Absorbent article

Abstract: A body exudates absorbent article 1 including a liquid-absorbent core 4 having transversely opposite side edges extending in parallel to each other in a longitudinal direction of the article, a liquid-pervious topsheet 2 covering an upper surface of the core 4 and a liquidimpervious backsheet 5 covering a lower surface of the core 4, the topsheet 2 being formed in a zone covering the core 4 with a plurality of alternating troughs 2a and crests 2b continuously undulating in a transverse direction of the article and these troughs 2a and the crests 2b extending in the longitudinal direction, and thereby maintaining an initial soft elasity of the topsheet.

Description: This invention relates to a body exudates absorbent article such as a sanitary napkin, a blood absorbent pad, an incontinent pad, a disposable diaper and the like. Body exudates absorbent articles such as sanitary napkins or disposable diapers generally comprises a liquid-pervious topsheet, a liquid-impervious backsheet and a liquid-absorbent core disposed between these two sheets. The topsheet is usually made of a nonwoven fabric or a synthetic resin film. An example of an absorbent article is disclosed in DE-A-4422956. Touch of such article during its actual use can be improved by using a soft and elastic nonwoven fabric. However, if so-called convex core which is convex only in its transversely middle zone is adopted in such article, a nonwoven fabric is forcibly pressed against said convex middle zone of the core and, in consequence, an initial soft elasticity of nonwoven fabric may be lost. On the other hand, a synthetic resin film cannot be expected to offer the soft elasticity of a nonwoven fabric. In view of the problem as has been described above, it is an object of the present invention to provide a body exudates absorbent article adapted to main a soft elasticity of a topsheet in spite of a liquid-absorbent core of a so-called convex type adopted in the article. According to the present invention, there is provided a body exudates absorbent article comprising a liquid-absorbent core having transversely opposite side edges extending in parallel to each other in a longitudinal direction of the article, a liquid-pervious topsheeet covering an upper surface of the core and a liquid-impervious backsheet covering a lower surface of the core, wherein the topsheet is formed in a zone covering the core with a plurality of alternating troughs and crests continuously undulating in a transversely direction of the core and the troughs and crests extend in the longitudinal direction, and an upper surface of said topsheet is covered with a barrier cover sheet (3) which is formed in a zone corresponding to a central zone of said core with a longitudinally large opening through which said troughs and said crests of said topsheet are exposed. With the body exudates absorbent article according to the present invention, the amount of body exudates discharged on the napkin flows into and spreads along the respective troughs and is prevented by the crests functioning as barriers from leaking sideways. Both the troughs and the crests easily restore their initial configurations as well as their initial soft touch immediately after their deformation due to a shift of the topsheet or some external pressure exerted thereon. In spite of the convex configuration of the core adopted by the article, the unique arrangement according to the present invention facilitates the topsheet to be transversely stretched without compressing the convex top of the core and thereby enables a soft elasticity of the core to be maintained. Consequently, the body exudates absorbent article according to the present invention allows a skin-contactable surface (i.e., the body surface) of the article to be reliably placed in close contact with the wearer's labium and thereby ensures the body exudates discharged thereon to be prevented from leaking through a gap which might otherwise formed between the absorbent surface and the wearer's labium. Fig. 1 is a perspective view showing an embodiment of a sanitary napkin according to the present invention as partially broken away; Fig. 2 is a sectional view taken along a line A-A in Fig. 1; and Fig. 3 is a fragmentary sectional view of a topsheet, showing a trough and a crest. Details of a body exudates absorbent article according to the present invention will be more fully understood from the description of a sanitary napkin as a specific embodiment given hereunder with reference to the accompanying drawings. Fig. 1 is a perspective view showing a sanitary napkin as partially broken away and Fig. 2 is a sectional view taken along a line A-A in Fig. 1. A sanitary napkin 1 comprises a liquid-pervious topsheet 2, a liquid-impervious backsheet 5, a liquid-absorbent core 4 disposed between these two sheets 2, 5, and a barrier cover sheet 3. A region of the topsheet 2 covering the core 4 is formed with a continuous undulation extending transversely of the core 4, which undulation comprises alternating troughs 2a and crests 2b each extending longitudinally of the core 4. While it is not essential to bond bottoms of the troughs 2a to an upper surface of the core 4, the bottoms of the troughs 2a are preferably bonded to the upper surface of the core 4 in order that the undulation can be easily restored even after the troughs 2a and crests 2b are buckled under external pressure. Obviously, it is also possible to form the topsheet 2 with the troughs 2a and crests 2b in the entire region of the topsheet 2 covering the core 4. However, a desired effect of the troughs 2a and crests 2b can be obtained even when they are formed only in a region of the topsheet 2 covering a central zone of the core 4 and not its peripheral zone. The topsheet 2 and the backsheet 5 have their inner surfaces bonded to each other by means of adhesive agent or heat-sealing technique along their portions extending outward beyond longitudinally opposite ends as well as along their portions extending outward beyond transversely opposite side edges of the core 4. The topsheet 2 and the core 4 are bonded together by a pair of compressed grooves 6, 6 respectively extending along the side edges of the core 4. The compressed grooves 6, 6 really lie slightly inside the side edges of the core 4 and are convexly curved toward a middle of the core 4. The compressed grooves 6, 6 function to prevent the topsheet 2 and the core 4 from being spaced from each other during actual use of the napkin 1. The barrier cover sheet 3 covering an upper surface of the napkin 1 along its outer peripheral zone has transversely opposite side edges folded back onto the backsheet 5 and bonded to an outer surface of the backsheet 5 by means of adhesive agent or heat-sealing. The barrier cover sheet 5 is formed in its zone corresponding to the central zone of the core 4 with a longitudinally larger opening 3a through which the troughs 2a and the crests 2b of the topsheet 2 are exposed. Along a periphery of the opening 3a, the topsheet 2 and the barrier cover sheet 3 are not bonded to each other so that a pocket 7 serving to receive body exudates and prevent from leaking may be formed between these two sheets 2, 3. Though not shown, at least transversely opposite side edges of the opening 3a making a part of the periphery may be provided with stretchable/contractable elastic members functioning to lift the opening 3a off from the topsheet 2. Fig. 3 is a fragmentary sectional view of the topsheet 2, showing the trough 2a and the crest 2b. Referring to Fig. 3, a height L as measured from a bottom of the trough 2a to an apex of the crest 2b is 1.5 - 10.0 mm, preferably 3.0 - 10.0 mm. The height L being less than 1.5 mm would facilitate an amount of body exudates to flow beyond the crests 2b transversely of the napkin and cause the amount of body exudates to leak sideways. A distance W between each pair of the adjacent crests 2b is 1.0 - 15.0 mm, preferably 5.0 - 15.0 mm. It is also possible to form the troughs 2a and the crests 2b so that the height L as well as the distance W may be varied depending on the zones of the topsheet 2 covering the core 4. Specifically, the troughs 2a and crests 2b are formed in the central zone of the topsheet 2 so that their height L as well as their distance W are larger than those of the troughs 2a and the crests 2b formed in a peripheral zone of the topsheet 2. The topsheet 2 may be made of a hydrophilic nonwoven fabric, for example, a hydrophobic nonwoven fabric treated with suitable agent making the nonwoven fabric hydrophilic or nonwoven fabric comprising fibers into which such agent has been kneaded. The nonwoven fabric used as the material for the topsheet 2 preferably comprises conjugated fibers which has been crimped by a heat treatment and thereby has a high cushioning effect. Fineness of such fibers is preferably in a range of 1 - 6 deniers. Basis weight of the nonwoven fabric is preferably in a range of 20 - 80 g/m 2 , more preferably in a range of 30 - 80 g/m 2 . The topsheet 2 may also comprise a laminate of an upper layer nonwoven fabric having a relatively low density per unit area and a lower layer nonwoven fabric having a relatively high density per unit area. For example, the upper layer may be a nonwoven fabric having a fineness of 4 deniers and a basis weight of 20 g/m 2 and the lower layer may be a nonwoven fabric having a fineness of 2 deniers and a basis weight of 40 g/m 2 . With the topsheet 2 of such an arrangement, a permeation rate for body exudates in an upper layer nonwoven fabric is higher than that in a lower layer nonwoven fabric. By permeating body exudates from an upper layer nonwoven fabric to the lower layer nonwoven fabric as rapidly as possible, an amount of body exudates which might stay on the outer surface of the topsheet 2 can be eliminated or minimized. The core 4 comprises a mixture of fluff pulp and superabsorptive hydrogel particles, the mixture being completely covered with a tissue paper and compressed to a desired thickness.

Claims: A body exudates absorbent article (1) comprising a liquid-absorbent core (4) having transversely opposite side edges extending in parallel to each other in a longitudinal direction of said article, a liquid-pervious topsheet (2) covering an upper surface of said core and a liquid-impervious backsheet (5) covering a lower surface of said core, wherein: said topsheet is formed in a zone covering said core with a plurality of alternating troughs (2a) and crests (2b) continuously undulating in a transverse direction of said article and extending in said longitudinal direction, and characterized in that an upper surface of said topsheet is covered with a barrier cover sheet (3) which is formed in a zone corresponding to a central zone of said core with a longitudinal opening (3a) through which said troughs and said crests of said topsheet (2) are exposed. A body exudates absorbent article according to Claim 1, wherein a height (L) as measured from a bottom of each said troughs to an apex of each said crests is in a range of 1.5 - 10.0 mm and a distance (W) between each pair of the adjacent said crests is in a range of 1.0 - 15.0 mm. A body exudates absorbent article according to Claim 1, wherein said core and said topsheet are bonded to each other along a pair of compressed grooves (6) extending in said longitudinal direction in proximity of said transversely opposite side edges of said core. A body exudates absorbent article according to Claim 1, wherein a transversely middle zone of said core is configured to be higher than a peripheral zone of said core. A body exudates absorbent article according to Claim 1, wherein transversely opposite side edges of said barrier cover sheet are folded back onto said backsheet and bonded to an outer surface of said backsheet. A body exudates absorbent article according to Claim 1, wherein a pocket (7) is formed between said topsheet and said barrier cover sheet along a periphery of said opening.

Inventors: MIZUTANI SATOSHI, MIZUTANI, SATOSHI, Mizutani, Satoshi, c/o Research &amp; Development
Applicants: UNI CHARM CORP, UNI-CHARM CORPORATION
Application year: 1999
Main classification: A61F13
IPC codes: A61F13