JP2024118140A - Absorbent articles - Google Patents

Abstract

To provide an absorbent article capable of leading excretory fluid in a deep of an absorbent core, effectively utilizing the absorbent core, and suppressing overflow and leakage of the excretory fluid.SOLUTION: An absorbent article (1) comprises absorbent cores (21-23) including liquid absorbent fibers (201) and a superabsorbent polymer. The absorbent cores (21-23) include, in order from a skin side: a skin-side layer (21), where volume occupied by the superabsorbent polymer is larger than volume occupied by the liquid absorbent fibers (201); an intermediate layer (22), where the volume occupied by the liquid-absorbent fibers (201) is greater than the volume occupied by the superabsorbent polymer; and a non-skin side layer (23), where the volume occupied by the superabsorbent polymer is larger than the volume occupied by the liquid absorbent fiber (201). The skin side layer (21) includes a low basis weight area (211), where the basis weight of the absorbent core (21-23) is lower than that of a periphery.SELECTED DRAWING: Figure 4

Description

The present invention relates to an absorbent article.

The absorbent article in Patent Document 1 discloses that the absorbent body includes an SAP layer made of SAP (super absorbent polymer), and an upper absorbent core and a lower absorbent core that are stacked so as to sandwich the SAP layer from above and below. The SAP layer has multiple SAP regions aligned in a planar direction, and the second sheet is folded so as to enter the gaps between the multiple SAP regions, preventing the multiple SAP regions that have absorbed bodily fluids and become jelly-like from sticking together and forming lumps.

JP 2019-141308 A

The upper absorbent core of the absorbent body of Patent Document 1 is a pulp layer made of pulp. Pulp has a faster liquid absorption rate than SAP. Therefore, if the pulp layer (upper absorbent core) is located on the skin contact side of the SAP layer as in the absorbent body of Patent Document 1, the pulp layer quickly absorbs the excreted liquid, making it difficult to draw the excreted liquid to the back side (non-skin contact side) of the absorbent body (absorbent core). This makes it difficult to effectively utilize the absorbent body, and reduces the absorbed water retention capacity of the absorbent body.
In addition, an SAP sheet having an SAP layer supported thereon may be used as an absorbent. However, in the case of an SAP sheet having no pulp layer, the excreted liquid cannot be temporarily stored in the pulp layer, which has a high absorption rate, and there is a risk that the excreted liquid will overflow and leak during excretion.

The present invention was made in consideration of the above problems, and aims to provide an absorbent article that can draw excrement to the back of the absorbent core, effectively utilize the absorbent core, and prevent excrement from leaking.

The main invention for achieving the above-mentioned object is an absorbent article having an absorbent core which, in an unfolded state, has a longitudinal direction, a width direction, and a thickness direction which are perpendicular to each other, and which contains liquid-absorbent fibers and a superabsorbent polymer, wherein the absorbent core has, from the skin side in the thickness direction, a skin-side layer in which the volume occupied by the superabsorbent polymer is larger than the volume occupied by the liquid-absorbent fibers, an intermediate layer in which the volume occupied by the liquid-absorbent fibers is larger than the volume occupied by the superabsorbent polymer, and a non-skin-side layer in which the volume occupied by the superabsorbent polymer is larger than the volume occupied by the liquid-absorbent fibers, and wherein the skin-side layer has a low basis weight region in which the basis weight of the absorbent core is lower than the surrounding area.
Other features of the present invention will become apparent from the following detailed description of the present invention and the accompanying drawings.

The present invention provides an absorbent article that draws excreted liquid deep into the absorbent core, effectively utilizing the absorbent core, and suppresses overflow and leakage of excreted liquid.

FIG. 1 is a schematic perspective view of a diaper 1. FIG. 2 is a plan view of the diaper 1 in an open and stretched state, as viewed from the skin side. FIG. 3 is a schematic cross-sectional view taken along the center line CL in FIG. 2 . FIG. 2 is a schematic cross-sectional view of the absorbent body 20 of the first embodiment. This is a plan view of absorbent cores 21 to 23 stacked together. 6A is a plan view of the skin side layer 21, and FIG. 6B is a plan view of the intermediate layer 22 and the non-skin side layer 23. As shown in FIG. 7A to 7C are plan views of modified examples of absorbent cores 21 to 23. FIG. 11 is a plan view of modified examples of absorbent cores 21 to 23. FIG. 9A and 9B are schematic cross-sectional views of modified examples of the absorbent body 20. FIG. 10A and 10B are schematic cross-sectional views of modified examples of the absorbent body 20. FIG. 10 is a schematic cross-sectional view of a modified example of the absorbent body 20. FIG. FIG. 11 is a schematic cross-sectional view of an absorbent body 20 according to a second embodiment.

At least the following matters will become apparent from the description of this specification and the accompanying drawings.
(Aspect 1)
An absorbent article having an absorbent core which, in an unfolded state, has a longitudinal direction, a width direction, and a thickness direction which are perpendicular to each other, and which contains liquid-absorbent fibers and a superabsorbent polymer, wherein the absorbent core has, from the skin side in the thickness direction, a skin-side layer in which the volume occupied by the superabsorbent polymer is larger than the volume occupied by the liquid-absorbent fibers, an intermediate layer in which the volume occupied by the liquid-absorbent fibers is larger than the volume occupied by the superabsorbent polymer, and a non-skin-side layer in which the volume occupied by the superabsorbent polymer is larger than the volume occupied by the liquid-absorbent fibers, and wherein the skin-side layer has a low basis weight region in which the basis weight of the absorbent core is lower than that of the surrounding area.

According to aspect 1, excreted liquid is likely to migrate quickly from the low basis weight region to the intermediate layer before it is absorbed by the superabsorbent polymer of the skin-side layer, and the excreted liquid can be quickly temporarily absorbed by the liquid absorbent fibers of the intermediate layer. This makes it possible to prevent the excreted liquid from overflowing or leaking. The excreted liquid absorbed between the liquid absorbent fibers of the intermediate layer then migrates by gravity to the non-skin-side layer, where it is absorbed and held by the superabsorbent polymer of the non-skin-side layer. This allows the excreted liquid to be drawn deep into the absorbent core, making effective use of the absorbent core.

(Aspect 2) The absorbent article according to aspect 1,
The absorbent article is characterized in that the skin side layer has a different type of superabsorbent polymer from the non-skin side layer, and the superabsorbent polymer in the skin side layer has a slower liquid absorption rate, as measured by a vortex method, than the superabsorbent polymer in the non-skin side layer.

According to aspect 2, excreted liquid is more likely to migrate to the intermediate layer before it is absorbed by the highly absorbent polymer in the skin-facing layer.

(Aspect 3)
An absorbent article having an absorbent core which, in an unfolded state, has a longitudinal direction, a width direction, and a thickness direction which are perpendicular to each other, and which contains liquid-absorbent fibers and a superabsorbent polymer, wherein the absorbent core has, from the skin side in the thickness direction, a skin-side layer in which the volume occupied by the superabsorbent polymer is larger than the volume occupied by the liquid-absorbent fibers, an intermediate layer in which the volume occupied by the liquid-absorbent fibers is larger than the volume occupied by the superabsorbent polymer, and a non-skin-side layer in which the volume occupied by the superabsorbent polymer is larger than the volume occupied by the liquid-absorbent fibers, wherein the skin-side layer has a different type of superabsorbent polymer from that of the non-skin-side layer, and the superabsorbent polymer in the skin-side layer has a slower liquid absorption rate, as measured by a vortex method, than the superabsorbent polymer in the non-skin-side layer.

According to aspect 3, excreted liquid is likely to migrate to the intermediate layer before it is absorbed by the superabsorbent polymer of the skin-side layer, and the liquid-absorbent fibers of the intermediate layer can quickly and temporarily absorb the excreted liquid. This makes it possible to prevent the excreted liquid from overflowing or leaking. The excreted liquid absorbed between the liquid-absorbent fibers of the intermediate layer then migrates by gravity to the non-skin-side layer, where it is absorbed and held by the superabsorbent polymer of the non-skin-side layer. This allows the excreted liquid to be drawn deep into the absorbent core, making effective use of the absorbent core.

(Aspect 4) The absorbent article according to aspect 1 or 2,
The absorbent article according to claim 1, wherein the low basis weight region is a slit penetrating the skin side layer in the thickness direction.

According to aspect 4, the discharged liquid falls into the slits, and the migration speed of the discharged liquid from the low basis weight area to the intermediate layer is increased.

(Aspect 5) An absorbent article according to any one of aspects 1 or 2,
At least one of the intermediate layer and the non-skin side layer has another low basis weight region in which the basis weight of the absorbent core is lower than that of the surrounding area.

According to aspect 5, excreted liquid is more likely to migrate from other low basis weight areas of the intermediate layer to the non-skin side layer, and from other low basis weight areas of the non-skin side layer to the deeper side of the non-skin side layer. This makes it easier to draw excreted liquid deep into the absorbent core.

(Aspect 6) The absorbent article according to aspect 5,
An absorbent article, characterized in that, in a plan view of the absorbent core, the low basis weight region has an area that overlaps with the other low basis weight region.

According to aspect 6, excreted liquid that flows through the low basis weight area of the skin-side layer is likely to flow to other low basis weight areas of the intermediate layer or non-skin-side layer, making it easier to draw excreted liquid deep into the absorbent core.

(Aspect 7) The absorbent article according to aspect 5 or 6,
The non-skin side layer has another low basis weight region, and the liquid absorbent fiber is arranged in the other low basis weight region of the non-skin side layer at a basis weight lower than the basis weight of the liquid absorbent fiber of the intermediate layer, characterized in that

According to aspect 7, the liquid absorbent fibers in the other low basis weight regions make it easier for the excreted liquid to spread in the planar direction, and the superabsorbent polymer is less likely to roll onto the other low basis weight regions, ensuring the functionality of the other low basis weight regions.

(Aspect 8) An absorbent article according to any one of aspects 5 or 6,
The non-skin side layer has the other low basis weight area, and the liquid absorbent fiber is not arranged in the other low basis weight area of the non-skin side layer.

According to aspect 8, excreted liquid is more likely to fall into other low basis weight areas, and the non-skin side layer absorbs the excreted liquid more quickly.

(Aspect 9) An absorbent article according to any one of aspects 5 to 8,
an absorbent article characterized in that the other low basis weight region is arranged inside both longitudinal ends of the intermediate layer or the non-skin side layer in which the other low basis weight region is arranged, and the low basis weight region has a longer longitudinal length than the other low basis weight region.

According to aspect 9, it is possible to prevent excreted liquid that has spread along other low basis weight regions from leaking outward in the longitudinal direction of the absorbent core. In addition, the excreted liquid can be transferred to the intermediate layer while being spread in the longitudinal direction along the low basis weight regions of the skin-side layer, so that the absorbent core can be effectively utilized in the longitudinal direction.

(Aspect 10) An absorbent article according to any one of aspects 5 to 9,
An absorbent article characterized in that the intermediate layer has another low basis weight region extending in the longitudinal direction, and at least a portion of the other low basis weight region of the intermediate layer is located in an area rearward of a center line that divides the absorbent article in an unfolded state in half in the longitudinal direction.

According to aspect 10, the other low basis weight regions become the folding starting points, and the absorbent core (particularly the intermediate layer) is easily deformed into a shape that is curved in the width direction along the buttocks of the wearer.

(Aspect 11) An absorbent article according to any one of aspects 1 to 10,
An absorbent article characterized in that, on a cut surface of the absorbent core after absorbing colored water, cut along the width direction, the number of superabsorbent polymers per unit area located in the skin side layer and the number of superabsorbent polymers per unit area located in the non-skin side layer are greater than the number of superabsorbent polymers per unit area located in the intermediate layer.

According to aspect 11, excreted liquid is more likely to migrate to the intermediate layer before it is absorbed by the skin-side layer. In the intermediate layer, the number of superabsorbent polymers per unit area is small, so the liquid-absorbent fibers are more likely to temporarily absorb excreted liquid, and overflow and leakage of excreted liquid can be suppressed. In addition, excreted liquid between the liquid-absorbent fibers in the intermediate layer is more likely to be absorbed and retained by the superabsorbent polymer in the non-skin-side layer, allowing the absorbent core to be effectively utilized to the innermost part.

(Aspect 12) An absorbent article according to any one of aspects 1 to 11,
The absorbent article is characterized in that the intermediate layer has an average thickness of 0.5 mm or more.

According to aspect 12, the amount of excreted liquid absorbed by the liquid absorbent fibers is increased compared to when the average thickness of the intermediate layer is less than 0.5 mm, and overflow of excreted liquid can be suppressed.

(Aspect 13) An absorbent article according to any one of aspects 1 to 12,
An absorbent article, comprising: an intermediate layer having an average thickness greater than the sum of an average thickness of the skin side layer and an average thickness of the non-skin side layer.

According to aspect 13, compared to when the average thickness of the intermediate layer is equal to or less than the sum of the average thicknesses of the skin-side layer and the non-skin-side layer, spaces are secured between the liquid-absorbent fibers of the intermediate layer, the amount of excreted liquid absorbed is increased, and overflow and leakage of excreted liquid can be suppressed.

(Aspect 14) An absorbent article according to any one of aspects 1 to 13,
At least one of the skin side layer and the non-skin side layer comprises the liquid-absorbent fiber.

According to aspect 14, the liquid-absorbent fibers increase the absorption rate of excreted liquid in the skin-side layer and non-skin-side layer.

(Aspect 15) An absorbent article according to any one of aspects 1 to 14,
At least one of the skin side layer and the non-skin side layer is laminated adjacent to the intermediate layer in the thickness direction without an adhesive.

According to aspect 15, it is possible to prevent the adhesive from interfering with the transfer of excreted fluid to the intermediate layer or the layer not facing the skin, and the absorption rate into the intermediate layer or the layer not facing the skin is increased.

(Aspect 16) An absorbent article according to any one of aspects 1 to 15,
At least one of the skin side layer and the non-skin side layer is laminated adjacent to the intermediate layer in the thickness direction without a nonwoven fabric therebetween.

According to aspect 16, it is possible to prevent the nonwoven fabric from impeding the transfer of excreted liquid to the intermediate layer or the layer not facing the skin, and the absorption rate into the intermediate layer or the layer not facing the skin is increased.

(Aspect 17) An absorbent article according to any one of aspects 1 to 16,
At least one of the skin side layer and the non-skin side layer is laminated adjacent to the intermediate layer in the thickness direction with a nonwoven fabric interposed therebetween.

According to aspect 17, excreted liquid is more likely to diffuse in the planar direction on the nonwoven fabric before migrating to the intermediate layer or non-skin-side layer. Therefore, excreted liquid that has diffused in the planar direction can migrate to the intermediate layer or non-skin-side layer, and the absorbent core can be effectively utilized.

(Aspect 18) The absorbent article according to aspect 17,
An absorbent article characterized in that it has a core wrap sheet on the skin side in the thickness direction of the skin side layer and on the non-skin side in the thickness direction of the non-skin side layer, and the basis weight of the nonwoven fabric is smaller than the basis weight of the core wrap sheet.

According to aspect 18, by reducing the basis weight (reducing the rigidity) of the nonwoven fabric disposed inside the absorbent core, the skin side layer and the non-skin side layer can be easily deformed together, and deformation of the absorbent core can be suppressed.

(Aspect 19) The absorbent article according to aspect 17 or 18,
An absorbent article characterized in that it has a core wrap sheet on the skin side in the thickness direction of the skin side layer and on the non-skin side in the thickness direction of the non-skin side layer, and the water absorption capacity of the nonwoven fabric is greater than the water absorption capacity of the core wrap sheet.

According to aspect 19, the nonwoven fabric disposed inside the absorbent core can also temporarily absorb excreted liquid, preventing the excreted liquid from overflowing or leaking.

(Aspect 20) An absorbent article according to any one of aspects 1 to 19,
The absorbent article is characterized in that the intermediate layer has a constricted portion at the center of the longitudinal direction, which is constricted on the inside in the width direction, and at least one of the skin side layer and the non-skin side layer extends outward in the width direction beyond the constricted portion.

According to aspect 20, the narrowed portion of the intermediate layer reduces the discomfort (feeling of stiffness) felt when worn, while the skin-side layer or non-skin-side layer extending from the narrowed portion can prevent leakage of excretory fluids.

(Aspect 21) An absorbent article according to any one of aspects 1 to 20,
the skin side layer has a different type of superabsorbent polymer than the non-skin side layer;
The absorbent article according to claim 1, wherein the superabsorbent polymer in the skin side layer has higher liquid permeability than the superabsorbent polymer in the non-skin side layer.

According to aspect 21, excreted liquid is likely to migrate to the intermediate layer before it is absorbed by the superabsorbent polymer of the skin-side layer, and the liquid absorbent fiber of the intermediate layer can quickly and temporarily absorb the excreted liquid. This makes it possible to prevent the excreted liquid from overflowing or leaking.

First Embodiment
The absorbent article according to the present invention will be described taking as an example a pants-type disposable diaper 1 for infants (hereinafter also referred to as "diaper 1"). However, the absorbent article according to the present invention also includes tape-type disposable diapers, shorts-type napkins, absorbent pads, sanitary napkins and other absorbent articles. Furthermore, the wearer of the absorbent article is not limited to infants, but may be an adult or a living organism such as an animal.

<Configuration of diaper 1>
Fig. 1 is a schematic perspective view of the diaper 1. Fig. 2 is a plan view of the diaper 1 in an unfolded and stretched state, as viewed from the skin side. Fig. 3 is a schematic cross-sectional view taken along the center line CL of Fig. 2. The "stretched state" of the diaper 1 refers to a state in which the diaper 1 as a whole is stretched without wrinkles, specifically, a state in which the dimensions of each component constituting the diaper 1 (e.g., the absorbent body 10 and waist circumference parts 30, 40, etc., described below) are stretched until they match or are close to the dimensions of the individual components. The "unfolded state" of the diaper 1 refers to a state in which the diaper 1 is opened and unfolded in a plane by separating a pair of side joint parts 2 provided on both sides of the diaper 1.

The diaper 1 has a vertical direction, a width direction, and a front-to-rear direction that are perpendicular to one another, and has a waist opening BH and a pair of leg openings LH. The upper side in the vertical direction corresponds to the waist opening BH side, and the lower side corresponds to the crotch side. The front side in the front-to-rear direction corresponds to the wearer's abdomen side, and the rear side corresponds to the wearer's back side. The width direction is a direction along the stretch direction of the rubber threads 33, 43 of the front waist section 30 and the rear waist section 40. The vertical direction is a direction along the orthogonal direction that is perpendicular to the stretch direction.

The diaper 1 is a so-called three-piece pants-type diaper having a liquid-absorbent main body 10 and a pair of waistbands 30, 40. Of the pair of waistbands, the one that covers the wearer's abdominal side is also referred to as the front waistband 30, and the one that covers the wearer's back side is also referred to as the rear waistband 40.

In the unfolded state of FIG. 2, the diaper 1 has a longitudinal direction, a width direction, and a thickness direction that are perpendicular to each other. The longitudinal direction is along the longitudinal direction of the absorbent body 10 and along the vertical direction of the pants-type diaper 1. The thickness direction is the direction in which the materials constituting the diaper 1 are layered, as shown in FIG. 3. In the thickness direction, the side that contacts the wearer's skin is the skin side, and the opposite side is the non-skin side. In addition, in the unfolded state, the front waist portion 30 and the rear waist portion 40 are arranged in parallel with each other at a distance in the longitudinal direction, and the absorbent body 10 is hung between them, with each end of the absorbent body 10 in the longitudinal direction being joined and fixed to the skin side of the nearest waist portion 30, 40, respectively, and the external shape is approximately H-shaped in plan view. Then, from this state, the absorbent body 10 is folded in half at the longitudinal center line CL. In this folded state, the front waistband portion 30 and the rear waistband portion 40 facing each other are joined and connected at both sides in the width direction to form a pair of side joints 2. The side joints 2 are formed by known joining methods such as welding or adhesion.

The absorbent body 10 has an absorbent body 20 (details will be described later), a liquid-permeable top sheet 12 arranged on the skin side of the absorbent body 20, and a back sheet 13 arranged on the non-skin side of the absorbent body 20. The back sheet 13 has a two-layer structure of a liquid-impermeable sheet 13a and a hydrophobic exterior sheet 13b arranged on the non-skin side. However, the absorbent body 10 may also include other sheet members. For example, a second sheet (not shown) may be provided between the top sheet 12 and the absorbent body 20 in the thickness direction.

A pair of leakage prevention walls 15 are provided along the longitudinal direction of the absorbent body 10 on both sides in the width direction of the absorbent body 10. In Fig. 3, a part of the exterior sheet 13b extends outward beyond both ends of the absorber 20 in the width direction and is folded toward the skin at multiple points to form the pair of leakage prevention walls 15. A leakage prevention wall elastic member 16 such as rubber thread is attached to the tip of the leakage prevention wall 15 in a stretched state along the longitudinal direction of the absorbent body 10, and the leakage prevention wall 15 is configured to be able to stand up toward the skin side.
Further, leg elastic members 17 such as rubber threads are attached to both widthwise sides of the absorbent body 10 in a stretched state along the longitudinal direction of the absorbent body 10 .

The front waist section 30 and the rear waist section 40 each have a skin-side sheet 31, 41, a non-skin-side sheet 32, 42, and multiple waist elastic members 33, 43 such as rubber threads. The multiple waist elastic members 33, 43 are arranged vertically between the skin-side sheet 31, 41 and the non-skin-side sheet 32, 42, and are attached in a stretched state in the width direction. The elasticity of the waist elastic members 33, 43 allows the front waist section 30 and the rear waist section 40 to fit the waist of the wearer. In addition, a cover sheet 34, 44 may be provided to cover the upper end of the absorbent body 10 from the skin side. The cover sheet 34, 44 can prevent the absorbent body 10 from opening.

As shown in FIG. 3, the planar shapes of the front waistline section 30 and the rear waistline section 40 in the unfolded and stretched state are different. The front waistline section 30 has a vertical length that is roughly the same as the side joint section 2, and is rectangular in shape that is long in the width direction. The rear waistline section 40 has a rectangular section that overlaps with the front waistline section 30, and a roughly trapezoidal section 40E that extends downward from that section. The extending section 40E can cover the wearer's buttocks.

The basic configuration of the diaper 1 has been described above, but the above configuration is merely an example and is not limited thereto. For example, the front waistline portion 30 and the rear waistline portion 40 may be formed from a single continuous member, or an exterior member for the crotch portion that connects the front waistline portion 30 and the rear waistline portion 40 may be provided. In addition, the elastic members such as the waistline elastic members 33, 43 may be sheet-like elastic members instead of rubber threads.

Regarding the absorbent body 20
Fig. 4 is a schematic cross-sectional view of the absorbent body 20 of the first embodiment. Fig. 5 is a plan view of the absorbent cores 21 to 23 superimposed on each other. Fig. 6A is a plan view of the skin side layer 21, and Fig. 6B is a plan view of the intermediate layer 22 and the non-skin side layer 23. Figs. 7A to 7C and 8 are plan views of modified examples of the absorbent cores 21 to 23. Figs. 9A, 9B, 10A, 10B, and 11 are schematic cross-sectional views of modified examples of the absorbent body 20.

As shown in FIG. 4, the absorbent body 20 has absorbent cores 21-23 between a core wrap sheet 24 on the skin side and a core wrap sheet 25 on the non-skin side. The absorbent cores 21-23 are members that absorb and retain excreted liquids such as urine, and include a liquid absorbent fiber 201 and a super absorbent polymer. The liquid absorbent fiber 201 and the super absorbent polymer (hereinafter also referred to as SAP) are not particularly limited as long as they can be used as an absorbent core of an absorbent article. For example, examples of the liquid absorbent fiber 201 include wood pulp fiber, non-wood pulp fiber such as bagasse, kenaf, bamboo, hemp, cotton, etc., regenerated cellulose fiber such as rayon fiber, and semi-synthetic fiber such as acetate fiber. Examples of SAP include starch-based, cellulose-based, and synthetic polymer-based polymer absorbents.
The core wrap sheets 24, 25 are liquid-permeable sheets, and examples of such sheets include tissue and nonwoven fabric.

The absorbent cores 21-23 have, in order from the skin side in the thickness direction, a skin side layer 21, an intermediate layer 22, and a non-skin side layer 23. The skin side layer 21 and the non-skin side layer 23 are layers in which the volume occupied by SAP is larger than the volume occupied by the liquid-absorbent fiber 201. The intermediate layer 22 is a layer in which the volume occupied by the liquid-absorbent fiber 201 is larger than the volume occupied by SAP. The skin side layer 21 has a low basis weight region 211 in which the basis weight of the absorbent core (i.e., the total basis weight of the liquid-absorbent fiber 201 and the SAP: g/m ² ) is lower than the surrounding area.

Therefore, when the wearer excretes into the diaper 1 and the absorbent body 20 receives the excreted liquid, the excreted liquid is quickly drawn from the low basis weight region 211 into the inside of the absorbent body 20 (intermediate layer 22). The liquid-absorbent fiber 201 has a faster liquid absorption speed than SAP. Since the volume occupancy rate of the liquid-absorbent fiber 201 is high in the intermediate layer 22, the excreted liquid that has migrated from the low basis weight region 211 to the intermediate layer 22 is quickly and temporarily absorbed by the intermediate layer 22.
Furthermore, the volume occupancy of SAP, which has a slow liquid absorption rate, is high in the skin side layer 21. Therefore, even in regions of the skin side layer 21 other than the low basis weight region 211, excreted liquid is likely to migrate to the intermediate layer 22 before being absorbed by the SAP of the skin side layer 21.
Thereafter, the excreted liquid absorbed between the fibers of the liquid-absorbent fibers 201 of the intermediate layer 22 gradually migrates by gravity to the non-skin side layer 23. The volume occupancy rate of SAP in the non-skin side layer 23 is high. Therefore, the excreted liquid is firmly absorbed and held by the SAP in the non-skin side layer 23.

If the volumetric occupancy rate of the liquid absorbent fibers in the skin-side layer were high, the excreted liquid would be quickly absorbed by the skin-side layer. This would make it difficult for the excreted liquid to penetrate deep into the absorbent core. In addition, the skin-side surface of the absorbent core would easily become damp.

In contrast, in the absorbent cores 21-23 of this embodiment, excreted liquid can be easily drawn into the non-skin side layer 23, and the absorbent cores 21-23 can be effectively utilized in the thickness direction. This increases the water absorption and retention capacity of the absorbent cores 21-23, and prevents leakage of excreted liquid even with repeated excretion. In addition, the dryness of the skin side of the absorbent cores 21-23 is ensured, improving the comfort of the diaper 1.

In addition, if excreted liquid from the intermediate layer 22 or non-skin side layer 23 attempts to return to the skin side, the SAP in the skin side layer 21 absorbs and retains the excreted liquid. This prevents the excreted liquid from rewetting. This also ensures that the skin side of the absorbent cores 21-23 remains dry.

Let us also assume that the absorbent core does not have an intermediate layer that quickly absorbs excreted liquid. For example, in the case of an absorbent core that is simply a stack of multiple SAP sheets, each of which has an SAP layer supported on a sheet, there is a risk that excreted liquid will overflow and leak during excretion. In contrast, the absorbent cores 21 to 23 of this embodiment have an intermediate layer 22 in which the volume occupancy rate of the liquid absorbent fiber 201 is high, and therefore it is possible to prevent excreted liquid from overflowing and leaking.

In addition, because the absorption speed of SAP is slow, in the skin-side layer 21, excreted liquid also diffuses in the planar direction while transferring to the intermediate layer 22. Therefore, the excreted liquid that has diffused in the planar direction can be transferred to the intermediate layer 22. However, this does not mean that the skin-side layer 21 does not absorb excreted liquid at all, and the SAP of the skin-side layer 21 also absorbs the excreted liquid appropriately, so that overflow and leakage of the excreted liquid can be suppressed. In addition, the excreted liquid that has migrated to the intermediate layer 22 also diffuses in the planar direction while transferring to the non-skin-side layer 23. Therefore, the excreted liquid that has diffused in the planar direction can be transferred to the intermediate layer 22. Therefore, the absorbent cores 21-23 can be effectively utilized in the planar direction as well.
As described above, according to the absorbent cores 21-23 of the first embodiment, excreted liquid can be drawn to the inner side (non-skin side layer 23) of the absorbent cores 21-23, thereby making effective use of the absorbent cores 21-23 and preventing excreted liquid from leaking.

The absorbent cores 21-23 are not necessarily all layered over the entire area thereof, but may have the three layers (21-23) layered at any location. Preferably, the three layers (21-23) are layered at the position where the wearer's urinary outlet contacts when the diaper 1 is worn and in the vicinity thereof. Similarly, the low basis weight region 211 of the skin-side layer 21 and the low basis weight regions 221, 231 of the intermediate layer 22 and the non-skin-side layer 23 described below are preferably provided at the position where the wearer's urinary outlet contacts and in the vicinity thereof. This allows the excreted liquid to be quickly drawn to the back of the absorbent cores 21-23 at the position where a large amount of excreted liquid is directly received during excretion.

For example, the skin side layer 21 illustrated in FIG. 5 has the same longitudinal length as the intermediate layer 22 and the non-skin side layer 23, but as in the modified examples shown in FIG. 7A and FIG. 7C, the longitudinal length of the skin side layer 21 may be short, and the skin side layer 21 may not be provided on the back side (rear side). Although not shown, the non-skin side layer 23 may not be provided on the back side. In this case, materials can be reduced, and the rigidity of the absorbent core on the back side is reduced and flexibility is increased. In addition, since the back side area is also away from the wearer's urinary excretion opening, the problem of excreted liquid overflowing and leaking is less likely to occur even if the skin side layer 21 and the non-skin side layer 23 are not present.

Moreover, the low basis weight region 211 of the skin side layer 21 is preferably a slit penetrating the skin side layer 21 in the thickness direction.
In this case, the excreted liquid falls into the low basis weight region 211, and the migration speed of the excreted liquid from the skin side layer 21 to the intermediate layer 22 increases. Therefore, overflow and leakage of the excreted liquid can be suppressed.

However, this is not limited to the above. Although not shown, liquid absorbent fibers 201 and SAP may be present in the low basis weight region 211 of the skin side layer 21. Also, the low basis weight region 211 may be a region of the skin side layer 21 that is recessed in the thickness direction.

The volumes occupied by the liquid-absorbent fibers 201 and the SAP in each layer of the absorbent cores 21 to 23 can be compared by a known method.
For example, in a diaper 1 that is in a natural and dry state with no external force acting thereon, the diaper 1 (absorbent body 20) is cut widthwise at an arbitrary position in the longitudinal direction of the absorbent body 20, specifically, at a position where the three layers 21 to 23 are laminated and away from the product folding position. Next, the cut surface is magnified (e.g., 30 to 100 times) and photographed using an optical microscope (e.g., Keyence Corporation's Digital Microscope VHX-7000, or an equivalent).
In the photographed cross-sectional image, the liquid absorbent fiber 201 and the SAP are identified. Then, in the cross-sectional image, it is confirmed that the skin side layer 21 in which the area occupied by the SAP is larger than the area occupied by the liquid absorbent fiber 201, the intermediate layer 22 in which the area occupied by the liquid absorbent fiber 201 is larger than the area occupied by the SAP, and the non-skin side layer 23 in which the area occupied by the SAP is larger than the area occupied by the liquid absorbent fiber 201 are laminated in this order from the skin side in the thickness direction. When the above is confirmed, they are regarded as the absorbent cores 21 to 23 of this embodiment. It is preferable to confirm that the three layers 21 to 23 are laminated in cross-sectional images of a plurality of positions in the longitudinal direction of the absorbent body 20.
Based on the captured cross-sectional image, it can also be confirmed that the skin side layer 21 has a low basis weight region 211, and that the low basis weight region 211 is a slit.

In addition, when the absorbent cores 21-23 that have absorbed the colored water are cut widthwise, it is preferable that the number of SAPs per unit area located in the skin-side layer 21 and the number of SAPs per unit area located in the non-skin-side layer 23 are greater than the number of SAPs per unit area located in the intermediate layer 22 on the cut surface.

The high number of SAPs per unit area of the skin-side layer 21 makes it easier for excreted liquid to migrate to the intermediate layer 22 before the skin-side layer 21 absorbs the liquid, and also makes it easier to ensure that the surface of the absorbent 20 is dry. In the intermediate layer 22, the number of SAPs per unit area is low, making it easier for the liquid-absorbent fibers 201 to temporarily absorb excreted liquid, and it is possible to prevent the excreted liquid from overflowing or leaking. In addition, the high number of SAPs per unit area of the non-skin-side layer 23 makes it easier for the excreted liquid between the liquid-absorbent fibers 201 of the intermediate layer 22 to be absorbed and retained by the SAPs of the non-skin-side layer 23. This allows the absorbent cores 21-23 to be effectively utilized all the way to the back.

The absorbent core in a state in which colored water has been absorbed is, for example, one in which the absorbent cores 21-23 are entirely immersed in blue-colored water for 10 minutes, and then the absorbent cores 21-23 are taken out and hung and left for 10 minutes, etc., to remove excess water. The diaper 1 may be immersed in the colored water either in its entirety, or in a state in which the absorbent main body 10 and the absorbent body 20 have been separated from the diaper 1 using toluene or the like.
Thereafter, the absorbent core is cut in the width direction at a portion where three layers (skin side layer 21, intermediate layer 22, non-skin side layer 23) are laminated. When the absorbent cores 21-23 have sufficiently absorbed the colored water, the SAP that has absorbed the colored water, swelled, and become colored becomes more visible. Therefore, by observing the cut surface of the absorbent core, the number of SAPs per unit area of each of the layers 21-23 can be compared. The cut surface may be observed visually or with an optical microscope. The color and concentration of the colored water are not particularly limited as long as they allow the SAP to be visually recognized.

The skin-side layer 21 may also have a different type of SAP than the non-skin-side layer 23. For example, it is desirable that the SAP in the skin-side layer 21 has a slower liquid absorption rate, as measured by the vortex method, than the SAP in the non-skin-side layer 23.

By doing so, excreted liquid is more likely to migrate to the intermediate layer 22 while diffusing in the planar direction before it is absorbed by the SAP in the skin-side layer 21. As a result, the absorbent cores 21-23 can be utilized more effectively. Absorption in the skin-side layer 21 is appropriately suppressed, ensuring dryness of the skin-side surfaces of the absorbent cores 21-23. It is also possible to prevent the SAP in the skin-side layer 21 from swelling and inhibiting liquid absorption.

The liquid absorption rate of SAP by the vortex method can be measured by a known method. For example, 50.0 ml (±0.5 ml) of saline solution with a concentration of 0.900% (±0.009%) and a temperature of 25°C (±2°C) is placed in a 100 ml beaker. The beaker is then placed on a magnetic stirrer and a stir bar is placed in the beaker. The stir bar is then rotated at 600 rpm (±30 rpm) to ensure that the saline solution in the beaker forms a stable vortex. A stopwatch is then started from the moment that 2.00 g (±0.02 g) of the SAP to be measured, taken from the diaper 1, is placed in the beaker, and the time until the vortex disappears and the liquid level becomes horizontal is measured. The longer this time, the slower the liquid absorption rate.

In addition, the SAP in the skin side layer 21 may have higher liquid permeability than the SAP in the non-skin side layer 23 .
This allows the excreted liquid to easily migrate to the intermediate layer 22 before it is absorbed by the SAP in the skin-side layer 21, thereby enabling effective use of the absorbent body 20. Furthermore, absorption in the skin-side layer 21 is appropriately suppressed, ensuring dryness of the skin-side surfaces of the absorbent cores 21-23. Furthermore, it is possible to prevent the SAP in the skin-side layer 21 from swelling and inhibiting liquid absorption.

In general, the lower the liquid permeability of an SAP, the higher the water retention capacity. Therefore, the lower the liquid permeability of the SAP in the non-skin side layer 23, the higher the water retention capacity. Therefore, most of the excreted liquid that has permeated deep into the absorbent cores 21-23 is retained by the SAP in the non-skin side layer 23, suppressing rewetting.

The liquid permeability of an SAP can be measured by a known method.
For example, the following method can be exemplified. First, 0.32 g of a measurement sample (SAP) was immersed in 150 ml of physiological saline for 30 minutes to prepare swollen gel particles. Then, the bottom of a vertically standing cylinder {diameter (inner diameter) 25.4 mm, length 40 cm, graduation lines at 60 ml and 40 ml from the bottom} was placed in a filtration cylindrical tube having a wire mesh (opening 106 μm, JIS Z8801-1:2006) and an openable/closable cock (inner diameter of the liquid passage part 5 mm) with the cock closed, and the prepared swollen gel particles were transferred together with physiological saline into the filtration cylindrical tube, and then a pressurizing shaft (weight 22 g, length 47 cm) with a circular wire mesh (opening 150 μm, diameter 25 mm) bonded perpendicularly to the wire mesh surface was placed on the swollen gel particles so that the wire mesh and the swollen gel particles were in contact with each other, and a weight (88.5 g) was placed on the pressurizing shaft and left to stand for 1 minute. Subsequently, the cock was opened, and the time (T1: seconds) required for the liquid level in the filtration cylindrical tube to drop from the 60 ml graduation line to the 40 ml graduation line was measured, and the gel permeation rate (ml/min) was calculated using the following formula.
Gel permeation rate of saline (ml/min) = 20 ml x 60/(T1-T2)
The temperature of the physiological saline used and the measurement atmosphere was 25° C.±2° C., and T2 was the time measured in the same manner as above in the absence of a measurement sample. The faster the gel permeation speed, the higher the liquid permeability.

However, without being limited to the above, the type of SAP contained in each of the skin side layer 21 and the non-skin side layer 23 may be the same. In that case, the manufacturing effort and cost can be reduced. Furthermore, when the types of SAP contained in the skin side layer 21 and the non-skin side layer 23 are different, both of the liquid absorption rate and the liquid permeability measured by the vortex method may be different, or only one of them may be different.

The skin side layer 21 illustrated in FIG. 6A has three longitudinally long rectangular divided regions 21a-21c. The three divided regions 21a-21c are arranged side by side with a gap in the width direction. The two regions between the three divided regions 21a-21c become low basis weight regions 211 (slits) of the skin side layer 21. The two low basis weight regions 211 are arranged symmetrically in the width direction across the center line CL2 of the skin side layer 21 in the width direction.

The intermediate layer 22 and non-skin side layer 23 illustrated in FIG. 6B are integrally formed and have the same planar shape. The intermediate layer 22 and non-skin side layer 23 have narrowed portions 222, 232 narrowed inward in the width direction at the center in the longitudinal direction. Note that the central region when the intermediate layer 22 and non-skin side layer 23 are divided into thirds at their maximum longitudinal length is defined as the longitudinal center, and at least a part of the narrowed portions 222, 232 may be located there.

When the intermediate layer 22 and the non-skin side layer 23 have the constricted portions 222, 232 as described above, it is preferable that the skin side layer 21 extends outward in the width direction beyond the constricted portions 222, 232 of the intermediate layer 22 and the non-skin side layer 23, as shown in Figure 5.
This allows the SAP to be disposed on the outside of the narrow constricted portions 222, 232 of the intermediate layer 22 and the non-skin side layer 23, while reducing the discomfort felt by the wearer when opening and closing their legs due to the constricted portions 222, 232. This makes it possible to suppress lateral leakage of excreted liquid.

Also, as in the modified example shown in Figures 10A and 10B, the absorbent body 20 may be one in which the skin side layer 21 and the intermediate layer 22 are integrally formed, and the non-skin side layer 23 is laminated thereon. In this case, although not shown, if the skin side layer 21 and the intermediate layer 22 have a shape with a constricted portion, the non-skin side layer 23 may be configured to extend outward in the width direction beyond the constricted portion.

Similarly to the skin side layer 21, at least one of the intermediate layer 22 and the non-skin side layer 23 preferably has a low basis weight region (corresponding to another low basis weight region) in which the basis weight of the absorbent core (i.e., the total basis weight of the liquid-absorbent fiber 201 and the SAP: g/ ^m2 ) is lower than that of the surrounding area. In the absorbent body 20 of this embodiment, as shown in Figure 4, both the intermediate layer 22 and the non-skin side layer 23 have low basis weight regions 221, 231.

By doing so, excreted liquid can easily migrate from the low basis weight region 221 of the intermediate layer 22 to the non-skin side layer 23, or from the low basis weight region 231 of the non-skin side layer 23 to the deeper side of the non-skin side layer 23. This allows excreted liquid to be quickly drawn deep into the absorbent cores 21-23, making effective use of the absorbent cores 21-23.

As shown in FIG. 5, preferably, in a plan view of the absorbent cores 21-23, the low basis weight region 211 of the skin side layer 21 has a portion that overlaps with the low basis weight regions 221, 231 of the intermediate layer 22 and the non-skin side layer 23. In this embodiment, the intermediate layer 22 and the non-skin side layer 23 each have two low basis weight regions 221, 231. The two low basis weight regions 221, 231 of the intermediate layer 22 and the non-skin side layer 23 each overlap with the two low basis weight regions 211 of the skin side layer 21.

By doing so, excreted liquid that has flowed into the low basis weight region 211 of the skin side layer 21 is more likely to flow directly into the low basis weight regions 221, 231 of the intermediate layer 22 and the non-skin side layer 23. This allows excreted liquid to be drawn more quickly into the deepest parts of the absorbent cores 21-23, enabling the absorbent cores 21-23 to be used more effectively.

The low-basis-weight regions 221, 231 of the intermediate layer 22 and the non-skin-side layer 23 may be slits that penetrate in the thickness direction, or the low-basis-weight regions 221, 231 may contain liquid-absorbent fibers 201 or SAP, or the low-basis-weight regions 221, 231 may be partially recessed in thickness.

In the low basis weight region 231 of the non-skin side layer 23 illustrated in FIG. 4 , the liquid absorbent fibers 201 are arranged with a basis weight lower than that of the liquid absorbent fibers 201 in the intermediate layer 22 .
In this way, the thin presence of the liquid absorbent fiber 201 in the low basis weight region 231 of the non-skin side layer 23 makes it difficult for the surrounding SAP to roll in the low basis weight region 231, ensuring the functionality of the low basis weight region 231 and suppressing deformation of the absorbent cores 21 to 23. In addition, excreted liquid is unlikely to stagnate in the low basis weight region 231 of the bottom layer, and is easily diffused in the planar direction along the low basis weight region 231.

9A and 10A, the liquid-absorbent fibers 201 may not be disposed in the low basis weight region 231 of the non-skin side layer 23. Preferably, the low basis weight region 231 of the non-skin side layer 23 is a slit.
By doing so, the excreted liquid is not temporarily absorbed by the liquid-absorbent fibers 201 in the low basis weight region 231 of the non-skin side layer 23 , so that the excreted liquid can be quickly drawn to the deeper side of the non-skin side layer 23 .

10A and 10B, in the case where the skin side layer 21 and the intermediate layer 22 are integrally formed, the liquid absorbent fiber 201 may be provided in the low basis weight region 221 of the intermediate layer 22 as shown in Fig. 10A. In this case, the excreted liquid can be diffused by the low basis weight region 221 and transferred to the non-skin side layer 23.
10B , a thin layer of liquid-absorbent fibers 221 may be provided in the low basis weight region 211 of the skin side layer 21 with a basis weight lower than that of the intermediate layer 21. In this case, excreted liquid can be diffused and transferred to the intermediate layer 22, and SAP is less likely to roll in the low basis weight region 211 of the skin side layer 21, ensuring the function of the low basis weight region 211.

As shown in FIG. 6B, the low basis weight regions 221, 231 of the intermediate layer 22 and non-skin side layer 23 are preferably arranged inside both longitudinal ends of the intermediate layer 22 or non-skin side layer 23 where the low basis weight regions 221, 231 are arranged. Furthermore, as shown in FIG. 5, it is preferable that the low basis weight region 211 of the skin side layer 21 has a longer longitudinal length than the low basis weight regions 221, 231 of the intermediate layer 22 and non-skin side layer 23.

This makes it possible to prevent excreted liquid that has spread along the low basis weight regions 221, 231 of the intermediate layer 22 and non-skin side layer 23 from leaking outward in the longitudinal direction of the absorbent cores 21-23. On the other hand, even if the low basis weight region 211 of the skin side layer 21 has a long longitudinal length, or even if it reaches both longitudinal ends of the skin side layer 21, the intermediate layer 22 and non-skin side layer 23 can receive the excreted liquid that has spread in the longitudinal direction. This makes it possible to prevent excreted liquid from leaking outward in the longitudinal direction of the absorbent cores 21-23. In addition, because the low basis weight region 211 of the skin side layer 21 is long in the longitudinal direction, excreted liquid can be transferred to the intermediate layer 22 while being diffused in the longitudinal direction. This makes it possible to effectively utilize the absorbent cores 21-23 in the longitudinal direction.

However, without being limited to the above, for example, the intermediate layer 22 and the non-skin side layer 23 may not have low basis weight regions 221, 231, and the low basis weight regions 221, 231 of the intermediate layer 22 and the non-skin side layer 23 may not overlap with the low basis weight region 211 of the skin side layer 21. Furthermore, the shape, size, number, arrangement position, etc. of the low basis weight regions 211 to 231 of each layer are not particularly limited.

For example, as shown in the modified examples of Figures 7B and 7C, each layer may have one low basis weight region 211-231, which may be located on the center line CL2 in the width direction of the absorbent cores 21-23. Also, as shown in the modified example of Figure 8, the low basis weight regions 21-23 of each layer 21-23 may completely overlap, or multiple low basis weight regions 221-231 may be arranged at intervals in the longitudinal direction.

Also, as shown in the modified example of FIG. 8, at least a portion of the low basis weight region 221 extending in the longitudinal direction of the intermediate layer 22 may be provided in an area on the rear side of the center line CL (product center line) that bisects the diaper 1 in the unfolded state in the longitudinal direction.

In this case, the low basis weight regions 221, 231 extending in the longitudinal direction become the folding starting points. Therefore, the intermediate layer 22, which has a high volume occupancy rate of the liquid absorbent fiber 201 and is relatively rigid, is likely to bend in the width direction along the buttocks of the wearer. This improves the fit and can disperse wrinkles that occur when the wearer closes their legs.
Furthermore, when the absorbent core is worn by a young baby who spends most of his or her time in a sleeping position, body pressure is likely to be applied to the back region of the absorbent cores 21 to 23. Therefore, by providing the low basis weight region 221 of the intermediate layer 22 and the low basis weight regions 211, 231 of the other two layers in the back region, excreted liquid can be quickly drawn to the back side of the absorbent core 21, and leakage on the back side can be suppressed.

The intermediate layer 22 preferably has a basis weight of 50 g/cm ² or more and 200 g/cm ² or less.
By doing so, compared to when the intermediate layer 22 has a basis weight of less than 50 g/ ^cm2 , for example, compared to when the intermediate layer 22 is a nonwoven fabric (sheet member) formed of pulp fibers or the like, the excreted liquid can be absorbed more easily between the fibers of the liquid absorbent fibers 201 of the intermediate layer 22. Therefore, the excreted liquid can be quickly and temporarily absorbed by the intermediate layer 22, and overflow and leakage of the excreted liquid during excretion can be suppressed.
On the other hand, the thickness of the intermediate layer 22 can be appropriately suppressed compared to when the basis weight of the intermediate layer 22 is greater than 200 g/ ^cm2 . This reduces the discomfort (feeling of stiffness) felt when worn, and also suppresses delamination of the intermediate layer 22 alone due to a weakening of the sense of unity between the skin side layer 21 and the non-skin side layer 23. The basis weight of the intermediate layer 22 can be measured by a known method.

The average thickness t2 of the intermediate layer 22 is preferably 0.5 mm or more.
By doing so, compared to when the average thickness of the intermediate layer 22 is less than 0.5 mm, for example, compared to when the intermediate layer 22 is a nonwoven fabric (sheet member) formed of pulp fibers or the like, the excreted liquid can be absorbed between the fibers of the liquid-absorbent fibers 201 of the intermediate layer 22. Therefore, the excreted liquid can be quickly and temporarily absorbed by the intermediate layer 22, and overflow and leakage of the excreted liquid during excretion can be suppressed.
However, if the intermediate layer 22 is too thick, as described above, a stiff feeling occurs, and therefore, it is preferable that the average thickness of the intermediate layer 22 is set to 2.5 mm or less.

The average thickness t2 of the intermediate layer 22 is preferably greater than the sum of the average thickness t1 of the skin side layer 21 and the average thickness t3 of the non-skin side layer 23 (t2>t1+t3).
By doing so, the thickness of the intermediate layer 22 is ensured and excreted liquid can be absorbed between the fibers of the liquid-absorbent fibers 201 of the intermediate layer 22, compared to when the average thickness t2 of the intermediate layer 22 is equal to or less than the sum t1 + t3 of the average thicknesses of the skin side layer 21 and the non-skin side layer 23. Therefore, the excreted liquid can be quickly and temporarily absorbed by the intermediate layer 22, and overflow and leakage of the excreted liquid during excretion can be suppressed. On the other hand, by suppressing the thicknesses t1 and t3 of the skin side layer 21 and the non-skin side layer 23, it is possible to prevent SAP from being distributed more than necessary in the absorbent cores 11-13.

The thickness of each layer 21 to 23 can be measured by a known method. For example, in a natural and dry state where no external force is acting, the diaper 1 (absorbent body 20) is cut in the width direction at an arbitrary position in the longitudinal direction of the absorbent body 20, specifically, at a position where the three layers 21 to 23 are laminated and away from the product folding position. Next, the cut surface is enlarged (e.g., 30 to 100 times) and photographed using an optical microscope (e.g., Keyence Digital Microscope VHX-7000 or equivalent). At this time, the enlarged photograph is taken with the focus on the liquid absorbent fiber 201.
In the photographed cross-sectional image, the layer in which the liquid-absorbent fiber 201 is visible is determined as the intermediate layer 22, and the portions of the absorbent core closer to the skin or closer to the skin than that are determined as the skin-side layer 21 and the non-skin-side layer 23, respectively. Furthermore, measurement positions at multiple locations (e.g., three locations) in the width direction are determined in the cross-sectional image, and the thickness of each of the layers 21 to 23 at each measurement position is obtained. Preferably, cross-sectional images of multiple locations in the longitudinal direction of the absorbent body 20 are photographed to obtain the thickness of each of the layers 21 to 23. The average value of the obtained thicknesses is calculated for each of the layers 21 to 23, and is set as the average thickness t1 of the skin-side layer 21, the average thickness t2 of the intermediate layer 22, and the average thickness t3 of the non-skin-side layer 23.

Moreover, it is preferable that the density of the intermediate layer 22 is lower than the density of the skin side layer 21 and lower than the density of the non-skin side layer 23 .
This ensures more space between the fibers of the liquid-absorbent fibers 201 in the intermediate layer 22 than when the density of the intermediate layer 22 is equal to or greater than the density of the skin side layer 21 and the non-skin side layer 23. Therefore, excreted liquid can be temporarily absorbed in the spaces between the fibers, and overflow and leakage of excreted liquid during excretion can be suppressed. The density of each of the layers 21 to 23 can be measured by a known method.

4 is formed integrally with the intermediate layer 22. Therefore, the non-skin side layer 23 may contain liquid absorbent fibers 201 in addition to SAP.
The liquid absorbent fibers 201 in the non-skin side layer 23 increase the absorption rate of excreted liquid from the intermediate layer 22 to the non-skin side layer 23. This allows the excreted liquid to be quickly drawn to the inner side of the absorbent cores 21-23, and prevents the excreted liquid from overflowing or leaking.

In addition, as shown in Figures 10A and 10B, when the skin-side layer 21 and the intermediate layer 22 are integrally formed, the skin-side layer 21 may have not only SAP but also liquid-absorbent fibers 201. In this case, too, the liquid-absorbent fibers 201 of the skin-side layer 21 quickly absorb excreted liquid, so that overflow and leakage of excreted liquid can be further suppressed.

The intermediate layer 22 and non-skin side layer 23 illustrated in FIG. 4 are integrally formed, so that the volume occupancy of the liquid absorbent fiber 201 decreases and the volume occupancy of the SAP increases from the intermediate layer 22 toward the non-skin side layer 23. Conversely, the volume occupancy of the liquid absorbent fiber 201 increases and the volume occupancy of the SAP decreases in the skin side layer 21 and intermediate layer 22 illustrated in FIG. 10A and FIG. 10B from the skin side layer 21 toward the intermediate layer 22. Such an absorbent core can be manufactured, for example, by adjusting the order, amount, timing, etc. of the SAP and liquid absorbent fiber 201 that are fed toward a mold (recess) that corresponds to the shape of the absorbent core and is provided on the outer circumferential surface of a rotating drum.

The non-skin side layer 23 illustrated in FIG. 4 is formed integrally with the intermediate layer 22, and is laminated adjacent to the intermediate layer 22 in the thickness direction without the adhesive HMA therebetween.
In this case, it is possible to prevent the adhesive HMA from interfering with the transfer of excreted liquid from the intermediate layer 22 to the non-skin side layer 23. Therefore, the excreted liquid can be quickly drawn to the deeper side of the absorbent cores 21 to 23. Furthermore, since the adhesive HMA is not provided, the rigidity of the absorbent body 20 is reduced, and the feeling of stiffness can be reduced.

The non-skin side layer 23 illustrated in FIG. 4 is formed integrally with the intermediate layer 22, and is laminated adjacent to the intermediate layer 22 in the thickness direction without any nonwoven fabric therebetween.
In this case, it is possible to prevent the nonwoven fabric from impeding the transfer of excreted liquid from the intermediate layer 22 to the non-skin side layer 23. Therefore, the excreted liquid can be quickly drawn to the deeper side of the absorbent cores 21 to 23. Furthermore, since no nonwoven fabric is provided, the rigidity of the absorbent body 20 is reduced, and the feeling of stiffness can be reduced.

As shown in Figures 10A and 10B, when the skin-side layer 21 and the intermediate layer 22 are integrally formed, the skin-side layer 21 can be adjacent to the intermediate layer 22 in the thickness direction without the adhesive HMA or nonwoven fabric. This prevents the adhesive HMA or nonwoven fabric from impeding the transfer of excreted fluid from the skin-side layer 21 to the intermediate layer 22.

The skin-side layer 21 illustrated in FIG. 4 is not formed integrally with the intermediate layer 22, but is laminated adjacent to the intermediate layer 22 in the thickness direction via the nonwoven fabric 26. In this case, before the excreted liquid migrates from the skin-side layer 21 to the intermediate layer 22, the excreted liquid diffuses in the planar direction on the nonwoven fabric 26. Therefore, the excreted liquid diffused in the planar direction can be migrated to the intermediate layer 22, and the absorbent cores 21-23 can be effectively utilized in the planar direction.

However, without being limited to the above, as shown in FIG. 9B, the skin-side layer 21 that is not integrally formed with the intermediate layer 22 may be laminated to the intermediate layer 22 without the adhesive HMA or nonwoven fabric. This prevents the nonwoven fabric or adhesive HMA from impeding the transfer of excreted liquid from the skin-side layer 21 to the intermediate layer 22. Similarly, as shown in FIG. 10B, the non-skin-side layer 23 that is not integrally formed with the intermediate layer 22 may be laminated to the intermediate layer 22 without the adhesive HMA or nonwoven fabric.

Furthermore, the intermediate layer 22 is not limited to being formed integrally with either the skin side layer 21 or the non-skin side layer 23, but may be formed integrally with both.
Alternatively, the three layers 21 to 23 may be formed separately and then laminated together. In this case, as shown in Fig. 11, nonwoven fabrics 26, 27 and adhesive HMA may or may not be provided between the skin side layer 21 and the intermediate layer 22, and between the intermediate layer 22 and the non-skin side layer 23, respectively.

In addition, the nonwoven fabric 26 disposed between the intermediate layer 21 and the skin side layer 21 or the non-skin side layer 23 preferably has a basis weight smaller than that of the core wrap sheets 24 , 25 .
By doing so, the layers 21 to 23 separated by the nonwoven fabric 26 are unlikely to separate from each other and are likely to deform integrally. This reduces discomfort when worn and prevents the absorbent cores 21 to 23 from losing their shape.

In addition, the water absorption capacity of the nonwoven fabric 26 disposed between the intermediate layer 21 and the skin side layer 21 or the non-skin side layer 23 is preferably greater than the water absorption capacity of the core wrap sheets 24 , 25 .
This allows the nonwoven fabric 26 inside the absorbent cores 21 to 23 to temporarily absorb the excreted liquid as well, thereby preventing the excreted liquid from overflowing and leaking during excretion.

The water absorption of the core wrap sheets 24, 25 and the nonwoven fabric 26 can be measured by a known method. For example, a sample separated from the diaper 1 using toluene or the like and dried is immersed in saline (e.g., 0.9%) for 10 minutes and then removed. The removed sample is hung and left for 10 minutes, etc., to remove excess water, and the mass of the sample is measured. The water absorption is then calculated from the following formula:
Water absorption (g/m ² )=sample mass after immersion−sample mass before immersion/sample area

Second Embodiment
FIG. 12 is a schematic cross-sectional view of an absorbent body 20 according to the second embodiment.
The diaper 1 (absorbent article) of the second embodiment is different from the diaper 1 of the first embodiment in the configuration of the absorbent body 20. The following mainly describes the differences from the first embodiment.

The absorbent core 21-23 of the second embodiment, like the first embodiment, has, in order from the skin side in the thickness direction, a skin side layer 21 in which the volume occupied by SAP is larger than the volume occupied by the liquid absorbent fiber 201, an intermediate layer 22 in which the volume occupied by the liquid absorbent fiber 201 is larger than the volume occupied by SAP, and a non-skin side layer 23 in which the volume occupied by SAP is larger than the volume occupied by the liquid absorbent fiber 201.

The skin-side layer 21 has a different type of SAP from the non-skin-side layer 23, and the SAP in the skin-side layer 21 has a slower liquid absorption rate measured by the vortex method than the SAP in the non-skin-side layer 23. The method for measuring the liquid absorption rate by the vortex method is the same as the method described in the first embodiment.

The skin side layer 21 of the absorbent body 20 of the second embodiment may or may not have a low basis weight region 211. The skin side layer 21 illustrated in FIG. 12 does not have a low basis weight region 211. Even in this case, the absorption speed of the SAP in the skin side layer 21 is slow, so that the excreted liquid is likely to migrate to the intermediate layer 22 before the skin side layer 21 absorbs the excreted liquid. The excreted liquid that has migrated to the intermediate layer 22 is quickly absorbed by the liquid absorbent fibers 201 of the intermediate layer 22. This makes it possible to suppress overflow and leakage of the excreted liquid. After that, the excreted liquid absorbed between the fibers of the liquid absorbent fibers 201 of the intermediate layer 22 gradually migrates to the non-skin side layer 23 by gravity. The volume occupancy rate of SAP is high in the non-skin side layer 23. Therefore, the excreted liquid is firmly absorbed and held by the SAP of the non-skin side layer 23.
As described above, according to the absorbent cores 21-23 of the second embodiment, excreted liquid can be drawn to the inner side (non-skin side layer 23) of the absorbent cores 21-23, thereby making effective use of the absorbent cores 21-23 and preventing excreted liquid from leaking.

In particular, because the absorption speed of SAP is slow, in the skin-side layer 21, excreted liquid migrates to the intermediate layer 22 while also diffusing in the planar direction. This allows the absorbent cores 21-23 to be effectively utilized in the planar direction as well. In addition, because the amount of SAP absorbed by the skin-side layer 21 is reduced, the dryness of the skin-side surfaces of the absorbent cores 21-23 is ensured. In addition, the SAP in the skin-side layer 21 can be prevented from swelling and inhibiting liquid absorption, and overflow and leakage of excreted liquid can be suppressed even in the case of repeated excretion.

In FIG. 12, the intermediate layer 22 and the non-skin side layer 23 do not have a low basis weight region, but the intermediate layer 22 and the non-skin side layer 23 may have a low basis weight region.

The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the scope of the present invention. The present invention may be modified or improved without departing from the spirit of the invention, and it goes without saying that the present invention includes equivalents.

1. Pants-type disposable diapers (absorbent articles)
2 side joints,
10 Absorbent body,
12 top sheet,
13a Back sheet (liquid-impermeable sheet),
13b back sheet (outer sheet),
15 leak-proof wall portion, 16 leak-proof wall elastic member,
17 leg elastic member,
20 absorbent,
201 Liquid absorbent fibers,
SAP superabsorbent polymer,
21 skin side layer (absorbent core), 211 low basis weight region,
22 intermediate layer (absorbent core), 221 low basis weight region,
23 non-skin side layer (absorbent core), 231 low basis weight region,
24 Core wrap sheet, 25 Core wrap sheet,
26 Nonwoven fabric, 27 Nonwoven fabric,
30 front waist portion,
31 skin side sheet, 32 non-skin side sheet,
33 waist elastic member,
34 cover sheet,
40 rear waist portion,
41 skin side sheet, 42 non-skin side sheet,
43 waist elastic member,
44 cover sheet,

Claims (21)

In a deployed state, the device has a longitudinal direction, a width direction, and a thickness direction which are perpendicular to each other,
An absorbent article having an absorbent core comprising liquid-absorbent fibers and a superabsorbent polymer,
The absorbent core includes, in order from the skin side in the thickness direction,
a skin side layer in which the volume occupied by the superabsorbent polymer is greater than the volume occupied by the liquid absorbent fiber;
an intermediate layer in which the volume occupied by the liquid absorbent fibers is greater than the volume occupied by the superabsorbent polymer;
a non-skin side layer in which the volume occupied by the superabsorbent polymer is greater than the volume occupied by the liquid absorbent fiber;
The absorbent article is characterized in that the skin side layer has a low basis weight region in which the basis weight of the absorbent core is lower than that of the surrounding area. The absorbent article according to claim 1,
the skin side layer has a different type of superabsorbent polymer than the non-skin side layer;
An absorbent article characterized in that the superabsorbent polymer contained in the skin side layer has a liquid absorption rate measured by a vortex method slower than the superabsorbent polymer contained in the non-skin side layer. In a deployed state, the device has a longitudinal direction, a width direction, and a thickness direction which are perpendicular to each other,
An absorbent article having an absorbent core comprising liquid-absorbent fibers and a superabsorbent polymer,
The absorbent core includes, in order from the skin side in the thickness direction,
a skin side layer in which the volume occupied by the superabsorbent polymer is greater than the volume occupied by the liquid absorbent fiber;
an intermediate layer in which the volume occupied by the liquid absorbent fibers is greater than the volume occupied by the superabsorbent polymer;
a non-skin side layer in which the volume occupied by the superabsorbent polymer is greater than the volume occupied by the liquid absorbent fiber;
the skin side layer has a different type of superabsorbent polymer than the non-skin side layer;
An absorbent article characterized in that the superabsorbent polymer contained in the skin side layer has a liquid absorption rate measured by a vortex method slower than the superabsorbent polymer contained in the non-skin side layer. The absorbent article according to claim 1 or 2,
The absorbent article according to claim 1, wherein the low basis weight region is a slit penetrating the skin side layer in the thickness direction. The absorbent article according to claim 1 or 2,
At least one of the intermediate layer and the non-skin side layer has another low basis weight region in which the basis weight of the absorbent core is lower than that of the surrounding area. The absorbent article according to claim 5,
In a plan view of the absorbent core,
The absorbent article according to claim 1, wherein the low basis weight region has an overlapping portion with the other low basis weight region. The absorbent article according to claim 5,
the non-skin side layer has the other low basis weight region,
An absorbent article characterized in that the liquid absorbent fibers are arranged in the other low basis weight region of the non-skin side layer at a basis weight lower than the basis weight of the liquid absorbent fibers in the intermediate layer. The absorbent article according to claim 5,
the non-skin side layer has the other low basis weight region,
an absorbent article, characterized in that the liquid-absorbent fibers are not arranged in the other low basis weight region of the non-skin side layer. The absorbent article according to claim 5,
the other low basis weight region is disposed on the inside of both longitudinal end edges of the intermediate layer or the non-skin side layer in which the other low basis weight region is disposed,
An absorbent article, characterized in that the low basis weight region has a length in the longitudinal direction longer than the other low basis weight regions. The absorbent article according to claim 5,
the intermediate layer has another low basis weight region extending in the longitudinal direction,
An absorbent article characterized in that at least a portion of the other low basis weight region of the intermediate layer is provided in an area rearward of a center line that divides the absorbent article in an unfolded state in half in the longitudinal direction. The absorbent article according to any one of claims 1 to 3,
An absorbent article characterized in that, on a cut surface of the absorbent core after absorbing colored water, cut along the width direction, the number of superabsorbent polymers per unit area located in the skin side layer and the number of superabsorbent polymers per unit area located in the non-skin side layer are greater than the number of superabsorbent polymers per unit area located in the intermediate layer. The absorbent article according to any one of claims 1 to 3,
The absorbent article is characterized in that the intermediate layer has an average thickness of 0.5 mm or more. The absorbent article according to any one of claims 1 to 3,
An absorbent article, comprising: an intermediate layer having an average thickness greater than the sum of an average thickness of the skin side layer and an average thickness of the non-skin side layer. The absorbent article according to any one of claims 1 to 3,
At least one of the skin side layer and the non-skin side layer comprises the liquid-absorbent fiber. The absorbent article according to any one of claims 1 to 3,
At least one of the skin side layer and the non-skin side layer is laminated adjacent to the intermediate layer in the thickness direction without an adhesive. The absorbent article according to any one of claims 1 to 3,
At least one of the skin side layer and the non-skin side layer is laminated adjacent to the intermediate layer in the thickness direction without a nonwoven fabric therebetween. The absorbent article according to any one of claims 1 to 3,
At least one of the skin side layer and the non-skin side layer is laminated adjacent to the intermediate layer in the thickness direction with a nonwoven fabric interposed therebetween. 18. The absorbent article of claim 17,
A core wrap sheet is provided on the skin side of the skin side layer in the thickness direction and on the non-skin side of the non-skin side of the non-skin side in the thickness direction,
An absorbent article characterized in that the basis weight of the nonwoven fabric is smaller than the basis weight of the core wrap sheet. 18. The absorbent article of claim 17,
A core wrap sheet is provided on the skin side of the skin side layer in the thickness direction and on the non-skin side of the non-skin side of the non-skin side in the thickness direction,
An absorbent article characterized in that the water absorption capacity of the nonwoven fabric is greater than the water absorption capacity of the core wrap sheet. The absorbent article according to any one of claims 1 to 3,
the intermediate layer has a constricted portion constricted inwardly in the width direction at a central portion in the longitudinal direction,
At least one of the skin side layer and the non-skin side layer extends outward in the width direction beyond the constricted portion. The absorbent article according to any one of claims 1 to 3,
the skin side layer has a different type of superabsorbent polymer than the non-skin side layer;
The absorbent article according to claim 1, wherein the superabsorbent polymer in the skin side layer has higher liquid permeability than the superabsorbent polymer in the non-skin side layer.

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