Stretchable sheet, worn article using the same, and stretchable sheet manufacturing apparatus

1. A stretchable sheet comprising:

a pair of sheets whose first surfaces oppose each other or are in contact with each other;

a plurality of elastic members that are arranged between the first surfaces of the pair of sheets and are arranged spaced apart from each other;

a plurality of attached portions, wherein the first surfaces of the pair of sheets are attached to each other by a welding construction without using an adhesive, at the attached portions; the attached portions hold the elastic members; the attached portions extend in a direction crossing a direction of stretch of the elastic members; and the attached portions are spaced apart from each other in the direction of stretch between adjacent elastic members of the elastic members; and

a plurality of folds that appear between the attached portions in a state where the elastic members are shrunk,

wherein the attached portions include:

a plurality of strongly-attached portions arranged on opposite sides of each of the elastic members in the crossing direction; and

a plurality of weakly-attached portions; each of the weakly-attached portions being arranged between adjacent elastic members of the elastic members and between adjacent strongly-attached portions of the strongly-attached portions,

wherein a strength of attachment between the pair of sheets at the weakly-attached portions is less than a strength of attachment between the pair of sheets at the strongly-attached portions.

2. The stretchable sheet according to claim 1 , wherein a length of the weakly-attached portions is greater than a length of the strongly-attached portions.

3. The stretchable sheet according to claim 1 , wherein a thickness of the weakly-attached portions is greater than a thickness of the strongly-attached portions.

4. A worn article comprising the stretchable sheet according to claim 1 , wherein:

the worn article has a skin-contact surface configured to be in contact with a skin of a wearer, and a non-skin-contact surface that is opposite to the skin-contact surface; and

the folds protrude on the skin-contact surface and/or the non-skin-contact surface.

5. An apparatus for manufacturing the stretchable sheet according to claim 1 , the manufacturing apparatus comprising:

an anvil roll for carrying the pair of sheets and the elastic members so that the elastic members are arranged between the pair of sheets; and

a welding device, in cooperation with the anvil roll, for welding together the pair of sheets so that the elastic members are held by the pair of sheets, wherein:

the anvil roll has a plurality of ridges that are formed on a circumferential surface of the anvil roll and extend in a width direction of the anvil roll;

each of the ridges includes a plurality of high ridge portions for producing the strongly-attached portions and a plurality of low ridge portions for producing the weakly-attached portions;

the high ridge portions and the low ridge portions are provided intermittently in the width direction; and

a height of the low ridge portions is lower than a height of the high ridge portions.

6. The manufacturing apparatus according to claim 5 , wherein a length of the low ridge portions in the width direction is longer than a length of the high ridge portions in the width direction.

7. The manufacturing apparatus according to claim 5 , wherein a height of the low ridge portions is lower by 2 to 30 μm than a height of the high ridge portions.

8. The manufacturing apparatus according to claim 5 , wherein:

each of the ridges of the anvil roll includes a plurality of carrying grooves that extend in a circumferential direction of the anvil roll, and carry the elastic members with the elastic members being held in the carrying grooves; and

each of the carrying grooves is defined by the high ridge portions that are on opposite sides of each of the carrying grooves in the width direction.

9. The manufacturing apparatus according to claim 5 , wherein the welding device is an ultrasonic welding device including an ultrasonic horn that opposes the ridges with the pair of sheets and the elastic members interposed between the ultrasonic horn and the ridges, and an ultrasonic energy is given to the ultrasonic horn.