Absorbent articles

Abstract

To improve liquid diffusibility and to suppress liquid return.SOLUTION: In an absorbent article 1, an absorbent core 4 is provided with an upper layer absorber 41 where a high absorbent material 413 is fixed between an upper absorber sheet 411 and a lower absorber sheet 412. In the upper layer absorber 41, a plurality of material existence areas 42 where the high absorbent material 413 is fixed are arranged with gaps in a width direction, and material non-existence areas 43 where there is no high absorbent material 413 are provided between adjacent material existence areas 42. In the respective material non-existence regions 43, the upper absorber sheet 411 and the lower absorber sheet 412 are bonded entirely. In at least one material non-existence region 43, a top sheet 21 and the upper absorber sheet 411 are partially bonded. Weight when a non-woven fabric forming the top sheet 21 is stretched 3% in the width direction is twice as heavy as or heavier than when the non-woven fabric forming the upper absorber sheet 411 is stretched 3% in the width direction.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to absorbent articles.

Background Art

[0002] Conventionally, absorbent articles such as disposable diapers have been used. In such absorbent articles, an absorbent core containing a highly absorbent material is disposed in a portion that receives urine or the like from the wearer, thereby improving the absorption capacity. For example, in the absorbent article of Patent Document 1, an absorbent mat (absorbent core) having a sheet-like water-absorbing layer containing water-absorbing resin powder and a fiber assembly layer containing pulp fibers is provided. In the sheet-like water-absorbing layer, the water-absorbing resin powder is encapsulated between a plurality of non-woven fabric sheets. The sheet-like water-absorbing layer has a region where the water-absorbing resin powder is present and a region where the water-absorbing resin powder is not present, and the non-woven fabric sheets are joined in the region where the water-absorbing resin powder is not present to form a sealing portion. In Patent Document 1, when the body fluid is absorbed and the water-absorbing resin swells, a gap is generated between the fiber assembly layer and the sealing portion. As a result, the body fluid that has leaked out from the fiber assembly layer diffuses through the gap portion, and the backflow of the liquid (liquid return) is prevented.

[0003] <00... In the absorbent article of Patent Document 2, in an absorber having fibrous substances, a plurality of regions where water-absorbing polymers are arranged are formed to be mutually separated in the planar direction. When the water-absorbing polymer absorbs urine, the thickness of the region where the water-absorbing polymer is arranged increases, and irregularities occur on the surface of the absorber. As a result, a space is formed between the absorber and the surface sheet, and the air permeability is improved. In the disposable diaper of Patent Document 3, the absorber has a large number of small absorbing portions arranged in the vertical and horizontal directions. Further, a crepe sheet is disposed on the skin contact surface side of the small absorbing portion so as to overlap substantially parallel to the surface sheet. After the excreted liquid passes through the surface sheet, it reaches the crepe sheet, and the crepe sheet covers the small absorbing portion and enters the valley portion between the small absorbing portions to form a valley passage portion. The valley passage portion allows the excreted liquid to move.

[0004] Patent Document 4 discloses an absorbent material having a water-absorbent resin between an upper sheet and a lower sheet, and without pulp fibers, in which the tensile stress of the lower sheet when stretched by 5% is 20% to 75% of the tensile stress of the upper sheet when stretched by 5%. As a result, the absorbent material tends to bulge more on the lower side than on the upper side, and large irregularities are less likely to form on the surface of the absorbent material facing the wearer. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 4502586 [Patent Document 2] Japanese Patent Publication No. 2009-72421 [Patent Document 3] Japanese Patent Publication No. 2011-135921 [Patent Document 4] Patent No. 6353237 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] As previously described, in the absorbent article of Patent Document 1, a void is formed between the fiber aggregate layer and the sealing portion, thereby improving liquid diffusion and suppressing liquid return, but this is not always sufficient. Therefore, there is a need for a novel method that can improve liquid diffusion while suppressing liquid return.

[0007] This invention has been made in view of the above problems, and aims to improve liquid diffusion and suppress liquid return. [Means for solving the problem]

[0008] The invention described in claim 1 is an absorbent article for receiving excrement from a wearer, comprising a liquid-permeable top sheet, a water-repellent or liquid-impermeable back sheet, and an absorbent core disposed between the top sheet and the back sheet and extending in the longitudinal direction, wherein the absorbent core comprises an upper absorbent layer in which a highly absorbent material is fixed between an upper absorbent sheet and a lower absorbent sheet, and a lower absorbent layer disposed between the upper absorbent layer and the back sheet and having a sheet-like fiber aggregate, wherein in the upper absorbent layer, a plurality of material-present regions to which the highly absorbent material is fixed are arranged with gaps in the width direction, and a material-absent region where the highly absorbent material is absent is provided between two adjacent material-present regions in the width direction, and in each material-absent region, a first joint is provided in which the upper absorbent sheet and the lower absorbent sheet are joined together as a whole, and in at least one material-absent region, a second joint is provided in which the top sheet and the upper absorbent sheet are partially joined, In the at least one material-free region where the second joint is provided, the area ratio of the joint region between the top sheet and the upper absorber sheet is 1% or more and 40% or less. The load when the nonwoven fabric forming the top sheet is stretched by 3% in the width direction is 2.0 times or more the load when the nonwoven fabric forming the upper absorbent sheet is stretched by 3% in the width direction. When the highly absorbent material swells, the top sheet peels off from the upper absorbent sheet in at least one material-free region, and a peel space is formed between the top sheet and the upper absorbent sheet in the at least one material-free region. ru.

[0009] The invention described in claim 2 is the absorbent article described in claim 1, wherein the tensile strength in the width direction of the nonwoven fabric forming the top sheet is greater than that of the nonwoven fabric forming the upper absorbent sheet.

[0010] The invention described in claim 3 is an absorbent article according to claim 1 or 2, wherein the fineness of the nonwoven fabric forming the top sheet is 1.1 times or more the fineness of the nonwoven fabric forming the upper absorbent sheet.

[0011] The invention described in claim 4 is an absorbent article according to any one of claims 1 to 3, wherein the basis weight of the nonwoven fabric forming the top sheet is 1.1 times or more the basis weight of the nonwoven fabric forming the upper absorbent sheet.

[0013] Claim 5 The invention described is as described in claims 1 to 4An absorbent article according to any one of the above, wherein the peel strength of the second joint portion is smaller than the peel strength of the first joint portion. Claim 6 The invention described in claim 5 is an absorbent article according to any one of claims 1 to

Advantages of the Invention

[0014] According to the present invention, it is possible to improve liquid diffusibility and suppress liquid return.

Brief Description of the Drawings

[0015] [Figure 1] It is a plan view showing an absorbent article. [Figure 2] It is a cross-sectional view showing an absorbent article. [Figure 3] It is a plan view showing a main body portion. [Figure 4] It is an enlarged cross-sectional view showing an absorbent core. [Figure 5] It is a diagram for explaining the joining of an upper absorbent body sheet and a top sheet. [Figure 6] It is a cross-sectional view showing an absorbent core in which a superabsorbent material has swollen.

Modes for Carrying Out the Invention

[0016] FIG. 1 is a plan view showing an absorbent article 1 according to one embodiment of the present invention in an unfolded state. The absorbent article 1 is an auxiliary absorbent pad that is attached to the inside (i.e., the wearer side) of an outer garment such as a disposable diaper worn by a wearer and receives excrement such as urine from the wearer. In FIG. 1, the absorbent article 1 is drawn with the side that contacts the wearer during wearing facing forward.

[0017] Figure 2 is a cross-sectional view of the absorbent article 1, taken by cutting it at position II-II in Figure 1 with a plane perpendicular to the longitudinal direction (vertical direction in Figure 1). As shown in Figures 1 and 2, the absorbent article 1 comprises a substantially sheet-like main body 2 and a pair of side sheets 3. The main body 2 comprises a permeable top sheet 21, a water-repellent or impermeable back sheet 23, and a substantially sheet-like absorbent core 4 positioned between the top sheet 21 and the back sheet 23. In Figure 2, for illustrative purposes, the components of the absorbent article 1 are drawn separated in the thickness direction. Also, in Figure 1, the outline of the absorbent core 4 is drawn with a thick dashed line to facilitate understanding of the figure.

[0018] As shown in Figure 1, the absorbent core 4 and the main body 2 are roughly rectangular in shape when viewed from above, extending in the longitudinal direction. More specifically, the absorbent core 4 and the main body 2 are hourglass-shaped, with the width at both ends in the longitudinal direction being greater than the width at the center. The outer shape of the absorbent core 4 is the same as the outer shape of the lower absorbent 46, which will be described later. The main body 2 is slightly larger than the absorbent core 4, and the entire absorbent core 4 is located inside the outer edge of the main body 2. The outer shape of the main body 2 is the same as the outer shape of the back sheet 23, and the length in the longitudinal direction and the width in the width direction of the back sheet 23 are greater than the length and width of the absorbent core 4. As shown in Figure 2, the top sheet 21 covers the main surface of the absorbent core 4 on the wearer side. The back sheet 23 covers the other main surface of the absorbent core 4, i.e., the main surface opposite to the wearer. In this embodiment, the top sheet 21 is roughly rectangular (see Figure 3, described later) and is joined to the back sheet 23 via hot melt adhesive or the like on the outside of the absorbent core 4 in the longitudinal direction.

[0019] The top sheet 21 is a permeable sheet material that quickly captures moisture from the wearer's excrement and moves it to the absorbent core 4. The absorbent core 4 absorbs the moisture that has permeated the top sheet 21 and quickly fixes it in place. The back sheet 23 prevents moisture from the excrement that has reached the back sheet 23 from seeping out of the main body 2. Details of the structure of the absorbent core 4 will be described later.

[0020] As shown in Figures 1 and 2, a pair of side sheets 3 are arranged on both sides of the main body 2 (i.e., both sides in the width direction perpendicular to the longitudinal direction) and extend over approximately the entire length of the main body 2 in the longitudinal direction. Each side sheet 3 comprises a side sheet body 31 and a side wall elastic member 32. As shown in Figure 2, the side sheet body 31 comprises a fixing portion 33 and a side wall portion 34. The fixing portion 33 extends over approximately the entire length of the main body 2 in the longitudinal direction on the side of the main body 2. The fixing portion 33 is fixed to the side of the main body 2. The fixing portion 33 and the main body 2 are fixed via an adhesive such as a hot melt adhesive.

[0021] The side wall portion 34 is continuous with the inside of the fixing portion 33 in the width direction and extends longitudinally together with the fixing portion 33. The side wall portion 34 is overlapped on the main body portion 2 at both ends in the longitudinal direction and fixed with hot melt adhesive or the like. In the absorbent article 1, a pair of side wall portions 34 are provided on the top sheet 21 side near both sides of the absorbent core 4. At the ends of each side wall portion 34, i.e., the free ends, a side wall elastic member 32 extending in the longitudinal direction is joined in an extended state with hot melt adhesive or the like. The side wall elastic member 32 includes at least one elastic element extending in the longitudinal direction. When the side wall elastic member 32 contracts, the side wall portion 34 rises toward the wearer, forming a three-dimensional gather.

[0022] As mentioned above, polyolefin-based, rubber-based, vinyl acetate-based, and the like can be used as hot melt adhesives. The joining of the top sheet 21 and the back sheet 23, and the joining of the side sheet 3 and the main body 2 may be performed by heat fusion bonding or ultrasonic bonding. In addition, the joining of the side wall elastic members 32 may be performed by ultrasonic bonding or the like.

[0023] The top sheet 21 is formed, for example, from a permeable nonwoven fabric. This nonwoven fabric is formed from hydrophobic fibers (such as polypropylene, polyethylene, polyester, polyamide, or nylon) whose surface has been hydrophilically treated with a surfactant. The nonwoven fabric may also be formed from hydrophilic fibers such as cellulose, rayon, or cotton. Examples of such nonwoven fabrics include air-through nonwoven fabrics, point-bonded nonwoven fabrics, spunbond nonwoven fabrics, or spunlace nonwoven fabrics.

[0024] The backsheet 23 is formed from, for example, a liquid-impermeable or liquid-repellent nonwoven fabric (such as spunbond nonwoven fabric, meltblown nonwoven fabric, or SMS (spunbond-meltblown-spunbond) nonwoven fabric) made of hydrophobic fibers, or from a liquid-impermeable or liquid-repellent plastic film. The backsheet 23 may also be a laminate of the nonwoven fabric and the plastic film. When a plastic film is used for the backsheet 23, it is preferable to use a plastic film that is breathable (i.e., has moisture permeability) from the viewpoint of preventing stuffiness in the absorbent article 1 and improving the wearer's comfort.

[0025] The side sheet body 31 is formed from, for example, an impermeable or liquid-repellent nonwoven fabric (such as air-through nonwoven fabric, point-bonded nonwoven fabric, spunbond nonwoven fabric, melt-blown nonwoven fabric, or SMS nonwoven fabric) made of hydrophobic fibers. As the elastic element of the side wall elastic member 32, for example, polyurethane yarn, a strip of polyurethane film, or yarn-like or strip-like natural rubber can be used. In this embodiment, polyurethane yarn is used as the elastic element.

[0026] Figure 3 is a plan view showing the main body 2 of the absorbent article 1, and the side sheet 3 is not shown. Figure 4 is a cross-sectional view showing an enlarged view of the absorbent core 4 in Figure 2. The absorbent core 4 comprises an upper absorbent 41 and a lower absorbent 46. The upper absorbent 41 is positioned above the lower absorbent 46 (on the wearer's side). That is, the lower absorbent 46 is positioned below the upper absorbent 41 (on the outside). In Figure 3, the outer shape of the upper absorbent 41 is shown by a dashed line.

[0027] The lower absorbent layer 46 has a sheet-like fiber aggregate. The lower absorbent layer 46 is positioned between the upper absorbent layer 41 and the backsheet 23 and is joined to one or both. For example, the size of the lower absorbent layer 46 in the width direction is larger than that of the upper absorbent layer 41, and the size of the lower absorbent layer 46 in the longitudinal direction is approximately the same as that of the upper absorbent layer 41. The lower absorbent layer 46 is formed from, for example, recycled hydrophilic fibers such as cellulose, rayon, or cotton, synthetic fibers, pulp fibers, etc. The lower absorbent layer 46 may also contain highly absorbent materials. Typically, the lower absorbent layer 46 is wrapped in tissue paper or a permeable nonwoven fabric. The shape of the lower absorbent layer 46 is not limited to that shown in Figure 3. For example, the lower absorbent layer 46 may be provided with recesses that extend in the longitudinal direction.

[0028] As shown in Figure 4, the upper absorbent 41 comprises a permeable upper absorbent sheet 411, a permeable lower absorbent sheet 412, and a highly absorbent material 413. The upper absorbent sheet 411 is positioned on the top sheet 21 side, and the lower absorbent sheet 412 is positioned on the back sheet 23 side relative to the upper absorbent sheet 411. The upper absorbent 41 is a roughly rectangular shape that is long in the longitudinal direction, and both the upper absorbent sheet 411 and the lower absorbent sheet 412 have shapes that extend in the longitudinal direction. The outer shapes of the upper absorbent sheet 411 and the lower absorbent sheet 412 are roughly the same. The upper absorbent 41 is provided with a plurality of material-present regions 42 to which the highly absorbent material 413 is fixed, and a plurality of material-absent regions 43 to which the highly absorbent material 413 is absent. In Figure 3, parallel diagonal lines are drawn over the material-present regions 42.

[0029] The multiple material-containing regions 42 are strip-shaped, each extending substantially parallel to the longitudinal direction, and are arranged with gaps in the width direction (i.e., separated from each other). In other words, multiple material-containing regions 42 are provided, arranged in a stripe-like pattern extending in the longitudinal direction. In each material-containing region 42, a highly absorbent material 413 is placed between the upper absorbent sheet 411 and the lower absorbent sheet 412 and fixed to one or both of them with a hot-melt adhesive or the like. In other words, the highly absorbent material 413 is fixed to the material-containing region 42. In the examples of Figures 3 and 4, the widths of the multiple material-containing regions 42 are approximately equal to each other, but they may be different.

[0030] The multiple material-free regions 43 are the regions in the upper absorber 41 excluding the multiple material-present regions 42. Each of the multiple material-free regions 43 is a strip extending along the longitudinal direction. In the examples of Figures 3 and 4, the widths of the multiple material-free regions 43 are equal, but they may be different. For example, the width of each material-free region 43 is smaller than the width of the material-present region 42. The material-free regions 43 and material-present regions 42 are arranged alternately in the width direction. That is, a material-free region 43 is provided between two adjacent material-present regions 42 in the width direction. In Figure 3, the boundary line between the material-free regions 43 and material-present regions 42 is shown by a dashed line thinner than the dashed line showing the outline of the upper absorber 41.

[0031] Typically, in each material-free region 43, the highly absorbent material 413 is not present between the upper absorbent sheet 411 and the lower absorbent sheet 412. The highly absorbent material 413 does not need to be substantially absent; a small amount may be present. In the material-free region 43, a first joint 44 is provided where the upper absorbent sheet 411 and the lower absorbent sheet 412 are joined to each other. The first joint 44 is the portion of the material-free region 43 of the joined upper absorbent sheet 411 and lower absorbent sheet 412. In one example, the first joint 44 is formed by adhesive bonding using a hot-melt adhesive or the like. Adhesive bonding is performed, for example, by slot coating, curtain coating, etc., and the adhesive is applied to the entire material-free region 43 between the upper absorbent sheet 411 and the lower absorbent sheet 412. Preferably, in addition to adhesive bonding, heat sealing (thermal fusion bonding) is performed. In this case, the first joint 44 is formed by a composite joining of the upper absorbent sheet 411 and the lower absorbent sheet 412. A composite joining is not necessarily required at the first joint 44.

[0032] At the first joint 44, the upper absorbent sheet 411 and the lower absorbent sheet 412 are joined over the entire material-free region 43. In a very small part of the material-free region 43, the upper absorbent sheet 411 and the lower absorbent sheet 412 may not be joined. In the material-free region 43, the ratio of the adhesive adhesion area between the upper absorbent sheet 411 and the lower absorbent sheet 412 to the area of ​​the material-free region 43, that is, the area ratio of the joint region between the upper absorbent sheet 411 and the lower absorbent sheet 412 in the material-free region 43, is, for example, 80% or more, preferably 85% or more, and more preferably 90% or more. As described above, the material-free region 43 may be a region containing only a small amount of the highly absorbent material 413, that is, a region where the density of the highly absorbent material 413 is sufficiently lower than that of the material-present region 42 (i.e., a low-density material region).

[0033] The upper absorbent sheet 411 is joined to the top sheet 21. The joining of the upper absorbent sheet 411 and the top sheet 21 is performed, for example, by spiral coating as shown in Figure 5. In spiral coating, a spiral pattern is formed in which an adhesive 451, such as a hot melt adhesive, is applied spirally along the longitudinal direction, and this spiral pattern is arranged in the width direction. Therefore, as shown in Figure 4, the upper absorbent sheet 411 and the top sheet 21 are partially joined by the adhesive 451. In the following description, the joint between the upper absorbent sheet 411 and the top sheet 21 in the material-free region 43 is referred to as the "second joint 45". The second joint 45 is the portion of the material-free region 43 of the upper absorbent sheet 411 and the top sheet 21 that are joined to each other. In the material-free region 43 where the second joint 45 is provided, the upper absorbent sheet 411 and the top sheet 21 are partially joined by the adhesive 451. In one example of the second joint 45, adhesive 451 is present only in a portion of the material-free region 43 in the width direction. In the second joint 45, adhesive 451 may be present discretely in the longitudinal or width direction.

[0034] The second joint 45 does not necessarily have to be provided in all material-free regions 43. In the example in Figure 4, the top sheet 21 and the upper absorbent sheet 411 are not joined in the central material-free region 43 in the width direction, and the second joint 45 is not provided. Of course, the second joint 45 may be provided in the central material-free region 43 (i.e., the second joint 45 may be provided in all material-free regions 43), and the top sheet 21 and the upper absorbent sheet 411 may not be joined in any material-free region 43 other than the central material-free region 43. In absorbent article 1, the top sheet 21 and the upper absorbent sheet 411 are partially joined in at least one material-free region 43, and the second joint 45 is provided.

[0035] In each material-free region 43 where the second joint portion 45 is provided, the ratio of the total area of ​​the area to which the adhesive 451 adheres to the material-free region 43, that is, the area ratio of the joint region between the top sheet 21 and the upper absorbent sheet 411 in the material-free region 43, is, for example, 50% or less, preferably 45% or less, and more preferably 40% or less. This makes it easier for the top sheet 21 to peel off from the upper absorbent sheet 411 in the material-free region 43 when the highly absorbent material 413 absorbs moisture and swells, as will be described later. The area ratio of the joint region is, for example, 1% or more. When manufacturing the absorbent article 1, it is preferable that the top sheet 21 and the upper absorbent sheet 411 are joined together and do not shift relative to each other. From this viewpoint, the area ratio of the joint region is, for example, 10% or more, preferably 15% or more, and more preferably 20% or more.

[0036] As previously described, at the first joint 44, the upper absorbent sheet 411 and the lower absorbent sheet 412 are joined together as a whole (in reality, a more complex joining is performed), and at the second joint 45, the top sheet 21 and the upper absorbent sheet 411 are joined together in part. Therefore, when a material-free region 43 is cut out from the absorbent article 1 and a peel test is performed on the first joint 44 and the second joint 45, the load at which the top sheet 21 and the upper absorbent sheet 411 peel and separate at the second joint 45 is smaller than the load at which the upper absorbent sheet 411 and the lower absorbent sheet 412 peel and separate at the first joint 44. In other words, the peel strength of the second joint 45 is smaller than the peel strength of the first joint 44.

[0037] The upper absorbent sheet 411 and the lower absorbent sheet 412 of the upper absorbent layer 41 are formed from a permeable nonwoven fabric, for example, similar to the top sheet 21. The nonwoven fabric is formed from hydrophobic fibers (polypropylene, polyethylene, polyester, polyamide, nylon, etc.) whose surface has been hydrophilically treated with a surfactant. The nonwoven fabric may also be formed from hydrophilic fibers such as cellulose, rayon, or cotton. The nonwoven fabric is, for example, an air-through nonwoven fabric, a point-bonded nonwoven fabric, a spunbond nonwoven fabric, or a spunlace nonwoven fabric. As the superabsorbent material 413, for example, granular superabsorbent polymer (SAP) or fibrous superabsorbent fiber (SAF) can be used.

[0038] Here, we compare the nonwoven fabric forming the top sheet 21 with the nonwoven fabric forming the upper absorbent sheet 411. In absorbent article 1, the fineness of the nonwoven fabric of the top sheet 21 is greater than that of the nonwoven fabric of the upper absorbent sheet 411. In one example, the fineness of the nonwoven fabric of the top sheet 21 is 4.4 dtex or greater. The fineness of the nonwoven fabric of the top sheet 21 is, for example, 1.1 times or more, preferably 1.5 times or more, compared to the fineness of the nonwoven fabric of the upper absorbent sheet 411. There is no particular upper limit, but for example, it is 3.5 times, preferably 3.0 times. Also, the basis weight of the nonwoven fabric of the top sheet 21 is greater than that of the nonwoven fabric of the upper absorbent sheet 411. In one example, the basis weight of the nonwoven fabric of the top sheet 21 is 25 g / m². 2 That concludes the explanation. The basis weight of the nonwoven fabric of the top sheet 21 is, for example, 1.1 times or more, preferably 1.2 times or more, than the basis weight of the nonwoven fabric of the upper absorbent sheet 411. The upper limit is not particularly limited, but for example it is 2.5 times, preferably 2.0 times.

[0039] In one example of absorbent article 1, the fiber orientation of the nonwoven fabric of the top sheet 21 (typically the longitudinal direction of the nonwoven fabric drawn from the roll) is substantially parallel to the longitudinal direction of the main body 2, and the fiber orientation of the nonwoven fabric of the upper absorbent sheet 411 is also substantially parallel to the longitudinal direction of the main body 2. Therefore, both the nonwoven fabric of the top sheet 21 and the nonwoven fabric of the upper absorbent sheet 411 are not easily stretched in the direction corresponding to the longitudinal direction of the main body 2 (hereinafter simply referred to as the "longitudinal direction").

[0040] Furthermore, in the tensile test described later, the load (hereinafter simply referred to as the "3% stretch load") when the nonwoven fabric of the top sheet 21 is stretched by 3% in the direction corresponding to the width direction of the main body 2 (hereinafter simply referred to as the "width direction") is 2.0 times or more the 3% stretch load in the width direction of the nonwoven fabric of the upper absorbent sheet 411. The 3% stretch load of the top sheet 21 in the width direction is preferably 2.2 times or more the 3% stretch load of the upper absorbent sheet 411. There is no particular upper limit, but for example it is 10.0 times. As described above, the top sheet 21 is less stretchable in the width direction than the upper absorbent sheet 411. In other words, the upper absorbent sheet 411 is more stretchable in the width direction than the top sheet 21. In practice, the lower absorbent sheet 412 is also more stretchable in the width direction than the top sheet 21.

[0041] In absorbent article 1, when the wearer excretes urine or other bodily fluids, some of the moisture that reaches the absorbent core 4 via the top sheet 21 passes through the material-free region 43 and is guided to the lower absorbent layer 46, where it is absorbed. The remaining portion of the moisture is absorbed by the superabsorbent material 413 in the material-present region 42 of the upper absorbent layer 41, causing the superabsorbent material 413 to swell, as shown in Figure 6. Figure 6 shows a state where a relatively large amount of moisture has been absorbed by the superabsorbent material 413.

[0042] At this time, the upper absorbent sheet 411 and the lower absorbent sheet 412 are easily stretched in the width direction, so in the material-present region 42, the upper absorbent sheet 411 and the lower absorbent sheet 412 deform in accordance with the swollen highly absorbent material 413. In the material-absent region 43, the joint (first joint 44) between the upper absorbent sheet 411 and the lower absorbent sheet 412 is maintained to some extent.

[0043] On the other hand, the top sheet 21 is not easily stretched in the width direction. Therefore, in the material-free region 43 where the second joint 45 (see Figure 4) is provided, if the swelling rate (water absorption) of the highly absorbent material 413 in the adjacent material-present region 42 increases, the top sheet 21 will no longer follow the deformation of the highly absorbent material 413, and the top sheet 21 will delaminate from the upper absorbent sheet 411 in the material-free region 43. In other words, the second joint 45 will delaminate. As a result, a space 81 (hereinafter referred to as the "delamination space 81") is formed between the top sheet 21 and the upper absorbent sheet 411 in the material-free region 43. In reality, the top sheet 21 and the upper absorbent sheet 411 do not delaminate over the entire material-free region 43 in the longitudinal direction, but rather delamination occurs in areas where the swelling rate of the highly absorbent material 413 in the adjacent material-present region 42 is large.

[0044] In absorbent article 1, the delamination space 81 promotes the diffusion of moisture in the longitudinal direction, making it possible to utilize a wide area of ​​the absorbent core 4 for moisture absorption. Furthermore, even if moisture seeps out from the lower absorbent layer 46 due to the wearer's body pressure, etc., the delamination space 81 retains the moisture, suppressing the seepage of moisture onto the wearer-facing side of the top sheet 21 (i.e., liquid return). From the viewpoint of improving liquid diffusion and suppressing liquid return, delamination between the top sheet 21 and the upper absorbent sheet 411 in the material-free region 43 only needs to occur in at least a portion of the longitudinal direction. Note that if there is a material-free region 43 where the second joint portion 45 is not provided (i.e., the top sheet 21 and the upper absorbent sheet 411 are not joined), a space similar to the delamination space 81 is formed between the top sheet 21 and the upper absorbent sheet 411 in that material-free region 43 as well.

[0045] Next, an experimental example relating to absorbent article 1 will be described. First, the tensile properties of the top sheet 21 and the upper absorbent sheet 411 were measured. For the measurement of tensile properties, a nonwoven fabric forming the top sheet 21 of absorbent article 1 and a nonwoven fabric forming the upper absorbent sheet 411 were prepared. In addition, a nonwoven fabric of a top sheet used in conventional absorbent articles (hereinafter referred to as the "comparative example top sheet") was also prepared. The fineness of the nonwoven fabric of the top sheet 21 is 4.4 dtex, the fineness of the nonwoven fabric of the upper absorbent sheet 411 is 2.0 dtex, and the fineness of the nonwoven fabric of the comparative example top sheet is 2.2 dtex. The basis weight of the nonwoven fabric of the top sheet 21 is 25 g / m². 2 The basis weight of the nonwoven fabric of the upper absorbent sheet 411 is 17 g / m². 2 In the comparative example, the basis weight of the nonwoven fabric top sheet was 18 g / m². 2 The fineness and basis weight of the top sheet 21 and upper absorbent sheet 411 in absorbent article 1 are not limited to those stated above. Tensile tests were performed on each nonwoven fabric in accordance with JIS L1913 6.3.1 in both the longitudinal and width directions, and the 3% elongation load, tensile strength, and tensile elongation were measured as tensile properties. Table 1 shows the measurement results of the tensile properties.

[0046] [Table 1]

[0047] As previously mentioned, the longitudinal direction is approximately parallel to the fiber orientation of the nonwoven fabric (typically the longitudinal direction of the nonwoven fabric as it is drawn from the roll), and the width direction is approximately perpendicular to the fiber orientation of the nonwoven fabric. The 3% elongation load is the load applied when the sample is stretched by 3% in each direction, relative to the sample length before testing. Nonwoven fabrics with larger 3% elongation loads in each direction require greater force to stretch by 3% of the standard length, and are therefore more difficult to stretch in that direction. Tensile strength is the value obtained by dividing the load applied when the sample is stretched until it breaks in the tensile test by the width of the sample (50 mm). Tensile elongation is the elongation rate of the sample until it breaks in the tensile test.

[0048] When focusing solely on the width direction, the nonwoven fabric of top sheet 21 was greater than that of the nonwoven fabric of the upper absorbent sheet 411 and the nonwoven fabric of the comparative example's top sheet in terms of 3% elongation load, tensile strength, and tensile elongation. Specifically, the 3% elongation load in the width direction of top sheet 21 was greater than that of the nonwoven fabric of the comparative example's top sheet and more than 2.0 times that of the nonwoven fabric of the upper absorbent sheet 411. Thus, top sheet 21 is less elongated in the width direction than the top sheet of the comparative example and significantly less elongated than the upper absorbent sheet 411. Furthermore, the tensile strength in the width direction of top sheet 21 is sufficiently greater than that of the nonwoven fabric of the upper absorbent sheet 411 and the nonwoven fabric of the comparative example's top sheet.

[0049] Next, the absorption properties of absorbent article 1 were measured. For the measurement of absorption properties, in addition to absorbent article 1, an absorbent article (hereinafter referred to as "comparative absorbent article") was prepared in which the top sheet 21 of absorbent article 1 was replaced with the top sheet of the comparative example. Then, the absorption rate and liquid return amount were measured as absorption properties for both absorbent article 1 and comparative absorbent article. Table 2 shows the measurement results of the absorption properties.

[0050] [Table 2]

[0051] In measuring the absorption rate, an absorption rate measuring ring (inner diameter 25 mm, height 200 mm, weight 1293 g) was placed in the center of the absorbent material to be measured. 150 ml of physiological saline (salt concentration 1.0%) was injected, and the time from the start of injection until the absorption of the physiological saline was completed was measured to determine the absorption time (seconds). After standing for 10 minutes, a second injection of physiological saline was performed, and the absorption time was determined. Furthermore, after standing for another 10 minutes, a third injection of physiological saline was performed, and the absorption time was determined.

[0052] For measuring the amount of liquid return, 150cc of physiological saline (1.0% sodium chloride concentration) was poured vertically into the center of the groin area of ​​the absorbent material using a separatory funnel. The vertical distance from the tip of the separatory funnel's dropping end to the top sheet of the absorbent material was 5cm. Time was measured simultaneously with the start of the inflow, and after 5 minutes, 25 sheets of filter paper with a diameter of 110mm were placed on top of the inflow area. A 3.5kg weight was then placed on top for 30 seconds, and the amount of liquid return (g) was measured by the difference in weight of the filter paper before and after the test. Furthermore, 10 minutes after the start of the first inflow, another 150cc of physiological saline was poured into the same area as the first measurement. 5 minutes after the start of the second inflow, 25 new sheets of filter paper were placed on top. 5 minutes and 30 seconds after the start of the second inflow, the amount of liquid return was measured in the same manner as the first measurement (second measurement). The amount of liquid return up to the third time was measured in the same manner as the first and second times.

[0053] Regarding the absorption rate, in the first measurement, the absorption time of absorbent article 1 was almost the same as that of the comparative absorbent article. However, in the second and third measurements, the absorption time of absorbent article 1 was significantly shorter than that of the comparative absorbent article. In other words, in the second and third measurements, the absorption rate of absorbent article 1 was higher than that of the comparative absorbent article.

[0054] Regarding the amount of liquid return, in the first measurement, the amount of liquid return in absorbent article 1 was almost the same as that in the comparative absorbent article. However, in the second and third measurements, the amount of liquid return in absorbent article 1 was significantly less than that of the comparative absorbent article. Thus, in absorbent article 1, the return of moisture from the absorbent core 4 to the wearer side of the top sheet was suppressed compared to the comparative absorbent article.

[0055] In the measurement of absorption properties, the reason why the absorption rate of absorbent article 1 increased and the amount of liquid return decreased (i.e., the absorption properties improved) is not entirely clear. However, in absorbent article 1, delamination occurred between the top sheet 21 and the upper absorbent sheet 411 in the material-free region 43, and it is thought that the delamination space 81 formed by this delamination contributed to the improvement in absorption properties.

[0056] As described above, in the absorbent article 1, the absorbent core 4 comprises an upper absorbent 41 in which a highly absorbent material 413 is fixed between an upper absorbent sheet 411 and a lower absorbent sheet 412, and a lower absorbent 46 having a sheet-like fiber aggregate. In the upper absorbent 41, a plurality of material-present regions 42 to which the highly absorbent material 413 is fixed are arranged with gaps in the width direction, and a material-absent region 43 in which the highly absorbent material 413 is absent is provided between two material-present regions 42 adjacent to each other in the width direction. In each material-absent region 43, a first joint 44 is provided in which the upper absorbent sheet 411 and the lower absorbent sheet 412 are joined together as a whole. In at least one material-absent region 43, a second joint 45 is provided in which the top sheet 21 and the upper absorbent sheet 411 are partially joined together. Furthermore, the load when the nonwoven fabric forming the top sheet 21 is stretched by 3% in the width direction is 2.0 times or more the load when the nonwoven fabric forming the upper absorbent sheet 411 is stretched by 3% in the width direction.

[0057] In absorbent article 1, the swelling of the highly absorbent material 413 causes the top sheet 21 to peel away from the upper absorbent sheet 411 in the material-free region 43, forming a peel space 81 between the top sheet 21 and the upper absorbent sheet 411. As a result, the peel space 81 improves liquid diffusion and suppresses liquid backflow. Furthermore, it prevents the top sheet 21 from significantly indenting towards the absorbent core 4 in the material-free region 43, thereby suppressing a decrease in wearing comfort.

[0058] Preferably, the tensile strength in the width direction of the nonwoven fabric forming the top sheet 21 is greater than that of the nonwoven fabric forming the upper absorbent sheet 411. This allows the top sheet 21 to be properly formed without damage, thereby more reliably achieving improved liquid diffusion and suppression of liquid backflow.

[0059] Preferably, the fineness of the nonwoven fabric forming the top sheet 21 is 1.1 times or more the fineness of the nonwoven fabric forming the upper absorbent sheet 411. In this way, the higher fineness of the top sheet 21 makes the surface area of ​​the fibers to which the adhesive adheres on the top sheet 21 smaller than that of the upper absorbent sheet 411, making it easier to peel the top sheet 21 from the upper absorbent sheet 411 in the material-free region 43.

[0060] Preferably, the basis weight of the nonwoven fabric forming the top sheet 21 is 1.1 times or more that of the nonwoven fabric forming the upper absorbent sheet 411. In this way, the higher basis weight of the top sheet 21 makes the rigidity of the top sheet 21 higher than that of the upper absorbent sheet 411, making it easier to peel the top sheet 21 from the upper absorbent sheet 411 in the material-free region 43.

[0061] Preferably, in the material-free region 43 where the second joint 45 is provided, the area ratio of the joint region between the top sheet 21 and the upper absorber sheet 411 is 1% or more and 50% or less. This allows for easy delamination of the top sheet 21 due to swelling of the highly absorbent material 413, thereby forming a delamination space 81. Furthermore, since the delamination strength of the second joint 45 is lower than that of the first joint 44, delamination of the top sheet 21 can be made more reliable.

[0062] The absorbent article 1 described above can be deformed in various ways.

[0063] If the 3% elongation load in the width direction of the nonwoven fabric of the top sheet 21 is 2.0 times or more the 3% elongation load of the nonwoven fabric of the upper absorbent sheet 411, then the tensile strength in the width direction of the nonwoven fabric of the top sheet 21 may be less than or equal to the tensile strength of the nonwoven fabric of the upper absorbent sheet 411. Similarly, the fineness of the nonwoven fabric of the top sheet 21 may be less than 1.1 times the fineness of the nonwoven fabric of the upper absorbent sheet 411, and the basis weight of the nonwoven fabric of the top sheet 21 may be less than 1.1 times the basis weight of the nonwoven fabric of the upper absorbent sheet 411.

[0064] If the swelling of the highly absorbent material 413 makes it possible to form a delamination space 81 between the top sheet 21 and the upper absorbent sheet 411, then the area ratio of the joint region between the top sheet 21 and the upper absorbent sheet 411 in the material-free region 43 may be greater than 50%. Furthermore, the delamination strength of the second joint 45 may be greater than or equal to the delamination strength of the first joint 44.

[0065] The joining of the upper absorbent sheet 411 and the lower absorbent sheet 412 at the first joint 44 may be by means other than adhesive bonding. Similarly, the joining of the top sheet 21 and the upper absorbent sheet 411 at the second joint 45 may be by means other than adhesive bonding.

[0066] The number and shape of the material-present regions 42 in the absorption core 4 can be varied. The material-absent regions 43 may not be linear; for example, they may extend continuously in a mesh-like pattern along the longitudinal direction.

[0067] The side sheet 3 may be omitted from the absorbent article 1. The structure of the absorbent article 1 may also be used for absorbent articles other than auxiliary absorbent pads, such as pant-type or tape-type disposable diapers.

[0068] The configurations in the above embodiments and each modified example may be combined as appropriate, as long as they do not contradict each other. [Explanation of symbols]

[0069] 1. Absorbent articles 4 Absorption core 21 Top Sheet 23 Backseat 41 Upper absorber 42 Material existence region 43 Material non-existence region 44 1st joint 45 Second joint 46 Lower absorber 411 Upper absorbent sheet 412 Lower absorbent sheet 413 Absorbent Materials

Claims

1. An absorbent article that receives excrement from the wearer, A permeable top sheet, A water-repellent or liquid-impermeable backsheet, An absorbent core is positioned between the top sheet and the back sheet and extends in the longitudinal direction, Equipped with, The aforementioned absorption core, An upper absorbent layer in which a highly absorbent material is fixed between the upper absorbent sheet and the lower absorbent sheet, A lower absorbent, which is disposed between the upper absorbent and the back sheet and has a sheet-like fiber aggregate, Equipped with, In the upper absorbent, a plurality of material-containing regions to which the highly absorbent material is fixed are arranged with gaps in the width direction, and a material-absent region where the highly absorbent material is absent is provided between two adjacent material-containing regions in the width direction. In each material-free region, a first joint is provided where the upper absorbent sheet and the lower absorbent sheet are joined together as a whole. A second joint is provided in which the top sheet and the upper absorber sheet are partially joined in at least one material-free region. In the at least one material-free region where the second joint is provided, the area ratio of the joint region between the top sheet and the upper absorber sheet is 1% or more and 40% or less. The load when the nonwoven fabric forming the top sheet is stretched by 3% in the width direction is 2.0 times or more the load when the nonwoven fabric forming the upper absorbent sheet is stretched by 3% in the width direction. An absorbent article characterized in that, when the highly absorbent material swells, the top sheet peels off from the upper absorbent sheet in at least one material-free region, and a peel space is formed between the top sheet and the upper absorbent sheet in the at least one material-free region.

2. The absorbent article according to claim 1, An absorbent article characterized in that the tensile strength in the width direction of the nonwoven fabric forming the top sheet is greater than that of the nonwoven fabric forming the upper absorbent sheet.

3. An absorbent article according to claim 1 or 2, An absorbent article characterized in that the fineness of the nonwoven fabric forming the top sheet is 1.1 times or more the fineness of the nonwoven fabric forming the upper absorbent sheet.

4. An absorbent article according to any one of claims 1 to 3, An absorbent article characterized in that the basis weight of the nonwoven fabric forming the top sheet is 1.1 times or more the basis weight of the nonwoven fabric forming the upper absorbent sheet.

5. An absorbent article according to any one of claims 1 to 4, An absorbent article characterized in that the peel strength of the second joint is less than the peel strength of the first joint.

6. An absorbent article according to any one of claims 1 to 5, An absorbent article characterized in that the top sheet and the upper absorbent sheet are joined together by a pattern of adhesive applied along the longitudinal direction being arranged in the width direction between the top sheet and the upper absorbent sheet.

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