Disposable diaper

Abstract

Provided is a disposable diaper having buttock cover portions that allow a wider area of buttocks to be hidden. A disposable diaper (1) is provided with a ventral portion (3), a dorsal portion (2), and an absorbent body (4). The absorbent body includes a body central portion (10) and a pair of leg gather portions (5) positioned at both ends of the body central portion in the width direction thereof. The dorsal portion includes a dorsal body portion (21) positioned on the outer side in the longitudinal direction and a dorsal extension portion (20) positioned on the inner side in the longitudinal direction. The dorsal extension portion includes an extension central portion (31) and a pair of buttock cover portions (30) positioned at both ends of the extension central portion in the width direction thereof. Each buttock cover portion is divided in the longitudinal direction into three equal areas: an upper area (30a), a central area (30b), and a lower area (30c). The contraction force of the lower area in the width direction is relatively high. Each buttock cover portion includes an overlapping area (OA) positioned on the inner side in the width direction and on the front side in the longitudinal direction, the overlapping area overlapping back ends of leg elastic members (5a) of one of the leg gather portions in the thickness direction.

Description

Disposable diapers

[0001] The present invention relates to a disposable diaper, and more particularly to a disposable diaper having a buttocks cover portion.

[0002] Disposable diapers with buttocks-covering portions for concealing the buttocks are known. For example, Patent Document 1 discloses a disposable wearing article with a buttocks-covering portion. The wearing article includes a front region, a rear region, a crotch region located between the front and rear regions, a waist opening, a pair of leg openings, annular elastic waist panels forming the front and rear regions, and a liquid-absorbent structure attached to the inner surface of the elastic waist panel and forming the crotch region. The rear region has a main rear waist portion facing the front region and a buttocks-covering portion adjacent to the crotch region. The main rear waist portion is divided into an upper region adjacent to the waist opening and a lower region adjacent to the crotch region, and the buttocks-covering portion has a lower elongation stress in a given width than the lower region of the main rear waist portion.

[0003] JP 2011-115229 A

[0004] In the disposable diaper (disposable wearing article) of Patent Document 1, leg elastic members (leg elastic contraction elements) for leg gathers extending along the longitudinal direction are arranged at both widthwise ends of the absorbent main body (absorbent structure). These leg elastic members are arranged so as to overlap each other over a wide longitudinal area of ​​the inner widthwise region of the buttocks cover portion in a plan view. When the buttocks cover portion and the leg elastic members overlap over a wide longitudinal area, depending on the strength of the leg elastic members, the inner widthwise region of the buttocks cover is more likely to contract longitudinally. In this case, the buttocks cover portion as a whole may contract longitudinally. This may make it difficult to expand the area of ​​the buttocks that the buttocks cover portion can cover.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a disposable diaper having a buttocks covering portion that can cover and conceal a wider range of the buttocks.

[0006] The disposable diaper of the present invention has, in an unfolded state, longitudinal, width and thickness directions which are orthogonal to one another, and comprises an abdominal section which covers the abdominal side of a wearer, a back section which covers the back side, and an absorbent main body which covers the crotch of the wearer and includes an absorbent body, wherein the absorbent main body has front and rear ends in the longitudinal direction connected to central portions in the width direction of the abdominal section and the back section, respectively, and is formed by joining a pair of abdominal joining portions on both side edges in the width direction of the abdominal section and a pair of back joining portions on both side edges in the width direction of the back section, wherein the absorbent main body includes a main body central portion located in the central portion in the width direction, and a pair of leg gathering portions located at both end portions in the width direction and having a plurality of leg elastic members extending along the longitudinal direction, and the back section has a back joining portion which occupies substantially the same area in the longitudinal direction as the back joining portion. and a back-side extending portion extending forward from a front end edge of the back-side main body portion in the longitudinal direction, the back-side extending portion including an extending central portion overlapping the main body central portion in the thickness direction, and a pair of buttocks covering portions extending outward from both side edges of the extending central portion in the width direction, each of the pair of buttocks covering portions being regions obtained by dividing the buttocks covering portion into three equal parts in the longitudinal direction, namely, a rear upper region, a central central region, and a front lower region. a region in which the contractile force in the width direction is higher in the lower region than in the upper region and the central region, and the buttocks-covering portion includes, in the inner region in the width direction, an overlapping region located on the front side in the longitudinal direction and overlapping with the rear ends of the plurality of leg elastic members in the thickness direction, and a non-overlapping region located on the rear side in the longitudinal direction and not overlapping with the plurality of leg elastic members in the thickness direction.

[0007] According to the present invention, it is possible to provide a disposable diaper having a buttocks cover portion that can cover and conceal a wider range of the buttocks.

[0008] FIG. 2 is a perspective view showing an example of the configuration of a disposable diaper according to an embodiment. FIG. 3 is a plan view of the example of the configuration of a disposable diaper according to an embodiment in an unfolded state. FIG. 4 is a cross-sectional view taken along the longitudinal center line CL in FIG. 2. FIG. 5 is a cross-sectional view taken along the widthwise center line CW in FIG. 2. FIG. 6 is a partial plan view of the example of the configuration of a disposable diaper according to an embodiment in an unfolded state. FIG. 7 is a partial plan view of the example of the configuration of a disposable diaper according to an embodiment in an unfolded state. FIG. 8 is a schematic view showing the example of the configuration of a disposable diaper according to an embodiment. FIG. 9 is a schematic view showing the example of the configuration of a disposable diaper according to an embodiment. FIG. 10 is a perspective view showing the disposable diaper according to an embodiment in a worn state.

[0009] The present embodiment relates to the following aspects.

[0010] [Aspect 1] A disposable diaper having, in an unfolded state, longitudinal, width, and thickness directions that are orthogonal to one another, a abdominal section that covers the abdominal side of a wearer, a dorsal section that covers the dorsal side, and an absorbent main body that covers the crotch of the wearer and includes an absorbent body, wherein the absorbent main body has front and rear ends in the longitudinal direction connected to central portions in the width direction of the abdominal section and the dorsal section, respectively, and is formed by joining a pair of abdominal joining portions on both side edges in the width direction of the abdominal section and a pair of dorsal joining portions on both side edges in the width direction of the dorsal section, wherein the absorbent main body includes a main body central portion located in the central portion in the width direction, and a pair of leg gathering portions located at both end portions in the width direction and having a plurality of leg elastic members extending along the longitudinal direction, and the dorsal section has a dorsal main body portion that occupies substantially the same area in the longitudinal direction as the dorsal joining portion. and a back-side extending portion extending forward from a front longitudinal edge of the back-side main body portion, the back-side extending portion including an extending central portion overlapping the main body central portion in the thickness direction, and a pair of buttocks-covering portions extending outward from both widthwise edges of the extending central portion, each of the pair of buttocks-covering portions including an upper rear region, a central central region, and a lower front region, which are regions obtained by dividing the buttocks-covering portion into thirds in the longitudinal direction, and the lower region has a higher contractile force in the width direction than the upper region and the central region, and the buttocks-covering portion includes, in its inner widthwise region, an overlapping region located on the front longitudinal side and overlapping with the rear longitudinal ends of the plurality of leg elastic members in the thickness direction, and a non-overlapping region located on the rear longitudinal side and not overlapping with the plurality of leg elastic members in the thickness direction.

[0011] In this disposable diaper, the buttocks-covering portion includes an upper region on the rear (back side), a central region, and a lower region on the front (ventral side) in the longitudinal direction, and the lower region has a higher contractile force in the width direction than the upper and central regions. Therefore, when the disposable diaper is put on, the lower region can be contracted while the upper and central regions can be less contracted. As a result, the buttocks-covering portion can easily assume a shape that is convex outward to cover the outer sides of the buttocks, while the lower region gently holds the buttocks and prevents them from separating from the buttocks. Furthermore, in this disposable diaper, the rear longitudinal ends of the leg elastic members of the leg gathers and the overlapping region, which is the longitudinal front (ventral side) region of the inner widthwise region of the buttocks-covering portion, overlap in the thickness direction. This allows the overlapping region on the longitudinal front side (ventral side) of the buttocks-covering portion to be pulled toward the longitudinal front side (ventral side) by the leg elastic members. Meanwhile, the leg elastic members of the leg gathers do not overlap in the thickness direction with the non-overlapping region, which is the longitudinal rear side (back side) region of the inner widthwise region of the buttocks-covering portion. This makes it difficult for the leg elastic members to stretch the non-overlapping region of the buttocks-covering portion. Pulling the overlapping region on the longitudinal front side (ventral side) of the buttocks-covering portion, and thus the lower region, toward the longitudinal front side (ventral side), i.e., the crotch side, prevents excessive longitudinal contraction of the region. At the same time, making it difficult for the non-overlapping region on the longitudinal rear side (back side) of the buttocks-covering portion, and thus the upper region, to stretch, reduces deformation in the region. As a result, the buttocks-covering portion does not contract too much overall, but rather gently bulges outward and easily conforms to the surface of the buttocks. This allows the buttocks-covering portion to wrap around and properly conceal the buttocks. Furthermore, by wrapping around and properly concealing the buttocks, the buttocks-covering portion can enhance the sense of security that body waste will not leak.

[0012] [Aspect 2] The disposable diaper according to Aspect 1, wherein a region of the buttocks-cover portion between the position of the back-side joint portion and the position of the edge of the absorbent main body on the buttocks-cover portion side in the width direction has a tensile stress in the width direction of 0.25 N or less.

[0013] In this disposable diaper, the buttocks cover portion has a tensile stress of 0.25 N or less in the region between the position of the back-side joint and the position of the edge of the absorbent main body in the width direction. This allows the buttocks cover portion to more reliably bulge outward in a gentle convex shape and conform to the surface of the buttocks without excessive contraction as a whole. In other words, the buttocks cover portion can more reliably envelop and adequately conceal the buttocks. This further enhances the sense of security that the buttocks cover portion provides regarding prevention of body waste leakage.

[0014] [Aspect 3] The disposable diaper according to aspect 1 or 2, wherein the overlapping region occupies a range of less than 50% of the length of the buttocks-covering portion in the longitudinal direction.

[0015] In this disposable diaper, the overlapping region, i.e., the region where the longitudinal rear ends of the leg elastic members and the longitudinal front portion of the widthwise inner region of the buttocks-covering portion overlap in the thickness direction, is less than 50% of the longitudinal length of the buttocks-covering portion. This more reliably prevents the buttocks-covering portion from contracting excessively in the longitudinal direction and allows the buttocks-covering portion to bulge gently outward. This more reliably envelops and properly conceals the buttocks. This increases the sense of security that the buttocks-covering portion provides to prevent body exudates from leaking.

[0016] [Aspect 4] The disposable diaper according to any one of Aspects 1 to 3, wherein the buttocks-covering portion has an inner region in the width direction joined to the leg gathered portion, the buttocks-covering portion has, in the lower region, buttocks elastic members extending along the width direction, and an innermost leg elastic member that is located innermost in the width direction among the plurality of leg elastic members does not overlap the buttocks elastic member in the thickness direction.

[0017] In this disposable diaper, the innermost leg elastic member among the plurality of leg elastic members does not overlap the buttocks elastic member in the thickness direction. In this case, the buttocks elastic member does not pull all of the plurality of leg elastic members, which prevents the leg gathers near the buttocks-covering portion from being pulled outward in the width direction (rolled up) by the buttocks elastic member. This allows the buttocks-covering portion to adequately cover the buttocks while allowing the leg gathers to adequately come into surface contact with the legs, thereby allowing the diaper to function properly.

[0018] [Aspect 5] The disposable diaper according to any one of Aspects 1 to 4, wherein the buttocks-covering portion has an inner region in the width direction joined to the leg gathered portion, the buttocks-covering portion has, in the lower region, buttocks elastic members extending along the width direction, and outermost leg elastic members that are positioned outermost in the width direction among the plurality of leg elastic members overlap the buttocks elastic members in the thickness direction.

[0019] In this disposable diaper, the outermost leg elastic members of the plurality of leg elastic members overlap the buttocks elastic members in the thickness direction. In this case, the buttocks elastic members pull the outermost leg elastic members of the plurality of leg elastic members, so that only the outer widthwise portions of the leg gathers near the buttocks-covering portions are pulled outward to an appropriate degree, allowing them to conform to the surface of the leg portions near the buttocks. This allows the buttocks to be appropriately covered by the buttocks-covering portions, while the leg gathers can be appropriately brought into surface contact with the leg portions near the buttocks, allowing them to properly perform their functions.

[0020] [Aspect 6] The disposable diaper according to any one of Aspects 1 to 5, wherein, when the disposable diaper is stretched in the longitudinal direction and the width direction and placed on a flat plate, the stretched longitudinal length and the stretched width length of the buttocks-covering portion are the lengths in the longitudinal direction and the width direction, respectively, and when the disposable diaper is stretched and then relaxed and placed on a flat plate, the ratio of the relaxed longitudinal length to the stretched longitudinal length is 90% or more and the ratio of the relaxed width length to the stretched width direction length is 50% or more.

[0021] In this disposable diaper, the ratio of the relaxed longitudinal length to the stretched longitudinal length is 90% or more, and the ratio of the relaxed widthwise length to the stretched widthwise length is 50% or more. That is, even when the disposable diaper is stretched during donning and then relaxed after donning, the buttocks-covering portion does not shrink significantly from its stretched size and maintains a relatively constant size. This allows the buttocks-covering portion to more reliably envelop and adequately conceal the buttocks. Furthermore, the buttocks-covering portion's large size that envelops and adequately conceals the buttocks provides a greater sense of security regarding the prevention of bodily exudate leakage.

[0022] [Aspect 7] The disposable diaper according to any one of Aspects 1 to 6, wherein, when the disposable diaper is stretched in the longitudinal direction and the width direction and placed on a flat plate, the stretched longitudinal length and the stretched width length are the lengths of the buttocks-cover portion in the longitudinal direction and the width direction, and when the disposable diaper is stretched and then relaxed and placed on a flat plate, the relaxed longitudinal length and the relaxed width length are the lengths of the buttocks-cover portion in the longitudinal direction and the width direction, respectively, and the relaxed longitudinal length and the relaxed width length are the lengths of the buttocks-cover portion in the longitudinal direction and the width direction when the disposable diaper is stretched and then relaxed and placed on a flat plate, the relaxed longitudinal length contracts to the stretched longitudinal length by 4 mm or less and the relaxed width length contracts to the stretched width length by 55 mm or less.

[0023] In this disposable diaper, the ratio of the relaxed longitudinal length to the extended longitudinal length is 4 mm or less, and the ratio of the relaxed widthwise length to the extended widthwise length is 55 mm or less. That is, even when the disposable diaper is stretched during donning and then relaxed after donning, the buttocks-covering portion does not shrink significantly from its extended size and maintains a relatively constant size. This allows the buttocks-covering portion to more reliably envelop and adequately conceal the buttocks. Furthermore, the buttocks-covering portion's large size allows for adequately enveloping and concealing the buttocks, further enhancing the sense of security regarding prevention of bodily exudate leakage.

[0024] Aspect 8 The disposable diaper according to any one of Aspects 1 to 7, wherein, when the disposable diaper is stretched in the longitudinal direction and the width direction, the circumference of a waist portion formed by the ventral portion and the dorsal portion is in the range of 590 to 1050 mm, and when the disposable diaper is stretched in the longitudinal direction and the width direction and then relaxed and placed on a flat plate, the relaxed width direction length, which is the length in the width direction of the buttocks-cover portion, is 55 mm or more.

[0025] When the circumference of the waist portion of this disposable diaper is in the range of 590 to 1050 mm, i.e., when this disposable diaper is for babies, the relaxed widthwise length is 55 mm or more. In other words, even when this disposable diaper is stretched when put on and then relaxed after put on, the buttocks-covering portion can maintain a relatively constant size without shrinking significantly from its stretched size. This allows the buttocks-covering portion to more reliably envelop and adequately conceal the buttocks. Furthermore, the buttocks-covering portion's large size, which envelops and adequately conceals the buttocks, further enhances the sense of security that body exudates are prevented from leaking.

[0026] Aspect 9 The disposable diaper according to any one of Aspects 1 to 8, wherein, when the disposable diaper is stretched in the longitudinal direction and the width direction, the circumference of a waist portion formed by the abdominal portion and the dorsal portion is in the range of 590 to 1050 mm, and when the disposable diaper is stretched in the longitudinal direction and the width direction, and then relaxed and placed on a flat plate, the disposable diaper has maximum lengths in the longitudinal direction and the width direction, i.e., a relaxed maximum length in the longitudinal direction and a relaxed maximum length in the width direction, which are the maximum lengths of the disposable diaper in the longitudinal direction and the width direction, and the relaxed maximum length in the width direction, which are the maximum lengths of the disposable diaper in the longitudinal direction and the width direction, respectively, and the relaxed maximum length in the width direction is greater than the relaxed maximum length in the longitudinal direction.

[0027] When the circumference of the waist portion of the disposable diaper is in the range of 590 to 1050 mm, i.e., when the disposable diaper is for a baby, the maximum length in the relaxed widthwise direction is greater than the maximum length in the relaxed longitudinal direction. That is, when the disposable diaper is stretched during donning and then relaxed after donning, the disposable diaper has a shape that is large in the widthwise direction. Here, the maximum length in the relaxed widthwise direction is the length including the buttocks-covering portion. Therefore, the disposable diaper has a shape that is large in the widthwise direction including the buttocks-covering portion, which can more reliably envelop and adequately cover the buttocks, thereby providing a greater sense of security regarding prevention of body exudate leakage.

[0028] [Aspect 10] The disposable diaper according to any one of Aspects 1 to 9, wherein when the disposable diaper is stretched in the longitudinal direction and the width direction, and then relaxed and placed on a flat plate, the relaxed area, which is the area of ​​the buttocks-covering portion, is 1800 mm2 or more.

[0029] The present disposable diaper has a relaxed area of ​​1800 mm2 or more. That is, when the present disposable diaper is stretched when put on and then relaxed after put on, the buttocks-covering portion of the present disposable diaper has a large shape with a wide area. Therefore, the large shape of the buttocks-covering portion of the present disposable diaper can more reliably envelop and adequately cover the buttocks, further enhancing the sense of security that body exudates are not leaking.

[0030] Aspect 11 The disposable diaper according to any one of Aspects 1 to 10, wherein, when the disposable diaper is stretched in the longitudinal direction and the width direction and then relaxed and placed on a flat plate, the relationship among the rear joint end distance between the longitudinal rear edges of the pair of back joint portions, the center joint distance between the longitudinal central portions of the pair of back joint portions, and the front buttocks cover end distance between the longitudinal front edges of the outer widthwise edges of the pair of buttocks cover portions is such that, when the rear joint end distance is taken as 100%, the value of ((the buttocks cover end distance) - (the joint center distance)) is 45% or more larger than the value of ((the joint center distance) - (the rear joint end distance)).

[0031] In this disposable diaper, when the distance between the rear joint ends is taken as 100%, the value of ((distance between buttocks cover ends) - (distance between joint centers)) is 45% or more greater than the value of ((distance between joint centers) - (distance between rear joint ends)). In other words, when this disposable diaper is stretched when put on, and then relaxed after put on, the area including the buttocks cover portion in the longitudinal direction has a shape that is larger in the width direction. Therefore, by having a shape in which the area including the buttocks cover portion is larger, this disposable diaper can more reliably wrap around and adequately cover the buttocks, thereby providing a greater sense of security that body waste leakage is prevented.

[0032] Aspect 12 The disposable diaper according to any one of Aspects 1 to 11, wherein, when the disposable diaper is stretched in the longitudinal direction and the width direction and then relaxed and placed on a flat plate, the relationship between the joint center distance between the longitudinal central portions of the pair of back joint portions and the buttocks cover end distance between the longitudinal front end edges of the outer widthwise edges of the pair of buttocks cover portions is such that the value of (the buttocks cover end distance) / (the joint center distance) is 1.4 to 1.8.

[0033] In this disposable diaper, the value of (the distance between the buttocks cover edges) / (the distance between the joint centers) is 1.4 to 1.8. That is, when the disposable diaper is stretched when put on and then relaxed after put on, the region including the buttocks cover portion in the longitudinal direction has a shape that is large in the width direction. Therefore, by having a large shape in the region including the buttocks cover portion, the disposable diaper can more reliably envelop and adequately cover the buttocks, thereby providing a greater sense of security that body exudates will not leak.

[0034] [Aspect 13] The disposable diaper according to any one of Aspects 1 to 12, wherein, when the disposable diaper is stretched in the longitudinal direction and the width direction and then relaxed and placed on a flat plate, the distance between the buttocks cover ends of the outer widthwise edges of the pair of buttocks cover portions on the front longitudinal sides is 220 mm or more.

[0035] In this disposable diaper, the distance between the buttocks cover edges is 220 mm or more. That is, when the disposable diaper is stretched when put on and then relaxed after put on, the region including the buttocks cover portion in the longitudinal direction of the disposable diaper has a shape that is large in the width direction. Therefore, the large shape of the buttocks cover portion of the disposable diaper can more reliably envelop and adequately cover the buttocks, further increasing the sense of security that body exudates are not leaking.

[0036] [Aspect 14] The disposable diaper according to any one of Aspects 1 to 13, wherein each of the pair of buttocks-covering portions includes, at an outer end in the width direction, a rigid portion that is continuously or intermittently arranged along the longitudinal direction.

[0037] In this disposable diaper, the buttocks-covering portion has rigid portions disposed continuously or intermittently along the longitudinal direction at the outer widthwise edges, which prevents the buttocks-covering portion from being folded or rolled up in the longitudinal direction, thereby more reliably enveloping and appropriately covering the buttocks and providing a greater sense of security in preventing bodily excrement leakage.

[0038] [Aspect 15] The disposable diaper according to any one of Aspects 1 to 14, wherein the buttocks-covering portion has buttocks elastic members extending along the width direction only in the lower region.

[0039] In this disposable diaper, the buttocks-covering portion has buttocks elastic members extending in the width direction only in the lower region. Therefore, the buttocks-covering portion lightly holds the buttocks in place in the lower region, preventing them from separating from the buttocks. The upper and central regions are aligned with the buttocks, and the buttocks-covering portion tends to bulge outward to cover the buttocks as a whole. This allows the buttocks-covering portion to properly encase and conceal the buttocks. Furthermore, by encasing and concealing the buttocks, the buttocks-covering portion provides an increased sense of security regarding the prevention of bodily exudate leakage.

[0040] Hereinafter, a disposable diaper according to an embodiment of the present invention will be described using a so-called three-piece type disposable diaper as an example. However, the present invention is not limited to this embodiment and example, and can be applied to various disposable diapers for children and adults without departing from the subject matter of the present invention, such as a so-called two-piece type disposable diaper.

[0041] 1 to 4 are diagrams showing a disposable diaper 1 according to this embodiment. FIG. 1 is a perspective view showing an example of the configuration of the disposable diaper 1. FIG. 2 is a plan view showing the example of the configuration of the disposable diaper 1 in an unfolded state, and therefore shows the state in which the elastic members and stretchable members are stretched. FIG. 3 is a cross-sectional view taken along the longitudinal center line CL in FIG. 2. FIG. 4 is a cross-sectional view taken along the widthwise center line CW in FIG. 2.

[0042] In the unfolded state shown in Figures 2 to 4, the disposable diaper 1 has a longitudinal direction L, a width direction W, and a thickness direction T that are perpendicular to one another. The disposable diaper 1 has a longitudinal centerline CL that passes through the center of the width direction W and extends along the longitudinal direction L, and a widthwise centerline CW that passes through the center of the longitudinal direction L and extends along the width direction W. Here, the directions and sides approaching the longitudinal centerline CL are referred to as the inward and inner sides of the width direction W, respectively, and the directions and sides moving away from the longitudinal centerline CL are referred to as the outward and outer sides of the width direction W, respectively. Meanwhile, the directions and sides approaching the widthwise centerline CW are referred to as the inward and inner sides of the longitudinal direction L, respectively, and the directions and sides moving away from the widthwise centerline CW are referred to as the outward and outer sides of the longitudinal direction L, respectively. Furthermore, the term "planar view" refers to the state in which the disposable diaper 1 is placed on a plane and viewed in the thickness direction T from a position perpendicular to the plane, and the shape as seen in the planar view is referred to as the "planar shape," and any direction within a plane including the longitudinal direction L and the width direction W is referred to as the "planar direction." The terms "skin side" and "non-skin side" refer to the side relatively closer to and farther from the wearer's skin surface in the thickness direction T of the disposable diaper 1 when the disposable diaper 1 is worn. In the longitudinal direction L, the side relatively closer to the ventral portion (described below) or the side relatively farther from the dorsal portion (described below) is also referred to as the ventral side or the front side, and the side relatively closer to the dorsal portion or the side relatively farther from the ventral portion is also referred to as the dorsal side or the rear side. The above definitions are also used for each material of the disposable diaper 1 and for the disposable diaper 1 in the state shown in FIG. 1 .

[0043] Note that a component, structure, shape, etc. aligned with the longitudinal direction L includes not only a component parallel to the longitudinal direction L but also a component within a range of ±30° relative to the longitudinal direction L. Similarly, a component aligned with the width direction W includes not only a component parallel to the width direction W but also a component within a range of ±30° relative to the width direction W. For components with curved or curved surfaces, the component is evaluated as described above for the tangents at each point on the curve.

[0044] The disposable diaper 1 comprises a ventral section 3, a dorsal section 2, and an absorbent main body 4 located between the ventral section 3 and the dorsal section 2. The ventral section 3 is a section of the disposable diaper 1 that covers the ventral side of the wearer. The absorbent main body 4 is a section of the disposable diaper 1 that covers the crotch area of ​​the wearer and includes an absorber 8. The dorsal section 2 is a section of the disposable diaper 1 that covers the dorsal side of the wearer. The front and rear ends of the absorbent main body 4 in the longitudinal direction L are connected to the central portions of the ventral section 3 and the dorsal section 2 in the width direction W, respectively, by, for example, an adhesive (e.g., a hot melt adhesive; the same applies hereinafter). The disposable diaper 1 is formed by joining a pair of ventral joining portions 3a located at both end edges of the ventral section 3 in the width direction W and a pair of dorsal joining portions 2a located at both end edges of the dorsal section 2 in the width direction W to each other. The pair of ventral-side joints 3a and the pair of dorsal-side joints 2a joined together are also referred to as a pair of side joints SC. In this case, in the disposable diaper 1, the ventral-side section 3 and the dorsal-side section 2 joined together at the pair of side joints SC form a waist section WP that covers the wearer's waist. Furthermore, the outer ends of the ventral-side section 3 and the dorsal-side section 2 in the longitudinal direction L define a waist opening WH through which the wearer's waist passes. Furthermore, in the disposable diaper 1, the opposite ends of the absorbent main body 4 in the width direction W and the inner ends of the ventral-side section 3 and the dorsal-side section 2 in the longitudinal direction L define a pair of leg openings LH through which the wearer's pair of legs pass.

[0045] In the unfolded state, the abdominal section 3 and the back section 2 each have a generally rectangular shape that is elongated in the width direction W and are spaced apart from each other in the longitudinal direction L. The absorbent main body 4 has a generally rectangular shape that is elongated in the longitudinal direction L, and one end in the longitudinal direction L is connected to the abdominal section 3 and the other end to the back section 2. The abdominal section 3, the absorbent main body 4, and the back section 2 are formed separately from each other. At least two of the abdominal section 3, the absorbent main body 4, and the back section 2 may be formed integrally or may be connected integrally by a separate outer sheet or the like. For example, if the abdominal section 3 and the back section 2 share at least one of the sheet members that constitute the abdominal section 3 and the back section 2 and are formed integrally from a continuous sheet member, the disposable diaper 1 can be said to be a two-piece type. A three-piece disposable diaper is a disposable diaper which, in an unfolded state, has a ventral portion 3, a dorsal portion 2, and a crotch portion between the ventral portion 3 and the dorsal portion 2, with the crotch portion joining the ventral portion 3 and the dorsal portion 2 and separating the ventral portion 3 and the dorsal portion 2. A two-piece disposable diaper is a disposable diaper which, in an unfolded state, has a ventral portion 3, a dorsal portion 2, and a crotch portion between the ventral portion 3 and the dorsal portion 2, with the crotch portion being joined to the ventral portion and the dorsal portion by a single outer body.

[0046] The ventral portion 3 and the back portion 2 are each formed from a liquid-impermeable sheet material. Each of the ventral portion 3 and the back portion 2 is formed by laminating at least a sheet material located on the skin side and a sheet material located on the non-skin side in the thickness direction T and joining them with an adhesive, heat sealing, or the like (adhesive, etc., the same applies hereinafter). The outer end of the sheet material on the non-skin side in the longitudinal direction L is folded back toward the skin side. In this case, the non-skin side sheet material at the folded position in each of the ventral portion 3 and the back portion 2 constitutes the end of the ventral portion 3 and the back portion 2 in the longitudinal direction L, respectively.

[0047] The abdominal portion 3 includes a plurality of waist-gathering elastic members 13 between the sheet member located on the skin side and the sheet member located on the non-skin side. The plurality of waist-gathering elastic members 13 extend from one end to the other end in the width direction W of the abdominal portion 3, except for a region overlapping with the center of the absorbent body 8 in the thickness direction T, along the width direction W, and are arranged at intervals in the longitudinal direction L. The skin- and non-skin-side sheet members and the plurality of waist-gathering elastic members 13 are joined with an adhesive or the like. The back portion 2 includes a plurality of waist-gathering elastic members 12a, 12b between the sheet member located on the skin side and the sheet member located on the non-skin side. The plurality of waist-gathering elastic members 12a extend from one end to the other end in the width direction W of the back portion 2, except for a region overlapping with the center of the absorbent body 8 in the thickness direction T, along the width direction W, and are arranged at intervals in the longitudinal direction L. The multiple waist elastic members 12b extend from one end of the back portion 2 to the other end along the width direction W in the back portion 2 and are spaced apart in the longitudinal direction L. The skin-side and non-skin-side sheet members and the multiple waist elastic members 12a, 12b are bonded with an adhesive or the like. The multiple waist elastic members 12a, 12b, 13 stretch the waist portion WP. The type of each elastic member is not particularly limited, but examples include thread-like or sheet-like rubber. The material of each elastic member is not particularly limited, but examples include styrene butadiene rubber and urethane rubber. The characteristics of each elastic member, such as the cross-sectional size (wire diameter, etc.) and elongation ratio, are appropriately selected depending on the magnitude of the tightening force corresponding to the position within the waist portion WP.

[0048] Examples of each sheet member include any liquid-impermeable sheet such as a liquid-impermeable nonwoven fabric or synthetic resin film, a composite sheet of these, an SB nonwoven fabric, or an SMS nonwoven fabric. The type of nonwoven fabric is not particularly limited, and examples include meltblown nonwoven fabric, spunbond nonwoven fabric, airlaid nonwoven fabric, and air-through nonwoven fabric. The material of the nonwoven fabric or synthetic resin film of the sheet member is not particularly limited as long as it can be used for sanitary products, and examples include polyolefin resins such as polypropylene and polyethylene, polyamide resins such as 6-nylon and 6,6-nylon, and polyester resins such as polyethylene terephthalate and polybutylene terephthalate. The basis weight of the nonwoven fabric of the sheet member is, for example, 5 to 100 g / m ２ and preferably 10 to 50 g / m ２ The length (thickness) of the sheet member in the thickness direction T is, for example, 0.1 to 5 mm, and preferably 0.1 to 2 mm. The sheet member constituting each of the ventral side portion 3 and the dorsal side portion 2 may be one sheet member or three or more sheets (not shown). The sheet member does not have to be folded (not shown).

[0049] In this embodiment, the disposable diaper 1 further includes an exterior sheet member 14 that bridges the gap between the ventral portion 3 and the dorsal portion 2. The exterior sheet member 14 is a liquid-impermeable sheet member, such as a nonwoven fabric, and both ends in the longitudinal direction L are laminated to the ventral portion 3 and the dorsal portion 2, respectively, and bonded thereto with an adhesive or the like. The type and material of the nonwoven fabric are as described above. The exterior sheet member 14 is also bonded with an adhesive or the like to the non-skin side of the absorbent main body 4, which is generally disposed between the ventral portion 3 and the dorsal portion 2, to support and protect the absorbent main body 4 from the non-skin side. The exterior sheet member 14 may be composed of two or more sheet members (not shown). A sheet member other than the exterior sheet member 14 may be provided on the non-skin side (not shown).

[0050] The disposable diaper 1 may further include a sheet-like elastic member 50 bonded with an adhesive to the skin side or non-skin side of at least one of the abdominal portion 3 and the back portion 2 and extending along the width direction W. In this embodiment, the sheet-like elastic member 50 is disposed on the skin side of the back portion 2 and on the skin side of the absorbent main body 4. The sheet-like elastic member 50 is a sheet-like member that is elastic in the width direction W, and functions as, for example, a waist gather and / or a sweat-absorbing sheet. Examples of types of the sheet-like elastic member 50 include elastic nonwoven fabrics that are composites of styrene rubber, olefin rubber, urethane rubber, or the like with nonwoven fabric, paper, or the like.

[0051] The absorbent main body 4 includes a main body central portion 10 located at the center in the width direction W and extending along the longitudinal direction L, and a pair of leg gather portions 5 located at both ends in the width direction W and extending along the longitudinal direction L. Each of the pair of leg gather portions 5 extends along the longitudinal direction L and has a plurality of leg elastic members 5a arranged at intervals in the width direction W.

[0052] The main body central portion 10 has a substantially rectangular shape and includes a liquid-permeable topsheet 7, a liquid-impermeable backsheet 9, and an absorbent body 8 that is positioned between the topsheet 7 and the backsheet 9 and absorbs and retains liquid. The absorbent body 8 is bonded to the topsheet 7 and the backsheet 9 with an adhesive, and the topsheet 7 and the backsheet 9 are bonded to each other with an adhesive at their peripheral edges. The shape of the main body central portion 10 is not limited to the above example as long as it is long in the longitudinal direction L, and examples include a rectangle with rounded corners, a rectangle with outwardly convex curved short sides, and an hourglass shape.

[0053] Examples of the top sheet 7 include liquid-permeable nonwoven fabrics or woven fabrics, synthetic resin films with liquid-permeable holes, and composite sheets of these. Examples of the back sheet 9 include liquid-impermeable nonwoven fabrics or synthetic resin films, composite sheets of these, and SMS nonwoven fabrics. The type of nonwoven fabric is not particularly limited, and examples include meltblown nonwoven fabrics, spunbond nonwoven fabrics, airlaid nonwoven fabrics, and air-through nonwoven fabrics. The type of synthetic resin film is not particularly limited, and known film materials can be used. Materials for the nonwoven fabric and synthetic resin film are not particularly limited as long as they are usable for sanitary products, and examples include olefin-based resins such as polyethylene and polypropylene, polyamide-based resins such as 6-nylon and 6,6-nylon, and polyester-based resins such as polyethylene terephthalate and polybutylene terephthalate. Cellulose-based fibers may also be used as the nonwoven fabric material. To impart breathability, the synthetic resin film may contain inorganic particles such as calcium carbonate.

[0054] The absorbent body 8 includes an absorbent core 8b that absorbs and retains liquid, a core wrap 8a that encases the absorbent core 8b, and grooves 8c that can diffuse liquid in the longitudinal direction L and the width direction W. The material of the absorbent core 8b can be an absorbent material, such as at least one of cellulose-based fibers and superabsorbent polymers. Examples of cellulose-based fibers include natural cellulose fibers such as pulp fibers (e.g., wood pulp fibers, crosslinked pulp fibers, and non-wood pulp fibers), regenerated cellulose fibers, and semi-synthetic cellulose fibers. Pulp fibers have an average fiber length of, for example, several tens of microns, preferably 20 to 40 microns, and an average fiber length of, for example, several millimeters, preferably 2 to 5 mm. Examples of superabsorbent polymers (SAPs) include polyacrylate-based, polysulfonate-based, and maleic anhydride-based superabsorbent polymers. The size (when dry) of the superabsorbent polymer may be, for example, an average particle size of several hundred μm, preferably 200 to 500 μm. The basis weight of the cellulosic fiber and the superabsorbent polymer may be, for example, 100 to 400 g / m2 each. Examples of materials for the core wrap 8a include nonwoven fabrics and liquid-permeable sheets such as tissue.

[0055] The main body central portion 10 includes a pair of leak-proof walls 6 arranged on both sides in the width direction W facing each other and extending along the longitudinal direction L. Each leak-proof wall 6 extends along the longitudinal direction L and is formed of a sheet member 6b containing multiple leak-proof elastic members 6a arranged at intervals in the width direction W. Each leak-proof wall 6 has an outer end in the width direction W bonded to at least one of the topsheet 7, absorbent body 8, and backsheet 9 with an adhesive or the like to form a fixed end, and an inner end in the width direction W to form a free end separated from the other sheets, including the topsheet 7. The multiple leak-proof elastic members 6a are bonded to the sheet member 6b with an adhesive near the free end. Examples of the sheet member 6b include hydrophobic nonwoven fabric and hydrophilic nonwoven fabric. The type and material of the nonwoven fabric are as described above. The multiple leak-proof elastic members 6a are exemplified by rubber thread, and the type and material of the elastic members are as described above. The properties of the elastic member, such as the cross-sectional size (wire diameter, etc.) and the elongation ratio, are appropriately selected depending on the function of the leak preventing walls 6. Note that the inner end of each leak preventing wall 6 in the width direction W may be further folded back outward in the width direction W.

[0056] A pair of leg gathers 5 are joined to both ends of the main body central portion 10 in the width direction W. Each leg gather 5 extends along the longitudinal direction L and includes multiple leg elastic members 5a spaced apart in the width direction W, and skin-side and non-skin-side sheet members 5b sandwiching the multiple leg elastic members 5a. Each leg gather 5 has its inner end in the width direction W joined to the non-skin-side surface of the width direction W end of the main body central portion 10 with an adhesive or the like to form a fixed end, and its outer end in the width direction W separated from the main body central portion 10 to form a free end. The multiple leg elastic members 5a are joined with an adhesive near the free ends of the skin-side and non-skin-side sheet members 5b. The multiple leg elastic members 5a stretch each leg gather 5. Examples of sheet members 5b include hydrophobic nonwoven fabrics and hydrophilic nonwoven fabrics. The type and material of the nonwoven fabric are as described above. The leg elastic members 5a are exemplified by rubber threads, and the types and materials of the elastic members are as described above. The properties of the elastic members, such as the cross-sectional size (linearity, etc.) and elongation ratio of the elastic members, are appropriately selected depending on the magnitude of the tightening force corresponding to the position in the leg gathered portion 5.

[0057] In the disposable diaper 1, the pair of leg gathers 5 are bridged by an exterior sheet member 14. Both ends of the exterior sheet member 14 in the width direction W are laminated to the inner ends of each of the pair of leg gathers 5 in the width direction W and joined with an adhesive or the like, thereby supporting and protecting the pair of leg gathers 5 from the non-skin side.

[0058] The back portion 2 includes a back main body portion 21 that occupies substantially the same area in the longitudinal direction L as the back joint portion 2a, and a back extension portion 20 that extends forward from the front edge of the back main body portion 21 in the longitudinal direction L. In other words, the back main body portion 21 is the rear region of the back portion 2 in the longitudinal direction L, and its length in the longitudinal direction L is substantially the same as that of the back joint portion 2a and its length in the width direction W is the same as that of the back portion 2. The waist elastic members 12a, 12b of the back portion 2 are arranged in the back main body portion 21. Therefore, the back main body portion 21 is the region where at least the waist elastic members 12a, 12b are arranged. The meaning of "substantially the same area as the back joint portion 2a" will be explained later. On the other hand, the back-side extension portion 20 is the region on the front side of the back portion 2 in the longitudinal direction L, and its length in the longitudinal direction L is the length of the back portion 2 minus the length of the back main body portion 21, and its length in the width direction W is the same as that of the back portion 2. The back-side extension portion 20 is the remaining region of the back portion 2 minus the back main body portion 21.

[0059] The back-side extending portion 20 includes an extending central portion 31 that overlaps the main body central portion 10 in the thickness direction T, and a pair of buttocks covering portions 30 that extend outward from both side edges of the extending central portion 31 in the width direction W. In other words, the extending central portion 31 is a central (inner) region of the back-side extending portion 20 in the width direction W, and its length in the width direction W is the same as the length of the main body central portion 10 and its length in the longitudinal direction L is the same as the length of the back-side extending portion 20. On the other hand, the buttocks covering portion 30 is a region of the back-side extending portion 20 outside in the width direction W, and its length in the width direction W is half the length of the back-side extending portion 20 minus the length of the main body central portion 10, and its length in the longitudinal direction L is the same as the length of the back-side extending portion 20. The buttocks covering portion 30 can also be said to be a region of the back-side extending portion 20 that does not overlap with the main body central portion 10 in the thickness direction T.

[0060] FIG. 5 is a partial plan view showing an example of the configuration of the disposable diaper 1 according to this embodiment in an unfolded state. This view is an enlarged view of the area near the buttocks-covering portion 30, and can also be considered a view showing the extended state. As described above, the length of the buttocks-covering portion 30 in the width direction W, i.e., the extended widthwise length dWa, is calculated by subtracting the length of the main body central portion 10 (or the extended central portion 31) from the length of the back-side extending portion 20, and then dividing the result by half. Meanwhile, the length in the longitudinal direction L, i.e., the extended longitudinal length dLa, is the same as the length of the back-side extending portion 20. The buttocks-covering portion 30 includes a buttocks elastic member 40 extending along the width direction W in an inner region of the longitudinal direction L. The effective portion of the buttocks elastic member 40 as an elastic member is within the width direction W of the buttocks-covering portion 40. The buttocks elastic member 40 is exemplified by rubber thread, and the type and material of the elastic member are as described above. The properties of the elastic member, for example, the cross-sectional size (linearity, etc.) and the elongation ratio of the elastic member, are appropriately selected according to the magnitude of the fastening force corresponding to the position inside the buttocks covering portion 30.

[0061] Here, when we say that "the dorsal main body portion 21 occupies substantially the same area as the dorsal joint portion 2a in the longitudinal direction L," the meaning of "substantially the same area as the dorsal joint portion 2a" is as follows. As shown in FIG. 5 , the end P on the inner side (front side) of the dorsal joint portion 2a in the longitudinal direction L is included in the dorsal extension portion 20, not the dorsal main body portion 21. However, the length of the end P in the longitudinal direction L is small compared to the entire length of the dorsal joint portion 2a. Therefore, the area that the dorsal main body portion 21 occupies in the dorsal portion 2 in the longitudinal direction L is the range obtained by excluding the length of the end P from the range of the dorsal joint portion 2a, but is still "substantially" the same area as the dorsal joint portion 2a. The ratio of the length of the end P to the length of the dorsal joint portion 2a in the longitudinal direction L is, for example, 2 to 4%, and the actual length is, for example, 2 to 5 mm.

[0062] The buttocks-covering portion 30 includes a plurality of rigid portions 2h arranged continuously or intermittently along the longitudinal direction L at the outer end in the width direction W. The rigid portions 2h are arranged side by side in the longitudinal direction L on the inside (front side) of the end P of the back-side joint portion 2a. The rigid portions 2h join the sheet member located on the skin side of the back-side portion 2 and the sheet member located on the non-skin side in the thickness direction T. The rigid portions 2h are exemplified by, for example, heat sealing.

[0063] The buttocks-covering portion 30 includes an upper rear region 30a, a central region 30b, and a lower front region 30c, which are obtained by dividing the buttocks-covering portion 30 into three equal regions in the longitudinal direction L. The contractile force of the lower region 30c in the width direction W is higher than the contractile force of the upper region 30a and the central region 30b in the width direction W. The magnitude of the contractile force can be compared, for example, by the number of elastic members, the cross-sectional size (wire diameter, etc.) of the elastic members, and the elongation ratio. For example, the number of buttocks elastic members 40 extending along the width direction W is greater in the lower region 30c than in the upper region 30a and the central region 30b. In this embodiment, the number of buttocks elastic members 40 is one in the lower region 30c, but zero in the upper region 30a and the central region 30b. Alternatively, the magnitude of the contractile force can be compared, for example, by measuring the values ​​measured with a tensile tester. The measurement method using a tensile tester will be described later. The contractile force in the width direction W of the central region 30b may be equal to or greater than the contractile force in the width direction W of the upper region 30a.

[0064] The buttocks-covering portion 30 includes an overlapping region OA and a non-overlapping region UA ​​in an inner region in the width direction W. The overlapping region OA is located on the front side in the longitudinal direction L and overlaps in the thickness direction T with the rear ends of the leg elastic members 5a in the longitudinal direction L. The non-overlapping region UA ​​is located on the rear side in the longitudinal direction L and does not overlap with the leg elastic members 5a in the thickness direction T. The buttocks-covering portion 30 has an inner region in the width direction W that overlaps with the leg gathered portion 5 in the thickness direction T and is joined to the leg gathered portion 5 with an adhesive or the like. The rear end region in the longitudinal direction L of the leg gathered portion 5 where the leg elastic members 5a are present overlaps with the overlapping region OA of the buttocks-covering portion 30 in the thickness direction T. The region of the leg gathered portion 5 where the leg elastic members 5a are not present overlaps with the non-overlapping region UA ​​of the buttocks-covering portion 30 in the thickness direction T.

[0065] As described above, in the disposable diaper 1, the buttocks-covering portion 30 includes an upper region 30a on the rear side (back side), a central region 30b in the longitudinal direction L, and a lower region 30c on the front side (belly side), and the lower region 30c has a higher contractile force in the width direction W than the upper region 30a and the central region 30b. Therefore, when the disposable diaper 1 is put on, the lower region 30c can be contracted while the upper region 30a and the central region 30b can be prevented from contracting too much. As a result, the buttocks-covering portion 30 is likely to assume a shape that bulges outward to cover the outside of the buttocks as a whole, with the lower region 30c gently holding the buttocks and preventing them from separating from the buttocks, and the upper region 30a and the central region 30b fitting along the buttocks.

[0066] Furthermore, in the disposable diaper 1, the rear ends of the multiple leg elastic members 5a of the leg gathers 5 overlap in the thickness direction T with an overlapping region OA, which is a region on the front (ventral) side in the longitudinal direction L of the inner region of the buttocks-covering portion 30 in the width direction W. This allows the overlapping region OA on the front (ventral) side in the longitudinal direction L of the buttocks-covering portion 30 to be pulled forward in the longitudinal direction L by the leg elastic members 5a. On the other hand, the multiple leg elastic members 5a of the leg gathers 5 do not overlap in the thickness direction T with a non-overlapping region UA, which is a region on the rear (back) side in the longitudinal direction L of the inner region of the buttocks-covering portion 30 in the width direction W. This makes it difficult for the leg elastic members 5a to stretch the non-overlapping region UA ​​of the buttocks-covering portion 30. In this way, the overlapping region OA on the front side (ventral side) in the longitudinal direction L of the buttocks-covering part 30, and therefore the lower region 30c, are pulled to the front side (ventral side) in the longitudinal direction L, i.e., toward the crotch side, so that these regions do not contract too much in the longitudinal direction L. At the same time, the non-overlapping region UA ​​on the rear side (back side) in the longitudinal direction L of the buttocks-covering part 30, and therefore the upper region 30a, become difficult to stretch, so deformation in these regions is suppressed.

[0067] FIG. 10 is a perspective view showing the disposable diaper 1 according to this embodiment in a worn state. As described above, the high contractile force in the width direction W in the lower region 30c and the presence of the overlapping region OA and non-overlapping region UA ​​combine to allow the buttocks-covering portion 30 to gently expand outward without excessive contraction, making it easier to conform to the surface of the buttocks. This allows the buttocks-covering portion 30 to properly encase and conceal the buttocks. In other words, the buttocks-covering portion 30 is prevented from collapsing (rolling up) on the inside in the width direction W and on the outside in the longitudinal direction L (toward the absorbent main body 4 and the back main body portion 21). Furthermore, the buttocks-covering portion 30 properly encases and conceals the buttocks, enhancing the sense of security regarding the prevention of body waste leakage.

[0068] Fig. 6 is a partial plan view showing an example of the configuration of a disposable diaper 1 according to this embodiment in an unfolded state. This view is an enlarged view of the area near the buttocks-covering portion 30, and can also be considered a view showing the extended state. In a preferred aspect of this embodiment, the buttocks-covering portion 30 has a tensile stress of 0.25 N or less in the region between the position of the back-side joining portion 2a and the edge of the absorbent main body 4 on the buttocks-covering portion 30 side in the width direction W (hereinafter also referred to as the "measurement region MA"). Here, in this embodiment, the position of the back-side joining portion 2a in the width direction W in the measurement region MA refers to the positions of the back-side joining portion 2a and the multiple rigid portions 2h arranged along the longitudinal direction L. Meanwhile, in this embodiment, the position of the edge of the absorbent main body 4 on the buttocks-covering portion 30 side in the width direction W in the measurement region MA refers to the outer edge 5e of the leg gather portion 5. In the measurement area MA, the range in the longitudinal direction L is the same as the range in the longitudinal direction L of the buttocks cover portion 30. Therefore, the length in the width direction W of the measurement area MA is dWm in Fig. 6, and the length in the longitudinal direction L of the measurement area MA is dLm in Fig. 6. The tensile stress in the width direction W of the measurement area MA may be 0.05 N or more, or may be 0.1 N or more.

[0069] Thus, in the disposable diaper 1, the buttocks-covering portion 30 has a tensile stress of 0.25 N or less in the region between the position of the back-side joint 2 a and the position of the edge 5 e of the absorbent main body 4 in the width direction W. This allows the buttocks-covering portion 30 to more reliably and gently bulge outward without excessive contraction as a whole, making it easier to conform to the surface of the buttocks. In other words, the buttocks-covering portion 30 can more reliably envelop and adequately conceal the buttocks. This further enhances the sense of security that the buttocks-covering portion 30 provides regarding prevention of body waste leakage. Furthermore, because the tensile stress is 0.05 N or more, the buttocks-covering portion 30 can more reliably and gently bulge outward.

[0070] The measurement method using a tensile tester is as follows: (1) Prepare a tensile tester (Universal Material Testing Machine Model No. 5565, manufactured by Instron Corporation). (2) Prepare a test specimen. For example, when measuring the contractile force of each of the upper region 30a, the central region 30b, and the lower region 30c, cut out the buttocks-covering portion 30 from the disposable diaper 1, and cut out the upper region 30a, the central region 30b, and the lower region 30c from the buttocks-covering portion 30 to prepare test specimens. Similarly, when measuring the tensile stress of the measurement region MA, cut out the measurement region MA from the buttocks-covering portion 30 to prepare test specimens. (3) Clamp one end of the test specimen in the upper chuck. (4) Raise the upper chuck until the test specimen hangs above the lower chuck and no longer touches the lower bar. (5) Correct the force to zero to remove the weight of the test specimen. (6) Lower the upper chuck to the initial chuck distance (20 mm). (7) Clamp the other end of the test piece in the lower chuck. The area between the upper and lower chucks is the measurement area. (8) Start the test and move the upper chuck upward at 100 mm / min until it reaches 80% of the template dimension (maximum stretched state = expanded state). (9) Then, immediately return the upper chuck to the initial chuck distance at the same speed. (10) Record the force at 80% of the template dimension (maximum stretched state). (11) Calculate the average tension (N) of n = 5 measured in (10) above. If the test piece is divided into upper region 30a, central region 30b, and lower region 30c, this average tension can be considered their contraction force. Furthermore, if the test piece is taken as the measurement area MA and this average tension is divided by the length dLm of the measurement area MA in the longitudinal direction L, it can be regarded as the tensile stress in the width direction W of the measurement area MA.

[0071] In a preferred aspect of the present embodiment, the overlapping region OA is in a range of less than 50% of the length (extended longitudinal length dLa) of the buttocks-covering portion 30 in the longitudinal direction L. Therefore, the length of the overlapping region OA in the longitudinal direction L is less than 50% of the extended longitudinal length dLa of the buttocks-covering portion 30, and the length of the non-overlapping region UA ​​in the longitudinal direction L is 50% or more of the extended longitudinal length dLa of the buttocks-covering portion 30. Note that the overlapping region OA may be in a range of less than 40% of the length (extended longitudinal length dLa) of the buttocks-covering portion 30 in the longitudinal direction L, but may also be in a range of at least 5% or more, or may be in a range of 10% or more.

[0072] Thus, in the disposable diaper 1, the overlapping region OA, i.e., the region where the rear ends of the leg elastic members 5a in the longitudinal direction L overlap with the front portions of the inner regions of the buttocks-covering portion 30 in the longitudinal direction L, is less than 50% of the length (extended longitudinal length dLa) of the buttocks-covering portion 30 in the longitudinal direction L. This more reliably prevents the buttocks-covering portion 30 from contracting excessively in the longitudinal direction L and allows the buttocks-covering portion 30 to bulge gently outward. This more reliably enables the buttocks-covering portion 30 to envelop and adequately conceal the buttocks. This enhances the sense of security that the buttocks-covering portion 30 provides to prevent bodily exudates from leaking. Furthermore, since the overlapping region OA is 5% or more, it more reliably prevents the buttocks-covering portion 30 from contracting excessively in the longitudinal direction L.

[0073] In a preferred aspect of this embodiment, the buttocks-covering portion 30 has its inner regions in the width direction W (overlapping region OA and non-overlapping region UA) joined to the leg gathered portion 5. The buttocks-covering portion 30 has, in its lower region 30c, buttocks elastic members 40 extending along the width direction W. Of the multiple leg elastic members 5a, the innermost leg elastic member 5ai, which is located on the innermost side in the width direction W, does not overlap with the buttocks elastic member 40 in the thickness direction T.

[0074] As described above, in the disposable diaper 1, the innermost leg elastic member 5ai of the plurality of leg elastic members 5a does not overlap the buttocks elastic member 40 in the thickness direction T. In this case, not all of the plurality of leg elastic members 5a are pulled by the buttocks elastic member 40. This prevents the leg gathers 5 near the buttocks-covering portion 30 from being pulled outward in the width direction W by the buttocks-covering portion 30 (from being rolled up). This allows the buttocks-covering portion 30 to appropriately cover the buttocks, while allowing the leg gathers 5 to appropriately come into surface contact with the legs, thereby allowing the leg gathers 5 to properly perform their function.

[0075] In a preferred aspect of this embodiment, the buttocks-covering portion 30 has its inner regions in the width direction W (overlapping region OA and non-overlapping region UA) joined to the leg gathered portion 5. The buttocks-covering portion 30 has, in its lower region 30c, buttocks elastic members 40 extending along the width direction W. The outermost leg elastic members 5ao, which are located on the outermost sides in the width direction W among the multiple leg elastic members 5a, overlap the buttocks elastic members 40 in the thickness direction T.

[0076] As described above, in the disposable diaper 1, the outermost leg elastic member 5ao of the plurality of leg elastic members 5a overlaps the buttocks elastic member 40 in the thickness direction T. In this case, the outermost leg elastic member 5ao of the plurality of leg elastic members 5a is pulled by the buttocks elastic member 40. As a result, only the outer portions of the leg gathers 5 near the buttocks-covering portion 30 in the width direction W are pulled outward to an appropriate extent, allowing them to conform to the surfaces of the legs near the buttocks. This allows the buttocks-covering portion 30 to appropriately cover and conceal the buttocks, while allowing the leg gathers 5 to appropriately come into surface contact with the legs near the buttocks, thereby allowing them to properly perform their functions.

[0077] Fig. 7 is a schematic diagram showing an example of the configuration of the disposable diaper 1 according to this embodiment. This diagram shows the disposable diaper 1 of Fig. 1 in a state where it has been stretched in the longitudinal direction L and the width direction W, and then relaxed and placed on a flat plate. The method for stretching the disposable diaper 1 in the longitudinal direction L and the width direction W, and then relaxed and placed on a flat plate will be described later.

[0078] As shown in Fig. 7 , when the disposable diaper 1 is stretched and then relaxed and placed on a flat plate, the lengths of the buttocks-covering portion 30 in the longitudinal direction L and width direction W are defined as a relaxed longitudinal length dLb and a relaxed width direction dWb, respectively. Meanwhile, as described above, when the disposable diaper 1 is stretched (not relaxed) in the longitudinal direction L and width direction W and placed on a flat plate, the lengths of the buttocks-covering portion 30 in the longitudinal direction L and width direction W are defined as an extended longitudinal length dLa and an extended width direction dWa (see Fig. 5 ). In this embodiment, in a preferred aspect, the ratio of the relaxed longitudinal length dLb to the extended longitudinal length dLa of the disposable diaper 1 is 90% or more, and the ratio of the relaxed width direction length dWb to the extended width direction length dWa is 50% or more.

[0079] The specific method for stretching the disposable diaper 1 in the longitudinal direction L and the width direction W, relaxing it, and placing it on a flat plate is as follows. The flat plate does not have to be plate-shaped as long as it has a horizontal surface on which the disposable diaper 1 can be placed. (1) The disposable diaper 1 shown in Fig. 1 is laid generally flat so that the ventral portion 3 and the back portion 2 overlap each other and the absorbent main body 4 is folded in half. Then, an operator grasps the upper end UE (non-skin side) of the waist portion WP and the lower end DE (non-skin side) of the absorbent main body 4 with one and the other hand, respectively, and lightly stretches and relaxes the diaper 1 in the vertical direction (longitudinal direction L) multiple times (e.g., two or three times). (2) Next, an operator grasps the pair of side joints SC with one and the other hand, respectively, and repeatedly stretches and relaxes the diaper 1 in the left-right direction (width direction W) multiple times (e.g., two or three times). (3) Then, the disposable diaper 1 is placed on a flat plate, and a transparent acrylic plate is placed on the disposable diaper 1. The acrylic plate has dimensions of 450 mm x 200 mm x 6 mm and a mass of 550 g. (4) The length is measured from above the acrylic plate.

[0080] Thus, in the disposable diaper 1, the ratio of the relaxed longitudinal length dLb to the extended longitudinal length dLa is 90% or more, and the ratio of the relaxed widthwise length dWb to the extended widthwise length dWa is 50% or more. That is, even when the disposable diaper 1 is stretched during donning and then relaxed after donning, the buttocks-covering portion 30 does not shrink significantly from its extended size and maintains a relatively constant size. This allows the buttocks-covering portion 30 to more reliably envelop and adequately conceal the buttocks. Furthermore, the buttocks-covering portion 30's ability to envelop and adequately conceal the buttocks provides a greater sense of security regarding the prevention of bodily exudate leakage.

[0081] As shown in Fig. 7 , when the disposable diaper 1 is stretched and then relaxed and placed on a flat plate, the lengths of the buttocks-covering portion 30 in the longitudinal direction L and width direction W are a relaxed longitudinal length dLb and a relaxed width direction dWb, respectively. On the other hand, as described above, when the disposable diaper 1 is stretched (not relaxed) in the longitudinal direction L and width direction W and placed on a flat plate, the lengths of the buttocks-covering portion 30 in the longitudinal direction L and width direction W are an extended longitudinal length dLa and an extended width direction dWa (see Fig. 5 ). In this embodiment, in a preferred aspect, the disposable diaper 1 has a contraction length of the relaxed longitudinal length dLb relative to the extended longitudinal length dLa of 4 mm or less, and a contraction length of the relaxed width direction dWb relative to the extended width direction length dWa of 55 mm or less.

[0082] Thus, in the disposable diaper 1, the ratio of the relaxed longitudinal length dLb to the extended longitudinal length dLa is 4 mm or less, and the ratio of the relaxed widthwise length dWb to the extended widthwise length dWa is 55 mm or less. That is, even when the disposable diaper 1 is stretched during donning and then relaxed after donning, the buttocks-covering portion 30 does not shrink significantly from its extended size and maintains a relatively constant size. This allows the buttocks-covering portion 30 to more reliably envelop and adequately conceal the buttocks. Furthermore, the buttocks-covering portion 30's ability to envelop and adequately conceal the buttocks provides a greater sense of security regarding the prevention of bodily exudate leakage.

[0083] Fig. 8 is a schematic diagram showing an example of the configuration of a disposable diaper 1 according to this embodiment. Fig. 8 also shows a schematic view of the disposable diaper 1 of Fig. 1 laid flat overall so that the ventral portion 3 and the back portion 2 overlap each other and the absorbent main body 4 is folded in half. The disposable diaper 1 is then placed on a flat plate in a stretched state (not relaxed) in the longitudinal direction L and the width direction W. In the stretched state, the distance between the rear edges of the pair of back-side joining portions 2a in the longitudinal direction L is defined as the stretched-joint rear-end distance DWa3, the distance between the central portions of the pair of back-side joining portions 2a in the longitudinal direction L is defined as the stretched-joint center-to-center distance DWa2, and the distance between the front edges of the pair of buttocks-cover portions 30 in the longitudinal direction L at their outer edges in the width direction W is defined as the stretched buttocks-cover end-to-end distance DWa1. In addition, the maximum lengths in the longitudinal direction L and width direction W of the disposable diaper 1 in the stretched state are defined as the maximum stretched longitudinal length and maximum stretched widthwise length, respectively. In the figure, the maximum stretched longitudinal length of the disposable diaper 1 is DLa1, and the maximum stretched widthwise length is DWa1 (= DWa2 = DWa3).

[0084] In a preferred embodiment of the present invention, the disposable diaper 1 has a waist circumference (approximately DWa1 (= DWa2 = DWa3) × 2) of 590 to 1050 mm when stretched in the longitudinal direction L and the width direction W (FIG. 8). When the disposable diaper 1 is stretched in the longitudinal direction L and the width direction W, relaxed, and placed on a flat plate, the relaxed widthwise length dWb, which is the length in the widthwise W of the buttocks-covering portion 30, is 55 mm or more.

[0085] Thus, when the circumference of the waist portion of the disposable diaper 1 is in the range of 590 to 1050 mm, i.e., when the disposable diaper 1 is for a baby, the relaxed widthwise length dWb is 55 mm or greater. That is, even when the disposable diaper 1 is stretched during donning and then relaxed after donning, the buttocks-covering portion 30 does not shrink significantly from its stretched size and can maintain a relatively constant size. This allows the buttocks-covering portion 30 to more reliably envelop and adequately conceal the buttocks. Furthermore, the buttocks-covering portion 30's ability to envelop and adequately conceal the buttocks provides a greater sense of security regarding the prevention of bodily excrement leakage.

[0086] FIG. 9 is a schematic diagram showing an example of the configuration of a disposable diaper 1 according to this embodiment. This figure shows the disposable diaper 1 stretched in the longitudinal direction L and the width direction W and then laid on a flat plate in a relaxed state. The maximum lengths of the disposable diaper 1 in the longitudinal direction L and the width direction W when the disposable diaper 1 is stretched in the longitudinal direction L and the width direction W and then laid on a flat plate in a relaxed state are designated as the relaxed maximum longitudinal length DLb1 and the relaxed maximum width direction DWb1, respectively. In this case, in a preferred aspect of this embodiment, when the disposable diaper 1 is stretched in the longitudinal direction L and the width direction W, the circumference of the waist portion formed by the ventral portion 3 and the dorsal portion 2 (approximately DWa1 (= DWa2 = DWa3) × 2) is in the range of 590 to 1050 mm. The relaxed maximum width direction length DWb1 is greater than the relaxed maximum longitudinal length DLb1 (DWb1 > DLb1).

[0087] Thus, when the circumference of the waist portion of the disposable diaper 1 is in the range of 590 to 1050 mm, i.e., when the disposable diaper 1 is for a baby, the maximum relaxed widthwise length DWb1 is greater than the maximum relaxed longitudinal length DLb1. That is, when the disposable diaper 1 is stretched when put on and then relaxed after put on, the disposable diaper 1 has a large shape in the width direction W. Here, the maximum relaxed widthwise length DWb1 is the length including the buttocks-covering portion 30. Therefore, the disposable diaper 1 has a large shape in the width direction W including the buttocks-covering portion 30, and can more reliably envelop and adequately cover the buttocks, thereby providing an increased sense of security regarding prevention of body waste leakage.

[0088] In a preferred embodiment of the present invention, when the disposable diaper 1 is stretched in the longitudinal direction L and the width direction W, and then relaxed and placed on a flat plate, the relaxed area RA (see FIG. 7 ), which is the area of ​​the buttocks-covering portion 30, is 1800 mm ２ That's all.

[0089] In this way, in the disposable diaper 1, the relaxed area of ​​the buttocks cover portion 30 is 1800 mm ２ That is, when the disposable diaper 1 is stretched during donning and then relaxed after donning, the buttocks-covering portion 30 of the disposable diaper 1 has a large shape with a wide area. Therefore, the large shape of the buttocks-covering portion 30 of the disposable diaper 1 allows the buttocks to be more reliably wrapped around and appropriately covered, thereby providing a greater sense of security regarding prevention of bodily exudate leakage.

[0090] 9, when one disposable diaper is stretched in the longitudinal direction L and the width direction W and then relaxed and placed on a flat plate, the distance between the rear edges of the pair of back-side joint portions 2a in the longitudinal direction L is defined as the rear-joining-end distance DWb3, the distance between the central portions of the pair of back-side joint portions 2a in the longitudinal direction L is defined as the joint-center distance DWb2, and the distance between the front edges of the pair of buttocks-cover portions 30 in the longitudinal direction L at their outer edges in the width direction W is defined as the buttocks-cover-end distance DWb1. The relaxed widthwise maximum length DWb1 and the buttocks-cover-end distance DWb1 are the same. In this case, in a preferred aspect of the present embodiment, the relationship between the distance DWb3 between the joint rear ends, the distance DWb2 between the joint centers, and the distance DWb1 between the buttock cover ends is such that, when the distance DWb3 between the joint rear ends is set to 100%, the value of ((distance DWb1 between the buttock cover ends) - (distance DWb2 between the joint centers)) is 45% or more larger than the value of ((distance DWb2 between the joint centers) - (distance DWb3 between the joint rear ends)).

[0091] Thus, in the disposable diaper 1, when the distance DWb3 between the rear joint ends is taken as 100%, the value of ((distance DWb1 between the buttocks cover ends) - (distance DWb2 between the joint centers)) is 45% or more larger than the value of ((distance DWb2 between the joint centers) - (distance DWb3 between the rear joint ends)). In other words, when the disposable diaper 1 is stretched once when put on and then relaxed after put on, the area including the buttocks cover portion 30 in the longitudinal direction L has a shape that is large in the width direction W. Therefore, by having a large shape for the area including the buttocks cover portion 30, the disposable diaper 1 can more reliably wrap around and adequately cover the buttocks, thereby providing an increased sense of security that body waste leakage is prevented.

[0092] As described above, when the disposable diaper 1 is stretched in the longitudinal direction L and the width direction W and then relaxed and placed on a flat plate, the distance between the central portions of the pair of back-side joint portions 2a in the longitudinal direction L is the joint center distance DWb2, and the distance between the front edges of the pair of buttocks-cover portions 30 in the longitudinal direction L at their outer edges in the width direction W is the buttocks-cover end distance DWb1. In this case, in a preferred aspect of the present embodiment, the relationship between the joint center distance DWb2 and the buttocks-cover end distance DWb1 is such that the value of (buttocks-cover end distance DWb1) / (join center distance DWb2) is 1.4 to 1.8.

[0093] Thus, in the disposable diaper 1, the value of (buttocks cover edge distance DWb1) / (joining center distance DWb2) is 1.4 to 1.8. In other words, when the disposable diaper 1 is stretched when put on and then relaxed after put on, the region including the buttocks cover portion 30 in the longitudinal direction L has a large shape in the width direction W. Therefore, by having a large shape in the region including the buttocks cover portion 30, the disposable diaper 1 can more reliably envelop and adequately cover the buttocks, thereby providing a greater sense of security in preventing leakage of body exudates.

[0094] In a preferred aspect of this embodiment, when the disposable diaper 1 is stretched in the longitudinal direction L and the width direction W and then relaxed and placed on a flat plate, the buttocks cover end distance DWb1, which is the distance between the front edges in the longitudinal direction L at the outer edges in the width direction W of the pair of buttocks cover portions 30, is 220 mm or more.

[0095] Thus, the buttocks cover end distance DWb1 is 220 mm or more in the disposable diaper 1. In other words, when the disposable diaper 1 is stretched when put on and then relaxed after put on, the area of ​​the disposable diaper 1 including the buttocks cover portion 30 in the longitudinal direction L has a large shape in the width direction W. Therefore, the disposable diaper 1, with the buttocks cover portion 30 having a large shape, can more reliably envelop and adequately cover the buttocks, further enhancing the sense of security that body waste leakage is prevented.

[0096] In a preferred aspect of the present embodiment, each of the pair of buttocks-covering portions 30 includes rigid portions 2h disposed continuously or intermittently along the longitudinal direction L at its outer end in the width direction W. This prevents the buttocks-covering portions 30 of the disposable diaper 1 from being folded or rolled up in the longitudinal direction L. This allows the buttocks-covering portions 30 to more reliably envelop and adequately cover the buttocks, further enhancing the sense of security that body exudates are prevented from leaking.

[0097] In a preferred aspect of this embodiment, the buttocks-covering portion 30 has buttocks elastic members 40 extending along the width direction W only in the lower region 30c (see Figure 5, etc.). Therefore, the buttocks-covering portion 30 lightly holds the buttocks in place in the lower region 30c, preventing them from separating from the buttocks, while the upper region 30a and central region 30b fit snugly around the buttocks, making it easier for the buttocks-covering portion 30 to assume an outwardly convex shape that covers the buttocks as a whole. This allows the buttocks-covering portion 30 to appropriately encase and conceal the buttocks. Furthermore, by encasing and concealing the buttocks, the buttocks-covering portion can enhance the sense of security that body waste leakage is prevented. The buttocks-covering portion 30 may have one or more buttocks elastic members 40.

[0098] The disposable diaper of the present invention is not limited to the above-described embodiment, and can be appropriately combined with or modified in accordance with known techniques, etc., within the scope of the object and spirit of the present invention.

[0099] REFERENCE SIGNS LIST 1 disposable diaper 2 back portion 3 ventral portion 4 absorbent body 5 leg gathering portion 5a leg elastic member 10 body center portion 20 back extension portion 21 back body portion 30 buttocks cover portion 30a upper region 30b center region 30c lower region 31 extension center portion OA overlap region UA ​​non-overlapping region

Claims

1. A disposable diaper having, in an unfolded state, longitudinal, width, and thickness directions which are orthogonal to one another, a ventral portion covering the ventral side of a wearer, a dorsal portion covering the dorsal side, and an absorbent main body covering the crotch of the wearer and including an absorbent body, wherein the absorbent main body has front and rear ends in the longitudinal direction connected to central portions in the width direction of the ventral portion and the dorsal portion, respectively, and is formed by joining a pair of ventral joining portions on both side edges in the width direction of the ventral portion and a pair of dorsal joining portions on both side edges in the width direction of the dorsal portion, wherein the absorbent main body includes: a main body central portion located in the central portion in the width direction; and a pair of leg gather portions located at both ends in the width direction and having a plurality of leg elastic members extending along the longitudinal direction, and the dorsal portion has: a dorsal main body portion occupying substantially the same area in the longitudinal direction as the dorsal joining portion; a back-side extending portion extending forward from a front longitudinal edge of the back-side main body portion, wherein the back-side extending portion comprises: an extending central portion overlapping the main body central portion in the thickness direction; and a pair of buttocks-covering portions extending outward from both widthwise edge portions of the extending central portion, wherein each of the pair of buttocks-covering portions comprises an upper rear region, a central central region, and a lower front region, which are regions obtained by dividing the buttocks-covering portion into thirds in the longitudinal direction, and wherein the lower region has a higher contractile force in the width direction than the upper and central regions, and wherein the buttocks-covering portion comprises, in its inner widthwise region, an overlapping region located on the front side in the longitudinal direction and overlapping with rear longitudinal end portions of the plurality of leg elastic members in the thickness direction, and a non-overlapping region located on the rear side in the longitudinal direction and not overlapping with the plurality of leg elastic members in the thickness direction.

2. The disposable diaper according to claim 1, wherein the region of the buttocks cover section between the position of the back-side joint and the position of the edge of the absorbent main body on the buttocks cover section side in the width direction has a tensile stress in the width direction of 0.25 N or less.

3. The disposable diaper according to claim 1 or 2, wherein the overlapping region occupies a range of less than 50% of the length of the buttocks-covering portion in the longitudinal direction.

4. A disposable diaper as claimed in any one of claims 1 to 3, wherein the buttocks covering portion has an inner region in the width direction joined to the leg gathering portion, the buttocks covering portion has a buttocks elastic member extending along the width direction in the lower region, and the innermost leg elastic member located furthest in the width direction among the plurality of leg elastic members does not overlap the buttocks elastic member in the thickness direction.

5. A disposable diaper as claimed in any one of claims 1 to 4, wherein the buttocks covering portion has an inner region in the width direction joined to the leg gathering portion, the buttocks covering portion has a buttocks elastic member extending along the width direction in the lower region, and the outermost leg elastic member located furthest outward in the width direction among the plurality of leg elastic members overlaps the buttocks elastic member in the thickness direction.

6. A disposable diaper according to any one of claims 1 to 5, wherein the stretched longitudinal length and stretched width length are the lengths in the longitudinal and width directions of the buttocks cover portion when the disposable diaper is stretched in the longitudinal and width directions and placed on a flat plate, and the relaxed longitudinal length and relaxed width length are the lengths in the longitudinal and width directions of the buttocks cover portion when the disposable diaper is stretched and then relaxed and placed on a flat plate, the ratio of the relaxed longitudinal length to the stretched longitudinal length is 90% or more, and the ratio of the relaxed width length to the stretched width length is 50% or more.

7. A disposable diaper according to any one of claims 1 to 6, wherein the stretched longitudinal length and stretched width length are the lengths in the longitudinal direction and the width direction of the buttocks cover portion when the disposable diaper is stretched in the longitudinal direction and the width direction and placed on a flat plate, and the relaxed longitudinal length and relaxed width length are the lengths in the longitudinal direction and the width direction of the buttocks cover portion when the disposable diaper is stretched and then relaxed and placed on a flat plate, wherein the contraction length of the relaxed longitudinal length relative to the stretched longitudinal length is 4 mm or less, and the contraction length of the relaxed width length relative to the stretched width length is 55 mm or less.

8. A disposable diaper as claimed in any one of claims 1 to 7, wherein, when the disposable diaper is stretched in the longitudinal direction and the width direction, the circumference of the waist portion formed by the abdominal side portion and the dorsal side portion is in the range of 590 to 1050 mm, and when the disposable diaper is relaxed after being stretched in the longitudinal direction and the width direction and then placed on a flat plate, the relaxed width direction length, which is the length in the width direction of the buttocks cover portion, is 55 mm or more.

9. A disposable diaper as claimed in any one of claims 1 to 8, wherein when the disposable diaper is stretched in the longitudinal direction and the width direction, the circumference of the waist portion formed by the abdominal side portion and the dorsal side portion is in the range of 590 to 1050 mm, and when the disposable diaper is stretched in the longitudinal direction and the width direction and then relaxed and placed on a flat plate, the maximum relaxed longitudinal length and maximum relaxed widthwise length, which are the maximum lengths of the disposable diaper in the longitudinal direction and the widthwise direction, are greater than the maximum relaxed longitudinal length.

10. When the disposable diaper is stretched in the longitudinal direction and the width direction and then relaxed and placed on a flat plate, the relaxed area, which is the area of ​​the buttocks cover portion, is 1800 mm ２ The disposable diaper according to any one of claims 1 to 9, wherein:

11. The disposable diaper according to any one of claims 1 to 10, wherein, when the disposable diaper is stretched in the longitudinal direction and the width direction and then relaxed and placed on a flat plate, the relationship between the distance between the rear longitudinal edges of the pair of back-side joint portions, the distance between the longitudinal center portions of the pair of back-side joint portions, and the distance between the longitudinal front edges of the outer widthwise edges of the pair of buttocks-cover portions is such that, when the distance between the rear longitudinal edges is taken as 100%, the value of ((the buttocks-cover end distance) - (the joint center distance)) is 45% or more larger than the value of ((the joint center distance) - (the joint rear end distance)).

12. A disposable diaper as claimed in any one of claims 1 to 11, wherein, when the disposable diaper is stretched in the longitudinal direction and the width direction and then relaxed and placed on a flat plate, the relationship between the joint center distance between the longitudinal central portions of the pair of back joint portions and the buttocks cover end distance between the longitudinal front end edges of the outer widthwise edges of the pair of buttocks cover portions is such that the value of (the buttocks cover end distance) / (the joint center distance) is 1.4 to 1.

8.

13. A disposable diaper as claimed in any one of claims 1 to 12, wherein, when the disposable diaper is stretched in the longitudinal direction and the width direction and then relaxed and placed on a flat plate, the distance between the buttocks cover ends of the outer widthwise edges of the pair of buttocks cover portions at the longitudinal front edges is 220 mm or more.

14. The disposable diaper according to any one of claims 1 to 13, wherein each of the pair of buttocks-covering portions has rigid portions disposed continuously or intermittently along the longitudinal direction at the outer ends in the width direction.

15. The disposable diaper according to any one of claims 1 to 14, wherein the buttocks-covering portion has buttocks elastic members extending along the width direction only in the lower region.

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