Patent Publication Number: US-2018028374-A1

Title: Absorbent article having a pair of rear side flaps

Description:
FIELD OF THE INVENTION 
     The present invention relates to absorbent articles such as sanitary napkins, pantiliners, and incontinence pads. More particularly, the present invention relates to a sanitary napkin having a pair of rear side flaps. 
     BACKGROUND OF THE INVENTION 
     Absorbent articles, such as sanitary napkins, pantiliners, and incontinence pads, are typically worn in the crotch region of an undergarment. These devices are designed to absorb and retain liquids and other discharges from the human body to prevent body and garment soiling. The aforementioned types of absorbent articles are typically placed in a garment such as the wearer&#39;s panty and worn between the wearer&#39;s legs, adjacent to the genital (or fluids discharge source) area of the body. 
     Conventional relatively thick, overnight, or extra protection sanitary napkin products currently marketed in Japan provide protection from soiling by utilizing a combination of increased product length and thickness (which may include a profiled or varied caliper). These products, however, are not believed to conform or fit to the body of the wearer during the entire period of the products usage. Specifically, these products typically have a pair of rear side flaps in the rear end region which is placed or adhered (if desired) to the inside surface of undergarments in use. However, the rear side flaps tend to cause bunching (or tend to be deformed or twisted) by a stress or friction which is generated between the rear side flaps and the undergarment during use. This tends to not only affect the comfortness (i.e., the comfort feeling) of the wearer but also cause a situation that these products can not be positioned at the right place during the entire use thereby causing leakage of body fluids. 
     Thus, there is a need for an absorbent article that has rear side flaps which can be effectively prevented from bunching. There is another need for a sanitary napkin that can improve the comfortness of the wearer during the entire use of the napkin. 
     SUMMARY OF THE INVENTION 
     In some embodiments, an absorbent article has a pair of longitudinal edges, front and rear transverse edges, a front end region, a rear end region, and a central region disposed between the front and rear end regions. The absorbent article further comprises a liquid pervious topsheet; a liquid impervious backsheet; and an absorbent core disposed between the topsheet and the backsheet at least in the central region and the rear end region, the absorbent core having a pair of longitudinal edges. The absorbent article also comprises a pair of central side flaps each extending laterally outward from the corresponding longitudinal edge of the absorbent core in the central region; a pair of rear side flaps each extending laterally outward from the corresponding longitudinal edge of the absorbent core in the rear end region; a continuous support layer disposed between the topsheet and the backsheet in the rear end region, the continuous support layer extending across the rear end region from one of the pair of rear side flaps to the other of the pair of rear side flaps and extending outboard of the longitudinal edges of the absorbent core but inboard of the longitudinal edges of the absorbent article such that the continuous support layer extends into at least a portion of the pair of rear side flaps, and wherein the continuous support layer is absent in the central side flaps; and a channel comprising a plurality of first areas having a first bottom surface and a plurality of second areas having a second bottom surface, the second bottom surface being subjacent the first bottom surface, and wherein the plurality of first areas and the plurality of second areas repeat and are alternately spaced along at least a portion of a length of the channel. 
     In some embodiments, an absorbent article has a pair of longitudinal edges, front and rear transverse edges, a front end region, a rear end region, and a central region disposed between the front and rear end regions. The absorbent article further comprises a liquid pervious topsheet; a liquid impervious backsheet; an absorbent core disposed between the topsheet and the backsheet at least in the central region and the rear end region, the absorbent core having a pair of longitudinal edges. The absorbent article further comprises a pair of central side flaps each extending laterally outward from the corresponding longitudinal edge of the absorbent core in the central region; a pair of rear side flaps each extending laterally outward from the corresponding longitudinal edge of the absorbent core in the rear end region; and a channel comprising a plurality of first areas and a plurality of second areas, each of the plurality of first areas having a thinner caliper than each of the plurality of second areas, wherein the plurality of first areas and the plurality of second areas repeat along a length of the channel 
     In some embodiments, an absorbent article has a pair of longitudinal edges, front and rear transverse edges, a front end region, a rear end region, and a central region disposed between the front and rear end regions. The absorbent article further comprises a liquid pervious topsheet; a liquid impervious backsheet; and an absorbent core disposed between the topsheet and the backsheet at least in the central region and the rear end region, the absorbent core having a pair of longitudinal edges. The absorbent article further comprises a pair of central side flaps each extending laterally outward from the corresponding longitudinal edge of the absorbent core in the central region, each of the pair of central side flaps comprising a discrete adhesive patch; a pair of rear side flaps each extending laterally outward from the corresponding longitudinal edge of the absorbent core in the rear end region, each of the pair of rear side flaps comprising a discrete adhesive patch; and a unitary release liner spanning and covering the discrete adhesive patches of the pair of central side flaps and the discrete adhesive patches of the pair of rear side flaps. 
     In some embodiments, an absorbent article has a pair of longitudinal edges, front and rear transverse edges, a front end region, a rear end region, and a central region disposed between the front and rear end regions, and a wearer-facing surface. The absorbent article further comprises a liquid pervious topsheet; a liquid impervious backsheet; and an absorbent core disposed between the topsheet and the backsheet at least in the central region and the rear end region, the absorbent core having a pair of longitudinal edges. The absorbent article further comprises a pair of central side flaps each extending laterally outward from the corresponding longitudinal edge of the absorbent core in the central region; a pair of rear side flaps each extending laterally outward from the corresponding longitudinal edge of the absorbent core in the rear end region; and a channel comprising a plurality of discrete first side wall portions and a plurality of discrete second side wall portions, wherein the first side wall portions extend to a first bottom surface and the second side wall portions extend to a second bottom surface, the first surface being closer to the wearer-facing surface than the second bottom surface, the plurality of discrete first side wall portions and the plurality of discrete second side wall portions alternating with one another along the length of the channel 
     In some embodiments, an absorbent article has a topsheet, a backsheet, and an absorbent core disposed between the topsheet and the backsheet. The absorbent article further comprises a pair of longitudinal edges, front and rear transverse edges, a front end region, a rear end region, and a central region disposed between the front and rear end regions, the front region having a transverse width which is less than a transverse width of the rear region; a pair of central side flaps each extending laterally outward from the corresponding longitudinal edge of the absorbent core in the central region, wherein each of the pair of central side flaps comprise a discrete patch of adhesive; and a pair of discrete adhesive patches disposed in the rear region on the backsheet, one of the pair of discrete adhesive patches being disposed inboard of one of the pair of longitudinal edges, the other of the pair of discrete adhesive patches being disposed inboard of the other of the pair of longitudinal edges; and an adhesive strip disposed on the backsheet and inboard of the pair of discrete adhesive patches in the rear region and inboard of the discrete patches of adhesive on the pair of central side flaps, the adhesive strip being continuous and disposed in the front end region, the central region, and the rear end region. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as forming the present invention, it is believed that the invention will be better understood from the following description which is taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a top plane view of a preferred embodiment of the absorbent article of the present invention; 
         FIG. 2  is a side view of the absorbent article shown in  FIG. 1 ; 
         FIG. 3  is a schematic cross-sectional view of the absorbent article shown in  FIG. 1  taken along line  3 - 3  of  FIG. 1 ; 
         FIG. 4  is a schematic cross-sectional view of the absorbent article shown in  FIG. 1  taken along line  4 - 4  of  FIG. 1 ; 
         FIG. 5  is a perspective view of an emboss channel formed in the absorbent article shown in  FIG. 1 ; 
         FIG. 6  is a plane view of the pair of outwardly convex longitudinal channels shown in  FIG. 1 ; 
         FIG. 7  is a bottom plane view of the absorbent article shown in  FIG. 1 ; 
         FIG. 8  is a top plane view of another preferred embodiment of the absorbent article of the present invention; 
         FIG. 9  is a schematic diagram of a specimen explaining the measurement for the bending stiffness; 
         FIG. 10  is a graph showing a hysteresis curve of a specimen; 
         FIG. 11  is a schematic diagram of a specimen explaining the measurement for the shear rigidity; and 
         FIG. 12  is a graph showing a shear hysteresis curve of a specimen. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Herein, “comprise” and “include” mean that other elements and/or other steps which do not affect the end result can be added. Each of these terms encompasses the terms “consisting of” and “consisting essentially of”. 
     Herein, “absorbent article” refers to articles which absorb and contain body exudates or discharges such as body fluids, and is intended to include sanitary napkins, pantiliners, diapers, and incontinence pads (and other articles worn in the crotch region of a garment). 
     Herein, “disposable” refers to articles which are intended to be discarded after a single use, composted, or otherwise disposed of in an environmentally compatible manner (That is, they are not intended to be laundered or otherwise restored or reused as an absorbent article.) 
     Herein, “sanitary napkin” refers to articles which are worn by females adjacent to the pudendal region which are intended to absorb and contain the various exudates which are discharged from the body (e.g., blood, menses, and urine). It should be understood, however, that the present invention is also applicable to other feminine hygiene or catamenial pads such as pantiliners, diapers, and incontinence pads (and other articles worn in the crotch region of a garment). 
     Herein, “joined” encompasses configurations in which an element is directly secured to another element by affixing the element directly to the other element; configurations in which the element is indirectly secured to the other element by affixing the element to intermediate member(s) which in turn are affixed to the other element; and configurations in which one element is integral with another element, i.e., one element is essentially part of the other element. 
     Herein, “body surface” refers to surfaces of absorbent articles and/or their component members which face the body of the wearer, while “garment surface” refers to the opposite surfaces of the absorbent articles and/or their component members that face away from the wearer when the absorbent articles are worn. Absorbent articles and components thereof, including the topsheet, backsheet, absorbent core, and any individual layers of their components, have a body surface and a garment surface. 
       FIG. 1  is a top plane view of a preferred embodiment of the absorbent article of the present invention. In preferred embodiments shown in  FIGS. 1-8 , the absorbent article is a relatively thick, overnight, extra protection, disposable sanitary napkin  20 . 
     The sanitary napkin  20  has two surfaces, a liquid pervious body-contacting surface or body surface  20 A and a liquid impervious garment surface  20 B.  FIG. 2  is a side view of the sanitary napkin  20  shown in  FIG. 1 . The body surface  20 A is intended to be worn adjacent to the body of the wearer. The garment surface  20 B of the sanitary napkin  20  is on the opposite side and is intended to be placed adjacent to the wearer&#39;s undergarments when the sanitary napkin  20  is worn. 
     Referring to  FIG. 1 , the sanitary napkin  20  has two centerlines, a longitudinal centerline L and a transverse centerline T. Herein, “longitudinal” refers to a line, axis or direction in the plane of the sanitary napkin  20  that is generally aligned with (e.g., approximately parallel to) a vertical plane which bisects a standing wearer into left and right body halves when the sanitary napkin  20  is worn. Herein, “transverse” or “lateral” refers to a line, axis or direction which lies within the plane of the sanitary napkin  20  that is generally perpendicular to the longitudinal direction. 
     The sanitary napkin  20  has two spaced apart longitudinal edges  22  and two spaced apart transverse or end edges (or “ends”)  24 , which together form the periphery  26  of the sanitary napkin  20 . The sanitary napkin  20  also has two end regions, i.e., a front end region  28  and a rear end region  30 . A central region  32  is disposed between the end regions  28  and  30 . The sanitary napkin  20  includes at least a pair of rear side flaps  54  in the rear end region  30 . Preferably, the sanitary napkin  20  further includes a pair of central side flaps  52  in the central region  32 . (In the preferred embodiments shown in  FIGS. 1 and 8 , the sanitary napkins  20  and  21  include both central side flaps  52  and rear side flaps  54 .) Each pair of central and rear side flaps  52  and  54  extends laterally outward from a main body portion  25  in the central region  32  and the rear end region  30 , respectively. 
     The front end region  28  is defined as the area that is placed to the front of the wearer&#39;s body when the sanitary napkin  20  is worn. The rear end region  30  is defined as the area that is placed to the rear of the wearer&#39;s body. The central region  32  is defined as the area that is generally located directly below the perineum of the wearer and which receives the greatest amount of menses. 
     In a preferred embodiment, each region can be defined with respect to the positions of the side flaps  52  and  54 . The front end region  28  ends at the transition area where the traversal distance between the two longitudinal edges  22  starts to increase towards the central region  32  as shown in  FIG. 1 . Similarly, the rear end region  30  ends at the transition area where the traversal distance between the two longitudinal edges  22  starts to increase towards the central region  32  as shown in  FIG. 1 . 
     In other words, each region can be defined with respect to the curve of the longitudinal edge  22 . The front end region  28  ends at the transition area where the curve of the longitudinal edge  22  starts to extend laterally outward at a higher rate than before as shown in  FIG. 1 . Similarly, the rear end region  30  ends at the transition area where the curve of the longitudinal edge  22  starts to extend laterally outward at a higher rate than before as shown in  FIG. 1 . 
       FIG. 3  is a cross-sectional view of the sanitary napkin  20  taken along the section line  3 - 3  in  FIG. 1 , which shows the individual components of the sanitary napkin  20  shown in  FIG. 1 . The sanitary napkin  20  shown in  FIG. 3  generally comprises at least three primary components, i.e., a liquid pervious topsheet  38 ; a liquid impervious backsheet  40 ; an absorbent core  42  having longitudinal edges  48  disposed between the topsheet  38  and the backsheet  40 . The central side flaps  52  extend laterally outward from the corresponding longitudinal edge  48  of the absorbent core  42  in the central region  32 . The topsheet  38 , backsheet  40 , and absorbent core  42  can comprise any types of materials known in the art as being suitable for such components of an absorbent article or a sanitary napkin. 
     The topsheet  38  is preferably compliant, soft feeling, and non-irritating to the wearer&#39;s skin. Further, the topsheet  38  is liquid permeable or pervious, permitting body fluids (e.g., menses and/or urine) to readily penetrate through its thickness. A suitable liquid permeable material for the topsheet  38  may be manufactured from a wide range of materials such as woven and nonwoven materials (e.g., a nonwoven web of fibers); polymeric materials such as apertured formed thermoplastic films, apertured plastic films, and hydroformed thermoplastic films; porous foams; reticulated foams; reticulated thermoplastic films; and thermoplastic scrims. Suitable woven and nonwoven materials can be comprised of natural fibers (e.g., wood or cotton fibers), synthetic fibers (e.g., polymeric fibers such as polyester, polypropylene, or polyethylene fibers) or from a combination of natural and synthetic fibers. When the topsheet  38  includes a nonwoven web, the web may be manufactured by a wide number of known techniques. For example, the web may be spunbonded, carded, wet-laid, melt-blown, hydroentangled, combinations of the above, or the like. 
     A particularly suitable material for the topsheet  38  includes an apertured formed film. Apertured formed films are preferred for the topsheet  38  because they are pervious to body fluids and, if properly apertured, have a reduced tendency to allow liquids to pass back through and rewet the wearer&#39;s skin. Thus, the body surface of the formed film (i.e., the body surface  22 A of the sanitary napkin  20 ) remains dry, thereby reducing body soiling and creating a more comfortable feel for the wearer. A preferred material for the topsheet  38  is a macroscopically expanded, three-dimensional formed polyethylene film. One preferred material for the topsheet  38  is available from Tredegar Film Products, Indiana, USA, under Code No. X-27121. 
     The backsheet  40  is impervious to body fluids and is preferably manufactured from a thin plastic film, although other flexible liquid impervious materials may also be used. Herein, “flexible” refers to materials which are compliant and will readily conform to the general shape and contours of the human body. The backsheet  40  prevents the body fluids absorbed and contained in the absorbent core  42  from wetting articles which contact the absorbent article such as bed sheets, pants, pajamas and undergarments. The backsheet  40  may thus include a woven or nonwoven material, polymeric films such as thermoplastic films of polyethylene or polypropylene, or composite materials such as a film-coated nonwoven material. The backsheet  40  can include a single layer material, or two or more layers of materials. The backsheet  40  preferably has a thickness of from about 0.012 mm (0.5 mil) to about 0.081 mm (3.4 mils). In a preferred embodiment, the backsheet  40  is a single layer polyethylene film. Such a preferred polyethylene film is available from Daedong Co. Ltd., KyungBuk-Do, Korea, under Code No. DNF-040712VL. 
     The backsheet  40  preferably has a microporous structure which can permit vapors to escape from the absorbent core  42  (often called “breathable backsheet”) while still preventing body fluids from passing through the backsheet  40 . A preferred microporous polyethylene film is available from Mitsubishi Chemical Corporation, Tokyo, Japan, under Code No. NPP2. The backsheet  40  can be embossed to provide a clothlike appearance. 
     The absorbent core  42  is capable of receiving, absorbing or retaining body fluids discharged. The absorbent core  42  is preferably compressible, conformable, and non-irritating to the wearer&#39;s skin. The absorbent core  42  can be formed by a single layer material or a plurality layers of materials. The absorbent core may include any of a wide variety of liquid-absorbent materials commonly used in absorbent articles, such as comminuted wood pulp, which is generally referred to as airfelt. A particularly preferred absorbent core material is an airfelt material which is available from Weyerhaeuser Company, Washington, USA, under Code No. NB416. 
     Examples of other suitable absorbent materials for use in the absorbent core include creped cellulose wadding; meltblown polymers including coform; chemically stiffened, modified or cross-linked cellulosic fibers; synthetic fibers such as crimped polyester fibers; peat moss; tissue including tissue wraps and tissue laminates; absorbent foams; absorbent sponges; absorbent gelling materials; or any equivalent material or combinations of materials, or mixtures of these. 
     The absorbent core  42  may be manufactured in a wide variety of sizes and shapes. The periphery of the absorbent core  42  thus can take any shape in its top plane view. Preferred shapes for the core periphery include an oval, a rectangle, an hourglass, and a combination of the oval and rectangle such as the one shown in  FIG. 1 . 
     In a preferred embodiment for a relatively thick, overnight, extra protection sanitary napkin, the sanitary napkin  20  has a total core length ranging between about 200 and 450 mm. A length shorter than about 200 mm typically does not extend far enough into the gluteal area to provide improved protection. A length longer than about 400 mm generally extends too far beyond the gluteal groove in the rear end region to conform to the wearer&#39;s buttocks, causing a poor gluteal fit. 
       FIG. 4  is a schematic cross-sectional view of the sanitary napkin  20  shown in  FIG. 1  taken along line  4 - 4  of  FIG. 1 . The rear side flaps  54  extend laterally outward from the corresponding longitudinal edge  48  of the absorbent core  42  in the rear end region  30 . The sanitary napkin  20  further includes a continuous support layer  44  which is disposed between the topsheet  38  and the backsheet  40  in (at least a part of) the rear end region  30  (and the front region  28  and the central region  32  if desired). In the preferred embodiments shown in FIGs, the continuous support layer  44  is disposed between the absorbent core  42  and the backsheet  40 . The continuous support layer  44  extends laterally into the rear side flaps  54  in the rear end region  30 . Herein, “continuous layer” means a layer (or member) that does not include two (or more) component materials physically separated (or spaced apart) within the layer. For example, if a layer (or member) includes two component materials which are not directly bonded or connected one another, that layer is not a continuous layer but a discontinuous layer. The continuous support layer  44  should have sufficient thickness, rigidity and resiliency to prevent the rear side flaps  54  from bunching (i.e., deforming or twisting) which tends to be cased by a stress generated between the rear side flaps  54  and the undergarment during use. 
     Specifically, to effectively prevent the rear side flaps  54  from bunching, the continuous support layer preferably includes a continuous material which has a shear rigidity value of at least 3.0 gf/cm·degree, more preferably 4.0-10.0 gf/cm·degree, and yet more preferably 5.0-9.0 gf/cm·degree in the longitudinal direction. Herein, “in the longitudinal direction” means that the continuous material is sheared in the direction which is parallel to the longitudinal centerline L. By limiting the shear rigidity value within the above ranges, the rear side flaps  54  can be effectively prevented from bunching. For example, if the shear rigidity value is too low (e.g., lower than 3.0 gf/cm·degree), the rear side flaps  54  tends to easily cause bunching since in that event the rear side flaps  54  become too soft and are easily affected by the shear force (i.e., stress or friction) which is applied from the undergarment due to the wearer&#39;s movement. On the other hand, if the shear rigidity value is too high (e.g., higher than 10.0 gf/cm·degree), the rear side flaps  54  tend to affect the comfortness to the wearer since in that event the rear side flaps  54  become too stiff, and as a result, the wearer feels uncomfortable in use. 
     In addition, the continuous support layer preferably includes a continuous material which has a bending stiffness value of 0.4-10.0 gf·cm 2 /cm, more preferably 0.5-7.0 gf·cm2/cm, and yet more preferably 0.7-2.0 gf·cm 2 /cm in the longitudinal direction. Herein, “in the longitudinal direction” means that the continuous material is bent with a bending axis which is parallel to the traversal centerline T. It should be noted that the bending stiffness value in the traversal direction can take any number, however, it is preferably within the same or similar range as that for the longitudinal direction. By limiting the bending stiffness value within the above ranges, both comfortness and easy handling of the absorbent article can be achieved. For example, if the bending stiffness value is too low (e.g., lower than 0.4 gf·cm 2 /cm), the rear side flaps  54  tend to be too soft and flexible, and as a result, they are easily folded when the absorbent article is applied to the undergarment by the wearer. On the other hand, if the bending stiffness value is too high (e.g., higher than 10.0 gf·cm 2 /cm), the rear side flaps  54  tend to affect the comfortness to the wearer since in that event the rear side flaps  54  do not fully conform to the curve of the body, and as a result, the wearer feels uncomfortable in use. 
     The continuous support layer  44  can be formed by a wide variety of materials (preferably hydrophilic), preferably fibrous materials. Preferred fibrous materials include nonwoven materials. The fibers or other components of such nonwoven materials may be synthetic or natural, or partially synthetic and partially natural. Suitable synthetic fibers include polyester, polypropylene, polyethylene, nylon, viscous rayon, or cellulose acetate fibers. Suitable natural fibers include cotton, cellulose, or other natural fibers. In preferred embodiments, the continuous support layer  44  includes a nonwoven material which has a basis weight of 40-200 g/m 2 , preferably 60-100 g/m 2 . 
     In one preferred embodiment, the continuous support layer  44  is an air laid nonwoven material. A preferred material is available from Kang Na Hsiung Enterprise Co., Ltd., Taipei, Taiwan, under Code No. AL080-BL01-10. This nonwoven material has basis weight of 80 g/m 2 , density of 0.07 g/cm 3 , and thickness of 1.16 mm. This nonwoven material is formed by a mixture of chemical pulp (or cellulose) fibers and polyethylene/polypropylene bi-component fibers through an air through process. In order to provide the desired support effect for the rear side flaps  54  under in-use conditions, it is desirable that the nonwoven material for the continuous support layer  44  preferably has basis weight of 30˜180 g/m 2 , density of 0.05˜0.20 g/cm 3 , and thickness of 0.3˜1.5 mm. 
     Referring again to  FIG. 4 , the sanitary napkin  20  preferably includes an adhesive layer (not shown in FIGs.) disposed between the continuous support layer  44  and the backsheet  40  in the rear end region  30 . Preferably, the adhesive layer is applied uniformly (thereby forming a uniform adhesive layer) between the continuous support layer  44  and the backsheet  40 . Herein, “uniform layer” refers to a layer that has a basis weight with a deviation of no more than 20% at every unit area within the layer. Herein, “unit area” is defined as an area of 12.5 mm×50 mm. Thus, in this embodiment the uniform adhesive layer preferably contains an adhesive which has a basis weight with a deviation of no more than 20% at every unit area within the layer. As a result, the uniform adhesive layer can uniformly bond the continuous support layer  44  to the backsheet  40  in the rear end region  30 . Preferably, the uniform adhesive layer is formed by a hot-melt adhesive. In preferred embodiments, the uniform adhesive layer has a basis weight of about 1.0-13 g/m 2 , more preferably 2.0-10 g/m 2 . In a preferred embodiment, the uniform adhesive layer has a basis weight of about 3.6 g/m 2 . Such a uniform adhesive layer is preferred since it can help provide a uniform thickness, rigidity and/or resiliency to the rear side flaps  54  which can also prevent the rear side flaps  54  from bunching which may be cased by a stress generated between the rear side flaps  54  and the undergarment during use. 
     The topsheet  38 , the backsheet  40 , the absorbent core  42  may be assembled in a variety of configurations known in the art. Preferred configurations are described in U.S. Pat. Nos. 4,950,264; 5,009,653 issued to Osborn; U.S. Pat. No. 4,425,130 issued to DesMarais; U.S. Pat. Nos. 4,589,876 and 4,687,478 issued to Van Tilburg, and U.S. Pat. No. 5,234,422 issued to Sneller, et al. 
     Referring again to  FIG. 1 , the sanitary napkin  20  has a pair of outwardly convex longitudinal central channels  62  formed at least in the central region  32 . Herein, “channel” refers to a generally elongated depression formed in at least a portion of an absorbent article. The channel can be formed by, for example, reducing the amount of the absorbent core at the channel portion, and/or compressing or embossing the absorbent core at the channel portion. 
     Typically, the channel is formed by applying a compressive force to both the topsheet and the absorbent core toward the backsheet. The topsheet at the channel portion is pushed down into the absorbent core, and the materials of the topsheet and the absorbent core are compressed at and below the bottom of the channel portion. By this operation (which is often called “embossing process”), the channel portion of the absorbent article has relatively higher density than the other portion(s) or the surrounding portion(s) of the channel portion. The channels of the present invention can be formed by any structures and processes known in the art. 
     The channel tends to preferentially diffuse or lead body fluids flow along the direction in which the channel extends. Therefore, the channel is useful to control body fluids flow within the absorbent article thereby preventing body fluids leakage from the absorbent article. The channel also tends to work as a preferential bending axis of the absorbent article. Therefore, the absorbent article may bend at the channel portion such that it provides an improved fit of the absorbent article to the wearer&#39;s body. It should be noted that such an improved fit of the absorbent article can also contributes an improvement in preventing body fluids leakage from the absorbent article. 
     The channel of the present invention can be either continuous or discontinuous. Herein, “discontinuous” means the channel can be separated by a non-channel portion (i.e., a portion where no channel is formed) such that the channel includes 2 or more elongated channel portions which are separated by a non-channel portion. The distance between the two succeeding channel portions (i.e., the length of the no channel portion) may be changed depending on the product design. Preferably, the length of the no channel portion is 0-20 mm, more preferably 2-10 mm, and yet more preferably 3-6 mm 
     In one preferred embodiment, channels are formed by applying a uniform (or a single level of) compressive force to the topsheet and the absorbent core toward the backsheet. Alternatively, channels can be formed by applying two or more levels of compressive forces to the topsheet and the absorbent core toward the backsheet thereby forming a “two (or more) stage channel structure”. 
     In the preferred embodiment shown in  FIG. 1 , the channels  62 ,  64 ,  65  and  66  are formed by applying two levels of compressive forces to the topsheet  38  and the absorbent core  42  toward the backsheet  40 . The application of the two levels of compressive forces (i.e., higher compression and lower compression) produces two stage depth portions (i.e., “two stage channel structure”) in the resulting the channels, i.e., first portion and second portion. 
       FIG. 5  is a perspective view of one channel formed in the sanitary napkin  20  shown in  FIG. 1 . In this embodiment, the channel  62  has two side walls (or channel walls)  83  and  84 . The first portions  81  are formed by a higher compression, while the second portion  82  is formed by a lower compression. The absorbent core  42  is more compressed at the portions  81  of higher compression than the portion  82  of lower compression. In the embodiment shown in  FIG. 5  (and also  FIG. 3 ), the portions  81  of higher compression form the lowest portions of the channel  62 , while the portion  82  of lower compression forms the higher portion in the channel  62 . The first portions  81  of higher compression have a higher density than the portion  82  of lower compression as a result of compression force differences. Such a two stage channel structure is preferred since it can provide a better comfort to the wearer&#39;s body in use compared with the channel structure which has no stage difference (formed by no compression force differences applied). In addition, since the compression force is more concentrated at the portions  81  of higher compression, the two stage channel structure can also increase the bonding strength between the topsheet  38  and the absorbent core  42  at the portions  81 . 
     The first portions  81  formed by a higher compression extend from one channel wall  83  but does not reach the other channel wall  84 . In the embodiment shown in  FIG. 5 , the shape of the first portions  81  formed by a higher compression is about a rectangular. However, the shape of the first portions  81  can vary depending on the channel design in the sanitary napkin  20 . The length, width and depth of the first portions  81  can also vary depending on the channel design in the sanitary napkin  20 . Similarly, the shape, the length, width and depth of the second portion  82  can also vary depending on the channel design in the sanitary napkin  20 . 
     The first portions  81  formed by a higher compression are spaced one another. The distance or interval of two adjacent portions  81  can be either consistent or inconsistent. In the embodiment shown in  FIG. 5 , the distance of two adjacent portions  81  is consistent. 
     In an alternative embodiment (not shown in FIGs.), the first portions  81  may be formed by lower compression, and the second portion  82  may be formed by higher compression. This produces an opposite geographic shape of the channels. 
     A variety of preferred channel structures which are applicable to the present invention are disclosed in, for example, U.S. Pat. No. 6,563,013 issued to Murota on May 13, 2003. This publication discloses examples of “two stage channel structure” which are preferably applicable to the embodiments of the present invention. 
     In the embodiment shown in  FIG. 5 , the first portion  81  formed by a higher compression extends from one channel wall  83  but does not reach the other channel wall  84 . This channel structure is referred to as a “stitched channel structure”. 
     However, this is not always necessary. Alternatively to such a stitched channel structure, the first portion  81  formed by a higher compression can extend from one channel wall  83  to the other channel wall  84 . Such a structure can be produced by an application of higher and lower compressions alternatively applied along the longitudinal direction of the channel  62 . Such channel structures are disclosed in, for example, U.S. Pat. No. 5,795,345 issued to Mizutani et al. on Aug. 18, 1998. 
       FIG. 6  is a plane view of the pair of outwardly convex longitudinal central channels  62  shown in  FIG. 1 . Herein, “outwardly convex” means the longitudinal channels have a curved line shape (including a polygonal lines shape and a curved line shape) which is outwardly extended when looking from the longitudinal centerline L. The longitudinal central channels  62  shown in  FIG. 1  have a circular arc shape which is outwardly curved when looking from the longitudinal centerline L of the sanitary napkin  20 . The traversal distance TD of the pair of outwardly convex longitudinal central channels  62  decreases towards the both ends of the central channels  62  to define a central closed area  72 . 
     Herein, “closed area” is an area that is disposed between the inside channel wall(s) of the outwardly convex longitudinal channels. When the traversal distance between the inside channel walls of the outwardly convex longitudinal channels reaches 60% of the maximum traversal distance, a closed area is defined at least at that position. However, the closed area can extend within the inside channel walls of the outwardly convex longitudinal channels until they stop at their ends (before they intersect). 
     In one preferred embodiment, the closed area is defined at least at the position where the traversal distance between the inside channel walls of the outwardly convex longitudinal channels reaches 20% (or less than 5% or about 0% if desired) of the maximum traversal distance. Thus, it should be noted that the “closed area” does not require an area that is physically “closed” by the outwardly convex longitudinal channels. The closed area has a maximum length (ML) and a maximum width (MW). The maximum length is defined as the longitudinal distance between the outermost walls at the both ends of the outwardly convex longitudinal channels. The maximum width is defined as the maximum traversal distance between the inside channel walls of the outwardly convex longitudinal channels. (These maximum length and width ML and MW of the closed area are shown in  FIG. 6 .) 
     In the embodiment shown in  FIG. 6 , the central closed area  72  is defined at least at the position P where the traversal distance TD between the outwardly convex longitudinal central channels  62  reaches 60% of the maximum traversal distance. However, the closed area  72  extends within the inside channel walls of the outwardly convex longitudinal channels  62  until they stop at their ends. 
     The closed area preferably has a periphery wherein 70-100% in length of the periphery is surrounded by the outwardly convex longitudinal channels. In other words, the rest (i.e., 0-30% in length) of the periphery may be surrounded by other channel(s). Preferably, 80-98% in length of the periphery of the closed area is defined by the outwardly convex longitudinal channels. 
     The closed area generally tries to maintain the body fluids absorbed underneath the closed area (e.g., an absorbent core). In addition, the closed area also works to prevent the material of the absorbent core from moving when it becomes wet by the absorbed body fluids. 
     The central closed area  72  shown in  FIG. 6  has a periphery  70  defined by the inside channel walls of the two central channels  62 . Preferably, 70-100% in length of the periphery  70  is surrounded by the outwardly convex longitudinal channels  62 . In the embodiment shown in  FIG. 6 , since there is about 2% in length of the periphery  70  of the closed area has no channel portion  63 , about 98% in length of the periphery  70  of the closed area  72  is defined by the outwardly convex longitudinal channels  62 . 
     The pair of outwardly convex longitudinal central channels  62  can take any shape that defines a central closed area  72 . Preferably, the central channels  62  takes an oval like shape. Preferred oval like shapes include, for example, an actual oval shape defined by mathematics and an eye shape (i.e., a shape formed by two arc like lines), and the like. In the preferred embodiment shown in  FIG. 1 , the central channels  62  has an eye shape consisting of two arc like lines, each of which is formed by five (5) circular arcs which are connected in series. Such oval like shapes have a maximum length ML and a maximum width MW. The central closed area  72  shown in  FIG. 6  has a maximum length ML and a maximum width MW. 
     Preferably, the central closed area  72  has a maximum length ML of 80-220 mm and a maximum width MW of 25-70 mm. More preferably, the central closed area  72  has a maximum length ML of 130-190 mm and a maximum width MW of 35-55 mm. In the preferred embodiment shown in  FIG. 1 , the central closed area  72  has a maximum length ML of 160 mm and a maximum width MW of 46 mm. 
     Referring again to  FIG. 1 , the sanitary napkin  20  preferably has a rear channel  64  defining a rear closed area  74  in the rear end region  30 . The rear closed area  74  can be formed not only within the rear end region  30  but both or either the central regions  32  and/or the rear end region  30 . For example, in the embodiment shown in  FIG. 1 , the rear closed area  74  is formed within the rear end region  30 . 
     Preferably, the maximum width of the rear closed area  74  is no greater than that of the maximum width of the central closed area  72 . By limiting the width of the rear closed area  74  within the maximum width of the central closed area  72 , the discharged body fluids are led along the longitudinal direction more than the traversal direction by the fluids control function of the rear channels  64 . Therefore, this configuration is useful to prevent the body fluids leakage from the longitudinal edges  22  of the sanitary napkin  20  in the rear end region  30 . In preferred embodiment shown in  FIG. 1 , the maximum width of the rear closed area  74  is about same as that of the maximum width of the central closed area  72 . 
     The rear channel  64  can take any shape that forms a closed area. The rear channel  64  preferably takes an oval like shape or an elongated U-character shape. Preferred oval like shapes include, for example, an actual oval shape defined by mathematics and an elongated U-character shape. A preferred elongated U-character shape has the traversal distance between the two arms of the elongated U-character shape decreases towards the central closed area  72  as shown in  FIG. 1 . 
     In a preferred embodiment, the sanitary napkin  20  further has an additional (or secondary) rear channel  65  within the rear closed area  74  in the rear end region  30  as shown in  FIG. 1 . The additional rear channel  65  does not need to form a closed area. The additional rear channel  65  is used to control the rigidity of the sanitary napkin  20  at the rear end region  30 . In addition, the additional rear channel  65  also can work to maintain the absorbed body fluids in the inside area of the channel  65 . The additional rear channel  65  can take any shape but it preferably takes an elongated U-character shape as shown in  FIG. 1 . 
     Referring again to  FIG. 1 , the sanitary napkin  20  preferably has a front channel  66  forming a front closed area  76  in the front end region  28 . 
     The front closed area  76  can be formed not only within the front end region  28  but both the central regions  32  and the front end region  28 . For example, in the embodiment shown in  FIG. 1 , the front closed area  76  is formed within the front end region  28 . 
     Preferably, the maximum width of the front closed area  76  is no greater than that of the maximum width of the central closed area  72 . By limiting the width of the front closed area  76  within the maximum width of the central closed area  72 , the discharged body fluids are led along the longitudinal direction more than the traversal direction by the fluids control function of the front channels  66 . Therefore, this configuration is also useful to prevent the body fluids leakage from the longitudinal edges  22  of the sanitary napkin  20  in the front end region  28 . In preferred embodiment shown in  FIG. 1 , the maximum width of the front closed area  76  is about same as that of the maximum width of the central closed area  72 . 
     The front channel  66  can also take any shape that forms a closed area. The front channel  66  preferably takes a horseshoe like shape, an oval or circle like shape or a U-character shape. One example of preferred horseshoe like shape is shown in  FIG. 1 . 
     In one embodiment, the absorbent core  42  is non-profiled within the central closed area  72  so that the central region  32  has the same caliper as the outside of the central closed area  72 . Preferably, the absorbent core  42  is profiled within the central closed area  72  so that the central region  32  has a caliper that is greater than the caliper of the outside of the central closed area  72  (i.e., a non-profiled portion) as shown in  FIGS. 2 and 3 . Herein, “profiled” means that one specified portion of a material has a caliper that is greater than that of the other portion to be compared. Herein, calipers are measured under a pressure of 0.5 psi using a circular comparator foot with a 1 inch diameter area. Typically, a profiled portion is formed by increasing the amount of material(s) at the profiled portion of the absorbent core than the other adjacent portion such that the profiled portion shows an expanded shape (or appearance) on the body surface  20 A compared to the other portion. In the embodiment of  FIG. 1 , the absorbent core  42  contains an increased amount of material(s) within the central closed area  72  than the outside of the central closed area  72  such that the sanitary napkin  20  is profiled at the central closed area  72  as sown in  FIG. 2 . 
     Preferably, the front end region  28  and the rear end region  30  have the same or similar caliper, while the central region  32  comprises the greatest caliper portion of the sanitary napkin  20  as a result of the profiled structure. The caliper ratio of the profiled portion to the non-profiled portion preferably ranges from about 1.1:1 to about 3:1, and more preferably from about 2:1 to about 2.6:1. In the sanitary napkin  20  shown in  FIG. 1 , the caliper ratio of the profiled portion to the non-profiled portion is about 2.2:1. 
     The sanitary napkin  20  can be of any caliper, including relatively thick, relatively thin, or even very thin. The embodiment of the sanitary napkin  20  shown in  FIG. 1  is intended to be an example of a relatively thick, overnight, extra protection sanitary napkin having a caliper of about 5 mm in the end regions  28  and  30  and a caliper of about 14 mm in the central region  32 . It should be understood, however, when viewing these figures the number of layers of material shown may cause the sanitary napkin  20  to appear much thicker than it actually is, particularly in cross-section. 
     As shown in  FIG. 1 , the sanitary napkin  20  is asymmetrically shaped so that the rear end region  30  is larger than the front end region  28 . In the preferred embodiment shown in  FIG. 1 , the sanitary napkin  20  is asymmetrically shaped such that the rear end region  30  has both a larger width and a longer length than the front end region  28 . The widths of the front and rear end regions are defined by the traversal distance between the longitudinal edges  22  of the sanitary napkin  20 . The ratio of the widths of the rear end region  30  to the front end region  28  preferably ranges from between about 1:1 and about 2.5:1. More preferably, the ratio of the widths of the rear end region  30  to the front end region  28  is about 1.4:1. The ratio of the longitudinal lengths of the front end region  28  to the central region  32  is from about 1:1 to about 1:4, and the ratio of the longitudinal lengths of the central region  32  to the rear end region  30  is from about 1:0.5 to about 1:3. In the preferred embodiment shown in  FIG. 1 , the ratio of the longitudinal lengths of the front end region  28  to the central region  32  and the rear end region  30  is about 1:1.7:2.5. 
     The topsheet  38  and the backsheet  40  typically have length and width dimensions generally larger than those of the absorbent core  42 . The topsheet  38  and backsheet  40  extend beyond the edges of the absorbent core  42 , and are joined together to form a pair of central side flaps  52  and a pair of rear side flaps  54 . These topsheet  38  and backsheet  40  can be joined any means (e.g., an adhesive) known in the art. 
     The central side flaps  52  can be in any suitable configuration and shape known in the art. Suitable flaps are described in U.S. Pat. No. 5,389,094 issued to Lavash, et al. on Feb. 14, 1995; and U.S. Pat. No. 5,558,663 issued to Weinberger, et al. on Sep. 24, 1996. 
     In the embodiment shown in  FIG. 1 , the central side flaps  52  and the rear side flaps  54  are integral with the main body portion  25  of the sanitary napkin  20  (i.e., these flaps comprise integral extensions of the topsheet  38  and the backsheet  40  from the main body portion  25 ). Alternatively, these flaps can be formed by separate materials from the topsheet  38  and the backsheet  40 , which are joined to the main body portion  25  of the sanitary napkin  20  in any suitable manner In that event, the flaps are each joined to (or associated with) the main body portion  25  along a juncture, typically a longitudinally-oriented (or “longitudinal”) juncture (not shown in Figs.). 
     The central side flaps  52  and the rear side flaps  54  are used to attach the sanitary napkin  20  to the wearer&#39;s panties or undergarment through adhesive fasteners as known in the art. The fasteners comprise a plurality of patches of adhesive adhered to the garment surface  20 B of the backsheet  40  of the sanitary napkin  20 . 
       FIG. 7  is a bottom plane view of the sanitary napkin  20  shown in  FIG. 1 . Typically one or two (or more if desired) adhesive patches (i.e., panty fastening adhesive  55 ) are disposed on the main body portion  25  of the sanitary napkin  20  such that the sanitary napkin  20  can adhere to the crotch area of the wearer&#39;s undergarment to keep the sanitary napkin  20  in place. 
     The panty fastening adhesive  55  is preferably at least about 50% as long as the absorbent core  42 , but is preferably no greater than about 100% of the length of the core  42 . The preferred length of the panty fastening adhesive  55  is between about 75% and about 90% the length of the absorbent core  42 . The width of the panty fastening adhesive  55  is preferably at least about 25% of the width of the portion of the absorbent core  42  lying in the front end region  28 , but should be no wider than about 100% the width of the portion of the core  42  in the front end region  28 . The preferred width of the panty fastening adhesive  55  is between about 70% and about 88% of the width of the first end region core width. 
     In addition, a pair of additional adhesive patches (i.e., central flap adhesives  56 ) are disposed on the garment surface  20 B of the central side flaps  52  of the sanitary napkin  20  to adhere to the undersides of the wearer&#39;s undergarment during use and to keep the napkin  20  in place to improve fit. 
     Preferably, another pair of additional adhesive patches (i.e., rear flap adhesives  57 ) are disposed on the garment surfaces  20 B of the rear side flaps  54  of the sanitary napkin  20  to additionally help keep the sanitary napkin  20  in place. The rear flap adhesives  57  adheres to the undersides of the wearer&#39;s undergarment during use and to keep the napkin  20  in place to improve fit. The rear flap adhesives  57  jointly work with the continuous support layer  44  in the rear side flaps  54  to prevent the rear side flaps  54  from undesirable bunching during the use of the sanitary napkin  20 . 
     The central side flaps  52 , which have panty fasteners thereon, adhere to the underside of the wearer&#39;s undergarment. The central side flaps  52  serve to keep the sanitary napkin  20  in place during wear. Keeping the sanitary napkin  20  in place prevents skewing of the napkin  20  in the panty, and undesirable bunching. The central side flaps  52  may also assist the central region  32  in forming into the desired W-shaped configuration, and the rear end region  30  in forming the desired inverted V-shaped configuration. 
     These adhesive patches are preferably covered by release strips before use as known in the art. Preferably, the central side flaps  52  are folded over the topsheet  38  and they are bridged by a single (or unitary) release strip through the central flap adhesives  56 . Similarly, the rear side flaps  54  are also folded over the topsheet and they are also bridged by a single (or unitary) release strip through the rear flap adhesives  57 . In a particularly preferred embodiment, both the central side flaps  52  and the rear side flaps  54  are bridged by a single (or unitary) release strip. Herein, “unitary” means the release strip member can be formed by either a single material or two (or more) joined materials. 
     The panty fastening adhesive  55  is also covered by a release strip. If desired, the panty fastening adhesive  55  is covered by a releasable wrapper that also serves as an individual wrapper package for the sanitary napkin  20 . A preferred structure is described in U.S. Pat. No. 6,074,376 issued to Mills on Jun. 13, 2000. 
     The sanitary napkin  20  is worn by the wearer so that the rear end region  30  is placed to the rear of the wearer&#39;s body to provide the best gluteal fit. The outwardly convex longitudinal central channels  62  assist the central region  32  of the sanitary napkin  20  in assuming a W-shaped cross-sectional configuration when the napkin  20  is laterally compressed by the wearer&#39;s thighs, thereby allowing improved contact with the wearer&#39;s genital area. This W-shaped configuration is formed by the sides compressing upwards and inwards and the center buckling upward into a convex upward configuration, with the densified region provided by the channels forming the fold lines. 
     In addition, due to the profiled configuration in the central region  32 , the central closed area  72  is brought more closely to the source area of body fluids thereby contributing to a further better fit to the wearer&#39;s body. The profiled configuration of the central closed area  72  cooperates with the W-shaped cross-sectional configuration thereby allowing the central closed area  72  to closely fit to the wearer&#39;s genital area. This cooperative function enables an improved leakage protection at the central region  32 . 
     The W-shape configuration of the central region  32  is transformed into an inverted V-shape configuration in the rear end region  30 . The inverted V-shape configuration retains the profiled central portion of the W-shape configuration to improve gluteal fit. The rear end region  30  is thus also able to closely fit into the crevice between the wearer&#39;s buttocks (that is, in the gluteal groove) for improved protection from end soiling. This occurs while the rear end region  30  maintains its area coverage due to the size of the same and the panty fastening adhesive. 
     As a result, in the embodiment shown in  FIG. 1 , all the asymmetrical shape of the sanitary napkin  20 , the embossed channels  62 ,  64  and  66 , the central and rear side flaps  52  and  54 , and the profiled configuration in the central closed area  72  cooperatively work together thereby providing an improved fit and leakage protection. 
       FIG. 8  is a top plane view of another preferred embodiment of the absorbent article of the present invention. In this embodiment, the absorbent article is also a relatively thick, overnight, extra protection, disposable sanitary napkin  21 . It should be noted that except the channels arrangements the sanitary napkin  21  is similar to the sanitary napkin  20  which is discussed hereinabove. Referring to  FIG. 8 , the sanitary napkin  21  has a pair of longitudinal channels  90  formed in the front end region  28 , the central region  32  and the rear end region  30 ; and a pair of central side flaps  52  each extending laterally outward from the central region  32 . Each of the longitudinal channel  90  includes (or divided into) an outwardly convex central channel  92 , an outwardly convex rear channel  94  and an outwardly convex front channel  96 . The longitudinal channel  90  has (1) an outwardly convex channel portion  97  in the central region, (2) a front inwardly concave channel portion  98  at the transition area between the front end region  28  and the central region  32 , and (3) a rear inwardly concave channel portion  99  at the transition area between the rear end region  30  and the central region  32 . 
     Herein, “inwardly concave” means the longitudinal channels have a curved line shape (including a polygonal lines shape and a curved line shape) which is inwardly curved when looking from the longitudinal centerline L. The longitudinal channels  90  shown in  FIG. 8  have a circular arc shape which is inwardly concave at the portions  98  and  99  when looking from the longitudinal centerline L of the sanitary napkin  20 . 
     In one embodiment, the absorbent core  42  can be non-profiled within the central closed area  72 . However, similarly to the sanitary napkin  20  shown in  FIG. 1 , the absorbent core  42  of the sanitary napkin  21  is preferably profiled in the central area  93  between the front inwardly concave channel portion  98  and the rear inwardly concave channel portion  99  so that the central region  32  has a caliper that is greater than the caliper of the outside of the central area  93  (i.e., a non-profiled portion). 
     Due to the profiled configuration in the central region  32 , the central area  93  is brought more closely to the source area of body fluids thereby contributing to a further better fit to the wearer&#39;s body. The profiled configuration of the central area  93  cooperates with the W-shaped cross-sectional configuration formed by the outwardly convex central channels  92  thereby allowing the central area  93  to closely fit to the wearer&#39;s genital area. This cooperative function enables an improved leakage protection at the central region  32 . 
     Test Methods 
     (1) Bending Stiffness Value Measurement 
     The bending stiffness value is a measure of the force required to bend a specimen, which is preferably measured by a Pure Bending Tester. In this measurement, the specimen has 6.0 cm in length and 6.0 cm in width. The both side edges of the specimen is fixed between two jaws of the tester. The effective dimension for the measurement (i.e., the effective specimen sizes between the two jaws) is 4.0 cm in length and 6.0 cm in width (rectangular). 
     Bending force is applied to the specimen by the tester to cause a bending deformation between the curvature K=−2.5 cm −1  and 2.5 cm −1 . The specimen is bent in the direction Db with the bending axis Ba as shown in  FIG. 9 . The bending rate is 0.1 cm −1 /sec. As a result, a bending hysteresis curve is obtained by the measurement as shown in  FIG. 10 . The horizontal axis shows the curvature K (cm −1 ) and the vertical axis shows the moment M (gf·cm 2 /cm). The bending stiffness value is obtained as Bf which is the slope value of the first forward cycle of the curve at K=0.1 cm −1 . This measurement is carried out for 5 specimens which are cut out from one material to be measured, and the average value of the 5 specimens is defined as a “bending stiffness value” (gf·cm 2 /cm). A preferred Pure Bending Tester is available from Kato Tech Co., Ltd., Kyoto, Japan, under Code No. KES-FB2. 
     (2) Shear Rigidity Value Measurement 
     The shear rigidity value is a measure of the force required to shear a specimen, which is preferably measured by a Fabric Shear Tester. In this measurement, the specimen has 6.0 cm in length and 6.0 cm in width. The both side edges of the specimen is fixed between two jaws of the tester. The effective dimension for the measurement (i.e., the effective specimen sizes between the two jaws) is 6.0 cm in length and 5.0 cm in width (rectangular). 
     Shear force Fs is applied to the specimen by the tester to cause a shear deformation between the shear angle Sa=0 degree and 8 degrees. The specimen is sheared in the direction Ds as shown in  FIG. 11  (Note: the direction Ds corresponds to the length direction of the specimen). The shearing rate is 0.417 mm/sec. As a result, a shearing hysteresis curve is obtained by the measurement as shown in  FIG. 12 . The horizontal axis shows the shear angle Sa (degrees) and the vertical axis shows the shear force Fs (gf·cm). The shear rigidity value is obtained as G which is the average slope value of the shearing hysteresis curve between the shear angle Sa=0.5 and 2.5 degrees. This measurement is carried out for 5 specimens which are cut out from one material to be measured, and the average value of the 5 specimens is defined as a “shear rigidity value” (gf/cm·degree). A preferred Fabric Shear Tester is available from Kato Tech Co., Ltd., Kyoto, Japan, under Code No. KES-FB1. 
     EXAMPLES 
     Example 1 
     An air laid nonwoven web which is available from Kang Na Hsiung Enterprise Co., Ltd., Taipei, Taiwan, under Code No. AL080-BL01-10 is prepared. This nonwoven web has basis weight of 80 g/m 2 , density of 0.07 g/cm 3 , and thickness of 1.16 mm. This nonwoven web is formed by a mixture of chemical pulp (or cellulose) fibers and polyethylene/polypropylene bi-component fibers through an air through process. This nonwoven web is a continuous material which has a bending stiffness value of 0.79 gf·cm 2 /cm and a shear rigidity value of 5.85 gf/cm·degree. 
     Example 2 
     An air laid nonwoven web which is available from BBA (China) Airlaid Co., Ltd., Tianjin, China, under Code No. B667M077P25 is prepared. This nonwoven web has basis weight of 77 g/m 2 , density of 0.096 g/cm 3 , and thickness of 0.80 mm. This nonwoven web is formed by two layers which are joined by multi-bonding process (i.e., a combination bonding of heart and latex), which include a polypropylene nonwoven (Layer 1); and a mixture of chemical pulp (or cellulose) fibers, polyethylene/polyester bi-component fibers (Layer 2). This nonwoven web is a continuous material which has a bending stiffness value of 2.74 gf·cm 2 /cm and a shear rigidity value of 5.32 gf/cm·degree. 
     Example 3 
     An air laid nonwoven web which is available from BBA (China) Airlaid Co., Ltd., Tianjin, China, under Code No. B889M180S17 is prepared. This nonwoven web has basis weight of 180 g/m 2 , density of 0.144 g/cm 3 , and thickness of 1.25 mm. This nonwoven web is formed by a mixture of chemical pulp (or cellulose) fibers, polyethylene/polyester bi-component fibers, ethylene vinyl acetate latex binder and super absorbent polymers (acrylic acid and sodium acrylate copolymer) through a multi-bonding process (combination of thermal bonding and latex bonding). This nonwoven web is a continuous material which has a bending stiffness value of 6.33 gf·cm 2 /cm and a shear rigidity value of 8.15 gf/cm·degree. 
     Example 4 
     An air laid nonwoven web which is available from Kang Na Hsiung Enterprise Co., Ltd., Taipei, Taiwan, under Code No. AL070-CS10-10 is prepared. This nonwoven web has basis weight of 70 g/m 2 , density of 0.07 g/cm 3 , and thickness of 1.00 mm. This nonwoven web is formed by a mixture of chemical pulp (or cellulose) fibers and polyethylene/polypropylene bi-component fibers through an air through process. This nonwoven web is a continuous material which has a bending stiffness value of 4.35 gf·cm 2 /cm and a shear rigidity value of 3.17 gf/cm·degree. 
     All documents cited in the Detailed Description of the Invention are, are, in relevant part, incorporated herein by reference; the citation of any document is not to be construed as an admission that it is prior art with respect to the present invention. To the extent that any meaning or definition of a term in this written document conflicts with any meaning or definition of the term in a document incorporated by reference, the meaning or definition assigned to the term in this written document shall govern. 
     While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.