toothbrush

Abstract

To provide a toothbrush capable of improving quantity and quality of foams while toothbrushing and thus capable of increasing cleaning effect.SOLUTION: An inner bristle bundle group 5 is composed of a bristle bundle 50 which does not have twist in a lengthwise direction and includes tapered bristles 51, and the inner bristle bundle group 5 is set higher than outer bristle bundle groups 6A / 6B. Height of the respective bristle bundles of the inner bristle bundle group 5 and height of the respective bristle bundles of the outer bristle bundle groups 6A / 6B are set almost the same; outlines composed of the inner bristle bundle group 5 and the left and right outside bristle bundle groups 6A, 6B have nearly projecting step shapes when seen from an axial direction of the toothbrush.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a toothbrush used for brushing teeth. [Background technology]

[0002] Conventionally, there has been a demand for toothbrushes with high foaming power to create a lather in toothpaste during brushing. Therefore, a technique is known to enhance foaming power by making the contour shape of the tips of the bristle bundles, obtained by cutting the bristle bundles planted on the head of the toothbrush along a plane parallel to the long axis of the handle, jagged like the teeth of a saw (see, for example, Patent Document 1).

[0003] However, when toothpaste is applied to a toothbrush with jagged bristle tips, the toothpaste does not adhere well to bristles other than those on the jagged, protruding parts. This causes the toothpaste to be scattered, reducing its ability to stay on the intended cleaning area. Furthermore, the cleaning effect of foam depends not only on the amount of foam but also on its quality. The smaller the bubbles, the easier it is for the toothpaste to reach fine areas such as between teeth, improving the cleaning effect. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2003-250632 [Overview of the project] [Problems that the invention aims to solve]

[0005] Therefore, in view of the above circumstances, the present invention aims to provide a toothbrush that can improve the quantity and quality of foam during brushing, thereby enhancing the cleaning effect. [Means for solving the problem]

[0006] In view of the current situation, the inventors have conducted diligent studies and have found that by providing a group of bristle bundles consisting of tapered bristles that do not twist along the length direction (bristle that twist have a shape in which the cross-section changes in the axial direction, causing adjacent bristles to interfere with each other and the bristle bundle to lose its flexibility), the flexibility and tapered shape of the tip allow air to be efficiently taken in into the gaps between the tapered bristles, enabling the toothpaste to be finely foamed, and the foamed toothpaste to remain attached to the tapered tip portion, enabling effective cleaning of the tooth surface and interdental spaces. Furthermore, by arranging a group of bristle bundles consisting of lower bristles adjacent to the outside, the foamed toothpaste can be kept in the area of ​​the inner group of tapered bristles without being swept away or hindering the intake of air from the side, thereby enhancing the cleaning effect, and thus the present invention has been completed.

[0007] This invention encompasses the following inventions. (1) A toothbrush comprising an inner bristle bundle group located approximately in the center of the head portion and an outer bristle bundle group located adjacent to the inner bristle bundle group, wherein the inner bristle bundle group consists of bristle bundles that do not have a twist along the length direction and include tapered bristles, and the height of the inner bristle bundle group is set higher than the height of the outer bristle bundle group.

[0008] (2) The height of each hair bundle in the inner hair bundle group and the height of each hair bundle in the outer hair bundle group are set to approximately the same height. The toothbrush according to (1), wherein, when viewed from the axial direction of the toothbrush, the contour line formed by the inner bristle bundle and the left and right outer bristle bundles has a substantially convex stepped shape.

[0009] (3) The toothbrush according to (1) or (2), wherein the height of the inner bristle bundle is set to be 1 to 3 mm higher than the height of the outer bristle bundle.

[0010] (4) The value obtained by multiplying the area of the inner region surrounded by the virtual line connecting the outer edges of the implant holes arranged outside the inner implant group in a plan view seen from the implant surface by the difference between the height of the inner hair bundle group and the height of the outer hair bundle group (hereinafter referred to as "inner protruding volume") is 250 mm 3 The toothbrush according to any one of (1) to (3) below.

[0011] (5) The toothbrush according to any one of (1) to (4), wherein 1 to 3 rows of the hair bundles arranged in a row at intervals in the longitudinal direction of the toothbrush are provided in the short hand direction in the inner implant group.

[0012] (6) The toothbrush according to any one of (1) to (5), wherein the outer hair bundle group is composed of hair bundles including tapered hairs with a tapered tip or rounded tip hairs. [Advantages of the Invention]

[0013] The toothbrush according to the present invention thus formed has an inner hair bundle group arranged substantially at the center of the head portion, which has no twist along the length direction and is composed of hair bundles including tapered hairs with a tapered tip. Adjacent to the outside thereof, an outer hair bundle group having a lower height than the inner hair bundle group is arranged. Therefore, due to the inner hair bundle group, due to its flexibility and tapered shape, air can be taken in between the hairs, the dentifrice can be finely foamed, and good foaming can be obtained. At the same time, the dentifrice foamed at the tapered tip side portion can be maintained in an attached state, and the tooth surface and the interdental area can be effectively cleaned.

[0014] Furthermore, due to the presence of the outer hair bundle group, the dentifrice foamed by the inner hair bundle group can be maintained while supplying air to the region of the inner hair bundle group, that is, the targeted cleaning site, during toothbrushing, without scattering the dentifrice foamed by the inner hair bundle group, and the above excellent cleaning effect can be maintained. Thus, the toothbrush of the present invention improves the amount and quality of the dentifrice foam during toothbrushing, obtains an excellent cleaning effect, and has good interdental insertion and cleaning properties because the inner hair bundle group with a high height is composed of tapered hairs.

[0015] Furthermore, if the height of each bristle in the inner bristle group and the height of each bristle in the outer bristle group are set to approximately the same height, and the contour line formed by the inner bristle group and the left and right outer bristle groups is approximately a convex stepped shape when viewed from the axial direction of the toothbrush, the structure will not sweep away the toothpaste foamed up by the inner bristle group, will not obstruct the intake of air, and will be able to easily retain the foamed toothpaste in the area of ​​the inner bristle group.

[0016] Furthermore, if the height difference between the inner bristle bundle and the outer bristle bundle is less than 1 mm, depending on the brushing method, the supply of air may be obstructed, and the foaming by the inner bristle bundle may not be sufficient, increasing the risk that the foamed toothpaste will be swept away by the outer bristle bundle. Also, if the height difference exceeds 3 mm, the effect of the outer bristle bundle in retaining the foamed toothpaste in the area of ​​the inner tapered bristle bundle is reduced, and the foamed toothpaste will be scattered around by the inner bristle bundle itself, increasing the risk that the cleaning effect will not be sustained.

[0017] Furthermore, the volume of the internal protrusion mentioned above is 250 mm 3 If the size exceeds a certain limit, the toothpaste foamed up by the inner bristle bundles themselves will scatter into the surrounding area, increasing the risk that the cleaning effect will not last. [Brief explanation of the drawing]

[0018] [Figure 1] A perspective view showing a toothbrush according to a typical embodiment of the present invention. [Figure 2] A plan view of the main part showing the head section. [Figure 3] A side view of the toothbrush, seen from the tip end. [Figure 4] An explanatory diagram showing how toothpaste foams up and is retained in the area of ​​the inner bristle bundles. [Figure 5] A diagram illustrating the key features of tapered bristles. [Figure 6] An explanatory diagram illustrating the volume of the internal protrusion. [Figure 7] An explanatory diagram showing the hair implantation morphology of the samples from Examples 1 to 5. [Figure 8] An explanatory diagram showing the hair implantation morphology of the samples from Examples 6 to 10. [Figure 9] An explanatory diagram showing the hair implantation morphology of the samples in Comparative Examples 1 to 6. [Figure 10] An explanatory diagram showing the experimental method. [Figure 11] A photo of the back teeth after brushing. [Figure 12] An explanatory diagram showing the extracted area where the bubbles spread. [Figure 13] An explanatory diagram showing how 10 large bubbles are picked out. [Figure 14] A graph showing the relationship between the area of ​​the foam zone and the diameter of the top 10 foams. [Figure 15] A graph showing the relationship between the volume of the convex portion and the foam quality. [Modes for carrying out the invention]

[0019] Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0020] As shown in Figures 1 to 3, the toothbrush 1 of the present invention comprises a substantially rod-shaped handle 2 and a head portion 3 provided at the tip of the handle 2. The head portion 3 comprises a substantially flat bristle base 4, an inner bristle bundle group 5 consisting of a plurality of bristle bundles 50 projecting from the approximate center of the bristle base 4, and outer bristle bundle groups 6A and 6B consisting of a plurality of bristle bundles 60 projecting outward adjacent to the inner bristle bundle group 5.

[0021] In this example, toothbrush 1 is a manual toothbrush in which the head 3, handle 2, and (neck) are integrally molded from synthetic resin. However, it may also be an electric toothbrush in which the toothbrush cleaning body, consisting of the head and neck, is connected to the tip of the main body, which serves as a gripping part containing a drive mechanism. Other forms are also acceptable, of course.

[0022] The bristle bundles 50 constituting the inner bristle bundle group 5 are bristle bundles that do not have a twist along the length direction and include tapered bristles 51 (filaments with tapered tips), and are taller than the bristle bundles 60 constituting the outer bristle bundle group 6A (6B). As shown in Figure 4, when brushing, the bristle bundles 50 of the inner bristle bundle group 5, due to their flexibility and tapered tip shape, enhance the mixing effect of the toothpaste 9 with air, allowing the toothpaste 9 to foam finely and produce good quality foam (foam E consisting of air bubbles 90). The symbol T indicates a tooth. The bristles constituting the bristle bundles 50 may also include bristles other than tapered bristles.

[0023] The bristle bundles 60 that make up the outer bristle bundles 6A and 6B are shorter than the bristle bundles 50, and the height of the outer bristle bundles 6A and 6B is set lower than the height of the inner bristle bundle 5. By providing outer bristle bundles 6A and 6B that are lower than the inner bristle bundle 5, as shown in Figure 4, the foamed toothpaste created by the inner bristle bundle 5 is not swept away to the sides as described above, and air is supplied to the area of ​​the inner bristle bundle 5, while the foamed toothpaste is maintained in the area of ​​the inner bristle bundle 5, i.e., the targeted cleaning area, during brushing, thereby maintaining the excellent cleaning effect described above.

[0024] Furthermore, the inner bristle bundle group 5, being made up of tapered bristles, is easily bent and soft, making it prone to collapsing. This could lead to larger movements that scatter the foamed toothpaste and reduce the cleaning effect. However, the presence of the outer bristle bundle groups 6A and 6B provides lateral support to the bristle bundle 50, preventing the toothpaste from being scattered and reducing the cleaning effect.

[0025] As shown in Figure 2, in this example, the inner bristle bundle group 5 has two rows of bristle bundles 50 arranged in the longitudinal direction (longitudinal direction of the toothbrush) of the bristle base 4, and two rows in the transverse direction (short direction). However, it may be one row or three or more rows. Providing multiple rows (preferably two or three rows) is preferable because it maintains the transverse width of the area of ​​the inner bristle bundle group 5, and provides an excellent retention effect for the toothpaste. Specifically, it is preferable to set the width to 2 mm or more. Also, in this example, the outer bristle bundle groups 6A and 6B are provided in one row each, but they may also be multiple rows.

[0026] In this example, outer bristle bundles 6A and 6B are provided adjacent to the left and right sides of the inner bristle bundle 5. However, similar outer bristle bundles may also be provided adjacent to the tip and base ends of the toothbrush, in addition to, or instead of, the left and right sides. Furthermore, in this invention, as long as there is a combination of an inner bristle bundle and an adjacent outer bristle bundle, other bristle bundles may exist.

[0027] The height difference H between the inner hair bundle group 5 and the outer hair bundle groups 6A / 6B is preferably set to 1 to 3 mm. The heights of the outer hair bundle group 5 and the inner hair bundle groups 6A and 6B refer to the height of the tallest hair bundle among the multiple hair bundles that make up each hair bundle group. The heights of the hair bundles 50 and 60 refer to the height of the tallest hair among the hairs that make up each hair bundle.

[0028] In this example, the hair bundles 60 that make up the outer hair bundle groups 6A and 6B are shown to be composed of rounded hairs with a nearly constant thickness and a rounded tip, or hairs with a flat tip. However, the hairs that make up these hair bundles 60 are not particularly limited to being hair-shaped, and may have shapes other than rounded or flat-tipped hairs. Similar to the hair bundles 50, tapered hairs can also be used.

[0029] Each bundle of hair 50 or 60 is formed by folding 5 to 100 filaments, each with a diameter of approximately 0.1 to 0.3 mm (excluding the tapered portion in the case of tapered hair), in half and implanting them into the implantation holes formed on the implantation base 4 using a flat wire. The thickness of the base of the hair bundle (the inner diameter of the implantation hole) is set to approximately 1 to 1.5 mm in diameter. It is not limited to those made with a flat wire; bundles of hair 50 or 60 can also be made using fusion bonding or in-mold methods, etc., without using a flat wire.

[0030] The material of each filament in the bristle bundle 50 / 60 is not particularly limited and may be artificial bristles made of resin materials such as nylon, polyester, or polyolefin, or natural bristles such as pig bristles. For example, saturated polyester is suitable for the tapered bristles 51, and nylon is suitable for the rounded-tip bristles. These may also be combined. In addition, a wide range of known shapes, such as cross-sectional shape and cross-sectional size, can be adopted.

[0031] Figure 5 is an explanatory diagram showing an example of the shape of the tip portion of the tapered bristles 51. The tip portion 51a of the tapered bristles 51 is defined as a region with a tapered shape that gradually decreases in diameter towards the tip. The diameter d1 on the proximal end side of the tip portion 51a is, for example, 0.1 to 0.3 mm, and the diameter d2 at the tip is, for example, 0.002 to 0.05 mm.

[0032] The axial length L1 of the tapered tip portion 51a is set to a length that exceeds, for example, 1 to 4 mm, preferably the dimension H (preferably 1 to 3 mm). This creates a gap at the base of the taper between the inner bristle group 5 and the outer bristle group 6, allowing for finer lathering through more flexible bending by the tapered bristles 51, and further enhancing the ability to retain the foamed toothpaste in the area of ​​the inner bristle group 5.

[0033] The heights of the multiple bristle bundles 50 of the inner bristle bundle group 5 are set to be approximately the same height. Similarly, the multiple bristle bundles 60 of the outer bristle bundle groups 6A / 6B are also set to be approximately the same height. In this way, when viewed from the axial direction of the toothbrush 1, the contour line formed by the inner bristle bundle group 5 and the left and right outer bristle bundle groups 6A and 6B is configured to have a roughly convex stepped shape. This makes it easier to keep the foamed toothpaste spread stably across the entire tip area of ​​the inner bristle bundle group 5.

[0034] As shown in Figure 6, in a plan view from the hair implantation surface, the area of ​​the inner region R1 enclosed by the imaginary line L1 that connects the outer edges of the hair implantation holes 50a located on the outside of the inner hair implantation group 5 (in this example, all hair implantation holes are included because there are two rows of hair implantation rows; all hair implantation holes are also included if there is one row) is multiplied by the height difference H between the inner hair bundle group 5 and the outer hair bundle groups 6A / 6B as described above. This value is defined as the inner protrusion volume, and if this inner protrusion volume is 250 mm², 3 The following is preferable. This inner hair bundle volume represents, so to speak, the volume of the portion where the inner hair bundle group 5 protrudes more than the outer hair bundle groups 6A and 6B. If the volume becomes too large, there is a high risk that the toothpaste foamed up by the inner hair bundle group 5 itself will scatter into the surrounding area.

[0035] Although embodiments of the present invention have been described above, the present invention is not limited in any way to these embodiments, and can be implemented in various forms without departing from the spirit of the invention. [Examples]

[0036] The following describes the results of evaluating the quantity and quality of foam during brushing using toothbrush samples from Examples 1-10 (bristle configurations shown in Figures 7 and 8) and Comparative Examples 1-6 (bristle configurations shown in Figure 9).

[0037] (Toothbrush sample) (Example 1) In Example 1, the inner hair bundles consist of bristles made of saturated polyester resin, with a square cross-section, no twist, and one end chemically tapered. The outer hair bundles consist of bristles made of saturated polyester resin, with no twist, straight, and rounded tips. These hair bundles are implanted in the implantation pattern shown in "Example 1" in Figure 7, and the height difference between the inner and outer hair bundles is 2.5 mm, as shown in "Hair Length Difference" in Table 1. The axial length (L1) of the tapered tip portion is 2.5 mm, as shown in "Taper Length" in Table 1. In a plan view from the implantation surface, the area of ​​the inner region (R1) enclosed by imaginary lines connecting the outer edges of the implanted holes located on the outside of the inner hair bundle by the shortest distance is 83.2 mm², as shown in "Convex Area" in Table 1. 2and the value obtained by multiplying this by the above "pile height difference" (inner protruding volume) is 208.1 mm as shown in the "protrusion volume" in Table 1 3 It is.

[0038] (Example 2) In Example 2, the hairs of the inner hair bundle group include those made of saturated polyester resin, having a round cross-section, being both-end chemically tapered hairs without twist and with the tips cut, and the hairs of the outer hair bundle group are straight tip-rounded hairs made of saturated polyester resin without twist. These hair bundles are implanted in the implanting pattern shown in "Example 2" of FIG. 7, and the above "pile height difference" is 2.0 mm. The above L1 is 3 mm as shown in the "taper length" in Table 1. The above "protrusion area" is 58.4 mm 2 and the "protrusion volume" is 116.8 mm 3 It is.

[0039] (Example 3) In Example 3, the hairs of the inner hair bundle group are mechanical (by mechanical polishing) tapered hairs made of saturated polyester resin with a round cross-section and without twist, and the hairs of the outer hair bundle group are straight tip-rounded hairs made of saturated polyester resin without twist. These hair bundles are implanted in the implanting pattern shown in "Example 3" of FIG. 7, and the above "pile height difference" is 2.0 mm. The above L1 is 3 mm as shown in the "taper length" in Table 1. The above "protrusion area" is 80.8 mm 2 and the "protrusion volume" is 161.6 mm 3 It is.

[0040] (Example 4) In Example 4, the hairs of the inner hair bundle group are single-end chemically tapered hairs made of saturated polyester resin with a round cross-section and without twist, and the hairs of the outer hair bundle group are straight tip-rounded hairs made of saturated polyester resin without twist. These hair bundles are implanted in the implanting pattern shown in "Example 4" of FIG. 7, and the above "pile height difference" is 2.5 mm. The above L1 is 4 mm as shown in the "taper length" in Table 1. The above "protrusion area" is 91.5 mm 2 and the "protrusion volume" is 228.7 mm 3 It is.

[0041] (Example 5) In Example 5, the inner hair bundles consist of hair made of saturated polyester resin, with a round cross-section, no twist, and chemically tapered ends. The outer hair bundles consist of hair made of saturated polyester resin, with no twist, and chemically tapered ends. These hair bundles are implanted in the hair implantation pattern shown in "Example 5" in Figure 7, and the "hair length difference" is 1.0 mm. The L1 is 4 mm, as shown in the "taper length" in Table 1. The "protrusion area" is 92.4 mm². 2 Therefore, the "volume of the convex part" is 92.4 mm³. 3 That is the case.

[0042] (Example 6) In Example 6, the inner hair bundles consist of hair made of saturated polyester resin, with a round cross-section, no twisting, chemically tapered ends, and cut tips. The outer hair bundles consist of hair made of saturated polyester resin, with no twisting, straight, and rounded ends. These hair bundles are implanted in the hair implantation pattern shown in "Example 6" in Figure 8, and the "hair length difference" is 2.0 mm. The L1 is 3 mm, as shown in the "taper length" in Table 1. The "protrusion area" is 38.1 mm². 2 Therefore, the "volume of the convex part" is 76.1 mm³. 3 That is the case.

[0043] (Example 7) In Example 7, the inner hair bundles consist of hair made of saturated polyester resin, with a round cross-section, no twisting, chemically tapered ends, and cut tips. The outer hair bundles consist of hair made of saturated polyester resin, with no twisting, straight, and rounded ends. These hair bundles are implanted in the hair implantation pattern shown in "Example 7" in Figure 8, and the "hair length difference" is 2.0 mm. The L1 is 3 mm, as shown in the "taper length" in Table 1. The "protrusion area" is 29.5 mm². 2 Therefore, the "volume of the convex part" is 59.0 mm³. 3 That is the case.

[0044] (Example 8) In Example 8, the inner hair bundles consist of hair made of saturated polyester resin, with a round cross-section, no twist, and one end chemically tapered. The outer hair bundles consist of hair made of saturated polyester resin, with no twist, straight, and rounded ends. These hair bundles are implanted in the hair implantation pattern shown in "Example 8" in Figure 8, and the "hair length difference" is 2.5 mm. The L1 is 4 mm, as shown in the "taper length" in Table 1. The "protrusion area" is 29.9 mm². 2 Therefore, the "volume of the convex part" is 74.6 mm³. 3 That is the case.

[0045] (Example 9) In Example 9, the inner hair bundles consist of bristles made of saturated polyester resin, with a round cross-section, no twist, and chemically tapered at one end. The outer hair bundles consist of bristles made of saturated polyester resin, with no twist, straight, and rounded ends. These hair bundles are implanted in the implantation pattern shown in "Example 9" in Figure 8, and the "hair length difference" is 2.5 mm. The L1 is 4 mm, as shown in the "taper length" in Table 1. The "protrusion area" is 29.9 mm². 2 Therefore, the "volume of the convex part" is 74.6 mm³. 3 That is the case.

[0046] (Example 10) In Example 10, the inner hair bundles consist of bristles made of saturated polyester resin, with a square cross-section, no twist, and chemically tapered at one end. The outer hair bundles consist of bristles made of saturated polyester resin, with no twist, straight, and rounded ends. These hair bundles are implanted in the implantation pattern shown in "Example 10" in Figure 8, and the "hair length difference" is 2.5 mm. The L1 is 2.5 mm, as shown in the "taper length" in Table 1. The "protrusion area" is 32.8 mm². 2 Therefore, the "volume of the convex part" is 82.0 mm³. 3 That is the case.

[0047] (Comparative Example 1) Comparative Example 1 consists of inner hair bundles made of saturated polyester resin, with twisted, chemically tapered ends, and outer hair bundles made of saturated polyester resin, with straight, rounded ends and no twisting. These hair bundles are implanted in the implantation pattern shown in "Comparative Example 1" in Figure 9, and the "hair length difference" is 5.0 mm. The L1 is 4 mm, as shown in the "taper length" in Table 1. The "protrusion area" is 57.3 mm². 2 Therefore, the "volume of the convex part" is 286.6 mm³. 3 That is the case.

[0048] (Comparative Example 2) In Comparative Example 2, the inner hair bundles consist of twisted, rounded-tipped hairs made of saturated polyester resin, while the outer hair bundles consist of straight, rounded-tipped hairs made of saturated polyester resin without twisting. These hair bundles are implanted in the hair implantation pattern shown in "Comparative Example 2" in Figure 9, and the "hair length difference" is 0.0 mm. In other words, there is no "protrusion area" or "protrusion volume."

[0049] (Comparative Example 3) Comparative Example 3 consists of inner hair bundles made of saturated polyester resin, with twisted, chemically tapered ends, and outer hair bundles made of saturated polyester resin, with straight, rounded ends and no twisting. These hair bundles are implanted in the implantation pattern shown in "Comparative Example 3" in Figure 9, and the "hair length difference" is 5.0 mm. The L1 is 4 mm, as shown in the "taper length" in Table 1. The "protrusion area" is 76.4 mm². 2 Therefore, the "volume of the convex part" is 382.0 mm³. 3 That is the case.

[0050] (Comparative Example 4) Comparative Example 4 consists of inner hair bundles made of polyester / polyether, without twisting, and branched at the tip into three strands. Similarly, the outer hair bundles are made of saturated polyester resin / nylon, without twisting, and branched at the tip into three strands. These hair bundles are implanted in the implantation pattern shown in "Comparative Example 4" in Figure 9, and the "hair length difference" is 0.5 mm. Since the hairs are not tapered, the above L1 does not exist. The above "protrusion area" is 83.2 mm². 2Therefore, the "volume of the convex part" is 41.6 mm³. 3 That is the case.

[0051] (Comparative Example 5) Comparative Example 5 consists of nylon hair bundles, both straight, rounded-tipped hairs without twisting, and nylon hair bundles, both straight, rounded-tipped hairs without twisting. These hair bundles are implanted in the implantation pattern shown in "Comparative Example 5" in Figure 9, and the "hair length difference" is 1.5 mm. Since the hairs are not tapered, the above L1 does not exist. The "protrusion area" is 77.9 mm². 2 Therefore, the "volume of the convex part" is 116.8 mm³. 3 That is the case.

[0052] (Comparative Example 6) Comparative Example 6 consists of inner hair bundles made of saturated polyester resin, with twisted, chemically tapered ends, and outer hair bundles made of saturated polyester resin, with no twisting, straight, rounded ends. These hair bundles are implanted in the implantation pattern shown in "Comparative Example 6" in Figure 9, and the "hair length difference" is 5.0 mm. The L1 is 4 mm, as shown in the "taper length" in Table 1. The "protrusion area" is 76.4 mm². 2 Therefore, the "volume of the convex part" is 382.0 mm³. 3 That is the case.

[0053] [Table 1]

[0054] (Experimental method) Figure 10 is an explanatory diagram showing an experimental method for evaluating the quantity and quality of foam during toothbrushing. As illustrated in Figure 10, the head portion 3 according to Examples 1 to 10 and Comparative Examples 1 to 6 were pressed against the molars T1 and T2 of the tooth model D, respectively, and brushing was performed with a load of 200g, a sliding distance of 20mm, 10 sliding cycles, and a sliding speed of approximately 1.67 reciprocations per second (100rpm).

[0055] For the test solution applied to molars T1 and T2, we used an aqueous solution prepared by diluting Sunstar Inc.'s "Toki no Chikara" paste with water in a 1:4 ratio, to which a plaque disclosing agent was added.

[0056] Figure 11 is a photograph of molar T1 taken with a microscope after brushing as shown in Figure 10. As shown in Figure 10, foam E generated by brushing accumulates in the depressions of molar T1. The greater the amount of foam E, the larger the area where foam E spreads (foam area) shown in the post-brushing photograph. From the photographs taken after brushing in Examples 1-10 and Comparative Examples 1-6, the areas where foam E spreads, as shown in the hatched area in Figure 12, were extracted, and the size of the area of ​​this hatched area (area of ​​the foam area) was measured.

[0057] In addition, the diameter of the bubbles was measured from the photographs taken after brushing in each example. As shown in Figure 13, the 10 largest bubbles (90) were selected in order, and the sum of their diameters was calculated (top 10 bubble diameters). It is believed that the smaller the bubble diameter, the better the bubble quality (higher bubble strength). If the area of ​​the bubble is large and the top 10 bubble diameters are small, it can be evaluated that both the quantity and quality of the bubbles are high. The experimental results are shown in Table 2 and Figures 14 and 15.

[0058] (Experimental results) The "Foam Quality" in Table 2 is the value obtained by dividing the area of ​​the foam region by the diameter of the top 10 bubbles. A larger value indicates higher foam quality and quantity. Figure 14 is a graph showing the relationship between the area of ​​the foam region and the diameter of the top 10 bubbles. Figure 15 is a graph showing the relationship between the volume of the convex area and foam quality.

[0059] [Table 2]

[0060] As can be seen from Figure 14, the samples of Examples 1 to 10 according to the present invention had a foam quality of 60 or higher, indicating high foam quantity and quality. However, Comparative Examples 1 to 6 all had foam quality below 60, confirming the effectiveness of the present invention. Furthermore, from Figure 15, the volume of the protrusion was 250 mm 3 It is preferable to keep it as follows. [Explanation of symbols]

[0061] 1. Toothbrush 2 handles 3. Head section 4. Hair implantation stand 5. Inner hair bundles 6A,6B Outer hair bundle group 9 Toothpaste 50 hair bundles 50a Hair transplant hole 51 Tapered hair 51a Tip side part 60 hair bundles 90 bubbles L1 virtual line R1 area H Height difference D. Dental Model T1, T2 molars E-foam

Claims

1. A toothbrush comprising an inner group of bristles positioned approximately in the center of the head, and an outer group of bristles positioned adjacent to the inner group of bristles, The inner hair bundles consist of bundles containing tapered hairs that do not have a twist along the length direction and whose tapered tip portion has an axial length that exceeds the difference between the height of the inner hair bundles and the height of the outer hair bundles, which is 2 to 3 mm. The height of the inner hair bundle group is set to be 2 to 3 mm higher than the height of the outer hair bundle group. In a plan view from the hair implantation surface, the area of ​​the inner region enclosed by imaginary lines connecting the outer edges of the hair implantation holes located on the outside of the inner hair bundle group with the shortest distance, multiplied by the difference between the height of the inner hair bundle group and the height of the outer hair bundle group, is 250 mm. ３ The toothbrush is as follows.

2. The height of each hair bundle in the inner hair bundle group and the height of each hair bundle in the outer hair bundle group are set to approximately the same height. The toothbrush according to claim 1, wherein, when viewed from the axial direction of the toothbrush, the contour line formed by the inner bristle bundle and the left and right outer bristle bundles has a substantially convex stepped shape.

3. The toothbrush according to claim 1 or 2, wherein the inner bristle bundles are provided with 1 to 3 rows of bristle bundles arranged in a single line at intervals in the longitudinal direction of the toothbrush, in the short direction.

4. The toothbrush according to any one of claims 1 to 3, wherein the outer bristle bundles consist of bristle bundles that include tapered bristles or rounded bristles.

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