of each filament 30 is constant from its base to its tip, stress concentration in the central portion of each filament 30 in the thickness direction can be suppressed. Therefore, localized large deflection of each filament 30 in the central portion in the thickness direction can be suppressed. This allows the portions of the toothbrush 1 extending from the filaments 30 to the neck portion 13 to bend in a more coordinated manner, thereby more effectively improving the interdental cleaning performance and more effectively improving the operability of the toothbrush 1.

[0091] According to this embodiment, the ratio of the first area S1, which is the area of ​​the cross section perpendicular to the thickness direction of the first filament portion 30a, to the second area S2, which is the area of ​​the cross section perpendicular to the thickness direction of the second filament portion 30b, is 20% or more and 30% or less. Toothbrushes generally have a configuration in which the distal end portion of the filament 30 is thinner than the base portion to facilitate insertion of the distal end portion into interdental spaces. However, in an integrally molded toothbrush in which each filament 30 is formed from a soft resin, if the ratio of the first area S1 to the second area S2 is less than 20%, the distal end portion of each filament 30 becomes too weak, making the distal end portion of each filament 30 prone to buckling during use of the toothbrush 1. This makes it difficult for each filament 30 to penetrate deep between teeth, thereby reducing the cleaning performance of the toothbrush 1. When the ratio of the first area S1 to the second area S2 is greater than 30%, the rigidity of the tip portion of each filament 30 becomes too high, resulting in stress concentration in the portion from the center to the base of each filament 30 in the thickness direction. Therefore, the portion from the center to the base of each filament 30 in the thickness direction is prone to buckling. As a result, each filament 30 as a whole is less likely to flex appropriately and uniformly, making it difficult for each filament 30 to penetrate deep between teeth. Furthermore, because the rigidity of each filament 30 is too high, the neck portion 13 flexes too much. This reduces the operability of the toothbrush 1. Furthermore, the movement of the tip of each filament 30 is less likely to be synchronized with the movement of the user's hand, resulting in reduced interdental cleaning performance. In contrast, according to this embodiment, the ratio of the first area S1 to the second area S2 is greater than or equal to 20% and less than 30%, thereby preventing buckling of the tip portion of each filament 30 and the portion from the center to the base of each filament 30 in the thickness direction. This allows the entire filament 30 to flex appropriately and uniformly in the thickness direction. Therefore, when using the toothbrush 1, it becomes easier for each filament 30 to penetrate deep between the teeth, thereby more suitably improving the cleaning performance of the toothbrush 1. Furthermore, the movement of the tip of each filament 30 is more likely to be linked to the movement of the user's hand, so it becomes easier to improve the cleaning performance between the teeth.Furthermore, since the rigidity of each filament 30 can be more effectively prevented from becoming too large, the bending of the neck portion 13 can be more effectively prevented. Therefore, the operability of the toothbrush 1 can be more effectively prevented from decreasing.

[0092] The fifth filament portion 30e is located between the first filament portion 30a and the third filament portion 30c. In the thickness direction, the ratio of the distance Lf5 between the tip of the filament 30 and the fifth filament portion 30e to the dimension Lf of the filament 30 is 25%. The fifth filament portion 30e is the portion of the filament 30 near the tip. The ratio of the fifth area S5, which is the area of ​​the cross section of the fifth filament portion 30e perpendicular to the thickness direction, to the second area S2 is 35% or more and 55% or less. This allows the entire filament 30 to bend more appropriately and more uniformly in the thickness direction. This can more appropriately improve the cleaning performance of the toothbrush 1 and more appropriately prevent a decrease in the operability of the toothbrush 1.

[0093] The sixth filament portion 30f is located between the third filament portion 30c and the fifth filament portion 30e. In the thickness direction, the ratio of the distance Lf6 between the tip of the filament 30 and the sixth filament portion 30f to the dimension Lf of the filament 30 is 50%. The sixth filament portion 30f is the central portion of the filament 30 in the thickness direction. The ratio of the sixth area S6, which is the area of ​​the cross section of the sixth filament portion 30f perpendicular to the thickness direction, to the second area S2 is 75% or more and 95% or less. This allows the entire filament 30 to bend more appropriately and more uniformly in the thickness direction. This can more appropriately improve the cleaning performance of the toothbrush 1 and more appropriately prevent a decrease in the operability of the toothbrush 1.

[0094] As shown in FIG. 5 , the area of ​​the top surface 21a, which is the front side of the brush base 21, i.e., the surface facing one side in the thickness direction (+Z side), is a third area S3. The third area S3 is the area surrounded by the outer edge of the top surface 21a. The sum of the second areas S2 of the second filament portions 30b of each of the multiple filaments 30, i.e., the areas of the cross sections perpendicular to the thickness direction, is a fourth area S4. According to this embodiment, the ratio of the fourth area S4 to the third area S3 is 25% or more and 35% or less. If the ratio of the fourth area S4 to the third area S3 is less than 25%, the number of filaments 30 will be too small, and the force applied to each filament 30 during use of the toothbrush 1 will be too great. This will result in excessive bending of each filament 30. Therefore, it will be difficult for each filament 30 to penetrate deep between teeth, thereby reducing the cleaning performance of the toothbrush 1. If the ratio of the fourth area S4 to the third area S3 is greater than 35%, the number of filaments 30 will be too large, resulting in too little force applied to each filament 30. Consequently, the deflection of each filament 30 will be too small. As a result, the brushing load applied to the brush head 20 will be difficult to absorb due to the deflection of each filament 30, causing stress to concentrate in the neck portion 13 and excessive deflection of the neck portion 13. This reduces the maneuverability of the head portion 5 in the oral cavity, thereby reducing the maneuverability of the toothbrush 1. In contrast, according to this embodiment, the ratio of the fourth area S4 to the third area S3 is greater than or equal to 25% and less than or equal to 35%, preventing the force applied to each filament 30 from becoming too large or too small. This allows each filament 30 to deflect appropriately, thereby preventing stress from concentrating on the neck portion 13. Therefore, the toothbrush 1 can bend in unison from each filament 30 to the rear end of the neck portion 13. This makes it easier for each filament 30 to penetrate deep between the teeth, thereby more effectively improving the cleaning performance of the toothbrush 1. In addition, this more effectively prevents the neck portion 13 from bending too much, more effectively preventing a decrease in the operability of the toothbrush 1.

[0095] The third area S3, i.e., the number of filaments 30 that the toothbrush 1 has per unit area of ​​the upper surface 21a of the brush base 21, is 80 / cm ２ More than 110 strands / cm ２ This makes it possible to more appropriately prevent the stress applied to each filament 30 from becoming too large or too small when the toothbrush 1 is in use, thereby allowing each filament 30 to bend more appropriately. This therefore makes it possible to more appropriately improve the cleaning performance of the toothbrush 1 and more appropriately prevent the operability of the toothbrush 1 from decreasing.

[0096] When viewed in the thickness direction, the shortest distance Ws between the outer edge of the brush base 21 and the multiple filaments 30 is preferably 3.0 mm or less. This allows for a larger number of filaments 30 to be arranged on the upper surface 21a, thereby reducing the stress applied to each filament 30 during use of the toothbrush 1. This prevents excessive bending of each filament 30, thereby more effectively improving interdental cleaning performance. The filament region Rf shown in FIG. 5 is a region that surrounds all parts of the upper surface 21a that are connected to each filament 30. The area of ​​the filament region Rf is the filament area Sf.

[0097] Figure 10 is an external view showing a first deflection test device 50. Next, the test method for the first deflection test and the test results of the first deflection test for the toothbrush 1 of this embodiment will be described. The first deflection test measures the reaction force of the toothbrush 1 when the portion of the toothbrush 1 from each filament 30 to the neck portion 13 bends toward the rear side (-Z side). The first deflection test is performed using the first deflection test device 50 shown in Figure 10.

[0098] In this embodiment, an autograph testing machine AGS-X manufactured by Shimadzu Corporation is used as the first flexure testing device 50. The first flexure testing device 50 has a pressure member 51 and a position measurement unit (not shown) that measures the position of the pressure member 51 in the thickness direction. A reaction force measurement unit 51a is provided on the surface of the pressure member 51 facing the rear side (-Z side). A piezoelectric element, for example, can be used as the reaction force measurement unit 51a. The reaction force measurement unit 51a is capable of measuring the load applied to the reaction force measurement unit 51a.

[0099] In the first deflection test, the toothbrush 1 is fixed to the fixing portion 52. In this embodiment, the fixing portion 52 has a first fixing portion 52a, a second fixing portion 52b, and a screw 52c. The first fixing portion 52a and the second fixing portion 52b each have a rectangular parallelepiped shape extending in a direction perpendicular to the thickness direction. The second fixing portion 52b is positioned closer to the front (+Z side) than the first fixing portion 52a. The gripping portion 12 of the toothbrush 1 is positioned between the first fixing portion 52a and the second fixing portion 52b. The gripping portion 12 is placed on the surface of the first fixing portion 52a facing the front side. The screw 52c is passed through a hole penetrating the second fixing portion 52b in the thickness direction and a hole penetrating the first fixing portion 52a in the thickness direction. When nut 52d is tightened onto the portion of screw 52c closer to the rear surface than first fixing portion 52a, grip portion 12 is fixed to fixing portion 52. At this time, when viewed from the thickness direction, second boundary portion 13b, which is the boundary between neck portion 13 and grip portion 12, overlaps with the tip of first fixing portion 52a and the tip of second fixing portion 52b. As a result, the rear end of neck portion 13, i.e., the end portion on the other side (-X side) in the longitudinal direction, is fixed to fixing portion 52.

[0100] The pressure member 51 contacts each filament 30 from the front side, i.e., one side (+Z side) in the thickness direction. More specifically, the reaction force measuring unit 51a contacts all of the filaments 30. The pressure member 51 is movable in the thickness direction. In the first deflection test, the pressure member 51 is moved toward the rear side, i.e., the other side (-Z side) in the thickness direction, to deflect the toothbrush 1 from each filament 30 to the neck portion 13, and the reaction force F1, which is the reaction force of the toothbrush 1, is measured by the reaction force measuring unit 51a. In the first deflection test, the pressure member 51 moves at a speed of 10 mm / sec. The first reaction force F1 is measured every time the pressure member 51 moves 0.002 mm toward the rear side. In other words, the sampling interval for the first deflection test is 0.002 mm.

[0101] Fig. 11 is a diagram showing an example of the first reaction force F1 of this embodiment. The horizontal axis of Fig. 11 is the first movement distance Z1. The first movement distance Z1 is the distance that the pressure member 51 moves toward the rear side. The origin of the first movement distance Z1 is the position where the pressure member 51 and the filament 30 start to come into contact with each other. The vertical axis of Fig. 11 is the first reaction force F1. As shown in Fig. 11 , in the toothbrush 1 of this embodiment, the first reaction force F1 monotonically increases as the first movement distance Z1 increases.

[0102] FIG. 12 is a diagram illustrating a method for calculating the first reaction force fluctuation rate RF1 according to this embodiment. FIG. 13 is a diagram illustrating an example of the first reaction force fluctuation rate RF1 according to this embodiment. The horizontal axis in FIG. 12 represents the first movement distance Z1. The left vertical axis in FIG. 12 represents the first reaction force F1. The right vertical axis in FIG. 12 represents the first reaction force fluctuation rate RF1. In this embodiment, the first reaction force fluctuation rate RF1 is the value obtained by dividing the amount of fluctuation in the first reaction force F1 when the position of the pressure member 51 in the thickness direction changes by the first predetermined distance dZ1 by the first predetermined distance dZ1. In other words, the first reaction force fluctuation rate RF1 is the rate of fluctuation of the first reaction force F1 with respect to the first movement distance Z1. Note that in this embodiment, the first predetermined distance dZ1 is 0.1 mm. As described above, the sampling interval for the first deflection test is 0.002 mm.

[0103] In the first deflection test, the first movement distance when the first reaction force F1 is measured the Mth time is defined as Z1(M) and the first reaction force is defined as F1(M). The first movement distance when the first reaction force F1 is measured the M+50th time is defined as Z1(M+50) and the first reaction force is defined as F(M+50). The distance between Z1(M+50) and Z1(M) is a first predetermined distance dZ1. Therefore, the amount of fluctuation in the first reaction force F1 when the position of the pressure member 51 in the thickness direction changes by the first predetermined distance dZ1 from Z1(M) is F1(M+50)-F1(M). Therefore, the first reaction force fluctuation rate RF1 is (F1(M+50)-F1(M)) / dZ1. By calculating the first reaction force fluctuation rate RF1 for all acquired first reaction forces F1 using this calculation method, the relationship between the first movement distance Z1 and the first reaction force fluctuation rate RF1 shown in FIG. 13 is obtained. In this embodiment, the first reaction force fluctuation rate RF1 may be a moving average of, for example, 50 first reaction force fluctuation rates RF1 calculated by the above calculation method, which reduces the influence of unexpected measurement errors on the first reaction force fluctuation rate RF1 when measuring the first reaction force F1, thereby making it possible to obtain a more accurate relationship between the first movement distance Z1 of the toothbrush 1 and the first reaction force fluctuation rate RF1.

[0104] 13, the first maximum value RF1max is the maximum value of the first reaction force fluctuation rate RF1 within a range in which the movement distance of the pressure member 51 is 3.0 mm or less. The first minimum value RF1min is the minimum value of the first reaction force fluctuation rate RF1 within a range in which the movement distance of the pressure member 51 is 3.0 mm or less. According to this embodiment, the first maximum value RF1max and the first minimum value RF1min satisfy the relationship RF1max-RF1min≦0.6 N / mm.

[0105] In a toothbrush 1 in which the difference between the first maximum value RF1max and the first minimum value RF1min is greater than 0.6 N / mm, at least one of the filaments 30, the head shaft 6, and the neck portion 13 is likely to locally flex when the toothbrush 1 is in use. Local flexing of the filaments 30 makes it difficult for the filaments 30 to penetrate deep between the teeth, thereby reducing the cleaning performance of the toothbrush 1. Furthermore, local flexing of the head shaft 6 and the neck portion 13 reduces the maneuverability of the head portion 5 in the oral cavity, thereby reducing the maneuverability of the toothbrush 1. In contrast, according to the present embodiment, the difference between the first maximum value RF1max and the first minimum value RF1min is 0.6 N / mm or less, so that the filaments 30, the head shaft 6, and the neck portion 13 do not locally flex, and instead the filaments 30, the head shaft 6, and the neck portion 13 flex uniformly in the longitudinal direction in unison. This prevents localized bending of each filament 30, thereby more effectively improving the cleaning performance of the toothbrush 1. Furthermore, this prevents localized bending of the head shaft 6 and the neck 13, more effectively preventing a decrease in the operability of the toothbrush 1.

[0106] The difference between the first maximum value RF1max and the first minimum value RF1min is preferably 0.5 N / mm or less. This allows the filament 30, the head shaft 6, and the neck portion 13 to bend more uniformly and preferably in conjunction with each other in the longitudinal direction, thereby more preferably improving the cleaning performance of the toothbrush 1 and more preferably preventing a decrease in the operability of the toothbrush 1. It is more preferable that the difference between the first maximum value RF1max and the first minimum value RF1min is 0.4 N / mm or less. This allows the filament 30, the head shaft 6, and the neck portion 13 to bend more uniformly and preferably in conjunction with each other in the longitudinal direction, thereby more preferably improving the cleaning performance of the toothbrush 1 and more preferably preventing a decrease in the operability of the toothbrush 1.

[0107] According to this embodiment, the first average value RF1ave, which is the average value of the first reaction force fluctuation rate RF1 when the movement distance of the pressure member 51 is within a range of 3.0 mm or less, is 0.5 N / mm or more and 1.0 N / mm or less. If the first average value RF1ave is less than 0.5 N / mm, the deflection of each filament 30 becomes too small during use of the toothbrush 1, making it easy for stress to concentrate in the neck portion 13. This causes the deflection of the neck portion 13 to become too large, reducing the operability of the toothbrush 1. If the first average value RF1ave is greater than 1.0 N / mm, the deflection of each filament 30 becomes too large during use of the toothbrush 1, or a portion of each filament 30 bends locally. This makes it difficult for each filament 30 to penetrate deep between the teeth, reducing the cleaning performance of the toothbrush 1. In contrast, according to the present embodiment, the first average value RF1ave is equal to or greater than 0.5 N / mm and equal to or less than 1.0 N / mm, which prevents excessive bending of each filament 30 and neck portion 13. This allows the filaments 30, head shaft 6, and neck portion 13 to bend more uniformly in the longitudinal direction in unison. This therefore makes it possible to more effectively improve the cleaning performance of the toothbrush 1 and more effectively prevent a decrease in the operability of the toothbrush 1.

[0108] The first average value RF1ave is preferably 0.5 N / mm or more and 0.8 N / mm or less. This more effectively prevents local bending of a portion of each filament 30, thereby more effectively improving the cleaning performance of the toothbrush 1. The first average value RF1ave is preferably 0.6 N / mm or more and 0.8 N / mm or less. This more effectively prevents excessive bending of the neck portion 13, thereby more effectively preventing a decrease in the operability of the toothbrush 1.

[0109] Fig. 14 is a side view showing the second deflection test device 60. Next, the test method for the second deflection test and the test results of the second deflection test for the toothbrush 1 of this embodiment will be described. The second deflection test measures the reaction force of the filament 30 when the filament 30 is deflected. The second deflection test is performed using the second deflection test device 60 shown in Fig. 14.

[0110] In this embodiment, an autograph testing machine AGS-X manufactured by Shimadzu Corporation was used as the second deflection testing device 60. The second deflection testing device 60 has a pressure member 61 and a position measuring unit (not shown) that measures the position of the pressure member 61 in the thickness direction. A reaction force measuring unit 61a is provided on the surface of the pressure member 61 facing the back side (-Z side).

[0111] In the second deflection test, the brush part 20 is supported in the thickness direction by the support stand 62. More specifically, the support stand 62 supports the brush base part 21 from the rear side (-Z side), i.e., the other side in the thickness direction. This determines the position of the brush part 20 in the thickness direction in the second deflection test.

[0112] The pressure member 61 contacts each filament 30 from the front side, i.e., one side (+Z side) in the thickness direction. More specifically, the reaction force measuring unit 61a contacts all of the filaments 30. The pressure member 61 is movable in the thickness direction. In the second deflection test, the pressure member 61 is moved toward the back side, i.e., the other side (-Z side) in the thickness direction, to deflect each filament 30 and measure the second reaction force F2. In the second deflection test, the movement speed of the pressure member 61 is 10 mm / sec. The second reaction force F2 is measured every time the pressure member 61 moves 0.002 mm toward the back side. In other words, the sampling interval for the second deflection test is 0.002 mm.

[0113] FIG. 15 is a diagram showing an example of the second pressure P of this embodiment. The second pressure P is the pressure obtained by dividing the second reaction force F2 by the filament area Sf. The second pressure P is the pressure that the pressure member 61 receives from each filament 30. FIG. 16 is a diagram showing an example of the second pressure fluctuation rate RP of this embodiment. The horizontal axis of FIG. 15 is the second movement distance Z2. The second movement distance Z2 is the distance that the pressure member 61 moves toward the rear side (-Z side). The origin of the second movement distance Z2 is the position where the pressure member 61 and the filament 30 start to contact each other. The vertical axis of FIG. 15 is the second pressure P. As shown in FIG. 15, in the toothbrush 1 of this embodiment, the second pressure P increases monotonically as the second movement distance Z2 increases.

[0114] The second pressure fluctuation rate RP shown in FIG. 16 is a value obtained by dividing the amount of fluctuation in the second pressure P when the position of the pressure member 61 in the thickness direction changes by the second predetermined distance dZ2 by the second predetermined distance dZ2. In this embodiment, the second predetermined distance dZ2 is 0.1 mm. In the second deflection test, the calculation method for calculating the second pressure fluctuation rate RP from the second pressure P is the same as the calculation method for calculating the first reaction force fluctuation rate RF1 from the first reaction force F1 in the first deflection test described above. According to this embodiment, when the movement distance of the pressure member 61 is within a range of 1.0 mm or less, the second pressure fluctuation rate RP is 0.0 N / mm ３ That's it, 10.0 x 10 －２ N / mm ３ The following is the result.

[0115] The second pressure fluctuation rate RP is 0.0 N / mm ３ If the second pressure fluctuation rate RP is smaller than 10.0×10, the bending of each filament 30 becomes too large or a portion of each filament 30 locally bends during use of the toothbrush 1. Therefore, it becomes difficult for each filament 30 to penetrate deep between the teeth, and the cleaning performance of the toothbrush 1 deteriorates. －２ N / mm ３ If the second pressure fluctuation rate RP is larger than 0.0 N / mm, the reaction force of each filament 30 becomes too large, resulting in too little deflection of each filament 30. As a result, stress tends to concentrate on the neck portion 13, causing the neck portion 13 to deflect too much. This reduces the operability of the toothbrush 1. Furthermore, the rigidity of each filament 30 becomes too large, resulting in a decrease in the comfort of each filament 30 when using the toothbrush 1. In contrast, in this embodiment, when the second pressure fluctuation rate RP is 0.0 N / mm ３ That's it, 10.0 x 10 －２ N / mm ３ Since the second pressure fluctuation rate RP is 0.5×10 or less, each filament 30 bends moderately and uniformly. Therefore, it is possible to more effectively prevent each filament 30 from bending locally, and therefore it is possible to more effectively improve the cleaning performance of the toothbrush 1. In addition, it is possible to more effectively prevent stress from concentrating on the neck portion 13, and therefore it is possible to more effectively prevent a decrease in the operability of the toothbrush 1. Note that the second pressure fluctuation rate RP is 0.5×10 －２ N / mm３ That's it, 8.0 x 10 －２ N / mm ３ This allows each filament 30 to bend appropriately and more uniformly, which can more suitably improve the cleaning performance of the toothbrush 1 and more suitably prevent the operability of the toothbrush 1 from decreasing.

[0116] As described above, the toothbrush 1 of this embodiment can improve the interdental cleaning performance while preventing a decrease in the operability of the toothbrush.

[0117] [Examples] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples and can be practiced with appropriate modifications within the scope of the invention.

[0118] (Examples 1 to 9, Comparative Examples 1 to 6) According to the specifications shown in Table 1, toothbrushes that differ in at least one of the maximum thickness of the head shaft (maximum dimension in the thickness direction of the head shaft); Th, width of the first boundary portion (minimum dimension in the width direction of the neck portion); Wa, first angle: θ1, width of the tip of the connecting portion; Wb, length of the connecting portion; Lc, second angle: θ2, and width of the rear end of the mating portion; Wm were used as samples for Examples 1 to 9 and Comparative Examples 1 to 6.

[0119]

[0120] The filament of each sample had a thickness dimension (hair length) of 10 mm. The cross-sectional shape of the filament of each sample was triangular. The second area of ​​the filament of each sample was 0.29 mm. ２ The shape of the filament of each sample as viewed in the width direction was a stepped tapered shape. The first area of ​​the filament of each sample was 0.079 mm ２ The number of filaments in each sample was 140 or more and 280 or less. The number of filaments per unit area of ​​the third area of ​​each sample was 100 / cm ２ The soft resin material of each sample was polyurethane. The maximum width of the head portion of each sample was 10 mm or more and 14 mm or less. The length of the head portion of each sample was 20.3 mm. The third area of ​​each sample was 1.4 mm ２More than 2.8 mm ２ The following were set. The length of the neck portion of each sample was 48.3 mm. The maximum width of the neck portion of each sample was 8.6 mm. The maximum thickness of the neck portion of each sample was 7.1 mm. The minimum thickness of the neck portion of each sample was 3.5 mm. The maximum thickness of the fitting portion of each sample was 2.0 mm. The length of the fitting portion of each sample was 18.3 mm. The hard resin material of each sample was polyacetal resin.

[0121] (Example 9, Comparative Examples 7-8) According to the specifications shown in Table 2, the toothbrushes used in Example 9 and Comparative Examples 7-8 were samples that differed in at least one of the following: hole penetrating the above-mentioned fitting portion, maximum thickness of the fitting portion; Tm, maximum thickness of the head shaft portion (maximum dimension in the thickness direction of the head shaft); Th, width of the tip of the connecting portion; Wb, length of the connecting portion; Lc, first angle; θ1, width of the first boundary portion (minimum dimension in the width direction of the neck portion); Wa, thickness of the first boundary portion (minimum thickness of the neck portion); Ta, side view shape of the neck portion, material of the hard resin, cross-sectional shape of the second filament portion, side view shape of the filament, number of filaments per unit area of ​​the third area, cross-sectional area of ​​the tip of the filament, second area; S2, and material of the soft resin.

[0122]

[0123] The thickness direction dimension (hair length) of the filament of each sample was 10 mm. The first area of ​​the filament of each sample was 0.079 mm. ２ The number of filaments in each sample was 140 or more and 280 or less. The maximum width of the head portion of each sample was 10 mm or more and 14 mm or less. The length of the head portion of each sample was 20.3 mm. The third area of ​​each sample was 1.4 mm ２ More than 2.8 mm ２ The following were set: The length of the neck portion of each sample was 48.3 mm. The maximum width of the neck portion of each sample was 8.6 mm. The maximum thickness of the neck portion of each sample was 7.1 mm. The length of the fitting portion of each sample was 18.3 mm.

[0124] [Evaluation of Usability] [Evaluation Method] In the evaluation of usability, the toothbrushes of Examples 1 to 9 and Comparative Examples 1 to 6 were evaluated based on the feeling of stiffness at the tip of the filament when cleaning between teeth, and the feeling that the bristles moved in conjunction with the operation of the toothbrush.

[0125] The toothbrushes of Examples 1 to 9 and Comparative Examples 1 to 6 were evaluated according to the following criteria: 7 points: Very noticeable 6 points: Very noticeable 5 points: Somewhat noticeable 4 points: Neither noticeable nor noticeable 3 points: Very little noticeable 2 points: Almost no noticeable 1 point: Not noticeable at all The average scores of the 10 expert panelists were calculated and evaluated on the following five-point scale: ☆ (star mark): 6.5 points or more ◎ (double circle mark): 5.5 points or more but less than 6.5 points ○ (circle mark): 4.5 points or more but less than 5.5 points △ (triangle mark): 3.5 points or more but less than 4.5 points × (cross mark): Less than 3.5 points In the evaluation column of each of Examples 1 to 9 and Comparative Examples 1 to 6 in Table 1, the average score of the scores of the 10 expert panelists is shown in parentheses along with the above five-point scale.

[0126] As shown in Table 1, for Examples 1 to 9, in which the maximum thickness of the head shaft was 3.0 mm or more and 4.5 mm or less, the width of the first boundary was 3.0 mm or more and 4.5 mm or less, and the first angle was 17° or more and 28° or less, the average evaluation score by 10 expert panelists was 3.5 points or more, and good results were obtained in terms of the feeling that the tip of the filament was firm when cleaning between teeth, and that the tip of the bristles moved in conjunction with the operation of the toothbrush.

[0127] In contrast, for Comparative Example 1, in which the maximum thickness of the head shaft was greater than 4.5 mm, the average score of the evaluation by 10 expert panelists was less than 3.5 points, and a favorable result was not obtained. As mentioned above, when the maximum thickness of the head shaft was greater than 4.5 mm, the rigidity of the head shaft became too great, resulting in too little deflection of the head shaft. This resulted in too much deflection of the filament, and the tip of the filament did not have a satisfactory stiff feel.

[0128] For Comparative Example 2, in which the maximum thickness of the head shaft was less than 3.0 mm, good results were not obtained. As mentioned above, when the maximum thickness of the head shaft was less than 3.0 mm, the rigidity of the head shaft became too small, resulting in excessive deflection of the head shaft. This made it difficult for the filament to bend, making it difficult for the tip of the filament to move. Therefore, it was not possible to obtain a satisfactory feeling that the bristles were moving in conjunction with the operation of the toothbrush.

[0129] In Comparative Example 3, where the width of the first boundary was greater than 4.5 mm, good results were not obtained. As described above, when the width of the first boundary was greater than 4.5 mm, the stiffness of the neck portion became too great, resulting in too little deflection of the neck portion. This resulted in too much deflection of the filament, and the tip of the filament did not have a satisfactory firm feel.

[0130] For Comparative Example 4, in which the width of the first boundary was less than 3.0 mm, good results were not obtained. As mentioned above, when the width of the first boundary was less than 3.0 mm, the rigidity of the neck portion became too small, resulting in excessive bending of the neck portion. This made it difficult for the filament to bend, making it difficult for the tip of the filament to move. Therefore, it was not possible to obtain a satisfactory feeling that the bristles were moving in conjunction with the operation of the toothbrush.

[0131] For Comparative Example 5, in which the first angle was less than 17°, good results were not obtained. As described above, when the first angle was less than 17°, the width of the neck and the joint became too wide, and the stiffness of the neck and the joint became too great. This resulted in too little deflection of the neck and the joint. Therefore, the deflection of the filament became too great, and the tip of the filament did not have a satisfactory firm feel.

[0132] For Comparative Example 6, in which the first angle was greater than 28°, good results were not obtained. As described above, when the first angle was greater than 28°, the width of the neck portion and the connecting portion became too narrow, resulting in too little rigidity of the neck portion and the connecting portion. This resulted in too much bending of the neck portion and the connecting portion, making it difficult for the filament to bend. Therefore, the tip of the filament became difficult to move, and it was not possible to obtain a pleasant feeling that the bristles were moving in conjunction with the operation of the toothbrush.

[0133] Compared to the configuration of Example 1, Example 3, in which the first angle was greater than 20°, produced better results than Example 1. In Example 3, the neck portion and the connection portion are more easily bent than in Example 1, so the stress applied to the filament can be reduced. Therefore, the bending of the filament can be suitably reduced, and the tip of the filament can be made to feel firmer.

[0134] Compared to the configuration of Example 2, Example 4, in which the first angle was smaller than 26°, produced better results than Example 2. In Example 4, the neck portion and the connection portion are more resistant to bending than Example 2, allowing for a more favorable increase in stress applied to the filament. This allows for a favorable increase in the bending of the filament while suppressing local bending of a portion of the filament. Therefore, the tip of the filament moves more favorably, providing a more favorable feeling that the bristles are moving in conjunction with the operation of the toothbrush.

[0135] Compared to the configuration of Example 3, Example 5, in which the second angle was greater than 10°, produced better results than Example 3. In Example 5, the head shaft is more easily bent than in Example 3, so the stress applied to the filament can be more suitably reduced. Therefore, the bending of the filament can be more suitably reduced, resulting in a more suitable feel of stiffness at the tip of the filament. Compared to the configuration of Example 5, Example 7, in which the second angle was greater than 12°, produced better results than Example 5 for the same reason.

[0136] Compared to the configuration of Example 4, Example 6, in which the second angle was smaller than 18°, produced better results than Example 6. In Example 6, the head shaft is more resistant to bending than Example 4, allowing for a more favorable increase in stress applied to the filament. This allows for more favorable increase in the bending of the filament while more favorably suppressing local bending of a portion of the filament. Therefore, the bristles move more favorably in conjunction with the operation of the toothbrush, providing a more favorable feeling that the tip of the filament is moving. Compared to the configuration of Example 6, Example 8, in which the second angle was smaller than 16°, produced better results than Example 6 for the same reason.

[0137] Compared to the configurations of Examples 7 and 8, Example 9, in which the width of the tip of the connection portion is 8 mm or more and 10 mm or less, achieved better results than Examples 7 and 8. In Example 9, the head shaft portion is more easily bent than in Examples 7 and 8, so local bending of a portion of the filament can be more suitably suppressed. Therefore, it is possible to obtain a more suitable feel of stiffness at the tip of the filament and a more suitable feel of the bristles moving in conjunction with the operation of the toothbrush.

[0138] [First Deflection Test] [Evaluation Method] The first deflection test was conducted according to the above-described test method for the first deflection test for the toothbrushes of Example 9 and Comparative Examples 7 and 8. The test results of the first deflection test are shown in Table 2.

[0139] FIG. 17 shows the first reaction force fluctuation rate in the first deflection test. As shown in FIG. 17 , when the movement distance of the pressure member is within a range of 3.0 mm or less, the fluctuation amount of the first reaction force fluctuation rate in Example 9 is smaller than the fluctuation amount of the first reaction force fluctuation rate in Comparative Examples 7 to 8. This means that, compared to the toothbrushes of Comparative Examples 7 to 8, the toothbrush of Example 9 has a relationship where the deflection amount of the toothbrush portion from the filament to the neck portion and the first reaction force are closer to a directly proportional relationship. This is because, as described above, when a force toward the other side in the thickness direction is applied to the filament, Example 9 allows the filament to deflect uniformly and in tandem from the filament to the neck portion, thereby preventing large localized deflections in the filament, head shaft, and neck portion. Therefore, in Example 9, the filaments can easily penetrate deep between the teeth during use, thereby favorably improving the cleaning performance of the toothbrush and favorably preventing a decrease in the operability of the toothbrush 1.

[0140] In contrast, in Comparative Example 7, in which the first angle is smaller than 17°, the width of the neck portion and the connecting portion becomes too wide, as described above, and the stiffness of the neck portion and the connecting portion becomes too great. As a result, stress is concentrated on the filament, causing the filament to bend too much. As a result, the difference between the first maximum value and the first minimum value becomes larger than 0.6 N / mm. As a result, the filament is prone to bending locally, and the cleaning performance of the toothbrush 1 deteriorates.

[0141] Furthermore, in Comparative Example 8, in which the maximum thickness of the head shaft was greater than 4.5 mm, the first angle was smaller than 17°, and the width of the first boundary portion was greater than 4.5 mm, the rigidity of the head shaft and neck portion was too high, as described above. Therefore, as in Comparative Example 7, the filament deflection was too large. As shown in FIG. 17 , the first reaction force fluctuation rate in Comparative Example 8 increased when the first movement distance was in the range of 0.5 mm to 1.0 mm. This indicates that the filament buckled due to a sudden increase in filament deflection in the first movement distance range of 0.5 mm to 1.0 mm. Therefore, as shown in Table 2, the difference between the first maximum value RF1max and the first minimum value RF1min was greater than 0.6 N / mm, and the first average value was greater than 1.0 N / mm. This made the filament more susceptible to localized deflection, thereby reducing the cleaning performance of the toothbrush 1.

[0142] In addition, in Comparative Examples 7 and 8, where the fitting portion is provided with a through hole, the rigidity of the fitting portion tends to be reduced, which makes the fitting portion prone to localized deflection, and therefore the fluctuation amount of the first reaction force fluctuation rate tends to be large.

[0143] Furthermore, in Comparative Examples 7 and 8, in which the neck portion is curved, stress tends to concentrate on the curved portion as described above, and therefore the curved portion tends to bend significantly locally, which tends to increase the amount of fluctuation in the first reaction force variation rate.

[0144] In addition, in Comparative Examples 7 and 8, in which the hard resin material is polypropylene resin, the rigidity of the neck portion tends to be small, so the neck portion tends to bend locally, and therefore the fluctuation amount of the first reaction force fluctuation rate tends to be large.

[0145] Furthermore, in Comparative Example 8, in which the filament has a rectangular shape in side view, the filament is difficult to bend uniformly and is prone to buckling. Therefore, the filament is prone to bend locally. Therefore, the fluctuation amount of the first reaction force fluctuation rate is likely to be large.

[0146] [Second Deflection Test] [Evaluation Method] The second deflection test was conducted according to the above-described test method for the second deflection test for the toothbrushes of Example 9 and Comparative Examples 7 and 8. The test results of the second deflection test are shown in Table 2.

[0147] FIG. 18 shows the second pressure fluctuation rate in the second deflection test. As shown in FIG. 18 , when the movement distance of the pressure member is 1.0 mm or less, the fluctuation amount of the second pressure fluctuation rate in Example 9 is smaller than that in Comparative Example 8. This means that, compared to the toothbrush in Comparative Example 8, the toothbrush in Example 9 has a relationship where the amount of filament deflection and the second pressure are closer to being directly proportional. This is because, as described above, in Example 9, when a force is applied to the filament toward the other side in the thickness direction, the filament can bend uniformly, thereby preventing large localized deflections in parts of the filament. Therefore, in Example 9, when the toothbrush is in use, each filament can easily penetrate deep between the teeth, thereby more effectively improving the cleaning performance of the toothbrush. Furthermore, stress concentration in the neck portion can be effectively prevented, thereby more effectively preventing a decrease in the operability of the toothbrush.

[0148] In contrast, the number of filaments per unit area of ​​the third area is 80 / cm ２ 18, in Comparative Example 8, where the second pressure fluctuation rate is less than 10.0×10, the stress applied to the filament becomes too large as described above. －２ N / mm ３ When the second movement distance is in the range of 0.0 mm or more and 0.2 mm or less, the filaments have a high repulsive force, so the tip of each filament is difficult to move. Also, when the second movement distance is in the range of 0.2 mm or more and 0.4 mm or less, where stress tends to concentrate in the neck portion, each filament buckles, so the second pressure fluctuation rate drops sharply to 0.0 N / mm ３ The second movement distance is smaller than the first movement distance. Furthermore, when the second movement distance is in the range of 0.2 mm or more and 0.4 mm or less, each filament is locally bent, resulting in no stiffness at the tip of each filament. Furthermore, in Comparative Example 8, the number of filaments is small, so the stress applied to the filaments is too large. Therefore, the filaments are prone to buckling. As a result, as shown in Table 2, the fluctuation in the first reaction force variation rate is likely to be large, making it difficult to improve the feel of use.

[0149] In Comparative Example 8, the cross-sectional shape of the filament is circular, and the shape is symmetrical in the longitudinal and width directions when viewed from the thickness direction. Therefore, when a force directed toward the back side is applied to the filament, the direction in which each filament bends varies, and the force applied to each filament tends to vary. As a result, the amount of bending of the filament to which a large force is applied becomes too large, and the second pressure fluctuation rate tends to fluctuate when the movement distance of the pressure member is 1.0 mm or less.

[0150] While the preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these examples. If the bending of each portion, such as the filament, head portion, and neck portion, can be uniformly flexed without bias, a substantially linear bending behavior can be obtained from the filament to the neck portion, and those skilled in the art can achieve the above-mentioned effects based on this indicator. Furthermore, the shapes and combinations of the components shown in the above examples are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention.

[0151] As described above, the first deflection test measures the first reaction force, which is the reaction force of the toothbrush, by deflecting the toothbrush from each filament to the neck portion. Therefore, the results of the second deflection test, which measures the reaction force of the filament 30, affect the results of the first deflection test. The above description illustrates a configuration in which the first pressure fluctuation rate and the second pressure fluctuation rate are set within a suitable range by adjusting the number of filaments and the cross-sectional shape of the filaments, thereby achieving uniform, interlocking deflection from the filament to the neck portion. However, the present invention is not limited to this example. For example, by combining multiple solutions, such as the first angle, the maximum thickness of the head shaft, the shape of the neck portion, the hard resin material, and the side view shape of the filament, it is possible to achieve uniform, interlocking deflection from the filament to the neck portion, thereby achieving a substantially linear deflection behavior from the filament to the neck portion. Therefore, by analyzing the results of the first deflection test and the second deflection test, a person skilled in the art can understand the characteristics of the toothbrush being analyzed, efficiently arrive at a solution to the problem, and confirm the effectiveness of the solution.

[0152] The configuration of the mating portion and mating hole is not limited to that of this embodiment, and may be, for example, a configuration in which the mating portion has a protrusion that protrudes in the width direction, and the mating hole is recessed in the width direction and has a recess that fits into the protrusion.

[0153] The method for molding the brush part is not limited to this embodiment, and for example, the handle body and the brush part may be molded in separate molds. In this case, after molding, the toothbrush is constructed by fitting the fitting part of the handle body into the fitting hole of the brush part.

[0154] The toothbrush according to the present invention can improve the interdental cleaning performance while suppressing a decrease in the operability of the toothbrush, and therefore can be suitably used as an integrally molded toothbrush.

[0155] DESCRIPTION OF SYMBOLS 1...toothbrush, 6...head shaft portion, 10...handle body, 13...neck portion, 13d...neck edge portion, 14...connection portion, 14a...connection tip portion, 14d...connection edge portion, 15...fitting portion, 15d...fitting edge portion, 20...brush portion, 21...brush base portion, 27...fitting hole, 30...filament, 30a...first filament portion, 30b...second filament portion, 51...pressure member, 61...pressure member, dZ1...first predetermined distance, dZ2...second predetermined distance, F1...first reaction force, J...central axis, L1...first distance, L2...distance between connection tip portion and first neck portion, L3...distance between connection tip portion and second neck portion, L4...distance between connection tip portion and third neck portion, P...second pressure, P1...first neck portion, P2...second neck portion, P3...third neck portion, RF1...first reaction force fluctuation rate, RF1ave...first average value, RF1max...first maximum value, RF1min...first minimum value, RP...second pressure fluctuation rate, S1...first area (area of ​​a cross section perpendicular to the thickness direction of the first filament portion), S2...second area (area of ​​a cross section perpendicular to the thickness direction of the second filament portion), T1...thickness of the first neck portion (dimension in the thickness direction of the first neck portion), T2...thickness of the second neck portion (dimension in the thickness direction of the second neck portion), T3...thickness of the third neck portion (dimension in the thickness direction of the third neck portion), Th...maximum thickness of the head shaft portion (maximum dimension in the thickness direction of the head shaft portion), V1...first virtual line, V2...second virtual line, Wa...width of the first boundary portion (minimum dimension in the width direction of the neck portion), W1: Width of the first neck portion (dimension in the width direction of the first neck portion), W2: Width of the second neck portion (dimension in the width direction of the second neck portion), W3: Width of the third neck portion (dimension in the width direction of the third neck portion)

Claims

1. A brush comprising a handle body formed of hard resin and extending in a longitudinal direction; and a brush section formed of soft resin and disposed on one side of the handle body in the longitudinal direction, wherein the brush section has a brush base section and a plurality of filaments molded integrally with the brush base section, each of the plurality of filaments protruding from the brush base section toward one side in a thickness direction intersecting the longitudinal direction, wherein the handle body has a neck section extending in the longitudinal direction, a connection section protruding from the neck section to one side in the longitudinal direction, a fitting section protruding from the connection section to one side in the longitudinal direction, a connection edge section which is a part of the connection section, and a neck edge section which is a part of the neck section, wherein the connection section, the fitting section, and the brush base section constitute a head shaft section, and the connection edge section is an end section of the connection section on one side in the longitudinal direction and an end section on one side in a width direction intersecting both the longitudinal direction and the thickness direction, a neck edge portion being an end portion on one side of the width direction of a portion of the neck portion having the smallest dimension in the width direction; a maximum dimension in the thickness direction of the head shaft portion being 3.0 mm or more and 4.5 mm or less; a minimum dimension in the width direction of the neck portion being 3.0 mm or more and 4.5 mm or less; and an angle formed by a first imaginary line passing through both the connecting edge portion and the neck edge portion and a central axis extending through the center of the handle body toward the longitudinal direction, when viewed from the thickness direction, is 17° or more and 28° or less.

2. The toothbrush of claim 1, wherein the brush base has a mating hole into which the mating portion is inserted and fitted, the handle body has a mating edge portion, the mating edge portion being the other end of the mating portion in the longitudinal direction and one end in the width direction, and when viewed from the thickness direction, the angle formed by a second imaginary line passing through both the neck edge portion and the mating edge portion and the central axis is greater than or equal to 10° and less than 18°.

3. The neck portion has a first neck portion, a second neck portion, and a third neck portion, and a first distance L1 is a distance in the long axis direction between a connection tip portion which is an end portion of the connection portion on one side in the long axis direction and an end portion of the neck portion on the other side in the long axis direction, and a ratio of the distance between the connection tip portion and the first neck portion to the first distance in the long axis direction is 20%, and a ratio of the distance between the connection tip portion and the second neck portion to the first distance in the long axis direction is 80%, and a ratio of the distance between the connection tip portion and the third neck portion to the first distance in the long axis direction is 100%, where W1 is the width dimension of the first neck portion, T1 is the thickness dimension of the first neck portion, W2 is the width dimension of the second neck portion, T2 is the thickness dimension of the second neck portion, W3 is the width dimension of the third neck portion, and T3 is the thickness dimension of the third neck portion. ４ ≦W1×T1 ３ ≦400mm ４ And, 450 mm ４ ≦W2×T2 ３ ≦1200mm ４ And, 2000mm ４ ≦W3×T3 ３ ≦5000mm ４ The toothbrush according to claim 1 or 2, which satisfies the relationship:

4. The toothbrush of claim 1 or 2, wherein each of the multiple filaments has a first filament portion and a second filament portion, and when viewed in the width direction, the amount of reduction in the dimension in the major axis direction per unit length in the thickness direction of each of the multiple filaments gradually increases from the brush base portion toward one side in the thickness direction, and in the thickness direction, the ratio of the distance between the end of the filament on one side in the thickness direction and the first filament portion to the dimension of the filament is 15%, the second filament portion is a portion connected to the brush base, and the ratio of the area of ​​the cross section perpendicular to the thickness direction of the first filament portion to the area of ​​the cross section perpendicular to the thickness direction of the second filament portion is 20% or more and 30% or less.

5. The toothbrush as described in claim 4, wherein the ratio of the area of ​​the surface facing one side in the thickness direction of the brush base portion to the area of ​​the sum of the cross-sectional areas of the second filament portions of each of the multiple filaments perpendicular to the thickness direction is 25% or more and 35% or less.

6. The toothbrush according to claim 1 or 2, wherein, when a pressure member is brought into contact with a plurality of filaments from one side in the thickness direction while the other end of the neck portion in the longitudinal direction is fixed, and the pressure member is moved to the other side in the thickness direction, a first reaction force is a reaction force that the pressure member receives from the plurality of filaments, a first reaction force fluctuation rate is a value obtained by dividing an amount of fluctuation of the first reaction force when the position of the pressure member in the thickness direction changes by a first predetermined distance, a first maximum value is a maximum value of the first reaction force fluctuation rate within a range where the movement distance of the pressure member is 3.0 mm or less, and RF1min is a first minimum value is a minimum value of the first reaction force fluctuation rate within a range where the movement distance of the pressure member is 3.0 mm or less, and when the first predetermined distance is 0.1 mm, the toothbrush satisfies the relationship RF1max-RF1min≦0.6 N / mm.

7. The toothbrush according to claim 6, wherein a first average value RF1ave, which is an average value of the first reaction force fluctuation rate within a range in which the movement distance of the pressure member is 3.0 mm or less, is 0.5 N / mm or more and 1.0 N / mm or less.

8. In a case where a pressing member is brought into contact with the plurality of filaments from one side in the thickness direction while the brush base is supported from the other side in the thickness direction, and the pressing member is moved to the other side in the thickness direction, the pressure that the pressing member receives from the plurality of filaments is defined as a second pressure, and a second pressure fluctuation rate RP is a value obtained by dividing the amount of fluctuation in the second pressure when the position of the pressing member in the thickness direction changes by a second predetermined distance, by the second predetermined distance, and when the second predetermined distance is 0.1 mm, the second pressure fluctuation rate RP is 0.0 N / mm when the moving distance of the pressing member is within a range of 1.0 mm or less. ３ That's it, 10.0 x 10 －２ N / mm ３ 3. The toothbrush according to claim 1 or 2, wherein:

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