Ultrasonic bonding method for absorbent article, ultrasonic bonding device for absorbent article, and absorbent article

An ultrasonic bonding device for use with an absorbent article having a plurality of granular particles, capable of absorbing a body fluid to swell, between two liquid-permeable non-woven fabric sheets facing each other, the device comprising:

• an anvil roll for carrying the two non-woven fabric sheets while the two non-woven fabric sheets are laid on each other;
• a plurality of protruding portions formed on the anvil roll so as to protrude outward in a radial direction of the anvil roll;
• a placement device for preventing the granular particles from being placed on the non-woven fabric sheets over the protruding portions;
• and
• a horn for ultrasonically vibrating so that the two non-woven fabric sheets are bonded together between the horn and the plurality of protruding portions, thereby forming bonded portions, the protruding portions comprising:
• at least one first protruding portion, which is away from the horn by a first distance when the first protruding portion comes closest to the horn, for forming at least one high-strength bonded portion such that the non-woven fabric sheets are unseparated from each other at the bonded portion by a peeling force urging the non-woven fabric sheets to peel off each other;
• and
• at least one second protruding portion, of which a second distance to the horn when the second protruding portion comes closest to the horn is greater than the first distance, for forming at least one low-strength bonded portion such that the non-woven fabric sheets are separatable from each other at the bonded portion by the peeling force urging the non-woven fabric sheets to peel off each other,
• wherein a difference between the first distance and the second distance is 3 μm to 60 μm.