Abstract:
A sanitary napkin  1  includes respective pairs of upper and lower layer flaps  11, 12  placed upon each other, each of the upper layer flaps  11  is elastically stretchable longitudinally of the napkin  1  and each of the lower layer flaps  12  is provided with a wing  13,  and thereby prevent the menstrual discharge from leaking sideways.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a sanitary napkin for absorption and containment of the menstrual discharge. 
     Japanese Patent Application Disclosure No. 1990-7956 describes a sanitary napkin having a pair of wings on its sides. According to this Application, the napkin is formed along its transversely opposite side edges with flaps adapted to be stretchable longitudinally of the napkin. Portions of these flaps extending outward from an undergarment worn by the wearer beyond peripheries of leg-openings are stretchable to follow the curvature of the peripheries as these portions when folded onto the outer surface of the crotch region of the undergarment. The portions of the flaps folded in this manner can be fastened to the outer surface of the undergarment by means of adhesive agent applied on the flaps. 
     The known napkin as has been mentioned above enables the flaps to cover the peripheries of leg-openings of the undergarment and thereby to prevent the peripheries from being stained with the menstrual discharge. However, it is still difficult for the known napkin to prevent the menstrual discharge leaking sideways from flowing down along the wearer&#39;s thighs. 
     SUMMARY OF THE INVENTION 
     It is an object of this invention to provide a sanitary napkin that is adapted to be fastened to the outer surface of the undergarment worn by the wearer so that menstrual discharge leaking sideways from the undergarment can be reliably prevented from flowing down along the wearer&#39;s thighs. 
     According to this invention, there is provided a sanitary napkin having a pair of transversely opposite side edges extending longitudinally of the napkin and a pair of longitudinally opposite ends extending transversely of the napkin, the napkin comprising: a liquid-pervious topsheet, a liquid-impervious backsheet, and a liquid-absorbent core disposed therebetween; the transversely opposite side edges comprising upper and lower layer flaps separably placed upon each other, each of the upper layer flaps having a length corresponding to 1/2˜1/1 of a full length of the napkin, the maximum width of 10˜30 mm and an elastic stretchability of 120˜300% longitudinally of the napkin, and each of the lower layer flaps laterally extending outward beyond an outer side edge of the upper layer flap and including a wing coated on a lower surface thereof with an adhesive agent. 
     This invention includes embodiments that: each of the upper layer flaps is formed by a sheet being elastically stretchable at least longitudinally thereof; each of the upper layer flaps comprises a sheet being non-stretchable longitudinally thereof and an elastic member secured thereto under tension longitudinally thereof to form the sheet with a plurality of gathers defined by crests and troughs alternately arranged longitudinally thereof; each of the upper layer flaps comprises the non-stretchable sheet formed with a plurality of zones crowded with the gathers so that these zones are intermittently arranged longitudinally of the non-stretchable sheet; and the lower layer flaps are elastically stretchable longitudinally thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a partially cutaway sanitary napkin according to this invention; 
     FIG. 2 is a sectional view taken along a line II—II in FIG. 1; 
     FIG. 3 is a sectional view of the napkin in its flat condition as put on the wearer&#39;s body; 
     FIG. 4 is a view similar to FIG. 1 of one embodiment; and 
     FIG. 5 is a view similar to FIG. 1 of another embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Details of a sanitary napkin according to this invention will be more fully understood from the description given hereunder with reference to the accompanying drawings. 
     FIG. 1 is a perspective view of a partially cutaway sanitary napkin  1 . The napkin  1  has a pair of transversely opposite side edges  6  extending longitudinally of the napkin  1  and a pair of longitudinally opposite ends  7  extending transversely of the napkin  1 , and comprises a liquid-pervious topsheet  2 , a liquid-impervious backsheet  3  and a liquid-absorbent core  4  disposed between these two sheets  2 ,  3 . The topsheet  2  and the backsheet  3  extend outward beyond a peripheral edge of the absorbent core  4  and are joined to each other along these extensions. The side edges  6  have upper layer flaps  11  each comprising a sheet  10  having a plurality of gathers  8  formed by crests and troughs transversely extending and alternately arranged longitudinally of the napkin  1  and an elastic member  9  extending longitudinally of the napkin  1 , and lower layer flaps  12  each underlying the upper layer flap  11  and provided with a wing  13 . The absorbent core  4  is generally hour glass, shaped. 
     FIG. 2 is a sectional view taken along a line II—II in FIG.  1 . The sheet  10  making a part of the upper layer flap  11  may be a non-stretchable or stretchable sheet and the inner edge  16  of this upper layer flap  11  may be joined to the side edge of the topsheet  2  and/or to a portion of the backsheet  3  extending laterally beyond the side edge of the topsheet  2  along a joining line  17 . Along the outer side edge  18  of the upper layer flap  11 , the sheet  10  is folded downward to wrap the elastic member  9  which is, in turn, secured under tension to the inner side of the sheet  10  so that the gathers  8  are formed under contraction of this elastic member  9 . A stretch stress of the elastic member  9  as this elastic member  9  is secured to the sheet  10  is preferably in a range of 10˜150 g. As will be apparent from FIGS. 1 and 2, the joining line  17  for the inner side edge  16  longitudinally extending along the side edge of the absorbent core  4  describes a curve convex inwardly of the napkin  1  and its longitudinally opposite ends cross the outer side edge  18  of the upper layer flap  11 . A longitudinal dimension B of the upper layer flap  11  is in a range of 1/2˜1/1 of a full length A of the napkin  1  and preferably can be stretched to 200 mm or larger. The maximum transverse dimension C of the upper layer flap  11  is preferably in a range of 10˜30 mm. A dimension D between the outer side edges  18  of the pair of upper layer flaps  11  is preferably in a range of 60˜120 mm and more preferably in a range of 80˜100 mm. 
     Each of the lower layer flaps  12  has its proximal side edge  14  formed by the portions of the topsheet  2  and the backsheet  3  extending laterally beyond the side edge of the absorbent core  4 . These two sheets  2 ,  3  are placed upon and joined to each other by means of hot melt adhesive agent in the vicinity of the side edge of the absorbent core  4 . The backsheet  3  further extends laterally beyond the side edge of the topsheet  2  to the outer side edge  18  of the upper layer flap  11  and partially further extends laterally to the wing  13 . The lower surface of the wing  13  is coated with an adhesive agent  22  which is, in turn, protected by a release sheet  23 . 
     FIG. 3 is a sectional view of the napkin  1  of FIG. 1 as put on the wearer&#39;s body. As shown, the napkin  1  is placed on the inner surface of a crotch region of an undergarment and the lower layer flaps  12  are folded onto the outer surface of the crotch region with the wings  13  fastened to the outer surface by means of the adhesive agent  22 . The lower layer flaps  12  folded in this manner cover the peripheries  27  of leg-openings of the undergarment  26  and prevent the peripheries  27  from being soiled with the menstrual discharge. 
     The upper layer flaps  11  are folded downward along the peripheries  27  of the leg-openings of the undergarment  26  and closely pressed against the wearer&#39; thighs  28 . This is because the gathers  8  as well as the elastic members  9  are forcibly stretched longitudinally of the napkin  1  as the upper layer flaps  11  are folded downward and therefore the gathers  8  as well as the elastic members  9  are biased to restore their initial positions that is, the napkin  1  is in its flat condition as shown in FIG.  2 . Therefore, the upper layer flaps  11  prevent the menstrual discharge from leaking at side edges of the napkin  1  and flowing down along the inner sides of the wearer&#39;s thighs  28 . 
     FIG. 4 is a view similar to FIG. 1 of one embodiment of this invention. With this napkin, the absorbent core  4  has a rectangular shape and, along the transversely opposite side edges of the absorbent core  4 , substantially rectangular upper layer flaps  11  and the lower layer flaps  12  provided with the wings  13  are formed. The upper layer flaps  11  are similar to them of FIG. 1 in that each of them extends substantially over the full length of the napkin  1  and has a width of 10˜30 mm but different from those of FIG. 1 in that an elastic sheet  10 A being stretchable by 120˜300% at least longitudinally thereof is used as stock material for the upper layer flaps  11 . The lower layer flaps  12  are similar to those of FIG.  1 . The napkin  1  according to this embodiment also takes the same posture as the napkin  1  of FIG. 1 when the napkin  1  is put on the wearer. The elastic sheet  10 A may be a stretchable sheet such as a natural rubber sheet or synthetic rubber sheet. 
     FIG. 5 is also a view similar to FIG. 1 of another embodiment of this invention. According to this embodiment, each of the upper layer sheets  11  is formed by a sheet  10 B which is non-stretchable longitudinally thereof and zones  15  crowded with gathers  8  defined by crests and troughs are alternately and intermittently arranged. The upper layer flaps  11  provided along their outer side edges with the elastic members  9  and the gathers  8  as well as the elastic members  9  are forcibly stretched longitudinally thereof as the napkin  1  is put on the wearer&#39;s body as shown in FIG.  3 . In this manner, the upper layer flaps  11  are closely pressed against the wearer&#39;s thighs  28 . 
     For exploitation of this invention, a nonwoven fabric or porous plastic film may be used as stock material for the topsheet  2 . As stock material for the backsheet  3 , a plastic film may be used. The absorbent core  4  may be formed by a fluff pulp or a mixture of fluff pulp and superabsorptive polymer particles. Stock material for the upper layer flaps  11  may be formed by a stretchable or non-stretchable and, in addition, preferably breathable, more preferably, breathable and sweat-absorbent nonwoven fabric or plastic film. While the lower layer flaps  12  are formed by portions of the backsheet  3  widely extending laterally in the illustrated embodiments, it is also possible for the lower layer flaps  12  to be formed by a nonwoven fabric or plastic film provided separately of the topsheet  2  and the backsheet  3  and joined to the topsheet  2  and/or the backsheet  3 . In order to facilitate the lower layer flaps  12  to be folded along the leg-openings of the undergarment, not only the proximal side edges  14  may be curved as shown in FIG. 1 but also the outer side edges  29  (See FIG. 1) may be curved inwardly of the napkin  1 . A dimension by which each of the lower layer flaps  12  extends laterally may be selected independently of such dimension in the upper layer flaps  12 . However, it is obvious that the wings  13  should have sufficient dimensions to reach the crotch region of the undergarment regardless the dimension of the lower layer flaps  12 . Furthermore, the lower layer flaps  12  may have an elastic stretchability also longitudinally thereof. Joining of the topsheet  2  and the backsheet  3  and the upper and lower layer flaps  11 ,  12  may be performed using a suitable adhesive agent such as a hot melt adhesive agent or sealing technique such as heat-sealing technique. 
     The sanitary napkin according to this invention has the upper layer flaps and the lower layer flaps so that the upper layer flaps may be closely pressed against the wearer&#39;s thighs and the lower layer flaps may be folded onto the outer surface of the crotch region of the undergarment with the wings being fastened to the outer surface. In this manner, the convenience for use offered by a so-called winged napkin is advantageously combined with the effect to prevent the menstrual discharge from flowing down along the wearer&#39;s thighs.