toothbrush

Abstract

This toothbrush comprises: a toothbrush body having a grip part that is long along a center line, a neck part extending from a tip of the grip part, and a head part provided on the neck part on the side opposite to the grip part; and a brush part composed of a plurality of bristle bundles implanted on the head part. The toothbrush body includes: a base member that is composed of a hard resin and that has a grip part body, the neck part, and the head part; and a foam molded body provided on a surface of the grip part body and composed of a soft resin. The foam molded body has a fill part and a plurality of void parts, and the storage elastic modulus of the foam molded body is 104 Pa to 106.5 Pa.

Description

[Technical Field]

[0001] The present invention relates to a toothbrush. This application claims priority based on Japanese Patent Application No. 2020-214656, filed on December 24, 2020, the contents of which are incorporated herein by reference. [Background technology]

[0002] Generally, a toothbrush is composed of a toothbrush body having a rod-shaped handle, a neck extending from the tip of the handle, and a head attached to the tip of the neck, and a plurality of bristle tufts attached to the head. The toothbrush body is made of a hard resin to prevent the handle from bending excessively during brushing and to ensure that the bristle tufts can apply sufficient force to the teeth.

[0003] However, toothbrushes with a body made solely of hard resin have a hard, flexible handle, making them difficult to grip, which can lead to mishandling of the toothbrush while brushing and potentially injuring the oral cavity.

[0004] To address this issue, toothbrushes have been proposed that improve grip when the handle is held in the hand, with handles in which the surface of a rod-shaped core made of hard resin is partially or entirely covered with soft resin (see, for example, Patent Document 1). Toothbrushes have also been proposed in which the soft resin and hard resin are exposed on the surfaces of the handle (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-000407 [Patent Document 2] International Publication No. 2016-208333 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the case of a configuration such as that of Patent Document 1, there are restrictions on the hardness of the soft resin used, and the soft resin needs to be designed to be thick in order to ensure sufficient gripping ability. Also, in the case of a configuration such as that of Patent Document 2, it is possible to use a softer resin, but the ratio of hard resin to soft resin in the gripping portion needs to be taken into consideration when designing. Therefore, there is a demand for a configuration that can improve grip without any design restrictions.

[0007] The present invention has been made in consideration of the above points, and an object of the present invention is to provide a toothbrush that can improve gripping ability without any design restrictions. [Means for solving the problem]

[0008] In one embodiment of the present invention, the toothbrush comprises a toothbrush body having a handle portion having a length along a center line, a neck portion extending from the tip of the handle portion, and a head portion provided on the opposite side of the neck portion from the handle portion; and a brush portion consisting of a plurality of bristle bundles implanted in the head portion, wherein the toothbrush body has a base member made of hard resin having a handle portion body, the neck portion, and the head portion, and a foam molded body made of soft resin provided on the surface of the handle portion body, wherein the foam molded body has a filled portion and a plurality of void portions, and the storage modulus G' of the foam molded body is 104 Pa or more and 106.5 Pa or less.

[0009] With this configuration, since a foam molded body is provided on the surface of the handle body, the handle can be deformed appropriately with normal gripping force, providing good grip in the hand and making brushing easier.

[0010] In the toothbrush according to one aspect of the present invention, the foamed molded body may have a loss modulus G'' of 104 Pa or more and 106.5 Pa or less.

[0011] With this configuration, when the toothbrush is gripped during brushing, the foamed molded body deforms gradually rather than instantaneously, and the deformation at the time of gripping is temporarily maintained immediately after the toothbrush is released.

[0012] In the toothbrush according to one aspect of the present invention, the soft resin may have a loss tangent (loss modulus divided by storage modulus) of 0.05 or greater.

[0013] With this configuration, when the toothbrush is gripped, the foam molded body deforms with a force that makes it easy to grip, and the speed of deformation is neither too fast nor too slow, making it easy for the user to hold.

[0014] In the toothbrush according to one aspect of the present invention, the soft resin may have a Shore A hardness of less than 30.

[0015] This configuration provides an excellent fit when the grip is held in the hand.

[0016] In one embodiment of the toothbrush of the present invention, the mode of size of the plurality of voids is 0.001 mm 2 More than 0.3mm 2 The configuration may be within the following ranges.

[0017] This configuration provides the effect of providing the foamed molded article with appropriate flexibility.

[0018] In one embodiment of the toothbrush of the present invention, 80% of all the voids in the foamed molded body have a size difference of ±0.3 mm with respect to the most frequent value of all the voids. 2 The configuration may be within the range.

[0019] This configuration provides the effect of providing the foamed molded article with more appropriate flexibility.

[0020] In one embodiment of the toothbrush of the present invention, the average occupancy rate of the plurality of voids in a cross section of the foamed molded body intersecting the center line may be in the range of 2% or more and 60% or less.

[0021] This configuration enhances the softness of the foam molded body, and provides a foam molded body that can be appropriately deformed when gripping the toothbrush.

[0022] In the toothbrush according to one aspect of the present invention, the soft resin may have a density in the range of 0.55 g / cm 3 or more and 0.8 g / cm 3 or less.

[0023] This configuration ensures the strength of the foam molded article while also providing flexibility.

[0024] In one form of the toothbrush of the present invention, the cross section of the gripping portion intersecting the center line may be made up of the base member and the foam molded body, and the cross-sectional area of ​​the foam molded body may be less than 50% of the total area obtained by adding the cross-sectional area of ​​the base member and the cross-sectional area of ​​the foam molded body.

[0025] With this configuration, the sinking effect of the foamed molded body is enhanced by the multiple voids, improving the softness of the gripping portion, and the presence of the base member inside the foamed molded body prevents the entire gripping portion from deforming, ensuring good operability of the toothbrush.

[0026] In the toothbrush according to one aspect of the present invention, the foam molded body may have a thickness of 2 mm or more and 5 mm or less.

[0027] According to this configuration, a moderate sinking effect can be obtained by the plurality of voids, and thus the gripping ability can be improved.

[0028] In one form of the toothbrush of the present invention, the grip portion may have a skin layer that forms the surface of the grip portion, and a foam layer in which the filling portion and the plurality of void portions are covered by the skin layer, and the thickness ratio of the skin layer to the foam layer at a cross section intersecting the center line may be in the range of 1:1 or more and 1:10 or less.

[0029] According to this configuration, there is no risk of the strength of the foamed molded article being reduced, and the effect of improving softness due to the multiple voids in the foamed layer can be obtained.

[0030] In the toothbrush according to one aspect of the present invention, the foamed molded body may be formed at a proportion of the entire length of the grip portion that is within a range of 50% to 100%.

[0031] With this configuration, when gripping the handle with your hand during brushing, the foamed molded body is provided over more than half of the area that comes into contact with your hand, making it easier to grip. [Effects of the Invention]

[0032] The present invention can provide a toothbrush that can improve gripping ability without any design restrictions. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 is a front view showing a toothbrush according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view taken along line II-II in FIG. [Figure 3] FIG. 3 is a graph showing the size distribution of voids in a foam molded article. DETAILED DESCRIPTION OF THE INVENTION

[0034] An embodiment of the toothbrush of the present invention will be described below with reference to FIGS. The following embodiment shows one aspect of the present invention, does not limit the present invention, and can be modified as desired within the scope of the technical concept of the present invention. In addition, in the following drawings, the scale and number of each structure are different from the actual structure to make each configuration easier to understand.

[0035] <Toothbrush> The toothbrush of the present invention will now be described with reference to the drawings. Fig. 1 is a front view showing a toothbrush 1 according to one embodiment of the present invention, and Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1.

[0036] As shown in FIG. 1, the toothbrush 1 of this embodiment is composed of a toothbrush body 2 and a brush head 3, and has an elongated shape with a length along a center line O. Toothbrush body 2 has grip portion 21 having a length along center line O, neck portion 22 extending from the tip of grip portion 21 along center line O, and head portion 23 provided on the tip side of neck portion 22 on the opposite side to grip portion 21. Note that toothbrush 1 may have a configuration in which neck portion 22 is not provided between grip portion 21 and head portion 23.

[0037] The head portion 23 is formed in a generally rectangular shape when viewed from the front. The head portion 23 has a tufting surface 23a on the front side. A plurality of tufting holes 23b are formed in the tufting surface 23a. In the present embodiment shown in Figure 1, 26 tufting holes 23b are formed in the tufting surface 23a, but the number of tufting holes 23b is not limited to this.

[0038] Each bristle hole 23b is fitted with a bristle bundle 31, which is a bundle of bristles bound into a generally cylindrical shape. The brush part 3 is made up of the bristle bundles 31 fitted in each bristle hole 23b.

[0039] The bristles constituting the bristle bundle 31 include straight bristles, bristles whose diameter gradually decreases towards the tip (tapered bristles), bristles with branched ends, spiral bristles, bristles with irregular cross sections, and the like. The tip shape of the tuft 31 may be flat, mountain-cut, convex, concave, or the like. The type of bristles used and the shape of the tip of the bristle bundle 31 are appropriately determined taking into consideration the cleaning effect desired for the brush part 3 and the feel against the gums.

[0040] Neck portion 22 is disposed between grip portion 21 and head portion 23 and connects grip portion 21 and head portion 23. In this embodiment, neck portion 22 extends with a predetermined width from head portion 23 toward grip portion 21, and is formed so that its width increases toward grip portion 21 at its rear end. The length and width of the neck portion 22 are set appropriately taking into consideration the material, etc., and are sized to ensure the necessary strength for the neck portion 22 while improving operability within the oral cavity and reachability to the back teeth.

[0041] The grip portion 21 is the portion that the user grips, and is formed in a long, cylindrical shape. To ensure a length sufficient for the user to grip and use the grip portion 21, it is preferable that the length from position W to the rear end of the toothbrush 1 in a front view be, for example, 80 mm or more and 140 mm or less. The grip portion 21 is connected to the rear end side of the neck portion 22 in a manner that forms a smooth curve that is continuous with the shape of the neck portion 22. In this embodiment, the grip portion 21 is defined as the length from position W1 shown in FIG. 1 to the rear end of the toothbrush 1, but the range of the grip portion 21 is not limited to this. For example, the length from the position W2 where the center of curvature changes on the rear end side of the neck portion 22 to the rear end of the toothbrush 1 may be defined as the grip portion 21.

[0042] The toothbrush body 2 thus constructed has a surface of the grip portion 21, which is held by hand during brushing, made of soft resin. Toothbrush body 2 is configured to include base member 201 made of hard resin and foam molded body 202 made of soft resin. Foam molded body 202 is provided to cover part of base member 201 (the part corresponding to grip part 21). The overall shape of toothbrush body 2 is smooth, with no steps at the boundary between base member 201 and foam molded body 202.

[0043] The base member 201 has a head portion 23, a neck portion 22, and a grip portion main body 21 A. The base member 201 can be produced by injection molding using a hard resin.

[0044] As a constituent material of the base member 201, for example, polypropylene (PP) is preferred because of its high adhesiveness with soft resins. Other examples include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycyclohexylene dimethylene terephthalate (PCT), polyacetal (POM), polyethylene naphthalate (PEN), polystyrene (PS), acrylonitrile-butadiene-styrene resin (ABS), cellulose propionate (CP), polyarylate, polycarbonate, and acrylonitrile-styrene copolymer resin (AS). Among these resin materials, POM, PBT, PEN, and the like are preferred because of their high strength and ease of thinning the head portion 23. The above resins may be used alone or in combination of two or more types.

[0045] The foam molded body 202 is a porous body with many internal pores, and is provided to cover the entire surface of the grip body 21A of the base member 201, which is closer to the rear end than the neck portion 22. In a direction intersecting the center line O, the grip body 21A has a cylindrical shape that is smaller in width and thickness than the rear end of the neck portion 22. The grip body 21A extends with a constant diameter in the length direction. The foam molded body 202 is formed so as to fill in a step 4 formed at the boundary between the neck portion 22 and the grip body 21A of the base member 201.

[0046] The grip portion main body 21A of the base member 201 is not limited to a cylindrical shape, and can be modified as appropriate.

[0047] The foam molded product 202 has a foam layer 202A and a skin layer 202B formed on the outermost surface of the foam layer 202A. The foam layer 202A has a filling portion 202b and a plurality of voids 202c formed within the filling portion 202b. The foam layer 202A has a closed-cell structure in which each of the plurality of voids 202c is surrounded by the filling portion 202b, and no voids 202c exist in the skin layer 202B. Therefore, the outer peripheral surface of the skin layer 202B (the surface of the grip portion 21) is a smoothly curved surface.

[0048] The soft resin that constitutes the foam molded body 202 can be a resin that is softer than the hard resin used for the base member 201, and in this embodiment, a resin with a Shore A hardness of less than 30 can be used.

[0049] Specific examples of soft resins constituting foam molded body 202 include styrene-based, olefin-based, and other elastomer resins with a Shore A hardness of less than 30. The Shore A hardness of the soft resin constituting foam molded body 202 is preferably within the range of 0 to 25, and more preferably within the range of 0 to 20. If the Shore A hardness of the soft resin is equal to or less than the upper limit, an excellent fit can be obtained when gripping handle 21 in the hand. If the Shore A hardness is higher than the upper limit, foam molded body 202 becomes difficult to deform, and toothbrush 1 does not fit well in the hand when gripped.

[0050] The Shore A hardness refers to the hardness measured in accordance with JIS K 7215 or JIS K 6253.

[0051] In this embodiment, it is preferable to use a styrene-based elastomer resin from the viewpoint of ease of deformation and softness.

[0052] As the soft resin constituting the foam molded body 202, one type may be used alone, or two or more types may be used in combination.

[0053] The storage modulus G' (compression conditions: temperature 23°C, frequency: 1 Hz) of the soft resin constituting the foamed molded product 202 is preferably in the range of 104 Pa or more and 106.5 Pa or less, and more preferably in the range of 105.5 Pa or more and 106.5 Pa or less. This allows for moderate deformation with a normal grip force, providing a good grip in the hand and making brushing easier.

[0054] If the storage modulus G' of foam molded body 202 is less than 104 Pa, it will deform with a weak force, causing foam molded body 202 to move during brushing, reducing gripping ability and making brushing difficult. Conversely, if the storage modulus G' of foam molded body 202 is greater than 106.5 Pa, foam molded body 202 will not deform unless a strong force is applied. Therefore, foam molded body 202 will not deform easily with a normal gripping force, reducing the fit when held.

[0055] The loss modulus G'' of the soft resin constituting foam molded body 202 is preferably in the range of 104 Pa or more and 106.5 Pa or less, and more preferably in the range of 104.5 or more and 105.5 or less. This allows foam molded body 202 to deform gradually rather than instantaneously when toothbrush 1 is gripped during brushing, and the deformation at the time of gripping is temporarily maintained immediately after releasing the toothbrush.

[0056] On the other hand, if the loss modulus G'' of the foam molded body 202 is small, less than 104 Pa, the deformation speed of the foam molded body 202 increases and the foam molded body 202 deforms instantaneously into the shape that the user is grasping. As a result, when the foam molded body 202 is grasped, the repulsive force of the foam molded body 202 is not immediately obtained, making it difficult to grasp and hold.

[0057] Conversely, if the loss modulus G'' of foam molded body 202 exceeds 106.5 Pa, the deformation speed of foam molded body 202 slows down, and it takes time for it to deform into the shape held by the user. Therefore, when changing the grip of the toothbrush, it takes time for it to change from the gripped shape before changing to the unclutched shape before changing. When foam molded body 202 is difficult to return to its original shape, it is less able to conform to the hand, and usability when changing the grip of the toothbrush during brushing is reduced.

[0058] The loss tangent tanδ (loss modulus G'' / storage modulus G') of the soft resin constituting foam molded body 202 is within the range of 0.05 or more and 0.3 or less. As a result, when toothbrush 1 is gripped during brushing, foam molded body 202 deforms with a force that is easy to grip, and the speed of deformation is also appropriate, making it easy for the user to grip.

[0059] If the loss tangent tanδ of the soft resin is less than 0.05, more force than normal brushing is required to deform it, and the repulsive force trying to return it to its original shape is also strong. On the other hand, the deformation speed is also fast, and it quickly conforms to the hand, so it becomes difficult to maintain the deformation unless it is constantly pressed down by hand, making it difficult to hold.

[0060] Furthermore, if the loss tangent tanδ of the soft resin exceeds 0.3, it can be deformed with a weak force, but the deformation speed tends to be slow, which makes it difficult to follow the shape when changing the grip of the hand while brushing, and makes it difficult to hold.

[0061] The foamed molded body 202 is formed from a foamed resin obtained by compounding a foaming agent with a soft resin and foaming it. There are no particular limitations on the foaming agent, and known chemical or physical foaming agents can be used. For example, examples of base polymers include polyethylene (PE), polypropylene (PP), polystyrene (PS), acrylonitrile butadiene styrene (ABS), and ethylene vinyl acetate (EVA). In this embodiment, it is preferable to use polyethylene as the foaming agent from the viewpoint of compatibility with elastomer resins.

[0062] As foaming molecules, organic compounds include azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DNPT), azobisisobutyronitrile, and azobisisobutyronitrile. Examples of suitable foaming molecules include benzotriazole, benzotriazole, barium azodicarboxylate, and p,p'-oxybisbenzenesulfonylhydrazine (OBSH). Examples of inorganic foaming molecules include carbonate compounds such as sodium bicarbonate, ammonium bicarbonate, sodium carbonate, and ammonium carbonate. In this embodiment, organic foaming molecules are preferably used in terms of compatibility with the elastomer resin and foaming temperature.

[0063] To promote foaming of the soft resin, a foaming assistant may be used together with the foaming agent, such as urea or a urea derivative. The amount of foaming agent to be mixed with the soft resin is not particularly limited and may be appropriately determined.

[0064] The foam molded body 202 is composed of a foam layer 202A made of a foamed resin and an unfoamed skin layer 202B. The foam layer 202A has a filling portion 202b and a plurality of voids 202c. In a cross section of the foam molded body 202 in a direction intersecting the central axis, each void 202c exists independently within the filling portion 202b. The skin layer 202B is formed on the entire surface of the foam layer 202A.

[0065] The most frequent size of the plurality of voids 202c in the foam molded body 202 is 0.001 mm 2 More than 0.3mm 2 The following range is preferable: 0.01 mm 2 More than 0.1mm 2 The following ranges are more preferable: This provides the effect of providing the foam molded article 202 with appropriate flexibility.

[0066] The most frequent size of each gap 202c is 0.001 mm 2If the thickness is less than this, the flexibility of the foamed molded body 202 is not obtained. In other words, the amount of deformation of each void 202c is small, and the sinking effect of the resin due to the deformation of the void 202c is not obtained easily. As a result, the toothbrush 1 does not fit well in the hand when held.

[0067] On the other hand, the most frequent size of the void 202c is 0.3 mm 2 If the thickness exceeds this value, the sinking effect cannot be effectively achieved when toothbrush 1 is held, so foam molded body 202 does not soften and the fit to the hand deteriorates. In other words, the upper and lower surfaces of cavity 202c (the surfaces facing each other in the direction in which force is applied) tend to come into contact, and the sinking effect of the resin due to deformation of the cavity cannot be effectively achieved. As a result, the fit to the hand of toothbrush 1 deteriorates when held.

[0068] Furthermore, the most frequent size of 80% of the plurality of voids 202c in the foam molded body 202 is ±0.3 mm. 2 It is preferable that the range is within ±0.2 mm. 2 This provides the effect of providing the foam molded article 202 with more appropriate flexibility. If the temperature exceeds the above range, the foamed molded article 202 cannot have the desired uniform softness.

[0069] The foamed molded article 202 can be molded by injection molding using a short shot method, a full shot method, a core-back method, etc. In this embodiment, it is preferable to use the short shot method for injection molding in order to effectively foam the organic foaming molecules.

[0070] In the cross section of foam molded body 202 intersecting center line O, the average occupancy rate of multiple voids 202c is preferably within a range of 2% to 60%, and more preferably 50% or less, which enhances the softness of foam molded body 202 and allows foam molded body 202 to be appropriately deformed when toothbrush 1 is held.

[0071] If the proportion of voids 202c in the cross section of molded foam 202 is less than 2%, it becomes difficult to obtain softness because the amount of deformation of molded foam 202 is small. Conversely, if the proportion exceeds 60%, the strength of molded foam 202 decreases, or closed cells in each void 202c cannot be maintained and open cells increase, thereby reducing the effect of improving softness.

[0072] The thickness of the foam molded body 202 is preferably 2 mm or more and 5 mm or less. This allows the gap 202c to provide a suitable sinking effect, improving grip. If the thickness of foam molded body 202 is less than 2 mm, the appropriate sinking effect due to voids 202c cannot be obtained, and the softness of foam molded body 202 decreases. Conversely, if the thickness of the foam molded article 202 exceeds 5 mm, when the handle 21 is gripped, the foam molded article 202 sinks in significantly and becomes too soft, making it difficult to grip.

[0073] The density of the filling portion 202b in the foamed molded body 202 is 0.55 g / cm 3 More than 0.8g / cm 3 It is preferable that the thickness is within the following range: This provides the effect of ensuring the strength of the foam molded body 202 while also providing flexibility.

[0074] In the foamed molded body 202, the density of the filling portion 202b is 0.55 g / cm 3 On the other hand, if the density of the filling portion 202b is less than 0.8 g / cm 3 If it exceeds this, flexibility cannot be ensured.

[0075] Molded foam 202 has skin layer 202B and foam layer 202A, and the ratio of their thicknesses is preferably 1:1 or more and 1:10 or less, and more preferably 1:5 or less. This prevents a decrease in the strength of molded foam 202, and provides the effect of improving softness due to voids 202c in foam layer 202A.

[0076] If skin layer 202B becomes too thick relative to foam layer 202A, the foam layer 202A containing voids 202c will be reduced, and the effect of improving softness due to voids 202c will no longer be obtained. Conversely, if skin layer 202B becomes too thin relative to foam layer 202A, voids 202c will be closer to skin layer 202B, which may result in voids 202c being exposed to the surface, which may result in a decrease in strength and poor appearance of foam molded article 202.

[0077] Furthermore, in this embodiment, the cross section of grip portion 21 intersecting center line O of toothbrush 1 is made up of base member 201 and molded foam 202, and the ratio of the cross-sectional area of ​​molded foam 202 to the total area obtained by adding together the cross-sectional areas of base member 201 and molded foam 202 is preferably less than 50%, and more preferably 20% to 40%. This enhances the sinking effect of molded foam 202 due to voids 202c, improving the softness of grip portion 21. Furthermore, the presence of base member 201 inside molded foam 202 prevents deformation of grip portion 21 as a whole, ensuring good operability of toothbrush 1.

[0078] If the proportion of the cross-sectional area of ​​foam molded body 202 is less than 20%, the sinking effect of foam molded body 202 due to voids 202c is reduced, resulting in a decrease in softness. Conversely, if the proportion of the cross-sectional area of ​​foamed molded body 202 is as large as 50% or more, the strength of toothbrush 1 becomes a concern.

[0079] The proportion of foam molded body 202 formed in the entire length direction of grip portion 21 is preferably 50% or more and 100% or less, and the lower limit is more preferably 80% or more. This means that when gripping grip portion 21 with the hand during brushing, foam molded body 202 is provided in more than half of the area that the hand touches, making it easier to grip.

[0080] If the proportion of foam molded body 202 formed in the length direction of grip portion 21 is small, it will not be possible to provide foam molded body 202 over the entire area that comes into contact with the hand when gripping grip portion 21 during brushing, and the hand will have to cover the boundary between base member 201 made of hard resin and foam molded body 202, making it difficult to grip. For this reason, it is preferable that foam molded body 202 be present over substantially the entire area of ​​grip portion 21 that is gripped by the hand.

[0081] As described above, toothbrush 1 of this embodiment is configured such that the entire axial circumference of grip main body 21A of base member 201 made of hard resin is covered with molded foam 202, so that molded foam 202 is present around the entire axial circumference of grip 21, which is gripped when holding toothbrush 1 in the hand during brushing. As a result, regardless of how the toothbrush is held, molded foam 202 deforms three-dimensionally, increasing the contact area with the hand, so that grip 21 fits snugly around the thumb, index finger, and palm. This improves the grip on toothbrush 1, making brushing easier and providing a toothbrush 1 that is comfortable to hold.

[0082] Furthermore, toothbrush 1 of this embodiment is made by first molding base member 201 made of hard resin, followed by secondary molding using soft resin to form foam molded body 202 that partially covers the surface of base member 201. In this way, toothbrush 1 can be produced without any design restrictions, and the design of toothbrush 1 can be improved.

[0083] [Example] The effects of the present invention will be made clearer by the following examples. Note that the present invention is not limited to the following examples and can be practiced with appropriate modifications within the scope of the present invention.

[0084] (Examples 1 to 16, Comparative Examples 1 and 2) In the present examples, toothbrushes of Examples 1 to 16 and Comparative Examples 1 and 2 were prepared according to the specifications shown in Tables 1 and 2 below and FIG. 2, as samples similar to the toothbrushes shown in FIGS.

[0085] The common specifications for Examples 1 to 16 and Comparative Examples 1 and 2 are as follows. Grip part 21: Total length 115mm, maximum width 14.5mm, maximum thickness 14.5mm Base member 201: length 110 mm, width 8.5 mm, thickness 8.5 mm Foam molding 202: Maximum coating thickness 3mm Boundary (position W) between neck portion 22 and grip portion 21: width 11 mm, thickness 11 mm Neck 22: Length 45mm, minimum width 5mm, minimum thickness 5mm Head 23: Length 25mm, width 11mm, thickness 4.5mm

[0086] Other specifications of the toothbrushes in Examples 1 to 10 are shown in Tables 1 and 2, and specifications of the toothbrushes in Examples 11 to 16 and Comparative Examples 1 and 2 are shown in Table 2. The handle body is made of PP resin.

[0087] The specifications for the samples of each example and comparative example were storage modulus, loss modulus, loss tangent, A hardness, mode of void size, and void occupancy rate, which were set for each sample.

[0088] "Storage modulus evaluation" A dynamic viscoelasticity apparatus (E4000) manufactured by UBM was used to evaluate the storage modulus. To evaluate the storage modulus, a test piece (a 10 mm square, 6 mm thick resin plate) was fixed to the dynamic viscoelasticity device described above, and the storage modulus and loss modulus were measured under compression conditions of a frequency of 1 Hz and a temperature of 23°C, and the loss tangent was calculated.

[0089] "Gap size evaluation" FIG. 3 is a graph showing the size distribution of voids 202c in foam molded article 202. As shown in FIG. In FIG. 3, the vertical axis indicates the number of voids 202c, and the horizontal axis indicates the size of the voids 202c. The cross section of the test piece was observed under a microscope, and the cross-sectional area of ​​the void portion 202c was measured (n=40). As shown in FIG. 3, the most common size of the gap 202c is 0.01 mm. 2 ~0.1mm 2 The average value was 0.025 mm. 2 It was.

[0090] [Table 1]

[0091] [Table 2]

[0092] [Evaluation method] (1) Ease of gripping the grip portion 21 (fits the hand) [Test method] Ten monitors held the toothbrush 1 and brushed their teeth, and evaluated the toothbrush 1 of each example in terms of "ease of gripping the grip portion 21 (fit to the hand)." The evaluation was made on an absolute scale of 7 points from 1 to 7. The average scores of the 10 monitors were classified according to the following criteria to determine the ease of gripping the grip portion 21. <Judgment criteria> ☆: Average score is 6.6 or higher ◎: Average score is 5.5 or more and less than 6.5 points ○: Average score is 4.6 points or more and less than 5.5 points △: Average score is between 3.6 and 4.5 points ×: Average score is less than 3.5 points

[0093] (2) Deformation speed of the gripping portion 21 [Test method] Ten monitors held toothbrush 1 and brushed their teeth to evaluate the "speed of deformation of the gripping portion" of each toothbrush in each example. The evaluation was made as an absolute evaluation on a 7-point scale from 1 point to 7 points. The average scores of the 10 monitors were classified into the following criteria, and the deformation speed (degree of deformation) of the grip portion 21 was judged. <Judgment criteria> ☆: Average score is 6.6 or higher ◎: Average score is 5.5 or more and less than 6.5 points ○: Average score is 4.6 points or more and less than 5.5 points △: Average score is between 3.6 and 4.5 points ×: Average score is less than 3.5 points

[0094] (3) Ease of brushing [Test method] Ten monitors held toothbrush 1 and brushed their teeth to evaluate the "ease of brushing" of the toothbrushes of each example. The evaluation was made on an absolute scale of 1 to 7 points. The average scores of the 10 monitors were classified according to the following criteria to determine the ease of brushing. <Judgment criteria> ☆: Average score is 6.6 or higher ◎: Average score is 5.5 or more and less than 6.5 points ○: Average score is 4.6 points or more and less than 5.5 points △: Average score is between 3.6 and 4.5 points ×: Average score is less than 3.5 points

[0095] As shown in [Table 1] and [Table 2], for the samples of Examples 1 to 16, whose "storage modulus G' (Log10)" values ​​were within the range of 4.0 or more and 6.5 or less, good results were obtained in all of the following: "ease of gripping the grip portion 21 (fit to the hand)," "degree of deformation of the grip portion 21," and "ease of brushing."

[0096] In contrast, for the samples of Comparative Example 1, in which the "storage modulus G' (Log10)" value was less than 4.0, and Comparative Example 2, in which the value exceeded 6.5, good results were not obtained in terms of "ease of gripping the grip portion 21 (fit in the hand)" and "ease of brushing."

[0097] Furthermore, as shown in Table 1 and Table 2, for the samples of Examples 5 to 16, whose "loss modulus G'' (Log10)" values ​​were within the range of 4.0 or more and 6.5 or less, good results were obtained in all of the following: "ease of gripping the grip portion 21 (fit to the hand)," "degree of deformation of the grip portion 21," and "ease of brushing."

[0098] Furthermore, as shown in Table 1 and Table 2, the samples of Examples 10, 11, 15, and 16, which had storage modulus G' (Log10), loss modulus G'' (Log10), loss tangent tanδ (Log10), and hardness of the foamed molded body 202 within the following ranges, showed particularly good results in all of "ease of gripping the grip portion 21 (fit to the hand)," "degree of deformation of the grip portion 21," and "ease of brushing."

[0099] Furthermore, among the samples of Examples 10, 11, 15, and 16, the most frequent value of the size of the voids 202c in the foamed molded article 202 was 0.01 mm 2 More than 0.1mm 2 The best results were obtained in Example 15, which was within the following range: The sample specifications of Example 15 can be said to be the best mode.

[0100] While the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to these examples. The shapes and combinations of the components shown in the above examples are merely examples, and various modifications can be made based on design requirements, etc., without departing from the spirit of the present invention. [Explanation of symbols]

[0101] 1...toothbrush, 2...toothbrush body, 3...brush part, 21...grip, 21A...grip body, 22...neck part, 23...head part, 31...bristle bundle, 201...base member, 202...foam molded body, 202b...filling part, 202c...void part, 202A...foam layer, 202B...skin layer, G''...loss modulus, G'...storage modulus, O...center line, tanδ...loss tangent

Claims

1. The toothbrush comprises a toothbrush body having a grip portion having a length along a center line, a neck portion extending from the tip of the grip portion, and a head portion provided on the neck portion on the opposite side to the grip portion, and a brush portion consisting of a plurality of bristle bundles implanted in the head portion, The toothbrush body is a base member made of hard resin having a grip body, the neck portion, and the head portion; a foam molded body made of a soft resin and provided on the surface of the grip body, The foam molded body has a filling portion and a plurality of void portions, The storage elastic modulus G' of the foamed molded body is 104 Pa or more and 106.5 Pa or less. toothbrush.

2. The loss modulus G″ of the foamed molded body is 104 Pa or more and 106.5 Pa or less. The toothbrush of claim 1.

3. The loss tangent of the soft resin (loss modulus G''÷storage modulus G') is 0.05 or more. The toothbrush according to claim 1 or 2.

4. The Shore A hardness of the soft resin is less than 30. The toothbrush according to any one of claims 1 to 3.

5. The most frequent size of the plurality of voids is 0.001 mm ２ Above, 0.3mm ２ Within the following range: The toothbrush according to any one of claims 1 to 4.

6. The number of 80% of all the voids in the foamed molded article is within ±0.3 mm of the most frequent value of the size of all the voids. ２ is within the range of 6. The toothbrush according to any one of claims 1 to 5.

7. In a cross section of the foamed molded body intersecting the center line, an average value of an occupation ratio of the plurality of voids is in the range of 2% or more and 60% or less.

7. The toothbrush according to any one of claims 1 to 6.

8. The density of the soft resin is 0.55 g / cm ３ Above, 0.8g / cm ３ Within the following range: The toothbrush according to any one of claims 1 to 7.

9. a cross section of the grip portion intersecting the center line is made up of the base member and the foam molded body, The ratio of the cross-sectional area of ​​the foamed molded body to the total area obtained by adding the cross-sectional area of ​​the base member and the cross-sectional area of ​​the foamed molded body is less than 50%.

9. The toothbrush of claim 1.

10. The thickness of the foamed molded body is 2 mm or more and 5 mm or less. The toothbrush of claim 7.

11. The gripping portion is a skin layer that forms the surface of the grip portion; a foam layer in which the filling portion and the plurality of void portions are covered by the skin layer, a thickness ratio of the skin layer to the foam layer in a cross section intersecting the center line is in the range of 1:1 or more and 1:10 or less; The toothbrush according to any one of claims 1 to 10.

12. The proportion of the foamed molded body formed in the entire length direction of the grip portion is in the range of 50% or more and 100% or less.

12. The toothbrush of any one of claims 1 to 11.

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