Absorbent article with elastic members

A pants-type disposable diaper includes a pair of strip projecting parts projecting laterally from a line of connection between front and rear parts located respectively on the belly and back sides of a wearer, a first waist elastic member joined to a first waist region that is an upper part of a waist region extending along a waist opening, and a second waist elastic member joined to a second waist region that is a lower part of the waist region. In a state in which an outer covering sheet is elongated in a right-left direction, a first unit contractile force that is a contractile force in the right-left direction per unit width of the first waist region in an up-down direction is smaller than a second unit contractile force in the second waist region.

This application is a national phase entry under 35 U.S.C. § 371 of PCT Patent Application No. PCT/JP2012/080876, filed on Nov. 29, 2012, which claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2011-287454, filed Dec. 28, 2011, both of which are incorporated by reference.

TECHNICAL FIELD

The present invention relates to a pants-type absorbent article.

BACKGROUND ART

Pants-type disposable diapers having a waist opening at the top end and a pair of leg openings in the lower portion have conventionally been used as one type of absorbent articles for receiving body waste discharged from a wearer. In front and rear parts of a pants-type disposable diaper that are located respectively on the belly and back sides of the wearer, a waist elastic member is provided along the edge of the waist opening. In a crotch part located between the front and rear parts, leg elastic members are provided along the edges of the pair of leg openings. In the front and rear parts, a middle elastic member is also provided between the waist elastic member and the leg elastic members in an up-down direction.

In a pants-type disposable diaper disclosed in Japanese Patent Application Laid-Open No. 2009-240694 (Document 1), front and rear parts located on the belly and back sides of a wearer are divided into a first expansible region that is located in the vicinity of the edge of a waist opening, a second expansible region that is located adjacent to the first expansible region and crosses a front end portion of an absorptive chassis, and third expansible regions that are located adjacent to the second expansible region and on both sides of the absorptive chassis. Setting the elongation stress of the second expansible region to be equal to or greater than that of the first expansible region suppresses the formation of creases in the second expansible region and the front end portion of the absorptive chassis due to the effect of elongation of the first expansible region when the wearer bends forward.

In pants-type absorbent articles disclosed in Japanese Patent Application Laid-Open Nos. 2009-125088 (Document 2) and 2009-125087 (Document 3), front and rear parts are divided into four strip-like regions of the same width that extend in the width direction, the four strip-like regions being referred to respectively as a first region, a second region, a third region, and a fourth region in order from the top. In the pants-type absorbent article disclosed in Document 2, the contractile forces in the respective regions are set such that the second region has a greater contractile force than those of the first and third regions, and the fourth region has a greater contractile force than that of the third region. In this way, setting a greater contractile force in the second and fourth regions where the wearer has bones that protrude to the surface of his or her body suppresses slipping off of the absorbent article, and setting a smaller contractile force in the first region that shifts greatly due to movement of the wearer makes the absorbent article more comfortable to wear. In Document 3, which aims to provide a pants-type disposable diaper capable of preventing slipping-off and being very comfortable to wear, the second and fourth regions are set to have an average contractile force greater than that of the third region, the fourth region on the belly side is set to have a contractile force greater than that of the forth region on the back side, and the second region is set to have an average contractile force greater than that of the first region.

In a disposable diaper disclosed in Japanese Patent Application Laid-Open No. 2010-69023 (Document 4), a front part is divided from the waist opening side into a first expansible region, a second expansible region, and a third expansible region, a rear part is divided from the waist opening side into a fourth expansible region, a fifth expansible region, and a sixth expansible region, and the elongation stresses of the respective expansible regions has the following correlation: sixth expansible region>second expansible region>third expansible region≥fifth expansible region>first expansible region, and sixth expansible region>second expansible region>third expansible region fifth expansible region>fourth expansible region.

In a pants-type disposable diaper disclosed in Japanese Patent Application Laid-Open No. 2001-178770 (Document 5), front and rear parts are divided from the waist opening side into a waist section, an upper side section, and a lower side section, and elastic expansion forces of the respective sections has the following correlation: lower side section≥upper side section>waist section.

In a pants-type disposable diaper disclosed in Japanese Patent Application Laid-Open No. 2006-61682 (Document 6), when the disposable diaper is worn, a first region located between a waist opening and leg openings has the highest pressure applied thereto, the waist opening has the second highest pressure applied thereto, and a second region located between the first region and the leg openings has the lowest pressure applied thereto. Such a structure not only effectively prevents the diaper slipping off when being worn, but also effectively prevents liquid leakage because the diaper fits the body of a wearer closely without discomfort.

Incidentally, in pants-type disposable diapers, a pair of strip projecting parts, each projecting laterally from a line of connection between front and rear parts, is formed when the front and rear parts are joined to each other on both right and left sides. The strip projecting parts are less flexible than the other parts of the disposable diaper because they are formed by joining laminated sheet members such as nonwoven fabric by thermal compression bonding, for example. Thus, in a state where the disposable diaper is worn, the upper end portions of the strip projecting parts may cut into the body of the wearer and make the wearer uncomfortable due to contraction of a waist elastic member provided in a waist region extending along the edge of the waist opening.

Documents 1 to 6 have proposed to reduce the contractile force in the waist region to smaller than that in the other region, but it is necessary to maintain the contractile force in the waist region at a certain level or higher in order to prevent the disposable diaper from slipping off the wearer. Thus, with the structures as disclosed in Documents 1 to 6, the upper end portions of the strip projecting parts will still cut into the body of a wearer.

SUMMARY OF INVENTION

The present invention is intended for a pants-type absorbent article, and it is an object of the present invention to suppress cutting in of the upper end portions of the strip projecting parts into the body of a wearer.

The absorbent article according to the present invention includes an outer covering sheet having a waist opening at an upper end and a pair of leg openings in a lower portion, and an absorbent body attached to a wearer side of the outer covering sheet to absorb body waste discharged from a wearer. The outer covering sheet includes a front part to be located on a belly side of the wearer, a rear part to be located on a back side of the wearer, both side ends of the rear part being connected to both side ends of the front part, a crotch part continuous with the front part and the rear part, a pair of strip projecting parts formed by joining inner surfaces of areas of the front part that are laterally continuous with both of the side ends of the front part and inner surfaces of areas of the rear part that are laterally continuous with both of the side ends of the rear part, each of the pair of strip projecting parts having a strip-like shape that extends in an up-down direction and projecting laterally from a line of connection between the front part and the rear part, a waist elastic member joined to the front part and the rear part in a waist region located along an edge of the waist opening, and configured to contract to form a waist opening gather, leg elastic members joined to the crotch part along edges of the pair of leg openings and configured to contract to form a pair of leg opening gathers, and a middle elastic member joined to the front part and the rear part in a space in the up-down direction between the waist elastic member and the leg elastic members, and configured to contract to form a middle gather. The waist elastic member includes a first waist elastic member disposed approximately in parallel with the edge of aid waist opening in a first waist region that is an upper part of the waist region, and a second waist elastic member disposed approximately in parallel with the first waist elastic member in a second waist region that is a region of the waist region below the first waist region. In a state in which the outer covering sheet is elongated in a right-left direction perpendicular to the up-down direction, a first unit contractile force that is a contractile force in the right-left direction per unit width of the first waist region in the up-down direction is smaller than a second unit contractile force that is a contractile force in the right-left direction per unit width of the second waist region in the up-down direction.

According to the present invention, it is possible to suppress cutting in of the upper end portions of the strip projecting parts into the body of a wearer.

Preferably, the waist region is located above an upper end of the absorbent body. In addition, the waist region has a width of 50 mm or less in the up-down direction.

In a preferred embodiment of the present invention, the outer covering sheet includes a folded portion formed by folding the outer covering sheet toward a wearer at the edge of the waist opening, and the waist elastic member is disposed between the folded portion and a portion of the outer covering sheet that faces the folded portion. Accordingly, the upper end portions of the strip projecting parts are formed by the fold in the continuous sheet member. It is thus possible to further suppress cutting in of the upper end portions of the strip projecting parts into the body of a wearer, as compared with the case in which a cut edge of the sheet member forms the upper end portions of the strip projecting parts.

In another preferred embodiment of the present invention, the waist region is formed by laminating a plurality of sheet members, and the number of sheet members in the first waist region is less than the number of sheet members in the second waist region. Accordingly, it is possible to further suppress cutting in of the upper end portions of the strip projecting parts into the body of a wearer.

In one aspect of the present invention, the outer covering sheet includes an auxiliary region between the second waist region and a middle elastic region in which the middle elastic member is disposed, and in a state in which the outer covering sheet is elongated in the right-left direction, a contractile force in the right-left direction per unit width of the auxiliary region in the up-down direction is smaller than any of a contractile force in the right-left direction per unit width of the middle elastic region in the up-down direction, the first unit contractile force, and the second unit contractile force. This makes it easy to firmly grasp the absorbent article by hooking fingers deep into the auxiliary region, enabling the absorbent article to be readily moved along the body of a wearer.

DESCRIPTION OF EMBODIMENT

FIGS. 1 and 2are respectively front and rear views of a disposable diaper1according to an embodiment of the present invention (i.e., views of areas located respectively on the belly and back sides of a wearer). As shown inFIGS. 1 and 2, the disposable diaper1is a pants-type absorbent article having a waist opening11at the upper end (i.e., the end on the upper side inFIGS. 1 and 2) and a pair of leg openings12in the lower portion, and is configured to receive body waste discharged from the wearer.

FIG. 3is a plan view of the laid out disposable diaper1viewed from the wearer side. The disposable diaper1includes an outer covering sheet4having the waist opening11and the pair of leg openings12(seeFIGS. 1 and 2) and a generally sheet-like absorbent body20that is attached to the inner surface of the outer covering sheet4(i.e., the surface on the wearer side) and is configured to absorb body waste discharged from the wearer. The outer covering sheet4includes an outer covering sheet main body40, and leg elastic members43, a waist elastic member44and a middle elastic member45which are joined to the outer covering sheet main body40.

In the disposable diaper1, the area on the upper side inFIG. 3covers the front side (skin on the belly side) of the wearer, and the area on the lower side inFIG. 3covers the rear side (skin on the back side) of the wearer. In the following description, areas of the outer covering sheet main body40that are located on the belly and back sides of the wearer are respectively referred to as a “front part401” and a “rear part403,” and an area that is located between and continuous with the front part401and the rear part403and covers a groin part of the wearer is referred to as a “crotch part402.” In the disposable diaper1, the outer covering sheet4includes the front part401, the crotch part402, and the rear part403, and the absorbent body20extends from the front part401of the outer covering sheet4to the rear part403via the crotch part402.

In the manufacture of the disposable diaper1, the outer covering sheet4is folded at the crotch part402together with the absorbent body20, and the inner surfaces of strip-like areas404that are located on both right and left sides of the front part401when the crotch part402is facing downward are joined to the inner surfaces of strip-like areas405that are located on both right and left sides of the rear part403by heat sealing through the application of heat and pressure. The inner surfaces of the strip-like areas404are surfaces that are laterally continuous with both of the side ends of the inner surface of the front part401that comes in contact with the wearer, and are surfaces on the near side inFIG. 3. The inner surfaces of the strip-like areas405are surfaces that are laterally continuous with both of the side ends of the inner surface of the rear part403that comes in contact with the wearer, and are surfaces on the near side inFIG. 3.

By joining the pair of strip-like areas404and the pair of strip-like areas405in this way, both of the side ends of the front part401and both of the side ends of the rear part403are connected as illustrated inFIGS. 1 and 2, forming the waist opening11at the upper ends of the front part401and the rear part403. Also, the pair of leg openings12is respectively formed on the right and left sides of the crotch part402below the front part401and the rear part403, and a pair of strip projecting portions13that extend in an up-down direction is formed between the waist opening11and the pair of the leg openings12. The strip projecting portions13are each a strip-like area that projects laterally from a line of connection400between the front part401and the rear part403.

FIG. 4is cross-sectional view of the disposable diaper1, taken along line IV-IV (i.e., at the crotch part402) inFIG. 3. InFIG. 4, for convenience of illustration, constituent elements of the disposable diaper1are illustrated separately from one another. As illustrated inFIGS. 3 and 4, the absorbent body20includes a generally sheet-like main body part2and a pair of side sheets3that is disposed on both side portions of the main body part2(i.e., both sides in a right-left direction perpendicular to the up-down direction) and that extends along approximately the entire longitudinal length of the main body part2. The main body part2includes a top sheet21, a back sheet23, and an absorbent core22disposed between the top sheet21and the back sheet23as illustrated inFIG. 4. In order to facilitate understanding of the illustration, the contour of the absorbent core22of the absorbent body20is shown by the bold broken line inFIG. 3(the same applies toFIGS. 1 and 2).

As illustrated inFIG. 3, the width of the absorbent core22at its both end portions in a longitudinal direction is greater than the width of the absorbent core22at its central portion in the longitudinal direction. In other words, the absorbent core22has a so-called hourglass shape. The back sheet23inFIG. 4is joined to the outer covering sheet4with a hot-melt adhesive or the like, and accordingly the absorbent body20is fixed to the outer covering sheet4.

As illustrated inFIG. 4, the pair of side sheets3each includes a strip-like joining part33and a side wall part34, the strip-like joining part33being an area on one side of a folding line39that extends along the entire length in the longitudinal direction, and the side wall part34being an area on the other side of the folding line39. The pair of joining parts33is joined with a hot-melt adhesive to the upper side (i.e., the wearer side) of the main body part2along approximately the entire longitudinal length in the vicinity of lateral edges of the main body part2. The pair of side wall parts34corresponds to areas that are continuous with the pair of joining parts33at the outer edges of the joining parts33in the right-left direction, i.e., the folding lines39, and extend along approximately the entire longitudinal length of the main body part2on both side portions of the main body part2.

The pair of side wall parts34is overlaid on the joining parts33at both end portions in the longitudinal direction and is fixed to the joining parts33by, for example, heat seal bonding, ultrasonic bonding, or bonding with a hot-melt adhesive. Side wall elastic members35are joined to free edges of the side wall parts34, and the side wall elastic members35are configured to contract to form gathers.

FIG. 5is a partial cross-sectional view of the disposable diaper1, taken along line V-V inFIG. 3.FIG. 5shows the front side of the disposable diaper1. The rear-side structure of the disposable diaper1is the same as the front-side structure shown inFIG. 5. As illustrated inFIGS. 4 and 5, the outer covering sheet main body40of the outer covering sheet4includes a first outer covering sheet41and a second outer covering sheet42that is directly laminated on the inner surface (i.e., the wearer side) of the first outer covering sheet41and joined thereto with a hot-melt adhesive or the like.

As illustrated inFIG. 5, the outer covering sheet main body40further includes an end sheet5that is directly laminated on the inner surface of the second outer covering sheet42and joined thereto with a hot-melt adhesive or the like. The end sheet5is provided along approximately the entire width of the outer covering sheet4in the right-left direction of the disposable diaper1(i.e., the lateral direction inFIG. 3) as illustrated inFIG. 3and sandwiches the upper end portion of the absorbent body20between itself and the second outer covering sheet42to fix the absorbent body20as illustrated inFIG. 5.

An upper end421of the second outer covering sheet42is at approximately the same level in the up-down direction as an upper end51of the end sheet5and is spaced from and downward of an edge111of the waist opening11, which is an upper end of the first outer covering sheet41. The upper end421of the second outer covering sheet42and the upper end51of the end sheet5are located above an upper end25of the absorbent body20.

The top sheet21of the absorbent body20illustrated inFIG. 4is a liquid-permeable sheet material that quickly catches moisture in body waste discharged from the wearer and moves the moisture to the absorbent core22. As the top sheet21, liquid-permeable nonwoven fabric (e.g., point-bonded nonwoven fabric, air-through nonwoven fabric, or spun-bonded nonwoven fabric) is used, for example, which is formed from hydrophobic fibers (e.g., polypropylene, polyethylene, polyester, polyamide, or nylon) having a surface that has undergone hydrophilic treatment using a surfactant. Alternatively, nonwoven fabric (e.g., spunlace nonwoven fabric) formed from hydrophilic fibers such as cellulose, rayon, or cotton may be used for the top sheet21.

The absorbent core22is formed by mixing super-absorbent material such as granular super-absorbent polymer (SAP) or super-absorbent fibers with hydrophilic fibers such as comminuted pulp fibers or cellulose fibers and then wrapping the mixture in tissue paper, a liquid-permeable nonwoven fabric, or the like. The absorbent core22absorbs and quickly traps moisture permeating through the top sheet21. The tissue paper, liquid-permeable nonwoven fabric, or the like that is wrapped around the hydrophilic fibers is joined to the hydrophilic fibers and water-absorbent material with a hot-melt adhesive, thereby preventing deformation of the hydrophilic fibers and detachment of the water-absorbent material (in particular, detachment after water absorption). In the present embodiment, the absorbent core22includes pulp fibers and SAP.

As the back sheet23, water-repellent or liquid-impervious nonwoven fabric formed from hydrophobic fibers (e.g., spunbond nonwoven fabric, meltblown nonwoven fabric, or spunbond-meltblown-spunbond (SMS) nonwoven fabric) or a water-repellent or liquid-impervious plastic film is used to prevent moisture or the like in body waste that has reached the back sheet23from leaking to the outside of the main body part2. In the case of using a plastic film for the back sheet23, it is preferable to use a permeable (breathable) plastic film from the viewpoint of preventing the disposable diaper1from becoming sweaty and improving the comfort of the wearer.

As a sheet main body of the side sheet3, water-repellent or liquid impermeable nonwoven fabric formed from hydrophobic fibers (e.g., spun-bonded nonwoven fabric, meltblown nonwoven fabric, or SMS nonwoven fabric) is used. As the side wall elastic members35, polyurethane yarn, a strip-like polyurethane film, or filiform or strip-like natural rubber is used, for example. In the present embodiment, polyurethane yarn is used for the side wall elastic members35.

Similarly to the back sheet23, as the first outer covering sheet41and the second outer covering sheet42of the outer covering sheet main body40and the end sheet5illustrated inFIG. 5, water-repellent or liquid impermeable nonwoven fabric formed from hydrophobic fiber or plastic films are used, or laminated sheets where such nonwoven fabric and plastic film are laminated, are used. It is preferable to use the plastic films having vapor permeability (breathability). Alternatively, as the first outer covering sheet41, the second outer covering sheet42, and the end sheet5, similarly to the top sheet21, nonwoven fabric formed from hydrophilic fibers or liquid-permeable nonwoven fabric formed from hydrophobic fibers that have undergone hydrophilic treatment may be used.

In a preferable example, the disposable diaper1uses spun-bonded nonwoven fabric, which is formed by melting a material that contains a thermoplastic resin (e.g., an olefin resin or a polyester resin) and a surfactant, for the first outer covering sheet41and the second outer covering sheet42. Here, the compounding ratio of the surfactant in the material is preferably 0.5 percent by mass or higher, and more preferably 1.0 percent by mass or higher, and is preferably 5.0 percent by mass or less, and more preferably 3.5 percent by mass or less. The olefin resin is preferably polyethylene or polypropylene, and the polyester resin is preferably polyethyleneterephthalate (PET), polybutyleneterephtalate (PBT), or polytrimethyleneterephtalate (PTT). The fineness of the nonwoven fabric is preferably 1.0 dtex or higher and is preferably lower than 1.5 dtex. The weight of the nonwoven fabric is preferably 10 g/m2or more and is preferably 35 g/m2or less. From the viewpoint of breathability and strength, the weight of the nonwoven fabric is more preferably 15 g/m2or more and is more preferably 25 g/m2or less.

The first outer covering sheet41of the outer covering sheet4includes a folded portion46formed by folding the first outer covering sheet41toward the wearer at the edge111of the waist opening11. A lower end461of the folded portion46is located below the upper end421of the second outer covering sheet42and the upper end51of the end sheet5and is located above the upper end25of the absorbent body20. An upper end portion of the second outer covering sheet42and an upper end portion of the end sheet5are sandwiched between the folded portion46and an opposing portion47that is an area of the first outer covering sheet41that faces the folded portion46. The folded portion46is joined to the opposing portion47and the upper end portion of the end sheet5.

Between the folded portion46and the opposing portion47and along the edge111of the waist opening11is disposed a waist elastic member44that extends in the right-left direction as shown inFIG. 3and is joined to the front part401and the rear part403. In the disposable diaper1, contraction of the waist elastic member44causes contraction of the outer covering sheet main body40, thereby forming waist opening gathers that come in contact with the wearer. In the present embodiment, the waist elastic member44includes six elastic threads as shown inFIG. 5. In the following description, two of these elastic threads that are closest to the edge111of the waist opening11, which is an upper end of the folded portion46, are referred to as “first elastic threads441,” and the other four elastic threads located below the first elastic threads441are referred to as “second elastic threads442.” The two first elastic threads441are also collectively referred to as a “first waist elastic member443,” and the four second elastic threads442are also collectively referred to as a “second waist elastic member444.” In other words, the waist elastic member44includes the first waist elastic member443that is disposed approximately in parallel with the edge111of the waist opening11, and the second waist elastic member444that is disposed approximately in parallel with the first waist elastic member443.

The two first elastic threads441are arranged in the up-down direction and extend approximately in parallel with the edge111of the waist opening11. The four second elastic threads442are arranged at approximately an equal pitch in the up-down direction and extend approximately in parallel with the plurality of first elastic threads441. The pitch in the up-down direction between the first elastic threads441, or in other words, a distance in the up-down direction between the two first elastic threads441, is greater than the pitch in the up-down direction between the second elastic threads442, or in other words, a distance in the up-down direction between any two second elastic threads442that are adjacent to each other in the up-down direction. In this way, the pitch of the first elastic threads441and the pitch of the second elastic threads442differ from each other. The pitch of the first elastic threads441and the pitch of the second elastic threads442are respectively 7 mm and 3.5 mm, for example. A distance in the up-down direction between the lower first elastic thread441and the uppermost second elastic thread442is approximately equal to the distance in the up-down direction between the two first elastic threads441(i.e., the pitch of the first elastic threads441).

The two first elastic threads441and the upper two second elastic threads442among the four second elastic threads442are disposed between the folded portion46and the opposing portion47of the first outer covering sheet41above the upper end421of the second outer covering sheet42and the upper end51of the end sheet5, and are directly joined to the folded portion46and the opposing portion47. The lower two second elastic threads442among the four second elastic threads442are disposed between the folded portion46and the end sheet5below the upper end421of the second outer covering sheet42and the upper end51of the end sheet5, and are directly joined to the folded portion46and the end sheet5.

If a region of the outer covering sheet4where the waist elastic member44is disposed is referred to as a “waist region406”, and in the waist region406which is a strip-like region extending along the edge111of the waist opening11, regions on which the first waist elastic member443and the second waist elastic member444are respectively disposed are respectively referred to as a “first waist region407” and a “second waist region408”, the first waist region407is a strip-like upper region of the waist region406, and the second waist region408is a strip-like lower region of the waist region406and is located below the first waist region407.

As described above, the waist region406is formed by laminating a plurality of sheet members that include the folded portion46and the opposing portion47of the first outer covering sheet41, the second outer covering sheet42, and the end sheet5. The first waist region407and the upper part of the second waist region408are formed by the folded portion46and the opposing portion47of the first outer covering sheet41, and the lower part of the second waist region408is formed by the folded portion46, the opposing portion47, the second outer covering sheet42, and the end sheet5. In other words, the number of sheet members in the first waist region407is two and less than the number (i.e., four) of sheet members in the lower part of the second waist region408.

Specifically, the first waist region407is a region that extends in the up-down direction from the edge111of the waist opening11to the middle of the distance in the up-down direction between the lower first elastic thread441and the uppermost second elastic thread442. The second waist region408is a region that extends from the middle of the distance in the up-down direction between the lower first elastic thread441and the uppermost second elastic thread442(i.e., the lower end of the first waist region407) to a position that is downwardly distant from the lowermost second elastic threads442by a distance equivalent to a half of the pitch of the second elastic threads442. The lower end of the second waist region408is located above the lower end461of the folded portion46(seeFIG. 5). The waist region406is located above the upper end25of the absorbent body20and preferably has a width of 50 mm or less in the up-down direction.

As illustrated inFIGS. 1 and 2, the leg elastic members43are disposed along edges121of the pair of leg openings12and joined between the first and second outer covering sheets41and42of the outer covering sheet4(seeFIG. 4). The upper end portions of each of the leg elastic member43on both sides are joined to the front part401and the rear part403, and the central part of each of the leg elastic members43between the upper end portions is joined to the crotch part402of the outer covering sheet main body40. The leg elastic members43each include a plurality of leg elastic threads431. In the disposable diaper1, contraction of the leg elastic members43causes contraction of the outer covering sheet main body40, thereby forming leg gathers that come in contact with the circumference of the legs of the wearer.

The middle elastic member45is disposed between the waist elastic member44and the upper end portions of the leg elastic members43in the up-down direction, extends in the right-left direction, and is joined to the front part401and the rear part403. As illustrated inFIG. 5, the middle elastic member45is disposed between the first outer covering sheet41and the second outer covering sheet42. The middle elastic member45includes a plurality of (in the present embodiment, 12) middle elastic threads451aand451bthat are arranged in the up-down direction and extend approximately in parallel with the first and second elastic threads441and442of the waist elastic member44. In the following description, the upper two of the middle elastic threads that are closest to the second elastic threads442are referred to as “first middle elastic threads451a,” and the lower ten of the middle elastic threads that are located below first middle elastic threads451aare referred to as “second middle elastic threads451b.” The two first middle elastic threads451aare also collectively referred to as a “first middle elastic member45a”, and the ten second middle elastic threads451bare also collectively referred to as a “second middle elastic member45b.” In other words, the middle elastic member45includes the first middle elastic member45athat is disposed approximately in parallel with the edge111of the waist opening11, and the second middle elastic member45bthat is disposed approximately in parallel with the first middle elastic member45a.

In the present embodiment, the interval between the two first middle elastic threads451ais 3.5 mm. The interval between any two second middle elastic threads451bthat are adjacent to each other alternately changes between 7 mm and 14 mm in the up-down direction. In other words, taking any two second middle elastic threads451bthat are disposed at an interval of 7 mm as a pair of second middle elastic threads, the plurality of pairs of second middle elastic threads are disposed at an interval of 14 mm. As described above, the regularity of arrangement of the plurality of first middle elastic threads451ain the up-down direction differs from that of the plurality of second middle elastic threads451b. Note that the second middle elastic threads451bmay be disposed at a fixed pitch in the up-down direction.

In the disposable diaper1, contraction of the middle elastic member45causes contraction of the outer covering sheet main body40, thereby forming middle gathers that come in contact with the lower abdominal and hip regions of the wearer. In the following description, a strip-like region of the outer covering sheet4where the middle elastic member45is disposed is referred to as a “middle elastic region409.” Specifically, the middle elastic region409is defined as a region that extends in the up-down direction from the uppermost first middle elastic thread451ato the lowermost second middle elastic thread451b. Similarly to the waist region406, the middle elastic region409is also located above the upper end25of the absorbent body20.

Assuming that in the strip-like middle elastic region409extending approximately in parallel with the edge111of the waist opening11, regions where the first middle elastic member45aand the second middle elastic member45bare respectively disposed are respectively referred to as a “first middle elastic region409a” and a “second middle elastic region409b”, the first middle elastic region409ais a strip-like upper region of the middle elastic region409, and the second middle elastic region409bis a strip-like lower region of the middle elastic region409and located below the first middle elastic region409a. Specifically, the first middle elastic region409ais a region that extends in the up-down direction from the uppermost first middle elastic thread451ato the middle of the distance between the lower first middle elastic thread451aand the uppermost second middle elastic thread451b. The second middle elastic region409bis a region that extends in the up-down direction from the middle of the distance between the lower first middle elastic thread451aand the uppermost second middle elastic thread451b(i.e., the lower end of the first middle elastic region409a) to the lowermost second middle elastic thread451b.

Between the second waist region408and the middle elastic region409of (the outer covering sheet main body40of) the outer covering sheet4is provided an auxiliary region410that has no elastic members disposed therein. An upper end of the auxiliary region410is in contact with the lower end of the second waist region408, and a lower end of the auxiliary region410is in contact with the upper end of the middle elastic region409. The width of the auxiliary region410in the up-down direction is preferably two times or more of the pitch of the second elastic threads442, and more preferably three times or more of the pitch of the second elastic threads442, and is less than or equal to the width of the waist region406in the up-down direction. In the present embodiment, the auxiliary region410has a width of 10 mm. In the disposable diaper1, all of the first and second elastic threads441and442of the waist elastic member44and all of the first middle elastic threads451aof the first middle elastic member45aare colored differently from the elastic threads of the other elastic members (i.e., the second middle elastic member45band the leg elastic members43). Specifically, the elastic threads of the other elastic members have a color of the same hue (e.g., white) as the outer covering sheet main body40, whereas the first and second elastic threads441and442and the first middle elastic threads451ahave a color of different hue from that of the outer covering sheet main body40. Thus, roughly the upper end of the auxiliary region410is visually recognizable by the second elastic threads442in the vicinity of the lower end of the second waist region408, and the lower end of the auxiliary region410is visually recognizable by the first middle elastic threads451aat the upper end of the middle elastic region409. Accordingly, the auxiliary region410is substantially visually recognizable. Alternatively, the auxiliary region410may be made visually recognizable by, for example, printing a strip-like pattern extending in the right-left direction on the auxiliary region410of the outer covering sheet main body40.

In the present embodiment, the plurality of first elastic threads441and the plurality of second elastic threads442of the waist elastic member44, the plurality of leg elastic threads431of the leg elastic members43(seeFIGS. 1 and 2), and the plurality of middle elastic threads451aand451bof the middle elastic member45are all polyurethane yarns having the same elastic modulus and the same fineness. The fineness of the polyurethane yarns is in the range of 100 to 2500 dtex, for example. These elastic threads may, of course, have different finenesses, and in another preferable example, the disposable diaper1may use first and second elastic threads441and442having a fineness of 940 dtex and middle elastic threads451aand451bhaving a fineness of 640 dtex.

These elastic threads are fixed to the outer covering sheet main body40by heat seal bonding or bonding with a hot-melt adhesive. Preferably, the first elastic threads441are fixed to the outer covering sheet main body40with an adhesive applied to the first elastic threads441. More preferably, no adhesive is applied to the first waist region407itself of the outer covering sheet main body40(the first outer covering sheet41and the folded portion46) from the viewpoint of improving the texture of the edge of the waist opening1. On the other hand, in the second waist region408, an adhesive may be applied to both or one of the second elastic threads442and the second waist region408of the outer covering sheet main body40. In the present embodiment, an adhesive is applied to the second waist region408of the folded portion46to fix the folded portion46to the opposing portion47and the upper end portion of the end sheet5, and no adhesive is applied to the first waist region407itself and to the auxiliary region410itself. Preferably, from the viewpoint of improving breathability in the middle elastic region409, the middle elastic threads451aand451bof the middle elastic member45are fixed to the outer covering sheet main body40with an adhesive applied to the middle elastic threads451aand451b, without any adhesive being applied to the middle elastic region409itself of the outer covering sheet main body40. In this case, it is possible to further improve breathability by applying an adhesive to some of the middle elastic threads451aand451b, only in areas in the vicinity of the pair of strip projecting parts13, i.e., only at both end portions of some of the middle elastic threads451aand451b.

The elongation rate of the first elastic threads441when joined to the first waist region407is equal to the elongation rate of the second elastic threads442when joined to the second waist region408. The number of first elastic threads441per unit width of the first waist region407in the up-down direction, that is, a value obtained by dividing the total number of first elastic threads441by the width of the first waist region407in the up-down direction, is less than the number of second elastic threads442per unit width of the second waist region408in the up-down direction. Thus, in a state in which the outer covering sheet4is elongated in the right-left direction (e.g., in a state in which the disposable diaper1is worn), a first unit contractile force that is a contractile force in the right-left direction per unit width of the first waist region407in the up-down direction is smaller than a second unit contractile force that is a contractile force in the right-left direction per unit width of the second waist region408in the up-down direction.

Accordingly, the second waist region408of the waist region406closely fits the waist area of the wearer, the first waist region407comes into relatively soft contact with the waist area of the wearer. As a result, cutting in of the upper end portions of the pair of strip projecting parts13into the skin of the wearer can be suppressed. In addition, by setting a relatively large second unit contractile force while setting a relatively small first unit contractile force so as to maintain the contractile force in the entire waist region406, it is possible to closely fit the first waist region407and the second waist region408to the wearer and to prevent the disposable diaper1from slipping off in the up-down direction when being worn. The first unit contractile force is preferably 70% or less of the second unit contractile force, and in the present embodiment, the first unit contractile force is approximately 50% of the second unit contractile force.

Here, when a pants-type disposable diaper is put on or taken off, the wearer's feet are put into the pair of leg openings of the disposable diaper and then the disposable diaper is pulled up along the body of a wearer, or the disposable diaper being worn by the wearer is pulled down along the body of the wearer. At this time, the waist opening is widened in order to avoid the edge of the waist opening catching on part of the body of the wearer. In such a case, in the disposable diaper1in which the first unit contractile force is smaller than the second unit contractile force, the edge of the waist opening11can be widened by a small force. It is thus possible to easily move the disposable diaper1along the body of the wearer.

From the viewpoint of preventing the disposable diaper1from slipping off in the up-down direction when being worn, the contractile force per unit width of the entire waist region406is preferably 1 cN/mm or more (more preferably, 2 cN/mm or more). The contractile force per unit width of the entire waist region406is measured as described below, using a “TENSILON (model type: RTG-1210)” manufactured by A&D Co., Ltd. as a measuring machine. Note that the first unit contractile force, the second unit contractile force, and a middle unit contractile force which will be described later, are also measured by the same method.

First, a test specimen is obtained by cutting out the waist region406of the disposable diaper1along the entire width thereof in the up-down direction. Next, both ends of the test specimen in the right-left direction (i.e., the direction in which the first elastic threads441and the second elastic threads442extend) are held by clamp portions of the measuring machine, and the test specimen is pulled in the right-left direction, and the load until the test specimen returns to its original shape is measured. At this time, the test specimen is pulled to up to 90% of the length in the right-left direction of a test specimen that is not provided with the first elastic threads441and the second elastic threads442(i.e., the length of a test specimen that does not contract). The pulling of the test specimen and measurement of load are repeated a plurality of times. Then, the measurement results are used to obtain the load at the time when the length of the test specimen is 180% of the length of the test specimen before being pulled (i.e., the length of the test specimen that contracts due to the first elastic threads441and the second elastic threads442) and to obtain an average load that is an average value of the loads obtained by the plurality of measurements. Then, the average load is divided by the width of the test specimen in the up-down direction so as to obtain the contractile force per unit width of the test specimen.

As described above, in the outer covering sheet4, the number of sheet members in the first waist region407is reduced to less than the number of sheet members in the second waist region408. This reduces the number of sheet members constituting the upper end portions of the pair of strip projecting parts13, thus making it possible to reduce stiffness. As a result, it is possible to further suppress cutting in of the upper end portions of the pair of strip projecting parts13into the skin of the wearer. In addition, the edge of the waist opening11can be widened by a small force.

The folded portion46is formed by folding the first outer covering sheet41of the outer covering sheet4at the edge111of the waist opening11, and the waist elastic member44is disposed between the folded portion46and the opposing portion47. In this way, the edge111of the waist opening11and the upper end portions of the pair of strip projecting parts13are formed by the fold in the continuous sheet member. It is thus possible to further suppress cutting in of them into the skin of the wearer, as compared with the case in which a cut edge of the sheet member forms the edge111of the waist opening11and the upper end portions of the strip projecting parts13. Moreover, in the waist region406, the pitch in the up-down direction between the plurality of first elastic threads441is made greater than the pitch in the up-down direction between the plurality of second elastic threads442. Thus, the first unit contractile force in the first waist region407can be readily reduced to smaller than the second unit contractile force in the second waist region408.

In the disposable diaper1, the elongation rate of the middle elastic threads451aand451bwhen joined to the middle elastic region409is equal to or lower than the elongation rate of the first elastic threads441when joined to the first waist region407. The number (average number) of middle elastic threads451aand451bper unit width of the middle elastic region409in the up-down direction is less than the number of first elastic threads441per unit width of the first waist region407in the up-down direction. Thus, in the state in which the outer covering sheet4is elongated in the right-left direction, the middle unit contractile force that is an average contractile force in the right-left direction per unit width of the middle elastic region409in the up-down direction is smaller than the first unit contractile force and the second unit contractile force described above. Accordingly, in the middle elastic region409, the disposable diaper1can closely fit the wearer while preventing the skin of the wearer from being excessively compressed.

As described above, in the outer covering sheet4, no elastic members are disposed in the auxiliary region410located between the second waist region408and the middle elastic region409. Accordingly, in the state in which the outer covering sheet4is elongated in the right-left direction, the contractile force in the right-left direction per unit width of the auxiliary region410in the up-down direction is smaller than any of the middle unit contractile force, the first unit contractile force, and the second unit contractile force. This allows the disposable diaper1, when being put on or taken off, to be easily and firmly grasped by hooking fingers deep into the auxiliary region410, enabling the disposable diaper1to be easily moved along the body of the wearer. The auxiliary region410can be easily recognized and used because it is visually recognizable. From the viewpoint of hooking fingers into the auxiliary region410, the auxiliary region410preferably has a width of 7 mm or more in the up-down direction.

In the case where the middle elastic region409is segmented into the first middle elastic region409aand the second middle elastic region409b, the elongation rate of the first middle elastic threads451awhen joined to the first middle elastic region409ais equal to the elongation rate of the second middle elastic threads451bwhen joined to the second middle elastic region409b. The number of first middle elastic threads451aper unit width of the first middle elastic region409ain the up-down direction is greater than the number of second middle elastic threads451bper unit width of the second middle elastic region409bin the up-down direction. Accordingly, in the state in which the outer covering sheet4is elongated in the right-left direction, the contractile force in the right-left direction per unit width of the first middle elastic region409ain the up-down direction is greater than the contractile force in the right-left direction per unit width of the second middle elastic region409bin the up-down direction.

Because the contractile force in the first middle elastic region409aadjacent to the auxiliary region410is greater than the contractile force in the second middle elastic region409blocated below the first middle elastic region409a, the first middle elastic region409areadily tracks and pulls up around its entire circumference when part of the auxiliary region410is pulled up at the time of putting on or taking off the disposable diaper1in which a great force acts locally on the auxiliary region410, thus enabling the disposable diaper1to be smoothly pulled up. In addition, in the disposable diaper1, the contractile force in the first middle elastic region409acan be easily made greater than the contractile force in the second middle elastic region409bby setting the elongation rates of the first middle elastic threads451aand the second middle elastic threads451bin joining to the same value and setting the pitch in the up-down direction between the first middle elastic threads451ato be smaller than the pitch (average pitch) between the second middle elastic threads451b.

Preferably, the elongation rate of the first middle elastic threads451awhen joined to the first middle elastic region409ais equal to the elongation rate of the second elastic threads442when joined to the second waist region408, and the number of first middle elastic threads451aper unit width of the first middle elastic region409ain the up-down direction is approximately equal to the number of second elastic threads442per unit width of the second waist region408in the up-down direction. Accordingly, in the state in which the outer covering sheet4is elongated in the right-left direction, the contractile force in the right-left direction per unit width of the first middle elastic region409ain the up-down direction is approximately equal to the second unit contractile force in the second waist region408(e.g., the difference between these contractile forces is 10% or less of one of the contractile forces). This allows the second waist region408and the first middle elastic region409alocated on both sides of the auxiliary region410in the up-down direction to closely fit the skin of the wearer at approximately the same pressure and prevents the skin of the wearer from being compressed locally. In the disposable diaper1, the contractile force in the first middle elastic region409acan be readily made equal to the second unit contractile force in the second waist region408by setting the elongation rates of the first middle elastic threads451aand the second elastic threads442when joined to the same elongation rate and setting the pitch in the up-down direction between the first middle elastic threads451aand the pitch in the up-down direction between the second elastic threads442to the same pitch.

In the disposable diaper1, the numbers of the first elastic threads441and the second elastic threads442may be appropriately changed as long as the first unit contractile force is smaller than the second unit contractile force. For example, in the case where the first waist elastic member443includes only one first elastic thread441, the upper end of the first waist region407is the edge111of the waist opening11, and the lower end of the first waist region407is at a position in the middle of the distance in the up-down direction between the first elastic thread441and the uppermost second elastic thread442. In the case where the second waist elastic member444includes only one second elastic thread442, the upper end of second waist region408is at a position in the middle of the distance in the up-down direction between the second elastic thread442and the lowermost first elastic thread441, and the lower end of the second waist region408is at a position distant from and below the second elastic thread442by the distance in the up-down direction between the upper end and the second elastic thread442. Similarly, the number of first middle elastic threads451aand second middle elastic threads451bmay be changed.

As described above, in the disposable diaper1, the first unit contractile force in the first waist region407is reduced to smaller than the second unit contractile force in the second waist region408by setting the pitch of the plurality of first elastic threads441in the up-down direction to be greater than the pitch of the plurality of second elastic threads442in the up-down direction. However, in the case where the first unit contractile force is reduced to smaller than the second unit contractile force by other methods, the pitch of the first elastic threads441may be smaller than or equal to the pitch of the second elastic threads442(the same applies to the pitch of the first middle elastic threads451aand the pitch of the second middle elastic threads451b).

For example, in the disposable diaper1, the first unit contractile force may be reduced to smaller than the second unit contractile force by setting the elongation rate of each first elastic thread441when the plurality of first elastic threads441of the first waist elastic member443are joined to the first waist region407to be lower than the elongation rate of each second elastic thread442when the plurality of second elastic threads442aof the second waist elastic member444are joined to the second waist region408. In this case as well, the first unit contractile force can be reduced to smaller than the second unit contractile force. Similarly, the contractile force in the first middle elastic region409amay be made greater than the contractile force in the second middle elastic region409bby setting the elongation rate of each first middle elastic thread451awhen the plurality of first middle elastic threads451aof the first middle elastic member45aare joined to the first middle elastic region409ato be higher than the elongation rate of each second middle elastic thread451bwhen the plurality of second middle elastic threads451bof the second middle elastic member45bare joined to the second middle elastic region409b. The elongation rates of these elastic threads are preferably in the range of 1.1 times to 5.0 times, for example.

Alternatively, the first unit contractile force may be reduced to smaller than the second unit contractile force by using, as the first waist elastic member443, first elastic threads441that have a lower elastic modulus than that of the second elastic threads442of the second waist elastic member444, or first elastic threads441that have a lower fineness than that of the second elastic threads442. In either case, the first unit contractile force can be readily reduced to smaller than the second unit contractile force. Similarly, the contractile force in the first middle elastic region409amay be easily made greater than the contractile force in the second middle elastic region409bby using, as the first middle elastic member45a, first middle elastic threads451athat have a higher elastic modulus than that of the second middle elastic threads451bof the second middle elastic member45b, or first middle elastic threads451athat have a higher fineness than that of the second middle elastic threads451b.

While the above has been a description of an embodiment of the present invention, the present invention is not limited to the embodiment described above, and various modifications are possible.

In the state in which the outer covering sheet4is elongated in the right-left direction, an elastic member may be provided in the auxiliary region410as long as the contractile force in the auxiliary region410is smaller than any of the middle unit contractile force, the first unit contractile force, and the second unit contractile force.

The leg elastic members43, the waist elastic member44, and the middle elastic member45may be strip-like polyurethane films, or filiform or strip natural rubber, for example, similarly to the side wall elastic member35of the side sheet3. Preferably, polyurethane yarn covered with fibers is used from the viewpoint of improving the texture of the disposable diaper1.

While the middle unit contractile force is smaller than the first unit contractile force and the second unit contractile force in the above-described embodiment, the middle unit contractile force may be greater than or equal to the first unit contractile force as long as slipping-off in the up-down direction of the disposable diaper1, when being worn, is prevented by setting the contractile force per unit width of the entire waist region406to an appropriate value.

The structure of the above-described disposable diaper1may be used for pants-type absorbent articles other than disposable diapers.

The configurations of the above-described preferred embodiments and variations may be appropriately combined as long as there are no mutual inconsistencies.

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