Patent Publication Number: US-2017348167-A1

Title: Absorbent article

Description:
TECHNICAL FIELD 
     The present invention relates to an absorbent article, and in particular, to a disposable diaper. 
     BACKGROUND ART 
     Absorbent articles such as sanitary napkins and disposable diapers include an absorber to absorb most of a body fluid such as discharged urine (hereinafter also referred to as a “body fluid”). Therefore, after an absorbent article absorbs the body fluid, a space between the skin and the absorbent article is humid, causing the skin to feel sticky. Conventional absorbent articles are designed to suppress a possible sticky feeling resulting from absorption of the body fluid. For example, regular fine recesses and protrusions such as a staggered pattern are formed on a front surface sheet of an absorbent article that comes into direct contact with the skin, as disclosed in PTL 1. Furthermore, PTL 2 discloses that a front surface sheet, along with an absorbent, is compressed into a recessed and protruding shape. As described above, the front surface sheet (or the front surface sheet and the absorbent) is provided with recesses and protrusions to allow tips of protruding portions to contact the skin. Thus, this configuration reduces the area of a part of the front surface sheet that contacts the skin, suppressing the sticky feeling, compared to a configuration with no recesses or no protrusions. 
     CITATION LIST 
     Patent Literature 
     PTL 1 Japanese Patent Laid-Open No. 2003-275239 
     PTL 2 Japanese Patent Laid-Open No. 2012-213488 
     SUMMARY OF INVENTION 
     Technical Problem 
     For example, a disposable diaper needs to have an absorbing capacity sufficient to reliably absorb an amount of urine corresponding to several times of urination. To enhance the absorbing capacity, many absorbers are formed of a mixture of pulp and a super absorbent polymer (hereinafter also referred to as a “SAP”). Thus, in a case where the absorbent article described in PTL 1 absorbs the body fluid, the absorber bulges significantly due to the effect of the SAP. The bulge of the absorber itself offsets the recesses and protrusions provided on the front surface sheet, which thus produce little effect. 
     Furthermore, in the absorbent article described in PTL 2, the recesses and protrusions are formed by compressing the front surface sheet and the absorbent article. However, the recesses and the protrusions still need to be improved in terms of dimensions in order to suppress the sticky feeling. 
     In view of these problems, an object of the present invention is to provide an absorbent article that restrains the skin from feeling sticky in a case where the skin comes into contact with an absorber having absorbed a body fluid. 
     Solution to Problem 
     An absorbent article in the present invention has a liquid-permeable front surface sheet, a liquid-impermeable back surface sheet, and an absorber disposed between the front surface sheet and the back surface sheet. The absorbent article in the present invention has a groove portion entirely or partly composed of a recessed portion, the recessed portion being formed on the front surface sheet side of the absorbent article by integrally joining the front surface sheet and the absorber together, and a flat portion enclosed by the groove portion. A diameter of a maximum inscribed circle inscribed in the flat portion is at least five times and at most 20 times as large as a width of the groove portion along a radial direction of the maximum inscribed circle. 
     Furthermore, the recessed portion may enclose at least 50% of an outer periphery of the flat portion. 
     The recessed portion is formed by compressing the front surface sheet and the absorber together, and a depth of the recessed portion is at least half of a thickness of each of the flat portion. 
     Additionally, the groove portions may be shaped like a lattice. 
     Furthermore, an absorbent article in the present invention has a liquid-permeable front surface sheet, a liquid-impermeable back surface sheet, and an absorber disposed between the front surface sheet and the back surface sheet. The absorbent article in the present invention has a groove portion entirely or partly composed of a recessed portion, the recessed portion being formed and arranged on the front surface sheet side of the absorbent article by integrally joining the front surface sheet and the absorber together and a flat portion positioned between the groove portions. A diameter of a maximum inscribed circle inscribed in the flat portion sandwiched between the two adjacent groove portions is at least five times and at most 20 times as large as a width of the groove portion along a radial direction of the maximum inscribed circle. 
     Additionally, the groove portions may be arranged at regular intervals. 
     Furthermore, an amount of SAP per unit area in the absorber may be at least 0.01 g/cm 2 . 
     Additionally, the absorbent article may be a disposable diaper. 
     Advantageous Effects of Invention 
     The absorbent article in the present invention includes the flat portion having at least a given area, and thus, the flat portion allows a body fluid to be quickly absorbed. Furthermore, in the present invention, the absorbent article does not perfectly fit a curved surface of a wearer&#39;s body but locally forms a gap between the absorbent article and the curved surface. Consequently, even after absorbing the body fluid, the absorbent article is likely to have a gap between the absorbent article and the skin and is thus unlikely to cause the wearer to feel sticky. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view depicting the appearance of Embodiment 1 in which an absorbent article according to the present invention is applied to a pull-up type disposable diaper; 
         FIG. 2  is a perspective view depicting a lower body wearing the diaper depicted in  FIG. 1 , as seen from the back side; 
         FIG. 3  is a perspective view illustrating that the diaper depicted in  FIG. 1  has been disassembled; 
         FIG. 4  is a partial top view of a groin portion of the diaper depicted in  FIG. 1 , as seen from a top sheet side; 
         FIG. 5  is a sectional view taken along a V-V direction of the groin portion of the diaper depicted in  FIG. 4 ; 
         FIG. 6  is a schematic diagram illustrating that after an absorbing portion of the diaper in Embodiment 1 absorbs a body fluid, the diaper contacts a curved surface of a wearer&#39;s body with gaps kept between the diaper and the curved surface; 
         FIG. 7  is an enlarged partial top view of a front surface of the absorbing portion of the diaper in Embodiment 1; 
         FIG. 8  is a partial top view illustrating an example in which compressed portions are arranged at intervals to form a recessed portion; 
         FIG. 9  is a sectional view taken along an IX-IX direction in  FIG. 8 ; 
         FIG. 10  is a sectional view taken along an X-X direction in  FIG. 8 ; 
         FIG. 11  is a partial top view illustrating an example of a flat portion pattern formed by arranging recessed portions in the absorbing portion at regular intervals; 
         FIG. 12  is a partial top view illustrating an example of a flat portion pattern formed by arranging wavelike recessed portions in the absorbing portion; 
         FIG. 13  is a partial top view illustrating an example of a flat portion pattern formed by arranging circular recessed portions in the absorbing portion at regular intervals; and 
         FIG. 14  is a partial top view illustrating an example of a flat portion pattern formed by arranging, in the absorbing portion, discontinuous recessed portions shaped like regular hexagons. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of an absorbent article according to the present invention will be described in detail with reference to  FIGS. 1 to 14 . However, the present invention is not limited to the aspects of the present embodiment. 
       FIG. 1  depicts a perspective view of the appearance of Embodiment 1 in which the present invention is applicable to a pull-up type disposable diaper (hereinafter simply referred to as a “diaper”)  10  as seen from a front side, and  FIG. 2  is a perspective view of the appearance as seen from a back side.  FIG. 2  depicts the lower body of an infant wearing the diaper  10  as seen from the back side. Moreover,  FIG. 3  illustrates that the diaper  10  depicted in  FIG. 1  and  FIG. 2  is in a divided state where the diaper  10  is torn and unfolded. 
     The diaper  10  in the present embodiment has a front body area  10 F, a back body area  10 R, and a groin area  10 C connecting the front body area  10 F and the back body area  10 R together. Furthermore, a waist opening  10 W is formed such that a wearer&#39;s waist portion is surrounded by the front body area  10 F and the back body area  10 R. A part of the front body area  10 F, a part of the back body area  10 R, and the groin area  10 C form a lateral pair of leg openings  10 L surrounding the thigh portions of the wearer&#39;s legs. 
     As depicted in  FIG. 2 , in a case where the diaper  10  is worn by the wearer, the front body area  10 F is positioned the wearer&#39;s abdominal side, whereas the back body area  10 R is positioned on the wearer&#39;s back side. The groin area  10 C covers the wearer&#39;s groin, and the wearer&#39;s legs are inserted through the lateral pair of leg openings  10 L, respectively. Therefore, the leg openings  10 L are each located at any position between the wearer&#39;s groin and the vicinity of the corresponding thigh. 
     Furthermore, on the back body area  10 R of the diaper  10 , a disposal tape  10 T is provided that is used to tape the rolled diaper  10  in a case where the diaper  10  is disposed of. 
     Now, a virtual line P will be described that extends in a direction along the central axis of the body in a case where the diaper  10  is worn in an appropriate orientation. As depicted in  FIG. 1  and  FIG. 2 , the virtual line P extends along the central axis of the body, and at a central portion of the diaper  10 , extends through the groin portion from the abdominal side toward the back side. Specifically, in a case where, for example, the waist side of the diaper  10  is designated as an upper side and the groin side is designated as a lower side, the virtual line P extends along the front surface of the diaper  10  and in an up-down direction and extends through the groin portion and also in the up-down direction on the back side. Positional relations among the areas of the diaper  10  will be described using the virtual line P as required, as follows. 
     Now, as depicted in  FIG. 3 , the diaper  10  in the present embodiment is formed by laying a cover sheet  11 , a back sheet (back surface sheet)  12 , an absorber  13 , a top sheet (front surface sheet)  14 , and a pair of side sheets  18  on top of one another in this order from the outside and joining these components together; the top sheet  14  contacts the wearer&#39;s skin, and the side sheets  18  allow raised gathering to be formed. Moreover, the cover sheet  11  is divided into a pad cover sheet  11 A placed under the back sheet  12 , an inner cover sheet  11 B, and an outer cover sheet  11 C all of which are formed of a thin nonwoven cloth so as to have a smooth feel. The inner cover sheet  11 B and the outer cover sheet  11 C, which define the front body area  10 F and the back body area  10 R of the diaper  10 , are joined together such that laterally opposite edges of the inner cover sheet  11 B face the corresponding laterally opposite ends of the outer cover sheet  11 C, thus forming closed portions  10 J. Consequently, the above-described waist opening  10 W is defined. The inner cover sheet  11 B and the outer cover sheet  11 C are each divided into two pieces at the groin area  10 C portion so as to expose the pad cover sheet  11 A at the groin portion. Therefore, the lateral pair of leg openings  10 L, which surrounds the thigh portions of the respective legs, is defined by ends of the pad cover sheet  11 A and ends of the closed portions  10 J. The back sheet  12 , which is impermeable to liquids, is joined to the pad cover sheet  11 A. The above-described absorber  13  is disposed between the back sheet  12  and the top sheet  14 , which is permeable to liquids. The top sheet  14  is joined to the back sheet  12  via the absorber  13 . The pair of side sheets  18  is joined to the top sheet  14 . Rubber threads  19  are stretched and joined to the pair of side sheets  18  at edges thereof in order to allow raised gathering to be formed. The inner cover sheet  11 B and the outer cover sheet  11 C may each be an integral sheet that is not discontinuous at the groin portion. The gathering may be formed at the leg openings  10 L by the rubber threads. 
       FIG. 4  is a partial top view of the groin portion of the diaper  10  as seen from the top sheet  14 . 
     The absorber  13  in the present embodiment, positioned under the top sheet  14 , is mainly formed of pulp and SAP. The ratio of the amount of SAP to the amount of pulp is preferably 1:0.8 to 1:1.5. Furthermore, the amount of SAP per unit area in the absorber  13  is preferably 0.01 g/cm 2 . In the absorber  13  in the present embodiment, the amount of pulp per unit area is 0.017 g/cm 2 , and the amount of SAP per unit area is 0.023 g/cm 2 . 
     The absorber  13  has an elongate shape so as to span the front body, the groin, and the back body. The absorber  13  is partitioned into three portions, a front body portion M 1 , a groin portion M 2 , and a back body portion M 3  as depicted in  FIG. 4 . In the groin portion M 2 , cutout portions  13 A are formed that are shaped like circular arcs conforming to the lateral pair of leg openings  10 L surrounding the thigh portions of the respective legs. The cutout portions  13 A may be omitted depending on the size of the absorber  13 . Furthermore, the absorber  13  in the present embodiment is provided with the cutout portions  13 A and shaped like a hourglass that is narrower at a central portion thereof than at each of a front and a back ends thereof. However, the shape of the absorber in the present invention is not limited to this. In a case where a direction from the front body portion toward the back body portion is designated as a front-back (up-down) direction and a direction orthogonal to the front-back direction is designated as a lateral direction, the absorber in the present invention may have various shapes as follows. For example, corners of the front and back ends (upper and lower ends) may be cut round or the absorber may be shaped like an ellipse that extends in the front-back (up-down) direction, a circle, a rectangle in which a front-back (up-down) length is different from a lateral length, or a square in which the front-back (up-down) length is the same as the lateral length. 
     An absorbing portion of the diaper  10  including the top sheet  14  and the absorber  13  (hereinafter simply referred to as an “absorbing portion”) includes a groove portion  21  and a flat portion  24 . In the descriptions in the specification and the claims, the “groove portion” refers to a portion entirely or partly composed of a recessed portion. In the descriptions in the specification and the claims, the “recessed portion” refers to that part of the absorbing portion of the absorbent article (in the present invention, the diaper  10 ) which has a thickness that is at most half the thickness of the uncompressed absorbing portion. Furthermore, in the descriptions in the specification and the claims, the “flat portion” refers to that part of the absorbing portion of the absorbent article which corresponds to the entire absorbing portion except for the groove portion. The flat portion may be shaped like a chevron, a wave, a trapezoid, a rectangle, or the like. In particular, for the chevron shape, a peak portion of the chevron shape contacts the skin, whereas a base portion of the chevron shape is unlikely to contact the skin. 
     The flat portion  24  has two types of flat portions, a first flat portion  24   a  that is enclosed by the groove portion  21  and a second flat portion  24   b  that is not enclosed by the groove portion  21 . In the present embodiment, as depicted in  FIG. 4 , all of the groove portions  21  are composed of the recessed portion  21   r,  and thus, the flat portion  24  has the first flat portion  24   a  that is enclosed by the recessed portion  21   r  and the second flat portion  24   b  that is not enclosed by the recessed portion  21   r.  The diaper  10  according to the present embodiment includes at least the first flat portion  24   a . In the present embodiment, as depicted in  FIG. 4  and  FIG. 5  described below, the absorbing portion is provided with the regularly arranged recessed portions  21   r  by being compressed from a front surface of the top sheet  14  toward the absorber  13 . Thus, a surface that contacts the skin is partitioned into a plurality of areas. 
     In other words, the absorbing portion, which is originally generally flat, is, for example, partly compressed and recessed by embossing to form the recessed portion  21   r.  The recessed portions  21   r  serve to divide the absorbing portion into a plurality of the flat portions  24 . Therefore, all the adjacent first flat portions  24   a  are separated from each other by the corresponding recessed portion  21   r  such that the first flat portions  24   a  and the recessed portions  21   r  are regularly arranged on the front surface of the absorbing portion. 
     In the present embodiment, the recessed portions  21   r  are not formed up to each end of the absorbing portion of the diaper  10  in a width direction (the lateral direction in  FIG. 4 ) but are formed like bands in a central portion of the diaper  10  along a longitudinal direction (the up-down direction in  FIG. 4 ). A recessed portion forming area N 1  is defined as an area of the absorbing portion where the recessed portions  21   r  are formed, and a recessed portion non-forming area N 2  is defined as areas located at widthwise opposite ends of the absorbing portion where no recessed portions  21   r  are formed. As described below, the configuration with the recessed portion  21   r  is more effective than a configuration with no recessed portion  21   r  so long as the recessed portion  21   r  are formed at least in the central portion of the diaper  10 . The present embodiment includes the recessed portion non-forming area N 2 . However, the present invention is not limited to this form. Of course, the recessed portion  21   r  may be formed up to each end of the absorber  13 . Therefore, in the present invention, the recessed portion non-forming area N 2  may be omitted. 
       FIG. 5  is a sectional view of the groin portion of the diaper depicted in  FIG. 4 , the view being taken along a V-V direction.  FIG. 5  depicts a section of the recessed portions  21   r  extending like diagonal lattices. An adhesive is applied to a surface of the top sheet  14  that contacts the absorber  13 . The top sheet  14  and the absorber  13  are compressed by embossing to form the recessed portions  21   r.  Consequently, the top sheet  14  and the absorber  13  are engaged with each other all over the recessed portion  21   r  spanning a bottom surface (bottom wall)  22   a  of the recessed portion  21   r  and a wall surface (side wall)  22   b  of the recessed portion  21   r,  and are thus integrally joined together. An example of the thickness of the top sheet  14  and the absorber  13  at the bottom portion of the recessed portion  21   r  (the thickness of the absorbing portion) is one-sixth of the thickness of the uncompressed absorbing portion. In this case, the depth reaches approximately 80% of the thickness of the top sheet  14  and the absorber  13  that are laminated to each other and is larger than in a case where the recesses and protrusions are formed only on the top sheet  14 . The magnitude of compression of the absorber  13  preferably corresponds to approximately half to one-seventh of the thickness of the uncompressed absorber  13 . More preferably, the magnitude of compression of the absorber  13  corresponds to approximately quarter to one-seventh of the thickness of the uncompressed absorber  13 . Furthermore, the depth of the recessed portion  21   r  is preferably six-sevenths to half and more preferably six-sevenths to three-fourths of the thickness of the flat portion  24 . The present invention is applicable to an absorber having a thickness that is not constant (that varies) before embossing. 
     For the diaper, for example, a large amount of urine discharged at a time needs to be instantaneously absorbed by the absorber  13 . On the other hand, the recessed portion  21   r,  where the top sheet  14  and the absorber  13  are compressed, is less likely to absorb the body fluid than an area where the absorber  13  is not compressed, because the absorber  13  is compressed in the recessed portion  21   r.  The main absorbing area is the flat portion  24  that is not compressed. Therefore, the flat portion  24  needs to have an area sufficient to allow the body fluid to be instantaneously absorbed and held. 
     For the flat portion  24  in the present invention, this area is determined based on observations described below. 
     As depicted in  FIG. 1  and  FIG. 2 , in a case where the diaper  10  is worn by the wearer, the absorber  13  is positioned so as to extend from the abdominal side toward the back side and to cover the entire groin portion. As seen in  FIG. 2 , while the wearer is standing, the diaper  10  is deflected and droop down (in a direction depicted by arrow J) such that the central portion of the groin area  10 C corresponds to the peak of the deflected shape. This prevents the wearer from coming into close contact with the central portion of the groin portion. The reason why this configuration is used is as follows. In a case where the absorber  13  bulged with the body fluid comes into close contact with the groin, the groin is likely to be steamed. Thus, a certain amount of space is preferably provided between the groin and the diaper  10 . On the other hand, a buttocks area K that is continuous with the groin area  10 C and that faces a round buttocks portion of the body is a portion that is likely to come into close contact with the skin in conjunction with an operation of pulling up the diaper  10 . 
     In a case where the wearer discharges the body fluid while lying on the wearer&#39;s back, the body fluid is likely to flow not only through the groin portion  10 C but also through the back body area  10 R. In particular, while the wearer is lying on the wearer&#39;s back, the buttocks area K is located at the lowest position and is thus an area into which the body fluid is likely to flow. Also in a case where the wearer sits up, the buttocks area K is located at the lowest position and is thus an area into which the body fluid is likely to flow. 
       FIG. 6  is a schematic diagram illustrating that after the absorbing portion of the diaper  10  in Embodiment 1 absorbs the body fluid, the diaper  10  contacts the curved surface of the wearer&#39;s body with gaps kept between the diaper and the curved surface. 
     As depicted in  FIG. 6 , in the diaper  10  in the present embodiment, the absorbing portion is provided with the first flat portions  24  having above certain sizes and the recessed portions  21   r  that separates the adjacent first flat portions  24   a  from each other. Therefore, in a case where the diaper  10  is positioned along the curved surface of the wearer&#39;s body B, the recessed portions  21   r  appear at regular intervals such that the recessed portions  21   r  arranged at the regular intervals form gaps between the diaper  10  and the skin. 
     In addition, the recessed portion  21   r  is likely to fold in the width direction of the recessed portion  21   r  at portions where both the top sheet  14  and the absorber  13  are compressed. That is, the absorbing portion folds at the bottom surfaces  22   a  of the recessed portion  21   r  so as to form valley folds or peak folds, and thus provides multiple surfaces arranged along the body so as to approximate the curved surface of the body with reference to the surface width of each first flat portion  24   a . Consequently, each of the first flat portions  24   a  is arranged along the curve of the body B, and thus, the absorbing portion does not perfectly fit the circular arc of the curved surface but a space B 1  is formed between the skin and the absorbing portion facing the skin. 
     Furthermore, even after the absorbing portion absorbs the body fluid, each first flat portion  24   a  bulges like a small dome such that the center of the first flat portion  24   a  corresponds to the peak of the dome. As depicted by a dotted line S in  FIG. 6 , the first flat portion  24   a  has a certain size and thus bulges like a dome (so as to have a vault-like cross section). Therefore, even in a case where the first flat portion  24   a  bulges and comes into contact with the skin, the contact area is not the entire area of the first flat portion  24   a  but corresponds to the peak of the dome. This reduces the area over which the first flat portion  24   a  contacts the skin, suppressing a possible sticky feeling. Furthermore, gaps are present in the areas other than the contact portions, thus providing ventilation and enabling the skin to be restrained from being steamed or getting diaper rash. 
     As described above, in order to suppress the sticky feeling, the first flat portion  24   a  needs to have a certain size. Specifically, the optimal size of the first flat portion  24   a  is determined based on the diameter of the maximum inscribed circle inscribed in the first flat portion  24   a  enclosed by the recessed portion  21   r  (a groove portion  21 ) and the width of the recessed portion  21   r  (a groove portion  21 ) along a radial direction of the maximum inscribed circle. Here, the diameter of the maximum inscribed circle is denoted by R 1 , and the above-described width of the recessed portion  21   r  is denoted by L 1 . 
     As depicted in  FIG. 7 , the width L 1  of the recessed portion  21   r  in the present embodiment is approximately 2 mm. With the feel taken into account, the width L 1  of the recessed portion  21   r  is preferably 1 mm or more and 5 mm or less. Furthermore, in the present embodiment, as depicted in  FIG. 7 , the recessed portion  21   r  enclose each first flat portion  24   a  so as to shape the first flat portion  24   a  like a square. Here, the length of each side of the square of the first flat portion  24   a  enclosed by the recessed portion  21   r  is denoted by L 2 . In the present embodiment, the length L 2  is approximately 30 mm. Therefore, the diameter R 1  of the maximum inscribed circle inscribed in the square is also approximately 30 mm. The size of the flat portion  24  is preferably such that 5 mm≦L 2 ≦40 mm and 5 mm≦R 1 ≦40 mm. Here, the diameter R 1  of the maximum inscribed circle is preferably at least five times and at most 20 times as large as the width L 1  of the recessed portion  21   r  and more preferably at least 10 times and at most 20 times as large as the width L 1 . In the present embodiment, the diameter R 1  is approximately 15 times as large as the width L 1 . 
     In a case where the diameter R 1  of the maximum inscribed circle is less than five times as large as the width L 1  of the recessed portion  21   r,  the first flat portions  24   a  themselves are small in area and are not very effectively arranged along the curved surface of the body while maintaining spaces between the absorbing portion and the body. Furthermore, even in a case where the first flat portion  24   a  has a certain size, in a case where the width L 1  of the recessed portion  21   r  is substantially large with respect to the first flat portion  24   a,  the area of the first flat portions  24   a  accounts for a low rate of the area of the entire absorbing portion. This causes the feel of the absorbing portion to be impaired and is not preferable. Furthermore, since the main absorbing area is the flat portion  24 , an increase in the area of the recessed portion  21   r  reduces the amount of body fluid that can be absorbed. This is not efficient. 
     On the other hand, in a case where the diameter R 1  of the maximum inscribed circle is more than 20 times as large as the width L 1  of the recessed portion  21   r,  the interval between the recessed portions  21   r  is excessively large, and the first flat portions  24   a  themselves fit the curved surface of the body and closely contact the skin. 
       FIG. 8  illustrates a variation of Embodiment 1 of the present invention and illustrates an example in which the recessed portion  21   r  is formed of an emboss pattern with a plurality of dots within a range Q that strides over the recessed portion forming area N 1  and the recessed portion non-forming area N 2 . The range Q is depicted by an alternate long and short dash line. In the present variation, all of the groove portions  21  are composed of the recessed portion  21   r  as is the case with Embodiment 1. The front surface of the top sheet  14  is compressed toward the absorber  13  using the dot-like emboss pattern to place compressed portions  22  at intervals. The compressed portions  22  are arranged at certain intervals to lower portions of the absorber  13  located near the compressed portions  22 , resulting in depressed portions  23  that are recessed with respect to the flat portion  24 . Therefore, the compressed portions  22  are formed contiguously or at intervals to form the recessed portions  21   r  each including the compressed portion  22  and the depressed portion  23 . 
     The width L 1  of the recessed portion  21   r  is preferably 1 mm≦L 1 ≦5 mm as is the case with Embodiment 1, and a center distance L 3  between the adjacent compressed portions  22  is preferably 1 mm≦L 3 ≦8 mm. In the present variation, the width L 1  is approximately 4 mm, and the distance L 3  is approximately 6 mm. 
     In a case where the thickness of the uncompressed portion of the absorber  13  located in the center of the flat portion  24  is 3 to 3.6 mm and the density of the uncompressed portion is 0.16 g/cm 3 , the thickness of the absorber  13  is 0.5 to 0.6 mm and the density of the absorber  13  is 0.96 g/cm 3  at each compressed portion  22 , and the thickness of the absorber  13  is 1 to 1.2 mm and the density of the absorber  13  is 0.48 g/cm 3  at each depressed portion  23 . As described above, in a case where the difference in density between the compressed portion  22  of the recessed portion  21   r  and that portion of the absorber  13  located in the center of the flat portion  24  which corresponds to the main absorbing area is such that the density of the compressed portion  22  is approximately six times as high as the density of the portion of the absorber  13 , the arrangement interval between the recessed portions  21   r  (or the length L 2 ) is desirably adjusted so as to set the difference in density between the compressed portion  22  and the depressed portion  23  of the recessed portion  21   r  such that the density of the compressed portion  22  is approximately twice to three times as high as the density of the depressed portion  23 . 
       FIG. 9  is a sectional view taken along an IX-IX direction in  FIG. 8 . 
     As depicted in  FIG. 9 , embossing is performed by interposing an adhesive between the top sheet  14  and the absorber  13  and compressing both the top sheet  14  and the absorber  13  from the front surface of the top sheet  14  as is the case with the diaper depicted in  FIG. 5 . 
       FIG. 10  is a sectional view taken along an X-X direction in  FIG. 8 . 
     As depicted in  FIG. 10 , the depressed portions  23  are positioned higher than the compressed portions  22  but lower than the flat portion  24  (the second flat portion  24   b  in  FIG. 10 ) and the recessed portion non-forming area N 2 . Therefore, the compressed portions  22  are formed at predetermined intervals to allow obliquely extending recessed portions  21   r  as is the case with continuous embossing. 
     As seen back in  FIG. 4 , the recessed portion  21   r  having a recessed shape in the present embodiment includes first recessed portions  21   a  extending so as to incline toward a first side (in  FIG. 4 , toward the right) in the width direction of the absorber  13  and a plurality of second recessed portions  21   b  extending so as to incline toward a second side (in  FIG. 4 , toward the left) in the width direction of the absorber  13 . The virtual line P is positioned on the absorber  13  so as to extend from an upper end of a front body portion M 1  toward a lower end of a back body portion M 3 . Specifically, as depicted in  FIG. 4 , in a case where the absorber  13  has an elongate shape, the virtual line P extends in a longitudinal direction. Each recessed portion  21   r  extends so as to incline with respect to the virtual line P. That is, the first recessed portion  21   a  is inclined at an angle α to the first side and the second recessed portion  21   b  is inclined at an angle β to the second side, with respect to a longitudinal direction of the absorber  13 , for example, a direction extending along sides of the absorber  13  in a case where the virtual line P is set as an axis. The angle α may be the same as or different from the angle β. Furthermore, in  FIG. 4 , the plurality of first recessed portions  21   a  are inclined at the same angle and arranged at regular intervals. That is, the first recessed portions  21   a  are arranged parallel to one another and at regular intervals. However, the present invention is not limited to this but includes a configuration in which the interval between the recessed portions  21   r  varies and a configuration in which the inclination angle varies among the recessed portions  21   r.  This also applies to the second recessed portion  21   b . In the present embodiment, the “maximum inscribed circle” is a perfect circle. However, the present invention includes an ellipse. In a case where the maximum inscribed circle is an ellipse, the interval between the recessed portions  21   r  maybe varied (may be irregular). The above-described R 1  for the case where the maximum inscribed circle is an ellipse is determined to be equal to the average of a major axis and a minor axis of the ellipse. The minor axis is preferably at least half of the major axis. The minor axis is set within this range to allow the adjacent recessed portions  21   r  to be appropriately spaced from each other and to allow the flat portion  24  to be provided with a sufficient area. The body fluid (for example, urine) flowing through the adjacent recessed portion  21   r  can be quickly absorbed by the flat portion  24 . 
     Other Embodiments 
     The flat portion pattern of the absorbing portion is not limited to an oblique arrangement of squares depicted in  FIG. 4  and described in Embodiment 1 of the present invention. The following patterns are also possible. Other embodiments will be described below using  FIGS. 11 to 14 . For the elements of the diaper  10  in this embodiment, those which have functions similar to the functions in Embodiment 1 are denoted by the same reference numerals and will not be described below. 
       FIG. 11  is a partial top view illustrating an example of a flat portion pattern formed by arranging the recessed portions  21   r  (groove portions  21 ) at regular intervals in the absorbing portion. In the example illustrated in  FIG. 11 , the recessed portions  21   r  extend orthogonally to the virtual line P to partition the absorbing portion into the flat portions  24  extending in the width direction of the absorber  13 . In the example illustrated in  FIG. 11 , the recessed portions  21   r  are arranged at regular intervals, and the flat portions  24  are each positioned between the recessed portions  21   r.  The adjacent flat portions  24  are separated from each other by the recessed portion  21   r.  In the example illustrated in  FIG. 11 , in order to suppress the sticky feeling, each flat portion  24  needs to have a certain size as is the case with Embodiment 1. Specifically, the optimal size of the flat portion  24  is determined based on the diameter R 1  of the maximum inscribed circle (in  FIG. 11 , depicted by an alternate long and short dash line) inscribed in the flat portion  24  sandwiched between the two recessed portions  21   r  adjacent to each other along an arranging direction of the recessed portions  21   r  and the width L 1  of the recessed portion  21   r  along the radial direction of the maximum inscribed circle. The relation between the diameter R 1  and the width L 1  is similar to the corresponding relation in Embodiment 1. 
     Furthermore, in the present invention, the groove portions  21  may be formed to extend parallel to the virtual line P or formed like a lattice along with recessed portions  21   r  extending parallel to the virtual line P (or no such recessed portions  21   r  are provided). Moreover, in the present invention, the groove portions  21  may be configured such that the recessed portions  21   r  are not arranged at regular intervals. 
       FIG. 12  is a partial top view illustrating an example of a flat portion pattern formed by arranging wavelike recessed portions  21   r  (groove portions  21 ) in the absorbing portion. As depicted in  FIG. 12 , the recessed portions  21   r  may be curves. In the example illustrated in  FIG. 12 , the recessed portions  21   r  are obtained by forming sine curve-like lines along the front-back direction of the absorber  13  and arranging a plurality of the sine curve-like lines in the width direction of the absorber  13 . Furthermore, as depicted in  FIG. 12 , the recessed portions  21   r  are formed by arranging the sine curves such that the adjacent sine curves are in contact with each other while being out of phase with each other by 180 degrees. As depicted in  FIG. 12 , parts of the flat portion  24  that are enclosed by the wavelike recessed portions  21   r  are first flat portions  24   a,  and parts of the flat portion  24  that are not enclosed by the wavelike recessed portions  21   r  are second flat portions  24   b.    
     The flat portion pattern depicted in  FIG. 12  also enables the sticky feeling to be suppressed in a case where a condition similar to the condition in Embodiment 1 is met by the relation between the diameter R 1  of the maximum inscribed circle inscribed in each first flat portion  24   a  enclosed by the recessed portions  21   r  and the width L 1  of the recessed portion  21   r  along the radial direction of the maximum inscribed circle. 
       FIG. 13  is a partial top view illustrating an example of a flat portion pattern formed by arranging circular recessed portions  21   r  (groove portions  21 ) at regular intervals in the absorbing portion. As depicted in  FIG. 13 , the first flat portions  24   a  each enclosed by the corresponding recessed portion  21   r  may be scattered like islands. In this case, the diameter R 1  of the maximum inscribed circle inscribed in each first flat portion  24   a  enclosed by the recessed portion  21   r  is set to meet the relation in which the diameter R 1  is at least five times as large as the width L 1  of the recessed portion  21   r  along the radial direction of the maximum inscribed circle. Moreover, the second flat portion  24   b  positioned between a plurality of the first flat portions  24   a  is generally flat and thus serves as the main absorbing area for the discharged body fluid. In a case where the adjacent first flat portions  24   a  are in proximity to each other, the skin is contacted mostly by the first flat portion  24   a . Consequently, the effect of this pattern is similar to the effect of the pattern in which the first flat portions  24   a  are separated from each other by the recessed portions  21   r  as depicted in  FIG. 4 ,  FIG. 11 , and  FIG. 12 . On the other hand, in a case where a certain separation distance is present between the adjacent first flat portions  24   a,  the skin is contacted both by the first flat portions  24   a  and by the second flat portion  24   b . The second flat portion  24   b  between the first flat portions  24   a  produces an effect similar to the effect of the first flat portions  24   a . Here, for the distance between the recessed portion  21   r  enclosing the first flat portion  24   a  and the adjacent recessed portion  21   r,  a distance in the longitudinal direction of the absorbing portion of the diaper  10  (the up-down direction in  FIG. 13 ) is denoted by L 4 , and a distance in a direction orthogonal to the longitudinal direction (the lateral direction in  FIG. 13 ) is denoted by L 5 . In this case, in a case where the diameter R 1  of the maximum inscribed circle inscribed in each first flat portion  24   a  enclosed by the recessed portion  21   r  is 10 mm or more and 30 mm or less, each of the distances L 4 , L 5  is preferably 5 mm or more and 30 mm or less. 
     In  FIG. 13 , the island-like first flat portions  24   a  are composed of a plurality of circles with the same size. However, in the present invention, the island-like first flat portions  24   a  may be configured by combining with a plurality of circles with different sizes. Furthermore, in the present invention, the island-like first flat portions  24   a  are not limited to circles. Various shapes such as a heart shape which are excellent in design are applicable. That is, any shape may be used so long as the area enclosed by the recessed portion  21   r  is flat. 
     Additionally, the island-like first flat portions  24   a may be densely provided in the groin portion M 2  and the back body portion M 3  rather than being evenly arranged all over the absorbing portion. 
     In the above-described embodiments, the case has been described where all of the groove portions  21  are composed of the recessed portion  21   r.  However, the present invention is effective for suppressing a possible sticky feeling even in a case where all of the groove portions  21  are entirely not composed of the recessed portion  21   r,  that is, parts of the groove portions  21  are composed of the recessed portion  21   r.    
       FIG. 14  is a partial top view illustrating an example of a flat portion pattern formed by arranging, in the absorbing portion, discontinuous recessed portions  21   r  shaped like regular hexagons. In the present embodiment, as depicted in  FIG. 14 , the groove portion  21  is partly composed of the recessed portion  21   r . In  FIG. 14 , the recessed portion  21   r  of the groove portion  21  is depicted by a solid line, and parts of the groove portion  21  in which no recessed portions  21   r  are formed are depicted by dashed lines, for convenience of description. As depicted in  FIG. 14 , the flat portion  24  has two types of flat portions, the first flat portion  24   a  that is enclosed by the groove portion  21  and the second flat portion  24   b  that is not enclosed by the groove portion  21 . 
     The flat portion pattern may be shaped like a honeycomb as depicted in  FIG. 14 . Furthermore, the first flat portion  24   a  need not be entirely enclosed by the recessed portion  21   r  as described above, but maybe partly enclosed by the recessed portion  21   r.  In a case where the first flat portion  24   a  is partly enclosed by the recessed portion  21   r,  in a case where at least 50% or more of the outer periphery of the first flat portion  24   a  is enclosed by the recessed portion  21   r,  the shape of the first flat portion  24   a  is easily maintained even after the body fluid is absorbed. 
     The flat portion pattern depicted in  FIG. 14  also enables the sticky feeling to be suppressed in a case where a condition similar to the condition in Embodiment 1 is met by the relation between the diameter R 1  of the maximum inscribed circle inscribed in each first flat portion  24   a  enclosed by the groove portion  21  and the width L 1  of the groove portion  21  along the radial direction of the maximum inscribed circle. 
     In the present invention, for the compressed portion  22 , not only circular dots but also various other shapes such as a semicircle, a quadrilateral, a triangle, star shape may be used. 
     In addition, the diaper may be formed by wrapping the absorber  13  with a hydrophilic sheet (for example, a core wrap) and then disposing the top sheet  14  on the absorber  13  instead of disposing the top sheet  14  directly on the absorber  13 . Furthermore, a liquid diffusion sheet that improves liquid diffusability may be provided between the top sheet  14  and the hydrophilic sheet or between the hydrophilic sheet and the absorber  13 . The liquid diffusion sheet allows the body fluid to diffuse easily. Alternatively, the hydrophilic sheet may be attached to the absorber  13  so as to wrap the absorber  13  or simply placed on each of the front and back surfaces of the absorber  13  without wrapping the ends of the absorber  13 . 
     The structure of the diaper  10  to which the present invention is directed is not limited to the above-described pull-up type. The diaper  10  may have any configuration so long as the diaper  10  includes the configuration of an absorbent article defined in the claims. For example, the present invention is applicable to well-known unfolding disposable diapers and incontinence pads. 
     In addition, the present invention is not limited to diapers for infants but is applicable to various absorbent articles such as diapers for adults and incontinence pads which are adapted for the growth stage, body type, sex, and the like of the wearer. 
     Furthermore, the above-described embodiments and variations thereof may be combined with one another. 
     REFERENCE SIGNS LIST 
     
         
           10  Diaper 
           10 F Front body area 
           10 R Back body area 
           10 C Groin area 
           10 W Waist opening 
           10 L Leg opening 
           10 J Closed portion 
           10 T Disposal tape 
           11  Cover sheet 
           11 A Pad cover sheet 
           11 B Inner cover sheet 
           11 C Outer cover sheet 
           12  Back sheet (back surface sheet) 
           13  Absorber 
           14  Top sheet (front surface sheet) 
           17  Rubber thread 
           18  Side sheet 
           19  Rubber thread 
           21  Groove portion 
           21   r  Recessed portion 
           21   a  First recessed portion 
           21   b  Second recessed portion 
           22  Compressed portion 
           24  Flat portion 
           24   a  First flat portion 
           24   b  Second flat portion