Abstract:
A body exudates absorbent article including 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 topsheet covering an upper surface of the core and a liquid-impervious backsheet covering a lower surface of the core, the topsheet being formed in a zone covering the core with a plurality of alternating troughs and crests continuously undulating in a transverse direction of the article and these troughs and the crests extending in the longitudinal direction, and thereby maintaining an initial soft elasity of the topsheet.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    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.  
           [0002]    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.  
           [0003]    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 can not be expected to offer the soft elasticity of a nonwoven fabric.  
         SUMMARY OF THE INVENTION  
         [0004]    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 maintain a soft elasticity of a topsheet in spite of a liquid-absorbent core of a so-called convex type adopted in the article.  
           [0005]    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 topsheet 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.  
           [0006]    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.  
           [0007]    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.  
           [0008]    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&#39;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&#39;s labium. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a perspective view showing an embodiment of a sanitary napkin according to the present invention as partially broken away;  
         [0010]    [0010]FIG. 2 is a sectional view taken along a line A-A in FIG. 1;  
         [0011]    [0011]FIG. 3 is a fragmentary sectional view of a topsheet, showing a trough and a crest;  
         [0012]    [0012]FIG. 4 is a view similar to FIG. 1 showing another embodiment of the sanitary napkin according to the present invention; and  
         [0013]    [0013]FIG. 5 is a sectional view taken along a line B-B in FIG. 4. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]    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.  
         [0015]    [0015]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 .  
         [0016]    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  2   a and crests  2   b  each extending longitudinally of the core  4 . While it is not essential to bond bottoms of the troughs  2   a  to an upper surface of the core  4 , the bottoms of the troughs  2   a  are preferably bonded to the upper surface of the core  4  in order that the undulation can be easily restored even after the troughs  2   a  and crests  2   b  are buckled under external pressure. Obviously, it is also possible to form the topsheet  2  with the troughs  2   a  and crests  2   b  in the entire region of the topsheet  2  covering the core  4 . However, a desired effect of the troughs  2   a  and crests  2   b  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.  
         [0017]    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 .  
         [0018]    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 .  
         [0019]    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  3   a  through which the troughs  2   a  and the crests  2   b  of the topsheet  2  are exposed. Along a periphery of the opening  3   a , 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  3   a  making a part of the periphery may be provided with stretchable/contractable elastic members functioning to lift the opening  3   a  off from the topsheet  2 .  
         [0020]    [0020]FIG. 3 is a fragmentary sectional view of the topsheet  2 , showing the trough  2   a  and the crest  2   b . Referring to FIG. 3, a height L as measured from a bottom of the trough  2   a  to an apex of the crest  2   b  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  2   b  transversely of the napkin and cause the amount of body exudates to leak sideways. A distance W between each pair of the adjacent crests  2   b  is 1.0˜15.0 mm, preferably 5.0˜15.0 mm. It is also possible to form the troughs  2   a  and the crests  2   b  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  2   a  and crests  2   b  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  2   a  and the crests  2   b  formed in a peripheral zone of the topsheet  2 .  
         [0021]    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.  
         [0022]    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.  
         [0023]    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.  
         [0024]    [0024]FIG. 4 is a view similar to FIG. 1, showing a sanitary napkin  10  embodied in an alternative manner and FIG. 5 is a sectional view taken along a line B-B in FIG. 4. The sanitary napkin  10  comprises a liquid-pervious topsheet  11 , a liquid-impervious backsheet  12  and a liquid-absorbent core  13  disposed between these two sheets  11 ,  12  and bonded to an inner surface of at least one of these two sheets  11 ,  12 .  
         [0025]    The core  13  disposed between the topsheet  11  and the backsheet  12  has a convex configuration defined by a transversely middle zone  13   a  and a peripheral zone  13   b  which is lower than the transversely middle zone  13   a . The topsheet  11  is formed in its zone lying above the middle zone  13   a  of the core  13  with alternating troughs  11   a  and crests  11   b  each extending longitudinally of the core  13  and continuously undulating transversely of the core  13 . The topsheet  11  is bonded to an upper surface of the core  13  along its peripheral zone  13   b  but not in the middle zone  13   a , by means of adhesive agent (not shown). The topsheet  11  has its portions extending outward beyond longitudinally opposite ends and extending outward beyond transversely opposite side edges of the core  13 , respectively, bonded to the backsheet  12  by means of adhesive agent or heat-sealing technique.  
         [0026]    In the middle zone  13   a  of the core  13 , the bottoms of the respective troughs  11   a  are not bonded to the upper surface of the core and therefore the topsheet  11  can be transversely stretched by a desired dimension in the middle zone  13   a  of the core when the topsheet  11  and the backsheet  12  are bonded together along a peripheral edge of the napkin  10 . With an advantageous consequence, in spite of the arrangement that the convex core  13  is sandwiched between the topsheet  11  and the backsheet  12 , the top of the core  13  is never compressed and an initial softness of the core  13  can be maintained. On the contrary, the troughs  11   a  and the crests  11   b  of the topsheet  11  function as a cushion in the middle zone  13   a  of the core  13  and give the wearer a soft touch.  
         [0027]    A height as measured from the bottom of the trough  11   a  to the apex of the crest  11   b  of the topsheet  11  is preferably in a range of 1.5˜4.0 mm. A distance between each pair of the adjacent crests  11   b  is preferably in a range of 2.0˜10.0 mm.