Patent Publication Number: US-2013237944-A1

Title: Disposable wearing article

Description:
TECHNICAL FIELD 
     The present invention relates to disposable wearing articles such as diapers, toilet-training pants and incontinence briefs, more particularly to diapers for newborn babies. 
     BACKGROUND 
     Conventionally, disposable wearing articles are known having a bodily fluid absorbent structure formed with a high stiffness region. For example, JP 2005-152241A (PTL 1) discloses a disposable wearing article including a liquid-pervious inner sheet, a liquid-impervious outer sheet and a bodily fluid absorbent structure interposed between these inner and outer sheets, wherein a given region of the bodily fluid absorbent structure is debossed to define a high stiffness region. 
     CITATION LIST 
     Patent Literature 
     
         
         {PTL 1} JP 2005-152241 A 
       
    
     SUMMARY 
     Technical Problem 
     In the disposable wearing article disclosed in PTL 1, as will be apparent from  FIG. 12  of the accompanying drawings, each of debosses  131  distributed in a high stiffness region  161  has a length dimension in a transverse dimension smaller than that in a longitudinal direction. Upon occurrence of urination, bodily fluids flow along these debosses  131  so that bodily fluids may be dispersed in the longitudinal direction and absorbed by an absorbent core  126 . 
     In such a wearing article, however, a plurality of transverse high stiffness zones  162  are formed by arranging a plurality of longitudinally long debosses  131  in the transverse direction in a state of being substantially contiguous to one another in the longitudinal direction. In consequence, this wearing article includes no transverse low stiffness zone extending in the transverse direction and having none of the debosses  131 . 
     When such a wearing article disclosed in PTL 1 is put on the wearer&#39;s body, a midsection of the crotch region  113  of the diaper is squeezed between the wearer&#39;s thighs and longitudinal creases  171  may appear in a bodily fluid absorbent structure  124  between adjacent debosses  131  or along extending directions of the debosses  131 . As a consequence, the debosses  131  adjacent to one another in the longitudinal direction come into a substantially connected state in the proximity of the creases  171  in the longitudinal direction, and the bodily fluid absorbent structure  124  may therefore be formed with a ridge  170  along such connected lines, extending toward the wearer&#39;s bottom cleavage  181 . Such a ridge  170  may dig into the wearer&#39;s bottom cleavage and not only make the wearer uncomfortable but also cause bodily fluids to move along the ridge and eventually leak sideways beyond the leg-openings. If for example the wearer is a newborn baby, the wearer often stays in a lying posture for a long time on a bed and, for example, when the wearer is picked up in a mother&#39;s arms, a relatively strong force is exerted on the bodily fluid absorbent structure  124  in the transverse direction. Consequently, while the shape of the ridges  170  is maintained, the longitudinal creases  171  in the bodily fluid absorbent structure  124  may be deepened. 
     Solution to Problem 
     According to the present invention, there is provided a disposable wearing article having a longitudinal direction and a transverse direction, including: 
     a chassis comprising a skin-facing side, a non-skin-facing side, a front waist region, a rear waist region and a crotch region extending in the longitudinal direction between the front and rear waist regions; and 
     a bodily fluid absorbent structure extending in the longitudinal direction across the crotch region into the front and rear waist regions wherein a region of the bodily fluid absorbent structure extending at least in a central area thereof is formed with a high stiffness region comprising a plurality of debosses spaced one from another in predetermined dimensions in the longitudinal and transverse directions. 
     In the disposable wearing article, the bodily fluid absorbent structure includes an absorbent core and at least one sheet covering a surface of the absorbent core; 
     the debosses are shaped so that the length dimension of each deboss is longer in the transverse direction than in the longitudinal direction; 
     the high stiffness region includes a plurality of longitudinal low stiffness zones extending in the longitudinal direction and formed with none of the debosses, a plurality of transverse high stiffness zones formed with the debosses being arranged at regular intervals in the transverse direction, and transverse low stiffness zones lying between each pair of transverse high stiffness zones and being formed with none of the debosses; and 
     the transverse low stiffness zones and transverse high stiffness zones being adjacent in the longitudinal direction. 
     Advantageous Effects of Invention 
     In the disposable wearing article according to the present invention, the debosses forming the high stiffness region of the bodily fluid absorbent structure are respectively shaped so that a length dimension thereof in the transverse direction (width) is longer than a length dimension thereof in the longitudinal direction (height); the high stiffness region includes the transverse high stiffness zones formed of the debosses intermittently arranged in the transverse direction; and the transverse low stiffness zones each defined between a pair of adjacent transverse high stiffness zones. With this unique arrangement, a plurality of the transverse creases can be easily developed on the bodily fluid absorbent structure of the diaper put on the wearer&#39;s body. Development of the transverse creases advantageously restricts development of the longitudinal creases in the longitudinal low stiffness zones which may cause the central portion of the bodily fluid absorbent structure to be convexly raised up toward the wearer&#39;s crotch region. In consequence, such ridge can be restricted as low as possible and such ridge should not dig into the wearer&#39;s bottom cleavage. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  A perspective view of a disposable diaper as an example of the disposable wearing article according to a first embodiment of the present invention. 
         FIG. 2  A partially cutaway plan view of the diaper of  FIG. 1  unfolded and as viewed from its skin-facing side. 
         FIG. 3  A sectional view of the diaper of  FIG. 1  taken along line in  FIG. 2 . 
         FIG. 4  A plan view of the unfolded diaper of  FIG. 1  similar to  FIG. 2 , showing the diaper with an inner sheet and barrier sheets having been omitted. 
         FIG. 5  An enlarged view of the region of the diaper of  FIG. 1  enclosed by dashed-dotted line and denoted by V in the diaper of FIG.  4 . 
         FIG. 6  A sectional view of the diaper of  FIG. 1  taken along line VI-VI in  FIG. 4 . 
         FIG. 7  A diagram illustrating a bodily fluid absorbent structure in the diaper of  FIG. 1  put on the wearer&#39;s body. 
         FIG. 8  Diagram illustrating two phases (a) and (b) of a measuring method utilizing a doll. 
         FIG. 9  A schematic diagram illustrating a part of a process to make the bodily fluid absorbent structure of the diaper of  FIG. 1 . 
         FIG. 10  An unfolded plan view similar to  FIG. 4 , showing a disposable diaper according to a second embodiment of the present invention. 
         FIG. 11  A sectional view of the diaper of  FIG. 10  taken along line XI-XI in  FIG. 10 . 
         FIG. 12  A diagram illustrating a bodily fluid absorbent structure in the diaper of prior art put on the wearer&#39;s body. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     Details of a disposable wearing article according to the present invention will be more fully understood from the description of a disposable diaper as one typical example of the disposable wearing article given hereunder with reference to the accompanying drawings. In  FIGS. 2 and 4 , the longitudinal axis and the transverse axis of a diaper are denoted by P and Q, respectively. 
     It should be appreciated that a diaper  10  will be described hereunder in terms of a diaper for babies. Relating to  FIGS. 1 to 3 , the diaper  10  includes a chassis  14  having a longitudinal direction Y, a transverse direction X being orthogonal to the longitudinal direction Y, a skin-facing side, a non-skin-facing side, a front waist region  11 , a rear waist region  12  and a crotch region  13  extending between the front and rear waist regions  11 ,  12 ; and a pair of tape-fastener tabs  15 ,  16  extending outward from opposite side edges  12   b  of the rear waist region  12  in the transverse direction X. The tape-fastener tabs  15 ,  16  are provided on the respective skin-facing side with first fastening zones  17 , for example defined by hook elements of a so-called mechanical fastener. The front waist region  11  is provided on the non-skin-facing side with a second fastening zone  18  for example including a backing sheet made of a fibrous nonwoven fabric or a plastic film and loop elements of the mechanical fastener being set thereon. 
     In putting the diaper  10  on a wearer, the first fastening zones  17  on the respective tape-fastener tabs  15 ,  16  can be detachably engaged with the second fastening zone  18  to join each of the side edges of the front and rear waist regions  11 ,  12  and thereupon to define a waist-opening  20  and a pair of leg-openings  21  (See  FIG. 1 ). 
     The chassis  14  includes a liquid-pervious inner sheet  22  lying on the skin-facing side, a liquid-impervious outer sheet  23  lying on the non-skin-facing side and a bodily fluid absorbent structure  24  interposed between the inner and outer sheets  22 ,  23 . Both the inner and outer sheets  22 ,  23  may extend outward beyond a periphery of the bodily fluid absorbent structure  24  and may be bonded to each other outboard of the periphery of the bodily fluid absorbent structure  24  with hot melt adhesives, for example (not shown). 
     The inner sheet  22  may be formed of, for example, a nonwoven fabric made of hydrophilic fibers or hydrophobic fibers modified to become hydrophilic, a porous plastic film or a laminate sheet thereof. As the nonwoven fabric, for example, the following materials may be used: an air-through fibrous nonwoven fabric, a spunbonded fibrous nonwoven fabric or a point bonded fibrous nonwoven fabric having a basis mass in a range of about 20 to about 50 g/m 2 , preferably in a range of about 20 to about 35 g/m 2 , and a fiber density in a range of about 0.01 to about 0.04 g/cm 3 , preferably in a range of about 0.025 to about 0.035 g/cm 3 . 
     The outer sheet  23  defines the outer surface of the chassis  14  and may be formed of, for example, a moisture-pervious plastic film, a hydrophobic fibrous nonwoven fabric or a laminate sheet thereof. As the nonwoven fabric, for example, the following materials may be used: an air-through fibrous nonwoven fabric, a spunbonded fibrous nonwoven fabric or a point bonded fibrous nonwoven fabric having a basis mass in a range of about 15 to about 40 g/m 2 , preferably in a range of about 25 to about 35 g/m 2 , and a fiber density in a range of about 0.06 to about 0.10 g/cm 3 , preferably in a range of about 0.07 to about 0.09 g/cm 3 . 
     The bodily fluid absorbent structure  24  includes an absorbent core  26  formed of, for example, a mixture of absorbent fibers such as fluff wood pulp and super-absorbent polymer particles and at least one sheet for covering at least a major (central) part of a surface of the absorbent core  26 ; preferably an upper sheet  27  formed of for example a dispersant sheet such as a tissue paper or a liquid-pervious fibrous nonwoven fabric adapted to cover the upper surface of the absorbent core  26 ; and a lower sheet adapted to cover the lower surface of the absorbent core  26 . The upper sheet  27  may be bonded to the absorbent core  26  with, for example, hot melt adhesives  29  applied in a curved line pattern such as in a wavy pattern or in an omega-pattern in which omega-like shaped curves are formed at intervals along one direction, and the lower sheet  28  may be fixed to the absorbent core  26  with, for example, hot melt adhesives  30  applied like a film (thin layer). The lower sheet  28  may extend outward beyond the periphery of the absorbent core  26  and any such protruding segment may be fixed to the upper surface of the upper sheet  27  to cover the absorbent core  26  as a whole with the upper and lower sheets  27 ,  28 . Though not shown in  FIG. 3 , the upper and lower sheets  27 ,  28  may be formed of a single sheet having a relatively wide width dimension. 
     The absorbent core  26  may be a mixture of absorbent fibers such as fluff wood pulp having a basis mass for example in a range of about 160 to about 180 g/m 2 , super-absorbent polymer particles having a basis mass for example in a range of about 190 to about 210 g/m 2 , and optionally thermoplastic synthetic fibers (staple fibers) having a basis mass for example in a range of about 10 to about 20 g/m 2 , wherein a mass percentage of the super-absorbent polymer particles in the absorbent core  26  as a whole is preferably in a range of 40 to 60%, so far as the effect of the present invention as will be described can be achieved. 
     As will be described in more detail, the bodily fluid absorbent structure  24 , in the crotch region  13  and on the skin facing side, is provided with a plurality of debosses  31 , for example in a zigzag-pattern (staggered pattern) as viewed in the longitudinal direction so that each of the adjacent debosses  31  may be spaced from each other in a given dimension in the longitudinal direction Y as well as in the transverse direction X. While the debosses  31  are formed on the side of the bodily fluid absorbent structure  24  facing the wearer&#39;s skin in one embodiment, the debosses  31  may alternatively be formed on the non-skin-facing side, or on both the skin-facing and non-skin-facing sides of the bodily fluid absorbent structure  24 , so far as the intended effect of the present invention can be achieved. 
     Between the inner and outer sheets  22 ,  23 , a leakage-barrier sheet  32  formed of a liquid-impervious, moisture-pervious plastic film may be fixed to the inner surface of one of the inner and outer sheets  22 ,  23 , for example with hot melt adhesives (not shown) applied to the inner surface, to cover the non-skin-facing side of the bodily fluid absorbent structure  24 . The leakage-barrier sheet  32  preferably has a sufficient length dimension extending outward beyond the entire peripheral edge of the bodily fluid absorbent structure  24  in order that bodily fluids seeping through the bodily fluid absorbent structure  24  can be prevented from leaking out. The diaper  10  may further include, on the skin-facing side, a pair of containment flaps  34 ,  35  provided outboard of the bodily fluid absorbent structure  24  as viewed in a transverse direction so as to be in a symmetric relationship about the longitudinal axis P. 
     The chassis  14  is contoured by front and rear ends  36 ,  37 , opposed to each other in the longitudinal direction Y and extending in the transverse direction X, and side edges  38 ,  39 , opposed to each other in the transverse direction X and extending in the longitudinal direction Y. The front and rear ends  36 ,  37 , and the side edges  38 ,  39  are defined by respective segments of the inner sheet  22 , the leakage-barrier sheet  32 , the outer sheet  23  and the containment flaps  34 ,  35  extending outward beyond the front and rear ends  24   a ,  24   b  of the bodily fluid absorbent structure  24  in the longitudinal direction Y and extending beyond the side edges  24   c ,  24   d  of the bodily fluid absorbent structure  24  in the transverse direction X and overlapping one another. Between the inner sheet  22  defining the front and rear ends  36 ,  37 , and the leakage-barrier sheet  32 , waist elastics  41 , for example made of an elastomer material such as natural rubber, synthetic rubber or urethane foam, may be interposed to extend in the transverse direction X. 
     In the front and rear waist regions  11 ,  12 , the outer sheet  23  and the leakage-barrier sheet  32  extend outward beyond the side edges of the inner sheet  22 , and the side edges of the leakage-barrier sheet  32  define the side edges  38 ,  39  in the transverse direction X. The segments of the outer sheet  23  and the leakage-barrier sheet  32  extending outward beyond the side edges  38 ,  39  respectively define front and rear side flaps  43 ,  44 . Proximal ends  15   a ,  16   a  of the paired tape-fastener tabs  15 ,  16  are interposed between the outer sheet  23  and the containment flaps  34 ,  35  in the respective rear side flaps  44  and fixed to these elements  23 ,  34 ,  35  with hot melt adhesives (not shown) applied to the respective inner surfaces of these elements  23 ,  34 ,  35 . Distal ends  15   b ,  16   b  of the tape-fastener tabs  15 ,  16  extend outward from the side edges of the rear side flaps  44  (i.e., the side edges  12   b  of the rear waist region  12 ) in the direction of the transverse axis Q as has previously been described. These distal ends  15   b ,  16   b  of the tape-fastener tabs  15 ,  16  are provided with the first fastener zones  17  on the skin-facing sides thereof. 
     The containment flaps  34 ,  35  respectively include proximal edges  45  defining portions of the side edges  38  and  39 , front and rear fixed ends  46   a ,  46   b  fixed to the skin-facing side of the inner and outer sheets  22 ,  23  in the front and rear waist regions  11 ,  12  and distal edges  47  extending in the longitudinal direction Y between the front and rear fixed ends  46   a ,  46   b  and defined by folding inner side edges of the containment flaps  34 ,  35  inward. Outboard of the opposite side edges of the leakage-barrier sheet  32  as viewed in the transverse direction X, two strand-like or string-like leg elastics  48  extending in the longitudinal direction Y are attached under tension contractibly between the proximal edges  45  of the respective containment flaps  34 ,  35  and the opposite sided edges of the outer sheet  23 . Two strand-like or string-like cuff elastics  49  extending in the longitudinal direction Y contractibly are attached in a contractible manner to each of the distal edges  47 . With the diaper  10  put on the wearer&#39;s body, the distal edges  47  are spaced upward from the skin-facing side of the inner sheet  22  under contraction of the cuff elastics  49  and thereby can contain bodily waste inboard of the containment flaps  34 ,  35 . 
     Referring to  FIGS. 2 and 3 , the inner surface of the outer sheet  23  opposed to the skin-facing side of the bodily fluid absorbent structure  24  in the crotch region  13  may be provided with indicator means  51  including for example three line segments extending in the longitudinal direction Y. Each of the indicator means  51  may be formed of an ink layer adapted to change color and to be visually recognized from the outside when it gets wet with bodily waste such as urine. Though not shown, a cover sheet containing a sufficient quantity of surfactant agent may be interposed between the indicator means  51  and the outer sheet  23  and thereby to facilitate the indicator means  51  to be visually recognized. 
     Referring to  FIG. 4 , the opposite side edges  24   c ,  24   d  of the bodily fluid absorbent structure  24  are segmented, for convenience of illustration, into front side edges  53  rectilinearly extending across the front waist region  11  and then slightly curving inward in the crotch region  13 , rear side edges  54  rectilinearly extending across the rear waist region  12  and then slightly curving inward in the crotch region  13 , and concavely curved side edges  56  extending between the front and rear side edges  53 ,  54 . The opposite side edges  24   c ,  24   d  respectively have front stiffness changing points  57  and rear stiffness changing points  58  corresponding to intersections of the front and rear side edges  53 ,  54  and the concavely curved side edges  56 . A stiffness boundary line  61   a  connecting the front stiffness changing points  57 , a stiffness boundary line  61   b  connecting the rear stiffness changing points  58 , and the opposite concavely curved side edges  56 , define a high stiffness region  61  in which a plurality of debosses are arranged, having a stiffness higher than the stiffness of the remaining region as a whole. 
     The present embodiment is exemplarily described herein on the basis of an S-sized diaper  10  for babies. Specifically, the length dimension L 1  of the chassis  14  as measured in the longitudinal direction Y is in a range of about 380 to about 420 mm and the length dimension L 2  of the bodily fluid absorbent structure  24  as measured in the longitudinal direction Y is in a range of about 330 to about 360 mm. More specifically, the length dimension L 3  as measured from the front end  24   a  of the bodily fluid absorbent structure  24  to the stiffness boundary line  61   a  connecting the front stiffness changing points  57  is in a range of about 70 to about 90 mm and the length dimension L 4  as measured in the longitudinal direction Y from the stiffness boundary line  61   a  connecting the front stiffness changing points  57  to the stiffness boundary line  61   b  connecting the rear stiffness changing points  58  (i.e., a length dimension of the high stiffness region  61  as measured in the longitudinal direction Y) is in a range of about 130 to about 160 mm. In addition, the distance L 5  between the stiffness boundary line  61   b  connecting the rear stiffness changing points  58  and the rear end  24   b  of the bodily fluid absorbent structure as measured in the longitudinal direction Y is in a range of about 110 to about 130 mm. As will be apparent from these specific dimensional values and the arrangement illustrated, the high stiffness region  61  is biased towards the front waist region  11 . 
     Conventionally, when a bodily fluid absorbent structure  24  is formed with concavely curved side edges  56 , such bodily fluid absorbent structure  24  tends to easily fit the wearer&#39;s thighs. However, a region of the absorbent core  26  between the opposite concavely curved side edges  56  may lose its initial shape due to being squeezed between the thighs. To overcome this problem, according to one embodiment, the high stiffness region  61  is defined between the opposite concavely curved side edges  56  and thereby the bodily fluid absorbent structure  24  can fit the wearer&#39;s body in the crotch region  13  and in addition should not noticeably lose its initial shape; in consequence, the bodily fluid absorption performance thereof should not be deteriorated. 
     Referring to  FIGS. 5 and 6 , the debosses  31  are arranged intermittently at regular intervals in a so-called zigzag-pattern (staggered pattern) in the longitudinal direction Y as well as in the transverse direction X. In  FIG. 6 , the thickness direction of the bodily fluid absorbent structure  24  is indicated by Z. The debosses  31  are formed by compressing the bodily fluid absorbent structure  24  from above using appropriate pressing means such as an debossing roller. Each deboss  31  has a density and a stiffness higher than that of a non-compressed zone. Specifically, the high stiffness region  61  includes transverse high stiffness zones  62  each defined by a plurality of debosses  31  arranged at regular intervals in transverse direction X and transverse low stiffness zones  63  each defined by a zone formed with none of the debosses  31 . The high stiffness region  61  further includes longitudinal low stiffness zones  64  extending in the longitudinal direction Y each defined by a zone formed with none of the debosses  31 . In  FIG. 5 , for convenience of illustration, the transverse low stiffness zone  63  is indicated by dots, the transverse high stiffness zone  62  is indicated by hatching, and the longitudinal low stiffness zone  64  is indicated by diagonal lines. 
     Each of the debosses  31  preferably has a generally elliptical shape which has a “height” in the longitudinal direction Y, in other words, a width dimension W 1  of the respective transverse high stiffness zones  62 , in a range of about 0.5 to about 3.0 mm, preferably in a range of about 0.8 to about 1.5 mm and a “width” in the transverse direction X in a range of about 2.0 to about 6.0 mm, preferably about in a range of about 2.5 to about 4.0 mm. The distance between each pair of debosses which are obliquely adjacent in the transverse direction X, in other words, a width dimension W 3  of the longitudinal low stiffness zone  64 , is in a range of about 3.0 to about 8.0 mm, preferably in a range of about 4.0 to about 6.0 mm, and a length dimension defined between each pair of the debosses  31  which are adjacent in the longitudinal direction Y, in other words, a width dimension W 4  of the transverse low stiffness zone is in a range of about 4.0 to 10.0 mm, preferably in a range of about 5.0 to about 8.0 mm. A distance W 5  between adjacent debosses  31  is in a range of about 5.0 to about 9.0 mm and by setting the distance W 5  at about 5.0 mm or longer, the force exerted on the debosses  31  in the longitudinal direction Y can be dispersed, as will be described later in detail. 
     Referring to  FIG. 6 , a thickness dimension H 1  of a non-compressed zone  66  defined between a pair of adjacent debosses  31  is in a range of about 2.5 to about 3.5 mm, preferably in a range of about 2.8 to about 3.2 mm, and a thickness dimension H 2  of each deboss  31  is in a range of about 1.0 to about 2.0 mm, preferably in a range of about 1.5 to about 2.0 mm. While the deboss  31  is illustrated by way of example as having a generally elliptical shape which is relatively long in the transverse direction X, the shape of the deboss  31  may be selected from other various shapes such as rectangle, rhombus and isosceles triangle, so far as the effect of the present invention can be achieved, in other words, the length dimension W 2  (width) in the transverse direction X is larger than the length dimension W 1  (height) in the longitudinal direction Y. 
     Referring again to  FIG. 4 , the indicator means  51  are preferably formed between each pair of the adjacent longitudinal low stiffness zones  64  to extend in the longitudinal direction Y and to overlap the plural arrays of the debosses  31  each arranged intermittently in the longitudinal direction Y. The indicator means  51  are formed in this manner to overlap zones in which the debosses  31  are intermittently arranged. These zones are strongly resistant to getting creased in the longitudinal direction Y and, in consequence, the visibility of the indicator means  51  should not be hindered by longitudinal creases. 
     Referring to  FIG. 7  showing the diaper  10  according to the present embodiment as put on the wearer&#39;s body, a height dimension H 3  of ridge  70  facing the wearer&#39;s crotch region (i.e., a dimension as measured from respective lower ends of the opposite concavely curved side edges  56  to an apex  70   a  of the ridge  70 ) is smaller than that in the diaper  110  of the prior art, as will be apparent from a comparison with  FIG. 12  which illustrates the bodily fluid absorbent structure  124  in the diaper of the prior art as put on the wearer&#39;s body. This is for the reason described below. With the diaper  110  of prior art put on the wearer&#39;s body, the bodily fluid absorbent structure  24  lying in the middle of the crotch region  13  may be formed with relatively significant longitudinal creases  171  as the structure  24  is squeezed between the wearer&#39;s thighs and may be forced to be displaced inward such that the ridge  170  might be formed. Such a ridge  170  may dig into the wearer&#39;s bottom cleavage and not only make the wearer uncomfortable but also cause bodily fluids to move along the ridge and eventually leak sideways beyond the leg-openings. 
     In the diaper  10  according to the present embodiment, the bodily fluid absorbent structure  24  is formed with the high stiffness region  61  including a plurality of debosses  31 , and consequently the stiffness in this region  61  is higher than in the remaining zone. In this way, the bodily fluid absorbent structure  24  is rarely twisted in this zone and is strongly resistant to the development of longitudinal creases. Particularly for the reason that each of the debosses  31  is shaped to be relatively long in the transverse direction X, sufficiently high stiffness in the transverse direction X is assured in the high stiffness region  61  to prevent the absorbent core  26  from significantly losing its initial shape even when the high stiffness region  61  is squeezed in the wearer&#39;s crotch region. With the diaper  10  put on the wearer&#39;s body, plural transverse creases  72  extending in the transverse direction X appear in the transverse low stiffness zones  63  and function to alleviate the development of any deep longitudinal creases. In consequence, the ridge  70  does not protrude upward to an unacceptable extent. Also in the longitudinal direction Y, the low stiffness zones  64  are formed and the longitudinal creases  71  also appear in these zones  64 . However, as will be apparent from  FIG. 5 , the width dimension W 4  of the transverse low stiffness zone  63  is larger than the width dimension W 3  of the longitudinal low stiffness zone  64  and the range in which the transverse creases  72  are formed is wider than the range in which the longitudinal creases  71  are formed. Consequently, development of the longitudinal creases  71  can be restricted or, at least, development of relatively large and deep longitudinal creases  71  can be restricted. 
     While the arrangement of the debosses  31  in a zigzag-pattern inevitably leads to the development of relatively small transverse creases  72  in the transverse high stiffness zones between each pair of adjacent debosses  31 , such transverse creases  72  are finely dispersed and therefore these small transverse creases do not link with one another and do not cooperate with the transverse low stiffness zone  63  to form relatively significant transverse creases  72 . Referring to  FIG. 5 , a force F 1  in the longitudinal direction Y which would lead to development of the longitudinal creases  71  is exerted on the respective debosses  31  when the crotch region  13  is squeezed between the wearer&#39;s thighs. However, the deboss  31  has a shape which is relatively long in the transverse direction X and, as indicated by arrows F 2 , F 3 , such force is dispersed toward the obliquely adjacent debosses  31 . Consequently, development of the longitudinal creases  71  is restricted and it is correspondingly difficult to maintain a temporary shape and height of the ridge  70 . 
     In this way, comparing to a diaper of the prior art, the ridge  70  of the bodily fluid absorbent structure  24  is relatively low and the shape of the ridge  70  is not maintained. In consequence, the ridge  70  should not dig into the wearer&#39;s bottom cleavage  81 . Specifically, to achieve the effect of the present invention, the height dimension H 3  of the convexly ridge  70  is preferably about 33 mm or less as indicated by the measurement result of the “compression test utilizing a doll” as described hereunder. 
     In order to define the high stiffness region  61  it may be possible to use, for example, flat press working to uniformly compress an area until the area has a thickness the same as that of the debosses  31 , and thereby increase the stiffness thereof so that development of the longitudinal creases can be restricted. In this case, however, the high stiffness region  61  as a whole will have uniformly high stiffness, and the absorbent core  26  may be deteriorated in flexibility as well as in cushioning properties and eventually may be uncomfortable to wear, and the absorption capacity of the core  26  may also be deteriorated. In contrast, in the diaper  10  according to the present embodiment, the debosses  31  are arranged in a zigzag-pattern so that the transverse high stiffness zones  62  and the transverse low stiffness zones  63  extending in the transverse direction X are alternately defined in the longitudinal direction Y in the high stiffness region  61 . With such a unique arrangement, the stiffness of the high stiffness region  61  as a whole does not be unacceptably increased. Therefore, the diaper  10  does not create an uncomfortable feeling against the wearer even when the high stiffness region  61  is squeezed between the wearer&#39;s thighs. 
     The crotch region  13  is apt to come into tight contact with the inguinal region of the wearer under a rather intense compression in the transverse direction X. Considering this, the high stiffness region  61  is formed at the section of the crotch region  13  biased toward the front waist region  11  so that development of the longitudinal creases  71  due to such compression may be restricted. 
     Stiffness values in the transverse direction X in the section of the bodily fluid absorbent structure  24  formed with the high stiffness region  61  and in the section of the bodily fluid absorbent structure not formed with the high stiffness region were measured by Taber&#39;s method in accordance with JIS P 8125. A series of measurements indicated that the former is in a range of 0.027 to 0.049N/m and the latter is in a range of 0.012 to 0.033N/m. The measurement was conducted for the respective zones on the basis of test pieces each having the longitudinal dimension of 38 mm×the transverse dimension of 70 mm and, as the measuring device, a Taber Stiffness Tester manufactured by Yasuda Seiki Seisakusho LTD. was used. 
     &lt;Compression Test Using a Doll&gt; 
       FIGS. 8(   a ) and  8 ( b ) illustrate how to conduct the compression test using doll. The measurement result of the compression test for the bodily fluid absorbent structure  24  using a doll simulating the diaper wearer is indicated in Table 1. A summary of the compression test is given below. The disposable diaper according to the present invention including the bodily fluid absorbent structure  24  formed with the high stiffness region  61  was used as the inventive example. A disposable diaper including the bodily fluid absorbent structure not formed with the high stiffness region  61  and therefore having a uniform stiffness was used as a comparative example 1. A disposable diaper including the bodily fluid absorbent structure formed with the high stiffness region  61  including the same debosses  31  as those according to the present invention in size as well as in shape but relatively long in the longitudinal direction Y was used as a comparative example 2. A disposable diaper including the bodily fluid absorbent structure flat press-worked to have a substantially uniform stiffness (0.035 N/m approximately equivalent to the stiffness value in the high stiffness region  61 ) was used as a comparative example 3. It should be noted here that, in the respective disposable diapers used for the compression test, the stiffness value in the high stiffness region of the bodily fluid absorbent structure was 0.036 N/m and the stiffness value in the remaining zone of the bodily fluid absorbent structure was 0.025 N/m. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Width dimension (mm) 
                   
               
               
                   
                 of the bodily fluid 
                 Height dimension (mm) 
               
               
                   
                 absorbent structure in 
                 of the ridge in the 
               
               
                   
                 the midsection of the 
                 midsection of the 
               
               
                   
                 crotch region 
                 crotch region 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 Inventive 
                 45 
                 30 
               
               
                 Example 
               
               
                 Comparative 
                 35 
                 35 
               
               
                 Example 1 
               
               
                 Comparative 
                 35 
                 35 
               
               
                 Example 2 
               
               
                 Comparative 
                 40 
                 37 
               
               
                 Example 3 
               
               
                   
               
            
           
         
       
     
     &lt;Measuring Method&gt; 
     For every measurement on the inventive example, the comparative example 1, the comparative example 2 and the comparative example 3, the respective diapers were put on the doll made of silicon and a transverse center line was drawn along the transverse axis of the respective diapers with ink. Then the transverse center line of the respective diaper was aligned with a longitudinal central part of the crotch region of the doll to adjust so that the respective outer ends of the front waist region and the rear waist region of the diaper may come at a generally same level. The doll was prepared so that an S-size diaper fits the doll well. Specifically, a width dimension of the inguinal region is about 240 mm, a circumferential dimension of respective leg-openings is about 265 mm, a circumferential waist dimension is about 390 mm, a circumferential buttock dimension is about 380 mm and a width dimension (i.e., transverse length dimension) of central portion in the crotch region is about 25 mm. 
     Referring to  FIG. 8(   a ), a series of actions, specifically, closing the doll&#39;s opened legs and opening the doll&#39;s closed legs are repeated ten (10) times at a rate of 100 to 140° per second under the above-mentioned dimensional conditions. In this measurement, the angle between two straight lines each extending from the toe to the groin is denoted as the angle alfa and this angle alfa is 75° in the state of the legs having been fully opened and 0° in the state of the legs having been fully closed. Now the action of closing the doll&#39;s opened legs and opening the doll&#39;s closed legs is repeated ten (10) times. 
     Referring now to  FIG. 8(   b ), the doll is placed on a measuring table with the legs fully closed to lie face up, and from this state the doll&#39;s upper limbs are vertically raised ten (10) times. Then, the doll is placed on the measuring table with the legs fully opened and the diaper is taken off from the doll with a deformation of the bodily fluid absorbent structure in the crotch region of the diaper due to the above-mentioned series of actions maintained. 
     In the middle of the inked up line in the respective diapers, having been taken off from the doll, the height of the region of the bodily fluid absorbent structure convexly raised toward the bottom cleavage of the doll, specifically, the distance from the apex of the above-mentioned region to the lower end thereof was denoted as “height dimension (mm) of the ridge in the midsection of the crotch region”, and the width dimension (i.e., transverse length dimension) of the midsection of the inked up line was designated as “width dimension (mm) of the bodily fluid absorbent structure in the midsection of the crotch region”. 
     &lt;Measurement Result&gt; 
     As will be apparent from Table 1, the height dimension of the ridge in the midsection of the crotch region is smaller in the inventive example than in the comparative examples 1 through 3 and the width dimension of the bodily fluid absorbent structure in the midsection of the crotch region is larger in the inventive example than in the comparative examples 1 through 3. This is for the reason that the bodily fluid absorbent structure in the diaper as the inventive example is formed with much more transverse creasing, serving to restrict development of longitudinal creases, than those in the diapers of the comparative examples. In consequence, the ridge is lower in the inventive example than in the comparative examples and the width dimension of the bodily fluid absorbent structure is correspondingly larger in the inventive example than in the comparative examples. In this manner, it is possible for the inventive example to avoid more reliably the problem that the ridge of the bodily fluid absorbent structure might dig into the bottom cleavage of the doll (wearer). 
       FIG. 9  is a schematic diagram illustrating a part of a process to make the bodily fluid absorbent structure. In  FIG. 9 , a machine direction is designated by MD. A region in  FIG. 9  enclosed by dashed-dotted line is a part of a roller  93  used in a second pressing step illustrated in an enlarged scale. 
     Referring to  FIG. 9 , a first web  85  of original fabric for the lower sheet  28  is conveyed by a conveyor belt  84  and the absorbent cores  26  are successively transferred from a rotary drum  86  onto the first web  85 . Then, a second web  87  is transported from the upstream and lain over the absorbent cores  26  from above. The inner surface of the first web  85  is coated, in a first coating step  88 , with hot melt adhesives applied like a film and the inner surface of the second web  87  is coated, in a second coating step  89 , with hot melt adhesives in an omega-pattern. Now in a first press working step using a roller  90  having a smooth outer peripheral surface and an anvil roll  91  opposed to the roller  90 , the first web  85  and the second web  87  with the absorbent cores  26  interposed therebetween are subjected to flat press working so that the assembly of these first and second webs  85 ,  87  are bonded together with the absorbent cores  26  with hot melt adhesives applied to the respective inner surfaces of the first and second webs  85 ,  87  to form a laminate web  92 . Then, in a second press working step using roller  93  having a plurality of bosses  93   a  planted on a part of its outer peripheral surface and an anvil roll  94  opposed to the roller  93 , a predetermined region of the laminate web  92  is debossed by pressing a plurality of bosses  93   a  formed on the outer peripheral surface of the roller against the predetermined region to form the high stiffness zone  62 . After this debos sing, the laminate web  92  is cut in the cutting step (not shown) to obtain the individual bodily fluid absorbent structures  24 . Each of the bosses  93   a  of the roller  93  has a generally elliptical shape which is relatively long in the direction extending orthogonally to the machine direction MD (i.e., the width direction of the conveyor belt  84 ). 
     As will be obviously understood from the above description, the bodily fluid absorbent structure  24  as a whole has been subjected to the flat press working before it is debossed. Consequently, the not debossed portion of the bodily fluid absorbent structure  24  and the non-compressed zone  66  of the high stiffness region  61  have a uniform thickness (about in a range of 2.0 to 2.5 mm), on one hand, and the shape of the absorbent core  26  is stabilized by the flat press working, on the other hand. In this way, the debossing is relatively easy. 
     As will be understood from the part of the peripheral surface of the roller  93  enclosed by dashed-dotted line and shown in an enlarged scale in  FIG. 9 , a plurality of the bosses  93   a  formed on a part of the outer peripheral surface of the roller  93  respectively preferably have a length dimension L 6  of about 3.0 mm. The bodily fluid absorbent structure  24  preferably has a thickness dimension in a range of 2.0 to 2.5 mm after the structure  24  has been flat press worked, and each of the bosses  93   a  of the roller  93  preferably has the length dimension L 6  of about 3.0 mm, so that spots on the bodily fluid absorbent structure  24  coming in contact with the bosses  93   a  are compressed but the remaining zone maintains the thickness immediately after being flat press worked. A differential thickness dimension of the debosses  31  and the remaining zone may be regulated so that the thickness dimension difference between the debosses  31  and the remaining zone preferably may be kept to about 0.5 mm or less. In this way, the contact surface of the bodily fluid absorbent structure  24  as a whole can be kept generally uniform and thereby the wearer&#39;s feeling to wear can be prevented from being deteriorated due to irregularity of the inner surface of the bodily fluid absorbent structure  24 . 
     An inclination angle alfa included between the outer peripheral surface of the roller  93  and the boss  93   a  is preferably about 130°. The boss  93   a  preferably has a generally elliptical shape which is relatively long in a direction orthogonal to the machine direction MD. Although it will be not easy for the bosses  93   a  to be separated from the laminate web  90  under ordinary circumstances, the inclination angle of the bosses  93   a  to the outer peripheral surface of the roller  93  may be set to be gentle according to the present embodiment to prevent the bosses  93   a  from being caught by the surface of the laminate web  90  and from damaging some part of the laminate web  90 . 
     After producing the diaper  10 , a thickness meter (Digital Thickness JA-257 manufactured by PEACOCK Corporation) was used to measure the thickness of the zone of the bodily fluid absorbent structure  24  in the crotch region  13  of the diaper  10  in which the high stiffness region  61  is formed and the zone in which the high stiffness region  61  is not formed after the bodily fluid absorbent structure  24  has not been creased in the longitudinal direction as well as in the transverse direction. The measurement result indicated that a thickness difference between the region in which the high stiffness region  61  is formed and the region in which the high stiffness region  61  is not formed at all is 0.5 mm or less. In view of such measurement result, the crotch region  13  of the diaper  10  as a whole can be determined to have a smooth surface. 
     Second Embodiment 
       FIG. 10  is a view similar to  FIG. 4 , showing a second embodiment of the diaper according to the present invention and  FIG. 11  is a view similar to  FIG. 6 , showing the second embodiment of the diaper  10  according to the present invention. The basic construction of the diaper  10  according to this embodiment is substantially the same as that of the first embodiment and only the feature different from that of the first embodiment will be described hereunder. 
     In the diaper  10  according to the present embodiment, a groove  96  extending in the transverse direction X is formed between adjacent debosses  31  in the bodily fluid absorbent structure  24 . In each of the grooves  96 , the absorbent core  26  is substantially not present so that the inner surface of the upper sheet  27  and the inner surface of the lower sheet  28  overlap and are bonded to each other by the intermediary of a joining layer formed of hot melt adhesives  29 ,  30 . According to the present embodiment, the grooves  96  may be formed to keep the stiffness of the high stiffness region  61  as a whole moderate. In this way, it is possible to restrict an excessive increase of stiffness in the high stiffness region  61  due to the presence of the debosses  31 . 
     The component members of the diaper  1  are not limited to those described in this specification but other various types of material widely used in the relevant technical field may be used without limitation. Terms “first” and “second” used in the specification and claims of the present invention are used merely to distinguish the similar elements, similar positions or other similar means. 
     The first aspects described above may be arranged in at least the following item: 
     (i) A disposable wearing article including a chassis having a longitudinal direction, a transverse direction, a skin-facing side, a non-skin-facing side, a front waist region, a rear waist region, a crotch region extending in the longitudinal direction between the front and rear waist regions, and a bodily fluid absorbent structure extending in the longitudinal direction across the crotch region into the front and rear waist regions, wherein a region of the bodily fluid absorbent structure extending at least in a central area thereof is formed with a high stiffness region including a plurality of debosses spaced one from another in predetermined dimensions in each of the longitudinal direction and the transverse direction, wherein: 
     the bodily fluid absorbent structure includes an absorbent core and an upper sheet covering a surface of the absorbent core; 
     the debosses are shaped so that the length dimension thereof in the transverse direction (width) is longer than the length dimension thereof in the longitudinal direction (height); and 
     the high stiffness region includes a plurality of longitudinal low stiffness zones extending in the longitudinal direction and formed with none of the debosses, a plurality of transverse high stiffness zones formed with the debosses arranged at regular intervals in the transverse direction, and transverse low stiffness zones lying between each pair of the transverse high stiffness zones and formed with none of the debosses, the transverse low stiffness zones and transverse high stiffness zones being adjacent in the longitudinal direction. 
     One or more aspect described in the above item (i) may provide one or more of the following advantageous effects: (a) The debosses forming the high stiffness region of the bodily fluid absorbent structure are respectively shaped so that a length dimension thereof in the transverse direction (width) is longer than a length dimension thereof in the longitudinal direction (height); the high stiffness region includes the transverse high stiffness zones formed of the debosses intermittently arranged in the transverse direction; and the transverse low stiffness zones each defined between a pair of adjacent transverse high stiffness zones. With this unique arrangement, a plurality of the transverse creases can be easily developed on the bodily fluid absorbent structure of the diaper put on the wearer&#39;s body. Development of the transverse creases advantageously restricts development of the longitudinal creases in the longitudinal low stiffness zones which may cause the central portion of the bodily fluid absorbent structure to be convexly raised up toward the wearer&#39;s crotch region. In consequence, such ridge can be restricted as low as possible and such ridge should not dig into the wearer&#39;s bottom cleavage. 
     Additionally, one or more of the following non-limiting embodiments are provided in accordance with further aspects: 
     (ii) The debosses are arranged in a zigzag-pattern on the skin-facing side or on the non-skin-facing side, or on both the skin-facing and non-skin-facing sides.
 
(iii) In the high stiffness region, the width dimension of the transverse low stiffness zones in the longitudinal direction is larger than the width dimension of the longitudinal low stiffness zones in the transverse direction.
 
(iv) Each pair of adjacent debosses are spaced from each other by about 5.0 mm or more.
 
(v) Each pair of adjacent debosses are spaced from each other by about 5.0 mm to about 9.0 mm
 
(vi) The high stiffness region is formed, between each pair of the debosses being adjacent in the transverse direction, with grooves extending in the transverse direction and substantially not occupied by the absorbent core.
 
(vii) The absorbent core has side edges concavely curved inward in the central zone of the crotch region, and the high stiffness region is formed between the concavely curved side edges.
 
(viii) The high stiffness region is formed in an area of the crotch region biased toward the front waist region.
 
(ix) In the crotch region, a differential thickness dimension between the area of the bodily fluid absorbent structure formed with the high stiffness region and the area of the bodily fluid absorbent structure not formed with the high stiffness region is about 0.5 mm or less.
 
     According to the embodiments in the above (ii) to (ix), the advantageous effect (s) set forth at (a) is/are better ensured. Further advantageous effects of the respective embodiments may be obtained as discussed in the respective related descriptions.