Stretch structure for absorbent article, and underpants-type disposable diaper using same
A stretchable structure of an absorbent article includes a stretchable region and a non-stretchable region. A laminate of a first sheet layer, second sheet layer, and elastic film between the first and second sheet layers extends over the stretchable and non-stretchable regions. The first and second sheet layers are bonded to each other at a large number of dot-like joints via through holes formed in the elastic film stretched along the surfaces of the first and second sheet layers in a stretchable direction. The dot-like joints are arrayed at intervals in the stretchable direction and a direction perpendicular to the stretchable direction. An end of the stretchable region adjacent to the non-stretchable region is a buffer stretchable section. The area rate of dot-like joints in the buffer stretchable section is larger than the area rate of dot-like joints in the main section not including the buffer stretchable section.
1. A stretchable structure of an absorbent article comprising:
a stretchable region stretchable in a stretchable direction; and
a non-stretchable region continuing from the stretchable region, wherein
a laminate comprising a first sheet layer, a second sheet layer, and an elastic film disposed between the first sheet layer and the second sheet layer extends over the stretchable region and the non-stretchable region,
the first sheet layer and the second sheet layer are bonded to each other at a large number of dot-like joints via through holes formed in the elastic film stretched along surfaces of the first sheet layer and the second sheet layer in the stretchable direction, the dot-like joints being arrayed at intervals in the stretchable direction and a direction perpendicular to the stretchable direction, wherein the stretchable region comprises the dot-like joints,
an area rate of the dot-like joints in the non-stretchable region is larger than an area rate of the dot-like joints in the stretchable region, and the non-stretchable region has an elongation at elastic limit of 130% or less in the stretchable direction,
the area rate of the dot-like joints in the stretchable region is smaller than the area rate of the dot-like joints in the non-stretchable region, and the stretchable region has an elongation at elastic limit of 200% or larger,
an end of the stretchable region adjacent to the non-stretchable region is a buffer stretchable section, an area rate of the dot-like joints in the buffer stretchable section being larger than an area rate of the dot-like joints in a main stretchable section not including the buffer stretchable section,
where the buffer stretchable section is configured to have an elongation at elastic limit smaller than a tensile elongation at a break in the stretchable direction of the elastic film having a width equal to an interval between two adjacent through holes formed in the elastic film in the non-stretchable region and arrayed in the direction perpendicular to the stretchable direction,
wherein the buffer stretchable section prevents rupture of the elastic film at a boundary between the stretchable region and the non-stretchable region.
2. The stretchable structure of the absorbent article according to claim 1 ,
wherein
the dot-like joints are formed by welding materials of the first sheet layer and the second sheet layer, and
at least edges of the through holes formed in the elastic film are cured.
3. The stretchable structure of the absorbent article according to claim 1 , wherein
each of the dot-like joints has an area of 0.14 to 3.5 mm 2 ,
each of the through holes has an area that is 1 to 1.5 times the area of each of the dot-like joints,
the area rate of the dot-like joints is 16 to 45% in the non-stretchable region,
the area rate of the dot-like joints is 1.8 to 19.1% in the main stretchable section,
the area rate of the dot-like joints is 8 to 22.5% in the buffer stretchable section.
4. The stretchable structure of the absorbent article according to claim 1 , wherein
the elastic film has a tensile strength of 8 to 25 N/35 mm in the stretchable direction, a tensile strength of 5 to 20 N/35 mm in the direction perpendicular to the stretchable direction, a tensile elongation of 450 to 1050% in the stretchable direction, and a tensile elongation of 450 to 1400% in the direction perpendicular to the stretchable direction.
5. An underpants-type disposable diaper comprising:
an outer member comprising a front body and a back body; and
an inner member comprising an absorber, the inner member being fixed to an internal face of the outer member, wherein
two side edges of the front body of the outer member are respectively bonded to two side edges of the back body of the outer member to define side seal portions, and an annular torso, a waist opening, and paired leg openings are thereby formed,
the outer member has the stretchable structure of the absorbent article according to claim 1 such that the stretchable structure is stretchable along a width direction, and
the non-stretchable region is a part of the outer member overlapping with the absorber, and the stretchable regions continue from two sides of the non-stretchable region in the width direction.