Toothbrush

Abstract

A toothbrush according to the present invention is provided with a handle body formed from a hard resin and a brush molded body formed from a soft resin. The handle body is provided with an insertion part protruding towards one side of the long axis direction. The brush molded body has a head base part and a plurality of filaments integrally molded with the head base part. The head base portion has an insertion hole into which the insertion portion is fitted. The plurality of filaments protrude toward the front side. The brush molded body has a width of 14 mm or more. If the total cross-sectional area obtained by adding the cross-sectional areas of the base parts of all the filaments is a first cross-sectional area, and the total cross-sectional area obtained by adding the cross-sectional areas of the base parts of the filaments disposed so as to overlap the insertion holes is a second cross-sectional area, the first cross-sectional area is 30 mm2 or more, and the ratio of the second cross-sectional area to the first cross-sectional area is 40%-90%.

Description

Technical Field

[0001] The invention relates to a toothbrush. This application claims priority based on Japanese Patent Application No. 2022-209301 filed in Japan on December 27, 2022, and the contents are incorporated herein by reference. Background Art

[0002] An integrally molded toothbrush manufactured using only an injection molding machine has been proposed (e.g., Patent Document 1). Since the integrally molded toothbrush integrally molds the filaments and the head base, it does not require a filament material supply and a hair transplanting machine, and can reduce manufacturing costs compared to hair transplanting toothbrushes.

[0003] A one-piece toothbrush is proposed in which a brush molded body having filaments and insertion holes and a handle body having an insertion portion at one end are molded separately and fitted together (for example, Patent Document 2). In the toothbrush described in Patent Document 2, since the brush molded body can be replaced, it is expected that only the brush molded body can be discarded and the handle body can be reused, thus saving resources. Prior Art Literature Patent Literature

[0004] Patent Document 1: Japanese Utility Model Publication No. 61-207233 Patent Document 2: Chinese Patent Application Publication No. 107041792 Summary of the invention Technical problem to be solved by the invention

[0005] In recent years, users who are not good at brushing their teeth or users who want to brush their teeth efficiently have been accepting wide-head type toothbrushes having a wide head width. In an integrally molded toothbrush, if the width of the brush molding body constituting the head is widened, the area where the filaments are arranged increases, and the number of filaments increases. Therefore, when molding such a brush molding body, the fluidity of the resin in the mold is likely to decrease, and the demolding resistance when the brush molding body is demolded from the mold is likely to increase. Therefore, the brush molding body is prone to poor molding.

[0006] The present invention has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a toothbrush capable of suppressing the occurrence of molding defects in the brush molded body even when a wide brush molded body molded by integral molding is used. Technical solutions for solving technical problems

[0007] The present invention includes the following structures. [1] A toothbrush comprising: a handle body formed of a hard resin and extending in a longitudinal direction; and a brush molding body formed of a soft resin and arranged on one side of the handle body in the longitudinal direction, the handle body having an insertion portion protruding to one side in the longitudinal direction, the brush molding body having a head base portion and a plurality of filaments integrally formed with the head base portion, the head base portion having an insertion hole for the insertion portion to be inserted and engaged, the plurality of filaments protruding from the head base portion toward one side in a thickness direction intersecting the longitudinal direction, and the brush The dimension of the molded body in the width direction orthogonal to the long axis direction and the thickness direction is greater than 14 mm. If the total cross-sectional area obtained by adding the cross-sectional areas of the sections of the portions of all the filaments connected to the head base portion orthogonal to the thickness direction is set as the first cross-sectional area, and the total cross-sectional area obtained by adding the cross-sectional areas of the sections of the portions of the filaments in the plurality of filaments overlapped with the insertion hole and connected to the head base portion orthogonal to the thickness direction is set as the second cross-sectional area, then the first cross-sectional area is 30 mm 2 In the above, the ratio of the second cross-sectional area to the first cross-sectional area is 40% or more and 90% or less. [2] According to the toothbrush described in [1], if the area of ​​the portion of the brush molding located on the side closer to the longitudinal direction than the end of the other side of the filament arranged on the other side closest to the longitudinal direction as observed in the thickness direction is set as the first head area, and the area of ​​the portion of the insertion hole located on the side closer to the longitudinal direction than the end of the other side of the filament arranged on the other side closest to the longitudinal direction as observed in the thickness direction is set as the insertion hole area, then the first head area is 250 mm 2 In the above, the ratio of the insertion hole area to the first head area is 30% or more and 70% or less. [3] According to the toothbrush described in [2], if the area of ​​the brush mold observed along the thickness direction is set as the head area, and the area of ​​the portion of the brush mold located on the other side of the long axis direction than the filament arranged on the other side closest to the long axis direction is set as the second head area, then the ratio of the second head area to the head area is greater than 2% and less than 10%. [4] According to the toothbrush described in [3], the second head area is 5mm 2 Above and 30mm 2 the following. [5] According to any one of [2] to [4], the brush forming body comprises: a first brush portion, and a second brush portion located on the other side of the first brush portion in the long axis direction, the plurality of filaments comprising a plurality of first filaments arranged in the first brush portion, and a plurality of second filaments arranged in the second brush portion, and when viewed along the thickness direction, the portion of the first filament connected to the head base portion and the portion of the second filament connected to the head base portion are respectively polygonal in shape, and the number of corners of the second filament is greater than the number of corners of the first filament. [6] According to the toothbrush described in [2], the brush forming body comprises: a first brush portion, and a second brush portion located on the other side of the first brush portion in the long axis direction, the plurality of filaments include a plurality of first filaments arranged in the first brush portion, and a plurality of second filaments arranged in the second brush portion, and when viewed along the thickness direction, the portion of the first filament connected to the head base portion is polygonal in shape, and at least a portion of the outer periphery of the portion of the second filament connected to the head base portion is arc-shaped. [7] In the toothbrush described in [5] or [6], if the area of ​​the first brush portion observed in the thickness direction is defined as a third head area, a ratio of the third head area to the first head area is greater than or equal to 15% and less than or equal to 35%. [8] The toothbrush according to any one of [1] to [7], wherein the shortest distance in the width direction between the outer edge of the head base portion and the plurality of filaments is greater than or equal to 0.3 mm and less than or equal to 1.5 mm when viewed in the thickness direction. [9] The toothbrush according to any one of [1] to [8], wherein the interval between the filaments adjacent to each other in the longitudinal direction is equal to or greater than the interval between the filaments adjacent to each other in the width direction.

[10] According to any one of [1] to [9], the handle body comprises: a handle portion extending along the long axis direction, and a neck extending from the handle portion to one side in the long axis direction, and the ratio of the minimum dimension of the neck in the width direction to the maximum dimension of the head base portion in the width direction is greater than 20% and less than 35%.

[11] According to the toothbrush described in any one of [1] to

[10] , if the dimension of the thickness direction of the head base portion is set as the head thickness, and the dimension of the thickness direction of the portion of the head base portion that is closer to the side in the thickness direction than the insertion hole is set as the first head thickness, then the first head thickness is greater than 1.0 mm and less than 2.0 mm, and the ratio of the first head thickness to the head thickness is greater than 20% and less than 35%. Effects of the Invention

[0008] The present invention can provide a toothbrush capable of suppressing the occurrence of molding defects in the brush molded body even when a wide brush molded body molded by integral molding is used. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a front view which shows the toothbrush of 1st Embodiment. Figure 2 It is a side view which shows the toothbrush of 1st Embodiment. Figure 3 It is a front view showing the handle body of the first embodiment. Figure 4 It is a front view which shows the insertion part of 1st Embodiment. Figure 5 It is a side view which shows the insertion part of 1st Embodiment. Figure 6 It is a front view which shows the brush molding body of 1st Embodiment. Figure 7 is a cross-sectional view showing a brush molding body according to a first embodiment, Figure 6 AA section view in. Figure 8 This is a second front view showing the brush molding according to the first embodiment. Fig. 9 It is a third front view which shows the brush molding body of 1st Embodiment. Fig.10 This is a first cross-sectional view showing a molding step of the brush molding body according to the first embodiment. Fig.11 This is a second cross-sectional view showing the molding step of the brush molding body according to the first embodiment. Fig.12 This is a third cross-sectional view showing the molding step of the brush molding body according to the first embodiment. Fig.13 It is a front view which shows the brush molding body of 2nd Embodiment. Fig.14 It is a front view which shows the brush molding body of 3rd Embodiment. DETAILED DESCRIPTION

[0010] Hereinafter, an example of the toothbrush of the present invention will be described based on the drawings. It should be noted that the dimensions and the like in the drawings shown in the following description are merely examples, and the present invention is not necessarily limited thereto, and can be implemented with appropriate changes within the scope of the gist thereof.

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

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

[0013] <First embodiment> Figure 1 It is a front view of the toothbrush 1 which concerns on this embodiment. Figure 2 It is a side view of the toothbrush 1. The toothbrush 1 includes a handle body 10 and a brush molding body 20. The handle body 10 and the brush molding body 20 are different components. The handle body 10 and the brush molding body 20 are respectively made of resin. The handle body 10 is rod-shaped and extends along the long axis direction. The brush molding body 20 is arranged on the front end side of the handle body 10, that is, one side (+X side) in the long axis direction. In the present embodiment, the brush molding body 20 is freely installed on the handle body 10. It should be noted that the brush molding body 20 can also be molded by insert molding the handle body 10 and the embedded component. In this case, the brush molding body 20 and the handle body 10 can also be integrated.

[0014] Figure 31 is a front view showing the handle body 10 of the present embodiment. The handle body 10 comprises: a handle body 11 which is in the shape of a rod extending in the long axis direction; and an insertion portion 15 which protrudes from the front end of the handle body 11 to the front end side, i.e., one side (+X side) in the long axis direction. In the toothbrush 1 of the present embodiment, the brush forming body 20 is mounted on the handle body 10 by fitting the insertion portion 15 into the insertion hole 27 of the brush forming body 20 described later. It should be noted that the length of the handle body 10 can be set to, for example, not less than 100 mm and not more than 200 mm.

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

[0016] The front view shape of the handle body 11 of this embodiment changes in a curved manner as follows: the width gradually narrows from the front end side toward the rear end side and reaches the first boundary portion 11a, and then extends with a constant width after reaching the first boundary portion 11a, and then the width gradually widens and then narrows. The front view shape of the rear end portion of the handle body 11 is roughly semicircular.

[0017] like Figure 2 As shown, the side view shape of the handle body 11 changes in a curve as follows: after extending from the front end side toward the rear end side with a constant thickness, the thickness gradually becomes thicker and reaches the second boundary portion 11b, and then changes in a curve in a manner in which the thickness gradually becomes thinner, and then extends with a substantially constant thickness, and then the thickness gradually becomes thinner. The side view shape of the rear end portion of the handle body 11 is substantially semicircular.

[0018] It should be noted that in the present invention, the shape of the handle body 11 is not limited to the shape of the present embodiment, and can be appropriately set in consideration of strength, operability, aesthetics, etc. The size of the handle body 11 is not particularly limited and can be appropriately set. The handle body 11 includes a handle portion 12, a neck portion 13, and a connecting portion 14.

[0019] The handle portion 12 is a portion of the handle body portion 11 that is closer to the rear end than the second boundary portion 11b. The handle portion 12 is rod-shaped and extends in the longitudinal direction. Figure 3As shown in the figure, a finger contact portion 17 is provided at the front end side of the surface of the handle portion 12 facing the front side. The finger contact portion 17 is molded from a soft resin. As the soft resin forming the finger contact portion 17, various elastomers such as polyurethane and styrene can be used. When the user uses the toothbrush 1, the user can improve the gripping performance of the toothbrush 1 by holding the handle portion 12 while bringing the finger into contact with the finger contact portion 17.

[0020] The neck 13 is a portion between the first boundary portion 11a and the second boundary portion 11b of the handle body 11. The neck 13 is rod-shaped and extends from the handle 12 toward the front end, that is, toward one side (+X side) in the long axis direction. The width of the end portion of the front end side of the neck 13 is the minimum width W3 of the neck 13, that is, the minimum dimension of the neck 13 in the width direction.

[0021] The connection portion 14 is a portion of the handle body 11 that is closer to the front end than the first boundary portion 11a. The connection portion 14 connects the neck portion 13 and the insertion portion 15. Figure 3 As shown in FIG. 1 , the connection portion 14 has a first facing surface 14 a. The first facing surface 14 a is a surface of the outer side surface of the connection portion 14 that faces the front end side.

[0022] like Figure 2 As shown in FIG. 1 , the insertion portion 15 is located inside the brush forming body 20 when the brush forming body 20 is installed in the handle body 10. Figure 3 As shown, the insertion portion 15 protrudes from the end portion on the distal side of the connection portion 14 toward the distal side, that is, toward one side (+X side) in the long-axis direction.

[0023] Figure 4 It is a front view which shows the insertion part 15 of this embodiment. Figure 5 It is a side view showing the insertion portion 15 according to the present embodiment. like Figure 4 As shown, the front view shape of the insertion portion 15 of this embodiment changes in a curved manner as follows: after extending from the rear end side toward the front end side with a constant width, at a pair of recessed portions 15a and recessed portions 15b, the width becomes wider after narrowing, and then becomes narrower. The width of the insertion portion 15 is narrower than the width of the first opposing surface 14a.

[0024] A pair of recessed portions 15a and 15b are respectively arranged at a position closer to the front end side than the center of the long axis direction of the insertion portion 15. In the long axis direction, the pair of recessed portions 15a and 15b are arranged at the same position as each other. One recessed portion 15a is recessed from the other side (-Y side) facing the width direction of the insertion portion 15 facing the width direction on the one side (+Y side). The other recessed portion 15b is recessed from the other side of the insertion portion 15 facing the width direction on the one side facing the width direction. The pair of recessed portions 15a and 15b are respectively approximately semicircular in front view.

[0025] like Figure 5 As shown, the side view shape of the insertion portion 15 changes in a curved manner in the following manner: after extending from the rear end side toward the front end side with a constant thickness, the thickness gradually becomes thinner. In more detail, the surface facing the front side of the outer side surface of the insertion portion 15 is a plane extending in a direction orthogonal to the thickness direction. After the surface facing the back side of the outer side surface of the insertion portion 15 extends linearly from the rear end side toward the front end side, it is located on the front side as it extends from the rear end side to the front end side. The dimension of the insertion portion 15 in the thickness direction is smaller than the dimension of the first opposing surface 14a in the thickness direction.

[0026] Figure 6 It is a front view which shows the brush forming body 20 of this embodiment. Figure 7 is a cross-sectional view showing a brush molding body 20 according to the present embodiment. Figure 6 AA section view in. Figure 8 This is a second front view showing the brush molded body according to this embodiment. Fig. 9 It is a third front view showing the brush molded body of this embodiment. In this embodiment, the brush molding 20 is molded from a soft resin. Figure 6 and Figure 7 As shown, the brush molding body 20 includes a head base portion 21 and a plurality of filaments 28 integrally molded with the head base portion 21 .

[0027] like Figure 6 As shown, the front view shape of the head base part 21 of this embodiment changes as follows: after changing in a curve in a manner that the width gradually widens from the rear end side to the front end side, it extends linearly in a manner that the width is constant, and then the width becomes narrower. The front view shape of the front end of the head base part 21 is a roughly semicircular shape protruding toward the front end side. Figure 7 As shown, the side view shape of the head base portion 21 of the present embodiment changes in a curved manner as follows: after extending from the rear end side toward the front end side with a constant thickness, the thickness gradually becomes thinner. In more detail, the surface facing the front side among the outer side surfaces of the head base portion 21, that is, the upper surface 21a, is a plane extending in a direction orthogonal to the thickness direction. After the surface facing the back side (-Z side) among the outer side surfaces of the head base portion 21 extends linearly from the rear end side toward the front end side, it is located on the front side as it extends from the rear end side to the front end side.

[0028] The head base portion 21 has a first portion 25a, a second portion 25b, and a third portion 25c. The first portion 25a is a portion of the head base portion 21 that is closer to the front side than the insertion hole 27. The first portion 25a is plate-shaped and extends in a direction orthogonal to the thickness direction. The second portion 25b is a portion of the head base portion 21 that is closer to the back side than the insertion hole 27. The portion on the front end side of the second portion 25b is plate-shaped and is located on the back side as it extends from the front end side to the rear end side; the portion on the rear end side of the second portion 25b is plate-shaped and extends along the long axis direction. The third portion 25c is located closer to the front end side than the insertion hole 27, and connects the end portion of the front end side of the first portion 25a to the end portion of the front end side of the second portion 25b.

[0029] The surface of the outer side surface of the head base portion 21 that faces the rear end is the second facing surface 21b. Although not shown in the figure, the second facing surface 21b is substantially rectangular when viewed along the long axis direction. Figure 1 As shown, the second facing surface 21b faces the first facing surface 14a of the handle body 10 in the long axis direction. In this embodiment, the second facing surface 21b contacts the first facing surface 14a in the long axis direction.

[0030] The head base portion 21 has an insertion hole 27 that is recessed from the second facing surface 21b toward the front end side. Figure 2 As shown in FIG. 1 , the insertion portion 15 is inserted and fitted into the insertion hole 27. Thus, the brush molding 20 is detachably mounted on the handle body 10. Figure 7 As shown, the side view shape of the insertion hole 27 changes in a curved manner as follows: after extending from the rear end side to the front end side with a constant size, the size in the thickness direction gradually decreases. In more detail, the surface facing the back side (-Z side) of the inner side surface of the insertion hole 27 is a plane extending in a direction orthogonal to the thickness direction. After the surface facing the front side (+Z side) of the inner side surface of the insertion hole 27 extends linearly from the rear end side to the front end side, it is located on the front side as it extends from the rear end side to the front end side.

[0031] like Figure 6 As shown, the front view shape of the insertion hole 27 of this embodiment changes in a curved line as follows: after extending from the rear end side toward the front end side with a constant width, the width becomes narrower at a pair of protrusions 27a and 27b, the width becomes wider, and then the width becomes narrower.

[0032] A pair of protrusions 27a and 27b are respectively arranged at a position closer to the front end side than the center of the long axis direction of the insertion hole 27. In the long axis direction, a pair of protrusions 27a and 27b are arranged at the same position with respect to each other. One protrusion 27a protrudes from the other side of the insertion hole 27 facing the width direction (-Y side) facing the width direction. Another protrusion 27b protrudes from the side facing the width direction (+Y side) of the insertion hole 27 facing the width direction. The pair of protrusions 27a and 27b are respectively roughly semicircular in front view. When the insertion part 15 is inserted into the insertion hole 27, the pair of protrusions 27a and 27b are respectively engaged with the pair of recessed parts 15a and 15b. Other structures of the head base part 21 will be described in detail later.

[0033] like Figure 6 and Figure 7 As shown in FIG. 2 , the plurality of filaments 28 protrude from the upper surface 21a of the head base portion 21 toward the front side, that is, one side (+Z side) in the thickness direction. Figure 6 As shown, on the upper surface 21a, a plurality of rows consisting of a plurality of filaments 28 arranged in the width direction are arranged at intervals from each other in the longitudinal direction. Figure 7 As shown, the side view shape of multiple filaments 28 is a tapered shape that tapers from the base to the front end. In the present embodiment, the taper angle of each filament 28 is different between the part on the back side and the part on the front side, and the taper angle of the part on the back side is greater than the taper angle of the part on the front side. It should be noted that the taper angle of each filament 28 can also be the same from the base to the front end. The shape of each filament 28, etc., will be described in detail later.

[0034] It should be noted that in the following description, Figure 6 The filament region 21d shown is a region in the upper surface 21a where a plurality of filaments 28 are provided. More specifically, the filament region 21d is an inner region of a closed curve, and connects the following ends: the end of one side of the filament 28 arranged in the width direction of each row (+Y side), the end of the front end side of each filament 28 constituting the row arranged in the front end side, the end of the other side of the filament 28 arranged in the width direction of each row (-Y side), and the end of the rear end side of each filament 28 constituting the row arranged in the rear end side. In addition, in the following description, there is a case where the portion of each filament 28 connected to the head base portion 21 is referred to as a base portion.

[0035] It should be noted that the surface of the outer side surface of the head base portion 21 provided with the filaments is not limited to the upper surface 21a, and for example, a plurality of filaments of different lengths may be provided on the surface facing the back side of the head base portion 21. In this case, the plurality of filaments can be used to clean the user's tongue, for example.

[0036] As the soft resin constituting the brush molded body 20, various elastomers can be used, but polyurethane is preferred. Polyurethane has a tendency to have a higher tensile strength than other elastomers such as styrene and polyester, so even if it is formed into a thin wall, it can ensure mechanical strength and can suppress damage when the insertion portion 15 is fitted into the insertion hole 27 and when the toothbrush 1 is used.

[0037] In addition, polyurethane has a wide range of hardness that can be selected compared with the other elastomers mentioned above. According to the thickness of the brush forming body 20, the resin hardness that takes into account its usability (for example, the bending of the front end of the brush forming body) can be selected. As the hardness of polyurethane, it is preferred that the Shore hardness is more than A90 and less than A100 or the Shore hardness is more than D40 and less than D70. In the case where the hardness of polyurethane is lower than Shore 90A, it is easy to deform when formed by thin walls, so the interlocking becomes weak, and the brush forming body 20 becomes easy to fall off when the toothbrush 1 is used. In the case where the hardness of polyurethane is higher than Shore 70D, when the back side of the head base 21 is tilted, pain may occur when the front end touches the oral tissue. By setting the hardness of polyurethane to more than Shore 90A and less than 70D, it is possible to suppress the falling off of the brush forming body 20 when the toothbrush 1 is used, and it is possible to suppress the pain when the front end of the head base 21 touches.

[0038] The polyurethane is mixed with 0.01wt% (mass %) or more and 1.0wt% (mass %) or less of saturated / unsaturated hydrocarbons of C10 or more, higher alcohols, fatty acid amides, fatty acid esters, low molecular weight polyethylene, polyethylene glycol (PEG), fatty acid metal salts, long-chain fatty acids, fatty acid glycerides, and any one or a combination of silicones to function as a lubricant or a release agent. In addition, as the polyurethane, ether polyurethane is preferably used from the viewpoint of ensuring water resistance and antibacterial properties.

[0039] Fig.10 This is a first cross-sectional view showing a molding step of the brush molding body 20 according to the present embodiment. Fig.11 This is a second cross-sectional view showing the molding process of the brush molding body 20 according to the present embodiment. Fig.12 2 is a third cross-sectional view showing the molding process of the brush molding body 20 of the present embodiment. Fig.10 As shown, in this embodiment, the mold 30 includes a first mold 31 , a second mold 32 , and a slide core 33 .

[0040] The first mold 31 is installed on the fixed side of the injection molding machine. The first mold 31 has: a first molding surface 31a, which molds the upper surface 21a of the brush molding body 20 when it is molded with the second mold 32; and a first cavity 31b, which molds a plurality of filaments 28. The first cavity 31b is composed of a plurality of holes recessed from the first molding surface 31a to the front side.

[0041] The second mold 32 is installed on the movable side of the injection molding machine. The second mold 32 can move in the thickness direction relative to the first mold 31. The second mold 32 uses the parting surface PL flush with the upper surface 21a as a joint surface to be molded with the first mold 31. The second mold 32 has: a second cavity 32a, a molding head base portion 21; a gate portion G and a contact surface 32b. The interior of the second cavity 32a is connected to the interior of the first cavity 31b. The gate portion G is connected to the end portion on the front end side of the second cavity 32a, and molten resin is introduced into the second cavity 32a and the first cavity 31b through the gate portion G. The contact surface 32b is a surface facing the rear end side. The contact surface 32b is connected to the end portion on the rear end side of the second cavity 32a.

[0042] The sliding core 33 can move toward the rear end side relative to the second mold 32. The sliding core 33 has a second molding surface 33a and a core portion 33b. The second molding surface 33a is a surface facing the front end side. The core portion 33b protrudes from the second molding surface 33a toward the front end side. The core portion 33b molds the insertion hole 27 of the head base portion 21. If the sliding core 33 is molded with the first mold 31 and the second mold 32, the back side portion of the second molding surface 33a abuts against the abutment surface 32b in the long axis direction, and the core portion 33b is arranged in the second cavity 32a. The portion of the second molding surface 33a that is closer to the front side than the abutment surface 32b molds the second opposing surface 21b of the head base portion 21. It should be noted that in the case where the handle body 10 is used as an embedded component to insert mold the brush molding body 20, the handle body 10 is used instead of the sliding core 33. In this case, the insertion portion 15 of the handle body 10 is arranged in the second cavity 32a.

[0043] When the first mold 31, the second mold 32, and the slide core 33 are closed, if molten resin is introduced into the mold 30 from the gate portion G, the resin flows toward the back side in the second cavity 32a and flows in the thickness direction in the first cavity 31b. Thus, the resin is filled in the first cavity 31b and the second cavity 32a, and the brush molded body 20 is molded.

[0044] If the brush forming body 20 is formed, Fig.11As shown, the second mold 32 is moved to the back side, and the first mold 31 is demolded from the plurality of filaments 28 respectively. At this time, the brush forming body 20 is held by the core 33b. Therefore, the demolding resistance generated by the friction between the plurality of filaments 28 and the first mold 31 can suppress the brush forming body 20 from moving to the front side. It should be noted that when the first mold 31 is demolded from the plurality of filaments 28, if the direction in which each filament 28 extends is inclined relative to the thickness direction, the demolding resistance between each filament 28 and the first mold 31 becomes larger, and the demolding property of the first mold 31 is reduced. When the first mold 31 is demolded, since the temperature of each filament 28 is high and it is in a soft state, if the demolding property of the first mold 31 is reduced, the filaments 28 are prone to tearing and cracking, and the shape and size of the filaments 28 are difficult to meet the desired specifications. In the following description, in the molding process of the brush molded body 20, there may be a case where tears and cracks occur in the brush molded body 20 including the filaments 28, and the shape of the brush molded body 20 does not meet the desired specifications, which is simply referred to as molding failure.

[0045] If the first mold 31 is demoulded from the plurality of filaments 28, Fig.12 As shown, the slide core 33 is moved to the rear end side to release the slide core 33 from the head base portion 21. Thereafter, when the brush molding body 20 is taken out from the second mold 32 to the front side, the molding process of the brush molding body 20 is completed.

[0046] like Figure 6 As shown, in the present embodiment, the width Wb of the brush molding 20, i.e., the dimension in the width direction, is 14 mm or more. Thus, since the head 5 of the toothbrush 1 can be set to a wide width, i.e., a wide head, the user can efficiently clean the tooth surface with the toothbrush 1. It should be noted that, in the present embodiment, the width Wb of the brush molding 20 is the maximum width of the brush molding 20. In addition, if the total cross-sectional area obtained by adding the cross-sectional areas of the cross sections of the bases of all the filaments 28, i.e., the parts connected to the head base 21, which are perpendicular to the thickness direction, is set as the first cross-sectional area Sc1, then the first cross-sectional area Sc1 is 30 mm. 2 As a result, the total cross-sectional area of ​​the plurality of filaments 28 included in the toothbrush 1 can be increased, so that the user can efficiently clean the tooth surface using the toothbrush 1 .

[0047] According to the present embodiment, if the total cross-sectional area obtained by adding the cross-sectional areas of the bases of the filaments 28 arranged to overlap the insertion hole 27, that is, the parts connected to the head base part 21, which are perpendicular to the thickness direction, is set as the second cross-sectional area Sc2, then the ratio of the second cross-sectional area Sc2 to the first cross-sectional area Sc1 is 40% or more and 90% or less. It should be noted that in the present invention, when the filaments 28 are arranged to overlap the outer edge of the insertion hole 27 when viewed in the thickness direction, the cross-sectional area of ​​the filament 28 of which more than half of the cross-sectional area of ​​the cross-sectional area of ​​the base part perpendicular to the thickness direction overlaps the insertion hole 27 is included in the second cross-sectional area Sc2. On the other hand, the cross-sectional area of ​​the filament 28 of which more than half of the cross-sectional area of ​​the cross-sectional area of ​​the base part perpendicular to the thickness direction does not overlap the insertion hole 27 is not included in the second cross-sectional area Sc2. In the following description, a cross section of the filament 28 perpendicular to the thickness direction may be simply referred to as the cross section of the filament 28 , and a cross-sectional area of ​​the cross section of the filament 28 perpendicular to the thickness direction may be simply referred to as the cross-sectional area.

[0048] As described above, in the molding process of the brush molding body 20, when the first mold 31 is demolded from the plurality of filaments 28, the brush molding body 20 is held by the core 33b inserted into the insertion hole 27 on the slide core 33. Therefore, when the first mold 31 is demolded, the extension direction of the filaments 28 arranged on the front side of the core 33b, that is, the front side of the insertion hole 27, among the plurality of filaments 28, is not easily inclined relative to the thickness direction. Therefore, the demolding resistance between the filaments 28 and the first mold 31, which increases due to the inclination of the filaments 28 relative to the thickness direction when the first mold 31 is demolded, can be suppressed. In the present embodiment, since the ratio of the second cross-sectional area Sc2 to the first cross-sectional area Sc1 is 40% or more, the number of filaments 28 arranged on the front side of the insertion hole 27 can be increased. Thus, since the demolding resistance between the plurality of filaments 28 and the first mold 31 can be suppressed from increasing, the demolding properties of the plurality of filaments 28 and the first mold 31 can be improved. In addition, it is possible to suppress the formation of poor filament 28 (poor demolding) caused by demolding the filament 28 from the first mold 31 in an inclined state. Therefore, even when using a wide brush molding body 20 molded by integral molding, it is possible to suppress the formation of poor brush molding body 20.

[0049] It should be noted that the length Li2 of the insertion hole 27 is preferably 55% or more relative to the length Lh of the head base portion 21. This makes it easy to make the ratio of the second cross-sectional area Sc2 to the first cross-sectional area Sc1 40% or more.

[0050] like Figure 7As shown, in the molding process of the brush molding body 20, in the portion of the head base portion 21 where the insertion hole 27 is provided, the resin flows from the front end side to the rear end side via the first portion 25a and the second portion 25b, but the dimension in the thickness direction of the resin flowing from the front end side to the rear end side is smaller than the dimension in the thickness direction of the insertion hole 27 compared to the portion of the head base portion 21 where the insertion hole 27 is not provided. Therefore, in the portion of the head base portion 21 where the insertion hole 27 is provided, it is difficult for the resin to flow from the front end side to the rear end side. Therefore, since it is difficult to fill the filament 28 arranged on the front side of the insertion hole 27 with resin, poor molding is likely to occur. Therefore, if the ratio of the second cross-sectional area Sc2 to the first cross-sectional area Sc1 is greater than 90%, the number of filaments 28 arranged on the front side of the insertion hole 27 becomes too large, so that multiple filaments 28 are likely to be poorly molded. In this embodiment, the ratio of the second cross-sectional area Sc2 to the first cross-sectional area Sc1 is 90% or less, so that the number of filaments 28 arranged on the front side of the insertion hole 27 can be prevented from becoming excessive, and molding defects of the plurality of filaments 28 can be prevented.

[0051] As described above, in this embodiment, if Figure 7 As shown, the side view shape of the plurality of filaments 28 is a tapered shape that tapers from the base to the front end. The smaller the difference between the cross-sectional area of ​​the base of each filament 28 and the cross-sectional area of ​​the front end, the smaller the difference between the demoulding resistance of the base of each filament 28 and the demoulding resistance of the front end can be reduced when the first mold 31 is demoulded from each filament 28, so that the formation of each filament 28 can be suppressed. In view of this, in the present embodiment, the ratio of the second cross-sectional area Sc2 to the first cross-sectional area Sc1 is 90% or less. Therefore, when observed in the thickness direction, the total cross-sectional area of ​​the filament 28 disposed in the part that does not overlap with the insertion hole 27 can be set to 10% or more, so it is easy to reduce the cross-sectional area of ​​the base of each filament 28. Therefore, since the difference between the cross-sectional area of ​​the base of each filament 28 and the cross-sectional area of ​​the front end can be reduced, the formation of each filament 28 can be suppressed. It should be noted that the size of the base of the plurality of filaments 28 is preferably less than 1.5mm on one side. In addition, the cross-sectional area of ​​the base of the plurality of filaments 28 is preferably 1.0 mm 2 Furthermore, when viewed in the thickness direction, the radius of the circumscribed circle tangent to the corners of the bases of the plurality of filaments 28 is preferably 1.8 mm or less.

[0052] In addition, in this embodiment, Figure 6The shortest distance between the outer edge of the head base portion 21 shown and the filament area 21d is preferably less than 3 mm. As described above, the brush forming body 20 of the present embodiment is wide, so the amount of resin constituting the brush forming body 20 is large. Therefore, in the molding process of the brush forming body 20, the fluidity of the resin flowing in the mold 30 is easily reduced. If the fluidity of the resin is reduced, it is difficult to fill the first cavity 31b of the first mold 31 with resin, so multiple filaments 28 are prone to poor molding. In addition, if the filling pressure of the resin filled into the mold 30 is increased in order to suppress the occurrence of this poor molding, the resin density of the filaments 28 is likely to increase, so the demolding resistance between each filament 28 and the first mold 31 is likely to increase, and the demolding property of the first mold 31 is reduced. In this regard, in the present embodiment, by setting the shortest distance between the outer edge of the head base portion 21 and the filament area 21d to less than 3 mm, the increase in the volume of the brush forming body 20 can be suppressed. Therefore, since the amount of resin filled in the mold 30 can be suppressed from increasing, the fluidity of the resin can be suppressed from decreasing. Therefore, since the release property of the first mold 31 can be suppressed from decreasing, the molding defects of the plurality of filaments 28 can be suppressed.

[0053] like Figure 8 As shown, the head base portion 21 has a first head area 23 and a second head area 24. The first head area 23 is a portion located closer to the front end side, that is, one side (+X side) in the long axis direction than the end of the rear end side of the filament 28 arranged at the rear end side in the head base portion 21, that is, the other side (-X side) in the long axis direction. The second head area 24 is a portion located closer to the rear end side than the filament 28 arranged at the rear end side in the brush forming body 20. According to the present embodiment, if the area of ​​the first head area 23 observed along the thickness direction is set to the first head area Sh1, the first head area Sh1 is 250 mm 2 As a result, the area of ​​the portion of the brush molding 20 where the plurality of filaments 28 are provided can be enlarged, and thus the number of filaments 28 provided in the brush molding 20 can be increased. Therefore, the user can efficiently clean the tooth surface with the toothbrush 1.

[0054] According to this embodiment, if the area observed along the thickness direction of the portion of the insertion hole 27 located closer to the front end side than the end portion on the rear end side of the filament 28 arranged on the rear end side is set as the insertion hole area Si, then the ratio of the insertion hole area Si to the first head area Sh1 is greater than 30% and less than 70%. If the ratio of the insertion hole area Si to the first head area Sh1 is less than 30%, in the molding process of the brush molding body 20, the area of ​​the portion of the head base portion 21 that is not held by the core portion 33b of the sliding core 33 becomes too large when viewed in the thickness direction. In addition, the brush molding body 20 is molded from a soft resin with low strength. Therefore, when the first mold 31 is demolded, the portion of the head base portion 21 that is easily deformed increases due to the demolding resistance between each filament 28 and the first mold 31. In addition, if the ratio of the insertion hole area Si to the first head area Sh1 is less than 30%, the number of filaments 28 that are not arranged on the front side of the core portion 33b increases. As a result, when the first mold 31 is demolded, the number of filaments 28 that are inclined relative to the thickness direction increases. Therefore, the demolding property of the first mold 31 is reduced, so the filaments 28 are prone to poor molding.

[0055] As described above, in the portion of the head base portion 21 where the insertion hole 27 is provided, the resin does not easily flow from the front end side to the rear end side. Therefore, if the ratio of the insertion hole area Si to the first head area Sh1 is greater than 70%, the fluidity of the resin is likely to decrease during the molding process of the brush molding body 20, and as described above, the plurality of filaments 28 are likely to be poorly molded. In addition, if the filling pressure of the resin filled into the mold 30 is increased in order to suppress the occurrence of such poor molding, the demolding property of the first mold 31 is reduced as described above.

[0056] In this embodiment, if Figure 8 As shown, since the ratio of the insertion hole area Si to the first head area Sh1 is 30% or more and 70% or less, it is possible to suppress a reduction in the releasability of the first die 31 and suppress molding defects of the plurality of filaments 28 .

[0057] The maximum width Wi1 of the insertion hole 27 is preferably not less than 8 mm and not more than 10 mm. In the present embodiment, when viewed in the thickness direction, the portion of the insertion hole 27 that overlaps with the end portion on the rear end side of the filament 28 disposed on the rear end side is the first insertion hole portion 27d. The portion of the insertion hole 27 that is located in the center of the long axis direction between the first insertion hole portion 27d and the end portion on the front end side of the insertion hole 27 is the second insertion hole portion 27e. When the maximum width of the portion between the first insertion hole portion 27d and the second insertion hole portion 27e in the insertion hole 27 is set to Wi2, the ratio of the maximum width Wi2 to the width Wb of the head base portion 21 is preferably 40% or more and 75% or less, and more preferably 50% or more and 75% or less. In the insertion hole 27, in the portion between the first insertion hole portion 27d and the second insertion hole portion 27e, the dimension obtained by adding the shortest dimension between the insertion hole 27 and the surface of the head base portion 21 on one side (+Y side) facing the width direction, and the shortest dimension between the insertion hole 27 and the surface of the head base portion 21 on the other side (-Y side) facing the width direction is preferably greater than 2 mm and less than 10 mm, and more preferably greater than 4 mm and less than 6 mm.

[0058] The ratio of the length Li between the first insertion hole portion 27 d of the insertion hole 27 and the end portion on the front end side of the insertion hole 27 to the length Lh1 of the first head region 23 is preferably 65% ​​or more and 85% or less. The length Lh1 of the first head region 23 is preferably not less than 18 mm and not more than 22 mm. The length Li between the first insertion hole portion 27d and the end portion on the front end side of the insertion hole 27 is preferably 15 mm or more and 20 mm or less. The difference between the length Lh1 of the first head region 23 and the length Li between the first insertion hole portion 27 d and the end portion on the front end side of the insertion hole 27 is preferably 3 mm or more and 5 mm or less.

[0059] In this embodiment, if the area of ​​the brush forming body 20 observed along the thickness direction is set as the head area Sh, and the area of ​​the second head region 24 observed along the thickness direction is set as the second head area Sh2, the ratio of the second head area Sh2 to the head area Sh is greater than 2% and less than 10%. In the molding process of the brush molding body 20, since the resin flowing toward the rear end side in the mold 30 is blocked by the abutment surface 32b of the slide core 33, the density of the resin near the end of the rear end side of the brush molding body 20 tends to increase. If the ratio of the second head area Sh2 to the head area Sh is less than 2%, the distance between the abutment surface 32b of the slide core 33 and the filament 28 arranged on the rear end side becomes too short, so the density of the resin of the filament 28 tends to increase. Therefore, the demolding property of the filament 28 from the first mold 31 tends to decrease, so the filament tends to be poorly molded.

[0060] If the ratio of the second head area Sh2 to the head area Sh is greater than 10%, the volume of the brush forming body 20 becomes too large, and the fluidity of the resin is easily reduced in the molding process of the brush forming body 20. Therefore, as described above, the plurality of filaments 28 are easily molded poorly.

[0061] In this embodiment, since the ratio of the second head area Sh2 to the head area Sh is 2% or more and 10% or less, the reduction in the releasability of the first die 31 can be suppressed, and molding defects of the plurality of filaments 28 and the like can be suppressed.

[0062] In addition, the ratio of the second head area Sh2 to the head area Sh is more preferably 2% or more and 8% or less, and further preferably 2% or more and 6% or less.

[0063] The length Lh2 of the second head region 24 is preferably 0.5 mm to 3.0 mm, and more preferably 0.5 mm to 2.0 mm.

[0064] According to this embodiment, the second head area Sh2 is 5 mm 2 Above and 30mm 2 the following. The second head area Sh2 is less than 5 mm 2 In this case, during the molding process of the brush molding body 20, the distance between the abutment surface 32b of the sliding core 33 and the filament 28 arranged on the rear end side becomes too short. Therefore, as described above, the density of the resin of the filament 28 arranged on the rear end side is likely to increase, and the demolding property of the filament 28 and the first mold 31 is likely to be reduced.

[0065] In addition, the second head area Sh2 is greater than 30 mm 2 In this case, the volume of the brush molding body 20 becomes too large, and therefore, as described above, in the molding process of the brush molding body 20, the fluidity of the resin decreases, and the molding of the plurality of filaments 28 is likely to be defective.

[0066] In this embodiment, the second head area Sh2 is 5 mm 2 Above and 30mm 2 Therefore, it is possible to suppress a decrease in the releasability of the first die 31 and suppress the occurrence of molding defects of the plurality of filaments 28 .

[0067] like Figure 6 As shown, multiple filaments 28 include multiple first filaments 28a and multiple second filaments 28b. Multiple first filaments 28a are arranged closer to the front end side than multiple second filaments 28b. Observed along the thickness direction, the base of the first filament 28a, that is, the part connected to the head base portion 21, and the base of the second filament 28b are respectively polygonal. In more detail, observed along the thickness direction, the base of the first filament 28a is triangular. Therefore, the base of the first filament 28a has three corners. Observed along the thickness direction, the base of the second filament 28b is quadrilateral. Therefore, the base of the second filament 28b has four corners. Therefore, the number of the corners of the second filament 28b is more than the number of the corners of the first filament 28a.

[0068] The brush forming body 20 of the present embodiment has a first brush portion 21e and a second brush portion 21f. The first brush portion 21e is a portion on the front end side of the head base portion 21. In the present embodiment, the main view shape of the first brush portion 21e is a roughly semicircular shape protruding toward the front end side. The second brush portion 21f is a portion on the rear end side of the head base portion 21. The second brush portion 21f is located closer to the rear end side than the first brush portion 21e, that is, on the other side (-X side) of the long axis direction. In the present embodiment, the main view shape of the second brush portion 21f is a shape that extends with a roughly constant width after the width widens in a curved shape from the front end side toward the rear end side.

[0069] A plurality of first filaments 28a are provided on the first brush portion 21e. In the present embodiment, in the first brush portion 21e, four rows consisting of a plurality of first filaments 28a arranged at intervals from each other in the width direction are arranged at intervals from each other in the long axis direction. In the present embodiment, the number of first filaments 28a constituting each row is greater than 4 and less than 11. The first brush portion 21e is a portion of the head base portion 21 that is closer to the front end side than the end portion of the rear end side of each of the plurality of first filaments 28a constituting the row of first filaments 28a arranged at the rear end side.

[0070] A plurality of second filaments 28b are provided in the second brush portion 21f. In the present embodiment, the second brush portion 21f is a portion of the head base portion 21 that is closer to the rear end side than the end portions of the rear end sides of the plurality of first filaments 28a constituting the columns of the first filaments 28a disposed at the rear end side. In the present embodiment, in the second brush portion 21f, 17 columns consisting of a plurality of second filaments 28b arranged at intervals from each other in the width direction are arranged at intervals from each other in the major axis direction. The number of second filaments 28b constituting each column is more than 12 and less than 13. Therefore, in the second brush portion 21f, the number of second filaments 28b arranged in the width direction is greater than the number of first filaments 28a arranged in the width direction in the first brush portion 21e. Therefore, in the second brush portion 21f, which is the rear end side portion of the brush forming body 20, the number of second filaments 28b provided per unit length in the long axis direction is greater than the number of first filaments 28a provided per unit length in the long axis direction in the first brush portion 21e. Therefore, in the molding process of the brush forming body 20, regarding the demolding resistance when the first mold 31 is demolded from the brush forming body 20, the demolding resistance of the second brush portion 21f is greater than the demolding resistance of the first brush portion 21e.

[0071] In contrast, according to the present embodiment, the number of corners of the second filament 28b is greater than the number of corners of the first filament 28a. The inner angle of the corner of the shape with a large number of corners of the filament 28 becomes larger. Therefore, the inner angle of the corner of the first cavity 31b of the first mold 31 also becomes larger. Therefore, when the first mold 31 is demolded from the brush molding 20, the more corners of the filament 28, the less likely the corner of the filament 28 is to be hooked on the corner of the first cavity of the first mold 31, so the demolding resistance between the first mold 31 and the filament 28 becomes smaller. In the present embodiment, as described above, since the number of filaments 28 per unit length in the long axis direction is large, the number of corners of the second filament 28b provided in the second brush portion 21f, which is easy to increase the demolding resistance compared with the first brush portion 21e, is greater than the number of corners of the first filament 28a provided in the first brush portion 21e, thereby suppressing the increase of the demolding resistance of the second brush portion 21f. Therefore, since it is possible to suppress a decrease in the mold releasability of the second brush portion 21f, it is possible to suppress the occurrence of molding defects in the second filaments 28b.

[0072] The ratio of the cross-sectional area of ​​the base of the second filament 28 b to the cross-sectional area of ​​the base of the first filament 28 a is preferably 90% or more and 115% or less. It should be noted that the bases of all the filaments 28 may be in the same shape when viewed in the thickness direction. That is, the bases of all the filaments 28 may be in a triangular shape or a quadrilateral shape when viewed in the thickness direction.

[0073] The fewer the number of corners of the filaments 28, the easier it is for the user of the toothbrush 1 to improve the cleaning feeling. In addition, when the toothbrush 1 is used, the filaments 28 disposed closer to the front end of the brush molding 20 are more likely to contact the tooth surface to be cleaned. In this embodiment, the number of corners of the first filament 28a of the first brush portion 21e disposed at the front end of the head base portion 21 is less than the number of corners of the second filament 28b, so that the user of the toothbrush 1 can improve the cleaning feeling.

[0074] like Figure 6 As shown, according to this embodiment, if the area of ​​the first brush portion 21e observed in the thickness direction is defined as the third head area Sh3, the third head area Sh3 is relative to Figure 8 The ratio of the first head area Sh1 , which is the area of ​​the first head region 23 viewed in the thickness direction, is 15% or more and 35% or less. If the ratio of the third head area Sh3 to the first head area Sh1 is less than 15%, the number of first filaments 28a having a small number of corners becomes too small, and the cleaning feeling of the user of the toothbrush 1 is likely to be reduced.

[0075] If the ratio of the third head area Sh3 to the first head area Sh1 is greater than 35%, the number of first filaments 28a having greater release resistance than the second filaments 28b increases as described above, and thus the releasability of the first die 31 is likely to decrease.

[0076] In this embodiment, since the ratio of the third head area Sh3 to the first head area Sh1 is 15% to 35%, the cleaning feeling of the user of the toothbrush 1 can be improved and the reduction in the releasability of the first mold 31 can be suppressed.

[0077] like Fig. 9 As shown, according to this embodiment, when viewed in the thickness direction, the shortest distance W1 in the width direction between the outer edge of the head base portion 21 and the plurality of filaments 28 is greater than or equal to 0.3 mm and less than or equal to 1.5 mm. Fig.10 The resin in the portion of the second cavity 32a located on the back side of the first cavity 31b shown in the figure is difficult to flow in the long axis direction. Therefore, in order to smoothly supply the resin to the portion on the rear side of the second cavity 32a and the portion on the rear side of the first cavity 31b, it is necessary to Fig. 9 The shortest distance W1 in the width direction of the head outer edge portion 26 between the outer edge of the head base portion 21 and the plurality of filaments 28 is lengthened to increase the amount of resin flowing from the front end side to the rear end side through the head outer edge portion 26 .

[0078] If the shortest distance W1 in the width direction of the head outer edge portion 26 is shorter than 0.3 mm, it becomes difficult for the resin to flow toward the rear end side through the head outer edge portion 26 during the molding process of the brush mold 20. Therefore, since it is difficult to fill the rear end side of the brush mold 20 with resin, the plurality of filaments 28 and the like located at the rear end side are prone to poor molding. If the filling pressure of the resin filled into the mold 30 is increased in order to suppress the occurrence of poor molding, the demolding property of the first mold 31 is reduced as described above.

[0079] If the shortest distance W1 in the width direction of the head outer edge portion 26 is longer than 1.5 mm, the volume of the brush forming body 20 becomes too large. Therefore, as described above, in the molding process of the brush forming body 20, the fluidity of the resin decreases, and the filaments 28 are easily molded poorly.

[0080] In the present embodiment, since the shortest distance W1 in the width direction of the head outer edge portion 26 is 0.3 mm to 1.5 mm, it is possible to suppress molding defects of the plurality of filaments 28 and the like, and to suppress reduction in the releasability of the first die 31 .

[0081] It should be noted that the shortest distance W1 in the width direction of the head outer edge portion 26 is more preferably not less than 0.4 mm and not more than 1.2 mm, and further preferably not less than 0.4 mm and not more than 1.0 mm.

[0082] According to the present embodiment, the interval between the filaments 28 arranged adjacent to each other in the long axis direction, i.e., the first interval Ls1, is greater than the interval between the filaments 28 arranged adjacent to each other in the width direction, i.e., the second interval Ls2. Usually, the tooth surface cleaning performed by the toothbrush 1 is performed by moving the head 5 along the long axis direction. Therefore, if the second interval Ls2 is large, it is possible to cause the brush to be missed, and the cleaning feeling is easily reduced. In addition, as described above, in the molding process of the brush molding body 20, since the resin is difficult to flow in the part where the filaments 28 are provided, if the first interval Ls1 is too small, the fluidity of the resin flowing from the outer edge portion 26 of the head toward the central side in the width direction is reduced. Therefore, since the amount of resin supplied to the filaments 28 arranged on the central side in the width direction is easily insufficient, the filaments 28 are prone to poor molding. In view of this, in the present embodiment, since it is easy to increase the first interval Ls1 and easy to reduce the second interval Ls2, it is possible to improve the cleaning feeling and suppress the poor molding of the filaments 28 arranged on the central side in the width direction.

[0083] It should be noted that the second interval Ls2 is preferably not less than 0.5 times and less than 1.0 times the first interval Ls1. The first interval Ls1 is preferably not less than 1.0 mm and not more than 2.0 mm. The second interval Ls2 is preferably not less than 0.5 mm and not more than 1.5 mm. The number of the filaments 28 per unit length provided in the width direction is preferably 0.3 filaments / cm or more and 1.0 filaments / cm or less. The number of filaments 28 per unit length provided in the long-axis direction is preferably 0.5 filaments / cm or more and 1.0 filaments / cm or less. The number of the filaments 28 arranged in the width direction is preferably 4 or more and 17 or less, and more preferably 7 or more and 13 or less. The number of the filaments 28 arranged in the longitudinal direction is preferably 10 or more and 27 or less, and more preferably 13 or more and 22 or less. The number of filaments 28 included in the brush molding 20 is preferably 140 or more and 320 or less.

[0084] like Figure 1 As shown, according to the present embodiment, the ratio of the minimum width W3 of the neck 13 , ie, the minimum dimension in the width direction, to the maximum width W2 of the head base portion 21 , ie, the maximum dimension in the width direction, is 20% or more and 35% or less. If the ratio of the minimum width W3 of the neck 13 to the maximum width W2 of the head base portion 21 is less than 20%, the strength of the neck 13 becomes too low, and the neck 13 may break when the toothbrush 1 is used.

[0085] If the ratio of the minimum width W3 of the neck 13 to the maximum width W2 of the head base 21 is greater than 35%, the volume of the brush mold 20 in the oral cavity increases when the toothbrush 1 is used, and thus the operability of the toothbrush 1 in the oral cavity may decrease.

[0086] In this embodiment, since the ratio of the minimum width W3 of the neck 13 to the maximum width W2 of the head base portion 21 is greater than 20% and less than 35%, the neck 13 can be prevented from breaking when the toothbrush 1 is used, and the operability of the toothbrush 1 in the oral cavity can be improved.

[0087] like Figure 7 As shown, according to the present embodiment, if the thickness of the head base portion 21, that is, the dimension in the thickness direction of the head base portion 21 is set to the head thickness Th, and the thickness of the portion of the head base portion 21 that is closer to the front side than the insertion hole 27, that is, the first portion 25a is set to the first head thickness Th1, then the first head thickness Th1 is greater than 1.0 mm and less than 2.0 mm, and the ratio of the first head thickness Th1 to the head thickness Th is greater than 20% and less than 35%.

[0088] If the first head thickness Th1 is thinner than 1.0 mm, the rigidity of the first portion 25a in the thickness direction becomes too small, so in the process of molding the brush molding body 20, when the first mold 31 is demolded from the brush molding body 20, the first portion 25a is easily bent in the thickness direction due to the demolding resistance between the plurality of filaments 28 and the first mold 31. Therefore, when the first mold 31 is demolded, the extension direction of the plurality of filaments 28 is inclined relative to the thickness direction, so as described above, the demolding property of the first mold 31 is reduced, and the filaments 28 are easily molded poorly. It should be noted that in the case where the ratio of the first head thickness Th1 to the head thickness Th is less than 20%, the rigidity of the first portion 25a in the thickness direction becomes too small, so the demolding property of the first mold 31 is reduced, and the filaments 28 are easily molded poorly.

[0089] If the first head thickness Th1 is thicker than 2.0 mm, the maximum dimension Ti of the insertion hole 27 in the thickness direction becomes relatively small. Fig.10The thickness of the core portion 33b of the sliding core 33 shown becomes too thin. Therefore, the rigidity of the core portion 33b in the thickness direction becomes too small, so in the process of molding the brush molding body 20, when the first mold 31 is demolded from the brush molding body 20, the deflection of the core portion 33b in the thickness direction becomes larger, so the extension direction of the plurality of filaments 28 is inclined relative to the thickness direction. Therefore, as described above, the demolding property of the first mold 31 is reduced, and the filaments 28 are prone to poor molding. It should be noted that in the case where the ratio of the first head thickness Th1 to the head thickness Th is greater than 35%, the thickness of the core portion 33b becomes too thin, so the demolding property of the first mold 31 is reduced, and the filaments 28 are prone to poor molding.

[0090] In the present embodiment, the first head thickness Th1 is greater than 1.0 mm and less than 2.0 mm. Since the ratio of the first head thickness Th1 to the head thickness Th is greater than 20% and less than 35%, the thickness of the first part 25a and the core part 33b of the sliding core 33 can be prevented from becoming too thin. Therefore, the demolding property of the first mold 31 can be prevented from being reduced, and the filament 28 can be prevented from being poorly molded.

[0091] As described above, in the toothbrush 1 of this embodiment, even when the wide brush molded body 20 molded by integral molding is used, it is possible to suppress the occurrence of molding defects in the brush molded body 20 .

[0092] <Second embodiment> Fig.13 1 is a front view showing a brush molded body 220 of a toothbrush 201 according to the present embodiment. In the following description, the same components as those of the first embodiment described above are denoted by the same reference numerals, and description thereof will be omitted.

[0093] The multiple filaments 228 of the brush forming body 220 of the present embodiment include multiple first filaments 28a provided in the first brush portion 21e, and multiple second filaments 228b provided in the second brush portion 21f. The structure of the first filament 28a of the present embodiment is the same as the structure of the first filament 28a of the first embodiment described above. Therefore, when observed in the thickness direction, the base of the first filament 28a is triangular in shape. That is, when observed in the thickness direction, the base of the first filament 28a has a corner. In more detail, the first filament 28a has three corners.

[0094] Observed along the thickness direction, the base of the second filament 228b is semicircular. That is, observed along the thickness direction, at least a portion of the outer periphery of the base of the second filament 228b, i.e., the portion connected to the head base portion 21, is arc-shaped. In the present embodiment, observed along the thickness direction, the straight portion in the outer periphery of the second filament 228b extends along the width direction, and the arc-shaped portion is located closer to the front end side than the straight portion. It should be noted that the arc-shaped portion may be located closer to the rear end side than the straight portion, or the straight portion may extend along the major axis direction, and the arc-shaped portion may be located closer to one side (+Y side) or the other side (-Y side) of the width direction than the straight portion.

[0095] In this embodiment, the configuration of the plurality of second filaments 228b is similar to Figure 6 The configuration of the plurality of second filaments 28b of the first embodiment shown is the same. Therefore, in the second brush portion 21f, which is the rear end side portion of the brush forming body 220, the number of second filaments 228b provided per unit length in the long axis direction is greater than the number of first filaments 28a provided per unit length in the long axis direction in the first brush portion 21e. Therefore, in the molding process of the brush forming body 220, with respect to the demolding resistance when the first mold 31 is demolded from the brush forming body 220, the demolding resistance of the second brush portion 21f is greater than the demolding resistance of the first brush portion 21e.

[0096] In contrast, according to the present embodiment, since at least a portion of the outer periphery of the second filament 228b is in an arc shape, in the molding process of the brush molding body 20, when the first mold 31 is demolded, the first cavity of the first mold 31 and the second filament 228b are not easily hooked, so that the demolding resistance when the first mold 31 is demolded can be reduced. Therefore, the demolding resistance of the second brush portion 21f can be better suppressed from increasing. Therefore, since the demolding property of the second brush portion 21f can be suppressed from being reduced, the molding failure of the second filament 228b can be suppressed.

[0097] It should be noted that in the present embodiment, the shape of the second filament 228b observed in the thickness direction is semicircular, but as long as at least a portion of the outer periphery of the second filament 228b is arc-shaped, for example, the shape of the second filament 228b observed in the thickness direction may be circular or fan-shaped. Even if the shape of the second filament 228b observed in the thickness direction is these shapes, the demolding resistance when demolding the first mold 31 can be reduced.

[0098] As described above, in the toothbrush 201 of this embodiment, even when the wide brush molded body 220 molded by integral molding is used, it is possible to suppress the occurrence of molding defects in the brush molded body 220 .

[0099] <Third embodiment> Fig.14 1 is a front view showing a brush molded body 320 of a toothbrush 301 according to the present embodiment. In the following description, the same components as those of the first embodiment described above are denoted by the same reference numerals, and description thereof will be omitted.

[0100] The plurality of filaments 328 included in the brush mold 320 of this embodiment include a plurality of first filaments 28a provided in the first brush portion 21e and a plurality of second filaments 328b provided in the second brush portion 21f. The structure of the first filaments 28a of this embodiment is the same as that of the first embodiment.

[0101] Observed along the thickness direction, the base of the second filament 328b is triangular. In the present embodiment, the shape of the second filament 328b is the same as the shape of the first filament 28a. Therefore, according to the present embodiment, the shapes of the plurality of holes constituting the first cavity 31b of the first mold 31 can all be set to the same shape, so the increase in the processing man-hours for setting the first cavity 31b in the first mold 31 can be suppressed. Therefore, the increase in the manufacturing cost of the toothbrush 301 can be suppressed.

[0102] [Example] Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples, and can be implemented with appropriate modifications within the scope of the present invention.

[0103] (Example 1 to Example 12, Comparative Example 1 to Comparative Example 2) According to the specifications shown in Table 1, at least one different toothbrush including the width of the brush forming body: Wb, the first cross-sectional area: Sc1, the second cross-sectional area: Sc2, the ratio of the second cross-sectional area to the first cross-sectional area: Sc2 / Sc1, the first head area: Sh1, the insertion hole area: Si, the ratio of the insertion hole area to the first head area: Si / Sh1, the head area: Sh, the second head area: Sh2, and the ratio of the second head area to the head area: Sh2 / Sh is used as a sample of Examples 1 to 12 and Comparative Examples 1 to 2.

[0104] The hair length of the filament of each sample was set to 11 mm. The shape of the base of the filament of each sample was set to a triangular shape. The cross-sectional area of ​​the base of the filament of each sample was set to 0.05 mm. 2 Above, 0.40mm 2Below. The side view shape of the filaments of each sample is set to a tapered shape that tapers from the base to the front end. Observed along the thickness direction, the size of one side of the portion of the back side 0.1mm from the front end of the filament of each sample is set to 0.02mm. The number of filaments arranged in the width direction of each sample is set to be greater than 8 and less than 16. The number of filaments arranged in the long axis direction of each sample is set to be greater than 13 and less than 24. The multiple filaments of each sample are arranged in a grid shape. The density of the filaments in the filament area of ​​each sample is set to 1 filament / mm 2 . The total number of filaments provided in each sample is set to be greater than 212 and less than 356. The soft resin constituting the brush molding of each sample is set to polyurethane resin (PU). The hard resin constituting the handle body of each sample is set to polypropylene resin (PP). The thickness of the head base portion of each sample, that is, the head thickness Th, is set to 4.0 mm. The maximum dimension Ti of the insertion hole of each sample in the thickness direction is 2.0 mm.

[0105] [Evaluation method] Each sample of Examples 1 to 12 and Comparative Examples 1 and 2 was evaluated based on the state of the filament base and the size of the filament.

[0106] (1) Method for evaluating the state of the filament base The bases of the filaments of 10 brush molded bodies molded under the same conditions were visually evaluated by two experts based on the following criteria, and the lowest evaluation result among the 10 brush molded bodies was used as the evaluation result of each sample. ×(cross mark): There is one or more tears △ (triangle mark): There is no tearing in all the filaments, but there are 5 or more cracks. ○ (circle mark): There is no tearing in all the filaments, but there are more than 1 and less than 4 cracks. ◎ (double circle mark): There are no tears or cracks in all the filaments, but there is one or more whitening. ☆(star mark): There is no tearing, cracking or whitening in all filaments.

[0107] (2) Evaluation method of filament size In each of the five brush molded products molded under the same conditions, two random filaments located at the front end, center, and rear end of the brush molded body were photographed using a microscope, and the size of the filaments was evaluated according to the following criteria. It should be noted that in this evaluation, the size of the filament is the size L1 of the side extending in the width direction among the three sides of the filament observed along the thickness direction, and the size L2 between the side extending in the width direction and the vertex opposite to the side extending in the width direction in the long axis direction (refer to Fig.14 ). In the following description, the dimension of the side extending in the width direction of the filament is referred to as the first dimension L1, and the dimension between the side extending in the width direction and the vertex opposite to the side extending in the width direction in the major axis direction is referred to as the second dimension L2. It should be noted that the center dimensions of the first dimension L1 and the second dimension L2 of each sample are as described in Table 1. × (cross mark): One or more filaments do not meet the specified length (11mm±0.5mm) △ (triangle mark): All filaments meet the prescribed dimensions of hair length, but one or more filaments do not meet the prescribed dimensions (±0.05 mm) of the first dimension L1 and the second dimension L2 of the portion 2 mm from the front end of the filament on the base side. 0 (circle mark): All the filaments meet the prescribed dimensions of the hair length and the first dimension L1 and the second dimension L2 of the portion on the base side 2 mm from the front end of the filament, but one or more filaments do not meet the prescribed dimensions (±0.05 mm) of the first dimension L1 and the second dimension L2 of the portion on the base side 5 mm from the front end of the filament. ◎(double circle mark): All filaments meet the prescribed dimensions of the hair length, the first dimension L1 and the second dimension L2 of the base side 2mm and 5mm from the front end of the filament, but more than one filament does not meet the prescribed dimensions of the first dimension L1 and the second dimension L2 of the base of the filament (±0.1) ☆(star mark): All filaments meet all the above specified dimensions.

[0108] [Table 1]

[0109] As shown in Table 1, for Examples 1 to 12 in which the ratio Sc2 / Sc1 of the second cross-sectional area to the first cross-sectional area was 40% or more and 90% or less, good results of △ (triangle mark) or more were obtained regarding the state of the filament base and the size of the filament.

[0110] In contrast, in Comparative Example 1, in which the ratio Sc2 / Sc1 of the second cross-sectional area to the first cross-sectional area is greater than 90%, the result related to the size of the filament is × (cross mark), and a good result cannot be obtained. This is because the number of filaments arranged overlapping the insertion hole becomes too large when viewed in the thickness direction, so the filling property of the resin into the filament is reduced.

[0111] Regarding Comparative Example 2 in which the ratio Sc2 / Sc1 of the second cross-sectional area to the first cross-sectional area is less than 40%, the result related to the state of the filament base is × (cross mark), and a good result cannot be obtained. This is because the number of filaments arranged not overlapping the insertion hole when viewed in the thickness direction becomes too large, so as described above, the demoldability of the filaments from the first mold is reduced. In addition, since the resin is preferentially filled from the filaments that are closer to the outside in the width direction than the insertion hole, it is difficult to fill the resin into the filaments that are arranged overlapping the insertion hole when viewed in the thickness direction, which is caused by the reduced filling property of the resin into the filaments.

[0112] In Example 3, in which the ratio Sc2 / Sc1 of the second cross-sectional area to the first cross-sectional area is less than 80%, better results were obtained regarding the size of the filaments than in Example 1. This is because the number of filaments arranged overlapping the insertion hole is reduced when viewed in the thickness direction, so the filling property of the resin into each filament is improved.

[0113] In Example 4, in which the ratio Sc2 / Sc1 of the second cross-sectional area to the first cross-sectional area is greater than 50%, a better result was obtained regarding the state of the filament base than in Example 2. This is because, when viewed in the thickness direction, the number of filaments that are not overlapped with the insertion hole is reduced, and thus the demolding property of the filaments from the first mold is improved.

[0114] In Example 5, in which the ratio Si / Sh1 of the insertion hole area to the first head area was less than 70%, a better result was obtained with respect to the size of the filament than in Example 3. This is because the insertion hole area observed in the thickness direction becomes smaller, so the resin easily flows from the front end side to the rear end side as described above, and in particular, the filling property of the resin into the filament arranged on the rear end side is improved.

[0115] Regarding Example 6 in which the ratio Si / Sh1 of the insertion hole area to the first head area is greater than 30%, a better result was obtained than Example 4 regarding the state of the filament base. This is because, as described above, the area of ​​the insertion hole becomes larger, so in the molding process of the brush molding body, the area of ​​the portion of the head base that is not held by the core of the sliding core can be suppressed from becoming too large. As a result, when the first mold is demolded, the portion of the head base that is easily deformed due to the demolding resistance with the first mold can be suppressed from increasing, and when observed in the thickness direction, the number of filaments arranged overlapping with the core increases, so the demolding property of the first mold is improved.

[0116] In Example 7, in which the ratio Si / Sh1 of the insertion hole area to the first head area was less than 65%, a better result was obtained with respect to the size of the filament than in Example 5. This is because the insertion hole area observed in the thickness direction becomes smaller, so the resin flows more easily from the front end side to the rear end side as described above, and in particular, the filling property of the resin into the filament arranged on the rear end side is further improved.

[0117] In Example 8 in which the ratio Si / Sh1 of the insertion hole area to the first head area was greater than 40%, a better result was obtained regarding the state of the filament base portion than in Example 6. This is because, as described above, since the area of ​​the insertion hole becomes larger, in the molding process of the brush molding body, the area of ​​the portion of the head base portion that is not held by the core portion of the sliding core can be more appropriately suppressed from becoming too wide, and when the first mold is demolded, the portion of the head base portion that is easily deformed due to the demolding resistance with the first mold can be more appropriately suppressed from increasing, and the number of filaments arranged overlapping with the core portion when viewed in the thickness direction is further increased, so that the demolding property of the first mold is more appropriately improved.

[0118] In Example 9, in which the ratio Sh2 / Sh of the second head area to the head area was less than 10%, better results were obtained regarding the filament size than in Example 8. This is because the volume of the brush molded body was reduced, so the fluidity of the resin was improved, and the filling property of the resin into each filament was improved.

[0119] In Example 10, in which the ratio Sh2 / Sh of the second head area to the head area was greater than 2%, a better result was obtained regarding the state of the filament base than in Example 7. This is because the second head area Sh2 becomes relatively larger relative to the head area Sh, and thus, as described above, the density of the resin of the filaments arranged on the rear end side of the brush molding body is suppressed from becoming too high, and thus the demolding property of the first mold is improved.

[0120] In Examples 11 and 12, in which the ratio Sh2 / Sh of the second head area to the head area was less than 6%, better results were obtained with respect to the filament size than in Example 9. This is because, as described above, the volume of the brush molding body is reduced, so the fluidity of the resin is improved, and the filling property of the resin into each filament is improved.

[0121] The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it is self-evident that the present invention is not limited to the examples involved. The shapes and combinations of the structural members shown in the above examples are examples, and various changes can be made according to design requirements, etc. without departing from the scope of the present invention.

[0122] For example, in the above-mentioned embodiment, a structure in which the filament protrudes from the upper surface of the head base portion toward the front side is illustrated, but it is not limited to this structure. For example, the head base portion may have a base portion protruding from the upper surface 21a, and the filament 28 protrudes from the base portion toward the front side.

[0123] In addition, the shape of the filament is not limited to the shape of the above-mentioned embodiment, for example, the shape observed along the thickness direction may also be a polygonal shape such as a pentagon, a circular shape, a star shape, etc. In addition, the filament may be a columnar shape protruding from the brush base portion toward the front side, or may be a tapered shape that becomes thinner from the brush base portion toward the front side. Industrial Applicability

[0124] The toothbrush according to the present invention can suppress the occurrence of molding defects in the brush molded body, and thus can be suitably used as a wide-headed integrally molded toothbrush. Description of Reference Numerals

[0125] 1, 201, 301…toothbrush, 10…handle body, 12…handle portion, 13…neck, 15…insertion portion, 20, 220, 320…brush molding, 21…head base portion, 21e…first brush portion, 21f…second brush portion, 27…insertion hole, 28, 228, 328…filament, 28a…first filament, 28b, 228b, 328b…second filament, Th…head thickness, Th1…first head thickness, W1…shortest distance in width direction between the outer edge of the head base portion and the plurality of filaments, W2…maximum width of the head base portion, W3…minimum width of the neck, Wb…width of the brush molding.

Claims

1. A toothbrush comprising: a handle body formed of hard resin and extending along the long axis direction; and a brush molding body, which is formed of soft resin and is disposed on one side of the handle body in the long axis direction; The handle body has an insertion portion protruding toward one side in the long axis direction. The brush molding body comprises a head base portion and a plurality of filaments integrally formed with the head base portion. The head base portion has an insertion hole into which the insertion portion is inserted and engaged. The plurality of filaments protrude from the head base portion toward one side in a thickness direction intersecting with the long axis direction. The brush molding body has a width dimension orthogonal to both the long axis direction and the thickness direction of 14 mm or more. If the total cross-sectional area obtained by adding the cross-sectional areas of the portions of all the filaments connected to the head base portion in the cross section perpendicular to the thickness direction is set as the first cross-sectional area, The second cross-sectional area is obtained by adding the cross-sectional areas of the sections perpendicular to the thickness direction of the sections of the plurality of filaments overlapped with the insertion hole and connected to the head base portion. Then the first cross-sectional area is 30 mm 2 above, A ratio of the second cross-sectional area to the first cross-sectional area is greater than or equal to 40% and less than or equal to 90%.

2. The toothbrush according to claim 1, wherein: If the area of ​​the portion of the brush molding body located closer to the longitudinal direction than the end of the filament on the other side of the longitudinal direction disposed closest to the other side of the longitudinal direction as observed in the thickness direction is defined as the first head area, The area of ​​the insertion hole is defined as the area of ​​the portion of the insertion hole located closer to the longitudinal direction than the end of the filament on the other side of the longitudinal direction located closest to the other side of the longitudinal direction. Then the first head area is 250mm 2 above, A ratio of the insertion hole area to the first head area is 30% or more and 70% or less.

3. The toothbrush according to claim 2, wherein: If the area of ​​the brush molding observed in the thickness direction is defined as the head area, The area of ​​the portion of the brush molding body located on the other side of the longitudinal direction relative to the filaments arranged on the other side closest to the longitudinal direction as observed in the thickness direction is set as the second head area, Then, the ratio of the second head area to the head area is greater than or equal to 2% and less than or equal to 10%.

4. The toothbrush according to claim 3, wherein: The second head area is 5mm 2 Above and 30mm 2 the following.

5. The toothbrush according to claim 2, wherein: The brush molding body includes a first brush portion and a second brush portion located on the other side of the first brush portion in the long axis direction. The plurality of filaments include a plurality of first filaments disposed on the first brush portion, and a plurality of second filaments disposed on the second brush portion. When viewed in the thickness direction, a portion of the first filament connected to the head base portion and a portion of the second filament connected to the head base portion are respectively polygonal, and the number of corners of the second filament is greater than the number of corners of the first filament.

6. The toothbrush according to claim 2, wherein: The brush molding body includes a first brush portion and a second brush portion located on the other side of the first brush portion in the long axis direction. The plurality of filaments include a plurality of first filaments disposed on the first brush portion, and a plurality of second filaments disposed on the second brush portion. When viewed in the thickness direction, a portion of the first filament connected to the head base portion is polygonal in shape, and at least a portion of an outer periphery of a portion of the second filament connected to the head base portion is arc-shaped.

7. The toothbrush according to claim 5, wherein: If the area of ​​the first brush portion observed in the thickness direction is defined as the third head area, Then, the ratio of the third head area to the first head area is greater than or equal to 15% and less than or equal to 35%.

8. The toothbrush according to any one of claims 1 to 7, wherein: When viewed in the thickness direction, the shortest distance in the width direction between the outer edge of the head base portion and the plurality of filaments is greater than or equal to 0.3 mm and less than or equal to 1.5 mm.

9. The toothbrush according to any one of claims 1 to 7, wherein: The interval between the filaments arranged adjacent to each other in the longitudinal direction is equal to or larger than the interval between the filaments arranged adjacent to each other in the width direction.

10. The toothbrush according to any one of claims 1 to 7, wherein: The handle body comprises: a handle portion extending along the longitudinal direction, and a neck portion extending from the handle portion to one side in the longitudinal direction. A ratio of a minimum dimension of the neck in a width direction to a maximum dimension of the head base portion in a width direction is 20% or more and 35% or less.

11. The toothbrush according to any one of claims 1 to 7, wherein: If the thickness dimension of the head base portion in the thickness direction is defined as the head thickness, The dimension in the thickness direction of a portion of the head base portion that is closer to the insertion hole in the thickness direction is defined as a first head thickness. Then the thickness of the first head is greater than 1.0 mm and less than 2.0 mm, A ratio of the first head thickness to the head thickness is greater than or equal to 20% and less than or equal to 35%.

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