Abstract:
A disposable diaper includes a pair of gasketing cuffs, each of the paired gasketing cuffs is divided into a high stiffness zone and a low stiffness zone in a transverse direction of the diaper.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to a disposable diaper for absorbing and containing excretion.  
           [0002]    U.S. Pat. No. 4,695,278 discloses a disposable diaper provided along transversely opposite side edge portions with a pair of gasketing cuffs and a pair of barrier cuffs. The gasketing cuffs flaps are formed by placing the portion of a topsheet covering a liquid-absorbent core and extending laterally beyond transversely opposite side edges of the core upon the portion of a backsheet extending laterally beyond the side edges of the core. The barrier cuffs are formed by bonding sheets provided separately of the topsheet to the top surface of the topsheet or by the portion of the topsheet partially projecting upward on the respective gasketing cuffs so as to describe inverted U-shapes, respectively. Each of the gasketing cuffs is provided along its outer side edge portion with a longitudinally extending elastic member secured under tension thereto. Each of the barrier cuffs has a proximal side edge portion bonded to the associated gasket cuff and a distal side edge transversely opposed to the proximal side edge and provided with a longitudinally extending elastic member secured under tension thereto.  
           [0003]    In the diaper of prior art, the distal side edge portion of the barrier cuff is biased under a contractile force of the elastic member to rise on the top surface of the diaper and thereby to function as a barrier. Contraction of the elastic member of the gasket cuff causes its outer side edge portion to swing around the associated side edge of the core inwardly of the diaper from its initial horizontal position toward the associated barrier cuff rising on the top surface of the diaper. Such tendency raises a problem when the diaper is put on a wearer&#39;s body since the gasket cuff which should directly cover the wearer&#39;s thighs may collapse inwardly of the diaper. Consequently, it is apprehended that the gasketing cuff could not fulfill its desired function and create a feeling of discomfort against a wearer. Furthermore, the gasketing cuff collapsing inwardly of the diaper may obstruct the barrier cuff from properly rising.  
         SUMMARY OF THE INVENTION  
         [0004]    It is an object of this invention to provide a disposable diaper improve so that the elastically stretchable side flaps can be reliably prevented from collapsing inwardly of the diaper put on the wearer.  
           [0005]    According to this invention, there is provided a disposable diaper having a transverse direction extending circumferentially around a wearer&#39;s torso and a longitudinal direction orthogonal to the transverse direction, comprising a liquid-pervious topsheet, a liquid-impervious backsheet, a liquid-absorbent core disposed therebetween and a pair of gasketing cuffs lying outside transversely opposite side edges of the core extending in the longitudinal direction and being elastically stretchable in the longitudinal direction, the gasketing cuffs being formed at least partially by respective first sheets extending laterally from the side edges of the core, wherein: each of the gasketing cuffs is formed by the first sheet and at least one separate second sheet laminated with the first sheet and provided with the elastic stretchability by securing a leg-hole elastic member extending in the longitudinal direction to each of the gasketing cuffs along a line spaced from the associated side edge of the core; a portion of the gasketing cuff defined between the side edge of the core and the elastic member is divided in said transverse direction at least in a longitudinal middle region of said diaper into a high stiffness zone and a low stiffness zone so that the high stiffness zone lies adjacent the core and the low stiffness zone lies adjacent the elastic member.  
           [0006]    With the disposable diaper according to this invention, the outer side edge portions of the respective gasket cuff swing outward laterally of the diaper when the diaper is put on the wearer and therefore the gasket cuffs can fulfill the function thereof without collapsing inwardly of the diaper. In this way, it is possible to avoid that a feeling of discomfort against the wearer be created and the barrier cuffs might be obstructed from swinging up both due to collapsing of the gasket cuffs.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a perspective view showing one embodiment of a partially cutaway disposable diaper according to this invention;  
         [0008]    [0008]FIG. 2 is a fragmentary sectional view taken along line II-II in FIG. 1;  
         [0009]    [0009]FIG. 3 is a view similar to FIG. 2 showing the diaper as it is put on a wearer;  
         [0010]    [0010]FIG. 4 is a view similar to FIG. 2 showing another embodiment of this invention;  
         [0011]    [0011]FIG. 5 is a view similar to FIG. 2 showing still another embodiment of this invention;  
         [0012]    [0012]FIG. 6 is a view similar to FIG. 2 showing further another embodiment of this invention; and  
         [0013]    [0013]FIG. 7 is a view similar to FIG. 2 showing further additional embodiment of this invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0014]    Details of a disposable diaper according to this invention will be more fully understood from the description given hereunder with reference to the accompanying drawings.  
         [0015]    A disposable diaper  1  shown by FIG. 1 in a perspective view as partially cutaway has a transverse direction extending circumferentially around a wearer&#39;s torso and a longitudinal direction orthogonal to the transverse direction. The diaper  1  is configured to define, in the longitudinal direction, a front waist region  6 , a rear waist region  7  and a crotch region  8  extending between these two waist regions  6 ,  7 . The diaper  1  comprises a liquid-pervious topsheet  2 , a liquid-impervious backsheet  3 , a liquid-absorbent core  4  disposed between these two sheets  2 ,  3 , a pair of end flaps  11 ,  12  extending in the transverse direction along longitudinally opposite ends of the core  4  and a pair of gasketing cuffs  13  extending in the longitudinal direction along and outside transversely opposite side edges of the core  4 . In addition, the diaper  1  is formed on its inner side with a pair of barrier cuffs  14  extending along the respective gasketing cuffs  13  in the longitudinal direction. A pair of tape fasteners  16  adapted to be anchored on the outer surface of the front waist region  6  are respectively attached to transversely opposite side edge portions of the rear waist region  7 . The end flap  12  of the rear waist region  7  is provided with a single or plural waist-hole elastic members  17  extending in the transverse direction and secured under tension to the inner surface of at least one of the top- and backsheets  2 ,  3  forming this end flap  12 . Each of the gasketing cuffs  13  is provided with a single or parallel plural leg-hole elastic members  18  extending in the longitudinal direction and each of the barrier cuffs  14  is provided with a single crotch region elastic member  19  extending in the longitudinal direction.  
         [0016]    [0016]FIG. 2 is a fragmentary sectional view taken along center line II-II bisecting a longitudinal dimension of the diaper  1 . The core  4  comprises a wad  21  substantially made of fluff pulp covered with a tissue paper  22 . The top- and backsheets  2 ,  3  extend outward beyond the transversely opposite side edges  23  placed upon and bonded to each other along the respective extensions by means of hot melt adhesive  10 . The backsheet  3  extends further outward beyond the topsheet  2  to respective side edges  24  of the horizontal gasketing cuff  13 . In each of the gasketing cuffs  13 , leg-hole elastic member  18  is secured under tension to the inner surface of the backsheet  3  by means of hot melt adhesive (not shown) and a liquid-impervious sheet  26  bonded to the inner surface of the backsheet  3  and the outer surface of the topsheet  2  by means of adhesive  10  so as to cover the elastic member  18 . A portion of this liquid-impervious sheet  26  branched from the gasketing cuff  13  and extending inwardly of the diaper  1  forms the barrier cuff  14 . In the case of the embodiment shown, the leg-hole elastic member  18  comprises three elastic elements E 1 , E 2 , E 3 .  
         [0017]    The barrier cuff  14  has a proximal side edge  28  along which the barrier cuff  14  is branched from the gasketing cuff  13  and a distal side edge  29  transversely opposed to the proximal side edge  28 . The liquid-impervious sheet  26  is folded back and bonded together along the distal side edge  29  to form a sleeve  31  and a crotch region elastic member  19  is secured under tension to the inner surface of the sleeve  31  by means of hot melt adhesive (not shown). The barrier cuff  14  collapses inwardly of the diaper  1  and has its longitudinally opposite end portions  32 ,  33  (See FIG. 1) are bonded to the outer surface of the topsheet  2 .  
         [0018]    The gasketing cuff  13  has a laminated construction presenting a sectional shape as shown by FIG. 2 at least along a part of its full length extending in the vicinity of the center line II-II. Referring to FIG. 2, the gasketing cuff  13  comprises, in the vicinity of the center line II-II, a first zone  41  in which the backsheet  3  and the liquid-impervious sheet  26  are placed upon and bonded to each other including the elastic member  18  therebetween and having a relatively low bending stiffness in the transverse direction, a second zone  42  in which the top- and backsheets  2 ,  3  and the liquid-impervious sheet  26  are placed upon and bonded one to another and having a relatively high bending stiffness in the transverse direction and a third zone  43  defined between the side edge of the core  4  and the proximal side edge  28  of the barrier cuff  14 , in which the top- and backsheets  2 ,  3  are placed upon and bonded to each other. The first zone  41  and the second zone  42  are contiguous to each other along a straight line M while the second zone  42  and the third zone  43  are contiguous to each other along a straight line N. The number of sheets laminated one upon another is different in the respective zones  41 ,  42 ,  43 . The first, second and third zones  41 ,  42 ,  43  respectively have their transverse dimensions p, q, r wherein, preferably, p=5˜100 mm, q=10˜50 mm and r=0˜30 mm. A distance D from the innermost leg-hole elastic member E 1  to the border line M of the second zone  42  is preferably 0.5˜30 mm, more preferably 1˜10 mm. The inventors measured stiffness of the first, second and third zones  41 ,  42 ,  43  by Clark method prescribed in JIS (Japanese Industrial Standards) L-1096 and found that, preferably, the first zone  41  has a stiffness G 1  in a range of 50˜100 mm, the second zone  42  has a stiffness G 2  in a range of 100˜250 mm and the stiffness G 2  is at least 30 mm higher than the stiffness G 1 . The stiffness G 3  of the third zone  43  is not specified and may be lower or higher than the stiffness G 2 . Values of the stiffness G 1 ˜G 3  can be measured using the test pieces prepared to have the same laminated construction as those of the relevant zones.  
         [0019]    [0019]FIG. 3 is a sectional view similar to FIG. 2 showing the diaper  1  immediately before it is put on the wearer. As the diaper  1  constructed as shown in FIGS. 1 and 2 is laid on a bed of the wearer immediately before it is put on the wearer, the leg-hole elastic members  18  as well as the crotch region elastic members  19  contract to generate gathers in the respective flaps  13 ,  14  and, at the same time, the diaper  1  is curved in the longitudinal direction with its inner side being concave. Thereupon the free distal side edge portions  29  of the respective barrier cuffs  14  swing up from the inner surface of the diaper  1  around the respective proximal side edges  28  as indicated by imaginary lines in FIG. 2 and the gasketing cuffs  13  also swing up inwardly of the diaper  1 . Taking account of the fact that it is difficult to put the diaper  1  in this curved state on the wearer, the diaper  1  may be slightly tensioned in the longitudinal direction and thereby the diaper  1  is substantially flattened. As a result, the first zone  41  of the gasketing cuffs  13  swings back around an axis defined between the border line M along which the first and second zones  41 ,  42  are contiguous to each other and the innermost elastic member E 1  to the position at which the first zone  41  extends laterally of the diaper  1 . The height of the barrier cuff  14  in its rising state slightly goes down as the diaper  1  is tensioned in the longitudinal direction. The diaper  1  may be put on the wearer with the gasketing cuffs  13  flattened as has been described to prevent the gasketing cuff  13  from collapsing inwardly of the diaper  1 . In other words, it is not apprehended that the gasketing cuffs  13  might be held between the core  4  and the wearer. In this way, the side flaps  13  are tightly placed around the wearer&#39;s thighs and thereby fulfill their function to reliably prevent leakage of body fluids. It is also avoided that the gasketing cuffs  13  collapsing inwardly of the diaper  1  might create a feeling of discomfort against the wearer and obstruct the barrier cuffs  14  from properly rising on the inner surface of the diaper  1 .  
         [0020]    FIGS.  4 ˜ 6  are views similar to FIG. 2 showing the other embodiments of this invention. In the case of the diaper  1  shown by FIG. 4, the backsheet  3  is formed by a relatively narrow liquid-impervious plastic film  51  and a relatively large nonwoven fabric  52  bonded to the outer surface of the film  51 . The first zone  41  including the leg-hole elastic member  18  comprises two layers, i.e., the nonwoven fabric  52  of the backsheet  3  and the liquid-impervious sheet  26  made of a nonwoven fabric and forming the barrier cuff  14 . The second zone  42  comprises four layers, i.e., the topsheet  2  made of a nonwoven fabric, a pair of backsheets  3  and the liquid-impervious sheet  26  and the third zone  43  comprises three layers, i.e., the topsheet  2  and a pair of backsheets  3 . The sheets laminated with one another as shown are bonded together by means of hot melt adhesive  10  so that the sheets thus bonded together may present the stiffness increasing in the order of the first zone  41 , the third zone  43  and the second zone  42 . In the case of this embodiment also, the side flap  13  can swing up and down around the border line along which the first and second zones  41 ,  42  are contiguous to each other. The first zone  41  can extend laterally of the diaper  1  immediately before the diaper  1  is put on the wearer.  
         [0021]    In the case of the diaper  1  shown by FIG. 5, a wad  4 A of the core  4  substantially formed by fluff pulp is covered with upper and lower sheets  53 ,  54  of tissue paper which extend outward beyond the wad  4 A and form parts of the gasketing cuffs  13 . Of the gasketing cuffs  13 , the first zone  41  including the leg-hole elastic member  18  comprises two layers, i.e., a hydrophobic sheet  56  prepared separately of the top- and backsheets  2 ,  3  and the liquid-impervious sheet  26 , on one hand, and the liquid-impervious sheet  26 , on the other hand. The second zone  42  partially comprises five layers, i.e., the top- and backsheets  2 ,  3 , the sheets of tissue paper  53 ,  54  and the liquid-impervious sheet  26  and partially comprises four layers, i.e., the top- and backsheets  2 ,  3 , the liquid-impervious sheet  26  and the hydrophobic sheet  56 . The third zone  43  comprises the top- and backsheets  2 ,  3  and the sheets of tissue paper  53 ,  54 . In this embodiment, the second zone  42  extending immediately inside the border line M presents the stiffness G 2  at least 30 mm higher than the stiffness G 1  presented by the first zone  41  and the first zone  41  can extend laterally of the diaper  1  as shown in FIG. 2. In this first zone  41 , a sheet having a high breathability may be used as stock material for the hydrophobic sheet  56  or for the hydrophobic sheet  56  and the liquid-impervious sheet  26  to improve the breathability desired around the wearer&#39;s thighs.  
         [0022]    In the case of the diaper  1  shown by FIG. 6, the first zone  41  comprises two layers, i.e., the backsheet  3  and the liquid-impervious sheet  26  and the second zone  42  comprises four layers, i.e., the top- and backsheets  2 ,  3 , the liquid-impervious sheet  26  and an appropriately stiffened sheet  57  prepared separately of these sheets  2 ,  3 ,  26 . The sheets laminated one with another are bonded together by means of hot melt adhesive  10  or heat-sealing technique and the barrier cuffs  14  lie along the respective side edges  23  of the core  4  and extend inwardly of the diaper  1 . In this diaper  1 , the dimension r of the third zone  43  is substantially zero, namely, the third zone  43  is practically absent in this diaper  1 . The sheet  57  is provided for the purpose of ensuring the second zone  42  to present the stiffness G 2  substantially higher than the stiffness G 1  presented by the first zone  41  and a nonwoven fabric or plastic film meets such purpose. In this diaper  1  also, the first zone  41  can extend outward laterally of the diaper  1  as shown in FIG. 3.  
         [0023]    [0023]FIG. 7 is also a sectional view similar to FIG. 2 showing further another embodiment of this invention. The diaper  1  of FIG. 7 is distinguished from the diaper  1  of FIG. 2 in that none of the barrier cuffs  14  is provided and a single belt-like elastic member is used as each of the leg-hole elastic members  18 . The first zone  41  including the leg-hole elastic member  18  comprises two layers, i.e., the backsheet  3  formed by a liquid-impervious plastic film or nonwoven fabric and an inner sheet  71  preferably formed by liquid-impervious nonwoven fabric, the second zone  42  comprises three layers, i.e., the top- and backsheets  2 ,  3  and the inner sheet  71  and the third zone  43  comprises two layers, i.e., the top- and backsheets  2 ,  3 . In the first zone  41 , the distance D from the inner side edge  18 A of the leg-hole elastic member  18  to the border line M along which the first and second zones  41 ,  42  are contiguous to each other is preferably in a range of 0.5˜30 mm, more preferably in a range of 1˜10 mm. While the gasketing cuff  13  swings up as indicated by imaginary lines in FIG. 2 as the diaper  1  is laid on the bed immediately before it is put on the wearer, the diaper  1  may be slightly tensioned in the longitudinal direction to make the gasket cuff  13  swing back in the vicinity of the border line M until the gasketing cuff  13  extends laterally of the diaper  1  as shown in FIG. 3. In order that the gasketing cuff  13  can easily swing back in this manner, the distance D is preferably minimized so that the second zone  42  and the inner side edge  18 A of the elastic member  18  may lie in vicinity as close as possible. For the embodiments shown by FIGS.  1 ˜ 6  in which the leg-hole elastic member  18  comprises a plurality of elastic elements, the distance D between the innermost elastic element  18  and the second zone  42  is preferably in a range of 0.5˜30 mm, more preferably in a range of 1˜10 mm as has previously been described in reference with FIG. 2. In the diaper  1  of FIG. 7 also, it is not apprehended that the gasketing cuff  13  might collapse inwardly of the diaper  1  and obstruct the associated barrier cuff  14  from swing up. Accordingly, leak of body fluids and creation of a feeling of discomfort against the wearer due to the collapse can be reliably avoided. In this diaper  1 , the dimension r of the third zone  43  will become zero when the inner sheet  71  is dimensioned so that its inner side edge  71 A may reach the associated side edge  23  of the core  4 .  
         [0024]    The desired difference between the stiffness G 1  of the first zone  41  and the stiffness G 2  of the second zone  42  can be ensured not only by varying the number of the sheets laminated in the respective zones but also varying thickness as well as material of the sheets laminated one with another.