Toothbrush

Abstract

To provide a toothbrush which facilitates brushing of a tooth flank and gums of a front tooth or the like positioned inward in an oral cavity and enables brushing of the tooth flank and gums with an appropriate brushing pressure by avoiding an excessive brushing pressure.SOLUTION: A toothbrush 10 includes a toothbrush body 15 including an implanting base 14 where a plurality of implanting holes 16 in which a bristle bundle 18 is implanted are formed, a gripping part 11, and a neck part 12 connecting the gripping part 11 and the implanting base 14. The gripping part 11 has a pinching part 19 pinched from both sides with a thumb and a forefinger in one end part 11a on a side of the neck part 12. The pinching part 19 has a vertically long cross section in which a width in a longitudinal direction perpendicular to a lateral direction is longer than a width in the lateral direction in parallel to an implanting surface 14A of the implanting base 14. The pinching part 19 is arranged on a side where the bristle bundle is raised with respect to a virtual extension line V1 along the implanting surface 14A of the implanting base 14.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a toothbrush.

Background Art

[0002] Brushing in the oral cavity using a toothbrush is often performed with the toothbrush held in the hand by sandwiching the middle part of the handle of the toothbrush between the thumb and the index finger and wrapping and gripping the part on the side opposite to the bristle base with the middle finger, ring finger, little finger, or palm. When holding the handle of the toothbrush, with the part of the little finger that wraps around the rearmost end side of the handle of the toothbrush as the fulcrum and the part of the thumb or index finger that sandwiches the middle part as the effort point, it is possible to brush the tooth surface and tooth gum while applying a brushing pressure to the bristle base where the tuft of bristles, which is the point of action, is implanted, according to the principle of a lever.

[0003] For example, Patent Document 1 discloses a toothbrush for massaging the tooth gum and polishing the tooth surface, which has a head part provided with bristles for massaging the tooth gum and brushing, and an elongated handle extending from this head part. The same document also discloses that the above-mentioned handle has a shape of a tapered grip part that is easy to rotate the toothbrush with the thumb and index finger during use of the toothbrush, and an extension part that extends from this grip part and fits exactly in the lateral direction of the palm during use, and also has a stabilization part that abuts against the hand during use of the toothbrush to assist in controlling the rotational movement.

[0004] Also, Patent Document 2 discloses a toothbrush composed of a brush part and a handle part for the purpose of massaging the tooth gum and polishing the tooth surface. The handle part consists of a neck part following the brush part, an extension part far from the brush part, and an intermediate part connecting the neck part and the extension part. This toothbrush is also disclosed in the same document to have a longitudinal width of the intermediate part substantially larger than the longitudinal widths of the neck part and the extension part, and the maximum longitudinal width of the intermediate part is at least twice the minimum longitudinal width of the neck part and at least 1.5 times the minimum longitudinal width of the extension part.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] By the way, when brushing teeth with excessive brushing pressure generated by the contact between the brush surface of a toothbrush and the tooth surface and tooth neck, the gum recedes and the root surface is likely to be exposed, which may cause "hypersensitivity" where cold things seep in, "dish-shaped defect" where the root surface is worn away, or "root caries" where the root surface becomes carious. Therefore, when brushing the oral cavity using a toothbrush, it is desirable to avoid excessive brushing pressure on the tooth surface and tooth neck and perform brushing with an appropriate brushing pressure. In addition, when brushing the tooth surface and tooth neck located inside the oral cavity for the front teeth, it is difficult to perform brushing while holding the handle of the toothbrush, and it is also difficult to appropriately control the brushing position. Regarding these points, the techniques described in Patent Documents 1 and 2 have not been studied at all.

[0007]

Means for Solving the Problems

[0008] The present invention relates to a toothbrush comprising a toothbrush body including a tuft base in which a plurality of implant holes for implanting tufts are formed, a gripping portion, and a neck portion connecting the gripping portion and the tuft base. In one embodiment, at the end portion of the gripping portion on the side of the neck portion, there is provided a pinch portion having a vertically long cross-sectional shape in which the width in the vertical direction perpendicular to the direction is longer than the width in the horizontal direction parallel to the tufting surface of the tufting table, and which can be pinched from both sides by the thumb and the index finger. In one embodiment, the pinch portion is disposed on the side where the tufts stand upright rather than on the virtual extension line along the tufting surface of the tufting table.

Advantages of the Invention

[0009] According to the present invention, it is possible to facilitate brushing of the tooth surfaces and tooth necks located inside the oral cavity such as the front teeth, etc., and to avoid excessive brushing pressure, and to brush the tooth surfaces and tooth necks located inside the oral cavity with an appropriate brushing pressure.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described with reference to the drawings based on its preferred embodiments. The toothbrush of the present invention includes a bristle base on which a plurality of implant holes for implanting tufts are formed, a gripping portion, and a neck portion connecting the gripping portion and the bristle base, and comprises a toothbrush body.

[0012] The toothbrush 10 according to the embodiment shown in FIGS. 1 to 3 includes a handle portion 13 including a gripping portion 11 extending in the longitudinal direction X and a neck portion 12 extending in the same direction X, and a toothbrush body 15 including a bristle base 14. The neck portion 12 connects the gripping portion 11 and the bristle base 14. That is, the toothbrush 10 of the present embodiment has a bristle base 14 at one end and a gripping portion 11 at the other end, and has a shape extending in one direction in which the neck portion 12 is disposed between the gripping portion 11 and the bristle base 14.

[0013] The bristle base 14 is a substantially plate-shaped member composed of a pair of main surfaces and side surfaces intersecting the main surfaces, and has a substantially elliptical shape when viewed in plan on the main surface. The bristle base 14 has a bristle-implanting surface 14A on one of its main surfaces, on which a plurality of implant holes 16 are formed in a dispersed arrangement and opened. In each of the implant holes 16, a tuft (brush tuft) 18 formed by bundling a plurality of filaments made of synthetic resin or the like is implanted, forming a brush surface 18A substantially parallel to the bristle-implanting surface 14A. As a result, the bristle-implanting surface 14A is the surface on the side of the bristle base 14 where the tufts stand. In the present embodiment, the thickness direction Z of the toothbrush 10 coincides with the standing direction of the tufts.

[0014] In the following description of the toothbrush 10, the surface on the side of the bristle base 14 where the tufts stand (that is, the bristle-implanting surface 14A) is also referred to as the "front surface", the surface on the side of the bristle base 14 where the tufts do not stand (that is, the surface opposite to the bristle-implanting surface 14A) is also referred to as the "back surface", and the side surface of the bristle base 14 is simply also referred to as the "side surface".

[0015] The gripping portion 11 forms the end portion of the toothbrush 10 on the side opposite to the bristle mounting base 14. The gripping portion 11 in the present embodiment includes one end portion 11a located on the side of the neck portion 12 of the gripping portion 11, that is, the side closer to the bristle mounting base 14, and the other end portion 11b located farther from the bristle mounting base 14. As will be described later, the gripping portion 11 is preferably configured to include a core material made of a primary resin forming portion A and a secondary resin forming portion B that covers the surface of the primary resin forming portion A. In this case, engaging portions 11j and 11h for engaging the primary resin forming portion A and the secondary resin forming portion B may be formed on the gripping portion 11.

[0016] The neck portion 12 constituting the toothbrush 10 forms a portion connecting the one end portion 11a in the gripping portion 11 and the bristle mounting base 14. The neck portion 12 in the present embodiment has a shape in which the cross-sectional area continuously decreases while maintaining a substantially rectangular cross-sectional shape from the one end portion 11a in the gripping portion 11 toward the connection portion 12a with the bristle mounting base 14.

[0017] In the toothbrush 10 of the embodiment shown in FIG. 1 and FIGS. 2(a) to (d), a knob portion 19 is provided at the one end portion 11a on the neck portion 12 side of the gripping portion 11. As shown in FIG. 2(a), both side surfaces of the knob portion 19 are substantially concave when viewed from the front or back of the toothbrush 10.

[0018] As shown in FIG. 2(c), when the knob portion 19 is viewed in cross section, it has a vertically long cross-sectional shape in which the width in the vertical direction, which is perpendicular to the horizontal direction, is longer than the width in the horizontal direction, which is parallel to the bristle planting surface 14A of the bristle mounting base 14. In the present embodiment, it has a substantially elliptical cross-sectional shape. The vertical direction in the cross-sectional view of the knob portion 19 is a direction along the thickness direction Z of the toothbrush 10 and is a direction intersecting or orthogonal to the front and back surfaces. Also, the horizontal direction in the cross-sectional view of the knob portion 19 is a direction along the width direction Y of the toothbrush 10 and is a direction intersecting or orthogonal to both side surfaces of the toothbrush 10. By adopting such a configuration, the knob portion 19 can be efficiently pinched by the thumb and index finger in a state where the gripping portion 11 of the toothbrush 10 and the palm are separated.

[0019] In a cross-sectional view, the knob portion 19 preferably has a width in the lateral direction (width direction Y), which is parallel to the hair-implanted surface 14A, of about 4 to 10 mm. Further, in a cross-sectional view of the knob portion 19, the width in the longitudinal direction (thickness direction Z) preferably has a size of about 8 to 15 mm.

[0020] As shown in FIG. 2(b), when the knob portion 19 is viewed from the side, it has a horizontally long side surface shape in which the length along the extending direction of the gripping portion 11 is longer than the length in the direction orthogonal to the extending direction. Specifically, in the present embodiment, it has a substantially elliptical side surface shape in which the length along the longitudinal direction X is longer than the length along the thickness direction Z. The side surface shape of the knob portion 19 is such that the longitudinal direction X and the extending direction of the major axis substantially coincide, and the thickness direction Z and the extending direction of the minor axis substantially coincide. Since the knob portion 19 has a horizontally long side surface shape, when the knob portion 19 is gripped with one hand during use of the toothbrush 10, it is induced to press the thumb and the index finger against both side surfaces of the knob portion 19, respectively, so that it can be easily pinched from both sides by the finger belly of the thumb and the finger belly of the index finger.

[0021] As shown in FIG. 2(d), the other end portion 11b of the gripping portion 11 has a substantially pentagonal cross-sectional shape. Further, the corner portions of the other end portion 11b are chamfered into a curved shape. In a cross-sectional view of the other end portion 11b, the width in the lateral direction (width direction Y), which is parallel to the hair-implanted surface 14A, preferably has a size of about 10 to 18 mm. Further, in a cross-sectional view of the knob portion 19, the width in the longitudinal direction (thickness direction Z) has a size of about 9 to 15 mm.

[0022] When the toothbrush 10 of the present embodiment is viewed from the side, the positional relationship between the hair-implanted base 14 and the knob portion 19 will be described. As shown in FIG. 2(b), the knob portion 19 is disposed on the side where the tufts of hair stand upright, rather than on the virtual extension line V1 along the hair-implanted surface 14A of the hair-implanted base 14. That is, with the virtual extension line V1 as a reference, the knob portion 19 is located on the front side of the hair-implanted surface 14A.

[0023] Whether the knob portion 19 is disposed on the side where the tuft stands with respect to the virtual extension line V1 can be determined based on the position of the centroid G in the side view of the knob portion 19. Specifically, if the position of the centroid G is on the virtual extension line V1 or on the side where the tuft stands with respect to the virtual extension line V1, it is considered that "the knob portion 19 is disposed on the side where the tuft stands", and if it is located on the side where the tuft does not stand with respect to the virtual extension line V1, it is considered that "the knob portion 19 is not disposed on the side where the tuft stands".

[0024] Examples of the mode in which the knob portion 19 is disposed on the side where the tuft stands with respect to the virtual extension line V1 include the following modes. For example, as shown in FIG. 2(b), the neck portion 12 is curved so as to incline from one end portion 11a of the gripping portion 11 toward the back side, and a mode in which the tufting surface 14A of the tufting base 14 is on the back side with respect to the second virtual extension line V2 along the axis of the gripping portion 11 can be mentioned. As shown in the same figure, it is also preferable that the virtual extension line V1 along the tufting surface 14A and the second virtual extension line V2 along the axis of the gripping portion 11 are parallel. With such a configuration, the gripping portion 11 and the tufting surface 14A can be moved in conjunction with each other in the same direction, so that the ease of handling during brushing of the tooth surface and the gum located inside the oral cavity can be further improved, and the brushing efficiency in a state where an appropriate brushing pressure is applied can be further improved. In the present embodiment, "parallel" includes both a mode in which the virtual extension line V1 and the second virtual extension line V2 are parallel and a mode in which the angle formed by the virtual extension line V1 and the second virtual extension line V2 is 5 degrees or less.

[0025] Instead of the embodiments shown in FIG. 1 and FIGS. 2(a) to (d), as an aspect in which the knob portion 19 is arranged on the side where the tuft stands up from the virtual extension line V1, for example, as shown in FIG. 3, the neck portion 12 is curved so as to incline from the one end portion 11a side of the gripping portion 11 toward the front side of the toothbrush 10, and the tufting surface 14A of the tufting base 14 may be in a mode on the front side of the second virtual extension line V2. As shown in FIG. 3, it is preferable that the virtual extension line V1 along the tufting surface 14A is arranged so as to incline from the second virtual extension line V2 along the axis of the gripping portion 11 toward the side where the tuft stands up. The angle formed by the acute angle side of the virtual extension line V1 and the second virtual extension line V2 in this embodiment is more than 5 degrees. Even in such a case, the ease of handling during brushing of the tooth surface and the tooth root located inside the oral cavity can be enhanced. Regarding the embodiment shown in FIG. 3, for the points not particularly described, the descriptions regarding the embodiments shown in the above-described FIG. 1 and FIGS. 2(a) to (d) are appropriately applied as appropriate.

[0026] In the toothbrush 10 having the above-described configuration, at one end portion 11a on the neck portion 12 side of the grip portion 11, a vertically long three-dimensional knob portion 19 is formed, so that the grip portion 11 of the toothbrush 10 and the palm are separated from each other, and the knob portion 19 can be guided to be pinched between the fingertip of the thumb and the fingertip of the index finger. As a result, for example, as shown in FIG. 4, when the tooth surfaces and tooth necks located inside the oral cavity such as the lower front teeth are the brushing target sites, the grip portion 11 other than the knob portion 19 pinched by the fingertip does not contact the palm, and the user can be made to grip the toothbrush 10 in a state where the bristle surface 14A faces the palm. At this time, the knob portion 19 pinched by the fingertip serves as the force point and the fulcrum, and the brush surface 18A formed by implanting bristles on the bristle base 14 serves as the action point for applying the brushing pressure to the tooth surface and the tooth neck. By performing brushing in this gripping state, compared with the brushing method of wrapping and gripping the entire grip portion 11 with the palm, the positions of the force point and the fulcrum substantially coincide, so that the brushing pressure applied to the tooth surface and the tooth neck from the brush surface, which is the action point, is prevented from becoming excessive, and the tooth surfaces and tooth necks located inside the oral cavity (for example, the portion indicated by reference numeral S in FIG. 4) can be brushed with an appropriate brushing pressure. In addition, since the knob portion 19 is disposed on the side where the bristle tufts 18 stand up rather than on the virtual extension line V1 along the bristle surface 14A of the bristle base 14, for example, when the toothbrush 10 is used for brushing the tooth surfaces and tooth necks located inside the oral cavity such as the lower front teeth, the toothbrush 10 can be prevented from accidentally hitting the upper lip or the upper front teeth, etc., and the brushing of the tooth surfaces and tooth necks located inside the oral cavity can be facilitated.

[0027] As long as the effects of the present invention described above are achieved, the toothbrush 10 may perform brushing in the oral cavity including the tooth surfaces and tooth gums located inside the oral cavity by pinching the knob portion 19 between the thumb and the index finger and gripping the gripping portion 11 by wrapping it with the middle finger, ring finger, little finger, or palm. Even in this case, the toothbrush 10 can brush the tooth surfaces and tooth gums with an appropriate brushing pressure while enhancing the handleability during brushing and avoiding excessive brushing pressure. This point is particularly advantageous in the aspect where the tufting surface 14A of the tufting base 14 is on the back side of the toothbrush 10 with respect to the second virtual extension line V2 along the axis of the gripping portion 11 as shown in FIG. 2(b).

[0028] From the viewpoint of making the above-described effects remarkable, the center position of the knob portion 19 in the toothbrush 10 is set as a length L1 (see FIG. 2(a)) along the longitudinal direction X between the tip 14a of the tufting base 14 and the center position, preferably 50 mm or more, more preferably 55 mm or more, still more preferably 60 mm or more, and preferably 100 mm or less, more preferably 95 mm or less, still more preferably 90 mm or less, and is arranged in such a region. By being arranged in such a region, the knob portion 19 is formed at a position close to the tufting base 14, so that it is easy to aim at the brushing target site during brushing, and the advantage of enhancing the removability of dirt at the brushing target site can also be achieved. The center position of the knob portion 19 can be the position of the centroid G in a side view.

[0029] From the same viewpoint, the percentage of the ratio of the length L1 from the tip 14a of the tufting base 14 to the center position of the knob portion 19 with respect to the total length L2 (see FIG. 2(a)) in the longitudinal direction X of the toothbrush 10 is preferably 25% or more, still more preferably 35% or more, and preferably 55% or less, still more preferably 45% or less. Also from the same viewpoint, the total length L2 in the longitudinal direction X of the toothbrush 10 is preferably 160 mm or more, still more preferably 170 mm or more, and preferably 200 mm or less, still more preferably 190 mm or less.

[0030] The knob portion 19 formed on the toothbrush 10 has a region that is substantially concave (hereinafter, this is also referred to as the "substantially concave region") formed independently on both side surfaces of the toothbrush 10, and each region has a step with its surroundings. In the present embodiment, the substantially concave region is the region of the primary resin forming portion A surrounded by the secondary resin forming portion B. When each of the above-described regions is viewed from the side, its area is preferably 50 mm 2 or more, more preferably 80 mm 2 or more, still more preferably 100 mm 2 or more, and preferably 200 mm 2 or less, more preferably 180 mm 2 or less, still more preferably 160 mm 2 or less. Also, from the viewpoint of the manufacturing efficiency of the toothbrush 10, it is also preferable that both side surfaces of the knob portion 19 have substantially the same area. By having such a configuration, when the knob portion 19 is gripped so as to be pinched between the thumb and the index finger, the toothbrush 10 can be held more stably, and unintended fluctuations in the brushing pressure can be prevented. In the present embodiment, the substantially concave region of the knob portion 19 is the region of the primary resin forming portion A surrounded by the secondary resin forming portion B. However, for example, as shown in FIG. 5, in an embodiment where the secondary resin forming portion B exists only at both end sides along the longitudinal direction X of the knob portion 19 in a side view of the knob portion 19, the substantially concave region is, in a side view of the knob portion 19, the upper end edge a1 and the lower end edge a2 of the primary resin forming portion A, and the boundary lines b1, b2 of the steps between the primary resin forming portion A and the secondary resin forming portion B. It can be defined by a line connecting them. Further, when the toothbrush 10 is formed only of the primary resin forming portion A, the substantially concave region can be defined by the contour line of the step in a side view of the knob portion 19.

[0031] In addition to this, it is preferable that the knob portion 19 has anti-slip portions 19a formed on both side surfaces. By this, when gripping the knob portion 19 with the thumb and index finger, it is possible to prevent the toothbrush 10 from accidentally falling off the fingers and hold the toothbrush 10 more stably. The anti-slip portions 19a in the present embodiment are formed by a plurality of linear uneven structures extending in a direction intersecting the longitudinal direction X on the outer surface of the knob portion 19.

[0032] For the toothbrush 10, the position of the center of gravity starting from the tip 14a of the bristle base 14 is preferably formed in a region of 60% or less of the ratio of the length from the tip 14a to the center of gravity to the total length L2 as a percentage. From the viewpoint of the balance between the ease of gripping the toothbrush and its thickness, it is practical that it is formed in a region of 40% or more of the total length L2. With such a configuration, it is possible to avoid applying an excessive brushing pressure to the bristle base 14 side during brushing, and it is possible to stably aim at the brushing target site, and further improve the removability of the dirt on the brushing target site. In order to form the toothbrush 10 to have such a center of gravity position, for example, as in the manufacturing method described later, in the materials constituting the neck portion 12 and the bristle base 14 and the material constituting the gripping portion 11, toothbrush bodies 15 may be manufactured using resins having different densities respectively.

[0033] Returning to the description of the neck portion 12 and the bristle base 14, from the viewpoints of the stability of the bristles and making it easy to move the bristle base 14 in the oral cavity even when a part of the neck portion 12 and the bristle base 14 are put into the oral cavity and making it easy to aim at the brushing target site, the thickness T1 (see FIG. 2(b)) along the thickness direction Z of the bristle base 14 is preferably 2.0 mm or more, preferably 4.0 mm or less, and more preferably 3.5 mm or less. The thickness along the thickness direction Z of the bristle base 14 can be measured using, for example, a ruler, calipers or a micrometer.

[0034] From the same perspective, the length T2 of the bristles 17 (see Fig. 2(b)) is preferably 5 mm or more, more preferably 8 mm or more, as the height from the implanting surface 14A of the implanting base 14, and preferably 15 mm or less, more preferably 13 mm or less.

[0035] Also, from the perspective of making it easier to move the implanting base 14 and the neck portion 12 in the oral cavity and making it easier to aim at the brushing target site, the cross-sectional area at the portion where the diameter of the neck portion 12 is the smallest is preferably 14.0 mm 2 or less, more preferably 12.0 mm 2 or less. From the perspective of exhibiting strength that can withstand practical use, 7.0 mm 2 or more is realistic. The above-mentioned cross-sectional area can be calculated by, for example, measuring the diameter along the direction orthogonal to the longitudinal direction X in the neck portion 12 using a ruler, calipers, or micrometer, etc., identifying the site with the smallest diameter, and performing image analysis on the cut surface of the site.

[0036] Also, from the same perspective, the diameter along the direction orthogonal to the longitudinal direction X of the neck portion 12 is preferably 3 mm or more, preferably 5 mm or less, more preferably 4 mm or less, at its smallest portion. The diameter of the neck portion 12 can be measured using, for example, a ruler, calipers, or micrometer. In the present embodiment, the site where the diameter of the neck portion 12 is the smallest is preferably located at or near the connection portion 12a between the neck portion 12 and the implanting base 14.

[0037] As materials for constituting the toothbrush body 15 including the gripping part 11, the neck part 12, and the bristle planting table 14, for example, synthetic resins generally used in the manufacture of the toothbrush 10 can be used without particular limitation. In the present embodiment, it is preferable to use a thermoplastic resin as the synthetic resin for forming the toothbrush body 15. Examples of the thermoplastic resin include polyacetal resin, polyester resin, polyolefin resin, polystyrene resin, polyethylene terephthalate resin, acrylonitrile-butadiene-styrene resin, cellulose propionate resin, polyarylate resin, polycarbonate resin, acrylonitrile-styrene resin, polytrimethylene terephthalate resin, polybutylene terephthalate resin, polyamide resin, polycyclohexane dimethylene terephthalate resin, and the like. These may be used alone or in combination of two or more.

[0038] From the viewpoint of achieving a balance between moldability during manufacturing and manifestation of mechanical strength during actual use, it is preferable that the materials constituting the neck part 12 and the bristle planting table 14 both include a thermoplastic resin having a flexural modulus and a tensile strength strain within a predetermined range, and it is more preferable that the thermoplastic resin includes at least one of polyacetal resin and polybutylene terephthalate resin.

[0039] Specifically, the thermoplastic resin constituting the neck part 12 and the bristle planting table 14 preferably has a flexural modulus of 2000 MPa or more, more preferably 2200 MPa or more, and preferably 4000 MPa or less. Also, the thermoplastic resin constituting the neck part 12 and the bristle planting table 14 preferably has a tensile fracture strain of 30% or more, more preferably 40% or more, and preferably 90% or less, more preferably 80% or less, and even more preferably 75% or less. By having at least one of such a flexural modulus and a tensile strength strain, the toothbrush 10 having a good balance between rigidity and toughness is obtained.

[0040] The flexural modulus (MPa) and tensile strength strain (%) of the above-mentioned thermoplastic resin can be measured, for example, by the following methods. The flexural modulus can be measured by using the resin to be measured to produce a dumbbell test piece of 80 mm × 10 mm × 4 mm and by the method specified in JIS K7171. The tensile strength strain can be measured as tensile strain in accordance with JIS K6251 by processing the resin to be measured into a dumbbell shape (No. 2).

[0041] The toothbrush 10 having the above configuration can be preferably manufactured by, for example, a two-color molding method as shown below. First, the molten primary resin is introduced into an injection mold, and the bristle base 14, the neck portion 12, the knob portion 19 having a shape complementary to the mold, and a core portion for forming the grip portion 11 are molded by injection molding to form a primary resin forming portion A. The primary resin forming portion A is formed such that the bristle base 14, the neck portion 12, and the knob portion 19 have substantially the same dimensions as the target toothbrush 10. That is, it is preferable that the knob portion 19 in the primary resin forming portion A is disposed on the side in the direction in which the bristle tufts are to be erected rather than on the virtual extension line V1 along the bristle surface 14A of the bristle base 14.

[0042] Next, using a second resin that is the same as or different from the first resin, the molten second resin is introduced into an injection mold having a shape complementary to the shape of the intended gripping portion 11. At the same time, the peripheral edge of the knob portion 19 in the first resin forming portion A and the core portion for forming the gripping portion 11 are injection molded so as to be coated with the second resin, and the second resin forming portion B is formed on the gripping portion 11. At this time, the outer surfaces of the bristle planting base 14, the neck portion 12, and the knob portion 19 are arranged so as not to be coated with the second resin. As a result, as shown in FIGS. 1 to 3, a toothbrush body 15 having a gripping portion 11 including a first resin forming portion A formed of the first resin and a second resin forming portion B formed of the second resin is formed. The toothbrush body 15 obtained through this step has an outer surface of the gripping portion 11 formed of the second resin. Further, the knob portion 19 is formed in a state of being exposed on the outer surface of the toothbrush body 15 and in a state where the outer peripheral edge of the knob portion 19 is surrounded by the second resin. Thereby, when the knob portion 19 is visually recognized, it can be configured such that the portion to be pinched by the finger can be easily discriminated by the user.

[0043] Finally, a plurality of bristles 17 are implanted into the implant holes 16 formed in the bristle planting surface 14A of the bristle planting base 14 in the toothbrush body 15 to obtain a toothbrush 10 in which a tuft 18 is formed on the bristle planting base 14. For implanting the bristles 17, for example, various known implanting methods such as flat wire implanting in which a filament is folded in half and a flat wire is driven in, or fusion implanting in which a molten mass is formed at one end and heat fused can be used.

[0044] When the knob portion 19 is arranged in a predetermined region, formed to have a predetermined area, or provided with an anti-slip on the knob portion 19, for example, at the position where the knob portion 19 is to be formed when injection molding the first resin forming portion A, injection molding may be performed using a mold complementary to the intended structure. Further, when the knob portion 19 is formed to have a predetermined area, for example, it can also be adjusted by appropriately changing the coating area of the second resin at the peripheral edge of the knob portion 19 in the first resin forming portion A.

[0045] Also, as described above, in order to control the center of gravity of the toothbrush 10 within a suitable range, for example, the density of the primary resin constituting the primary resin forming portion A and the density of the secondary resin constituting the peripheral portion of the grip portion 19 and the surface of the holding portion 11 may be configured to be different from each other. Specifically, for example, the toothbrush 10 may be manufactured using a secondary resin having a density smaller than that of the primary resin. As such a configuration, for example, as the primary resin, a resin containing at least one of a polyacetal resin and a polybutylene terephthalate resin may be used, and as the secondary resin, a polypropylene resin or a styrene-butadiene copolymer resin may be used. In addition to such a method, for example, the overall length of only the primary resin forming portion A formed by the primary resin may be shortened, the covering area and the covering amount of the primary resin forming portion A by the secondary resin may be appropriately changed, or the toothbrush may be manufactured so as to provide a portion where no resin such as a cavity or a through hole exists in the holding portion 11, thereby enabling adjustment. In particular, by using a resin containing at least one of a polyacetal resin and a polybutylene terephthalate resin as the primary resin, there is also an advantage that the implant base 14 and the neck portion 12 having the above-described flexural modulus and tensile strength strain can be easily obtained.

[0046] Regardless of whether the above-described primary resin and secondary resin are the same resin or not, it is preferable that the primary resin and the secondary resin are colored in different colors. As the dyes for coloring these resins, dyes generally used as plastic-based dyes can be used without particular limitation. As such dyes, for example, dyes such as azo, anthraquinone, quinophthalone, styryl, di- or triphenylmethane, oxazine, triazine, xanthene, methine, azomethine, thricine, and diazine can be used. In particular, since the primary resin and the secondary resin are colored in different colors from each other, the grip portion 19 can be easily visually recognized, and it can be easily induced to grip the grip portion 19 with the thumb and index finger.

[0047] As described above, the present invention has been explained based on its preferred embodiments, but the present invention is not limited to the above embodiments. For example, the toothbrush 10 in each of the above-described embodiments has been described as an embodiment using a primary resin and a secondary resin, but it is not limited to these forms, and as long as the effects of the present invention are achieved, it may be an integrally molded body made of a single resin.

[0048] Also, the knob portion 19 in each of the above-described embodiments has been described as having a substantially concave shape when viewed from the front or back of the toothbrush 10, but it is not limited to this form, and as long as the effects of the present invention are achieved, it may have a substantially convex shape.

[0049] In FIG. 4, a method of brushing the tooth surface and tooth root located inside the oral cavity of the lower front teeth with the toothbrush 10 has been described as an example, but it is not limited to this method. Even when the tooth surface and tooth root located inside the oral cavity such as the upper front teeth are used as the brushing target site, the effects of the present invention can be sufficiently achieved. In this case, the toothbrush 10 is held by the user in a state where the part of the gripping portion 11 other than the knob portion 19 pinched by the finger belly and the palm are separated, and the front of the gripping portion 11 and the palm face each other. Even when brushing is performed in this gripping state, since the positions of the force point and the fulcrum substantially coincide, it is possible to avoid an excessive brushing pressure being applied to the tooth surface and tooth root from the brush surface which is the point of action, and to brush the tooth surface and tooth root located inside the upper oral cavity with an appropriate brushing pressure. In addition, since the knob portion 19 is arranged on the side where the tuft 18 stands upright rather than on the virtual extension line V1 along the tufting surface 14A of the tufting base 14, for example, when the toothbrush 10 is used for brushing the tooth surface and tooth root located inside the oral cavity such as the upper front teeth, it is possible to prevent the toothbrush 10 from accidentally hitting the lower lip or the lower front teeth, etc., and to facilitate the brushing of the tooth surface and tooth root located inside the oral cavity.

Explanation of Reference Numerals

[0050] 10 Toothbrush 11 Gripping portion 11a One end portion 11b Other end portion 12 Neck portion 12a Connection portion with the bristle planting table 13 Handle portion 14 Bristle planting table 14A Bristle planting surface 15 Toothbrush body 16 Bristle planting holes 17 Bristles 18 Bristle tufts 19 Knob portion

Claims

1. A toothbrush comprising a toothbrush body including a bristle base having a plurality of bristle implantation holes in which bristle bundles are implanted, a grip portion, and a neck portion connecting the grip portion and the bristle base, a knob portion is provided at an end portion of the grip portion on the neck side, the knob portion having a longitudinal cross-sectional shape in which the width in a vertical direction perpendicular to the tufting surface of the tufting table is longer than the width in a horizontal direction parallel to the tufting surface of the tufting table, The grip portion includes a core material formed of a primary resin forming portion and a secondary resin forming portion covering the primary resin forming portion, The knob portion is a generally concave region, the substantially concave region is a region of the primary resin forming portion surrounded by the secondary resin forming portion, The gripping portion is disposed on the side where the hair bundle is erected, relative to an imaginary extension line along the hair implantation surface of the hair implantation table, The toothbrush further comprises a gripping portion formed with an engaging portion that engages a core material made of the primary resin forming portion with the secondary resin forming portion that covers the primary resin forming portion.

2. The toothbrush according to claim 1 , wherein the substantially concave region is defined by a contour line of a step between the primary resin forming portion and the secondary resin forming portion.

3. 3. The toothbrush according to claim 1, wherein the knob portion has a horizontally elongated side shape whose length along the extension direction of the grip portion is longer than its length perpendicular to said direction.

4. The area of ​​the approximately concave region is 50 mm2 or more and 200 mm ２ 3. The toothbrush according to claim 1 or 2, wherein:

5. The thickness of the bristle base is 2.0 mm or more and 4.0 mm or less, The cross-sectional area of ​​the neck portion at its smallest diameter is 14.0 mm ２ 3. The toothbrush according to claim 1 or 2, wherein:

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