JP7367247B2 - absorbent articles - Google Patents

Description

The present invention relates to absorbent articles.

A sanitary napkin that absorbs excretory fluids such as menstrual blood is known as an example of an absorbent article. Such sanitary napkins include an absorbent core (absorbent core), and the absorbent core contains water-retentive fibers. Usually, softwood pulp fibers with long interfiber distances are used as water-retentive fibers. Patent Document 1 also discloses a water-retentive fiber that uses hardwood pulp fibers having a shorter interfiber distance than softwood pulp fibers.

Special Publication No. 2004-538024

In absorbent cores using softwood pulp fibers, since the distance between the fibers is long, there is a problem in that the excretory fluid once absorbed into the absorbent core is likely to return to the wearer's skin, causing rewetting.

Therefore, in the absorbent article of Patent Document 1, hardwood pulp fibers with a short interfiber distance are mixed with softwood pulp fibers, but they are formed using the same manufacturing method (air-laid method) as nonwoven fabrics, and have excellent absorbent properties. Adhesive is applied to the core. Such an adhesive may reduce the liquid absorbency and liquid diffusivity of the absorbent core.

The present invention was made in view of the above-mentioned problems, and its purpose is to improve the liquid dispersibility and liquid absorption of the absorbent core compared to the case where an adhesive such as Airlaid is used. It is to enhance one's sexuality.

The main invention for achieving the above purpose is:
It has a longitudinal direction, a width direction, and a thickness direction that are orthogonal to each other,
An absorbent article comprising a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent core provided between the top sheet and the back sheet,
The absorbent core has crushed fibers,
The pulverized fibers include hardwood water-retentive fibers made of hardwood and softwood water-retentive fibers made of softwood,
At least in the center of the absorbent core in the thickness direction, the crushed fibers are intertwined with each other to form the absorbent core without using an adhesive;
The hardwood water-retentive fiber has a total weight of the skin side portion of the absorbent core when divided into two equal parts in the thickness direction, which is greater than the total weight of the non-skin side portion of the absorbent core.
The softwood water-retentive fiber is characterized in that the total weight of the non-skin side portion of the absorbent core when divided into two equal parts in the thickness direction is greater than the total weight of the skin side portion of the absorbent core. It is an absorbent article.

Other features of the present invention will become apparent from the description of this specification and the accompanying drawings.

According to the present invention, it is possible to improve the liquid diffusibility and liquid absorbency of the absorbent core compared to the case where an adhesive such as Airlaid is used.

FIG. 2 is a schematic plan view of the napkin 1 viewed from the skin side in the thickness direction. 2 is a schematic cross-sectional view taken along the line AA in FIG. 1. FIG. FIG. 3 is a diagram for explaining a method of manufacturing the absorbent body 10. FIG. FIG. 2 is an explanatory diagram showing how the fibers of the second sheet 4 and the fibers of the absorbent body 10 are intertwined. FIG. 2 is a diagram illustrating the difference in average interfiber distance between hardwood pulp and softwood pulp. FIG. 1 is a diagram (Table 1) showing the average interfiber distance Dp of fibers. FIG. 2 is a diagram showing the fiber length distribution of hardwood pulp fibers and softwood pulp fibers. FIG. 2 is a schematic plan view of the napkin 1 viewed from the non-skin side in the thickness direction. FIG. 2 is a diagram showing the fiber width distribution of hardwood pulp and softwood pulp.

From the description of this specification and the attached drawings, at least the following matters will become clear.

A liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent material having a longitudinal direction, a width direction, and a thickness direction that are orthogonal to each other, and provided between the top sheet and the back sheet. An absorbent article comprising: a core; the absorbent core has pulverized fibers, and the pulverized fibers include hardwood water-retaining fibers made of hardwood and softwood water-retention fibers made of softwood. The absorbent core is formed without using an adhesive by intertwining the crushed fibers with each other at least in the center of the absorbent core in the thickness direction. An absorbent article characterized by:

According to such an absorbent article, the liquid diffusibility and liquid absorbency of the absorbent core can be improved compared to the case where an adhesive such as Airlaid is used.

In such an absorbent article, the hardwood water-retentive fibers are such that, when divided into two equal parts in the thickness direction, the total weight of the skin side portion of the absorbent core is the total weight of the non-skin side portion of the absorbent core. , the total weight of the non-skin side portion of the absorbent core when divided into two equal parts in the thickness direction is greater than the total weight of the skin side portion of the absorbent core. is desirable.

According to such an absorbent article, it is possible to provide an absorbent article that fits the body, improves the diffusivity of menstrual blood, etc., and suppresses deformation.

In such an absorbent article, the average inter-fiber distance of the crushed fibers on the skin side portion of the absorbent core is equal to the average inter-fiber distance of the crushed fibers on the non-skin side portion of the absorbent core. It is desirable that it be smaller than the distance.

According to such an absorbent article, it is possible to suppress the diffusion of menstrual blood, etc. in the non-skin side portion where the average interfiber distance is large, and it is possible to suppress the leakage of menstrual blood, etc.

In such an absorbent article, it is desirable that the absorbent article is provided with an elastic member that expands and contracts in the longitudinal direction.

According to such an absorbent article, as the elastic member expands and contracts, the skin-side surface, which has a large amount of soft hardwood pulp, moves in conjunction with the movement of the body, so that the fit can be further improved.

In such an absorbent article, the hardwood water-retentive fiber is such that the total weight of the non-skin side portion of the absorbent core when divided into two equal parts in the thickness direction is the total weight of the skin side portion of the absorbent core. , the total weight of the skin side portion of the absorbent core when divided into two equal parts in the thickness direction is greater than the total weight of the non-skin side portion of the absorbent core. is desirable.

According to such an absorbent article, it is possible to make maximum use of the absorbent body by increasing the liquid diffusion area on the non-skin side while suppressing a decrease in the liquid absorption rate on the skin side.

In such an absorbent article, the average inter-fiber distance of the crushed fibers on the skin side portion of the absorbent core is equal to the average inter-fiber distance of the crushed fibers on the non-skin side portion of the absorbent core. It is desirable that it be larger than the distance.

According to such an absorbent article, it is possible to suppress a decrease in the liquid absorption rate on the skin side portion, and it is possible to quickly move menstrual blood and the like to the non-skin side where liquid diffusion is good.

In such an absorbent article, the total weight of the hardwood water-retentive fibers is determined by comparing the front side and rear side when the longitudinal direction is divided into two, and when the width direction is divided into two. In both cases, the difference is 10 %, and the total weight of the softwood water-retentive fibers is the same as when comparing the front side and rear side when the longitudinal direction is divided into two equal parts, and the left side when the width direction is divided into two equal parts. In both cases, the difference is within 10% when comparing the skin side and the right side, and when comparing the skin side and non-skin side when dividing the thickness direction into two. It is desirable that there be.

According to such an absorbent article, it is possible to suppress the overall shape of the article while improving its fit to the body and the diffusivity of liquids such as menstrual blood.

In such an absorbent article, it is desirable that the total weight of the hardwood water-retaining fibers in the absorbent core is greater than the total weight of the softwood water-retaining fibers in the absorbent core.

According to such an absorbent article, since the amount of hardwood pulp is larger, the liquid diffusibility and rewetting ability can be improved compared to when the amount is less.

Such an absorbent article, wherein the total weight of the water-retaining softwood fibers in the absorbent core is greater than the total weight of the water-retaining hardwood fibers in the absorbent core.

According to such an absorbent article, since the amount of softwood pulp is larger, deformation can be suppressed compared to the case where the amount is smaller.

In such an absorbent article, the absorbent core is formed by laminating the pulverized fibers, and the absorbent core is such that the weight of the hardwood water-retaining fiber is greater than the weight of the softwood water-retaining fiber. and a softwood layer in which the weight of the softwood water-retaining fiber is heavier than the weight of the hardwood water-retaining fiber, and the hardwood layer is provided closer to the skin than the softwood layer, When viewed in the thickness direction, it is desirable that the outer circumferential edge of the hardwood layer is located inside the outer circumferential edge of the softwood layer.

According to such an absorbent article, while further suppressing deformation, it is possible to suppress a decrease in liquid diffusivity in the outer peripheral area of the absorbent core, and it is possible to suppress external leakage of excreted liquid.

In this absorbent article, the absorbent article has a skin-side sheet made of fibers, the skin-side sheet is provided adjacent to the skin side of the absorbent core, and the skin-side sheet is made of fibers, and the skin-side sheet is provided adjacent to the skin side of the absorbent core. At least some of the water-retaining fibers protrude from the skin-side surface of the absorbent core and extend into the skin-side sheet, and at least some of the hardwood water-retaining fibers protrude from the skin-side surface of the absorbent core and extend into the skin-side sheet. It is desirable that the portion is in contact with the fibers of the adjacent skin-side sheet.

According to such an absorbent article, menstrual blood and the like can easily enter the inside of the absorbent core through the hardwood water-retaining fibers, and the liquid absorption rate can be improved.

In such an absorbent article, the absorbent core has synthetic fibers, and the synthetic fibers have a larger area than the non-skin side portion of the absorbent core when divided into two equal parts in the thickness direction. It is preferable that the synthetic fibers are contained in large amounts in the skin side portion, and that the skin side portion of the absorbent core has a portion where the synthetic fibers are fused to each other.

According to such an absorbent article, since the synthetic fibers are connected and fused to each other, liquid diffusivity is improved on the skin side portion, and deformation is suppressed due to improved rigidity.

In such an absorbent article, the absorbent article includes a cover sheet, the cover sheet is joined to the absorbent core adjacent to the non-skin side of the absorbent core, and the cover sheet is joined to the absorbent core adjacent to the non-skin side of the absorbent core. The sheet is joined to the cover sheet adjacent to the non-skin side of the back sheet, and the non-skin side of the back sheet includes a slip stopper extending in a first direction and a slip stopper extending in a first direction. It is desirable that a plurality of fibers are provided at intervals in two directions, and that the minimum value of the spacing in the second direction of the anti-slip is greater than the average fiber length of the water-retaining fibers made of hardwood.

According to such an absorbent article, since the absorbent core is easily bent between the slippage stops, the absorbent article can easily move in conjunction with body movements, and the fit is improved.

In such an absorbent article, the average fiber width of the hardwood water-retaining fibers is 15 μm or less, and the number of the hardwood water-retaining fibers contained per unit area of the absorbent core is 300 fibers/mm or more, 2500 fibers/mm2 or more. It is desirable to have a superabsorbent polymer between the plurality of hardwood water-retaining fibers.

According to such an absorbent article, the excreted liquid contained in the hardwood pulp is easily drawn into the superabsorbent polymer between the hardwood pulps, so that liquid return can be reduced even when excreted liquid is absorbed multiple times. I can do it.

In such an absorbent article, it is preferable that the standard deviation of the fiber length of the water-retaining hardwood fiber is 0.27 or less, and the standard deviation of the fiber width of the water-retaining hardwood fiber is 7.55 or less.

According to such an absorbent article, it is easy to maintain a uniform fiber density in the absorbent body, so that the fibers are easily diffused concentrically with less deviation in the plane direction.

In such an absorbent article, the value obtained by adding the standard deviation of the fiber length of the hardwood water-retaining fiber to the average fiber length of the hardwood water-retaining fiber is twice the average fiber length of the hardwood water-retaining fiber. The value obtained by subtracting the standard deviation of the fiber length of the hardwood water-retaining fiber from the average fiber length of the hardwood water-retaining fiber is smaller than 1/2 of the average fiber length of the hardwood water-retaining fiber. It is also desirable that it is large.

According to such an absorbent article, it is easy to maintain a uniform fiber density in the absorbent body, so that the fibers are easily diffused concentrically with less deviation in the plane direction.

In such an absorbent article, the absorbent core includes a plurality of thermoplastic fibers, and has a compression section that integrally compresses the absorbent core in the thickness direction, and in the compression section, , it is desirable that the thermoplastic fibers are fused to each other.

According to such an absorbent article, even when the wearer moves his or her body significantly, it is possible to easily prevent the absorbent core 10 from losing its shape or from deteriorating its water absorbency.

===First embodiment===
<<Basic composition of sanitary napkins>>
A sanitary napkin 1 (hereinafter also simply referred to as napkin 1) will be described as an example of an absorbent article according to the present embodiment. In the following description, a sanitary napkin will be explained as an example of an absorbent article, but the absorbent article of this embodiment also includes a so-called vaginal discharge sheet (for example, a panty liner), a light incontinence pad, etc. It is not limited to sanitary napkins.

FIG. 1 is a schematic plan view of the napkin 1 viewed from the skin side in the thickness direction. FIG. 2 is a schematic cross-sectional view taken along the line AA in FIG. Furthermore, in the following description, each direction will be defined as shown in FIGS. 1 and 2. That is, the "longitudinal direction" along the product longitudinal direction of the napkin 1, the "width direction" perpendicular to the longitudinal direction along the product transverse direction of the napkin 1, and the "thickness" perpendicular to the longitudinal direction and the width direction, respectively. Define "direction". In the longitudinal direction, the direction facing the wearer's ventral side when using the napkin 1 is defined as the "front side", and the direction facing the wearer's back side is defined as the "rear side". In the thickness direction, the side that comes into contact with the wearer's skin when the napkin 1 is worn is defined as the "skin side (upper side)", and the opposite side is defined as the "non-skin side (lower side)".

The napkin 1 is a sheet-like member having a vertically elongated shape in a plan view, and includes a pair of side sheets 2, a top sheet 3, a second sheet 4, an absorbent body 10, a cover sheet 6, and a back sheet 5 in the thickness direction. The skin is laminated in order from the skin side to the non-skin side (see Fig. 2). Each of these members is bonded to an adjacent member in the thickness direction using an adhesive such as hot melt adhesive (HMA). Note that examples of the adhesive application pattern include an Ω pattern, a spiral pattern, and a stripe pattern.

The napkin 1 also includes a napkin main body 20 provided with the absorbent body 10, and a pair of wing parts 30 extending from the longitudinal center region of the napkin main body 20 to both outer sides in the width direction. The central region in the longitudinal direction where the wing portion 30 is provided is the region that comes into contact with the wearer's excretion opening (crotch region) when the napkin 1 is in use.

The top sheet 3 is a member that comes into contact with the wearer's skin when the napkin 1 is used, and allows liquid such as menstrual blood to permeate from the skin side to the non-skin side in the thickness direction and transfer to the absorbent body 10. Therefore, for the top sheet 3, an appropriate liquid-permeable flexible sheet such as an air-through nonwoven fabric is used.

The second sheet 4 (corresponding to the skin-side sheet) is a sheet made of liquid-permeable fibers, and can be exemplified by the same air-through nonwoven fabric as the top sheet 3. The second sheet 4 is provided on the skin side of the absorbent body 10 (adjacent to the skin side), and plays roles such as preventing the return of excreta such as menstrual blood, improving the diffusion of excreta, and improving cushioning properties. . However, the napkin 1 does not need to have the second sheet 4 (for example, the top sheet 3 may be used instead).

The cover sheet 6 may be a liquid-permeable sheet or a liquid-impermeable sheet, and examples include tissue paper and SMS (spunbond/meltblown/spunbond) nonwoven fabric. The cover sheet 6 is provided between the absorbent body 10 and the back sheet 5. That is, the napkin 1 includes a cover sheet 6, the cover sheet 6 is joined to the absorbent body 10 adjacent to the non-skin side of the absorbent body 10, and the back sheet 5 is connected to the 6 non-skin side of the cover sheet. It is joined to the cover sheet 6 adjacent to the side. However, the napkin 1 does not need to have the cover sheet 6 (for example, the back sheet 5 may be used instead).

The backsheet 5 prevents liquid that has passed through the topsheet 3 and been absorbed by the absorbent body 10 from seeping out to the clothing side (non-skin side) such as underwear when the napkin 1 is used. For the back sheet 5, an appropriate liquid-impermeable flexible sheet such as a polyethylene (PE) resin film is used. Note that the top sheet 3 and the back sheet 5 have a planar size larger than that of the absorbent core 10.

Further, the back sheet 5 is provided with a rubber thread 5a (corresponding to an elastic member) that expands and contracts in the longitudinal direction. By expanding and contracting the thread rubber 5a, the fit to the body can be further improved (details will be described later). Note that the elastic member is not limited to the rubber thread 5a, and for example, an elastic sheet may be provided.

The side sheet 2 may be a liquid-permeable sheet or a liquid-impermeable sheet, and examples include SMS nonwoven fabric and the same air-through nonwoven fabric as the top sheet 3.

As shown in FIGS. 1 and 2, the outer peripheral edges of the side sheet 2, top sheet 3, and back sheet 5 are joined by adhesive or welding, so that there is no absorption between these sheets. A body 10 is held. Further, the pair of side sheets 2 extend outward in the width direction from both sides of the top sheet 3 in the width direction, and form a pair of wing portions 30 together with the back sheet 5.

Appropriate adhesive (for example, hot melt adhesive) is applied to the non-skin side surface of the napkin main body 20 in the thickness direction (that is, the non-skin side surface of the back sheet 5) in a plurality of strip-shaped regions along the longitudinal direction. A main body adhesive part 21 (corresponding to a slip prevention member) is provided (see FIGS. 2 and 8). That is, on the non-skin side of the backsheet 5, a plurality of slip preventers extending in the longitudinal direction are provided at intervals in the width direction. When the napkin 1 is used, the main body adhesive part 21 is attached to the side of the skin of underwear, etc., thereby fixing the napkin 1 to the underwear, etc.

Similarly, a wing adhesive portion 31 is provided on the non-skin side surface of each wing portion 30 in the thickness direction (that is, the non-skin side surface of the backsheet 5) (see FIG. 2). When the napkin 1 is used, the wing portion 30 is bent toward the non-skin side, and the wing adhesive portion 31 is attached to the non-skin side of the underwear, etc., thereby fixing the napkin 1 to the underwear or the like.

The absorbent body 10 (corresponding to an absorbent core) is a vertically elongated member that is long in the longitudinal direction, and absorbs liquid (excrement) such as menstrual blood and retains it inside. Details of the absorber 10 will be described later. The second sheet 4, the absorbent core 10, and the cover sheet 6 have the same planar shape and are laminated in the thickness direction. Note that in this embodiment, these members are bonded to each other by hot melt adhesive (HMA), but they do not need to be bonded.

Further, the napkin 1 is provided with a plurality of compressed portions 40 (recessed portions). The compressed portion 40 is a region where the top sheet 3, second sheet 4, and absorbent core 10 are integrally compressed and is recessed from the skin side to the non-skin side in the thickness direction, and the density of the absorbent core 10 is This area has a higher density than the surrounding area. That is, the top sheet 3, the second sheet 4, and the absorbent core 10 have uneven portions on the skin side. This causes menstrual blood, etc. to flow from the convex portions to the concave portions on the skin side of the member, and the movement speed of menstrual blood, etc. can be improved.

<<About the absorber 10>>
The absorbent body 10 has water-retaining fibers that absorb liquid, and is formed into a vertically elongated shape when viewed from above. The water-retentive fibers according to this embodiment include softwood pulp fibers (hereinafter also referred to as softwood pulp, equivalent to softwood water-retentive fibers) and hardwood pulp fibers (hereinafter also referred to as hardwood pulp, equivalent to hardwood water-retentive fibers). Pulp is crushed and used. Then, the absorbent body 10 is formed by entangling the crushed fibers (water-retentive fibers) without using an adhesive.

Examples of the softwood pulp and hardwood pulp include, for example, the softwood pulp is a wood pulp obtained by crushing southern yellow pine, and the hardwood pulp is a wood pulp obtained by crushing eucalyptus.

Further, the absorbent body 10 may include liquid absorbent particles such as super absorbent polymer (so-called SAP).

As a method for manufacturing the absorbent body 10, a method of accumulating pulverized pulp, superabsorbent polymer, etc. is known.

FIG. 3 is a diagram for explaining a method of manufacturing the absorber 10. Here, a case will be described in which an absorbent body 10 containing water-retentive fibers (softwood pulp and hardwood pulp) and a superabsorbent polymer (SAP) is manufactured.

The rotating drum 70 is a hollow cylindrical drum, and a plurality of recesses 71 are formed at a predetermined pitch on the circumferential surface as molds for filling absorbent material. When the rotary drum 70 rotates and the recess 71 enters the material supply section 80 , the absorbent material supplied from the material supply section 80 is deposited (accumulated) in the recess 71 due to the suction of the suction section 72 .

The material supply section 80 with a hood 80a is formed to cover the upper part of the rotating drum 70, and the material supply section 80 is provided with a pulverized pulp (crushed fiber) obtained by pulverizing a pulp sheet with a pulverizer (not shown). is supplied to the recess 71 by air conveyance. At this time, the pulverized pulps are fed so as to be entangled with each other (after that, they are firmly intertwined by suction from the suction section 72). Further, the material supply section 80 includes a particle supply section 81 that supplies super absorbent polymer particles, and supplies the super absorbent polymer particles to the recess 71 . The water-retaining fibers and superabsorbent polymer particles are deposited in a mixed state in the recess 71, and the absorbent body 10 is formed in the recess 71.

Due to further rotation of the rotating drum 70, when the recess 71 containing the absorbent body 10 reaches the lowest part of the drum, the absorbent body 10 is removed from the recess 71, and the base material (cover sheet 6, etc.) conveyed by the conveyor is removed. It will be placed on top and passed on to the next process.

In addition, in subsequent steps, for example, hot melt adhesive (HMA) is applied to the skin-side surface of the absorbent body 10 in order to join the second sheet 4 and the absorbent body 10, and the second sheet 4 is bonded to the absorbent body 10. Being pushed. In this case, the absorbent body 10 will have an adhesive on the skin-side surface layer (the surface and the part where the adhesive penetrates into the inside of the absorbent body 10). 10 does not reach the center in the thickness direction.

The absorbent body described in Patent Document 1 uses pulp fibers, thermoplastic resin fibers, powder, and the like formed into a sheet shape (airlaid) using the same manufacturing method as nonwoven fabric (airlaid method). An adhesive is applied to the airlaid (that is, the adhesive is present throughout the absorbent body), and by using such adhesive, the rigidity of the absorbent body is higher than that of the absorbent body 10 manufactured by the manufacturing method shown in FIG. becomes high, and the liquid diffusivity and liquid absorption of excretory fluid decrease. In other words, when the absorbent body 10 is manufactured using the manufacturing method shown in FIG. An absorbent body 10 with high absorbency can be manufactured.

In other words, the adhesive in the absorbent body reduces the liquid diffusibility and liquid absorption of excreted liquid, so by forming the absorbent body 10 without using an adhesive, it is possible to reduce the amount of liquid when using an adhesive such as Airlaid. In comparison, liquid diffusibility and liquid absorbency can be improved at least at the center of the absorber 10 in the thickness direction. Further, compared to the absorbent body 10 containing only softwood pulp, the absorbent body 10 containing hardwood pulp is softer and has better liquid absorption properties, and compared to the absorbent body 10 containing only hardwood pulp, the absorbent body 10 containing softwood pulp is softer and has better liquid absorbency. is hard to twist and crumble. In other words, by including both hardwood pulp and softwood pulp in the absorbent body 10, the softwood pulp becomes a skeleton and the hardwood pulp is filled in between, resulting in a napkin that is soft and has good absorbency, and is hard to twist and crumble. 1 can be provided.

That is, the absorbent body 10 has pulverized fibers, and the pulverized fibers include a hardwood pulp made of hardwood and a softwood pulp made of coniferous trees, and the absorbent body 10 has at least a thickness in the thickness direction. At the center, the pulverized fibers intertwine with each other to form the absorbent body 10 without using an adhesive.

Further, by pressing the second sheet 4 and the absorbent body 10 in the thickness direction, the water-retentive fibers of the absorbent body 10 are entangled with the fibers of the second sheet 4. FIG. 4 is an explanatory diagram showing how the fibers of the second sheet 4 and the fibers of the absorbent body 10 are intertwined. As will be described later, since hardwood pulp is thin, the fibers tend to get stuck in between the fibers, causing entanglements, whereas softwood pulp is thick, so it is difficult to get between the fibers, making it difficult for such entanglements to occur (or not). In other words, the water-retentive fibers in FIG. 4 represent hardwood pulp.

Looking at FIG. 4, inside the second sheet 4, the hardwood water-retentive fibers 10f (indicated by black lines in the enlarged view) of the absorber 10 come into contact with the fibers 4f (indicated by white lines in the enlarged view) of the second sheet 4. are doing. That is, at least a portion of the hardwood water-retaining fibers 10f protrudes from the skin-side surface of the absorbent body 10 and extends to the inside of the second sheet 4. A part of it is in contact with the fibers of the second sheet 4.

This contact between the fibers makes it easier for the excreted liquid to travel from the fibers 4f of the second sheet 4 to the hardwood water-retentive fibers 10f and enter the absorbent body 10, thereby increasing the liquid absorption rate. In addition, since the water-retentive fibers become caught in the skin-side sheet, twisting of the absorbent body 10 can be suppressed, and deformation of the absorbent body 10 can be suppressed.

Further, the thickness of the absorber 10 is desirably 2 mm or more and 10 mm or less. If the thickness of the absorbent body 10 is less than 2 mm, it will be too thin and will twist, and if it exceeds 10 mm, it will be too hard and the wearer may feel uncomfortable.

Further, the fiber number density of hardwood pulp is thinner than that of softwood pulp, and the distance between fibers is shorter than that of softwood pulp, so the fiber number density of hardwood pulp is higher than that of softwood pulp. Note that the fiber number density corresponds to the average number of fibers per unit area, and is a value calculated by calculating the number of fibers included per unit area in the case of a close-packed structure using fiber thickness + average inter-fiber distance. . Looking at this trial value, the fiber number density of hardwood pulp is 1182.2 fibers/mm 2 , which is about six times the fiber number density of softwood pulp (200.3 fibers/mm 2 ). Therefore, when hardwood pulp is used, higher density can be achieved than when softwood pulp is used.

The fiber number density is preferably 300 fibers/mm 2 or more and less than 2,500 fibers/mm 2 .
If the fiber number density is less than 300 fibers/mm2, the absorbent body 10 will become thin and twist during use, resulting in a decrease in the area of the absorbent body and a tendency to leak. If the fiber number density is 2,500 fibers/mm2 or more, the absorbent body 10 will be finished too hard, increasing discomfort during use. When the fiber number density is 300 fibers/mm 2 or more and less than 2,500 fibers/mm 2 , the capillary effect can be enhanced, and the film can be made thinner and more flexible, thereby increasing absorbency.

Further, it is preferable that the fiber number density of hardwood pulp is higher than that of softwood pulp. In this way, the capillary effect can be increased while maintaining the softness of the absorbent body 10.

<<About the blend of hardwood pulp and softwood pulp>>
Next, the blending of hardwood pulp and softwood pulp in the absorbent body 10 will be explained. In this embodiment, on the skin side of the absorbent body 10, there is more hardwood pulp than softwood pulp, and on the non-skin side of the absorbent body 10, there is more softwood pulp than hardwood pulp (weight composition.The weight is, for example, Measured using an electronic balance HF-300 manufactured by Kensei Kogyo Co., Ltd.). That is, when hardwood pulp is divided into two equal parts in the thickness direction, the total weight of the skin side part of the absorbent body 10 is greater than the total weight of the non-skin side part of the absorbent body 10. The total weight of the non-skin side portion of the absorbent body 10 when divided into two equal parts is greater than the total weight of the skin side portion of the absorbent body 10.

Such adjustment of the composition in the thickness direction can be realized, for example, by manufacturing the absorber 10 as follows. First, prepare a hardwood pulp roll and a softwood pulp roll. Then, each pulp roll is pulverized with a saw mill or the like, and the mixing ratio of each pulp roll is adjusted between the pulverization and the pattern plate. Although it is preferable to use two saw mills, this is just one example, and each pulp is ground with one saw mill, and the hardwood pulp and softwood pulp are mutually mixed at the stage between grinding and lamination. All you have to do is change the ratio. Then, on the skin side of the absorber 10 (the bottom side of the recess 71), there is more hardwood pulp than the softwood pulp, and on the non-skin side of the absorber 10 (the opening side of the recess 71), the softwood pulp is more than the hardwood pulp. can do.

According to such a napkin 1, since the hardwood pulp is mostly on the skin side, the napkin 1 is easy to bend, soft and fits the body, and the diffusivity of liquids such as menstrual blood is improved, and the softwood pulp is on the non-skin side. Since it is abundant in the skin, a skeleton is formed on the non-skin side parts and deformation is suppressed. In other words, it is possible to provide a napkin 1 that fits the body, improves the diffusion of menstrual blood, etc., and suppresses deformation. Furthermore, since the absorbent core is provided with hardwood pulp, it has the effect of trapping menstrual blood and the like once drawn in, thereby increasing rewetability (reducing liquid return).

Further, in the present embodiment, the total weight of the hardwood pulp in the absorbent body 10 is greater than the total weight of the softwood pulp in the absorbent body 10. In this case, since there is more hardwood pulp than softwood pulp, the average interfiber distance (described later) can be made shorter than when there is less hardwood pulp. If the average distance between fibers is short, capillary phenomenon is likely to occur, so liquid diffusivity can be improved and liquid return (rewetting) can be reduced.

Furthermore, as described above, the backsheet 5 is provided with a rubber thread 5a (elastic member) that expands and contracts in the longitudinal direction. Then, as in this embodiment, the absorbent body 10 containing a large amount of hardwood pulp on the skin side is expanded and contracted by the thread rubber 5a, so that the absorbent body 10 is deformed to follow the curve of the body, so that it fits the body. (Softwood pulp is hard and hard to deform, hardwood pulp is soft and easy to deform, so if there is a lot of hardwood pulp on the skin side, it will be easier to follow the curves of the body).

<<Average interfiber distance evaluation>>
Next, the average interfiber distance of hardwood pulp and softwood pulp was evaluated by the following method.

Samples of 100% hardwood pulp, 100% softwood pulp, and 50% hardwood pulp + 50% softwood pulp were prepared as samples, and the 3D image linking function of a microscope (manufactured by KEYENCE VHX-2000, lens VH-Z20W aperture open) was used. Using this technology, we obtain an enlarged image that is in focus from the surface of the sample to a depth of 100 μm (for example, a 500x image for hardwood and a 100x image for softwood), and based on that enlarged image, we can identify the fibers that are in focus. Extracted the outside of. The surface formed there is defined as a fiber space. The diameter of the maximum inscribed circle of the fiber space was defined as the fiber space distance, and the average value of 100 fiber spaces was defined as the average interfiber distance (Dp).

Figure 5 is a diagram illustrating the difference in average interfiber distance between hardwood pulp and softwood pulp. The left diagram shows the average interfiber distance in hardwood pulp, and the right diagram shows the average interfiber distance in softwood pulp. . As shown in FIG. 5, the diameter of the maximum inscribed circle in each fiber space is the inter-fiber distance, so softwood pulp has a long average inter-fiber distance, and hardwood pulp has a short average inter-fiber distance.

FIG. 6 is a diagram showing the average interfiber distance Dp of fibers. As shown in FIG. 6, 100% hardwood pulp has a smaller average interfiber distance Dp than 100% softwood pulp. And 50% hardwood pulp + 50% softwood pulp is larger than 100% hardwood pulp and smaller than 100% softwood pulp. In other words, when the composition of hardwood pulp and softwood pulp changes, the average interfiber distance Dp of the fibers also changes.

In the absorbent body 10, there is more hardwood pulp than softwood pulp in the skin side part, and more softwood pulp than hardwood pulp in the non-skin side part. That is, the average inter-fiber distance Dp of the crushed fibers (water-retaining fibers) on the skin side of the absorbent body 10 is equal to the average inter-fiber distance Dp of the crushed fibers (water-retaining fibers) on the non-skin side of the absorbent body 10 smaller than Dp.

Then, since the average interfiber distance Dp is smaller on the skin side than on the non-skin side, menstrual blood, etc. can be diffused in the skin side, and the movement of menstrual blood, etc. to the non-skin side can be reduced due to the capillary effect. I can do it. That is, it is possible to suppress the diffusion of menstrual blood, etc. in the non-skin side portion where the average inter-fiber distance Dp is large, and the leakage of menstrual blood, etc. can be suppressed.

The average interfiber distance Dp can be evaluated, for example, by peeling off the used side sheet (second sheet 4) of the absorbent body 10 and examining the exposed surface of the absorbent body 10 using the above-mentioned microscope. Measure the average interfiber distance Dp in the non-skin side part, peel off the unused side sheet (cover sheet 6) of the absorbent body 10, and use the above-mentioned microscope to examine the exposed surface of the absorbent body 10. This can be done by measuring the average interfiber distance Dp.

<<About the average fiber length of water-retaining fibers>>
Next, the relationship between the average fiber length of the water-retentive fibers and the adhesive portion 21 for the main body portion will be explained. FIG. 7 is a diagram showing the fiber length distribution of hardwood pulp fibers and softwood pulp fibers. The horizontal axis shows fiber length (mm), and the vertical axis shows frequency (%). As shown in the figure, the average fiber length of the softwood pulp is 2.5 mm, and the fiber length distribution width is wide (including fibers of 3 mm or more. Standard deviation is 1.6). On the other hand, the average fiber length of hardwood pulp is 0.79 mm, and the fiber length distribution width is narrow (standard deviation is 0.27).

Note that the average fiber length means a length-weighted average fiber length as measured by the center fiber length (Cont). The length-weighted average fiber length is measured as the L(l) value by Kajaani FiberLab fiber properties (off-line) manufactured by Metso Automation. Note that this is also a method recommended by JIS P 8226-2 (Pulp-engineering automatic analysis method based on fiber length measurement method, based on non-polarized light method). Further, as described in the JIS evaluation method, the average fiber length and the fiber width described below are the results of measurements excluding fiber lumps.

FIG. 8 is a schematic plan view of the napkin 1 viewed from the non-skin side in the thickness direction. As shown in FIG. 8, on the non-skin side of the backsheet 5, a main body adhesive part 21 extending in the longitudinal direction (corresponding to the first direction) is arranged in the width direction (corresponding to the first direction) orthogonal to the longitudinal direction (first direction). A plurality of fibers are provided at intervals of 21g in the width direction (corresponding to two directions), and the minimum value of the widthwise (second direction) intervals of 21g is greater than the average fiber length of water-retentive fibers made of hardwood.

Therefore, when receiving a deforming force from the underwear, it is possible to reduce water-retentive fibers that straddle the installed and non-installed parts of the adhesive section 21 for the main body, and the absorbent body 10 can be moved between the adhesive section 21 for the main body. Since the napkin 1 can be bent easily, the napkin 1 can easily move with the body's movements and the fit can be improved.

In addition, although the main body adhesive parts 21 shown in FIG. 8 are provided in plurality extending in the longitudinal direction and spaced apart from each other in the width direction by 21 g, the present invention is not limited to this. They may be provided at intervals in the longitudinal direction.

<<About the average fiber width of water-retaining fibers>>
Next, the average fiber width of the water-retaining fibers will be explained. Note that the measurement is performed in the same manner as for the average fiber length described above, and is measured as FiberWidth.

FIG. 9 is a diagram showing the distribution of average fiber widths of hardwood pulp and softwood pulp. The horizontal axis shows the fiber width (μm), and the vertical axis shows the frequency (%). As shown in FIG. 9, the average fiber width of the softwood pulp is about 30 μmm (upper figure), and the fiber width distribution is wide (standard deviation is 11.9). On the other hand, the average fiber width of hardwood pulp is about 15 μm (see the figure below), and the fiber width distribution width is narrow (standard deviation is 7.55). In the napkin 1 of this embodiment, by using hardwood pulp for the absorber 10, the average fiber width of the water-retentive fibers is shorter than when only softwood pulp is used.

The average fiber width of the hardwood pulp is 15 μm or less, the fiber number density is 300 to 2,500 fibers/mm2 as described above, and the hardwood pulp has a superabsorbent polymer between the fibers. desirable. In this case, the hardwood pulp, which is characterized by its fibers being less likely to entangle and having a short fiber width, becomes densely packed, making it easier for the fibers to contain excrement fluid, and the excrement fluid contained in the hardwood pulp is distributed between the hardwood pulps. Since it is easily drawn into the superabsorbent polymer, liquid return can be reduced even when excreted liquid is absorbed multiple times.

Furthermore, looking at the distribution width, hardwood pulp has a narrower fiber length and fiber width distribution than softwood pulp. That is, the standard deviation of the fiber length of hardwood pulp is 0.27 or less, and the standard deviation of the fiber width of hardwood pulp is 7.55 or less. Furthermore, the value obtained by adding the standard deviation of the fiber length of hardwood pulp to the average fiber length of hardwood pulp (0.79 + 0.27 = 1.06) is twice the average fiber length of hardwood pulp (1.58). The value obtained by subtracting the standard deviation of the fiber length of hardwood pulp from the average fiber length of hardwood pulp (0.79 - 0.27 = 0.52) is 1/2 of the average fiber length of hardwood pulp. (0.395).

When the distribution width is narrow and the standard deviation is small in this way, it is easy to maintain a uniform fiber density in the absorbent body, so that it is easy to diffuse concentrically with less deviation in the plane direction.

In this way, when looking at the average fiber length and average fiber width of water-retentive fibers, compared to hardwood pulp, softwood pulp is thicker and longer, so the pulps are more likely to intertwine with each other, forming a solid skeleton. do. On the other hand, hardwood pulp is thin and short, so it is difficult for the pulps to intertwine with each other, but it is easy to get stuck between the softwood pulps, so by filling the skeleton made of softwood pulp with hardwood pulp, it becomes more resistant to twisting. It is possible to provide a napkin 1 with high liquid diffusion properties and high rewetting properties.

===Second embodiment===
Next, regarding the second embodiment, description of the same points as the first embodiment described above will be omitted, and differences from the first embodiment will be described.

The difference between the second embodiment and the first embodiment is the combination of hardwood pulp and softwood pulp in the absorbent body. In many cases, the non-skin side of the absorbent material contains more hardwood pulp than softwood pulp. In other words, when hardwood pulp is divided into two equal parts in the thickness direction, the total weight of the non-skin side of the absorbent body is greater than the total weight of the skin side part of the absorbent body, and with softwood pulp, it is divided into two equal parts in the thickness direction. The total weight of the skin side portion of the absorbent body when separated is greater than the total weight of the non-skin side portion of the absorbent body.

In this case, since softwood pulp is more abundant on the skin side, the strike-through property (liquid permeability, and if the strike-through property is high, the liquid absorption rate is less likely to decrease) will be improved, and the hardwood pulp will be more abundant on the non-skin side. Therefore, liquid drawing property and liquid diffusivity are improved. In other words, by increasing the liquid diffusion area on the non-skin side while suppressing a decrease in the liquid absorption rate on the skin side, the absorber can be utilized to the fullest. Furthermore, since the absorbent body is provided with hardwood pulp, it has the effect of trapping menstrual blood, etc. once drawn in, and can improve rewetting properties.

Regarding the average inter-fiber distance Dp, as mentioned above, since the average inter-fiber distance Dp of hardwood pulp and softwood pulp is different (see FIGS. 5 and 6), when the composition of hardwood pulp and softwood pulp changes, the fiber The average interfiber distance Dp also changes. In the absorbent body according to the second embodiment, there is more softwood pulp than hardwood pulp in the skin side part, and more hardwood pulp than softwood pulp in the non-skin side part. That is, the average inter-fiber distance Dp of crushed fibers (water-retaining fibers) on the skin side of the absorbent body is greater than the average inter-fiber distance Dp of crushed fibers (water-retaining fibers) on the non-skin side of the absorbent body. It's also big.

Then, since the skin side part has a larger average interfiber distance Dp than the non-skin side part, it is possible to suppress a decrease in the liquid absorption rate in the skin side part, and quickly transfer menstrual blood etc. It can be moved to the side.

Further, in the second embodiment, the total weight of the softwood pulp in the absorbent body is greater than the total weight of the hardwood pulp in the absorbent body. In this case, since there is more softwood pulp than hardwood pulp, more water-retentive fibers with a longer average fiber length are used than in the case where there is less softwood pulp, and fiber entanglement increases, so it is possible to suppress the absorbent body from losing its shape.

===Third embodiment===
Next, differences between the third embodiment and the above-described embodiments will be described.

The difference in the third embodiment is the combination of hardwood pulp and softwood pulp in the absorbent body, and in the third embodiment, the total weight of the hardwood pulp is equal to Comparing the side part, comparing the left side and right side when dividing the width direction into two, and comparing the skin side and non-skin side when dividing the thickness direction into two. In both cases, the difference is within 10%, and the total weight of the softwood pulp is: Comparing the left side and right side when dividing the width direction into two, and comparing the skin side and non-skin side when dividing the thickness direction into two. Also, the difference is within 10%.

Then, since the hardwood pulp and softwood pulp are uniformly mixed throughout the absorbent body, it is possible to prevent the entire absorbent from losing its shape while improving its fit to the body and the diffusibility of liquids such as menstrual blood.

===Fourth embodiment===
Next, differences between the fourth embodiment and the above-described embodiments will be described.

The difference in the fourth embodiment is that the absorbent body is formed of a layer of crushed fibers, and has a hardwood layer containing a lot of hardwood pulp, and a softwood layer containing a lot of softwood pulp on the non-skin side of the hardwood layer. The layer is provided inside the coniferous layer in the plane direction.

Such a structure of the hardwood layer and the softwood layer can be realized, for example, by preparing another set of rotary drums 70 shown in FIG. 3, etc., and providing them continuously on the production line. In the case of such a production line, the outer edge of the recess 71 on the upstream side is made larger than the outer edge of the recess 71 on the downstream side. Then, on the upstream side, an absorbent layer of softwood is formed and placed on the base material conveyed by a conveyor, and on the downstream side, an absorbent layer of hardwood is formed and placed on top of the absorbent layer of softwood. In this manner, the absorbent body according to the fourth embodiment can be manufactured. In addition, since two rotating drums are used, as mentioned above, both of the two rotating drums can crush hardwood pulp rolls and softwood pulp rolls, and by changing the ratio, a hardwood layer and a softwood layer can be manufactured. can.

In other words, the absorbent body according to the fourth embodiment is formed by laminating crushed fibers, and includes a hardwood layer in which the weight of the hardwood pulp is heavier than the weight of the softwood pulp, and a hardwood layer in which the weight of the softwood pulp is heavier than the weight of the hardwood pulp. It has a heavy coniferous layer, and the hardwood layer is provided closer to the skin than the coniferous layer, and when viewed in the thickness direction, the outer edge of the hardwood layer is located inside the outer edge of the coniferous layer. ing.

By placing the hardwood layer closer to the skin than the softwood layer, rewetability is improved near the vaginal opening or urinary opening, and the softwood layer is placed over a wider area than the hardwood layer when viewed in the thickness direction. By doing so, the outer circumferential area of the absorbent body becomes difficult to twist and loses its shape, and the decrease in liquid diffusivity in the outer circumferential area of the absorbent body can be suppressed. (leakage that occurs when water stagnates and accumulates in one place) can be suppressed.

===Other embodiments===
The above-described embodiments are provided to facilitate understanding of the present invention, and are not intended to be interpreted as limiting the present invention. It goes without saying that the present invention may be modified and improved without departing from its spirit, and that equivalents thereof are included in the present invention.

Further, in the above embodiment, hardwood pulp and softwood pulp of wood pulp are used as the water-retentive fibers of the absorbent body 10, but they are not limited to these, and examples include bagasse, kenaf, bamboo, hemp, and cotton. Non-wood pulp such as (for example, cotton linters); regenerated cellulose fibers such as rayon fibers; semi-synthetic fibers such as acetate fibers, etc. may also be used. Further, the absorbent body 10 may contain thermoplastic resin fibers (corresponding to synthetic fibers). For example, if thermoplastic resin fibers are included, it is desirable that the absorbent body contains many of them on the skin side, and that the thermoplastic resin fibers are fused to each other.

In other words, when the absorbent body has synthetic fibers, the synthetic fibers are contained more in the skin side part than in the non-skin side part when the absorbent body is divided into two equal parts in the thickness direction, and in the skin side part of the absorbent body, It is desirable that the synthetic fibers have a portion where they are fused together. Then, since the synthetic fibers are connected and fused to each other on the skin side, liquid diffusivity is improved on the skin side, and deformation is suppressed due to improved rigidity.

Furthermore, rayon fibers, which are water-retentive fibers, may be used as fibers added to or in place of the thermoplastic resin fibers. That is, the absorbent body may include at least one of rayon fibers and synthetic fibers. In this case, the rigidity of the absorbent core is improved by at least one of the rayon fiber and the synthetic fiber, so that the absorbent core is prevented from losing its shape, and a decrease in fit can be suppressed.

In addition, when thermoplastic resin fibers are included, it is desirable that the thermoplastic resin fibers are fused to each other in the pressing section that integrally compresses the absorbent core in the thickness direction. In other words, the absorbent core includes a plurality of thermoplastic fibers and has a compressed part that integrally compresses the absorbent core in the thickness direction, and in the compressed part, the thermoplastic fibers are fused to each other. It is desirable to be present.

That is, when forming the compressed portion, the thermoplastic fibers are fused to each other, thereby strengthening the integrity of the top sheet 3 and the absorbent core 10, and making it easier to stabilize the shape of the absorbent core 10. Thereby, even if the wearer makes a large body movement while wearing the napkin, for example, it is possible to easily prevent the absorbent body 10 from losing its shape or from deteriorating its water absorbency.

1 Sanitary napkins (absorbent articles)
2 Side sheet 3 Top sheet 4 Second sheet (skin side sheet)
4f Second sheet fiber 5 Back sheet 5a Thread rubber (elastic member)
6 Cover sheet 10 Absorbent body (absorbent core)
10f Hardwood water-retentive fiber 20 Napkin main body 21 Adhesive part for main body (slip prevention)
30 Wing part 31 Adhesive part for wing part 40 Pressed part 50L Hardwood pulp (hardwood water-retentive fiber)
50N softwood pulp (softwood water-retentive fiber)
70 rotating drum 71 recess 72 suction part,
80 material supply section 80a hood,
81 Particle supply section

Claims (13)

It has a longitudinal direction, a width direction, and a thickness direction that are orthogonal to each other,
An absorbent article comprising a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent core provided between the top sheet and the back sheet,
The absorbent core has crushed fibers,
The pulverized fibers include hardwood water-retentive fibers made of hardwood and softwood water-retentive fibers made of softwood,
At least in the center of the absorbent core in the thickness direction, the crushed fibers are intertwined with each other to form the absorbent core without using an adhesive;
The hardwood water-retentive fiber has a total weight of the skin side portion of the absorbent core when divided into two equal parts in the thickness direction, which is greater than the total weight of the non-skin side portion of the absorbent core.
The softwood water-retentive fiber is characterized in that the total weight of the non-skin side portion of the absorbent core when divided into two equal parts in the thickness direction is greater than the total weight of the skin side portion of the absorbent core. Absorbent articles. The absorbent article according to claim 1,
The average inter-fiber distance of the crushed fibers in the skin side portion of the absorbent core is smaller than the average inter-fiber distance of the crushed fibers in the non-skin side portion of the absorbent core. absorbent articles. The absorbent article according to claim 1 or 2,
An absorbent article characterized in that the absorbent article is provided with an elastic member that expands and contracts in the longitudinal direction. It has a longitudinal direction, a width direction, and a thickness direction that are orthogonal to each other,
An absorbent article comprising a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent core provided between the top sheet and the back sheet,
The absorbent core has crushed fibers,
The pulverized fibers include hardwood water-retentive fibers made of hardwood and softwood water-retentive fibers made of softwood,
At least in the center of the absorbent core in the thickness direction, the crushed fibers are intertwined with each other to form the absorbent core without using an adhesive;
The hardwood water-retentive fibers have a total weight of the non-skin side portion of the absorbent core when divided into two equal parts in the thickness direction, which is greater than the total weight of the skin side portion of the absorbent core.
The softwood water-retentive fiber is characterized in that the total weight of the skin side portion of the absorbent core when divided into two equal parts in the thickness direction is greater than the total weight of the non-skin side portion of the absorbent core. Absorbent articles. The absorbent article according to claim 4,
The average inter-fiber distance of the crushed fibers in the skin side portion of the absorbent core is larger than the average inter-fiber distance of the crushed fibers in the non-skin side portion of the absorbent core. absorbent articles. The absorbent article according to any one of claims 1 to 5,
An absorbent article characterized in that the total weight of the water-retaining hardwood fibers in the absorbent core is greater than the total weight of the water-retaining softwood fibers in the absorbent core. The absorbent article according to any one of claims 1 to 5,
An absorbent article characterized in that the total weight of the softwood water-retaining fibers in the absorbent core is greater than the total weight of the hardwood water-retaining fibers in the absorbent core. It has a longitudinal direction, a width direction, and a thickness direction that are orthogonal to each other,
An absorbent article comprising a liquid-permeable top sheet, a liquid-impermeable back sheet, and an absorbent core provided between the top sheet and the back sheet,
The absorbent core has crushed fibers,
The pulverized fibers include hardwood water-retentive fibers made of hardwood and softwood water-retentive fibers made of softwood,
At least in the center of the absorbent core in the thickness direction, the crushed fibers are intertwined with each other to form the absorbent core without using an adhesive;
The absorbent core is formed by laminating the pulverized fibers,
The absorbent core has a hardwood layer in which the hardwood water-retentive fibers are heavier than the softwood water-retentive fibers, and a softwood layer in which the softwood water-retentive fibers are heavier than the hardwood water-retentive fibers. and
The hardwood layer is provided closer to the skin than the softwood layer,
An absorbent article characterized in that, when viewed in the thickness direction, the outer peripheral edge of the hardwood layer is located inside the outer peripheral edge of the softwood layer. The absorbent article according to any one of claims 1 to 8,
The absorbent article has a skin-side sheet made of fibers,
The skin side sheet is provided adjacent to the skin side of the absorbent core,
At least a portion of the hardwood water-retentive fibers protrude from the skin-side surface of the absorbent core and extend into the skin-side sheet,
An absorbent article characterized in that, inside the skin-side sheet, at least a portion of the hardwood water-retaining fibers are in contact with fibers of the adjacent skin-side sheet. The absorbent article according to any one of claims 1 to 9 ,
The absorbent article includes a cover sheet,
The cover sheet is joined to the absorbent core adjacent to the non-skin side of the absorbent core,
The back sheet is joined to the cover sheet adjacent to the non-skin side of the cover sheet,
A plurality of slip preventers extending in a first direction are provided on the non-skin side of the backsheet at intervals in a second direction perpendicular to the first direction,
An absorbent article characterized in that the minimum value of the interval in the second direction of the slip stopper is larger than the average fiber length of the hardwood water-retaining fiber. The absorbent article according to any one of claims 1 to 10 ,
The average fiber width of the hardwood water-retentive fiber is 15 μm or less,
The number of the hardwood water-retaining fibers contained per unit area of the absorbent core is 300 pieces/mm ² or more and less than 2500 pieces/mm ² ,
An absorbent article comprising a superabsorbent polymer between a plurality of the hardwood water-retaining fibers. The absorbent article according to any one of claims 1 to 11 ,
The standard deviation of the fiber length of the hardwood water-retentive fiber is 0.27 or less,
An absorbent article characterized in that the standard deviation of the fiber width of the hardwood water-retaining fiber is 7.55 or less. The absorbent article according to claim 12 ,
The value obtained by adding the standard deviation of the fiber length of the hardwood water-retaining fiber to the average fiber length of the hardwood water-retaining fiber is smaller than twice the average fiber length of the hardwood water-retaining fiber,
The value obtained by subtracting the standard deviation of the fiber length of the hardwood water-retentive fiber from the average fiber length of the hardwood water-retentive fiber is greater than 1/2 of the average fiber length of the hardwood water-retentive fiber.
An absorbent article characterized by:

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