toothbrush

Abstract

To provide a toothbrush in which a brush part has flexibility and restorability.SOLUTION: A toothbrush includes a head part, and a plurality of brush parts projecting to a front surface side from a support surface located in the front surface side of the head part in a thickness direction. A centerline in a proximal end side of the brush part among center lines passing the center of a cross section of the brush part has a bending part that bends with a curvature as approaching the front surface side from the support surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a toothbrush. [Background technology]

[0002] Patent Document 1 discloses a toothbrush that provides an excellent feeling of contact with teeth and gums, a cleaning sensation, and has strong bristles when bundled together. The toothbrush disclosed in Patent Document 1 has spiral bristles formed by twisting an n-sided polygonal pillar around a central axis. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-37496 Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology of Patent Document 1, when the bristles are bundled, the bristles become stiff, but if the bristles have a large diameter, the bristles become too close together, which can limit the flexibility of the bristles. Also, when the bristles have a large diameter, the diameter of the bristles formed in the bristles implantation surface becomes larger, but if the distance between adjacent bristles is short, manufacturing problems such as cracks can occur, and there is a limit to how much the cleaning experience can be improved.

[0005] On the other hand, if priority is given to flexibility and the hair is made easy to bend, the hair will be hard to return to its original shape after bending, resulting in a problem of lack of restorability.

[0006] The present invention has been made in consideration of the above points, and an object of the present invention is to provide a toothbrush whose bristle part has flexibility and resilience. [Means for solving the problem]

[0007] According to a first aspect of the present invention, there is provided a toothbrush having a head portion and a plurality of bristle portions protruding toward the front side from a support surface located on the front side of the thickness direction of the head portion, wherein the center line passing through the center of the cross section of the brush portions at the base end side of the brush portions has a curved portion that curves with a curvature as it moves from the support surface toward the front side. [Effects of the Invention]

[0008] The present invention can provide a toothbrush whose bristle part has flexibility and resilience. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of the appearance of a toothbrush 1 according to a first embodiment. [Figure 2] FIG. 2 is an enlarged view of one brush part 21. [Figure 3] 10 is a diagram showing the relationship between the sixth power of the wire diameter and the spring constant in a circular spiral portion 30. FIG. [Figure 4] 10 is a diagram showing the relationship between the minimum gap dimension S1 and the spring constant in a circular spiral portion 30. FIG. [Figure 5] 10 is a diagram showing the relationship between the square of the reciprocal of the maximum gap dimension in the direction parallel to the support surface 5 in the spiral portion 30 and the spring constant. FIG. [Figure 6] FIG. 10 is a side view of the toothbrush 1 according to the second embodiment, viewed in the minor axis direction. [Figure 7] FIG. 10 is an external perspective view of a toothbrush 1 according to a third embodiment. [Figure 8] FIG. 10 is an external perspective view of a toothbrush 1 according to a fourth embodiment. [Figure 9] FIG. 2 is a side view of the wave-like portion 32 as viewed in the minor axis direction. [Figure 10] 10 is a diagram showing the relationship between the cube of the thickness t of the wave-like portion 32 and the spring constant. FIG. [Figure 11] 10 is a diagram showing the relationship between the fifth root of the gap dimension M in the wave-like portion 32 and the spring constant. FIG. [Figure 12] FIG. 10 is a diagram showing the relationship between the square root of the reciprocal of the gap dimension C and the spring constant. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the toothbrush of the present invention will be described with reference to FIGS. The following embodiment shows one aspect of the present invention, does not limit the present invention, and can be modified as desired within the scope of the technical concept of the present invention. In addition, in the following drawings, the scale and number of each structure are different from the actual structure to make each configuration easier to understand.

[0011] [First embodiment of toothbrush] FIG. 1 is a perspective view of the appearance of a toothbrush 1 according to the first embodiment. As shown in FIG. 1, the toothbrush 1 includes a handle body 10 and a brush head 20. The handle body 10 includes a head portion 3, a grip portion (not shown) located rearward of the head portion 3 in the longitudinal direction, and a neck portion 4 connecting the head portion 3 and the grip portion. The head portion 3 is located at the tip end of the handle body 10 in the longitudinal direction.

[0012] The brush unit 20 includes a plurality of bristle portions 21. The bristle portions 21 protrude toward the front side from the support surface 5 located on the front side in the thickness direction of the head unit 3. The bristle portions 21 protrude from the support surface 5 toward the front side of the support surface 5.

[0013] In the following description, the normal direction to the support surface 5 and the thickness direction of the head portion 3 will be referred to as the normal direction. The width direction of the head portion 3, which is perpendicular to the normal direction and perpendicular to the long axis direction of the handle body 10, will be referred to as the short axis direction. In the normal direction, the support surface 5 side of the head portion 3 will be referred to as the front side.

[0014] As shown in Fig. 1, the brush units 21 are arranged in a lattice pattern. The arrangement of the brush units 21 may be either a lattice pattern or a staggered pattern.

[0015] FIG. 2 is an enlarged view of one brush part 21. The cross-sectional shape of the bristles 21 can be selected from circular, elliptical, polygonal, etc. Making the cross-section of the bristles 21 star-shaped or polygonal increases frictional force and improves cleaning power. The bristles 21 extend linearly along a center line J that passes through the center of the cross section of the bristles 21. When the cross-sectional shape of the brush part 21 is circular, the cross-sectional center is the center of curvature of the circular cross-section. When the cross-sectional shape of the brush part 21 is elliptical, the cross-sectional center is the intersection of the major axis and minor axis of the elliptical cross-section. When the cross-sectional shape of the brush part 21 is polygonal, the cross-sectional center is the position of the center of gravity in the cross-section. The tip side of the brush part 21 may be conical from the base end to the tip end.

[0016] When the cross-sectional shape of the brush part 21 is circular, the wire diameter d (mm) is preferably 0.3 mm or more, more preferably 0.5 mm or more. It is also preferably 1.5 mm or less, more preferably 1.0 mm or less, and even more preferably 0.6 mm or less. It is also preferably 0.3 mm or more and 1.5 mm or less, more preferably 0.5 mm or more and 1.0 mm or less, and even more preferably 0.3 mm or more and 0.6 mm or less. Furthermore, when the cross-sectional shape of the bristle part 21 is elliptical, it is preferable that the length of the major axis is within the above range. Furthermore, when the cross-sectional shape of the bristle part 21 is polygonal, it is preferable that the diameter of the circumscribed circle is within the above range.

[0017] In the embodiment of FIG. 2, the bristle portion 21 has a spiral portion 30 and a first straight portion 40 . The spiral portion 30 is located on the base end side of the brush portion 21. The center line J passing through the cross-sectional center of the brush portion 21 in the spiral portion 30 extends along a first intersecting line L1 (normal to the support surface 5) that intersects with the support surface 5, and as it moves toward the front side, it curves continuously in an arc shape when viewed in the direction of the first intersecting line (normal to the support surface 5). In other words, the spiral portion 30 constitutes a curved portion. As shown in Figure 2, the center line J passing through the cross-sectional center of the brush portion 21 in the spiral portion 30 of this embodiment circles as it moves toward the front side. 2, the first intersecting line L1 is a normal to the support surface 5, and the first intersecting line direction is the normal direction to the support surface 5. Therefore, hereinafter, the first intersecting line L1 will be referred to as the normal line, and the first intersecting line direction will be referred to as the normal direction. However, the first intersecting line L1 in the embodiment of Fig. 2 is merely one example of an intersecting line that intersects with the support surface 5, and does not have to be a normal line as long as it intersects with the support surface 5. That is, as in the embodiment of Fig. 2, the first intersecting line L1 may extend while continuously curving in an arc shape in the first intersecting line direction (normal direction of the support surface 5) perpendicular (at an angle of 90 degrees) to the support surface 5, or may extend while continuously curving in an arc shape in the first intersecting line direction inclined with respect to the support surface 5 (at an angle of more than 0 degrees and less than 90 degrees). The center line J passing through the cross-sectional center of the bristles 21 of the spiral portion 30 located on the base end side curves in an arc as it moves toward the front side along the normal direction, allowing the bristles 21 to elastically deform in the direction along the normal direction at the base end and in the direction along the support surface 5. Therefore, the bristles 21 are flexible and easily return to their original shape due to their elastic restoring force (resilience). As a result, the bristles 21 will not break during brushing, even when formed using a 3D printer, as described below, and provide good cleaning performance.

[0018] In particular, in the embodiment of Figure 2, the center line J passing through the cross-sectional center of the brush part 21 in the spiral part 30 extends spirally and curves circumferentially with the first normal line (first intersection line) L1 extending in the normal direction to the support surface 5 as its "center." The center line J extends spirally with a constant radius of curvature and curves circumferentially with the first normal line L1 as its "center." Note that the center line does not necessarily have to be the "center," and may extend spirally "near the center" and curve circumferentially. The spiral portion 30 intersects the first normal line L1 at least two times in a side view seen in the minor axis direction. The center line J passing through the cross-sectional center of the bristles 21 of the spiral portion 30 located on the base end side extends spirally around (or near) the first normal line L1 extending in the normal direction, and curves in the circumferential direction, making the bristles 21 equivalent to a coil spring extending in the normal direction, and the base end side can elastically deform and expand / contract in the normal direction and in directions along the support surface 5. Therefore, the bristles 21 are easy to bend (flexible) and easy to return to their original shape due to elastic restoring force (resilience). As a result, even when the bristles 21 are formed using, for example, a 3D printer described below, they will not break during brushing, and good cleaning performance can be achieved.

[0019] The center line J of the spiral portion 30, which passes through the center of the cross section of the brush portion 21, may be configured to extend spirally and curve in the circumferential direction with a constant radius of curvature around the first normal line L1 (or near the center), or it may be configured to extend spirally and curve in the circumferential direction with a gradually decreasing radius of curvature around the first normal line L1. When this configuration is adopted, a spiral portion 30 is obtained that tapers toward the front side.

[0020] The number of turns (effective number of turns; Na) of the spiral portion 30 in the bristle portion 21 is preferably 1.5 to 10, more preferably 2 to 6, and even more preferably 2.5 to 4.

[0021] The spring constant k (N / mm) of the spiral portion 30 as a coil spring is expressed as follows: the load is P (N), the displacement is δ (mm), and the modulus of transverse elasticity of the material of the spiral portion 30 is G (N / mm 2 = MPa), the wire diameter of the spiral portion 30 is d (mm), the number of effective turns is Na, and the average diameter of the spiral portion 30 ((outer diameter + inner diameter) / 2) is D (mm), which can be expressed by the following formula (1). In this application, when the cross-sectional shape of the brush portion 21 is circular, the wire diameter d and the average diameter D are considered to be the diameter. When the cross-sectional shape of the brush portion 21 is elliptical, they are considered to be the average diameter of the lengths of the major and minor axes. When the cross-sectional shape of the brush portion 21 is polygonal, they are considered to be the diameter of the circumscribed circle.

[0022]

number

[0023] As expressed by formula (1), the larger the wire diameter d of the helical portion 30, the smaller the number of effective turns Na, and the smaller the average diameter D of the helical portion 30, the larger the spring constant k, resulting in a harder coil spring. In other words, the smaller the wire diameter d of the helical portion 30, the larger the number of effective turns Na, and the larger the average diameter D of the helical portion 30, the smaller the spring constant k, resulting in a softer coil spring with high cushioning (shock-absorbing) properties.

[0024] The minimum gap dimension S1 between adjacent brush parts 21 in the normal direction in the spiral part 30 is preferably 0.2 mm or more and 2.0 mm or less. The minimum gap dimension S1 is defined as the dimension of the shortest outer gap between the brush parts 21 adjacent to each other in the normal direction as shown in FIG. If the minimum gap dimension S1 is less than 0.2 mm, the tube will be difficult to return to its original shape and will have reduced restorability, but will bend more easily and will have increased flexibility.If the minimum gap dimension S1 is more than 2.0 mm, the tube will be difficult to return to its original shape and will have reduced flexibility, but will be easy to return to its original shape and will have increased restorability. The minimum gap dimension S1 is more preferably 0.3 mm or more, more preferably 1.5 mm or less, and even more preferably 1.0 mm or less.

[0025] FIG. 3 is a diagram showing the relationship between the "sixth power of the wire diameter" and the "spring constant" in the spiral part 30 of the brush part 21 having a circular cross section. FIG. 4 is a diagram showing the relationship between the "minimum gap dimension S1" and the "spring constant" in the spiral part 30 of the brush part 21 having a circular cross section.

[0026] As shown in Figure 3, the "sixth power of the wire diameter" and the "spring constant" are proportional to each other. As shown in FIG. 4, the "minimum gap dimension S1" and the "spring constant" are proportional to each other. Therefore, the product of the "minimum gap dimension S1" and the "sixth power of the wire diameter" is proportional to the spring constant. Because of this relationship, when the minimum gap dimension S1 in the spiral portion 30 is large and when the wire diameter is large, the spiral portion 30 becomes less flexible and less flexible, but becomes easier to return to its original shape and has higher restoring ability. Furthermore, when the minimum gap dimension S1 in the spiral portion 30 is small and the wire diameter is small, the wire becomes difficult to return to its original shape and the restorability decreases, but the wire bends more and becomes more flexible. Furthermore, since the product of the gap dimension between the wires in the normal direction and the sixth power of the wire diameter is proportional to the spring constant, when the gap dimension between the wires in the spiral section 30 in the normal direction is small or when the wire diameter is small, the wire becomes difficult to return to its original shape and its restorability decreases, while it bends more and its flexibility increases.

[0027] Using the wire diameter d (mm) in the spiral portion 30, d 6 × S1 (unit: mm 7 (units will be omitted below) is preferably 0.000025 or more, more preferably 0.0001 or more, and even more preferably 0.004 or more. Also, it is preferably 50 or less, more preferably 1 or less, and even more preferably 0.01 or less. It is preferably 0.000025 or more and 50 or less, more preferably 0.0001 or more and 1 or less, and even more preferably 0.004 or more and 0.01 or less. d 6 If the value expressed by ×S1 is less than 0.000025, the material will be difficult to return to its original shape, reducing its restorability, while it will bend more and become more flexible. d 6 When the value expressed by ×S1 exceeds 50, the material becomes harder to bend and its flexibility decreases, but it returns to its original shape more easily and its restorability increases.

[0028] FIG. 5 is a diagram showing the relationship between the square of the reciprocal of the maximum gap dimension (inner diameter S2) in the direction parallel to the support surface 5 in the spiral part 30 of the brush part 21 having a circular cross section, and the spring constant. The maximum gap dimension in the direction parallel to the support surface 5 in the spiral portion 30 is the inner diameter S2 of the spiral portion 30, as shown in FIG. As shown in FIG. 5, the "square of the reciprocal of the inner diameter S2" and the "spring constant" are proportional to each other. Also, as mentioned above, the "sixth power of the wire diameter" and the "spring constant" are proportional to each other. Therefore, the product of the sixth power of the wire diameter and the square of the reciprocal of the inner diameter S2 is proportional to the spring constant. Due to this relationship, when the "inner diameter S2" is large and the "wire diameter" is small, it becomes difficult to return to its original shape and its restorability decreases, but it bends more easily and its flexibility increases. Also, when the "inner diameter S2" is small and the "wire diameter" is large, it becomes difficult to bend and its flexibility decreases, but it becomes easier to return to its original shape and its restorability increases.

[0029] The product of "the sixth power of the wire diameter" and "the square of the reciprocal of the inner diameter S2" is d 6 ×(1 / S2) 2 The value expressed in mm 4 (units will be omitted below) is preferably 0.000064 or more, more preferably 0.0001 or more, and even more preferably 0.005 or more. Also, it is preferably 500 or less, more preferably 10 or less, and even more preferably 0.05 or less. It is preferably 0.000064 or more and 500 or less, more preferably 0.0001 or more and 10 or less, and even more preferably 0.005 or more and 0.05 or less. d 6 ×(1 / S2) 2 If the value expressed by is less than 0.000064, the material will be hard to return to its original shape and the restorability will decrease, while the material will bend more and become more flexible. d 6 ×(1 / S2) 2 If the value exceeds 500, the material will be less flexible and will return to its original shape more easily, while the material will have higher restoring properties.

[0030] The inner diameter S2 is preferably 0.2 mm or more, more preferably 0.25 mm or more, and even more preferably 0.3 mm or more. The inner diameter S2 is preferably 2.0 mm or less, more preferably 1.5 mm or less, and even more preferably 1.0 mm or less. Furthermore, the inner diameter S2 is preferably 0.2 mm or more and 2.0 mm or less. If the inner diameter S2 is less than 0.2 mm, the tube becomes difficult to bend and has reduced flexibility, but it returns to its original shape easily and has high restorability. If the inner diameter S2 exceeds 2.0 mm, the tube becomes difficult to return to its original shape and has reduced restorability, but it returns to its original shape easily and has high flexibility.

[0031] The first straight portion 40 is located closer to the tip in the normal direction than the spiral portion 30 and extends linearly in the normal direction. Providing the first straight portion 40 at the tip side of the brush part 21 improves cleaning power and ease of insertion between teeth. From the standpoint of ease of insertion, it is more preferable that the tip of the first straight portion 40 has a tapered shape toward the front side.

[0032] The bristle length, which is the dimension in the normal direction from the base end of the bristle part 21 on the support surface 5 side to the tip of the first straight part 40, is preferably 9 mm or more, more preferably 10 mm or more, and even more preferably 11 mm or more. The bristle length, which is the dimension in the normal direction from the base end of the bristle part 21 on the support surface 5 side to the tip of the first straight part 40, is preferably 15 mm or less, more preferably 14 mm or less, and even more preferably 12 mm or less. Furthermore, the bristle length, which is the dimension in the normal direction from the base end of the bristle portion 21 on the support surface 5 side to the tip of the first straight portion 40, is preferably 9 mm or more and 15 mm or less.

[0033] The ratio of the dimension of the first straight portion 40 to the bristle length of the bristle portion 21 is preferably 60% or less, more preferably 55% or less, and even more preferably 25% or less. The ratio of the dimension of the first straight portion 40 to the bristle length of the bristle portion 21 is preferably 5% or more, more preferably 10% or more, and even more preferably 20% or more. If the ratio of the dimension of the first straight portion 40 to the bristle length of the brush portion 21 is less than 5%, the cleaning power and the ability to insert between teeth will be insufficient. If the ratio of the dimension of the first straight portion 40 to the bristle length of the brush portion 21 exceeds 60%, the ease with which the brush portion 21 bends and returns due to the spiral portion 30 will be insufficient. By setting the ratio of the dimension of the first straight portion 40 to the bristle length of the brush portion 21 to be between 5% and 60%, it is possible to improve the cleaning power and the ability to insert between teeth, as well as the ease with which the brush portion 21 bends and returns.

[0034] There are no particular limitations on the method of manufacturing the bristle part 21 of the toothbrush 1 configured as described above. For example, the bristle part 21 may be manufactured using a well-known method of manufacturing a resin coil spring, and the resin coil spring may be fixed to the support surface 5 of the head part 3 by welding or adhesive.

[0035] It is also possible to produce the brush part 21 as an additively shaped object by repeatedly curing the liquid resin layer by layer and stacking the cured resin in multiple layers along the normal direction on the support surface 5. When producing the brush part 21 as an additively shaped object, a three-dimensional printer (3D printer) having a stage that can move up and down and a light irradiation unit that irradiates energy light onto a material placed on the stage to harden it can be used. When using a 3D printer to form the brush part 21, for example, a stereolithography method, an inkjet method (multi-jet printing method), or a powder lamination method can be selected.

[0036] The photopolymerization method is a method of forming the brush part 21 as a layered object stacked along the normal direction by repeatedly irradiating liquid resin placed on a stage with energy light, such as ultraviolet light (ultraviolet light), to harden the liquid resin layer by layer, and then moving the stage vertically and irradiating the liquid resin in the next layer with ultraviolet light to harden it and form a hardened body.

[0037] The inkjet method involves ejecting droplets of ultraviolet-curing resin onto a stage and then irradiating the impacted droplets with ultraviolet light to form a hardened body, repeatedly doing so to form the brush part 21 as a layered object stacked along the normal direction.

[0038] The powder lamination method is a method of forming the brush part 21 as a layered object stacked along the normal direction by repeatedly irradiating a powdered material placed on a stage with energy light, for example, laser light, to sinter the material and form a hardened body, and then moving the stage vertically and irradiating the next layer of powdered material with laser light to harden it and form a hardened body.

[0039] If the brush portion 21 is linear and single, it is also possible to form the brush portion 21 using a material extrusion deposition method in which a linear resin material in a heated and molten state is extruded from a nozzle and hardened while moving the stage and nozzle, or the nozzle.

[0040] When manufacturing the bristle part 21 using a manufacturing method for a resin coil spring, the material of the bristle part 21 is not particularly limited, and examples include synthetic resin materials such as polyamide (6-12 nylon, 6-10 nylon, 12-nylon, etc.), polyester (polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, etc.), polyolefin (polypropylene, etc.), elastomer (olefin-based, styrene-based, etc.), and natural materials.

[0041] When manufacturing the brush part 21 as an additive manufacturing product, the material of the brush part 21 is not particularly limited, and examples include a material polymerized from (A) a component having an acrylic acid skeleton and (B) a component having a terminal amine with a valence of two or more. Preferred examples of component (A) include trimethylolpropane trimethacrylate, dodecyl methacrylate, diethylene glycol monomethyl ether methacrylate urethane dimethacrylate, polyethylene glycol dimethacrylate, 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane, tricyclo[5.2.1.02,6]decane dimethanol diacrylate, methoxydiethylene glycol methacrylate, and polydimethylsiloxane acrylate. As the component (B), 4,4'-methylenebis(2-methylcyclohexylamine), polyetheramine, trimethylolpropane poly(oxypropylene)triamine, poly(propylene glycol)triamine, 4,4'-diaminodiphenyl sulfone, and 3,3'-diaminodiphenyl sulfone are preferred.

[0042] In the toothbrush 1 of this embodiment, the center line J at the base end of the bristle portion 21 extends and curves in a direction intersecting the normal direction as it moves toward the front side of the support surface 5, thereby allowing the bristle portion 21 to have flexibility and resilience.

[0043] Furthermore, in conventional toothbrushes 1, the bristle bundle diameter was increased to change from a soft feel to a harder feel, but the size of the bristle bundle diameter was limited in order to ensure sufficient clearance between the bristle holes. In contrast, in the toothbrush 1 of the present embodiment, in such cases, the spring constant k can be increased and the bristle bundle can be made harder by, for example, reducing the average diameter D of the spiral portion 30. This eliminates restrictions on the placement of the bristle portion 21 on the support surface 5, allowing for greater design freedom. Furthermore, regardless of the radial direction of the spiral portion 30, the feel can also be made harder by adjusting the specifications in the normal direction, such as by reducing the effective number of turns Na. This allows for easy adjustment of the force of contact and brushing performance according to the user's needs.

[0044] [Second embodiment of toothbrush] Next, a toothbrush 1 according to a second embodiment will be described with reference to FIG. In this figure, the same elements as those in the first embodiment shown in FIGS. 1 to 5 are given the same reference numerals, and the description thereof will be omitted.

[0045] FIG. 6 is a side view of the toothbrush 1 according to the second embodiment, seen in the minor axis direction. As shown in Fig. 6, in this embodiment, three brush units 21 are arranged at equal intervals in the circumferential direction around the first normal line L1. The three brush units 21 are arranged at 120° intervals in the circumferential direction around the first normal line L1. By arranging the three brush units 21 at equal intervals in the circumferential direction around the first normal line L1, the spiral units 30 of the three brush units 21 are arranged with equal gaps between them in the normal direction. The other configurations are the same as those of the first embodiment.

[0046] In addition to achieving the same effects and advantages as the first embodiment, the toothbrush 1 of this embodiment has multiple first straight portions 40, which increases the contact area with the tooth surface, improving cleaning effectiveness and increasing bristle stiffness. Furthermore, with the toothbrush 1 of this embodiment, even if one of the three bristles 21 breaks off at its base end, the bristles remain intertwined with the other bristles 21, preventing them from falling out.

[0047] In this embodiment, three brush units 21 are arranged at equal intervals in the circumferential direction around the first normal line L1, but the present invention is not limited to this configuration. Two brush units 21 may be arranged at equal intervals in the circumferential direction, or four or more brush units may be arranged.

[0048] [Third embodiment of toothbrush] Next, a toothbrush 1 according to a third embodiment will be described with reference to FIG. In this figure, the same elements as those in the second embodiment shown in FIG. 6 are denoted by the same reference numerals, and the description thereof will be omitted.

[0049] FIG. 7 is a perspective view showing the appearance of the toothbrush 1 according to the third embodiment. 7, the brush unit 21 has a spiral portion 30, a connecting portion 31, and a second brush unit 21A. Three spiral portions 30 are arranged at equal intervals in the circumferential direction around the first normal line L1.

[0050] The connecting portion 31 is connected to the tip of the spiral portion 30. The connecting portion 31 is plate-shaped and approximately parallel to the support surface 5, with dimensions approximately the same as the maximum diameter of the spiral portion 30. "Approximately parallel" means that, in a side view, the intersection of an imaginary line parallel to the support surface 5 and an imaginary line in the thickness direction of the connecting portion 31 is within ±10 degrees. As shown in Figure 7, it may be cylindrical. The second brush portion 21A side of the connecting portion 31 may also be uneven or curved. The support surface 5 side of the connecting portion 31 may also be uneven or curved. The connecting portion 31 is disk-shaped, with the first normal line L1 as its center. The second brush portion 21A is provided on the connecting portion 31.

[0051] The second brush portion 21A extends in the normal direction from the connecting portion 31. The base end of the second brush portion 21A is connected to the connecting portion 31. A plurality of second brush portions 21A (five in FIG. 7) are arranged at intervals in the circumferential direction centered on the first normal line L1. The number of second brush portions 21A may be four or less or six or more. In the embodiment of FIG. 7, the number of second brush portions 21A is different from the number of spiral portions 30. At least one position of the second brush portion 21A in a plane approximately parallel to the support surface 5 is different from the position where the spiral portion 30 is connected to the connecting portion 31. The number of second brush portions 21A may be the same as the number of spiral portions 30. The position where the spiral portion 30 is connected to the connecting portion 31 may be the same. The other configurations are the same as those of the second embodiment.

[0052] In addition to achieving the same effects and advantages as the second embodiment, toothbrush 1 of this embodiment also provides connecting portion 31, which makes it possible to provide second bristle unit 21A in a number and position that is independent of the number and position of spiral portions in spiral unit 30. Furthermore, in toothbrush 1 of this embodiment, even if one of the three spiral units 30 breaks, the tip of the broken spiral unit 30 is connected to connecting portion 31, preventing it from falling off.

[0053] In the present embodiment, the spiral portion 30 is disposed at equal intervals in the circumferential direction around the first normal line L1, but the present invention is not limited to this configuration. The spiral portion 30 may be disposed in a single configuration, or in two or more configurations at equal intervals in the circumferential direction. It is preferable to dispose a plurality of spiral portions 30, since even if a spiral portion 30 breaks, it can be connected to the connecting portion 31 and prevented from falling off.

[0054] [Fourth embodiment of toothbrush] Next, a toothbrush 1 according to a fourth embodiment will be described with reference to FIGS. In these figures, the same elements as those in the first embodiment shown in FIGS. 1 to 5 are denoted by the same reference numerals, and the description thereof will be omitted.

[0055] FIG. 8 is a perspective view of the appearance of the toothbrush 1 according to the fourth embodiment. 8, the bristle unit 21 of this embodiment has a wavy portion 32 and a second straight portion 41. The wavy portion 32 is located on the base end side of the bristle unit 21. 9 is a side view of the wavy portion 32 as viewed in the minor axis direction. A center line J passing through the center of the cross section of the brush part 21 in the wavy portion 32 moves back and forth in a direction (first direction) perpendicular to the normal direction as it moves toward the front side along the normal direction. That is, the center line J passing through the center of the cross section of the bristle unit 21 extends toward the front side so as to cross multiple times the normal direction of the second intersection line L2 that intersects with the support surface 5. Therefore, in the embodiment of FIG. The curved portion 33 is disposed at a position where the wave-like portion 32 turns in a direction perpendicular to the normal direction. The curved portion 33 curves with a greater curvature toward the front side. The main difference between the fourth embodiment and the first to third embodiments is that in the first to third embodiments, "the center line J extends around or near the center at the line of intersection where it intersects with the support surface (i.e., extends spirally)," whereas in the fourth embodiment, "it extends without circling."

[0056] By providing the wavy portion 32 having the curved portion 33 on the base end side, the brush portion 21 can elastically deform in the normal direction and expand and contract. Because the wavy portion 32 can expand and contract on the base end side of the brush portion 21, the base end side of the brush portion 21 can elastically deform in the direction along the normal direction and in the direction perpendicular to the normal direction along the support surface 5. Therefore, the brush portion 21 can ensure ease of bending (flexibility) and ease of returning to its original shape (resilience).

[0057] The cross-sectional shape of the wavy portion 32 can be selected from a circle, an ellipse, a polygon, etc. In this embodiment, the cross-sectional shape of the wavy portion 32 is a rectangle having long and short sides. In the rectangular cross-sectional shape, the curved portion 33 is formed by the surface that constitutes the long side.

[0058] The thickness of the corrugated portion 32 in the normal direction is defined as t (mm). The thickness t is the dimension of the rectangular cross section of the corrugated portion 32 in the short side direction. In the wavy portion 32, when viewed from the side in the short axis direction as shown in Figure 9, the gap dimension of the wavy portion 32 located on the second intersection line L2 that passes near the center of the width direction W2 of the brush part 21 perpendicular to the normal direction and intersects with the support surface 5 is defined as M (mm). Note that in this embodiment, the second intersection line L2 is a normal to the support surface 5. Therefore, hereinafter, the second intersection line L2 will be referred to as the second normal line L2, and the direction of the second intersection line will be referred to as the normal direction. However, the second intersection line L2 is an example of an intersection line that intersects with the support surface 5, and it does not have to be a normal line as long as it intersects with the support surface 5. That is, as in the embodiment of Figure 9, it may extend in a direction perpendicular to the second intersecting line direction (normal direction of the support surface 5) perpendicular to the support surface 5 (at an angle of 90 degrees), while moving back and forth in a direction perpendicular to the normal direction, or it may extend in a direction perpendicular to the normal direction in a direction tilted to the support surface 5 (at an angle greater than 0 degrees and less than 90 degrees), while moving back and forth in a direction perpendicular to the normal direction.

[0059] The thickness t of the wavy portion 32 is preferably 0.2 mm or more, more preferably 0.3 mm or more, and even more preferably 0.4 mm or more. The thickness t of the wavy portion 32 is preferably 2.0 mm or less, more preferably 1.5 mm or less, and even more preferably 1.0 mm or less.

[0060] The gap dimension M in the wavy portion 32 is preferably 0.2 mm or more, more preferably 0.5 mm or more, and even more preferably 1.0 mm or more. The gap dimension M in the wavy portion 32 is preferably 3.0 mm or less, more preferably 2.0 mm or less, and even more preferably 1.0 mm or less. If the gap dimension M is less than 0.2 mm, the tube will be difficult to return to its original shape and will have reduced restorability, but will bend more easily and will have increased flexibility.If the gap dimension M exceeds 3.0 mm, the tube will be difficult to return to its original shape and will have reduced flexibility, but will be easy to return to its original shape and will have increased restorability.

[0061] FIG. 10 is a diagram showing the relationship between the "cube of the thickness t in the direction of the short side in the normal direction" and the "spring constant" of the wave-like portion 32. FIG. 11 is a diagram showing the relationship between the "fifth root of the gap dimension M in the direction of the short side in the normal direction" and the "spring constant" in the wave-like portion 32.

[0062] As shown in FIG. 10, the "cubed thickness t in the direction of the short side in the normal direction" and the "spring constant" are proportional to each other. As shown in FIG. 11, the "fifth root of the gap dimension M in the direction of the short side in the normal direction" and the "spring constant" are in a proportional relationship. Therefore, the product of "the cube of the thickness t in the normal direction of the short side" and "the fifth root of the gap dimension M in the normal direction of the short side" is proportional to the "spring constant." Due to this relationship, when the thickness t is large and the gap dimension M is large, the material is less likely to bend and its flexibility decreases, but it is easier to return to its original shape and its restorability increases. Furthermore, because of this relationship, when the thickness t is small and the gap dimension M is small, the return becomes difficult and the restorability decreases, but on the other hand, the bending becomes large and the flexibility increases.

[0063] When "cube of thickness t in the direction of the short side in the normal direction" is t3 and "fifth root of gap dimension M in the direction of the short side in the normal direction" is M5, the value expressed by t3 x M5 (unit: mm 3 / 5 (In the following description, the units will be omitted) is preferably 0.001 or more, more preferably 0.05 or more, and even more preferably 0.1 or more. It is also preferably 5 or less, more preferably 1 or less, and even more preferably 0.2 or less. It is also preferably 0.01 or more and 5 or less, more preferably 0.05 or more and 1 or less, and even more preferably 0.1 or more and 0.2 or less. If the value expressed by t3 x M5 is less than 0.01, the material will be difficult to return to its original shape and its recovery will decrease, but it will bend more easily and become more flexible.If the value expressed by t3 x M5 is more than 5, the material will be difficult to return to its original shape and its recovery will increase.

[0064] The gap dimension in the normal direction in the wave-like portion 32 is defined as C (mm). The gap dimension C relates to the curved portions 33 adjacent to each other in the normal direction. 9, it is the distance in the direction perpendicular to the normal direction between a first position Q1 in the curved portion 33 that protrudes on one side in the direction perpendicular to the normal direction and a second position Q2 in the curved portion 33 that is adjacent in the normal direction and protrudes on the other side from the first position Q1. In other words, it is the repeated distance around L2 when extending back and forth in the direction perpendicular to the normal direction.

[0065] The gap dimension C is preferably 0.5 mm or more and 3.0 mm or less. The gap dimension C is more preferably 1.0 mm or more, and even more preferably 1.5 mm or more. The gap dimension C is more preferably 2.9 mm or less, and even more preferably 2.8 mm or less. When the gap dimension C is less than 0.5 mm, the tube becomes less flexible and less flexible, but returns to its original shape more easily and has high restorability. When the gap dimension C exceeds 3.0 mm, the tube becomes less flexible and less flexible, but returns to its original shape more easily and has high flexibility.

[0066] FIG. 12 is a diagram showing the relationship between the "square root of the reciprocal of the gap dimension C in the direction perpendicular to the normal direction" and the "spring constant." As shown in FIG. 12, the "square root of the reciprocal of the gap dimension C in the direction perpendicular to the normal direction" and the "spring constant" are in a proportional relationship. Furthermore, as mentioned above, the "cubed thickness t in the direction of the short side in the normal direction" and the "spring constant" are proportional to each other. Therefore, the product of "the cube of the thickness t in the direction of the short side in the normal direction" and "the square root of the reciprocal of the gap dimension C in the direction perpendicular to the normal direction" is proportional to the "spring constant." Due to this relationship, when the thickness t is large and the gap dimension C is large, the return becomes difficult and the restorability decreases, but on the other hand, the bending becomes large and the flexibility increases. Furthermore, because of this relationship, when the thickness t is small and the gap dimension C is small, the material is less likely to bend and its flexibility decreases, but it is easier to return to its original shape and its restorability increases.

[0067] If the "square root of the reciprocal of the gap dimension C in the direction perpendicular to the normal direction" is C2, then the value expressed as t3 x C2 (unit: mm 3 / 2 (units will be omitted in the following description) is preferably 0.02 or more and 10 or less. If the value expressed by t3 x C2 is less than 0.02, the material will be difficult to return to its original shape and its restorability will decrease, but it will bend more easily and become more flexible.If the value expressed by t3 x C2 is more than 10, the material will be difficult to return to its original shape and its restorability will increase. The value expressed by t3×C2 is more preferably 0.04 or more, and even more preferably 0.4 or more. The value expressed by t3×C2 is more preferably 4 or less, and even more preferably 1 or less.

[0068] The dimension W1 in the major axis direction of the wavy portion 32 shown in Figure 8 is preferably 0.2 mm or more and 2.0 mm or less, more preferably 0.7 mm or more and 1.8 mm or less, and even more preferably 1.0 mm or more and 1.5 mm or less. The dimension W2 in the minor axis direction of the wavy portion 32 shown in Figure 9 is, for example, 2.0 mm. The bristle length, which is the dimension in the normal direction from the base end on the support surface 5 side of the brush part 21 having the wavy portion 32 to the tip of the second straight portion 41, is preferably 9 mm or more and 15 mm or less, more preferably 10 mm or more and 14 mm or less, and even more preferably 11 mm or more and 12 mm or less.

[0069] The pitch (fold interval) W3 of the wavy portion 32 is preferably 0.5 mm or more, more preferably 0.7 mm or more, and even more preferably 1.0 mm or more. The pitch (fold interval) W3 of the wavy portion 32 is preferably 3.0 mm or less, more preferably 2.5 mm or less, and even more preferably 2.0 mm or less. Furthermore, the pitch (fold interval) W3 of the wavy portion 32 is preferably 0.5 mm or more and 3.0 mm or less. The number of pitches (fold intervals) of the wavy portion 32 is preferably 1.5 or more, more preferably 2 or more, and even more preferably 2.5 or more. The number of pitches (fold intervals) of the wavy portion 32 is preferably 10 or less, more preferably 6 or less, and even more preferably 4 or less. The number of pitches (fold intervals) of the wavy portion 32 is preferably 1.5 times or more and 10 times or less.

[0070] The second straight portion 41 is located closer to the tip end of the wavy portion 32 in the normal direction and extends linearly in the normal direction. Two second straight portions 41 are arranged with a gap in the short axis direction. Providing the second straight portion 41 at the tip end of the brush part 21 improves cleaning power and ease of insertion between teeth. From the viewpoint of ease of insertion, it is more preferable that the tip end of the second straight portion 41 is tapered toward the front side. A configuration in which one second straight portion 41 is arranged for each wavy portion 32 may be used.

[0071] The ratio of the dimension of the second straight portion 41 to the bristle length, which is the dimension in the normal direction from the base end of the brush portion 21 on the support surface 5 side to the tip of the second straight portion 41, is preferably 65% ​​or less, more preferably 60% or less, and even more preferably 55% or less. The ratio of the dimension of the second straight portion 41 to the bristle length of the brush portion 21 is preferably 5% or more, more preferably 10% or more, and even more preferably 15% or more. If the ratio of the dimension of the second straight portion 41 to the bristle length of the brush portion 21 is less than 5%, the cleaning power and the ability to insert between teeth will be insufficient. If the ratio of the dimension of the second straight portion 41 to the bristle length of the brush portion 21 exceeds 65%, the ease with which the brush portion 21 bends and returns to its original shape due to the wavy portion 32 will be insufficient. By setting the ratio of the dimension of the second straight portion 41 to the bristle length of the brush portion 21 to be between 5% and 65%, it is possible to improve the cleaning power and the ability to insert between teeth, as well as the ease with which the brush portion 21 bends and returns to its original shape.

[0072] In addition to achieving the same effects and advantages as the first embodiment, the toothbrush 1 of this embodiment has anisotropy in the direction of bending and straightening because the wavy portion 32 extends back and forth in the longitudinal direction as it approaches the front. Therefore, the toothbrush 1 of this embodiment can have different directions for bending and straightening, and directions that are less likely to bend but offer better cleaning properties when brushing. Therefore, the toothbrush 1 of this embodiment can arbitrarily set the directions for bending and straightening, and the directions that offer better cleaning properties when brushing.

[0073] In the toothbrush 1 having the wavy portion 32 described above, the brush head 21 has the second straight portion 41 provided on the tip side of the wavy portion 32, but the configuration is not limited to this. The brush head 21 may not have the second straight portion 41 on the tip side. [Example]

[0074] The effects of the present invention will be made clearer by the following examples. Note that the present invention is not limited to the following examples and can be practiced with appropriate modifications within the scope of the present invention.

[0075] (Examples 1 to 27, Comparative Example 1) In this example, samples 1 to 7 similar to the toothbrush of the first embodiment shown in FIG. 1 were prepared according to the specifications shown in Table 1 below. In this example, samples 8 to 12 were prepared according to the specifications shown in Table 2 below, in which two bristle parts were arranged at equal intervals in the circumferential direction around the first normal line, as compared to the toothbrush of the second embodiment shown in FIG. 6. In this example, samples 13 to 18 similar to the toothbrush of the second embodiment shown in FIG. 6 were prepared according to the specifications shown in Table 3 below, in which three bristle parts were arranged at equal intervals in the circumferential direction around the first normal line. In this example, sample 19 similar to the toothbrush of the third embodiment shown in FIG. 7 was prepared according to the specifications shown in Table 3 below, in which three bristle parts were arranged at equal intervals in the circumferential direction around the first normal line and connected to a connecting part at their tips.

[0076] In this example, samples of Examples 20 to 26 were produced in which the bristles did not have the second straight portion and were formed only with wavy portions, in accordance with the specifications shown in Table 4 below, for the toothbrush of the fourth embodiment shown in Figure 8. In this example, sample of Example 27 was produced in which the bristles had the second straight portion, in accordance with the specifications shown in Table 4 below, in accordance with the sample of Example 23 shown in Figure 8.

[0077] In Comparative Example 1, a toothbrush sample was used, in accordance with the specifications shown in Table 4 below, in which the bristles were cylindrical and had no spiral or wavy parts.

[0078] [Evaluation method] All samples of Examples 1 to 27 and Comparative Example 1 were printed using the resin "VisiJet M3 Crystal" on a 3D printer "Projet MJP 3600" manufactured by 3D Systems, and the evaluation items were compared. Some of the examples were printed using the resin "FPU50" on a 3D printer "Carbon M2" manufactured by Carbon, and each item was additionally compared.

[0079] [Evaluation items] [Ease of bending] Five monitors pressed the bristles of each toothbrush with their fingertips to deform them, and compared and evaluated the feel of their fingertips. An average score of 4 points or more was marked "◎", 2 points or more but less than 4 points was marked "○", and less than 2 points was marked "×". <Evaluation criteria> 5 points: Very easy to bend. 4 points: Easy to bend. 3 points: Neither. 2 points: Difficult to bend. 1 point: Very difficult to bend.

[0080] [Easy to return] Five monitors pressed the bristles of each toothbrush with their fingertips to deform them, and compared and evaluated how easily the bristles returned to their original shape when they released their fingers. An average score of 4 points or more was marked "◎", 2 points or more but less than 4 points was marked "○", and less than 2 points was marked "×". <Evaluation criteria> 5 points: Very easy to return. 4 points: Easy to return. 3 points: Neither. 2 points: Difficult to return. 1 point: Very difficult to return.

[0081] [Table 1]

[0082] [Table 2]

[0083] [Table 3]

[0084] [Table 4]

[0085] As shown in Tables 1 to 4, the samples of Examples 1 to 27, in which the bristles had either a spiral portion or a wavy portion, were evaluated as being good in both ease of bending and ease of returning.

[0086] For samples with a spiral brush part, among the samples of Examples 13 to 19 in which three brush parts are arranged at equal intervals in the circumferential direction around the first normal line, samples of Examples 15 to 16 and 19 in which the product of "the sixth power of the wire diameter d" and "the square of the reciprocal of the maximum gap dimension S2" is in the range of 0.000064 to 500, and the product of "the sixth power of the wire diameter d" and "the minimum gap dimension S1" is in the range of 0.000025 to 50, were evaluated as particularly good in both ease of bending and ease of returning. In particular, sample of Example 19 in which the spiral part and the first straight part are connected via a connecting part was evaluated as the highest value in terms of the average score for both ease of bending and ease of returning.

[0087] For samples with wavy brush portions, samples of Examples 22 to 24, in which the product of the cube of thickness t and the fifth root of gap dimension M was in the range of 0.01 or more and 5 or less, and the product of the cube of thickness t and the square root of the reciprocal of gap dimension C was in the range of 0.02 or more and 10 or less, received particularly good ratings for both ease of bending and ease of returning.

[0088] On the other hand, the sample of Comparative Example 1, in which the bristles had neither a spiral portion nor a wavy portion, did not receive a good evaluation for ease of return.

[0089] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to these examples. The shapes and combinations of the components shown in the above examples are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention.

[0090] For example, in the above embodiment, a configuration in which the first straight portion 40 is provided on the brush unit 21 having the spiral portion 30 is exemplified, but this configuration is not limiting. The brush unit 21 may not have the first straight portion 40 on the tip side.

[0091] In addition, in the above embodiment, a configuration in which the spiral portion 30 and the wavy portion 32 are provided independently has been exemplified, but a configuration in which the spiral portion 30 and the wavy portion 32 are provided mixed on the support surface 5 may also be used. When this configuration is adopted, it is possible to set various directional characteristics regarding flexibility and resilience with respect to bending in the planar direction parallel to the support surface 5 by setting the number and positions of the isotropic spiral portions 30 and the anisotropic wavy portions 32.

[0092] In the above embodiment, the wavy portion 32 is folded back and forth in the long axis direction as it approaches the front side, but this configuration is not limiting. For example, the wavy portion 32 may be folded back and forth in the short axis direction as it approaches the front side, or may be folded back and forth in a diagonal direction intersecting the long axis direction and the short axis direction. Furthermore, the wavy portion 32 may be a mixture of wavy portions 32 that fold back and forth in the long axis direction as it approaches the front side, wavy portions 32 that fold back and forth in the short axis direction as it approaches the front side, and wavy portions 32 that fold back and forth in a diagonal direction as it approaches the front side. When this configuration is adopted, it is possible to set various directional characteristics regarding flexibility and restorability.

[0093] In the above embodiment, the configuration in which the connecting portion 31 is provided at the tip of the spiral portion 30 is exemplified, but the present invention is not limited to this configuration. For example, a connecting portion large enough to span a plurality of (for example, four) wavy portions 32 in a planar direction parallel to the support surface 5 may be provided, the tips of the plurality of wavy portions 32 are connected to the connecting portion, and a plurality of second linear portions 41 extend in the normal direction from the connecting portion. By adopting this configuration, the same effect as when the connecting portion 31 is provided at the tip of the spiral portion 30 can be obtained. [Explanation of symbols]

[0094] 1...toothbrush, 3...head portion, 5...support surface, 21...bristle portion, 21A...second brush portion, 30...spiral portion (curved portion), 31...connecting portion, 32...wavy portion, 33...curved portion, 40...first straight portion, 41...second straight portion, J...center line, L1...first normal line (first intersecting line), L2...second normal line (second intersecting line)

Claims

1. A head portion and A plurality of brush parts protruding from a support surface located on the front side in the thickness direction of the head part to the front side; and Of the center lines passing through the cross-sectional center of the brush part, the center line on the base end side of the brush part has a curved portion that curves with a curvature as it moves from the support surface toward the front side, The base end side of the brush part has a spiral part that extends spirally around or near a center line where the center line intersects with the support surface, The brush portion has a first linear portion extending in a normal direction to the support surface on the tip side of the spiral portion, the brush part is an additively manufactured object in which hardened bodies, each of which is hardened layer by layer, are stacked on the front side of the support surface, The wire diameter in the spiral portion is 0.5 mm or more, The minimum gap dimension between the brush portions adjacent to each other in the normal direction in the spiral portion is 0.2 mm or more and 2.0 mm or less, The inner diameter of the spiral portion is 0.2 mm or more and 2.0 mm or less, The ratio of the dimension of the first linear portion to the bristle length of the brush portion is 5% or more and 60% or less, The spiral portion extends spirally around the support surface as a starting point of the curvature.

2. The center line is The wire diameter in the spiral portion is d (mm), If the minimum gap dimension between adjacent brush parts in the spiral part in the normal direction of the support surface is S1 (mm), d ６ The value expressed by ×S1 is 0.000025 mm ７ Above 50 mm ７ Below is the The toothbrush of claim 1.

3. The wire diameter in the spiral portion is d (mm), If the maximum gap dimension in the spiral portion in the direction parallel to the support surface is S2 (mm), d ６ × (1 / S2) ２ The value expressed is 0.000064 mm ４ Over 500mm ４ Below is the The toothbrush according to claim 1 or 2.

4. The brush part has a connecting part that is connected to the tip of the spiral part, the connecting portion is a plate-like member parallel to the support surface, A plurality of second brush portions extending linearly from the connecting portion to the front side in a normal direction of the support surface are provided.

4. The toothbrush according to claim 1.

5. The base end side of the brush part is As the center line moves toward the front side, the center line has a wavy portion that moves back and forth in a direction perpendicular to the normal direction of the support surface, The center line of the wavy portion extends without going around a line of intersection that intersects with the support surface at or near the center. The toothbrush of claim 1.

6. In the wavy portion The thickness in the normal direction is t (mm), The cube of the thickness t is t3, The gap dimension in the normal direction is M (mm), If the fifth root of the gap dimension M is M5, then The value expressed as t3 x M5 is 0.01 mm －２ More than 5 mm －２ Below is the 6. The toothbrush of claim 5.

7. The gap dimension in the wave-shaped portion in a direction perpendicular to the normal direction is C (mm), If the square root of the reciprocal of the gap dimension C is C2, then The value expressed by t3 x C2 is 0.02 mm －３／２ More than 10 mm －３／２ Below is the The toothbrush according to claim 5 or 6.

8. The brush part has a second straight portion extending in the normal direction on the tip side of the wavy portion.

8. The toothbrush according to any one of claims 5 to 7.

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