CN107847046B9

CN107847046B9 - Tooth brush

Info

Publication number: CN107847046B9
Application number: CN201680042389.3A
Authority: CN
Inventors: 明间洋子; 木村笃人; 奥田靖; 村田善保
Original assignee: Lion Corp
Current assignee: Lion Corp
Priority date: 2015-07-24
Filing date: 2016-07-22
Publication date: 2020-06-19
Anticipated expiration: 2036-07-22
Also published as: WO2017018340A9; CN107847046B; WO2017018340A1; MY189446A; JPWO2017018340A1; CN107847046A; JP6858123B2

Abstract

The invention aims to provide a toothbrush which can effectively remove tartar and has excellent cleaning feeling, and can ensure excellent hair bending durability even when the hair unfolding durability is improved. A toothbrush in which a plurality of tufts (112) are implanted into a bristle implanting surface (118a) of a head (118), the tufts (112) having tapered bristles (120) each provided at a tip portion thereof with a tapered portion (121) that decreases in diameter as it approaches the tip, and the ratio B1/A1 of the maximum stress B1 to the maximum stress A1 calculated by a predetermined stress calculation method being 1.0 to 1.9.

Description

Tooth brush

Technical Field

The present invention relates to toothbrushes.

The present application claims priority based on Japanese patent application No. 2015-.

Background

In particular, since tartar accumulated in gaps such as interdental portions and cervical portions is difficult to remove, a toothbrush is required to have excellent tartar removal performance. The plaque removal performance of a toothbrush is affected by the arrangement of tufts and the specifications of the individual bristles that form the tufts. As bristles excellent in plaque removal efficiency and cleaning feeling that are deposited in gaps such as interdental portions and cervical portions, there is known a tapered bristle in which a tapered portion that decreases in diameter as it goes toward the tip end is provided at the tip end portion.

Further, not only tartar removal but also sufficient hair spreading durability are required for toothbrushes. Since the toothbrush having sufficient durability is developed, the toothbrush can be used continuously for a certain period of time, and thus the frequency of replacement of the toothbrush can be suppressed from increasing excessively. In particular, since the processing technique for manufacturing the tapered bristles is complicated and thus the cost is high, and a toothbrush including the tapered bristles is expensive, sufficient bristle spreading durability is required so as not to excessively increase the replacement frequency of the toothbrush.

The durability of the developed bristles of a toothbrush is affected not only by the arrangement of the tufts and the specifications of the bristles, but also by the material of the bristles. As bristles having excellent bristle spreading durability, for example, bristles made of polytrimethylene terephthalate (PTT) are known (for example, patent document 1).

Documents of the prior art

Patent document

Patent document 1: international publication WO2005/039355

Disclosure of Invention

Problems to be solved by the invention

However, in some cases, when the bristles formed of PTT or the like and having improved bristle spreading durability are used continuously, the bristles are bent near the base of the bristles (the portion where the opening surface of the implanted pore is located). Even if the spreading of the bristles is suppressed, it is difficult to sufficiently improve the durability of the toothbrush if the bristles are easily bent. As described above, in a toothbrush, it is important that not only tartar can be efficiently removed and the toothbrush is excellent in cleaning feeling, but also excellent hair folding durability can be secured even when the hair spreading durability is improved.

The present invention has an object of 1 st to provide a toothbrush which can efficiently remove plaque and has an excellent cleaning feeling, and can secure excellent bristle bending durability even when the bristle spreading durability is improved.

It is a2 nd object of the present invention to provide a toothbrush which can secure excellent hair folding durability even when the hair unfolding durability is improved.

Means for solving the problems

The 1 st aspect of the present invention has the following configuration.

[1] A toothbrush comprising a bristle part formed by implanting a plurality of tufts into a bristle-implanting surface of a head part, wherein the tufts have tapered bristles,

the taper hair is provided with a taper part at the tip part, the diameter of the taper part is reduced along with the tip, the ratio B1/A1 of the maximum stress B1 to the maximum stress A1 calculated by a stress calculation method comprising the following step (a1) and the following step (B1) is 1.0-1.9,

(a1) rubbing the bristle part on a spherical surface of a radius of 85mm in such a manner that a load applied to the tip of the bristle part was 200g, measuring a displacement amount x1(mm) of the tapered bristle tip with respect to the base in the plane direction of the flocked surface at that time,

(b1) an engineering simulation was performed on a state in which the tip end of the tapered hair was displaced by only the displacement amount x1(mm) in a direction perpendicular to the axial direction of the tapered hair, and the maximum stress a1 generated at the base of the tapered hair rather than the tapered portion and the maximum stress B1 generated at the tapered portion were calculated.

[2] The toothbrush according to [1], wherein the length of the tapered portion is 3 to 11.5 mm; the position of the boundary between the base part and the conical part in the conical hair is equal to the position of the hair-planting surface, or the base part is positioned outside the hair-planting surface.

[3] The toothbrush according to [1] or [2], characterized in that a diameter of a portion 0.1mm away from a tip of the tapered portion is 0.07mm or less.

[4] The toothbrush according to any one of [1] to [3], characterized in that the tapered bristles are formed of polytrimethylene terephthalate.

The 2 nd aspect of the present invention has the following configuration.

[5] A toothbrush comprising a bristle part formed by implanting a plurality of tufts into a bristle-implanting surface of a head, wherein the tufts have bristles, and the bristles are provided with a diameter part having a cross-sectional area of 14% or less of the cross-sectional area of a base part at a position closer to the base part and 0.1mm or more from the tips of the bristles, and have a region extending from the base part to the tips and having a cross-sectional area larger than the diameter part.

[6] The toothbrush according to [5], wherein the maximum stress A2 and the maximum stress B2 calculated by a stress calculation method comprising the following step (a2) and the following step (B2) satisfy A2>0 and B2>0, (a2) so that a load applied to the tip of the brush part is 200g, rubbing the brush part on a spherical surface having a radius of 85mm, measuring a displacement amount x2(mm) of a tip end of the bristle with respect to a base in a plane direction of the bristle-implanted surface at this time, (B2) performing an engineering simulation of a state in which the tip end of the bristle is displaced by only the displacement amount x2(mm) in a direction perpendicular to an axial direction of the bristle, and calculating a maximum stress a2 at a stress concentration portion of the bristle generated closest to the base and a maximum stress B2 at a stress concentration portion generated closer to the tip end side than the maximum stress a 2.

[7] The toothbrush according to [5], wherein the maximum stress A2 and the maximum stress B2 calculated by a stress calculation method comprising the following step (a2) and the following step (B2) satisfy B2. gtoreq.A 2>0,

(a2) rubbing the brush part on a spherical surface having a radius of 85mm so that a load applied to the tip of the brush part becomes 200g, measuring a displacement x2(mm) of the tip of the bristle part with respect to the base part in the plane direction of the flocked surface at that time,

(b2) an engineering simulation was performed on a state in which the hair tip was displaced by only the displacement amount x2(mm) in a direction perpendicular to the axial direction of the hair, and a maximum stress a2 at a stress concentration portion generated most toward the base and a maximum stress B2 at a stress concentration portion generated more toward the tip side than that in the hair were calculated.

[8] The toothbrush according to any one of [5] to [7], wherein the bristles are tapered bristles provided with a tapered portion that decreases in diameter as it goes toward a tip end, and the tapered portion has the diameter portion.

[9] The toothbrush according to any one of [5] to [8], wherein the bristles are formed of polytrimethylene terephthalate.

[10] The toothbrush according to [8] or [9], characterized in that it has tapered bristles in which the ratio B2/A2 of the maximum stress B2 to the maximum stress A2 is 1.0 to 1.9.

In addition, in the case of the taper-shaped bristles used in the embodiment 2, the maximum stress a2 and the maximum stress B2 are the same as the maximum stress a1 and the maximum stress B1 in the embodiment 1.

ADVANTAGEOUS EFFECTS OF INVENTION

The toothbrush according to claim 1 of the present invention can efficiently remove plaque to provide an excellent cleaning feeling, and can ensure excellent durability against bending of bristles even when the durability against spreading of the bristles is improved.

The toothbrush according to claim 2 of the present invention can ensure excellent durability of bristle bending even when the durability of bristle spreading is improved.

Drawings

Fig. 1 is a side view showing an example of a toothbrush according to embodiment 1 of the present invention.

Fig. 2 is an enlarged plan view of the head of the toothbrush of fig. 1.

Fig. 3 is a cross-sectional view of the toothbrush of fig. 1, with the vicinity of 1 tuft enlarged.

Fig. 4 is a schematic diagram illustrating a step (a1) of the stress calculation method according to embodiment 1 of the present invention.

Fig. 5 is a side view showing an example of the toothbrush according to embodiment 2 of the present invention.

Fig. 6 is an enlarged plan view of the head of the toothbrush of fig. 5.

Fig. 7 is an enlarged cross-sectional view of the vicinity of 1 tuft in the head of the toothbrush of fig. 5.

Fig. 8 is a schematic diagram illustrating a step (a2) of the stress calculation method according to embodiment 2 of the present invention.

Fig. 9 is a side view showing another example of bristles in the toothbrush according to the 2 nd aspect of the present invention.

Fig. 10 is a side view showing another example of bristles in the toothbrush according to the 2 nd aspect of the present invention.

Fig. 11 is a side view showing another example of bristles in the toothbrush according to claim 2 of the present invention.

Description of the symbols

11. 21 toothbrush

110. 210 handle body

112. 212 wool bundle

114. 214 handle

116. 216 neck part

118. 218 head

118a, 218a flocking face

119. 219 straight part

120 conical wool

120a, 220a tip

120b, 220b base

121. 221 taper portion

122 bristle part

122a bristle part tip

123. 228 hair planting holes

124. 226 flat wire (flat plate)

220 wool

222 small diameter part

224 bristle part

224a bristle part tip

Detailed Description

[ means 1]

An example of the toothbrush according to embodiment 1 of the present invention will be described below.

The toothbrush 11 of the present embodiment includes, as shown in fig. 1 to 3, a handle 110 and a brush portion 122 formed of a plurality of tufts 112 implanted in the handle 110. The shank 110 includes: a rod-shaped handle 114, a neck 116 extending from the tip of the handle 114 and being thinner than the handle 114, and a head 118 disposed at the tip of the neck 116. A plurality of tufts 112 are implanted in hair-planting surface 118a of head 118.

The stem body according to embodiment 1 may be formed in a known manner.

In the handle body 110, a handle portion 114 and a neck portion 116 are integrally formed with a head portion 118.

The handle portion 114 is a portion to be held by hand during brushing, and has a rod shape.

The shape of the cross section perpendicular to the axial direction (longitudinal direction) of the stem is not particularly limited, and examples thereof include a shape in which the corners of a rectangle are rounded, a rectangle, and a circle.

The thickness and length of the handle portion can be appropriately designed according to the intended person using the toothbrush.

A neck 116, which is rod-shaped in plan view thinner than the shank 114.

The length, width and thickness of the neck portion are not particularly limited, and may be appropriately designed according to the person who uses the toothbrush.

Head 118 is the portion of neck 116 that is disposed at the tip of neck and that implants plurality of tufts 112. The upper surface of head 118 is a hair-planting surface 118a for planting hair bundle 112. The head 118 has a plate shape in which corners of a rectangular shape in the axial direction are rounded in plan view.

The length, width and thickness of the head are not particularly limited, and may be appropriately designed according to the person who uses the toothbrush.

When the material for forming the stem is selected in consideration of the rigidity, mechanical properties, and the like required for toothbrushes, for example, a high-hardness resin having a flexural modulus of elasticity (JIS K7203) of 500MPa to 3000MPa may be used. Examples of the high-hardness resin include polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycyclohexylenedimethylene terephthalate (PCT), Polystyrene (PS), acrylonitrile-butadiene-styrene resin (ABS), Cellulose Propionate (CP), polyarylate, polycarbonate, acrylonitrile-styrene copolymer resin (AS), polyacetal resin (POM), and the like. These resins may be used alone in 1 kind, or 2 or more kinds may be used in appropriate combination. The head, neck and handle may be partially or entirely covered with a soft resin such as an elastomer.

The brush portion 122 is formed by a plurality of tufts 112 implanted in the bristle-implanted surface 118a of the head 118.

The toothbrush of claim 1 is not particularly limited as to the manner of implanting tufts in the bristle-implanting surface of the head. In the toothbrush 11 of this example, 24 tufts 112 are implanted so that 3 tufts 112 are implanted in the width direction, 4 tufts 112 are arranged in the width direction in the region therebetween, and 6 tufts 112 are arranged in the axial direction, respectively, near the tip end and near the rear end of the implantation surface 118 a.

Tuft 112 is formed of a plurality of tapered bristles 120 in a bundle.

The shape of the tufts 112 is not particularly limited, and may be cylindrical or prismatic.

The length and thickness of the tufts 112 can be determined in consideration of the stiffness of the bristles required for the tufts 112.

The tufts 112 of this example are implanted on the hair-setting surface 118a by the flat-line hair-setting method. Specifically, as shown in fig. 3, a plurality of tapered bristles 120 each having a tapered portion 121 at both ends thereof are folded into two by a flat wire 124 in a bundle, and are fitted into a hair-setting hole 123 formed in a hair-setting surface 118a of a head 118, whereby a hair bundle 112 is set.

The method of implanting the hair bundle into the hair-implanting surface of the head is not limited to the flat line hair-implanting method, and may be a heat seal hair-implanting method, an in-mold spheroidizing method (in-mold process), or the like.

The tapered hair 120 is the following tapered hair (hereinafter, referred to as tapered hair (X1)). A tapered portion 121 that decreases in diameter toward the tip end is provided at a portion on the tip end side of the straight portion 119, and the ratio B1/A1 of the maximum stress B1 to the maximum stress A1, which is calculated by a stress calculation method including a step (a1) and a step (B1) described later, is 1.0 to 1.9. In addition, the tapered portion means a portion from a position where the diameter in the tapered hair starts to decrease up to the tip.

The toothbrush of claim 1, wherein the tufts of bristles are provided with tapered bristles (X1), not only can plaque be removed efficiently and the toothbrush is excellent in cleaning feeling, but also excellent durability against bending of the bristles can be ensured even when the durability against spreading of the bristles is improved.

The tapered bristles 120 forming the tufts 112 of this example are all tapered bristles (X1). In the bristle bundle in the toothbrush according to claim 1 of the present invention, the tapered bristles (X1) may be used in combination with bristles other than the tapered bristles (X1) such as straight bristles.

The ratio of the number of tufts of the tapered bristles (X1) to the total number of bristles forming a tuft is preferably 50% or more, more preferably 75% or more, and particularly preferably 100%.

The maximum stress a1 and the maximum stress B1 were calculated by a stress calculation method including the following step (a1) and the following step (B1), and by this, the ratio B1/a1 in the cone hair was calculated.

(a1) When the bristle part was rubbed on a spherical surface having a radius of 85mm by applying a load of 200g to the tip of the bristle part, the amount of displacement x1(mm) of the tip of the tapered hair from the base in the plane direction of the flocked surface was measured.

(b1) The tip of the tapered hair was subjected to engineering simulation in a state of being displaced by the displacement amount x1(mm) in a direction perpendicular to the axial direction of the tapered hair, and the maximum stress a1 generated at the base of the tapered hair and the maximum stress B1 generated at the tapered hair were calculated.

(Process (a1))

For example, in the case of the toothbrush 11, as shown in fig. 4, the brush part 122 is pressed against a spherical surface 1100 having a radius of 85mm, and is moved back and forth in the axial direction of the handle body 110 to rub. Then, in a state where the bristle part tip 122a is applied with a load of 200g by rubbing the bundle of bristles 112, the displacement amount x1(mm) of the tip 120a relative to the base 120b of the tapered hair 120 in the plane direction of the bristle planting surface 118a of the head 118, that is, the deflection amount of the tapered hair 120 was measured.

Further, "a load of 200g is applied to the bristle part tip" means that a reaction force value applied to the bristle part tip is 200g in a state where the bristle part of the toothbrush is rubbed against a spherical surface. That means that, for example, when the bristle part of a toothbrush is rubbed onto a scale, a force reading 200g from said scale is applied to the bristle part tip.

The "base of the tapered hair" is a portion of the tapered hair that is not tapered, and means a portion corresponding to the position of the bristle-implanted surface of the head, among portions having the shape of the bristles before tapering. When both end portions are tapered bristles, a portion corresponding to the bristle surface of the head portion among straight portions of the middle portion in the longitudinal direction of the tapered bristles is a base portion.

The material of the member having the spherical surface for rubbing the brush part is not particularly limited, and examples thereof include a material having rigidity equivalent to that of a gum.

(step (b1))

In the step (a1), when the displacement amount x1(mm) of the tapered hair 120 in the toothbrush 11 is measured, the position of the tapered hair having the same shape and material as the tapered hair 120 corresponding to the base of the tapered hair is fixed, and a state in which the tip of the tapered hair is displaced by only the displacement amount x1(mm) in the direction perpendicular to the axial direction of the tapered hair is simulated by engineering. In this case, in the tapered hair in the engineering simulation, stress concentration is observed in each of the tapered portion and the straight portion closer to the base than the tapered portion. In the engineering simulation, the maximum stress generated in the tapered portion at the base of the tapered hair is calculated as the maximum stress a1, and the maximum stress generated in the tapered portion is calculated as the maximum stress B1.

As the engineering simulation, for example, 3-dimensional Finite Element Method (FEM) analysis using LS-DYNA (analysis software, manufactured by LSTC corporation) can be used. The engineering simulation can be performed by inputting the shape of the tapered hair (hair length, length of the tapered portion, tip diameter, etc.) and the young's modulus of the material used for the tapered hair as conditions for the tapered hair.

The ratio B1/A1 of the cone-shaped hair (X1) is 1.0 to 1.9, preferably 1.0 to 1.7, and more preferably 1.5 to 1.7. When the ratio B1/A1 is within the above range, not only can tartar in the narrow part be removed efficiently and the feeling of cleaning is excellent, but also excellent hair folding durability can be ensured even when the hair spreading durability is improved.

The ratio B1/A1 of the taper hair (X1) can be adjusted by, for example, the length and material of the taper portion.

The axial length L1 (FIG. 3) of the tapered portion of the tapered hair (X1) is preferably 3 to 11.5mm, more preferably 4 to 7 mm. When the length of the tapered portion is within the above range, it is easy to ensure excellent bending resistance against burrs. When the length of the tapered portion is equal to or greater than the lower limit value, the tapered portion easily enters a gap between the interdental portion and the cervical portion, and plaque accumulated in the gap is easily scraped off. When the length of the tapered portion is equal to or less than the upper limit, tartar in the narrow portion can be easily scraped off by appropriate rigidity of the bristles.

The ratio of the axial length L1 of the tapered portion to the hair length of the tapered hair (X1) is preferably 5 to 100%, more preferably 20 to 100%.

The average length in the axial direction of the tapered part in the tapered hair (X1) forming a tuft is preferably 3 to 11.5mm, more preferably 4 to 7 mm.

In the tapered hair (X1), the boundary position between the straight portion and the tapered portion is preferably equal to the position of the hair-planted surface of the head, or the straight portion is preferably located outside the hair-planted surface. That is, in the tapered hair (X1), the straight portion is preferably just hidden by being housed in the implantation hole of the head, or the straight portion is preferably exposed from the head.

The diameter of the portion of the tapered hair (X1) that is offset from the tip of the tapered portion by 0.1mm in the direction of the base portion (hereinafter also referred to as the tip diameter) is preferably 0.07mm or less, more preferably 0.02mm or less, and still more preferably 0.01 to 0.02 mm. When the tip diameter of the tapered hair (X1) is 0.02mm or less, the tapered portion easily enters into a gap such as an interdental portion and a cervical portion, and plaque accumulated in the gap is easily scraped off, so that an excellent brush feeling is easily obtained.

In the mode 1, the average value of the tip diameters of the tapered hairs (X1) forming the bundle of hairs is preferably 0.07mm or less.

The average diameter of the straight portion of the tapered hair (X1) may be determined in consideration of the material quality, and when the cross section of the straight portion is circular, it is, for example, 4 to 10 mils (1 mil-1/1000 inch-0.0254 mm). The cross-sectional shape of the tapered bristles may be any shape.

The average hair length H1 (fig. 3) of the tapered hair (X1), that is, the average length from the position corresponding to the hair-planted surface to the tip of the tapered hair (X1), is not particularly limited, and may be, for example, 5 to 15 mm.

The material for forming the tapered bristles is not particularly limited, and examples thereof include polyesters such as polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polybutylene naphthalate (PBN); polyamides such as 612 nylon and 610 nylon; polyolefins such as Polyethylene (PE) and polypropylene (PP). Among them, in view of excellent hair spread resistance, PTT is preferable. In the invention of claim 1, even when the tapered bristles are PTT bristles, excellent bending resistance can be ensured.

(production method)

The method for manufacturing the toothbrush according to embodiment 1 of the present invention is not particularly limited, and a known method can be used.

As a method of manufacturing the stem body, injection molding (injection molding) or the like can be exemplified. As a method for producing the tapered hair (X1), for example, a method of immersing both end portions of the used hair obtained by spinning in a solution such as an acid or alkali solution for a predetermined time, and performing extraction, neutralization, water washing treatment, and the like can be mentioned. Examples of the method of implanting the hair bundle include a flat wire type hair-planting method, a thermal fusion type hair-planting method, and an in-mold spheroidizing method.

In the toothbrush according to the above-described aspect 1 of the present invention, since the bristles for forming tufts are provided with the tapered bristles (X1), tartar accumulated in the gaps such as the interdental portion and the cervical portion can be removed efficiently, and the toothbrush is excellent in cleaning feeling. Further, since the tapered bristles (X1) having a B1/A1 ratio of 1.0 to 1.9 are provided as the bristles, and the stress concentration portion during brushing is located at both the base portion and the tapered portion of the tapered bristles, it is possible to suppress the stress concentration only in the vicinity of the base portion of the bristles and the local repetition of the stress concentration portion to accumulate fatigue. Therefore, in the embodiment 1 of the present invention, the tapered bristles (X1) are formed of PTT or the like, and thus even when the bristle spreading durability is improved, excellent bristle folding durability can be ensured. In particular, when the tapered bristles (X1) are formed of PTT, excellent bristle spreading durability and bristle bending durability can be achieved at the same time.

[ means 2]

A toothbrush according to claim 2 of the present invention includes a brush portion formed by implanting a plurality of tufts into a bristle-implanted surface of a head. The toothbrush according to claim 2 of the present invention is a bristle tuft comprising bristles, wherein a small diameter portion having a cross-sectional area of 14% or less of the cross-sectional area of a base portion is provided at a position closer to the base portion and spaced from the tip end of the bristles by 0.1mm or more, and the small diameter portion has a region extending from the base portion toward the tip end and having a cross-sectional area larger than that of the small diameter portion.

When a force is applied to the bristle tip in a direction perpendicular to the axial direction, the bristle having such a small diameter portion generates a stress concentration portion near the base and on the tip side thereof. This can suppress the stress from concentrating only in the vicinity of the base of the bristles and locally repeating at that portion to accumulate fatigue. Therefore, even when the hair spreading durability is improved, excellent hair folding durability can be ensured by the hair for forming PTT and the like.

An example of the toothbrush according to embodiment 2 of the present invention will be described below.

The toothbrush 21 of the present embodiment includes a handle 210 and a brush portion 224 formed of a plurality of tufts 212 implanted in the handle 210, as shown in fig. 5 to 7. The handle body 210 includes: a rod-shaped handle 214, a neck 216 extending from the tip of the handle 214 and thinner than the handle 214, and a head 218 disposed at the tip of the neck 216. A plurality of tufts 212 are implanted in hair-planting surface 218a of head 218.

The stem body according to embodiment 2 may be formed in a known manner.

In the handle body 210, the handle portion 214 is integrally formed with the neck portion 216 and the head portion 218.

The handle 214 is a portion to be held by hand during brushing, and has a rod shape.

The shape of the cross section perpendicular to the axial direction (longitudinal direction) of the stem is not particularly limited, and examples thereof include a rectangular shape with rounded corners, a rectangular shape, and a circular shape.

The neck portion 216 has a rod shape thinner than the handle portion 214 in a plan view.

Head 218 is a portion that is disposed at the tip of neck 216 and that implants the plurality of tufts 212. The upper surface of head 218 is the hair-planting surface 218a of implanted hair bundle 212. The head 218 has a shape with a rounded plate at the corner of an axially rectangular rectangle in plan view.

When the material for forming the handle body in embodiment 2 is selected in consideration of the rigidity, mechanical properties, and the like required for toothbrushes, for example, a high-hardness resin having a flexural modulus of elasticity (JIS K7203) of 500MPa to 3000MPa may be used. Examples of the high-hardness resin include the high-hardness resins listed in embodiment 1. Furthermore, polybutylene terephthalate (PBT) can also be used. These resins may be used alone in 1 kind, or 2 or more kinds may be used in appropriate combination. The head, neck and handle may be partially or entirely covered with a soft resin such as an elastomer.

The bristle part 224 is formed by a plurality of tufts 212 implanted in the bristle-implanting surface 218a of the head 218.

The mode for implanting tufts in the bristle-implanting surface of the head in the toothbrush of the 2 nd aspect is not particularly limited. In the toothbrush 21 of this example, 24 tufts 212 are implanted so that 3 tufts 212 are implanted in the width direction, 4 tufts 212 are arranged in the width direction in the area between them, and 6 tufts 212 are arranged in the axial direction, respectively, near the tip and near the rear end of the implantation surface 218 a.

The hair bundle 212 is formed by bundling a plurality of bristles 220.

The shape of the tufts 212 is not particularly limited, and may be cylindrical or prismatic.

The length and thickness of tufts 212 can be determined in consideration of the stiffness of the bristles required for tufts 212.

In this example, the hair bundle 212 is implanted into the hair-planted surface 218a by a flat-line hair-planting method. Specifically, as shown in fig. 7, a plurality of bristles 220 are bundled and folded into two by a flat wire 226, and are inserted into an implantation hole 228 formed in an implantation surface 218a of the head 218, thereby implanting the bristle bundle 212.

The method of implanting the hair bundle into the hair-implanting surface of the head is not limited to the flat-line hair-implanting method, and may be a thermal fusion type hair-implanting method, an in-mold spheroidizing method, or the like.

In the 2 nd aspect, the bristles having the small diameter portions are preferably tapered bristles.

The bristles 220 are tapered bristles provided with tapered portions 221 that decrease in diameter toward the tip ends on both end side portions of the straight portion 219. The tapered portion 221 of the bristles 220 has a small diameter portion 222 having a cross section of 14% or less of the cross section of the base portion 220b at a position closer to the base portion 220b and at a distance of 0.1mm or more from the tip portion 220 a. Further, since the bristles 220 include the straight portion 219, they have a region extending from the base portion 220b toward the tip end 220a and having a larger cross-sectional area than the small-diameter portion 222.

In addition, in the 2 nd aspect, the cross-sectional area of the base portion means the cross-sectional area of the base portion of the bristles when the base portion is cut in the direction perpendicular to the axial direction. The same applies to the cross-sectional area of the small diameter portion.

In the tapered hair having the small diameter portion in the tapered portion, when the ratio of the cross-sectional area of the position spaced 0.1mm from the hair tip in the axial direction to the cross-sectional area of the base portion is 14%, the position spaced 0.1mm from the hair tip in the axial direction in the tapered portion is the small diameter portion. Further, when the ratio of the cross-sectional area at a position 0.1mm apart from the burr tip in the axial direction with respect to the cross-sectional area of the base portion is less than 14%, a position 0.1mm apart from the burr tip in the axial direction in the tapered portion to a position where the ratio is 14% is a small diameter portion.

In the case of a tapered hair having a small diameter portion in the tapered portion, the ratio of the cross-sectional area at a position 0.1mm away from the hair tip in the axial direction to the cross-sectional area of the base portion is 14% or less, preferably 0.1 to 14%.

The form of the small diameter portion is not particularly limited, and the following forms can be exemplified: for example, the outer peripheral surface of the bristle 220 is inclined with respect to the axial direction in a side view, such as a linear form that is reduced in diameter toward the tip of the bristle, like the small diameter portion 222 of the tapered portion 221. Further, in the small diameter portion 222 of the hair 220, both sides of the outer peripheral surface are inclined to be close to each other in a side view. However, the form of the small diameter portion is not limited to this form, and may be a form in which only one side of the outer peripheral surface is inclined in a side view.

The form of the small diameter portion is not limited to the form of a tapered portion provided in the tapered hair. For example, the diameter-reduced portion may be formed by: the outer peripheral surface of the bristles is recessed around the entire circumference in the circumferential direction so as to have an arc-like shape in a side view. Further, the small diameter portion may be formed by: the outer peripheral surface of the bristles is recessed so that one side of the outer peripheral surface of the bristles is recessed in an arc shape in a side view. In the case of these methods, the diameter-reducing portion may be located closer to the base than to the position 0.1mm from the tip of the bristle.

In the case of the small-diameter portion of these embodiments, the ratio of the cross-sectional area of the small-diameter portion to the cross-sectional area perpendicular to the axial direction of the base portion is 14% or less, preferably 0.1 to 14%.

The number of the diameter-reduced portions in one hair is 1 in the case of the hair 220, but may be 2 or more. The larger the number of the small diameter portions in one bristle, the larger the number of the stress concentration portions when a force is applied to the tip of the bristle in a direction perpendicular to the axial direction. For example, when one bristle has 2 small diameter portions, when a force is applied to the tip of the bristle in a direction perpendicular to the axial direction, a stress concentration portion is generated in the vicinity of the base and 2 small diameter portions or 3 in total in the vicinity thereof.

In the 2 nd aspect, the bristles having the small diameter portions need only have small diameter portions, and are not limited to tapered bristles. In the bristle bundle in the toothbrush of claim 2, bristles having a small diameter portion may be used in combination with bristles having no small diameter portion, such as straight bristles.

The ratio of the number of bristles having a small diameter portion to the total number of bristles forming a tuft is preferably 50% or more, more preferably 75% or more, and particularly preferably 100%.

In the hair having a small diameter portion according to embodiment 2, when the maximum stress a2 and the maximum stress B2 calculated by a stress calculation method including the step (a2) and the step (B2) described below are included, a2>0, B2>0, and B2 ≧ a2>0 are preferable.

Hereinafter, a stress calculation method will be described. The stress calculation method according to claim 2 includes the following steps (a2) and (b 2).

(a2) When the brush part was rubbed on a spherical surface of a radius of 85mm in such a manner that a load of 200g was applied to the tip of the brush part, the amount of displacement x2(mm) of the tip of the bristle part relative to the base part in the plane direction of the bristle-implanted surface of the toothbrush was measured.

(b2) An engineering simulation was performed on a state in which the tip of the hair was displaced by only the displacement amount x2(mm) in a direction perpendicular to the axial direction of the hair, and the maximum stress a2 at the stress concentration portion generated by the hair at the most proximal portion and the maximum stress B2 at the stress concentration portion generated at the tip side than that were calculated.

(Process (a2))

For example, in the case of the toothbrush 21, as shown in fig. 8, the brush portion 224 is pressed against a spherical surface 2100 having a radius of 85mm, and is moved back and forth in the axial direction of the handle 210 by friction. Then, in a state where the bristle tuft 212 is rubbed and a load of 200g is applied to the bristle portion tip 224a, the displacement amount x2(mm) of the tip 220a of the hair 220 for use in the plane direction of the hair-planted surface 218a of the head 218 with respect to the base 220b, that is, the deflection amount of the hair 220, is measured.

Further, "the load applied to the bristle part tip is set to 200 g" means that the reaction force value applied to the bristle part tip is set to 200g in a state where the toothbrush bristle part is rubbed against the spherical surface. That is, for example, when the brush portion of the toothbrush is rubbed against the scale, a force is applied to the tip of the brush portion when the scale reads 200 g.

The "base portion of the hair is a portion corresponding to the position of the hair-planted surface of the head portion, among the portions having the largest diameter, such as the portions of the hair, on which tapering is not performed.

(step (b2))

In the step (a2), when the displacement amount x2(mm) of the bristles 220 in the toothbrush 21 is measured, the bristles having the same shape and material as the bristles 220 are fixed at positions corresponding to the bases of the bristles, and the bristles are subjected to engineering simulation in a state where the tips thereof are displaced by the displacement amount x2(mm) in a direction perpendicular to the axial direction of the bristles. In this case, the hairs used in the engineering simulation were observed to have stress concentrations in the vicinity of the base and the small diameter portion or the vicinity of the small diameter portion on the tip side of the base. In the engineering simulation, the maximum stress at the stress concentration portion closest to the base, that is, the stress concentration portion near the base is calculated as the maximum stress a2, and the maximum stress at the stress concentration portion closer to the tip end is calculated as the maximum stress B2. When 2 or more small diameter portions are provided in the bristles and 2 or more stress concentration portions are observed other than the stress concentration portion near the base portion, the maximum stress B2 is calculated for each stress concentration portion other than the stress concentration portion near the base portion.

As the engineering simulation, the same engineering simulation as that exemplified in embodiment 1 can be used.

The relationship of maximum stress a2 to maximum stress B2 can be adjusted by adjusting, for example, the ratio of the cross-sectional area of the diameter section in the bristles to the cross-sectional area of the base section. When the hair is a tapered hair, the adjustment can be made by adjusting the tip diameter of the tapered hair, the length of the tapered portion, and the like.

In addition, in the 2 nd aspect, the tip diameter of the tapered hair means the diameter at a position 0.1mm away from the tip of the tapered hair on the base side.

When the bristles are tapered bristles, the axial length L2 (FIG. 7) of the tapered portion is preferably 1 to 15mm, more preferably 3 to 7 mm. When the length of the tapered portion is within the above range, it is easy to ensure excellent bending resistance against burrs. When the length of the tapered portion is equal to or greater than the lower limit value, the tapered portion easily enters a gap between the interdental portion and the cervical portion, and plaque accumulated in the gap is easily scraped off. When the length of the tapered portion is equal to or less than the upper limit, the stiffness (rigidity) of the bristles is ensured, and tartar can be easily scraped off. In addition, it is possible to prevent the hair tip from being easily opened due to repeated use.

When the bristles are tapered bristles, the ratio of the axial length L2 of the tapered portion to the bristle length of the tapered bristles is preferably 5 to 100%, more preferably 20 to 100%.

When the bristles are tapered bristles, the average axial length of the tapered portions of the tapered bristles forming the bristle bundle is preferably 1 to 15mm, more preferably 3 to 7 mm.

When the hair is a cone-shaped hair, the diameter of the tip of the cone-shaped hair is preferably 0.01mm to 0.07 mm. When the tip diameter of the tapered hair is within the above range, when a force is applied to the tip of the tapered hair in a direction perpendicular to the axial direction, a stress concentration portion is likely to be generated in the small diameter portion located on the tip side portion of the tapered portion, and the stress at the base portion is likely to be dispersed to the small diameter portion or its vicinity, thereby easily ensuring sufficient hair bending durability.

The hair is used as the tapered hair, and when the relationship between the maximum stress A2 and the maximum stress B2 is that B2 is more than or equal to A2>0, the diameter of the tip of the tapered hair is more preferably 0.01-0.03 mm.

In the case of the mode 2, when the hair is a cone-shaped hair, the average value of the diameters of the tips of the cone-shaped hairs (X1) forming the hair bundle is preferably 0.01 to 0.07 mm.

The diameter of the base portion of the bristles can be determined in consideration of the material, and the cross section of the base portion is circular, and is, for example, 4 to 10 mils (1mil or 1/1000inch or 0.0254mm), and more preferably 5 to 8 mils. In addition, the cross section of the bristles may be polygonal, and is not limited to circular.

The average hair length H2 (fig. 7) of the bristles, that is, the average length from the position corresponding to the implanted surface to the tip of the bristles is not particularly limited, and may be, for example, 5 to 15 mm.

The material for forming the bristles is not particularly limited, and examples thereof include the same materials as those exemplified in embodiment 1. Among them, in view of excellent hair spread resistance, PTT is preferable. In embodiment 2, even when PTT bristles are used as the bristles, excellent bending resistance can be ensured.

(production method)

The method for manufacturing the toothbrush according to embodiment 2 is not particularly limited, and a known method can be used.

Examples of the method for producing the stem body include injection molding. As a method for producing the tapered hair as the hair for use, for example, the same method as that exemplified in embodiment 1 can be exemplified. As a method for implanting the hair bundle, as in the case of embodiment 1, a flat wire type hair-planting method, a thermal fusion type hair-planting method, an in-mold spheroidizing method, and the like can be exemplified.

In the toothbrush according to the 2 nd aspect of the present invention described above, the tufts of bristles have small diameter portions having a cross-sectional area of 14% or less of the cross-sectional area of the base portion at positions closer to the base portion, which are spaced from the bristle tips by 0.1mm or more. Further, the bristles have a region extending from the base toward the tip and having a larger cross-sectional area than the small-diameter portion. With this, in the toothbrush of the 2 nd aspect, since a plurality of stress concentration portions are generated in the bristles for brushing near the base and on the tip side thereof, it is possible to suppress stress concentration only near the base of the bristles and fatigue accumulation due to local repetition in the portions. Therefore, in the case of embodiment 2, the excellent hair folding durability can be ensured even when the hair spreading durability is improved by the formation of the hair of PTT or the like. In particular, when the PTT-formed bristles are used, excellent durability against both development and bending of the bristles can be achieved.

In addition, in the case of embodiment 2 of the present invention, in particular, when tapered bristles are used as the bristles having the small diameter portions, tartar accumulated in gaps such as interdental portions and tooth neck portions can be removed efficiently, and a toothbrush having a more excellent cleaning feeling can be obtained.

The toothbrush according to embodiment 2 of the present invention is not limited to the toothbrush 21. For example, the toothbrush according to claim 2 may be a toothbrush provided with bristles 220A illustrated in fig. 9.

The bristles 220A are the following tapered bristles: on the tip end side of the straight portion 219, tapered bristles of a tapered portion 221A are provided which are tapered so as to decrease in diameter toward the tip end as one side of the outer peripheral surface approaches the other side in a side view. The tapered portion 221A of the hair 220A has a reduced diameter portion 222A at a position closer to the base portion and spaced from the tip 220A by 0.1mm or more, and the reduced diameter portion 222A has a cross-sectional area of 14% or less of the cross-sectional area of the base portion, as in the hair 220.

In the toothbrush having the backup bristles 220A, since the stress concentration portion is generated near the small diameter portion 222A and at the tip end side thereof in the backup bristles 220A during brushing, accumulation of fatigue is suppressed by locally repeating the stress concentration portion near the base portion, and therefore, even when the bristle spreading durability is improved, excellent bristle bending durability can be secured.

The toothbrush according to embodiment 2 may be a toothbrush provided with bristles 220B illustrated in fig. 10.

The bristles 220B are provided with a small diameter portion 222B formed by: the outer peripheral surface of the bristles is recessed around the entire circumference in the circumferential direction so as to have a shape in which both sides of the outer peripheral surface are recessed into arc shapes in a side view. The small diameter portion 222B may be provided at a base portion spaced apart from the tip 220a of the bristle 220B by 0.1mm or more.

In the toothbrush having the backup bristles 220B, since the stress concentration portion is generated near the small diameter portion 222B and at the tip end side thereof in the backup bristles 220B during brushing, accumulation of fatigue is suppressed by locally repeating the stress concentration portion near the base portion, and therefore, excellent bristle bending durability can be secured even when the bristle spreading durability is improved.

The toothbrush according to claim 2 may be a toothbrush provided with bristles 220C illustrated in fig. 11.

The bristles 220C are tapered bristles provided with a tapered portion 221C including a diameter portion 222C that decreases in diameter toward the tip end at the tip end side portion, and provided with a diameter portion 222D at the base end side of the tapered portion 221C. The diameter-reduced portion 222C is provided at a base portion of the tapered portion 221C of the bristles 220, which is spaced from the tip 220a by 0.1mm or more, and has a cross-sectional area of 14% or less of the cross-sectional area of the base portion. The small diameter portion 222D is provided on the base side of the tapered portion 221C by: the outer peripheral surface of the bristles 220C is recessed around the entire circumference in the circumferential direction so that both sides of the outer peripheral surface of the bristles 220C are recessed in an arc shape in a side view. The small diameter portion 222D has a cross-sectional area that is 14% or less of the cross-sectional area of the base portion in the bristles 220C.

In this manner, the bristles 220C have a shape in which the bristles 220B are combined with the bristles 220C.

In the toothbrush having the bristles 220C, since the stress concentration portion is generated in the vicinity of the base portion and the tip side of the bristles 220C during brushing, and the accumulation of fatigue is suppressed by locally repeating the stress concentration portion in the vicinity of the base portion, it is possible to secure excellent durability of bending the bristles even when the durability of spreading the bristles is improved.

In the toothbrush of claim 2, a plurality of types of bristles having a small diameter portion can be used in combination.

The toothbrush according to claim 2 may be a toothbrush in which a bundle of bristles having a small diameter portion is combined with a bundle of bristles having no small diameter portion. In this case, it is preferable that the hair length of the bundle of bristles having the small diameter portion is longer than the hair length of the bundle of bristles not having the small diameter portion. Thus, the force applied to the bristles without the small diameter portions during brushing is reduced by the bristle bundles formed of the bristles with the small diameter portions. Therefore, compared to when no bundle of bristles formed of bristles having a small diameter portion is combined, the bending of bristles having no small diameter portion is suppressed.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following descriptions.

[ example 1]

A toothbrush 11 exemplified in FIGS. 1 to 3 was produced.

In the hair-planted surface 118a of the head 118, 24 hair-planted holes 123 are formed in such a manner that 3 hair-planted holes 123 are formed in the width direction, 4 are arranged in the width direction in the region therebetween, and 6 are arranged in the axial direction, respectively, near the tip end and near the rear end thereof. The diameter of the implant hole 123 is 1.5 mm.

As the taper bristles 120, PTT taper bristles having taper portions formed at both end portions are used. The tapered bristles 21 are bundled, folded into two with flat wires 124, and fitted into the respective fitting holes 123 to be fitted into the bristle bundles 112, thereby forming the bristle part 122. The length H1 of the tapered hairs (tapered hairs 120) in the tufts 112 was 11.5 mm. In the tapered bristles, the average of the tip diameters (the diameters of portions 0.1mm away from the tips on the base side) was 0.02mm, the length L1 of the tapered portion was 3.0mm, and the diameter of the straight portion was 7.5mil (0.19 mm).

Step (a 1):

as shown in FIG. 4, in a state where the brush part 122 is pressed against a spherical surface 1100 having a radius of 85mm, the friction is moved back and forth in the axial direction of the stem body 110. The displacement x1(mm) of the tip 120a of the tapered hair 120 relative to the base 120b in the planar direction of the bristle planting surface 118a of the head 118 was measured and found to be 4.20mm in a state where a load of 200g was applied to the bristle portion tip 122 a.

Step (b 1):

PTT (Young's modulus 245 kg/mm) for the same shape as the cone hair 120²) A tapered hair was produced, and a position 11.5mm away from the tip (position corresponding to the base) was fixed, and an engineering simulation was performed in a state where the tip was displaced by 4.20mm in a direction perpendicular to the axial direction of the tapered hair. For the engineering simulation, 3-dimensional Finite Element Method (FEM) analysis using LS-DYNA (analytical software, manufactured by LSTC corporation) was used. In the engineering simulation it was confirmed that: the stress is concentrated in the conical part of the cone-shaped bristle and at the base 2 compared to the conical part. The distance from the maximum stress generating position at the base to the tip is 11.33mm, and the maximum stress A1 is 1.58kg/mm². The maximum stress generation position of the tapered part is 0.070mm away from the tip, and the maximum stress B1 is 2.09kg/mm². The ratio B1/A1 was 1.32.

[ examples 2 to 6]

A toothbrush was produced in the same manner as in example 1 except that the length L1 of the tapered portion was changed as shown in table 1, and the ratio B1/a1 was determined by a stress calculation method.

Comparative example 1

A toothbrush was produced in the same manner as in example 1, except that straight PTT bristles (tip diameter: 0.19mm) were used instead of tapered PTT bristles. Then, the stress calculation method was performed on the obtained toothbrush in the same manner as in example 1, and it was confirmed in engineering simulation that: no stress concentration was observed at the tip portion of the straight hair, and the stress was concentrated only near the base. The distance from the maximum stress generating position at the base to the tip is 11.35mm, and the maximum stress A1 is 1.59kg/mm²。

The dimensions of the bristles, the displacement amount (deflection amount) x1 in the step (a1), the maximum stress a1, the distance from the tip to the position where the maximum stress a1 was generated, the distance from the tip to the position where the maximum stress B1 and the maximum stress B1 were generated, and the ratio B1/a1 in each example are shown in table 1.

[ TABLE 1]

In the toothbrush of comparative example 1, the bristles are likely to bend near the base of the straight bristles during continuous use. This is considered to be mainly due to the fact that, as confirmed by engineering simulations, stress is concentrated only in the vicinity of the base of each straight hair during brushing, and fatigue is locally accumulated repeatedly.

In contrast, in the toothbrushes according to examples 1 to 6, stress is concentrated in each of the tapered bristles during brushing at the tapered portion and at the base portion 2 with respect to the tapered portion. Therefore, in the toothbrushes according to examples 1 to 6, since the stress is continuously concentrated only in the vicinity of the base of each of the tapered bristles during brushing and fatigue is locally accumulated, the durability of bending of the bristles is excellent as compared with the toothbrush according to comparative example 1.

[ example 7]

A toothbrush 21 exemplified in FIGS. 5 to 7 was produced.

In the hair-planted surface 218a in the head 218, 24 hair-planted holes 228 are formed in such a manner that 3 hair-planted holes 228 are formed in the width direction, 4 are arranged in the width direction in the region therebetween, and 6 are arranged in the axial direction, respectively, near the tip end and near the rear end thereof. The diameter of the implant hole 228 is 1.5 mm.

As the bristles 220, PTT-made tapered bristles having tapered portions formed at both end portions are used. The bundle of tapered bristles 21 is bundled, folded into two with a flat wire 226, and fitted into the respective fitting holes 228 to fit the bundle 212, thereby forming a bristle part 224. The length H2 of the tapered hairs (with hairs 220) in tuft 212 is 11.5 mm. In the tapered bristles, the average of the tip diameters (the diameters of the portions 0.1mm away from the tip on the base side) was 0.01mm, the length L2 of the tapered portion was 7.0mm, and the diameter of the base in the straight portion 219 was 7.5mil (0.1905 mm). In the tapered bristles (bristles 220), the ratio of the cross-sectional area at a position spaced 0.1mm from the base tip on the base side to the cross-sectional area perpendicular to the axial direction of the base was 0.28%. That is, the tapered hair (the hair 220) is a tapered hair having a tapered portion provided with a small diameter portion.

Step (a 2):

as shown in FIG. 7, in a state where the brush portion 224 is pressed against the spherical surface 2100 having a radius of 85mm, the friction is moved back and forth in the axial direction of the shank 210. The displacement x2(mm) of the tip 220a of the tapered hair 120 (used hair 220) relative to the base 220b in the planar direction of the bristle-implanted surface 218a of the head 218 was measured and found to be 4.63mm in a state where a load of 200g was applied to the bristle portion tip 224 a.

Step (b 2):

PTT (Young's modulus: 245 kg/mm) in the same shape as the tapered hair (with the hair 220)²) A tapered hair was produced, and an engineering simulation was performed in which the position of the tip (corresponding to the base) was fixed to a position of 11.5mm, and the tip was displaced by 4.63mm in a direction perpendicular to the axial direction of the tapered hair. For the engineering simulation, 3-dimensional Finite Element Method (FEM) analysis using LS-DYNA (analytical software, manufactured by LSTC corporation) was used. The engineering simulation experiment confirms that: stress is concentrated in the vicinity of the small diameter portion and the vicinity of the base portion in the tapered hair 2. The maximum stress generation position near the base was 11.35mm from the tip, and the maximum stress A2 was 1.499kg/mm². The distance between the maximum stress generation position near the small diameter part and the tip is 0.275mm, and the maximum stress B2 is 2.740kg/mm²。

[ examples 8 to 13]

A toothbrush was produced in the same manner as in example 7 except that the tip diameters of the tapered bristles were changed as shown in table 2, and the maximum stress a2 and the maximum stress B2 were determined by a stress calculation method.

Comparative examples 2 and 3

A toothbrush was produced and a stress calculation method was performed in the same manner as in example 7, except that the tip diameter of the tapered bristles was changed as shown in table 2. However, both comparative examples 2 and 3 were confirmed in engineering simulations: no stress concentration was observed on the tapered portion in the tapered bristles, and the stress was concentrated only near the base.

Comparative example 4

A toothbrush was produced in the same manner as in example 7, except that straight bristles made of PTT (tip diameter: 0.1905mm) were used in place of tapered bristles made of PTT. Then, the stress calculation method was performed on the obtained toothbrush in the same manner as in example 7, and it was confirmed in engineering simulation that: no stress concentration was observed at the tip portion of the straight hair, and the stress was concentrated only near the base.

The dimensions of the bristles, the displacement amount (deflection amount) x2 in the step (a2), the maximum stress a2, the distance from the tip to the position where the maximum stress a2 was generated, the distance from the tip to the position where the maximum stress B2 and the maximum stress B2 were generated, and the ratio B2/a2 in each example are shown in table 2.

[ TABLE 2]

In the toothbrushes of comparative examples 2 to 4, the bristles tend to bend near the base of the bristles when the toothbrush is used continuously. This is considered to be mainly due to the fact that, as confirmed in engineering simulation experiments, stress is concentrated only in the vicinity of the base of each bristle during brushing, and fatigue is locally accumulated by repeating the process.

In contrast, in the toothbrushes according to examples 7 to 13, the stress concentration points in the tapered bristles during brushing were 2 points near the diameter portion and near the base portion. Therefore, in the toothbrushes according to examples 7 to 13, since the stress is continuously concentrated only in the vicinity of the base of each of the tapered bristles during brushing and fatigue is locally accumulated, the durability of bending of the bristles is excellent as compared with the toothbrushes according to comparative examples 2 to 4.

Claims

1. A toothbrush having a bristle part formed by implanting a plurality of tufts into a bristle-implanting surface of a head part,

the tufts are provided with a tapered shape of hair,

(b1) engineering simulation was performed on a state in which the tip end of the tapered hair was displaced by only the displacement amount x1(mm) in a direction perpendicular to the axial direction of the tapered hair, and the maximum stress a1 generated at the base of the tapered hair rather than the tapered portion and the maximum stress B1 generated at the tapered portion were calculated,

the tapered bristles are formed from poly (trimethylene terephthalate),

in the step (b1), the tapered bristles have stress concentrations at both the tapered portion and the base portion of the tapered portion.

2. The toothbrush of claim 1,

the length of the tapered part is 3-11.5 mm,

the boundary position of the base part and the conical part in the conical hair is equal to the position of the hair-planting surface, or the base part is positioned outside the hair-planting surface.

3. A toothbrush according to claim 1 or 2, characterised in that the diameter of the portion which is 0.1mm from the tip of the cone is below 0.07 mm.

4. A toothbrush having a bristle part formed by implanting a plurality of tufts into a bristle-implanted surface of a head part,

the hair bundle is provided with the hair used,

the bristle is provided with a diameter part having a cross-sectional area of 14% or less of the cross-sectional area of the base part at a position closer to the base part than a position 0.1mm from the tip end of the bristle, and has a region extending from the base part toward the tip end and having a cross-sectional area larger than the diameter part,

the bristle is a tapered bristle having a tapered portion whose diameter decreases toward the tip end, the tapered portion having the small diameter portion,

the bristles are formed from poly (trimethylene terephthalate),

when the hair is subjected to engineering simulation in a state where the tip end of the hair is displaced by only a displacement amount x2(mm) in a direction perpendicular to the axial direction of the hair, stress concentrates in the vicinity of the base and in the vicinity of the diameter portion or the diameter portion on the tip end side thereof.

5. The toothbrush according to claim 4, wherein the maximum stress A2 and the maximum stress B2 calculated by a stress calculation method comprising the following step (a2) and the following step (B2) satisfy A2>0 and B2> 0in the bristles,

(b2) an engineering simulation was performed on a state where the hair tip was displaced by only the displacement amount x2(mm) in a direction perpendicular to the axial direction of the hair, and a maximum stress a2 at a stress concentration portion of the hair generated most toward the base and a maximum stress B2 at a stress concentration portion generated more toward the tip side than that were calculated.

6. The toothbrush according to claim 4, wherein the maximum stress A2 and the maximum stress B2 calculated by a stress calculation method comprising the following step (a2) and the following step (B2) satisfy B2. gtoreq.A 2>0,