Patent Description:
There has been know an absorbent article (for example, a pants-type disposable diaper) including a stomach-side portion and a back-side portion and having a joining portion in which at least one end portion of the stomach-side portion and at least one end portion of the back-side portion, both the end portions being in the lateral direction, are joined to each other along the longitudinal direction in a state of being overlapped in the thickness direction. For example, Patent Literature <NUM> discloses a pants-type absorbent article. In this absorbent article, the side seal portion (joining portion) is divided into an upper region, an intermediate region, and a lower region from the waist opening to the leg opening, the average peeling strength in the longitudinal direction is substantially the same in the upper region and the lower region and is lower in the intermediate region than in other regions. According to Patent Literature <NUM>, it is said that it is possible to achieve both of a seal strength at which a seal can withstand use as a side part and a seal strength at which a seal can be relatively easily broken by this configuration.

Patent Literature <NUM>: <CIT> <CIT>discloses an underpants-type disposable diaper having a pair of side-seal parts formed by the fusing of overlap parts where two side edges of a stomach part and two side edges of a back part are overlapped with each other.

The joining portion of the absorbent article of Patent Literature <NUM> as described above includes a plurality of fused portions in which a sheet member on the stomach-side portion and a sheet member on the back-side portion are joined by thermal fusion bonding. Here, the sheet member on the stomach-side portion (hereinafter, also referred to as "stomach-side sheet member") and the sheet member on the back-side portion (hereinafter, also referred to as "back-side sheet member") are usually formed of a nonwoven fabric. However, there may be some unevenness in the thickness of the nonwoven fabric. In addition, when an absorbent article is manufactured, it is usual to perform thermal fusion bonding while continuously transporting a semi-finished product formed of a nonwoven fabric, but there may be a fluctuation (manufacturing error) in the position of the semi-finished product while being transported and the like. Therefore, fused portions in each of which the thermal fusion bonding is not perfect, that is, very heterogeneous fused portions, are formed in a part of the plurality of fused portions in which the stomach-side sheet member and the back-side sheet member are joined by thermal fusion bonding. Incidentally, in the case where the used absorbent article is removed from the wearer, a method of pulling apart the stomach-side sheet member and the back-side sheet member from each other at the joining portions is usually used. That is, the stomach-side sheet member and the back-side sheet member are continuously pulled apart from each other in the longitudinal direction by breaking the sheet members at each fused portion or peripheral portion thereof. However, as described above, in the case where the very heterogeneous fused portions are present in a part of the plurality of fused portions, there is a concern that the following problems may occur when the joining portion is pulled apart. For example, since the peeling strength when the stomach-side sheet member and the back-side sheet member are pulled apart from each other is significantly different in a part of the plurality of fused portions, the sheet members cannot be pulled apart from each other with almost the same force from the starting to the end of the pulling and it is difficult to continuously pull apart the sheet members. Alternatively, during the pulling, tearing occurs in a part of the fused portions and proceeds to a section other than the joining portion of the stomach-side sheet member and the back-side sheet member, for example, the central part where an absorbent body is positioned, and thus it is difficult to pull apart the sheet members to the end at the joining portion or it is necessary to repeat the pulling many times. In the absorbent article of Patent Literature <NUM>, the pattern of the fused portion of the side seal portion (joining portion) is changed depending on the position of the fused portion, but there is a possibility that very heterogeneous fused portions as described above may be formed as well. Therefore, there is a concern that the above problems may occur as well.

Therefore, an object of the present invention is to provide an absorbent article having a joining portion capable of, when removing the absorbent article, continuously and stably separating a stomach-side sheet portion and a back-side sheet portion with almost the same force without breaking the sheet member in a section other than the joining portion.

An absorbent article according to the present invention is (<NUM>) an absorbent article having a longitudinal direction, a lateral direction, and a thickness direction that are orthogonal to each other, and including a stomach-side portion including a stomach-side sheet member, a back-side portion including a back-side sheet member, and a joining portion in which at least one end portion of the stomach-side portion and at least one end portion of the back-side portion in the lateral direction are joined to each other in a state of being overlapped in the thickness direction along the longitudinal direction, wherein the joining portion includes a plurality of fused portions which are separated from each other and disposed along the longitudinal direction, each of the plurality of fused portions includes a core section in which the stomach-side sheet member and the back-side sheet member are fused to each other in the thickness direction, and a peripheral wall portion in which the stomach-side sheet member and the back-side sheet member are fused to each other in the thickness direction to extend in a tubular shape in the thickness direction from a peripheral edge of the core portion, a surface of the core portion is flat, in a peeling test of the joining portion in which one end portion of a sample including the joining portion in the longitudinal direction is held by two jigs, and while peeling off the joining portion to widen a distance between the two jigs, a load to be applied between the two jigs is measured, a graph showing the load with respect to the distance has a plurality of protruding portions in which the load temporarily shows local maximum values at respective positions of the plurality of fused portions, and in the peeling test, when the one end portion of the sample in the longitudinal direction is an end portion of either a waist opening side or a leg opening side of the absorbent article, a standard deviation with respect to an average value of the local maximum values in the plurality of protruding portions corresponding to the plurality of fused portions is <NUM> N or less.

In this absorbent article, the surface of the core portion is flat. Therefore, when each fused portion is viewed, it can be said that the fusion is properly performed and the thickness of the core portion is almost even, and therefore it can be seen that the individual fused portions are substantially homogeneous. Further, since the standard deviation from the average value of the local maximum values of the loads in the plurality of protruding portions corresponding to the plurality of fused portions is <NUM> N or less in the peeling test of the joining portion, the local maximum value of the load required for peeling each of the plurality of fused portions, that is, the peeling strength of each of the plurality of fused portions is almost the same. Therefore, when the plurality of fused portions are viewed as a whole, it can be said that the fusion is properly performed and the plurality of fused portions are substantially homogeneous as a whole. As described above, since the individual fused portions are substantially homogeneous and the plurality of fused portions are substantially homogeneous as a whole, during the pulling of the joining portion, the occurrence of tearing in a part of the fused portions can be suppressed and the joining portion can be continuously pulled apart with almost the same force from the start to the end of the pulling. The upper limit of the standard deviation of <NUM> N is set based on the grip strength and grab strength of an elderly person in a manner such that even in the case where the peeling strength between the fused portions is changed when the joining portion is continuously pulled apart, it is possible for the wearer or the caregiver who is an elderly person to cope with the change. Therefore, when removing the absorbent article having the joining portion, it is possible to appropriately separate the stomach-side portion and the back-side portion continuously and stably with almost the same force without breaking the sheet member in a section other than the joining portion. The details of the flatness of the surface of the core portion and the peeling test of the joining portion will be described later.

The absorbent article of the present invention may be (<NUM>) the absorbent article according to (<NUM>) above, wherein in the peeling test, the average value of the local maximum values in the plurality of protruding portions corresponding to the plurality of fused portions is <NUM> N or more and <NUM> N or less. In the absorbent article, the average value of the local maximum values of the load (peeling strength) in the peeling test of the joining portion is <NUM> N or more and <NUM> N or less. Therefore, each fused portion can be pulled apart from the stomach-side sheet member or the back-side sheet member with a relatively small force, whereby the joining portion can be pulled apart with a relatively small force. That is, it is possible to separate the stomach-side portion and the back-side portion continuously and stably with almost the same force and easily with a relatively small force without breaking the sheet member in a section excluding the joining portion. The upper limit of the peeling strength of <NUM> N is set based on the grip strength and grab strength of an elderly person in a manner such that even in the case where the peeling strength in the fused portion is high when the joining portion is continuously pulled apart, it is possible for the wearer or the caregiver who is an elderly person to peel off the fused portion.

The absorbent article of the present invention may be (<NUM>) the absorbent article according to (<NUM>) or (<NUM>) above, wherein in the peeling test, an energy required for peeling off the joining portion is <NUM> J or more and <NUM> J or less. In the absorbent article, since the energy required for peeling off the joining portion in the peeling test of the joining portion is <NUM> J or more and <NUM> J or less, it is possible to pull apart the joining portion with a relatively small amount of work. That is, it is possible to separate the stomach-side portion and the back-side portion continuously and stably with almost the same force and easily with a relatively small amount of work without breaking the sheet member in a section other than the joining portion. The upper limit of the energy of <NUM> J required to peel off the joining portion is set based on the grip strength and grab strength of an elderly person in a manner such that even in the case where the energy is high when the joining portion is continuously pulled apart, it is possible for the wearer or the caregiver who is an elderly person to continuously peel off the fused portion.

The absorbent article of the present invention is (<NUM>) the absorbent article according to any one of (<NUM>) to (<NUM>) above, where in a puncture test of the stomach-side sheet member and the back-side sheet member, a maximum load of the stomach-side sheet member and a maximum load of the back-side sheet member are <NUM> N or more and <NUM> N or less. In the absorbent article, since the maximum load (breaking strength) of the stomach-side sheet member and the maximum load (breaking strength) of the back-side sheet member are <NUM> N or more and <NUM> N or less, it is possible to easily break the sheet members with a relatively small force when the stomach-side portion and the back-side portion are separated. Due to that, it is possible to separate the stomach-side portion and the back-side portion continuously and stably with almost the same force and easily with a relatively small force without breaking the sheet member in a section other than the joining portion. The upper limit of the breaking strength of <NUM> N of the sheet member is set based on the grip strength and grab strength of an elderly person in a manner such that even in the case where the breaking strength of the sheet member is high when the joining portion is continuously pulled apart, it is possible for the wearer or the caregiver who is an elderly person to break the sheet member in the fused portion.

The absorbent article of the present invention is (<NUM>) the absorbent article according to (<NUM>) above, wherein in the puncture test, a difference between the maximum load of the stomach-side sheet member and the maximum load of the back-side sheet member is <NUM> N or more and <NUM> N or less. In the absorbent article, since the difference between the maximum load (breaking strength) of the stomach-side sheet member and the maximum load (breaking strength) of the back-side sheet member in the puncture test is <NUM> N or more and <NUM> N or less, it is possible to relatively easily break a sheet member having a relatively small maximum load from each fused portion when the stomach-side portion and the back-side portion are separated. Due to that, it is possible to separate the stomach-side portion and the back-side portion continuously and stably with almost the same force and more easily with a relatively small force without breaking the sheet member in a section excluding the joining portion. The upper limit of the difference in breaking strength of <NUM> N is set based on the grip strength and grab strength of an elderly person in a manner such that even in the case where the difference in the breaking strength of the sheet member between fused portions is changed when the joining portion is continuously pulled apart, it is possible for the wearer or the caregiver who is an elderly person to cope with the change.

The peeling test may be performed by using the one end portion of the sample in the longitudinal direction as each of an end portion on the waist opening side and an end portion on the leg opening side. In this absorbent article, each of the end portion of the waist opening side and the end portion of the leg opening side is held by two jigs and subjected to the peeling test. Therefore, in both case, the standard deviation of the local maximum values at least in the protruding portions is <NUM> N or less and the like. Therefore, when the absorbent article having the joining portion is removed, it is possible to appropriately separate the stomach-side portion and the back-side portion continuously and stably with almost the same force without breaking the sheet member in a section other than the joining portion regardless of the positions where the pulling is started (the end portion on the waist opening side and the end portion on the leg opening side).

According to the present invention, it is possible to provide an absorbent article having a joining portion capable of, when removing the absorbent article, continuously and stably separating a stomach-side sheet portion and a back-side sheet portion with almost the same force without breaking a sheet member in a section other than the joining portion.

Hereinafter, an absorbent article according to an embodiment of the present invention will be described using a pants-type disposable diaper (hereinafter, also simply referred to as a "disposable diaper") as an example. However, the present invention is not limited to the example and is applicable to a variety of absorbent articles without departing from the subject matter of the present invention. Examples of the absorbent article include so-called three-piece type and two-piece type disposable diapers.

<FIG> and <FIG> are views showing a disposable diaper <NUM> according to the present embodiment. <FIG> is a perspective view showing a constitution example of the disposable diaper <NUM>, and <FIG> is a plan view showing a state in which the disposable diaper <NUM> is unfolded. In the state shown in <FIG>, the disposable diaper <NUM> has a longitudinal direction L, a lateral direction W, and a thickness direction T that are orthogonal to each other and has a central axis CL that passes through the center in the lateral direction W and extends in the longitudinal direction L and a central axis CW that passes through the center in the longitudinal direction L and extends in the lateral direction W. Here, the orientation toward and the side facing the central axis CL are respectively defined as inward and the inner side in the lateral direction W, and the orientation and the side away from the central axis CL are respectively defined as outward and the outer side in the lateral direction W. On the other hand, the orientation toward and the side facing the central axis CW are respectively defined as inward and the inner side in the longitudinal direction L, and the orientation and the side away from the central axis CW are respectively defined as outward and the outer side in the longitudinal direction L. Further, viewing the disposable diaper <NUM> placed on a plane in the thickness direction T from the vertically upper side of the plane is referred to as "plan view", the shape grasped in the plan view is referred to as "planar shape", and any direction in the plane including the longitudinal direction L and the lateral direction W is referred to as "in-plane direction". The terms "skin side" and "non-skin side" respectively mean sides that are relatively close to and far from the skin surface of a wearer in the thickness direction T of the disposable diaper <NUM> when the wearer wears the disposable diaper <NUM>. It should be noted that the respective definitions described above will also be used for each material for the disposable diaper <NUM> or the disposable diaper <NUM> in the state shown in <FIG>.

The disposable diaper <NUM> includes a stomach-side portion <NUM>, a back-side portion <NUM>, and an intermediate portion <NUM> between the stomach-side portion <NUM> and the back-side portion <NUM>. The stomach-side portion <NUM> is a portion of the disposable diaper <NUM> that faces the abdomen of a wearer. The intermediate portion <NUM> is a portion of the disposable diaper <NUM> that faces the crotch portion of the wearer. The back-side portion <NUM> is a portion of the disposable diaper <NUM> that faces the hip portion or back portion of the wearer. The stomach-side portion <NUM> and the back-side portion <NUM> are joined to each other with a pair of joining portions 14a and 14b positioned at both ends of the stomach-side portion <NUM> and the back-side portion <NUM> in the lateral direction W. The joining portion 14a is formed of one end portion 11a of the stomach-side portion <NUM> in the lateral direction W and one end portion 13a of the back-side portion <NUM> in the lateral direction W that are joined to each other along the longitudinal direction L in a state of being overlapped in the thickness direction T. Similarly, the joining portion 14b is formed of the other end portion 11b of the stomach-side portion <NUM> in the lateral direction W and the other end portion 13b of the back-side portion <NUM> in the lateral direction W that are joined to each other along the longitudinal direction L in a state of being overlapped in the thickness direction T. In this case, in the disposable diaper <NUM>, a waist opening WO through which the waist of a wearer passes is defined by an end portion 11e of the stomach-side portion <NUM> on the outer side in the longitudinal direction L and an end portion 13e of the back-side portion <NUM> on the outer side in the longitudinal direction L. In addition, in the disposable diaper <NUM>, a pair of leg openings LO and LO through which the legs of the wearer pass are defined by side portions 12a and 12b of the intermediate portion <NUM> on both sides in the lateral direction W. It should be noted that the longitudinal direction, the lateral direction, and the thickness direction of each joining portion 14a or 14b in the state shown in <FIG> are the same as the longitudinal direction L, the lateral direction W, and the thickness direction T in the state shown in <FIG>.

In the present embodiment, in the unfolded state shown in <FIG>, the stomach-side portion <NUM> and the back-side portion <NUM> each have an almost rectangular shape that extends in the lateral direction W and are separated from each other in the longitudinal direction L. The intermediate portion <NUM> is positioned between the stomach-side portion <NUM> and the back-side portion <NUM>, and both side edges in the lateral direction W are recessed inward in the lateral direction W. The stomach-side portion <NUM>, the intermediate portion <NUM>, and the back-side portion <NUM> are integrally formed with each other. In another embodiment (not shown), the stomach-side portion <NUM>, the intermediate portion <NUM>, and the back-side portion <NUM> are formed separately from each other.

In the present embodiment, the disposable diaper <NUM> is provided with a plurality of elastic members 8a and 8b for waist gather on the stomach-side portion <NUM> and the back-side portion <NUM>, respectively. The plurality of elastic members 8a extend along the end portion 11e of the stomach-side portion <NUM> in the longitudinal direction L from one end portion 11a to the other end portion 11b in the lateral direction W and are disposed at intervals in the longitudinal direction L. Similarly, the plurality of elastic members 8b extend along the end portion 13e of the back-side portion <NUM> in the longitudinal direction L from one end portion 13a to the other end portion 13b in the lateral direction W and are disposed at intervals in the longitudinal direction L. The plurality of elastic members 8a and 8b stretch and contract the waist opening WO and are exemplified by elastic strings.

In the present embodiment, the disposable diaper <NUM> includes a plurality of elastic member 8c and 8c' for leg gathers from the intermediate portion <NUM> to the back-side portion <NUM> and the stomach-side portion <NUM>. The plurality of elastic members 8c and 8c' are continuously disposed at intervals to extend along the lateral direction W in the center of the intermediate portion <NUM> in the longitudinal direction L, reach both end portions of the intermediate portion <NUM> in the lateral direction W, and then extend along the longitudinal direction L up to the end portions 13a and 13b of the back-side portion <NUM> and the end portions 11a and 11b of the stomach-side portion <NUM>, respectively. The plurality of elastic members 8c and 8c' stretch and contract the pair of leg openings LO and LO respectively and are exemplified by elastic strings.

In the present embodiment, the stomach-side portion <NUM>, the intermediate portion <NUM>, and the back-side portion <NUM> of the disposable diaper <NUM> are formed of a liquid-impermeable cover sheet (sheet member) <NUM>. <FIG> is a schematic view of the stomach-side portion <NUM> and the back-side portion <NUM> in the joining portion 14a or 14b as seen from the side of the end portion in the lateral direction W. However, for the sake of clarity, each cover sheet <NUM> is shown separately, and the description of the elastic member is omitted. The cover sheet <NUM> includes a cover sheet 5a that is positioned on the skin side and a cover sheet 5b that is positioned on the non-skin side, and the cover sheet 5a and the cover sheet 5b are laminated together in the thickness direction T and joined to each other with an adhesive or the like. Both end portions of the cover sheet 5b in the longitudinal direction L are folded back toward the skin side to cover both end portions of the cover sheet 5a in the longitudinal direction L. In this case, the cover sheet 5b in the folded-back positions in the stomach-side portion <NUM> and the back-side portion <NUM> constitutes the end portion 11e of the stomach-side portion <NUM> and the end portion 13e of the back-side portion <NUM>, respectively. A region A is a region where three layers of the cover sheet are present, and a region B is a region where two layers of the cover sheet are present. Therefore, the end portion 11e of the stomach-side portion <NUM> and the end portion 13e of the back-side portion <NUM> have a three-layer structure in which three cover sheets 5b, 5a, and 5b are laminated together. The length of each three-layer structure in the longitudinal direction L is, for example, <NUM> to <NUM>. In the present embodiment, the plurality of elastic members 8a, 8b, 8c, and 8c' are positioned between the cover sheet 5a and the cover sheet 5b.

Examples of the cover sheet <NUM> include any liquid-impermeable sheets such as liquid-impermeable nonwoven fabric or synthetic resin films, composite sheets thereof, SB nonwoven fabric, and SMS nonwoven fabric. Examples of the material of the cover sheet <NUM> include polyolefin-based materials such as polypropylene or polyethylene. The basis weight of the cover sheet <NUM> is, for example, <NUM> to <NUM>/m<NUM> and preferably <NUM> to <NUM>/m<NUM>. The dimension (thickness) of the cover sheet <NUM> in the thickness direction T is, for example, <NUM> to <NUM> and preferably <NUM> to <NUM>. In another embodiment, the cover sheet <NUM> includes one cover sheet or two or more cover sheets (not shown). In still another embodiment, the cover sheet 5b may not be folded back.

In the present embodiment, the disposable diaper <NUM> includes an absorbent main body <NUM> on a skin side surface of the cover sheet <NUM>. The absorbent main body <NUM> has a substantially rectangular shape and includes a liquid-permeable top-surface sheet <NUM>, a liquid-impermeable back-surface sheet <NUM>, and an absorbent body <NUM> that is positioned between the top-surface sheet <NUM> and the back-surface sheet <NUM> and absorbs and holds liquid. Examples of the top-surface sheet <NUM> include liquid-permeable nonwoven fabric or woven fabric, synthetic resin films having a liquid permeable hole formed therein, composite sheet thereof, and the like. Examples of the back-surface sheet <NUM> include liquid-impermeable nonwoven fabric or synthetic resin films, composite sheets thereof, SMS nonwoven fabric, and the like. In the present embodiment, the absorbent body <NUM> includes an absorbent body core that absorbs and holds liquid and a core wrap that contains the absorbent body core. As the absorbent body <NUM>, pulp fibers, synthetic fibers, absorbent polymers, or the like is exemplified. The absorbent body <NUM> is respectively joined to the top-surface sheet <NUM> and the back-surface sheet <NUM> with an adhesive or the like, and the top-surface sheet <NUM> and the back-surface sheet <NUM> are joined to each other with the adhesive at the peripheral edge parts. The adhesive is a well-known material that is common for the disposable diaper <NUM>, and examples thereof include thermoplastic adhesives. The shape of the absorbent main body <NUM> is not limited to the above example as long as the shape is long in the longitudinal direction L, and examples thereof include a rectangular shape with rounded corners, a rectangular shape whose short sides protrude to the outer side and curved, and an hourglass shape.

In the present embodiment, the disposable diaper <NUM> includes liquid-impermeable leakproof walls 6a and 6b. The leakproof walls 6a and 6b are disposed along the longitudinal direction L on both sides of the top-surface sheet <NUM> in the lateral direction W. In the end portions of the leakproof walls 6a and 6b on the inner side in the lateral direction W, a plurality of elastic members 8d and 8e that respectively extend in the longitudinal direction L and are aligned at intervals in the lateral direction W are disposed. The plurality of elastic members 8d and 8e respectively stretch and contract the leakproof walls 6a and 6b. As the elastic members 8d and 8e, elastic strings are exemplified.

Next, an example of a method for manufacturing the disposable diaper <NUM> will be described. First, a disposable diaper continuous body (not shown) is formed in which disposable diapers in the unfolded state shown in <FIG> are continuously coupled to each other in the lateral direction W. The disposable diaper continuous body has a structure in which the end portion 11b of the stomach-side portion <NUM> and the end portion 13b of the back-side portion <NUM> of one of disposable diapers adjacent to each other are coupled to the end portion 11a of the stomach-side portion <NUM> and the end portion 13a of the back-side portion <NUM> of the other disposable diaper. The disposable diaper continuous body is transported in a manner such that the lateral direction W becomes parallel to a machine direction MD. Subsequently, the disposable diaper continuous body is transported in the machine direction MD and folded in the longitudinal direction L along the central axis CW with a folding device (not shown). That is, in the disposable diaper continuous body, the end portions 11a of the stomach-side portions <NUM> and the end portions 13a of the back-side portions <NUM> of the respective disposable diapers are laminated together, and the end portions 11b of the stomach-side portions <NUM> and the end portions 13b of the back-side portions <NUM> are laminated together. Next, in the disposable diaper continuous body, both end portions of the stomach-side portions <NUM> and the back-side portions <NUM> are respectively joined to each other by ultrasonic wave sealing using a joining portion forming apparatus (not shown). <FIG> is a schematic view for describing a method of forming the joining portion. This view shows a part of the region B in <FIG>. Specifically, a laminated portion of the end portion 11a of the stomach-side portion <NUM> and the end portion 13a of the back-side portion <NUM> in a disposable diaper continuous body S, and a laminated portion of the end portion 11b of the stomach-side portion <NUM> and the end portion 13b of the back-side portion <NUM> are respectively pinched between an ultrasonic horn <NUM> of a joining portion forming apparatus and a protruding portion <NUM> of an anvil. Energy of a predetermined ultrasonic wave is supplied to the pinched portions for a predetermined period of time. Therefore, the plurality of cover sheet 5b, 5a, 5a, and 5b in the laminated portions are fused to each other, thereby forming fused portions <NUM> each including a core portion MC and a peripheral wall portion SW. Both end portions of the stomach-side portion <NUM> and the back-side portion <NUM> are joined to each other with the fused portions <NUM>, and the pair of joining portions 14a and 14b is formed. The shape of the core portion MC and the peripheral wall portion SW can be controlled by the magnitude of the energy supplied from the joining portion forming apparatus, the timing and period of supply of the energy, and the like. Examples of such joining portion forming apparatus include the apparatuses described in <CIT> and <CIT>. For example, the following control is possible: the transport speed is set to be slower than usual, energy is set to be higher than usual, or the size of the protruding portion <NUM> is set to be smaller than usual, thereby increasing the density per unit area of energy that is to be supplied to a region in which the fused portion of the cover sheets is to be formed and efficiently using energy, which enables energy to be sufficiently given not only to the front end of the protruding portion <NUM> but also to the periphery of the protruding portion <NUM>. Therefore, it is possible to form not only the core portion MC, which is usually formed at the front end of the protruding portion <NUM>, but also the peripheral wall portion SW in the periphery of the protruding portion <NUM>. It should be noted that the protruding portion <NUM> may be formed in the ultrasonic horn and the anvil may be formed flat.

Next, the constitution of the joining portions 14a and 14b will be described. Here, the joining portion 14a and the joining portion 14b are almost the same in terms of the constitution except for the difference in position (right and left) in the lateral direction W. Therefore, hereinafter, the constitution of the joining portion 14a will be mainly described, and the constitution of the joining portion 14b will not be described.

<FIG> is a plan view schematically showing a constitution example of the joining portion 14a in the disposable diaper <NUM>. <FIG> is a view of the joining portion 14a as seen from the back-side portion <NUM> side. In the present embodiment, in the joining portion 14a, an end edge 11ae of the end portion 11a in the stomach-side portion <NUM> on the outer side in the longitudinal direction L and an end edge 13ae of the end portion 13a in the back-side portion <NUM> on the outer side in the longitudinal direction L are almost overlapped with each other. The dimensions of the joining portion 14a in the longitudinal direction L and the lateral direction W are, for example, <NUM> to <NUM> and <NUM> to <NUM>, respectively. In another embodiment, the end edge 11ae and the end edge 13ae deviate from each other in the longitudinal direction L by a predetermined length (for example, <NUM> to <NUM>) (not shown).

The joining portion 14a includes a plurality of the fused portions <NUM> that are separated from each other and disposed along the longitudinal direction L. In this case, the end portion 11a and the end portion 13a are joined to each other with at least the plurality of fused portions <NUM>. The stomach-side portion and the back-side portion are not joined to each other at portions in the joining portion 14a at which the fused portions <NUM> are not formed. In another embodiment, portions in the joining portion 14a at which the fused portions <NUM> are not formed are fully or partially joined to each other with an adhesive (for example, hot-melt adhesive) (not shown).

In the present embodiment, in the joining portion 14a, the plurality of fused portions <NUM> are disposed to be aligned side by side at intervals along the longitudinal direction L, thereby constituting a fused portion line <NUM>. The fused portion line <NUM> is one line, and the intervals between the fused portions <NUM> in the longitudinal direction L are constant. However, in another embodiment, a plurality of the fused portion lines <NUM> are aligned side by side at intervals in the lateral direction W (not shown). In addition, in still another embodiment, in all or part of the fused portion line <NUM>, the intervals between the fused portions <NUM> in the longitudinal direction L vary depending on positions (not shown).

In the present embodiment, the plurality of elastic members 8a are provided between the cover sheets 5a and 5b in the stomach-side portion <NUM> to extend in the lateral direction W up to the joining portions 14a and 14b and to be aligned at intervals in the longitudinal direction L. Similarly, the plurality of elastic members 8b are provided between the cover sheets 5a and 5b in the back-side portion <NUM> to extend in the lateral direction W up to the joining portions 14a and 14b and to be aligned at intervals in the longitudinal direction L. In addition, the plurality of elastic members 8a and 8b (preferably also the elastic members 8c and 8c') are disposed not to overlap with the plurality of fused portions <NUM> in the thickness directions T at least in the joining portion 14a.

In the present embodiment, the joining portion 14a has, in the longitudinal direction L, a waist-side end region <NUM> including the end portion on the waist opening WO side, a leg-side end region <NUM> including the end portion on the leg opening LO side, and a central region <NUM> between both regions. The waist-side end region <NUM> and the leg-side end region <NUM> are regions that range from <NUM>/<NUM> to <NUM>/<NUM> of the joining portion 14a in the longitudinal direction L from the end edges of the waist opening WO and the leg opening LO, respectively, and the central region <NUM> is the remaining region. The waist-side end region <NUM> and the leg-side end region <NUM> have the same length in the longitudinal direction L. In each region, the fused portions <NUM> are disposed in the same number of lines at the same interval (with a manufacturing error). In another embodiment, the waist-side end region <NUM> and the leg-side end region <NUM> have different lengths in the longitudinal direction L (not shown). In another embodiment, in at least one region, at least one of the size, interval, and number of lines of the fused portions <NUM> is different from that of other regions (not shown).

<FIG> is a plan view for describing a constitution example of the plurality of fused portions <NUM> in the joining portion 14a. <FIG> shows the fused portions <NUM> (fused portion line <NUM>) as seen from the side of the back-side portion <NUM> in the thickness direction T, and <FIG> shows the shape and disposition of the protruding portion <NUM> at the front end portion of the anvil (or ultrasonic horn) in which the fused portion <NUM> is formed by the ultrasonic wave sealing method. In the present embodiment, as the fused portion line <NUM>, the plurality of fused portions <NUM> in the waist-side end region <NUM>, the central region <NUM>, and the leg-side end region <NUM> all have the same planar shape. In other words, in the case of forming the respective fused portions <NUM> in the respective regions by the ultrasonic wave sealing method, the planar shapes of the protruding portions <NUM> of the anvil for the respective fused portions <NUM> in the respective regions are the same. Here, the planar shape of the protruding portion <NUM> is not particularly limited, and examples thereof include a circular shape, an elliptical shape, a rectangular shape, a rounded rectangular shape, a polygonal shape, and the like. In the present embodiment, the planar shape of the protruding portion <NUM> is an elliptical shape, a dimension d21 (minor axis) in the longitudinal direction L is smaller than a dimension d22 (major axis) in the lateral direction W, and the sizes thereof are, for example, <NUM> to <NUM>. A distance d23 between the protruding portions <NUM> adjacent to each other in the longitudinal direction L (the distance between the major axes) is, for example, <NUM> to <NUM>.

Next, the constitution of the fused portion <NUM> will be further described. Here, the constitution of the fused portion <NUM> in the central region <NUM> will be described. It should be noted that the constitution of the fused portion <NUM> in the leg-side end region <NUM> and the constitution of the waist-side end region <NUM> (excluding the number of the cover sheets <NUM>) are also the same as the constitution of the fused portion <NUM> in the central region <NUM> and thus will not be described again. <FIG> is a plan view and a perspective view showing an example of the constitution of the fused portion <NUM>. Here, <FIG> is a plan view of the fused portion <NUM> in the central region <NUM>, and <FIG> is a perspective view including a cross section of the fused portion <NUM> in the central region <NUM> as seen in the longitudinal direction L. The fused portion <NUM> includes the core portion MC and the peripheral wall portion SW.

In the present embodiment, the core portion MC has a constitution in which the plurality of cover sheets 5a and 5b in the stomach-side portion <NUM> and the plurality of cover sheets 5a and 5b in the back-side portion <NUM> are fused to each other in the thickness direction T. The core portion MC is formed through a process that the plurality of cover sheets 5b, 5a, 5a, and 5b are pinched between the front end portion of the ultrasonic horn and the protruding portion of the anvil, melted by energy that is supplied from the ultrasonic horn, while compressed in the thickness direction T, and then solidified. Therefore, the core portion MC is joined extremely strongly in the thickness direction T. A dimension (thickness) dT of the core portion MC in the thickness direction T is, for example, <NUM> to <NUM>. The dimension dT of the core portion MC is significantly smaller than the dimension of the plurality of cover sheets 5b, 5a, 5a, and 5b in the stomach-side portion <NUM> and the back-side portion <NUM> that are simply laminated together in the thickness direction T (for example, <NUM> to <NUM>). When dT is smaller than <NUM>, the cover sheets are not stably fused to each other, and a hole is easily opened during fusion. When dT is more than <NUM>, the cover sheets are not fully fused to each other, and there is a concern that the cover sheets may be easily broken.

In addition, in the present embodiment, the planar shape of the core portion MC is almost the same as the planar shape of the protruding portion <NUM> of the anvil, and examples thereof include a circular shape, an elliptical shape, a rectangular shape, a rounded rectangular shape, a polygonal shape, and the like. In the present embodiment, the planar shape of the core portion is an elliptical shape. At this time, the dimension in the longitudinal direction L and the dimension in the lateral direction W are almost the same as the dimension d21 in the longitudinal direction L and the dimension d22 in the lateral direction W of the protruding portion <NUM> and are <NUM> to <NUM>. In the case where each dimension of the core portion MC is smaller than <NUM>, the fused portions <NUM> are too small and are easily broken, and there is a concern that the joining portion 14a may be unintentionally peeled off while the disposable diaper <NUM> is worn. In the case where each dimension of the core portion MC is more than <NUM>, the fused portion <NUM> is too large, and there is a concern that a wearer may sense discomfort by feeling hardness. In addition, the distance between the core portions MC adjacent to each other is almost the same as the distance between the protruding portions <NUM> adjacent to each other and is <NUM> to <NUM>. In the case where the distance is smaller than <NUM>, the number of the fused portions <NUM> in the joining portion 14a increases, and there is a concern that the disposable diaper <NUM> may be less likely to be pulled apart when attempted to be removed. In the case where the distance is more than <NUM>, the number of the fused portions <NUM> decreases, and there is a concern that the joining portion 14a may be unintentionally peeled off while the disposable diaper <NUM> is worn.

Furthermore, in the present embodiment, in the fused portion <NUM>, the position of the core portion MC in the thickness direction T is shifted toward the stomach-side portion <NUM> or the back-side portion <NUM> from the boundary between the stomach-side portion <NUM> and the back-side portion <NUM>. Here, the position of the core portion MC in the thickness direction T is defined as the position of the center of the core portion MC in the thickness direction T. In the case where the core portion MC is not flat, the position of the core portion MC in the thickness direction T is defined as the position of the center of the core portion MC in the thickness direction T in the coupling portion of the core portion MC and the peripheral wall portion SW in the longitudinal direction L. For example, in the example of <FIG>, the position of the core portion MC in the thickness direction T is shifted toward the stomach-side portion <NUM> side and is a position between the cover sheet 5a and the cover sheet 5b of the stomach-side portion <NUM>. The shift in the thickness direction T from the boundary between the stomach-side portion <NUM> and the back-side portion <NUM> is, for example, <NUM> to <NUM>. In another embodiment, in the thickness direction T, the position of the end surface of the core portion MC coincides with the position of the end surface of the cover sheet <NUM> in the stomach-side portion <NUM> or the back-side portion <NUM> (not shown).

In the present embodiment, the peripheral wall portion SW has a constitution in which the plurality of cover sheets 5a, 5b of the stomach-side portion <NUM> and the plurality of cover sheets 5a, 5b of the back-side portion <NUM> are fused to each other in the thickness direction T to extend in a tubular shape in the thickness direction T from the peripheral edge of the core portion MC while surrounding the core portion MC. In the present embodiment, the peripheral wall portion SW is formed through a process that the plurality of cover sheet 5b, 5a, 5a, and 5b are melted by energy that is supplied from the front end portion of the ultrasonic horn or heat that is generated during the fusion of the core portion MC, while slightly compressed in the thickness direction T due to the compression of the core portion MC, and then solidified. Therefore, the peripheral wall portion SW is joined relatively strongly in the thickness direction T. A dimension (thickness) DT of the peripheral wall portion SW in the thickness direction T is, for example, <NUM> to <NUM>. The dimension DT of the peripheral wall portion SW is smaller than the dimension of the plurality of cover sheets 5b, 5a, 5a, and 5b in the stomach-side portion <NUM> and the back-side portion <NUM> that are simply laminated together in the thickness direction T (for example, <NUM> to <NUM>). However, since the peripheral wall portion SW is not pressurized by the front end portion of the ultrasonic horn or the protruding portion <NUM> of the anvil, the dimension DT of the peripheral wall portion SW is larger than the dimension dT of the core portion MC (for example, <NUM> to <NUM>). When the size of DT is smaller than <NUM>, the breaking strength of the peripheral wall portion SW becomes weak, and there is a concern that the cover sheet may be broken in an unexpected direction at the time of removing the disposable diaper. When the size of DT is more than <NUM>, there is a concern that a wearer or a caregiver may sense discomfort when the peripheral wall portion comes into contact with the skin of the wearer or the caregiver.

Here, the peripheral wall portion SW has a tubular form and has an outer surface OS that constitutes the surface of the tube on the outer side and an inner surface IS that constitutes the surface of the tube on the inner side. Therefore, the dimension of the peripheral wall portion SW in the in-plane direction (thickness) can be said as the distance between the outer surface OS and the inner surface IS. When the fused portion <NUM> is cut in a cross section parallel to the thickness direction T, the outer surface OS and the inner surface IS are the surface on the outer side and the surface on the inner side of the peripheral wall portion provided to stand along the thickness direction T from the peripheral edge of the core portion MC in the cross section. That perpendicular cross section can be obtained by observation with, for example, a scanning electron microscope. The outer surface OS is a boundary surface between a portion of the cover sheet <NUM> where there is no fused portion <NUM> and the fused portion <NUM>. Therefore, a fiber in the cover sheet <NUM> is released from the surface of the outer surface OS, and accordingly, the outer surface OS is a somewhat uneven surface. On the other hand, the inner surface IS is a surface in contact with the protruding portion <NUM> of the anvil. Therefore, although there is the case where the fiber in the cover sheet <NUM> remains in a part of the inner surface IS, the inner surface IS is a relatively flat surface. In addition, the outer surface OS and the inner surface IS do not necessarily intersect perpendicularly with the surface of the core portion MC and may be inclined to some extent (for example, ±<NUM>° with respect to the vertical direction). Here, the tubular form (or tubular shape) refers to a long and narrow hollow shape or a pipe shape. The tubular form may bend or meander as long as the tubular shape extends in the thickness direction T, may have a variety of shapes such as a circular shape, an elliptical shape, a polygonal shape, and a combined shape on a cross section perpendicular to the thickness direction T, and may have a shape and an area on a cross section perpendicular to the thickness direction T that are not constant in the thickness direction T.

In addition, in the present embodiment, the planar shape of the peripheral wall portion SW has a ring shape that surrounds the core portion MC in an almost even width DP, and examples thereof include a circular ring, an elliptical ring, a rectangular ring, a rounded rectangular ring, a polygonal ring, and the like. In the present embodiment, the planar shape of the peripheral wall portion SW is an elliptical ring. In addition, in the peripheral wall portion SW, the variation of the width DP depending on the position in the ring is small, the width DP rarely becomes partially thin or thick abruptly, and the shape is almost even. That is, the width DP (or wall thickness) of the peripheral wall portion SW in the in-plane direction is almost even. Here, the expression "even" refers to the fact that, in the peripheral wall portion SW, there is no place where the width DP becomes as small a value as equal to or smaller than <NUM>/<NUM> of the average value or there is no place where the width DP becomes as large a value as equal to or larger than twice the average value. It should be noted that, when the width DP is not constant in the thickness direction T, the width at the boundary between the stomach-side portion <NUM> and the back-side portion <NUM> is used as the width DP. The size of the width DP is, for example, <NUM> to <NUM>. In the case where the width DP is smaller than <NUM>, the peripheral wall portion SW is too thin and is easily broken, and there is a concern that the joining portion 14a may unintentionally peel off while the disposable diaper <NUM> is worn. In the case where the DP is more than <NUM>, the peripheral wall portion SW is too thick, and there is a concern that a wearer may sense discomfort by feeling hardness.

In the present embodiment, in the fused portion <NUM>, an area Sa of the peripheral wall portion SW is in a range of <NUM>% to <NUM>% as seen in the thickness direction T (in a plan view) when an area Sb of the core portion MC is regarded as <NUM>%. The area Sa of the peripheral wall portion SW is preferably in a range of <NUM>% to <NUM>% and more preferably in a range of <NUM>% to <NUM>% of the area Sb of the core portion MC. When the area Sa of the peripheral wall portion SW is less than <NUM>%, the breaking strength of the peripheral wall portion SW decreases, and there is a concern that the peripheral wall portion SW itself may be broken at the time of removing the disposable diaper. When the area Sa of the peripheral wall portion SW is more than <NUM>%, the peripheral wall portion SW becomes too large, and there is a concern that a wearer may sense discomfort by feeling hardness.

Incidentally, in the case where the above-mentioned disposable diaper <NUM> is removed from the wearer after use, the disposable diaper <NUM> is removed by peeling off the stomach-side portion <NUM> and the back-side portion <NUM> from each other at each of the joining portions 14a and 14b instead of removing the disposable diaper <NUM> while maintaining the original shape as if the underwear is removed. That is, the cover sheet <NUM> on the stomach-side portion <NUM> and the cover sheet <NUM> on the back-side portion <NUM> are continuously pulled apart from each other in the longitudinal direction L, and the disposable diaper <NUM> is removed. In that case, in order to facilitate continuous pulling, as will be described later, it is important that the individual fused portions <NUM> are substantially homogeneously formed and the plurality of fused portions are substantially homogeneous as a whole.

Whether or not the individual fused portions <NUM> are substantially homogeneous can be evaluated by the flatness of the surface of the core portion MC. The reason therefor is as follows. In the case where the flatness of the surface of the core portion MC is high, the unevenness of the surface of the core portion MC is small, so that the thickness dT of the core portion MC can be considered to be almost even. Due to that, it can be said that the core portion MC is substantially homogeneous as a whole. Since the core portion MC is substantially homogeneous as a whole, it can be said that the thickness DT and width DP of the peripheral wall portion SW formed at the same time as the core portion MC by ultrasonic wave sealing are also substantially homogeneous. That is, it is possible to evaluate whether or not each fused portion <NUM> is substantially homogeneous based on the flatness of the surface of the core portion MC.

The flatness of the surface of the core portion MC can be evaluated by a line roughness test on the surface of the core portion MC (according to JISB0601-<NUM>). <FIG> is a schematic view for describing a line roughness test of the fused portion. <FIG> schematically shows the position of the fused portion <NUM> where the line roughness test is performed in a plan view when evaluating the flatness of the surface of the core portion MC. In the line roughness test, the line roughness is measured along the line segment RL having the maximum dimension parallel to the longitudinal direction L, and the line roughness is measured along the line segment RW having the maximum dimension parallel to the lateral direction W. Specifically, the method of the line roughness test is as follows.

(<NUM>) A portion of the disposable diaper <NUM> including a part of the joining portion <NUM> (including the fused portion <NUM>) is cut out into a size of <NUM> in the longitudinal direction L × <NUM> in the lateral direction W as a sample. (<NUM>) The sample is disposed in the measuring portion of KS1100 manufactured by KEYENCE Co. (<NUM>) In the core portion MC of the fused portion <NUM>, the line roughness (surface roughness) is measured along the line segment RL of the maximum dimension in the longitudinal direction L to obtain the arithmetic average roughness Ra, and the line roughness (surface roughness) is measured along the line segment RW of the maximum dimension in the lateral direction W to obtain the arithmetic average roughness Ra. (<NUM>) A product of the arithmetic average roughness (Ra (longitudinal direction L) × Ra (lateral direction W)) is obtained. The average value of the products of the arithmetic average roughness of at least five samples is calculated as the final value.

In the present embodiment, the fact that the surface of the core portion MC is "flat" means that the product of the arithmetic average roughness in the longitudinal direction L (Ra (longitudinal direction L)) and the arithmetic average roughness in the lateral direction W (Ra (lateral direction W)) is <NUM><NUM> or less. In the case where the surface of the core portion MC is "flat", the thickness dT of the core portion MC is almost even, and the core portion MC is substantially homogeneous as a whole. Therefore, for the reasons described above, it can be said that the individual fused portions <NUM> are substantially homogeneously formed.

The index for evaluating the flatness of the surface of the core portion MC is not limited to the above example, and other indexes can be used. As other indexes, for example, each of the arithmetic average roughness in the longitudinal direction L (Ra (longitudinal direction L)) and the arithmetic average roughness in the lateral direction W (Ra (lateral direction W)) (for example, when both the arithmetic average roughness values are <NUM> or less, the surface is flat), the product of the root mean square roughness in the longitudinal direction L (RMS (longitudinal direction L)) and the root mean square roughness in the lateral direction W (RMS (lateral direction W)) (for example, when the product is <NUM><NUM> or less, the surface is flat), and each of the root mean square roughness in the longitudinal direction L (RMS (longitudinal direction L)) and the root mean square roughness in the lateral direction W (RMS (lateral direction W)) (for example, when both the root mean square roughness values are <NUM> or less, the surface is flat).

On the other hand, whether or not the plurality of fused portions are substantially homogeneous as a whole can be evaluated by a small variation in the peeling strength of the plurality of fused portions. This is because, since the peeling strength of the fused portion changes depending on the fusion state, when the peeling strengths are almost the same among the plurality of fused portions, that is, when the variation in the peeling strengths among the plurality of fused portions is small, the fusion states among the plurality of fused portions are almost the same. Whether or not the plurality of fused portions are substantially homogeneous as a whole can be evaluated by a peeling test between the cover sheet <NUM> of the stomach-side portion <NUM> and the cover sheet <NUM> of the back-side portion <NUM> in the joining portion 14a and/or the joining portion 14b (hereinafter, also referred to as "joining portion <NUM>") having the plurality of fused portions <NUM>. <FIG> is a schematic view for describing the peeling test of the joining portion. <FIG> shows a sample SA taken out from the disposable diaper, and <FIG> shows a testing machine <NUM> that performs a peeling test for the joining portion. In the peeling test of the joining portion, in the present embodiment, using the testing machine <NUM> for T-type peeling test, one end portion of the sample SA including the joining portion <NUM> in the longitudinal direction L is held between two chucks (jigs) <NUM> and <NUM> so as to widen a distance Dm between the two chucks <NUM> and <NUM>, and while peeling off the joining portion 14a, the relationship between a load F applied between the two chucks <NUM> and <NUM> and the distance Dm is measured. Specifically, the peeling test of the joining portion is performed as follows.

(<NUM>) The end portion of the disposable diaper <NUM> in the lateral direction W is cut out in a strip extending in the longitudinal direction L including the joining portion <NUM> from the end portion of the disposable diaper <NUM> on the waist opening WO side to the end portion on the leg opening LO side as a sample SA. The size of the sample SA is such that the length of the lateral direction W is approximately the sum of the length of the joining portion <NUM> and the width of the chuck, and the length of the longitudinal direction L is the length of the joining portion <NUM>. In the present embodiment, the size of the sample SA is <NUM> in the lateral direction W× <NUM> in the longitudinal direction L. (<NUM>) Using the testing machine <NUM> for peeling test, the cover sheet <NUM> of the stomach-side portion <NUM> and the cover sheet <NUM> of the back-side portion <NUM> are respectively held with the two chucks <NUM> and <NUM> of the testing machine <NUM> from the longitudinal direction L side in a portion 5p that does not include the joining portion <NUM> in the lateral direction W at one end portion of the sample SA in the longitudinal direction L (for example, the end portion on the waist opening WO side) (the central part of the disposable diaper <NUM> before being cut out). At this time, in the present embodiment, the portion 5p of the cover sheet <NUM> is pinched between holding sheets <NUM> so that the cover sheet <NUM> can be easily held by the chucks <NUM>, and the holding sheets <NUM> are held by the chucks <NUM>. However, the distance (initial value) between the chucks <NUM> and <NUM> at the time of holding is set to <NUM> in advance. (<NUM>) In the testing machine <NUM>, the two chucks <NUM> and <NUM> are pulled at a constant speed (for example, <NUM>/min) so as to widen the distance Dm between the two chucks <NUM> and <NUM>, and while peeling off the cover sheet <NUM> of the stomach-side portion <NUM> and the cover sheet <NUM> of the back-side portion <NUM> in the joining portion <NUM> in the <NUM>° direction, the distance Dm between the two chucks <NUM> and <NUM> and the load F applied to the two chucks <NUM> and <NUM> are measured. Then, the sample SA (joining portion <NUM>) is peeled off from one end portion in the longitudinal direction L (for example, the end portion on the waist opening WO side) to the other end portion (for example, the end portion on the leg opening LO side). In the case where the sample SA is torn in the lateral direction W and cannot be peeled off during the peeling, the above (<NUM>) and (<NUM>) are performed again for the remaining portion of the sample SA that has not been peeled off. (<NUM>) The relationship (graph) between the load F applied between the two chucks <NUM> and <NUM> and the distance D between the two chucks <NUM> and <NUM> when the sample SA is completely peeled off from one end portion to the other end portion in the longitudinal direction L is obtained. This graph has a protruding portion in which the load F temporarily shows a local maximum value (peeling strength at the fused portion <NUM>) at almost each position of the plurality of fused portions <NUM>. From the graph, the local maximum value of each of a plurality of protruding portions corresponding to the plurality of fused portions <NUM>, the average value of the plurality of the local maximum values in the plurality of protruding portions, and the variation of the plurality of the local maximum values with respect to the average value (for example, standard deviation) are calculated. However, the average value of at least three samples is calculated as the final evaluation value.

<FIG> is a graph showing an example of the relationship between the load F and the distance D in the peeling test of <FIG>. The horizontal axis shows the distance D (=Dm-<NUM> (initial value)) (mm) between the two chucks <NUM> and <NUM>, that is, from one end edge of the sample SA in the longitudinal direction L which is the position where the peeling starts (for example, the end edge on the waist opening WO side). On the other hand, the vertical axis shows the load F (N) applied between the two chucks <NUM> and <NUM>. As shown in the graph, the load F periodically alternately indicates a local maximum value FMk and a local minimum value FNk. However, k = <NUM> to n: n indicates the number of the fused portions <NUM>. The position DMk showing the local maximum value FMk is substantially the position of the fused portion <NUM>, and the position DNk indicating the local minimum value FNk is substantially the position between the fused portions <NUM> adjacent to each other. Therefore, the local maximum value FMk is the peeling strength at the fused portion <NUM> at the k-th position from the position, that is, the position where the peeling starts. The area of the region Kk interposed between the local minimum values FNk-<NUM> and FNk before and after the above position is the energy required for peeling at the k-th fused portion <NUM>, and the total sum is the energy required for peeling off the entire joining portions <NUM>. This graph can be seen as a graph having a plurality of protruding portions (regions Kk) corresponding to the plurality of fused portions <NUM>. Therefore, from such a graph, it is possible to obtain the local maximum value FMk of each protruding portion (= region Kk), the average value of the local maximum values FMk, and the variation (for example, standard deviation) of the plurality of the local maximum values FMk with respect to the average value. In the actual measurement, the number of regions Kk is basically the same as the number of the plurality of fused portions <NUM> of the joining portion <NUM>.

In the present embodiment, from the viewpoint that the plurality of fused portions <NUM> are substantially homogeneous as a whole, the standard deviation with respect to the average value of the local maximum values FMk in the plurality of protruding portions is <NUM> N or less in the graph. The upper limit of <NUM> N is set as follows. In the case where the wearer or caregiver is an elderly person, when the peeling strengths differ too much among the fused portions at the time of continuously pulling apart the joining portion, it is not possible to cope with the change such as a rapid increase or decrease in the peeling strength, and thus there is a concern that the plurality of fused portions may not be continuously peeled off. In the absorbent article, the upper limit of the change (standard deviation) in peeling strength is set to a value of <NUM> N based on the grip strength and grab strength of the elderly person to the extent that even such an elderly person can cope with.

The action and effect of the disposable diaper <NUM> having the above-described constitution will be described with reference to <FIG> and <FIG> is a schematic view for describing the appearance of the fused portion <NUM> being pulled apart. In the disposable diaper <NUM> of the present embodiment, each fused portion <NUM> in the joining portion 14a has the core portion MC and the peripheral wall portion SW. The peripheral wall portion SW is formed of the cover sheet <NUM> in the stomach-side portion <NUM> (stomach-side sheet member) and the cover sheet <NUM> in the back-side portion <NUM> (back-side sheet member) that are melted, integrated in the thickness direction, and solidified in a tubular wall shape. Therefore, usually, the peripheral wall portion SW is strong and is less likely to be broken compared with the cover sheet <NUM> in the stomach-side portion <NUM> or the back-side portion <NUM> in the periphery of the peripheral wall portion SW. Therefore, in the case of peeling off the joining portion 14a, the peripheral wall portion SW itself is less likely to be broken, and the cover sheet <NUM> in the stomach-side portion <NUM> or the back-side portion <NUM> in the periphery of the peripheral wall portion SW is easily broken at a boundary portion PB with the peripheral wall portion SW or the peripheral portion of the boundary portion PB (hereinafter, simply referred to as "boundary portion PB"). Therefore, as shown in <FIG> and <FIG>, when the joining portion 14a is pulled apart to remove the disposable diaper <NUM>, first, in a section other than the fused portion <NUM>, it is possible to easily pull apart the joining portion 14a at a boundary QB between the cover sheet <NUM> of the stomach-side portion <NUM> and the cover sheet <NUM> in the back-side portion <NUM>. In addition, in the fused portion <NUM> and the periphery of the fused portion <NUM>, pulling is likely to occur at the boundary portion PB with (the peripheral wall portion SW of) the fused portion <NUM> in the cover sheet <NUM> of the stomach-side portion <NUM> or the back-side portion <NUM>. Due to that, as shown in <FIG>, for example, the stomach-side portion <NUM> and the back-side portion <NUM> of the joining portion 14a can be easily and continuously pulled apart from each other in the longitudinal direction L so as to form a hole in which the fused portion <NUM> remains on the cover sheet <NUM> of the stomach-side portion <NUM>, and the fused portion <NUM> is removed from the cover sheet <NUM> of the back-side portion <NUM>. In the present embodiment, such a form of peeling is also referred to as peeling of the fused portion <NUM>, and the local maximum value FMk and energy associated with the peeling are also referred to as peeling strength and energy required for peeling, respectively.

However, in the case where the fusion of the fused portion <NUM> is incomplete, for example, when the width DP of the peripheral wall portion SW of the fused portion <NUM> is not even and partially small, the peripheral wall portion SW is partially weakened. Therefore, in the vicinity of such a fused portion <NUM>, breakage or tearing easily occurs not at the boundary portion PB between the cover sheet <NUM> of the stomach-side portion <NUM> or the back-side portion <NUM> and the peripheral wall portion SW of the fused portion <NUM> but in the peripheral wall portion SW and the core portion MC. In such a case, for example, as shown in <FIG>, during pulling apart the joining portion 14a, tearing KB occurring in the peripheral wall portion SW of the fused portion <NUM> may proceed to the cover sheet <NUM> in a section other than the joining portion 14a in the stomach-side portion <NUM> and the back-side portion <NUM>, for example, the cover sheet <NUM> in the central part of the stomach-side portion <NUM> or the back-side portion <NUM>. Due to that, there is a concern that it may be difficult to pull apart parts of the stomach-side portion <NUM> and the back-side portion <NUM> of the joining portion 14a continuously in the longitudinal direction L to the end, or it is necessary to repeat the pulling many times. In addition, for example, even when the tearing KB occurring in the peripheral wall portion SW of the fused portion <NUM> does not proceed to the cover sheet <NUM> in the central part of the stomach-side portion <NUM> and the back-side portion <NUM> and the like, in the case where a part of the plurality of fused portions <NUM> are such fused portions <NUM>, pulling cannot be performed with almost the same force from the start to the end of the pulling and it is difficult to perform continuous pulling.

Therefore, the disposable diaper <NUM> of the present embodiment has the following constitution. First, the surface of the core portion MC is flat. That is, in the present embodiment, the product of the arithmetic average roughness (RaL) in the longitudinal direction L and the arithmetic average roughness (RaW) in the lateral direction W on the surface of the core portion MC is <NUM><NUM> or less. Due to that, the thickness dT of the core portion MC is almost even, and the core portion MC is substantially homogeneous as a whole. Therefore, it can be said that the thickness DT and width DP of the peripheral wall portion SW formed at the same time as the core portion MC are also substantially even. That is, since the surface of the core portion MC is flat, it can be said that the fused portion <NUM> including the core portion MC is also substantially homogeneous. Therefore, each of the plurality of fused portions <NUM> is substantially homogeneous. From the viewpoint of further improving the flatness, the product of the arithmetic average roughness (RaL) in the longitudinal direction L and the arithmetic average roughness (RaW) in the lateral direction W is preferably <NUM><NUM> or less and more preferably <NUM><NUM> or less.

Further, in the peeling test of the joining portion, the standard deviation of the local maximum values FMk of the load F in the plurality of protruding portions (region Kk: k = <NUM> to n (n is the number of fused portions <NUM>) corresponding to the plurality of fused portions <NUM>) with respect to the average value is <NUM> N or less. Therefore, it can be said that the local maximum value FMk of the load F required for peeling each of the plurality of fused portions <NUM>, that is, the peeling strength of each of the plurality of fused portions <NUM> is almost the same. Here, in general, the peeling strength of the fused portion changes depending on the state of fusion. Therefore, when the peeling strengths are almost the same among the plurality of fused portions <NUM>, that is, when the change in the peeling strength among the plurality of fused portions <NUM> is small, it can be said that the fused states are almost the same among the plurality of fused portions <NUM>. Therefore, when the plurality of fused portions <NUM> are viewed as a whole, it can be said that the fusion is properly performed and the plurality of fused portions <NUM> are substantially homogeneous as a whole. The standard deviation is preferably <NUM> N or less and more preferably <NUM> N or less.

As described above, in the present embodiment, since the individual fused portions <NUM> are substantially homogeneous and the plurality of fused portions <NUM> are substantially homogeneous as a whole, during the pulling of the joining portion 14a, the occurrence of tearing in a part of the fused portions <NUM> can be suppressed and the joining portion 14a can be continuously pulled apart with almost the same force from the start to the end of the pulling. That is, when the disposable diaper <NUM> having the joining portion 14a is removed, the stomach-side portion <NUM> and the back-side portion <NUM> can be appropriately separated continuously and stably with almost the same force without breaking the sheet members other than the joining portion 14a.

As a preferred embodiment of the present embodiment, in the peeling test of the joining portions <NUM> (14a, 14b), the average value of the local maximum values FMk in the plurality of protruding portions (regions Kk) corresponding to the plurality of fused portions <NUM> is <NUM> N or more and <NUM> N or less. In the disposable diaper <NUM>, since the average value of the local maximum values FMk (peeling strength) is <NUM> N or more and <NUM> N or less, each fused portion <NUM> can be pulled apart from the cover sheet <NUM> of the stomach-side portion <NUM> or the back-side portion <NUM> with a relatively small force, and thus, the joining portion <NUM> can be pulled apart with a relatively small force. That is, the stomach-side portion <NUM> and the back-side portion <NUM> can be separated continuously and stably with almost the same force and easily with a relatively small force without breaking the cover sheet <NUM> in a section other than the joining portion <NUM>. The average value of the local maximum values FMk is preferably <NUM> N or more and <NUM> N or less, and more preferably <NUM> N or more and <NUM> N or less. However, when the average value of the local maximum values FMk in the protruding portions (regions Kk) is less than <NUM> N, the peeling strength is too small, and thus the joining portion <NUM> may be peeled off while the disposable diaper <NUM> is being worn. On the other hand, when the average value of the local maximum values FMk in the protruding portions (regions Kk) is more than <NUM> N, the peeling strength is too large and thus it may be difficult to pull apart the joining portion <NUM> when undressing the disposable diaper <NUM>. In particular, the upper limit of <NUM> N is set as follows. In the case where the wearer or caregiver is an elderly person, when the peeling strength of the fused portion is too large at the time of continuously pulling apart the joining portion, even if a small number of fused portions may be peeled off, there is a concern that all of the plurality of fused portions may not be continuously peeled off. In this absorbent article, the upper limit of the peeling strength is set to a value of <NUM> N based on the grip strength and grab strength of the elderly person to the extent that even such an elderly person can cope with.

As a preferred embodiment of the present embodiment, in the peeling test of the joining portion <NUM>, the energy required for peeling off the joining portion <NUM> is <NUM> J or more and <NUM> J or less. In the disposable diaper <NUM>, the energy required for peeling off the joining portion <NUM> is <NUM> J or more and <NUM> J or less, and thus the joining portion <NUM> can be pulled apart with a relatively small amount of work. That is, the stomach-side portion <NUM> and the back-side portion <NUM> can be separated continuously and stably with almost the same force and easily with a relatively small amount of work without breaking the cover sheet <NUM> in a section other than the joining portion <NUM>. The energy is preferably <NUM> J or more and <NUM> J or less, and more preferably <NUM> J or more and <NUM> J or less. However, in the case where the energy required for peeling off the joining portion is less than <NUM> J, the amount of work is too small and the joining portion may be broken while the absorbent article is being worn. On the other hand, in the case where the energy required for peeling off the joining portion is more than <NUM> J, the amount of work is too large, and when undressing the absorbent article, there is a concern that it may be difficult to pull apart the joining portion. In particular, the upper limit of <NUM> J is set as follows. In the case where the wearer or caregiver is an elderly person, when the energy required for peeling is too high at the time of continuously pulling apart the joining portion, even if the joining portion may be peeled off halfway, there is a concern that the entire joining portion may not continuously peeled off. In this absorbent article, the upper limit of the energy required for peeling is set to a value of <NUM> J based on the grip strength and grab strength of the elderly person to the extent that even such an elderly person can peel off the entire joining portion.

As a preferred embodiment of the present embodiment, in the puncture test of the cover sheet <NUM> (stomach-side sheet member) of the stomach-side portion <NUM> and the cover sheet <NUM> (back-side sheet member) of the back-side portion <NUM>, the maximum load of the cover sheet <NUM> of the stomach-side portion <NUM> and the maximum load of the cover sheet <NUM> of the back-side portion <NUM> are <NUM> N or more and <NUM> N or less. In the disposable diaper <NUM>, since both the maximum loads (breaking strength) of the cover sheets <NUM> of the stomach-side portion <NUM> and the back-side portion <NUM> are <NUM> N or more and <NUM> N or less, the cover sheets <NUM> can be easily broken with a relatively small force when the stomach-side portion <NUM> and the back-side portion <NUM> are separated. Due to that, the cover sheet <NUM> is not broken in a section other than the joining portion <NUM>, and the stomach-side portion <NUM> and the back-side portion <NUM> can be easily separated continuously and stably with almost the same force and easily with a relatively small force. The breaking strength is preferably <NUM> N or more and <NUM> N or less, and more preferably <NUM> N or more and <NUM> N or less. However, in the case where the maximum load of the cover sheet <NUM> is less than <NUM> N, the breaking strength is too small, and the joining portion <NUM> may be broken while the disposable diaper <NUM> is being worn. On the other hand, in the case where the maximum load of the cover sheet <NUM> is more than <NUM> N, the breaking strength is too large and it may be difficult to pull apart the joining portion <NUM>. In particular, the upper limit of <NUM> N is set as follows. In the case where the wearer or caregiver is an elderly person, when the breaking strength of the cover sheet is too high at the time of continuously pulling apart the joining portion, even if the cover sheet can be broken in a small number of fused portions, there is a concern that the cover sheet may be continuously broken in all of the plurality of fused portions. In this absorbent article, the upper limit of the breaking strength is set to a value of <NUM> N based on the grip strength and grab strength of the elderly person to the extent that even such an elderly person can cope with.

However, the puncture test of the cover sheets <NUM> of the stomach-side portion <NUM> and the back-side portion <NUM> is a test for measuring the breaking strength of the cover sheets <NUM> when a predetermined jig is punched into the cover sheets <NUM>. <FIG> is a schematic view for describing a puncture test. In the puncture test, the cover sheet <NUM> is used as a sample, the sample is placed on the upper surface of a sample table <NUM> of a testing machine <NUM> and fixed with a fixture <NUM> or the like. Then, a jig <NUM> which is disposed to be inserted through a hole portion <NUM> which extends inward from the upper surface of the sample table <NUM> is lowered from above the sample and penetrated into the sample so as to be inserted through the hole portion <NUM>. At that time, the load applied to the jig is measured. Specifically, the puncture test is performed as follows.

(<NUM>) The cover sheet <NUM> (unused) of the stomach-side portion <NUM> and the cover sheet <NUM> (unused) of the back-side portion <NUM> are cut out into a size of <NUM> × <NUM>, respectively, as samples. (<NUM>) Each sample (cover sheet <NUM>) is placed on the upper surface of the sample table <NUM> and fixed with the fixture <NUM> or the like. The hole portion <NUM> (diameter <NUM> × depth <NUM>) extending toward the inside of the sample table <NUM> is formed on the upper surface of the sample table <NUM>, and the sample is fixed so as to cover the hole portion <NUM>. (<NUM>) The sample table <NUM> is set on a stand (not shown). The stand includes a columnar member (not shown) that extends vertically upward. A digital force gauge FGP-<NUM> (manufactured by Nidec-Shimpo Co. ), in which the columnar jig <NUM> (diameter <NUM> × length <NUM>) is connected to the tip end of a gauge head, is attached to the columnar member. The jig <NUM> is disposed above the sample table <NUM> and is arranged so as to be inserted through the hole portion <NUM>. (<NUM>) The jig <NUM> is lowered from above the sample at a speed of <NUM>/min, and the load applied to the jig <NUM> is measured until the sample is broken and the jig <NUM> penetrates the sample. The maximum load at this time is defined as the breaking strength (N) of the sheet member (cover sheet <NUM>).

As a preferred embodiment of the present embodiment, in the puncture test, a difference between the maximum load of the cover sheet <NUM> (stomach-side sheet member) of the stomach-side portion <NUM> and the maximum load of the cover sheet <NUM> (back-side sheet member) of the back-side portion <NUM> is <NUM> N or more and <NUM> N or less. In the disposable diaper <NUM>, since the difference in maximum load (breaking strength) between the cover sheet <NUM> of the stomach-side portion <NUM> and the cover sheet <NUM> of the back-side portion <NUM> is <NUM> N or more and <NUM> N or less, the cover sheet <NUM> having a relatively small maximum load can be relatively easily broken from each fused portion when the stomach-side portion <NUM> and the back-side portion <NUM> are separated. Due to that, the cover sheet <NUM> is not broken in a section other than the joining portion <NUM>, and the stomach-side portion <NUM> and the back-side portion <NUM> are separated continuously and stably with almost the same force and more easily with a relatively small force. However, in the case where the difference in maximum load (breaking strength) between the cover sheet <NUM> of the stomach-side portion <NUM> and the cover sheet <NUM> of the back-side portion <NUM> is less than <NUM> N, the difference in breaking strength is too small and when the joining portion <NUM> is pulled apart, one of the two cover sheets <NUM> is broken in the vicinity of one fused portion <NUM> and the other is broken in the vicinity of another fused portion <NUM>. The broken cover sheet <NUM> may be broken apart, making it difficult to continuously and stably separate the stomach-side portion <NUM> and the back-side portion <NUM>. On the other hand, in the case where the difference in the maximum load (breaking strength) between the cover sheets <NUM> is more than <NUM> N, the difference in breaking strength is too large, and the cover sheet <NUM> having a weak breaking strength may be broken apart while the disposable diaper is being worn or it may be difficult to pull apart the cover sheet <NUM> having a strong breaking strength. In particular, the upper limit of <NUM> N is set as follows. In the case where the wearer or caregiver is an elderly person, when the difference in breaking strength between the cover sheets of the stomach-side portion and the back-side portion is large at the time of continuously pulling apart the joining portion, it is not possible to cope with the cover sheet having a strong breaking strength, and even if the cover sheet may be broken in a small number of fused portions, there is a concern that the cover sheet may not be continuously broken in all of the plurality of fused portions. In the absorbent article, the upper limit of the difference in breaking strength is set to a value of <NUM> N based on the grip strength and grab strength of the elderly person to the extent that even such an elderly person can cope with.

As a preferred embodiment of the present embodiment, a peeling test is performed with one end portion of the sample in the longitudinal direction L as each of the end portion of the waist opening WO side and the end portion of the leg opening LO side. In the disposable diaper <NUM>, the peeling test is performed on each of the end portion of the waist opening WO side and the end portion of the leg opening LO side, and therefore, in each case, the standard deviation of the local maximum values FMk at least in the protruding portions (regions Kk) is 3N or less. Therefore, when the disposable diaper <NUM> having the joining portion <NUM> is removed, in any of the case where the joining portion <NUM> is pulled apart from the end portion on the waist opening WO side, and the case where the joining portion <NUM> is pulled apart from the end portion on the leg opening LO side, the stomach-side portion <NUM> and the back-side portion <NUM> can be appropriately separated continuously and stably with almost the same force and without breaking the cover sheet in a section excluding the joining portion <NUM>. That is, the stomach-side portion <NUM> and the back-side portion <NUM> can be appropriately separated regardless of the pulling direction desired by the wearer or the caregiver.

Similarly, in the disposable diaper <NUM>, a peeling test is performed on each of the end portion of the waist opening WO side and the end portion of the leg opening LO side, and in each case, it is preferable to satisfy the following requirements. That is, the average value of the local maximum value FMk in the plurality of protruding portions (regions Kk) corresponding to the plurality of fused portions <NUM> is preferably <NUM> N or more and <NUM> N or less, and the energy required for peeling the joining portion <NUM> is <NUM> J or more and <NUM> J or less.

In addition, as another embodiment, in the fused portion line <NUM>, the shapes of the plurality of fused portions <NUM> in the central region <NUM> and in the leg-side end region <NUM> may be different from the shapes of the plurality of fused portions <NUM> in the waist-side end region <NUM>.

<FIG> is a plan view for describing another constitution example of the plurality of fused portions <NUM> in the joining portion 14a. <FIG> shows the fused portions 30a to 30c (fused portion line <NUM>) as seen from the side of the back-side portion <NUM> in the thickness direction T, and <FIG> show the shapes and dispositions of the protruding portions 41a to 41c of the anvil in which the fused portions 30a to 30c are formed by the ultrasonic wave sealing method. In the present embodiment, the respective fused portions 30a, 30b, and 30c in the waist-side end region <NUM>, the central region <NUM>, and the leg-side end region <NUM> have mutually different planar shapes. Therefore, in the case of forming the fused portions 30a, 30b, and 30c by the ultrasonic wave sealing method, the protruding portions 41a, 41b, and 41c of the anvil for the fused portions 30a, 30b, and 30c are different from each other. The planar shape of the protruding portion 41a of the anvil for forming the fused portion 30a in the waist-side end region <NUM> is a circular shape (truly circular shape), and a dimension d11 in the longitudinal direction L is equal to a dimension d12 in the lateral direction W. d11 and d12 are, for example, <NUM> to <NUM>. A distance d13 between the fused portions 30a adjacent to each other in the longitudinal direction L (the distance between the centers of the circles) is <NUM> to <NUM>. The planar shape of the protruding portion 41c of the anvil for forming the fused portion 30c in the leg-side end region <NUM> is a shape of a semicircle having a chord in the lateral direction W, and two protruding portions 41c are aligned close to each other in the lateral direction W. A dimension d31 in the longitudinal direction L, a dimension d32 in the lateral direction W, and a dimension d34 between both ends of the front end portion aligned in the lateral direction W are, for example, <NUM> to <NUM>. A distance d33 between the fused portions 30c adjacent to each other in the longitudinal direction L (the distance between the centers of the circles) is <NUM> to <NUM>.

<FIG> is a plan view showing an example of the constitution of the fused portion <NUM> in the joining portion 14a. <FIG> shows the fused portion 30a, and <FIG> shows the fused portion 30c. The fused portion 30b is the same as the fused portion <NUM> in <FIG>. Each of the fused portions 30a and 30c includes the core portion MC and the peripheral wall portion SW. The core portion MC and the peripheral wall portion SW are the same as the core portion MC and the peripheral wall portion SW of the fused portion <NUM> in <FIG> except that the shapes thereof in a plan view are different. In addition, it is not necessary that all of the fused portions in the joining portion 14a have the constitutions of the fused portion <NUM> or the fused portions 30a to 30c as described above. For example, only the fused portions in a portion that covers at least <NUM>% of the joining portion 14a in the longitudinal direction L from the end edges 11ae and 13ae, which are portions on the side of the end portions 11e and 13e on the waist opening WO side where the joining portion 14a begins to be pulled apart (begins to break), may have the above-described constitution. Similarly, only the fused portions in a portion that covers at least <NUM>% of the joining portion 14a in the longitudinal direction L from the end edges 11ae' and 13ae', which are portions on the side of the end portions 11e' and 13e' on the leg opening LO side where the joining portion 14a begins to be pulled apart (begins to break), may have the above-described constitution. In these cases, it is possible to easily start to pull apart the joining portion 14a.

Hereinafter, the present invention will be more specifically described by exemplifying examples and comparative examples, however the present invention is not limited only to such examples.

Example <NUM>: A disposable diaper shown in <FIG> was prepared. For the cover sheet on the stomach-side portion and the cover sheet on the back-side portion, a nonwoven fabric of <NUM> to <NUM>/m<NUM> was used. Comparative Examples <NUM> to <NUM>: Disposable diapers A, B, and C of other companies having almost the same structure as in Example <NUM> were used, respectively. Both the cover sheets on the stomach-side portion and the back-side portion were formed of a nonwoven fabric of <NUM> to <NUM>/m<NUM>.

In the disposable diaper of Example <NUM>, the line roughness test for the surface of the core portion was performed on the joining portion 14a on the left side in the lateral direction W as seen from the front side. Similarly, in the disposable diapers of Comparative Examples <NUM> to <NUM>, the line roughness test for the surface of the core portion was performed on each of the joining portion on the left side and the joining portion on the right side in the lateral direction as seen from the front side.

In the disposable diaper of Example <NUM>, the above peeling test of the joining portion was performed on each of the joining portion 14a on the left side and the joining portion 14b on the right side in the lateral direction W as seen from the front side. Similarly, in the disposable diapers of Comparative Examples <NUM> to <NUM>, the peeling test of the joining portion was performed on each of the joining portion on the left side and the joining portion on the right side in the lateral direction as seen from the front side.

The evaluation results are shown in Table <NUM> below. In Table <NUM>, Ra indicates the arithmetic average roughness, RMS indicates the root mean square roughness, W indicates that the line roughness is measured along the lateral direction W, and L indicates that the line roughness is measured along the longitudinal direction L. W × L indicates Ra (lateral direction W) × Ra (longitudinal direction L) and RMS (lateral direction W) × RMS (longitudinal direction L).

In the disposable diaper of Example <NUM>, the product of the arithmetic average roughness (Ra) in the lateral direction W and the arithmetic average roughness (Ra) in the longitudinal direction L was <NUM><NUM> and the value was <NUM><NUM> or less. Therefore, the core portion of the disposable diaper of Example <NUM> was flat, and the individual fused portions <NUM> were substantially homogeneously formed. On the other hand, in the disposable diapers of Comparative Examples <NUM> to <NUM>, the products of the arithmetic average roughness (Ra) in the lateral direction W and the arithmetic average roughness (Ra) in the longitudinal direction L were <NUM><NUM>, <NUM><NUM>, and <NUM><NUM>, and the values were more than <NUM><NUM>. Therefore, the core portions of the disposable diapers of Comparative Examples <NUM> to <NUM> were not flat, and the individual fused portions were not substantially homogeneously formed.

Regarding each of the arithmetic average roughness (Ra) in the lateral direction W and the arithmetic average roughness (Ra) in the longitudinal direction L, in Example <NUM>, the arithmetic average roughness values were <NUM> and <NUM>, and both values are <NUM> or less. Thus, the core portion is flat. On the other hand, in Comparative Examples <NUM> to <NUM>, the arithmetic average roughness value are <NUM>, <NUM> / <NUM>, <NUM> / <NUM>, and <NUM>, and the values are more than <NUM>. Thus, the core portion is not flat. In addition, regarding the product of the root mean square roughness (RMS) in the longitudinal direction L and the root mean square roughness (RMS) in the lateral direction W, in Example <NUM>, the product is <NUM><NUM> and the value is <NUM><NUM> or less. Thus, the core portion is flat. On the other hand, in Comparative Examples <NUM> to <NUM>, the products are <NUM><NUM>, <NUM><NUM>, and <NUM><NUM> and the values are more than <NUM><NUM>. Thus, the core portion is not flat. Regarding each of the root mean square roughness in the longitudinal direction L and the root mean square roughness in the lateral direction W, in Example <NUM>, the root mean square roughness values are <NUM> and <NUM>, and the both values are <NUM> or less. Thus, the core portion is flat. On the other hand, in Comparative Examples <NUM> to <NUM>, the root mean square roughness values are <NUM>, <NUM> / <NUM>, <NUM> / <NUM>, and <NUM>, and the values are more than <NUM>. Thus, the core portion is not flat.

The evaluation results are shown in Tables <NUM> to <NUM> below. However, in Tables <NUM> to <NUM>, W left indicates that the sample including the left side joining portion <NUM> of the disposable diaper is peeled from the end portion on the waist opening WO side. W right indicates that the sample including the right side joining portion <NUM> of the disposable diaper is peeled from the end portion on the waist opening WO side. L left indicates that the sample including the left side joining portion <NUM> of the disposable diaper is peeled off from the end portion on the leg opening LO side. L right indicates that the sample including the right side joining portion <NUM> of the disposable diaper is peeled off from the end portion on the leg opening LO side. E (J) indicates the energy required to peel off the joining portion <NUM> from one end portion on the waist opening WO side or the end portion on the leg opening LO side to the other end portion. The protrusion average (N) indicates the average value of the local maximum values FMk in the protruding portions (regions Kk). The lateral tearing (times) indicates the number of times in which the cover sheet is torn during peeling off the joining portion from one end portion on the waist opening WO side or the end portion on the leg opening LO side to the other end portion, from the joining portion <NUM> toward the central part of the disposable diaper (in the lateral direction W) and thus the peeling is interrupted. AVE indicates the average value of each value (E, protrusion average, and lateral tearing) in a plurality of samples, and STD indicates the standard deviation with respect to the average value.

In the disposable diaper of Example <NUM>, as shown in Table <NUM>, the standard deviation with respect to the average value of the local maximum values FMk in the protruding portions (regions Kk) in each of W left, W right, L left, and L right was <NUM> to <NUM>, that is, <NUM> N or less. Since the standard deviation was <NUM> N or less, the peeling strength of each of the plurality of fused portions <NUM> was almost the same, and thus the plurality of fused portions <NUM> as a whole were substantially homogeneous. Therefore, in the disposable diaper of Example <NUM>, the individual fused portions <NUM> were substantially homogeneously formed, and the average value of the number of times the peeling was interrupted, that is, the number of times the pulling of the joining portion was failed in the middle of the pulling was <NUM> to <NUM> times and was very small. As described above, since the individual fused portions <NUM> were substantially homogeneous and the plurality of fused portions <NUM> were substantially homogeneous as a whole, during the pulling of the joining portion, the occurrence of tearing in a part of the fused portions can be suppressed and the joining portion can be continuously pulled apart with almost the same force from the start to the end of the pulling. In addition, the average value of the local maximum values FMk in the protruding portions (regions Kk) was <NUM> N to <NUM> N, that is, <NUM> N or more and <NUM> N or less and was very small, and the joining portion could be pulled apart easily with a relatively small force. The average value of the energy E required for peeling off the joining portion was <NUM> J to <NUM> J, that is, <NUM> J or more and <NUM> J or less, and was very small, and the joining portion could be pulled apart easily with a relatively small amount of work.

In the disposable diapers of Comparative Examples <NUM> and <NUM>, as shown in Tables <NUM> and <NUM>, the standard deviation with respect to the average value of the local maximum values FMk in the protruding portions (regions Kk) was not included in a range of <NUM> N or less in a part or all of each of W left, W right, L left, and L right. The peeling strength of each of the plurality of fused portions was different, and therefore the plurality of fused portions as a whole were not substantially homogeneous. Therefore, in the disposable diapers of Comparative Examples <NUM> and <NUM>, the individual fused portions were not substantially homogeneous, and the average value of the number of times the peeling was interrupted, that is, the number of times the pulling of the joining portion was failed in the middle of the pulling was <NUM> to <NUM> times and was very large. Further, in the disposable diaper of Comparative Example <NUM>, as shown in Table <NUM>, the standard deviation with respect to the average value of the local maximum values FMk in the protruding portions (regions Kk) in each of W left, W right, L left, and L right was <NUM> N or less. However, since the individual fused portions were not substantially homogeneous (Table <NUM>), the average value of the number of times the peeling was interrupted, that is, the number of times the pulling of the joining portion was failed in the middle of the pulling, was <NUM> to <NUM> times and was very large. As described above, since the individual fused portions were not substantially homogeneous and the plurality of fused portions were not substantially homogeneous as a whole, a part of the fused portions were torn during the pulling of the joining portion, and it was not possible to continuously pull apart the joining portion with almost the same force from the start to the end of pulling. Further, the average value of the local maximum values FMk in the protruding portions (regions Kk) was larger than the range of <NUM> N to <NUM> N, a relatively large force was required to pull apart the joining portion, and the average value of the energy E required for peeling off the joining portion was larger than the range of <NUM> J to <NUM> J. A relatively large amount of energy was required to pull apart the joining portion.

Examples <NUM> to <NUM>: As Example <NUM>, the cover sheet on the back-side portion and the cover sheet on the stomach-side portion used for the disposable diaper of Example <NUM> were prepared. As Examples <NUM> to <NUM>, the cover sheet on the back-side portion and the cover sheet on the stomach-side portion that could be used for the disposable diaper of Example <NUM> were prepared. As the cover sheets, a nonwoven fabric of <NUM> to <NUM>/m<NUM> was used. Comparative Examples <NUM> to <NUM>: The cover sheet of the back-side portion and the cover sheet of the stomach-side portion used for the disposable diapers A to C of other companies in Comparative Examples <NUM> to <NUM> were prepared. As the cover sheets, a nonwoven fabric of <NUM> to <NUM>/m<NUM> was used.

The above puncture test was performed on each of the cover sheets of Examples <NUM> to <NUM> and Comparative Examples <NUM> to <NUM>.

The evaluation results are shown in Table <NUM> below. However, in Table <NUM>, O/B indicates the maximum load (breaking strength) of the cover sheet on the back-side portion, and O/T indicates the maximum load (breaking strength) of the cover sheet on the stomach-side portion.

In the cover sheets of Examples <NUM> to <NUM>, the maximum load (breaking strength) of the cover sheet of the stomach-side portion and the maximum load (breaking strength) of the cover sheet of the back-side portion were <NUM> N to <NUM> N, and the values were <NUM> N or more and <NUM> N or less. Therefore, when the stomach-side portion and the back-side portion were separated, the cover sheet can be easily broken with a relatively small force. The difference between the maximum load of the cover sheet of the stomach-side portion and the maximum load of the cover sheet of the back-side portion was <NUM>. 6N to <NUM>. 2N, and the value was <NUM> N or more and <NUM> N or less. Therefore, when the stomach-side portion and the back-side portion are separated, the cover sheet having a relatively small maximum load can be relatively easily broken.

In the cover sheets of Comparative Examples <NUM> to <NUM>, the difference between the maximum load of the cover sheet of the stomach-side portion and the maximum load of the cover sheet of the back-side portion was smaller than the range of <NUM> N to <NUM> N excluding the cover sheet of Comparative Example <NUM>. Due to that, when the stomach-side portion and the back-side portion are separated, it is difficult to relatively easily break any one of the cover sheets, and it is difficult to continuously and stably separate the stomach-side portion and the back-side portion.

Claim 1:
An absorbent article having a longitudinal direction (L), a lateral direction (W), and a thickness direction (T) that are orthogonal to each other, and including a stomach-side portion (<NUM>) including a stomach-side sheet member, a back-side portion (<NUM>) including a back-side sheet member, and a joining portion (14a, 14b) in which at least one end portion (11a, 11b) of the stomach-side portion (<NUM>) and at least one end portion (13a, 13b) of the back-side portion (<NUM>) in the lateral direction (W) are joined to each other in a state of being overlapped in the thickness direction (T) along the longitudinal direction (L),
wherein the joining portion (14a, 14b) includes a plurality of fused portions (<NUM>) which are separated from each other and disposed along the longitudinal direction (L),
each of the plurality of fused portions (<NUM>) includes
a core portion (MC) in which the stomach-side sheet member and the back-side sheet member are fused to each other in the thickness direction (T), and
a peripheral wall portion (SW) in which the stomach-side sheet member and the back-side sheet member are fused to each other in the thickness direction (T) to extend in a tubular shape in the thickness direction (T) from a peripheral edge of the core portion (MC),
a surface of the core portion (MC) is flat,
in a peeling test of the joining portion (14a, 14b) in which one end portion of a sample (SA) including the joining portion (14a, 14b) in the longitudinal direction (L) is held by two jigs (<NUM>), and while peeling off the joining portion (14a, 14b) to widen a distance between the two jigs, a load (F) to be applied between the two jigs is measured, a graph showing the load (F) with respect to the distance (D) has a plurality of protruding portions (Kk) in which the load temporarily shows local maximum values (FMk) at respective positions of the plurality of fused portions (<NUM>), and
in the peeling test, when the one end portion of the sample (SA) in the longitudinal direction (L) is an end portion of either a waist opening (WO) side or a leg opening (LO) side of the absorbent article, a standard deviation with respect to an average value of the local maximum values (FMk) in the plurality of the protruding portions (Kk) corresponding to the plurality of fused portions (<NUM>) is <NUM> N or less, measured as described in the description.