toothbrush

Abstract

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

Description

[Technical Field]

[0001] This invention relates to a toothbrush. This application claims priority based on Japanese Patent Application No. 2023-162902, filed in Japan on September 26, 2023, and the contents of that application are incorporated herein by reference. [Background technology]

[0002] A one-piece molded toothbrush having filaments formed from a soft resin has been proposed (for example, Patent Document 1). In such a toothbrush, because the filaments are flexible, it is easier to obtain a gentler brushing sensation than with a toothbrush in which the brush part is formed from spinning bristles. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2019 / 055364 [Overview of the project] [Problems that the invention aims to solve]

[0004] In the above toothbrush, since the brush part is formed of a soft resin, the volume of the hard resin constituting the head part is smaller than that of a toothbrush in which the bristle part is formed of spinning hair. In the above toothbrush, it has been common to widen the widths of the head part and the neck part to increase the rigidity from the head part to the neck part and suppress deformation of the head part. However, in such a toothbrush, if the deflection of the neck part becomes too small, the brushing load concentrates on the filaments, and thus the deflection of the filaments may become too large. In this case, it becomes difficult for the filaments to enter between the teeth, and thus the cleaning performance between the teeth deteriorates. Further, if the rigidity of the neck part is made too small, the deflection of the neck part becomes too large, and thus the operability of the head part in the oral cavity deteriorates. As a result, the operability of the toothbrush deteriorates. Further, during brushing, the movement of the tip (the tip of the hair) of the filament is difficult to be linked with the movement of the user's hand, which affects the cleaning performance between the teeth.

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

Means for Solving the Problems

[0006] The present invention includes the following configurations. [1]A toothbrush comprising a handle body formed of a hard resin and extending in the longitudinal axis direction, and a brush part formed of a soft resin and disposed on one side of the handle body in the longitudinal axis direction. The brush part has a brush base part and a plurality of filaments integrally formed with the brush base part. Each of the plurality of filaments protrudes from the brush base part toward one side in the thickness direction intersecting the longitudinal axis direction. The handle body has a neck part extending in the longitudinal axis direction, a connecting part protruding from the neck part toward one side in the longitudinal axis direction, a fitting part protruding from the connecting part toward one side in the longitudinal axis direction, a connecting edge part which is a part of the connecting part, and a neck edge part which is a part of the neck part. The connecting part, the fitting part, and the brush base part constitute a head shaft part. The connecting edge part is an end part of the connecting part on one side in the longitudinal axis direction and an end part on one side in the width direction intersecting both the longitudinal axis direction and the thickness direction. The neck edge part is an end part on one side in the width direction of the part where the dimension of the neck part in the width direction is the smallest. The maximum dimension of the head shaft part in the thickness direction is 3.0 mm or more and 4.5 mm or less. The minimum dimension of the neck part in the width direction is 3.0 mm or more and 4.5 mm or less. The angle formed by a first virtual line passing through both the connecting edge part and the neck edge part as viewed from the thickness direction and the central axis line extending in the longitudinal axis direction of the handle body is 17° or more and 28° or less. [2]The brush base part has a fitting hole into which the fitting part is inserted and fitted. The handle body has a fitting edge part. The fitting edge part is an end part of the fitting part on the other side in the longitudinal axis direction and an end part on one side in the width direction. The angle formed by a second virtual line passing through both the neck edge part and the fitting edge part as viewed from the thickness direction and the central axis line is 10° or more and 18° or less. The toothbrush according to [1]. [3] The neck portion has a first neck portion, a second neck portion, and a third neck portion. The distance in the longitudinal axis direction between the connection tip portion, which is one end portion of the connection portion in the longitudinal axis direction, and the other end portion of the neck portion in the longitudinal axis direction is defined as a first distance L1. In the longitudinal axis direction, the ratio of the distance between the connection tip portion and the first neck portion to the first distance is 20%, the ratio of the distance between the connection tip portion and the second neck portion to the first distance is 80% in the longitudinal axis direction, and the ratio of the distance between the connection tip portion and the third neck portion to the first distance is 100% in the longitudinal axis direction. If the dimension in the width direction of the first neck portion is W1, the dimension in the thickness direction of the first neck portion is T1, the dimension in the width direction of the second neck portion is W2, the dimension in the thickness direction of the second neck portion is T2, the dimension in the width direction of the third neck portion is W3, and the dimension in the thickness direction of the third neck portion is T3, then 130mm 4 , 3 , , ≤ W1 × T1 3 ≤ 400mm 4 and, 450mm 4 ≤ W2 × T2 3 ≤ 1200mm 4 and, 2000mm 4 ≤ W3 × T3 3 ≤ 5000mm 4 and satisfies the relationship of, the toothbrush according to [1] or [2]. [4] Each of the plurality of filaments has a first filament portion and a second filament portion. When viewed from the width direction, for each of the plurality of filaments, as it goes from the brush base portion toward one side in the thickness direction, the decrease amount of the dimension in the longitudinal axis direction with respect to the unit length in the thickness direction gradually increases. In the thickness direction, the ratio of the distance between one end portion of the filament in the thickness direction and the first filament portion to the dimension of the filament is 15%. The second filament portion is a portion connected to the brush base portion, and the ratio of the cross-sectional area of the first filament portion orthogonal to the thickness direction to the cross-sectional area of the second filament portion orthogonal to the thickness direction is 20% or more and 30% or less. The toothbrush according to any one of [1] to [3]. [5] The toothbrush according to [4], wherein the ratio of the area of ​​the surface of the brush base portion facing one side in the thickness direction to the sum of the areas of the cross-sections of each of the multiple filaments perpendicular to the thickness direction is 25% or more and 35% or less. [6] A toothbrush according to any one of [1] to [5], wherein, with the other end of the neck portion in the longitudinal direction fixed, a pressurizing member is brought into contact with a plurality of filaments from one side in the thickness direction, and the pressurizing member is moved to the other side in the thickness direction, the reaction force received by the pressurizing member from the plurality of filaments is defined as the first reaction force, the first reaction force fluctuation rate is defined as the value obtained by dividing the amount of change in the first reaction force when the position of the pressurizing member in the thickness direction changes by a first predetermined distance, the first maximum value which is the maximum value of the first reaction force fluctuation rate within a range of 3.0 mm or less for the movement distance of the pressurizing member is defined as RF1max, the first minimum value which is the minimum value of the first reaction force fluctuation rate within a range of 3.0 mm or less for the movement distance of the pressurizing member is defined as RF1min, and the first predetermined distance is 0.1 mm, satisfying the relationship RF1max - RF1min ≤ 0.6 N / mm. [7] The toothbrush according to [6], wherein the first average value RF1ave, which is the average value of the first reaction force fluctuation rate within a range of 3.0 mm or less for the travel distance of the pressurizing member, is 0.5 N / mm or more and 1.0 N / mm or less. [8] When the brush base is supported from the other side in the thickness direction and the pressurizing member is brought into contact with the plurality of filaments from one side in the thickness direction, and the pressurizing member is moved to the other side in the thickness direction, the reaction force received by the pressurizing member from the plurality of filaments is defined as the second pressure, and the second pressure fluctuation rate RP is the value obtained by dividing the amount of change in the second pressure when the position of the pressurizing member in the thickness direction changes by a second predetermined distance, and the second predetermined distance is 0.1 mm, then within a range of 1.0 mm or less for the movement distance of the pressurizing member, the second pressure fluctuation rate RP is 0.0 N / mm 3 The above is 10.0 × 10 -2 N / mm 3 A toothbrush as described in any one of the following items [1] through [7]. [Effects of the Invention]

[0007] The present invention provides a toothbrush that can improve interdental cleaning performance while suppressing a decrease in the operability of the toothbrush. [Brief explanation of the drawing]

[0008] [Figure 1] This is a front view showing a toothbrush according to an embodiment. [Figure 2] This is a side view showing a toothbrush according to an embodiment. [Figure 3] This is a front view showing the handle body of the embodiment. [Figure 4] This is a side view showing the handle body of the embodiment. [Figure 5] This is a front view showing the brush portion of the embodiment. [Figure 6] This is a cross-sectional view showing the brush portion of the embodiment, and is a cross-sectional view taken from VI-VI in Figure 5. [Figure 7] This is a cross-sectional view showing a part of the brush portion of the embodiment. [Figure 8] This is a diagram showing a part of the toothbrush according to the embodiment. [Figure 9] This is a front view showing a part of the toothbrush according to the embodiment. [Figure 10] This is a side view showing the first deflection test apparatus. [Figure 11] This figure shows an example of the first reaction force of the embodiment. [Figure 12] This figure shows the method for calculating the first reaction force fluctuation rate in the embodiment. [Figure 13] This figure shows an example of the first reaction force fluctuation rate of the embodiment. [Figure 14] This is a side view showing the second deflection test apparatus. [Figure 15] This figure shows an example of the second pressure in the embodiment. [Figure 16] This figure shows an example of the second pressure fluctuation rate of the embodiment. [Figure 17]This figure shows the first reaction force fluctuation rate in the first deflection test. [Figure 18] This figure shows the second pressure fluctuation rate in the second deflection test. [Modes for carrying out the invention]

[0009] The toothbrush of the present invention will be described below with reference to an example shown in the drawings. Note that the dimensions and other specifications shown in the following description are examples only, and the present invention is not necessarily limited to them. It can be modified as appropriate without altering its essence.

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

[0011] In the following explanation, the dimension in the longitudinal direction of a component may be simply referred to as "length." Similarly, the dimension in the width direction of a component may be simply referred to as "width." Furthermore, the dimension in the thickness direction of a component may be simply referred to as "thickness." Additionally, viewing an object from the front may be referred to as a "front view," and the shape of an object viewed from the front may be referred to as the "front view shape." Furthermore, viewing an object from the width direction may be referred to as a "side view," and the shape of an object viewed from the width direction may be referred to as the "side view shape."

[0012] Figure 1 is a front view showing the toothbrush 1 of this embodiment. Figure 2 is a side view showing the toothbrush 1 of this embodiment. As shown in Figure 1, the toothbrush 1 comprises a handle body 10 and a brush part 20. The handle body 10 and the brush part 20 are separate components. The handle body 10 and the brush part 20 are made of resin. The handle body 10 is rod-shaped and extends in the direction of its long axis. The brush part 20 is positioned on the tip side of the handle body 10, that is, on one side (+X side) in the direction of its long axis.

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

[0014] In this embodiment, the handle body 10 is formed of a rigid resin. Examples of rigid resins used to form 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 is preferred when considering manufacturing costs as it is a general-purpose resin, while polybutylene terephthalate resin and polyacetal resin are preferred when considering strength.

[0015] As shown in Figure 3, the front view shape of the handle body 11 in this embodiment is such that the width gradually narrows from the front end to the rear end until it reaches the first boundary 13a, and then the width gradually widens until it reaches the second boundary 13b. After that, the width gradually narrows, then widens, and then narrows again. The front view shape of the rear end of the handle body 11 is approximately semicircular. The first boundary 13a is the tip of the portion that extends in the longitudinal direction with the same width when the front view shape of the handle body 11 gradually narrows from the front end to the rear end and then extends in the longitudinal direction with the same width. The central axis J shown in Figure 3 is a straight line that extends from the center of the handle body 10 in the longitudinal direction when viewed from the thickness direction. The front view shape of the handle body 11 is a plane-symmetric shape with the plane passing through the central axis J and extending in a direction perpendicular to the width direction as the plane of symmetry.

[0016] As shown in Figure 4, the side view shape of the handle body 11 of this embodiment is such that, from the front end to the rear end, the thickness gradually decreases as it reaches the first boundary 13a, then gradually increases as it curves to reach the second boundary 13b, and after reaching the second boundary 13b, the thickness gradually decreases as it curves, then extends at a substantially constant thickness, and then changes to decrease as it curves. The side view shape of the rear end of the handle body 11 is substantially semicircular. More specifically, the second boundary 13b is the part where the first upper edge 11a, whose front side (+Z side) edge is curved upward as it moves from the front end to the rear end, and the second upper edge 11b, whose front side edge is curved downward as it moves from the front end to the rear end, connect. Although not shown in the illustration, the centers of curvature of the first upper edge 11a and the centers of curvature of the second upper edge 11b are located above the handle body 11. The second boundary portion 13b is the part of the handle body portion 11 where a convex vertex protruding towards the front is formed.

[0017] If no convex vertex is formed on the handle body 11, or if the convex vertex is not visible, the second boundary portion 13b is the portion where the center of curvature of the front edge (+Z side) of the handle body 11 changes. If the portion where the center of curvature of the front edge of the handle body 11 changes cannot be identified, the second boundary portion 13b is the portion where the hard resin and the soft resin come into contact in the longitudinal direction. Furthermore, if the portion where the hard resin and the soft resin come into contact in the longitudinal direction cannot be identified, the second boundary portion 13b is the portion 73 mm behind the tip of the head portion 5, which will be described later. In this embodiment, the tip of the head portion 5 is the tip of the brush portion 20.

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

[0019] The gripping portion 12 is the part of the handle body portion 11 that is located at the rear end of the second boundary portion 13b. The gripping portion 12 is rod-shaped and extends in the longitudinal direction. As shown in Figures 1 and 2, a finger rest portion 17 is provided on the outer surface of the gripping portion 12. The finger rest portion 17 is made of a soft resin. Various elastomers such as polyurethane and styrene can be used as the soft resin forming the finger rest portion 17. When the user uses the toothbrush 1, the gripping of the toothbrush 1 can be improved by gripping the gripping portion 12 and placing their fingers on the finger rest portion 17.

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

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

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

[0023] As shown in Figure 2, when the brush portion 20 is attached to the handle body 10, the fitting portion 15 is located inside the brush portion 20. As shown in Figures 3 and 4, the fitting portion 15 protrudes toward the tip from the first opposing surface 14b of the connecting portion 14. As shown in Figure 3, the fitting portion 15 is provided with a pair of recesses 15a and 15b. One recess 15a is recessed from the surface of the fitting portion 15 facing one side in the width direction (+Y side) toward the other side in the width direction (-Y side). The other recess 15b is recessed from the surface of the fitting portion 15 facing the other side in the width direction toward one side in the width direction. Each of the pair of recesses 15a and 15b is approximately semicircular in shape when viewed from the front.

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

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

[0026] As shown in Figure 5, the front view shape of the brush base portion 21 in this embodiment changes in a curved shape so that the width gradually increases from the front end to the rear end. The front view shape of the front end of the brush base portion 21 is approximately semicircular. As shown in Figure 6, the side view shape of the brush base portion 21 in this embodiment changes so that the thickness gradually increases from the front end to the rear end. More specifically, the surface of the brush base portion 21 facing the rear side (-Z side) is located on the rear side as you move from the front end to the rear end. The top surface 21a, which is the surface of the brush base portion 21 facing the front side (+Z side), is a plane that extends in a direction perpendicular to the thickness direction.

[0027] The outer surface of the brush base portion 21 facing the rear end is the second opposing surface 21d. Although not shown in the figure, the second opposing surface 21d is approximately rectangular when viewed from the direction of the long axis. As shown in Figure 1, when the brush portion 20 is attached to the handle body 10, the second opposing surface 21d faces the first opposing surface 14b of the handle body 10 in the direction of the long axis. In this embodiment, the second opposing surface 21d is in contact with the first opposing surface 14b in the direction of the long axis.

[0028] As shown in Figure 6, the brush base portion 21 has a fitting hole 27 that is recessed toward the tip side from the second opposing surface 21d. As shown in Figure 2, the fitting portion 15 is arranged inside the fitting hole 27. As shown in Figure 6, of the inner surfaces of the fitting hole 27, the surface facing the rear side (-Z side) is a plane that extends in a direction perpendicular to the thickness direction. Of the inner surfaces of the fitting hole 27, the surface facing the front side (+Z side) is located toward the rear side as you move from the tip side toward the rear end side.

[0029] As shown in Figure 5, the fitting hole 27 is provided with a pair of projections 27a and 27b. One projection 27a protrudes from the surface of the fitting hole 27 facing the other side in the width direction (-Y side) to the other side in the width direction. The other projection 27b protrudes from the surface of the fitting hole 27 facing the one side in the width direction (+Y side) to the one side in the width direction. Viewed from the thickness direction, each of the pair of projections 27a and 27b is approximately semicircular in shape. Each of the pair of projections 27a and 27b is fitted into the pair of recesses 15a and 15b, respectively.

[0030] As shown in Figure 6, each of the multiple filaments 30 protrudes from the upper surface 21a of the brush base 21 toward the front side, i.e., one side in the thickness direction (+Z side). Each filament 30 is made of soft resin. As shown in Figure 5, on the upper surface 21a, multiple rows composed of multiple filaments 30 arranged along the width direction are arranged in the direction of the long axis. 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 that connects to the brush base 21. The tip of the filament 30 is the end on the front side of the filament 30. The shape of the filament 30 will be described in detail later.

[0031] Various elastomers can be used as the soft resin constituting the brush portion 20, but polyurethane is preferred. Compared to other elastomers such as styrene-based and polyester-based materials, polyurethane has higher tensile strength, so mechanical strength can be ensured even when the material is thin. Therefore, damage to the toothbrush 1 during use can be suppressed.

[0032] Furthermore, polyurethane offers a wider range of selectable hardnesses compared to the other elastomers mentioned above, allowing for the selection of resin hardness that takes into account the operability (for example, the bending of the tip of the brush portion 20) according to the thickness of the brush portion 20. Preferably, the hardness of the polyurethane is such that the Shore hardness is A90 or higher and A100 or lower, or D40 or higher and D70 or lower. If the hardness of the polyurethane is softer than Shore 90A, it will deform easily when formed in a thin wall, resulting in a weaker fit and making it easier for the brush portion 20 to fall off when using the toothbrush 1. If the hardness of the polyurethane is harder than Shore 70D, and the back surface of the brush base portion 21 has a sloping shape, there is a risk of pain when the tip of the brush base portion 21 touches the oral cavity. By setting the hardness of the polyurethane to Shore 90A or higher and 70D or lower, it is possible to prevent the brush part 20 from falling off when using the toothbrush 1, and to prevent pain from occurring when the tip of the brush base part 21 touches the oral cavity.

[0033] The polyurethane contains, or is blended with, 0.01 wt% or more and 1.0 wt% or less of any of the following: saturated / unsaturated hydrocarbons of C10 or higher, higher alcohols, fatty acid amides, fatty acid esters, low molecular weight polyethylene, polyethylene glycol (PEG), fatty acid metal salts, long-chain fatty acids, fatty acid glycerin, or silicone, or a combination thereof, which functions as a lubricant and mold release agent. Furthermore, from the viewpoint of ensuring water resistance and antibacterial properties, it is preferable to use ether-based polyurethane as the polyurethane.

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

[0035] The maximum width of the head portion 5 is preferably 11 mm or less. This improves the maneuverability of the head portion 5 in the oral cavity, thereby enhancing the cleaning performance in the oral cavity.

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

[0037] Figure 8 shows a part of the toothbrush 1 of this embodiment. More specifically, Figure 8(a) is a side view showing a part of the toothbrush 1 of this embodiment. Figure 8(b) is a side view showing a part of the handle body 10 of this embodiment. Figure 8(c) is a front view showing a part of the handle body 10 of this embodiment. In this embodiment, the maximum thickness Th of the head shaft portion 6 shown in Figure 8(b), that is, 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.

[0038] Next, the shape of the neck portion 13 of this embodiment will be described in detail. As described above, the neck portion 13 is the part of the handle body 10 between the first boundary portion 13a and the second boundary portion 13b. As shown in Figure 8(c), the width of the neck portion 13 of this embodiment gradually widens from the first boundary portion 13a to the second boundary portion 13b. The width of the neck portion 13 is narrowest at the first boundary portion 13a and widest at the second boundary portion 13b. As shown in Figure 8(b), the thickness of the neck portion 13 of this embodiment extends toward the rear end from the first boundary portion 13a to the second boundary portion 13b with the same thickness, then changes linearly so that the thickness gradually increases, and then extends toward the rear end while changing curvely so that the thickness gradually increases. The thickness of the neck portion 13 is thinnest at the first boundary portion 13a and thickest at the second boundary portion 13b.

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

[0040] In 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 a brushing load is applied to the brush part 20 in the thickness direction during use, the head shaft 6 and neck 13 do not flex easily. Therefore, the head shaft 6 and neck 13 do not flex well enough to absorb the brushing load applied to the brush part 20, and stress concentrates on each filament 30. As a result, when using the toothbrush 1, if the flexing of each filament 30 becomes too large, it becomes difficult to penetrate deep into the interdental spaces. Consequently, it becomes difficult to remove plaque from between teeth with each filament 30, and the interdental cleaning performance decreases. Also, if the rigidity of the head shaft 6 and neck 13 is too low, the flexing of the head shaft 6 and neck 13 becomes too large during use. Therefore, the maneuverability of the head part 5 in the oral cavity decreases. This resulted in a decrease in the maneuverability of the toothbrush 1. Furthermore, the movement of the tip of each filament 30 did not easily synchronize with the user's hand movements, resulting in reduced interdental cleaning performance. In contrast, according to this embodiment, the maximum thickness Th of the head shaft portion 6, that is, 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 suppress the rigidity of the head shaft portion 6 from becoming too large, and also to suppress the rigidity of the head shaft portion 6 from becoming too small. As a result, when using the toothbrush 1, the head shaft portion 6 flexes appropriately, which suppresses the concentration of stress on each filament 30. Therefore, the portion of the toothbrush 1 from each filament 30 to the head shaft portion 6 flexes in conjunction. Consequently, it is possible to suppress the excessive flexing of each filament 30, thereby improving the interdental cleaning performance. Furthermore, because it is possible to suppress the excessive flexing of the head shaft portion 6, it is possible to suppress a decrease in the operability of the toothbrush 1, and because the movement of the tip of each filament 30 is easily linked to the movement of the user's hand, the interdental cleaning performance can be more effectively improved.

[0041] Furthermore, according to this embodiment, the width Wa of the first boundary portion 13a, that is, the minimum width dimension of the neck portion 13, is 3.0 mm or more and 4.5 mm or less. Therefore, it is possible to suppress the rigidity of the neck portion 13 from becoming too large, and also to suppress the rigidity of the neck portion 13 from becoming too small. As a result, when the toothbrush 1 is used, the neck portion 13 flexes appropriately, so that stress concentration on each filament 30 is suppressed. Therefore, the portion of the toothbrush 1 from each filament 30 to the neck portion 13 flexes in conjunction. Therefore, it is possible to suppress the excessive flexing of each filament 30, so that the interdental cleaning performance can be more effectively improved. Also, it is possible to suppress the excessive flexing of the neck portion 13. As a result, it is possible to more effectively suppress a decrease in the operability of the toothbrush 1, and the movement of the tip of each filament 30 is more easily linked to the movement of the user's hand, so that the interdental cleaning performance can be more effectively improved.

[0042] Furthermore, according to this embodiment, the connecting edge 14d is the tip side of the connecting portion 14, that is, the end on one side in the longitudinal direction (+X side) and the end on one side in the width direction (+Y side), and the neck edge 13d is the end on one side in the width direction of the part of the neck portion 13 that has the smallest width dimension. Viewed from the thickness direction, the first angle θ1 formed by the first imaginary line V1 that passes through both the connecting edge 14d and the neck edge 13d and the central axis J that extends from the center of the handle body 10 toward the longitudinal direction is 17° or more and 28° or less. If the first angle θ1 is less than 17°, the width of the neck portion 13 becomes too large relative to the width of the connection portion 14, resulting in excessive rigidity of the neck portion 13. As a result, when using the toothbrush 1, the deflection of the neck portion 13 becomes too small, causing the deflection of each filament 30 to become too large. Consequently, it becomes difficult to penetrate deep into the interdental spaces between teeth, reducing the interdental cleaning performance. Furthermore, if the first angle θ1 is greater than 28°, the width of the neck portion 13 becomes too small compared to the width of the connection portion 14, resulting in insufficient rigidity of the neck portion 13. This causes excessive deflection of the neck portion 13 and the connection portion 14, reducing the maneuverability of the head portion 5 in the oral cavity and thus reducing the maneuverability of the toothbrush 1. In contrast, according to this embodiment, the first angle θ1 is 17° or more and 28° or less, so when the toothbrush 1 is used, the neck portion 13 and the connecting portion 14 bend moderately and uniformly along the long axis. This more effectively suppresses the concentration of stress on each filament 30 and more effectively suppresses excessive bending of the neck portion 13 and the connecting portion 14. Therefore, since excessive bending of each filament 30 can be more effectively suppressed, the interdental cleaning performance can be more effectively improved and the operability of the toothbrush 1 can be more effectively suppressed. In this embodiment, when we say that the member bends uniformly along the long axis, we mean that the member bends along the entire long axis, rather than only a part of the member bending locally along the long axis.

[0043] Furthermore, the first angle θ1 is preferably between 18° and 26°. This allows for a more favorable improvement in interdental cleaning performance and a more favorable suppression of a decrease in the operability of the toothbrush 1. Furthermore, it is more preferable that the first angle θ1 is between 20° and 26°. This allows for a more favorable improvement in interdental cleaning performance and a more favorable suppression of a decrease in the operability of the toothbrush 1.

[0044] Preferably, the width Wb at the tip of the connecting portion 14 and the width Wa of the first boundary portion 13a, i.e., the minimum width of the neck portion 13, satisfy the relationship 2.0 ≤ Wb / Wa ≤ 2.8 as shown in Figure 8(c). By satisfying this relationship, it is possible to better suppress the rigidity of the neck portion 13 and the connecting portion 14 from becoming too large or too small, so that the neck portion 13 and the connecting portion 14 flex more appropriately when the toothbrush 1 is in use. Therefore, the interdental cleaning performance can be more effectively improved, and the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

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

[0046] The length Lc of the connecting portion 14 shown in Figure 8(c) is preferably 5 mm or more and 10 mm or less. This allows the connecting portion 14 to flex more appropriately when the toothbrush 1 is in use. Therefore, the interdental cleaning performance of the toothbrush 1 can be more effectively improved, and the deterioration of the operability of the toothbrush 1 can be more effectively suppressed.

[0047] The second imaginary line V2 shown in Figure 3 is a straight line that passes through both the neck edge 13d and the fitting edge 15d when viewed from the thickness direction. The second angle θ2 formed by the second imaginary line V2 and the central axis J is between 10° and 18°. If the second angle θ2 is less than 10°, the width of the head shaft portion 6 becomes too wide, resulting in excessive rigidity of the head shaft portion 6. As a result, when using the toothbrush 1, the head shaft portion 6 does not flex easily, causing each filament 30 to flex excessively. Consequently, it becomes difficult to penetrate deep into the interdental spaces between teeth, reducing the interdental cleaning performance. Furthermore, if the second angle θ2 is greater than 18°, the width of the head shaft portion 6 becomes too narrow, resulting in insufficient rigidity of the head shaft portion 6. This causes excessive deflection of the head shaft portion 6, reducing the maneuverability of the head portion 5 in the oral cavity and thus reducing the maneuverability of the toothbrush 1. In contrast, according to this embodiment, since the second angle θ2 is 10° or more and 18° or less, the head shaft portion 6 bends appropriately and uniformly in the longitudinal direction when the toothbrush 1 is in use. This makes it possible to more effectively suppress excessive bending of each filament 30, and also to more effectively suppress excessive bending of the head shaft portion 6. This makes it possible to more effectively suppress a decrease in the operability of the toothbrush 1, and because the movement of the tip of each filament 30 is more easily linked to the movement of the user's hand, the interdental cleaning performance can be more effectively improved.

[0048] Furthermore, the second angle θ2 is preferably between 11° and 16°. By setting the second angle θ2 within this range, it is possible to more effectively suppress the rigidity of the head shaft portion 6 from becoming too large or too small. This allows for more effective suppression of excessive deflection of each filament 30, as well as more effective suppression of excessive deflection of the head shaft portion 6. Consequently, the interdental cleaning performance can be more effectively improved, and the operability of the toothbrush 1 can be more effectively suppressed. Furthermore, it is more preferable that the second angle θ2 is between 12° and 16°. By setting the second angle θ2 within this range, it is more effectively possible to suppress the rigidity of the head shaft portion 6 from becoming too large. Consequently, it is more effectively possible to suppress the deflection of the head shaft portion 6 from becoming too small, and thus more effectively to suppress the deflection of each filament 30 from becoming too large. This allows for a more effectively improved interdental cleaning performance.

[0049] It is preferable that the width Wm at the rear end of the fitting portion 15 shown in Figure 8(c) and the width Wa of the first boundary portion 13a, i.e., the minimum width of the neck portion 13, 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, so that when the toothbrush 1 is used, the head shaft portion 6 flexes more appropriately and more uniformly in the longitudinal direction. Therefore, the cleaning performance between teeth can be further improved, and the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

[0050] The width Wm at the rear end of the fitting portion 15 is preferably 6 mm or more and 12 mm or less. This allows the head shaft portion 6 to flex more appropriately and more uniformly along the long axis when the toothbrush 1 is in use. Therefore, the interdental cleaning performance can be more effectively improved, and the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

[0051] As shown in Figure 9, the head portion 5 has a first head portion 5a and a head edge portion 5d. The first head portion 5a is the part of the head portion 5 where the width of the head portion 5 is maximum. In this embodiment, the first head portion 5a is located between the center of the brush portion 20 in the longitudinal direction and the rear end of the brush portion 20. Note that if the head portion 5 has a shape that extends in the longitudinal direction with its maximum width, the rear end of the part that extends in the longitudinal direction with its maximum width is defined as the first head portion 5a. The head edge portion 5d is the end on one side (+Y side) in the width direction of the first head portion 5a. In a front view, the head edge portion 5d is located on one side in the width direction of the first boundary portion 13a.

[0052] The third imaginary line V3 shown in Figure 9 is a straight line that passes through both the neck edge 13d and the head edge 5d when viewed from the thickness direction. The third angle θ3 formed by the third imaginary line V3 and the central axis J is preferably 15° or more and 25° or less. By setting the third angle θ3 within this range, it is possible to further suppress the rigidity of the head shaft portion 6 from becoming too large or too small, so that when the toothbrush 1 is used, the head shaft portion 6 flexes more appropriately and more uniformly in the longitudinal direction. Therefore, the interdental cleaning performance can be more effectively improved, and the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

[0053] It is preferable that the width Wh of the first head portion 5a, i.e., the maximum width of the head portion 5, and the width Wa of the first boundary portion 13a, i.e., the minimum width of the neck portion 13, satisfy the relationship 2.5 ≤ Wh / Wa ≤ 4.5. By satisfying this relationship, when the toothbrush 1 is used, the head shaft portion 6 bends more appropriately and more uniformly in the longitudinal direction. Therefore, the cleaning performance between teeth can be more effectively improved, and the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

[0054] The width Wh of the first head portion 5a, i.e., the maximum width of the head portion 5, is preferably 10 mm or more and 16 mm or less. This allows the head shaft portion 6 to flex more appropriately and more uniformly along the long axis when the toothbrush 1 is in use. Therefore, the interdental cleaning performance can be more effectively improved, and the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

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

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

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

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

[0059] According to this embodiment, the width W1 of the first neck portion P1 and the thickness T1 of the first neck portion P1 are 130 mm 4 ≤W1×T1 3 ≤400mm 4 The following relationship is satisfied. The width W2 of the second neck portion P2 and the thickness T2 of the second neck portion P2 are 450 mm. 4 ≤W2×T2 3 ≤1200mm 4The following relationship is satisfied. The width W3 of the third neck part P3 and the thickness T3 of the third neck part P3 are 2000 mm. 4 ≤W3×T3 3 ≤5000mm 4 It satisfies the following relationship. W1×T1 3 130mm 4 If the size is smaller, the rigidity of the tip portion of the neck portion 13, including the first neck portion P1, becomes too small, causing the tip portion of the neck portion 13 to flex locally significantly when the toothbrush 1 is used. Consequently, the maneuverability of the head portion 5 in the oral cavity decreases. This reduces the maneuverability of the toothbrush 1. In addition, the movement of the tip of each filament 30 does not easily synchronize with the movement of the user's hand, resulting in reduced interdental cleaning performance. W2×T2 3 450mm 4 If the value is smaller, the rigidity of the rear end portion of the neck portion 13, including the second neck portion P2, becomes too low, causing the rear end portion of the neck portion 13 to flex significantly locally when the toothbrush 1 is used. Consequently, the operability of the toothbrush 1 decreases, as does its interdental cleaning performance. W3×T3 3 2000mm 4 If the value is smaller than this, the rigidity of the rear end of the neck portion 13 becomes too low, causing the rear end of the neck portion 13 to bend significantly locally when the toothbrush 1 is used. Consequently, the operability of the toothbrush 1 decreases, as does its interdental cleaning performance. W1×T1 3 400mm 4 If the value is larger, the rigidity of the tip portion of the neck portion 13, including the first neck portion P1, becomes too large. As a result, when using the toothbrush 1, the deflection of the tip portion of the neck portion 13 becomes too small, and the deflection of each filament 30 becomes too large. Consequently, the interdental cleaning performance decreases. W2×T2 3 1200mm 4If the value is larger, the rigidity of the rear end portion of the neck portion 13, including the second neck portion P2, becomes too large. As a result, when using the toothbrush 1, the deflection of the rear end portion of the neck portion 13 becomes too small, and the deflection of each filament 30 becomes too large. Consequently, the interdental cleaning performance deteriorates. W3×T3 3 5000mm 4 If the value is greater than this, the rigidity of the rear end of the neck portion 13 becomes too large. As a result, when using the toothbrush 1, the deflection of the rear end of the neck portion 13 becomes too small, and the deflection of each filament 30 becomes too large. Consequently, the interdental cleaning performance decreases.

[0060] In contrast, in this embodiment, in order to satisfy the above relationship, it is possible to suppress the localized large bending of a portion of the neck portion 13 when using the toothbrush 1. Therefore, when using the toothbrush 1, the neck portion 13 bends more appropriately and more uniformly in the longitudinal direction, and it is possible to suppress the bending of each filament 30 from becoming too large. In other words, the bending can be coordinated from each filament 30 to the rear end of the neck portion 13. Therefore, it is possible to more effectively suppress a decrease in the operability of the toothbrush 1, and because the movement of the tip of each filament 30 is more easily coordinated with the movement of the user's hand, the interdental cleaning performance can be more effectively improved.

[0061] The width W1 of the first neck portion P1 is preferably 3.5 mm or more and 4.5 mm or less, and the thickness T1 of the first neck portion P1 is preferably 3.5 mm or more and 4.5 mm or less. As a result, when using the toothbrush 1, the tip portion of the neck portion 13 flexes more appropriately and more uniformly along the long axis. Therefore, the interdental cleaning performance can be more effectively improved, and the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

[0062] The width W2 of the second neck portion P2 is preferably 4.5 mm or more and 5.5 mm or less, and the thickness T2 of the second neck portion P2 is preferably 4.5 mm or more and 5.5 mm or less. As a result, when using the toothbrush 1, the rear end portion of the neck portion 13 flexes more appropriately and more uniformly along the long axis. Therefore, the interdental cleaning performance can be more effectively improved, and the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

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

[0064] In the longitudinal direction, the fourth neck portion P4 is located between the first neck portion P1 and the second neck portion P2. In the longitudinal direction, the ratio of the distance between the connecting tip portion 14a and the fourth neck portion P4 to the first distance L1 is 40%. The fourth neck portion P4 is the tip portion of the neck portion 13. The width W4 of the fourth neck portion P4 is preferably 3.5 mm or more and 4.5 mm or less, and the thickness T4 of the fourth neck portion P4 is preferably 3.5 mm or more and 4.5 mm or less. As a result, when using the toothbrush 1, the tip portion of the neck portion 13 flexes more appropriately and more uniformly in the longitudinal direction. Therefore, the interdental cleaning performance can be more effectively improved, and the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

[0065] In the longitudinal direction, the fifth neck portion P5 is located between the fourth neck portion P4 and the second neck portion P2. In the longitudinal direction, the ratio of the distance between the connecting tip portion 14a and the fifth neck portion P5 to the first distance L1 is 60%. The fifth neck portion P5 is the rear end portion of the neck portion 13. The width W5 of the fifth neck portion P5 is preferably 4.0 mm or more and 5.0 mm or less, and the thickness T5 of the fifth neck portion P5 is preferably 4.0 mm or more and 5.0 mm or less. As a result, when the toothbrush 1 is used, the rear end portion of the neck portion 13 flexes more appropriately and more uniformly in the longitudinal direction. Therefore, the interdental cleaning performance can be more effectively improved, and the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

[0066] The seventh neck portion P7 is located further back than the first boundary portion 13a. The distance in the longitudinal direction between the first boundary portion 13a and the seventh neck portion P7 is the same length as the length Lm of the fitting portion 15. The thickness T7 of the seventh neck portion P7 is preferably 5.0 mm or less. This prevents the rigidity of the neck portion 13 from becoming too large, so that the neck portion 13 flexes appropriately when the toothbrush 1 is used. Therefore, the flexing of each filament 30 is prevented from becoming too large, and the interdental cleaning performance can be more effectively improved.

[0067] Preferably, the thickness Ta of the first boundary portion 13a, which is the minimum thickness of the neck portion 13, the thickness T7 of the seventh neck portion P7, and the maximum thickness Tm of the fitting portion 15 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 easier to reduce the difference between the thickness Ta of the first boundary portion 13a and the thickness T7 of the seventh neck portion P7. This prevents the thickness T7 of the seventh neck portion P7 from becoming too thick. Therefore, it is possible to prevent the rigidity of the portion of the neck portion 13 between the first boundary portion 13a and the seventh neck portion P7 from becoming too high relative to the rigidity of the head shaft portion 6. Thus, when using the toothbrush 1, the head shaft portion 6 and the neck portion 13 flex more appropriately and more uniformly in the longitudinal direction. Therefore, the interdental cleaning performance can be more favorably improved, and the decrease in the operability of the toothbrush 1 can be more favorably suppressed.

[0068] The eighth neck portion P8 is located further back than the seventh neck portion P7. The distance in the long axis direction between the first boundary portion 13a and the eighth neck portion P8 is the same as twice the length Lm of the fitting portion 15. The thickness T8 of the eighth neck portion P8 is preferably 8.0 mm or less. This prevents the rigidity of the neck portion 13 from becoming too large, so that the neck portion 13 flexes appropriately when the toothbrush 1 is used. Therefore, the flexing of each filament 30 is prevented from becoming too large, and the interdental cleaning performance can be more effectively improved.

[0069] It is preferable that the thickness Ta of the first boundary portion 13a, the thickness T8 of the eighth neck portion P8, and the maximum thickness Tm of the fitting portion 15 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 easier to reduce the difference between the thickness Ta of the first boundary portion 13a and the thickness T8 of the eighth neck portion P8. This prevents the thickness T8 of the eighth neck portion P8 from becoming too thick. Therefore, it is possible to prevent the rigidity of the portion of the neck portion 13 between the first boundary portion 13a and the eighth neck portion P8 from becoming too large relative to the rigidity of the head shaft portion 6. Thus, the head shaft portion 6 and the neck portion 13 flex more appropriately and more uniformly in the longitudinal direction. Consequently, the interdental cleaning performance can be more favorably improved, and the decrease in the operability of the toothbrush 1 can be more favorably suppressed.

[0070] It is preferable that the thickness Ta of the first boundary portion 13a and the maximum thickness Tm of the fitting portion 15 satisfy the relationship Ta ≤ 2.5 × Tm. By satisfying this relationship, 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 portion 13, and thus 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, thereby further improving the operability of the toothbrush 1.

[0071] The ninth neck portion P9 is located between the seventh neck portion P7 and the eighth neck portion P8. The position of the ninth neck portion P9 is not limited to this; it may be located closer to the front than the seventh neck portion P7, or closer to the rear than the eighth neck portion P8. The thickness T9 of the ninth neck portion P9 is the same as the maximum thickness Tb of the brush base portion 21. In the longitudinal direction, the distance L6 between the rear end of the fitting portion 15 and the ninth neck portion P9 is longer than the length Lb of the brush portion 20. This allows the length of the thin portion in the neck portion 13 to be longer than the maximum thickness Tb of the brush base portion 21, thereby preventing the rigidity of the neck portion 13 from becoming too large. Therefore, when using the toothbrush 1, the neck portion 13 flexes appropriately, preventing the flexing of each filament 30 from becoming too large. Thus, the interdental cleaning performance can be more effectively improved.

[0072] The ratio of the distance L7 in the longitudinal direction between the connecting tip portion 14a and the first boundary portion 13a of the connecting portion 14 to the first distance L1 is preferably 10% or more and 50% or less, and more preferably 10% or more and 30% or less. This allows the first boundary portion 13a, which is the thinnest part of the neck portion 13, to be positioned closer to the fitting portion 15. Therefore, when using the toothbrush 1, the part of the neck portion 13 closest to the fitting portion 15 flexes, thereby reducing the stress applied to the fitting portion 15. Consequently, the excessive flexing of the fitting portion 15 can be effectively suppressed, thereby further improving the operability of the toothbrush 1.

[0073] Preferably, the ratio of the length Ln of the neck portion 13 to the distance L8 between the tip of the head portion 5 and the rear end of the neck portion 13 is 60% or more. This allows the neck portion 13 to flex appropriately when the toothbrush 1 is in use. Therefore, the interdental cleaning performance can be more effectively improved, and the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

[0074] The ratio of the length Lm of the fitting portion 15 to the length Lb of the brush portion 20 is preferably 80% or more. This increases the contact area between the inner surface of the fitting hole 27 of the brush portion 20 and the outer surface of the fitting portion 15, thereby increasing the frictional force between the brush portion 20 and the fitting portion 15. As a result, when using the toothbrush 1, movement of the brush portion 20 in the longitudinal direction relative to the handle body 10 is suppressed, and the deterioration of the operability of the toothbrush 1 is more effectively suppressed.

[0075] In this embodiment, the brush portion 20 is formed by insert molding using the handle body 10 as an insert member. This allows for a larger contact area between the inner surface of the fitting hole 27 of the brush portion 20 and the outer surface of the fitting portion 15, thereby increasing the bonding force between the brush portion 20 and the fitting portion 15. Consequently, when using the toothbrush 1, movement of the brush portion 20 in the longitudinal direction relative to the handle body 10 can be suppressed, thus more effectively preventing a decrease in the operability of the toothbrush 1.

[0076] The 10th neck portion P10 is located between the 8th neck portion P8 and the 2nd boundary portion 13b. The position of the 10th neck portion P10 is not limited to this, and it may be located closer to the tip than the 8th neck portion P8. The width W10 of the 10th neck portion P10 is the same as the width Wm of the rear end of the fitting portion 15. The distance L5 between the 1st boundary portion 13a and the 10th neck portion P10 is preferably greater than or equal to the length Lh of the head portion 5. This makes it possible to make the width of the neck portion 13 between the 1st boundary portion 13a and the 10th neck portion P10 narrower than the width Wm of the rear end of the fitting portion 15, thereby preventing the rigidity of the portion of the neck portion 13 between the 1st boundary portion 13a and the 10th neck portion P10 from becoming too large relative to the rigidity of the fitting portion 15. Therefore, when using the toothbrush 1, the head shaft portion 6 and the neck portion 13 flex more appropriately and more uniformly in the longitudinal direction. Therefore, the interdental cleaning performance can be more effectively enhanced, and the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

[0077] The ratio of the length Lh of the head portion 5 to the distance L8 between the tip of the head portion 5 and the rear end of the neck portion 13 is preferably 40% or less. This prevents the length of the neck portion 13 from becoming too short, allowing the neck portion 13 to flex more appropriately when the toothbrush 1 is in use. Therefore, it is possible to prevent the head portion 5 from flexing too much, thereby improving the operability of the toothbrush 1.

[0078] The side view shape of the neck portion 13 is preferably a shape that extends in a straight line from the tip side to the rear end side. If the side view shape of the neck portion 13 is a curved shape having a curved portion such as an S-shape, stress tends to concentrate in the curved portion when the toothbrush 1 is used, so that the curved portion tends to bend significantly locally. In contrast, in this embodiment, the side view shape of the neck portion 13 is a shape that extends in a straight line from the tip side to the rear end side, so that the concentration of stress in a part of the neck portion 13 can be suppressed. Therefore, since the local bending of a part of the neck portion 13 can be suppressed, the operability of the toothbrush 1 can be more favorably improved.

[0079] It is preferable that the difference between the width dimension and the thickness dimension of the tip portion of the neck portion 13 is small. It is preferable that the ratio of the thickness dimension to the width dimension of the tip portion of the neck portion 13 is 75% or more and 130% or less. It is preferable that the shape of the cross section perpendicular to the long axis of the tip portion of the neck portion 13 is a shape such as a circle or a square, in which the difference between the width dimension and the thickness dimension is small. The tip portion of the neck portion 13 is, for example, the portion of the neck portion 13 whose distance from the first boundary portion 13a is 30% or less of the length Ln of the neck portion 13.

[0080] It is preferable not to provide a hole in the fitting portion 15 that penetrates the fitting portion 15 in the thickness direction. This prevents a decrease in the rigidity of the fitting portion 15, and thus prevents the head portion 5 from bending too much when the toothbrush 1 is in use. Therefore, the operability of the toothbrush 1 can be more favorably improved.

[0081] Next, the shape of the filament 30 in this embodiment will be described in detail. As described above, each of the multiple filaments 30 protrudes from the upper surface 21a of the brush base portion 21 toward the front side (+Z side). As shown in Figure 5, the shape of the cross section perpendicular to the thickness direction of each filament 30 is a roughly equilateral triangle protruding toward the tip side. As shown in Figure 6, each filament 30 is a roughly triangular pyramidal shape that becomes thinner toward the front side. As shown in Figure 7, when viewed from the width direction, each filament 30 has a shape in which the decrease in the dimension in the long axis direction relative to the unit length in the thickness direction increases in stages as it moves from the brush base portion 21 toward the front side. Note that the shape of the filament 30 is not limited to this embodiment, and for example, the shape of the cross section perpendicular to the thickness direction may be a polygon such as a quadrilateral, a circle, a semicircle, a star shape, or other shapes. Furthermore, in the following description, the shape in which the decrease in the dimension in the long axis direction relative to the unit length in the thickness direction increases in stages as it moves from the brush base portion 21 toward the front side when viewed from the width direction may be called a stepped taper shape. Each filament 30 has a first filament section 30a, a second filament section 30b, a third filament section 30c, a fourth filament section 30d, a fifth filament section 30e, a sixth filament section 30f, a first section 31, a second section 32, and a third section 33. The filament 30 is composed of the first section 31, the second section 32, and the third section 33. The first section 31, the second section 32, and the third section 33 are arranged in this order from the brush base section 21 toward the front. The filament 30 is distributed in the order of the first section 31, the second section 32, and the third section 33 in accordance with the stepped taper from the brush base section 21 toward the front.

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

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

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

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

[0086] The first portion 31 is the rear 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 of the filament 30 between the second filament portion 30b and the third filament portion 30c. In this embodiment, when viewed from the width direction, the rear end edge of the first portion 31 is a straight line extending substantially toward the front side. When viewed from the width direction, the front end edge of the first portion 31 is a straight line located toward the rear end as it approaches the front side. When viewed from the width direction, the dimension of the first portion 31 in the longitudinal direction decreases as it approaches the front side. When the length of the first portion 31 in the thickness direction is M1, the first reduction rate R1, which is the amount of decrease in the dimension in the longitudinal direction relative to the unit length in the thickness direction of the first portion 31, is (D2-D3) / M1.

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

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

[0089] If the length of the filament 30 is the same from the base to the tip, the rigidity of the filament 30 tends to be high. As a result, when using the toothbrush 1, the deflection of the filament 30 becomes too small. This makes it difficult for the brushing load applied to the brush part 20 to be absorbed by the deflection of the filament 30, causing stress to concentrate in the neck part 13 and making the deflection of the neck part 13 tend to be large. Consequently, the maneuverability of the head part 5 in the oral cavity decreases. This resulted in a decrease in the maneuverability of the toothbrush 1. In addition, because the movement of the tip of each filament 30 does not easily correspond to the movement of the user's hand, the interdental cleaning performance is reduced. Furthermore, if the decrease in the length along the long axis relative to the unit length in the thickness direction is constant from the base to the tip of the filament 30, stress tends to concentrate in the center of each filament 30 in the thickness direction when the toothbrush 1 is used. As a result, the amount of deflection in the center of each filament 30 in the thickness direction tends to increase locally. Consequently, it becomes difficult to penetrate deep into the interdental spaces between teeth, thus reducing the cleaning performance between teeth.

[0090] 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, when viewed from the width direction, the amount of reduction in the length axis dimension relative to a unit length in the thickness direction increases stepwise as each of the multiple filaments 30 moves from the brush base portion 21 toward the front side, i.e., toward one side in the thickness direction (+Z side). Therefore, compared to the case where the length axis dimension is the same from the root to the tip of each filament 30, it is possible to suppress the rigidity of each filament 30 from becoming too large, and thus it is possible to suppress the deflection of the neck portion 13 from becoming too large. Also, compared to the case where the amount of reduction in the length axis dimension relative to a unit length in the thickness direction is constant from the root to the tip of each filament 30, it is possible to suppress the concentration of stress in the center of each filament 30 in the thickness direction. Therefore, it is possible to suppress the localized increase in the deflection of the center of each filament 30 in the thickness direction. As a result, the portion of the toothbrush 1 from each filament 30 to the neck portion 13 can bend in a more controlled manner. Therefore, the interdental cleaning performance can be more effectively improved, and the operability of the toothbrush 1 can be more effectively improved.

[0091] According to this embodiment, the ratio of the first area S1, which is the area of ​​the cross-section perpendicular to the thickness direction of the first filament portion 30a, to the second area S2, which is the area of ​​the cross-section perpendicular to the thickness direction of the second filament portion 30b, is 20% or more and 30% or less. In toothbrushes, the tip portion of the filament 30 is generally made thinner than the base portion to facilitate penetration into the gaps between teeth. However, in a one-piece molded toothbrush where each filament 30 is formed from soft resin, if 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, making it prone to buckling when the toothbrush 1 is used. Consequently, it becomes difficult to penetrate deep into the gaps between teeth, reducing the cleaning performance of the toothbrush 1. When the ratio of the first area S1 to the second area S2 is greater than 30%, the rigidity of the tip portion of each filament becomes too high, causing stress to concentrate in the portion of each filament 30 from the center to the root in the thickness direction. Therefore, the portion of each filament 30 from the center to the root in the thickness direction is prone to buckling. As a result, the entire filament 30 does not bend moderately and uniformly, making it difficult to penetrate deep into the interdental spaces. In addition, the excessive rigidity of each filament 30 causes the neck portion 13 to bend excessively. This reduces the maneuverability of the toothbrush 1. Furthermore, the movement of the tip of each filament 30 does not easily synchronize with the movement of the user's hand, resulting in reduced interdental cleaning performance. In contrast, according to this embodiment, since the ratio of the first area S1 to the second area S2 is 20% or more and 30% or less, buckling of the tip portion of each filament 30 and the portion from the center to the root in the thickness direction of each filament 30 can be suppressed. As a result, the entire filament 30 bends appropriately and uniformly in the thickness direction. Therefore, when using the toothbrush 1, it becomes easier to penetrate deep into the interdental spaces between teeth, thereby more effectively improving the cleaning performance of the toothbrush 1. Furthermore, since the movement of the tip of each filament 30 is easily linked to the movement of the user's hand, the interdental cleaning performance can be more effectively improved. In addition, since the rigidity of each filament 30 can be more effectively suppressed from becoming too rigid, the bending of the neck portion 13 can be more effectively suppressed from becoming too flexible. Therefore, a decrease in the operability of the toothbrush 1 can be more effectively suppressed.

[0092] The fifth filament portion 30e is located between the first filament portion 30a and the third filament portion 30c. In the thickness direction, the ratio of the distance Lf5 between the tip of the filament 30 and the fifth filament portion 30e to the dimension Lf of the filament 30 is 25%. The fifth filament portion 30e is the tip-side portion of the filament 30. The ratio of the fifth area S5, which is the area of ​​the cross-section of the fifth filament portion 30e perpendicular to the thickness direction, to the second area S2 is 35% or more and 55% or less. As a result, the entire filament 30 bends more appropriately and more uniformly in the thickness direction. Therefore, the cleaning performance of the toothbrush 1 can be more effectively improved, and the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

[0093] The sixth filament portion 30f is located between the third filament portion 30c and the fifth filament portion 30e. In the thickness direction, the ratio of the distance Lf6 between the tip of the filament 30 and the sixth filament portion 30f to the dimension Lf of the filament 30 is 50%. The sixth filament portion 30f is the central part of the filament 30 in the thickness direction. The ratio of the sixth area S6, which is the area of ​​the cross-section of the sixth filament portion 30f perpendicular to the thickness direction, to the second area S2 is between 75% and 95%. As a result, the entire filament 30 flexes more appropriately and more uniformly in the thickness direction. Therefore, the cleaning performance of the toothbrush 1 can be more effectively improved, and the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

[0094] As shown in Figure 5, the area of ​​the upper surface 21a of the brush base portion 21, which is the front side, i.e., the side facing one side in the thickness direction (+Z side), is the third area S3. The third area S3 is the area enclosed by the outer edge of the upper surface 21a. The second area S2 of the second filament portion 30b of each of the multiple filaments 30, i.e., the sum of the areas of the cross-sections perpendicular to the thickness direction, 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. If the ratio of the fourth area S4 to the third area S3 is less than 25%, the number of filaments 30 becomes too small, resulting in excessive force being applied to each filament 30 when using the toothbrush 1. This causes each filament 30 to bend excessively. Consequently, it becomes difficult to penetrate deep into the interdental spaces, reducing the cleaning performance of the toothbrush 1. If the ratio of the fourth area S4 to the third area S3 is greater than 35%, the number of filaments 30 becomes too large, resulting in too little force being applied to each filament 30. Consequently, the deflection of each filament 30 becomes too small. Therefore, the brushing load applied to the brush part 20 is not easily absorbed by the deflection of each filament 30, causing stress to concentrate in the neck part 13, and the deflection of the neck part 13 becomes too large. Consequently, the maneuverability of the head part 5 in the oral cavity decreases, and the maneuverability of the toothbrush 1 decreases. 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, so that the force applied to each filament 30 does not become too large or too small. As a result, each filament 30 bends appropriately, so that stress concentration in the neck portion 13 is suppressed. Therefore, the toothbrush 1 can bend in conjunction from each filament 30 to the rear end of the neck portion 13. Consequently, it becomes easier for each filament 30 to penetrate deep into the interdental spaces, thus more effectively improving the cleaning performance of the toothbrush 1. Furthermore, since excessive bending of the neck portion 13 can be more effectively suppressed, the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

[0095] The third area S3, that is, the number of filaments 30 on the toothbrush 1 per unit area of ​​the upper surface 21a of the brush base portion 21, is 80 filaments / cm². 2 In total, 110 strands / cm 2This is preferable. This allows for a more favorable suppression of excessive or insufficient stress on each filament 30 when using the toothbrush 1, so that each filament 30 bends more appropriately. Therefore, the cleaning performance of the toothbrush 1 can be more favorably improved, and a decrease in the operability of the toothbrush 1 can be more favorably suppressed.

[0096] When viewed from the thickness direction, the shortest distance Ws between the outer edge of the brush base portion 21 and the multiple filaments 30 is preferably 3.0 mm or less. This increases the number of filaments 30 that can be arranged on the upper surface 21a, thereby reducing the stress applied to each filament 30 when the toothbrush 1 is used. Therefore, it is possible to suppress excessive bending of each filament 30, thereby more effectively improving the interdental cleaning performance. In Figure 5, the filament region Rf is the region surrounding all parts of the upper surface 21a that are connected to each filament 30. The area of ​​the filament region Rf is the filament area Sf.

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

[0098] In this embodiment, a SHIMAZDU AGS-X autograph tester was used as the first deflection test apparatus 50. The first deflection test apparatus 50 has a pressurizing member 51 and a position measuring unit (not shown) for measuring the position of the pressurizing member 51 in the thickness direction. A reaction force measuring unit 51a is provided on the surface of the pressurizing 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 is capable of measuring the load applied to the reaction force measuring unit 51a.

[0099] In the first deflection 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 a screw 52c. Each of the first fixing part 52a and the second fixing part 52b is a rectangular parallelepiped that extends in a direction perpendicular to the thickness direction. The second fixing part 52b is positioned on the front side (+Z side) of the first fixing part 52a. The gripping part 12 of the toothbrush 1 is positioned between the first fixing part 52a and the second fixing part 52b. The gripping part 12 is placed on the front-facing surface of the first fixing part 52a. The screw 52c is passed through a hole that penetrates the second fixing part 52b in the thickness direction and a hole that penetrates the first fixing part 52a in the thickness direction, respectively, in the thickness direction. When the nut 52d is tightened onto the portion of the screw 52c that is on the rear side of the first fixing portion 52a, the gripping portion 12 is fixed to the fixing portion 52. At this time, when viewed from the thickness direction, the second boundary portion 13b, which is the boundary between the neck portion 13 and the gripping portion 12, coincides with the tip of the first fixing portion 52a and the tip of the second fixing portion 52b. As a result, the rear end of the neck portion 13, that is, the end on the other side (-X side) in the longitudinal direction, is fixed to the fixing portion 52.

[0100] The pressure member 51 contacts each filament 30 from the front side, i.e., one side in the thickness direction (+Z side). More specifically, the reaction force measuring section 51a contacts all of the filaments 30. The pressure member 51 is movable in the thickness direction. In the first deflection test, the pressure member 51 is moved to the back side, i.e., the other side in the thickness direction (-Z side), thereby deflecting the portion of the toothbrush 1 from each filament 30 to the neck portion 13, and the reaction force measuring section 51a measures the first reaction force F1, which is the reaction force of the toothbrush 1. In the first deflection test, the movement speed of the pressure member 51 is 10 mm / second. 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 for the first deflection test is 0.002 mm.

[0101] Figure 11 shows an example of the first reaction force F1 in this embodiment. The horizontal axis in Figure 11 represents the first travel distance Z1. The first travel distance Z1 is the distance the pressurizing member 51 moves to the back side. The origin of the first travel distance Z1 is the position where the pressurizing member 51 and the filament 30 begin to make contact. The vertical axis in Figure 11 represents the first reaction force F1. As shown in Figure 11, in the toothbrush 1 of this embodiment, the first reaction force F1 increases monotonically as the first travel distance Z1 increases.

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

[0103] In the first deflection test, when the first reaction force F1 is measured at the Mth measurement, the first displacement distance is Z1(M) and the first reaction force is F1(M). When the first reaction force F1 is measured at the M+50th measurement, the first displacement distance is Z1(M+50) and the first reaction force is F(M+50). The distance between Z1(M+50) and Z1(M) is the first predetermined distance dZ1. Therefore, the amount of change in the first reaction force F1 when the position of the pressurizing member 51 in the thickness direction changes by the first predetermined distance dZ1 from Z1(M) is F1(M+50)-F1(M). Thus, the first reaction force fluctuation rate RF1 is (F1(M+50)-F1(M)) / dZ1. By calculating the first reaction force fluctuation rate RF1 for all obtained first reaction forces F1 using this calculation method, the relationship between the first displacement distance Z1 and the first reaction force fluctuation rate RF1 shown in Figure 13 is obtained. In this embodiment, the first reaction force fluctuation rate RF1 may be the moving average of, for example, 50 first reaction force fluctuation rates RF1 calculated by the above calculation method. This reduces the influence of measurement errors that occur unexpectedly when measuring the first reaction force F1 on the first reaction force fluctuation rate RF1, thereby allowing for a more accurate relationship between the first travel distance Z1 of the toothbrush 1 and the first reaction force fluctuation rate RF1.

[0104] As shown in Figure 13, the first maximum value RF1max is the maximum value of the first reaction force fluctuation rate RF1 within the range where the movement distance of the pressurizing member 51 is 3.0 mm or less. The first minimum value RF1min is the minimum value of the first reaction force fluctuation rate RF1 within the range where the movement distance of the pressurizing member 51 is 3.0 mm or less. According to this embodiment, the relationship RF1max - RF1min ≤ 0.6 N / mm is satisfied between the first maximum value RF1max and the first minimum value RF1min.

[0105] In toothbrush 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. When each filament 30 bends locally, it becomes difficult to penetrate deep into the interdental spaces, thus reducing the cleaning performance of toothbrush 1. Furthermore, when the head shaft 6 and the neck 13 bend locally, the maneuverability of the head 5 in the oral cavity decreases, thus reducing the maneuverability of toothbrush 1. In contrast, according to this embodiment, since the difference between the first maximum value RF1max and the first minimum value RF1min is 0.6 N / mm or less, each filament 30, the head shaft portion 6, and the neck portion 13 do not bend locally, and instead the filaments 30, the head shaft portion 6, and the neck portion 13 bend uniformly in the longitudinal direction in conjunction with each other. Therefore, since local bending of each filament 30 can be suppressed, the cleaning performance of the toothbrush 1 can be more effectively improved. Furthermore, since local bending of the head shaft portion 6 and the neck portion 13 can be suppressed, the decrease in the operability of the toothbrush 1 can be more effectively suppressed.

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

[0107] According to this embodiment, the first average value RF1ave, which is the average value of the first reaction force fluctuation rate RF1 within a range of 3.0 mm or less for the travel distance of the pressurizing member 51, is 0.5 N / mm or more and 1.0 N / mm or less. When the first average value RF1ave is less than 0.5 N / mm, the deflection of each filament 30 becomes too small when using the toothbrush 1, causing stress to concentrate in the neck portion 13. As a result, the deflection of the neck portion 13 becomes too large, reducing the operability of the toothbrush 1. If the first average value RF1ave is greater than 1.0 N / mm, the deflection of each filament 30 becomes too large, or a portion of each filament 30 bends locally, when using the toothbrush 1. Consequently, it becomes difficult to penetrate deep into the interdental spaces, reducing the cleaning performance of the toothbrush 1. In contrast, according to this embodiment, since the first average value RF1ave is 0.5 N / mm or more and 1.0 N / mm or less, it is possible to suppress excessive deflection of each filament 30 and the neck portion 13. As a result, the filaments 30, the head shaft portion 6, and the neck portion 13 deflect more uniformly and suitably in the longitudinal direction in conjunction. Therefore, the cleaning performance of the toothbrush 1 can be more suitably improved, and the deterioration of the operability of the toothbrush 1 can be more suitably suppressed.

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

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

[0110] In this embodiment, a SHIMAZDU Autograph testing machine AGS-X was used as the second deflection testing apparatus 60. The second deflection testing apparatus 60 has a pressurizing member 61 and a position measuring unit (not shown) for measuring the position of the pressurizing member 61 in the thickness direction. A reaction force measuring unit 61a is provided on the surface of the pressurizing member 61 facing the back side (-Z side).

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

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

[0113] Figure 15 shows 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 that the pressurizing member 61 receives from each filament 30. Figure 16 shows an example of the second pressure fluctuation rate RP in this embodiment. The horizontal axis in Figure 15 is the second travel distance Z2. The second travel distance Z2 is the distance that the pressurizing member 61 has moved toward the back side (-Z side). The origin of the second travel distance Z2 is the position where the pressurizing member 61 and the filament 30 begin to make contact. The vertical axis in Figure 15 is the second pressure P. As shown in Figure 15, in the toothbrush 1 of this embodiment, the second pressure P increases monotonically as the second travel distance Z2 increases.

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

[0115] The second pressure fluctuation rate RP is 0.0 N / mm 3 If the size is smaller, when using the toothbrush 1, the bending of each filament 30 becomes too large, or a portion of each filament 30 bends locally. Consequently, it becomes difficult to penetrate deep into the interdental spaces, reducing the cleaning performance of the toothbrush 1. The second pressure fluctuation rate RP is 10.0 × 10 -2 N / mm 3If the value is larger, the reaction force of each filament 30 becomes too large, causing the deflection of each filament 30 to become too small. As a result, stress tends to concentrate in the neck portion 13, causing the deflection of the neck portion 13 to become too large. Consequently, the operability of the toothbrush 1 decreases. In addition, the rigidity of each filament 30 becomes too large, resulting in a reduced feel of each filament 30 when using the toothbrush 1. In contrast, in this embodiment, the second pressure fluctuation rate RP is 0.0 N / mm 3 The above is 10.0 × 10 -2 N / mm 3 As described below, each filament 30 bends appropriately and uniformly. Therefore, localized bending of each filament 30 can be more effectively suppressed, thereby more effectively improving the cleaning performance of the toothbrush 1. In addition, stress concentration in the neck portion 13 can be more effectively suppressed, thereby more effectively preventing a decrease in the operability of the toothbrush 1. Furthermore, the second pressure fluctuation rate RP is 0.5 × 10⁻⁶ -2 N / mm 3 The above is 8.0 x 10 -2 N / mm 3 The following is preferable. This allows each filament 30 to bend appropriately and more uniformly, thereby more effectively improving the cleaning performance of the toothbrush 1 and more effectively suppressing a decrease in the operability of the toothbrush 1.

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

[0117] [Examples] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples and can be implemented with appropriate modifications without departing from its essence.

[0118] (Examples 1-9, Comparative Examples 1-6) In accordance with the specifications shown in [Table 1], toothbrushes with at least one of the following characteristics differed as samples for Examples 1-9 and Comparative Examples 1-6: maximum thickness of the head shaft (maximum dimension in the thickness direction of the head shaft); Th, width of the first boundary (minimum dimension in the width direction of the neck); Wa, first angle: θ1, width of the tip of the connecting part; Wb, length of the connecting part; Lc, second angle; θ2, and width of the rear end of the fitting part; Wm.

[0119] [Table 1]

[0120] The thickness dimension (hair length) of the filament in the thickness direction of each sample was set to 10 mm. The cross-sectional shape of the filament of each sample was set to triangular. The second area of ​​the filament of each sample was 0.29 mm². 2 The shape of each sample filament, as viewed from the width direction, was a stepped taper shape. The first area of ​​each sample filament was 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 of ​​the third area of ​​each sample was 100 filaments / cm². 2 The soft resin material for each sample was polyurethane. The maximum width of the head portion of each sample was set to 10 mm or more and 14 mm or less. The length of the head portion of each sample was set to 20.3 mm. The third area of ​​each sample was 1.4 mm². 2 Above, 2.8mm 2 The following specifications were used: The length of the neck section of each sample was 48.3 mm. The maximum width of the neck section of each sample was 8.6 mm. The maximum thickness of the neck section of each sample was 7.1 mm. The minimum thickness of the neck section of each sample was 3.5 mm. The maximum thickness of the mating section of each sample was 2.0 mm. The length of the mating section of each sample was 18.3 mm. The hard resin material of each sample was polyacetal resin.

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

[0122] [Table 2]

[0123] The thickness dimension (hair length) of the filament in the thickness direction of each sample was set to 10 mm. The first area of ​​the filament of each sample was 0.079 mm². 2 The following specifications were used: The number of filaments in each sample was set to be between 140 and 280. The maximum width of the head section of each sample was set to be between 10 mm and 14 mm. The length of the head section of each sample was set to 20.3 mm. The third area of ​​each sample was 1.4 mm². 2 Above, 2.8mm 2 The following specifications were used: The length of the neck section of each sample was 48.3 mm. The maximum width of the neck section of each sample was 8.6 mm. The maximum thickness of the neck section of each sample was 7.1 mm. The length of the mating section of each sample was 18.3 mm.

[0124] [User experience evaluation] [Evaluation Method] In the usability evaluation, for the toothbrushes of Examples 1-9 and Comparative Examples 1-6, we evaluated the feeling of the bristles moving in conjunction with the toothbrush's operation while cleaning between teeth, while maintaining firmness at the tip of the filaments.

[0125] The toothbrushes of Examples 1-9 and Comparative Examples 1-6 were evaluated according to the following criteria. 7 points: Very much so. 6 points: Very much so. 5 points: Slightly noticeable 4 points: Neither 3 points: I don't really feel it. 2 points: I hardly feel it. 1 point: I don't feel it at all. Then, the average score from the evaluations of the 10 expert panelists was calculated, and the following five-point scale was used for evaluation. ☆(star mark): 6.5 points or more ◎ (double circle mark): 5.5 points or higher, less than 6.5 points ○ (circle mark): 4.5 points or higher, less than 5.5 points △ (triangle mark): 3.5 or higher, but less than 4.5 points. × (cross mark): Less than 3.5 points In addition, in the evaluation column for each of Examples 1-9 and Comparative Examples 1-6 in Table 1, the average score from the evaluations of the 10 expert panelists is indicated in parentheses, along with the 5-point rating scale mentioned above.

[0126] As shown in [Table 1], for Examples 1 to 9, in which the maximum thickness of the head shaft was 3.0 mm or more and 4.5 mm or less, the width of the first boundary was 3.0 mm or more and 4.5 mm or less, and the first angle was 17° or more and 28° or less, the average score from evaluations by 10 expert panelists was 3.5 points or higher, indicating good results regarding the feeling of the bristles moving in conjunction with the operation of the toothbrush while the tip of the filament has firmness when cleaning between teeth.

[0127] In contrast, for Comparative Example 1, where the maximum thickness of the head shaft was greater than 4.5 mm, the average score from the evaluation by the 10 expert panelists was less than 3.5 points, indicating that a favorable result was not obtained. As mentioned above, when the maximum thickness of the head shaft exceeds 4.5 mm, the rigidity of the head shaft becomes too large, resulting in too little deflection of the head shaft. This causes the filament to deflect too much, making it impossible to obtain a desirable feel of stiffness at the tip of the filament.

[0128] In Comparative Example 2, where the maximum thickness of the head shaft was less than 3.0 mm, satisfactory results were not obtained. As mentioned above, when 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 of the head shaft. This makes it difficult for the filament to bend, and therefore the tip of the filament does not move easily. Consequently, the desirable sensation of the bristles moving in conjunction with the operation of the toothbrush could not be obtained.

[0129] In Comparative Example 3, where the width of the first boundary was greater than 4.5 mm, satisfactory results were not obtained. As described above, when the width of the first boundary is greater than 4.5 mm, the rigidity of the neck becomes too large, resulting in too little deflection of the neck. As a result, the deflection of the filament becomes too large, and the desirable firmness of the filament tip cannot be obtained.

[0130] In Comparative Example 4, where the width of the first boundary was less than 3.0 mm, satisfactory results were not obtained. As described above, when the width of the first boundary is less than 3.0 mm, the rigidity of the neck becomes too small, resulting in excessive bending of the neck. This makes it difficult for the filament to bend, and therefore the tip of the filament becomes difficult to move. Consequently, the desirable sensation of the bristles moving in conjunction with the operation of the toothbrush could not be obtained.

[0131] In Comparative Example 5, where the first angle was less than 17°, satisfactory results were not obtained. As described above, when the first angle is less than 17°, the width of the neck and connection becomes too wide, resulting in excessive rigidity of the neck and connection. This reduces the deflection of the neck and connection too much. Consequently, the deflection of the filament becomes too large, and the desired firmness of the filament tip cannot be obtained.

[0132] In Comparative Example 6, where the first angle was greater than 28°, satisfactory results were not obtained. As described above, when the first angle is greater than 28°, the width of the neck and connection becomes too narrow, resulting in a decrease in the rigidity of the neck and connection. This causes the neck and connection to flex too much, making it difficult for the filament to flex. Consequently, the tip of the filament becomes difficult to move, and the desirable sensation of the bristles moving in conjunction with the operation of the toothbrush could not be obtained.

[0133] Compared to the configuration of Example 1, Example 3, in which the first angle is greater than 20°, yielded better results than Example 1. In Example 3, the neck and connecting parts are more flexible than in Example 1, thus reducing the stress applied to the filament. Therefore, the deflection of the filament can be suitably reduced, resulting in a more preferable feel of stiffness at the tip of the filament.

[0134] Compared to the configuration of Example 2, Example 4, in which the first angle is less than 26°, yielded better results than Example 2. In Example 4, the neck and connecting parts are less prone to bending than in Example 2, allowing for a more favorable increase in the stress applied to the filament. This suppresses localized bending of a portion of the filament while allowing for a favorable increase in the filament's bending. Therefore, the tip of the filament moves more favorably, resulting in a more favorable feel where the bristles move in conjunction with the operation of the toothbrush.

[0135] Compared to the configuration of Example 3, Example 5, where the second angle is greater than 10°, yielded better results than Example 3. In Example 5, the head shaft is more easily flexible than in Example 3, allowing for a more favorable reduction in stress applied to the filament. Therefore, the filament's flexing can be more favorably reduced, resulting in a more favorable feel of stiffness at the tip of the filament. Compared to the configuration of Example 5, Example 7, where the second angle is greater than 12°, yielded better results than Example 5 for similar reasons.

[0136] Compared to the configuration of Example 4, Example 6, in which the second angle is less than 18°, yielded better results than Example 6. In Example 6, the head shaft is less prone to bending than in Example 4, allowing for a more favorable increase in the stress applied to the filament. This allows for a more favorable increase in filament bending while more favorably suppressing localized bending of a portion of the filament. Therefore, the bristles move more favorably in conjunction with the operation of the toothbrush, resulting in a more favorable feeling of the filament tip moving. Compared to the configuration of Example 6, Example 8, in which the second angle is less than 16°, yielded better results than Example 6 for similar reasons.

[0137] Compared to the configurations of Examples 7 and 8, Example 9, in which the width of the tip of the connecting part is 8 mm or more and 10 mm or less, yielded better results than Examples 7 and 8. In Example 9, the head shaft is more easily flexible than in Examples 7 and 8, so the localized bending of a part of the filament can be more effectively suppressed. Therefore, it is possible to obtain a more preferable feel of the stiffness of the filament tip while more effectively obtaining the feeling that the bristles are moving in conjunction with the operation of the toothbrush.

[0138] [First deflection test] [Evaluation Method] The first bending test was performed on the toothbrushes of Example 9 and Comparative Examples 7-8 based on the test method of the first bending test described above. The results of the first bending test are shown in Table 2.

[0139] Figure 17 shows the first reaction force fluctuation rate in the first deflection test. As shown in Figure 17, in the range where the movement distance of the pressurizing member is 3.0 mm or less, the amount of fluctuation in the first reaction force fluctuation rate of Example 9 is smaller than the amount of fluctuation in the first reaction force fluctuation rate of Comparative Examples 7 to 8. This means that, compared to the toothbrushes of Comparative Examples 7 to 8, in the toothbrush of Example 9, the amount of deflection of the part of the toothbrush from the filament to the neck and the first reaction force are nearly directly proportional. This is because, as described above, in Example 9, when a force directed toward the other side in the thickness direction is applied to the filament, the part from the filament to the neck can bend uniformly in conjunction, thus suppressing localized large deflections in parts of the filament, head shaft, and neck. Therefore, in Example 9, when using the toothbrush, it is easier to penetrate each filament deep into the interdental spaces, thereby suitably improving the cleaning performance of the toothbrush and suitably suppressing a decrease in the operability of the toothbrush 1.

[0140] In contrast, in Comparative Example 7, where the first angle is less than 17°, the width of the neck and connection becomes too wide, as described above, resulting in excessive rigidity of the neck and connection. This causes stress to concentrate in the filament, leading to excessive filament deflection. Consequently, the difference between the first maximum value and the first minimum value becomes greater than 0.6 N / mm. This makes the filament more prone to localized deflection, reducing the cleaning performance of toothbrush 1.

[0141] Furthermore, in Comparative Example 8, where the maximum thickness of the head shaft is greater than 4.5 mm, the first angle is less than 17°, and the width of the first boundary is wider than 4.5 mm, the rigidity of the head shaft and neck becomes too large, as described above. Therefore, similar to Comparative Example 7, the deflection of the filament becomes too large. As shown in Figure 17, the first reaction force fluctuation rate of Comparative Example 8 increases in the range of the first travel distance from 0.5 mm to 1.0 mm. This indicates that the filament buckled due to a rapid increase in the deflection of the filament in the range of the first travel distance from 0.5 mm to 1.0 mm. Therefore, as shown in Table 2, the difference between the first maximum value RF1max and the first minimum value RF1min becomes greater than 0.6 N / mm, and the first average value becomes greater than 1.0 N / mm. As a result, the filament is prone to localized deflection, and the cleaning performance of toothbrush 1 decreases.

[0142] Furthermore, in Comparative Examples 7 and 8, where through holes are provided in the mating portion, the rigidity of the mating portion tends to be lower, making it prone to localized deflection. Consequently, the fluctuation amount of the first reaction force fluctuation rate tends to be larger.

[0143] Furthermore, in comparative examples 7 and 8, where the neck portion has a curved shape, stress tends to concentrate in the curved portion as described above, making it prone to localized and significant deflection. Consequently, the fluctuation amount of the first reaction force fluctuation rate tends to be large.

[0144] Furthermore, in Comparative Examples 7 and 8, where the hard resin material is polypropylene resin, the rigidity of the neck tends to be low, making the neck prone to localized bending. Consequently, the fluctuation amount of the first reaction force fluctuation rate tends to be large.

[0145] Furthermore, in Comparative Example 8, where the filament's side view shape is rectangular, the filament is less likely to bend uniformly and is more prone to buckling. Therefore, the filament is more likely to bend locally. Consequently, the fluctuation amount of the first reaction force fluctuation rate tends to be large.

[0146] [Second deflection test] [Evaluation Method] The second bending test was performed on the toothbrushes of Example 9 and Comparative Examples 7-8, based on the test method for the second bending test described above. The results of the second bending test are shown in Table 2.

[0147] Figure 18 shows the second pressure fluctuation rate in the second deflection test. As shown in Figure 18, in the range where the movement distance of the pressurizing member is 1.0 mm or less, the amount of fluctuation in the second pressure fluctuation rate of Example 9 is smaller than the amount of fluctuation in the second pressure fluctuation rate of Comparative Example 8. This means that, compared to the toothbrush of Comparative Example 8, the relationship between the amount of filament deflection and the second pressure is close to a direct proportional relationship in the toothbrush of Example 9. This is because, as mentioned above, in Example 9, when a force is applied to the filament in the other direction in the thickness direction, the filament can bend uniformly, thus suppressing localized large bending of a part of the filament. Therefore, in Example 9, when using the toothbrush, it is easier to penetrate each filament deep into the interdental spaces, thus more effectively improving the cleaning performance of the toothbrush. In addition, since stress concentration in the neck can be effectively suppressed, the decrease in the operability of the toothbrush can be more effectively suppressed.

[0148] In contrast, the number of filaments per unit area for the third area is 80 filaments / cm². 2 For Comparative Example 8, which has a lower value than the above, the stress applied to the filament becomes too large. As shown in Figure 18, for Comparative Example 8, the second pressure fluctuation rate is 10.0 × 10 -2 N / mm 3 In the range of 0.0 mm to 0.2 mm, where the second displacement distance is larger, each filament has a high repulsive force, making it difficult for the tip of each filament to move. Also, in the range of 0.2 mm to 0.4 mm, where stress tends to concentrate in the neck, each filament buckles, causing a rapid decrease in the second pressure fluctuation rate to 0.0 N / mm 3It becomes even smaller. Also, in the range of 0.2 mm to 0.4 mm for the second travel distance, each filament bends locally, so the tip of each filament does not become rigid. In addition, in Comparative Example 8, because the number of filaments is small, the stress applied to the filaments becomes too large. Therefore, the filaments are prone to buckling. As a result, as shown in Table 2, the fluctuation of the first reaction force fluctuation rate tends to become large, making it difficult to improve the user experience.

[0149] Furthermore, in Comparative Example 8, where the filament cross-section is circular, the shape is symmetrical in the longitudinal axis direction and width direction when viewed from the thickness direction. Therefore, when a force is applied to the filament facing the back side, the direction in which each filament bends varies, making it easy for the force applied to each filament to vary. As a result, the amount of bending of filaments subjected to large forces becomes too large, making it easy for the second pressure fluctuation rate to fluctuate in the range where the movement distance of the pressurizing member is 1.0 mm or less.

[0150] Although preferred embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to these examples. If the deflection of each part, such as the filament, head, and neck, can be uniform without bias, a substantially linear deflection behavior can be obtained from the filament to the neck, and those skilled in the art can obtain the above-mentioned effects based on this indicator. Furthermore, the various shapes and combinations of the constituent members shown in the above-described examples are merely examples, and can be modified in various ways based on design requirements, etc., without departing from the spirit of the present invention.

[0151] As described above, in the first deflection test, the first reaction force, which is the reaction force of the toothbrush, is measured by deflecting the neck portion from each filament of the toothbrush. Therefore, the results of the second deflection test, which measures the reaction force of the filament 30, affect the results of the first deflection test. In the above description, a configuration in which the filament and neck portion deflect uniformly in conjunction is illustrated by setting the first and second pressure fluctuation rates within a suitable range by devising the number of filaments and the cross-sectional shape of the filaments. However, the present invention is not limited to such examples. For example, by combining multiple solutions such as the first angle, the maximum thickness of the head shaft portion, the shape of the neck portion, the material of the hard resin, and the side view shape of the filament, it is possible to achieve uniform deflection in conjunction from the filament to the neck portion and obtain substantially linear deflection behavior from the filament to the neck portion. Therefore, by analyzing the results of the first and second deflection tests, a person skilled in the art can grasp the problem characteristics of the toothbrush being analyzed, efficiently arrive at a solution to the problem, and confirm the effectiveness of the solution.

[0152] The configuration of the fitting portion and the fitting hole is not limited to the configuration of this embodiment. For example, the fitting portion may have a projection that protrudes in the width direction, and the fitting hole may have a recess that is recessed in the width direction and has a recess that engages with the projection.

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

[0154] The toothbrush according to the present invention can be used suitably as a one-piece molded toothbrush because it can improve interdental cleaning performance while suppressing a decrease in the operability of the toothbrush. [Explanation of Symbols]

[0155] 1...toothbrush, 6...head shaft, 10...handle body, 13...neck, 13d...neck edge, 14...connecting part, 14a...connecting tip, 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 predetermined distance, dZ2...second predetermined distance, F1...first reaction force, J...center axis, L1...first distance, L2...distance between connecting tip and first neck, L3...distance between connecting tip and second neck, L4...distance between connecting tip and third neck, P...second pressure, P1...first neck P2...Second neck section, P3...Third neck section, RF1...First reaction force fluctuation rate, RF1ave...First average value, RF1max...First maximum value, RF1min...First minimum value, RP...Second pressure fluctuation rate, S1...First area (area of ​​the cross-section perpendicular to the thickness direction of the first filament section), S2...Second area (area of ​​the cross-section perpendicular to the said thickness direction of the second filament section), T1...Thickness of the first neck section (dimension in the thickness direction of the first neck section), T2...Thickness of the second neck section (dimension in the thickness direction of the second neck section), T3...Thickness of the third neck section (dimension in the thickness direction of the third neck section), Th...Maximum thickness of the head shaft section (maximum dimension in the thickness direction of the head shaft section), V1...First imaginary line, V2...Second imaginary line, Wa...Width of the first boundary section (minimum dimension in the width direction of the neck section), W1...Width of the first neck section (dimension in the width direction of the first neck section), W2…Width of the second neck section (dimension in the width direction of the second neck section), W3…Width of the third neck section (dimension in the width direction of the third neck section)

Claims

1. A handle body made of hard resin, extending in the direction of the long axis, A brush portion formed of soft resin and positioned on one side of the handle body in the direction of the long axis, Equipped with, The brush portion comprises a brush base portion and a plurality of filaments integrally molded with the brush base portion. Each of the multiple filaments protrudes from the brush base toward one side in the thickness direction intersecting the long axis direction, The handle body has a neck portion extending in the longitudinal direction, a connecting portion protruding from the neck portion to one side in the longitudinal direction, a fitting portion protruding from the connecting portion to one side in the longitudinal direction, a connecting edge portion which is a part of the connecting portion, and a neck edge portion which is a part of the neck portion. The aforementioned connecting portion, fitting portion, and brush base portion constitute the head shaft portion. The connecting edge is one end of the connecting portion in the longitudinal direction and one end in the width direction that intersects both the longitudinal direction and the thickness direction. The neck edge is the end on one side in the width direction of the portion of the neck that has the smallest width dimension. 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 in the width direction of the neck portion is 3.0 mm or more and 4.5 mm or less. Viewed from the thickness direction, the angle formed by 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 in the direction of the long axis, is 17° or more and 28° or less. If the width of the tip of the connecting portion is Wb and the minimum width of the neck portion is Wa, 2.0 ≤ Wb / Wa ≤ 2.8 Satisfying the relationship, The neck portion has a first neck portion, a second neck portion, and a third neck portion. The distance in the longitudinal direction between the connecting tip, which is one end of the connecting portion in the longitudinal direction, and the other end of the neck portion in the longitudinal direction is defined as the first distance. In the longitudinal axis direction, the ratio of the distance between the connecting tip and the first neck portion to the first distance is 20%. In the longitudinal axis direction, the ratio of the distance between the connecting tip and the second neck portion to the first distance is 80%. In the longitudinal axis direction, the ratio of the distance between the connecting tip and the third neck portion to the first distance is 100%. If the width dimension of the first neck portion is W1, the thickness dimension of the first neck portion is T1, the width dimension of the second neck portion is W2, the thickness dimension of the second neck portion is T2, the width dimension of the third neck portion is W3, and the thickness dimension of the third neck portion is T3, 130mm 4 ≤ W1 × T1 3 ≤ 400mm 4, 450mm 4 ≤ W2 × T2 3 ≤ 1200mm 4, 2000mm 4 ≤ W3 × T3 3 ≤ 5000mm 4, A toothbrush that satisfies the relationship.

2. A handle body made of hard resin and extending in the direction of the long axis, A brush portion formed of soft resin and positioned on one side of the handle body in the direction of the long axis, Equipped with, The brush portion comprises a brush base portion and a plurality of filaments integrally molded with the brush base portion. Each of the multiple filaments protrudes from the brush base toward one side in the thickness direction intersecting the long axis direction, The handle body has a neck portion extending in the longitudinal direction, a connecting portion protruding from the neck portion to one side in the longitudinal direction, a fitting portion protruding from the connecting portion to one side in the longitudinal direction, a connecting edge portion which is a part of the connecting portion, and a neck edge portion which is a part of the neck portion. The aforementioned connecting portion, fitting portion, and brush base portion constitute the head shaft portion. The connecting edge is one end of the connecting portion in the longitudinal direction and one end in the width direction that intersects both the longitudinal direction and the thickness direction. The neck edge is the end on one side in the width direction of the portion of the neck that has the smallest width dimension. 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 in the width direction of the neck portion is 3.0 mm or more and 4.5 mm or less. Viewed from the thickness direction, the angle formed by 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 in the direction of the long axis, is 17° or more and 28° or less. When the other end of the neck portion in the longitudinal direction is fixed, and the pressure member is brought into contact with the multiple filaments from one side in the thickness direction, and the pressure member is moved to the other side in the thickness direction, The reaction force that the pressurizing member receives from the plurality of filaments is defined as the first reaction force. The first reaction force fluctuation rate is defined as the value obtained by dividing the amount of change in the first reaction force when the position of the pressurizing member in the thickness direction changes by a first predetermined distance, The first maximum value, which is the maximum value of the first reaction force fluctuation rate within a range of 3.0 mm or less for the movement distance of the pressurizing member, is defined as RF1max. The first minimum value, which is the minimum value of the first reaction force fluctuation rate within the range of the movement distance of the pressurizing member being 3.0 mm or less, is defined as RF1min. If the first predetermined distance is 0.1 mm, RF1max-RF1min≦0.6N / mm A toothbrush that satisfies the relationship.

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

4. Each of the plurality of filaments has a first filament portion and a second filament portion, Viewed from the width direction, each of the plurality of filaments has a progressively larger decrease in the length along the long axis relative to a unit length in the thickness direction as it moves from the brush base toward one side in the thickness direction. In the thickness direction, the ratio of the distance between one end of the filament in the thickness direction and the first filament portion to the dimensions of the filament is 15%. The second filament portion is the part that connects to the brush base portion, The toothbrush according to claim 1 or 2, wherein the ratio of the area of ​​the cross-section of the first filament portion perpendicular to the thickness direction to the area of ​​the cross-section of the second filament portion perpendicular to the thickness direction is 20% or more and 30% or less.

5. The toothbrush according to claim 4, wherein the ratio of the area obtained by adding the area of ​​the cross-sectional area of ​​each of the multiple filaments perpendicular to the thickness direction to the area of ​​the surface of the brush base facing one side in the thickness direction is 25% or more and 35% or less.

6. The toothbrush according to claim 2, wherein the first average value RF1ave, which is the average value of the first reaction force fluctuation rate within a range of 3.0 mm or less for the travel distance of the pressurizing member, is 0.5 N / mm or more and 1.0 N / mm or less.

7. When the brush base is supported from the other side in the thickness direction, and the pressure member is brought into contact with the plurality of filaments from one side in the thickness direction, and the pressure member is moved to the other side in the thickness direction, The pressure received by the pressurizing member from the plurality of filaments is defined as the second pressure. Let RP be the second pressure fluctuation rate, which is the value obtained by dividing the amount of change in the second pressure when the position of the pressurizing member in the thickness direction changes by the second predetermined distance. If the second predetermined distance is 0.1 mm, Within a range of 1.0 mm or less in the movement distance of the pressurizing member, the second pressure fluctuation rate RP is 0.0 N / mm ３ The above is 10.0 x 10 －２ N / mm ３ The toothbrush according to claim 1 or 2, which is as follows:

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