JP7681391B2 - toothbrush - Google Patents

Description

The present invention relates to a toothbrush .

The main purpose of a toothbrush is to clean the surfaces of teeth and gums, and between teeth and the neck of teeth. For this reason, various ideas have been put into the material, tip shape, thickness, etc. of the brush bristles, the arrangement of the bristles, the number of bristles, etc., so that plaque can be effectively removed by efficiently performing appropriate cleaning according to the type of tooth (front teeth, back teeth, etc.) and the part of the tooth (interdental spaces, tooth surface, neck, etc.). For example, a toothbrush is known in which the tip of the brush bristles is tapered so that the radial width gradually decreases toward the tip, making it easier for the brush bristles to reach areas that are difficult for the brush bristles to reach, such as between teeth and the gum margin, thereby improving cleaning performance. Patent Document 1 describes a toothbrush in which the tip of the filament is chemically treated to form a tapered part at the tip, improving the ability of the brush bristles to penetrate between teeth and other gaps, thereby improving cleaning performance.

JP 2004-313365 A

However, although the tapered portion improves the ability of the brush bristles to reach between the teeth and the gum line, the stiffness of the brush bristles may decrease, resulting in weaker bristles. As a result, not only is the ability to clean the tooth surface reduced, but the ability to clean between the teeth and the neck of the teeth is also unsatisfactory.

In order to solve the above problems, the toothbrush of the present invention is a toothbrush in which a bundle of bristles consisting of multiple brush bristles is fixed to each of multiple bristles implantation holes formed on the bristle implantation surface of the head part, and the brush bristles have a first brush bristles formed by chemically treating the filament and having a first pointed tip portion formed at the tip, the radial width of which gradually decreases toward the tip, and a second brush bristles formed by mechanically treating the filament and having a second tapered tip portion formed at the tip, the radial width of which gradually decreases toward the tip and the axial length of which is shorter than that of the first tip portion, and the first tip portion is formed in a tapered shape such that the radial cross-sectional width at a position 1.0 mm from the tip of the first brush bristles is 25% to 55% of the radial width of the filament forming the first brush bristles, and the radial cross-sectional width at a position 2.0 mm from the tip of the first brush bristles is 50% to 90% of the radial width of the filament forming the first brush bristles, and the surface of the first tip portion is formed with fine irregularities formed by mechanical roughening treatment.

According to the above configuration, the tip of the first brush bristles is formed with a sharp first tip, so that the brush bristles can easily reach areas that are difficult for brush bristles to reach, such as between the teeth and the gum line. In addition, the surface of the first tip is formed with fine irregularities, so that the fine irregularities act to entangle and capture plaque and scrape it away, allowing the plaque remaining in the oral cavity to be efficiently removed.

The tip of the second brush bristles is formed with a tapered second tip that is shorter in the axial direction than the first tip. Here, the tapered shape means a shape in which the radial width gradually decreases toward the tip, such as a conical tapered shape or a hemispherical rounded tip. Since the tip of the second brush bristles is tapered or rounded with a shorter axial length than the first tip, the second brush bristles act to reinforce the weakness of the first brush bristles. This improves the cleaning performance not only of the interdental spaces and gingival margins, but also of the tooth surfaces and necks. In addition, compared to a case in which the second tip is not formed and the so-called flat shape is formed, the contact with the gums is softer, making it less likely to damage the gums.

In the above configuration, it is preferable that a length of the first brush bristles protruding from the bristle implantation hole is longer than a length of the second brush bristles protruding from the bristle implantation hole.
According to the above configuration, since the first tip portion having a sharp tip shape is formed at the tip of the first brush bristles that protrude from the bristle implantation surface by a long distance, the first brush bristles can more easily reach areas that are difficult for brush bristles to reach, such as between the teeth and the gum margin. Also, since the second tip portion having a tapered tip shape with a shorter axial length than the first tip portion is formed at the tip of the second brush bristles that protrude from the bristle implantation surface by a short distance, the second brush bristles are more likely to act to suppress bending of the first brush bristles, and the weakness of the sharp-pointed first brush bristles can be more effectively reinforced.

In the above configuration, it is preferable that the bristle bundle has the first tip portion formed at one end and the second tip portion formed at the other end, and the bristles are folded in half and fixed to the bristle implantation hole.

With the above configuration, since a first tip and a second tip are formed on one brush bristle, the brush bristle can be folded in half and fixed in the bristle hole, making it easy to adjust the first and second brush bristles, which have different protruding lengths from the bristle implantation surface.

In the above configuration, it is preferable that the surface of the first tip portion has an average line roughness Ra of 0.4 μm or more and 0.9 μm or less in the range of 1.0 mm to 1.1 mm from the tip of the brush hair.

In the above configuration, it is preferable that the surface of the first tip portion has an average line roughness Ra of 0.5 μm or more and 1.0 μm or less in a range of 2.0 mm to 2.1 mm from the tip of the brush hair.

According to the above configuration, the surface of the first tip portion is roughened by the fine unevenness formed on the surface of the first tip portion, which makes it possible to effectively remove plaque from the oral cavity.

In order to solve the above problems, the toothbrush manufacturing method of the present invention is a method for manufacturing a toothbrush in which a bristle bundle consisting of multiple brush bristles is fixed to each of multiple bristle implantation holes formed in the bristle implantation surface of the head part, and includes a chemical treatment process in which one end of the filament is chemically treated to form brush bristles having a first tip portion at the one end portion with a radial width gradually decreasing toward the tip, a bristle implantation process in which a bristle bundle consisting of multiple brush bristles is fixed to each of the multiple bristle implantation holes, and a mechanical treatment process in which the surface of the fixed bristle bundle is mechanically treated, and in the mechanical treatment process, the surface of the first tip portion is roughened and the other end side of the filament in the brush bristles is cut to form a tapered second tip portion that is shorter in the axial direction than the first tip portion.

According to the above configuration, a first tip with a sharp tip shape is formed at one end of the filament by chemical processing, the surface of the first tip is roughened by mechanical processing to make it rough, and the tip shape of the other end of the filament can be a second tip with a tapered shape shorter in the axial direction than the first tip. Here, the tapered shape is a shape in which the radial width gradually decreases toward the tip, for example, a conical tapered shape or a hemispherical rounded tip shape. Therefore, a toothbrush with good gap penetration ability based on the sharp first tip and good plaque removal ability based on the surface condition of the first tip, and excellent rigidity can be manufactured because the second tip reinforces the weakness of the bristles of the first tip. This makes it possible to manufacture a toothbrush with excellent cleaning ability not only for interdental and gingival marginal areas but also for tooth surfaces, necks, etc. In addition, compared to a case in which the second tip is not formed and the so-called flat shape is formed, the toothbrush comes into contact with the gums, etc. softer and is less likely to damage the gums, etc.

In the above configuration, in the bristle implantation process, the brush bristles are folded in half and fixed in the bristle implantation hole so that the length of the first tip protruding from the bristle implantation surface is longer than the length of the second tip protruding from the bristle implantation surface.

According to the above configuration, by fixing the brush bristles in the bristle implantation process, it is possible to increase the protruding length from the implantation surface of the first brush bristles having a sharp first tip, and to decrease the protruding length from the implantation surface of the second brush bristles having a tapered second tip that is shorter in axial length than the first tip. This makes it easy to manufacture toothbrushes with strong bristles.

The toothbrush and manufacturing method of the present invention can effectively remove plaque from the entire oral cavity, resulting in a toothbrush with excellent cleaning properties.

1A and 1B are schematic diagrams of a head portion of a toothbrush according to an embodiment of the present invention, in which (a) is a side view of the head portion, and (b) is a top view of the head portion. FIG. 4 is a schematic diagram illustrating the state of brush bristles. 4A is a partial enlarged view of a first brush bristle, and FIG. 4B is a partial enlarged view of a chemical taper portion. 5A and 5B are enlarged views of a portion of a second brush bristle, in which FIG. 5A shows a mechanical taper portion and FIG. Schematic diagram illustrating bristles of a toothbrush according to a modified example. FIG. 13 is a diagram showing the results of cleaning performance evaluation test 1. 13A and 13B are diagrams showing images of the results of cleaning performance test result 2.

Hereinafter, one embodiment of the toothbrush of the present invention will be described.
1(a) and (b), a plurality of bristle implantation holes 3 are formed in the bristle implantation surface 2a of the head portion 2 of the toothbrush 1. The number, shape, and arrangement of the bristle implantation holes 3 can be selected as desired. In the toothbrush 1 of this embodiment, 22 bristle implantation holes 3 are formed.

As shown in FIG. 1(a), a bristle bundle 4 consisting of multiple brush bristles 10 is fixed in each bristle hole 3. The number of brush bristles 10 constituting one bristle bundle 4 is not particularly limited. For example, it can be about 10 to 20. In addition, one method of fixing the bristle bundle 4 is to fold multiple brush bristles 10 in half and insert them into the bristle hole 3 together with a flat metal wire.

As shown in FIG. 1(a), the tip of the bristle bundle 4 fixed to each bristle implantation hole 3 is approximately parallel to the implantation surface 2a of the head part 2 when the head part 2 is viewed from the side. The protruding length H1 of the bristle bundle 4 from the implantation surface 2a is preferably about 8.0 mm or more and 14.0 mm or less, and more preferably about 9.0 mm or more and 13.0 mm or less.

The material of the filaments constituting the brush bristles 10 is not particularly limited, and any conventionally known synthetic resin material can be used. Examples of synthetic resin materials include polyamides such as nylon 610 and nylon 612, polyesters such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate, polyolefins such as polypropylene, olefin-based elastomers, and styrene-based elastomers. The synthetic resin materials may be used alone or in combination of two or more types.

The hardness and thickness (radial width) of the filaments that make up the brush bristles 10 can be set as appropriate. The hardness and thickness of the brush bristles 10 may be constant in each bristle implantation hole 3, or the hardness and thickness of the brush bristles 10 may be varied in some of the bristle implantation holes 3. For example, as shown by the bristle implantation holes 3 with black circles in Figure 1(b), thick brush bristles 10 may be used for the bristle bundle rows in the center of the head part 2, and as shown by the bristle implantation holes 3 with white circles in Figure 1(b), bristle bristles 10 of a different thickness may be used for the bristle bundle rows on the outer side of the head part 2.

The radial cross-sectional shape of the filaments constituting the brush bristles 10 can be set as appropriate. The radial cross-sectional shape may be circular, semicircular, elliptical, or polygonal, such as triangular or rectangular. It may also be irregular, such as an indefinite shape. The filaments may extend straight in the axial direction, or may be spiral bristles twisted in the axial direction. Furthermore, the bristle bundles 4 fixed to all of the bristle implantation holes 3 may be made of filaments with the same cross-sectional shape, or filaments with different cross-sectional shapes may be mixed. The cross-sectional shapes of the filaments may be different in the bristle implantation holes 3.

Next, the specific shape of the brush bristles 10 constituting the bristle bundle 4 fixed in the bristle implantation hole 3 will be described together with its function.
As shown in Fig. 2, in the toothbrush 1 of this embodiment, the brush bristles 10 folded in half and fixed in the bristle implantation hole 3 include a first brush bristles 11 having a long protruding length H1 from the bristle implantation surface 2a and a second brush bristles 12 having a short protruding length H2 from the bristle implantation surface 2a. A single brush bristles 10 is folded in half at a position shifted from the center and fixed in the bristle implantation hole 3, so that one of the folded bristles constitutes the first brush bristles 11 and the other constitutes the second brush bristles 12. Note that a plurality of brush bristles 10 are fixed in the bristle implantation hole 3 to form a bristle bundle 4, but in order to make it easier to understand the implantation state of the brush bristles 10, Fig. 2 shows a schematic state of one brush bristles 10 in the bristle implantation hole 3.

The protruding length H1 of the first brush bristles 11 from the bristle implantation surface 2a is the protruding length H1 of the bristle bundle 4 from the bristle implantation surface 2a. The difference between the protruding length H1 of the first brush bristles 11 and the protruding length H2 of the second brush bristles 12, i.e., the step S1 between the tip of the first brush bristles 11 and the tip of the second brush bristles 12, is preferably about 5.0 mm or less, more preferably about 4.0 mm or less, and even more preferably about 2.0 mm or less. When the step S1 is about 5.0 mm or less, the first brush bristles 11 can be made to penetrate into gaps well. When the step S1 is about 4.0 mm or less, the second brush bristles 12 act to reinforce the bending of the first brush bristles, improving the cleaning performance of the tooth surface. When the step S1 is about 2.0 mm or less, the second brush bristles 12 make good contact with the tooth surface and the first brush bristles 11 can be inserted between the teeth well, improving the cleaning performance of both the tooth surface and the teeth. In the toothbrush 1 of this embodiment, the protruding length H1 of the first brush bristles 11 from the bristle implantation surface 2a is about 11.0 mm, the protruding length H2 of the second brush bristles 12 from the bristle implantation surface 2a is about 9.0 mm, and a step S1 of about 2.0 mm is formed between the tip of the first brush bristles 11 and the tip of the second brush bristles 12. It is preferable to calculate the step S1 from the average of the protruding length H1 from the bristle implantation surface 2a of the multiple first brush bristles 11 that make up the bristle bundle 4 and the protruding length H2 from the bristle implantation surface 2a of the multiple second brush bristles 12 that make up the bristle bundle 4.

As shown in FIG. 3(a), the tip of the first brush bristles 11, which have a long protruding length H1 from the bristle implantation surface 2a, is formed with a sharp-pointed chemical taper section 21 whose radial width gradually decreases toward the tip of the first brush bristles 11. The axial length H3 of the chemical taper section 21 is preferably about 1.0 mm to 5.0 mm, and more preferably about 2.0 mm to 4.0 mm. When the chemical taper section 21 is formed in this range, the brush bristles 10 can reach between the teeth and the gingival margins well, improving the plaque removal performance in these areas. Note that the "axial length H3 of the chemical taper section 21" refers to the distance from a point that is about 80% of the "radial width L5 of the filament" described later to the tip of the brush bristles 10. In other words, the "chemical taper section 21" refers to the portion ranging from the tip of the filament to a point where the radial width L5 of the filament is about 80%.

The chemical taper section 21 is formed by chemically treating the end of the filament, melting the resin material that constitutes the filament. Therefore, after only being chemically treated, the surface of the chemical taper section 21 does not have fine irregularities.

3(b), the radial width L1 at the portion 0.1 mm from the tip of the first brush bristles 11 in the chemical taper portion 21 is preferably in the range of 3% to 15% of the radial width L5 at the base end of the brush bristles 10, and more preferably in the range of 4% to 11%. The radial width L2 at the portion 0.5 mm from the tip of the first brush bristles 11 in the chemical taper portion 21 is preferably in the range of 14% to 33% of the radial width L5 at the base end of the brush bristles 10, and more preferably in the range of 18% to 27%. The radial width L3 at the portion 1.0 mm from the tip of the first brush bristles 11 in the chemical taper portion 21 is preferably in the range of 25% to 55% of the radial width L5 at the base end of the brush bristles 10, and more preferably in the range of 30% to 46%. The radial width L4 of the chemical taper section 21 at a portion 2.0 mm from the tip of the first brush bristles 11 is preferably in the range of 50% to 90% of the radial width L5 at the base end of the brush bristles 10, and more preferably in the range of 57% to 80%.

The radial width refers to the "length of a line segment passing through the center of the radial cross section of the brush bristles 10." For example, if the radial cross section is circular, the radial width corresponds to the diameter, and if the radial cross section is rectangular, the radial width corresponds to the diagonal. In addition, the radial width L5 at the base end of the brush bristles 10 is equal to the radial width of the filaments that make up the brush bristles 10.

A fine unevenness (not shown) is formed on the surface of the chemical taper section 21. The fine unevenness is formed by mechanically roughening the surface of the chemical taper section 21, which is formed by chemically treating the end of the filament, using a grinder equipped with a grinding stone or the like. In other words, the fine unevenness is formed by chemically treating the end of the filament to melt the resin material that constitutes the filament, and then rubbing it with a grinding stone or the like to make it rough.

The fine unevenness is formed from the tip of the chemical taper section 21. The fine unevenness may be formed over the entire length of the chemical taper section 21, but does not necessarily have to be formed over the entire length of the chemical taper section 21. The fine unevenness is formed in a mechanical processing step described later, and the range of its formation is adjusted depending on the grind depth in the mechanical processing step. From the viewpoint of efficient plaque removal, it is preferable that the range of the fine unevenness is formed within a range of approximately 7.0 mm from the tip of the chemical taper section 21.

By forming the fine unevenness, the line roughness Ra of the surface of the chemical taper portion 21 is greater than the line roughness Ra of the surface of the filament. Here, the line roughness Ra of the surface of the chemical taper portion 21 can be obtained as the arithmetic line roughness Ra by measuring a predetermined area of the surface of the roughened brush bristles 10 with a laser microscope. Then, from the measured values of the obtained arithmetic line roughness Ra, the maximum and minimum values are obtained, and the average value is calculated.

The average value of the line roughness Ra of the surface of the chemical taper portion 21 is preferably 0.4 μm to 0.9 μm in the range of 1.0 mm to 1.1 mm from the tip of the first brush bristles 11, and more preferably 0.6 μm to 0.7 μm. Also, in the range of 2.0 mm to 2.1 mm from the tip of the first brush bristles 11, it is preferably 0.5 μm to 1.0 μm in the range of 0.7 μm to 0.8 μm in the range of 2.0 mm to 2.1 mm from the tip of the first brush bristles 11. By forming fine irregularities on the surface of the chemical taper portion 21 so that the line roughness Ra falls within this range, plaque remaining in the oral cavity is efficiently scraped out and becomes entangled and captured on the surface of the chemical taper portion 21, improving plaque removal.

As shown in Figures 4(a) and (b), the tip of the second brush bristles 12, which have a short protruding length H2 from the bristle implantation surface 2a, is formed in a tapered shape in which the radial width gradually decreases toward the tip of the second brush bristles 12. As shown in Figure 4(a), the tip of the second brush bristles 12 includes a tapered mechanical taper portion 22 and a hemispherical rounded tip portion 23.

The mechanical taper portion 22 and the rounded tip portion 23 are formed by mechanically cutting the filament that constitutes the brush bristles 10. Specifically, they are formed by mechanically cutting the end of the filament, which is formed as a flat surface perpendicular to the axial direction, using a grinder equipped with a grinding wheel or the like.

The mechanical taper section 22 has a common shape with the chemical taper section 21 in terms of the tapered shape, but differs in that the axial length H4 at the tip of the second brush bristles 12 is shorter than the axial length H3 of the chemical taper section 21. In other words, the axial length H4 of the mechanical taper section 22 is preferably about 0.2 mm to 2.0 mm, and more preferably about 0.3 mm to 1.0 mm. The protruding length H2 of the second brush bristles 12 from the bristle implantation surface 2a is shorter than the protruding length H1 of the first brush bristles 11 from the bristle implantation surface 2a, and the mechanical taper section 22 with an axial length H4 shorter than that of the chemical taper section 21 is formed at the tip of the second brush bristles 12, so that the second brush bristles 12 act to reinforce the flexibility of the first brush bristles 11. The toothbrush 1 has a stronger bristles stiffness, improving the cleaning feel and durability.

The axial length H5 of the hemispherical rounded tip portion 23 is preferably approximately 0.1 mm to 1.0 mm, and more preferably approximately 0.2 mm to 0.7 mm. The protruding length H2 of the second bristles 12 from the bristle implantation surface 2a is shorter than the protruding length H1 of the first bristles 11 from the bristle implantation surface 2a, and the rounded tip portion 23 is formed at the tip of the second bristles 12 with an axial length H5 shorter than the axial length H3 of the chemical taper portion 21. This acts to reinforce the flexibility of the first bristles 11, just like the second bristles 12 with the mechanical taper portion 22. This strengthens the bristles of the toothbrush 1, improving the cleaning feel and durability.

In addition, like the "axial length H4 of the mechanical taper portion 22" and the "axial length H5 of the rounded tip portion 23," the "axial length H3 of the chemical taper portion 21" refer to the distance from the point that is 80% of the "radial width L5 of the filament" to the tip of the brush bristles 10.

Next, a method for manufacturing the toothbrush 1 will be described.
The manufacturing method of the toothbrush 1 includes a chemical processing step in which the end of the filament is chemically treated to form the brush bristles 10, a bristle implantation step in which a bristle bundle 4 consisting of a plurality of brush bristles 10 is fixed to the bristle implantation hole 3, and a mechanical processing step in which the tip of the bristle bundle 4 is mechanically treated.

In the chemical treatment process of this embodiment, one end of the filament is chemically treated to form brush bristles 10 having a chemical taper section 21 in which the radial width gradually decreases toward the tip. The chemical treatment can be performed by a conventionally known method, and the treatment time, treatment temperature, etc. can be adjusted as appropriate. By the chemical treatment, brush bristles 10 are formed at one end of the filament having a chemical taper section 21 in which the radial width gradually decreases toward the tip, such that widths L1, L2, L3, and L4 are within the above range. At this time, the other end of the filament is not chemically treated in the same way as the one end. Therefore, the other end is held in a flat shape with a flat surface perpendicular to the axial direction of the filament. Here, the other end held in a flat shape is referred to as the flat section.

In the bristle implantation process, multiple brush bristles 10 are bundled together to form bristle bundles 4, and each bristle bundle 4 is fixed to a bristle implantation hole 3 formed in the bristle implantation surface 2a of the head portion 2. The bristle bundles 4 can be fixed by a conventionally known method. For example, multiple brush bristles 10 are folded in half and inserted into the bristle implantation hole 3 together with a flat metal wire.

The brush bristles 10 are folded in half at a position offset from the center in the length direction and fixed to the bristle implantation hole 3. At this time, they are folded in half at a position where the side where the chemical taper section 21 is formed is longer than the side where the flat section is formed. In this way, in the brush bristles 10 fixed to the bristle implantation hole 3, the side where the chemical taper section 21 is formed constitutes the first brush bristles 11 with a long protruding length H1 from the implantation surface 2a, and the side where the flat section is formed constitutes the second brush bristles 12 with a short protruding length H2 from the implantation surface 2a.

Next, mechanical processing is performed on the tip of the bristle bundle 4 of the toothbrush 1 to which the bristle bundle 4 is fixed. An example of a tool for performing mechanical processing is a grinder equipped with a disk-shaped grinding wheel. By rotating the grinder, the tip of the first brush bristles 11 with the long protruding length H1 is physically roughened, and fine irregularities are formed on the surface of the chemical taper portion 21. In addition, the tip of the second brush bristles 12 with the short protruding length H2 is physically cut, and the flat portion is scraped off to form the mechanical taper portion 22 and the rounded tip portion 23.

The mechanical treatment is performed by contacting the grindstone on the disk from the tip of the first brush bristles 11 and the second brush bristles 12 to a predetermined depth. When mechanical treatment is performed on the brush bristles 10, a range of approximately 1.0 mm to 2.0 mm shorter than the set depth to which the grindstone is applied is roughened or cut. For example, if the set depth for the chemical taper portion 21 is set to approximately 6.0 mm, a fine uneven portion is formed in a range of approximately 4.0 mm to approximately 5.0 mm from the tip of the chemical taper portion 21, and the roughening treatment is performed. This is because the chemical taper portion 21 has a sharp shape, and the rotation of the grindstone attached to the grinder makes it easier for the bristles to escape. Therefore, in the following, the actual depth from the tip of the brush bristles 10 where the mechanical treatment tool such as a grindstone contacts is referred to as the grinding depth. In other words, the grind depth is not the preset depth to which the grindstone is applied, but the depth to which the first brush bristles 11 and second brush bristles 12 are actually mechanically processed.

In the toothbrush 1 of this embodiment, the protruding length H1 of the first brush bristles 11 from the bristle implantation surface 2a is approximately 11.0 mm, and the protruding length H2 of the second brush bristles 12 from the bristle implantation surface 2a is approximately 9.0 mm, and a step S1 of approximately 2.0 mm is formed between the tips of the first brush bristles 11 and the second brush bristles 12. Therefore, for example, if the grind depth of the first brush bristles 11 is approximately 3.0 mm, the grind depth of the second brush bristles 12 is approximately 1.0 mm.

In the case of a chemical taper portion 21 that has been roughened by mechanical processing, the deeper the grind depth, the more excellent the appearance of the chemical taper portion 21 tends to be. For example, in the case of brush bristles 10 with a filament diameter of 0.150 mm, if the grind depth of the first brush bristles 11 is approximately 3.0 mm or more, the tips of the first brush bristles 11 do not break or bend, and good fine irregularities are formed on the surface of the chemical taper portion 21. On the other hand, if the grind depth is shallow, some of the tips of the first brush bristles 11 may be broken or bent, but this does not cause any problems in use as a toothbrush 1.

On the flat side of the brush bristles 10, the shape of the tip portion due to mechanical processing differs depending on the grind depth. The rounded tip portion 23 shown in FIG. 4(b) is formed when the grind depth for the second brush bristles 12 is relatively shallow, and the mechanical tapered portion 22 shown in FIG. 4(a) is formed when the grind depth for the second brush bristles 12 is relatively deep. In addition, at a depth intermediate between the grind depth at which the rounded tip portion 23 is formed and the grind depth at which the mechanical tapered portion 22 is formed, the second brush bristles 12 with the rounded tip portion 23 formed and the second brush bristles 12 with the mechanical tapered portion 22 formed are mixed. In other words, as the grind depth increases, the proportion of the mechanical tapered portion 22 tends to be greater than the proportion of the rounded tip portion 23.

In this way, through each process, a toothbrush 1 is obtained in which the surface of the chemical taper portion 21 formed at the tip of the first brush bristles 11 with the long protruding length H1 is rough, and the surface of the mechanical taper portion 22 and the rounded tip portion 23 are formed at the tip of the second brush bristles 12 with the short protruding length H2.

Next, the effects of the toothbrush 1 of this embodiment will be described.
(1) In the toothbrush 1 of this embodiment, the tips of the first bristles 11, which have a long protruding length H1 from the bristle implantation surface 2a, are formed with chemical taper sections 21 by chemically treating the filaments, and the tips of the second bristles 12, which have a short protruding length H2 from the bristle implantation surface 2a, are formed with mechanical taper sections 22 and rounded tip sections 23 by mechanically cutting the filaments. The axial length H3 of the chemical taper section 21 is longer than the axial length H4 of the mechanical taper section 22 and the axial length H5 of the rounded tip section 23.

Therefore, the chemical taper portion 21 can easily reach areas that brush bristles have difficulty reaching, such as between teeth and the gum line. It has excellent gap penetration ability. In addition, the mechanical taper portion 22 and the rounded tip portion 23 are formed at the tip of the second brush bristles 12, which have a short protruding length H2 from the bristles implantation surface 2a, so that the second brush bristles 12 can reinforce the weak bristles of the first brush bristles 11. This improves cleaning performance not only for between teeth and the gum line, but also for tooth surfaces, tooth necks, etc.

(2) The surface of the chemically tapered portion 21 is provided with minute projections and recesses formed by mechanical roughening treatment.
Therefore, the fine unevenness makes the surface of the chemical taper portion 21 rough, and it is possible to effectively trap and scrape off plaque adhering to the tooth surface, the neck of the tooth, between the teeth, etc. A toothbrush 1 having good gap penetration ability due to the chemical taper portion 21 and good plaque removal ability based on the surface condition of the chemical taper portion 21 is obtained.

(3) The surface of the chemical taper portion 21 has an average line roughness Ra of 0.4 μm or more and 0.9 μm or less in the range of 1.0 mm to 1.1 mm from the tip of the brush bristles 10, and an average line roughness Ra of 0.5 μm or more and 1.0 μm or less in the range of 2.0 mm to 2.1 mm from the tip of the brush bristles 10.

Therefore, the fine irregularities formed on the surface of the chemical taper section make the surface of the chemical taper section moderately rough, which allows for effective removal of plaque from the oral cavity.

(4) The tip of the second brush bristles 12 is formed with the mechanical taper portion 22 and the rounded tip portion 23 .
Therefore, compared to when the tip portions of the second bristles 12 are flat, the second bristles 12 softly contact the tooth surface, the neck of the tooth, etc. This makes it difficult to damage the gums, etc., and improves the feel of the toothbrush 1 when in use.

(5) In the manufacturing method of the toothbrush 1 of this embodiment, the brush bristles 10, which have one end of the filament chemically treated to form a chemical taper section 21, are bundled together as a bristle bundle 4 and implanted in the bristle implantation hole 3. The implanted bristle bundle 4 is then mechanically treated with a grinder equipped with a grinding wheel to roughen the surface of the chemical taper section 21 and to cut the side that has been made flat.

Therefore, in the mechanical processing step, the roughening process of the chemical taper portion 21 and the cutting process of the mechanical taper portion 22 and the rounded tip portion 23 can be performed simultaneously. This simplifies the manufacturing process of the toothbrush 1.

(6) In the bristle implantation process, the brush bristles 10 are implanted so that one end and the other end of the brush bristles 10 protrude from the implantation surface 2a by different lengths.
Therefore, by simply using one type of brush bristles 10 in which one end of the filament has been chemically treated, it is possible to easily form first brush bristles 11 having a chemical taper portion 21 and second brush bristles 12 having a mechanical taper portion 22 and a rounded tip portion 23.

(7) Depending on the grind depth in the mechanical process, a mechanical taper portion 22 can be formed on the flat side of the brush bristles 10, a rounded tip portion 23 can be formed, or a mixture of these can be formed.

Therefore, by adjusting the grind depth appropriately, toothbrush 1 can be easily manufactured according to the intended use.
The above embodiment can be modified as follows: The above embodiment and the following modified examples can be applied in combination with each other to the extent that there is no technical contradiction.

- In the toothbrush 1 of the above embodiment, the brush bristles 10, which are folded in half and fixed in the bristle holes 3, have first brush bristles 11 with a long protruding length H1 from the bristle implantation surface 2a and second brush bristles 12 with a short protruding length H2 from the bristle implantation surface 2a, and a step S1 is formed between the tip of the first brush bristles 11 and the tip of the second brush bristles 12. However, the step S1 does not necessarily have to be formed, and the protruding length H1 of the first brush bristles 11 from the bristle implantation surface 2a and the protruding length H2 of the second brush bristles 12 from the bristle implantation surface 2a may be equal.

- The tips of all of the first brush bristles 11 that form the bristle bundle 4 do not have to have the chemical taper portion 21 of the above shape. There may be a mixture of first brush bristles 11 with tapered shapes whose widths L1, L2, L3, and L4 are outside the above range. In addition to first brush bristles 11 with tapered tips, there may also be a mixture of first brush bristles 11 with tips of other shapes.

- In the toothbrush 1 of the above embodiment, one brush bristles 10 is folded in half at a position shifted from the center, so that one of the folded bristles forms the first brush bristles 11 with a long protruding length H1, and the other forms the second brush bristles 12 with a short protruding length H2. However, the brush bristles 10 constituting the bristle bundle 4 are not limited to this. For example, as shown in FIG. 5, long and short brush bristles 10 may be mixed in one bristle bundle 4. In other words, the long brush bristles 10 may be folded in half at the center and fixed to the bristle implantation hole 3 to form only the first brush bristles 11 with a long protruding length H1, and the short brush bristles 10 may be folded in half at the center and fixed to the bristle implantation hole 3 to form only the second brush bristles 12 with a short protruding length H2.

In this case, in the chemical treatment process, both ends of the long brush bristles 10 are chemically treated to form chemical taper portions 21 at both ends, and both ends of the short brush bristles 10 are left flat. In the bristle implantation process, both the long and short brush bristles 10 are folded in half at the center to form a bristle bundle 4 and fixed to the bristle implantation hole 3. Then, by performing a mechanical treatment process similar to the above embodiment, both ends of the long brush bristles 10 can be roughened and both ends of the short brush bristles 10 can be cut.

Note that multiple long and short brush bristles 10 are mixed together in the bristle implantation hole 3 to form a bristle bundle 4 and are fixed in place, but to make it easier to understand how the brush bristles 10 are implanted, both the left and right figures in Figure 5 show a schematic diagram of one brush bristles 10 in the bristle implantation hole 3.

- In FIG. 3, the chemical taper portion 21 is shown as having a shape that is symmetrical with respect to the central axis of the filament, but the shape of the chemical taper portion 21 is not limited to this. For example, it may be asymmetrical with respect to the central axis of the filament, with the tip of the chemical taper portion 21 being at a position offset from the central axis of the filament. In other words, when the filament is viewed from above, the apex of the mountain does not have to be at the center. More specifically, as long as the chemical taper portion 21 is formed in a pointed shape in which the radial width gradually decreases toward the tip of the brush bristles 10, it may be symmetrical or asymmetrical with respect to the central axis. The same applies to the mechanical taper portion 22 in FIG. 4(a) and the rounded tip portion 23 in FIG. 4(b).

The fine concave-convex portion does not have to be formed at a position symmetrical with respect to the axial direction of the brush bristles 10 at the tip of the brush bristles 10, and may be formed at an asymmetrical position.
In the above embodiment, the toothbrush 1 has been described in which the tips of the bristle bundles 4 fixed to all of the bristle implantation holes 3 are substantially parallel to the bristle implantation surface 2a, but the shape of the tips of the bristle bundles 4 is not limited to this. When the row of bristle bundles 4 fixed to the multiple bristle implantation holes 3 arranged in succession in the short direction is taken as a bristle bundle row, the tips of the bristle bundle rows adjacent in the longitudinal direction may form a mountain-shaped mountain-like portion as a whole. For example, the bristle bundles 4 fixed to the bristle implantation holes 3 formed in the second and third rows from the tip side of the head part 2 may be formed into a mountain-shaped portion with the apex being the position where the bristle bundles 4 in the second and third rows face each other, thereby forming a mountain-shaped mountain-like portion. By forming a mountain-shaped portion, it is possible to improve the ability to penetrate into gaps between teeth, the gum margin, and the like.

- The roughening process does not have to be performed using a grinder with an attached grindstone. Any mechanical process can be used to make the surface of the brush bristles 10 rough.

The toothbrush of the present invention will be described in more detail with reference to the following examples. Note that the present invention is not limited to the configurations described in the examples.
<Specifying the Shape of the Chemical Taper Portion 21>
First, a number of prototypes with different shapes and hardnesses of brush bristles 10 were created, and the shape and dimensions of the chemical taper portion 21 were specified.

(Prototype 1)
A bundle of brush bristles 10 made of polybutylene terephthalate and having a circular cross section in the radial direction was folded in two and inserted into the brush bristles 3 formed in the brush bristles surface 2a of the head part 2 having the shape shown in FIG. 1(b), and fixed by fitting a flat wire. The brush bristles 10 used had a chemical taper part 21 formed at one end and a flat part at the other end. The filaments constituting the brush bristles 10 had a width (diameter) of 0.170 mm. The number of brush bristles 10 filled in each brush bristles hole 3 was 25 to 30. The brush bristles 10 were adjusted so that the protruding length H1 of the brush bristles 10 on the chemical taper part 21 side from the brush bristles surface 2a was about 10.5 mm, and the protruding length H2 of the brush bristles 10 on the flat part side from the brush bristles surface 2a was about 9.5 mm.

Then, a grindstone attached to a grinder was applied to the tips of the brush bristles 10 to mechanically roughen the surface of the chemical taper portion 21 to form fine irregularities, and a mechanical cutting process was performed on the flat portion. The grind depth was set to a depth of approximately 2.9 mm from the tip of the bristles (chemical taper portion 21). The toothbrush 1 created in this way was designated as prototype 1.

(Prototype 2)
Prototype 1 was produced in the same manner as prototype 1, except that the protrusion length H1 was adjusted to approximately 12.5 mm, the protrusion length H2 was adjusted to approximately 7.5 mm, and the grind depth was set to a depth of approximately 4.6 mm from the tip of the bristle bundle (chemical taper portion 21).

(Prototype 3)
This was made in the same manner as Prototype 1, except that the brush bristles 10 were not mechanically treated.

(Prototype 4)
The brush was produced in the same manner as prototype 1, except that the brush bristles 10 used had a width (diameter) of 0.150 mm and contained 35 to 40 bristles, and that no mechanical treatment was performed on the brush bristles 10.

(Prototype 5)
The brush was produced in the same manner as prototype 1, except that the brush bristles 10 had a width (diameter) of 0.180 mm and contained 23 to 26 bristles, and that no mechanical treatment was performed on the brush bristles 10.

(Dimensional Measurement of Chemical Taper Portion 21)
The dimensions of the chemical taper portion 21 were measured for prototypes 1, 3 to 5. A microscope (product name VHX-6000, manufactured by Keyence Corporation) was used to measure the dimensions, and measurements were made approximately 30 times for each prototype. The dimensions were measured by measuring the radial widths (diameters) L3 and L4 of the brush bristles 10 at positions 1.0 mm and 2.0 mm from the tip of the chemical taper portion 21. The maximum, minimum, average, and standard deviation (SD) of the measured values for each prototype were calculated as a percentage (%) of the radial width (diameter) L5 of the filament forming the brush bristles 10. The results are shown in Table 1.

From the results of prototypes 1 and 3 in Table 1, the shape of the chemical taper portion 21 was the same regardless of whether or not the surface was roughened by a grindstone attached to the grinder. Specifically, in both prototype 1 in which the chemical taper portion 21 was roughened and prototype 3 in which the chemical taper portion 21 was not roughened, the diameter at a position 1.0 mm from the tip of the chemical taper portion 21 was 25% to 55% of the diameter of the filament. In addition, the diameter at a position 2.0 mm from the tip of the chemical taper portion 21 was 50% to 90% of the diameter of the filament. Furthermore, regardless of whether or not the surface was roughened, the average value of the diameter at a position 1.0 mm from the tip of the chemical taper portion 21 was 37.0 to 39.0% of the diameter of the filament, and the average value of the diameter at a position 2.0 mm from the tip of the chemical taper portion 21 was 63.0 to 69.0% of the diameter of the filament.

In addition, even in prototypes 4 and 5, which have different filament diameters, the shape of the chemical taper portion 21 was the same as in prototypes 1 and 3. Furthermore, based on the results of prototypes 1 and 3, the shape of the chemical taper portion 21 was the same after the roughening treatment, so it can be said that the shape of the chemical taper portion 21 is the same for prototypes 4 and 5, which have brush bristles 10 with different filament diameters that have been roughened, regardless of whether or not the roughening treatment has been performed.

(Measurement of Line Roughness Ra of Chemical Taper Portion 21)
In order to examine how rough the surface of the chemical taper portion 21, in which fine irregularities were formed by the roughening treatment, was, for prototypes 1 to 3, the line roughness Ra of the chemical taper portion 21 was measured. For each of prototypes 1 to 3, five brush bristles 10 implanted in the implantation holes 3 of the head portion 2 were randomly extracted. The arithmetic linear roughness Ra of each brush bristles 10 was measured using a laser microscope in the ranges of 1.0 mm to 1.1 mm and 2.0 mm to 2.1 mm from the tip. From the measured values of the arithmetic linear roughness Ra in each region, the maximum and minimum values were obtained, and the average value and standard deviation (SD) were calculated. The results are shown in Table 2.

From the results of prototypes 1 and 2 in Table 2, the line roughness Ra of the surface of the chemical taper portion 21 was roughly the same regardless of the grind depth. Specifically, in both prototype 1, which has a grind depth of about 2.9 mm, and prototype 2, which has a grind depth of about 4.6 mm, the average line roughness Ra in the range of 1.0 mm to 1.1 mm from the tip of the chemical taper portion 21 was 0.6 μm or more and 0.7 μm or less. In both prototypes 1 and 2, the average line roughness Ra in the range of 2.0 mm to 2.1 mm from the tip of the chemical taper portion 21 was 0.7 μm or more and 0.8 μm or less. This was higher than the average line roughness Ra of 0.183 μm in the range of 1.0 mm to 1.1 mm from the tip of the chemical taper portion 21 in prototype 3, which did not undergo roughening treatment using a grinder, and the average line roughness Ra of 0.247 μm in the range of 1.0 mm to 1.1 mm from the tip of the chemical taper portion 21.

Although the results are not shown, five brush bristles 10 were removed from each of three prototype toothbrushes 1 that had been roughened and measured. As a result, for all prototypes, the average line roughness Ra in the range of 1.0 mm to 1.1 mm from the tip of the chemical taper portion 21 was approximately 0.4 μm or more and 0.9 μm or less. Also, the average line roughness Ra in the range of 2.0 mm to 2.1 mm from the tip of the chemical taper portion 21 was approximately 0.5 μm or more and 1.0 μm or less.

<Evaluation of cleaning ability>
Next, the cleaning ability was evaluated for the toothbrush 1 of the example in which the tips of the brush bristles 10 were mechanically treated, and the toothbrush 1 of the comparative example in which the tips were not mechanically treated.

Example 1
A bundle of brush bristles 10 made of polybutylene terephthalate and having a circular cross section in the radial direction was folded in half and inserted into each of the 22 brush bristles 3 formed on the brush bristles surface 2a of the head part 2 shown in FIG. 1(b), and fixed by fitting a flat wire. The head part had a width of 11.3 mm in the short direction and a brush bristles area of 1.21 ^cm2 . The brush bristles 10 had a chemical taper part 21 formed at one end and a flat shape at the other end. The filaments constituting the brush bristles 10 had a width (diameter) of 0.180 mm. The chemical treatment of the filaments was performed under the same conditions as those of the prototypes 1 to 5. The number of brush bristles 10 filled in each brush bristles hole 3 was 21 to 26. The brush bristles 10 were adjusted so that the protruding length H1 from the bristles implanted surface 2a of the brush bristles 10 on the chemical taper portion 21 side was approximately 11.0 mm, and the protruding length H2 from the bristles implanted surface 2a of the brush bristles 10 on the flat portion side was approximately 9.0 mm.

Then, a grinder was applied to the tip of the brush bristles 10, and the surface of the chemical taper portion 21 was mechanically roughened to form fine irregularities, and a mechanical cutting process was performed on the flat portion. The grind depth was about 2.0 mm from the tip of the chemical taper portion 21. The toothbrush 1 produced in this manner was designated Example 1.

Example 2
The grinding depth was set to about 3.0 mm from the tip of the chemical taper portion 21, but the grinding depth was the same as in Example 1.

Example 3
The grinding depth was set to about 3.5 mm from the tip of the chemical taper portion 21, but the grinding depth was the same as in Example 1.

Example 4
The filaments constituting the brush bristles 10 had a width (diameter) of 0.170 mm, and were produced in the same manner as in Example 1, except that the number of filaments packed was 23 to 32.

Example 5
The grinding depth was set to about 3.0 mm from the tip of the chemical taper portion 21, but the grinding depth was the same as in Example 4.

Example 6
The grinding depth was set to about 3.5 mm from the tip of the chemical taper portion 21, but the grinding depth was the same as in Example 4.

(Example 7)
The filaments constituting the brush bristles 10 had a width (diameter) of 0.150 mm, and were produced in the same manner as in Example 1, except that the number of filaments packed was 30 to 38.

(Example 8)
The grinding depth was set to about 3.0 mm from the tip of the chemical taper portion 21, and the other factors were the same as in Example 7.

(Example 9)
The grinding depth was set to about 3.5 mm from the tip of the chemical taper portion 21, but the grinding depth was the same as in Example 7.

(Comparative Example 1)
The brush was produced in the same manner as in Example 6, except that the tips of the brush bristles 10 were not subjected to a grinder, and the surface and flat portion of the chemical taper portion 21 were not subjected to mechanical treatment.

(Comparative Example 2)
The brush was produced in the same manner as in Example 9, except that the tips of the brush bristles 10 were not subjected to a grinder, and the surface and flat portion of the chemical taper portion 21 were not subjected to mechanical treatment.

(Evaluation of the shape of the chemical taper portion 21, the portion on the flat shape side)
For the toothbrushes 1 of Examples 1 to 9, the shapes of the chemical taper portion 21 and the portion that had a flat shape during the chemical treatment were evaluated.

The chemical taper portion 21 was evaluated for changes in the surface condition due to the roughening treatment. The evaluation criteria were as follows. The results are shown in Table 3.

◯: The entire surface is evenly rough.
△: The entire surface is rough, but there are some areas where the tips of the bristles are broken or bent.

The flat side was evaluated for how the tip shape changed as a result of the cutting process. Brush bristles 10 whose flat portion had become almost entirely a mechanically tapered portion 22 were classified as "tapered," brush bristles whose flat portion had become almost entirely a rounded portion 23 were classified as "rounded," and brush bristles that had a mixture of mechanically tapered portion 22 and rounded portion 23 were classified as "mixed." The results are shown in Table 3.

When the chemical taper portion 21 was roughened, fine irregularities were formed on the surface of the chemical taper portion 21, and the surface was satisfactorily roughened, regardless of the filament diameter or grind depth, in all toothbrushes 1. Among them, in the toothbrushes 1 with filament diameters of 0.18 mm and 0.17 mm and a grind depth of 3.5 mm or more, there were no broken or bent bristles, and the external shape of the chemical taper portion 21 was well maintained. In the toothbrushes 1 with a relatively shallow grind depth, the bristles had some broken or bent bristles at the tips of the first brush bristles 11, but this was not so severe as to interfere with the use of the toothbrush 1.

In addition, on the flat side, the tip shape due to mechanical processing differed depending on the grind depth. The shallower the grind depth, the easier it was to form a rounded tip 23, and the deeper the grind depth, the greater the proportion of mechanically tapered portions 22.

(Cleaning Ability Evaluation Test 1)
The toothbrushes 1 of Example 6 and Comparative Example 1, and Example 9 and Comparative Example 2 were subjected to cleaning performance evaluation test 1. The cleaning performance evaluation test 1 was performed by preparing a jaw model coated with artificial plaque, and having the robot hold the toothbrushes 1 of Example 6 and Comparative Example 1, and brushing the cheek side of the jaw model (upper jaw) #26 to #23 for 2 seconds per tooth with an average brushing pressure of 200 g, a stroke of 20 mm, and a speed equivalent to 150 rpm. After brushing, the removal rate (%) of the artificial plaque on the entire tooth surface and between the teeth was calculated. The same was performed for Example 9 and Comparative Example 2. The results are shown in Table 4 and FIG. 6.

From Table 4 and Fig. 6, in the case of the brush bristles 10 with a filament diameter of 0.17 mm, the artificial plaque removal rate (%) on the tooth surface was 2.6% higher in Example 6, which was mechanically treated, than in Comparative Example 1, which was not mechanically treated. Also, the artificial plaque removal rate (%) between teeth was 42.9% higher in Example 6, which was mechanically treated, than in Comparative Example 1, which was not mechanically treated. This is considered to be due to the fact that the brush bristles 10 with the chemical taper portion 21 have excellent penetration into gaps between teeth and the gingival margin, and that the fine unevenness formed on the surface of the chemical taper portion 21 improves the plaque removal ability of the brush bristles 10 that penetrate into the gaps. The same tendency was observed in Example 9 and Comparative Example 2, which used brush bristles 10 with a filament diameter of 0.15 mm.

The chemical taper section 21 formed at the tip of the brush bristles 10 makes it easier for the brush bristles 10 to reach areas that are difficult to reach, and the fine unevenness formed on the surface acts to scrape off plaque, making it possible to efficiently remove plaque from gaps. In addition, the tip shape of the flat section side, which protrudes less from the bristles surface 2a than the chemical taper section 21, is formed as a mechanical taper section 22, which has a shorter axial length than the chemical taper section 21, and a rounded tip section 23. This means that the mechanical taper section 22 and rounded tip section 23 act to reinforce the weak bristles of the sharp-pointed chemical taper section 21, and it is believed that plaque removal is improved not only between teeth, but also on the tooth surface, neck, etc.

(Cleaning Ability Evaluation Test 2)
The cleaning performance evaluation test 2 was carried out on the brush bristles 10 of the toothbrush 1 of Example 6 and Comparative Example 1. The cleaning performance evaluation test 2 was carried out to verify the extent to which the roughened chemical taper portion 21 could entangle and capture plaque. A colored powder of a spray occluder for occlusion check (Pascal, USA) was applied to a wrap, and the toothbrush 1 of Example 6 and Comparative Example 1 was moved back and forth on the occluder at intervals of 5 cm. The tip of the bristles of the toothbrush 1 after the back and forth movement was photographed with a microscope (product name VHX-6000, manufactured by Keyence Corporation), and a color analysis was carried out with Photoshop (registered trademark). For the color analysis, the photographed image was binarized with Photoshop (registered trademark), and the occluder adhesion rate (%) was calculated. The results are shown in Table 5 and FIG. 7.

From the results of Table 5, in the brush bristles 10 of the toothbrush 1 of Example 6 in which the surface of the chemical taper portion 21 is formed with fine unevenness and the line roughness Ra is large, the occluded adhesion rate was increased by more than two times compared to the brush bristles 10 of the toothbrush 1 of Comparative Example 1 in which the fine unevenness is not formed. In the image of FIG. 7(a), it was observed that the occluded adhered to the surface of the brush bristles 10 over the entire length of the roughened portion of the chemical taper portion 21. In contrast, in the image of FIG. 7(b), the occluded adhered only to the tip of the brush bristles 10. This shows that the roughened surface of the chemical taper portion 21 efficiently scrapes off plaque remaining in the oral cavity and traps it on the surface of the chemical taper portion 21.

H1, H2...protrusion length L1, L2, L3, L4, L5...width 1...toothbrush 2...head portion 2a...bristle implantation surface 3...bristle implantation hole 4...bristle bundle 10...brush bristles 11...first brush bristles 12...second brush bristles 21...chemical taper portion (first tip portion)
22... Mechanical taper portion (second tip portion)
23...Rounded tip (second tip)

Claims (5)

A toothbrush in which a bristle bundle consisting of a plurality of brush bristles is fixed to each of a plurality of bristle implantation holes formed in a bristle implantation surface of a head portion,
The brush bristles include first brush bristles having a first pointed tip portion at a tip end, the first tip portion having a radial width gradually decreasing toward the tip, and second brush bristles having a second tapered tip portion at a tip end, the second tip portion having a radial width gradually decreasing toward the tip and a shorter axial length than the first tip portion,
the first tip portion is formed in a tapered shape such that a width of a radial cross section at a position 1.0 mm from the tip of the first brush bristles is 25% to 55% of a radial width of a filament forming the first brush bristles, and a width of a radial cross section at a position 2.0 mm from the tip of the first brush bristles is 50% to 90% of a radial width of a filament forming the first brush bristles;
A fine uneven portion is formed on the surface of the first tip portion,
The toothbrush, characterized in that the second brush bristles include a mixture of bristles whose second tip portion is formed in a hemispherical shape and bristles whose second tip portion is formed in a conical shape. The toothbrush according to claim 1, characterized in that the length of the first brush bristles protruding from the bristle implantation hole is longer than the length of the second brush bristles protruding from the bristle implantation hole. The toothbrush according to claim 1 or 2, characterized in that the bristle bundle is made up of multiple brush bristles, one end of which has the first tip and the other end of which has the second tip, folded in half and fixed to the bristle implantation hole. The toothbrush according to any one of claims 1 to 3, characterized in that the surface of the first tip portion has an average line roughness Ra of 0.4 μm or more and 0.9 μm or less in the range of 1.0 mm to 1.1 mm from the tip of the brush bristles. The toothbrush according to any one of claims 1 to 4, characterized in that the surface of the first tip portion has an average line roughness Ra of 0.5 μm or more and 1.0 μm or less in a range of 2.0 mm to 2.1 mm from the tip of the brush bristles.