Topsheets that have been used in absorbent articles, such as disposable diapers and sanitary napkins, include nonwoven fabrics prepared by various methods, perforated nonwoven fabrics, and perforated films of organic resins such as polyethylene.
Characteristics primarily required of absorbent articles include absorption characteristics relating to absorbing performance and surface characteristics for giving no adverse influences to the wearer's skin, such as an itch and a rash.
Conventional topsheets have satisfied the requirements for the absorption characteristics to some extent in letting low-viscosity waste liquids pass through and be absorbed quickly by an absorbent member lying under the topsheet but still leave room for improvement on the properties of making high-viscosity waste matter pass through and be absorbed. With respect to the surface characteristics for having no adverse influences on the skin, further improvements have been desired for alleviating skin irritation.
Skin troubles by absorbent articles are assumed attributed to the following causes. An absorbent article, while worn, creates an internal environment in which the skin is apt to be hydrated and swollen because of temperature and humidity rises, adhesion and remaining of the waste, e.g., urine or blood, and the like. The skin in such a condition is readily susceptible to physical irritation, i.e., the friction of the topsheet against the skin, and chemical irritation, namely, percutaneous absorption of irritants such as urine, soft stools or blood, resulting in skin troubles. It seems that the physical irritation is largely dependent on the surface characteristics of the topsheet with which the wearer's skin is in direct contact, and the chemical irritation is ascribable chiefly to high-viscosity waste that is less absorbable and likely to remain on the topsheet.
Under these circumstances, studies have been made to develop a topsheet for absorbent articles which feels soft.
JP-W-10-502000 (unexamined published international patent application) discloses a topsheet having a large number of protrusions extending along its longitudinal direction to have a wavy profile. The protrusions extending in the longitudinal direction contribute to soft feel but fail to retain their shape, being easily collapsed under the pressure while worn. More specifically, because the protrusions have a protuberant mountain-like profile, sticking out from the base (fixed part between adjacent projections), they have poor resistance against compression. As the protrusions are collapsed more and more, the contact area between the protrusions and the skin increases considerably. Therefore, they are not expected to suppress discomfort (overhydration) or skin troubles such as a rash. In addition, the protrusions having such a profile have limited conformability to the movement of the wearer's body. Due to the increase in contact area with the skin and the limited conformability, it is very likely that the topsheet causes friction on the skin, resulting in a failure to maintain the advantage of the wavy unevenness, i.e., soft feel, as designed.
JP-A-11-347062 discloses a topsheet having unevenness made by heat embossing. However, the top of the bosses are in a flat film form, the flat tops are hard and ruin the softness of the whole sheet.
Hence, the topsheets of related art do not have such protrusions that are flexible and deformable as would follow the body movement. A topsheet which securely prevents an itch, a rash, etc. while giving a wearer comfort of softness has not yet been provided.