Pant-type disposable diapers

Abstract

To provide a pants-type disposable diaper having an excellent fitting property and external appearance when being worn.SOLUTION: A pants-type disposable diaper 1 comprises an absorbent body 5 including an absorbent core 40, and an outer wrapper 3 disposed on a non-skin-facing surface side of the absorbent body 5. The absorbent core 40 includes a lower-layer core 45 and an upper-layer core 41. The upper-layer core 41 and the lower-layer core 45 respectively include low-rigidity parts 42 and 46 extending in a longitudinal direction X at positions spaced from both side edges along the longitudinal direction X of the upper-layer core 41 toward a center side. The outer wrapper 3 includes a stretchable sheet with stretchability in a lateral direction Y in a dorsal part B. In plan view, a low-rigidity-part overlapping area Kt where the low-rigidity part 42 of the upper-layer core 41 and the low-rigidity part 46 of the lower-layer core 45 overlap each other and at least a part of a joint area S of the absorbent body 5 and the outer wrapper 3 overlap each other. In the dorsal part B, the stretchable sheet and at least a part of the lower-layer core 45 overlap each other.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pant-type disposable diaper.

Background Art

[0002] Generally, a pant-type disposable diaper generally includes an absorber including an absorbent core that serves as a main liquid-absorbing part. Further, it is known to provide slits in the absorbent core in consideration of wearing comfort, absorption performance, and the like. For example, Patent Document 1 describes an absorbent article in which a central slit is formed in the center in the width direction of an absorbent core, and side slits are formed on both sides of the central slit. Further, the same document describes that the absorbent core has a two-layer structure including a first layer and a second layer disposed on the non-skin-facing surface side of the first layer.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, when the disposable diaper of the same document is worn, the part of the central slit is deformed so as to be convex toward the wearer to form a top surface, while the part of the side slit is deformed so as to be convex toward the non-skin-facing surface side, and the cross section along the width direction of the absorber becomes a W shape. Since the disposable diaper of the same document is deformed so as to be convex toward the non-skin-facing surface side in the part of the side slit, it is difficult to closely adhere to the skin of the wearer in the part of the side slit. Therefore, the absorbent article of the same document may have a reduced fit. Further, in a disposable diaper, it is required to have an appearance like underwear when worn, but in the same document, this point has not been considered at all, and there is room for improvement. [Means for solving the problem]

[0005] The present invention relates to a disposable pant-type diaper comprising an absorbent body having an absorbent core, an absorbent body having an absorbent core, and an outer body disposed on the non-skin-facing side of the absorbent body, having a longitudinal direction extending from the ventral direction through the crotch to the ventral direction and a transverse direction perpendicular to the longitudinal direction, with the center of the longitudinal direction as the boundary when worn, a front body that is disposed on the ventral side of the wearer and a back body that is disposed on the back side of the wearer, and having a waist opening and a pair of leg openings. In one embodiment, it is preferable that the absorbent core has a lower core and an upper core positioned on the skin-facing side of the lower core. Preferably, the lower core has both ends in the lateral direction and one or both ends in the vertical direction extending from the edge of the upper core. Preferably, the upper core and the lower core each have a low-rigidity portion extending in the vertical direction at a position spaced apart from both side edges of the upper core along the vertical direction toward the center. Preferably, the exterior body has a stretchable sheet on its back side that is stretchable in the lateral direction. In a plan view, it is preferable that the upper core has a low-rigidity overlapping region where the low-rigidity portion of the upper core and the low-rigidity portion of the lower core overlap. In a plan view, it is preferable that the overlapping region of the low-rigidity portion and at least a part of the joining region between the absorbent body and the outer casing overlap, and that at least a part of the stretchable sheet and the lower core overlap on the back side. [Effects of the Invention]

[0006] The present invention provides excellent fit and appearance when worn. [Brief explanation of the drawing]

[0007] [Figure 1]Figure 1 is a diagram showing one embodiment of the pants-type disposable diaper of the present invention, and is a schematic unfolded plan view showing the skin-facing side of the diaper in an unfolded and stretched state. [Figure 2] Figure 2 is an exploded perspective view of the disposable diaper shown in Figure 1. [Figure 3] Figure 3 is a cross-sectional view taken along line III-III in Figure 1. [Figure 4] Figure 4 is a cross-sectional view taken along line IV-IV in Figure 1. [Figure 5] Figure 5 is a plan view showing the joint area between the absorbent body and the outer casing in the diaper shown in Figure 1. [Figure 6] Figure 6(a) is a rear view showing the diaper being worn as shown in Figure 1, and Figure 6(b) is a schematic cross-sectional view showing the diaper being worn as shown in Figure 1. [Figure 7] Figure 7(a) is a schematic perspective view showing the saddle-shaped curved surface of the diaper shown in Figure 1, Figure 7(b) is a cross-sectional view in the X direction of Figure 7(a), and Figure 7(c) is a cross-sectional view in the Y direction of Figure 7(a). [Modes for carrying out the invention]

[0008] The present invention will be described below with reference to the drawings, based on preferred embodiments. Figures 1 to 6 show one embodiment of the pants-type disposable diaper 1 of the present invention (hereinafter simply referred to as "diaper 1"). As shown in Figure 1, diaper 1 has an abdominal portion A that is positioned on the wearer's abdominal side when worn, a dorsal portion B that is positioned on the wearer's back side, and a crotch portion C located between the abdominal portion A and the dorsal portion B. The crotch portion C is the part that is positioned in the wearer's crotch area when diaper 1 is worn. The abdominal portion A is the part that is positioned on the wearer's abdominal side, i.e., in front of the crotch portion C when diaper 1 is worn. The dorsal portion B is the part that is positioned on the wearer's back side, i.e., in rear of the crotch portion C when diaper 1 is worn. As shown in Figure 1, diaper 1 has a longitudinal direction X corresponding to the wearer's front-to-back direction and a transverse direction Y perpendicular to it. In this specification, "wearer's front-to-back direction" refers to the direction extending from the wearer's ventral side through the crotch area to the dorsal side. Diaper 1 extends in the longitudinal direction X from the ventral side A through the crotch area C to the dorsal side B.

[0009] As shown in Figure 1, diaper 1 is divided into a front panel F, which is positioned on the front (abdominal) side of the wearer when worn, and a back panel R, which is positioned on the back (rear) side of the wearer, with the vertical center line (vertical center line CLx) as the boundary. The vertical center line CLx is a hypothetical straight line that bisects diaper 1 in its unfolded and stretched state, as shown in Figure 1, in the vertical direction X and extends in the horizontal direction Y. The "unfolded and stretched state" of diaper 1 refers to the state in which diaper 1 is separated at the side seal section described later to unfold it, and then the elastic members of each part of the unfolded diaper 1 are stretched to the design dimensions (the same dimensions as when spread flat in a planar state with the influence of the elastic members completely eliminated). 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 vertical X or horizontal Y direction, refer to the dimensions (design dimensions) when the elastic members of each part are stretched and the members are extended.

[0010] The diaper 1 comprises an absorbent body 5 having a liquid-retaining absorbent material 4, and an outer casing 3 positioned on the non-skin-facing side of the absorbent body 5. The outer casing 3 has both side edges AS and BS along the longitudinal direction X on the ventral A and dorsal B portions, respectively, which are joined together by known joining means 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 side edges AS and BS are joined, and further has a waist opening through which the wearer's torso passes, and a pair of leg openings (not shown) through which the wearer's lower limbs pass.

[0011] As used herein, the "skin-facing surface" refers to the surface of a disposable diaper or its component members (e.g., the surface sheet 12) that faces the wearer's skin side when the disposable diaper is worn, that is, the side relatively closer to the wearer's skin. The "non-skin-facing surface" refers to the surface of the disposable diaper or its component members that faces the side opposite to the skin side when the disposable diaper is worn, that is, the side relatively farther from the wearer's skin. The "when worn" as referred to herein means a normal proper wearing position, that is, a state in which the correct wearing position of the absorbent article (disposable diaper) is maintained.

[0012] The absorbent body 5 has a rectangular shape in plan view and extends in the longitudinal direction X. With its longitudinal direction aligned with the longitudinal direction X of the diaper 1 in the unfolded and extended state, it is disposed at the central portion in the transverse direction Y of the outer cover 3. The absorbent body 5 is joined to the outer cover 3 by known joining means such as an adhesive. In the present embodiment, as shown in FIG. 5, the joining region S between the absorbent body 5 and the outer cover 3 has a substantially rectangular shape extending along the longitudinal direction X. The joining region S includes a central joining region Sc located in the central region in the transverse direction Y of the absorbent body 5, and side joining regions Ss, Ss located on both sides of the central joining region Sc, respectively.

[0013] In the absorbent body 5 of the present embodiment, the skin-facing surfaces at both ends in the longitudinal direction X are covered by end fixing sheets 34, 34 and are fixed to the outer cover 3. The end fixing sheets 34 are joined to the outer cover 3 and the absorbent body 5 by known joining means such as an adhesive (see FIGS. 1 and 2).

[0014] The absorbent body 5 includes a liquid-permeable surface sheet 12 forming the skin-facing surface, a liquid-impermeable or liquid-hardly-permeable or water-repellent leakage-preventing sheet 13 forming the non-skin-facing surface, and a liquid-retaining absorbent body 4 disposed between these surface sheet and leakage-preventing sheet. These are integrally formed by known joining means such as an adhesive. As shown in FIG. 3, the absorber 4 of the present embodiment includes an absorbent core 40 and a core wrap sheet 49 that covers the surface of the absorbent core 40. In the absorber 4 of the present embodiment, the entire surface including the skin-facing surface and the non-skin-facing surface is covered with the core wrap sheet 49. Instead of this, the skin-facing surface of the absorbent core 40 may be covered with the liquid-permeable core wrap sheet 49. Further, the absorber 4 may not include the core wrap sheet 49. Details of the absorbent core 40 will be described later.

[0015] The absorbent main body 5 of the present 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 thereof. The intermediate elastic member 48 of the present embodiment is arranged in an extended state between the surface sheet 12 and the leak-proof sheet 13 outside the lateral direction Y of the absorber 4. When the absorbent main body 5 includes the intermediate elastic member 48, the intermediate elastic member 48 may be arranged in an extended state between the core wrap sheet 49 and the absorbent core 40, or may be arranged in an extended state between the surface sheet 12 and the absorbent core 40. Further, 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 deployed and extended state of the diaper 1 and the natural state of the diaper 1. For example, the intermediate elastic member 48 may be located substantially at the center of the height of the absorber 4 in the natural state, or may be located on the non-skin-facing surface side of the center of the height of the absorber 4 in the deployed and extended state.

[0016] The diaper 1 of this embodiment has a pair of leak-proof cuffs 6, 6 made of a liquid-resistant or water-repellent and breathable sheet material on both the left and right sides along the longitudinal direction X on the skin-facing surface of the absorbent body 5 (see Figures 1 and 3). The leak-proof cuff 6 of this embodiment has a cuff-forming sheet 60 and a cuff elastic member 61, with the cuff elastic member 61 arranged in an extended state between two folded cuff-forming sheets 60. The inner end of the leak-proof 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 body 5, i.e., the non-skin-facing side of the leak-proof sheet 13, and fixed between the leak-proof sheet 13 and the outer casing 3 with an adhesive or the like. One or more thread-like cuff elastic members 61 extending in the longitudinal direction are arranged in an extended state near the free end of the leak-proof cuff 6 (see Figure 3). The leak-proof cuff 6, when the cuff elastic member 61, which is positioned in an extended state, contracts, stands upright at least in the crotch area C, preventing the outflow of excretory fluids such as urine in the lateral direction Y outwards. For the sake of clarity, the leak-proof cuff 6 is not shown in Figure 2.

[0017] The outer casing 3 forms the outer shape of the diaper 1, that is, the outer shape of the ventral part A, the crotch area C, and the dorsal part B. As shown in Figure 1, in a plan view when unfolded and extended, the outer casing 3 has a rectangular shape in the ventral part A and dorsal part B, where the length in the lateral direction Y is longer than the length in the longitudinal direction X, and in the crotch area C, the side edges along the longitudinal direction X, that is, the pair of leg edges LE, LE, are hourglass-shaped, tapering inward in the lateral direction Y. In this embodiment, in a plan view when unfolded and extended, the side edges along the longitudinal direction X of the ventral part A and dorsal part B protrude outward in the lateral direction Y than the side edges along the longitudinal direction X of the crotch area C. Furthermore, the outer casing 3 has a longitudinal X outer edge WE of the ventral part A and a longitudinal X outer edge WE of the dorsal part B that extends in the lateral direction Y, forming a waist opening in the diaper 1 where the side seal portion is formed. In other words, these vertical X outer edges become the peripheral edges WE of the waist opening.

[0018] The outer casing 3 is constructed by laminating multiple sheets. In this embodiment, as shown in Figure 2, the outer casing 3 is constructed by laminating an outer layer sheet 31, an inner layer sheet 33, and a fixing sheet 35 in that 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 A and dorsal B portions, and as shown in Figures 1 and 2, it is divided into a front outer layer sheet 31a located on the front body F and a rear outer layer sheet 31b located on the back body R. The inner layer sheet 33 is located between the outer layer sheet 31 and the fixing sheet 35 and is fixed by being spanned across both outer layer sheets 31a and 31b of the front body F and back body R. In this embodiment, the inner layer sheet 33 is continuous in the vertical direction X from the peripheral edge WE of the waist opening of the ventral A portion to the peripheral edge WE of the waist opening of the dorsal B portion. In other words, the inner layer sheet 33 is continuous along 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 positioned on the skin-facing side of the inner layer sheet 33 and fixes the leg elastic member 37, which will be described later, between itself and the inner layer sheet 33. These sheets 31, 33, and 35 that constitute the outer casing 3 are joined together by known bonding means such as adhesives.

[0019] In this embodiment, the outer layer sheet 31a, 31b of the outer layer sheet 31a, 31b is folded back towards the skin-facing side along the peripheral edge WE of the waist opening (see Figure 2). That is, the outer layer sheets 31a, 31b form the peripheral edge WE of the waist opening, and the folded portion of the sheets 31a, 31b extends inward in the vertical direction X from the peripheral edge WE. In this embodiment, the inner layer sheet 33 of the outer casing 3 is also folded back along the peripheral edge WE of the waist opening towards the skin-facing side, similar to the outer layer sheets 31a and 31b described above. Near the peripheral edge WE of the waist opening of the outer casing 3 (not shown in Figure 4), the folded portion of the outer layer sheets 31a and 31b and the folded portion of the inner layer sheet 33 overlap on the skin-facing side (see Figure 4).

[0020] The outer casing 3 of this embodiment is equipped with a plurality of thread-like or strip-like elastic members 32 that are sandwiched and fixed in an extended state in the folded portion of the inner layer sheet 33. Specifically, in the areas of the ventral portion A and the dorsal portion B that are located around the wearer's waist, a plurality of elastic members 32 (hereinafter referred to as "waist elastic members 32") are intermittently arranged in an extended state in the lateral direction Y and at predetermined intervals in the vertical direction X. The waist elastic members 32 are located between the side edges along the vertical direction X in the ventral portion A and the dorsal portion B, that is, between the side seal portions in the lateral direction Y, and in an area that extends outward in the vertical direction X from the edge of the absorbent body 5 in the vertical direction X. When worn, this area is located around the wearer's waist and its vicinity. The waist elastic members 32 extend over substantially the entire length in the lateral direction Y of the ventral portion A and the dorsal portion B in the outer casing 3 and are arranged in a state in which elastic stretchability is exhibited. This creates a substantially continuous, annular waist gather along the entire circumference of the waist opening.

[0021] The outer casing 3 is equipped with a plurality of thread-like or strip-like leg elastic members 37 arranged in an extended state between the inner layer sheet 33 and the fixing sheet 35. Specifically, one or more leg elastic members 37 for forming leg gathers are arranged in an extended state at the leg edge portion LE that forms the periphery of each of the pair of leg openings in the front body F (see Figure 1). As a result, leg gathers are formed at the periphery of each of the pair of leg openings in the front body F. In this embodiment, the diaper 1 has leg elastic members 37 only on the front body F. That is, the back body R does not have leg elastic members 37. Alternatively, leg elastic members 37 may be provided at the leg edges LE of both the front panel F and the back panel R.

[0022] The outer casing 3 has an elastic sheet on its dorsal side B that stretches along the transverse direction Y. Furthermore, the outer casing 3 may also have an elastic sheet on its ventral side A that stretches along the transverse direction Y. In this embodiment, the outer casing 3 has elastic sheets on both the dorsal side B and the ventral side A. Specifically, the front outer layer sheet 31a and the rear outer layer sheet 31b are elastic sheets. The outer casing 3 may have an elastic sheet only on the dorsal side B, but from the viewpoint of further improving the fit to the wearer's body, it is preferable to have elastic sheets on both the dorsal side B and the ventral side A.

[0023] The outer garment 3 of this embodiment has a front stretchable region FE on the front body F that is stretchable along the horizontal direction Y, and a rear stretchable region RE on the back body R that is stretchable along the same direction Y. These front stretchable region FE and rear stretchable region RE are collectively referred to as the "stretchable region". These "stretchable regions" of this embodiment are made of a stretchable sheet, which is one of the multiple sheets that make up the outer garment 3. The stretchable region of this embodiment is made of a front outer layer sheet 31a and a rear outer layer sheet 31b. Because the outer garment 3 is equipped with a stretchable sheet, the diaper 1 fits the body when worn, and an appearance similar to underwear is obtained.

[0024] An elastic sheet is a sheet that has elasticity in the lateral direction Y, and the total length b in the lateral direction Y after stretching is released is 1 / 3 or less of the amount of stretch. "Total length b in the lateral direction Y after stretching is released" is the total length of the elastic sheet in the lateral direction Y after the sheet has been stretched to its maximum length and the tensile force has been released. "Amount of stretch" is the length (ab) obtained by subtracting the total length b in the lateral direction Y of the elastic sheet when the tensile force in the maximum stretched state is released from the total length a in the lateral direction Y of the elastic sheet when the tensile force in the maximum stretched state is released.

[0025] Preferably, the stretchable sheets used in the present invention include (1) a stretchable nonwoven fabric in which an elastic fiber layer has an expandable fiber layer integrated on both or one side of an elastic fiber layer, (2) a stretchable nonwoven fabric in which an expandable fiber layer has an expandable fiber layer integrated on both or one side of a net-like elastic sheet, (3) a stretchable nonwoven fabric in which an elastic sheet made of an elastic film has an expandable fiber layer integrated on both or one side of an elastic sheet, and (4) a stretchable nonwoven fabric in which a large number of elastic filaments arranged to extend in one direction without intersecting each other are integrated into an expandable fiber layer. The term "stretchable fiber layer" as used herein includes not only fiber layers that are stretchable before integration with an elastic material, but also fiber layers that have been made stretchable by machining or other means after integration with an elastic material. Methods for integrating an elastic fiber layer with an extendable fiber layer include, for example, laminating them and entangling the fibers by water flow entanglement or air passage, or joining them by heat embossing, adhesive, or ultrasound. Elastic fibers can be made from thermoplastic elastomers such as styrene elastomers, polyolefin elastomers, polyester elastomers, or polyurethane elastomers, or from elastic resins such as rubber. Non-elastic fibers can be made from thermoplastic resins.

[0026] The stretchable nonwoven fabric described in (4) above includes, for example, a fabric having a structure in which thread-like elastic filaments are sandwiched between stretchable fiber layers mainly composed of inelastic fibers, thereby integrating them. Such a stretchable nonwoven fabric is composed of two fiber sheets as fiber layers and elastic filaments interposed between these two sheets. This stretchable nonwoven fabric can be manufactured, for example, according to the method described in Japanese Patent Application Publication No. 2009-61743.

[0027] In the stretchable nonwoven fabric described in (4) above, both fiber sheets are stretchable. These two fiber sheets are stretchable in the same direction as the stretching direction of the elastic filaments. The stretchable form includes (a) a form in which the constituent fibers of the sheet itself stretch, and (b) a form in which, even if the constituent fibers themselves do not stretch, the sheet as a whole stretches due to mechanical processing, etc., causing fibers that were bonded at intersections to separate, or due to bonding between fibers, etc., causing a structural change in the three-dimensional structure formed by multiple fibers, or due to the tearing of constituent fibers. Examples of mechanical processing in (b) above include heat treatment, stretching between rolls, stretching by jamming with tooth grooves or gears, and tensile stretching with a tenter.

[0028] In the stretchable nonwoven fabric described in (4) above, the elastic filaments can be formed by stretching an elastic resin in a melted or softened state. Multiple elastic filaments are arranged continuously in one direction and are positioned to extend in that direction without intersecting each other. The elastic filaments are joined to two fiber sheets in a substantially non-stretched state. This joining is achieved by fusing the constituent fibers (non-elastic fibers) of the two fiber sheets to the elastic filaments while they are embedded within the elastic filaments, and is not done using an adhesive such as a hot-melt adhesive. Therefore, there is no adhesive between the two fiber sheets (stretchable fiber layers mainly composed of non-elastic fibers) and the elastic filaments joined thereto.

[0029] The two fiber sheets constituting the stretchable nonwoven fabric described in (4) above can each be various types of nonwoven fabrics, such as air-through nonwoven fabric, heat-rolled nonwoven fabric, spunlace nonwoven fabric, spunbond nonwoven fabric, or meltblown nonwoven fabric. The two fiber sheets may be of the same type or different types. Here, "sheets of the same type" means sheets in which the manufacturing process, the type of constituent fibers, the fiber diameter and length of the constituent fibers, the thickness and basis weight of the sheets, etc., are all the same. If at least one of these is different, they are "different types of sheets." The elastic filament is made from materials such as thermoplastic elastomer or rubber. In particular, when thermoplastic elastomer is used as a raw material, melt spinning using an extruder is possible, similar to ordinary thermoplastic resins, and the elastic filament obtained in this way is easy to heat-seal, making it suitable for stretchable nonwoven fabrics. From the viewpoint of further improving the fit to the wearer's body, it is preferable that the stretchable sheet disposed on the back side B of the outer casing 3 is made of the stretchable nonwoven fabric described in (4) above. In this case, the direction in which the elastic filaments of the stretchable sheet disposed on the back side B of the outer casing 3 extend coincides with the transverse direction Y.

[0030] The outer casing 3 has a non-stretchable region NE located between the front stretchable region FE and the rear stretchable region RE. In this embodiment, the non-stretchable region NE is a region in the outer casing 3 that does not stretch in the lateral direction Y, and is a region where no stretchable members such as the aforementioned stretchable sheet are provided. 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 where the outer layer sheet 31 is not provided, and only the inner layer sheet 33, which is a non-stretchable sheet, is provided. In this embodiment, the non-stretchable region NE is located in the central part of the vertical direction X in the front panel F and the back panel R, and is sandwiched between the front stretchable region FE and the back stretchable region RE in the vertical direction X.

[0031] A non-stretchable sheet is a sheet that is substantially non-stretchable in a certain direction. In this embodiment, it is preferably a sheet that is non-stretchable in at least the transverse direction Y, and preferably a sheet that is non-stretchable in both the longitudinal direction X and the transverse direction Y. A non-stretchable sheet means that even if a tensile force is applied to the sheet in that certain direction, the sheet hardly stretches. For example, if a sheet sample with a length of 15 cm and a width of 5 cm is pulled in the longitudinal direction of the sample using a material tensile tester such as Tensilon, and the elongation at break when the sample breaks is 10% or less, then the sample is substantially non-stretchable in the longitudinal direction. This elongation at break can be calculated as (length of the sample at break - original length of the sample) / (original length of the sample) × 100.

[0032] In this embodiment, the absorbent core 40 has a lower core 45 and an upper core 41 positioned on the skin-facing side of 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 stacked.

[0033] The lower core 45 of this embodiment, like the absorber 4, has a shape that is elongated in the vertical direction X, and has an hourglass shape in which both side edges in the center of the vertical direction X are constricted in the horizontal direction Y. The lower core 45 has a low-rigidity portion (hereinafter also referred to as the "lower low-rigidity portion") 46 that extends in the vertical direction X (see Figure 1). The lower low-rigidity portion 46 is positioned spaced apart from both side edges of the upper core 41 along the vertical direction X toward the center. The lower low-rigidity portion 46 of this embodiment is surrounded by the core-forming material of the lower core 45. The lower low-rigidity portion 46 is a portion of the lower core 45 that is less rigid than other parts. For example, the lower low-rigidity portion 46 is a low-basis-weight portion of the core-forming material forming the lower core 45 where the basis weight is lower than other parts, or a portion where the core-forming material is missing. Examples of the latter include a slit (through hole) or a bottomed recess that penetrates the lower core 45. In this embodiment, the lower low-rigidity portion 46 is a slit extending in the vertical direction X, and the basis weight of the material forming the absorbent core 40 (lower core 45) is 0 g / m². 2This configuration is preferable in that it further improves the wearability and underwear-like appearance (silhouette) of the diaper 1, which will be described later. From the viewpoint of further improving the conformability of the lower core 45 to the body, the lower low-rigidity part 46 is preferably a slit (through hole) extending in the vertical direction X. In this embodiment, the lower core 45 has only one lower low-rigidity portion 46, but alternatively, the lower core 45 may have multiple lower low-rigidity portions 46.

[0034] The lower low-rigidity portion 46 may have its entire length contained within the non-stretchable region NE, or it may have a portion extending from the non-stretchable region NE. For example, the end on the ventral side A of the lower low-rigidity portion 46 may extend into the anterior stretchable region FE, and the end on the dorsal side B of the lower low-rigidity portion 46 may be located in the non-stretchable region NE. Alternatively, the end on the ventral side A of the lower low-rigidity portion 46 may be located in the non-stretchable region NE, and the end on the dorsal side B of the lower low-rigidity portion 46 may extend into the posterior stretchable region RE. Furthermore, the end on the ventral side A of the lower low-rigidity portion 46 may extend into the anterior stretchable region FE, and the end on the dorsal side B of the lower low-rigidity portion 46 may extend into the posterior stretchable region RE. From the viewpoint of making the appearance of the diaper 1 when worn, particularly the appearance of the part corresponding to the wearer's buttocks, a neat silhouette like underwear, it is preferable that the end on the dorsal side B of the lower low-rigidity portion 46 extends into the posterior stretchable region RE. In this embodiment, both ends of the lower low-rigidity section 46 in the vertical direction X are located in the non-stretchable region NE.

[0035] The upper core 41 of this embodiment, like the lower core 45, has a shape that is elongated in the vertical direction X. The upper core 41 has a substantially rectangular shape in plan view. The upper core 41 has a low-rigidity portion (hereinafter also referred to as the "upper low-rigidity portion") 42 that extends in the vertical direction X. The upper low-rigidity portion 42 is positioned spaced apart from both side edges of the upper core 41 along the vertical direction X toward the center. The upper low-rigidity portion 42 of this embodiment is surrounded by the core-forming material of the upper core 41. The upper low-rigidity portion 42 is a low-basis-weight portion of the core-forming material forming the upper core 41, where the basis weight is lower than other parts, or a portion where the core-forming material is missing, and the same description as the lower low-rigidity portion 46 described above applies. From the viewpoint of further improving the conformability of the upper core 41 to the body, the upper low-rigidity portion 42 is preferably a slit (through hole) extending in the vertical direction X. In this embodiment, the upper core 41 has only one upper low-rigidity portion 42, but instead, the upper core 41 may have multiple upper low-rigidity portions 42.

[0036] The lower core 45 has both ends in the lateral direction Y extending from the edge of the upper core 41. The lower core 45 also has one or both ends in the vertical direction X extending from the edge of the upper core 41. In this embodiment, the lower core 45 has both ends in the vertical direction X extending from the edge of the upper core 41. The dimensions of the lower core 45 in the vertical direction X and the lateral direction Y are larger than those of the upper core 41, and the upper core 41 is positioned such that, when viewed from above, the entire upper core 41 is located within a region inside the outer edge of the lower core 45. Because the lateral Y end of the lower core 45 extends from the lateral Y edge of the upper core 41, when the diaper 1 is worn, the portions 47a and 47b of the lower core 45 that extend from the lateral Y edge of the upper core 41 (hereinafter also referred to as "lateral extensions") tend to bend towards the non-skin-facing side, starting from the lateral Y edge of the upper core 41. In other words, when viewed along the lateral Y direction, the absorbent material 4 tends to take on a convex curved shape toward the skin-facing side.

[0037] Furthermore, because the end of the lower core 45 in the vertical direction X extends from the edge of the upper core 41 in the vertical direction X, when the diaper 1 is worn, the portions of the lower core 45 that extend from the edge of the upper core 41 in the vertical direction X (hereinafter also referred to as "vertical extensions") 48a, 48b tend to bend towards the skin-facing side, starting from the edge of the upper core 41 in the vertical direction X. In other words, when viewed along the vertical direction X, the absorbent material 4 tends to take on a convex curved shape toward the non-skin-facing side. Thus, when viewed along the horizontal direction Y, the absorbent material 4 tends to have a curved shape that is convex toward the skin-facing side, and when viewed along the vertical direction X, it tends to have a curved shape that is convex toward the non-skin-facing side. As a result, when the diaper 1 is worn, the absorbent material 4 tends to deform to conform to the shape of the wearer's buttocks. Therefore, the diaper 1 of this embodiment provides an excellent fit and allows the appearance of the diaper 1 when worn to have a neat silhouette like underwear (see Figure 6(a)).

[0038] The lower core 45 extends from the upper core 41 on both sides in the longitudinal direction X. The length of the longitudinal extension 48b on the dorsal side B and the length of the longitudinal extension 48a on the ventral side A may be the same or different. From the viewpoint of making the absorbent material 4 more easily deformable to conform to the shape of the wearer's buttocks when the diaper 1 is worn, it is preferable that the length of the longitudinal extension 48b on the dorsal side B is longer than the length of the longitudinal extension 48b on the ventral side A.

[0039] The lower core 45 extends from the upper core 41 on both sides in the lateral direction Y. The length in the lateral direction Y of the lateral extension 47b on one side and the length in the lateral direction Y of the lateral extension 47a on the other side may be the same or different. From the viewpoint of making the absorbent material 4 more easily deformable to conform to the shape of the wearer's buttocks when the diaper 1 is worn, it is preferable that the length in the lateral direction Y of the lateral extension 47b on one side and the lateral extension 47a on the other side are the same. In this embodiment, if the length in the lateral direction Y of the lateral extensions 47a and 47b is not constant in the vertical direction X, the length in the lateral direction Y of the lateral extensions 47a and 47b means the shortest length from the lateral direction Y edge of the upper core 41 to the lateral direction Y edge of the lower core 45.

[0040] Diaper 1 has a low-rigidity overlapping region Kt in a plan view where the upper low-rigidity portion 42 and the lower low-rigidity portion 46 overlap. The upper low-rigidity portion 42 and the lower low-rigidity portion 46 may overlap so that the positions of their outer edges completely coincide in a plan view, or only a part of the upper low-rigidity portion 42 and the lower low-rigidity portion 46 may overlap. Also, the upper low-rigidity portion 42 and the lower low-rigidity portion 46 may overlap so that the entire upper low-rigidity portion 42 is located within the region enclosed by the outer edge of the lower low-rigidity portion 46, or vice versa. The lower low-rigidity portion 46 extends from the end edge in the vertical direction X of the upper low-rigidity portion 42. In this embodiment, the lower low-rigidity portion 46 extends from both ends of the upper low-rigidity portion 42 in the vertical direction X, but instead, it may extend from only one end edge. The position of the lateral edge in the lateral direction Y of the lower low-rigidity section 46 coincides with the position of the lateral edge in the lateral direction Y of the upper low-rigidity section 42.

[0041] The upper core 41 has an upper low-rigidity portion 42, which makes the upper core 41 more easily bendable along the vertical direction X at the upper low-rigidity portion 42. Similarly, the lower core 45 has a lower low-rigidity portion 46, which makes the lower core 45 more easily bendable along the vertical direction X at the lower low-rigidity portion 46. As the upper core 41 and lower core 45 become more easily bendable along the vertical direction X, when viewed along the horizontal direction Y, the absorbent material 4 becomes more easily curved in a convex shape toward the skin-facing side, further improving the fit and appearance of the diaper 1. As in this embodiment, as the upper low-rigidity portion 42 and the lower low-rigidity portion 46 overlap in a plan view, the absorbent material 4 becomes more easily bendable along the vertical direction X at the portion where the upper low-rigidity portion 42 and the lower low-rigidity portion 46 overlap, further improving the fit and appearance of the diaper 1.

[0042] In diaper 1, in a plan view, the core overlap region Kc, where the upper core 41 and the lower core 45 overlap, overlaps with at least a portion of the joining region S of the absorbent body 5 and the outer casing 3. The core overlap region Kc and the joining region S may overlap so that the positions of their outer edges are perfectly aligned, or only a portion of the core overlap region Kc and the joining region S may overlap. Furthermore, the core overlap region Kc and the joining region S may overlap so that the entire core overlap region Kc is located within the region enclosed by the outer edge of the joining region S, or vice versa. In this embodiment, a portion of the core overlap region Kc and a portion of the joining region S overlap. Specifically, the core overlap region Kc and the central joining region Sc overlap. The central joining region Sc extends from the vertical X edge of the core overlap region Kc. The core overlap region Kc extends from the horizontal Y edge of the central joining region Sc.

[0043] Because the core overlapping region Kc and the joining region S overlap, when the absorbent material 4, particularly the lower core 45, bends from the edge of the upper core 41 towards the skin-facing side or the non-skin-facing side, the outer casing 3 deforms to follow the movement of the absorbent material 4. Therefore, the outer casing 3 also deforms to conform to the shape of the buttocks of the wearer of the diaper 1, thereby further improving the appearance of the diaper 1. From the viewpoint of making this effect even more pronounced, it is preferable that the core overlapping region Kc and the joining region S overlap when the diaper 1 is unfolded and stretched, and it is even more preferable that they overlap in both the natural state of the diaper 1 and when the diaper 1 is unfolded and stretched.

[0044] From the viewpoint of making the outer casing 3 more easily deformable to conform to the shape of the buttocks of the wearer of the diaper 1, and further improving the appearance of the diaper 1, it is preferable that the low-rigidity overlapping region Kt, where the upper low-rigidity portion 42 and the lower low-rigidity portion 46 of the core overlapping region Kc overlap, overlaps with at least a part of the joining region S. The low-rigidity overlapping region Kt and the joining region S may overlap so that the positions of their outer edges are perfectly aligned, or only a part of the low-rigidity overlapping region Kt and the joining region S may overlap. Furthermore, the low-rigidity overlapping region Kt and the joining region S may overlap so that the entire low-rigidity overlapping region Kt is located within the region enclosed by the outer edge of the joining region S, or vice versa. In this embodiment, a part of the low-rigidity overlapping region Kt and a part of the joining region S overlap. Specifically, the two overlap so that the low-rigidity overlapping region Kt is included within the central joining region Sc. From the viewpoint of further improving the appearance of diaper 1, it is preferable that the low-rigidity overlapping region Kt and the joining region S overlap when diaper 1 is unfolded and extended, and it is more preferable that they overlap in both the natural state of diaper 1 and when diaper 1 is unfolded and extended.

[0045] In diaper 1, the stretchable sheet and at least a portion of the lower core 45 overlap at the dorsal portion B. In this embodiment, a portion of the rear outer layer sheet 31b, which is the stretchable sheet, overlaps with a portion of the lower core 45. In this specification, the expression that two objects, such as the stretchable sheet and at least a portion of the lower core 45, overlap includes both cases where one and the other directly overlap and cases where they do not directly overlap. Specifically, the end of the rear outer layer sheet 31b on the crotch side C in the lateral Y central region overlaps with the end of the lower core 45 on the dorsal side B. Because the stretchable sheet and the lower core 45 overlap, when the diaper 1 is worn, the contraction force of the stretchable sheet, which is stretched when put on, causes the lower core 45 and the wide areas on both sides of it to fit the wearer's body as a surface, and as the stretchable sheet repeatedly stretches and contracts, the fit is maintained well during wear. As a result, the wearing comfort of the diaper 1 is further improved, and the appearance of the diaper 1 when worn becomes even more like a neat underwear silhouette. From the viewpoint of further improving the wearing comfort and appearance of the diaper 1, it is preferable that the stretchable sheet and the lower core 45 overlap when the diaper 1 is unfolded and stretched, and it is even more preferable that they overlap in both the natural state of the diaper 1 and when the diaper 1 is unfolded and stretched. Thus, the diaper 1 of this embodiment offers excellent fit and appearance when worn.

[0046] In this embodiment, when the diaper 1 is worn, the skin-facing surface of the diaper 1 has a saddle-shaped curved surface P. Figure 7 shows a schematic diagram of the skin-facing surface of the diaper 1 when worn. A "saddle-shaped curved surface" means a curved surface that curves convexly toward the skin-facing surface when viewed along the transverse direction Y (see Figures 7(a) and (b)), and also curves convexly toward the non-skin-facing surface when viewed along the longitudinal direction X (see Figures 7(a) and (c)). When diaper 1 is worn, the skin-facing surface of diaper 1 has a saddle-shaped curved surface (hereinafter also referred to as "saddle-shaped curved surface") P, which makes it easier for diaper 1 to deform to conform to the shape of the wearer's buttocks, thereby further improving the fit and appearance of diaper 1. From the viewpoint of making this effect even more pronounced, it is preferable that when diaper 1 is worn, the saddle-shaped curved surface P extends further toward the dorsal side B in the longitudinal direction X than the wearer's buttock groove Q (see Figure 6(b)).

[0047] In diaper 1, it is preferable that the distance between the edge of the upper core 41 in the vertical direction X and the overlapping region Kt of the low-rigidity part be short. This point will be explained below. The edge of the upper core 41 in the vertical direction X is the starting point when the absorbent material 4 bends along the horizontal direction Y. The overlapping region Kt of the low-rigidity part is the starting point when the absorbent material 4 bends along the vertical direction X. By making the distance between the edge of the upper core 41 in the vertical direction X and the overlapping region Kt of the low-rigidity part short, the starting point when bending along the horizontal direction Y and the starting point when bending along the vertical direction X can be brought closer together, so that the saddle-shaped curved surface P can be formed more easily when diaper 1 is worn. From the viewpoint of making this effect even more pronounced, it is preferable that the length L1 in the vertical direction X of the overlapping region Kt of the low-rigidity part be longer than either of the following distances (1) and (2). (1) The distance L2 from the ventral side A edge of the upper core 41 in the longitudinal direction X to the ventral side A edge of the upper low-rigidity portion 42 in the longitudinal direction X (2) The distance L3 from the edge of the back portion B side of the upper core 41 in the vertical direction X to the edge of the back portion B side of the upper low rigidity portion 42 in the vertical direction X

[0048] The ratio of the distance L2 to the length L1, L2 / L1, is preferably 0.9 or less, and more preferably 0.8 or less. The ratio of the distance L3 to the length L1, L3 / L1, is preferably 0.9 or less, and more preferably 0.8 or less. The distances L2 and L3 may be the same or different. Furthermore, either L2 or L3 may be 0.

[0049] The lower low-rigidity portion 46 does not necessarily have to extend from the upper core 41 in the vertical direction X, but it is preferable that it does. Because the lower low-rigidity portion 46 extends from the upper core 41 in the vertical direction X, the lower low-rigidity portion 46, which is the starting point when the absorbent material 4 bends along the vertical direction X, and the edge of the upper core 41 in the vertical direction X, which is the starting point when the absorbent material 4 bends along the horizontal direction Y, overlap, making it easier to form a saddle-shaped curved surface P. From the viewpoint of making it easier to form a saddle-shaped curved surface P on the dorsal side B and further improving the fit and appearance on the dorsal side B, it is preferable that the lower low-rigidity portion 46 extends from the upper core 41 at least on the dorsal side in the vertical direction X. From the viewpoint of further improving the fit and appearance of the diaper 1, it is preferable that the lower low-rigidity portion 46 extends from the upper core 41 on both sides in the vertical direction X. In this embodiment, the rear end of the dorsal side B of the lower low-rigidity portion 46 extends further towards the dorsal side B than the rear end of the dorsal side B of the upper core 41 in the vertical direction X. Also, the rear end of the ventral side A of the lower low-rigidity portion 46 extends further towards the ventral side A than the rear end of the ventral side A of the upper core 41 in the vertical direction X.

[0050] The ratio L4 / L of the length L4 of the extension portion L4 from the back side B edge of the upper core 41 in the vertical direction X to the total length L of the absorber 4 in the vertical direction X is preferably 0.03 or more, more preferably 0.08 or more, from the viewpoint of ensuring that the bent portion along the vertical direction X and the bent portion along the transverse direction Y intersect in the absorber 4 and facilitating the formation of a saddle-shaped curved surface P.

[0051] The ventral side of the upper core 41 in the longitudinal direction X relative to the total length L of the absorber 4 in the longitudinal direction X. A The ratio L5 / L of the length L5 of the extension portion from the side edge is preferably 0.03 or more, more preferably 0.08 or more, from the viewpoint of ensuring that the bent portion along the longitudinal direction X and the bent portion along the transverse direction Y in the absorber 4 intersect reliably, and facilitating the formation of a saddle-shaped curved surface P. The lengths L4 and L5 may be the same or different.

[0052] In a plan view, it is preferable that the stretchable sheet and the upper low-rigidity portion 42 or the lower low-rigidity portion 46 overlap in the diaper 1. This allows the stretchable sheet to expand and contract in the lateral direction Y, and the absorbent material 4 to bend more easily along the vertical direction X, starting from the upper low-rigidity portion 42 or the lower low-rigidity portion 46. From the viewpoint of further improving the fit and appearance of the diaper 1, it is even more preferable that the stretchable sheet and the lower low-rigidity portion 46 overlap.

[0053] When the diaper 1 is worn, it is preferable that the upper low-rigidity portion 42 or the lower low-rigidity portion 46 extends further toward the dorsal side B in the longitudinal direction X than the wearer's gluteal crease Q. This allows the diaper 1 to fit more closely to the wearer's gluteal crease, further improving the feel and appearance of the diaper 1. From the viewpoint of achieving this effect even more significantly, it is more preferable that the lower low-rigidity portion 46 extends further toward the dorsal side B in the longitudinal direction X than the wearer's gluteal crease Q.

[0054] In a plan view, it is preferable that the joining region S of the diaper 1 overlaps with the entire lengthwise X area of ​​the upper core 41. This makes it easier for the outer casing 3 to follow the movement of the absorbent material 4, further improving the appearance of the diaper 1. In addition, since the outer casing 3 is joined to the absorbent body 5 at the edge of the upper core 41 in the lengthwise X direction, which is the starting point when the absorbent material 4 bends along the lateral Y direction, it is possible to further form a saddle-shaped curved surface P when the diaper 1 is worn.

[0055] Next, the materials used to form each part of the diaper 1 will be described. For the inner layer sheet 33 and the fixing sheet 35, various materials conventionally used as outer coverings in this type of absorbent article can be used without particular limitation. For example, as the inner layer sheet 33, nonwoven fabrics manufactured by various methods such as spunbond nonwoven fabric, air-through nonwoven fabric, and needle-punched nonwoven fabric can be used.

[0056] The elastic members 32, 37, 61, and 63 of the leg elastic members are preferably made from stretchable materials such as natural rubber, polyurethane resin, foamed urethane resin, and hot-melt stretchable material, formed into thread-like (thread-like rubber) or strip-like (flat rubber) shapes. Various nonwoven fabrics and perforated films can be used as the surface sheet 12, and resin films or laminates of resin films and nonwoven fabrics can be used as the leak-proof sheet 13.

[0057] The absorbent core 40 of the absorbent body 4 is formed from core-forming materials such as hydrophilic fibers including pulp and cellulose, and water-absorbent polymers. The absorbent core 40 is composed of, for example, a stack of hydrophilic fibers, a mixed stack of hydrophilic fibers and water-absorbent polymers, a deposit of water-absorbent polymers, or a laminated structure in which water-absorbent polymers are supported between two water-absorbent sheets. For the core wrap sheet 49, for example, a thin paper made of hydrophilic fibers or a nonwoven fabric that is permeable to liquids can be used.

[0058] Although the present invention has been described above based on its preferred embodiments, the present invention is not limited in any way to the above embodiments and can be modified as appropriate without departing from the spirit of the invention. [Explanation of Symbols]

[0059] 1. Pant-type disposable diapers (diapers) 3. Exterior 4 Absorbent 5 Absorbent body 6 Leak proof cuff 12 Surface sheet 13 Leak-proof sheet 31 Outer layer sheet 32 Elastic member around the torso 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 45 Lower core 46 Lower layer low rigidity part 48 Intermediate elastic member 49 Core Wrap Sheet 60 Cuff Forming Sheets 61 Cuff elastic member A. Ventral part B Dorsal part C Inseam F Front R Back Kc core overlap region Kt Low-rigidity overlapping region S junction area X vertical direction Y (horizontal direction)

Claims

1. A disposable pant-type diaper comprising an absorbent body having an absorbent core, an absorbent body having an absorbent core, and an outer body disposed on the non-skin-facing side of the absorbent body, having a longitudinal direction extending from the ventral direction through the crotch to the ventral direction and a transverse direction perpendicular to the longitudinal direction, with the center of the longitudinal direction as the boundary, and both side edges along the longitudinal direction of the ventral and ventral sections being joined to form a waist opening, a pair of side seals and a pair of leg openings, respectively, The absorbent core comprises a lower core and an upper core positioned on the skin-facing side of the lower core, wherein both ends in the lateral direction and one or both ends in the vertical direction of the lower core extend from the edge of the upper core. Each of the upper core and the lower core has a low-rigidity portion extending in the vertical direction, located at a position spaced apart from both side edges of the upper core along the vertical direction toward the center. The exterior body has a stretchable sheet on its back side that is stretchable in the lateral direction, The aforementioned stretchable sheet is positioned from the back to a portion of the crotch area, In a plan view, The upper core and the lower core have overlapping low-rigidity regions where they overlap. The absorbent core does not have slits extending in the vertical direction in the portions located on both sides in the lateral direction, with respect to the overlapping region of the low-rigidity portion. A disposable diaper in which the overlapping region of the low-rigidity portion and at least a portion of the joining region of the absorbent body and the outer casing overlap, and the stretchable sheet and at least a portion of the lower core overlap on the dorsal side.

2. The lower core does not have the low-rigidity portion extending in the lateral direction, The disposable diaper according to claim 1, wherein, when worn, the skin-facing surface of the disposable diaper has a saddle-shaped curved surface.

3. The disposable diaper according to claim 2, wherein when the disposable diaper is worn, the curved surface extends further toward the dorsal side in the longitudinal direction than the buttock crease of the wearer.

4. The disposable diaper according to claim 1 or 2, wherein the vertical length of the overlapping region of the low-rigidity portion is longer than either of the following distances (1) and (2). (1) The distance from the ventral edge of the upper core in the longitudinal direction to the ventral edge of the low-rigidity portion of the upper core in the longitudinal direction (2) The distance from the edge of the upper core on the back side in the longitudinal direction to the edge of the lower rigidity portion of the upper core on the back side in the longitudinal direction

5. The disposable diaper according to claim 1 or 2, wherein the rear end of the low-rigidity portion of the lower core on the dorsal side in the longitudinal direction extends further toward the dorsal side than the rear end of the upper core on the dorsal side in the longitudinal direction.

6. The disposable diaper according to claim 1 or 2, wherein, in a plan view, the stretchable sheet and the low-rigidity portion of the upper core or the low-rigidity portion of the lower core overlap.

7. The disposable diaper according to claim 1 or 2, wherein when the disposable diaper is worn, the low-rigidity portion of the upper core or the low-rigidity portion of the lower core extends further toward the dorsal side in the longitudinal direction than the buttock groove of the wearer.

8. The disposable diaper according to claim 1 or 2, wherein, in a plan view, the joining region overlaps with the entire vertical area of ​​the upper core.

9. The disposable diaper according to claim 1 or 2, wherein the low-rigidity portion of the upper core or the low-rigidity portion of the lower core is a slit.

Images