JP7574146B2 - Absorbent articles - Google Patents

Description

The present invention relates to an absorbent article.

Absorbent articles such as disposable diapers and sanitary napkins are known.

JP 2007-97643 A

In absorbent articles, it is preferable that bodily waste does not remain on the surface of the absorbent article, and that bodily waste that has been absorbed does not return to the surface of the absorbent article. For example, Patent Document 1 discloses a disposable diaper with improved absorption and retention performance for loose stool, etc., but there is a demand for absorbent articles that can better absorb high-viscosity bodily waste such as loose stool while further reducing the risk of bodily waste that has been absorbed returning to the skin side.

The present invention was made in consideration of the above problems, and its purpose is to make it easier to absorb excrement and reduce the amount of excrement that returns to the skin side once absorbed, thereby reducing discomfort for the wearer.

The main invention for achieving the above-mentioned object is an absorbent article having an absorbent body that absorbs liquid, a skin-side layer located closer to the skin than the absorbent body, and an intermediate layer located between the skin-side layer and the absorbent body, wherein the intermediate layer has a plurality of manifested crimp fibers, and the manifested crimp fibers are fixed to each other with an adhesive at a plurality of fixing portions, and the manifested crimp fibers are single fibers having a spiral shape, and the absorbent article is characterized in that after 40 ml of artificial urine is injected from the skin side of the skin-side layer of the absorbent article toward the intermediate layer, in the overlapping portion that overlaps with the portion into which the artificial urine was injected in a planar view, the intermediate layer is more hydrophilic than the skin-side layer.
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 makes it easier to absorb excrement and reduces the amount of excrement that returns to the skin surface once absorbed, thereby reducing discomfort for the wearer.

FIG. 1 is a plan view of a tape-type disposable diaper 1 in an open and extended state. 2 is a cross-sectional view taken along line AA shown in FIG. 1. FIG. 2 is a schematic perspective view of a second seat 35. 2 is a schematic perspective view showing the top sheet 22, the second sheet 35, and the absorbent body 21 of the absorbent main body 50 separated from each other. FIG. FIG. 13 is a diagram showing a method for measuring the amount of liquid return. FIG. 6 is a diagram showing a measurement result obtained by the measurement method of FIG. 5 . 2 is an enlarged schematic view of a portion of the second seat 35. FIG. Fig. 8A is an enlarged photograph of a portion of the second seat 35. Fig. 8B is a view in which auxiliary lines are added to the enlarged photograph of Fig. 8A. Fig. 9A is a diagram showing an enlarged photograph of a portion of the second seat 35. Fig. 9B is a diagram in which auxiliary lines are added to the enlarged photograph of Fig. 9A.

At least the following points will become apparent from the description of this specification and the accompanying drawings.
The absorbent article has an absorbent body that absorbs liquid, a skin-side layer that is located closer to the skin than the absorbent body, and an intermediate layer that is located between the skin-side layer and the absorbent body, wherein the intermediate layer has a plurality of manifested crimp fibers, and the manifested crimp fibers are fixed to each other with an adhesive at a plurality of fixing portions, and the manifested crimp fibers are single fibers having a spiral shape, and the absorbent article is characterized in that after 40 ml of artificial urine is injected from the skin side of the skin-side layer of the absorbent article toward the intermediate layer, in the overlapping portion that overlaps with the portion into which the artificial urine was injected in a planar view, the intermediate layer is more hydrophilic than the skin-side layer.

In such an absorbent article, the intermediate layer formed by fixing single-fiber manifested crimped fibers to each other at multiple fixing parts makes it easier to give the manifested crimped fibers a larger spiral shape, and can be made bulkier than when composite fibers are used in the intermediate layer. Furthermore, by providing the spiral-shaped manifested crimped fibers in the intermediate layer of the absorbent article, it becomes easier to absorb high-viscosity excrement such as loose stool, while the intermediate layer is more hydrophilic than the skin-side layer, which makes it easier to reduce the risk that excrement once absorbed in the intermediate layer will return to the skin-side layer and come into contact with the wearer's skin, causing discomfort. In particular, it makes it easier to reduce the return of excrement that has been repeatedly excreted to the skin-side layer.

In such an absorbent article, it is desirable that the skin-side layer in the overlapping portion is less hydrophilic after the artificial urine is poured in than before the artificial urine is poured in.

With such an absorbent article, the skin-side layer once through which the excrement has passed becomes less hydrophilic than it was before the excrement passed through, thereby reducing the risk of the excrement once absorbed returning to the surface of the skin-side layer.

In such an absorbent article, it is desirable that the adhesive be hydrophilic.

With such an absorbent article, the hydrophilicity of the intermediate layer can be increased, making it easier for the intermediate layer to absorb excrement received from the skin-side layer, while reducing the risk of excrement once absorbed by the intermediate layer returning to the skin-side layer.

In such an absorbent article, it is desirable that the surface of the manifested crimped fiber is subjected to a hydrophilic treatment.

In such absorbent articles, the hydrophilically treated manifested crimped fibers are more likely to have improved affinity with adhesives.

In such an absorbent article, it is preferable that the skin-side layer comprises a plurality of fibers, and that the plurality of fibers are coated with a hydrophilic agent to increase the hydrophilicity of the skin-side layer.

With such an absorbent article, the hydrophilicity of the skin-side layer can be increased, so when the wearer first puts on the absorbent article, the skin-side layer is more likely to absorb excrement. However, once the excrement passes through the skin-side layer, the intermediate layer has a higher hydrophilicity than the skin-side layer, reducing the risk of the excrement returning from the intermediate layer to the skin-side layer.

In such an absorbent article, it is desirable that the fixing portion has a portion where the manifested crimp fibers are fixed in a state of contact with each other.

With such an absorbent article, the strength of the multiple manifested crimp fibers fixed to each other can be improved, making it easier to improve the rigidity of the intermediate layer.

In such an absorbent article, it is desirable that the fixing portion has a portion in which the manifested crimp fibers are fixed in a spaced apart state.

With such an absorbent article, the fixing portion can be made thicker, making it easier to improve the rigidity of the intermediate layer.

In such an absorbent article, it is desirable that the spiral shape of the manifested crimped fibers has arc-shaped fiber aggregates, at least some of which are fixed together with the adhesive.

With such an absorbent article, the strength of the arc portions that are fixed to each other can be improved, making it easier to maintain the helical shape of the developed crimped fibers.

It is desirable for such an absorbent article to have a plurality of the fiber aggregates, and for the fiber aggregates to have portions in which the fiber aggregates, which are convex in different directions in a plan view, are fixed together with the adhesive.

With such an absorbent article, the strength of the arc portion can be further improved, making it easier to maintain the helical shape of the developed crimped fibers.

In such an absorbent article, it is desirable that at least a portion of the plurality of manifested crimp fibers have tips that are not fixed by the fixing portion.

In such an absorbent article, the tip portion not provided with a fixed portion can approach the adjacent manifested crimped fibers due to external pressure when worn, etc., making it easier to retain excrement through capillary action and reducing the risk of excrement returning from the intermediate layer to the skin-facing layer.

In such an absorbent article, it is desirable that the skin side layer has a plurality of holes penetrating in the thickness direction.

Such an absorbent article makes it easier for excrement received by the skin-facing layer to be transferred to the intermediate layer, helping to reduce discomfort for the wearer.

====Embodiment====
As an absorbent article according to the present invention, an embodiment will be described taking as an example a tape-type disposable diaper 1 for babies (hereinafter, simply referred to as "diaper 1"). However, the absorbent article according to the present invention may also be a pants-type disposable diaper, sanitary shorts, sanitary napkin, light incontinence pad, absorbent pad, etc.

<Basic configuration of tape-type disposable diaper 1>
Fig. 1 is a plan view of a tape-type disposable diaper 1 (hereinafter also referred to as "diaper 1") in an unfolded and stretched state, the diaper 1 being viewed from the skin side. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. The unfolded state of the diaper 1 refers to a state in which the diaper 1 as a whole is unfolded in a plane. The stretched state of the diaper 1 refers to a state in which the diaper 1 has been stretched to such an extent that wrinkles that have occurred in the diaper 1 are substantially no longer visible, and refers to a state in which the diaper 1 has been stretched to such an extent that the dimensions of each component constituting the diaper 1 (e.g., the top sheet 22 described below, etc.) are the same as or close to the dimensions of the component alone.

In the unfolded and stretched state shown in FIG. 1 etc., the diaper 1 has a longitudinal direction, a width direction, and a thickness direction which are perpendicular to one another, and from one side in the longitudinal direction, has a ventral portion 3, a crotch portion 5, and a back portion 7. The ventral portion 3 is a portion which is located on the ventral side (front side) of the wearer when the diaper 1 is worn. The back portion 7 is a portion which is located on the back side (rear side) of the wearer when the diaper 1 is worn. The crotch portion 5 is located between the ventral portion 3 and the back portion 7.

The "thickness direction" of the diaper 1 refers to the direction in which the various components constituting the diaper 1 are layered, with the side in contact with the wearer being referred to as the "skin side" and the opposite side being referred to as the "non-skin side." In Figure 1 and other figures, the center line C-C is the center in the width direction, and the center line CL is the center in the longitudinal direction. In Figure 2, the adhesive that joins the various components is omitted. Also, for convenience, the visible portion on the longitudinal back side of the cross section of line A-A is omitted.

The diaper 1 has, in the widthwise center, a liquid-absorbent absorbent 21, a liquid-permeable top sheet 22 covering the absorbent 21 from the skin side, a liquid-permeable second sheet 35 located closer to the skin than the absorbent 21, a liquid-impermeable back sheet 23 covering the absorbent 21 from the non-skin side, and an exterior sheet 27 (e.g., nonwoven fabric) covering the back sheet 23 from the non-skin side, which constitutes the exterior of the diaper 1, and forming the outer shape of the diaper 1. In addition, the diaper 1 has a pair of side sheets 26 arranged side by side on the upper side of the top sheet 22, a target tape 29 on the abdominal side 3, and fastening tapes 30 extending from both ends in the width direction of the dorsal side 7.

The top sheet 22 is a "skin-side layer" located closer to the skin than the absorbent body 21. Examples of the top sheet 22 include sheet members such as air-through nonwoven fabrics, spunbond nonwoven fabrics, and other air-through nonwoven fabrics. The top sheet 22 has a plurality of holes 22a penetrating in the thickness direction, and the area of the open regions of the plurality of holes 22a is 30% of the total area of the top sheet 22.

The second sheet 35 is an "intermediate layer" located between the top sheet (skin side layer) 22 and the absorbent body 21. The second sheet 35 can be, for example, a sheet member such as a nonwoven fabric made of polyester. The detailed configuration of the second sheet 35 will be described later.

The back sheet 23 can be, for example, a sheet member such as a resin film, such as a polyethylene film, and the exterior sheet 27 can be, for example, a flexible sheet member, such as a spunbond nonwoven fabric or an SMS nonwoven fabric (spunbond/meltblown/spunbond nonwoven fabric).

The absorbent body 21 has a rectangular shape that is long in the longitudinal direction when viewed in a plan view, and is disposed across the abdominal portion 3, the crotch portion 5, and the dorsal portion 7. The absorbent body 21 has an absorbent core 24 that absorbs waste materials such as urine and feces, and a liquid-permeable core wrap sheet 25 that covers the absorbent core 24 on both the skin side and the non-skin side in the thickness direction.

The absorbent core 24 has a roughly hourglass shape in plan view, which is an example of a predetermined shape. The liquid absorbent material constituting the absorbent core 24 may be, for example, liquid absorbent fibers such as pulp fibers, or liquid absorbent granular materials such as superabsorbent polymers (so-called SAP). It may also contain liquid absorbent materials other than liquid absorbent fibers and liquid absorbent granular materials. Examples of suitable materials for the core wrap sheet 25 include tissue paper and nonwoven fabric. However, these core wrap sheets 25 are not essential components.

In the width direction, leg gather elastic members 15 that stretch along the longitudinal direction are provided on the outer side of the absorbent body 21. The leg gather elastic members 15 are elastic members that stretch along the longitudinal direction and provide elasticity to the leg openings when the diaper 1 is worn. That is, the leg gather elastic members 15 are leg elastic members that make the leg openings of the diaper 1 fit the legs of the wearer. The leg gather elastic members 15 can be made of a band-shaped elastic sheet having elasticity or multiple rubber threads. The leg gather elastic members 15 provide elasticity to the side sheets 26 and the back sheet 23 of the crotch portion 5, thereby forming leg gathers. The leg gathers allow each side end of the diaper 1 in the width direction to fit the legs of the wearer when worn, thereby suppressing leakage of excrement.

The diaper 1 also includes leg side gather elastic members 18 (e.g., rubber thread) that are stretchable in the longitudinal direction together with the side sheets 26 on both widthwise sides, inside the leg gather elastic members 15, forming a pair of three-dimensional gathers as leakage prevention walls. The leg side gather elastic members 18 are fixed to the side sheets 26 in a stretched state in the longitudinal direction. The three-dimensional gathers rise up toward the wearer's skin, thereby preventing side leakage of excrement and the like.

The number, shape, material, etc. of the leg gather elastic members 15 and leg side gather elastic members 18 are not limited to those shown in FIG. 1, etc. For example, the number of each elastic member can be set arbitrarily, and they may be elastic nonwoven fabric made of elastic fibers or elastic films formed by melting thermoplastic elastomer resin into a film shape.

The abdominal portion 3 has a target tape 29 on the non-skin side (non-skin side of the outer sheet 27) in the center of the width direction, and the back portion 7 has fastening tapes 30 extending outward from both ends in the width direction. The target tape 29 is a member that can be engaged with the fastening tape 30, and is formed of, for example, a nonwoven fabric. The target tape 29 constitutes a target area for engaging the fastening tape 30. The fastening tape 30 has a tape base material and a hook material, and the tape base material is, for example, a nonwoven fabric member and has a substantially rectangular shape that is long in the horizontal direction. The hook material (for example, a male member of a hook-and-loop fastener) is provided on the skin side of the tape base material that extends outward in the width direction from the back portion 7. By engaging each fastening tape 30 with the target tape 29, a waist opening and a leg opening of the diaper 1 are formed, and the position of the diaper 1 can be fixed relative to the wearer's body (torso). Instead of placing a target tape 29 as a separate member on the non-skin side of the exterior sheet 27, the outermost nonwoven fabric layer constituting the exterior sheet 27 may be used as the target area, and the fastening tape 30 may be directly fastened to the non-skin side of the exterior sheet 27.

<About liquid return>
The second sheet 35 (middle layer) preferably has good liquid permeability and absorbency. In particular, in the case of an absorbent article that absorbs highly viscous liquids (loose stool, etc.) such as the diaper 1, the second sheet 35 is required to have a configuration that allows highly viscous liquids (loose stool, etc.) to easily pass through.

The second sheet 35 is a sheet member made of multiple manifested crimped fibers 35f that have high liquid permeability and cushioning properties. Figure 3 is a schematic perspective view of the second sheet 35. A crimped fiber is a fiber that has a crimped shape (zigzag, Ω, spiral, etc.), and the second sheet 35 is made of spiral crimped fibers.

As spirally crimped fibers, latent spirally crimped fibers (hereinafter also referred to as latent crimped fibers) and manifest spirally crimped fibers (hereinafter also referred to as manifest crimped fibers) are known. Latent crimped fibers are fibers that shrink when heated to develop a spiral shape, so it is difficult to control the development of the spiral shape. When nonwoven fabric is formed from latent crimped fibers, the spiral shape becomes small and the structure tends to be high density, which may prevent high viscosity liquids from passing through. In contrast, the second sheet 35 of this embodiment is formed from manifest crimped fibers 35f that have a spiral shape from the beginning as the crimped fibers. In addition, the manifest crimped fibers 35f of this embodiment are single fibers (single component fibers) composed of a single component (e.g. polyester).

Known nonwoven fabrics are those made of single fibers and those made of composite fibers. Single fibers are those made by spinning a stock solution containing one type of component (single component) from a spinneret into a single fiber. Composite fibers are those made by simultaneously spinning stock solutions containing two different types of components (composite components) from two separate spinnerets into a single fiber. Composite fibers include those with a structure in which two components are bonded together (the so-called side-by-side structure) and those with a core-sheath structure.

The second sheet 35 is a sheet-like nonwoven fabric formed by fixing multiple apparently crimped fibers having a single fiber helical shape together with an adhesive at multiple fixing parts 35m (Figure 7).

Specifically, the second sheet 35 is made of a helical shape of apparently crimped fiber obtained by melting a single component polyester, spinning it through a spinneret, blowing a predetermined amount of air onto the fiber bundle immediately after it is spun from the spinneret to form an undrawn yarn, applying a spinning oil to the undrawn yarn tow, stretching the undrawn yarn tow at a predetermined temperature, and further performing a relaxation heat treatment. As shown in FIG. 3, the second sheet 35 has a plurality of arc portions 35c visible from the surface. The apparently crimped fiber of the second sheet 35 of this embodiment has a single fiber fineness of 0.7 to 20 dtex. In addition, it is preferable that the fiber contains fibers whose length in the stretched state is longer than 25 mm, and it is more preferable that the average length of the fibers is longer than 25 mm. By making the length of the apparently crimped fiber 35f 25 mm or more, the bulk of the second sheet 35 can be made higher than when it is shorter than 25 mm, and the cushioning properties can be improved. Furthermore, the bulk of the intermediate layer made of the manifested crimped fibers is high, which increases the amount of excrement that can be retained in the intermediate layer. By providing multiple fixing parts 35m in which the manifested crimped fibers 35f having such a spiral shape are fixed together with an adhesive such as a hot melt adhesive, the manifested crimped fibers 35f become a sheet-like nonwoven fabric.

In the second sheet 35, the length of the apparently crimped fibers 35f in the stretched state may be shorter than 25 mm or longer than 40 mm. The components of the apparently crimped fibers 35f are not limited to polyester, and may be polyamide, polyolefin, polyphenylene sulfide, etc.

The method for manufacturing the second sheet 35 includes a fiber-opening process in which the manifested crimped fibers 35f are opened using a carding machine, a web-forming process in which the manifested crimped fibers 35f are made into a web after the fiber-opening process, and a nonwoven fabric-forming process in which multiple manifested crimped fibers 35f are fixed together with an adhesive to form fixed portions 35m after the web-forming process to form a nonwoven fabric, followed by a cutting process in which the resulting nonwoven fabric is cut to a predetermined size to produce the second sheet 35.

In the fiber-spreading process, a carding machine is used to loosen the fibers, which not only makes the fiber-spreading process more efficient, but also reduces the uneven distribution of the apparent crimped fibers 35f. When a carding machine is used in the fiber-spreading process, it is preferable to set the length of the apparent crimped fibers 35f to be longer than 25 mm. This allows the fiber-spreading process to be performed more appropriately using the carding machine than when the length of the apparent crimped fibers 35f is 25 mm or less.

However, the manufacturing method is not limited to the above, and the second sheet 35 may be a nonwoven fabric sheet formed by subjecting the developed crimped fibers 35f to an airlaid process and bonding the fibers together with an adhesive.

By using a second sheet 35 in which such manifested crimped fibers 35f are fixed with adhesive at fixing portions 35m, the spiral shape of the manifested crimped fibers 35f can be maintained while forming a sheet-like nonwoven fabric with adhesive, so that the second sheet 35 tends to become a bulky sheet with cushioning properties.

Latent crimp fibers that develop a helical shape when heated have been widely known, and a known example of a latent crimp fiber is a composite fiber (a fiber made of two components). It is difficult to control the helical shape of this latent crimp fiber, and the diameter of the helical shape tends to become small, so nonwoven fabrics using this fiber end up being high density and low bulk. In addition, it is difficult to control the diameter of the helical shape so that it does not become excessively small, and it is difficult to form the intended helical shape because the fiber is prone to irregular deformation.

In contrast, the second sheet 35 of this embodiment is a nonwoven fabric having fixing parts 35m in which multiple single-fiber spirally shaped manifested crimped fibers 35f are fixed together with an adhesive, making it possible to produce a bulkier nonwoven fabric than one using composite fiber manifested crimped fibers. A bulkier nonwoven fabric made of spirally shaped manifested crimped fibers 35f makes it easier to secure space between the fibers, and since the sheet has a spiral shape in which the spaces between the fibers are expanded, it is easier to absorb highly viscous excrement such as loose stools.

In this embodiment, the second sheet 35 is made of water-repellent polyester fibers that have been subjected to a hydrophilic treatment. The hydrophilic treatment of the manifested crimped fibers makes it easier to improve the affinity with adhesives. As the hydrophilic treatment, known hydrophilic techniques such as SR treatment, application of hydrophilic oil, graft polymerization of hydrophilic monomers, plasma treatment, etc. can be used. It is preferable that the hydrophilicity of the second sheet 35 does not decrease regardless of whether or not liquid (excrement, artificial urine) passes through it. In addition, it is preferable that the second sheet 35 has, for example, a hydrophilic polyester resin processing agent (hydrophilic binder) applied to the manifested crimped fibers 35f. By applying a hydrophilic binder to the manifested crimped fibers 35f, it becomes easier to bond the manifested crimped fibers 35f of the second sheet 35 to each other, and it becomes easier to increase the rigidity of the nonwoven fabric sheet.

As shown in FIG. 4 and other figures, the second sheet 35 of the diaper 1 is provided on the non-skin side of the top sheet 22 and on the skin side of the absorbent 21. After 40 ml of artificial urine is poured from the skin side of the top sheet 22 of the diaper 1 equipped with such a second sheet 35 toward the second sheet 35, that is, after 40 ml of artificial urine is poured in the thickness direction from the skin side to the non-skin side of the diaper 1, the hydrophilicity of the second sheet 35 in the overlapping portion that overlaps the portion into which the artificial urine is poured in the plan view of the diaper 1 is higher than that of the top sheet 22. Therefore, it is possible to reduce the possibility that the excrement once absorbed by the second sheet 35 will return to the top sheet 22. As a result, it is easy to reduce the risk that the excrement once absorbed by the diaper 1 will return to the skin side of the top sheet 22 and come into contact with the wearer's skin, causing discomfort to the wearer. The average amount of urine voided by a young infant is about 40 ml per urination.

The artificial urine is a liquid prepared by dissolving 200 g of urea, 80 g of sodium chloride, 8 g of magnesium sulfate, 3 g of calcium chloride, and about 1 g of Blue No. 1 dye in 10 L of ion-exchanged water. Instead of artificial urine, artificial soft stool may be used to compare hydrophilicity and absorbency. The artificial soft stool may be prepared by adding 1.0% by mass of sodium chloride, 15.0% by mass of glycerin, 2.0% by mass of sodium carboxymethylcellulose (NaCMC), 0.05% by mass of Triton X-100, 0.05% by mass of Red No. 102 dye, and 10.0% by mass of powdered cellulose to 71.9% by mass of ion-exchanged water, stirring and mixing, and then adding ion-exchanged water to adjust the viscosity to 2000 mPa/s.

The "hydrophilicity" of each sheet means that liquid spreads easily on the surface of the sheet and that the surface of the sheet has a contact angle of 90° or less. Also, "hydrophobicity" means that liquid does not spread on the surface of the sheet and that the surface of the sheet has a contact angle of more than 90°. The contact angle is the angle between the horizontal plane and the tangent of the contour curve of the liquid at the intersection point of the contour curve and the horizontal plane when the sheet having a horizontal plane (horizontal surface) is in contact with water (droplet) dropped on the horizontal plane. The hydrophilicity of the top sheet 22 and the second sheet 35 can be compared by comparing the measured contact angles. Specifically, artificial urine is poured into the skin side of the diaper 1, the top sheet 22 and the second sheet 35 are removed, and the hydrophilicity of the top sheet 22 and the second sheet 35 at the overlapping portion that overlaps the portion where the artificial urine was poured in when viewed from above is compared. In other words, if the contact angle between the second sheet 35 and ion-exchanged water is smaller than the contact angle between the top sheet 22 and ion-exchanged water, the hydrophilicity of the second sheet 35 is higher than that of the top sheet 22.

The top sheet 22 is a hydrophobic nonwoven fabric comprising a plurality of hydrophobic fibers, and is preferably made hydrophilic by applying a treatment (hydrophilic treatment) to the plurality of hydrophobic fibers. By increasing the hydrophilicity of the top sheet 22 of an unused diaper 1, when the wearer first puts on the diaper 1, the top sheet 22 becomes more likely to absorb excrement, and the excrement is more likely to be transferred from the top sheet 22 to the absorbent body 21 via the second sheet 35. Once the excrement has passed through the top sheet 22, the top sheet 22 is less hydrophilic than the second sheet 35, so that the risk of the excrement returning from the second sheet 35 to the top sheet 22 can be reduced.

In addition, in a plan view of the diaper 1, the top sheet 22 is preferably less hydrophilic after the injection of artificial urine at the overlapping portion where 40 ml of artificial urine is injected from the skin side of the top sheet 22 toward the second sheet 35. In this embodiment, the hydrophilicity of the top sheet 22 before absorbing excrement (artificial urine) (unused state) is increased by performing a treatment (hydrophilic treatment) to attach a predetermined oil agent. Then, when the diaper 1 absorbs a predetermined amount of excrement (40 ml of artificial urine), the hydrophilic effect of the oil agent attached by the hydrophilic treatment decreases as the excrement (artificial urine) passes through, and the top sheet 22 becomes less hydrophilic after the diaper 1 absorbs a predetermined amount of excrement (after the injection of 40 ml of artificial urine) than before absorbing the predetermined amount of excrement (before the injection of 40 ml of artificial urine).

As a result, when the diaper 1 is first worn, the top sheet 22 is more likely to absorb excrement, and the excrement is more likely to move from the top sheet 22 to the second sheet 35 and absorbent body 21. Once the excrement has been absorbed, the second sheet 35 is more hydrophilic than the top sheet 22, which helps reduce the risk of the absorbed excrement returning from the second sheet 35 to the top sheet 22.

It is preferable to use a specific oil agent that is applied to the unused top sheet 22 and whose hydrophilic effect is reduced by a specific amount of liquid (excrement). The hydrophilicity of the top sheet 22 of the diaper 1 in an unused state (before 40 ml of artificial urine is poured) may be higher than that of the second sheet 35 in an unused state (before 40 ml of artificial urine is poured) or lower than that of the second sheet 35 in an unused state (before 40 ml of artificial urine is poured) by a hydrophilic treatment such as a treatment by applying a specific oil agent.

As shown in FIG. 4, it is preferable that the top sheet 22 has a plurality of holes 22a penetrating in the thickness direction. The holes 22a in the top sheet 22 make it easier for the excrement received by the top sheet 22 to move to the second sheet 35, and make it easier to reduce discomfort to the wearer caused by excrement remaining on the skin side of the top sheet 22.

Furthermore, since the hydrophilicity of the second sheet 35 after absorbing a predetermined amount of artificial urine is higher than that of the top sheet 22, even in cases where the diaper 1 absorbs excrement multiple times, the risk of the absorbed excrement returning to the skin side of the top sheet 22 is reduced, making it easier to reduce discomfort for the wearer even when worn for long periods of time. Figures 5A to 5C are diagrams showing a method for measuring the amount of liquid return. Figure 6 is a diagram showing the results of measurement using the measurement method of Figure 5. "Amount of liquid return" refers to the amount of liquid that has returned to the outermost surface and the amount of liquid remaining on the outermost surface out of the liquid that has been absorbed.

A top sheet piece 22p is used as a test piece for the top sheet 22, a second sheet piece 35p is used as a test piece for the second sheet 35, and an absorbent piece 21p is used as a test piece for the absorbent 21. In the measurement, each test piece is made to be the same size, for example, 70 mm x 150 mm. The top sheet piece 22p is a sheet piece with multiple holes (opening rate 30%) penetrating in the thickness direction, similar to the top sheet 22 of the diaper 1. First, as STEP 1, as shown in FIG. 5A, the top sheet piece 22p, the second sheet piece 35p, and the absorbent piece 21p are stacked in order from the top, and a cylindrical jig with a circular through hole with a diameter of 50 mm penetrating in the thickness direction is placed above them, and 40 ml of artificial urine is poured through the through hole. Then, as STEP 2, as shown in FIG. 5B, the cylindrical jig is removed after 3 minutes. In STEP 3, 5 minutes after the artificial urine is poured, as shown in FIG. 5C, a filter paper (area 100 mm x 100 mm) whose weight has been measured in advance is placed on top of the top sheet piece 22p so as to cover the entire area of the part into which the artificial urine was poured (the part where the through hole of the cylindrical jig was located), and a weight with a bottom area of 100 mm x 100 mm and a weight of 3.5 kg is placed on top of the filter paper and left to stand for 3 minutes. In STEP 4, after 3 minutes, the weight of the filter paper is measured, so that the weight of the artificial urine absorbed by the filter paper can be calculated, and the amount of liquid returning to the surface of the top sheet piece 22p is calculated (first time). Then, after a predetermined time has passed, the above-mentioned STEPs 1 to 4 are repeated for the part into which the artificial urine was poured (the part where the through hole of the cylindrical jig was located) (second time).

Specifically, because the average amount of urine voided by a young infant is about 40 ml per urination, measurements were performed by injecting 40 ml of artificial urine twice (a total of 80 ml) for samples (1) to (3). As the top sheet piece 22p, sample (1) is a water-repellent sheet in which the water-repellent fibers have not been hydrophilically treated, and is a nonwoven fabric with an average fineness of 2.6 dtex, a fiber composition of polyethylene (PE)/polyethylene terephthalate (PET), and a basis weight of 26 gsm. Sample (2) is a hydrophilic sheet A in which the water-repellent fibers have been hydrophilically treated to reduce the hydrophilicity due to the passage of liquid, and is a nonwoven fabric with an average fineness of 2.6 dtex, a fiber composition of PE/PET, and a basis weight of 30 gsm. Sample (3) is a hydrophilic sheet B in which the water-repellent fibers have been hydrophilically treated to prevent the hydrophilicity from decreasing due to the passage of liquid, and is a nonwoven fabric with an average fineness of 2.6 dtex, a fiber composition of PE/PET, and a basis weight of 25 gsm. The second sheet piece 35p is the same for samples (1) to (3) and is a nonwoven fabric with an average fineness of 7.4 dtex, a fiber composition of polyethylene terephthalate (PET), and a basis weight of 48 gsm. The absorbent piece 21p is the same for samples (1) to (3) and is a part of the absorbent of the diaper 1 described above. After absorbing 40 ml of artificial urine, the hydrophilicity of the water-repellent sheet of sample (1) and the hydrophilic sheet A of sample (2) is lower than that of the second sheet piece 35p. On the other hand, after absorbing 40 ml of artificial urine, the hydrophilicity of the hydrophilic sheet B of sample (3) is higher than that of the second sheet piece 35p.

The measurement results shown in Figure 6 are the results of measuring the amount of liquid returning after the second injection of artificial urine. As shown in Figure 6, the average amounts of liquid returning for sample (1) and sample (2) are 1.8 g and 2.7 g, respectively, while the amount of liquid returning for sample (3) is 4.6 g, and it is clear that the amount of liquid returning for sample (3) is greater. From this result, by making the hydrophilicity of the second sheet 35 higher than that of the top sheet 22 after absorbing a predetermined amount of artificial urine, it is possible to reduce the risk of the absorbed excrement returning to the skin-side surface of the top sheet 22 even in cases where the diaper 1 absorbs excrement multiple times.

Figure 7 is an enlarged schematic diagram of a portion of the second sheet 35. As shown in Figure 7, the manifested crimp fibers 35f are fixed together at multiple fixing parts 35m to form a nonwoven fabric sheet. It is preferable that the adhesive for forming these fixing parts 35m is hydrophilic. By making the adhesive in the second sheet 35 hydrophilic, the hydrophilicity of the second sheet 35 is increased, which makes it easier to make the hydrophilicity of the second sheet 35 higher than that of the top sheet 22, and makes it easier to reduce the risk of excrement once absorbed returning from the second sheet 35 to the top sheet 22.

As shown in FIG. 7, the fixing portion 35m preferably has abutting fixing portion 35t where the manifested crimp fibers 35f are fixed in abutting state, and preferably has spaced fixing portion 35s where the manifested crimp fibers 35f are fixed in a spaced state. By having abutting fixing portion 35t, the strength of the multiple manifested crimp fibers 35f fixed to each other can be improved, making it easier to improve the rigidity of the second sheet 35. By having spaced fixing portion 35s, the adhesive portion between the fixed manifested crimp fibers 35f and the manifested crimp fibers 35f can be included in the fixing portion 35m (35s), making it possible to make the fixing portion 35m (spaced fixing portion 35s) thicker, making it easier to improve the rigidity of the second sheet 35.

7, it is preferable that at least some of the multiple manifested crimped fibers 35f have tip portions 35e that are not fixed by the fixing portions 35m. In other words, by having tip portions 35e of the manifested crimped fibers 35f that are not fixed anywhere in the second sheet 35 of the unused diaper 1, when worn, the manifested crimped fibers 35f can approach adjacent ones in the second sheet 35 due to external pressure such as pressure due to contact with the wearer's skin and pressure due to absorption of excrement, and therefore it is possible to provide portions with higher fiber density, which makes it easier to retain excrement due to capillary action and reduces the risk of excrement returning from the second sheet 35 to the top sheet 22.

Figure 8A is a diagram showing an enlarged photograph of a portion of the second sheet 35. Figure 8B is a diagram showing the enlarged photograph of Figure 8A with auxiliary lines added. The manifested crimped fibers 35f of the second sheet 35 have arcuate portions 35c (see Figure 7, etc.), and as shown in Figures 8A and 8B, it is preferable to have an arcuate fiber assembly in which at least some of the arcuate portions 35c are bonded together. The thick lines in Figure 8B indicate the fiber assembly. It can be seen from Figures 8A and 8B that there is a ring-shaped fiber assembly formed by multiple manifested crimped fibers 35f. By having this fiber assembly, the strength of the portion with the arcuate shape can be improved by the multiple arcuate portions 35c in a state of being fixed to each other, making it easier to maintain the spiral shape of the manifested crimped fibers 35f.

Moreover, it is more preferable that the manifested crimped fiber 35f of the second sheet 35 has a plurality of fiber aggregates, and has a portion where fiber aggregates having different convex directions in a plan view of the diaper 1 are fixed together with an adhesive. Fig. 9A is a view showing an enlarged photograph of a portion of the second sheet 35. Fig. 9B is a view showing the enlarged photograph of Fig. 9A with auxiliary lines added. In other words, as shown in Figs. 9A and 9B, the second sheet 35 has a plurality of ring-shaped fiber aggregates, and the outer side of each fiber aggregate is abutted against the outer side of the ring of the adjacent fiber aggregate, and fixed thereto, which can further improve the strength of the arc portion and makes it easier to maintain the spiral shape of the manifested crimped fiber 35f.

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

1 Diapers (tape-type disposable diapers, absorbent articles),
3 ventral part,
5. Crotch area,
7 dorsal part,
15 Leg gather elastic member,
18 Leg side gather elastic member,
21 absorbent,
22 Top sheet (skin side layer),
22a hole,
23 back seat,
24 absorbent core,
25 core wrap sheet,
26 Side sheet,
27 Exterior sheet,
29 target tape,
30 fastening tape,
35 Second seat (middle layer),
35f apparent crimp fiber,
35c arc portion,
35m fixed part

Claims (11)

An absorbent that absorbs liquid;
a skin side layer located closer to the skin than the absorbent body;
an intermediate layer located between the skin side layer and the absorbent body;
An absorbent article having
The intermediate layer includes a plurality of manifested crimp fibers, and the manifested crimp fibers are fixed to each other at a plurality of fixing portions with an adhesive,
The apparently crimped fiber is a single fiber having a helical shape,
After injecting 40 ml of artificial urine from the skin side of the skin side layer of the absorbent article toward the intermediate layer,
an absorbent article, characterized in that, in a plan view, the intermediate layer has a higher hydrophilicity than the skin-side layer in an overlapping portion that overlaps with a portion into which the artificial urine is poured. The absorbent article according to claim 1,
The absorbent article is characterized in that, in the overlapping portion, the skin side layer has a lower hydrophilicity after the artificial urine is poured therein than before the artificial urine is poured therein. The absorbent article according to claim 1 or 2,
The absorbent article is characterized in that the adhesive is hydrophilic. The absorbent article according to any one of claims 1 to 3,
The absorbent article is characterized in that the surface of the apparently crimped fiber has been subjected to a hydrophilization treatment. The absorbent article according to any one of claims 1 to 4,
The skin side layer includes a plurality of fibers,
The absorbent article is characterized in that a hydrophilic agent is applied to the plurality of fibers to enhance the hydrophilicity of the skin side layer. The absorbent article according to any one of claims 1 to 5,
An absorbent article characterized in that the fixed portion has a portion where the apparently crimped fibers are fixed in a state of contact with each other. 7. The absorbent article according to claim 1,
An absorbent article, characterized in that the fixed portion has a portion where the apparently crimped fibers are fixed in a spaced-apart state. The absorbent article according to any one of claims 1 to 7,
The helical shape of the apparently crimped fiber has an arc portion,
An absorbent article comprising an arc-shaped fiber assembly portion, at least a portion of which is fixed to each other by the adhesive. 9. The absorbent article of claim 8,
The fiber assembly includes a plurality of fiber aggregates,
An absorbent article, comprising: a fiber assembly portion having, in a plan view, portions each having convex directions different from each other and fixed to each other by the adhesive. 10. The absorbent article according to claim 1 ,
An absorbent article, characterized in that at least a portion of the plurality of apparently crimped fibers have tip portions that are not fixed by the fixing portion. The absorbent article according to any one of claims 1 to 10,
The absorbent article is characterized in that the skin side layer has a plurality of holes penetrating therethrough in the thickness direction.

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