The present invention relates to absorbent articles, such as sanitary napkins, disposable diapers, urinary incontinent pads, panty liners, underlaying sheets for pets, and the like. More particularly, it relates to absorbent articles which are free from adhesion failure or damage in their sealed parts and are therefore excellent in appearance and leakproofness.
Absorbent articles, such as sanitary napkins, having a liquid permeable topsheet, a liquid impermeable backsheet, and a liquid retentive absorbent member interposed between the topsheet and the backsheet are widely known. The topsheet and the backsheet are joined together in their peripheries with an adhesive or by heat sealing, ultrasonic sealing and the like thereby to form a sealed part. Although it is desirable to use no, or a small amount of, an adhesive from the standpoint of speeding up of the production line and economy, the joining method by heat sealing or ultrasonic sealing tends to bring about sealing defects such as an adhesion failure (lifting or separation) or damage such as a cut, which may lead to deteriorated appearance or leakage. Such sealing defects or damage are particularly liable to occur in cases where the sealed part has a difference in level or basis weight due to, for example, other sheeting members disposed between the topsheet and the backsheet.
In connection with the backsheet of the absorbent article, Japanese Patent Laid-Open Publication No. 61-179307 discloses a backsheet made of a polyolefin resin composition having an Elmendorf tear strength of 15 kg.cm/cm.sup.2 or more. Japanese Patent Laid-Open Publication No. 9-206331 discloses a backing material made of a porous sheet having a tensile yield strength of 120 kg/cm.sup.2 or more. However, since no consideration is given to the heat sealing properties in these Publications at all, there is a fear that adhesion failures and damage in the sealed part occur in the absorbent articles using the backsheets disclosed therein.
Japanese Patent Laid-Open Publication No. 10-75978 discloses to provide a non-skin contact layer formed by extensible and/or stretchable materials containing films obtained by catalysis of metallocene for the purpose of an easy fit to the body or prevention of the occurrence of misposiioning in use. Japanese Patent Laid-Open Publication No. 8-164164 discloses to use in a shorts type throw-away diaper a backsheet having a strength of 1500 gf/50 mm or more in the transverse direction of the diaper, aiming to enhance the ease of tearing joint parts of the both sides. However, the extensible materials and backsheets disclosed in this publication are a composite material of nonwoven fabric, which makes it difficult to produce absorbent articles inexpensively.