JP5066527B2 - toothbrush - Google Patents

Description

The present invention relates to a toothbrush using a hair made of polytrimethylene terephthalate (PTT) resin.
This application claims priority with respect to the Japan patent application 2006-252676 for which it applied on September 19, 2006, and uses the content here.

Synthetic resins such as nylon resin (6-12 nylon, 6-10 nylon) and polybutylene terephthalate (PBT) resin are generally used for toothbrush bristles, some of which are natural like pork hair. Hair is also used.
In recent years, toothbrushes using monofilaments made of polytrimethylene terephthalate (PTT) resin, which is a polyester resin, are used as the hair (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3), and transparency and flexibility. A toothbrush made of polytrimethylene terephthalate monofilament having durability has been proposed (see, for example, Patent Document 4 and Patent Document 5). Toothbrushes using PTT resin as bristles are superior in bending recovery and flexibility, so that the bristles are less likely to spread and maintain high cleaning power for a long period of time compared to using nylon resin or PBT resin. it can.

  However, toothbrushes using bristle made of PTT resin are used for a long period of time because the bristle is difficult to spread and the time for replacement of the toothbrush is unclear. Mechanical breakage such as hair tearing or breaking may occur.

In order to provide a toothbrush in which the bristle made of PTT resin does not break, a toothbrush using synthetic resin monofilament made of PTT resin and polyester resin has been proposed (see, for example, Patent Document 6). ).
Moreover, in order to display a deterioration state in the toothbrush using the hair made of PTT resin, the PTT hair used for the hair has a double core-sheath structure, and the color or darkness of the hair changes due to wear. The thing is proposed (refer patent document 7). With the technique described in Patent Document 7, it is possible to notify the replacement timing of the toothbrush without depending on how the bristles open.

On the other hand, there is a toothbrush bristle that forms irregularities around the bristle and the entire cut end face to improve tooth cleaning and gum massage (see Patent Document 8). In addition, as a toothbrush using a PTT resin, there is a toothbrush in which a string bristle in which a fine thread is knitted by stringing is implanted around a core made of PTT fibers (see Patent Document 9).
JP-A-8-173244 International publication 01/75200 pamphlet JP-T-2001-511379 JP 2006-2256 A JP 2006-37273 A JP-A-2005-270366 JP 2005-103184 A Japanese Utility Model Publication No. 61-177027 JP 2004-81647 A

  However, the conventional toothbrushes equipped with bristles using PTT resin may be used for a long time because the bristles are difficult to spread, and sufficiently prevent mechanical breakage such as tearing or breaking of the bristles. I couldn't.

  The present invention has been made in view of the above points, and provides a toothbrush in which mechanical breakage such as tearing or breaking of the hair is unlikely to occur, and the replacement timing of the toothbrush is clarified depending on how the hair is spread. With the goal.

The inventor studied the mechanical breakage of PTT bristle as described below, and arrived at the toothbrush of the present invention.
That is, when PTT bristle is implanted in a toothbrush, the bristle is difficult to open due to high bend recovery, so that it is used for a longer period of time than when nylon resin or PBT resin is used. For this reason, the load on the hair for brushing will also last for a long time. Usually, the toothbrush hair is straight, and the stress applied to the hair during brushing is concentrated at the root of the hair (the root portion planted on the flocking table), which places a heavy load on the root of the hair. . For this reason, mechanical breakage such as tearing or breaking of the hair occurs at the root of the hair.

  In order to prevent mechanical breakage of the PTT bristle, it is conceivable to clarify the timing for replacing the toothbrush, promote the toothbrush replacement, and replace the toothbrush before mechanical breakage occurs in the PTT bristle. In order to clarify the replacement time of the toothbrush, it is conceivable to make the hair diameter narrower to make the hair easier to spread and to make a visual judgment. However, if the hair diameter is simply reduced, the hair becomes soft and the brushing force is lowered, and the strength of the hair is lowered and the hair may be broken.

  Therefore, the present inventor has conducted extensive research, and the shape of the PTT hair is not concentrated only on the root of the hair by brushing the teeth, and further, the extent of the hair spread (planting portion opening rate) Thus, the toothbrush of the present invention has been found that makes it possible to prevent the mechanical breakage of the PTT bristle by clarifying the replacement time of the toothbrush while ensuring sufficient durability by making the shape corresponding to the deteriorated state of the bristle.

The toothbrush of the present invention is a toothbrush in which a bunch of bristles made of PTT resin is bundled on a flocked surface, and a plurality of recesses are formed on the surface of the bristles, and the recesses are formed. The minimum cross-sectional area of the bristle at the position is 40% to 80% of the maximum cross-sectional area of the bristle.
As described above, when a plurality of recesses are formed on the surface of the hair, the stress applied to the hair during the brushing is dispersed in the plurality of recesses, so that the stress during the brushing is concentrated on the root of the hair. Therefore, the stress applied to the base of the hair is reduced as compared with the case where the concave portion is not formed on the surface of the hair.
In addition, when the concave portion is formed on the surface of the bristle, the bristle is likely to spread due to the stress applied to the concave portion that is loaded at the time of brushing, so it is possible to visually clarify the replacement time of the toothbrush, It is possible to prompt the user to replace the toothbrush before the bristle breaks mechanically. Therefore, according to the present invention, it is possible to realize a toothbrush that is less likely to be broken or broken, and that has a clear replacement time.

In the toothbrush of the present invention, the concave portion has a pitch in the extension direction of the bristle of 0.3 mm or more and 1.2 mm or less, a length in the extension direction of 0.1 mm or more and 0.8 mm or less, and a depth. The hair diameter may be 0.1 to 0.5 times the hair diameter.
By setting the pitch of the recesses, the length in the extending direction, and the depth in the above ranges, the flocking portion opening rate of the PTT hair becomes better, and high mechanical strength can be ensured.
In addition, the hair diameter here means a diameter when the hair cross-sectional shape is circular, and when the hair cross-sectional shape is a regular polygon such as a regular triangle or a square, it indicates the length of one side.

  According to the present invention, it is possible to prevent the hair from being torn or broken by reducing the stress concentration applied to the base of the hair. And the replacement time can be clarified visually.

FIG. 1 is a side view showing an example of the toothbrush of the present invention. FIG. 2 is an enlarged perspective view showing one of the bristles constituting the toothbrush shown in FIG. 1 in an enlarged manner. FIG. 3 is a side view of the hair shown in FIG. FIG. 4 is a cross-sectional view of the hair shown in FIG. 2 and is a cross-sectional view of a portion where a recess is formed.

Explanation of symbols

  1 bristles, 2 recesses, 10 toothbrushes, 11 head parts, 12 flocked surfaces, 13 handle parts, 15 hair bundles, 21 and 22 recess units, A pitch, B length in extension direction (width), C depth, D Hair diameter (thickness), E central axis, S1 minimum cross-sectional area, S2 maximum cross-sectional area.

Next, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiment described below.
FIG. 1 is a side view showing an example of the toothbrush of the present invention. FIG. 2 is an enlarged perspective view showing one of the hairs constituting the toothbrush shown in FIG. 1 in an enlarged manner. FIG. 3 is a side view of the hair shown in FIG. 2, and FIG. 4 is a cross-sectional view of a portion where the concave portion of the hair shown in FIG. 2 is formed.

A toothbrush 10 shown in FIG. 1 includes a head portion 11 having a flocked surface 12 and a handle portion 13 extending from the rear end of the head portion 11. The handle portion 13 is for gripping the toothbrush 10, and can have an arbitrary shape suitable for a brushing operation using the toothbrush 10.
The head part 11 and the handle part 13 can be formed by integral molding with a resin such as a hard resin, for example. In addition, in order to make it easy to hold | grip the resin which comprises the handle | steering-wheel part 13, you may use flexible resin, such as an elastomer, for at least one part.

  Specific examples of the material for the head portion 11 and the handle portion 13 include polystyrene resin (PS), polypropylene resin (PP), polyethylene terephthalate resin (PET), acrylonitrile butadiene styrene resin (ABS), and cellulose propionate resin ( CP), polyarylate resin, saturated polyester resin (PCTA, PCTG), polycarbonate resin (PC), acrylonitrile styrene resin (AS), polyacetal resin (POM), polybutylene terephthalate (PBT), biodegradable resin, etc. It can be used alone or in combination. Moreover, it is also preferable to set it as the multicolor molded handle | steering_wheel which combined these resins, thermoplastic elastomer, silicone resin, etc. The material of the head part 11 and the handle part 13 is not limited by the above description.

  A plurality of hair bundles 15 in which hairs are bundled are planted on the hair planting surface 12 of the head portion 11. As a method for flocking the hair bundle 15 to the head portion 11, it can be fixed by a conventional method, for example, a flat wire (metal such as brass or stainless steel, biodegradable plastic, hard plastic, etc. A flat wire flocking method in which the hair bundle 15 is folded in two with a retaining member), and one end of the hair bundle 15 is joined by means of heat or the like, and the resin that becomes the head portion 11 in a state where the joining portion is in the mold. In-mold flocking for filling and fixing (for example, JP-A-61-268208, JP 9-512724), heat fusion flocking for fusion-bonding one end of the hair bundle 15 and the head portion 11 by means of heat or the like (for example, It can be carried out by a method such as Kaisho 60-241404).

  Moreover, the shape of the flocked hole formed in the flocked surface 12 may be a normal circle, a square hole, a substantially elliptical shape, a substantially oval shape, a substantially rectangular shape, or the like having different major and minor diameters. In addition, the flock holes are usually arranged in a lattice shape or a staggered pattern, but a combination of flock hole shapes or a combination of arrangements can be appropriately selected according to the intended function. Further, the shape and size of the head part 11 are not limited at all. For example, as the minimum thickness of the head part 11, there is a slight difference depending on a flocking method using a flat line or a flocking method not using a flat line. However, the thickness may be about 2 mm to 6 mm.

  The bristle 1 constituting the bristle bundle 15 of the toothbrush 10 shown in FIG. 1 is made of polytrimethylene terephthalate (PTT) resin. In addition, the monofilament used as the hair 1 can be modified within a range that does not significantly impair the properties of the hair 1. Specifically, for example, PTT resin that becomes a monofilament, heat and light stabilizers, flame retardants, fillers, surface lubricants, antistatic agents, antibacterial materials (antibacterial materials) and other modifiers, and other hard materials One kind or two or more kinds of resins and elastomers may be appropriately blended or applied to a monofilament.

Further, the hair 1 can be used as transparent (natural) hair, or can be used as transparent coloring hair with pigments or dyes or opaque coloring (including white) hair. It is appropriately selected in consideration of the merchantability of appearance. For the transparent hair, the transparent coloring hair, and the opaque coloring (including white) hair, two or more of them may be used in combination in the hair bundle unit or the hair bundle, if necessary. .
Coloring hairs such as transparent coloring hairs and opaque coloring (including white) hairs, as commonly used, a method of coloring the resin itself during spinning, or after spinning or accompanying the spinning process, It can be manufactured by a method of coloring from the surface. In addition, it is possible to color only the tip portion of the bristle 1 or the entire bristle 1 in a cut piece state (a bundle of hair length of about 25 to 35 mm) before flocking to the toothbrush 10 or after flocking. I can do it.

When the concave portion 2 is provided on the surface of the bristle 1, the stress applied to the bristle at the time of brushing is concentrated in the concave portion 2, so that the stress applied to the base of the bristle 1 is reduced and the bristle 1 is likely to spread. However, in order to sufficiently prevent the bristle 1 from being torn or broken, it is not only necessary to provide the concave part 2 on the surface of the bristle 1, and the minimum of the bristle 1 at the position where the concave part 2 is formed. The cross-sectional area S1 needs to be 40% or more and 80% or less of the maximum cross-sectional area S2 of the hair 1.
As shown in FIG. 4, the minimum cross-sectional area S1 referred to here is a hair cross-sectional area that is minimum when cut in a concave portion perpendicularly to the longitudinal direction of the hair (shaded portion in the figure). The maximum cross-sectional area S2 is a hair cross-sectional area obtained by extrapolating a line obtained by connecting the outermost sides before and after the recess formed in the hair.

  If the minimum cross-sectional area S1 is less than 40% of the maximum cross-sectional area S2 of the hair 1 ((S1 / S2) × 100 <40 (%)), the mechanical strength of the portion where the recess 2 is formed is significantly reduced. The original strength as the hair 1 cannot be exhibited, and the bending strength is significantly reduced. Moreover, the spread of the hair 1 by tooth brushing becomes the same level as general nylon hair, and the good bending durability of the PTT hair disappears. On the other hand, if the minimum cross-sectional area S1 exceeds 80% of the maximum cross-sectional area S2 of the bristle 1 ((S1 / S2) × 100> 80 (%)), because of the excellent bending durability of the PTT resin, the use by brushing Not only does the opening of the hair 1 become inadequate and the replacement time becomes unclear, but the hair 1 may break due to continuous use.

Moreover, it is preferable that the pitch A of the recessed part 2 shown in FIG. 3 is 0.3 mm or more and 1.2 mm or less, More preferably, 0.5 mm or more and 1.0 mm or less are good. In addition, the pitch A of the recessed part 2 here means the distance between the recessed parts 2 adjacent to the extension direction of the hair 1. Moreover, the distance between the adjacent recessed parts 2 means the distance between the extension direction center positions of the hair 1 in the recessed part 2.
Further, the length B (width) in the extending direction of the recess 2 is preferably 0.1 mm or more and 0.8 mm or less, and more preferably 0.2 mm or more and 0.5 mm or less.
Further, the depth C, which is the distance from the line obtained by connecting the outermost sides of the recess 3 shown in FIGS. 3 and 4 to the valley bottom of the recess 2, is 0.1 to 0.5 times the hair diameter D. It is preferable that the ratio is 0.1 times or more and 0.3 times or less.

  The thickness of the hair 1 is 3 to 10 mil (0.076 to 0.254 mm), preferably 5 to 8 mil (0.125 to 0.203 mm). In consideration of the cleaning effect, durability, and the like, a plurality of bristles having different thicknesses may be used in combination as bristles constituting one toothbrush. In particular, in the specification in which a large number of flock holes are arranged on the flocked surface 12, the strength of the hair is increased or changed (thickness, material, length, color, cross-sectional shape) from the outside toward the center. It is also preferable in terms of feeling and appearance.

  Furthermore, the cross-sectional shape of the hair is circular, elliptical, triangular, polygonal, such as a quadrilateral, star shape, three-leaf or four-leaf clover shape, straight lines, curved lines, or an indefinite shape combining straight lines and curved lines. It is also good.

Although the manufacturing method of the monofilament used as such hair 1 is not specifically limited, For example, it can manufacture using the method etc. which manufacture a normal co-extrusion monofilament.
Further, the method for forming the recess 2 provided on the surface of the hair 1 is not particularly limited. For example, before or after the stretching step or the annealing step in manufacturing the monofilament, for example, the recess 2 is formed. A roller having a U-shaped convex section corresponding to the shape can be formed by arranging the monofilament between the opposed rollers arranged vertically and horizontally. In addition, the recessed part 2 can also be formed by allowing a monofilament to pass between the rollers arrange | positioned oppositely, performing heat processing, when passing a monofilament between the rollers arranged oppositely.

  Moreover, about the formation position of the recessed part 2, it is not limited to the said embodiment. For example, in the above-described embodiment, the rows of the concave units 21 and 22 are provided on the surface of the hair 1, but the concave units may be arranged in one row. Moreover, in the said embodiment, although the two rows of recessed units 21 and 22 were arrange | positioned symmetrically with respect to the central axis E of the hair 1, the position of the recessed part of the recessed unit 21 in the extending | stretching direction of the hair 1 is shown. The recess unit 22 may be disposed so as to be in the center of the adjacent recesses.

The shape of the concave portion 2 of the hair 1 may be a U-shape, V-shape, U-shape, or C-shape when viewed in the direction of extension of the hair 1. Furthermore, the shape of all the concave portions of the hair 1 may be the same, or part or all of them may be different. Further, the concave portion of the bristle may be a groove provided over the entire circumference of the bristle. Further, the concave portion of the hair is preferably applied over the entire length of the hair, but may be appropriately selected depending on the size of the concave portion, the cross-sectional shape of the hair, the diameter of the hair.
When forming a concave portion having such a shape, a convex portion corresponding to the shape of the concave portion to be formed, such as a hemisphere, a substantially polygonal shape (rectangle, triangle), a substantially oval shape, etc. By using a roller having, it can be formed in the same manner as the hair 1 of the above embodiment.

Further, as another example of the bristle 1 having a concave portion 2 on the surface, for example, when spinning the bristle 1, an inorganic material is put in a master batch in advance, and the surface of the bristle spun using this Mention may be made of hair having random recesses on the surface obtained by dissolving the precipitate.
Further, the tip of the hair may be tapered by a chemical method in which the hair is dissolved in an acid or an alkaline agent or a polishing method in which the hair tip is mechanically polished after being implanted into a toothbrush. As the polishing method, for example, the brush pruning surface and the planting are planted by a polishing body that rotates along the first rotating shaft and the bearing that supports the first rotating shaft rotates along the second rotating shaft. The method using the manufacturing apparatus which processes it into a smooth taper shape between surfaces can be mentioned.
In addition, the depth of the recessed part in the case where the hair tip is tapered means the distance from the line obtained by connecting the outermost sides before and after the recessed part formed in the tapered part to the valley bottom of the recessed part.

  Further, depending on the manufacturing method of the toothbrush 10 after spinning, a predetermined number of bristles are bundled and wound on a spool, or cut to a certain length and straightened to a diameter of several cm to 10 cm. In order to further reduce the residual strain of the hair after being bundled or wound with paper or film, for example, off-line heat treatment can be performed at 60 to 160 ° C. for several minutes to several days.

  Further, the hair cutting (or profile) shape and the hair length of the end portion of the toothbrush 10 can be arbitrarily set. For example, the tooth brush 10 may have a single flat shape, a mountain shape, or an uneven shape. The outer side and the inner side, the front end part and the rear end part may have different shapes.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
"Example 1 to Example 10, Comparative Example 1 to Comparative Example 3"
A hair bundle in which hairs made of PTT resin shown in Table 1 or Table 2 were bundled was implanted on a flocked surface having 23 flock holes, and a toothbrush having a head part and a handle part made of PCTA resin was manufactured.
“Comparative Example 4”
Toothbrushes were produced in the same manner as in Examples 1 to 10 and Comparative Examples 1 to 3, except that the hair made of nylon resin was used.

  In Table 1 or Table 2, the side view of the bristles used in the toothbrushes of Examples 1 to 10 and Comparative Examples 1 to 4, the cross-sectional view at the position of the arrow shown in the side view, and the minimum cross-sectional area S1 The ratio ((S1 / S2) × 100 (%)) of the maximum cross-sectional area S2, the hair dimensions (pitch, depth, width), and the hair diameter are shown. Note that, in the cross-sectional views of Tables 1 and 2, the area of the portion indicated by diagonal lines is the minimum cross-sectional area S1, and the portion surrounded by the dotted line is the maximum cross-sectional area S2.

  Using the toothbrushes of Examples 1 to 10 and Comparative Examples 1 to 4, the following (1) hair durability test and (2) sensory evaluation were performed. The results are shown in Table 3.

(1) Bristle endurance test The toothbrushes of Examples 1 to 10 and Comparative Examples 1 to 4 were set in a model durability tester, and as shown below, the flocking portion opening rate and the bristle break The following tests were conducted. The test method consists of placing the toothbrush head part on the metal corrugated plate and facing the corrugated plate parallel to the corrugated plate so that the bristle tip is in contact with the corrugated plate surface. Is immersed in warm water at 35 ° C. Then, with the load of 400 g applied to the head part of the toothbrush, the head part was reciprocated 100,000 times with a reciprocating speed of 150 times / min and a brushing stroke of 40 mm in a direction perpendicular to the wave of the corrugated plate. Then, the opening ratio of the flocked portion of the toothbrush and the broken hair were evaluated.

<Flocking area opening rate>
Measure the width of the flocked part of the flocking group that has been flocked to the head before the brushing (before the hair durability test) (the total width at the tip of the flocking group in the direction perpendicular to the handle longitudinal direction). After a predetermined number of times (100,000 times) of wiping with a durability tester, the width of the flocked portion was measured again, and the difference was divided by the width of the flocked portion before the brushing, multiplied by 100 and displayed as a percentage. In addition, the flocked part width | variety was measured in the position containing the hair | bristle bundle which faced the outermost side. Moreover, the flocked part opening rate was evaluated according to the following criteria.
Flocked portion opening ratio (%) = ((Flocked portion width after brushing−Flocked portion width before brushing) / (Flocked portion width before brushing)) × 100
○: 30% or more and less than 60% Δ: 20% or more and less than 30% or 60% or more and less than 80% ×: Less than 20% or 80% or more

<For broken hair>
After the predetermined number of times of brushing, the occurrence of breakage at the root of the hair was visually observed and evaluated according to the following criteria.
○: No broken hair ×: Broken hair

(2) Sensory evaluation To determine whether the open state of the toothbrush is linked to the replacement time, a seven-step sensory evaluation was conducted by 20 professional panelists using the toothbrush after the brush durability test was completed. It was evaluated with.
1: Not linked at all 2: Not quite linked 3: Not linked very much 4: Neither can be said 5: Somewhat linked 6: Very linked 7: Very linked ○ : Average score is 6 points or more △: Average score is more than 4 points and less than 6 points ×: 4 points or less

Comprehensive evaluation was judged based on the results of flocked portion opening rate, broken hair, and sensory evaluation.
○: All are “○”
△: Evaluation is “◯” or “△” and there is no “×”.

As shown in Tables 1 to 3, a plurality of concave portions are formed on the surface of the hair, and the minimum cross-sectional area S1 of the hair is 40% or more and 80% or less of the maximum cross-sectional area S2 of the hair. In Examples 1 to 10, all evaluations for broken hair were evaluated as ◯, and the overall evaluation was evaluated as ◯ or Δ.
On the other hand, in Comparative Example 1 in which the concave portion is not formed on the hair, and in Comparative Example 2 in which the depth of the concave portion is shallower than the preferred range and the ratio of the maximum cross-sectional area S2 to the minimum cross-sectional area S1 exceeds 80%. The flocked part opening rate was very low, and the evaluation of the flocked part opening rate was x. Moreover, in Comparative Example 1 and Comparative Example 2, the sensory evaluation was also “x”, and it was found that the extent to which the hair spreads (the flocked portion opening rate) did not correspond to the replacement timing of the toothbrush. Moreover, in Comparative Example 1 and Comparative Example 2, the evaluation of the broken hair was also x, and the overall evaluation was x.
In Comparative Example 3 in which the ratio of the maximum cross-sectional area S2 to the minimum cross-sectional area S1 is less than 40% and Comparative Example 4 using the hair made of nylon resin, there was no breakage of the hair, but the flocked portion opening rate Was very high, and the evaluation of the flocked part opening rate was x.

Next, another example of the present invention will be shown.
"Example 11 to Example 18"
Toothbrushes were manufactured in the same manner as in Examples 1 to 10 and Comparative Examples 1 to 4, except that the hairs made of PTT resin shown in Table 3 were used.

  Table 4 shows a side view of the bristle used in the toothbrushes of Examples 11 to 18, a cross-sectional view at the position of the arrow shown in the side view, and a ratio of the maximum cross-sectional area S2 to the minimum cross-sectional area S1 ((S1 / S2 ) × 100 (%)), hair dimensions (pitch, depth, width), hair diameter. Note that, in the cross-sectional view of Table 4, the area of the portion indicated by diagonal lines is the minimum cross-sectional area S1, and the portion surrounded by the dotted line is the maximum cross-sectional area S2.

  Using the toothbrushes of Examples 11 to 18, the (1) hair durability test and (2) sensory evaluation were performed in the same manner as in Examples 1 to 10 and Comparative Examples 1 to 4. . The results are shown in Table 5.

  As shown in Table 4 and Table 5, a plurality of recesses are formed on the surface of the hair, and the minimum cross-sectional area S1 of the hair is 40% or more and 80% or less of the maximum cross-sectional area S2 of the hair. In 11-Example 18, all evaluations for broken hair were ○, and the overall evaluation was ○ or Δ.

  The toothbrush of the present invention can prevent the bristle from breaking or breaking by reducing stress concentration on the root of the bristle. In addition, according to the present invention, it is possible to provide a toothbrush that can visually clarify the replacement time.

Claims (2)

A toothbrush in which a bunch of bristles made of polytrimethylene terephthalate resin is bundled on a flocked surface,
A plurality of recesses are formed on the surface of the hair, and the minimum cross-sectional area of the hair at the position where the recess is formed is 40% or more and 80% or less of the maximum cross-sectional area of the hair. A toothbrush characterized by being.   The recess has a pitch in the extension direction of the hair of 0.3 mm or more and 1.2 mm or less, a length in the extension direction of 0.1 mm or more and 0.8 mm or less, and a depth of 0.1 or more times the hair diameter. The toothbrush according to claim 1, wherein the toothbrush is 0.5 times or less.