Pants-type disposable diapers

Abstract

To provide a pants-type disposable diaper capable of achieving both of absorption performance of an absorber and a fitting property.SOLUTION: A pants-type disposable diaper 1 comprises an absorbent body 5 including an absorbent core 40, and an outer wrapper 3. The outer wrapper 3 includes stretchable areas FE and RE with stretchability, respectively provided along a lateral direction Y in a front body F and a back body R, a non-stretchable area NE located between the stretchable areas, and a precut area 3R between second parts of leg elastic members 37. The absorbent core 40 includes a lower-layer core 45 and an upper-layer core 41, and the entire upper-layer core 41 is disposed in the non-stretchable area NE. The lower-layer core 45 includes a lower-layer low rigidity part 46 extending in a longitudinal direction X, and the upper-layer core 41 includes an upper-layer low rigidity part 42 and an upper-layer high rigidity part 43. In the precut area, an end high rigidity part 44 in the upper-layer high rigidity part 43 and the lower-layer low rigidity part 46 overlap each other in plan view.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a pants-type disposable diaper. [Background technology]

[0002] Pants-type disposable diapers generally comprise an absorbent body including an absorbent core that serves as the main liquid-absorbing portion, and an outer body disposed on the non-skin-facing side of the absorbent body. Taking into consideration the wearing comfort and absorption performance, it is known that the absorbent core is provided with openings or low basis weight portions, and the outer body is provided with leg elastic members that form leg gathers around the opening edges of the leg openings. For example, the present applicant previously proposed a pants-type absorbent article (Patent Document 1) that comprises an outer body having a stretchable outer layer sheet and leg elastic members, and an absorbent core having an opening formed so as to extend in the vertical direction, with the opening having an opening on the skin-facing side or the non-skin-facing side.

[0003] Patent Document 2 discloses a pants-type absorbent article comprising an absorbent body with slits and a rear outer layer backsheet having elastic members that form leg gathers and absorbent body crossing gathers at the middle crotch edge. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6559940 [Patent Document 2] Patent No. 5486347 Summary of the Invention [Problem to be solved by the invention]

[0005] The leg elastic members described above are effective in providing a good fit around the wearer's legs, but if the leg elastic members and the absorber overlap as in Patent Document 2, the absorber may come into excessive contact with the wearer's skin as the leg elastic members contract, potentially reducing comfort. Also, if the absorber does not come into contact with the skin easily, the absorbency of the absorber may be reduced. The pants-type disposable diapers of Patent Documents 1 and 2 have room for improvement in terms of achieving both the absorption performance of the absorbent body and the wearing comfort.

[0006] The present invention relates to a pants-type disposable diaper that can achieve both the absorption performance of an absorbent body and a comfortable fit. [Means for solving the problem]

[0007] The present invention relates to a pants-type absorbent article comprising an absorbent main body having a ventral portion arranged on the ventral side of a wearer, a dorsal portion arranged on the dorsal side of the wearer, and a crotch portion located between the ventral portion and the dorsal portion, the absorbent main body having an absorbent body including an absorbent core, and an outer body arranged on the non-skin-facing side of the absorbent main body, the absorbent article having a vertical direction extending from the ventral portion through the crotch portion to the dorsal portion and a horizontal direction perpendicular to the vertical direction, the absorbent article being divided into a front body arranged on the ventral side of the wearer and a back body arranged on the dorsal side of the wearer when worn, with the center of the vertical direction as the boundary, and the absorbent article having a waist opening and a pair of leg openings. In one embodiment, it is preferable that the outer body has a front stretchable region in the front body that is stretchable along the horizontal direction, a back stretchable region in the back body that is stretchable along the horizontal direction, and a non-stretchable region located between the front stretchable region and the back stretchable region. In one embodiment, the absorbent core has a lower layer core and an upper layer core arranged on the skin-facing side of the lower layer core, and it is preferable that the entire upper layer core is arranged within the non-stretchable region. In one embodiment, the lower core preferably has a lower low stiffness portion extending in the longitudinal direction and a lower high stiffness portion having stiffness higher than that of the lower low stiffness portion. In one embodiment, the upper core preferably has an upper low-rigidity portion extending in the longitudinal direction and an upper high-rigidity portion having a higher rigidity than the upper low-rigidity portion. In one embodiment, the outer body has leg elastic members that form leg gathers, and the leg elastic members preferably have a first portion that runs along the periphery of the leg opening, and a second portion that is continuous with the first portion and extends toward the lateral center. In one embodiment, the exterior body preferably has a pre-cut region between the second portions of the left and right leg elastic members, where stretchability is not exhibited. In one embodiment, in the pre-cut region, it is preferable that the end high rigidity portion located further outward in the longitudinal direction than the upper low rigidity portion in the upper high rigidity portion overlaps with the lower low rigidity portion in a planar view. [Effects of the Invention]

[0008] According to the pants-type disposable diaper of the present invention, both the absorption performance of the absorbent body and the wearing comfort can be achieved. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing one embodiment of a pants-type disposable diaper of the present invention, and is a developed plan view schematically showing the skin-facing side of the diaper in a developed and stretched state. [Figure 2] FIG. 2 is a developed plan view schematically showing the non-skin-facing side of the disposable diaper shown in FIG. [Figure 3] FIG. 3 is an exploded perspective view of the disposable diaper shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line II-II in FIG. [Figure 5] FIG. 5 is a cross-sectional view taken along line III-III in FIG. [Figure 6] FIG. 6 is an enlarged plan view of the pre-cut area shown in FIG. [Figure 7] FIG. 7 is a schematic cross-sectional view for explaining the function and effect of the disposable diaper shown in FIG. [Figure 8] FIG. 8 is a plan view showing a joining portion that joins the exterior body and the absorbent main body shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will now be described based on preferred embodiments with reference to the drawings. Figures 1 to 8 show one embodiment of a pants-type disposable diaper 1 (hereinafter simply referred to as "diaper 1") of the present invention. As shown in Figures 1 and 2, the diaper 1 has a ventral portion A that is located on the ventral side of the wearer when worn, a dorsal portion B that is located on the dorsal side of the wearer, and a crotch portion C that is located between the ventral portion A and the dorsal portion B. The crotch portion C is a portion that is located in the crotch area of ​​the wearer when the diaper 1 is worn. The ventral portion A is a portion that is located closer to the ventral side, i.e., closer to the front, of the wearer than the crotch portion C when the diaper 1 is worn. The dorsal portion B is a portion that is located closer to the dorsal side, i.e., closer to the back, of the wearer than the crotch portion C when the diaper 1 is worn. As shown in Figures 1 and 2, the diaper 1 has a longitudinal direction X corresponding to the front-to-back direction of a wearer and a transverse direction Y perpendicular to the longitudinal direction. In this specification, the "front-to-back direction of a wearer" refers to the direction extending from the wearer's abdominal side through the crotch region to the dorsal side. The diaper 1 extends in the longitudinal direction X from the abdominal region A through the crotch region C to the dorsal region B.

[0011] As shown in Figures 1 and 2, the diaper 1 is divided into a front body F, which is located in front of the wearer (toward the belly) when worn, and a back body R, which is located behind the wearer (toward the back) with the longitudinal center (longitudinal centerline CLx) as the boundary. The longitudinal centerline CLx is an imaginary line extending in the transverse direction Y, dividing the diaper 1 in an unfolded and stretched state as shown in Figures 1 and 2 into two equal parts in the longitudinal direction X. The "unfolded and stretched state" of the diaper 1 refers to a state in which the diaper 1 is unfolded by separating it at the side seal portions (described later) and stretching the elastic members of each portion until the diaper 1 reaches its designed dimensions (the same dimensions as when the diaper 1 is unfolded flat without any influence of the elastic members). In this specification, unless otherwise specified, the dimensions of each part of the diaper 1 (e.g., the absorbent core 40), such as the length (width) in the longitudinal direction X or the lateral direction Y, refer to the dimensions (design dimensions) when the elastic members of each part are stretched and each part is stretched.

[0012] The diaper 1 comprises an absorbent body 5 having a liquid-retaining absorbent core 4, and an exterior body 3 disposed on the non-skin-facing side of the absorbent body 5. The exterior body 3 has both side edge portions AS and BS along the longitudinal direction X in the ventral and dorsal portions A and B joined together by a known joining method such as adhesive, heat sealing, or ultrasonic sealing. As a result, the diaper 1 has a pair of side seal portions (not shown) where the both side edge portions AS and BS are joined together, as well as a waist opening through which the wearer's torso is passed and a pair of leg openings (not shown) through which the wearer's lower legs are passed.

[0013] In this specification, the "skin-facing side" refers to the side of a disposable diaper or a component thereof (e.g., the topsheet 12) that faces the wearer's skin when the disposable diaper is worn, i.e., the side that is relatively close to the wearer's skin, and the "non-skin-facing side" refers to the side of a disposable diaper or a component thereof that faces away from the skin when the disposable diaper is worn, i.e., the side that is relatively far from the wearer's skin. "When worn" here refers to the normal, proper wearing position, i.e., the state in which the absorbent article (disposable diaper) is maintained in the correct wearing position.

[0014] The absorbent main body 5 has a rectangular shape in a plan view, extends in the longitudinal direction X, and is disposed at the center of the exterior body 3 in the lateral direction Y, with its longitudinal direction coinciding with the longitudinal direction X of the diaper 1 in the unfolded and stretched state. The absorbent main body 5 is joined to the exterior body 3 by a known joining means such as an adhesive. In the absorbent main body 5 of this embodiment, the skin-facing surfaces of both ends in the longitudinal direction X are covered with end-fixing sheets 34, 34 and fixed to the exterior body 3. The end-fixing sheets 34 are joined to the exterior body 3 and the absorbent main body 5 by a known joining means such as an adhesive (see FIGS. 1 and 3).

[0015] The absorbent body 5 comprises a liquid-permeable top sheet 12 that forms the skin-facing side, a liquid-impermeable or hardly liquid-permeable or water-repellent leak-proof sheet 13 that forms the non-skin-facing side, and a liquid-retaining absorbent body 4 arranged between the top sheet and the leak-proof sheet 13, which are integrated together using known joining means such as an adhesive. As shown in Fig. 4, the absorbent body 4 of this embodiment is configured to include an absorbent core 40 and a core wrap sheet 49 that covers the surface of the absorbent core 40. The entire surface of the absorbent body 4 of this embodiment, including the skin-facing surface and non-skin-facing surface, is covered with the core wrap sheet 49. Alternatively, the skin-facing surface of the absorbent core 40 may be covered with the liquid-permeable core wrap sheet 49. Furthermore, the absorbent body 4 does not necessarily have to include the core wrap sheet 49. Details of the absorbent core 40 will be described later.

[0016] The absorbent body 5 of this embodiment has elastic members 48 (hereinafter also referred to as "intermediate elastic members 48") extending in the longitudinal direction X on both sides in the lateral direction Y. The intermediate elastic members 48 of this embodiment are arranged in a stretched state between the topsheet 12 and the leak-barrier sheet 13 on the outer sides of the absorbent body 4 in the lateral direction Y. When the absorbent main body 5 includes an intermediate elastic member 48, the intermediate elastic member 48 may be disposed in a stretched state between the core wrap sheet 49 and the absorbent core 40, or may be disposed in a stretched state between the topsheet 12 and the absorbent core 40. The position of the intermediate elastic member 48 in the height direction Z is not particularly limited, and the position in the height direction Z may be different between the unfolded and stretched state of the diaper 1 and the natural state of the diaper 1. For example, the intermediate elastic member 48 may be located approximately in the center of the height of the absorbent core 4 in the natural state, or may be located closer to the non-skin-facing side than the center of the height of the absorbent core 4 in the unfolded and stretched state.

[0017] The diaper 1 of this embodiment has a pair of leakage-preventing cuffs 6, 6 made of a liquid-resistant or water-repellent and breathable sheet material on both left and right sides along the longitudinal direction X of the skin-facing surface of the absorbent main body 5 (see FIGS. 1 and 4). The leakage-preventing cuffs 6 of this embodiment have cuff-forming sheets 60 and cuff elastic members 61, with the cuff elastic members 61 arranged in a stretched state between the cuff-forming sheets 60 folded in half. The inner end of each leakage-preventing cuff 6 in the lateral direction Y is a free end, and the outer end in the lateral direction Y is wrapped around the non-skin-facing side of the absorbent main body 5, i.e., the non-skin-facing side of the leakage-preventing sheet 13, and is fixed between the leakage-preventing sheet 13 and the exterior body 3 with an adhesive or the like. Near the free end of each leakage-preventing cuff 6, one or more thread-like cuff elastic members 61 extending in the longitudinal direction X are arranged in a stretched state (see FIG. 4). The leak-proof cuffs 6 stand up at least in the crotch region C as the cuff elastic members 61 arranged in a stretched state contract, thereby preventing the outflow of excreted fluids such as urine in the lateral direction Y outward. For ease of explanation, the leak-proof cuffs 6 are not shown in FIG.

[0018] The exterior body 3 forms the outer shape of the diaper 1, i.e., the outer shapes of the abdominal portion A, the crotch portion C, and the back portion B. As shown in Figs. 1 and 2, in a plan view in an unfolded and stretched state, the abdominal portion A and the back portion B of the exterior body 3 have a rectangular shape in which the length in the horizontal direction Y is longer than the length in the vertical direction X. In the crotch portion C, both side edges along the vertical direction X, i.e., a pair of leg edges LE, LE, form an hourglass shape tapered inward in the horizontal direction Y. In a plan view in an unfolded and stretched state, the exterior body 3 of this embodiment has both side edges along the vertical direction X of the abdominal portion A and the back portion B projecting outward in the horizontal direction Y beyond both side edges along the vertical direction X of the crotch portion C. In addition, the outer edge WE of the abdominal portion A in the vertical direction X and the outer edge WE of the back portion B in the vertical direction X of the exterior body 3 extend in the horizontal direction Y, forming a waist opening in the diaper 1 having side seals. That is, these outer edges in the longitudinal direction X form the peripheral edge WE of the waist opening.

[0019] The outer body 3 is constructed by laminating multiple sheets. As shown in Fig. 3, the outer body 3 of this embodiment comprises an outer layer sheet 31, an inner layer sheet 33, and a fixing sheet 35 laminated in this order from the non-skin-facing side to the skin-facing side. The outer layer sheet 31 forms the outer surface, i.e., the non-skin-facing side, of the diaper 1 at least in the ventral portion A and the back portion B. As shown in Figs. 1 and 3, the outer layer sheet 31 is divided into a front outer layer sheet 31a disposed in the front body portion F and a back outer layer sheet 31b disposed in the back body portion R. The inner layer sheet 33 is disposed between the outer layer sheet 31 and the fixing sheet 35, and is fixed by spanning both the outer layer sheets 31a, 31b of the front body portion F and the back body portion R. In this embodiment, the inner layer sheet 33 is continuous in the longitudinal direction X from the peripheral edge WE of the waist opening in the ventral portion A to the peripheral edge WE of the waist opening in the back portion B. That is, the inner layer sheet 33 extends continuously over the entire length of the diaper 1, and the front outer layer sheet 31a and the rear outer layer sheet 31b in the longitudinal direction X form the outer surface of the diaper 1. The fixing sheet 35 is disposed on the skin-facing side of the inner layer sheet 33, and fixes leg elastic members 37 (described later) between the fixing sheet 35 and the inner layer sheet 33. These sheets 31, 33, and 35 constituting the outer body 3 are joined together by known joining means such as adhesives.

[0020] In the outer cover 3 of this embodiment, the outer sheets 31a, 31b are folded back toward the skin-facing side along the peripheral edge WE of the waist opening (see FIG. 3). That is, the outer sheets 31a, 31b form the peripheral edge WE of the waist opening, and the folded-back portions of the sheets 31a, 31b extend inward in the longitudinal direction X from the peripheral edge WE. In the outer cover 3 of this embodiment, the inner sheet 33 is also folded back toward the skin-facing side along the peripheral edge WE of the waist opening, similar to the outer sheets 31a and 31b described above. Near the peripheral edge WE of the waist opening of the outer cover 3, the folded-back portions of the outer sheets 31a and 31b and the folded-back portion of the inner sheet 33 overlap on the skin-facing side (see FIG. 5).

[0021] The outer casing 3 of this embodiment includes a plurality of thread- or strip-like elastic members 32 sandwiched and fixed in a stretched state between the folded-back portions of the inner-layer sheet 33. Specifically, a plurality of elastic members 32 (hereinafter referred to as "waist elastic members 32") are stretched in the horizontal direction Y and intermittently arranged at predetermined intervals in the vertical direction X in each of the abdominal portion A and the back portion B, which are arranged around the waist of the wearer. The waist elastic members 32 are arranged between both side edges along the vertical direction X in each of the abdominal portion A and the back portion B, i.e., between the side seal portions in the horizontal direction Y, in a region extending outward in the vertical direction X from the edge of the absorbent main body 5 in the vertical direction X. This region is arranged around the waist of the wearer and in the vicinity thereof when the garment is worn. The waist elastic members 32 extend over substantially the entire length of the abdominal portion A and the back portion B in the horizontal direction Y, and are arranged in an elastically stretchable state. This forms a substantially continuous annular waist gather along the entire circumference of the waist opening.

[0022] The outer casing 3 has a plurality of thread-like or strip-like leg elastic members 37 arranged in a stretched state between the inner-layer sheet 33 and the fixing sheet 35. Specifically, the leg elastic members 37 forming one or more leg gathers are arranged in a stretched state at the leg edges LE that form the peripheries of each of the pair of leg openings in the front body F (see FIGS. 1 and 2). The leg elastic members 37 are arranged at each of the pair of left and right leg edges LE in the front body F. These leg elastic members 37 form leg gathers at the peripheries of each of the pair of leg openings in the front body F. In the diaper 1 of this embodiment, the leg elastic members 37 are arranged only in the front body F. That is, the leg elastic members 37 are not arranged in the back body R. Alternatively, leg elastic members 37 may be arranged at the leg edges LE of the front body F and the back body R, respectively.

[0023] The leg elastic members 37 have a first portion 37a that runs along the leg edge LE, and a second portion 37b that is continuous with the first portion 37a and extends toward the center in the lateral direction Y. The first portion 37a is a portion that curves along the leg edge LE, and the second portion 37b is a portion that runs along the lateral direction Y (see FIGS. 1 and 2). In this embodiment, the second portion 37b overlaps with the absorbent core 4 in a plan view. The exterior body 3 has a pre-cut region 3R between the second portions 37b, 37b of the left and right leg elastic members 37. The pre-cut region 3R is a region sandwiched between the inner ends in the horizontal direction Y of the second portions 37b of the pair of left and right leg elastic members 37, and its position in the vertical direction X coincides with the region where the inner ends in the horizontal direction Y are located (see FIGS. 1 and 6). In this embodiment, the pre-cut region 3R does not have any leg elastic members 37, and therefore does not exhibit stretchability in the lateral direction Y. Alternatively, the pre-cut region 3R may be one in which the leg elastic members 37 are processed to be finely divided so as not to exhibit elastic stretchability.

[0024] The outer casing 3 of this embodiment has a front elasticized region FE in the front body F that is elastic in the lateral direction Y, and a back elasticized region RE in the back body R that is elastic in the same direction Y. These front elasticized region FE and back elasticized region RE are collectively referred to as "elasticized regions." In this embodiment, these "elasticized regions" are formed by an elastic sheet, which is one of the multiple sheets that make up the outer casing 3. In this embodiment, the elasticized region is formed by a front outer layer sheet 31a and a rear outer layer sheet 31b. By providing the outer casing 3 with an elasticized sheet, the diaper 1 fits the body well when worn, giving it an underwear-like appearance.

[0025] The breaking elongation of the elastic sheet is preferably 30% or more and 200% or less, more preferably 50% or more and 180% or less, from the viewpoint of further improving the wearing comfort of the diaper 1. The method for measuring breaking elongation will be described later.

[0026] The stretchable sheet used in the present invention may preferably be, for example, (1) a stretchable nonwoven fabric in which a stretchable fiber layer is integrated on one or both sides of an elastic fiber layer, (2) a stretchable nonwoven fabric in which a stretchable fiber layer is integrated on one or both sides of a net-like elastic sheet, (3) a stretchable nonwoven fabric in which a stretchable fiber layer is integrated on one or both sides of an elastic sheet made of an elastic film, or (4) a stretchable nonwoven fabric in which a large number of elastic filaments arranged so as to extend in one direction without crossing each other are integrated into a stretchable fiber layer. The term "stretchable fiber layer" as used herein includes not only a fiber layer that is stretchable before being integrated with an elastic material, but also a fiber layer that has been made stretchable by mechanical processing or the like after being integrated with an elastic material. Methods for integrating the elastic fiber layer and the extensible fiber layer include, for example, laminating them and entangling the fibers by hydroentangling or air-through, or bonding them by heat embossing, adhesives, ultrasonic waves, etc. As the elastic fiber, a fiber made from a thermoplastic elastomer such as a styrene-based elastomer, a polyolefin-based elastomer, a polyester-based elastomer, or a polyurethane-based elastomer, or an elastic resin such as rubber can be used. As the non-elastic fiber, a fiber made from a thermoplastic resin can be used.

[0027] The stretchable nonwoven fabric (4) may be, for example, one having an integrated structure in which thread-like elastic filaments are sandwiched between extensible fiber layers mainly composed of inelastic fibers. Such a stretchable nonwoven fabric is composed of two fiber sheets as fiber layers and elastic filaments interposed between the two sheets. This stretchable nonwoven fabric can be produced, for example, according to the method described in JP 2009-61743 A.

[0028] In the stretchable nonwoven fabric of (4) above, both of the two fiber sheets are stretchable. These two fiber sheets are stretchable in the same direction as the extension of the elastic filaments. Stretchable forms include (a) a form in which the constituent fibers of the sheet themselves stretch, and (b) a form in which the constituent fibers themselves do not stretch, but the sheet as a whole stretches as a result of mechanical processing or the like causing fibers bonded at their intersections to separate, or structural changes to the three-dimensional structure formed by multiple fibers due to fiber-to-fiber bonding, or the constituent fibers to tear. Examples of mechanical processing in (b) above include heat treatment, inter-roll stretching, meshing stretching using teeth or gears, and tensile stretching using a tenter.

[0029] In the stretchable nonwoven fabric of (4) above, the elastic filaments can be formed by stretching the elastic resin in a molten or softened state. The multiple elastic filaments are each continuously arranged in one direction, extending in that direction without crossing each other. The elastic filaments are bonded to the two fiber sheets in a substantially unstretched state. This bonding is achieved by fusing the constituent fibers (non-elastic fibers) of the two fiber sheets to the elastic filaments while they are embedded in the elastic filaments, rather than using an adhesive such as a hot-melt adhesive. Therefore, no adhesive is present between the two fiber sheets (stretchable fiber layers mainly composed of non-elastic fibers) and the elastic filaments bonded thereto.

[0030] The two fiber sheets constituting the stretchable nonwoven fabric (4) can each be a variety of nonwoven fabrics, such as air-through nonwoven fabrics, heat-rolled nonwoven fabrics, spunlace nonwoven fabrics, spunbonded nonwoven fabrics, and meltblown nonwoven fabrics. The two fiber sheets can be the same or different. Here, "same type of sheet" refers to sheets that are identical in terms of the sheet manufacturing process, the type of fibers constituting the sheet, the fiber diameter and length of the fibers constituting the sheet, the sheet thickness, and the basis weight. If at least one of these is different, the sheets are considered "different types of sheets." Elastic filaments are made from, for example, thermoplastic elastomers or rubber. Thermoplastic elastomers, in particular, can be melt-spun using an extruder in the same way as ordinary thermoplastic resins, and the elastic filaments obtained in this way are easily heat-sealed, making them suitable for stretchable nonwoven fabrics. From the viewpoint of further improving the fit to the wearer's body, it is preferable that the stretchable region is formed from the stretchable nonwoven fabric of (4) above. In this case, the direction of extension of the elastic filaments of the stretchable nonwoven fabric forming the stretchable region coincides with the transverse direction Y.

[0031] The front outer layer sheet 31a of this embodiment extends inward in the longitudinal direction X beyond the inner end of the abdominal portion A, reaching the end of the abdominal portion A side of the crotch portion C. The back outer layer sheet 31b of this embodiment also extends inward in the longitudinal direction X beyond the inner end of the dorsal portion B, reaching the end of the dorsal portion B side of the crotch portion C. As a result, in the longitudinal direction X, the front elasticized region FE extends to the end of the crotch portion C on the abdominal portion A side, and the rear elasticized region RE extends to the end of the crotch portion C on the dorsal portion B side (see FIG. 2).

[0032] The exterior body 3 has a non-stretchable region NE located between the front stretchable region FE and the back stretchable region RE. In this embodiment, the non-stretchable region NE is a region of the exterior body 3 that does not stretch in the lateral direction Y and is a region that is not provided with a stretchable member such as the stretchable sheet described above. In this embodiment, only a non-stretchable sheet is provided in the non-stretchable region NE. Specifically, the non-stretchable region NE is a region that does not have an outer layer sheet 31, and is provided with only an inner layer sheet 33, which is a non-stretchable sheet (see FIG. 2). In this embodiment, the non-elastic region NE is located in the center of the front body F and the back body R in the longitudinal direction X, and is sandwiched in the longitudinal direction X between the front elastic region FE and the back elastic region RE.

[0033] A non-stretchable sheet is a sheet that has virtually no stretchability in a certain direction. In this embodiment, it is a sheet that has no stretchability at least in the transverse direction Y, and preferably a sheet that has no stretchability in either the longitudinal direction X or the transverse direction Y. A non-stretchable sheet means that the sheet hardly stretches even when a pulling force is applied to the sheet in that certain direction. For example, a 15 cm long x 5 cm wide sheet sample is pulled in the longitudinal direction of the sample using a material tensile tester such as a Tensilon. If the breaking elongation at the time the sample breaks is 10% or less, the sample has virtually no stretchability in the longitudinal direction. This breaking elongation can be calculated by (sample length at break - original length of the sample) / (original length of the sample) × 100.

[0034] The absorbent body 4 of this embodiment is arranged so as to bridge the front stretchable region FE and the rear stretchable region RE via the non-stretchable region NE (see FIG. 2). The absorbent core 40 has a lower core 45 and an upper core 41 arranged closer to the skin than the lower core 45 (see Figures 3 and 4). That is, the absorbent core 40 has a laminated structure in which the upper core 41 and the lower core 45 are laminated.

[0035] The lower core 45 of this embodiment, like the absorbent body 4, has an elongated shape in the longitudinal direction X and an hourglass shape with both side edges at the center in the longitudinal direction X tapered inward in the transverse direction Y. The lower core 45 has a lower low-rigidity portion 46 extending in the longitudinal direction X and a lower high-rigidity portion 47 having higher rigidity than the lower low-rigidity portion 46 (see FIGS. 1 and 2). The lower low-rigidity portion 46 is a portion of the lower core 45 that has lower rigidity than the lower high-rigidity portion 47, which is the remaining portion. For example, the lower low-rigidity portion 46 is a low-basis weight portion in which the basis weight of the core-forming material that forms the lower core 45 is lower than the remaining portions, or a portion in which the core-forming material is missing. Examples of the latter include a slit (through-hole) that penetrates the lower core 45, or a bottomed recess. The lower high stiffness portion 47 of this embodiment surrounds the lower low stiffness portion 46 and forms the outer edge (outline) of the lower core 45. The lower high stiffness portion 47 of this embodiment has a higher basis weight of the core-forming material than the lower low stiffness portion 46.

[0036] The upper core 41 of this embodiment has a shape that is long in the longitudinal direction X, similar to the lower core 45, and is disposed in the center of the lower core 45 in the longitudinal direction X. The entire upper core 41 is disposed within the non-stretchable region NE. That is, the upper core 41 has an end 41b on the back portion B side and an end 41a on the ventral portion A side in the longitudinal direction X that are present in the non-stretchable region NE. The upper core 41 has an upper low-rigidity portion 42 extending in the longitudinal direction X, and an upper high-rigidity portion 43 having higher rigidity than the upper low-rigidity portion 42 (see FIGS. 4 and 5). The upper low-rigidity portion 42 is a low-basis weight portion in which the basis weight of the core-forming material that forms the upper core 41 is lower than other portions, or a portion in which the core-forming material is missing, and the same explanation as for the lower low-rigidity portion 46 described above applies to the upper low-rigidity portion 42. The upper high rigidity portion 43 of this embodiment surrounds the periphery of the upper low rigidity portion 42 and forms the outer edge (contour) of the upper core 41. The upper high rigidity portion 43 of this embodiment has a higher basis weight of the core-forming material than the upper low rigidity portion 42. The upper-layer high-rigidity portion 43 has end high-rigidity portions 44, 44 located on both sides of the upper-layer low-rigidity portion 42 in the longitudinal direction X. In other words, the end high-rigidity portions 44, 44 are located outward in the longitudinal direction X from the upper-layer low-rigidity portion 42 (see FIGS. 1 and 2).

[0037] In the present embodiment, both end portions in the longitudinal direction X of the lower core 45 are arranged in the stretchable region, and the narrowed central portion in the longitudinal direction X is arranged in the non-stretchable region NE (see FIG. 2). The lower low-rigidity portion 46 of this embodiment extends from the upper core 41 to both the ventral region A and the dorsal region B in the longitudinal direction X. That is, the lower low-rigidity portion 46 is longer in the longitudinal direction X than the upper core 41. Furthermore, the entire length of the lower low-rigidity portion 46 of this embodiment is contained within the non-elastic region NE. Alternatively, the lower low-rigidity portion 46 may be located in the non-elastic region NE, and the end of the lower low-rigidity portion 46 in the longitudinal direction X may extend into either or both of the front elastic region FE and the rear elastic region RE.

[0038] From the viewpoint of further improving the fit and absorption performance of the absorbent body 4, it is preferable that at least one of the upper-layer low-stiffness section 42 and the lower-layer low-stiffness section 46 is a slit (through-hole), and it is more preferable that both of these low-stiffness sections 42, 46 are slits (through-holes). Such a configuration is preferable in that it increases the flexibility of the absorbent core 40, improving the fit of the absorbent body 4, and also improving liquid diffusibility. In this embodiment, the upper low-stiffness portion 42 and the lower low-stiffness portion 46 are each a slit extending in the longitudinal direction X, and the basis weight of the material forming the absorbent core 40 (lower core 45) is 0 g / m 2 It is as follows.

[0039] In the precut region 3R, the end high-rigidity portions 44 and the lower low-rigidity portions 46 in the upper high-rigidity portions 43 overlap in a planar view. More specifically, in a planar view, the end high-rigidity portions 44 and the lower low-rigidity portions 46 at least partially overlap in a planar view within the precut region 3R (see FIG. 6). In the diaper 1 of this embodiment, the lower low-rigidity portions 46 overlap longitudinally across the precut region 3R, and the end high-rigidity portions 44 overlap the entire precut region 3R.

[0040] The absorbent core 40 of this embodiment has an upper layer core 41 arranged on the skin-facing surface of the lower layer core 45, so that the upper layer core 41 forms a convex portion that protrudes into the skin. When worn, the upper layer core 41 fits the wearer's crotch area, and the absorbent core 40 has a two-tier structure of an upper layer and a lower layer, so it has good absorption performance. In the diaper 1 of this embodiment, the high-rigidity end portions 44 and the low-rigidity end portions 46 overlap in the precut region 3R, which allows the lower core 45 to easily bend in a mountain-like fashion starting from the low-rigidity end portions 46, resulting in the high-rigidity end portions 44 curving appropriately toward the wearer's skin (see FIG. 7). This allows the upper core 41 to form a shape that easily fits closely to the wearer's crotch, resulting in a good fit. Furthermore, the fit of the upper core 41 allows for efficient absorption of excretions such as urine, resulting in excellent absorbency. Because the upper core 41 is entirely located within the non-elastic region NE, unintended deformation due to the elasticity of the elastic region is unlikely to occur. This allows the absorbent core 40 to maintain a good conforming state to the wearer's body, resulting in an excellent wearing comfort.

[0041] In order to further improve the fit of the upper core 41 and thereby further enhance the above-mentioned effects, the diaper 1 preferably has the following configuration. The width W10 (see Figure 6) of the precut region 3R is preferably 95% or more, more preferably 100% or more, and preferably 120% or less, more preferably 110% or less, of the width W3 (see Figure 1) of the upper core 41, and is preferably 95% or more and 120% or less, more preferably 100% or more and 110% or less. When the width W3 of the upper core 41 varies in the longitudinal direction X, the width is the maximum width. If the width W10 of the precut region 3R varies in the vertical direction X, the width is the maximum width.

[0042] The width W10 (see Figure 6) of the precut region 3R is preferably 35 mm or more, more preferably 40 mm or more, and is preferably 60 mm or less, more preferably 70 mm or less, and is preferably 35 mm or more and 70 mm or less, more preferably 40 mm or more and 60 mm or less. The length L10 (see Figure 6) of the precut area 3R in the vertical direction X is preferably 5 mm or more, more preferably 10 mm or more, and is preferably 30 mm or less, more preferably 20 mm or less, and is preferably 5 mm or more and 30 mm or less, more preferably 10 mm or more and 20 mm or less. The width W1 (see Figure 2) of the lower layer low rigidity portion 46 is preferably 5 mm or more, more preferably 8 mm or more, and is preferably 20 mm or less, more preferably 15 mm or less, and is preferably 5 mm or more and 20 mm or less, more preferably 8 mm or more and 15 mm or less.

[0043] In order to further improve the fit of the absorbent core 40, the width W3 (see Figure 1) of the upper core 41 is preferably 40% or more, more preferably 50% or more, and preferably 80% or less, more preferably 70% or less, and also preferably 40% or more and 80% or less, more preferably 50% or more and 70% or less, of the width W5 (see Figure 1) of the lower core 45 in the non-stretchable region NE. When the width W5 of the lower core 45 varies in the longitudinal direction X, the width is set to the minimum width.

[0044] In this embodiment, the leg elastic members 37 overlap the lower high-rigidity portions 47 of the lower core 45 in plan view (see FIG. 6). In other words, the second portions 37b of the leg elastic members 37 extend inward in the lateral direction Y of the lower core 45, and the inner ends of the second portions 37b in the lateral direction Y overlap the lower core 45. This allows the absorbent core 40 to deform appropriately, further improving the fit. When the lower core 45 has a constricted portion as in the present embodiment, it is preferable that the second portion 37b terminates within the maximum width of the lower core 45. When the maximum width of the lower core 45 differs between the dorsal side and the ventral side across the constricted portion, it is preferable that the second portion 37b terminates within the narrower maximum width. To further improve fit, the distance L9 (hereinafter also referred to as "overlapping distance L9") between the inner end of the second portion 37b in the lateral direction Y and the position in the lateral direction Y corresponding to the maximum width of the lower core 45 is preferably 10 mm or more and 60 mm or less, more preferably 20 mm or more and 50 mm or less. The position in the lateral direction Y corresponding to the maximum width is the position in the lateral direction Y of the side edge of the lower core 45 along the longitudinal direction X at the position where the lower core 45 has the maximum width, and the distance (length in the lateral direction Y) between the inner end of the second portion 37b in the lateral direction Y and an imaginary line aL (see FIG. 6) extending in the longitudinal direction X through the position in the lateral direction Y of the side edge is the overlapping distance L9 (see FIG. 6).

[0045] The upper low-stiffness portion 42 and the lower low-stiffness portion 46 are preferably disposed in the center of the diaper 1 in the transverse direction Y (see Figs. 1 and 2). In this case, when the entire length of the diaper 1 in the transverse direction Y is divided into three equal regions, the lower low-stiffness portion 46 is preferably located in the central region. This configuration allows the central portion of the absorbent core 40 to easily fit along the wearer's urinary area when worn (see Fig. 7).

[0046] As described above, the entire upper core 41 is disposed within the non-stretchable region NE. In addition, it is preferable that the entire lower low-stiffness portion 46 is also disposed within the non-stretchable region NE. This configuration prevents the absorbent core 40 from digging too deeply into the body or the leg edge portion LE of the back body piece R from digging too deeply into the buttocks due to the wearer's movements. Furthermore, by disposing the easily deformable low-stiffness portion within the non-stretchable region NE, deformation and displacement of the absorbent core 40 due to stretching of the stretchable region can be prevented. In this embodiment, the entire length of the lower low-stiffness portion 46 in the longitudinal direction X is contained within the non-stretchable region NE.

[0047] To ensure the above-mentioned effects, the length L5 of the lower low-rigidity portion 46 in the longitudinal direction X is preferably 80% or more, and more preferably 90% or more, of the length L8 (see FIG. 2) of the non-elastic region NE in the longitudinal direction X. The length L5 (see FIG. 2) of the lower low-rigidity portion 46 in the longitudinal direction X is preferably 200 mm or more, more preferably 250 mm or more, and is preferably 350 mm or less, more preferably 300 mm or less, and is preferably 200 mm or more and 350 mm or less, more preferably 250 mm or more and 300 mm or less.

[0048] From the viewpoint of further improving the fit, it is preferable that the upper core 41 has the following configuration. The length L3 (see FIG. 2) of the upper low-rigidity portion 42 in the longitudinal direction X is preferably 25% or more, more preferably 30% or more, and is preferably 90% or less, more preferably 80% or less, and is preferably 25% or more and 90% or less, more preferably 30% or more and 80% or less, of the length L4 (see FIG. 2) of the upper core 41 in the longitudinal direction X. The width W7 (see Figure 1) of the upper layer low rigidity portion 42 is preferably 10% or more, more preferably 15% or more, and preferably 40% or less, more preferably 30% or less, and also preferably 10% or more and 40% or less, more preferably 15% or more and 30% or less, of the width W3 (see Figure 1) of the upper layer core 41. The length L3 (see Figure 2) of the upper low-rigidity portion 42 in the longitudinal direction X is preferably 60 mm or more, more preferably 70 mm or more, and is preferably 210 mm or less, more preferably 180 mm or less, and is preferably 60 mm or more and 210 mm or less, more preferably 70 mm or more and 180 mm or less. The width W7 (see Figure 1) of the upper layer low rigidity portion 42 is preferably 5 mm or more, more preferably 8 mm or more, and is preferably 20 mm or less, more preferably 15 mm or less, and is preferably 5 mm or more and 20 mm or less, more preferably 8 mm or more and 15 mm or less.

[0049] From the viewpoint of further improving the fit to the body and the liquid diffusibility of the absorbent body 4, it is preferable that the lower low-rigidity section 46 and the upper low-rigidity section 42 at least partially overlap in a plan view (see FIGS. 1 and 2). With this configuration, the low-rigidity sections overlap, which improves the ability to conform to the wearer's body and improves the wearing comfort. In the absorbent core 40 of this embodiment, the entire upper low-stiffness portion 42 overlaps with the lower low-stiffness portion 46 . From the viewpoint of further enhancing the above-mentioned effect, the length in the longitudinal direction X of the portion where the lower low-rigidity portion 46 and the upper low-rigidity portion 42 overlap is preferably 80% or more, more preferably 90% or more, and preferably 100% or less, more preferably 98% or less, of the length L3 in the longitudinal direction X of the upper low-rigidity portion 42, and is preferably 80% or more and 100% or less, more preferably 90% or more and 98% or less.

[0050] FIG. 8 shows the arrangement of joints 14, 16 between the exterior body 3 and the absorbent main body 5. For ease of explanation, the elasticized and non-elasticized regions NE are not shown in FIG. 8. As described above, the exterior body 3 and the absorbent main body 5 are joined by a known joining means such as an adhesive. That is, the diaper 1 has joints 14, 16 joining the exterior body 3 and the absorbent main body 5 (FIG. 8). The diaper 1 of this embodiment has a pair of vertical joints 14 extending in the longitudinal direction X and a pair of horizontal joints 16 extending in the transverse direction Y. The vertical joints 14 are arranged on both sides of the non-skin-facing surface (leak-barrier sheet 13) of the absorbent main body 5 along the longitudinal direction X of the absorbent main body 5. The horizontal joints 16 are arranged on the non-skin-facing surface (leak-barrier sheet 13) of the absorbent main body 5 on both sides of the longitudinal direction X of the absorbent main body 5, i.e., on the end on the ventral side A side and the end on the dorsal side B side.

[0051] From the viewpoint of further improving the wearing comfort, it is preferable that at least the lower low-stiffness portion 46 does not overlap the joining portions 14, 16 in a plan view, and it is more preferable that neither the upper low-stiffness portion 42 nor the lower low-stiffness portion 46 overlaps the joining portions 14, 16. This makes it difficult for the stretch of the stretchable region to be transmitted to the lower low-stiffness portion 46 via the joining portions 14, 16, and prevents the absorbent core 40 from shifting or digging excessively into the wearer's body. The vertical joints 14 and horizontal joints 16 of this embodiment are arranged so as to surround the upper low-rigidity portion 42 and the lower low-rigidity portion 46 but not overlap these low-rigidity portions 42, 46 (see FIG. 8).

[0052] In order to achieve a better balance between fit and absorbency, the basis weight of the upper core 41 is preferably 100 g / m 2 More preferably, 130 g / m 2 or more, and preferably 200 g / m 2 or less, more preferably 180 g / m 2 and preferably 100 g / m 2 More than 200g / m 2 or less, more preferably 130 g / m 2 More than 180g / m 2 The following is the result. From the same viewpoint as above, the basis weight of the lower core 45 is preferably 80 g / m 2 More preferably, 90 g / m 2 or more, and preferably 130 g / m 2 or less, more preferably 120 g / m 2 and preferably 80 g / m 2 More than 130g / m 2 Less than 90 g / m 2 More than 120g / m 2 The following is the result. The basis weights of the upper core 41 and the lower core 45 are the basis weights of the high stiffness portions 43 and 47 .

[0053] When either or both of the upper low-rigidity portion 42 and the lower low-rigidity portion 46 are low-basis weight portions in which the core-forming material that forms the upper core 41 or the lower core 45 is present, in order to ensure the fit of the absorbent core 40, it is preferable that the basis weight of the upper core 41 or the lower core 45 be in the following range. The upper core 41 has a difference in basis weight between the upper low-rigidity portion 42 and the other portions of the upper core 41 of preferably 50 g / m 2 More preferably, 70 g / m 2 or more, and preferably 200 g / m 2 or less, more preferably 180 g / m 2 and preferably 50 g / m 2 More than 200g / m 2 Less than 70 g / m 2 More than 180g / m 2 The following is the result. The lower core 45 has a difference in basis weight between the lower low-rigidity portion 46 and the other portions of the lower core 45 of preferably 30 g / m 2 More preferably, 50 g / m 2 or more, and preferably 180 g / m 2 or less, more preferably 150 g / m 2 and preferably 30 g / m 2 More than 180g / m 2 Less than 50 g / m 2 More than 150g / m 2 The following is the result.

[0054] In order to make the outer body 3 fit the body and achieve a more underwear-like appearance, the elongation percentage of the elastic region is preferably 105% or more, more preferably 110% or more, and also preferably 130% or less, more preferably 125% or less, and also preferably 105% or more and 130% or less, more preferably 110% or more and 125% or less. The elongation rate of the elastic region is measured by the following method.

[0055] [Method for measuring elongation rate] Since the stretchable region is made of a sheet material such as a stretchable sheet, the sheet material that exhibits stretchability in the outer body is the object of measurement. First, with the diaper in its natural state, two marks are made on the sheet material that constitutes the stretchable region of the outer body, spaced 50 mm apart in the stretch direction (lateral direction Y). With the sheet material in its maximally stretched state, the distance between the two marks is measured as the stretch distance (mm). The stretch rate of the stretchable region is then calculated using the following formula (1): Elongation rate of the stretchable area (%) = [elongation distance (mm) / 50 (mm)] × 100 (1)

[0056] Next, we will explain the materials forming each part of the diaper 1. Various materials conventionally used as exterior bodies in this type of absorbent article can be used without any particular restrictions for the inner layer sheet 33 and the fixing sheet 35. For example, the inner layer sheet 33 can be made of nonwoven fabrics produced by various methods, such as spunbond nonwoven fabrics, air-through nonwoven fabrics, and needle-punched nonwoven fabrics.

[0057] The elastic members 32, 37, 48, 61 such as the leg elastic members are preferably made of elastic materials such as natural rubber, polyurethane resin, urethane foam resin, hot melt elastic material, etc., formed into threads (thread rubber) or strips (flat rubber). The top sheet 12 may be made of various nonwoven fabrics or perforated films, and the leak-proof sheet 13 may be made of resin film or a laminate of resin film and nonwoven fabric.

[0058] The absorbent core 40 of the absorbent body 4 is formed from a core-forming material such as hydrophilic fibers such as cellulose, including pulp, and a water-absorbent polymer. The absorbent core 40 is made of, for example, a stack of hydrophilic fibers, a mixed stack of the hydrophilic fibers and a water-absorbent polymer, a pile of water-absorbent polymer, or a laminated structure in which a water-absorbent polymer is supported between two absorbent sheets. The core wrap sheet 49 may be, for example, tissue paper made of hydrophilic fibers or liquid-permeable nonwoven fabric.

[0059] The present invention has been described above based on its preferred embodiments, but the present invention is not limited to the above embodiments and can be modified as appropriate within the scope of the invention. For example, the diaper 1 of the above-described embodiment has leg elastic members 37 only on the front body panel F, but it may have leg elastic members 37 on both the front body panel F and the back body panel R. Furthermore, in the diaper 1 of the above-described embodiment, the lower core 45 has an hourglass shape, but the side edges of the lower core 45 do not have to be constricted inward in the horizontal direction Y, and the side edges may be parallel to the vertical direction X. [Explanation of symbols]

[0060] 1. Pants-type disposable diapers (diapers) 3. Exterior body 4. Absorber 5. Absorbent body 6 Leak proof cuff 12 Surface sheet 13 Leak-proof sheet 31 outer layer sheet 32 waist elastic member 33 Inner layer sheet 34 End fixing sheet 35 Fixing sheet 37 Leg elastic member 40 absorbent core 41 Upper Core 42 Upper layer low rigidity part 43 Upper layer high rigidity part 45 Lower Core 46 Lower layer low rigidity part 47 Lower layer high rigidity part 48 Intermediate elastic member 49 Core Wrap Sheet 60 Cuff forming sheet 61 Cuff elastic member A. Ventral part B Dorsal part C Inseam F Front R back FE front stretch area RE Posterior stretch area NE non-stretchable region X vertical direction Y horizontal direction

Claims

1. a pants-type absorbent article comprising an absorbent main body having a ventral side portion disposed on the ventral side of a wearer, a dorsal side portion disposed on the dorsal side of the wearer, and a crotch portion located between the ventral side portion and the dorsal side portion, the absorbent main body having an absorber including an absorbent core, and an exterior body disposed on the non-skin-facing side of the absorbent main body, the article having a longitudinal direction extending from the ventral side portion through the crotch portion to the dorsal side portion and a lateral direction perpendicular to the longitudinal direction, the article being divided into a front body portion disposed on the ventral side of the wearer when worn and a back body portion disposed on the dorsal side of the wearer, with the longitudinal direction being the boundary at the center, and the article having a waist opening and a pair of leg openings, The outer body has a front stretchable region in the front body that is stretchable along the lateral direction, a back stretchable region in the back body that is stretchable along the lateral direction, and a non-stretchable region located between the front stretchable region and the back stretchable region, the absorbent core has a lower layer core and an upper layer core disposed closer to the skin-facing surface than the lower layer core, and the upper layer core is disposed entirely within the non-stretchable region; the lower core has a lower low-rigidity portion extending in the longitudinal direction and a lower high-rigidity portion having a higher rigidity than the lower low-rigidity portion, the upper core has an upper low-rigidity portion extending in the longitudinal direction and an upper high-rigidity portion having a higher rigidity than the upper low-rigidity portion, the outer body has leg elastic members that form leg gathers, and the leg elastic members have a first portion that is along the periphery of the leg opening and a second portion that is continuous with the first portion and extends toward the center in the lateral direction; the exterior body has a pre-cut region between the second portions of the left and right leg elastic members, where stretchability is not exhibited; In the pre-cut region, an end high stiffness portion located outward in the longitudinal direction from the upper low stiffness portion in the upper high stiffness portion overlaps with the lower low stiffness portion in a planar view.

2. The absorbent article according to claim 1 , wherein the upper low-stiffness portion and the lower low-stiffness portion are disposed at the center of the absorbent article in the lateral direction.

3. The absorbent article according to claim 1 or 2, wherein at least one of the upper low-stiffness portion and the lower low-stiffness portion is a slit.

4. The absorbent article according to claim 3 , wherein both the upper low-stiffness portion and the lower low-stiffness portion are slits.

5. A joining portion is provided to join the outer body and the absorbent main body, The absorbent article according to claim 1 or 2, wherein at least the lower low-stiffness portion does not overlap the joint portion in a plan view.

6. The absorbent article according to claim 1 or 2, wherein the entire lower low-stiffness portion is disposed within the non-elastic region.

7. The absorbent article according to claim 1 or 2, wherein the front elasticized region and the rear elasticized region are formed of elastic sheets that are elastic in the lateral direction.

8. The absorbent article according to claim 1 or 2, wherein the upper low-stiffness portion and the lower low-stiffness portion at least partially overlap each other in a plan view.

Images