Patent Description:
An underpants-shaped disposable diaper is known as an absorbent article. For example, Patent Literature <NUM> discloses an underpants-shaped disposable diaper in which a waist opening is formed by joining front and back belt portions (<NUM>, <NUM>) at two side portions by side-edge joining portions (<NUM>). In such an underpants-shaped disposable diaper, when removing the soiled diaper after use from the wearer's body, it is common to open the waist opening and remove the diaper by peeling locking portions (side-edge joining portions) on two side portions of the waist portion (belt portion). In addition, when peeling off the locking portion, a front waist portion and a back waist portion are pulled in opposite directions (for example, in a front-back direction) along the locking portion, thereby peeling off the locking.

Other prior art arrangements of underpants-shaped disposable diapers are known from <CIT>, <CIT> and <CIT>.

In recent years, from viewpoints of reducing in material cost, comfort to wear, and breathability, there has been an increasing need for a thinner material. There is a demand to use a sheet member (for example, nonwoven fabric) whose basis weight is as low as possible for a material constituting waist portions of a diaper. However, decreasing the basis weight of the sheet member also decreases a material strength of the sheet member, and accordingly, in some cases, a part of the sheet member is torn along a lateral direction at a time during peeling off the locking portion. In this case, there is a risk that the diaper cannot be removed or that excrement adhering to the inside of the diaper leaks outside.

The present invention was achieved in light of conventional problems such as that described above and an aspect of the present invention is, in an underpants-shaped disposable diaper formed of a material having a low basis weight, to suppress laterally tearing of a material that constitutes a front waist portion and a back waist portion, when peeling off a locking portion of the waist portions.

A main aspect of the present invention for achieving the above-described aspect is a underpants-shaped disposable diaper having a vertical direction, a lateral direction, and a front-back direction that intersect each other, the underpants-shaped disposable diaper including: a liquid-absorbent absorbent main body; a front waist portion and a back waist portion that are provided on a non-skin side of the absorbent main body; and a pair of locking portions that lock two lateral end portions of the front waist portion and two lateral end portions of the back waist portion, in each of the front waist portion and the back waist portion, a sum of a basis weight of a skin-side sheet member arranged the farthest on a skin side and a basis weight of a sheet member arranged the farthest on a non-skin side being <NUM>/m<NUM> or less, the skin-side sheet member overlapping the locking portions in two end portions in the lateral direction, the skin-side sheet member including a non-joining portion in a region adjacent to inside of the locking portion in the lateral direction, the non-joining portion being a portion that is not joined to a sheet member overlaid on a non-skin side of the skin-side sheet member, a tearing strength for tearing the skin-side sheet member along the lateral direction being greater than a peeling strength of the locking portion.

Features of the present invention other than the above will become clear by reading the description of the present specification with reference to the accompanying drawings.

According to the present invention, in the underpants-shaped disposable diaper using a material having a low basis weight, it is possible to suppress the tearing of the material that constitutes the front waist portion and the back waist portion, in the lateral direction, when peeling off the locking portion of the waist portions.

At least following matters will become clear with description of this specification and attached drawings.

A underpants-shaped disposable diaper having a vertical direction, a lateral direction, and a front-back direction that intersect each other, the underpants-shaped disposable diaper including: a liquid-absorbent absorbent main body; a front waist portion and a back waist portion that are provided on a non-skin side of the absorbent main body; and a pair of locking portions that lock two lateral end portions of the front waist portion and two lateral end portions of the back waist portion, in each of the front waist portion and the back waist portion, a sum of a basis weight of a skin-side sheet member arranged the farthest on a skin side and a basis weight of a sheet member arranged the farthest on a non-skin side being <NUM>/m<NUM> or less, the skin-side sheet member overlapping the locking portions in two end portions in the lateral direction, the skin-side sheet member including a non-joining portion in a region adjacent to inside of the locking portion in the lateral direction, the non-joining portion being a portion that is not joined to a sheet member overlaid on a non-skin side of the skin-side sheet member, a tearing strength for tearing the skin-side sheet member along the lateral direction being greater than a peeling strength of the locking portion.

According to the underpants-shaped disposable diaper, the total of the basis weights of the skin-side sheet member and of the non-skin-side sheet member which constitute the waist portion is <NUM>/m<NUM> or less, and athis makes it possible to realize a diaper having excellent manufacturing cost and breathability. In addition, even in the case of using a material having a low basis weight as described above, in an operation of peeling off the locking portion in order to remove the diaper from the wearer's body, it is possible to suppress the skin-side sheet member provided in the waist portion from being torn along the lateral direction.

In such a underpants-shaped disposable diaper, it is desirable that in at least one of an upper end region and a lower end region of the locking portion, of at least one of the front waist portion and the back waist portion, a basis weight of a sheet member arranged the farthest on the skin side is equal to or more than a basis weight of a sheet member arranged the farthest on the non-skin side.

According to the underpants-shaped disposable diaper, compared to the skin-side sheet member, a large force is less likely to act on the non-skin-side sheet member when peeling off the locking portion. For such a non-skin-side sheet member, it is possible to use a sheet member having a smaller basis weight than that of the skin-side sheet member. This makes it possible to realize a diaper in which the waist portions are less likely to be torn when peeling off the locking portions and whose manufacturing cost is low.

In such a underpants-shaped disposable diaper, it is desirable that in both the upper end region and the lower end region of the locking portion, of at least one of the front waist portion and the back waist portion, a basis weight of a sheet member arranged the farthest on the skin side is equal to or more than a basis weight of a sheet member arranged the farthest on the non-skin side.

According to the underpants-shaped disposable diaper, it possible to realize a diaper whose manufacturing cost is low and in which the waist portions are less likely to be torn in both cases of peeling off the locking portion from the upper side and peeling off the locking portion from the lower side, when removing the diaper from the wearer's body.

In such a underpants-shaped disposable diaper, it is desirable that the front waist portion and the back waist portion each have a waist elastic member, and that the waist elastic member is arranged on the non-skin side with respect to a central position in a thickness direction of at least one of the front waist portion and the back waist portion.

According to the underpants-shaped disposable diaper, in the waist portion, the distance between the waist elastic member and the wearer's skin increases, and accordingly, the waist elastic member can be suppressed from tightly digging into the wearer's skin due to a contractive force generated by the waist elastic member.

In such a underpants-shaped disposable diaper, it is desirable that in at least one of the front waist portion and the back waist portion, a thickness of a sheet member arranged the farthest on the skin side is equal to or more than a thickness of a sheet member arranged the farthest on the non-skin side.

According to the underpants-shaped disposable diaper, increase in thickness of the skin-side sheet member can further make it less likely to tear the skin-side sheet member at the time of peeling off the locking portion, while suppressing the tightening by the waist elastic member.

In such a underpants-shaped disposable diaper, it is desirable that an average value of a width of the locking portion in the lateral direction is <NUM> or less.

According to the underpants-shaped disposable diaper, the peeling strength of the locking portion is not excessively strong, and therefore it is possible to peel off the locking portion easily while suppressing the tearing of the skin-side sheet when removing the diaper from the wearer's body.

In such a underpants-shaped disposable diaper, it is desirable that in at least one of the front waist portion and the back waist portion, a number of overlaid sheet members that are overlaid in a thickness direction in a certain region in the vertical direction is different from a number of overlaid sheet members that are overlaid in the thickness direction in another region in the vertical direction.

According to the underpants-shaped disposable diaper, the peeling strength when peeling off the locking portion along the vertical direction can be adjusted for each of the regions. Accordingly, in a portion of the waist portion that is likely to be torn in the lateral direction, adjustment can be made such as decreasing the peeling strength of the locking portion.

In such a underpants-shaped disposable diaper, it is desirable that in at least one of the front waist portion and the back waist portion, the locking portion has a different locking pattern for each of regions in which the number of overlaid sheet members overlaid in the thickness direction is different.

According to the underpants-shaped disposable diaper, by varying the locking pattern for each of the regions in the waist portion in which the number of sheets overlaid in the thickness direction is different, it is possible to suppress the locking strength from becoming excessively strong or weak depending on the regions in which the number of overlaid sheets is different.

In such a underpants-shaped disposable diaper, it is desirable that in at least one of the front waist portion and the back waist portion, in the vertical direction, a position where the locking pattern changes is different from a position where the number of overlaid sheet members that are overlaid in the thickness direction changes.

According to the underpants-shaped disposable diaper, the position where the number of overlaid sheet members in the waist portion changes and the position where the locking strength of the locking portion changes are shifted. This makes the force that acts in a case of peeling the locking portion off change gradually. That is, the sudden change of the force acting on the waist portion at the time of peeling off the locking portion is suppressed, making it less likely to tear the waist portion.

In such a underpants-shaped disposable diaper, it is desirable that at least one of the front waist portion and the back waist portion includes: a first region having a larger number of overlaid sheet members that are overlaid in the thickness direction; and a second region having a smaller number of overlaid sheet members that re overlaid in the thickness direction, than in the first region, and a peeling strength of the locking portion in the first region is weaker than a peeling strength of the locking portion in the second region.

According to the underpants-shaped disposable diaper, in the first region where a larger number of sheet members are overlaid, the locking portion is more likely to be peeled off compared to the second region where a smaller number of sheets are overlaid. This makes it possible to reduce the force acting on the skin-side sheet member in the first region. This makes it less likely to tear the skin-side sheet member.

In such a underpants-shaped disposable diaper, it is desirable that in the region adjacent to inside of the locking portion in the lateral direction, the skin-side sheet member and the sheet member overlaid on the non-skin side of the skin-side sheet member include a joining portion where the skin-side sheet member and the sheet member are joined.

According to the underpants-shaped disposable diaper, in the adjacent region, the skin-side sheet member and the sheet member adjacent to the non-skin side thereof are at least partially joined in the thickness direction. Accordingly, the material strength of the waist portions increases, making it easier to suppress tearing in the lateral direction.

Hereinafter, an embodiment of an absorbent article according to the present invention will be described by way of example of a underpants-shaped disposable diaper for adults (hereinafter also referred to as a "diaper <NUM>"). It should be noted that the absorbent article according to the present invention is applicable to an underpants-shaped disposable diapers for infants or others.

<FIG> is a schematic front view of the diaper <NUM>. <FIG> is a schematic plan view of the diaper <NUM> in an unfolded and stretched state. <FIG> is a schematic cross-sectional view taken along a line I-I in <FIG>.

<FIG> is a schematic cross-sectional view taken along a line A-A in <FIG>. It should be noted that the "stretched state" of the diaper <NUM> refers to a state in which the entire diaper <NUM> (the entire product) has been stretched to eliminate wrinkles, or more specifically, a state in which the diaper has been stretched until the dimensions of constituent members of the diaper <NUM> (e.g., an absorbent body <NUM>, waist portions <NUM> and <NUM>, or the like that will be described later) match or are close to the dimensions of the members on their own.

In the underpants-shaped state shown in <FIG>, the diaper <NUM> has a vertical direction, a lateral direction, and a front-back direction that intersect with each other and has a waist opening BH and a pair of leg openings LH. The upper side in the vertical direction corresponds to the waist opening BH side, and the lower side corresponds to the crotch side. In addition, the front side in the front-back direction corresponds to the wearer's stomach side, and the back side corresponds to the wearer's back side. In addition, in the unfolded state of <FIG>, the diaper <NUM> has the front-back direction and the lateral direction that intersect each other. The front-back direction corresponds to the longitudinal direction of the absorbent body <NUM>. In addition, as shown in <FIG> and <FIG>, a direction in which materials for configuring the diaper <NUM> are overlaid is referred to as a thickness direction. In the thickness direction, the side that comes into contact with the wearer is referred to as the skin side, and the side opposite to the skin side is referred to as the non-skin side.

The diaper <NUM> has an absorbent main body <NUM>, a front waist portion <NUM>, and a back waist portion <NUM>. In the diaper <NUM> in an underpants-shaped state, the absorbent main body <NUM> (later-described absorbent core <NUM>) is arranged extending along the vertical direction, and is folded in front-back direction in the vertically lower end portion. In addition, the front waist portion <NUM> is joined to the front upper end portion of the absorbent body <NUM> from the non-skin side, and the back waist portion <NUM> is joined to the back upper end portion of the absorbent body <NUM> from the non-skin side.

When the diaper <NUM> is in the unfolded state of <FIG>, the front waist portion <NUM> and the back waist portion <NUM> are arranged such that the longitudinal directions thereof conform to the lateral direction of the diaper <NUM>. In addition, the longitudinal one-side (front) end portion of the absorbent body <NUM> is arranged in the lateral central portion of the front waist portion <NUM>, and the longitudinal other-side (back) end portion of the absorbent body <NUM> is arranged in the lateral central portion of the back waist portion <NUM>. When the diaper <NUM> is in the unfolded state shown in <FIG>, the absorbent main body <NUM> is folded one time at substantially the center position CL in the front-back direction (longitudinal direction). The two lateral side portions of the front waist portion <NUM> are respectively locked with two lateral side portions of the back waist portion <NUM> by a pair of locking portions <NUM> and <NUM>, thereby forming the diaper <NUM> into an underpants shape as in <FIG>. In the present embodiment, the locking portions <NUM> are formed by a joining means such as welding. The locking portions <NUM> will be described later in detail.

The absorbent body <NUM> includes: the absorbent core <NUM> that absorbs excrement; a hydrophilic skin-side sheet <NUM> arranged on the wearer's skin side of the absorbent core <NUM>; a liquid-impermeable non-skin-side sheet <NUM> arranged on the non-skin side of the absorbent core <NUM>; and a sheet member <NUM>. The two lateral side portions of the skin-side sheet <NUM> are folded back to the non-skin side so as to wrap the absorbent core <NUM>. The sheet member <NUM> is arranged on the non-skin side with respect to the non-skin-side sheet <NUM>, and forms the leak-proof wall portions <NUM> on the skin side with respect to the skin-side sheet <NUM>.

The absorbent core <NUM> is made by shaping liquid absorbent fibers (e.g., pulp fibers) containing a superabsorbent polymer (SAP), into a predetermined shape. In addition, the absorbent core <NUM> may be covered with a liquid-permeable core-wrapping sheet <NUM>.

In addition, the absorbent core <NUM> of the present embodiment includes a narrow portion 11C in the central portion in the front-back direction, and the narrow portion 11C is a portion where the lateral length of the absorbent core <NUM> is shorter (has a narrower width) compared with the front end portion and the back end portion. Accordingly, the absorbent core <NUM> has a substantially hourglass shape in a plan view as shown in <FIG>. This narrow portion 11C is a portion that is sandwiched between the wearer's legs while the diaper <NUM> is put on, and the absorbent core <NUM> more easily fits to the wearer's crotch due to the decreased lateral length (decreased width) of this portion.

A pair of the leak-proof wall portions <NUM> are respectively provided on two lateral side portions of the absorbent body <NUM>, extending along the front-back direction (the longitudinal direction of the absorbent body <NUM>). In the present embodiment, the pair of leak-proof wall portions <NUM> are each formed by folding the sheet member <NUM> that constitutes the exterior of the absorbent main body <NUM> at a plurality of positions as shown in <FIG>. In addition, in the leak-proof wall portion <NUM>, a plurality of leak-proof-wall stretchable members <NUM> such as an elastic string and the like are fixed in a state of being stretched in the front-back direction of the absorbent main body <NUM> (corresponding to the vertical direction of the diaper <NUM>). While the diaper <NUM> is put on, the leak-proof wall portion <NUM> contracts along the front-back direction of the absorbent main body <NUM> and rises to the skin side of the wearer due to the stretchability exhibited by the leak-proof-wall stretchable member <NUM>, thereby fitting to the wearer's crotch portion.

The front waist portion <NUM> includes: an inner-layer sheet <NUM>; an outer-layer sheet <NUM> which is arranged on the non-skin side with respect to the inner-layer sheet <NUM>; waist elastic members <NUM>; and a skin surface sheet <NUM> which is arranged on the skin side of the inner-layer sheet <NUM>. The inner-layer sheet <NUM> and the outer-layer sheet <NUM> are sheet members having a rectangular shape in a plan view as shown in <FIG>, and are made of SMS nonwoven fabric or the like. The waist elastic members <NUM> are arranged side-by-side in the vertical direction between the inner-layer sheet <NUM> and the outer-layer sheet <NUM>, and are fixed in a state of being stretched in the lateral direction. The front waist portion <NUM> fits to the wearer's waist due to the stretchability exhibited by the waist elastic members <NUM>. In <FIG>, the skin surface sheet <NUM> is a sheet member which is arranged so as to cover the upper end portion of the absorbent main body <NUM> from the skin side, and functions as a cover sheet. Accordingly, it is possible to suppress the upper end edge of the absorbent main body <NUM> from digging into the wearer's waist portion while the diaper <NUM> is put on. The skin surface sheet <NUM> is made of SMS nonwoven fabric or the like.

It should be noted that, in the diaper <NUM>, the skin surface sheet <NUM> is provided so as to be continuous from one end to the other end in the lateral direction, and arranged so as to overlap the locking portion <NUM> in two end portions in the lateral direction. That is, the skin surface sheet <NUM> together with the inner-layer sheet <NUM> and the outer-layer sheet <NUM> are locked to the back waist portion <NUM> by the locking portion <NUM>. However, the skin surface sheet <NUM> may be provided only in the central region in the lateral direction and arranged so as not to overlap the locking portion <NUM>. In addition, the diaper <NUM> does not necessarily have to include the skin surface sheet <NUM>.

In addition, as shown in <FIG>, in the front waist portion <NUM>, a region on an upper side with respect to the upper end of the skin surface sheet <NUM> in the vertical direction is defined as 20U (upper end region), a region which overlaps the skin surface sheet <NUM> is defined as 20C (central region), and a region on a lower side with respect to the lower end of the skin surface sheet <NUM> is defined as 20D (lower end region). In the front waist portion <NUM>, the sheet member which is arranged the farthest on the skin side in the thickness direction is referred to as a "skin-side sheet member". In the case of the front waist portion <NUM> shown in <FIG>, in the upper end region 20U and the lower end region 20D, the inner-layer sheet <NUM> corresponds to the skin-side sheet member, and, in the central region 20C, the skin surface sheet <NUM> corresponds to the skin-side sheet member.

The back waist portion <NUM> has substantially the same function and structure as the front waist portion <NUM>. That is, the back waist portion <NUM> includes: an inner-layer sheet <NUM>; an outer-layer sheet <NUM> which is arranged on a non-skin side with respect to the inner-layer sheet <NUM>; waist elastic members <NUM>, and a skin surface sheet <NUM> (see <FIG>).

In addition, in the back waist portion <NUM>, a region on an upper side with respect to the upper end of the skin surface sheet <NUM> in the vertical direction is defined as 30U (upper end region), a region which overlaps the skin surface sheet <NUM> is defined as 30C (central region), and a region on a lower side with respect to the lower end of the skin surface sheet <NUM> is defined as 30D (lower end region). In the case of the back waist portion <NUM> of the diaper <NUM>, in the upper end region 30U and the lower end region 30D, the inner-layer sheet <NUM> corresponds to the skin-side sheet member, and, in the central region 30C, the skin surface sheet <NUM> corresponds to the skin-side sheet member.

In addition, in the unfolded and stretched state of <FIG>, the back waist portion <NUM> includes an overlapping portion 30A which is to overlap the front waist portion <NUM> in the front-back direction, and an extension portion 30B which is to extend downward beyond the front waist portion <NUM>. The overlapping portion 30A has a rectangular shape in a plan view, and the extension portion 30B has an inverted trapezoidal shape in a plan view. The wearer's buttocks can be covered with the extension portion 30B. On the other hand, the front waist portion <NUM> has a shorter vertical length than the back waist portion <NUM>, and does not extend to the vicinity of the wearer's crotch. For this reason, leg movement is not hindered when the wearer lifts their legs toward their stomach while walking for example, making it easier for the wearer to walk.

Extension-portion elastic members <NUM> are provided extending along the lower end of the extension portion 30B of the back waist portion <NUM>. Specifically, the extension-portion elastic members <NUM> each include a pair of inclined portions <NUM> which are inclined downward and laterally inward, and a straight portion <NUM> which extends along the lateral direction between the pair of inclined portions <NUM>. Similarly to the waist elastic members <NUM>, the extension-portion elastic members <NUM> are fixed in a stretched state between the inner-layer sheet <NUM> and the outer-layer sheet <NUM>. The extension-portion elastic members <NUM> make the extension portion 30B fit to the wearer's buttocks, suppressing the extension portion 30B being curled up.

However, the present invention is not limited to the above configuration. For example, a configuration is possible in which the front waist portion <NUM> has the same shape as the back waist portion <NUM> in a plan view, and includes the elastic members similar to the extension-portion elastic members <NUM> of the back waist portion <NUM>. Specifically, the front waist portion <NUM> may include inclined elastic members that are inclined downward and laterally inward in the lower end portion. Conversely, a configuration is possible in which the back waist portion <NUM> has the same rectangular shape as the front waist portion <NUM> in a plan view, and does not include the extension-portion elastic members <NUM>.

An operation of removing the diaper <NUM> after excresion (after use), from the wearer's body during usage of the diaper <NUM> will be described.

<FIG> is a schematic view showing the diaper <NUM> in the underpants-shaped state when seen from one side in the lateral direction (right side in <FIG>). At the time of removing the underpants-shaped disposable diaper such as the diaper <NUM> from the wearer's body, the following method is generally used: peeling off the locking portions <NUM> which lock the waist portions <NUM> and <NUM> in two lateral end portions of the front waist portion <NUM> and two lateral end portions of the back waist portion <NUM>, and separating the front waist portion <NUM> and the back waist portion <NUM>. That is, the diaper <NUM> is removed from the wearer's body by peeling the lockings of the front waist portion <NUM> and the back waist portion <NUM>, which form in an annular shape along the wearer's waist, and unfolding the diaper <NUM> as shown in <FIG>.

The locking portions <NUM> can be peeled off by pulling the front waist portion <NUM> and the back waist portion <NUM> in opposite directions. In <FIG>, a user pulls the front waist portion <NUM> forward (toward stomach side) in the front-back direction, and pulls the back waist portion <NUM> backward (toward back side) in the front-back direction, making it possible to peel off the locking portions <NUM>. At this time, it is recommended that, by grabbing upper end portions (or lower end portions) of the waist portions <NUM> and <NUM> and pulling away the grabbed portions from each other in the front-back direction with a predetermined tensile force F, it makes the locking portion <NUM> be peeled along the vertical direction from the upper end <NUM> (or lower end <NUM>) of the locking portion <NUM>.

<FIG> are schematic diagrams illustrating the peeling of the locking portion <NUM>. Similarly to <FIG>, <FIG> show a state where the locking portion <NUM> of the diaper <NUM> is seen from one side (right side) in the lateral direction.

<FIG> shows a force that acts on the front waist portion <NUM> and the back waist portion <NUM> when peeling off the locking portion <NUM> from the upper end <NUM> toward the lower end <NUM> in the vertical direction. As described above, in a case where the user grabs the upper end portions of the front waist portion <NUM> and the back waist portion <NUM> and pulls away the grabbed portion from each other in the front-back direction with a tensile force F1, the upper end <NUM> of the locking portion <NUM> is peeled off at the timing when the tensile force F1 becomes larger than the peeling strength of the locking portion <NUM>, separating the upper end 61a of the front waist portion <NUM> and the upper end 61b of the back waist portion <NUM>. If continuously keeping pulling the waist portions <NUM> and <NUM> in the front-back direction, the locking portion <NUM> is peeled off in order from the upper side (upper ends 61a and 61b) to the lower side (lower end <NUM>) in the vertical direction. That is, a peeling point <NUM> at which the locking portion <NUM> is being peeled off moves along the locking portion <NUM> from the upper side to the lower side. It should be noted that, in the case of peeling off the locking portion <NUM>, the locking portion <NUM> may be peeled off from the lower side (lower end <NUM>) to the upper side (upper end <NUM>).

At this time, at locations between the upper end 61a and the peeling point <NUM> in the front waist portion <NUM>, tension F2 as shown in <FIG> acts due to the tensile force F1. Similarly, at locations between the upper end 61b and the peeling point <NUM> in the back waist portion <NUM>, the tension F2 acts.

In addition, in the case where the tension F2 becomes equal to or greater than a predetermined magnitude, there is a risk that a part of the sheet member constituting the waist portions <NUM> and <NUM> is torn at any position between the upper end 61b and the peeling point <NUM>. <FIG> shows a case where a part of the front waist portion <NUM> is torn in the peeling operation of the locking portion <NUM> described in <FIG>. Specifically, in <FIG>, the tension F2 becomes greater than the tearing strength at the time of tearing the sheet member constituting the front waist portion <NUM>, and this causes breakage at the peeling point <NUM>, separating the peeling point into 63a and 63b. Thereby, the front waist portion <NUM> is torn along the lateral direction, forming a tear CT.

In the case where such a tear is formed in the waist portions <NUM> and <NUM>, it makes it difficult to further peel off the locking portions <NUM>, and there is a risk that the removing operation of the diaper <NUM> is obstructed. In addition, in the case where the tear is large, there is a risk that the excrement such as feces adhering to the inside of the diaper <NUM> (absorbent main body <NUM>) leaks to the outside.

Next, among a plurality of sheet members constituting the waist portions <NUM> and <NUM>, a sheet member that is likely to be torn at the time of peeling off the locking portion <NUM> will be described. <FIG> is a schematic cross-sectional view taken along a line C-C in <FIG>. <FIG> is a schematic enlarged view of a region D (locking portion <NUM>) in <FIG>.

As shown in <FIG>, in the locking portions <NUM>, the followings sheets are joined (locked) with being overlaid in the thickness direction: the inner-layer sheet <NUM>, the outer-layer sheet <NUM>, and the skin surface sheet <NUM> which constitute the front waist portion <NUM>; and the inner-layer sheet <NUM>, the outer-layer sheet <NUM>, and the skin surface sheet <NUM> which constitute the back waist portion <NUM>. In the case of peeling off the locking portion <NUM>, among the sheet members of the front waist portion <NUM> and the back waist portion <NUM>, it is necessary to peel off the sheet members whose located-the-farthest-on-the-skin-side surface are in direct contact with each other, in the locking portion <NUM>. In the example of <FIG>, in the locking portion <NUM>, the skin surface sheet <NUM> is arranged as the skin-side sheet member that is located the farthest on the skin side in the front waist portion <NUM>, and the skin surface sheet <NUM> is arranged as the skin-side sheet member that is located the farthest on the skin side in the back waist portion <NUM>. Accordingly, in the case shown in <FIG>, in order to peel off the locking portion <NUM>, it is necessary to peel off a joining surface (interface) which joins the skin surface sheet <NUM> of the front waist portion <NUM> and the skin surface sheet <NUM> of the back waist portion <NUM>.

In <FIG>, in a case where the front waist portion <NUM> and the back waist portion <NUM> are each pulled away from each other in the front-back direction, a force acts in a direction in which the joining surfaces (interfaces) of the skin-side sheet member (skin surface sheet <NUM>), on the front side and the skin-side sheet member (skin surface sheet <NUM>) on the back side are peeled off. As a result, in the locking portion <NUM> shown with hatched lines in <FIG>, the front waist portion <NUM> and the back waist portion <NUM> are peeled off.

Here, the skin surface sheet <NUM> and the skin surface sheet <NUM>, which are the skin-side sheet members, are joined to the corresponding sheet members that are respectively overlaid on the non-skin sides of the sheet <NUM> and <NUM>, with an adhesive such as a hot-melt adhesive. Specifically, the skin surface sheet <NUM> is joined to the inner-layer sheet <NUM> (outer-layer sheet <NUM>), and the skin surface sheet <NUM> is joined to the inner-layer sheet <NUM> (outer-layer sheet <NUM>) (see <FIG> and <FIG>). The adhesive is not uniformly applied to the surface of the sheet member, and is intermittently applied, for example, by spiral coating or Ω-shaped coating (not shown). Accordingly, the skin-side sheet members (the skin surface sheet <NUM> and the skin surface sheet <NUM>) each include: a joining portion where the skin-side sheet member is joined to the sheet member that is overlaid on the non-skin side thereof; and a non-joining portion that is not joined.

In such a non-joining portion, at the time of peeling off the locking portions <NUM>, a force acts so as to pull off the skin surface sheet <NUM> (skin surface sheet <NUM>) from the inner-layer sheet <NUM> (inner-layer sheet <NUM>). The tensile force for peeling off the locking portion <NUM> of the waist portions <NUM> and <NUM> is more likely to most strongly act on the skin-side sheet member (skin surface sheets <NUM> and <NUM>) arranged the farthest on the skin side. In the case where the joining portion is formed in the entire region of the interface between the skin surface sheet <NUM> (<NUM>) and the inner-layer sheet <NUM> (<NUM>), the force for peeling off the skin surface sheet <NUM> (<NUM>) acts on the skin surface sheet <NUM> (<NUM>) and the inner-layer sheet <NUM> (<NUM>) as a unit. On the other hand, in the case where there is a non-joining portion at the interface between the skin surface sheet <NUM> (<NUM>) and the inner-layer sheet <NUM> (<NUM>) as in the present embodiment, the unity of the skin surface sheet <NUM> (<NUM>) and the inner-layer sheet <NUM> (<NUM>) is lost, and accordingly, a force for peeling off the interface between the skin surface sheets <NUM> and <NUM> greatly acts on the skin surface sheet <NUM> (<NUM>). Therefore, the skin surface sheet <NUM> (<NUM>) which has received a large force is likely to be torn.

Particularly, an adjacent region A60 which is adjacent to inside of the locking portion <NUM> in the lateral direction includes a non-joining portion where the skin surface sheet <NUM> (<NUM>) and the inner-layer sheet <NUM> (<NUM>) are not joined. In adjacent region A60, the front waist portion <NUM> and the back waist portion <NUM> are not joined to each other (see <FIG>), and accordingly, the tensile force for peeling off the locking portion <NUM> is likely to act directly on the skin surface sheets <NUM> and <NUM>. As described above, there is a risk that the skin surface sheets <NUM> and <NUM> (skin-side sheet members) are torn along the lateral direction when peeling off the locking portions <NUM>.

In contrast, in the diaper <NUM> of the present embodiment, the tearing strength of the skin-side sheet member (skin surface sheet <NUM> and <NUM>) which is arranged the farthest on the skin side of the waist portion <NUM> (<NUM>), at the time of tearing it along the lateral direction, becomes greater than the peeling strength of the locking portion <NUM> at the time of peeling it off. This prevents the skin-side sheet member from being torn at the time of peeling apart the locking portion <NUM>.

In this case, increasing the basis weight of the skin-side sheet member can increase the tearing strength of the skin-side sheet member. However, since the skin-side sheet member is a member having a high possibility of coming into direct contact with the wearer's body while the diaper <NUM> is put on, there is a risk that wearing comfort to wear and breathability of the diaper <NUM> deteriorates in the case of using the sheet member having an excessively high basis weight. In addition, there is a risk that the manufacturing cost (material cost) of the diaper <NUM> increases. Therefore, in the diaper <NUM> of the present embodiment, the basis weight of the skin-side sheet member is set to be equal to or lower than a predetermined value. Specifically, a nonwoven fabric sheet or the like is used in which a total value of the basis weights of the skin-side sheet member and the sheet member located the farthest on the non-skin side is <NUM>/m<NUM> or less. This makes it possible to suppress the increase in manufacturing cost and the deterioration of breathability.

It should be noted that, in the adjacent region A60 of <FIG>, the skin-side sheet member (skin surface sheet <NUM>) and the sheet member adjacent to the non-skin side thereof (inner-layer sheet <NUM>) have a joining portion where they are at least partially joined to each other. That is, the skin-side sheet member and the sheet member adjacent to the non-skin side thereof are joined in a part of the region, in a state of being overlaid in the thickness direction. Accordingly, the material strength of the waist portion <NUM> (<NUM>) increases, making it easier to suppress the tearing in the lateral direction. In addition, when peeling off the locking portion <NUM>, it is possible to suppress peeling and separating apart into pieces the sheet members that are overlaid in the waist portion <NUM> (in <FIG>, the skin surface sheet <NUM> and the inner-layer sheet <NUM>).

Next, a method for measuring the tearing strength of the skin-side sheet member and the peeling strength of the locking portions <NUM> will be described. The tearing strength of the skin-side sheet member can be measured as follows. <FIG> is a diagram illustrating a test piece used for measuring the tearing strength of the skin-side sheet member. <FIG> is a conceptual diagram illustrating a method for measuring the tearing strength of the skin-side sheet member.

In the measurement of the tearing strength of the skin-side sheet member, firstly, taking test pieces shown in <FIG> from the skin-side sheet member to be measured (for example, the skin surface sheets <NUM> and <NUM>) is performed. First, in the vicinity of the locking portion <NUM> of the diaper <NUM>, the front waist portion <NUM> (back waist portion <NUM>) is cut off, and the overlaid sheet members are separated into individual sheets by being immersed in toluene or the like. Then, a skin-side sheet member, which is a target, is collected. From the collected skin-side sheet member, five rectangular sheets are cut out to have a long side of <NUM> or more and a short side of <NUM> or more. At this time, a long-side direction of the sheet is set to a direction extending along the lateral direction of the diaper <NUM>. Then, for each of the cut sheets, a notch having a length of <NUM> is made from the center in a short-side direction to obtain a test piece (see <FIG>). The portion where the notch is provided serves as a gripping margin.

Subsequently, a tensile test is performed on the test pieces using a commercially available constant-speed extension-type tensile tester (e.g., a tensile tester manufactured by Shimadzu Corporation: Model No. AG-1kNI). As shown in <FIG>, a pair of gripping portions provided in the tensile tester are arranged apart from each other at a distance of <NUM> vertically, and each test piece is fixed so as not to loosen by making the gripping margins of the test piece each be sandwiched. In this state, the test piece is pulled in the vertical direction at a speed of <NUM>/min, a magnitude of a force at the time when the test piece starts to tear is recorded as a maximum strength. The average value of measurements of the five test pieces is taken as the tearing strength of the skin-side sheet member.

In addition, the peeling strength of the locking portion <NUM> can be measured as follows. <FIG> is a diagram illustrating a test piece used for measuring the peeling strength of the locking portion <NUM>. In the measurement of the peeling strength of the locking portions <NUM>, as shown in <FIG>, sheet pieces having a length of <NUM> or more in the vertical direction and <NUM> or more in the lateral direction are cut out from each of the regions obtained by dividing the locking portion <NUM> of the diaper <NUM> into three equal parts in the vertical direction (an upper end portion, a central portion, and a lower end portion). Then, the sheet pieces are taken as test pieces. However, in the case where the number of sheet members overlaid in the thickness direction in the locking portion <NUM> is different as in the diaper <NUM>, test pieces are prepared for each of the regions where the number of layers of the sheet members is different. In the diaper <NUM> of the present embodiment, five test pieces are prepared for each of the regions 20U, 20C, and 20D (30U, 30C, and 30D) shown in <FIG>.

Next, a gripping margin is produced for each test piece by peeling off the locking portion <NUM> from the upper end (or lower end) by approximately <NUM> in the vertical direction. Next, a front gripping margin of the test piece is made sandwiched in the gripping portion on one side of the same tensile tester as that described in <FIG>, and a back gripping margin of the test piece is made sandwiched in the gripping portion on the other side of the tensile tester. It should be noted that measuring can be made easier by splicing the gripping margin of the test piece and a gummed tape or the like having a length longer than that of the gripping margin, to extend the gripping margin. Then, by setting a space between the pair of gripping portions to <NUM>, the test piece is fixed so as not to loosen. In this state, the test piece is pulled in the vertical direction at a speed of <NUM>/min, a magnitude of a force at the time when the locking portion <NUM> has been completely peeled off is recorded as a maximum strength. The average value of measurements for the five test pieces is taken as the peeling strength of the locking portion <NUM>.

<FIG> is a table showing results of the measurement. <FIG> shows results obtained for the front waist portion <NUM> by the following manner: five types of diaper were prepared as samples A to E in which the basis weight of the skin-side sheet member arranged the farthest on the skin side in the thickness direction is different and in which the basis weight of the sheet member located the farthest on the non-skin side in the thickness direction is different; and the tearing strength of the skin-side sheet member in the lateral direction and the peeling strength of the locking portion <NUM> were measured for each of the samples by the method described above. The operation of actually peeling the locking portion <NUM> was performed a plurality of times for each sample. A case where no tearing of the sheet member in the lateral direction occurred was evaluated as GOOD, a case where the tearing of the sheet member inevitably occurs was evaluated as POOR, and a case where the tearing occurs in some not all of the plurality of times of operations was evaluated as OK.

It should be noted that the "basis weight" is a weight per unit area of the sheet member to be measured. For example, the basis weight can be determined as follow: sheet pieces having a predetermined size are cut out at a plurality of locations (e.g., ten locations) from the skin-side sheet member <NUM>; the weight of each sheet piece is measured using an electronic balance or the like; and the average value of values obtained by dividing the weights of the sheet pieces by the area of the sheet pieces, to be the basis weight.

As a result of the measurement, in the front waist portion <NUM> where the sum of the basis weight of the sheet member (skin-side sheet member) arranged the farthest on the skin side and the basis weight of the sheet member arranged the farthest on the non-skin side was <NUM>/m<NUM> or less, in the case where the tearing strength in the lateral direction was greater than the peeling strength of the locking portions <NUM> (in the case of samples A to C in <FIG>), the locking portion <NUM> could be peeled off without causing any lateral tearing of the sheet member. Therefore, it has been clarified that, in the underpants-shaped disposable diaper, by satisfying such conditions, it is possible to suppress the tearing of the material constituting the waist portion in the lateral direction when peeling the locking portion between the front waist portion and the back waist portion.

It should be noted that, though <FIG> shows the results of measurement for the front waist portion <NUM>, but a sheet member having the same basis weight as that of the front waist portion <NUM> can be used also for the back waist portion <NUM>. For the back waist portion <NUM> of each sample measured in <FIG>, the same sheet member having the same basis weight as that of the front waist portion <NUM> was used. In addition, even if materials having different basis weights are used for the front waist portion <NUM> and the back waist portion <NUM>, the diaper <NUM> of the present embodiment is applicable as long as the relationship described above is satisfied. That is, it is sufficient that the sum of the basis weight of the sheet member arranged the farthest on the skin side (skin-side sheet member) and the basis weight of the sheet member arranged the farthest on the non-skin side is <NUM>/m<NUM> or less, and that the tearing strength in the lateral direction is greater than the peeling strength of the locking portions <NUM>.

In addition, from the results of <FIG>, it has been clarified that, in the case where the basis weights of the skin-side sheet members arranged the farthest on the skin side of the waist portions <NUM> and <NUM> is equal to or more than the basis weights of the sheet members arranged the farthest on the non-skin side, it is less likely to cause lateral tearing of the waist portions <NUM> and <NUM>. That is, in <FIG>, in samples A and B in which the basis weight of the skin-side sheet member is equal to or more than the basis weight of the non-skin-side sheet member, no lateral tearing of the waist portions <NUM> and <NUM> occurred. On the other hand, in samples C and D in which the basis weight of the skin-side sheet member is less than the basis weight of the non-skin-side sheet member, the lateral tear of the waist portions <NUM> and <NUM> occurred in some cases.

As described above, in the operation of peeling off the locking portion <NUM> of the waist portions <NUM> and <NUM>, a great force is likely to act on the skin-side sheet member arranged the farthest on the skin side. That is, among the plurality of sheet members constituting the waist portions <NUM> and <NUM>, the skin-side sheet member (for example, the skin surface sheets <NUM> and <NUM>) is most likely to be torn. Accordingly, for the skin-side sheet member, it is desirable to use a sheet member having as a great basis weight as possible, within an applicable range (the sum of the basis weights of the skin-side sheet member and the non-skin-side sheet member is <NUM>/m<NUM> or less). On the other hand, a force is less likely to act on the non-skin-side sheet member when peeling off the locking portion <NUM> than on the skin-side sheet member, and the non-skin-side sheet member is less likely to be torn. Therefore, a sheet member having a basis weight smaller than that of the skin-side sheet member can be used as the non-skin-side sheet member. As described above, in the waist portions <NUM> and <NUM>, on the non-skin side with respect to the skin-side sheet members, it is possible to use a sheet member having a smaller basis weight than that of the skin-side sheet member. This makes it possible to reduce the material cost of the entire diaper <NUM>.

Note that it is sufficient that the relationship described above is satisfied in at least one of the upper end region and the lower end region of the locking portion <NUM>. In the case where the locking portion <NUM> is to be peeled off at the time of removing the diaper <NUM> from the wearer's body, either one of the following operations is performed: peeling off the locking portion <NUM> from the upper end <NUM> toward the lower end <NUM> of the locking portion <NUM>; or peeling off the locking portion <NUM> from the lower end <NUM> toward the upper end <NUM> of the locking portion <NUM>. That is, the upper end <NUM> or the lower end <NUM> serves as a peeling start point of the locking portion <NUM>. Therefore, according to the use aspect of the diaper <NUM>, it is sufficient that in at least one of the upper end region and the lower end region of the locking portion <NUM>, the basis weight of the sheet member (skin-side sheet member) arranged the farthest on the skin side is equal to or more than the basis weight of the sheet member arranged the farthest on the non-skin side.

However, it is more preferable that, in both of the upper end region and the lower end region of the locking portion <NUM>, the basis weight of the sheet member (skin-side sheet member) arranged the farthest on the skin side is equal to or more than the basis weight of the sheet member arranged the farthest on the non-skin side. With the configuration described above, it makes the tearing of the waist portions <NUM> and <NUM> easier to be suppressed in both cases of peeling off the locking portion <NUM> from the upper side and peeling off the locking portion <NUM> from the lower side. It should be noted that, in the diaper <NUM> of the present embodiment, in the locking portion <NUM>, all of the sheet members arranged in the upper end regions (20U and 30U in <FIG>) and the lower end regions (20D and 30D in <FIG>) of the waist portions <NUM> and <NUM> are the same (inner-layer sheets <NUM> and <NUM>). Accordingly, in both the upper end region and the lower end region of the locking portion <NUM>, the basis weight of the skin-side sheet member (inner-layer sheets <NUM> and <NUM>) can be equal to or more than the basis weight of the sheet member (outer-layer sheets <NUM> and <NUM>) arranged the farthest on the non-skin side.

In addition, it is recommended that the arrangement of the waist elastic members <NUM> (<NUM>) provided in the waist portion <NUM> (<NUM>) is adjusted as follows. <FIG> is a schematic cross-sectional view showing how components of the front waist portion <NUM> are overlaid in the thickness direction. In the front waist portion <NUM>, the skin surface sheet <NUM>, the inner-layer sheet <NUM>, the waist elastic members <NUM>, and the outer-layer sheet <NUM> are overlaid in this order from the skin side toward the non-skin side in the thickness direction. In this state, it is desirable that the waist elastic members <NUM> are arranged on the non-skin side with respect to the central position of the front waist portion <NUM> in the thickness direction. In <FIG>, in the thickness direction, the center c23 of the waist elastic members <NUM> is positioned on the non-skin side with respect to the center c20 of the front waist portion <NUM>. According to the configuration described above, when the diaper <NUM> is put on, the distance between the waist elastic members <NUM> and the wearer's skin increases in the front waist portion <NUM>, making it possible to suppress the waist elastic members <NUM> from tightly digging into the wearer's skin. That is, a contractive force generated by the waist elastic members <NUM> is less likely to directly act on the wearer's skin, making it possible to suppress the wearer feeling discomfort.

In addition, it is desirable that, among the sheet members constituting the waist portion <NUM> (<NUM>), the thickness of the skin-side sheet member arranged the farthest on the skin side is equal to or more than the thickness of the sheet member arranged the farthest on the non-skin side. In <FIG>, the thickness t25 of the skin surface sheet <NUM>, which serves as the skin-side sheet member, is equal to or more than the thickness t22 of the outer-layer sheet <NUM> arranged the farthest on the non-skin side (t25 ≥ t22). Increase in thickness of the skin-side sheet member can make it less likely to tear the skin-side sheet member at the time of peeling off the locking portions <NUM>, while suppressing the tightening by the waist elastic members <NUM>.

Next, a specific shape of the locking portion <NUM> will be described. <FIG> are enlarged plan views illustrating the shape and arrangement of the locking portion <NUM>. It should be noted that <FIG> shows the locking portion <NUM> provided at a right end in the lateral direction when the diaper <NUM> is seen from the front side in the front-back direction. As shown in <FIG>, the locking portion <NUM> of the diaper <NUM> is formed of two types of locking patterns. Specifically, the locking portion <NUM> is formed by arranging a plurality of first patterns <NUM> shown in <FIG> and second patterns <NUM> shown in <FIG> intermittently side-by-side along the vertical direction. The first pattern <NUM> is a locking pattern in which two semielliptical patterns are arranged side-by-side in the lateral direction, and the second pattern <NUM> is an elliptical locking pattern.

In the locking portion <NUM> of the diaper <NUM>, as shown in <FIG>, the width of the first pattern <NUM> and the width of the second pattern <NUM> in the lateral direction are both equal to or less than <NUM>. Also when the entire locking portion <NUM> is seen, the average value of the widths in the lateral direction is <NUM> or less (see <FIG>). It should be noted that the average value of the widths of the locking portion <NUM> in the lateral direction refers to the average value of the widths of all the locking patterns constituting the locking portion <NUM>. For example, in a case of <FIG>, the average of the values of the widths that are measured in the lateral direction for all of the locking patterns (the first patterns <NUM> and the second patterns <NUM>) included in the locking portion <NUM> is the average value of the widths of the locking portion <NUM>.

In the case of locking the front waist portion <NUM> and the back waist portion <NUM> by the locking portion <NUM>, as the total value of areas of the first patterns <NUM> and the second patterns <NUM> constituting the locking portion <NUM> increases, the strength (locking strength) of the locking portion <NUM> increases. However, if the locking strength of the locking portions <NUM> is excessively strong, there is a risk that the locking portions <NUM> cannot be peeled off when removing the diaper <NUM> from the wearer's body. In addition, as described above, if the peeling strength of the locking portions <NUM> is stronger than the tearing strength of the skin-side sheet members of the waist portions <NUM> and <NUM>, there is a risk that the skin-side sheet member is torn. In contrast, in the diaper <NUM>, by setting the width of the locking portions <NUM> in the lateral direction to <NUM> or less, the locking portion <NUM> can be easily peeled off during the operation of removing of the diaper <NUM>. In addition, from experimental results in <FIG>, in the case where the width of the locking portions <NUM> in the lateral direction is set to <NUM> or less, the tearing strength of the waist portions <NUM> and <NUM> can is stronger than the peeling strength of the locking portion <NUM>. This enables to make the waist portions <NUM> and <NUM> difficult to be torn while peeling the locking portion <NUM> easily.

In addition, the waist portions <NUM> and <NUM> have regions in which the number of overlaid sheet members in the thickness direction is different. In other words, the number of overlaid sheet members that are overlaid in the thickness direction in a certain region in the vertical direction is different from the number of overlaid sheet members that are overlaid in the thickness direction in another region in the vertical direction. In <FIG>, in the front waist portion <NUM>, two sheet members are overlaid in the thickness direction in the upper end region 20U and the lower end region 20D, and three sheet members are overlaid in the thickness direction in the central region 20C. As described above, by providing the waist portions <NUM> and <NUM> with regions in which the number of overlaid sheet members is different, it makes it possible to adjust the peeling strength when peeling off the locking portion <NUM> along the vertical direction, for each of the regions. For example, in portions of the waist portions <NUM> and <NUM> that are likely to be torn in the lateral direction, decrease in peeling strength of the locking portion <NUM> makes it possible to smoothly peel off the locking portion <NUM> so as not to tear the waist portions <NUM> and <NUM>.

It should be noted that, in the waist portions <NUM> and <NUM>, regarding the locking portion <NUM>, the locking strength in each of the regions can be appropriately adjusted by varying the locking pattern for each of the regions where the number of sheet members overlaid in the thickness direction is different. In <FIG>, the locking portion <NUM> in the upper end region 20U and the lower end region 20D of the waist portion <NUM> is formed of the first patterns <NUM>, and the locking portion <NUM> in the central region 20C of the waist portion <NUM> is formed of the second patterns <NUM>.

As shown in <FIG>, in the upper end region 20U and the lower end region 20D of the waist portion <NUM>, two sheet members are overlaid in the thickness direction, whereas, in the central region 20C, three sheet members are overlaid in the thickness direction. Accordingly, in the case where the locking portion <NUM> is formed in the same pattern (e.g., first patterns <NUM>) in all the regions, there is a risk that the locking strength in the upper end region 20U and the lower end region 20D is excessive, or conversely, the locking strength in the central region 20C becomes weak. In contrast, in the present embodiment, by varying the locking pattern for each of the regions in which the number of sheets that are overlaid in the thickness direction of the waist portion <NUM> is different, it becomes less likely to cause unevenness in the locking strength across the regions. This makes possible to suppress the unintentional tearing of the locking portion <NUM> while the diaper <NUM> is put on, or to suppress that it makes it difficult to peel off the locking portion <NUM> when removing the diaper <NUM>.

In addition, in the diaper <NUM>, regarding the peeling strength of the locking portion <NUM>, the patterns of the locking portion are adjusted so that the peeling strength in a region having a larger number of overlaid sheets in the thickness direction (defined as the first region, in <FIG>, the central region 20C) is less than the peeling strength in a region where a smaller number of overlaid sheets in the thickness direction (defined as the second region, in <FIG>, the upper end region 20U and the lower end region 20D). By making it easier to peel off the locking portion <NUM> in the region where a larger number of sheet members are overlaid (the first region, the central region 20C) compared to the region where a smaller number of sheet members are overlaid (the second region, the upper end region 20U and the lower end region 20D), it is possible to reduce the force acting on the skin-side sheet member (the skin surface sheet <NUM>) in the first region (the central region 20C). This makes it less likely to tear the skin-side sheet member (the skin surface sheet <NUM>).

It should be noted that, in the vertical direction, a position where the locking pattern changes and a position where the number of overlaid sheet members in the thickness direction of the waist portion <NUM> (<NUM>) changes may be shifted from each other. In <FIG>, letting a region in the locking portion <NUM> where the second patterns <NUM> are arranged be 60C, letting regions where the first patterns <NUM> are arranged be 60U and 60C, the boundary position in the vertical direction between the region 60U and the region 60C is a position different from the boundary position in the vertical direction between the upper end region 20U and the central region 20C of the waist portion <NUM> , for example. It should be noted that, in <FIG>, the boundary position in the vertical direction between the region 60U and the region 60C refers to the central position between the lower end position of the first patterns <NUM> and the upper end position of the second patterns <NUM>.

In the case where a position where the locking pattern changes and a position where the number of overlaid sheets of the waist portion <NUM> (<NUM>) changes are the same in the vertical direction, the number of overlaid sheet members of the waist portion <NUM> and the locking strength of the locking portion <NUM> simultaneously change in the changing position. Accordingly, the applied force suddenly changes when peeling off the locking portions <NUM> along the vertical direction, and this causes a risk that the waist portion <NUM> (skin-side sheet member) is easily torn. In contrast, in the diaper <NUM> of the present embodiment, since the position where the number of overlaid sheet members of the waist portion <NUM> changes and the position where the locking strength of the locking portions <NUM> changes are shifted from each other, it makes change in force gradual at the time of peeling off the locking portion <NUM> along the vertical direction. This enables to make the waist portion <NUM> difficult to be torn.

The front waist portion <NUM> and the back waist portion <NUM> of the diaper <NUM> can also be deformed as follows. <FIG> are schematic cross-sectional views showing modified examples of the waist portion <NUM> (<NUM>).

<FIG> shows a case where the skin surface sheet <NUM> (<NUM>) is not provided on the skin-side surface of the waist portion <NUM> (<NUM>). In this case, the inner-layer sheet <NUM> (<NUM>) is a skin-side sheet member arranged the farthest on the skin side of the waist portion <NUM> (<NUM>). In addition, in <FIG>, a part of the outer-layer sheet <NUM> (<NUM>) extends upward in the vertical direction, and the extended portion is folded back inward in the front-back direction at an upper end 20eu (30eu) of the waist portion <NUM> (<NUM>), and a folded-back portion 22f (32f) overlaid on the skin side of the inner-layer sheet <NUM> (<NUM>) is formed. In this case, in the region where the folded-back portion 22f (32f) is present, the folded-back portion 22f (32f) is a skin-side sheet member arranged the farthest on the skin side of the waist portion <NUM> (<NUM>).

In both cases, by configuring the diaper <NUM> so that the sum of the basis weight of the skin-side sheet member and the basis weight of the non-skin-side sheet member is equal to or less than <NUM>/m<NUM> and so that the tearing strength of the skin-side sheet member in the lateral direction is stronger than the peeling strength of the locking portions <NUM>, it is possible to suppress the tearing of the waist portions <NUM> and <NUM> in the operation of removing the diaper <NUM> from the wearer's body.

Although the above embodiment of the present invention has been described, but the above-described embodiment is intended to facilitate the understanding of the present invention and are not intended to limit the interpretation of the present invention.

In the above-described embodiment, a diaper in which the front waist portion <NUM> and the back waist portion <NUM> are separate members has been exemplified. However, the front waist portion <NUM> and the back waist portion <NUM> may be a single member that is continuous by a crotch portion provided between the front waist portion <NUM> and the back waist portion <NUM>.

Claim 1:
A underpants-shaped disposable diaper (<NUM>) having a vertical direction, a lateral direction, and a front-back direction that intersect each other,
the underpants-shaped disposable diaper (<NUM>) comprising:
a liquid-absorbent absorbent main body (<NUM>);
a front waist portion (<NUM>) and a back waist portion (<NUM>) that are provided on a non-skin side of the absorbent main body (<NUM>); and
a pair of locking portions (<NUM>) that lock two lateral end portions of the front waist portion (<NUM>) and two lateral end portions of the back waist portion (<NUM>),
in each of the front waist portion (<NUM>) and the back waist portion (<NUM>),
a sum of a basis weight of a skin-side sheet member (<NUM>, <NUM>) arranged the farthest on a skin side and a basis weight of a sheet member (<NUM>, <NUM>) arranged the farthest on a non-skin side being <NUM>/m<NUM> or less,
the skin-side sheet member (<NUM>, <NUM>) overlapping the locking portions (<NUM>) in two end portions in the lateral direction,
the skin-side sheet member (<NUM>, <NUM>) including a non-joining portion in a region (A60) adjacent to inside of the locking portion (<NUM>) in the lateral direction,
the non-joining portion being a portion that is not joined to a sheet member overlaid on a non-skin side of the skin-side sheet member (<NUM>, <NUM>),
a tearing strength for tearing the skin-side sheet member (<NUM>, <NUM>) along the lateral direction being greater than a peeling strength of the locking portion (<NUM>).