Toothbrush

Abstract

In the present invention, a toothbrush is provided with a handle body formed from a hard resin, and a brush part formed from a soft resin. The brush portion has a brush base portion and filaments. The filaments protrude from the brush base portion toward one side in the thickness direction. The handle body is provided with a neck part, a connecting part and an embedding part. The connecting portion, the fitting portion, and the brush base portion constitute a head shaft portion. The connecting edge portion is an end portion on one side of the connecting portion in the long axis direction and an end portion on one side of the connecting portion in the width direction. The neck edge portion is an end portion on one side in the width direction of a portion where the dimension in the width direction of the neck portion is smallest. The maximum dimension of the head shaft portion in the thickness direction is 3.0 mm or more and 4.5 mm or less. The minimum dimension of the neck portion in the width direction is 3.0 mm or more and 4.5 mm or less. An angle formed by a first imaginary line passing through both the connecting edge portion and the neck edge portion and the central axis is 17-28 DEG.

Description

Technical Field

[0001] This invention relates to toothbrushes.

[0002] This application claims priority based on Japanese Patent Application No. 2023-162902, filed in Japan on September 26, 2023, the contents of which are incorporated herein by reference. Background Technology

[0003] A one-piece molded toothbrush having filaments formed from soft resin has been proposed (for example, Patent Document 1). In the toothbrush in question, due to the softness of the filaments, it is easier to obtain a superior contact feel compared to a toothbrush where the bristles are formed from spun bristles.

[0004] Existing technical documents Patent documents Patent Document 1: International Publication No. 2019 / 055364 Summary of the Invention

[0005] The technical problem that the invention aims to solve In the toothbrushes described above, the brush head is molded from soft resin, thus reducing the volume of the hard resin head compared to toothbrushes where the bristles are made of spun fibers. The toothbrushes described above typically feature structures that increase the width of the head and neck, enhance rigidity from the head to the neck, and suppress head deformation. However, in the toothbrushes in question, if the neck's deflection is too small, the brushing load is concentrated on the filaments, sometimes resulting in excessive filament deflection. In this case, the filaments struggle to penetrate between the teeth, thus reducing interdental cleaning performance. Furthermore, if the neck's rigidity is too small, the neck's deflection becomes excessive, reducing the operability of the head within the mouth. This reduces the toothbrush's operability. Additionally, during brushing, the movement of the filament tips (bristle tips) is difficult to coordinate with the user's hand movements, thus affecting interdental cleaning performance.

[0006] The present invention was made with the above-mentioned points in mind, and one of its objectives is to provide a toothbrush that can improve the cleaning performance between teeth and prevent the toothbrush from becoming less maneuverable.

[0007] Technical solutions for solving technical problems The present invention contains the following structure.

[0008] [1] A toothbrush comprising: a handle body formed of hard resin and extending along a long axis; and a brush portion formed of soft resin and disposed on one side of the handle body along the long axis, the brush portion having: a brush base portion; and a plurality of filaments integrally formed with the brush base portion, each of the plurality of filaments protruding from the brush base portion toward a thickness direction intersecting the long axis direction, the handle body having: a neck extending along the long axis direction; a connecting portion protruding from the neck toward one side along the long axis direction; a fitting portion protruding from the connecting portion toward one side along the long axis direction; a connecting edge portion being a part of the connecting portion; and a neck edge portion being a part of the neck, the connecting portion, the fitting portion, and The brush base portion constitutes the head shaft portion. The connecting edge portion is the end of the connecting portion on one side in the long axis direction and the end of the connecting portion on one side in the width direction, which intersects both the long axis direction and the thickness direction. The neck edge portion is the end of the neck portion on one side in the width direction of the smallest part in the width direction. The maximum dimension of the head shaft portion in the thickness direction is 3.0 mm or more and 4.5 mm or less. The minimum dimension of the neck portion in the width direction is 3.0 mm or more and 4.5 mm or less. When viewed from the thickness direction, the angle between the first imaginary line passing through the connecting edge portion and the neck edge portion and the central axis extending from the center of the handle body toward the long axis direction is 17° or more and 28° or less.

[0009] [2] According to the toothbrush of [1], the brush base portion has a fitting hole for the fitting portion to be inserted and fitted, the handle body has a fitting edge portion, the fitting edge portion is the end of the fitting portion on the other side of the long axis direction and the end of the fitting portion on the side of the width direction, and the angle between the second imaginary line passing through the neck edge portion and the fitting edge portion and the central axis is more than 10° and less than 18° when viewed from the thickness direction.

[0010] [3] According to the toothbrush described in [1] or [2], wherein the neck has a first neck, a second neck and a third neck, and the distance in the long axis direction between the end of the connecting portion on one side of the long axis direction, i.e. the connecting front end, and the end of the neck on the other side of the long axis direction is set as a first distance (L1), in the long axis direction, the ratio of the distance between the connecting front end and the first neck to the first distance is 20%, in the long axis direction, the ratio of the distance between the connecting front end and the second neck to the first distance is 80%, in the long axis direction, the ratio of the distance between the connecting front end and the third neck to the first distance is 100%, and when the dimension in the width direction of the first neck is set as W1, the dimension in the thickness direction of the first neck is set as T1, the dimension in the width direction of the second neck is set as W2, the dimension in the thickness direction of the second neck is set as T2, the dimension in the width direction of the third neck is set as W3, and the dimension in the thickness direction of the third neck is set as T3, 130mm is satisfied. 4 ≤W1×T1 3 ≤400mm 4 450mm 4 ≤W2×T2 3 ≤1200mm 4 And 2000mm 4 ≤W3×T3 3 ≤5000mm 4 The relationship.

[0011] [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 from the width direction, the size of each of the plurality of filaments in the long axis direction decreases in stages relative to the unit length in the thickness direction as it moves from the brush base portion toward the thickness direction, and in the thickness direction, the distance between the end of the filament on the thickness direction side and the first filament portion is 15% of the size of the filament, the second filament portion is a portion connected to the brush base portion, and the area of ​​the cross section of the first filament portion orthogonal to the thickness direction is 20% or more and 30% or less of the area of ​​the cross section of the second filament portion orthogonal to the thickness direction.

[0012] [5] According to the toothbrush of [4], the ratio of the area obtained by adding the areas of the cross sections of the second filament portion of each of the plurality of filaments that are orthogonal to the thickness direction to the area of ​​the surface of the brush base portion facing the thickness direction is 25% or more and 35% or less.

[0013] [6] The toothbrush according to any one of [1] to [5], wherein, when the pressure member is brought into contact with the plurality of filaments from one side of the thickness direction with the end of the neck fixed on the other side of the long axis direction, and the pressure member is moved to the other side of the thickness direction, the reaction force received by the pressure member from the plurality of filaments is defined as the first reaction force, the value obtained by dividing the change in the first reaction force by the first given distance when the position of the pressure member in the thickness direction changes only by the first given distance is defined as the first reaction force variation rate, the maximum value of the first reaction force variation rate within the range where the movement distance of the pressure member is less than 3.0 mm is defined as the first maximum value, the minimum value of the first reaction force variation rate within the range where the movement distance of the pressure member is less than 3.0 mm is defined as the first minimum value, and the first given distance is defined as 0.1 mm, the relationship RF1max-RF1min≤0.6N / mm is satisfied.

[0014] [7] According to the toothbrush of [6], wherein the average value of the first reaction force variation rate within the range of the moving distance of the pressure member being less than 3.0 mm, i.e., the first average value RF1ave, is more than 0.5 N / mm and less than 1.0 N / mm.

[0015] [8] The toothbrush according to any one of [1] to [7], wherein, when the pressure member is brought into contact with the plurality of filaments from one side of the thickness direction in a state where the brush base is supported from the other side of the thickness direction, and the pressure member is moved to the other side of the thickness direction, the reaction force received by the pressure member from the plurality of filaments is defined as the second pressure, and the second pressure variation rate is defined as the value obtained by dividing the amount of change of the second pressure when the position of the pressure member in the thickness direction changes only by the second given distance by the second given distance, and the second given distance is defined as 0.1 mm, the second pressure variation rate RP is 0.0 N / mm in the range where the moving distance of the pressure member is 1.0 mm or less. 3 Above and 10.0×10 -2 N / mm 3 the following.

[0016] Invention Effects In this invention, a toothbrush is provided that can improve the cleaning performance between teeth and prevent the toothbrush from becoming less operable. Attached Figure Description

[0017] Figure 1 This is a front view of the toothbrush used in the embodiment.

[0018] Figure 2This is a side view of the toothbrush used in the embodiment.

[0019] Figure 3 This is a front view of the handle body representing the implementation method.

[0020] Figure 4 This is a side view of the handle body in the embodiment.

[0021] Figure 5 This is a front view showing the brush section of the implementation method.

[0022] Figure 6 This is a cross-sectional view showing the brush portion in the embodiment. Figure 5 Sectional view VI-VI in the middle.

[0023] Figure 7 This is a cross-sectional view showing a portion of the brush section in an embodiment.

[0024] Figure 8 This is a diagram showing a portion of a toothbrush used in an embodiment.

[0025] Figure 9 This is a front view showing a portion of the toothbrush used in the embodiment.

[0026] Figure 10 This is a side view of the first flexure test apparatus.

[0027] Figure 11 This is a diagram illustrating an example of the first reaction force in the implementation method.

[0028] Figure 12 This is a diagram illustrating the calculation method for the rate of change of the first reaction force in the implementation method.

[0029] Figure 13 This is a diagram illustrating an example of the rate of change of the first reaction force in an embodiment.

[0030] Figure 14 This is a side view of the second flexure test apparatus.

[0031] Figure 15 This is a diagram illustrating an example of the second pressure in an implementation method.

[0032] Figure 16 This is a graph illustrating an example of the second pressure variation rate in the implementation method.

[0033] Figure 17 This is a graph representing the rate of change of the first reaction force in the first flexure test.

[0034] Figure 18 This is a graph representing the second pressure variation rate in the second flexure test. Detailed Implementation

[0035] The following description illustrates an example of the toothbrush of the present invention, based on the accompanying drawings. It should be noted that the dimensions and other details in the figures illustrated in the following description are merely examples, and the present invention is not limited thereto; it can be implemented with appropriate modifications without altering its spirit.

[0036] In the accompanying figures, the XYZ coordinate system is shown as a three-dimensional orthogonal coordinate system. In the XYZ coordinate system, the X-axis direction is the major axis direction. The major axis direction is the direction in which the toothbrush extends. The +X side is the front end side of the toothbrush, and the -X side is the rear end side of the toothbrush. In the following description, the front end side of the toothbrush will be simply referred to as the "front end side" or "one side along the major axis," and the rear end side of the toothbrush will be simply referred to as the "rear end side" or "the other side along the major axis."

[0037] The Z-axis direction intersects the X-axis direction and represents the thickness direction of the toothbrush. In this embodiment, the Z-axis direction is orthogonal 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 back side of the toothbrush will be simply referred to as the "back side" or "the other side in the thickness direction."

[0038] The Y-axis direction intersects both the X-axis and Z-axis directions and represents the width direction of the toothbrush. In this embodiment, the Y-axis direction is orthogonal to both the X-axis and Z-axis directions. The +Y side is one side of the toothbrush's width direction, and the -Y side is the other side. In the following description, one side of the toothbrush's width direction will be simply referred to as "one side of the width direction," and the other side of the toothbrush's width direction will be simply referred to as "the other side of the width direction."

[0039] In the following descriptions, the dimension along the major axis of a component may be referred to simply as "length". Similarly, the dimension along the width of a component may be referred to simply as "width". The dimension along the thickness of a component may be referred to simply as "thickness". Furthermore, the view of an object from the front may be called the "front view", and the shape of the object viewed from the front may be called the "front view shape". Additionally, the view of an object from the width direction may be called the "side view", and the shape of the object viewed from the width direction may be called the "side view shape".

[0040] Figure 1 This is a front view of the toothbrush 1 according to this embodiment. Figure 2 This is a side view showing the toothbrush 1 according to this embodiment. Figure 1 As shown, the toothbrush 1 includes a handle body 10 and a brush part 20. The handle body 10 and the brush part 20 are separate and independent components. The handle body 10 and the brush part 20 are made of resin. The handle body 10 is a rod-shaped component extending along its long axis. The brush part 20 is located on the front end side of the handle body 10, i.e., on one side along its long axis (+X side).

[0041] Figure 3 This is a front view of the handle body 10 in this embodiment. Figure 4 This is a side view showing the handle body 10 of this embodiment. (See attached image.) Figure 3 As shown, the handle body 10 includes: a handle main body 11, which is rod-shaped and extends along its long axis; a fitting portion 15, which protrudes from the front end of the handle main body 11 toward the front end side, i.e., one side (+X side) along the long axis; and a fitting edge portion 15d. In the toothbrush 1 of this embodiment, the brush part 20 is mounted to the handle body 10 by fitting the fitting portion 15 into the fitting hole 27 of the brush part 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.

[0042] In this embodiment, the handle body 10 is formed of a rigid resin. Examples of rigid resins forming the handle body 10 include resins with a flexural modulus (JIS K7171) of 1500 MPa or more and 3000 MPa or less. Specifically, 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, as a general-purpose resin, is preferred from a manufacturing cost perspective, while polybutylene terephthalate resin and polyacetal resin are preferred from a strength perspective.

[0043] like Figure 3 As shown, the main view shape of the handle body 11 in this embodiment gradually narrows in width from the front end to the rear end, reaching the first boundary 13a. Upon reaching the first boundary 13a, the width gradually widens, reaching the second boundary 13b. Then, the width changes in a manner that gradually narrows, then widens, and then narrows again. The main view shape of the rear end of the handle body 11 is approximately semi-circular. It should be noted that when the main view shape of the handle body 11 gradually narrows in width from the front end to the rear end and then extends along the long axis with the same width, the first boundary 13a is the front end of the portion extending along the long axis with the same width. Viewed from the thickness direction, Figure 3 The central axis J shown is a straight line extending from the center of the handle body 10 toward the long axis. The main view shape of the handle body 11 is a plane-symmetrical shape that passes through the central axis J and has a plane of symmetry that extends in a direction orthogonal to the width direction.

[0044] like Figure 4As shown, the side view shape of the handle body 11 in this embodiment changes as follows: from the front end to the rear end, it curves in a manner that gradually thins and then gradually increases in thickness after reaching the first boundary 13a, reaching the second boundary 13b. Upon reaching the second boundary 13b, it curves in a manner that gradually thins and then extends with a substantially constant thickness, after which the thickness thins again. The side view shape of the rear end of the handle body 11 is approximately semi-circular. More specifically, the second boundary 13b is the portion where the edge of the front side (+Z side) curves upwards from the front end to the rear end, connecting to the first upper edge 11a, and the edge of the front side curves downwards from the front end to the rear end. Although not shown in the figure, the center of curvature of the first upper edge 11a and the center of curvature of the second upper edge 11b are each located higher than the handle body 11. The second boundary portion 13b is the portion of the handle body portion 11 that has a convex shape with a apex protruding towards the front side.

[0045] It should be noted that, furthermore, when the handle body 11 does not have a convex apex, or when the convex apex cannot be visually identified, the second boundary portion 13b is the portion where the curvature center of the edge on the front side (+Z side) of the handle body 11 changes. When the portion where the curvature center of the edge on the front side of the handle body 11 changes cannot be determined, the second boundary portion 13b is the portion where hard resin and soft resin contact in the long axis direction. Furthermore, when the portion where hard resin and soft resin contact in the long axis direction cannot be determined, the second boundary portion 13b is the portion 73 mm from the rear end of the head 5 (described later). In this embodiment, the front end of the head 5 is the front end of the brush portion 20.

[0046] It should be noted that in this invention, the shape of the handle body 11 is not limited to the shape of this embodiment, and can be appropriately set considering strength, operability, and aesthetic design. The size of the handle body 11 is not particularly limited and can be appropriately set. Figure 3 As shown, the handle body 11 has a gripping part 12, a neck 13, a connecting part 14, a neck edge 13d, and a connecting edge 14d.

[0047] The grip portion 12 is the part of the handle body 11 that is further back than the second boundary portion 13b. The grip portion 12 is a rod-shaped part extending along its long axis. Figure 1 as well as Figure 2As shown, a finger contact portion 17 is provided on the outer surface of the grip portion 12. The finger contact portion 17 is formed of a soft resin. Various elastomers such as polyurethane-based and styrene-based resins can be used as the soft resin for forming the finger contact portion 17. When the user uses the toothbrush 1, the grip of the toothbrush 1 is improved by holding the grip portion 12 while making contact with the finger contact portion 17.

[0048] like Figure 3 As shown, the neck 13 is the portion between the first boundary portion 13a and the second boundary portion 13b in the handle body portion 11. The neck 13 is rod-shaped and extends along its long axis. In this embodiment, the second boundary portion 13b is the boundary between the neck 13 and the grip portion 12. The shape of the neck 13, etc., will be described in detail later.

[0049] The connecting portion 14 is the part of the handle body 11 that is further forward than the first boundary portion 13a. The first boundary portion 13a is the boundary between the connecting portion 14 and the neck 13. The connecting portion 14 protrudes from the neck 13 towards the front end, i.e., the side along the long axis (+X side). The connecting portion 14 connects the neck 13 to the fitting portion 15. The width of the connecting portion 14 changes in a curved shape, being widest at the front end and gradually narrowing towards the rear end, becoming narrowest at the rear end. Figure 4 As shown, the thickness of the connecting portion 14 is thickest at the front end and gradually thins towards the rear end, being thinnest at the rear end. The connecting portion 14 has a first opposing surface 14b. The first opposing surface 14b is the surface of the outer surface of the connecting portion 14 facing the front end.

[0050] like Figure 3 As shown, the connecting edge 14d is a part of the connecting portion 14. The connecting edge 14d is the end of the connecting portion 14 on one side (+X side) in the long axis direction and on one side (+Y side) in the width direction. In the front view, the connecting edge 14d is the portion of the connecting portion 14 located on the side closest to the width direction. The connecting edge 14d is located on the side closest to the width direction than the first boundary portion 13a.

[0051] like Figure 2 As shown, with the brush portion 20 mounted on the handle body 10, the fitting portion 15 is located inside the brush portion 20. Figure 3 and Figure 4 As shown, the fitting portion 15 protrudes from the first opposing surface 14b of the connecting portion 14 toward the front end side. (As indicated...) Figure 3 As shown, a pair of recesses 15a and 15b are provided in the fitting portion 15. One recess 15a is recessed from the side of the fitting portion 15 facing the width direction (+Y side) to the other side facing the width direction (-Y side). The other recess 15b is recessed from the side of the fitting portion 15 facing the width direction to the other side facing the width direction. Each of the pair of recesses 15a and 15b is approximately semi-circular in front view.

[0052] The mating edge 15d is the end of the mating portion 15 on the other side (-X side) in the long axis direction and on the other side (+Y side) in the width direction. The mating edge 15d is located on the side further in the width direction than the first boundary portion 13a. The mating edge 15d is located on the other side (-Y side) in the width direction than the connecting edge 14d. It should be noted that even in a structure where the mating portion 15 has a through hole, the mating portion 15 still exists; in this case, the hard resin portion covered by soft resin is the mating portion.

[0053] Figure 5 This is a front view showing the brush section 20 of this embodiment. Figure 6 This is a cross-sectional view showing the brush section 20 of this embodiment. Figure 5 Sectional view VI-VI in the middle. Figure 7 This is a cross-sectional view showing a portion of the brush portion 20 according to the embodiment. The brush portion 20 is formed of a soft resin. For example... Figure 5 and Figure 6 As shown, the brush portion 20 has a brush base portion 21 and a plurality of filaments 30 integrally formed with the brush base portion 21. In this embodiment, the brush portion 20 is formed by molding the handle body 10, which is made of hard resin, as an insert member. That is, the toothbrush 1 of this embodiment is a one-piece toothbrush in which the brush portion 20 and the handle body 10 are integrally formed. The toothbrush 1 of this embodiment is a one-piece toothbrush in which the filaments 30 are made of soft resin.

[0054] like Figure 5 As shown, the brush base portion 21 of this embodiment has a curved shape in which the width gradually increases from the front end to the rear end. The front end of the brush base portion 21 has a roughly semi-circular shape in its main view. Figure 6 As shown, the side view shape of the brush base portion 21 in this embodiment varies in thickness from the front end side to the rear end side. More specifically, the surface of the brush base portion 21 facing the back side (-Z side) is located on the back side as it moves from the front end side to the rear end side. The surface of the brush base portion 21 facing the front side (+Z side), i.e., the upper surface 21a, is a plane that extends in a direction orthogonal to the thickness direction.

[0055] The surface facing the rear end of the outer side of the brush base portion 21 is the second opposing surface 21d. Although not shown in the figure, the second opposing surface 21d is approximately rectangular when viewed along its long axis. Figure 1 As shown, with the brush portion 20 mounted on the handle body 10, the second opposing surface 21d and the first opposing surface 14b of the handle body 10 are opposed in the long axis direction. In this embodiment, the second opposing surface 21d and the first opposing surface 14b are in contact in the long axis direction.

[0056] like Figure 6 As shown, the brush base portion 21 has a fitting hole 27 recessed from the second opposing surface 21d toward the front end side. Figure 2 As shown, a fitting part 15 is disposed inside the fitting hole 27. (As indicated...) Figure 6 As shown, the inner surface of the fitting hole 27 facing the back side (-Z side) is a plane that extends in a direction orthogonal to the thickness direction. The inner surface of the fitting hole 27 facing the front side (+Z side) is located on the back side as it moves from the front end side toward the rear end side.

[0057] like Figure 5 As shown, a pair of protrusions 27a and 27b are provided in the fitting hole 27. One protrusion 27a protrudes from the side of the fitting hole 27 facing the width direction (-Y side). The other protrusion 27b protrudes from the side of the fitting hole 27 facing the width direction (+Y side). Viewed in the thickness direction, each of the protrusions 27a and 27b is approximately semi-circular. Each of the protrusions 27a and 27b engages with a pair of recesses 15a and 15b.

[0058] like Figure 6 As shown, multiple filaments 30 each protrude from the upper surface 21a of the brush base portion 21 toward the front side, i.e., the thickness direction (+Z side). Each filament 30 is formed of soft resin. Figure 5 As shown, on the upper surface 21a, multiple rows of filaments 30 arranged along the width direction are arranged in the long axis direction. In the following description, the root of the filament 30 is the end on the back side of the filament 30, which is the part connected to the brush base portion 21. The front end of the filament 30 is the end on the front side of the filament 30. The shape of the filament 30, etc., will be described in detail later.

[0059] Various elastomers can be used as the soft resin constituting the brush part 20, but polyurethane is preferred. Compared with other elastomers such as styrene-based and polyester-based elastomers, polyurethane has high tensile strength, so mechanical strength can be ensured even when it is made into a thin-walled form. Therefore, it is possible to prevent the toothbrush 1 from breaking during use.

[0060] Furthermore, compared to other elastomers mentioned above, polyurethane offers a wider range of selectable hardness. Depending on the thickness of the brush portion 20, a resin hardness that takes into account its operability (e.g., the bending of the tip of the brush portion 20) can be chosen. Preferably, the hardness of the polyurethane is a Shore hardness of A90 or higher and A100 or lower, or a Shore hardness of D40 or higher and D70 or lower. When the hardness of the polyurethane is lower than Shore 90A, it is prone to deformation due to its thin wall structure, resulting in weaker fit and making it easier for the brush portion 20 to detach during toothbrush 1 use. When the hardness of the polyurethane is higher than Shore 70D, the angled shape of the back of the brush base portion 21 may cause pain when the tip of the brush base portion 21 touches the mouth. By setting the hardness of the polyurethane to Shore 90A or higher and 70D or lower, it is possible to prevent the brush portion 20 from detaching during toothbrush 1 use and to suppress pain when the tip of the brush base portion 21 touches the mouth.

[0061] Polyurethane can be mixed with 0.01 wt% (by mass) or more and 1.0 wt% (by mass) of any component selected from 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 glycerides, and organosilicones, or in combination, to function as a lubricant and release agent. Furthermore, from the viewpoint of ensuring water resistance and antibacterial properties, ether-based polyurethanes are preferred.

[0062] like Figure 1 and Figure 2 As shown, the toothbrush 1 of this embodiment includes a head 5 and a head shaft 6. In this embodiment, the connecting part 14, the fitting part 15, and the brush part 20 constitute the head 5. The head 5 is the portion of the toothbrush 1 that is further forward than the first boundary part 13a. When using the toothbrush 1, the head 5 is located inside the mouth and is the part used to clean the inside of the mouth.

[0063] The maximum width of the head 5 is preferably 11 mm or less. This improves the operability of the head 5 in the oral cavity, thereby enhancing oral cleaning performance.

[0064] 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 5. The head shaft portion 6 is the portion after the multiple filaments 30 have been removed from the head 5. The head shaft portion 6 is the portion of the handle body 10 that is further forward than the first boundary portion 13a.

[0065] Figure 8 This is a diagram showing a portion of the toothbrush 1 according to this embodiment. More specifically, Figure 8 (a) is a side view showing a portion of the toothbrush 1 of this embodiment. Figure 8(b) is a side view showing a portion of the handle body 10 of this embodiment. Figure 8 (c) is a front view showing a portion of the handle body 10 in this embodiment.

[0066] In this embodiment, Figure 8 The maximum thickness Th of the head shaft portion 6 shown in (b) is 3.0 mm or more and 4.5 mm or less in the thickness direction.

[0067] Next, the shape of the neck 13 in this embodiment will be described in detail. As described above, the neck 13 is the portion between the first boundary portion 13a and the second boundary portion 13b in the handle body 10. Figure 8 As shown in (c), in this embodiment, the width of the neck 13 gradually increases from the first boundary portion 13a toward the second boundary portion 13b. The width of the neck 13 is narrowest at the first boundary portion 13a and widest at the second boundary portion 13b. Figure 8 As shown in (b), in this embodiment, the thickness of the neck 13 extends towards the rear end with the same thickness from the first boundary portion 13a toward the second boundary portion 13b, then changes linearly in a manner that gradually increases in thickness, and then changes in a curved manner in a manner that gradually increases in thickness as it extends towards the rear end. The thickness of the neck 13 is thinnest at the first boundary portion 13a and thickest at the second boundary portion 13b.

[0068] Figure 9 This is a front view showing a portion of the toothbrush 1 according to this embodiment.

[0069] like Figure 9 As shown, the neck edge 13d is a part of the neck 13. The neck edge 13d is the end of the first boundary portion 13a on one side (+Y side) in the width direction. As described above, the first boundary portion 13a is the narrowest part of the neck 13. Therefore, the neck edge 13d is the end of the portion of the neck 13 with the smallest dimension in the width direction on one side in the width direction. In this embodiment, the width Wa of the first boundary portion 13a, i.e., the minimum dimension in the width direction of the neck 13, is 3.0 mm or more and 4.5 mm or less. Viewed from the thickness direction, Figure 9 The first imaginary line V1 shown is a straight line passing through both the connecting edge 14d and the neck edge 13d. In this embodiment, when viewed from the thickness direction, the angle formed by the first imaginary line V1 and the central axis J is the first angle. θ 1 is between 17° and 28°.

[0070] In a one-piece molded toothbrush where the filaments 30 are made of soft resin, if the rigidity of the head shaft 6 and neck 13 is too high, when using the toothbrush 1, if a brushing load in the thickness direction is applied to the brush part 20, the head shaft 6 and neck 13 will be difficult to bend. Therefore, it is difficult to absorb the brushing load applied to the brush part 20 through the bend of the head shaft 6 and neck 13, and stress concentrates on each filament 30. Consequently, if the bend of each filament 30 becomes too large when using the toothbrush 1, it is difficult for each filament 30 to penetrate deep into the interdental spaces. Therefore, it is difficult to remove plaque from between the teeth through the filaments 30, thus reducing the interdental cleaning performance. Conversely, if the rigidity of the head shaft 6 and neck 13 is too low, the bend of the head shaft 6 and neck 13 becomes too large when using the toothbrush 1. Therefore, the operability of the head 5 in the oral cavity is reduced. Thus, the operability of the toothbrush 1 is reduced. Furthermore, the movement of the tips of each filament 30 is difficult to coordinate with the user's hand movements, thus reducing the interdental cleaning performance.

[0071] In contrast, according to this embodiment, the maximum thickness Th of the head shaft portion 6, i.e., the maximum dimension in the thickness direction of the head shaft portion 6, is 3.0 mm or more and 4.5 mm or less. Therefore, it is possible to prevent the rigidity of the head shaft portion 6 from becoming excessively large and to prevent the rigidity of the head shaft portion 6 from becoming excessively small. As a result, when using the toothbrush 1, the head shaft portion 6 flexes appropriately, thus preventing stress concentration on each filament 30. Therefore, the portion of the toothbrush 1 from each filament 30 to the head shaft portion 6 flexes in conjunction. Therefore, it is possible to prevent the flexing of each filament 30 from becoming excessive, thus improving the interdental cleaning performance. Furthermore, it is possible to prevent the flexing of the head shaft portion 6 from becoming excessive, thus preventing a decrease in the operability of the toothbrush 1, and the movement of the tips of each filament 30 is easily coordinated with the user's hand movements, thus further improving the interdental cleaning performance.

[0072] Furthermore, according to this embodiment, the minimum dimension of the width Wa of the first boundary portion 13a, i.e., the width direction of the neck 13, is 3.0 mm or more and 4.5 mm or less. Therefore, it is possible to prevent the rigidity of the neck 13 from becoming excessively large and to prevent the rigidity of the neck 13 from becoming excessively small. Thus, when using the toothbrush 1, the neck 13 flexes appropriately, thereby preventing stress concentration on each filament 30. Therefore, the portion of the toothbrush 1 from each filament 30 to the neck 13 flexes in conjunction. Therefore, it is possible to prevent the flexing of each filament 30 from becoming excessive, thereby improving the interdental cleaning performance more appropriately. In addition, it is possible to prevent the flexing of the neck 13 from becoming excessive. Therefore, it is possible to more appropriately prevent a decrease in the operability of the toothbrush 1, and the movement of the tips of each filament 30 is more easily and appropriately coordinated with the movement of the user's hand, thereby improving the interdental cleaning performance more appropriately.

[0073] Furthermore, according to this embodiment, the connecting edge 14d is the end of the connecting part 14 on the front end side, i.e., on the side of the long axis direction (+X side), and on the side of the width direction (+Y side), and the neck edge 13d is the end of the neck 13 on the side of the width direction of the smallest portion in the width direction. Viewed from the thickness direction, the first imaginary line V1 passing through both the connecting edge 14d and the neck edge 13d forms a first angle with the central axis J extending from the center of the handle body 10 towards the long axis direction. θ 1 is between 17° and 28°.

[0074] First angle θ When the angle is less than 17°, the width of the neck 13 becomes too large relative to the width of the connecting portion 14, and therefore, the rigidity of the neck 13 becomes too large. As a result, when using the toothbrush 1, the deflection of the neck 13 becomes too small, and therefore, the deflection of each filament 30 becomes too large. Therefore, it is difficult for each filament 30 to penetrate deep into the interdental spaces, and thus, the interdental cleaning performance is reduced.

[0075] In addition, from the first angle θ When the angle is greater than 28°, the width of the neck 13 becomes too small relative to the width of the connecting portion 14, and therefore, the rigidity of the neck 13 becomes too small. As a result, the deflection of the neck 13 and the connecting portion 14 becomes too large, thus reducing the operability of the head 5 in the oral cavity and reducing the operability of the toothbrush 1.

[0076] In contrast, according to this embodiment, the first angle θ The angle is 17° or higher and 28° or lower. Therefore, when using toothbrush 1, the neck 13 and the connecting portion 14 flex appropriately and more uniformly in the long axis direction. This allows for more appropriate suppression of stress concentration on each filament 30 and more appropriate suppression of excessive flexing of the neck 13 and the connecting portion 14. Consequently, excessive flexing of each filament 30 can be more appropriately suppressed, thus improving interdental cleaning performance and reducing the operability of toothbrush 1. It should be noted that in this embodiment, uniform flexing of the component in the long axis direction means that the component flexes uniformly throughout the long axis direction, rather than only partially flexing a portion of it.

[0077] It should be noted that, from the first perspective θ 1 is preferably 18° or higher and 26° or lower. This allows for more appropriate improvement in interdental cleaning performance and more appropriate suppression of reduced operability of the toothbrush 1.

[0078] Furthermore, from the first angle θ More preferably, the angle is 20° or higher and 26° or lower. This allows for a more appropriate improvement in interdental cleaning performance and a more appropriate suppression of reduced operability of the toothbrush 1.

[0079] Figure 8 The width Wb of the front end of the connecting portion 14 shown in (c) and the width Wa of the first boundary portion 13a, i.e., the minimum width of the neck 13, preferably satisfy the relationship 2.0 ≤ Wb / Wa ≤ 2.8. By satisfying this relationship, it is possible to further suppress the rigidity of the neck 13 and the connecting portion 14 from becoming too large or too small, and therefore, the neck 13 and the connecting portion 14 can bend more appropriately when using the toothbrush 1. Therefore, the interdental cleaning performance can be improved more appropriately, and the reduction in the operability of the toothbrush 1 can be suppressed more appropriately.

[0080] The width Wb of the front end of the connecting portion 14 is preferably 8 mm or more and 14 mm or less. This allows the connecting portion 14 to bend more appropriately when using the toothbrush 1. Therefore, the interdental cleaning performance of the toothbrush 1 can be improved more appropriately, and the reduction in the operability of the toothbrush 1 can be more appropriately suppressed.

[0081] Figure 8 The length Lc of the connecting portion 14 shown in (c) is preferably 5 mm or more and 10 mm or less. Therefore, the connecting portion 14 flexes more appropriately when the toothbrush 1 is used. This allows for more appropriate improvement in the interdental cleaning performance of the toothbrush 1 and more appropriate suppression of decreased operability of the toothbrush 1.

[0082] Viewed from the thickness direction, Figure 3 The second imaginary line V2 shown is a straight line passing through both the neck edge 13d and the fitting edge 15d. The second angle formed by the second imaginary line V2 and the central axis J... θ 2 is between 10° and 18°.

[0083] Second angle θ When the angle is less than 10°, the width of the head shaft portion 6 becomes too wide, and therefore, the rigidity of the head shaft portion 6 becomes too great. As a result, the head shaft portion 6 is difficult to bend when using the toothbrush 1, and therefore, the bending of each filament 30 becomes too great. Consequently, it is difficult for each filament 30 to penetrate deep into the interdental spaces, and therefore, the interdental cleaning performance is reduced.

[0084] Additionally, from the second angle θ When the angle is greater than 18°, the width of the head shaft portion 6 becomes too narrow, and therefore, the rigidity of the head shaft portion 6 becomes too low. As a result, the deflection of the head shaft portion 6 becomes too large, thus reducing the operability of the head 5 in the oral cavity and reducing the operability of the toothbrush 1.

[0085] In contrast, according to this embodiment, the second angle θThe angle of 2 is between 10° and 18°, therefore, when using toothbrush 1, the head shaft 6 flexes moderately and uniformly in the long axis direction. This more appropriately suppresses excessive flexing of each filament 30, and also more appropriately suppresses excessive flexing of the head shaft 6. Consequently, the operability of toothbrush 1 is more appropriately suppressed, and the movement of the tips of each filament 30 is more easily coordinated with the user's hand movements, thus more appropriately improving interdental cleaning performance.

[0086] It should be noted that the second perspective θ 2 is preferably 11° or higher and 16° or lower. By using the second angle... θ By setting 2 within this range, it is possible to more appropriately suppress the excessive rigidity of the head shaft portion 6 and the excessively insufficient rigidity of the head shaft portion 6. As a result, it is possible to more appropriately suppress excessive deflection of each filament 30 and excessive deflection of the head shaft portion 6. Therefore, it is possible to more appropriately improve the interdental cleaning performance and more appropriately suppress the decrease in the operability of the toothbrush 1.

[0087] Furthermore, from the second angle θ 2 is more preferably 12° or more and 16° or less. By using the second angle θ By setting 2 within this range, the rigidity of the head shaft 6 can be more appropriately suppressed from becoming excessive. Therefore, the deflection of the head shaft 6 can be more appropriately suppressed from becoming excessive, and thus, the deflection of each filament 30 can be more appropriately suppressed from becoming excessive. As a result, the inter-tooth cleaning performance can be more appropriately improved.

[0088] Figure 8 The width Wm of the rear end of the fitting portion 15 shown in (c) and the width Wa of the first boundary portion 13a, i.e., the minimum width of the neck 13, preferably satisfy the relationship 1.5 ≤ Wm / Wa ≤ 3.5. By satisfying this relationship, it is possible to further suppress the rigidity of the head shaft portion 6 from becoming too large or too small. Therefore, when using the toothbrush 1, the head shaft portion 6 flexes more appropriately and more uniformly in the long axis direction. Thus, it is possible to further improve the interdental cleaning performance and more appropriately suppress the reduction in the operability of the toothbrush 1.

[0089] The width Wm of the rear end of the fitting portion 15 is preferably 6 mm or more and 12 mm or less. Therefore, when using the toothbrush 1, the head shaft portion 6 flexes more appropriately and more evenly in the long axis direction. This allows for more appropriate improvement in interdental cleaning performance and more appropriate suppression of decreased operability of the toothbrush 1.

[0090] like Figure 9As shown, the head 5 has a first head 5a and a head edge portion 5d. The first head 5a is the widest part of the head 5. In this embodiment, the first head 5a is located between the center of the brush portion 20 in the long axis direction and the rear end of the brush portion 20. It should be noted that when the head 5 is shaped to extend along the long axis direction with the maximum width, the rear end of the portion extending along the long axis direction with the maximum width is used as the first head 5a. The head edge portion 5d is the end of the first head 5a on one side (+Y side) in the width direction. In the front view, the head edge portion 5d is located on the side further in the width direction than the first boundary portion 13a.

[0091] Viewed from the thickness direction, Figure 9 The third imaginary line V3 shown is a straight line passing through both the neck margin 13d and the head margin 5d. The third angle formed by the third imaginary line V3 and the central axis J... θ 3 is preferably 15° or more and 25° or less. This is achieved by adjusting the third angle. θ By setting 3 within this range, the rigidity of the head shaft portion 6 can be further suppressed from becoming too large or too small. Therefore, when using the toothbrush 1, the head shaft portion 6 flexes more appropriately and more evenly in the long axis direction. As a result, the interdental cleaning performance can be improved more appropriately, and the reduction in the operability of the toothbrush 1 can be suppressed more appropriately.

[0092] Figure 9 The width Wh of the first head 5a (the maximum width of the head 5) and the width Wa of the first boundary portion 13a (the minimum width of the neck 13) preferably satisfy the relationship 2.5 ≤ Wh / Wa ≤ 4.5. By satisfying this relationship, the head shaft portion 6 flexes more appropriately and more uniformly in the long axis direction when using the toothbrush 1. Therefore, the interdental cleaning performance can be improved more appropriately, and the reduction in the operability of the toothbrush 1 can be suppressed more appropriately.

[0093] The width Wh of the first head 5a, i.e., the maximum width of the head 5, is preferably 10 mm or more and 16 mm or less. Therefore, when using the toothbrush 1, the head shaft 6 flexes more appropriately and more evenly in the long axis direction. This allows for more appropriate improvement in interdental cleaning performance and more appropriate suppression of decreased operability of the toothbrush 1.

[0094] like Figure 8 As shown, the neck 13 has a first neck P1, a second neck P2, a third neck P3, a fourth neck P4, a fifth neck P5, a seventh neck P7, an eighth neck P8, a ninth neck P9, and a tenth neck P10. The first neck P1, the second neck P2, the third neck P3, the fourth neck P4, the fifth neck P5, the seventh neck P7, the eighth neck P8, the ninth neck P9, and the tenth neck P10 are each a part of the neck 13.

[0095] In the long axis direction, the first neck P1 is located between the first boundary portion 13a and the second boundary portion 13b. Figure 8 The first distance L1 shown is the distance along the long axis between the front end portion 14a, which is the end portion of the connecting portion 14 on one side (+X side) of the long axis direction, and the end portion of the second boundary portion 13b, which is the end portion of the neck 13 on the other side (-X side) of the long axis direction. In the long axis direction, the ratio of the distance L2 between the front end portion 14a and the first neck P1 to the first distance L1 is 20%. The first neck P1 is the front end portion of the neck 13. The width W1 of the first neck P1 is wider than the width Wa of the first boundary portion.

[0096] In the long axis direction, the second neck P2 is located between the first neck P1 and the second boundary portion 13b. In the long axis direction, the ratio of the distance L3 between the connecting end portion 14a and the second neck P2 to the first distance L1 is 80%. The second neck P2 is the rear end portion of the neck 13. The width W2 of the second neck P2 is wider than the width W1 of the first neck P1. The thickness T2 of the second neck P2 is thicker than the thickness T1 of the first neck P1.

[0097] In the long axis direction, the third neck P3 is located further rearward than the second neck P2. In this embodiment, the third neck P3 is the second boundary portion 13b. That is, the third neck P3 is the rear end of the neck 13. In the long axis direction, the ratio of the distance L4 between the connecting front end portion 14a and the third neck P3 to the first distance L1 is 100%. The width W3 of the third neck P3 is wider than the width W2 of the second neck P2. The thickness T3 of the third neck P3 is thicker than the thickness T2 of the second neck P2.

[0098] According to this embodiment, the width W1 of the first neck P1 and the thickness T1 of the first neck P1 satisfy 130mm. 4 ≤W1×T1 3 ≤400mm 4 The relationship is as follows: The width W2 of the second neck P2 and the thickness T2 of the second neck P2 satisfy 450mm. 4 ≤W2×T2 3 ≤1200mm 4 The relationship between the width W3 and the thickness T3 of the third neck P3 is 2000mm. 4 ≤W3×T3 3 ≤5000mm 4 The relationship.

[0099] In W1×T1 3 Less than 130mm 4In this case, the rigidity of the front portion of the neck 13, including the first neck P1, becomes too low. Therefore, when using the toothbrush 1, the front portion of the neck 13 locally flexes significantly. Consequently, the operability of the head 5 in the oral cavity is reduced. Thus, the operability of the toothbrush 1 is reduced. In addition, the movement of the tips of each filament 30 is difficult to coordinate with the user's hand movements, thereby reducing the interdental cleaning performance.

[0100] In W2×T2 3 Less than 450mm 4 In this case, the rigidity of the rear end portion of the neck 13, including the second neck P2, becomes too low. Therefore, when using the toothbrush 1, the rear end portion of the neck 13 locally flexes significantly. Consequently, the operability of the toothbrush 1 is reduced, and its interdental cleaning performance is diminished.

[0101] In W3×T3 3 Less than 2000mm 4 In this case, the rigidity of the rear end of the neck 13 becomes too small, and therefore, when using the toothbrush 1, the rear end of the neck 13 locally flexes significantly. As a result, the operability of the toothbrush 1 is reduced, and the interdental cleaning performance is also reduced.

[0102] In W1×T1 3 Greater than 400mm 4 In this case, the rigidity of the front end portion of the neck 13, including the first neck P1, becomes too high. Consequently, when using the toothbrush 1, the deflection of the front end portion of the neck 13 becomes too low, and therefore, the deflection of each filament 30 becomes too high. As a result, the interdental cleaning performance is reduced.

[0103] In W2×T2 3 Greater than 1200mm 4 In this case, the rigidity of the rear end portion of the neck 13, including the second neck P2, becomes too high. Consequently, when using the toothbrush 1, the deflection of the rear end portion of the neck 13 becomes too low, and therefore, the deflection of each filament 30 becomes too high. As a result, the interdental cleaning performance is reduced.

[0104] In W3×T3 3 Greater than 5000mm 4 In this case, the rigidity of the rear end of the neck 13 becomes too large. As a result, when using the toothbrush 1, the deflection of the rear end of the neck 13 becomes too small, and therefore, the deflection of each filament 30 becomes too large. Consequently, the interdental cleaning performance is reduced.

[0105] In contrast, in this embodiment, because the above-described relationship is satisfied, large-scale localized bending of a portion of the neck 13 can be suppressed when using the toothbrush 1. Therefore, when using the toothbrush 1, the neck 13 bends more moderately and more uniformly in the long axis direction, and excessive bending of each filament 30 can be suppressed. That is, bending can occur in conjunction from each filament 30 to the rear end of the neck 13. Therefore, the decrease in operability of the toothbrush 1 can be suppressed more appropriately, and the movement of the tip of each filament 30 is more easily and appropriately coordinated with the movement of the user's hand, thus improving the interdental cleaning performance more appropriately.

[0106] The width W1 of the first neck P1 is preferably 3.5 mm or more and 4.5 mm or less, and the thickness T1 of the first neck P1 is preferably 3.5 mm or more and 4.5 mm or less. Therefore, when using the toothbrush 1, the front portion of the neck 13 flexes more appropriately and more uniformly in the long axis direction. This allows for more appropriate improvement in interdental cleaning performance and more appropriate suppression of reduced operability of the toothbrush 1.

[0107] The width W2 of the second neck P2 is preferably 4.5 mm or more and 5.5 mm or less, and the thickness T2 of the second neck P2 is preferably 4.5 mm or more and 5.5 mm or less. Therefore, when using the toothbrush 1, the rear end portion of the neck 13 flexes more appropriately and more uniformly in the long axis direction. This allows for more appropriate improvement in interdental cleaning performance and more appropriate suppression of decreased operability of the toothbrush 1.

[0108] The width W3 of the third neck P3 is preferably 6.0 mm or more and 10.0 mm or less, and the thickness T3 of the third neck P3 is preferably 6.0 mm or more and 10.0 mm or less. Therefore, when using the toothbrush 1, the rear end of the neck 13 flexes more appropriately. This improves the interdental cleaning performance and reduces the decrease in the operability of the toothbrush 1 more effectively.

[0109] In the long axis direction, the fourth neck P4 is located between the first neck P1 and the second neck P2. In the long axis direction, the ratio of the distance between the connecting end portion 14a and the fourth neck P4 to the first distance L1 is 40%. The fourth neck P4 is the front end portion of the neck 13. The width W4 of the fourth neck P4 is preferably 3.5 mm or more and 4.5 mm or less, and the thickness T4 of the fourth neck P4 is preferably 3.5 mm or more and 4.5 mm or less. Therefore, when using the toothbrush 1, the front end portion of the neck 13 flexes more appropriately and more uniformly in the long axis direction. Thus, the interdental cleaning performance can be improved more appropriately, and the reduction in the operability of the toothbrush 1 can be more appropriately suppressed.

[0110] In the long axis direction, the fifth neck P5 is located between the fourth neck P4 and the second neck P2. In the long axis direction, the ratio of the distance between the connecting end portion 14a and the fifth neck P5 to the first distance L1 is 60%. The fifth neck P5 is the rear end portion of the neck 13. The width W5 of the fifth neck P5 is preferably 4.0 mm or more and 5.0 mm or less, and the thickness T5 of the fifth neck P5 is preferably 4.0 mm or more and 5.0 mm or less. Therefore, when using the toothbrush 1, the rear end portion of the neck 13 flexes more appropriately and more uniformly in the long axis direction. Thus, the interdental cleaning performance can be improved more appropriately, and the reduction in the operability of the toothbrush 1 can be more appropriately suppressed.

[0111] The seventh neck P7 is located further rearward than the first boundary portion 13a. The distance along the long axis between the first boundary portion 13a and the seventh neck P7 is the same as the length Lm of the mating portion 15. The thickness T7 of the seventh neck P7 is preferably 5.0 mm or less. This prevents the neck 13 from becoming too rigid, thus allowing the neck 13 to flex appropriately when using the toothbrush 1. This also prevents excessive flexing of the filaments 30, thereby improving the interdental cleaning performance more effectively.

[0112] The minimum thickness of the neck 13, i.e., the thickness Ta of the first boundary portion 13a, the thickness T7 of the seventh neck 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 P7. As a result, it is possible to prevent the thickness T7 of the seventh neck P7 from becoming too thick. Therefore, it is possible to prevent the rigidity of the portion of the neck 13 between the first boundary portion 13a and the seventh neck P7 from becoming too large relative to the rigidity of the head shaft portion 6. Therefore, when using the toothbrush 1, the head shaft portion 6 and the neck 13 flex more appropriately and more uniformly in the length direction. Therefore, it is possible to improve the interdental cleaning performance more appropriately and to suppress the decrease in the operability of the toothbrush 1 more appropriately.

[0113] The eighth neck P8 is located further back than the seventh neck P7. The distance along the long axis between the first boundary portion 13a and the eighth neck P8 is the same as twice the length Lm of the fitting portion 15. The thickness T8 of the eighth neck P8 is preferably 8.0 mm or less. This prevents the neck 13 from becoming too rigid, and therefore, the neck 13 flexes moderately when using the toothbrush 1. This also prevents the flexing of each filament 30 from becoming too large, and thus, the interdental cleaning performance can be improved more appropriately.

[0114] The thickness Ta of the first boundary portion 13a, the thickness T8 of the eighth neck 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 P8. As a result, it is possible to prevent the thickness T8 of the eighth neck P8 from becoming too thick. Therefore, it is possible to prevent the rigidity of the portion of the neck 13 between the first boundary portion 13a and the eighth neck P8 from becoming too large relative to the rigidity of the head shaft portion 6. Therefore, the head shaft portion 6 and the neck 13 flex more appropriately and more uniformly in the length direction. Therefore, it is possible to improve the interdental cleaning performance more appropriately and to suppress the decrease in the operability of the toothbrush 1 more appropriately.

[0115] The thickness Ta of the first boundary portion 13a and the maximum thickness Tm of the fitting portion 15 preferably satisfy the relationship that Ta ≤ 2.5 × Tm. By satisfying this relationship, it is possible to prevent the maximum thickness Tm of the fitting portion 15 from becoming too thin relative to the thickness of the neck 13, and thus, it is possible to prevent the rigidity of the fitting portion 15 from becoming too small. Therefore, when using the toothbrush 1, it is possible to prevent the deflection of the head shaft portion 6 from becoming too large, and thus, it is possible to improve the operability of the toothbrush 1 more appropriately.

[0116] The ninth neck P9 is located between the seventh neck P7 and the eighth neck P8. The position of the ninth neck P9 is not limited to this; it can also be located further forward than the seventh neck P7, or further backward than the eighth neck P8. The thickness T9 of the ninth neck P9 is the same as the maximum thickness Tb of the brush base portion 21. In the long axis direction, the distance L6 between the rear end of the fitting portion 15 and the ninth neck P9 is longer than the length Lb of the brush portion 20. Therefore, in the neck 13, the length of the portion thinner than the maximum thickness Tb of the brush base portion 21 can be increased, thus preventing the neck 13 from becoming too rigid. Therefore, when using the toothbrush 1, the neck 13 flexes moderately, thus preventing excessive flexing of the filaments 30. Therefore, the interdental cleaning performance can be improved more appropriately.

[0117] The ratio of the distance L7 in the long axis direction between the connecting front end 14a of the connecting portion 14 and the first boundary portion 13a to the first distance L1 is preferably 10% or more and 50% or less, more preferably 10% or more and 30% or less. This allows the first boundary portion 13a, the part with the smallest thickness in the neck 13, to be positioned close to the fitting portion 15. Consequently, when using the toothbrush 1, the portion of the neck 13 near the fitting portion 15 flexes, thus reducing the stress applied to the fitting portion 15. Therefore, excessive flexing of the fitting portion 15 can be appropriately suppressed, thereby improving the operability of the toothbrush 1 more appropriately.

[0118] The ratio of the length Ln of the neck 13 to the distance L8 between the front end of the head 5 and the rear end of the neck 13 is preferably 60% or more. Therefore, the neck 13 flexes appropriately when the toothbrush 1 is used. This improves the interdental cleaning performance and reduces the decrease in operability of the toothbrush 1.

[0119] 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 improving the friction between the brush portion 20 and the fitting portion 15. Consequently, when using the toothbrush 1, movement of the brush portion 20 relative to the handle body 10 along its long axis can be suppressed, thus more effectively preventing a decrease in the operability of the toothbrush 1.

[0120] It should be noted that in this embodiment, where the brush part 20 is formed by molding the handle body 10 as an insert member, the contact 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. Therefore, the contact force between the brush part 20 and the fitting part 15 can be improved. Consequently, when using the toothbrush 1, movement of the brush part 20 relative to the handle body 10 in the long axis direction can be suppressed, and thus, the reduction in the operability of the toothbrush 1 can be more appropriately suppressed.

[0121] The tenth neck P10 is located between the eighth neck P8 and the second boundary portion 13b. The position of the tenth neck P10 is not limited to this; it can also be located further forward than the eighth neck P8. The width W10 of the tenth neck 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 P10 is preferably a length Lh or longer than the length of the head 5. Therefore, the width between the first boundary portion 13a and the tenth neck P10 in the neck 13 can be narrower than the width Wm of the rear end of the fitting portion 15, thus preventing the rigidity of the portion between the first boundary portion 13a and the tenth neck P10 in the neck 13 from becoming excessively high relative to the rigidity of the fitting portion 15. Therefore, when using the toothbrush 1, the head shaft portion 6 and the neck 13 flex more appropriately and more uniformly in the length direction. Therefore, the interdental cleaning performance can be improved more appropriately, and the reduction in the operability of the toothbrush 1 can be more appropriately suppressed.

[0122] The ratio of the length Lh of the head 5 to the distance L8 between the front end of the head 5 and the rear end of the neck 13 is preferably 40% or less. This prevents the neck 13 from becoming too short, thus allowing for more moderate bending of the neck 13 when using the toothbrush 1. Consequently, excessive bending of the head 5 is prevented, thereby improving the operability of the toothbrush 1.

[0123] The side view shape of the neck 13 is preferably a straight line extending from the front end to the rear end. When the side view shape of the neck 13 is a curved shape with a bend, such as an S-shape, stress tends to concentrate at the bend when the toothbrush 1 is used, causing the bend to easily deflect significantly in a localized area. In contrast, in this embodiment, the side view shape of the neck 13 is a straight line extending from the front end to the rear end, thus suppressing stress concentration in a portion of the neck 13. Therefore, it is possible to suppress significant localized deflection of a portion of the neck 13, thereby improving the operability of the toothbrush 1 more appropriately.

[0124] Preferably, the difference between the width and thickness dimensions of the front end portion of the neck 13 is small. The ratio of the thickness dimension to the width dimension of the front end portion of the neck 13 is preferably 75% or more and 130% or less. The shape of the cross-section orthogonal to the major axis of the front end portion of the neck 13 is preferably a circle or a square, where the difference between the width and thickness dimensions is small. It should be noted that the front end portion of the neck 13 is, for example, the portion of the neck 13 whose distance from the first boundary portion 13a is 30% or less relative to the length Ln of the neck 13.

[0125] Preferably, no hole penetrating the fitting portion 15 along the thickness direction is provided in the fitting portion 15. This suppresses a decrease in the rigidity of the fitting portion 15, thus preventing excessive deflection of the head 5 when using the toothbrush 1. Therefore, the operability of the toothbrush 1 can be improved.

[0126] Next, the shape of the filaments 30 in this embodiment will be described in detail. As described above, each of the plurality of filaments 30 protrudes from the upper surface 21a of the brush base portion 21 toward the front side (+Z side). Figure 5 As shown, the cross-section of each filament 30, orthogonal to the thickness direction, is approximately an equilateral triangle protruding towards the front end. Figure 6 As shown, each filament 30 is roughly triangular-pyramidal in shape, tapering as it faces the front. (As shown...) Figure 7As shown, viewed from the width direction, each filament 30 has a shape in which the dimension in the long axis direction gradually increases relative to the unit length in the thickness direction as it moves from the brush base portion 21 toward the front side. It should be noted that the shape of the filament 30 is not limited to this embodiment; for example, the shape of the cross-section orthogonal to the thickness direction can also be a polygon such as a quadrilateral, a circle, a semicircle, a star, or other shapes. Furthermore, in the following description, there are cases where the shape in which the dimension in the long axis direction gradually increases relative to the unit length in the thickness direction as it moves from the brush base portion 21 toward the front side, as viewed from the width direction, is referred to as a stepped cone 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 part 31, the second part 32, and the third part 33 are arranged sequentially from the brush base 21 toward the front side. The filaments 30 are distributed in the order of the first part 31, the second part 32, and the third part 33, along with the stepped cone shape from the brush base 21 toward the front side.

[0127] The first filament portion 30a is located further towards the front side (+Z side) than the center of the filament 30 in the thickness direction. 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 in the thickness direction to the size Lf of the filament 30 is 15%. The first filament portion 30a is the tip side portion of the filament 30.

[0128] The second filament portion 30b is the root of the filament 30. The second filament portion 30b is the part of the filament 30 that is connected to the brush base portion 21. The second filament portion 30b is the end portion on the back side of the first portion 31.

[0129] The third filament 30c is located between the first filament 30a and the second filament 30b. The third filament 30c is the boundary between the first part 31 and the second part 32. The third filament 30c is the end of the front side (+Z side) of the first part 31 and the end of the back side (-Z side) of the second part 32. The dimension D3 of the third filament 30c in the long axis direction is smaller than the dimension D2 of the second filament 30b in the long axis direction.

[0130] The fourth filament portion 30d is located between the first filament portion 30a and the front end of the filament 30. The fourth filament portion 30d is the boundary between the second part 32 and the third part 33. The fourth filament portion 30d is the end of the front side (+Z side) of the second part 32 and the end of the back side (-Z side) of the third part 33. The dimension D4 of the fourth filament portion 30d in the long axis direction is smaller than the dimension D3 of the third filament portion 30c in the long axis direction.

[0131] The first portion 31 is the back side (-Z side) portion of the filament 30. The first portion 31 protrudes from the upper surface 21a of the brush base portion 21 toward the front side (+Z side). The first portion 31 is the portion between the second filament portion 30b and the third filament portion 30c of the filament 30. In this embodiment, viewed from the width direction, the rear end edge of the first portion 31 is a straight line extending approximately toward the front side. Viewed from the width direction, the front end edge of the first portion 31 is a straight line located at the rear end side as it moves toward the front side. Viewed from the width direction, the length of the first portion 31 in the major axis direction decreases as it moves toward the front side. When the length of the first portion 31 in the thickness direction is set to M1, the reduction in the length of the first portion 31 in the major axis direction relative to the unit length in the thickness direction, i.e., the first reduction rate R1, is (D2-D3) / M1.

[0132] The second portion 32 protrudes from the first portion 31 toward the front side (+Z side). The second portion 32 is the portion between the third filament portion 30c and the fourth filament portion 30d in the filament 30. In this embodiment, the length M2 of the second portion 32 in the thickness direction is longer than the length M1 of the first portion 31 in the thickness direction. The length M2 of the second portion 32 in the thickness direction may be shorter than the length M1 of the first portion 31 in the thickness direction, or it may be the same length. In this embodiment, viewed from the width direction, the rear end edge of the second portion 32 is a straight line extending approximately toward the front side. Viewed from the width direction, the front end edge of the second portion 32 is a straight line located at the rear end side as it moves toward the front side. Viewed from the width direction, the dimension of the second portion 32 in the major axis direction decreases as it moves toward the front side. The reduction in the dimension of the second portion 32 in the major axis direction relative to the unit length in the thickness direction, i.e., the second reduction rate R2, is (D3-D4) / M2. In this embodiment, the second reduction rate R2 is greater than the first reduction rate R1.

[0133] The third portion 33 is the part of the filament 30 that is closer to the front side (+Z side) than the fourth filament portion 30d. In this embodiment, the length M3 of the third portion 33 in the thickness direction is shorter than the length M2 of the second portion 32 in the thickness direction. In this embodiment, viewed from the width direction, the rear end edge of the third portion 33 is a straight line extending approximately towards the front side. Viewed from the width direction, the upper edge of the front end of the third portion 33 is a straight line located towards the rear end side as it moves towards the front side. The length dimension Dt of the end of the third portion 33 on the front side is smaller than the length dimension D4 of the end of the third portion 33 on the back side (-Z side). Viewed from the width direction, the length dimension of the third portion 33 in the major axis direction decreases as it moves towards the front side. The reduction in length dimension of the third portion 33 relative to the unit length in the thickness direction, i.e., the third reduction rate R3, is (D4-Dt) / M3. In this embodiment, the third reduction rate R3 is greater than the second reduction rate R2.

[0134] When the filaments 30 have the same length along their long axis from the root to the tip, their rigidity tends to increase. Therefore, when using the toothbrush 1, the flexure of the filaments 30 becomes too small. Consequently, it becomes difficult to absorb the brushing load applied to the brush head 20 through the flexure of the filaments 30, leading to stress concentration at the neck 13, which then tends to flex excessively. This reduces the operability of the head 5 within the mouth, thus reducing the operability of the toothbrush 1. Furthermore, the movement of the tips of each filament 30 is difficult to coordinate with the user's hand movements, resulting in reduced interdental cleaning performance.

[0135] Furthermore, when the reduction in the length of the filament 30 along its long axis from the root to the tip is constant relative to the unit length in the thickness direction, stress tends to concentrate at the center of the thickness direction of each filament 30 when using the toothbrush 1. Consequently, the deflection at the center of the thickness direction of each filament 30 tends to increase locally. Therefore, it becomes difficult for each filament 30 to penetrate deep into the interdental spaces, thus reducing the interdental cleaning performance.

[0136] In contrast, according to this 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, viewed from the width direction, the reduction in the length of the major axis of each of the plurality of filaments 30 relative to the unit length in the thickness direction increases progressively as it moves from the brush base portion 21 toward the front side, i.e., the thickness direction side (+Z side). Therefore, compared to the case where the length of the major axis of each filament 30 is the same from the root to the tip, it is possible to suppress the excessive rigidity of each filament 30, and thus, it is possible to suppress excessive deflection of the neck 13. Furthermore, compared to the case where the reduction in the length of the major axis of each filament 30 relative to the unit length in the thickness direction is constant from the root to the tip, it is possible to suppress stress concentration in the central portion of the thickness direction of each filament 30. Therefore, it is possible to suppress the localized increase in deflection in the central portion of the thickness direction of each filament 30. Therefore, the neck 13 portion of the toothbrush 1, starting from each filament 30, can move and flex more appropriately. This improves the interdental cleaning performance and the operability of the toothbrush 1.

[0137] According to this embodiment, the ratio of the area of ​​the first filament portion 30a's cross section orthogonal to the thickness direction, i.e., the first area S1, to the area of ​​the second filament portion 30b's cross section orthogonal to the thickness direction, i.e., the second area S2, is 20% or more and 30% or less.

[0138] In toothbrushes, the following structure is conventional: to facilitate the penetration of the tip portion of the filament 30 into the interdental spaces, the tip portion of the filament 30 is thinner than the root portion. However, in a one-piece molded toothbrush where each filament 30 is made of soft resin and the ratio of the first area S1 to the second area S2 is less than 20%, the rigidity of the tip portion of each filament 30 becomes too low. Therefore, when using the toothbrush 1, the tip portion of each filament 30 is prone to buckling. Consequently, it becomes difficult for each filament 30 to penetrate deep into the interdental spaces, thus reducing the cleaning performance of the toothbrush 1.

[0139] 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 becomes excessive. Therefore, stress concentrates from the center of the filament 30 in the thickness direction to the root portion. Consequently, the portion from the center of the filament 30 in the thickness direction to the root portion is prone to buckling. As a result, it is difficult for each filament 30 as a whole to bend appropriately and uniformly, making it difficult for each filament 30 to penetrate deep into the interdental spaces. Furthermore, the excessive rigidity of each filament 30 leads to excessive deflection of the neck 13. This reduces the operability of the toothbrush 1. Additionally, the movement of the tip of each filament 30 is difficult to coordinate with the user's hand movements, thus reducing the interdental cleaning performance.

[0140] In contrast, according to this embodiment, the ratio of the first area S1 to the second area S2 is 20% or more and 30% or less. Therefore, it is possible to suppress the bending of the tip portion of each filament 30 and the portion of each filament 30 from the center to the root in the thickness direction. As a result, the filament 30 as a whole bends moderately and uniformly in the thickness direction. Therefore, when using the toothbrush 1, it is easy for each filament 30 to penetrate deep into the interdental spaces, thus improving the cleaning performance of the toothbrush 1 more appropriately. Moreover, the movement of the tip of each filament 30 is easily coordinated with the movement of the user's hand, thus improving the interdental cleaning performance more appropriately. In addition, it is possible to more appropriately suppress the excessive rigidity of each filament 30, thus suppressing excessive bending of the neck 13 more appropriately. Therefore, it is possible to better suppress the decrease in the operability of the toothbrush 1.

[0141] 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 on the tip side of the filament 30. The ratio of the area of ​​the cross-section of the fifth filament portion 30e orthogonal to the thickness direction, i.e., the fifth area S5, to the second area S2 is 35% or more and 55% or less. Therefore, the filament 30 as a whole flexes more appropriately and more uniformly in the thickness direction. Thus, the cleaning performance of the toothbrush 1 can be improved more appropriately, and the reduction in the operability of the toothbrush 1 can be more appropriately suppressed.

[0142] 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 area of ​​the cross-section of the sixth filament portion 30f orthogonal to the thickness direction, i.e., the sixth area S6, to the second area S2, is 75% or more and 95% or less. Therefore, the filament 30 as a whole flexes more appropriately and more uniformly in the thickness direction. Consequently, the cleaning performance of the toothbrush 1 can be improved more appropriately, and the reduction in the operability of the toothbrush 1 can be more appropriately suppressed.

[0143] like Figure 5As shown, the area of ​​the upper surface 21a, which is the side facing the brush base 21 in the thickness direction (+Z side), is the third area S3. The third area S3 is the area surrounded by the outer edge of the upper surface 21a. The second area S2 of the second filament portion 30b of each of the plurality of filaments 30 is the area obtained by adding the areas of the cross sections orthogonal to the thickness direction, which is the 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.

[0144] When the ratio of the fourth area S4 to the third area S3 is less than 25%, the number of filaments 30 becomes too small, and therefore, the force applied to each filament 30 becomes too great when using the toothbrush 1. As a result, the deflection of each filament 30 becomes too great. Consequently, it becomes difficult for each filament 30 to penetrate deep into the interdental spaces, thus reducing the cleaning performance of the toothbrush 1.

[0145] When the ratio of the fourth area S4 to the third area S3 is greater than 35%, the number of filaments 30 becomes excessive, and therefore, the force applied to each filament 30 becomes too small. Consequently, the deflection of each filament 30 becomes too small. Therefore, it is difficult to absorb the brushing load applied to the brush head 20 through the deflection of each filament 30, and thus, stress concentrates at the neck 13, and the deflection of the neck 13 becomes excessive. Consequently, the operability of the head 5 in the oral cavity decreases, and the operability of the toothbrush 1 decreases.

[0146] In contrast, according to this embodiment, the ratio of the fourth area S4 to the third area S3 is 25% or more and 35% or less, thus preventing the force applied to each filament 30 from becoming too large or too small. Consequently, each filament 30 flexes appropriately, thus preventing stress concentration at the neck 13. Therefore, each filament 30 in the toothbrush 1 can flex in conjunction with the rear end of the neck 13. Therefore, each filament 30 can easily penetrate deep into the interdental spaces, thus improving the cleaning performance of the toothbrush 1 more appropriately. Furthermore, excessive flexing of the neck 13 can be more appropriately prevented, thus preventing a decrease in the operability of the toothbrush 1 more appropriately.

[0147] The toothbrush 1 has 80 filaments 30 per unit area relative to the third area S3, i.e., the upper surface 21a of the brush base 21. 2 The preferred value is 110 strands / cm. 2 Therefore, when using toothbrush 1, it is possible to more appropriately suppress the stress applied to each filament 30 from becoming too large or too small, thus allowing each filament 30 to bend more appropriately. Consequently, the cleaning performance of toothbrush 1 can be improved more appropriately, and the reduction in the operability of toothbrush 1 can be more appropriately suppressed.

[0148] Viewed in the thickness direction, the shortest distance Ws between the outer edge of the brush base 21 and the plurality of filaments 30 is preferably 3.0 mm or less. This increases the number of filaments 30 that can be disposed on the upper surface 21a, thus reducing the stress applied to each filament 30 when using the toothbrush 1. Therefore, excessive deflection of each filament 30 can be suppressed, thereby improving the interdental cleaning performance more appropriately. It should be noted that... Figure 5 The filament region Rf shown is the region that surrounds all portions of the upper surface 21a that are connected to each filament 30. The area of ​​the filament region Rf is equal to the filament area Sf.

[0149] Figure 10 This is an external view of the first flexure test apparatus 50.

[0150] Next, the test method for the first flexure test and the test results of the first flexure test of the toothbrush 1 of this embodiment will be explained. The first flexure test measures the reaction force of the toothbrush 1 when it flexes towards the back side (-Z side) from each filament 30 to the neck 13. The first flexure test is conducted by... Figure 10 The first flexure test device 50 shown is used for the test.

[0151] In this embodiment, a SHIMAZDU universal testing machine AGS-X is used as the first flexural testing apparatus 50. The first flexural testing apparatus 50 includes a pressure member 51 and a position measuring unit (not shown) for measuring the position of the pressure member 51 in the thickness direction. A reaction force measuring unit 51a is provided on the surface of the pressure member 51 facing the back side (-Z side). For example, a piezoelectric element can be used as the reaction force measuring unit 51a. The reaction force measuring unit 51a can measure the load applied to it.

[0152] In the first flexure test, the toothbrush 1 is fixed to the fixing part 52. In this embodiment, the fixing part 52 has a first fixing part 52a, a second fixing part 52b, and screws 52c. The first fixing part 52a and the second fixing part 52b are each cuboid in shape, extending in a direction orthogonal to the thickness direction. The second fixing part 52b is positioned further forward (+Z side) than the first fixing part 52a. The grip part 12 of the toothbrush 1 is positioned between the first fixing part 52a and the second fixing part 52b. The grip part 12 is placed on the front-facing surface of the first fixing part 52a. The screws 52c pass through holes in the second fixing part 52b and the first fixing part 52a in the thickness direction, respectively. If the nut 52d is screwed into the portion of the screw 52c further backward than the first fixing part 52a, the grip part 12 is fixed to the fixing part 52. At this point, viewed from the thickness direction, the second boundary portion 13b, which forms the boundary between the neck 13 and the grip portion 12, overlaps with the front end of the first fixing portion 52a and the front end of the second fixing portion 52b. As a result, the rear end of the neck 13, i.e., the other side (-X side) in the long axis direction, is fixed to the fixing portion 52.

[0153] The pressure member 51 contacts each filament 30 from the front side, i.e., the side in the thickness direction (+Z side). More specifically, the reaction force measuring unit 51a contacts all the filaments 30. The pressure member 51 is movable in the thickness direction. In the first flexure test, by moving the pressure member 51 to the back side, i.e., the other side in the thickness direction (-Z side), the portion of the toothbrush 1 from each filament 30 to the neck 13 is flexed, and the reaction force of the toothbrush 1, i.e., the first reaction force F1, is measured by the reaction force measuring unit 51a. In the first flexure test, the moving speed of the pressure member 51 is 10 mm / s. The first reaction force F1 is measured every time the pressure member 51 moves 0.002 mm to the back side. That is, the sampling interval of the first flexure test is 0.002 mm.

[0154] Figure 11 This is a diagram illustrating an example of the first reaction force F1 in this embodiment. Figure 11 The horizontal axis represents the first moving distance Z1. The first moving distance Z1 is the distance that the pressure member 51 moves towards the rear side. The origin of the first moving distance Z1 is the position where the pressure member 51 begins to contact the filament 30. Figure 11 The vertical axis represents the first reaction force F1. For example... Figure 11 As shown, in the toothbrush 1 of this embodiment, the first reaction force F1 increases monotonically as the first moving distance Z1 increases.

[0155] Figure 12 This is a diagram illustrating the calculation method of the first reaction force variation rate RF1 in this embodiment. Figure 13This is a diagram showing an example of the first reaction force variation rate RF1 in this embodiment.

[0156] Figure 12 The horizontal axis represents the first movement distance Z1. Figure 12 The left axis of the twelfth vertical axis represents the first reaction force F1. The right axis of the twelfth vertical axis represents the first reaction force variation rate RF1. In this embodiment, the first reaction force variation rate RF1 is the value obtained by dividing the change in the first reaction force F1 when the position of the pressure member 51 in the thickness direction changes only by a first given distance dZ1 by the first given distance dZ1. That is, the first reaction force variation rate RF1 is the rate of change of the first reaction force F1 relative to the first movement distance Z1. It should be noted that in this embodiment, the first given distance dZ1 is 0.1 mm. As described above, the sampling interval of the first flexure test is 0.002 mm.

[0157] In the first flexure test, the first movement distance when the first reaction force F1 is measured for the Mth time is set as Z1(M), and the first reaction force is set as F1(M). The first movement distance when the first reaction force F1 is measured for the (M+50)th time is set as Z1(M+50), and the first reaction force is set as F(M+50). The distance between Z1(M+50) and Z1(M) is the first given distance dZ1. Therefore, the change in the first reaction force F1 when the position of the pressurized member 51 in the thickness direction changes only from Z1(M) by the first given distance dZ1 is F1(M+50) - F1(M). Therefore, the first reaction force variation rate RF1 is (F1(M+50) - F1(M)) / dZ1. If the first reaction force variation rate RF1 under all the first reaction forces F1 obtained by this calculation method is calculated, then the result is obtained. Figure 13 The relationship between the first moving distance Z1 and the first reaction force variation rate RF1 is shown. It should be noted that in this embodiment, the moving average of, for example, 50 first reaction force variation rates RF1 calculated using the above method can also be used as the first reaction force variation rate RF1. Therefore, when measuring the first reaction force F1, the impact of sudden measurement errors on the first reaction force variation rate RF1 can be reduced, and thus, the relationship between the first moving distance Z1 of the toothbrush 1 and the first reaction force variation rate RF1 can be obtained with higher accuracy.

[0158] Figure 13The first maximum value RF1max shown is the maximum value of the first reaction force variation rate RF1 within the range of the movement distance of the pressurizing member 51 being less than 3.0 mm. The first minimum value RF1min is the minimum value of the first reaction force variation rate RF1 within the range of the movement distance of the pressurizing member 51 being less than 3.0 mm. According to this embodiment, the first maximum value RF1max and the first minimum value RF1min satisfy the relationship RF1max-RF1min≤0.6N / mm.

[0159] In toothbrushes 1 where 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 13 is prone to localized bending during use. If the filaments 30 are locally bent, it becomes difficult for them to penetrate deep into the interdental spaces, thus reducing the cleaning performance of the toothbrush 1. Furthermore, if the head shaft 6 and the neck 13 are locally bent, the operability of the head 5 within the oral cavity is reduced, thus reducing the operability of the toothbrush 1.

[0160] In contrast, according to this embodiment, since the difference between the first maximum value RF1max and the first minimum value RF1min is less than 0.6 N / mm, each filament 30, the head shaft portion 6, and the neck 13 will not locally flex, and the filaments 30, the head shaft portion 6, and the neck 13 will flex uniformly in the length direction in a coordinated manner. Therefore, local flexing of each filament 30 can be suppressed, and thus the cleaning performance of the toothbrush 1 can be improved more appropriately. Furthermore, local flexing of the head shaft portion 6 and the neck 13 can be suppressed, thus the reduction in the operability of the toothbrush 1 can be more appropriately suppressed.

[0161] The difference between the first maximum value RF1max and the first minimum value RF1min is preferably less than 0.5 N / mm. As a result, the filament 30, the head shaft portion 6, and the neck 13 are coordinated to bend more appropriately and uniformly in the length direction, thereby improving the cleaning performance of the toothbrush 1 and suppressing the decrease in the operability of the toothbrush 1.

[0162] The difference between the first maximum value RF1max and the first minimum value RF1min is preferably less than 0.4 N / mm. As a result, the filament 30, the head shaft portion 6, and the neck 13 are more appropriately and uniformly flexed in the length direction in a coordinated manner, thereby improving the cleaning performance of the toothbrush 1 more appropriately and suppressing the decrease in the operability of the toothbrush 1 more appropriately.

[0163] According to this embodiment, the average value of the first reaction force variation rate RF1, i.e., the first average value RF1ave, is 0.5 N / mm or more and 1.0 N / mm or less within the range of the movement distance of the pressure member 51 being 3.0 mm or less.

[0164] When the first average value RF1ave is less than 0.5 N / mm, the deflection of each filament 30 becomes too small when using toothbrush 1, and therefore, stress tends to concentrate at the neck 13. As a result, the deflection of the neck 13 becomes too large, and thus, the operability of toothbrush 1 is reduced.

[0165] When the first average value RF1ave is greater than 1.0 N / mm, the flexure of each filament 30 becomes excessive, or a portion of each filament 30 becomes locally flexed, when using the toothbrush 1. Therefore, it becomes difficult for each filament 30 to penetrate deep into the interdental spaces, thus reducing the cleaning performance of the toothbrush 1.

[0166] In contrast, according to this embodiment, the first average value RF1ave is 0.5 N / mm or more and 1.0 N / mm or less, thus preventing excessive deflection of each filament 30 and neck 13. Consequently, the filaments 30, head shaft 6, and neck 13 deflect more appropriately and uniformly in the length direction in conjunction. Therefore, the cleaning performance of the toothbrush 1 can be improved more appropriately, and the reduction in the operability of the toothbrush 1 can be more appropriately suppressed.

[0167] The first average value RF1ave is preferably 0.5 N / mm or more and 0.8 N / mm or less. This allows for more appropriate suppression of localized bending of a portion of each filament 30, thereby improving the cleaning performance of the toothbrush 1.

[0168] The first average value RF1ave is preferably 0.6 N / mm or more and 0.8 N / mm or less. This allows for more appropriate suppression of excessive deflection of the neck 13, and thus more appropriate suppression of reduced operability of the toothbrush 1.

[0169] Figure 14 This is a side view of the second flexure test apparatus 60.

[0170] Next, the test method for the second flexure test and the test results of the second flexure test of the toothbrush 1 of this embodiment will be explained. The second flexure test measures the reaction force of the filament 30 when it flexes. The second flexure test is conducted through... Figure 14 The second flexure test apparatus 60 shown is used for the test.

[0171] In this embodiment, a SHIMAZDU universal testing machine AGS-X is used as the second flexural testing apparatus 60. The second flexural testing apparatus 60 has a pressure member 61 and a position measuring unit (not shown) for measuring 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).

[0172] In the second flexure test, the brush portion 20 is supported by the support platform 62 in the thickness direction. More specifically, the support platform 62 supports the brush base portion 21 from the back side (-Z side), that is, the other side in the thickness direction. Thus, the position of the brush portion 20 in the thickness direction in the second flexure test is determined.

[0173] The pressure member 61 contacts each filament 30 from the front side, i.e., the side in the thickness direction (+Z side). More specifically, the reaction force measuring part 61a contacts all the filaments 30. The pressure member 61 is movable in the thickness direction. In the second flexure test, by moving the pressure member 61 to the back side, i.e., the other side in the thickness direction (-Z side), each filament 30 is flexed, and the second reaction force F2 is measured. In the second flexure test, the moving speed of the pressure member 61 is 10 mm / s. The second reaction force F2 is measured every time the pressure member 61 moves 0.002 mm to the back side. That is, the sampling interval of the second flexure test is 0.002 mm.

[0174] Figure 15 This diagram illustrates an example of the second pressure P in 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 exerted on the pressure member 61 from each filament 30. Figure 16 This is a graph illustrating an example of the second pressure variation rate RP in this embodiment. Figure 15 The horizontal axis represents the second moving distance Z2. The second moving distance Z2 is the distance that the pressure member 61 moves towards the back side (-Z side). The origin of the second moving distance Z2 is the position where the pressure member 61 begins to contact the filament 30. Figure 15 The vertical axis represents the second pressure P. For example... Figure 15 As shown, in the toothbrush 1 of this embodiment, the second pressure P increases monotonically as the second moving distance Z2 increases.

[0175] Figure 16 The second pressure variation rate RP shown is the value obtained by dividing the change in the second pressure P when the position of the pressurized member 61 changes only by a second given distance dZ2 in the thickness direction by the second given distance dZ2. In this embodiment, the second given distance dZ2 is 0.1 mm. In the second flexure test, the calculation method for the second pressure variation rate RP based on the second pressure P is the same as the calculation method for the first reaction force variation rate RF1 based on the first reaction force F1 in the first flexure test described above. According to this embodiment, the second pressure variation rate RP is 0.0 N / mm when the movement distance of the pressurized member 61 is less than or equal to 1.0 mm. 3 Above and 10.0×10 -2 N / mm 3 the following.

[0176] The second pressure variation rate RP is less than 0.0 N / mm. 3 In some cases, when using toothbrush 1, the filaments 30 become excessively flexed, or a portion of each filament 30 becomes partially flexed. As a result, it becomes difficult for the filaments 30 to penetrate deep into the spaces between the teeth, thus reducing the cleaning performance of toothbrush 1.

[0177] When the second pressure variation rate RP is greater than 10.0 × 10 -2 N / mm 3 In this situation, the reaction force of each filament 30 becomes too large, and therefore, the deflection of each filament 30 becomes too small. As a result, stress tends to concentrate at the neck 13, and therefore, the deflection of the neck 13 becomes too large. Therefore, the operability of the toothbrush 1 decreases. Furthermore, because the rigidity of each filament 30 becomes too large, the tactile feedback of each filament 30 is reduced when using the toothbrush 1.

[0178] In contrast, in this embodiment, the second pressure variation rate RP is 0.0 N / mm. 3 Above and 10.0×10 -2 N / mm 3 Therefore, each filament 30 is appropriately and uniformly bent. Thus, localized bending of each filament 30 can be more appropriately suppressed, thereby improving the cleaning performance of the toothbrush 1. Furthermore, stress concentration at the neck 13 can be more appropriately suppressed, thus reducing the operability of the toothbrush 1 can be more appropriately suppressed.

[0179] It should be noted that the second pressure variation rate RP is preferably 0.5 × 10⁻⁶. -2 N / mm 3 Above and 8.0×10 -2 N / mm 3 Therefore, each filament 30 is bent more appropriately and more evenly, thus improving the cleaning performance of the toothbrush 1 more appropriately and suppressing the decrease in the operability of the toothbrush 1 more appropriately.

[0180] As explained above, in the toothbrush 1 of this embodiment, the interdental cleaning performance can be improved and the reduction in the operability of the toothbrush can be suppressed.

[0181] [Example] The present invention will be described in detail below with reference to the embodiments shown, but the present invention is not limited to the following embodiments and can be implemented by appropriate modifications without departing from its spirit.

[0182] (Examples 1-9, Comparative Examples 1-6) According to the specifications shown in [Table 1], the maximum thickness of the head shaft portion (the maximum dimension in the thickness direction of the head shaft portion): Th, the width of the first boundary portion (the minimum dimension in the width direction of the neck): Wa, and the first angle: θ 1. Width of the front end of the connector: Wb; Length of the connector: Lc; Second angle: θ 2. Width of the rear end of the mating part: At least one different toothbrush in Wm was sampled as Examples 1-9 and Comparative Examples 1-6.

[0183] [Table 1] The thickness dimension (fiber length) of each sampled filament is set to 10 mm. The cross-sectional shape of each sampled filament is set to triangular. The second area of ​​each sampled filament is set to 0.29 mm². 2 The shape of each sampled filament, viewed from the width direction, is set as a stepped cone shape. The first area of ​​each sampled filament is set to 0.079 mm². 2 The number of filaments in each sample was set to be between 140 and 280. The number of filaments per unit area relative to the third area was set to 100 filaments / cm². 2 The material of the soft resin used for each sampling is polyurethane. The maximum width of the sampling head is set to be between 10 mm and 14 mm. The length of the sampling head is set to 20.3 mm. The third area of ​​each sampling is set to 1.4 mm². 2 Above and 2.8mm 2 The following parameters are specified: The length of the neck for each sample is set to 48.3 mm. The maximum width of the neck for each sample is set to 8.6 mm. The maximum thickness of the neck for each sample is set to 7.1 mm. The minimum thickness of the neck for each sample is set to 3.5 mm. The maximum thickness of the interlocking portion for each sample is set to 2.0 mm. The length of the interlocking portion for each sample is set to 18.3 mm. The material of the rigid resin for each sample is polyacetal resin.

[0184] (Example 9, Comparative Examples 7-8) According to the specifications shown in [Table 2], the hole penetrating the above-mentioned fitting part, the maximum thickness of the fitting part: Tm, the maximum thickness of the head shaft part (the maximum dimension in the thickness direction of the head shaft part): Th, the width of the front end of the connecting part: Wb, the length of the connecting part: Lc, and the first angle: θ 1. Width of the first boundary portion (minimum dimension in the width direction of the neck): Wa; Thickness of the first boundary portion (minimum thickness of the neck): Ta; Side view shape of the neck; Material of hard resin; Cross-sectional shape of the second filament portion; Side view shape of the filament; Number of filaments per unit area relative to the third area; Cross-sectional area of ​​the filament tip; Second area: S2; At least one different toothbrush of soft resin material was sampled as Example 9 and Comparative Examples 7-8.

[0185] [Table 2] The thickness dimension (fiber length) of each sampled filament was set to 10 mm. The first area of ​​each sampled filament was set to 0.079 mm². 2 The number of filaments in each sample is set to between 140 and 280. The maximum width of the sample head is set to between 10 mm and 14 mm. The length of the sample head is set to 20.3 mm. The third area of ​​each sample is set to 1.4 mm². 2 Above and 2.8mm 2 The following parameters are specified: The length of the neck for each sample is set to 48.3 mm. The maximum width of the neck for each sample is set to 8.6 mm. The maximum thickness of the neck for each sample is set to 7.1 mm. The length of the fitting portion for each sample is set to 18.3 mm.

[0186] [User Experience Review] [Evaluation Method] In the evaluation of user experience, the toothbrushes of Examples 1-9 and Comparative Examples 1-6 were evaluated for the tactile sensation of the bristles rebounding at the tip while cleaning between teeth, and the bristle tips moving in conjunction with the operation of the toothbrush.

[0187] The toothbrushes of Examples 1-9 and Comparative Examples 1-6 were evaluated according to the following benchmarks.

[0188] 7 points: Strong feeling 6 points: Very touching 5 points: I have a slight feeling about it. 4 points: Feels neither strong nor weak 3 points: Not really feeling anything 2 points: Almost no feeling 1 point: No feeling at all Then, calculate the average score of the evaluations from 10 professional evaluators, and conduct evaluations at the following 5 levels.

[0189] ☆ (star mark): 6.5 points or higher ◎ (Double circle mark): 5.5 points or higher but less than 6.5 points ○ (circle mark): 4.5 points or higher but less than 5.5 points △ (triangle mark): 3.5 or higher but less than 4.5 points × (cross mark): Less than 3.5 points It should be noted that in the evaluation columns of Examples 1-9 and Comparative Examples 1-6 in Table 1, the average score of the evaluations by 10 professional evaluators is recorded together with the above-mentioned 5-level evaluation in parentheses.

[0190] As shown in [Table 1], for Examples 1 to 9, where the maximum thickness of the head shaft portion is 3.0 mm or more and 4.5 mm or less, the width of the first boundary portion is 3.0 mm or more and 4.5 mm or less, and the first angle is 17° or more and 28° or less, the average evaluation score of 10 professional evaluators was 3.5 points or more. Good results were obtained regarding the tactile sensation of the bristles moving in conjunction with the operation of the toothbrush while the bristles have a springy tip when cleaning between teeth.

[0191] In contrast, in Comparative Example 1, where the maximum thickness of the head shaft was greater than 4.5 mm, the average score from 10 professional evaluators was less than 3.5, indicating a poor result. As mentioned above, if the maximum thickness of the head shaft is greater than 4.5 mm, the rigidity of the head shaft becomes too high, and therefore, the deflection of the head shaft becomes too low. Consequently, the deflection of the filament becomes too high, and therefore, a suitable tactile feel of the filament's tip rebound cannot be obtained.

[0192] Comparative Example 2, where the maximum thickness of the head shaft is less than 3.0 mm, did not yield satisfactory results. As described above, if the maximum thickness of the head shaft is less than 3.0 mm, the rigidity of the head shaft becomes too low, resulting in excessive deflection. Consequently, the filaments become difficult to bend, making it difficult for the tips of the filaments to move. Therefore, a suitable tactile feedback that allows the bristles to move in conjunction with the operation of the toothbrush cannot be obtained.

[0193] Comparative Example 3, where the width of the first boundary portion is greater than 4.5 mm, did not yield satisfactory results. As described above, if the width of the first boundary portion is greater than 4.5 mm, the rigidity of the neck becomes too large, and therefore, the deflection of the neck becomes too small. Consequently, the deflection of the filament becomes too large, and therefore, a suitable tactile feel of the filament's tip cannot be obtained.

[0194] Comparative Example 4, where the width of the first boundary portion is less than 3.0 mm, did not yield satisfactory results. As described above, if the width of the first boundary portion is less than 3.0 mm, the rigidity of the neck becomes too low, and therefore, the deflection of the neck becomes too large. Consequently, the filaments become difficult to bend, and therefore, the tips of the filaments become difficult to move. Therefore, a suitable tactile sensation that moves in conjunction with the operation of the toothbrush cannot be obtained.

[0195] Comparative Example 5, where the first angle is less than 17°, did not yield satisfactory results. As described above, if the first angle is less than 17°, the width of the neck and connecting portion becomes too wide, and therefore, the rigidity of the neck and connecting portion becomes too large. Consequently, the deflection of the neck and connecting portion becomes too small. Therefore, the deflection of the filament becomes too large, and thus, a suitable tactile feel of the filament's tip cannot be obtained.

[0196] Comparative Example 6, where the first angle is greater than 28°, did not yield satisfactory results. As described above, if the first angle is greater than 28°, the width of the neck and connecting portion becomes too narrow, and therefore, the rigidity of the neck and connecting portion becomes too low. Consequently, the deflection of the neck and connecting portion becomes excessive, making it difficult for the filaments to bend. Consequently, the tip of the filaments becomes difficult to move, and therefore, a suitable tactile sensation of the bristles moving in conjunction with the operation of the toothbrush cannot be obtained.

[0197] Compared to the structure of Example 1, Example 3, where the first angle is greater than 20°, yielded better results than Example 1. In Example 3, compared to Example 1, the neck and connecting portion become more easily and moderately flexible, thus reducing the stress applied to the filament. Therefore, the filament deflection can be appropriately reduced, resulting in a more suitable tactile feel with better rebound at the filament tip.

[0198] Compared to the structure of Example 2, Example 4, where the first angle is less than 26°, yielded better results than Example 2. In Example 4, compared to Example 2, the neck and connecting portion became less prone to moderate bending, thus allowing for a more appropriate increase in the stress applied to the filament. Consequently, localized bending of a portion of the filament could be suppressed, and the bending of the filament could be appropriately increased. Therefore, the tip of the filament became easier to move, resulting in a more suitable tactile feedback where the bristles moved in conjunction with the operation of the toothbrush.

[0199] Compared to the structure of Example 3, Example 5, with a second angle greater than 10°, yielded better results than Example 3. In Example 5, compared to Example 3, the head shaft portion became more easily and moderately flexible, thus allowing for a more appropriate reduction in the stress applied to the filament. Consequently, the filament's deflection was reduced more appropriately, resulting in a more suitable tactile feel with the filament's tip rebound. Compared to the structure of Example 5, Example 7, with a second angle greater than 12°, yielded better results than Example 5 for the same reason.

[0200] Compared to the structure of Example 4, Example 6, with a second angle of less than 18°, yielded better results than Example 6. In Example 6, compared to Example 4, the head shaft became less prone to moderate bending, thus allowing for a more appropriate increase in the stress applied to the filament. Consequently, localized bending of a portion of the filament could be more appropriately suppressed, and the bending of the filament could be more appropriately increased. Therefore, the bristle tip became easier to move appropriately in conjunction with the operation of the toothbrush, resulting in a more suitable tactile feel from the movement of the filament's tip. Compared to the structure of Example 6, Example 8, with a second angle of less than 16°, yielded better results than Example 6 for the same reason.

[0201] Compared to the structures of Embodiments 7 and 8, Embodiment 9, in which the width of the front end of the connecting portion is 8 mm or more and 10 mm or less, yielded better results than Embodiments 7 and 8. In Embodiment 9, compared to Embodiments 7 and 8, the head shaft portion becomes easier to bend moderately, thus, it is possible to more appropriately suppress partial local bending of the filament. Therefore, a more suitable tactile feel in the rebound of the filament's front end can be obtained, and a more appropriate tactile feel in which the bristles move in conjunction with the operation of the toothbrush can be obtained.

[0202] [First Flexibility Test] [Evaluation Method] For the toothbrushes of Example 9 and Comparative Examples 7-8, a first flexure test was performed based on the test method of the first flexure test described above. The test results of the first flexure test are shown in Table 2.

[0203] Figure 17 This is a graph representing the rate of change of the first reaction force in the first flexure test. (Example) Figure 17 As shown, within a range where the movement distance of the pressure member is 3.0 mm or less, the variation in the first reaction force variation rate of Example 9 is less than that of Comparative Examples 7-8. This means that, compared to the toothbrushes of Comparative Examples 7-8, in the toothbrush of Example 9, the amount of deflection from the filaments to the neck is approximately proportional to the first reaction force. This is because, as described above, in Example 9, if a force is applied to the filaments on the other side in the thickness direction, they can bend uniformly and continuously from the filaments to the neck, thus suppressing large-scale local deflection of the filaments, the head shaft, and the neck. Therefore, in Example 9, when using the toothbrush, it is easy for the filaments to penetrate deep into the spaces between the teeth, thus appropriately improving the cleaning performance of the toothbrush and appropriately suppressing the decrease in the operability of the toothbrush 1.

[0204] In contrast, regarding Comparative Example 7, where the first angle is less than 17°, as described above, the width of the neck and connecting portion becomes excessively wide, thus resulting in excessive rigidity of the neck and connecting portion. Consequently, stress concentrates on the filament, leading to excessive filament deflection. Therefore, the difference between the first maximum value and the first minimum value is greater than 0.6 N / mm. Consequently, the filament is prone to localized deflection, thus reducing the cleaning performance of the toothbrush 1.

[0205] Furthermore, in Comparative Example 8, where the maximum thickness of the head shaft portion is greater than 4.5 mm, the first angle is smaller than 17°, and the width of the first boundary portion is wider than 4.5 mm, as described above, the rigidity of the head shaft portion and the neck becomes excessive. Therefore, similar to Comparative Example 7, the deflection of the filament becomes excessive. Figure 17As shown, the rate of change of the first reaction force in Comparative Example 8 increases within the range of 0.5 mm to 1.0 mm of the first moving distance. This indicates that the filament deflection increases sharply within the range of 0.5 mm to 1.0 mm, resulting in filament buckling. Therefore, as shown in Table 2, the difference between the first maximum value RF1max and the first minimum value RF1min becomes greater than 0.6 N / mm, and the first average value becomes greater than 1.0 N / mm. Consequently, the filament is prone to localized deflection, thus reducing the cleaning performance of toothbrush 1.

[0206] Furthermore, in Comparative Examples 7 and 8 where a through hole is provided in the fitting portion, the rigidity of the fitting portion tends to decrease, and therefore, the fitting portion is prone to localized deflection. Consequently, the variation in the rate of change of the first reaction force tends to increase.

[0207] Furthermore, regarding Comparative Examples 7 and 8, where the neck is curved, as described above, stress tends to concentrate at the curved portion, and therefore, this curved portion is prone to significant local deflection. Consequently, the variation in the rate of change of the first reaction force tends to increase.

[0208] Furthermore, in Comparative Examples 7 and 8, where the rigid resin material is polypropylene resin, the rigidity of the neck tends to decrease, thus the neck is prone to localized deflection. Consequently, the variation in the rate of change of the first reaction force tends to increase.

[0209] Furthermore, in Comparative Example 8, where the filament's side view shape is rectangular, the filament is difficult to bend uniformly and is prone to buckling. Therefore, the filament is prone to localized bending. Consequently, the variation in the rate of change of the first reaction force tends to increase.

[0210] [Second flexure test] [Evaluation Method] For the toothbrushes of Example 9 and Comparative Examples 7-8, a second flexure test was conducted based on the test method of the second flexure test described above. The test results of the second flexure test are shown in Table 2.

[0211] Figure 18 This is a graph representing the rate of change of the second pressure during the second flexure test. (Example) Figure 18As shown, within the range where the movement distance of the pressure member is less than 1.0 mm, the variation in the second pressure variation rate of Example 9 is less than that of Comparative Example 8. This means that, compared to the toothbrush of Comparative Example 8, in the toothbrush of Example 9, the amount of filament deflection is approximately directly proportional to the second pressure. This is because, as described above, in Example 9, if a force is applied to the filament in the opposite direction of the thickness, the filament can bend uniformly, thus suppressing large-scale local deflection of a portion of the filament. Therefore, in Example 9, when using the toothbrush, it is easy for each filament to penetrate deep into the interdental spaces, thus improving the cleaning performance of the toothbrush more appropriately. In addition, stress concentration at the neck can be appropriately suppressed, thus suppressing the decrease in the operability of the toothbrush more appropriately.

[0212] In contrast, the number of filaments per unit area relative to the third area is less than 80 filaments / cm. 2 In Comparative Example 8, as described above, the stress applied to the filament becomes excessive. Figure 18 As shown, regarding Comparative Example 8, when the second pressure variation rate is greater than 10.0 × 10⁻⁶, -2 N / mm 3 Within the range of 0.0 mm to 0.2 mm for the second moving distance, each filament exhibits high resilience, making it difficult for the leading edge of each filament to move. Furthermore, within the range of 0.2 mm to 0.4 mm for the second moving distance, where stress tends to concentrate at the neck, each filament buckles, causing the second pressure variation rate to decrease sharply, becoming less than 0.0 N / mm. 3 Furthermore, within the range of 0.2 mm to 0.4 mm for the second movement distance, each filament locally flexes, thus preventing the tip of each filament from springing back. Additionally, in Comparative Example 8, due to the small number of filaments, the stress applied to the filaments becomes excessive. Therefore, the filaments are prone to buckling. Consequently, as shown in Table 2, the variation rate of the first reaction force tends to increase, making it difficult to improve the user experience.

[0213] Furthermore, in Comparative Example 8, where the cross-sectional shape of the filament is circular, it exhibits a symmetrical shape in both the long axis and width directions when viewed from the thickness direction. Therefore, if a force is applied to the filament towards the back side, the direction of deflection of each filament deviates, and thus, the force applied to each filament is prone to deviation. Consequently, since the amount of deflection of the filament subjected to a large force becomes excessive, the second pressure variation rate tends to fluctuate within a range where the movement distance of the pressure member is 1.0 mm or less.

[0214] The preferred embodiments of the present invention have been described above. However, the present invention is not limited to this example. As long as the flexure of each part, such as the filament, head, and neck, can be uniformly flexed without deviation, a generally straight flexure behavior can be obtained from the filament to the neck. Those skilled in the art can obtain the above-mentioned effects based on this indicator. In addition, the shapes and combinations of the structural components shown in the above examples are just examples. Various modifications can be made according to design requirements, etc., without departing from the spirit of the present invention.

[0215] As described above, in the first flexure test, the portion of the toothbrush from each filament to the neck is flexed, and the reaction force of the toothbrush, i.e., the first reaction force, is measured. Therefore, the result of the second flexure test, which measures the reaction force of the filaments 30, affects the result of the first flexure test. In the above description, an example is given of a structure in which the first pressure variation rate and the second pressure variation rate are set within an appropriate range by studying the number of filaments and the cross-sectional shape of the filaments, thereby achieving a structure in which the filaments flex uniformly from the neck. 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, the material of the hard resin, and the side view shape of the filaments, it is possible to achieve uniform flexing from the neck to the filaments, and to obtain a roughly linear flexing behavior from the neck to the filaments. Therefore, by analyzing the results of the first flexure test and the second flexure test, those skilled in the art can understand the characteristics of the toothbrush as the subject of analysis, and can efficiently reach a solution to the problem, and further confirm the effectiveness of the solution.

[0216] The structure of the fitting part and the fitting hole is not limited to the structure of this embodiment. For example, the fitting part may have a protrusion that protrudes in the width direction, and the fitting hole may have a recess that is recessed in the width direction and fits with the protrusion.

[0217] The method for forming the brush part is not limited to this embodiment. For example, the handle body and the brush part can be formed separately using separate molds. In this case, the toothbrush is formed by fitting the fitting part of the handle body into the fitting hole of the brush part after forming.

[0218] Industrial applicability The toothbrush of the present invention can improve the cleaning performance between teeth and prevent the toothbrush from becoming less operable, and therefore can be suitable for use as a one-piece molded toothbrush.

[0219] Symbol Explanation 1…toothbrush, 6…head shaft, 10…handle body, 13…neck, 13d…neck edge, 14…connecting part, 14a…connecting front end, 14d…connecting edge, 15…fitting part, 15d…fitting edge, 20…brush part, 21…brush base, 27…fitting hole, 30…filament, 30a…first filament part, 30b…second filament part, 51…pressure member, 61…pressure member, dZ1…first given distance, dZ2…second given distance, F1…first reaction force, J…central axis, L1…first distance, L2…distance between connecting front end and first neck, L3…distance between connecting front end and second neck, L4…distance between connecting front end and third neck, P…second pressure, P1…first neck, P2…second neck, P3…third neck, RF1…rate of change of first reaction force, RF1ave…first average value, RF1max…first… Maximum value, RF1min…first minimum value, RP…second pressure variation rate, S1…first area (area of ​​the cross section of the first filament orthogonal to the thickness direction), S2…second area (area of ​​the cross section of the second filament orthogonal to the thickness direction), T1…thickness of the first neck (dimension in the thickness direction of the first neck), T2…thickness of the second neck (dimension in the thickness direction of the second neck), T3…thickness of the third neck (dimension in the thickness direction of the third neck), Th…maximum thickness of the head shaft (maximum dimension in the thickness direction of the head shaft), V1…first imaginary line, V2…second imaginary line, Wa…width of the first boundary (minimum dimension in the width direction of the neck), W1…width of the first neck (dimension in the width direction of the first neck), W2…width of the second neck (dimension in the width direction of the second neck), W3…width of the third neck (dimension in the width direction of the third neck).

Claims

1. A toothbrush, characterized in that, have: The handle body, formed of hard resin, extends along its long axis; and The brush portion, formed of soft resin, is disposed on one side of the handle body along its long axis. The brush portion includes: a brush base portion; and a plurality of filaments integrally formed with the brush base portion. Each of the plurality of filaments protrudes from the brush base portion toward a side in the thickness direction intersecting the long axis direction. The handle body has: a neck that extends along the long axis; and a connecting portion that protrudes from the neck to one side along the long axis. The fitting portion protrudes from the connecting portion toward one side in the direction of the long axis; the connecting edge portion is part of the connecting portion; and the neck edge portion is part of the neck. The connecting part, the fitting part, and the brush base part constitute the head shaft part. The connecting edge is the end portion of the connecting portion on one side along its long axis, and also the end portion on one side along its width direction, which intersects both the long axis and the thickness direction. The neck edge is the end of the portion of the neck that has the smallest dimension in the width direction on one side in the width direction. The maximum dimension in the thickness direction of the head shaft portion is 3.0 mm or more and 4.5 mm or less. The minimum dimension of the neck in the width direction is 3.0 mm or more and 4.5 mm or less. Viewed from the thickness direction, the angle between the first imaginary line passing through both the connecting edge and the neck edge and the central axis extending from the center of the handle body toward the long axis direction is 17° or more and 28° or less.

2. The toothbrush according to claim 1, wherein, The brush base portion has a fitting hole for the fitting portion to be inserted and fitted. The handle body has a fitting edge. The fitting edge is the end portion on the other side of the fitting portion along its long axis, and also the end portion on one side along its width. Viewed from the thickness direction, the angle between the second imaginary line passing through both the neck edge and the fitting edge and the central axis is more than 10° and less than 18°.

3. The toothbrush according to claim 1 or 2, wherein, The neck has a first neck, a second neck, and a third neck. The distance in the long axis direction between the end of the connecting part on one side, i.e. the front end of the connection, and the end of the neck on the other side of the long axis direction is defined as the first distance (L1). In the long axis direction, the ratio of the distance between the connecting front end and the first neck to the first distance is 20%. In the long axis direction, the ratio of the distance between the connecting front end and the second neck to the first distance is 80%. In the long axis direction, the ratio of the distance between the connecting front end and the third neck to the first distance is 100%. When the width dimension of the first neck is set to W1, the thickness dimension of the first neck is set to T1, the width dimension of the second neck is set to W2, the thickness dimension of the second neck is set to T2, the width dimension of the third neck is set to W3, and the thickness dimension of the third neck is set to T3, 130mm is satisfied. 4 ≤W1×T1 3 ≤400mm 4 450mm 4 ≤W2×T2 3 ≤1200mm 4 and 2000mm 4 ≤W3×T3 3 ≤5000mm 4 The relationship.

4. The toothbrush according to claim 1 or 2, wherein, Each of the plurality of filaments has a first filament portion and a second filament portion. Viewed from the width direction, as each of the plurality of filaments moves from the brush base towards the thickness direction, the decrease in the length of its major axis relative to its unit length in the thickness direction gradually increases. In the thickness direction, the distance between the end of the filament on one side in the thickness direction and the first filament portion is 15% of the filament's dimension. The second filament portion is the part connected to the brush base portion. The ratio of the area of ​​the cross section of the first filament portion orthogonal to the thickness direction to the area of ​​the cross section of the second filament portion orthogonal to the thickness direction is 20% or more and 30% or less.

5. The toothbrush according to claim 4, wherein, The ratio of the area obtained by adding the areas of the cross sections of the second filament portion of each of the plurality of filaments that are orthogonal to the thickness direction to the area of ​​the brush base portion facing the thickness direction is 25% or more and 35% or less.

6. The toothbrush according to claim 1 or 2, wherein, With the end of the neck fixed on the other side of the long axis direction, the pressure member is brought into contact with the plurality of filaments from one side of the thickness direction, and the pressure member is moved to the other side of the thickness direction. The reaction force exerted on the pressurizing member by the plurality of filaments is defined as the first reaction force. The first reaction force variation rate is defined as the value obtained by dividing the change in the position of the pressurized member in the thickness direction by only a first given distance. The maximum value of the first reaction force variation rate, i.e., the first maximum value, is set as RF1max within the range where the movement distance of the pressurizing member is less than 3.0 mm. The minimum value of the first reaction force variation rate within the range of the movement distance of the pressurizing member being less than 3.0 mm, i.e., the first minimum value, is set as RF1min. And when the first given distance is set to 0.1mm, The relationship RF1max-RF1min≤0.6N / mm must be satisfied.

7. The toothbrush according to claim 6, wherein, The average value of the first reaction force variation rate, i.e., the first average value RF1ave, is above 0.5 N / mm and below 1.0 N / mm within the range of the movement distance of the pressurizing member being less than 3.0 mm.

8. The toothbrush according to claim 1 or 2, wherein, When the pressure member is brought into contact with the plurality of filaments from one side of the thickness direction while supporting the brush base from the other side of the thickness direction, and the pressure member is moved to the other side of the thickness direction... The pressure exerted on the pressurizing member by the plurality of filaments is defined as the second pressure. The second pressure variation rate, denoted as RP, is the value obtained by dividing the change in the second pressure by the second given distance when the position of the pressurizing member in the thickness direction changes by a second given distance. And when the second given distance is set to 0.1mm, Within the range where the movement distance of the pressurizing member is less than 1.0 mm, the second pressure variation rate RP is 0.0 N / mm. 3 Above and 10.0×10 -2 N / mm 3 the following.

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